Age-Dependent Changes in Brain GABA Turnover Rates in Two Inbred Strains of Mice

gamma-Aminobutyric acid (GABA) steady-state levels and turnover rates have been determined in 15 brain areas of 21-day- and 3-month-old DBA/2J (DBA) and C57B1/6J (C57) mice. These two inbred strains differ by their susceptibility to audiogenic seizures; moreover, the involvement of GABAergic neurotransmission has been suggested in the control of this behavior. Turnover rates are generally higher at 21 days than at 3 months of age. There are few significant differences in the GABA steady-state levels between 21-day-old seizure-prone DBA mice when compared with seizure-resistant C57 mice. In the DBA mice, the steady-state level is higher in the olfactory bulbs and lower in the posterior colliculus and the olfactory tubercles than in the C57 mice. Although there are some significant differences in GABA turnover rates and steady-state levels, intra or inter strains, it is difficult to correlate directly these differences with seizure susceptibility.     

Regulation of the growth and differentiation of a human monocytic cell line by lymphokines. I. Induction of superoxide anion production and chemiluminescence

The U937 human monocytic cell line was studied to determine its ability to generate a respiratory burst after stimulation with phorbol myristate acetate (PMA) or opsonized zymosan. U937 cells cultured in normal medium produced virtually no superoxide anion or chemiluminescence in response to either stimulus. In contrast, U937 cells cultured in medium containing soluble factors from activated lymphocytes produced significant O2- and chemiluminescence when stimulated with PMA or opsonized zymosan. The chemiluminescence in response to PMA was maximal in U937 cells precultured with these soluble factors for 3 days, whereas maximal responsiveness to opsonized zymosan was not observed until 5 to 6 days of lymphokine exposure. Although this ability to generate a respiratory burst persisted for a number of days in U937 cells that were subsequently recultured in normal medium, this responsiveness was gradually lost in the continued absence of these factors. The data indicate that the U937 monocytic cell line can be activated or induced to differentiate by soluble factors released by activated lymphocytes. In the process, these cells acquire the ability to generate a respiratory burst. The U937 cell line may serve as a useful model for the study of the ontogeny and regulation of the respiratory burst during human monocytic differentiation.     

Effects of proximate cholesterol precursors and steroid hormones on mouse myeloma growth in serum-free medium

Summary The proximate cholesterol precursors lathosterol, 7-dehydrocholesterol and desmosterol supported the growth of NS-1 and X63 mouse myeloma cells. These cells and X63.653 cells are cholesterol auxotrophs, yet each was able to convert [³H]lathosterol to [³H]cholesterol. These results are consistent with the conclusion that cholesterol auxotrophy in these myeloma cells is due to a deficiency in 3-ketosteroid reductase activity. The steroid hormones testosterone, progesserone and hydrocortisone could not replace cholesterol as a medium supplement. These results provide a greater understanding of the cholesterol auxotrophy characteristic of cell lines clonally-derived from the MOPC 21 myeloma tumor, and they provide a rational basis for the use of sterols in defined culture medium for mouse myeloma cells. This work was supported by National Institute of Health grants CA40294 and CA37589 to G. H. Sato and by a grant from RJR nabisco Inc. Editor's Statement These results help identify the defect in myeloma cells leading to cholesterol auxotrophy. The use of these cells in hybridoma derivation adds practical utility to a detailed appreciation of cholesterol metabolism in these cultures.     

Heterogeneous mechanisms of human cytotoxic T lymphocyte generation. I. Differential helper cell requirement for the generation of cytotoxic effector cells from CD8+ precursor subpopulations.

The subpopulations of CD8+ T cells defined by CD45RA Ag expression have been hypothesized to represent cells varying in their relative maturation along a common, activation-dependent differentiation pathway. Previous studies have shown that both the CD8+CD45RA+ and CD8+CD45RA- subsets contain precursor cells capable of developing into alloreactive CTL. In the current study, we have examined the mechanisms involved in the generation of CTL effector cells from these two CD8+ subsets. Purified CD8+CD45RA+ or CD8+CD45RA- cells were stimulated with allogeneic non-T cells, either alone or in the presence of CD4+ Th cells. Although the generation of CTL from CD8+CD45RA- precursor cells consistently required the presence of CD4+ Th cells, cytotoxic effector cells could be generated from CD8+CD45RA+ precursor cells in the absence of CD4+ cells. Several lines of evidence indicated that the helper cell-independent generation of cytotoxic effector cells from CD8+CD45RA+ precursors resulted from the unique ability of this subset to produce and use IL-2 in an autocrine fashion: 1) exogenous IL-2 could replace the effects of CD4+ helper cells for either CD8+ subset; 2) the helper cell-independent functional maturation of CD8+CD45RA+ cells could be blocked by anti-CD25 or anti-IL-2 antibodies; and 3) CD8+CD45RA+ cells produced IL-2 after activation with allogeneic cells. The finding that precursors for helper cell-independent CTL generation are restricted to the CD8+CD45RA+ subset suggests that this capability may vary as a function of the maturation of CD8+ cells.     

Characterization of an antiserum to guinea pig antithrombin III (AT III). II. Stimulation of T lymphocyte proliferation

A goat antibody specific for an antigenic determinant shared between guinea pig antithrombin III (AT III) and thymocytes was shown to be mitogenic for lymph node T lymphocytes in the presence of macrophages. Although the antiserum was not mitogenic for purified populations of B lymphocytes, B lymphocytes were as efficient as T lymphocytes in absorbing the mitogenic activity of the serum. The shared antigenic determinant appeared to be carbohydrate in nature in that native and guanidine-treated AT III, but not periodate oxidized AT III, were capable of inhibiting the mitogenic activity of the serum when added continuously to the cultures. The possibility that the plasma protease inhibitor AT III or an antigenically related membrane protein are involved in the regulation of T cell activation is discussed.     

Long-lasting effects of audiogenic seizures on neurotransmitter amino acids in Rb mice

The existence of long-lasting (15–18 h) alterations of neurotrasmitter amino acid levels following a single or repeated acoustic stimulations in audiogenic seizure-prone Rb1 and Rb2 mice and suizure-resistant Rb3 mice were investigated. The levels of glutamate, aspartate, glycine, taurine, and of some of their precursors: glutamine and serine were determined. Fourteen brain areas were examined. Alterations were found only in 6 brain areas (pons, olfactory bulbs, superior colliculus, inferior colliculus, olfactory tubercles and raphe). Most frequent occuring changes were observed in pons and olfactory tubercles. These changes concerned mainly the excitatory amino acids, glutamate, and aspartate. Alterations of taurine, glycine and serine were also recorded.Abbreviations GABA 4-aminobutyrate - Tau taurine - Gly glycine - Asp aspertate - Glu glutamate - Gln glutamine - Ser serine - OB olfactory bulbs - OT olfactory tubercles - Sr striatum - Se septum - Hy hypothalamus - Th thalamus - Hi hippocampus - A amygdala - SC superior colliculus - IC inferior colliculus - FC frontal cortex - C cerebellum - P pons medulla - Ra raphe - AA neurotransmitter amino acids - I inhibitory - E excitatory - SSL steady-state level Plesant memories of Lawrence Austin's sojourn in my group at Strasbourg gather upon me when I dedicate this article on this occasion for the contribution that Lawrence Austin has made for the cause of neurochemical researchers.     

Useful Species Richness,Proportion of Exotic Species,and Market Orientation on Amazonian Dark Earths and Oxisols<Superscript>1</Superscript>

Useful Species Richness, Proportion of Exotic Species, and Market Orientation on Amazonian Dark Earths and Oxisols Anthropogenic soils of Amazonia, known as Amazonian Dark Earths (ADE), are environments with elevated soil fertility that can produce crops that otherwise yield poorly on the leached and highly acidic Oxisols that dominate much of the basin. While ADE sites near urban centers often attract commercial horticultural production of nutrient–demanding exotics, these soils are also considered possibly unique reservoirs of endemic agrobiodiversity because of their relationship to pre–Columbian indigenous occupation. Through botanical surveys and interviews with smallholder farmers, this study compared useful species richness, proportion of exotic species, and market orientation of farms situated on ADE and non–anthropogenic Oxisols in the municipality of Borba in Central Brazilian Amazonia. Species richness was similar on Amazonian Dark Earth and Oxisol farms (19.6 spp vs. 18.3 spp); however, ADE farms showed significantly higher proportions of exotic species (39% vs. 26%; p = 0.025). Furthermore, ADE farms in Borba demonstrated significantly higher market orientation (61.0% vs. 47.3%; p = 0.028), likely a result of the advantage of Amazonian Dark Earths for production of crops that are nutrient–demanding or pH–sensitive crops that have higher values in the nearby regional market of Manaus.     

Genetic studies of the leptin receptor gene in morbidly obese French Caucasian families

Family studies have shown that in some populations up to 75% of the variation of body mass index can be explained by genetic factors. However, in humans, no major obesity gene has been identified to date. In contrast, there are a number of genetically well defined animal models for obesity. In two of those models (ob/ob and db/db), defects in the same pathway are responsible for obesity. Recently, some evidence has been found for the OB gene also being involved in human obesity. In this study we investigated the potential role of the OB receptor (OBR) in the etiology of massive obesity in humans using familial linkage analyses and case-control association studies. The typing of two microsatellite markers (D1S198 and D1S209), flanking the OBR gene, in 256 sib pairs showed no evidence for linkage with obesity. In order to be able to detect small gene effects, association studies with a 3′-UTR insertion/deletion polymorphism were carried out. The results of these analyses remained non-significant (χ² = 3.442, P = 0.18). However, subjects heterozygous for the insertion/deletion polymorphism showed a slight trend towards lower insulin values 30 min after an oral glucose load compared to homozygous individuals (P = 0.02). In summary, our results do not support a major role of the human OBR gene in the development of morbid obesity in our population. Received: 4 December 1996 / Accepted: 25 June 1997     

A genetic linkage map of Theobroma cacao L.

A linkage map of the cocoa genome comprising 193 loci has been constructed. These loci consist of 5 isozymes, 101 cDNA/RFLPs, 4 loci from genes of known function, 55 genomic DNA/RFLPs and 28 RAPDs. A population of 100 individuals derived from a cross between two heterozygous genotypes was used. Segregation analyses were performed with the JoinMap program. Ten linkage groups, which putatively correspond to the ten gametic chromosomes of cocoa, were identified. The map covers a total length of 759 cM with a 3.9 cM average distance between 2 markers. A small fraction (9%) of the markers deviated significantly from the expected Mendelian ratios.