High-affinity alpha-aminobutyric acid A/benzodiazepine ligands: synthesis and structure-activity relationship studies of a new series of tetracyclic imidazoquinoxalines

A series of tetracyclic imidazoquinoxaline analogs was developed which constrain the carbonyl group of the partial agonist 3-(5-cyclopropyl-1,2,4-oxadiazol-3-yl)-5-[(dimethylamino)carbonyl] - 4,5-dihydroimidazo[1,5-alpha]quinoxaline (2, U-91571) away from the benzene ring. These analogs orient the carbonyl group in the opposite direction of the previously reported full agonist 1-(5- cyclopropyl-1,2,4-oxadiazol-3-yl)-12,12a-dihydroimidazo[1,5- alpha]pyrrolo [2,1-c]quinoxalin-10(11H)-one (3, U-89267). A number of approaches were utilized to form the "bottom" ring of this tetracyclic ring system including intramolecular cyclizations promoted by Lewis acids or base, as well as metal-carbenoid conditions. The size and substitution pattern of the additional ring was widely varied. Analogs within this series had high affinity for the benzodiazepine receptor on the alpha-aminobutyric acid A chloride ion channel complex. From TBPS shift and Cl- current assays, the in vitro efficacy of compounds within this class ranged from antagonists to partial agonists with only 18a identified as a full agonist. Additionally, several analogs were quite potent at antagonizing metrazole-induced seizures indicating possible anticonvulsant or anxiolytic activity. Unlike 3, analogs in this series did not have high affinity for the diazepam insensitive alpha 6 beta 2 delta 2 subtype. These results suggest that either constraining the carbonyl group away from the benzene ring or the greater planarity that results from the additional cyclic structure provides analogs with partial agonist properties and prevents effective interaction with the alpha 6 beta 2 delta 2 subtype.     

Magnetic resonance imaging of bovine ovaries in vitro

A sample of 20 bovine ovaries were imaged in vitro using nuclear magnetic resonance (NMR) techniques to determine the visibility of various physiologic structures. In particular, the possibility of using NMR imaging to differentiate atretic follicles from physiologically selected and ovulatory follicles was examined. Five of the 20 ovaries were preserved in formalin, whereas the remaining 15 were preserved in a saline solution and imaged within 18 hours of death. Images weighted by T1 and T2 proton spin relaxation rates were obtained along with some three-dimensional (3-D) data sets acquired via a fast imaging with steady-state precession technique. Physiologically different structures were easily identified in the images from their morphology, especially in the 3-D images. Weighting by T1 and T2 was able to separate structures in the fresh ovaries in the following manner. Atretic and "cohort" follicles appear dark in T1-weighted images and bright in T2-weighted images. Ovulatory follicles appear bright in both T1- and T2-weighted images, whereas prephysiologic selection follicles present an intermediate brightness in T1-weighted images and appear dark in T2-weighted images. The corpus luteum appears bright in T1-weighted images and dark in T2-weighted images, whereas cysts in the corpus luteum appear dark in T1-weighted images and bright in T2-weighted images. The varying brightness of the follicles at different stages of development is hypothesized to be related to different hormone and protein concentrations in the follicular fluid. For example, it is known that physiologically selected preovulatory follicles contain high concentrations of estrogens in a viscous follicular fluid. The increased viscosity may occur only when the follicle fluid contains high concentrations of estrogen and contributes to bright T1-weighted images. The possibility of using nuclear relaxation-weighted NMR imaging for the study of follicular dynamics and other ovarian biology therefore shows great promise.     

Engineered complementation in Escherichia coli aspartate transcarbamoylase. Heterotropic regulation by quaternary structure stabilization

Escherichia coli aspartate transcarbamoylase regulates pyrimidine biosynthesis by altering its activity homotropically in response to one of its substrates and heterotropically in response to nucleotide effectors. The mechanism of this regulation involves two structurally and functionally different forms of the enzyme, one with low activity and low affinity for substrates (T state) and the other with high activity and high affinity for substrates (R state). Heterotropic regulation may be due to the direct transmission of a regulatory "signal" between the regulatory site and the active site some 60 A away and/or may involve altering the relative stability of the two forms of the enzyme. By combining a T state-stabilized mutant version of the enzyme, previously thought to have a defect in a heterotropic transmission pathway, with a known R state-stabilized mutant enzyme, we were able to restore some properties of the wild-type enzyme. These data imply that the relative stabilization of the T and R states of the enzyme is in part responsible for the homotropic and heterotropic properties of aspartate transcarbamoylase and that direct pathways for transmission of the heterotropic signals are unlikely.     

Influenza surveillance in England and Wales: October 1995 to June 1996

This report summarises information collected for the surveillance of influenza virus infection in England and Wales from October 1995 to June 1996 (weeks 40/95 to 25/96). Total respiratory disease' activity, as reported by the Birmingham Research Unit of the Royal College of General Practitioners, rose to peaks in weeks 48/95, 51/95, and 01/96. The first peak coincided with a peak in "influenza and flu-like illness'. The subsequent peaks were accounted for by an increase in reports of acute bronchitis, including bronchiolitis, and may have been associated with the annual rise in infections with respiratory syncytial virus. Influenza A virus was responsible for most infections, with moderate activity occurring in the early part of the winter, peaking in December (week 48/95). Influenza A subtype H3N2 predominated until week 07/96, after which subtype H1N1 accounted for most infections. Influenza activity was first seen in central and northern England, followed by the south of England, Wales, and Scotland. Circulating influenza viruses were antigenically similar to the components of the 1995/96 vaccine. International surveillance during 1995/96 has led to a different H3N2 component being included in the influenza vaccine recommended for 1996/97.     

Amniotic fluid lecithin/sphingomyelin ratio changes related to centrifugal force

Lecithin/sphingomyelin ratio (L/S ratio) in amniotic fluid has gained wide clinical acceptance as an index of fetal lung maturity. We determined L/S ratios of amniotic fluids centrifuged at various "g-forces." Our studies demonstrate that the L/S ratio value is highly dependent on the g-force used to prepare the fluid. We recommend standardization of the g-force, time, and temperature used in preparation of the amniotic fluid for L/S ratio determination.     

The developing caudate nucleus in the euthyroid and hypothyroid rat

The basal ganglia are presently implicated in learning, and thyroid deficiency induced neonatally is known to affect mentation. The effects of such a deficiency on the developing causate nucleus might be used to provide insight into structure and function of the normal subcortical brain, as well as possible influences of these extrapyramidal structures on mental retardation. Propylthiouracil was added to the diet of lactating rat dams and observations of the developing caudate nuclei of normal hypothyroid rats were made at 8, 14, 20, 30 and 42 days by using various tissue stains and Golgi-Cox preparations. Seven different types of neurons were distinguished in the caudate nucleus. Differences in the size of cell somata and the varying morphology of axons and dendrites were criteria used to make distinctions. Normally, the nucleus acquires cytoarchitectural complexity during the first three postnatal weeks. Within this period, neuron incidence increases in the caudate neuropil with age while the germinal matrix density decreases. Neuron accumulation reaches a plateau after the third week and cell migration is essentially complete at the end of the first postnatal month as shown by computer analysis of Nissl stained cell counts. Branching of cellular processes, attainment of receptor spines and complexity of the fiber network also appeared during this period. Retardation of structural development with thyroid hormone deficiency was shown by decreased numbers of neurons, inhibition of dendritic arborization, decreased numbers of dendritic spines and a reduced complexity of axonal plexuses. Thyroid deficiency delays cell migration during the first three weeks when compared to age-matched normal controls. The lack of thyroid hormone does not appear to influence the size of neuron somata, and the extent of related dendritic fields, nor does hypothyroidism affect a specific cell type population. Generalized disturbances of caudate nuclear morphological maturation are caused by the deficiency. An apparent compensatory process, including a spurt of neural growth and differentiation, takes place in the period between days 14 and 30 in the deficient animals and a seemingly "normal" caudate cytoarchitecture is seen after the third postnatal week. Quantitative data, however, show that this rapid "catch up" process is inadequate. The developmental imperfection of the caudate nucleus which persists might be a part of the underlying substrate for the mental retardation, disturbed motor performance and perceptual handicaps which are found in the human patient.     

The clinical effect of a new infant formula in term infants with constipation: a double-blind,randomized cross-over trial

Background  

Nutrilon Omneo (new formula; NF) contains high concentration of sn-2 palmitic acid, a mixture of prebiotic oligosaccharides and partially hydrolyzed whey protein. It is hypothesized that NF positively affects stool characteristics in constipated infants.