Fate and transport of ethoprophos in the Jamaican environment

The hydrolytic half lives of ethoprophos in distilled, river, brackish and open sea water were 25, 133, 65 and 81 days, respectively. Under laboratory conditions, volatilisation of the residues after 12 h was 1.4 - 3.6, 2.3 - 4.5 and 6.5 - 20.2 percent from a sandy loam soil with 1, 10 and 20 percent moisture levels, respectively. Photolysis in soil was significantly faster (P< 0.05) in direct sunlight (T 1/2 of 12.3 days). The microbial degradation of ethoprophos from unweeded plantation soil at 23 degrees slope was significantly (P=0.015) less than at 38 degrees slope; the amounts lost after 9 weeks and 27.5 mm of rainfall were 89.4 and 91.2 percent respectively, of the applied amount from the two respective slopes. In the weeded plots, 93.6 and 92.4 percent of the applied insecticide were lost from 23 degrees and 38 degrees slopes, respectively. Under laboratory conditions, between 67.0 and 85.1 percent of ethoprophos leached through the soil columns. Under field conditions, after 9 weeks and 25 mm of rainfall, only 2.8 and 2.0 percent residues were recovered at a depth of 10-15 cm from unweeded and weeded slopes, respectively at 23 degrees slope, and 2.2 and 1.9 percent from the two respective plots at 38 degrees slope. (AU)

Urea kinetics in healthy women during normal pregnancy

Urea kinetics were measured in normal women aged 22-34 years at weeks 16, 24 and 32 on either their habitual protein intake (HABIT) or a controlled intake of 60 g protein/d (CONTROL), using primed-intermittent oral doses of [15N15N] urea and measurement of plateau enrichment in urinary urea over 18 h (ID) or a single oral dose of [15N15N] urea and measurement of enrichment of urea in urine over the following 48 h (SD). The intake of protein during HABIT-ID (80 g/d) was greater than that on HABIT-SD (71 g/d); urea production as a percentage of intake was significantly greater at week 16 for HABIT-ID than HABIT-SD, whereas urea hydrolysis at week 16 was greater for HABIT-SD than HABIT-ID and urea excretion at week 32 was greater for HABIT-ID than HABIT-SD . The combined results for HABIT-ID and HABIT-SD showed a significant reduction in urea production at week 32 compared with week 24. Urea excretion decreased significantly from week 16 to week 24 with no further decrease to week 32 and urea hydrolysis was significantly greater at week 24 than either week 16 or week 32. Compared with HABIT, on CONTROL there was a decrease in urea production at week 16, and urea excretion was significantly reduced at week 16. For all time periods urea production was closely related to the sum of intake plus hydrolysis. Hydrolysis was greatest at week 24 and closely related to urea production. There was a significantly inverse linear relationship overall for hydrolysis as a proportion of production and excretion as proportion of intake. The results show that on HABIT N is more effectively conserved in mid-pregnancy through an increase in urea hydrolysis and salvage, and during late pregnancy through a reduction in urea formation. Lowering protein intake at any stage of pregnancy increased the hydrolysis and salvage of urea. The staging of these changes was later than that in pregnancy in Jamaica.(AU)

Urea kinetics varies in Jamaican women and men in relation to adiposity, lean body mass and protein intake

OBJECTIVE: We have measured urea kinetics in normal adult men and women of different body composition to determine whether adiposity is associated with differences in the rate of urea production or endogenous urea hydrolysis. DESIGN: Urea kinetics were determined from the excretion of [15N15N] urea in urine over a period of 48 h following a single oral dose of [15N15N] urea, in nine lean and nine obese women and in seven light and seven heavy males while they were consuming their habitual diets. Urinary 5-L-oxoproline was measured as an index of glycine metabolic status. SETTING: The studies were carried out in the research ward of the Tropical Metabolism Research Unit, University of the West Indies. RESULTS: Successful studies were completed in eight obese and five lean women and in six heavy and five light men. When compared with lean women, in obese women the rate of urea production and hydrolysis was significantly greater and this difference could not be accounted for by the greater fat-free mass alone, and was in part associated directly with the increase in fat mass. The rate of urea production and hydrolysis was greater in heavy men than in light men, a difference which was attributed to an increase in dietary protein. In obese women and heavy men there was a significantly higher rate of excretion of 5-Loxoproline in urine when compared with lean women and lean men respectively. CONCLUSION: This paper highlights the difficulty in identifying an appropriate reference with which to express results in people of different body composition. In obese women urea production and the hydrolysis of urea are increased, in part related to the increase fat-free mass, but also related to the increased fat mass itself. In obese women and men on high protein diets the greater rate of hydrolysis urea may be a reflection of an increased demand for the sythesis of non-essential amino acids, especially glycine.(AU)

Urea kinetics: comparisons of oral and intravenous dose regimens

Urea kinetics were measured on two seperate occasions in five adults with normal haemoglobin genotype (HbAA) and in four who were homozygous for sickle cell disease (HbSS). Prime/intermittent dose of {15N15N} urea were given orally on one occasion and intravenously on the other. In three of the nine individuals there appeared to be significant hydrolysis of the oral dose of urea before absorption, leading to spurious results for the urea kientics. When only the studies in which the isotope was given intravenously were considered, there was a difference in the rate at which urea-N was salvaged, with more urea-N being salvaged by HbSS subjects than HbAA. It is concluded that the oral presentation of isotope can be used to measure urea kinetics provided care is taken to exclude those subjects who are kikely to display upper intestinal hydeolysis, and that there are differences in aspects of urea kinetics between HbAA and HbSS which may be of metabolic importance. (Au)

Urea kinetics in adults with homozygous sickle cell disease

The kinetics of urea metabolism were measured in four adults with homozyguous sickle cell disease (HbSS). On a dietary intake of 1.2 to 2.7g protein /kg/d. A relatively small proportion of the urea was excreted in the urine (40 per cent), with a high fixed rate of hydrolysis in the bowel, 145 mg nitrogen /kg/d. Although 50 per cent of the nitrogen from hydrolysed urea was resynthesized to urea, and a further 10 per cent may have been lost in the stool, it is estimated that 58 mg nitrogen /kg/d was available for synthetic metabolic activity. Urea kinetics in sickle cell disease subjects are markedly different from normals, and this may be a reflection of the metabolic demands for increased red cell synthesis. (AU)

Increased urea metabolism in sickle cell disease - abstract

In normal man, a portion of the urea produced in the body (20-30 percent) is potentially made available for metabolism by hydrolysis in the bowel. In sickle cell disease (HbSS), continuing haemolysis modifies the metabolism of protein, with the probability that urea production, and possibly hydrolysis, is increased. We have therefore compared urea metabolism in 5 adults with HbSS (age 38ñ15yrs, weight 56ñ10Kg) with 6 normal adults (age 31ñ4 years, weight 72ñ8Kg). Urea metabolism was measured with an oral primed intermittent infusion of 30N urea over 24 hours, on a daily intake, of 36-44 Kcal/Kg and 1.2 gm protein/Kg. The enrichment in urinary urea and daily urea excretion was used to calculate urea production rate, rate of urea hydrolysis in the bowel, and rate of recycling of hydrolysed urea-nitrogen to urea synthesis. All aspects of urea metabolism were significantly increased in HbSS compared to normal. Whereas production ö intake was 70 percent for normals, it was 120 percent in HbSS, in large part due to the recycling of urea-N to urea synthesis. A greater proportion of urea was excreted in normals (70 percent) than in HbSS (50 percent). Consequently, the rate of urea hydrolysis in HbSS was significantly increased. The results would suggest that the increased nitrogen demands in HbSS associated with augmented red cell synthesis enhance urea recycling. The pattern of urea metabolism seen in HbSS is similar to that seen in normals taking a low-protein diet. These findings serve to support the suggestion that protein requirements in HbSS are greater than in normal (AU)