Effects of carbachol on contractile force and action potentials of isolated atria at different rates of stimulation

Dose-response curves for the negative inotropic effect and the shortening of the action potential duration induced by carbachol were established in isolated left atria of rats and guinea pigs. Various experimental conditions were chosen, including two different frequencies of stimulation (0.1 and 2 Hz) and the application of ouabain. Under all experimental conditions, very similar dose-response curves were obtained for the electrical activity. In contrast, the dose-response curves for the negative inotropic effect were markedly affected, since carbachol was less effective in depressing contractile force at 0.1 Hz and in the presence of ouabain. A lesser negative inotropic effect of carbachol could also be demonstrated after a single prolongation of the beat interval for various periods of time. It is suggested that the differences in the dose-response curves for the electrical and mechanical activities reflect changes in the efficacy of excitation-contraction coupling.

[Clinical use of lyophilized dura in diaphragmatic defects]

A short survey about pathology and clinic of diaphragmatic defects and injuries is given. The different operative possibilities of plastic diaphragmatic defect surgery are discussed. Direct, autoplastic, alloplastic and homoioplastic closure of diaphragmatic defects are used today. We report about two patients. In both cases we used lyophilized human dura for closing the diaphragmatic defect with success.

Accumulation of drugs by guinea pig isolated atria. Quantitative correlations

The time course of the tissue accumulation of 16 neutral, cationic, and anionic drugs by resting and 2-Hz stimulated atria of the guinea pig was measured. The accumulation of the substances was quantified by means of their tissue to medium ratios (T/M). Auricles driven with 2 Hz accumulated the drugs faster and during a long period of time to a greater extent than resting atria. By extrapolation of the binding characteristics, the final equilibrium T/M values were estimated. The variance in these accumulation data at equilibrium (log T/M) Could be best described by a linear combination of log P (octanol/water) and the ability of the drugs to bind to atrial homogenate (log percent bound/percent free). A parameter calculated from protein binding appeared less significant. Comparable results were obtained for the accumulation data measured in resting and 2-Hz stimulated atrial muscles. It is suggested that the degree of accumulation of drugs into atrial tissue is determined by the facility of their penetration of the plasma membrane and the extent of their intracellular binding.

Studies on biosynthesis, assembly and expression of human major transplantation antigens

Biosynthesis and regulation of expression of transplantation as detected by a monoclonal antibody to HLA-A,B,C antigens (human leucocytic antigen) and a polyclonal antiserum to beta 2-microglobulin have been investigated using radioactive amino acids and sugars to label human lymphoid cells. We found unbalanced synthesis of HLA heavy chains and beta 2-microglobulin, the latter being in excess and secreted to the extracellular medium. In DAUDI cells, which are defective in beta 2-microglobulin, no HLA-A,B,C could be detected intracellularly even in the presence of added beta 2-microglobulin. Treatment of BRI-8 cells with tunicamycin, an antibiotic which inhibits glycosylation of polypeptides, almost had no effect on the levels of beta 2-microglobulin, while it markedly decreased that of HLA heavy chains, both on the cell surface and intracellularly. Glycosylation of the HLA heavy chains appeared to be an essential requirement for the normal expression of HLA-A,B,C antigens. The translation in vitro in a messenger-dependent reticulocyte system with total polysomes obtained from BRI-8 cells showed that beta 2-microglobulin was synthesized as a precursor. This larger polypeptide was converted into mature beta 2-microglobulin when protein synthesis was performed with microsomes instead of polysomes.

Accumulation of drugs by resting or beating cardiac tissue

The rate and degree of accumulation of 12 neutral, anionic and cationic drugs were studied in resting and 2 Hz-stimulated isolated left auricles of the guinea pig. The uptake process was accelerated in muscles driven electrically. The time needed to reach equilibrium was related to the extent of accumulation which in turn corresponded with the lipophilicity of the drug. The frequency-induced changes in the kinetics of the accumulation disappeared under reduced mechanical activity of the muscle. It is suggested that the increased mechanical activity enhances drug disposition within the extracellular space, so that more drug is available for transmembrane penetration.

Time courses of carbachol-induced responses in guinea pig atria under the influence of ouabain, calcium, and rate of stimulation

The response of isolated left atria of guinea pigs to carbachol was measured in the presence and during washout of the drug. The time courses of the negative inotropic effect and of the rate of shortening in action potential duration were compared. The initial rapid decline in force of contraction was followed by a slowly developing partial recovery (fading). After removal of the drug, a transient phase of hypercontractility was observed before the control level was reached again. In contrast to the mechanical effect, the drug-induced shortening of the action potential duration proceeded monophasically. The fading and hypercontractility phenomena shown by the mechanical response to the drug were influenced by the stimulation rate and by the presence of ouabain. From the dissociation of electrical and mechanical effects it is concluded that fading and hypercontractility are not due to changes of receptor sensitivity but reflect a change in cellular calcium distribution.

[Importance of hormones and free fatty acids in the pathogenesis of carbohydrate metabolic disorders in myocardial infarct]

The increase in the content of the somatotropic hormone and cortisol in blood plasma as well as the increase in the content of free fatty acids in serum in the acute period of myocardial infarction are more marked in patients with impaired tolerance than in those with normal tolerance. The authors believe that free fatty acids are of utmost importance among the factors causing the development of insulin resistance in patients with acute myocardial infarction. Their increased concentration is due to hypersecretion of catecholamines, somatotropic hormone, and cortisole.

[Clinical experience in 80 patients with intramedullary trochanteric nailing]

Report on the clinical experience in 80 patients with the intramedullary trochanteric nailfixation according to KUNTSCHER of pertrochanteric, or subtrochanteric femur fractures. This procedure in our opinion enlarges the operative methods for treatment of fractures of the trochanteric region in elderly patients with a high operative risk.

Monoclonal antibodies as probes for differentiation and tumor-associated antigens: a Forssman specificity on teratocarcinoma stem cells

A set of monoclonal antibodies derived by fusing P3-NS1/1-Ag4-1 myeloma cells with spleen cells from a rat immunized with mouse spleen were screened for activity against a tumor cell panel. One of these antibodies was found to react only with mouse embryonal carcinoma cells and no other tumor cell type tested, including differentiated derivatives of teratocarcinomas. In the adult mouse, this antigen is expressed by subpopulations of cells in the spleen, bone marrow, lymph node, brain, kidney and testes, although not in liver and thymus. This antigen has a species and tissue distribution consistent with that of Forssman antigen. The molecules which carry this specificity on the embryonal carcinoma cells appear to be glycolipids.

Production of monoclonal antibodies to group A erythrocytes, HLA and other human cell surface antigens-new tools for genetic analysis

Antibody-secreting hybrid cells have been derived from a fusion between mouse myeloma cells and spleen cells from a mouse immunized with membrane from human tonsil lymphocyte preparations. Hybrids secreting antibodies to cell surface antigens were detected by assaying culture supernatants for antibody binding to human tonsil cells. Six different antibodies (called W6/1, /28, /32, /34, /45 and /46 were analyzed. These were either against antigens of wide tissue distribution (W6/32, /34, and /46) or mainly on erythrocytes (W6/1 and W6/28). One of the anti-erythrocyte antibodies (W6/1) detected a polymorphic antigen, since blood group A1 and A2 erythrocytes were labeled while B and O were not. Antibodies W6/34, /45 and /46 were all against antigens which were mapped to the short arm of chromosome 11 by segregation analysis of mouse-human hybrids. Immunoprecipitation studies suggest that W6/45 antigen may be a protein of 16,000 dalton, apparent molecular weight, while W6/34 and /46 antigens could not be detected by this technique. Antibody W6/32 is against a determinant common to most, if not all, of the 43,000 dalton molecular weight chains of HLA-A, B and C antigens. This was established by somatic cell genetic techniques and by immunoprecipitation analysis. Tonsil leucocytes bound 370,000 W6/32 antibody molecules per cell at saturation. The hybrid myelomas W6/32 and W6/34 have been cloned, and both secrete an IgG2 antibody. W6/32 cells were grown in mice, and the serum of the tumor-bearing animals contained greater than 10 mg/ml of monoclonal antibody. The experiments established the usefulness of the bybrid myeloma technique in preparing monospecific antibodies against human cell surface antigens. In particular, this study highlights the possibilities not only of obtaining reagents for somatic cell genetics, but also of obtaining mouse antibodies detecting human antigenic polymorphisms.

A myeloma hybrid producing antibody specific for an allotypic determinant on "IgD-like" molecules of the mouse

A hybrid cell line was produced by fusing a mouse myeloma line with spleen cells from BALB/c mice immunized with B10 cells. The hybrid line grew in tissue culture and in syngeneic mice and produced IgM antibody specific for "IgD-like" molecules of mice with the Igb haplotype. The concentration of monoclonal antibody in the serum of tumor-bearing animals reached about 2 mg/ml and gave cytotoxic titers of up to 1:800 000. The derivation of the line, some properties of the antibody secreted and the nature of its antigenic target are described.