Agrin induces phosphorylation of the nicotinic acetylcholine receptor

Agrin causes acetylcholine receptors (AChRs) on chick myotubes in culture to aggregate, forming specializations that resemble the postsynaptic apparatus at the vertebrate skeletal neuromuscular junction. Here we report that treating chick myotubes with agrin caused an increase in phosphorylation of the AChR beta, gamma, and delta subunits. H-7, a potent inhibitor of several protein serine kinases, blocked agrin-induced phosphorylation of the gamma and delta subunits, but did not prevent either agrin-induced AChR aggregation or phosphorylation of the beta subunit. Experiments with anti-phosphotyrosine antibodies demonstrated that agrin caused an increase in tyrosine phosphorylation of the beta subunit that began within 30 min of adding agrin to the myotube cultures, reached a plateau by 3 hr, and was blocked by treatments known to block agrin-induced AChR aggregation. Anti-phosphotyrosine antibodies labeled agrin-induced specializations as they do the postsynaptic apparatus. These results suggest that agrin-induced tyrosine phosphorylation of the beta subunit may play a role in regulating AChR distribution.

[Analysis of trace elements in cataractous lenses and environmental samples in Tibet]

Trace elements of Cu, Fe, Zn, Mg, and Se in Tibetan cataractous lenses and also in local samples of earth, drinking water, and staple foods were analyzed to estimate the possible relationship between environmental factors and primary cataract formation in Tibet. The Fe, Mg and Se contents in Tibetan cataracts were significantly lower in comparison with levels in those of Chengdu area, particularly the Se contents were low in both cataracts and local environment, suggesting a probable correlation between cataract formation and low Se contents in food and water.

[Correlation of SPECT, EEG and CT in patients with epilepsy. A preliminary report]

Single photon emission computed tomography (SPECT) were performed in 14 patients with epilepsy. Among 6 patients with GTC, five had no focal abnormalities in EEG and CT scan, SPECT also showed no changes of regional cerebral perfusion. In another one patient EEG was normal, CT scan showed hypodensity in right frontal area, SPECT showed decreased regional cerebral perfusion in right frontotemporal area. AVM in frontal lobe was found at operation. In 3 patients with complex partial seizures and 5 patients with complex partial seizures and GTC, SPECT showed regional cerebral perfusion coincided with the area of focal epileptic form discharges in EEG. In one patient with complex partial seizures and GTC EEG showed right antero-temporal focal sharp wave discharges, discrete calcification in superior suprasella cisterna on CT, SPECT showed decreased regional perfusion in right temporal area, pathological examination revealed hematoma in right temporal lobe. SPECT is useful for localizing epileptogenic foci in epileptics.

[Fundus examination of newborns on Tibet plateau]

Fundus examination of 255 newborns in high altitude Tibet revealed that the optic discs were of orange-pink colour with clear margin and over ten small vessels. The C/D ratio in 500 eyes (98.04%) was 0.3 or less, and none was 0.6 or over. The C/D ratio in both eyes of 242 babies (94.90%) was symmetrical and in only 1 case (0.39%) it differed by 0.2. The macula of all infants was dark red with no foveal reflection. Some of the veins were engorged. Retinal hemorrhages were found in 64 cases (25.10%), 12 cases in the macular region and 1 case on the optic disc. Retinal edema was present in 30 cases, cotton wool exudates in 30 cases, vitreous artery in 6 cases, and congenital cataracts in 1 case. The mechanism of retinal changes were discussed.

Insect immunity: isolation and structure of cecropins B and D from pupae of the Chinese oak silk moth, Antheraea pernyi

The immune system in the Chinese oak silk moth, Antheraea pernyi, has been compared with that of the Cecropia moth which has been characterized earlier. Antibacterial activity against Escherichia coli was induced in diapausing pupae by injection of viable E. coli or Enterobacter cloacae. The activity reached a maximum on day 7-8 after which the response gradually declined. The pupae produced a set of immune proteins with P4 and P5 as major labelled components similar to that earlier found in Cecropia. The major antibacterial factor in A. pernyi was cecropin D. A procedure is described for the isolation of cecropin B and D, which is in principle similar to the one used for the isolation of the corresponding cecropins from Cecropia pupae. Amino acid sequence analyses of the A. pernyi cecropins show the D form to contain 36 amino acid residues and that both cecropins have blocked C-termini. The general structure of cecropins having a charged N-terminal region (residues 1-21) followed by a long hydrophobic stretch (residues 22-32) is well conserved. Cecropin B and D from A. pernyi differ from the corresponding proteins in Cecropia by four and three conservative amino acid replacements, respectively. The homology between the cecropins from the two insects suggests that they orginate from a single ancestral gene. The antibacterial activity was tested against nine different bacterial species. Evolutionary aspects of the cecropins are discussed.