A new recessive mutation, bradypneic (bd), causes variable weight retardation beginning as early as 3 to 5 days. Severely affected mice die within the first 2 weeks; less severely affected mice may survive to weaning or to adulthood and may be fertile. Bradypneic mice tested at 3 weeks or older breathed at half the normal rate, but breathing was deeper and O2 consumption per unit of body surface was normal. No obstruction was found in the nasal passages, pharynx, trachea, or bronchi. The lungs were somewhat emphysematous and, probably in consequence, the right atrium was enlarged. The only other pathological conditions found were dilation of some of the distal tubules of the kidney and large amounts of gas in the stomach and intestines. The investigation did not reveal the cause of the breathing defect, but it is possible that the breathing defect is responsible for the emphysema, intestinal gas, small size, and early death. Extensive linkage tests have not yet revealed the chromosomal location of bd.

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The nuclear genomes of hypotrichous ciliates: maintaining the maximum and the minimum of information.

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Characterization of the Euplotes crassus macronuclear rDNA and its potential as a DNA transformation vehicle.

We have cloned the macronuclear linear DNA molecule carrying the ribosomal RNA genes from the ciliated protozoan Euplotes crassus. DNA sequence analysis was carried out to locate coding regions and to determine whether sequences that have been mutated to confer antibiotic resistance are conserved in the E. crassus genes. The beginning and end of the primary transcript were mapped. In order to determine whether conserved sequences that might serve as replication origins were present, the 5' and 3' non-coding sequences from E. crassus were compared to the corresponding sequences from the macronuclear linear rDNA molecules from the following euplotid species: Euplotes vannus, Euplotes minuta, Euplotes raikovii and Euplotes rariseta. A DNA transformation construct was made by generating a putative anisomycin resistant mutation along with a mutation generating a restriction site polymorphism. Microinjection of the construct into the developing macronucleus of mated cells resulted in exconjugant cell lines with increased resistance to anisomycin. The injected rDNA with the restriction site polymorphism is detectable in the anisomycin resistant cells and appears to represent a minor fraction of the rDNA.

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