Two generations of insulinotropic imidazoline compounds

The imidazoline RX871024 increased basal- and glucose-stimulated insulin release in vitro and in vivo. The compound inhibited activity of ATP-sensitive K(+) channels as well as voltage-gated K(+) channels, which led to membrane depolarization, an increase in the cytosolic Ca(2+) concentration ([Ca(2+)](i)), and insulin release. Importantly, RX871024 also enhanced the insulinotropic effect of glucose in cells with clamped [Ca(2+)](i) but in the presence of high ATP and Ca(2+)concentration inside the cell. We believe that the latter effect on insulin exocytosis was at least in part mediated by a rise in diacylglycerol, which then activated protein kinase C (PKC) and increased the generation of arachidonic acid (AA) metabolites. Activation of both the PKC and AA pathways resulted in potentiation of glucose effects on insulin secretion. Unlike RX871024, the novel imidazoline BL11282 did not block ATP-dependent K(+) channels, but similarly to RX871024, it stimulated insulin secretion in depolarized or permeabilized islets. Accordingly, BL11282 did not influence glucose and insulin levels under basal conditions either in vitro or in vivo, but it markedly enhanced the insulinotropic effects of glucose. BL11282 restored the impaired insulin response to glucose in islets from spontaneously diabetic GK rats. We conclude that BL11282 belongs to a new class of insulinotropic compounds that demonstrate a strong glucose-dependent effect on insulin exocytosis.     

Synaptic anchoring of glycine receptors in developing collicular neurons under control of metabotropic glutamate receptor activity

The role of GlyRs in supramedullar neurons is still enigmatic: although present in the plasma membrane, they seem to be excluded from synaptic transmission. Two distinct stages of inhibitory synaptogenesis in cultured collicular neurons were defined on the basis of strychnine sensitivity of IPSCs, presence of EPSCs, KCC2 expression, and transmitter-induced Ca(2+) responses. In the absence of KCC2 and glutamatergic transmission, newborn VIAAT-labeled boutons contained GlyT2, released glycine, and accumulated postsynaptic gephyrin and GlyRs. With ongoing maturation, when neurons expressed KCC2 and displayed glutamatergic activity, inhibitory synapses contained GAD65, released GABA, and accumulated postsynaptic gephyrin and GABA(A)Rs, but not GlyRs. This activity- and transmitter-specific regulation of GlyR distribution could be challenged by chronic blockade of group I mGluRs. It is thus concluded that glutamatergic transmission can contribute to the regulation of synaptic GlyR stabilization during inhibitory synapse development.     

Motor control and cerebral hemispheric specialization in highly qualified judo wrestlers

With the purpose of investigating motor and cognitive lateralization profiles associated with long-term motor training, we investigated differences in hemispheric specialization between proficient judo sportsmen and controls through the assessment of a number of handedness and footedness items including postural preferences as well as dichotic listening and lateralized visual field tests. Our data show that: (1) the different handedness and footedness items did differently relate to each other within the athlete and control groups as revealed by a principle component analysis (PCA); (2) stand side correlated differently to these motor profile factors in athletes and controls; (3) athletes preferred more frequently to perform certain movements with the left hand than controls, although overall right-handed; (4) this was especially true for athletes which proved to be most proficient/skilled; and (5) in a lateralized verbal listening task and a lateralized visual field task athletes revealed enhanced right-hemispheric involvement relative to controls. Our results suggest that during motor and postural skill acquisitions (long-term judo training) lateral preferences are modified, probably due to neuroplasticity. Moreover, the present findings support the multidimensional view of handedness by Steenhuis and Bryden [Cortex 25 (1989) 289] and the notion of a right-hemispheric "praxis system" involved in skilled action routines within peripersonal space [Brain and Cognition 23 (1993) 181].     

Visualization and cytogenetic analysis of second polar body chromosomes following its fusion with a one-cell mouse embryo

Purpose This study was designed to visualize the second polar body (2PB) chromosomes using its electrofusion with a one-cell-stage mouse embryo to approach preconception diagnosis of chromosomal disorders. Results Eighty to 90% hybridization efficiency has been achieved by electrofusion of 2PB with mouse zygotes. 2PB chromosomes were visualized in 40–50% of hybrids. Sixty-five percent of 2PB chromosomes were visualized when fused with the cytoplast obtained microsurgically by removing pronuclei from a one-cell embryo. As much as 33–43% of these resulting metaphases appeared to contain chromosomal aberrations. The follow-up of the development of the reconstructed one cell-stage hybrids in vitro revealed a significant decrease in their viability. The hybrid embryos resulting from 2PB electrofusion with enucleated zygotes did not develop beyond the two-cell stage. Conclusion Electrofusion is an efficient approach for hybridization of 2PB with a one-cell mouse embryo and may be useful for visualization and cytogenetic analysis of 2PB chromosomes. The visualization rate of 2PB chromosomes is higher if 2PB is fused with enucleated zygotes. However, the method induces over 30% of chromosomal aberrations and may lead to a significant decrease in the viability of the resulting one-cell embryos.     

Development of Immunosorbents for apoB-Containing Lipoproteins Apheresis

Abstract: Three types of sorbents were developed for the specific removal of atherogenic apoB-containing low-density lipoprotein (LDL) and lipoprotein LDL(a) (Lp[a])from human plasma. Two sorbents contained monospecific sheep polyclonal or mouse monoclonal antibodies against human apoprotein B-100. The third one was intended for specific removal of Lp(a) and contains sheep antibodies against human Lp(a). Thirty patients were treated for up to 9 years by LDL apheresis with anti-LDL immunosorbents. A pilot study of Lp(a) apheresis with 3 patients was conducted during 3 years. The results showed that extracorporeal immunosorption is safe and effective for lowering LDL and Lp(a). These procedures may be used both for metabolic investigations and for studies on possible regression of atherosclerosis.     

PAS-lead hematoxylin as a stain for small-granule endocrine cell populations in the lungs,other pharyngeal derivatives and the gut

Epithelial cells of the several subtypes that comprise the small-granule cell population of the respiratory system are little studied, partly because adequate silver, monoamine fluorescence and other specific light microscopical preparations have been more difficult to obtain than in the gut and other organs possessing diffuse endocrine systems. Periodic acid-Schiff (PAS) in combination with MacConaill-Solcia's lead hematoxylin has in our hands proven dependable for routine staining of serial 2-m?m glycol methacrylate sections used in mapping the distributions of these cells along the airway. In lungs of mice, hamsters, kittens, and fetal rabbits, typical small-granule cells stain weakly or not at all with lead hematoxylin alone, hence are easily overlooked. PAS adds to the cytoplasm a diffuse magenta coloration; and because it is diastase-resistant, less brilliant than that of mucus but more so than bronchiolar cell secretions, and finer textured than lysosomal staining of other cells present, the effect is to highlight small-granule cells whether solitary or in clusters. Additional PAS staining of basement membranes and lead hematoxylin staining of cilia enhance the combined stain's resolving power. In thyroid gland, parafollicular cells stand out boldly against follicular elements; in small intestine, hematoxylin-positive endocrine cells are well differentiated from absorptive, mucous, and Paneth cells that surround them. Using a complementary monoamine fluorescence technique on plastic sections of lungs from control and 5-hydroxytryptophan-pretreated animals prior to staining, we can show that fluorescent epithelial cells are identical with those stained by PAS-lead hema-toxylin.     

Optimal population designs for PK models with serial sampling

In various pharmaceutical applications, repeated measurements are taken from each subject, and model parameters are estimated from the collected data. Examples include dose response modeling and PK/PD studies with serial blood sampling, among others. The quality of the information in an experiment is reflected in the precision of estimates of model parameters, which is traditionally measured by their variance-covariance matrix. In this article, we concentrate on the example of a clinical PK study where multiple blood samples are taken for each enrolled patient, which leads to nonlinear mixed effects regression models with multiple responses. The sampling scheme for each patient is considered a multidimensional point in the space of admissible sampling sequences. We demonstrate how to optimize the precision of parameter estimates by finding the best number and allocation of sampling times. It is shown that a reduced number of samples may be taken without significant loss of precision of parameter estimates. Moreover, our approach allows for taking experimental costs into account, which leads to a more meaningful comparison of sampling schemes and to potential cost savings.     

Pyridoxamine lowers oxalate excretion and kidney crystals in experimental hyperoxaluria: a potential therapy for primary hyperoxaluria

In order to prevent kidney stones and nephrolithiasis in hyperoxaluria, a new treatment that specifically reduces oxalate production and therefore urinary oxalate excretion would be extremely valuable. Pyridoxamine(PM) could react with the carbonyl intermediates of oxalate biosynthesis, glycolaldehyde and glyoxylate, and prevent their metabolism to oxalate. In PM treated rats, endogenous urinary oxalate levels were consistently lower and became statistically different from controls after 12 days of experiment. In ethylene glycol-induced hyperoxaluria, PM treatment resulted in significantly lower (by ~50%) levels of urinary glycolate and oxalate excretion compared to untreated hyperoxaluric animals, as well as in a significant reduction in calcium oxalate crystal formation in papillary and medullary areas of the kidney. These results, coupled with favorable toxicity profiles of PM in humans, show promise for the therapeutic use of PM in primary hyperoxaluria and other kidney stone diseases.