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Biomedical subjects

F Hofmann

Publications and source records attributed to F Hofmann.

At least 55 records · Page 3Linked to original sources
PubMed1993

Discrepancy between plasma and aortic wall cyclic guanosine monophosphate in an experimental model of congestive heart failure.

OBJECTIVES: The state of the vasodilator systems in congestive heart failure is poorly defined. Plasma atrial natriuretic peptide is increased, whereas endothelium derived relaxing factor activity can be decreased. Atrial natriuretic peptide and endothelium derived relaxing factor both cause vascular relaxation by generating cyclic guanosine monophosphate (cGMP), by activating the particulate and the soluble guanylate cyclase, respectively. This study examines the biological effects of atrial natriuretic peptide and endothelium derived relaxing factor in experimental heart failure by assessing the plasma, urinary, and tissue concentrations of their common second messenger cGMP. METHODS: Myocardial infarctions (n = 31) were induced and sham operations (n = 25) were performed on Wistar rats, and the rats were monitored for three months. Aortic and pulmonary cGMP contents were measured, as the aorta is mainly matrix and smooth muscle cells, and the lung is particularly rich in capillaries, hence in endothelial cells. The concentrations of the other second messenger cyclic adenosine monophosphate (cAMP) was also determined, as were those of cGMP dependent protein kinase in the arteries. RESULTS: 17 of the 31 rats with myocardial infarction had oedema. The total heart weight to body weight ratio and the ratio of the myocardium haemodynamically upstream from the infarcted left ventricle to body weight were increased in proportion to the infarct size. Plasma atrial natriuretic peptide and plasma and urinary cGMP concentrations were increased in proportion to the degree of heart failure (p < 0.0001). The pulmonary cGMP concentration was significantly higher in the rats with myocardial infarction than in the control group (p < 0.0001). Pulmonary cGMP concentrations were correlated with the plasma concentrations of atrial natriuretic peptide and cGMP (r2 = 0.59 and 0.66 respectively, p < 0.0001). The cGMP, cAMP, and cGMP, and cGMP dependent kinase concentrations in the aortic wall of rats with myocardial infarctions were the same as in control rats. CONCLUSIONS: The increase in plasma, urinary, and pulmonary cGMP in rats with myocardial infarctions were highly correlated with the increase in circulating atrial natriuretic peptide. By contrast, the aortic cGMP concentration was unchanged in these rats, despite high plasma atrial natriuretic peptide. In congestive heart failure, a discrepancy seems to exist between pulmonary (mainly endothelium) and aortic wall (mainly smooth muscle cells) cGMP.

Animals↗
PubMed1993

Stable co-expression of calcium channel alpha 1, beta and alpha 2/delta subunits in a somatic cell line.

1. The high-voltage-activated L-type calcium channel is a multi-protein complex of alpha 1, alpha 2/delta, beta and gamma subunits. The alpha 1 subunit contains the voltage-dependent calcium-conducting pore. Chinese hamster ovary (CHO) cells were stably transfected with the complementary DNA of the alpha 1, beta and alpha 2/delta subunits. These subunits were not detected in wild-type CHO cells. 2. The alpha 1 (CaCh2b) subunit itself directed the expression of functional calcium channels which bound calcium channel blockers and showed voltage-dependent activation and inactivation. 3. The co-expression of the alpha 1 subunit with the beta subunit (CaB1 gene) enhanced the density of the dihydropyridine binding sites 2- to 3-fold and increased dihydropyridine-sensitive barium inward currents (IBa) up to 3.5-fold from -13.3 microA/cm2 (alpha 1 subunit) to -46.7 microA/cm2 (alpha 1 and beta subunits). 4. Co-expression of the beta subunit did not change the sensitivity of IBa towards dihydropyridines, but accelerated current activation and inactivation and shifted the half-maximal steady-state activation and inactivation to slightly more hyperpolarizing potentials. 5. The co-expression of the alpha 2/delta subunit together with alpha 1 and beta subunits accelerated the inactivation kinetics of the channel without a major effect on the other parameters. 6. These results indicate that the beta and alpha 2/delta subunit interact with the alpha 1 subunit and modulate thereby the properties of the alpha 1 subunit-dependent inward current.

Animals↗
PubMed1993

Subunit-dependent modulation of recombinant L-type calcium channels. Molecular basis for dihydropyridine tissue selectivity.

At least four calcium channel subtypes (P, T, N, and L) have now been classified on the basis of their biophysical and/or pharmacological properties. L-type channels, a channel family particularly important to physiological function of the cardiovascular system, are identified by their slow voltage- and calcium-dependent inactivation as well as their sensitivity to dihydropyridine (DHP) calcium channel antagonists. In this study, we report the results of experiments in which we have measured the DHP modulation of recombinant calcium channel activity in cells transfected with alpha 1 subunits of cardiac and smooth muscle L-type calcium channels. We find subunit-dependent differences in the voltage and concentration dependence of channel modulation. Our results provide evidence for a molecular basis for DHP sensitivity of heart and smooth muscle calcium channels and, additionally, indicate that, even within one family of calcium channels, slight differences in channel structure can cause marked differences in channel pharmacology.

Animals↗
PubMed1992

Serum antibodies to L-type calcium channels in patients with amyotrophic lateral sclerosis.

BACKGROUND AND METHODS: Sporadic amyotrophic lateral sclerosis is a chronic, progressive degenerative disease of the motor neurons of the spinal cord and motor cortex. The cause is unknown. Recent electrophysiologic studies in animals indicate that immunoglobulins from patients with this disease alter presynaptic voltage-dependent calcium currents and calcium-dependent release of neurotransmitters. To determine whether similar interactions might be identified biochemically, we used an enzyme-linked immunosorbent assay (ELISA) to detect the reaction of serum IgG with purified complexes of L-type voltage-gated calcium channels from rabbit skeletal muscle. The results from patients with amyotrophic lateral sclerosis were compared with those obtained from patients with other types of motor neuron disease, patients with autoimmune and non-autoimmune neurologic diseases, and normal subjects. RESULTS: Serum samples from 36 of 48 patients with sporadic amyotrophic lateral sclerosis (75 percent) contained IgG that reacted with L-type calcium-channel protein, and serum reactivity on ELISA correlated with the rate of disease progression (Spearman rank-correlation coefficient, 0.62). Reactive serum was present in only 1 of 25 normal subjects and 1 of 35 control patients with no motor neuron disease. Antibodies to L-type voltage-gated calcium channels were identified in 6 of 9 patients with Lambert-Eaton syndrome, and in 3 of 15 patients with Guillain-Barré syndrome. CONCLUSIONS: Antibodies to L-type voltage-gated calcium channels are present in the serum of patients with amyotrophic lateral sclerosis, and antibody titers correlate with the rate of disease progression. Together with previous data, these results suggest a role for autoimmune mechanisms in the pathogenesis of sporadic amyotrophic lateral sclerosis.

Amyotrophic Lateral Sclerosis↗
PubMed1992

Detection of cGMP dependent protein kinase isozymes by specific antibodies.

Two isozymes of cGMP-dependent protein kinase (cGMP kinase) have been identified. Polyclonal antibodies were developed which recognize both isozymes or specifically the I alpha and I beta isoform. The specificity of these antibodies was verified by using the recombinant or purified I alpha and I beta isozymes. The antibodies cross-reacted with the purified isozymes of cGMP kinase from bovine tracheal smooth muscle. The tissue concentration of cGMP kinase was determined by ELISA. High concentrations (greater than 10 pmol/g wet tissue) were present in bovine lung, rumen, trachea, aorta, uterus and stomach. The tissue distribution of the isozymes I alpha and I beta was investigated by immunoblots using crude extracts of the different tissues. The I beta-specific antibody yielded strong signals with extracts of trachea, aorta, stomach and uterus, whereas heart, cerebellum and lung apparently contain mainly the I alpha isozyme.

Amino Acid Sequence↗
PubMed1992

Modulation of cardiac Ca2+ channels in Xenopus oocytes by protein kinase C.

L-Type calcium channel was expressed in Xenopus laevis oocytes injected with RNAs coding for different cardiac Ca2+ channel subunits, or with total heart RNA. The effects of activation of protein kinase C (PKC) by the phorbol ester PMA (4 beta-phorbol 12-myristate 13-acetate) were studied. Currents through channels composed of the main (alpha 1) subunit alone were initially increased and then decreased by PMA. A similar biphasic modulation was observed when the alpha 1 subunit was expressed in combination with alpha 2/delta, beta and/or gamma subunits, and when the channels were expressed following injection of total rat heart RNA. No effects on the voltage dependence of activation were observed. The effects of PMA were blocked by staurosporine, a protein kinase inhibitor. beta subunit moderate the enhancement caused by PMA. We conclude that both enhancement and inhibition of cardiac L-type Ca2+ currents by PKC are mediated via an effect on the alpha 1 subunit, while the beta subunit may play a mild modulatory role.

Alkaloids↗
PubMed1992

A monoclonal antibody recognizes an epitope in the first extracellular loop of the plasma membrane Ca2+ pump.

A monoclonal antibody against the human erythrocyte Ca2+ pump (1E4) reacted with the enzyme in intact erythrocytes. Using trypsinized preparations of the pump the antibody only reacted with the N-terminal fragments of 33.5 and 35 kDa. The fragments span from the N terminus (35 kDa) or from residue 19 (33.5 kDa) to residue 314 of the hPMCA4 isoform of the pump. Exhaustive degradation with a number of agents produced smaller peptides which reacted with the antibody. Sequencing analysis on two chymotryptic fragments of 8.8 and 13.5 kDa identified the epitope in an approximately 80-residue domain beginning with Gly-81. Two peptides corresponding to the putative extramembrane portions of this region of the pump were synthesized. The antibody reacted with one of them, spanning residues Phe-121 to Gly-152 and containing the first putative external loop of the pump. Peptides corresponding to overlapping portions of this peptide were synthesized, leading to the location of the epitope in a 13-residue sequence (Glu-130 to Glu-142) in the first predicted extracellular loop (Verma, A. K., Filoteo, A. G., Stanford, D. R., Wieben, E. D., Strehler, E. E., Fischer, R., Heim, R., Vogel, G., Mathews, S., Strehler-Page, M-A., James, P., Vorherr, T., Krebs, J., Penniston, J. T., and Carafoli, E. (1988) J. Biol. Chem. 263, 14152-14159).

Amino Acid Sequence↗
PubMed1992

Calcium channel beta subunit heterogeneity: functional expression of cloned cDNA from heart, aorta and brain.

Complementary DNAs encoding three novel and distinct beta subunits (CaB2a, CaB2b and CaB3) of the high voltage activated (L-type) calcium channel have been isolated from rabbit heart. Their deduced amino acid sequence is homologous to the beta subunit originally cloned from skeletal muscle (CaB1). CaB2a and CaB2b are splicing products of a common primary transcript (CaB2). Northern analysis and specific amplification of CaB2 and CaB3 specific cDNAs by polymerase chain reactions showed that CaB2 is predominantly expressed in heart, aorta and brain, whereas CaB3 is most abundant in brain but also present in aorta, trachea, lung, heart and skeletal muscle. A partial DNA sequence complementary to a third variant of the CaB2 gene, subtype CaB2c, has also been cloned from rabbit brain. Coexpression of CaB2a, CaB2b and CaB3 with alpha 1heart enhances not only the expression in the oocyte of the channel directed by the cardiac alpha 1 subunit alone, but also effects its macroscopic characteristics such as drug sensitivity and kinetics. These results together with the known alpha 1 subunit heterogeneity, suggest that different types of calcium currents may depend on channel subunit composition.

Amino Acid Sequence↗
PubMed1992

Stable and functional expression of the calcium channel alpha 1 subunit from smooth muscle in somatic cell lines.

Voltage-activated calcium channels are membrane spanning proteins that allow the controlled entry of Ca2+ into the cytoplasm of cells. The principal channel forming subunit of an L-type calcium channel is the alpha 1 subunit. Transfection of Chinese hamster ovary (CHO) cells with complementary DNA encoding the calcium channel alpha 1 subunit from smooth muscle led to the expression of functional calcium channels which bind calcium channel blockers and show the voltage-dependent activation and slow inactivation and unitary current conductance characteristic of calcium channels in smooth muscle. The currents mediated by these channels are sensitive towards dihydropyridine-type blockers and agonists indicating that the calcium channel blocker receptor sites were present in functional form. The smooth muscle alpha 1 subunit cDNA alone is sufficient for stable expression of functional calcium channels with the expected kinetic and pharmacological properties in mammalian somatic cells.

Animals↗
PubMed1992

Immunogenicity, reactogenicity and consistency of a new, inactivated hepatitis A vaccine--a randomized multicentre study with three consecutive vaccine lots.

We investigated immunogenicity, reactogenicity and consistency of three consecutive lots of an inactivated hepatitis A vaccine in 204 seronegative volunteers. Each volunteer received a total of three doses of vaccine (720 EIU) according to a 0, 1 month primary vaccination schedule with a booster dose given at month 6. Mild, moderate and mostly local side effects were reported in 49.7% after the first and in less than 30% after the third injection. Seroconversion rate after one vaccine dose was as high as 91%. All subjects but one had already seroconverted by 1 month after the second injection, corresponding to a seroconversion rate of 99%. The geometric mean titres (GMT) increased with each dose of vaccine administered. Our results show that this inactivated hepatitis A vaccine is highly immunogenic, safe and well tolerated. Furthermore, there were no significant differences between the three vaccine lots in respect to seroconversion rate, size of antibody titre or reactogenicity.

Antibodies, Viral↗
PubMed1992

Hepatitis A as an occupational hazard.

Few studies have been carried out to evaluate the role of hepatitis A virus (HAV) as an occupational hazard. Our analysis of data on occupational diseases in Germany showed that hepatitis A ranks as third among infectious occupational diseases. Morbidity based on the frequency of compensation (15.2%) was in the same range as that observed for hepatitis B (19.7%). In another study, data were collected on anti-HAV prevalence among 2293 hospital workers in southwest Germany. Anti-HAV prevalence of hospital staff responsible for patient care and that of the general population were comparable, while food-handlers under the age of 30 years had a higher degree of anti-HAV prevalence. When an evaluation of anti-HAV prevalence data was carried out on persons younger than 30 years who comprised subsets of the medical staff, the relative risk was: charwomen 4.2, food-handlers 2.49, and paediatric nurses 1.84, showing that they had higher prevalence rates than nurses 1.25, physicians 1.09 and laboratory assistants 0.93. Vaccinations for the prevention of hepatitis A should therefore reach individuals that have an increased occupational risk: food-handlers, health care workers in infectious diseases and paediatrics, medical staff in laboratories handling stool samples, medical charwomen and, according to previously published work, staff of day care centres and sewerage workers.

Food Handling↗
PubMed1992

Hepatitis A vaccination: schedule for accelerated immunization.

Hepatitis A vaccine, strain HM175, was investigated for immunogenicity and tolerability in a prospective multicentre trial. The following vaccination schedules and antigen contents were evaluated: days 0 and 14 with 720 ELISA units (El.U) of antigen, days 0 and 28 with 720 El.U and days 0 and 28 with 360 El.U. In all study groups, the seroconversion rates following two vaccinations were between 95 and 100%. Higher geometric mean concentrations of antibody to hepatitis A virus (anti-HAV) were reached by the vaccine containing 720 El.U of HAV antigen. The vaccine was equally well tolerated in all groups. In addition, an abbreviated schedule, in which 720 El.U of HAV antigen was given on days 0 and 14, resulted in 100% seroconversion by day 28 and a level of anti-HAV that was substantially higher than that observed after passive immunization. This implies that such a vaccine could replace immune globulin administration if time permits.

Adult↗
PubMed1992

Reactogenicity and immunogenicity of three different lots of a hepatitis A vaccine.

To study the immunogenicity and reactogenicity of an inactivated hepatitis A vaccine, 204 healthy individuals were randomized into three equal groups, each to receive a different vaccine lot. Each subject received a total of three doses, each of 720 ELISA units of hepatitis A vaccine HM175, according to a 0 and 1 month primary vaccination schedule, with a booster dose given at month 6. Side effects were low and were < 30% after the second injection. All subjects but one had antibodies to hepatitis A virus two months after the first dose of vaccine. At month 6 all vaccinees had seroconverted. There were no differences between the three vaccine lots with respect to side effects, seroconversion rates and geometric mean titre of antibodies. We conclude that the three lots of inactivated hepatitis A vaccine are safe, well tolerated and equally immunogenic.

Adult↗
PubMed1992

Hormonal regulation of calcium current in freshly isolated airway smooth muscle cells.

Single freshly isolated smooth muscle cells of adult bovine trachea were voltage clamped, and the calcium inward current was separated from K+ currents by blocking the large outward currents with intra- and extracellular Cs+ and extracellular tetraethylammonium chloride. Isoproterenol stimulated peak calcium current (ICa) in a dose-dependent manner through the beta-adrenergic receptor. The isoproterenol effect was not mediated or caused by the stimulation of a K+ or Na+ current, a decrease in the intracellular concentrations of Ca2+ or H+, the stimulation of the Na(+)-H+ or the Na(+)-Ca2+ exchanger. Neither basal nor isoproterenol-stimulated ICa was affected by internal dialysis of the cell with adenosine 3',5'-cyclic monophosphate (cAMP), cAMP analogues, or the catalytic subunit of cAMP-kinase. Internal dialysis of the cells with guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) blocked the stimulation of isoproterenol whereas dialysis with guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) induced an isoproterenol-like maximal increase of ICa. These results show that the beta-adrenergic receptor stimulates the L-type calcium current of isolated tracheal smooth muscle cells independent of cAMP and cAMP-kinase through a GTP/GDP regulated protein.

Albuterol↗
PubMed1992

Cyclic GMP-dependent protein kinase and smooth muscle relaxation.

Cyclic guanosine monophosphate (cGMP)-dependent protein kinase has been cloned from bovine trachea. The isozymes I alpha and I beta, which differ only in their amino-terminal domains were expressed transiently in COS-7 cells. Both isozymes were activated by cGMP and cyclic adenosine monophosphate (cAMP). However, approximately 10-fold higher concentrations of cyclic nucleotides were needed to activate the I beta enzyme than the I alpha enzyme. The KA values for cAMP were 9.1 and greater than 20 microM for the I alpha and I beta isozymes, respectively. It is therefore unlikely that an unmodified I beta enzyme that occurs in high concentrations in vascular smooth muscle can be activated in vivo by cAMP.

Animals↗