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M Vanderlaan

Publications and source records attributed to M Vanderlaan.

49 records · Page 3Linked to original sources
PubMed1982

Ultrastructure of the rat urothelium in en face section.

We examined en face the fine structure of rat urothelium and describe here some unique subcellular features distinguishable in the various tissue layers by this technique. The most striking finding is that large, compact fibrous bundles lie in the cytoplasm at both sides of the superficial cell tight junction for the entire length around it apical surface. Basal to these bundles, an intricate series of desmosomes alternates with other specialized elaborations of the plasma membrane. These desmosomes anchor the extensive filamentous network that interconnects the nucleus, flattened superficial vesicles, and plaques of the lumenal membrane. En face sections of the urothelium show that large numbers of vesicles form inthe intermediate cell Golgi complexes and are then stored just under the apical membrane. These intermediate vesicles are smaller, more round, and less variable in size than superficial vesicles. After intermediate cells reach the superficial layer, the vesicles mature, undergoing modifications that apparently increase their tendency to fuse.

Animals↗
PubMed1981

gamma-Glutamyltranspeptidase: a tumour cell marker with a pharmacological function.

The distribution of gamma-glutamyltranspeptidase activity (gamma GT) in adult, foetal, and neoplastic tissues in rats and humans is reviewed. The normal adult kidney, pancreas, and jejunum are high in this activity. Around the time of birth, gamma GT activity increases transiently in the liver, colon, and skin; many tumours of these organs often have elevated activity as well. Although this activity in tumour tissue may reflect a general expression of onco-foetal genes, subpopulations of cells having abnormally high gamma GT may have a selective growth advantage over their normal counterparts. We explore this latter possibility by considering the pharmacological function this enzyme may play. gamma GT may facilitate the detoxification of electrophiles by glutathione conjugation, so that cells can survive in an otherwise toxic environment. This growth advantage may be particularly important to the development of liver tumours in rats during chemical carcinogenesis.

Aging↗
PubMed1980

Alkaline phosphatase and an acid arylamidase as marker enzymes for normal and transformed WI-38 cells.

A survey of eleven enzyme activity levels in normal and SV40 transformed (VA-13) WI-38 cells revealed that the transformed cell enzymes differed by a quantitative and qualitative change of alkaline phosphatase and a quantitative loss of an arylamidase. Alkaline phosphatase activity was found to be elevated in the transformed cells at confluency but not in log phase cultures. This elevated activity was heat stable, L-homoarginine resistant and L-phenylalanine sensitive and is probably the term placental isoenzyme. In nontransformed WI-38 cells, the alkaline phosphatase was heat labile, L-homoarginine sensitive and L-phenylalanine resistant and so is probably the liver isoenzyme. While the arylamidase activity from both normal and transformed WI-38 cells had identical pH optima and Km values, the activity was approximately 20 times higher in confluent WI-38 cells than in confluent VA-13 cells. Cytochemical staining techniques for both activities are described that permit identification of fluorescent product within the cells, analysis of activity levels, and separation of cells with high and low activities. Mixtures of WI-38 cells and VA-13 cells separated by flow cytometry on the basis of arylamidase activity were subsequently evaluated for alkaline phosphatase isoenzyme and found to have been simultaneously separated into heat labile and heat stable samples.

Alkaline Phosphatase↗
PubMed1979

Flow microfluorometric identification of liver cells with elevated gamma-glutamyltranspeptidase activity after carcinogen exposure.

We have developed a fluorometric cytochemical assay for gamma-glutamyltranspeptidase (gamma-GT) using the substrate gamma-glutamyl-4-methoxy-2-naphthylamide in which the released methoxynaphthylamine was coupled with 5-nitrosalicylaldehyde to form a yellow fluorescent crystalline product within the cells. Single cell suspensions were obtained by collagenase perfusion of livers from rats that had either received a two-thirds partial hepatectomy followed 24 hr later by a single injection of diethylnitrosamine (DEN) or received a partial hepatectomy alone. Cultured HTC cells were used as a source of gamma-GT+ cells. Fluorescence (gamma-GT activity) was low in most of the cells from both DEN-exposed and control rats, but high in HTC cells. The livers of both DEN-exposed and control rats had a subpopulation of cells that were gamma-GT+; this population could be quantitated and sorted by flow cytometry. Five weeks post injection the number of GT+ cells from the rats exposed to DEN was more than 20 times that from the control rats. Increased gamma-GT activity may be a useful cytochemical marker for preneoplastic liver cells.

Animals↗
PubMed1979

A fluorescent assay of proteinases in cultured mammalian cells.

We have demonstrated proteinase activity in unfixed cells grown on tissue culture plates with a technique using 5-nitrosalicylaldehyde and peptide derivatives of 4-methoxy-2-naphthylamine. The 4-methoxy-2-naphthylamine liberated by proteinase activity reacts with 5-nitrosalicylaldehyde to form a fluorescent product. The substrates CBZ-alanyl-arginyl-arginyl-4-methoxy-2-naphthylamine and lysyl-alanyl-4-methoxy-2-naphthylamine, were used for the direct visual detection of two arylamidase activities in BALB/c 3T3 and C3H 10T 1/2 cells. With low magnification these enzyme activities can be detected in single clones; with higher magnification the fluorescent product can be seen within the cytoplasm of single cells.

Animals↗
PubMed1977

Split-dose recovery for radiation-induced tumours in rat skin.

Tumour-related recovery in rat skin was estimated from the dependence of tumour yield on time between split doses of electron radiation. Tumour yield versus dose was established at nine dose points, and at three points the dose was split into two equal fractions spaced 0-25, 3-2 or 6-3 hours apart. After irradiation the rats were observed periodically for at least 64 weeks, and at death the tumours were examined histologically. The dependence of yield on dose for single doses was consistent with a quadratic function up to a peak yield at about 1600 rad. The effect of split doses on tumour yield depended on the position on the dose--response curve. At the lowest split dose, the yield declined with a half-time of about 1-8 hours. At the intermediate split dose, an initial increase was followed by a decline with a half-time of about 3-9 hours. At the highest split dose, the tumour yield increased with time between exposures. Fractionation-induced increases in tumour yield were explained as a sparing effect on cell lethality, whereas tumour-related recovery per se was indicated at the lower two doses.

Animals↗
PubMed1977

Effect of carcinogens on chicken atherosclerosis.

Weekly i.m. injections of the polycyclic hydrocarbon carcinogens, 7,12-dimethylbenz(a,h)anthracene (DMBA; 25 mg/kg/injection) and benzo(a)pyrene (50 mg/kg/injection) were given for a period of up to 22 weeks to chickens (SC strain) beginning at age 4 weeks. Atherosclerotic lesions of the abdominal aorta occurred more frequently and were larger in the DMBA- and benzo(a)pyrene-treated birds than in controls. These lesions were proliferative in character as indicated by a higher [3H]thymidine autoradiographic labeling index compared to the underlying medial cells of the aorta. Measurements of serum cholesterol in DMBA-treated birds showed no differences from controls. Although both carcinogens accelerated the development of atherosclerotic plaques, DMBA was more potent than benzo(a)pyrene.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1976

Regression kinetics of mouse skin papillomas.

The persistence and proliferation rate of mouse skin papillomas were studied in HA/ICR mice initiated with 7,12-dimethylbenz(a)anthracene and promoted three times weekly with phorbol myristate acetate. When the promoter treatments were stopped, rapid (half-time, 24 days) and slow (half-time, greater than 140 days) components of papilloma regression were observed. When the promoter dose was increased, the major effect was an increase among the rapidly regressing papillomas. Increases in the epidermal pulse-labeling index and the number of dermal inflammatory cells produced by phorbol myristate acetate in normal skin were reversible when the phorbol myristate acetate was stopped, but high pulse-labeling index values in papillomas were not reversible. Antithymocyte serum had no effect on regression, although ethylphenylpropriolate, a nonpromoting irritant, slowed the regression sufficiently to increase the half-time from 24 to 57 days. The action of the promoter in overcoming the regression tendency of the papillomas may explain certain features of the role of nonspecific irritation and the importance of promotion frequency in determining tumor yield.

9,10-Dimethyl-1,2-benzanthracene↗
PubMedDate not supplied

A two-dimensional protein map of Chinese hamster ovary cells.

Chinese hamster ovary (CHO) cells are used extensively for the expression of biopharmaceutical protein products. As part of our effort to better understand CHO cell physiology and protein expression changes caused by modified culture conditions, we have begun to map CHO cell polypeptides. A parental cell line reference map was established using two-dimensional gel electrophoresis with immobilized pH gradients (pH 3-10) in the first dimension and a linear acrylamide gradient (9-18%T) in the second dimension. The map is composed of over 1000 silver-stained protein spots. Protein identification is proceeding using a combination of immunostaining, NH2-terminal sequencing, and mass spectrometric analyses. Among the proteins so far identified are glucose-regulated protein 78 (GRP78), protein disulfide isomerase (PDI), galectin-1, and several heat-shock proteins. The goal is to generate a database which emphasizes those proteins most relevant to the use of CHO cells as a host for recombinant protein expression.

Animals↗
PubMedDate not supplied

Characterization of filter extractables by proton NMR spectroscopy: studies on intact filters with process buffers.

Studies were conducted to characterize potential extractables from sterilizing grade filters. The focus of this report is the 0.22 micron Durapore (hydrophilic modified PVDF) filter which is used throughout our recovery processes. The objectives of this study are (1) to identify potential filter extractables from the hydrophilic PVDF filters; (2) to show that NMR spectroscopy may be used to detect filter extractables in the presence of product and excipients; and (3) to establish levels of filter extractables obtained by extraction with a variety of buffers. The data show that the primary source of filter extractables is the hydrophilic modification of the PVDF membrane surface. Extractables from the modified hydrophilic PVDF filter include propylene glycol (PG) and soluble oligomers of the hydroxypropyl acrylate and cross-linker. Propylene glycol, arising from the hydrolysis of the hydroxypropyl acrylate, appears to be the primary extractable in buffers above pH 11. Since the 1H-NMR method can easily detect the methyl proton signals of PG, an NMR assay was developed to detect PG in the presence of buffer excipients and final product. Propylene glycol can be used as a marker for the extractables from Durapore hydrophilic PVDF filters. Although numerous buffers were used to generate extractables from the PVDF filter, significant extractables (PG and soluble oligomers) were found only in high pH extraction buffers. As a result of this finding, only a limited number of new buffers or new PVDF filters will require testing for future validation studies. Process validation studies have shown that neither PG nor soluble oligomers are at levels that impact the quality or safety of the product.

Buffers↗