摘要:

The purpose of the present studies using artificial light was to determine how the timing and duration of exposure influence the light‐induced suppression of pineal melatonin levels in hamsters. An 8‐min exposure to 0.186 μW/cm2of cool white fluorescent light caused a continued depression of pineal melatonin even when animals were returned to darkness. In addition, the pineal gland does not appear to change its sensitivity to light throughout the night. A 20‐min exposure to 0.019 μW/cm2of cool white fluorescent light did not significantly suppress pineal melatonin during any time of the melatonin peak, whereas a 20‐min exposure to 0.186 μW/cm2was capable of always suppressing melatonin. Furthermore, increasing the duration of 0.019‐μW/cm2exposure to 30, 60, 120, or 180 min does not increase the capacity of this irradiance to depress melatonin.Similar to artifical light, natural light has a variable capacity for suppressing nocturnal levels of pineal melatonin. Twilight irradiances of 0.138 μW/cm2or less did not suppress nocturnal melatonin whereas twilight irradiances of 3.0 μW/cm2or greater did suppress pineal melatonin. A few animals did have lower melatonin after a 40‐min exposure to full moonlight during July (0.045 μW/cm2) or January (0.240 μW/cm2). However, pineal melatonin levels remained high in the majority of animals expose

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1984.tb00202.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The morphology of the pineal gland was studied in protein‐calorie‐malnourished (PCM) rats. Twenty‐day‐old male Sprague‐Dawley rats were placed in a 14:10 photoperiod and fed either an 8% low protein diet (LPD) or a standard laboratory diet (SLD) containing 27% protein for 30 d. At 50 d of age, rats from both animal groups were sacrificed at 0900 h and at 2400 h, and the pineal glands were immersion‐fixed for either light or electron microscopic analysis. The cytoplasm and nuclei of the pinealocytes from the SLD‐fed rats were consistently larger than those of the animals maintained on the LPD. Additionally, the lipid droplets were larger and more prominent in the controls at both 0900 h and 2400 h. Even though the size of these inclusions did not vary among animals given the same diet as a function of the time of sacrifice, they were more numerous in both the well‐fed and malnourished rats during the dark phase of the photoperiod. In contrast neither diet nor sampling time affected the size or number of pinealocyte mitochondria. These morphological observations lend further support to the premise than PCM impairs the cellular activity of t

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1984.tb00203.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Serotonin N‐acetyltransferase activity (NAT) exhibited a daily cycle in light:dark (LD) 14:10 when it was measured in pineal glands taken from rats killed at a sequence of time points. The ratio of peak subjective night NAT to minimum subjective day NAT was 10.9/0.3 nmol per pineal gland per hour. When the rats were placed in constant dark the rhythm persisted (8.2/0.02). When the rats were placed in constant light the rhythm persisted with markedly attenuated amplitude (0.6/0.02).We also measured NAT profiles in rat pineal glands, Harderian glands, and retinas with alternative methods. We kept rats on six LD 14:10 light‐dark cycles with lights‐out beginning at midnight, 2 AM, 4 AM, 6 AM, 8 AM, or 10 AM and killing all the rats at one time point, 10 AM. We examined the NAT time profiles 4, 8, and 11 days following placement of the rats in the phase‐shifted cycles. In addition, we measured the NAT profile in LD 2:22 and LD 22:2 by keeping the rats on twelve cycles for 11 days and killing all the rats at one time.Pineal NAT exhibited a rhythm in all the cycles: peak‐dark/nadir‐light values (nmol product per gland per hour) were 15.6/0.1 in LD 14:10, controls killed at successive time points. The ratios for the profiles obtained using the one time point procedure were 16.7/0.1 in LD 14:10 8.5/0.2 in LD 22.2, and 12.9/0.2 in LD 2.22. Increasing the photoperiod reduced the time to the NAT peak.In LD 14:10, Harderian NAT was 31–39 nmol per gland per hour but the peak/ nadir radio was only 1.2; retinal NAT was low (0.2–0.7 nmol per retina per hour) and had only a 3.5‐fold

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1984.tb00204.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The size of synaptic ribbons (SR) in photoreceptor cells of the goldfish pineal organ was quantified over 24‐h light:dark cycles of long (16:8) and short (10:14) photoperiods during summer and winter months, respectively. The amplitude of both rhythms was similar with peak values occurring toward the latter part of the photophase or early dark. When fish were entrained to the long photoperiod and exposed to continual light, SR size continued to increase during the expected dark time. The effect of extending the photoperiod into the expected dark time was diminished when fish were entrained to a short photoperiod and presented with 6 h of darkness at the end of the 24‐h period. The size increase in response to environmental lighting is believed to reflect a greater demand for either vesicle attachment sites or neurotransmitter storage sites since vesicles (neurotransmitter) have been hypothesized to accumulate in the synaptic pedicles during inhibition by light. From a comparative standpoint it is noteworthy that synaptic ribbons (vesicle‐crowned rods) in mammals react in a similar manner to both normal and experimental lighting condi

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1984.tb00205.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The combination of pituitary grafts and daily injections of gonadotrophin‐releasing hormone (GnRH) completely prevents gonadal atropy in blind (BL) and melatonin (Mel)‐treated male hamsters. In order to avoid potential problems associated with the use of pituitary grafts and further define the interactions between prolactin (PRL) and GnRH in preventing reproductive regression, we injected various doses of each hormone either alone or in combination into BL or Mel‐treated male hamsters. In another experiment, BL hamsters received either weekly beeswax implants of estradiol benzoate (EB) (1 mg) alone or EB implants in combination with daily injections of GnRH (2 μg). In each experiment the hamsters were BL and/or treated with hormones for 10 wk. Either GnRH (8 fig) or PRL (5 μg) per d partially prevented gonadal atrophy in BL hamsters. However, increasing doses of GnRH plus PRL wre more effective than either hormone alone in preventing gonadal atrophy. The combined effect of these hormones was greater than the algebraic sum of their individual effects. Injections of either GnRH or PRL alone resulted in a significant maintenance of gonadal and accessory organ size in Mel‐treated animals. The combination of GnRH and PRL resulted in virtually complete maintenance of testicular weight while the accessory sex organs remained atrophic. The combined effect of these hormones was equivalent to the algebraic sum of their individual effects. The treatment of BL animals with EB implants with or without GnRH did not prevent reproductive regression in spite of elevated serum PRL levels. In conclusion, the effects of GnRH and PRL were synergistic in BL hamsters and additive in Mel‐treated animals. The data suggest that there is a differential responsiveness of BL v. Mel‐treated hamsters to the individual as well as the combined actions of

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1984.tb00206.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Glycogen level in and size of pinealocytes of the feral, white‐footed mousePeromyscus leucopus, were studied by a semiquantitative histochemical method to determine whether seasonal changes exist in them under natural conditions, what temporal pattern they exhibit, and whether 24‐hour changes in these parameters exist in different seasons, as shown in the laboratory dd‐mice. Marked seasonal changes were seen in both glycogen levels and nuclear densities (ANOVA P<0.005). The size of pinealocytes at 09:00 to 10:00 showed one peak (and nadir) seasonal change, with the smallest size in winter (December and February) and a larger size in warmer seasons, with the maximum value in July. Glycogen level in pinealocytes at 09:00 to 10:00 showed bimodal seasonal changes, with lower levels in fall and spring and higher levels in winter and summer. In fall, a circadian trend in glycogen level in pinealocytes was seen, with a higher level at the end of the light period. In winter, the glycogen levels were very high at 09:00, 13:00, 17:00, and 21:00 examined and showed dampening of time‐of‐day differences. On the other hand, the size of pinealocytes followed a time‐of‐day change (P<0.005), being largest at 13:00 and smallest at 21:00. Thus, marked changes in quantitative structure and chemical activities, suggesting changes in functional activity, in pinealocytes were noted especially in severe

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1984.tb00207.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

In a previous study, measurements of arginine vasotocin‐immunoactivity (iAVT) in immature rats over a period of 14 months, led to the discovery of a significant yearly variation, with peak levels of iAVT in August. In the present study, iAVT was measured in pineals obtained from mature male and female rats and hamsters once or twice weekly from July until early September 1982. For all groups, mean pineal AVT‐immunoactivity was less that 7 pg/gland in early July, but then increased significantly by August 11–13. For hamsters, maximum values of 1,272 ± 49 (mean ± S.E.: n = 3) and 1,065 ± 62 pg/gland were recorded for males and females, respectively. For rats, peak values measured were 940 ± 12 pg/gland for males and 1,040 ± 34 for females. The AVT‐activity levels then decreased to less than 100 pg/gland by early September. Thus, a dramatic August elevation of pineal iAVT is characteristic of hamsters as well as rats, and of mature as well as imma

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1984.tb00208.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Male Sprague‐Dawley rats were housed in alternate light/dark conditions (light on, 7:00 AM, light off, 7:00 PM). Corticosterone was determined by radioimmunoassay from blood samples that were obtained by tail clip at 4‐h intervals. Pinealectomized animals have shown significant increase of corticosterone levels at 7:00 AM, 11:00 AM and 7:00 PM in comparison with 2‐month‐old intact rats. There were no differences in serum corticosterone rhythm between 24‐month‐old and pinealectomized animals. Twelve‐month‐old rats have shown significant increase of corticosterone levels at 7:00 and 11:00 AM in comparison with 2‐month‐old animals.The age‐associated increase of serum corticosterone and the similarity between serum corticosterone circadian rhythm in aged and pinealectomized animals suggest that an age‐related decrease in melatonin production [Reiter et al., 1981] may contribute to age related changes of hypothalamic‐pituitar

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1984.tb00209.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

As previous circadian studies of pineal “synaptic” ribbon numbers and melatonin formation suggested that a positive correlation of the two variables exists, in the present investigation this problem was examined in individual pineal glands of rats killed at 1200 h and 2400 h, respectively. For this purpose, one half of the gland was processed for electron microscopy and the ribbons were counted in an area of 20,000 μm2tissue; in the other half serotonin N‐acetyltransferase (NAT) activity and melatonin content were determined. No correlation was found to exist between ribbon numbers and pineal NAT activity, pineal melatonin levels and serum melatonin levels, either at day‐ or at nighttime. It is concluded that the ribbons may perhaps be more closely related to the innervation of the pineal gland than to melatonin f

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1984.tb00210.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Adult female golden hamsters were used to study the effect of short photoperiod on the endogenous opioid system and the effect of pinealectomy on the serum β‐endorphin‐iike immunoreactivity (β‐end LI) levels. Hamsters were housed under either long photoperiod (14L:10D) or short photoperiod (2L:22D) and the regularity of the estrous cycles was determined by daily vaginal exfoliative cytology. Hamsters under short photoperiod became acyclic after about 7 wk. At the end of 8 wk, all the hamsters were decapitated and medial basal hypothalamic (MBH) content of LHRH and methionine‐enkephalin (met‐enkephalin) were measured by specific radioimmunoassays (RIA). Both LHRH and met‐enkephalin levels of the MBH were significantly elevated in the short‐photoperiod hamsters as compared to the normally cycling control animals under long photoperiod. In a second experiment, the effect of pinealectomy (PNX) on the serum levels of β‐end LI in the short‐photoperiod hamsters was determined. The serum β‐end LI levels were increased approximately threefold in the noncyclic hamsters housed under 8 wk of short‐photoperiod conditions. Pinealectomized hamsters kept under 8 wk of short‐photoperiod exhibited lower serum β‐end LI levels similar to those of normally cycling hamsters kept under long photoperiod. These results indicate a possible functional relationship between increased pineal activity (as a result of short photoperiod) and increased MBH met‐enkephalin,

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1984.tb00211.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY