Explore the vast range of titles available.

The bacteria that grow on methane aerobically (methanotrophs) support populations of non-methanotrophs in the natural environment by excreting methane-derived carbon. One group of excreted compounds are short-chain organic acids, generated in highest abundance when cultures are grown under O 2 -starvation. We examined this O 2 -starvation condition in the methanotroph Methylomicrobium buryatense 5GB1. The M. buryatense 5GB1 genome contains homologs for all enzymes necessary for a fermentative metabolism, and we hypothesize that a metabolic switch to fermentation can be induced by low-O 2 conditions. Under prolonged O 2 -starvation in a closed vial, this methanotroph increases the amount of acetate excreted about 10-fold, but the formate, lactate, and succinate excreted do not respond to this culture condition. In bioreactor cultures, the amount of each excreted product is similar across a range of growth rates and limiting substrates, including O 2 -limitation. A set of mutants were generated in genes predicted to be involved in generating or regulating excretion of these compounds and tested for growth defects, and changes in excretion products. The phenotypes and associated metabolic flux modeling suggested that in M. buryatense 5GB1, formate and acetate are excreted in response to redox imbalance. Our results indicate that even under O 2 -starvation conditions, M. buryatense 5GB1 maintains a metabolic state representing a combination of fermentation and respiration metabolism.

A single application of Mitomycin C (MMC) is used clinically in ophthalmology to reduce scarring and enhance wound resolution after surgery. Here we show in vitro that a 3-hour MMC treatment of primary and telomerase immortalized human corneal limbal epithelial (HCLE) cells impacts their migration and adhesion. Transient MMC treatment induces HCLE expression of senescence associated secretory factors, cytokine secretion, and deposition of laminin 332 for several days. Transient MMC treatment also reduces migration and deposition of transforming growth factor-β1 (TGFβ1)-stimulated collagen by corneal fibroblasts. Using conditioned media from control and MMC treated cells, we demonstrate that factors secreted by MMC-treated corneal epithelial cells attenuate collagen deposition by HCFs whereas those secreted by MMC-treated HCFs do not. These studies are the first to probe the roles played by corneal epithelial cells in reducing collagen deposition by corneal fibroblasts in response to MMC.

Recent evidence implicates adult hippocampal neurogenesis in regulating behavioral and physiologic responses to stress. Hippocampal neurogenesis occurs across the lifespan, however the rate of cell birth is up to 300% higher in adolescent mice compared to adults. Adolescence is a sensitive period in development where emotional circuitry and stress reactivity undergo plasticity establishing life-long set points. Therefore neurogenesis occurring during adolescence may be particularly important for emotional behavior. However, little is known about the function of hippocampal neurons born during adolescence. In order to assess the contribution of neurons born in adolescence to the adult stress response and depression-related behavior, we transiently reduced cell proliferation either during adolescence, or during adulthood in GFAP-Tk mice. We found that the intervention in adolescence did not change adult baseline behavioral response in the forced swim test, sucrose preference test or social affiliation test, and did not change adult corticosterone responses to an acute stressor. However following chronic social defeat, adult mice with reduced adolescent neurogenesis showed a resilient phenotype. A similar transient reduction in adult neurogenesis did not affect depression-like behaviors or stress induced corticosterone. Our study demonstrates that hippocampal neurons born during adolescence, but not in adulthood are important to confer susceptibility to chronic social defeat.

The immune response to BALB/c IgA myeloma proteins (Ir-IgA) was determined in mice of various H-2 types from five different linkage groups of immunoglobulin heavy chains (IgCH). Antisera were examined for antibodies to idiotypic (Fab) and allotypic (Fc) specificities. No immune response to IgA myeloma proteins was found in mice with the same linkage group as BALB/c but with different H-2 alleles. In mice with immunoglobulin heavy chains that are different than BALB/c, a high immune response to IgA myeloma proteins was found in H-2 types a, k, r, and s; a low response is associated with H-2band H-2dtypes. Chromosome mapping of Ir-IgA genes in the H-2 locus indicate that they are on the right side of the chromosome, to the right of the Ss locus. Ir-IgA genes are controlled by dominant autosomal genes.

Splenic macrophages were identified as at least one source of C5 elaboration in normal mice. Hybrid cells were formed from splenic macrophages from C5-deficient mice and either kidney cells from mice with normal amounts of C5 or chicken erythrocytes. These hybrids elaborated C5 in vitro. C5-Deficient mice inoculated with these hybrid cells developed, in their serum, antigenically active mouse C5, as well as both hemolytic and biologic complement activity. These studies demonstrate the feasibility of genetic ``repair'' in mammals.

Immunoglobulin A (γA) myeloma proteins secreted by plasmacell tumors of mice are of two types, a common four-chain molecule and a rare two-chain (3.9S) molecule. The close similarity between two-chain γ A molecules and four-chain γA molecules and their polymers is demonstrated in tryptic peptide maps of isolated polypeptide chains and by precipitin reactions with rabbit antiserums to γA immunoglobulins. However, a difference between these two types is distinguishable with homologous antiserums. Homologous antiserums to two-chain γA immunoglobulins are specific and do not cross-react with four-chain γ A immunoglobulins.

The serums of 123 wild mice from six different geographic locations in the United States contain five of the six known heavy-chain antigenic determinants that have been identified in immunoglobulin of inbred laboratory strains of mice. On the basis of the distribution of determinants in inbred strains, 44 of the mice were judged to be heterozygotes of various combinations and two had combinations of determinants that were unusual and could only have occurred in laboratory inbred mice by recombination.

Allotypic specificities were identified on two different myeloma proteins and the corresponding normal γG-immunoglobulins of BALB/c mice. When the sera of F$_{2}$ progeny from a cross between BALB/c mice having the a1 allotype and AL mice having the a4 allotype were tested for these specificities, it was found that the two allotypic specificities of the BALB/c mice were either both present (87 mice) or both absent (36 mice), an indication of linkage in their genetic control.

Ascitic fluid containing high titers of antibody was induced in mice by Staphylococcus . Two to three intraperitoneal inoculations of 0.3 ml of a killed suspension of S. aureus mixed with complete Freund's adjuvant, given at 5-day intervals, produced ascites in 100 percent of the mice tested.