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Biomedical subjects

W Braun

Publications and source records attributed to W Braun.

At least 181 records · Page 10Linked to original sources
PubMed1986

Proabsorptive properties of forskolin: disposition of glycine, leucine and lysine in rat jejunum.

The effects of forskolin on mucosal cyclic AMP levels and active transport of glycine, L-lysine and L-leucine were studied in rat jejunum in vitro. Furthermore, the effects on lysine and glycine incorporation into mucosal protein and on mucosal cell volume were investigated. Elevation of intestinal mucosal cyclic AMP to threefold control levels by 10 mumol 1(-1) forskolin was accompanied by increased absorption of glycine (+33%), L-leucine (+72%) and L-lysine (+188%), as determined in a three compartment model suitable to measure active transport. Increased intracellular accumulation could be demonstrated for lysine as a transport substrate. Accordingly, using a dual label method, calculated values for uphill transport of lysine at the site of the brush border membrane were markedly enhanced. Forskolin up to 10 mumol 1(-1) had no effects on the fraction of lysine or glycine incorporated into TCA-precipitable proteins of jejunal absorptive cells. Serosal to mucosal transfer, as well as basolateral entry into mucosal cells remained unchanged for all three amino acids. Likewise, intracellular fluid space, calculated from distribution spaces for 14C-inulin and 3H2O as well as the response of cellular volume to an osmotic gradient were not affected by forskolin. As comparable stimulatory effects of forskolin on active hexose transport were reported earlier, it is suggested that forskolin - known to inhibit sodium-coupled fluid absorption - may stimulate active transport by enhancing sodium availability for sodium dependent intestinal cotransporters in general.

Animals↗
PubMed1986

Evidence for amino acid induced cholestasis in very-low-birth-weight infants with increasing enteral protein intake.

In the present investigation 32 very-low-birth-weight (VLBW) infants fed at three different levels of protein intake (2.92 g/kg/d from human milk, 3.22 and 4.06 g/kg/d from formula) were studied at the mean age of 21 days. Serum total alpha-amino nitrogen concentration correlated directly to total bile acid concentration. The serum and urine alpha-amino nitrogen and the serum bile acid concentration correlated with protein intake. The increase in protein intake was accompanied by a concomitant decrease in the intraluminal bile acid concentration in the AGA infants. The results offer indirect evidence of decreased bile flow in VLBW-infants on excessive oral protein intake. The cholestatic effect could be mediated by an increase in the plasma amino acid concentration.

Amino Acids↗
PubMed1986

Circadian fluctuation of plasma melatonin in Prader-Willi's syndrome and obesity.

In 3 groups of 8 children and adolescents each with Prader-Willi-Labhart's Syndrome (PW-S), obese patients matched for body weight (control I), and normal weight subjects matched for pubertal stage (control II) plasma concentrations of melatonin, cortisol, growth hormone (hGH), insulin, gonadal hormones, and gonadotropins were measured every 1 to 4 hours in 24-hour-profiles. All hormones were determined by radioimmunoassay. The specific melatonin antibody was raised in rabbits. Criteria of the melatonin assay were as follows: detection limit for plasma concentrations of 13 pg/ml, intraassay and interassay variations: 8.4 and 11.2%, respectively. PW-S-patients showed cortisol fluctuations within normal limits. hGH was lower than 5 micrograms/l even during sleep, insulin ranged between 5 and 170 mU/l, and no excessively high glucose levels were found. Estradiol and testosterone were low for age and for pubertal development in all patients except in two girls. Basal LH and FSH levels were in the low normal range and showed sluggish response to LHRH. Plasma melatonin was low during the day, increased at mid-night and peaked at 3 a.m. Melatonin levels in PW-S were not significantly different from those in both control groups. We concluded that the impairment of gonadotropin secretion in patients with PW-S is not due to elevated levels of plasma melatonin.

Adolescent↗
PubMed1986

[Divorces, 1984].

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Age Factors↗
PubMed1986

[Divorces, 1985].

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Developed Countries↗
PubMed1986

Bile acids in the serum and duodenal content of newborn infants of different classification.

Total serum bile acids were determined in 83 infants of different classification. In 33 mature infants total bile acids were measured after feeding human milk (n = 17) or formula (Milasan). Statistically significant elevations of total bile acids were found on the 14th day of life, if mature infants were formula fed. In low-birth-weight infants appropriate for gestational age total bile acids are not higher on the 8th day of life than in mature infants, but on the 14th day of life the elevations become significant. Low-birth-weight infants small for gestational age and infants suffering from fetal distress syndromes show the highest total bile acids with great variations. Low-birth-weight infants small for gestational age had serum total bile acid concentrations related to the degree of fetal growth retardation (r = -0.871). Some newborns suffering from late metabolic acidosis had lowest intraluminal total bile acids, especially dihydroxy bile acids. We found a direct hyperbolic dependence between total bile acids in the serum and the duodenal content (r = +0.93). In cases of serum total bile acids above 50 mumol/l, concentrations in duodenal content do not exceed 2 mmol/l. Therefore, the degree of fetal growth retardation, fetal distress syndromes, and the nutrition after birth have great influence on bile acid metabolism.

Aging↗
PubMed1985

Calculation of protein conformations by proton-proton distance constraints. A new efficient algorithm.

We have developed a method to determine the three-dimensional structure of a protein molecule from such a set of distance constraints as can be determined by nuclear magnetic resonance studies. The currently popular methods for distance geometry based on the use of the metric matrix are applicable only to small systems. The method developed here is applicable to large molecules, such as proteins, with all atoms treated explicitly. This method works in the space of variable dihedral angles and determines a three-dimensional structure by minimization of a target function. We avoid difficulties hitherto inherent in this type of approach by two new devices: the use of variable target functions; and a method of rapid calculation of the gradient of the target functions. The method is applied to the determination of the structures of a small globular protein, bovine pancreatic trypsin inhibitor, from several artificial sets of distance constraints extracted from the X-ray crystal structure of this molecule. When a good set of constraints was available for both short- and long-range distances, the crystal structure was regenerated nearly exactly. When some ambiguities, such as those expected in experimental information, are allowed, the protein conformation can be determined up to a few local deformations. These ambiguities are mainly associated with the low resolving power of the short-range information.

Aprotinin↗
PubMed1985

Response of rat small intestinal active aldohexose transport to elevation of mucosal cyclic AMP by forskolin and 3-isobutyl-1-methylxanthine in vitro.

The phosphodiesterase-inhibitor 3-isobutyl-1-methylxanthine (IBMX) was able to elevate rat small intestinal cyclic AMP levels to 300% of basal values. Active jejunal D-glucose transport was enhanced parallel to the rise of intracellular cyclic AMP levels to 140% of control values at 100 mumol/l IBMX. Transport parameters, as determined in a three compartment model in vitro using a dual label method, indicate increased 'uphill' glucose transport at the site of the brush border membrane, higher intracellular accumulation of the sugar, with unchanged passive permeabilities. Phlorizin-inhibited D-glucose transport and L-glucose transfer in the rat were not affected by the persisting cyclic AMP elevation produced by IBMX. Stimulating effects could also be demonstrated with D-galactose as a substrate. IBMX 100 mumol/l also increased active D-glucose as well as 3-O-methylglucose transport in mouse jejunum. Stimulatory effects on intestinal hexose transport and mucosal cyclic AMP levels were also found with the adenylate-cyclase activator forskolin. In the present study, forskolin effects on jejunal mucosal cyclic AMP levels were enhanced in the presence of 100 mumol/l IBMX, resulting in a 20-fold increase compared to controls at 20 mumol/l forskolin. The concentration response for the effect of forskolin in the presence of 100 mumol/l IBMX on D-glucose transport did not produce a significant increase compared to transport stimulation with IBMX alone. At higher concentrations of forskolin however, glucose transport decreased to levels well below the IBMX controls. The elevation of cellular cyclic AMP levels had no effects on passive permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1985

Forskolin-induced elevation of rat jejunal cyclic AMP levels and stimulation of active glucose transport in vitro.

The adenylate cyclase stimulator forskolin enhanced both mucosal cyclic AMP levels and D-aldohexose transport in rat jejunum in vitro in a concentration-dependent manner. With mucosal cyclic AMP elevated to 400% of basal values, active D-glucose transport was at 200% of control values. Transport parameters, as determined in a three compartment model using a dual label method, indicate a) increased "uphill" glucose transport at the brush border membrane with higher intracellular accumulation, b) unchanged serosal to mucosal glucose fluxes and passive permeabilities. Transport stimulating effects of forskolin were also present with D-galactose in the rat. In mouse jejunum active transport of D-glucose and 3-O-methylglucose was increased by forskolin 10 mumol/l. Phlorizin inhibited D-glucose transport as well as L-glucose transport in the rat were not changed by the persisting cyclic AMP elevation induced by forskolin. The results show a positive correlation of active intestinal hexose transport with a modest elevation of mucosal cyclic AMP. In accordance to current models of cyclic AMP-induced changes in intestinal fluid absorption, rat jejunal net fluid transport was reduced by 40% with 20 mumol/l forskolin.

Animals↗
PubMed1985

Visualization of the coronary microcirculation using digital image processing.

A system was constructed to allow direct visualization of the coronary microcirculation of a beating rat heart under a microscope. An electrocardiogram (EKG) triggered strobe is used on the video recording and display system to "stop" the action of the beating heart so the surface microvessels can be directly observed. Experimental results are recorded on videotape and played back for frame-by-frame analysis of the data using digital image extraction, image enhancement and edge detection. The digital image processing techniques are designed for multi-purpose applications using recorded video images.

Animals↗
PubMed1985

Renal transplantation in the older recipient.

From 1976 to 1983, 13 living related and 54 cadaver renal transplants were done in 62 patients more than 50 years old. Patients with no coronary or myocardial disease upon coronary angiography were selected preferentially for transplantation. Over-all 1-year patient and graft survival rates were 88 and 70 per cent, respectively. Among cadaver recipients graft survival was improved (p less than 0.001) when prophylactic antilymphoblast globulin was used. There were fewer steroid-related complications (p less than 0.001) in recipients managed with a low dose rather than a high dose maintenance prednisone regimen. With careful patient selection and a steroid-sparing immunosuppressive regimen, renal transplantation can be done safely in older recipients with no increased risk of death or graft loss.

Age Factors↗