Effects of ethinyl estradiol on intestinal membrane structure and function in the rabbit

Structural and functional properties of the small intestinal microvillus membrane were evaluated in the rabbit after administration of ethinyl estradiol, a synthetic estrogen with a demonstrated propensity to alter hepatic membrane lipid fluidity, and promote cholestasis. In the jejunum, no estrogen-induced changes in microvillus membrane total lipid, cholesterol or phospholipid content were observed. However, the ileal microvillus membrane in estradiol-treated animals demonstrates significant reductions vs. controls (per mg protein) in total lipid (0.55 milligrams vs. 0.89 milligrams) [corrected] and phospholipid (206.7 micrograms vs. 304.91 micrograms) (p less than 0.001) content, as well as modifications in specific phospholipid species. The increase in the ileal microvillus membrane cholesterol: phospholipid molar ratio (0.65 vs. 0.51, p less than 0.05) was associated with a significant decrease in membrane lipid fluidity reflected by an increase in fluorescence anisotropy measurements utilizing diphenyl hexatriene as the fluorophore (r at 25 degrees C = 0.306 vs. 0.282, p less than 0.05). Thermotropic lipid phase transitions, assessed by Arrhenius plots of both fluorescence data and ileal microvillus membrane p-nitrophenylphosphatase activity demonstrate that phase changes occur between and 24 and 28 degrees C in both treated and untreated groups. Within the temperature range studied (40-10 degrees C) no differences from control were observed in microvillus membrane alkaline phosphatase activity following estrogen treatment. These data therefore indicate that ethinyl estradiol-induced effects on microvillus membrane lipid composition and physical properties occur predominantly in the ileum and appear to be related, in part, to specific alterations in the availability of phospholipid following estrogen treatment.     

Studies of cloned simian immunodeficiency virus-specific T lymphocytes. gag-specific cytotoxic T lymphocytes exhibit a restricted epitope specificity.

CD8+ CTL inhibit the replication of HIV and simian immunodeficiency virus of macaques (SIVmac) in PBL and, therefore, are likely to play an important role in containing the spread of the AIDS virus in infected individuals. We have generated a series of gag-specific lytic T lymphocyte clones from PBL: of an SIVmac-infected rhesus monkey. These T cell clones are CD3+CD8+ and are MHC class I-restricted in their target specificity. They are, therefore, CTL. Interestingly, all gag-specific CTL clones, as well as the gag-specific lytic activity of PBL of this monkey, demonstrated specificity for a single 25 amino acid fragment of the SIVmac gag protein. Moreover, they were restricted in their lytic function by a single MHC class I allele. These findings illustrate a powerful method for cloning AIDS virus-specific T lymphocytes and demonstrate a remarkably restricted epitope specificity of this AIDS virus-specific CTL response.     

Detection of a specific isoform of alpha-actinin with antisera directed against dystrophin

We have characterized a protein immunologically related to dystrophin, the protein product of the Duchenne muscular dystrophy gene. We identify this related protein as a fast-twitch glycolytic isoform (mouse extensor digitorum longus-specific) of myofibrillar alpha-actinin. This specific isoform of alpha-actinin exhibits a more restricted pattern of expression in skeletal muscle than fast-twitch-specific isoforms of both myosin and Ca2+-ATPase. Our results provide evidence that dystrophin and myofibrillar alpha-actinin are related proteins, reinforcing the previous data concerning the sequence homologies noted between nonmuscle cytoskeletal alpha-actinin and dystrophin. In addition, we describe the first antisera directed against a specific myofibrillar skeletal muscle isoform of alpha-actinin.     

Computer determination of perfusion patterns in pulmonary capillary networks

Hanger, Christopher C., Robert G. Presson, Jr., Osamu Okada,Steven J. Janke, John J. Watkins, Wiltz W. Wagner, Jr., and Ronald L. Capen. Computer determination of perfusion patterns in pulmonarycapillary networks. J. Appl. Physiol.82(4): 1283-1289, 1997.Individual pulmonary capillaries are notsteadily perfused. By using in vivo microscopy, it can readily bedemonstrated that perfusion continually switches between capillarysegments and between portions of the network within a single alveolarwall. These changes in capillary perfusion occur even when upstream pressure and flow are constant. Flow switching between capillary segments in the absence of hemodynamic changes in large upstream vessels suggests that capillary perfusion patterns could be random. Tocalculate the probability that perfusion patterns could occur bychance, it is necessary to know the total number of possible perfusionpatterns in a given capillary network. We developed a computer programthat can determine every possible perfusion pattern for any givencapillary network, and from that information we can calculate whetherperfusion of individual segments in the network is random. With theresults of the computer program, we have obtained statistical evidencethat some capillary segments in a network are nonrandomly perfused.

     

Secretion of neurophysins by the ovary in sheep

Measurements of venoarterial concentration differences across the ovary in anesthetized sheep have demonstrated that the ovary secretes ovine neurophysin I/II (oNP I/II) and that this process is stimulated by the prostaglandin F2 alpha analogue, cloprostenol. A parallel increase in the secretion of oxytocin (OT) was observed in response to cloprostenol, and the mean molar ratio of oNP I/II to OT secreted was 1.2. There was no detectable ovarian secretion of oNP III. Secretion of oNP I/II and OT was absent after hysterectomy. The data support other evidence indicating that the corpus luteum synthesizes OT, and confirm that the neurophysin associated with OT in the sheep is oNP I/II.     

Paleoecology of a low-diversity silurian community from the tofta beds of Gotland

The Silurian (Wenlockian) Tofta Beds at Galgberget 1, Gotland, Sweden, formed in a protected intertidal setting. Massive fenestral limestone at this locality contains a low diversity community dominated by stromatoporoids, calcareous algae, and ostracods, with less common rugose corals, bryozoans, brachiopods, and trilobites. Abundance of stromatoporoids, which form about 40% of sediment volume, suggests reef-like conditions. The Tofta community differs from typical Silurian reef communities, however, in its low diversity, very limited tiering, and absence of groups such as crionozoans and tabulates. These differences are possibly due to intertidal conditions which precluded upward growth of a mound structure and subjected the community to periodic desication.     

Effect of microsomal enzyme inducing agents on hepatic biotransformation in cotton rats (Sigmodon hispidus): comparison to that in Sprague-Dawley rats.

1. Activities of several biotransformation enzymes were determined in male and female Sigmodon hispidus. Benzphetamine N-demethylase and glutathione S-transferases toward 1-chloro-2,4-dinitrobenzene and sulfobromophthalein were higher in male Sigmodon hispidus than the female animals. 2. The study also determined the effect of microsomal enzyme inducing agents on hepatic biotransformation in male Sigmodon hispidus. 3. Cytochrome P-450 concentration was similar in cotton and Sprague-Dawley rats, and was increased after phenobarbital, pregnenolone-16 alpha-carbonitrile, or 3-methylcholanthrene treatment. 4. Benzphetamine N-demethylase was 4-fold higher in Sigmodon hispidus and was induced by 75-100% after phenobarbital. 5. UDP-Glucuronosyltransferase toward estrone, 1-naphthol, diethylstilbestrol and testosterone was 2- to 4-fold higher in cotton rats and was not altered by treatment with the inducing agents. 6. Conjugation of 1-chloro-2,4-dinitrobenzene, ethacrynic acid and sulfobromophthalein with glutathione was similar in both rodent species and was not inducible. 7. Sulfation of 2-naphthol was 15-30% of that in Sprague-Dawley rats and was not increased by inducer administration.     

The synthesis of DNA by DNA-membrane complexes from irradiated E. coli B/r and Bs-1: the role of the membrane.

DNA-membrane complexes were isolated from lysed E. coli B/r and Bs-1, either by low g forces from a low salt solution, or by high g forces through a discontinuous sucrose gradient. The latter method was more gentle. Irradiation of the intact bacteria had no effect on the membrane macromolecules or on RNA components of these complexes. DNA loss was not significant after irradiation under anoxic conditions but complexes isolated from from Bs-1 irradiated in air showed an appreciable decrease in DNA content. In the presence of the appropriate nucleotide mixture, both 'free' DNA, found in the supernatant fractions, and rapidly sedimented membrane-associated DNA were able to synthesize DNA in the absence of added polymerase. DNA synthesis associated with 'free' DNA was more sensitive to radiation than that associated with DNA bound to the membrane, which appeared to moderate the effects of radiation on new DNA synthesis. It is concluded that the depression of DNA synthesis is primarily a result of irradiation-induced changes on genome-DNA. The interpretation of earlier work from our laboratories that DNA-membrane complexes contained the macromolecular structure which responded to radiation with a high o.e.r. is not supported by the evidence in this work.