Ornithine Decarboxylase Exhibits Negative Thermal Modulation in the Sea Star Asterias vulgaris: Potential Regulatory Role During Temperature-Dependent Testicular Growth

The common northern sea star Asterias vulgaris is exposed to seasonal variation in temperature from -2 to 17°C. A. vulgaris exhibits an annual reproductive cycle, i.e., the testes increase slowly in size during fall and winter, and reach maximal size in early spring. Slow testicular growth in the winter has been attributed to low field temperatures. Previous studies indicate that the specific activity of ornithine decarboxylase and the levels of the polyamines putrescine, spermidine, and spermine decrease in mid-winter and increase in the spring, coincident with changes in field temperatures. Kinetic studies show that ornithine decarboxylase assayed from individuals collected in March exhibits negative thermal modulation (Km of ornithine is 0.22 mM and 0.65 mM at 15 and 0°C, respectively). Q10 values are highest at low substrate concentrations and at low temperatures. We hypothesize that during the cold winter months a decrease in the amount of ODC and an increase in the apparent Km causes polyamine synthesis to decline, leading to decreased growth and development of the testis. We suggest that thermal modulation of ODC (and polyamine synthesis) is a mechanism by which seasonal temperature fluctuations influence seasonal spermatogenesis in A. vulgaris. We further suggest that growth of various tissues in many other ectothermal invertebrates may be similarly controlled.

Histamine H3 receptor binding sites in rat brain membranes: modulations by guanine nucleotides and divalent cations

The binding of [3H](R)alpha-methylhistamine, a potent and specific agonist at histamine H3 receptors, was investigated with membranes of rat cerebral cortex. In phosphate buffer the specific binding defined with thioperamide, an H3 receptor antagonist, displayed characters of reversibility and saturability with a Bmax of approximately 30 fmol/mg protein. The KD, derived from either dissociation/association rates or saturation kinetics at equilibrium, was approximately 0.5 nM at 25 degrees C. Competition studies indicated that the binding occurred with a stereoselectivity and pharmacological specificity similar to that of functional H3 autoreceptors regulating histamine release in brain slices. However, whereas the potency of antagonists was closely similar in the two assay systems, that of agonists was approximately 10-fold higher in the binding assay. Among antagonists burimamide was the only one to compete with a pseudo-Hill coefficient significantly different from unity (nH = 0.48 +/- 0.03), indicating a possible heterogeneity among binding sites. The presence of 2.6 mM Ca2+, in a modified Krebs-Ringer medium, promoted the conversion of a larger fraction of sites into a low-affinity component with a KD of 16 nM. The presence of guanylnucleotides in the Krebs-Ringer medium with Ca2+ abolished the binding to this low-affinity component whereas in a phosphate buffer only the KD was slightly increased. It is concluded that the H3 receptor, like many other amine receptors, is coupled to its still unidentified effector system via a G-protein and regulated by Ca2+. However, unlike the latter, the H3 receptor is down-regulated by the divalent cation.

Relationship between arterial carbon dioxide and end-tidal carbon dioxide when a nasal sampling port is used

End-tidal carbon dioxide (ETCO2) values obtained from awake nonintubated patients may prove to be useful in estimating a patient's ventilatory status. This study examined the relationship between arterial carbon dioxide tension (PaCO2) and ETCO2 during the preoperative period in 20 premedicated patients undergoing various surgical procedures. ETCO2 was sampled from a 16-gauge intravenous catheter pierced through one of the two nasal oxygen prongs and measured at various oxygen flow rates (2, 4, and 6 L/min) by an on-line ETCO2 monitor with analog display. Both peak and time-averaged values for ETCO2 were recorded. The results showed that the peak ETCO2 values (mean = 38.8 mm Hg) correlated more closely with the PaCO2 values (mean = 38.8 mm Hg; correlation coefficient r = 0.76) than did the average ETCO2 values irrespective of the oxygen flow rates. The time-averaged PaCO2-ETCO2 difference was significantly greater than the PaCO2-peak ETCO2 difference (P less than 0.001). Values for subgroups within the patient population were also analyzed, and it was shown that patients with minute respiratory rates greater than 20 but less than 30 and patients age 65 years or older did not differ from the overall studied patient population with regard to PaCO2-ETCO2 difference. A small subset of patients with respiratory rates of 30/min or greater (n = 30) did show a significant increase in the PaCO2-ETCO2 difference (P less than 0.001). It was concluded that under the conditions of this study, peak ETCO2 values did correlate with PaCO2 values and were not significantly affected by oxygen flow rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of children with Plasmodium falciparum to chloroquine and development of a national malaria treatment policy in Zaire

In vivo sensitivity of Plasmodium falciparum to chloroquine was evaluated in 4 of 9 regions of Zaire in 1985 to develop a national strategy for treatment of malaria. Children less than 5 years of age were treated with either a single dose of chloroquine base, 10 mg/kg, or a dose of 25 mg/kg given over 3 d. A modified 7-day World Health Organization in vivo test was used with follow-up 2, 3 and 7 d after the start of treatment. 339 children were studied. In Bwamanda 92% of children were aparasitaemic 7 days after chloroquine, 10 mg/kg, but in Kinshasa only 44% were free of parasites after 25 mg/kg chloroquine. The mean drop in parasite density among those who did not clear parasites by day 7 was greater than 98% of the initial value. Although the parasite density decreased markedly, the failure of most subjects to become aparasitaemic indicated a marked decrease in parasite sensitivity since 1983. Only one child of 51 who were initially febrile remained febrile, although 14 (28%) of these had resistant parasites. The decrease in parasitaemia and temperature, even among children with resistant strains, led the Ministry of Health to recommend 25 mg/kg chloroquine as first line treatment for fever/malaria in their national malaria control plan. The plan includes drug sensitivity surveillance and a referral system for patients who do not respond to chloroquine treatment.

Malaria infection in pregnant women in Zaire: the effects and the potential for intervention

In five maternity centres in urban and rural Zaire we evaluated the maternal prevalence of Plasmodium falciparum parasitaemia and recorded fever, the frequency of abortions and stillbirths, newborn birth weights and the feasibility of delivering antimalarial chemoprophylaxis. Women in their first and second pregnancy, compared to others (greater than or equal to third pregnancies), had a higher frequency of parasitaemia (38 v. 15%, respectively, P less than 0.001), higher parasite densities (geometric mean densities 927 per mm3 v. 277 per mm3, respectively, P = 0.01), higher rates of stillbirths and low birth weight babies (24% v. 6.4%, P less than 0.001). On average, pregnant women first attended prenatal clinics in the sixth to seventh month of gestation and made three to four visits before delivery. In these areas of Zaire, antimalarial interventions during pregnancy would have the largest impact if they were targeted to women in their first and second pregnancy. In the study areas, maternal attitudes and prenatal care-seeking behaviours do not appear to be barriers to providing an antimalarial intervention.

Specific opioid binding sites for dermorphin in rat brain. A radioreceptor assay using the tritiated hormone as primary ligand

Dermorphin, a heptapeptide amide isolated from amphibian skin, is the most potent of the naturally occurring opioid peptides. (3H)-dermorphin (52 Ci/mmol, 1294 GBq/mmol) was prepared by catalytic tritiation of the synthetic (2,5-iodotyrosyl 1,5)-dermorphin precursor. High affinity specific binding sites for dermorphin were labeled in rat brain membranes using tritiated dermorphin as primary ligand. The binding was saturable and time-dependent. Scatchard analysis revealed a single population of non-interacting high affinity sites (Kd = 0.86 nM). Dermorphin and the specific opiate antagonist naloxone inhibited specific (3H)-dermorphin binding in a concentration dependent manner. The displacement curves could be fit to a simple competitive model assuming only one population of binding sites, with IC 50 of 1.6 nM and 3.4 nM for dermorphin and naloxone, respectively. The use of tritiated dermorphin will be helpful to ascertain unequivocally the selectivity of dermorphin for the different opioid receptor subtypes in the central nervous system.

Alcohol treatment outcome evaluation methodology: state of the art 1980-1984

The methodology of alcohol treatment outcome studies published during two sequential intervals from 1976 through mid-1984 is critically reviewed. Although considerable methodological improvements have occurred over time, major methodological deficiencies continue to characterize much of the literature, with inadequate reporting of subjects' pretreatment characteristics (e.g., severity of dependence) being the most striking problem. Pervasive differences across studies regarding the types of data gathered and the ways in which findings are reported seriously impede attempts to compare studies and weaken the types of conclusions that can be drawn about treatment efficacy in general. It is suggested that journal editors establish standards of reporting for follow-up studies.

Chemically fixed human umbilical cord vein grafts as arterial substitutes: potential and limits

In spite of reported successes, synthetic fabric grafts and microporous and plain synthetic conduits have proven unsuitable for aorto-coronary bypasses and showed weaknesses below the knee. Readily available and uniform diameter vascular substitutes with biological and mechanical properties comparable to human vessels would be of paramount interest. Following reported successes with chemically fixed human umbilical veins (HUV), we have attempted to develop smaller diameter blood conduits and have improved the currently prevalent techniques of fixation, preparation and storage to generate more convenient surgical products. In vitro assessment of the processed HUV demonstrated that the HUV can be easily processed to make an arterial substitute that can be preserved either in a liquid medium or as a dry product. However, the in vivo implantations in dogs led to disappointing results for liquid-preserved or albuminated veins. Critical-point dried grafts gave better results, unfortunately they do not heal and they can only degrade after implantation.

Photoaffinity labeling of D-2 dopamine binding subunits from rat striatum, anterior pituitary and olfactory bulb with a new probe, [3H]azidosulpride

A novel photoaffinity probe [3H] azidosulpride has been developed for biochemical studies of D-2 dopamine receptors. This ligand binds to the receptors with high affinity (Kd = 3.1 +/- 0.2 nM) and, upon photoactivation, about 20% of the radioactivity bound to membranes becomes covalently incorporated. More than 90% of this irreversible binding is protectable by dopaminergic agents including D-2 selective compounds, whereas D-1 selective and non-dopaminergic compounds are ineffective. Analysis by sodium dodecylsulfate polyacrylamide gel electrophoresis reveals a single band at Mr = 85 kDa for labeled receptors in striatum, anterior pituitary or olfactory bulb, where pharmacologically distinct binding sites have been previously detected.