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Biomedical subjects

S M Swanson

Publications and source records attributed to S M Swanson.

42 records · Page 3Linked to original sources
PubMed1979

Reproducibility of ejection-fraction determinations by equilibrium radionuclide angiography in response to supine bicycle exercise: concise communication.

Sixteen patients with stable, chronic coronary artery disease were studied twice within and average of 15 days to evaluate the reproducibility of ejection fraction (EF) determined by equilibrium radionuclide angiography (EQ) at rest, during supine bicycle exercise (ex), and in the recovery period (rec). Following injection of 20--25 mCi of Tc-99m-tagged human serum albumin, data were analyzed for 2-min periods at rest, during several stages of exercise (submax, max), and during recovery (rec1 = minutes 2 + 3, rec2 = minutes 9 + 10). Each patient reached similar (heart rate) X (blood pressure) products in the two studies: 21280 +/- 5200 compared with 20390 +/- 4140 mmHg/min. Mean EFs for the first and second studies were: at rest (53.0 +/- 10.8)%, 52.5 +/- 10.4)% (r = 0.95; submax ex (51.4 +/- 12.0)%, (52.1 +/- 12.8)%, (r = 0.91); max ex (50.6 +/- 12.6)%, (51.6 +/- 12.9)% (r = 0.97); rec1 (62.7 +/- 11.6)%, (62.4 +/- 12.2)% (r = 0.95); rec2 (55.5 %/- 10.8)%, (57.2 +/- 11.7)% (r = 0.91). In stable patients, the reproducibility of EF determined by EQ is excellent during rest, supine bicycle exercise, and recovery from exercise.

Adult↗
PubMedDate not supplied

A rapid and sensitive bioassay involving cultured rat glioma cells to screen for substances capable of elevating intracellular cyclic AMP concentration.

Cultured rat glioma (ASK) cells are morphologically converted from a spindle to an astrocyte form when treated with dibutyryl cAMP. This morphologic transformation is discernible by light microscopy and can be visually quantitated. As described herein, dose-dependent astrocyte generation was demonstrated by treatment of confluent monolayers with forskolin [1], a compound known to activate adenylate cyclase, and the potency of four forskolin derivatives was found to correlate with previously established biologic potential. Neither a crude ginseng extract nor purified ginsenosides were active in the process, but supplementation of the otherwise inactive ginseng extract with 1 demonstrated 50% of the cells were morphologically converted to the astrocyte form at a concentration of approximately 0.0008%. Retinoic acid was also active in this test system; the morphologic transformation was reversed on treatment with colchicine, and intracellular cAMP concentration was elevated approximately 10-fold. Evaluation of 15 retinoids established a general correlation between the activity in this system and other systems reported in the literature. Thus, the astrocyte formation assay appears to provide several advantages that make it attractive as a screen for the detection or evaluation of substances capable of elevating intracellular cAMP concentration. In addition to technical ease, the procedure is rapid, sensitive, and relatively inexpensive.

Animals↗
PubMedDate not supplied

Antimicrobial and cytotoxic activity of rottlerin-type compounds from Hypericum drummondii.

Hexane extracts of Hypericum drummondii showed significant activity against the Gram-positive bacteria Staphylococcus aureus, Bacillus subtilis, and the acid-fast bacterium Mycobacterium smegmatis in an agar well diffusion assay. Employing bioassay-directed fractionation procedures, four new rottlerin-type compounds (drummondins A, B, C[1-3], and F [4]) were isolated and identified by spectral and physical characterization. The antimicrobial activity of these compounds was comparable to or greater than that demonstrated by streptomycin and generally correlated with cytotoxic activity determined with cultured P-388, KB, or human cancer cell lines (breast, colon, lung, melanoma). No cell-type selectivity was observed. In addition, two known compounds, albaspidins A-A [5] and P-P [6], were isolated and structured characterized. Neither demonstrated appreciable antimicrobial or cytotoxic activity.

Anti-Bacterial Agents↗
PubMedDate not supplied

Hormone levels and mammary epithelial cell proliferation in rats treated with a regimen of estradiol and progesterone that mimics the preventive effect of pregnancy against mammary cancer.

Women who bear their first child by their late teens have about half the risk of developing breast cancer relative to nulliparous women. The rat is a good model for studying the role of hormones in breast cancer since, for example, young rats become nearly refractory to mammary carcinogenesis after delivering a litter of pups. Short term administration of estradiol and progesterone (E & P) provides virgin rats protection from mammary carcinogenesis as effectively as pregnancy. The purpose of these studies were twofold: first, to evaluate potential long-term toxicity of the E & P treatments and second, to compare hormone treated rats and pregnant rats with respect to circulating E & P levels as well as mammary epithelial cell proliferation and differentiation. To test for toxicity, rats were treated with E & P (20 micrograms and 4 mg, respectively) or vehicle by s.c. injections 5 times per week for 5 weeks beginning at 40 days of age. The animals were weighed biweekly and sacrificed at 500 days of age when detailed necropsies were performed. No significant difference in weight gain was observed between the two groups nor was any toxicity grossly observable in the hormone-treated rats. Furthermore, there was no increase in the number of spontaneous mammary or pituitary tumors in the E & P treated group relative to controls. To evaluate serum hormone titers and mammary proliferation, rats were treated with steroids or vehicle daily beginning at 65 days of age. At 6 and 24 hours after the 1st, 14th and 35th injection, serum E & P were measured by RIA and mammary epithelial cell proliferation by immunohistochemistry (PCNA). At 6 hours after each injection, E & P levels were 3 to 5 fold those observed late in pregnancy. By 24 hours, however, E & P levels subsided to late pregnancy levels or lower. The mammary epithelial cell proliferation index in either E & P treated or late pregnant rats was 6 to 14%. Histologic sections and wholemounts of mammary glands showed a similar degree of differentiation between rats treated with E & P for 14 days or longer and late pregnant rats. These data further suggest that E & P treatments are a non-toxic means of mimicking the protective effect of pregnancy against mammary cancer and that pregnancy or hormone treatments may achieve this prophylaxis through a differentiation mechanism.

Aging↗
PubMedDate not supplied

Changes in the parous rat mammary gland environment are involved in parity-associated protection against mammary carcinogenesis.

Parity in rats results in protection from methylnitrosourea (MNU)-induced mammary cancer. Our goal was to determine if systemic alterations in the mammary gland environment after a full-term pregnancy rendered the parous rat an inadequate host for promotion of initiated mammary epithelial cells to become cancerous. Lewis rat MNU-treated mammary epithelial cells were transplanted into uniparous (UP), age-matched virgin (AMV) (both 130-150 d), or young virgin (YV) (50-60 d) syngeneic hosts to examine if differences in the systemic environments of the three hosts had an effect on hyperplasia and cancer formation. More transplants in YV and AMV hosts contained hyperplasias and adenocarcinomas as compared to transplants in UP hosts. In addition, UP host transplants had significantly fewer numbers of hyperplastic lesions than transplants from the virgin hosts. The evidence presented here shows that the uniparous host environment is less supportive than that of the virgin host for hyperplasia and cancer development.

Animals↗