P-glycoprotein and bilirubin disposition

P-glycoprotein (Pgp), an ATP-dependent plasma membrane efflux pump, is expressed in abundance on the luminal aspect of brain capillary endothelial cells and astrocytes of the blood-brain barrier where it limits the passage of a variety of lipophilic substrates into the central nervous system. This review summarizes current evidence characterizing (1) unconjugated bilirubin as a potential substrate for Pgp and (2) the ontogeny of Pgp expression at the blood-brain barrier and apical brush border epithelium of the gastrointestinal tract, findings that may provide insights regarding the disposition of bilirubin in immature subjects.

Are the effects of psychosocial exposures attributable to confounding? Evidence from a prospective observational study on psychological stress and mortality

STUDY OBJECTIVES

To examine the association between perceived psychological stress and cause specific mortality in a population where perceived stress was not associated with material disadvantage.

DESIGN

Prospective observational study with follow up of 21 years and repeat screening of half the cohort five years from baseline. Measures included perceived psychological stress, coronary risk factors, and indices of lifecourse socioeconomic position.

SETTING

27 workplaces in Scotland.

PARTICIPANTS

5388 men (mean age 48 years) at first screening and 2595 men at second screening who had complete data on all measures.

MAIN OUTCOME MEASURES

Hazard ratios for all cause mortality and mortality from cardiovascular disease (ICD9 390-459), coronary heart disease (ICD9 410-414), smoking related cancers (ICD9 140, 141, 143-9, 150, 157, 160-163, 188 and 189), other cancers (ICD9 140-208 other than smoking related), stroke (ICD9 430-438), respiratory diseases (ICD9 460-519) and alcohol related causes (ICD9 141, 143-6, 148-9, 150, 155, 161, 291, 303, 571 and 800-998).

RESULTS

At first screening behavioural risk (higher smoking and alcohol consumption, lower exercise) was positively associated with stress. This relation was less apparent at second screening. Higher stress at first screening showed an apparent protective relation with all cause mortality and with most categories of cause specific mortality. In general, these estimates were attenuated on adjustment for social position. This pattern was also seen in relation to cumulative stress at first and second screening and with stress that increased between first and second screening. The pattern was most striking with regard to smoking related cancers: relative risk high compared with low stress at first screening, age adjusted 0.64 (95% CI 0.42, 0.96), p for trend 0.016, fully adjusted 0.69 (95% CI 0.45, 1.06), p for trend 0.10; high compared with low cumulative stress, age adjusted 0.69 (95% CI 0.44, 1.09), p for trend 0.12, fully adjusted 0.76 (95% CI 0.48, 1.21), p for trend 0.25; increased compared with decreased stress, age adjusted 0.65 (95% CI 0.40, 1.06), p for trend 0.09, fully adjusted 0.65 (95% CI 0.40, 1.06), p for trend 0.08.

CONCLUSIONS

This implausible protective relation between higher levels of stress, which were associated with increased smoking, and mortality from smoking related cancers, was probably a product of confounding. Plausible reported associations between psychosocial exposures and disease, in populations where such exposures are associated with material disadvantage, may be similarly produced by confounding, and of no causal significance.

The great divide

In November 1937, a group of masked nurses marched through London's streets, carrying placards proclaiming their demand for improved pay and conditions. The campaign they and like-minded nurses fought was to have far reaching consequences. Trade unionism was established elsewhere in nursing, but this was to be an important first step in breaking down the hegemony of the professional associations in general nursing as well as the service's dominant culture of subordination and loyalty to a mythic but compelling vocational ideal.

The socioeconomic position of employed women, risk factors and mortality

Many studies have demonstrated the graded association between socioeconomic position and health. Few of these studies have examined the cumulative effect of socioeconomic position throughout the lifecourse, and even fewer have included women. Those that have explored gender differences affirm the importance of studying the factors that predict women and men's health separately. This study addresses the associations between cross-sectional and longitudinal socioeconomic position, risk factors for cardiovascular disease and mortality from various causes. Analyses are based on data from a cohort of working Scottish women recruited between 1970 and 1973. Five socioeconomic measures were explored in relation to diastolic blood pressure, plasma cholesterol concentration, body mass index, forced expiratory volume in 1 s (FEV1). amount of recreational exercise taken, cigarette smoking and alcohol consumption. In general, for each of the five measures of socioeconomic position, there were significant differences in at least one of the age-adjusted physiological risk factors for cardiovascular disease (diastolic blood pressure, plasma cholesterol concentration, body mass index, FEV1). There were also significant differences in the percentage of current cigarette smokers according to different measures of socioeconomic position, although this was not the case for the other behavioural risk factors for cardiovascular disease (amount of recreational exercise taken, and alcohol consumption). Measures of socioeconomic position were also examined in relation to cause of death for the women who died before 1 January 1999. After adjusting for age and risk factors, a composite measure of lifetime socioeconomic experience was a more potent predictor of all cause mortality and mortality from cardiovascular disease than other measures of socioeconomic position. It therefore seems that conventional measurcs of socioeconomic position, estimated at one point in time, do not adequately capture the effects of socioeconomic circumstances on the risk of mortality among employed women. Thus, a broader range of explanatory factors for mortality differentials than currently exists must be considered, and must include consideration of factors operating throughout the lifecourse.

Milk, coronary heart disease and mortality

STUDY OBJECTIVE

To study the association between reported milk consumption and cardiovascular and all cause mortality.

DESIGN

A prospective study of 5765 men aged 35-64 at the time of examination.

SETTING

Workplaces in the west of Scotland between 1970 and 1973.

PARTICIPANTS

Men who completed a health and lifestyle questionnaire, which asked about daily milk consumption, and who attended for a medical examination.

MAIN RESULTS

150 (2.6%) men reported drinking more than one and a third pints a day, Some 2977 (51.6%) reported drinking between a third and one and a third pints a day and 2638 (45.8%) reported drinking less than a third of a pint a day. There were a total of 2350 deaths over the 25 year follow up period, of which 892 deaths were attributed to coronary heart disease. The relative risk, adjusted for socioeconomic position, health behaviours and health status for deaths from all causes for men who drank one third to one and a third pints a day versus those who drank less than a third of a pint was 0.90 (95% CI 0.83, 0.97). The adjusted relative risk for deaths attributed to coronary heart disease for men who drank one third to one and a third pints a day versus those who drank less than one third of a pint was 0.92 (95% CI 0.81, 1.06).

CONCLUSIONS

No evidence was found that men who consumed milk each day, at a time when most milk consumed was full fat milk, were at increased risk of death from all causes or death from coronary heart disease.

Ontogeny of P-glycoprotein in mouse intestine, liver, and kidney

BACKGROUND

P-glycoprotein (Pgp) is an ATP-dependent, integral plasma-membrane efflux pump that is constitutively expressed on (i) adult apical brush-border epithelial cells of the intestine, (ii) the bile canalicular face of hepatocytes, and (iii) the brush border epithelium of renal proximal tubules. This Pgp tissue distribution and localization affects the absorption, distribution, metabolism, and excretion of Pgp substrates. Little is known regarding the ontogeny of Pgp expression in these tissues.

METHODS

Postnatal expression of Pgp on brush border membranes of small intestine, liver, and kidney as a function of maturity from birth through adulthood was determined using Western immunoblotting and immunohistochemical techniques. Tissue was isolated from FVB mice at four different ages: day of life 0 (D0), day of life 7 (D7), day of life 21 (D21), and adult (Ad). The relative expression of Pgp protein on Western immunoblots was assessed by scanning densitometry and indexed as a percentage (mean+/-SEM) of the adult levels.

RESULTS

On Western immunoblots, Pgp expression was limited at birth (19+/-6% of Ad) and increased significantly with maturation in intestine (ANOVA, P<0.005). In contrast, hepatic (113+/-12% of Ad) and renal (96+/-15% of Ad) Pgp expression were at adult levels at birth. The tissue-specific developmental pattern of Pgp expression was confirmed by immunohistochemistry.

CONCLUSIONS

We conclude that Pgp is expressed in a tissue-specific and developmentally regulated fashion and speculate that developmental modulation of intestine-Pgp expression may affect the oral bioavailability of Pgp substrates.

Reversible male sterility: a novel system for the production of hybrid corn

Hybrid corn seed is traditionally produced using either mechanical/hand detasseling or cytoplasmic male sterility, or a combination of both. In recent years, the development of transgenic systems to produce hybrid seed in several crops has attracted much attention. Here we describe a transgenic mechanism for production of hybrid corn, reversible male sterility (RMS), in which the action of the cytotoxic gene used to introduce male sterility is suppressed by the application of a chemical to the plant. Reversion of the sterility allows the RMS parent to be self-fertilized, a step which overcomes the need to remove fertile sib plants prior to making the hybrid cross. The key enabling technology in RMS is the use of a plant gene promoter which is specifically induced by chemical application. We have exemplified RMS in transgenic corn plants and believe that it provides specific benefits in the production of hybrid corn seed.

Dendritic cells infected with recombinant fowlpox virus vectors are potent and long-acting stimulators of transgene-specific class I restricted T lymphocyte activity

The identification of dendritic cells (DC) as the major antigen-presenting cell type of the immune system, combined with the development of procedures for their ex vivo culture, has opened possibilities for tumour immunotherapy based on the transfer of recombinant tumour antigens to DC. It is anticipated that the most effective type of response would be the stimulation of specific, MHC class I restricted cytotoxic T lymphocytes capable of recognising and destroying tumour cells. In order to make this approach possible, methods must be developed for the transfer of recombinant antigen to the DC in such a way that they will initiate an MHC class I restricted response. Here, we demonstrate that murine DC infected with a recombinant fowlpox virus (rFWPV) vector stimulate a powerful, MHC class I restricted response against a recombinant antigen. A rFWPV containing the OVA gene was constructed and used to infect the DC line DC2.4. The infected DC2.4 cells were found to stimulate the T-T cell hybridoma line RF33. 70, which responds specifically to the MHC class I restricted OVA peptide SIINFEKL. The stimulatory ability of the rFWPV-infected DC2.4 cells lasted for at least 72 h after infection and was eventually limited by proliferation of uninfected cells. By comparison, DC2.4 cells pulsed with synthetic SIINFEKL peptide stimulated RF33.70 well initially, but the stimulatory ability had declined to zero by 24 h after pulsing. FWPV infection of DC2.4 up-regulated MHC and costimulatory molecule expression. rFWPV was also found to infect both immature and mature human DC derived from cord blood CD34+ progenitors and express transgenes for up to 20 days after infection. We conclude that rFWPV shows promise as a vector for antigen gene transfer to DC in tumour immunotherapy protocols.

Searching for kinesin's mechanical amplifier

Kinesin, a microtubule-based motor, and myosin, an actin-based motor, share a similar core structure, indicating that they arose from a common ancestor. However, kinesin lacks the long lever-arm domain that is believed to drive the myosin power stroke. Here, we present evidence that a much smaller region of ca. 10-40 amino acids serves as a mechanical element for kinesin motor proteins. These 'neck regions' are class conserved and have distinct structures in plus-end and minus-end-directed kinesin motors. Mutagenesis studies also indicate that the neck regions are involved in coupling ATP hydrolysis and energy into directional motion along the microtubule. We suggest that the kinesin necks drive motion by undergoing a conformational change in which they detach and re-dock onto the catalytic core during the ATPase cycle. Thus, kinesin and myosin have evolved unique mechanical elements that amplify small, nucleotide-dependent conformational changes that occur in their similar catalytic cores.

Height and risk of death among men and women: aetiological implications of associations with cardiorespiratory disease and cancer mortality

OBJECTIVES

Height is inversely associated with cardiovascular disease mortality risk and has shown variable associations with cancer incidence and mortality. The interpretation of findings from previous studies has been constrained by data limitations. Associations between height and specific causes of death were investigated in a large general population cohort of men and women from the West of Scotland.

DESIGN

Prospective observational study.

SETTING

Renfrew and Paisley, in the West of Scotland.

SUBJECTS

7052 men and 8354 women aged 45-64 were recruited into a study in Renfrew and Paisley, in the West of Scotland, between 1972 and 1976. Detailed assessments of cardiovascular disease risk factors, morbidity and socioeconomic circumstances were made at baseline.

MAIN OUTCOME MEASURES

Deaths during 20 years of follow up classified into specific causes.

RESULTS

Over the follow up period 3347 men and 2638 women died. Height is inversely associated with all cause, coronary heart disease, stroke, and respiratory disease mortality among men and women. Adjustment for socioeconomic position and cardiovascular risk factors had little influence on these associations. Height is strongly associated with forced expiratory volume in one second (FEV1) and adjustment for FEV1 considerably attenuated the association between height and cardiorespiratory mortality. Smoking related cancer mortality is not associated with height. The risk of deaths from cancer unrelated to smoking tended to increase with height, particularly for haematopoietic, colorectal and prostate cancers. Stomach cancer mortality was inversely associated with height. Adjustment for socioeconomic position had little influence on these associations.

CONCLUSION

Height serves partly as an indicator of socioeconomic circumstances and nutritional status in childhood and this may underlie the inverse associations between height and adulthood cardiorespiratory mortality. Much of the association between height and cardiorespiratory mortality was accounted for by lung function, which is also partly determined by exposures acting in childhood. The inverse association between height and stomach cancer mortality probably reflects Helicobacter pylori infection in childhood resulting in--or being associated with--shorter height. The positive associations between height and several cancers unrelated to smoking could reflect the influence of calorie intake during childhood on the risk of these cancers.