The Effects of Alpha-2 Agonist, Medetomidine and its Antagonist, Atipamezole on Reaction and Movement Times in a Visual Choice Reaction Time Task in Monkeys

Alpha-2 adrenoceptor agonists have been shown to improve the working memory task performance of aged monkeys. Suggestions offered to explain this finding include improved short-term memory processing, slight sedation, and decreased distractiveness. Although sedation is evident at high doses, it may also contribute to the working memory task performance at low doses. The aim of the present work was to find out whether the positive effects of an alpha-2 agonist, medetomidine, on working memory performance could be explained by its sedative effects. This was accomplished by measuring the reaction and movement times of monkeys performing a visual choice reaction time task under the influence of medetomidine or its antagonist atipamezole. In the task a trial began with the monkey holding a central pad. After a short period one of two lateral light emitting diodes was turned on for 300 ms and the monkeys were trained to release the central bar and touch either of the bars, situated below the diodes, depending on the location of the stimulus. The reaction and movement times were significantly longer than on saline control only at the highest dose of medetomidine (10.0 μg/kg). At the lowest dose of atipamezole (0.01 mg/kg), the reaction times were significantly shorter than on saline control. The results of this study demonstrate that low doses of medetomidine, which have earlier been shown to improve working memory performance, do not induce sedation as measured by reaction and movement times.     

Important roles for angiotensin III and IV in the brain renin-angiotensin system

Considerable evidence now suggests that the precursors and enzymes necessary for the formation and degradation of biologically active forms of angiotensins are present in brain tissues, accompanied by at least three specific binding sites. It also appears that several forms of angiotensin may serve as signaling agents at these sites. There is accumulating support for the notion that AngII must be converted to AngIII in order to bind at the AT₁ and AT₂ receptor subtypes, and AngIII must be converted to AngIV in order to activate the AT₄ receptor subtype. Further, AngII(1–7) may activate a separate binding site concerned with antidiuresis, however, characterization of this site has not been completed. The AT₁ site appears to mediate the classic angiotensin functions concerned with body water balance, maintenance of blood pressure, and cyclicity of reproductive hormones and sexual behaviors. This receptor site also exerts some control over the secretion of pituitary hormones. Less is known about the functional importance of the AT₂ site, however, it has been implicated in vascular growth, control of blood flow, and perhaps modulation of NMDA receptors. The AT₄ site is heavily distributed in neocortex, hippocampus, cerebellum, and basal ganglia structures, as well as several peripheral tissues. This site appears to mediate memory acquisition and retrieval, the regulation of blood flow, neurite outgrowth, angiogenesis, and kidney function. In addition to the well-studied functions of the brain renin-angiotensin system, additional less well investigated responses are reviewed. These include electrophysiological activation, tachyphylaxis, long term potentiation, learning and memory, and cognitive affect.     

A study of the proliferative activity of the long junctional epithelium using argyrophilic nucleolar organizer region (AgNORs) staining

The proliferative activity of the long junctional epithelium (LJE) in rats was examined using stains for argyrophilic proteins of the nucleolar organizer region (AgNORs protein). The LJE was experimentally produced by insertion of a rubber piece between maxillary molars for 1 wk. After removal of the rubber, the length and AgNORs parameters of the LJE were measured and analyzed statistically. The LJE widely covered the apical side of the exposed root surface 4 wk after the removal. Its length was longest after 4 and 8 wk; it became shorter subsequently. The AgNORs were visible as black dots of various sizes and numbers on the sections. A high potential for proliferation was obvious in the LJE after 4 wk and was maintained until 12 wk after the removal. The AgNORs ratio on the connective tissue interface of the LJE was about twice of that of normal junctional epithelium after 4-12 wk. The proliferative activity on the root surface side was slightly increased after 4 wk. There was no significant difference in proliferative activity between the coronal and apical sides. These results suggest that the proliferative activity of the LJE is maintained continuously at a high level on the connective tissue interface supplying the epithelial cells. Basal cells proliferate at the connective tissue interface of the LJE, migrate directly to the root surface or via the apical portion and finally desquamate from the surface of the epithelium.     

Are adult transcranial Doppler systems suitable for application in neonates?

Transcranial Doppler systems have not been available for monitoring of cerebral blood flow velocities in neonates because of potential hazardous effects of energy output from standard instruments developed for adult application. Aim of the study was to test commercially available transcranial Doppler instruments for their applicabiltiy in neonates and to develop guidelines for adaptation for safe neonatal use. Energy output of five commercially available transcranial Doppler instruments was measured with a hydrophone system and a radiation force balance. At the highest setting and at the nominal 10% attenuation level, five out of five and two out of five instruments, respectively, had an energy output above the recommended limits. Power reduction was not linear in one instrument. Evaluation of safety devices (alarm, freeze mode, energy reduction facilities, display of energy values) showed that none of the tested instruments had an optimal setting for safe neonatal application.Part of this study has been presented at the ESPR Meeting 1994 [15]     

Extended workshifts and excessive fatigue

SUMMARY  Studies of overtime have pointed to fatigue as a potential factor producing, for example, a three-fold increase in accident rate after 16 h of work, increases in back injuries, hospital outbreaks of bacterial infection, or nuclear-power plant safety compromises. Fatigue has been measured more directly in studies of scheduled long workshifts, where performance decrements in both work-related tasks and laboratory-type behavioural tests have been observed, and significant loss of sleep and increases in subjective sleepiness have been reported. Analyses of accidents or injuries during scheduled extended workshifts, however, have produced equivocal results. Factors which could compound the fatiguing effects of extended workshifts, such as workload, noise, chemical exposure, or duties and responsibilities outside of the workplace, rarely have been studied systematically. It is concluded that extended workshift schedules should be instituted cautiously and evaluated carefully, with appropriate attention given to staffing levels, workload, job rotation, environmental exposures, emergency contingencies, rest breaks, commuting time, and social or domestic responsibilities.     

The Long QT Syndrome with Impaired Atrioventricular Conduction: A Malignant Variant in Infants

Distal Conduction Disease in the Long QT Syndrome. Introduction : The long QT syndrome (LQTS) is occasionally complicated by impaired AV conduction, mostly 2:1 AV block. This form of LQTS can manifest before birth or during neonatal life, and it is more sporadic than familial. It is usually an isolated disorder, although it can be accompanied by a variety of cardiovascular and other anomalies. In spite of different treatment modes, mortality is high.
Methods and Results : The reported case presented not only with 2:1 AV conduction, but also with Wenckebach episodes with impaired right and left bundle branch conduction, and decremental conduction in the His-Purkinje axis. We also observed sinus pauses and accelerated AV junctional escape beats.
Conclusion : Our findings, and similar observations by others., suggest involvement of the sinus node and the distal conduction system in this form of the LQTS. Several histologic studies have documented abnormalities within the conduction system, including apoptosis. Because of the rare occurrence and poor prognosis of the LQTS with impaired AV conduction, international guidelines for diagnosis and treatment are needed. Development of an internal cardiac defibrillator for this young age group is necessary.     

A Case of Antirabies Inoculation Encephalitis with a Long Clinical Course

Abstract: In 1950, a 24-year-old man developed gait disturbance, incontinence of urine and increasing lethargy a week after a course of antirabies vaccination. He was diagnosed as having post-rabies vaccination encephalitis and had been in hospital for 37 years before he died in 1987. This is one of the rare cases in which the course of this disease was traced for an exceptionally long period. His personality began to deteriorate at an early stage of the illness, but his intellectual faculties seemed to be maintained rather well until a few years prior to his death. A neuropathological study revealed disseminated, patchy and somewhere perivascularly located demyelinated lesions in the cerebral white matter. Inflammatory lymphocytic infiltration was also remarkable in the CNS regions. But while the superimposed lesions due to convulsive attacks, traumatic contusion and terminal anoxia were remarkable, the whole aspect of neuropathological changes in rabies inoculation encephalitis cannot be observed.     

Prenatal protein-energy malnutrition and its recovery of mandible and long bone in newborn rats

Pregnant rats were fed either a 25% protein diet as controls or a 10% protein diet from day 13 of gestation to birth. Immediately after birth (day 1), calcium uptake and collagen synthesis were studied in the mandible and long bone of the new-borns. Control dams were fed continuously a 25% protein diet and prenatally malnourished dams were fed either a 25% protein diet or continuously a 10% protein diet untill day 15. The mandibles and long bones were then studied to determine the recovery of the prenatal malnutrition at day 15. At the time of birth, body weight and the weights of the mandibles and long bones were affected to approximately the same extent. Calcium and collagen contents of the mandible in the malnourished groups were less when compared to the controls, but no differences were observed in the long bone between groups. On the other hand, calcium uptake and collagen synthesis in the mandibles were greater in the malnourished group than that of the controls, but no differences in the long bones were observed. At day 15, body weight and the weights of the mandibles and long bones in the rehabilitated group were about the same as that of the controls. Furthermore, there was no difference in calcium and collagen contents as well as collagen systhesis between these groups, but calcium uptake in the rehabilitated group was greater. The differences in body weights and the weights of the mandibles and long bones of the continuously malnourished group compared to the controls were increased by day 15. The calcium and collagen contents of this group were less, also. However, calcium uptake and collagen synthesis in the mandibles and long bones in the continuously malnourished group were increased compared to the control group. It is concluded that both mandibles and long bones can be successfully rehabilitated, if refeedings are initiated properly and early.     

THE LONG TERM PROGNOSIS OF NON-OBSTRUCTIVE URINARY TRACT INFECTION IN INFANCY AND CHILDHOOD AFTER THE ADVENT OF SULPHONAMIDES

One hundred and seven cases of urinary tract infection in children, hospitalized during the years 1940-1949, were reinvestigated with an observation time ranging from 15 to 24 years. Primary and late mortality was low. Non-obstructive urinary infections in boys show a good prognosis, concerning recurrence as well as progressive renal disease. Non-obstructive urinary tract infection in girls seems to be a potentially serious disease, where recurrence developed in half the cases in spite of the initial sulpha-treatment given. A minimum of 19 % of the girls showed progressive renal disease according to radiological examinations. Early recurrence, according to the primary report, increased the risk of progressive renal disease from 4 to 30%. In 40% of the girls with late symptomatic recurrence, progressive renal disease could be diagnosed at about 20 years of age. The reinvestigation shows that in certain individuals the child's susceptability to recurrent urinary tract infection is retained even in the adult, in whom it manifests itself as acute pyelonephritis. It is of special interest to note that between one half to one third of those who had been pregnant had suffered from urinary tract infection of pregnancy. At about 20 years observation time negative results of single determination of blood pressure, sedimentation rate, haemoglobin, serum-creatinine, protein or leucocytes or bacteria in the urine and maximal urinary concentration capacity does not seem to guarantee the ab-scence of chronic or recurrent pyelonephritis. A thorough case history, including a paediatric history, is recommended in dealing with urinary tract infections in children and young adults.     

Repeated femoral vein puncturing for maintenance haemodialysis vascular access.

BACKGROUND: When access cannot be achieved using a native arteriovenous fistula or a synthetic prosthetic graft, central venous catheters are usually placed. This mode of access is short-lived, prone to infection, stenosis and thrombosis of central veins. To overcome access problems, we developed a new native vascular access ('femoral vein access') and devices. We report here on our experience with the availability, longevity, procedure and morbidity of haemodialysis (HD) using femoral vein access. METHODS: Repeated (three times a week) patient's native femoral vein puncturing has been used as the vascular access (femoral vein access) for maintenance HD in 30 patients (mean age +/- SD: 61.70 +/- 15.27 years old; 18 female/12 male). The femoral vein was punctured beneath the inguinal ligament (on a length ranging from 30 to 100 mm) after disinfection and local anaesthesia. Long (effective length 56 mm) 19- and 18-gauge needles with four side holes were used for the femoral vein puncture as an arterial site of the extracorporeal circuit of HD and shorter (effective length 40 mm) similar gauge needles for the subcutaneous vein puncture used as the return site. The needle is inserted blind into the femoral vein after the femoral artery has been located by palpation and the perception of a pulse. Patients returned home the same day. RESULTS: The mean duration of HD treatment using femoral vein repeated puncture was 4.99 +/- 3.42 years (up to 16.0 years). This represented a total experience of 23 369 femoral vein punctures. The mean blood flow achieved on dialysis was 165 +/- 20 ml/min. The average Kt/V was 1.74 +/- 0.48 per session. CONCLUSIONS: The femoral vein repeated puncture technique has substantial advantages over venous catheters. It does not require surgery, while permitting adequate blood flow. This method can be used as a long-term (over 10 years) blood access. Apart from a few local haematomas, no serious complications have been observed. Moreover, it does not carry a heavy financial burden.