Evidence for dysfunction in the regulation of cytosolic Ca2+ in excitation-contraction uncoupled dysgenic muscle

In noncontracting, dysgenic murine muscle, excitation is uncoupled from contraction. To test whether the gene lesion is expressed as a defect in the regulation of the intracellular free Ca2+ levels, cultured normal and dysgenic muscle at various stages of development (proliferative myoblasts, early, late, and mature myotubes) were exposed to increasing increments (0.5-mM steps) of extracellular Ca2+ in ionophore A23187-Ca2+-EGTA-buffered media. Normal and dysgenic muscle at all stages (except myoblast) displayed contractures at approximately 500 microM free Ca2+ and higher. Experiments using finer increments of Ca2+ and different ionophore concentrations indicated an external Ca2+ threshold for contracture at 265 microM Ca2+ for early and late myotubes and 47-78 microM for mature normal and dysgenic myotubes. Low extracellular concentrations of calcium (14 microM and 0.76 nM) caused elongation of both normal and dysgenic myotubes. Mature cells were depolarized by exposure to increasing extracellular K+ and monitored by intracellular recording; normal and dysgenic myotubes showed similar reductions in membrane potentials. Depolarization to -35 mV elicited contractures in normal myotubes, but even depolarization to -9 mV in dysgenic cells elicited no response. Thus steady-state depolarization of dysgenic muscle does not cause contractures, which can, however, be elicited by increasing the intracellular free Ca2+. These results offer new evidence for a possible defect in the regulation of Ca2+ levels in dysgenic muscle.     

Sampling properties of DNA sequence data in phylogenetic analysis

We inferred phylogenetic trees from individual genes and random samples of nucleotides from the mitochondrial genomes of 10 vertebrates and compared the results to those obtained by analyzing the whole genomes. Individual genes are poor samples in that they infrequently lead to the whole-genome tree. A large number of nucleotide sites is needed to exactly determine the whole-genome tree. A relatively small number of sites, however, often results in a tree close to the whole-genome tree. We found that blocks of contiguous sites were less likely to lead to the whole-genome tree than samples composed of sites drawn individually from throughout the genome. Samples of contiguous sites are not representative of the entire genome, a condition that violates a basic assumption of the bootstrap method as it is applied in phylogenetic studies.      

Membrane potentials and resistances of giant mitochondria. Metabolic dependence and the effects of valinomycin

The membrane potentials and resistances of giant mitochondria from mice fed cuprizone have been studied. They were found to correspond approx. 10-20 mV, positive inside, and 2 M omega, respectively. These properties were found to be independent of the metabolic state. The microelectrodes were in the inner mitochondrial space since (a) the potentials in the presence of valinomycin depended on the K+ concentration of the medium and magnitude of the K+ diffusion potentials was consistent with the presence of a high internal concentration of K+, (b) almost identical results were obtained with mitochondria from which the external membrane had been removed and the cristae were evaginated, and (c) punch-through experiments, in which the microelectrodes were advanced until they emerged through the other side of the mitochondria, showed an identical membrane potential both in the presence and in the absence of valinomycin. The potentials were stable under a variety of conditions and showed no sign of decay of membrane leakiness. Detailed evidence that the impaled mitochondria are metabolically viable will be presented in a separate publication.     

Some observations on the effect of Daflon (micronized purified flavonoid fraction of Rutaceae aurantiae) in bancroftian filarial lymphoedema

BACKGROUND: Morbidity management is a core component of the global programme for the elimination of lymphatic filariasis. In a double-blind clinical trial, the tolerability and efficacy of Daflon (500 mg) + DEC (25 mg) or DEC (25 mg) alone, twice daily for 90 days, was studied in 26 patients with bancroftian filarial lymphoedema. RESULTS: None of the patients in either drug group reported any adverse reaction throughout the treatment period (90 days). Haematological and biochemical parameters were within normal limits and there was no significant difference between the pre-treatment (day 0) and post-treatment (day 90) values. The group receiving Daflon showed significant reduction in oedema volume from day 90 (140.6 PlusMinus; 18.8 ml) to day 360 (71.8 PlusMinus; 20.7 ml) compared to the pre-treatment (day 0, 198.4 PlusMinus; 16.5 ml) value. This accounted for a 63.8% reduction in oedema volume by day 360 (considering the pre-treatment (day 0) as 100%). In the DEC group, the changes in oedema volume (between day 1 and day 360) were not significant when compared to the pre-treatment (day 0) value. The percentage reduction at day 360 was only 9%, which was not significant (P > 0.05). CONCLUSION: This study has shown that Daflon (500 mg, twice a day for 90 days) is both safe and efficacious in reducing oedema volume in bancroftian filarial lymphoedema. Further clinical trials are essential for strengthening the evidence base on the role of this drug in the morbidity management of lymphatic filariasis.     

Mesozooplankton of the Kosi Bay lakes,South Africa

The Kosi coastal lake system, a chain of four interconnected basins, is located in the subtropical north-eastern corner of South Africa. Little information is available on zooplankton of the system and the main aim of this study is to report on zooplankton samples collected during 2002 and 2003. The set of samples consists of seasonal, subsurface mesozooplankton samples that were collected during nighttime in each of the lakes. A well-developed salinity gradient was evident along the interconnected lakes in the subsurface water during all seasons, ranging from freshwater in the upper lake Amanzamnyama to a maximum of 22 recorded in Lake Makhawulani. The zooplankton community structures of the lakes reflected the salinity gradient of the system, with some coastal marine taxa recorded in the lakes closer to the mouth and only freshwater taxa recorded in Lake Amanzamnyama. Mesozooplankton diversity and abundance were relatively low compared to other estuarine systems along the eastern coast of South Africa. The dominant taxa were calanoid copepods Acartiella natalensis and Pseudodiaptomus stuhlmanni and the mysid Mesopodopsis africana in the lower lakes, whereas cyclopoids Mesocyclops sp. and Thermocyclops sp. dominated the freshwater lake Amanzamnyama.     

Identification of transposable elements which activate gene expression in Pseudomonas cepacia.

This study demonstrated that transposable elements in Pseudomonas cepacia could be inserted upstream of a poorly expressed gene and increase its expression more than 30-fold. Five elements, TnPc1, IS402, IS403, IS404, and IS405, were isolated by their ability to increase expression of the beta-lactamase gene of the broad-host-range plasmid pRP1. Increased expression resulted only from insertion of these elements, suggesting that insertional activation is an important means of elevating gene expression in this organism. Four of the elements inserted between a PstI site within the beta-lactamase gene and a BamHI site located 375 base pairs upstream of its promoter. The element IS403 inserted distal to the BamHI site within the coding region for the gene tnpR, suggesting that insertional activation can act over greater than expected distances. In addition, the element IS402 activated the beta-lactamase genes carried on plasmids pRP1 and pMR5 (temperature-sensitive pRP1) equally well in opposite orientations, demonstrating that insertional activation by this element occurs independent of its orientation.     

Serum creatine kinase activity varies with ovulatory status in regularly exercising, premenopausal women

BACKGROUND/AIMS: The clinical complications associated with an unopposed estrogen environment and luteal phase defects observed in exercising women prompted the examination of the relationship of exercise and endogenous ovarian steroids with serum creatine kinase (CK) activity. METHODS: Subjects (n = 34) were classified into three groups according to their exercise and menstrual status, sedentary and exercising ovulatory groups (SedOvul, ExOvul), and an exercising amenorrheic group (ExAmen). Daily urine samples were collected to assess urinary ovarian steroid exposure and menstrual status. Serum CK activity was assayed in each menstrual cycle of all subjects. RESULTS: Exercise increased serum CK activity in all exercising subjects (p < 0.01), but the increase was greater in amenorrheic women compared to ovulatory women (SedOvul: 33.0 +/- 3.4; ExOvul: 43.7 +/- 4.1; ExAmen: 54.4 +/- 3.6, p < 0.05). When the ovulatory women were further divided into those with normal steroid production (ExOvul subgroup) and those with a suppressed progesterone luteal phase environment (ExLPD), both the ExOvul (51.9 +/- 5.4 IU/l) subgroup and ExAmen group had higher serum CK activity (p < 0.05) than the ExLPD (36.6 +/- 5.2 IU/l) subjects or the sedentary controls. CONCLUSIONS: These data demonstrate the complex association between ovarian hormone status and the normal serum CK response to regular mechanical stress imposed by chronic exercise training.     

Specific glycanforms of type IX collagen accumulate in embryonic chick sterna after 17 days of development

Type IX collagen is a key component of the extracellular matrix of cartilage where it occurs at the surfaces of type II collagen fibrils as a glycanated molecule. The function of the glycosaminoglycan (GAG) side chain of the molecule is, however, unknown. We have shown that type IX collagen in chicken sternal cartilage is synthesized with a unimodal distribution of GAG chain size, but at post 17 days of development three predominant glycanforms of type IX collagen accumulate. Such accumulation did not occur in sterna from day 15 embryos. In day 17 embryos predominant glycanforms were found in the caudal region of the sternum. By day 19 of development the three predominant glycanforms are widespread throughout the caudal and cephalic regions. The results indicate that developmental and anatomical changes occur to type IX collagen that depend on the size of the GAG chain attached to the alpha2(IX) chain of the molecule.