Met-enkephalin effects on associations formed in utero

Rat fetuses exposed to an odor stimulus and an aversive stimulus in utero showed an aversion to the odor when tested 16 days postnatally. Fetuses that also received 80 μg/kg Met-enkephalin showed a greater aversion to the odor stimulus than those subjects that did not receive the peptide. The difference between these groups was marginally significant. Control subjects did not show an aversion. But, subjects exposed to the odor and Met-enkephalin without the aversive stimulus, when tested, showed a significant preference for the odor over other control groups. These data show that associative learning in rat fetuses at 20 days of gestation may be enhanced by administration of Met-enkephalin.     

Purification and structural properties of adenylylated and deadenylylated glutamine synthetase from Rhodopseudomonas sphaeroides

Glutamine synthetase (GS) of Rhodopseudomonas sphaeroides is regulated by adenylylation and deadenylylation. The extent of adenylylation/deadenylylation of the enzyme in cell free extracts was influenced by inorganic phosphate (P _i), -ketoglutarate, ATP and other nucleotides. While P _i and -ketoglutarate stimulated deadenylylation, ATP and other nucleotides enhanced adenylylation of the GS. By using proper combinations of the effectors and incubation conditions, any desired adenylylation state of GS could be adjusted in vitro. The enzyme was purified to electrophoretic homogenity by three steps including affinity chromatography on 5-AMP-Sepharose. Adenylylated and deadenylylated enzyme showed different UV-spectra and isoelectric points. The native enzyme had a molecular weight of 600,000, deadenylylated subunits of 50,000±1,000. Electron microscopic investigations revealed a dodecameric arrangement of subunits in two hexameric planes.     

Isolation and characterization of nuclear genes coding for subunits of the yeast ubiquinol-cytochrome c reductase complex

Nuclear genes coding for the M_r 17000, 14000 and 11000 subunits of the ubiquinol-cytochrome c reductase complex (complex III) in yeast have been isolated from a clone bank of yeast nuclear DNA by use of a mRNA hybridization-competition assay. This is based on our observations that levels of mRNAs for these subunits are much reduced during glucose repression and in cytoplasmic petite mutants and the procedure should be of general application for the isolation of other inducible or repressible genes coding for mRNAs present at low levels in the cell. A first characterization of the clones is presented. The genes are not closely linked in the genome and those coding for M_r 14000 and 11000 subunits are present in unique genomic environments, which suggests that there are only single copies of each in the nuclear genome.     

Isolation of a cloned DNA segment containing a ribosomal protein gene of Drosophila melanogaster

A Drosophila genomic DNA library in the vector Charon 4 was screened using cDNA derived from the small (6S-12S) poly(A)+ mRNA of 2-6-h-old Drosophila embryos. This fraction of mRNA is enriched for ribosomal protein-coding sequences. The selected recombinants were hybridized to total mRNA under conditions which allowed for isolation of homologous mRNAs. The mRNA from these RNA/DNA hybrids was eluted and translated in vitro. The translation products were analyzed by one- and two-dimensional electrophoresis with authentic ribosomal proteins as standards. One cloned DNA segment was found to contain a ribosomal protein gene, and a sequence which hybridizes strongly to at least 5 other ribosomal protein mRNAs.     

Human cytomegalovirus DNA: BamHI, EcoRI and PstI restriction endonuclease cleavage maps

The cloned HindIII fragments of human cytomegalovirus (HCMV) strain AD169 DNA were mapped with respect to the BamHI, EcoRI and PstI restriction endonuclease cleavage sites. Composite restriction endonuclease cleavage maps for the entire virus genome were constructed using the previously established linkages between the HindIII fragments.     

Ultrastructural observations on cortical granules in human follicular oocytes cultured in vitro

The fine structure, distribution, and fate of cortical granules in human oocytes cultured in vitro are reported. Follicular maturation in women with blocked Fallopian tubes was induced by clomiphene citrate and human chorionic gonadotropin, and preovulatory eggs were obtained by improved methods of laproscopy and oocyte recovery. These oocytes were then inseminated and cultured in a modified Ham's F10 medium for 3 to 72 hr to assess their fertilizability. Cortical granules were observed in all 17 unfertilized oocytes investigated, which had completed various stages of meiotic maturation. A marked increase in their numbers was observed in oocytes cultured for 3 to 6 hr. There was no evidence of spontaneous cortical granule release in any of the oocytes studied. It is concluded that cortical maturation expressed by proliferation of cortical granules is as significant a criterion as nuclear maturation in assessing maturity and fertilizability of oocytes cultured in vitro. A short sojourn in culture before insemination could improve chances of normal fertilization and embryo development, which has been recently achieved in our laboratory.     

Comparison of the chromosomes of Triticum timopheevi with related wheats using the techniques of C-banding and in situ hybridization

Summary The chromosomes of the tetraploid wheats Triticum timopheevi (Genome AAGG) and T. araraticum (Genome AAGG) were C-banded at mitosis. The identity of the banded and unbanded chromosomes was then established by firstly making comparisons with the hexaploid species T. zhukovskyi which has the genome formula AAAAGG. Secondly, the meiotic pairing in F₁ hybrids between T. timopheevi and diploid wheats was examined by means of C-banding. The results showed that the banded chromosomes belonged to the G genome, while the unbanded chromosomes belonged to the A genome. Only one of the two pairs of satellited chromosomes had strong heterochromatic bands. The relationship between the genomes of T. timopheevi and T. dicoccum (Genome AABB) was then assessed at meiosis in hybrids between these species, using the techniques of C-banding and in situ hybridisation of a cloned ribosomal RNA gene probe. It was concluded that there were differences both in the amount and distribution of heterochromatin and also translocation differences between the species.     

Investigation of a preferentially transmitted Aegilops sharonensis chromosome in wheat

Summary An attempt to produce a set of addition lines of Aegilops sharonensis to the wheat variety Chinese Spring produced only one addition line. This was due to preferential transmission of one chromosome from Ae. sharonensis. This chromosome was studied in detail by established cytological methods of chromosome observation and by the newer techniques of C-banding and in situ hybridization of a cloned DNA sequence. The chromosome was found to be partially homologous to an Ae. sharonensis chromosome of similar behaviour in another wheat addition line. The incomplete homology of the two Ae. sharonensis chromosomes was due to the presence of a translocated segment of a wheat chromosome. — Substitution lines of the Ae. sharonensis chromosome for wheat homoeologous group 4 were produced and the Ae. sharonensis chromosome thereby designated 4 S ^l .     

A study of methods for in situ X-ray energy dispersive analysis of polyphosphate bodies in Plectonema boryanum

A variety of preparative methods for in situ X-ray energy dispersive analysis were tested to determine their effects on the elemental composition of polyphosphate bodies in P. boryanum. The bodies were found to contain large amounts of P and K and small amounts of Ca and Mg. Air drying, freeze-drying and freeze-drying from a liquid nitrogen slush all gave similar results. Fixation of the cells in glutaraldehyde and/or OsO₄ resulted in loss of the K and enhancement of the Ca peak. Magnesium was lost during embedding in epoxy.