2006 Paper A Flashcards
There is considerable variation in the age at which teeth erupt. Which of the following are usually the first teeth to erupt?
A. Lower central incisors.
B. Lower first molars.
C. Lower lateral incisors.
D. Upper central incisors.
E. Upper lateral incisors.
A. Lower central incisors.
The epithelial sodium channel located in the collecting duct is regulated by which of the following?
A. Adrenocorticotrophic hormone (ACTH).
B. Aldosterone.
C. Amiloride.
D. Cyclic AMP .
E. Renin.
B. Aldosterone
Aldosterone is a hormone that increases the reabsorption of sodium ions and water and the release (secretion) of potassium ions in the collecting ducts and distal convoluted tubule of the kidneys’ functional unit, the nephron.
Amiloride works by directly blocking the epithelial sodium channel (ENaC) thereby inhibiting sodium reabsorption in the late distal convoluted tubules, connecting tubules, and collecting ducts in the kidneys.
Telomeres are best defined as:
A. cis-acting DNA elements responsible for segregation of chromosomes at mitosis and meiosis.
B. proteins which bind to promotor elements to initiate transcription of a gene.
C. specialised structures which “cap” the ends of chromosomes.
D. the major non-DNA component of chromatin.
E. the sites at which crossovers occur during pachytene.
C. specialised structures which “cap” the ends of chromosomes.
A telomere is a region of repetitive DNA sequences at the end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. The telomere regions deter the degradation of genes near the ends of chromosomes by allowing for the shortening of chromosome ends, which necessarily occurs during chromosome replication.[1] Over time, due to each cell division, the telomere ends do become shorter. During cell division, enzymes that duplicate DNA cannot continue their duplication all the way to the end of chromosomes. If cells divided without telomeres, they would lose the ends of their chromosomes, and the necessary information they contain. The telomeres are disposable buffers blocking the ends of the chromosomes, are consumed during cell division, and are replenished by an enzyme, telomerase reverse transcriptase.
The embryonic gonad is bipotential. Which of the following hormones determine early differentiation towards the male phenotype?
A. Activin.
B. Antimüllerian hormone.
C. Dihydrotestosterone.
D. Human chorionic gonadotropin.
E. Inhibin.
B. Antimüllerian hormone.
Pyloric stenosis is a disorder with polygenic inheritance. The male to female ratio is about 4:1. Who of the following is most likely to develop pyloric stenosis?
A. The brother of an affected boy.
B. The daughter of an affected woman.
C. The daughter of an affected man.
D. The son of an affected man.
E. The son of an affected woman.
E. The son of an affected woman.
Which of the following blood group combinations is most frequently associated with isoimmune haemolytic disease of the newborn?
B. Mother A neg, Infant O pos
- when also incompatible with group A or B, mother partially protected against sensitization by rapid removal of Rh-positive cells from circulation by preexisting anti-A or anti-B (IgM Ab)
- therefore answers D and E protective
- if ABO only: usually mother is type O and infant type A or B
- ABO occurs in 20-25% pregnancies, haemolytic disease develps in only 10% of such offspring and infants generally type A1 (more antigenic than A2)
The major objective of a phase III clinical trial is to determine which one of the following?
A. Cost effectiveness.
B. Efficacy of an experimental therapy.
C. Efficacy of a standard therapy.
D. Maximum tolerated dose.
E. Toxicity profile.
B. Efficacy of an experimental therapy.
Renin release from juxtaglomerular cells is stimulated by:
A beta sympathetic blockade.
B cortisol.
C increased plasma chloride.
D increased vagal activity.
E sodium depletion.
E sodium depletion.
The peptide hormone is secreted by the kidney from specialized cells called granular cells of the juxtaglomerular apparatus via 3 responses:
- A decrease in arterial blood pressure (that could be related to a decrease in blood volume) as detected by baroreceptors (pressure-sensitive cells). This is the most causal link between blood pressure and renin secretion (the other two methods operate via longer pathways).
- A decrease in sodium chloride levels in the ultra-filtrate of the nephron. This flow is measured by the macula densa of the juxtaglomerular apparatus.
- Sympathetic nervous system activity, which also controls blood pressure, acting through the beta1 adrenergic receptors.
An otherwise normal five-year-old child is brought to see you because of recurrent generalised convulsions. The child had his first febrile convulsion at 12 months of age, and subsequently has had six afebrile seizures. He is on anticonvulsant therapy. There is no family history of febrile convulsions or epilepsy. His mother asks about risk for sudden, unexplained [unexpected] death due to epilepsy (SUDEP). Which of the following is the greatest risk factor for SUDEP?
A. Idiopathicepilepsy.
B. Male sex.
C. Neurological deficit.
D. Symptomatic epilepsy.
E. Young age.
C. Neurological deficit.
Risk factors for SUDEP include early age of epilepsy onset, frequent generalized tonic-clonic seizures, and intractable epilepsy. Case-control and cohort studies of SUDEP have identified certain clinical and demographic features as potential risk factors, although these are not all consistently found in all studies:
- Seizure frequency (>1/month)
- Medication noncompliance, subtherapeutic AED level
- Age 20 to 45 years
- Generalized tonic-clonic seizures
- Polytherapy
- Duration of epilepsy (>10 years)
- Alcoholism
- Male gender
- Nocturnal seizures
According to Dr Silberstein - Symptomatic Epilepsy
Which of the following best describes the mode of action of aminoglycoside antibiotics?
A. Disruption of cytoplasmic membrane function.
B. Inhibition of bacterial DNA gyrase.
C. Inhibition of cell wall synthesis.
D. Inhibition of protein synthesis.
E. Interference with bacterial folic acid metabolism.
D. Inhibition of protein synthesis.
Aminoglycosides have concentration-dependent bactericidal activity. They bind to the 30S ribosome, thereby inhibiting bacterial protein synthesis.
Pulse oximetry is widely utilised in clinical practice to measure the oxygen saturation of haemoglobin. In which of the following situations is the measured saturation likely to be falsely elevated?
A. Carbon dioxide retention.
B. Methaemoglobinaemia.
C. Persistent fetal haemoglobin.
D. Profoundanaemia.
E. Sickle cell anaemia.
B. Methaemoglobinaemia.
When hemoglobin loses an electron and becomes oxidized, it is converted to the ferric state (Fe3+) or methemoglobin. Methemoglobin lacks the electron that is needed to form a bond with oxygen and, thus, is incapable of oxygen transport.
Methemoglobin absorbs light at wavelengths that also absorb deoxyhemoglobin and oxyhemoglobin. Thus, methemoglobin interferes with the colorimetric testing that is used to obtain the percentage of oxyhemoglobin to deoxyhemoglobin.
Traditional pulse oximetry is inaccurate and unreliable in patients with high methemoglobin fractions. Traditional pulse oximetry of patients with low-level methemoglobinemia often reveals falsely low values for oxygen saturation, and it often reveals falsely high values in those with high-level methemoglobinemia.
Which of the following anticonvulsants is most likely to decrease the half-life of lamotrigine in a clinically significant manner?
A. Carbamazepine.
B. Clonazepam.
C. Gabapentin.
D. Sodium valproate.
E. Vigabatrin.
A. Carbamazepine.
Carbamazepine: Lamotrigine may enhance the adverse/toxic effect of Carbamazepine. Carbamazepine may increase the metabolism of Lamotrigine. Carbamazepine administration can decrease serum lamotrigine concentrations by approximately 40%.5 Such is likely due to carbamazepine induction of CYP isoenzymes responsible for lamotrigine metabolism.
Sodium Valproate: May enhance the adverse/toxic effect of Lamotrigine and may increase the serum concentration of Lamotrigine.
Infants and children with a large patent ductus arteriosus will develop significant cardiomegaly. The mechanism of this is:
A. pressure loading of left ventricle.
B. pressure loading of right ventricle.
C. volume loading of left ventricle.
D. volume loading of left and right ventricle.
E. volume loading of right ventricle.
C. volume loading of left ventricle.
PDA allows blood passage from aorta to pulmonary artery, which returns to left heart via lungs.
Many challenging behaviours of children are best understood in terms of the developmental phase the child is negotiating. Which of Erikson’s developmental stages best explains toddler tantrums?
A. Autonomy.
B. Identity.
C. Industry.
D. Initiative.
E. Trust.
A. Autonomy.
A study is comparing the bioavailability of a new oral preparation of a drug (100 mg tablet) with the marketed intravenous preparation (50 mg in 2 mLs). In this crossover study, healthy volunteers were given in random order one 100 mg tablet or 50 mg intravenously (IV). The drug has linear kinetics within the range of concentrations studied. The mean results are as follows:
Which of the following is the best estimate of the oral bioavailability of the tablet?
A. 12.5%.
B. 40%.
C. 50%.
D. 90%.
E. 96%.
D. 90%.
100x (45x50)/(25x100) = 90%
A four-month-old girl presents to the emergency department with a two day history of coryza and low grade fever. Her parents are concerned as they have noticed increasingly noisy breathing today and the baby is not feeding as well as usual. On examination the baby is miserable with a clear nasal discharge, intercostal recession, nasal flaring and grunting respirations.
Which of the following best describes the physiological basis for the audible grunt in this patient?
A. Decreasing residual volume.
B. Generation of negative end-expiratory pressure.
C. Generation of positive end-expiratory pressure.
D. Increasing tidal volume.
E. Respiratory muscle fatigue.
C. Generation of positive end-expiratory pressure.
Metformin is the drug of choice in the treatment of Type 2 (non-insulin-dependent) diabetes mellitus in childhood and adolescence. Which of the following is its most frequent side-effect?
A. Gastrointestinal disturbance.
B. Hypoglycaemia.
C. Rash.
D. Taste disturbance.
E. Weight gain.
A. Gastrointestinal disturbance.
A 20-month-old boy presents with an acute febrile illness. As part of his work-up he has a full blood examination.
Results are as follows: (image below)
Blood film demonstrates hypochromia and microcytosis of the red blood cells, with an immature neutrophilia and some toxic granulations. Some atypical lymphocytes were also seen.
Dietary history is notable for cow milk intake of over 1000mL/day, with little meat, chicken or fish. His parents are Indian. He was born in Australia.
The next day he has some further investigations. His serum ferritin level is 11μg/L [8-160], and his Hb electrophoresis shows a HbA2 of 3.3% [1.8 - 3.5].
Which of the following is the most likely explanation for his anaemia?
A. Alpha thalassaemia minor.
B. Beta thalassaemia major.
C. Beta thalassaemia minor.
D. Iron deficiency anaemia.
E. Iron deficiency anaemia and beta thalassaemia minor.
E. Iron deficiency anaemia and beta thalassaemia minor.
- Microcytic anaemia, inflam changes, low MCH and MCV
- Iron deficient hx
- Low ferritin
- Raised HbA2
- HbA2 rarely alters – increased level (>3.4%, normal level 2-3.4%) found in most pts with β-thal trait and in megaloblastic anaemias secondary to vit B12 and folic acid deficiency, decreased levels in iron-def anaemia and α-thal
- Level of serum ferritin (iron-storage protein) provides estimate of body iron stores in absence of inflammatory disease
- decreased levels accompany iron deficiency
- Beta-thal – mild microcytic anaemia characterised by elevated levels of HbA2 and/or fetal Hb concentration, serum iron, total transferrin and ferritin normal, no abn Hb seen on electrophoresis
An eight-year-old boy presents to the emergency department with a three day history of double vision.
Examination reveals that the two images are most separated when looking to the right. When looking to the right with the left eye covered, the more medial image disappears.
The nerve involved is the:
A. left abducens.
B. left oculomotor.
C. left trochlear.
D. right abducens.
E. right oculomotor.
D. right abducens.
Binocular diplopia is present with both eyes open and absent when either eye is closed. Binocular diplopia reflects conditions in which the visual axes are misaligned. In general, most patients will close the eye with the dysfunctional muscle unless that is the eye with the much better vision.
The orbital muscles are innervated by cranial nerve III except for the superior oblique (cranial nerve IV) and the lateral rectus (cranial nerve VI) muscles. Any condition that results in palsy of the third, fourth, or sixth cranial nerves can cause binocular diplopia.
When the eyes fix on an image, impairment in the movement of one eye results in projection of the image upon the macular area in the normal eye and to one side of the macula in the paretic eye and thus 2 images are perceived. The image seen by the paretic eye (false image) is ALWAYS outermost. For this boy, diplopia is maximal on looking to the right, and the medial (true) image disappears when covering the left eye. This leaves only the false image. Thus, the abnormality is on abduction of the right eye, initiated by the lateral rectus muscle and innervated by the Right abducens (6th) nerve.
A: Left abducens - Lateral rectus. Patients complain of horizontal diplopia. There is esotropia (inward deviation) of the left eye, worse with gaze into the field of the weak lateral rectus muscle (i.e. to the left). Patients assume a compensatory face turn in the direction of the paralysed muscle. Abduction is commonly limited on the side of the lesion. The patient would complain of diplopia on left lateral gaze, and the medial (true) image would disappear on covering the right eye.
B: Left Occulomotor - may cause both horizontal and vertical diplopia. If complete palsy, patients have ptosis and large unreactive pupil, paralysis of adduction, elevation and depression. The eye rests in the position of abduction, depression and intorsion (medial rotation of upper pole). The left eye deviates laterally in the resting position due to unopposed action of the intact left lateral rectus muscle.
C: Left Trochlear - Superior Oblique. Common cause of vertical diplopia, most palsies being traumatic or idiopathic. The eyes appear conjugate in the primary position, but testing eye movements reveals defective depression of the left eye when adducted (i.e. patient looks to right and down, left eye is adducted but does not look down. More often patients complain of diplopia on looking downwards (when descending stairs or reading) and the head may tilt to the side opposite the weak superior oblique (i.e. to the right) to minimise the diplopia.
D: Right abducens - controls lateral rectus muscle of right eye, thus preventing abduction of this eye. When looking toward the field of the weak muscle (i.e. the right), diplopia is greatest. The eyes appear conjugate in the primary position. Diplopia is horizontal (true and fake image side by side) and is present only when looking to the paralysed side and maximal at the extreme of binocular lateral vision.
The electrocardiogram (ECG) of a child with a history of frequent recurrent supraventricular tachycardia is shown above. Which of the following drugs should be avoided because of the increased risk of ventricular tachyarrhythmias secondary to enhanced conduction through the bypass tract?
A. Amiodarone.
B. Digoxin.
C. Flecainide.
D. Propranolol.
E. Sotolol.
B. Digoxin.
ECG shows WPW. Digoxin is contraindicated as it can accelerate conduction across the accessory pathway, shortens refractory period of accessory pathway and can lead to VT. Treatment is with beta blockers, propranolol is first line.
Which of the following is the most frequent side-effect of selective serotonin reuptake inhibitor (SSRI) anti-depressants in children?
A. Behavioural activation.
B. Insomnia.
C. Nausea.
D. Suicidal ideation.
E. Tremor.
C. Nausea.
Gastrointestinal symptoms, mostly pain, diarrhea, and nausea, may be problematic, but are often manageable by dose reduction or by assuring that the child takes the medication after eating. Sexual side effects, such as decreased libido or anorgasmia, which are often major deterrents to treatment in adults, are rarely problematic with teens. Although the SSRIs result in weight gain or loss only occasionally, it is a good idea to monitor weight during the first few months of treatment.
However, on October 15, 2004, the FDA issued a public health advisory that directed manufacturers of all antidepressant drugs, including the SSRIs, to revise the labeling for their products to include a boxed warning and expanded warning statements that alert health care providers to an increased risk of suicidality (suicidal thinking and behavior) in children and adolescents being treated with these agents.
The key event which directly initiates myocardial fibre contraction is:
A. active uptake of calcium into sarcoplasmic reticulum.
B. rapid entry of sodium through fast ion specific channels.
C. release of stored calcium from sarcoplasmic reticulum.
D. slow inward calcium current.
E. slow inward sodium current.
C. release of stored calcium from sarcoplasmic reticulum.
Genomic imprinting is best defined as:
A. a process by which there is selective expression of either the paternally or maternally inherited allele of a gene.
B. inheritance of both copies of a chromosome from one parent.
C. massive amplification of a triplet repeat sequence within a gene.
D. skewing of X-inactivation.
E. the combined effect on a chromosomal locus of methylation of DNA and acetylation of associated histones.
A. a process by which there is selective expression of either the paternally or maternally inherited allele of a gene.
What is the major determinant of vocabulary size at age three years?
A. Amount of language stimulation.
B. Child’s birth weight.
C. Child’s sex.
D. Maternal education level.
E. Maternal IQ.
A. Amount of language stimulation.
Which of the following is most strongly associated with substance abuse in adolescence?
A. Adolescent anxiety disorder.
B. Conduct disorder in childhood.
C. Infantile separation anxiety disorder.
D. Learning disorder in childhood.
E. Maternal smoking.
B. Conduct disorder in childhood.
Which of the following drugs is most likely to increase the serum levels of cyclosporin to toxic levels?
A. Cotrimoxazole.
B. Erythromycin.
C. Flucloxacillin.
D. Ibuprofen.
E. Rifampicin.
B. Erythromycin.
A previously well two-year-old boy presents to his general practitioner with tonsillitis and a macular red rash over his body. He is treated with oral Penicillin V. After two days he is admitted with a sudden onset of fever (38.5°C), irritability and painful skin. On examination he is miserable; screams when touched; has erythema of the face, axillae, neck, buttocks and groin; and peeling skin at the tip of his penis. Rubbing the skin leads to wrinkling and erosions of the epidermis. He has crusting around the mouth and nose and mild conjunctivitis. On day two of admission he develops large flaccid bullae on areas of red skin as shown in the photographs below. Investigations on admission include:
- Haemoglobin 136 g/L [100-140]
- Platelets 434 x 109/L [150-400]
- White Cell Count 15.9 x 109/L [6.0-13.0]
- Neutrophils 10.8 x 109/L [2.0-6.0]
- Serum creatinine 30 μmol/L [27-62]
- C-Reactive Protein < 3mg/L [<8]
- Gram stain of skin: No organisms seen.
A skin biopsy from this patient would be expected to show a cleavage plane in the:
A. granular layer with a perivascular lymphocytic and neutrophilic infiltrate.
B. granular layer with no inflammatory cell infiltrate.
C. subepidermal layer with eosinophilic infiltration of the dermis.
D. subepidermal layer with full-thickness epidermal necrosis.
E. subepidermal layer with intense perivascular and interstitial mononuclear cell infiltrate.
B. granular layer with no inflammatory cell infiltrate.
Staphylococcal Scalded Skin syndrome. This also usually affects younger children. The disease starts with local peri-oral erythema that spreads over the whole body and progresses to widespread, flaccid bullae that rupture causing exfoliation of the skin that resembles an extensive third-degree burn. There are no organisms that can be cultured from the fluid of the bullae, indicating that the bullae are caused by the toxin and not the bacteria themselves.
Before the bullae form, slight pressure on the apparently normal epidermis may separate it at the basal layer. It may be rubbed off when pressed with a sliding motion. This is Nikolsky’s sign.
BIOPSY - cleavage at or below stratum granulosum, no inflammatory cells in bullae or dermis
S&S - prodromal fever, tender skin evolve to generalised erythema with flexural accentuation and then flaccid bullae formation; Nikolsky’s sign (lateral pressure on unblistered skin in a bullous eruption with resultant shearing off of the epithelium) present, desquamation follows starting in flexural areas; in contrast to toxic epidermal necrolysis, does not affect oral mucosa and may be a helpful clue to diagnosis.
Eczema is associated with a Th2 cytokine profile as evidenced by increased production of which one of the following?
A. Interferon alpha (IFN alpha).
B. Interleukin-2.
C. Interleukin-4.
D. Tumour necrosis factor alpha (TNF alpha).
E. Transforming growth factor beta (TGF beta).
C. Interleukin-4.
Atopic eczema – T cells express skin homing receptor cutaneous lymphocyte-associated antigen (CLA) produce increased levels of TH2 cytokines incl IL-4 and IL-13 → induce isotype switching to IgE synthesis.