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At least 919 records · Page 51Linked to original sources
PubMed1980

Hyphal tip growth in Achlya. I. Cytoplasmic organization.

Growing apices of Achlya ambisexualis Raper hyphae were examined by electron microscopy using cytochemical techniques. Apical vesicles can be grouped into two major classes based upon size and cytochemical reactions. Vesicles of the most prominent class are about 150 nm in diameter and possess contents which appear fibrous in thin section. This fibrous material reacts positively with the periodic acid-silver methenamine (PASM) cytochemical test for polysaccharides. Most of these same vesicles also display IDPase activity, and a smaller number display acid phosphatase activity. Vesicles of the second class are about 80 nm in diameter, and include coated vesicles and others which react positively for IDPase activity. They show a negative PASM reaction in contrast with the larger vesicles. Some of these smaller vesicles are stained by the phosphotungstic acid-chromic acid (PTA-CrO3) stain, whereas 150-nm vesicles are not. The source of at least some vesicles of both major classes appears to be the Golgi apparatus. It is proposed that the IDPase activity and carbohydrate content of the 150-nm cytoplasmic vesicles could serve as useful markers in their isolation.

Cell Membrane↗
PubMed1972

Biophysical and biochemical heterogeneity of purified hepatitis B antigen.

Hepatitis B antigen of the D (a+, d+, y-) subtype was purified from plasma of apparently healthy persons and from hepatitis patients. The original samples contained 20- and 42-nm particles and tubular forms (20-nm diameter). Ultracentrifugation during the purification procedure yielded pellets which were then treated at pH 2.4. Both the large, 42-nm Dane particles and the tubular forms were lost during the acid treatment of the pelleted particles, yielding a preparation containing a mixture of particles approximately 20 and 25 nm in diameter. This difference in size was substantiated in that two distinct molecular weights were calculated from high-speed equilibrium data, 3.6 x 10(6) and 4.5 x 10(6). Further heterogeneity was observed in that hepatitis B antigenic activity was present in purified particles with an isoelectric pH of 4.0 and also in those with a pH of 4.4. No significant differences were observed in the gross amino acid composition of purified antigen obtained from plasma of three different persons. (125)I-labeled, purified antigen was found to contain six distinct polypeptides with molecular weights ranging from 10,000 to 39,000.

Amino Acids↗
PubMed1994

The mouse plasma PAF acetylhydrolase: I. Characterization and properties.

Mouse plasma platelet-activating factor acetylhydrolase (PAF-AH) has an apparent Km of 7.4 microM and a Vmax of 21.6 nmol/min per mg protein. Comparison with values reported for the human and the rat enzymes shows at least a 5-fold higher Vmax and similar enzyme-substrate affinity. Although lecithin:cholesterol acyltransferase (LCAT) and one component of the PAF-AH share similar masses and lipoprotein association, they are distinct enzymes. Similarly, PAF-AH is distinct from the phospholipase A2 (PLA2) and the lysophospholipase of mouse plasma. A series of PAF structural analogs showed either competitive inhibition or a mixed type of inhibition of PAF-AH. Mouse plasma PAF-AH is highly sensitive to 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) and is activated by deoxycholate. SDS-PAGE showed that two distinct proteins with molecular masses of 46 and 63 kDa contribute to the PAF-AH activity. The HDL-VHDL lipoprotein associated PAF-AH is precipitated to an extent of about 60% by phosphotungstate-MgCl2 and Tween 20 only partially solubilises the precipitated enzyme under conditions which can precipitate and solubilise the human enzyme.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1974

Proteinaceous virus-like particles from an isolate of Aspergillus flavus.

Virus-like particles were purified from a single nonaflatoxin-producing isolate of Aspergillus flavus. The virus-like particles were spherical, measuring 27 to 30 nm in diameter, were electrophoretically homogeneous, and sedimented at approximately 49S. The particles had a buoyant density of 1.28 g/cm(3) in CsCl and contained no detectable nucleic acid.

Aflatoxins↗
PubMed1997

Biochemical and immunological studies and assay of rat sublingual mucins.

Original studies of rat sublingual mucins raised questions as to the existence of a second mucin species as distinguished by binding to hydroxyapatite. The existence of multiple mucin species is of concern in pharmacological studies of mucous-cell secretion as each species could represent distinct mucous-cell populations that respond differently to secretagogues. Thus a separate hydroxyapatite-bound mucin pool expressed in rat sublingual glands was isolated and characterized. Biochemical comparison of hydroxyapatite-bound mucins to total and hydroxyapatite-unbound sublingual mucins demonstrated no substantial differences in either amino acid and carbohydrate contents or in size distributions. In addition, a radioimmunoassay was developed using antisera prepared previously against unbound mucins. The three mucin pools exhibited equal specificities in displacement of radiolabelled unbound mucin tracer in the radioimmunoassay. Thus, bound and unbound mucins are indistinguishable, both immunologically and in biochemical composition. The radioimmunoassay was then evaluated for use in pharmacological studies of acinar mucous-cell secretion. Measurement by radioimmunoassay of secretion from isolated acini in response to carbachol was concentration-dependent (EC50 approx. 0.3 microM and maximal stimulation at 1 microM carbachol). In immunolocalization studies the antiserum was highly selective for mucous cells, recognized all mucous cells within histological sections, and was localized subcellularly to mucous-cell secretion granules and trans-Golgi, further validating the radioimmunoassay as a method to detect exocrine secretion from the entire pool of acinar mucous cells. Moreover, the radioimmunoassay was compared and found equivalent to an acid-precipitation method to assess relative secretion, suggesting the acid-precipitation method is also valid for pharmacological studies of isolated acini.

Animals↗
PubMed1968

Determination of uric acid levels in uraemia by enzymatic and colorimetric techniques.

Serum uric acid levels were determined by specific and non-specific methods in uraemia in order to investigate the correlation between non-specific chromogen and serum urea level. The correlation was moderate and the magnitude of the non-specific chromogen was smaller than had been reported previously. The ratio [Formula: see text] urate was found to be 0.85 in both acute and chronic renal failure, a ratio very similar to that previously reported for normal and gouty subjects. In chronic renal failure the true uric acid level is correlated with urea level and there is a suggestion that serum uric acid levels in chronic renal failure are lower for a given urea value than in acute renal failure.

Acute Kidney Injury↗
PubMed1979

[Ultrastructural cytochemistry of the mouse juxtaglomerular apparatus (author's transl)].

The ultrastructural cytochemistry of the mouse juxtaglomerular apparatus has been studied. The specific granules of the juxtaglomerular cells were found to be argentaphobic when ultrathin sections of araldite-embedded renal cortex were stained according to the periodic acid-thio-carbohydrazide-silver proteinate technique of Thiery. This technique revealed an abundant glycogen of type beta in the specific granules and in the cytosol of these cells. The rim of specific granules was positive when ultrathin sections of glutaraldehyde-fixed, glycol methacrylate-embedded kidneys were stained with phosphotungstic-hydrochloric acids at a low pH. A reaction was also shown by the cell coat, lysosomes, autophagolysosomes, residual bodies and part of the Golgi complex. These results indicate that the specific granules of the mouse juxtaglomerular apparatus contains glycoproteins that are glycosylated in the Golgi complex.

Animals↗
PubMed1972

Osmiophilic polymer generation: catalysis by transition metal compounds in ultrastructural cytochemistry.

A transition metal compound that is bound in tissues by any appropriate cytochemical reaction may catalyze the generation of an insoluble osmiophilic polymer from organic monomers such as 3,3'-diaminobenzidine. When the polymers are treated with osmium tetroxide, electron-opaque, insoluble osmium blacks (coordination polymers of osmium) are formed at the sites of the particular macromolecule or enzyme permitting its light, and electron, microscopic localization. This approach represents a distinct advantage over earlier cytochemical methods because the shorter incubation time needed here results in less artifactual deposition of metal ions, and less tendency to crystallize the reaction product. In addition, the shorter incubation times permit longer fixation of tissues and hence less artifact due to enzyme diffusion.

Acid Phosphatase↗
PubMed1972

Flagellar assembly mutants in Escherichia coli.

Genetic and biochemical analysis of mutants defective in the synthesis of flagella in Escherichia coli revealed an unusual class of mutants. These mutants were found to produce short, curly, flagella-like filaments with low amplitude ( approximately 0.06 mum). The filaments were connected to characteristic flagellar basal caps and extended for 1 to 2 mum from the bacterial surface. The mutations in these strains were all members of one complementation group, group E, which is located between his and uvrC. The structural, serological, and chemical properties of the filament derived from the mutants closely resemble those of the flagellar hook structure. On the basis of these properties, it is suggested that these filaments are "polyhooks", i.e., repeated end-to-end polymers of the hook portion of the flagellum. Polyhooks are presumed to be the result of a defective cistron which normally functions to control the length of the hook region of the flagellum.

Alkanesulfonates↗
PubMed1973

Membrane synthesis in synchronous cultures of Bacillus subtilis 168.

Synthesis of bacterial membranes has been investigated in Bacillus subtilis by examining incorporation of amino acids and glycerol into the protein and lipid of membranes of synchronous cultures. A simple reproducible fractionation scheme divides cellular proteins into three classes (i) truly cytoplasmic, (ii) loosely membrane bound, released by chelating agents, and (iii) tightly membrane bound. These comprise approximately 75, 10, and 15%, respectively, of cellular proteins in this organism. Incorporation of radioactivity into these fractions, using steady-state and pulse labeling has been followed during the cell cycle. Cytoplasmic proteins and the loosely membrane-bound proteins are labeled at an exponential rate throughout the cell cycle. The membrane fraction is labeled discontinuously in the cell cycle, with periods of rapid synthesis over the latter part of the cycle and a period with no net synthesis during the early part of the cycle. Pulse labeling indicates that synthesis of membrane occurs at a linear rate that doubles at a fixed time in each cycle, which coincides with the period of zero net synthesis. Rates of membrane synthesis measured by pulse labeling during the period of rapid membrane synthesis are significantly less than indicated by steady-state labeling. These discrepancies are consistent with the hypothesis that during the cell cycle certain proteins are added to the membrane from the cytoplasm and that during the period of zero net synthesis there is an efflux of proteins from the membrane. Evidence in favor of this has been presented. The activity of succinic dehydrogenase (a representative of class c) varies in a step-wise manner with periods of rapid increase, approximately coincident with bursts of membrane protein synthesis, alternating with periods without any increase in activity. The activities of malate dehydrogenase (class a) and reduced nicotinamide adenine dinucleotide dehydrogenase (class b) increased throughout the cell cycle. Phospholipid synthesis is continuous throughout the cell cycle.

Amino Acids↗