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B Cheng

Publications and source records attributed to B Cheng.

152 records · Page 9Linked to original sources
PubMed1970

Intestinal absorption of two dipeptides in Hartnup disease.

The results of oral tolerance tests of two dipeptides and of their constitutent amino acids are compared in normal subjects and in a case of Hartnup disease. In the control subjects the rate of absorption of phenylalanine from phenylalanyl-phenylalanine and of tryptophan from glycyl-tryptophan was slower than after the equivalent amount of the free amino acids. Absorption of the two essential amino acids (tryptophan and phenylalanine) in the patient was almost zero after administration in the free form, but was much greater after the dipeptide. Results of experiments on absorption and hydrolysis of the two peptides in the rat small intestine are also reported. It is suggested that whereas normal subjects absorb essential amino acids by a dual mechanism of mucosal uptake of free amino acids and oligopeptides, nutrition in Hartnup disease is largely dependent on uptake of oligopeptides containing the amino acids affected by the intestinal transport defect of the disease.

Adult↗
PubMedDate not supplied

Characterization and presynaptic modulation of stimulation-evoked exocytotic co-release of noradrenaline and neuropeptide Y in guinea pig heart.

The relationship between noradrenaline and neuropeptide Y (NPY) release was investigated in the in situ perfused guinea pig heart with intact sympathetic innervation. For determination of NPY concentrations in the perfusate, a specific radioimmunoassay was employed and further characterized. Electrical stimulation of the left stellate ganglion (4, 8, 12, and 50 Hz; for 10 min) evoked a calcium-dependent and frequency-related overflow of noradrenaline and NPY, which was positively correlated (r = 0.83; p less than 0.001; n = 25). When two subsequent stimulations (12 Hz; each for 1 min) were performed in the same heart, addition of noradrenaline (10 microM) 5 min prior to the second stimulation reduced NPY overflow by 43 +/- 10%. The stimulated release of noradrenaline and NPY was increased by the alpha 2-adrenoceptor antagonist yohimbine (1 microM) to 170 +/- 10% and 199 +/- 26%, and attenuated by the alpha 2-adrenoceptor agonist B-HT 920 (1 microM) to 70 +/- 9% and 68 +/- 9%, respectively. The adenosine analogue cyclohexyladenosine (1 microM) significantly reduced the stimulated overflow of both noradrenaline (to 57 +/- 5%) and NPY (to 73 +/- 8%). Exogenous NPY (100 nM) attenuated the stimulated overflow of noradrenaline by 30 +/- 6%. Uptake1 blockade with desipramine (100 nM) or nisoxetine (100 nM) prior to the second stimulation significantly increased noradrenaline overflow and attenuated that of NPY; the attenuation of the stimulation-evoked overflow of NPY was abolished by yohimbine (1 microM). Our results indicate that electrical stimulation induces a calcium-dependent, exocytotic co-release of noradrenaline and NPY.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗