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Biomedical subjects

K Hempel

Publications and source records attributed to K Hempel.

At least 19 recordsLinked to original sources
PubMed1995

Mutant frequency at the H-2K class 1 and HPRT genes in T lymphocytes from the X-ray-exposed mouse.

The frequency of H-2Kk and HPRT-deficient T cells was measured in the H-2Kb, kDd,k genotype mouse 8-10 weeks after X-ray exposure at doses up to 6 Gy to compare the mutant frequency (MF) of an autosomal gene with that of an X-chromosomal gene. H-2K mutants were enriched by magnetic cell separation (MACS) using the H-2Kk-specific monoclonal antibody H100.5/28 and were isolated by limiting dilution cloning. Finally, the mutant phenotype was verified by flow cytometric analysis in a representative number of clones. The frequency of HPRT-deficient T cells rises from 2.5 x 10(-6) at 0 Gy to a maximum of 1.13 x 10(-4) at 4 Gy, and decreases to 2.9 x 10(-5) at 6 Gy. The H-2K- MF in the non-irradiated mouse was 8.4 x 10(-7). It increases with dose to a maximum of 8.1 x 10(-6) at 4 Gy and declines to 3.3 x 10(-6) at 6 Gy. The H-2K- MF measured depends on the monoclonal antibody used for the isolation of mutants. In a pilot study with another H-2Kk-specific monoclonal antibody (11.4.1), the spontaneous MF was four times higher than in experiments with the H100.5/28 monoclonal antibody. The expression of other class 1 antigens was investigated in H-2K- clones. The H-2Dd antigen had also disappeared in six of 41 clones from irradiated animals. This gene is situated at a distance of 1500 kb from the K-locus. The H-2Kb antigen was present in every investigated clone. In the discussion a model is presented that explains the shape of the dose-response curve of MF by selection against mutants in vivo systems under homeostasis. The results of the present investigation indicate that observed X-ray mutagenicity depends on many factors and that several genes have to be explored before reliable risk estimates are possible.

Animals↗
PubMed1995

[Ambulatory surgery--definition, socioeconomic and legal aspects].

One of the most important intentions of GSG 1992 is the favourization of traditional ambulatory surgery by legislative measures. However in general surgery a much higher potential for a significant reduction in cases of classical hospitalization and thus concomitant substantial financial savings lies in short-stay eg. one-day/one-night procedures. At present methods of laparoscopic cholecystectomy, thyroid surgery and herniorrhaphy-together about 50% of common hospital patients-are developed enough to be practiced safely under this strategy. In the future further suitable techniques could evolve from minor access surgical concepts.

Ambulatory Surgical Procedures↗
PubMed1994

Arthroscopy of the knee without pathological findings.

From 1983 to 1990, 82 knee arthroscopies (8.2%) carried out in our patients found nothing pathological. Sixty-four percent of these patients were active in sports, but trauma was noted in 32% of the cases only. Football and other ball games, skiing, and track and field athletics were the main causes. Twenty-six percent of the patients had undergone previous surgery in the affected knee. At a mean of 4.6 years postoperatively, clinical and radiological re-assessment was conducted so as to compare our pre- and intraoperative findings with the further course of events. We found that 48.2% of the patients were symptom-free after the diagnostic arthroscopy, 37.5% had persistent discomfort and 14.3% had a recurrence of discomfort after 6 months to 2 years. The objective measurement score (Zarins Rowe score), at 47.5 out of 50 points, was better than the subjective score, at 40 out of 50 points. Our diagnoses had to be changed retrospectively: meniscal lesions were diagnosed too frequently, while chondropathia patellae and instability were often missed. Additionally, complaints could be related to abnormal axis, limited range of motion of the hip or knee, leg length inequality and hypermobility. Being unable to verify a presumed intra-articular lesion arthroscopically is frustrating for both doctor and patient. Our data suggest that meniscal signs should be looked at more critically and emphasise the need for a complete evaluation of the whole locomotor system.

Adolescent↗
PubMed1994

Dose and dose-rate dependence of the frequency of HPRT deficient T lymphocytes in the spleen of the 137Cs gamma-irradiated mouse.

The frequency of hypoxanthine phosphoribosyl transferase (HPRT) deficient splenic T lymphocytes was measured in the 137Cs gamma-irradiated mouse by the T cell cloning method. Doses from 0.3 to 6 Gy were applied at the dose-rates 0.5 Gy/min, 1 Gy/day and 1 Gy/week. Mutants were determined 8-10 and 30-40 weeks after the end of exposure. Radiation-induced mutant frequency (MFi) was calculated by subtracting the age corrected spontaneous mutant frequency (MFsp) from total mutant frequency (MF) found in irradiated animals. Data were fitted to linear and linear-quadratic dose-response models. MFi depended markedly on dose, dose-rate and time after exposure. When mutants were determined 8-10 weeks after acute irradiation (0.5 Gy/min) the dose-effect curve fitted the linear-quadratic equation MFi = 6.9 x 10(-6) Gy + 1.2 x 10(-6) Gy2, whereas in low dose-rate experiments (1 Gy/day, 1 Gy/week) the dose-effect curves were linear. The slope of the linear regression was about 3 x 10(-6). When low dose-rate-irradiated animals were killed 30-40 weeks after irradiation, MFi was about one-third of that observed after 8 weeks. The dose dose-rate effectiveness factor (DDREF) for radiation mutagenicity was calculated in animals that had been exposed 8-10 weeks previously. For doses < 2 Gy the reduction in effectiveness was about 1.5 when the irradiation dose-rate was < or = 1 Gy/day. For higher doses DDREF was 3-5.

Animals↗
PubMed1994

[Characterization of 24-hour survival rate and duration of survival of hydroxyethyl starch cryopreserved erythrocytes after autologous transfusion in the dog].

BACKGROUND: Cryopreservation of erythrocytes using hydroxyethyl starch (HES) as cryoprotecting additive could result in a nearly unlimited storage stability of preserved red cells. In addition, it would allow its immediate use for transfusion. In order to assess the therapeutic efficacy of erythrocytes cryopreserved with HES, their 24-hour post-transfusion survival and long-term survival was evaluated. MATERIALS AND METHODS: The experiments were carried out with dog erythrocytes as an animal model for human erythrocytes. To each of 6 German shepherd dogs a 15-ml sample of erythrocyte suspension, labeled with 51Cr (25 microCi) after thawing, was autologously injected. Caused by hemolysis 29% of the formerly cryopreserved erythrocytes have not been labeled. To each of 6 control animals 15 ml of a suspension of freshly drawn and 51Cr-labeled erythrocytes was injected. The 51Cr radioactivity in later taken blood samples was a measure for the number of injected erythrocytes having remained in the circulation until the moment of blood withdrawal. The effect of cryopreservation was assessed by comparison of the test group with the control group. RESULTS: In both groups 30% of the applied cells left the circulation within 30 min. This was effected by pharmacological enlargement of the dogs' spleen and not by hemolysis of the erythrocytes. After the first 24 h all of the cryopreserved labeled erythrocytes had survived to the same amount (> 95%) as the labeled fresh red cells. Between 12 h and 20 days after injection, in both groups the 51Cr activity decreased exponentially by 4.8 and 4.5%/d. This difference was not significant. The area under the curve amounted to 1253 and 1257% d, respectively. CONCLUSIONS: There exists a subpopulation of red cells that is destroyed by freezing stress. As a result the freed stroma would be a serious transfusion risk. All erythrocytes having survived the cryopreservation procedure resemble the fresh erythrocytes with regard to the in-vivo survival; their therapeutic efficacy is not impaired. In the context of in-vitro results with human erythrocytes it can be expected that at the present developmental state of the cryopreservation procedure at least 93% of the human erythrocytes cryopreserved with HES have a normal 24-hour and long-term post-transfusion survival.

Animals↗
PubMed1993

Rapid alterations in cAMP accumulation in brain nuclei of rats following microinjections of vasoactive intestinal polypeptide (VIP) into the lateral ventricle.

The in vivo effect of exogenous vasoactive intestinal polypeptide (VIP) on the accumulation of cAMP in 21 microdissected brain nuclei was investigated 3 and 7 min after intraventricular injections in rats. VIP elicited significant (up to 20-fold) increases in cAMP levels. This effect is region specific varying considerably among the brain regions investigated. VIP dramatically increased the cAMP content of the lateral septal nucleus, several hypothalamic nuclei, the habenula, the midbrain central gray and the locus coeruleus. Smaller increases were observed elsewhere including some VIP-rich brain areas such as the cerebral cortex and the hippocampus.

Animals↗
PubMed1991

Experimental allergic encephalomyelitis-prophylactic and therapeutic treatment with the cyclooxygenase inhibitor piroxicam (Feldene).

Prophylactic administration of Piroxicam (Feldene), a reversible inhibitor of prostaglandin biosynthesis, significantly reduced the occurrence of paralytic signs and the amount of antibodies against myelin basic protein in the model of mild acute experimental allergic encephalomyelitis in the Lewis rat. Mononuclear infiltration of the central nervous system remained unaffected. A therapeutic intervention with piroxicam, however, increased paresis and CNS pathology. Immunohistochemical studies revealed an increased proportion of ED1-positive macrophages and monocytes in the infiltrates of the spinal cord in animals treated with piroxicam. Possible reasons for the different effects of the prophylactic and therapeutic treatment are discussed in the study.

Administration, Oral↗