Rotational asymmetry of Escherichia coli flagellar motor in the presence of arsenate.

The flagellar motor of Escherichia coli (E. coli) is driven by a proton-motive force (PMF), hence it was of interest to determine whether the motor is symmetrical in the sense that it can be rotated by any polarity of PMF. For this purpose the cells had to be deenergized first. Conventional deenergization procedures caused irreversible loss of motility, presumably due to ATP-dependent degradative processes. However, E. coli cells deenergized by incubation with arsenate manifested a slow, reversible depletion of PMF. In this procedure there was a sufficiently long time window, during which a considerable proportion of the cells lost their motility and could be made to rotate again by an artificially-imposed PMF. The motors of these cells rotated in response to any PMF polarity, but positive and negative polarities rotated different sub-populations of cells and the direction was almost exclusively counterclockwise. The reason for the unidirectionality of the rotation was not the intervention of the chemotaxis system. A number of potential reasons are suggested. One is the arsenate effect on the motor function found previously [Margolin, Y., Barak, R. and Eisenbach, M. (1994) J. Bacteriol. 176, 5547-5549]. A possible interaction between arsenate and the motor is discussed.

Arsenate arrests flagellar rotation in cytoplasm-free envelopes of bacteria.

The effect of arsenate on flagellar rotation in cytoplasm-free flagellated envelopes of Escherichia coli and Salmonella typhimurium was investigated. Flagellar rotation ceased as soon as the envelopes were exposed to arsenate. Inclusion of phosphate intracellularly (but not extracellular) prevented the inhibition by arsenate. In a parallel experiment, the rotation was not affected by inclusion of an ATP trap (hexokinase and glucose) within the envelopes. It is concluded that arsenate affects the motor in a way other than reversible deenergization. This may be an irreversible damage to the cell or direct inhibition of the motor by arsenate. The latter possibility suggests that a process of phosphorylation or phosphate binding is involved in the motor function.

Mechanisms for the antigonadotropic action of the ovarian gonadotropin-releasing hormone-binding inhibitor protein/histone H2A on ovarian cells.

A GnRH-binding inhibitor (GnRH-BI) was recently purified from bovine ovaries. On the basis of amino acid composition and partial sequence analysis this antigonadotropic GnRH-BI was identified as histone H2A. In the present study the mechanism for the antigonadotropic action of histone H2A was examined and compared to that of GnRH and poly-L-lysine. The potential sites examined were the receptor-coupled pathway of second message synthesis including receptor binding of hormone, G protein activation, and adenylyl cyclase activation. Histone H2A inhibited (ID50 = 2 microM) the binding of hCG by membrane receptors from luteinized rat ovaries in a noncompetitive and dose-dependent manner. The binding of FSH by membrane receptors from immature rat ovaries was not inhibited by histone H2A. Binding of GnRH by pituitary membrane receptors was inhibited by histone H2A, and the ID50 of 8 microM was similar to that previously observed for GnRH binding sites in rat ovarian membranes. No high-affinity binding of histone H2A by rat ovarian membranes was detected. Near-maximal doses of histone H2A (7 microM), poly-L-lysine (10 microM), and GnRH (1 microM) inhibited LH-stimulated cAMP production in isolated rat luteal cells. Inhibition by H2A and poly-L-lysine was larger than by GnRH. Furthermore, histone H2A and poly-L-lysine inhibited cholera toxin (CT)-stimulated cAMP production, but GnRH did not. Like GnRH, neither histone H2A nor poly-L-lysine inhibited forskolin (FK)-stimulated cAMP production. In isolated rat granulosa cells, histone H2A and poly-L-lysine inhibited FSH-, CT-, and FK-stimulated cAMP production.(ABSTRACT TRUNCATED AT 250 WORDS)

[Substance abuse among mental patients].

Abuse of alcohol and other drugs by mental patients has been reported extensively in the past decade, especially in the USA. It has seemed to us that drug abuse has become more common among mental patients treated at this psychiatric hospital and at outpatient clinics in Jerusalem in recent years. Therefore, 100 patients admitted consecutively were questioned with regard to alcohol and drug abuse. A quarter of the male patients were diagnosed as having both a psychiatric disorder and drug abuse. Drug abuse was even more common among male schizophrenics aged 26 to 35, but only 2 reported alcohol abuse. Drugs used were mainly opiates (heroin and methadone) and hashish, and in most cases both. The results indicate that mental patients, especially young men with schizophrenia, may be another risk group for drug abuse in Israel.

Xanthine oxidase and dehydrogenase activities in rat ovarian tissues.

The production of reactive oxygen species in the ovary is rapidly inducible, but the nature of the generator is unknown. One possibility is xanthine oxidase (XO), an enzyme that produces superoxide in the presence of hypoxanthine (or xanthine) and oxygen. The objective of the present studies was to measure levels of XO in follicular and luteal tissue to determine whether XO may be a source of reactive oxygen species in the rat ovary. Ovarian levels of XO were about one-fifth of that seen in the liver and adrenal, and XO levels were about one-third of xanthine dehydrogenase (XDH). Preovulatory ovarian levels of XO activity were unchanged after induction of ovulation with gonadotropin and in follicles incubated with gonadotropin. Luteal XO activity was not changed during natural or prostaglandin F2 alpha (PGF2 alpha)-induced luteolysis. Allopurinol, an inhibitor of XO, did not inhibit ovulation or PGF2 alpha-induced luteal regression. Finally, neither catalase and superoxide dismutase nor oxypurinol altered luteal cell function in the presence of hypoxanthine. Thus, while XO is present in the ovary, it does not appear that it is a major source of reactive oxygen species in this organ.

Antigonadotropic and antisteroidogenic actions of peroxide in rat granulosa cells.

Reactive oxygen species are produced in the ovary. In luteal cells, peroxide abruptly inhibits LH-sensitive cAMP and progesterone production, and may serve a role as a mediator of luteolysis by such mechanisms. The objective of the present studies was to evaluate the acute actions of peroxide in rat granulosa cells. Peroxide at concentrations in the low micromolar range produced a marked and dose-dependent inhibition of FSH-sensitive cAMP accumulation and progesterone production, and depleted cell levels of ATP within 1 min. Longer treatment with peroxide (60 min) caused complete abrogation of the actions of FSH. Peroxide-induced depletion of ATP was prevented by 3-aminobenzamide, an inhibitor of DNA repair, but maintenance of cell levels of ATP did not prevent the anti-FSH effects of peroxide. Peroxide also abrogated cAMP accumulation and progesterone production in response to LH in granulosa cells. Unlike that seen with LH, inhibition of FSH-sensitive cyclic AMP accumulation by peroxide was partially reversed with isobutylmethyl xanthine, an inhibitor of cyclic AMP phosphodiesterase. Although peroxide inhibited cAMP accumulation in response to cholera toxin, it did not inhibit this same response to forskolin, which indicates that peroxide may interfere with G-protein-dependent activation of adenylate cyclase. Peroxide inhibited steroidogenesis in response to cholera toxin, forskolin, and 8-bromo-cAMP. The marked inhibitory actions of peroxide on gonadotropic hormone action and steroidogenesis in granulosa cells raise the possibility that peroxide may mediate events associated with loss of follicular function.

Competency for military arrest as a psychiatric problem.

Military law does not invest doctors with the authority to determine whether a soldier is competent to enter military arrest. This determination is legal in nature. Therefore, medical (or psychiatric) examination which is carried out before or within military arrest or detention, is aimed at preventing deterioration in the health of the soldier in prison. Hence, medical opinion serves only as 'credentials' of sorts. This is the formal language of the military law. In reality, the examining psychiatrist has to consider many factors, bearing in mind that his conclusions will probably become a prominent basis for the final decision on the military legal officer (whether to enforce military arrest). In order to illustrate the complicated considerations which are set forth before military psychiatrists, several case reports are presented of soldiers, who were examined in the Israel Defence Forces central psychiatric clinic for the determination of competency for military arrest.

Gonadotropin-releasing hormone binding inhibitors in the ovary.

A protein present in ovaries and other tissues of many species competitively and reversibly inhibits high affinity binding of gonadotropin-releasing hormone (GnRH) to rat ovarian membranes, but this protein is not GnRH. This protein has been partially purified and characterized from bovine ovaries. The absence of GnRH binding inhibitory (GBI) activity in plasma and follicular fluid indicates that this protein may act in a localized manner within or near its site of production or release. The bovine ovarian GBI protein evokes antigonadotropic activity in ovarian cells from both the rat and the bovine. The biological effect of GBI may occur independently of interaction with high affinity binding sites for GnRH, since these are absent from the bovine ovary. Thus, the GBI protein may abrogate gonadotropin-dependent responses in ovarian cells by mechanisms separate from interaction with GnRH receptors. A complete characterization of the GBI protein and evaluation of its mechanism of action in ovarian and pituitary cells will dictate conclusions on the physiological importance of this protein.

Voltage clamp effects on bacterial chemotaxis.

To examine whether or not sensory signaling in bacteria is by way of fluctuations in membrane potential, we studied the effect of clamping the potential on bacterial chemotaxis. The potential was clamped by valinomycin, a K+ -specific ionophore, in the presence of K+. Despite the clamped potential, sensory signaling did occur: both Escherichia coli and Bacillus subtilis cells were still excitable and adaptable under these conditions. It is concluded that signaling in the excitation and adaptation steps of chemotaxis is not by way of fluctuations in the membrane potential.

Distinction between changes in membrane potential and surface charge upon chemotactic stimulation of Escherichia coli.

Galactose and other chemotactic attractants have been shown to trigger an apparent hyperpolarization in Escherichia coli (Eisenbach, M., 1982, Biochemistry, 21:6818-6825). The probe used to measure membrane potential in that study, tetraphenylphosphonium (TPP+), may respond also to surface-charge changes in the membrane. The distinction between true changes in membrane potential and changes in the surface charge of the membrane is crucial for the study of this phenomenon in bacterial chemotaxis. To distinguish between these parameters, we compared the response to galactose with different techniques: K+ distribution in the presence of valinomycin (measured with a K+-selective electrode), TPP+ distribution (measured with a TPP+-selective electrode) at different ionic strengths, absorbance changes of bis(3-phenyl-5-oxoisoxazol-4-yl)pentamethineoxonol (oxonol V), and fluorescence changes of three probes with different mechanisms of response. All the techniques revealed stimulation by galactose of transient hyperpolarization, of comparable magnitude. This indicates the involvement of ion currents rather than alterations of local surface properties.

Treatment of benign prostatic hyperplasia with hydroxyprogesterone-caproate: placebo-controlled study.

A placebo-controlled study with progesterone compound, 17-alpha-hydroxyprogesterone 17-n-caproate (Primostat), in 39 patients with benign enlargement of the prostate is reported. Statistical analysis of the results showed no evidence of significant improvement in patients receiving hydroxyprogesterone-caproate. No evidence of an effect as compared with the placebo was found when the residual urine, prostatic size, and histologic and ultrastructural changes of the removed prostatic gland in 6 of the patients, and in the luteinizing hormone, follicle-stimulating hormone, and estrogen urine levels in 21 patients were examined. Subjective effects, when carefully analyzed, provided some beneficial evidence, however not substantiated, when the patients' mode of voiding was carefully watched. The reported beneficial subjective improvement might be attributed to the enhancement of the beta-adrenergic response by the progesterone compound of the adrenergic receptors in the posterior urethra and bladder, presumably causing relaxation of its smooth muscle. The problems associated with the choice and measurement of parameters to be used in this type of investigation are discussed, and the absolute necessity of proper controls, statistical analysis, and close follow-up of the patients is pointed out.