Biomedical subjects
J L Antunes
Publications and source records attributed to J L Antunes.
[Perimesencephalic hemorrhage].
Among 293 subarachnoid hemorrhages admitted to the Neurology and Neurosurgery departments of Sta Maria Hospital, 108 patients had a normal cerebral angiography. Twenty-three meet the radiological criteria for perimesencephalic hemorrhage (center of the hemorrhage located in front of the mesencephalon, without blood in the interhemispheric and lateral sylvian fissures, nor significant intraventricular hemorrhage). The clinical picture was one of sudden, severe headache with meningeal signs, without focal signs or decreased alertness. Evolution was benign: there was no intrahospital mortality, morbidity or rebleeds on follow-up (3.5 years). In this subgroup of subarachnoid hemorrhage there is no need for a repeated angiogram if the first angiography is considered normal.
[Neuroradiology in the physiopathologic diagnosis of subarachnoid hemorrhage--cerebral aneurysm].
The clinical importance of the cerebral aneurismatic lesion in well known. In Portugal we still do not have reliable statistics regarding the occurrence of the subarachnoid hemorrhage, however we can make a comparison through Kassel's and Drake's studies where they refer that annually 28,000 North-Americans suffer from subarachnoid hemorrhage attributed to the rupture of the cerebral aneurysm. This is a clinical situation that needs to be analyzed, more so because if it is not diagnosed and treated in time, it can cause a high level of morbidity and mortality. From 1984 to 1990, the authors studied 208 clinical cases of in-patients at the Santa Maria Hospital who had been diagnosed as having subarachnoid hemorrhage-cerebral aneurysm. They analyzed 172 cranium-encephalic Tomographies and 190 cerebral Angiographies. They found levels that overlapped the series already published with respect to the location of the lesion, dimensions and age groups involved. They tried to relate the presence aneurysm in the willis arterial circle with the occurrence of locoregional anatomic variants that were detected in 51% of the patients with aneurysm of the anterior communicating artery and in 33% of the cases in the posterior communicating artery. The high occurrence of serious forms of tomodensitrometric presentation should also be emphasized. As a matter of fact, 42.6% of the patients studied were grouped in degree IV of the Fisher Scale. This result translates the effort that is still required towards an early clinical and imaging diagnosis of warning hemorrhage to avoid or prevent a catastrophic hemorrhage recurrence.
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.
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.
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.
Neural control of reproduction.
The feedback loops involved in the neural control of reproductive cyclicity in primates are reviewed. A combination of morphological, endocrinological, and surgical experimental approaches was used to identify the different mechanisms involved. The main signal for pituitary secretion of gonadotropins is the estrogen secreted by the ovary. Estrogen probably affects the hypothalamic secretion of gonadotropin-releasing hormone (GnRH), which in turn stimulates the pituitary production of gonadotropins. These may in turn, through a short feedback loop, regulate the secretion of GnRH. Evidence for a direct effect of estrogen on the pituitary is presented. Future possible areas of research, including extrahypothalamic influences on reproductive mechanisms, are briefly outlined.
Artificial vision for the blind by electrical stimulation of the visual cortex.
Artificial vision for the blind may be feasible by interfacing a television camera with electronics stimulating the visual cortex. The status of a major collaborative effort involving the College of Physicians and Surgeons of Columbia University, the University of Utah, and the University of Western Ontario is reviewed. Results have been very encouraging, although much work remains to be done.
Pneumocephalus after ventriculoatrial shunt.
Pneumocephalus developing after a ventriculoatrial shunting procedure is described. This was found to be caused by a defect in the posterior wall of the frontal sinus, possibly secondary to chronically increased intracranial pressure. A review of the pertinent literature revealed only two other similar cases.
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.
Pedro Almeida Lima.
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Reproductive function in temporal lobe epilepsy: the effect of temporal lobectomy.
We have examined sexual and reproductive changes in 25 patients (11 men and 14 women; mean follow-up 13 years) with temporal lobe epilepsy who underwent temporal lobectomy. Five men and two women had sexual dysfunction preoperatively, in particular, decreased libido. This improved after temporal lobectomy in three of these patients. One woman developed a partial Klüver-Bucy syndrome. Reproductive dysfunction was present in one man (oligospermia) and in ten women (four had the onset of seizures either at pregnancy or menarche; four had increased frequency of seizures during menarche or pregnancy, and two had amenorrhea). The man fathered two children post-operatively, and an appreciable improvement in both the seizure activity and the reproductive dysfunction was noted in the majority of the women.
Neural control of gonadotropin secretion in primates.
In the rhesus monkey, there is abundant evidence to indicate that ovarian secretions, mainly estradiol-17beta, control "tonic" as well as "cyclic" secretion of gonadotropins during the menstrual cycle. This mechanism of control ensures coordination of ovarian morphology and anterior pituitary secretory patterns. The primary site of action of estradiol in controlling both "tonic" and "cyclic" secretion of gonadotropins has been circumscribed to the medial basal hypothalamic-pituitary unit. A modulatory role in "cyclic" secretion by neural structures situated within the anterior hypothalamic-preoptic area or by efferent fibers in passage through this region also has been postulated. However, the accrued evidence indicates that in the primate, contrary to the rodent, the role of these rostral neural structures is not essential for menstrual cyclicity. Strong evidence also indicates that the isolated pituitary gland can respond to estrogen signals as well. Secretion of gonadotropin-releasing hormone, the hypothalamic decapeptide, into the long portal vessels is, however, essential to maintain function of the gonadotroph. Further, pulsatile release of luteinizing hormone is distinctly under the control of a similarly paced hypothalamic clock.
The hypothalamic magnocellular system of the rhesus monkey: an immunocytochemical study.
The hypothalamic magnocellular system of the adult female rhesus monkey is studied here, using immunoperoxidase technique and antisera to estrogen stimulated neurophysin (ESN), nicotine stimulated neurophysin (NSN), oxytocin (OT) and vasopressin (VP). These observations confirm and enlarge previous descriptions by others using Gomori techniques. It is apparent from this study that the magnocellular system spreads through a broader area than is generally accepted. A group of cells ventral to the head of the caudate nucleus and medial to the internal capsule is described. The general orientation of the nuclei and their tracts can only be appreciated when coronal, horizontal and sagittal sections are compared. Our observations suggest that the supraoptic nucleus is made up of a single group of cells that straddles the optic pathways, and is not divided in three segments, as it is generally described. It is also shown that the rostral extensions of the paraventricular and supraoptic nuclei merge above the optic chiasm. Cells containing ESN/OT and NSN/VP are evenly dispersed in the paraventricular nucleus but a topographical arrangement is present in the supraoptic nucleus. The magnocellular nuclei project to the organum vasculosum of the lamina terminalis, zona externa of the median eminence and pars nervosa of the pituitary gland. Reactive fibers were also seen within islets of cells from the pars intermedia located inside the pars nervosa. A globular structure containing small blood vessels surrounded by positive fibers was noticed protruding into the floor of the third ventricle, at the level of the median eminence.
Period of risk for recurrence in medulloblastoma.
Ninety-nine patients with medulloblastoma who received surgery and radiotherapy, and had a statistically sufficient follow-up period were analyzed for factors influencing survival and the relevance of the "period of risk for recurrence" hypothesis. This postulate states that the period of risk for recurrence of a congenital tumor is equal to the age at presentation of illness plus 9 months' gestational time. The assumption is made that a tumor of embryonic origin will become manifest after a period of time determined by its inherent rate of growth and that tumor cells surviving treatment will multiply and present with recurrence in an equal period of time. Ten of 43 patients survived the period of risk, a presumed cure rate of 23%. None of these patients has subsequently developed evidence of tumor recurrence. Older patients at initial surgery had a somewhat greater survival rate for the first 5 years after treatment (10 of 26 older patients (38%) versus 15 of 54 younger patients (28%)), but by 10 years there was no appreciable difference in survival rates between those over 16 years of age and those younger. The beneficial effect of total neuraxis megavoltage radiotherapy is indicated by the improved 5-year survival rate from 9 of 41 patients (22%) to 16 of 39 patients (41%) with the newer techniques.
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.
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.
Vasopressin and corticotropin-releasing factor: an axonal pathway to portal capillaries in the zona externa of the median eminence containing vasopressin and its interaction with adrenal corticoids.
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