Four neuropeptides that inhibit juvenile hormone synthesis by the corpora allata have been isolated from brains of the virgin female cockroach Diploptera punctata. These allatostatins are 8-13 amino acids long, are amidated, and show sequence similarity, including a 3-amino acid sequence at the C-terminal end that is common to all four peptides. The peptide sequences are as follows: allatostatin 1, Ala-Pro-Ser-Gly-Ala-Gln-Arg-Leu-Tyr-Gly-Phe-Gly-Leu-
Hair mineral analysis from these laboratories was unreliable, and we recommend that health care practitioners refrain from using such analyses to assess individual nutritional status or suspected environmental exposures. Problems with the regulation and certification of these laboratories also should be addressed.
A method is described for the measurement of nanogram or subnanogram amounts of Sn(IV) and the halides of methyltin, dimethyltin, trimethyltin, diethyltin, triethyltin, n-butyltin, din-butyltin, tri-n-butyltin, and phenyltin. These compounds in aqueous solution react with NaBH, to produce volatile hydrides which are detected by atomic absorption spectrometry. The hydrides are separated on the basis of their differing boiling points. Detection limits range from 0.4 ng for Sn(IV) to 2 ng for tri-n-butyltin chloride. Compounds yielding dimethyltin dihydride are found in San Diego Bay seawater at levels of 15 to 45 ng/L, usually exceeding the concentrations of methyltin and inorganic tin. Compounds yielding n-butyltin trihydride and di-n-butyltin dihydride are found in Lake Michigan water at 10-1600 ng/L, also generally higher than the methyl species or inorganic tin. Tin( IV) concentrations are reported for seawater, lake water, marine algae, and sediments from Narragansett Bay.
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