Current-distance relations of axons mediating circling elicited by midbrain stimulation

Stimulation of mediocaudal midbrain in rats produces ipsiversive circling due to the stimulation of longitudinal axons. The refractory periods of these axons were measured by delivering trains of conditioning and testing pulses via a single electrode at various conditioning-testing (C-T) intervals. As C-T interval increased from 0.3 to 2.0 ms, the frequency required to produce a constant amount of circling halved. The current-distance relations of these axons were measured by placing two electrodes lateral to one another, and delivering conditioning pulses via one electrode and testing pulses via the second electrode. The required frequency decreased less at C-T intervals in the refractory period range using two electrodes rather than using a single electrode. This partial refractoriness suggests that only part of the axons were stimulated by both electrodes. The refractoriness increased as current increased or as interelectrode distance decreased. The overlap in the fields of stimulation at each current was calculated from the refractoriness observed in single and double electrode experiments. The results suggest that the axons mediating circling have a wide range of thresholds rather than a single threshold. The current required to activate an axon is roughly equal to K X r2, were K is a constant and r is the radial distance from electrode to axon. K must range from 400 to at least 3000 microA/mm2, to account for the circling data. For axons mediating medial forebrain bundle self-stimulation3, K must range from 1000 to at least 6400 microA/mm2. Estimation of the K distribution allows calculation of the effects of electrode size, placement and current on the recruitment of axons with different thresholds.     

Intrapulmonary shunting in the biliary atresia/polysplenia syndrome: reversal after liver transplantation

One hundred and seventy three children, including 93 with biliary atresia, received liver grafts at Addenbrooke's Hospital between 1983 and 1993. Of these, only seven developed cyanosis due to intrapulmonary shunting as a complication of their liver disease, and all seven of these had the biliary atresia/polysplenia syndrome. Intrapulmonary shunting was confirmed by a radioisotope scan in four children. Only one child with the syndrome did not have cyanosis when undergoing transplantation. Seven of the eight children are alive 6-54 months after transplantation, with normal pulmonary and hepatic function. Cyanosis recurred in one child who developed chronic rejection with liver failure. In conclusion: (a) there is a strong association between the biliary atresia/polysplenia syndrome and cyanosis due to intrapulmonary shunting; (b) intrapulmonary shunting is fully reversible after successful liver transplantation; and (c) cyanosis, once present, is progressive, and these children should be considered for liver transplantation as soon as it occurs.     

Childhood Pityriasis Rosea

Abstract: Pityriasis rosea (PR) is an acute, self‐limiting papulosquamous disorder of unknown etiology. Published studies of childhood PR are scarce and most are reviews. The aim of this study was to determine the demographic and clinical features of childhood PR.     

Neurological and adrenal dysfunction in the adrenal insufficiency/alacrima/achalasia (3A) syndrome

Review of 20 patients with glucocorticoid deficiency (three cases also with salt loss) associated with absent tear secretion (19 cases) and achalasia of the cardia (15 cases) revealed neurological abnormalities in 17 including hyper-reflexia, muscle weakness, dysarthria, and ataxia together with impaired intelligence and abnormal autonomic function, particularly postural hypotension. These findings indicate that significant neurological problems are common in this multisystem disorder.     

Lack of effect of omeprazole, a potent inhibitor of gastric (H+ + K+) ATPase, on hepatic lysosomal integrity and enzyme activity

The substituted benzimidazole, omeprazole, is a potent inhibitor of the ATP-dependent proton pump of the parietal cell. Since there is accumulating evidence that hepatic lysosomes also possess an ATP-dependent proton pump system to maintain internal acidification, and since antibodies to the putative lysosomal proton pump protein are immunologically similar to the parietal cell (H+ + K+) ATPase, we studied the effects in rats of six days of omeprazole treatment on hepatic lysosomal function. Omeprazole, 5 mg kg-1, a dose five times the ED50 for gastric acid secretion inhibition in rats, did not alter the activity of three representative lysosomal enzymes in liver (acid phosphatase, beta-galactosidase and N-acetyl-beta-glucosaminidase) nor did it alter lysosomal enzyme latency, a measure of the integrity of the lysosomal membrane. Furthermore, bile flow and the secretion of lysosomal enzymes into bile were also unaffected by omeprazole. These data indicate that in rats short-term treatment with omeprazole, in doses that markedly inhibit gastric acid secretion, has no major biological effect on liver lysosomal integrity and lysosomal enzyme activity.     

The effect of air medical transport on survival after trauma in Johannesburg, South Africa.

OBJECTIVES: To assess the difference in survival of trauma patients transported to a trauma unit via either road or air in Johannesburg, South Africa. DESIGN: Prospective database analysis. SETTING: Multicentre study utilising two trauma units. SUBJECTS: The study evaluated 428 subjects admitted to the two sites. OUTCOME MEASURES: Actual survival rates in each group (road and air) were compared with the predicted survival rates. RESULTS: In the road group, 38.96 people were predicted to die and 51 actually died, therefore 23.61% (or 12.04 people) died 'unnecessarily', i.e. they died after having been predicted to live. In the helicopter group, 38.15 people were predicted to die and 39 actually died, therefore 0.85 (39-38.15) people were not expected to die. The 0.85 people represent 2.18% (0.85/39) of the total number of dead in the helicopter group who died 'unnecessarily'. Therefore one could argue that introduction of helicopter transport reduces the number of dead by 21.43% (23.61-2.18). CONCLUSIONS: Patients with a certain injury severity are more likely to survive if transported by air to a trauma unit.