Structure-based design and mechanisms of allosteric inhibitors for mitochondrial branched-chain α-ketoacid dehydrogenase kinase

The branched-chain amino acids (BCAAs) leucine, isoleucine, and valine are elevated in maple syrup urine disease, heart failure, obesity, and type 2 diabetes. BCAA homeostasis is controlled by the mitochondrial branched-chain α-ketoacid dehydrogenase complex (BCKDC), which is negatively regulated by the specific BCKD kinase (BDK). Here, we used structure-based design to develop a BDK inhibitor, (S)-α-chloro-phenylpropionic acid [(S)-CPP]. Crystal structures of the BDK-(S)-CPP complex show that (S)-CPP binds to a unique allosteric site in the N-terminal domain, triggering helix movements in BDK. These conformational changes are communicated to the lipoyl-binding pocket, which nullifies BDK activity by blocking its binding to the BCKDC core. Administration of (S)-CPP to mice leads to the full activation and dephosphorylation of BCKDC with significant reduction in plasma BCAA concentrations. The results buttress the concept of targeting mitochondrial BDK as a pharmacological approach to mitigate BCAA accumulation in metabolic diseases and heart failure.     

Molecular detection and quantification of pertussis and correlation with clinical outcomes in children

Pertussis is an under-recognized serious infection. Conventional cultures are insensitive and of limited utility after antibiotic exposure. We corroborated the utility of real-time polymerase chain reaction (PCR) as a diagnostic tool in pertussis and investigated its role as a prognostic tool by evaluating its benefit in the quantification of pertussis bacterial load. All pertussis-positive PCR tests (n = 104) submitted over 5 years were collected for retrospective study. PCR cycle threshold was compared to quantitative culture in 43. Compared to PCR, the sensitivity of culture was 41%. Our PCR assay reliably quantified bacterial load and was quantitatively reproducible. Higher bacterial load correlated with longer duration of hospitalization (P = 0.0003), and multivariate logistic regression models demonstrated this association to be independent. The study confirmed PCR as a superior diagnostic tool in pertussis. PCR quantification of bacterial load at initial diagnosis predicts later clinical disease severity, suggesting a potential benefit of PCR as a prognostic tool in pertussis.     

The interhemal membrane of the spotted hyena: an immunohistochemical reappraisal.

On the basis of specific immunohistochemical staining for vimentin and cytokeratin, we conclude that in the mature placenta of the spotted hyena the interhemal membrane is haemomonochorial rather than endotheliochorial, as in other carnivores. We concur that the intrasyncytial laminae are remnants of the maternal endothelial basal lamina.     

An observer study for direct comparison of clinical efficacy of electronic to film portal images

: To directly compare clinical efficacy of electronic to film portal images.

: An observer study was designed to compare clinical efficacy of electronic to film portal images acquired using a liquid matrix ion-chamber electronic portal imaging device and a conventional metal screen-film system. Both images were acquired simultaneously for each treatment port and the electronic portal images were printed on gray-level thermal paper. Four radiation oncologists served as observers and evaluated a total ot 44 sets of images for four different treatment sites: lung, pelvis, brain, and head/neck. Each set of images included a simulation image, a double-exposure portal film, and video paper prints of electronic portal images. Eight to nine anatomical landmarks were selected from each treatment site. Each observer was asked to rate each landmark in terms of its clinical visibility and to rate the ease of making the pertinent verification decision in the corresponding electronic and film portal images with the aid of the simulation image.

Resultings for the vesibility of landmarks and for the verification decision of treatment ports were similar for electronic and film images for most landmarks. However, vertebral bodies and several landmarks in the pelvis suchs as the acetabulum and pubic symphsis were more visible in the portal film images than in the electronic portal images.

The visibility of landmarks in electronic portal images is comparable to that in film portal images. Verification of treatment ports based only on electronic portal images acquired using an electronic portal imaging device is generally achievable.     

Redistribution of connexin 43 by cAMP: a mechanism for growth control in adrenal cells

In order to investigate the regulation of connexin distribution in rapidly growing cells, we evaluated the effects of dibutyryl cyclic adenosine monophosphate (DbcAMP) treatment on the cellular location of endogenous connexin 43 (Cx43) in an adrenal tumor cell population. Polyclonal antibodies to Cx43 and a Cx43 green fluorescent fusion protein (Cx43-GFP) were used to localize Cx43 gap junction protein in plaques at sites of cell-cell contact and in spherical packets within the cytoplasm. Treatment with DbcAMP significantly decreased the number and size of packets within the cytoplasm, and significantly increased surface gap junction plaque size. These data support the theory that cAMP can influence the availability of gap junction protein at the points of cell contact where it is required for cell-cell communication, and thus has the potential to be an important regulator of adrenal tumor cell proliferation.     

Clinical implications of CNS penetration of antiretroviral drugs

The CNS serves as an important sanctuary site for HIV replication. The presence of HIV in this compartment may contribute to neurological complications in individuals infected with HIV. Understanding the CNS penetration capabilities of available antiretroviral agents may help clinicians to design treatment regimens with neuroprotective effects. Although numerous clinical studies and anecdotal reports have examined CSF antiretroviral drug exposure as a marker of CNS penetration, understanding the clinical relevance of these findings is difficult. Challenges with study design and subject recruitment often limit the investigator's ability to collect comprehensive data. Upon review of available data, the antiretroviral agents zidovudine, stavudine, lamivudine, nevirapine, efavirenz and indinavir demonstrate consistent penetration into the CSF. Zidovudine-, stavudine-, lamivudine-, didanosine- and protease inhibitor-based regimens also appear to suppress CSF viraemia or improve HIV neurological disease. These agents may be appropriate candidates for neuroprotective antiretroviral treatment regimens. Despite these data, several unanswered questions about the CSF antiretroviral drug exposure-response relationship still remain. Prospective, controlled studies examining this relationship are needed before absolute clinical recommendations are founded.     

Teaching of occupational medicine to undergraduates in UK schools of medicine

OBJECTIVES: To assess any recent change in the commitment to teaching of occupational medicine in UK undergraduate medical curricula. DESIGN: A questionnaire survey of the teaching of occupational medicine to undergraduates in all medical schools listed in the UK Universities and Colleges Admissions Service prospectus for 1999-2000 (n = 24). RESULTS: Nineteen UK medical schools returned a completed questionnaire, giving a response rate of 79%. A comparison of results from this survey with previous surveys of teaching of occupational medicine to undergraduates in the UK shows that fewer schools now provide lectures, project work or ward-based tuition in the subject. Workplace visits were not undertaken by any institution. Only two of the schools setting an examination question also had a syllabus. CONCLUSION: Despite the prominence given to issues related to occupational health in recent UK government policy, this study suggests a declining commitment to occupational medicine on the part of UK medical schools. Urgent action needs to be taken to address the lack of training in occupational medicine in UK medical schools.