More monensin-sensitive, ammonia-producing bacteria from the rumen

Two monensin-sensitive bacteria which utilized carbohydrates poorly and grew rapidly on amino acids were isolated from the bovine rumen. The short rods (strain SR) fermented arginine, serine, lysine, glutamine, and threonine rapidly (greater than 158 nmol/mg of protein per h) and grew faster on casein digest containing short peptides than on free amino acids ().34 versus 0.29 h(-1)). Gelatin hydrolysate, an amino acid source containing an abundance of long peptides, was unable to support growth or ammonia production, but there was a large increase in ammonia production if strain SR was cocultured with peptidase-producing ruminal bacteria (Bacteroides ruminicola or Streptococcus bovis). Cocultures showed no synergism with short peptides. Strain SR washed out of continuous culture ().1 h(-1)) at pH 5.9. The irregularly shaped organisms (strain F) deaminated glutamine, histidine, glutamate, and serine rapidly (greater than 137 nmol/mg of protein per min) and grew faster on free amino acids than on short peptides ().43 versus 0.21 h(-1)). When strain F was provided with casein or gelatin hydrolysate and cocultured with peptidase-producing bacteria, there was a more than additive increase in ammonia production. Strain F grew in continuous culture (0.1 h(-1)) when the pH was as low as 5.3. The irregularly shaped cells and short rods were present at less than 10(9)/ml in vivo, but they ahd very high specific activities of ammonia production (greater than 310 nmol of ammonia/mg of protein per min) and could play an important role in ruminal amino acid fermentation.     

Aglycosylation of human IgG1 and IgG3 monoclonal antibodies can eliminate recognition by human cells expressing Fc gamma RI and/or Fc gamma RII receptors.

Aglycosylated human IgG1 and IgG3 monoclonal anti-D (Rh) and human IgG1 and IgG3 chimaeric anti-5-iodo-4-hydroxy-3-nitrophenacetyl (anti-NIP) monoclonal antibodies produced in the presence of tunicamycin have been compared with the native glycosylated proteins with respect to recognition by human Fc gamma RI and/or Fc gamma RII receptors on U937, Daudi or K562 cells. Human red cells sensitized with glycosylated IgG3 form rosettes via Fc gamma RI with 60% of U937 cells. Inhibition of rosette formation required greater than 35-fold concentrated more aglycosylated than glycosylated human monoclonal anti-D (Rh) antibody. Unlabelled polyclonal human IgG and glycosylated monoclonal IgG1 and anti-D (Rh) antibody inhibited the binding of 125I-labelled monomeric human IgG binding by U937 Fc gamma RI at concentrations greater than 50-fold lower than the aglycosylated monoclonal IgG1 anti-D (Rh) (K50 approximately 3 x 10(-9) M and approximately 6 x 10(-7) M respectively). Similar results were obtained using glycosylated and aglycosylated monoclonal human IgG1 or IgG3 chimaeric anti-NIP antibody-sensitized red cells rosetting with Fc gamma RI-/Fc gamma RII+ Daudi and K562 cells. Rosette formation could be inhibited by the glycosylated form (at greater than 10(-6) M) but not by the aglycosylated form. Haemagglutination analysis using a panel of murine monoclonal antibodies specific for epitopes located on C gamma 2, C gamma 3 or C gamma 2/C gamma 3 interface regions did not demonstrate differences in Fc conformation between the glycosylated or aglycosylated human monoclonal antibodies. These data suggest that the Fc gamma RI and Fc gamma RII sites on human IgG are highly conformation-dependent and that the carbohydrate moiety serves to stabilize the Fc structure rather than interacting directly with Fc receptors.     

Concepts of coevolution

The word coevolution has become a standard part of the lexicon of evolutionary biology. More than 1000 papers during the past decade have used coevolution in the title or abstract. Hundreds more have used the word in passing in the body of the paper. A half dozen books now include coevolution in the title. As usage of coevolution has increased, so have the views on the processes and mechanisms of coevolutionary change. The problem now is to understand the ecological and genetic conditions that favor different modes and outcomes of coevolution.     

Microbial growth and accumulation in industrial metal-working fluids.

The dynamics of microbial growth in metal-working fluids (MWF) and the effect of the addition of biocides were studied in large fluid systems, in this case, one central tank which holds 150 m3. In this system, populations of Pseudomonas pseudoalcaligenes (greater than 10(8) CFU/ml) were sustained for a year, although large quantities of biocides were added. Quantitation of 3-OH lauric acid, a marker for many Pseudomonas spp., by gas chromatography indicated that the bacterial biomass exceeded the viable counts by approximately 15 times. Fungi were grown on several occasions, the dominating genera being Fusarium and Candida. Soon after the old MWF was removed and the tank was provided with fresh MWF, which consisted of an emulsion of mineral oil in water, there was a massive growth of P. pseudoalcaligenes that reached levels of greater than 10(8) bacteria per ml. Initially, only low concentrations of other species were found for some weeks. After this period, different enterobacteria and other gram-negative rods often appeared at high concentrations (10(7) and 10(8) bacteria per ml, respectively). Bacteria identified as P. pseudoalcaligenes showed great variation with respect to colony morphology and a certain heterogeneity with respect to biochemical characteristics. Certain bacterial species grew as microcolonies on metal strips immersed in the circulating MWF, but P. pseudoalcaligenes was not recovered from this habitat. The total bacterial count in the air surrounding the machines in the metal-working shop showed an inverse relation to increasing distance from the machine. The concentration of bacteria in the air varied because of the number of machines in use, temperature, and humidity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Elastase activities of human bladder cancer cell lines derived from high grade invasive tumours

Elastase activities in intact human bladder cancer cell lines, established from three patients, were measured using a fluorogenic substrate highly specific for elastase, under conditions of physiological pH and ionic strength. This method allowed separation of cell-associated from secreted enzyme activity. As secreted elastase accounted for only 8% of the total, we concluded that the elastases were present at the cell surface. Inhibition studies using extracts of cell-surface elastases showed them to be serine proteinases which were also inhibited by alpha 1-antitrypsin. Partially purified fractions showing the highest specific activity towards the fluorogenic substrate hydrolysed insoluble elastin thus confirming the presence of elastases. This is the first time that elastase activity has been demonstrated in human bladder cancer cells and may represent a mechanism involved in tumour invasion.     

Agents affecting adenylate cyclase activity modulate the stimulatory action of 1,25-dihydroxyvitamin D3 on the production of osteocalcin by human bone cells

The stimulation of osteocalcin synthesis by human osteoblast-like cells in response to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) is antagonised by several bone regulatory agents. We have shown that agents which activate adenylate cyclase inhibit this action of 1,25(OH)2D3 on human osteoblast-like cells. Activation of adenylate cyclase, either via the stimulatory GTP-binding protein using cholera toxin, or directly at the catalytic via the stimulatory GTP-binding protein using cholera toxin, or directly at the catalytic subunit using forskolin, results in a suppression of osteocalcin synthesis. Whilst the activation of adenylate cyclase induces this inhibitory response, neither exogenous dibutyryl cyclic AMP nor the phosphodiesterase inhibitor, IBMX, exerted any apparent effect on the production of osteocalcin. The tumour promoting phorbol ester, 4 beta-phorbol 12,13-dibutyrate, also inhibited 1,25(OH)2D3-stimulated osteocalcin production. This was not apparent in response to the non-tumour promoting phorbol ester 4 beta-phorbol suggesting the involvement of protein kinase C.     

Modulation of human chondrocyte metabolism by recombinant human interferon gamma: in-vitro effects on basal and IL-1-stimulated proteinase production, cartilage degradation and DNA synthesis

Human articular chondrocytes in monolayer culture and fragments of human articular cartilage were treated with recombinant human interferon gamma (IFN-gamma) both alone and in combination with interleukin 1 (IL-1). IFN-gamma alone inhibits metalloproteinase production, as measured in the caseinase assay, and decreases glycosaminoglycan release from cartilage fragments in culture. The synthesis of DNA, as measured by [3H]thymidine incorporation, is stimulated by IFN-gamma. Similar effects are seen in the presence of IL-1. Thus, IFN-gamma opposes the stimulatory effect of IL-1 on caseinase production and decreases IL-1-stimulated cartilage degradation, as measured by glycosaminoglycan release. In contrast, IFN-gamma has no effect on IL-1-stimulated prostaglandin production, and acts synergistically with IL-1 to cause a large stimulation of DNA synthesis. These results show that IFN-gamma has a number of effects on articular chondrocytes in-vitro and suggest a possible role for IFN-gamma in limiting cartilage degradation in inflammatory joint conditions.