Biomedical subjects
J M Sorrell
Publications and source records attributed to J M Sorrell.
Epitope-specific changes in chondroitin sulfate/dermatan sulfate proteoglycans as markers in the lymphopoietic and granulopoietic compartments of developing bursae of Fabricius.
The types and distributions of chondroitin sulfate proteoglycans within developing chick bursae of Fabricius were determined by indirect immunocytochemical analyses using mAb specific for chondroitin/dermatan sulfate epitopes. Analyses obtained from the use of well characterized mAb known to specifically identify chondroitin 4- and dermatan sulfates (antibody 2B6) and chondroitin 6-sulfate (antibody 3B3) were compared with those obtained from two additional mAb raised against chick chondroitin sulfates proteoglycans derived from hemopoietic tissue. The results indicate that chondroitin sulfate compositions of the adjacent lymphopoietic and granulopoietic compartments differ. Chondroitin 6-sulfate, notably absent from lymphopoietic regions, is a major chondroitin sulfate species in granulopoietic regions of day 13 bursae. Moreover, chondroitin 6-sulfate disappears from the granulopoietic compartment in a time course that corresponds to the decline in granulopoietic activity. Simultaneously, there is an apparent increase in chondroitin sulfates associated with developing medullary regions of lymphoid follicles. The content of chondroitin 4-/dermatan sulfates and, most significantly, of chondroitin/dermatan sulfates identified by antibodies raised against chick proteoglycans, increases within developing follicles. As a consequence, by day 18 of incubation, immunostained follicles become clearly demarcated from the connective tissue of the tunica propria. This study provides evidence that chondroitin sulfates are constituents of both lymphopoietic and granulopoietic microenvironments and that subtle changes occur within these proteoglycan structures during bursal development. These developmental changes in chondroitin sulfate compositions are consistent with these molecules playing a functional role in hemopoiesis.
Development of arteries in embryonic chick bone marrow with special reference to the appearance of periarterial granulopoietic sheaths.
Arterial development was studied in embryonic chick bone marrow starting on day 11 of incubation and continuing until day 18. Arteries first appear on day 11 as vessels with two components to their wall structure, namely a thin, complete endothelium and a nearly complete pericyte layer. With advancing age, three distinct layers--an endothelium, a complete muscularis, and adventitia--appear. Long, narrow endothelial cells form cellular junctions at their basal surfaces. Smooth muscle cells remain relatively undifferentiated and do not consist of more than three layers even in the largest arteries. The adventitia consists of a hypocellular zone containing fibroblasts and a collagenous extracellular matrix. Unmyelinated nerves are located at the peripheral margin of the adventitia. All of the larger arteries are surrounded by a sheath of heterophilic granulopoietic cells. These cells do not intrude into the adventitia, but basophilic or mast cells often do intrude. The stromal cells of the periarterial granulopoietic sheaths remain as either fibroblastic cells or as multilocular preadipocytes. They, unlike those stromal cells beyond the sheath, never become unilocular adipocytes. By day 18, granulopoiesis is restricted to the periarterial sheaths and to the endosteal regions of the marrow. These studies indicate that fibroblastic stromal cells and preadipocytes, but not fully developed adipocytes, support granulopoiesis in the chick marrow. The stromal cells in the periarterial sheaths either represent a subpopulation of cells that do not develop into adipocytes or represent cells whose development into adipocytes is locally inhibited.
Ultrastructural localization of peanut lectin binding to extravascular white blood cells in the bone marrow of embryonic chicks.
Labelling by the galactose-specific lectin peanut agglutinin was studied in bone marrow of the embryonic chick at the electron-microscopic level by use of both a gold-conjugated lectin and an indirect, ferritin-conjugated, biotinylated lectin. Cell surface labelling is exclusively restricted to developing and mature heterophilic granulocytes, monocyte/macrophages, mast cells/basophils, all of which appear to develop and reside in the extravascular spaces of the bone marrow. Resident small lymphocytes, which comprise a minor portion of the cell population, are also labelled. Erythroid cells and thrombocytic cells, which develop inside venous sinusoidal vessels, display no labelling. The latter cells, like extravascular leukocytes, contain surface galactosyl residues located in subterminal positions on cell surfaces, since they are labelled by the galactose-specific Ricinus communis agglutinin-I. It is postulated that terminal galactosyl residues might be involved in interactions between the surfaces of extravascular leukocytes and extracellular matrix and/or stromal cell surfaces.
Immunochemical characterization and ultrastructural localization of chondroitin sulfates and keratan sulfate in embryonic chick bone marrow.
Monoclonal antibodies directed against specific carbohydrate epitopes on chondroitin 4-/dermatan sulfate, chondroitin 6-sulfate, keratan sulfate, and a monoclonal antibody directed against the hyaluronate binding region were used to characterize proteoglycans extracted from embryonic chick bone marrow. About half of the proteoglycans separate into the high density fraction on a CsCl gradient. Glycosaminoglycan-specific antibodies recognize proteoglycans from all fractions; this includes an antibody directed against keratan sulfate. Some proteoglycans, principally in the high buoyant density fraction, contain sites recognized by the antibody specific for the hyaluronate binding region. Within limits of detection, all core proteins belong to the high-molecular-weight category, with weights in excess of 212 kD. Antibodies directed against chondroitin 4-/dermatan sulfate and against keratan sulfate primarily bind to extracellular matrix material located in the extracellular spaces and to matrix elements in the pericellular regions of fibroblastic stromal cells. The antibody that recognizes chondroitin 6-sulfate binds to sites on surfaces of fibroblastic stromal cells and also to extracellular matrix material. Little or no antibody binding is detected on surfaces of granulocytic cells. These studies indicate that chondroitin sulfate and keratan sulfate chains are both present in the proteoglycan extract.
Ultrastructural localization of fibronectin in bone marrow of the embryonic chick and its relationship to granulopoiesis.
Fibronectin was immunolocated in embryonic chick bone marrow by the use of both a direct peroxidase conjugated antiserum and an indirect Streptavidin bridge technique. Fibronectin is located in the extravascular granulopoietic compartment and, to a lesser extent, in the vascular, erythropoietic compartment. There is no evidence of fibronectin being associated with blood-stromal cell interactions involving either erythropoiesis or thrombopoiesis. However, mature thrombocytes display a substantial surface coat containing fibronectin. Much of the fibronectin appears to be situated on surfaces of those fibroblastic stromal cells which support granulopoiesis. Fibronectin containing extracellular material connects surfaces of developing granulocytes with surfaces of stromal cells. Fibronectin is a surface component of granulocytes as well as nearby stromal cells. However, there appear to be fewer ferritin particles per unit of surface on granulocytic cells. Many of the ferritin particles are not clearly associated with amorphous matrix material at cell surfaces. Immunocytochemical attempts to identify laminin were unsuccessful. These studies indicate that fibronectin is situated at sites where it could mediate adhesive interaction between granulopoietic cells and their stromal cells. Furthermore, cell surface-matrix interaction involving fibronectin could mediate migration of blood cells within the extravascular spaces.
Immunochemical and biochemical comparisons between embryonic chick bone marrow and epiphyseal cartilage chondroitin/dermatan sulphate proteoglycans.
Chrondroitin sulphate proteoglycans obtained from embryonic chick bone marrow and epiphyseal cartilage were compared using immunochemical and biochemical analyses. Proteoglycans from each tissue, separated on CsCl density gradients, under dissociative conditions, into high (1.6 g ml-1), medium (1.5 g ml-1) and low (1.4 g ml-1) buoyant density fractions, were immunochemically analysed, using a panel of monoclonal antibodies that specifically recognize chondroitin 4-/dermatan sulphates, chondroitin 6-sulphate, keratan sulphate, the hyaluronate binding region present on connective tissue proteoglycans, and link protein. The same antibodies were used in Western blot analyses to detect intact proteoglycan monomers and core proteins that had been fractionated by agarose-polyacrylamide and by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Specific differences between marrow and cartilage proteoglycans were detected. In CsCl gradients, marrow proteoglycans displayed a higher degree of heterogeneity in terms of buoyant densities and hexuronate distribution. Keratan sulphate chains were constituents of the majority of 'large' proteoglycans in the marrow; however, a portion of the large proteoglycans in marrow middle buoyant density fraction either lacked keratan sulphate chains or were substituted with a form different from that found on cartilage proteoglycans. Marrow lacked 'small' chondroitin/dermatan sulphate proteoglycans that were present in cartilage and contained a more heterogeneous population of proteoglycans, particularly in the lower buoyant density fractions. Both marrow and cartilage were similar in that they contained, as their major components, large, aggregating proteoglycans and link proteins that were immunochemically and biochemically identical. The significance of these differences between marrow and cartilage proteoglycans remains to be determined, but they may, in part, be responsible for imparting unique characteristics to the haematopoietic extracellular matrices.
Ultrastructural localization of heparan sulfate and chondroitin sulfates associated with granulopoiesis in embryonic chick bone marrow.
Sulfated glycoconjugates were ultrastructurally localized within embryonic chick marrow by using the high iron diamine-silver proteinate stain. Stain was concentrated in the extravascular, granulopoietic compartment, indicating that granulopoiesis, but not erythropoiesis, proceeded in a highly sulfated environment. It was likely that most of the stainable material represented sulfated proteoglycans since staining was abrogated by predigesting tissue with enzymes and other treatments known to degrade specific glycosaminoglycan chains. Chondroitinase/hyaluronidase digestion resulted in the removal of most of the stainable material associated with the extracellular matrix and a portion of the stainable material associated with fibroblastic cell surfaces. Unaffected material lay in close proximity to fibroblastic cell membranes. Heparitinase/heparinase digestion had essentially the opposite effect. Sulfated material associated with matrix components was largely unaffected, but the fibroblastic plasmalemmal material was now absent. These results suggest that there are at least two categories of sulfated proteoglycans in the granulopoietic compartment, each differentially distributed. The plasmalemmal material likely represented heparan sulfate which in this tissue appeared to be associated in a uniform layer with fibroblastic stromal cell membranes and not with blood or endothelial cell membranes. Material identified as chondroitin sulfates was found within patches of amorphous matrix that was located on fibroblastic stromal cell surfaces and that was interspersed with fibrils in the extracellular matrix. Chondroitin sulfates were sparsely distributed on granulocytic cell surfaces.
Factors influencing comprehension of information for informed consent: ethical implications for nursing research.
Empirical studies on comprehension of information for informed consent show that research subjects often do not understand major portions of that to which they have consented. This raises the ethical question of whether or not the consent process has accomplished its purpose--the protection of the individual's right to self-determination. This article focuses on the following factors derived from the research literature that influence comprehension of information for informed consent: the nature of information, method of presentation of information, demographic factors, and personal factors. From these factors and methodological considerations, ethical implications for nursing research are addressed.
Intercellular junctions in the hematopoietic compartments of embryonic chick bone marrow.
Avian embryonic marrow is segregated into distinct erythropoietic and granulopoietic compartments. Within each compartment presumptive stem cells and immature blood cells establish intimate contact with their respective stromal cell. In this study we have examined one aspect of potential hematopoietic cell-stromal cell interaction by looking for the presence of intercellular junctions between these two elements. In previous studies, after aldehyde fixation, junctions were not observed, but after perfusion fixation with tannic acid-glutaraldehyde, pentilaminar junctions became evident. These junctions were most characteristically located in the intravascular erythropoietic compartment, but were also found in the extravascular granulopoietic compartment. Junctions frequently joined presumptive stem cells with sinusoidal endothelial cells as well as joining immature erythroblasts with sinusoidal endothelial cells; and less frequently, junctions connected adjacent erythroid cells. However, reticulocytes and erythrocytes were never seen to have formed junctions with any other type of cell. Similar junctions within the extravascular compartment connected contiguous reticular cells and also, on occasion, reticular cells with sinusoidal endothelial cells. Hematopoietic cell-reticular cell junctions were restricted to two classes of blood cells--extravascular presumptive stem cells and mast cells. There was no evidence of junctions connecting mature or maturing granuloid cells and any other cell type. The presence of intercellular junctions between immature blood cells and their respective stromal cells suggests that such interactions might play an important role in avian hematopoiesis. However, further work will be needed to determine if these junctions are merely adherence sites or whether they represent sites of intercellular communication. In either event, these junctions appear to reflect a mechanism whereby the marrow stroma could regulate erythroid maturation.
The cellular organization of fibroblastic cells and macrophages at regions of uncalcified cartilage resorption in the embryonic chick femur as revealed by alkaline and acid phosphatase histochemistry.
Resorption of uncalcified cartilage in the embryonic chick femur appears to be mediated by two types of mononuclear cells. One cell type lies flattened and adherent along the surface of the cartilage matrix into which it extends cellular processes. Cytological characteristics of a large, euchromatic nucleus containing a nucleolus, and cytoplasm containing moderate to extensive amounts of rough endoplasmic reticulum indicate that these are protein synthetic cells. Macrophages, characterized by a pleomorphic shape and cytoplasm containing numerous mitochondria and vesicles, comprise the second cell type. These may be seen lying in contact with cartilage matrix, but are more likely located in the nonhematopoietic marrow adjacent to resorbing cartilage, where they establish close cellular associations with protein synthetic cells. Alkaline and acid phosphatase histochemical studies differentiate these two cellular types. Marrow alkaline phosphatase activity is restricted to the cartilage-marrow interface from which it diffuses a short distance into cartilage matrix, but does not diffuse into nearby marrow. Intracellular alkaline phosphatase is present only in protein synthetic cells that line the surface of cartilage, and thus appears to be produced by these cells. Acid phosphatase positive macrophages are scattered throughout the marrow, but are found in greatest concentrations in the region of cartilage resorption. They are rarely in direct contact with cartilage, and there is no evidence that acid phosphatase is released from these cells. The relative localizations and the presence of cellular interactions of these two cell types suggests that protein synthetic cells may be of fibroblastic origin, and may play a primary role in cartilage degradation, while macrophages, in keeping with biochemical evidence, play an adjunct or possibly a regulative role.
Development of the embryonic chick phagocytic system: intraembryonic erythrophagocytosis induced by phenylhydrazine.
The intraembryonic reticuloendothelial response to phenylhydrazine-induced hemolytic anemia was studied embryonic chicks (days 13-16) by light and electron microscopy and histochemical and biochemical assays for acid phosphatase. Phenylhydrazine was given on day 13 and tissue taken at 2, 5, and 10 h and at 1, 2, and 3 days after injections. The response varied in the three major reticuloendothelial organs. The spleen first demonstrated an increase in erythrophagocytosis that was accompanied by increased acid phosphatase levels. Erythrophagocytosis occurred primarily in the red pulp resulting in increased numbers of macrophages, increased to enlarge the spleens. By 2 days after phenylhydrazine injection, greatly enlarged macrophages began to migrate into the venous system, where some erythrophagocytosis continued to occur. The liver was also a major erythroclastic organ in which Kupffer cells became increasingly erythrophagocytic. However, erythrophagocytosis began later than in the spleen, and as measured by acid phosphatase levels, the liver was not as effective in removing damaged erythroid cells. Marrow erythrophagocytosis was only slightly enhanced; however, the marrow responded by increasing its production of red blood cells. Thus, the intraembryonic reticuloendothelial organs of the embryonic chick responded to phenylhydrazine-induced hemolytic anemia in much the same manner as might be expected of the adult bird.
Cell interactions between hematopoietic and stromal cells in the embryonic chick bone marrow.
Light microscopic, scanning electron microscopic, and transmission electron microscopic studies of the early developmental stages of chick embryonic bone marrow disclose characteristic associations of the first hematopoietic cells with stromal cells. The first hematopoietic cells, large basophilic cells that we have termed presumptive stem cells, segregate into erythropoietic and granulopoietic regions. Intravascular erythropoietic cells associate with sinusoidal endothelial cells, while granulopoietic cells associate with extravascular reticular cells. Extensive, intimate contacts between erythroid and endothelial cells are maintained, in part, by marginal arrays of microtubules, which promote a flattening of the adherent erythroid cell surface. In addition, cell surface components of opposing cells, visualized by ruthenium red staining, appear to merge and possibly to interact. Granulopoietic cells establish intimate but less extensive associations with reticular cells through cell-surface interactions. Stationary granuloid cells appear to be held in place by small, thin processes emanating from the sheet-like reticular cells. Granuloid cells are capable of moving within the extravascular region, using reticular cell surfaces as a substrate. Intimate associations also occur among granulopoietic cells, the significance of which is unclear. Thus, sinusoidal endothelial cells and reticular cells comprise the critical non-hematopoietic or stromal elements of avian bone marrow, where they have a putative role in segregating presumptive stem cells into erythrocyteic and granulocytic compartments. They serve as an architectual, and possibly regulatory, framework on which hematopoiesis occurs.
A light and electron microscopic study of the region of cartilage resorption in the embryonic chick femur.
It has long been known that uncalcified cartilage of embryonic chick long bones is removed to make way for invading marrow. However, no one has clearly established which cells are responsible for this erosion. Using the light and electron microscopes, we have studied the cartilage-marrow interface, which we presume to be the region of resorption. Here, we found two types of mononuclear cells in intimate contact with cartilage matrix. 1. The predominate cell type had a euchromatic nucleus with a nucleolus and a cytoplasm containing extensive profiles of rough endoplasmic reticulum; also, processes extended from these cells into the adjoining cartilage matrix. 2. Macrophages containing many lysosomal vesicles, which often became swollen, were found on or near the surface of cartilage. In addition, a few cells with an intermediate appearance were present. A decrease in the amount of sulfated material in a 25-30 micrometer zone of cartilage in advance of the interface and an alteration in the orientation, and in some cases the integrity, of collagenous fibers were associated with the presence of the above mentioned cells. These alterations in cartilage were not due to the synthesis of sulfated or of collagenous material. The above evidence, although not conclusive, suggests that these mononuclear cells are responsible for cartilage resorption. In this respect, the removal of avian uncalcified cartilage is similar to the resorption of uncalcified articular cartilage which occurs in rheumatoid arthritis.
The lived experiences of students in nursing: voices of caring speak of the tact of teaching.
The purpose of this phenomenological, Heideggerian hermeneutical study was to describe the lived experiences of 23 undergraduate nursing students in relation to their perceptions of "caring" experiences in their nursing programs. Data were collected by the primary investigators at a statewide nursing convention, with students relating stories of critical student experiences related to caring. Themes related to caring experiences included "caring as offering," "leaps ahead caring," and "creating a caring place." A recurrent pattern of "power inherent in teaching" was identified across student narratives, suggesting the need to study how teachers can use the tact of teaching to empower students. Implications drawn from the data suggest the need to explore how nursing students' learning is shaped by caring interactions with nurse clinicians and other health professionals as well as with nursing faculty.
Responding to student writing.
Sunday evening. You can't put off any longer the chore of correcting the stack of student papers. Picking up the first one, you scan it. It isn't good. The paper is full of sentence fragments and typographical errors. You decide that this is going to be a long evening. Scenes like this, hours spent correcting students' papers, only to discover that the students barely look at the comments, may lead faculty to avoid assigning writing. Fortunately, there are effective ways to respond to student writing without tying oneself down to hours of tedious correcting. These techniques can help nursing faculty enjoy reading and responding to students' papers, as well as help students to improve their writing skills.
Use of clinical journals to enhance critical thinking.
The clinical journal offers a valuable medium through which faculty can teach critical thinking. Both analysis and evaluation of the interactions and relationships between clinical practice, theory, and research can be greatly enhanced through careful structuring of clinical journal assignments. The authors discuss ideas about structuring clinical and journal assignments and strategies for giving feedback.
Designing class participation experiences for the introverted student.
Class participation for students is such a common expectation of nurse educators that it is easy to overlook the need to tailor class participation activities to individual student needs. An understanding of the various temperaments of individuals, especially preferences related to extroversion and introversion, can help nurse educators to plan class participation experiences that foster skills in critical thinking and enhance personal growth.