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Presents a study which determined the spin-wave polarization in single domain ferromagnetic uranium selenide. Background information on the magnetic behavior of uranium chalcogenides; Methods; Results of inelastic neutron scattering measurements.

One defining characteristic of skilled motor performance is the ability to complete the task with minimum energy expenditure. This experiment was designed to examine practice effects on coordination and control, metabolic energy expenditure, and muscle activation. Participants rowed an ergometer at 100 W for ten 16-min sessions. Oxygen consumption and perceived exertion (central and peripheral) declined significantly with practice and movement economy improved (reliably) by 9%. There was an associated but non-significant reduction in heart rate. Stroke rate decreased significantly. Peak forces applied to the ergometer handle were significantly less variable following practice and increased stability of the post-practice movement pattern was also revealed in more tightly clustered plots of hip velocity against horizontal displacement. Over practice trials muscle activation decreased, as revealed in integrated EMG data from the vastus lateralis and biceps brachii, and coherence analysis revealed the muscle activation patterns became more tightly coordinated. The results showed that practice reduced the metabolic energy cost of performance and practice-related refinements to coordination and control were also associated with significant reductions in muscle activation., (Copyright 2002 Elsevier Science B.V.)

Rats administered amphetamine prior to access to milk in bottles develop tolerance to the hypophagic effect of the drug by learning to suppress stereotyped behaviours that interfere with feeding. When tolerant rats are later allowed to drink milk from a bottle in an unintoxicated state, tolerance is lost, even when drug exposure is held constant by administration of the drug after the test. In the present experiment, we show that tolerance can also be lost in the face of continued administration of amphetamine prior to milk tests, as a result of changes in the contingencies of reinforcement that govern the suppression of stereotypy. Rats were injected with 2 mg/kg amphetamine and given access to milk in bottles for 16 trials. Tolerance to the hypophagic effect was confirmed by dose-response tests in which milk was available in bottles. The rats were then injected with 2 mg/kg amphetamine prior to intraoral milk infusions for 21 trials. This method of feeding did not require the suppression of stereotypy to obtain milk. Subsequent dose-response tests in which milk was again presented in bottles revealed that tolerance was lost, even though intoxicated feedings were never interrupted. These results demonstrate that the contingencies of reinforcement governing the suppression of stereotypy determine whether tolerance is retained or lost.

Hyperkalemia is a regularly encountered electrolyte abnormality. Less commonly recognized is pseudohyperkalemia. In vitro clotting results in the release of potassium from the formed elements of blood; this falsely elevates the serum potassium concentration. Usually attributed to thrombocytosis, leukocytosis, or hemolysis it is rarely reported in the postsplenectomy trauma patient. A 49-year-old man underwent splenectomy for a grade IV splenic injury. He developed an elevated serum potassium on postoperative day 16. His renal function remained normal, and an active search for causes of hyperkalemia failed to delineate a source for his elevated potassium. Pseudohyperkalemia was proposed as an etiology and confirmed by analyzing simultaneous serum (5.9 mEq/L) and plasma potassium levels (3.9 mEq/L). The serum potassium showed a concomitant rise with the evolution of the patient's postsplenectomy thrombocytosis. This is a case report of our patient and a literature review of this rarely reported and underestimated cause of a potentially serious electrolyte abnormality. We found through our patient that pseudohyperkalemia does occur in the postsplenectomy population and that this should be included in the differential diagnosis of any patient with an elevated serum potassium level and thrombocytosis.

Blunt traumatic carotid artery dissection remains controversial in terms of diagnostic screening, reported incidence, and management. Treatment options include observation, anticoagulation and endovascular stenting, and aggressive surgical repair of the carotid artery injury. Blunt traumatic carotid artery dissections were reviewed through a retrospective study of trauma registry records. Seven patients were identified from 3342 patients over 3 years. Six patients were identified incidentally during magnetic resonance imaging (MRI) cervical spine/brain screening and one patient during angiographic evaluation for possible penetrating neck injury without MRI/magnetic resonance angiography (MRA). A total of 189 patients underwent MRI screening over this 3-year period, demonstrating a relative incidence of 3.7 per cent, contrasting with the reported incidence of 0.08 to 0.4 per cent for all trauma patients. All seven patients suffered severe head injuries (mean Glasgow Coma Score = 4.7) requiring mean intensive care unit and hospital stays of 15.6 and 23.7 days, respectively. None of the patients showed evidence of stroke with CT scanning on presentation. None of the patients demonstrated clinical focal neurologic signs or symptoms indicating carotid injury or stroke. Six patients survived their acute trauma and were discharged to rehabilitation after initiation of observation (one patient) or anticoagulation (five patients). All six patients showed neurological improvement without deterioration clinically or radiographically. In conclusion we propose early aggressive screening through MRI/MRA of severely injured patients to detect occult carotid artery dissections. Conservative medical treatment for this occult injury has been effective in this series of patients.

Bryostatin 1 (Bryo), currently in clinical trials, has been shown to induce a biphasic concentration-response curve for down-regulating protein kinase C (PKC) delta, with protection of the enzyme from down-regulation at high Bryo doses. In our ongoing studies to identify the basis for this unique behavior of PKCdelta, we examined the participation of the two ligand binding sites (C1a and C1b) in the regulatory domain of the enzyme. Three mutants of PKCdelta prepared by introducing a point mutation in either C1a or Clb or both C1a and Clb were overexpressed in NIH 3T3 cells. All of the constructs retained a biphasic response to down-regulation assessed after 24-h treatment with Bryo. However, the roles of the individual C1 domains were different for the two phases of the response. For down-regulation, both the C1a and the C1b mutants displayed equivalent 3-4-fold reductions in their affinities for the ligand. For protection from down-regulation, a reduced protection was observed for the C1a mutant, which showed a broader biphasic curve compared with those for wild-type PKCdelta and the Clb mutant. Like wild-type PKCdelta, all of the mutants showed the same subcellular partitioning of the protected enzyme to the particulate fraction of the cells, arguing against changes in sensitivity to Bryo due to differences in localization. Likewise, relatively similar patterns of localization were observed using green fluorescent protein-PKCdelta constructs. We conclude that the C1 domains of PKCdelta do not have equivalent roles in inducing protection against Bryo-induced down-regulation. The C1a domain plays a critical role in conferring the degree of protection at high concentrations of Bryo. Elucidation of the differential effect of Bryo on PKCdelta may suggest strategies for the design of novel ligands with Bryo-like activities.

According to the homeostatic model, the loss of tolerance to amphetamine-induced hypophagia requires a period of unrestricted feeding in the drug-free state, which transforms the compensatory response mediating tolerance ("hyperhunger") into a functional disturbance to homeostasis. In the absence of such a disturbance, tolerance should be retained. To test this prediction, rats tolerant to amphetamine's hypophagic effect were given a 4-week tolerance retention period during which milk intakes were restricted and deprivation levels held relatively constant. During this period the rats were assigned to one of the following drug treatment conditions: 1) saline injections both before and after daily milk tests (saline group); 2) saline injections before, and amphetamine injections after, daily milk tests (after group); 3) no injections and no milk tests (no-treatment group); or 4) amphetamine injections before, and saline injections after, milk tests (before group). Despite the restricted feeding regimen, both the saline and after groups lost tolerance. These results do not support the homeostatic model, but are consistent with the instrumental learning model, which views drinking milk in the undrugged state as analogous to receiving noncontingent reinforcement.

In previous research, sensitization of stereotypy induced by injections of 2.5 mg/kg amphetamine did not interfere with subsequent tolerance development to the hypophagic effect of 2 mg/kg. This study examined the effect of a higher sensitizing dose. Rats given intermittent injections of 5 mg/kg amphetamine and then challenged with various doses of amphetamine showed focused head scanning at 2 mg/kg and oral stereotypy at 4 mg/kg. In contrast, saline controls showed diffuse sniffing and head scanning at 2 and 4 mg/kg. Subgroups from each condition were then given daily injections of either amphetamine (2 mg/kg) or saline and access to milk for 30 min. Dose-response tests revealed that both drugged groups learned to suppress stereotypy in order to feed at 2 mg/kg, but only the non-sensitized group could do so at 4 mg/kg. These results demonstrate that (1) rats learn to suppress only those stereotyped movements that they experience in the context of feeding and (2) instrumental contingencies can influence the expression of behavioral sensitization.

Human immunodeficiency virus (HIV) seroprevalence rates among rural trauma patients range between 0.15 and 1.32 per cent. A random sample of trauma patients treated at our rural trauma center between September 1994 and November 1995 was enrolled into a blind HIV serosurvey. Five hundred sixty-six of 1315 trauma patients (43%) were tested. Two of the 566 patients (0.35%) were HIV positive. A review of aggregate data for HIV infection among rural trauma patients in the United States show that 28 of the 4639 patients (0.60%) are HIV positive. We conclude that there was a low HIV incidence among our trauma patients from September 1994 to November 1995, and the cost-effectiveness of HIV testing for rural trauma patients is questionable with incidences between 0.5 and 1.0 per cent.

Tolerance to amphetamine-induced hypophagia is lost when drug injections are withdrawn for 4 weeks while milk tests are continued (Wolgin and Hughes 1996). The purpose of this study was to determine whether the loss of tolerance is a function of drug withdrawal per se. Rats made tolerant to amphetamine (2 mg/kg, IP) were assigned to one of three groups. During the next 4 weeks (phase), one group continued to receive amphetamine injections prior to daily milk tests (Before group), one group received drug injections after the milk tests (After group), and one group received injections of saline prior to the milk tests (Saline group). Dose-response tests revealed that the Before group retained tolerance, whereas the After and Saline groups lost tolerance. When retested with chronic injections of amphetamine prior to milk, the After and Saline groups reacquired tolerance more rapidly, and to a greater extent, than non-tolerant controls. These results demonstrate that the loss of tolerance is not due to drug withdrawal per se, but may be due to the unlearning of behavioral strategies previously acquired under the drug.

Few studies compare complications of continuous and bolus epidural analgesia. Ninety-eight postoperative and trauma patients receiving epidural infusions over 15 months were retrospectively studied. Continuous epidural analgesia was used for pain management in 60 patients (61%). Bolus epidural analgesia was administered to 38 patients (39%). Sixty patients reported 98 complications. Sixty-eight per cent of complications occurred in patients receiving continuous infusions. For the continuous infusions, motor blockade (18%), nausea/vomiting, (18%), and catheter leaks (12%) were the most common complications. For bolus infusions, nausea/vomiting (25%), mental status changes (21%), and erythema at placement site (13%) were encountered. Continuous infusions were associated with an increased incidence of complications compared with bolus infusions (P < 0.05). Patients undergoing abdominal surgery had an increased incidence of complications compared with other patients (P < 0.05). Epidural catheters are safe and effective for pain management, but they are not without risk. Hemodynamic stability and pulmonary status should be considered when evaluating patients.