Characterization of the metallo-beta-lactamase determinant of Acinetobacter baumannii AC-54/97 reveals the existence of bla(IMP) allelic variants carried by gene cassettes of different phylogeny

The metallo-beta-lactamase determinant of Acinetobacter baumannii AC-54/97, a clinical isolate from Italy that was previously shown to produce an enzyme related to IMP-1, was isolated by means of a PCR methodology which targets amplification of gene cassette arrays inserted into class 1 integrons. Sequencing revealed that this determinant was an allelic variant (named bla(IMP-2)) of bla(IMP) found in Japanese isolates and that it was divergent from the latter by 12% of its nucleotide sequence, which evidently had been acquired independently. Similar to bla(IMP), bla(IMP-2) was also carried by an integron-borne gene cassette. However, the 59-base element of the bla(IMP-2) cassette was unrelated to those of the bla(IMP) cassettes found in Japanese isolates, indicating a different phylogeny for the gene cassettes carrying the two allelic variants. Expression of the integron-borne bla(IMP-2) gene in Escherichia coli resulted in a significant decrease in susceptibility to a broad array of beta-lactams (ampicillin, carbenicillin, cephalothin, cefoxitin, ceftazidime, cefepime, and carbapenems). The IMP-2 enzyme was purified from an Escherichia coli strain carrying the cloned determinant, and kinetic parameters were determined with several beta-lactam substrates. Compared to IMP-1, the kinetic parameters of IMP-2 were similar overall with some beta-lactam substrates (cefoxitin, ceftazidime, cefepime, and imipenem) but remarkably different with others (ampicillin, carbenicillin, cephaloridine, and meropenem), revealing a functional significance of at least some of the mutations that differentiate the two IMP variants. Present findings suggest that the environmental reservoir of bla(IMP) alleles could be widespread and raise a question about the global risk of their transfer to clinically relevant species.     

Evidence that cerebral blood volume can provide brain activation maps with better spatial resolution than deoxygenated hemoglobin

With the aim of evaluating the relative performance of hemodynamic contrasts for mapping brain activity, the spatio-temporal response of oxy-, deoxy-, and total-hemoglobin concentrations were imaged with diffuse optical tomography during electrical stimulation of the rat somatosensory cortex. For both 6-s and 30-s stimulus durations, total hemoglobin images provided smaller activation areas than oxy- or deoxy-hemoglobin images. In addition, analysis of regions of interest near the sagittal sinus vein show significantly greater contrast in both oxy- and deoxy-relative to total hemoglobin, suggesting that oximetric contrasts have larger draining vein contributions compared to total hemoglobin contrasts under the given stimulus conditions. These results indicate that total hemoglobin and cerebral blood volume may have advantages as hemodynamic mapping contrasts, particularly for large amplitude, longer duration stimulus paradigms.     

Distribution of neurochemical abnormalities in patients with narcolepsy with cataplexy: An in vivo brain proton MR spectroscopy study

Narcolepsy with cataplexy is characterised by excessive daytime sleepiness, sudden drops of muscle tone triggered by emotions, termed cataplexy, disrupted nocturnal sleep and other dissociated rapid eye movement (REM) sleep phenomena. Narcolepsy has been linked to a loss of hypothalamic neurons producing hypocretins, neuropeptides implicated in the regulation of the arousal system. Neuroimaging and neurometabolic studies have shown the pathophysiological involvement of other brain structures such as cerebral cortex and thalamus, but, overall with inconsistent results.We investigated, by using an advanced quantitative MR technique, proton MR spectroscopy (¹H-MRS), the distribution of brain neurochemical abnormalities in narcolepsy with cataplexy patients. Single voxel ¹H-MRS study was performed in the thalamus, hypothalamus, and parietal–occipital cortex of hypocretin deficient, narcolepsy with cataplexy patients, HLA-DQB1*0602-positive, drug free. No significant changes were detected in the thalamus and parietal–occipital cortex of the patients. On the other hand, the neuronal marker N-acetyl-aspartate was reduced in the hypothalamus of narcolepsy with cataplexy patients compared to controls.These ¹H-MRS findings further support that in narcolepsy with cataplexy patients, the hypothalamus is the primary site of neural lesions. The absence of ¹H-MRS neurodegenerative changes in the thalamus and cerebral cortex suggests that the abnormalities detected in these brain regions by other neuroimaging techniques are likely of functional nature.     

Left atrial volume provides independent and incremental information compared with exercise tolerance parameters in patients with heart failure and left ventricular systolic dysfunction

Objective

Left atrial volume (LAV) is a powerful predictor of outcome in patients with chronic heart failure (CHF) independently of symptomatic status, age and left ventricular (LV) function. It is unknown whether LAV provides independent and incremental information compared with exercise tolerance parameters.

Methods

273 patients with CHF (mean (SD) 62 (9) years; 13% female) prospectively underwent echocardiography and exercise testing with maximal oxygen consumption (Vo₂). The primary end point was composite and included cardiac death, hospitalisation for worsening heart failure or cardiac transplantation.

Results

At Cox proportional hazard analysis, LAV normalised for body surface area (LAV/BSA) was strongly associated with mortality (hazard ratio (HR) = 1.027 (95% CI 1.018 to 1.04), p<0.001). The predictive value of LAV/BSA was independent of Vo₂ and LV ejection fraction (EF) (HR = 1.014 (1.002 to 1.025), p = 0.02; HR = 0.95 (0.91 to 0.99), p = 0.02; HR = 0.89 (0.82 to 0.98), p = 0.02 for LAV/BSA, EF and Vo₂, respectively). Receiver operator characteristic (ROC) curve analysis identified the best cut‐off values for prediction of the end point. LAV/BSA >63 ml, EF <30% and Vo₂ <16 ml/kg/min were considered to be risk factors. Patients with three risk factors had an HR of 38 (95% CI 11 to 129) compared with patients with no risk factors.

Conclusion

LAV provides powerful prognostic information incrementally and independently of Vo₂. LAV, EF and Vo₂ can be used to build a risk prediction model, which can be used clinically.     

Genotype-by-sex interaction on fasting insulin concentration: the HyperGEN study

Recent studies have demonstrated the importance of sex effects on the underlying genetic architecture of insulin-related traits. To explore sex-specific genetic effects on fasting insulin, we tested for genotype-by-sex interaction and conducted linkage analysis of fasting insulin in Hypertension Genetic Epidemiology Network families. Hypertensive siblings and their first-degree relatives were recruited from five field centers. We performed a genome scan for quantitative trait loci influencing fasting insulin among 1,505 European Americans and 1,616 African Americans without diabetes. Sex-stratified linear regression models, adjusted for race, center, and age, were explored. The Mammalian Genotyping Service typed 391 microsatellite markers, spaced roughly 9 cM. Variance component linkage analysis was performed in SOLAR using ethnic-specific marker allele frequencies and multipoint IBDs calculated in MERLIN. We detected a quantitative trait locus influencing fasting insulin in female subjects (logarithm of odds [LOD] = 3.4) on chromosome 2 at 95 cM (between GATA69E12 and GATA71G04) but not in male subjects (LOD = 0.0, P for interaction = 0.007). This sex-specific signal at 2p13.2 was detected in both European-American (LOD = 2.1) and African-American (LOD = 1.2) female subjects. Our findings overlap with several other linkage reports of insulin-related traits and demonstrate the importance of considering complex context-dependent interactions in the search for insulin-related genes.     

The nature of skin pigmentations in chronic venous insufficiency: a preliminary report.

BACKGROUND: Chronic Venous Insufficiency (CVI) provokes skin pigmentation commonly seen in the gaiter region of the leg. The exact nature and pathogenesis of this are poorly understood. OBJECTIVE: To evaluate the presence of melanin and haemosiderin in histological sections of the skin of limbs with primary varicose veins. METHODS: Histological investigations were performed in 49 biopsies from pigmented and non-pigmented skin of limbs with varicose veins and control limbs. RESULTS: All samples from pigmented skin showed a higher content of melanin than controls. In contrast, haemosiderin was found in only a few biopsies taken from the more severely pigmented skin in areas of lipodermatosclerosis. Erythrocyte diapedesis was observed only where an intense inflammatory process was also present. CONCLUSIONS: Our findings suggest that in the initial phases of skin changes due to venous disease, pigmentation is attributable to melanin. Haemosiderin seems to play a role in the evolution of skin changes toward lipodermatosclerosis and ulceration. Erythrocyte diapedesis is likely to occur only during acute phases of the inflammatory process. Further investigations are needed to explain the cause and the exact cellular and molecular mechanisms responsible for hypermelanisation occurring in early phases of skin changes in CVI.