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Biomedical subjects

P W Carmel

Publications and source records attributed to P W Carmel.

18 recordsLinked to original sources
PubMed1979

The pars tuberalis of the rhesus monkey secretes luteinizing hormone.

The presence of luteinizing hormone within the pars tuberalis of the adenohypophysis and its secretion into pituitary stalk vessels were investigated in adult rhesus monkeys. Portal blood was collected in 9 monkeys, after section of the pituitary stalk. In 22 out of 26 samples, portal to peripheral LH ratios, as measured by radioimmunoassay, ranged from 2 to 48. Portal LH levels were highest in 3 animals studied at the time of the midcycle surge. No differences between portal and peripheral growth hormone (GH) and prolactin levels were observed. Immunocytochemical studies in 4 normal and 3 ovariectomized female monkeys indicated that LH, but not GH, prolactin or thyroid stimulating hormone were present within the pars tuberalis. Cells containing these hormones were identified within the pars distalis. These results indicate that the pars tuberalis forms and secretes LH via the hypophyseal portal circulation.

Animals↗
PubMed1979

Regeneration of the magnocellular system of the rhesus monkey following hypothalamic lesions.

The hypothalamic magnocellular system of the rhesus monkey was studied with specific immunocytochemical techniques in animals that had undergone hypothalamic lesions. The results indicate that this system maintains a regenerative capacity even when its tracts are interrupted within the hypothalamus. New neurohemal units are reconstituted from newly formed vessels within the scar as well as from preexistent blood vessels, such as perforating and pial arterioles, and the vessels of the pars tuberalis of the pituitary gland, which normally do not contain neurosecretory terminals.

Animals↗
PubMed1979

Estrogen-induced gonadotropin surges in female rhesus monkeys after pituitary stalk section.

In order to investigate the primary site of action of estradiol, whether pituitary or hypothalamic, gonadotropin responses to estrogen were studied in female rhesus monkeys before and immediately after pituitary stalk section. The estrogen challenge, consisting of either an injection of estradio benzoate (400 microgram) or an implant of three silastic capsules containing 17 beta-estradiol, was initiated on days 2--5 of the menstrual cycle. The estrogen was given not later than 8 h after stalk section. Estrogens induced LH surges in all five animals before and after stalk section. FSH increases were observed in four of five intact and three of four stalk-sectioned animals. Mean FSH and LH levels in three stalk-sectioned animals treated with oil alone did not differ significantly from preinjection controls. These experiments suggest that the locus of estrogens on gonadotropin release in the rhesus monkey may well reside within the pituitary gland itself.

Animals↗
PubMed1979

Increased intraventricular pressure without ventriculomegaly in children with shunts: "normal volume" hydrocephalus.

Five patients with shunt-dependent hydrocephalus were observed to have apparently normal ventricular size despite marked increases in ventricular pressure after shunt malfunction. Elastance (dP/dV) was determined in four of these patients by removing increments of cerebrospinal fluid and measuring the resulting pressure. These patients without ventricular enlargement and with markedly increased ventricular pressure had high elastance. This group of patients with "normal volume" hydrocephalus had distal shunt occlusions, in contrast to previously reported patients with cephalic shunt obstructions after ventricular decompression. Initial shunting in early infancy, prolonged shunt dependency, and lack of recent shunt revision were common factors in these patients. Markedly elevated pressure with normal volume is a threatening clinical entity, requiring prompt surgical intervention

Abducens Nerve↗
PubMed1979

Collection of blood from the pituitary stalk and portal veins in monkeys, and from the pituitary sinusoidal system of monkey and man.

A transorbital, transsphenoidal microsurgical approach to the pituitary stalk and gland was used to collect blood from the hypothalamo-hypophyseal portal system in monkeys. Specimens may be obtained from the entire pituitary stalk, individual long portal veins, or the pituitary sinusoidal bed, with little risk of mortality. Continuous stalk blood sampling was carried out for periods of up to 10 hours. Pituitary sinusoidal-system blood was also collected during transsphenoidal surgery in man. The uses of data concerning hypothalamic-hypophyseal regulation obtained by these methods are illustrated.

Animals↗
PubMed1979

The specificity of serum prolactin as a diagnostic indicator of pituitary adenoma.

Serum prolactin levels were determined in 205 patients with a variety of intracranial diseases, including 70 cases with pituitary tumors. It is concluded that although the absence of elevated prolactin levels does not help to rule out pituitary pathology, the presence of hyperprolactinemia is highly specific for diseases of the pituitary and hypothalamus, and prolactin determination should be part of the regular work-up of pituitary tumor suspects. Excluding known causes of hyperprolactinemia, such as tranquilizing drug ingestion, the presence of neurological disease outside the hypothalamic-pituitary area was not associated with increased serum prolactin concentrations.

Acromegaly↗
PubMed1978

Aseptic meningitis and hydrocephalus after posterior fossa surgery.

In an attempt to define the tissue of origin of substances causing aseptic meningitis and secondary hydrocephalus after posterior fossa surgery, analysis of several marker substances from blood, brain, tumour and muscle in the CSF was performed early in seven postoperative patients. No clear pattern emerged which could relate the substances, CSF reaction, and meningeal scarring. The effects of various factors such as contrast studies, drainage, and steroids were also not clear. Review of the literature reveals that all four tissues can cause inflammation. Certain facts about the anatomy of the basilar cisterns and arachnoid villi probably make them logical sites for problems in CFS circulation. Children, for several reasons, are most susceptible to this complication. The complexity of factors in human cases suggests that the problem should be studied in an animal model.

Adolescent↗
PubMed1978

Luteinizing hormone-releasing hormone in human pituitary blood.

Luteinizing hormone (LH) and LH-releasing hormone (LHRH) were measured by radioimmunoassay in blood samples collected from the pituitary gland during transsphenoidal surgery in 19 patients. Detectable levels of LHRH were present in 12 patients. Wide fluctuations of LHRH were seen in sequential samples collected at 10-minute intervals, suggesting a pulsatile mode of release. This technique may yield useful data on hypothalamic control of pituitary secretion.

Adolescent↗
PubMed1977

Projections from the paraventricular nucleus to the zona externa of the median eminence of the rhesus monkey: an immunohistochemical study.

Immunoperoxidase techniques and light microscopy were used to investigate the origin of the fibers containing vasopressin, oxytocin and related neurophysins (neurohypophyseal peptides), in the zona externa of the median emience of the rhesus monkey. Unilateral lesions were produced in the paraventricular nucleus using a modified Halasz-type knife. Complete destruction of the paraventricular nucleus resulted in a total depletion of all four neurohypophyseal peptides in the ipsilateral zona externa of the median emience. Partial lesions of different segments of the paraventricular nucleus resulted in depletion in different parts of the zona externa. These observations indicate that the paraventricular nucleus is the source of vasopressin, oxytocin and neurophysin in axons which end in the zona externa of the median eminence. These projections are strictly ipsilateral and arranged topographically, so that the more caudal paraventricular neurons project to the dorsal part of th zona externa and the rostral ones to the ventral segment. The supraoptic nucleus does not appear to project to the zona externa, and sends the great majority of its fibers to the neurohypophysis.

Animals↗
PubMed1977

Conservative management of a pituitary tumor during pregnancy following induction of ovulation with gonadotropins.

Ovulation induced with human menopausal gonadotropin-human chorionic gonadotropin in a 27-year-old woman who had been amenorrheic for 7 years resulted in pregnancy. Although pretreatment neurologic evaluation was normal, significant loss of vision was found at 30 weeks' gestation, and a skull x-ray revealed enlargement and erosion of the sella turcica. As an attempt to delay surgery, 12 mg of dexamethasone daily arrested further visual deterioration, and the pregnancy continued uneventful for 36 weeks, when triplets were born. Five days after delivery the visual fields were normal. Trans-sphenoidal resection of a prolactin-secreting chromophobe adenoma of the pituitary was carried out 6 months later. It is suggested that when disturbance in visual perception due to a pituitary tumor occurs during pregnancy, a course of high-dose corticosteroids with frequent monitoring of visual fields and acuity might be tried before surgical intervention. Although further rapid deterioration in vision may dictate immediate surgical decompression, conservative management may result in stabilization, allowing the patient to carry the pregnancy to term and obviating the need for emergency surgery.

Adenoma, Chromophobe↗
PubMed1976

Pituitary stalk portal blood collection in rhesus monkeys: evidence for pulsatile release of gonadotropin-releasing hormone (GnRH).

Hypothalamic-pituitary stalk portal blood was collected from 12 female rhesus monkeys. The pituitary stalk was approached transorbitally and cut at the level of the diaphragma sellae under direct visualization. After complete heparinization of the animal, stalk portal blood was obtained continuously, for periods of 30 minutes to 9 hours, using a constant exfusion pump at a rate of 30 to 40 mul/min. The mean GnRH in portal blood, as measured by radioimmunoassay, was 66 +/- 6.6 pg/ml (+/- SE) in 7 ovariectomized animals and 51 +/- 5.3 pg/ml (+/- SE) in 2 monkeys during the early follicular phase. Fluctuations in portal blood GnRH were most prominent in ovariectomized animals, with peak levels of 200-800 pg/ml and intervals of 1 to 3 hours between pulses. Peaks of GnRH during the early follicular phase did not exceed 200 pg/ml. The administration of estradiol (1000 ng, iv) to 3 monkeys did not decrease GnRH levels within the next 2 hours. These data provide direct evidence for a hypothalamic mediation of pituitary LH pulsatile release.

Animals↗
PubMed1976

Suppression of prolactin secretion by L-dopa in the stalk-sectioned rhesus monkey.

The effects of iv administration of L-dopa on serum prolactin were studied in both normal female rhesus monkeys and in monkeys in which the pituitary stalk had been previously sectioned. Revascularization of the pituitary gland was prevented by the insertion of a silastic barrier over the diaphragma sellae. Prolactin secretion was increased in all stalk-sectioned monkeys and, in contrast to intact animals, chlorpromazine administration was ineffective in further releasing prolactin. In both normal and stalk-sectioned monkeys, iv administration of L-dopa (3-120 mg) significantly inhibited prolactin release from the pituitary (P less than .005 normal; P less than .001 stalk section). L-dopa also suppressed the TRH-induced release of prolactin in both groups. These results indicate that L-dopa or dopamine may act directly on the anterior pituitary to inhibit prolactin secretion.

Animals↗
PubMed1976

Phencyclidine sedation as a technique for handling rhesus monkeys: effects on LH, GH, and prolactin secretion.

Rhesus monkeys, sedated with phencyclidine hydrochloride (Sernylan), were quieted for prolonged periods of time, while maintaining somatic reflexes, muscle tone, and respiration. Brief daily periods of sedation did not interfere with the menstrual cycle. Prolonged sedation, however, interfered with the experimentally estrogen-induced LH surge, but not with the inhibitory action of estrogen on LH tonic secretion. Pulsatile release of LH, GH, and prolactin persisted even under prolonged sedation. The secretion of prolactin in response to the administration of TRH was increased in animals sedated with phencyclidine.

Animals↗