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Biomedical subjects

H Leonhardt

Publications and source records attributed to H Leonhardt.

At least 73 records · Page 4Linked to original sources
PubMed1980

[Treatment of central retinal venous and arterial occlusion by isovolemic hemodilution (author's transl)].

(1) Ten patients (mean age 71) with fully developed central retinal venous occlusion were treated by isovolemic hemodilution over a period of four to six weeks. Hematocrit was lowered in steps to about 30% to improve retinal microcirculation. For two to four days, 500 ml whole blood were exchanged daily for about 250 ml hydroxyethyl starch and 250 ml plasma. The procedure was repeated every five to ten days whenever the hematocrit exceeded 35%. Visual acuity was considered to be improved when the patient could read at least two more lines on the test card. Four to six weeks after starting hemodilution therapy visual acuity had improved in seven patients, deteriorated in one, and was unchanged in two. In the follow-up study six months after treatment visual acuity, as compared to data before treatment, had improved in four patients, deteriorated in two and was unchanged in four. Three patients developed a neovascular glaucoma and had to undergo photocagulation treatment. (2) As expected, hemodilution failed to improve visual acuity in five patients who had had a complete central retinal arterial occlusion for more than four hours. (3) This is the first time that a beneficial effect of isovolemic hemodilution on visual acuity, probably mediated by an improvement in retinal blood flow, has been demonstrated in man. However, only in retinal tissue with at least minimal blood flow (venous but not arterial occlusion) can this method be effective. Except for severe anemia or thrombocytosis there are no absolute contraindications. No adverse side-effects were observed. To prevent neovascularization it is planned to use a combination of hemodilution and photocoagulation.

Aged↗
PubMed1979

[Effect of uric acid lowering drugs in low dosage in patients with hyperuricemia and hypertriglyceridemia in a randomized group study].

The serum uric acid lowering effects of 100 mg Allopurinol (A), 20 mg Benzbromarone (B) and the combination of both were tested in a randomized block-trial in 12 male patients suffering from hyperuricemia and hyperlipoproteinemia type IIb/IV. Therapy periods lasted 4 weeks each. Allopurinol lowered the uric acid concentrations from 7,54 mg/100 ml to 5,95 mg/100 ml, Benzbromarone from 7,54 mg/100 ml to 6,11 mg/100 ml and the combination from 7,54 mg/100 ml to 4,90 mg/100 ml, all three significantly. The difference between the effect of the combination drug and Allopurinol and Benzbromarone respectively was also significant. An additive effect of both components is evident. Serum creatinin concentration remained constant. Uric acid and creatinin excretion could not be evaluated because of failure of patient compliance in the collecting of urine.

Adult↗
PubMed1979

Influence of the adrenal cortex on allograft rejections in rats.

I. The bibliography about corticosteroid influence on immune response is briefly reviewed. Generally, it is admitted that corticosteroids are immunosuppressive when administered in large amounts. Divergent opinions are recalled. II. The aims of the experiments are summarized: A) Investigate on the influence of corticoids (given in just substitutive amounts) on skin allograft rejection. B) Investigate on possible interactions between adrenal cortex and thymus with this test. III. It was observed, that A) Adrenalectomy resulted in a significant delay of allograft rejection. B) This could be suppressed partially by administering aldosterone, corticosterone, and desoxycorticosterone and completely by administering at least two of these hormones. C) Cortisol had shown a minor inhibitory influence. D) There was no obvious difference between adrenalectomized and thymectomized rats and those adrenalectomized only. IV. These observations are replaced in the context of bibliography and their significance is discussed.

Adrenal Cortex↗
PubMed1979

[Influence of the thymus hormone on radioleucosis in mice].

A partially purified thymic extract has determined the development of leucosis in 10 thymectomized irradiated CC57Bl mice out of 25. The pure hormone isolated from the same extract prevented the development of leucosis in intact irradiated Mice. This seems to indicate the presence of a second active substance in the extract (enhancing the development of the leucosis).

Animals↗
PubMed1979

Influence of clofibrate on blood viscosity in primary hyperlipoproteinemia.

In patients with primary hyperlipoproteinemia (23 patients type II a and II b, 13 patients type IV), changes in lipoprotein concentrations (lipid fraction), fibrinogen concentrations, in kinematic serum and plasma viscosity (determined by means of a capillary viscosimeter) and changes in relative apparent viscosity at shear rate 46 s-1 and 115 s-1 (determined by means of a plate-cone-viscosimeter) were measured before and after a clofibrate therapy (2 X 1 g/day) lasting for 7 to 9 weeks. Serum and plasma viscosity was lowered significantly in both types II and IV. The apparent viscosity decreased at shear rate 46 s-1 in type IV, whereas it remained unchanged in type II. Moreover, there exists a qualitative correlation between changes in serum viscosity and changes in lipoprotein concentration. Fibrinogen concentration remained unaltered.

Blood Viscosity↗
PubMed1979

Demonstration of a somatostatin-like activity in retinal cells of the rat.

A somatostatin-like substance is demonstrated by light microscopic immunohistochemistry (PAP-method) in perikarya and cell processes of the retina of adult and infant rats. These perikarya are identified according to their size, arrangement and distribution. Each of the first two neuronal orders (receptors, bipolar cells, ganglionic cells) of the visual pathway can be associated with retinal cells reacting positively with anti-somatostatin. In the adult rat, perikarya and processes of (i) horizontal cells, (ii) amacrine cells and (iii) large neurons in the ganglionic layer are specifically labeled. The staining of middle-sized and small ganglion cells is probably caused by the close attachment of labeled fibers to non-reacting cells. Postnatally, the immunoreactive elements develop in parallel to the differentiation of the corresponding retinal layers. It is discussed whether the three types of retinal cells containing a somatostatin-like substance provide an inhibitory system to each of the two orders of retinal neurons.

Age Factors↗
PubMed1979

Amelioration of blood viscosity in sickle cell anemia by pentoxifylline. A case report.

An 18 year old female patient with homozygous sickle cell anemia (HbSS: HbS 65% and HbF 4.9%) has been suffering from painful hemolytic crises about once a week since her childhood. Under treatment with pentoxifylline (2.4 gm daily in three divided doses), the blood viscosity decreased from 6.7 to 4.9 cP (normal: 4.3 to 5.3 cP at shear rate 46/sec) and the erythrocyte filtration accelerated from 127 to 77 sec (normal: 30 to 49 sec). Though hemolysis could not be prevented by pentoxifylline, there was no further demand for analgesic medication even in the hemolytic state. By decreasing blood viscosity and improving microcirculation, pentoxifylline may prevent the vasoocclusive complications of sickle cell anemia.

Adolescent↗
PubMed1979

Hormonal influences on the secretion of the thymus.

The bibliography concerning the interaction of the thymus with other endocrines is summarized. The thymus, the lymph nodes and the spleen of Sprague-Dawley rats were extracted with the method of Bezssonoff and Comsa and the extracts fractionated with the method of Bernardi and Comsa. The animals were (1) normal, (2) adrenalectomized, (3) adrenalectomized and substituted with one or several corticosteroids, (4) adrenalectomized and thymectomized, (5) thyroidectomized, (6) thyroidectomized and substituted with thyroxine, (7 and 8) castrated (males or females), (9 and 10) castrates substituted with sexual hormones, (11) castrated and adrenalectomized, (12) castrated and thyroidectomized, (13) castrated, adrenalectomized and thyroidectomized, (14) hypophysectomized, and (15) hypophysectomized and substituted with one hypophyseal hormone. In the Bernardi-Comsa preparations hormone was determined by UV-spectrophotometry. Adrenalectomy resulted in a significant decrease of the hormone content of the thymus (which was still more attenuated by cortisol) and its increase in the lymph nodes and the spleen. Corticosterone and desoxycorticosterone increased the hormone content in all three tissues, whilst aldosterone increased it in the thymus and decreased it in the lymph nodes and the spleen. Thyroidectomy resulted in a significant decrease of the hormone in the thymus and its quasi-disappearance from the lymph nodes and the spleen. This was prevented by thyroxine therapy. Castration resulted in an increase of the hormone content in all three tissues. This was prevented by sexual hormone therapy. Hypophysectomy resulted in decrease of the hormone content in all three tissues. This was prevented by injections with growth hormone, corticotropin and thyrotrophin. These results were compared with those of histological examinations of thymus, lymph nodes and spleen in the corresponding experimental groups. The consistency was found satisfactory.

Adrenalectomy↗
PubMed1978

The functional and structural border between the CSF- and blood-milieu in the circumventricular organs (organum vasculosum laminae terminalis, subfornical organ, area postrema) of the rat.

The present study continues a previous investigation on the median eminence (EM) (Krisch et al., 1978). In rats with high levels of neurohormones (LHRH, vasopressin) a limited immunohistochemical labeling of perivascular tanycyte processes can be observed surrounding capillaries in the marginal region of the organum vasculosum laminae terminalis (OVLT) and in the inner part of the subfornical organ (SFO). This labeling extends from the perivascular space a short distance along the tanycyte processes. By conventional electron microscopy and by freeze-etching, tight junctions are demonstrated at a distance from the capillary lumen which corresponds to the borderline of the immunohistochemical labeling of perivascular tanycyte processes in light microscopic preparations. The tight junctions are arranged in several parallel and helical rows and correspond to those found in the median eminence. Consequently, the immunohistochemical labeling the OVLT and in the SFO marks the intercellular cleft. In the circumventricular organs the immunostaining labels the extension of the perivascular space characterized by the hemal milieu. The perivascular space is separated off by tight junctions from the CSF-milieu of the adjacent neuropil. Furthermore, the present study demonstrates tight junctions in the marginal region of the area postrema (AP) between the perivascular processes of the tanycytes.

Animals↗
PubMed1978

The functional and structural border of the neurohemal region of the median eminence.

In stressed rats the tanycytes of the ventrolateral wall of the third ventricle exhibit by light microscopic immunohistochemistry a positive staining for neurohormones which is distinctly limited to the distal perivascular end of the tanycyte process. Since by electron microscopic immuncytochemistry the tanycyte cytoplasm does not show any reaction product, the light microscopic reaction most likely results from a labeling of the intercellular space in the direct vicinity of the subendothelial cleft. Whether this subendothelial space is permeable to neurohormones was tested by injection of HRP1. In the region of the arcuate nucleus 30 min after intravenous application, the marker is affixed to the membranes of the perivascular tanycyte processes in the subendothelial cleft of capillaries possessing non-fenestrated endothelia. Occasionally, HRP penetrates for a short distance between the tanycytes. Then the labeling of the intercellular cleft ends abruptly. Here, several parallel ridges of tight junctions between the perivascular distal tanycyte processes are found by the freeze-etching technique. Since HRP cannot reach the subendothelial clefts of this region by passing through capillary walls due to the presence of a blood-brain barrier, it is suggested that the marker penetrates from the median eminence this far via the subendothelial extracellular space. It is prevented from spreading further by the tight junctions of the perivascular tanycyte endings. The same way may be taken by the neurohormones. Hence, a border area exists adjacent to the dorsolateral aspect of the neurohemal region of the median eminence where the tanycytes isolate the neuropil from the cerebrospinal fluid not only by their apical tight junctions, but also by basal tight junctions from the subendothelial cleft. This communicates with the perivascular space of the portal vessels.

Animals↗
PubMed1978

The rhombencephalic recess in the rat. A light and electron microscopic study.

The rhombencephalic recess, an ependymal organ, has been studied for the first time by light- and electron microscopy. It is situated mediosagitally on the floor of the rhomboid fossa at the level of the colliculus facialis. The recess and the superimposed tissue are built up by tanycytes, their apices being connected by tight junctions. HRP, injected into the c.s.f., does not penetrate into the intercellular clefts of the recess area. The recess area reveals a certain autonomy regarding its supply with arteries and capillaries. A blood-brain barrier exists, but shows slight leakage in circumscribed areas as a result of intense transendothelial vesicular transport. The organization of the recess area is compared with that of other ependymal organs, especially circumventricular organs.

Animals↗
PubMed1978

[Blood viscosity and red cell deformability in primary hyperlipoproteinemia (author's transl)].

In patients with primary hyperlipoproteinemia (types IIa, IV, IIb) we determined by means of a Wells-Brookfield plateconeviscometer and an Ubbelohde capillary-viscometer the serum-, plasma-, apparent and relative apparent blood viscosity as well as the red cell deformability with a filtration technique. All parameters were found to be significantly changed in comparison to those of a normolipidemic control-group: The viscosity values of type IIb showed the greatest increase and of type IIa the smallest, while the red cell deformability was reduced in all types to the same degree.

Blood Viscosity↗
PubMed1978

[Microrheological studies in healthy subjects. Effect of cigarette smoke and oral contraceptives on erythrocyte flexibility].

Erythrocyte flexibility was tested in 29 healthy subjects, using whole-blood filtration through membrane filters with 5 micron pores, special attention being given to cigarette smoking and oral contraceptives as risk factors. Red cell flexibility was significantly reduced in male smokers compared with non-smokers (P is less than 0.0001), and in all male and female smokers (P is less than 0.05) An influence of oral contraceptives to erythrocyte flexibility could not be found. Reduced erythrocyte flexibility in smokers as a factor contributing to an abnormal microcirculation and to the development of arterial occlusive disease is discussed.

Adolescent↗
PubMed1978

Paired vessels in the spinal cord of Rhesus monkey and cat.

In the spinal cord of the rhesus monkey and of the cat paired vessels near the central canal are described. These paired vessels, consisting of one artery and one vein, are enveloped by a common glial sheath. In some Virchow-Robin's spaces two arteries and two veins can be observed. The physiological significance of this morphological feature is briefly discussed.

Animals↗
PubMed1978

Viscosity of duodenal juice examined in patients with excretory pancreas insufficiency by the pancreocymin secretin test compared to a control group and patients with cholelithiasis.

The viscosity of duodenal juice obtained during the pancreocymin secretin test from patients with excretory pancreas insufficiency was significantly higher compared to the viscosity of duodenal secretions from a control group or from patients with gall bladder stones. Since the viscosity was inversely related to the total volume as well as the bicarbonate and trypsin concentrations, it is concluded that the increased viscosity is due to a reduction in the secretory activity of the pancreas. The viscosity measurements found for patients with cholelithiasis reflects merely the higher viscosity of the gall bladder bile.

Adult↗