Some observations on the choice of detergent for solubilization of the human erythrocyte membrane.

Solubilization of the human erythrocyte membrane by seven detergents is described. Components released into the supernatant or retained in the residue were identified by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Two non-ionic detergents exhibiting little u.v. absorption were more efficient than u.v.-absorbing Triton X-100. Evidence is presented of an interchange between protein PAS 1 and protein PAS 2.     

Enzyme-linked immunosorbent analysis for aflatoxin B1.

An enzyme-linked immunosorbent analysis (ELISA) permitted the detection of less than 10 pg of aflatoxin B1 per ml. The antitoxin was most specific for aflatoxins B1 and B2alpha, and least specific for aflatoxin G1.     

Control of the production of orthophosphate repressible extracellular enzymes in Neurospora crassa

Summary N-1, a plasmid isolated from a strain ofShigella flexneri in Japan more than 10 years ago, mediates the phage inhibition phenotype which has recently been found to be characteristic of plasmids of the H₂ incompatibility group. Using the criteria of phage inhibition, surface exclusion and incompatibility, the N-1 plasmid is shown to be closely related to H₂ plasmids isolated from non-typhoid salmonella and distantly related to H₁ plasmids isolated fromSalmonella typhi. Plasmids of other incompatibility groups did not show the H₂ type of phage inhibition.     

Chromosome damage in Chinese hamster cells sensitized to near-ultraviolet light by psoralen and angelicin

The clastogenic effect of furocoumarins psoralen and angelicin in the presence of near-UV (320-380 nm) differs greatly, as do their modes of interaction with DNA. Psoralen, which requires only one-fifth as much light energy to produce the same lethal effect as angelicin at equimolar concentrations, is able to cross-link DNA whereas angelicin cannot. The frequency of micronuclei which arise from chromosomal fragments shows the same differential effect as lethality. Indeed aberrations account for much or all of the lethality observed. Metaphase analysis at comparable aberration frequencies revealed that angelicin and psoralen both induce chromatid deletions and a wide spectrum of chromatid exchanges. These data show that both cross-links and monoadducts to the DNA can result in chromosomal aberrations. The relative contributions of cross-links and monoadducts to chromosomal aberrations still remain to be determined. It is noteworthy that extensive chromosomal damage is induced in mammalian cells by the combination of psoralen and near-UV, a treatment which is currently widely used in the therapy of psoriasis.     

Antimicrobial resistance and resistance plasmids in Salmonella from Ontario, Canada.

Collections of 589 human and 204 animal strains of Salmonella isolated in Ontario during the summer of1974 were examined for susceptibility to 12 antimicrobial agents. Many isolates were found to be resistant to both chloramphenicol (12.4% of the human and 38.2% of the animal sample) and ampicillin. The chloramphenicol resistance almost always occurred in strains which were also resistant to ampicillin and was usually due to a self-transmissible plasmid with a resistance pattern of CmKmSmTc (chloramphenicol, kanamycin, streptomycin, and tetracycline) or CmTc. Ampicillin resistance in these strains was mediated by a variety of plasmids with patterns ApSu (ampicillin and sulfa drugs) and ApSmSu, many of which were nonself-transmissible. Ampicillin resistance in chloramphenicol-sensitive strains was transferable from 21% of the strains, and it was associated with resistance patterns which were different from the self-transferable ampicillin patterns from the chloramphenicol-resistance strains.     

Techniques for Preparing Seeds with Water-Impermeable Coats for Light and Electron Microscopy

An improved method for fixing and embedding seeds with impermeable coats for microscopic study has been developed. Entry portals are cut into seed coats to permit better penetration of fixative. This makes it possible to obtain semithin sections of whole seeds for light microscopy and thin sections of selected areas for electron microscopy. Seed tissues may thereby be studied relative to their position in the seed and to surrounding tissues. This permits studies of imbibition and developmental morphology of seeds in histological and cytological detail previously possible only with soft or dissected seeds.     

Radioiodinated iodobenzoyl conjugates of a monoclonal antibody Fab fragment. In vivo comparisons with chloramine-T-labeled Fab

A comparative investigation of the biodistributions of radioiodinated p- and m-iodobenzoyl conjugates of a monoclonal antibody Fab fragment, NR-LU-10 Fab, and the same antibody Fab fragment radioiodinated by the chloramine-T (ChT) method has been carried out in mice. Coinjected, dual-isotope studies in athymic mice with tumor xenografts have demonstrated that there are only minor differences in the in vivo distributions of the iodobenzoyl-labeled Fabs, except in the excretory organs, kidneys, and intestines, where major differences were observed. Similarly, coinjection of either the p-iodobenzoyl or m-iodobenzoyl conjugate of NR-LU-10 Fab with the Fab radioiodinated with ChT/radioiodide into BALB/c mice provided additional data that indicated that the two iodobenzoyl conjugates distributed similar in a number of selected tissues. The tissue-distribution differences of the regioisomeric iodobenzoyl conjugates in relation to the ChT-radioiodinated Fab were large for the stomach and neck, consistent with previous studies. The most notable difference between the two iodobenzoyl conjugates was the kidney activity, where the m-iodobenzoyl conjugate was similar to the directly labeled Fab, but the p-iodobenzoyl-conjugated Fab was higher by nearly a factor of 2.     

Type VI collagen microfibrils: evidence for a structural association with hyaluronan

Type VI collagen, a widespread structural component of connective tissues, has been isolated in abundance from fetal bovine skin by a procedure involving bacterial collagenase digestion under nonreducing, nondenaturing conditions and gel filtration chromatography. Rotary shadowing electron microscopic analysis revealed that the collagen VI was predominantly in the form of extensive intact microfibrillar arrays. These microfibrils were seen in association with hyaluronan, which was identified by its ability to bind the G1 fragment of cartilage proteoglycan. Treatment with highly purified hyaluronidase largely disrupted the collagen VI microfibrils into component tetramers, double tetramers, and short microfibrillar sections. Subsequent incubation of disrupted collagen VI in the presence of hyaluronan facilitated a partial repolymerization of the microfibrils. In vitro binding studies have also demonstrated that type VI collagen binds hyaluronan with a relatively high affinity. These studies demonstrate that a specific structural relationship exists between type VI collagen and hyaluronan. This association is likely to be of primary importance in the growth and remodeling processes of connective tissues.