Biomedical subjects

R V Andrews

Publications and source records attributed to R V Andrews.

At least 19 recordsLinked to original sources

PubMed1997

Surgical treatment of intractable seizures with multilobar or bihemispheric seizure foci (MLBHSF).

BACKGROUND: Patients with multilobar or bihemispheric seizure foci (MLBHSF) are generally not considered candidates for major resective surgery because of the high risk of complications. A combination of relatively less invasive surgical procedures were used to treat 19 patients with intractable seizures with MLBHSF. METHODS: Epileptogenic areas were identified via standard techniques. Locations of the seizure foci were in two lobes of a hemisphere in 11 patients, three lobes of a hemisphere in four patients, four lobes of a hemisphere in one patient, and both hemispheres in three patients. All 19 patients had multiple subpial transections; in addition, seven patients had small topectomies and nine patients had amygdala hippocampotomies. RESULTS: The longest follow-up is 54 months and the median for follow-up is 33 months. Nine patients (47%) are either free of seizures or have only rare seizures; eight patients (41%) have greater than 90% reduction in seizure frequency; one patient (6%) has complete cessation of myoclonic seizures and secondary generalization, and greater than 50% reduction in partial complex seizures; and one patient (6%) has greater than 50% reduction in seizure frequency. There were no permanent operative complications. CONCLUSION: Though the follow-up is relatively short and the number of patients is small, these results are encouraging, because the majority of patients in this group were poor surgical candidates.

Adolescent↗

PubMed1993

Seasonal acclimation of prairie deer mice.

Prairie deer mice responded to long nights by reducing their metabolic rates, core temperatures, thermal conductances and incremental metabolic responses to cold stimulus, while increasing their capacities for nonshivering thermogenesis. Some winter animals spontaneously entered daily torpor in the mornings and thereby further reduced their metabolic rates and core temperatures. Provision of exogenous melatonin (by subdermal implants) mimiced short photoperiod effects on metabolic rates and core temperatures of wild-caught, laboratory maintained animals. Provision of supplemental dietary tryptophan to laboratory animals conditioned to natural light cycles mimiced metabolic effects of long nights in summer animals, and further reduced metabolic rates of winter mice, but did not affect their core temperature levels. Newly caught, laboratory maintained deer mice responded to natural seasonal clues of short-photoperiod and increased dietary tryptophan by reducing their resting energy requirements through both lower metabolic and lower core temperature levels. Short photoperiod and seasonal change also promoted gonadal involution, and resulted in more socially tolerant huddling by mice with reduced core temperature. Reduced 24-hour LH excretion rates were also observed in winter animals which were exposed to seasonal light cycles at warm (25 degrees C) room temperatures. We propose that seasonal acclimatization involves pineal effects on sex hormone-influenced social behaviors and on resting metabolism. These effects serve to conserve resting energy expenditure and promote hypothermic insulation by wild prairie deer mice.

Acclimatization↗

PubMed1993

Season affects tolerance of cohabitation by deer mice.

We measured the resting metabolic rates of Peromyscus maniculatus for 7 days before and 7 days following forced pairing in order to determine whether seasonal light cycles influenced the rates of behavioral and metabolic habituation of deer mice to cohabitation. We had earlier shown that winter photoperiod and/or huddling results in lower resting metabolic rates and core temperatures of deer mice. Seasonal photoperiods were simulated by conditioning wild-caught mice to 24-h light cycles with differing durations of light exposure during the 24 h day. These experiments demonstrated that winter mice adjusted their resting metabolic rates from solitary to huddling levels much more rapidly than summer mice. Initial, high metabolic rate responses of paired mice persisted much longer than expressions of agonistic behaviors between paired mice. We propose that winter photoperiod enables animals to more efficiently make the transition to spontaneous, amicable huddling as a winter acclimatization strategy.

Animals↗

PubMed1988

Differential effects of adrenergic blockade on seasonal changes in core temperatures and thermal conductances of deer mice maintained in thermal neutral environments.

1. Resting, daytime, thermal conductances and metabolic rates of mice conditioned to winter (10:14LD) and summer (14:10LD) photoperiods were reduced by social huddling; huddling resulted in group size related elevations in core temperature during summer, but not with winter light-dark cycle exposures. 2. Core temperatures of resting, solitary winter animals were lower than those of summer; both summer and winter animals' core temperatures were further reduced by increased thermal conductance resulting from (phentolamine) alpha receptor blockade. 3. Social huddling reduction of the heat loss from phentolamine treatment was more effective for winter (10:14LD) animals. 4. While phentolamine treatment resulted in increased thermal conductance and lower core temperatures of the mice, propranalol treatment resulted in lower core temperatures and resting metabolic rates, with a resulting decrease in thermal conductance. 5. Since adrenergic blockade was less dose-effective on winter animals, we reasoned that winter animals display higher levels of endogenous adrenergic capacity than summer animals and that lower winter thermoregulatory set points provide for energy conservation with enhanced capacity for meeting cold challenge.

Animals↗

PubMed1987

Metabolic and thermoregulatory consequences of social behaviors between Microtus townsendii.

1. Townsend voles responded to each other by raising their core temperatures. 2. Increments of temperature increases that accompanied hostile reactions between voles, were proportional to the intensity of the behavioral displays. 3. Amicable behaviors (huddling) were also associated with higher body temperatures that were proportional to group size. 4. Huddling voles conserved metabolic energy expenditure by reducing their metabolic rates and thermal conductances. 5. Such conservation required 1 or more days of amicable behavior to develop, and to be reversed. 6. The degree of metabolic rate reduction that accompanied amicable huddling behavior and the associated reduction of thermal conductance was independent of group size.

Animals↗

PubMed1986

Bioenergetic benefits of huddling by deer mice (Peromyscus maniculatus).

Both short photoperiod and communal social living conserve metabolic energy by deer mice held in thermal neutral ambient temperatures. Initial socialization was energetically more costly than solitary living, but huddling behaviors reduced thermal conductance and mass specific metabolic rate by 30% within 5 days. While short photoperiod reduced metabolic energy expenditure by decreasing thermoregulatory demand, huddling mediated behavioral conservation was achieved with hyperthermic core temperatures.

Animals↗

PubMed1986

Photoperiodic adjustment of thermal conductance in deer mice.

Seasonal changes in metabolic rate can be induced in mice held in thermal neutral (26-29 degrees C) ambient temperatures. The metabolic effect of winter photoperiod is a lower metabolic rate without compromise to metabolic reserve. Manipulations of photoperiod or melatonin backgrounds adjust the thermoregulatory setting for core temperature level and affect thermal conductance.

Acclimatization↗

PubMed1985

Metabolic and thermoregulatory effects of photoperiod and melatonin on Peromyscus maniculatus acclimatization.

A photoperiod-related seasonal rhythm in active period (scotophase), metabolic rate and core temperature was documented for animals held at 21.0 +/- 0.1 degrees C ambient; animals that were habituated to long nights (10:14LD) had a greater metabolic reserve than those held in summer photoperiods (14:10LD). While relative weights of gonads and sex accessory tissues of mice show typical "winter" regression, interscapular brown adipose tissue mass was unaffected by photoperiod; moreover, IBAT beta adrenergic responses under "winter" photoperiods did not differ from "summer" photoperiods in the absence of cold stimulus. Thermogenic efficiency, measured as the increment of active temperature level achieved per increment of active period metabolic effort, was highest for animals exposed to short photoperiods. Thermal conductance was reduced in animals exposed to short (10:14LD) photoperiods. Heat conservation and thermogenic response capacity was enhanced by melatonin treatment and short photoperiod.

Acclimatization↗

PubMed1983

Hyperthermic reactions of voles to novel and repetitive psychogenic stimuli.

Montane voles (Microtus montanus) respond to brief conspecific encounters with strange voles by adrenergic reactions which result in elevations of their core temperatures by approximately 1.0 degrees C. Elevations of body temperatures and agonistic behaviors decrease in intensity with sequential encounters between the same conspecific challengers but are restored when one of the challengers is replaced by a new "strange" vole. The rates of habituation of agonistic behaviors and of hyperthermic response are a function of the number of encounters permitted, rather than time between encounters. Levels of hyperthermic responses resulting from contact between previously habituated animals are higher than those elicited by non-specific stimuli such as noise or handling. Radiotelemetry of feral animal temperature homeostasis may provide a useful measure of low-frequency social encounters between conspecific voles.

Animals↗

PubMed1983

Efficacy of alpha-chlorhydrin in sewer rat control.

A single application of the male chemosterilant, alpha-chlorhydrin, to a problem sewer rat infestation resulted in reductions of rat numbers and distribution which was comparable to effects of warfarin baiting methods. Rat numbers were reduced by more than 85% by both methods. More rapid mortality and recruitment were evident for warfarin effects; the alpha-chlorhydrin treated population had a longer lag phase of growth so that reinfestation of sewer habitat to pre-treatment numbers, and distribution over a 40 square block area, required approximately 1.5-2 times longer after alpha-chlorhydrin treatment when compared with warfarin treatment. Comparisons of changes in rat densities in infested sewers following the two treatments indicate that recovery of warfarin treated populations is achieved by reproductive recruitment followed by dispersal while alpha-chlorhydrin treated populations recover by slower immigration and later reproductive recruitment. Alpha-chlorohydrin should be a useful addition to a limited arsenal of rat control agents because of its specificity for the Norway rat, its single dose effectiveness as a toxicant-chemosterilant, and its short environmental half-life.

Animals↗

PubMed1982

Pharmacological evidence for adrenergic activation of hyperthermic responses associated with psychosocial stimulation.

1. Brief social encounters between strange voles living adjacent compartments of a population cage lead to rapid increases of more than 1 degrees C in their core temperatures. 2. Socially induced core temperature responses remain elevated for more than 1 hr following social contact, and are of greater amplitude and duration than can be elicited by handling, noise or exercise. 3. Pretreatment of opponents with adrenergic blockers reduces the amplitude and duration of hyperthermic response proportional to drug intake; both alpha and beta blocking effects are completely reversed within 24 hr. 4. The dynamics of the hyperthermic response and effects of the drugs suggest that the rapid rise in core temperature is due to both vasoconstrictor (alpha) heat conservation and metabolic (beta) heat generating mechanisms, and that the protracted elevation of core temperature is primarily due to (beta) metabolic activation.

Animals↗

PubMed1977