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A glass-lined trough was divided into six compartments by vertical transverse partitions and filled with soil to a height of 5 cm above the top of each partition. The base of the box and the surface of the soil sloped forwards one end with a gradient of 1 in 3·7. Dieldrin was applied (22 kg active ingredient/ha) to the soil surface in the uppermost compartment and the movement of dieldrin into leachate and down the slope was followed for 17 weeks. During this time 19·5 cm of rain fell. Less than 0·02% of the dieldrin appeared in the leachate and 99% of this was collected during the first 9 weeks, mainly from the uppermost compartment. Very little dieldrin moved down the slope and it was not detected in the leachate from compartments other than the treated one during 9–17 weeks after treatment. In other experiments, 3 cylinders were filled respectively with sandy loam, heavy clay loam and peat which were transferred from the field as intact cores. Three other cylinders were filled with soils of the same types but broken up. Approximately 2% of the dieldrin leached through one column but usually it was much less than 0·1%. The largest amounts of dieldrin were leached down columns of heavy clay loam, intermediate amounts down columns of peat, and least through sandy loam. Ten times as much dieldrin leached down the columns of intact soil as through those with broken soil. The results indicate that the movement of dieldrin from treated soil into water systems by leaching is limited and is unlikely to be a major pathway for the contamination of water. 相似文献
63.
Results are presented for the determination of organochlorine insecticide residues in grain, pulses and nuts sampled on arrival in Britain during the 2½ years up to June 1969. BHC was detected in nearly every sample but the general level was low, most samples containing less than 0·1 ppm. DDT was found less frequently. Very few samples contained more than 1 ppm of either insecticide. DDE in trace amounts was found in about 10% of the samples of grain and nuts and TDE was found in one sample of grain. The only other organochlorine compounds detected were aldrin in one sample of pulses and hexachlorobenzene in 7 samples of wheat. 相似文献
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Three experiments were performed to test the following hypotheses: 1) stallions and/or progesterone-estradiol-treated geldings could serve as models for the effects of a single implant of the GnRH analog, deslorelin acetate, on LH and FSH secretion by mares; and 2) multiple implants of deslorelin acetate could be used as a means of inducing ovarian atrophy in mares for future study of the mechanisms involved in the atrophy observed in some mares after a single implant. In Exp. 1, nine light horse stallions received either a single deslorelin implant (n = 5) or a sham injection (n = 4) on d 0. In Exp. 2, 12 geldings received daily injections of progesterone on d -20 through -4, followed by twice-daily injections of estradiol on d -2 to 0. On the morning of d 0, geldings received either a single deslorelin implant (n = 6) or a sham injection (n = 6). Daily injections of progesterone were resumed on d 2 through 15. In Exp. 1, plasma LH and FSH were elevated (P < 0.05) in the treatment group relative to controls at 4, 8, and 12 h after implant insertion. In the treated stallions, FSH was decreased (P < 0.05) on d 3 to 13, and LH was decreased on d 6 to 13. In Exp. 2, plasma LH and FSH were elevated (P < 0.05) at 4,8, and 12 h after deslorelin implant insertion. Plasma LH was suppressed (P < 0.05) below controls on d 2 to 7, 9, and 11 to 15; plasma FSH was suppressed (P < 0.05) on d 4 to 15. In Exp. 3, 21 mares were used to determine whether multiple doses of deslorelin would cause ovarian atrophy. Mares received one of three treatments: 1) sham injections; 2) three implants on the first day; or 3) one implant per day for 3 d (n = 7 per group). Treatment with multiple implants increased (P < 0.05) the interovulatory interval by 14.8 d and suppressed (P < 0.01) LH and FSH concentrations for approximately 25 d; no mare exhibited ovarian atrophy. In conclusion, after an initial short-term increase in LH and FSH secretion, deslorelin implants caused long-term suppression of both gonadotropins in stallions as well as in geldings treated with progesterone and estradiol to mimic the estrous cycle. It is likely that either of these models may be useful for further study of this suppression in horses. Although multiple implants in mares suppressed gonadotropin secretion longer than a single implant, the lack of ovarian atrophy indicates that the atrophy observed after a single implant in previous experiments was likely due to the susceptibility of individual mares. 相似文献
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A chondrodysplasia characterised by dwarfism and varus deformity of the forelimbs has been recognised over four seasons in Texel and Texel-cross lambs on three related properties. Affected lambs appear normal at birth, but by 2 weeks of age have reduced growth rate, shortened neck and legs, varus forelimb deformities and a progressive reluctance to walk. Most die within the first 4 months of life. Some affected lambs have had normal co-twins. Post mortem examination of two severely affected 3-month-old lambs revealed extensive loss of articular cartilage and exposure of subchondral bone on the weight-bearing surfaces of the proximal humeri and femurs. Articular and physeal cartilages were thicker than normal, suggesting delayed or impaired endochondral ossification. Histopathologically, there was disorganisation of chondrocytes in articular and physeal cartilage of all bones examined. In addition, there were multiple foci of chondrolysis, which coalesced in some areas to form large clefts. The chondroid matrix surrounding chondrocytes had an abnormal fibrillar appearance. One lamb that exhibited early signs of the disease died of an unrelated cause at 3 weeks of age, and although there was no erosion of articular cartilage, characteristic microscopic lesions were present in articular and physeal cartilage. Although most of the affected lambs were born on a commercial property with a mix of different sheep breeds, all had Texel genes on both sire and dam sides of the pedigree. The farmer had been purchasing his Texel rams from the same flock for several seasons. Circumstantial evidence favours a genetic aetiology, characterised by either autosomal recessive inheritance or over dominance. Studies on the genetic and biochemical basis of the disease are continuing. 相似文献