Shedding of antibody complexes by Strongyloides ratti (Nematoda) larvae

Antigens on the epicuticular surface of Strongyloides ratti infective third-stage larvae (L3) could be demonstrated by an indirect fluorescent antibody technique under certain conditions. Infective L3 shed anti-antibody complexes at room temperature, but not at 4 C or in the presence of sodium azide or colchicine. Shedding of antibody did not appear to involve epicuticular antigens, and only occurred when anti-rat IgG was complexed to rat anti-larval antibody. However, parasitic L3 removed from rats did not exhibit this shedding reaction, suggesting that an important developmental change in cuticle physiology occurs during the transition from a free-living existence to a parasitic mode. The ability to shed foreign objects from the epicuticle of free-living infective L3 may be a defensive or protective response to soil microorganisms.     

A comparison of UV induced DNA photoproducts from isolated and non-isolated developing bacterial forespores

UV-induced photoproduct formation has been compared in non-isolated and isolated developing forespores. We have found that levels of spore type photoproducts are greatly affected by mother cell DNA. We have also observed the presence of the photoproduct 6-4′-(pyrimidin-2′-one)-thymine in developing forespores. We conclude from these and other data in the literature that the degree of hydration around the forespore DNA is reduced by the presence of dipicolinic acid which influences photoproduct formation without causing a change in conformational state.     

Nitrogen metabolism in marine methanotrophs

Two new methane-oxidizing bacteria have been isolated from seawater samples from Plymouth Sound. These marine methanotrophs have an obligate requirement for NaCl and exhibit many properties of typical Type I methanotrophs previously isolated from freshwater environments. However, they are different from all other methanotrophs thus far described in that they failed to grow on all solid media tested. The nitrogen metabolism of both strains was investigated. They were not N₂-fixers nor would they use ammonia as nitrogen source. They appeared to utilize the glutamate dehydrogenase pathway for the assimilation of ammonia under all growth conditions tested.     

Distribution of calcium and other elements in cryosectioned Bacillus cereus T spores, determined by high-resolution scanning electron probe x-ray microanalysis.

The distribution of a number of key elements in Bacillus cereus T spores was determined by high-resolution scanning electron probe X-ray microanalysis. To circumvent the redistribution of soluble or weakly bound elements, freeze-dried cryosections of spores, which had been rapidly frozen in 50% aqueous polyvinyl pyrrolidone, were employed. The sections were examined by using a modified Philips EM400 electron microscope fitted with a field emission gun, scanning transmission electron microscopy attachment, and a computer-linked energy-dispersive X-ray microanalysis system. X-ray maps for selected elements and the corresponding electron image were produced simultaneously by scanning the cryosections with a fine electron beam in a raster pattern, using the scanning transmission electron microscopy attachment. The results indicated that almost all of the calcium, magnesium, and manganese, together with most of the phosphorus, was located in the core region. An unexpectedly high concentration of silicon was found in the cortex/coat layer. Granules containing high concentrations of calcium, manganese, and phosphorus were demonstrated in spores containing reduced levels of dipicolinic acid. Spot mode analyses, in which a stationary beam was located over the region of interest in the spore cryosection, confirmed the results obtained with the scanning mode and also provided a more accurate quantitation of the elemental concentrations on a dry weight bases.     

Functional expression in Escherichia coli of proteins B and C from soluble methane monooxygenase of Methylococcus capsulatus (Bath).

Methylococcus capsulatus (Bath) uses a soluble methane monooxygenase (sMMO) to catalyse the oxidation of methane to methanol. sMMO is comprised of three components; A, B and C. Protein C (the reductase) transfers electrons from NADH to protein A (the hydroxylase) which contains the active site, and protein B regulates this electron flow. The five genes encoding the sMMO proteins and their subunits are clustered and have been cloned in Escherichia coli. A DNA fragment containing mmoB, the gene encoding protein B, was subcloned into pT7-5, a plasmid of the T7 RNA polymerase promoter expression system. Upon induction, E. coli expressed protein B which was fully functional after purification. The gene encoding protein C, mmoC, was amplified with unique restriction sites at each end using the polymerase chain reaction and then subcloned into pT7-7 (a plasmid similar to pT7-5 but containing its own ribosome-binding site and ATG start codon). Protein C expressed in E. coli was also found to be functional. This is the first report of the functional expression of methanotroph methane monooxygenase genes in a heterologous host and represents a significant step forward in our analysis of the assembly and catalysis of sMMO.     

Epoxidation of gaseous alkenes by aRhodococcus sp.

Summary A propane-oxidising strain ofRhodococcus rhodochrous produced 1,2-epoxyalkanes from short chain terminal alkenes at rates equivalent to or greater than many previously described systems. It appeared to produce a single product that was not further metabolised. Its oxygease enzyme also appeared capable of tolerating high levels of product (1 mM) without inhibition. Addition of exogenous reductant did not stimulate epoxidation activity.     

Use of Ultraviolet Radiation to Locate Dipicolinic Acid in Bacillus cereus Spores

A novel method is described that allows a direct determination of the location of a portion of the dipicolinic acid (DPA) in spores. Ultraviolet (UV) irradiation is shown to cause cross-linkage of DPA to spore proteins which have the characteristics of membrane proteins. We suggest that DPA resides in the inner forespore membrane (IFSM) and spore cytoplasm (i.e., the spore protoplast). Only that portion of the DPA in the vicinity of the IFSM appeared to form UV-induced DPA-protein adducts.     

Schistosoma mansoni: immediate hypersensitivity to adult antigens in the rat

Antigen fractions from adult S. mansoni, obtained from infected mice, were isolated by a variety of methods. A readily soluble fraction was obtained in good yield by freezing and thawing the schistosomes, while the less soluble residue was fractionated by the use of a number of the methods currently used for the extraction of tissue and cell surface antigens. The dialyzed, centrifuged products were characterized by acrylamide gel disc electrophoresis methods, agar gel precipitin reactions with antisera from rabbits immunized with whole schistosome homogenate, and by Prausnitz-Kustner (P-K) assay with sera from schistosome infected rats. The pattern of P-K reactivity suggested that there were a number of different antigen specificities involved in the reaginic antibody response to schistosome infection in rats. With repeated infection and increased duration of infection, more different antigens seemed to be involved in the reagin response. The schistosome antigen fraction obtained by freezing and thawing was especially reactive with both early infection rat sera and sera from multiply infected rats. Both the soluble fraction isolated by freezing and thawing and residue solubilized materials were found to be able to induce the formation of reagin antibodies on immunization with alum and B. pertussis vaccine.     

Schistosoma mansoni: vaccination of mice with cryopreserved irradiated schistosomules.

In our earlier experiments, NIH/Nmri (CV) mice developed protective immunity to a Schistosoma mansoni cercarial challenge when previously exposed percutaneously to highly ⁶⁰Co-irradiated homologous cercariae. Experiments reported here were conducted to assess the immunogenicity of unfrozen and frozen and thawed schistosomules derived from ⁶⁰Co-irradiated cercariae (irradiated schistosomules). Immunization of NIH/Nmri (CV) mice by ⁶⁰Co-irradiated unfrozen schistosomules reduced worm burdens from a subsequent percutaneous challenge with normal cercariae by 41 to 72%. Immunogenicity was not narrowly dependent on irradiation dose rates between 1 and 8 kR/min, or on the total dose of irradiation given the schistosomules between 25 and 50 kR. Comparable protective immunity developed after injection of irradiated schistosomules which had been frozen to ?196 C in liquid nitrogen and thawed. Cryopreservation appears to offer a solution to the problem of storage of attenuated, immunogenic S. mansoni schistosomules.     

Characterization of the immunosuppressive state during Schistosoma mansoni infection.

Analysis of a murine model of schistosomiasis revealed that both the thymus (T)- and bursa (B)-derived compartments of the immune system are modified during acute infection. The functional capacity of T and B lymphocytes to respond to mitogenic stimuli and the humoral response to thymus-dependent (SRBC) and thymus-independent (DNP-Ficoll) antigens are severely depressed. In addition, it was found that suppressor cells capable of inhibiting the response of normal lymphocytes to SRBC arise during acute infection. Although the splenic frequency of T (theta) and B (Ig+) cells remained constant during chronic infection, quantitative changes were detected in each population. In the T cell pool there was a decrease in the percentage of Ly-1+ cells and a concomitant increase in Ly-1+, 2+, 3+, cells, whereas the B cell pool showed a progressive loss of complement receptor-bearing lymphocytes, which apparently was the result of inactivation of surface complement receptor by a serum factor specifically found in infected mice. Characterization of the serum factor strongly suggests it is an immune complex. Thus, it appears that both suppressor cells and immune complexes contribute to changes noted in the immune system during acute schistosomiasis. Additional studies carried out in mice after unisexual infection revealed that egg production is not a necessary prerequisite for several of the immunologic phenomena associated with acute schistosomiasis.