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Biomedical subjects

D R Stewart

Publications and source records attributed to D R Stewart.

At least 55 records · Page 3Linked to original sources
PubMed1987

Hormonal changes associated with induced late abortions in the mare.

Two mares received PGF-2 alpha twice daily until abortion and 2 mares received a combined treatment with oestradiol benzoate and oxytocin. The mares were about 150 days pregnant. The PG-treated animals aborted after 37 and 61 h, respectively, and the fetuses were expelled in intact fetal membranes. The other 2 mares aborted 13 and 27 h after the first oxytocin injection, respectively, and showed strong uterine contractions and expelled the fetuses in disrupted fetal membranes. Concentrations of 15-ketodihydro-PGF-2 alpha increased both after PG and oxytocin injections and in association with the abortion, but after the PG-induced abortion there was an immediate return to basal levels and after the oxytocin-induced abortion there was a large increase in the concentrations, indicating damage of the uterus. Progesterone and relaxin concentrations followed the placental function and decreased in association with the abortions. Oestrone sulphate values differed in the two groups; the oxytocin-treated animals showed a rapid decrease while the mares treated with PG showed first a marked increase and then a decrease. Concentrations of PMSG appeared to be unaffected by the abortions.

Abortion, Induced↗
PubMed1986

Purification and characterization of equine relaxin.

It has been previously determined that the equine placenta is the sole significant source of relaxin during pregnancy and that relaxin immunoactivity is also present in term placentas. Therefore, placentas obtained at the time of foaling were selected for starting material for purification of equine relaxin. Frozen whole placentas were ground and then extracted with 0.5 N HCl-85% acetone. Relaxin was precipitated by raising the acetone concentration to 97%. Equine relaxin was further purified by stepwise elution ion exchange, gel filtration, and gradient elution ion exchange chromatographies and trichloroacetic acid precipitation. Equine relaxin purified in this manner was shown to be heterogeneous with one major form (R-1) and several minor forms (two of which are identified as R-2 and R-3). About 1.5 mg R-1 were obtained per kg placenta. Purity was assessed by slab and disc gel electrophoresis and dansyl end group analysis. R-1 had a potency of 28 U/mg, as measured in the mouse inter-pubic ligament bioassay and displayed a dose-response curve parallel with porcine relaxin. Amino acid analysis indicated the presence of tyrosine, histidine, and proline, amino acids absent in porcine relaxin. Dansyl end group analysis indicated the blockage of N-terminal groups on R-1 and the presence of Lys on R-3. A lower molecular weight was indicated by the electrophoretic migration of relaxin reduced with 2-mercaptoethanol suggesting that equine relaxin consists of two chains.

Adnexa Uteri↗
PubMed1986

Development of a homologous equine relaxin radioimmunoassay.

Equine relaxin (eRlx) immunoactivity has previously been measured in the mare during pregnancy using the porcine relaxin (pRlx) RIA (pRlx-RIA). This was not the optimal system for measurement of eRlx because the dose-response curve obtained with equine plasma was not parallel to the pRlx standard curve. A homologous eRlx-RIA has been developed and used to measure relaxin immunoactivity during pregnancy and parturition in the mare. Highly purified eRlx was used for the generation of antiserum in rabbits, preparation of tracer, and as assay standards. A double antibody eRlx RIA (eRlx-RIA) was developed which was highly specific and sensitive (0.023 ng relaxin/tube). The dose-response curve obtained with eRlx plasma was parallel to the equine standard curve while there was no parallelism noted between the pRlx and eRlx standard curves. This assay was utilized to measure eRlx in samples collected during pregnancy which were previously measured for relaxin content in the pRlx-RIA. It was found that the two assay systems gave almost identical patterns of secretion throughout pregnancy. The two assays differed in the amount of relaxin measured, with the eRlx-RIA measuring considerably higher amounts during gestation than the pRlx assay. In oxytocin-induced foalings, the differences became greater with the equine assay measuring as much as 10-fold greater concentrations.

Animals↗
PubMed1985

Relaxin activity in the pregnant cat.

Plasma relaxin activity was measured by radioimmunoassay (RIA) in the domestic cat utilizing two different antisera developed against highly purified porcine relaxin. One was the 5858 antiserum from our laboratory and the other was the R6 antiserum of Dr. Bernard Steinetz. Relaxin activity could not be detected during the estrous cycle or during pseudopregnancy. Relaxin immunoactivity during early gestation was not detected by either antiserum. Plasma relaxin immunoactivity was first detected by both antisera on about Day 25 of gestation. Relaxin concentrations then increased rapidly, with a plateau reached between Days 30 and 35 that was maintained until 10-15 days prepartum. Relaxin concentrations then declined gradually until parturition. No prepartum increase was observed. Relaxin concentrations were undetectable within 24 h of delivery. Although amounts of immunoactivity measured with the R6 antiserum were consistently higher than measurements with the 5858 antiserum, the patterns of secretions observed were similar for both antisera.

Animals↗
PubMed1984

Concentrations of 15-keto-13, 14-dihydro-prostaglandin F2 alpha in the mare during spontaneous and oxytocin induced foaling.

Changes in plasma 15-keto-13, 14-dihydro-prostaglandin F2 alpha were monitored at frequent intervals before, during and after spontaneous deliveries (three mares) and foalings induced by oxytocin (eight mares). No evidence of increased concentrations of the prostaglandin metabolite was observed in the final 10 days of gestation. In spontaneously delivering mares, there was a marked increase from 3 ng/ml at -125 mins to 18 ng/ml at -65 mins to the highest observed value of 182 ng/ml at 20 mins pre-partum. Following delivery, concentrations declined rapidly to around 0.2 ng/ml. Further release of prostaglandins was seen on Days 1 and 3 post partum. In oxytocin induced mares, maximal concentrations of about 100 ng/ml were observed to occur very close to the time of delivery. Large increases were observed as early as 2 mins following oxytocin injection. The significance of these findings is discussed in relation to parturient and post parturient events and changes in levels of the hormone relaxin during the same period.

Animals↗
PubMed1982

Relaxin activity in foaling mares.

Plasma relaxin concentrations were measured hourly by radio immunoassay in 4 pregnant mares from 11 days before until 4 days after natural foaling. Pre-partum levels ranged from 4 to 7 ng/ml without any surge until the second stage of labour when they increased rapidly to about 11 ng/ml. In 3 of these mares, relaxin activity declined immediately after the expulsion of the placenta and was below detectable levels within 36 h. In the other mare relaxin activity did not fall until after the mechanical removal of the placenta 7 h after foaling. Eight mares were induced to foal by the administration of oxytocin. In 5 out of 6 mares induced with a single i.v. injection of 40 i.u. plasma relaxin increased following injection and peaked at 17 ng/ml shortly after foaling and expulsion of placenta. Activity then rapidly declined. In the 6th mare, which retained the placenta, relaxin activity did not decrease after foaling. Administration of more oxytocin to this mare after foaling resulted in a further increase in plasma relaxin activity, but oxytocin treatment of other mares after placental delivery failed to elicit a similar increase. In the 7th mare 2 i.v. injections of 40 i.u. oxytocin induced a relaxin concentration of 34 ng/ml whereas in the remaining mare one i.m. injection of 40 i.u. oxytocin led to a relaxin profile similar to that in naturally foaling mares. Oxytocin may therefore be responsible for the increased secretion rate of relaxin at foaling. These data support the concept that the placenta is the sole significant source of relaxin in the pregnant mare.

Animals↗
PubMed1979

Infantile obstructive cholangiopathy.

The relationship between neonatal hepatitis and biliary atresia has been extensively discussed. Clinical and laboratory evaluations are often unsuccessful in distinguishing between the two diseases. Laparotomy, cholangiogram, and liver biopsy are often required. Several authors have proposed that the two diseases may represent variable expressions of one entity. A case that illustrates infantile obstructive cholangiopathy is presented and the clinical implications are discussed.

Biliary Tract↗
PubMed1979

Use of the barium enema in the diagnosis of acute appendicitis and its complications.

The value of barium enema examination in diagnosing acute appendicitis in patients with equivocal findings has been confirmed by our experience with five patients. Cecal spasm, extrinsic compression of the cecum, nonvisualization of the appendix, and partial visualization of the appendix appear to be useful roentgenographic signs, either singly or in combination, in diagnosing acute appendicitis. We have had absolute pathologic correlation between the barium enema findings andthe subsequent clinical course of all the patients in whom we conducted this examination. When performed by an experienced radiologist, the barium enema examination carries no increased risk, and we have seen no complications from this procedure.

Acute Disease↗
PubMed1977

Neonatal small left colon syndrome.

Neonatal small left colon syndrome is a functional disease of the lower colon which produces typical signs and symptoms of intestinal obstruction. It is manifest in the first 24-48 hours of life, particularly in infants of diabetic mothers and, if detected early, it can be fully cured by radiographic contrast enemas, not unlike meconium plug syndrome. Intestinal perforation and death may occur, however. The etiology of the disease is unknown but it may relate to neurohumoral imbalances between the autonomic nervous system and glucagon.

Colonic Diseases↗
PubMed1977

Evaluation of gastroesophageal reflux surgery in children.

Fifty-five infants and children with complications of gastroesophageal reflux required operative management for control of symptoms. All patients, except those with severe esophageal stricture, received a six-week trial with 60-degree constant elevation before an operation was considered necessary. The operation was performed to control (1) persistent vomiting, (2) vomiting with growth retardation, (3) esophagitis, (4) esophagitis with stricture, and (5) recurrent aspiration pneumonia. Preoperative and postoperative evaluation involved both X-ray fluoroscopy and esophageal manometry with pH studies. A good surgical result was not dependent upon an increase in the lower esophageal pressure following operation. The Boerema anterior gastropexy is simple and effective for controlling gastroesophageal reflux for cases uncomplicated by esophagitis, stricture, or previous operation. Complex cases with inflammatory or operative changes in the lower esophagus are more effectively treated by Nissen fundoplication.

Child, Preschool↗