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Biomedical subjects

S S Smith

Publications and source records attributed to S S Smith.

At least 163 records · Page 9Linked to original sources
PubMed1984

Maternal modulation of infantile ovarian development and available ovarian luteinizing hormone-releasing hormone (LHRH) receptors via milk LHRH.

In the rat, ovarian LHRH receptor content, measured by the binding of [125I]D-Ala6-Pro9-LHRH ([125I]A-LHRH) to ovarian membranes, declines during the days preceding the first preovulatory LH surge. The present results show that LHRH receptor content is low during neonatal-infantile days (days 5-15) and increases markedly thereafter to a maximum by day 25. When ovarian membranes from 10-day-old rats were pretreated with MgCl2 to dissociate endogenously bound hormone, LHRH-binding capacity increased to levels similar to those in untreated ovaries from 25-day-old rats. No significant increase was observed in ovaries from the latter group after MgCl2 exposure. Equilibrium association constants were similar (6-8 X 10(9) M-1) in MgCl2-treated and control ovaries, indicating that the increase in binding was not due to a change in receptor affinity. Pups prevented from suckling for various time intervals (1-24 h) exhibited an increase in available ovarian LHRH-binding sites which was maximal by 4 h. When pups were allowed to suckle subsequent to a 6-h fast, available ovarian LHRH receptors decreased rapidly (1 h). This decline was not due to a local increase in LHRH triggered by a neural reflex in response to suckling and/or stomach distension. Intragastric administration of milk reproduced the decline in available receptors induced by suckling, whereas stomach distension produced by saline was ineffective. Concomitant with the decline in receptors, suckling produced a significant increase in both stomach content and plasma levels of an LHRH-like material. Fractionation of acid milk extracts in Sephadex G-25 yielded two peaks, one in a position similar to that of synthetic LHRH. Milk LHRH purified in a C-18 Sep-Pak column displaced binding of [125I]A-LHRH to ovarian membranes and yielded a parallel binding curve in the LHRH RIA. This milk LHRH also released LH and FSH from pituitaries in vitro and inhibited FSH-induced estradiol and progesterone secretion from granulosa cells in culture in a dose-related manner, comparable to A-LHRH. The suckling-induced decrease in available LHRH receptors was prevented by iv administration of a specific LHRH antiserum directed against all 10 amino acids of native LHRH, suggesting that milk LHRH reaches the ovary via the bloodstream. The results indicate that an LHRH-like substance of milk origin binds to LHRH receptors in the pup ovary, thereby controlling receptor availability.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1983

The influence of agarose--DNA affinity on the electrophoretic separation of DNA fragments in agarose gels.

The effects of DNA concentration, buffer composition, added "carrier" DNA, and chemical modification of agarose on the electrophoretic separation of DNA restriction fragments in agarose gels were tested. Electrophoretic zones of migrating DNA were found to broaden by trailing as sample load was decreased, and this effect was found to be more pronounced for species of higher molecular weight. As DNA sample load was increased, DNA fragments were found to move faster in the direction of electrophoresis (front forward). Sharp, well-resolved electrophoretic zones were obtained at very low DNA loads only when a high-salt, high-pH, high-EDTA buffer was employed or when "carrier DNA" having a broad and uniform molecular weight distribution was included in the sample. Moreover, DNA in high concentration was found to displace DNA in low concentration from a given gel region. Unmodified agaroses were found to differ only slightly in their effectiveness in retarding DNA fragments at a given agarose concentration. However, hydroxyethylated agarose was much more effective in retarding DNA, at a given gel concentration, than the unmodified agaroses tested. These results show that it is useful to consider the agarose gel matrix as possessing the properties of both a molecular sieve and a chromatographic adsorbent when designing electrophoretic separation techniques for DNA. A model for these separations which includes the effects of DNA-agarose interaction and molecular sieving is discussed.

Buffers↗
PubMed1983

Texas Consortium for Physical Therapy Clinical Education. A model for Interinstitutional Consortium arrangements.

This article describes the Texas Consortium for Physical Therapy Clinical Education, which exemplifies one type of collaborative arrangement among universities. Coordination of physical therapy clinical education among five Texas universities is the major function of the Texas Consortium. Although originally developed from a federally funded project (1977-1980), it currently functions with sole financial support from the participating universities. The collaborative efforts of the Texas Consortium have resulted in 1) developing and implementing a common evaluation tool for students' clinical performance; 2) coordinating development of new clinical education centers, development of clinical instructors, and visits to students at clinical education centers; and 3) developing and using a shared computer program for data on clinical education centers. The successful functioning of the Texas Consortium with a resultant decrease in duplication of time, effort, and costs of clinical education demonstrates that this type of arrangement is feasible and beneficial.

Costs and Cost Analysis↗
PubMed1982

Different levels of DNA modification at 5'CCGG in murine erythroleukemia cells and the tissues of normal mouse spleen.

The DNA of a Friend erythroleukemic cell line (clone DS-19) and that of mouse spleen from which it was derived were compared with respect to modification at 5'CCGG. Methylation patterns in clone DS-19 DNA were very different from those in normal spleen DNA. Our results suggest that the mechanism by which the internal cytosine in the 5'CCGG sequence is modified has been partially inactivated in clone DS-19. We observed a general decrease of about two-fold in total modification at this site in DS-19 DNA. This general decrease was shown to extend to 5'CCGG sites in specific classes of repeated sequences with two-dimensional displays of restriction fragments. Interspersed repeated sequences which are concertedly modified (i.e., modified at many different chromosomal locations) in spleen, were found to be unmodified at these locations in the cell line. However, we did not detect a difference in DNA modification at 5'CCGG with these techniques when uninduced and hexamethylene-bis-acetamide (HMBA) induced cells of clone DS-19 were compared. In other experiments, we obtained further evidence that selected classes of repeated sequences in Physarum polycephalum are methylated to the same extent independent of chromosomal location.

Animals↗
PubMed1982

Potassium ion concentration alters glucagon secretion independently of insulin secretion in the isolated rat pancreas.

In the arginine-stimulated perfused rat pancreas, elevated concentrations of potassium ion inhibited glucagon secretion while stimulating the secretion of insulin. Decreased potassium ion produced the reverse effect. The observed inverse correlation between changes in insulin and glucagon secretion (r = -0.64; p less than 0.001) was suggestive of local interactions between islet hormones, and prompted us to determine whether potassium-induced changes in glucagon secretion were dependent upon concurrent changes in insulin release. We found that when insulin secretion was greatly suppressed, either through acute induction of diabetes with streptozotocin or by utilization of a glucose-free perfusate, no qualitative differences in glucagon responsiveness to altered potassium ion were evident, although the amplitude of these glucagon changed was enhanced. Similarly, when exogenous insulin (20,000 mU/l) was added to the perfusate in order to render potassium-induced changes in endogenous insulin secretion insignificant, glucagon responsiveness to altered potassium ion was maintained. Exogenous insulin alone had no effect on arginine-stimulated glucagon secretion. We conclude that any indirect effects of potassium ion on arginine-stimulated glucagon secretion are not mediated by insulin, but could be related to changes in somatostatin secretion.

Animals↗
PubMed1982

Starvation increases gastrointestinal somatostatin in normal and obese Zucker rats: a possible regulatory mechanism.

Normal, male Sprague-Dawley (S-D) rats and female, lean and obese Zucker rats were studied in the fed state and after 48 hours of food deprivation. Somatostatin-like immunoreactivity (SLI) was measured from acetic acid extracts of oesophagus-cardia, stomach, small and large intestine, pancreas, hypothalamus, pituitary and cerebellum. Within the CNS, the highest levels of SLI were found in the hypothalamus, while in the gut, these levels were highest in the stomach and pancreas. All Zucker rats displayed higher hypothalamic levels of SLI than did S-D rats. Obese Zucker rats in the fed state differed from their lean littermates in that SLI levels were lower in oesophagus-cardia, stomach and hypothalamus, while being higher in pancreas and pituitary. The response to starvation in both obese and lean Zucker rats was qualitatively similar, and included significant increases in stomach and oesophagus-cardia SLI, but with a significant fall hypothalamic SLI. We have concluded that the increase in gastrointestinal SLI with starvation in Zucker as well as in S-D rats may represent a significant regulatory mechanism in nutrient homeostasis. We postulate that gastric SLI may decrease the availability of intestinal insulin secretagogues in the fasting state. This adaptive mechanism appears to be intact in the obese Zucker rat.

Animals↗
PubMed1982

Vitreous fluorophotometry in three models of experimental diabetes mellitus.

Fluorophotometry was performed on rats eight to ten days after they were made diabetic with streptozotocin (85 mg/kg), alloxan (50 mg/kg), or pancreatectomy. When compared with normal control animals, no significant differences in aqueous or vitreous fluorescein levels were noted in any of the diabetic models studied. We did note significant depressions of plasma fluorescein levels in pancreatectomized and streptozotocin-treated rats. We normalized our data for these plasma differences by calculating the ratios of aqueous and vitreous fluorescein to plasma fluorescein levels (RA and RV). Both RA and RV were significantly elevated in streptozotocin-induced diabetes; RV alone was elevated following pancreatectomy, while no change in either ratio was apparent in diabetes induced with alloxan. Treatment of streptozotocin-diabetic rats with cortisol for one week caused plasma fluorescein levels and RV to return toward normal, although RA remained elevated. We are cautious in assigning any meaning to changes in RA and RV, especially in view of the paucity of information on the behavior of fluorescein in the blood.

Alloxan↗
PubMed1981

The two-dimensional restriction analysis of Drosophila DNAs: males and females.

Two-dimensional restriction analysis has been applied to terminally labeled restriction segments from adult male and female flies that were the progeny of ten successive single-pair, brother-sister matings. Many of the 2500-4000 different bands that can be seen on autoradiographs are of widely different density, a fact that suggests the superposition of multiple restriction segments of similar sequence. The number of bands observed is significantly fewer than expected. Nearly all of the bands seen in male-DNA displays appear equivalent to those seen in female-DNA displays, but a few sex differences (male-dense and female-dense bands) can be identified--much fewer than expected. When the HpaII-MspI test was applied to fractionated BamHI fragments, between 900 and 1800 discrete C-C-G-G sites were found to be cleaved in a completely equivalent fashion by each isoschizomer.

Animals↗
PubMed1980

Hyperglucagonemia after removal of lower bowel in rats.

Surgical removal of the jejunum, ileum, and colon from rats (LBX) results in greatly elevated levels of plasma immunoreactive glucagon (pIRG) 24 h after surgery (0.98 +/- 0.07 ng/ml, n = 51 vs. 0.20 +/- 0.02 ng/ml, n = 34 in sham-operated controls). Such elevations in pIRG were not noted after gut transection or the removal of ileum, jejunum, or colon alone, ileum plus jejunum, or stomach plus duodenum. Coupled with the failure of adrenal demedullation, adrenalectomy or ganglionic blockade to lower pIRG in LBX animals, these findings suggest that surgical stress alone is an unlikely cause for LBX-induced hyperglucagonemia. It was also shown that alpha-cells in LBX animals retained their responsiveness to both the inhibitory effects of somatostatin and glucose infusion as well as the stimulatory effects of arginine infusion. Chromatography revealed a normal pattern of IRG in the plasma of LBX animals. It is postulated that LBX-induced hyperglucagonemia may result from the removal of an inhibitory factor present in the lower bowel.

Animals↗
PubMed1978

A new method for the purification of RNA polymerase II (or B) from the lower eukaryote Physarum polycephalum. The presence of subforms.

The DNA-dependent RNA polymerase II or B from the lower eukaryote Physarum polycephalum has been purified to apparent homogeneity by a new method employing poly(ethylene imine) precipitation and elution, and heparin-Sepharose affinity chromatography. The method is readily scaled up or down and affords a purification of over 5000-fold with a yield of 35-45%. The procedure is easy to perform and can be carried out in less than three days even on a large scale. Furthermore, it gives enzyme of higher purity and in at least 10-fold greater yield than previously published procedures for its purification from this organism. These improvements have allowed the detection of a series of subforms of the enzyme. The combination of precipitation using poly(ethylene imine) with chromatography on heparin-Sepharose may prove useful in the preparation of other proteins which interact with nucleic acids.

Chromatography, Affinity↗
PubMed1978

Carcinoma of the breast. A clinical study.

An analysis of 1,686 surgically treated carcinomas of the breast in one community showed no statistically significant differences in five- and ten-year survival for simple, modified radical, or radical mastectomy. Further confirmation was obtained by computation of relative survival which in addition showed that older women more nearly approach normal life expectancy than younger ones. Bilaterality was found to be a decreasing function of age. Patients with medial and lateral tumors did not have significantly different rates of survival or sites of distant metastases.

Adult↗