1 School of Kinesiology and Health Science, Faculty of Health, York University, Toronto, Ontario; and 2 Children's Exercise and Nutrition Centre, McMaster University, Hamilton, Ontario, Canada
...Submitted 26 November 2007
; accepted in final form 4 June 2008
The range of exercise intensities that elicit high fat oxidation rates (FOR) in youth and the influence of pubertal status on peak FOR are unknown. In a longitudinal design, we compared FOR over a range of exercise intensities in a small cohort of developing prepubertal male subjects. Five boys all at Tanner stage 1 (ages 11–12 yr) and nine men (ages 20–26 yr) underwent an incremental cycle ergometry test to volitional exhaustion. FOR curves were determined from indirect calorimetry during the final 30 s of each increment. The same protocol was duplicated annually in the boys as they progressed through puberty. The peak FOR was considerably higher ( P < 0.05) in boys at Tanner 1 (8.6 ± 1.5 mg·kg lean body mass –1 ·min –1 ) (mean ± SD) compared with men (4.2 ± 1.1 mg·kg lean body mass –1 ·min –1 ). FOR dropped as boys developed through puberty (Tanner 2/3 peak rate = 7.6 ± 0.6 mg·kg lean body mass –1 ·min –1 ; Tanner 4 peak rate = 5.4 ± 1.8 mg·kg lean body mass –1 ·min –1 , main effect of Tanner stage; P < 0.05) to the levels found in men (not significant). The exercise intensity that elicited peak FOR was higher in the boys at Tanner 1 56 ± 6% peak aerobic power ( O 2 peak ) than in men (31 ± 4% O 2 peak ) ( P < 0.001). This value tended to decrease by Tanner stage 4 (45 ± 10% O 2 peak , main effect of Tanner stage; P = 0.06). We conclude that, compared with men, prepubertal boys have higher relative FOR throughout a wide range of exercise intensities and that FOR drops as boys develop through puberty.
children; adults; substrate utilization; indirect calorimetry; fat metabolism; cycling
Address for reprint requests and other correspondence: M. C. Riddell, School of Kinesiology and Health Science, 4700 Keele St., Toronto, ON, Canada M3J 1P3 (e-mail: mriddell{at}yorku.ca )
Aim
To determine the effects of acute caffeine ingestion on glycaemia during moderate to vigorous intensity aerobic exercise and in recovery in individuals with Type 1 diabetes.
Methods
A total of 13 ...patients with Type 1 diabetes eight women, five men: mean ± sd age 25.9 ± 8.8 years, BMI 71.9 ± 11.0 kg, maximal oxygen consumption 46.6 ± 12.7 ml/kg/min, body fat 19.9 ± 7.2%, duration of diabetes 14.4 ± 10.1 years and HbA1c 55 ± 8 mmol/mol (7.4 ± 0.8%) were recruited. Participants ingested capsules that contained gelatin or pure caffeine (6.0 mg/kg body mass) and performed afternoon exercise for 45 min at 60% maximal oxygen consumption on two separate visits with only circulating basal insulin levels.
Results
The main finding was that a single caffeine dose attenuates the drop in glycaemia by 1.8 ± 2.8 mmol/l compared with placebo intake during exercise (P=0.056). Continuous glucose monitoring data, however, showed that caffeine was associated with elevated glycaemia at bedtime after exercise, compared with placebo, but lower glucose concentrations in the early morning the next day.
Conclusions
Caffeine intake should be considered as another strategy that may modestly attenuate hypoglycaemia in individuals with Type 1 diabetes during exercise, but should be taken with precautionary measures as it may increase the risk of late‐onset hypoglycaemia.
What's new?
We examined the role of caffeine ingestion on exercise‐associated hypoglycaemia in individuals with Type 1 diabetes.
We found that caffeine intake increased hypoglycaemia awareness and elevated blood glucose concentrations during 45‐min exercise in patients with diabetes.
We also found that a single caffeine dose did not protect against nocturnal hypoglycaemia in the early‐morning hours and may, in fact, increase the risk.
The aim of this study was to identify factors associated with awareness, treatment and control of hypertension in a rural setting in India. Following screening of the population, all individuals with ...hypertension (blood pressure (BP) ⩾140/90 mm Hg or taking antihypertensive medications) were invited to participate in this study. We measured BP, height, weight, skinfolds, waist and hip circumference, and administered a questionnaire to obtain information regarding socioeconomic and behavioural characteristics. Multivariable logistic regression was used to determine factors associated with awareness, treatment and control of hypertension. We recruited 277 individuals with hypertension. Awareness (43%), treatment (33%) and control (27%) of hypertension were poor. Greater distance to health services (odds ratio (OR) 0.56 (95% confidence interval (CI)) 0.32-0.98) was associated with poor awareness of hypertension while having had BP measured within the previous year (OR 4.72, 95% CI 2.71-8.22), older age and greater per cent body fat were associated with better awareness. Factors associated with treatment of hypertension were having had BP measured within the previous year (OR 6.18, 95% CI 3.23-11.82), age ⩾65 years, physical inactivity and greater per cent body fat. The only factor associated with control of hypertension was greater per cent body fat (OR 1.05, 95% CI 1.01-1.11). Improving geographic access and utilisation of health services should improve awareness and treatment of hypertension in this rural population. Further research is necessary to determine drivers of control.
Many transgenic plant studies use constitutive promoters to express transgenes. For certain genes, deleterious effects arise from constant expression in all tissues throughout development. We ...describe a chemically inducible plant gene expression system, with negligible background activity, that obviates this problem. We demonstrate its potential by showing inducible manipulation of carbon metabolism in transgenic plants. Upon rapid induction of yeast cytosolic invertase, a marked phenotype appears in developing leaves that is absent from leaves that developed before induction or after it has ceased.
Summary
We describe a chemically induced gene control mechanism for plants based on the ALCR transcription factor and
alcA
promoter of
Aspergillus nidulans
, which we have called the
alc
system. ...Ethanol, the chemical inducer, is not toxic at levels required for induction, and can be applied to the plants by spraying, root drenching and addition to liquid growth media. The
alc
system is very sensitive to ethanol and the induction is rapid; 0.01% (1.7 mM) ethanol in liquid growth media initiates chloramphenicol acetyl transferase (CAT) reporter gene expression within 4 h, with maximal expression occurring after 4 days. In the complete absence of ethanol, there is no detectable expression of CAT, nor do we observe induction in plants subjected to wound, cold or drought stress, or following treatment with either salicylic acid or methyl jasmonate. However, extreme anoxia resulting in elevated levels of alcohol dehydrogenase activity in both roots and leaves gave substantial induction of CAT in leaves but not in roots. We believe that the
alc
system will have broad utility in the exogenous control of plant gene expression in pure science and that it also has considerable potential in agriculture.
Recent studies have shown that exposed, in vitro-derived embryos remain contaminated with bovine viral diarrhea virus (BVDV) after washing. However, introduction of a Genotype II versus Genotype I ...strain of BVDV into an IVF system was reported to provide greater potential for transmission of disease. The primary objective of this study was to compare the potentials for different strains of noncytopathic BVDV to replicate in an IVF system, associate with IVF embryos and infect co-cultured cells via association with washed embryos. The secondary objective was to compare the effect of different strains of BVDV on embryonic development. Two Genotype I (SD-1 and NY-1) and 2 Genotype II (CD-87 and PA-131) strains of BVDV were evaluated. After IVM and IVF of oocytes, presumptive zygotes were washed and transferred into in vitro cultures containing uterine tubal cells (UTC) and medium that was free of BVDV-neutralizing activity. Immediately before addition of zygotes, the cultures were inoculated with 10
5 cell culture infective doses (50%, CCID
50) of a strain of BVDV or maintained as a negative control. Cultures of zygotes were then incubated for 7 d. Embryonic development was observed on Days 3 and 7, and attempts were made to isolate BVDV from UTC and medium on Day 7. Also on Day 7, groups of intact, washed blastocysts were either transferred into virus-free secondary cultures containing UTC or sonicated with sonicate fluid assayed by both virus isolation and single-closed-tube reverse transcription nested polymerase chain reaction (RT-nPCR). After 3 d in secondary culture, hatched embryos were enumerated, and medium from the cultures, washed UTC and embryos were tested for BVDV by virus isolation. In addition, washed UTC and embryos were tested for BVDV using RT-nPCR. All strains of BVDV persisted and replicated in the embryo culture environment, but cleavage beyond the 4-cell stage, blastocyst development and hatching varied among cultures contaminated with different strains of virus. Further, the quantity of BVDV associated with washed embryos from both initial and secondary cultures varied among strains, but the variation was unrelated to difference in genotype (SD-1 and PA-131 greater than NY-1 and CD-87). Although all strains of BVDV replicated in UTC in the initial in vitro cultures and remained associated with washed blastocysts, susceptible UTC in the secondary in vitro cultures were seldom infected by any strain of virus.
Bovine viral diarrhea virus (BVDV) has been shown to replicate in embryo culture systems and remain associated with bovine embryos developing in vitro. In this study, novel antiviral agents were ...evaluated for capability to inhibit replication of BVDV without affecting embryonic development. Serial concentrations of 2-5(6)-{2-imidazolinyl}-2-benzimidazolyl-5-(4-aminophenyl)furan (DB456) or 2-(4-2-imidazolinylphenyl)-5-(4-methoxyphenyl)furan (DB606) were prepared in IVC medium. Then, bovine uterine tubal epithelial cells (UTC) were placed in IVC media with varying concentrations of DB456 or DB606. Within 1
h, a genotype I or II strain of BVDV was added to the cultures. Cultures were maintained for 7 days. Infectious virus was quantitated in IVC media collected on days 3 and 7 and in UTC lysates harvested on day 7. The effective antiviral concentrations of DB606 were much lower than effective antiviral concentrations of DB456. In subsequent experiments, IVF presumptive zygotes were cultured in IVC medium with or without DB456 or DB606 at multiple concentrations for 7 days to evaluate effect of the compound on conceptus development. On day 7, stage of embryonic development was observed, and blastocysts were harvested and stained using Hoechst 33342 to enumerate embryonic cells. While DB456 inhibited blastocyst development, DB606 at 20 times the effective antiviral concentration did not hinder blastocyst development or reduce the mean number of cells per blastocyst. These preliminary results indicated that bovine embryo cultures might be safely supplemented with effective concentrations of an antiviral agent.
Lifestyle changes that include a nutritionally balanced diet and increased physical activity (PA) are effective intervention options for persons with prediabetes who want to prevent progression to ...type 2 diabetes mellitus. Although nutritional counseling is standard practice for patients in a clinical setting, an individualized PA prescription, including recommendations on the type, frequency, duration, and intensity, is much less likely to occur. This is surprising because lifestyle modifications including a PA program are at least as effective in diabetes prevention as any single pharmacological agent. The success of regular PA in improving glycemic control in persons with either prediabetes or type 2 diabetes likely results from adaptations that occur in several organs and tissues, including adipose, skeletal muscle, liver, and pancreas. Increased insulin sensitivity is an important link between increased PA, body composition, and metabolic health, and it is at this link where increases in PA and energy expenditure exert much of their effect on preventing metabolic disorders and improving symptoms of existing disease. In addition to improving insulin sensitivity, regular PA has several cardioprotective effects, especially for persons with metabolic dysfunction, and has been shown to elicit minimal adverse events in these populations. Effective PA prescription is contingent on an understanding of the underlying physiological adaptations and the differing responses to diverse modes and intensities of PA. This article highlights recent findings on the beneficial role of regular PA for improving and/or maintaining insulin sensitivity in persons with prediabetes. We also provide an evidence-informed prescription for the type, intensity, and duration of both resistance and aerobic PA in persons with prediabetes.
In vitro embryo production has been used extensively in research and is now offered as a commercial service, yet the hazards of introducing specific infectious agents into in vitro embryo production ...systems have not been completely defined. The introduction of noncytopathic bovine viral diarrhea virus (BVDV) is a special concern. One objective of this study was to determine if noncytopathic BVDV-infected uterine tubal cells in IVF and IVC systems affected the rate of cleavage and development. An additional objective was to determine if either degenerated ova or embryos produced in the presence of the infected cells had virus associated with them after washing. Follicular oocytes (n = 645) collected from slaughterhouse ovaries were matured and fertilized in vitro, and presumptive zygotes were cultured for 7 d. Primary cultures of uterine tubal cells for use during IVF and IVC were divided into 2 groups. One-half of the cultures was infected with noncytopathic BVDV while the other half was not exposed to the virus. Approximately equal groups of mature oocytes were inseminated, and the presumptive zygotes were cultured with infected or noninfected uterine tubal cells. After 7 d in IVC, zona pellucida-intact (ZP-I) morulae and blastocysts and degenerated ova were washed and assayed for the presence of infectious virus. Infections of uterine tubal cells were not apparent and did not reduce rates of cleavage and development (P > 0.05; Chi-square test for heterogeneity). After washing, BVDV was isolated at a significantly higher rate from groups of virus-exposed degenerated ova (79%) than from individual virus-exposed morulae and blastocysts (37%; P = 0.0002; Mantel-Haenszel summary, Chi-square).
Sensitive RT-nPCR assays can be used for the rapid detection of viruses. The objective of this research was to validate an RT-nPCR assay for detection of BVDV associated with various samples ...collected from an IVF system.
In 12 research replicates, we maintained matured COCs as negative controls or exposed them to 1 of 4 noncytopathic strains (SD-1, NY-1, CD-87, or PA-131) of BVDV for 1 h immediately before IVF. After 4 d of IVC, we harvested groups of 5 nonfertile ova or degenerated embryos (NFD) and some associated cumulus cells and transferred developing embryos and the remaining cumulus cells into secondary IVC drops. On the seventh d of IVC, cumulus cells, groups of 5 washed NFD and groups of 5 developed, washed embryos were harvested. We also collected single developed embryos after washing, washing with trypsin, washing and cryopreservation in ethylene glycol, or washing with trypsin and cryopreservation in ethylene glycol. All washes were performed according to International Embryo Transfer Society standards. Developed embryos and NFD were sonicated prior to assay. All samples were assayed for BVDV using virus isolation and RT-nPCR.
The virus isolation and RT-nPCR assays determined that all negative control samples were BVDV-free. Virus was detected in association with all exposed cumulus cells and groups of developed embryos using both virus isolation and RT-nPCR. Results from viral assays of other exposed samples indicate enhanced sensitivity of the RT-nPCR assay.
The RT-nPCR assay used in this research exhibited acceptable sensitivity, specificity, predictive value and repeatability for rapid detection of BVDV associated with the various samples obtained from an IVF system.
