Identification and characterization of a B cell activation factor (BCAF) produced by a human T cell line

A human T cell line, Peer, that expresses the T cell helper phenotype produces discrete activation and growth factors for tonsillar B cells. The B cell activation factor produced by Peer is biochemically and physiologically distinct from other lymphokines known to enhance B cell proliferation, namely, interleukin 1, interleukin 2, interferon, and previously characterized B cell growth factors (BCGF). The BCGF produced by Peer is functionally similar to previously described BCGF but has a m.w. of approximately 30,000 daltons. The identification and characterization of a T cell-derived activation factor that can induce apparently resting (Go phase) B cells to enter S phase in the absence of an exogenous first signal has important implications in the additional dissection of the complex steps in the human B cell cycle.     

Characterization of a concanavalin A supernatant-derived idiotype-specific T helper cell factor

We have previously demonstrated the requirement of two T helper (Th) populations for the expression of plaque-forming cells (PFC) that bear the dominant cross-reactive idiotype (CRI) associated with the phenyltrimethylammonium (TMA) response (1). In addition to the classic major histocompatibility complex-restricted Th cell, the response was also dependent upon the so-called second order Th2 population, which binds to idiotypic determinants, is carrier specific, but does not require hapten linked to carrier for function. This cell type can be replaced by supernatant (Sn) media from concanavalin A (Con A)-stimulated naive spleen cells. This report involves the study of the Con A Sn derived factor(s) responsible for the expression of CRI bearing PFC populations. When the Brucella abortus (BA)-trinitrophenol (TNP) conjugated antigen is added to TNP-ovalbumin-primed A/J-derived spleen cells in culture, anti-TNP PFC are generated of which only less than or equal to 5% bear the CRI normally associated with anti-TMA antibodies. Upon addition of Con A Sn, the total number of generated anti-TNP PFC doubles, whereas the percentage and number of CRI+ PFC increases approximately eightfold to 10-fold. The factor(s) responsible for this activity are T cell derived, bear Jk serologic determinants, and can be detected in the Sn as early as 4 hr after Con A stimulation. The material appears to be late acting, because it can augment the CRI+ anti-TNP response when added as late as 24 hr before termination of the cultures. In addition, the factor(s) can be bound to and eluted from CRI+ anti-TMA and anti-TNP monoclonal antibodies coupled to Sepharose 4B beads, but not from their CRI- counterparts (i.e., CRI- anti-TMA and anti-TNP antibodies), nor from A/J normal mouse immunoglobulin-coupled beads. Most interestingly, the factor(s) also bind to and can be eluted from the TMA ligand coupled to Sepharose 4B, but not from TNP-Sepharose conjugates. All of these results are consistent with the support the contention that the factor(s) is derived from a Th2-like subpopulation. As assayed by standard protocols, the isolated material contains no T cell replacing factor, interleukin 2, or B cell growth factor activity.     

Binding of the Novel Serotonin Agonist 8-Hydroxy-2-(Di-n-Propylamino) Tetralin in Normal and Alzheimer Brain

Binding of [3H]8-hydroxy-2-(di-n-propylamino) tetralin, a putative ligand for the 5-hydroxytryptamine (5-HT, serotonin) 1A recognition site, was measured in neocortex from postmortem human brain. The substance was found to bind to a saturable site with a KD value and pharmacological profile similar to that of rat. Binding to membranes from normal human temporal cortex was found to significantly correlate (inversely) with age. A significant reduction in binding, reflecting decreased density of recognition sites, was observed in the frontal cortex of patients with Alzheimer's disease (48% loss). This region in the dement brains showed unaltered presynaptic 5-HT function (5-HT and 5-hydroxyindoleacetic acid content) whereas 5-HT concentration was reduced in the temporal cortex.     

The critical segment for the Langer-Giedion syndrome: 8q24.11----q24.12

An 18-year-old intellectually normal male with characteristic features of the Langer-Giedion syndrome is reported. High resolution chromosome analysis showed a small deletion in the region of bands 8q24.11 and 8q24.12 in addition to an apparently balanced de novo translocation (2;9)(q21;q13). This finding provides additional information on the minimum deleted segment required to produce the Langer-Giedion syndrome and may indicate that deletions of this size or smaller are not necessarily associated with mental retardation.     

Evidence for titratable gating charges controlling the voltage dependence of the outer mitochondrial membrane channel,VDAC

Summary A voltage-dependent anion-selective channel, VDAC, is found in outer mitochondrial membranes. VDAC's conductance is known to decrease as the transmembrane voltage is increased in either the positive or negative direction. Charged groups on the channel may be responsible for this voltage dependence by allowing the channel to respond to an applied electric field. If so, then neutralization of these charges would eliminate the voltage dependence. Channels in planar lipid bilayers which behaved normally at pH 6 lost much of their voltage dependence at high pH. Raising the pH reduced the steepness of the voltage dependence and raised the voltage needed to close half the channels. In contrast, the energy difference between the open and closed state in the absence of a field was changed very little by the elevated pH. The groups being titrated had an apparent pK of 10.6. From the pK and chemical modification, lysine epsilon amino groups are the most likely candidates responsible for VDAC's ability to respond to an applied electric field.     

Biochemical pathways in prokaryotes can be traced backward through evolutionary time

For the first time, a credible prokaryotic phylogenetic tree is being assembled by Woese and others using quantitative sequence analysis of oligonucleotides in the highly conservative rRNA. This provides an evolutionary scale against which the evolutionary steps that led to the arrangement and regulation of contemporary biochemical pathways can be measured. This paper presents an emerging evolutionary picture of aromatic amino acid biosynthesis within a large superfamily assemblage of prokaryotes that is sufficiently developed to illustrate a new perspective that will be applicable to many other biochemical pathways.      

Application of a competition model to the growth of Streptococcus mutans and Streptococcus sanguis in binary continuous culture.

Streptococcus mutans 6715-15 and Streptococcus sanguis 10558 were grown together in continuous culture with glucose as the limiting carbon source. The relationship of growth rate to substrate concentration was determined for pure cultures of each organism in continuous and batch cultures. A model based on competition for a growth-limiting substrate (glucose) was used to predict the proportions of each organism when grown in binary cultures. The results indicate that interactions other than competition for glucose carbon exist between S. mutans and S. sanguis grown under these conditions.     

Characterization of gibberellins from dark-grown Phaseolus coccineus seedlings by gas-liquid chromatography and combined gas chromatography-mass spectrometry

Summary An extract from 6000 dark-grown Phaseolus coccineus seedlings was purified by countercurrent distribution and G-10 Sephadex followed by gradient elution from a silicic acid partition column with increasing amounts of ethyl actetate in n-hexane. 25 fractions were collected and tested with the barley-aleurone, Tan-ginbozu dwarf-rice, lettuce, cucumber, dwarf-pea, d-1, d-2, d-3 and d-5 maize, oat first-internode, and sugarcane-spindle bioassays. Major gibberellin (GA)-like activity was detected in fractions 4 (500g GA₃-equivalents) and 12–13 (270 g GA₃-equivalents) with smaller amounts in fractions 6, 8–9, 15–16, 18, 20, 23 and 25. The extracts were also applied to AMO-1618=dwarfed Ph.-coccineus seedlings. Fractions 4, 8 and 12 promoted the growth of both light- and dark-grown seedlings. GA₁, GA₃, GA₄ and GA₈ were active in the Phaseolus bioassay but GA₈-glucoside was inactive.The biological and chromatographic properties of fractions 4, 8–9 and 12–13 correspond with those of GA₄, GA₁₉ and GA₁. The identity of GA₄ in fraction 4 was conclusively established by combined gas chromatography-mass spectrometry (GC-MS) of the methyl ester and the trimethylsilyl ether of the methyl ester. Gasliquid-chromatography peaks corresponding to these derivatives of GA₁₉ and GA₁ were detected on QF-1 and SE-33 columns but their intensities were too weak to permit conclusive identification by GC-MS.Supported by an S.R.C. StudentshipSupported by a NATO Grant.Supported by NRC Grant A-5727.     

Further investigations into hormone-directed transport in stems

Summary The effect of IAA and three synthetic auxins on the upward movement of ³²P-orthophosphate and ¹⁴C-sucrose has been investigated in decapitated stems of Phaseolus vulgaris L., Pisum sativum L., Coleus blumci L. and Helianthus annuus L. IAA greatly enhanced the accumulation of ³²P-orthophosphate in Phaseolus vulgaris and Pisum sativum, whereas in C. blumei and H. annuus it did not. 2,4-D like IAA, caused an increase in ¹⁴C-sucrose and ³²P-orthophosphate accumulation in Phaseolus vulgaris but, unlike IAA, caused no increase in Pisum sativum. The downward transport of ¹⁴C-IAA, ¹⁴C-NAA, ¹⁴C-2,4-D and ¹⁴C-2,4,5-T from the decapitated apex was also studied. Results are discussed in terms of current theories of hormone-directed transport.For abbreviations see Table 1.     

Phycobilisomes in Blue-Green Algae

Fifteen species of freshwater blue-green algae, including unicellular, filamentous, and colonial forms, were subjected to a variety of fixatives, fixation conditions, and stains for comparison of the preservation of phycobilisomes. Absorption spectra of the corresponding in vivo and released photosynthetic pigments, in 10 of the species that were maintained in culture, demonstrated the presence of phycocyanin in all 10 species and phycoerythrin in only 2 of them. Spectroscope and electron microscope evidence was obtained for localization of phycobiliproteins in phycobilisomes of Nostoc muscorum. Phycobilisomes were observed in all species examined in situ, strenghening the hypothesis that phycobilisomes are common to all phycobiliprotein-containing photosynthetic blue-green algae.