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Biomedical subjects

K Korn

Publications and source records attributed to K Korn.

69 records · Page 4Linked to original sources
PubMed1992

Viral culture and p24 antigenemia of human immunodeficiency virus (HIV)-infected individuals correlated with antibody profiles determined with recombinant polypeptides of all HIV-1 open-reading frames.

The association between viral activity and antibody profiles was investigated in 202 individuals infected by the human immunodeficiency virus (HIV) grouped according to their Walter Reed clinical stage. Each study group was subdivided into subjects positive or negative for markers of active viral replication: presence of serum p24 antigen and viral culture. In Western blots using recombinant antigens, sera of HIV-positive individuals with positive viral markers had a significantly lower antibody reactivity to several viral proteins than did individuals without viral markers. Noticeably, proteins of the gag (p24, p17) and env (gp120, COOH-terminal part of gp41) open-reading frames revealed a decreased reactivity. The antibody response to the regulatory proteins revealed no or poor association with viral activity in the host. The results suggest that seroreactivity is mainly influenced by factors reflecting the viral activity of an HIV-infected individual, while the clinical stage of the patient is less important. Especially, reductions in antibodies against gp120 and p17 were useful markers associated with increased viral activity.

Adult↗
PubMed1992

Case management in rural areas. Definition, clients, financing, staffing, and service delivery issues.

How does case management in rural areas differ from that in urban areas? How does the informal system of family, church, neighbors, and volunteers affect case management in rural areas? What are the strengths and problems of rural case management? The authors report the attitudes of rural case managers and attendees at a conference sponsored by two homecare organizations to these and other questions related to rural case management.

Aged↗
PubMed1991

Cleavage and purification of prokaryotically expressed HIV gag and env fusion proteins for detection of HIV antibodies in the ELISA.

Parts of the gag p24 and the gp41 transmembrane protein of the human immunodeficiency virus HIV-1 were expressed as fusion proteins in Escherichia coli, using an expression vector carrying aa 1-375 of the lac-Z gene linked to the recognition sequence for the blood coagulation factor Xa. Fusion proteins were cleaved into the bacterial and viral portion and the viral polypeptide was purified by a molecular sieve column. The purified viral antigens were tested with 288 human sera in the enzyme-linked immunosorbent assay (ELISA) technique. Comparison with commercially available tests showed comparable sensitivity and a higher specificity of the gag/env-ELISA for borderline reactive sera.

Chromatography, Gel↗
PubMed1990

Two substrate sites in the renal Na(+)-D-glucose cotransporter studied by model analysis of phlorizin binding and D-glucose transport measurements.

Time courses of phlorizin binding to the outside of membrane vesicles from porcine renal outer cortex and outer medulla were measured and the obtained families of binding curves were fitted to different binding models. To fit the experimental data a model with two binding sites was required. Optimal fits were obtained if a ratio of low and high affinity phlorizin binding sites of 1:1 was assumed. Na+ increased the affinity of both binding sites. By an inside-negative membrane potential the affinity of the high affinity binding site (measured in the presence of 3 mM Na+) and of the low affinity binding site (measured in the presence of 3 or 90 mM Na+) was increased. Optimal fits were obtained when the rate constants of dissociation were not changed by the membrane potential. In the presence of 90 mM Na+ on both membrane sides and with a clamped membrane potential, KD values of 0.4 and 7.9 microM were calculated for the low and high affinity phlorizin binding sites which were observed in outer cortex and in outer medulla. Apparent low and high affinity transport sites were detected by measuring the substrate dependence of D-glucose uptake in membrane vesicles from outer cortex and outer medulla which is stimulated by an initial gradient of 90 mM Na+ (out greater than in). Low and high affinity transport could be fitted with identical Km values in outer cortex and outer medulla. An inside-negative membrane potential decreased the apparent Km of high affinity transport whereas the apparent Km of low affinity transport was not changed. The data show that in outer cortex and outer medulla of pig high and low affinity Na(+)-D-glucose cotransporters are present which contain low and high affinity phlorizin binding sites, respectively. It has to be elucidated from future experiments whether equal amounts of low and high affinity transporters are expressed in both kidney regions or whether the low and high affinity transporter are parts of the same glucose transport molecule.

Animals↗
PubMed1990

Prokaryotic expression of the major capsid protein of human cytomegalovirus and antigenic cross-reactions with herpes simplex virus type 1.

The major capsid protein (MCP) of human cytomegalovirus (HCMV) was expressed in three portions as beta-galactosidase fusion proteins, covering about 75% of the open reading frame (ORF). Fusion protein SH 1 contained nucleotides 101 to 1243 of the ORF, fusion protein FS 1 contained nucleotides 1944 to 3089 and fusion protein SS 1 covered nucleotides 2624 to 3793. The recombinant proteins were tested for their immunoreactivity with human sera. Fusion protein FS 1 was found to represent the immunodominant region. The recombinant proteins were used to generate polyvalent rabbit antisera to investigate cross-reactivities with the major capsid protein (VP5) of herpes simplex virus type 1 (HSV-1). A monospecific antiserum raised against the fusion protein close to the N terminus of the MCP, as well as a monoclonal antibody and a monospecific rabbit antiserum directed against the viral MCP, cross-reacted with the VP5 as shown by immunoblotting and immunofluorescence. In order to detect common epitopes of the major capsid proteins of HCMV and HSV-1, the recombinant proteins were conjugated to CNBr-activated Sepharose and taken for purification of MCP antibodies from HCMV and HSV-1 seropositive individuals. Using this affinity chromatography method, cross-reactivity could be observed with HCMV- and HSV-positive human antisera in immunoblot experiments.

Antibodies, Monoclonal↗
PubMed1989

The provision of home health care services through health maintenance organizations.

The vast majority of the HMOs responding to the survey in this study use home health care as a substitute for acute inpatient hospitalization, contract out for services with community-based home health agencies, reimburse on a discounted fee-for-service basis, and use prior authorization and concurrent review as the primary methods to control the use of home health care. These findings suggest that HMO home health care services mirror the inadequacies of Medicare home health care in that they are acute care-focused and not intended to fill the supportive and maintenance care needs of the chronically ill elderly. HMOs, however, are typically more flexible in their service provision than is Medicare. Need for home health care is determined primarily on prospective, case-by-case evaluations of cost effectiveness, not on retrospective determinations based on strict, and sometimes arbitrary, guidelines and limitations. This, however, does raise some important issues for access and quality and for the relationship between HMOs and home health agencies. Is cost containment the only legitimate reason for providing home health care? Should home health care be used solely as a substitute for acute inpatient hospitalization? Where does the locus of authority lie for deciding coverage of home health care services? This study uncovered several issues related to the provision of home health care in HMOs that created conflict and uncertainty for all parties. These issues included: conflicting roles for HMOs, whether to provide services internally or externally, contracting between HMOs and home health agencies, the locus of authority for utilization review, the role of physicians, quality assurance, and perceived problems with the Health Care Financing Administration. HMOs are often perceived as failing to do an adequate job of providing home health care services because of the difficulty in satisfying conflicting considerations in three key areas: whether home health care should be focused on cost containment or meeting unmet needs, whether home health care should be focused on acute or long term care, and the unrealistic expectations patients and providers have of HMOs. HMOs primarily provide home health care in an effort to contain costs, particularly by using home health care to substitute for inpatient hospitalization. While HMO representatives acknowledge the importance of home health care in improving the patient's and family's quality of life by providing supportive or chronic maintenance care, the use of home health care for this purpose is generally not allowed by HMOs.(ABSTRACT TRUNCATED AT 400 WORDS)

Acute Disease↗
PubMed1988

Monoclonal antibodies against the renal Na+-D-glucose cotransporter. Identification of antigenic polypeptides and demonstration of functional coupling of different Na+-cotransport systems.

Eight monoclonal antibodies are described which are directed against the renal Na+-D-glucose cotransporter. In porcine renal brush-border membranes, the antibodies either bind to one or to three polypeptides which have been identified as components of the Na+-D-glucose cotransporter (Neeb, M., Kunz, U., and Koepsell, H., (1987) J. Biol. Chem. 262, 10718-10727). Their molecular weights and isoelectric points are 75,000 and pH 5.5, 60,000 and pH 5.2, and 47,000 and pH 5.4. Six antibodies were able to influence Na+-dependent D-glucose uptake and/or Na+-dependent high affinity phlorizin binding. In the presence of Na+, the binding of all antibodies to native membrane proteins was altered by D-glucose but not by D-mannose. Since this effect was observed with D-glucose concentrations less than 1 x 10(-8) M, a high affinity D-glucose-binding site on the D-glucose transporter has been implied. Some of the antibodies probably interact also with other Na+-coupled transporters since their binding was altered by micromolar concentrations of L-lactate, L-alanine, or L-glutamate but not by the nontransported control substances D-alanine and D-glutamate. L-lactate increased the binding of one antibody in the absence but not in the presence of D-glucose. Effects of L-lactate and L-alanine on the binding of another antibody were only observed when D-glucose was present. Thus, some epitopes on the Na+-D-glucose cotransporter are altered by D-glucose and also by substrates of other Na+ cotransporters. This finding suggests functional coupling of different Na+-cotransport systems.

Animals↗
PubMed1984

Reconstitution and partial purification of several Na+ cotransport systems from renal brush-border membranes. Properties of the L-glutamate transporter in proteoliposomes.

Brush-border membranes of renal proximal tubules were solubilized with deoxycholate and some proteins were separated and incorporated into proteoliposomes by a reconstitution procedure which was analyzed in detail. The proteoliposomes contained mainly polypeptides with molecular weights of 152,000, 94,000, and 52,000, each of which could be separated further into homologous polypeptides with different isoelectric points. In the proteoliposomes, Na+ cotransport systems for D-glucose, acidic and neutral amino acids, and mono- and dicarboxylic acids were demonstrated by showing that due to an inwardly directed Na+ gradient the substrate concentrations in the proteoliposomes increased significantly over their respective equilibrium values. Using inhibition experiments, selectivity of the different transporters could be demonstrated. Studying the reconstituted L-glutamate transporter in detail, countertransport of L-glutamate and K+ was shown (i) at Na+ equilibrium the intraliposomal L-glutamate concentration increased significantly over the equilibrium value if an outside-directed K+ gradient was applied; (ii) Rb+ influx was significantly stimulated by the outflux of L-glutamate. By applying a K+ diffusion potential across the liposomal membrane by addition of valinomycin it could be shown that during L-glutamate transport in the presence of Na+ and K+ positive charge is transferred together with L-glutamate and Na+. The apparent Km value of L-glutamate uptake driven by concentration differences of 89 mM Na+ (out greater than in) and 89 mM K+ (in greater than out) was 26.3 +/- 1.3 microM. The Vmax value of 70.2 +/- 2.3 pmol X mg of protein-1 X S-1 was half the value measured in intact membranes.

Amino Acid Transport System X-AG↗
PubMed1978

[Incidence of abortive ova among spontaneous abortions].

345 spontaneous abortions of the period 1975/76 are investigated histologically. 174 of them content chorionic villi (100 per cent). Among these we have found 91 abortive ovas (52.3 per cent), 7 hydatiform moles (4.0 per cent) and 35 histological regular abortions (20.1 per cent). Furthermore, 41 cases are suspicious of abortive ova (23.6 per cent) and, 22 cases show signs of early disturbances of placental maturation (12.7 per cent). In all groups there is inflammation of the maternal side and of the endometrium. Regressive changes of the villi are particularly severe in abortive ovas and in the suspicious cases. On the base of our own study of legal abortions as well as this material of spontaneous abortions we estimate the frequency of abortive ovas among all the pregnancies for about 15--25 per cent.

Abortion, Spontaneous↗