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K E Williams

Publications and source records attributed to K E Williams.

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

Heterogeneity of binding site for adsorptive pinocytosis of simple proteins by rat yolk sacs.

1. When rat yolk sacs were incubated in serum-free medium 199, the 125I-labelled forms of both formaldehyde-treated bovine serum albumin and ribonuclease were captured far more rapidly than 125I-labelled polyvinylpyrrolidone. Extensive adsorption of these proteins to the plasma membrane is the main cause of this effect. 2. Quantitative analysis of the adsorptive-phase pinocytosis of these two proteins showed curved Hofstee plots, suggesting either the presence of multiple classes of binding site on the surface of pinocytically-active yolk-sac cells or a single class of binding site that exhibits negative cooperativity in the binding of these proteins. The values of Km were similar, ranging over 0.6-11.8 microM for 125I-labelled ribonuclease and over 0.31-4.7 microM for formaldehyde-treated 125I-labelled albumin. 3. Competitive uptake studies, in which tracer amounts of each of the 125I-labelled proteins were ingested from serum-free medium containing a higher concentration of one of a series of unlabelled proteins, revealed marked differences between the two radiolabelled proteins. These findings suggest that formaldehyde-denatured albumin is captured by binding to hydrophobic binding sites on the plasma membrane whereas ribonuclease is captured by binding to negatively charged sites.

Adsorption↗
PubMed1981

Rates of pinocytic capture of simple proteins by rat yolk sacs incubated in vitro.

The rates of pinocytic uptake of a number of small 125I-labelled simple proteins (insulin, ribonuclease A and lysozyme) by rat yolk sacs incubated in vitro were determined both before and after treating these proteins with reagents that are known to increase the rate of capture of 125I-labelled bovine serum albumin. Uptake of the untreated forms of all three proteins was extremely rapid, indicating that adsorptive pinocytosis is the principal mechanism by which yolk-sac cells capture these simple proteins, but these rates show no simple correlation with molecular charge. In contrast with albumin, the rates of uptake of treated proteins were either unchanged or lower than that of the corresponding untreated protein preparations; polymeric forms of 125I-labelled lysozyme larger than dimers were ingested at rates significantly lower than that of the monomer.

Animals↗
PubMed1981

Adsorptive pinocytosis of 125I-labelled lactate dehydrogenase isoenzymes H4 and M4 by rat yolk sacs incubated in vitro.

The pinocytic uptake of 125I-labelled porcine lactate dehydrogenase isoenzymes H4 and M4 by 17.5-day rat visceral yolk sac incubated in vitro was saturable and binding obeyed Michaelis-Menten kinetics. The uptake characteristics of the two isoenzymes were very similar. For the H4 and the M4 isoenzymes, the dissociation constants of the protein-plasma-membrane complex were 0.62 microM and 0.84 microM respectively, and the maximum rates of uptake 0.13 and 0.26 nmol/mg of yolk-sac protein per h respectively. These findings contrast with those from studies in vivo, which show the M4 form is taken up by rat liver sinusoidal cells at a much higher rate than the H4 form, and point to different recognition systems for the adsorptive pinocytosis of simple non-conjugate proteins in yolk-sac epithelial cells and liver sinusoidal cells. Competition experiments indicate that binding of the H4 isoenzyme to the yolk-sac cells is restricted to hydrophobic interactions, whereas the binding of the M4 isoenzyme involves hydrophobic as well as positively charged sites on the protein molecules.

Adsorption↗
PubMed1981

Effects of microbial proteinase inhibitors on the degradation of endogenous and internalized proteins by rat yolk sacs.

1. The effects of leupeptin and other microbial proteinase inhibitors were measured in rat yolk sacs on the uptake and degradation of formaldehyde-denatured 125I-labelled bovine serum albumin as well as on the degradation of 3H-labelled endogenous protein. 2. Leupeptin, at concentrations between 1 and 100 micrograms/ml, inhibits the degradation of added albumin without affecting pinocytic uptake. Accordingly large amounts of undegraded albumin accumulate within the tissue. 3. Removal of leupeptin produces a rapid recovery of the capacity to degrade albumin. 4. Endogenous protein degradation is rapidly inhibited by leupeptin, but to a far lesser extent than the breakdown of albumin. However, the inhibition is only slightly reversed on removal of leupeptin. 5. Degradation of both albumin and endogenous protein in intact yolk sacs is inhibited by the microbial proteinase inhibitors in the order: leupeptin greater than antipain greater than chymostatin; elastatinal, pepstatin and bestatin are ineffective. 6. Similar results are found when albumin is incubated in yolk-sac homogenates at pH 4 with the inhibitors. 7. The marked inhibitory effects of leupeptin, antipain and chymostatin suggest that cathepsin B and possibly cathepsin L participate in the degradation of 125I-labelled albumin in yolk sacs. By comparison, the smaller inhibitory effects of the proteinase inhibitors on endogenous protein breakdown imply a minor role of lysosomal cathepsins in this process.

Animals↗
PubMed1981

Localisation of experimental staphylococcal abscesses by 99MTC-technetium-labelled liposomes.

The accumulation of 99mTc-technetium-labelled liposomes in abscesses was studied. Abscesses were produced in the thighs of albino rats by intramuscular injection of Staphylococcus aureus. After 4 days these abscesses were used to determine the localisation of 99mTc-technetium-labelled anionic, cationic and neutral liposomes in the abscess area. This was achieved by radionuclide images produced by a gamma camera and an associated data-processing system. There was a pronounced uptake of 99mTc-technetium-labelled anionic liposomes in the abscess area compared with the corresponding unaffected thigh. Similar uptake was not shown by the 99mTc-technetium-labelled cationic and neutral liposomes. Abscess uptake of anionic liposomes was maximal at or before 30 min after injection and was not enhanced by prior opsonisation with aggregated rat immunoglobulin.

Abscess↗
PubMed1981

The Rye classification of a population based series of Hodgkin's disease patients in Western Australia.

Data are presented on the incidence in Western Australia of subtypes of Hodgkin's disease which were obtained by review of all cases of the disease notified between 1960 and 1974. Observations were also made on within- and between-observer agreement on the use of the Rye classification by a group of 9 surgical pathologists, all in the day-to-day practice of pathology. Although many consensus diagnoses were made only after spirited discussion by the Group, the results suggested that general surgical pathologists can perform nearly as well as lymphoma experts. A comparison of the incidence of Hodgkin's disease and distribution of Rye subtypes in Western Australia with 4 other populations showed a similar overall incidence but appreciable variation in the relative frequency of the subtypes--mainly in the proportions of nodular sclerosing and mixed cellularity.

Adolescent↗
PubMed1981

Endocytosis of simple proteins by rat yolk sacs and by rat peritoneal macrophages incubated in vitro.

The specificity of endocytosis of the 125I-labelled forms of LDH H4 and M4 and BSA was investigated in rat yolk sac and resident rat peritoneal macrophages incubated in vitro. The rate of uptake of the more basic LDH M4 by yolk sac is only slightly higher than that of LDH H4, but in macrophages the isoenzyme M4 is taken up three times more rapidly than the H4 form. Both cell types possess little affinity for BSA, but an increase in the hydrophobicity of this protein by formaldehyde-denaturation resulted in a several-fold increase in uptake by yolk sac cells as well as by macrophages. Apparently, yolk sacs and macrophages both contain binding sites for positively charged and hydrophobic proteins, but, in yolk sac hydrophobicity is relatively more important, whereas in macrophages positive charge is the main characteristic for adsorptive pinocytosis of simple proteins. In this respect, the binding characteristics of peritoneal macrophages resemble those of sinusoidal liver cells. The study also compares the serum-dependence of fluid-phase pinocytosis in both cell types; a decrease in serum concentration gives rise to an increase in the rate of pinosome formation in yolk sac, but has the opposite effect in macrophages.

Animals↗
PubMed1980

Effects of weak bases on the degradation of endogenous and exogenous proteins by rat yolk sacs.

In rat yolk sacs incubated in vitro, the rates of degradation of endogenous [3H]leucine-labelled proteins and of pinocytically ingested 125I-labelled bovine serum albumin were both decreased in the presence of either ammonium, methylammonium or ethylammonium ions (0-20 mM) or much lower concentrations of chloroquine (0-500 microM). These effects were also accompanied by an inhibition of pinocytosis, as measured by the rate of uptake of 125I-labelled polyvinylpyrrolidone, and by a fall in the [ATP]/[ADP] ratio within the tissue. Re-incubation in inhibitor-free medium of yolk sacs previously exposed to a weak base restored pinocytic and proteolytic capacities, except for tissues exposed to chloroquine at concentrations above 0.1 mM (these appeared to be cytotoxic); an attendent rise in [ATP]/[ADP] ratios to near normal values was also observed. Weak bases, at concentrations that fully arrested the breakdown of 125I-labelled albumin, failed to inhibit by more than 45% the degradation of [3H]leucine-labelled endogenous proteins. Since 125I-labelled bovine serum albumin has been shown to be degraded entirely intralysosomally by yolk sacs, this suggests either that the hydrolysis of endogenous proteins is shared between lysosomes and some other site or that, unlike 125I-labelled albumin, some endogenous proteins can be degraded within lysosomes at abnormally high pH.

Adenine Nucleotides↗
PubMed1980

Mechanism of stimulation of pinocytosis by trypan blue.

Trypan blue at 50 microgram/ml stimulates the pinocytic uptake of 125I-labelled PVP, but not of colloidal 198Au or formaldehyde-denatured 125I-labelled bovine serum albumin, by the 17.5-day rat visceral yolk sac incubated in vitro. Neither Trypan blue nor a combination of the dye with 125I-labelled PVP stimulated the rate of pinocytosis of liquid by the tissue. Trypan blue itself was shown to enter the yolk-sac cells by adsorptive pinocytosis. It is proposed that an interaction between Trypan blue and 125I-labelled PVP enables the latter substrate to enter the cells adsorptively by so-called 'piggy-back' pinocytosis.

Animals↗
PubMed1980

Gas chromatographic analysis of acetic acid in air.

A gas chromatographic (GC) method is presented for the specific determination of acetic acid in air. Air samples are collected in fritted midget bubblers containing aqueous sodium carbonate. Aliquots of the absorbent solution are esterified and GC analysis performed on the headspace. The formation of the ester is directly proportional to the concentration of the acetic acid concentration in the absorbent. The method is applicable to concentrations of acetic acid in air over the range of 2.0 mg/m3 to 75 mg/m3, and can be extended to include higher concentrations by quantitative dilution of samples.

Acetates↗
PubMed1980

Preparation and properties of liposome-associated gentamicin.

Gentamicin was successfully incorporated into neutral, anionic, and cationic liposomes, and the percentage of gentamicin incorporated was found to be a function of lipid concentration. Gentamicin did not leak out of the liposomes over a 3-week period at 4 degrees C. When liposome-associated gentamicin was administered intravenously to rabbits, its serum half-life was greatly prolonged. Intragastric administration of dipalmitoylphosphatidylcholine liposomes containing gentamicin resulted in the appearance of gentamicin in serum. Liposome-associated gentamicin, when administered intravenously, led to the appearance of gentamicin in the liver and spleen, which was not observed when rabbits were injected with free gentamicin.

Animals↗
PubMed1979

Hydrolysis of an exogenous 125I-labelled protein by rat yolk sacs. Evidence for intracellular degradation within lysosomes.

When added to the serum-free medium in which 17.5-day rat yolk sacs were incubated, formaldehyde-denatured 125I-labelled bovine serum albumin was rapidly degraded. More than 80% of the radiolabelled digestion products appearing in the incubation medium consisted of [125I]iodo-L-tyrosine; larger digestion products were found only in association with the yolk-sac tissue. In the early stages of an incubation, low-molecular-weight digestion products began to appear in the incubation medium only after they could be detected within the tissue, and progressive association of trichloroacetic acid-insoluble radioactivity with the tissue preceded both these events. None of the observed proteolysis could be attributed to proteinases released into the incubation medium. Tissue-associated acid-insoluble radioactivity showed a lysosomal distribution on sub-cellular fractionation, and cell-free homogenates of yolk sacs degraded albumin only at acid pH values. Progressively decreasing the rat of pinosome formation (either by progressively lowering the incubation temperature or by the use of increasing concentrations of the metabolic inhibitor rotenone) caused a corresponding decrease in the rate of degradation of albumin. These findings indicate that, in vitro, formaldehyde-denatured 125I-labelled bovine serum albumin is digested by rat yolk sacs exclusively intracellularly, within lysosomes.

Animals↗
PubMed1979

Rate of pinocytic capture of macromolecular substrates by rat yolk sac incubated in serum-free culture medium.

Pinocytic activity was quantified for rat yolk sacs incubated in a medium that was either serum-free or contained 10% (v/v) of calf serum. Absence of serum from the medium caused a small increase in the rate of pinosome formation, as determined by the rates of capture of both 125I-labelled poly(vinylpyrrolidone) and [14C]sucrose. In contrast, the rates of uptake of substrates ingested by adsorptive pinocytosis were greatly enhanced when serum proteins, which compete for the same binding sites on the plasma membrane as used by adsorbing substrates, were absent. Elimination of such competition greatly simplifies the quantitative analysis of the binding process, and permitted a detailed study of the binding to the plasma membrane of formaldehyde-denatured bovine serum albumin, a protein that is rapidly digested within the lysosomal system after its pinocytic capture. Binding obeyed Michaelis-Menten kinetics and showed a dissociation constant of approx. 1 micron, indicating the high affinity of this protein for binding sites on the surface of actively pinocytosing yolk-sac cells.

Animals↗
PubMed1979

Assessment of hazardous air pollutants from disposal of munitions in a prototype fluidized bed incinerator.

As part of the control technology development for the disposal of waste munitions, an assessment of potential emissions of hazardous air pollutants from a prototype fluidized bed incinerator was conducted. Assessment program elements included identification of potentially toxic emissions through material input analysis and computer simulation modeling of the combustion cycle; development of emission limitations criteria for substances having no present air pollution emission standards; evaluation and development of analytical procedures; and design of a sampling system to condition an emission stream characterized by high temperature and humidity resulting from burning water slurries of explosive materials. Emphasis is placed on the potential emission of nickel and its compounds, particulate and vapor emissions of cyanides, nitrogen oxides, and TNT and RDX energetic residuals.

Air Pollutants↗
PubMed1977

A quantitative study of pinocytosis and intracellular proteolysis in rat peritoneal macrophages.

A method for the culture of rat peritoneal macrophages in vitro is described, in which pinocytic uptake of colloidal [198 Au]gold, 125I--labelled poly(vinylpyrrolidone) and [14C]sucrose proceeds at contant and fairly reproducible rates for several hours. The rat of uptake of colloidal [198 Au]gold, which wxhibited some inter-batch variation, was approx. 100 times that of the other two substrates. Colloidal gold did not affect the rate of uptake of 125I-labelled poly(vinylpyrrolidone) and therefore its own high rate of uptake could not be attributed to a stimulation of the formation of pinocytic vesicles. It conclude that uptake of collodial gold is highly dependent on adsorption on binding sites on the plasma membrane. Uptake of formaldehyde-treated 125I-labelled bovine serum albumin was followed by the release of [125I]iodo-L-tyrosine into the culture medium and took place at a rate intermediate between those of collodial [198Au]gold and the other two non-digestible substrates, 125I-labelled poly(vinylpyrrolidone) and [14C]sucrose.

Animals↗
PubMed1977

The pinocytosis of 125I-labelled poly(vinylpyrrolidone), [14C]sucrose and colloidal [198Au]gold by rat yolk sac cultured in vitro.

The rates of uptake of 125I-labelled poly(vinylpyrrolidone), [14C]sucrose and colloidal [198Au]gold by 17.5-day rat yolk sac cultured in vitro were studied. Over a 6.5h period each substrate was accumulated at a constant and reproducible rate of approx. 2microliter/h per mg of protein. After accumulation in vitro, the three substances were released from the tissue into substrate-free medium at low rates. Sucrose present in the medium at concentrations up to 10 mg/ml was without effect on the accumulation of either [14C]sucrose or 125I-labelled poly(vinylpyrrolidone), but at higher concentrations inhibited the uptake of both substrates. Some batches of colloidal [198Au]gold had a significantly higher Endocytic Index (up to 5 microliter/h per mg of protein). The Endocytic Index of such a batch decreased with increasing substrate concentration, but colloidal gold did not decrease the Endocytic Index of 125I-labelled poly(vinylpyrrolidone). It is concluded that the three substrates enter the yolk sac by pinocytosis in the liquid phase. Those batches of colloidal [198Au]gold with higher Endocytic Indices are considered to enter also by adsorption on membrane binding-sites.

Animals↗
PubMed1977

The effect of chemical treatments of albumin and orosomucoid on rate of clearance from the rat bloodstream and rate of pinocytic capture of rat yolk sac cultured in vitro.

Portions of a 125I-iodinated bovine serum albumin preparation were exposed to freezing, acetic acid (pH 3.5, 3.0 or 2.5), urea or formaldehyde, and the effect of these treatments on the rates of pinocytic uptake by yolk sacs from 17.5-day-pregnant rats cultured in vitro and of clearance from the rat bloodstream were studied. Uptake of albumin by the yolk sac was followed by rapid release of [125I]iodo-L-tyrosine into the culture medium. Similarly clearance of albumin in vivo was accompanied by the appearance of trichloroacetic acid-soluble radioactivity in the bloodstream. In both systems the rates of uptake of modified albumin preparations formed a series: formaldehyde or urea greater than acetic acid greater than freezing. The increased rates of uptake of modified albumin preparations could not be ascribed to the formation of aggregates nor, in the yolk-sac system, to an increase in the rate of pinosome formation. It is concluded that the various treatments to which the albumin was subjected increase to varying degrees the affinity of the albumin molecule for binding sites on that region of the plasma membrane from which pinocytic vesicles are formed. Some comparable experiments with native and desialylated human orosomucoid indicate that the rat yolk-sac epithelial cells do not possess the recognition system for uptake of asialoglycoproteins that exists on the surface of hepatic parenchymal cells.

Acetates↗