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Biomedical subjects

J F Jackson

Publications and source records attributed to J F Jackson.

At least 55 records · Page 3Linked to original sources
PubMed1981

Control of Pyrimidine Biosynthesis in Synchronously Dividing Cells of Helianthus tuberosus.

Factors with potential for regulating pyrimidine biosynthesis in plant tissue have been explored in quiescent cells of Helianthus tuberosus induced to divide by auxin addition. Investigations confined to the first highly synchronous cell cycle of the tuber explants revealed that the relative activity of asparate carbamoyltransferase (ACTase) to ornithinecarbamoyltransferase (OCTase) (enzymes competing for carbamoyl phosphate for the pyrimidine and arginine pathways, respectively) changes from 0.5 in quiescent cells to 3.0 by the end of the first cell cycle. This was interpreted as a change in the state of cell function from accumulation of storage arginine to cell division with a concomitant demand for pyrimidine nucleotides for nucleic acid synthesis. The rise in ACTase activity began at the same time as the initiation of DNA synthesis and was dependent on continued DNA synthesis. OCTase activity declined whether or not auxin was added to the medium, whereas ACTase activity was observed to decline only in the absence of DNA synthesis.The low cellular concentration of the shared substrate, carbamoyl phosphate (2 micromolar), favored utilization of this substrate by the pyrimidine pathway over the arginine pathway because of the low K(m) (0.08 80 micromolar) for this substrate by ACTase compared to that for OCTase (9.0 millimolar). Unexpectedly, the total concentration of the feedback inhibitor for the pyrimidine pathway, UMP, was found to have more than doubled in dividing tissue at a time when pyrimidine nucleotide demand had increased. It is concluded that compartmentation decreased UMP in the vicinity of ACTase and/or that the extra UMP stabilizes newly synthesized ACTase in preparation for an even greater demand for nucleic acid synthesis in the second and subsequent cell cycles.

Journal Article↗
PubMed1980

Linkage studies in spinocerebellar ataxia (SCA).

Data are now available on 9 pedigrees in detail and 4 pedigrees as lod scores only. Linkage to HLA is significant (Z = 5.53 at recombination rates of 0.223 in males and 0.327 in females). Tight linkage is excluded. Nine pedigrees which appear to be typical olivopontocerebellar atrophy (OPCA I) have recombination rates of 0.150 in males and 0.300 in females. The remaining 4 pedigrees are clinically atypical or include discrepant data and give no evidence for linkage. The symbol SCA1 is proposed for a locus on chromosome 6 (loosely linked to HLA), at which at least one allele produces OPCA I (Menzel type). It is not yet clear whether other clinical types are determined by alleles at different loci, although this is suggested by several pedigrees, including a Danish pedigree of OPCA with dementia. Linkage evidence will be decisive in delineating the ataxias.

Adolescent↗
PubMed1980

Isolation of transforming DNA: cloning the hamster aprt gene.

We have isolated the hamster gene coding for the enzyme adenine phosphoribosyl transferase (aprt) using gene transfer and molecular cloning of transforming DNA. Mouse aprt- cells were transformed to the aprt+ phenotype with the product of ligation of Hind III-cleaved hamster genomic DNA and pBR322 DNA. In this manner, the aprt gene was linked to a marked plasmid sequence and segregated from other hamster sequences. A lambda-recombinant phage containing pBR322 DNA sequences was isolated from a library of aprt+ transformed cell DNA. The phage DNA transfers hamster aprt+ activity at a frequency expected of a pure gene. Furthermore, sequences homologous to this clone are present in all hamster aprt+ transformants examined. This experimental design should in theory permit the isolation of any gene coding for selectable or identifiable functions for which DNA-mediated gene transfer can be effected.

Adenine Phosphoribosyltransferase↗
PubMed1980

Spontaneous and X-ray induced chromosomal aberrations in selected connective tissue diseases.

Chromosome studies were performed on peripheral blood lymphocytes of 28 patients with connective tissue disease (6 with progressive systemic sclerosis, 6 with systemic lupus erythematosus, 6 with anti-nuclear antibody positive rheumatoid arthritis, 6 with anti-nuclear antibody negative rheumatoid arthritis, and 4 with mixed connective tissue disease) and on 17 controls to determine the frequency of spontaneous as well as X-ray (75 rads) induced aberrations. The mean spontaneous chromosomal aberration frequency for the 28 patients (9.1%) was significantly (P = 0.038) greater than that of controls (6.4%). When patients were categorized into specific clinically designated connective tissue disease subdivisions for comparison with the controls, only X-irradiated cells from the progressive systemic sclerosis group displayed significantly elevated levels of total chromosomal aberrations over those of the control group. The X-irradiated lymphocytes from these patients had an average of 23.6% aberrations per patient, while those of the control group showed an average of 14.9% per patient (P less than 0.05).

Adolescent↗
PubMed1979

Spleen size and chromosome analysis as prognostic factors in chronic myelogenous leukemia.

Of 72 patients with chronic myelogenous leukemia (CML), 37 were Ph1 positive, eight were negative, and 27 were not evaluated for the Ph1 chromosome. Of the 37 patients positive for Ph1, 31 had adequate evaluation. These 31 patients were reviewed for survival with reference to spleen size. Seventeen patients with spleens 3 cm or less below the left costal margin had a 50% survival of 75 months, with a mean survival of 53.9 months. Fourteen patients with spleens greater than 3 cm below the left costal margin had a 50% survival of 21 months, with a mean survival of 19 months (P = .0014). It is concluded that small splenic size in CML is associated with longer survival. It may be that this observation should be taken into consideration when considering splenectomy in the management of patients with CML.

Adolescent↗
PubMed1978

Prenatal diagnosis of the Lesch-Nyhan syndrome.

Amniocentesis provides the prenatal diagnosis of chromosomal abnormalities and many biochemical disorders. Many of the biochemical assays are not routinely performed in many institutions. Those institutions utilizing autoradiographic studies routinely can make a diagnosis of biochemical disorders satisfactorily by utilizing a combination of bank cells, amniotic fluid cells and autoradiographic techniques. An example is given of this technique used in a patient with a family history of Lesch-Nyhan syndrome.

Amniocentesis↗
PubMed1977

Spinocerebellar ataxia and HLA linkage: risk prediction by HLA typing.

To determine the possibility of genetic linkage of spinocerebellar ataxia with the histocompatibility loci, we performed HLA typing and linkage analysis on 19 members of a kindred in which spinocerebellar ataxia was segregating in an autosomal dominant inheritance pattern. The ataxia locus was located on chromosome 6 at 12-cM distance from the HLA complex with lod score of 3.15 (odds is greater than 1400:1 favoring linkage over chance findings). Thus, the presence of the ataxia gene in members of this kindred at risk can be predicted with about 90 per cent accuracy by means of HLA typing in informative matings.

Cerebellar Ataxia↗
PubMed1976

Thymidine phosphotransferase and nucleotide phosphohydrolase of the fern Asplenium nidus. General properties and inhibition by adenosine 3':5'-cyclic monophosphate.

1. Extracts of several plant species contained nucleoside-AMP phosphotransferase activity. The ratio of activity with thymidine to that with uridine as nucleoside substrate was essentially constant, both between species and throughout plant development. Evidence is presented that the total thymidine-AMP phosphotransferase activity of the leaves of Asplenium nidus (bird's-nest fern) and of Helianthus tuberosus (Jerusalem artichoke) increases during maturation. 2. Thymidine-AMP phosphotransferase was purified 22-fold from a very rich source of this activity, extracts of A. nidus. 3. A broad specificity towards both nucleoside and nucleoside 5'-monophosphate substrates is displayed by this preparation, and the evidence suggests that all could be due to a single enzyme. 4. Nucleosides that act as substrates will also inhibit phosphotransfer to other nucleosides, with Ki values close to the corresponding Km values found when utilized as substrates. 5. Ca2+-activated ATP phosphohydrolase was separated from the phosphotransferase by differential complexing to Blue Dextran in the presence of urea, whereas an AMP phosphohydrolase activity was closely associated with thymidine-AMP phosphotransferase through all separation techniques used. 6. Metal ions did not activate either of the latter two activities, and 1,10-phenanthroline was found to inhibit the phosphotransferase. 7. Km values for AMP for the respective activities were 0.11 mM (thymidine phosphotransferase) and 0.20 mM (AMP phosphohydrolase) and for thymidine (phosphotransferase only) 0.88 mM. 8. 3':5'-Cyclic AMP was found to inhibit both phosphotransferase and AMP phosphohydrolase activities, with Ki values of 0.056 mM and 0.15 mM respectively. It is suggested that this inhibitor would be of value in revealing the existence of thymidine kinase in plant extracts with high thymidine phosphotransferase activity.

Adenosine Monophosphate↗
PubMed1976

Chicken globin gene number.

Using complementary DNA prepared from adult chicken globin messenger RNA, we show the existence of 2-3 non-cross-hybridising globin sequences in the chicken genome, each of which is present in only one copy per haploid genome. This was done by solution hybridization to total DNA under conditions of cDNA excess. The data agreses with results of RNA-driven hybridisation of globin complementary DNA, and with protein data.

Animals↗
PubMed1976

Clinical diagnosis of Down's syndrome.

A physical examination checklist of 25 signs of Down's syndrome was used to predict the presence of absence of 21-trisomy in 291 individuals examined for suspected Downs syndrome. Using only total numbers of signs present, 21-trisomy was unambiguously predicted in about half those examined. Discriminant analysis using the most informative 10 signs misclassified only 11 of 169 infants aged 2 years or less, and allowed non-overlapping classification into Down's and non-Down's of almost three-fourths of suspected individuals. The risk for Down's syndrome in the overlap area was 58%.

Child, Preschool↗