Solid-phase extraction and high-performance liquid chromatographic determination of articainic and its metabolite articainic acid in human serum

A new method is described using solid-phase extraction (SPE) for preconcentration of articaine and the metabolite articainic acid and high-performance liquid chromatography (HPLC) for the determination of both compounds in human serum. Articaine and articainic acid were extracted in one step with SDB-RPS disk cartridges after precipitation of the serum proteins by perchloric acid. The HPLC separation was then performed on a reversed-phase C8 column using phosphate buffer-acetonitrile (88:12, v/v). UV absorption at 274 nm was used for measuring the analytes with a low limit of quantitation of about 10 ng/ml, which is appropriate for pharmacokinetic studies of low dose submucosal injections of the local anaesthetic agent articaine hydrochloride in dentistry.     

Evidence for striatal dopaminergic overactivity in paroxysmal dystonia indicated by microinjections in a genetic rodent model

Mutant dystonic hamsters (dt(sz)), a model of primary paroxysmal dystonia, display attacks of generalized dystonia in response to mild stress in an age-dependent manner. Recent studies in dystonic hamsters have revealed decreased densities of dopamine D(1) and D(2) in the dorsal striatum. This finding has been interpreted as a down-regulation in response to enhanced dopamine release because systemic treatments with neuroleptics reduced the severity of dystonia while levodopa exerted prodystonic effects. Therefore, in the present study we investigated the effects of amphetamine as well as of selective D(1) or D(2) receptor agonists and antagonists on the severity of dystonia after systemic administrations and after microinjections into the dorsal striatum. Amphetamine and the dopamine D(2) agonist quinpirole increased the severity of dystonia after systemic and striatal injections, while the dopamine D(1) agonist SKF 38393 exerted only moderate prodystonic effects after systemic administration of a high dose but not after striatal injections. These results suggest that a predominant overstimulation of D(2) receptors is pathogenetically involved in the dystonic syndrome. Combined systemic or striatal administrations of the D(1) and D(2) receptor agonists did not reveal synergistic prodystonic effects at the examined doses. The selective D(1) antagonist SCH 23390 as well as the D(2) antagonist raclopride tended to decrease the severity of dystonia after systemic administration but failed to exert significant effects after striatal injection. The coadministration of ineffective doses of the antagonists SCH 23390 and raclopride, however, exerted an enormous antidystonic efficacy after both systemic and striatal injections.Since striatal injections of compounds which enhance dopaminergic activity aggravated dystonia, while coinjections of dopamine D1 and D2 receptor antagonists reduced the severity of dystonia, the present findings clearly support the hypothesis that striatal dopaminergic overactivity plays a crucial role for the manifestation of dystonic attacks in the hamster model of paroxysmal dystonia.     

Do children with focal cerebellar lesions show deficits in shifting attention?

More recent findings suggest a possible role of the cerebellum in nonmotor functions. Disability of individuals with cerebellar damage in rapidly shifting attention is one frequently used example to support cerebellar involvement in mental skills. The original proposal was based on findings in five children with chronic surgical lesions of the cerebellum and a young adult with a degenerative disorder. The aim of the present study was to repeat Akshoomoff and Courchesne's initial findings in a larger group of children with focal cerebellar lesions. Ten children with cerebellar lesions and 10 age- and sex-matched controls were tested. Neocerebellar areas were affected in all children with cerebellar damage except one based on detailed analysis of MRI scans. Subjects had to perform a focus and a shift attention task. Two visual and two auditory stimuli were presented in a pseudorandom order. An ellipse and a high-pitched tone were presented less frequently than a circle and a low-pitched tone. Rare stimuli were presented at five different time intervals. In the focus tasks, subjects had to react to the same rare stimulus of one of the two modalities. In the shift task, subjects had to switch between the two rare stimuli. Motor deficits based on reaction times were small in cerebellar children compared with controls. The ability of target detection did not significantly differ in the children with cerebellar lesions compared with the control children in both the focus and the shift attention task. In particular, children with cerebellar damage showed no significant impairment in rapid (<2 s) shifts of attention. The present findings indicate that the cerebellum may be less critical in attention related processes than suggested previously.     

The role of testosterone in the feedback control of male FSH and LH secretion

Summary Intramuscular administration of 250 mg testosterone oenanthate per week over a period of 21 weeks treatment rapidly and sustainedly suppressed serum LH as well as FSH levels in seven normal males, while serum testosterone rose by a factor of approximately two. These together with other data provide increasing evidence for a feedback control of FSH secretion by gonadal steroids in the male in addition to the already described but as yet undefined tubular testicular factor.     

Candidate vaccine antigens identified by antibodies from mice vaccinated with 15- or 50-kilorad-irradiated cercariae of Schistosoma mansoni.

In murine schistosomiasis, the highest levels of resistance to cercarial challenge are obtained by vaccination with radiation-attenuated cercariae. To identify candidate vaccine antigens relevant to the vaccine model, we examined parasite antigens recognized by antibodies from mice vaccinated with irradiated cercariae of Schistosoma mansoni. To optimize recognition of a wide spectrum of antigens, several factors that influence the level of protection in this model were varied; specifically, we examined the effect of (i) single versus multiple vaccinations with irradiated cercariae, (ii) the dose of irradiation (15 or 50 kilorads) administered to the cercariae, and (iii) the genetic background of mouse strains, high-responder (C57BL/6J) versus moderate-responder (CBA/J) mice. We found that the number of vaccinations did not alter antibody specificity but modified the relative antibody titers against particular antigens. The dose of irradiation used to attenuate the immunizing cercariae had a similar effect on antibody titers but in addition influenced antibody specificity. Only mice that had been vaccinated with moderately irradiated cercariae recognized cathepsin B (Sm31) and Sm32. Interestingly, when vaccinated mice of the two strains, C57BL/6J and CBA/J, were compared, differences in antibody responses to particular antigens were observed. Both strains recognized the integral membrane protein Sm23, glutathione S-transferase, and cathepsin B, whereas Sm32 and paramyosin were recognized only by CBA/J mice, and heat shock protein 70 was recognized exclusively by C57BL/6J mice. In this study, we conclusively identified six distinct antigens that are specifically recognized by the humoral immune response of vaccinated mice.     

Anoxic disturbance of the isolated respiratory network of neonatal rats

Tissue oxygen (PO₂), K⁺ (aK_e), pH (pH_e) and Ca²⁺ ([Ca²⁺]_e) were measured in the region of the ventral respiratory group (VRG) in the in vitro brainstem-spinal cord preparation of neonatal rats. During tissue anoxia, elicited by superfusion of N₂-gassed solutions, an initial increase in the frequency of respiratory activity, lasting between 2 and 12 min, turned into a frequency depression. During anoxia periods of up to 60 min, respiratory activity persisted in solutions containing CO₂/bicarbonate, whereas a complete blockade was observed after 15–25 min in N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid- (Hepes)-buffered salines. After such anoxic apnea, respiratory rhythmicity could be reactivated by superfusion of hypoxic, CO₂/bicarbonate-buffered solutions. In both types of hypoxic solutions, aK_e increased by maximally 1.5mM, whereas an initial increase of pH_e by up to 0.05 pH units turned, after 2–4 min, into an acidification which could exceed 0.5 pH units. In contrast, [Ca²⁺]_e remained unaffected by anoxia. Addition of 2–5 mM cyanide (CN^-) to oxygenated Hepes-buffered saline evoked an increase in PO₂ in the VRG from 100 to more than 300 mmHg. The effects of CN^- on respiratory activity, aK_e and pH_e were almost identical to those during anoxia. In oxygenated, CO₂/bicarbonatefree solutions of different pH, however, an increase in pH_e in the VRG led to a decrease in respiratory frequency, whereas a fall of pH_e produced a frequency acceleration. A rise of aK_e in the VRG by more than 2 mM as induced by superfusion of a 7 mM K⁺ solution led to a sustained increase of respiratory frequency. The results indicate that blockade of aerobic metabolism does not severely perturb K⁺ and Ca²⁺ homeostasis and that the biphasic response to anoxia is not directly related to the observed changes in PO₂, aK_e, pH_e, or [Ca²⁺]_e. In the respiratory network of neonatal mammals, CO₂ might provide a stimulus for long-term maintenance of respiratory activity under oxygen depletion.     

Microembolic Renal Disease in Rats Induced with Sephadex: Hypertension, Lesions and Serum Urea Nitrogen

Sephadex particles (20-80 μ in size) were injected into the abdominal aorta of 134 male Sprague-Dawley rats near the renal arteries. In 31 rats, the right kidney was then removed. The Sephadex particles lodged in glomerular capillaries, afferent glomerular arterioles and interlobular arteries, creating renal infarcts, some of which were grossly visible. Shortly after injection, arterial blood pressure rose significantly in most animals. The hypertension in uninephrectomized rats was not demonstrably different from that in rats with two Kidneys. Severity and duration of hypertension (up to 8 months) were positively correlated with the number of Sephadex particles in renal vessels, and there was also a positive correlation between the degree of hypertension and serum urea nitrogen levels, and between degree of hypertension and degree of cardiac hypertrophy. The vascular permeability in acutely hypertensive rats was abnormal, as judged from penetration of iron-dextran into vessel walls. This experimental model resembles atheromatous microembolic renovascular disease, which may play a significant role in the pathogenesis of unexplained hypertension in patients with advanced aortic atherosclerosis.     

Immunoglobulin determinants on the surface of lymphoid cells of carps.

Immunoglobulin determinants were detected by indirect immunofluorescence on the surface of numerous lymphocytes of perpheral blood, spleen, and pronephros of craps. The most interesting finding was the high proportion (65–68 %) of Ig⁺ lymphocytes in the thymus of early adult carps, possibly related to thymus function.