A specific method of glycosylated hemoglobin using furosine measurement

In order to get an accurately specific determination of glycosylated hemoglobin (GHb-f), the furosine assay method, which can detect epsilon-amino-lysine-bound glucose, was investigated. A good correlation was found between GHb-f values obtained by this method and HbA1 values by conventional ion exchange column chromatography. It was, therefore, considered that this technique would be a new useful method for determining glycosylated hemoglobin.     

The effect of neuropeptide Y on the hypothalamic-pituitary-adrenal axis in the dog

There is increasing evidence that neuropeptide Y (NPY) affects the release of pituitary hormones, including adrenocorticotropic hormone (ACTH). The present study was designed to clarify the mechanism by which NPY activates the hypothalamic-pituitary-adrenal (HPA) axis in the dog. Mongrel dogs were equipped with a chronic cannula allowing intra-third (i.t.v.) or intra-lateral (i.l.v.) cerebroventricular administration. A 1.19 nmol, i.t.v. dose of NPY produced as great an ACTH and cortisol response as did equimolar ovine corticotropin releasing factor (CRF). This action of NPY was dose-dependent and shared by peptide YY (PYY) and pancreatic polypeptide (PP), other members of the PP family peptide. Intravenously (i.v.) administered NPY (1.19-11.9 nmol) was much less potent than i.v. CRF in stimulating ACTH and cortisol secretion. However, i.v. NPY significantly increased plasma ACTH and cortisol concentrations, raising the possibility that NPY may modulate the activity of corticotrophs. We next investigated the possible relationship between NPY and CRF on the HPA axis. Pretreatment with a novel CRF antagonist, alpha-helical CRF9-41 (130.9 nmol i.t.v. or 261.5 nmol i.v.), partly but significantly attenuated the ACTH and cortisol responses to i.t.v. NPY (1.19 nmol). Furthermore, adding a subthreshold dose of i.t.v. NPY (0.119 nmol) to i.t.v. CRF (1.19 nmol) or i.v. NPY (2.38 nmol) to i.v. CRF (0.595 nmol) resulted in the potentiation of CRF-induced ACTH secretion. These results indicate that NPY may activate the HPA axis in concert with CRF probably at hypothalamic and/or pituitary levels. The present findings that NPY evokes ACTH secretion and potentiates the effectiveness of CRF as a secretagogue, together with high concentrations of NPY in the hypothalamus and pituitary portal blood, suggest the NPY is involved in the multihormonal control of ACTH release.     

Effect of hydrocortisone on the synthesis of 2,3-diphosphoglycerate in human erythrocytes

Studies were carried out on the mechanism of action of glucocorticoids on erythrocyte glycolysis. Inosine increased the levels of 2,3-DPG, lactate, and ATP in red blood cell samples with very low glucose concentrations in which the glycolytic system was unable to utilize glucose. With inosine and hydrocortisone added to red blood cells, 2,3- DPG and lactate increased more than in red blood cells supplemented with inosine alone. There was no significant increase in the level of ATP when glucose and inosine were added compared to the addition of inosine only. There were no changes in the activity of enzymes such as PFK and PGK. From these findings, it is suggested that glucocorticoids increase the level of red blood cell 2,3-DPG, by activating the conversion of 1,3-DPG to 2,3-DPG during glycolysis, probably by stimulating 2,3-DPG mutase.     

Effects of glycosylation on physiological and biological activities of substances

Hemoglobin A₁ (HbA₁) increases in old erythrocytes. These erythrocytes with increased HbA₁ had decreased oxygen dissociation ability, resulting in decreased function. l-Triiodothyronine (T₃) underwent glycosylation to form glycosylated T₃. The biological activity of glycosylated T₃ was assayed utilizing the metamorphosis of tadpoles. It was found that glycosylated T₃ was less than one-tenth as biologically active as T₃.     

Determination of carbamylated plasma protein and its clinical application to renal failure

We determined carbamylated plasma protein (CPP) according to the method of Hunninghake in patients with renal failure and normal subjects. CPP values were significantly higher in patients with renal failure than in normal subjects. In patients with renal failure, a significant correlation was found between CPP levels and blood urea nitrogen. Thus, CPP appears to be a new indicator of the status of renal failure, irrespective of hemodialysis.     

Acceleration of fructose mediated collagen glycation

The effect of fructose on the formation of advanced Maillard reaction products which show fluorescence and have crosslinking was investigated. Type I collagen was added to various concentrations of glucose and fructose which were then incubated at 37 degrees C for 4 weeks. The level of furosine and the fluorescence intensity both increased in direct proportion to glucose and fructose levels and to the duration of incubation. Incubation with fructose produced less furosine but more intense fluorescence than incubation with glucose. Furthermore, collagen was significantly less soluble after incubation with fructose than after incubation with glucose. These results suggest that fructose in the polyol pathway plays an important role in the formation of advanced Maillard products.