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Biomedical subjects

D E Sims

Publications and source records attributed to D E Sims.

31 records · Page 2Linked to original sources
PubMed1991

Erythrocyte dyscrasia, anemia, and hypothyroidism in chronically underweight llamas.

A syndrome characterized by anemia, erythrocyte dyscrasia, low body weight, and hypothyroidism was observed in 8 llamas (Lama glama). At initial examination (1 to 23 months of age; median, 7.5 months), llamas (3 males, 5 females) were markedly underweight (29 to 55 kg; median, 36 kg) and anemic (PCV, 12.9 to 25.5% [median, 19%]). Five of the llamas became progressively more anemic over time; in 2 of them, PCV decreased to less than 10%. Erythrocyte changes included severe poikilocytosis, anisocytosis, asymmetric distribution of hemoglobin within the cytoplasm, and cytoplasmic extensions from one or both poles. Six llamas had moderate to severe valgus deformities of the carpus. All llamas had low baseline serum thyroxine concentration and diminished response to thyrotropin administration. Baseline and post-thyrotropin triiodothyronine concentrations did not have consistent patterns. Five llamas were hypophosphatemic and 7 had low serum iron concentration (iron concentration was not determined in 1 llama). Orally administered iron supplementation did not induce clinical improvement. Because 3 of the affected llamas were full sisters, a genetic basis for the problem has to be considered. It was not possible to evaluate the familial relationship of the other 5 affected llamas. Although the underlying cause of the problem was not established, the prognosis for affected llamas is guarded to poor.

Anemia↗
PubMed1991

Orientation of adhering junctions between bovine pulmonary fibroblasts.

The ultrastructure and orientation of microfilament-attaching junctions between pulmonary fibroblasts (also known as myofibroblasts or contractile interstitial cells) of bovine lung septa were investigated by transmission electron microscopy. Adhering junctions similar to the fascia adherens of the intercalated disc, but of a macular design, link microfilament bundles of adjacent fibroblasts. The bundles of microfilaments joined by junctions were usually aligned perpendicularly to the axis of the alveolar wall. Gap junctions were located in close proximity to the adhering junctions, presumably to co-ordinate the contraction of the cells. The data indicate that fibroblasts are able to form multicellular contractile units within healthy, mature lung parenchyma.

Actin Cytoskeleton↗
PubMed1991

Preservation of tracheal mucus by nonaqueous fixative.

Two nonaqueous fixatives, composed of fluorocarbon solvents with dissolved osmium tetroxide, were used to determine the feasibility of preserving the mucous coat in bovine and rat trachea for light and electron microscopy. Aqueous fixatives, while providing excellent cytological preservation, wash away the mucous lining, precluding ultrastructural analysis. Inclusion of ruthenium red or alcian blue within aqueous fixative improved retention of mucus, but provided incomplete, patchy results. Fixation with nonaqueous fluorocarbon solvent and dissolved osmium tetroxide preserved a continuous mucous epiphase layer above a clear hypophase layer. Subcomponents of the mucus included an electron dense surface layer, interrupted patches of mucus above the surface layer and electron dense membrane-like material within the mucus. This method of fixation will preserve mucus for light, scanning and transmission electron microscopy, using either intratracheal or immersion methods of fixation. The latter would enable use of materials from large animal models, autopsy or an abattoir.

Animals↗
PubMed1991

Recent advances in pericyte biology--implications for health and disease.

This review highlights the contributions of recent pericyte research towards our understanding of normal and pathological functioning of microvessels. Pericytes are implicated in a variety of microvascular alterations, including wound healing, diabetes, inflammation, hypertension and neoplasia. They are capable of changing into other mesodermally derived cell types, including smooth muscle cells, osteoblasts and chondrocytes. The contractile properties of pericytes are being systematically examined in vitro; in addition to their tendency to contract spontaneously, pericytes can contract further in response to mediators of inflammation. In vivo studies indicate pericytes are concentrated near endothelial cell junctions along venules where they likely participate in inflammatory events. As agents are identified which modify pericyte responses to disease states, better therapeutic approaches will become possible.

Animals↗
PubMed1991

Alteration of primate ovary surface epithelium by exposure to hexachlorobenzene: a quantitative study.

Hexachlorobenzene (HCB) is a fungicide and a pollutant of increasing concern in industrialized regions of the world. Reproductive failure is one of the effects of HCB upon mammals. Alteration of cell shape in the ovary surface epithelium (OSE) of Cynomolgus monkeys following oral administration of HCB was observed in this study. At the lowest dose used, 0.1 mg/kg body weight, a dosage that is associated with follicular degeneration, HCB caused quantifiable changes in length-to-width ratios of OSE. Measurement of cell shape by light microscopy offers a reliable indication of OSE changes induced by HCB.

Animals↗
PubMed1990

Ultrastructure of pericytes in early stages of histamine-induced inflammation.

Physiological and ultrastructural assessment of changes in the walls of venules in the rat cremaster muscle after administration of histamine indicates that pericytes have essential roles in the normal functioning of venules during inflammation. Fluorescein-labelled albumin was used to quantitate macromolecular leakage and to select suitable venules for ultrastructural analysis 4 and 7 minutes after addition of histamine. Pericytes were concentrated over endothelial cell junctions and gaps. At 4 minutes, when albumin leakage was becoming detectable, gaps between endothelial cells were observed in the venule wall. In 24 serially sectioned gaps, pericytes formed covers, with contact points to the endothelial cells along the sides of the gaps. At 7 minutes, when albumin leakage was maximal, gaps with pericyte covers were still evident, but more commonly observed were pericyte covers over closed endothelial cell junctions. Spaces between the innermost pericytes and endothelial cells were enlarged by an order of magnitude, from 95 nm in controls to 872 nm at 4 minutes and 958 nm at 7 minutes. Pericytes formed coverings or bridges over inclusions of extravasated cells, fluid, proteins, and the vascular label monastral blue. The data indicate that pericytes protect the endothelial lining of venules during histamine-induced inflammation by forming a cohesive covering across gaps.

Animals↗
PubMed1989

Erythrophagocytosis in the caprine hemal node.

Caprine hemal nodes were studied by transmission electron microscopy after glutaraldehyde fixation and epoxy resin embedding. Hemal node macrophages were observed to be engaged in erythrophagocytosis. In the early stages of endocytosis, intact erythrocytes were contained in some of the heterophagic vacuoles of macrophages. Later, granular, electron-dense material appeared on erythrocytes, presumably as a result of lysosomal degradation of their matrices. Subsequently, the matrix fragmented and probably formed 'myelin-like figures' and residual bodies that dominated the macrophage cytoplasm. In addition, images of sinusoidal endothelium, reticular cells, lymphocytes and, rarely, eosinophils were observed that depicted structures resembling various stages of lysosomal digestion of erythrocyte matrix noted in macrophages. Our study provides evidence to support the fact that effete erythrocytes are filtered, besides known organs, also in caprine hemal nodes. The morphology and location of hemal nodes suggest that the organ can be an efficient blood filter.

Animals↗
PubMed1986

Contractile elements in the regulation of macromolecular permeability.

The leakage of macromolecules from the vasculature to the interstitium is greatly accentuated by mediators of edema such as histamine and bradykinin. The mechanism for this effect is not well delineated although many agents that affect smooth muscle tone may also affect macromolecular leakage. Leakage occurs primarily from the small venules. The demonstration that mediators of edema produce interendothelial gaps in the venules as well as changes in the shape of the endothelial nuclei has led to the hypothesis that a contraction of a vascular wall component may be responsible for the observed leakage of macromolecules. This component does not appear to be the vascular smooth muscle itself. Two other elements of the vascular wall, the endothelium and the pericytes, have been shown to contain many of the same elements of the contractile machinery present in smooth muscle. Most recent studies have presumed that endothelial cell contraction is responsible for the formation of the interendothelial gaps through which the macromolecules move. However, endothelial contraction has been difficult to demonstrate experimentally. Alternatively, inasmuch as pericytic processes can end near endothelial junctions and there is an abundance of fibronectin between the pericytes and the endothelium, it may be a pericytic contraction that causes the interendothelial gap formation.

Actins↗
PubMed1983

Analysis of relationships between pericytes and gas exchange capillaries in neonatal and mature bovine lungs.

Neonatal and mature bovine lungs were examined ultrastructurally to quantitatively assess pericyte envelopment of gas exchange capillaries and proximities of pericyte margins to endothelial cell junctions. Pericytes were observed on 91% of the cross-sectioned capillary profiles examined, with 18 and 26% coverage in neonatal and mature lungs, respectively. Chi-square analysis indicated a random occurrence of endothelial cell junctions under pericytes; however, pericyte processes tended to end near endothelial cell junctions. In the neonatal and mature lungs, 38 and 40%, respectively, of all endothelial junctions were within 0.5 microns of the margins of pericyte processes; such distances covered only 16 and 17% of the circumferences of the capillary profiles examined. Thus, endothelial cell junctions were located near pericyte margins over twice as often as would occur in a random distribution. If pericytes are contractile cells, as recent research indicates, they may function as regulators of lymph formation by influencing the permeability of endothelial cell junctions in the gas exchange capillaries.

Animals↗
PubMed1982

Microfilament-associated adhering junctions (6 nm F-maculae adherentes) connect bovine pulmonary fibroblasts in vivo.

Fibroblasts in the pulmonary alveolar septa of neonatal and mature cattle form spot-shaped intercellular junctions with each other where 6 nm microfilaments adhere to the plasma membranes. The junctions have variable cleft widths (10-20 nm) and a diffuse periodic intracleft substance. Impinging 6 nm microfilaments and plaque specializations were present in thin sections of junctions ranging from 0.4 to 0.6 micron in length. The microfilaments involved in junctions are parts of either cortical cytoplasmic webs or highly organized bundles. Two or more fibroblasts may form one complex of junctions and multiple junctions may occur between two fibroblasts. It is proposed that the in vivo fibroblast junction be named a 6 nm F-macula adherens, based on size of the associated microfilaments and type of junctional specialization.

Animals↗
PubMed1980

Neuro-epitheliomuscular cell and neuro-neuronal gap junctions in Hydra.

Gap junctions have been described ultrastructurally between neurons and epitheliomuscular cells and between neurons and their processes in the hypostome, peduncle and basal disc of Hydra. All gap junctions examined in Hydra exhibit two apposed plasma membranes having a 2-4 nm gap continuous with the extracellular space. The gap junctions are variable in length from 0.1-1.6 micrometers and appear linear or V-shaped in section. Neuronal gap junctions in Hydra occur infrequently as compared to chemical synapses. Electron microscopy of serial sections has demonstrated the presence of adjacent electrical and chemical synapses (neuromuscular junctions) formed by the same neuron. In addition, multiple gap junctions were present between two neurons. This is the first ultrastructural demonstration of electrical synapses in the nervous system of Hydra. Such synapses occur in neurons previously characterized as sensory-motor-interneurons on the basis of their chemical synapses; these neurons appear to represent a type of stem cell characterized by having both electrical and chemical synapses.

Animals↗