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Biomedical subjects

I C Lamb

Publications and source records attributed to I C Lamb.

6 recordsLinked to original sources
PubMed1993

Effects of naloxone, metaclopramide and domperidone on plasma levels of prolactin and LH following suckling in the female rabbit.

Saline, naloxone, domperidone or metaclopramide was injected into lactating rabbits immediately before suckling. Blood samples were taken prior to injection (0 minutes) and then at 15, 30, 45 and 60 minutes after the start of suckling, after which the samples were assayed for plasma prolactin and LH concentrations. In all the does there was a significant increase in prolactin concentration, which was highest 15 minutes after the start of suckling, and which declined exponentially thereafter to levels significantly higher than before suckling. The increase in prolactin concentration was similar in does given saline and naloxone, but it was significantly enhanced in does given metaclopramide; with domperidone the increase was intermediate and not significantly different from that following treatment with saline. In does given saline, domperidone, and metaclopramide plasma LH concentrations declined slowly during the hour after suckling but the concentration was increased significantly in does given naloxone. The inverse correlations between prolactin and LH were low weak and were not significant.

Journal Article↗
PubMed1992

Nucleotide sequence of the cDNA encoding the common alpha subunit of the chicken pituitary glycoprotein hormones.

Recombinant cDNA clones that encode the alpha subunit of the chicken pituitary glycoprotein hormones were isolated from a pituitary library. The longer of the two cDNA clones that were sequenced was 754 bp in length. It contained 81 nucleotides of the 5'-untranslated region (UTR), an open-reading frame of 360 bp that encoded a 24 amino acid leader polypeptide sequence as well as the 96 amino acid mature alpha subunit, and 268 nucleotides of the 3'-UTR, followed by a 45 bp poly(A) tract. There was 69-79% homology between the nucleotide sequence of the coding region for the chicken and mammalian alpha-subunit cDNAs. Northern blot analysis revealed that the steady-state levels of an approximately 800 bp alpha-subunit specific transcript increased quantitatively when dispersed chicken pituitary glands were treated in culture with chicken gonadotrophin-releasing hormone-I.

Amino Acid Sequence↗
PubMed1991

Effects of reducing the remating interval after parturition on the fertility and plasma concentrations of luteinizing hormone, prolactin, oestradiol-17 beta and progesterone in lactating domestic rabbits.

Primiparous crossbred does were remated on Day 1 (n = 15) or 14 (n = 25) post partum and killed on Day 10 post coitum to assess their fertility. Blood samples were taken during the pre- (0-12 h post coitum) and post- (1-10 days post coitum) ovulatory periods and plasma was assayed for luteinizing hormone (LH), prolactin, oestradiol-17 beta and progesterone. Ovulation response was significantly greater (P less than 0.01) and ovulation rate significantly lower (P less than 0.001) in does mated on Day 1 than in those mated on Day 14 post partum. Does failing to ovulate on Day 14 post partum exhibited no preovulatory LH surge and had significantly lower (P less than 0.05) premating concentrations of oestradiol-17 beta and prolactin than those ovulating at this time. No significant differences in hormone concentrations were observed during the preovulatory period between does ovulating on Days 1 and 14 post partum, with the exception of oestradiol-17 beta. Concentrations of this hormone were significantly lower (P less than 0.01) in does mated on Day 1, at 1 h post coitum. We conclude that (i) fertility was affected by the remating interval after parturition, (ii) ovulation failure was associated with an absence of the preovulatory LH surge and a reduction in premating concentrations of oestradiol-17 beta and prolactin and (iii) the lower ovulation rate in early lactation was apparently caused by a reduction in ovarian competence to respond to the gonadotrophic stimulus.

Animals↗
PubMed1988

Fertility of the early postpartum, lactating domestic rabbit.

Sixty-four crossbred primiparous lactating does each suckling six pups were allocated at random into four groups and were mated on either Day 1, 2, 3, or 4 post partum (where Day 0 = the day of parturition). They were subsequently killed on Day 10 post coitum (where Day 0 = the day of mating) to assess fertility. There were no significant differences between treatment groups in their mating response (97% overall), ovulation response (77% overall), implantation response (83% overall), implantation rate (8.7 overall), or preimplantation mortality rate (24% overall). Ovulation rate was significantly increased in does mated on Days 3 and 4 (13.3 and 13.1, respectively), compared with those mated on Day 1 (10.2, P<0.05) and Day 2 (9.6, P<0.01) post partum. From these results we conclude that fertility is high throughout the early postpartum period in the lactating rabbit.

Journal Article↗
PubMedDate not supplied

Mixture risk assessment: a case study of Monsanto experiences.

Monsanto employs several pragmatic approaches for evaluating the toxicity of mixtures. These approaches are similar to those recommended by many national and international agencies. When conducting hazard and risk assessments, priority is always given to using data collected directly on the mixture of concern. To provide an example of the first tier of evaluation, actual data on acute respiratory irritation studies on mixtures were evaluated to determine whether the principle of additivity was applicable to the mixture evaluated. If actual data on the mixture are unavailable, extrapolation across similar mixtures is considered. Because many formulations are quite similar in composition, the toxicity data from one mixture can be extended to a closely related mixture in a scientifically justifiable manner. An example of a family of products where such extrapolations have been made is presented to exemplify this second approach. Lastly, if data on similar mixtures are unavailable, data on component fractions are used to predict the toxicity of the mixture. In this third approach, process knowledge and scientific judgement are used to determine how the known toxicological properties of the individual fractions affect toxicity of the mixture. Three examples of plant effluents where toxicological data on fractions were used to predict the toxicity of the mixture are discussed. The results of the analysis are used to discuss the predictive value of each of the above mentioned toxicological approaches for evaluating chemical mixtures.

Adipates↗