Effect of orally-administered epidermal growth factor on intestinal iron absorption and mucosal permeability

A progressive increase in intestinal 59Fe3+ absorption was observed on oral feeding of mice with physiological doses of EGF/UGO. Maximal changes were apparent after 3d and appeared to be dose-dependent. In addition to a small increase in intestinal cell proliferation, as reflected by increased ornithine decarboxylase activity, EGF/UGO-feeding increased mucosal permeability (evaluated with [51Cr]-EDTA): the latter could account for the increase in iron absorption. Sialoadenectomy, to remove the major source of endogenous EGF/UGO, had no appreciable effect on the intestinal absorption of iron.     

Sublethal effects of aldicarb on the behaviour of Aphis fabae and two clones of Myzus persicae and on the transmission of beet mosaic virus by these aphids

In laboratory experiments treatment of sugar-beet plants with aldicarb stimulated the mobility of Aphis fabae and two clones of Myzus persicae which were susceptible (S) and resistant (R) to carbamate-based insecticides, respectively. On the other hand, the number of aphids probing and the total number of probes made was reduced, and hence the transmission of beet mosaic virus (BMV) was restricted. In outdoor experiments the spread of BMV from aldicarb-treated plants by naturally infesting aphids was also restricted. The number of infected plants decreased with increasing distance from the sources of infection.

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Résumé Des plantes de betterave traitées au laboratoire avec de l'aldicarbe ont stimulé la mobilité d'Aphis fabae et de deux clones de Myzus persicae, l'un sensible et l'autre résistant à des insecticides contenant des carbamates. Par ailleurs, le nombre de pucerons en train de sonder les feuilles ainsi que le nombre total de sondages ont été réduits et ainsi la transmission du virus de la mosaïque de la betterave (BMV) a été limitée. Dans des expériences à l'extérieur, la vitesse de propagation de BMV par des pucerons sur des plantes traitées à l'aldicarbe a été aussi plus limitée. Le nombre de plantes contaminées diminuait avec la distance de la source de contamination.

     

Disruption of the Rad52 Gene Alters the Spectrum of Spontaneous Sup4-O Mutations in Saccharomyces Cerevisiae

Defects in the RAD52 gene of the yeast Saccharomyces cerevisiae confer a mutator phenotype. To characterize this effect in detail, a collection of 238 spontaneous SUP4-o mutations arising in a strain having a disrupted RAD52 gene was analyzed by DNA sequencing. The resulting mutational spectrum was compared to that derived from an examination of 222 spontaneous mutations selected in a nearisogenic wild-type (RAD52) strain. This comparison revealed that the mutator phenotype was associated with an increase in the frequency of base-pair substitutions. All possible types of substitution were detected but there was a reduction in the relative fraction of A.T----G.C transitions and an increase in the proportion of G.C----C.G transversions. These changes were sufficient to cause a twofold greater preference for substitutions at G.C sites in the rad52 strain despite a decrease in the fraction of G.C----T.A transversions. There were also considerable differences between the distributions of substitutions within the SUP4-o gene. Base-pair changes occurred at fewer sites in the rad52 strain but the mutated sites included several that were not detected in the RAD52 background. Only two of the four sites that were mutated most frequently in the rad52 strain were also prominent in the wild-type strain and mutation frequencies at almost all sites common to both strains were greater for the rad52 derivative. Although single base-pair deletions occurred in the two strains with similar frequencies, several classes of mutation that were recovered in the wild-type background including multiple base-pair deletions, insertions of the yeast transposable element Ty, and more complex changes, were not detected in the rad52 strain.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of stream order and season on mineralization of [14C]-phenol in streams

Mineralization of trace levels of [¹⁴C]-phenol by heterotrophic microorganisms was quantified at 4 sites along a river continuum in southwestern Virginia. Significant phenol mineralization rates were detected in surface sediment and seston samples at all sites from August 1985 through May 1986. Phenol degradation was strongly affected by season (ANOVA; P < 0.0001). From a baseline rate in August (range: 1.19 × 10^-5 to 897 × 10^-4 mg phenol mineralized mg AFDW^-1 h^-1) phenol mineralization rose to a yearly maximum in October (range: 1.21 × 10^-4 to 1.16 × 10^-3 mg phenol mineralized mg AFDW^-1 h^-1) despite decreasing stream temperatures. This autumnal peak in phenol degradation was attributed to the pulsed input of allochthonous detritus, especially leaf litter, which contains substantial quantities of phenols and related compounds. Although phenol mineralization was significant in these streams, phenols were metabolized at much slower rates than more labile compounds present in the dissolved organic matter (DOM) pool. Estimates of turnover rates for three major components of DOM revealed that glucose and glutamate turnover rates (0.064–0.140 h^-1 mg sediment AFDW^-1 and 0.140–0.610 h^-1 mg sediment AFDW^-1, respectively) were, respectively, 2.2–4.7 × and 9.6–16.9 × greater than phenol turnover rates (0.015–0.064 h^-1 mg sediment AFDW^-1). Although the relatively low rates of utilization of refractory phenolic materials suggest that these compounds may accumulate and become more prevalent components of the DOM pool, phenol concentrations at the 4 study sites remained below detectable levels (i.e., < 1 g 1^-1) throughout the study. Consequently, it seems that although phenolic materials are metabolized more slowly than labile DOM, phenols are degraded at rates which preclude accumulation in the water column.     

Disruption of pattern formation in palatal rugae in fetal mice heterozygous for First arch (Far)

The purpose of this study was to document the extent of disruption in the pattern of palatal rugae caused by the presence of one copy of the First arch mutation. The palatal ruga pattern was found to be disrupted in 86% of 15- to 17-day mouse fetuses that were heterozygous for the First arch mutation in the ICR/Bc strain, compared with 9% in ICR/Bc fetuses of normal (+/+) genotype. This new observation in First arch heterozygotes, together with the previously reported dominant effects of the First arch mutation, particularly the bifurcation of the maxillary nerve (100% in both BALB/cGaBc and ICR/Bc strains), the disruption of maxillary vibrissa pattern (80% in ICR/Bc), and the hemifacial deficiency (38% in ICR/Bc), has led us to redefine the First arch mutation as a semidominant, Far. Like the other defects caused by Far, the rugal defects are in tissue derived from the embryonic maxillary prominence. The rugal defects observed in +/Far palates were always asymmetrical and most often involved fragmentation and misalignment of two or more of rugae 4-7. The relatively large degree of variation in ruga pattern observed in fetuses of normal genotype suggests that it is a less well canalized trait than the normal pattern of maxillary vibrissae which varies only in a few very specific and minor ways. The First arch mutation, which in heterozygotes disrupts pattern formation in both palatal rugae and maxillary vibrissae, can be used to study genetic control of pattern formation in mammalian embryos.     

Expression of the FGF-related proto-oncogene int-2 during gastrulation and neurulation in the mouse.

The proto-oncogene int-2 has been implicated in the formation of mouse mammary-tumour-virus-induced mammary tumours. Analysis of the predicted coding sequence indicates that int-2 is a member of the fibroblast growth factor family. Previous studies using Northern blot analysis suggested that normal expression of int-2 may be confined to extra-embryonic endoderm lineages of embryonic stages of mouse development. We have used in situ hybridization and Northern blot analysis to examine directly int-2 expression in embryo stem cells and in the developing embryo from early gastrulation to midsomite stages. Complex patterns of accumulation of int-2 RNA were observed in embryonic and extra-embryonic tissues. The data suggest multiple roles for int-2 in development which may include migration of early mesoderm cells and induction of the otocyst.     

Restriction pattern and polypeptide homology among plasmid-borne mercury resistance determinants

The structural and functional properties of mercury resistance determinants cloned from a series of independently isolated conjugative plasmids were compared with those of the prototype HgR determinants from Tn501 and plasmid R100 (containing Tn21). Restriction endonuclease mapping classified the HgR determinants into at least three different but related structural groups which are distantly related to those from Tn501 and R100. These relationships were confirmed by the functional analysis of sub-clones and gamma delta insertion mutations and from the polypeptides specified by the cloned HgR determinants. Each mercury resistance clone synthesized polypeptides equivalent in size to the merA, merT, and merP gene products. However, those for merA and merT showed considerable size variation. No polypeptide equivalent to merD or merC of R100 was detected.     

Inverse relationship between proliferation and differentiation in a human TNP-specific B cell line. Cell cycle dependence of antibody secretion

Studies of an EBV-transformed and TNP-specific human B cell line revealed that, unlike myeloma or hybridoma cell lines that consist mainly of fully differentiated cells, most of the cloned EBV-transformed cells were not fully differentiated, as judged by inability to bind TNP-SRBC and to secrete anti-TNP antibody. The minority of more differentiated cells were selected by TNP-SRBC rosetting. They were found to proliferate to a lesser extent than nonrosetting cells and to contain increased numbers of antibody-secreting cells. This inverse relationship between proliferation and differentiation was also shown to be cell cycle related in that the TNP-SRBC rosetting cells resided, to a greater extent than the nonrosetting cells, in the G1 phase of the cell cycle. The finding that the G1 phase of the cell cycle was associated with differentiation into anti-TNP secreting cells was confirmed by demonstrating that treatment with hydroxyurea, which arrests the cells in G1, resulted in decreased proliferation and an increased proportion of antibody-secreting cells. Similarly, addition of phorbol ester resulted in increased antibody secretion and decreased proliferation, suggesting a role for protein kinase C in this differentiation pathway. The strategy of increasing the number of antibody-producing cells in this human EBV line, by promoting differentiation of the cells in G1, may be relevant to the large scale production of specific human mAb for the treatment and diagnosis of human diseases.