The hippocampus is not necessary for a place response but may be necessary for pliancy

Rats with kainate-colchicine hippocampal lesions (HL) and controls (C) were initially trained in the Morris water maze with procedures that deterred their prepotent thigmotaxic response. Training began with an escape platform that occupied nearly the entire pool. The area to which the rats could escape was made smaller by substituting smaller platforms as training progressed. In contrast to standard procedures, HL rats and C rats showed comparable performance during acquisition and preferentially searched the goal quadrant on probe trials during which the platform was removed. In a follow-up experiment, the platform was moved to a random position along the wall, which required a switch to a thigmotaxic response for most effective escape. HL rats that were thigmotaxic before place training did not switch to a thigmotaxic response as readily as did controls, behavior consistent with the view that hippocampal damage reduces pliancy.     

Alcohol use following liver transplantation: a comparison of follow-up methods

Alcoholic cirrhosis is one of the most common indications for liver transplantation. Previous researchers have studied rates of return to drinking following transplantation, however, few have employed prospective measures of alcohol use. The authors prospectively studied the alcohol use of patients transplanted for alcoholic liver disease. The authors improved the accuracy of monitoring alcohol use by using various methods for tracking patient's alcohol consumption, and we report on the time to first alcohol use after transplantation comparing these different methods. The authors found that alcohol use can occur very early after transplantation, even within the first 3 months posttransplant. Thirty-eight percent of the patients consumed any alcohol after transplantation. The clinical interviews by the psychiatrist were the most successful method for identifying posttransplant alcohol use. Posttransplant alcohol use was significantly associated with prior nonalcohol substance use (P < 0.025), family history of alcoholism in a first-degree relative (P < 0.025), and prior alcohol rehabilitation experience (P < 0.05) but not with a prior psychiatric history or less than 6 months of pretransplant sobriety. The authors indicate that prospective monitoring, using a combination of methods, is the most accurate approach to identify alcohol consumption. With this type of accuracy, risk factors can be identified and alcohol use can be compared with alcohol-related morbidity posttransplant.     

Phase II trial of oral 1,25-dihydroxyvitamin D (calcitriol) in hormone refractory prostate cancer

Epidemiologic and experimental data support a role for 1,25-dihydroxyvitamin D₃ in the growth regulation of prostate cancer. We conducted a phase II clinical trial evaluating calcitriol (1,25(OH)₂D₃) in patients with hormone refractory prostate cancer. We enrolled 14 patients in this study. 1,25(OH)₂D₃ was initiated at a daily oral dose of 0.5 μg and escalated to 1.5 μg daily. No objective responses were observed. However, in two patients decreases of 25% and 45% in prostate specific antigen levels were seen. Hypercalcemia was the predominant toxicity. We conclude that 1,25(OH)₂D₃ given in this manner is inactive in advanced prostate cancer. Dose escalation of oral 1,25(OH)₂D₃ is limited by hypercalcemia.     

Publication rates of abstracts presented at the 1993 annual Academy meeting

What percent of abstracts presented at the American Academy of Orthopaedic Surgeons annual meeting are submitted, survive peer review, and eventually are published? The answer to this fundamental question is important because many national meeting attendees use the unscrutinized information that is presented to alter their surgical practices. At the 1993 American Academy of Orthopaedic Surgeons meeting, 573 abstracts were presented. After a 5-year period, 44% of abstracts presented were published as papers in a peer reviewed journal. The results suggest that for various reasons, the majority of presented material at the Academy meeting has not been authenticated scientifically to be as accurate as papers that survive the rigors of peer review.     

Extended transbasal approach: anatomy, technique, and indications

Appropriate indications for the transbasal approach have not been clearly established. The focus of this study is to determine the feasibility of maximal exposure of the clivus and surrounding regions via this strategy. Further, we sought to determine the key anatomical landmarks and morphometric data necessary for safe, radical exposure. In 20 injected cadaveric specimens, anatomical observations were made grossly and microscopically with 4-40 x magnification. The three basic variations of the transbasal craniotomy were compared with regard to surgical exposure. Maximum exposure of the ventral clivus could be obtained by total ethmoidectomy and sphenoidectomy through the extensive transbasal craniotomy. The lateral limits of exposure were found to be the optic nerves, intracavernous carotid arteries, and hypoglossal canals. Inferiorly, the foramen magnum is the limit of exposure. Morphometric measurements were determined between the key landmarks and were found helpful in subsequent dissections due to the lack of bony structures in relation to neural and vascular structures within the bone. The keys to optimizing the transbasal approach are beyond the simple initial steps of the craniotomy. Maximal exposure from the suprasellar compartment to the foramen magnum is possible via the extended transbasal approach.     

NTS catecholamine cell recruitment by hemorrhage and hypoxia

Immunolabelling for Fos and tyrosine hydroxylase was used to determine the patterns of activation of nucleus tractus solitarius catecholamine cells in response to graded levels of hemorrhage (0, 4, 8, 12 and 16 ml/kg) and systemic hypoxia (21, 14, 12, 10 and 8% O2) in conscious rats. Both stimuli elicited graded catecholamine cell recruitment with thresholds of 8 ml/kg and 12% O2. The majority of responsive neurons were A2 noradrenergic rather than C2 adrenergic cells. After hemorrhage most Fos-positive catecholamine cells were found below obex whereas most hypoxia-responsive cells were rostral to obex. These distinctive patterns of catecholamine cell recruitment may explain the differences in neuroendocrine responses to these stimuli.     

Relative medial and dorsal cortex volume in relation to foraging ecology in congeneric lizards

The need to locate distributed resources such as mates, food, and nests is correlated with an enlarged hippocampus in many mammalian and avian species. This correlation is believed to be a consequence of selection for spatial ability. Little is known about how such ecological needs affect non-mammalian, non-avian species. In lizards, the putative hippocampal homologues are the dorsal cortex (DC) and medial cortex (MC). We examined the relationship between foraging ecology and the size of the DC and MC in congeneric male lizards. We predicted based on the mammalian and avian literature that Acanthodactylus boskianus, an active forager that captures clumped, immobile prey would have a larger MC and DC than A. scutellatus, a sit-and-wait predator, that captures mobile prey. Our previous behavioral studies showed that A. boskianus did not differ from A. scutellatus on a spatial task but that A. boskianus was significantly better at the reversal of a visual discrimination, another task that is hippocampally dependent in mammals. In the current study, we found that, relative to telencephalon volume, the MC and DC were larger in the active forager whereas a control region, the lateral, olfactory, cortex, was similar in size between species. The current anatomical results suggest that MC and DC size is related to active foraging in lizards and, along with our previous behavioral studies, show that it is possible for this relationship to occur in the absence of evidence for species differences in spatial memory. Copyright (R) 2000 S.Karger AG, Basel