Selective activation by thymus-dependent antigens of distinct B cell subpopulations expressing a major cross-reactive idiotype

We determined the B cell subpopulations that produce the major cross-reactive idiotype (CRIA) associated with the anti-phenylarsonate (ARS) antibody response of A/J mice. Specifically, we examined the B2 subpopulation found in normal mice which, in H-2b mice, bears the I-Ab-encoded determinant Ia.W39; the B1 subpopulation found in mice expressing the CBA/N X-linked immunodeficiency trait (xid); and the B1 subpopulation found in normal mice after the cytotoxic elimination of B2 cells with anti-Ia. W39 and complement. CRIA is expressed in each of these B cell subpopulations. Antigen plays a selective role in the stimulation of distinct B cell sets. ARS conjugates of keyhole limpet hemocyanin (KLH) can activate both the B1 and B2 subpopulations. In contrast, ARS conjugates of synthetic polypeptides under Ir gene control selectively activate the B2 subpopulation in strains that are genetic responders to the carrier. This leads to the establishment of CRIA dominance where CRIA+ anti-ARS antibody is 70 to 95% of the total anti-arsonate antibody response. This class of antigens fails to activate the B1 cells in either normal or xid mice. We compared the CRIA+ antibody produced by selectively activated B2 cells to that produced by the B1 subpopulation in xid mice. For these comparisons, we used competitive radioimmunoassays that employed polyspecific anti-CRIA antiserum or monoclonal anti-CRIA antibodies specific for distinct idiotopes on the heavy chain of CRIA+ antibody. B2 cells produce a CRIA+ anti-ARS antibody that is idiotopically uniform among individual mice, and that closely approximates the hybridoma protein 36-65 (the heavy chain of 36-65 represents the germ line-encoded sequence of the unique CRIA structural gene (25]. In contrast, the CRIA+ antibody produced by the B1 cell subset of xid mice is idiotopically diverse among individual mice, and differs markedly from the 36-65 hybridoma protein. The extent of diversification found in CRIA+ antibody depends on the B cell subpopulation that produces it.     

Infectious diarrhea of infant rats produced by a rotavirus-like agent.

During the investigation of an outbreak of diarrhea in suckling rats, a virus morphologically identical to but antigenically distinct from rotaviruses was identified. The disease was characterized clinically by erythema and cracking and bleeding of the perianal skin associated with the excretion of poorly formed fecal pellets, liquid, and gas. Light microscopy-observable changes consisted of small intestinal villous atrophy, villous epithelial necrosis, and villous epithelial syncytial cell formation. The cytoplasm of the epithelial syncytial cells contained large numbers of 80-nm viral particles that were often associated with reticular aggregates of electron-dense material. Viral infection principally involved the luminal one-fourth to one-third of the intestinal villi as determined by indirect immunofluorescence. This rotavirus-like agent contained 11 double-stranded RNA segments; however, the migration pattern of these segments in polyacrylamide gels differed from the electrophoretic pattern which is characteristic of the typical rotaviruses. The agent had a buoyant density in CsCl of 1.36 to 1.4 g/cm3 and was labile at pH 3 and at 56 degrees C; however, infectivity of viral inocula was not altered by extensive treatment with ether or by pH 5 buffers. This disease, which we have named infectious diarrhea of infant rats, is the first recognized viral diarrhea of rats and appears to be a good model for the study of the recently recognized group of atypical rotaviruses.     

Thermotoga maritima sp. nov. represents a new genus of unique extremely thermophilic eubacteria growing up to 90°C

A novel type of bacterium has been isolated from various geothermally heated locales on the sea floor. The organisms are strictly anaerobic, rod-shaped, fermentative, extremely thermophilic and grow between 55 and 90°C with an optimum of around 80°C. Cells show a unique sheath-like structure and monotrichous flagellation. By 16S rRNA sequencing they clearly belong to the eubacteria, although no close relationship to any known group could be detected. The majority of their lipids appear to be unique in structure among the eubacteria. Isolate MSB8 is described as Thermotoga maritima, representing the new genus Thermotoga.Dedicated to Otto Kandler on the occasion of his 65th birthday Present addresses: University of South Dakota, Vermillion, USA; University of Illinois, Urbana, USA; Universität für Bodenkultur, Wien, Austria     

Methyl bromide inhibits ripening and ethylene production in tomato (lycopersicon esculentum mill.) fruit

Tomato fruit ripening and ethylene production were inhibited following treatment with methyl bromide (MB). Methyl bromide significantly delayed ripening initiation in mature-green (MG) fruit and retarded the rate of ripening of turning (T) fruit as measured by color development and flesh softening. Treatment with MB caused an initial transient burst of ethylene production, but the subsequent ripening-associated increase in ethylene was delayed. Ethylene treatment partially overcame MB inhibition in MG fruit but had no affect on T fruit. The inhibition of ethylene production by MB appears to be due to lack of formation of 1-aminocycloprone-1-carboxylic acid (ACC) in MG fruit, whereas in T fruit lack of conversion of ACC to ethylene is indicated. A key feature of MB inhibition of ripening in tomato appears to be reduced sensitivity to ethylene.     

A detailed examination of the iodination of beta-galactosidase: stoichiometric inactivation by nonspecific iodination

The incorporation of 125I, using lactoperoxidase, and the subsequent inactivation of beta-galactosidase in the period when incorporation and inactivation were stoichiometric were investigated in detail. The high pressure liquid chromatographic (HPLC) radioactive profiles of the tryptic peptides of samples taken in the stoichiometric period showed that, although two labelled peptides predominated, there were other labelled peptides. The predominating peptides were shown to be the mono- and di-iodinated forms of the peptide containing Tyr-253. This confirmed the result of an earlier study, but quantitation showed that this iodination accounted for only 15-18% of the total. To show that the other labelled peptides in the HPLC profiles were not merely oxidized or partially digested forms of the peptide containing Tyr-253, two experiments were carried out. In one of the experiments, two of the other labelled peptides were isolated and identified as iodinated forms of the peptide containing Tyr-285 (5-7% of the incorporation). In the other experiment, four additional labelled fractions from the HPLC eluate were treated further with trypsin. No further digestion was observed and thus these peptides did not result from incomplete digestion of the sequence containing Tyr-253. Overall, these results show that, although the incorporation of 125I was stoichiometric with inactivation, no single Tyr was responsible for the inactivation as was tentatively suggested previously. The competitive inhibitor isopropyl-beta-D-thiogalactopyranoside (IPTG) was effective in reducing the rates of inactivation of the enzyme and incorporation of 125I, but the same peptides were labelled in the presence of IPTG as in its absence.     

Changes in Starch Formation and Activities of Sucrose Phosphate Synthase and Cytoplasmic Fructose-1,6-bisphosphatase in Response to Source-Sink Alterations

Short term experiments were conducted with vegetative soybean plants (Glycine max L. Merr. `Ransom' or `Arksoy') to determine whether sourcesink manipulations, which rapidly changed the `demand' for sucrose and partitioning of photosynthetically fixed carbon into starch, were associated with alterations in activities of sucrose-P synthase and/or cytoplasmic fructose-1,6-bisphosphatase in leaf extracts. When demand for sucrose from a particular source leaf was increased by defoliation of other source leaves, starch accumulation was restricted and activities of both enzymes were markedly enhanced. When demand for sucrose from source leaves was limited by excision, starch accumulation in the detached leaves was increased while activity of sucrose-P synthase declined sharply. The consistent responsiveness of sucrose-P synthase activity to changes in demand for sucrose supports the contention that regulation of sucrose-P synthase is an integral component of the system which controls sucrose biosynthesis and partitioning of carbon between starch and sucrose biosynthesis in the light.     

Modulation of endogenous prostaglandins by thymosin-α1 in lymphocytes

The effects of thymosin-α₁ on the stimulation of specific release of prostaglandin E₂ (PGE₂) from splenic lymphocytes and thymocytes were studied. Experiments were also performed to study in parallel the absolute levels of thymosin-α₁ in the blood and the induction of serum FTS activity and of azathioprine sensitivity of spleen cells from adult thymectomized (ATx) mice. A significant difference in the release of PGE₂ between normal splenocytes and splenocytes from ATx mice was observed. Thymosin-α₁ at certain concentrations was able to stimulate PGE₂ release from lymphocytes of ATx mice while inhibiting release in lymphocytes of normal mice. Also, thymocytes were stimulated to release PGE₂ after incubation with α₁ in a manner similar to that seen in spleen cells of ATx mice. Approximately the same concentration of α₁ was found to also correct the low azathioprine sensitivity of splenocytes from ATx mice. Determinations of FTS-like activity in the blood and the pharmacokinetics of α₁ after administration of this synthetic molecule show a clear dissociation. A maximum peak of α₁ activity was obtained after 1 hr, while maximal FTS-like activity was observed after 24 hr. The inhibition of the induction by α₁ of FTS-like activity and of Thy 1.2 antigen by indomethacin suggests that the action of α₁ requires prostaglandin biosynthesis.     

Enzyme des Stärkeumsatzes in Bündelscheiden- und Palisadenchloroplasten von Zea mays

Summary Isolated chloroplasts from the bundle sheath cells show considerable activity of the ADPG- and UDPG-pyrophosphorylase (EC 2.7.7.9), ADPG- and UDPG-transglucosylase (EC 2.4.1.21), and the starch phosphorylase (EC 2.4.1.1). In chloroplasts of the palisade cells, on the other hand, only the UDPG-pyrophosphorylase is remarkably active.