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.     

Cellular origin and distribution of transforming growth factor-β1 in the normal rat myocardium

Summary Transforming growth factor- (TGF-) is a biologically active polypeptide present in normal tissues as well as transformed cells. Two structurally related forms of this peptide are TGF- ₁ and TGF- ₂. Using freshly isolated cardiomyocytes and non-myocyte heart cells, and a [³²P]-labelled cDNA probe to human TGF- ₁, we demonstrated that mRNA for TGF- ₁ could be detected only in the nonmyocyte fraction of heart cells. In the present study, the distribution of TGF- ₁ in the heart was determined by immunofluorescence staining by use of a polyclonal antibody to porcine TGF- ₁ in cryostat sections of rat heart. Immunofluorescence staining was intense around the blood vessels and radially diffuse in the surrounding myocardium.     

Changes of Escherichia coli cell cycle parameters during fast growth and throughout growth with limiting amounts of thymine

It is generally accepted that during fast growth of Escherichia coli, the time (D) between the end of a round of DNA replication and cell division is constant. This concept is not consistent with the fact that average cell mass of a culture is an exponential function of the growth rate, if it is also accepted that average cell mass per origin of DNA replication (M_i) changes with growth rate and negative exponential cell age distribution is taken into account. Data obtained from cell composition analysis of E. coli OV-2 have shown that not only (M_i) but also D varied with growth rate at generation times () between 54 and 30 min. E. coli OV-2 is a thymine auxotroph in which the replication time (C) can be lengthened, without inducing changes in , by growth with limiting amounts of thymine. This property has been used to study the relationship between cell size and division from cell composition measurements during growth with different amounts of thymine. When C increased, average cell mass at the end of a round of DNA replication also increased while D decreased, but only the time lapse (d) between the end of a replication round and cell constriction initiation appeared to be affected because the constriction period remained fairly constant. We propose that the rate at which cells proceed to constriction initiation from the end of replication is regulated by cell mass at this event, big cells having shorter d times than small cells.Abbreviations OD₄₅₀ and OD₆₃₀ Optical density at a given wavelength in nm Dedicated to Dr. John Ingraham to honor him for his many contributions to Science     

The biennial life strategy in a random environment

In a previous paper (J. Math. Biol. 26, 199–215 (1988)) we calculated the mean and variance of the long-run geometric growth rate of a discrete-time population model with two age classes in a random environment. The formula which was used in that paper as the starting point for the computation of the variance represents only the contribution of the one-period variances. Here we supplement these results by a calculation of the exact variance. All qualitative conclusions reached before are unaffected.     

The 18 kDa cytosolic acid phosphatase from bovine liver has phosphotyrosine phosphatase activity on the autophosphorylated epidermal growth factor receptor

In this paper we demonstrate that the cytosofic low-M_r acid phosphatase purified from bovine liver has phosphotyrosine protein phosphatase acitivity on ³²P-autophosphorylated epidermal growth factor (EGF) receptor. This activity was significantly inhibited by orthovanadate and p-hydroxymercuribenzoate; the latter result indicates that free sulfhydryl groups are required for phosphotyrosine phosphatase activity. The enzyme was active in a broad pH range, with maximum activity between pH 5.5 and 7.5. The apparent K_m for ³²P-EGF receptor dephosphorylation was 4 nM. The enzyme appeared to be specific for phosphotyrosine in that it dephosphorylated the autophosphorylated EGF receptor and L-phosphotyrosine, but not ³²P-Ser-casein, L-phosphoserine or L-phosphothreonine. These data suggest that the cytosolic low-M_r acid phosphatase might play a regulatory role in EGF receptor-dependent transmembrane signalling.     

Intentional cranial vault deformation and induced changes of the cranial base and face

Three morphologically distinct populations of Peruvian crania (n = 130) were metrically analysed to quantify changes resulting from intentional artificial vault deformation. Two of these samples are artificially deformed (anteroposterior [AP] and circumferential [C] types). Measurements taken from lateral radiographs demonstrated that alternative forms of the cranial base angle (N-S-Ba, planum angle, planum sphenoidale to plane of the clivus and PANG angle, planum sphenoidale to basion-sella plane) and the orbital and OANG angles (orbital roof to plane of the clivus and basion-sella plane, respectively) of both deformed groups increased while the angle S-Ba-O decreased significantly with respect to the undeformed (N) sample. Changes in the AP group are largely due to anteroinferior displacement of the basion-sella plane. Similar changes in group C are amplified by this group's posterosuperior frontal migration. This migration results in a relatively shallow orbit at the orbital plate/frontal squama interface. Unlike the deformation experienced by the external vault plates, the basion-sella plane orientation remains stable with respect to the Frankfort Horizontal. Additionally, nasal region measurements such as maximum nasal aperture breadth and nasal height were largely stable between each deformed group and the undeformed group. However, facial (bimaxillary and bizygomatic), basicranial, cranial, and frontal breadths decreased significantly from group AP to group N to group C. Thus, gross morphological facial changes between each undeformed group and the control group are largely accounted for by dimensional changes in peripheral structures. These results stress the importance of the dynamic interrelationship between the cranial vault and base in the development of the craniofacial complex.     

Associations between blood groups, blood protein polymorphisms and breeding values for production traits in Swedish Red and White Dairy bulls

The relationships of nine blood group systems and two blood protein polymorphisms with breeding values for several production traits were examined in dairy cattle of the Swedish Red and White (SRB) breed. The material consisted of 2212 bulls; the bulls were performance tested for growth rate and their breeding values for milk yield, fat and protein content in milk were estimated from progeny tests. The direct effect of marker alleles or marker phenotypes was analysed in a multiple regression model. Several significant associations were found; many supported earlier findings. However, the contribution of the markers to the total variation of the breeding values was very small. Linkage between marker loci and production loci was studied in offspring from heterozygous sires by estimating the interactions between sire and marker alle using a model eliminating the direct effects of sire and marker alle. There were strong indications of linkage between some marker loci (e.g. B, J and Am-1 loci) and loci with large effects on production traits.     

Stimulation and inhibition of cardiac myocyte proliferation in vitro

Summary We have examined the effect of crude cardiac tissue extracts as well as that of several growth factors and triiodothyronin (T3) on DNA synthesis of cardiac myocytes in culture. Extracts from embryonic and adult cardiac tissue stimulated DNA synthesis of myocytes. Atrial myocytes exhibited overall higher degree of stimulation than their ventricular counterparts and extracts from adult atrial tissue had the highest apparent mitogenic activity for atrial myocytes. We have shown that adult heart contains basic fibroblast growth factor (bFGF), especially in the atria [1]. Transforming growth factor (TGF) and insulin-like growth factors (IGFs) are also accumulated in cardiac tissues [2, 3]. We found that bFGF and the IGFs stimulate myocyte cell proliferation and DNA synthesis. These factors also stimulate cardiac non-muscle proliferation, especially in the presence of serum. TGF inhibited proliferation and DNA synthesis and cancelled the effect of bFGF or IGFs on the myocytes. T3 also diminished the bFGF-induced mitogenic stimulation of cardiomyocytes. Our data suggest that these factors may be involved in the regulation of cardiomyocyte proliferation in vivo.Abbreviations bFGF basic Fibroblast Growth Factor - BSA Bovine Serum Albumin - DM Defined Medium - Fes Fetal calf serum - FITC Fluorescein - IGF Insulin-like Growth Factor - IgG Immunoglobulin - LI Labeling Index - PBS Phosphate Buffered Saline - T3 Triiodothyronine - TGF Transforming Growth Factor      

Preparation of affinity-purified,biotinylated tetanus toxin,and characterization and localization of cell surface binding sites on nerve growth factor-treated PC12 cells

Biotinylated derivatives of tetanus toxin were prepared and isolated by chromatofocusing and ganglioside-affinity chromatography. Biotinylation was monitored by the appearance of a 210,00 dalton complex upon SDS-polyacrylamide gel electrophoresis in the presence of avidin, and by selective binding to an avidin-Sepharose gel. At molar biotin:toxin ratios from 11 to 201 only biotinylated derivatives with low toxicity were obtained; these derivatives, however, retained 60–80% of their specific binding affinity for brain synaptosomes. A biotinylated tetanus toxin derivative purified by ganglioside-affinity chromatography was used to identify and localize tetanus toxin binding sites on PC12 cells. Electron microscopic analysis with streptavidin-gold revealed very low levels of tetanus toxin binding sites on the surface of untreated cells, and the appearance of such binding sites during the second week of nerve growth factor-induced differentiation. Examination of micrographs of the differentiated cells indicated that the tetanus toxin binding sites sites are concentrated on the neurites, with relatively few appearing on the cell bodies. Cognate studies using¹²⁵I-labeled, affinity-purified tetanus toxin revealed an increase in PC12 binding capacity from about 0.07 nmol/mg protein in untreated cells to 0.8 nmoles/mg protein in cells treated for 14 days with nerve growth factor. Cells treated in suspension for 2–3 weeks with nerve growth factor do not express tetanus toxin binding sites; upon plating, these cells required one week for the appearance of binding sites, although neurites grew much more rapidly from these primed cells. The high binding capacity of these tetanus toxin sites, as well as their sensitivity to neuraminidase, is indicative of a polysialoganglioside structure. The advantages of biotinylated tetanus toxin derivatives are discussed and the significance of nerve growth factor-differentiated PC12 cells grown as monolayers as a model for the study of the development, localization, and function of neuraminidase-sensitive tetanus toxin binding sites is presented.Abbreviations PBS phosphate-buffered saline - STS sucrose-Tris-serum solution - NGF nerve growth factor - C collagen - PL polylysine - BBG bovine brain ganglioside mixture - GM₁ gafactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosyl ceramide - GD_1a [N-acetylneuraminyl]-galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosyl ceramide - GT_1a [N-aceylneuraminyl]-galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosyl ceramide - GD_1b galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl-N-acetylneuraminyl]-galactosylglucosyl ceramide - GT_1b [N-acetylneuraminyl]-galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl-N-acetylneuraminyl] galactosylglucosyl ceramide - NANA N-acetylneuraminic acid     

The selection of microbial communities by constant or fluctuating temperatures

Abstract The diversity of bacterial communities isolated from Antarctic lake sediment in chemostats under constant low temperature (8°C) or diurnally fluctuating temperature (1°C to 16°C) was examined. The median optimum temperature for growth of the freshwater bacteria isolated from the fluctuation chemostat was significantly lower ( P < 1%) than that for those from the constant temperature chemostat. The diversity of the enriched bacterial community isolated in the chemostat culture subjected to short-term temperature fluctuations was greater than that enriched under constant temperature. At least 4 different groups of bacteria, that occupied separate 'temperature niches', were isolated from the fluctuating chemostat compared to only one group isolated from the stable chemostat. Furthermore, a pseudomonad from the fluctuating chemostat was shown to out-compete another pseudomonad from the stable chemostat when both were subjected to the fluctuating temperature regime. However, the pseudomonad of constant (8°C) temperature origin out-competed that isolated under fluctuating conditions when subjected to a stable temperature regime.