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Biomedical subjects

M R Landauer

Publications and source records attributed to M R Landauer.

46 records · Page 3Linked to original sources
PubMed1980

Responses of male hamsters to the ear gland secretions of conspecifics.

The behavioral responses of sexually experienced males toward anesthetized conspecifics were examined. Males directed more mounts and spent significantly more time investigating the ears and genital region of castrated males and diestrous females than intact males. Castrated males were treated in a similar manner to females, suggesting that the absence of an androgen-dependent factor(s) renders an animal more sexually attractive. Males were also administered paired preference tests in which they investigated the odors from the ear glands of diestrous females, castrated males, and intact males. Subjects spent significantly more time investigating the odors originating from ear glands of females and gonadectomized males than intact males. There was no significant difference in the amount of time males spent with the ears of castrated males and diestrous females. These experiments demonstrate that sexually experienced male hamsters can utilize odors associated with the ears to discriminate the gender of conspecifics.

Animals↗
PubMed1976

Regulation of female sexual behavior in the golden hamster: behavioral effects of mating and ovarian hormones.

In the female hamster, sexual receptivity was abbreviated following copulation. Short-term effects of mating, lasting approximately 24-48 hr, were observed in females mated in either estradiol- or estradiol-and-progesterone-induced estrus. Long-term effects of copulation, of 9 days or more in duration, were apparent only in females chronically treated with both estradiol and progesterone, suggesting that progesterone exposure prolongs the inhibitory effects of mating. When progesterone stimulation was intermittent through the use of short-acting injection procedures, recovery from mating could be detected in 48 hr and was complete within 96 hr after copulation. The pattern of behavioral response to ovarian hormones in unmated females was also documented, replicating the "biphasic" effect of progesterone in this species. The inhibitory effects of mating and progesterone summate to produce consistent decrements in female sexual receptivity. It is postulated that short-term postcopulatory abbreviations in receptivity would reduce the vulnerability of the estrous female while long-term inhibitions, interacting with sustained progesterone stimulation, would reduce the probability of mating during pregnancy when hormone levels are elevated for a prolonged period.

Adrenalectomy↗
PubMed1975

Neonatal hormone experience and adult lordosis and fighting in the golden hamster.

Androgenization by testicular secretions or exogenous testosterone propionate (TP treatments administered 24-48 hr post partum) suppressed sexual receptivity in the golden hamster. In response to prolonged adult estradiol benzoate (EB) treatment, gonadectomized normal females and neonatally castrated males exhibited significantly longer total lordosis durations than normal male or neonatally TP-treated (20 mug or 200 mug) females. These results suggest that one aspect of androgen-induced masculinization in the hamster involves reduced estrogen sensitivity. Responses to sequential EB followed by progesterone treatment were also lower in the androgenized groups. Neonatally castrated males did not differ significantly from normal females in their lordosis behavior. Irrespective of adult hormone treatment, androgenized animals fought more than normal females or neonatally castrated males. A genital mask was used to reduce sex differences in peripheral stimulation during testing.

Age Factors↗
PubMedDate not supplied

Radioprotective and locomotor responses of mice treated with nimodipine alone and in combination with WR-151327.

The effect of combining a radiation-protective phosphorothioate with another agent was investigated in an attempt to increase radioprotection and reduce toxicity. The calcium channel blocker nimodipine (NIMO) was administered alone (1 or 10 mg kg-1) or in combination with 200 mg kg-1 of the phosphorothioate radioprotector WR-151327 (WR) (S-3-(3-methylaminopropylamino)propylphosphorothioic acid). Radioprotection as measured (30-day survival) of mice treated i.p. 30 min before (60)Co irradiation at a dose rate of 1 Gy min-1 was evaluated in CD2F1 male mice. The effects of nimodipine and WR-151327 on locomotor activity were investigated also in a separate group of non-irradiated mice. The LD(50/30) for the Emulphor vehicle control group was 8.56. For nimodipine alone (1 or 10 mg kg-1) the LD(50/30)was 8.39 and 10.21 Gy, respectively, yielding dose modification factors (DMFs) of 0.98 and 1.19, respectively. When WR-151327 was given alone, the <LD(50/30) was 12.48 Gy (DMF = 1.46; P < 0.05 from vehicle). WR-151327 combined with 1 or 10 mg kg-1 nimodipine resulted in an LD(50/30) of 12.73 Gy (DMF 1.49, P < 0.05 from vehicle), and when WR-151327 was combined with 10 mg kg-1 nimodipine the LD(50/30) was 14.29 Gy (DMF = 1.67, P < 0.001 from WR-151327). For either dose of nimodipine, locomotor activity did not differ from vehicle. WR-151327 and WR-151327 + 1 mg kg-1 nimodipine resulted in locomotor decrements for up to 4 h post-administration (P < 0.05 from vehicle), and WR-151327 + 10 mg kg-1 nimodipine for up to 6 h (P < 0.05 from WR-151327). Therefore, although there was an additive radioprotective effect when the higher dose of nimodipine was combined with WR-151327, the locomotor decrement was also enhanced. These results demonstrate that a combination of nimodipine and a phosphorothioate such as WR-151327 may be useful as a clinical setting where behavioral and physiological side-effects can be monitored. Published in 2001 by John Wiley & Sons, Ltd.

Animals↗
PubMedDate not supplied

Acute behavioral toxicity of the organophosphate sarin in rats.

Three experiments were performed to determine the behavioral effects of acutely administered isopropyl methylphosphonofluoridate, sarin (61-115 micrograms/kg, SC) to male rats. Dosages of 71 micrograms/kg or greater produced conditioned flavor aversions while spontaneous locomotor activity was increased at 61 micrograms/kg and significantly decreased at dosages of 84 to 115 micrograms/kg, when compared to vehicle control levels. Significant decrements in rotorod performance were observed at 98 and 115 micrograms/kg sarin. The LD50 of sarin was determined to be 165 micrograms/kg. Behavioral alterations were thus obtained at dosages that were between 37 and 59 percent of the LD50.

Animals↗
PubMedDate not supplied

Taste aversions to several halogenated hydrocarbons.

Five halogenated hydrocarbons (chloral; trichloroethylene; 1,2-dichloroethylene; 1,2-dichloroethane and 1,1,2-trichloroethane) were evaluated in the taste aversion paradigm to determine thresholds for producing aversion effects. Comparisons were made between threshold determination for acute and repetitive conditioning trials. All of the compounds produced saccharin aversions following one pairing of the chemical exposure with saccharin ingestion. Repetitive conditioning trials did not alter the thresholds for producing aversions with any of the five compounds evaluated. Potencies of the compounds in producing conditioned taste aversions were chloral greater than 1,1,2-trichloroethane greater than 1,2-dichloroethane greater than 1,2-dichloroethylene greater than trichloroethylene.

Animals↗
PubMedDate not supplied

Trichloromethane-induced taste aversions in mice.

In Experiment 1 four groups (N = 10) of individually housed mice were given access to deionized water for 30 min daily. When fluid consumption stabilized, they were given 30-min access to a 0.3% saccharin solution. This was followed by oral doses of 3, 10 or 30 mg/kg trichloromethane (TCM) or the vehicle (Emulphor). Beginning 24 hr later the subjects were given a two-bottle choice test (saccharin vs water) followed by the appropriate injection in that group. This procedure continued for 10 days. A dose of 30 mg/kg produced a taste aversion on the first choice test and a reduction in total fluid intake which continued throughout the 10-day test period, while doses of 3 and 10 mg/kg TCM or vehicle did not affect either measure. To determine whether the aversion produced by 30 mg/kg TCM was specific to gavage, animals in Experiment 2 received IP injections of 10, 30 or 100 mg/kg TCM or vehicle. All TCM groups showed taste aversions which lasted for the 10-day test period. Although concomitant fluid reductions occurred for all doses on day one, only the 100 mg/kg group maintained this drop throughout the 10-day test period. Thus, TCM produces taste aversions when given at relatively low doses by both oral and IP routes of administration.

Animals↗