Use of modified Fraser's stain in Promoting Activity Test (PAT)

The Promoting Activity Test (PAT) requires a staining procedure that allows rapid, accurate and reliable counting of mitotic figures. We propose use of Fraser's kernechtrot-crystal violet technique, but eliminating the picric-alcoholic differentiation to avoid fading. This modified protocol gives higher mitotic counts in adult mouse adrenal cortex than the hematoxylin-eosin originally used, especially with respect to less conspicuous prophases.     

Interaction between the splotch mutation and retinoic acid in mouse neural tube defects in vitro

The interaction between the splotch gene (Sp) and all-trans retinoic acid (RA) was investigated using cytogenetically marked Sp/+ and +/+ mouse embryos cultured in the presence of RA. Retinoic acid retarded the development of and had a teratogenic effect on mouse embryos in culture. In particular, RA had seemingly opposite effects on the posterior neural tube, inducing abnormally early fusion in some embryos and causing a dose-dependent delay in others. When the effects of RA on identified Sp/+ and +/+ embryos were compared, the only observed difference in their responses was in the degree of the delay in posterior neuropore (PNP) closure. At the end of the culture period, among the untreated control embryos, the Sp heterozygotes showed retardation of PNP closure compared to +/+ embryos. In addition, the RA treatment was found to have induced a greater delay in posterior neural tube closure in Sp/+ than in +/+ embryos. The basis for this difference in response to RA is presumed to be the retardation of PNP closure that is caused by the Sp gene in heterozygous form. The effects of the gene and the teratogen are additive and the gene carriers thus have greater mean PNP lengths at the end of culture. Since the length of the PNP is an indication of an embryo's likelihood of developing spina bifida, this provides an explanation for the observation that Sp/+ embryos are more sensitive to the spina bifida-causing effects of RA than are +/+ embryos.     

In vivo topoisomerase II cleavage of the Drosophila histone and satellite III repeats: DNA sequence and structural characteristics.

We have identified two classes of in vivo topoisomerase II cleavage sites in the Drosophila histone gene repeat. One class co-localizes with DNase I-hypersensitive regions and another novel class maps to a subset of consecutive nucleosome linker sites in the scaffold-associated region (SAR) of the histone gene loop. Prominent topoisomerase II cleavage is also observed in one of the linker regions of the two nucleosomes spanning satellite III, a centromeric SAR-like DNA sequence with a repeat length of 359 bp. At the sequence level, in vivo topoisomerase II cleavage is highly site specific. Comparison of 10 nucleosome linker sites defines an in vivo cleavage sequence whose major characteristic is a prominent GC-rich core. These GC-rich cleavage sites are flanked by extensive arrays of oligo(dA).oligo(dT) tracts characteristic of SAR sequences. Treatment of cells with distamycin selectively enhances cleavage at nucleosome linker sites of the SAR and satellite regions, suggesting that AT-rich sequences flanking cleavage sites may be involved in determining topoisomerase II activity in the cell. These observations provide evidence for the association of topoisomerase II with SARS in vivo.     

Effect of recombinant bovine somatotropin (somidobove) in a sustained release vehicle on plasma somatotropin level and lactational performance of dairy cows.

The effects of administration of recombinantly derived bovine somatotropin (somidobove) in a sustained-release vehicle on the profiles of concentrations of bovine somatotropin (bST) in the blood plasma and on the milk yield of dairy cows of three herds were examined. Cows (36-87 days post partum) were treated subcutaneously with recombinant bST at 28-day intervals. In control animals, basal concentrations of bST averaged 1.4 ng.ml-1 in first-calf heifers and 1.5 ng.ml-1 in multiparous cows. In somidobove treated first-calf heifers, the concentration of bST was increased to 10.7, 14.5, and 27.0 ng.ml-1 at 24 h postinjection and in multiparous cows to 6.6, 11.0, and 11.7 ng.ml-1 on day 2 postinjection of 320, 640, and 960 mg of somidobove, respectively. On day 8 postinjection the average plasma bST levels of both parity groups are similar (on the average 3.4, 8.6, and 12.5 ng.ml-1 for three doses of somidobove respectively) and for the two highest doses being still significantly increased. During the 2nd week postinjection plasma bST concentration declined returning to control levels on day 15 postinjection. Somidobove-treated first-calf heifers produced 10.9, 16.7 and 17.9% and multiparous animals 25.5, 24.2 and 32.5% more milk than the controls when given 320, 640 and 960 mg somidobove, respectively. The cyclic pattern in milk yield within each 28-day injection interval was observed consistently in all herds. The milk yield increased to a maximum between day 4 to 8 postinjection and then slowly declined. Milk composition was not affected by somidobove treatment.     

Nutrient transfer between the root zones of soybean and maize plants connected by a common mycorrhizal mycelium

The objective of the study was to determine whether nutrient fluxes mediated by hyphae of vesicular-arbuscular mycorrhizal (VAM) fungi between the root zones of grass and legume plants differ with the legume's mode of N nutrition. The plants, nodulating or nonnodulating isolines of soybean [ Glycine max (L.) Merr.], were grown in association with a dwarf maize ( Zea mays L.) cultivar in containers which interposed a 6-cm-wide root-free soil bridge between legume and grass container compartments. The bridge was delimited by screens (44 μm) which permitted the passage of hyphae, but not of roots and minimized non VAM interactions between the plants. All plants were colonized by the VAM fungus Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe. The effects of N input to N-sufficient soybean plants through N₂-fixation or N-fertilization on associated maize-plant growth and nutrition were compared to those of an N-deficient (nonnodulating, unfertilized) soybean control. Maize, when associated with the N-fertilized soybean, increased 19% in biomass, 67% in N content and 77% in leaf N concentration relative to the maize plants of the N-deficient association. When maize was grown with nodulated soybean, maize N content increased by 22%, biomass did not change, but P content declined by 16%. Spore production by the VAM fungus was greatest in the soils of both plants of the N-fertilized treatment. The patterns of N and P distribution, as well as those of the other essential elements, indicated that association with the N-fertilized soybean plants was more advantageous to maize than was association with the N₂-fixing ones.     

Ovarian function and pregnancy rates in reindeer calves (Rangifer tarandus ) in Southern Norway

Reindeer calves (n = 632) were slaughtered in November/December (n = 476) or in January (n = 156). Dressed weights and amount of perirenal fat were recorded, and the reproductive organs were collected. A separate group of 130 reindeer calves were weighed at 7 months of age and were followed up with repeated weighings and pregnancy examinations up to 21 months. The onset of puberty and the pregnancy rate were significantly influenced by body weight and the amount of perirenal fat. Approximately 60 g of perirenal fat and 22 kg dressed weight were found at the lower limits for pregnancy. A total of 222 (35%) animals had reached puberty and 126 (20%) were pregnant when examined after slaughter. Animals which conceived during their first autumn showed only a moderate weight gain the following year, and the calf mortality rate in these animals was 47.4%. It was concluded that calf pregnancies are common among the reindeer of Southern Norway and that measures need to be taken to prevent them.     

Chemotaxis of Rhizobium meliloti to the plant flavone luteolin requires functional nodulation genes.

Luteolin is a phenolic compound from plants that acts as a potent and specific inducer of nodABC gene expression in Rhizobium meliloti. We have found that R. meliloti RCR2011 exhibits positive chemotaxis towards luteolin. A maximum chemotactic response was observed at 10(-8) M. Two closely related flavonoids, naringenin and apigenin, were not chemoattractants. The presence of naringenin but not apigenin abolished chemotaxis of R. meliloti towards luteolin. A large deletion in the nif-nod region of the symbiotic megaplasmid eliminated all chemotactic response to luteolin but did not affect general chemotaxis, as indicated by swarm size on semisoft agar plates and chemotaxis towards proline in capillary tubes. Transposon Tn5 mutations in nodD, nodA, or nodC selectively abolished the chemotactic response of R. meliloti to luteolin. Agrobacterium tumefaciens GMI9050, a derivative of the C58 wild type lacking a Ti plasmid, responded chemotactically to 10(-8) M luteolin. The introduction of a 290-kilobase nif-nod-containing sequence of DNA from R. meliloti into A. tumefaciens GMI9050 enabled the recipient to respond to luteolin at concentrations peaking at 10(-6) M as well as at concentrations peaking at 10(-8) M. The response of A. tumefaciens GMI9050 to luteolin was also abolished by the presence of naringenin.     

The isolation and genetic analysis of aCaenorhabditis elegants translocation (szT1) strain bearing an X-chromosome balancer

A single X-chromosome balancer-bearingCelegans ♂+, as a founder of a strain (AF1), was isolated directly from Fl progeny of irradiated+dpy-8unc-3/lon-2++ hermaphrodites on the basis of the absence of recombinant F2 categories. The balancer chromosome (Bal-X-1) suppresses recombination over a two-thirds section of the X chromosome (between genesdpy-8 andlet-2) and is associated with a reciprocal translocation between linkage groups (LG) X and I. Animals homozygous for the translocation (szT1(X:1)) are nonviable. Hermaphrodites heterozygous for the translocation segregate male selfprogeny at a frequency of 0.08-0.12.Bal-X-l carries the marker mutationlon-2(e678) and can be detected cytologically. This balancer chromosome proved useful for rnaimaininga number of X-linked lethal mutations and deficiencies inC. elegans.