Functional fitness of adults with Down syndrome: a longitudinal study.

BACKGROUND: Individuals with Down syndrome (DS) are born with and develop many health-related complications. The purpose of this study was to determine the longitudinal functional fitness profile of adults with DS. METHODS: The functional fitness of adults with DS was tested twice, 12 years apart. Sixty-six adults with DS were tested for body mass, stature and 10 functional fitness tests. Data were categorised according to gender and age-specific categories. RESULTS: Static balance, shoulder flexibility, trunk strength and aerobic capacity deteriorated significantly with medium to large effect sizes for both DS men and women (most age categories). For women, dynamic balance deteriorated significantly, and for men, leg- and upper body-strength deteriorated significantly. CONCLUSIONS: Practitioners working in the field of adapted physical activity should take cognisance of the functional fitness ageing profile of adults with DS and timeously develop habitual physical activity interventions to reduce the effect of accelerated ageing experienced by this population.

The effect of 8 weeks of freestyle swim training on the functional fitness of adults with Down syndrome.

BACKGROUND: Studies conducted on adults with Down syndrome have demonstrated the improvement of functional fitness (aerobic capacity, muscular strength, balance, flexibility, functional ability, body mass or body mass index) with varying exercise modalities but often with one or two components in isolation. Such modalities included walking, running, cycling, rowing or resistance training. Freestyle swim training has shown significant improvements of all parameters associated with functional fitness in the general population. Swimming is an aerobic activity where many of the large muscle groups are involved and may provide more functional fitness benefits. As a consequence, the purpose of our study was to investigate the effect of freestyle swim training on the functional fitness of adults with Down syndrome. METHODS: Twenty-six adults with Down syndrome (33 ± 6 years; 34 ± 9 kg/m2 ) were randomly allocated to an exercise (n = 13; 81.3 kg) or control group (n = 13; 81.5 kg). The exercise group performed 8 weeks of freestyle swim training, three times a week, 30 min per session (increased to 40 min after 4 weeks). To evaluate differences between groups, a one-way analysis of variance was used, controlling for differences at baseline. RESULTS: After 8 weeks of training, the results showed significant differences between the exercise and control group for body mass, body mass index, aerobic capacity, dynamic balance, muscular strength, 12-m swim time and functional ability (P < 0.05). Effect sizes ranged from small to large. CONCLUSIONS: Various components of functional fitness improved significantly after an intervention period of freestyle swim training. The collective improvement of many functional fitness parameters shown by this study may hold benefits for these often-neglected and in many cases functionally impaired individuals.

Effects of detraining on anthropometry, aerobic capacity and functional ability in adults with Down syndrome.

BACKGROUND: Structured exercise has shown to improve parameters of functional fitness in adults with Down syndrome (DS). However, few, if any, continue to exercise after exercise intervention studies. Consequently, the purpose of this study was to determine the effects of detraining on anthropometry, aerobic capacity and functional ability of adults with DS. METHODS: In a previous study, forty-two participants either performed 12 weeks of interval training, continuous aerobic training or no training (CON). After 3 months of detraining, the same participants were tested again for anthropometry, aerobic capacity, leg strength and functional ability. RESULTS: Significant reductions in maximal aerobic capacity, time to exhaustion and both functional test items were reported for both exercise groups compared to CON (p < .05). No significant differences were reported between the exercise groups concerning aerobic and functional capacity reductions. CONCLUSION: Detraining occurred significantly in both exercise groups regarding parameters associated with aerobic and functional capacity.

Accuracy of the prediction equation for the determination of maximum heart rate in adults with Down syndrome.

BACKGROUND: The purpose of the study was to determine if the regression formula developed for the prediction of maximum heart rate (HR) is valid for adults with Down syndrome (DS). METHODS: Thirty-six adults with DS (31.7 ± 6.8 years; 20 men, 16 women) completed a maximal aerobic test. Maximum HR and VO2 peak were measured directly on a motorised treadmill with a metabolic analyser. Predicted HR was estimated with the regression equation developed for individuals with DS (Fernhall et al. 2001). Differences between measured versus predicted maximum HR were assessed with a dependent T-test and the relationship with Pearson correlational analyses. Agreement was assessed with Bland-Altman analysis. RESULTS: There was a significant difference between directly measured maximum HR and predicted maximum HR (P < 0.01). There was no significant relationship between these variables. Bland-Altman analysis indicated that there was measurement bias (+4.7) and large limits of agreement (+26.7 and -17.4) between measured and predicted maximum HR. The Bland-Altman plot also demonstrated the presence of heteroscedasticity. CONCLUSIONS: The results indicate that the regression formula developed for individuals with DS was not accurate in this sample of DS adults aged 19 to 46 years. Future studies should develop different prediction equations for more specific age and body mass index categories for individuals with DS.

Effect of continuous aerobic vs. interval training on selected anthropometrical, physiological and functional parameters of adults with Down syndrome.

BACKGROUND: A large percentage of adults with Down syndrome (DS) are overweight and have extremely low aerobic capacities compared with the general population and persons with intellectual disability without DS. Previous aerobic training intervention studies showed limited potential to significantly ameliorate anthropometrical and cardiovascular variables. The primary purpose of this study was to determine the effect of continuous aerobic training (CAT) vs. interval training (IT) on selected anthropometrical, health, physical and functional parameters of adults with DS. METHODS: Forty-two adults with DS (25 men and 17 women) and a mean age of 33.8 (±8.6) years were randomly allocated to one of three groups (IT, CAT and control). Training was performed for 12 weeks. The IT group performed 10-30 s all out sprints with 90 s (1:3 work-rest ratio) of low cadence, low intensity cycling or walking. The CAT group performed continuous cycling and walking at an intensity of 70-80% of VO2 peak. Heart rate monitors were used for monitoring training intensities. After 6 weeks of training, the intensity of the CAT was increased to 85% of VO2 peak, whilst the intensity of the IT group remained 'all out'. An increase of 5 min in duration was implemented after 6 weeks for both training groups. To evaluate pre-post differences between groups, a repeated analysis of covariance with post hoc Bonferroni test was performed RESULTS: After 12 weeks of training, body weight and body mass index decreased significantly more in the IT group compared with control and CAT (P < 0.05). Participants in the IT group decreased their body weight from 71.4 ± 8 to 69.4 ± 8 kg and their body mass index from 29.3 ± 4 to 28.5 ± 4 kg/m2 . Significant ameliorations for functional parameters and leg strength were shown for CAT compared with control (P < 0.05). Participants in the CAT group improved their performance in the 6 minute walk distance (499 ± 78 to 563 ± 75 m), 8-ft up-and-go (5.9 ± 1.2 to 4.8 ± 0.9) and leg strength (13.1 ± 2 to 15.2 ± 2). VO2 peak and time to exhaustion significantly improved in both the IT and CAT group compared with control (P < 0.01). Moreover, a significant improvement for relative VO2 peak was also determined for IT compared with CAT (P < 0.05). Participants in the IT group increased their VO2 peak from 32 ± 8 to 37 ± 8 mL/min/kg. Submaximal heart rate and VO2 values improved significantly within both exercise groups (P < 0.05). CONCLUSION: Interval training and CAT can both be pursued by adults with DS to positively impact on various parameters of anthropometry, fitness and functional ability, with IT more appropriate for improving body weight and aerobic capacity.

Test-retest reliability and minimal detectable change scores of twelve functional fitness tests in adults with Down syndrome.

AIM: The purpose of the study was to explore the test-retest reliability and minimal detectable change of selected functional fitness test items in adults with Down syndrome. METHODS: Forty-three adults with Down syndrome (24 men and 19 women) aged 18-50 years completed a battery of tests twice in a two-week period. The battery of tests consisted of two balance items, two flexibility items, five muscular strength and endurance items, two aerobic items, and one functional task. All items were considered valid and reliable tests in a general elderly or intellectually disabled population. The test-retest relative reliability for all repeated tests was assessed with intraclass correlation coefficient performing one-way analysis of variance. The test-retest absolute variability was measured by using the standard error of measurement (SEM) to calculate the minimal detectable change at the 90% confidence interval (MDC90). Reliability data was visualised with a Bland-Altman plot. RESULTS: All tests showed excellent intraclass correlation coefficients (ICC's>0.9). All SEM values demonstrated acceptable measurement precision (SEM

The functional fitness capacity of adults with Down syndrome in South Africa.

BACKGROUND: It is well established that there is a relationship between physical inactivity and increased risk for diseases of lifestyle. Persons with Down syndrome (DS) are especially at risk because of physical and health impairments, as well as perceived and real barriers to participation in exercise. The purpose of the study was to establish the functional fitness capacity and predictors of performance of DS adults. METHODS: Data were collected at various intellectual disability centres and private homes in seven provinces of South Africa. Three hundred and seventy-one DS individuals (199 men and 172 women) from 18 to 66 years were tested for balance, flexibility, coordination, muscular strength and endurance, aerobic capacity and functional ability. Data were categorised according to gender and age groups (18-25, 26-35, 36-45, and >45 years). Multiple regression analysis was performed to determine the relationship between the functional task and physical test items. RESULTS: Down syndrome men performed significantly better on all but two tests compared with the women (P < 0.05). DS women performed better on the sit-and-reach flexibility item and the chair stand test; however, differences were not statistically significant from the men. Significant differences across age groups were observed for nine of the 13 functional fitness tests (P < 0.05). Muscular strength items, especially leg strength, significantly predicted functional performance in DS men and women. Aerobic capacity only predicted functional performance in DS men and sit-and-reach flexibility and dynamic balance only in DS women. CONCLUSIONS: Findings of this study provide important information on the functional capacity of DS adults and show which physical attributes contribute to functional performance. Consequently appropriate training programmes can be tailored for this population whom is known to have poor functional fitness.

How to correct for errors in mRNA quantitation by competitive PCR due to heteroduplex formation of amplification products.

The Q-RT-PCR method for determining mRNA levels is an internally-controlled quantitative reverse transcriptase linked polymerase chain reaction to assess gene activity by monitoring the accumulated stable transcript level, in a given sample of extracted total RNA. Internal and competitive standards are used for mRNA titration because of the exponential nature of PCR; possible variations in RT efficiency are corrected for by the use of riboprobe RNA standards. A renin mRNA assay has been optimized by altering PCR primer parameters. Q-RT-PCR suffers from the occurrence of heteroduplex DNA formation between amplification products from homologous standard and target mRNA. Co-migration of various PCR products is shown to occur on neutral agarose gels, and this will lead to serious errors in mRNA determinations. Adjustment of the standard electrophoresis conditions is required for absolute mRNA quantitation by Q-RT-PCR.

Rapid activation of the type B versus type A natriuretic factor gene by aortocaval shunt induced cardiac volume overload.

OBJECTIVE: The aim was to compare activities of the type A and type B natriuretic factor genes during development of cardiac hypertrophy by use of a non-radioactive method designed for assessment of stable atrial and brain natriuretic factor (ANF, BNF) transcript levels in biopsy sized tissue samples. METHODS: At 1 and 7 days after aortocaval shunt or sham surgery in rats, quantitative reverse transcriptase mediated polymerase chain reaction (Q-RT-PCR) was used to determine mRNA levels in cardiac tissues. Phosphoglycerate kinase-1 (PGK-1) mRNA levels served as an external standard for Q-RT-CR. RESULTS: The shunt increased left ventricular end diastolic pressure at days 1 and 7, and cardiac weight was increased by day 7. By day 1, left ventricular BNF mRNA levels were twice those of controls, whereas ANF mRNA levels were not changed. By day 7, left ventricular BNF mRNA levels were increased 15-fold, and those for ANF were increased fivefold; the BNF mRNAs were also increased in right atria and right ventricle, about fivefold in both cases. CONCLUSIONS: Both natriuretic factor genes were activated by cardiac volume overload, and the increase in the level of left ventricular BNF transcripts-observed for the first time-was in fact more rapid and exceeded that of ANF. The Q-RT-PCR assay will be of value to investigate the response to increased work load of cardiac muscle in vivo.

Random primer p(dN)6-digoxigenin labeling for quantitation of mRNA by Q-RT-PCR and ELISA.

The ability to accurately measure mRNA levels in samples of total RNA is essential for studies on control of gene expression. The mRNAs from the housekeeping gene for phosphoglycerate kinase (PGK-1) can serve as a quality control for RNA samples. We describe an enzyme-linked immunosorbent assay (ELISA) method for mRNA determination by Q-RT-PCR, a quantitative reverse transcriptase-mediated PCR assay with competitive internal standards. After PCR, two biotinylated capture primers, one specific for PGK-1 cDNA and another one for internal standard, are annealed in separate assays so that each can attach DNA to a streptavidin-coated microplate. The captured DNA is either internally labeled with digoxigenin (DIG) or is "developed" after annealing with DIG-labeled primers. Bound DNA is then quantitated by adding DIG-specific antibody with attached alkaline phosphatase and measuring phosphatase activity with a chromogenic substrate and a plate reader. We compared different capturing methods and various primers labeled with DIG at their 3' ends. We determined that amplified PGK-1 DNA specifically captured with biotinylated primers was efficiently assayed with random p(dN)6-DIG.

Stretch-mediated activation of cardiac renin gene.

This study was designed to quantitate cardiac mRNA levels encoding components of the local renin-angiotensin system during the development of volume overload-induced cardiac hypertrophy. Changes in cardiac renin mRNA levels were measured in relation to renin activity in the left ventricle (LV) and in plasma after acute passive stretch of the heart caused by an aortovenocaval shunt in the rat. A quantitative reverse-transcriptase polymerase chain reaction method with competitive internal standards was used to measure mRNA levels in total RNA derived from cardiac tissues after shunt. Seven days after shunt surgery, LV weight was increased by 23%. Renin activities were elevated four- and twofold in plasma and LV, respectively. LV angiotensinogen mRNAs were not significantly increased by shunt surgery; they were twofold higher than phosphoglycerate kinase mRNA from the housekeeping gene PGK-1. By day 7, LV levels for renin mRNA were significantly increased from well below 0.25% to approximately 1% of PGK-1 mRNA. Identity between renin polymerase chain reaction products from kidney and heart cDNAs and absence of "reninlike" amplification products were supported by Southern blotting. Volume overload caused increased expression of the renin gene in the stretched myocardium. This finding is consistent with the concept of a myocardial renin-angiotensin system that can be activated by locally produced renin and contributes to the hypertrophy of cardiac muscle.

Activation of the gene for type-b natriuretic factor in mouse stem cell cultures induced for cardiac myogenesis.

We assessed the temporal transcriptional activity profiles of the genes for type-B natriuretic factor, BNF, the isoform ANF, and other cardiac muscle proteins in differentiating cultures derived from multipotential mouse cell lines. P19 embryonal carcinoma cells and D3 embryonic stem cells were induced for in vitro cardiac myogenesis; RNA was isolated at regular intervals throughout the differentiation programs, and mRNAs were detected by reverse transcriptase mediated polymerase chain reactions. The transcriptional activation profiles of the ANF and BNF gene were similar, but there were quantitative differences that were best assayed by use of competitive internal DNA standards. The levels of induced BNF transcripts were highest in the P19 developmental system reaching approximately 10% of adult mouse ventricular muscle levels; those for ANF were lower, but also readily detected. The cell lines may be used to define the regulatory control elements for natriuretic factor gene expression, in stably transfected cell lines, during cardiac muscle growth.

Activation of the gene for atrial natriuretic factor during in vitro cardiac myogenesis by P19 embryonal carcinoma cells.

We examined the transcriptional activity profile of the gene for atrial natriuretic factor (ANF) in mouse embryonal carcinoma P19 cells which had been induced for in vitro cardiac myogenesis. Differentiation was assessed visually, by the degree of spontaneous beating activity, and by the appearance of striated muscle structures detected by immunofluorescence with a myosin heavy chain antibody. Northern blot analysis of RNA isolated at regular intervals throughout the differentiation program revealed abundant cardiac alpha-actin transcripts beginning at Day 6, reaching maximum levels during Days 7 to 8 and declining to low levels by Days 12 to 15. Throughout this period, the transcriptional profile of the ANF gene was similar to that of alpha-actin but at lower levels; thus, in vivo stages of abundant ANF and structural muscle gene transcription were not reached and these gene expression states appear to be uncoupled. Using the more sensitive assay of reverse transcriptase-mediated polymerase chain reactions, we observed the presence of ANF transcripts even in small samples of muscle-induced P19 cells and not in neuron-induced or undifferentiated P19 cells. Induced ANF transcript levels reached about 5-10% that found in adult atrium muscle tissue. ANF gene activity was further corroborated by nuclear transcriptional run-on assays. The P19 stem cell model system will be of value in the study of early events during cardiac muscle commitment and differentiation.

A decade of atrial natriuretic factor research.

Present views on the biological significance of atrial natriuretic factor (ANF) relate this polypeptide hormone to the regulation of blood pressure and volume through its modulating effects on renal function, on blood vessel tone and permeability, and on the renin-angiotensin-aldosterone system. Although very important advances in the understanding of ANF have been made over the decade since its discovery, some fundamental facts about ANF biosynthesis and release remain to be elucidated. Stretch-induced enhancement of ANF release appears as the most significant mechanism underlying the endocrine response of the atria to acute volume load. This response decays over a period of minutes, indicating that chronic stimulation of ANF release involves mechanisms different from, or in addition to, those acting during acute stretch-stimulated release. In neither acute nor chronic conditions are the cellular or molecular mechanisms underlying ANF release understood. To better understand long-term stimulation of ANF release, we have conducted extensive in vitro testing of several hormones and neurotransmitters to determine their ability to modify ANF release. From these studies, clear-cut evidence of ANF stimulation was obtained with the vasopressor peptide endothelin. Investigations on the cell and molecular biology of cardiac muscle development and hypertrophy have shown that ANF is involved in cardiac growth. The role played by ANF in these processes is now being determined, but this is one line of evidence that suggests that this hormone, together with other natriuretic peptides, may have autocrine or paracrine functions.(ABSTRACT TRUNCATED AT 250 WORDS)

Short dispersed repeats localized in spacer regions of Chlamydomonas reinhardtii mitochondrial DNA.

In the mtDNA of Chlamydomonas reinhardtii, a unicellular green alga, we have identified a set of short repeated sequences up to 65 nucleotides long, each of which contains the palindromic consensus motif CTCGG(N4-14)CCGAG. Most of these repeated elements are localized in spacer regions that flank the transcribed coding regions of C. reinhardtii mtDNA. These algal mitochondrial repeats have features reminiscent of short repeats in some fungal mtDNAs, such as GC clusters in Saccharomyces cerevisiae and PstI palindromes in Neurospora crassa. The location of these elements suggests that they could play a role in gene expression, e.g., post-transcriptional processing, in C. reinhardtii mitochondria.

Polymorphisms in the coding and noncoding regions of murine Pgk-1 alleles.

The mouse X-linked Pgk-1 gene encodes phosphoglycerate kinase. When transfected into human cells, the Pgk-1b allele causes the appearance of mouse PGK-1b enzyme activity. We describe here cloning of mouse Pgk-1a, an allele of Pgk-1 which encodes an enzyme, PGK-1a, with distinct electrophoretic mobility. We constructed recombinants between the DNA encoding Pgk-1b and Pgk-1a and transfected these constructs into human cells to assess the electrophoretic characteristics of each recombinant. In this way the charge variation between the two proteins was localized to exons 4 or 5. Sequencing of these exons revealed a single base-pair difference between the two alleles at codon 155, which predicts the amino acids lysine and threonine in PGK-1b and PGK-1a, respectively. A number of other DNA sequence polymorphisms exist between Pgk-1b and Pgk-1a including part of an L1 repeated element unique to Pgk-1a.

Transfer RNA genes and the genetic code in Chlamydomonas reinhardtii mitochondria.

Only three tRNA genes are present within a sequenced 12.35 kbp region of the 15.8 kbp mtDNA of Chlamydomonas reinhardtii, a unicellular green alga. The corresponding tRNAs, whose anticodons are specific for TGG (Trp), CAA/G (Gln) and ATG (Met) codons, all display conventional secondary structures. The tRNA(Met) gene encodes an elongator rather than initiator species. The standard genetic code is used in C. reinhardtii mitochondria, but codon distribution is highly biased: in a collection of six identified protein coding genes, nine codons (including TGA) are not used at all, while four other sense codons occur very infrequently. In spite of the absence of certain codons, a minimum of 23 tRNAs (assuming separate initiator and elongator tRNAs(Met) are used) is needed to translate the C. reinhardtii mitochondrial genetic code. It appears unlikely that this minimal tRNA set is encoded by C. reinhardtii mtDNA.

Scrambled ribosomal RNA gene pieces in Chlamydomonas reinhardtii mitochondrial DNA.

We describe here a bizarre organization of the single large subunit (LSU) and small subunit (SSU) rRNA genes in the mitochondrial DNA of Chlamydomonas reinhardtii. Each gene is discontinuous, with gene pieces encoding specific rRNA domains ("modules") interspersed with one another and with intact protein coding and tRNA genes throughout a 6 kbp region. Transcript mapping experiments reveal the presence of abundant small rRNAs whose sizes approximate the sizes of the modules encoding them. Evidently, rRNA splicing does not occur in this system; instead, secondary structure modeling supports the view that the SSU and LSU rRNAs each functions as a noncovalent network of small RNAs, rather than as a single covalently continuous molecule. We propose that such a modular pattern may reflect the structure of the primordial ribosome.

Genes encoding a subunit of respiratory NADH dehydrogenase (ND1) and a reverse transcriptase-like protein (RTL) are linked to ribosomal RNA gene pieces in Chlamydomonas reinhardtii mitochondrial DNA.

Two long and uninterrupted reading frames, specifying the ND1 and RTL genes, are embedded within fragmented rRNA genes in the 15.8-kb mitochondrial genome of Chlamydomonas reinhardtii, a unicellular green alga. The ND1 gene encodes a subunit of respiratory NADH dehydrogenase, a standard mitochondrial gene, while the RTL gene is related to the reverse transcriptase-like part of some optional introns and plasmids in fungal mitochondria. The universal genetic code is used in both the ND1 and RTL genes; however, the latter is distinguished from the other protein coding genes of C. reinhardtii mtDNA by several characteristics which suggest that RTL may be a more recently acquired gene. Flanking each of the protein coding genes, whose mRNAs are of similar abundance, are some of the 'scrambled' rRNA gene pieces that are a unique feature of C. reinhardtii mtDNA. These sub-genic modules give rise to high-abundance, small-sized pieces of rRNA, which are not spliced in this genetic system. Judging by the observed juxtaposition of transcripts as they hybridize to the genome, the mature rRNA and mRNA species from this region appear to be generated by precise endonucleolytic cleavages of a long RNA precursor. We suggest a model, involving reverse transcription of rRNAs and insertion of the resulting cDNAs into the mitochondrial genome, that might account for the pattern of dispersed rRNA gene pieces in C. reinhardtii mitochondrial DNA.