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Biomedical subjects

D R Stewart

Publications and source records attributed to D R Stewart.

18 recordsLinked to original sources
PubMed1992

Purification and sequence determination of canine relaxin.

Relaxin immunological activity has been observed in the plasma of pregnant bitches, and preliminary studies in our laboratory indicated that the highest relaxin concentrations were found in placentas. Therefore, canine placentas were collected at term and also from spay and relaxin was purified by methods developed for equine relaxin. Tissue was prepared by homogenization and purification on a C18 column. The preparation was further purified by stepwise elution ion-exchange chromatography, gel filtration, and gradient elution ion-exchange chromatography. One predominant peak in relaxin immunoactivity was collected. Canine relaxin was found to be larger than either porcine or equine relaxin as determined by SDS-PAGE. It migrated faster under reducing conditions, indicating a subunit structure. Purified canine relaxin was used for tracer and standard in a canine radioimmunoassay (RIA) using an antiporcine relaxin antibody. Concentrations of relaxin immunoactivity using the canine assay were up to 300-fold higher in placental preparations than those measured in the porcine relaxin assay. Sequence analysis of canine relaxin revealed a structure similar to other relaxins in the presence and placement of cystine residues.

Amino Acid Sequence↗
PubMed1992

Analysis of the basis for persistence of herpes simplex virus type 1 in undifferentiated U937 cells.

Replication of herpes simplex type 1 (HSV-1) is inhibited in the human monocyte-like cell line, U937, when the cells are in the undifferentiated state, but when the cells are stimulated to differentiate by treatment with the phorbol ester, phorbol 12-myristate 13-acetate virus is replicated. Because HSV-1 has been shown to persist in these cells and in their in vitro counterparts freshly isolated human blood monocytes, we initiated an analysis of viral persistence in undifferentiated U937 cells. No appreciable HSV-1 DNA replication was observed in undifferentiated U937 cells compared with differentiated U937 cells and with fully permissive Vero cells. However, using in situ hybridization, we established that a significant percent of the undifferentiated U937 cells contained viral DNA sequences. Interestingly, when analyzed by Southern blot hybridization, this DNA was found to have assumed a nonlinear configuration similar to that found in latently infected neurons. Analysis of viral proteins in undifferentiated U937 cells revealed a marked absence of proteins of all three kinetic classes. However, in transient transfection assays, the major viral transactivating protein ICP4, functioned normally, whereas ICP0, a promiscuous transactivator of both viral and cellular genes, was unable to transactivate viral promoters in undifferentiated U937 cells. Thus, a subtle dysfunction in the activity of ICP0 may account, at least in part, for the inability of undifferentiated U937 cells to support replication of HSV-1.

Animals↗
PubMed1992

Breed differences in circulating equine relaxin.

Equine relaxin has been previously determined in a small number of pregnant Thoroughbred mares. To better define the normal pregnancy pattern of relaxin, the current study reports on a much larger number of mares. It also was designed to determine if all equids have the same gestational pattern of relaxin secretion. Plasma samples were collected weekly in 24 Standardbred mares, every 7-10 days in 10 pony mares, and daily in late pregnancy from 16 burros. Standardbreds had higher concentrations of relaxin than that reported for Thoroughbreds during most of gestation and did not exhibit the midpregnancy nadir in relaxin concentrations observed in Thoroughbreds. Relaxin concentrations in Standardbreds showed a small but steady decline from Day 150 until delivery. Pony mares had lower relaxin concentrations throughout pregnancy than other mares and had continuously increasing concentrations during gestation. Burros had relaxin concentrations intermediate to ponies and other mares in late gestation. Burros induced to foal with oxytocin showed a sharp increase in relaxin concentrations. No effect of the sex of the offspring was observed in relaxin profiles in Standardbred mares. Each of three Standardbreds with abnormal termination of pregnancy exhibited abnormally low relaxin concentrations at some point in the gestation prior to termination of the pregnancy. Thus, relaxin may be an indicator of placental functioning and used to assess at-risk pregnancies in mares.

Animals↗
PubMed1992

Serum relaxin concentrations in patients with out-of-phase endometrial biopsies.

When luteal phase relaxin concentrations were summed to give an integrated measure (pg/mL per cycle), relaxin was found to be significantly lower in those cycles with an out-of-phase endometrial biopsy. In addition, peak relaxin concentrations were lower in out-of-phase cycles compared with normal cycles. These data indicate that relaxin secretion may be related to normal luteal function and suggest that shortening of the luteal phase results in reduced relaxin production. Measurement of circulating relaxin may prove to be useful in making the diagnosis of out-of-phase biopsy and needs to be assessed for its usefulness in diagnosing abnormal luteal function.

Biopsy↗
PubMed1991

Affinity purification and sequence determination of equine relaxin.

Relaxin, a polypeptide hormone normally associated with pregnancy, has been purified from many species, and the sequence determined for a growing number. Equine relaxin has been previously purified by acetone extraction, gel filtration, and ion exchange chromatographies. In an attempt to develop a more rapid and efficient method for relaxin purification, the use of affinity chromatography coupled with HPLC was explored. Monoclonal antibodies were raised against highly purified equine relaxin; large quantities of antibody were obtained by ascites production and attached to a solid phase support. An extract of term equine placentas was passed through the affinity column and washed, and relaxin was eluted by a change in pH. The isoforms of equine relaxin were separated by HPLC using a C18 (ODS) reverse phase column and a linear gradient of 25-30% acetonitrile. Four major and several minor isoforms of equine relaxin were obtained. The isoforms share similar mol wt by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), are composed of subunits (SDS-PAGE under reducing conditions), and have similar charges (native PAGE). Five isoforms tested positive for biological activity in the mouse interpubic ligament bioassay. Equine relaxin was sequenced by Edman degradation, and the sequence was confirmed by fast atom bombardment mass spectrometry. The isoforms of equine relaxin were found to be due to heterogeneity of the C-terminus of the B-chain. Equine relaxin appears to be the smallest relaxin sequenced. The A-chain consists of 20 residues, and the B-chain has 28 residues, with a total mol wt of 5253. Equine relaxin shares the greatest sequence homology with porcine relaxin (67% identity).

Amino Acid Sequence↗
PubMed1991

Determination of the source of relaxin immunoreactivity during pregnancy in the dog.

We investigated the source of immunoreactive relaxin (IR) in the dog during pregnancy using the following: (1) controls, (2) dogs ovariectomized during pregnancy and maintained on progesterone, (3) dogs hysterectomized during pregnancy or immediately postpartum, (4) corpora lutea, uteri, and placentas collected at various times during pregnancy for determination of IR, and (5) maternal (overian and uterine vein) and fetal (cardiac) blood and amniotic and allantoic fluid. Plasma IR patterns remained unchanged in animals subjected to ovariectomy, whereas in the controls IR was first detected at about Day 20 of pregnancy, peaked on Day 35, and was then remained at the same level until parturition. Hysterectomy, on the other hand, resulted in IR values becoming undetectable within 2 to 3 days. The highest tissue concentrations of IR were found in the placenta. These findings indicate that the source of relaxin in the pregnant dog is the placenta.

Animals↗
PubMed1990

Relaxin in the peri-implantation period.

The time of appearance of relaxin in peripheral blood was determined in conceptive and non-conceptive cycles using a sensitive and specific double-antibody enzyme-linked immunoassay for human relaxin. For study of relaxin in early pregnancy, daily plasma samples were collected from women receiving artificial insemination of donor semen. The day of ovulation was determined by daily LH monitoring and ultrasound observation. In three conceptive cycles, relaxin was significantly elevated over baseline 9-10 days following the LH peak. Relaxin concentrations quickly rose over the next 15 days of observation to over 800 pg/ml. Relaxin was observed to increase 1 to 2 days prior to the first detectable increase in plasma hCG as measured by enzyme-linked immunosorbent assay. To compare the relaxin profile in conceptive cycles with normal luteal phase concentrations, relaxin was also measured in daily plasma samples collected from women contracepting with barrier methods, bilateral tubal ligation, or abstinence. A small but consistent rise in relaxin in the late luteal phase was observed in nine of eleven women, which began 6-9 days after the LH peak, averaged approximately 50 pg/ml, and was declining by the next menses. It is concluded that a small but measurable rise in plasma relaxin is associated with the normal luteal phase and that relaxin secretion is accelerated around the time that hCG is first detected in conceptive cycles. This acceleration of relaxin secretion which is associated with the onset of hCG may provide additional evidence for identification of transient early pregnancy.

Chorionic Gonadotropin↗
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↗
PubMed1976

Malrotation of the bowel in infants and children: a 15 year review.

One hundred and fifty-nine patients with malrotation treated in the Children's Hospital Medical Center between 1951 and 1967 are presented and analyzed with regard to the factors contributing to the success or failure of their management. There were 28 deaths, the majority of which occurred in patients who were less than one month old, had multiple congenital anomalies, or had volvulus of the small bowel with gangrene and perforation. Some of the points we have found most helpful in making the diagnosis are reviewed and the disease as it presents in older children is considered briefly.

Abnormalities, Multiple↗
PubMed1975

Management of acquired tracheal obstructions in infancy.

Endoscopic resection of tracheal subglottic stenosis can be performed safely and effectively. With careful selection, some stenotic rings can be excised without the requirement for prior tracheostomy. Endoscopic resection does not supplant other methods of dilatation, injection, or stenting of subglottic scars, but early resection in appropriate cases may reduce the number of dilatations and obviate the need for a stent and systemic steroids.

Dilatation↗