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Biomedical subjects

E C Carlson

Publications and source records attributed to E C Carlson.

At least 55 records · Page 3Linked to original sources
PubMed1982

An ultrastructural analysis of isolated basement membranes in the acellular renal cortex: a comparison study of human and laboratory animals.

Freshly harvested kidneys from New Zealand white rabbits, Sprague-Dawley white rats, rhesus monkeys, and transplant-quality human kidneys were used in this study. Minced renal cortical tissue blocks (less than 2 mm3) were treated with 1 mM EDTA, 3% Triton X-100, 0.025% DNAse, and 4% sodium deoxycholate in an effort to remove all cellular elements and leave the extracellular matrix (ECM) intact. These preparations showed remarkable structural preservation and all components of the ECM, including basement membranes (BMs), maintained their in vivo histoarchitectural relationships. By light microscopy, at least four major BM types were recognizable, including Bowman's capsular BM (BCBM), tubular BM (TBM), glomerular BM (GBM), and peritubular capillary BM (PTCBM). Scanning electron microscopy demonstrated that, despite the lack of supporting interstitium, GBMs in human, monkey, and rat (and rabbit to a lesser degree) exhibit intrinsic structural rigidity such that their convoluted spheroidal shapes are maintained following cell removal. Transmission electron microscopy showed that major BM types are morphologically heterogeneous and vary markedly within and between species. Randomized measurements showed that isolated BM thicknesses (lamina densa only) compared favorably with those reported in cellular preparations. Mean thicknesses of GBMs were within normal ranges in all species with or without power transformations to reduce right-sided skew of distribution curves. In all species, thickness of BCBM greater than TBM greater than GBM greater than PTCBM. The striking morphologic heterogeneity of major BM types demonstrated in the acellular renal cortex is not surprising in view of recent biochemical analyses that show that BMs derived from different sources are compositionally disparate. We conclude that BMs should be evaluated and characterized individually and that morphologic definition of isolated BMs necessary prior to further analysis.

Animals↗
PubMed1980

Surface ultrastructure of the isolated avian notochord in vitro: the effect of the perinotochordal sheath.

The perinotochordal sheath (PNS) is a "tube" of extracellular matrix (ECM) that surrounds the avian notochord beginning in the second day of development. Somites, like the notochord, derive from chordamesoblast but are encased by a less substantial perisomitic matrix (PSM). Initially both tissue types exhibit epithelioid characteristics. Somitic cells subsequently disperse, however, while notochordal histoarchitecture is maintained until much later. To test the possible shape-preserving role of the PNS, otochords were isolated from chick embryos by homogenization (which retains the sheath) or by trypsinization (which removes the sheath). Somites were similarly isolated. Tissues were cultured 12-72 hours and studied by LM, SEM and TEM. Mechanically isolated notochords are initially rigid with smooth surfaces. During the culture period a few cells grow outward from cut ends of the notochord, but its overall rod shape and intact PNS are maintained. In contrast, uncultured trypsinized notochords are flaccid, denuded cylinders with numerous cytoplasmic blebs. They adhere to the substratum within 12 hours of culture when a few cells break away from the central tissue rod, migrate laterally, and appear mesenchymal. This cellular dispersion is directional (perpendicular to the long notochordal axis) and continuous (up to 72 hours). At this time a flattened ovoid growth area is formed. Cultured somites form flat circular growth areas within 12 hours of culture irrespective of the isolation method. These data suggest that the maintenance of an epithelial configuration by notochords in vivo may be due in part to physical restraints of the PNS. It seems possible that notochordal secretions (manifested by the formation of a PNS) could result in its compartmentation and axial confinement while its unrestrained somitic relatives are free to disperse.

Animals↗
PubMed1980

Preparation and histoarchitecture of ultrastructurally pure glomerular basement membrane.

Our recent morphological studies showed that basement membranes isolated from renal tubules tended to collapse and form folded sheets while glomerular basement membranes were more resilient. In an effort to study the shapes of various isolated basement membranes in undissociated tissues, a method was developed to remove all cellular elements and leave the extracellular matrix and associated basement membranes intact. Accordingly, transplant quality human kidneys were harvested, perfused with Collin's medium and transported to the laboratory on ice. The renal cortex was then peeled away by blunt dissection, further minced to 2 mm3 and placed in 1 mM EDTA (with gentle intermittent stirring) for 72 h at 4 degrees C. Solubilization of cellular materials was carried out by successive washings with 3% Triton X-100, 0.025% DNAse and 1-4% sodium deoxycholate (all with gentle stirring or shaking at 22 degrees C). Each solution contained 0.1% sodium azide. At the level of fine structure, glomerular, tubular, Bowman's capsular and peritubular capillary basement membranes all maintained their respective shapes and did not collapse. Glomerular basement membrane was particularly striking in this regard and exhibited an open, lobulated form that closely resembled its in vivo histoarchitecture. Moreover, when the acellular tissue blocks were prepared for scanning electron microscopic observation, the glomerular basement membranes exposed at the surface of the block showed a remarkable structural rigidity. These basement membranes were free-standing, convoluted electron-dense sheets, continuous with highly folded central mesangial regions. It seems significant that glomerular basement membranes maintain their in vivo conformation irrespective of the presence of other extracellular matrix components while removal of these materials by organ subfractionation results in folding and general shapelessness of tubular basement membrane. It is possible that in addition to its unique role in filtration, glomerular basement membrane may also serve to preserve glomerular shape, regardless of changing cell populations or alterations in hydrostatic pressures.

Basement Membrane↗
PubMed1979

Biosynthesis of basement membrane matrix by isolated rat renal glomeruli.

The incorporation of radioactive precursors into the extracellular basement membrane matrix has been investigated in a purified preparation of isolated rat kidney glomeruli. Using deoxycholate extraction of isolated glomeruli which were incubated with radioactively labeled amino acids and carbohydrates, as an assay system for the measurement of incorporation of basement membrane precursors into intact deoxycholate insoluble basement membrane material, we demonstrated the in vitro biosynthesis of this structure. The assay system minimized the possibility of contamination of the isolated labeled basement membrane with labeled cell membrane fragments which may occur with the standard isolation procedures involving sonication and centrifugation. A linear incorporation of labeled proline, lysine, glycine, glucosamine, and galactose into glomerular basement membrane was shown. Basement membrane synthesis was inhibited by metabolic poisons and protein synthesis inhibitors as well as by inhibitors of collagen synthesis, but not by colchicine, an inhibitor of collagen secretion. Rhe appearance of 14C-hydroxyproline in the basement membrane matrix was negligible during the first 4 hours of incubation and rose only to 1% of the total proline counts thereafter. The results are consistent with the characterization of glomerular basement membrane synthesis and deposition as a two component system comprising a rapidly synthesized and deposited noncollagenous glycoprotein component(s) and a collagenous component which is only deposited after a delay of 4 to 6 hours.

Aminopropionitrile↗
PubMed1978

An ultrastructural study of developing extracellular matrix in vitelline blood vessels of the early chick embryo.

This investigation was designed to describe the morphological events in embryonic development of peripheral blood vessels (vasculogenesis) and to relate this process to the appearance of extracellular matrix (ECM) during growth and maturation of these tissues. Extraembryonic vitelline vessels of the early chick embryo were chosen for this study and light, transmission, and scanning electron microscopy were carried out on vessels excised from chick embryos (Hamburger-Hamilton stages 8 through 23). Our data show that early (stage 10) vessels are composed of two distinct epithelial layers, an inner layer of presumptive endothelium surrounded by a layer of splanchnopleuric mesoderm. During development, the inner layer gives rise to mature vascular endothelium while splanchnopleuric mesoderm differentiates to form primitive vascular smooth muscle. Ultrastructural studies show the presence of collagen and basal lamina in the extracellular space between these two layers during initiation of endothelial and smooth muscle cytodifferentiation. Furthermore, ruthenium red-positive material is present on basal surfaces of developing vascular endothelium at this time, indicating possible glycosaminoglycans (GAG) or other polyanionic components of the ECM. These data suggest that the sequential production of basal lamina, collagen (s), and/or GAG's by developing peripheral vessel wall epithelia may be critical to their final differentiation.

Animals↗
PubMed1977

Isolation and characterization of myocytes from the adult rat heart.

Spontaneously contracting myocytes were isolated from ventricles of the adult rat heart. Hearts were perfused retrogradally via the aorta for 30 minutes at 37 degrees C with Ca2+-free phosphate-buffered saline containing collagenase and hyaluronidase. The venticles were divided into pieces and incubated 15 minutes with the enzymes. Dislodged cells were decanted, diluted with cold buffer and allowed to settle. The washed cells were then sedimented through 3% Ficoll. This procedure yielded approximately 50 mg of protein from 1 gm of heart. Viability measured by trypan-glue exclusion is 90-95%. Approximately 80% of the cells were beating. Scanning electron microscopic studies suggest that the isolated myocytes are morphologically intact. The cells oxidize glucose, pyruvate, citrate and palmitate to CO2 and synthesize protein and RNA. Uptake of glucose, 2-deoxyglucose, leucine and taurine was saturable. Glucose uptake was stimulated by insulin. The cells retained LDH and CPK as well as their capacity to oxidize substrates after 24 hours at 4 degrees C or 4 hours at 37 degrees C. After 24 hours at 4 degrees C the cells resume contracting when returned to room temperature. The procedure reported here for the isolation of spontaneously contracting, adult, rat heart myocytes provides cells with a high index of viability and greater yield than previously reported methods. The cells retain metabolic activity and withstand storage for longer periods than other described preparations.

Amino Acids↗
PubMed1977

Effect of zinc on peritoneal macrophages in vitro.

Rat peritoneal macrophages incubated in a medium with 10% autologous serum showed 50% inhibition of O2 consumption by 0.4 mM zinc only when activated by yeast. Zinc ions had no effect on resting macrophages. The inhibitory efficiency of zinc depended on the ratio of yeast particles to macrophages; with more activated cells, the inhibition was less. The multiple-shaped intact macrophages changed into rounded cells in the presence of 0.1 and 0.5 mM Zn2+ as shown by photomicrography and scanning electron microscopy. When the incubation medium was replaced by zinc-free medium, cells recovered and became irregularly shaped. The reversibility of zinc effect on cell morphology corresponded with uptake and release of zinc by macrophages. The presence of serum in the medium interfered with the magnitude of zinc uptake by macrophages. We conclude that besides already reported effects of zinc on mast cells, platelets, and granulocytes, zinc ions also inhibit some functions of macrophages.

Animals↗
PubMed1976

Early changes in the arterial wall of chickens fed a cholesterol diet.

A total of 160 1-2 day old chickens were fed a 2% cholesterol diet for a period of 8 to 42 days and compared with an equal number of controls. Aortas were analyzed for various indexes of reactivity of connective tissue, cholesterol content and scanning electron microscopy (SEM) characteristics of the endothelial lining. Cholesterol feeding for a period up to 6 weeks resulted in doubling the level of serum cholesterol. It was, however, without effect on the activity of prolyl hydroxylase, lysyl oxidase, collagenase and collagen content in the aortic wall. As early as 3 weeks of feeding significant changes occurred in total and esterified cholesterol content. At the same time endothelial cells were characteristically contracted with several long cytoplasmic elongations and protrusions. A significant decrease of activity of the above enzymes was found in aortic tissue with increased age of the chicken. Collagen content in aortas increased with age of chickens. It is concluded that cholesterol as an atherogenic agent induces marked changes in endothelial cells and lipids of chicken aorta at earlier periods, prior to the activation of connective tissue.

Animals↗