c-Myb is critical for murine colon development.

The mammalian colon develops from a simple tube of undifferentiated cells into a complex, highly ordered organ, with a continuously self-renewing epithelial layer. We have previously described c-Myb expression in the epithelia of murine and human colon crypts and documented increased expression in colorectal adenocarcinoma cells. To investigate the role of c-Myb in colonic epithelium development, we have used embryos with a disrupted c-myb gene. Prior to the in utero death of these embryos at E15, we excised colon tissue and transplanted it under the kidney capsule of recipient mice to allow further development and cyto-differentiation. Compared to the colons of wildtype and heterozygous littermates, the c-myb homozygous knockout colon is highly irregular with a disordered epithelium and abnormal crypts. In addition, the expression of Bcl-2, a known target of c-Myb, is reduced and apoptosis is increased, indicating a critical requirement for c-Myb in normal colon development.     

Altered lymphocyte acetylcholinesterase activity in patients with senile dementia

Reductions in the acetylcholinesterase (AChE) activity of certain brain areas in patients with senile dementia of Alzheimer type (SDAT) have been found to correlate with the severity of the disease, suggesting a central cholinergic lesion. Since AChE is expressed on the surface of various blood cells too, the AChE activity of lymphocytes and erythrocytes was determined to test the possibility whether the cholinergic lesion is also reflected on these readily available cells. The AChE activity of lymphocytes in SDAT and in alcoholic dementia (AD) were significantly lower as compared to those of the age-matched healthy volunteers. In contrast, there was no significant difference in the activity of lymphocyte AChE between age-matched healthy controls and patients with multi-infarct dementia of vascular origin (MID). No changes could be demonstrated in the erythrocyte AChE activities of the patients studied, and the age-matched healthy individuals, when comparing them to the healthy blood donors. The AChE activity of lymphocytes may thus be a useful marker to follow the alterations in the metabolism of acetylcholine (ACh) in the central nervous system (CNS) of different types of dementia.     

Consequences,conditions and caveats: a qualitative exploration of the influence of undergraduate health professions students at distributed clinical training sites

Background

Traditionally, the clinical training of health professionals has been located in central academic hospitals. This is changing. As academic institutions explore ways to produce a health workforce that meets the needs of both the health system and the communities it serves, the placement of students in these communities is becoming increasingly common. While there is a growing literature on the student experience at such distributed sites, we know less about how the presence of students influences the site itself. We therefore set out to elicit insights from key role-players at a number of distributed health service-based training sites about the contribution that students make and the influence their presence has on that site.

Methods

This interpretivist study analysed qualitative data generated during twenty-four semi-structured interviews with facility managers, clinical supervisors and other clinicians working at eight distributed sites. A sampling grid was used to select sites that proportionally represented location, level of care and mix of health professions students. Transcribed data were subjected to thematic analysis. Following an iterative process, initial analyses and code lists were discussed and compared between team members after which the data were coded systematically across the entire data set.

Results

The clustering and categorising of codes led to the generation of three over-arching themes: influence on the facility (culturally and materially); on patient care and community (contribution to service; improved patient outcomes); and on supervisors (enriched work experience, attitude towards teaching role). A subsequent stratified analysis of emergent events identified some consequences of taking clinical training to distributed sites. These consequences occurred when certain conditions were present. Further critical reflection pointed to a set of caveats that modulated the nature of these conditions, emphasising the complexity inherent in this context.

Conclusions

The move towards training health professions students at distributed sites potentially offers many affordances for the facilities where the training takes places, for those responsible for student supervision, and for the patients and communities that these facilities serve. In establishing and maintaining relationships with the facilities, academic institutions will need to be mindful of the conditions and caveats that can influence these affordances.

     

Ribosylative inactivation of rifampin by Mycobacterium smegmatis is a principal contributor to its low susceptibility to this antibiotic.

Mycobacterium smegmatis inactivates rifampin by ribosylating this antibiotic. The gene responsible for this ability was cloned and was shown to confer low-level resistance to this antibiotic (MIC increase, about 12-fold) in related organisms. A 600-bp subclone responsible for ribosylating activity and resistance carried an open reading frame of 429 bp. Targeted disruption of the gene in M. smegmatis resulted in mutants with much increased susceptibility to rifampin (MICs of 1.5 instead of 20 microg/ml) as well as the loss of antibiotic-inactivating ability. Also, disruption of this gene led to a much lower frequency of occurrence of spontaneous high-level rifampin-resistant mutants.     

Confirmation of an association between single nucleotide polymorphisms in the VDR gene with respiratory syncytial virus related disease in South African children

Respiratory syncytial virus is a leading cause of lower respiratory tract infection in infants. Disease severity has been linked to host immune responses and polymorphisms in genes associated with innate immunity. A large‐scale genetics study of single nucleotide polymorphisms (SNPs) in children in the Netherlands identified SNPs in the vitamin D receptor (VDR) and JUN genes which have a strong association with an increased risk of developing bronchiolitis following the first respiratory syncytial virus (RSV) infection. The Toll‐like receptor 4 (TLR4) gene has two SNPs which have been associated previously with RSV disease severity in various populations. The aim of this study was to determine if these SNPs may be associated with RSV disease in African children in South Africa. RSV patient (n = 296) and control (n = 113) groups were established (median ages: 3 and 3.5 months) and DNA extracted from the collected specimens. Real‐time polymerase chain reaction using hydrolysis probes was used to screen for SNPs in the VDR (Thr1Meth; rs10735810), TLR4 (Asp299Gly; rs4986790 and Thr399Ile; rs4986791) and JUN (c.750G/A; rs11688) genes. Carriers of the VDR (Thr1Meth) SNP minor T allele were more prone to RSV disease than individuals in the control group. The TLR4 (Asp299Gly), TLR4 (Thr399Ile), and JUN (c.750G/A) SNPs showed no significant association with RSV disease. It is concluded that children carrying the minor T allele of the VDR (Thr1Meth) SNP may be predisposed to RSV disease, as this SNP was identified as a risk factor for severe RSV disease in South African children, confirming the findings in the Netherlands. J. Med. Virol. 83:1834–1840, 2011. © 2011 Wiley‐Liss, Inc.     

Drosophila orthologue of WWOX, the chromosomal fragile site FRA16D tumour suppressor gene, functions in aerobic metabolism and regulates reactive oxygen species

Common chromosomal fragile sites FRA3B and FRA16D are frequent sites of DNA instability in cancer, but their contribution to cancer cell biology is not yet understood. Genes that span these sites (FHIT and WWOX, respectively) are often perturbed (either increased or decreased) in cancer cells and both are able to suppress tumour growth. While WWOX has some tumour suppressor characteristics, its normal role and functional contribution to cancer has not been fully determined. We find that a significant proportion of Drosophila Wwox interactors identified by proteomics and microarray analyses have roles in aerobic metabolism. Functional relationships between Wwox and either CG6439/isocitrate dehydrogenase (Idh) or Cu-Zn superoxide dismutase (Sod) were confirmed by genetic interactions. In addition, altered levels of Wwox resulted in altered levels of endogenous reactive oxygen species. Wwox (like FHIT) contributes to pathways involving aerobic metabolism and oxidative stress, providing an explanation for the 'non-classical tumour suppressor' behaviour of WWOX. Fragile sites, and the genes that span them, are therefore part of a protective response mechanism to oxidative stress and likely contributors to the differences seen in aerobic glycolysis (Warburg effect) in cancer cells.     

Glucagon-like peptide-1 and its receptor agonist exendin-4 modulate cholangiocyte adaptive response to cholestasis

BACKGROUND & AIMS: Cholangiopathies are characterized by progressive dysregulation of the balance between proliferation and death of cholangiocytes. In the course of cholestasis, cholangiocytes undergo a neuroendocrine transdifferentiation and their biology is regulated by neuroendocrine hormones. Glucagon-like peptide-1 (GLP-1), secreted by neuroendocrine cells, sustains beta-cell survival in experimental diabetes and induces the neuroendocrine transdifferentiation of pancreatic ductal cells. GLP-1 receptor (GLP-1R) selective agonist exendin-4 is used in humans as a novel therapeutic tool for diabetes. The aim of this study was to define if GLP-1 modulates cholangiocyte biologic response to cholestasis. METHODS: Expression of GLP-1R in cholangiocytes was determined. Effects on cholangiocyte proliferation of the in vitro and in vivo exposure to GLP-1 or exendin-4, together with the intracellular signals, were then studied. Synthesis of GLP-1 by cholangiocytes and the effects of GLP-1R blockage on their growth were also determined. RESULTS: Cholangiocytes express the GLP-1 receptor, which is up-regulated in the course of cholestasis. GLP-1 and exendin-4 increase cholangiocyte growth both in vitro and in vivo. The GLP-1R signal is mediated by the phosphatidyl-inositol-3-kinase, cAMP/Protein Kinase A, and Ca(2+)-CamKIIalpha but not by the ERK1/2 and PKCalpha pathways. Proliferating cholangiocytes synthesize GLP-1: neutralization of its action by GLP-1R antagonist blunts cholangiocyte response to cholestasis. CONCLUSIONS: GLP-1 is required for the cholangiocyte adaptive response to cholestasis. Cholangiocytes are susceptible to the activation of GLP-1R and respond with increased proliferation and functional activity. Exendin-4 availability for employment in humans and these data may open novel perspectives for the medical treatment of cholangiopathies.     

The influence of dose and <Emphasis Type="Italic">N</Emphasis>-acetyltransferase-2 (NAT2) genotype and phenotype on the pharmacokinetics and pharmacodynamics of isoniazid

Objective This study evaluated the pharmacokinetics of isoniazid (INH) associated with optimal early bactericidal activity (EBA), defined as 90% of the maximum EBA (EBA₉₀) and the influence of N-acetyltransferase-2 (NAT2) subtype on the ability of pulmonary tuberculosis (PTB) patients to reach the identified pharmacokinetic values after INH doses ranging from 0.2 to 10–12 mg/kg body weight. Methods INH serum concentrations and NAT2 subtype were determined during four studies of PTB patients in three of whom the EBA of INH was determined. The relationship of EBA to area under the curve (AUC) and 2-h serum concentrations was examined by exponential regression and fitted curves estimated the and 2-h serum concentrations at which EBA₉₀ was reached. Results EBA₉₀ was reached at an of 10.52 μg/ml per hour and 2-h serum concentrations of 2.19 μg/ml. An of 10.52 μg/ml per hour was reached by all 66 patients receiving a 10–12 mg/kg INH dose and all 21 receiving 6 mg/kg, except 1 of 10 (10%) homozygous fast (FF) acetylators; however, at 5 mg/kg, 4 of 12 (33%) FF and 26 of 27 (96%) heterozygous fast (FS), but all 21 homozygous slow (SS) acetylators did so; and 1 of 3 (33%) FF, 2 of 6 (33%) FS, but all 4 SS acetylators at dose 3 mg/kg. An INH 2-h serum concentration of 2.19 μg/ml was reached by all 66 patients receiving 10–12 mg/kg and all 21 receiving 6 mg/kg, except for 2 (20%) FF acetylators at a dose of 5 mg/kg; however, only 3 (25%) of 12 FF acetylators, but 26 (96%) of 27 FS acetylators, and all 21 SS acetylators reached this concentration; and at a dose of 3 mg/kg, 1 (33%) of 3 FF acetylators, 2 (33%) of 6 FF, but all 4 SS acetylators. Conclusions At a 6 mg/kg dose, all except a minority of FF NAT2 acetylators, achieve an INH and 2-h INH serum concentrations associated with EBA₉₀, as did all 4 SS acetylators receiving 3 mg/kg. Any dose reduction below 6 mg/kg body weight will tend to disadvantage a significant proportion of faster acetylators, but, conversely, SS acetylators require only a 3 mg/kg dose to achieve a satisfactory exposure to INH.