Biomedical subjects

K Hasegawa

Publications and source records attributed to K Hasegawa.

At least 19 recordsLinked to original sources

PubMed1996

cDNA cloning of a 20-kDa protein (p20) highly homologous to small heat shock proteins: developmental and physiological changes in rat hindlimb muscles.

A cDNA clone encoding p20, a novel member of the small heat-shock protein family in mammals, was isolated from a rat soleus cDNA library. The clone contained an insert of 1.3 kb with an open reading frame specifying a polypeptide of 162 amino-acid residues. Southern blot analysis suggested that the p20 gene is a single gene in rat genome. Developmental changes and a sciatic nerve denervation experiment suggested that the expression of p20 in rat hindlimb muscle is related to muscle contraction, and specifically in slow-twitch muscles.

Animals↗

PubMed1996

Hematopoietic cell phosphatase, SHP-1, is constitutively associated with the SH2 domain-containing leukocyte protein, SLP-76, in B cells.

Src homology region 2 (SH2) domain-containing phosphatase 1 (SHP-1; previously named HCP, PTP1C, SH-PTP1, and SHP) is a cytosolic protein tyrosine phosphatase that contains two SH2 domains. Recent data have demonstrated that the gene encoding SHP-1 is mutated in motheaten (mc) and viable motheaten (mc') mice resulting in autoimmune disease. More recently, SHP-1 has been shown to negatively regulate B cell antigen receptor (BCR)-initiated signaling. To elucidate potential mechanisms of SHP-1 action in BCR signal transduction, we studied proteins that interact with SHP-1 in B cells. Both anti-SHP-1 antibody and the two SH2 domains of SHP-1 expressed as glutathione S-transferase fusion proteins precipitated at least three phosphoproteins of approximately 75, 110, and 150 kD upon anti-immunoglobulin M stimulation of the WEHI-231 immature B cell line. Binding of SHP-1 to the 75- and 110-kD proteins appeared to be mediated mainly by the NH2-terminal SH2 domain of SHP-1, whereas both the NH2- and COOH-terminal SH2 domains are required for maximal binding to the 150-kD protein. Immunoprecipitation and Western blot analysis revealed that the SHP-1-associated 75-kD protein is the hematopoietic cell-specific, SH2-containing protein SLP-76. Further, this protein-protein association was constitutively observed and stable during the early phase of BCR signaling. However, significant tyrosine phosphorylation of SLP-76 as well as of SHP-1 was observed after BCR ligation. Constitutive association of SHP-1 with SLP-76 could also be detected in normal splenic B cells. Collectively, these results suggest possible mechanisms by which SHP-1 may modulate signals delivered by BCR engagement.

Adaptor Proteins, Signal Transducing↗

PubMed1996

Enhancement of stress-induced synthesis of hsp27 and alpha B crystallin by modulators of the arachidonic acid cascade.

The regulation by intrinsic factors of responses to stress of two small stress proteins, hsp27 and alpha B crystallin, was examined in C6 rat glioma cells. Levels of hsp27 and alpha B crystallin were low in C6 glioma cells in confluent cultures. However, levels of the two proteins increased after exposure of cells to heat (42 degrees C for 30 min) or arsenite (50 microM for 1 h) stress. When cells were exposed to arsenite or hear in the presence of indomethacin (50 microM), an inhibitor of cyclooxygenase, or in the presence of nordihydroguaiaretic acid (NDGA; 50 microM), an inhibitor of lipoxygenase, induction of hsp27 and alpha B crystallin was markedly stimulated as detected by specific immunoassays, Western blot analysis, and Northern blot analysis. The presence of melittin (1 microM), an activator of phospholipase A2, during the stress period also stimulated the induction of the two proteins. The expression of hsp70 to each stress was also enhanced in the presence of indomethacin, NDGA, or melittin. The gel mobility shift assay revealed that these chemicals prolonged the arsenite-induced activation of heat shock element (HSE)-binding activity of heat shock transcriptional factor (HSF) in cells. Induction of hsp27 and alpha B crystallin in adrenal glands of heat-stressed (42 degrees C for 15 min) rats was also enhanced by prior injection of aspirin, another inhibitor of cyclooxygenase. These results indicate that the responses to stress of hsp27 and alpha B crystallin, as well as the response of hsp70, are coupled with the metabolic activity of the arachidonic acid cascade and the mechanism for regulation of stress responses observed in C6 cells is operative in tissues and organs in vivo.

Animals↗

PubMed1996

Comitogenic effects of vasoactive intestinal polypeptide on rat hepatocytes.

The primary mitogens such as epidermal growth factor and transforming growth factor-alpha are known to stimulate DNA synthesis in primary cultures of adult rat hepatocytes. Vasoactive intestinal polypeptide (VIP) was found to amplify DNA synthesis induced by the primary mitogens and thus acted as a comitogen. The comitogenic effect of VIP was specific for the culture medium, suggesting that minor components in the medium were required for hepatocytes to fully respond to VIP. Glutamic acid is probably one of these minor components, although other components present in the nutrient-rich medium were also necessary for the full comitogenic effect. Other comitogens such as insulin, vasopressin, and angiotensin II interacted additively with low concentrations of VIP. The comitogenic effect of VIP was also found in hepatocytes cultured from regenerating rat liver after a partial hepatectomy. In the regenerating hepatocyte cultures, VIP can act as a mitogen even in the absence of the primary mitogen EGF. VIP mRNA was found in several organs including brain, intestine, and liver, and its expression was slightly induced in liver 24 h after a partial hepatectomy. These results suggest that VIP can act as a hepatic comitogen and may play a role in liver cell proliferation.

Animals↗

PubMed1996

Estrogen-induced cell transformation and DNA adduct formation in cultured Syrian hamster embryo cells.

To study the possible involvement of DNA damage in cell transformation induced by estrogens, we examined whether DNA adduct formation is elicited in cultured Syrian hamster embryo (SHE) cells treated with estrogens and their derivatives by means of the 32P-postlabeling assay. Morphological transformation of the cells was induced by treatment with diethylstilbestrol (DES) at 1-10 micrograms/mL for 24 h but not by treatment with its derivatives trans, trans-dienestrol (alpha-DIES) or cis, cis-dienestrol (beta-DIES) at 1-10 micrograms/mL for 24 h. Similarly, DNA adduct formation was elicited by exposure of SHE cells to DES at 1-10 micrograms/mL for 24 h but not by either alpha-DIES or beta-DIES. Treatment of SHE cells with DES at 1-10 micrograms/mL for 2 h in the presence of exogenous metabolic activation with rat liver post-mitochondrial supernatant enhanced morphological transformation in a dose-dependent manner. Our previous studies have demonstrated that exposure of SHE cells to DES under the same conditions with exogenous metabolic activation induces somatic mutations at the Na+/K+ ATPase locus. Therefore, we examined whether with exogenous metabolic activation DES induced DNA adduct formation in SHE cells. DNA adducts were not detected when SHE cells were treated with DES at 1-10 micrograms/mL for 2 h in the presence of exogenous metabolic activation. Treatment with 17 beta-estradiol (E2), 2-hydroxyestradiol (2-OH E2), or 4-hydroxyestradiol (4-OH E2) at 1 microgram/mL for 24 h induced DNA adduct formation in the cells, in parallel with the induction of cell transformation. The rank order of DNA adduct formation was 4-OH E2 > 2-OH E2 > E2. The results indicate that estrogens induce DNA adduct formation in cultured SHE cells, but the induction may not be the only mechanism relevant to the initiation of cell transformation.

Animals↗

PubMed1996

Existence of a small population of IL-2R beta hi TCRint cells in SCG and MRL-lpr/lpr mice which produce normal Fas mRNA and Fas molecules from the lpr gene.

Mice carrying the lpr gene, SCG and MRL-lpr/lpr mice, were used to characterize the phenotype and lpr gene of abnormally proliferating T cells in these mice. A major population which expanded in these mice were T cells expressing intermediate (int) levels of T cell receptor (TCR) (and CD3) and the phenotype of interleukin-2 receptor (IL-2R) beta lo alpha- (possibly abnormal TCRint cells). The levels of TCRhi cells of thymic origin (generated through the mainstream of T cell differentiation in the thymus) profoundly decreased after the onset of disease. However, a small population of normal TCRint cells (i.e. IL-2R beta hi alpha-) were also found to exist in all tested organs. For example, the majority of abnormal IL-2R beta lo TCRint cells were CD4-8- CD2-, while normal IL-2R beta hi TCRint cells were a mixture of single-positive cells (mainly CD8+), CD4-8- cells and CD2+ cells. Moreover, normal TCRint cells preferentially produced normal Fas mRNA and Fas molecules from the lpr gene. This phenomenon explains the leaky appearance of normal Fas mRNA and Fas molecules in mice carrying the lpr gene. It is suggested that a small population of IL-2R beta hi TCRint cells are resistant to the lpr genetic abnormality.

Animals↗

PubMed1996

Intraepithelial lymphocytes in colon have similar properties to intraepithelial lymphocytes in small intestine and hepatic intermediate TCR cells.

Recently, properties of intraepithelial lymphocytes (IEL) in the colon (C-IEL) have been analyzed in comparison with those of IEL in the small intestine (SI-IEL). We compared the properties of C-IEL with those of SI-IEL and hepatic intermediate TCR cells, two other types of extrathymic T cells. C-IEL and intermediate TCR cells contain many NK1+T cells, although SI-IEL contain few. V gamma and V delta usage of C-IEL was the same as that SI-IEL, and that of intermediate TCR cells was different. C-IEL responded to Con A while SI-IEL did not. As to adhesion molecules, C-IEL include both extrathymic and thymus-originated type T cells. With age, TCR- alpha beta(+) CD4+ CD8+ cells do not increase among C-IEL but do increase among SI-IEL. IL-2R beta(+) or CD4- CD8- C-IEL increase as observed in the liver. These results indicate that these organ-specific T cells have different roles at their respective sites and that they may be of different lineages.

Animals↗

PubMed1996

Structure-activity relationship of lepidimoide and its analogues.

The structure-activity relationship of lepidimoide and its analogues was investigated by means of the Amaranthus caudatus L. hypocotyl elongation test. In addition, the activities of alpha-D-galacturonic acid and L-(+)-rhamnose, which are component sugars of lepidimoide, were also studied. The carboxylic acid free type of lepidimoide showed growth-promoting activity as high as the original lepidimoide (sodium type). The acetylated compound showed considerably higher activity than lepidimoide, whereas the methylated lepidimoide did not show any activity. The hydroxylated lepidimoide without a double bond in the C-4,5 position showed lower activity. The sugar alcohol type of lepidimoide [2-O-(alpha-D-glucopyranosyl)-L-rhamnose] showed the highest activity in all the compounds studied. alpha-D-Galacturonic acid, L-(+)-rhamnose and their mixtures, which are component sugars of lepidimoide, exhibited only slight or no activity, respectively. D-Glucose and the mixture of D-glucose and L-(+)-rhamnose were also slightly active or inactive. These data suggest that the active sites in the chemical structure of the lepidimoide are the uronic acid derivative bearing an alpha,beta-unsaturated carboxylate bonded to rhamnose via an alpha-glucoside linkage and a double bond in the C-4,5 position in the uronic acid.

Carbohydrate Sequence↗

PubMed1996

Tumour necrosis factor is expressed in cardiac tissues of patients with heart failure.

Tumour necrosis factor (TNF), a cytokine produced mainly by macrophages, has also been found in vascular smooth muscle cells. Elevated serum levels of TNF have been reported in various cardiac diseases, especially congestive heart failure (CHF). Although the myocardium produces several cytokines, the expression of TNF in human cardiac tissue has not yet been demonstrated. We examined TNF expression in right atrial (RA) specimens obtained from 15 patients during cardiac surgery with immunohistochemistry using an anti-human TNF monoclonal antibody, enzyme-linked immunosorbent assay (ELISA) and reverse transcriptase polymerase chain reaction (RT-PCR). TNF immunoreactivity was found only in cardiac myocytes and some vascular smooth muscle cells of small vessels of specimens from patients with severe CHF (3/5), and not in those from patients without severe CHF (0/10). ELISA of four RA specimens revealed that RA tissues from two patients with severe CHF contained more TNF than did those from two patients without severe CHF (3.1 and 4.7 pg/mg vs. 0.1 and 0.3 pg/mg). RT-PCR revealed TNF mRNA in all seven cases we examined. It was concluded that TNF mRNA is expressed by atrial tissue. The production of immunoreactive TNF-like peptides by myocytes and vascular smooth muscle cells is augmented in patients with severe CHF.

Aged↗

PubMed1996

Modulation of the stress-induced synthesis of hsp27 and alpha B-crystallin by cyclic AMP in C6 rat glioma cells.

The possible participation of cyclic AMP in the stress-induced synthesis of two small stress proteins, hsp27 and alpha B-crystallin, in C6 rat glioma cells was examined by specific immunoassays, western blot analysis, and northern blot analysis. When C6 cells were exposed to arsenite (50-100 microM for 1 h) or heat (42 degrees C for 30 min), expression of hsp27 and alpha B-crystallin was stimulated, with levels of the two proteins reaching a maximum after 10-16 h of culture. Induction of hsp27 was markedly enhanced when cells were exposed to arsenite in the presence of isoproterenol (20 microM) or epinephrine (20 microM) but not in the presence of phenylephrine. The stimulatory effects of isoproterenol and epinephrine were blocked completely by propranolol, an antagonist of beta-adrenergic receptors. Cholera toxin (2 micrograms/ml), forskolin (20 microM), and dibutyryl cyclic AMP (2.5 mM), all of which are known to increase intracellular levels of cyclic AMP, also stimulated the arsenite- or heat-induced accumulation of hsp27. Treatment of cells with each of these modulators alone did not result in the induction of hsp27. The level of hsp70 in C6 cells, as estimated by western blot analysis, was also enhanced by arsenite or heat stress. However, induction of hsp70 by stress was barely stimulated by isoproterenol. By contrast, induction of alpha B-crystallin by heat or arsenite stress was suppressed when isoproterenol, cholera toxin, forskolin, or dibutyryl cyclic AMP was present during the stress period. Northern blot analysis of the expression of mRNAs for hsp70, hsp27, and alpha B-crystallin showed that the modulation of the stress-induced accumulation of the three hsps by the various agents was regulated at the level of the corresponding mRNA. These results indicate that stress responses of hsp70, hsp27, and alpha B-crystallin in C6 rat glioma cells are regulated differently and, moreover, that when the level of cyclic AMP increases in cells, the response to stress of hsp27 is stimulated but that of alpha B-crystallin is suppressed.

Adrenergic beta-Agonists↗

PubMed1996

A molecular analysis of viral persistence in surface antigen-negative chronic hepatitis B.

To identify the mechanisms of viral persistence in patients with chronic hepatitis B after the acquisition of anti-hepatitis B surface antigen antibodies (antiHBs), we serially analyzed the nucleotide sequence of the envelope region in a cohort of infected patients. Four patients with histological diagnoses of chronic hepatitis B who had at least 5 years of observance by our hospital staff were studied. All but one showed normalization of serum alanine aminotransferase (ALT) concentration after clearance of the hepatitis B surface of antigen (HBsAg) and the appearance of anti-HBs. Hepatitis B virus (HBV) DNA was still detectable by polymerase chain reaction (PCR) amplification assay in serum specimens from two patients, even in the presence of circulating anti-HBs. The envelope gene was amplified by PCR in serum samples obtained both before and after seroconversion, and direct cycle sequencing of the PCR products was performed. A mutation resulting in a premature stop codon was found in the pre-S1 region of one patient just prior to clearance of HBsAg. Two years later, the stop codon was converted to a leucine codon and three mutations developed in the "a" loop. In the other patient, 16 amino acids had been deleted between amino acids 8 and 23 in the pre-S2 region before clearance of HBsAg. After the appearance of circulating anti-HBs, the pre-S2 gene reverted to the wild type but three additional mutations appeared inside the "a" loop. These results suggest that HBV mutates when HBsAg is cleared, which may contribute to viral persistence due to an evasion of the host immune surveillance.

Amino Acid Sequence↗

PubMed1996

Effects of cell proliferation and cell death (apoptosis and necrosis) on the early stages of rat hepatocarcinogenesis.

An experiment was performed to investigate whether, during regression of the liver hyperplasia induced by a direct mitogen, apoptosis differentially affects replicated and non-replicated hepatocytes. After a single dose of the direct mitogen lead nitrate (LN), male Wistar rats were given repeated injections of tritiated thymidine, and were killed either 3 days (time of maximal hepatic DNA increase) or 15 days (complete regression of the hyperplasia) after mitogen treatment. Determination of liver DNA radioactivities and labelling indices (LIs) at the two time points revealed an approximately 40% loss in total liver DNA radioactivity, a 20% decrease in the specific activity of DNA, and a 20% reduction in the cell LI. Three days after LN administration 64% of the apoptotic bodies contained thymidine grains in their nuclear fragments. The results indicated that apoptosis affects both hepatocytes that replicated, and those that did not replicate, the former being slightly more sensitive. A second experiment was then performed to investigate whether and to what extent different types of cell death (apoptosis versus necrosis) influence the growth of hepatocytes initiated by a chemical carcinogen. Male Wistar rats were given a single dose of diethylnitrosamine, and 2 weeks thereafter either a single dose of LN, or a necrogenic dose of carbon tetrachloride (CCl4). Bromodeoxyuridine was next infused for 5 days, and some of the animals were killed at this time point, and others after an additional 3 weeks. Administration of CCl4 resulted in an increase in both the average size and the percentage area occupied by placental glutathione S-transferase-positive lesions. In contrast, administration of lead nitrate resulted in a strong reduction (50%) in the number of positive lesions with no remarkable change in the percentage area occupied by them. These differential effects occurred even though comparable LIs were observed in rats treated with the two agents. The results suggest that lead nitrate leads to a loss of initiated hepatocytes, due to the apoptosis that occurs during regression of the LN-induced hyperplasia.

Animals↗

PubMed1996

Disturbance of the cell cycle with colchicine enhances the growth advantage of diethylnitrosamine-initiated hepatocytes in rats.

The effect of cell cycle disturbance due to colchicine on the induction of enzyme-altered foci during liver regeneration in rats was studied. For initiation, diethylnitrosamine (DEN) at a dose of 10 mg/kg was injected intraperitoneally and partial hepatectomy (PH) was performed 4 h thereafter. Colchicine at doses of 0, 0.1, 0.25 and 0.5 mg/kg was injected intraperitoneally 1 and 3 days after the initiation, followed by application of selection pressure consisting of 2-acetylaminofluorene (AAF) and carbon tetrachloride (CCl4) administration. As end point lesions, gamma-glutamyltransferase (GGT)-positive enzyme-altered foci were assayed at week 5. There was no significant effect of colchicine on numbers of foci. However, a significant, dose-dependent increase in the area of GGT-positive lesions in the groups treated with colchicine was observed. Bromodeoxyuridine labeling indices were higher in foci induced in colchicine-treated rats than in the untreated rats. In a separate experiment, serum glutamic pyruvic transaminase was not increased significantly after DEN and colchicine treatment, and the mitotic index at 6 days after PH was increased in the liver of colchicine-treated rats. These results suggest that the cell cycle disturbance induced by colchicine causes more pronounced selective growth of cells initiated by DEN and colchicine, and this experimental model may be useful for analyzing the mechanisms underlying that growth advantage and the effects of cell cycle abnormalities in liver carcinogenesis.

Animals↗

PubMed1996

Lung uptake of lidocaine during hyperoxia and hypoxia in the dog.

BACKGROUND: Lidocaine has been shown to accumulate in the lung following its administration. This study was undertaken to determine effects of dose of lidocaine on lung uptake during hyperoxic and hypoxic ventilation. METHODS: Using cross-circulation of ventilation and constant-flow perfusion of the left lower lobe independently from all other lobes of the dog lung under nitrous oxide and halothane anesthesia, lidocaine was infused into the inflow system, so that plasma lidocaine concentrations in the inflow blood were maintained at 5, 10, 20, 40 and 70 micrograms/ml respectively during ventilation with 50% O2 or 3% O2. During 20 micrograms/ml lidocaine infusion, indocyanine green (ICG), an intravascular marker, was mixed with the lidocaine solution, in such a fashion that plasma ICG concentration in the inflow blood was maintained at 20 micrograms/ml. Actual plasma lidocaine and ICG concentrations in blood drawn from the inflow ([Lid]pa,[ICG]pa) and the outflow ([Lid]pv,[ICG]pv)systems were measured, 1, 3, 5, 7 and 10 minutes after the beginning of lidocaine infusion. Percent lung uptake of perfused lidocaine was calculated as ¿1-([Lid]pv/[Lid]pa)/([ICG]pv/[ICG]pa)¿ x 100. RESULTS: During ventilation hyperoxia, mean percent lung uptakes of lidocaine were 41-52% 1 minute after the beginning of lidocaine infusion, and decreased in time-dependent fashion to 7-12% 10 minutes later. Curves of percent lung uptake of lidocaine over time were similar for the 5 predetermined lidocaine concentration groups (5-70 micrograms/ml). There were no significant differences in percent lung uptakes of lidocaine between the ventilation hyperoxia and hypoxia conditions. CONCLUSIONS: These findings suggest that percent lung uptake of lidocaine is unaffected by hypoxic ventilation and by varying the concentration of lidocaine in the perfusion through the recipient dog lung lobe.

Adsorption↗

PubMed1996

Interleukin-1 alpha produced in human gingival fibroblasts induces several activities related to the progression of periodontitis by direct contact.

Previous observations suggest that interleukin-1 (IL-1) may play an important role in the progression of periodontitis. In the present study, we investigated whether a cell-associated IL-1 alpha (CAIL-1 alpha) produced in human gingival fibroblasts (HGF) induces biological activities related to the progression of periodontitis. HGF were treated with recombinant human IL-1 beta (rhIL-1 beta) for 12 h. After that, the cell layers of HGF were washed 3 times with fresh medium and were then fixed with 1% paraformaldehyde. The fixed cell layers of HGF were used for assays for bone resorbing activity, prostaglandin E2 (PGE2) production and collagenase activity. Fixed cell layers of HGF treated with rhIL-1 beta enhanced not only calcium release from BALB/c mouse calvaria but also PGE2 production and collagenase activity in HGF and human periodontal ligament fibroblasts (HPLF) cultured on the fixed cell layers. These activities were neutralized by treatment with monoclonal mouse anti-human IL-1 alpha antibody, but monoclonal mouse anti-human IL-1 beta antibody showed no effects on these activities. The induction of these activities by fixed cell layers of HGF required direct contact between the fixed cell layers and the calvaria, HGF, or HPLF. These results suggest that CAIL-1 alpha produced in HGF treated with rhIL-1 beta induces bone resorbing activity, PGE2 production and collagenase activity in the target cells by direct contact; CAIL-1 alpha may play an important role in the progression of periodontitis.

Animals↗

PubMed1996

Distinct gene expression patterns in skeletal and cardiac muscle are dependent on common regulatory sequences in the MLC1/3 locus.

The myosin light-chain 1/3 locus (MLC1/3) is regulated by two promoters and a downstream enhancer element which produce two protein isoforms in fast skeletal muscle at distinct stages of mouse embryogenesis. We have analyzed the expression of transcripts from the internal MLC3 promoter and determined that it is also expressed in the atria of the heart. Expression from the MLC3 promoter in these striated muscle lineages is differentially regulated during development. In transgenic mice, the MLC3 promoter is responsible for cardiac-specific reporter gene expression while the downstream enhancer augments expression in skeletal muscle. Examination of the methylation status of endogenous and transgenic promoter and enhancer elements indicates that the internal promoter is not regulated in a manner similar to that of the MLC1 promoter or the downstream enhancer. A GATA protein consensus sequence in the proximal MLC3 promoter but not the MLC1 promoter binds with high affinity to GATA-4, a cardiac muscle- and gut-specific transcription factor. Mutation of either the MEF2 or GATA motifs in the MLC3 promoter attenuates its activity in both heart and skeletal muscles, demonstrating that MLC3 expression in these two diverse muscle types is dependent on common regulatory elements.

Animals↗

PubMed1996

Endothelin-1 and its receptor in hypertrophic cardiomyopathy.

Endothelin-1, a potent vasoconstrictor produced by vascular endothelial cells, activates the hypertrophic program in cultured heart muscle cells. However, the role of endothelin-1 in cardiac hypertrophy in humans is unknown. Therefore, we studied hypertrophic cardiomyopathy patients with normal pulmonary arterial pressure, in whom cardiac hypertrophy is a specific feature of the disease. Radioimmunoassay with a monoclonal antibody to human endothelin-1 showed that the plasma level of immunoreactive endothelin was more than twofold higher in hypertrophic cardiomyopathy patients than in control subjects (P < .005). In situ hybridization analysis of endomyocardial biopsy specimens showed positive signals of endothelin-1 type A receptor mRNA in ventricular myocytes of all specimens. The receptor expression in ventricular myocytes was similar between hypertrophic cardiomyopathy patients and control subjects. We propose that endothelin-1 might represent an important factor involved in hypertrophic cardiomyopathy. Whether endothelin-1 plays a causal role in cardiac hypertrophy or is a marker of its occurrence needs to be clarified.

Analysis of Variance↗

PubMed1996

Activation of chicken gizzard myosin light chain kinase by Ca2+/calmodulin is inhibited by autophosphorylation.

Myosin light chain kinase (MLCK) is a calmodulin-dependent protein kinase which phosphorylates the 20,000 dalton regulatory light chain of myosin II. Here we show that activation of chicken gizzard MLCK by Ca2+/ calmodulin is inhibited by autophosphorylation at 2 sites in the absence of Ca2+/calmodulin. Two phosphorylation sites are located in the functional domain of the kinase, the threonine site toward the actin binding domain near the N-terminus of MLCK and the serine site in immediate proximity to the calmodulin binding site. The autophosphorylation was significantly inhibited by the binding of calmodulin to MLCK in the presence of Ca2+.

Animals↗