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Results for “increased precipitation”

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At least 19 recordsLinked to original sources

PubMed2026

Increased precipitation decelerates temporal succession of grassland soil microbial communities.

Global precipitation regimes have been shifted in recent decades, imposing significant consequences in water-limited grassland ecosystems. However, the effects of increased precipitation on the succession of soil microbial communities remain unclear, mainly due to the scarcity of long-term experiments with time-series data. Here, we examined temporal succession of grassland soil microbial communities in a long-term increased precipitation experiment. Both soil microbial taxonomic and functional structures were significantly altered by increased precipitation. Increased precipitation significantly decelerated the succession rates of soil microbial functional structure (i.e. time-decay relationships). Consistent with the increased microbial decomposition and heterotrophic respiration, the abundances of soil microbial carbon decomposition genes were markedly enhanced by increased precipitation. Furthermore, increased precipitation stimulated genes involved in nutrient cycling processes, potentially promoting plant growth. Collectively, the contributions of stochastic processes in shaping microbial communities were increased under increased precipitation, suggesting that microbial successional trajectories may shift toward multiple alternative states characterized by greater stochasticity under future altered precipitation regimes.

Soil Microbiology↗

PubMed1979

Hydroxyl content of solution-precipitated calcium phosphates.

A method is described for determination of the titratable hydroxide ion in calcium phosphate precipitates. The procedure requires accurate analysis of the other titratable species in the crystal lattice but is unaffected by the presence of other lattice constituents or impurities. The method was applied to precipitates that had been previously analyzed by solution thermodynamic techniques, and the results were consistent with the earlier observations. The hydroxide content of the precipitates increased with crystal maturity and with increasing pH of the precipitation medium. The hydroxide content of the amorphous phase and the immediate postamorphous-crystalline transformation phase was shown to be nearly zero. After 3 to 4 days' maturation, the hydroxide content of precipitates prepared at pH values of 7, 8, and 9 was shown to increase to approximately 23, 40, 56% of that required for pure hydroxyapatite.

Calcium Phosphates↗

PubMed1977

Ultrastructural localization of calcium in normal and abnormal skeletal muscle.

Calcium was demonstrated ultrastructurally as a fine black reaction product with unbuffered 2% saturated potassium pyroantimonate, pH 9.4. In comparison with normal muscle, there was increased precipitate in degenerating skeletal muscle fibers and some degenerating-regenerating fibers occurring in pathologic human muscle, regardless of disease entity, and in experimentally injured rat muscle. The pathologically increased calcium was mainly within the sarcoplasmic reticulum and mitochondria. Both structures could be completely blackened. Nuclear calcium was also increased, the precipitates being localized as circular profiles within the nucleoli and heterochromatin as well as being associated with the nuclear envelope. Myofibrillar calcium was only modestly increased. When normal rat muscle was preincubated in 136 mM calcium-enhanced Hanks' medium, calcium accumulated in the muscle fibers--it was especially heavy in the mitochondria and sarcoplasmic reticulum and appeared identical with the pathologic human and rat muscle fibers. Preincubation of normal rat muscle in 0.1 M acetate buffer (pH 4.65) before calcium loading augmented myofibrillar staining, mainly in the H-zone of the A-bands excluding the M-zone and in broad irregular N1, N2, and "N3" lines of the I-bands. EMMA-4 electron probe microanalysis and EGTA (ethylene glycolbis (beta-aminoethyl ether)N,N'-tetraacetic acid) chelation prior to staining confirmed that the precipitate in the several loci was calcium antimonate. It is proposed that in skeletal muscle fibers injured by various pathologic processes, a breach of the plasmalemma barrier to calcium occurs as a very early abnormality. Extracellular calcium would then pour into the aqueous sarcoplasm of the muscle fiber, from which it would be withdrawn by and accumulated with the still active organelles normally having a great avidity for uptake of this ion, especially the mitochondria and sarcoplasmic reticulum. The resultant organellar calcification would impair function and damage the structure of proteins and phospholipids.

Animals↗

PubMedDate not supplied

[Method of isolating the surface antigen of hepatitis B].

Hepatitis B antigen was isolated from HBs-positive human blood. A method of precipitation with polyethylene glycol (PEG) was used for concentration of HBs-antigen. The regularities of HBs-antigen precipitation were studied, and the degree of HBs-antigen precipitation increased with an increase of the molecular mass and concentration of PEG. Optimal precipitation conditions were selected, and the precipitation was found to go selectively and with large yields in an acid medium at pH 4.5. As a result of employment of a set of physico-chemical methods, highly purified HBs-antigen was isolated.

Animals↗

PubMed1975

Distribution of teichoic acid in the cell wall of Bacillus subtilis.

Hydrolysis of the cell wall of Bacillus subtilis 168 by autolysins or lysozyme resulted in the exposure of glucosylated teichoic acid molecules as evidenced by increased precipitation of [14C] concanavalin A. The number of concanavalin A-reactive sites increased significantly after only limited enzymatic digestion of the walls. Quantitative analyses of [14C] concanavalin A-treated wall or wall hydrolysate complexes indicate that approximately one-half of the teichoic acid molecules are surface-exposed, whereas the remainder are probably embedded within the peptidoglycan matrix. Treatment of the cell walls with sodium dodecyl sulfate or Triton X-100 did not result in new concanavalin A-reactive sites. Partial autolysis diminished the ability of the cell walls to adsorb bacteriophage phi25. Fluorescein-labeled concanavalin A bound intensely over the entire surface of growing B. subtilis 168 cells, suggesting that teichoic acid molecules are located on the total solvent-exposed surface area of the bacteria.

Adsorption↗

PubMed1977

[Effect of tetracycline base crystallization on the conditions properties of the powders and drug forms obtained. The development of directed crystallization procedures for tetracycline base].

The study of the process of tetracycline base crystallization showed that with an increase in the rate of pH, temperature and mixed rotation changes, the specific surface of the crystalline precipitate increased with a simultaneous decrease in the bulk weight, looseness and volume density of the powder. The residual content of tetracycline in the mother solution decreased. The level of the effect of various parameters on the final results was different.

Chemistry, Pharmaceutical↗

PubMed1977

[Detection of circulating immune complexes by three techniques using polyethylene glycol (author's transl)].

The search for circulating immune complexes (IC) by precipitation tests using polyethylene glycole was performed in a large series of normal (150 subjects) and 1200 pathological sera (over 800 patients). Increased precipitability of IgG and C4 was seen in a great percentage (80%) of pathological sera giving positive PEG precipitation without direct influence of IgG, IgM, C1q, C3 and C4 serum levels. The labeled C1q binding test gave similar results in 90 normal and 640 pathological sera. The C1q binding test could be replaced by the more direct and simple evaluation of the amount of C4 precipitated with IgG by 3.5% PEG. Positive results obtained in the three methods were particularly found in patients with diseases generally presumed to represent immune complexes diseases including acute glomerulonephritis, systemic lupus erythematosus, polyarteritis nodosa, subacute bacterial endocarditis, and acute or chronic hepatitis.

Antigen-Antibody Complex↗

PubMedDate not supplied

[Participation of heterotrophic microorganisms in the purification of drainage waters from heavy metal ions].

Heterotrophic microorganisms can grow in the presence of toxic components contained in industrial drainage of non-ferrous metal industry. The content of microorganisms correlates with the concentration of organic substances of plant origin in drainage waters. In the course of mineralization, heavy metal ions are immobilized and precipitated as stable metal-organic complexes with microbial metabolites. The rate of metal precipitation increases in the presence of aerobically decomposed plant material. The results obtained can be employed for purification of drainage waters from metal ions.

Bacteria↗

PubMed1978

Factors affecting methionine toxicity and its alleviation in the chick.

Young male crossbred chicks were fed crystalline amino acid diets containing excess L-methionine or DL-homocysteine to evaluate factors causing methionine toxicity. Chicks were fed diets containing graded levels of excess methionine from 0% to 2.0%. Rate of gain was reduced at all levels of excess methionine, but the magnitude of depression was greater between 1% and 2% than between 0% and 1% excess methionine. Methionine accumulated in plasma of birds fed excess methionine, but plasma levels of homocysteine, cystathionine and cystine remained essentially unchanged. Spleen iron levels increased linearly and blood hemoglobin decreased linearly when chicks were fed diets containing greater than 1% excess methionine, a level equivalent to about 3 times the chicks' requirement. Chicks fed 1.36% homocysteine had reduced gain and gain:feed values, but spleen iron and hemoglobin levels were unchanged. 3-Methylthiopropionate, a possible metabolite in a proposed alternate pathway, caused a precipitous increase in spleen iron levels. Various methyl sources (betaine, choline, methyl acetate) when fed in excess failed to increase spleen iron levels. Methyl mercaptan and methyl mercaptoacetate likewise did not result in an increase in spleen iron deposition. Both the hemosiderosis condition and the reduced food utilization caused by excess methionine were reversed by supplemental glycine plus threonine.

Animals↗

PubMed1978

The cytochemical localization of adenylate cyclase: fact or artifact?

In a study of the location of adenylate cyclase activity in rat pancreas with the method of Reik et al. (Science 168:382, 1970), as modified by Howell and Whitfield (J Histochem Cytochem 20:873, 1972) it was found that (a) unspecific staining occurs in rat pancreatic tissue fragments incubated in the Reik-Howell medium in the absence of substrate; (b) addition of adenylyl-imidodiphosphate (AMP-PNP) as substrate, either alone or together with stimulants of rat pancreas adenylate cyclase (secretin. NaF), does not result in increased precipitation; (c) cytochemical incubation of isolated rat pancreatic acinar cells and of rat liver and kidney fragments does not lead to substrate-specific precipitation. In subsequent chemical studies we have found that cyclic adenosine monophosphate (AMP) formation from [alpha32P]AMP-PNP in the presence of rat pancreatic particulate matter is very low in the Reik-Howell medium without lead ions, but is stimulated by addition of lead nitrate (4 mM). Whereas heat-treatment of the particulate matter abolishes all cyclic AMP formation in the absence of lead ions, it actually increases cyclic AMP production in the presence of 4 mM lead nitrate. This indicates that the cyclic AMP formation in the complet Reik-Howell medium occurs by a nonenzymatic mechanism. In addition, this medium shows a tendency to become turbid, particularly when calcium ions are added to the medium, suggesting a possible explanation for the apparently specific cytochemical detection observed by other authors. A revised cytochemical medium, with barium replacing lead and with a pH of 8.9 (optimal for adenylate cyclase with AMP-PNP substrate), leaves rat pancreatic adenylate cyclase activity intact and hormone sensitive, while it is still able to precipitate imidodiphosphate. However, cytochemical incubation of isolated rat pancreatic acinar cells in this revised medium in the presence of AMP-PNP and secretin does not yield an electron-dense precipitate, showing that the enzyme activity is to low to produce sufficient imidodiphosphate. These findings throw further doubt on the validity of the cytochemical detection of adenylate cyclase, reported by other investigators, notwithstanding the alleged positive results.

Adenylyl Cyclases↗

PubMed1977

Adsorption of mercury to urinary cells or particles.

Urine of a young healthy man was added with varying amounts of mercuric chloride, incubated for 10 to 375 min, and separated into supernatant solution and precipitate by centrifugation at 105,000 X g for 60 min. Percentage of mercury amount in precipitate increased with the increase of mercury amount added. But this adsorption of mercury to urinary cells or particles could not completely account for the amount of mercury in human urine reported (Suzuki and Shishido 1975). The hypothesis that desquamation of tubular cells is a route of urinary mercury excretion in man is still sustained.

Adsorption↗

PubMed1977

Oral toxicity of 1,1-dichloroethylene in the rat: effects of sex, age, and fasting.

Mortality curves for groups of fasted male rats treated with single, oral doses of 1,1-dichloroethylene (1,1-DCE, vinylidene chloride) were not monotonically increasing sigmoids, but were complex with maxima or extended plateaus in the region of dose between 100 and 700 mg of 1,1-DCE/kg. The exact shape was a function of the size (age) of the rat used. When groups of rats of various sizes were dosed with 50 mg/kg, mortality and hepatotoxicity were greatest for those groups whose average weight was between 100 and 150 g. Smaller and larger male rats were less susceptible to 1,1-DCE intoxication. The toxicity of 1,1-DCE was less severe in female rats and there was no significant effect of rat size on 1,1-DCE toxicity in females. In rats of both sexes the dose dependence of the hepatotoxic response was complex, possessing a threshold level, a region of precipitous increase, and a plateau, where larger doses were ineffective in increasing hepatotoxicity. The threshold in male rats of 100-150 g occurred near 50 mg/kg, and for females it was closer to 100 mg/kg. Considered in their entirety these data suggest that 1,1-DCE is metabolized to a toxic intermediate via some saturable pathway. Based on the effects of pretreatment with microsomal enzyme inhibitors and activators on 1,1-DCE toxicity in rats of various sizes, it appears that there are at least two microsomal reactions involved in 1,1-DCE metabolism.

Administration, Oral↗

PubMed1978

IgG autoantibody to human serum albumin studied by the ELISA-technique.

ELISA was applied for analysis of the HSA-human IgG autoantibody system responsible for the immunoelectrophoretic 'Tailing Albumin' (TA) phenomenon induced in most of the TA patients by prolonged nitrofurantoin therapy. Both hyperimmune porcine anti-HSA and autoimmune human anti-HSA antibodies of the IgG class were detectable by ELISA. The presence of autologous or added HSA had some inhibitory effect upon the detectability of the anti-HSA antibodies. Partial elimination of the autologous HSA by sucrose gradient ultracentrifugation or salt precipitation increased or unmasked the anti-HSA activity of some TA sera. The sensitivity of the ELISA as detector of the anti-HSA autoantibodies of whole human sera was roughly equal to that of the immunoelectrophoretic TA phenomenon. The analogy of the anti-HSA autoantibodies and the rheumatoid factors and the theoretical interest of both of them is stressed.

Antigen-Antibody Complex↗

PubMed1979

A nephelometric study of the reaction of monoclonal rheumatoid factor with heat aggregated gamma globulin and sera from patients with immune complex diseases.

Monoclonal rheumatoid factors (MCRF) have previously been used in a variety of assays for the detection of IgG-containing circulating immune complexes. We have isolated a MCRF from a patient with a lymphoproliferative disorder and have used a nephelometric technique to characterize its reaction with heat-aggreagated gammaglobulin (HAGG) used as a source of artificial immune complexes. The method is simple, economical and rapid and will detect as little as 6 microgram/ml of HAGG over a wide range of physicochemical conditions. A clinical study demonstrated that the sera from thirty-five out of fifty-eight patients (59%) with rheumatoid arthritis and twenty-one out of seventy-four patients (28%) with systemic lupus erythematosus (SLE) gave increased precipitation with MCRF compared with 232 blood donors. However, in marked contrast to previous studies, sucrose gradient ultracentrifugal analysis of nine strongly precipitating sera revealed that in eight the MCRF precipitated with material sedimenting in the monomeric IgG position. In only one specimen did the MCRF react with material sedimenting in heavier regions. It is suggested that different MCRFs vary in the specificity for binding IgG complexes and these reagents should be carefully characterized before becoming established in nephelometric assays for circulating immune complexes.

Adult↗

PubMed1976

Cytological and microspectrophotometric analysis of mesodermalized explants of Triturus gastrula ectoderm.

Using isolated presumptive ectoderm of the newt (Triturus pyrrhogaster) embryos as a reactor and extract of rat bone marrow as a mesodermal inductor, changes of cell number and mitotic index of the reactor cells were studied. In early stages of cultivation the increase in cell number in the mesodermalized ectodermal piece was slower than in the non-mesodermalized epidermal piece; but after 24 h it showed abrupt increase and reached a cell population equal to that of the control at 48 h of cultivation. In the experimental series, the mitotic index was 0 at 4 h after the application of the inducing stimulus, but increased precipitously in the next 8 h and reached a level of 4-4% at 12 h and thereafter decreased gradually. The cell cycle stopped at the S phase and stayed in it for several hours after the application of inductor. A sudden fall in cell number, observed in the mesodermalized epidermal piece between the 4th and the 8th h after the application of inducing stimulus, seems to be attributable to cell death which was brought about by the inducing stimulus. In the histogenetic process phases of repression on mitosis by an inducing stimulus, cell proliferation and nonproliferation seem to succeed each other.

Animals↗

PubMed1979

Ultracytochemical calcium distribution in B cells in relation to biphasic glucose-stimulated insulin release by the perfused rat pancreas.

Calcium distribution in B cells of the isolated perfused rat pancreas was examined by the pyroantimonate precipitation technique in relation to the insulin secretory pattern of the perfused pancreas in response to 3 mM or 20 mM D-glucose or 20 mM D-glucose in calcium-depleted ethylene glycol tetra-acetic acid (EGTA) medium. Perfusion fixation after various time intervals from 3 to 30 min allowed appropriate relation to secretory phases. Qualitative and quantitative evaluation of the precipitation patterns revealed a significant increase in cell membrane associated percipitates after 3--5 min of perfusion with 20 mM glucose compared with the results after perfusion with 3 mM glucose. After 10--30 min of perfusion with 20 mM glucose there was an additional significant increase in precipitates located in the cytoplasm and the halos of the secretory granules. Perfusion with 20 mM glucose in calcium-deprived EGTA medium strongly reduced the number of precipitates within the B cells. The results suggest that cell membrane associated calcium may be involved in exocytosis, and by its sudden increase may trigger the first phase of insulin secretion. The calcium stores in the cytoplasm and the granules may be of importance for long-term regulation of insulin release.

Animals↗

PubMed1975

Quantitative immunoelectrophoresis of proteins in human erythrocyte membranes. Analysis of protein bands obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

1. We have defined conditions that permit quantitative immunoelectrophoresis in agarose gels of dodecyl sulfate-solubilized erythrocyte membrane proteins. 2. Using human serum albumin, transferrin, MN-glycoprotein (glycophorin) and crude spectrin as test proteins, we found that accurate analyses are possible if samples and gels are 1% in non-ionic detergent (Berol EMU-043) or Triton X-100) and if no more than 100 nmol free dodecyl sulfate is applied per sample. 3. Dodecyl sulfate treated membranes analyzed by crossed immunoelectrophoresis using rabbit antibodies against membrane material yielded optimal precipitation patterns in gels containing 1% of non-ionic detergent. 4. Crossed immunoelectrophoresis in the presence of 1% of Berol revealed precipitates when 10 protein bands defined and isolated by preparative dodecyl sulfate-polyacrylamide gel electrophoresis were run against anti-membrane antibodies. Seven of these bands showed more than one precipitation arc, indicating the presence of more than one antigenic component. 5. Crossed-line immunoelectrophoresis showed that dodecyl sulfate-polyacrylamide gel electrophoresis bands 1, 2 and 2.1 shared common antigenic components. The MN-glycoprotein was present in bands 3, 4A, 4B and 5, where antigenic components of the major intrinsic erythrocyte membrane protein, band 3, were also found. 6. After absorption of the anti-membrane antibody with intact erythrocytes, immunoelectrophoresis showed the disappearance of the MN-glycoprotein precipitates. An increase in the area below the precipitate corresponding to the major intrinsic protein (band 3) was also observed, indicating exposure of some antigens of this protein on the outer surface of intact cells. 7. After absorption of the antibody preparation with washed erythrocyte membranes, immunoprecipitates were not seen in any experiments, indicating that all antigenic determinants observed are exposed at one or both surfaces of the membrane. 8. Our analyses indicate that the peptide moieties of serum lipoproteins do not constitute a significant component of erythrocyte membranes.

Antibody Specificity↗

PubMed1978

Subcellular B cell calcium and insulin secretion in vitro. Comparative ultracytochemical studies after glucose stimulation and cyproheptadine inhibition.

Using the ultracytochemical pyroantimonate technique different patterns of calcium containing precipitates were found in the B cells of the isolated perfused rat pancreas under conditions of stimulated and inhibited insulin secretion. The calcium specificity of the ultracytochemical method was assessed by perfusion with a EGTA containing calcium-free medium, which markedly reduced the extent of precipitation. Perfusion with 20 mM D-glucose over a period of 30 min resulted in calcium distribution patterns which could be related to the biphasic insulin release. The calcium patterns differed significantly in their quality and quantitative morphometry from those after 5 mM D-glucose or cyproheptadine (CPH) perfusion (20 mM D-glucose plus 0.1 mM CPH). After 3--5 min of 20 mM glucose perfusion there was an increased calcium precipitation along the inner side of the B cell membranes. After 20--30 min an additional increase in precipitation was found in the cytoplasmic matrix and in the secretory granules. B cells in a CPH-inhibited state of secretion and also after perfusion with 5 mM glucose lacked these findings. The data suggest that an increase in the membrane associated calcium may induce the first phase of insulin secretion by triggering the exocytosis of peripheral granules, while the cytoplasmic calcium may be involved in long term regulation of insulin release.

Animals↗