Ursodeoxycholate stabilizes phospholipid-rich membranes and mimics the effect of cholesterol: investigations on large unilamellar vesicles

Ursodeoxycholate is used to treat primary biliary cirrhosis and is incorporated into hepatocyte plasma membranes. Its steroid nucleus binds to the apolar domain of the membrane, in a similar position to cholesterol. Therefore the question arises whether ursodeoxycholate has a similar effect on membrane structure and stability as cholesterol. Using differential scanning calorimetry the thermotropic behavior of egg phosphatidylcholine and dimyristoylphosphatidylcholine were studied after incubation with cholesterol or ursodeoxycholate. Large unilamellar vesicles were prepared with cholesterol contents of 0-50%. Following incubation of these vesicles with different amounts of ursodeoxycholate, vesicle stability in a gravitational field was investigated by measuring the phospholipid and cholesterol release. Vesicle size was studied by laser light scattering after incubation with cheno- and ursodeoxycholate, and the release of entrapped carboxyfluorescein was measured by means of fluorescence spectroscopy. Increasing cholesterol diminished the enthalpy of the phase transition in the membrane. Ursodeoxycholate decreased the enthalpy of the phase transition at even lower concentrations. Lipid release from vesicles in a high gravitational field diminished with increasing cholesterol content of the vesicles. Ursodeoxycholate had a comparable effect, which increased as the cholesterol content of the vesicles was decreased. Chenodeoxycholate damaged vesicles, whereas ursodeoxycholate did not. Cholesterol and ursodeoxycholate (below its critical micellar concentration) decreased the carboxyfluorescein release from vesicles induced by chenodeoxycholate. Thus like cholesterol, ursodeoxycholate is incorporated into phospholipid model membranes and reduces the change in enthalpy of the gel to liquid-crystalline phase transition. Like cholesterol ursodeoxycholate also maintains membrane stability and prevents membrane damage induced by mechanical and chemical stress.

Learning from our patients: one participant's impact on clinical trial research and informed consent

This Perspective includes an essay on modifying phase I clinical trials, written by George Zimmer, who was a professor of English and a commentary on that essay. Professor Zimmer was a cancer patient who participated in the phase I clinical trial program at the University of Chicago. His ideas are eloquently expressed and have had a profound effect on our investigational research for anticancer agents. Although at times his suggestions may seem radical, Professor Zimmer urges us to reconsider the 50-year-old Nuremberg paradigm that participants in human research are ignorant and vulnerable and must be protected. Although we must protect patients who have life-threatening diseases from coercive inducements and misplaced hopes, we must also listen carefully and thoughtfully to our patients. This is particularly true when, as research participants in the face of sacrifice and the threat of a life-ending diagnosis, they have made the effort to express their concerns. With the effect of the acquired immunodeficiency syndrome movement on clinical studies and on drug research and development, a precedent has been set that allows patients to reshape their role as participants in research trials. On a personal level, the essay by Professor Zimmer has had a significant effect on our research methods and, indeed, the focus of our research efforts. Thus, it is with a sense of respect and honor that we share George Zimmer's thoughts and our comments about the influence he has had on our research practices.

The cell receptor level is reduced during persistent infection with influenza C virus

Persistent influenza C virus infection of MDCK cells perpetuates the viral genome in a cell-associated form. Typically, virus production remains at a low level over extended periods, in the absence of lytic effects of replication. In this study, we demonstrate that persistently infected cells are very restricted in permissiveness for superinfection. By reconstitution experiments, using bovine brain gangliosides as artificial receptors, the degree of super-infection was markedly increased. Analysis of cellular receptor expression revealed reduced concentrations of sialoglycoproteins in general and a limited presentation of the major receptor gp40. Cocultures of persistently infected and uninfected cells (the latter carrying normal receptor levels) initiated a transient rise in virus titers. This kind of induction of virus synthesis appeared to be mainly receptor-linked, since a receptor-deprived subline, MDCK II, did not give rise to a similar effect. Susceptibility of MDCK II cocultures could be partly restored by ganglioside treatment. In accordance to related virus systems, these findings on influenza C virus suggest a role of cell receptor concentrations in the regulation of long-term persistence.

Electron paramagnetic resonance studies on nitroxide radical 2,2,5,5-tetramethyl-4-piperidin-1-oxyl (TEMPO) redox reactions in human skin

Electron paramagnetic resonance (EPR) is currently being explored for the study of living biological systems. Among biophysical and biochemical applications, the study of nitroxide radical interactions with tissue antioxidants and oxidants is of growing interest. Skin is a target organ of the EPR methodology and is frequently exposed to oxidative stress. We investigated the piperidine-type nitroxide 2,2,5,5-tetramethyl-4-piperidin-1-oxyl (TEMPO) because it is skin permeable and readily accepts electrons in biological systems. TEMPO is readily scavenged on the surface of cultured human skin. Pretreatment of skin cultures with butylhydroperoxide, which decreases intracellular ascorbate and glutathione, causes inhibition of nitroxide scavenging. Exposure of skin cultures to dehydroascorbate, which is internalized and converted to ascorbate, leads to stimulation of nitroxide scavenging. In human keratinocytes and fibroblasts, the TEMPO radical is reversibly reduced to the hydroxylamine depending on the oxygen concentration and the availability of intracellular glutathione and ascorbate. Cell exposure to the glutathione synthetase inhibitor buthionine-sulfoximine depleted intracellular glutathione and inhibited nitroxide reduction; exposure to dehydroascorbate or glutathione-monoethylester increased intracellular ascorbate or glutathione concentration and stimulated nitroxide reduction. Quantitative considerations indicate that the major reduction site of TEMPO in skin and skin cells is the cytosol ascorbate/glutathione redox cycle. We suggest that analysis of TEMPO radical scavenging by the EPR technique is a convenient method for measuring skin ascorbate and thiol-dependent antioxidant activity in vitro and in vivo.

Virus entry into a polarized epithelial cell line (MDCK): similarities and dissimilarities between influenza C virus and bovine coronavirus

We have analysed the uptake of influenza C virus and bovine coronavirus (BCV) by a polarized epithelial cell line, Madin-Darby canine kidney (MDCK) cells. Both viruses use N-acetyl-9-O-acetylneuraminic acid as a receptor determinant for attachment to cells. Virus binding assays with immobilized proteins indicated that a glycoprotein of 40 kDa is the major surface protein containing the receptor determinant for the two viruses. MDCK cells grown on filters for permeable support were found to have differential sensitivity to infection by these viruses. Both viruses were able to initiate infection via the apical domain of the plasma membrane, but only influenza C virus also accomplished infection via the basolateral plasma membrane. The resistance of MDCK cells to BCV infection from the basal filter chamber was overcome when the cell polarity was abolished by maintaining the cells in calcium-free medium. This finding indicates that the resistance to basolateral infection by BCV is a property of the cell line and not due to a technical problem related to the use of filters. Our results indicate that two viruses which use the same receptor for attachment to cells may differ in their ability to enter polarized cells. The possible involvement of an accessory molecule in the entry of BCV is discussed.

Digestive leishmaniasis in acquired immunodeficiency syndrome: a light and electron microscopic study of two cases

An increased incidence of visceral leishmaniasis in patients infected with the human immunodeficiency virus (HIV) is observed in areas in which both infectious diseases are endemic. Intensive worldwide traveling has also resulted recently in an increasing number of leishmanial and HIV coinfections in nonendemic areas. We describe the clinical, light microscopic, and ultrastructural features of two cases of imported, HIV-related, visceral leishmaniasis involving the alimentary tract, including the esophagus, the stomach, the duodenum, the ileum, the colon, and the rectum. We also discuss the differentiation of leishmanial infections from other HIV-related gastrointestinal opportunistic infections.

Interaction of glucose and metformin with isolated red cell membrane

Isolated human erythrocyte membranes (red blood cell (RBC) ghosts) were incubated with glucose at 5, 10, 20 and 100 mmol/l concentrations, with insulin (0.01 to 200 mU/l) and metformin (CAS 657-24-9) 0.5 up to 50.0 mumol/l). Binding studies with 14C-glucose and subsequent gel electrophoresis revealed 60% of the radioactivity around ban 4.2-4.5 at 5 mmol/l, whereas a random distribution of radioactivity over all protein bands of the RBC membrane was found at 20 mmol/l concentration after incubation for 30 min or 48 h. Metformin does not bind covalently to RBC membranes, however, after photochemical linkage of 14C-metformin via the aminoreactive linker azidophenylglyoxal the highest radioactivity (21%) was counted in the range of band 4.2-4.5. In parallel with an increase of order parameters of 5-doxyl-stearic acid the thiol status of the membranes decreases as determined by monobromobimane fluorescence. 20 and 100 mmol/l concentrations of glucose decrease the reactivity of membrane thiols towards bromobimane significantly to 73 and 62% of the controls. Concomitantly, membrane fluidity at polar sites is diminished as measured by order parameters of spin label 5-doxyl stearic acid. In RBC membranes pretreated with 20 mmol/l glucose the decreased fluorescence is significantly raised again by insulin and metformin. This effect is even more pronounced, if insulin and metformin are incubated together. Reaction of membrane thiols with a maleimido spin label detects modification in the ratio of mobile and immobilized spin label populations in the electron paramagnetic resonance signal under the above conditions, indicative of conformational changes of membrane proteins.

Comparative study on four enzyme-linked immunosorbent assays and a cocultivation assay for the detection of antigens associated with the bovine viral diarrhoea virus in persistently infected cattle

Four commercially available ELISAs for detection of antigens associated with the bovine viral diarrhoea virus in persistently infected cattle have been compared. The tests are equally specific (100%) and the sensitivity of three ELISAs is comparable with that of a conventional cocultivation assay. Performing ELISA on samples from young animals that received colostrum may yield false negative results because of interference of maternal antibodies in the tests. It is concluded that ELISA can be a valuable tool in eradications programs when large numbers of cattle are to be monitored.

Determination of rate constants of the reactions of thiols with superoxide radical by electron paramagnetic resonance: critical remarks on spectrophotometric approaches

Two new EPR approaches were developed for determination of rate constants of reaction glutathione (GSH), N-(2-mercaptopropionyl) glycine (MPG), dihydrolipoic acid (BNL), and tetranor-dihydrolipoic acid (TNL) with superoxide radical. In both cases the competition between thiols and spin-trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) for superoxide radical was used. In the first method the dependence of amplitude of EPR spectrum of DMPO-OOH spin adduct on concentration of thiols in a superoxide-generating system was studied. In the second approach the changes in reduced thiol concentration due to reaction with superoxide radical were measured by nitroxide biradical containing disulfide bond. Observed rate constants were the following: GSH, 1.8 x 10(5) M-1s-1; MPG, 2.2 x 10(5) M-1s-1; TNL, 1.2 x 10(5) M-1s-1; BNL, 2.5 x 10(5) M-1s-1; DHL, 4.8 x 10(5) M-1s-1. The determination of the rate constants of reaction of superoxide radical with thiols by spectrophotometrical cytochrome C assay could result in an underestimation of the values due to the reduction of cytochrome C by thiols. Use of epinephrine for this purpose could lead to an overestimation of experimental rate constants because the adrenochrome formed in the reaction of epinephrine with superoxide radical reacts with thiols.

T cell responses in calcineurin A alpha-deficient mice

We have created embryonic stem (ES) cells and mice lacking the predominant isoform (alpha) of the calcineurin A subunit (CNA alpha) to study the role of this serine/threonine phosphatase in the immune system. T and B cell maturation appeared to be normal in CNA alpha -/- mice. CNA alpha -/- T cells responded normally to mitogenic stimulation (i.e., PMA plus ionomycin, concanavalin A, and anti-CD3 epsilon antibody). However, CNA alpha -/- mice generated defective antigen-specific T cell responses in vivo. Mice produced from CNA alpha -/- ES cells injected into RAG-2-deficient blastocysts had a similar defective T cell response, indicating that CNA alpha is required for T cell function per se, rather than for an activity of other cell types involved in the immune response. CNA alpha -/- T cells remained sensitive to both cyclosporin A and FK506, suggesting that CNA beta or another CNA-like molecule can mediate the action of these immunosuppressive drugs. CNA alpha -/- mice provide an animal model for dissecting the physiologic functions of calcineurin as well as the effects of FK506 and CsA.

[Controlled reperfusion of the extremities for preventing local and systemic damage after prolonged ischemia. An experimental study with the swine model]

Our previous studies in isolated rat hindlimbs using crystalloid perfusion solutions have shown that control of the initial reperfusion reduces postischemic complications. However, no experimental study has been undertaken to evaluate the concept of controlled limb reperfusion experimentally in an in-vivo blood-perfused model and to assess the local as well as systemic effects of normal blood reperfusion and controlled limb reperfusion. Of twenty pigs undergoing preparation of the infrarenal aorta and iliac arteries, six were observed for 7.5 hours and served as controls. Fourteen other pigs underwent 6 hours of complete infrarenal occlusion. Thereafter, embolectomy was stimulated in 8 pigs by removing the aortic clamp and establishing normal blood reperfusion at systemic pressure. In 6 other pigs, control of the composition of the reperfusate and control of the conditions of reperfusion was done during the first 30 min, followed by normal blood reperfusion. Six hours of infrarenal aortic occlusion lead to a severe decrease in high energy phosphates and muscle temperature and a slight increase in creating kinase (CK) and potassium in the systemic circulation. Normal blood reperfusion resulted in severe reperfusion injury: massive edema developed (80.6% vs. 76.6%, p < 0.0009), the tissue showed a marked decrease in oxygen consumption (7.3 +/- 1.1 vs. 14.3 +/- 2.5 mL )2/100 g/min, p < 0.02), glucose consumption (0.19 +/- 0.06 vs. 0.51 +/- 0.03 mg/100 g/min, p < 0.06), tissue ATP (18.3 +/- 1.9 vs. 36.1 +/- 0.9 mumol/g protein, p < 0.000001), total adenine nucleotides (26.3 +/- 2.6 vs. 45.8 +/- 1.5 mumol/g protein, p < 0.00001), muscle pH (5.9 +/- 0.1 vs. 7.3 +/- 0.1, p < 0.000006) and total calcium in the femoral vein (2. +/- 0.1 vs. 2.7 +/- 0.1 mmol/L, p < 0.002). Furthermore, a massive increase was seen in CK concentration (12,743 +/- 2,562 vs. 513 +/- 80 U/L, p < 0.0003), potassium (7.9 +/- 0.3 vs. 4.4 +/- 0.2 mmol/L, p < 0.000001) and muscle rigidity (60 +/- 11 vs. 122 +/- 1 degree, p < 0.00008). In sharp contrast, initial treatment of the ischemic skeletal muscle by controlled limb reperfusion resulted in normal water content (77.6 +/- 0.4 vs. 76.8 +/- 0.3%), oxygen consumption (13.2 +/- 1.6 vs. 14.9 +/- 3.2 mL O2/100 g/min), glucose consumption (0.58 +/- 0.18 vs. 0.46 +/- 0.11 mg/100 g/min), flow (5.4 +/- 1.1 vs. 4.6 +/- 4.6 +/- 0.5 mL/100 g/min) and muscle rigidity (106 +/- 4 vs. 122 +/- 1 degree). Furthermore, controlled limb reperfusion resulted in higher total adenine nucleotides content (78% vs. 57% of control), less tissue acidosis (6.6 +/- 0.2 vs. 5.9 +/- 0.1, p < 0.002), severely reduced CK release (2,618 +/- 702 vs. 12,743 +/- 2.562, p < 0.02) and potassium release (5.1 +/- 0.3 vs. 7.9 +/- 0.3 mmol/L, p < 0.0002) as compared to normal blood reperfusion. In conclusion this study shows that 6 hours of acute infrarenal aortic occlusion will result in a severe reperfusion injury (postischemic syndrome) if normal blood at systemic pressure is given in the initial reperfusion phase. In contrast, initial treatment of the ischemic skeletal muscle by controlled limb reperfusion reduces the metabolic, functional and biochemical alterations.

Decrease of red cell membrane fluidity and -SH groups due to hyperglycemic conditions is counteracted by alpha-lipoic acid

Human red cell membranes (ghosts) were treated by 5 min of incubation with fasting or hypo- and hyperglycemic concentrations of D-glucose. This simulation of nondiabetic or diabetic conditions revealed an influence on membrane fluidity and on protein -SH reactivity. Protein -SH groups, measured with Ellman's reagent, generally behave in the same way as membrane fluidity determined with diphenylhexatriene. Maximal values were obtained with 5 mM D-glucose, whereas decrease was observed above 10 mM D-glucose. Addition of alpha-lipoic acid (4 nmol/mg protein) resulted in a significant increase in membrane fluidity and titratable -SH groups at glucose concentrations of 10 mM and above. Dithiothreitol diminished titrable-SH groups and did not restore membrane fluidity. 2-Mercaptopropionylglycine was only effective in restoration of -SH groups. By contrast to D-glucose, other sugars such as L-glucose, D-fructose, or sucrose revealed no comparable changes on membrane fluidity and titratable membrane -SH groups between concentrations of 5 and 10 mM. The hyperglycemic effects of D-glucose were corroborated with isolated, reconstituted membrane proteins and erythrocyte glucose carrier, indicating that, in general, the observed divergent biochemical/biophysical changes of the red cell membrane are influenced by the glucose transport protein GluT1. The natural R-form and the S-form of alpha-lipoic acid were compared with racemic R-/S-forms for their efficiencies in alterations of red cell membrane fluidity. Decreased fluidities in presence of 10 mM glucose were found to be influenced in differentiated ways: the S-form was highly active in increasing fluidity at 4 nmol/mg and increasingly less active up to 20 nmol/mg protein. By contrast the R-form of lipoic acid was moderately efficient in increasing fluidity through a larger concentration range between 4 and 80 nmol/mg protein.

The influence of vitamin E and dihydrolipoic acid on cardiac energy and glutathione status under hypoxia-reoxygenation

The combination of vitamin E supplementation with dihydrolipoic acid perfusion synergistically improves cardiac functional recovery during post-ischemic reperfusion or post-hypoxic reoxygenation of the rat heart. To elucidate the mechanism of this effect, isolated rat hearts were perfused using a working heart system. In hearts perfused with a buffer containing dihydrolipoic acid, ATP levels were significantly higher than those of hearts perfused without addition of dihydrolipoic acid during 90 min of reoxygenation following 30 min of hypoxia. Cardiac tissue glutathione status measured in hearts after perfusion experiments showed significant elevation of reduced glutathione in vitamin E supplemented normoxic rat hearts without hypoxia. Significant elevation of oxidized glutathione was observed in dihydrolipoic acid perfused heart after hypoxia-reoxygenation. It is concluded that vitamin E and dihydrolipoic acid exert separate and synergistic effects in the protection of the hypoxic-reoxygenated heart.

ATP synthesis by purified ATP-synthase from beef heart mitochondria after coreconstitution with bacteriorhodopsin

An ATP-synthase complex active in ATP synthesis was isolated from beef heart mitochondria by solubilization of submitochondrial particles with dodecyl-beta-D-maltoside and purified in a one-step procedure by subsequent ion-exchange chromatography. The electrophoretic analysis resulted in 14 subunits for the F0 F1 complex. ATP hydrolysis activity of the purified enzyme was 25 mumol ATP min-1 mg-1F0F1. ATP hydrolysis could be stimulated by addition of lipid vesicles. Further stimulation was observed in the presence of uncoupler. The inhibitors dicyclohexylcarbodiimide and oligomycin reduced hydrolytic activity to 70 and 40%, respectively. The preservation of ATP synthesis capability was demonstrated by reconstitution of the purified enzyme together with the light-driven proton pump bacteriorhodopsin. Upon illumination of ATP-synthase/bacteriorhodopsin proteoliposomes ATP synthesis activity was detectable for at least 7 min. At reduced temperature this time could be increased to 20 min. The maximum synthesis rate of 58 nmol ATP min-1 mg-1 F0F1 was obtained after reconstitution into liposomes made from crude soy bean lecithin by a detergent dialysis procedure using octyl-beta-D-glucopyranoside and monomeric bacteriorhodopsin. ATP synthesis was partially inhibited by oligomycin or dicyclohexylcarbodiimide and was completely abolished in the presence of uncoupler. The ability of the purified enzyme to synthesize ATP shows that the described isolation procedure results in an ATP-synthase complex which is intact in structure and function.

Use of benchmarking techniques to justify the evolution of antibiotic management programs in healthcare systems

OBJECTIVE

To apply basic benchmarking techniques to hospital antibiotic expenditures and clinical pharmacy personnel and their duties, to identify cost savings strategies for clinical pharmacy services.

DESIGN

Prospective survey of 18 hospitals ranging in size from 201 to 942 beds. Each was asked to provide antibiotic expenditures, an overview of their clinical pharmacy services, and to describe the duties of clinical pharmacists involved in antibiotic management activities. Specific information was sought on the use of pharmacokinetic dosing services, antibiotic streamlining, and oral switch in each of the hospitals.

RESULTS

Most smaller hospitals (< 300 beds) did not employ clinical pharmacists with the specific duties of antibiotic management or streamlining. At these institutions, antibiotic management services consisted of formulary enforcement and aminoglycoside and/or vancomycin dosing services. The larger hospitals we surveyed employed clinical pharmacists designated as antibiotic management specialists, but their usual activities were aminoglycoside and/or vancomycin dosing services and formulary enforcement. In virtually all hospitals, the yearly expenses for antibiotics exceeded those of Millard Fillmore Hospitals by $2,000-3,000 per occupied bed. In a 500-bed hospital, this difference in expenditures would exceed $1.5 million yearly. Millard Fillmore Health System has similar types of patients, but employs clinical pharmacists to perform streamlining and/or switch functions at days 2-4, when cultures come back from the laboratory.

CONCLUSIONS

The antibiotic streamlining and oral switch duties of clinical pharmacy specialists are associated with the majority of cost savings in hospital antibiotic management programs. The savings are considerable to the extent that most hospitals with 200-300 beds could readily cost-justify a full-time clinical pharmacist to perform these activities on a daily basis. Expenses of the program would be offset entirely by the reduction in the actual pharmacy expenditures on antibiotics.

TUDCA and UDCA are incorporated into hepatocyte membranes: different sites, but similar effects

The aim of this paper is to point out that: 1) CDCA and DCA increase the polarity of cell membranes and cause the release of cholesterol and phospholipid from the membranes; 2) the extent of this damage is inversely correlated with the cholesterol content of the membrane investigated; 3) UDCA, TUDCA and GUDCA decrease membrane polarity; 4) they prevent membrane damage when added prior to CDCA or DCA; 5) UDCA appears to be incorporated into the apolar domain of the membrane, TUDCA, GUDCA into the interface; 6) UDCA decreases HLA class I expression on hepatocyte membranes; 7) CDCA induces GLDH-release from liver mitochondria and increases mitochondrial membrane polarity and mobility; and 8) UDCA reduces the release of GLDH from mitochondria caused by CDCA.

Dose/response curves of lipoic acid R-and S-forms in the working rat heart during reoxygenation: superiority of the R-enantiomer in enhancement of aortic flow

Micromolar concentrations of lipoic acid racemate added to a working rat heart during hypoxia have been previously found to improve aortic flow during subsequent reoxygenation. Since the R-form represents the naturally occurring form of lipoic acid, and the S-form does not reveal a positive influence on ATP synthesis in isolated mitoplasts, a dose/response curve of both enantiomers has been performed in working rat hearts. After the end of perfusion mitochondria were isolated and further analysed. At a concentration of 0.05-0.1 mumol of the R-enantiomer, aortic flow rises precipitously during reoxygenation, reaching over 70% of normoxic values compared to 50% of the controls. By contrast, with the S-enantiomer a value of about 60% is attained at 1 mumol, only. Accordingly, ATPase activity in mitochondria isolated from rat hearts previously treated with 0.05-0.1 mumol of the R- or S-enantiomer was significantly decreased or increased respectively. Consequently, whereas mitochondrial ATP synthesis was increased when the R-enantiomer was previously added to the working heart at 0.05-0.1 mumol concentration, with the S-enantiomer ATP synthesis remained within the control range. Mitochondrial membrane fluidity, measured with diphenylhexatriene, revealed a trend towards increase with the R- and decrease with the S-enantiomer. The total amount of thiol added at 0.1 mumol concentration is consistent with a value of 2 nmol/mg mitochondrial protein. This value has previously been found to be connected with -SH groups which add oligomycin-sensitivity to the ATPase complex. It is suggested that oligomycin-sensitive mitochondrial -SH groups contribute to the overall efficiency of low concentrations of lipoic acid R-enantiomer to enhance aortic flow.

Identification of a 40-kDa cell surface sialoglycoprotein with the characteristics of a major influenza C virus receptor in a Madin-Darby canine kidney cell line

Infection of cells by influenza C virus is known to be initiated by virus attachment to cell surface glycoconjugates containing N-acetyl-9-O-acetylneuraminic acid. Using an in vitro virus binding assay, we have detected this carbohydrate on several glycoproteins of Madin-Darby canine kidney cells (type I), a polarized epithelial cell line permissive for infection with influenza C virus. Among these proteins, only one was found to be present to a significant extent on the cell surface. This protein, gp40, was characterized as an O-glycosylated (mucin-type) integral membrane protein of 40 kDa, which was predominantly localized on the apical plasma membrane of filter-grown cells. It is a major cell surface sialoglycoprotein in this cell line and was shown to be subject to constitutive and rapid endocytosis. Thus, this glycoprotein can mediate not only the binding of influenza C virus to the cell surface, but also its delivery to endosomes, where penetration occurs by membrane fusion. Other highly sialylated cell surface glycoproteins were also detected but did not mediate influenza C virus binding to a significant extent, indicating that only gp40 contains 9-O-acetylated sialic acids.

[Catecholamines, myofibrillary degeneration of the heart muscle and cardiac troponin T in various types of agony]

The stress of agony (the death struggle) induces a rise in serum catecholamines. High doses of catecholamines cause myofibrillar degeneration (MFD), a form of cardiac injury. Severely damaged cardiac myocytes release troponin T (TnT), a myofibrillar cardiac protein, into the circulation. We studied serum catecholamine levels, MFD and TnT in 119 medico-legal autopsy cases. Catecholamine levels increased with the duration of agony: In the instantaneous death cases, the levels were similar to levels in humans at rest, whereas the levels in prolonged agony were comparable to concentrations found in humans in acute maximal stress. Still, it was not possible to infer the duration of agony from the catecholamine level in an individual case. The exceptionally high dopamine levels found in the group 'resuscitation and/or intensive care before death 'were most likely caused by antemortal treatment with dopamine. Slight MFD was diagnosed in nearly all hearts; its severity was neither related to catecholamine levels nor to duration of agony. TnT, not found in blood of healthy people, was present in nearly all postmortem samples, indicating autolytic effects. Heart blood contained more TnT than femoral blood. We could not detect a relationship between the serum cardiac troponin T level and MFD; but cardiac deaths had significantly higher levels of TnT in heart blood than deaths from other causes. The postulated interrelation between catecholamines, MFD and TnT was not evident from the results.