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Biomedical subjects

H Hommel

Publications and source records attributed to H Hommel.

At least 19 recordsLinked to original sources
PubMed2004

Formation of weak polyelectrolyte multilayers studied by spin labeling.

Multilayers of alternately adsorbing poly(allylamine) (PAH) and poly(acrylic acid) (PAA) of opposite charges on silica have been studied by the spin labeling technique, as a function of pH. The two polyelectrolytes have been labeled independently by a nitroxide free radical. Its electron paramagnetic resonance spectrum is mainly sensitive to the local Brownian motion and shows lines typical of two different environments, namely, loops protruding in solution with a fast motion and trains adsorbed on the solid with a hindered motion. These two parts have been evaluated for each of the polymer layers separately, and the thickness of the coatings has been described more precisely by characterizing the four contributions existing, for example, for a bilayer. Complexation is demonstrated by the loss of loops and tails belonging to the first polyelectrolyte. The overall picture emerging from the data is explained in terms of compensation of charges and entropy of confinement.

Journal Article↗
PubMed2000

[Acetabular component implantation in coxarthrosis due to dysplasia after high congenital hip dislocation].

A total of 71 (25-110) months after primary total hip replacement, 17 patients with high congenital hip dislocation and false iliac acetabulum were clinically and radiologically assessed. Twenty-one threaded cups were placed, 16 at the site of the true acetabulum, one at the site of the acetabular rim and four at the site of the false acetabulum. The Harris hip score increased from 37.1 (20.2-55.5) points preoperatively to 84.7 (67.4-97.7) points postoperatively. Radiologically there were no signs of cup migration. It can be concluded that even complicated dysplastic hips can be treated successfully by total hip replacement, without prior ileofemoral distraction or additional acetabular augmentation.

Acetabulum↗
PubMed1999

Molecular Conformation and Mobility of Polyamines Adsorbed on Silica Studied by Spin Labeling.

Poly(ethyleneimine) and poly(4-vinylpyridine) chains adsorbed on Nucleosil silica have been randomly labeled with nitroxide free radicals. The EPR signal is very sensitive to the molecular Brownian motion of the segments and shows generally at least two different environments: trains adsorbed on the surface with a restricted mobility, and loops and tails protruding into the solution with a fast motion. The rotational correlation times and the relative fraction of each population are given as functions of the coverage achieved and of the specific surface area of the silica for the samples in contact with methanol and sometimes water. The overall picture is consistent with a diffuse layer for the PEI and a more compact one with some heterogeneities for the P4VP. Copyright 1999 Academic Press.

Journal Article↗
PubMed1996

High-resolution 29Si solid-state NMR study of silicon functionality distribution on the surface of silicas.

29Si solid-state NMR allows us to distinguish silicon atoms involved in siloxane bridges (Q4), single silanol (Q3) and geminal silanol groups (Q2) on the surface of silica. The relative proportions of each species can be obtained by Magic Angle Spinning (MAS) associated with 1H-->29Si crosspolarization (CP/MAS). This preliminary study deals with the silicon functionality of MCM-41, a purely siliceous, amorphous and mesoporous silica. From the 29Si spectra the relative proportions are estimated to be 3.7% Q2 27.3% Q3 and 69.0% Q4, while the ratio Q2/Q2 + Q3) is 0.12. These results are found to be in perfect agreement with a binomial probability distribution of sites.

Isotopes↗
PubMed1982

The influence of selective pancreatic denervation on plasma insulin and glucose tolerance in dogs.

The mechanism of reflex plasma insulin responses after oral stimulation and the influence of autonomic control on glucose- and meal -induced insulin secretion needs to be elucidated. Dogs with chronic pancreatic fistulas were studied two months after selective pancreatic denervation or bilateral truncal vagotomy and compared with fistulated controls. The normal glucose- and amino acid-independent insulinogenic reflex after an oral glucose load or after a meal was inhibited in the experimental groups. Glucose-related insulin secretion (oral or intravenous loads) and glucose tolerance were clearly reduced after vagotomy, but only partly diminished in the denervated animals. The plasma insulin increase after meat ingestion was inhibited in both experimental groups. It is concluded that the B-cells work under integrated tonic control of both the vagal and the sympathetic systems. Independent of this control, a vago-vagal insulinogenic reflex is initiated by enteric stimuli. These two mechanisms might be considered as part of the gastroentero-pancreatic axis in a broader sense.

Animals↗
PubMed1979

[Triplet pregnancy with papyraceous foetuses (author's transl)].

Reported is the case of a primigravida, 22 years of age, with a triplet pregnancy. Two of the three foetuses were papyraceous. One case of this kind is related to 32,800 deliveries. An attempt was made towards aetiopathogenetic elucidation of the phenomenon.

Adult↗
PubMed1978

[Vagotomy and exocrine pancreatic secretion (author's transl)].

In dogs supplied with chronic pancreatic fistulas, there is no change of the basal exocrine secretion of volume three weeks after a bilateral truncular vagotomy. The normal initial reflex secretion during meal ingestion or glucose loading are abolished. On the whole, the secretory activity is reduced by about 50% after feeding. Secretions of volume and of enzyme protein are inhibited to the same extent, but that of bicarbonate is more strongly influenced. After vagotomy the inhibitory influence on all secretions of a rabidly produced hyperglycemia is reinforced. In pancreatic juice there is immunocreactive insulin activity (less than 1% fo the daily secreted amount). Insulin secreted in pancreatic juice after feeding is strongly reduced after vagotomy. This is the best reproducible proof of an influence on the exocrine pancreatic function of vagotomy.

Administration, Oral↗
PubMed1978

Pancreatic and hepatic balances of endogenous insulin and of glucose in the anaesthetized dog during primed and non-primed infusions of glucose and of mannitol.

Simultaneous monitoring of pancreatic and hepatic blood flows and serial analyses of blood glucose and immunoreactive insulin activity in arterial, portal, intestinal and hepatic venous blood were performed in anaesthetized laparotomized dogs. Based on these measurements, the rates of pancreatic insulin secretion, of hepatic insulin uptake and the hepatic glucose balance were computed. Under basal conditions pancreatic output was about 40% of the total hepatic insulin input. 30% of hepatic insulin inflow were actually taken up in the liver. During a primed i.v. glucose infusion (steady blood glucose concentration about 330 mg/100 ml) pancreatic and hepatic blood flows increase rapidly and the insulin secretion exhibits a biphasic pattern. The relative part of hepatic insulin inflow taken up in the liver remained unchanged. A non-primed i.v. glucose infusion provoked a slow increase of blood flow and a rapid but monophasic increase of insulin release. Under these conditions the relative hepatic insulin uptake was transiently increased. During both loads hepatic glucose balance switched from release to uptake. However the non-primed infusion was more effective. When pancreatic and hepatic blood flows were increased without any blood glucose alteration by an infusion of mannitol, insulin secretion did not change; hepatic uptake of insulin decreased, but hepatic glucose output was clearly reduced. A correlation between the rates of insulin secretion, of hepatic insulin inflow and of insulin uptake was observed under all conditions. However, the hepatic glucose balance was correlated to the inflow of insulin or glucose and to the hepatic insulin uptake under certain conditions in individual experiments only.

Animals↗
PubMed1977

[The effect of Suisynchron on the glucose tolerance and the plasma insulin in bitches].

Suisynchron, a derivative of bisthio-urea commonly used for oestric synchronisation, was applied to nine female Alsatians over 21 days. All animals received intravenous glucose injections before ten, and 21 days from the beginning of treatment as well as 21, and 84 days after the end of treatment. The glucose-stimulated plasma insulin levels were significantly reduced during Suisynchron treatment and 21 days after the end of treatment. Both glucose tolerance and response of free fatty acids remained unaffected. This phenomenon might be attributable to a stimulated hepatic insulin degradation, to a biguanid-like effect on "peripheral" glucose turnover, or to an inhibited secretion of hormonal insulin antagonists of the anterior lobe of the pituitary gland. However, the long persistence of the Suisynchron action after interruption of treatment, could not be explained by any of these effects.

Animals↗
PubMed1976

The effect of meal feeding and of sham-feeding on insulin secretion in dogs.

After feeding intact conscious dogs 1000 g mashed meat, peripheral venous immunoreactive insulin activity (IRI) increases before any enhancement of amino nitrogen concentration. This course of IRI is paralleled by a decrease of free fatty acids. Meal feeding in dogs, whose pancreatic juice is completely diverted from the gut by a fistula, is followed by a similar IRI increase without a distinct enhancement of amino nitrogen. In oesophagus fistula dogs, sham-feeding meat in 9 out of 15 experiments results in a considerable early IRI increase which is correlated with a small but a significant decrease of blood glucose and free fatty acid concentrations. In these tests there was no amino nitrogen alteration either.

Amino Acids↗
PubMed1976

Pancreatic blood flow in conscious dogs after oral administration of glucose.

Dogs with electromagnetic flowprobe implanted around the superior pancreaticoduodenal artery and with an hydraulic occluder implanted upstream from the flowprobe were examined between the 3rd and the 8th postoperative day. During an oral glucose load, blood flow increased from the beginning of administration to about 25 minutes, but not when blood glucose and plasma IRI exhibit their maxima. The rise of pancreatic blood flow is assumed to be produced by reflexes similar to those stimulating insulin secretion and exocrine pancreatic function during the early phase of an oral glucose load.

Administration, Oral↗
PubMed1976

[Evidence of pseudoisocyanine--positive endocrine cells in the gastric mucosa of the dog].

The tunica mucosa of the stomach and the other parts of the intestine (duodenum, jejunum, ileum colon) of the dog has been investigated in order t to demonstrate insulin producing cells. By means of thepseudoisocyanine-reaction it was possible to visualize in the lamina epithelialis of the stomach singular cells containing metachromatically reacting granules. It was possible to distinguish these cells from mast cells localised outside of the lamina epithelialis of the tunica mucosa. The value of this observation is given by the fact that until now hormone producing cells could be demonstrated in the laimina epithelialis of stomach and intestine of mammalia with exception of insulin-producing cells.

Animals↗
PubMed1976

[Influence of vagotomy on glucose tolerance and on the responses of plasma insulin and exocrine pancreatic function followed glucose load or food ingestion in dogs].

A part of the intrapancreatic nerve fibres of dogs show 1-2 months after bilateral truncal vagotomy a decay of the medullary sheath; in addition, the histochemically demonstrable insulin content of the B-cells is reduced. These animals do no longer react to oral glucose administration or feeding a meat meal with a reflectoric early rise of plasma insulin concentration and of exocrine functional parameters (all the animals were bearing exocrine pancreas fistulas). The glucose tolerance and and the decrease of free fatty acids in serum were restricted. Also, the content of bicarbonate and protein in the pancreatic juice and the insulin secretion of vagotomized animals are strongly reduced in the subsequent test phase (up to 120 min) following oral or i.v. glucose administration and after feeding meat. The inhibition of exocrine volume secretion following i.v. glucose administration was enhanced by the intervention. The findings confirm the involvement of the N. vagus in the mechanisms of the enteroinsular axis that becomes active together with exocrine gastro- and duodenopancreatic reflexes to any kind of physiological enteral stimulation.

Animal Feed↗
PubMed1976

The mechanism of insulin secretion after oral glucose administration. VII. Exocrine pancreatic function and plasma-IRI in dogs with chronic pancreatic fistulas.

During an intravenous glucose test, conscious dogs with exocrine pancreatic fistulas showed a reduction in the secretions of water, protein and of bicarbonate. This reduction is related to hyperglycemia and to IRI increase in the peripheral venous blood. After oral administration of glucose, however, a biphasic stimulation of the exocrine function was observed. During the first 15 minutes when insulin secretion increases independently of the blood glucose increase, all exocrine pancreatic functions are transiently stimulated, too. A second peak of the exocrine secretions is to be observed when glucose absorption and insulin secretion exhibit their maximum.

Administration, Oral↗
PubMed1976

The mechanism of insulin secretion after oral glucose administration. VIII. Pancreatic juice insulin excretion after glucose loading and meal ingestion in normal and vagotomized dogs.

On pancreatic fistula dogs, in the pancreatic juice, immunoreactive insulin has been identified. Insulin excretion is shown to be inhibited by an intravenous glucose load and to be stimulated in a biphasic manner by an oral glucose load or by ingestion of mashed meat. Insulin excretion is reduced 2 months after bilateral truncular vagotomy and the reaction to both oral stimuli is abolished. -- There is no statistical correlation between pancreatic juice insulin and blood glucose, plasma IRI, or plasma amino nitrogen concentrations. Single extrainsular B-cells shown by histologic examination are suggested to be the source of pancreatic juice insulin. Compared to insulin secreted into the portal blood flow, insulin in the pancreatic juice amounts to only 0.1--0.2% of the daily secretory rate of the islets of Langerhans.

Administration, Oral↗
PubMed1975

Dynamics of canine pancreatic blood flow and of insulin secretion during an intravenous glucose load.

Blood flow through the superior pancreaticoduodenal artery of anaesthetized dogs increases immediately after an i.v. glucose load and parallels to glycemia, but not to insulin output. Flow of superior mesenteric, and femoral arteries as well as of portal vein are also enhanced after rapid i.v. injections of glucose or mannitol. Extent and duration of all flow increases are dose-dependent and strongly related to the alterations of arterial plasma osmolality (maximum increase 24 mosmoles/kg). Heart rate, mean arterial blood pressure, and hematocrit remain unchanged after the first test minute. There is a considerable decrease of peripheral vascular resistance in the circulatory regions investigated. Flow through aorta ascendens is augmented for a short time. Possible mechanisms of vasodilatation are reflexes produced by osmoreceptors and/or local effects of osmolality on the tonus of vascular muscle. Within the physiological range pancreatic perfusion does not determine the amount of insulin released.

Animals↗
PubMed1975

Estimation of pancreatic IRI output rate and its relations to glucose tolerance in normal anasthetized dogs.

The pancreaticoduodenal and portal venous blood flows were recorded electromagnetically in anaesthetized dogs. Blood glucose and IRI were measured in the arterial, portal, and peripheral venous as well as in the intestinal venous blood. By a mathematical model the actual net IRI output of the whole pancreas was estimated. Under basal conditions it is 10.2 +/- 2.4 mU/min (n = 30; 26 kg mean body wt.). After i.v. glucose injection, IRI output is rapidly enhanced. The biphasic nature of this reaction was unequivocally demonstrated by consideration of the ratio IRI output : blood glucose. Pancreaticoduodenal blood flow increases transiently in relation to the increased blood glucose concentration. The IRI secretion rate is well correlated with the blood glucose concentration and to the amounts of glucose or of blood reaching the whole pancreas. It is also correlated with the portal IRI Concentration. The overall peripheral venous or arterial IRI concentrations are correlated with the IRI secretion rate, but not in all individual experiments. The different phases of IRI output (basal rate, stimulated output 1-10 min and 10-60 min) show no influence on each other, nor are they correlated with the peripheral IRI concentration area. Basal IRI output is negatively correlated with the glucose assimilation constants. These constants or the peripheral BG areas, however, are independent of the stimulated IRI output rate. However, both the assimilation constants and the peripheral BG areas are related to the peripheral IRI concentration areas. Hepatic uptake of insulin and dynamics of pancreatic blood flow seem to contribute considerably to the estimated correlation pattern.

Animals↗