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Biomedical subjects

M Kessler

Publications and source records attributed to M Kessler.

At least 217 records · Page 12Linked to original sources
PubMed1993

Thiocyanate equally increases affinity for two DL-alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA) receptor states.

The effects of potassium thiocyanate on the binding of DL-alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), and L-glutamate to the AMPA receptor complex were studied in rat brain membranes. Thiocyanate increased the affinity of AMPA receptors for both AMPA and L-glutamate and decreased the affinity for CNQX. Displacement of [3H]CNQX binding by AMPA revealed that the affinity for AMPA of both the high and the low affinity states of the receptor increased in the presence of thiocyanate, whereas the proportion of the two states was unchanged. In soluble fractions, which exhibit an apparently homogeneous population of the high affinity state of the receptor, the affinity for AMPA was increased by a magnitude similar to that seen for the high affinity state in the membranes. These results indicate that thiocyanate enhances AMPA binding not by converting low affinity receptors into the high affinity state but by equally increasing the affinities of the high and the low affinity states of AMPA receptors.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1993

Diagnosis and treatment of chronic lead poisoning in CAPD patients.

In order to screen for abstruse lead poisoning in continuous ambulatory peritoneal dialysis (CAPD) patients, delta-aminolevulinic acid dehydratase (ALAD) levels were measured in 18 CAPD patients, 156 patients treated with hemodialysis (HD), and 420 control patients with normal renal function (NRF). An EDTA (ethylenediamine tetraacetic acid) mobilization test was performed in patients with low levels of ALAD (< 0.40 mumol of porphobilinogen formed per milliliter of red blood cells): 1 g of EDTA was infused IV followed by 20 L of hemofiltrate in HD patients and four bags of dialysate in CAPD patients. Lead was assayed in the ultrafiltrate liquid, the bags of dialysate, and in the 24-hour urine. ALAD levels were significantly lower in CAPD and HD patients than in the NRF subjects. ALAD was significantly correlated with EDTA mobilized lead in both dialysis and NRF patients. Using the usual criteria (EDTA mobilized lead > 800 micrograms/24 hours), the rate of lead poisoning observed was similar in the two groups. These results suggest that ALAD assay followed by the EDTA mobilization test is as effective in CAPD patients as in NRF subjects to diagnose and to treat chronic abstruse lead poisoning.

Chronic Disease↗
PubMed1993

Evolution of intraperitoneal hydrostatic pressure following peritoneal catheter implantation.

Intraperitoneal hydrostatic pressure (IPP) was measured in 10 patients for 15 days (until day 15) following peritoneal catheter implantation. Tenckhoff catheters were surgically implanted using a transrectal approach. The patients began peritoneal dialysis (PD) immediately, initially with small intraperitoneal fluid volumes (500 mL), gradually increasing to reach 2000 mL by day 7. In one patient PD was delayed until day 7 because of an initial leakage of dialysate. Inspiratory and expiratory IPP were measured daily, with the zero point fixed at the midaxillary line with the patient in the supine position. Despite the small intraperitoneal fluid volumes used initially (500 mL), IPP was much higher in the first 3 days following implantation than in the next 12 days (17 +/- 3 cm of water vs 11 +/- 1 cm of water). IPP remained high until day 3, then gradually decreased in a linear fashion until day 12, despite the increased intraperitoneal volumes used, and then remained constant. In conclusion, IPP was found to be significantly higher for 3 days following intraperitoneal catheter implantation, whichever intraperitoneal volume was used. This may be due to tense abdominal muscles from pain caused by the surgery or because of reduced intraperitoneal compliance at the beginning of PD.

Adult↗
PubMed1993

Intraperitoneal hydrostatic pressure and ultrafiltration volume in CAPD.

The intraperitoneal hydrostatic pressure (IPP) and overall ultrafiltration (UF) volume were measured in 34 patients after a 2-hour exchange with 2 L of dialysate containing 3.86% glucose. These patients had been treated with continuous ambulatory peritoneal dialysis (CAPD) on average for 26 +/- 20 months under stable conditions. The patients were at rest during the 2-hour exchange. The normal IPP measured with the patient lying completely flat was on inspiration (IPPinsp) 14 +/- 4 cm of water (cmH2O) and on expiration (IPPexp) 12 +/- 3 cm H2O, for an intraperitoneal volume of 2820 +/- 319 mL. The mean UF was 744 +/- 323 mL. The mean IPP (IPPmean), defined by (IPPinsp+IPPexp)/2, had a negative linear correlation to the UF volume (r = 0.66; p = 0.0001). The linear regression test showed that an increase of 1 cm H2O in the IPPmean reduced the overall UF volume by 70 mL in 2 hours. In conclusion, even though the UF is produced by the osmotic pressure of the dialysate, it is also influenced to a great extent by the intraperitoneal hydrostatic pressure, which should not be ignored.

Adult↗
PubMed1993

Role of the kidney in the expression of low molecular weight factors with growth factor activity.

Small molecules of peptidic nature, called low molecular weight growth factors (LMW-GF < 1000 Da) are present in normal human serum ultrafiltrate. They enhance the somatomedin activity as measured by the incorporation of 35SO4 into chick embryo cartilages. On the basis of this in vitro test, LMW-GF activities were measured in serum ultrafiltrates of hemodialyzed patients and renal transplant recipients during the post-transplantation follow-up. LMW-GF activity was always zero in patients with chronic renal failure. It was checked that these results were not due to the presence of low molecular weight somatomedin inhibitors or to the increased sulfate concentration. After successful renal transplantation, the LMW-GF activity of patients ultrafiltrates returned to normal at the same time or before the improvement of renal function. In case of post-transplant complications, a decrease in LMW-GF activity accompanied or even occurred prior to impairment of renal function. In functioning graft, LMW-GF activity reappears rapidly, whereas its normalization is delayed in case of tubular nephropathy or episode of acute rejection. It was suggested that the kidney is involved in LMW-GF molecules production or processing. It could be speculated that LMW-GF activity might be a prognostic factor in renal transplantation.

Adult↗
PubMed1993

[Endothelin and kidney].

Endothelial and epithelial cells release a potent 21-residue peptide, endothelin (ET) which is an endothelium-derived-contracting-factor (EDCF). The peptide causes contraction of vessels and induces sustained blood pressure elevation. Beside its role in the vasoconstriction ET has strong inotropic effect on the myocardium and induces smooth muscle cells contractions. Renal actions, similar to angiotensin and norepinephrine, focus on its potential importance in nephrology. Acute and chronic renal failure showed increased plasma and urinary ET levels. An understanding of the regulation of the release of ET may provide knowledge about the pathogenesis of acute renal failure, the progression of chronic renal failure and cyclosporin A induced toxicity. Further research is needed to substantiate the new and promising perspective of ET in human diseases and therapy.

Animals↗
PubMed1992

[Polycythemia after kidney transplantation].

Between 1971 and 1990, 251 kidney transplanted patients with a well functioning graft were evaluated to determine the frequency of post-transplant erythrocytosis (PTE). Thirty-one patients (13 percent) developed polycythaemia 10.6 +/- 10 months after transplantation. Thromboembolic complications occurred in 22 percent of the cases. The frequency of PTE was higher in males than in females (sex ratio: 7.2 vs 2.1; P < 0.05). Patients with renal dysplasia had a lower incidence of PTE (3 vs 22 percent; P < 0.05) as did those who had been treated with azathioprine (9.4 vs 19 percent; P < 0.05). None of the patients treated with recombinant erythropoietin before transplantation developed PTE during a mean follow-up of 15.1 +/- 4.5 months. The majority of polycythaemic patients had normal erythropoietin levels. These results show that there is an erythropoietin-independent proliferation due to an increased sensitivity of erythroid progenitors or to an erythroid stem cell stimulation by cytokines.

Adult↗
PubMed1992

Parameters affecting the elongation block by RNA polymerase II at the SV40 attenuator 1 in vitro.

We have previously suggested that folding of the SV40 attenuator RNA 1 into two hairpin elements leads to a block of transcription elongation. Using site-directed mutagenesis, we created three templates that either strengthened or weakened the proposed hairpin structures. The mutated and wild-type templates were cloned downstream from the adenovirus 2 MLP, and transcription patterns were compared among the templates, in cell-free extracts. In this report, we show that at the standard temperature (30 degrees C) the elongation block occurs at elevated KCl concentrations (0.5-1.2 M KCl) while at high temperature (65 degrees C), although the transcription elongation rate increases, the block to elongation occurs at lower KCl concentrations (less than 0.5 M KCl) as well. Since under the conditions tested the extent of the elongation block is directly dependent on the stability of the hairpin structure of the RNA, as assessed by a comparison of transcription of the wild-type and mutated templates, we suggest that elevated KCl concentrations and high temperatures are favored conditions for optimizing the processes whereby the hairpin structures are recognized by the polymerase as an attenuation signal. Moreover, the present experiments indicate that cellular elongation factors are not directly involved in modulating the extent of the elongation block at the SV40 attenuator 1 in vitro. The SV40 attenuator 1 is the only eukaryotic system known to date which has been shown to have structural characteristics so similar to rho-independent terminator in prokaryotes. We discuss the similarities between the mechanisms which lead to elongation blocks at these eukaryotic and prokaryotic sites.

Base Sequence↗
PubMed1992

Stochastic progression of new states in psychotherapy.

This paper presents a study of the stochastic behaviour of the entry of a 5-dimensional, 2400 state, system into new states. Each state consists of five measurements on variables that are sensitive measures of the degree of activated unconscious communication. The data come from six psychotherapy consultation sessions. The study sought to investigate the manner in which patient and therapist progress into new configurations (new states) of the five variables, and the way tension accumulates to the point of overcoming the inertia in the patient/therapist system. We show that the time series that consists of the time intervals between successive new states is a generalized Poisson process. That is, the process is inherently governed by a Poisson parameter that is a continuous piecewise linear function of time. It increases rapidly in the opening moments of an interview and decreases slowly thereafter. This non-linear, non-stationary Markov model fits the data well according to the Kolmogorov-Smirnoff criterion. We discuss the model's implications for the nature of psychotherapy and its participants.

Communication↗
PubMed1992

Monitoring of redox-state of respiratory enzymes and myoglobin oxygenation in the working rat heart in normoxia and oxygen deficiency.

The cellular oxygen supply in the isolated, hemoglobin-free perfused, working rat heart can be determined by measurements of myoglobin oxygenation. However, for a precise analysis of mitochondrial hypoxia and anoxia (pO2 < 0.01 Torr) redox-state of respiratory enzymes must be known. By use of the EMPHO (Frank et al. 1989) it is possible to perform a high speed spectrometry within very small tissue volumes. Because of the characteristic absorption spectra of oxygenated and deoxygenated myoglobin and of the oxidized and reduced cytochrome aa3 within the wavelength interval from 500 to 630 nm it is possible to isolate these two pigments from the remission spectra and to determine the oxygenation state of myoglobin and the redox-state of cytochrom aa3.

Animals↗
PubMed1992

Dialysis-associated arthropathy: a multicentre survey of 171 patients receiving haemodialysis for over 10 years. The Co-operative Group on Dialysis-associated Arthropathy.

In order to determine the prevalence of dialysis-associated arthropathy (DAA) and what factors favour its development, we conducted a survey in 19 centres in northeastern France, of all patients receiving haemodialysis for over 10 years (171). A diagnosis of DAA was made in 84 patients (49%) by two investigators, using as criteria single or combined presence of carpal tunnel syndrome (32%), erosions and bone cysts of the large limb joints (33%) and destructive spondylarthropathy (14%). The 84 patients with DAA were compared with the 87 dialysis patients free of these clinical or radiological abnormalities. The affected patients were significantly older at the start of dialysis than unaffected patients. The risk of developing carpal tunnel syndrome increased with the duration of dialysis. Amyloid deposits were found in carpal tunnel tissue obtained from 24 of the 39 operated patients (62%) during surgery. Destructive spondylarthropathy was significantly associated with the presence of disc calcifications and more frequent in AN 69-treated patients in whom secondary hyperparathyroidism appeared to be more severe. The use of an AN 69 membrane for at least 90% of the dialysis period (in 15 patients) was not associated with a lower prevalence of DAA. We found that after 10 years of haemodialysis DAA occurred whatever type of membrane was used and the prevalence increased with the patient's age and the duration of dialysis.

Adolescent↗
PubMed1992

Evidence that high- and low-affinity DL-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) binding sites reflect membrane-dependent states of a single receptor.

Binding of DL-alpha-[3H]amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid ([3H]AMPA) to lysed rat brain membranes in the presence of potassium thiocyanate resulted in curvilinear Scatchard plots that could be resolved by regression analysis into a large low-affinity component and a small high-affinity component. Solubilization with Triton X-100 resulted in solubilized and nonsolubilized fractions that were considerably enriched in the high-affinity component and correspondingly reduced in the low-affinity component. It thus appears that solubilization converts low-affinity AMPA receptors into high-affinity receptors. Also, synaptic plasma membranes were found to be greatly enriched in the low-affinity form and deficient in the high-affinity form of the AMPA receptor. These experiments provide evidence for the hypothesis that the high- and low-affinity components of AMPA binding are interconvertible states of the same receptor rather than separate binding sites and that the conversion of these receptors from their native high-affinity state to the low-affinity state occurs on insertion of the receptors into synapses.

Animals↗