Search PubMed⌕ Search

Biomedical subjects

J Williamson

Publications and source records attributed to J Williamson.

At least 73 records · Page 4Linked to original sources
PubMed1998

Kinetic model of folate metabolism in nonpregnant women consuming [2H2]folic acid: isotopic labeling of urinary folate and the catabolite para-acetamidobenzoylglutamate indicates slow, intake-dependent, turnover of folate pools.

In a 10-wk study of folate metabolism in nonpregnant women (21-27 y, n -6 per group), subjects were fed a diet containing approximately 68 nmol/d (30 microg/d) folate from food. The remainder of the ingested folate was provided as folic acid in apple juice (as nonlabeled during wk 1-2, as [2H2]folic acid during wk 3-10) to yield a constant intake of 454, 680 or 907 nmol/d (200, 300 or 400 microg/d). Isotopic enrichment of total urinary folate and the primary catabolite para-acetamidobenzoylglutamate (ApABG) was determined. Isotopic enrichment of ApABG served as an indicator of labeling of tissue folates. A kinetic model consisting of fast- and slow-turnover nonsaturable pools and a saturable slow-turnover pool, with provisions for urinary and fecal excretion, catabolism and enterohepatic circulation, yielded a close fit to the data. Mean residence times for total body folate were 212, 169 and 124 d for folate intakes of 454, 680, and 907 nmol/d, respectively. The model predicted that variation in folate intake over this range had little effect on the mass of the large saturable folate pool; however, the fast-turnover nonsaturable pools increased in proportion to folate intake, whereas the slow nonsaturable pool also tended to increase. This model will aid in evaluation of folate turnover and in predicting kinetic consequences of physiologic conditions associated with altered folate requirements.

Adult↗
PubMed1998

Urinary excretion of [2H4]folate by nonpregnant women following a single oral dose of [2H4]folic acid is a functional index of folate nutritional status.

In a 10-wk study with nonpregnant women (21-27 y, n = 5-6 per group), subjects were fed a diet containing approximately 68 nmol/d (30 microg/d) folate from food that was supplemented with folic acid in apple juice to yield a constant intake of 454, 680 or 907 nmol/d (200, 300 or 400 microg/d) to evaluate folate status and long-term in vivo kinetics. Reported here is an additional phase of this protocol conducted to determine the relationship between short-term urinary excretion after a single isotopically labeled dose and various measures of folate nutritional status. It was hypothesized that urinary excretion from a single [glutamate-2H4]folic acid ([2H4]folic acid) dose would increase in proportion to folate nutritional status due to saturable cellular uptake and retention processes along with saturation of renal reabsorption. Each subject was given 1.13 micromol (500 microg) of [2H4]folic acid orally on the morning of d 70 of the study, followed by a complete 24-h urine collection. Urine was analyzed to determine the isotopic enrichment of urinary folate by gas chromatography-mass spectrometry and the concentration of urinary folate by HPLC. Urinary excretion of [2H4]folate was greatest at the 907 nmol/d intake and was positively correlated with serum folate concentration but was not correlated with erythrocyte folate. Excretion of [2H4]folate tended to be greatest when plasma homocysteine concentrations were low (<8 micromol/L), although this relation was not significant. These results suggest that 24-h urinary excretion after a single oral dose of isotopically labeled folate is a functional indicator of folate nutritional status that complements other measures of folate nutriture.

Adult↗
PubMed1998

Assessing condom use practices. Implications for evaluating method and user effectiveness.

BACKGROUND: Consistent and correct condom use remains important to human immunodeficiency virus (HIV) prevention. Although many studies evaluate consistent condom use, few examine how condoms are used during intercourse. GOALS: Assess how user practices affect exposure to risks of pregnancy and infection during condom use. STUDY DESIGN: A cross-sectional survey on condom behaviors in the past month was conducted among 98 male students attending two Georgia universities. RESULTS: Altogether, 35 of 270 total condom uses (13.0%, 95% confidence interval, 7.4-18.5) resulted in potential exposure to sexually transmitted disease and/or HIV infection or pregnancy. Both consistent and inconsistent users were similarly likely to report potential exposures during condom use. CONCLUSION: These findings suggest condom problems occur among both consistent and inconsistent users. Future studies of condom effectiveness must distinguish whether condoms were used both consistently and correctly.

Adolescent↗
PubMed1998

Detection of Mycoplasma pneumoniae in the airways of adults with chronic asthma.

Infection with Mycoplasma pneumoniae has been shown to exacerbate asthma in humans. However, the role of M. pneumoniae in the pathogenesis of chronic asthma has not been defined. Eighteen asthmatics with chronic, stable asthma and 11 nonasthmatic control subjects underwent evaluation of the upper and lower airways and serologic analysis to determine the presence of M. pneumoniae, Chlamydia pneumoniae, and seven respiratory viruses through culture, enzyme-linked immunoassay (EIA) and polymerase chain reaction (PCR). M. pneumoniae was detected by PCR in 10 of 18 asthmatics and one of 11 control subjects (p = 0.02). In nine of the 10 patients, the organism was detected in bronchoalveolar lavage or bronchial biopsies. Seven of 18 asthmatics and one of 11 control subjects were also positive for M. fermentans and M. genitalium by PCR. All patients' cultures, EIAs, and serology were negative for M. pneumoniae. All PCR and cultures were negative for C. pneumoniae, and all EIAs for respiratory viruses were negative in all subjects. Nine asthmatics and one control subject exhibited positive serology for C. pneumoniae (p = 0.05). M. pneumoniae was present in the lower airways of chronic, stable asthmatics with greater frequency than control subjects, and may play a role in the pathogenesis of chronic asthma.

Adult↗
PubMed1997

Thalidomide: lack of mutagenic activity across phyla and genetic endpoints.

The human and rabbit teratogen thalidomide has been tested for mutagenicity in a wide range of assays, ranging from bacterial gene mutation assays conducted in vitro to in vivo cytogenetic assays conducted using rabbits, and including a variety of human-derived tissues. Thalidomide was not mutagenic to 6 strains of Salmonella when tested both in the presence and absence of Aroclor-induced rat liver S9 mix. This inactivity was confirmed in strains TA98 and TA100 using a 1-h pre-incubation assay protocol with the same S9 mix (10% S9), and additionally, in strain TA98 using 3 concentrations of S9 (4%, 10% and 30% S9 in S9 mix). Thalidomide was not clastogenic either to cultured human lymphocytes (whole blood cultures, minus S9 mix) or to Chinese hamster ovary (CHO) cells treated in vitro. Further, no cytotoxicity was observed in purified human lymphocytes when exposed to thalidomide up to the limit of its solubility in the medium in the presence and absence of liver S9 from Aroclor-induced pregnant rabbit. The CHO assays were conducted without metabolic activation and in the presence of a variety of sources of auxiliary metabolic activation (PB/beta NP-induced rat liver S9 mix, pooled male and female human liver S9 mix, uninduced and Aroclor-induced pregnant rabbit liver S9 mix and foetal rabbit S9 mix). Thalidomide did not induce micronuclei in isolated human lymphocytes (minus S9 mix) and it was non-mutagenic to mouse lymphoma L5178Y TK+/- cells when tested to the limits of its solubility in the culture medium (+/- S9 mix). No indication of recombinogenic or clastogenic activity was observed for thalidomide when tested in Drosophila. In addition, it failed to induce chromosome aberrations in grasshopper neuroblasts when tested in the presence and absence of Aroclor-induced rat liver S9 mix. Some unusual chromosome morphologies were observed in the grasshopper cytogenetic preparations indicating a potential of thalidomide to interact with chromosomal proteins. However, this potential was not evident in the human lymphocyte micronucleus assay, and thalidomide was apparently not reactive to the proteins of the mouse skin, as it gave negative results in a mouse local lymph node assay for skin sensitizing agents. Thalidomide was inactive in bone marrow micronucleus assays conducted using males and females from two strains of mice, and female New Zealand white rabbits. It is concluded that thalidomide is neither a mutagen nor an aneugen. This conclusion is discussed within the context of the results of earlier mutagenicity studies, the recent claim that thalidomide may be a heritable germ cell mutagen to humans, and the current interest in thalidomide for the treatment of immune system-related diseases.

Abnormalities, Drug-Induced↗
PubMed1997

Gene structure, cDNA sequence, and expression of murine Bak, a proapoptotic Bcl-2 family member.

To facilitate the creation of Bak knockout mice and the further analysis of this Bcl-2 family member, we have isolated and sequenced the complete mouse Bak cDNA. The cDNA is 2 kb long and shares an overall nucleotide identity to the human Bak cDNA of 62%. The mouse Bak protein is 208 amino acids long with a predicted molecular weight of 23 kDa. The mouse Bak mRNA could be detected in all mouse tissues examined. In addition we mapped the murine bak gene. It consists of six exons spanning about 10 kb on chromosome 17B. The 5' region of the murine bak gene is unmethylated on the dinucleotide CpG in the area around exon 1. Furthermore, it contains potential binding sites for transcription factors such as Sp1 and c-Myb.

Amino Acid Sequence↗
PubMed1997

Blockade of the voltage-gated potassium channel Kv1.3 inhibits immune responses in vivo.

The voltage activated K+ channel (Kv1.3) has recently been identified as the molecule that sets the resting membrane potential of peripheral human T lymphoid cells. In vitro studies indicate that blockage of Kv1.3 inhibits T cell activation, suggesting that Kv1.3 may be a target for immunosuppression. However, despite the in vitro evidence, there has been no in vivo demonstration that blockade of Kv1.3 will attenuate an immune response. The difficulty is due to species differences, as the channel does not set the membrane potential in rodent peripheral T cells. In this study, we show that the channel is present on peripheral T cells of miniswine. Using the peptidyl Kv1.3 inhibitor, margatoxin, we demonstrate that Kv1.3 also regulates the resting membrane potential, and that blockade of Kv1.3 inhibits, in vivo, both a delayed-type hypersensitivity reaction and an Ab response to an allogeneic challenge. In addition, prolonged Kv1.3 blockade causes reduced thymic cellularity and inhibits the thymic development of T cell subsets. These results provide in vivo evidence that Kv1.3 is a novel target for immunomodulation.

Animals↗
PubMed1997

Clinical features and molecular analysis of a family with multiple colon tumours and reduced plasminogen activator activity.

A family is reported in which a pair of brothers has developed recurrent venous thromboses, which have been shown in one brother (the proband) to result from a reduced level of tissue plasminogen activator (t-PA) activity. Both brothers have also developed multiple synchronous and metachronous colorectal adenomas. Other pedigree members have developed colon cancers, but not multiple colonic tumours. We have shown that HNPCC and FAP/AAPC are unlikely causes of the family's phenotypes. Previous studies have found low levels of t-PA in sporadic colon tumours. In this family, mutations in the t-PA gene, at a linked locus, or at a locus controlling t-PA activity/release may modify the colon tumour phenotype to cause multiple lesions.

Adenoma↗
PubMed1997

Measuring cervical ectopy: direct visual assessment versus computerized planimetry.

OBJECTIVE: Cervical ectopy has been identified as a possible risk factor for heterosexual transmission of human immunodeficiency virus. To accurately assess the importance of cervical ectopy, methods for measuring ectopy with precision need to be developed. The objective of this study was to evaluate the reliability of two methods of measuring cervical ectopy: direct visual assessment and computerized planimetry. STUDY DESIGN: Cervical photographs of 85 women without cervical disease were assessed for cervical ectopy by three raters using direct visual assessment and a computer planimetry method. Agreement between the two methods, among the three raters, and among measurements by each rater over time was calculated with use of intraclass correlation coefficients, where 1.0 represents perfect agreement and 0 represents no agreement except by chance. RESULTS: The intraclass correlation coefficient among the three raters (interrater agreement) was 0.58 for direct visual assessment without application of acetic acid to the cervix compared with 0.72 for direct visual assessment with acetic acid and 0.82 for computerized planimetry with acetic acid. The intraclass correlation coefficient among measurements by each rater over time (intrarater agreement) was 0.66 for direct visual assessment without acetic acid compared with 0.77 for direct visual assessment and 0.83 for computerized planimetry after application of acetic acid. When acetic acid was used, the intraclass correlation coefficient between the two methods was 0.69. CONCLUSIONS: Computerized planimetry of cervical photographs may provide the most consistent estimate of the percent of ectopy. However, if time and resources make the use of computer planimetry difficult, direct visual assessment after application of 5% acetic acid appears to provide comparable estimates.

Cervix Uteri↗
PubMed1997

Early induction of mRNA for calbindin-D28k and BDNF but not NT-3 in rat hippocampus after kainic acid treatment.

The influence of kainic acid (KA), which induces acute seizures, on expression of mRNA for the calcium-binding protein, calbindin-D28k, brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and early-response genes [c-fos, zif268 (NGFI-A), nur77 (NGFI-B)] was examined in rat hippocampus by Northern blot analysis. A significant increase (3.2-fold) in BDNF mRNA was observed 1 h after KA injection (12 mg/kg i.p.) and peak expression (9.4-fold) occurred 3 h after KA. The induction of BDNF mRNA was preceded by the induction of c-fos, mRNA (30 min after KA) and was followed by the induction of calbindin-D28k mRNA (3.5-fold 3 h after KA; a maximal response was at 3-6 h after KA). Region-specific changes, analyzed by immunocytochemistry and in situ hybridization, indicated that the most dramatic increases in calbindin protein and mRNA after KA treatment were in the dentate gyrus. Although calbindin-D28k and BDNF mRNAs were induced, a 3.4-3.8-fold decrease in NT-3 mRNA was observed by Northern analysis 3-24 h after KA treatment. Calbindin-D28k gene expression was also examined in rats with a chronic epileptic state characterized by recurrent seizures established with an episode of electrical stimulation-induced status epilepticus (SE). When these animals were examined 30 days post-SE, no changes in hippocampal calbindin-D28k mRNA were observed. Our findings suggest that the induction of calbindin-D28k mRNA (which may be interrelated to the induction of BDNF mRNA) is an early response which may not be related to enhanced neuronal activity or seizures per se, but rather to maintaining neuronal viability.

Animals↗
PubMed1997

From vision to reality--managing change in the provision of library and information services to nurses, midwives, health visitors and PAMs: (professions allied to medicine) a case study of the North Thames experience with the Inner London Consortium.

One of the North Thames' pioneering consortia, the Inner London Consortium (ILC) is a complex body which includes NHS Trusts with teaching hospital university connections, community-based Trusts and general hospital acute Trusts. Within the consortium there are 12,000 trained nurses, midwives, health visitors and other professional staff working in the professions allied to medicine (PAMs), all of whom require access to and provision of appropriate library information services. In 1994, taking into account experiences elsewhere in the Region and nationally, it became clear that library issues were complex and would become acute with the move of nursing libraries from ILC Trust sites over a very short timescale. A report on the issues commissioned by the Consortium recommended that a library project, which built on existing NHS Trust PGMDE funded library resources and moved these to a multidisciplinary base to serve the consortium membership, be implemented. The objective of providing access to library information services for nurses and PAMs was achieved. Successes that emerged from the implementation included: The registration in Trust libraries of almost 12 000 new members within the initial 6-month monitoring period. The development of service level agreements and standards for the delivery of services to these new user groups. This paper describes the processes behind these significant and complex changes.

Allied Health Personnel↗
PubMed1997

Access files.

Explore the source record for details and available documents.

Counseling↗