Variation In Surface Proteins In Tetrahymena*

SYNOPSIS. Surface proteins of Tetrahymena were identified by lactoperoxidase iodination, and comparisons were made between a number of strains and species within the genus. an adequate procedure for strain comparisons was found to be solubilization of whole cells following iodination, separation of total cell protein using polyacrylamide gel electrophoresis, and identification of surface proteins by autoradiography of dried gels. the results obtained in the present study show the existence of both interspecific and intraspecific variation in surface proteins of Tetrahymena, but the differences tend to be small within species and large between species. the relation of these cell surface fingerprints to the present taxonomic designations within the genus is discussed. Questions are raised about the functional significance of these surface proteins.     

右美托咪定的临床麻醉应用进展

右美托咪定(dexmedetomidine,Dex)是高选择性α2-肾上腺素受体激动剂,具有镇静、镇痛、抑制交感神经活性、无呼吸抑制等药理性质。多项研究证实:围术期或ICUs住院期间给予患者右美托咪定,可以增加患者机械通气耐受力,减少机械通气时间,改善患者病情恢复,减少呼吸抑制,稳定血流动力学,减少麻醉剂用量及降低麻醉剂不良反应发生率,抑制应激反应,保护肺脏、神经功能、心脏功能,降低谵妄发生率,抗寒颤等作用特点。虽然右美托咪定存在心动过缓及低血压等不良反应,故应控制给药速度、剂量,合理用药在以便循环波动可控范围内。目前,右美托咪定可用于重症监护病房(ICUs)、全身麻醉、区域麻醉、小儿麻醉、日间手术及无痛检查等辅助用药。本文主要对右美托咪定的临床麻醉应用做以下介绍。     

C-Myc Expression In Exfoliated Cells In Serous Effusions

In an attempt to improve the discrimination between benign and malignant cells in pleural and peritoneal fluids, 32 effusions were investigated for c-myc expression. Smears were prepared from cells harvested from the fluids for immunocytochemical staining to identify the presence of c-myc protein. Recombinant DNA technology (Northern blotting, slot blotting and in situ hybridization) was used to detect c-myc mRNA. No significant difference in expression of c-myc was noted in benign or malignant effusions. Although the results are inconclusive, the recombinant DNA technology developed for this research could be used to investigate the expression of other oncogenes in cytological material.     

In memoriam

Microcosm experiments were performed to identify the influence of bacterial cell surfaces on the morphology, mineralogy, size and solubility of CaCO₃ precipitated in response to the enzymatic hydrolysis of urea in an artificial groundwater (AGW) by the ureolytic bacteria, Bacillus pasteurii. In each microcosm, B. pasteurii were contained within a cellulose dialysis membrane (10 K Dalton MWCO), resulting in bacteria-inclusive and bacteria-free AGW solution. Urea hydrolysis by B. pasteurii resulted in the production of ammonium and an increase in pH in the whole AGW solution. This initiated predominantly rhombohedral calcite precipitation at the same critical saturation state ( S _critical = 12) in the B. pasteurii-inclusive and bacteria-free zone of the AGW, indicating the mineralogy and morphology of CaCO₃ precipitation is not controlled by B. pasteurii surfaces. However, the temporal evolution of distinctly different lognormal crystal-size-distributions in the B. pasteurii-inclusive and bacteria-free zone of the AGW resulted from identical changes in bulk solution chemistry. Specifically, B. pasteurii increased the size and size variance of crystals, and led to a greater crystal growth rate throughout the experiments, relative to bacteria-free AGW. Calculated crystal solubility (ln K _S0 ) was lower for crystals > 4000 nm in diameter, reflecting smaller molar surface areas. This suggests that the larger crystals generated in the presence of B. pasteurii have a lower affinity for re-dissolution than those generated in the bacteria-free AGW, which may act as a positive feedback to maintain larger crystal sizes in the presence of B. pasteurii. During ureolysis, higher bacterial concentrations may therefore generate larger and less soluble carbonate crystals. This has important implications for the adaptation of bacterial ureolysis as a method for precipitating calcium carbonate and co-precipitating metals and radionuclides in contaminated aquifers.     

In Appreciation

Marine animals can induce metallothioneins (MTs) in their responses to exposure to certain trace metals in the environment. MTs generally function as metal storage/detoxification or homeostatic regulation of both essential and non-essential metals. This review discusses the important roles of MTs in metal biokinetics other than metal detoxification and homeostasis in marine animals. Recent studies have revealed the complicated cellular and biochemical processes involving intracellular ligands (cytosolic proteins and insoluble deposits) during metal uptake and elimination. The responses of metal biokinetics to MT induction are metal- and organism-specific. Depending on the different marine animals and metals, all biokinetic parameters such as dissolved metal uptake rate, dietary assimilation efficiency and elimination (efflux) rate can be significantly impacted by MT induction. Among the different metal biokinetic parameters, dietary assimilation efficiency and elimination rate appear to be most impacted by MT induction. MT turnover kinetics can also significantly affect metal uptake kinetics, but again, such influence is also dependent on the organism, particularly its predominant pathway of metal detoxification. Even though the total MT pool in aquatic animals may remain constant, the turnover of MTs, involving MT synthesis and breakdown, can potentially lead to a major change of metal accumulation biokinetics. We propose several issues that need to be further addressed in studying the interaction between MT induction and metal accumulation biokinetics.     

In Vitro and In Vivo Characterization of Pyocin

Pyocin, a bacteriocin obtained from lysates of ultraviolet-induced cultures of Pseudomonas aeruginosa was characterized in vitro and in vivo after 1,000-fold purification by chemical, column, and differential centrifugation procedures. Electron micrographs of negatively stained pyocin preparations contained rod-shaped particles which resembled the contractile tail protein of the T-even phages of Escherichia coli. Although two separate and distinct pyocin fractions were eluted from diethylaminoethyl cellulose (pH 7.5) during the purification procedure, the particles appeared identical. In addition, the two fractions exhibited a close correlation between their titers and the particle numbers as observed in the electron microscope. The particles were approximately 20 by 90 mmu with a core diameter of 5 mmu and a sheath length of 50 mmu. Neither intact phage nor ghosts were seen in any of the preparations, although ringlets of two different diameters, which appeared to correspond to the diameters of the sheath and inner core, were observed. Other studies indicated that, although crude preparations were stable to freezing and thawing, purified preparations lost all of their activity under similar treatment. However, the addition of 50% glycerol to purified preparations completely protected activity. Conversely, aged normal human or rabbit sera enhanced the antibacterial activity of pyocin approximately fourfold, although serum albumin and hemoglobin had no effect. In vivo studies indicated that purified pyocin was not lethal for mice when injected intraperitoneally in concentrations of 28,000 to 1,400,000 units (5.6 to 276 mug of protein), nor was 7,200 to 36,000 units dermonecrotic for rabbits.