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).     

Tumor necrosis factor-mediated interactions between inflammatory response and tumor vascular bed

Summary: Solid tumor therapy with chemotherapeutics greatly depends on the efficiency with which drugs are delivered to tumor cells. The typical characteristics of the tumor physiology promote but also appose accumulation of blood-borne agents. The leaky tumor vasculature allows easy passage of drugs. However, the disorganized vasculature causes heterogeneous blood flow, and together with the often-elevated interstitial fluid pressure, this state results in poor intratumoral drug levels and failure of treatment. Manipulation of the tumor vasculature could overcome these barriers and promote drug delivery. Targeting the vasculature has several advantages. The endothelial lining is readily accessible and the first to be encountered after systemic injection. Second, endothelial cells tend to be more stable than tumor cells and thus less likely to develop resistance to therapy. Third, targeting the tumor vasculature can have dual effects: (i) manipulation of the vasculature can enhance concomitant chemotherapy, and (ii) subsequent destruction of the vasculature can help to kill the tumor. In particular, tumor necrosis factor α is studied. Its action on solid tumors, both directly through tumor cell killing and destruction of the tumor vasculature and indirectly through manipulation of the tumor physiology, is complex. Understanding the mechanism of TNF and agents with comparable action on solid tumors is an important focus to further develop combination immunotherapy strategies.     

Connective tissue growth factor expression and Smad signaling during mouse heart development and myocardial infarction.

Connective tissue growth factor (CTGF) is reported to be a target gene of transforming growth factor beta (TGFbeta) and bone morphogenetic protein (BMP) in vitro. Its physiological role in angiogenesis and skeletogenesis during mouse development has been described recently. Here, we have mapped expression of CTGF mRNA during mouse heart development, postnatal adult life, and after experimental myocardial infarction. Furthermore, we investigated the relationship between CTGF and the BMP/TGFbeta signaling pathway in particular during heart development in mutant mice. Postnatally, CTGF expression in the heart became restricted to the atrium. Strikingly, 1 week after myocardial infarction, when myocytes have disappeared from the infarct zone, CTGF and TGFbeta expression as well as activated forms of TGFbeta but not BMP, Smad effector proteins are colocalized exclusively in the fibroblasts of the scar tissue, suggesting possible cooperation between CTGF and TGFbeta during the pathological fibrotic response.     

The effects of co-culture with human fibroblasts on human embryo development in vitro and implantation

In a human in-vitro fertilization (IVF) programme, the effect of co- culture of embryos with human fibroblasts was evaluated with respect to pregnancy rate and embryo development. Patients were included in the study after giving informed written consent. The IVF treatments were randomly assigned by stratification of both age (<36 versus > or =36 years) and previous IVF attempts (yes versus no). After fertilization was established, the zygotes were transferred to a 4-well dish with or without fibroblasts and cultured for 2 days. On the third day after ovum pick-up (OPU), cell number and quality [5 (good) to 1 (poor)] of the embryos were scored and a maximum of three embryos was transferred. Supernumerary embryos of good quality were cryopreserved. The design of this study was a group sequential trial with the objective of detecting differences between pregnancy rates following IVF with conventional incubation or incubation in co-culture with fibroblasts. This design included one evaluation at half-way data collection. In the study, 148 patients had an OPU, of whom 77 were allocated to the co-culture group. There was no statistically significant difference in pregnancy rate, cell number and embryo quality between the two groups. The ongoing pregnancy rate per embryo transfer was 27% in co-culture and 30% in the conventional culture group. The implantation rates per transferred embryo were 17 and 18% respectively. Using a multivariate logistic regression model for the probability of ongoing pregnancies, the odds ratio of co-culture, adjusted for age and previous IVF attempts, was not statistically significant. In conclusion, co-culture with human fibroblasts does not contribute to an improvement of embryo quality nor to a higher pregnancy rate after IVF in an unselected group of patients.      

Electrotonic characteristics of alpha motoneurones of varying size

1. The neuronal membrane responses to long constant current pulses (essentially current steps) have been studied in cat triceps surae motoneurones identified as to the type of muscle fibres, fast twitch (type F) or slow twitch (type S), innervated by the cell being studied. For each motoneurone the membrane time constant, τ_M, and input resistance, R_N, were determined from the response to a current step. In addition, shorter time constants (`equalizing time constants') resulting from current spread into the dendrites were estimated by graphical analysis.

2. The electrotonic length of the combined motoneurone soma and dendritic tree was estimated from the current step data using the neuronal equivalent cylinder model formulated by Rall (Rall, 1969). The mean electrotonic length of the motoneurone equivalent cylinder was approximately 1·5 in both type F and type S motoneurones. The mean membrane time constant of type F cells was 5·6 msec and that of type S motoneurones was 6·7 msec. This difference in mean τ_M values was of border line statistical significance.

3. The results indicate that the electrotonic length of the combined dendritic trees of both large type F and small type S motoneurones is essentially the same. The implication of this conclusion for interpretation of previous analyses of the monosynaptic EPSP is discussed.