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At least 19 recordsLinked to original sources
PubMed1976

Effects of various hydrodynamic conditions on dissolution rate determinations.

An automated potentiometric procedure was used in dissolution rate studies to determine the effects of various hydrodynamic conditions on dissolution rate determinations. Changes in the hydrodynamics of the system resulted from using various sizes and shapes of dissolution vessels. Dissolution rate constants for benzoic acid prills in distilled water at pH-stat 6.2 were used as a measure of the agitation intensities present in the different shaped vessels. Great variations in the dissolution rates occurred in vessels with the same diameter and stirrer blade position when the shapes of the bottom of the vessel were varied. A similar order of dissolution rates was obtained at 100 and 150 rpm for the individual vessels at various propeller heights. The order differed from one vessel to another, depending on the shape of the bottom (concave, convex, or flat) of the vessel. In some cases, a change in the type of bottom resulted in the opposite order of rates for vessels with the same diameter.

Benzoates↗
PubMed1975

Hydrodynamic analog model for pharmacokinetics II: critical examination of model and its contribution to pharmacokinetics.

A comparison of the conventional pharmacokinetic models and the previously proposed hydrodynamic diffusion analog model is presented. A significant result that an n-compartment system can exhibit at best (n - 1) extremum times in the concentration-time plot of the central compartment under appropriate values of physiological parameters is presented. The observation of kinks experimentally in certain physiological-drug systems is thus shown to be amenable to explanation.

Dicumarol↗
PubMed1975

[The influence of isoglaucon on the hydrodynamics and haemodynamics of the eye (author's transl)].

By animal experiments and clinically we could prove that isoglaucon instillation caused the decrease in IOP due to both increase in outflow and reduction of humor secretion; the IOP decrease and changes in hydrodynamics being manifested more markedly in the fellow-eye. As reoophthalmography demonstrated "Isoglaucon" produced lumen narrowing in the anterior portion of the uveal tract. "Isoglaucon" was prescribed to 20 patients having open-angle-glaucoma, Two hours after instillation the 23 decreased in 26 eyes (of 28) by 9.3 +/- 1.0 mm Hg. When prescribed regularly "Isoglaucon" raised the outflow facility coefficient from 0.10 +/- 0.01 to 0.20 +/-0.02. The secretion decreased from 2.0 +/- 0.2 to 0.9 +/- 0.15. Thus, IOP decrease after "Isoglaucon" is accounted for by both improved outflow and reduction of aqueous humor secretion. The "isoglucon" instillation produced a rather moderate decrease in the total arterial pressure, though no expected parallelism in arterial and intraocular pressure was marked.

Animals↗
PubMed1978

The role of Ca2+ on pH-induced hydrodynamic changes of bovine pancreatic deoxyribonuclease A.

DNase A studied by gel filtration on Sephadex G-100 at pH 7.4 in 40 mM Tris-HCl buffer, behaves hydrodynamically as a spherical monomeric macromolecule of around 31,000 molecular weight, with a Stokes radius = 24.7 A, f/fo = 1.19, and D20,W = 8.69. Similar results were obtained by analytical dialysis using zinc chloride-modified cellophane membranes. The elution volume of DNase A decreases as the pH increases between pH 4.7 and pH 9.5. This effect has been attributed to a change in the tridimensional structure of the protein and interpreted as a modification in the axial ratio due to unfolding of the polypeptide chain with increase in the apparent Stokes radius. The addition of Ca2+ produce reversion of the pH-induced changes at pH 9.5. The transition occurs when Ca2+ binds to at least two binding sites (n = 1.66 in a Hill plot) with a Kd = 8.9 X 10(-5) M and the effect appears to be cooperative. These findings support the hypothesis that Ca2+-binding to DNase A causes a conformational change that maintains a more active structure of the enzyme, especially when the pH-induced unfolding reduces its activity.

Animals↗
PubMedDate not supplied

Effect of proteolytic activation on intraocular hydrodynamics the pressure of O2, CO2 and pH in the aqueous humor.

The effect of proteolytic activation on the tonographic indices and secretion of the aqueous humor was studied. It was found that active peptides rise the secretion of intraocular fluids increasing the permeability of capillary plexuses and decreasing the metabolic processes in the structures secreting the aqueous. They may perticipate in haemodynamic and hydrodynamic intraocular autoregulation.

Animals↗
PubMed1976

[The hydrodynamic mucosa-cytology by means of ultrastructures filters in upper respiratory tract and oesophagus].

A rinse-and-suck-sound is presented, which conveys cytological material to a special filter mechanism. The heart of the system is a well-known filter, an electric pump, and a new constructed vacuum chamber. After Papanicolaou staining the filters are being cleared and allow a light-microscopical judgement. A reduction of possibilities of error in exfoliative cytology can be noticed.

Biopsy↗
PubMed2025

Retinal hypoxia reversal with PLGA-oxygen nanobubbles.

Pathologies associated with retinal hypoxia, including diabetic retinopathy, central/branch retinal artery occlusion (CRAO/BRAO), central/branch retinal vein occlusion (CRVO/BRVO), retinopathy of prematurity, sickle cell retinopathy, etc., have limited effective therapeutic intervention strategies. To address this shortcoming, herein we propose a biocompatible and biodegradable poly (lactic-co-glycolic acid) shell-based oxygen nanobubbles (PLGA-ONBs) platform, formulated with PLGA, polyvinyl alcohol (PVA), and NaHCO3. The formulation of a novel PLGA-ONBs was proposed, and the synthesis process was optimized with respect to dependent (sonication power, PVA, and NaHCO3 concentrations) and response (hydrodynamic diameter and oxygen capacity) variables. The optimized formulation has a concentration of (13.8 ± 0.01) × 1010 particles per ml with a hydrodynamic diameter of 142.83 ± 11.46 nm, and oxygen loading capacity of 47.2 ± 2.4 mg L-1. After 4 weeks of storage, the ONBs were found to have an oxygen concentration of 38.9 ± 2.9 mg L-1, indicating excellent oxygen retention capability. The PLGA-ONBs tested in vitro in Muller and R28 retinal cell lines demonstrated excellent biocompatibility and potential to mitigate hypoxia. In addition, the PLGA-ONBs treatment on hypoxic cells demonstrated restoration of mRNA expression of three key hypoxic genes (HIF-1α, PAI-1, and VEGF-A) to normoxic states, indicating hypoxia reversal potential. Biosafety of the PLGA-ONBs was demonstrated in a rabbit model, demonstrating promise in clinical translation. The PLGA-ONBs developed exhibited excellent oxygen loading and retention, potential in hypoxia mitigation, and a safety profile that could be a promising route to treating ischemic diseases of the eye.

Polylactic Acid-Polyglycolic Acid Copolymer↗
PubMed1979

The temperature and pH dependence of conformational transitions of the chromatin subunit.

Hydrodynamic, spectroscopic, and chemical crosslinking studies on monomer chromatin subnits are reported as a function of ionic strength, pH, and temperature. In earlier studies, two salt-dependent conformational transitions were described (Gordon et al., Proceedings of the National Academy of Science, 75, 660, 1978). Transition one occurred between 0.7 and 2.0 mM ionic strength and transition two occurred between 5.0 and 11.0 mM ionic strength. Crosslinking at 11 mM ionic strength with formaldehyde suppressed both transitions. In this communication we report that the second transition was characterized by changes in the circular dichroism spectra in the 260--320 nm region as well as by changes in the hydrodynamic properties. As the ionic strength was increased from 5.0 to 11.0 mM, [theta]282 decreased from 2000 TO 1500 DEG CM2/DMOLE AND [THETA]295 decreased from 0 to -400 deg cm2/dmole. Both transitions occurred in the pH range from pH 6.0 to 9.2. At pH 5.0, the two ionic strength-dependent transitions were no longer observed and the characteristic changes in the circular dichroism spectra were suppressed. The spectra of the monomer subunits at pH 5.0 showed only small changes with ionic strength and resembled the spectra of the subunits at 11 mM ionic strength above pH 6.0. In order to characterize the transitions in thermodynamic terms an ionic strength near the midpoint of each transition was selected. Then, changes in s20,w and D20,w were measured as a function of temperature. These data allow an estimation to be made of the enthalpies and entropies of the transitions.

Chromatin↗
PubMed2026

Diffusive Noise Controls Early Stages of Genetic Demixing.

Theoretical descriptions of the stepping-stone model, a cornerstone of spatial population genetics, have long overlooked diffusive noise arising from migration dynamics. We derive a fluctuating hydrodynamic description of this model from microscopic rules, which we then use to demonstrate that diffusive noise significantly alters early-time genetic demixing, which we characterize through heterozygosity, a key measure of diversity. Combining macroscopic fluctuation theory and microscopic simulations, we demonstrate that the scaling of allele-number fluctuations in a spatial domain displays an early-time behavior dominated by diffusive noise. Our results underscore the need for additional terms in existing continuum theories and highlight the necessity of including diffusive noise in models of spatially structured populations.

Models, Genetic↗
PubMed1975

Analysis in deoxycholate of three antigenic specificities associated with the rat Thy-1 molecule.

Three antigens similar in tissue distribution can be identified on rat thymocytes; the Thy-1.1 antigen, a rat specific xenoantigen, and a rat-mouse cross-reacting xenoantigen. To determine if these three antigens were on the same molecule their behavior in detergent-solubilized extracts from thymocytes was studied. Membrane fragments containing Thy-1.1 activity were prepared by a rapid method involving the use of Tween-40 detergent, and were solubilized in deoxycholate. The 150 000 x g supernatant from this extract contained approximately 50% of the original Thy-1.1 and xenoantigen activity. The supernatant was chromatographed on Sephadex G-200, and subjected to zone sedimentation on sucrose gradients in H2O and 2H2O to determine the hydrodynamic properties of the antigens. The three antigens migrated in identical fashion in all cases, and behaved as a molecule of 28 000 daltons molecular weight. When the antigenically active fraction, recovered after chromatography on Sephadex G-200, was passed through an immunoabsorbent consisting of rabbit antibody to one of the xenoantigens, all three antigens were equally depleted compared with passage through a control column. The results of these experiments suggested that Thy-1.1 antigen and the two xenoantigens were closely associated and most probably all on the Thy-1 molecule.

Animals↗
PubMed1975

[Interaction between proteins and acid polysaccharides].

The intereaction between proteins and acid polysaccharides is electrostatic in nature and leads to the formation of soluble charged and insoluble neutral complexes. The complex formation in the system casein-dextran sulphate is followed by means of turbidimetric titration. It depends on the pH value and the electrolyte concentration. On free electrophoresis, complexes formed below the isoelectric point of the protein exhibit anodic mobility, whereas pure casein migrates to the cathode. The protein in the complex is not able to bind amido black. Consequently, it cannot be detected electrophoretically by dyebinding. The results from viscosity and diffusion measurements are indicative of an increased hydrodynamic volume of the complexes.

Amido Black↗
PubMed1977

Heterogeneity in alpha-lactalbumins. I. Human alpha-lactalbumin.

alpha-Lactalbumin from human milk shows an heterogeneous behaviour when subjected to ion exchange chromatography with DEAE-Sephadex. Two components have been separated, showing identical patterns in the following studies: amino acid compositions, fluorescence and circular dichroism spectra, transition temperature of denaturation, antigenicity, lactose synthase specifying activity and hydrodynamic properties. After rechromatography of either peak, these two components appeared to be in equilibrium. This equilibrium varies with the temperature and the pH of chromatography. Moreover, an increase of n-alcohol concentration in the eluting buffer also induces an increase of the second protein peak eluting at higher ionic strength. These two peaks seem to be the result of some conformational change induced upon the binding of the protein to the solid anionic matrix.

Amino Acids↗
PubMed1976

Evaluation of the blood-CSF barrier by protein gradients and the humoral immune response within the central nervous system.

A linear correlation was found between the serum/cerebrospinal fluid (CSF) concentration ratios of albumin, caeruloplasmin and alpha2-macroglobulin and their hydrodynamic radii in a semilogarithmic plot. This protein gradient is used as a parameter to evaluate the blood-CSF barrier under normal and pathological conditions. Irrespective of vastly different transfer rates, the ratio/size permeation curves of proteins at the blood-CSF barrier and the blood-lymph barrier have comparable characteristics. Therefore the protein gradients found in various disease states are interpreted by means of Renkin's general law of lymph formation. Declined gradients are caused either by an increased permeability of the barrier sites or by a decreased turnover rate of the CSF within the compartment punctured. The concentration ratios of immunoglobulins are related to the gradient that is constructed with the ratios of the barrier-indicative marker proteins. As judged by comparative disc electrophoresis of serum and CSF, those disease states that are dominated by barrier impairment are used to establish the range of concentration ratios, compatible with a passive immunoglobulin transfer in any condition in which the barrier is disordered. A mathematical approach is described, which allows the quantitative evaluation of the minimal immunoglobulin portion that is synthesized within the central nervous system.

Adult↗
PubMed2024

Intrahepatic Exhausted Antiviral Immunity in an Immunocompetent Mouse Model of Chronic Hepatitis B.

BACKGROUND & AIMS: Targeting exhausted immune systems would be a promising therapeutic strategy to achieve a functional cure for HBV infection in patients with chronic hepatitis B (CHB). However, animal models recapitulating the immunokinetics of CHB are very limited. We aimed to develop an immunocompetent mouse model of CHB for intrahepatic immune profiling. METHODS: CHB mice were created by intrahepatic delivery of the Sleeping Beauty transposon vector tandemly expressing the hepatitis B virus (HBV) genome and fumarylacetoacetate hydrolase (FAH) cDNA into C57BL/6J congenic FAH knockout mice via hydrodynamic tail vein injection. We profiled the viral and intrahepatic immune kinetics in CHB mice with or without treatment with recombinant IFNα or the hepatotropic Toll-like receptor 7 agonist SA-5 using single-cell RNA-seq. RESULTS: CHB mice exhibited sustained HBV viremia and persistent hepatitis. They showed intrahepatic expansion of exhausted CD8+ T (Tex) cells, the frequency of which was positively associated with viral load. Recruited macrophages increased in number but impaired inflammatory responses in the liver. The cytotoxicity of mature natural killer (NK) cells also increased in CHB mice. IFNα and SA-5 treatment both resulted in viral suppression with mild hepatic flares in CHB mice. Although both treatments activated NK cells, SA-5 had the capacity to revitalize the impaired function of Tex cells and liver-recruited macrophages. CONCLUSIONS: Our novel CHB mouse model recapitulated the intrahepatic exhausted antiviral immunity in patients with CHB, which might be able to be reinvigorated by a hepatotropic TLR7 agonist.

Animals↗
PubMed2025

Tracking microplastic contamination across seasons in a freshwater reservoir: Evidence from surface water, sediments, and fishes.

Microplastics (MPs) are prevalent contaminants in aquatic environments, posing substantial ecological and health risks. These particles migrate within the different layers of aquatic bodies with time and affect the respective biota. Thus, to get an in-depth understanding of the particles, this current study investigated the seasonal distribution, morphological and chemical characteristics, along with potential ecological and human health impacts in the samples including surface water, sediment, and fish from a drinking water supplying reservoir in eastern India. Across three different seasons, pre-monsoon, monsoon, and post-monsoon samples were collected using optimized methods. Results revealed distinct seasonal trends: MP abundance in surface water peaked during the monsoon (mean: 1.15 MPs/L), while sediment showed the highest concentrations in the pre-monsoon (mean: 596 MPs/kg), indicating temporal accumulation dynamics influenced by runoff, hydrodynamics, and sedimentation. Fish gut analysis confirmed ingestion of MPs across five species, with concentrations ranging from 26 to 100 MPs/kg, depending on feeding habits. The most dominant MP type were fragments, followed by fibers, films, and beads. Polymer analysis via µFTIR identified polyethylene, polypropylene, and polyvinyl chloride as prevalent, with hazard assessments (i.e., Polymer Hazard Index (PHI)) indicating medium to very high ecological risks. Heavy metal association was more dominant in the MPs isolated from sediments than the waterborne MPs. Pollution Load Index (PLI) values were > 1 in most seasons, confirming contamination. Health risk analysis suggested potential exposure through both drinking water and fish consumption. This study emphasizes the need for seasonal monitoring, improved waste management, and mitigation strategies to address MP pollution in freshwater ecosystems.

Microplastics↗