Antihypertensive and cardiac effects of two novelβ-adrenoceptor blocking drugs

Summary Two new-adrenoceptor blocking drugs with acute antihypertensive and positive inotropic effects are described: Compound A (2-[4-(3-tert. butylamino-2-hydroxypropoxy)phenyl]-4-trifluoromethylimidazole) and MK-761 (2-(3-tert. butylamino-2-hydroxypropoxy)-3-cyanopyridine hydrochloride). In SH rats both compounds, given orally, lowered arterial pressure and were more potent than hydralazine. The antihypertensive effect of compound A but not of MK-761 was antagonized by timolol. Both compounds had positive inotropic activity on cat heart papillary muscles; these effects were antagonized by timolol. The pretreatment of animals with reserpine greatly reduced the positive inotropic effect of MK-761 but not of compound A. The acute antihypertensive and positive inotropic effects of compound A are likely to be at least partially due to stimulation of-adrenoceptors, e.g. intrinsic sympathomimetic activity. The effects of MK-761 on the same parameters appear to be mediated by different mechanisms.     

Comparison of the effects of lithium,β-phenylethylamine and tyrosine onXenopus embryos

Résumé On a étudié les effets du lithium, de la -phényléthylamine et de la tyrosine sur le développement embryonnaire deXenopus laevis. La tyrosine n'a pas d'effet, mais le lithium ou la -phényléthylamine ont végétalisé les embryons s'ils ont été exposés avant le stade blastula.     

Age- and sex-related differences in the content of prothymosinα in rat tissues

Differences in the tissue content of prothymosin during the early postnatal development of male and female rats are reported. Thymus and spleen have been found to contain significantly higher amounts of prothymosin in the newborn and prepubertal animals, as compared to adults, whereas liver has been found to contain low levels of prothymosin throughout development. These findings indicate a functional association of prothymosin with the proliferating lymphoid tissues of the young rat.     

Functions of Periostin in dental tissues and its role in periodontal tissues’ regeneration

The goal of periodontal regenerative therapy is to predictably restore the tooth’s supporting periodontal tissues and form a new connective tissue attachment of periodontal ligament (PDL) fibers and new alveolar bone. Periostin is a matricellular protein so named for its expression primarily in the periosteum and PDL of adult mice. Its biological functions have been widely studied in areas such as cardiovascular physiology and oncology. Despite being initially identified in the dental tissues and bone, investigations of Periostin functions in PDL and alveolar-bone-related physiopathology are less abundant. Recently, several studies have suggested that Periostin may be an important regulator of periodontal tissue formation. By promoting collagen fibrillogenesis and the migration of fibroblasts and osteoblasts, Periostin might play a pivotal part in regeneration of the PDL and alveolar bone following periodontal surgery. The aim of this article is to provide an extensive review of the implications of Periostin in periodontal tissue biology and its potential use in periodontal tissue regeneration.     

The anticonvulsant effects of propranolol and β-adrenergic blockade

Summary The anticonvulsant activity of racemic and (+)-propranolol was studied in rats. Neither drug changed the current to produce a minimal seizure in 50% of animals. Both drugs were effective in the maximal electroshock seizure test, the (+) isomer being more potent than the racemic form. Since the (+) isomer is practically devoid of -adrenergic blocking activity, the anticonvulsant effects of propranolol do not result from -adrenergic blockade.We wish to thank Hana Boucek for skilful technical assistance. Propranolol and (+)-propranolol were obtained through the courtesy of Ayerst Laboratories Ltd, in Montreal. This research was supported by the Medical Research Council of Canada, grant MA-4754.     

The role of mammalian target of rapamycin (mTOR) in the regulation of pancreatic β-cell mass: implications in the development of type-2 diabetes

Type-2 diabetes mellitus (T2DM) is a disorder that is characterized by high blood glucose concentration in the context of insulin resistance and/or relative insulin deficiency. It causes metabolic changes that lead to the damage and functional impairment of organs and tissues resulting in increased morbidity and mortality. It is this form of diabetes whose prevalence is increasing at an alarming rate due to the 'obesity epidemic', as obesity is a key risk factor in the development of insulin resistance. However, the majority of individuals who have insulin resistance do not develop diabetes due to a compensatory increase in insulin secretion in response to an increase in insulin demand. This adaptive response is sustained by an increase in both β-cell function and mass. Importantly, there is increasing evidence that the Serine/Threonine kinase mammalian target of rapamycin (mTOR) plays a key role in the regulation of β-cell mass and therefore likely plays a critical role in β-cell adaptation. Therefore, the primary focus of this review is to summarize our current understanding of the role of mTOR in stimulating pancreatic β-cell mass and thus, in the prevention of type-2 diabetes.     

Opposite effects ofβ-adrenoceptor stimulation and 8-bromo-cyclic AMP on potassium efflux in mammalian heart muscle

Summary -adrenoceptor stimulation by isoprenaline increases the potassium efflux in beating guinea-pig atria. This effect is not mimicked by 8-bromo-cyclic AMP, a cyclic AMP analogue which exerts a positive inotropic effect in this preparation.     

What constitutes a network in the acinar cells of amphibian and mammalian pancreas?

Résumé Il a été montré que l'appareil réticulaire classique de Golgi dans les cellules pancréatiques des amphibies et des mammifères est un produit artificiel. Un certain nombre de raisons sont proposées pour expliquer ce fait.     

Neurogenic effects of β-amyloid in the choroid plexus epithelial cells in Alzheimer’s disease

β-amyloid (Aβ) can promote neurogenesis, both in vitro and in vivo, by inducing neural progenitor cells to differentiate into neurons. The choroid plexus in Alzheimer’s disease (AD) is burdened with amyloid deposits and hosts neuronal progenitor cells. However, neurogenesis in this brain tissue is not firmly established. To investigate this issue further, we examined the effect of Aβ on the neuronal differentiation of choroid plexus epithelial cells in several experimental models of AD. Here we show that Aβ regulates neurogenesis in vitro in cultured choroid plexus epithelial cells as well as in vivo in the choroid plexus of APP/Ps1 mice. Treatment with oligomeric Aβ increased proliferation and differentiation of neuronal progenitor cells in cultured choroid plexus epithelial cells, but decreased survival of newly born neurons. These Aβ-induced neurogenic effects were also observed in choroid plexus of APP/PS1 mice, and detected also in autopsy tissue from AD patients. Analysis of signaling pathways revealed that pre-treating the choroid plexus epithelial cells with specific inhibitors of TyrK or MAPK diminished Aβ-induced neuronal proliferation. Taken together, our results support a role of Aβ in proliferation and differentiation in the choroid plexus epithelial cells in Alzheimer’s disease.     

Histochemistry of the so-called ‘golgi complex’ in the mammalian spermatid

Résumé L'examen histochimique des spermatides du bouc et du buffle montre que le «complexe de Golgi» des auteurs comprend l'idiosome constitué par des protéides et des lipidoprotéides, les bâtonnets et granules constitués par des phospholipides et peut-être des protéides et enfin les vacuoles.     

Localisation of acetylcholinesterase in rat myotubes in the presence of β-endorphin and β-endorphin-(1-27)

Summary In rat embryo skeletal myotubes, acetylcholinesterase is present, as multiple forms, and can be detected in deposits at the cell surface. Myotubes cultured in the presence of -endorphin, exhibit an increased predominance of the globular (precursor) forms of the enzyme, which are largely restricted to intracellular sites associated with nuclei. In the presence of -endorphin-(1-27), the relative proportions of the different forms of acetylcholinesterase is similar to that seen in the controls, but the enzyme is intracellular and has a characteristic focal localisation in the myotube.     

The effects of γ-aminobutyric acid and picrotoxin on the junctional potential and the contraction of crayfish muscle

Résumé L'acide-amino-butyrique et la-alanine reproduisent l'action du transmetteur inhibiteur du système neuromusculaire de l'écrevisse. Ces deux acids aminés diminuent la contraction musculaire. L'acide-amino-butyrique réduit la différence de potentiel et augmente sa décomposition. L'action de ces acides aminés est bloquée par la picrotoxine comme l'est celle du transmetteur inhibiteur.

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The study was supported by Grants B-1089 and B-31 from the National Institute of Neurological Diseases and Blindness, United States Public Health Service. Some of this work was done at the Department of Zoology, Cornell University. We are grateful to Prof.S. C. Wang, Columbia University, for generous assistance.     

Cys-tRNACys formation and cysteine biosynthesis in methanogenic archaea: two faces of the same problem?

Aminoacyl-tRNA (transfer RNA) synthetases are essential components of the cellular translation machinery as they provide the ribosome with aminoacyl-tRNAs. Aminoacyl-tRNA synthesis is generally well understood. However, the mechanism of Cys-tRNACys formation in three methanogenic archaea ( Methanocaldococcus jannaschii, Methanothermobacter thermautotrophicus and Methanopyrus kandleri) is still unknown, since no recognizable gene for a canonical cysteinyl-tRNA synthetase could be identified in the genome sequences of these organisms. Here we review the different routes recently proposed for Cys-tRNACys formation and discuss its possible link with cysteine biosynthesis in these methanogenic archaea.     

Roles of melatonin and its receptors in cardiac ischemia–reperfusion injury

Acute myocardial infarction (AMI) has been an economic and health burden in most countries around the world. Reperfusion is a standard treatment for AMI as it can actively restore blood supply to the ischemic site. However, reperfusion itself can cause additional damage; a process known as cardiac ischemia/reperfusion (I/R) injury. Although several pharmacological interventions have been shown to reduce tissue damage during I/R injury, they usually have undesirable effects. Therefore, endogenous substances such as melatonin have become a field of active investigation. Melatonin is a hormone that is produced by the pineal gland, and it plays an important role in regulating many physiological functions in human body. Accumulated data from studies carried out in vitro, ex vivo, in vivo, and also from clinical studies have provided information regarding possible beneficial effects of melatonin on cardiac I/R such as attenuated cell death, and increased cell survival, leading to reduced infarct size and improved left-ventricular function. This review comprehensively discusses and summarizes those effects of melatonin on cardiac I/R. In addition, consistent and inconsistent reports regarding the effects of melatonin in cases of cardiac I/R together with gaps in surrounding knowledge such as the appropriate onset and duration of melatonin administration are presented and discussed. From this review, we hope to provide important information which could be used to warrant more clinical studies in the future to explore the clinical benefits of melatonin in AMI patients.     

Effects of two kinds of social deprivation on testosterone and estradiol-17β plasma levels in the male rat

Summary The effect of complete and tactile isolation on plasma testosterone and estradiol-17 was studied in male rats at the age of 60 and 180 days. A decrease in the plasma levels of the two hormones was observed.     

Occurrence of β-chitin in the cuticle of a Pentastomid Raillietiella gowrii

Summary The purified chitin from the cuticle of a pentastomid was examined by X-ray method. The X-ray photograph discloses that the chitin in question is of -type. Since the arthropod cuticle contains -chitin, it is suggested that Pentastomida may be considered an independent phylum.Thanks are due to Prof. Dr. G. Sundara Rajulu for guidance and encouragement.     

Application of the ‘low-temperature plasma ashing method for biological tissues’ to studies in the field of virology

Summary It was found that the behavior of a virus in host plant is reflected in the pattern of crystalline inorganic components of the host plant by the technique of the low-temperature plasma ashing method for biological tissues.     

Some relationships between the pancreatic β-cells and the metabolism of the epiphyseal cartilage

Riassunto È stato studiato il contenuto di ATP nella cartilagine epifisaria di giovani ratti diabetici per allossana. Il deficit insulinico da diabete allossanico provoca, oltre ad arresto dell'accrescimento scheletrico, una diminuzione della concentrazione di ATP nella cartilagine di coniugazione. Il significato biologico di questo risultato è messo in relazione col meccanismo d'azione dell'insulina e con l'importanza dell'ATP nel processo di ossificazione encondrale.     

Some relationships between the pancreatic β-cells and the metabolism of the epiphyseal cartilage

Riassunto Studiando il meccanismo biochimico con cui la insulina controlla il processo di osteogenesi, si è stabilito che in condizioni di deficit insulinico (diabete allossanico) esiste nel ratto accanto ad un arresto dell'accrescimento scheletrico, una notevole riduzione dell'attività cocarbossilasica nella cartilagine epifisaria. Si conclude che nella cartilagine di coniugazione ATP e cocarbossilasi sono strettamente interdipendenti per quanto riguarda la loro biosintesi; inoltre che il loro normale metabolismo è indispensabile al normale svolgersi del processo di osteogenesi.