Performance of academically at-risk medical students in a problem-based learning programme: a preliminary report.

INTRODUCTION: Racially segregated schooling, a legacy of Apartheid policies, continues to hamper education in South Africa. Students entering university from suboptimal circumstances are at significant risk of demonstrating poor academic performance and dropping out of their programmes. Attempts to address the educational needs of these students have included the introduction of extended medical programmes at several universities. Such a programme, the Academic Development Programme (ADP), was implemented at the University of Cape Town in 1991. Over the past decade the programme has graduated more than 100 students. Upon implementation of a new problem-based learning (PBL) programme in 2002, the ADP was discontinued and all students were entered directly into the new PBL programme. Students who demonstrate a need for additional academic support by the end of the first semester enter the Intervention Programme for 1 year before proceeding to the second semester of the PBL programme. An interim analysis was performed to compare the retention rates and academic performance of academically at-risk students in the new PBL programme and the ADP. METHODS: The records of all academically at-risk students entering the ADP (1991-2000) and the new PBL programme (2002) were reviewed. Retention rates for all years of study, and academic performance in the fourth year clerkship courses of the respective programmes were compared. RESULTS: A total of 239 academically at-risk students in the ADP and 43 at-risk students in the new PBL programme were studied. The median retention rates, per year of study, for at-risk students in the PBL programme was significantly better than for at-risk students in the ADP (p<0.02). Academic performance of the at-risk students in all the fourth year clinical clerkship courses of the PBL programme was significantly better than the mean performance over 10 years for at-risk students in the same fourth year courses in the ADP. CONCLUSION: The introduction of PBL at the University of Cape Town has not had a deleterious effect on the performance of academically at-risk medical students. Interim analysis suggests that retention rates and academic performance in the PBL programme are better than those achieved in the extended traditional programme.

Formative assessment promotes learning in undergraduate clinical clerkships.

INTRODUCTION: Clinical clerkships, typically situated in environments lacking educational structure, form the backbone of undergraduate medical training. The imperative to develop strategies that enhance learning in this context is apparent. This study explored the impact of longitudinal bedside formative assessment on student learning in a medical clerkship. METHODS: We studied a class of 4th-year students completing a 14-week medical clerkship at the University of Cape Town in South Africa. Clinician educators assessed student performance during weekly bedside teaching sessions using blinded patient encounters (in which students had no prior knowledge of the patient's diagnosis or access to the clinical records). Student feedback was standardised using performance rating scales. The impact of formative assessment on student learning was determined from questionnaire responses. RESULTS: A total of 575 formative assessments took place during the study period. Students perceived blinded patient encounters to be a valuable learning activity that improved their clinical reasoning skills and assessed progress fairly. They reported that feedback helped inform them of their level of competence and learning needs, motivated them to read more, and significantly improved their participation in patient-centred learning activities. Participating clinicians agreed that this formative assessment strategy enhanced the learning potential of bedside teaching sessions. CONCLUSIONS: Longitudinal formative assessment, using blinded patient encounters, was successfully integrated into undergraduate clerkship bedside teaching. According to both students and staff this assessment strategy enhanced bedside learning and improved student participation in patient-centred learning activities during the clerkship.

Formative Assessment Promotes Learning in Undergraduate Clinical Clerkship

INTRODUCTION: Clinical clerkships; typically situated in environments lacking educational structure; form the backbone of undergraduate medical training. The imperative to develop strategies that enhance learning in this context is apparent. This study explored the impact of longitudinal bedside formative assessment on student learning in a medical clerkship.METHODS: We studied a class of 4th-year students completing a 14-week medical clerkship at the University of Cape Town in South Africa. Clinician educators assessed student performance during weekly bedside teaching sessions using blinded patient encounters (in which students had no prior knowledge of the patient's diagnosis or access to the clinical records). Student feedback was standardised using performance rating scales. The impact of formative assessment on student learning was determined from questionnaire responses. RESULTS: A total of 575 formative assessments took place during the study period. Students perceived blinded patient encounters to be a valuable learning activity that improved their clinical reasoning skills and assessed progress fairly. They reported that feedback helped inform them of their level of competence and learning needs; motivated them to read more; and significantly improved their participation in patient-centred learning activities. Participating clinicians agreed that this formative assessment strategy enhanced the learning potential of bedside teaching sessions. CONCLUSIONS: Longitudinal formative assessment; using blinded patient encounters; was successfully integrated into undergraduate clerkship bedside teaching. According to both students and staff this assessment strategy enhanced bedside learning and improved student participation in patient-centred learning activities during the clerkship

Glycine toxicokinetics: vitreous fluid concentration and visual impairment.

We report the results of kinetic experiments in sheep. Following systemic loading with 45 g glycine, plasma, cerebral spinal fluid (CSF), and vitreous fluid from the vitreous body of the eye were assayed for glycine concentrations. Mean baseline plasma, CSF, and vitreous glycine concentrations were 730, 46, and 191 mumol/L respectively. One hour after loading, values were 21292, 1103, and 1150 mumol/L respectively. During the succeeding 7 h plasma and CSF concentrations fell in parallel but remained above normal. In contrast the vitreous concentrations remained high and did not change significantly during the 7 h post-infusion period. Retinal glycine receptors may be particularly vulnerable to neurotoxic effects of glycine because of these pharmacokinetic properties.

Retinal pigment epithelium response and the use of the EOG and Arden Ratio in depression.

Supersensitivity to light in depression has been observed with both neuroendocrine and ophthalmological assessment methods. The biological defect underlying this abnormality may be localized in either the photoreceptors, the retinal pigmented epithelium, or some interaction of the two. The present study assessed responses of the retinal pigmented epithelium (RPE). All subjects underwent thorough ophthalmological and mood assessments. The electrooculogram (EOG) was used to measure standing potentials of the RPE in response to light and dark in 20 normal controls and 20 unmedicated depressed patients. Both groups were matched for age, sex, time of day for the procedure, and prior lighting history. Reproducibility of the EOG measure on two independent occasions for 13 control subjects had an intrasubject reliability coefficient of 0.70. The mean +/- SD Arden Ratio (light peak/dark trough) of the control group (2.13 +/- 0.42) compared to the depressed group (2.28 +/- 0.72) showed no statistical difference. There was, however, a significant difference between groups in response to darkness; depressed patients had a lower standing potential in the dark compared to controls, suggesting supersensitivity to light. No difference between groups was detected in standing potentials at baseline or in response to light. Supersensitivity to light in depression may be related to abnormal function of the RPE, but the inherent reliability of the EOG precludes the use of this instrument in pursuing this hypothesis.

Microscopic polyarteritis--a treatable cause of rapidly progressive renal failure due to necrotising glomerulonephritis.

The clinical features of 25 patients with microscopic polyarteritis are reviewed. Major indications of disease were haematuria and proteinuria accompanied by significant renal dysfunction, which was rapidly progressive in the majority of patients. Unrewarding investigations aimed at defining a cause of haematuria that could be treated surgically only served to delay diagnosis, which could be promptly made by renal biopsy. Early institution of cyclophosphamide therapy led to ablation of the inflammatory process and stabilisation of renal function. In men, who were affected twice as often as women, there was a striking association with employment in the goldmining industry.

The effect of lithium on pupillary response to pulses of light in sheep.

Administration of lithium carbonate to sheep in the dose range of 600-1800 mg/day resulted in a linearly described rise in lithium levels in plasma and red blood cells. In contrast to the rodent model but in agreement with the human condition, plasma lithium levels exceeded those of red blood cells. Polydipsia and body weight changes were not evident. At plasma levels of 0.70-0.8 mM/l, lithium attenuated the ability of the pupil to constrict in response to 30-sec pulses of light in the 25-150 microW/cm2 intensity range but not the ability to dilate in the dark. Thus, similar to observations in normal human volunteers and bipolar patients, lithium reduces sensitivity to light. The sheep is proposed as a useful model for studying the actions of lithium.

Antidepressant medication reverses increased sensitivity to light in depression: preliminary report.

1. Sensitivity to blue light was quantified using a Friedman Central Field Analyzer and the Dark Adaptation Threshold procedure. 2. Patients diagnosed as having a major depressive disorder using research diagnostic criteria had dark adaptation thresholds quantified after a 10 day drug wash out and again after antidepressant drug therapy. 3. Prior to drug treatment patients were significantly more sensitive to light than controls as measured by cone but not rod thresholds. 4. Following drug treatment both cone and rod thresholds were reduced in patients. In comparison to controls, drug treatment normalized cone threshold and reduced rod threshold in patients. 5. These data provide ophthalmological evidence for increased sensitivity to light in non medicated depressive disorder and a reduction in sensitivity following antidepressant drug therapy. 6. The possibility of altered retinal function and consequently the ability to perceive and use light for entrainment of circadian rhythm in affective disorder deserves further study.

Effect of chronic lithium on sensitivity to light in male and female bipolar patients.

1. Sensitivity to white light was quantified in euthymic bipolar male and female patients maintained on long term lithium therapy and age and sex matched unmedicated controls. 2. The Dark Adaptation Threshold procedure was used to assess sensitivity of both the cone and rod photoreceptors to short pulses of light. 3. Male and female controls did not differ in sensitivity to light. 4. Male patients in comparison to both controls and female patients evidenced reduced sensitivity to light during the cone and rod portion of the dark adaptation procedure. 5. Female patients did not differ from controls on sensitivity to light. 6. Using these and other published data the results were interpreted as suggesting that lithium reduces sensitivity to light during adaptation to dark.

Glycine inhibition of pupillary responses to pulses of light in conscious sheep.

The use of a 1.5% glycine solution as a bladder irrigant during surgical removal of the prostate has been associated with transient visual impairment. Glycine is thought to be an inhibitory retinal transmitter. Adult female sheep were infused with a 1.5% glycine solution to provide a dose of 0, 7.5, 15, 30, or 60 g of glycine. The volume control was a solution of dextrose and saline. The degree of constriction of the pupil in response to 30 seconds of bright light following dilation in the dark was used as an index of visual response. Observations were made before and 2, 4, 6, 12, 24, 48, 96, and 192 hours after a single infusion. Significant inhibition of pupil response to light but not to the dark was apparent following systemically administered glycine resulting in plasma levels over 5000 mumol/L. Inhibition of pupil response was paralleled by behavioral indices of visual impairment but not by changes in plasma sodium, potassium, chloride or osmolality. The duration of the effect was dose dependent with visual impairment following a single high dose of glycine being detectable five days later and long after glycine levels had returned to normal. However, the relationship between dose, time, and effect appears to be complex. It is important to note that the present observations occurred at plasma glycine levels frequently experienced in routine surgical practice. The finding that significant long term detrimental effects of glycine could be detected should evoke a re-evaluation of the use of glycine as an irrigating solution for surgical procedures and stimulate further investigation of the effects of glycine on retinal function and the ability to perceive light.

Bipolar patients taking lithium have increased dark adaptation threshold compared with controls.

Recent epidemiological studies of mania suggest that admissions correlate with length of day and sunlight. As well, seasonal affective disorder--a depression occurring in winter, is reported to respond to light therapy and it has been proposed that supersensitivity to light is a trait-marker of manic-depressive illness. Dark adaptation threshold (D.A.T.)--a measure of night vision--was assessed in 19 euthymic manic-depressive patients stabilized on lithium, and in 19 drug-free healthy controls. The D.A.T. was significantly raised in the patients taking lithium. It is concluded that lithium induces subsensitivity to light.

Effects of antidepressants on entrainment of circadian rhythms.

1. Anti-depressant drugs alter the period of circadian rhythms under free running conditions. We have examined whether treatment with anti-depressants alters such rhythms under conditions of entrainment to a lighting cycle or following a phase advance of the lighting. 2. In the first experiment, following entrainment to a 10L:14D lighting schedule, male Long Evans rats were injected daily for three weeks, with either saline, desipramine or clomipramine at a dose of 10 mg/kg. Under these conditions, the resting circadian patterns of serum corticosterone and melatonin were not affected. 3. In a second experiment, male Wistar rats, adapted to a 12L:12D lighting cycle, were implanted with transmitters, permitting continuous recording of temperature. Animals were given chow supplemented with clomipramine or desipramine so that plasma clomipramine levels were within the normal therapeutic range for humans and desipramine levels were at 4-6 times the therapeutic range. After three weeks of drug treatment, the mean 24 h pattern of temperature was decreased and phase advanced by 72 min in the desipramine group compared to clomipramine or controls. Following a 6 h phase advance in the lighting cycle, the three groups responded differently. The clomipramine group evidenced the most rapid advance in the acrophase, equivalent to 6.9 h, while the saline and desipramine treated groups re-entrained significantly more slowly. 4. Clomipramine, given to achieve clinically meaningful blood levels, does not alter the circadian temperature rhythm under constant conditions of alternating light and dark, but significantly accelerates the rate of re-entrainment to a 6 h phase advance of the lighting schedule.

Lithium and the retina.

Recent interest in light therapy for depression has stimulated consideration of the nature of the biological defect in affective disorder. One line of thinking suggests that manic-depressive patients are supersensitive to light and that lithium may act by altering light sensitivity and hence entrainment of biological rhythms. This paper focuses on possible mechanisms whereby lithium may influence retinal physiology and the ability to perceive light. Preliminary data were generated using the Dark Adaptation Threshold procedure with a repeated measure protocol. When depressed and unmedicated the patient was found to have significantly lowered thresholds for light detection compared to control values. This supersensitivity was alleviated following lithium treatment. Data are interpreted as suggesting that some of the therapeutic effects of lithium are localized in the retina. It is proposed that: (1) lithium primarily alters the ability of the retina to detect light and not visual acuity; (2) lithium influences sensitivity to light by modulating the functional environment of the rod photoreceptors in the retina and (3) future research should focus on the effect of lithium on the function of rod photoreceptors and the pigmented epithelial cells in patients with affective disorder.

Acute renal failure--10-year experience of the Johannesburg Hospital renal unit.

The 10-year experience of Johannesburg Hospital's renal unit in treating acute renal failure (ARF) is described; 290 patients were treated by haemodialysis--169 drawn from the surgical disciplines, 109 from the medical disciplines and 12 from obstetrics and gynaecology, suffering 55%, 41% and 33% mortality rates, respectively. The mortality rates were found to correlate strongly with the cumulative number of acute insults to renal function accruing as a result of the particular surgical or medical illness ('precipitating event') and culminating in ARF. Age was also shown to have a powerful influence on outcome, the survival rate falling steadily with each decade of life. A plea is made to limit the potential insults to renal function actively, particularly in the elderly, in an attempt to further reduce the high mortality rate with which ARF continues to be stubbornly associated.

Lithium and rhythms of beta-adrenergic ([3H]CGP-12177) binding in intact rat retina, pineal gland, and hypothalamus.

A new assay technique for the determination of neurotransmitter binding in retinal fragments has been used to characterize and quantify beta-adrenergic receptors with the ligand [3H]CGP-12177. This assay allowed us to quantify beta-adrenergic receptors in the retina, pineal gland, and hypothalamus obtained from individual rats during a 10-hr period around the switch from light to dark under a 12-hr light/12-hr dark lighting cycle. A significant rhythm of beta-adrenergic binding was observed in the retina and pineal gland. These rhythms were abolished by chronic lithium treatment. In contrast to previous observations in whole brain preparations, lithium did not affect beta-adrenergic binding in brain tissue (hypothalamus) using this assay. Our data suggest that lithium may attenuate beta-adrenergic receptor down-regulation in pineal and retinal tissue. To the extent that this mechanism is important for the coding of information about light and dark in the environment, these observations might assist in our understanding of the clinical chronopharmacological properties reported for lithium.

Effects of fornix transection and pituitary-adrenal modulation on extinction behavior.

We examined whether the absence of a dynamic pituitary-adrenal response contributes to the behavioral deficit seen in hippocampally damaged rats following the transition to extinction of a learned behavior. In the first experiment, total lever presses and detailed behaviors of rats with fornix transection and replacement ACTH4-10 or ACTH were compared with the behavior of fornix-transected and sham-transection groups during acquisition and extinction of lever pressing. Fornix-transected rats showed increased resistance to extinction and an altered pattern or mode of extinction responding. ACTH4-10 or ACTH acted similarly in reducing extinction lever presses in fornix-transected rats without altering the mode of extinction responding. In the second experiment the extinction behaviors of rats with fornix transection were compared with those of normal, sham-transection adrenalectomized, or dexamethasone-treated rats. Fornix-transected rats again showed increased resistance to extinction and a different mode of responding during extinction. Adrenalectomized rats showed an extinction deficit but differed from fornix-transected rats. The behavior of dexamethasone-treated rats was similar to that of controls. The results are interpreted to mean that ACTH and corticosterone both affect extinction behavior (in opposite ways) but do not account for the extinction deficit seen in hippocampally damaged rats.