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Biomedical subjects

K Hoffmann

Publications and source records attributed to K Hoffmann.

At least 289 records · Page 16Linked to original sources
PubMed1986

[Diagnosis and evaluation of monoclonal immunoglobulins in the aged with reference to plasmacytoma].

A study on the epidemiological situation of the appearance of monoclonal immunoglobulins (mIg) in the district of Leipzig is presented. 443 accidentally selected test persons from old people's and nursing homes of a dispensary consulting hour and a ward for diagnostics in internal medicine at the age of more than 50 years were examined. Agargel electrophoresis and BSR, the usual diagnostic follow-up methods for the proof of mIg, were used. Depending upon age 88 examined patients showed increasingly extragradients (EG), 21 of them could all be identified as mIg. Significant sex differences after the 74th year of age refer to an at this time more distinct disturbance of the B-cell regulation in males. One third of the test persons had transitory mIg, among the persisting ones after all two patients with multiple myeloma were found. While the BSR is not suitable as screening method, the agargel electrophoresis (sensitivity and specifity in each case 84%, positive predictive value 24%) in the present prevalency of 4.7% is recommended for the detection of this phenomenon. The clinical consequences require the formation of risk groups, their mass examination and the aimed control in immunologically and haematologically orientated centres.

Aged↗
PubMed1986

Change in duration of the nighttime melatonin peak may be a signal driving photoperiodic responses in the Djungarian hamster (Phodopus sungorus).

A regime of 14 h of light and 10 h of darkness (LD 14:10) induced regression of testes and accessory glands in adult Djungarian hamsters maintained originally in LD 16:8, but recrudescence of these organs in hamsters maintained originally in LD 8:16. Duration of the period of elevated nighttime melatonin levels in LD 14:10 was the same irrespective of whether hamsters had come from LD 16:8 or from LD 8:16. It is suggested that a change in duration of the nighttime melatonin peak and its direction rather than absolute duration of the melatonin peak may be a hormonal signal driving photoperiodic responses in adult Djungarian hamsters.

Animals↗
PubMed1986

Photoperiodic effects in the Djungarian hamster. Rate of testicular regression and extension of pineal melatonin pattern depend on the way of change from long to short photoperiods.

In the Djungarian hamster, short photoperiods induce regression of testes and accessory glands. There is evidence that the length of time melatonin levels are elevated is the signal conveying the photoperiodic effects to the neuroendocrine axis. When the temporal course of decompression of the pattern of pineal melatonin content was followed after a change from long to short photoperiods by symmetrical extension of the dark time, extension proceeded first into the morning hours. The present study investigated whether, after transition from long to short photoperiods by either extending the dark period into the morning hours, or starting the dark time at noon, differences in the gonadal reaction and in the rate of extension of the pineal pattern ensue. Three and 7 weeks after transition from long to short photoperiods highly significant differences were found in the rate of involution of testes and accessory glands. Regression was more advanced after extension of the dark period into the morning hours. The length of time that pineal melatonin content was elevated also differed markedly between the two groups. After 3 weeks in short photoperiods, the length of the melatonin peak was more than 9 h when the dark period was extended into the morning, but only about 7 h if it was extended into the afternoon. It is suggested that the different rate of gonadal regression after different ways of transition into the same photoperiod is due to the different rate of decompression of the melatonin pattern.

Animals↗
PubMed1985

Comparison of pineal melatonin rhythms in young adult and old Djungarian hamsters (Phodopus sungorus) under long and short photoperiods.

The pattern of the pineal melatonin rhythm was studied in 3-6- and 17-22-month-old female Djungarian hamsters under light-dark (LD) schedules, LD 16:8 and LD 8:16. Under both photoperiods, the amplitude of the melatonin rhythm was 2.5 times higher in young adult hamsters than in old ones. Two weeks after the change from LD 16:8 to LD 8:16, the period of elevated nocturnal melatonin levels lengthened by about 3 h in both age groups. It is suggested that old Djungarian hamsters, as well as young adults, might be able to recognize the length of a photoperiod and its change.

Age Factors↗
PubMed1985

Arrest of the circadian pacemaker driving the pineal melatonin rhythm in hibernating golden hamsters, Mesocricetus auratus.

Pineal melatonin rhythm in golden hamsters was abolished during hibernation. After arousal in darkness, pineal melatonin increased rapidly regardless of whether the arousal was induced during the day or at night. Rapid increase of pineal melatonin after arousal was markedly diminished in animals exposed to light. In hamsters aroused at midnight, the melatonin rhythm in constant darkness ran with the reversed phase relative to hamsters aroused at noon. Since after arousal the melatonin rhythm obviously starts anew from the same phase, we conclude that the circadian pacemaker driving the rhythm might be arrested during hibernation at the day-time phase.

Animals↗
PubMed1985

[Availability of propylphenazocine from suppositories. 1. In vitro bioavailability].

Comparing examinations of the in-vitro availability of propyphenazone from suppositories of different fat bases (Rosupol U, Witepsol H 15) did not display any differences in the release behaviour. Compared with propyphenazone preparations, aminophenazone suppositories of the same concentration exhibit a significantly increased in-vitro availability.

Antipyrine↗
PubMed1984

Pineal melatonin in hibernating and aroused golden hamsters (Mesocricetus auratus).

Daily changes of pineal melatonin content were determined in warm-adapted nonhibernating and cold-adapted hibernating golden hamsters (Mesocricetus auratus). Pineal melatonin in nonhibernating golden hamsters showed marked daily rhythm with the night values about 20 times higher than the daytime ones. In hamsters hibernating for 2 and 3 days the melatonin rhythm was abolished, since no increase of pineal melatonin over basal levels occurred throughout 24 hr period. After arousal from hibernation melatonin increased rapidly regardless whether the hamsters were provoked to arousal during day or night.

Animals↗
PubMed1984

A procedure for phonetic transcription by consensus.

A consensus transcription procedure is presented, and representative data are reported. The procedure includes explicit response definitions for mapping narrow phonetic transcription onto dichotomous, nonerror/error scores and 17 rules for obtaining consensus between two transcribers. The data include descriptive statistics for consensus rule use based on over 18,000 sounds transcribed during a normative study of speech sound acquisition in children aged 3-6 years. Validity and reliability issues in phonetic transcription are discussed.

Child↗
PubMed1984

Influence of photoperiodism on testicular function and sebaceous glands in Syrian hamster.

The photoperiod (i.e., the daylight fraction of the 24-h day and its seasonal changes) influences the annual cycle of many mammalian species. Especially the Syrian hamster (Mesocricetus auratus), which is an appropriate animal model to investigate the sebaceous gland activity, shows a strong photoperiodism controlling the sexual development as well as the function of androgen-controlled organs such as sebaceous glands. Short photoperiods with accompanying long dark periods lead to a sexual regression while long photoperiods stimulate the recrudescence. In light-physiologic studies Syrian hamsters were exposed to different light schedules. The daily light exposure was increased from 8 to 12, 13, 14, and 16 h. Sebaceous gland areas, weight of testes and accessory glands, tubular areas, and plasma levels of testosterone were determined. Syrian hamsters are sexually stimulated at a daily light exposure of 14 h. Below this light threshold the sexual regression begins. At a light schedule of 8 h the testes shrink, plasma testosterone levels and sebaceous gland areas show a significant reduction ("photoperiodic castration"). Therefore, in experiments of androgen-controlled organs of the Syrian hamster a minimum daily light period of 14 or 16 h is necessary for a sufficient testicular function and therefore for an effective stimulation of the sebaceous gland activity. Control animals of the same age and the same light schedule should be required to avoid pitfalls of photoperiodic effects.

Animals↗
PubMed1984

Adjustment of pineal melatonin and N-acetyltransferase rhythms to change from long to short photoperiod in the Djungarian hamster Phodopus sungorus.

In the Djungarian hamster Phodopus sungorus, the daily temporal pattern of synthesis and release of pineal hormone melatonin, mainly the length of the period of elevated melatonin levels, may be involved in transferring the information on day length to the neuroendocrine-gonadal axis. The present study investigated the time course of adjustment of the rhythm in melatonin production and concentration to the change from long to short photoperiods. Adult female Djungarian hamsters, maintained on a regime of 16 h of light and 8 h of darkness per day (LD 16:8) were transferred to the LD regime 8:16 and the daily rhythms in the pineal melatonin concentration and in the pineal N-acetyltransferase activity, as an indicator of melatonin formation, were studied at various intervals following the transfer. Under LD 16:8, the nocturnal melatonin concentration was elevated for 4.8 h. After 3 days on LD 8:16, no extension of the period of high melatonin levels occurred. 2, 4 and 6 weeks after the transfer to LD 8:16, the period of elevated melatonin levels lasted for 8.1, 9.3 and 11.5 h, respectively. Extension of the melatonin pattern proceeded first predominantly into the morning hours. Only after this extension was completed, a considerable extension into the evening hours began. Extension of the N-acetyltransferase rhythm on short photoperiods proceeded in the same way as that of the melatonin rhythm. The data show that while a change in the photoperiod might be seen by hamsters within 2 weeks after the transfer to LD 8:16, the full shortening of the photoperiod might be recognized only within 6 weeks or later.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyltransferases↗
PubMed1983

Regulation of the pineal melatonin concentration in the rat (Rattus norvegicus) and in the Djungarian hamster (Phodopus sungorus).

1. Rapid changes of melatonin concentration in pineals of rats (Rattus norvegicus) after isoproterenol administration or in the course of a day were accompanied by parallel changes of N-acetyltransferase but not of hydroxyindole-O-methyltransferase activity. 2. In pineals of Djungarian hamsters (Phodopus sungorus) the evening and morning melatonin changes were also parallel with N-acetyltransferase changes. 3. In both species, melatonin concentration during its rise had approached the maximum earlier than N-acetyltransferase reached its highest activity. 4. It is proposed that the N-acetyltransferase rhythm drives the melatonin rhythm both in rats and in Djungarian hamsters; the maximum melatonin production may, however, depend also on hydroxyindole-O-methyltransferase activity and substrate concentration.

Acetylserotonin O-Methyltransferase↗