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J L Thomas

Publications and source records attributed to J L Thomas.

At least 109 records · Page 6Linked to original sources
PubMed1989

Generation of a helper cell line for packaging avian leukosis virus-based vectors.

We constructed an avian leukosis virus-based packaging cell line, pHF-g, containing Rous-associated virus DNA with several alterations to abolish RNA packaging. One of them is a 52-base-pair deletion encompassing the putative encapsidation signal in the leader region. The 3' long terminal repeat was also removed and replaced by the polyadenylation sequence from the herpes simplex virus thymidine kinase gene. When pHF-g cells were transfected by an avian leukosis virus-based vector, they produced replication-defective virus at high titer but they did not release any replication-competent particles. Proviral DNA was shown to be correctly integrated as well as correctly expressed. Viral RNAs were shown to be correctly translated into gag-related polypeptides.

Animals↗
PubMed1989

Full length cDNA structure and deduced amino acid sequence of human 3 beta-hydroxy-5-ene steroid dehydrogenase.

Polyclonal antibodies raised against 3 beta-hydroxysteroid dehydrogenase isolated from human placenta were used to screen a lambda gt11 expression cDNA library from the same tissue. The protein deduced from cDNA sequences contains 372 amino acids with a calculated mol wt of 42,216. Since 3 beta-hydroxysteroid dehydrogenase is the enzyme catalyzing the formation of all classes of hormonal steroids, the availability of the cDNA encoding this enzyme opens new possibilities for a detailed investigation of the factors regulating the expression and activity of this crucial enzyme in adrenal, gonadal as well as peripheral tissues.

3-Hydroxysteroid Dehydrogenases↗
PubMed1989

Gender and perceptions of grandparenthood.

Grandparents (N = 301) were interviewed concerning their relationship with one grandchild; topics included the meaning of the relationship, responsibility toward the grandchild, and satisfaction with the relationship. Grandparent gender by grandchild gender by maternal/paternal grandparent MANOVA's revealed no differences in the relationships associated with grandchild gender or with maternal/paternal grandparent status; nor were there significant interaction effects. Grandmothers expressed greater satisfaction than did grandfathers; grandfathers stressed family extension through grandchildren and the pleasures of indulging grandchildren to a greater extent than did grandmothers. These gender differences may reflect personality development in adulthood and the cultural context of the research.

Adult↗
PubMed1989

Behavioral factors related to elderly alcohol abuse: research and policy issues.

Although researchers have provided valuable descriptions of samples of older problem drinkers and have discussed possible causes of and treatments for alcohol abuse among the aged, important questions remain. Risk factors associated with the onset of alcohol abuse in later life have not yet been clearly identified. Practitioners and researchers serving this population in the future will require a comprehensive understanding of the characteristics and needs of older clients experiencing alcohol-related problems. This paper reviews the existing literature with regard to elderly alcohol abuse and outlines future directions for research activity.

Aged↗
PubMed1988

Human placental 3 beta-hydroxy-5-ene-steroid dehydrogenase and steroid 5----4-ene-isomerase: purification from microsomes, substrate kinetics, and inhibition by product steroids.

In human pregnancy, placental 3 beta-hydroxy-5-ene-steroid dehydrogenase and steroid 5----4-ene-isomerase produce progesterone from pregnenolone and metabolize fetal dehydroepiandrosterone sulfate to androstenedione, an estrogen precursor. The enzyme complex was solubilized from human placental microsomes using the anionic detergent, sodium cholate. Purification (500-fold, 3.9% yield) was achieved by ion exchange chromatography (Fractogel-TSK DEAE 650-S) followed by hydroxylapatite chromatography (Bio-Gel HT). The purified enzyme was detected as a single protein band in sodium dodecylsulfate-polyacrylamide gel electrophoresis (monomeric Mr = 19,000). Fractionation by gel filtration chromatography at constant specific enzyme activity supported enzyme homogeneity and determined the molecular mass (Mr = 76,000). The dehydrogenase and isomerase activities copurified. Kinetic constants were determined at pH 7.4, 37 degrees C for the oxidation of pregnenolone (Km = 1.9 microM, Vmax = 32.6 nmol/min/mg) and dehydroepiandrosterone (Km = 2.8 microM, Vmax = 32.0 nmol/min/mg) and for the isomerization of 5-pregnene-3,20-dione (Km = 9.7 microM, Vmax = 618.3 nmol/min/mg) and 5-androstene-3,17-dione (Km = 23.7 microM, Vmax = 625.7 nmol/min/mg). Mixed substrate analyses showed that the dehydrogenase and isomerase reactions use the appropriate pregnene and androstene steroids as alternative, competitive substrates. Dixon analyses demonstrated competitive inhibition of the oxidation of pregnenolone and dehydroepiandrosterone by both product steroids, progesterone and androstenedione. The enzyme has a 3-fold higher affinity for androstenedione than for progesterone as an inhibitor of dehydrogenase activity. Based on these competitive patterns of substrate utilization and product inhibition, the pregnene and androstene activities of 3 beta-hydroxy-5-ene-steroid dehydrogenase and steroid 5----4-ene-isomerase may be expressed at a single catalytic site on one protein in human placenta.

3-Hydroxysteroid Dehydrogenases↗
PubMed1988

Predictors of satisfaction with children's help for younger and older elderly parents.

In structured interviews, parents aged 60 to 90 described their children's work and family responsibilities, the practical and affective support they exchanged with each of their children, their satisfaction with assistance received from their children, and their values regarding family relationships. Self-reported general health, proximity values, and kin-orientation values predicted satisfaction with children's help for the total sample. For parents aged 74 and younger, proximity values, reciprocity in help exchanges, number of children helping relatives other than the participant, and number of children working outside of the home predicted satisfaction; for parents aged 75 and older, self-reported general health and kin-orientation values predicted satisfaction. It is concluded that values regarding families, interdependence, and autonomy provide a critical context for reactions to help by adult children.

Age Factors↗
PubMed1987

A modified digitonin-precipitation radioassay for 3 beta-hydroxy-delta 5-steroid dehydrogenase.

An improved digitonin-precipitation radioassay for 3 beta-hydroxy-delta 5-steroid dehydrogenase is presented. It is linear for enzyme protein concentrations up to 0.6 mg and for 37 degrees C incubation times up to 10 min. Sensitivity and reproducibility are improved nine- and sevenfold, respectively, over the method of Philpott and Peron. There is a good correlation with the Philpott and Peron assay (r = 0.958) and with a thin-layer chromatography method (r = 0.997). Beyond being faster, simpler, and more sensitive than other analyses, this radioassay uses one-tenth the quantity of [3H]pregnenolone substrate and is, therefore, a safer and less expensive procedure.

3-Hydroxysteroid Dehydrogenases↗
PubMed1987

Lack of linkage between HLA and multiple endocrine neoplasia type 2 in a French family.

In this study, linkage between HLA and a dominant gene determining multiple endocrine neoplasia type 2 (MEN 2) in a large pedigree was investigated. All lod scores for recombination fractions ranging from 0 to 0.45 were negative. If we pool data from our family and the families studied by Jackson et al. (1976) and Simpson & Falk (1982), a link between HLA and the locus for MEN 2 can be excluded. Linkage studies with various markers and pooled data should be pursued to permit detection of high risk individuals and to identify a genetic defect.

Genetic Linkage↗
PubMed1987

[Ultrastructural analysis of anionic sites of the basal membrane of the seminiferous tubules of subjects with severe oligospermia].

Several morphological alterations of the basement membrane of the seminiferous tubules have been reported in the patients presenting with a testicular sterility. The proteoglycans are one of the major components of the basal membrane and may be ultrastructurally defined by the use of the cationic marker polyethyleneimine (PEI). In comparaison to the normal distribution of the anionic sites labelled by PEI which is characterized by a regular pattern of distribution along both the epithelial and the interstitial faces of the lamina densa, the pattern of distribution of the sites is largely altered in 6 patients, 27 to 40 years of age, with oligo- or azoospermia. Several types of alterations are reported: parallel thickening of the lamina densa with an abnormal distribution of the anionic sites inside the lamina densa, stratifications of the basal membrane depressing the seminiferous epithelium with anionic sites labelled on both faces of the lamina densa-like layers, massive expansions of the lamina densa with either a regularly circumferential labelling of the sites or a random type of distribution. The digestion of the sites by the enzyme heparitinase is highly suggestive of the presence of proteo-heparan-sulfate. The analysis of the distribution of the anionic sites may represent a usefull tool for studying the pathogenesis of testicular sterility.

Adult↗
PubMed1986

The affinity alkylators, 11 alpha-bromoacetoxyprogesterone and estrone 3-bromoacetate, modify a common histidyl residue in the active site of human placental 17 beta,20 alpha-hydroxysteroid dehydrogenase.

Purified human placental 17 beta,20 alpha-hydroxysteroid dehydrogenase (native enzyme) was completely inactivated by the affinity alkylator, estrone 3-bromoacetate, in the presence of cofactor (NADPH). The inactivated enzyme was reactivated to 100% activity by base-catalyzed hydrolysis of the steroidal ester-enzyme conjugate and then repurified by dialysis. Control enzyme in mixtures which contained estrone in place of alkylator was treated the same as the reactivated enzyme. 11 alpha-Bromo[2'-14C]acetoxyprogesterone, an active site-directed affinity alkylator of the enzyme, produced 5.0-fold less radiolabeled 3-(carboxymethyl)histidine and S-(carboxymethyl)cysteine plus 1.4-fold more 1,3-bis(carboxymethyl)-histidine in the reactivated enzyme than in the control enzyme. The lesser amount of S-(carboxymethyl)cysteine and greater amount of 1,3-bis(carboxymethyl)histidine resulted from nonspecific interactions between the reactivated enzyme and the progestin radioalkylator. The nonradiolabeled 3-(carboxymethyl)histidine originally produced by estrone 3-bromoacetate in the enzyme active site hindered radioalkylation of this amino acid by 11 alpha-bromo[2'-14C]acetoxyprogesterone to yield 5-fold less radiolabeled 3-(carboxymethyl)histidine in the reactivated enzyme relative to control enzyme. Thus, the estrogen and progestin affinity alkylators modified a common histidyl residue in the active site. These studies are direct evidence that the estradiol 17 beta-dehydrogenase and 20 alpha-hydroxysteroid dehydrogenase activities reside at a common locus on a single protein.

Alkylation↗
PubMed1986

3 beta-Hydroxysteroid dehydrogenase in human placental microsomes and mitochondria: co-solubilization of androstene and pregnene activities.

3 beta-Hydroxysteroid dehydrogenase (3 beta-HSD) was solubilized from human term-placental microsomes and mitochondria using the non-ionic detergent, polyoxyethylene 20 cetyl ether (BrijR-58). Electron photomicrographs showed microsomes and mitochondria well disrupted by the detergent. The pregnene (C-21) and androstene (C-19) activities co-solubilized over a range (0.04-0.44) of BrijR-58/protein (B/P) concentration ratios (w/w). Optimal solubilization of the C-19 and C-21 activities were 63.3 +/- 2.6% (mean +/- SEM) from mitochondria (B/P ratio 0.37) and 71.8 +/- 2.1% from microsomes (B/P ratio 0.34). Detergent treatment of microsomes and mitochondria--varying time (5-90 min, pH 7.4) or varying pH (6.0-7.8, 90 min)--yielded C-19 activities identical with C-21 activities. The C-21/C-19 specific activity ratios of 3 beta-HSD in particulate, solubilized and chromatographed preparations were 2.28 +/- 0.16 (mean +/- SEM) for mitochondria and 1.97 +/- 0.07 for microsomes. 3 beta-HSD molecular weight estimates were 208,000 (microsomes) and 220,000 (mitochondria). These studies argue that a single protein is responsible for both the C-19 and C-21 activities of 3 beta-HSD and that this protein is the same in microsomes and mitochondria.

3-Hydroxysteroid Dehydrogenases↗
PubMed1986

Gender differences in satisfaction with grandparenting.

Grandmothers (n = 177) and grandfathers (n = 105) completed mail questionnaires covering demographic and family background, and grandparenting satisfaction and perceived responsibilities (disciplining, caretaking, helping, advising). Grandmothers' satisfaction scores significantly exceeded those of grandfathers, and different variables predicted men's and women's satisfaction scores. Discussion focuses on possible sources of these gender differences, and consequences of these differences for further research.

Aged↗
PubMed1986

Age and sex differences in perceptions of grandparenting.

This study considered age and sex differences in grandparenting satisfaction and in perceived grandparenting responsibilities. Two hundred seventy-seven grandparents in three age groups (45 to 60, 61 to 69, 70 to 90) completed measures of perceptions of grandparenting experience. An Age group X Sex multivariate analysis of variance indicated that younger grandparents expressed greater responsibility for disciplining, caretaking, and offering childrearing advice. Grandfathers also expressed greater responsibilities for caretaking and offering childrearing advice, but less satisfaction with grandparenting. When number of grandchildren and grandchildren's ages were statistically controlled, younger grandparents and grandfathers expressed greater responsibility for offering childrearing advice; grandfathers also expressed greater responsibility for caretaking but less satisfaction with grandparenting. Findings are discussed with respect to possible developmental changes in grandparenting and cohort differences in perceptions of grandparenting.

Aged↗
PubMed1986

[Treatment of thyroid ophthalmopathies by external orbital radiotherapy].

From January, 1977, through December 1983, 62 patients with thyroid edematous ophthalmopathy were given external orbital radiotherapy according to S.S. Donaldson's technique: 5,5 MV photons produced by a linear accelerator were used to irradiate the muscular conus, with a total of 20 grays in 10 sessions over 2 weeks. Good results were obtained in 46 patients (77%). This simple therapy may be a first choice in recent ophthalmopathy.

Adult↗
PubMed1985

Reactivation of human placental 17 beta,20 alpha-hydroxysteroid dehydrogenase affinity alkylated by estrone 3-(bromoacetate): topographic studies with 16 alpha-(bromoacetoxy)estradiol 3-(methyl ether).

Estradiol 17 beta-dehydrogenase and 20 alpha-hydroxysteroid dehydrogenase, oxidoreductase activities copurified from the cytosol of human-term placenta as a homogeneous protein (native enzyme), were reactivated at equal rates to 100% activity following complete inactivation in the presence of cofactor (NADPH) with the affinity alkylator estrone 3-(bromoacetate). Reactivation was accomplished by base-catalyzed hydrolysis of steroidal ester-amino acid linkages in the enzyme active site. The rate of enzyme reactivation was pH dependent. In identical studies without NADPH, only 12% of the original enzyme activity was restored. Completely reactivated enzyme was repurified by dialysis. Enzyme in control mixtures (control enzyme) that contained estrone in place of alkylator was treated the same as the reactivated enzyme. Reactivated enzyme exhibited a 6.0-fold lower affinity for common substrates, a 1.8-fold lesser affinity for NAD+ and NADH, and the same affinity for NADP+ and NADPH compared to control enzyme. In incubations that included NADPH, the reactivated enzyme maintained full activity during a 20-h second exposure to estrone 3-(bromoacetate), but in identical incubations without NADPH, the reactivated enzyme was rapidly inactivated at the same rate as the control and native enzymes. The control and reactivated enzymes were inactivated at equal rates by 16 alpha-(bromoacetoxy)estradiol 3-(methyl ether) in the presence or absence of cofactor (NADP+) and exhibited similar Kitz and Wilson inhibition constants for this affinity alkylator. Estrone 3-(bromo[2'-14C]acetate) incubated with native enzyme and NADPH produced radiolabeled 3-(carboxymethyl)histidine and S-(carboxymethyl)cysteine.(ABSTRACT TRUNCATED AT 250 WORDS)

17-Hydroxysteroid Dehydrogenases↗
PubMed1985

Visual memory: adult age differences in map recall and learning strategies.

Age differences in two aspects of map learning performance were examined: the amounts of material recalled and the reported learning strategies of young, middle-aged, and elderly adults were compared. Thirty women in each age group (mean ages 21, 43, and 69) learned three groups of eight landmarks on a single street map. Subjects learned one group of landmarks in each of three trial blocks; cumulative retention tests followed learning of each group of landmarks. After the session, subjects described their learning strategies. The age groups differed significantly in mean numbers of landmarks recalled; although age groups also differed significantly in the types of strategies reportedly used, the age group difference in reported learning strategy type did not account for the age group difference in recall performance. It was concluded that the age difference in map learning performance reflected either an age difference in ability or in reaction to the learning situation.

Adult↗