An extracellular retinol-binding glycoprotein in the eyes of mutant rats with retinal dystrophy: development, localization, and biosynthesis

Interstitial retinol-binding protein (IRBP) is a soluble glycoprotein in the interphotoreceptor matrix of bovine, human, monkey, and rat eyes. It may transport retinol between the retinal pigment epithelium and the neural retina. In light-reared Royal College of Surgeons (RCS) and RCS retinal dystrophy gene (rdy)+ rats, the amount of IRBP in the interphotoreceptor matrix increased in corresponding proportion to the amount of total rhodopsin through postnatal day 22 (P22). In the RCS-rdy+ rats, the amount increased slightly after P23. However, in the RCS rats there was a rapid fall in the quantity of IRBP as the photoreceptors degenerated between P23 and P29. No IRBP was detected by immunocytochemistry in rats at P28. The amount of rhodopsin fell more slowly. Although retinas from young RCS and RCS-rdy+ rats were able to synthesize and secrete IRBP, this ability was lost in retinas from older RCS rats (P51, P88) but not their congenic controls. The photoreceptor cells have degenerated at these ages in the RCS animals, and may therefore be the retinal cells responsible for IRBP synthesis. The putative function of IRBP in the extracellular transport of retinoids during the visual cycle is consistent with a defect in retinol transport in the RCS rat reported by others.     

在我国患急性腹泻成人中发现一种新轮状病毒

从3例急性成人腹泻患者粪便中,经电镜观察,成人腹泻轮状病毒—酶联免疫吸附试验(ADRV-ELISA)、普通轮状病毒—酶联免疫吸附试验(Rota-ELISA),猪抗C型(组)轮状病毒和鸡抗D型(组)轮状病毒血清分别与本病毒的免疫电镜试验以及RNA电泳等实验结果,发现了一种新轮状病毒,该病毒的形态结构与普通轮状病毒(Rotavirus)、成人腹泻论状病毒(Adult Diarrhoea Rotavirus,简称ADRV)极为相似,但抗原性与普通轮状病毒(A组),成人腹泻轮状病毒(B组),C型轮状病毒(C组),D型轮状病毒(D组)显然无关。基因分析表明,该病毒基因组由11个双链RNA片段组成,但其RNA电泳图型具有独自的特点,与目前公认的A组、B组、C组、D组论状病毒韵RNA电泳图型均不同,免疫电镜证实,该病毒能被人恢复期血清所凝集,表明该病毒可能是腹泻病人的病因。     

流行性成人腹泻病人排出成人腹泻轮状病毒的持续时间

成人腹泻轮状病毒(Adult Diarrhoea Rotavirus,简称ADRV)是引起青壮年急性胃肠炎的主要病原之一,1983年至1985年在我国许多地区暴发流行,严重危害着人民健康,至今尚无治疗药物。因此,摸清病人排病毒情况或规律,对及时控制传染源,预防ADRV大量传播有着重要意义。现将本文实验结果报告如下。     

Prostaglandin 12 reduces activation of human arterial smooth muscle cells in-vivo

Patients suffering from peripheral vascular disease have been “ultima ratio”-treated with PGI2 at a rate of 5 ng/kg/min for 6 hours a day and 5 consecutive days i.v. 20 of them underwent surgery thereafter as therapy was not sufficient. A histological examination and quantification of vascular tissue revealed that the number of activated smooth muscle cells was significantly lower in treated patients vascular segments than in untreated ones in all the different age groups. A comparable suppression was found in the intima and the media as well. It is thus concluded, that PGI2 inhibits smooth muscle cell proliferation most probably by inhibiting PDGF-release from the platelets and stimulation of smooth muscle cell cAMP. To achieve a more beneficial PGI2-effect at the vascular level, a prolonged PGI2-therapy looks rather promising.     

Differential effects of camptothecin and interactions with plant hormones on seed germination and seedling growth

Effects of camptothecin, a naturally occurring alkaloid, on seed germination varied from promotive to inhibitory, depending on the species used. It markedly inhibited seedling root growth but its inhibition of hypocotyl growth varied among species. Camptothecin inhibited GA₃-induced dark germination of lettuce (Lactuca sativa L.) seeds and hypocotyl elongation of seedlings. In contrast to ABA, the camptothecin inhibition of GA₃-induced germination could not be overcome by cytokinin. When seeds were germinated at 29C with a 0.5 h light treatment, little or no germination occurred in the camptothecin treatment, but addition of cytokinin overcame this inhibition.     

Initiation of swimming activity by trigger neurons in the leech subesophageal ganglion

The aim of this study was to identify neurons in the subesophageal ganglion of the medicinal leech which initiate swimming activity and to determine their output connections. We found two bilaterally symmetrical pairs of interneurons, Tr1 and Tr2, located in the first division of the subesophageal ganglion which initiate swimming activity in the isolated nervous system when depolarized with brief (1-3 s) current pulses. Tr1 and Tr2 are considered trigger neurons because elicited swimming episodes outlast the stimulus duration, and because the length of elicited swim episodes is nearly independent of the intensity with which Tr1 and Tr2 are stimulated. Tr1 and Tr2 have similar morphologies. The neurites of both cells cross contralaterally in the subesophageal ganglion, project posteriorly, and exit the subesophageal ganglion in the contralateral connective. The axons of Tr1 and Tr2 extend as far posterior as segmental ganglion 18 of the ventral nerve cord. Tr1 provides direct excitatory drive to three groups of segmental neurons which are capable of initiating swimming: swim-initiating interneurons (cells 204 and 205), serotonin-containing interneurons (cells 61 and 21), and the serotonergic Retzius cells. In addition, all Retzius cells in the subesophageal ganglion are excited directly by Tr1. These three groups of neurons are excited even if Tr1 stimulation is subthreshold for swim initiation. In contrast to Tr1, Tr2 stimulation evokes transient inhibition in swim-initiating and serotonin-containing interneurons, and has little immediate effect on Retzius cells. In addition, Tr2 indirectly inhibits several oscillator neurons, including cells 208, 33, and 60. When Tr1 is stimulated during a swimming episode the swim period decreases for several cycles, while stimulation of Tr2 during swimming episodes reliably resets the ongoing swimming rhythm. Our findings indicate that Tr1 and Tr2 are trigger neurons which initiate swimming activity by different pathways. These neurons also have functional interactions with the swim oscillator network since either Tr1 or Tr2 stimulation during swimming can modulate the ongoing swimming rhythm.     

Intracellular localisation of phytochrome in oat coleoptiles by electron microscopy

We have analysed the intracellular localisation of phytochrome in oat coleoptile cells by electron microscopy and confirm and extend light-microscopical findings of previous authors. We used indirect immuno-labeling with polyclonal antibodies against 60-KDa phytochrome from etiolated oat seedlings, and a gold-coupled second antibody, on ultrathin sections of LR-white-embedded material. In dark-grown seedlings, phytochrome-labeling is distributed diffusely throughout the cytoplasm. Organelles and membranes are not labeled. After photoconversion of the red-absorbing form of phytochrome to the far-red absorbing form (Pfr) (5-min red light; 660 nm), the label is sequestered uniquely in electron-dense areas within the cytoplasm. These areas are irregularly shaped, are often located in the vicinity of the vacuole, are not surrounded by a membrane, exclude cellular organelles and ribosomes and are not found in dark-grown material; an immediate 5-min farred light pulse after the red light does not cause these structures to disappear. After a dark period of 3–4 h following red-light irradiation, these electron-dense structures disappear together with any specific labeling. We suggest a Pfr-induced aggregation of an unknown, phytochrome-binding protein or proteins.Abbreviations Pr and Pfr phytochrome in its red and far-red absorbing form, respectively     

Similarity of activation of yeast phosphofructokinase by AMP and fructose-2,6-bisphosphate

Phosphofructokinase from yeast is effectively activated by AMP and fructose-2,6-bisphosphate by increasing the affinity of the enzyme to fructose-6-phosphate and the maximum activity toward this substrate. The enzyme is activated by AMP and fructose-2, 6-bisphosphate both at high and at low concentrations of ATP. The half maximum stimulation concentrations of AMP and fructose-2, 6-bisphosphate are about 200 microM and 2 microM, respectively. At saturating concentrations of AMP and fructose-2, 6-bisphosphate similar maximum activities were observed in the dependence of enzyme activity on the concentrations of fructose-6-phosphate. The fructose-6-phosphate affinity is more enhanced by fructose-2, 6-bisphosphate than by AMP.     

Comparative kinetic studies of the dealkylation reaction and steroid hydroxylations in various oxygen and carbon monoxide:oxygen atmospheres

The time-course kinetics of the cytochrome P-450-catalyzed dealkylations of the exogenous compounds benzphetamine, ethylmorphine, codeine, and 7-ethoxycoumarin were compared to the hydroxylation of the endogenous compound testosterone. Using liver microsomes from phenobarbital-induced rats, the time course of the demethylations of ethylmorphine, codeine, and especially benzphetamine was characterized by a fast initial phase of enzymatic activity and then a steady decline in the rate throughout the remainder of the reaction. In contrast, under the same experimental conditions, both the dealkylation of 7-ethoxycoumarin and the hydroxylation of testosterone showed no initial fast phase of activity and a constant rate of product formation for most of the remainder of the time course. The difference also held for the carbon monoxide inhibition studies in which the degree of inhibition of the demethylation reactions by a variety of CO:O₂ mixtures was time dependent, in contrast to the constant, time-independent degree of CO inhibition of the other two reactions. The kinetics of the demethylation reactions could not be explained by enzyme destruction, back reaction, or product adduct formation and were further confirmed by measurements of the rate of O₂ utilization and NADPH oxidation. The complexity of the demethylation reaction should be taken into consideration in any detailed studies of the monooxygenation reaction system.     

The key role of residue 5 in angiotensin II

The conformation–biological activity relationships in a series of angiotensin II analogs substituted in position 5 were studied. Results indicated that only analogs with β-branched residue in position 5 possess spectral and biological properties identical to that of parent angiotensin II.