Circumscription of Fulbrightiella gen. nov. and Sherwoodiella gen. nov., Two Novel Genera in the Calotrichaceae (Nostocales,Cyanobacteria)

Three novel strains in Calotrichaceae from tropical habitats were isolated and characterized with regard to their morphology, phylogenetic placement, and secondary structures of conserved domains in the 16S-23S internal transcribed spacer (ITS). The strains fell into two clades formerly identified as Calothrix from freshwater and brackish habitats. Based on both morphology and ecology, they differed from the type species of Calothrix, C. confervicola, which is marine, has wide trichomes with short cells, and narrows abruptly to a hyaline hair. The first clade grouped species with heteropolar filaments widened at the base and narrowed gradually toward the apex but not ending in a hair, with basal heterocytes that are formed in series as the apically placed heterocytes senesce; this clade is being named Fulbrightiella gen. nov., with two named species, F. bharadwajae sp. nov. and F. oahuensis sp. nov. The second clade was comprised of a single species with isopolar trichomes that are untapering as hormogonia, but which widen midfilament and taper toward both ends following growth. These trichomes develop pairs of heterocyte mid-filament, causing fragmentation into heteropolar trichomes with basal heterocytes and ends that taper, but not to a hair. This clade consists of a single species at present, Sherwoodiella mauiensis. With this action, four clades in the Calotrichaceae have been named: Macrochaete, Dulcicalothrix, Fulbrightiella, and Sherwoodiella. Calothrix sensu stricto is truly marine, morphologically distinct, and unsequenced; finding and sequencing the generitype for Calothrix remains as the most important and unfinished task in the revision of the Calotrichaceae.     

CD studies of peptides that mimic the four helicoidal sequences of the uteroglobin monomer

Summary Short peptides spanning the helicoidal sequences of the uteroglobin monomer (crystal forms P2₁ and C222₁) were synthesized and studied by circular dichroism spectroscopy. None of them showed any secondary structure in the absence of HFIP. However, most peptides achieved a helical conformation when this structuring agent was used, with the exception of the analogue corresponding to the helicoidal fragment 19–24 (helix II, crystal P2₁). These results indicate that other factors, such as interchain interactions, have to contribute to helix stabilization in the molecule. On the other hand, while peptides corresponding to N- and C-terminal fragments that contain the first and fourth helices of the monomer, respectively (1–14 and 48–70) achieved a -like structure when 10–15% of HFIP was used, this behaviour was not observed when TFE was used. Moreover, substitution of cysteine by -aminobutyric acid at position 3 increased both the helicity of fragment 1–14 and its ability to adopt a -like structure, but the opposite effect was observed for fragment 48–70 when -aminobutyric acid was introduced at position 69. These results indicate that this part of the protein might be sensitive to the chemical environment it is exposed to and that the two cysteine residues at positions 3 and 69 of the monomer could play a different role in the folding process.     

A Nucleoside Diphosphate Kinase from Paramecium tetraurelia with Protein Kinase Activity

Nucleoside diphosphate kinase (NDP kinase) from Paramecium was purified to homogeneity. The native enzyme was 80 kDa (by gel filtration), with subunits of 18 and 20 kDa. Near the amino terminus, 15 of 20 residues were identical with those in human NDP kinase, and 17 of 20 with the awd gene product from Drosophila. NDP kinase bound α-labeled ATP and GTP, and a photoreactive GTP analog labeled both subunits. Purified NDP kinase underwent autophosphorylation on a histidine and a serine residue using either ATP or GTP as a substrate. The enzyme also catalyzed acid-stable phosphorylation of casein and phosvitin. This protein kinase activity is distinct from the histidine phosphorylation that is part of the NDP kinase catalytic cycle. Antiserum against the purified protein from Paramecium cross-reacted with 16- to 20-kDa proteins in most species tested, and with a larger protein (44 kDa) in Paramecium, Xenopus, and two human lines. The multiple forms (20 and 44 kDa) of the NDP kinase in Paramecium and its protein kinase activity, suggest that the protein is more than a housekeeping enzyme; it may have regulatory roles such as those of the NDP kinase-like awd protein of Drosophila and Nm23 protein of humans.     

Nitric oxide is involved in heat-induced HSP70 accumulation

Heat shock potentiated the nitric oxide production (EPR assay) in the liver, kidney, heart, spleen, intestine, and brain. The heat shock-induced sharp transient increase in the rate of nitric oxide production preceded the accumulation of heat shock proteins (HSP70) (Western blot analysis) as measured in the heart and liver. In all organs the nitric oxide formation was completely blocked by the NO-synthase inhibitor (L-NNA). L-NNA also markedly attenuated the heat shock-induced accumulation of HSP70. The results suggests that nitric oxide is involved in the heat shock-induced activation of HSP70 synthesis.     

CD23McAb抑制活化B细胞增殖机制的初步探讨

本研究用ＣＤ２３单克隆抗体交联活化的人扁桃体Ｂ细胞,证明ＣＤ２３ＭｃＡｂ对Ｂ细胞呈双向调节效应,即：高浓度区抑制Ｂ细胞增殖,低浓度区促进Ｂ细胞增殖,继而,用对Ｂ细胞有抑制效应浓度的ＣＤ２３ＭｃＡｂ交联Ｂ细胞膜ＣＤ２３分子,通过研究抑制效应恢复条件,探讨了ＣＤ２３ＭｃＡｂ产生抑制效应的作用机制。结果显示：去除ＣＤ２３ＭｃＡｂ后,抑制作用不能恢复,用ＳＡＣ再次活化,使Ｂ细胞恢复增殖状态,用促Ｂ细胞增殖     

Immunological characterization of a 36 kDa Fe deficiency specific peptide in barley roots

In a previous paper we reported that an acidic 36 kDa peptide is the most strongly induced peptide among several peptides induced by Fe deficiency in barley roots. In this paper, polyclonal antibodies were raised against the 36 kDa peptide. This peptide appeared in the roots of all the graminaceous species tested (barley, rye, wheat, oat, maize, sorghum and rice) in response to Fe deficiency. More of the peptide was found in the roots of graminaceous species which secrete higher amounts of mugineic acids (MAs) under Fe deficient nutrition status. Induction of the 36 kDa peptide was first observed on the third day of Fe deficiency, rising to a maximum value on the seventh day. The trend has a positive correlation with secretion of MAs during Fe deficiency. Further, resupply of Fe resulted in a decrease in peptide production on the second day, reaching a control level on the seventh day. The rate of decrease in peptide production was observed to be slower than that of MA secretion. Other nutrient stresses such as B excess, B deficiency, Cu excess, Cu deficiency, Mn excess, Mn deficiency, Zn excess and Zn deficiency induced far less of the peptide. The specific expression of the 36 kDa peptide in roots of graminaceous species under Fe deficiency suggested the positive association of the peptide with a specific Fe deficiency tolerance mechanism in graminaceous plants.     

Influence of carbon and nitrogen sources on glutathione catabolic enzymes inCandida albicans during dimorphism

The effect of carbon sources, glucose and sucrose, and nitrogen sources such as ammonia, glutamate andl-citrulline on the activities of glutathione metabolic enzymes has been studied. Yeast and mycelial cells were used to identify changes in activity levels of glutathione reductase (GSSGR), glutathione transferase (GST), glutathione peroxidase (GPX) and -glutamyl transpeptidase (GGT). Enzyme activities from cells grown in sucrose media were lower than in glucose media regardless of the enzyme tested, morphological form, or the growth interval. In all enzymes except GST, activity was higher in yeast form than in mycelia, regardless of nitrogen source, with lower activity from 24 to 72 h than at 96 h. In citrulline media, yeast form showed the maximum GST, GGT, and GPX activity. In ammonia-amended media, mycelia showed maximum activity in GGT, whereas in glutamate media, mycelia showed the maximum activity in GST. Also, the type of nitrogen source had no effect on GPX activity in the mycelial form. Finally, changing the nitrogen source showed no significant effect on GSSGR activity, either in the yeast or mycelial form.     

Spontaneous missense mutation of an immunoglobulin in a mouse myeloma cell line.

The characterisation of the alteration in amino acid sequence of the immuno globulin heavy chain of IF4, a charge mutant of the myeloma line MOPC 21, is described. This was achieved by comparing the sequence of mutant IF4 heavy chain with the known sequence of the wild type. The peptic fragment (Fab′)₂ from whole immunoglobulin, and all the ten CNBr fragments of MOPC 21 wild-type and mutant IF4 heavy chains, were identified and characterised. The only difference was in a tryptic peptide of the C-terminal CNBr fragment which had the same amino acid composition, but different electrophoretic mobilities. Thermolysin digestion products showed that asparagine 415 of wild-type heavy chain had been replaced by an aspartate in the mutant. Analysis of newly synthesized immunoglobulins from wild type and mutant showed the same charge difference, which did not seem therefore to result from deamidation.Fingerprints of the [³²P]mRNA of IF4 heavy chain were prepared. The T₁ ribonuclease oligonucleotide that includes the coding sequence for residue 415 in wild type was not found in mutant IF4.The mechanism is most likely a missense point mutation (A to G transition) in the MOPC 21 heavy chain structural cistron.