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Biomedical subjects

K Hoffmann

Publications and source records attributed to K Hoffmann.

At least 271 records · Page 15Linked to original sources
PubMed1989

Effect of aminophylline on cisplatin nephrotoxicity in the rat.

1. The effect of the methylxanthine aminophylline on cisplatin (5 mg kg-1 i.v.)-induced acute renal failure was investigated in the rat. Renal function was measured 5 days after cisplatin administration. 2. Cisplatin caused a polyuric acute renal failure. The creatinine clearance was significantly reduced. 3. Aminophylline (24 mg kg-1 12h-1) ameliorated the cisplatin nephrotoxicity when administered during the maintenance phase of acute tubular necrosis. However, it had no effect when only administered prophylactically before the cisplatin application. 4. Enprofylline (20 mg kg-1 4h-1 with dose adjustment), a methylxanthine lacking adenosine receptor antagonism in comparison to aminophylline, had no protective effect on cisplatin nephrotoxicity. 5. Adenosine is a renal vasoconstrictor and decreases glomerular filtration rate. Endogenous adenosine in the kidney is formed by degradation of ATP and is thought to be involved in various forms of acute renal failure. The results suggest that adenosine may be involved in the haemodynamic changes in the kidney induced by cisplatin.

Acute Kidney Injury↗
PubMed1989

Different mechanisms of phase delays and phase advances of the circadian rhythm in rat pineal N-acetyltransferase activity.

The circadian rhythm in rat pineal N-acetyltransferase (NAT) activity, which drives the rhythm in melatonin production, is controlled by a pacemaker located in the suprachiasmatic nucleus of the hypothalamus. As the NAT rhythm has two well-defined phase markers--namely, the time of the evening activity rise and of the morning decline--it is suitable for studies of the entrainment of the pacemaker by environmental light. Phase delays of the NAT rhythm proceed more rapidly than phase advances. One day after a brief light pulse applied before midnight, or after a delay in evening lights-off, or a delay of a light-dark (LD) cycle, phase delays of the evening NAT rise result in almost corresponding delays of the morning NAT decline. Consequently, the NAT rhythm is phase-shifted, but its pattern does not change. One day after a brief light pulse applied past midnight, or after bringing forward morning lights-on, or after an advance of an LD cycle, the morning NAT decline is phase-advanced, but the evening rise is not phase-advanced at all or may even by phase-delayed. Consequently, the phase relationship between the evening NAT activity onset and the morning offset may be compressed considerably, and it may take several transient cycles before phase advances of the morning NAT decline are followed by corresponding advances of the evening NAT rise. Due to the phase-delaying effect of evening light on the NAT rise and to the phase-advancing effect of morning light on the NAT decline, the phase relationship between the NAT rise and the decline is compressed on long days and decompressed on short days. Different phase shifts of the evening NAT rise and of the morning decline, even in opposite directions, are consistent with the hypothesis of a complex, two-component (evening-morning, or E-M) pacemaker controlling the NAT rhythm. As the E-M phase relationship determines duration of the high night melatonin production, and the duration of the nocturnal melatonin pulse may convey information on daylength, the data are consistent with the internal coincidence model for photoperiodic time measurement.

Animals↗
PubMed1989

[Student survey on the topic of AIDS in the city of Bochum April 1988].

70% of the pupils of public schools in the city of Bochum who were questioned in an opinion poll conducted by the Public Health Office were interested in knowing more about AIDS. More than 80% of the boys and girls approached during the questioning know the causative virus and how persons can get infected. It is also relatively well known how a person can protect himself or herself against HIV infection by meaningful measures. However, it is very surprising that only about 24% of all questioned pupils believe that anybody without exception can be involved. The school, TV and magazines or newspapers are named as principal sources of information. About 40% of all questioned persons are very afraid or afraid of AIDS. About 50% of the schoolgirls and schoolboys approached during the poll wanted to know how they should act when coming into contact with AIDS patients. Schoolgirls and schoolboys prefer to discuss problems of prevention and subjects like AIDS with their girlfriend or boyfriend or at the most with their mother. Almost 80% of all persons questioned believed that they could at least do something, albeit little, to prevent AIDS from spreading further by their own behaviour. The following column histograms show some of the exact percentage distributions.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Photoperiodic influence on the innervation of the ductus epididymidis and ductus deferens of Phodopus sungorus--light microscopic studies.

The influence of long (LD 16:8) and short (LD 8:16) photoperiods on the autonomic innervation of the ductus epididymidis and ductus deferens of Phodopus sungorus was studied using the glyoxylic acid-induced catecholamine fluorescence and acetylcholinesterase (ACHE) histochemical methods. ACHE-positive nerve fibres could be demonstrated in the smooth muscle layer along the whole sperm transporting duct, in the lamina propria and within the epithelium of the ductus deferens. The extent and intensity of enzymatic reaction did not change between LD 16:8 and LD 8:16 conditions. An adrenergic nerve plexus was found in the smooth muscle layer of the sperm transporting duct. Especially in the ductus deferens, the intensity of fluorescence and the number of adrenergic nerves decreased in animals kept at short photoperiods. The influence of androgens on the sympathetic innervation of the ductus epididymidis and ductus deferens was discussed.

Acetylcholinesterase↗
PubMed1988

Photoperiod-dependent changes in TSH-like immunoreactivity of cells in the hypophysial pars tuberalis of the Djungarian hamster, Phodopus sungorus.

Certain secretory cells in the hypophysial pars tuberalis of the Djungarian hamster display marked circannual structural alterations. The present investigation deals with the immunohistochemical properties of this cell group. A distinct TSH-like immunoreactivity was found in secretory cells of this type in the pars tuberalis of animals exposed to long photoperiods, whereas under short photoperiods the TSH-like immunoreactivity was nearly absent. In the pars distalis, the number and distribution of TSH-positive cells did not differ significantly between animals maintained under long and under short photoperiods. LH- and FSH-positive cells could not be detected in the pars tuberalis, but they are clearly present in the pars distalis of both groups of hamsters. Our immunocytochemical results suggest that photoperiodic stimuli influence the secretory activity of TSH-like immunoreactive cells in the pars tuberalis. A connection with the neuroendrocrine-thyroid axis is discussed.

Animals↗
PubMed1988

Distributional pattern of oxytocin- and vasopressin-immunoreactivity in the neurohypophysis of the Djungarian hamster (Phodopus sungorus).

The topography of oxytocin (OT)- and vasopressin (VP)-containing axons of the hypothalamo-neurohypophyseal system was studied in the neurohypophysis of the Djungarian hamster (Phodopus sungorus) by means of immunohistochemistry. Compared with other mammalian species, the neurohypophysis of Phodopus shows some peculiarities. Accumulations of OT-immunoreactivity around the distal vessels of the primary portal plexus can be observed in the distal median eminence and neural stem. This staining pattern indicates that OT is secreted into portal blood. In the neural lobe, OT- and VP-immunopositive fibers terminate in different areas. The vast majority of the OT-containing axons is distributed in the dorsal part of the neural lobe. In contrast, VP-containing axons are mainly found in the centre of the neural lobe up to the pars intermedia.

Animals↗
PubMed1988

Pineal and pituitary involvement in the photoperiodic regulation of body weight, coat color and testicular size of the Djungarian hamster, Phodopus sungorus.

Hypophysectomy of 40-day-old male hamsters kept under long photoperiods resulted in a change in coat color from the brownish summer coat to the whitish winter coat, within 5 wk of the surgery, cessation of growth, and, most frequently, an additional loss in body weight. The testes of the hypophysectomized animals were involuted within 14 days after surgery. Continuous substitution of prolactin by implantation of two anterior pituitaries under the kidney capsule was able to reverse partly or totally the inhibitory effects of hypophysectomy on coat color and body weight, although there was no influence on testicular volume. The same effects could be achieved by daily s.c. injections of prolactin (100 micrograms ovine-PRL/day) into hypophysectomized hamsters, whereas the injection of adrenocorticopropic hormone (5 IU porcine-ACTH/day) or melanocyte-stimulating hormone (35 micrograms synthetic alpha-MSH/day) was ineffective. Additional pinealectomy influenced neither the inhibitory effects of hypophysectomy on coat pigmentation and body weight nor the stimulatory effects of prolactin substitution in hypophysectomized animals. Thus, the study provides evidence that the effects of the pineal gland on annual changes in body weight and coat color are mediated via the pituitary.

Adrenocorticotropic Hormone↗
PubMed1987

Adjustment of the rat pineal N-acetyltransferase rhythm to eight-hour shifts of the light-dark cycle: advance of the cycle disturbs the rhythm more than delay.

After an 8-h delay of a light-dark (LD) cycle by lengthening of one light period, the rat pineal N-acetyltransferase (NAT) rhythm adjusted to the delay shift almost within one cycle. After an 8-h advance of the LD cycle by shortening of one dark period, the NAT rhythm adjusted to the advance shift within 5 cycles only; during the first 2-3 cycles the rhythm was abolished.

Acetyltransferases↗
PubMed1987

Glial cells positive for glial fibrillary acidic protein in the neurohypophysis of the Djungarian hamster (Phodopus sungorus). An immunohistochemical and ultrastructural study.

The presence and distribution of the glial fibrillary acidic protein (GFAP; an astrocytic marker protein associated with glial filaments) in the neurohypophysis of the Djungarian hamster (Phodopus sungorus) were investigated immunohistochemically. Our study revealed characteristic GFAP-staining patterns within the median eminence, infundibular stem and neural lobe. In the whole neurohypophysis, few glial cells showed immunoreactivity. In the neural lobe, immunopositive pituicytes appeared preferentially in the periphery. At the ultrastructural level, we found some pituicytes containing filaments, most notably in their processes. We thus demonstrated that, in contrast to the GFAP-immunoreactivity of cultured pituicytes, pituicytic GFAP-expression in vivo coincides with the presence of electron-microscopically detectable filaments.

Animals↗
PubMed1987

Hematoporphyrin derivative and anthracyclines mutually inhibit cellular uptake and toxicity.

Hematoporphyrin derivative (HpD) is a fluorescent photosensitizer which localizes selectively in tumors and is used in photoirradiation therapy of various types of cancer. Photoirradiation is a local form of treatment. There may be advantages in combining it with systemic chemotherapy, and we therefore studied the interaction of HpD and various cytotoxic drugs [daunorubicin (DR), adriamycin (AD), mitozantrone (MI), cis-platinum (CP) and 5-fluorouracil (FU)] with respect to cellular uptake and toxicity. Cultured cells were incubated with HpD and the cytotoxic drugs, either simultaneously or sequentially. The amount of DR, AD and HpD taken up by cells was quantitated by measuring cellular fluorescence and by determining the specific cytotoxic action of the drugs (light-induced cell kill for HpD and loss of proliferative potential for the cytotoxic drugs). The presence of 100 mg/l HpD during drug incubation caused 30-, 12- and 6-fold reductions in the cytotoxicity of DR, AD and MI respectively. HpD-associated fluorescence and photosensitization were reduced upon co-incubation of cells with HpD and AD. When cells were incubated with HpD and AD sequentially, fluorescence was equal to the sum of fluorescence values achieved by treatment with HpD and AD alone, and the cytotoxicity was not reduced. This suggests that the effects were due to an interaction of HpD with the drugs outside the cells, resulting in a reduction of free drug available for cellular uptake. CP and FU did not interact with HpD. The results suggest that protocols which combine photoirradiation therapy and chemotherapy with anthracyclines or similar compounds need to take this interaction into account.

Animals↗
PubMed1987

[Antibody to lipoid A in the treatment of septic shock].

The protective effect of high-titer anti-lipid A hyperimmune globulin with respect to the course of the disease and the mortality rate was studied in patients with septicemia verified by positive blood cultures. Six patients were treated with anti-lipid A in an open study. Dramatic improvement in fever curves and clinical condition in some of the patients encouraged us to start a randomized double blind study. So far, 17 patients have entered the study, 16 of whom were evaluable. Immediately after a positive blood culture was found, patients received either high doses of anti-lipid A or placebo (saline solution) on two subsequent days. Before and after each infusion blood samples were taken in order to assess serum bactericidal activity and anti-lipid A titers. Because of the still small numbers of patients the results of both studies were summarized. In all patients treated with anti-lipid A clear-cut increases in anti-lipid A titers were shown. Patients with repeated gram-negative infections showed higher median anti-lipid A titers than patients without such a history. The patients treated with anti-lipid A immune globulin ran a significantly milder course than the placebo group. The severe signs of septic shock were reversed in seven of 15 patients on anti-lipid A compared to two of seven patients treated with placebo. In the anti-lipid A-treated group, three of 15 patients died, and in the placebo group two of seven. This difference is not statistically significant.

Antibody Formation↗