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Biomedical subjects

L Beck

Publications and source records attributed to L Beck.

At least 55 records · Page 3Linked to original sources
PubMed1997

[Classification of regular atrial tachycardia].

ECG criteria which for many years formed the basis of the classification of regular atrial tachycardias may now be completed by the results of endocavitary studies (stimulation and mapping). Flutter is a macroreentry phenomenon in the right atrium, anticlockwise in typical, common or classical forms, and more variable in atypical forms: sometimes antidromic and clockwise, sometimes functional more rapid without a gap of excitability, or in other cases, skirting around the sears of atriotomy, especially right-sided. Tachycardias are paroxysmal and often secondary to reentry; more rarely permanent, they are then often due to increased automaticity especially in young patients. The concordance with surface ECG changes is not perfect and the distinction between flutter and tachycardia often depends on the frequency of the tachycardia and the leads studied.

Anti-Arrhythmia Agents↗
PubMed1996

Comparison of monocytes and B cells for activation of human T helper cell subsets.

Human rye grass allergen Lol p I-specific T helper cell clones of Thp, Th0, Th1 and Th2 subtype were activated with Lol p I and monocytes or B cells as antigen-presenting cells, and cell proliferation, interleukin (IL)-2, interferon-gamma, and IL-4 secretion were measured. Monocytes induced activation of T cell clones of all four T helper cell subsets and were usually more potent antigen-presenting cells than B cells. B cells and monocytes similarly induced proliferation and IL-4 secretion by Th2 clones, whereas B cells, in contrast to monocytes, only weakly activated Th1 clones. However, exceptions to this rule existed within each T helper cell subset suggesting that individual T cell clones, regardless of the subset to which they belong, may have quantitatively and/or qualitatively different requirements for secondary activation signals which are provided by the antigen-presenting cells. The data demonstrate that, in general, monocytes are more effective than B cells in activating human T cell clones of all subtypes and that B cells were efficient antigen-presenting cells only for Th2 cells. However, individual T cell clones of any given T helper cell subset vary with respect to their activation by monocytes or B cells.

Allergens↗
PubMed1996

Regulation of leucine transport by intracellular pH in Bacillus pasteurii

The kinetics, specificity and mechanism of leucine uptake were studied in the alkaliphilic bacterium Bacillus pasteurii DSM 33 (ATCC 11859). Leucine was accumulated up to 200-fold by a sodium-dependent secondary transport system for branched-chain amino acids. Apparent Kt values of 9.6 μM for leucine, 8.9 μM for isoleucine, 9.3 μM for valine, and 0.71 mM for sodium were determined, and maximum uptake activity was observed at an external pH of 8.5 and at 35degreesC. The effect of several ionophores indicated that transport was energized by the membrane potential and a sodium gradient; each gradient alone was sufficient to drive the uptake of leucine. The activity of the leucine transport system was regulated by the intracellular pH and was inhibited at an internal pH below 7.0.

Journal Article↗
PubMed1996

Renal expression of Na+-phosphate cotransporter mRNA and protein: effect of the Gy mutation and low phosphate diet.

The X-linked Gy mutation is closely linked, but not allelic, to Hyp and is characterized by rickets, hypophosphatemia, decreased renal tubular maximum for phosphate (Pi) reabsorption (TmP) and a specific reduction in renal brush-border membrane (BBM) Na+-Pi cotransport. Gy mice, like their normal littermates, respond to a low-Pi diet with an increase in BBM Na+-Pi cotransport, but fail to show an adaptive increase in Tmp. Using an antibody raised against the NH2 terminal peptide of the rat renal-specific Na+-Pi cotransporter (NaPi-2) and a NaPi-2 cDNA probe, we examined the effect of the Gy mutation and low-Pi diet (0.03% Pi) on NaPi-2 protein and mRNA abundance. The reduction in BBM Na+-Pi cotransport in Gy mice (51 +/- 5% of normal, P < 0.05) was associated with a decrease in NaPi-2 protein (46 +/- 12% of normal, P < 0.05) and mRNA abundance (76 +/- 5%, P < 0.05). The low-Pi diet elicited a two- to three-fold increase in Na+-Pi cotransport in both normal and Gy mice that was accompanied by a large increase in NaPi-2 protein (10.2-fold in normal and 16.9-fold in Gy mice) and a modest increase in NaPi-2 mRNA (1.3-fold in both mouse strains, P < 0.05). The present data demonstrate that (1) the renal defect in BBM Pi transport in Gy mice can be ascribed to a deficit in NaPi-2 protein and mRNA abundance, (2) both normal and Gy mice respond to low Pi with an adaptive increase in NaPi-2 protein that exceeds the increase in Na+-Pi cotransport activity and NaPi-2 mRNA, (3) the adaptive increase in NaPi-2 protein and mRNA are not sufficient for the overall increase in TmP following Pi restriction.

Animals↗
PubMed1996

Release kinetics of serum cardiac troponin I in ischemic myocardial injury.

OBJECTIVES: The study was undertaken to evaluate the release kinetics of cardiac troponin I (cTn-I) in ischemic myocardial injury. DESIGN AND METHODS: The reference range for cTn-I was established by determination of cTn-I in sera and plasma obtained from 622 healthy volunteers (Group 1). cTn-I was compared to: (a) Creatine kinase (CK) MB mass and myoglobin in 12 patients with severe skeletal muscle damage (Group 2); (b) CK-MB activity in 48 patients with myocardial infarction (MI) receiving intravenous thrombolysis (Group 3) (in this group, an additional 43 patients with MI were analyzed separately to characterize cTn-I patterns in thrombolyzed and nonthrombolyzed populations): and in 44 patients with unstable angina (Group 4). RESULTS: In Groups 1 and 2, no positive results (> or = 0.1 microgram/L) were obtained. In Group 3, the time-courses of cTn-I were mostly monophasic in form. A pathologic increase occurred earlier in cTn-I than in CK-MB activity (p = 0.0002); the period with increased cTn-I was longer (p = 0.001), the overall sensitivity of cTn-I (93.9%) was higher than that of CK-MB activity (p = 0.00001). cTn-I was more sensitive at admission (p = 0.0004). In additional patients, the cTn-I peak occurred and cTn-I disappeared significantly later in nonthrombolyzed than in the thrombolyzed group. In Group 4, positive tests results were detected in 45% of patients for cTn-I, 16% for CK-MB activity, and 32% for CK-MB mass. CONCLUSIONS: The cTn-I assay appears to be ideally suited for the detection of ischemic myocardial injury in complex clinical situations because of its high specificity; cTn-I indicates myocardial tissue damage in patients with unstable angina and is superior to CK-MB activity and mass in this respect.

Adult↗
PubMed1996

Renal Na(+)-phosphate cotransporter gene expression in X-linked Hyp and Gy mice.

The X-linked Hyp and Gy mutations are murine homologues of X-linked hypophosphatemia (XLH), a dominant disorder of phosphate (Pi) homeostasis characterized by growth retardation, rickets, hypophosphatemia and decreased renal tubular maximum for Pi reabsorption relative to glomerular filtration rate (Tmp/GFR). In Hyp and Gy mice, the decrease in Tmp/GFR is associated with a reduction in renal brush-border membrane (BBM) Na(+)-Pi cotransport that can be ascribed to a decrease in renal-specific, Na(+)-Pi cotransporter (NPT2) mRNA and protein abundance. Although renal NPT2 gene expression is reduced in Hyp and Gy mice, the NPT2 gene does not map to the X chromosome. These findings exclude NPT2 as a candidate gene for murine and human X-linked hypophosphatemias and suggest that genes at the Hyp, Gy and XLH (HYP) loci are involved in regulation of NPT2 gene expression. Both Hyp and Gy mice respond to low Pi diet with an increase in BBM Na(+)-Pi cotransport, NPT2 mRNA and protein. The increase in NPT2 protein in Pi-depleted mice far exceeds the increase in NPT2 mRNA, suggesting that translational or post-translational mechanisms are involved in the adaptive process. NPT2 protein is localized to the apical surface of the proximal tubule, where immunostaining in both normal and Hyp mice is increased in response to low Pi diet. Pi-deprived Hyp and Gy mice fail to show an increase in Tmp/GFR, indicating that adaptation at the BBM is not sufficient for the overall increase in Tmp/GFR in response to low Pi diet.

Animals↗
PubMed1996

Professionalism behaviors of hospital nurse executives and middle managers in 10 western states.

What is the level of professionalism of nurse managers? These leaders of nurses are expected to establish a climate in which professional practice can flourish. In this study, the authors used the Professionalism Inventory to determine professional behaviors of 144 nurse executives and 135 middle managers. Nurse executives performed at consistently higher levels except for the categories concerning autonomy and knowledge of the Code for Nurses.

Adult↗
PubMed1996

[Value of human cardiac troponin I determination in the diagnosis of acute myocardial infarction].

Immunoenzymatic assay (IEMA) of human cardiac Troponin I (TnI c) was used in patients admitted to the coronary care unit with acute myocardial infarction (AMI). TnI c was detected in all patients with AMI. The detection of TnI c was earlier after the onset of pain (4.5 +/- 2.3 hours) than that of CKMB activity (6.3 +/- 3.6 hours), p = 0.003. The kinetics of TnI c are usually monophasic and parallel to that of CKMB activity. The peak value occurs 12.2 +/- 4.6 hours and 15.8 +/- 9.0 hours after the onset of pain in patients treated by thrombolysis. The TnI c disappears from the plasma between 5 and 9 days after the onset of pain, later than CKMB activity (p = 0.0001). In 49 patients admitted for AMI treated by thrombolysis, the comparative sensitivities of TnI c (threshold: 0.1 ng/ml) and of CKMB activity (threshold: 15 IU/l; CK > or = 100 Ul/l) were, at the first sampling on admission, 61% and 22% respectively (p = 0.0002) (average interval from onset of pain to first blood sampling: 3.4 +/- 1.3 hours). TnI c was not detected in the plasma of 145 normal subjects nor in any of the 6 patients with severe muscular trauma or rhabdomyolosis (specificity: 100%). This IEMA is a specific and a sensitive method of diagnosing acute and subacute myocardial infarction. It is ideal for the detection of myocardial necrosis in complex clinical situations when the usual enzymatic markers may be ineffective.

Adult↗
PubMed1995

Down-regulation by progesterone of CFTR expression in endometrial epithelial cells: a study by competitive RT-PCR.

To determine the effect of progesterone on the CFTR mRNA level in glandular epithelial cells of guinea-pig endometrium, a competitive RT-PCR was developed using an an internal standard a competitor with the same sequence as CFTR RNA except for a 20 nucleotide insertion. Using this method, the results showed that the CFTR mRNA level decreased in cells treated with estradiol plus progesterone compared to cells receiving estradiol alone. The decrease in CFTR mRNA level was maximal at 12 h incubation and was 27.3% of the CFTR mRNA level in estradiol-treated cells. The effect of progesterone was mimicked by the progestagen, R5020 and was inhibited by antiprogestins, RU 38,486 and ZK 98,299. Results are discussed in relation to the changes taking place in the endometrium in preparation for implantation of the embryo.

Animals↗
PubMed1995

Anti-CD3-induced anergy in cloned human Th0, Th1, and Th2 cells.

In the mouse, activation of T cells by T cell receptor (TCR) crosslinking with anti-CD3 antibodies in the absence of a costimulatory signal induces Th1 but not Th2 cell anergy. Furthermore, anti-CD3 induces anergy of Th1- but not Th2-type lymphokine secretion in Th0 cells. This study was designed to determine whether this is also the case in man. Human rye grass allergen Lol p I-specific cloned CD4+ T helper cells of subtypes Th0, Th1, and Th2 were treated with immobilized anti-CD3. The cells were rested for 4 days and then activated under optimal conditions with antigen and antigen-presenting cells (APCs). Cell proliferation and IL-2, IFN-gamma, and IL-4 secretion was determined to test for the anergic state. The initial anti-CD3 treatment induced cell proliferation, IL-2, IFN-gamma, and/or IL-4 secretion by T cells of all three subsets which was followed by an anergic state in Th0, Th1, and Th2 cells as shown by a 51 to > 94% decrease in cell proliferation and IFN-gamma and/or IL-4 secretion after subsequent APC and Lol p I activation. Addition of IL-2 or IL-4 during anti-CD3 treatment of the cells did not prevent unresponsiveness. However, the addition of IL-2 but not IL-4 during APC and Lol p I stimulation partially reversed the anergic state. These data demonstrate that, contrary to the mouse, cloned T cells of all three human T helper cell subtypes are anergized by anti-CD3 TCR activation in the absence of costimulatory signals. The fact that human Th2 cells can be anergized may be important for the development of new treatments in Th2-mediated allergic disorders.

Allergens↗
PubMed1995

Immunosuppressive actions of 1,25-dihydroxyvitamin D3: preferential inhibition of Th1 functions.

1,25-Dihydroxyvitamin D3 [1,25-(OH)2-D3] is known to be an immunosuppressive hormone. This review primarily deals with in vitro and in vivo effects of 1,25-(OH)2-D3 and analogue, 1,25-dihydroxy-16ene-vitamin D3 [1,25-(OH)2-16ene-D3], on T helper subsets type 1 (Th1) or type 2 (Th2) that have distinctive functional characteristics in humans. Th1 secrete interferon (IFN-gamma), interleukin (IL-2) and induce B cells to produce immunoglobulin IgG2a while Th2 secrete IL-4, IL-10 and induce the production of IgG1 and IgE by B cells. The sterol inhibits the secretion of IL-12, a cytokine produced by monocytes and B cells, which leads to the activation and differentiation of Th1. In addition, 1,25-(OH)2-D3 directly inhibits IFN-gamma secretion by Th1 clones while it has little effect on IL-4 secretion by Th2 clones. The analogue, 1,25-(OH)2-16ene-D3, is 100-fold more potent than 1,25-(OH)2-D3 in inhibiting IFN-gamma secretion but also has little effect on IL-4 secretion. In mice, when given in vivo, the sterol prevents the induction of spontaneous and induced autoimmune diseases and inhibits Th1 induce IgG2a responses. These actions of the vitamin D3 compounds suggest that it may have potential therapeutic applications in Th1-mediated clinical situations such as autoimmunity and transplantation.

Animals↗
PubMed1995

Adenosine 3',5'-monophosphate mediates progesterone effect on sulfate uptake in endometrial epithelial cells.

We have previously shown that progesterone increased sulfate uptake in glandular epithelial cells of guinea pig endometrium. To investigate whether cAMP might be the cause of the progesterone effect on sulfate uptake, cAMP accumulation and the effect of cAMP on sulfate uptake were evaluated in cells treated with 17 beta-estradiol alone or with progesterone. Progesterone provoked an increase in the intracellular cAMP accumulation in cells treated with 17 beta-estradiol. Moreover, cAMP or forskolin elicited the same marked increase in sulfate uptake as that observed with progesterone. The effect of progesterone on sulfate uptake was abolished by blocking either the cAMP pathway or the genomic action of progesterone and was independent of the cAMP-activatable apical chloride channel. This study is the first evidence of cAMP activation of sulfate uptake and suggests a genomic effect of progesterone on the production of cAMP which activates the sulfate transport system in a short term activation and a long term activation independent of transcriptional or translational events. The endometrium is a unique tissue that undergoes profound highly regulated modifications during the secretory phase in providing a suitable environment for embryo implantation. The regulation of sulfate uptake could participate in this process.

Animals↗
PubMed1995

[Ventricular fibrillation and defibrillation; electrophysiological bases and clinical applications].

During sinus rhythm, the successive responses to the application of electrical stimuli of increasing intensity during the vulnerable period are cardiac stimulations followed by repetitive ventricular responses and then ventricular fibrillation. An impulse of even greater intensity is not followed by ventricular fibrillation (shock at the upper limit of vulnerability) suggesting that defibrillatory shock is effective only when it does not reinduce fibrillation. Two other hypotheses are also proposed in fibrillation, that of critical mass and that of extension of the refractory periods, in particular after biphasic shocks. Clinically, the measurement of the threshold of defibrillation is difficult as it is a random process which does not obey the all or nothing principle. Ideally, a graph of efficacy versus energy should be constructed but this is only possible under experimental conditions. The effects of different antiarrhythmic drugs have been studied in this manner; in general, the sodium channel blockers improve the energies of defibrillation.

Animals↗
PubMed1995

[New indications for cardiac pacing].

New indications have recently appeared for cardiac pacing with haemodynamic and antiarrhythmic objectives without any symptomatic bradycardia. The best documented indication, though relatively rare, is stimulation of obstructive hypertrophic cardiomyopathy; initially reserved for cases with favorable results of an acute haemodynamic test, it is now used in other cases without this criterion; hypertrophic cardiomyopathy without permanent obstruction, atrial fibrillation or left bundle branch block. The improvement observed during follow-up is always greater as a real remodeling of the myocardium seems to occur with ventricular dilatation and/or septal thinning. However, the position of the atrial, and above all, of the ventricular pacing catheters is critical as is regulation of the pacemaker which should allow complete ventricular capture with an AV delay allowing good filling. The follow-up of these patients must therefore be regular and the effects on longevity are unknown. DDD pacing has also been proposed in dilated cardiomyopathy. The results are contradictory and only very selected cases with left bundle branch block and long PR interval seem justified with, again, optimisation of the pacing sites with high septal or biventricular stimulation. Recurrent atrial tachycardia, special algorithms preventing extrasystoles have been tried with variable results. In cases with inter-atrial block, atrial resynchronisation by bi-atrial stimulation has been assessed with promising results but many technical problems remain unsolved.

Adolescent↗