Promoter methylation and progressive transgene inactivation inArabidopsis

Agrobacterium-transformedArabidopsis plants were generated and the stability of their T-DNA-encoded resistance to kanamycin was examined. Of seven families, each homozygous for a single insertion event, two showed progressive inactivation of resistance over four generations of inbreeding. Loss of resistance was associated with methylation of anSst II site in thenos promoter of the kanamycin resistance gene. Treatment of plant roots from inactive lines with the demethylating agent 5-azacytidine restored the ability of such lines to form callus on kanamycin-containing media. These observations are consistent with the view that methylation is a factor in the progressive inactivation of transgenes inArabidopsis.     

Thermal Denaturation of Native Striatal Tyrosine Hydroxylase: Increased Thermolability of the Phosphorylated Form of the Enzyme

Tyrosine hydroxylase was purified from bovine corpus striatum. The native enzyme had a half-life of 15 +/- 3 min at 50 degrees C. Phosphorylation of tyrosine hydroxylase with protein kinase purified from both corpus striatum and heart activated the enzyme, but activity was rapidly lost with additional preincubation of the enzyme at 30 degrees C. Thermal denaturation studies indicated that phosphorylated tyrosine hydroxylase had a half-life of 5 +/- 2 min at 50 degrees C     

Genetics of formamidase-5 (brain formamidase) in the mouse: Localization of the structural gene on chromosome 14

A single formamidase, which is different from the formamidases found in other tissues, occurs in the brains of mice. This enzyme is here called formamidase-5 and the gene symbol is designated For-5. Two alleles are recognized on the basis of their differential heat sensitivity: For-5 ^b is relatively heat stable and is present in strain C57BL/6J, while For-5 ^d is relatively heat sensitive and is present in strain DBA/2J. The heat sensitivity of formamidase-5 in 44 other inbred strains and substrains was tested and found to resemble that of C57BL/6J or DBA/2J. Thirty-six recombinant inbred strains derived from progenitors that differed at For-5 were studied to test for single-gene inheritance and linkage with other loci. Complete concordance was found with the esterase-10 locus (Es-10), indicating close linkage. The 99% upper confidence limit of the distance between For-5 and Es-10 is 3.7 centimorgans (cM). Es-10 is located on chromosome 14 about 19 cM from the centromere. An independent demonstration of linkage of For-5 with Es-10 and another chromosome 14 marker, hairless (hr), is provided by the finding that the HRS/J strain, which has been sibmated for 60 generations with forced heterozygosity at the hr locus, is cosegregating at For-5 and Es-10. A survey of 32 inbred strains and substrains revealed that the For-5 ^d allele is associated with the Es-10 ^b allele, and that the For-5 ^b allele is associated with Es-10 ^a and Es-10 ^c. Formamidase-5 segregates as expected in the F₂ generation of crosses between strains bearing For-5 ^b and For-5 ^d alleles. It is possible that this unique formamidase of the brain is involved in the metabolism of a neurotransmitter substance.This research was sponsored in part by the Department of Energy under contract with the Union Carbide Corporation and in part by NIH Research Grant GM-18684 from the National Institute of General Medical Sciences. J. C. F. is a predoctoral Fellow supported by Grant CA 09104 from the National Cancer Institute. The Biology Division of Oak Ridge National Laboratory and the Jackson Laboratory are fully accredited by the American Association for Accreditation of Laboratory Animal Care.     

The utilisation of arginine by oral streptococci grown glucose-limited in a chemostat

Abstract Legionella pneumophila occurring in drinking water was subjected to environmental stress through holding tests at ambient and elevated temperatures and by chemical disinfection. The bacterium in its native environment was more resistant to adverse conditions, as compared with laboratory-grown organisms. Of the several chemical disinfectants acceptable to drinking water treatment and tested for Legionella inactivation, ozonation was the most efficient method. The C · t ' products indicated that free chlorine was superior to mono- and dichloramines.     

The modification of cortical reorganization and chronic pain by sensory feedback

Recent neuroscientific evidence has revealed that the adult brain is capable of substantial plastic change in areas such as the primary somatosensory cortex that were formerly thought to be modifiable only during early experience. We discuss research on phantom limb pain as well as chronic back pain that revealed functional reorganization in both the somatosensory and the motor system in these chronic pain states. In phantom limb pain patients, cortical reorganization is correlated with the amount of phantom limb pain; in low back pain patients the amount of reorganizational change increases with chronicity. We present a model of the development of chronic pain that assumes an important role of somatosensory pain memories. In phantom limb pain, we propose that those patients who experienced intense pain prior to the amputation will later likely develop enhanced cortical reorganization and phantom limb pain. We show that cortical plasticity related to chronic pain can be reduced by behavioral interventions that provide feedback to the brain areas that were altered by somatosensory pain memories.     

Molecular basis of bacterial resistance to chloramphenicol and florfenicol

Chloramphenicol (Cm) and its fluorinated derivative florfenicol (Ff) represent highly potent inhibitors of bacterial protein biosynthesis. As a consequence of the use of Cm in human and veterinary medicine, bacterial pathogens of various species and genera have developed and/or acquired Cm resistance. Ff is solely used in veterinary medicine and has been introduced into clinical use in the mid-1990s. Of the Cm resistance genes known to date, only a small number also mediates resistance to Ff. In this review, we present an overview of the different mechanisms responsible for resistance to Cm and Ff with particular focus on the two different types of chloramphenicol acetyltransferases (CATs), specific exporters and multidrug transporters. Phylogenetic trees of the different CAT proteins and exporter proteins were constructed on the basis of a multisequence alignment. Moreover, information is provided on the mobile genetic elements carrying Cm or Cm/Ff resistance genes to provide a basis for the understanding of the distribution and the spread of Cm resistance--even in the absence of a selective pressure imposed by the use of Cm or Ff.     

Organization of the Connections between the Parietal Associative Zone and the Primary Sensory Zones in the Cat Neocortex

In acute experiments on cats, we studied the impulse activity of 262 neurons of the parietal associative zone (PAZ, field 5). Among them, 129 cells [100 silent units and 29 units generating background activity (BA)] were identified as output neurons, while 133 cells with the BA were interneurons of the intrinsic cortical neuronal circuits. Electrical stimulation of the primary visual, auditory, or somatosensory cortices evoked no impulse responses in silent output PAZ neurons, while output neurons with the BA and interneurons (more than 65 and 80% of the cell units, respectively) generated clear responses (more frequently, phasic). Stimulation of the auditory and visual cortices exerted mostly inhibitory effects, while stimulation of the somatosensory cortex provided mostly excitatory influences. The ratios of neurons generating primary excitatory and inhibitory responses to stimulation of the visual, auditory, and somatic cortices were 0.3:1, 0.6:1, and 3.2:1, respectively. More than 95% of the field-5 neurons were influenced from the primary sensory zones via di- and/or polysynaptic pathways. Monosynaptic excitatory inputs from the visual cortex were identified for 3.8% of interneurons and 6.9% of output PAZ neurons; for the auditory cortical inputs, the respective figures were 1.7 and 3.5%. Monosynaptic connections with the somatic cortex were found only for 4% of the interneurons under study. It has been concluded that interaction of heteromodal signals coming to the PAZ via the corticopetal and associative inputs occurs on neurons of all the cortical layers.