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Biomedical subjects

J Daniel

Publications and source records attributed to J Daniel.

At least 55 records · Page 3Linked to original sources
PubMed1989

Use of a laser diffraction particle sizer for the measurement of mean diameter of multicellular tumor spheroids.

Increasing use is being made of tumor cell lines cultured as cell aggregates (generally referred to as multicellular spheroids) in in vitro radiosensitivity and/or chemosensitivity tests. Conventional procedures for the determination of mean spheroid diameters for the construction of growth delay curves employ a microscope-image analyzer. However, this approach can prove excessively time consuming when large numbers of samples have to be measured. We have, therefore, been exploring the use of a Laser Diffraction Particle Sizer, the Malvern 2600 long bench model, for the measurement of mean spheroid diameter and size distribution. We report here a direct comparison between measurements carried out by the instrument and under the microscope. Also a comparison of growth curves for six cell lines constructed from measurements by the microscope and by the instrument. A number of factors that might affect the accuracy of spheroid diameter measurement by the instrument have been investigated: The effect of stirring to maintain the spheroids in suspension during measurement. Sampling error due to removal of a series of spheroid samples from culture flasks for measurement. Optimum numbers of scans to be carried out by the instrument to reach a constant value for mean diameter, and minimum SE of the mean.

Animals↗
PubMed1989

Fecapentaene concentration and mutagenicity in 718 North American stool samples.

The fecapentaenes (FP) are the predominant fecal mutagens identified to date, but they have not been shown to be carcinogenic. Epidemiologists looking for other fecal mutagens that may be related to colorectal cancer must disentangle from their investigations the pervasive mutagenic effect of the fecapentaenes. As a first step to studying the epidemiology of fecal mutagenicity independent of fecapentaenes, we compared FP measurements and Salmonella mutagenicity assay results for 718 acetone-extracted stool samples collected from a variety of subjects in the Washington DC metropolitan areas. In this large group, 50% of mutagenic samples contained elevated fecapentaenes. Specifically, three-quarters of the samples mutagenic in TA100 contained high FP levels. In contrast, mutagenicity in TA98 was not generally explainable by fecapentaenes, suggesting that non-fecapentaene TA98 mutagenicity should be one focus of future efforts to uncover colorectal carcinogens of etiologic importance.

Feces↗
PubMed1989

Oral temperature and performance in 8 h and 12 h shifts.

Operators in an 8 h (n = 18) and a 12 h (n = 16) h shift went through an experiment in which oral temperature, disjunctive reaction time (DRT), tapping, logical reasoning, memory and search tasks were measured at 4 h intervals. A performance curve in DRT and in tapping over a 24 h cycle tended to follow the pattern of the body temperature curve. The curves of mental curves were flattened. The values measured in the two groups of Ss revealed differences of statistical significance.

Body Temperature↗
PubMed1988

Radiological score in the assessment of clubfoot.

The clinical appearance and the radiographs of 31 patients with 47 clubfeet taken before the start of treatment have been studied. In spite of making a careful clinical evaluation, 14 feet (29.8%) remained "borderline" and could not be definitely classified into the easy or resistant groups. The radiological score of the foot, which is an objective representation of the severity of the deformities at all important levels and in all planes, has been found to be an accurate and sensitive index which enables such a distinction to be made.

Ankle Joint↗
PubMed1987

Effects of hyperthermia, irradiation, and cytotoxic drugs on fluorescein isothiocyanate staining intensity for flow cytofluorometry.

Measurement of fluorescein isothiocyanate (FITC) staining intensity of cultured lymphoblastoid cells following hyperthermia showed large increases without concomitant increases in nuclear protein. Similar measurements of cells following incubation with cytotoxic drugs showed fluorescent intensity increases that exceeded the increases in nuclear protein that were due to the cell cycle blocking action of the drug. The reverse, however, was true for cells following irradiation. In contrast, FITC staining intensity and nuclear protein measurements of cells proceeding through the cell cycle after removal of the cycle blocking agent showed nearly parallel changes, although there were reproducible minor differences, especially following blocking with hydroxyurea. These results suggest that FITC staining intensity is a function not only of nuclear protein content but also of stain access to the reaction sites of the protein constituents of the chromatin. Thus, it is possible that FITC staining may be used as a probe of changes in chromatin structure following experimental manipulation of cells in vitro or treatment of tumors in vivo.

Antineoplastic Agents↗
PubMed1987

The activation of adenylate cyclase by guanyl nucleotides in Saccharomyces cerevisiae is controlled by the CDC25 start gene product.

In the thermosensitive cdc25 start mutant of Saccharomyces cerevisiae, the regulation of adenylate cyclase by guanyl nucleotides was rapidly nullified when the enzyme was prepared from nonsynchronized cells shifted to the restrictive temperature. In agreement with previous in vivo complementation studies, this biochemical defect was fully suppressed by the expression of either the whole cloned CDC25 gene or its C-terminal portion. Moreover, membranes prepared from cdc25(Ts) cells grown at the permissive temperature evinced an altered regulation of adenylate cyclase by guanyl nucleotides. These results indicate that the CDC25 protein, together with RAS, is involved in the regulation of adenylate cyclase by guanyl nucleotides and raise the possibility that adenylate cyclase might form a ternary complex with RAS and CDC25.

Adenylyl Cyclases↗
PubMed1987

Direct evidence for the interaction of the nucleotide affinity analog 5'-p-fluorosulfonylbenzoyl adenosine with a platelet ADP receptor.

Previous reports have indicated that the nucleotide affinity analog 5'-p-fluorosulfonylbenzoyl adenosine (FSBA) at concentrations between 40 and 100 mumol/L and at times greater than 20 minutes covalently modifies a single protein component on the external platelet membrane surface and that adenosine diphosphate (ADP) protects against this reaction. That this protein is an ADP receptor linked to platelet activation is shown by FSBA inhibition of ADP-mediated platelet shape change, aggregation, and fibrinogen receptor exposure. In this report, further evidence for the interaction of FSBA with the ADP receptor on platelets is provided by the observation that FSBA at high concentrations (100 to 500 mumol/L) behaves as a weak agonist to produce platelet shape change within one minute as detected by spectroscopic assay and scanning electron microscopy with concomitant phosphorylation of the light chain of platelet myosin. The specificity of FSBA as an agonist is demonstrated by inhibition of FSBA-induced shape change by ATP and the covalent incorporation of SBA as well as the failure of 5'-fluorosulfonylbenozoyl guanosine (FSBG) to cause shape change. In contrast, incubation of platelets with low concentrations of [3H]-FSBA (40 mol/L) is not associated with stimulation of platelet shape change or myosin light chain phosphorylation.

Adenosine↗
PubMed1986

Clones from two different genomic regions complement the cdc25 start mutation of Saccharomyces cerevisiae.

We have cloned the CDC25 gene of Saccharomyces cerevisiae whose product is required for traversing the Go phase of the cell cycle. A preliminary physical characterization of the CDC25 gene region is presented. In addition, we show that another gene, when cloned in a high-copy number plasmid, is able to partially suppress growth thermosensitivity of a strain carrying the cdc25 mutation. We briefly discuss the possible interaction of these gene products with adenylate cyclase encoded by the CDC35 gene.

Alleles↗
PubMed1986

2-Ketoglutarate as a possible regulatory metabolite involved in cyclic AMP-dependent catabolite repression in Escherichia coli K12.

2-Ketoglutarate--unlike any other derivative of the citric acid cycle--was found to strongly repress catabolite-sensitive genes, such as the lactose operon (lac) or the tryptophanase gene (tna), when added to cells grown in glycerol. 2-ketoglutarate affects the expression of these genes by decreasing cyclic AMP synthesis. Such inhibition of cyclic AMP synthesis requires the presence of enzyme III, a component of the phosphoenol pyruvate:sugar phosphotransferase transport system (PTS). Thus, it is proposed that 2-ketoglutarate is one of the catabolite repressors postulated by Magasanik in 1961. In addition, by studying the effect of 2-ketoglutarate in various mutants, we show the existence of a cyclic AMP-independent catabolite repression mechanism whose mediator is synthesized from 2-ketoglutarate.

Cyclic AMP↗
PubMed1986

Kinetic and physical studies of cell death induced by chemotherapeutic agents or hyperthermia.

The kinetics of three physical parameters: cell density, relative cytoplasmic viscosity and DNA stability to denaturation have been measured during the period preceding cell death induced by hyperthermia, methylprednisolone and a series of cancer chemotherapeutic agents. This series of measurements employed cultured human lymphoblastoid cells as an experimental system to establish the changes that can be observed in the early stages of cell death, prior to applying such measurements to tissue biopsies from solid human tumours. Cell death, induced by hyperthermia up to 43 degrees C, methylprednisolone, vincristine, 5-fluorouracil, BCNU and melphalan, showed essentially identical and reproducible changes corresponding to those which characterize programmed cell death (apoptosis). Such changes could also be observed following hyperthermia above 43 degrees C, but reproducibility was poor and increasing damage to the cell membranes was evident. In cells treated with adriamycin or methotrexate, cell sub-populations showing an increase in cell density were not detected. Measurements of DNA stability were readily performed by flow cytofluorometry thus allowing rapid quantitation of the fraction of cells in the early stages of cell death. Modified flow cytometric instrumentation would further allow measurement of cytoplastic viscosity as an additional parameter to indicate entry into programmed cell death. This suggests that these measurements could readily be applied to cell suspensions derived from tumour tissue biopsies for a more accurate assessment of tumour growth rate, and to allow monitoring of response to therapy in sequential tumour biopsies.

Antineoplastic Agents↗
PubMed1985

A comparison of the susceptibility of three human gut tumour-derived differentiated epithelial cell lines, primary monkey kidney cells and human rhabdomyosarcoma cell line to 66-prototype strains of human enteroviruses.

The growth of prototype strains of 31 serotypes of ECHO, 3 polio, 6 Coxsackie B, 24 Coxsackie A and enterovirus serotypes 70 and 71 were tested in parallel in primary monkey kidney cells (PMK), RD cells and three gut tumour-derived differentiated epithelial cell lines (HRT-18 HT-29 in SKCO-1). All 31 serotypes of ECHO viruses grew in HT-29, 27 and SKCO-1, 5 in HRT-18, 29 in PMK and 29 in RD. There was good growth of poliovirus serotypes in all five cell types. Coxsackie B viruses grew well in all the cell lines except RD. Fifteen of the Coxsackie A viruses grew in SKCO-1, 4 in HT-29, 3 in HRT-18 and 7 in RD. Enterovirus serotypes 70 and 71 grew only in RD cells after 3 serial passages. These results showed that 2 of the gut tumour-derived cell lines, HT-29 and SKCO-1 had a markedly wider susceptibility, with comparable or wider sensitivity, for enteroviruses, than PMK and RD. While their use for field isolation from clinical samples is not yet fully established HT-29 and SKCO-1 would appear to be ideal for a variety of laboratory manipulations of the majority of enteroviruses.

Animals↗
PubMed1985

An epidemic of acute diarrhoea in rural southern India associated with echovirus type 11 infection.

An epidemic of diarrhoea with two distinct waves affected a village of 1375 people in southern India in 1983. The first wave of the epidemic, from the last week of December 1982, had a sharp peak in January 1983 and was over by March. Echovirus type 11 was isolated from patients, who also had a serum antibody response to the virus. During the second wave of the epidemic, from May to September 1983, the clinical features were different and Shigella flexneri was isolated without significant viral isolates. Infection during the first wave did not protect from the second wave. Virus isolation was in human intestinal tumour-derived differentiated epithelial cell lines; such cell lines may be useful for the isolation and identification of enteroviruses in clinical samples.

Diarrhea↗
PubMed1984

Isolation and identification of enteroviruses from faecal samples in a differentiated epithelial cell line (HRT-18) derived from human rectal carcinoma.

A human rectal carcinoma-derived differentiated epithelial cell line, HRT-18, was inoculated with faecal samples in an attempt to grow coronavirus-like particles (CVLP), which are widely prevalent in human stools in southern India. While CVLP did not grow in this cell line, a variety of enteroviruses were isolated from 48 of the 114 stool samples from healthy controls and patients with diarrhoea. The results suggest that human gastrointestinal tumour-derived differentiated epithelial cells in continuous culture may be useful for the primary isolation of enteroviruses and merit further study.

Adult↗
PubMed1984

Role of 2-ketobutyrate as an alarmone in E. coli K12: inhibition of adenylate cyclase activity mediated by the phosphoenolpyruvate: glycose phosphotransferase transport system.

2-ketobutyrate and its analogues were found to inhibit strongly and transiently the rate of beta-galactosidase synthesis in Escherichia coli K12. This effect was ascribed to a strong and transient inhibition of the adenylate cyclase activity. By using pts mutants, we showed, in agreement with our previous results (Daniel et al. 1983), that the likely target of 2-ketobutyrate and its analogues is the phosphoenolpyruvate: glycose phosphotransferase transport system (PTS). Furthermore, evidence for such a cascade effect caused by 2-ketobutyrate and its analogues allowed us to corroborate our previous proposal (Daniel et al. 1983) that 2-ketobutyrate, a precursor of isoleucine, acts as an E. coli alarmone monitoring the passage from anaerobic to aerobic growth conditions.

Adenylyl Cyclase Inhibitors↗
PubMed1984

Metabolic alterations mediated by 2-ketobutyrate in Escherichia coli K12.

We have previously proposed that 2-ketobutyrate is an alarmone in Escherichia coli. Circumstantial evidence suggested that the target of 2-ketobutyrate was the phosphoenol pyruvate: glycose phosphotransferase system (PTS). We demonstrate here that the phosphorylated metabolites of the glycolytic pathway experience a dramatic downshift upon addition of 2-ketobutyrate (or its analogues). In particular, fructose-1,6-diphosphate, glucose-6-phosphate, fructose-6-phosphate and acetyl-CoA concentrations drop by a factor of 10, 3, 4, and 5 respectively. This result is consistent with (i) an inhibition of the PTS by 2-ketobutyrate, (ii) a control of metabolism by fructose-1,6-diphosphate. Since fructose-1,6-diphosphate is an activator of phosphoenol pyruvate carboxylase and of pyruvate kinase, the concentration of their common substrate, phosphoenol pyruvate, does not decrease in parallel.

Butyrates↗
PubMed1984

Enzyme III stimulation of cyclic AMP synthesis in an Escherichia coli crp mutant.

Cyclic AMP (cAMP) synthesis in Escherichia coli is altered in cAMP receptor protein mutants and in phosphoenolpyruvate:sugar phosphotransferase transport system mutants. The stimulation of cAMP synthesis observed in cAMP receptor protein-deficient mutants is largely dependent upon enzyme III of the phosphoenolpyruvate:sugar phosphotransferase transport system. The phosphoenolpyruvate:sugar phosphotransferase transport system enzyme I is not required for elevated cAMP synthesis. These results suggest that enzyme III plays an important role in regulating adenylate cyclase activity.

Adenylyl Cyclases↗