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Biomedical subjects

H Lippert

Publications and source records attributed to H Lippert.

At least 271 records · Page 15Linked to original sources

[Biomechanics of human tendons: connection between stress relaxation and stress recovery (author's transl)].

108 tendons of the m. extensor hallucis longus were examined with a tensile testing machine within 36 h after death. The specimen were kept at a resting length of 20 mm. After the "steady state" was reached by cyclic loading, the tendons were stretched up to a maximum load of 18 kp, then deloaded to a certain level and after that the elongation was kept constant. At high loading level the tension of the tendon decreases with time (relaxation). At medium and low loading level the tension increases slightly (mechanical recovery). Between that two regions there is a certain load, where the tension will not change with time (isorheological point). The position of the isorheological point depends on the velocity of the elongation. At low velocity (2 mm/min) the isorheological point is situated at 70%, at high velocity (12 mm/min) at 60% of the maximum load. One will find the maximum relaxation, when no deloading occurs. The mechanical recovery, however, has its maximum at 5--25% of the maximum load. But when the tendon is totally deloaded, there seems to occur no recovery. The maximum relaxation is 5 to 6 times larger than the maximum recovery. Supposingly the relaxation- and recovery-processses will happen at the same time but with different intensity depending on the loading level. At least the relaxation-process consists of different relaxation components with different relaxation times. This will explain the phenomenon of a "secondary relaxation": After a long time of registration the recovery will turn into a slight relaxation.

Adolescent↗

[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↗

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↗

[Transplantation of isolated islets of Langerhans into the liver of diabetic dogs (author's transl)].

Isolated islets of Langerhans were transplanted through the portal vein in the liver of 8 diabetic dogs; In 4 dogs a homologous transplantation was performed and another group of four dogs received isolated islets from their sisters or brothers. In both groups, there was an immediate effect on the blood glucose level. After pancreatectomy and injection of Alloxan the blood glucose rose to between 350 and 420 mg per 100 ml and after islet implantation the blood glucose decreased between 80 to 160 mg per 100 ml. The iv GTT'S were after islet implantation clear better than in the diabetic control animals. These results could maintained in the recipients with homologues islets over a period of 6 to 8 weeks and in the other group of dogs over a period of 6 to 12 months. We were able to show, that the islet implantation in the liver of diabetic dogs did not disturb the microscopic architecture of the liver. No signs of portal hypertension, hepatic congestion and embolism were found.

Animals↗

[Biomechanical investigations on the parry fracture of the ulna (author's transl)].

108 ulnae from the cadavers of 50 men and 6 women were fractured in four positions with a tension testing machine with electronic measurement of force. Stress-strain-diagrams were registered, and the values of breaking load, breaking energy, breaking stress and ultimate deflection were correlated to the areas of cross sections of compacta and medulla. Breaking load and breaking energy decrease distally: medium breaking load in the upper portion of the ulna about 320 kp, in the lower portion about 100 kp; breaking energy in the upper portion about 65 kpcm, in the lower about 20 kpcm. Breaking stress is greatest in the middle portion of the ulna (19 kp/mm-2 in contrast to 11-14 kp/mm-2 near the joints). With increasing age the cross sections of the medulla increase significantly, but breaking load, breaking energy, breaking stress and area of cross section of the compacta decrease significantly. Ulnae from females are less resistant than those from males. Intact periosteum rises resistance to breaking and ultimate deflection. Experimental data agree with clinical observations.

Adult↗