Effect of 6-methoxybenzoxazolinone on sex ratio and breeding performance in Microtus montanus

The plant derivative, 6-mathoxybenzoxazolinone (6-MBOA), which has been demonstrated to initiate reproduction in field populations of the montane meadow vole (Microtus montanus), was administered via feeding or Silastic capsule implants to mated pairs of laboratory bred M. montanus. The animals remained paired for 120 days, and the number, size, and sex ratios of the resulting litters were recorded. Both the size and frequency of litters were significantly greater in 6-MBOA-treated pairs than in controls. By using implants, it was possible to treat one or both sexes in a mated pair. The positive effects of this compound on litter size and number of litters occurred when the females received implants, which indicates that the male has no influence on these parameters. The most unusual result of these experiments was that 6-MBOA has a significant effect on the sex ratio of the litters. Animals receiving 6-MBOA produced significantly more females than did control pairs. This result occurred regardless of the method of administration, and in the case of the implant studies, regardless of which sex received the active implants. These findings are discussed in relation to the ecology and life history strategy of Microtus montanus.     

Tissue alterations in Microtus montanus chronically infected with Trypanosoma brucei gambiense

Changes in liver, spleen, kidneys, heart, and brain are reported for Microtus montanus chronically infected with Trypanosoma brucei gambiense. An increase in body weight of infected animals was attributable to a significant increase in total mass of spleen, liver and kidney. Cellular infiltrate consisting primarily of lymphocytes and plasma cells was observed in all organs and was particularly evident in intralobular connective tissue of the liver, adipose tissue of the hilum, and adjacent medullary region of the kidney, spleen, and the meninges. Disruption of normal metabolism and the pathological changes observed in liver and kidney suggest that the survival of trypanosome-infected voles is dependent largely on the physiological response occurring in these organs.     

Hormonal regulation of preputial gland function in male Microtus montanus, the montane vole

1. Preputial gland function in male Microtus montanus is androgen-dependent, both in terms of preputial weights and in the production of a series of lipids which are present in M. montanus and absent from Microtus pennsylvanicus. 2. Production of these species-typical lipids is decreased but not eliminated in castrates, as well as in adrenalectomized castrates treated with corticosterone. Therefore, in the total absence of androgens, a low level of these lipids is still produced. 3. 5 alpha-dihydrotestosterone and 17 beta-estradiol enanthate have limited effects on maintenance of preputial weight, suggesting that testosterone itself is the active steroid in the preputial gland of this species.     

Multiple alpha-keto aciduria in Microtus montanus chronically infected with Trypanosoma brucei gambiense

Microtus montanus chronically infected with a monomorphic strain of Trypanosoma brucei gambiense excreted in urine greatly elevated quantities of not only the aromatic alpha-keto acids, phenylpyruvic and 4-hydroxyphenylpyruvic acids, but also two aliphatic alpha-keto acids, pyruvic and alpha-ketoglutaric acids. Elevated keto acid excretion began approximately midway through infection and quantities remained elevated until death. Daily keto acid excretion did not correlate with daily parasitemia. Thus, a large metabolic disturbance exists in laboratory animals infected with African trypanosomes. The multiple alpha-keto aciduria potentially contributes to the pathogenesis of chronic African trypanosomiasis.     

Growth and reproductive development of male Microtus montanus is affected by the prenatal photoperiod

Rates of growth and sexual maturation of microtine rodents vary in response to photoperiod. Previous work with Microtus montanus has shown that the photoperiod present prior to weaning influences how voles will respond to photoperiods seen following weaning. The data presented demonstrate that information about the photoperiod seen by the mother during pregnancy influences the postweaning development of male M. montanus. Adult M. montanus were paired in photoperiods consisting of 8, 14 or 16 h light/day. Their litters were conceived and born in these photoperiods. On the day of birth the litters were recorded and retained in the gestation photoperiod (Groups C8, C14 and C16) or transferred to the 14-h photoperiod (Groups E8 and E16). The growth of males was followed from weaning until 74 days of age, at which time the voles were sacrificed and their reproductive organs weighed. There were no differences in body weight or length between groups at 18 days of age. At 74 days of age the development of the voles could be ranked in the following sequence: C8 less than E16 less than C14 less than E8 less than C16.     

Effects of inducer pretreatment on liver function and morphology in the mountain vole Microtus montanus

Liver function and morphology of the mountain vole, Microtus montanus, were examined after i.p. injections of phenobarbital, beta-naphthoflavone, or Aroclor 1254 at three dose levels. The results of the liver function tests showed serum glutamic pyruvic transaminase and serum malathion carboxylesterase activities were normal in all the treatment groups. The histological results showed no necrotic tissue but did reveal two different morphological stages related to the level of monooxygenase activity; a low induction state was represented by foamy vacuolated hepatocytes while high induction states were related to enlarged, swollen, hypertrophied cells.     

The olfactory responses of mirid bugs to six plant extracts and their volatiles

Many methods for management of mirid bugs, one of the major pest species in cotton fields, have been developed in recent decades. The use of attractive plant volatiles may be a safe and effective alternative compared with chemical pesticides. Very little is known about the responses of the bugs to some specific volatiles. In this study, the attractive effects for the mirid bug Apolygus lucorum were evaluated and compared among ethanol extracts obtained from six types of plants. The results showed that A. lucorum had the highest selection response rate to the extract from Allium tuberosum seeds and 70.51% of the adults tended to choose this odour source. Among 40 identified compounds of the volatiles comprising A. tuberosum seed extracts, diethyl phthalate and methyl levulinate had significantly higher attractive effects than that of cotton leaves, but the respective selection response rates were less than 65%. We found that when methyl levulinate and diethyl phthalate were mixed in volume ratios of 3:7 and 6:4, the selection response rates of A. lucorum for the mixtures were 54.67% and 63.65%, respectively. These response rates were significantly higher than those for the two compounds presented alone. Furthermore, the selection response rates of A. lucorum based on these mixtures reached 82.75% and 75.73%, respectively when compared with cotton leaves. The two volatile mixtures also showed a significantly higher attractive effect for Adelphocoris suturalis, with respective selection response rates at 74.58% and 77.80% when compared with cotton leaves. Moreover, the two attractants showed no difference between the responses of male and female mirid bugs. We concluded that an appropriate application of the attractants described herein has the potential to develop a safe and effective approach for the monitoring and control of mirid bugs in cotton fields.     

Effects of varying inducer type and dose on hepatic monooxygenase activities in the mountain vole Microtus montanus

Hepatic monooxygenase activities of the mountain vole, Microtus montanus, were measured after i.p. injections of phenobarbital, B-naphthoflavone and Aroclor 1254 at doses ranging from 5 to 80 mg/kg. The results showed that mountain voles differed in their induction of hepatic monooxygenase activity relative to other rodents. The results also suggest substrate specificity in the detection of enzymatic induction and the importance of considering effects of varying inducer doses on hepatic monooxygenases.