27Al-NMR studies of aluminum transport across yeast cell membranes

Aluminum (Al) transport across yeast cells was studied using Dy(NO3)3 as a shift reagent by 27Al-NMR spectroscopy. The results showed that (a) Al enters the yeast cells at 15 min and over a period of time, within 4 h, an equilibrium sets in between outside and inside Al; (b) citrate does not favor Al going into the yeast cells at pH 5.0; and (c) EDTA brings out all the Al that has entered the yeast cells.     

The changing role of village health volunteers in northeast Thailand: an ethnographic field study

Aspergillus sinusitis is an uncommon complication of advanced human immunodeficiency virus (HIV) infection. We describe 2 patients with AIDS who developed histologically proven invasive Aspergillus sinusitis. We also review the findings of 14 histologically documented and 5 probable cases of invasive Aspergillus sinusitis. The literature on the prevalence, predisposing factors, diagnosis, treatment, and prognosis of the infection is reviewed. Major risk factors for the disease are advanced AIDS, chronic sinusitis or otitis, neutropenia, use of corticosteroids and prolonged use of broad spectrum antibiotics. The most common presenting symptoms are nonspecific and include fever, local pain, and swelling. Despite the newer diagnostic and therapeutic approaches discussed herein, the infection is usually fatal in HIV-infected patients. Early diagnosis and aggressive treatment remain the only available means to improve the currently dismal prognosis of Aspergillus sinusitis.     

Free and combined sterols ofPavlova gyrans

Pavlova gyrans, a unicellular alga of interest as food for oysters, was cultured axenically and examined for sterol composition. Desmethyl monohydroxy sterols, which are frequently seen in algae, made up 40% of the total sterols and were observed primarily in the free sterol fraction. The principal sterols of this group were 5-ergostenol, poriferasterol, and clionasterol, as well as some poriferast-22-enol and poriferastanol. Several “methyl” sterols with unusual structures made up 27% of the total sterols. The principal “methyl sterols” were 4α-methyl ergostanol, 4α-methyl poriferastanol, and 4α-methyl poriferast-22-enol. Methyl sterols were found primarily in the ester fraction. Also observed was a new class of dihydroxysterols composing 33% of the total sterols. These sterols are structurally related to the methyl and desmethyl sterols ofPavlova but contain an extra nuclear hydroxyl which can be acetylated when present on a desmethyl sterol, but which is nonreactive with acetic anhydride in 4α-methyl sterols. None of these sterols were observed in ester form but are concentrated in the acid-hydrolyzable, bound fraction. The unique nature of these sterols suggests potential taxonomic utility. Based on a paper presented at the Symposium on Plant and Fungal Sterols: Biosynthesis, Metabolism and Function, held at the AOCS Annual Meeting, Baltimore, MD, April 1990.     

Skeletal muscle myosin heavy chain synthesis in type 1 diabetes

Although insulin's anticatabolic effect on protein metabolism in type 1 diabetes has been clearly shown to be related to the inhibition of protein breakdown, insulin's effect on muscle protein synthesis remains controversial. Cross-limb studies and measurements of synthesis rates of mixed muscle protein have yielded conflicting results. These measurements represent the mean synthesis of several muscle proteins and may miss changes in the synthesis rates of individual muscle proteins. We measured the fractional synthesis rates of myosin heavy chain (MHC), the principal muscle contractile protein, and mixed muscle protein (MMP) in six type 1 diabetic patients during insulin deprivation and insulin treatment. Comparisons were made with six healthy control subjects. Muscle biopsies were taken at 2 h and 8 h during a primed continuous infusion of L-[1-13C]leucine. MHC was purified by a preparative continuous elution gel electrophoresis, and fractional synthesis rates were calculated. We found that in type 1 diabetic subjects, the fractional synthesis rates of MHC and MMP during insulin treatment are similar to those of control subjects. Acute insulin deprivation did not affect either the synthesis rate or the ratio of MHC to MMP in type 1 diabetic subjects. In the postabsorptive state, acute insulin deprivation has no effect on MHC or MMP synthesis in type 1 diabetic patients.     

A new anthracycline antibiotic, IT-62-B, converts the morphology of ras-transformed cells back to normal: taxonomy, fermentation, isolation, structure elucidation and biological characterization

beta-(2-Hydroxyethoxy)-5 alpha-cholest-8(14)-en-15-one, a synthetic inhibitor of cholesterol biosynthesis, was shown to exhibit a high affinity to oxysterol binding protein. This was proved by ultracentrifugation of the protein fraction from rabbit liver in the presence of the 3H-labeled inhibitor, 3 beta-(2-hydroxy-2-[3H]ethoxy)-5 alpha-cholest-8(14)-en-15-one, or by the substitution of the [3H]-25-hydroxycholesterol in its complex with the oxysterol binding protein. In human hepatoma Hep G2 cells, the inhibitor decreased activity of 3-hydroxy-3-methylglutaryl CoA reductase [ID50 (2.7 +/- 0.7) x 10(-5) M] and was transformed into 3 beta-[2-(9-Z-octadecenoyloxy)ethoxy]-5 alpha-cholest-8(14)-en-15-one.     

Epithelial folding in vitro: studies on the cellular mechanism underlying evagination of thyrocyte monolayers

Epithelial monolayers in suspension culture fold in a way which closely resembles epithelial evagination. We have used freshly isolated segments of porcine thyroid follicles to study the mechanism underlying this evagination process. Epithelial folding was accompanied by dramatic changes in cell shape: the cells elongated and apical cell surfaces widened, whereas the basal cell portions were narrowed to about 20% of their original width. Apparently, enzymatic separation of thyroid epithelial cells from their underlying extracellular matrix resulted in an extension of the lateral cell-cell interactions on the expense of the basal cell surface area. Epithelial folding in vitro was Ca2+ dependent and reversibly blocked by cytochalasin D, by which the reorganization of the F-actin network was disturbed. This inhibitory effect was also observed by the action of cAMP analogues known to cause rounding of cells by their effect on cortical F-actin. Moreover, evagination in vitro was reversibly blocked at intracellular pH values of 5.8 and below. Under these conditions, protein phosphorylation was entirely inhibited. Inhibitors of protein kinases, specifically of myosin light chain kinase, were able to disrupt the evagination process, suggesting that protein phosphorylation, presumably of the myosin light chain, was essential for folding. We conclude that enzymatic separation of epithelial monolayers from their extracellular matrix initiated a cascade consisting of extended cell-cell interactions of the lateral plasma membranes and of reorganization of the apical actin-myosin network, finally resulting in profound changes in cell shape characteristic of epithelial evagination.     

A role for oestrogens in the male reproductive system

Oestrogen is considered to be the 'female' hormone, whereas testosterone is considered the 'male' hormone. However, both hormones are present in both sexes. Thus sexual distinctions are not qualitative differences, but rather result from quantitative divergence in hormone concentrations and differential expressions of steroid hormone receptors. In males, oestrogen is present in low concentrations in blood, but can be extraordinarily high in semen, and as high as 250 pg ml(-1) in rete testis fluids, which is higher than serum oestradiol in the female. It is well known that male reproductive tissues express oestrogen receptors, but the role of oestrogen in male reproduction has remained unclear. Here we provide evidence of a physiological role for oestrogen in male reproductive organs. We show that oestrogen regulates the reabsorption of luminal fluid in the head of the epididymis. Disruption of this essential function causes sperm to enter the epididymis diluted, rather than concentrated, resulting in infertility. This finding raises further concern over the potential direct effects of environmental oestrogens on male reproduction and reported declines in human sperm counts.     

Impedance of a goat eye lens

Cyclins are essential proteins in cell cycle control, and their deranged expression has been reported to be associated with malignant transformation. Involvement of cyclins in the development of endometrioid carcinomas of the endometrium was studied immunohistochemically using antibodies against both cyclin A and tumor suppressor gene product p53, and their expression was compared with that of Ki-67 antigen. Sixty-two cases of endometrial endometrioid carcinoma and 20 cases of normal endometrium (10 proliferative and 10 secretory phase) were examined. Of the 62 endometrioid carcinomas, atrophic endometrium and hyperplasia were found adjacent to the cancers in 30 and 19 cases respectively. Cyclin A was expressed in < 1% of the glandular cells of normal endometrium in the proliferative phase and in hyperplasia, but was negligible in normal secretory phase and atrophic endometrium. p53 was almost always negative in normal endometrium and hyperplasia. Of the 62 endometrioid carcinomas, 12 tumors (19.4%) overexpressed cyclin A and 21 tumors (33.8%) overexpressed p53 (positive cells > 1%). Cyclin A and p53 were more frequently expressed in poorly differentiated tumors than in well differentiated tumors (cyclin A, p = 0.002; p53, p = 0.016). In addition, cyclin A-positive cells were topographically related to those cells positive for p53 as well as Ki-67. In conclusion, the abnormal expression of cyclin A and p53 is associated with high-grade endometrial endometrioid carcinomas.     

Homologous recombination of a flanking repeat gene cluster is a mechanism for a common contiguous gene deletion syndrome

Smith-Magenis syndrome (SMS), caused by del(17)p11.2, represents one of the most frequently observed human microdeletion syndromes. We have identified three copies of a low-copy-number repeat (SMS-REPs) located within and flanking the SMS common deletion region and show that SMS-REP represents a repeated gene cluster. We have isolated a corresponding cDNA clone that identifies a novel junction fragment from 29 unrelated SMS patients and a different-sized junction fragment from a patient with dup(17)p11.2. Our results suggest that homologous recombination of a flanking repeat gene cluster is a mechanism for this common microdeletion syndrome.