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Biomedical subjects

P Kern

Publications and source records attributed to P Kern.

At least 145 records · Page 8Linked to original sources
PubMed1992

Soluble tumor necrosis factor receptors correlate with parasitemia and disease severity in human malaria.

Elevated serum or plasma concentration of immunoreactive tumor necrosis factor (TNF) is consistently detected in patients with malaria. TNF levels correlate with high parasitemia and clinical severity but not always with outcome. Since the effects of TNF may be neutralized by soluble TNF receptors, sera of 30 nonimmune patients with malaria were analyzed before and during antimalarial therapy. High concentrations of receptors R1 (55 kDa) and R2 (75 kDa) were detected immunologically in all sera of untreated patients. Levels of immunoreactive TNF correlated closely with levels of soluble TNF R1 and R2 (r = .75 and .59, respectively). In contrast, sera lacked cytotoxic activity against target cells in the TNF bioassays. Soluble TNF receptor levels remained elevated for days after treatment. These results suggest that excessive release of TNF induced by the asexual stage of malaria parasites is controlled by a subsequent shedding of soluble TNF receptors that may bind and deactivate biologically functional TNF.

Adolescent↗
PubMed1992

In vivo evaluation of photoprotection against chronic ultraviolet-A irradiation by a new sunscreen Mexoryl SX.

In a previous study on the hairless mouse it was shown that sub-erythemal doses of pure UV-A enhanced the numerous changes normally observed during chronological aging. A new sunscreen (a bis-benzylidene campho sulfonic acid derivative) has been synthesized in our research laboratory (lambda max: 345 nm, epsilon: 47,000). Its photoprotective properties against UV-A induced damages were assessed in our mouse model. Three month old albino hairless mice were exposed for 1 y to suberythemal doses (35 J/cm2) of UV-A obtained from a xenon source filtered through a WG 345 filter. One group of animals was exposed untreated, the other received a formulation containing 5% of the sunscreen prior to irradiation. At the end of the study the cutaneous properties of protected mice were compared to those of unprotected animals and to 3 and 15 month old unirradiated controls. We found that the visible changes induced by UV-A irradiation were mainly sagging and wrinkling. Histological and electron microscopic alterations consisted of hyperkeratosis, increased density of elastic fibers with alteration of fiber orientation and increased glycosaminoglycan deposits. Biochemical changes consisted of decreases in total collagen and collagen hydroxylation and increases in both collagen III/I + III ratio and fibronectin biosynthesis. All these changes were reduced or abolished by the sunscreen.

Animals↗
PubMed1991

Relative rates of biosynthesis of collagen type I, type V and type VI in calf cornea.

The biosynthesis of type I, type V and type VI collagens was studied by incubation of calf corneas in vitro with [3H]proline as a marker. Pepsin-solubilized collagen types were isolated by salt fractionation and quantified by SDS/PAGE. Expressed as proportions of the total hydroxyproline solubilized, corneal stroma comprised 75% type I, 8% type V and 17% type VI collagen. The rates of [3H]proline incorporation, linear up to 24 h for each collagen type, were highest for type VI collagen and lowest for type I collagen. From pulse-chase experiments, the calculated apparent half-lives for types I, V and VI collagens were 36 h, 10 h and 6 h respectively.

Animals↗
PubMed1991

Progression of HIV-1 infection. Monitoring of HIV-1 DNA in peripheral blood mononuclear cells by PCR.

We present data on the distribution of human immunodeficiency virus (HIV-1) proviral DNA in different subsets of peripheral blood mononuclear cells (PBMCs) over an observation period of eight months. Eleven patients with well documented HIV-1 infection were studied. The PBMCs were obtained at two intervals and purified by fluorescence-activated cell sorting (FACS) after staining with FITC-labelled monoclonal antibodies. Varying numbers of FACS-sorted CD4+ cells, CD8+ cells and peripheral monocytes were assayed for HIV-1 proviral DNA (env and gag region) by PCR. Samples from patients at CDC stages II or III had to contain 10(3)-10(4) cells in order to allow detection of proviral HIV-1 DNA. At CDC stage IV, however, HIV-1 DNA was detected in as few as 100 CD4+ T-lymphocytes. In contrast, in peripheral monocytes HIV-1 DNA was not regularly found. CD8+ cells did not harbor detectable amounts of proviral DNA. During an observation period of eight months, the rate of infected CD4+ T-lymphocytes increased significantly in three patients while staying constant in the remaining eight patients. This increase of the infection rate was paralleled by clinical progression in one patient and by a decrease of the absolute number of CD4+ cells in another patient. The percentage of CD4+ cells harboring the viral genome increases in the course of the disease. These results may help to explain the decrease in CD4+ T-lymphocyte counts during HIV-1 infection.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Activation of the host response in human Plasmodium falciparum malaria: relation of parasitemia to tumor necrosis factor/cachectin, thrombin-antithrombin III, and protein C levels.

PURPOSE: Hemostatic alterations and elevated tumor necrosis factor/cachectin (TNF alpha) serum levels may contribute to the pathogenesis of organ complications in human Plasmodium falciparum malaria. Therefore, we examined whether altered protein C (PC) and thrombin-antithrombin III (TAT) plasma levels correlated with TNF alpha serum concentrations, parasitemia, and the clinical course of human P. falciparum malaria. PATIENTS AND METHODS: Forty-seven patients with P. falciparum malaria were evaluated prospectively before and during antiparasitic therapy. TNF alpha serum levels were determined by immunoradiometric assay, PC and TAT plasma antigen by enzyme-linked immunosorbent assay, and PC and PC inhibitor-1 (PCI-1) activity levels by functional tests. Cultured endothelial cells were incubated with serum from four patients with malaria and from healthy control subjects and then assayed for procoagulant activity. Northern blot hybridization was used to detect tissue factor mRNA. RESULTS: In vivo, TNF alpha serum concentrations were elevated (median: 38.6 pg/mL; n = 47) while plasma levels of PC (antigen 55.4%; activity 39.0%; n = 47) and PCI-1 (0.56 U/L) were decreased in almost all patients before antiparasitic treatment. At the same time, TAT concentrations were high. These alterations correlated significantly (p less than 0.01) both with the severity of the disease (as defined by organ impairment) and with the number of circulating parasitized erythrocytes. Low PCI-1 activity correlated with low PC activity (p less than 0.001) and antigen (p less than 0.05) levels. The plasma level of coagulation factor IX, another vitamin K-dependent protein, was not significantly changed. In vitro, incubation of endothelial cells with patient serum (severe P. falciparum malaria) increased both endothelial cell procoagulant activity and cytoplasmic tissue factor mRNA levels. CONCLUSION: Elevated levels of TNF alpha and TAT, decreased plasma levels of anticoagulant PC, and the induction of procoagulant activity in endothelial cells by patient serum indicate a shift in the balance of hemostatic activity towards a procoagulant state in P. falciparum malaria. The alterations in TNF alpha, TAT, and PC levels may be a response to infection, since they correlate with parasitemia and are reversed during antiparasitic treatment.

Animals↗
PubMed1991

Age-dependent variations of the biosyntheses of fibronectin and fibrous collagens in mouse skin.

Skin explant cultures from hairless mice of increasing age were incubated with radioactive precursors in order to determine the age-dependent variations of the biosyntheses of fibronectin and fibrous collagens (types I and III). Total collagen synthesis expressed as a percentage of total protein synthesis did not vary with age but, if expressed as micrograms hydroxyproline per mg wet weight of skin, decreased by about 30% between 2 and 22 months of age. Hydroxylation of collagen, expressed as the ratio of 3H-hypro over 3H (pro + hypro) incorporated in freshly synthesized collagen, decreased with age by about 40% between 2 and 22 months of age. The proportion of type III collagen expressed as % of type I + type III collagens increased progressively with age by about 25% at 12 months to 60% at 22 months of age. Fibronectin biosynthesis, determined by immunoprecipitation of 35S-methionine labeled peptides in SDS-extracts of skin increased progressively with age from about 2% of total incorporated radioactivity in fibronectin at 2 months to 4% at 22 months. Plasma fibronectin, of hepatic origin, was shown already to increase with age in humans. It appears thus that the expression of genes coding for extracellular matrix macromolecules is under age-dependent regulation. This regulation appears to be different for the investigated macromolecules.

Aging↗
PubMed1991

Characterization of monoclonal antibodies against alpha-hemolysin of Escherichia coli.

Monoclonal antibodies (MAbs) were raised against native and denatured alpha-hemolysin (HlyA) of Escherichia coli. Binding of the MAbs to native, denatured, and erythrocyte-complexed active wild-type hemolysin and mutant derivatives was tested. All 15 MAbs analyzed bound to native hemolysin, even when the toxin was complexed with human erythrocytes. While some MAbs were unable to bind to a specific native mutant hemolysin, others could not even bind to mutant hemolysin carrying deletions remote from their actual binding sites. A rough determination of the binding sites of 15 MAbs on HlyA was performed by Western immunoblot analysis using CNBr fragments of HlyA and mutant hemolysin proteins. Interestingly, the binding sites of the MAbs against native hemolysin seem to be more randomly distributed on HlyA than are those of MAbs against denatured hemolysin. Three MAbs inhibited the hemolytic activity significantly. Two of these MAbs bound to the hydrophobic region, and the other one bound to the repeat domain of HlyA. The use of synthetic peptides from these regions allowed determination of the linear epitopes for two of these MAbs.

Animals↗
PubMed1991

Neither heparin nor acetylsalicylic acid influence the clinical course in human Plasmodium falciparum malaria: a prospective randomized study.

Procoagulant alterations and thrombocytopenia in falciparum malaria correlate with parasitemia, serum levels of tumor necrosis factor alpha (TNF alpha), and clinical severity. Thus, heparin or acetylsalicylic acid (ASA), which are used frequently to prevent thrombosis and (in the case of ASA) to control fever, could be potentially beneficial. We randomized 97 patients with falciparum malaria into three groups: 33 patients received low-dose heparin subcutaneously, 31 received ASA intravenously, and 33 did not receive either drug. All patients received appropriate antiparasitic treatment. Eighteen of 97 patients (seven receiving heparin, five receiving ASA, and 6 in the control group) had complications upon admission. During therapy, elevated TNF alpha and lactate dehydrogenase levels and decreased platelet counts returned to normal values. Except for a minimal partial thromboplastin time prolongation with heparin, heparin or ASA did not affect any laboratory parameter, duration of parasitemia, fever clearance, or the length of hospitalization. Thus, it appears that ASA and heparin do not influence the course of falciparum malaria. Hence, in view of possible side effects, these substances should not be recommended for routine use in the treatment of human malaria.

Aspirin↗
PubMed1990

[Recombinant interferon alpha-2A in the treatment of HIV-associated Kaposi sarcoma. Long-term results].

47 HIV-positive male patients with cutaneous Kaposi's sarcoma (KS) were treated with recombinant interferon alpha-2A (IFN) in an open, prospective study. 45 patients received 18 million I.U. IFN s.c. daily for the first three months. From the fourth month, the patients received 18 million I.U. IFN s.c. three times weekly. Four of the 45 patients withdrew from therapy because of side effects during the first weeks (weeks 2 to 6) of treatment. The remaining 41 patients were treated for a minimum period of two years or until their death. Two further patients received 36 million I.U. IFN daily for three months. After three months of IFN therapy we observed complete remission (CR) in five of the 41 patients (12%), partial remission (PR) in seven patients (17%), stable disease in seven patients (17%) and progressive disease (PD) in 22 patients (54%). The mean survival time from the beginning of IFN therapy to date is 26 months for the 19 responders (patients with CR, PR or SD; six are still alive) and nine months for the 22 non-responders (patients with PD; all died). Recurrence of tumor progression occurred in 15 of the 19 responders after an average of ten months of continuous IFN therapy. The longest time of survival in this group is 54 months up to now. Of the four remaining patients, all in the CR group, two died after 24 and 26 months of IFN therapy, without any recurrence of KS growth (causes of death: Burkitt's lymphoma and unknown). The two other patients, both still alive, have not suffered any recurrence of tumor progression after 40 and 41 months, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

CD34+ hematopoietic progenitor cells are not a major reservoir of the human immunodeficiency virus.

Hematologic abnormalities occur in the majority of patients with acquired immunodeficiency syndrome (AIDS). Infection of the hematopoietic progenitor cells has been proposed as a potential explanation. In this study, different bone marrow cell populations, including the CD34+ hematopoietic progenitor cells, were purified by a fluorescence-activated cell sorter (FACS) and analyzed for the presence of human immunodeficiency virus-1 (HIV-1) proviral DNA using the polymerase chain reaction. A group of 14 patients with AIDS or AIDS-related complex (ARC) was studied (11 with peripheral blood cytopenias). The CD4+ helper cells in the bone marrow were found positive for HIV-1 DNA in all patients. In contrast, CD34+ progenitor cells were positive in only one patient. Two monocyte samples and two samples of CD4-/CD34- lymphocytes/blasts (mainly B and CD8 lymphocytes) were positive. Proviral DNA could not be detected in granulocytes. FACS analysis showed that the percentage of CD34+ hematopoietic progenitor cells was not altered in the bone marrow of AIDS patients in comparison with the HIV-1 seronegative controls. In contrast, the number of CD4+ lymphocytes was markedly reduced in the bone marrow of AIDS patients. These results show that the hematologic abnormalities in AIDS patients are neither explained by direct infection of the hematopoietic progenitor cells with HIV-1 nor by a depletion of progenitor cells.

Antigens, CD34↗
PubMed1990

Inhibition of HIV progression by dithiocarb. German DTC Study Group.

60 patients with HIV-1 infection in Walter Reed stages 2-4 were randomised to treatment with intravenous or oral dithiocarb (diethyldithiocarbamate, DTC) or placebo for 24 weeks in a paired double-blind design. 55 patients were evaluable at the end of the study: no patient who had received DTC but 6 placebo patients had AIDS, a significant difference. Significantly delayed disease progression was observed in the intravenous DTC group compared with its matching placebo. The benefit in the oral DTC group was not statistically significant. During an 18-month follow-up 3 deaths occurred in the original placebo groups, whereas no patient who had initially received DTC died. A significant delay in progression to AIDS was observed in the DTC groups.

Acquired Immunodeficiency Syndrome↗
PubMed1990

[Malaria tropica with activation of blood coagulation and detection of tumor necrosis factor (NF-alpha) in serum].

A 38-year-old patient with cerebral P. falciparum malaria was admitted 12 days after a short trip to Kenya. The serum level of tumor necrosis factor (TNF-alpha) was elevated (251 pg/ml). In contrast, Protein C (plasma activity 36.1%; antigen concentration 31.7%) and protein C inhibitor 1 (activity 0.55 U/ml) levels were decreased. This suggested a state of functional activation of the clotting system which was confirmed by elevated levels (4.8 ng/ml) of circulating thrombin-antithrombin-III-complexes (TAT). Protein S (total and free) and coagulation factor IX levels were within normal range. Under successful antiparasitic therapy, TNF-alpha as well as protein C and protein C inhibitor 1 levels returned to baseline within one week. In the context of other studies that demonstrate procoagulant effects of TNF-alpha, it is remarkable that in the case of complicated P. falciparum malaria, an elevated concentration of TNF-alpha can be paralleled by a decreased plasma level of protein C and an increase in TAT suggesting a procoagulant state.

Adult↗
PubMed1989

Biosyntheses of interstitial collagens and fibronectin by porcine aorta smooth muscle cells. Modulation by low-molecular-weight heparin fragments.

The effect of low-molecular-weight heparin fragments (CY222) on the biosynthetic phenotype of porcine aortic smooth muscle cells (SMC) was investigated in vitro on overconfluent cell cultures. Addition of increasing concentrations of CY222 to the culture medium of early passage SMC resulted in a dose-dependent decrease of type III to type I collagen ratio without change in total collagen biosynthesis. In the same range of concentrations CY222 did not affect the biosynthesis of fibronectin. However, heparin fragments decreased the proportion of the freshly synthesized pericellular form of fibronectin with a concomitant increase of neosynthesized intracellular fibronectin, indicating an inhibitory effect of CY222 on fibronectin secretion. Our results demonstrate that the biosynthetic phenotype of SMC in vitro can be modulated by low-molecular-weight heparin fragments and confirm also that interactions between cells and extracellular matrix molecules can modify the biosynthetic pattern of mesenchymal cells.

Animals↗
PubMed1989

Heparin fragments regulate collagen phenotype and fibronectin synthesis in the skin of genetically diabetic mice.

The biosyntheses of interstitial collagens of type I and III and of fibronectin were studied in genetically diabetic KK mice, as compared to control C57 Black mice, as well as the effect of low-Mr heparin fragments (CY 222) on these biosyntheses. An increased production of type III collagen, as compared to type I collagen, could be demonstrated in explant cultures of KK mice skins. Fibronectin biosynthesis was also increased. In vivo treatment of KK mice with 1 mg/kg of CY 222 decreased the biosyntheses of type III collagen and of fibronectin to normal levels. These experiments suggest that low-Mr heparin fragments can modulate the expression of extracellular matrix macromolecules.

Animals↗
PubMed1989

Elevated tumor necrosis factor alpha and interleukin-6 serum levels as markers for complicated Plasmodium falciparum malaria.

PURPOSE: Tumor necrosis factor alpha (TNF-alpha) has been implicated in the pathology of experimental malaria. To establish its relevance to human malaria, we studied serum levels of two monocyte-derived cytokines, TNF-alpha and interleukin-6 (IL-6), as well as of the lymphocyte-derived mediator interferon gamma (IFN-gamma) in patients with malaria before and during antiparasitic treatment. PATIENTS AND METHODS: One hundred twenty serum samples of 40 patients with malaria (Plasmodium falciparum [n = 32], Plasmodium vivax [n = 8]) were analyzed. IL-6 was measured by a highly sensitive and specific bioassay, TNF-alpha by immunoradiometric assay, and IFN-gamma by radioimmunoassay. RESULTS: Elevated cytokine levels could be detected in the majority of patients with P. falciparum malaria before treatment (31 of 32, 21 of 32, and 21 of 32 for TNF-alpha, IL-6, and IFN-gamma, respectively), but only in some patients with P. vivax malaria (four of eight, one of eight, and zero of eight for TNF-alpha, IL-6, and IFN-gamma, respectively). Serum concentrations of the monokines TNF-alpha and IL-6 correlated significantly with parasitic density (p less than 0.001). No such correlation was obtained with the circulating IFN-gamma concentration. The levels of monokines TNF-alpha and IL-6 were markedly elevated in 18 P. falciparum-infected patients with complicated clinical courses (median values for TNF-alpha 172 pg/mL, for IL-6 16 U/mL, peak values: 896 pg/mL and 1,000 U/mL, respectively). The correlation between TNF-alpha and IL-6 concentrations in serum (n = 40, r = 0.56, p = 0.0002) suggests co-ordinate production of those mediators. CONCLUSION: Organ impairment in human malaria was found to be correlated with the amount of circulating cytokine levels of TNF-alpha and IL-6. Thus, imbalances of the cytokine network in untreated P. falciparum infection serve as markers of severity of disease. Modulation of cytokine response could represent a novel approach to the treatment of severe organ dysfunctions in human malaria.

Adult↗
PubMed1989

Collagen synthesis and deposition in cultured fibroblasts from subcutaneous radiation-induced fibrosis. Modification as a function of cell aging.

Acute local gamma-irradiation of porcine skin induces, as in human skin, extensive mutilating sclerosis, characterized by continuous expansion of the fibrosis invading the adjacent muscle and by accumulation of extracellular matrix macromolecules. Collagen synthesis, content, and types were studied by measuring the incorporation of the radiolabeled precursor [3H]-proline into confluent primary cultures and subcultures of porcine fibroblasts obtained from normal and irradiated fibrotic dermis. A significant increase in collagen biosynthesis and deposition, with a preferential enhancement of type III collagen, was observed in primary cultures of fibrotic fibroblasts when compared to those of normal dermis. However, the percentage (36%) of neosynthesized collagen in relation to the total neosynthesized non-collagenous and collagenous proteins remained unchanged. In subcultures of normal cells, collagen synthesis and content remained constant until about the 10th passage and then progressively declined until death of the fibroblasts, at around the 15th passage. During the senescence phase, normal fibroblasts acquired the capacity to synthesize higher levels of non-collagenous proteins. On the contrary, collagen synthesis and content diminished in subcultures of fibrosis-induced fibroblasts from the second passage, and then progressively declined as a function of aging; particularly the ratio of type III to type I collagen returned to normal values from the second passage. Moreover, these fibroblasts did not become senescent, persisted in synthesizing low levels of collagen, and acquired later (around the 40th passage) a higher capacity to synthesize non-collagenous proteins. These results demonstrate that primary cultures of porcine fibroblasts obtained from normal or radiation-induced fibrotic dermis reproduce the in vivo situation. The results strongly suggest that: 1) the modification of collagen synthesis, content, and types observed in primary cultures of fibroblasts might be due to factors causing long-lasting changes in phenotypic expression and/in stimulation of the expansion of some fibroblast clones engaged in the accelerated synthesis of extracellular matrix macromolecules, such as collagen or non-collagenous proteins. 2) the rapid decrease in this active capacity to synthesize and accumulate collagen, observed in subcultures of fibrosis-induced fibroblasts, might be related to the loss of some activation factors or to the dedifferentiation of the cells. 3) the switch from collagen to non-collagenous protein synthesis during later subcultures of fibroblasts obtained from radiation-induced fibrosis, might be due to molecular modification at the transcriptional or DNA level.

Animals↗