Erythrocyte 2,3-diphosphoglycerate in anaemic sheep

Summary Experimental anaemia resulted in an increase of red cell 2,3-DPG from 0.11 M/gHb to 0.99 M in haemoglobin A sheep and from 0.21 M to 1.5 M in haemoglobin B sheep. Production of haemoglobin C as a result of anaemia was confined to haemoglobin A only. The results, therefore, appear to suggest that the rise in 2,3-DPG in the red blood cells of different haemoglobin types is independent of haemoglobin C.This work was supported by grants from the National Health and Medical Research Council, The Clive and Vera Ramaciotti New South Wales Foundations and Helena Rubinstein Foundation, Inc. We wish to thank Mr J. Sheedy for his expert technical assistance, and Professor G. J. Brewer for his constructive criticism.     

Platelet aggregation is inhibited by phycolectins

Lectins from four marine algal species were examined for interaction with human platelets. The lectin designated hypnin A, from the red algaHypnea japonica, inhibited adenosine diphosphate (ADP)-or collagen-induced human platelet aggregation in a dose-dependent manner. Complete inhibition was observed at concentrations of 100 and 5 g/ml of the lectin with, ADP (2 M) and collagen (0.2 g/ml)-induced platelet aggregation, respectively. At the inhibitory concentration of 0.5 to 100 g/ml, the lectin did not induce aggregation of resting platelets. Lectins from the other three algal species also inhibited ADP-induced human platelet aggregation. These results indicate that the algal lectins are a new group of inhibitors and may be useful to study glycoconjugates on platelet membranes and to design novel platelet aggregation inhibitors.     

Antihypertensive effect of Co-factors of the synthesis and precursors of nucleic acids in experimental hypertension

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Unusual antimicrobial compounds fromAeollanthus buchnerianus

Using bioassay guided isolation, three novel 12 carbon polyoxygenated fatty acids and a novel abietane diterpene have been isolated from the the chloroform extract of aerial parts ofAeollanthus buchnerianus (Lamiaceae). Rigorous spectroscopic methods were used for compound identification. (Z,Z)-8-acetoxy-5-hydroxydodeca-2,6-dienoic acid and (Z,Z)-5,8-dihydroxydodeca-2,6-dienoic acid inhibited the spore germination ofCladosporium cucumerinum (both with Minimum Inhibitory Dose (MID) values of 1 g) andAspergillus niger (MID 5 and 25 g respectively). Further, they also reduced the hyphal growth ofPythium ultimum. (Z)-5-hydroxy-6,7,8-triacetoxydodeca-2-dienoic acid exhibited short term inhibition of the growth ofCladosporium cucumerinum. The novel abietane diterpenoid, (rel)-14-acetoxyabiet-7-en-18-oic acid inhibited the growth of the gram positive bacteriaBacillus subtilis, staphylococcus aureus andStreptomyces scabies (MIC values 80, 20 and 20 g ml^–1 respectively).     

Storage of irradiated human blood; a source of error in quantitative chromosome analysis

Summary Human whole blood was irradiated with 2.5 Gy of 220 kVp X-rays and stored before culture with 9.7 M BrdU and 19.4 or 38.7 M BrdU for 0, 24, 48 and 72 h. The frequency of dicentrics and ring chromosomes was determined in cells staining as first division (M1) metaphases with the fluorescence plus Giemsa technique. Storage had no influence on the observed aberration yields in 44 h cultures containing 9.7 M BrdU. In 66 h cultures at 19.4 M BrdU the observed yields after 2 and 3 days' storage were significantly lower as compared to cultures from fresh blood. No storage effect was revealed in 66 h cultures containing 38.7 M BrdU. In cases where cytogenetic radiation dosimetry has to be carried out using blood samples which have been in transit for 2–3 days, the findings are of relevance for a correct determination of the chromosome damage in M1 cells.     

Giant pigment granules in dermal melanocytes of rat scrotal skin

Summary Giant melanosomes, ellipsoidal (1.5 m×1.3 m) or spherica (1.1 m–1.4 m in diameter) exist in the scrotal skin of the black pelted Long Evans rat. They are longer and wider than normal stage IV melanosomes (0.7 ×0.4 m) found in theses dermal melanocytes.The authors acknowledge with gratitude, the technical assistance of Evelyn Ann Flynn. This work was supported by grant AM 20669-16 from the National Institute of Arthritis, Metabolism, and Digestive Diseases, USPHS.     

Reduction of high affinity glutamate uptake in rat hippocampus by two polyamine-like toxins isolated from the venom of the predatory waspphilanthus triangulum F

Summary Two components of the venom of the predatory waspPhilanthus triangulum F. significantly reduce — to a greater or less extent — the high affinity uptake of glutamate in rat hippocampus. A concentration of 10 M -PTX caused a reduction of 74%, while the other component, -PTX, at the same concentration, caused a reduction of 18%. Hence the effect of -PTX on high affinity glutamate uptake in the hippocampus is comparable with its effect on high affinity glutamate uptake in insect neuromuscular junctions. Contrary to our previous findings that -PTX has no effect on high affinity glutamate uptake in insect glutamatergic terminal axons, however, -PTX significantly reduces high affinity glutamate uptake in the hippocampus, albeit less effectively than -PTX.     

Geminus and the concept of mean motion in Greco-Latin astronomy

Conclusion Geminus account of lunar motion in chapter 18 of hisIntroductio astronomiae is, in our view, an important contribution to Greco-Latin astronomy because, in attempting to reconstruct arithmetically (the parameters of) the Moon's motion in longitude, he undermines the task astronomers had hitherto set for themselves. This undermining of a commonly acknowledged view of the purpose of astronomy is articulated in a whole new set of questions concerning the nature and place of both observation and mathematical reasoning in the science of the heavens. Yet, one must not overlook the fact thatGeminus reconstruction also indicates resources for addressing these questions. Of these resources, the most powerful proved to be the idea that irregular motion could be quantified as a systematic departure from a mean motion, and the idea that observational data could be organized and structured by means of genetic arithmetical reconstructions.But, since we limit our attention to extant treatises and decline to speculate about works or parts of works that have not survived, we must say that it would takePtolemy to discern the new direction for astronomy thatGeminus opened up and to pursue it. In part, this involved straightening out the conflated conception of mean motion in chapter 18 — the qua arithmetic mean daily displacement can only be anapparent lunar motion in longitude and not one the Moonreally makes, but the same need not be true of the qua periodic mean daily displacement — and determining its proper relation to real and apparent planetary motion. Indeed,Ptolemy's genius lay, we think, in seeing that even though, in assimilating Babylonian astronomy, earlier and contemporary Greco-Latin writers betrayed a confused, inconsistent, and unsophisticated grasp of the proper role of arithmetic, geometry, and observation in astronomical argument [seeBowen 1994], the solution lay in a mathematical reconstruction of the observed celestial motions, in which mean motion played an essential role.     

Different effects of D-glucose anomers for respiration of bacterial germinated spores

Summary Effects of - or -D-glucose on the respiration of germinated spores (only germinated spores not including swollen spores and elongated spores) ofBacillus subtilis andB. megaterium were studied. In our conditions, net amount of oxygen consumed by 10¹⁰ germinated spores ofB. subtilis per min after addition of - or -D-glucose was 1.6 g or 6.6 g (/=4.13), while that byB. megaterium was 4.5 g or 6.8 g (/=1.51), respectively. However, the net amounts of oxygen consumed by 10¹⁰ vegetative cells per min after addition of - or -D-glucose were identical, forB. subtilis in both cases 443.0 g and forB. megaterium in both cases 604.4 g.     

Antidiuretic effects of oxytocin in the Brattleboro rat

Summary The antidiuretic activity of oxytocin (OT) was measured in Brattleboro rats with congenital diabetes insipidus. A dose dependent antidiuretic response was found in animals receiving chronic infusions of 0.1 g/h, 1.0 g/h, and 5 g/h of OT. OT infused at the rate of 5 g/h over a 7-day period completely reversed the symptoms of diabetes insipidus. The results support the concept that OT serves as a weak agonist of vasopressin at the level of the kidney and at pharmacological levels exhibits antidiuretic activity.     

A correlation of responses of the resistance and capacitance vessels of the intestine and kidney to changes of impulse in postganglionic nerves under pressor reflexes

Summary The responses of resistance vessels of the intestine and kidney were induced by high amplitude impulses (over 15 V), while those of capacitance vessels in these organs were induced by low amplitude impulses (15 V and lower) of postganglionic sympathetic fibres.     

Repercussions de l'hyperthyroïdie sur le contenu total en ADN du cervelet de rat âgé de 6 et 35 jours. Effets comparés de la LT3 et de la DLT4

Summary The total cerebellar proteins RNA and DNA contents from DLT4- and LT3-treated rats was studied at 6 and 35 days of age. The effect of injections of 5 g/j of DLT4 is comparable to that of 25 g of LT3 at birth, followed by 0.5 g every 2 days. On the other hand, injection of 0.5 g of LT3 every 2 days does not induce any significant modification of the total DNA contents in the cerebellum.     

Synthesis and pharmacological properties of [1-N4-dimethyl-asparagine]-angiotensin II

Summary [1-N⁴-Dimethyl-asparagine]-angiotensin II was synthesized by Merrifield's solid-phase procedure. The analogue gave rat blood pressure about 70% relative potency to Hypertensin (Ciba). Rabbit aorta strips gave intrinsic activity _E=1, a PD₂ of 6.92±0.09 and an affinity relative to [Asn¹]-angiotensin II of 6.5%.The editors do not hold themselves responsible for the opinions expressed in the authors' brief reports. — Les auteurs sont seuls responsables des opinions exprimées dans ces brèves communications. — Für die Kurzmitteilungen ist ausschliesslich der Autor verantwortlich. — Per le brevi comunicazioni è responsabile solo l'autore. — . — Solo los autores son responsables de las opiniones expresadas en estas comunicationes breves.Acknowledgment. The authors wish to express their appreciation to Dr Emanuel Escher, School of Medicine, Centre Hospitalier Universitaire, Sherbrooke, Quebec, for his help in providing the biological data and critical comments.     

Central nicotinic receptor blockade inhibits emotionally conditioned pressor responses in rats

A conditioned stimulus previously paired with electric footshock produced an increase in blood pressure in conscious, freely moving rats. The conditioned pressor response was reproducible. Intracerebroventricular injection of the nicotinic receptor antagonists hexamethonium (1–10 g) or pentolinium (10 g) but not the muscarinic receptor antagonist methylatropine (3 g) produced an inhibition of the conditioned pressor response, whereas intraarterial injection of hexamethonium (10 g) did not affect the response. Intraventricular injection of the cholinesterase inhibitor physostigmine (3–10 g) produced an enhancement of the conditioned pressor response. These results are consistent with the possibility that central nicotinic receptors play a role in the expression of the emotionally conditioned pressor response in rats.     

A study of the mechanism of polymyxin M inactivation

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The participation of kinins in the pathogenesis of early disturbances in the skin capillary permeability in localβ-ray irradiation

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Some functional characteristics of the electroreceptors (the ampullae of lorenzini) of elasmobranchs

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The effect of insulin on the electrophoretic mobility of rat hepatocytes

Summary The addition of insulin (10 U) to a suspension of isolated hepatocytes in Krebs-Ringer bicarbonate solution. causes an increase in the negative electrophoretic mobility of the cells from –1.68 m sec^–1 V^–1 cm to 2.26 m sec^–1 V^–1 cm. This observation supports the findings by other workers that the binding of insulin to its receptor leads to a marked change in the membrane.Acknowledgment. We wish to thank the Medical Research Council for the provision of the microelectrophoresis apparatus and initial running costs of the project.     

Effect of dipyridamole on glomerular mesangial cell ecto-5′-nucleotidase expression

Although dipyridamole has been extensively studied as an anti-aggregating agent, its mechanism of action has not been elucidated. Cultured mesangial cells were treated with dipyridamole 1–100 M from 6–72 h. Ecto-5-nucleotidase activity approximately doubled (from 115±11 to 226±14 nmol/min/mg) after treatment with 100 M dipyridamole for 72 h. This effect was concentration- and time-dependent. Cycloheximide, an inhibitor of protein synthesis, did not alter basal 5-nucleotidase activity. However, it prevented stimulation by 5 M dipyridamole. Adenosine availability at the receptor sites was increased by dipyridamole and S-(p-nitrobenzyl)-6-thioinosine (NBTI), which inhibit adenosine uptake into the cell. Addition of dipyridamole or NBTI to the adenosine-treated mesagial cells produced an additive increase in ecto-5-nucleotidase activity. Dipyridamole, through its effect on extracellular adenosine and ecto-5-nucleotidase, may have an influence upon regulation of the glomerular microcirculation.