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Biomedical subjects

N Middleton

Publications and source records attributed to N Middleton.

9 recordsLinked to original sources
PubMed2005

Cardiovascular autonomic control in endurance-trained and sedentary young women.

This study aimed to investigate whether endurance-trained (ET) female athletes demonstrate differences in cardiovascular autonomic control compared with sedentary controls. Eighteen healthy eumenorrhoeic subjects, nine trained (22.4 +/- 3 years) and nine sedentary (21.0 +/- 1 years), volunteered for the study. Heart rate variability (HRV) and cardiovagal baroreflex sensitivity (BRS) measures were adopted to assess cardiac autonomic control. HRV was recorded for 30 min under both controlled (0.25 Hz) and spontaneous breathing conditions. Cardiovagal BRS was assessed using the Valsalva manoeuvre. Analysis of the HRV showed a longer R-R interval (1089 +/- 114 ms versus 865 +/- 100 ms; P<0.001) in the trained subject but only in the spontaneous breathing condition. Conversely, athletes exhibited higher normalized low frequency (LFnu, 44.2 +/- 8.5% versus 29.5 +/- 6.8%; P<0.001) and lower normalized high frequency (HFnu, 55.8 +/- 8.5% versus 69.9 +/- 7.7%; P<0.01) only during the controlled breathing condition, consequently the LF/HF ratio was also higher in the trained group in the same condition (0.83 +/- 0.3 versus 0.47 +/- 0.1, P<0.01). BRS was significantly lower in the ET group (7.95 +/- 4.0 ms mmHg(-1) versus 13.00 +/- 4.4 ms mmHg(-1), P<0.05). Further studies are necessary to elucidate the potential role of training and altered hormonal profile in the genesis of the observed differences in cardiovascular autonomic control between highly trained and sedentary control female subjects.

Adolescent↗
PubMed2004

Errors associated with milk cell counting.

The accuracy of somatic cell counts in milk samples was investigated in four studies. First, the counts recorded by one milk buyer in one supply over six months ranged from 105,000 to 401,000 cells/ml with no apparent changes in the volume of milk consigned or the level of mastitis in the herd that would explain this wide range. Secondly, the counts in daily samples from one bulk milk supply for 28 days ranged from 84,000 to 282,000 cells/ml, again with no apparent changes in the performance of the herd to explain the wide range. Thirdly, the replicated counts recorded for one sample by three separate laboratories agreed closely; however, when a sample with a high cell count was interspersed then two of the three laboratories reported high cell counts suggestive of 'carry-over' in excess of the 2 per cent 'allowable' Finally, cell count data from three separate laboratories on samples from 21 cows for 33 days revealed problems with the misidentification of samples on the farm in 1 per cent of the samples, and misidentification and mishandling of 1 to 2.6 per cent of the samples in the laboratories. All three laboratories differentiated samples from cows with subclinical and clinical mastitis, but the mean cell count of the uninfected cows varied between the laboratories with one of them recording statistically significantly higher counts over the period.

Animals↗
PubMed2004

Whole blood and mononuclear cell glutathione response to dietary whey protein supplementation in sedentary and trained male human subjects.

Sedentary male subjects (n=9) on a controlled diet were fed two doses (0.8 or 1.6 g/kg body mass) of a whey protein isolate (WPI), in addition to an isocaloric placebo; blood samples were drawn over a 4-h period and glutathione concentration determined. There was no effect of the supplementation at either level over the 4-h sampling period. The effects of a WPI supplemented diet on glutathione concentrations in whole blood as well as peripheral mononuclear cell populations were also investigated over a 6-week period in male subjects (n=18) involved in arduous aerobic training; blood was collected prior to and following a 40 km simulated cycling trial. The aerobic training period resulted in significantly lower glutathione concentrations in whole blood, an effect that was mitigated by WPI supplementation. A significant increase in mononuclear cell glutathione was also observed in subjects receiving the WPI supplement following the 40 km simulated cycling trial.

Adult↗
PubMed2002

Socioeconomic inequality and meningococcal disease.

Incidence of meningococcal disease was associated with socioeconomic deprivation across a rural English region. In young children the incidence was twice as high in the most deprived compared with the least deprived electoral wards. By addressing social inequalities the incidence of this serious infection could be reduced.

Child↗
PubMed2001

Secular trends in antidepressant prescribing in the UK, 1975-1998.

BACKGROUND: We have examined secular trends in age- and sex-specific prescribing of antidepressants to determine whether these mirror changes in other population measures of mental health. METHOD: An analysis was carried out of age- and sex-specific rates of antidepressant prescribing by a representative sample or panel of UK general practitioners (GPs) in the period 1975-1998. RESULTS: The number of antidepressant prescriptions issued increased more than twofold in the period 1975-1998 and, in 1998, a total of 23.4 million antidepressant prescriptions were issued by GPs in the United Kingdom. Rates of antidepressant prescribing increased markedly in all age and sex groups with as much as a threefold increase in the older age groups. With the exception of 12-19-year-olds, these increases have been more marked in males, although absolute levels of prescribing are still at least two times higher in females. CONCLUSIONS: Antidepressant prescribing has increased in all age and sex groups. This indicates either that there have been changes in the presentation, recognition and management of depression in general practice or that the prevalence of depression has increased, or a combination of these two phenomena. The higher prescribing rate in females is in keeping with evidence from psychiatric morbidity surveys suggesting that women experience higher levels of psychiatric morbidity than men. Decreases in the ratio of female to male prescribing, however, support other data indicating that, relative to females, the mental health of young males has declined in recent years. Changes in patterns of help-seeking may also contribute to the observed trends.

Adolescent↗
PubMed2000

Method availability and the prevention of suicide--a re-analysis of secular trends in England and Wales 1950-1975.

BACKGROUND: In England and Wales in the 1960s there were marked declines in suicide rates. These reductions were partly attributable to the detoxification of the domestic gas supplies; however, their extent varied by age and gender, with the most striking effects seen in older men. The objective of this study was to investigate method-specific trends in suicide between 1950 and 1975 to elucidate possible explanations for the patterns seen in different demographic groups. METHODS: An analysis of age-standardised method-specific suicide rates for England and Wales between 1950 and 1975 was carried out using routinely available mortality and population statistics. RESULTS: As has previously been shown, there were marked reductions in suicides by gassing in men and women of all ages between 1960 and 1975. In women and younger men, the effects of these reductions on overall suicide rates were partially offset by rises in drug overdose deaths (method substitution), but there were no immediate increases in the use of other suicide methods. In contrast, in older men, reductions in suicide by gassing were accompanied by only a slight increase in overdose suicides as well as reductions in rates of suicide using all other methods. The modest rise in overdose fatalities in older men occurred despite the fact that they were more often prescribed barbiturates and tricyclic antidepressants than younger men. CONCLUSIONS: Accessibility to and the lethality of particular methods of suicide may have profound effects on overall suicide rates. Such effects appear to depend upon the popularity of the method and the extent to which alternative methods that are acceptable to the individual are available. Social and psychological interpretations of fluctuations in suicide rates should only be made after assessing the possible contribution to these of changes in method availability and lethality.

Adolescent↗
PubMed1998

Immunostimulation of murine spleen cells by materials associated with bovine milk protein fractions.

Purified bovine milk proteins that were added to cultures of murine spleen cells significantly increased cell proliferation and production of immunoglobulin M. Casein and a whey mixture consisting of alpha-lactalbumin, bovine serum albumin, bovine gamma globulin, and beta-lactoglobulin (beta-LG) were stimulatory. Of the three beta-LG preparations that are commercially available (beta-LG containing variants A and B, purified variant A, and purified variant B), the unseparated mixture containing both the A and B variants showed the most immunomodulatory activity. Both alkaline treatment and trypsin digestion of the beta-LG preparation markedly reduced its effectiveness. Polymyxin B, while greatly diminishing the stimulatory effect of lipopolysaccharide, had no significant effect on either the enhancement of cell proliferation or the enhancement of immunoglobulin production by beta-LG. In the presence of S-(n-butyl)-homocysteine sulfoxamine, the stimulatory effect of beta-LG on cell proliferation and IgM production in vitro was markedly reduced.

Animals↗