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 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We wish to determine what cellular and functional alterations are associated with the development of glomeruloscierosis when rats with one kidney are fed an excess of salt or protein. Rats with one kidney are more likely to develop pronteinuria and glomerulosclerosis than control animals. Blood pressure recordings indicate that proteinuria and glomerulosclerosis occur before hypertension is evident. Fluorescent antibody studies disclose that albumin accumulates in the epithelial cells of glomeruli and tubules. Ultrastructural examination shows that vacuolozation of epithelial cells and basement membrane thickening precede the sclerotic collapse of capillary loops. Increased concentrations of sodium or urea that are found in urines of these rats favor the point of view that an elevation of solute load when combined with a reduction of renal mass will on some unknown manner accelerate the deterioration of glomeruli.
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PMID:Protein overload nephropathy in rats with unilateral nephrectomy. A correlative light immunogluorescence and electron microscopical analysis. 4 49

The melting transition of the magnesium salt of DNA has been systematically examined in the presence of various types of anions. The addition of ClO4- to a concentration of 3.0 N results in the biphasic optical transition, with the first phase exhibiting rapid reversibility and independence of the DNA concentration. This subtransition, which is interpreted as an intramolecular condensation to a collapsed form of DNA, is followed by a DNA concentration-dependent aggregation reaction. The aggregation can be reversed by increasing the ClO4- concentration to 6.0 N while elevating the temperature to post-transition levels. Alternatively, both the collapse and the aggregation can be prevented by melting in the presence of trichloroacetate, the most strongly chaotropic solvent for DNA which has been reported (K. Hamaguchi and E. P. Geiduschek (1962), J. Am. Chem. Soc. 84, 1329). The forces responsible for mediating both the collapse and the aggregation are superficially similar to those involved in maintaining duplex stability. The collapsed form, in particular, possibly possesses features in common with the condensed structures which can be produced in aqueous solution of certain polymers, such as polyethylene glycol (Lerman, L.S. (1971), Proc. Natl. Acad. Sci. U.S.A. 68, 1886).
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PMID:The DNA melting transition in aqueous magnesium salt solutions. 16 26

Sonicated vesicles of phosphatidylserine and phosphatidylserine/phosphatidylcholine mixtures were recombined with spectrin-actin from human erythrocyte ghosts. Morphological properties and physicochemical characteristics of the recombinates were studied with freeze etch electron microscopy, 31P NMR and differential scanning calorimetry. Sonicated dimyristoyl phosphatidylserine vesicles show a decrease in enthalpy change of the lipid phase transition upon addition of spectrin-actin. These vesicles collapse and fuse, into multilamellar structures in the presence of spectrin-actin, as demonstrated by freeze fracturing and NMR. Spectrin-actin cannot prevent the salt formation between phosphatidylserine and Ca2+, all phosphatidylserine is withdrawn from the lipid phase transition. In contrast a protection against the action of Mg2+ could be observed. Mixed bilayers of dimyristoyl phosphatidylserine/dimyristoyl phosphatidylcholine show phase separations at molar ratios above 1/1 (van Dijck, P.W.M., de Kruijff, B., Verkleij, A.J., van Deenen, L.L.M. and de Gier, J. (1978) Biochim. Biophys. Acta 512, 84--96). These phase spearations can be prevented by spectrin-actin. Ca2+-induced lateral phase separations in cocrystallizing phosphatidylserine/phosphatidylcholine mixtures, can be reduced by spectrin-actin. Formation of the Ca2+-phosphatidylserine salt, occurring in addition to lateral phase separation when mixtures contain more than 30 mol % phosphatidylserine, cannot be prevented by spectrin-actin.
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PMID:The interaction of spectrin-actin and synthetic phospholipids. II. The interaction with phosphatidylserine. 42 Aug 34

The volume of the cells and lateral intercellular spaces were measured in living Necturus gallbladder epithelium. Under control conditions, the volume of the lateral spaces was 9% of the cell volume. Replacement of mucosal NaCl by sucrose or tetramethylammonium chloride (TMACl) caused intercellular spaces to collapse. During mucosal NaCl replacement, cell volume decreased to 79% of its control value. When NaCl was reintroduced into the mucosal bath, the intercellular spaces reopened and the cells returned to control volume. The NaCl active transport rate, calculated from the rate of cell volume decrease, was 266 pM/cm2.s, close to the observed rate of transepithelial salt transport. It was calculated from the decrease in cell volume that all of the intracellular NaCl was transported out of the cell during removal of mucosal NaCl. The flux of salt across the apical membrane, calculated from the rate of cell volume increase upon reintroducing mucosal NaCl, was 209 pM/cm2.s, in good agreement with estimates by other methods. The electrical resistance of the tight junctions was estimated to be 83.9% of the total tissue resistance in control conditions, suggesting that the lateral intercellular spaces normally offer only a small resistance to electrolyte movement.
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PMID:Fluid transport and the dimensions of cells and interspaces of living Necturus gallbladder. 43 73

Nucleoids obtained from metaphase-arrested HeLa cells by gentle lysis in non-ionic detergent and 2 M salt were prepared for electron microscopy by Kleinschmidt spreading techniques. From biophysical studies nucleoids have been shown to contain high molecular weight DNA which is supercoiled and topologically constrained. The contents of nucleoids disperse and collapse into 2 dimensions on the water surface as discrete particles (spreads), which are provisionally equated with metaphase chromosomes. In some cases separate spreads are linked. The structure of the spreads is complex. A preliminary description is presented, although we believe that some of the structures reported may be products of preparation and spreading rather than significant features of the organization of intact nucleoids. There is considerable variation in the appearance of different spreads which may be related to the degree of unfolding, spreading or damage of the different preparations. Each spread consists of one or more core areas surrounded by a network of fibres. Cores are composed, at least in part, of compressed fibres and superficially appear to constrain fibres of the network. In the network the inter-twining of pairs of fibres and the occurrence of flat fibre spirals (disks) are interpreted as evidence of DNA supercoiling, but other fibres of similar thickness are not visibly supercoiled. High-order structures including groupings of disks are observed: these may be the structural correlates of the folded domains of supercoiled DNA established biophysically. The relative proportion of disks and other network structures varies between spreads.
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PMID:The organization of supercoiled DNA from human chromosomes. 52 72

Using the ability to sporulate as a measure of viability, the effects of exposure of unsporulated oocysts of 10 species of coccidia of chickens, rabbits and cattle to saturated NaCl solution has been studied. Although appreciable deformation and collapse of the oocyst occurred after 1-2 days contact, the effect was reversible after washing free from salt and incubating. Some reduction in ability to sporulate following several days contact with saturated salt was noted in most species, although no effect was seen with Eimeria stiedai following 7 days exposure, Eimeria tenella was one of the more sensitive species studied. Culture titration experiments in chickens with E. tenella indicated that oocysts which had sporulated following prolonged exposure to salt were in no way inferior in virulence or ability to retain virulence on prolonged storage to oocysts prepared with minimal contact with salt. No evidence was obtained to contra-indicate the use of salt-flotation methods for the separation of oocysts from faeces.
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PMID:Effects of saturated sodium chloride solution on coccidial oocysts. 75 24

Sporocysts of Isospora endocallimici, a parasite of marmosets, were exposed to minimal essentials medium (MEM) or a trypsin-bile salt solution (TBS) and then fixed and prepared for transmission electron microscopy. Excystation occurred in TBS but not MEM. The sporocyst wall has 2 layers, a thin outer layer (15 to 110 nm thick) and a thick inner layer (65 to 180 nm thick), which is composed of 4 separate curved plates. The outer layer consists of 1 to 3 membranes interspersed with lipid droplets. In the inner layer, a thin layer of material connects the peripheral margins of 2 apposing plates. Immediately beneath this layer, a thin strip of material is interposed between the 2 apposing plates. Ultrastructural changes preparatory to excystation occur primarily in the inner layer of the sporocyst wall. The TBS acts upon the site of apposition between 2 plates causing the interposed strip to swell and separate from the margin of each plate which leads to collapse of the sporocyst. As the sporocyst collapses, the margins of each curved plate curl inward toward the center of the sporocyst.
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PMID:Ultrastructure of the sporocyst wall during excystation of Isospora endocallimici. 82 16

Two case reports demonstrate the importance of an early diagnosis for the therapy of adrenal hemorrhage. In the first case with unilateral hemorrhage, the hemorrhage as such was of importance. In the second case with bilateral hemorrhage, the course was dominated by acute adrenal insufficiency with circulatory collapse and major salt loss. The diagnosis was supported by the typical changes in electrolyte levels as well as by radiography, and endocrinological results. With early therapy (in the first instance by surgery, and in the latter by substitution of corticosteroids), both children safely passed the critical period. In the second child ACTH administration did not, in the first phase of the disease, result in a significant rise of plasma cortisol. However, two months later there was a normal rise of the cortisol level following ACTH administration. From this observation we conclude that a favourable regeneration of the adrenal glands has resulted.
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PMID:[Acute adrenal hemorrhage in newborn infants: the importance of early diagnosis (author's transl)]. 94 72

High-molecular-weight DNA is known to collapse into very compact particles in a salt solution containing polymers like poly(ethylene oxide) [(EO)n] or polyacrylate. The biological relevance of this phenomenon is suggested by our recent finding that high concentrations of the highly acidic internal peptides found in the mature T4 bacteriophage head, as well as poly(glutamic acid) and poly(aspartic acid), can collapse DNA in a similar manner. The structure of DNAs collapsed by various methods has been studied with electron microscope. We find (EO)n collapses T4 or T7 bacteriophage DNA into compact particles only slightly larger than the size of the T4 and T7 head, respectively. In contrast, polylysine collapses DNA into different types of structures. Double-stranded DNA collapsed with (EO)n is cut by the single-strand specific Neurospora crassa endonuclease (EC 3.1.4.21) into small fragments. Extensive digestion only occurs above the critical concentration of polymer required for DNA collapse, demonstrating the (EO)n-collapsed DNA contains enzyme-vulnerable regions (probably at each fold), which are preferentially attacked. The size of the DNA fragments produced by limit-digestion with the nuclease ranges between 200 and 400 base pairs when DNA is collapsed by (EO)n. Only fragments of DNA which are larger than 600 base pairs are cut by the endonuclease in (EO)n-containing solution.
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PMID:Characterization of DNA condensates induced by poly(ethylene oxide) and polylysine. 106 Jan 8

The first phase of accidental drowning begins with asphyxia, due to either laryngospasm (10-15 percent of cases) or water aspiration. The second phase is characterized by water and electrolyte changes in the blood. The physiopathological modifications caused by drowning in fresh water differ from those of drowning in sea water. The hypotonic fresh water quickly diffuses in the bloodstream. The consequences are, in many cases, hypervolemia with pulmonary edema, hemolysis, hyperkalemia with risk of ventricular fibrillation, diminution of hemoglobin, and a relative decrease in plasma concentration of Na, Cl, Ca, and albumin. Further, inactivation and washing out of the anti-atelectasis factor from the alveoli by fresh water facilitate the formation of atelectasis. In cases of accidental drowing in sea water the osmotic gradient is in inverse: the electrolytes of aspirated salt water diffuse in the circulation, whereas the blood serum and the plasma albumin pass into the alveoli. Acute pulmonary edema often follows these pathological changes. Hypovolemia with circulatory collapse, hemoconcentration with rise in hemoglobin, hematocrit, sodium, potassium and albumin, and, finally, an elevated risk of thromboembolism due to increased blood viscosity, represent further complications. On the other hand, ventricular fibrillation is rare, hemolysis is absent and atelectasis usually does not occur.
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PMID:[Physiopathology of accidental drowning]. 112 62


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