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Biomedical subjects

B Koch

Publications and source records attributed to B Koch.

At least 289 records · Page 16Linked to original sources
PubMedDate not supplied

Comparative studies of ventricular ejection phase parameters for the detection of impaired cardiac function.

Experimental studies were carried out in 11 anesthetized pigs in order to compare the sensitivity of left ventricular ejection phase parameters as determined by quantitative angiocardiographic methods, for detection of mild or moderate ventricular dysfunction. The experimental setup implied various degrees of nonadequate muscular hypertrophy in relation to chronic volume overload by aortic insufficiency. Left ventricular stroke volume, flow, ejection fraction and mean circumferential fiber shortening did not demonstrate impairment of ventricular function reserve when studied in the resting state of the circulation, but became indicative to some degree by their abnormal pattern of response to acute afterload stress (angiotensin infusion). Mean normalized systolic ejection rate as well as normalized values of systolic ejection time were found to be the most sensitive indices of ventricular function in this study.

Angiotensin II↗
PubMedDate not supplied

Activation of protein kinase C differentially regulates corticotropin-releasing factor-stimulated peptide secretion and cyclic AMP formation of intermediate and anterior pituitary cells in culture.

The present study was aimed at investigating the effect of protein kinase C (PKC) activation on CRF receptor function of proopiomelanocortin (POMC) cells in culture. Incubation of tissues with the phorbol ester PMA selectively potentiated corticotropin-releasing factor (CRF)-stimulated ACTH secretion and cyclic AMP formation of anterior pituitary (AP) cells, while, in sharp contrast, it failed to similarly affect intermediate pituitary (IP) cells and AtT-20 corticotrophs exposed to CRF. Unexpectedly, however, long-term treatment of cultures with PMA, which depletes cell stores of PKC, resulted in a similar dramatic attenuation of stimulated peptide release from both corticotrophs and melanotrophs, while being without significant effect on cyclic AMP production. Exposure of cells to PMA did not change either basal or CRF-enhanced levels of POMC mRNA. We conclude that activation of PKC fails to synergize with CRF-mediated signalling in IP and AtT-20 cells, although optimal CRF receptor expression requires the presence of a functional kinase C pathway, thus suggesting cross-talks between both messenger systems.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

The superposition of steady on oscillatory shear and its effect on the viscoelasticity of human blood and a blood-like model fluid.

To understand the pulsatility of human blood flow in vivo, it is necessary to separately investigate (1) steady shear and oscillatory flow, and (2) the superposition of steady shear flow on oscillatory flow performed under in vitro conditions. In this study a variable steady shear rate was superimposed in parallel on oscillatory shear at a constant frequency (0.5 Hz) for human blood (45% hematocrit), and an aqueous polyacrylamide polymer solution (AP 30E, concentration 300 ppm). The effect of superposition of the above two shear flows on the viscoelasticity of blood was more pronounced for the elastic (eta") than for the viscous (eta') component of viscoelasticity. With increasing superimposed shear rate, both eta' and eta" decreased, especially at the low shear region. This behavior can be explained by the viscoelastic properties of blood and the phenomenon of blood aggregation and disaggregation. Quantitatively, the dependence of the viscous component of complex viscosity on superimposed shear for both blood and polymer solution is described by a modified Carreau equation. The elastic component of complex viscosity decreased exponentially with increasing superimposed shear, and it is described by an exponential model.

Blood Viscosity↗
PubMedDate not supplied

Moexipril as add-on therapy to hydrochlorothiazide in moderate to severe hypertension.

This double-blind study was conducted to investigate the efficacy, safety and tolerability of three dose levels of moexipril in comparison to placebo as add-on therapy to hydrochlorothiazide (HCTZ) in patients with moderate to severe hypertension. Two hundred patients who did not respond adequately to a 4-week monotherapy with HCTZ-sitting diastolic blood pressure between 95 and 114 mm Hg- entered the 8-week double-blind period. Patients were randomized to once daily placebo or moexipril 3.75, 7.5 or 15 mg as add-on therapy to open-label HCTZ 25 mg. At biweekly visits, blood pressure and heart rate measurements were obtained and the occurrence of adverse experiences was documented. At the 8-week endpoint, adjusted mean reductions from baseline were significantly (p = 0.003) greater in patients receiving moexipril 3.75, 7.5 and 15 mg compared to placebo (-8.4, -8.8 and -8.9 vs. -4.6 mm Hg). No significant differences between the three dose levels of moexipril could be observed. Moexipril was generally well tolerated. The most frequently reported adverse events for moexipril and placebo were headache, flu syndrome and dizziness (6, 7, 5 vs. 4, 0, 4%). The results indicate that the combination of moexipril and HCTZ is a clinically valuable combination in the treatment of patients with moderate to severe hypertension.

Administration, Oral↗
PubMedDate not supplied

Dynamics of infection with human herpesvirus-6 in EBV-negative infectious mononucleosis: data acquisition for computer modeling.

Ten adult patients with active HHV-6 variant A infections and clinical infectious mononucleosis-like disease (IM) were studied over a period of 32 weeks after onset of disease for their viral DNA load, changes in peripheral blood T-lymphocytes and subpopulations and frequency of cell death in peripheral blood cells. The data were collected as the basis for an advanced computer simulation study for which available data in the literature were too varied. Since the exact time of primary infection of the patients was not known and thus no time relationship of viral effects at cellular level were determined, we supplemented such data from separate tissue culture studies using HHV-6 alpha infection of HSB2 cells. Patients with IM demonstrate an increase in-HHV-6 DNA copies from 0 to 8.2 log 10/5 microL blood within 4 weeks return to normal by 16 weeks. Total T-lymphocytes follow infection with a 20-fold increase above normal peaking at 8-10 weeks and then return to normal by 24-28 weeks. Coincidently, less mature lymphoid cells carrying markers for stem cells, thymic cortical and medullary cells increase 8-10-fold indicating an enhanced mobilization of such cells from premature cell compartments. Cell death in peripheral mononuclear cells peaked with 30% at 8 weeks after onset of clinical disease and normalized by 24 weeks. HHV-6 replication in cell culture as determined by antigen expression, electron microscopy and harvest of infectious virus indicated a complete cycle of virus infection and replication of at least 6 days. The presented data compare well with others from the literature and will serve for testing in a computer simulation model, which is the subject of a forthcoming paper.

Adolescent↗
PubMedDate not supplied

Dynamics of chronic active herpesvirus-6 infection in patients with chronic fatigue syndrome: data acquisition for computer modeling.

Ten adult patients with persistent active HHV-6 variant A infection and clinical chronic fatigue syndrome (CFS) were studied over a period of 24 months after initial clinical diagnosis. CFS was diagnosed according to IIIP-revised CDC-criteria as defined by the CFS Expert Advisory Group to the German Federal Ministry of Health in 1994. Changes in HHV-6 antibody titer, viral DNA load, peripheral blood T lymphocytes and subpopulations, as well as CD4/CD8 cell ratio and cell death (apoptosis) were monitored. Data were collected for comparison with respective changes in acute HHV-6 infection and as a basis for future computer simulation studies. The results showed variable but slightly elevated numbers of HHV-6 DNA copies in the blood of patients with CFS, while PBL (peripheral blood lymphocyte) apoptosis rates were clearly increased. CD4/CD8 cell ratios varied from below 1 up to values as seen in autoimmune disorders. Contrary to acute HHV-6 infection, T lymphocytes do not exhibit the usual response to HHV-6, that is elevation of mature and immature populations suggesting a certain degree of unresponsiveness. The data suggest that persistent low-dose stimulation by HHV-6 may favor imbalanced immune response rather than overt immune deficiency. This hypothesis requires confirmation through additional functional studies.

Adolescent↗
PubMedDate not supplied

Dynamics of active progressive infection with HIV1: data acquisition for computer modeling.

Nineteen adult patients with progressive HIV1 infection, which progressed within 5 years from acute HIV syndrome to final AIDS were studied. Changes in HIV antibody titer, viral RNA load, peripheral T lymphocytes and subpopulations as well as CD4/CD8 cell ratio and cell death (apoptosis) were monitored. The data were collected for comparison with HHV-6 infection, which involves the same cell populations yet patients usually recover, and to serve as a further basis for future computer simulation studies. The results showed progressive increases of viral RNA copies in the patients' plasma even during clinical latency, which correlates with lymphocyte apoptosis and CD4 cell loss. Besides apparent direct CD4 cell destruction, there was indication of a disturbed intrathymic T cell differentiation. Pathologic cell changes in HIV infection continue until final death of the patient and do not return to normal after variable times as in HHV-6 infection. While HHV-6 infection can serve as models for immunostimulation, with or without immune dysregulation in computer simulation studies, HIV infection is a model for immunostimulation with final immune deficiency and cellular aplasia.

Adult↗
PubMedDate not supplied

Isolation of human herpesvirus-6 (HHV-6) from patients with collagen vascular diseases.

The prevalence and activity of human herpesvirus-6 in patients with collagen vascular diseases (CVD) was determined. One hundred and fifty patients with CVD (56 with systemic lupus erythematosus-SLE, 92 with rheumatoid arthritis-RA, 1 with Sharp's syndrome and 1 with atypical polyclonal lymphoproliferation-APL and rheumatoid features) were screened serologically (IFA and ELISA) for antibodies against human herpesvirus-6 (HHV-6), Epstein-Barr virus (EBV) and cytomegalovirus (CMV). Virus isolation was attempted from peripheral blood lymphocytes (PBL) of 25 persons with various disorders. PBL were grown in tissue culture and tested with standard HHV-6-positive antisera for viral antigen expression. Supernatants of the patient's lymphocyte cultures were used to infect HSB2 cells, and virus infection in these cells was proven by IFA, in situ hybridization and by electron microscopy. Fifty-five percent of the SLE patients, 6.5% of the RA patients and both patients with Sharp's syndrome or with APL had antibody titers indicative of active HHV-6 infection. Virus cultures were positive in 9 of the 25 attempts with establishment of stable virus lines. These patients were 5 with SLE or UCVD, and one each with RA, CFS, APL as well as one healthy control. Reactivated and chronic active HHV-6 infections are frequent in SLE like EBV in RA. The role of these viruses in the pathogenesis of the diseases or in their reactivation still needs further investigation.

Adult↗
PubMedDate not supplied

Human herpesvirus-6 infection may predispose cells to superinfection by other viruses.

Double infection of cells by HHV-6, Epstein-Barr virus (EBV) and by human immunodeficiency virus (HIV-1) can enhance viral effects though genetic transactivation. It remained to be clarified, however, by which mechanism different viruses may enter the same cell. We have shown that HHV-6 infection of immature lymphoid cells rigidifies the cytoplasmic membrane and causes receptor proteins for viruses such as CD4 for HIV-1 and CR2 for EBV to be expressed. In our experiments, HHV-6 infected cells were superinfected by HIV1 and caused enhanced cell death. The mechanisms by which receptors were expressed after HHV-6 infection appears independent of cell membrane rigidification alone and is suppressed by cycloheximide only to a certain extent.

Cell Line↗
PubMedDate not supplied

[Prostaglandin E2, interleukin 1 and gamma interferon production of mononuclear cells of patients with inflammatory and degenerative joint diseases].

Inflammatory joint diseases exhibit distinct pathohistological and immunological characteristics. The studies performed demonstrated that in comparison to normal controls peripheral blood mononuclear cells from patients with rheumatoid arthritis (RA) presented an increased percentage of monocytic cells. Peripheral blood mononuclear cells from patients with RA produced significantly increased amounts of prostaglandin E2 and significantly decreased amounts of interferon-gamma following mitogen stimulation with LPS or PWM respectively. The spontaneous production of interleukin 1 was found to be elevated. A significantly increased LPS induced production of prostaglandin E2 could also be observed in monocyte depleted rheumatoid peripheral cells and in peripheral cells of patients with osteoarthritis and HLAB27 associated joint diseases. Mononuclear cells from rheumatoid synovial tissue produced increased amounts of prostaglandin E2 and decreased amounts of interferon-gamma; the spontaneous prostaglandin E2 production was similar to the values obtained by mitogen stimulation which may originate from the distinct cellular composition of synovial tissue.

Adult↗
PubMedDate not supplied

Teaching electrocardiography: computer assisted learning vs lecture method.

This study investigated nursing students' responses to a basic electrocardiography computer assisted learning (CAL) program and a lecture on the same topic. There were no significant differences between the CAL and lecture groups on cognitive outcomes (measured by a 20 item test on electrocardiogram knowledge) or transfer of learning outcomes (measured in the clinical setting by the students' ability to identify and interpret six electrocardiogram tracings). However, CAL students displayed more positive affective responses. They also took between 10 and 32 minutes to complete the program while all lecture students took a mandatory 50 minutes or more.

Adult↗
PubMedDate not supplied

The estimation of circulating immune complexes, C3d, and anti-ds-DNA-antibody serum levels in the monitoring of therapeutic plasmapheresis in a patient with systemic lupus erythematosus. A case report.

A short-time monitoring of therapeutic plasmapheresis in a patient with systemic lupus erythematosus (SLE) by the estimation of circulating immune complexes, C3d serum levels and anti-ds-DNA-antibodies is described. It was found that serum immune complexes, C3d, and anti-DNA-antibodies decreased even further shortly after plasma exchange. The decrease found in C1q binding material in the patient's serum was paralleled by a decrease in serum immune complexes containing acridine orange binding material, possibly representing ds-DNA. A rapid increase of serum immune complexes, C3d, and anti-ds-DNA-antibodies after plasma exchange therapy indicated an antibody rebound phenomenon followed by a relapse of the disease.

Adult↗