Identification of Nucleoside Analogs as Inducers of Neuronal Differentiation in a Human Reporter Cell Line and Adult Stem Cells

Nucleoside analogs (NSAs) were among the first chemotherapeutic agents and could also be useful for the manipulation of cell fate. To investigate the potential of NSAs for the induction of neuronal differentiation, we developed a novel phenotypic assay based on a human neuron‐committed teratocarcinoma cell line (NT2) as a model for neuronal progenitors and constructed a NT2‐based reporter cell line that expressed eGFP under the control of a neuron‐specific promoter. We tested 38 structurally related NSAs and determined their activity to induce neuronal differentiation by immunocytochemistry of neuronal marker proteins, live cell imaging, fluorometric detection and immunoblot analysis. We identified twelve NSAs, which induced neuronal differentiation to different extents. NSAs with highest activity carried a halogen substituent at their pyrimidine nucleobase and an unmodified or 2′‐O‐methyl substituted 2‐deoxy‐β‐D‐ribofuranosyl residue as glyconic moiety. Cladribine, a purine nucleoside with similar structural features and in use to treat leukemia and multiple sclerosis, induced also differentiation of adult human neural crest‐derived stem cells. Our results suggest that NSAs could be useful for the manipulation of neuronal cell fate in cell replacement therapy or treatment of neurodegenerative disorders. The data on the structure and function relationship will help to design compounds with increased activity and low toxicity.     

Risk factors for trachoma in Mali

OBJECTIVES: Prior to commencing a campaign to eliminate blinding trachoma in Mali, a national disease prevalence survey was conducted from March 1996 to June 1997. The prevalence of trachoma was estimated and potential risk factors were studied. METHODS: In each of Mali's seven regions (excluding the capital Bamako), a sample of 30 clusters was taken from the general population, in accordance with the principle of probability proportional to the size of the community. All children under 10 years of age were examined. The simplified clinical coding system proposed by the World Health Organization was used. The position of each village was established and subsequently related to the nearest meteorological station. Socioeconomic and environmental information was collected at both village and household level. The mother or caretaker of each child was questioned about availability and use of water for washing the child. At the time of examination, facial cleanliness and the presence of flies on the face were noted. RESULTS: A total of 15,187 children under 10 years of age were examined. The prevalence of active trachoma (follicular [TF] or intense trachoma [TI]) was 34.9% (95% CI : 32.3-37.6) and the prevalence of TI was 4.2% (95% CI : 3.5-5.0). Aridity/environmental dryness appears to be a risk factor influencing the current geographical distribution of trachoma. Small villages had considerably higher trachoma prevalence than their larger neighbours. The proximity of a medical centre and the existence of social organizations such as a women's association were associated with lower levels of trachoma. Crowded living conditions increased the risk. Using a monetary marker of wealth, we observed a linear inverse relation between wealth and trachoma prevalence. The presence of a dirty face was strongly associated with trachoma (odds ratio [OR] = 3.67) as was the presence of flies on the child's face (OR = 3.62). Trachoma prevalence increased with distance to a water source. Disease prevalence decreased with a higher frequency of both face washing and bathing. CONCLUSIONS: Of all the risk factors examined, facial cleanliness had the strongest association with the prevalence of trachoma. This was followed by the presence of flies on the child's face. Both face washing and bathing showed beneficial effects. Socioeconomic factors such as wealth were significantly explanatory. It is likely that hygiene education and fly control by environmental improvement could have a very significant impact on the prevalence of trachoma in Mali.     

Assessment of personal qualities in relation to admission to medical school

BACKGROUND: Recently there has been much scrutiny of the medical school admissions process by universities, the General Medical Council and the public. Improved objectivity, fairness and effectiveness of selection procedures are desirable. The ultimate outcome sought is the graduation of competent doctors who reflect the values of and are in tune with the communities they serve. METHODS: Applicants to the Scottish medical schools sat a battery of psychometric tests to measure cognitive ability, personality traits and moral/ethical reasoning (Personal Qualities Assessment, PQA). Analysis determined the potential impact of the latter variables, and those of educational background and socioeconomic class (assessed by residential 'deprivation category'), upon success in gaining a place to study medicine. RESULTS: Cognitive ability did not vary significantly as a function of gender or educational background, although there was a trend for it to be lower in individuals from more deprived backgrounds. Women as a group were more empathic, with a greater communitarian orientation, than men. There was no significant difference between individuals attending independent and state-funded schools in respect of any of the qualities measured by the PQA. Applicants from deprived backgrounds and those attending state-funded schools would not be disadvantaged by an admissions process based on the PQA. CONCLUSION: The incorporation of an assessment tool such as the PQA may have positive implications for widening access and the objective selection of suitable medical students, resulting in the training of doctors who are more representative of the community at large. A longterm follow-up of the professional careers of those medical students who completed the PQA will be undertaken.     

Measurement of the T2 relaxation time of ethanol and cerebral metabolites, in vivo.

The SPACE volume selection technique was combined with a spin-echo sequence to measure the transverse relaxation time of the resonances of ethanol and cerebral metabolites in the dog brain, in vivo. The method was extended to measure brain metabolite T2 values in the rat using 1H NMR microspectroscopy. The T2 decays for the resonances of the metabolites N-acetylaspartate, creatine/phosphocreatine, and choline/phosphorylcholine were found to be biexponential with long T2 components of 490, 260, and 350 ms for the dog and 490, 220, and 355 ms for the rat brain, respectively. The existence of a second T2 component may originate from J-coupled nonresolved metabolite resonances. The relaxation decay for the ethanol triplet could be fitted to a single exponential giving a T2 relaxation time of 335 ms. However, given the large errors in the measurement of ethanol peak intensities at short echo times because of overlapping lipid signal and the effects of J-modulation, a biexponential decay with a long T2 component of 335 ms cannot be ruled out. Ambiguities regarding the reported partial detection of the 1H NMR signal of ethanol in the brain are discussed.     

The study of human organs by phosphorus-31 topical magnetic resonance spectroscopy

The potential clinical use of topical magnetic resonance spectroscopy (volume selection by static magnetic field gradients) was tested in 50 studies in volunteers. Topical magnetic resonance spectroscopy (MRS) was shown to be a straightforward method for localising 31P spectra of brain and liver. However, the spherical shape and fixed position of the selected volume posed serious limitations to the study of heart and transplanted kidney by topical MRS. Phosphorus-31 spectra of approximately 30 cm-3 of brain or liver could be obtained in 8 min. Ratios of metabolite concentrations could be determined with a coefficient of variation ranging from 10% to 30%. The ratios of phosphocreatine/ATP and inorganic phosphate/ATP in brain were 1.8 and 0.3, respectively. The ratio of inorganic phosphate/ATP in liver was 0.9. Intracellular pH was 7.03 in brain and 7.24 in liver. The T1 relaxation times of phosphocreatine, inorganic phosphate and gamma-ATP in brain were 4.8 s, 2.5 s and 1.0 s, respectively.     

Analysis of rat heart in vivo by phosphorus nuclear magnetic resonance.

High-resolution 31P nuclear magnetic resonance spectra at 73.83 MHz are reported for rat heart in vivo. In live rats, it was possible to observe the cardiac content of ATP, phosphocreatine, and Pi. Only a small amount of whole-blood 2,3-diphosphoglycerate was observed in the spectra, precluding the possibility that blood phosphate compounds were masking the spectra of cardiac phosphate compounds. The 31P nuclear magnetic resonance spectra of in vivo and perfused rat hearts were similar and support the utilization of the perfused rat heart as a model system for studying high-energy phosphate metabolism of the heart in vivo. The dynamic flux of high-energy phosphate compounds was investigated by subjecting the rat to respiratory arrest. In this experiment, the heart followed the classic metabolic pattern known to occur during cardiac arrest; phosphocreatine and then ATP decreased in concentration while Pi increased in concentration. The 31P nuclear magnetic resonance analysis of rat heart in vivo is demonstrated to be a practical and feasible method for studying cardiac high-energy phosphate metabolism.     

The installation of high-field NMR equipment in a hospital environment

Installing high-field magnets in hospital environments has implications for safety, for the performance of the equipment and for the well-being of the subjects who will be examined. This paper outlines the relevant properties of magnets and identifies the requirements necessary for a safe and usable installation. One approach to the meeting of these requirements is described.     

Why is it so hard to consider personal qualities when selecting medical students?

Abstract

Having ‘good’ doctors is important to everybody. How to select medical students better has been discussed repeatedly for more than seventy years, implying that prevailing methods could be improved. A significant body of research exists about selection methods and their application in medicine. Yet most medical schools world-wide continue to use prior academic performance and cognitive ability as their major criteria for selection, with minor or no consideration of personal qualities and interpersonal skills (possibly assuming they will develop naturally during training and practice). We describe the main methods available for assessing personal qualities of applicants to medical school and have attempted to identify some reasons and systemic disincentives working against their adoption.