AnAnolis skin melanophore assay suitable for photoaffinity labeling studies with α-MSH

Summary Visual determination of MSH-induced pigment migration in melanophores of small pieces ofAnolis carolinensis skin is standardized by first measuring photoelectrometrically the change in reflection/transmission of the whole dorsal skin in response to different hormone concentrations. This method allows the rapid and precise recording of time-response curves after photoaffinity labeling of MSH receptors or of dose-response curves of large series of synthetic compounds.Acknowledgments. We wish to thank Ms V. Jäggin, Ms C. Schulthess and Ms G. van Hees for excellent technical assistance, Dr. R. Andreatta, Ciba-Geigy AG, Basel, for his generous gift of -MSH and Prof. A Pletscher for his continuous interest. This work was supported by the Swiss National Science Foundation.     

Internal interactions within the human circadian system: the masking effect

Summary In the realm of human circadian rhythms, the masking effect is defined as the change in the course of deep body temperature induced by changes in the degree of physical activity, or by the alteration between sleep and wake. This effect is particularly obvious during internal desynchronization where the rhythms of deep body temperature, and the sleep-wake sleep-wake sleep cycle — i.e. one of the masking factors — run with different periods.Every sleep onset is accompanied by a rapid drop, and wake onset by a rapid rise in deep body temperature, each one with an overshoot of about 50% of the steady state variations. When rhythms are calculated, with the dominant temperature period as the screening period, exclusively from data obtained during sleep episodes, on the one hand, and from those obtained exclusively during wake, on the other, two average cycles emerge: the sleep temperature curve and the wake temperature curve. Both run in parallel but are separated by the masking effcct. As derived from many experiments, the mean masking effect amounts to 0.28±0.06°C. The masking effect also depends to some extent on the phase of the temperature rhtthm; it is larger than average around the temperature maximum and during the descending phase of the temperature cycle, where the alertness commonly is highest and the probability to sleep, in general, and the REM sleep propensity, in particular, are smaller than average. This also can be interpreted to indicate that the sleep temperature curve is phase advanced relative to the wake temperature curve; this, on the average, by 0.9±0.3 h.If the individually determined amount of masking is added to the temperature data obtained during sleep, or substracted from the temperature data obtained during wake, a temperature curve emerges that can be though of as being purified of the masking effect. Analyses of this artificial curve allow estimation of that part of the internal interactions uninfluenced by the masking effect. On the average, about half of the amount of interaction between the rhythm of sleep-wake and that of deep body temperature is explained by the masking effect, whereas the other half is oscillatory interaction. Both types of interaction are inherent and inseparable parts of the circadian clock mechanism, as can be deduced from model considerations.     

Ecdysteroids: possible candidates for the hormone which triggers salivary gland degeneration in the ixodid tickAmblyomma hebraeum

Summary Following engorgement, female ixodid ticks secrete a tick salivary gland degeneration factor (TSGDF) into the hemolymph. Here we show that the arthropod ecdysteroid hormones, ecdysome and 20-hydroxyecdysone, induce degeneration of tick salivary glands maintained in organ culture. The effective dose range in vitro is 30–300 ng/ml, a range reported to be physiological for this species following repletion. In addition, infusion of 20-hydroxyecdysome in vivo induces salivary gland degeneration. We therefore propose that TSGDF may be an ecdysteroid.Acknowledgments. Some of the data reported here were presented to the annual meeting of the Canadian Society of Zoologists, 15–18 May 1983; Program of abstracts, page 53. Financial support of the Canadian National Sportsmen's Fund and NSERC Canada to W.R.K. is gratefully acknowledged.     

Juvenile hormone titre and regulation in the cockroachDiploptera punctata

Summary Titres of juvenile hormone (JH) have been determined in both hemolymph and whole body extracts of femaleDiploptera punctata during the first gonotrophic cycle using a method employing gas chromatography/mass spectrometry for qualitative and quantitative analysis. JH III is the sole JH found in both adult and last instarD. punctata. Maximum values of 1500 ng/ml (6M) were observed at the middle of the gonotrophic cycle, when basal oocyte growth rate was greatest. Changes in rates of JH release in vitro by corpora allata paralleled closely the changes in JH titre, suggesting that biosynthesis is a major regulator of titre. JH levels per animal were calculated from observed JH titres, and at certain time points in the gonotrophic cycle JH levels obtained from analysis of whole bodies were significantly greater than those predicted from hemolymph titres. These results suggest the existence of a nonhemolymph JH pool inD. punctata. Decay in JH titre after allatectomy of 5 day females has also been studied. Following a rapid initial decline, the rate of decay slowed appreciably 4 h post-operation. Thus, use of a first-order rate constant to estimate half-life of JH significantly underestimated the longevity of the hormone. The apparent persistence of JH following allatectomy may be due to the existence of a nonhemolymph JH pool.     

In vitro mutagenicity testing of a potent,new, benzoyl urea insect growth regulator

Summary Bacterial mutagenicity assay to detect potential chronic toxicity of a potent, new, benzoyl urea insect growth regulator (CGA-112913 or IKI-7899, formerly UC-62644) was conducted using 5 histidine auxotrophs ofSalmonella typhimurium. Tests within the concentration range of 0.9–500 g (saturating)/plate of the compound with and without the 5–9 mammalian metabolic activation system showed no mutagenic effects clearing the way for long-term chronic toxicology studies.The authors thank Professor Bruce N. Ames for supplying the tester strains together with all the relevant information for conducting the bioassays and Ms. Norma Charlebois for her meticulous technical assistance.     

Adrenocortical metabolism and plasma corticosterone in soman intoxicated rabbits

Summary The organophosphate neurotoxin soman produced impairments in adrenocortical RNA and protein metabolism. Fasciculate and reticular cell RNA and protein contents were supporessed with sublethal to acutely lethal dosages (20, 30 and 40 g/kg, s.c.) during the acute excitatory phase of intoxication and at 6–8 h post injection. All three dosages produced ca 90% inactivation of plasma cholinesterase. A transient elevation of plasma corticosterone occurred with 20 g/kg soman whereas there was a protracted increase with 30 g/kg. Corticosterone was not significantly elevated with 40 g/kg, but death occurred at 13±4 min. Thus, the magnitude and/or nature of soman-induced metabolic impairments does not appear to prevent adrenal activation.Supported by US Army Medical Research and Development Command Contract DAMD 17-81-C-1202.     

A new semisynthetic ergot peptide alkaloid: DCN 203-922

Summary We report the synthesis, stereochemistry and preliminary pharmacological evaluation of DCN 203-922, a novel ergot alkaloid of the cyclol type, which contains in its peptide moiety the uncommon amino acid L-allo-isoleucine.Part of this paper was reported by this author at the Herbstversammlung der Schweizerischen Chemischen Gesellschaft, Bern, in October 1986.     

Occurrence of thiaminase II inSaccharomyces cerevisiae

Summary It was found that cell-free extracts ofSaccharomyces cerevisiae contain thiaminase II which hydrolyzes thiamine and thiamine analogs. The possible involvement of this enzyme and thiamine-synthesizing enzymes in thiamine production from thiamine antagonists is discussed.30 September 1986Acknowledgments. We thank the late Dr S. Yurugi, Takeda Pharmaceutical Industries, Osaka, for his generous gifts of dimethialium, 2-northiamine, -hydroxyethylthiamine, hydroxymethylpyrimidine, 2-norhydroxymethylpyrimidine and hydroxyethylthiazole. We also thank Prof. H. Nakayama, Yamaguchi Women's College, for his kind supply ofEscherichia coli 70–17 and 26–43.     

Differential effects of prostaglandins and isoproterenol on cAMP content and Na,K pump activity in rat submandibular acini

Summary The -adrenergic agonist isoproterenol and prostaglandins E₁ and E₂ (but not F₂) increased the cAMP content of rat submandibular acini in vitro, but only isoproterenol enhanced ouabain-sensitive⁸⁶Rb (K) uptake. These findings suggest that cAMP is not involved in the activation of the Na, K pump in salivary cells.     

Cell-to-cell coupling studied in isolated ventricular cell pairs

Summary Cell pairs isolated from adult rat and guinea pig ventricles were used to study the electrical properties of the nexal membrane. Each cell of a pair was connected to a voltage-clamp system so as to enable whole-cell, tight-seal recording. The current-voltage relationship of the nexal membrane was found to be linear, revealing a resistance r_n of 2–4 M. r_n was insensitive to the sarcolemmal membrane potential (range:–90 to +30 mV), and exerted no time-dependent gating behavior (range: 0.1 to 10 s). Lowering pH_i yielded a small increase in r_n. Vigorous elevations in [Ca²⁺]_i gave rise to an increase in r_n which was associated with a cell shortening. Uncoupling caused by aliphatic alcohols or halothane did not produce cell shortening. Cell pairs were also used to study action potential transfer.