Organization and nucleotide sequence of the genes for ribosomal protein S2 and elongation factor Ts in Spirulina Platensis

A 6.5 kb region from the genome of the cyanobacterium Spirulina platensis was cloned using as a probe the Escherichia coli gene for ribosomal protein S2. Sequence analysis revealed, in this region, the presence of the gene for ribosomal protein S2 and part of the gene for the elongation factor Ts (EF-Ts). The arrangement rpsB-spacer-tsf resembles that reported for E. coli. The deduced amino acid sequences of the platensis S2 and EF-Ts show significant homology with the E. coli counterparts.     

Binding of flunitrazepam to differentiating neurons cultured in a chemically defined,hormone-supplemented medium

[³H]Flunitrazepam (FNZ) binding to cortical neurons from fetal rat brain was investigated in vitro. The use of a synthetic medium specific for neurons made it possible to plot a developmental curve of³H-FNZ binding in an almost pure neuronal culture. Detectable specific binding was present in vitro at time 0 (that is, the 16th gestational day). A progressive increase of binding, due to an increment in the number of recognition sites, was observed on the subsequent days. The affinity of the specific binding sites to³H-FNZ was enhanced by the addition of exogenous GABA, whereas the density was not affected.     

The cytotaxonomy ofEmilia spp. (Asteraceae: Senecioneae) occurring in Brazil

Analysis of several populations in a large part of the distribution area of the genusEmilia in Brazil has revealed only two species: the diploidE. sonchifolia and the tetraploidE. fosbergii. The more widely reportedE. coccinea was not found. They show a karyotype constancy in morphology and chromosome number (2n = 10 and 2n = 20, respectively), C-banding pattern and number of secondary constrictions. Some indications were found thatE. fosbergii may be an allopolyploid and that its ancestors had different genome sizes.     

Production,cross reactivity,and epitope analysis of monoclonal antibodies against rat kidney gamma glutamyltransferase

Eighteen IgGl monoclonal antibodies (blabs) have been produced against gamma-glutamyl transferase (GGT) from rat kidney. They were specific to the light subunit of the enzyme with affinity constants ranging from 0.3 to 7.5 10⁸ M^–1, while they did not react with GGT from other sources i.e. human and pig kidney, rat and guinea pig liver, suggesting species and organ specificity. Two of the blabs (N° 11 and 21) lost their immunoreactivities towards rat kidney GGT in the presence of N-acetyl-neuraminic acid, while immunoreactivities of the other blabs were unchanged. Furthermore, Mabs No 11 and 21 did not react with desialylated rat kidney GGT. These findings suggest that N-acetyl-neuraminic acid is involved in the epitopes recognized by these two Mabs.Abbreviations ELISA enzyme linked immunosorbent assay - GGT gamma-glutamyltransferase - Mab monoclonal antibody - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis     

Pericentric inversion of chromosome 19 in three families

Summary Pericentric inversion of chromosome 19 has been found in several members of three unrelated families from a restricted geographical region. In one of the families, an additional pericentric inversion of chromosome 9 was observed. Reproductive problems, multiple abortions in two families and a neonatal death in the third, were present. A review of previously described cases is included, and the genetic risk connected with this type of rearrangement is also discussed.     

DR antigen expression on ovarian carcinoma cells does not correlate with their capacity to elicit an autologous proliferative response

Summary Expression of HLA-DR antigens by purified preparations of human ovarian carcinoma cells freshly isolated from surgical specimens was examined in parallel with the capacity of tumor cells to elicit a blastogenic response from autologous lymphocytes in mixed lymphocyte-tumor culture (MLTC) assay. Of 21 tumor preparations, 11 (52%) reacted with monoclonal antibodies 279 and/or 949 specific for a monomorphic determinant of HLA-DR antigens, with heterogeneous positivity, ranging between 30% and 95%. In this series of patients positive MLTC occurred in 8/21 individual experiments. The HLA-DR expression was proportionally similar in tumors giving positive MLTC (4/8=50%) and negative MLTC (7/13=53%). The lack of correlation between DR expression on tumor cells and stimulatory activity in autologous MLTC and the fact that DR-negative tumors could induce lymphocyte stimulation, support the hypothesis that blastogenesis occurs upon recognition of tumor-associated antigens, different from DR molecules, possibly tumor-specific antigens.     

The Salmonella wien virulence plasmid pZM3 carries Tn1935, a multiresistance transposon containing a composite IS1936-kanamycin resistance element

Tn1935, a 23.5-kb transposon mediating resistance to ampicillin, kanamycin, mercury, spectinomycin, and sulfonamide was isolated from pZM3, an IncFIme virulence plasmid from Salmonella wien. Tn1935 possesses the entire sequence of Tn21 and contains two additional DNA segments of 0.95 and 2.7 kb carrying the ampicillin and kanamycin resistance genes, respectively. The latter is part of a composite element since it is flanked by two IS15-like insertion sequences (IS1936) in direct orientation. IS1936 is about 800 bp long and is closely related to IS15 delta, IS26, IS46, IS140, and IS176. Functional analysis of IS1936-mediated cointegrates shows that both insertion sequences are active and able to form cointegrates at the same frequency. Resolution of the cointegrates requires the presence of the host Rec system. The presence of the composite IS1936-element within Tn1935 supports the hypothesis that multidrug resistance transposons evolved by insertion of antibiotic determinants which are themselves transposable.     

Aromatic l-Amino Acid Decarboxylase Activity of the Rat Retina Is Modulated In Vivo by Environmental Light Maria Hadjiconstantinou

Aromatic L-amino acid decarboxylase (AAAD) activity of rat retina is low in animals placed in the dark. When the room lights are turned on, activity rises for almost 3 h and reaches values that are about twice the values found in the dark. A study of the kinetics of the enzyme revealed that the apparent Km values for L-3,4-dihydroxyphenylalanine and pyridoxal-5'-phosphate were unchanged in light- and dark-exposed animals, whereas the Vmax increased in the light. Treating the animals with cycloheximide before exposure to light prevented the increase of enzyme activity. Immunotitration with antibodies to AAAD suggested that more enzyme molecules are present in the light than in the dark. When the room lights are turned off AAAD activity drops rapidly at first and then more slowly, suggesting that at least two processes are responsible for the fall of enzyme activity. Exposure to short periods of dark followed by light results in a rapid increase of AAAD activity. Mixing homogenates from light- and dark-exposed rats results in activity values that are less than expected, suggesting the presence of an endogenous inhibitor(s). These studies demonstrate that AAAD activity is modulated in vivo.     

Sequence of the human erythrocyte phosphoglycerate mutase by microsequencer and mass spectrometry

We have previously reported the isolation in pure form of the human erythrocyte phosphoglycerate mutase isozyme B. We now report the sequence of the whole protein and the identification of its N-terminal blocking group. The protein tryptic peptides of phosphoglycerate mutase isozyme B were isolated by high performance liquid chromatography and their sequence determined by microsequencing. The sequence and the nature of the blocking group of the N-terminal tryptic peptide was shown to be N-acetyl-Ala-Ala-Tyr-Lys by mass spectrometry. Overlaps of the tryptic peptides were obtained by studying the V8 Staphylococcus aureus protease peptides of the aminoethylated phosphoglycerate mutase isozyme B either by microsequencing or by mass spectrometry. The procedure used allowed us to obtain the sequence on a very small amount of material and in a short period of time. Our data agree well with those derived from the cDNA nucleotide sequence described by Sakoda et al. (Sakoda, S., Shanske, S., DiMauro, S., and Schon, E. A. (1988) J. Biol. Chem. 263, 16899-16905). In addition, our data directly indicate that the initiation codon does not introduce a methionine as N-terminal amino acid and allowed the identification of the acetyl N-terminal group.     

Tricyclic Imipramine Modification of the Circadian Rhythms of Hypothalamic Serotonin, its Precursors and Acid Catabolite in Individually Housed Rats

Circadian rhythms of serotonin (5HT), its precursors tryptophan (TP) and 5-hydroxy-tryptophan (5HTP) and its acid catabolite 5-hydroxy-indoleacetic acid (5HIAA), were determined in the hypothalamus of control rats and rats which had been treated continuously with subcutaneous imipramine (10 mg/kg/day) for 2 weeks.

Rats were individually housed and entrained to LD12:12. Controls showed the 5HT and TP peaks in the light and dark periods respectively, as reported in the literature, but no inverted correlation (antiphase) between SHT and 5HIAA rhythms.

Imipramine significantly modified circadian rhythm characteristics: the 5HT acrophase was advanced, that of TP and 5HIAA was delayed. Imipramine also significantly increased hypothalamic SHT and TP concentrations.