Mutations for the autosomal recessive and autosomal dominant forms of polycystic kidney disease are not allelic

Summary The autosomal dominant form of polycystic kidney disease (ADPKD) has been linked to the -globin gene locus on 16p. Linkage studies between the autosomal recessive type (ARPKD) and the 3 HVR of the -globin gene cluster showed that the ARPKD and ADPKD are not allelic.     

Plasmid-associated transfer of tetracycline resistance in Bacteroides ruminicola

Tetracycline resistance was transferred at frequencies between 10(-7) and 10(-6) per recipient cell in anaerobic matings between two strains of the strictly anaerobic rumen bacterium Bacteroides ruminicola. The donor strain, 223/M2/7, was a multiple-plasmid-bearing tetracycline-resistant strain from the ovine rumen, and the recipient, F101, was a rifampin-resistant mutant of B14, a bovine strain belonging to B. ruminicola subsp. brevis. Resistance transfer could occur in the presence of DNase, but not in dummy mating mixtures in which filtrate from a donor culture replaced donor cells. Acquisition of tetracycline resistance by the recipient was accompanied by the appearance of a 19.5-kilobase pair plasmid (designated pRRI4) which was homologous with a plasmid of similar size and restriction pattern present in the donor strain. A transconjugant (F115) carrying pRRI4 was also able to act as a donor of tetracycline resistance and plasmid DNA in matings with another recipient. Derivatives of F115 that had spontaneously lost tetracycline resistance lacked detectable plasmid DNA. It is concluded that pRRI4 mediated the transfer of tetracycline resistance. Transfer of resistance was not detectably enhanced by pregrowth of the donor in medium containing tetracycline. Transfer of tetracycline resistance was not detected from 223/M2/7 to a strain, 23 belonging to B. ruminicola subsp. ruminicola.     

The marginal regions of thylakoid membranes: A partial characterization by polyoxyethylene sorbitan monolaurate (Tween 20) solubilization of spinach thylakoids

The detergent Tween-20 solubilized preferentially portions of the marginal regions of Spinacea oleracea L. thylakoid membranes and, thus, opened the inside of the grana to the external media. Differential centrifugation. following Tween-20 solubilization. enabled separate fractions of grana and stromal-exposed membranes to be isolated. Analysis of Tween-20 solubilized material, after pelleting all membrane material by centrifugation at 100 000 g, revealed polypeptides associated with the coupling factor (CF₁) particles, cytochrome b₆/f and photosystem II complexes, suggesting that the marginal membranes contain these proteins. Concomitantly, the 100 000 g pellet was depleted in cytochrome b₆/f and P700, determined spectroscopically, Thus. our results reveal the margin to be a distinct membrane region, which does not contain the light-harvesting centers of photosystem II (LHC II). The implication of these results, in terms of the energetic interaction of components of granal and stromalexposed membrane regions, is discussed.     

Rat lens gamma-crystallins. Characterization of the six gene products and their spatial and temporal distribution resulting from differential synthesis

We have isolated, purified and characterized six individual gamma-crystallin polypeptides present in the rat lens. Comparison of their amino acid compositions with the known structure of the six gamma-crystallin genes permits a one-to-one correspondence to be made between each protein synthesized and the encoding gene. This demonstrates that each of the six genes is actually expressed in vivo. Two classes of three gamma-crystallins each, which we have designated classes gamma ABC and gamma DEF, are known to exist, on the basis of internal sequence homology. We have measured the temperature-dependent phase-separation characteristics of solutions of the six purified gamma-crystallins, and find that the three members of the gamma DEF class (gamma 2-2, gamma 3-1 and gamma 4-1) are all cryo-proteins with relatively high phase-separation temperatures, whereas the three gamma ABC crystallins (gamma 1-1, gamma 1-2 and gamma 2-1) do not show phase separation above -7 degrees C. We have measured the spatial distribution in rat lens of each of the alpha-, beta- and gamma-crystallins as a function of age from 1 to 420 days, using size-exclusion and ion-exchange high-pressure liquid chromatography (HPLC). Our findings in the cortical layer permit us to establish the differential synthesis of each of the crystallins during lens development. Particular attention has been devoted to the spatial and temporal distribution of the six individual gamma-crystallins. Up to birth, synthesis of the three components of the gamma DEF class predominates, and in particular that of gamma 2-2. In subsequent development the three components of the gamma ABC class assume a greater proportion of monomeric crystallins synthesized, while beta s-crystallin synthesis predominates in late development. Our analysis of different layers within single lenses provides novel information on spatial gradients of the water-soluble and water-insoluble protein fractions as a function of age. We consider the consequences of these findings for lens transparency and opacity in both rat and mouse lens. We show that the high concentrations of gamma DEF-crystallins appear to be responsible for the opacity known to occur in young rat lenses. We conclude from these observations that close control of the differential synthesis of gamma-crystallins plays an important role in maintaining lens transparency during development.     

Isolation of transketolase from human erythrocytes

Transketolase was isolated from human red blood cells with over 6,200 fold purification by a new method. The stepwise procedure for the isolation of the enzyme from erythrocyte hemolysate included the use of ethanol/chloroform precipitation, chromatography on hydroxyapatite and finally, affinity adsorption on carboxymethyl-cellulose. The molecular weight of erythrocyte transketolase, as determined by polyacrylamide gel electrophoresis, appeared to be about 140,000. The pH optimum for activity was between 7.6 and 7.8 and the optimum temperature for activity was 50 degrees C. The Km values for xylulose-5-phosphate, ribose-5-phosphate and fructose-6-phosphate were 2.0 x 10(-4) M, 3.2 x 10(-4) M and 2.0 x 10(-3) M, respectively.     

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.     

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.