Biomedical subjects

W B Stewart

Publications and source records attributed to W B Stewart.

At least 55 records · Page 3Linked to original sources

PubMed1986

Beagle puppy model of perinatal cerebral insults. Cerebral blood flow changes and intraventricular hemorrhage evoked by hypoxemia.

Asphyxia, with its attendant hypoxemia, is by far the most common cause of neonatal cerebral infarction, and frequently results in lesions of the parieto-occipital white matter in addition to other neuropathological changes. This study examines the effects of hypoxemia on regional cerebral blood flow (CBF) in the newborn beagle pup. The animals were anesthetized, underwent a tracheotomy, and were paralyzed. Pups were randomly divided into two groups: one group was subjected to hypoxemia produced by altering the oxygen concentration in the inspired air, and the other received no insult. In the hypoxemic pups, the pO2 was 13.1 +/- 2.1 mm Hg (mean +/- standard deviation). Autoradiographic determinations of CBF were performed by the carbon-14-iodoantipyrine technique 15 minutes after randomization. Significant increases in CBF were found throughout the brains of the hypoxemic pups. The CBF was increased to cortical and central gray regions and to frontal and temporal white matter but was unchanged in the parietal white matter, one of the classic sites of radiological and neuropathological injury in neonates with perinatal asphyxia. An unexpected finding was the increased incidence of germinal matrix and/or intraventricular hemorrhages in the hypoxemic pups.

Animals↗

PubMed1986

Beagle puppy model of perinatal cerebral infarction. Regional cerebral prostaglandin changes during acute hypoxemia.

Perinatal cerebral infarction, or stroke, is a not uncommon finding in newborns who survive after intensive care. Asphyxia, with its component parts hypoxemia and hypotension, represents the most common cause of perinatal cerebral infarction and may result in neuropathological changes in the periventricular white matter. Previous studies have demonstrated regional alterations in cerebral blood flow (CBF) in response to hypoxemic insult. This work examines the effects of hypoxemia on regional cerebral prostaglandin levels in the developing brain, since some observers believe that local CBF is controlled in part by prostaglandins. In this study, newborn beagle pups were anesthetized, subjected to tracheotomy and artificially ventilated to maintain normoxemia and normocarbia. Mean arterial blood pressure (MABP) was continuously monitored by means of an indwelling catheter and transducer, and craniectomies were performed. When the pups were physiologically stabilized, they were randomly assigned to receive acute hypoxemic insult (pO2 14.0 +/- 1.55 mm Hg, mean +/- standard deviation) accomplished by altering the oxygen concentration in the inspired air) or to receive no insult (mean pO2 84.3 +/- 13.0 mm Hg). Fifteen minutes following stable hypoxemic or normoxic conditions, all pups underwent in vivo freezing of the intracranial contents under anesthesia followed by rapid sacrifice. No significant differences were noted between the MABP, pH, or pCO2 values for the control and hypoxemic pups during the experimental period. Regional cerebral prostaglandin data demonstrated a significant increase in prostaglandin (PG)E2 in the gray matter of hypoxemic pups when compared to the normoxic controls (p less than 0.02). No significant differences were noted for 6-keto-PGE1 alpha, the stable metabolite of prostacyclin, or thromboxane (TX)B2, the stable metabolite of TXA2, in the gray matter. In addition, although 6-keto-PGE1 alpha was significantly lower in the periventricular white matter of the hypoxemic pups (p less than 0.05), there were no changes in the white matter in either PGE2 or TXA2. This regional differential synthesis of PGE2 in response to hypoxemic insult may explain the relative failure of CBF to the periventricular white matter and thus the neuropathological alterations attributed to it.

Acute Disease↗

PubMed1985

Labelling of olfactory bulb glomeruli following horseradish peroxidase lavage of the nasal cavity.

The transport of horseradish peroxidase (HRP) from the nasal cavity to the olfactory bulb was examined in rat. HRP was present primarily in the olfactory nerve and glomerular layer. In some animals the glomeruli were densely filled with product while in others there was considerable interglomerular variation in density. Examination of the decalcified noses revealed a restricted distribution of HRP in those rats with partially labelled olfactory bulbs. The presence of small groups of densely labelled glomeruli was also noted using the 2-deoxyglucose method to examine odor-induced metabolic activity.

Animals↗

PubMed1985

Randomized indomethacin trial for prevention of intraventricular hemorrhage in very low birth weight infants.

We admitted 48 preterm neonates (600 to 1250 gm birth weight, normal 6-hour echoencephalograms) to a randomized prospective indomethacin or placebo trial for the prevention of neonatal intraventricular hemorrhage. Beginning at 6 postnatal hours, indomethacin or placebo was administered intravenously every 12 hours for a total of five doses. Cardiac ultrasound studies to assess the status of the ductus arteriosus were performed at 6 postnatal hours and on day 5. Urinary output, serum electrolytes, and renal and clotting functions were monitored. No differences in birth weight, gestational age, Apgar scores, or ventilatory needs were noted between the two groups. Six infants given indomethacin had intraventricular hemorrhage, compared to 14 control infants (P = 0.02). The indomethacin-treated group had significant decreases in serum prostaglandin values 30 hours after the initiation of therapy. The overall incidence of patent ductus arteriosus was 82% at 6 postnatal hours; 84% of the indomethacin-treated infants experienced closure of the ductus, compared to 60% of the placebo-treated patients. Closure of the ductus was not related to incidence of intraventricular hemorrhage. We speculate that indomethacin may provide some protection against neonatal intraventricular hemorrhage by acting on the cerebral microvasculature.

6-Ketoprostaglandin F1 alpha↗

PubMed1985

Bimanual endoscopic orbital biopsy. An emerging technique.

Diagnostic biopsy specimens from six posterior orbital lesions have been obtained under direct endoscopic view with either a fine needle aspiration or an intracannular microbiopsy forcep. This method is comparable to earlier fine needle aspiration techniques, but has the decided advantage of providing a specimen from visually indentified abnormal tissue. In those cases where inadequate specimens are obtained by fine needle aspiration, a microforcep is used to obtain a substantial specimen. The microinvasive endoscopic biopsy technique of the Orbital Unit at Pacific Medical Center is described with an analysis of six cases. The emerging technology of fiberoptic illumination, minified color video cameras, sophisticated imaging, efficient microsurgical instruments and laser delivery methods make the potential for deep orbital endoscopic microinvasive surgery exciting.

Aged↗

PubMed1985

Calcifications in lesions of the fossa of the lacrimal gland.

It is frequently reported that calcification in the fossa of the lacrimal gland is a reliable sign of malignancy. We present a small, previously unreported series of lacrimal gland fossa calcifications, in which in three out of five cases the lesion was benign. Calcification can be a misleading radiographic sign and should not, in and of itself, be considered diagnostic of malignancy. This is important because proper preoperative diagnosis of lacrimal fossa tumors is essential as management differs.

Adult↗

PubMed1985

Beagle puppy model of intraventricular hemorrhage. Effect of superoxide dismutase on cerebral blood flow and prostaglandins.

Intraventricular hemorrhage (IVH) represents a major problem for preterm neonates and is thought to occur secondary to alterations in cerebral blood flow (CBF) to damaged germinal matrix tissues. Many investigators believe that both local CBF and changes in capillary morphology and permeability may be partially controlled by prostaglandins. To evaluate this hypothesis, the authors have studied the effects of superoxide dismutase (SOD), a known free-radical scavenger, on newborn beagle pups that were randomly assigned by computer to four groups consisting of either SOD- or saline-pretreated animals that underwent either insult by hemorrhagic hypotension/volume reexpansion or no insult. Prostaglandin levels were determined prior to and 60 minutes following the administration of the solutions, and carbon-14 iodoantipyrine autoradiography was performed for determination of CBF. It was demonstrated that, although SOD significantly decreased the incidence of IVH in this model (p less than 0.05), it caused no alterations in baseline CBF or prostaglandin levels. In addition, SOD did not prevent either the systemic blood pressure changes or the alterations in CBF found in response to a hemorrhagic hypotensive insult. The authors propose that neonatal IVH results from a combination of factors, one of which is prostaglandin-mediated alterations in CBF to a damaged capillary matrix.

Animals↗

PubMed1985

Beagle puppy model of perinatal cerebral infarction. Acute changes in cerebral blood flow and metabolism during hemorrhagic hypotension.

Asphyxia, with its attendant hypotension, is by far the most common cause of neonatal cerebral infarction and frequently results in lesions of the parieto-occipital white matter. This study examines the effects of hypotension on regional cerebral blood flow (CBF), local cerebral glucose utilization (LCGU), and serum prostaglandin levels in newborn beagle pups. The animals (24 to 96 hours old) were anesthetized, tracheotomized, and paralyzed. Pups were randomly divided into two groups: one was subjected to hemorrhagic hypotension and the other received no insult. Hypotension was induced by slow venous hemorrhage to maintain a mean arterial blood pressure of 20 to 30 mm Hg. Autoradiographic determinations of LCGU using carbon-14 (14C)-2-deoxyglucose were performed 45 minutes after randomization to groups. Autoradiographic determinations of CBF were performed using 14C-iodoantipyrine on a second group of pups 15 minutes after randomization. Prostaglandins were measured immediately before and 15 minutes after insult or control manipulation. There were no significant differences in the values for thromboxane B2 or 6-keto-prostaglandin F1 alpha, the stable breakdown products of thromboxane A2, and prostacyclin. Prostaglandin E2 levels significantly increased in response to hemorrhagic hypotensive insult. In addition, although regional CBF was maintained in cortical and central gray matter structures during hypotension, CBF to the periventricular temporal and parietal white matter zones significantly decreased, and LCGU was increased in these same regions during hypotensive insult. The uncoupling of CBF and metabolism in these periventricular white matter regions may be responsible for the neuropathological sequelae of perinatal asphyxia.

Animals↗

PubMed1985

Beagle puppy model of perinatal cerebral infarction. Acute changes in regional cerebral prostaglandins during hemorrhagic hypotension.

Perinatal cerebral infarction is a not uncommon finding in newborn babies surviving intensive care. Asphyxia, with its attendant hypotension, is the most common cause of this problem and may result in neuropathological changes in the periventricular white matter. Previous studies have demonstrated uncoupling of cerebral blood flow and metabolism in the periventricular white matter regions of newborn beagle pups exposed to hemorrhagic hypotension. This work examines the effects of hypotension on serum and regional cerebral prostaglandin levels in the newborn beagle pup. The animals were anesthetized, tracheostomized, and paralyzed. Pups were randomly assigned to two groups: one was subjected to hemorrhagic hypotension and the other received no insult. Hypotension was induced by slow venous hemorrhage calculated to maintain a mean arterial blood pressure at 20 to 30 mm Hg. Serum prostaglandin determinations were made immediately before and 15 minutes after random assignment to hypotension or control groups. In addition, regional cerebral prostaglandin determinations were performed 15 minutes after randomization. Analysis of the serum prostaglandin data revealed that there were no significant differences in the values for thromboxane B2 or 6-keto-prostaglandin (PG) F1 alpha, which are the stable breakdown products of thromboxane A2 and prostacyclin, respectively. Prostaglandin E2 levels increased in response to hemorrhagic hypotension insult. Regional cerebral prostaglandin determinations demonstrated decreases in thromboxane B2 and 6-keto-PGF1 alpha in both gray and white matter. Although gray matter PGE2 was increased in pups exposed to hemorrhagic hypotension, this increase was not found in the periventricular white matter of injured pups. This regional difference in PGE2 synthesis in response to insult may explain the periventricular white matter neuropathological changes attributed to it.

Animals↗

PubMed1985

Periorbital osteosarcoma: an unusual case report and review of the clinical and histopathological features.

We will describe a case of a rapidly growing osteoma of the orbit in a young boy presenting with orbital cellulitis. The subsequent discussion elucidates the clinical and radiographic features of osteoma and attempts to clarify the confusing terminology surrounding the histopathology of the three main types of osteoma. Patients with osteoma of the skull should be referred for appropriate gastrointestinal studies to rule out the occurrence of Gardner's syndrome.

Adolescent↗

PubMed1984

Beagle puppy model of intraventricular hemorrhage: ethamsylate studies.

Intraventricular hemorrhage (IVH) remains a major problem of preterm neonates, and ethamsylate, an inhibitor of specific prostaglandin-synthetic enzymes has been demonstrated to prevent IVH in these patients. We have examined the effects of ethamsylate on newborn beagle pups who were, by randomized computerized design, assigned to four cells consisting of (a) either ethamsylate or saline pretreatment and (b) either insulted or not insulted with hemorrhagic hypovolemia/volume re-expansion. Prostaglandin levels were obtained prior to and thirty minutes following administration of the solutions and 14C iodoantipyrine autoradiography was performed for cerebral blood flow (CBF) determinations. Ethamsylate produced a significant decrease in the incidence of IVH in this model (p less than 0.05). Following drug administration, ethamsylate-pretreated pups had significant declines in thromboxane B2 and 6-keto PGF1 alpha levels, the major breakdown products of thromboxane A2 and prostacyclin. Although ethamsylate significantly lowered baseline CBF in all brain regions examined in insulted and non-insulted pups (p less than 0.05), in the drug-treated group it did not prevent the changes seen in CBF to the germinal matrix region which were detected in the saline-pretreated pups. Nor did it significantly blunt the blood pressure changes in response to the hemorrhagic hypovolemia/volume re-expansion insult found in the latter group of animals. In addition, only ethamsylate pretreated pups had marked hypotensive responses to the reperfusion phase of the insult. Although the diminution of baseline CBF may contribute to the prevention of neonatal IVH which this drug has been demonstrated to exhibit, ethamsylate may also act as a capillary stabilizing agent.

Animals↗

PubMed1984

Specific olfactory receptor populations projecting to identified glomeruli in the rat olfactory bulb.

A critical gap exists in our knowledge of the topographical relationship between the olfactory epithelium and olfactory bulb. The present report describes the application to this problem of a method involving horseradish peroxidase conjugated to wheat germ agglutinin. This material was iontophoretically delivered to circumscribed glomeruli in the olfactory bulb and the characteristics and distribution of retrogradely labeled receptor cells were assessed. After discrete injections into small glomerular groups in the caudomedial bulb, topographically defined populations of receptor cells were labeled. Labeled receptor cell somata appeared at several levels within the epithelium. The receptor cell apical dendrites followed a tight helical course towards the surface of the epithelium. The data thus far demonstrate that functional units within the olfactory system may include not only glomeruli as previously suggested but, in addition, a corresponding matrix of receptor cells possessing functional and topographical specificity.

Animals↗

PubMed1984

Beagle puppy model of intraventricular hemorrhage. Effect of indomethacin on local cerebral glucose utilization.

The newborn beagle puppy has been demonstrated to provide a good model for neonatal intraventricular hemorrhage (IVH). A study was designed to determine if indomethacin can prevent IVH, and if indomethacin would produce changes in local cerebral glucose utilization (LCGU). By computerized random design, newborn beagle puppies were pretreated with either indomethacin (a known inhibitor of prostaglandin synthetase) or saline, and then assigned either to receive a hemorrhagic hypotension/volume reexpansion insult or to receive no insult. Pretreatment with indomethacin produced a marked drop in the incidence of IVH as well as significant alterations in the blood pressure responses to the hemorrhagic hypotension/volume reexpansion insult. Carbon-14 autoradiography was used to determine LCGU: no alterations were demonstrated in cerebral metabolism in uninjured pups pretreated with indomethacin compared to saline-pretreated animals. In addition, although the hemorrhagic hypotension/volume reexpansion insult produced marked alterations in LCGU in both groups of traumatized pups, indomethacin prevented the changes in LCGU in the germinal matrix and white matter that were found in the saline-pretreated animals.

Animals↗

PubMed1983

Evidence for olfactory function in utero.

Pregnant rats received 2-[14C]deoxy-D-glucose (2DG) intravenously on the last day of gestation, and their fetuses were delivered 1 hour later by cesarean section. Fetal brains showed high 2DG uptake spread throughout the accessory olfactory bulb and little or no differential uptake in the main olfactory bulb. These findings demonstrate that functional activity occurs in the accessory olfactory bulb in utero and suggest that the accessory olfactory system may be the pathway by which fetal rats detect the odor quality of their intrauterine milieu.

Animals↗

PubMed1983

Intravascular papillary endothelial hyperplasia of the eyelid.

Intravascular papillary endothelial hyperplasia (IPEH), a benign lesion histopathologically characterized by intravascular fibrous papillary fronds covered by pleomorphic endothelium, is usually found in the subcutaneous tissues of the head and extremities. We describe the clinical and histologic findings of IPEH in the upper eyelid of a 20-year-old woman. Intravascular papillary endothelial hyperplasia has been confused with angiosarcoma. The differential diagnosis and key distinguishing features are discussed and the literature is reviewed.

Adult↗

PubMed1983

The effect of intranasal zinc sulfate treatment on odor-mediated behavior and on odor-induced metabolic activity in the olfactory bulbs of neonatal rats.

This study describes the effect of lesions of the peripheral olfactory receptor sheet on odor-mediated behavior and on odor-induced metabolic activity in the neonatal olfactory bulb. Nine-day-old rats were treated by intranasal irrigation with a solution of 1% ZnSO4 or 5% ZnSO4 or saline. At 1 and 5 days following treatment they were tested for maternally-directed behaviors which are mediated in large part by olfactory cues. At 1 day following treatment the pups treated with ZnSO4 solutions had significant deficits in their odor-directed behavior. By 5 days however, most pups treated with 1% ZnSO4 had recovered to control levels, while the pups treated with 5% ZnSO4 continued to exhibit profound behavioral deficits. Following the behavioral testing, the pups were tested using the 2-deoxyglucose method for amyl acetate odor-induced metabolic activity in their olfactory bulbs. Control pups had large regions of high focal activity in their anterolateral and caudomedial olfactory bulbs. The 1% ZnSO4 pups had smaller foci which were confined primarily to the medial olfactory bulb. The 5% ZnSO4 pups had very little focal uptake in their olfactory bulbs. There was a clear correlation between intact olfactory nerve and glomerular layers and sites of increased functional activity. The results of this study demonstrate that there is a relationship between the degree of behavioral deficit and the extent of odor-induced functional activity in the olfactory bulb.

Animals↗

PubMed1983

Beagle puppy model of intraventricular hemorrhage: randomized indomethacin prevention trial.

The newborn beagle puppy has been demonstrated to provide a good model for neonatal intraventricular hemorrhage (IVH). By randomized computerized design, indomethacin, a known inhibitor of prostaglandin synthetase, was administered to newborn beagle puppies, all of which underwent the experimental model of hemorrhagic hypotension followed by volume reexpansion for the production of IVH, to determine whether indomethacin can prevent intraventricular hemorrhage in this model. Nine percent of all pups receiving indomethacin experienced intraventricular hemorrhage, compared with 80% of animals who received the saline vehicle. In addition, significant alterations in the blood pressure responses to the hemorrhagic hypotension/volume reexpansion insult were noted in this group when compared with control animals.

Animals↗

PubMed1983

Beagle puppy model of intraventricular hemorrhage. Effect of indomethacin on cerebral blood flow.

The newborn beagle puppy has been demonstrated to provide a good model for neonatal intraventricular hemorrhage (IVH). A study was designed to determine if indomethacin can prevent IVH and if indomethacin would produce changes in cerebral blood flow (CBF). Newborn beagle puppies were randomized by computer into two groups: one was pretreated with indomethacin, a known inhibitor of prostaglandin synthetase, and the other was saline. The dogs in both groups were then assigned either to undergo hemorrhagic hypotension/volume reexpansion insult or to receive no insult. Twenty percent of all pups receiving indomethacin and undergoing the insult experienced IVH, compared to 71% of the pups undergoing insult that had been pretreated with saline. Significant alterations in the blood pressure responses to the hemorrhagic hypotension/volume reexpansion insult were noted in the former group compared to the saline-pretreated pups subjected to insult. Finally, employing carbon-14 autoradiography for the determination of CBF, it was demonstrated that indomethacin decreases resting CBF of the newborn beagle pups and, in indomethacin-pretreated animals subjected to insult, prevents the increases in CBF seen in the saline-pretreated traumatized pups.

Animals↗