Showing papers by "Katholieke Universiteit Leuven published in 1976"

The Purification and Characterisation of the Human-Serum Binding Protein for the 25-Hydroxycholecalciferol (Transcalciferin) Identity with Group-Specific Component

Abstract: The binding protein for 25-hydroxyvitamin D3 has been isolated from human serum by monitoring the recovery of 3H-labeled 25-hydroxyvitamin D3. After a 500-fold purification a pure protein was obtained as judged from the constant specific activity (ratio of absorbance versus radioactivity) on agarose and DEAE-Sephadex chromatography and on the presence of a single band on both cellulose acetate and polyacrylamide gel electrophoresis. The molecular weight of the purified protein was measured by gel filtration on agarose (56000), Sephadex G-75 (58000) and dodecylsulfate-polyacrylamide gel electrophoresis (56000). On sucrose gradient ultracentrifugation a sedimentation coefficient of 4.1 S was found. The isoelectric point was 4.89 S on isoelectric focusing. The stability of the protein at 60 degrees C was enhanced by the presence of excess 25-hydroxyvitamin D3. On tandem crossed immunoelectrophoresis the purified binding protein was found to be identical to the one present in whole serum. The activity of the isolated protein was demonstrated by a Ka at 4 degrees C of 1.2 X 10(10) l-mol-1. A binding capacity of 0.8 binding site/molecule was measured on a Sephadex G-25 column. During immunological studies with this protein it became evident that the binding protein is identical with another serum protein known as group-specific component (Gc). In analogy to other serum binding proteins we propose to call this group-specific component/25-hydroxyvitamin-D3-binding protein transcalciferin.

Asymmetry in bicycle ergometer pedalling.

Abstract: The effects of changes in speed and resistance setting on the bilateral symmetry of work output on the bicycle ergometer were studied. The cranks of a Monarch bicycle ergometer were instrumented with foil strain gauges and the bridge outputs were integrated on-line and analyzed by a program running in a Hewlett Packard 2115A computer. Twenty male subjects performed three thirty-second trials at each of nine speed and resistance combinations. Indices of asymmetry from 66-178 were found using kicking dominance (n = 20) and 56-135 using a strength dominance classification (n = 13). Day to day reliability of the index of asymmetry was found to be only 0.47; within day reliability was 0.87 for day one and 0.79 for day two. No significant effects for speed or resistance changes were shown on either day for the strength dominant subjects. When kicking dominance was considered main effects were encountered on both days for speed although there was no clear directional trend. The findings of these experiments have important implications for studies where measurements are made on the lower extremity during cycle ergometer exercise, and for competitive cyclists engaged in endurance competition.

Sulfated Bile Acids in Germ‐Free and Conventional Mice

Abstract: Sulfated and non-sulfated bile acids were determined in the intestines and in the feces of 7-month-old germ-free and conventional male mice. 1. The bile acid pools in the gall bladder and small intestine were 21.13 mg/100g body weight in germ-free and 11.50 mg in conventional mice. The bile acid pools in the cecum and large intestine of germ-free mice were 3.03 mg/100 g body weight as compared to 1.24 mg in conventional mice. Fecal bile acid excretion was 2.93 mg and 4.12 mg/100 g body weight in 24 h in germ-free and conventional mice respectively. 2. The major bile acids from germ-free mice were cholic acid, alpha-muricholic acid and beta-muricholic acid. Small amounts of chenodeoxycholic and allocholic acid were also present. In addition to these primary bile acids the following secondary bile acids were identified in conventional mice: lithocholic, deoxycholic and omega-muricholic acid. 3. In both germ-free and conventional animals significant amounts of chenodeoxycholic and cholic acid were present as the 7-monosulfate esters. The sulfate esters of these bile acids did not exceed 2% of the total bile acids in the small intestine, but accounted for approximately 50% of the bile acids in the cecum and the large intestine. In contrast, the muricholic acids were nearly exclusively found in the non-sulfate fraction. 4. Alkaline hydrolysis without prior solvolysis of the sulfate esters resulted in loss of bile acids and production of artifacts. Hence, the bile acids of the mouse cannot be analysed by methods involving alkaline deconjugation unless a solvolysis step is included in the procedure.

Biotransformation and excretion of lorazepam in patients with chronic renal failure

Abstract: To evaluate the effect of end-stage renal insufficiency and haemodialysis on the elimination of lorazepam, single oral doses of the drug (2.5 mg) were administered to normal subjects and patients with chronic renal failure (CC(r) : less than 2 ml/min) in the interdialysis period and during haemodialysis. The concentration of lorazepam and its major metabolite, lorazepam-glucuronide, were assayed using electron capture g.l.c. Plasma half-life (T1/2) of unchanged lorazepam in the patient group (11.3 +/- 0.6 h) was not different from that obtained in normals (11.1 +/- 0.9 h). Only minor quantities of the unchanged drug could be recovered in the 24 h urine in both groups: 0.3% of the ingested dose in normals and trace amounts in the patient group. No unchanged lorazepam could be detected in the ultrafiltrate from the coil kidney. Since the lower sensitivity of the method is about 5 ng/ml, this would indicate the in vivo binding of the active drug to plasma proteins to be at least 70%. The effect of haemodialysis on lorazepam plasma T1/2 was also insignificant (9.4 +/- 1.0 h). Urinary excretion of lorazepam-glucuronide was found to be considerably decreased in chronic renal failure associated with accumulation of high concentrations of this conjugate in plasma during days after a single oral dose. The plasma T1/2 of this conjugate in normals was 20.7 +/- 2.1 h. Roughly 35% of this main metabolite's concentration in plasma was detected in the ultrafiltrate from the coil kidney indicating the dialyzability of this conjugate and that the extent of plasma protein binding of lorazepam-glucuronide in vivo was approximately 65%. The above results indicate that after a single oral dose (2.5 mg) the biotransformation of lorazepam to its glucuronide conjugate remains unaltered and that high concentrations of this metabolite accumulate in plasma in the presence of severe renal function impairment.

The differential impact of some soil loss factors on flow, runoff creep and rainwash

Abstract: The Hortonian model of runoff flow which had been thought to be applicable in arid areas has previously been shown not to be valid, notably in Israel, where inverse relations have been observed between slope angle, and runoff discharge and slope erosion. The paper discusses laboratory experiments on simulated slope conditions in a rather arid environment. It is shown by rain simulation on granite grus that infiltration capacity is a function of rainfall intensity, slope angle and runoff discharge. The infiltration capacity f can equal the rainfall intensity beyond a critical distance x(m) so that discharge becomes constant. Debris covers affect runoff hydraulics, especially on poorly cohesive soils, and both slow downslope and upslope movements which correspond to the process of so-called runoff creep can occur. Coarse debris and grass covers, as roughness factors, induce hydraulic discontinuities and activate local turbulent flow and slope erosion. Instead of being merely protective elements these factors tend to catalyze the slope wash, in comparison with naked surfaces, if the Reynolds number of the flow exceeds a certain critical value.

Effect of temperature and pressure on polymerisation equilibrium of neuronal microtubules

Abstract: MICROTUBULES are fibres, sometimes many micrometres long, present in all eukaryotic cells, formed by the reversible polymerisation of the protein tubulin. These fibres not only have a structural role, but the process of their assembly and disassembly itself controls several cell functions1.

A specific population of gonadotrophs purified from immature female rat pituitary

Abstract: When dispersed pituitary cells from 14-day-old female rats were sedimented in a bovine serum albumin gradient, a fraction was isolated which consisted of almost 90 percent of large cells that stained purple in the periodic acid-Schiff (PAS) reaction. Immunostaining indicated that over 85 percent of these PAS-purple cells were gonadotrophs containing both follicle stimulating and luteinizing hormone. Reproducible cell cultures could be obtained on poly-L-lysine coated dishes. As early as the second day in culture, the secretion of both follicle stimulating and luteinizing hormone was highly stimulated by luteinizing hormone-releasing hormone. The effect of FSH was as marked as that on LH. The data suggest that the isolated gonadotrophs are a specific functional subtype.

Fate of thiazolidine ring during fragmentation of penicillin by exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R61

Abstract: LIKE various β-lactamases, acylases and esterases1, the exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R61 degrades benzylpenicillin and other β-lactam antibiotics2-4. The R61 enzyme, however, markedly differs from the other penicillin-degrading enzymes in causing fragmentation of the penicillin nucleus. By using 8-14C-benzylpenicillin (benzyl labelled) as substrate, one of the fragments produced was shown to be 14C-phenylacetylglycine5. The reaction with the R61 enzyme is also peculiar in that it is a slow process. This is because of the long half life of the stoichiometnc complex transitorily formed between the antibiotic and the enzyme. Thus, for example, the value of the half life for the complex formed with benzylpenicillin is 80 min in 10 mM phosphate buffer (pH 7.0) and at 37 °C. As breakdown of the complex proceeds, however, phenylacetylglycine (when benzylpenicillin is used as substrate) is released and the enzyme concomitantly recovers its ability to bind penicillin. We have now characterised the fragment (hereby designated as the Y product) arising from the thiazolidine ring of penicillin as a result of the fragmentation of the antibiotic molecule by the R61 enzyme.

Hypoxia increases potassium efflux from mammalian myocardium.

Abstract: Hypoxia with or without simultaneous depletion of extracellular glucose increases42K-efflux in cat and guinea-pig papillary muscles and bovine Purkinje fibres. The change observed in K efflux may be the result of an increase in K conductance at rest.

Action of nucleases on double-stranded RNA.

Abstract: Double-stranded RNAs from Penicillium chrysogenum virus have been treated with RNAse III, pancreatic RNAse A and RNAse T1 and the degradation of the RNAs has been studied under different conditions. It was found that only the two former enzymes cut across both strands, RNase T1 cannot cleave double strands. RNase III was shown to digest double-stranded RNA by a two step process: an initial phase of specific cleavage is followed by random degradation. In the first phase the enzyme exhibited a definite preference for some specific base pattern. Partial or complete degradation with pancreatic RNase A could also be achieved in media with high salt concentration provided that the enzyme: substrate ratio was increased together with the salt concentration. By combining different assay techniques, the process of degradation was followed from the early stages to complete digestion and the breakdown products were characterised. It is suggested that a structural change in the enzyme molecules enables them to act on double-stranded RNA. RNAse T1, being unable to cleave double strands, provides a useful tool for studying the secondary structure of RNA molecules. Treatment with different nucleases yielded some new information on the structure of different RNA species in Penicillium stoloniferum virus.

Synthesis of aroma components during the spontaneous fermentation of lambic and gueuze

Abstract: Lambic is a type of Belgian beer obtained by spontaneous fermentation of wort. The fermentation in casks takes almost two years, and after that period the beer may be re-fermented in bottles and is then called gueuze. To gain insight into the many microbiological transformations occurring during this process, a qualitative and quantitative study of several components formed over a two-year period was undertaken. It was found that lambic and gueuze are characterized by high contents of ethyl acetate, ethyl lactate, lactic acid and acetic acid. Two phases of fermentation may be distinguished: a primary phase lasting for about three months during which almost all the ethanol and higher alcohols are formed and a very long secondary phase during which lactic acid is formed first, followed by ethyl lactate. Some lower fatty acids, including all the acetic acid, are made at the very beginning of the first phase. An important part of the ethyl acetate is made during the first phase but the amounts increase slowly to high levels during the second phase. Unusually low amounts of isoamyl acetate are detected. Several components are above the reported threshold levels of taste and are thus probably involved in the genesis of the typical aroma of lambic and gueuze. These results will allow a further study of the relations between the components found and the microbial populations involved in the spontaneous fermentation inherent in the brewing of lambic and gueuze.