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Biomedical subjects

H Weber

Publications and source records attributed to H Weber.

At least 559 records · Page 31Linked to original sources
PubMed1977

New prospects for a prolonged functional life-span of artificial hip joints by using the material combination polyethylene/aluminium oxide ceramin/metal.

Investigations over the years have shown that the mirror-finished Al2O3 ceramic is a much more suitable frictional counterpart to ultrahigh molecular weight (UHMW) polyethylene than metal. Despite the extremely gread hardness difference between polyethylene and Al2O3 ceramic, a considerable lower wear rate is obtained for the polyethylene socked with this new low-friction material combination. The unexpectedly favorable tribological behavior of this ceramic material in contact with polyethylene may be attributed to the following factors: better values for corrosion resistance characteristics, wettability with liquids, surfact gloss, hardness, and scratch resistance of the ceramic material in comparison with those of the hitherto used metallic implant materials (AISI-316L steel or cast Co-Cr-Mo alloy). It appears that, by using this new combination of materials for the socket and the ball, it will be possible to prolong the service life of artificial hip joints considerably without having effecy any fundamental changes in the present design and implantation principle retaining the hitherto used anchorage shaft made of wrought Co-Ni-Cr-Mo-Ti alloy Protasul-10 of extremely high corrosion fatigue strength.

Alloys↗
PubMed1977

Double blind evaluation of extradural methyl prednisolone for herniated lumbar discs.

A double blind study was carried out in 51 patients suffering from lumbar root compression syndrome of 12 days to 36 weeks duration. All patients had signs, symptoms and radiological abnormalities related to a herniated lumbar disc. Each patient received an extradural injection of either 2 ml (80 mg) methyl prednisolone or 2 ml normal saline solution. Neurological examination and interview of the patients with the aid of a questionnaire before and after extradural injection failed to demonstrate any statistically significant difference in outcome between the two groups. At follow-up 14 +/- 6 months after extradural injection 58.3 per cent of the patients in the control group and 51.9 per cent of the patients in the treatment group had undergone surgical treatment with laminectomy. Our results indicate that a single extradural injection of methyl prednisolone (80 mg) is no more effective than a placebo injection in relieving chronic symptoms due to myelographically demonstrable lumbar disc herniation.

Clinical Trials as Topic↗
PubMed1977

Purification of a protein inhibitor of adenosine 3':5'-monophosphate-dependent protein kinase from bovine myocardium by a non-denaturing procedure.

The activities of adenosine 3':5'-monophosphate (cyclic AMP)-dependent protein kinase may be partially controlled by a ubiquitous acidic heat-stable protein which inhibits the phosphotransferase reaction by interaction with the catalytic subunit of protein kinase (Walsh, D.A. et al. (1971), J. Biol. Chem. 246, 1977-1985). Since reported purification of this inhibitor involved subjecting tissue extracts to denaturing conditions, its existence under physiological conditions remained uncertain. A protein inhibitor, molecular weight 22,500, has been isolated from bovine myocardium by methods that do not include exposure to extreme heat or acid precipitation. The activity of this acidic protein is destroyed by exposure to trypsin and is unaffected by treatment with neuraminidase, RNAse or DNAse.

Animals↗
PubMed1977

Inhibition of adenosine 3':5'-monophosphate-dependent protein kinase: comparison of a protein inhibitor with polyanions and substrate analogs.

The mechanism of inhibition of adenosine 3':5'-monophosphate (cyclic AMP)-dependent protein kinase was studied using a protein inhibitor isolated by a non-denaturing procedure from bovine heart. This protein inhibitor interacts with the catalytic subunit of protein kinase and binds to some substrates of the kinase. Protein kinase activity can also be inhibited by polyanions which, like the protein inhibitor, bind to basic substrates but do not bind to the catalytic subunit of protein kinase. Peptides such as L-lysyl-L-tyrosyl-L-threonine that resemble the phosphate accepting site of protein kinase substrates competitively inhibit phosphorylation of histone. Protein kinase activity can thus be inhibited in vitro by interaction of the protein inhibitor with substrates, and/or the catalytic subunit of the kinase, by competition of substrate analogs with "natural" substrates and by direct interaction of polyanions with basic protein substrates for the phosphotransferase reaction.

Animals↗
PubMed1976

The binding site for coat protein on bacteriophage Qbeta RNA.

The site of interaction of phage Qbeta coat protein with Qbeta RNA was determined by ribonuclease T1 degradation of complexes of coat protein and [32P]-RNA obtained by codialysis of the components from urea into buffer solutions. The degraded complexes were recovered by filtration through nitrocellulose filters, and bound [32P]RNA fragments were extracted and separated by polyacrylamide gel electrophoresis. Fingerprinting and further sequence analysis established that the three main fragments obtained (chain lengths 88, 71 and 27 nucleotides) all consist of sequences extending from the intercistronic region to the beginning of the replicase cistron. These results suggest that in the replication of Qbeta, as in the case of R17, coat protein acts as a translational repressor by binding to the ribosomal initiation site of the replicase cistron.

Base Sequence↗
PubMed1976

Enhanced end-organ responsiveness of the uremic kidney to the natriuretic factor.

In chronic renal disease, the addition of a fixed quantity of Na to the extracellular fluid (ECF) will evoke a natriuretic response per nephron which is inversely proportional to the glomerular filtration rate (GFR). One factor that could contribute to this "magnification" phenomenon is an increased sensitivity of residual nephrons to physiologic natriuretic forces. The present studies were designed to examine this possibility. Natriuretic urine fractions from uremic patients, infused into one renal artery of normal rats, produced a small but significant unilateral natriuresis. Infusion of the same fractions in identical amount into remnant kidneys of stage II nonuremic rats (i.e., rats with a contralateral normal kidney in situ) produced a natriuresis in the remnant kidney only which was equivalent to that observed in the normal kidneys. The i.v. infusion of natriuretic fractions into stage II rats produced comparable increments in the fractional excretion of sodium (FENa) bilaterally. However, when the natriuretic fractions were infused into remnant kidneys of stage III rats (no contralateral kidney), deltaFENa was significantly greater than in the foregoing groups. Because stage III rats have increased control values for FENa, baseline FENa was increased to an equivalent level in normal rats by unilateral renal denervation. Natriuretic factor was administered into the ipsilateral renal artery. Although the natriuretic response was increased, it was significantly less than in the stage III remnant kidneys. The data support the view that the uremic state per se is associated with an enhanced responsiveness of the residual nephrons to the natriuretic factor found in the urine (and blood) of uremic patients.

Animals↗
PubMed1976

Cyclic nucleotide metabolism in compensatory renal hypertrophy and neonatal kidney growth.

Cyclic nucleotide metabolism was investigated in growing kidneys of rats during compensatory hypertrophy and during neonatal development. After unilateral nephrectomy a mild and short-lasting decrease in cyclic 3':5" adenosine monophosphate (cAMP) was observed in the hypertrophying kidney. In contrast, cyclic 3':5' guanosine monophosphate (cGMP) showed a sharp decline to 20% of control at 15 min and a rapid rise to 200-300% above base-line at 1-72 hr. The alterations in renal tissue levels of cGMP were associated with parallel changes in the soluble, 100,000 X g supernatant guanylate cyclase activity [GTP pyrophosphate-lyase (cyclizing): EC 4.6.1.2]. No change was observed in total cGMP phosphodiesterase (3':5'-cyclic-nucleotide 5'-nucleotidohydrolase; EC 3.1.4.17). In the rapidly growing kidney of newborn rats cAMP levels were 983 +/- 65 and 833 +/- 42 pmol/g of kidney at 4 and 7 days after birth, and increased to adult levels (1518 +/- 57 pmol/g) at 21 days whereas cGMP levels were 59.8 +/- 6.8 and 92.5 +/- 13.9 pmol/g at 4 and 7 days and decreased to adult levels (36 +/- 1.5) at 21 days. The results indicate that compensatory renal hypertrophy and neonatal kidney growth are associated with changes in cAMP and cGMP metabolism.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1976

A study of the intrarenal recycling of urea in the rat with chronic experimental pyelonephritis.

The concentrating ability of the kidney was studied by clearance and micropuncture techniques and tissue slice analyses in normal rats with two intact kidneys (intact controls), normal rats with a solitary kidney (uninephrectomized controls), and uremic rats with a single pyelonephritic kidney. Urinary osmolality after water deprivation for 24 h and administration of antidiuretic hormone was 2,501+/-217 and 2,874+/-392 mosmol/kg H2O in intact and uninephrectomized control rats, respectively, and 929+/-130 mosmol/kg H2O in pyelonephritic rats (P less than 0.001 compared to each control group). Fractional water reabsorption and concentrating ability were significantly decreased in the pyelonephritic group, and, to achieve an equivalent fractional excretion of urea, a greater fractional excretion of water was required in the pyelonephritic rats than in the control rats. Whole animal glomerular filtration rate was 1.57+/-0.19 ml/min and 1.39+/-0.18 ml/min in intact and in uninephrectomized controls, respectively, and 0.30+/-0.07 ml/min in pyelonephritic rats (P less than 0.001 compared to each control group). Single nephron glomerular filtration rate was 35.6+/-3.8 nl/min in intact control rats and was significantly increased (P less than 0.05) in both uninephrectomized (88.0+/-10.8 nl/min) and pyelonephritic rats (71.5+/-14.4 nl/min). In all groups fractional water delivery and fractional sodium delivery were closely comparable at the end of the proximal convoluted tubule and at the beginning of the distal convoluted tubule. In contrast, fractional urea delivery out of the proximal tubule was greater in the intact control group (73+/-8%) than in either the uninephrectomized (52+/-2%) or the pyelonephritic group (53+/-3%) (P less than 0.005). Fractional urea delivery at the early part of the distal tubule increased significantly to 137+/-11% and 93+/-6% of the filtered load in intact control and uninephrectomized control rats, respectively (P less than 0.001 compared to the late proximal values of each group), but failed to increase significantly in pyelonephritic rats (65+/-13%), indicating interruption of the normal recycling of urea in the latter group. Analysis of tissue slices demonstrated a rising corticopapillary gradient for total tissue water solute concentration as well as for tissue water urea concentration in both groups of control rats. In contrast, the pyelonephritic animals exhibited no similar gradients from cortex to papilla. These data indicate that the pyelonephritic kidney fails to recycle urea and accumulate interstitial solute. The latter must inevitably lead to a concentrating defect.

Animals↗