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R Smith

Publications and source records attributed to R Smith.

At least 883 records · Page 49Linked to original sources
PubMed1991

Release of insulin-like growth factor I by the sheep placenta in vitro.

This study has utilized a tissue perifusion system to examine the release of insulin-like growth factor I (IGF I) from different regions of the sheep placenta at two stages of gestation. Placentae were obtained from ewes at either 116 +/- 7 (mean +/- s.e.) or 144 +/- 1.5 days of gestation and separated into the maternal basal plate or chorionic villous tissue. At both ages, the maternal basal plate tissue released approximately three times more IGF I than the chorionic villous tissue. No difference was found between the rate of release of IGF I from the maternal basal plate at 120 and 140 days of gestation, whereas the chorionic villous tissue released less IGF I later in gestation. Maternal basal plate tissue was less responsive to a depolarizing dose of KCl than was chorionic villous tissue at either age. After acid gel chromatography, perfusate from the basal plate had three peaks of IGF immunoreactivity (corresponding to binding protein, IGF I and a form with an intermediate molecular weight). In contrast, the chorionic villous tissue released only a form with a high molecular weight, corresponding to binding protein. These results demonstrate that the sheep placenta produced IGF I, that secretion varies between different placental zones which contain different cell types and that there are maturational changes in placental IGF I secretion. The IGFs may be involved in placental growth.

Animals↗
PubMed1991

Perifused ovine placental tissue secretes beta-endorphin immunoreactivity.

In vitro release of one of the pro-opiomelanocortin (POMC)-derived peptides, the endogenous opioid beta-endorphin (beta EP) has been examined in the sheep placenta by means of a perifusion system. Two zones of the cotyledon, the chorionic villus (highly vascularized fetal and maternal tissues in close apposition) and the maternal basal plate (or capsule), were examined in placenta at two stages of gestation--120 days (119.0 +/- 4.7, N = 4) and 140 days (143 +/- 1.8, N = 5) just before term. The chorionic villous tissue released more beta EP-like immunoreactivity (beta EP-IR) than did the basal plate tissue at both gestational ages. At 120 days' gestation the basal concentration of beta EP-IR released from the chorionic villus was 52 +/- 0.5 fmol mL-1 (n = 4), almost double the maternal basal plate tissue at 28.4 +/- 0.4 fmol mL-1 (n = 8). beta EP-IR secretory capacity increased significantly (P less than 0.05) with advancing gestational age. By Day 140, release had increased 3-4-fold to 181.8 +/- 0.8 fmol mL-1 (n = 16) in the chorionic villous tissue, and to a lesser extent in the basal plate tissue to 50.7 +/- 0.6 fmol mL-1 (n = 14). No stimulation of beta EP-IR secretion was observed in any tissue as a result of 30 min exposure to corticotrophin-releasing hormone (100 nmol L-1), a vital physiological secretagogue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Intravenous vitamins for very-low-birth-weight infants.

Term infants and children appear to adapt to large variations in vitamin intakes. This is supported by the finding of similar blood levels of vitamins despite several-fold differences in intake on a body weight basis. By contrast, the finding of marked elevation of some vitamins and low levels of others seen in very-low-birth-weight (VLBW) infants (less than 1500 g) suggest that this group has less adaptive capacity to high- or low-dose intakes. This indicates that their vitamin intakes need to be more closely aligned with actual needs. This paper reviews previously published data on vitamins A, E, B2, and B6 from VLBW infants receiving total parenteral nutrition (TPN). Vitamin A. VLBW infants are relatively deficient in retinol (R) at birth. During TPN large losses of R onto the delivery sets result in a further decline in stores of R as reflected in a progressive decline in plasma R during TPN. Because of the reported lower incidence of bronchopulmonary dysplasia associated with intramuscular vitamin A treatment, alternative methods of vitamin A delivery during TPN have been suggested. First, the vitamins were mixed with Intralipid (IL) and, second, retinyl palmitate (RP) rather than R was used. There was little in vitro loss of R when mixed with IL, and in vivo treatment resulted in higher blood levels after 1 month of retinol administration in IL than seen previously (21.4 +/- 4.2 vs 14.1 +/- 3.7 micrograms/dl).(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-Response Relationship, Drug↗
PubMed1991

Laparoscopic cholecystectomy: a multicenter study.

Laparoscopic cholecystectomy has been developed as an alternative to open cholecystectomy for the treatment of symptomatic cholelithiasis. A collaborative study of 261 patients undergoing laparoscopic cholecystectomy at three Texas institutions was performed to determine the effectiveness and safety of this technique. There were 65 males and 196 females with a mean age of 49 years (range 17-94 years). Acute cholecystitis was present in 38 patients and chronic cholecystitis in 223 patients. Mean length of surgery was 80 minutes (20 min to 4 hr). Fifteen patients were converted to the open technique intraoperatively due to bleeding, adhesions, or difficulty of dissection. There were no perioperative deaths and morbidity was 3% including urinary retention, small bowel obstruction, arrhythmia, wound infection, and bile leakage. There were no common duct injuries. Hospitalization ranged from outpatient surgery to 7 postoperative days with a mean of 1.2 days. We conclude that laparoscopic cholecystectomy can be performed safely and with low morbidity and offers shorter hospitalization and postoperative recovery.

Adolescent↗
PubMed1991

A limited association of generalized osteoarthritis with alleles at the type II collagen locus: COL2A1.

A significant genetic influence in osteoarthritis has been observed in the combination of Heberden's nodes and generalized osteoarthritis. We examined whether mutation in the gene encoding the major cartilage matrix protein type II collagen was responsible by comparing allele frequencies at the locus (COL2A1) in a group of 61 patients with nodal GOA with a control population and by analysing the COL2A1 genotypes of 21 affected sibling pairs. There were no significant allele differences but a slightly increased tendency over chance alone for affected siblings to have inherited the same COL2A1 alleles from their parents.

Alleles↗
PubMed1991

Toxicity and pharmacokinetics of subconjunctival amphotericin B. An experimental study.

The pharmacokinetics and toxicity of subconjunctival (S/C) amphotericin B (AmB) were evaluated in Dutch-belted rabbits. Following the S/C injection of 1,500 micrograms of AmB, corneal and aqueous levels were determined by bioassay. The highest levels were present in the periphery of debrided corneas at 1 h (90.12 +/- 2.4 micrograms/g). The debrided central cornea contained 30.84 micrograms/g, almost double the amount present in the intact central cornea. These levels were transient; in the central intact cornea only 2.08 micrograms/g could be detected at 2 h. Peak aqueous levels were low (0.95 +/- .24 micrograms/mL in debrided corneas at 1 h). The S/C injection of 1,500 micrograms of AmB in sodium deoxycholate produced a severe inflammatory response in the conjunctiva, episclera, iris, anterior chamber, and superior rectus muscle that persisted 10 days. Injection of sodium deoxycholate alone produced a similar but less severe response.

Amphotericin B↗
PubMed1991

Histological evaluation of biodegradable and non-degradable membranes placed transcutaneously in rats.

The aim of this study was to assess histologically the response to membrane materials that might be used for guided tissue regeneration procedures, using a transcutaneous model on the dorsal surface of the rat. The materials included expanded polytetrafluoroethylene (PTFE) membrane (Gore-Tex), PTFE Millipore filter, biodegradable polylactic acid (PLA) and polyhydroxybutyrate/polyhydroxyvalerate copolymer membranes. 70 implants were placed in 10 rats under general anaesthesia. At 2 weeks after the operative procedure, the specimens were assessed histologically for the composition of the tissue surrounding the material, the types of cell in the infiltrate and the degree of absorption particularly in the superficial tissues. PTFE was associated with greater epithelial downgrowth and a mainly polymorphonuclear infiltrate. PLA showed a high incidence of absorption, with a mainly monocytic infiltrate. Considerable variation was found between these extremes. It was concluded that the healing responses associated with the membranes were complex and varied, and further work is required to establish the factors which govern the variation in the healing response. The findings are of relevance to regenerative procedures which rely on the guiding influence of artificial membranes on the healing tissues. The PLA material was well tolerated and was gradually absorbed. Further research may enable this material to form the basis of a one stage guided tissue regeneration procedure.

Absorption↗
PubMed1991

Association between the 65-kilodalton heat shock protein, Streptococcus sanguis, and the corresponding antibodies in Behçet's syndrome.

The etiology of Behcet's syndrome (BS) is unknown, but a number of streptococcal species have been implicated. A hypothesis was postulated that a shared antigen, such as a stress protein, might account for some of these findings. Indeed, a rabbit antiserum against a 65-kDa heat shock protein of Mycobacterium tuberculosis revealed a corresponding 65-kDa band with all six Streptococcus sanguis strains examined and S. pyogenes but not with S. salivarius. By applying a panel of nine monoclonal antibodies to the mycobacterial 65-kDa heat shock protein, an approximately 65-kDa antigen was identified in the uncommon serotypes of S. sanguis ST3 and H.83 and one with a different Mr was identified in KTH-1 and S. pyogenes. Monoclonal antibodies Y1.2, C1.1, II H9, and ML30, which reacted with these streptococci, recognize residues 11 to 27, 88 to 123, 107 to 122, and 276 to 297 of the 65-kDa heat shock protein, respectively, suggesting that these residues are conserved among some uncommon serotypes of S. sanguis and S. pyogenes. Immunoblot analyses of sera from patients with BS for immunoglobulin A (IgA) and IgG antibodies revealed bands of 65 to 70 kDa with the mycobacterial heat shock protein, S. sanguis strains, and S. pyogenes, although these reactivities were also found to a lesser extent in controls. A 65- to 70-kDa band was found more frequently with S. sanguis KTH-2 or KTH-3 and IgA in serum from patients with BS than with serum from controls (P less than 0.02). Antibodies in serum were then studied by a radioimmunoassay, and in patients with BS this revealed significantly raised IgA antibodies to the recombinant 65-kDa mycobacterial heat shock protein and to soluble protein extracts of S. sanguis ST3, KTH-1, KTH-2, and KTH-3. Whereas significant anti-65-kDa heat shock protein and anti-S. sanguis ST3 antibodies were also found in sera from patients with rheumatoid arthritis and recurrent oral ulcers, the anti-S. sanguis KTH-1, KTH-2, and KTH-3 antibodies were confined to BS. The results are consistent with the hypothesis that some of the streptococcal antigens are associated with heat shock or stress proteins, which will need to be formally established by isolating heat shock proteins from streptococci.

Amino Acid Sequence↗