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Biomedical subjects

L M Walker

Publications and source records attributed to L M Walker.

At least 37 records · Page 2Linked to original sources
PubMed1999

Radiographic, ultrasonographic, and endoscopic findings in cats with inflammatory bowel disease of the stomach and small intestine: 33 cases (1990-1997).

OBJECTIVE: To characterize imaging findings in cats with confirmed inflammatory bowel disease (IBD) of the upper gastrointestinal tract (i.e., stomach and small intestine) and relate these findings to clinical signs and histologic changes. DESIGN: Retrospective study. ANIMALS: 32 cats with clinical and histopathologic diagnoses of IBD. PROCEDURE: Medical records were reviewed for signalment, clinical signs, clinicopathologic findings, radiographic and ultrasonographic findings, and results of endoscopic examination. Histologic findings were reviewed and characterized by severity and type of inflammatory infiltrate. RESULTS: All cats had 1 or more clinical signs (e.g., vomiting, diarrhea, weight loss, and anorexia) consistent with IBD. Lymphocytic and plasmacytic infiltrates were observed in histologic sections of gastrointestinal tissue. Crypt distortion, villous blunting and fusion, and fibrosis were most commonly seen in cats with moderate or severe IBD. Clinicopathologic findings of some cats included anemia, leukocytosis or leukopenia, hypocholesterolemia, and hyper- or hypoproteinemia. Abnormalities were not found on abdominal radiographic views in 9 of 9 cats. However, contrast studies using barium revealed radiographic abnormalities in 1 of 3 cats. In 13 of 17 cats, abdominal ultrasonography revealed several intestinal abnormalities (e.g., poor intestinal wall layer definition, focal thickening) and large mesenteric lymph nodes with hypoechoic changes consistent with IBD. Endoscopic observation revealed findings (e.g., erythema, plaques, mucosal friability) consistent with inflammation in 9 of 18 cats. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with endoscopy of the gastrointestinal tract or abdominal radiography, clinical signs and ultrasonographic findings appear to have the best association with histologic grade of IBD in cats.

Anemia↗
PubMed1999

Mechanotransduction pathways in bone: calcium fluxes and the role of voltage-operated calcium channels.

Changes in strain distribution across the vertebrate skeleton induce modelling and remodelling of bone structure. This relationship, like many in biomedical science, has been recognised since the 1800s, but it is only the recent development of in vivo and in vitro models that is allowing detailed investigation of the cellular mechanisms involved. A number of secondary messenger pathways have been implicated in load transduction by bone cells, and many of these pathways are similar to those proposed for other load-responsive cell types. It appears that load transduction involves interaction between several messenger pathways, rather than one specific switch. Interaction between these pathways may result in a cascade of responses that promote and maintain bone cell activity in remodelling of bone. The paper outlines research on the early rapid signals for load transduction and, in particular, activation of membrane channels in osteoblasts. The involvement of calcium channels in the immediate load response and the modulation of intracellular calcium as an early signal are discussed. These membrane channels present a possible target for manipulation in the engineering of bone tissue repair.

Biomechanical Phenomena↗
PubMed1997

Stereological analysis of gravitropism in protonemata of the moss Ceratodon.

Apical cells of dark-grown protonemata of the moss Cerotodon purpureus are negatively gravitropic. Previous light microscopy has shown that reorientation to the horizontal induces amyloplast sedimentation and redistribution of microtubules. To determine whether other components become redistributed laterally or axially, the apical 35 micrometers of both vertical and horizontal apical cells were compared stereologically using transmission electron microscopy. Reorientation to the horizontal changed the longitudinal distributions of tubular ER, Golgi stacks, and vesicles but not cisternal ER, mitochondria, and plastids. Only plastids showed a statistically significant lateral redistribution after horizontal placement. Qualitative examination of the sedimentation zone showed plastids sedimented close to peripherally located ER with vacuoles displaced above plastids. These results argue against a model where differential tip growth results from a redistribution of Golgi stacks or exocytic vesicles.

Bryopsida↗
PubMed1996

Clinical and clinicopathologic findings in dogs with acute respiratory distress syndrome: 19 cases (1985-1993).

OBJECTIVE: To describe clinical and clinicopathologic findings from dogs with histologic pulmonary lesions consistent with human adult respiratory distress syndrome and to identify potential factors. DESIGN: Retrospective study. ANIMALS: 19 dogs with acute respiratory distress. PROCEDURE: Medical records of dogs were reviewed. Signalment, physical examination and clinicopathologic findings at admission, and thoracic radiographic and necropsy findings were recorded. RESULTS: The most common clinical sign was dyspnea. Respiratory rate ranged from 36 to 140 breaths/min and abnormal breathing patterns were detected. Crackles were auscultated in 7 dogs. Severe diffuse interstitial and alveolar infiltrates were observed on thoracic radiography in 9 dogs shortly after arrival and developed later in 4 dogs. Four dogs were leukopenic and neutropenic. Disseminated intravascular coagulation was diagnosed in 2 dogs, and hypoalbuminemia was found in 8 dogs. Respiratory status deteriorated rapidly in all dogs, and 10 dogs were mechanically ventilated. Death was attributed solely to respiratory failure in 8 dogs. In the other 11 dogs, severe lesions in nonpulmonary organs, sepsis, or both may have contributed to death. The most common associated conditions that may have contributed to acute respiratory failure were microbial pneumonia, sepsis, aspiration pneumonia, and shock, with more than 1 factor found in 11 of 19 dogs. CLINICAL IMPLICATIONS: The index of suspicion for acute respiratory distress syndrome should be high in dogs with bilateral pulmonary infiltrates and acute respiratory distress that rapidly progresses to failure.

Animals↗
PubMed1996

Respiratory function and treatment in dogs with acute respiratory distress syndrome: 19 cases (1985-1993).

OBJECTIVE: To characterize respiratory function and treatment in dogs with findings compatible with those of human adult respiratory distress syndrome (ARDS) and to evaluate the application in dogs of clinical for diagnosis of ARDS. DESIGN: Retrospective review of medical records. ANIMALS: 19 dogs with acute respiratory distress syndrome. RESULTS: Arterial blood pH was 7.30 +/- 0.59 (mean +/- SD). Nine dogs had metabolic acidosis. In nonmechanically ventilated dogs, PaCO2 was 15.0 to 54.9 mm of Hg. Respiratory acidosis developed in 2 mechanically ventilated dogs. Hypoxemia was observed in 4 of 5 dogs breathing room air. In 4 mechanically ventilated dogs, oxygenation was inadequate, despite use of > 60% inspired O2 and positive end-expiratory pressure in 3 dogs. Alveolar-to-arterial oxygen tension gradients were widened in 4 dogs breathing room air and in 6 dogs ventilated with 100% O2. Ten dogs were mechanically ventilated; ventilatory rate was 18 to 60 breaths/min. Tidal volume was 12 +/- 3.8 ml/kg of body weight in 4 dogs, minute ventilation > 400 ml/kg/min in 2 dogs, and peak airway pressures > 25 cm of H2O in 6 dogs. Positive end-expiratory pressure was used in 8 dogs. Pneumothorax was detected in 5 ventilated dogs. Human clinical criteria for diagnosis of ARDS were fulfilled in 7 dogs. Fluid treatment consisted of IV crystalloids and synthetic colloids. Drugs most often administered were antibiotics and loop diuretics. CLINICAL IMPLICATIONS: Human clinical criteria for identification of ARDS may be helpful in diagnosis of acute respiratory distress syndrome in dogs.

Acid-Base Equilibrium↗
PubMed1996

The long-term stability and predictive validity of trait measures of affect.

This study examined the long-term temporal stability and predictive utility of trait Positive Affect and Negative Affect scales. Participants were assessed initially as undergraduates: They rated how they felt generally (general sample) or during the past year (year sample). They were retested on a general affect measure and on scales assessing current depression and anxiety approximately 6 (general sample) or 7 (year sample) years later. By this time, all of them had graduated from college and most were working full-time. Negative Affect scores declined significantly over the study. Nevertheless, the Negative and Positive Affect scales both displayed a significant, moderate level of stability. Moreover, initial scores on both scales correlated significantly with measures of current symptoms that were completed several years later. Thus, trait affect scales were substantially stable--and maintained significant predictive power--even across extended time spans.

Adult↗
PubMed1995

Microfilament distribution in protonemata of the moss Ceratodon.

Microfilaments were visualized in dark-grown protonemata of the moss Ceratodon to assess their possible role in tip growth and gravitropism. The relative effectiveness of rhodamine phalloidin (with or without m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS)) and of immunofluorescence (using the C4 antibody) was evaluated for actin localization in the same cell type. Using immunofluorescence, microfilaments were primarily in an axial orientation within the apical cell. However, a more complex network of microfilaments was observed using rhodamine phalloidin after MBS pretreatment, especially when viewed by confocal laser scanning microscopy. This method revealed a rich three dimensional network of fine microfilaments throughout the apical cell, including the extreme apex. Although there were numerous internal microfilaments, peripheral microfilaments were more abundant. No major redistribution of microfilaments was detected after gravistimulation. The combination of MBS, rhodamine phalloidin, and confocal laser scanning microscopy preserves and reveals microfilaments remarkably well and documents perhaps the most extensive F-actin network visualized to date in any tip-growing cell.

Actin Cytoskeleton↗
PubMed1995

Ultrastructural analysis of cell component distribution in the apical cell of Ceratodon protonemata.

A distinctive feature of tip-growing plant cells is that cell components are distributed differentially along the length of the cell, although most ultrastructural analyses have been qualitative. The longtitudinal distribution of cell components was studied both qualitatively and quantitatively in the apical cell of dark-grown protonemata of the moss Ceratodon. The first 35 micrometers of the apical cell was analyzed stereologically using transmission electron microscopy. There were four types of distributions along the cell's axis, three of them differential: (1) tubular endoplasmic reticulum was evenly distributed, (2) cisternal endoplasmic reticulum and Golgi vesicles were distributed in a tip-to-base gradient, (3) plastids, vacuoles, and Golgi stacks were enriched in specific areas, although the locations of the enrichments varied, and (4) mitochondria were excluded in the tip-most 5 micrometers and evenly distributed throughout the remaining 30 micrometers. This study provides one of the most comprehensive quantitative, ultrastructural analyses of the distribution of cell components in the apex of any tip-growing plant cell. The finding that almost every component had its own spatial arrangement demonstrates the complexity of the organization and regulation of the distribution of components in tip-growing cells.

Bryopsida↗
PubMed1994

How IPAs fail.

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Bankruptcy↗