Lipids of isolated neurons

1. Lipids were extracted from neurons isolated from the lateral vestibular nucleus of ox (Bos taurus L.) and the ganglia of Aplysia punctata Cuvier. 2. Thin-layer chromatography of ox-neuron lipid revealed three major fractions corresponding to neutral lipid, phosphatidylethanolamine and phosphatidylserine. Part of the phosphatidylethanolamine was present as the plasmalogen. 3. Aplysia-neuron lipid contained neutral lipid, phosphatidylethanolamine and phosphatidylserine. Both phospholipids appeared to be present predominantly as the plasmalogen form. 4. The fatty acids of alkali-labile lipids of ox neurons were examined by gas–liquid chromatography. The major fatty acids were oleic acid, stearic acid and palmitic acid.     

The activities of nicotinamide mononucleotied adenylyltransferase and of nicotinamide–adenine dinucleotide kinase in the livers of rats subjected to different hormonal treatments

1. The activities of NMN adenylyltransferase and of NAD(+) kinase have been measured in the livers of adrenalectomized or alloxan-diabetic rats and in the livers of rats treated with glucagon, pituitary growth hormone or thyroxine. 2. The activities of these enzymes have been compared with the effects of the same treatments on the nicotinamide nucleotide concentrations in the liver. 3. Alloxandiabetes (+37%) and thyroxine (+27%) both increased the activity of NMN adenylyltransferase. The other treatments were without effect on this enzyme. 4. Only thyroxine increased the activity of NAD(+) kinase significantly (+26%) although both adrenalectomy and glucagon tended to increase its activity. 5. The activity of NAD(+) glycohydrolase was measured in the livers of diabetic rats, and in the livers of rats treated with either growth hormone or thyroxine. Of these treatments, only growth hormone altered the enzyme activity (+26%, calculated on a total hepatic activity basis). 6. Female rats had a greater hepatic NAD(+)-kinase activity than males but there was no sex difference with respect to NMN adenylyltransferase. 7. The lack of correlation between the maximum potential activity of these three enzymes and the known changes of the nicotinamide nucleotides in each of the hormone conditions is discussed.     

Segregation products of male mice doubly heterozygous for the RB(6.16) and RB(16.17) translocations: Influence of sperm karyotype on fertilizing competence under varying mating frequencies

The meiotic segregants of male mice heterozygous for Rb(6.16)24Lub and Rb(16.17)7Bnr were viewed, for the first time, at first cleavage metaphase. Chromosomes were analyzed after G-banding, C-banding, and karyotyping. To study sperm aging effects, chromosomes of 202 one-cell zygotes derived from males mating at intervals of approximately 3,14, and 21 days were examined. At least 89.6% of sperm-derived complements were products of 2:2 segregation; at most, a possible 6.4% were 3:1 segregants. The six expected types of 2:2 segregants, both balanced and unbalanced, were equifrequent in the total zygote population derived from sperm of all ages. When the data were analyzed according to mating frequency, the 3-day sperm population considered most likely to be fresh showed a deficiency of the segregant nullisomic for chromosome 6 and disomic for chromosome 17, when compared with the reciprocal segregant (P < 0.025) as well as to all other 2:2 segregants (P < 0.05). However, these sperm fertilized in greater numbers (P < 0.01) than their reciprocal segregant (disomic for 6 and nullisomic for 17) in the 14-day sperm population. While sperm with chromosomal abnormalities are capable of fertilization, the competence of segregants nullisomic for 6 and disomic for 17 apparently depends on the prior storage period in the male. Further, the results suggest that the effect of aneuploidy on sperm function is dependent on the specific chromosome(s) involved.     

Evolutionary analysis of the multigene pregnancy-specific β1-Glycoprotein family: Separation of historical and nonhistorical signals

The pregnancy-specific ₁-glycoproteins (PSG) form a large family of closely related proteins. Using newly developed methods of sequence analysis, in combination with protein modeling, we provide a framework for investigating the evolution and biological function of genes like the PSG. Evolutionary trees, based on C-terminal sequence, group PSG genes in a manner consistent with their genomic organization. Trees constructed using the N-terminal domain sequences are unreliable as an indicator of phylogeny because of non-neutral processes of sequence change. During duplication of the PSG genes, evolutionary pressures have resulted in a gradient of constrained change across each gene. The N-terminal domains show a nonrandom pattern of amino acid substitutions clustered in the immunoglobulin complementarity-determining region (CDR)-like regions, which appear to be important in the function of the protein.     

Human HepG2 and Rat Fao Hepatic-Derived Cell Lines Show Different Responses to Ciprofibrate, a Peroxisome Proliferator: Analysis by Flow Cytometry

Peroxisome proliferators, and especially hypolipidemic drugs such as ciprofibrate, are known to be hepatocarcinogens in rodents, but their effect in humans is controversial. In an attempt to investigate the effects of ciprofibrate at a cellular level, the analysis of individual whole cells was performed by flow cytometry on samples from two hepatic-derived cell lines: the rat Fao cell line and the human HepG2 cell line. The increase of light scatter signals in rat Fao cells treated for 3 days with ciprofibrate at 250 μMwas related to modifications of intrinsic cellular parameters, such as size and cytoplasmic granularity. Conversely, no variations appeared in human HepG2-treated cells. Moreover, the study of the cell cycle distribution of asynchronously growing cells showed an increase in the percentage of proliferative cells in Fao-treated cells, but not in HepG2-treated cells. In order to give a simultaneous assessment of changes in cellular parameters and cell metabolism, these flow cytometric experiments were completed with the measurements of the palmitoyl–CoA oxidase activity, used as a marker of peroxisome proliferation. The cellular modifications in the rat Fao cell line were accompanied by a great increase in this enzymatic activity, whereas the human HepG2 cell line, which failed to exhibit changes of cytometric data, presented no, or weak, increase in this oxidase activity. The cellular modifications observed in the rat Fao cell line may be related to the well-known hepatocarcinogenicity of ciprofibrate in rodents, whereas the absence of response of HepG2 cells is in favor of the noncarcinogenicity of this drug in humans. This report validates another methodological approach for the investigation of the safety of peroxisome proliferators in humans.     

Conformation of 4-thio-l-lyxono-1,4-lactone in solution and in the crystalline state

The conformation in ²H₂O of 4-thio-l-lyxono-1,4-lactone (1) was studied by nuclear magnetic resonance spectroscopy, by means of homonuclear (J_1H,1H) and heteronuclear (J_1H,13C) coupling constants. The couplings were directly measured by a two-dimensional heteronucleus-coupled ω₁ hetero-half-filtered proton-proton correlation (HETLOC) experiment, which does not require ¹³C isotopic enrichment. In solution, the thiolactone ring of 1 adopts preferentially the E₃ conformation, and its hydroxymethyl group populates mainly the gt rotamer. The X-ray diffraction data of a single crystal of 1 indicates that also in the solid state the thiolactone ring adopts an E₃ conformation, with a puckering somewhat larger than that observed for aldono-1,4-lactones and furanose rings. The molecules are linked by hydrogen bonds, which form chains. Particularly, O-5 is fully engaged as donor and acceptor in hydrogen bonding and the rotameric conformation of the hydroxymethyl group of 1 is fixed in the tg form.     

A Second Gene for Cerulean Cataracts Maps to the β Crystallin Region on Chromosome 22

Congenital cataracts are one of the most common major eye abnormalities and often lead to blindness in infants. At least a third of all cases are familial. Within this group, highly penetrant, autosomal dominant forms of congenital cataracts (ADCC) are most common. ADCC is a genetically heterogeneous group of disorders, in which at least eight different loci have been identified for nine clinically distinct forms. Among these, Armitageet al.(Nature Genet.9: 37–40, 1995) mapped a gene for cerulean blue cataracts to chromosome 17q24. Bodkeret al.(Am. J. Med. Genet.37: 54–59, 1990) described a large family with cerulean blue cataracts, in which the affected daughter of affected first cousins was presumed to be homozygous for the purported gene. We report linkage in this family to the region on chromosome 22q that includes two β crystallin genes (CRYBB2, CRYBB3) and one pseudogene (CRYBB2P1). The affected female in question is homozygous at all markers.     

Polymorphic Admixture Typing in Human Ethnic Populations

A panel of 257 RFLP loci was selected on the basis of high heterozygosity in Caucasian DNA surveys and equivalent spacing throughout the human genome. Probes from each locus were used in a Southern blot survey of allele frequency distribution for four human ethnic groups: Caucasian, African American, Asian (Chinese), and American Indian (Cheyenne). Nearly all RFLP loci were polymorphic in each group, albeit with a broad range of differing allele frequencies (δ). The distribution of frequency differences (δ values) was used for three purposes: (1) to provide estimates for genetic distance (differentiation) among these ethnic groups, (2) to revisit with a large data set the proportion of human genetic variation attributable to differentiation within ethnic groups, and (3) to identify loci with high δ values between recently admixed populations of use in mapping by admixture linkage disequilibrium (MALD). Although most markers display significant allele frequency differences between ethnic groups, the overall genetic distances between ethnic groups were small (.066–.098), and <10% of the measured overall molecular genetic diversity in these human samples can be attributed to “racial” differentiation. The median δ values for pairwise comparisons between groups fell between .15 and .20, permitting identification of highly informative RFLP loci for MALD disease association studies.