Sequences and expression patterns of alkaline phosphatase isozymes in preattachment bovine embryos and the adult bovine.

We report the cloning and partial sequences of two novel bovine tissue-specific alkaline phosphatase (AP) isozymes (TSAP2 and TSAP3) from in vitro-produced bovine blastocysts. Using a reverse-transcribed polymerase chain reaction (RT-PCR)-based assay for mRNA expression and in vitro-produced preattachment bovine embryos, TSAP2 mRNA was detected first at the four-cell stage prior to the major burst of embryonic transcription in cattle and TSAP3 at the eight-cell stage with the major burst in transcription. Furthermore, the transcription of TSAP2 and TSAP3 displays a curious "on-off" pattern during early cleavages between 40 and 120 hr after insemination. Activity of bovine AP, measured by an azo-dye coupling technique, indicates that at least one AP isozyme is functional in oocytes and embryos throughout bovine preattachment development. However, maternal and embryonic-derived AP activity may have different cell-surface distributions. This novel expression pattern of the bovine AP isozymes could provide a useful tool for identifying and clarifying the events controlling transcription and gene expression during early embryo development.

Expression and localization of relaxin in the ovary of the mare.

Immunoreactive, chromatographic and molecular techniques were used to study the expression of relaxin in mare ovaries at different stages of the oestrous cycle. Relaxin in follicular fluid ranged from 1.6 to 2.5, from 1.4 to 5.2, from 1.2 to 6.7 and from 1.0 to 3.5 ng ml-1 in small (< or = 2 cm), medium (> 2 < or = 3 cm), medium-large (> 3 < or = 4 cm) and large (> 4 cm) follicles, respectively, and total content of fluid relaxin per follicle increased (P < 0.05) with follicular size. When subjected to reverse phase HPLC analysis, follicular fluid yielded absorbance profiles corresponding closely to those of purified relaxin, and immunoreactive peaks in follicular fluid fractions measured by radioimmunoassay matched peaks of the relaxin standard. While relaxin was localized immunocytochemically to granulosa and theca cells of preovulatory follicles, northern blot and reverse transcriptase-PCR followed by Southern blot analysis failed to detect a relaxin transcript in these tissues. A single relaxin transcript (428 bp) corresponding to mRNA encoding relaxin was identified in early, mid- and late stage corpora lutea but not in corpora haemorrhagica or albicantia. Northern blot analysis revealed a weakly expressed 1 kb transcript in total cellular RNA from mature corpora lutea. In situ hybridization studies localized the mRNA to the large luteal cells of mature corpora lutea and relaxin protein was detected by immunocytochemistry in the same tissue. This is the first report demonstrating relaxin in the equine ovary and its expression by luteal cells, thereby suggesting a role for relaxin in follicular or corpus luteum function in cyclic mares.

Relaxin is not associated with poor milk yield in the postpartum sow.

Porcine relaxin (pRXN) titers were measured in 109 plasma samples drawn between 24 and 120 h post-partum from good (n = 34), and poor (n = 25) milking sows and from sows (n = 12) exhibiting overt signs of hypogalactia located on six swine farms in Ontario. Mean plasma pRXN titers among the three groups at 24 h post-partum were not significantly different although there was considerable variation. By 48 h however, the pRXN titers had declined markedly in all groups and between 72 and 120 h, pRXN was cleared from the plasma of all sows examined except one hypogalactic animal that had a titer of 1.13 ng/mL at 96 h. These results suggest that, although pRXN may be identifiable in the corpora lutea during the puerperium, it does not contribute to either hypogalactia or poor lactational performance in sows. The data also encourage the view that pRXN could be used at farrowing without deleterious effects on suckling.

Technical note: is there a season for iodinating relaxin?

We report a loss of antibody binding in our porcine relaxin radioimmunoassay that has occurred during the coldest periods of the past three winters. We do not know the reason for this seasonal variation but we have eliminated cold deterioration of the iodide used for radioiodination and equipment failures as explanations.

Lithium-induced inhibition of 125I accumulation by thyroids and growing oocytes of Japanese quail.

A single dose of 975 mumol. Li Cl suppressed thyroidal accumulation of iodide in laying Japanese quail as measured at 1, 6, and 18 hr. after injecting 125 I and in mature male quail at 1 hr. Thyroidal accumulation was above control values in males by 18 hr. Levels of 125 I were unchanged in growing oocytes but in testes were 3 to 60 times the control levels. When accumulations were expressed relative to the concentration of 125I in the plasma, in lithium-treated quail levels in thyroids were 0.02 to 0.5 times, in oocytes 0.2 to 0.9 and in testes 0.7 to 0.8 times control values. Results indicate that a single large dose of LiCl caused retention of 125I in the extracellular fluid of Japanese quail and thereby in the testes but inhibited transport of the tracer into the thyroid and growing oocytes.

Accidental suppression of the accumulation of radioiodide by the thyroids of Japanese quail exposed to an iodinated disinfectant.

The walls and floor of a room housing a Japanese quail colony were treated with a commercial disinfectant containing iodine complexed to organic molecules. The room was washed vigorously with hot water using a pressure hose, a procedure discouraged by instructions on the shipping container. A condensate, tinged yellow-brown presumably by elemental iodine, settled on the walls, ceiling and quail pens. Accumulations of tracer doses of iodide-125 or iodide-131 by the thyroid glands of these birds were approximately one-seventh (6-hour uptake) to one-thirtieth (18-hour uptake) as great as for control birds from non-disinfected areas.