Human polysaccharide-specific B cells are responsive to pokeweed mitogen and IL-6

The responsiveness of polysaccharide-specific B cells to PWM was examined in vitro. Spleen cells from six patients immunized with Haemophilus influenzae type b-diphtheria toxoid, pneumococcal and meningococcal vaccines were T cell-depleted and separated by Percoll density gradient centrifugation. In each B cell fraction, spontaneous antibody production was demonstrated to capsular polysaccharides as well as diphtheria toxoid. The peak of spontaneous antibody production was demonstrated to be five to seven days after immunization. When T cells and PWM were added, the total Ig secretion increased in all B cell fractions. PWM also enhanced IgG antibody directed to each of three polysaccharide Ag measured. This enhancement was most noticeable for nonresting B cells. The PWM effect was not confined to IgG, as IgM and IgA to Neisseria meningitidis type C were measured and also enhanced. The kinetics of the PWM response demonstrated the most IgG antibody to polysaccharide Ag from spleens immunized five to seven days before splenectomy. When the patients were immunized either 2 days or 4 mo before splenectomy, no spontaneous IgG antibody to polysaccharides was detected although PWM induced small amounts of antibody. Finally, anti-IL-6 antibody blocked PWM-induced total and polysaccharide-specific antibody production. We conclude that human polysaccharide-specific B cells are responsive to PWM and IL-6. We suggest that polysaccharide B cells are not truly "T cell-independent" and may respond to T cell lymphokines and thus are similar to protein-specific B cells.     

Cerebral interneurons controlling fictive feeding in Limax maximus

Summary Initiation and modulation of fictive feeding by cerebral to buccal interneurons (CBs) was examined in an isolated CNS preparation of Limax maximus. Three CBs which are phasically active during fictive feeding, CB₁, CB₃ and CB₄, will reliably trigger bouts of fictive feeding when activated alone or in pairs. Another phasic CB, CB_EC, is not effective for triggering feeding. One CB which is tonically active during fictive feeding, CB_ST, drives fictive feeding in 50% of preparations when activated alone and enhances triggering of feeding when co-activated with phasic CBs. The metacerebral giant cell (MGC) was found to be capable of triggering fictive feeding in preparations with an intact subcerebral commissure. The MGC was especially effective at increasing the effectiveness of other CBs for initiation of feeding. Short high-frequency bursts of phasic CB or MGC action potentials are capable of resetting ongoing fictive feeding. Resetting effects of CB action potentials are relatively independent of the phase of the bite-cycle in which they are activated. CB₄ phase-advances the bite-cycle while the other phasic CBs phase-delay the bite cycle. Moderate frequency stimulation of CB₄ speeds up the bite rate while moderate frequency stimulation of CB₃ slows biting. All CBs, except the tonic CB, CB_DL, increase the intensity of buccal motor neuron bursting during feeding. The excitatory effects of phasic CBs and the tonic CB, CB_EPSP, on fictive feeding persist for many seconds after the offset of stimulation. CBs form both monosynaptic excitatory and monosynaptic inhibitory connections with different BG motor neurons.Abbreviations BG buccal ganglion - BR buccal root - CB cerebral-buccal interneuron - CBC cerebral-buccal connective - CPG central pattern generator - FB fast burster neuron - FMP feeding motor program - IBI interbite interval - MGC metacerebral giant cell     

Natural relationships among sulfate-reducing eubacteria

Phylogenetic relationships among 20 nonsporeforming and two endospore-forming species of sulfate-reducing eubacteria were inferred from comparative 16S rRNA sequencing. All genera of mesophilic sulfate-reducing eubacteria except the new genus Desulfomicrobium and the gliding Desulfonema species were included. The sporeforming species Desulfotomaculum ruminis and Desulfotomaculum orientis were found to be gram-positive organisms sharing 83% 16S rRNA sequence similarity, indicating that this genus is diverse. The gram-negative nonsporeforming species could be divided into seven natural groups: group 1, Desulfovibrio desulfuricans and other species of this genus that do not degrade fatty acids (this group also included "Desulfomonas" pigra); group 2, the fatty acid-degrading "Desulfovibrio" sapovorans; group 3, Desulfobulbus species; group 4, Desulfobacter species; group 5, Desulfobacterium species and "Desulfococcus" niacini; group 6, Desulfococcus multivorans and Desulfosarcina variabilis; and group 7, the fatty acid-oxidizing "Desulfovibrio" baarsii. (The quotation marks are used to indicate the need for taxonomic revision.) Groups 1 to 3 are incomplete oxidizers that form acetate as an end product; groups 4 to 7 are complete oxidizers. The data were consistent with and refined relationships previously inferred by oligonucleotide catalogs of 16S rRNA. Although the determined relationships are generally consistent with the existing classification based on physiology and other characteristics, the need for some taxonomic revision is indicated.     

Effect of IBMX and alkaline phosphatase inhibitors on Cl- secretion in G551D cystic fibrosis mutant mice

Some cysticfibrosis transmembrane conductance regulator (CFTR) mutations, such asG551D, result in a correctly localized Cl channel at the cellapical membrane, albeit with markedly reduced function. Patch-clampstudies have indicated that both phosphatase inhibitors and3-isobutyl-1-methylxanthine (IBMX) can induceCl secretion through theG551D mutant protein. We have now assessed whether these agents caninduce Cl secretion incftr^G551D mutantmice. No induction of Clsecretion was seen with the alkaline phosphatase inhibitorsbromotetramisole or levamisole in either the respiratory or intestinaltracts of wild-type orcftr^G551D mice.In contrast, in G551D intestinal tissues, IBMX was able to produce asmall CFTR-related secretory response [means ± SE: jejunum,1.8 ± 0.9 µA/cm²,n = 7; cecum, 3.7 ± 0.8 µA/cm²,n = 7; rectum (in vivo),1.9 ± 0.9 mV, n = 5]. Thiswas approximately one order of magnitude less than the wild-typeresponse to this agent and, in the cecum, was significantly greaterthan that seen in null mice(cftr^UNC). Inthe trachea, IBMX produced a transientCl secretory response (37.3 ± 14.7 µA/cm²,n = 6) of a magnitude similar to thatseen in wild-type mice (33.7 ± 4.7 µA/cm²,n = 9). This response was also presentin null mice and therefore is likely to be independent of CFTR. Noeffect of IBMX on Clsecretion was seen in the nasal epithelium ofcftr^G551D mice.We conclude that IBMX is able to induce detectable levels ofCFTR-related Cl secretionin the intestinal tract but not the respiratory tract through the G551Dmutant protein.

     

Synthesis, Biological Properties, and Structure-Activity Relationships of Quinoxaline Angiotensin II Receptor Antagonists

Quinoxaline heterocycle containing angiotensin II receptor antagonist analogs were prepared. All five analogs reported here display potent antagonistic activities and most interestingly, quinozaline bis-N-oxide 10 exhibits very potent activities both in binding and functional assays.     

Acetylation of chromosome squashes of Drosophila melanogaster decreases the background in autoradiographs from hybridization with [125I]-labeled RNA.

DNA in prepared chromosomes from the larval salivary glands of Drosophila melanogaster was hybridized with [125I]-labeled 5S and tRNA from the same organism. Autoradiography revealed that radioactivity was frequently bound to all regions of the slides, masking labeling of the chromosomes. Acetylation of the preparations before hybridization prevented the formation of this background and revealed the specific chromosomal sites.     

Stimulation of vitamin K-dependent carboxylation by pyridoxal-5'-phosphate.

This paper presents evidence that the approximately two-fold increase in vitamin K-dependent carboxylation of the pentapeptide PheLeuGluGluLeu, but not of endogenous protein substrate, brought about by pyridoxal-5′-phosphate, is due to binding of the pyridoxal-5′-phosphate to microsomal enzyme(s), rather than to the pentapeptide. Pyridoxine inhibits this peptide carboxylation, while pyridoxal, pyridoxamine, and pyridoxamine-5′-phosphate have no effect on the reaction.     

Synthesis, biological activity, and tritiation of L-3, 4-dehydroproline-containing peptides

A series of analogs of thyroliberin (TRH) ([L-delta3Pro3]-TRH, [D-delta3Pro3]-TRH, [L-3-MeHis2, L-delta3Pro3]-TRH) in which proline was replaced by L- or D-3, 4-dehydroproline was synthesized. The analogs exhibited approximately the same biological activity as the corresponding proline-containing peptides. These analogs and others in which 3, 4-dehydroproline is present at the NH2-terminal, COOH-terminal or internal positions in the peptide were successfully reduced with deuterium or tritium to provide the 3, 4-2H2-proline or 3,4-3H2-proline analogs, respectively, with near theoretical values of substitution. A novel procedure for the chemical resolution of DL-3, 4-dehydroproline is also described.