A chloramphenicol-streptomycin-resistance plasmid from a clinical strain of Staphylococcus sciuri and its structural relationships to other staphylococcal resistance plasmids

A 5.1-kb plasmid, designated pSCS12, isolated from a naturally occurring Staphylococcus sciuri conferred resistance to chloramphenicol (CmR) and streptomycin (SmR). Restriction endonuclease analyses of pSCS12 revealed partial structural homologies to the CmR-plasmids pC221 from S. aureus and pSCS1 from S. intermedius, to the SmR-plasmids pSAI-1 from S. hyicus and pS194 from S. aureus, as well as to the CmR/SmR plasmid pSK68 from S. aureus. Southern-blot hybridization with specific CmR- and SmR-gene probes confirmed these similarities and allowed the mapping of the CmR- and SmR-determinants in the S. sciuri plasmid pSCS12. These observations lead to the suggestion that CmR/SmR-plasmids, such as pSCS12, may have evolved from CmR- and SmR-plasmids by interplasmidic recombination.     

Delta 5-3 beta-hydroxysteroid dehydrogenase, succinate dehydrogenase and glucose-6-phosphate dehydrogenase in the bovine corpus luteum of estrous cycle: a quantitative histochemical study

Genital organs and blood were obtained from dairy cows at a local abattoir. 3 recently ovulated follicles and 20 corpora lutea of estrous cycle (CLC) were used for the quantitative enzyme histochemical demonstration of delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta-OHSDH), succinate dehydrogenase (SDH) and glucose-6-phosphate dehydrogenase (G-6-PDH) activity, employing a computerized microscope photometer. Progesterone was determined in blood serum by radioimmunoassay. Luteal tissue was grouped into several stages of development according to micromorphological criteria. Activities per volume unit of 3 beta-OHSDH and SDH in large luteal cells (LLC), as well as in small luteal cells (SLC), and luteal tissue (LT), relative amounts of the 3 beta-OHSDH-positive tissue fraction (PLCC), and progesterone concentrations in blood serum exhibited a significant pattern corresponding to the morphological development of the endocrine gland. G-6-PDH showed an increase in activity per volume unit during tissue development lasting until the beginning of regressive changes, and as significant in LLC and LT. Activities per volume unit of 3 beta-OHSDH (p less than or equal to 0.001) and SDH (p less than or equal to 0.01) were higher in LLC than in SLC, indicating superior steroidogenic capacities, while G-6-PDH activity was distinctly higher in the latter (p less than or equal to 0.001). Almost all parameters tested were correlated positively. 3 beta-OHSDH and SDH exhibited a significantly positive correlation in LLC (p less than or equal to 0.01) and LT (p less than or equal to 0.001) during periods of measureable progesterone secretion. In SLC this correlation was nonsignificant (p greater than 0.05). G-6-PDH showed a relative poor correlation to 3 beta-OHSDH (LLC, p less than or equal to 0.05; LT, p less than or equal to 0.01) and SDH (LT, p less than or equal to 0.05). Enzyme activities in LLC as well as in SLC were generally positively correlated (p less than or equal to 0.001). All enzymes tested exhibited a significantly positive correlation with progesterone concentrations in blood serum. This was significant for SDH only during measurable progesterone secretion, and less marked for G-6-PDH.     

Simian virus 40 large T antigen DNA helicase. Characterization of the ATPase-dependent DNA unwinding activity and its substrate requirements

The ATPase of SV40 large T antigen (T antigen) which is essential for the replication of SV40 minichromosomes was recently shown to be functionally related to a newly discovered DNA helicase activity. The T antigen helicase unwinds DNA duplices of several kilobase pairs in a reaction depending on the presence of hydrolyzable ribo- or deoxyribonucleoside triphosphates. The in vitro rate of movement through duplex DNA was found to be about 100 base pairs/min at 37 degrees C. For DNA unwinding, T antigen requires a 3'-single strand extension of a partially double-stranded substrate and invades the double strand section processively, in a 3' to 5' direction. The minimum length of the single-stranded tail was determined to be less than 5 nucleotides. Unwinding studies in the presence of the Escherichia coli single strand-specific DNA-binding protein and competition experiments indicate that T antigen helicase binds preferentially at the single-stranded/double-stranded DNA junction. This DNA structure is therefore proposed to serve as an entry site for the T antigen helicase. Previously reported data suggest that T antigen is the replicative helicase of the SV40 minichromosome. The results presented here are consistent with these findings and imply that T antigen migrates actively and processively along the template for the leading strand.     

Effects of ethinyl estradiol on intestinal membrane structure and function in the rabbit

Structural and functional properties of the small intestinal microvillus membrane were evaluated in the rabbit after administration of ethinyl estradiol, a synthetic estrogen with a demonstrated propensity to alter hepatic membrane lipid fluidity, and promote cholestasis. In the jejunum, no estrogen-induced changes in microvillus membrane total lipid, cholesterol or phospholipid content were observed. However, the ileal microvillus membrane in estradiol-treated animals demonstrates significant reductions vs. controls (per mg protein) in total lipid (0.55 milligrams vs. 0.89 milligrams) [corrected] and phospholipid (206.7 micrograms vs. 304.91 micrograms) (p less than 0.001) content, as well as modifications in specific phospholipid species. The increase in the ileal microvillus membrane cholesterol: phospholipid molar ratio (0.65 vs. 0.51, p less than 0.05) was associated with a significant decrease in membrane lipid fluidity reflected by an increase in fluorescence anisotropy measurements utilizing diphenyl hexatriene as the fluorophore (r at 25 degrees C = 0.306 vs. 0.282, p less than 0.05). Thermotropic lipid phase transitions, assessed by Arrhenius plots of both fluorescence data and ileal microvillus membrane p-nitrophenylphosphatase activity demonstrate that phase changes occur between and 24 and 28 degrees C in both treated and untreated groups. Within the temperature range studied (40-10 degrees C) no differences from control were observed in microvillus membrane alkaline phosphatase activity following estrogen treatment. These data therefore indicate that ethinyl estradiol-induced effects on microvillus membrane lipid composition and physical properties occur predominantly in the ileum and appear to be related, in part, to specific alterations in the availability of phospholipid following estrogen treatment.     

Behavioral treatment of irritable bowel syndrome: A 1-year follow-up study

Sixteen clients afflicted with irritable bowel syndrome (IBS) were reassessed 1 year following completion of a multicomponent treatment package incorporating progressive muscle relaxation, thermal biofeedback, cognitive therapy, and IBS education. For the 14 patients who kept a 2-week symptom diary, significant reductions in ratings of abdominal pain and tenderness, diarrhea, and flatulence were obtained comparing pretreatment and follow-up symptom-diary ratings. Eleven of 14 clients were improved over pretreatment levels, 57% met the criteria for clinical improvement of at least a 50% reduction in major symptom scores, and all but 1 of 16 rated themselves as subjectively improved.     

Desensitization of mouse Leydig cells in vivo: evidence for the depletion of cellular cholesterol

The study presents a characterization of the refractory state in purified mouse Leydig cells desensitized by a single injection of human chorionic gonadotropin (hCG) in vivo. The treatment of mice with 1 microgram hCG i.p. for 48 h followed by Leydig cell isolation and purification resulted in a decrease in the maxima of hCG-induced cAMP accumulation and testosterone production by approximately 70% and approximately 55%, respectively, when compared to cells of control mice. Despite a 55% reduction in 125I-hCG binding sites, the sensitivity of stimulation was not changed. The refractoriness in testosterone production in vitro was also present when the Leydig cells were stimulated with cholera toxin or dibutyryl cAMP; however, it was not observed when testosterone production was induced by the addition of pregnenolone or 20 alpha- and 22(R)-hydroxycholesterol. Mouse lipoproteins, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) in natural composition, were also able to overcome the steroidogenic block (although not always completely). On the basis of the cholesterol content of the lipoproteins, the two classes were similarly effective. They increased maximal hCG-induced testosterone production not only in desensitized cells, but also in control cells (by 80-100%), whereas their effect on basal testosterone production was negligible. In desensitized cells from hCG-treated mice (2 micrograms i.p., 48 h) cellular unesterified and esterified cholesterol were decreased by 21% and 81%, respectively, when compared to control cells. This loss occurred in the face of unchanged plasma cholesterol levels. In conclusion, our data indicate that the impaired steroidogenesis in mouse Leydig cells desensitized in vivo by a single injection of hCG is the result of a depletion in cellular cholesterol, rather than of an impaired conversion of cholesterol to testosterone.     

Amino acid sequence of Manduca sexta adipokinetic hormone elucidated by combined fast atom bombardment (FAB)/tandem mass spectrometry

Combination of Fast Atom Bombardment Tandem Mass Spectrometry with Amino Acid Analysis assigns the amino acid sequence of the Manduca sexta adipokinetic hormone as pGlu-Leu-Thr-Phe-Thr-Ser-Ser-Trp-GlyNH2. Similarities and differences with other invertebrate hormones and with mammalian glucagon are discussed.     

Microsome- and hepatocyte-mediated mutagenicity of hydroxyurea and related aliphatic hydroxamic acids in V79 Chinese hamster cells

The potential of N-hydroxyurea to induce gene mutations in V79 Chinese hamster cells was investigated. Upon metabolic activation by liver microsomes from phenobarbital-treated rats or by isolated rat hepatocytes co-cultured with the V79 cells, hydroxyurea caused a concentration-dependent increase in the frequency of HGPRT-deficient mutants. Hydroxyurea was not mutagenic in the absence of metabolic activation. Addition of catalase inhibited microsome-mediated mutagenicity, indicating that hydrogen peroxide was involved in the formation of the mutagenic DNA lesion. Acetohydroxamic acid and N-hydroxyurethane also induced hepatocyte-mediated mutagenicity, suggesting that the potential to elicit metabolism-dependent mutagenicity may be a common property of aliphatic hydroxamic acids.     

Irreversible binding to the receptor of bacteriophages T5 and BF23 does not occur with the tip of the tail.

Treatment of purified tails of bacteriophage T5 with 0.05% sodium dodecyl sulfate specifically removed pb2, a protein of 108,000 molecular weight (108K), from the tail. Although these tails were devoid of the single straight tail fiber, they still inhibited adsorption of T5 to Escherichia coli cells. Reconstitution of these tails with pb2 increased the efficiency of inhibition of T5 adsorption. Treatment of tails with 0.1% sodium dodecyl sulfate removed, in addition to pb2, a protein of 67K from phage T5 and one of 60K from phage BF23. These tails failed to inhibit phage adsorption, and no reconstitution was achieved. Reconstitution of T5 tails with pb2 from BF23, and of BF23 tails with pb2 from T5, did not alter the host receptor specificity of the tails. Binding of untreated T5 tails to small FhuA receptor particles revealed that binding occurred with the conical part of the tail and that pb2 was most likely released from the tail upon binding. From these results and from recent observations with T5-BF23 hybrid phages (K.J. Heller, Virology 139:11-21, 1984), we conclude that the receptor-binding proteins of T5 and BF23 are the 67K and 60K proteins, respectively, and that they are not located at the tip of the tail but rather at or near the site where the straight tail fiber is attached to the conical part of the tail.