A study of hybridoma cell growth and antibody production kinetics in continuous culture

Summary A detailed study of cell growth and antibody production kinetics in continuous culture found that the specific rate of antibody production reached a maximum saturated profile at a specific growth rate less than the maximum. This observation is novel and of importance in the understanding of the mechanism of antibody production and/or antibody transport.     

Trypanosoma cruzi infection of BSC-1 fibroblast cells causes cytoskeletal disruption and changes in intracellular calcium levels.

The disruption of vimentin and actin filaments of host BSC-1 fibroblast cells by Trypanosoma cruzi was investigated using a mouse monoclonal anti-vimentin antibody and rhodamine phalloidin, respectively. Indirect immunofluorescence microscopy demonstrated that infection of BSC-1 cells by T. cruzi caused disruption of both cytoskeletal components. The disruption was greater as infection progressed. Mechanisms other than mechanical ones may play a role in the disruption since disrupted cytoskeletal elements were well removed from the parasites. In the determination of intracellular calcium concentrations using Fura-2 AM, infected and uninfected cells both showed an initial increase in intracellular calcium levels. At later times of infection (3 to 5 days), intracellular calcium levels of infected cells were significantly lower than those of control cells. There was no specific localization of intracellular calcium in the infected host cells as determined by image analysis.     

Tissue-specific posttranslational processing of pre-prosomatostatin encoded by a metallothionein-somatostatin fusion gene in transgenic mice

The somatostatins are neuropeptides of 14 and 28 amino acids that inhibit the release of growth hormone and other hypophyseal and gastrointestinal peptides. These neuropeptides are cleaved posttranslationally from a common precursor, pre-prosomatostatin. We report here the production and processing of pre-prosomatostatin by transgenic mice carrying a metallothionein-somatostatin fusion gene. The most active site of somatostatin production, as determined by hormone concentrations in the tissues, is the anterior pituitary, a tissue that does not normally synthesize somatostatin-like peptides. Anterior pituitary processed pre-prosomatostatin almost exclusively to the two biologically active peptides, somatostatin-14 and somatostatin-28, whereas the liver and kidney synthesized much smaller quantities of predominantly a 6000 dalton somatostatin-like peptide. The growth of the transgenic mice was normal despite high plasma levels of the somatostatin-like peptides. These studies indicate that proteases which cleave prosomatostatin to somatostatin-28 and somatostatin-14 are not specific to tissues that normally express somatostatin.     

msbB deletion confers acute sensitivity to CO2 in Salmonella enterica serovar Typhimurium that can be suppressed by a loss-of-function mutation in zwf

Background  

Pathogens tolerate stress conditions that include low pH, oxidative stress, high salt and high temperature in order to survive inside and outside their hosts. Lipopolysaccharide (LPS), which forms the outer-leaflet of the outer membrane in Gram-negative bacteria, acts as a permeability barrier. The lipid A moiety of LPS anchors it to the outer membrane bilayer. The MsbB enzyme myristoylates the lipid A precursor and loss of this enzyme, in Salmonella, is correlated with reduced virulence and severe growth defects that can both be compensated with extragenic suppressor mutations.     

Somatostatin is targeted to the regulated secretory pathway of gonadotrophs in transgenic mice expressing a metallothionein-somatostatin gene

The pituitaries of transgenic mice that express a metallothionein-somatostatin fusion gene contain high concentrations of somatostatin-14 exclusively in the gonadotrophic cells. The purpose of this study was to determine whether somatostatin expressed from the foreign fusion gene enters the normal secretory pathway within these cells. Immuno-gold labeling of serial thin sections localized somatostatin to the secretory granules of gonadotropin-producing cells. The gonadotroph-specific hypophysiotropic factor, luteinizing hormone-releasing hormone caused a dose-dependent secretion of somatostatin when applied to primary pituitary cultures from these mice. Growth hormone-releasing hormone, thyrotropin-releasing hormone, corticotropin releasing factor, and dopamine did not affect somatostatin secretion. These experiments demonstrate that a neurosecretory peptide encoded by a foreign gene can enter the regulated secretory pathway of pituitary cells from transgenic mice.