The receptors for prolactin and growth hormone are localized in the same region of human chromosome 5

Prolactin receptor (PRLR) and growth hormone receptor (GHR) are encoded by members of a gene family containing regions of identical sequences. To determine their chromosomal locations, cDNA probes for these genes were used. Analysis of hybridization to several somatic cell hybrids, together with hybridization in situ to metaphase chromosomes, resulted in the assignment of the loci for both receptors to human chromosome 5 in the region p13----p14. Thus, these proteins may be encoded by a cluster of related genes that evolved from a common ancestral gene, in a manner consonant with that of their ligands.     

The influence of snow on lynx and coyote movements: does morphology affect behavior?

Summary We studied sympatric lynx (Lynx canadensis) and coyotes (Canis latrans) to assess how morphological disadvantages to locomotion over snow affected movement patterns. Both species are of similar size and mass, but the feet of lynx are much larger, and coyotes were found to have 4.1–8.8 times the foot-load (ratio of body mass to foot area) of lynx. This resulted in greater mean sinking depths of coyote limbs, although the magnitude of the difference was less than that in foot-load. Coyotes exhibited stronger use of behavioral patterns that reduced negative effects of snow on movements. Coyotes were most abundant at low elevations where snow was shallow, whereas lynx were mostly at higher elevations. Coyotes also used areas at both elevations where snow was shallower than average, while lynx used areas where snow was deeper. further, both species used travel routes where snow was shallower than it was near the track. Coyotes traveled on harder snow and used trails more frequently, thereby tending to reduce sinking depths to those similar to lynx. The behavioral repertoire of coyotes reduced the morphological advantage of large feet possessed by lynx; however, overall sinking depths were still greater in coyotes. Snowshoe hares (Lepus americanus) were the main prey of both species, and their foot-load was less than that of either predator. Hare kills by coyotes occurred after fewer bounds than did those by lynx, and the large difference between foot-loads of both species of predators may have forced coyotes to ambush rather than chase hares, as did lynx.     

Heterogeneity of hepatic microsomal UDP-glucuronosyltransferase(s) activities: comparison between human and mammalian species activities

The first comparative profiles of UDP-glucuronosyltransferase(s) (UDPGT) activities obtained under standard conditions in vitro in mammals (man, rat [Wistar and Gunn], mouse, monkey [Papio papio and Cynomolgus], pig, guinea pig, rabbit, dog) are presented for 16 aglycones. A decreasing scale of these activities was obtained from planar to bulky molecules. The scale was identical for each of the mammals studied, including man. Statistical analysis of the results revealed a division of the aglycones into three groups, one being correlated with the molecular form called GT1 the two others with the GT2 form. The profile of activities in the Gunn rat revealed very weak activity towards planar molecules (GT1). These results provide evidence that under standard conditions, human UDPGT activities are comparable to those from other animals.     

Identification of a cDNA encoding a long form of prolactin receptor in human hepatoma and breast cancer cells

Human PRL receptor cDNA clones from hepatoma (Hep G2) and breast cancer (T-47D) libraries were isolated by using a rat PRL receptor cDNA probe. The nucleotide sequence predicts a mature protein of 598 amino acids with a much longer cytoplasmic domain than the rat liver PRL receptor. Although this extended region has additional segments of localized sequence identity with the human GH receptor, there is no identity with any consensus sequences known to be involved in hormonal signal transduction. This cDNA will be a valuable tool to better understand the role of PRL in the development and growth of human breast cancer.     

Metabolite effectors for short-term nitrogen-dependent enhancement of phosphoenolpyruvate carboxylase activity and decrease of net sucrose synthesis in wheat leaves

It has been demonstrated previously that field pea (Pisum sativum L. cv. Express) grown in hydroponic culture on a complete nutrient solution with low NH₄⁺ concentrations (<0.5 mM) will produce a larger than normal proliferation of nodules. Peas grown in the absence of mineral N in hydroponic culture have been shown to rapidly autoregulate nodulation, forming a static nodule number by 14 to 21 days after planting. The present study further characterizes the effect of NH₄⁺ concentration in hydroponic culture on nodulation and nodule growth. Peas were grown continually for 4 weeks at NH₄⁺ concentrations that were autoregulatory (0.0 mM), stimulatory (0.2 mM) or inhibitory (1.0 mM), or peas were transferred between autoregulatory or NH₄⁺ inhibited and stimulatory solutions after 2 weeks. The peas nodulated as expected when grown under constant autoregulatory, stimulatory or inhibitory concentrations of NH₄⁺. When peas were transferred from the inhibitory (1.0 mM) to the stimulatory solution (0.2 mM) a massive proliferation of nodule primordia over the entire root system was observed within 3 days of the transfer. When they were transferred from the autoregulatory (0.0 mM) to the stimulatory (0.2 mM) solution a 10-day delay occurred before a proliferation in nodule primordia occurred at distal regions of the root system. These findings support our hypothesis that low concentrations (<1.0 mM) of NH₄⁺ in hydroponic culture cause a suppression of autoregulation in pea. In addition, the temporal and spatial differences in nodule proliferation between transfer treatments demonstrate at a whole plant level that autoregulation and NH₄⁺ inhibition suppress early nodule development via different mechanisms.     

Tyrosine protein kinase assays

Protein kinases form a large family of enzymes that play a major role in a number of live processes. The study of their action is important for the understanding of the transformation mechanisms and of the normal and pathological growth events. The quality of an enzyme assay is often the key point of an enzymatic study. It must be flexible and compatible with various experimental conditions, such as those for the purification process, the screening of inhibitors and the substrate specificity studies. As will be shown in the present review, two categories of substrates, peptidic and proteic, should be distinguished. The use of peptide substrates facilitates the determination of the recognition requirements of the enzyme and of the kinetic effects of even minute variations in their sequence. These linear peptide structures are assumed to mimic a complex interaction between the enzyme and a proteic substrate in which distant amino acids in the sequence are vicinal in the folded substrate. Less amenable to a systematic study, but probably more adequate to investigate the natural substrate of a given kinase, are the proteic substrates. Obviously the tools to measure protein kinase activities are not the same in these two cases. The main difficulty in assaying protein kinases is the use of labelles γ-ATP, mostly at large excess concentration, since the final product of the reaction has to be separated from the non-reacted labelled ATP. In the case of peptide substrates, the difficulty is to separate them from ATP basing on differences of molecular mass. Despite the efforts of many investigators to rely upon differences in solubility, in charges or in “affinity”, this separation, which is crucial for the assay, is still an unsolved experimental problem. Chromatographic, as well as electrophoretic assays appeared relatively late in this domain, and more work in assessing new methodologies might bring new breakthroughs in the next few years. Specific, simple and reliable kinase assays are still a major challenge. Their improvement will help to conduct specificity studies, to elucidate complex growth mechanisms in which they are involved and to discover more selective potent inihibitors.     

An Ustilago maydis Mutant Partially Blocked in P45014DM Activity Is Hypersensitive to Azole Fungicides

An Ustilago maydis ergosterol biosynthesis mutant (A14) which is partially blocked in sterol 14alpha-demethylase (P45014DM) activity is described. This mutant accumulated the abnormal 14alpha-methyl sterols, eburicol, 14alpha-methylfecosterol, and obtusifoliol, along with significant amounts of ergosterol. Although the A14 mutant grew nearly as well as the wild type, it was impaired in cell extension growth, which indicated a dysfunction in apical cell wall synthesis. The mutant was also found to be hypersensitive to the azole fungicides penconazole and tebuconazole.     

Genome conservation among three legume genera detected with DNA markers.

A set of 219 DNA clones derived from mungbean (Vigna radiata), cowpea (V. unguiculata), common bean (Phaseolus vulgaris), and soybean (Glycine max) were used to generate comparative linkage maps among mungbean, common bean, and soybean. The maps allowed an assessment of linkage conservation and collinearity among the three genomes. Mungbean and common bean, both of the subtribe Phaseolinae, exhibited a high degree of linkage conservation and preservation of marker order. Most linkage groups of mungbean consisted of only one or two linkage blocks from common bean (and vice versa). The situation was significantly different with soybean, a member of the subtribe Glycininae. Mungbean and common bean linkage groups were generally mosaics of short soybean linkage blocks, each only a few centimorgans in length. These results suggest that it would be fruitful to join maps of mungbean and common bean, while knowledge of conserved genomic blocks would be useful in increasing marker density in specific genomic regions for all three genera. These comparative maps may also contribute to enhanced understanding of legume evolution.