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Biomedical subjects

M E Baker

Publications and source records attributed to M E Baker.

At least 181 records · Page 10Linked to original sources
PubMed1984

Sperm motility on postcoital testing correlates with male autoimmunity to sperm.

To assess whether or not immunologic factors in husbands, wives, or both, influence the motility of sperm in the female reproductive tract, hemagglutination and cytotoxicity sperm antibody (Ab) assays and postcoital tests (PCTs) were performed in 293 infertile couples. More couples without male autoimmunity to sperm (64% of 66; P less than 0.001) had greater than or equal to 10 motile sperm per high power field (adequate PCT), as compared with 26% of 122 couples with untreated male autoimmunity, 19% of 77 couples with corticosteroid-treated male autoimmunity without a pregnancy, and 36% of 28 couples with successfully treated male autoimmunity to sperm. Good correlation was obtained among pregnancy achievement, lack of sperm antibodies, and adequate sperm motility in the PCT (P less than 0.0001). Sperm motility in the PCT correlated positively with sperm motility in the semen and inversely with cytotoxic sperm Ab in the serum and seminal plasma of men and women and hemagglutinating sperm Ab in the cervical mucus samples. Sperm motility in the PCT has a predictive value of 72% for male autoimmunity and 57% for female isoimmunity to sperm in the presence of normal cervical mucus and in the absence of infections.

Adrenal Cortex Hormones↗
PubMed1983

Diethylpyrocarbonate, a histidine selective reagent, inhibits progestin binding to chick oviduct cytosol.

In this report we describe experiments showing that diethylpyrocarbonate, a histidine selective reagent, inhibits progestin binding to the chick oviduct progesterone receptor. Because this inhibition is reversed by hydroxylamine, we suggest that the chick oviduct progesterone receptor contains one or more histidine residues that regulate progestin binding. We also find that the progestin R5020 protects the progesterone receptor from diethylpyrocarbonate mediated inhibition of progestin binding. From this we infer that the progestin binding site contains a histidine residue(s) important for progesterone binding to its receptor in chick oviduct.

Animals↗
PubMed1982

Inhibition of estrogen binding to rat alpha-fetoprotein by tryptophan p-nitrophenyl esters.

Rat alpha-fetoprotein (AFP) contains a site that both binds the protease substrate tryptophan methyl ester (TrpOMe) and influences estrogen binding. We have studied the effect of changing the amino acid and ester portions of this compound on its binding to AFP, as measured by the ability of the ester to inhibit binding of [3H]-estrone to AFP. We find that: (1) AFP binds tryptophan esters better than phenylalanine or tyrosine esters, (2) substitution of butyl or benzyl for the methyl group in TrpOMe increases binding for AFP by 30- to 100-fold, (3) substitution of p-nitrophenol at the ester position increases binding for AFP by 10(5), (4) p-nitrophenyl substitution in the ester position of tyrosine or phenylalanine methyl ester increases the affinity for AFP by 10(3) to 10(4), (5) inhibition of estrogen binding to AFP by tryptophan p-nitrophenyl esters is reversible and competitive, and (6) the hydrolysis products of tryptophan p-nitrophenyl ester are ineffective in inhibiting estrogen binding to AFP. Based on these results, we suggest that AFP contains a tryptophan ester recognition site which binds p-nitrophenyl esters with high affinity and influences estrogen binding. The ester binding site may be located spatially near the estrogen binding site.

Animals↗
PubMed1980

Binding of the chymotrypsin substrate, tryptophan methyl ester, by rat alpha-fetoprotein.

We studied how tryptophan methyl ester and related compounds inhibit binding of estrone to rat alpha-fetoprotein and find that: (a) like chymotrypsin, alpha-fetoprotein binds tryptophan esters with higher affinity than tryptophan or its amides; (b) the affinity of alpha-fetoprotein for tryptophan methyl ester is 3.7 . 10(-4) M, which is close to the affinity of chymotrypsin (10(-4) M); (c) alpha-fetoprotein binding of tryptophan methyl ester is stereoselective and pH dependent. All of these observations suggest that there is a specific interaction between alpha-fetoprotein and the chymotrypsin substrate, tryptophan methyl ester, and that rat alpha-fetoprotein contains a site with some structural similarities to the catalytic site in chymotrypsin. Since we also find that tryptophan methyl ester is a competitive inhibitor of estrone binding to alpha-fetoprotein, it is possible that the protease substrate binding site on alpha-fetoprotein is spatially close to the estrone binding site.

Animals↗
PubMed1978

Inhibition by protease inhibitors of binding of adrenal and sex steroid hormones.

Binding of steroid hormones is inhibited by protease inhibitors and substrates. The protease inhibitors phenylmethyl sulphonylfluoride, tosyl-lysine chloromethyl ketone, and tosylamide-phenylethyl-chloromethyl ketone and the protease substrates tosyl arginine methyl ester and tryptophan methyl ester eliminate specific binding of aldosterone, dexamethasone, dihydrotestosterone, estrogen, and progesterone to their respective receptors. These protease inhibitors and substrates also inhibit binding of progesterone to the 20,000 molecular weight mero-receptor formed from the progesterone receptor in chick oviduct. The binding of estradiol to rat alpha-fetoprotein is inhibited by the protease inhibitors and substrates but not by tryptophan or tryptophan amide, indicating the importance of an ester structure in the inhibition of steroid binding. Our results suggest that all steroid hormone receptors have a site with both common structural features and a role in the regulation of steroid hormone binding.

Aldosterone↗
PubMed1976

Proposed role of the alpha subunit of the 7 S nerve growth factor protein: implications for the regulation of NGF activity.

Four electrophoretically distinct alpha subunits can be isolated from mouse 7 S nerve growth factor protein (7 S NGF). It is proposed that each alpha subunit confers on its 7 S NGF species a different dissociation constant, and that the heterogeneity in dissociation constants of the different 7 S NGF species provide a mechanism for regulating the structure of betaNGF. A hypothesis that the different betaNGF structures have altered receptor affinities and/or physiological properties which can functionally differentiate NGF activity is also presented.

Nerve Growth Factors↗
PubMed1975

Molecular weight and structure of 7 S nerve growth factor protein.

The molecular weight of 7 S nerve growth factor has been studied in the analytical ultracentrifuge between pH values 6.8 and 7.8. At pH 6.8, where no dissociation is observed, the molecular weight was found to be 137,000 plus and minus 7,000. Between pH values 7.4 and 7.8 there is some dissociation. Using the data from this study and results in the literature, a model of 7 S nerve growth factor, (alpha beta gamma)2, in reversible equilibrium with a subunit complex, (alpha beta gamma), is proposed.

Hydrogen-Ion Concentration↗