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Developmental patterns in turkeys of tissue ornithine decarboxylase (ODC) activity and nucleic acid concentrations were studied in a randombred control (RBC2), in a subline of RBC2 selected for increased 16-wk BW (F), and in a commercial sire line (C). Lines F and C were similar in BW, but Line C had greater breast weight than Line F. Lines F and C were heavier and had greater breast weights than the RBC2 population. Tissue ODC activity reached its highest level on Day 2 posthatch, declined rapidly through 13 d of age, and remained relatively low through 144 d of age. The ODC activity of liver tissue was greater than that of either breast or leg muscle. Line C had greater tissue ODC activity at 2 and 8 d of age than the RBC2 population, but Line F was not different from C or RBC2. There were no line differences for ODC activity at the other ages tested, resulting in a age by line interaction. The DNA content of muscle tissue was greatest at hatch and declined to baseline values by 55 d of age. The DNA content of breast muscle was higher than for leg muscle at hatch, but this pattern was reversed following Day 8. Muscle tissue from Lines F and C had a lower DNA content than that of the RBC2 population. Although the RNA content of muscle tissue was similar across lines, the RNA content of breast muscle was greater than for leg muscle during the early posthatch period just prior to the onset of rapid growth in this tissue. Results of the present experiment demonstrate changes in muscle functional cellularity during the growth phase in association with genetic increases in BW, but not breast muscle development. In contrast, tissue ODC activity was increased in association with genetic increases in breast muscle development, but not BW.

Using a chicken Class II MHC clone in Northern blot analysis, tissue-specific expression of turkey Class II MHC genes was observed in the embryonic bursa of Fabricius as well as in the adult spleen. In contrast, there was no detectable expression in the embryonic liver, brain, or spleen. Southern blot analysis of BamHI-digested turkey DNA revealed two restriction fragment length polymorphism (RFLP) patterns that did not deviate significantly from single-gene Mendelian inheritance. Further analysis of PvuII-digested DNA from 325 turkeys showed four distinct RFLP patterns that segregated within the turkey lines studied. Because the chicken Class II MHC clone hybridized specifically to mRNA in immune-associated tissues, and because it identified polymorphisms among turkeys, the chicken clone is suggested to identify four turkey Class II MHC genotypes. The current study provides good evidence that RFLP analysis of DNA can be used as a means for molecular genotyping at the MHC in turkeys.

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.

Two cDNA clones of nearly full length that encode the turkey pituitary common alpha-subunit glycoprotein hormone have been isolated from a pituitary cDNA library and their nucleotide sequences have been determined. The longer alpha-subunit clone was 777 bp in length. It contained 88 bp of the 5'-untranslated region (UTR), an open reading frame of 360 bp (that encodes the turkey alpha-subunit 24 amino acid leader polypeptide fragment and 96 amino acid apoprotein), and a 312-bp 3'-UTR followed by a 17-bp poly A tract. When the nucleotide sequence of the turkey alpha-subunit was compared with the sequence of the chicken alpha-subunit clone, the coding region was greater than 98% homologous, but was only 69 to 76% homologous when compared with mammalian alpha-subunit sequences. Northern blot analysis showed an approximate 800 bp processed transcript that hybridized to the labeled turkey alpha-subunit cDNA. There was a greater than fourfold up-regulation of the steady-state levels of turkey alpha-subunit transcription when intact cultured pituitaries were treated with chicken gonadotropin-releasing hormone I.

Near-full length complementary DNA (cDNA) clones encoding turkey growth hormone (GH) have been isolated from a pituitary library. The longer of the two turkey GH cDNA clones that were sequenced is 803 base pairs (bp) in length and contains 41 nucleotides of the 5'-untranslated region (UTR), an open reading frame of 648 bp that encodes a 25 amino acid leader polypeptide segment as well as a 191 amino acid mature turkey GH protein, and a 3'-UTR that is 92 bp long followed by a 22 bp poly A tract. Comparison of the turkey GH nucleotide sequence to that of other avian GH clones shows the coding region to be greater than 93% homologous while the homology to mammalian GH sequences is between 68 and 78%. Northern blot analysis showed an approximate 800 bp turkey GH processed mRNA transcript that hybridized to the turkey GH cDNA probe. A large up-regulation of turkey GH transcription occurred when intact cultured pituitaries were treated with 1 nM human growth hormone releasing hormone but only modest changes were observed when cultures were treated with thyroid releasing hormone or somatostatin.

Using a modification of the collagenase dispersion method of Dufau et al., we examined changes in DNA synthesis produced by estrogens in the interstitial cells of mice that develop malignant Leydig cell tumors after prolonged estrogen administration. Previous work in cryptorchid mice indicated that during continuous estrogen administration [3H]thymidine incorporation into DNA rises to a maximum in 3 to 4 days and then falls to approximately base levels within 2 to 3 weeks. This was confirmed both in Leydig cell concentrates of estrogen-treated mice after either injection with [3H]thymidine or incubation with [3H]thymidine in vitro. This DNA synthesis was blocked by hydroxyurea. DNA synthesis in cells of estrogen-treated BALB/c mice of the Huseby substrain, which have a high incidence of Leydig cell tumors, was 5 to 11 times that in untreated controls. Cells from estrogen-treated C3H/Bi mice, which have a low incidence of Leydig cell tumors, showed only a 2- to 3-fold increase. In the Huseby substrain the rise of DNA synthesis is a peak and subsequent recession were paralleled by a rise and fall in DNA polymerase alpha activity. DNA polymerase beta did not show this variation. In C3H/Bi mice, neither polymerase showed significant change. The evidence suggests that the early estrogen-stimulated DNA synthesis is probably replicative and is associated with increased DNA polymerase alpha activity.

A cDNA library was constructed from poly(A)+ RNA derived from late passage WI-38 cells and differentially screened with cDNA probes from early and late passage cells. From a number of clones which exhibited differences in intensity of hybridization to the early or late passage probes, one was chosen for further analysis because of its large increase in hybridization to the late passage probe. This clone accounted for approximately 1% of the recombinants in the library. The partial cDNA clone shows complete sequence homology to elongation factor I alpha (EF-I alpha). Northern analysis of poly(A)+ RNA from cells at various population doublings suggested that a 2.2-kb transcript, homologous to EF-I alpha accumulates as cells near the end of their replicative life span (phase III). When early and late passage cells were reexposed to serum after serum starvation, this transcript decreased in abundance. Additionally, a lower molecular weight transcript (1.6 kb) was detected 18 h following serum stimulation in early passage cells and 9 h after stimulation in late passage cells.