Cell-to-cell coupling studied in isolated ventricular cell pairs

Cell pairs isolated from adult rat and guinea pig ventricles were used to study the electrical properties of the nexal membrane. Each cell of a pair was connected to a voltage-clamp system so as to enable whole-cell, tight-seal recording. The current-voltage relationship of the nexal membrane was found to be linear, revealing a resistance rn of 2-4 M omega. rn was insensitive to the sarcolemmal membrane potential (range: -90 to +30 mV), and exerted no time-dependent gating behavior (range: 0.1 to 10 s). Lowering pHi yielded a small increase in rn. Vigorous elevations in [Ca2+]i gave rise to an increase in rn which was associated with a cell shortening. Uncoupling caused by aliphatic alcohols or halothane did not produce cell shortening. Cell pairs were also used to study action potential transfer.

Autoantibodies of various specificities encoded by genes from the VH J558 family bind to foreign antigens and share idiotopes of antibodies specific for self and foreign antigens

We examined the binding to foreign antigens and the expression of crossreactive idiotypes by a panel of 20 murine monoclonal autoantibodies encoded by V genes from the VH J558 family. 9 of 20 antibodies bound to foreign antigens such as bacterial polysaccharides, poly(Glu50, Tyr50), poly(Glu54,Lys37,Phe9), arsonate, and lysozyme, known to interact with antibodies encoded by genes from the VH J558 family. A high proportion of our panel of autoantibodies expressed crossreactive idiotypes originally borne by monoclonal rheumatoid factors, anti-Sm, and anti-DNA antibodies, all encoded by V genes from the VH J558 family. Some of these VH J558+ autoantibodies shared crossreactive idiotypes with VH J558+ antibodies directed against foreign antigens such as influenza virus hemagglutinin, poly(Glu60,Ala30,Tyr10), arsonate, and dextran. The implications of these findings are discussed with respect to the process of activation of self-reactive clones.

Cell pairs isolated from adult guinea pig and rat hearts: effects of [Ca2+]i on nexal membrane resistance

Cell pairs isolated from adult rat and guinea pig ventricles were used to study the resistance of the nexal membrane, rn. Each cell of a cell pair was connected to a voltage-clamp circuit to obtain simultaneous whole-cell, tight-seal recordings. With this technique, rn was determined under experimental conditions aimed at primarily modifying [Ca2+]i. Moderate changes in [Ca2+]i (produced by trains of depolarizing voltage-clamp pulses activating the slow inward current, or alterations in [Ca2+]o from 0.5 to 10 mM), resulted in no change in rn for normally coupled cell pairs (rn = 5 M omega), but small and reversible changes in slightly uncoupled preparations (rn greater than or equal to 50 M omega). Large increases in rn developed with substantial elevations in [Ca2+]i (secondary to [Na+]o-withdrawal, exposure to strophanthidin in conjunction with isi, or Ca2+-dialysis). Increases in rn brought about via elevation in [Ca2+]i always were accompanied by cell shortening consistent with a sustained contracture. The current-voltage relationship of the nexal membrane was ohmic regardless of whether rn was low (control) or elevated (after increasing [Ca2+]i).

The reliability of a historical interview with physically disabled respondents

This study investigated the reliability of a historical interview with 20 respondents with physical disabilities. An existing interview, the Occupational Role History, was modified and a companion rating scale was developed. Analysis of the test-retest and interrater reliabilities suggest that a stable clinical judgment can be formed from data gathered in a historical interview.

6-phospho-D-gluconate dehydrogenase from Pseudomonas fluorescens. Properties and subunit structure

1. The 6-phospho-D-gluconate dehydrogenase (decarboxylating) (EC 1.1.1.44) from Pseudomonas fluorescens, a B-side stereospecific enzyme, is active with both NAD+ and NADP+, having a specific activity of the homogeneous enzyme of 121 mumols NADH and 23 mumols NADPH, respectively, formed min-1 mg protein-1. The pI of the native enzyme is 4.62, the pH optimum is about 8.2. 2. The molecular weight of the native enzyme has been determined to be 126000 by sedimentation equilibrium studies. The molecular weight of the polypeptide chains composing the enzyme has been found to be 32000 by dodecylsulfate/polyacrylamide gel electrophoresis and 31000 by sedimentation equilibrium studies in presence of 6 M guanidine hydrochloride. The native enzyme is composed of four polypeptide chains. 3. Reacting enzyme centrifugation studies gave at pH 8.2 a sedimentation coefficient s20, w of 8.04 S and a diffusion coefficient D20, w of 6.56 F, resulting in a molecular weight of 115000 for the catalytically active form. Thus, the enzyme is active as the tetramer. So far the enzyme from P. fluorescens is the sole 6-phospho-D-gluconate dehydrogenase (decarboxylating) composed of four polypeptide chains.

[The clinical significance of the unstable bladder (author's transl)]

The anamnestic, clinical and urodynamic findings of 377 consecutively investigated women were evaluated. 86 (23%) patients showed bladder instability. The intensity of involuntary bladder contractions and the occurrence of incontinence in association with involuntary detrusor contractions influenced the clinical significance of unstable bladders. The maximum urethral closure pressure however had no influence on it. Urge incontinence was the most reliable symptom distinguishing those patients with bladder instability. Frequency of micturition, nocturia and nocturnal enuresis were less reliable in this respect. Urinary tract infections showed no correlation to bladder instability.

The synthesis of prostaglandins by bovine cerebral microvessels

Bovine cerebral microvessels (arterioles and capillaries) synthesize prostacyclin (PGI2, measured as 6-keto PGF1 alpha), PGF2 alpha, PGE2 and thromboxane A2 (measured as TXB2) when incubated in glucose-bicarbonate buffer for 30 minutes. Rapid freezing and thawing decreased the subsequent synthesis of 6-keto PGF1 alpha by cerebral microvessels and raised the basal levels of this metabolite within the incubation medium. At low concentrations, the addition of arachidonic acid (0.16 microM) did not stimulate prostacyclin or prostaglandin production; at higher concentrations (16 microM), the synthesis of PGI2 and PGF2 alpha was inhibited. Activation of lipase by the peptide melittin stimulated the synthesis of all arachidonic acid metabolites to the same extent. Thus cerebral microvessels deacylate cellular lipids and metabolize endogenous arachidonic acid to form prostaglandins, prostacyclin and related compounds as previously demonstrated in larger blood vessels. The synthesis and release of these molecules may be important for modulating the tone and reactivity of small blood vessels within the brain.

[Arthrodesis of the ankle. A study of the complications and long term results (author's transl)]

The authors have studied the complications and long term results of 91 cases of tibio-talar arthrodesis and 43 cases of tibio-talar arthrodesis associated with subtalar arthrodesis. Minor complications such as limited skin necrosis were noted in 13 p. 100 of the cases, and no-fusion occurred in 7 p. 100. The results were satisfactory in 75 p. 100 of the cases, fair in 13 p. 100, poor in 12 p. 100. Most of the poor results were related to painfull subtalar joints after isolated tibio-talar arthrodesis. This happened often following conditions : excessive equinus, protrusion of screws in the subtalar joint, preoperative lesions of the subtalar joint. In cases of associated tibio-tarsal and subtalar arthrodesis, the long term study revealed moderate and painless secondary arthrosis of the mid-tarsal joint. It is concluded that associated fusion of the subtalar joint should always be considered when tibio-talar arthrodesis is indicated.

Benzylidenemalononitrile derivatives as substrates and inhibitors of a new NAD(P)H dehydrogenase of erythrocytes. Purification and crystallisation of two forms of the enzyme

Using the powerful lachrymator (2-chlorobenzylidene)malononitrile as electron acceptor, two types of NAD(P)H dehydrogenases have been isolated from human blood. Crystallisation of the homogenous enzymes was performed in 50% polyethylene glycol solution. The enzymes (average molecular weight 18 000) are composed of only one polypeptide chain and have a very similar amino acid composition. B-side stereospecificity was determined with respect to the cofactor by gas chromatography-mass spectrometry for the reductase. Besides (2-chlorobenzylidene)malononitrile, 2,6-dichloroindophenol, methylene blue, 4-benzoquinone, FMN and FAD are also reduced using NADH or NADPH as hydrogen donor with the rates decreasing in the given order. Reduction of methemoglobin is observed only upon addition of methylene blue, FMN or FAD as carriers. (2-Chlorobenzylidene)malononitrile reduction is inhibited by most of the compounds known to be decouplers of oxidative phosphorylation.

[Combined carotid and femoral angiography in arterial occlusive disease (author's transl)]

"Asymptomatic" carotid stenosis with a murmur is an indication for carotid angiography, particularly in patients with peripheral arterial occlusive disease. Carotid angiography in the neck, carried out in two planes, makes it possible to differentiate different types of stenosis. Plaques and ulcerating strictures are a source of micro-emboli. The extent and localisation of extracranial carotid stenoses must be precisely defined because of their haemodynamic effects, particularly before major vascular surgery, which may result in a transient fall in blood pressure. Carotid angiography can be combined with femoral angiography in patients with peripheral arterial occlusive disease. In our experience, the combined angiography does not result in any increase in the complication rate. This experience is based on 38 patients seen in the last 14 months.