摘要:

The pineal glands of pregnant nursing sows were studied by light electron microscopy. Similar structural changes in the pineal glduring pregnancy lactation were noted as follows, 1) a proliferation of glial cells concurrent with a decrease in the number of pinealocytes, 2) a relative increase in the number of pinealocytes with cytoplasmic accumulation of dense bodies, 3) an increase in number of presumptive microglia. It appears that pregnancy lactation exert a complex influence on pineal function, with a predominantly stimulating effect.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00849.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The objective of this study was to evaluate the effect of lighting (day‐night) changes on pinealocyte synaptic ribbon shape (conformation) and numbers. Three‐dimensional reconstruction analysis of pinealocyte basal processes revealed that 30% (6/20) of all ribbons from dark‐adapted animals were either curved or split. Synaptic ribbons from light‐adapted animals did not show this variant morphology; all were linear structures. An analysis of each section from each series, containing curved or split ribbons, revealed that 44% (16/36) of all ribbon profiles would yield inflated counts if used in random morphometric sampling protocols. Therefore, split and curved (variant) ribbon morphologies could result in an overestimation of synaptic ribbon populations of approximately 13% (0.44 × 30%) of dark‐adapted samples. In spite of this potential sampling error, the fourfold increase in the number of synaptic ribbons observed during the dark phase of a light‐dark cycle remains highly significan

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00850.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Plasma melatonin levels of laboratory rats were elevated both during acute heat exposure (43°C for 40 min) and chronic exposure (33°C for 17 days) suggesting a possible correlation between melatonin and thermoregulatory mechanisms. Pinealectomy reduced the nighttime elevation in oxygen consumption and evaporative water loss. In addition, pinealectomized animals exhibited a significantly lower cutaneous evaporative water loss both at night and during the day when exposed to an acute heat exposure of 38°C for 45 min. Pinealectomy elevated the blood pressure over the control group whereas melatonin infusion depressed the blood pressure without altering the cardiac output. This relationship implies an action by melatonin on the peripheral vasculature. In support of this conclusion, melatonin pretreatment tended to dampen the vasopressive effect of infused norepinephrine. These data, therefore, suggest a role of the pineal gland and melatonin in thermoregulation through an influence on the cardiovascular system and evaporative water lo

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00851.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The effect of various cations on activity of hydroxyindole‐O‐methyltransferase (HIOMT) and N‐acetyltransferase (NAT) from pineal gland was studied. Copper inhibited both enzymes while calcium and magnesium inhibited HIOMT; the mechansims of these inhibitions are unknown at this stage. Calcium, magnesium, potassium, and sodium initially stimulated NAT activity, and as the cation concentration increased inhibitory activity was observed. These differential effects on NAT activity may in some way be involved in pineal regulation of cation l

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00852.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Dynamics of radioactive accumulation in rat greater salivary glfollowing systemic administration of3H‐melatonin was studied to determine a possible action of the hormone in the gland. Progressive decline of3H‐melatonin concentrations was found in the serum, lung, skeletal muscle, liver, kidney, salivary glduring 60 min following the administration. On the contrary, there was a progressive accumulation of radioactive substance other than3H‐melatonin in the salivary glbut not in other tissues mentioned. The radioactivity was also progressively preferentially localized in the nuclear fraction of the glcells. These results suggest a possible direct action of melatonin derivative in rat salivary

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00853.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Human plasma saliva were collected at frequent intervals throughout the night after a nocturnal challenge by exposure to 3,000 Ix of light for 1 h in the middle of the night. Melatonin, as measured by radioimmunoassay, was found to correlate highly in plasma saliva, described by a linear regression equation: y = 55x ‐ 2.6 (r = 0.90). The nocturnal melatonin rhythm in saliva was parallel to that observed in plasma. A good correlation was also observed between plasma salivary melatonin on exposure to light. Melatonin in both fluids showed a significant fall during light exposure. Levels returned to normal nocturnal values within 2 h after returning to darkness. These results indicate that salivary melatonin, although lower than plasma melatonin, may be used as an index of pineal glrelease of melatonin. It is suggested that saliva may be useful as a non‐invasive technique for obtaining data on melatonin profiles, especially in pilot‐test screening situa

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00854.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

It has recently been shown that a 1.5‐ml subcutaneous saline injection into the dorsal aspect of the hind limb induces a dramatic and rapid fall in N‐acetyltransferase activity and melatonin content of the rat pineal gland at night. Since many studies have shown the opposite response to stress during the day, the first experiment was undertaken to test whether the timing of the saline injection at night influences the response of the pineal gland. In the present studies, rats were kept under light:dark (LD) cycles of 14:10 with lights out daily at 2000 h. Groups of rats were then given a saline injection at one of the following times: 2315, 0015, 0115, 0215, or 0315. Early in the dark phase (2315 and 0015) the saline injection depressed both the N‐acetyltransferase (NAT) activity and the melatonin content of the pineal. As the animals were treated later in the dark period, the response became more blunted and, finally, disappeared. In the second experiment, animals that were kept in light during the usual dark period showed no pineal response when subjected to a hind leg injection of saline at either 2315 or 0315. Additionally, no response was seen in the two pineal parameters when rats had darkness onset delayed by 4 h (to 2400) and were then treated with saline at 0410. The results of these studies indicate that the pineal response to saline injection is time dependent. Also, if the nighttime rise in melatonin is suppressed by light exposure, a saline injection has no further inhibitory effect on pineal NAT activity or melatonin l

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00855.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Although there is little evidence that melatonin may have a direct antimitotic effect on various cells, it has been shown that this pineal compound may influence the cell proliferation of either normal or neoplastic cells. Therefore, the influence of melatonin on the mitotic activity of regenerating adrenal cortex of rats was studied. The mitotic activity was counted in the adrenal cortex or rats on days 2, 7, and 12 following enucleation of the adrenals. Melatonin did not influence the mitotic activity of regenerating adrenal cortex in the rat.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00856.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The circadian plasma melatonin profile of German Landrace sows was determined at 1‐h intervals for 31 h after exposure to each of four different artificial photoperiods. Under 12L:12D, melatonin concentrations in four sows during the light phase ranged from 22 ± 5.9 to 96 ± 25.1 pg/ml (mean ± SEM). During the dark phase (total dark) the individual concentrations increased two‐to fivefold over the peak individual light phase values in three sows. This nocturnal surge was of 3.8 h duration and peaked at 190, 294, and 546 pg/ml at 0100 h, which was 5.5 h after the onset of dark. The surge was abolished in these animals after exposure to 16L:8D and could not be reinstated by the subsequent exposure to 8L:16D. During the latter two photoperiods the mean concentrations were consistently less than the maximum mean value of 30.8 ± 10 pg/ml during the dark phase and 55 ± 21.9 pg/ml during the light phase. All the sows displayed regular estrous cycles during the study, and the day of the estrous cycle on which the samples were obtained under each photoperiod was not significantly correlated with the presence or absence of the nocturnal surge. A separate experiment using different animals confirmed the nocturnal surge under 12L:12D. In two out of four cycling sows the peak concentrations during the dark phase (122 and 110 pg/ml at 0400 and 0500 h) were two‐to sixfold higher than those of the light phase. Absence of the nocturnal surge under long and short daylengths may be a factor contributing to the decline in reproductive performance during the summer and win

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00857.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The pineal of viscacha (Lagostomus maximus maximus) is formed by two main cellular populations of pinealocytes and interstitial cells. A connective capsule surrounds the gland sending numerous septa containing blood vessels and nerves. In the specimens collected during summer the pinealocyte displays a defined contour and a clear cytoplasm with abundant ribosomes and numerous cisternae of endoplasmic reticulum. The pinealocytes observed during winter have cytological characteristics of active cells with dense and elongated mitocondria, dense bodies, and a developed Golgi complex. These seasonal glandular changes could be related to the environmental condition and mainly to the summer photoperiod. The presence of abundant nerve terminals in the perivascular spaces suggests a neural control on the blood vessels.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00858.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY