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Results for “Hypophysectomy”

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At least 1,135 records · Page 63Linked to original sources
PubMed1987

Hypophysectomy does not alter the effects of somatostatin or growth hormone on canine splanchnic biogenic amine release.

We have demonstrated previously that growth hormone (GH) and somatostatin (somatotropin release inhibitory factor, SRIF) exert comparable effects on the release of splanchnic biogenic amines. The purpose of the present investigation was to study further the response of the two hormones and see whether the similarity persists in dogs completely deprived of endogenous GH. Experiments were conducted in seven hypophysectomized dogs fitted with an indwelling portal catheter. Two to 4 weeks after surgery the responsiveness of their catecholaminergic neurons was tested by an injection of human beta-endorphin (20 micrograms/kg); it caused a rise in portal catecholamine levels equivalent to that seen in intact dogs. Then the effect of a spike concentration of SRIF or GH on hepatic portal and peripheral levels of free serotonin and catecholamines was studied, all by radioenzymatic methods. The intravenous injection of ovine GH (100 micrograms/kg) or equimolar amounts of SRIF (7.5 micrograms/kg) produced in the hepatic portal circulation a transient but statistically significant rise of serotonin and a concomitant reduction in the concentration of dopamine, norepinephrine, and epinephrine. No changes were found in the peripheral circulation. The response patterns to SRIF or GH were virtually identical, which is in keeping with our other data, suggesting that the effect of GH on splanchnic biogenic amine secretion is SRIF-dependent and mediated by SRIF-containing neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Analgesia induced by cold-water stress: attenuation following hypophysectomy.

In addition to the well-known activation of the pituitary-adrenal axis, acute exposure to severe stressors includes a temporary analgesia in rats. Thus, the present study investigates whether the pituitary was involved in the mediation of analgesia induced by severe cold-water swim (CWS) stress. Flinch-jump thresholds were measured 30 min following 3.5-min swims in water temperatures ranging from 2-35 degrees C. Compared with untreated normal rats, hypophysectomized rats, receiving corticosterone and thyroxin, displayed significantly less CWS-induced analgesia, while similarly-supplemented normal rats exhibited significantly more CWS-induced analgesia. In a second experiment, operant liminal escape pain thresholds were determined following acute and chronic CWS. Whereas normal rats exhibited profound analgesia following the initial swims, the hypophysectomized rats never displayed any CWS-induced operant escape shifts. Stress-induced alterations in general activity levels and/or thermoregulation were shown to be unrelated to the diminished effectiveness of CNS to produce analgesia in hypophysectomized rats. These data imply that the pituitary is involved in the mediation of CWS-induced analgesia.

Adrenocorticotropic Hormone↗
PubMed1988

Transnasal hypophysectomy--an unusual sporting injury.

A case is presented of a traumatic penetrating nasal injury, resulting in panhypopituitarism and memory loss. Certain aspects of the diagnosis and treatment are discussed, and in conclusion some principles of management are suggested. The patient was last seen 8 months after the injury and had not required any desmopressin for 6 weeks.

Adult↗
PubMed1978

Automatic measurement of drinking in rats: effects of hypophysectomy.

A new apparatus for the continuous measurement of drinking in the rats was assembled. The principle of the device is as follows: a cartridge which makes water drops (0.05 ml) is inserted between a water tank and a drinking spout. When a rat drinks, water falls into the cartridge drop by drop and the number of drops is electrically counted. The total count of drops per day, as well as counts at definite intervals, can be atuomatically printed out. To test apparatus reliability and applicability, drinking behavior in hypophysectomized rats was investigated in the light and dark phases, alternating every 12 hr. Activity and feeding in these phases were also observed. In the sham-operated rats, the total daily water intake was 30-40 ml, which corresponded to 10-15% of the body weight, and 85-95% of the total daily drinking counts were recorded in the dark phase. In the hypophysectomized rats, a large amount of water was drunk immediately after the operation. However, the high rate of drinking rapidly returned to near the normal level within a few days. Drinking in the dark phase decreased to about 75% of the total daily, but synchronization with the light-dark cycle was still maintained. The daily patterns of activity and eating ran nearly parallel with the drinking behavior. These results indicate that our drinkometer could have extensive applications within many fields of research.

Animals↗
PubMed1980

Facilitation of copulatory performance in male rats by naloxone: effects of hypophysectomy, 17 alpha-estradiol, and luteinizing hormone releasing hormone.

Three experiments were performed to explore the mechanism whereby systemic administration of the opiate receptor antagonist, naloxone hydrochloride (20 mg/kg) causes reductions in the frequency of intromissions preceding ejaculation and latency to ejaculation in sexually experienced male rats. Administration of naloxone to male rats which were hypophysectomized in addition to being castrated and implanted SC with 30 mm silastic capsules containing testosterone caused such behavioral changes, suggesting that these behavioral effects of naloxone do not result from interference with the binding of endophin of pituitary origin. Surprisingly, a significant facilitatory effect of naloxone on sexual performance was absent in castrated controls bearing 30 mm testosterone implants. Recent evidence suggests that 17 alpha-hydroxylated estrogens, which may be produced in gonadally intact males, possess appreciable affinity for opioid receptors. However, daily administration of 17 alpha-estradiol (50 micrograms) to castrated, testosterone-implanted males failed to make them as behaviorally responsive to naloxone as gonadally intact animals. Administration of LHRH (1 microgram given SC 1.5 hr prior to testing) caused a significant reduction in ejaculation latency in gonadally intact males but not in castrated males bearing 30 mm testosterone implants. It is suggested that the facilitatory effect of naloxone on masculine sexual performance results, in part, from a drug-induced release of LHRH.

Animals↗
PubMed1985

Skeletal muscle aging in the hind limb of the old male Wistar rat: inhibitory effect of hypophysectomy and food restriction.

By age 1 100 days (37 mth) hind leg paralysis was found in 50% of ad libitum fed (control) male Wistar rats, but only 10% of food restricted rats and no hypophysectomized rats of that age had this disease. Gastrocnemius muscle weight declined at a faster rate than whole body weight in old ad libitum fed rats but not in old hypophysectomized or food restricted rats. Light microscopic and ultrastructural changes were studied in the muscles of the hind limbs of 11 control, 5 food-restricted and 5 hypophysectomized rats aged 805 to 1 307 days. Light microscopic changes in muscles involved progressive degeneration demonstrated by the accumulation of adipocytes and degenerative inclusion bodies. The main ultrastructural changes were associated with myofibrillar breakdown. In addition there was thickening of the basal lamina around blood capillaries. However, muscle from hypophysectomized and food restricted rats of the same age range as controls possessed normal morphology with reduced thickening of the capillary basal lamina.

Aging↗