Nuclease-hypersensitive sites in chromatin of the estrogen-inducible apoVLDL II gene of chicken.

DNAseI-hypersensitive sites were localized in apoVLDL II chromatin from chicken. In the liver two sites at 1.75 and 1.0 kb upstream from the cap-site are present before the gene is activated. After induction by estradiol a number of additional sites appear, three in the promotor region of the gene, one within the coding region and two behind the poly-A signal. These sites disappear when the expression of the gene is shut off upon estradiol withdrawal. All sites appear to be tissue-specific in that they are not found in other tissues of the rooster. However, in oviduct of the laying hen we find a hypersensitive site at 1.6 kb in front of the gene.     

Alkaline and acid phosphatase demonstration in human bone and cartilage: effects of fixation interval and methacrylate embedments

Human bone and cartilage specimens were evaluated for acid and alkaline phosphatase localization following varying fixation periods for fresh or frozen tissue. Formalin fixations of up to 183 hr were followed by embedment in methyl methacrylate; frozen tissue was examined either without fixation or following fixation for up to 1 hr and subsequent glycol or methyl methacrylate embedding. The humeral epiphysis of a young patient with osteogenic sarcoma showed optimum acid and alkaline phosphatase localization following fixation for periods up to 15 hr and embedding in methyl methacrylate. Frozen costochondral junction from a newborn with osteogenesis imperfecta type II showed optimum acid and alkaline phosphatase localization following 30 min fixation in formalin and embedding in methyl methacrylate or after 5 min fixation and embedding in glycol methacrylate.     

Comparison of the organization and fine structure of a chicken and a Xenopus laevis vitellogenin gene

The structural organization and the coding nucleotide sequence of the Xenopus laevis A2 and the chicken major vitellogenin genes have been compared. Both genes show the same exon-intron organization. However, the degree of homology between the nucleotide and derived amino acid sequences varies extensively along the genes. Several of the 35 exons are quite similar, and a unique cysteine motif in the lipovitellin II domain is conserved between the two genes. In contrast, one internal region is quite divergent. Part of this region encodes phosvitin, which appears to have evolved rapidly by both point mutations and duplications of serines or short other amino acid stretches. On the basis of these observations, we discuss the possible mechanism of evolution of phosvitin in vertebrates.     

Purification and substrate specificity of BcmI restriction endonuclease

A strain producing the new specific restriction endonuclease BcmI has been found in the Bacillus generum. The enzyme has been purified by chromatography on the blue sepharose, phosphocellulose PII, heparin sepharose. The analogous purification has been obtained when the blue sepharose has been substituted for the orange sepharose, the home produced sorbent. The BcmI enzyme has been shown by the substrate specificity definition to be an isoschizomer of the restriction endonuclease ClaI.     

Conserved sequences and cell-specific DNase I hypersensitive sites upstream from the co-ordinately expressed alpha I- and alpha II-globin genes of Xenopus laevis

The globin gene family of Xenopus laevis comprises pairs of closely related genes that are arranged in two clusters, each pair of genes being co-ordinately and stage-specifically expressed. To get information on putative regulatory elements, we compared the DNA sequences and the chromatin conformation 5' to the co-ordinately expressed adult alpha-globin genes. Sequence analysis revealed a relatively conserved region from the cap site up to position -289, and further upstream seven distinct boxes of homology, separated by more diverged sequences or deletions/insertions. The homology boxes comprise 22 to 194 base-pairs showing 78 to 95% homology. Analysis of chromatin conformation showed that DNase I preferentially cuts the upstream region of both genes at similar positions, 5' to the T-A-T-A and the C-C-A-A-T boxes, only in chromatin of adult erythroblasts and erythrocytes, where adult globin genes are expressed, but not in chromatin of adult liver cells or larval erythrocytes, where these genes are silent. This suggests that cell- and stage-specific activation of these genes coincides with specific changes in chromatin conformation within the proximal upstream region. No difference was found in the nucleotide sequence within the DNase I hypersensitive region proximal to the adult alpha 1-globin gene in DNA from embryonic cells, in which this gene is inactive, and adult erythrocytes, expressing this gene.     

Increased oxygen consumption associated with breathing activity in fetal lambs

To examine the relationship between fetal O2 consumption and fetal breathing movements, we measured O2 consumption, umbilical blood flow, and cardiovascular and blood gas data before, during, and after fetal breathing movements in conscious chronically catheterized fetal lambs. During fetal breathing movements, O2 consumption increased by 30% from a control value of 7.7 +/- 0.7 (SE) ml X min-1 X kg-1. Umbilical blood flow was 210 +/- 21 ml X min-1 X kg-1 before fetal breathing movements; in 9 of 16 samples it increased by 52 +/- 12 ml X min-1 X kg-1, while in the other 7 it decreased by 23 +/- 9 ml X min-1 X kg-1. Umbilical arterial and venous O2 partial pressures and pH fell during fetal breathing movements, and the fall was greater when umbilical blood flow was decreased. Partial CO2 pressure rose in both vessels, and again the increase was greatest when umbilical blood flow fell during fetal breathing movements. Also associated with a fall in umbilical blood flow was the transition from low-amplitude irregular to large-amplitude regular fetal breathing movements. It is concluded that fetal breathing movements increase fetal O2 demands and are associated with a transient deterioration in fetal blood gas status, which is most severe during large-amplitude breathing movements.     

A correlative ultrastructural and enzymatic study of cotyledonary microbodies following germination of fat-storing seeds

Summary Sunflower, cucumber, and tomato cotyledons, which contain microbodies in both the early lipid-degrading and the later photosynthetic stages of post-germinative growth, were processed for electron microscopy according to conventional procedures and examined 1, 4 and 7 days after germination. Homogenates of sunflower cotyledons were assayed for enzymes characteristic of glyoxysomes and leaf peroxisomes (both of which are defined morphologically as microbodies) at stages corresponding to the fixations for electron microscopy. The particulate nature of these enzymes was demonstrated by differential and equilibrium density centrifugation, making it possible to relate them to the microbodies seen in situ.One day after germination, the microbodies are present as small organelles among large numbers of protein and lipid storage bodies; the cell homogenate contains catalase but no detectable isocitrate lyase (characteristic of glyoxysomes) or glycolic acid oxidase (characteristic of leaf peroxisomes). 4 days after germination, numerous microbodies (glyoxysomes) are in extensive and frequent contact with lipid bodies. The microbodies often have cytoplasmic invaginations. At this stage the cells are rapidly converting lipids to carbohydrates, and the homogenate has high isocitrate lyase activity. 7 days after germination, microbodies (peroxisomes) are appressed to chloroplasts and frequently squeezed between them in the green photosynthetic cells. The homogenate at this stage has substantial glycolic acid oxidase activity but a reduced level of isocitrate lyase. It is yet to be determined whether the peroxisomes present at day 7 are derived from preexisting glyoxysomes or arise as a separate population of organelles.     

Effect of estradiol on the RNA content and the activity of nucleolar RNA polymerase from rooster liver

Estradiol administration to roosters results in changes in the macromolecular composition of the liver. Besides a gradual increase in liver protein and a sudden enhancement of liver DNA after 24 hours, the most pronounced change occurs in the RNA content, viz. an increase up to 190% of controls starting 26 hours after estradiol administration.The activity of nucleolar RNA polymerase -solubilized and chromatographed on DEAE-Sephadex- is increased four-fold 26 hours after estradiol treatment. This increase was found to be due to an increased initiation frequency. Concurrently, the initiation characteristics of nucleolar RNA polymerase are changed.     

Selective inhibition of prostaglandin biosynthesis by gold salts and phenylbutazone

Gold salts and phenylbutazone selectively inhibit the synthesis of PGF_2α and PGE₂ respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE₂ and PGF_2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action in vivo and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function.