Patricia J. Berger

Dynamics of 6-methoxybenzoxazolinone in winter wheat. Effects of photoperiod and temperature

Abstract6-Methoxybenzoxazolinone (6-MBOA), a compound derivable from some freshly growing plants, is known to stimulate reproduction in some mammals and birds. Winter wheat was studied under controlled laboratory conditions to determine the effects of photoperiod and temperature on derivable 6-MBOA content. Longer photoperiods decrease the amount of derivable 6-MBOA per gram of fresh material in 4-day-old wheat seedlings. Higher temperatures also decrease the amount of derivable 6-MBOA in 4-day-old wheat. 6-MBOA content decreases as the plant ages. Comparisons of only the first centimeter above the seed produced the same age-related result. 6-MBOA is concentrated in the meristematic region with decreasing amounts found in higher portions of the plant. Roots from 9-day-old plants contain 6-MBOA. Unsprouted wheat seeds contain negligible amounts of 6-MBOA. These results demonstrate that environmental variables have a significant effect on derivable 6-MBOA levels, but that under all the regimes studied, 6-MBOA is present in freshly sprouted wheat.

Recognition of Kin and Avoidance of Inbreeding in the Montane Vole, Microtus montanus

Young females of Microtus montanas were housed with an adult male for 9 days postweaning and their sexual maturation noted. Males caused sexual maturation (seen from increased uterine weight) in strange females, but not in daughters. When litters were cross-fostered at birth, males caused sexual maturation in biological daughters that were separated from them at birth, but not in foster daughters. This shows that this species has a mechanism for avoiding inbreeding, with recognition of kin based on familiarity.

Mammalian Reproductive Physiology

Not many years ago, environments were regarded as being relatively stable and species were presumed to have evolved life histories in equilibrium with such environments. More recently, however, attention has been drawn to the fluctuating and uncertain nature of most environments and the necessity of organisms to adapt to this heterogeneity or perish (Levins, 1968). Biologists have begun seriously to consider life history strategies as phenotypic traits that are responding to sets of environmental variables. Today there is increasing awareness of the great complexity of selective forces acting on the evolution of life histories at both the genetic and phenotypic levels (Boyce, 1984; Emlen, 1984).

Influence of Dietary Supplements of Fresh Lettuce on Ovariectomized Microtus montanus

Juvenile Microtus montanus were ovariectomized and fed a standard laboratory diet supplemented in experimental groups with daily fresh lettuce. At sacrifice the uteri were removed and weighed. Intact and sham-operated control groups with and without the lettuce supplement had significantly heavier uteri than the ovariectomized animals. Intact animals receiving the dietary supplement had significantly heavier uteri than intact animals receiving only the standard diet. This would indicate that uterine hypertrophy in M. montanus is caused by substances in plant foods and that these substances are not estrogenic in nature.

Reproductive responses of male Microtus montanus to photoperiod, melatonin, and 6-MBOA.

Juvenile male Microtus montanus were examined for the effects of photoperiod, melatonin, and the naturally occurring reproductive stimulant 6‐MBOA on growth and sexual maturation. 6‐MBOA, present in sprouting grass, is an important environmental cue used for the initiation of reproduction in natural populations of this species. Long photoperiod (16:8) was stimulatory to body, testes, and seminal vesicle growth, while short photoperiod (8:16) inhibited these parameters. The pineal hormone melatonin, administered via daily afternoon injections (5 μg), was also inhibitory to all of the above parameters as well as to serum testosterone. 6‐MBOA, administered via injection (0.0001–100 μg) or dietary means (0.1 or 1.0 μg/gm unsifted chow), appeared unable to augment the rate of maturation in long‐photoperiod‐stimulated animals. When short‐photoperiod animals were treated with high doses of the compound (100 μg injected or 1.0 μg/gm sifted chow), body and gonadal growth was inhibited to a greater extent than when animals were exposed to short photoperiod alone, and serum LH was reduced. Lower doses of the compound had no effect. Melatonin‐treated animals experienced less maturational inhibition when simultaneously given a low dose of 6‐MBOA‐coated chow (1.0 μg/gm unsifted chow). A higher dose of 6‐MBOA (1.0 μg/gm sifted chow) was ineffective in preventing the response to melatonin. These results indicate that 1) male M. montanus utilize photoperiod, rather than 6‐MBOA, as a primary environmental cue, 2) high doses of 6‐MBOA can be inhibitory under short photoperiod, 3) juvenile male voles are highly sensitive to the inhibitory effects of exogenously administered melatonin, and 4) 6‐MBOA can partially prevent the inhibitory effects of melatonin on growth and sexual maturation.

Uterotropic 6-methoxybenzoxazolinone is an adrenergic agonist and a melatonin analog

6-Methoxybenzoxazolinone (MBOA) is a compound isolated from grasses which has gonadotropic effects in a variety of animals. The weak beta-adrenergic agonist character of MBOA is shown by its in vitro stimulation of adenylate cyclase from several tissues. Tritiated MBOA bound specifically to particulate fractions from uterus is also displaced by alpha- and beta-adrenergic compounds. The adrenergic properties of MBOA suggest it may exert diverse effects including direct actions on gonadotropin synthesis and release. The mixed adrenergic agonist ephedrine and the antidepressant imipramine were also found to be uterotropic in the vole Microtus montanus following injection protocols used with MBOA. MBOA is structurally similar to melatonin (5-methoxy-N-acetyltryptamine); [3H]melatonin which binds to uterine and pineal membranes is displaced by MBOA and by other adrenergic agents. The fact that MBOA is a beta-adrenergic agonist and a melatonin analog can account for stimulatory and inhibitory effects of this compound on sexual development.

Pineal weight response to a dietary variable in Microtus montanus

Le régime de contrôle (alimentation de laboratoire des lapins) deMicrotus montanus a été augmenté de plantes vertes. La glande pinéale des animaux recevant le supplément eut un poids inférieur à celui de la glande des témoins (p<0,01).