[Changes in the seasonal birth rate in Munster (1890-1991)].
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Birth Rate↗
Biomedical subjects
A Lerchl
Publications and source records attributed to A Lerchl.
Changes in seasonality of birth rates in Germany from 1951 to 1990.
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Birth Rate↗
Type II iodothyronine 5'-deiodinase in mouse brown adipose tissue is stimulated by a single injection of isoproterenol in an oil/water emulsion.
A single subcutaneous morning injection of the beta-adrenergic agonist isoproterenol (ISO) (10 mg/kg body weight) in an oil/water emulsion (70/30; v/v) caused a marked increase in the activity of the enzyme type II iodothyronine 5'-deiodinase (5'-D II) in the interscapular brown adipose tissue of BDF-1 mice. After a delay of 4 hours, the 5'-D II activity began to rise in an almost linear fashion and was increased 3-fold after 8 hours, when compared to the control values. The results indicate that this method of ISO administration may be a valid tool for artificial stimulation of brown adipose tissue in animals by beta-adrenergic agonists.
Adipose Tissue, Brown↗
Restoration of spermatogenesis by follicle-stimulating hormone despite low intratesticular testosterone in photoinhibited hypogonadotropic Djungarian hamsters (Phodopus sungorus).
By exposing male Djungarian hamsters to short-day photoperiods, a hypogonadotropic condition resembling that of hypophysectomized animals can be achieved without resorting to surgery. By use of this animal model, differential effects of gonadotropins on spermatogenesis have been studied revealing that FSH selectively restimulates spermatogenesis up to the level of spermatids. In the present study, we investigated whether FSH (6 IU/day) also restores fertility in hamsters exposed to short-day photoperiods (8L:16D). Animals kept under long-day photoperiod (16L:8D) served as controls. After 8 wk under 8L:16D, gonads were involuted and the animals (n = 9-10 per group) were treated with FSH, or testosterone implants, or both for the following 33 days. An additional group received FSH for 33 days and, for the last 12 days only, FSH plus testosterone to induce copulatory and ejaculatory behavior. The implants caused no increase in intratesticular testosterone as compared to that in short-day controls. All males were paired with adult females for the last 5 days of treatment, and killed thereafter. Litter sizes were determined 22 days later. The examination of the testes by flow-cytometrical techniques revealed qualitatively normal spermatogenesis in animals receiving FSH, whereas testosterone caused an insignificant increase to a few round spermatids. In most FSH-treated animals, sperm were present in the epididymides. In hamsters receiving FSH along with testosterone, treatment resulted in restoration of full fertility as compared to long-day controls. Fertility was also restored in animals receiving testosterone only for the last 12 days of FSH treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Diurnal variations in scrotal temperature of normal men and patients with varicocele before and after treatment.
Scrotal temperature was monitored using a portable data recorder for periods of 24 h in six normal volunteers and 48 infertile patients with unilateral varicocele while subjects pursued their regular daily activities. Temperatures during sleep (TS) were generally higher than daytime values (TD), probably as a consequence of thermal insulation in bed. These diurnal variations were found to be less pronounced in the infertile patients than in volunteers (TS - TD = 0.29 degrees C +/- 0.06 degrees C vs 0.88 degrees C +/- 0.12 degrees C; P < 0.01). Moreover, scrotal temperatures at night of patients and volunteers were indistinguishable statistically, but were different during daytime hours. After successful ligation or embolization of the spermatic-vein in 16 patients, no change in scrotal temperature was observed. Although sperm counts were higher after treatment, this difference was not significant (67.4 +/- 17.2 x 10(6) vs 105.8 +/- 25.5 x 10(6); P > 0.05). The data support the view that varicocele-related damage to the testis results from a lack of adequate cooling, and that treatment does not normalize the temperature pattern.
Adult↗
Influence of photoperiod on pineal melatonin synthesis, fur color, body weight, and reproductive function in the female Djungarian hamster, Phodopus sungorus.
In order to investigate female Djungarian hamsters' reactions to changes of the photoperiod, the following two experiments were performed. Experiment I: Age-matched female hamsters were exposed to either short (8L:16D) or long days (16L:8D) for 38 weeks. Initially, the short-day group showed a decline in body weight, associated with changes in gonadal function and fur color. This was not maintained by the short-day group which returned, on the most part, to long-day levels, thus becoming insensitive to this regressive lighting regimen. The time courses of these events compare well with those observed in males, which suggests a common mechanism. Experiment II: Two groups of female hamsters were exposed for 8 weeks to either long days or short days. At the end of the test period, the diurnal variations in pineal content of melatonin, serotonin, hydroxyindole acetic acid, and serum melatonin were estimated, revealing marked differences between the two groups. Not only was there a prolongation of melatonin synthesis observed in the short-day animals, but there was also a significant elevation of the melatonin levels when compared to the long-day animals. Together with recent findings in males, these findings lend support to the hypothesis that, in the Djungarian hamster, the elevation of nocturnal melatonin levels may be of additional significance, with respect to the physiological changes induced by short-day photoperiods.
Animals↗
Serotonin content and melatonin production in the pineal gland of the male Djungarian hamster (Phodopus sungorus).
Diurnal variations in serum melatonin levels and pineal concentrations of serotonin (5-HT), N-acetylserotonin (NAS), 5-hydroxyindole acetic acid (5-HIAA), and melatonin were estimated in adult male Djungarian hamsters kept under long-day (LD 16:8) or short-day (LD 8:16) photoperiods. The nocturnal increase in melatonin production was accompanied by a marked drop in pineal serotonin concentrations. Serotonin levels, however, decreased approximately 4 hr before pineal melatonin increased. Correlations of the mean values for pineal serotonin and pineal melatonin indicated significant correlations at both LD 16:8 (r = -0.92, P less than 0.001) and LD 8:16 (r = -0.85, P less than 0.001). The mean levels of pineal serotonin and serum melatonin were correlated as well (LD 16:8, r = -0.91, P less than 0.001; LD 8:16, r = -0.81, P less than 0.01). The levels of pineal serotonin declined at approximately the same time as serum melatonin levels increased. These data suggest that the drop in pineal serotonin is primarily a consequence of melatonin production (as reflected by increasing serum concentrations). Consequently, pineal concentrations of melatonin may not be the best estimate of actual melatonin production, but a measure of how much melatonin is accumulated within the pineal due to high synthesis rates while the release of the hormone from the gland is limited.
Animals↗
Interruption of nocturnal pineal melatonin synthesis in spontaneous recrudescent Djungarian hamsters (Phodopus sungorus).
The duration of nighttime synthesis of the pineal hormone melatonin is believed to determine the breeding season in many mammalian species. Hamsters exposed to short days undergo gonadal involution followed by a return to normal function, suggesting a developed insensitivity to regressive photoperiods. This recrudescence may be due to either exhaustion of the pineal or to target-desensitization. Both theories have been tested previously but failed to explain this phenomenon. We performed an experiment in the Djungarian hamster (Phodopus sungorus), a well-characterized photosensitive species with a type C melatonin pattern (prolonged peak during majority of dark phase), in an attempt to resolve this issue. Among age-matched male hamsters exposed to short days for either 16 weeks (involuted) or 38 weeks (spontaneous recrudescent), marked phase differences in diurnal pineal melatonin rhythms were observed. Furthermore, in recrudescent hamsters the melatonin pattern was divided into two parts, possibly no longer recognizable as a typical short-day rhythm.
Animals↗
Food restriction retards aging of the pineal gland.
The effects of chronic (40%) food restriction from 6 weeks of age were studied in aging male Fisher 344 rats. When compared with 3-month-old, ad libitum fed rats, pineal N-acetyltransferase (NAT) activity had declined to less than 30% and pineal and serum levels of melatonin to 40% after 28 months when feeding had been ad libitum. Food restriction significantly retarded this development (P less than 0.05) giving NAT and melatonin levels which were twice as high as in the ad libitum fed group. Nighttime levels of pineal serotonin (5-HT) were similar in food-restricted and ad libitum fed old rats but were nearly twice as high (P less than 0.05) as in young rats. There was also a tendency for increased production of 5-hydroxyindoleacetic acid (5-HIAA) in the pineal gland with higher levels of 5-HT. It is concluded that aging in the rat (Fisher 344) is accompanied by a reduction of pineal NAT activity, thereby reducing the production of melatonin and causing a buildup of 5-HT in the pineal gland. It is furthermore proposed that food restriction, which markedly increases the life span and reduces age-related physiological deterioration and diseases in many animals, may mediate some of its effects through a sustained pineal activity in old age.
Aging↗
Evidence that extremely low frequency Ca(2+)-cyclotron resonance depresses pineal melatonin synthesis in vitro.
The effects of ion cyclotron resonance (ICR)-type magnetic fields on pineal glands were investigated. Both the synthesis and the release of pineal melatonin, the gland's major hormone, were significantly (P less than 0.001 in each case) reduced by Ca(2+)-ICR-exposure, presumably caused by a reduced activity (P less than 0.05) of the enzyme N-acetyltransferase. It is concluded that this type of exposure may help to explain some of the effects of electromagnetic fields on biological systems. An extension to the existing ICR theory is presented which explains that ICR-like conditions may occur under various environmental circumstances.
Animals↗
Evidence that interferon-gamma alters pineal metabolism both indirectly via sympathetic nerves and directly on the pinealocytes.
1. Interferon-gamma (IFN-gamma) has been shown to suppress N-acetyltransferase (NAT) activity in cultured rat pineal glands when stimulated with isoproterenol (ISO). 2. Conversely, IFN-gamma has also been shown to increase the melatonin content of the rat pineal gland in organ culture. 3. Circumstantial evidence leads to a hypothesis that the NAT suppressive effect may be due to the action of IFN-gamma on the sympathetic nerve terminals. 4. To test this hypothesis, pineal glands from intact (INT) and superior cervical ganglionectomized (SCGX) rats, which had been operated 5 days earlier, were cultured with either ISO or ISO + IFN-gamma. 5. The concentration of ISO was 10(-8) M and that of IFN-gamma was 300 antiviral units/ml. 6. The pineals were incubated for a total period of 5.5 hr, after which the activities of NAT and hydroxyindole-O-methyltransferase (HIOMT) and the levels of melatonin and cAMP were estimated. 7. Suppression of NAT by IFN-gamma was observed in the pineals from INT rats, but not in those from SCGX animals. 8. IFN-gamma significantly enhanced melatonin levels over those in ISO-stimulated pineals and culture media from the SCGX animals, but not from the INT animals. 9. IFN-gamma treatment had no effect on either the HIOMT activity or cAMP levels. 10. The results indicate that the IFN-gamma-induced NAT suppression requires the integrity of the sympathetic nerve terminals and the IFN-gamma-induced enhancement of melatonin production is accomplished through its direct action on pinealocytes.
Acetylserotonin O-Methyltransferase↗
Low temperature stimulates pineal activity in Syrian hamsters.
The effect of 24-hr exposure to cold (5 degrees C) was studied in male Syrian hamsters adapted to short days (LD 8:16). Both pineal N-acetyltransferase (NAT) activity and pineal and serum concentrations of melatonin showed a clear, diel rhythm with a moderate but significant increase late in the dark period. The nighttime peak levels of NAT activity and pineal and serum melatonin were significantly higher in the animals that had been exposed to cold than in those remaining in warm (22 degrees C) conditions. The activity of type-II 5'-deiodinase (5'D) in the brown adipose tissue (BAT) was not different after 24 hr of cold exposure between cold- and warm-exposed hamsters, and the enzyme did not show any diel rhythmicity. It has been speculated that some effects of cold exposure may be simulated by melatonin treatment; the present data further support this notion. The apparent lack of response in BAT 5'D activity remains enigmatic and needs further investigation.
Adipose Tissue↗
Adenosine effects on the rat pineal gland in vitro: cyclic adenosine monophosphate levels, N-acetyltransferase, and thyroxine type II 5'-deiodinase activities and melatonin production.
The presence of adenosine and its receptors in the pineal gland suggests that they could have a regulatory influence on pineal physiology. Rat pineal glands cultured in the presence of the adenosine analog 5'-N-ethylcarboxamido adenosine (NECA) promoted a significant increase in pineal adenosine 3'5'-monophosphate (cAMP) content, similar to that caused by the beta-adrenergic receptor agonist isoproterenol (ISO). A potentiation of the cAMP response occurred when the glands were simultaneously stimulated with both NECA and ISO. Whereas high cAMP levels induced by ISO were associated with an increased N-acetyltransferase (NAT) activity and rise in the melatonin production and release, the NECA-induced rise in cAMP concentration failed to promote an increase in the activity of either NAT or another pineal enzyme thyroxine 5'-deiodinase type II; likewise, pineal melatonin levels did not rise.
Adenosine↗
Pineal gland "magnetosensitivity" to static magnetic fields is a consequence of induced electric currents (eddy currents).
During the past decade, a number of reports indicated that the mammalian pineal gland is magnetosensitive in terms of spatial orientation. This indication is based on observations that artificial alterations of the direction of the earth's magnetic field (MF) markedly decreased the gland's capability to synthesize melatonin. These findings, however, seem paradoxical since animals as well as humans experience such alterations whenever they turn their heads. Therefore, the potential of the pineal for sensing magnetic fields was re-investigated. During the dark phase, rats were exposed to repeatedly inverted MFs, generated by two identical pairs of Helmholz coils; one pair connected to a power supply automatically, the other pair manually using an integrated potentiometer. Only the pineals of animals exposed to the automatically activated field responded with a reduced activity of the rate-limiting enzyme serotonin-N-acetyltransferase, lower melatonin levels and increases in serotonin and 5-hydroxyindole acetic acid. Hence, MF exposure itself did not affect the pineal. Rather, induced eddy currents in the animals, resulting from rapid On/Off transients of the artificially applied MF, are most likely the explanation.
Analysis of Variance↗
Endocrine and metabolic effects of life-long food restriction in rats.
The effects of chronic (40%) food restriction from 6 weeks of age were studied in 28-month-old male Fischer-344 rats; the results were compared with ad libitum-fed, old and young male rats at 28 and 3 months of age, respectively. Pituitary luteinizing hormone was similar in all old rats and was significantly lower than in young rats. In old ad libitum-fed, but not in food-restricted rats, serum levels of LH, testosterone and T4 were significantly lower than in young rats. Serum levels of T3 did not differ between young and old rats. Type-II 5'-deiodinase activity in brown adipose tissue was similar in both groups of old animals and was significantly depressed as compared with that in young rats. Serum levels of triglycerides were significantly depressed in food-restricted rats, but were significantly increased in ad libitum-fed rats as compared with young rats. Both groups of old rats had significantly elevated serum levels of cholesterol over that in young rats, but the level was significantly lower in food-restricted as compared to ad libitum-fed animals. The results are consistent with the notion that life-long food restriction tends to preserve the activity of many metabolic functions.
Aging↗
Marked rapid alterations in nocturnal pineal serotonin metabolism in mice and rats exposed to weak intermittent magnetic fields.
Adult AMES mice and male Sprague Dawley rats were exposed to an artificial magnetic field, generated by Helmholtz coils. 3.5 hours after the onset of darkness the coils were activated for one hour resulting in an inversion of the horizontal component of the earth's magnetic field. The coils were activated and deactivated at 5 min intervals during the 1 hour exposure period. In both mice and rats, the levels of serotonin in the pineal were markedly increased by the exposure. In rats, an increase of pineal 5-hydroxyindole acetic acid and a decrease of the activity of the pineal enzyme serotonin-N-acetyltransferase also was observed. However, pineal and serum melatonin levels were not altered. The results indicate that the metabolism of serotonin in the pineal is quickly affected by the exposure of animals to a magnetic field.
Animals↗
Locomotor activity registration by passive infrared detection in saddle back tamarins and tree shrews.
Locomotor activities of tamarins and tree shrews were monitored using a passive infrared detector (PID) and a small hand-held computer as a recording unit. It is a low-cost system, easy to install and to handle without any disturbing effects on the animals investigated. Recording activity is not limited to specific sites in the cage. A temporal resolution of about two seconds for activity detection will meet most experimental requirements. The method was validated by a comparison of PID-recorded signals with simultaneous behavioral observations using a video-recorder. PID is highly specific, detecting only those movements which involve a change in location. The recording system can be adapted to various experimental conditions or other mammalian species.
Animals↗
Declining sperm counts in European men--fact or fiction?
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Europe↗