Reproductive activity in Finnish Landrace x Rambouillet ewes exposed to various daylength cycles applied over periods of six months

Twenty-six Finnish Landrace x Rambouillet ewes were exposed to a series of artificial daylength cycles over periods of 6 mo. The cycles in general consisted of 3 mo. of long or increasing daylength, followed by 3 mo. of short or decreasing daylength. Increasing daylength to 22 hr.; 17.5 hr. or 15.75 hr. but not 14 hr. resulted in the onset of anestrus in all ewes. Only four of eight ewes in the 14 hr. cycle became anestrus. Abrupt decreases in daylength resulted in a more rapid return to reproductive cyclicity than a gradual decline. In addition, there appeared to be an inverse relationship between the length of the longest day of a treatment cycle and the time taken for ewes to return to reproductive cyclicity, following a subsequent abrupt decrease in daylength. Reducing daylength form 22 hr. to 17.5 hr. did not induce reproductive cyclicity. Reducing daylength from 17.5 hr. to 15 hr.; 12.75 hr. or 7.5 hr. did result in the onset of reproductive cyclicity. Finally, extending the period of long day exposure in a daylength cycle decreased the response time to a subsequent reduction in daylength. It was concluded that reproductive seasonality may be initiated by the interaction of darkness with a daily photosensitive phase in the ewe.     

Morphine, naloxone and the gonadotrophin surge in ewes

Possible endogenous opioid peptide regulation of the preovulatory gonadotrophin surge was examined in ewes during the breeding season. Intact ewes (n = 54) were synchronized by treatment for 12 days with intravaginal sponges releasing medroxyprogesterone acetate. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion prior to and during the gonadotrophin surge were not affected by naloxone (0.33 mg/kg body wt per h) administered from the time of medroxyprogesterone acetate withdrawal until 30 h after the onset of oestrus (n = 6). Morphine was administered in 4 patterns: (i) 0.25 mg morphine/kg body wt per h from medroxy-progesterone acetate withdrawal until 30 h after the onset of oestrus (n = 6), (ii) 0.25 mg morphine/kg body wt per h from 24 to 48 h after medroxyprogesterone acetate withdrawal (n = 6), (iii) 0.50 mg morphine/kg body wt per h from 24 to 36 h after medroxyprogesterone acetate withdrawal (n = 6) and (iv) 0.50 mg morphine/kg body wt per h from 18 to 30 h after medroxyprogesterone acetate withdrawal (n = 6). Oestrus and the gonadotrophin surge were delayed, but not blocked, in all cases of morphine administration (P less than 0.05). Inconsistent effects of morphine on circulating oestradiol and gonadotrophin concentrations prior to the gonadotrophin surge suggest that the delays are not due to reduced gonadotrophic support of ovarian oestradiol output. Morphine may reduce responsiveness of central behavioural and gonadotrophin surge-generating centres to the oestradiol signal. The absence of effects of naloxone on gonadotrophin secretion suggest that suppression of LH secretion by opioid peptide activity is reduced after the end of the luteal phase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cloning, nucleotide sequence, and enzymatic characterization of an alpha-amylase from the ruminal bacterium Butyrivibrio fibrisolvens H17c.

A Butyrivibrio fibrisolvens amylase gene was cloned and expressed by using its own promoter on the recombinant plasmid pBAMY100 in Escherichia coli. The amylase gene consisted of an open reading frame of 2,931 bp encoding a protein of 976 amino acids with a calculated Mr of 106,964. In E. coli(pBAMY100), more than 86% of the active amylase was located in the periplasm, and TnphoA fusion experiments showed that the enzyme had a functional signal peptide. The B. fibrisolvens amylase is a calcium metalloenzyme, and three conserved putative calcium-binding residues were identified. The amylase showed high sequence homology with other alpha-amylases in the three highly conserved regions which constitute the active centers. These and other conserved regions were located in the N-terminal half, and no similarity with any other amylase was detected in the remainder of the protein. Deletion of approximately 40% of the C-terminal portion of the amylase did not result in loss of amylolytic activity. The B. fibrisolvens amylase was identified as an endo-alpha-amylase by hydrolysis of the Phadebas amylase substrate, hydrolysis of gamma-cyclodextrin to maltotriose, maltose, and glucose and the characteristic shape of the blue value and reducing sugar curves. Maltotriose was the major initial hydrolysis product from starch, although extended incubation resulted in its hydrolysis to maltose and glucose.     

L’electromyographie du penis: Une nouvelle exploration du muscle lisse caverneux et de son controle neurologique?

The authors have investigated the electrical activity of corpus cavernous, first according to Wagner and Gerstenberg’ method, then, since one year, according to Stief method, in the basal state and following intracavernosal injection of vasoactive agents, or following various stimulation tests. They have found again the electrical activity described by these authors, but have been confronted with the difficulty in quantifying the data. Specially single potential analysis seems to them little reliable and reproducible for an objective interpretation. At this stage of their experience, they test two simpler criteria interpretation: the richness of the electrical activity, and the reactivity of the recording to various stimulations. Their preminary results suggest a correlation between those criteria and the state of the autonomic nervous system of the penis.     

The influence of estradiol-17beta and progesterone on peripheral serum concentrations of luteinizing hormone and follicle stimulating hormone in the ovariectomized ewe

Serum gonadotropin concentrations were high and variable and fluctuated episodically in short and long term ovariectomized ewes. Treatment with solid silastic implants releasing progesterone (serum levels 1.81 +/- 0.16 ng/ml) had no consistent effect. Treatment with implants releasing estradiol-17beta significantly depressed mean serum gonadotropin concentrations and peak height to values usually seen in intact ewes. This occurred regardless of implant size and serum estradiol-17beta concentrations (range 11 +/- 0.3 pg/ml to 98 +/- 12.8 pg/ml). Progesterone and estradiol-17beta together significantly depressed the frequency of peaks in LH concentration. Following progesterone removal, 95% of the ewes treated with progesterone and estradiol-17beta implants experienced a transient increase in serum LH concentrations similar to the preovulatory surge in intact ewes. Eighty-four percent of the LH surges were accompanied by a surge in serum FSH concentrations. However, following progesterone removal, 5.1 +/- 2.1 FSH surges were observed over six days. Gonadotropin surges occurred regardless of estradiol-17beta implant size and with or without the influence of supplemental estradiol-17beta.     

Complete sequences of the rRNA genes of Drosophila melanogaster

In this, the first of three papers, we present the sequence of the ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of D. melanogaster rDNA encode four individual rRNAs: 18S (1,995 nt), 5.8S (123 nt), 2S (30 nt), and 28S (3,945 nt). The ribosomal DNA (rDNA) repeat of D. melanogaster is AT rich (65.9% overall), with the spacers being particularly AT rich. Analysis of DNA simplicity reveals that, in contrast to the intergenic spacer (IGS) and the external transcribed spacer (ETS), most of the rRNA gene regions have been refractory to the action of slippage-like events, with the exception of the 28S rRNA gene expansion segments. It would seem that the 28S rRNA can accommodate the products of slippage-like events without loss of activity. In the following two papers we analyze the effects of sequence divergence on the evolution of (1) the 28S gene "expansion segments" and (2) the 28S and 18S rRNA secondary structures among eukaryotic species, respectively. Our detailed analyses reveal, in addition to unequal crossing-over, (1) the involvement of slippage and biased mutation in the evolution of the rDNA multigene family and (2) the molecular coevolution of both expansion segments and the nucleotides involved with compensatory changes required to maintain secondary structures of RNA.      

Mixotrophic Growth of a Thiobacillus ferrooxidans Strain

Mixotrophic growth of a Thiobacillus ferrooxidans strain is described. DNA moles percent guanine plus cytosine and homology determinations confirmed that the mixotrophically grown T. ferrooxidans cultures were not contaminated with heterotrophic Acidiphilium strains.     

Identification and sequence of the basic replication region of a broad-host-range plasmid isolated from Thiobacillus ferrooxidans.

The minimum region required for replication of the broad-host-range Thiobacillus ferrooxidans plasmid pTF-FC2 in Escherichia coli was shown to be contained on a 2.05-kilobase fragment of DNA. A 184-base-pair fragment that was required in cis for plasmid replication was identified. This region was also involved in plasmid incompatibility. Nucleotide sequencing of this region revealed three perfectly conserved 22-base-pair tandemly repeated sequences. A comparison of this region with the equivalent region of the broad-host-range plasmid R1162 showed that the repeated sequences had 60% nucleotide homology. The 106-base-pair region immediately adjacent to the repeated sequences was 75% homologous. These plasmids were compatible.