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R Konrad

Publications and source records attributed to R Konrad.

7 recordsLinked to original sources
PubMed2006

Cell junctional proteins in the human corpus luteum: changes during the normal cycle and after HCG treatment.

BACKGROUND: Regulation of tissue remodelling and ovarian permeability by intercellular adhesion complexes may be involved in normal and pathological ovarian function. Therefore, the occurrence, distribution and hormonal control of the adherens junction protein vascular endothelial cadherin (VE-cadherin) and the tight junction proteins occludin and claudin in the human corpus luteum (CL) were investigated. METHODS: CLs from patients undergoing hysterectomy for benign reasons were enucleated during early, mid- and late stages of the functional luteal phase and after HCG rescue in vivo. Immunostaining for occludin, claudins 1 and 5 and VE-cadherin was carried out on fixed tissue. Endothelial cells, granulosa lutein cells and theca lutein cells were identified by reference to serial sections immunostained for CD34, 17alpha-hydroxylase and 3beta-hydroxy-steroid-dehydrogenase. Quantitative analyses were performed using image analyses. RESULTS: Occludin was localized to the plasma membrane of granulosa lutein cells and endothelial cells but was absent in theca lutein cells. Claudin 1 was exclusively localized to the plasma membrane of steroidogenic cells. Claudin 5 and VE-cadherin were only present in endothelial cells. After HCG administration in vivo, adherens and tight junction proteins were significantly down-regulated (P < 0.05). CONCLUSIONS: The decrease of junctional proteins after HCG treatment suggests a hormonal control of tight and adherens junctions in the CL associated with tissue remodelling and an increase in luteal permeability during early pregnancy.

Antigens, CD↗
PubMed2001

In vitro comparison of the two hard-hard articulations for total hip replacements.

Polyethylene particle disease is one of the major causes of late aseptic loosening of total hip replacement. Two hard-hard articulations (alumina-on-alumina and metal-on-metal) have been developed in Europe as an alternative to the ultra-high molecular weight polyethylene (UHMWPE) articulations. Even though these hard-hard articulations are on the market and numerous reports have been published about them, only a very limited number of studies allowing a direct in vitro comparison of the two articulations have been published so far. This paper compares in vitro these two types of articulation (alumina-on-alumina and metal-on-metal), which have been tested with a hip simulator for their tribological behaviour using exactly the same experimental methodology. This comparison shows that these two types of hard-hard articulation have very similar abrasive wear behaviour with four main features: 1. A running-in wear period (1 x 10(6) cycles) gives a cumulative wear of about 20 microns with head diameters of 28 mm. 2. After the running-in wear, there is a stabilization of the linear wear behaviour with a low linear wear rate/10(6) cycles for both types of articulation. 3. The volumetric wear rate of both articulations (< 2.0 mm3/year for head diameters of 28 mm) is significantly lower than that observed for metal-on-polyethylene or ceramic-on-polyethylene articulations having the same head diameter. 4. Abrasive wear is readily apparent (indicating a mixed lubrication regime) with both types of articulation. The extremely low wear performance of these articulations is confirmed and they constitute a low-wear alternative to the UHMWPE articulations currently used.

Arthroplasty, Replacement, Hip↗
PubMed2001

Pediatric generalists and subspecialists: determinants of career satisfaction.

OBJECTIVES: To evaluate the work life and job satisfaction of pediatric generalists and subspecialists in comparison to each other and to a group of general internists and internal medicine subspecialists. METHODS: Data were collected by survey of a national sample of 5704 general pediatricians, subspecialty pediatricians, general internists, internal medicine subspecialists, and family physicians who were selected randomly from the American Medical Association Masterfile using stratified sampling with disproportionate weighting to ensure ethnic diversity and representation of high managed care areas. Surveys were mailed up to 4 times and contained 150 items that reflected 10 facets of physician job satisfaction as well as an assessment of individual and practice demographic information. This study reports data from all groups except for family medicine. RESULTS: The adjusted response rate was 58% for general pediatricians (n = 590), 67% for specialty pediatricians (n = 345), and 52% (n = 1823) for the entire pool. In comparison with general internists, general pediatricians were more likely to be female (44% vs 24%); to work part time (20% vs 12%); to have lower annual income ($125 679 vs $143 875); and to report significantly higher levels of job, career, and specialty satisfaction on a 5-point scale (3.81 vs 3.52, 3.80 vs 3.55, and 3.76 vs 3.17 respectively). In comparison with internal medicine subspecialists, pediatric subspecialists were more likely to be female (42% vs 22%); to work in academically affiliated settings (35% vs 17%); to have lower incomes ($156 284 vs $192 006); to receive significantly less time for a complete history and physical examination (39 minutes vs 51 minutes); and to report similar levels of job, career, and specialty satisfaction (3.69 vs 3.71, 3.74 vs 3.78, and 3.60 vs 3.47 respectively). Of all 4 physician groups, general pediatricians worked the fewest hours (50/week), spent the greatest percentage of time in the office and the lowest percentage in the hospital (58% and 16%, respectively), saw the lowest percentage of patients with complex medical and complex psychosocial problems (15% and 17%, respectively), and were the least likely to endorse symptoms of burnout or job stress (13% and 18%, respectively). In comparison, pediatric subspecialists worked longer hours (59/week), spent the lowest percentage of time in the office and the greatest percentage of time in the hospital (22% and 44%, respectively), saw a much higher percentage of patients with complex medical and complex psychosocial problems (46% and 25%, respectively), and reported significantly higher levels of burnout and job stress (23% and 26%, respectively). CONCLUSIONS: Despite lower incomes, general pediatricians reported the highest levels of satisfaction and the least job stress of all 4 physician groups, whereas pediatric subspecialists reported levels of stress and burnout that raise significant concerns for the workforce of pediatric subspecialists of the future. Initiatives that improve clinical workload, balance inpatient and outpatient hours, and increase personal time of pediatric subspecialists should be considered.

Burnout, Professional↗
PubMed1996

Hemicellulose-degrading bacteria and yeasts from the termite gut.

Termites play a major role in the recycling of photosynthetically fixed carbon. With the aid of their symbiotic intestinal flora, they are able to degrade extensively wood constituents such as cellulose and hemicellulose. Nevertheless, the microbial species involved in the degradation of hemicelluloses are poorly defined. The purpose of this paper was to examine the microflora involved in hemicellulose degradation. Different aerobic and facultatively anaerobic bacteria and yeasts were isolated using xylan, arabinogalactan and carboxymethylcellulose as substrates. Gram-positive isolates belonged to the genera Bacillus, Paenibacillus, Streptomyces or the actinobacteria group, while the Gram-negative strains were assigned to the genera Pseudomonas, Acinetobacter, Ochrobactrum, and to genera belonging to the family Enterobacteriaceae. The spectrum and activity of xylan- and arabinogalactan-hydrolysing glycosidases of these new isolates, together with additional bacterial strains originally obtained from enrichments with aromatic compounds were determined.

Animals↗
PubMed1990

[The arterial-end tidal CO2 partial pressure difference during anesthesia].

Arterial CO2 partial pressure (PaCO2) can be continuously and noninvasively estimated by monitoring end-tidal CO2 partial pressure (PetCO2). However, the difference between the two (P(a-et)CO2) may vary considerably between patients. In 26 patients undergoing general anesthesia for various surgical procedures, P(a-et)CO2 was measured. We tested the hypothesis that certain clinical characteristics are associated with higher P(a-et)CO2 values in a given patient. In addition, we tested the hypothesis that P(a-et)CO2 remains constant during anesthesia by comparing the mean of eight P(a-et)CO2 values, which were measured at 15-min intervals, with the initial (P(a-et)CO2 value. Impaired lung function, defined as a lung score above 6, age above 50 years, and overweight (defined as greater than 120% of ideal body weight) were associated with increased P(a-et)CO2 (mean +/- SD: 6.27 +/- 1.85; 5.27 +/- 2.11; and 6.19 +/- 1.95 mmHg respectively) when compared to normal lung function (lung score less than or equal to 6), age below 50 years, and normal weight (less than 120% of ideal body weight, 3.87 +/- 2.31; 3.55 +/- 2.58; and 3.77 +/- 2.25 respectively). Although these differences are statistically significant, the standard deviations are large and do not allow the prediction of P(a-et)CO2 in a given patient. Initial P(a-et)CO2 correlated well with subsequent P(a-et)CO2 (R = 0.91, P less than 0.001). The mean difference of the subsequent P(a-et)CO2 values from the initial values was 0.05 +/- 0.80 mmHg (mean +/- SD) and was not significantly different from zero. In the patient population studied, P(a-et)CO2 thus remained generally constant during anesthesia.

Adult↗
PubMed1981

Purification, characterization, and reconstitution of the Ca2+-transport system (high-affinity Ca2+, Mg2+-ATPase) of the human erythrocyte membrane.

The Ca2+-transport system of human erythrocyte membranes was solubilized by deoxycholate in the presence of the nonionic detergent Tween 20 and was purified by calmodulin affinity chromatography. The method yields a functional enzyme, which as compared with the erythrocyte membrane was purified 207-fold based on specific activity, and about 330-fold based on protein content. The activity of the isolated enzyme can be increased about 9-fold by the addition of calmodulin, resulting in a specific activity of 10.1 mumoles/mg . min at 37 degrees C. Triton X-100 and deoxycholate stimulate the calmodulin-deficient Ca2+-ATPase in a concentration dependent manner, which results in a loss of the calmodulin-sensitivity. The Ca2+-transport ATPase could be reconstituted after solubilization of the ATPase by deoxycholate and controlled dialysis near room temperature. The system was reconstituted to form membraneous vesicles capable of energized Ca2+ accumulation. The membrane vesicles showed a protein to lipid ratio (approx. 60% protein and 40% lipid) similar to that of the original erythrocyte membrane. The stimulation by calmodulin of the calmodulin-depleted membrane-bound and partially purified Ca2+-ATPase is strongly time dependent. At a Ca2+-concentration of 40 microM and low calmodulin concentrations, approx. 120 min are required to regain full activity. This time period is decreased to about 15 min in the presence of a high excess of calmodulin. Vice versa, at fixed concentrations of calmodulin, the time necessary for regain of full activity is decreased as the Ca2+ concentrations is increased. The dependence of the Ca2+-ATPase activity on the calmodulin concentration shows strong deviation from Michaelis-Menten kinetics at Ca2+ concentrations below (4--10 microM) and above (200 microM) the optimum concentration of 40 microM. Mathematical analysis of the results at 200 microM Ca2+ leads to the assumption that 4 calmodulin molecules interact with one oligomer of Ca2+-ATPase consisting of 4 identical subunits.

Biological Transport, Active↗