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Biomedical subjects

J H Christy

Publications and source records attributed to J H Christy.

15 recordsLinked to original sources
PubMed2000

Dishonest signalling in a fiddler crab.

Animal communication theory predicts that low-frequency cheating should be common in generally honest signalling systems. However, perhaps because cheats are designed to go undetected, there are few examples of dishonest signals in natural populations. Here we present what we believe is the first example of a dishonest signal which is used commonly by males to attract mates and fight sexual rivals. After losing their large claw male fiddler crabs (Uca annulipes) grow a new one which has less mass, is a less effective weapon and costs less to use in signalling than an equivalent-length claw of the original form. Males with original claws do not differentially fight males with regenerated claws even though they are likely to win. Regenerated claws effectively bluff fighting ability and deter potential opponents before they fight. During mate searching, females do not discriminate against males with low-mass, regenerated claws, indicating that they are deceived as to the true costs males pay to produce sexual signals. Up to 44% of males in natural populations have regenerated claws, a level unanticipated by current signalling theory. The apparent rarity of cheating may be an artefact of the usual difficulty of detecting cheats and dishonesty may be quite common.

Aggression↗
PubMed1998

Outcomes of therapy for Cushing's disease due to adrenocorticotropin-secreting pituitary macroadenomas.

We reviewed our experience with 21 patients who had Cushing's disease due to ACTH-secreting macroadenomas to clarify the natural history of this disease. All patients had typical clinical and biochemical features of ACTH-dependent hypercortisolism. Their mean maximal tumor diameter was 1.6 +/- 0.1 cm, and the range was 1.0-2.7 cm. Six patients had cavernous sinus invasion, three had invasion of the floor of their sella, and nine had suprasellar extension. The observed remission rate was significantly lower in macroadenoma patients than in microadenoma patients (67% vs. 91%; chi 2 = 5.7; P < 0.02). Cavernous sinus invasion (odds ratio, 35; 95% confidence interval, 2.6-475; P < 0.008) and presence of a maximum tumor diameter 2.0 cm or more (odds ratio, 12.9; 95% confidence interval, 1.4-124; P < 0.02) emerged as the only predictors of residual disease after surgery. The observed recurrence rate was significantly higher in macroadenoma patients than in microadenoma patients (36% vs. 12%; chi 2 = 4.2; P < 0.05). Macroadenoma patients tended to suffer from recurrences earlier than did microadenoma patients (16 vs. 49 months). Stepwise multiple logistic regression did not identify any predictors of disease recurrence in macroadenoma patients. Eight macroadenoma patients underwent a total of nine repeat surgical procedures, but none of these resulted in clinical remissions. Only four of seven (57%) patients followed for a sufficient period of time achieved normal urinary free cortisol levels after conventional radiotherapy. Three (75%) of these four patients had re-recurrent hypercortisolism after brief periods of eucortisolism. Pharmacological agents and adrenalectomy were effective in the management of hypercortisolism in patients with residual and recurrent disease. Our results indicate that ACTH-secreting macroadenomas are more refractory to conventional treatments than are ACTH-secreting microadenomas.

Adenoma↗
PubMed1993

Transsphenoidal adenomectomy for growth hormone-secreting pituitary adenomas in acromegaly: outcome analysis and determinants of failure.

The results of transsphenoidal adenomectomy for growth hormone (GH)-secreting pituitary adenomas in acromegaly performed over a 17-year period were analyzed retrospectively to determine which preoperative factors significantly influenced the long-term surgical outcome. These variables were then used to develop a logistic regression model to determine the probability of surgical failure. The series consisted of 103 patients. Long-term follow-up study (mean duration 102 +/- 64 months) was performed to derive outcome analysis and determinants of failure. Surgical control was defined as a long-term postoperative serum basal GH level of less than 5 micrograms/liter, a long-term postoperative serum somatomedin C (SM-C) level of less than 2.2 U/ml, and a favorable clinical response. Eighteen (17.5%) patients did not meet these criteria. The overall control rate by the GH criteria was 81.3% and by the SM-C criteria 76.2%. By multivariate logistic regression analysis, tumor stage was the strongest predictor of outcome (p < 0.05). The preoperative GH level, tumor grade, and preoperative SM-C level were significant univariate predictors (p < 0.05). There were statistically significant differences in mean preoperative GH and SM-C levels (p < 0.05, t-test) and tumor stage (p < 0.05, chi-squared test) between patients whose acromegaly was controlled by surgery and those whose acromegaly was not. Furthermore, estimates were derived of the probability of surgical failure based on preoperative GH level, preoperative SM-C level, and tumor grade and stage. The authors believe these findings will enhance clinical decision-making for neurosurgeons considering transsphenoidal microsurgery in patients with acromegaly.

Acromegaly↗
PubMed1978

Transsphenoidal microsurgery for pituitary tumors associated with hyperprolactinemia.

The results of transsphenoidal microsurgery in treating 37 patients (30 women and seven men) with pituitary tumors associated with hyperprolactinemia are presented. Immediate (10-day) postoperative fasting prolactin levels were normal (less than 25 ng/ml) in 19 of 26 patients whose preoperative prolactin level was less than 200 ng/ml, and in only three of 11 patients in whom preoperative prolactin was greater than 200 ng/ml. Twelve of 13 patients with normal preoperative pituitary-target organ function maintained normal axes postoperatively. Thirteen other patients had preoperative deficiencies in one or more pituitary-target organ axes. Postoperatively, in these latter 13 patients, a pituitary-target organ axis that was deficient preoperatively returned to normal in six cases; there was no change in five, and there was impairment in another axis in four instances. Although gross total tumor removal was believed to be complete in 35 of 37 patients, serial postoperative prolactin determinations in four of these 35 patients indicate tumor regrowth. The authors conclude that transsphenoidal microsurgery is currently the operative procedure of choice for the majority of pituitary tumors associated with hyperprolactinemia.

Adenoma, Acidophil↗
PubMed1977

Hypothyroid Graves' disease.

Graves' disease has recently been shown to exist in a euthyroid form in untreated patients. Sporadic reports of a hypothyroid form are beginning to emerge, thus illustrating the multifaceted nature of this disorder, with thyrotoxicosis at one end of the spectrum and hypothyroidism at the other. Three patients with nonthyrotoxic Graves' disease and concomitant hypothyroidism were seen at Emory University Hospital in one year, and deatailed studies were made to help elucidate the nature of this unusual combination. Results of these studies are reported and briefly discussed. It is suggested that, until more is known about this intriguing aspect of the Graves' disease spectrum, the label "hypothyroid Graves' disease" is justifiable.

Adult↗
PubMed1977

Pain relief in metastatic cancer other than breast and prostate gland following transsphenoidal hypophysectomy. A preliminary report.

Hypophysectomy was performed in six patients with advanced carcinoma other than from breast and prostate gland to alleviate pain. Two patients received significant and lasting relief of pain; one achieved relief but died from progression of disease 5 weeks after surgery; one patient, initially relieved, had recurrence of pain 3 months later; one had about 50% relief; and one received no benefit. Possible mechanisms for pain relief include changes in pituitary hormones, prostaglandins, and the newly isolated brain peptides, alpha and beta endorphin. These preliminary observations will require further critical evaluation in a larger series to determine the effectiveness of hypophysectomy in relieving pain in cancer other than from the breast and prostate. The results, nevertheless, do imply that a different approach to pain, namely endocrine manipulation, may be beneficial in certain cancer patients.

Adult↗
PubMed1976

Hypophysectomy in the treatment of disseminated carcinoma of the breast and prostate gland.

Transsphenoidal hypophysectomy offers gratifying palliative relief of pain to patients with metastatic cancer of the breast and prostate. This report represents the results of two years' experience with this procedure at Emory University School of Medicine. The physiologic rationale and clinical indications for hypophysectomy are described, as is the operative technic using the open transsphenoidal microsurgical approach. The series of cases reported here includes 20 men with disseminated prostatic carcinoma and 23 women and one man with metastatic carcinoma of the breast. All 44 procedures were done by the transsphenoidal microsurgical approach. Pain was the preoperative indication for surgery in 41, while three patients were operated on for extensive disease without pain. Satisfactory relief of pain was obtained in 76% of the patients with prostatic cancer and in 83% of the breast cancer patients. While the results are gratifying with regard to relief of pain, the duration of follow-up is not sufficient to comment on the value of the procedure in significantly prolonging life.

Adult↗
PubMedDate not supplied

Anterior pituitary function before and after trans-sphenoidal microsurgical resection of pituitary tumors.

Anterior pituitary lobe function was measured pre- and postoperatively in 40 patients with pituitary tumors who were managed surgically by the trans-sphenoidal approach. Of 23 patients with normal anterior lobe function preoperatively, 21 (91%) were normal postoperatively. Of 17 preoperatively impaired patients, 7 (40%) regained normal function, 3 (18%) improved, 4 (24%) remained the same, and 3 (18%) were further impaired by the surgery. In this small series, the likelihood of recovery of pituitary function varied inversely with the degree of preoperative impairment and the size of the tumor, suggesting that more aggressive surgical management of small, minimally symptomatic pituitary tumors is justified.

Adenoma↗