Recent X-ray diffraction studies of muscle contraction and their implications

Recent studies on the interference fringes in the myosin meridional reflections provide a new source of structural information on cross-bridge movement during mechanical transients and steady shortening. Many observations can be interpreted satisfactorily by the tilting lever-arm model, with some assumptions, including the presence of fixed repeating structures contributing to the M3 and higher-order meridional reflections. In isometric contraction, the lever arms are oriented near the start of the working stroke, with a dispersion of ca+/-20-25 degrees . Upon a rapid release of 10-12 nm, they move to the end of the stroke, with a well-known T2 delay of 1-2 ms. This delay must represent additional processes, which have to occur even in tension-generating heads, or activation of attached heads, which initially do not develop force. Surprisingly, in muscles shortening at moderate loads (0.5-0.6 P0), the mean position of the heads moves only 2-3 nm closer to the M-line than in the isometric case, reminiscent of the Piazzesi-Lombardi model.     

Influence of cholinergic and adrenergic blocking drugs on hyperglycemia and brain glycogenolysis in diazinon-treated animals

Diazinon, an organophosphorous compound, produced hyperglycemia and reduced the glycogen content of the brain 2 h after its administration to rats (40 mg/kg, i.p.). The activities of the glycogenolytic enzymes, glycogen phosphorylase and phosphoglucomutase, were significantly increased, while that of glucose-6-phosphatase was not altered. Atropine (20 mg/kg, i.p.) given immediately after diazinon abolished the changes; tolazoline or propranolol (each at 10 mg/kg, i.p.) injected 30 min before the administration of diazinon significantly reduced the hyperglycemia and the increase in brain glycogenolysis. A combination of tolazoline and propranolol was more effective than either of them alone and completely abolished the hyperglycemia and the changes in brain glycogenolysis. It may be concluded that diazinon initially activates central cholinergic processes leading to hyperglycemia and increased cerebral glycogenolysis in animals.     

Effects of adrenergic and cholinergic drugs on electrical and mechanical activities of the rat cauda epididymidis in vitro

Electrical and mechanical activities of the rat epididymis (at 29 +/- 1.1 cm from the junction of the vas deferens) were recorded in vitro. The frequency of the spontaneous activity was 2.7 +/- 0.15/min. Adrenaline, phenylephrine, isoprenaline and carbachol increased the basal tension, frequency and amplitude of the contractions. Phentolamine, an alpha-adrenergic blocking agent, abolished the stimulatory effects of adrenaline and isoprenaline, but not those of carbachol. Propranolol and metoprolol, beta-adrenergic blocking agents, did not inhibit the stimulatory effects of isoprenaline. Atropine abolished the response to carbachol. The results suggest that alpha-adrenergic receptors but not beta-receptors are present in the rat epididymis.     

The new approach in development of anti-Alzheimer's disease drugs via the cholinergic hypothesis

A wide range of evidences show that cholinesterase (ChE) inhibitors can interfere with the progression of Alzheimer's disease (AD). The earliest known ChE inhibitors, namely, physostigmine and tacrine, showed modest improvement in the cognitive function of AD patients. However, clinical studies show that physostigmine has poor oral activity, brain penetration and pharmacokinetic parameters while tacrine has hepatotoxic liability. Studies were then focused on finding a new type of acetylcholinesterase (AChE) inhibitor that would overcome the disadvantages of these two compounds. During the study, by chance we found a seed compound. We then conducted a structure-activity relationship (SAR) study of this compound. After four years of exploratory research, we found donepezil hydrochloride (donepezil). Recently, acetylcholinesterase inhibitors (AChEIs) have been studied for other mechanisms of action, such as neuroprotective action and lowering of beta-amyloid (beta-amyloid). Donepezil also reduced beta-amyloid plaque in in vitro. The amyloid hypothesis is believed to be the most promising approach in the development of anti-AD drugs. We speculate the mechanism of lowering beta-amyloid by donepezil implicate alpha-secretase (alpha-secretase) enhancer.     

Effects of cholinergic and adrenergic drugs on intraluminal pressures and contractility of the rat testis and epididymis in vivo

Intravenous administration of methacholine (200 micrograms/kg) caused no changes in the seminiferous tubules of rats, but significantly increased intraluminal pressures and contractility of the caput, the corpus and the cauda epididymidis. The effect of methacholine was abolished by pretreatment with atropine (500 micrograms/kg), but not by phentolamine (400 micrograms/kg) or propranolol (400 micrograms/kg). Adrenaline (5-40 micrograms/kg), noradrenaline (5-40 micrograms/kg) and phenylephrine (100-400 micrograms/kg) had no effect on the seminiferous tubules, but dose-dependently elevated intraluminal pressures and enhanced the contractility of all regions of the epididymis. Isoproterenol (100-800 micrograms/kg) did not affect intraluminal pressures of the seminiferous tubules and the epididymal duct. The stimulatory effect of adrenergic agonists was specifically blocked by phentolamine, but not by propranolol or atropine. Cholinergic and adrenergic antagonists did not alter spontaneous contraction of the epididymis. The results suggest that the contractility of all segments of the rat epididymis, but not the seminiferous tubules, can be increased by autonomic drugs. The enhancing effect of adrenergic drugs is probably the result of activation through alpha-adrenergic receptors.     

Localization and release of lysozyme from ferret trachea: Effects of adrenergic and cholinergic drugs

Summary Lysozyme is a bacteriolytic enzyme found in respiratory tract fluid. In this study, immunocytochemistry was used to determine the cells of origin of tracheal lysozyme in the ferret. Lysozyme was found in secretory granules of serous but not mucous cells in the submucosal glands, and was absent from the surface epithelium, cartilage, and connective tissue. The exclusive presence of lysozyme in serous gland cells renders it useful as a biochemical marker of that cell type.Measurements of lysozyme assayed from the incubating medium indicated that bethanechol stimulated lysozyme release by 260±80.9% (mean ±SE), phenylephrine by 80±16.4%, and terbutaline by 25±10.2%. Electron-microscopic and immunocytochemical analysis of incubated tissues revealed loss of serous granules and lysozyme immuno-reactivity in response to the drugs. Atropine, propranolol, and phentolamine blocked the stimulatory effects of bethanechol, terbutaline, and phenylephrine, respectively.These findings establish the usefulness of lysozyme as a serous-cell marker and demonstrate that secretory responses of different magnitude are evoked by equimolar concentrations of alpha- and beta-adrenergic and cholinergic drugs.     

对两用生物技术发展现状与生物安全的思考

生命科技的蓬勃发展与全球化步伐的持续加速,为人类社会带来了诸多福祉。然而,生物技术的两用特征和传染病严峻的流行趋势带来了一系列生物安全隐患,引发了世界性的生物安全问题。随着国际形势的日趋复杂,生物安全这一非传统安全问题已成为国家安全体系的重要组成部分。本文通过分析典型两用生物技术的潜在威胁及新发突发传染病的发展趋势,指出我国生物安全领域面临的挑战性问题。同时结合研究发达国家在战略、政策与技术方面应对生物安全的重要举措,从战略布局、科技创新、团队建设、政策支持等方面为我国在两用生物技术的生物安全领域的发展提出建议。     

The influence of adrenergic and cholinergic blocking drugs on the glycogen content of the brain in rats deprived of paradoxical sleep

Recent studies have pointed out biochemical and pharmacological phenomena associated with the mechanism or mechanisms of sleep, especially in its paradoxical phase (Jouvet, 1964; Mandel, 1964). Our previous experiments have shown that paradoxical sleep (PS) deprivation leads to the fall of total glycogen content in certain regions of the brains of cats (Mr?ulja, Raki? and Radulova?ki, 1967; Mr?ulja and Raki?, 1968) and rats (Karad?i? and Mr?ulja, 1969). It was shown that changes of glycogen content correspond to PS deprivation and that PS deprivation is a specific stress to which the CNS responds selectively. Alterations in the glycogen concentration in a number of different brain structures lead us to conclude that neural areas affected by PS deprivation are widely distributed. Jouvet (1962) was one of the first to suggest that a neurohumoral mechanism may be concerned in the control of and characteristics of sleep. Experiments have shown that both cholinergic and adrenergic mechanisms may be involved in the initiation, maintenance and control of sleep. It has also been pointed out that paradoxical sleep can be started and maintained by cholinergic drugs (Matsuzaki, Okada and Shuto, 1967, 1968), blocked or reduced by anticholinergic compounds (Matsuzaki et al., 1968), and stimulated by noradrenaline or by its precursor, DOPA (Matsumoto and Jouvet, 1964). Bowers, Hartmann and Freedman (1966) showed that the ACh level of the rat telencephalon decreases with PS deprivation while the levels of norpinephrine and serotonin remain the same (Barchas and Freedman, 1963). More recently, Pujol, Mouret, Jouvet and Glowinski (1968) found the increased turnover of cerebral norepinephrine during rebound of PS in the rat. It is also of interest to point out that probably both adrenergic and cholinergic processes participate in the glycogenolytic effect of physostigmine (Mr?ulja, Terzi? and Varagi?, 1968). It was suggested that physostigmine initiates the cholinergic processes which then trigger off adrenergic processes. The aim in the present work was to determine the glycogen content in certain brain regions of rats which were subjected to PS deprivation lasting 72 hr and treated with some cholinergic or beta-adrenergic blocking agents, as well as with a catecholamine depleting drug.     

Membrane properties of cultured rat sympathetic neurons: Morphological studies of adrenergic and cholinergic differentiation

Dissociated neurons from the newborn rat superior cervical ganglion were grown under conditions which lead to either adrenergic or cholinergic differentiation. Lectins and toxins were used to detect differences in the cell membrane associated with transmitter status, age of the neurons, or location on the neurons. These ligands were made visible in the light or electron microscope by coupling to rhodamine or colloidal gold. The density of binding sites for concanavalin A (Con A), ricin (RCA₆₀), and wheat germ agglutinin (WGA) increased with age in culture on both adrenergic and cholinergic cells. Soybean agglutinin (SBA) binding increased about threefold on adrenergic axons, but failed to increase on neurons induced to become cholinergic by medium conditioned by rat heart cells (CM). The effect of CM on SBA binding paralleled previously described effects of CM on transmitter production; the CM binding pattern developed slowly and was not readily reversible. Mature adrenergic neurons also appeared to bind more WGA than neurons in CM cultures. Tetanus toxin gold binding was uniform, but low, on axons of adrenergic and cholinergic neurons at all ages. In contrast, cholera toxin binding decreased with age on adrenergic axons. Binding sites for SBA and tetanus toxin were found to be less numerous on the cell body surface than on the axonal surface. Thus growth in CM induces fundamental changes in the phenotype of developing sympathetic neurons involving the cell membrane as well as transmitter choice. Differences also appear with maturation and between axonal and somatic cell surface membranes.     

A method for the localization of adrenergic nerves during early development

Summary Problems associated with the low intensity and fast fading of the formaldehydeinduced fluorescence of adrenergic nerves in young foetal human and rat gut have been overcome by loading the nerves with a primary catecholamine. This has been achieved by incubating the tissue, before freeze-drying, in Krebs solution containing added noradrenaline or -methyl-noradrenaline. With this method fluorescent nerves have been revealed at a stage before any were demonstrable by normal procedures.This work was supported by the Australian Research Grants Committee and the National Heart Foundation of Australia. One of us (J. B. R.) was in receipt of a Commonwealth of Australia Postgraduate Award. We thank Prof. C. Wood for the human foetal material obtained, by hysterotomy, at legal terminations of pregnancy.