Yeast invertase: Subcellular distribution and possible relationship between the isoenzymes

The intracellular invertase ofSaccharomyces cerevisiae is mainly found in a soluble form (91–95%), while only minor amounts are found bound to the internal (4–8%) and plasma membranes (less than 1%). In the processes of derepression or repression, inhibition of RNA or protein synthesis, or in the presence of 2-deoxy-d-glucose, the levels of the membrane-bound and external activities are modified in a way in which their relation is clear, while the soluble enzyme does not change at all. These results, together with the fact that the membrane-bound and the external enzymes are glycoproteins, suggest a precursor-product relationship between the enzymic forms.     

Variation in sensitivity of the cardiac glycoside receptor characteristics of (Na+ + K+)-ATPase to lipolysis and temperature.

1. The rate of binding of [3H]ouabain to untreated membrane preparations of [Na+ +K+]-ATPase is a timperature--dependent process displaying a thermal transition close to 25degreesC. The apparent energies of activation which can be calculated above and below this transition are similar to, but not identical with, those previously reported for activation of the enzyme by cations. 2. Treatment of the enzyme preparation with detergents or lipolysis with phospholipase A eliminates the thermal transition resulting in linear Arrhenius plots. 3. The number of sites available for [3H]ouabain binding is not temperature dependent as the amount of [3H]ouabain bound at equillbrium is not changed between 10 and 37 degrees C. 4. Treatment of the enzyme with phospholipase A results in time-dependent changes in the number of binding sites for [3H]ouabain at equilibrium. 5. Treatment of the membrane enzyme preparations with detergents reveals additional [3H]ouabain binding sites which are extremely sensitive to lipolysis with phospholipase A. 6. There are a number of [3H]ouabain binding sites which remain resistant to lipolysis by phospholipase A in either untreated or detergent-treated membrane preparations. 7. It is suggested that [3H]ouabain binding sites exist in the membrane in at least two different environments, one of which is resistant the other sensitive to attack by phopholipase A.     

Mutants of Saccharomyces cerevisiae cell division cycle defective in cytokinesis. Biosynthesis of the cell wall and morphology

The four temperature-sensitive mutants of Saccharomyces cerevisiae in the cell division cycle defective in cytokinesis (cdc, 3, 10, 11 and 12), have been analyzed with respect to the biosynthesis of the cell wall polymers. After 3 hours of incubation at the non-permissive temperature (37°C) these strains stop growing. The synthesis of glucan, mannan and chitin (wall polymers) level off in a similar time, but glucan, mannan and chitin synthases remained active for at least 4 hours.If the mutants are analyzed by transmission and scanning electron microscopy different pictures emerge. Two of the mutants cdc 10 and cdc 12, after 3 hours of incubation at 37°C present apparently normal cytoplasms and cell wall surfaces with multiple elongated buds. The other two mutants, cdc 3 and cdc 11, present a completely disarranged cytoplasmic content and damage at the level of the plasma membrane is evident.These and other observations, suggest that between the execution points of cdc 3 (0.27) and cdc 10 (0.58), essential processes in the assembly of cell membrane occur.This work was supported in part by a grant from la Comisión de Investigación Científica y Técnica of the Spanish Ministerio de Educación y Ciencia (Project no. 4593-1980).     

Scanning electron microscopy of Setaria cervi adult male worms

Scanning electron microscopy studies of adult Setaria cervi male worms showed the presence of horn-like lateral appendages and characteristic striated bands on the ventral side of the tail. All other features were indistinguishable from other members of the genus Setaria.     

Amblyomma americanum: characterization of salivary prostaglandins E2 and F2 alpha by RP-HPLC/bioassay and gas chromatography-mass spectrometry.

Secretagogue-induced saliva of the tick, Amblyomma americanum (L.) was fractionated by reversed-phase-high-performance liquid chromatography (RP-HPLC) and bioassayed in smooth muscle preparations. Material with retention times of authentic prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) were found to cause contraction of preparations of rat colon and rat stomach strips. Gas chromatography-mass spectra of selected ions of both HPLC-purified fractions confirmed the existence of PGE2 and PGF2 alpha. Bioassay of individual samples obtained from ticks stimulated to salivate with pilocarpine, dopamine + theophiline, or dopamine + theophiline + GABA indicated that all these secretagogues induced similar amounts of prostaglandin secretion, averaging 469 ng PGE2/ml. These pharmacological doses of prostaglandin are hypothesized to assist in tick feeding by inducing vasodilation and/or other pharmacological events in their hosts.     

Effect of hydrogen sulfide on growth of sulfate reducing bacteria

A culture of sulfate reducing bacteria (SRB) growing on lactate and sulfate was incubated at different pH values in the range of 5.8-7.0. The effect of pH on growth rate was determined in this pH range; the highest growth rate was observed at pH 6.7. Hydrogen sulfide produced from sulfate reduction was found to have a direct and reversible toxicity effect on the SRB. A hydrogen sulfide Concentration of 547 mg/L (16.1 mM) completely inhibited the culture growth. Comparison between acetic acid and hydrogen sulfide inhibition is presented and the concomitant inhibition kinetics are mathematically described. (c) 1992 John Wiley & Sons, Inc.     

Immunocytochemical identification of neuroendocrine markers in human cardiac paraganglion — like structures

Summary Paraganglion-like structures (PLS) containing chromaffin-positive cells have been reported to be present in the adult human heart. The present work was initiated in order to evaluate the densitity of these structures in the interatrial septum and to study the presence of immunoreactivity of their cells to NSE and PGP 9,5 antibodies, two neuroendocrine markers. Six hundred 6-m paraffin serial sections were obtained from the upper third of the interatrial septum from six adult human hearts. From 2 to 12 paraganglia were found in each case, and their principal cells stained positively with NSE and PGP 9,5 antibodies. Depending on how these PLS related to other cardiac structures, four different types were identified: Type I — True paraganglia (located adjacent to ganglia or nerve fibers); Type II — Free paraganglia (immersed in the interatrial adipose tissue, without evident connection to other structures); Type III — Intraganglionic paraganglia (located within the nervous ganglia); Type IV — Intramyocardic paraganglia (small nests of immunoreactive cells closely related to myocardiocyte bundles). These cardiac paraganglia, which probably belong to the visceral-autonomic group, may have a role in the regulation of the cardiac function and in the adaptive mechanisms of the heart. Its is also possible that they originate functioning and non-functioning tumours.Work supported by grants from FINEP and CNPq (Brazil)     

The steroid antagonist RU38486 is metabolized by the liver microsomal P450 mono-oxygenases

Microsomal preparations from adult male rat liver actively oxidized RU38486 into the 11 beta-monodemethylated, 11 beta-didemethylated and 17 alpha-hydroxylated derivatives, metabolites which are known to be formed in vivo. These oxidative reactions were inhibited at different degrees by P450 chemical inhibitors. Pretreatment of the animals by P450 mono-oxygenase prototype inducers led to drastic changes in RU38486 metabolization. Methylcholanthrene treatment carried out a significant decrease while phenobarbital markedly increased the metabolic activity of the liver microsomes. Moreover, antibodies to methylcholantrene-inducible P450 forms did not affect the metabolic activity while a complete blockade-of RU38486 oxidation was observed in the presence of antibodies to phenobarbital- inducible forms. The present results demonstrate that liver P450 mono-oxygenases are engaged in different oxidative steps of RU38486 metabolism and that phenobarbital-inducible but not methylcholanthrene-inducible P450 forms are active in RU38486 degradation.     

The bull shark (Carcharhinus leucas) and largetooth sash (Pristis perotteti) in Lake Bayano,a tropical man-made impoundment in Panama

Synopsis The Río Bayano in eastern Panama is one of many tropical rivers in which bull sharks (Carcharhinus leucas) and largetooth sawfish (Pristis perotteti) have been known to occur. Since both species can osmoregulate in fresh water throughout life, theoretically, both could survive in landlocked situations for many years.P. perotteti reproduces in fresh water, butC. leucas ordinarily does not, so only the former would appear to have the potential for establishing a breeding stock in such a landlocked freshwater body.The damming of the Rio Bayano and the creation of a large impoundment in 1976 provides a test of the ability of members of both species trapped there to survive and to establish breeding stocks. In 1980 and 1981 three mature femaleC. leucas were found dead in Lake Bayano and three sub-adult femaleP. perotteti were taken by trammel net. These events confirm the ability of both to survive in fresh water for long periods, but the establishment of breeding stocks appears doubtful and the question may not be answered for many years.     

Determination of 3-methoxy-4-hydroxyphenylglycol in urine by high-performance liquid chromatography with amperometric detection

A reversed-phase high-performance liquid chromatographic method has been used for the quantitative determination of 3-methoxy-4-hydroxyphenylglycol (MHPG) in urine. After incubation with glusulase, free MHPG is extracted into ethyl acetate and further isolated by a combination of thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). The addition of amperometric detection provides increased sensitivity to a highly specific assay.