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Biomedical subjects

S Kent

Publications and source records attributed to S Kent.

At least 55 records · Page 3Linked to original sources
PubMed1991

Interactions between body temperature and wheel running over the estrous cycle in rats.

Female rats were housed in Wahmann wheels under a 12:12 light-dark (LD) photoperiod for 36 days and then were switched to LD 10:14 for 36-64 days. Running was 95-100% nocturnal. Overall amounts of running were higher in LD 12:12, but changes over the estrous cycle were similar. On the night of proestrus running increased by 64% in LD 12:12 and 123% in LD 10:14 (p less than 0.0001) compared to the first night of diestrus. Nighttime Tb's were correlated with running levels. In LD 12:12 Tb on proestrus was higher by 0.3 +/- 0.0 degrees C (p less than 0.0001); in LD 10:14 it was higher by 0.2 +/- 0.0 degrees C (p less than 0.001) compared to diestrus-1. During L, Tb was lowest on proestrus and highest on estrus. Half of the rats exhibited a consistent phase advance of at least 30 min in both Tb and activity on proestrus. The advanced Tb acrophase was correlated with both the activity acrophase (r = .91; p less than 0.0001) and the amount of running (r = .60; p less than 0.01). The wheels of 6 rats were then locked at night in LD 10:14. There were no significant Tb changes from diestrus-1 across the cycle. However, Tb acrophase was delayed a mean of 76 +/- 16 min (p less than 0.01) in these rats. Also, the Tb acrophase across all days of the estrous cycle was delayed by 94 +/- 18 min (p less than 0.001) compared to when the wheels were open.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Phentolamine and thermoregulation in rats.

Phentolamine (PHEN), a nonselective alpha-adrenoceptor antagonist, causes a dose and ambient temperature (Ta)-dependent fall in body temperature (Tb) when injected intraperitoneally. In this paper, we investigated whether this was caused by integrated behavioral and autonomic thermoregulatory responses and whether it was due to a central action of the drug. Male rats were trained to press a bar for warm air in the cold or cold air in the heat. Rats were tested in both conditions near their Tb peaks and troughs after injections of saline or PHEN (5 and 10 mg/kg, IP). Tb fell significantly within the first 30 min post-PHEN, and after that, in the cold, the rats worked to increase Ta. In the heat they did not change Ta. To determine what was responsible for the Tb fall, we measured heat loss and heat production after saline or PHEN (10 mg/kg; IP) at Ta 2, 20, and 30 degrees C. Decreases in Tb at 2 and 20 degrees C were caused by increased heat loss during the first 15-30 min post-PHEN. At 2 degrees C, heat production increased after the drop in Tb. We conclude that the main reason the rats do not start to work immediately to prevent their core temperature from falling is that skin temperature is high, due to peripheral vasodilation, and that skin temperature is the major stimulus for regulating preferred Ta. We believe these effects are mediated by peripheral mechanisms because intracerebro-ventricular injections of PHEN did not cause a fall in Tb.

Animals↗
PubMed1991

Circadian rhythms of body temperature and drinking and responses to thermal challenge in rats after PCPA.

Body temperature (Tb) and drinking were measured for five days in male and female rats. On day 6 (S1) the rats were injected with saline. On day 7 (P1) they were injected with PCPA (300 mg/kg IP). Measurements continued for 12 days. Immediately after PCPA Tb dropped. After that, the amplitude of the daily Tb rhythm was significantly decreased from days P2-P5. Females were more affected than males. Nocturnality of drinking was decreased on days P2-P4. Because the peak of the Tb rhythm advanced after PCPA, while the peak of the drinking rhythm was delayed, we conclude that the attenuation of the Tb rhythm was a direct result of PCPA treatment rather than a masking effect due to the attenuation of other rhythms. Other rats were thermally challenged during the first week post-PCPA. There were no differences in ability to regulate Tb in the cold, and the small variations in the heat were overshadowed by gender differences.

Animals↗
PubMed1991

Elevated body temperature in female rats after exercise.

Female Sprague-Dawley rats living in basin cages (sedentary rats) under a 12:12 light-dark cycle normally have body temperatures (Tb; measured via telemetry) that vary from a mean peak of 38.1 +/- 0.1 degrees C in the dark to a mean trough of 36.0 +/- 0.1 degrees C C in the light. We have found that if rats are housed in activity wheels, their mean peak Tb in the dark, when they run in the wheels, rises to about 39.5 degrees C. Mean trough Tb in the light also rises, to about 36.5 degrees C, although they never or very rarely run in the wheels in the light. Other rats were rotated through two cycles of wheel-open (WO) and wheel-locked (WL) conditions. During the first WO cycle their mean Tb in the dark gradually rose over the first 2 wk, and their mean Tb in the light gradually fell. In the first WL, mean Tb in the dark fell immediately to sedentary levels, and mean Tb in the light fell more gradually. In the second WO condition, both dark and light Tb rose almost immediately. Since rats in locked wheels have Tb similar to sedentary controls, these results support the hypothesis that steady exercise at night results in an upward resetting of a thermoregulatory set-point during the day.

Animals↗
PubMed1990

Influence of ambient temperature on sleep and body temperature after phentolamine in rats.

Phentolamine, an alpha-adrenoceptor antagonist, both decreases rapid-eye-movement sleep (REMS) and causes a dose- and ambient temperature (Ta)-dependent drop in body temperature (Tb). The purpose of this paper was to examine the correlation between changes in sleep and changes in Tb after phentolamine at various Ta's. Tb and sleep were recorded in male rats for 4 h after i.p. injection of either saline or phentolamine (1 mg/kg at Ta 20 degrees C; 5 mg/kg at 20, 30 and 32 degrees C; 10 mg/kg at 20, 30, 32, and 34 degrees C). Changes in sleep were highly correlated with changes in Tb: when Tb dropped, amounts of sleep, especially REMS, also were decreased. The largest effects were seen at Ta 20 degrees C. After 5 mg/kg, Tb was below normal for 2 h and latency to REMS increased 82 +/- 27 min (P less than 0.025). After 10 mg/kg Tb was decreased for 3 h, and latency to REMS increased 91 +/- 19 min (P less than 0.001). While Tb was lower amounts of REMS were also decreased. Smaller effects were observed on slow wave sleep. At those conditions where phentolamine had no effect on Tb (i.e. Ta 20 degrees C, 1 mg/kg, and Ta 32 degrees C, 5 and 10 mg/kg) no differences were found in any measure of sleep. These results demonstrate that the effects of phentolamine on sleep are not caused by direct action on sleep mechanisms, but rather by its actions on thermoregulatory and possibly other mechanisms that modulate sleep.

Animals↗
PubMed1989

Effects on C3H mouse mammary cancer of changing from a high fat to a low fat diet before, at, or after puberty.

A low fat/low calorie (LF/LC) diet is a relative inhibitor of murine mammary cancer. Because the mammary gland may be most sensitive to the action of a carcinogen at or near the age of puberty, we studied whether beginning a LF/LC diet before puberty would decrease C3H/OuJ mouse mammary cancer incidence more than if such a diet was begun at or after puberty. We also studied whether the advancement of the age of puberty by a high fat/high calorie (HF/HC) diet would in itself be a mammary cancer risk factor and whether dietary fat levels would affect mammary cancer metastases. In the first study, mice were changed from a HF/HC diet to a LF/LC diet at 12 days of age, puberty, or 60 days of age. Other groups were always HF/HC or always LF/LC. In a second experiment, mice were fed a high fat diet for the same length of time, i.e., from 21 to 75 days of age (before and through puberty) or 75 to 129 days of age (well after puberty). In one aspect of the first study, puberty was advanced by feeding a HF/HC diet until the first day of puberty. However, tumor latency, incidence, and multiplicity were not statistically different from those of the LF/LC control. Other results of the first study indicated, in general, that mice consuming a LF/LC diet beginning at or before puberty had a longer tumor latency and a lower tumor incidence and multiplicity than mice either beginning a LF/LC diet at 60 days of age or continuously fed a HF/HC diet. Lung metatases were greater in mice fed a HF/HC diet continuously compared to LF/LC continuously. In the second study, beginning the high fat diet before or after puberty did not result in statistically significant differences in tumor latency, incidence, or multiplicity. It was concluded that the longer a LF/LC diet was fed, the lower was the mammary cancer risk. An early puberty in itself was not a mammary cancer risk factor and mouse puberty had no particular significance as an age before which a LF/LC diet should begin.

Animals↗
PubMed1989

Maternal malignant melanoma with placental metastasis: a case report with literature review.

Histologic detection of micrometastatic melanoma in the placenta led to the clinical diagnosis in the mother. Metastases were present in the intervillous space and in villous stroma. The infant has survived and has no evidence of disease at one year of age. The mother died of metastatic disease 6 months post-partum. Literature review shows that only 25% of infants with placental metastatic melanoma succumb to the disease. In a review series of 16 cases, there are some maternal clinical factors which seem to have some bearing on the likelihood of fetal metastasis and death from disease. Features that are associated with an unfavorable fetal/infant prognosis are: maternal age less than 30 years, primiparity, leg primary site, disease onset greater than 3 years prior to pregnancy, node-1 metastatic status prior to pregnancy, M4 status in third trimester, birth at greater than 36 weeks' gestation, male sex. Extent of penetration of metastases into the villi does not have prognostic significance.

Adult↗
PubMed1989

Pulmonary thromboembolism from a large hemangioma in a 4-week-old infant.

A female infant with an extensive congenital hemangioma of the left knee region was treated medically for consumption coagulopathy; the hemangioma began to shrink, the coagulopathy improved, and the infant was clinically well when she died suddenly at the age of 4 weeks. The cause of death was a saddle pulmonary thromboembolus which had originated in the hemangioma. This is the first documented case of fatal thromboembolism complicating a conservatively managed extensive neonatal hemangioma. Causes of neonatal thromboembolism are reviewed.

Dexamethasone↗
PubMed1988

Fever alters characteristics of sleep in rats.

This study examined the effects of a fungal infection on body temperature (Tb) and sleep states. Tb and sleep were recorded in male rats for 24 hr after a saline injection and 48 hr after a subcutaneous injection of live brewer's yeast, at ambient temperatures (Ta's) of 20 degrees and 30 degrees C. Peak fevers of 1.6-3.1 degrees C occurred within 6-10 hr at both Ta's. The rats remained febrile for the next 12-24 hr. For the first 24 hr postyeast, amounts of SWS increased by 19 +/- 3% at 20 degrees C and 12 +/- 2% at 30 degrees C. Specifically, SWS was significantly increased from hr 5-8 (lights-on) and 13-24 (lights-off) at 20 degrees, and from hr 5-8 and 17-24 at 30 degrees C. Ta did not affect the changes in Tb or the changes in SWS after either saline or yeast. Duration of REMS varied with Ta after saline. After yeast, REMS increased by 21 +/- 12% at 20 degrees and decreased by 28 +/- 6% at 30 degrees C, with the net result that REMS at the two Ta's was equal during the fever. Furthermore, while the rats were febrile the normal diurnal variation in REMS was eliminated. Sleep and Tb returned to control values during the second fever day. These results suggest that an activated immune system both increases SWS and overrides the diurnal and thermoregulatory modulations of REMS.

Animals↗
PubMed1987

Decreases in REM sleep after phentolamine depend on the ambient temperature.

According to monoaminergic theories of rapid-eye-movement (REM) sleep, phentolamine (PHEN), an alpha-adrenoceptor antagonist that diminishes noradrenergic activity, should decrease REM sleep. However, PHEN also causes a fall in body temperature (Tb) that depends on the ambient temperature (Ta). When REM sleep and Tb were recorded in the same rats at 4 Ta's, after intraperitoneal injections of either PHEN or saline, the two measures were highly correlated. When PHEN lowered Tb, at Ta 20 degrees C, latency to REM sleep increased and total REM time decreased compared to controls. At Ta 32 degrees C, where PHEN had no effect on Tb, drug-treated rats had as much REM sleep as did controls.

Animals↗
PubMed1987

Brachial artery injuries associated with posterior elbow dislocation.

Posterior elbow dislocation is rarely associated with brachial arterial injury, occurring in two of 23 patients. A cool pulseless hypesthetic arm associated with swelling at the elbow after a history of a fall on an outstretched arm indicates arterial injury associated with posterior elbow dislocation. Concomitant neurologic and bone injury may occur as well. Arterial repair and stabilization of the elbow is the treatment of choice and should result in a functional extremity.

Adult↗
PubMed1986

Formation of O6-ethylthioethylguanine in DNA by reaction with the sulfur mustard, chloroethyl sulfide, and its apparent lack of repair by O6-alkylguanine-DNA alkyltransferase.

The reactions of the monofunctional sulfur mustard, chloroethyl ethyl sulfide, with calf thymus DNA have been studied in vitro. In addition to extensive alkylation of the 7 position of guanine and the 3 position of adenine, approximately 0.1% of the total alkylation is on the O6 position of guanine. Since chloroethyl ethyl sulfide is a model for S-adenosylmethionine and for the reactive intermediates generated from glutathione by certain environmental agents, this result establishes a route by which these compounds could be mutagenic. A DNA substrate modified for repair studies has been produced by incubating calf thymus DNA with [14C]chloroethyl-labelled chloroethyl ethyl sulfide. This DNA contains 6 nmol/mg of alkylated products including 6 pmol/mg O6-ethylthioethylguanine. Incubation of this substrate with up to a 20-fold excess of mammalian O6-alkylguanine-DNA alkyltransferase has indicated that O6-ethylthioethylguanine is either not a substrate or a poor one for this DNA repair system.

Adenine↗
PubMed1984

Patients' evaluation of a post-myocardial infarction teaching programme administered by nurses.

Two-hundred and twenty-eight patients admitted to a District General Hospital Coronary Care Unit with a confirmed myocardial infarction were given a detailed information session by nurses. Information included a detailed programme of exercise during convalescence and attitudes toward diet, smoking and sexual intercourse. Patients were asked to assess the value of these sessions using questionnaires administered during convalescence. Between 76% and 91% of patients considered the presentation necessary and there was a significant improvement in their understanding of what an infarction was. More than 80% of patients found a booklet entitled Recovering from your Heart Attack particularly helpful. The great majority of patients believed that more health education should be given at school and that members of the general public should be taught the techniques of cardio-pulmonary resuscitation. The teaching programme appears to have reduced the admitted smoking habits of patients. On admission 56% of patients were smokers. This fell to 7% at the end of 3 weeks, but had risen to 17% at 6 months.

Attitude to Health↗
PubMed1984

Cytolytic T lymphocyte and antibody responses to synthetic peptides of influenza virus hemagglutinin.

Two peptides corresponding to HA1(181-204) and HA2(103-123) of the A/Japan/305/57 influenza virus hemagglutinin (HA) were chemically synthesized by solid-phase methods and were tested for their ability to generate murine secondary anti-influenza cytolytic T lymphocytes (CTL) in vitro and to bind monoclonal anti-HA antibodies. Peptide HA1(181-204) could only generate CTL in the presence of helper factors contained in supernatant fluids from either Concanavalin A-stimulated mouse spleen cultures or WEHI-3 cells grown in vitro. Peptide HA2(103-123) stimulated the induction of anti-influenza CTL independent of helper factors, but the stimulation was also greatly increased if helper factors were added. A 10-fold molar excess of peptide HA2(103-123) was required to obtain optimal CTL activation over the quantities required in the HA1(181-204) system. This molar ratio remained unchanged, even in the presence of helper factors. Induction of influenza-specific CTL was antigen-dependent in both systems, even though some killing of noninfected target cells was also occasionally observed. Our results suggest that synthetic peptides can be recognized as antigenic determinants in the generation of H-2-restricted anti-viral CTL capable of killing appropriately infected target cells. The inability of peptide HA1(181-204) to generate sufficient help for CTL development suggests that certain regions of the HA can be recognized by CTL precursors, but not by all of the required helper cells. Peptide HA1(181-204) also reacted with three monoclonal anti-HA antibodies as well as mouse anti-influenza (A/Japan/305/57) immune sera. This antibody reactivity suggests the possibility of a shared antigenic epitope or region between T and B cells, and therefore provides new insight in our understanding of viral antigenicity.

Animals↗
PubMed1983

Malignant neoplasms of the nose and paranasal sinuses. A survey of cases treated in a regional centre.

A review of 250 patients with malignant disease of the nose and paranasal sinuses treated over a 20 year period is presented. Treatment could be divided broadly into three groups consisting of subradical surgery plus radiotherapy; a drainage procedure plus radiotherapy and radiotherapy alone. Three and 5 year survival rates are presented for each mode of treatment for tumours originating in four anatomical sites. In tumours of the maxillary antrum the 5 year survival was significantly higher in patients who underwent a partial maxillectomy or palatal fenestration before radiotherapy. In the other anatomical sites the survival rates were not significantly different. Although this is an uncontrolled retrospective review, it does add further data to that already published on this uncommon but difficult management problem.

Adolescent↗