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Biomedical subjects

T J Green

Publications and source records attributed to T J Green.

At least 19 recordsLinked to original sources
PubMed1998

Oral contraceptives did not affect biochemical folate indexes and homocysteine concentrations in adolescent females.

OBJECTIVE: The study was designed to determine the impact of currently available oral contraceptive agents (OCAs), smoking, and alcohol on biochemical indexes of folate and vitamin B-12 in adolescent females. DESIGN: Subjects completed a 3-day weighed food record along with a detailed lifestyle questionnaire that included questions on OCA, cigarette, and alcohol use. After subjects had fasted overnight, blood samples were collected and analyzed for levels of serum and red blood cell (RBC) folate and serum B-12 and homocysteine. SUBJECTS/SETTINGS: Two hundred twenty-nine adolescent females (aged 14 to 20 years) were recruited from southern Ontario, Canada, by advertisements in newspapers, high schools, universities, shopping malls, adolescent drop-in centers, and community groups. STATISTICAL ANALYSES PERFORMED: Multiple regression models were used to determine the effect of lifestyle factors and covariates (e.g., dietary folate intake, supplemental folate intake, and age) on biochemical indexes. RESULTS: OCA use, alcohol use, and smoking were not significantly associated with lower serum or RBC folate levels, after controlling for folate intake. Serum homocysteine levels were not associated with smoking or OCA use; however, we estimated a 13% higher concentration among alcohol users than nonusers. Smoking and alcohol use were not associated with serum B-12 levels, but OCA use was associated with an estimated 33% lower serum B-12 level than nonuse. APPLICATIONS: Our findings provide no evidence to suggest that currently available OCAs have a negative impact on the folate status of adolescent females; thus, dietary advice designed to specifically encourage an increase in folate intake among adolescents who use OCAs is not supported. In contrast, serum B-12 levels were lower among OCA users than nonusers, which suggests that an interaction between OCA and some vitamins may persist. The suboptimal biochemical folate indexes of smokers may have more to do with the dietary quality of smokers than previously appreciated. Thus, efforts to improve dietary folate intakes of adolescents who smoke may be an important strategy for improving the folate status of young women.

Adolescent↗
PubMed1998

A three-day weighed food record and a semiquantitative food-frequency questionnaire are valid measures for assessing the folate and vitamin B-12 intakes of women aged 16 to 19 years.

The purpose of this study was to validate a food-frequency questionnaire (FFQ) and a 3-d weighed food record (3d-WFR) by comparing nutrient intakes estimated using these methods with serum folate, RBC folate and serum vitamin B-12 concentrations in 105 females aged 16-19 y. During an early morning clinic visit, subjects completed a self-administered, 116-item FFQ, blood was collected and they were trained to complete a 3d-WFR. Folate intakes as determined by the 3d-WFR (r = 0.65, P < 0.01) exhibited a stronger association with serum folate than did intakes from the FFQ (r = 0.48, P < 0.01) (P = 0.017). The correlations between folate intakes and RBC folate as determined by the FFQ (r = 0.42, P < 0.01) and 3d-WFR (r = 0.50, P < 0.01) methods did not differ. Vitamin B-12 intakes showed only a modest association with serum vitamin B-12 when supplement users were included in the analyses (FFQ, r = 0.25, P < 0.05; 3d-WFR, r = 0.32, P < 0.05). After excluding supplement users from the analyses, the relationship between vitamin B-12 intakes as determined by FFQ and serum vitamin B-12 was no longer significant. Median daily folate intakes (346 vs. 212 microgram) and vitamin B-12 (4.9 vs. 1.9 microgram) estimated from the FFQ were higher than those obtained from the 3d-WFR. In sum, these data suggest that both the FFQ and 3d-WFR are valid measures of assessing the folate intake of young women, and both appear to be useful in determining vitamin B-12 intake when supplemental users are included. The markedly different conclusions about absolute folate and vitamin B-12 intakes obtained using these two dietary methodologies should be taken into consideration when making recommendations about optimal folate intakes in relation to disease prevention.

Adolescent↗
PubMed1997

Association between dietary fiber intake and the folate status of a group of female adolescents.

The main objective of this study was to assess the association between dietary fiber intake and the folate status of Canadian female adolescents. We also assessed dietary folate intakes and evaluated the prevalence of biochemical folate deficiency in these subjects. Female adolescents aged 14-19 y (n = 224) were recruited and fasting blood samples were collected. Dietary intakes (3-d food record) were recorded and participants were classified as lactoovovegetarians, semivegetarians, or omnivores on the basis of food-consumption patterns assessed with food-frequency questionnaires. Fourteen percent, 17%, and 26% of lactoovovegetarians, semivegetarians, and omnivores, respectively, had dietary folate intakes below their predicted requirements; 1%, 4%, and 23%, respectively, had serum folate concentrations indicative of deficiency. Despite low dietary folate intakes and serum folate concentrations, few subjects had homocysteine concentrations indicative of deficiency, suggesting that the degree of folate depletion had not yet produced functional consequences. Most important, results suggest that the consumption of nonstarch polysaccharide is significantly associated with serum folate concentrations (P < 0.001). For each 1-g increase in nonstarch polysaccharide intake, a 1.8% increase in serum folate concentration is expected. In summary, we propose that an increase in nonstarch polysaccharide intake may promote the intestinal biosynthesis of folate, providing a complementary strategy to enhance the folate nutriture of humans.

Adolescent↗
PubMed1997

Role of sialyloligosaccharide binding in Theiler's virus persistence.

Theiler's murine encephalomyelitis viruses (TMEVs) belong to the Picornaviridae family and are divided into two groups, typified by strain GDVII virus and members of the TO (Theiler's original) group. The highly virulent GDVII group causes acute encephalitis in mice, while the TO group is less virulent and causes a chronic demyelinating disease which is associated with viral persistence in mice. This persistent central nervous system infection with demyelination resembles multiple sclerosis (MS) in humans and has thus become an important model for studying MS. It has been shown that some of the determinants associated with viral persistence are located on the capsid proteins of the TO group. Structural comparisons of two persistent strains (BeAn and DA) and a highly virulent strain (GDVII) showed that the most significant structural variations between these two groups of viruses are located on the sites that may influence virus binding to cellular receptors. Most animal viruses attach to specific cellular receptors that, in part, determine host range and tissue tropism. In this study, atomic models of TMEV chimeras were built with the known structures of GDVII, BeAn, and DA viruses. Comparisons among the known GDVII, BeAn, and DA structures as well as the predicted models for the TMEV chimeras suggested that a gap on the capsid surface next to the putative receptor binding site, composed of residues from VP1 and VP2, may be important in determining viral persistence by influencing virus attachment to cellular receptors, such as sialyloligosaccharides. Our results showed that sialyllactose, the first three sugar molecules of common oligosaccharides on the surface of mammalian cells, inhibits virus binding to the host cell and infection with the persistent BeAn virus but not the nonpersistent GDVII and chimera 39 viruses.

Amino Acid Sequence↗
PubMed1996

Advanced practice nurses: change agents for clinical practice.

The article presents the role of advanced practice nurses as change agents in the clinical setting. Research utilization is needed to shape and form the basis of nursing practice. As change agents, the advanced practice nurses in one institution established a research-based minimal stimulation protocol for the very low-birth weight infant and implemented it using a video presentation. Knowledge of change theory, research utilization, and video production was necessary in making this project a success.

Clinical Nursing Research↗
PubMed1995

An antibacterial vitamin E derivative from Tovomitopsis psychotriifolia.

The crude ethanol extract from the leaves of Tovomitopsis psychotriifolia (Clusiaceae) exhibits antibacterial activity against Bacillus cereus, Staphylococcus aureus, and Pseudomonas aeruginosa. The biologically active agent in the extract has been isolated by chromatographic techniques and identified by NMR spectroscopy as trans-delta-tocotrienoloic acid.

Anti-Bacterial Agents↗
PubMed1995

A cytotoxic diacetylene from Dendropanax arboreus.

The crude ethanol extract from the leaves of Dendropanax arboreus (Araliaceae) from Monteverde, Costa Rica, exhibits cytotoxic activity against Hep-G2, A-431, H-4IIE, and L-1210 tumor cell lines, but is not toxic against normal hepatocytes. The active component has been isolated by activity-directed separation and identified by 1H- and 13C-NMR spectroscopy as the acetylenic compound cis-1,9,16-heptadecatriene-4,6-diyne-3,8-diol.

Alkynes↗
PubMed1994

Antigenic analysis of Dictyocaulus viviparus by use of test-positive bovine sera.

An antigen extract of Dictyocaulus viviparus was analyzed by use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the antigen-recognition patterns of serum antibody from cattle not infected, cattle infected with D viviparus, and cattle with unknown history of D viviparus were analyzed by the use of ELISA and western blotting techniques. Cross-reactive antibody-recognition patterns were determined by comparing western blots of D viviparus-positive sera with blots of D viviparus-negative sera obtained from cattle singly infected with Bunostomum phlebotomum, Cooperia oncophora, C punctata, Nematodirus helvetianus, Oesophagostomum radiatum, or Ostertagia ostertagi. Five antigen bands unique to D viviparus were identified, and their frequency of appearance in western blots of sera from verified D viviparus-positive and -negative cattle, and sera from cattle exposed to the parasite, but with unknown D viviparus immune status, were determined. Of the 5 antigens unique to D viviparus, 29- and 19-kd bands had the highest frequencies of reaction (45.9 and 59.0%, respectively) with the test sera. These bands had strong reactivity with sera containing antibodies to D viviparus and did not react with the heterologous sera. We conclude that the 29- and 19-kd antigens may be useful for developing an improved serodiagnostic test for D viviparus infections in cattle.

Animals↗
PubMed1990

Identification of common surface antigens among Babesia bigemina isolates by using monoclonal antibodies.

A group of monoclonal antibodies (MAb) was used to immunochemically characterize Babesia bigemina surface components. Two surface reactive MAb by an IFAT test were subsequently shown to bind to epitopes on the external surface of the parasite plasma membrane as evidenced by immunoelectron microscopy. Parasite components with relative sizes of 68, 62, 60, 58, 56, 54, 51, 49, 48, 47, 43, 36 kDa were identified with the group of MAb in at least 6 geographically different B. bigemina isolates. The antigenic components were demonstrated to be species-specific and apparently predominant. Both polyclonal antibodies (immune bovine serum) and highly diluted MAb specifically reacted with such bands producing a strong signal in Western blots.

Animals↗
PubMed1990

Monoclonal IgM rheumatoid factor-like anti-globulins enhance the inhibitory effects of Plasmodium falciparum-specific monoclonal antibodies in vitro.

Monoclonal IgM rheumatoid factor-like anti-globulins were produced by in vitro stimulation of naive BALB/c spleen cells with lipopolysaccharide, and by hyperimmunization of mice with merozoites of Plasmodium falciparum, followed by fusion of the spleen cells to mouse myelomas. In vitro, these anti-globulins augmented the inhibitory effects of P. falciparum-specific polyclonal mouse sera and monoclonal IgG1 and IgG2b antibodies by binding to Fc fragments of IgG molecules attached to blood-stage parasites. In some instances, the presence of anti-globulins correlated with an increase in the number of schizonts which failed to disperse merozoites. In other cases, parasitaemia remained low in the absence of the schizont inhibition phenomenon, suggesting that anti-globulins contribute to host cell protection not only by agglutinating merozoites, but also by increasing the density of the antibody coat surrounding the parasites, thus interfering with parasite receptor-erythrocyte ligand interactions. The anti-globulins were not inhibitory when added to parasite cultures containing IgG not specific for P. falciparum. These results may help explain the function of IgM anti-globulins found at elevated serum levels in some patients with malaria or other chronic infectious diseases.

Animals↗
PubMed1988

The oxygen dependence of mitochondrial oxidative phosphorylation measured by a new optical method for measuring oxygen concentration.

Oxygen-dependent quenching of phosphorescence has been used to measure the dependence of mitochondrial oxidative phosphorylation on oxygen concentration in suspensions of isolated rat liver mitochondria. An instrument has been designed which simultaneously monitors the phosphorescence lifetime of a fluorophor and the reduction of cytochrome c by dual wavelength spectrophotometry. The phosphorescence lifetime method gives very rapid (less than 100 ms) measure of the oxygen concentration (Vanderkooi, J. M., Maniara, G., Green, T. J., and Wilson, D. F. (1987) J. Biol. Chem. 262, 5476-5482) from concentrations characteristic of air-saturated media to as low as 2 x 10(-8) M. The results may be summarized as follows. For well coupled rat liver mitochondria at pH 7.0 and in the presence of ATP, as the oxygen concentration was lowered, increased cytochrome c reduction was observed to begin at oxygen concentrations greater than 20 microM. For mitochondria in the presence of uncoupler, cytochrome c reduction began at oxygen concentrations less than 1.0 microM. The oxygen dependence of reduction of cytochrome c in well coupled mitochondria treated with ATP was strongly dependent on the pH of the suspending medium. Reduction of cytochrome c began at higher oxygen concentrations as the pH was made more alkaline. The oxygen concentration for half-maximal respiratory rates was much larger for well coupled mitochondria treated with ATP (approximately 0.7 microM) than for mitochondria treated with uncoupler (less than 0.1 microM). It is concluded that the oxygen dependence of mitochondrial oxidative phosphorylation is such that mitochondria could function in their proposed role of tissue oxygen sensors for regulation of such diverse functions as local blood flow and electrical activity in the carotid body.

Adenosine Triphosphate↗
PubMed1988

Phosphorimeters for analysis of decay profiles and real time monitoring of exponential decay and oxygen concentrations.

A phosphorimeter which can be assembled at low cost from mainly commercially available components and which has better time resolution, data acquisition rate, sensitivity, and flexibility than commercially available instruments is described. As a phosphorescence analyzer the instrument can measure phosphorescence lifetimes ranging from approximately 30 microseconds to seconds from samples with variable intensity, excitation, and emission spectra and which may follow complex decay behavior. Configured as a phosphorescence monitor it is designed for fast, repetitive calculation of phosphorescence lifetime, assuming single-exponential decay, and can be used to calculate oxygen concentration in biological samples in real time.

Luminescent Measurements↗
PubMed1987

An optical method for measurement of dioxygen concentration based upon quenching of phosphorescence.

An optical method for measuring oxygen concentrations in aqueous solutions is described. This method is based upon the oxygen-dependent quenching of phosphorescence. Phosphorescence excitation and emission spectra and lifetimes of some of the probe molecules suitable for measurement of oxygen in aqueous solutions are given. The probes include fluorescein derivatives, 4'5'-diiodofluorescein, eosin Y, 5(and 6)-carboxyeosin, erythrosin, and 5(and 6)-carboxyerythrosin as well as the Zn(II), Y(III), Sn(IV), Lu(III), and Pd(II) derivatives of meso-tetra-(4-sulfonatophenyl)-porphine, meso-tetra-(N-methyl-4-pyridyl)-porphine and coproporphyrin. The phosphorescence lifetimes of the given probes were found to depend upon the oxygen concentration by a simple Stern-Volmer relationship with a quenching constant of approximately 10(9) M-1 S-1. Binding of the molecules to bovine serum albumin decreased the quenching constant for oxygen by approximately an order of magnitude and also inhibited probe self-quenching, indicating that at the protein binding site the probes are somewhat protected from collision with quenchers. The use of this optical method for measuring oxygen is demonstrated for reactions catalyzed by glucose oxidase and by cytochrome c oxidase. It is shown that, using this method oxygen concentrations can be measured from approximately 250 microM (air saturation) down to the nanomolar range.

Animals↗
PubMed1987

A versatile and sensitive method for measuring oxygen.

Oxygen dependence of the lifetime of the excited triplet state of phosphorescent molecules can be used to measure the oxygen concentration in aqueous media. These measurements are insensitive to much of the optical interference that limits the usefulness of measurements based on the oxygen dependent quenching of luminescence intensity. The measurements also extend to significantly lower oxygen concentrations than are normally attainable using oxygen electrodes. The phosphorescence lifetimes can be accurately measured from a few microseconds to seconds, permitting a wide dynamic range of oxygen concentration measurements. With currently available probes, for example, it is possible to make continuous measurement of oxygen concentrations from 10(-4) M to 10(-8) M in a single experiment.

Animals↗
PubMed1987

A sensitive urea-silver stain method for detecting trace quantities of separated proteins in polyacrylamide gels.

An ultrasensitive method using a urea-silver staining procedure to detect trace quantities of proteins in polyacrylamide gels (PAGE) is described. This technique is sensitive enough to detect picogram quantities of proteins resolved on sodium dodecyl sulfate-polyacrylamide gels. The major advantages of our method are that it provides a clear background and it is more sensitive than other techniques allowing it to substitute for radioisotopic techniques in some cases.

Electrophoresis, Polyacrylamide Gel↗
PubMed1987

Reference values for peripheral blood lymphocytes from Aotus lemurinus ssp. griseimembra (owl monkey).

The reactivities of several monoclonal antibodies that define human lymphocyte cell-surface antigens have been tested with peripheral blood lymphocytes of Aotus lemurinus ssp. griseimembra. Based on reactivity patterns in humans, reactive MoAb were identified that mark pan-T, helper/inducer, suppressor/cytotoxic, pan-B, and natural killer cells. Reference values of these subsets in Aotus are presented. These MoAb should provide a useful tool for further phenotypic and functional dissection of the immune system in this simian model of human disease.

Animals↗