Differential effects of caffeine and perchlorate on excitation-contraction coupling in mammalian skeletal muscle.

1. Enzymatically dissociated single muscle fibres of the rat were studied under voltage clamp conditions in a double Vaseline gap experimental chamber. Intramembrane charge movement and changes in intracellular calcium concentration ([Ca2+]i) were measured and the rate of calcium release (Rrel) from the sarcoplasmic reticulum (SR) was calculated.

Effects of tetracaine on sarcoplasmic calcium release in mammalian skeletal muscle fibres.

1. Single muscle fibres were dissociated enzymatically from the extensor digitorum communis muscle of rats. The fibres were mounted into a double Vaseline gap experimental chamber and the events in excitation-contraction coupling were studied under voltage clamp conditions in the presence and absence of the local anaesthetic tetracaine.

Distinct subpopulations in HaCaT cells as revealed by the characteristics of intracellular calcium release induced by phosphoinositide-coupled agonists.

Intracellular calcium release induced by transient applications of phosphoinositide agonists was measured using adherent single HaCaT keratinocytes loaded with the acetoxymethyl derivative of fura-2. Application of ATP, bradykinin and formyl-Met-Leu-Phe (fMLP) resulted in a transient increase in intracellular calcium concentration ([Ca2+]i) with an average half-width of 40+/-21 s and a decay time constant of 15+/-10 s (mean +/- SD, n = 108), irrespective of the agonist applied. The cells could be classified into two groups: in 53% of the cells repeated stimulation brought about a progressively smaller change in [Ca2+]i (type 1 cells), whereas in the remaining cells the amplitude of the calcium transients was essentially unchanged (type 2 cells).

Kinetics of contractile activation in voltage clamped frog skeletal muscle fibers.

Excitation-contraction coupling events leading to the onset of contraction were studied in single skeletal frog muscle fibers. This entailed the simultaneous measurement of the changes in intracellular calcium concentration using antipyrylazo III and fura-2, isometric force, and clamp voltage in a modified single vaseline gap chamber for the first time. The calcium transients were incorporated into an analysis of calcium binding to regulatory sites of troponin C (TnC) that permitted both a linear and a cooperative interaction.

Systemic inflammatory response syndrome (SIRS) induced by carbon tetrachloride in rats.

We have observed the symptoms of systemic inflammatory response syndrome (SIRS) in male rats intoxicated by carbon tetrachloride (CCl(4)). Severe hypothermia, tachypnoea and increase in the heart beat min were diagnosed. These symptoms developed in the first hour of intoxication.

Concentration-dependent effects of tetracaine on excitation-contraction coupling in frog skeletal muscle fibres.

The effects of low (10-100 microM) concentrations of tetracaine on intermembrane charge movement and on the rate of calcium release (Rrel) from the sarcoplasmic reticulum (SR) were studied in cut skeletal muscle fibres of the frog using the voltage clamp technique. The fibres were mounted in a single or double vaseline gap chamber to study the events near the contraction threshold or in a wide membrane potential range. Although the 'hump' component of charge movement (Q gamma) was suppressed to some extent, the voltage dependence and the parameters of the Boltzmann distribution were not modified significantly at tetracaine concentrations below 50 microM.

Effects of cardiac glycosides on excitation-contraction coupling in frog skeletal muscle fibres.

1. The effects of digoxin and ouabain on the calcium release flux from the sarcoplasmic reticulum (SR), isometric tension and intramembrane charge movement were studied in voltage clamped skeletal muscle fibres of the frog. 2.

Repopulation of Langerhans cells during wound healing in an experimental human skin/SCID mouse model.

The epidermal repopulation of Langerhans cells (LCs) during wound healing was examined using a human skin severe combined immunodeficient (SCID) mouse model. The experiments, were carried out after proving the human origin of keratinocytes repopulating the wound beds using the W6/32 monoclonal antibody. It was shown that CD1a- and HLA-DR-positive dendritic cells (mostly LCs) are already detectable 2 days after injury within the newly formed epithelium.

Activation of the volume-sensitive chloride current in vascular endothelial cells requires a permissive intracellular Ca2+ concentration.

Combined patch clamp and Ca2+-measurements (Fura-2) were used to study the dependence of volume-activated Cl--currents (ICl,vol) of endothelial cells from bovine pulmonary artery on the intracellular Ca2+-concentration [Ca2+]i. Loading the cells with high concentrations of EGTA or BAPTA via ruptured membrane patches or by preincubating them with 50 microM BAPTA-AM caused a substantial decrease of ICl,vol. This reduction was independent of the activation state of the current: the current amplitude was not only diminished if [Ca2+]i was lowered at the peak of the volume-activated current, but this low Ca2+-concentration also prevented activation of the current by a second hypotonic challenge.

Modification of glutamine synthetase in Streptomyces griseus by ADP-ribosylation and adenylylation.

Addition of NH4+ to STreptomyces griseus 2682 cells grown in NO3- containing medium resulted in a rapid decline in glutamine synthetase activity due to covalent modification of the enzyme. The NH4+ promoted inactivation of the enzyme was inhibited by the ADP-ribosyltransferase inhibitor 3-methoxybenzamide. In the presence of ADP-ribosyltransferase activity the purified glutamine synthetase was also inhibited by NAD+ in a concentration-dependent manner.

Expression of thrombospondin-1 (TSP1) and its receptor (CD36) in healthy and diseased human skin.

In the present study, an analysis was made of the expression pattern of thrombospondin-1 (TSP1) and its receptor (CD36) in skin biopsies obtained from healthy volunteers and from patients with lichen planus, lupus erythematosus, cutaneous T-cell lymphoma and psoriasis vulgaris. Using monoclonal antibodies against TSP1 in biopsies from the healthy volunteers and from both clinically involved and uninvolved skin of the patients, a specific peroxidase-positive reaction was detected around the sweat glands in the dermis. In all cases investigated, the CD36-positive lesional keratinocytes remained TSP1-negative.

A sensitive simple ELISA for quantitation of sensitizing IgG from dissolved erythrocytes.

A simple enzyme-linked immunosorbent assay has been developed for quantitating the rabbit IgG present on the surface of sensitized red blood cells. A suitable cell lysis was carried out by an alkaline buffer, which dissolved the erythrocytes without forming any precipitate and without disruption of IgG, and facilitated the dissociation of the immune complexes, i.e.

A modified model of reversible middle cerebral artery embolization in rats without craniectomy.

A detailed description is given of a new model of reversible focal cerebral ischaemia in rats. A spherical embolus, attached to the end of an 8-0 surgical thread was injected into the middle cerebral artery (MCA) via the external and internal carotid arteries (ECA and ICA) and could be withdrawn by pulling the extravascular portion of the thread when reperfusion was to follow ischaemia. In contrast to similar techniques, the 8-0 thread did not block blood flow in either the common carotid artery (CCA) or the ICA during ischaemia and, as the CCA did not have to be ligated, flow could be restored via the ipsilateral CCA and ICA after the ischaemic period.

Thermogenic responses to selective and nonselective beta-adrenerg agonists in hypothyroidism of Sprague-Dawley rats.

Resting oxygen consumption (VO2) and mitochondrial GDP binding were measured in hypothyroid and euthyroid rats after administration of selective and nonselective beta-adrenoceptor agonists (BRL 35135A and Isoprenaline--BRL, ISO). Resting VO2, VO2 increment and mitochondrial GDP binding after beta-agonists were lower in hypothyroid rats than in the euthyroid group. The reduced response was more marked for ISO than for BRL.

Cell membrane fluidity in blast cells of children with acute leukaemia.

Plasma membrane fluidity has been investigated by determining steady-state fluorescence polarization (FP) of the apolar stain 1,6-diphenyl-1,3,5,-hexatriene in intact blast cells, separated from peripheral blood and bone marrow of children with various types of acute leukaemia. FP-values of blast cells taken before antileukaemic therapy were compared with FP-values of peripheral blood and bone marrow mononuclear cells separated from patients in complete remission as well as from control patients and from healthy volunteers. Moreover, fluorescence polarization measurements were also performed using blast cells of leukaemic patients on short-term single-drug prednisolone pretreatment.

Prenatal diagnosis and management of chondrodysplasias.

Thorough ultrasound examination of fetal limbs and fetal movements allows us to recognize several types of osteochondrodysplasia, both in high risk pregnancies (with a family history of chondrodysplasia) and up on routine screening. Correct diagnosis of growth retardation requires nomograms for bone length, and we have developed our own standards for the humerus, ulna, femur and tibia. Since some types of osteochondrodysplasia are compatible with life and others not, it is important to make the correct diagnosis using several differential diagnostic criteria.

A study of the levels of tobramycin and gentamicin in human serum and renal cortex and of changes in in vitro bacterial sensitivity.

Concentration of gentamicin and tobramycin in sera and renal tissue was determined. Though between the 2nd and 6th day of the treatment, gentamicin cumulated in the renal tissue, but it did not reach toxic value. Tobramycin did not show cumulation tendency.

Effect of experimental airway inflammation on bronchial hyper-responsiveness induced by Broncho-Vaxom in dogs.

We studied correlation between airway hyper-responsiveness induced by local exposure to a macrophage inductor Broncho-Vaxom and the development of airway inflammation in dogs. To detect airway inflammation, bronchoalveolar lavage and biopsy of airway mucosa were performed. The airway responsiveness was registered by capnograph measuring gas-exchange disturbances during obstructive reactions provocated by inhalation of various concentrations of acetylcholine aerosol.

Echocardiographic tests in chronically haemodialysed patients.

Fifty-two patients kept alive by chronic dialysis have been subjected to echocardiography carried out by means of a Picker Echoview equipment with M-mode 2D technique. The revealed alterations were suggestive of hypertropic, dilatative uraemic cardiomyopathy, associated with impaired diastolic compliance. Left auricular dilatation as a source of inference for the degree of compliance diminution was found in a high percentage of patients.

Thrombosis promoting changes in chronic liver diseases.

Causes of haemorrhagic tendency in liver disorders have been widely studied. Deficiency of procoagulants is the best explanation for it. Not seldom a thrombotic tendency or even overt thrombosis occurs and may be satisfactorily explained.

Chemotactic activity of bronchoalveolar lavage fluid from children with recurrent obstructive bronchitis.

Boyden's method was used to assess the chemotactic activity of bronchoalveolar lavage (BAL) fluid samples from patients aged 1-6 ys with recurrent obstructive bronchitis when signs of chronic mucosal inflammation were observed bronchoscopically. BAL was performed to reveal features of this mucosal inflammation by analysing the lavagable cells and soluble factors. In comparison with the chemotactic effect of casein, the activity of the fluid proved to be high for polymorphonuclear leukocytes (PMNs), but significantly low for mononuclear cells.