Diaphragm afferent modulation of phrenic motor drive

Experiments were performed in eight lightly anesthetized thiopental sodium (Pentothal) cats to examine whether diaphragmatic afferents can significantly alter the neural drive to the diaphragm when the animal is exposed to lower body negative pressure. Moving-time-averaged diaphragmatic electromyograms (EMGma) were recorded and compared before and during exposure to lower body negative pressure in each of three consecutive conditions: C7 spinalization, bilateral vagotomy, and cervical dorsal rhizotomy. Application of lower body negative pressure in C7-spinalized animals resulted in a decrease in inspiratory time and peak diaphragmatic activity compared with control levels. After bilateral vagotomy, EMGma activity was prolonged with the application of lower body negative pressure. However, there was no increase in peak EMGma activity. After transection of the cervical dorsal roots subserving the phrenic nerve, the prolongation of diaphragmatic activity negative was eliminated. Therefore, we conclude that the significant increase in duration of inspiration in response to application of lower body negative pressure in the C7-spinalized, bilaterally vagotomized cat is mediated by phrenic nerve afferents.     

The gene for glycogen-storage disease type 1b maps to chromosome 11q23.

Glycogen-storage disease type 1 (GSD-1), also known as "von Gierke disease," is caused by a deficiency in microsomal glucose-6-phosphatase (G6Pase) activity. There are four distinct subgroups of this autosomal recessive disorder: 1a, 1b, 1c, and 1d. All share the same clinical manifestations, which are caused by abnormalities in the metabolism of glucose-6-phosphate (G6P). However, only GSD-1b patients suffer infectious complications, which are due to both the heritable neutropenia and the functional deficiencies of neutrophils and monocytes. Whereas G6Pase deficiency in GSD-1a patients arises from mutations in the G6Pase gene, this gene is normal in GSD-1b patients, indicating a separate locus for the disorder in the 1b subgroup. We now report the linkage of the GSD-1b locus to genetic markers spanning a 3-cM region on chromosome 11q23. Eventual molecular characterization of this disease will provide new insights into the genetic bases of G6P metabolism and neutrophil-monocyte dysfunction.