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Biomedical subjects

M V Williams

Publications and source records attributed to M V Williams.

At least 127 records · Page 7Linked to original sources
PubMed1984

Demonstration of a herpes simplex virus type 2-induced deoxyuridine triphosphate nucleotidohydrolase in infected KB cells and in biochemically transformed HeLa cells.

The deoxyuridine triphosphate nucleotidohydrolase (dUTPase) activity which is induced in KB cells infected with herpes simplex virus type 2 (HSV-2) and expressed in biochemically transformed HeLa cells was separated from the host dUTPase activity using either gel filtration or chromatofocusing chromatography. The HSV-2-induced dUTPase differed from the host dUTPase activity in its molecular weight (53000 versus 46000) and isoelectric point (pI 5 X 9 versus 6 X 4). However, it was similar to the host enzyme in that only dUTP served as a substrate for the enzyme.

Cell Transformation, Viral↗
PubMed1984

Properties of an alkaline phosphatase from Sinclair swine melanoma.

In Sinclair swine, there is an increase in alkaline phosphatase activity in spontaneously arising melanoma tumors when compared to normal skin. While alkaline phosphatase activity could be detected in melanomas from animals 1 day old, the maximum levels of alkaline phosphatase activity occurred in tumors from animals greater than 30 days old. The alkaline phosphatase was purified from cutaneous melanomas using chloroform precipitation, Phenyl-Sepharose chromatography, and concanavalin A Sepharose chromatography approximately 146-fold, with an overall recovery of 15%. The purified enzyme exhibited optimal activity over the pH range of 8.9-10.6. The apparent Km of the enzyme for p-nitrophenyl phosphate was 0.15 mM. The enzyme exhibited a relative mobility of 0.04 in nondenaturing polyacrylamide gels. The molecular weight of the enzyme was estimated by gel filtration chromatography to be 122,000 and it was composed of two identical subunits each having a molecular weight of 67,000. The enzyme was thermolabile at 56 degrees C (T50, 18 min) and its activity was inhibited by L-homoarginine, levamisole, and vanadate, but not by L-phenylalanine or L-phenylalanylglycylglycine. These characteristics distinguished the enzyme from the intestinal isoenzyme that is found in normal swine skin but were similar to those exhibited by the porcine placental isoenzyme of alkaline phosphatase. These results suggest that the development of malignant melanoma in Sinclair swine is accompanied by the expression of a placental-like alkaline phosphatase activity.

Alkaline Phosphatase↗
PubMed1984

Purification and characterization of a dUTPase from Acholeplasma laidlawii B-PG9.

dUTP was purified 120-fold from extracts of Acholeplasma laidlawii B-PG9 by Blue-Sepharose, Phenyl-Sepharose, hydroxyapatite, and DEAE-Sephacel chromatography techniques. The only substrate for the enzyme was dUTP with an apparent Km of 4.5 microM. The only reaction products were dUMP and PPi. The dUTPase did not exhibit any specific divalent cation requirement, but it was inhibited by EDTA. The enzyme was not inhibited by Pi or p-hydroxymercuribenzoate. The molecular weight of the enzyme was estimated by gel filtration chromatography to be 48,000, and its isoelectric point was 5.3. The enzyme was thermostable at 55 degrees C for 1 h. A. laidlawii dUTPase was distinguishable from KB (human epidermoid carcinoma) dUTPase by differences in electrophoretic migration, isoelectric point, and thermostability. The enzyme is important in preventing dUTP from being incorporated into DNA and may have a significant role in both the synthesis of thymidine- and PPi-dependent phosphorylations.

Acholeplasma↗
PubMed1984

Purification and properties of a nucleoside triphosphatase from Sinclair swine.

A nonspecific nucleoside triphosphatase was partially purified from skin and cutaneous melanoma tumors from Sinclair swine using chloroform precipitation, hydrophobic, ion-exchange and affinity chromatography techniques. The enzyme was not stimulated by Na+, K+ or Mg2+ but it was inhibited by EDTA. The enzyme was not inhibited by quercetin, proflavin, azide or ovabain. The enzyme exhibited optimal activity over a pH range of 8-9 and the activation energy was 10.4 and 9.8 kcal/mol for dUTP and ATP, respectively. The apparent Km of the enzyme for dUTP and dTTP was approximately 20 mumol/l while the apparent Km for dATP, ATP, dCTP, CTP and UTP was in the range of 65-80 mumol/l.

Animals↗
PubMed1984

Radiation-induced renal damage: the effects of hyperfractionation.

The response of mouse kidneys to multifraction irradiation was assessed using three nondestructive functional end points. A series of schedules was investigated giving 1, 2, 4, 8, 16, 32, or 64 equal X-ray doses, using doses per fraction in the range of 0.9 to 16 Gy. The overall treatment time was kept constant at 3 weeks. Kidney function was assessed from 19 to 48 weeks after irradiation by measuring changes in isotope clearance, urine output, and hematocrit. The degree of anemia (assessed from the hematocrit measurements) is a newly developed assay which is an early indicator of the extent of renal damage after irradiation. All three assays yielded steep dose-effect curves from which the repair capacity of kidney could be estimated by comparing the isoeffective doses in different schedules. There was a marked influence of fractionation, with increasing dose being required to achieve the same level of damage for increasing fraction number, even between 32 and 64 fractions. The data are well fitted by a linear quadratic dose-response equation, and analysis of the data in this way yields low values (approximately 3.0 Gy) for the ratio alpha/beta. This would suggest that hyperfractionation , using extremely small X-ray doses per fraction, would spare kidneys relative to tumors and acutely responding tissues.

Animals↗
PubMed1984

Increased collagen and fluid content of mouse kidneys at 9 months after single or fractionated X irradiation.

Mouse kidneys have been analyzed at sacrifice, 9 months after single-dose and fractionated irradiation, using wet and dry weight, a biochemical determination of hydroxyproline, and quantitation of dilated renal tubules in histological preparations. Dose-response curves have been constructed to determine the sensitivity and precision of the assays and to study the influence of dose fractionation on a variety of radiation responses of the kidney. There was a marked loss of kidney weight, measured either wet or dry, with maximum changes from control values by factors of 3 and 5, respectively. The wet:dry weight ratio increased with X-ray dose, indicating that relative fluid content was increased even 9 months after irradiation. This could be partly attributed to dilated renal tubules. Total collagen content per kidney, determined by a hydroxyproline assay, showed a less marked dose dependence, with a maximum increase of a factor of 1.4. However, hydroxyproline per dry weight increased by a factor of 7, and this ratio proved to be the most sensitive and precise measure of radiation damage. The "fibrosis" that is detected in histological sections appears to be more a relative than an absolute alteration in connective tissue. The loss of parenchymal cell mass, particularly in the proximal tubules, is the predominant factor; the increase in the absolute amount of collagen per kidney contributes to a lesser degree. The influence of radiation dose fractionation was analyzed using a linear-quadratic response model. The alpha/beta ratios were between 0.9 and 2.9 Gy.

Animals↗
PubMed1983

Modification of the radiation response of the mouse kidney by misonidazole and WR-2721.

The radiation response of the mouse kidney has been assayed after a range of X ray doses given with or without the nitroimidazole misonidazole or the aminothiol WR-2721. Sensitization and protection of the kidney were investigated by comparing the X ray dose needed to achieve a particular level of injury in the presence or absence of the drug. Two functional assays and kidney weight at sacrifice were used to obtain dose response curves. Urine output and 51Chromium EDTA excretion were used as functional assays at 25 and 49 weeks after irradiation. They demonstrated no radio-sensitization by misonidazole with 1, 2 or 5 fractions of X rays. Significant radioprotection was seen when 400 mg kg 1 WR-2721 was given before single X ray doses (PF = 1.34). Similar radioprotection was observed when renal weight at 1 year after irradiation was used as the third assay of damage. These results confirm that the kidney responds as a well-oxygenated normal tissue with only a small protection being afforded against radiation injury by WR-2721.

Amifostine↗
PubMed1983

Sequential functional testing of radiation-induced renal damage in the mouse.

Two nondestructive assays of functional impairment were developed to measure renal damage in mice after local irradiation of both kidneys with 240-kV X rays. Daily urine output after irradiation was measured indirectly by determining urination frequency. A dose-related response began 17 weeks after treatment and then progressed; dose-response curves with a threshold of 12 Gy were established by 22 weeks. The time of onset of damage was dose related and there was some recovery of kidney function between 25 and 38 weeks. The rate of excretion of 51Cr-EDTA was measured as an estimate of glomerular filtration either by sequential external counting over 20 min or from the activity remaining in a single blood sample at 60 min. Both methods gave dose-response curves, but the results from the blood sample were more precise. These assays are suitable for sequential testing of individual mice and have been used to establish a dose-related latent period of approximately 17 weeks after bilateral renal irradiation.

Animals↗
PubMed1982

In vivo assessment of basic 2-nitroimidazole radiosensitizers.

The radiosensitizing efficiencies of 4 structural analogues of misonidazole (MISO) have been compared with that of the parent compound. Three of these were charged basic compounds, previously shown in vitro to be 10 times more efficient. Enhancement ratios were measured from pairs of tumour growth-delay curves for the mouse fibrosarcoma SA Fab. Two routes of administration and ranges of drug dose and intervals between injection and irradiation were tested. Drug concentrations in blood, brain and tumor were measured using high-performance liquid chromatography. The peak concentration in tumours coincided with the peak in radiosensitization: 20 min after i.v. injection and 40 min after i.p. injection. The concentration in tumours was similar for either route. Comparison of radiosensitizing efficiency on the basic of equal administered dose showed no difference between the 5 compounds, but after equimolar doses the charged compounds achieved lower tumour concentrations. Comparison of sensitizing efficiency on the basis of tumour concentration showed that they were 3 times more potent than MISO, as predicted from their higher electron-affinity. The resultant improvement in radiosensitization at low, clinically relevant, concentrations is so slight that any therapeutic benefit would depend on reduced drug toxicity in man.

Animals↗
PubMed1982

Transport mechanisms of 6-diazo-5-oxo-L-norleucine in Escherichia coli K-12.

The diazo antibiotic 6 diazo-5-oxo-L-norleucine is transported into Escherichia coli using the general aromatic amino acid transport system and a specific phenylalanine transport system. Resistance to this antibiotic is the result of a decreased rate of transport of the antibiotic and also the result of a more rapid rate of efflux of the antibiotic from the cell.

Amino Acids↗
PubMed1980

Changes in the size of pelvic lymph nodes in patients being followed after radiotherapy for Hodgkin's disease.

Serial abdominal radiographs of 10 patients who had shown fluctuation in the size of opacified pelvic lymph nodes were reviewed. All had previously been treated for Hodgkin's disease by irradiation alone. Three of the patients studies were finally diagnosed as having recurrent Hodgkin's disease, but the other seven were diagnosed as having reactive change and have remained well without evidence of relapse in the pelvis or abdomen after four years follow-up; one of these patients received quadruple chemotherapy for recurrent disease at the presenting site in the neck. The differential diagnosis of enlarging pelvic lymph nodes in irradiated Hodgkin's patients may be difficult and recurrent lymphoma should not be assumed. Radiologically, reactive change is favoured by the simultaneous enlargement of several groups of nodes, whereas recurrence is favoured by the selective increase in size of solitary or neighbouring lymph nodes. In case of doubt, cytological or histological confirmation of relapse should be sought.

Diagnosis, Differential↗
PubMed1980

Azaserine resistance in Escherichia coli: chromosomal location of multiple genes.

Resistance to azaserine in Escherichia coli is the result of mutations in at least three different loci. All spontaneously arising azaserine-resistant mutants harbor a lesion in the aroP gene. However, a lesion in this gene is not solely responsible for resistance. All spontaneously arising intermediate-level azaserine-resistant mutants also harbor a lesion in a gene designated azaA, which lies near min 43 on the chromosome. High-level resistant mutants harbor lesions in the aroP and azaA genes and in a third gene designated azaB, which lies near min 69 on the chromosome. Transport studies demonstrate that mutants harboring lesions in the azaA gene are not defective in the transport of the aromatic amino acids, but that mutants which harbor lesions in the azaB gene are defective in phenylalanine transport but not in tyrosine or tryptophan transport.

Amino Acids↗
PubMed1980

Glycyl-L-histidyl-L-lysine, a growth promoting factor for human cells.

The growth promoting activity of a synthesis tripeptide, glycyl-L-histidyl-L-lysine (GHL) as a possible serum substitute was determined using human KB cells. GHL was found to stimulate the growth of human KB, and HeLa cells, but not WI-38 cells when employed in serum limited medium containing bovine serum albumin (BSA). The rate of growth of cells in this medium was similar to that of cells grown in medium containing 5% serum. While BSA did enhance slightly the growth of cells, its major function appeared to be in maintaining cellular viability. The growth promoting activity was specific for GHL; other synthetic peptides which were similar in composition had no activity, but they did interfere with the growth promoting activity of GHL. These observations suggest that by modifying GHL, analogues could be developed which might regulate cell growth and be useful in cancer chemotherapy.

Cell Division↗