Characterization of Mycobacterium montefiorense sp. nov., a novel pathogenic Mycobacterium from moray eels that is related to Mycobacterium triplex

The characterization of a novel Mycobacterium sp. isolated from granulomatous skin lesions of moray eels is reported. Analysis of the hsp65 gene, small-subunit rRNA gene, rRNA spacer region, and phenotypic characteristics demonstrate that this organism is distinct from its closest genetic match, Mycobacterium triplex, and it has been named M. montefiorense sp. nov.     

Genes for glycosylphosphatidylinositol toxin biosynthesis in Plasmodium falciparum

About 2.5 million people die of Plasmodium falciparum malaria every year. Fatalities are associated with systemic and organ-specific inflammation initiated by a parasite toxin. Recent studies show that glycosylphosphatidylinositol (GPI) functions as the dominant parasite toxin in the context of infection. GPIs also serve as membrane anchors for several of the most important surface antigens of parasite invasive stages. GPI anchoring is a complex posttranslational modification produced through the coordinated action of a multicomponent biosynthetic pathway. Here we present eight new genes of P. falciparum selected for encoding homologs of proteins essential for GPI synthesis: PIG-A, PIG-B, PIG-M, PIG-O, GPI1, GPI8, GAA-1, and DPM1. We describe the experimentally verified mRNA and predicted amino acid sequences and in situ localization of the gene products to the parasite endoplasmic reticulum. Moreover, we show preliminary evidence for the PIG-L and PIG-C genes. The biosynthetic pathway of the malaria parasite GPI offers potential targets for drug development and may be useful for studying parasite cell biology and the molecular basis for the pathophysiology of parasitic diseases.     

Effects of Purified Staphylococcal Alpha Toxin on the Ultrastructure of Human and Rabbit Erythrocytes

Previous studies have suggested that the primary site of action of purified staphylococcal alpha toxin is the cell membrane. Scanning and transmission electron microscopy studies were undertaken, therefore, to define toxin-induced alterations in the surface morphology of rabbit and human red blood cells. During the prelytic lag phase, scanning electron microscopy revealed multiple discrete blisters on the surface of rabbit red blood cells; during hemolysis, cellular collapse and ghosts were seen, but most striking was the separation of large fragments of cell membrane from red blood cell surfaces. In contrast, alterations in less sensitive human red blood cells were limited to occasional fingerlike protrusions during the period of accelerated lysis. Transmission electron microscopy substantiated these changes. These studies have provided further evidence that the cell membrane is the primary site of action of staphylococcal alpha toxin.     

Subarachnoid hemorrhage in the African-American population: a cooperative study.

The clinical outcome of patients following subarachnoid hemorrhage is complicated by delayed cerebral ischemia and contributing factors such as hypertension. To observe the impact of hypertension and delayed cerebral ischemia on the outcome of a predominantly African-American cohort following subarachnoid hemorrhage, both retrospective (n = 42) and prospective (n = 21) studies were conducted. In the total pool (n = 63), the mean age was 49.7 years (range: 17 to 80) with a preponderance of female patients (70%). Aneurysm formation was significant in the region of the posterior communicating artery. Of the patients reviewed, 73.8% had preexisting hypertension and 45.9% developed delayed cerebral ischemia. Approximately 89% of the patients who suffered from delayed cerebral ischemia had hypertension. Results failed to display any significant beneficial association between the use of the calcium channel blocker nimodipine and delayed cerebral ischemia. Use of the antifibrinolytic drug aminocaproic acid demonstrated a worse patient outcome. It is not recommended that aminocaproic acid be used in this population. Subsequently, due to the proportional occurrence of delayed cerebral ischemia in hypertensive patients following subarachnoid hemorrhage, it is suggested that prophylactic surgical management of unruptured intracranial aneurysms be considered in hypertensive patients. Further study is needed to discern the association between hypertension, delayed cerebral ischemia, and stroke in patients following subarachnoid hemorrhage.     

Intracellular calcium changes in rat aortic smooth muscle cells in response to fluid flow

Vascular smooth muscle cells (VSM) are normally exposed to transmural fluid flow shear stresses, and after vascular injury, blood flow shear stresses are imposed upon them. Since Ca²⁺ is a ubiquitous intracellular signaling molecule, we examined the effects of fluid flow on intracellular Ca²⁺ concentration in rat aortic smooth muscle cells to assess VSM responsiveness to shear stress. Cells loaded with fura 2 were exposed to steady flow shear stress levels of 0.5–10.0 dyn/cm² in a parallel-plate flow chamber. The percentage of cells displaying a rise in cytosolic Ca²⁺ ion concentration ([Ca²⁺]_i) increased in response to increasing flow, but there was no effect of flow on the ([Ca²⁺]_i) amplitude of responding cells. Addition of Gd³⁺ (10 M) or thapsigargin (50 nM) significantly reduced the percentage of cells responding and the response amplitude, suggesting that influx of Ca²⁺ through ion channels and release from intracellular stores contribute to the rise in ([Ca²⁺]_i) in response to flow. The addition of nifedipine (1 or 10 M) or ryanodine (10 M) also significantly reduced the response amplitude, further defining the role of ion channels and intracellular stores in the Ca²⁺ response. © 2002 Biomedical Engineering Society. PAC2002: 8716Uv, 8719Uv, 8716Dg, 8719Ff     

Association of EGFR Gene Amplification and CDKN2 (p16/MTS1) Gene Deletion in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) can be divided into genetic subsets: approximately one-third of GBM, primarily in older adults, have EGFR amplification; another one-third, primarily in younger adults, have TP53 mutation. The majority of GBM also have homozygous deletions of the CDKN2 (p16/MTS1) gene, resulting in cell cycle deregulation and elevated proliferation indices. We evaluated the relationship between CDKN2 deletions and the GBM subsets as defined by EGFR amplification or TP53 mutation in 70 GBM. Twenty-eight cases (40%) had EGFR amplification, 21 (30%) had TP53 mutation, and 21 (30%) had neither change. CDKN2 deletions were present in 36 (51%) GBM. Of the 28 GBM with EGFR amplification, 20 (71%) had CDKN2 deletion (p = 0.0078). The remaining 16 cases with CDKN2 loss were divided between GBM with TP53 mutations (6 cases) and GBM with neither EGFR amplification nor TP53 mutation (10 cases). Thus, CDKN2 deletions occur twice as commonly in GBM with EGFR amplification (71%) than in GBM with TP53 mutation (29%). CDKN2 deletions occurred in GBM from patients somewhat older than those patients with GBM lacking CDKN2 deletion (mean age 53 vs. 48 years). Specifically among GBM with EGFR amplification, those with CDKN2 deletions also occurred in patients slightly older than those few GBM without CDKN2 deletions (mean age 55 vs. 51 years). The presence of CDKN2 deletions in most GBM with EGFR amplification and in generally older patients may provide one explanation for the potentially more aggressive nature of such tumors.     

Isolation of mutants of CHO cells resistant to 6(p-hydroxyphenylazo)-uracil I. A novel BrdU cross-resistant phenotype

Three classes of mutants resistant to the drug 6(p-hydroxyphenylazo)-uracil have been isolated from mutagenized cultures of CHO cells. One class of these mutants designated HPU ^R A exhibits a unique form of cross-resistance to bromodeoxyuridine in that it is resistant to this drug only in the presence of thymidine. The molecular basis of the BrdU resistance is unknown but does not appear to involve the known targets of the drug. An interesting feature of these mutants is that they give rise, at a high frequency, to a subpopulation of cells which are much more resistant to BrdU.