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Biomedical subjects

S Fischer

Publications and source records attributed to S Fischer.

At least 415 records · Page 23Linked to original sources
PubMed1985

Phosphoinositides are not phosphorylated by the very active tyrosine protein kinase from the murine lymphoma LSTRA.

We studied the ability to phosphorylate phosphoinositides by 3 different subcellular preparations, and immunopurified tyrosine protein kinase (TPK) from two murine lymphoma cell lines induced by the Moloney murine leukemia virus: LSTRA with a very active TPK and MBL2 without significant TPK activity. We could not find any difference in the phosphorylation of phosphoinositides by these preparations. The TPK purified with two antibodies which phosphorylate actively tyrosine on exogenous substrate were unable to phosphorylate phosphoinositides.

Animals↗
PubMed1985

Inhibition of leukotriene B4 formation in human neutrophils after oral nafazatrom (Bay g 6575).

Three grams of nafazatrom (Bay g 6575), given orally to healthy male volunteers in a single dose, significantly reduce the formation of leukotriene B4 in polymorphonuclear leukocytes. LTB4 synthesis fell from 57.1 +/- 17.0 ng/10(7) PMNL, mean +/- S.D., in control to 34.3 +/- 14.4 ng/10(7) PMNL 3 hr after nafazatrom (2 P less than 0.001). In vitro, nafazatrom inhibited LTB4 formation in human PMNL in a dose dependent manner. At 1 microM nafazatrom LTB4 formation was reduced to 65% of the control value. Nafazatrom had no effect on the excretion of 2,3-dinor-6-keto-PGF1 alpha and 2,3-dinor-TXB2, the major urinary metabolites of endogenously synthesized PGI2 and TXA2, respectively. Serum levels of TXB2 in clotted whole blood also remained unchanged. The inhibitory effect of nafazatrom on leukotriene biosynthesis in human PMNL suggests a therapeutic potential of this drug in processes like allergy and chronic inflammation, where leukotrienes play a pathogenetic role.

Administration, Oral↗
PubMed1985

[Benefits of routine automatic blood picture differentiation].

The benefits of automated blood smear differential cell counting as a supplementary laboratory examination have been studied. The investigations focussed on patients of whom hematology requisitions were limited to total leukocyte count and hemoglobin determination. The specimens were derived from patients of departments of surgery and obstetrics and gynecology. For specimen collection the vacutainer system was used. The blood smears were prepared in a Coulter Electronics slide spinner, stained with a Hematek II slide stainer and analyzed in the Coulter Electronics Diff 3-50 cell classifier. A total of 1700 blood smears were examined. Following processing of each sample, the classification of each cell was inspected. Corrections were performed, if necessary, and the number of classification changes performed for each smear was registered. Using the in-house normal ranges, 34.5% were pathological smears. Since this group included a large number of borderline cases, new discrimination limits for clinically relevant pathological findings were set empirically. According to these wider ranges, the fraction of pathological slides amounted to 15.2%. Among these, immature granulocytes, eosinophilia and lymphopenia were the most frequent pathological findings. Microscopic control proved in 57.6% of the total number of smears. This complemental procedure was not found to be time-consuming.

Automation↗
PubMed1985

Modulation of adenylate cyclase by guanine nucleotides and Kirsten sarcoma virus mediated transformation.

Certain tumour cells contain activated ras genes that code for 21 000 dalton proteins (p21). These proteins associate with the inner face of the plasma membrane and bind guanine nucleotides specifically. In order to determine whether p21s have functions similar to other GTP binding proteins, we investigated the regulation, by guanine nucleotides, of adenylate cyclase (AC) activity in membrane preparations isolated from fibroblasts (C127) transformed by a temperature sensitive mutant of Kirsten sarcoma virus (Ts 371). The degree of AC stimulation by GMP P(NH)P increased when these cells were shifted from the permissive temperature (33 degrees C) to the non-permissive temperature (39 degrees C). This effect was more pronounced at low Mg++ and low GMP P(NH)P concentrations. AC stimulation remained unchanged in rat fibroblasts infected with a temperature sensitive mutant of Rous Sarcoma virus. AC activity was depressed in C127 cells infected with wild type KiMSV. Our data illustrate the feasibility of correlating alterations in the AC system with ras gene expression and using such experimental approaches to elucidate the physiological functions of the p21 proteins.

Adenylyl Cyclases↗
PubMed1985

alpha-MSH and neurofilament M-protein share a continuous epitope but not extended sequences. An explanation for neurofibrillary staining with alpha-MSH antibodies.

The long recognized neurofibrillary immunoreactivity of the nervous system with alpha-MSH antibodies arises from an epitope on neurofilament M-protein which we have now characterized. It is situated in the amino terminal residues where M-protein and alpha-MSH exhibit similar but not identical sequences. Their divergence past residue 5 precludes a physiological significance of the crossreactivity which seems to have arisen fortuitously. Our results question previous speculations as to the existence of extrapituitary alpha-MSH-like hormones.

Acetylation↗
PubMed1985

The influence of adenosine triphosphate, adenosine diphosphate and cytochalasin B on nucleotide exchange of F-actin. Evidence that treadmilling is not involved.

[14C]ATP-containing G-actin was polymerized to [14C]ADP-containing F-actin. The exchange of the filament-bound nucleotide with nucleotides of the medium was investigated by measuring the loss of radioactivity from the filaments under various conditions. Nucleotide exchange was faster in the presence of ATP than of ADP (this could be observed in the presence of Mg2+ as well as in the presence of Ca2+). Cytochalasin B had a small accelerating effect in the presence of ATP but had no effect in the presence of ADP. The kinetics of exchange remained unchanged when the filaments contained a 'cap' of actin with non-radioactive nucleotides, suggesting that nucleotide exchange was not a property of the filament ends.

Actins↗
PubMed1985

Thromboxane (TX)A3 and prostaglandin (PG)I3 are formed in man after dietary eicosapentaenoic acid: identification and quantification by capillary gas chromatography-electron impact mass spectrometry.

The low incidence of myocardial infarction in Greenland Eskimos has been related to their traditional marine diet rich in eicosapentaenoic acid. However, whether dietary eicosapentaenoic acid is indeed transformed in man to antiaggregatory PGI3 and weakly proaggregatory TXA3 has not been clarified. In our studies we ingested either cod liver oil or mackerel both rich in eicosapentaenoic acid. Formation of TXB3, the hydrolysis product of TXA3, in platelet-rich plasma stimulated ex vivo with collagen was traced by capillary GC/EIMS. Via external standard, TXB3 formation in platelets was estimated to be 5-15% of TXB2 formation. From urine we extracted dinor metabolites of PGI according to a selective method. We utilized delta 17-2,3-dinor-6-keto-PGF1 alpha (PGI3-M) as an index of total body production of PGI3 in analogy to 2,3-dinor-6-keto-PGF1 alpha (PGI2-M), the major urinary metabolite of PGI2. We separated PGI2-M and PGI3-M as the Me, MO, Me3Si derivatives by capillary gas chromatography and identified PGI3-M by EI mass spectrometry. Excretion of PGI3-M, which was not detectable under control conditions, was 83 +/- 25 ng/24 h (SD) after ingestion of cod liver oil and 134 +/- 38 ng/24 h after mackerel ingestion, while excretion of PGI2-M was 162 +/- 52 ng/24 h and 236 +/- 32 ng/24 h, respectively. Our findings with diets rich in EPA show that it is possible in man to change in vivo the spectrum of biologically active prostanoids by nutritional means and alter it in a favourable direction.

Blood Platelets↗
PubMed1985

Protein-chemical characterization of NF-H, the largest mammalian neurofilament component; intermediate filament-type sequences followed by a unique carboxy-terminal extension.

NF-H has the highest mol. wt. of the three mammalian neurofilament components (NF-L, NF-M, NF-H). In spite of its unusually large mol. wt., estimated to be 200 K by gel electrophoresis, NF-H contains sequences which identify it as an integral intermediate filament (IF) protein in its amino-terminal region. We have isolated and partially characterized a basic, non-alpha-helical segment located at the amino-terminal end with properties similar to headpieces of other non-epithelial IF proteins. The highly alpha-helical 40-K fragment excised by chymotrypsin is now identified by the amino acid sequence of a 17-K fragment. This sequence can be unambiguously aligned with the rod region of other IF proteins and covers about half of the presumptive coiled-coil arrays. NF-H and NF-M show 45% sequence identity in this region. The extra mass of NF-H in comparison with most other IF proteins arises from a carboxy-terminal extension thought to be responsible for inter-neurofilament cross-bridges in axons. This autonomous domain has a unique amino acid composition characterized by a high content of proline, alanine and particularly of lysine and glutamic acid. The NF-H tailpiece extension also carries a large number of serine phosphates, which are not evenly distributed, but are restricted to the amino-terminal part. Having now delineated the intermediate filament-type sequences for all three neurofilament proteins it seems very likely that the three components interact via coiled-coil interactions. They all carry unique carboxy-terminal extensions which increase in length from NF-L to NF-H and seem to extend from the filament wall.

Journal Article↗
PubMed1985

Synthesis and phosphorylation of cytoskeleton components in foetal, regenerating and adult normal rat hepatocytes during culture.

Detergent insoluble material (DIM) was prepared by gentle treatment with detergent from foetal, regenerating and adult normal rat hepatocytes cultured for various times. It retained to some degree the morphology of the cells. After incubation of intact cells with 35S-methionine, most of the labelled DIM proteins were found to be components of the cytoskeleton. They included several cytokeratins, vimentin and actin. The synthesis rate varied with the age of animals and culture conditions. The high synthetic rate of vimentin in foetal and regenerating hepatocytes could be associated with cell proliferation. No correlation was found between cytokeratin synthesis and hepatocyte growth. Most of the cytoskeleton proteins could be phosphorylated in intact cells and in DIM from cultured hepatocytes. However the degree of phosphorylation of these proteins was not related to their synthetic rate. The decreased phosphorylation level in cultured adult rat hepatocytes could be related to the rapid loss of specific functions.

Animals↗
PubMed1985

Pneumococcal antibodies (IgG, IgM) in patients with chronic obstructive lung disease 3 years after pneumococcal vaccination.

An enzyme-linked immunoassay was used to determine serum content of IgG and IgM antibodies against eight capsular polysaccharides of Streptococcus pneumoniae in 19 patients with chronic obstructive lung diseases 3 years after inoculation with a polyvalent pneumococcal vaccine (Moniatrix); 21 unvaccinated patients with comparable diseases served as the control group. The vaccinated group showed slightly more pronounced IgG antibody reactions than the unvaccinated group, but the differences were not statistically significant. These results show that pneumococcal vaccination does not provide long-term protection at least for patients with chronic obstructive lung disease.

Adult↗
PubMed1985

Acute myeloblastic leukemia with active tyrosine protein kinase.

High level of tyrosine protein kinase activity was found in a membrane fraction isolated from an acute myeloblastic leukemia, out of 24 leukemias of different origin investigated. The major substrate for tyrosine phosphorylation in vitro was a 58 kDA protein (p58). The phosphorylation proceeded actively at 0 degrees C and was strongly stimulated by Mn2+ ions. Comparison by partial proteolysis of the p58 with similar phosphoproteins from a T-lymphoma line (KE37) and from lectin stimulated lymphocytes showed high similarity. The possible role of the tyrosine kinase activity in this leukemia is discussed.

Gastrins↗
PubMed1985

Detection of tyrosine-specific protein kinases with gastrin as exogenous substrate.

Gastrin was recently shown to be phosphorylated on its single tyrosine by the epidermal growth factor (EGF)-stimulated tyrosine protein kinase (TPK). The TPK previously detected in the murine lymphoma (LSTRA) induced by the Moloney murine leukemia virus phosphorylates gastrin, the apparent Km is 65 microM and the maximum rate 1900 pmol/min per mg; the kinase is more efficient with MnCl2 than with MgCl2, is stimulated by NaVO3 and inhibited by ZnCl2. Gastrin phosphorylation is observed only when a TPK is expressed by the cell: extracts of fibroblasts infected with a temperature-sensitive mutant of the Rous sarcoma virus had no gastrin kinase activity when grown at the non-permissive temperature whereas cells grown at the permissive temperature were transformed and disclosed a clear gastrin kinase activity. Gastrin kinases were detected in various transformed cells: human lymphomas, K562 cells, cells from a patient with acute proliferative leukemia, and normal cells: human T and B lymphocytes.

Animals↗
PubMed1985

Leukotriene B5 is formed in human neutrophils after dietary supplementation with icosapentaenoic acid.

Incorporation and conversion of icosapentaenoic acid (20:5, n - 3) by human polymorphonuclear leukocytes were studied in volunteers (n = 6) ingesting a normal Western diet supplemented with icosapentaenoic acid (approximately equal to 4 g daily). Ingestion of icosapentaenoic acid leads to formation of biologically less active leukotriene B5 (LTB5) from polymorphonuclear leukocytes (PMNL) stimulated with ionophore A23187. LTB5 was identified on HPLC by UV absorption and by GC/MS and showed a behavior identical to that of in vitro synthesized LTB5 produced by incubation of human PMNL with icosapentaenoic acid. The ratio of icosapentaenoic acid/arachidonic acid (20:4, n - 6) in cellular phospholipids increased from 0.045 during control to 0.28 after the supplemented period. LTB5 increased from undetectable values to 70.2 +/- 18.7 pmol of LTB5 per 10(7) PMNL during the experimental period. Synthesis of LTB4 did not change significantly (control, 218.8 +/- 89.1; icosapentaenoic acid-enriched diet, 253.6 +/- 18.7 pmol per 10(7) PMNL). The ratio of LTB4/LTB5 corresponded to the ratio of arachidonic acid/icosapentaenoic acid in PMNL phospholipids. Our findings prove that LTB5, which is 10 to 30 times less potent than LTB4 to cause aggregation, chemotaxis, and degranulation of PMNL, can be formed in vivo in man after dietary icosapentaenoic acid. This may modify the contribution of leukotrienes in processes in which these metabolites are of pathogenetic relevance.

Adult↗
PubMed1985

Phosphorylation of the N and M1 proteins of rabies virus.

Phosphorylation of rabies virus proteins was followed in vivo and in vitro. The N and M1 proteins were both found to be phosphorylated. The M1 protein was present in the virion in two phosphorylated states, but only the hypophosphorylated form of M1 was found in infected cells. The hypothesis that some of the M1 molecules become hyperphosphorylated during the maturation process by a membrane-bound kinase was examined. The phosphorylation of the viral proteins by the kinase present in purified rabies virions was studied using an in vitro transcriptase assay: under the conditions of the assay, additional phosphate groups were rapidly attached to the N protein. The M1 protein was similarly hyperphosphorylated although more slowly. Whether the hyperphosphorylation of the N protein is responsible for the poor efficiency of the in vitro transcriptase reaction is not clear. No detectable change in the phosphorylation of cellular proteins was observed in the course of rabies virus infection.

Animals↗
PubMed1985

Long-term effects of dietary marine omega-3 fatty acids upon plasma and cellular lipids, platelet function, and eicosanoid formation in humans.

We studied the incorporation and metabolism of eicosapentanoic (EPA) and docosahexaenoic acid in six human volunteers who supplemented their normal Western diet for 5 mo daily with 10-40 ml of cod liver oil, rich in omega-3 polyunsaturated fatty acids. EPA and docosahexaenoic acid were incorporated into the total phospholipids of plasma, platelets, and erythrocytes in a dose- and time-dependent manner. During omega-3 fatty acid ingestion serum triacylglycerols were lowered and platelet aggregation upon low doses of collagen was reduced. Concomitantly, formation and excretion of prostanoids showed a characteristic change. As measured in serum from whole clotted blood, thromboxane A3 was formed in small amounts, whereas thromboxane A2 formation was reduced to 50% of control values. Excretion of the main urinary thromboxane A metabolites was unaltered in subjects with low basal excretion rates, but decreased markedly in two subjects with high control values. As determined from the main urinary metabolite, prostaglandin I3 was formed from EPA at rates up to 50% of unaltered prostaglandin I2 formation. The biochemical and functional changes observed lasted for the entire supplementation period of 5 mo and were reversible within 12 wk after cessation of cod liver oil intake. Favorable changes induced by long-chain omega-3 fatty acids include a dose-related and sustained shift of the prostaglandin I/thromboxane A balance to a more antiaggregatory and vasodilatory state.

Administration, Oral↗
PubMed1985

A comparative study of eicosapentaenoic acid metabolism by human platelets in vivo and in vitro.

During long-term dietary n-3 fatty acid supplementation, eicosapentaenoic acid (EPA) is not incorporated into phosphatidylinositol or -serine of human platelets in vivo and is not detectable in phosphatidic acid upon stimulation with thrombin. However, EPA is released from platelet phospholipids and metabolized to thromboxane B3 (TXB3). In contrast, in vitro, platelets incorporate [14C]EPA into phosphatidylinositol, whether they contain endogenous EPA in their cellular lipids or not. Following platelet stimulation, [14C]EPA appears in phosphatidic acid, as free fatty acid, and is transformed to TXB3. We conclude that the fatty acid compositions of platelet phospholipid subclasses are regulated with a high degree of specificity in vivo. Qualitative differences exist between in vivo and in vitro uptake of EPA into platelet phospholipid subclasses. After in vivo incorporation, EPA is released by action of a phospholipase A2.

Adult↗