A possible pain control system in a non-mammalian vertebrate (a lizard, Gekko gecko)

In a lizard (Gekko gecko) the anterograde tracer PHA-L was microiontophoretically applied to the predominantly serotonergic nucleus raphes inferior. Extensive spinal projections from the rostral magnocellular part of this nucleus were demonstrated to the superficial layers of the dorsal horn and to the intermediate zone, more sparsely to the ventral horn. But, in addition, retrogradely labeled neurons were found in and just below a periventricular cell group in tegmentum mesencephali, i.e. the laminar nucleus of the torus semicircularis, a cell group which receives spinal afferents and projects to the spinal cord as the mammalian periaqueductal gray. These data suggest the presence of a three-tiered pain control system in a lizard composed of projections from the laminar nucleus of the torus semicircularis to the rostral part of the inferior raphe nucleus which in its turn projects to the superficial layers of the dorsal horn of the spinal cord.     

Neck sprain in patients injured in car accidents: a retrospective study covering the period 1970–1994

During the 25-year period 1970–1994 694 patients were diagnosed with neck sprain resulting from a car accident at the Emergency Room of the University Hospital Groningen. The purpose of the present study was to analyse the prevalence, groups at risk and trends in these patients, taking into account changes in the number of cars per inhabitant and the average number of kilometres driven. We defined the population as car accident victims diagnosed with neck sprain. Binominal tests were used to obtain measures of statistical significance. Over the 25-year period a steady increase in the number of these patients was observed, from 10 in 1970 to 122 in 1994. The highest prevalence was found for the age group 25- to 29-year olds (28.3 per 100,000), followed by 40- to 44-year-olds (27.9 per 100,000). Across the life span, the male: female ratio was 1 : 0.98. Eight percent of the victims were treated as inpatients. The increase in the number of car accident victims with neck sprain appears not to be an isolated phenomenon, because a parallel rise in the number of cars per inhabitant and in the average number of kilometres driven was found. No direct relation was observed between seat belt legislation and the increase in neck sprain injuries. The effect of the media on awareness of the consequences of car accidents is discussed. Received: 9 May 1997 Revised: 17 December 1997 Accepted: 10 January 1998     

Development of spinocerebellar afferents in the clawed toad, Xenopus laevis

The development of spinocerebellar projections in the clawed toad, Xenopus laevis, was studied with horseradish peroxidase as an anterograde and retrograde tracer. Early in development cells of origin of spinocerebellar projections were found, contralaterally, in or close to the medial motor column. In older tadpoles ipsilaterally projecting spinal neurons were also labeled from the cerebellum. These are virtually indistinguishable from the large primary motoneurons that occupy a very similar position in the spinal cord. Most of the labeled spinal cells were found in the thoracic spinal cord; they lie halfway between the brachial and lumbar secondary motor columns. Surprisingly, no primary spinocerebellar projection arising from dorsal root spinal ganglion cells could be demonstrated in X. laevis tadpoles and adult toads. Therefore, fibers in the cerebellum that were labeled anterogradely from the spinal cord can be expected to originate exclusively from the secondary spinocerebellar tract cells. These fibers appear to cross the cerebellum in or at the border of the granular layer. The present data suggest that in X. laevis early in the development of the cerebellum a distinct secondary spinocerebellar projection is already present, originating in neurons that can be compared with the "spinal border cells" in mammals. The relative sparseness of this secondary spinocerebellar projection and the apparent absence of primary spinocerebellar afferents probably indicate that spinocerebellar pathways are only of minor importance in X. laevis. The possibility remains, however, that the expansion of the secondary spinocerebellar pathway only starts when metamorphosis has been completed.     

Dentists' opinions of their dental education; results of a survey of dentists who studied in Amsterdam between the years 1982-1990

Four hundred and fifty dental graduates from the Free University (VU), the University of Amsterdam (UvA) or the Academic Center for Dentistry Amsterdam (ACTA) between 1982 and 1990 were asked by questionnaire to give their opinion about the undergraduate dental training they received. Most respondents felt that their undergraduate education prepared them reasonably well for general practice. Yet imperfections in the education were noticed. These imperfections show resemblance to conclusions from similar surveys in other countries.     

Saliva, a physiological medium

Plaque and plaque fluid, rather than saliva, are of prime importance in determining the result of the interaction between tooth enamel and its environment. The concentration of calcium and phosphate ions is higher in plaque fluid than in saliva. Local supersaturation may result in the remineralization of white spot lesions or in the formation of calculus. The latter may be inhibited with containing dentifrices. Undersaturation, resulting from bacterial acids production, promotes dental caries. Fluorides are effective against caries, although the limited transporting properties of saliva would be recognized when designing caries preventive treatments. Suppleting saliva with calcium and phosphat ions through mouthrinses is another method to fight caries, while stimulation of the secretion by chewing gum is also very effective.     

Effects of cromakalim (BRL 34915) on potassium conductances in CA3 neurons of the guinea-pig hippocampus in vitro

Summary The action of the potassium channel activator, cromakalim (BRL 34915), on membrane potential, input resistance and current-voltage-relationship of CA3 neurons in a slice preparation of the guinea-pig hippocampus was investigated by means of intracellular recordings. In the presence of tetrodotoxin, cromakalim (30–100 mol/l) produced a hyperpolarization up to 4 mV associated with a decrease in input resistance up to 10 MOhms. Determination of the equilibrium potential of the cromakalim action revealed that the hyperpolarization is due to the activation of a potassium conductance. This cromakalim-activated potassium conductance was voltage-dependent, i.e. it increased with hyperpolarization. Among a number of potassium channel blockers tested, only Cs⁺ (2 mmol/l) and Ba²⁺ (0.5 mmol/1) were able to inhibit the cromakalim-induced effects. Simultaneously, both cations suppressed the hyperpolarizing inward rectification (anomalous rectification) in these neurons, indicating that cromakalim activated or potentiated an inwardly rectifying potassium conductance. In addition, cromakalim slightly enhanced both amplitude and duration of afterhyperpolarizations following single calcium-dependent action potentials, suggesting that cromakalim might have a weak facilitatory effect on calcium-dependent potassium conductances.Send offprint requests to C. Alzheimer at the above address     

Single-cycle immunodeficiency viruses provide strategies for uncoupling in vivo expression levels from viral replicative capacity and for mimicking live-attenuated SIV vaccines

To reduce the risks associated with live-attenuated immunodeficiency virus vaccines, single-cycle immunodeficiency viruses (SCIVs) were developed by primer complementation and production of the vaccine in the absence of vif in a vif-independent cell line. After a single intravenous injection of SCIVs into rhesus monkeys, peak viral RNA levels of 10(3) to 10(4) copies/ml plasma were observed, indicating efficient expression of SCIV in the vaccinee. After booster immunizations with SCIVs, SIV-specific humoral and cellular immune responses were observed. Although the vaccine doses used in this pilot study could not protect vaccinees from subsequent intravenous challenge with pathogenic SIVmac239, our results demonstrate that the novel SCIV approach allows us to uncouple in vivo expression levels from the viral replicative capacity facilitating the analysis of the relationship between viral expression levels or viral genes and immune responses induced by SIV.     

Evaluation of the immunosuppressive effects of cyclophosphamide in patients with multiple sclerosis.

In a group of eight patients suffering from clinically definite multiple sclerosis, we studied the effects of treatment with cyclophosphamide on the immune reactivity in vitro and in vivo. The results are compared with those obtained in a control group consisting of eight patients who received no drug therapy and who were matched with the former group for age, sex and severity of disease. The results indicate that therapy with cyclophosphamide at a mean dose of 100 mg/day induces a profound lymphocytopenia in peripheral blood involving both T and B cells. Serum levels of immunoglobulins as well as primary and secondary antibody responses were depressed. In tests with standardized cell numbers, proliferative responses of lymphocytes in vitro and cytotoxic T cell function remained normal, whereas K and NK cell activities were diminished. Secondary cellular immune responses in vivo remained intact; however, the primary cellular immune response in vivo was markedly depressed. From these data, it is concluded that therapy with cyclophosphamide in man mainly affects humoral immune functions, but also cellular immunity, although to a lesser extent.     

Effects of glycine and GABA,and blocking actions of strychnine and picrotoxin in the hypoglossus nucleus

Summary Neutral ω-amino acids were applied iontophoretically in the hypoglossus nucleus. Intracellular recordings revealed inhibitory actions involving hyperpolarization and conductance increase of the membrane. The antidromic field potential was reduced most effectively by glycine, as judged by the comparison of iontophoretic currents. Picrotoxin, ejected electrophoretically, clearly interfered with the action of GABA, glycine effects being reduced only with rather high currents. Strychnine had very specific blocking ability against glycine actions. Supported by the Deutsche Forschungsgemeinschaft (Br 242/7).