Biomedical subjects

D A Godfrey

Publications and source records attributed to D A Godfrey.

76 records · Page 5Linked to original sources

PubMed1975

Enzymes of the cholinergic system in islets of Langerhans.

Quantitative radiometric assays were employed to measure activities of choline acetyltransferase and acetylcholinesterase in freeze-dried pieces of islets of Langerhans and exocrine tissue from rat pancreas. The activities of both enzymes were about an order of magnitude higher in islets than in exocrine tissue. This difference in activity was found in rats made diabetic with streptozotocin as well as in the controls. Although the enzyme activities in islets from diabetic rats averaged about 30-40% higher than those in islets from control rats, the differences were statistically only marginally significant. Since the islets of diabetic rats are probably much smaller than those of control rats, it is suggested that cholinergic elements associated with pancreatic islets are lost following induction of streptozotocin diabetes.

Acetylcholinesterase↗

PubMed1975

Fast and slow axoplasmic flow in sciatic nerve of diabetic rats.

Accumulation of acetylcholinesterase (AChE) and choline acetylase (ChAc) activities proximal to a tie placed on the sciatic nerve was measured in control, untreated diabetic, and insulin-treated diabetic rats. In the diabetic animals AChE accumulation was reduced by about 20% and ChAc accumulation by about 40%. Insulin treatment eliminated the impairment. It remains an open question whether these reversible functional changes in rat have any counterpart in the diabetic neuropathy of man.

Acetylcholinesterase↗

PubMedDate not supplied

Enzymes of acetylcholine metabolism in the rat cochlea.

The distributions within the rat cochlea of choline acetyltransferase and acetylcholinesterase activities were measured to evaluate the prominence of cholinergic mechanisms in cochlear function. Samples obtained by microdissection of freeze-dried bony labyrinths were assayed radiometrically. Activities of both enzymes were highest in regions containing olivocochlear fibers and terminals, especially the organ of Corti and spiral ganglion. Within the organ of Corti, activities of both enzymes were consistently higher in the vicinity of the inner hair cells than in that of the outer hair cells and were much lower in the apical turn than in middle or basal turns. Surgical cuts in the brain stem transecting the olivocochlear pathway on one side led within seven days to total loss of choline acetyltransferase activity in the ipsilateral organ of Corti. It is concluded that all cholinergic structures in the rat organ of Corti derive from the brain stem and that synapses on or near both inner and outer hair cells are cholinergic.

Acetylcholine↗

PubMedDate not supplied

Quantitative distribution of amino acids in the rat vestibular nuclei.

The normal concentrations of 12 amino acids in the vestibular nuclei of rats were quantitatively measured using microdissection of freeze-dried brain sections combined with high performance liquid chromatography (HPLC) analysis. Both excitatory amino acids, aspartate and glutamate, showed only small variation across the vestibular nuclei. The distribution of glutamine tended to parallel that of glutamate. The inhibitory amino acids, gamma-aminobutyrate (GABA) and glycine, were much more concentrated in some regions than in others. GABA tended to be more concentrated than glycine in dorsal and rostral nuclei, while glycine tended to be more concentrated than GABA in ventral and caudal nuclei. The distribution of taurine was comparable to that of GABA, suggesting a close relationship with GABA function. Asparagine, serine, threonine, arginine, alanine and tyrosine had relatively low concentrations without significant differences among vestibular nuclei. Our results suggest that (1) different parts of the vestibular nuclear complex may receive similar amounts of excitatory amino acid afferents, (2) there is predominance of GABA or glycine as an inhibitory transmitter in different parts of the vestibular nuclear complex, and (3) there may be a close functional relationship between taurine and GABA within the vestibular nuclear complex. These results provide data basic to further research on the details of amino acid functions in the normal and abnormal vestibular system, as well as studies of plasticity in this system.

Amino Acids↗