BIO - TERMS - CELL Flashcards
activation-induced cell death
A process by which autoreactive T cells are induced to die if they complete thymic maturation and migrate to the periphery.
adhesion belt
Adherens junctions in epithelia that form a continuous belt (zonula adherens) just beneath the apical face of the epithelium, encircling each of the interacting cells in the sheet.
agonist selection
A process by which T cells are positively selected in the thymus by their interaction with relatively high-affinity ligands.
alarmone
A chemical signal that promotes a cell’s response to environmental stress.
alkaline battery
A dry-cell battery that employs half-reactions in a basic medium.
amphitrichous
Having flagella at both ends of a cell.
Anchorage independence
Th e ability of some cells to grow in the absence of a surface on which to adhere; oft en detected by the ability to form colonies in semisolid media. (Chapter 6)
Animalia
The kingdom composed of multicellular eukaryotes lacking cell walls.
aorta-gonad-mesonephros (AGM)
An embryonic region in which hematopoietic cells arise during development.
Apical domain
The specialized surface of an epithelial cell exposed to the environment. Also called apical surface. (Chapters 2, 9, and 12)
asexual spore
A reproductive cell produced by mitosis and cell division (eukaryotes) or binary fission (actinomycetes).
axon terminal
The end region of an axon, usually a site of synaptic contact with another cell; also called terminal bouton or presynaptic terminal.
B-cell mitogens
Any substance that nonspecifically causes B cells to proliferate.
Basolateral domain
The nonspecialized surface of an epithelial cell that contacts an internal basal lamina or adjacent or underlying cells in the tissue. Also called basolateral surface. (Chapters 2, 9, and 12)
batch production
An industrial process in which cells are grown for a period of time after which the product is collected.
Bcl-6
A transcriptional repressor that opposes differentiation of B cells into plasma cells.
binary fission
Prokaryotic cell reproduction by division into two daughter cells.
binocular competition
A process believed to occur during the development of the visual system whereby the inputs from the two eyes actively compete to innervate the same cells.
binocular visual field
The portion of the visual fi eld viewed by both eyes. bipolar cell In the retina, a cell that connects photoreceptors to ganglion cells.
biogenesis
The theory that living cells arise only from preexisting cells.
Biomarker
Biological parameters at the cellular and multicellular level indicating biochemical changes under environmental stress.
biotechnology
The industrial application of microorganisms, cells, or cell components to make a useful product.
blastoconidium
An asexual fungal spore produced by budding from the parent cell.
BLIMP-1
A transcriptional repressor that promotes B-cell differentiation into plasma cells and suppresses proliferation, and further class switching and affinity maturation.
budding yeast
Following mitosis, a yeast cell that divides unevenly to produce a small cell (bud) from the parent cell.
Calcium channel blockers
Drugs that block voltagegated calcium channels in excitable cells.
callus
(kal′ŭs) Composite mass of cells and extracellular matrix that forms at a fracture site to establish continuity between the bone ends.
cancer stem cells
Rare cancer cells capable of dividing indefinitely.
cartilage
Form of connective tissue composed of cells (chondrocytes) embedded in a matrix rich in type II collagen and chondroitin sulfate proteoglycan.
CCL19
Chemokine made by dendritic cells and stromal cells in T-cell zones of lymph nodes that binds CCR7 and functions to attract naive T cells.
CCL20
Chemokine made by follicle-associated epithelial cells and binds CCR6, recruiting activated T and B cells, NK cells, and dendritic cells into GALT.
CCL21
Chemokine made by dendritic cells and stromal cells in T cell zones of lymph nodes that binds CCR7 and functions to attract naive T cells.
CCL25 (TECK)
Chemokine made by small-intestinal epithelial cells that binds CCR9 to recruit gut-homing T and B cells.
CCL28 (MEC, mucosal epithelial chemokine)
Chemokine made by colonic intestinal cells, salivary gland, and lactating mammary gland cells that binds CCR10 to recruit B lymphocytes producing IgA into these tissues.
CCL9 (MIP-1γ)
Chemokine made by follicle-associated epithelial cells and binds CCR6, recruiting activated T and B cells, NK cells, and dendritic cells into GALT.
CD45RO
An alternatively spliced variant of CD45 that serves as a marker for memory T cells.
CD70
The ligand for CD27 that is expressed on activated dendritic cells and delivers a potent co-stimulatory signal to T cells early in the activation process.
cell culture
Eukaryotic cells grown in culture media; also called tissue culture.
cell determination
Process whereby a cell progressively loses the potential to form other cell types, as development proceeds.
cell signaling
Biochemical processes in a cell responsible for communication and coordination of events.
central (primary) lymphoid organ
Organ in which T or B lymphocytes are produced from precursor cells. In adult mammals, these are the thymus and bone marrow, respectively.
centroblasts
Large, rapidly dividing activated B cells present in the dark zone of germinal centers in follicles of peripheral lymphoid organs.
centrocytes
Small B cells that derive from centroblasts in the germinal centers of follicles in peripheral lymphoid organs; they populate the light zone of the germinal center.
cerebellar granule cell
A neuron in the cerebellar cortex that receives input from mossy fibers and gives rise to parallel fibers that innervate Purkinje cells. Plasticity of the synapses between granule cells and Purkinje cells is believed to be important for motor learning.
Checkpoint
A mechanism that halts progression through the eukaryotic cell cycle.
chondroblast
(kon′drō-blast) A dividing cell in cartilage, which produces the cartilage matrix.
chondrocyte
(kon′drō-sı̄t) Mature, nondividing cartilage cell.
ciliary escalator
Ciliated mucosal cells of the lower respiratory tract that move inhaled particulates away from the lungs.
climbing fiber
An axon of an inferior olive neuron that innervates a Purkinje cell of the cerebellum. Climbing fiber activity is an important trigger for LTD, a form of synaptic plasticity believed to be important for motor learning.
clue cells
Sloughed-off vaginal cells covered with Gardnerella vaginalis.
coenocytic hypha
A fungal filament that is not divided into uninucleate cell-like units because it lacks septa.
color-opponent cell
A cell in the visual system with an excitatory response to wavelengths of light of one color and an inhibitory response to wavelengths of another color; the color pairs that cancel each other are red–green and blue–yellow.
columnar
(kol-ŭm′năr) Relating to epithelial cells that are taller than they are wide.
committed precursor
Cell derived from a stem cell that divides for a limited number of times before terminally differentiating; also known as a transit amplifying cell.
common lymphoid progenitor (CLP)
Stem cell that can give rise to all the types of lymphocytes with the exception of innate lymphoid cells (ILCs).
contractile ring
Ring containing actin and myosin that forms under the surface of animal cells undergoing cell division. Contracts to pinch the two daughter cells apart.
convergent extension
Rearrangement of cells within a tissue that causes it to extend in one dimension and shrink in another.
cortical plate
A cell layer of the immature cerebral cortex containing undifferentiated neurons.
cuboidal
(kū-boy′dăl) Relating to cells that are cube-shaped.
CXCL12 (SDF-1)
Chemokine produced by stromal cells in the dark zone of the germinal center that binds CXCR4 expressed by centroblasts.
CXCL13
Chemokine produced in the follicle and the light zone of the germinal center that binds CXCR5 expressed on circulating B cells and centrocytes.
cytoarchitecture
The arrangement of neuronal cell bodies in various parts of the brain.
cytoplasmic streaming
The movement of cytoplasm in a eukaryotic cell.
Damage-associated molecular patterns
Host components that are released upon cellular damage. (Chapter 3)
dark-field microscopy
Type of light microscopy in which oblique rays of light focused on the specimen do not enter the objective lens, but light that is scattered by components in the living cell can be collected to produce a bright image on a dark background.
Daughter cell
A product of cell division.
DC-SIGN
A lectin on the dendritic-cell surface that binds ICAM-3 with high affinity.
degranulation
The release of contents of secretory granules from mast cells or basophils during anaphylaxis.
delayed hypersensitivity
Cell-mediated hypersensitivity.
dendritic epidermal T cells (dETCs)
A specialized class of γ:δ T cells found in the skin of mice and some other species, but not humans. They express Vγ5:Vδ1 and may interact with ligands such as Skint-1 expressed by keratinocytes.
Determination
Process by which undifferentiated cells in an embryo become committed to develop into specific cell types, such as neuron, fibroblast, and muscle cell.
differential centrifugation
Separation of cell organelles or other particles of different size by their different rates of sedimentation in a centrifugal field.
diploid cell line
Eukaryotic cells grown in vitro.
Diploid cell strains
Cell cultures that consist of a homogeneous population of a single type and that can divide up to 100 times before dying. (Chapter 2)
direct microscopic count
Enumeration of cells by observation through a microscope.
direction selectivity
The property of cells in the visual system that respond only when stimuli move within a limited range of directions.
distributed memory
The concept that memories are encoded by widespread synaptic modifications of many neurons, not by a single synapse or cell.
DN1, DN2, DN3, DN4
Substages in the development of CD4+CD8+ double-positive T cells in the thymus. Rearrangement of the TCRβ-chain locus starts at DN2 and is completed by DN4.
donor lymphocyte infusion (DLI)
Transfer of mature lymphocytes (i.e., T cells) from donor into patients during bone marrow transplantation for cancer treatment to help eliminate residual tumor.
dorsal horn
The dorsal region of the spinal cord containing neuronal cell bodies.
E-cadherin
Integrin expressed by epithelial cells important in forming the adherens junctions between adjacent cells.
effector caspases
Intracellular proteases that are activated as a result of an apoptotic signal and mediate the cellular changes associated with apoptosis. To be distinguished from initiator caspases, which act upstream of effector caspases to initiate the caspase cascade.
Embryoid bodies
Masses of differentiated and undifferentiated cells derived from embryonic stem cells.
endomysium
(en′dō-miz′ē-ŭm, -mis′ē-ŭm) Areolar connective tissue layer surrounding a muscle cell or fiber.
endosymbiotic theory
A model for the evolution of eukaryotes which states that organelles arose from prokaryotic cells living inside a host prokaryote.
Energy charge
A measure for the energy status of a cell.
enteroadherent
Escherichia coli Referring to multiple strains of E. coli capable of attachment to, and infection and destruction of cells of the intestinal microvilli, causing colitis and diarrheagenic diseases.
ependymal
(ep-en′di-mal) Relating to the cellular lining of the brain ventricles and central canal of the spinal cord; assists in production and circulation of CSF.
ependymal cell
A type of glial cell that provides the lining of the brain’s ventricular system.
excitability
The ability of a cell to respond to a stimulus.
excitation–contraction coupling
The physiological process by which the excitation of a muscle cell leads to its contraction.
executioner caspases
Apoptotic caspases that catalyze the widespread cleavage events during apoptosis that kill the cell.
Extracellular
Outside the cells.
extracellular fluid (ECF)
Fluid located outside of cells; plasma and interstitial fluid.
extracellular pathogens
Pathogens that disturb host cells and can cause serious disease without replicating in host cells.
fate map
Representation showing which cell types will later derive from which regions of a tissue; e.g. from the blastula.
fission yeast
Following mitosis, a yeast cell that divides evenly to produce two new cells.
flow cytometry
A method of counting cells using a flow cytometer, which detects cells by the presence of a fluorescent tag on the cell surface.
fluorescence-activated cell sorter (FACS)
A modification of a flow cytometer that counts and sorts cells labeled with fluorescent antibodies.
Foci
(plural) Clusters of cells that are derived from a single progenitor and share properties, such as unregulated growth, that cause them to pile up on one another. One such cluster is called a focus. (Chapter 2)
G1-cyclin
Cyclin present in the G1 phase of the eukaryotic cell cycle. Forms complexes with Cdks that help govern the activity of the G1/S-cyclins, which control progression to S phase.
G1/S-cyclin
Cyclin that activates Cdks in late G1 of the eukaryotic cell cycle and thereby helps trigger progression through Start, resulting in a commitment to cell-cycle entry. Its level falls at the start of S phase.
gametocyte
A male or female protozoan cell.
ganglion cell layer
A layer of the retina closest to the center of the eye, containing ganglion cells.
Gastrula
An early animal embryo consisting of two layers of cells; an embryological stage following the blastula.
Germ plasm
The hereditary material transmitted to the offspring through the germ cells.
germ-line cell
A type of animal cell that is formed early in embryogenesis and may multiply by mitosis or produce by meiosis cells that develop into gametes (egg or sperm cells).
Germline mutation
Mutation arising in the cell lineage that gives rise to gametes.
gland
Organ or individual cells that secrete a substance.
granulocyte/macrophage (GM) progenitor cell
Committed progenitor cell in the bone marrow that gives rise to neutrophils and macrophages.
gray matter
Brain or spinal cord tissue composed of neuron cell bodies, dendrites, and unmyelinated axons.
group 1 ILCs (ILC1s)
The subtype of innate lymphoid cells (ILCs) characterized by IFN-γ production.
Hemoglobin S
Sickle cell hemoglobin.
heterocyst
A large cell in certain cyanobacteria; the site of nitrogen fixation.
high-energy bond
Cellular chemical bond (normally phosphate) by which energy is stored and subsequently released to drive a biochemical reaction.
HIP/PAP
An antimicrobial C-type lectin secreted by intestinal cells in humans. Also known as RegIIIα.
horizontal cell
A cell in the retina of the eye that projects neurites laterally in the outer plexiform layer.
hyperplasia
(hı̄-per-plā′zhē-ă) Increase in the number of cells in a tissue.
hypha
A long filament of cells in fungi or actinomycetes.
hypothalamic-pituitary-adrenal (HPA) axis
A system of CNS neurons and endocrine cells that regulates the release of cortisol from the adrenal gland. Dysfunction of the HPA system has been implicated in anxiety disorders and affective disorders.
idiophase
The period in the production curve of an industrial cell population in which secondary metabolites are produced; a period of stationary growth following the phase of rapid growth. See also trophophase.
ILC1
A subset of innate lymphoid cells characterized by production of IFN-γ.
imiquimod
Drug (aldara) approved for treatment of basal cell carcinoma, genital warts, and actinic keratoses known to activate TLR-7, although not approved as an adjuvant for vaccines.
Immortality
Th e capacity of cells to grow and divide indefi nitely. (Chapter 6)
induced regulatory T cell
A regulatory T cell (Treg cell) that develops from naive helper T cells when they are activated in the presence of TGFβ in the absence of IL6.
inflammatory cells
Cells such as macrophages, neutrophils, and effector TH1 lymphocytes that invade inflamed tissues and contribute to the inflammation.
inner nuclear layer
A layer of the retina of the eye containing the cell bodies of bipolar, horizontal, and amacrine cells.
inner plexiform layer
A layer of the retina of the eye, located between the ganglion cell layer and the inner nuclear layer; contains the neurites and synapses between bipolar cells, amacrine cells, and ganglion cells.
insoluble fiber
Fiber that is insoluble in water, such as cellulose, hemicellulose, lignin, and modified cellulose.
Insulinoma
An insulin-secreting tumor of pancreatic β-cells.
integrin α4:β7
Integrin binding to VCAM-1, MAdCAM-1, and fibronectin and expressed by various cells, such as IELs, that traffic to intestinal lamina propria.
Intracellular
Inside the cells.
intraepithelial lymphocytes (IELs)
Lymphocytes present in the epithelium of mucosal surfaces such as the gut. They are predominantly T cells, and in the gut are predominantly CD8 T cells.
invadopodia
Actin-rich protrusions extending in threedimensions that are important for cells to cross tissue barriers by degrading the extracellular matrix.
isolated lymphoid follicles (ILF)
A type of organized lymphoid tissue in the gut wall that is composed mainly of B cells.
karyogamy
Fusion of the nuclei of two cells; occurs in the sexual stage of a fungal life cycle.
keratinocyte
(ke-rat′i-nō-sı̄t) The most abundant cell type in the epidermis and found throughout the epidermis; cells that produce keratin.
kinin
A substance released from tissue cells that causes vasodilation.
koniocellular LGN layer
A layer of the lateral geniculate nucleus containing very small cells, lying just ventral to each magnocellular and parvocellular layer.
L form
Prokaryotic cells that lack a cell wall; can return to walled state.
lamellipodium (plural lamellipodia)
Flattened, sheetlike protrusion supported by a meshwork of actin filaments, which is extended at the leading edge of a crawling animal cell.
late pro-B cell
Stage in B-cell development in which VH to DJH joining occurs.
lophotrichous
Having two or more flagella at one end of a cell.
lymphopoiesis
The differentiation of lymphoid cells from a common lymphoid progenitor.
lysogenic conversion
The acquisition of new properties by a host cell infected by a lysogenic phage.
lytic cycle
A mechanism of phage multiplication that results in host cell lysis.
M-Cdk (M-phase Cdk)
Cyclin-Cdk complex formed in vertebrate cells by an M-cyclin and the corresponding cyclindependent kinase (Cdk).
M-cyclin
A cyclin found in all eukaryotic cells that promotes the events of mitosis.
macroautophagy
The engulfment by a cell of large quantities of its own cytoplasm, which is then delivered to the lysosomes for degradation.
magnocellular LGN layer
A layer of the lateral geniculate nucleus receiving synaptic input from M-type retinal ganglion cells.
magnocellular pathway
A visual informationprocessing pathway that begins with M-type retinal ganglion cells and leads to layer IVB of striate cortex; believed to process information about object motion and motor actions.
Marr–Albus theory of motor learning
The theory that parallel fiber synapses on Purkinje cells are modified when their activity coincides with climbing fiber activity.
master transcription regulator
A transcription regulator specifically required for formation of a particular cell type. Artificial expression of master transcription regulators (alone or in combination with others) will often convert one cell type into another.
mastocytosis
The overproduction of mast cells.
megakaryocyte
Large myeloid cell with a multilobed nucleus that remains in the bone marrow when mature. Buds off platelets from long cytoplasmic processes.
Megaspore
The single large cell produced at the end of meiosis in the female reproductive tissues of plants.
metabolic control
The mechanisms by which the flux through a metabolic pathway is changed to reflect a cell’s altered circumstances.
metabolic regulation
The mechanisms by which a cell resists changes in the concentration of individual metabolites that would otherwise occur when metabolic control mechanisms alter the flux through a pathway.
metabolic pathway
A sequence of enzymatically catalyzed reactions occurring in a cell.
metaphase-to-anaphase transition
Transition in the eukaryotic cell cycle preceding sister-chromatid separation at anaphase. If the cell is not ready to proceed to anaphase, the cell cycle is halted at this point.
Metformin
An antidiabetic drug that reduces cellular energy charge.
microionophoresis
A method of applying drugs and neurotransmitters in very small quantities to cells.
Monolayer
A layer of cultured cells growing in a cell culture dish. (Chapter 2)
morphogenesis
Developmental process in which cells undergo movements and deformations in order to assemble into tissues and organs with specific shapes and sizes.
mossy fiber
An axon of a pontine neuron that innervates cerebellar granule cells. This term is also used to describe the axons from dentate gyrus granule cells that innervate area CA3 of the hippocampus.
Mother cell
A cell that is prepared to divide mitotically or meiotically.
motor neuron
A neuron that synapses on a muscle cell and causes muscle contraction.
mucosal mast cells
Specialized mast cells present in mucosa. They produce little histamine but large amounts of prostaglandins and leukotrienes.
multipotent progenitor cells (MPPs)
Bone marrow cells that can give rise to both lymphoid and myeloid cells but are no longer self-renewing stem cells.
multipotent stem cells
Adult stem cell that can differentiate into a few specific cell types.
myeloid-derived suppressor cells (MDSCs)
Cells in tumors that can inhibit T-cell activation within the tumor.
myocyte
A muscle cell.
natural regulatory T cell
A regulatory T cell (Treg cell) that develops in the thymus and helps maintain self-tolerance.
neoplasm
(nē′ō-plazm) An abnormal tissue that grows by cell proliferation more rapidly than normal.
neural precursor cell
An immature neuron before cell differentiation.
neuromuscular
(nūr-ō-mus′kular) Relationship between a neuron and a muscle cell (or muscle fiber).
nonM–nonP ganglion cell
A ganglion cell in the retina that is not of the M type or P type, based on cell morphology and response properties. Of the variety of cell types in this category, some are known to be sensitive to the wavelength of light.
nude
A mutation in mice that results in hairlessness and defective formation of the thymic stroma, so that mice homozygous for this mutation have no mature T cells.
OFF bipolar cell
A bipolar cell of the retina that depolarizes in response to dark (light OFF) in the center of its receptive field.
ON bipolar cell
A bipolar cell of the retina that depolarizes in response to light (light ON) in the center of its receptive field.
One-step growth curve
A single reproduction cycle that occurs synchronously in every infected cell. (Chapter 2)
oocyst
An encysted apicomplexan zygote in which cell division occurs to form the next infectious stage.
optic nerve
The bundle of ganglion cell axons that passes from the eye to the optic chiasm.
optic tract
A collection of retinal ganglion cell axons stretching from the optic chiasm to the brain stem. Important targets of the optic tract are the lateral geniculate nucleus and superior colliculus.
orientation selectivity
The property of a cell in the visual system that responds to a limited range of stimulus orientations.
osteoprogenitor
(os′tē-ō-prō- jen′i-ter) Precursor to bone cells.
outer nuclear layer
A layer of the retina of the eye containing the cell bodies of photoreceptors.
outer plexiform layer
A layer of the retina of the eye between the inner nuclear layer and the outer nuclear layer; contains the neurites and synapses between photoreceptors, horizontal cells, and bipolar cells.
ovum
(ō′vŭm; pl., ova, -vă) Female sex cell that has been fertilized and has completed meiosis II.
paracortical areas
The T-cell area of lymph nodes.
parallel fiber
An axon of a cerebellar granule cell that innervates Purkinje cells. Plasticity of the synapse between a parallel fiber and a Purkinje cell is believed to be important for motor learning.
parvo-interblob pathway
A visual information processing pathway that begins with P-type retinal ganglion cells and leads to the interblob regions of striate cortical layer III; believed to process information about fi ne object shape.
parvocellular LGN layer
A layer of the lateral geniculate nucleus receiving synaptic input from P-type retinal ganglion cells.
passengers
Mutations that have occurred in the same cell as driver mutations, but which are irrelevant to the development of the cancer.
peak development period
Embryologic time frame during which cellular organization and construction of an organ framework occurs.
periarteriolar lymphoid sheath (PALS)
Part of the inner region of the white pulp of the spleen; it contains mainly T cells.
peritrichous
Having flagella distributed over the entire cell.
Permissivity
A cellular environment that provides all cellular components required for viral reproduction. (Chapter 2)
phosphorylation potential (DGp)
The actual free-energy change of ATP hydrolysis under the nonstandard conditions prevailing in a cell.
Physiological pH
The pH of 7.3 that exists inside cells.
PI-3-kinase–Akt pathway
Intracellular signaling pathway that stimulates animal cells to survive and grow.
pilin
An adhesin of Neisseria gonorrhoeae allowing attachment to and infection of epithelial cells of urinary and reproductive tracts.
planar cell polarity
Type of cellular asymmetry seen in some epithelia, such that each cell has a polarity vector oriented in the plane of the epithelium.
Plantae
The kingdom composed of multicellular eukaryotes with cellulose cell walls.
plasmablasts
A B cell in a lymph node that already shows some features of a plasma cell.
plasmogamy
Fusion of the cytoplasm of two cells; occurs in the sexual stage of a fungal life cycle.
plasmolysis
Loss of water from a cell in a hypertonic environment.
pleuripotent cells
Embryonic stem cells that can differentiate into any cell type (except cells of the placenta).
polar flagella
Having flagella at one or both ends of a cell.
Polarized cell
Differentiated cells with surfaces divided into functionally specialized regions. (Chapter 12)
positive (direct) selection
A procedure for picking out mutant cells by growing them.
Primary cell
Cells that have been freshly derived from an organ or tissue. (Chapter 1)
Primary cell culture
Cell cultures prepared from animal tissues; these cultures include several cell types and have a limited life span, usually no more than 5 to 20 cell divisions. (Chapter 2)
primary cell wall
The first cell wall produced by a developing plant cell; it is thin and flexible, allowing room for cell growth.
primary metabolite
A product of an industrial cell population produced during the time of rapid logarithmic growth. See also secondary metabolite.
programmed cell death
A form of cell death in which a cell kills itself by activating an intracellular death program.
prostheca
A stalk or bud protruding from a prokaryotic cell.
pseudohypha
A short chain of fungal cells that results from the lack of separation of daughter cells after budding.
pseudopod
An extension of a eukaryotic cell that aids in locomotion and feeding.
psoriasis
Chronic autoimmune disease thought to be driven by T cells manifested in skin, but which can also involve nails and joints (psoriatic arthropathy).
purified cell-free system
Fractionated cell homogenate that retains a particular biological function of the intact cell, and in which biochemical reactions and cell processes can be more easily studied.
Purkinje cell
A cell in the cerebellar cortex that projects an axon to the deep cerebellar nuclei.
radial glial cell
A glial cell in the embryonic brain extending a process from the ventricular zone to the surface of the brain; immature neurons and glia migrate along this process.
refractory period
Time period when a cell is either unresponsive or less responsive to a stimulus.
regulatory tolerance
Tolerance due to the actions of regulatory T cells.
replicative cell senescence
Phenomenon observed in primary cell cultures in which cell proliferation slows down and finally irreversibly halts.
restriction point
Important transition at the end of G1 in the eukaryotic cell cycle; commits the cell to enter S phase. The term was originally used for this transition in the mammalian cell cycle; in this book we use the term Start.
reticular lamina
A thin sheet of tissue in the inner ear that holds the tops of hair cells in the organ of Corti.
retina
A thin layer of cells at the back of the eye that transduces light energy into neural activity.
S-Cdk
Cyclin–Cdk complex formed in vertebrate cells by an S-cyclin and the corresponding cyclin-dependent kinase (Cdk).
sarcoplasm
(sar′kō-plazm) Cytoplasm of a muscle cell.
secondary cell wall
Permanent rigid cell wall that is laid down underneath the thin primary cell wall in certain plant cells that have completed their growth.
secondary metabolism
Pathways that lead to specialized products not found in every living cell.
sensory bristles
Miniature sense organs present on most exposed surfaces of Drosophila, consisting of a sensory neuron and supporting cells and responding to chemical or mechanical stimuli.
septate hypha
A hypha consisting of uninucleate cell-like units.
Sexual reproduction
Reproduction involving the formation of mature germ cells (that is, eggs and sperm).
slime layer
A glycocalyx that is unorganized and loosely attached to the cell wall.
Sodium cotransport
A symport system that brings a substrate into the cell together with a sodium ion.
Spermatids
The four cells formed by the meiotic divisions in spermatogenesis. Spermatids become mature spermatozoa or sperm.
Spermatocyte (sperm mother cell)
The cell that undergoes two meiotic divisions (spermatogenesis) to form four spermatids; the primary spermatocyte before completion of the first meiotic division; the secondary spermatocyte after completion of the first meiotic division.
Spermatogonium (pl, spermatogonia)
Primordial male germ cell that may divide by mitosis to produce more spermatogonia. A spermatogonium may enter a growth phase and give rise to a primary spermatocyte.
Spot desmosome
A spotlike cell-cell adhesion that is linked to intermediate filaments.
squamous
(skwā′mŭs) Referring to cell or area that is flat.
standard cell potential (standard emf) (E°cell)
The cell potential for a system in standard states (solute concentration of 1 M and gaseous reactant partial pressure of 1 atm).
Start (restriction point)
Important transition at the end of G1 in the eukaryotic cell cycle. Passage through Start commits the cell to enter S phase. The term was originally used for this point in the yeast cell cycle only; the equivalent point in the book we use Start for both.
stem-cell niche
The specialized microenvironment in a tissue in which self-renewing stem cells can be maintained.
stereocilium
A hairlike cilium attached to the top of a hair cell in the inner ear.
Stomata
Pores in the leaf or stem epidermis cell layers which allow the uptake of CO2 from the atmosphere. Two guard cells around the pore regulate the opening.
streptobacilli (singular: streptobacillus)
Rods that remain attached in chains after cell division.
stromal cells
The nonlymphoid cells in central and peripheral lymphoid organs that provide soluble and cell-bound signals required for lymphocyte development, survival, and migration.
summation
(sŭm-ā′shŭn) Accumulation of stimuli occurring in neurons or muscle cells; e.g., wave summation.
superficial mycosis
A fungal infection localized in surface epidermal cells and along hair shafts.
synapse elimination
Process by which each muscle cell at first receives synapses from several motor neurons, but is ultimately left innervated by only one.
synaptic scaling
A cell-wide adjustment of synaptic strengths in response to a change in the average firing rate of the postsynaptic neuron.
synaptic transmission
The process of transferring information from one cell to another at a synapse.
T regulatory (Treg) cells
Lymphocytes that appear to suppress other T cells.
T-cell plasticity
Flexibility in the developmental programming of CD4 T cells such that effector T-cell subsets are not irreversibly fixed in their function or the transcriptional networks that underpin those functions.
terminal bouton
The end region of an axon, usually a site of synaptic contact with another cell; also called axon terminal.
thick filament
A part of the cytoskeleton of a muscle cell containing myosin, lying between and among thin fi laments and sliding along them to cause muscle contraction.
thin filament
A part of the cytoskeleton of a muscle cell containing actin, anchored to Z lines and sliding along thick filaments to cause muscle contraction.
thymic stroma
The epithelial cells and connective tissue of the thymus that form the essential microenvironment for T-cell development.
thymus
A central lymphoid organ, in which T cells develop, situated in the upper part of the middle of the chest, just behind the breastbone.
trans-acting
A term describing substances that are diffusable and that can affect spatially separated entities within cells.
transit amplifying cell
Cell derived from a stem cell that divides a limited number of times before terminally differentiating.
transitional stages
Defined stages in the development of immature B cells into mature B cells in the spleen, after which the B cell expresses B-cell coreceptor component CD21.
trophoblast
(trof′ō-blast, trō′fō- blast) Cell layer covering the blastocyst that will allow the embryo to receive nourishment from the mother.
trophophase
The period in the production curve of an industrial cell population in which the primary metabolites are formed; a period of rapid, logarithmic growth. See also idiophase.
turgor pressure
Large hydrostatic pressure developed inside a plant cell as the result of the intake of water by osmosis; it is the force driving cell expansion in plant growth and it maintains the rigidity of plant stems and leaves.
type 1 diabetes mellitus
Disease in which the β cells of the pancreatic islets of Langerhans are destroyed so that no insulin is produced. The disease is believed to result from an autoimmune attack on the β cells. It is also known as insulin-dependent diabetes mellitus (IDDM), because the symptoms can be ameliorated by injections of insulin.
unipotent stem cells
Adult stem cells that can differentiate into only one specific cell type.
ventral horn
The ventral region of the spinal cord containing neuronal cell bodies.
vesicular compartments
One of several major compartments within cells, composed of the endoplasmic reticulum, Golgi, endosomes, and lysosomes.
viral entry inhibitors
Drugs that inhibit the entry of HIV into its host cells.
Virulent phage
A phage (virus) that destroys the host (bacterial) cell (cf. Temperate phage).
volutin
Stored inorganic phosphate in a prokaryotic cell. See also metachromatic granule.
Weibel–Palade bodies
Granules within endothelial cells that contain P-selectin.
Zonula adherens
“Belt desmosome” that holds the cells of single-layered epithelia together.
amacrine cell
A neuron in the retina of the eye that projects neurites laterally in the inner plexiform layer.
CD8 T cells
T lymphocytes that carry the coreceptor CD8 on their surfaces.
cell body
The central region of the neuron containing the nucleus; also called soma or perikaryon.
complex cell
A type of visual cortical neuron that has an orientation-selective receptive fi eld without distinct ON and OFF subregions.
Foam cell
A macrophage filled with droplets of cholesterol esters.
grid cell
Neurons in the entorhinal cortex that have multiple place fi elds arranged in a hexagonal grid.
place cell
A neuron in the rat hippocampus that responds only when the animal is in a certain region of space.
Sickle cell trait
Heterozygosity for hemoglobin S.
simple cell
A neuron found in primary visual cortex that has an elongated orientation-selective receptive field with distinct ON and OFF subregions.
stellate cell
A neuron characterized by a radial, star-like distribution of dendrites.
unit cell
The smallest divisible unit of a crystal that, when repeated in three dimensions, reproduces the entire crystal lattice.
