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Biomedical subjects

D J Lamb

Publications and source records attributed to D J Lamb.

At least 127 records · Page 7Linked to original sources
PubMed1986

Evidence for a single steroid-binding protein in the rabbit progesterone receptor.

The rabbit uterine progesterone receptor copurifies as two molecular weight (Mr) forms of about 105,000 and 78,000. To investigate whether these are different proteins, we have used protease digestion, reversible denaturation, and photoaffinity labeling in studies on the steroid-binding domain of the receptor. Digestion of the Mr 105,000 and 78,000 forms, photoaffinity labeled with [3H]R5020, with Staphylococcus aureus V8 protease revealed identical peptide fragments of Mr 43,000, 39,000, and 27,000-30,000. When receptor in cytosol was denatured, separated by electrophoresis, and then reconstituted, [3H]progesterone bound specifically to a single form at about Mr 105,000. After partial purification, the reversible denaturation procedure revealed both the larger and the smaller progesterone-binding species similar to the photoaffinity-labeled species in this preparation. Receptor in uterine cytosol prepared under mild conditions appeared as a predominant large molecular weight form on photoaffinity labeling with [17 alpha-methyl-3H]R5020, [6,7-3H]R5020, or [3H]RU27987. Further purification of this cytosol showed the generation of a smaller labeled species. These results from three different approaches reinforce the view that the rabbit progesterone receptor contains a single steroid-binding protein.

Animals↗
PubMed1985

The fracture topography of acrylic dentures broken in service.

The fracture surfaces of full dentures that failed in service, and others broken under controlled conditions, have been examined using scanning electron microscopy. The results allow the direction of crack propagation to be deduced and indicate that brittle impact is the predominant mode of fracture. Improvements in the strength of the denture tooth/denture base bond may be the most effective means of achieving an increase in the strength of full dentures.

Acrylic Resins↗
PubMed1984

An investigation of the role of true hypha production in the pathogenesis of experimental oral candidosis.

From 427 cases of human oral candidosis 2135 yeast clones were screened for the presence of germ tube-negative C. albicans and variants that formed only pseudohyphae in serum; one strain of each was found. The pathogenic potential of the serum-pseudohyphal and germ tube-negative C. albicans variants was investigated in the oral cavity of the rat; both variants failed to induce palatal candidosis, in contrast to a germ tube-positive C. albicans control strain. The pathogenic potential of C. albicans strains appears to be dependent on the formation of true germ tubes.

Animals↗
PubMed1984

Heterogeneous deoxyribonucleic acid-binding forms of rabbit uterine progesterone receptor.

This study investigated the subunit structure of the rabbit uterine progesterone receptor (PR) using ion-exchange and DNA-cellulose chromatography. The mol wts of receptor were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after photoaffinity labeling the receptors with the progestin [3H]R5020. Cytosols were labeled with [3H]progesterone or 17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione [( 3H]R5020) and chromatographed on DE-52 cellulose. Greater than 80% of the PR bound to DE-52 and elution with a KCl gradient gave two peaks of activity at 50-75 mM (peak I) and at 125-200 mM KCl (peak II). Chromatography on QAE-Sephadex also separated two peaks. Peak I was abolished by addition of molybdate, or by passage over phosphocellulose. All (greater than 80%) of the PR from peaks I and II bound to DNA-cellulose and eluted as a single, symmetrical peak at 0.29 M KCl in both cases. Peak I could not be directly generated from peak II by exposure to salt or by ammonium sulfate precipitation. After peak II receptor had been bound and eluted from a DNA-cellulose column, however, it eluted subsequently from QAE as peak I. Photoaffinity labeling of peak I and peak II with [3H] R5020 in the presence of 10 microM cortisol revealed two proteins in each peak with mol wt of 102,000 and 78,000 (n = 13). Both mol wt forms were present in the DNA-eluates both of peak I and peak II. The [3H]R5020 binding to these mol wt forms could be completely displaced under exchange conditions with 10 nM progesterone or R5020. Deoxycorticosterone, dihydrotestosterone, and estradiol were nearly ineffective competitors at 10 nM. Without phosphocellulose chromatography before chromatography on DE-52 and DNA-cellulose, numerous receptor fragments were found. Fragments containing both steroid- and DNA-binding domains were found at 102,000, 78,000, 54-60,000, 43,000, 33-34,000, and 21,000, suggesting proteolysis. This proteolytic activity was removed by passage over phosphocellulose. The rabbit uterine PR contains at least two major proteins of 78,000 and 102,000 mol wt which cannot be distinguished on the basis of their ionic or DNA-binding characteristics or steroid-binding specificity.

Animals↗
PubMed1983

Hydrophobic interaction chromatography of the rabbit uterine progesterone receptor.

The chromatographic behavior of the rabbit uterine progesterone receptor interaction on several different hydrophobic matrices was characterized. Receptor, prepared in 0.6 M NaCl, exhibited a progressive retardation of elution, followed by retention, on a series of alkyl agarose columns as the length of the alkyl chain [(CH2)nH-] increased (n = 0-10), reflecting the presence of hydrophobic regions on the protein. Adsorption did not occur directly at the steroid binding site of the molecule and did not require activation to the DNA-binding form. Elution could be achieved by a decrease in the ionic strength of the buffer or the addition of glycerol, resulting in partial purification of receptor. Receptor bound tightly to phenyl agarose, although elution of the receptor under mild conditions (decreasing salt gradient, increasing glycerol gradient) resulted in poor yield and only modest purification. Passage of the non-activated progesterone receptor over Reactive Blue Sepharose effectively removed albumin, presumably by a hydrophobic interaction, although receptor was not retained. In the activated form, approximately 25% of receptor was bound to Reactive Blue Sepharose, reflecting an interaction of the Cibacron Blue dye with the polynucleotide binding site of the receptor. Hydrophobic chromatography may be an important adjunct to methods for purification of the progesterone receptor.

Animals↗
PubMed1983

An in vitro and in vivo study of the effect of incorporation of chlorhexidine into autopolymerizing acrylic resin plates upon the growth of Candida albicans.

Chlorhexidine acetate was incorporated into autopolymerizing acrylic resin and, after studying its ability to diffuse out in vitro, an investigation was made into the potential of the mixture to treat palatal candidosis in the rat. Chlorhexidine was found to diffuse out of acrylic in fungicidal concentrations for up to three weeks when mixed with the acrylic powder in the proportion of 7.5% (w/w). At this concentration it was found that palatal candidosis as produced by the technique of Shakir et al. was cured or prevented. However, rats fitted with chlorhexidine supplemented plates were found not to take sufficient food during the experimental period to maintain their body weight.

Acrylic Resins↗
PubMed1982

Specificity and nature of the rapid steroid-stimulated increase in Sertoli cell nuclear RNA polymerase activity.

This report explores the ability of various steroids to rapidly stimulate Sertoli cell RNA polymerase II activity and to compete with [3H]-androgens for nuclear and cytosol binding sites. Nuclear RNA polymerase II activity was significantly stimulated by a 1 nM concentration of the androgenic compounds testosterone, dihydrotestosterone (17 beta-hydroxy-5 alpha-androstan-3-one). R1881 (methyltrienolone) and 5 alpha, 17 beta-diol and also by the potent progestins 6 alpha methylprogesterone and R5020 (17,21-dimethyl-19-nor-4-pregna-3,20-dione). Progesterone, 17 alpha-hydroxyprogesterone, estradiol, androsterone, and 5 alpha-androstan-3 beta, 17 beta-diol were ineffective at 1 nM. Cytosol binding and nuclear accumulation of [3H]-androgen was effectively reduced by 100 fold molar excess of those androgens and progestins which stimulated RNA polymerase II activity. These data suggest that androgens and progestins bind to at least some of the same proteins in the Sertoli cell and may elicit the rapid stimulation of RNA polymerase II activity via a common mechanism. Agarose gel electrophoresis of the nuclear RNA synthesized as a result of exposure to testosterone indicated that is was heterodisperse and in part polyadenylated. Electrophoresis of the poly A+-RNA demonstrated that testosterone administration increased the incorporation of [3H]-UTP into RNA that was larger than 28 S.

Androgens↗
PubMed1982

Characterization of Sertoli cell RNA synthetic activities in vitro at selected times during sexual maturation.

In this study, Sertoli cell RNA synthetic activity in vitro was characterized at selected times during sexual maturation. Sertoli cells, isolated from rat testes undergoing the first wave of spermatogenesis and placed in culture for 4 days, exhibited 2-fold increases in soluble ribonucleotide pools and in total RNA concentrations over the age span of 18-35 days. High performance liquid chromatographic analysis of the ribonucleotide pools in Sertoli cells cultured from 18- and 33- to 34-day-old rats revealed that, in addition to the overall age-related doubling of concentrations, uridine triphosphate (UTP) and cytidine triphosphate (CTP) pools were disproportionately increased 4- and 6-fold, respectively. In general, Sertoli cell contained relatively small amounts of UTP in comparison to several other cell types, but exhibited a high ADP:ATP ratio. A uniform 2-fold increase in the base composition of Sertoli cell RNA per mg DNA was observed over the age span of 18-35 days, with no preferential increase in any one specific nucleotide. There was no change in [3H]uridine incorporation (2 h) into RNA per cell (pmol/mg DNA), but decreased specific activity of the RNA (pmol/mg RNA) in Sertoli cells cultured from 35-day-old rats as compared to those from 18- to 19-day-old rats. Similar differences were noted in the specific activity of label incorporated into specific RNA bases. In contrast, the specific activity of the UTP-CTP soluble pool/mg DNA was only slightly increased. These data indicate that processes related to RNA synthesis in the Sertoli cell undergo a number of changes during the period of sexual maturation.

Animals↗