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Biomedical subjects

J C Lewis

Publications and source records attributed to J C Lewis.

At least 73 records · Page 4Linked to original sources
PubMed1990

Image analysis and mathematical correlation between cell number and diameter of colonies in soft agar as a measurement of growth in soft agar.

Automated image analysis was used to measure the colony diameter and estimate the cell number in colonies under conditions for anchorage-independent growth (AIG). The calculated values for the number of AIG cells in a colony of a diameter greater than or equal to 60 microns were decidedly different from the actual values obtained by either automated or manual cell counting. Like animal cells that exhibit AIG, these colonies demonstrating anchorage independence can be enumerated reproducibly. However, the assumption is incorrect that the number of cells (N) in a colony expressing AIG varies directly with a change in the diameter of a colony (d). Whether one counts the number of cells manually in a colony of a definite diameter or arbitrarily uses a diameter function of greater than or equal to 60 microns as a linear distance that indicates the presence of 50 or more cells in a colony, each procedure has its own built-in bias. In procedures that require quantitative data, the most reliable procedure is to standardize the values for diameter of colonies with cell numbers in colonies.

Agar↗
PubMed1990

Early atherogenesis in White Carneau pigeons: effect of a short-term regression diet.

The intracellular distribution of lipid shifts from cytoplasmic to lysosomal localization during the progression of atherosclerosis. It has been suggested that this shift may relate to regressability of lesions. The effects of reducing plasma cholesterol on the regression of early cholesterol-induced atherosclerosis were evaluated. Most small, early lesions disappeared after 5 weeks on the regression regimen. Larger lesions, however, did not change in extent even following 10 weeks regression. Although large lesions were not reduced in size under the regression conditions, total cytoplasmic lipid decreased. Paradoxically, the size of residual intracellular lipid deposits increased. The structural features of these remaining deposits suggest that they were lipid-filled lysosomes. Leukocyte adherence to endothelium, which increases 10- to 20-fold during progression, returned to control levels over most areas of large lesions. Levels of adherent leukocytes remained elevated, however, over small lesions and at the edges of larger lesions. Our data indicate that regression is not a uniform process, but rather, even in early lesions, varies within separate intimal microdomains. In addition, our data suggest that part of the difference may reside in differential partitioning of lipid into lysosomes.

Animals↗
PubMed1990

Fibrinogen and glycoprotein IIb/IIIa localization during platelet adhesion. Localization to the granulomere and at sites of platelet interaction.

Platelet membrane glycoprotein IIb-IIIa plays a focal role in primary hemostasis by serving as the cell surface receptor for fibrinogen. Recent studies by several groups have suggested that GPIIb-IIIa, which is dispersed randomly in the resting cell, undergoes migration leading to receptor clustering after platelet activation. The authors have investigated this activation-dependent relocation of fibrinogen receptors on platelets adherent to a standardized artificial surface. The correlative use of immunogold electron microscopy, ligand-gold binding, and stereo (three-dimensional) electron microscopy (EM) revealed specific localization of fibrinogen and its receptor at points of platelet to platelet interaction. Fibrinogen distribution on the plasma membrane, studied through the use of fibrinogen-gold conjugates with whole-mount adherent platelets, was primarily over the granulomere and at the cell periphery corresponding to sites of platelet-platelet interaction. Compared with the general hyalomere, fibrinogen density over the granulomere and at contact regions was increased 12-fold and 22-fold, respectively, and the specificity of binding at these sites was verified by positive competition with native fibrinogen, one of its degradation products (Fragment D1), and by monoclonal antibodies (HP1-1d and AP-2) specific for GPIIb-IIIa. The distribution of receptor antigens, localized by immunogold EM using antibodies against GPIIb-IIIa, also was localized over the hyalomere, where fibrinogen did not bind. To understand this apparently nonfunctional hyalomere GPIIb-IIIa further, correlative immunocytochemistry was performed using polyclonal and monoclonal antibodies for GPIIb and GPIIIa simultaneously. Colocalization of the antigens was observed consistently over the granulomere and at regions of cell contact, whereas the hyalomere antigens tended to be nonassociated. The studies document GPIIb-IIIa as a function complex at sites of cell interaction where fibrinogen binds.

Cell Communication↗
PubMed1989

Morphological characterization of beta-VLDL and acetylated-LDL binding and internalization by cultured pigeon monocytes.

The ultrastructure of binding, internalization, and translocation of beta-migrating very low density lipoprotein (beta-VLDL) and acetylated low density lipoprotein (Ac-LDL) by cultured pigeon monocytes was examined using lipoprotein-gold conjugates. Through morphometry, differences in the binding and uptake of beta-VLDL-gold and Ac-LDL-gold were documented. Cells exposed to either beta-VLDL-gold or Ac-LDL-gold for 2 hr at 4 degrees C had the label over noncoated regions of the plasma membrane. Upon warming the cells to 37 degrees C for 2 min, 35% of the surface-bound beta-VLDL-gold was within coated pits on the cell surface. Although coated pits occupied less than 2% of the surface, binding of beta-VLDL-gold was 53 times more concentrated in coated pits as compared to noncoated membrane regions. In contrast, Ac-LDL-gold neither bound to coated pits nor relocated into coated regions of the membrane upon warming to 37 degrees C. Both the beta-VLDL-gold and the Ac-LDL-gold were internalized when the cells were rewarmed at 37 degrees C. Most of the internalized gold particles for both lipoproteins were located in electron-lucent vesicles; however, 9% of the intracellular beta-VLDL-gold was observed within coated vesicles at early times. Upon prolonged rewarming (30-90 min), both lipoprotein-gold conjugates were within acid phosphatase-positive lysosomes. Ultimately 83% of the Ac-LDL-gold and 90% of the beta-VLDL-gold were within electron-dense and electron-lucent lysosomes. These results suggested that the receptor-mediated binding and internalization of beta-VLDL and Ac-LDL by pigeon monocyte macrophages proceeded by separate, distinct routes; beta-VLDL by both coated and noncoated pathways while Ac-LDL was internalized exclusively by noncoated mechanisms. Regardless of these internalization differences, both lipoproteins were delivered to lysosomes for degradation.

Acid Phosphatase↗
PubMed1989

Effects of varying dietary fatty acid ratios on plasma lipids and platelet function in the African green monkey.

The influence of varying dietary fatty acid ratios on plasma lipids, platelet function and the potential for thrombosis was evaluated in the African green monkey (Cercopithecus aethiops), an animal model widely used in cardiovascular research. Ten adult animals, 5 males and 5 females, at intervals of 2 months, were fed a series of 7 diets with fatty acid ratios (P:S) ranging from 3:1 to 1:4. Platelet aggregation in vitro, plasma levels of beta-thromboglobulin and platelet factor 4, platelet membrane fatty acid composition and plasma lipids including total cholesterol, HDL and LDL were monitored at the end of each dietary period. Platelet hypersensitivity to ADP aggregation (3 and 10 microM) and plasma beta-thromboglobulin were elevated in both males and females when dietary P:S exceeded 1.5:1 (beta-TG = 45 ng/ml) as compared to control diets either reflecting current North American or that recommended as a desirable dietary goal (P:S = 1:1, beta-TG = 10 ng/ml). Diets enriched in saturated fatty acids (P:S = 1:2) also altered platelet function, but the effects were most consistently observed in female animals (beta-TG = 32 ng/ml). Platelet hypersensitivity was lost and beta-TG levels were at baseline when the animals were returned to the control diets. Platelet sensitivity did not correlate with membrane composition which generally reflected dietary composition. Both the saturated and the polyunsaturated fatty acid enriched diets lowered plasma HDL levels, and the saturated fatty acid diets elevated plasma LDL.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

beta-VLDL and acetylated-LDL binding to pigeon monocyte macrophages.

Blood-derived monocytes are an important source of foam cells in atherosclerotic lesions of White Carneau pigeons. Based upon studies with cultured blood monocytes (monocyte macrophages) and peritoneal macrophages from a variety of mammalian species, it has been proposed that these cells become loaded with cholesteryl esters through the uptake of lipoproteins including beta-migrating very low density lipoproteins (beta-VLDL) and low density lipoproteins that have been chemically modified in a manner analogous to experimental acetylation (Ac-LDL). The purpose of this study was to determine whether similar mechanisms functioned in pigeon monocyte macrophages. Radioiodinated pigeon beta-VLDL and Ac-LDL were incubated with White Carneau pigeon monocyte macrophages that had been maintained in culture for 7 days. Scatchard analysis of the specific binding data revealed the presence of specific and saturable receptors for both beta-VLDL and Ac-LDL. beta-VLDL receptors had both low and high affinity binding components, whereas Ac-LDL receptors displayed a single class of high affinity binding sites. beta-VLDL binding remained relatively constant from 3 to 10 days in culture while Ac-LDL binding increased with time in culture. Competition studies demonstrated a high degree of binding specificity for 125I-Ac-LDL, but less for 125I-beta-VLDL. Binding of 125I-beta-VLDL was not competed for by Ac-LDL, but was by beta-VLDL and by low density lipoproteins from both normal and hypercholesterolemic pigeons. Following binding of beta-VLDL and Ac-LDL, the lipoproteins were rapidly internalized and degraded. Although the majority of degradation was secondary to internalization by the monocyte macrophages, approx. 5% of the degradation resulted from enzymatic activity in the culture medium, presumably due to secretion of proteolytic enzymes by the cells. As measured by esterification of [14C]oleate to cholesterol, it was shown that the cholesterol liberated from the degradation of both beta-VLDL and Ac-LDL stimulated cholesteryl ester synthesis in pigeon monocyte macrophages. These studies confirm the existence of specific beta-VLDL and Ac-LDL receptors on the surface of pigeon monocyte macrophages which facilitate both internalization of the lipoproteins and subsequent stimulation of cholesteryl ester synthesis. This is the first demonstration of beta-VLDL and Ac-LDL receptors on monocyte macrophages from an avian species, and the findings support the potential role for the receptor-mediated uptake of a variety of abnormal lipoproteins in the formation of monocyte-derived foam cells in the arterial wall of White Carneau pigeons during the development of atherosclerosis.

Animals↗
PubMed1988

Babesiosis in a litter of pups.

Babesia canis infection was diagnosed in a litter of seven 3-week-old Mastiff pups kept in a north Florida kennel. The pups were evaluated because of poor weight gain; the smallest pup also was markedly lethargic. Six of the pups were anemic and thrombocytopenic. A positive linear correlation between PCV and absolute reticulocyte count suggested that the variation in PCV may have been related more to the ability of a pup to increase erythrocyte production than to a difference in magnitude of erythrocyte destruction. All pups recovered from clinical signs and hematologic abnormalities attributable to babesiosis within 2.5 weeks after treatment with diminazene aceturate. Transient neurologic signs observed in 1 pup 3 days after treatment were believed to represent an adverse drug reaction. The dam of the litter had a serum titer of 1:640 for B canis, but appeared healthy, as did approximately 30 other adult dog in the kennel. The strain of B canis infecting dogs in the kennel caused severe illness and death in some pups, but clinically inapparent disease in adult dogs.

Animals↗
PubMed1988

Biomaterial-centered sepsis and the total artificial heart. Microbial adhesion vs tissue integration.

The principal barrier to the extended use of the total artificial heart is infection that is centered on the biomaterial constituting the prosthetic device and exacerbated by the surrounding damaged tissue. Ultrastructural studies of total artificial hearts removed from two patients indicate a failure of true tissue integration and diffuse, adhesive bacterial colonization of biomaterial surfaces. Biomaterials are, in part, susceptible to infection because, at the present state of the art, they are usually not well integrated with host tissue or, if hemodynamic, not optimally biocompatible or antiadhesive.

Aorta↗
PubMed1988

Lysosomal alterations during coronary atherosclerosis in the pigeon: correlative cytochemical and three-dimensional HVEM/IVEM observations.

Lysosomal changes have been implicated as one of the major factors contributing to the progression and complications of atherosclerosis, and recently foam cell formation has been correlated with increases in several acid hydrolases. To explore at the subcellular level relationships among lesion progression, cellular lipid accumulation, and lysosomal change, atherosclerotic lesions from hypercholesterolemic White Carneau pigeons have been studied through combined ultrastructural cytochemistry and stereo (three-dimensional) high-voltage electron microscopy. Lysosomal enzyme activity in the prelesion intima and in foam cells of early lesions was in discrete lysosomes of macrophage foam cells. Foam cell lipid at the early stages was primarily (72%) in cytoplasmic droplets, which formed a three-dimensional network with the small (0.25-0.8 microM in diameter), reaction-positive lysosomes suspended at the vertices of a cytoplasmic lattice that delineated individual lipid pools. Concomitant with lesion progression and increasing complexity, foam cell lysosome number, size, and complexity increased. The complexity was characterized by lysosome lipid accumulation (60% of cell lipid) and the fusion of lysosomes to form multilobulated organelles in which the acid phosphatase reaction product typically was circumferential to the lysosomal lipid core. The involvement of lysosomes climaxed in the more advanced region of lesions with foam cells in which the bulk of cytoplasmic volume was occupied by large (15-20 microM in diameter), multicompartmental, lipid-containing lysosomes. It is suggested that this progressive involvement of lysosomes is responsible for cell and tissue necroses characteristic of advanced lesions.

Acid Phosphatase↗
PubMed1988

Serum alpha-tocopherol, all-trans retinol, total lipids and cholesterol in the black rhinoceros (Diceros bicornis).

1. Mean concentration of serum alpha-tocopherol (Vitamin E) in 28 free-living black rhinoceroses sedated during translocation in Zimbabwe was 1.92 (SD, 0.43) mg/l. 2. Alpha-tocopherol was not detectable (less than 0.15 mg/l) in five captive black rhinoceroses held at London Zoo. 3. Circulating levels of all-trans retinol (Vitamin A) were not different between the two groups. 4. The low level of alpha-tocopherol in captive rhinoceroses suggests a risk of acute haemolytic anaemia.

Anemia, Hemolytic↗
PubMed1988

Orientation and specificity of fibrin protofibril binding to ADP-stimulated platelets.

We have investigated the molecular basis of platelet:fibrin binding by studying interactions between platelets and protofibrils, soluble two-stranded polymers of fibrin, which are intermediates on the fibrin assembly pathway. The specificity of these interactions was examined with transmission electron microscopy (TEM), which clearly showed thin fibers with lengths to 150 nm attached to the cell surface of normal, stimulated platelets. Immunogold electron microscopy using rabbit anti-human fibrinogen as the first stage antibody verified the identity of the surface-bound molecules, and the immunogold distribution paralleled that observed with the fibrin/fibrinogen molecules alone. Contacts between the ends of the fibers and the platelets were frequently observed, but lateral contacts were also evident. Given the diameter at the point of fibrin contact (18.2 +/- 1.3 nm), it is possible that several glycoprotein receptors were involved in binding each protofibril. Morphometric analyses demonstrated that normal platelets stimulated by ADP in the absence of exogenous fibrin(ogen) or in the presence of fibrin protofibrils and antibodies directed against the GPIIb/IIIa complex lacked this molecular layer on the surface. Neither protofibrils nor fibrin fibers adhered to the surface of Glanzmann's thrombasthenic platelets, as demonstrated by TEM and microfluorimetry. Synthetic peptides of sequence RGDS and HHLGGAKQAGDV effectively blocked the binding of protofibrils to the surface of normal, stimulated platelets while synthetic GHRP had no effect. These results provide direct evidence for multiple points of attachment between fibrin protofibrils and the glycoprotein IIb/IIIa complexes present in a functional conformation on the surface of normal, stimulated platelets.

Adenosine Diphosphate↗
PubMed1988

The surface morphology of normal and atherosclerotic coronary arteries in male Macaca fascicularis and the effect of coronary angiography.

Selective coronary angiography is one of the procedures used frequently in the diagnosis and management of coronary artery disease. Macaca fascicularis monkeys were used to study the effects of coronary angiography on coronary artery surface morphology. Fourteen M. fascicularis were fed either an atherogenic diet (0.34 mg of cholesterol/kcal and 40 to 43% of the calories as fat) for six to nine months or a control diet. For six of these animals the Judkin method of selective left coronary angiography was done 24 h prior to necropsy. The ascending aorta, right coronary artery, left circumflex (LCX), left anterior descending (LAD) and left main (LM) coronary arteries were examined using scanning electron microscopy (SEM). The animals fed an atherogenic diet had 27% of the ascending aorta and 7% of the coronary arteries covered with raised lesions. The surface of these coronary arteries differed from those of animals fed a control diet in that the surface appeared smoother and often had numerous adherent leukocytes. The animals undergoing coronary angiography had 25% of the ascending aorta and 10% of the LM surface injured by the catheter. These areas were denuded of endothelium and covered with adherent platelets. There were no morphologic changes observed by SEM following angiography within the LCX or LAD arteries. Thus even in a setting of hypercholesterolemia exposure to contrast media during the coronary angiography procedure did not lead to surface alterations.

Angiocardiography↗
PubMed1987

The interleukin 1 receptor. Dynamics of interleukin 1 binding and internalization in T cells and fibroblasts.

In this study, we have demonstrated that a murine T cell lymphoma, EL 4, and a murine fibroblast cell line, Swiss 3T3, possess a single class of high affinity interleukin 1 (IL 1) receptors that exist in a dynamic state of equilibrium that is influenced by IL 1. In the absence of IL 1, the IL 1 receptor appears to turnover with a t1/2 of approximately 11 hr. However, when cells are incubated in the presence of IL 1, the IL 1 receptor undergoes extensive ligand-induced down-regulation. IL 1 itself is internalized at 37 degrees C; 50% of the surface-bound IL 1 is internalized in 60 to 120 min. IL 1 does not undergo degradation for at least 6 hr after internalization. By using electron microscopy and autoradiography, we observed several important features of the internalization process. When cells having bound 125I-IL 1 at 4 degrees C were shifted to 37 degrees C, IL 1 moved from the cell membrane to the cytoplasm where it was found in proximity to nuclei or within lysosomes. IL 1 appeared to progressively accumulate in nuclei. Six hours after shifting cells to 37 degrees C, 30 to 35% of the internalized 125I-IL 1 is associated with the cell nucleus. The accumulation of relatively high levels of IL 1 in the nucleus raises the interesting possibility that IL 1 may not only interact in a highly specific manner with cell surface receptors, but also with potentially important nuclear receptors.

Animals↗
PubMed1987

Extended-wear lenses, biofilm, and bacterial adhesion.

While medical scientific knowledge pertaining to bacterial adhesion to biomaterials has become a rapidly growing field in most areas of medicine, its significance in ophthalmic infections has not been emphasized. Corneal bacterial ulceration in patients wearing extended-wear contact lenses has become a problem of epidemic proportions. The designation of the contact lens itself as a suitable substratum for bacterial colonization and as a source of subsequent inoculum to compromised epithelial cells are important factors in the pathophysiology of corneal ulcer formation. We demonstrate polysaccharide- (biofilm-)mediated adhesion to two ophthalmic pathogens (Pseudomonas aeruginosa and Staphylococcus epidermidis) to the surface of a typical extended-wear contact lens in vitro using cytochemistry and scanning and transmission electron microscopic techniques. This interaction between the biomaterial and bacterial organisms, which represents a favorable self-protective environment for propagation and inoculation, is a previously overlooked area of importance in the mechanism of corneal ulceration associated with hydrophilic (soft) contact lenses.

Bacterial Adhesion↗
PubMed1987

Carotid plaque as a source of emboli in humans: a scanning electron microscopic study.

Ten fresh carotid plaques obtained from patients undergoing carotid endarterectomy were fixed, and their luminal surfaces were examined with a scanning electron microscope. Luminal surface defects, characterized in scanning electron microscopy as endothelial discontinuities having diameters of 50 to 1500 microns, were a frequent finding, but their presence did not correlate well with the location of ulcers seen on angiography. Potential sources of emboli found were peels of subendothelial matrix, fibrin-platelet aggregates, fibrin-red blood cell clusters, and, possibly, damaged endothelial cells. Areas of endothelial cell injury consisting of small denuded patches, sheets of endothelial cytoplasm, and distorted endothelial cell profiles were observed. These areas resembled the type of damage seen in experimental ischemic vessel lesions and were believed to be the result of carotid cross clamping. Their presence suggests that a similar mechanism may result in loss of endothelial cells and exposure of the "raw" plaque surface in vivo.

Brain Ischemia↗
PubMed1987

Early atherogenesis in the White Carneau pigeon. III. Lipid accumulation in nascent foam cells.

The role of lysosomes in aortic atherogenesis in White Carneau pigeons was examined by means of acid phosphatase cytochemistry. Foam cells were the major constituent of nascent atherosclerotic lesions in pigeons fed a 0.5% cholesterol diet for either 5 or 10 weeks. Seventy-four percent of foam cell lipid from animals at 5 weeks was in cytoplasmic droplets. The remaining lipid appeared in secondary lysosomes. After 10 weeks of cholesterol feeding, lysosomal lipid accounted for 73% of the lipid volume. The lipid accumulation correlated with increases in both size and number of lysosomes. An average of 2.4 lysosomes per 10(4) cu mu of cytoplasm was observed at 5 weeks. This value doubled by 10 weeks. The average lysosome diameter also increased between 5 and 10 weeks from 2.2 mu to 5.75 mu. Concomitantly, the complexity of lysosomes increased from simple, spherical organelles at 5 weeks to complex, multichambered organelles at 10 weeks. In contrast, lipid storage within cytoplasmic lipid droplets did not change either in size or in number. These observations suggest that by 5 weeks lipid storage within cytoplasmic droplets was maximized, and continued increases in lipid stores occurred predominantly through lysosomal loading.

Animals↗