Search PubMed⌕ Search

Biomedical subjects

D D Smith

Publications and source records attributed to D D Smith.

158 records · Page 9Linked to original sources
PubMed1969

Endogenous encystment of Azotobacter vinelandii.

When young cells of Azotobacter vinelandii are impinged on membrane filters, washed free of carbon substrate, and placed on a mineral salts basal medium, the culture will proceed to encyst although at a slower rate than if n-butanol were supplied as a substrate. The endogenous cysts are depleted in polybeta-hydroxybutyrate and have a narrower intine but show an increased resistance to desiccation and are susceptible to lysis by chelating agents. Membrane-supported cells reveal details of the encystment process such as the formation of a zone within the capsule prior to exine formation and the early deposition of exine structures.

Azotobacter↗
PubMedDate not supplied

Stimulation of bone resorption and inhibition of bone formation in vitro by human tumour necrosis factors.

When leukocytes are exposed to mitogens or antigens in vitro, they release bone-resorbing activity into the culture supernatants which can be detected by bioassay. Like many lymphocyte-monocyte products, this activity has been difficult to purify because of its low abundance in activated leukocyte cultures and the unwieldy bioassay required to detect biological activity. Partially purified preparations of this activity inhibit bone collagen synthesis in organ cultures of fetal rat calvariae. Recent data suggest that both activated lymphocytes and monocytes release factors which could contribute to this activity. Recently, monocyte-derived tumour necrosis factor alpha (TNF-alpha) and lymphocyte-derived tumour necrosis factor beta (TNF-beta) (previously called lymphotoxin), two multifunctional cytokines which have similar cytotoxic effects on neoplastic cell lines, have been purified to homogeneity and their complementary DNAs cloned and expressed in Escherichia coli. As both of these cytokines are likely to be present in activated leukocyte supernatants, we tested purified recombinant preparations for their effects on bone resorption and bone collagen synthesis in vitro, and report here that both cytokines at 10(-7) to 10(-9) M caused osteoclastic bone resorption and inhibited bone collagen synthesis. These data suggest that at least part of the bone-resorbing activity present in activated leukocyte culture supernatants may be due to these cytokines.

Animals↗
PubMedDate not supplied

Uterine effects of tamoxifen: a prospective study.

The purpose of the study was to evaluate tamoxifen-associated changes in the vagina and uterus in postmenopausal breast cancer patients. Between June 1994 and December 1998, 45 patients enrolled in a prospective study before commencing tamoxifen therapy. Patients with endometrial thickness >5 mm or neoplasia were excluded. Transvaginal ultrasonography, vaginal maturation indexes (VMI), and endometrial biopsy were performed at baseline and repeated at 6 months (n= 42), 1 year (n= 39), 2 years (n= 32), 3 years (n= 26), 4 years (n= 19), and 5 years (n= 15). For the 39 patients followed for 1 year, VMI (% parabasal/intermediate/superficial) was 21/71/8 at baseline compared with 1/90/9 at 1 year (P value = 0.0008/0.001/0.78). At baseline, mean endometrial thickness and uterine volume were 2.6 mm and 64 cm(3), respectively, compared with 5.8 mm and 84 cm(3) at 1 year (P= 0.0002, 0.002). At baseline, 80% of patients had atrophic endometrium and 9% proliferative endometrium compared with 61% and 26% at 1 year, respectively (P= 0.04). No cases of endometrial hyperplasia or adenocarcinoma were detected. Findings observed at 6 months persisted through 5 years of follow-up. Tamoxifen exerts a weak estrogenic effect on the vagina and uterus in highly prescreened postmenopausal women without preexisting endometrial pathology.

Adult↗