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Biomedical subjects

W Stephan

Publications and source records attributed to W Stephan.

At least 91 records · Page 5Linked to original sources
PubMed1985

Inactivation of the Hutchinson strain of non-A, non-B hepatitis virus by combined use of beta-propiolactone and ultraviolet irradiation.

A beta-propiolactone/ultraviolet irradiation procedure (beta PL/UV) has been evaluated for its ability to inactivate 30,000 chimpanzee infectious doses of the Hutchinson strain of non-A, non-B (NANB) virus. The chimpanzees were inoculated with plasma to which this dose of the titrated virus had been added prior to application of the beta PL/UV process in accordance with a procedure used for licensed blood derivatives in Germany. Neither animal developed hepatitis. When subsequently challenged with the same contaminated plasma, which had not been sterilized, both animals promptly developed typical NANB hepatitis. This study extends the high (approximately 10(7)-fold) process efficiency of the beta PL/UV procedure previously reported for hepatitis B virus to a blood-borne NANB virus.

Animals↗
PubMed1985

Complex membrane transport systems. A non-Markovian approach.

This paper suggests a method of how to deal with complex membrane transport systems such as ion channels or ion pumps formed by proteins. The complexity of these systems results from the fact that proteins may undergo an internal dynamics of conformational changes and may thereby affect the transmembrane transport. Usually, complex transport systems are mapped into multi-state graphs and couched in terms of Markovian master equations. It is shown in this paper how the dimensionality of such multi-state systems can be reduced. The resulting description may be expressed in the form of a generalized master equation with a memory function as integral kernel. The memory function reflects the protein's own dynamics and its overall effect on the transport. This formalism, non-Markovian in nature, is applied to describe the time-dependent action of ion pumps. A general model is constructed on the basis of the rate theory which contains all the essential parts of ion pumps such as a catalytic unit and a channel-like conduit for ion translocation and which is still analytically tractable. The short-time behaviour of the pumping process turns out to be of particular interest, since it reveals the dynamics of the catalytic unit itself. A strong correlation of the particle's motion over times less than a certain correlation time has been found. This result is compared with experimental findings on the proton pump of Halobacterium halobium. It is concluded that such a perfect short-time memory could be a generic property of active transport systems.

Adenosine Triphosphatases↗
PubMed1985

Quantitative assays for evaluation of HTLV-III inactivation procedures: tri(N-butyl)phosphate:sodium cholate and beta-propiolactone.

Human T-lymphotropic retrovirus type III (HTLV-III) can be quantitatively assayed for infectivity by inoculation of serial dilutions into cultures of the H-9 cell line and testing for reverse transcriptase in the culture supernatants. Sequential harvests revealed that 14 days of incubation of cultures fed twice weekly was sufficient to reveal maximal titers. Stocks prepared from unconcentrated H9:HTLV-IIIb supernatants have contained from 10(4.5) to 10(6.0) (TCID50)/ml. Stocks prepared by 100-fold concentration of such fluids by pelleting or by polyethylene glycol precipitation followed by pelleting onto sucrose cushions contained 10(6.0)-10(6.5) TCID50/ml. Preliminary studies are under way to utilize this system for evaluation of sterilization processes which can be applied to blood derivatives. Exposure of HTLV-III suspended in Factor VIII preparations to 0.3% tri(n-butyl)phosphate-0.2% sodium cholate resulted in inactivation of greater than or equal to 10(4.5) TCID50 in 2.5 h at 27 degrees C. Exposure of HTLV-III suspended in 4 g of gamma-globulin per 100 ml to 0.14% beta-propiolactone for 4 h at room temperature at pH 8.0 inactivated greater than or equal to 10(4.5) TCID50. However, exposure to gamma-globulin alone inactivated about 99% of HTLV-III infectivity.

Cell Line↗
PubMed1985

[Inhibitory and immunological profile of therapeutic serum protein solutions].

Biseko is prepared from pooled human plasma by specific stepwise adsorption of the coagulation factors avoiding spontaneous coagulation. Biseko is manufactured from pooled plasma from more than 1000 donors. In order to ensure its hepatitis safety, the starting plasma is cold sterilized by beta-propiolactone and UV-irradiation. The inhibitory and immunological profile of the cold sterilized Biseko was compared with another commercial serum preserve and normal serum. alpha 1-antitrypsin, alpha 2-macroglobulin and antithrombin III are present in Biseko and normal serum in their biologically active forms. A certain amount of the opsonin, fibronectin, is heparin-precipitable in normal serum and has thus retained its native character, while the fibronectin in the commercial serum preserve examined is not heparin-precipitable. Biseko contains fibronectin only in trace amounts. The IgG, IgA and IgM immunoglobulin concentrations and activities in the serum preserves are equivalent to those in normal serum. One major difference between normal serum and the cold sterilized Biseko is that metabolites from the coagulation pathways are absent in Biseko. Normal serum is not suitable for therapeutic purposes because of activated enzymes formed during coagulation. The chemical analysis of the protein pattern in Biseko resembles more fresh frozen plasma without coagulation factors than normal serum.

Blood Proteins↗
PubMed1985

[Properties and efficacy of a human immunoglobulin M preparation for intravenous administration].

From Cohn fraction III a new immunoglobulin (Ig) preparation (Pentaglobin) was prepared. This preparation contains 72% IgG and is enriched in IgM (12%) and IgA (16%). Due to a treatment with beta-propiolactone it is suitable for intravenous application. This IgM-enriched immunoglobulin preparation is prominent in high antibody titers (passive hemagglutination) against gram-negative as well as gram-positive germs and shows significantly higher efficacy in mouse protection tests than intravenous standard IgG. The high IgM content of this preparation in particular is responsible for the binding of bacterial antigens. Thus a marked advancement in the treatment of bacterial infections is to be expected by this new intravenously tolerable immunoglobulin preparation.

Animals↗
PubMed1984

Inactivation of non-A, non-B virus infectivity by a beta propiolactone/ultraviolet irradiation treatment and Aerosil adsorption procedure used for preparation of a stabilized human serum.

Inoculation of chimpanzees revealed that starting material for the preparation of a pooled stabilized human serum preparation was contaminated with non-A, non-B hepatitis virus(es). This material was subjected to beta-propiolactone/ultraviolet irradiation treatment and adsorption with an insolubilized silicic acid under conditions employed for sterilization of the final product (Biseko, Biotest). The treated material did not transmit hepatitis to 2 inoculated chimpanzees. These animals were subsequently found to be susceptible to non-A, non-B infection by challenge with the untreated material. These findings demonstrate a non-A, non-B type hepatitis virus to be susceptible to inactivation by the methods employed for sterilization of this stabilized human serum preparation.

Adsorption↗
PubMed1984

Modulation of hepatitis B infection by intravenous application of an immunoglobulin preparation that contains antibodies to hepatitis B e and core antigens but not to hepatitis B surface antigen.

Repeated administration of an intravenous immunoglobulin containing antibody to hepatitis B e antigen (anti-HBe) and antibody to hepatitis B core antigen (anti-HBc) but free of antibody to hepatitis B surface antigen (anti-HBs) before and after the inoculation of 10(4.9) 50% chimpanzee infective doses of hepatitis B virus (HBV) markedly prolonged the incubation period of HBV in experimentally infected chimpanzees. Similar administration of an immunoglobulin preparation containing anti-HBc but free of anti-HBe and anti-HBs or intramuscular administration of a single dose of immunoglobulin containing anti-HBe and anti-HBc 3 days before or after inoculation with HBV did not appear to modulate HBV infection. These observations suggested that anti-HBe, or an unidentified antibody associated with it, may have biological activity in the modulation of HBV replication.

Animals↗
PubMed1983

Rate theory models for ion transport through rigid pores. III. Continuum vs discrete models in single file diffusion.

In studying the single file model in its discrete as well as in its continuum form the relationship between the phenomenological continuum theory of diffusion and the rate theory approach is analyzed. The single file model in its original form is discrete and represents the most general rate theory model for ion transport through rigid pores in biological membranes. In neglecting the interionic interactions which the single file model takes into account, the Nernst-Planck equation of macroscopic free diffusion can be derived from single file by means of the procedure n leads to infinity (where n is the number of binding sites within a pore) and the classical diffusion theory can thereby be integrated into the more general concept of single filing transport. Moreover, the single file model has been transformed in the limit n leads to infinity into the corresponding continuum form involving interionic interactions. The essential differences between the two derived continuum forms are: In the macroscopic diffusion model, the interionic interactions are regarded in the form of a "mean field". Thus we only get one equation of motion (Nernst-Planck equation) for the ionic concentration c(x, t) within the membrane. In the continuum version of the single file model, however, we obtain a hierarchy of Fokker-Planck equations for the probability density functions Pm(x1, . . . , xm, t) (where m is the number of ions within a pore). The interactions of the single file system are incorporated in detail into the Fokker-Planck equation as well as into the corresponding boundary conditions. As a consequence, the boundary conditions are highly complex in comparison with periodic conditions or Dirichlet conditions often used for the Nernst-Planck equation in electrophysiology. Two types of boundary conditions have been found which are principally different: The first one is to regulate the entry and exit of the ions at the pore mouth by a negative feedback mechanism, the second one describes the collisions of the ions within multiply occupied pores. In this context the question is discussed of whether the continuum version of single file has advantages over the discrete one.

Binding Sites↗
PubMed1983

Inactivation of hepatitis B and non-A, non-B viruses by combined use of Tween 80, beta-propiolactone, and ultraviolet irradiation.

To assess the sterilization efficacy of a combined Tween 80, beta-propiolactone and ultraviolet irradiation procedure applied to a F VIII preparation to which an estimated 10(5.9) chimpanzee infectious doses (CID50) of hepatitis B virus had been added per ml, two chimpanzees were inoculated with 10 ml each of treated and untreated preparations. The untreated preparation, which was obtained from donors with normal alanine aminotransferase (ALT) levels, induced non-A, non-B hepatitis in both recipient animals, and delayed hepatitis B infection in one of these. Neither animal receiving the treated preparation developed either type of hepatitis. When subsequently challenged with the untreated material, both of the latter animals developed non-A, non-B and hepatitis B infection, proving their susceptibility to both types of infection. It was concluded that the combined procedure inactivated an estimated 10(6.9) CID50 of hepatitis B virus and an unknown quantity of a non-A, non-B virus. The finding of non-A, non-B virus infectivity in a pooled F VIII preparation despite careful ALT screening of plasma donors emphasizes the necessity of subjecting such preparations to sterilization procedures.

Animals↗
PubMed1983

Rate theory models for ion transport through rigid pores. II. Time-dependent analysis of the single-file model with special reference to oscillatory behavior.

This article deals with the time-dependent evolution of the single-file movement of ions through channels of both biological and artificial membranes. The single-file transport process may exhibit not only the usual relaxation behaviour but also oscillatory behaviour as a steady state is approached after an initial perturbation. A necessary condition for the occurrence of oscillations is that the system acts sufficiently far from equilibrium. The occurrence of oscillations is due to the interactions within the transport system which are taken into account by the single-file model; these are the electrostatic repulsion between the ions being transported, and the competition of the ions for the free binding sites within the pore. Information about the strength of the interactions can be obtained by measuring the damping of the transport observables (e.g. the electric current): The stronger the inter-ionic repulsion, the more apparent the oscillatory behaviour will become. Furthermore, the damping is influenced by the microscopic structure of the transport system (i.e. the energy profile of the pores). With an increasing degree of microscopicity, i.e. with a decreasing number of binding sites and an increasingly irregular pore profile, the oscillations become more damped. However, a considerable oscillatory behaviour can only be predicted for pores with both a sufficiently regular structure and a sufficiently large number of binding sites. For this class of pores, however, the measurement of the damping represents an appropriate method of gaining information which could exceed that obtainable from the usual methods of measuring stationary quantities (e.g. stationary conductance). Moreover, our goal is to explain theoretically how the oscillatory behaviour can be interpreted in terms of the order inherent in the ionic movement, which is determined by both the external and internal forces and the microscopic properties of the system.

Binding Sites↗
PubMed1983

Rate theory models for ion transport through rigid pores. I. Time-dependent analysis in the case of vanishing interactions.

In this first of a series of papers concerning the theoretical analysis of rate theory models for ion transport through rigid pores, the case of vanishing interactions is investigated. "Rigidity" means that ions crossing membranes through pores see a fixed structure of the pores, not changing in time. A single pore is considered to be a sequence of (n + 1) activation barriers separated by n energy minima. The explicit analytical treatment is restricted to pores with regular internal barrier structure, including the nonequilibrium situation of an applied electric field. In this case the connection with continuum diffusion models is demonstrated by performing in the limit n leads to infinity (n = number of binding sites within the pores) the transition to continuum. Thus, from diffusion equations describing a discrete number of jumps, the corresponding diffusion-like partial differential equations and boundary conditions are generated. For regular pores, from the time dependent solutions of the discrete equations, the corresponding solutions of the continuum equations are explicitly generated. The time-dependent relaxation behaviour of the discrete model is in good agreement with the continuum model if one assumes more than two binding sites in the pores.

Binding Sites↗
PubMed1983

Evaluation of thrombogenicity of beta-propiolactone/ultraviolet (beta-PL/UV) treated PPSB in chimpanzees.

The thrombogenicity of beta-PL/UV-treated PPSB (factor IX concentrate) was evaluated in chimpanzees. PPSB isolated from beta-propiolactone-treated and UV-irradiated plasma was injected into chimpanzees at a dose of approximately 100 units/kg body weight. An FDA licensed PPSB preparation served as the negative control, and a preparation containing activated as well as precursor clotting factors served as the positive control. 15 minutes, 1 h, 4 h, and 24 h after the PPSB application the following parameters were determined in the chimpanzee blood: factors II, VII, IX, X, VIII, fibrinogen, AT III, thrombin coagulase, Quick value, APTT and platelet count. Neither the untreated control preparation, nor the PPSB isolated from beta-propiolactone-treated and UV-irradiated plasma, showed signs of thrombogenicity in the chimpanzee model. The positive control indicated that the chimpanzee is a suitable model for the thrombogenicity testing of activated clotting factors.

Animals↗