Transgenic markers for mammalian chimeras

Summary We describe the construction of aggregation chimeras between normal and transgenic embryos containing multiple copies of mouse -globin genes. The transgenic component of the chimeras is then detected in tissue sections by a DNA-DNA in situ hybridization technique, using a biotinylated DNA -globin probe and an avidin-linked alkaline phosphatase detection system. The general advantages of transgenic markers for chimeras are discussed.     

Studies on haemosiderin and ferritin from iron-loaded rat liver

Summary Haemosiderin has been isolated from siderosomes and ferritin from the cytosol of livers of rats iron-loaded by intraperitoneal injections of iron-dextran. Siderosomal haermosiderin, like ferritin, was shown by electron diffraction to contain iron mainly in the form of small particles of ferrihydrite (5Fe₂O₃ · 9H₂O), with average particle diameter of 5.36±1.31 nm (SD), less than that of ferritin iron-cores (6.14±1.18 nm). Mössbauer spectra of both iron-storage complexes are also similar, except that the blocking temperature,T _B, for haemosiderin (23 K) is lower than that of ferritin (35 K). These values are consistent with their differences in particle volumes assuming identical magnetic anisotropy constants. Measurements of P/Fe ratios by electron probe microanalysis showed the presence of phosphorus in rat liver haemosiderin, but much of it was lost on extensive dialysis. The presence of peptides reacting with anti-ferritin antisera and the similarities in the structures of their iron components are consistent with the view that rat liver haemosiderin arises by degradation of ferritin polypeptides, but its peptide pattern is different from that found in human-thalassaemia haemosiderin. The blocking temperature, 35 K, for rat liver ferritin is near to that reported, 40 K, for human-thalassaemia spleen ferritin. However, the haemosiderin isolated from this tissue, in contrast to that from rat liver, had aT _B higher than that of ferritin. The iron availability of haemosiderins from rat liver and human-thalassaemic spleen to a hydroxypyridinone chelator also differed. That from rat liver was equal to or greater, and that from human spleen was markedly less, than the iron availability from either of the associated ferritins, which were equivalent. The differences in properties of the two types of haemosiderin may reflect their origins from primary or secondary iron overload and differences in the duration of the overload.     

Variants of the anti-Müllerian hormone gene in a compound heterozygote with the persistent Müllerian duct syndrome and his family

Summary The human genome contains a large number of interspersed simple repeat sequences that are variable in length and can therefore serve as highly informative, polymorphic markers. Typing procedures include conventional multilocus and single locus probing, and polymerase chain reaction aided analysis. We have identified simple sequences in a cosmid clone stemming from the human Y chromosome and consisting of (gata)_n repeats. We have compared these with two equivalent simple repeat loci from chromosome 12. After amplifying the tandemly repeated motifs, we detected between four and eight different alleles at each of the three loci. Codominant inheritance of the alleles was established in family studies and the informativity of the simple repeat loci was determined by typing unrelated individuals. The polymorphisms are suitable for application in linkage studies, practical forensic case work, deficiency cases in paternity determination, and for studying ethnological questions. The mutational mechanisms that bring about changes in simple repeats located both on the autosomes and on the sex chromosomes, are discussed.Professor Dr. Otto Prokop (Humboldt-Universität Berlin) on the occasion of his 70th birthday     

Expression of human nerve growth factor receptor on cells derived from all three germ layers

Nerve growth factor (NGF) is a protein which promotes the survival and differentiation of neuronal cells in vitro and plays an important role in neuronal development. In this study, we have examined the expression of the receptor for NGF (NGFR) in human neuronal and nonneuronal cells, both in tissue culture and in vivo. In addition to cell lines derived from neuroblastoma, astrocytoma, and melanoma, all of which share a common neuroectodermal origin, NGFR was detected in a number of cultured cells of mesenchymal, epithelial, and hematopoietic derivation. Immunohistochemical analysis showed that NGFR is expressed in several nonneural human tissues, and the cell types in which NGFR was found include derivatives from all three germ layers. Thus, our findings demonstrate that NGFR is much more widely expressed in human cells and tissues than was previously thought.     

Antibacterial activity of some α- substituted 2-Methyl-5-nitrofurans

The minimum inhibitory concentration values against Gram-negative and Gram-positive bacteria were determined and compared for a selected group of synthesized alpha-substituted 2-methyl-5-nitrofuran derivatives. In vitro oxidation of thiols to disulfides by 2-(iodomethyl)-5-nitrofuran indicated that oxidation of enzyme-thiol groups to disulfide bonds was a possible mode of action; but was discounted by noninhibition of thiol enzymes by these compounds. Electron-microscopic studies of the morphology of bacteria after treatment with these derivatives showed the formation of unusual elongation, branching and atypical rod shapes in E. coli, while S. aureus manifested multibud formation with some cytoplasmic protrusions. The possible mode of action of these compounds is discussed.     

Fatty acid desaturation in the intestinal mucosa

Information as to the ability of the enterocyte to desaturate fatty acids is lacking. This is important in understanding whether the source of intestinal arachidonic (20:4(n-6) acid is biliary or from de novo synthesis. Delta 9- and delta 6-desaturase enzymes were assayed in homogenates of rat jejunum, ileum and liver. Rat small intestine possesses desaturase activity to convert palmitic (16:0) to palmitoleic (16:1) and linoleic (18:2(n-6) to linolenic (18:3(n-6) acid. Enzyme activities were highest in liver relative to activity in jejunal and ileal homogenates. It is concluded that delta 9- and delta 6-desaturase activities may have an important role in determining physico-chemical properties and thus transport properties of enterocyte membranes.     

Contrasting evolutionary histories among tightly linked HLA loci

Genes comprising the major histocompatibility complex (MHC) play a central role in governing the immune response of vertebrates. A great deal of information has been revealed on the molecular biology and physiology of these loci, but three features-the high polymorphism, tight linkage among the loci, and the nonrandom association of alleles-make the system of particular interest from the perspective of population genetics. Information on the dynamic evolutionary forces that have acted on a locus can be inferred from the number and distribution of alleles that it carries. Ten loci from the HLA region of the human MHC, each sampled from several different populations, have been examined for departures from the expected value of homozygosity under the condition of selective neutrality. The homozygosities of five class I and II loci that code for membrane glycoproteins, HLA-A, -B, -C, -DR, and -DQ, and of glyoxylase I (GLO) were significantly less than the neutrality expectations. This suggests the presence of some form of balancing selection. In spite of being closely linked, in fact, located between the class I and class II histocompatibility loci, the homozygosities of the four class III or complement loci C2, Bf, C4A, and C4B, which are detected by electrophoresis, were indistinguishable from, or exceeded, that expected under neutrality. Although this conforms to the suggestion that, in general, electrophoretic variants are neutral, because of the tight linkage to loci demonstrating a history of selection, it is possible that the mechanism for generating variation in the class III loci may be different from that of the class I and class II loci.     

Comparative studies of pollen and fluorescent dye transport by bumble bees visiting Erythronium grandiflorum

Summary In the Colorado Rocky Mountains the glacier lily Erythronium grandiflorum exhibits a striking dimorphism in pollen color and is commonly pollinated by the bumble bee Bombus occidentalis. We induced bees to visit sequences of flowers in a flight cage, and compared dispersal of distinctively-colored pollen and fluorescent pigment (dye) that the bee had picked up at a single donor flower. Nonparametric and parametric analyses showed that dispersal properties of pollen and dye differed; consistently less pollen was deposited and it was carried consistently shorter distances than dye. Dye thus does not provide an accurate means of assessing exacty where or how far pollen travels in this plant-pollinator system. On the other hand, both pollen and dye responded similarly to several experimental manipulations of donor and recipient flowers. Hence dye may well be of value for a qualitative investigation of how floral traits influence pollen dispersal.