Biomedical subjects

B J Cook

Publications and source records attributed to B J Cook.

29 records · Page 2Linked to original sources

PubMed1985

Proctolin, its presence in and action on the oviduct of an insect.

Proctolin has been isolated from oviduct extracts of Leucophaea maderae by HPLC. Quantitative bioassay with the hindgut of L. maderae demonstrated a proctolin titre of 0.93 +/- 0.15 ng/oviduct. Exposure to proctolin produced three changes in the spontaneous contractile activity of the oviduct: an increase in muscle tonus, an increase in the amplitude and frequency of phasic contractions. The sensitivity of the oviduct to proctolin was compared with the hindgut and foregut organ preparations from the same insect. Oviducts were responsive to proctolin in a calcium-free medium and the peptide also appeared to facilitate the reentry of calcium after depleted preparations were returned to normal levels of external calcium.

Animals↗

PubMed1985

The role of proctolin and glutamate in the excitation-contraction coupling of insect visceral muscle.

Proctolin (1 X 10(-10) to 1 X 10(-9) M) had a minimal effect on the spontaneous and evoked electrical events of the hindgut of the cockroach Leucophea maderae. Spontaneous action potentials and contractile activity stopped when the hindgut was exposed to 2 mM Mn2+. Eighty per cent of the response of the hindgut to glutamate was blocked by manganese, but only 35% of the response to proctolin. Hindguts were responsive to proctolin in a calcium-free medium, but not to glutamate. Moreover, proctolin appeared to facilitate the reentry of calcium after depleted preparations were returned to normal levels of external calcium. The results offer evidence for two calcium transmembrane channels in insect visceral muscle.

Action Potentials↗

PubMed1984

Isolation and partial characterization of five myotropic peptides present in head extracts of the cockroach Leucophaea maderae.

Five peptides were isolated by reverse-phase HPLC from head extracts of the cockroach Leucophaea maderae. Four of the peptides were inactivated by aminopeptidase M (APM). The inability of APM to digest the fifth peptide suggests a blocked NH2-terminus. Four of the peptides were inactivated by carboxypeptidase Y (CPY). The activity of the fraction which would have contained proctolin was decreased by about 20%. The complete deactivation of proctolin by CPY indicated that a second peptide, co-eluting with proctolin but refractory to CPY digestion, was responsible for 80% of the biological activity in that fraction. Concentrations of the peptides necessary to produce a threshold response from the isolated cockroach hindgut ranged from 0.009 to 0.083 head equivalents/ml.

Aminopeptidases↗

PubMed1983

Isolation and partial characterization of a second myotropic peptide from the hindgut of the cockroach, Leucophaea maderae.

Proctolin and a second myotropic peptide were extracted from the hindgut of the cockroach Leucophaea maderae with methanol-water-acetic acid (90:9:1). The two peptides were easily separated by HPLC on a mu-Bondapak-phenyl column. Like proctolin, the second peptide was heat stable and was inactivated by the exopeptidases aminopeptidase M and carboxypeptidase Y. The response of the isolated hindgut to the new peptide was distinguishable from the response to proctolin by the following features: (a) a longer interval following application (1-4 min) to reach a maximum contraction, and (b) a much larger amplitude for single phasic contractions. Like proctolin, the new peptide could cause a protracted stimulation of the hindgut for more than 2 hr.

Animals↗

PubMed1981