Postnatal phenotype and localization of spinal cord V1 derived interneurons

Developmental studies identified four classes (V0, V1, V2, V3) of embryonic interneurons in the ventral spinal cord. Very little is known, however, about their adult phenotypes. Therefore, we characterized the location, neurotransmitter phenotype, calcium-buffering protein expression, and axon distributions of V1-derived neurons in the adult mouse spinal cord. In the mature (P20 and older) spinal cord, most V1-derived neurons are located in lateral LVII and in LIX, few in medial LVII, and none in LVIII. Approximately 40% express calbindin and/or parvalbumin, while few express calretinin. Of seven groups of ventral interneurons identified according to calcium-buffering protein expression, two groups (1 and 4) correspond with V1-derived neurons. Group 1 are Renshaw cells and intensely express calbindin and coexpress parvalbumin and calretinin. They represent 9% of the V1 population. Group 4 express only parvalbumin and represent 27% of V1-derived neurons. V1-derived Group 4 neurons receive contacts from primary sensory afferents and are therefore proprioceptive interneurons. The most ventral neurons in this group receive convergent calbindin-IR Renshaw cell inputs. This subgroup resembles Ia inhibitory interneurons (IaINs) and represents 13% of V1-derived neurons. Adult V1-interneuron axons target LIX and LVII and some enter the deep dorsal horn. V1 axons do not cross the midline. V1-derived axonal varicosities were mostly (>80%) glycinergic and a third were GABAergic. None were glutamatergic or cholinergic. In summary, V1 interneurons develop into ipsilaterally projecting, inhibitory interneurons that include Renshaw cells, Ia inhibitory interneurons, and other unidentified proprioceptive interneurons.     

Role of disengagement failure and attentional gradient in unilateral spatial neglect - a longitudinal study

Purpose: To assess the importance of 'disengagement failure' and 'attentional gradient' in unilateral spatial neglect (USN) and in recovery from neglect.

Method: Eight right-hemisphere-damaged stroke patients performed the standardized Behavioural-Inattention-Test battery for visual neglect, line-bisection tests, and two computerized reaction-time (RT) tasks: a variant of Posner's 'Spatial-Cueing' paradigm (with special emphasis on the magnitude of leftward disengagement time) and a signal-detection task (marking the spatial gradient of attention by the distribution of RTs to target stimuli in different spatial locations). The correlation between the different measures was assessed at two points in time, before and after a period of rehabilitation treatment.

Results: A recovery pattern could be identified in both RT paradigms. However, the correlation between standard measures of neglect and performance on both, spatial-cueing and signal-detection tasks, was weak.

Conclusion: Neither difficulty disengaging attention from an ipsilesional stimulus nor changes in the attentional gradient can fully explain the processes underlying USN and its recovery. A large interpersonal variance exists among USN patients in the expression of disengagement and other spatial-attention deficits. Hence, individual patients should be tested by measuring different factors known to play a role in USN. This information is crucial for assigning the appropriate treatment for each patient in accord with the specific deficit revealed.     

The postoperative blood-sparing efficacy of oral versus intravenous tranexamic acid after total knee replacement

To assess the blood-sparing efficacy of tranexamic acid (TA) administered orally or via a variable IV infusion, 80 healthy patients undergoing elective total knee replacement were studied according to a prospective, controlled, randomized, single-blinded study design. Patients were allocated to one of four treatment groups. In group TA-long, 30 min before deflation of the limb tourniquet, an IV bolus dose of TA 15 mg/kg was administered over 30 min. Thereafter, a constant IV infusion of 10 mg . kg(-1) . h(-1) was administered until 12 h after final deflation of the limb tourniquet. In group TA-short, a similar regimen was followed; however, the constant IV infusion was discontinued 2 h after final deflation of the limb tourniquet (time of discharge from the postanesthesia care unit). Thereafter, oral TA 1 g was administered after 6 and 12 h. In group TA-oral, 60 min before surgery an oral dose of TA 1 g was administered. After surgery, a similar dose of TA was administered every 6 h for the next 18 h. In the control group, TA was not administered. At patient discharge, postoperative allogeneic blood administration was significantly more in group Control when compared with each of the three TA treatment groups. Because oral drug administration is simple and does not require specific infusion equipment, the authors suggest that oral TA is a superior blood-sparing strategy compared with IV drug administration.     

The drug-user husband and his wife: attachment styles,family cohesion,and adaptability

This study which assesses the association between the attachment styles of drug-user husbands (n = 56) and their wives (n = 56) and their perceptions of family dynamics was conducted in 1998. The population study included heroin (52.9%) and multidrug detoxified outpatients. All subjects completed the Adult Attachment Style Scale and the FACES III. Results indicated that the perceptions of family adaptability and cohesion among the drug-user husbands and their wives did not differ from the Israeli norm. Most of the drug users (60.7%) were characterized by the avoidant attachment style, followed by the secure style (26.8%), and the anxious/ambivalent style (12.5%). Half the wives (53.6%) were characterized by the secure style, followed by the avoidant style (42.9%) and the anxious/ambivalent style (3.6%). A secure style in husband and wife was associated with higher levels of family cohesion and adaptability, and the anxious/ambivalent style with a lower perception of family cohesion and adaptability. These findings have important implications for rehabilitation prospects and for planning intervention programs.     

Interaction between LIS1 and doublecortin, two lissencephaly gene products

Mutations in either LIS1 or DCX are the most common cause for type I lissencephaly. Here we report that LIS1 and DCX interact physically both in vitro and in vivo. Epitope-tagged DCX transiently expressed in COS cells can be co-immunoprecipitated with endogenous LIS1. Furthermore, endogenous DCX could be co-immunoprecipitated with endogenous LIS1 in embryonic brain extracts, demonstrating an in vivo association. The two protein products also co-localize in transfected cells and in primary neuronal cells. In addition, we demonstrate homodimerization of DCX in vitro. Using fragments of both LIS1 and DCX, the domains of interaction were mapped. LIS1 and DCX interact with tubulin and microtubules. Our results suggest that addition of DCX and LIS1 to tubulin enhances polymerization in an additive fashion. In in vitro competition assays, when LIS1 is added first, DCX competes with LIS1 in its binding to microtubules, but when DCX is added prior to the addition of LIS1 it enhances the binding of LIS1 to microtubules. We conclude that LIS1 and DCX cross-talk is important to microtubule function in the developing cerebral cortex.     

Aging has a complex effect on a rat model of ischemic stroke

Stroke in humans is usually associated with advanced age. Nevertheless, almost all animal models of ischemic stroke are based on young animals. The present study was designed to assess the effect of age on the development of ischemic injury in a model of focal brain ischemia in rats. Two age groups of Wistar rats were used: young adult (3 months) and old (24-26 months). Under halothane anesthesia, polyethylene microspheres (50 microm in diameter) were injected into the left common carotid artery following a temporary occlusion of the external carotid artery. Sham-operated rats underwent the same procedure but were injected with an identical volume (100 microl) of saline only. Rats of both experimental groups displayed neurological impairment after surgery. However, contrary to expectation, the young rats were more affected than the old rats. Young rats displayed an abrupt 30% decrement in neurological functions in the first week and then showed a partial functional recovery into a 12% decrement from the second week on. Old rats developed the neurological impairment gradually over a 2-week period (6.3% in the first week and 11% in the second week and thereafter). One month later, rats were tested in a water maze task. Again, performance was more impaired in the young ischemic rats than in the old rats. Histological evaluation revealed more extensive neurological damage in young ischemic as compared to old rats. Thus, although increased age has a critical effect on the evolution of the neurological impairment following focal brain ischemia and stroke, its effects in the rat model were more pronounced in the young animals.