Linked Life Data

9835363

Source:http://linkedlifedata.com/resource/pubmed/id/9835363

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1-4
pubmed:dateCreated
1999-1-28
pubmed:abstractText
In reviewing the literature, this paper assesses the current level of understanding of the hormonal control of the ovarian cycle and pregnancy in the elephant. Data are compiled from two genera, Elephas maximus and Loxodonta africana, recognizing differences where known to exist. Measurements of various steroid and peptide hormones, but most notably immunoreactive progesterone (iP), indicate an overall cycle length of 15-16 weeks, comprising an 8-11-week luteal phase and a shorter inter-luteal (follicular) period of 4-6 weeks. Oestrogen related phenomena suggest the occurrence of two (possibly more) waves of follicular development with a 3-week periodicity, although oestrogen levels are low and fluctuate without clear pattern. The inter-luteal period is characterized by two discrete LH peaks also 3 weeks apart, but only the second is associated with an iP rise. Ovulation rate is variable and additional luteal structures lacking ovulation points are probably formed each cycle. The post-ovulatory period is associated with elevated progestogen levels, mainly 5alpha-reduced compounds, while progesterone itself is a minor secretory product. A revised model for the elephant ovarian cycle is presented. Detailed information on the endocrinology of pregnancy is lacking. Elevated progestins beyond the normal luteal phase indicate that conception extends the functional lifespan of the CL, with maximum steroidogenic activity between 3-15 months. The nature of the luteotrophic support is not known and placental gonadotrophins have not been conclusively demonstrated. Progestins fluctuate at or slightly above luteal phase values throughout pregnancy. There is a marked increase in prolactin levels after 16-24 weeks and a relationship with oestrogen secretion may exist since circulating and urinary levels show a progressive increase from 6-8 months. A placental contribution to progestin secretion is likely, although direct evidence is lacking. Considerable enlargement of foetal gonads during the second half of pregnancy in African elephants suggests a possible steroidogenic function, but none has been defined. The endocrine events leading to parturition are unknown. In the Asian elephant, a fall in iP precedes parturition; oestrogen levels decline and cortisol increases at the time of birth. The paper concludes with a brief selection of priorities for future research.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0378-4320
pubmed:author
pubmed:issnType
Print
pubmed:volume
53
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
3-18
pubmed:dateRevised
2005-11-16
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Endocrinology of the ovarian cycle and pregnancy in the Asian (Elephas maximus) and African (Loxodonta africana) elephant.
pubmed:affiliation
German Primate Centre, Department of Reproductive Biology, Göttingen. khodges@gwdg.de
pubmed:publicationType
Journal Article, Review