LeGrande C. Ellis

Monoamine oxidase activity of the hypothalamus and pituitary: Alterations after pinealectomy, changes in photoperiod, or additions of melatonin in vitro

Rat pituitary MAO activity was reduced by constant darkness and by additions of melatonin in vitro and was increased by constant light and by pinealectomy. Hypothalamic MAO activity followed the same pattern but was less dramatically affected. The data suggest that MAO may be a target enzyme for melatonin.

Seasonal cycles in melatonin synthesis by the pineal gland as related to testicular function in the house sparrow (Passer domesticus)

Abstract Free-living male house sparrows were collected monthly for one year. Pineal glands were assayed for HIOMT activity, beak color was scored for degree of pigmentation, and testicular size was measured gravimetrically. Additional experiments were undertaken in order to evaluate the role of photoperiod and androgens on pineal function. HIOMT activity of the pineal was inversely related to testicular weight, the larger testicular weights occurring in the spring and being associated with an increase in photoperiod. The data negated the possibility that the pineal gland through melatonin synthesis could be responsible for the seasonal cycle of testicular development. We observed that beak color intensified in the birds as their testicular size increased. Neither exogenously administered nor endogenously produced testosterone could be held responsible for the decrease in pineal HIOMT activity that occurred during seasons of reproductive activity. When birds were subjected to an increased photoperiod of red light, HIOMT activity decreased while the testes enlarged. In contrast, when birds were placed on a white-light regime using fluorescent bulbs, HIOMT activity increased. These results were explained by the fact that the fluorescent light bulbs emitted very little energy in the red end of the spectrum. These data corroborated the finding of other workers that red light is much more effective than green light for stimulating the growth of the testes. The pineal gland did not appear to be the driving factor behind reproductive cycles in the sparrow, but the data were consistent with this organ serving as a neuroendocrine transducer, mediating light effects on the testes via hormones that either synchronize reproductive cycles to the season or attenuate sexual activity.

Prostaglandin E1 Induced Inhibition of Rabbit Testicular Contractions in Vitro

Summary Intact rabbit testes contracted autorhythmically in vitro with a frequency of 2-3 beats/min. When (PGE1) was added to the bathing media, there were alterations in amplitude of contractions, rate, overall tone, and mode of contraction. At relatively high levels of PGE1 (greater than 36 nM) the contractions were completely effaced; with lower concentrations of PGE1, recovery was evident after 5 to 6 min. The effects of PGE1 on amplitude, rate, and tonus were dose-dependent. The above observations, plus those of other workers that prostaglandins are present in mammalian testes, that a mechanism for their synthesis appears to be present in this organ, and that these compounds modulate androgen synthesis and inhibit testicular capsular contraction, suggest a possible physiological role for these unsaturated fatty acid derivatives in normal testicular function.

A rapid simple radiometric assay for phospholipase A2 activity

Abstract A rapid, simple radiochemical assay for phospholipase A2 (PLA2) activity is described in which incubations of homogenized tissue were directly applied to columns of silica gel absorbent. The metabolites and substrate were eluted from the columns with two different solvent systems so that each could be separated and quantified.

Species differences in contractility of seminiferous tubules and tunica albuginea as related to sperm transport through the testis.

Frequency and depth of contractions and tonus--i.e., diameter of the tubule or shift of the baseline for the capsule--of both the seminiferous tubules and the tunica albuginea were quantified for rat, mouse, rabbit, hamster and ground squirrel tests. In the ground squirrel, contractility was measured prior to, during and after breeding. The rat testes had the strongest tubular contractions; those of the mouse, squirrel and rabbit exhibited intermediate values, and the hamster tests had the weakest tubular contractions. The rabbit tests exhibited the strongest, most well-developed rhythmical capsular contractions while the rat, mouse, hamster and squirrel tests showed no definite rhythmical contractions. Hamster tests apparently depend primarily upon fluid secretion by the seminiferous tubules for sperm transport through the tests to the epididymis, while the squirrel, rat and mouse tests utilize both fluid secretion and some tubular contractions. The rat apparently utilizes tubular contractions more so than the other rodents studied for sperm transport.

Contractions of rabbit testes in vitro: permissive role of prostaglandins for the actions of calcium and some smooth-muscle stimulating agents.

Abstract Rinsing actively contracting rabbit testes in vitro with fresh Tyrodes solution abolished capsular contractions and the response of this preparation to either Ca++, serotonin, or acetylcholine. Adding exogenous prostaglandin E2 (PGE2) to the medium restored contractility and the responses of the preparation to each of the above three agents. 4 A reciprocal dependency was observed between Ca++ and PGE2 in stimulating contractions. PGE2 potentiated, but was not required for the stimulatory action of either epinephrine or histamine. The stimulation of contractility by epinephrine, but not prostaglandin was inhibited by the α-blocking agent, ergotamine tartrate. 4 This action of epinephrine did not involve prostaglandin release, nor was it inhibited by indomethacin pretreatment. 4 Isoproterenol inhibited testicular contractions evoked by PGE2.

Prostaglandin-like substances: initiation and maintenance of rabbit testicular contraction in vitro.

Summary The spontaneous contractions that occur in rabbit testes in vitro were abolished by changing the bathing medium. Adding the initial medium from an active to an inactive preparation induced activity in the inactive testis. Extraction of the initial medium at pH 3 into ethyl acetate, a system used for recovering prostagandins, yielded a residue that restored the activity. Acetylcholine and serotonin had little effect on the inactive preparation nor could a smooth-muscle active substance be extracted from these preparations. Oxytocin stimulated neither the active nor the inactive testis appreciably. Epinephrine increased tonus in both inactive or active preparations, but did not induce rhythmic contractions. Prostaglandins of the E-type were stimulatory at low, but inhibitory at higher concentrations. A myogenic agent with prostaglandin-like properties was present only in the bathing media from active preparations and appeared to determine the response that was obtained by treatment with exogenous prostaglandins or some pharmacological agents in vitro. This work was supported by U. S. Atomic Energy Commission Grant No. AT(11–1)–1602 and Utah State University Research Grant U-300. We thank Dr. John E. Pike, Upjohn Co. for the generous contribution of the prostaglandins.

Melatonin reduces mortality from Aleutian disease in mink (Mustela vison).

Abstract: Aleutian disease (AD) results from a persistent parvoviral infection that results in marked hypergammaglobulinemia and immune complex mediated lesions of the kidney, liver, lungs and, arteries. Melatonin protected both a wild type or demi strain and a demi/dark crossed strain of mink from AD. The biogenic amine also afforded protection against other non‐diagnosed diseases naturally found on mink farms when it was available from a subcutaneously‐placed reservoir. Some genetic strains of mink apparently differed in the resistance of mink to the virus and in the protective ability of melatonin. The demi strain was the most resistant followed by pastels, mahogany, darks, and those strains with the double recessive Aleutian gene. The protective action of melatonin appeared to result from melatonins ability to scavenge free radicals, but it could also be due to the induction of antioxidant enzymes or to the modulation of immunity. Melatonin also protected mink against distemper.

Age and seasonal differences in the synthesis and metabolism of testosterone by testicular tissue and pineal HIOMT activity of Uinta ground squirrels (Spermophilus armatus).

Abstract Male Uinta ground squirrels ( Spermophilus armatus ) were sacrificed from a free-living population (a) during the breeding season, which immediately followed emergence from hibernation; (b) after the reproductive season; (c) and just prior to aestivation/hibernation. HIOMT activity of the pineal gland was assayed and related to the ability of the gonads to synthesize and metabolize testosterone. Older squirrels had higher HIOMT activity than did the younger animals. The activity of this enzyme was lowest in squirrels during the breeding season. HIOMT activity increased after the breeding season to its highest level just before the squirrels enter aestivation/hibernation. At this time, testicular weight increased concomitant with an apparent increase in HIOMT activity. Testicular size and weight were largest at the time of emergence of the animals from hibernation. Androgen synthesis was also greatest during the breeding season. As would be expected, both decreased rapidly there-after. The testes formed little 17α,20α-dihydroxyprogesterone during or after the breeding season, contrary to what has been reported for rats and house sparrows. The older squirrels demonstrated a greater capacity for testosterone metabolism during the breeding season than did the younger animals.

Mechanisms and interactions in testicular steroidogenesis and prostaglandin synthesis

Prostaglandin synthesis by rat testicular tissue was observed to be gonadotrophin and adrenal dependent, and to have the same distribution in the gonad as the steroidogenic enzymes. The synthesis was increased by 5-HT, but decreased by melatonin. Lipid peroxidation increases with age, FSH treament, linoleic and arachidonic acid and melatonin, but was decreased by serotonin, c-AMP, LH, prolactin and ephinephrine. Testicular lysosomes were labilized by LH, adrenal demedullation, testosterone, Vit. A and acetylcholine, but were stabilized by c-AMP, epinephrine and cortisol. Contractility of rat seminiferous tubules was observed to be prostaglandin dependent, stimulated by 5-HT, and inhibited by melatonin and c-AMP. Evidence was obtained indicating that a phospholipase A2 is present in rat testicular lysosomes, and that it is liberated by radiation, heat or certain chemicals. This enzyme hydrolyses PUFA from membrane phospholipids, the former of which are converted into prostaglandins. The prostaglandins appear to initially stimulate contractility of seminiferous tubules, but at higher concentrations they stimulate adenyl cyclase, which increases c-AMP levels in the tubules thereby inhibiting contractility and cellular division. The process of prostaglandin synthesis also produced malonaldehyde, and endoperoxides that contribute to alterations in steroidogenesis by Schiffs base formation and to cellular lysis by membrane permeability changes. Prostaglandins appear to be synthesized physiologically from PUFA derived from cholesterol esters, but pathologically in much larger quantities from membrane phospholipids. Prostaglandins apparently inhibit androgen synthesis by their effects on cholesterol esterase and other steroidogenic enzymes rather than by changing blood flow.