Cardiorespiratory capacity of individuals with mental retardation including Down syndrome.

This study evaluated the cardiorespiratory capacity of persons with MR with and without Down syndrome. Analyses of individual data records of maximal exercise tests with metabolic analyses were conducted on tests of 111 subjects (31 men and 16 women with DS; 35 men and 29 women without DS) from six participating centers. All centers used a walking treadmill protocol previously shown to produce valid and reliable maximal tests with this population. Peak oxygen uptake and peak minute ventilation were higher in men than in women (P < 0.006), and in subjects without DS (P < 0.006). Peak heart rate was also higher in subjects without DS (P < 0.006). Peak respiratory exchange ratio (RER) was higher in subjects without DS (P < 0.006). Using peak RER as a covariate did not change the results. An analysis of peak minute ventilation, heart rate and VO2 of subjects with a peak RER above 1.1 revealed the same results. These data show that individuals with mental retardation have low levels of peak VO2, consistent with low levels of cardiovascular fitness. Individuals with Down syndrome have even lower levels of peak VO2 than their peers without Down syndrome, a finding that is possibly mitigated by the lower peak heart rates of the individuals with Down syndrome.

Validation of the Rockport Fitness Walking Test for adults with mental retardation.

This study determined if the generalized equations created for the Rockport Fitness Walking Test were a valid estimation of cardiorespiratory fitness for adults with mental retardation (MR). Subjects included 25 males and females (mean age = 33.3 +/- 7.4 yr) with MR. A maximal treadmill test was administered (mean VO2peak = 29.5 +/- 7.2 ml.kg-1 x min-1; 2.2 +/- 0.62 l.min-1). Subjects' age, weight, sex, walk time, and immediate post-HR were used in the generalized equations for predicting VO2peak (mean VO2peak = 36.5 +/- 7.6 ml.kg-1 x min-1 and 2.7 +/- 0.66 l.min-1). Significant correlations (P < 0.01) were obtained between the measured and predicted peak VO2 levels. However, significant and consistent differences were also observed between the measured and predicted VO2peak values (P < 0.02). Only 28% (l.min-1) and 36% (ml.kg-1 x min-1) of the subjects' measured VO2peak fell within the prespecified value of the predicted VO2peak, thus indicating that the prediction equations overestimated the VO2peak and cardiovascular fitness levels of adults with MR.

Reduction of 4-nitroquinoline 1-oxide to 4-hydroxyaminoquinoline 1-oxide in lysates of cytomegalovirus-infected cells.

The rates of virus inactivation by 4-nitroquinoline 1-oxide (NQO) and 4-hydroxyaminoquinoline 1-oxide (HAQO) were compared and samples of cytomegalovirus (CMV)-infected cell lysates to which NQO had been added were examined for the presence of HAQO. These experiments demonstrated that (i) CMV inactivation by HAQO was more rapid than with NQO, (ii) virus inactivation by either NQO or HAQO failed to demonstrate a photodynamic component, and (iii) NQO-treated stocks contained HAQO, indicating reduction of NQO to HAQO. The results support the concept that metabolism of NQO to HAQO enhances the genotoxic effect of NQO.

Transport of aminophosphonic acids in Lactobacillus plantarum and Streptococcus faecalis.

Aminophosphonic acids analogous to glutamic acid, aspartic acid, alanine, and valine were actively accumulated by Lactobacillus plantarum. Uptake was dependent on the availability of glucose and, in all cases, the estimated intracellular concentrations substantially exceeded extracellular levels. During uptake, there was little metabolism of tritiated 2-amino-3-phosphonopropionic acid (APP), the aspartic acid analogue, and a negligible incorporation of isotope from this substance into the nucleic acid, lipid, protein, or cell wall fractions of the cell. Competition studies with APP indicated that its transport in L. plantarum and in Streptococcus faecalis was antagonized only by structurally related compounds such as glutamic, aspartic, and cysteic acids. Kinetic studies showed that APP was taken up by a single catalytic system in S. faecalis. A mutant strain of this organism which lacks one of two kinetically distinguishable dicarboxylic amino acid transport systems failed to accumulate measurable amounts of APP. These experiments indicate that the aminophosphonic acids are accumulated by the amino acid transport systems in these bacteria with minimal metabolic changes.

Transamination of aminoalkylphosphonic acids with alpha ketoglutarate.

Dialyzed homogenates prepared from Escherichia coli, Tetrahymena pyriformis, sea anemone (Anthopleura elegantissima), and mouse liver were tested for ability to transaminate 17 aminoalkylphosphonic acids with alpha-ketoglutarate. 2-Aminoethylphosphonic acid (2-AEP), which occurs naturally in Tetrahymena and anemone, was transaminated by these latter organisms more than any of the substances tested, but not by preparations from liver or E. coli. 3-Aminopropylphosphonic acid was transaminated by all preparations, but much less by Tetrahymena or anemone than was 2-AEP. 2-Amino-3-phosphonopropionic acid was transaminated by all preparations. 2-Amino-4-phosphonobutyric acid was transaminated by three of the preparations, but not by liver. Of the other 13 substances tested, the following gave positive results: DL-1,2-diaminoethylphosphonic acid with E. coli, DL-1,2-diaminoethylphosphonic and aminomethylphosphonic acids with Tetrahymena, DL-1-aminopropylphosphonic acid with anemone, and DL-1-aminoethylphosphonic and DL-1-aminobutylphosphonic acids with liver. The significance of these transaminations is discussed.