Search PubMed⌕ Search

Biomedical subjects

F Ashall

Publications and source records attributed to F Ashall.

35 records · Page 2Linked to original sources
PubMed1990

Electrophoretic detection of Trypanosoma cruzi peptidases.

Peptidases of Trypanosoma cruzi epimastigotes were examined by polyacrylamide gel electrophoresis in gels containing gelatin as peptidase substrate. Mini-gels were far superior to large gels in their sensitivity of peptidase detection. Patterns of peptidases were similar between different strains of T. cruzi, although some inter-strain heterogeneity was found. In strain Y, at least five peptidases were detected: four of these enzymes were shown to be cysteine-type peptidases with acidic pH optima. The other peptidase was a 60-kDa membrane-associated peptidase that was sensitive to o-phenanthroline; it was tentatively characterised as a metallopeptidase, and was optimally active at alkaline pH. This membrane-associated peptidase was conserved between strains of T. cruzi.

Animals↗
PubMed1989

On the DNA content of Trypanosoma cruzi.

The DNA contents of three different Trypanosoma cruzi strains were compared by direct microfluorometry. The maximal difference found was 40% of the lowest value. Two of the cloned strains, reported in an earlier study to differ by 48% in their total DNA content, showed a difference of 33%. The kinetoplast of the Y strain made up about one third of its total genome. The absolute DNA content of T. cruzi was estimated at 125 to 200 fg.

Animals↗
PubMed1988

Specificity of the cAMP-induced gene exposure reaction in CHO cells.

Previous studies demonstrated that in the transformed CHO (Chinese hamster ovary) cell a substantial part of the genome behaves as though its genes are sequestered from effective contact with soluble constituents of the intracellular fluid. The reverse transformation reaction, initiated by cAMP derivatives, causes this cell to regain the morphology, growth regulation, surface characteristics, and sensitivity of its DNA to digestion by DNase I that are characteristic of normal fibroblasts. In this paper we show that this action of cAMP is gene specific. In examination of 47 different genetic loci, some, like ribosomal RNA genes, are found to be sensitive to DNase I hydrolysis both in the absence and in the presence of cAMP; some are resistant under both conditions; and some are resistant in the untreated cell but become sensitive after cAMP treatment. Unlike other gene exposure reactions, which are irreversible and connected with differentiation phenomena, that produced by cAMP is readily reversed when the reagent is removed. A sequence of events is observed after cAMP treatment, the first of which is reorganization of the cytoskeleton. Afterwards, metabolic changes occur over periods as long as 72 hr. The cAMP-induced cytoskeleton-mediated gene exposure reaction appears to be an important genetic regulatory mechanism in mammalian cells and to have special implications for cancer.

Animals↗
PubMed1988

Radiolabeled total parasite DNA probe specifically detects Trypanosoma cruzi in mammalian blood.

A DNA-DNA hybridization procedure is described in which radiolabeled total parasite DNA is used to detect Trypanosoma cruzi spotted directly onto nylon membrane. Under conditions that favor hybridization of repetitive DNA sequences, the radiolabeled total DNA was able to detect as few as five parasites spotted onto nylon membrane. Trypanosomes were detectable in blood from mice with T. cruzi parasitemias spotted directly onto membranes. All 10 strains of T. cruzi examined, which came from different areas of the United States and South America, were readily detected with a total DNA probe from any 1 strain of the parasite. No signals were detected with up to 20,000 Trypanosoma rangeli, T. brucei, Crithidia fasciculata, or Leishmania parasites or with normal mouse blood or mammalian DNA. The hybridization method is sensitive, specific, rapid, and inexpensive and is potentially applicable to the detection of other parasites.

Animals↗
PubMed1984

Cytoskeletal involvement in cAMP-induced sensitization of chromatin to nuclease digestion in transformed Chinese hamster ovary K1 cells.

The cAMP-induced reverse transformation of CHO-K1 cells, which restores fibroblastic morphology, normal nuclear structure, specific membrane structures and biochemical activities, and cell growth regulation, also restores the sensitivity of nuclear chromatin digestion by DNase I to that resembling the normal fibroblast. All of these aspects of the reverse-transformation reaction require integrity of the cytoskeleton. The nuclease-sensitivity effect is achieved only when the entire cell rather than the isolated nucleus is incubated with cAMP derivatives, indicating linkage between the cytoskeleton and nuclear components. Evidence is presented to show that the DNA sensitization to digestion involves interaction between DNA and other chromatin components and affects different regions of the genome in specific ways. Normal fibroblasts display greater endogenous nuclease activity than the transformed cell. The data are interpreted in terms of a genetic regulatory system extending from the membrane to the nucleus and utilizing the cAMP-induced cytoskeleton.

Animals↗
PubMed1982

A new marker for human cancer cells. 1 The Ca antigen and the Ca1 antibody.

In a search for antibodies that might distinguish between malignant and non-malignant cells a panel of matched pairs of hybrid cells produced by fusion of diploid fibroblasts with malignant cells originating from a cervical carcinoma was used as a screen. Each pair consisted of a hybrid in which malignancy was suppressed and a malignant segregant derived from this hybrid. A monoclonal antibody, designated Ca1, was found that discriminated absolutely between the hybrids in which malignancy was suppressed and the malignant segregants. This antibody detected an antigen present in the cell membranes of a wide variety of malignant human cells lines but not of diploid human cell strains. The antigen was found in very low concentrations, if at all, in homogenates of normal adult or fetal tissues. It could be immunoprecipitated by the Ca1 antibody from extracts of malignant cells but not from extracts of non-malignant cells. After reduction, the immunoprecipitated antigen separated in sodium dodecyl sulphate acrylamide gels as two bands with proximate molecular masses of 390 000 and 350 000. These two components had a properties of glycoproteins with a high carbohydrate content; both bound the Ca1 antibody. The antigenic determinant resisted boiling at 100 degrees C and extraction by range of organic solvents. The binding of the Ca1 antibody to the antigen was substantially reduced by treatment of the antigen with neuraminidase, and the antigenic determinant was largely destroyed by certain endoglycosidases and by extensive proteolysis. Pending its further characterisation, this antigen had been called the Ca antigen.

Antibodies, Monoclonal↗
PubMed1982

A new marker for human cancer cells, 2 immunohistochemical detection of the Ca antigen in human tissues with the Ca1 antibody.

The Ca1 antibody has been used in an immunohistochemical procedure to detect the Ca antigen in sections of tissues routinely embedded in paraffin wax. A representative sample of benign and malignant tumours from all the systems of the human body has been examined. The majority of malignant tumors express the Ca antigen. The exceptions are: prostatic carcinomas, testicular teratocarcinomas and seminomas, some sarcomas, some lymphomas, malignant brain tumours, neuroblastomas, and melanomas. The antigen is least readily detected in epithelial malignancies of the alimentary system, particularly of the colon. The Ca1 antibody does not react with any benign tumour. The only normal tissues that react specificity with this antibody are the epithelium of the fallopian tube and the transitional epithelium of the urinary tract. The Ca1 antibody also readily distinguishes malignant cells in smears of malignant effusions. These findings indicate that the Ca1 antibody may be useful in the diagnosis of malignancy in routine clinical practice where the morphological interpretation of the biopsy or cytological smear is in doubt.

Antibodies, Monoclonal↗
PubMedDate not supplied

Human urine stimulates growth of Leishmania in vitro.

Enhancement of trypanosomatid metacyclogenesis by insect urine components led us to test the effect of human urine as a culture additive. The addition of 1-5% urine to Schneider's Drosophila medium containing 10% foetal calf serum enhanced the growth of 11 Leishmania strains representing 8 different taxonomic groups. Cell division was stimulated in cultures with non-dividing organisms. Peak cell density was increased, as was the efficiency with which L. donovani could be isolated from infected hamsters. Preliminary work suggested that the modified medium would be useful for field isolation of L. donovani and L. braziliensis. The active nutrients or growth factors are not known.

Animals↗