Extensive variation in synonymous substitution rates in mitochondrial genes of seed plants

Background  

It has long been known that rates of synonymous substitutions are unusually low in mitochondrial genes of flowering and other land plants. Although two dramatic exceptions to this pattern have recently been reported, it is unclear how often major increases in substitution rates occur during plant mitochondrial evolution and what the overall magnitude of substitution rate variation is across plants.     

Calcium as a counteractive agent to streptomycin induced respiratory depression: an in vivo electrophysiological observation.

Effect of streptomycin on respiratory function in cats was studied. It was observed that streptomycin at a dose of 40 mg/kg body weight intravenously (i.v.) caused respiratory failure or streptomycin induced respiratory depression (SIRD). This respiratory failure is not linked with Herring-Breuer stretch receptors because the effect remained unaltered in artificially ventilated cats. The involvement of central structures in SIRD can be discarded since intracarotid and intraventricular administration of streptomycin failed to produce any change in respiration. Studies on monosynaptic reflex, dorsal and ventral root activities of spinal phrenic and intercostal nerves, and on fusimotor and alpha-motor neuron activities of spinal intercostal and phrenic nerves in decerebrated cats indicated clearly that respiratory depression is not only due to blockade at neuromuscular junction but due to functional depression at the level of muscle receptors and spinal cord motor neurons. The respiratory depression induced by streptomycin was more or less completely reversed when calcium was administered intravenously from external source. It is speculated that streptomycin induced respiratory depression may be mediated through calcium inhibition which can be treated with external calcium in conjunction with artificial respiration.     

Estradiol benzoate induced changes in protein synthesis and lysosomal hydrolases in the pituitary of male rats

In vitro protein synthesis, lysosomal hydrolases activity and peroxidase activity in the anterior pituitary were estimated in adult male rats treated with 50 micrograms of estradiol benzoate (EB) for 1 day or 7 days. Pituitary protein synthesis, protein and RNA content increased after 7 days. A significant increase in total and membrane-bound acid phosphatase was noted after 1 day or 7 days of EB treatment whereas total beta-glucuronidase activity decreased in both 1 and 7 day group. Cathepsin activity increased after 7 days and pituitary peroxidase system did not change by EB treatment. These findings suggest that immediate change in the enzyme milieu may be one of the first reactions by which EB expresses its feedback control.