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Biomedical subjects

W B Stewart

Publications and source records attributed to W B Stewart.

At least 73 records · Page 4Linked to original sources
PubMed1982

Reconstruction of the periocular mucous membrane by autologous conjunctival transplantation.

We have extended the concept of autologous conjunctival transplantation for corneal resurfacing as recommended by Thoft to reconstruction in 14 patients with unilateral abnormalities of the bulbar and palpebral conjunctiva caused by alkali burns (2), irradiation (2), neoplasms (3), degenerative diseases (5), trauma (1), and developmental anomalies (1). Large, free conjunctival grafts from bulbar and forniceal donor sites were used. No complications have been noted at the recipient or donor sites. Grafts of normal conjunctiva provided intact basement membrane, goblet cells, and epithelium that help restore normal ocular and lid surfaces. The use of free conjunctival grafts provides significant advantage over the use of buccal mucous membrane grafts. The techniques and results of our experience with free conjunctival grafts in 14 patients are discussed.

Adolescent↗
PubMed1982

Beagle puppy model of intraventricular hemorrhage.

Intraventricular hemorrhage (IVH) is a major neurological problem of the preterm infant and originates in the germinal matrix tissues of the developing brain. The newborn beagle pup has been demonstrated to provide an excellent model for this neonatal neuropathological condition. By the production of hemorrhagic hypotension followed by relative volume reexpansion, such hemorrhages can be produced in this animal. Carbon-14 (14C)-iodoantipyrine was used for measuring the cerebral blood flow in this experimental model and demonstrated that, although the germinal matrix is a relatively low-flow area in the newborn beagle pup, the selective flow to this region increases significantly in animals with IVH.

Animals↗
PubMed1982

Local cerebral glucose utilization in the beagle puppy model of intraventricular hemorrhage.

Local cerebral glucose utilization has been measured by means of carbon-14(14C)-autoradiography with 2-deoxyglucose in the newborn beagle puppy model of intraventricular hemorrhage. Our studies demonstrate gray matter/white matter differentiation of uptake of 14C-2-deoxyglucose in the control pups, as would be expected from adult animal studies. However, there is a marked homogeneity of 14C-2-deoxyglucose uptake in all brain regions in the puppies with intraventricular hemorrhage, possibly indicating a loss of the known coupling between cerebral blood flow and metabolism in this neuropathological condition.

Animals↗
PubMed1981

Topographical and laminar localization of 2-deoxyglucose uptake in rat olfactory bulb induced by electrical stimulation of olfactory nerves.

Experiments were carried out to examine the topographical projection of the olfactory nerves to the olfactory bulb in the rat, using the Sokoloff [14C]2-deoxyglucose (2-DG) technique. Electrical stimulation of a medially located bundle of olfactory nerves produced a discrete zone of 2-DG uptake at the rostral pole of the bulb. Increasing stimulus strength yielded a slightly larger focus at this site. In contrast, electrical stimulation of laterally situated bundles of olfactory nerves resulted in a broad zone of activity extending along the lateral wall of the bulb, and increasing stimulus intensity produced a more extensive area of uptake. Laminar analyses provided information on the relation between activity in the glomerular layer, where the olfactory nerves terminate, and activity in deeper layers. The results support previous studies of the topographical projections of the olfactory nerves to the olfactory bulb. They also support the hypothesis that odor-induced 2-DG uptake in the olfactory bulb represents activation of groups of receptors in the olfactory epithelium whose axons terminate in activated glomerular regions in the olfactory bulb.

Animals↗
PubMed1981

Effect of trauma dose on spinal cord edema.

The spinal cord of anesthetized cats was subjected to impact trauma of different intensities to determine how changes in trauma magnitude affect the formation and distribution of edema. All animals underwent a laminectomy to expose the cord segments corresponding to the T5--7 vertebrae. Fourteen cats were injected with fluorescein-labeled albumin, and then subjected to 260, 360, 500, or 700 gm-cm injury to the spinal cord. They were sacrificed at 8 hours after trauma. Twelve cats were injected with fluorescein-labeled dextrans of 20,000, 40,000, 70,000, or 150,000 molecular weight (MW) prior to 500 gm-cm injury, and sacrificed 8 hours after trauma. Serial cord sections from both groups were studied by fluorescence microscopy. In nine cats, sections of cord were removed 8 hours after trauma of 260, 360, or 500 gm-cm impact, and 1-cm sections were assayed for dry weight. Extravasated tracers were present in areas of hemorrhage at the site of impact in all animals. Extension of tracers and increases in tissue water rostrally and caudally from the site of impact were observed consistently with time only in animals receiving 500 or 700 gm-cm trauma. The distance of migration was similar for all tracers. The longitudinal distribution of increased tissue water was consistent with the distribution of fluorescein markers. The findings indicate that the longitudinal extension of posttraumatic edema is directly related to the amount of initial trauma.

Albumins↗
PubMed1980

2-Deoxyglucose uptake in the cat spinal cord during sustained and habituated activity in the plantar cushion reflex pathway.

[14C]2-deoxy-D-glucose (2-DG) was administered intravenously to anesthetized cats during electrical stimulation of the plantar cushion (central foot pad). Afferent volleys and the efferent reflex were monitored by recording from the tibial nerve at the ankle. Plantar cushion stimulation at 3 HZ, 5 x threshold for 45 minutes led to a discrete region of increased 2-DG uptake dorsomedially in the dorsal horn, predominantly in Rexed's laminae III and IV, ipsilateral to the stimulation. A less marked increase in labeling was also sometimes observed in the medial portion of lamina V. No labeling specific to stimulation was observed in the ventral horns. A control preparation, to determine the effects of surgical manipulations alone, confirmed that the labeling was indeed specific to the plantar cushion stimulation. A pattern of labeling identical to that seen during 3 Hz, 5 x threshold stimulation occurred when 2-DG was administered during 10 Hz, 5 x threshold stimulation, after the reflex elicited by plantar cushion stimulation had completely habituated. The most straightforward interpretation of our results suggests that the increases in 2-DG labeling produced by stimulation of the plantar cushion probably occurred in regions with heavy concentrations of axon collaterals of the primary afferent A alpha beta fibers from the plantar cushion, at or near their sites of termination in the dorsal horn.

Afferent Pathways↗
PubMed1980

Eyelid tumors anmd renal transplantation.

The high incidence of malignant neoplasms in renal transplant recipients and other immunosuppressed patients is well recognized. A large proportion of these neoplasms are skin cancers. The frequent occurrence of other ocular complications, such as cataract, elevated intraocular pressure, hypertensive retinopathy, cytomegalovirus retinitis, and herpetic keratitis in patients after kidney transplant, has also been described. This report presents the clinical and histopathologic features of eyelid involvement by keratoacanthoma and squamous cell carcinoma in two patients after renal transplantation and alerts ophthalmologists to the potential for this association.

Adolescent↗
PubMed1980

Comparison of hydrogen clearance and 14C-antipyrine autoradiography in the measurement of spinal cord blood flow after severe impact injury.

Spinal cord blood flow was measured by two different techniques in normal and traumatized cat spinal cord. Flow was measured in the thoracic cord after severe (500-gm-cm) impact injury at T-6. Blood flow was measured sequentially at two sites for 7 hours after trauma using the hydrogen clearance technique, and spatially at many sites but at selected times by means of the 14C-antipyrine autoradiographic method. The two techniques gave similar results. Control white-matter blood flow in the lateral funiculus was 11.13 +/- 1.29 ml/min/100 gm in the hydrogen clearance series, and 11.07 +/- 3.16 gm blood/min/100 gmin the antipyrine series. Following injury, blood flow remained in the control range until 1 hour after trauma, when ischemia became the major pattern. From 4 to 8 hours following trauma, several categories of flow patterns emerged. In one group of animals, white-matter blood flow returned to control levels at some points along the length of cord surveyed, but remained depressed at adjacent cord levels. In another category of animals, most sites in the white matter had flows approaching control levels by 7 to 8 hours. In yet another group, all sites examined, although a limited number, showed ischemia. In contrast, gray-matter ischemia appeared earlier (25% of control levels at 1 hour), had a sharper focus, and persisted in the period examined. The differences in blood flow between gray and white matter and the longitudinal variation in white-matter flow suggested that the hydrogen clearance method should be verified by autoradiography for accuracy of spatial flow patterns.

Animals↗
PubMed1979

Functional organization of rat olfactory bulb analysed by the 2-deoxyglucose method.

The spatial patterns of activity elicited in the rat olfactory bulb under different odor conditions have been analysed using the 2-deoxyglucose (2DG) technique. Rats were injected with 14C-2DG, exposed to controlled environments of amyl acetate, camphor, cage air, dimethyl disulfide, and pure air and autoradiographs prepared by the method of Sokoloff. Amyl acetate was associated with regions of glomerular layer densities in the anterolateral and mid- to posteromedial parts of the bulbar circumference, as previously reported. The extents of the densities increased with increasing concentration. Camphor odor was associated with regions of increased density in the anterodorsal and mid- to posteromedial parts of the bulb. Exposure to cage air produced scattered densities in the posteromedial and posterolateral bulb. Exposure to dimethyl disulfide gave variable results. Pure air was associated with a minimal number of small dense foci. The results with amyl acetate, camphor and cage air suggest that patterns for different odors are distinguishably different but overlapping. The regions of activity are greatest in extent and density with the highest odor concentrations. These define the regions within which more restricted and isolated foci appear at lower concentrations. The results thus provide evidence for the specific role of spatial factors in the neural processing of odor quality and odor concentration.

Acetates↗
PubMed1979

Mechanisms of augmented field potential responses in the rat olfactory bulb.

Olfactory bulb field potential and single unit responses to paired pulse stimulation of the lateral olfactory tract were observed in the rat. In agreement with previous reports, surgical levels of barbiturate anesthesia prolonged the period of diminution of the field potential responses to the test pulse relative to the effect seen under light anesthesia. Very deep barbiturate anesthesia (sufficient to depress the EEG) led to decreased responses to the primary pulse but augmented responses to the test pulse. Urethane and ether anesthesia produced augmented test responses without severely depressing the EEG and without producing a period of diminished test responses. Single unit recordings failed to show external plexiform layer units excited at the time of maximal augmentation of the field potential. Simultaneous single unit and field potential recordings showed that prolonged diminution of the field potential response was associated with prolonged suppression of unit responses to the test pulse, while augmented field potential responses were associated with decreased suppression of unit responses to the test pulse. These observations are most easily explained by the assumption of temporal facilitation in the synaptic output of mitral and tufted cells. This facilitation is masked by feedback inhibition under some conditions, particularly under barbiturate anesthesia.

Anesthesia, General↗
PubMed1979

Lacrimal gland and fossa lesions: an approach to diagnosis and management.

Lesions of the fossa of the lacrimal gland present special problems in diagnosis and management. Clinical recognition and differentiation of benign mixed cell lacrimal gland tumors from other inflammatory and neoplastic lesions of the lacrimal gland fossa are feasible and should provide the basis for the approach to proper management. Lesions conforming to the clinical picture of benign mixed cell lacrimal gland tumors need not undergo incisional biopsy, but require en bloc excision with adjacent tissues through a lateral orbitotomy to ensure complete excision and to prevent late recurrence. Incisional biopsy is indicated and should not be delayed in suspected infectious and noninfectious inflammatory lesions that have not responded rapidly to medical therapy, and in other lesions suspected of being neoplastic and not amenable to total local excision. An expedient approach to these lesions is essential if the prognosis of epithelial lacrimal gland neoplasms is to be improved.

Adult↗
PubMed1979

Clinical presentation and management of lacrimal gland tumours.

This paper presents the clinical and pathological findings in 40 consecutive patients seen with primary tumours arising from the lacrimal gland. Twenty patients had a benign mixed-cell tumour. They presented in a recognisable clinical manner with a painless mass in the region of the lacrimal gland which slowly enlarged over a period of at least 1 year before consultation. Twenty patients had a carcinoma of the lacrimal gland. They had a short history and experienced pain. On clinical grounds they could not be distinguished from inflammatory lesions in the region of the lacrimal gland. The method of treating these 2 groups of patients is described and methods of dealing logically with their problems are suggested.

Adult↗
PubMed1979

Vascular ectasias of the colon.

Vascular ectasias are an acquired type of arteriovenous malformation distinct from neoplastic and congenital lesions. They can be the source of occult, recurrent or massive colonic bleeding usually in elderly patients but, occasionally, in younger adults. The vascular lesions are usually small but can be quite diffuse. The majority occurs in the right colon, but in our group of patients, a substantial number occurred distal to the hepatic flexure. The diagnosis can be made preoperatively, with colonoscopy but, more consistently, with arteriography. Therefore, arteriography should be performed in any patient with bleeding of the colon before surgical intervention. We recommend resection of the involved segment of the intestine as the treatment of choice.

Angiography↗