Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction

Winter is energetically demanding Physiological and behavioral adaptations have evolved among nontropical animals to cope with winter because thermoregulatory demands increase when food availability decreases Seasonal breeding is central within the suite of winter adaptations among small animals Presumably, reproductive inhibition during winter conserves energy at a time when the adds of producing viable young are low In addition to the well-studied seasonal cycles of mating and birth, there are also significant seasonal cycles of illness and death among many populations of mammals and birds in the field Challenging winter conditions, such as low ambient temperatures and decreased food availability, can directly induce death via hypothermia, starvation or shock In some cases, survival in demanding winter conditions puts individuals under great physiological stress, defined here as an adaptive process that results in elevated blood levels of glucocorticoids The stress of coping with energetically demanding conditions can also indirectly cause illness and death by compromising immune function Presumably, the increased blood concentrations of adrenocortical steroids in response to winter stressors compromise immune function and accelerate catabolic mechanisms in the field, although the physiological effects of elevated glucocorticoids induced by artificial stressors have been investigated primarily in the laboratory However, recurrent environmental stressors could reduce survival if they evoke persistent glucocorticoid secretion The working hypothesis of this article is that mechanisms have evolved in some animals to combat seasonal stress-induced immunocompromise as a temporal adaptation to promote survival Furthermore, we hypothesize that mechanisms have evolved that allow individuals to anticipate periods of immunologically challenging conditions, and to cope with these seasonal health-threatening conditions The primary environmental cue that permits physiological anticipation of season is the daily photoperiod; however, other environmental factors may interact with photoperiod to affect immune function and disease processes The evidence for seasonal fluctuations in lymphatic organ size, structure, immune function, and disease processes, and their possible interactions with recurrent environmental stressors, is reviewed Seasonal peaks of lymphatic organ size and structure generally occur in late autumn or early winter and seasonal minima are observed prior to the onset of breeding Although many of the field data suggest that immune function and disease processes are also enhanced during the winter, the opposite seasonal pattern is also observed in some studies We propose that compromised immune function may be observed in some populations during particularly harsh winters when stressors override the enhancement of immune function evoked by short day lengths Because so many factors covary in field studies, assessment of our proposal that photoperiod mediates seasonal changes in immune function requires laboratory studies in which only photoperiod is varied A review of the effects of photoperiod on immune function in laboratory studies reveals that exposure to short day lengths enhances immune function in every species examined Short day exposure in small mammals causes reproductive inhibition and concomitant reduction in plasma levels of prolactin and steroid hormones, as well as alterations in the temporal pattern of pineal melatonin secretion These hormones affect immune function, and influence the development of opportunistic diseases, including cancer: however, it appears that either prolactin or melatonin secretion is responsible for mediating the effects of photoperiod on immune function Taken together, day length appears to affect immune function in many species, including animals that typically do not exhibit reproductive responsiveness to day length

Seasonal changes in immune function.

https://bioone.org/journals/the-wilson-journal-of-ornithology/volume-121/issue-3/1559-4491-121.3.664/Identification-Guide-to-North-American-Birds-Part-II/10.1676/1559-4491-121.3.664.pdf

Identification Guide to North American Birds. Part II

Biology and Comparative Physiology of Birds

The hypothalamo-neurohypophysial system (HNS) is the major peptidergic neurosecretory system through which the brain controls peripheral physiology. The hormones vasopressin and oxytocin released from the HNS at the neurohypophysis serve homeostatic functions of water balance and reproduction. From a physiological viewpoint, the core question on the HNS has always been, "How is the rate of hormone production controlled?" Despite a clear description of the physiology, anatomy, cell biology, and biochemistry of the HNS gained over the last 100 years, this question has remained largely unanswered. However, recently, significant progress has been made through studies of gene identity and gene expression in the magnocellular neurons (MCNs) that constitute the HNS. These are keys to mechanisms and events that exist in the HNS. This review is an inventory of what we know about genes expressed in the HNS, about the regulation of their expression in response to physiological stimuli, and about their function. Genes relevant to the central question include receptors and signal transduction components that receive and process the message that the organism is in demand of a neurohypophysial hormone. The key players in gene regulatory events, the transcription factors, deserve special attention. They do not only control rates of hormone production at the level of the gene, but also determine the molecular make-up of the cell essential for appropriate development and physiological functioning. Finally, the HNS neurons are equipped with a machinery to produce and secrete hormones in a regulated manner. With the availability of several gene transfer approaches applicable to the HNS, it is anticipated that new insights will be obtained on how the HNS is able to respond to the physiological demands for its hormones.

Gene regulation in the magnocellular hypothalamo-neurohypophysial system.

Effects of corticosterone, metapyrone, and ACTH on testicular function at different stages of the breeding cycle in migratory redheaded bunting, Emberiza bruniceps

The hypothalamo-hypophyseal-gonadal axis mediated differential photosexual responses in quail kept under different simulated photoperiodic conditions have been studied in details. Local testicular GnRH-GnIH and their receptor system has been hypothesized to be modulated in quail showing different photo-sexual responses and thus influence the testicular activity and steroidogenesis through local (paracrine and autocrine) action. To validate this hypothesis, we studied the expression of gonadotropin releasing hormone receptor (GnRH-R), gonadotropin inhibiting hormone receptor (GnIH-R) mRNA, growth hormone receptor (GH-R), proliferating cell nuclear antigen (PCNA), 14-3-3, Connexin-43 (Cnx-43), steroidogenic factor-1 (SF-1), Steroidogenic Acute Regulatory protein (StAR), steroidogenic enzyme (3β HSD) in testis as well as androgen receptor (AR) in testis and epididymis of photosensitive (PS), scotorefractory (SR), photorefractory (PR) and scotosensitive (SS) quail. Experimental findings clearly indicate the increased expression of GnIH-R mRNA and suppression of GnRH-R, GH-R, PCNA, 14-3-3, Connexin-43, SF-1, StAR, 3β HSD in testis as well as AR in testis and epididymis of PR and SS quail, while PS and SR quail exhibited the opposite results i.e., significantly decreased expression of GnIH-R mRNA and increased expression of GnRH-R, GH-R, PCNA, 14-3-3, Cnx-43, SF-1, StAR, 3β HSD in testis as well as AR in testis and epididymis. The significantly increased intra-testicular testosterone has been observed in the PS and SR quail while, PR and SS quail showed opposite results. Hence, we conclude that PS and SR quail showed significantly increased testicular activity and steroidogenesis while opposite pattern was observed in PR and SS quail.

Simulated photoperiod influences testicular activity in quail via modulating local GnRHR-GnIHR, GH-R, Cnx-43 and 14-3-3

Changes in vasotocin immunoreactivity of paraventricular nuclei and adrenal function of Japanese quail in relation to different phases of sexual development.

Herbicide Paraquat provokes the stress responses of HPA axis of laboratory mouse, Mus musculus.

To study the interaction of photoperiod and circadian neurotransmitter activity, L-DOPA L-dihydroxyphenylalanine, dopamine precursor) was administered daily, 12 hr after 5-HTP (5-hydroxy tryptophan, serotonin precursor) in sexually immature Japanese quail, raised under short photoperiod (LD8:16) since hatching. The 12 hr treatment of 5-HTP and L-DOPA was given under continuous condition of light for 11 days. After treatment the quail were transferred to intermediate day length (LD 13.5:10.5). The cloacal gland size of drug treated group increased significantly in comparison to control. The quail were then transferred to short photoperiod (LD 8:16). The cloacal gland size of both the groups started decreasing gradually but the rate was significantly low in drug treated quail in comparison to control. The results indicate that the endogenous mechanism controlling seasonality may be reset by drugs that influence serotonergic and dopaminergic activity. The 12 hr relation between the two drugs is stimulatory for gonadal growth under intermediate day length and retards the rate of regression when transferred to short days.

Chandra Mohini Chaturvedi

Papers

Effects of corticosterone, metapyrone, and ACTH on testicular function at different stages of the breeding cycle in migratory redheaded bunting, Emberiza bruniceps

Simulated photoperiod influences testicular activity in quail via modulating local GnRHR-GnIHR, GH-R, Cnx-43 and 14-3-3

Changes in vasotocin immunoreactivity of paraventricular nuclei and adrenal function of Japanese quail in relation to different phases of sexual development.

Herbicide Paraquat provokes the stress responses of HPA axis of laboratory mouse, Mus musculus.

Effect of 12 hr temporal relation of serotonin and dopamine precursor drugs (5-HTP and L-DOPA) on photosexual responses of immature Japanese quail.