Chromosomal localization and racial distribution of the polymorphic human dihydrofolate reductase pseudogene (DHFRP1).

The human dihydrofolate reductase (DHFR) gene family comprises one functional gene and at least four intronless processed pseudogenes. The functional DHFR gene is on chromosome 5, and DHFRP4 is on chromosome 3. Using in situ hybridization, we have now localized the functional DHFR gene to the region q11.1-q13.3 on chromosome 5. By genomic DNA analysis of a panel of human X rodent somatic-cell hybrids, we determined the chromosomal assignment of the DHFRP1 pseudogene to chromosome 18 and that of the DHFRP2 pseudogene to chromosome 6. The DHFRP1 pseudogene exhibits a novel form of polymorphism in humans in that it is present in the DNA of some individuals and absent in that of others. We investigated the racial distribution of this pseudogene in five racial groups. The allelic frequency as defined by analysis of 180 chromosomes was found to be 94% in Mediterraneans, 77% in Asian Indians, 67% in Chinese, 57% in Southeast Asians, and 32% in American blacks. These data suggest that the transposition of this "perfect" pseudogene occurred prior to the inception of the human racial groups.     

A note on the use of cross-linked starch in microbiology with special reference to detecting amylase production

Anilogel-E, a cross-linked starch, can be used with distinct advantages where native starch or soluble starch are conventionally used, e.g. in scoring for amylolytic organisms, as an ingredient of fermentation media, and in enhancing protoplast regeneration. It is particularly useful for the direct visualization of amylase producing micro-organisms on solid media, making prior replication of colonies unnecessary.     

Enhanced reappearance of fast fibers in regenerating crayfish claw closer muscles

In the pristine claws of adult crayfish the muscle fibers of the closer are all of slow type as judged by sarcomere lengths of greater than 6 micron, and a uniform degree of myofibrillar ATPase activity. In regenerating claws of mature and immature crayfish, the muscle has a central band of fast type fibers as characterized by shorter sarcomeres (less than 6 micron) and a higher degree of ATPase activity than the surrounding slow fibers. During primary development, the closer muscle has a fiber composition similar to that of the regenerating muscle except for a smaller proportion of fast fibers. Thus the reappearance of fast fibers during regeneration recapitulates ontogeny while their enhanced proportions may reflect epigenetic influences such as restriction of nerve-mediated muscle activity in the limb bud.     

Innervation of the limb accessory flexor muscle in several decapod crustaceans. II. Electrophysiology

The innervation of the distal and proximal heads of the accessory flexor muscle in three portunid crabs and two non-portunid decapods was studied electrophysiologically. In all species studied, the proximal head received only the two previously reported accessory flexor axons, an excitor and an inhibitor. The same two axons also innervated the distal head in all species, but in the portunids the distal head also received excitation from at least three, and probably sometimes four, of the main flexor excitor efferents. The accessory inhibitor exerted very strong effects in the tonic muscle fibers found in the proximal head and in the most proximal bundle of the distal head. The newly described inhibitory and excitatory distributions may have important implications for locomotory behavior.     

Hydroxylation of benzoate and its chlorinated derivatives in Aspergillus niger

Comparison of the properties of a purified benzoate-4-hydroxylase, using benzoic acid and its chlorinated derivatives as substrate, suggests that the same enzyme operates during the initial hydroxylation of benzoate, 2-chlorobenzoate (2-cba), and 3-chlorobenzoate (3-cba) in A.niger.     

Monoclonal antibody-based immunoassay for type A Clostridium botulinum toxin is comparable to the mouse bioassay

A monoclonal antibody (BA11) has been produced against Clostridium botulinum type A neurotoxin by the fusion of myeloma cells (P3 NS1/1-Ag4-1) with spleen cells from BALB/c mice immunized with botulinum type A neurotoxoid. The antibody bound specifically to botulinum type A neurotoxin, showing no cross-reactivity with types B and E botulinum toxins or with any of several other bacterial toxins tested. The monoclonal antibody did not bind to botulinum type A neurotoxin which had been denatured with sodium dodecyl sulfate and bound only weakly to each of the separated heavy and light subunits of the neurotoxin, suggesting a conformational requirement for the antigenic determinant of the antibody. A sensitive immunoassay for C. botulinum type A toxin with monoclonal antibody BA11 in conjunction with an enzyme amplication system has been developed which allows detection of 5 to 10 mouse 50% lethal doses ml-1 of purified neurotoxin. The assay was equally sensitive when applied to the detection of crude toxin in food stuffs; the average value for the minimum level of detectable toxin in extracts of tinned salmon or corned beef was 9 +/- 3.1 mouse 50% lethal doses ml-1.     

Post harvest Spoilage of Mangoes by Penicillium cyclopium and its Control by Gamma-Radiation and a Fungicide

Penicillium cyclopium has been isolated from spoiled ripe alphonso mango, Spores were found resistant up to a 500 krad dose of γ-radiation. A 25 krad dose treatment which is normally used for the prolongation of shelf life of mangoes could not protect them against artificial or natural infection. Bavistin (2-(methoxy carbamoyl)- benzimidazole) inhibited completely spore germination at a concentration of 100 mg/1. A post harvest dip of unripe mangoes into an aqueous solution of this fungicide lowered the degree of spoilage considerably.