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Biomedical subjects

M G Evans

Publications and source records attributed to M G Evans.

At least 55 records · Page 3Linked to original sources
PubMed1989

Histopathologic findings and energy dispersive X-ray spectroscopic analysis of experimentally induced foreign-body pneumonias in rats.

To document the diagnostic features of foreign-body pneumonias, four commonly used orally administered medicaments were instilled into the lungs of Sprague-Dawley rats. Rats in each group received a single 0.4 ml dose of either barium sulfate suspension (BaSO4), mineral oil, Pepto-bismol, or Kaopectate inoculated into a lung via a mainstem bronchus. The other lung served as a non-inoculated control. Rats were euthanatized on post-inoculation day 2 or 7 in order to document fully-developed acute pulmonary lesions and developing, chronic pulmonary lesions, respectively. Light microscopic features of BaSO4-inoculated lungs were distinctive from changes in mineral oil-inoculated lungs at both post-inoculation days. On post-inoculation day 2, rats inoculated with BaSO4 had pneumonia characterized by large numbers of alveolar macrophages containing green-to-brown granular material. There was minimal interstitial involvement. On post-inoculation day 2, mineral oil caused pneumonia characterized by giant cells and alveolar macrophages that had cytoplasms distended with variably-sized clear vacuoles. Lungs inoculated with BaSO4 or mineral oil had changed little on post-inoculation day 7 compared to the light microscopic features observed on day 2. On post-inoculation day 2, rats inoculated with either Pepto-bismol or Kaopectate had broncho-interstitial pneumonia with areas of necrosis and hemorrhage. On post-inoculation day 7, lungs inoculated with Pepto-bismol or Kaopectate had extensive fibrosis within alveolar lumens. Energy dispersive spectroscopy performed on sections of lung from rats given BaSO4, Pepto-bismol, and Kaopectate yielded a unique elemental spectrum for each compound in situ on post-inoculation days 2 and 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Clinicopathologic characterization of canine juvenile cellulitis.

The syndrome of canine juvenile cellulitis was observed and characterized throughout its clinical course when it occurred spontaneously in a litter of dogs. Histologically, pyogranulomatous inflammation was seen in facial skin and mandibular and superficial cervical lymph nodes of affected dogs. The predominant inflammatory cell characterized by light and electron microscopy and by immunohistochemical staining was an epithelioid macrophage. The same pyogranulomatous inflammatory process was seen in a lymph node anatomically distant from the site of apparent disease. Interestingly, a littermate with neither clinically evident dermal lesions nor lymphadenopathy had histologic evidence of a milder, but similar inflammatory process in a mandibular lymph node. The observation of canine juvenile cellulitis in clusters of dogs between 1 and 4 months of age and its apparent systemic nature suggest an infectious etiology. Bacterial, fungal, or viral agents were not isolated from affected lymph nodes. Attempts to transfer the disease by inoculation of neonatal puppies with tissue from affected dogs were also unsuccessful.

Animals↗
PubMed1989

Comparison of sites for transplantation of canine pancreatic microfragments.

The ideal site to transplant pancreatic islets has yet to be determined. To evaluate this problem, we have compared the efficacy of pancreatic microfragments transplanted into the splenic, intrahepatic and renal subcapsular sites. Function was assessed by plasma glucose (PG) and intravenous glucose tolerance test (ivGTT). Portal pressures and coagulation profiles (PT, PTT, FDP, Platelet count) were measured following intrasplenic and intraportal transplants. Liver enzymes (LDH, Alk. Phos., SGOT), serum bilirubin, BUN and creatinine were assessed serially in all groups. Nine of 10 dogs that received islets refluxed into the spleen were normoglycemic (mean PG = 94.5 mg/dL) at 1 mo with one dog failing four days following implantation (PG = 350 mg/dL). Following intraportal embolization, two of six dogs remained normoglycemic (PG = 95.7 mg/dL) at 1 mo. One dog died due to mesenteric venous thrombosis, two died suddenly within 24 h of engraftment without obvious cause, and a fourth died six days following transplantation (PG = 678 mg/dL). None of the six renal subcapsular transplants induced normoglycemia (mean PG = 430 mg/dL) at 1 mo. Mean rise in portal pressure (cmH2O +/- SEM) during intrasplenic and intraportal transplantation of islets was 1.7 +/- 0.6 and 31.2 +/- 3.3 respectively (p less than 0.001). Following intrasplenic and intrahepatic engraftment, significant coagulation abnormalities did not occur. Elevation of liver enzymes occurred 24 h following implantation to all three recipient sites but returned to preoperative values by 1 mo. Bilirubin was not affected. Renal function tests were not significantly altered in any groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Neuroaxonal dystrophy in a rottweiler pup.

An 8-month-old Rottweiler pup was evaluated for neurologic disorder. Clinical signs included ataxia, hypermetria of all 4 limbs, intention tremors of the head, lack of a menace reflex bilaterally, and mild proprioceptive deficits. The pup was euthanatized because of the progressive nature of the disease. Histopathologic findings consisted of decreased numbers of Purkinje cells in the cerebellum and moderate numbers of axonal spheroids in the nucleus cuneatus. This latter finding confirmed the diagnosis of neuroaxonal dystrophy.

Animals↗
PubMed1988

Rehospitalization of very-low-birth-weight infants.

Very-low-birth-weight (VLBW) infants are at high risk of mortality, morbidity, and rehospitalization in the first years of life, but little information is available to predict which VLBW infants are likely to require rehospitalization. This study describes a sample of 79 VLBW infants cared for in a charity hospital. The sample was predominantly black, and the majority of the mothers were young and unmarried. Some of the infants were followed up by a multidisciplinary High-Risk Follow-up Clinic, and all were tracked until their second birthdays to determine the rate of rehospitalization. Using multiple regression, we present herein a model that accounts for 51% of the variance in rehospitalization; the model includes mother's age, education, and marital status; infant birth weight and gestational age; the use of prenatal care and the High-Risk Follow-up Clinic; and three quadratic terms. Although the significance of the quadratic factors in the model makes explanation of these results difficult, results suggest that the model can be used to predict whether infants will require rehospitalization in the first two years of life.

Follow-Up Studies↗
PubMed1988

Concentration/response effect of 2,2', 4,4', 5,5'-hexabromobiphenyl on cell-cell communication in vitro: assessment by fluorescence redistribution after photobleaching ("FRAP").

Inhibition of gap junction-mediated cell-cell communication might be a mechanism for several types of cellular dysfunctions, including tumor promotion. Although many different assays have been designed to measure gap junction-mediated intercellular communication, we applied a new technique, termed Fluorescence Redistribution After Photobleaching ("FRAP"), to assess the ability of a known tumor promoter, 2,2', 4,4', 5,5'-hexabromobiphenyl (245-HBB), to inhibit cell-cell communication in a concentration-dependent manner. WB-F344 (rat epithelial) cells were plated at low density, exposed to noncytotoxic concentrations of 1, 5, or 20 micrograms 245-HBB/ml medium, and stained with 6-carboxyfluorescein diacetate. Single cells in pairs or clusters of touching cells in each exposure group were examined with FRAP. The results revealed an inverse correlation between the degree of fluorescence redistribution in photobleached cells and the concentration of 245-HBB. Therefore, FRAP appears to be a sensitive and rapid technique for determining complete or partial inhibition of chemically induced intercellular communication in vitro. These results also provide further evidence for the ability of 245-HBB to inhibit gap junction-mediated cell-cell communication in a concentration-dependent manner.

Cell Communication↗
PubMed1988

Voltage oscillations and ionic conductances in hair cells isolated from the alligator cochlea.

Tall hair cells were isolated by enzymatic and mechanical dissociation from selected regions of the apical half of the alligator (A. mississippiensis) cochlea. Single cells were subjected to voltage-clamp and current-clamp using the tight-seal whole-cell recording technique. Most hair cells isolated from the apex of the cochlea produced slowly regenerative depolarizations or Na action potentials during current injection, whereas hair cells isolated from more basal regions usually produced voltage oscillations (ringing) in response to depolarizing current injection, an indication of electrical resonance. Resonant frequencies ranged from 50 to 157 Hz in different cells. The higher-frequency cells tended to have larger and more rapidly activating outward currents than did the lower-frequency cells. An inward Ca current and an outward Ca-activated K current were present in all hair cells. In addition, an inwardly rectifying current and a small, transient outward current were often seen. Thus, we conclude that an electrical tuning mechanism is present in alligator hair cells. The role of the ionic conductances in shaping hair cell responses to current injection, and the possible contributions of these electrical responses to cochlear function are discussed.

Action Potentials↗
PubMed1988

Anchored cell analysis/sorting coupled with the scrape-loading/dye-transfer technique to quantify inhibition of gap-junctional intercellular communication in WB-F344 cells by 2,2',4,4',5,5'-hexabromobiphenyl.

Inhibition of intercellular communication has been hypothesized to play a role in tumor promotion. The compound 2,2',4,4',5,5'-hexabromobiphenyl (245-HBB) is a tumor promoter in vivo and blocks intercellular communication in vitro. The scrape-loading/dye-transfer (SL/DT) assay was used to assess this in vitro effect at varying concentrations of 245-HBB. The SL/DT technique is based on the intracellular loading of a fluorescent dye, lucifer yellow (LY), and monitoring its transfer into adjacent cells via patent gap junctions. Confluent WB-F344 (rat epithelial) cells were exposed to various noncytolethal concentrations of 245-HBB. Transfer of LY was then quantified with anchored cell analysis/sorting (ACAS 470, Meridian Instruments, Okemos, Mich.). The results indicate an inverse correlation between the degree of fluorescence in secondary LY-recipient cells and the treatment concentration. The coupling of these two new methods of cellular biology provided rapid quantitative analysis of dye transfer in measuring the concentration/response of modulation of gap-junctional permeability in cultured cells.

Animals↗
PubMed1988

Quantification of nuclear pores in tumor promoter-induced hepatic nodules in rats: a freeze-fracture study.

Twelve-week-old outbred female Sprague-Dawley rats weighing 190-210 g were partially hepatectomized and given diethylnitrosamine intraperitoneally (10 mg/kg) 24 h later. Thirty days later, rats were fed a diet containing tumor-promoting doses of two polybrominated biphenyl (PBB) congeners for 140 d. Rats were then maintained on diets free of PBBs until d 480, at which time they were killed and necropsied. Sections of liver containing hepatic nodules as well as nonnodular sections of liver were freeze-fractured and examined with transmission electron microscopy to quantify nuclear pores. Numbers of nuclear pores per square micrometer in sections of hepatic nodules were not significantly different from those in nonnodular liver. It is concluded that there are minimal quantitative differences in the numbers of nuclear pores in PBB-induced hepatic nodules when compared to nonnodular hepatic tissue from the same animal.

Animals↗
PubMed1988

Electrical tuning in hair cells isolated from the chick cochlea.

Tall (inner) hair cells were isolated from specific locations in the chick cochlea. The electrical membrane properties of these cells were recorded using the tight-seal whole-cell technique. Depolarizing current steps elicited damped voltage oscillations that ranged in frequency from 100 to 250 Hz among cells from the middle third of the cochlea (basal cells). The current-voltage relation obtained under voltage clamp was dominated by calcium-activated potassium current in the voltage range over which these oscillations occurred. Tall hair cells isolated from the apical tip of the cochlea (apical cells) exhibited action potentials and lower frequency voltage oscillations (5-14 Hz) during depolarizing current steps. Outward currents in these cells were 20-fold slower than those found in the basal cells. These results suggest that electrical tuning of hair cells may play a role in determining the frequency selectivity of the chick cochlea.

Animals↗
PubMed1987

Cystic mucinous hyperplasia in the gallbladder of a ferret.

An 8-year-old male ferret had icterus, hepatomegaly and an enlarged gallbladder. Microscopically, the gallbladder had numerous mucinous cysts and papillary hyperplasia of the mucosa, consistent with a diagnosis of cystic mucinous hyperplasia. No previous published reports of this condition in ferrets were found.

Animals↗
PubMed1987

Tetrodotoxin-sensitive, voltage-dependent sodium currents in hair cells from the alligator cochlea.

We have used whole-cell patch clamp techniques to record from tall hair cells isolated from the apical half of the alligator cochlea. Some of these cells gave action potentials in response to depolarizing current injections. When the same cells were voltage clamped, large transient inward currents followed by smaller outward currents were seen in response to depolarizing steps. We studied the transient inward current after the outward current had been blocked by external tetraethylammonium (20 mM) or by replacing internal potassium with cesium. It was found to be a sodium current because it was abolished by either replacing external sodium with choline or by external application of tetrodotoxin (100 nM). The sodium current showed voltage-dependent activation and inactivation. Most of the spiking hair cells came from the apex of the cochlea, where they would be subject to low-frequency mechanical stimulation in vivo.

Alligators and Crocodiles↗
PubMed1987

Septicemic listeriosis in a reindeer calf.

Septicemic listeriosis is described in a 2-day-old reindeer calf (Rangifer tarandus tarandus) from a local zoo. The gross and microscopic lesions were typical of disease caused by bacterial septicemia. Major lesions included necrosis of the liver, lung, adrenal gland, spleen, and lymph node. The diagnosis was suspected by special histopathological stains and confirmed by isolation of Listeria monocytogenes from multiple organs. This is the first report of listeriosis in a reindeer.

Adrenal Glands↗