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Biomedical subjects

J E Fleming

Publications and source records attributed to J E Fleming.

At least 55 records · Page 3Linked to original sources
PubMed1990

Ascorbic acid uptake by young and aged guinea pig lenses.

The dynamics of in vitro uptake of [14C]-ascorbic acid into intact lenses of young (50 days old) and old (730 days old) guinea pigs was evaluated in this study. Two-dimensional protein gel analysis of [35S]-methionine labeled proteins provided evidence that the isolated lenses were viable throughout the culture period. It was found that the in vitro uptake of ascorbate into these lenses follows similar saturation kinetics for lenses from both age groups. Moreover, the linear uptake rate was identical. Ascorbate transport was inhibited by phloretin, p-chloromercuribenzoate, insulin, glucose and ouabain; however, no inhibition was observed with 2,4-dinitrophenol or NaF. These results suggest that the lenticular ascorbate concentration is regulated by a facilitated diffusion process and it not energy-dependent. Data on ascorbate transport into lenses from aged guinea pigs provide strong evidence that the abnormally low ascorbic acid concentrations in lenses of old mammals is not likely the result of a decreased lenticular uptake ability.

Aging↗
PubMed1990

Epidemiology of childhood depressive disorders: a critical review.

The methodology of 14 recent epidemiological studies of childhood and adolescent depressive disorders was critically reviewed and findings summarized for prevalence, comorbidity, correlates, risk factors, and outcome. Shortcomings in sampling and considerable inconsistency in the measurement of depression in the studies made it difficult to draw firm conclusions about the prevalence and correlates of depression in young people. Nonetheless, it is likely that major depressive disorder is relatively uncommon in prepubertal children, increases in frequency in adolescents, and is significantly associated with such variables as family dysfunction and low self-esteem. Comorbidity of depression with other psychiatric disorders was also high in these nonpatient samples and it will be important in future work to assess the implications of this for the etiology, treatment, and prognosis of depressive disorders in children and adolescents.

Adolescent↗
PubMed1989

Preparation of antibodies against xanthine oxidase from human milk.

1. Human xanthine oxidase [XO; EC 1.2.3.2.] was isolated by a non-proteolytic method from fresh human milk. Final purification of the protein was achieved by hydroxyapatite chromatography. Most (less than 95%) of the enzyme was released in the 0.40 M phosphate fraction at pH 6.8. 2. The specific activity of this preparation was found to be 0.047 microM min-1 mg-1 with xanthine as substrate. 3. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) separated two subunits, each with a mol. wt approximately 122 kDa. 4. On non-denaturing acrylamide gels both of these subunits exhibited oxidase-like activity with xanthine as substrate in the presence of nitroblue tetrazolium and molecular oxygen. 5. Immunoconjugates of XO were prepared by the keyhole limpet hemocyanin (KLH)- and glutaraldehyde-crosslinking techniques. 6. Polyclonal antibodies to XO were raised by i.m. injection of these conjugates into female New Zealand rabbits. 7. Western blot analysis using the semi-dry technique was employed to confirm the specificity of the antibody.

Animals↗
PubMed1989

Ontario Child Health Study. Summary of selected results.

Selected results from the Ontario Child Health Study (OCHS), a cross-sectional community survey of Ontario children four to 16 years of age, are presented in the areas of prevalence, risk indicators and service utilization. The six month prevalence of one or more of four psychiatric disorders (conduct disorder, hyperactivity, emotional disorder, and somatization), in children four to 16 years of age, in Ontario was 18.1%. The highest rate was in 12 to 16 year old girls, and the lowest rate in four to 11 year old girls. Co-morbidity among these four disorders was high while the proportion of disorders identified by more than one respondent was low. Psychiatric disorders co-occurred significantly with other morbidities in children, including poor school performance, chronic health problems, substance use and suicidal behaviour. Chronic medical illness in the child as well as single parent status, living in a family on social assistance and residing in subsidized housing, were all strong indicators of increased rates of psychiatric disorders in children. Specialized mental health/social services, over a six month period, reached fewer than one of five children with psychiatric disorders, as measured in the study. In contrast, ambulatory medical care (primarily visits to family doctors and pediatricians) served almost 60% of Ontario children four to 16 years old, over the same six month period. The results are compared with those in the literature.

Adolescent↗
PubMed1989

Prevalence of childhood and adolescent depression in the community. Ontario Child Health Study.

Data from a cross-sectional community survey of 2852 children were used to provide estimates of the prevalence of a 'DSM-III-like' major depressive syndrome in children aged 6 to 16. The severity of symptoms required to define a 'case' was varied to generate three levels of diagnostic certainty (DC). The overall estimates of prevalence made with high DC were 0.6% for pre-adolescents and 1.8% for adolescents. Corresponding rates determined with medium DC were 2.7% and 7.8%, whereas the figures for low DC were 17.5% and 43.9%. Utilisation of mental health and social services, comorbidity (combined disorders), poor school performance, problems in getting along with others and need for professional help all increased as diagnostic certainty increased. There was wide disagreement in data supplied by the different groups of respondents, i.e. parents, teachers and adolescents.

Adolescent↗
PubMed1988

Aging results in an unusual expression of Drosophila heat shock proteins.

We used high-resolution two-dimensional polyacrylamide gel electrophoresis to evaluate the effect of aging on the heat shock response in Drosophila melanogaster. Although the aging process is not well understood at the molecular level, recent observations suggest that quantitative changes in gene expression occur as these fruit flies approach senescence. Such genetic alterations are in accord with our present data, which clearly show marked differences in the synthesis of heat shock proteins between young and old fruit flies. In 10-day-old flies, a heat shock of 20 min results in the expression of 14 new proteins as detectable by two-dimensional electrophoresis of [35S]methionine-labeled polypeptides, whereas identical treatment of 45-day-old flies leads to the expression of at least 50 new or highly up-regulated proteins. In addition, there is also a concomitant increase in the rate of synthesis of a number of the normal proteins in the older animals. Microdensitometric determinations of the low molecular weight heat shock polypeptides on autoradiographs of five age groups revealed that their maximum expression occurs at 47 days for a population of flies with a mean life span of 33.7 days. Moreover, a heat shock effect similar to that observed in senescent flies occurs in young flies fed canavanine, an arginine analogue, before heat shock.

Aging↗
PubMed1987

Ultrasound exposure time in routine obstetric scanning.

The duration of exposure to ultrasound was measured in 1274 patients having a routine examination during their first visit to an antenatal clinic. The measured median exposure time was 105 s. Since pulsed ultrasound was used (duty cycle of 1 in 800) the actual median maternal exposure time was 131 ms. Exposure of the fetus would usually be less since it rarely occupies the full width of the image. The relevance of exposure time to the safety of diagnostic ultrasound and the implications for users and manufacturers are discussed.

Female↗
PubMed1986

The role of arginyl residues in porphyrin binding to ferrochelatase.

The role of cationic amino acid residues in the binding of porphyrin substrates by purified bovine ferrochelatase (protoheme ferro-lyase, EC 4.99.1.1) have been examined via chemical modification with camphorquinone-10-sulfonic acid, phenylglyoxal, butanedione, and trinitrobenzene sulfonate. The data obtained show that modification of arginyl, but not lysyl, residues results in the rapid inactivation of ferrochelatase. The 2,4-disulfonate deuteroporphyrin, which is a competitive inhibitor of mammalian ferrochelatase, protects the enzyme against inactivation. Ferrous iron has no protective effect. Reaction with radiolabeled phenylglyoxal shows that modification of 1 arginyl residue causes maximum inhibition of enzyme activity. The inactivation does not follow simple pseudo-first order reaction kinetics, but is distinctly biphasic in nature. Comparison of the enzyme kinetics for modified versus unmodified enzyme show that modification with camphorquinone-10-sulfonic acid has no effect on the Km for iron but does alter the Km for porphyrin.

Amino Acids↗
PubMed1986

In vitro translation products of Drosophila mitochondria are contaminated with newly synthesized bacterial proteins.

A previous study reported in this journal suggested that in vitro synthesis of Drosophila mitochondrial polypeptides could be performed provided certain bacterial growth inhibitors were employed in the medium (Alziari, S., Stepien, G., and Durand, R. (1981) Biochem. Biophys. Res. Comm. 99, 1-8). We report here that despite the absence of microbial proliferation, bacteria isolated from adult Drosophila synthesize a significant number of proteins in such a medium. Thus, considerable caution must be exercised in the interpretation of studies utilizing this medium which claim to provide data on the translation products of isolated mitochondria from adult insects.

Animals↗
PubMed1986

Age-dependent changes in proteins of Drosophila melanogaster.

Several molecular theories of aging postulate that there are age-dependent changes in gene expression and that these changes contribute to the reduction in the viability of senescent cells. High-resolution, semiautomated, quantitative two-dimensional gel electrophoresis of many soluble proteins was used to test this hypothesis in Drosophila. Two-dimensional protein gel patterns were analyzed for each of three age groups of [(35)S]methionine-labeled adult male Drosophila melanogaster, which, except for their spermatocytes, consist entirely of fixed postmitotic cells. Seven relatively abundant polypeptides expressed in middle-aged (28-day-old) flies were absent in both young(10-day-old) and old (44-day-old) flies. Quantitative analyses of an additional 100 polypeptides were carried out by computer-assisted microdensitometry of fluorograms of the gel preparations. These analyses revealed a significant age-related heterogeneity in the quantitative distribution of radiolabel in these proteins. The data indicate that the qualitative pattern of gene expression is identical in young and old flies, but that profound quantitative changes occur in the expression of proteins during the Drosophila life-span.

Aging↗
PubMed1986

The measurement of fetal systolic time intervals: lessons from ultrasound.

Fetal systolic time intervals (pre-ejection period, iso-volumetric contraction time and ventricular ejection time) can be measured using Doppler ultrasound to detect valve movements and the fetal ECG to indicate the onset of ventricular depolarisation. Continuous recordings of FSTI, fetal heart rate and uterine activity depict changes reflecting progressive cord compression and have the potential for providing improved differentiation of late and variable decelerations. However, the continual adjustment of the ultrasound transducer required to maintain a good signal limits the technique. Recent improvements in phono indicate that this may provide a useful alternative, provided that suitable signal-processing is developed.

Electrocardiography↗
PubMed1986

Age dependent changes in the expression of Drosophila mitochondrial proteins.

A subset of 43 [35S]methionine labeled mitochondrial proteins, identified on two dimensional electrophoresis gels of whole body extracts of adult Drosophila, were compared between two age groups. These flies, which except for their spermatocytes consist entirely of postmitotic cells, were 6 days old and 38 days old, with the mean life span of this inbred strain being 32.5 days. Qualitative changes in any of these mitochondrial polypeptides were not found, but significant quantitative differences were observed. Quantitation of the 43 mitochondrial proteins was carried out by computer assisted microdensitometry of autoradiograms of the gel patterns. The total amount of isotope incorporated into the mitochondrial proteins of the senescent flies decreased to 71% of that of the young insects. This decrease was heterogeneously distributed among the 43 proteins; however, six remained unchanged and one protein (mol. wt = 75; pI = 7.4) was increased 2.4 times in the senescent flies. These data clearly provide evidence that the age-dependent changes in the expression of mitochondrial proteins are quantitative and not qualitative.

Aging↗
PubMed1986

Ferrochelatase from Rhodopseudomonas sphaeroides: substrate specificity and role of sulfhydryl and arginyl residues.

Purified ferrochelatase (protoheme ferrolyase; EC 4.99.1.1) from the bacterium Rhodopseudomonas sphaeroides was examined to determine the roles of cationic and sulfhydryl residues in substrate binding. Reaction of the enzyme sulfhydryl residues with N-ethylmaleimide or monobromobimane resulted in a rapid loss of enzyme activity. Ferrous iron, but not porphyrin substrate, had a protective effect against inactivation by these two reagents. Quantitation with 3H-labeled N-ethylmaleimide revealed that inactivation required one to two sulfhydryl groups to be modified. Modification of arginyl residues with either 2,3-butanedione or camphorquinone 10-sulfonate resulted in a loss of ferrochelatase activity. A kinetic analysis of the modified enzyme showed that the Km for ferrous iron was not altered but that the Km for the porphyrin substrate was increased. These data suggested that arginyl residues may be involved in porphyrin binding, possibly via charge pair interactions between the arginyl residue and the anionic porphyrin propionate side chain. Modification of lysyl residues had no effect on enzyme activity. We also examined the ability of bacterial ferrochelatase to use various 2,4-disubstituted porphyrins as substrates. We found that 2,4-bis-acetal- and 2,4-disulfonate deuteroporphyrins were effective substrates for the purified bacterial enzyme and that N-methylprotoporphyrin was an effective inhibitor of the enzyme. Our data for the ferrochelatase of R. sphaeroides are compared with previously published data for the eucaryotic enzyme.

Arginine↗
PubMed1985

Age-related changes in turnover and concentration of a subset of thorax polypeptides from Drosophila melanogaster.

Six polypeptides from Drosophila melanogaster were analyzed by two-dimensional polyacrylamide gel electrophoresis for age-related changes in protein turnover and protein concentration. The protein samples, from thoraces of 6 day (young), 26 day (middle) and 45 day (old) flies, were compared using autoradiography for [35S]methionine labeled proteins and silverstaining for unlabeled preparations. The combination of these two techniques has permitted determination of the relative turnover rate as well as the steady-state concentration of these proteins as a function of age. The autoradiographs reveal that all of the analyzed proteins decrease in turnover rate whereas the absolute protein concentrations, as determined from the silverstained gels, show a decrease for three proteins, no change for two, and an increase in one protein with age. These findings show a remarkable quantitative heterogeneity of ageing changes in proteins, but absence of alterations in the fidelity of the translation of these polypeptides.

Aging↗
PubMed1985

The role of ascorbic acid in senile cataract.

The reductone ascorbic acid, present in the crystalline lens in concentrations higher than those of glucose, is capable of undergoing nonenzymatic "browning" in the presence of lenticular proteins. We studied the nonenzymatic browning with ascorbate in model systems employing bovine serum albumin and lens crystallins. When bovine serum albumin, alpha-crystallin, or gamma-crystallin was incubated with [14C]ascorbic acid, the formation of yellow and then brown condensation products appeared to correlate with increasing protein-associated radioactivity. The fluorescence spectrum of these products was similar to that of homogenates of human cataractous lenses. We suggest that the nonenzymatic reaction of lens crystallins with ascorbic acid may contribute, at least in part, to the color changes of aging lenses and to the physical lenticular deterioration leading to senile cataract. High dietary intake of ascorbic acid did not affect the fluorescence spectrum of murine lenses; thus, we assume that the speed and extent of the lenticular browning reactions must depend on a deterioration of other factors of the multicomponent antioxidant system of the eye.

Anaerobiosis↗
PubMed1984

A two-step hypothesis on the mechanisms of in vitro cell aging: cell differentiation followed by intrinsic mitochondrial mutagenesis.

Despite vigorous research, there is yet no agreement on the biochemical mechanisms responsible for the loss of replicative potential of diploid cultured cells. In contrast to the program theories of in vitro cell aging, we propose that, as already suggested by Minot in 1907, senescence is the result of cell differentiation. We further maintain that the fundamental cause of cell aging is an instability of the mitochondrial genome because of a lack of balance between mitochondrial repair and the disorganizing effects of oxygen radicals which arise in the respiring mitochondria of terminally differentiated cells. This probably results in intrinsic mitochondrial mutagenesis which may be followed by endonuclease degradation of the altered mitochondrial DNA. Since the mitochondrial genome controls the synthesis of several hydrophobic proteins of the inner mitochondrial membrane, the postulated denaturation or loss of mtDNA will prevent the replication of the organelles. Thus, deprived of the ability to regenerate their mitochondrial populations, the cells will sustain an irreversible decline in their ability to synthesize ATP, with concomitant senescent degradation of physiological performance and eventual death.

Adenosine Triphosphate↗