Relations between pigments and proteins in the photosynthetic membranes of Rhodopseudomonas spheroides

We have isolated from Rhodopseudomonas spheroides a pigment-protein complex of apparent weight 9 kdaltons that bears more than 60% of the light harvesting bacteriochlorophyll. The isolation procedure involved exposure to 1% lauryl dimethyl amine oxide (LDAO). The purified 9-kdalton fraction showed the light harvesting bacteriochlorophyll components B800 and B850, plus carotenoids. The ratio of bacteriochlorophyll to protein was 17%. This protein is probably the same as the “band 15” protein of Fraker and Kaplan. It may exist in vivo as characteristic aggregates of higher molecular weight. LDAO added to Rps. spheroides chromatophores converted the bacteriochlorophyll component B870 to a form absorbing at 770 nm but had little effect on the “B800 + B850” system, causing only a reversible shift of the 850-nm band to 845 nm. Anti-reaction center serum, added to subcellular fractions from Rps. spheroides with 1% LDAO, precipitated reaction center chromoprotein unaccompanied by light harvesting bacteriocholorophyll. Other antisera precipitated light harvesting components and left the reaction center chromophores in solution. A major protein of apparent weight 45 kdaltons was found in relatively nonpigmented fractions from Rps. spheroides, associated with cell wall fragments. The 45-kdalton protein showed considerable interstrain variability, whereas the 9-kdalton and reaction center proteins appeared constant.     

BRCA2 deficiency in mice leads to meiotic impairment and infertility

The role of Brca2 in gametogenesis has been obscure because of embryonic lethality of the knockout mice. We generated Brca2-null mice carrying a human BAC with the BRCA2 gene. This construct rescues embryonic lethality and the mice develop normally. However, there is poor expression of the transgene in the gonads and the mice are infertile, allowing examination of the function of BRCA2 in gametogenesis. BRCA2-deficient spermatocytes fail to progress beyond the early prophase I stage of meiosis. Observations on localization of recombination-related and spermatogenic-related proteins suggest that the spermatocytes undergo early steps of recombination (DNA double strand break formation), but fail to complete recombination or initiate spermiogenic development. In contrast to the early meiotic prophase arrest of spermatocytes, some mutant oocytes can progress through meiotic prophase I, albeit with a high frequency of nuclear abnormalities, and can be fertilized and produce embryos. Nonetheless, there is marked depletion of germ cells in adult females. These studies provide evidence for key roles of the BRCA2 protein in mammalian gametogenesis and meiotic success.     

Accelerated onset of heart failure in mice during pressure overload with chronically decreased SERCA2 calcium pump activity

We recently developed a mouse model with a single functional allele of Serca2 (Serca2+/-) that shows impaired cardiac contractility and relaxation without overt heart disease. The goal of this study was to test the hypothesis that chronic reduction in sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA)2 levels in combination with an increased hemodynamic load will result in an accelerated pathway to heart failure. Age-matched wild-type and Serca2+/- mice were subjected to 10 wk of pressure overload via transverse aortic coarctation surgery. Cardiac hypertrophy and heart failure were assessed by echocardiography, gravimetry/histology, hemodynamics, and Western blotting analyses. Our results showed that approximately 64% of coarcted Serca2+/- mice were in heart failure compared with 0% of coarcted wild-type mice (P < 0.05). Overall, morbidity and mortality were greatly increased in Serca2+/- mice under pressure overload. Echocardiography assessment revealed a significant increase in left ventricular (LV) mass, and LV hypertrophy in coarcted Serca2+/- mice converted from a concentric to an eccentric pattern, similar to that seen in human heart failure. Coarcted Serca2+/- mice had decreased contractile/systolic and relaxation/diastolic performance and/or function compared with coarcted wild-type mice (P < 0.05), despite a similar duration and degree of pressure overload. SERCA2a protein levels were significantly reduced (>50%) in coarcted Serca2+/- mice compared with noncoarcted and coarcted wild-type mice. Our findings suggest that reduction in SERCA2 levels in combination with an increased hemodynamic load results in an accelerated pathway to heart failure.     

Sarcoptic mange in raccoons in Michigan

Sarcoptic mange is a cause of pruritic skin disease in domestic dogs and a wide range of wildlife species. We describe sarcoptic mange in free-ranging raccoons (Procyon lotor). Three adult raccoons from upper Wayne County, Michigan (USA), were captured, killed, and submitted for diagnostic evaluation. The animals were intensely pruritic, and two had advanced alopecic and crusting lesions over their dorsum and hind limbs. Skin scrapings and skin biopsies revealed crusting and hyperkeratotic dermatitis with high numbers of Sarcoptes scabiei adults, larvae, nymphs, and eggs. These raccoons were not otherwise debilitated, with minimal internal parasites, good body condition, and no evidence of infectious bacterial or viral diseases. Because sarcoptic mange is highly contagious and affects many species, including humans, transiently, it is important that wildlife biologists and rehabilitators include sarcoptic mange in their differential list for raccoons exhibiting pruritus and alopecia.     

Regulation of primary spinal neuron lineages after deletion of a major progenitor

Vertebrate embryos are able to reconstitute the body plan when early blastomeres are deleted, but it is not known whether this is accomplished by cells local to the lesion or by a readjustment of the entire pattern of the embryo. We distinguished between these two possibilities by studying which embryonic cells change primary spinal neuronal fates after deletion of a major spinal cord progenitor. After ablation of the V1.2 blastomere of the 16-cell Xenopus embryo, the spinal cord contained normal numbers of Rohon-Beard neurons and primary motoneurons, indicating that the remaining blastomeres numerically reconstituted these populations. Using lineage-tracing techniques we revealed a global response: 10 out of the 15 remaining blastomeres significantly changed the number of one or both neuronal types they produced. This widespread response indicates that position in the early embryo plays an important role in regulating the production of primary spinal neurons. However, not all cells are influenced solely by position; a vegetal cell transplanted into the position of the deleted V1.2 did not take on the neuronal fate of its new position. Thus, restitution of pattern relies on a combination of positional cues and intrinsic fate restrictions.     

Highly potent and long-acting trimeric and tetrameric inhibitors of influenza virus neuraminidase

A set of trimeric and tetrameric derivatives 6-11 of the influenza virus neuraminidase inhibitor zanamivir 1 have been synthesized by coupling a common monomeric zanamivir derivative 3 onto various multimeric carboxylic acid core groups. These discrete multimeric compounds are all significantly more antiviral than zanamivir and also show outstanding long-lasting protective activity when tested in mouse influenza infectivity experiments.     

Effects of reducing agents on glutathione metabolism and the function of carotid body chemoreceptor cells

Two current hypotheses of O2 sensing in the carotid body (CB) chemoreceptors suggest participation of oxygen reactive (ROS) species, but they are mechanistically opposed. One postulates that hypoxia decreases ROS levels; the other that hypoxia increases them. Yet, both propose that the ensuing alteration in the cellular redox environment is the key signal triggering hypoxic chemoreception. Since the glutathione redox pair is the main cellular buffer for ROS and the main determinant of the general redox environment of the cells, a way to test whether ROS participate in chemoreception is to determine glutathione levels and to correlate them with the activity of CB chemoreceptor cells. We found that hypoxia does not alter the glutathione reduction potential but that it activates chemoreceptor cell neurosecretion. Incubation of tissues with reduced glutathione increases the glutathione-reducing potential but does not activate chemoreceptor cells in normoxia nor does it modify hypoxic activation. Like reduced glutathione, N-acetylcysteine promoted a general reducing environment in the cells without alteration of chemoreceptor cell activity. N-(mercaptopropionyl)-glycine, like the two previous agents, increases the reduction potential of glutathione. In contrast, the compound activated chemoreceptor cells in normoxia, promoting a dose- and Ca(2+)-dependent neurosecretion and a potentiation of the hypoxic responses. The existence of multiple relationships between glutathione reduction potential in the cells and their activity indicates that the general cellular redox environment is not a factor determining chemoreceptor cell activation. It cannot be excluded that the local redox environments of restricted microdomain(s) in the cells with specific regulating mechanisms are important signals for chemoreceptor cell activity.     

Systemic host inflammatory and coagulation response in the Dengue virus primo-infection

BACKGROUND: Dengue virus infection has been rising in tropical countries. Clinical manifestations range from fever and general malaise to hemorrhagic manifestations and death. The role of endothelial damage and cytokines has not been well established for dengue infection. OBJECTIVE: Determine the profile of the pro-inflammatory cytokines and several markers of coagulopathy of dengue infection. METHODS: Patients admitted between September 2000 and April 2001, who met the WHO dengue diagnosis criteria, were enrolled. Blood samples were collected at 0, 6, 12, 24, 48, 72 h and 5 and 7 days after hospitalization. Profile of pro-inflammatory cytokines, markers of coagulopathy, protein C, protein S, d-dimer, prothrombin time, activated partial thromboplastin time, fibrinogen and activated protein C levels were determined. RESULTS: Thirty-three patients were enrolled. Median (range) age was 31 (13-70) years; 51.5% (17/33) were female. Ten of 33 (30%) presented with hemorrhagic manifestations. Patients were classified: Grade 1: 23/33 (70%), Grade II: 10/33 (30%). At study entry IL-6 was the most elevated, followed by IL-8 and TNF alpha. IL-10 was not elevated. No significant differences (P < 0.05) were demonstrated in the levels of any of the haemostatic or cytokine markers by disease severity (Grade I versus Grade II patients). CONCLUSION: The systemic host inflammatory and coagulation activation response occurs early in patients with dengue viral infection in the absence of severe hemorrhagic manifestations, and provides the basis for considering future clinical study in the use of recombinant human activated protein C to treat patients with severe sepsis from dengue infection.     

Calcium dynamics in the failing heart: restoration by beta-adrenergic receptor blockade

Changes in calcium (Ca2+) regulation contribute to loss of contractile function in dilated cardiomyopathy. Clinical treatment using beta-adrenergic receptor antagonists (beta-blockers) slows deterioration of cardiac function in end-stage heart failure patients; however, the effects of beta-blocker treatment on Ca2+ dynamics in the failing heart are unknown. To address this issue, tropomodulin-overexpressing transgenic (TOT) mice, which suffer from dilated cardiomyopathy, were treated with a nonselective beta-receptor blocker (5 mg. kg-1. day-1 propranolol) for 2 wk. Ca2+ dynamics in isolated cardiomyocytes of TOT mice significantly improved after treatment compared with untreated TOT mice. Frequency-dependent diastolic and Ca2+ transient amplitudes were returned to normal in propranolol-treated TOT mice and but not in untreated TOT mice. Ca2+ kinetic measurements of time to peak and time decay of the caffeine-induced Ca2+ transient to 50% relaxation were also normalized. Immunoblot analysis of untreated TOT heart samples showed a 3.6-fold reduction of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA), whereas Na+/Ca2+ exchanger (NCX) concentrations were increased 2.6-fold relative to nontransgenic samples. Propranolol treatment of TOT mice reversed the alterations in SERCA and NCX protein levels but not potassium channels. Although restoration of Ca2+ dynamics occurred within 2 wk of beta-blockade treatment, evidence of functional improvement in cardiac contractility assessed by echocardiography took 10 wk to materialize. These results demonstrate that beta-adrenergic blockade restores Ca2+ dynamics and normalizes expression of Ca2+-handling proteins, eventually leading to improved hemodynamic function in cardiomyopathic hearts.