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.     

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.     

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

The Patient Self-Determination Act was implemented in December 1991. Before and after its implementation, we used a structured interview of 302 randomly selected patients to determine their awareness, understanding, and use of advance directives. Implementation of the Act did not have a major effect on these. Although more than 90% of patients were aware of the living will, only about a third selected the correct definition or the correct circumstances in which it applied, and less than 20% of patients had completed one. About a third of patients were aware of a Durable Power of Attorney for Health Care and chose the correct definition, and about half identified the correct circumstances in which it applies; less than 10% had completed such a document. Surprisingly, patients who said they had completed advance directives did not demonstrate better understanding of these documents. Our results indicate that many patients, including some who have completed advance directives, do not fully understand them. It may be unwise to regard these documents as carefully considered, compelling statements of patients'' preferences. Appropriate responses to our findings include increased public education, revising state statutes to bring them into congruence with public perception, and expanding the dialogue between physicians and patients.     

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 Memoriam

Practicing physicians are just becoming aware of the animal rights movement, which during the 1980s spawned numerous acts of violence against research facilities throughout the United States. The animal rightists are challenging physicians to show moral justification for the human exploitation of nature and the world of subhuman species. They have aroused public interest in animal welfare, sparked protective legislation for experimental animals, and indirectly encouraged the creation of committees to oversee the conduct of animal experimentation and the conditions of animal confinement. This controversy has necessitated a closer look at the questions of animal experimentation and animal rights against the backdrop of human experimentation and human rights. Physicians and specialists in animal care seek to alleviate suffering and anxiety, and, as moderates, they may be able to bring both sides of the animal rights controversy together in a spirit of mutual tolerance and in the common cause of promoting both human and animal welfare.     

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 Memoriam

Thirteen cows, Experiment I, were injected at 1 h post-partum with saline (n=4) or Human Chorionic Gonadotropin, (HCG) (n=9). Eleven additional cows, Experiment II, were ovariectomized (ovx) unilaterally at 10 days pre-partum (n=4) or 4 h post-partum (n=7) to remove the only corpus luteum (CL). These ovx post-partum animals (n=7) were also injected as part of Experiment I with saline (n=2) or HCG (n=5). All CL were sliced and incubated in media alone and with LH, tritium-labeled-pregnenolone (³HP₅) or both. Blood samples were collected pre- and post-injection, Experiment I and pre- and post-surgery, Experiment II. Plasma and media samples were analyzed for progesterone (P₄) by radioimmunoassay. Media samples with ³HP₅ were chromatographed for determination of P₅ conversion to P₄. No significant differences (P > 0.1) between P₄ profiles for saline or HCG treated animals were observed. Pre- and post-partum CL slices were able to convert P₅ to P₄. Post-partum CL slices were unresponsive to LH whereas pre-partum slices responded. These data indicate the decline in luteal function peri-partum is probably not due to withdrawal of gonadotropin support.     

In Memoriam

Abstract

We are saddened to report the death of Professor Richard T. Walker of the University of Birmingham, England, on November 20, 1997. His passing is both a professional loss to the scientific community and a personal loss to those of us who knew him.     

In Memory

Abstract

Dr. Mathias P. Mertes, well-known medicinal chemist, member of the Editorial Advisory Board of Nucleosides & Nucleotides, and a good friend, died unexpectedly earlier this year. An obituary written by Drs. Gary Grunewald and Robert Hanzlik of the University of Kansas is presented below followed by a list of the publications of Dr. Mertes. Many of us have pleasant memories of stimulating interactions with Matt. We can hope that the spirit and enthusiasm with which Matt approached science has rubbed off on some of us. He will be missed.     

In Memoriam

A key element of the self‐critique in contemporary anthropology centres on the idea that categories such as culture and society have exaggerated human differences. This paper argues that the work of Anthony Cohen, which has attempted to frame “localities” as a new anthropological object, can be criticized on similar grounds. A close reading of Cohen's theoretical and ethnographic writings shows that the “anthropology of locality”, while claiming to be a critique of nationalhomogenization, in fact replicates ata lower level of scale features of the national units. Consideration of this particular example of the exaggeration of (local) difference, moreover, occasions reflection on the wider critique of generalization within anthropology.     

In Vivo,In Vitro,and In Silico Characterization of Peptoids as Antimicrobial Agents

Bacterial resistance to conventional antibiotics is a global threat that has spurred the development of antimicrobial peptides (AMPs) and their mimetics as novel anti-infective agents. While the bioavailability of AMPs is often reduced due to protease activity, the non-natural structure of AMP mimetics renders them robust to proteolytic degradation, thus offering a distinct advantage for their clinical application. We explore the therapeutic potential of N-substituted glycines, or peptoids, as AMP mimics using a multi-faceted approach that includes in silico, in vitro, and in vivo techniques. We report a new QSAR model that we developed based on 27 diverse peptoid sequences, which accurately correlates antimicrobial peptoid structure with antimicrobial activity. We have identified a number of peptoids that have potent, broad-spectrum in vitro activity against multi-drug resistant bacterial strains. Lastly, using a murine model of invasive S. aureus infection, we demonstrate that one of the best candidate peptoids at 4 mg/kg significantly reduces with a two-log order the bacterial counts compared with saline-treated controls. Taken together, our results demonstrate the promising therapeutic potential of peptoids as antimicrobial agents.     

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。     

Regulation of Pyruvate Decarboxylase In Vitro and In Vivo

Results presented in this paper strongly support the view thatregulation of the key enzyme of alcoholic fermentation, pyruvatedecarboxylase (PDC), is achieved in a number of ways, all associatedwith possible lowering of the cytoplasmic pH during anoxia.These mechanisms include not only the well-known acid pH optimumof PDC, but also long-term, reversible changes in characteristicsof the enzyme established both in vitro and in vivo. Following transfer of desalted extracts from pH 6.0 to 7.4,maximal activity of PDC was decreased, while there was a considerableincrease in the lag before maximal activity was reached. Similarchanges in enzyme characteristics were observed when wheat (Triticumaestivum L. cv. Gamenya) roots and rice (Oryza sativa L. cv.Calrose) coleoptiles were transferred from anoxic to aerobicsolutions, provided PDC was assayed within 10 min of the startof maceration. All of the above changes were usually readilyreversible when extracts were returned to pH 6.0, or when plantswere returned to anoxic solutions. Additional regulation of PDC would be achieved by the S_0.5 forpyruvate which is 0.75 mol m^–3 at pH 6.0, 1.0 mol m^–3at pH 6.8, and 2.5 mol m^–3 at pH 7.4; the latter is wellabove estimates for pyruvate concentrations in the cytoplasmof aerated tissues. We assess that the combined effects of the acid pH optimum,the high S_0.5 at pH 7.4 and the long-term decreases in activityobserved during incubation at pH 7.4 would reduce PDC activityin aerobic cells to at most 7% of the activity in anoxic cells.Possible additional controls for the pathway of alcoholic fermentationare briefly considered. Key words: PDC, regulation, anoxia