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Biomedical subjects

L E Donaldson

Publications and source records attributed to L E Donaldson.

At least 19 recordsLinked to original sources
PubMed1996

A critical role for stem cell factor and c-kit in host protective immunity to an intestinal helminth.

In common with many intestinal nematode infections, Trichinella spiralis infections in mice are associated with a pronounced intestinal mast cell hyperplasia. The expulsion of the parasite from the gut is temporally associated with intestinal mastocytosis and mast cell function reflected by the secretion of mast cell protease into tissue and serum. In vivo, mucosal mast cell production is highly dependent upon T cell-derived cytokines including IL-3 and IL-4. We present data here to show that intestinal mast cell hyperplasia induced by helminth infection is also dependent upon the production of stem cell factor (SCF). Neutralization of SCF by anti-SCF or anti-SCF receptor mAb completely abrogated the mast cell hyperplasia generated by T. spiralis infection. Moreover, worm expulsion was dramatically delayed in treated mice and a reduced intestinal eosinophilia was observed. These effects did not appear to be mediated through alteration of Th cell responses and the parasite-specific serum antibody response was not affected. The reduction in the mast cell response and worm expulsion observed after SCF neutralization were reversible following cessation of monoclonal treatment. The data presented here clearly demonstrate a major role for SCF in the generation of intestinal mastocytosis and the host protective immune response following parasitic infection.

Animals↗
PubMed1986

Day of embryo collection, quality and pregnancy rates in cattle.

In 1300 donor cows, total embryos increased from 8.5 to 15.3, (P less than 0.001), the mean number of transferable embryos from 3.1 to 6.5 (P = 0.067) and pregnancies increased from 1.3 to 3.3 (P = 0.584) as the day of collection increased from six to 7.5. Most of the embryos recovered on day 6, 7.5 and 8 were morulae, early blastocysts and late blastocysts respectively. Morulae formed the majority of the embryos collected on days 6 and 6.5. Pregnancy rates in early and late blastocysts were highest on days 7 (54.4 and 60.2 per cent) and 7.5 (53.6 and 53.1 per cent, P = 0.009 and 0.004). There were significant differences in pregnancy rates between embryo stages on days 7 and 7.5 (P less than 0.001), embryo grades on days 7, 7.5 and 8 (P less than 0.001), and within embryo grades 1 (P = 0.015) and 3 and 4 (pooled, P = 0.009). On all days combined there were significant differences in pregnancy rates between both embryo stages (P = 0.007) and embryo grades (P less than 0.001). It appears that the concept of embryo fitness may be applied to blastocysts but not to morulae.

Animals↗
PubMed1985

Matching of embryo stages and grades with recipient oestrous synchrony in bovine embryo transfer.

The efficacy of matching embryos with recipients on the basis of embryo stage and grade and donor-recipient oestrous synchrony was investigated using the records of 13,663 embryos that were collected and transferred at a commercial embryo transfer centre. The selection of early blastocysts for exact oestrous synchrony cows was effective and resulted in the highest pregnancy rates. Selection of early morulae was effective for recipients in oestrus after the donor but not when transferred into exact and negative recipients. The matching of late morulae with recipients in oestrus after the donor was not effective and had no influence on pregnancy rates. The selection of late, hatched and collapsed blastocysts for transfer into recipients in oestrus before the donor was ineffective and pregnancy rates were higher in exact and +12 hour recipients. Pregnancy rates declined 23.6 per cent in quality grades 1 to 4 whereas the range between stages was 13.3 per cent. Higher quality embryos of all stages gave the highest pregnancy rates. Examination of pregnancy rates of grades within stages suggested that the more developed the embryo the more difficult it is to grade. The difference in pregnancy rates between exact and -24 (6.9 per cent) and +24 (4.8 per cent) hour recipients was small and declined a further 4.7 per cent and 9.8 per cent in -36 and +36 hour recipients. Grade 3 and 4 embryos tolerated asynchrony better than grade 1 and 2, and early morulae tolerated asynchrony better than the other stages. It was concluded that the matching of certain embryo stages with the donor-recipient oestrous synchrony is advantageous but not always possible.

Animals↗
PubMed1985

Estimation of superovulation response in donor cows.

Estimates were made of the superovulation response in donor cows using ovarian size, the number of corpora lutea (palpated per rectum) and blood progesterone levels. Neither the estimated number of corpora lutea nor ovarian size gave a satisfactory prediction of superovulation response. There was a large discrepancy between the number of corpora lutea present on the ovaries of nine superovulated cows (166) and the estimated number (106). All the corpora lutea on superovulated ovaries were smaller than normal (1.95 g). Blood progesterone levels at the time of embryo recovery were correlated with both the number of corpora lutea on the superovulated ovaries (r = 0.9, P less than 0.001) and the weight of the corpora lutea (r = 0.95, P less than 0.001). There were 67 embryos and ova recovered from the nine donors, representing 40 per cent of the actual and 63 per cent of the palpated corpora lutea. However, neither ovarian size, the number of corpora lutea nor blood progesterone levels were correlated with embryo production.

Animals↗
PubMed1985

Effect of insemination regimen on embryo production in superovulated cows.

Three experiments tested the effects of six insemination regimens on embryo production in superovulated cows. One, two or three inseminations with one unit of semen at each time produced the same percentage fertilised (74, 68 and 74 per cent, P = 0.673) and the same number of fertilised embryos (8.2, 6.3 and 9.1, P = 0.136). However, the one and two inseminations group had less transferable (P = 0.008) and total (P = 0.051) embryos (3.9/9.6 and 3.9/8.9) than the three inseminations group (6.8/13.2). The percentage transferable remained the same (42, 45 and 58 per cent, P = 0.161). When two units of semen were used at the first or middle insemination and one, two and three inseminations were compared, the percentage fertilised (65, 77 and 77 per cent, P = 0.082) and the number fertilised (7.0, 7.4 and 8.6, P = 0.565) were again the same but the number (P = 0.047) and percentage transferable (P = 0.000) increased between the one and two inseminations (3.8 vs 5.7 and 30 per cent vs 54 per cent). The increase in transferable embryos with multiple inseminations could not be explained physiologically, but is of concern since transferable embryos are the "sales product' of superovulation. Two inseminations with one unit of semen was as effective as two inseminations with three units of semen, in terms of percentage fertilised (68 and 70 per cent, P = 0.762), number fertilised (10.3 and 8.3, P = 0.582), transferable embryos (6.7 and 5.7 P = 0.532), percentage transferable (44 and 46 per cent, P = 0.737) and total embryos recovered (14.8 and 12.7, P = 0.54).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

LH and FSH profiles at superovulation and embryo production in the cow.

The variability of the superovulation response in cattle is an important problem to the commercial embryo transfer industry. Plasma LH and FSH concentrations around the time of estrus and ovulation were studied in relation to embryo production, to try and elucidate this problem. Sixteen cows were superovulated with 38 mg FSH-P and estrus synchronized with prostaglandin F(2) alpha. On the third and fourth day of superovulation increases in plasma LH but not FSH were detected. The LH and FSH profiles appeared to be normal in the size of the surge but in many cases they were were abnormal in timing. Transferable embryo production appeared to be lower in cows in which the LH and FSH surges were not coincident, and in cows where the surges were early or late with reference to estrus. FSH appeared to be primarily responsible for the number of embryos produced and LH for their quality, i.e. the number transferable.

Journal Article↗
PubMed1984

Dose of FSH-P as a source of variation in embryo production from superovulated cows.

Various superovulation treatments were evaluated retrospectively in a commercial embryo transfer program. When it appeared that embryo production was dependent on the dose of FSH-P, a dose response curve to FSH-P was developed and embryo production compared using several treatment regimes. There was a significant effect of dose of FSH-P on embryo production in superovulated cows. At doses in excess of 28 mg, embryo production declined from 5.9 transferable embryos per collection (28 mg) to 2.7 (60 mg). Total embryos collected declined from 14.9 to 6.8 and the percent transferable from 57% to 40%. There was no advantage in using a five-day treatment over a four-day treatment regimen or in using a level over a declining dose regimen. There was a large individual variation in cow response rendering decisions on treatment changes based on single records unreliable. The percentage of zero collections increased with dose rate. Adoption of a 28-mg dose rate in commercial donors resulted in the embryo production forecast by these studies.

Journal Article↗
PubMed1984

Embryo production in superovulated cows: Transferable embryos correlated with total embryos.

Embryo production was studied in 1,263 donor cows. The number of transferable (good) embryos per collection was highly correlated with the total embryos and ova in a collection (r = 0.64). Total ova and embryos per collection averaged 10.1 with a range from 0-70; the number of good embryos averaged 4.5 with a range from 0-37. Of all collections, 15.3% failed to yield any embryos or ova, and 32.4% did not yield any good embryos. The percentage of good embryos averaged 46.1 while the ratio of good embryos produced (5,680) to total embryos and ova produced (12,699) was 0.45.

Journal Article↗
PubMed1984

The day of the estrous cycle that FSH is started and superovulation in cattle.

A total of 993 commercial donor cows were superovulated with 28 mg FSH-P. The first injection of FSH-P was administered on one of days 9 through 13 of the donor's estrous cycle. The day that FSH was started did not affect total embryos collected, the number of transferable embryos or the percent transferable. These results did not support the current hypothesis that because the population of antral and preantral follicles in the ovaries on days 9 and 10 is higher, best embryo production should be achieved by starting donor cows on day 9 or 10 of the estrous cycle.

Journal Article↗
PubMed1983

The effect of prostaglandin F2 alpha treatments in superovulated cattle on estrus response and embryo production.

Approximately 10% of cows in a commercial embryo transfer center that were superovulated for embryo production did not show estrus at the right time and therefore did not produce embryos. This problem was investigated by studying the effects of prostaglandin F2 alpha (PGF) treatment regime and dose rate on the superovulatory process. The cows in estrus following superovulation (96% vs. 86.6%), the % cleaved (62% vs. 51%) and the transferable embryo production (5.4 vs. 3.8) was increased when 50 mg. PGF was administered in three divided doses rather than in two doses. In a second experiment doses of 15 mg, 30 mg and 45 mg (each administered as three divided doses 6 hours apart) all produced the same estrus response (95.6, 97.9 and 95%) and production of transferable embryos (4.9, 3.6 and 4.6). Three-times-a-day PGF reduced the time interval from treatment to the onset of estrus, but the time from PGF to estrus was not correlated with embryo production.

Journal Article↗
PubMed1982

Comparison of two dose rates and two management systems for synchronization of estrus in cattle.

Two dose rates and 2 management systems for the synchronization of estrus in cattle, using prostaglandin F 2 alpha (PGF2 alpha), were compared within 3 dairy and 3 beef herds. There was no statistical difference in responses between herds or breeds. There was no statistical difference between the estrous response produced by the 12.5-mg dose rate (53.6%) and that produced by the 25-mg dose rate (56.7%, P = 0.5). The 10-day, 1-injection management system produced a 21.7% better estrous response than that produced by the 2-injection system (64.5% vs 42.8%, respectively; P = 0.0001). Most (79.5%) of the difference in estrous response between management systems was accounted for by cows not responding to the 2nd injection of the 2-injection system. The interval from injection to estrus after 1 PGF2 alpha injection was shorter than after 2 PGF2 alpha injections (63.6 +/- 25.2 vs 70.3 +/- 23.8 hours, respectively). The percentage of all cows in the artificial insemination program that were in estrus 56 to 80 hours after injection was 27.4%.

Animals↗
PubMed1977

Synchronisation of oestrus in beef cattle artificial breeding programs using prostaglandin F2alpha.

PGF2alpha either as a subcutaneous injection (8 or 10mg) or intrauterine infusion (dose 5 mg) successfully synchronised oestrus in beef cattle AI programs. The beef cattle programs were managed by 1 of the following 2 systems. 1. Two 10-day insemination periods, 1 for the first and the second for the repeat inseminations. Oestrus was detected and oestrus cows inseminated for the first 4 days of the first period. On the fifth day all cows not inseminated were treated with PGF2alpha. The treated cattle came into oestrus and were inseminated over the following 2 to 5 days. 2. Two PGF2alpha treatments 10 days appart followed by two 4-day insemination perids. During the first 4-day period, cows exhibiting synchronised oestrus were inseminated. Cows returning to oestrus were inseminated during the second 4-day period, about 18 days after the first, period. Synchronisation of oestrus was not sharp, oestrus being distributed over 7 days, with the majority of cows being in oestrus on the third (42.3%) and fourth (22.4%) days. The route of administration of PGF2alpha (injection or infusion) did not effect oestrus synchronisation. PGF2alpha by either route of administration did not effect the fertility of cows inseminated at either the synchronised or subsequent oestrus. Pregnancy rates at the synchronised oestrus were higher when cows were inseminated after dectection of oestrus than when they were inseminated without reference to oestrus at a fixed time 3 days after PGF2alpha treatment (mass injection). Oestrus synchronisation greatly reduced the input of time, labour and feed required during the total program. However, oestrus synchronisation did not alter the overall efficiency of artificial breeding programs measured in terms of the proportion of cattle entering a program that were inseminated and became pregnant. The main problem encountered was drug wastage through unknowingly treating cows and heifers that were not cycling.

Animals↗
PubMed1977

Some causes of wastage in beef cattle artificial breeding.

Causes of reproductive loss in beef cattle AI programs were inadequate oestrus detection, use of vasectomised bulls, reduced inseminator efficiency, inadequate nutrition and infectious reproductive diseases (vibriosis and IPV). Nine case histories were presented detailing the symptoms and diagnosis of low reproductive performance.

Animals↗
PubMed1976

Artificial insemination of beef cattle.

A system for the artificial insemination fo beef cattle was described. The system involved preparation of the cattle and facilities, visual oestrous detection twice a day, drafting each morning and insemination of oestrous cows twice a day. The AI program was evaluated during the course of the program and at pregnancy test 35 to 90 days after the end of the insemination period. The insemination period was from 25 to 60 days depending on efficiency, with programs from 25 to 35 days being favoured. Results for 12218 first inseminations (65.9%) and 2222 second inseminations (57.8%) in 56 AI programs compared favourably with results in dairy AI. Pregnancy rates in lactating cows (70.5%) were significantly higher than in nonlactating cows and heifers (66.1%). Overall efficiency of well-managed AI programs were represented by 63% of cows put into a program becoming pregnant in a 29-day insemination period. Seventy-two per cent of the cows put into the program were inseminated yielding an 88% pregnancy rate. The efficiency of visual oestrous detection was 95% but this estimate did not include false positives. Efficiency of AI programs were effected by management, nutrition, infection, inseminators, facilities and the origin and type of cattle put into a program. Environmental factors such as handling, stress and thunderstorms did not effect efficiency except via a nutritional effect.

Animal Husbandry↗
PubMed1976

Custom collection and processing of bull semen.

Three systems of custom collection and processing of semen are reported. In the first system, semen was collected, evaluated and partially diluted and returned to a central Government laboratory for final dilution and freezing. In the second system the procedure was similar to the first except the semen was returned to the author's laboratory for final dilution and freezing. System 2 reduced the failure to process rate from 20.4% to 6%, but did not significantly improve fertility (64% v's 68% for systems 1 and 2 respectively). A single-stage diluent was used in system 3 and the time from collection to freezing in the author's laboratory was reduced. Both the failure to process rate (0.1%) and the fertility rate of the semen (76%) improved over the other 2 systems.

Animals↗