Radioimmunological determination of neopterin in blood donors

In 518 sera from blood donors below 30 years of age Neopterin was determined by radioimmunoassay. 21 of these patients (= 4.05%) showed elevated serum levels for Neopterin. By clinical investigation of these cases viral infections of the upper airways were found. Furthermore after elimination of elevated values significant differences in normal Neopterin serum levels could be demonstrated for female and male blood donors (p less than 0.01). Because elevated Neopterin serum levels indicate immune responses to several antigens, determination of Neopterin from serum may be useful for detection of infectious blood samples.     

Radioimmunological determination of ACTH and its clinical use]

Since radioimmunological methods have been introduced, it has become possible to measure the concentration of ACTH in human plasma directly. We report on first experiences with commercial testing sets. We proved the clinical usefulness of the determination of ACTH in the cases of 13 healthy adult subjects and 8 healthy children. Furthermore patients with evidence of primary adrenal insufficiency and with disturbances in the hypothalamicpituitary system were included in our investigations. The obtained values are in agreement with the known conception of the hypothalamic-pituitary-adrenal system.     

Transactivation assay for determination of glucocorticoid bioactivity in human serum

We have developed a mammalian cell (COS-1) bioassay, which measures glucocorticoid bioactivity (GBA) directly from a small amount of human serum. The assay is based on the expression of human glucocorticoid receptor (GR) together with a coactivator protein and reporter plasmid containing GR response elements upstream of the luciferase gene. Ten microliters of human serum, in duplicate, are added directly to the cell culture medium, and GBA is derived from reporter gene activity. The assay differentiates between biopotencies of synthetic steroids, and importantly, mifepristone (RU486) is able to block glucocorticoid-induced response. The assay is sensitive (<15.6 nM cortisol in fetal calf serum) and precise, with the within- and between-assay coefficients of variation less than 8% and 10%, respectively. We measured serum GBA (bioassay) and cortisol (RIA) levels in 34 asthmatic children (age range, 5.7-14.2 yr) at baseline and after treatment with either inhaled budesonide (800 microg/d, n = 14), fluticasone propionate (500 microg/d, n = 14), or cromones (control group, n = 6). Pretreatment serum GBA and cortisol levels correlated strongly (r = 0.90, P < 0.0001, n = 34). Two months of treatment with inhaled budesonide resulted in excess GBA in circulation, which was not attributable to endogenous cortisol (P < 0.001). In the fluticasone propionate group, the presence of serum excess GBA was at the borderline of statistical significance (P < 0.08) after 2 months of inhalation therapy, and no excess GBA was detected in the cromone group. In conclusion, our bioassay enables measurement of mammalian cell response to bioactive glucocorticoids in circulation and provides a novel means to investigate patients receiving drugs acting through the GR.     

A case of secretin-responsive insulinoma with low serum C-peptide levels

Insulinoma is the most common cause of fasting hypoglycemia resulting from autonomous insulin hypersecretion. A 59-year-old woman who had previously had an insulinoma and had undergone a partial pancreatectomy was admitted to our hospital because of recurrence of hypoglycemia after 27 years. She had two unusual endocrinological features: 1) the serum insulin response to intravenous secretin injection was not impaired, and 2) the serum C-peptide levels and ratios of serum C-peptide to insulin were relatively low. Two pancreatic tumors were readily detectable by computed tomography (CT) and magnetic resonance imaging (MRI). The selective arterial calcium injection (SACI) test showed a hyperinsulinemic response by calcium administration to the gastroduodenal artery. A partial pancreatectomy was done and her hypoglycemia disappeared. Histology revealed that the tumors were composed of monotonous, small round cells that were positive for both insulin and cathepsin B. As previous in vitro studies have shown that C-peptide can be metabolized within human insulinoma cells by proteolytic cleavage by cathepsin B, our patient's low serum C-peptide levels might have been caused by degradation of C-peptide by cathepsin B. According to the data from the literature, the molar ratio of serum C-peptide to insulin is generally decreased in patients with insulinoma than normal subjects. This case highlights the need for careful interpretation of C-peptide levels and the intravenous secretin injection test in the diagnosis of insulinoma.     

Variation of endogenous insulin secretion in association with treatment status: assessment by serum C-peptide and modified urinary C-peptide.

The variation of endogenous insulin secretion in association with fasting plasma glucose (FPG) level and the modality of treatment was assessed using serum C-peptide levels before and after breakfast and the corrected value of 24-h urinary C-peptide (24 h-UCP) in inpatients with non-insulin-dependent diabetes mellitus. The corrected value calculated as 24 h-UCP/(urinary C-peptide to creatinine clearance (CCP/CCR) ratio in the fasting state x 10) was correlated with the sum of day-long serum C-peptide levels (r = 0.93) more closely than the measured value of 24 h-UCP (r = 0.79) in 9 patients. In 52 patients treated with diet alone, 38 with sulfonylurea and 28 with insulin, fasting serum C-peptide level did not vary with FPG level, and the increment of serum C-peptide level after breakfast and the corrected value of 24 h-UCP decreased with the rise in FPG level in each treatment. These indexes were the lowest in insulin treatment among the patients with similar FPG levels. In conclusion, 24 h-UCP was demonstrated to be able to reflect day-long endogenous insulin secretion more faithfully after the correction with the CCP/CCR ratio. It was estimated that the insulin response to breakfast and day-long insulin secretion decreased with the rise in FPG level, but basal insulin secretion was maintained over a wide range of FPG levels in each treatment. Endogenous insulin secretion seemed to be somewhat suppressed or rested by exogenous insulin in insulin-treated patients.     

Association of increased C-peptide serum levels and testosterone in type 2 diabetes

Background: The purpose of our study was to investigate the association of C-peptide and steroid hormones in males and females with type 2 diabetes compared to controls. Methods: In 562 subjects, matched for age and body mass index (BMI), 126 female type 2 diabetic patients (known diabetes duration: 7.8±0.8 years, HbA_1c: 7.6±0.14%), 126 healthy female subjects, 155 male type 2 diabetic patients (known diabetes duration: 6.4±0.6 years, HbA_1c: 7.7±0.11%), and 155 healthy male controls, C-peptide levels and serum levels of steroid hormones (progesterone, cortisol, DHEAS, estradiol, and testosterone) were measured by immunometric assays. Ratios of steroid hormones were calculated to investigate shifts in steroidogenesis. Results: In female patients, testosterone was significantly higher than in controls (1.7±0.1 vs. 1.4±0.2 pmol/l; P<0.05), something that was also demonstrated for the ratio of testosterone/estradiol (P<0.05). In male patients, lower levels of testosterone (11.8±0.5 vs. 14.3±0.5 pmol/l; P<0.05) and higher cortisol levels (257.5±9.9 vs. 228.2±7.9 μmol/l, P<0.01) were found than in controls. The progesterone/DHEAS ratio (P<0.05) and the progesterone/testosterone ratio (P<0.001) were significantly higher and DHEAS/cortisol significantly lower in type 2 diabetic males than in controls. In a multiple linear regression analysis that controlled for age, BMI, C-peptide, HDL-cholesterol, and HbA_1c, testosterone was significantly and positively correlated with C-peptide levels in female (P<0.05) but not in male type 2 diabetic patients. Conclusions: Testosterone levels were higher in female patients than in controls and correlated with C-peptide levels while testosterone levels were lower in male patients than in controls and showed no correlation with C-peptide. A higher ratio of testosterone/estradiol in type 2 diabetic females and of progesterone/DHEAS and progesterone/testosterone in type 2 diabetic males than in controls may indicate gender-dependent shifts in steroidogenesis. Whether the shifts in steroidogenesis contribute to insulin resistance in diabetic patients should be the subject of further studies.     

Disappearance rate of endogenous human C-peptide from blood

Summary Glucagon (1 mg) and glucose (60 ml of 50% solution) were infused over 60 min to three normal and one obese subjects and two insulinoma patients. Plasma C-peptide immunoreactivity (CPR) and immunoreactive insulin (IRI) increased during the infusion. Half time of CPR after cessation of the infusion was 20.1±4.0 min, and that of IRI 9.8±1.3 min, respectively. This difference partly explains the higher molar concentration in plasma of CPR than IRI.     

A comparison of serum C-peptide response to intravenous glucagon, and urine C-peptide, as indexes of insulin dependence

Serum C-peptide (SCPR) at fasting and after intravenous injection of glucagon was evaluated in diabetic patients with various degrees of insulin dependence, and compared with 24 h urine C-peptide (UCPR). Fasting SCPR did not differ between healthy subjects and sulfonylurea-treated patients (SU) who were considered to have definite non-insulin-dependent diabetes (NIDDM); but was significantly lower in patients with insulin-dependent diabetes (IDDM) (0.24 +/- 0.10 ng/ml in IDDM vs. 1.43 +/- 0.61 ng/ml in SU, P less than 0.001). SCPR reached a peak at 6 min after glucagon injection, except for the IDDM group. The SCPR response at 6 min after 1 mg glucagon injection was significantly lower in the SU (NIDDM) group than in the normal group (2.86 +/- 1.21 v. 4.69 +/- 1.47 ng/ml, P less than 0.001). In the IDDM group, there was no increase of SCPR after glucagon injection. Among diabetic patients, SCPR response to glucagon correlated positively to the amounts of UCPR (P less than 0.001). By analysis of the distribution patterns of SCPR response to intravenous glucagon, SCPR of 1.0 ng/ml and the increment of SCPR of 0.5 ng/ml at 6 min are to be used as cut-off points to differentiate IDDM and NIDDM. These values correspond roughly to the UCPR values below 20 micrograms/day and above 30 micrograms/day, which we previously proposed as indexes to differentiate insulin-dependent and non-insulin-dependent diabetes.     

Radioimmunological determination of luteinizing hormone in the hypophysis and blood of rats during the estrous cycle]

A study was made of the dynamics of the synthesis and secretion of the luteinizing hormone in the course of the sexual cycle in female rats by its determination by the radioimmunological method. Depending on the stages of the sexual cycle there were seen regular changes in the LH content in the hypophysis and the blood of female rats. LH content in the hypophysis was the minimal at 3 p.m. at the estrus stage and the maximal at 6 p.m. at the proestrus stage.     

Infusion of synthetic human C-peptide does not affect plasma glucose, serum insulin, or plasma glucagon in healthy subjects

We studied six healthy male subjects to determine whether a four-hour infusion of synthetic human C-peptide sufficient to achieve mean (+/- SD) peripheral plasma concentrations of 1.3 +/- 0.7 pmol/mL affected plasma glucose, serum insulin, or plasma glucagon. Subjects were studied in a fasting state and following an oral glucose load during four-hour 0.9% NaCl (control) and C-peptide (mean dose: 70 nmol) infusions. No differences were observed between saline and C-peptide infusions for mean values of fasting plasma glucose (94 +/- 6 v 87 +/- 5 mg/dL), serum insulin (3 +/- 1 v 2 +/- 1 microU/mL), or plasma glucagon (124 +/- 65 v 112 +/- 70 pg/dL). Following oral glucose ingestion no differences were detected between saline and C-peptide infusions for mean peak values of plasma glucose (168 +/- 18 v 168 +/- 31) and serum insulin (59 +/- 6 v 57 +/- 21) or mean nadir values of plasma glucagon (80 +/- 73 v 75 +/- 70). There was a slight delay in the insulin rise following oral glucose on the C-peptide infusion day, but differences between mean values for individual sampling times were not statistically significantly different.     

C肽与颈动脉内膜中层厚度的相关性研究

目的通过测定不同C肽（C-P）水平患者的颈动脉内膜中层厚度（IMT）,研究C-P与动脉粥样硬化的关系。方法以正常糖代谢、糖耐量减低及2型糖尿病病程小于5年的112例患者为研究对象,根据C-P三分位间距分为A、B、C组,应用彩色多普勒超声仪测定颈动脉IMT,并测量腰围、体质指数、血糖、血脂、尿酸等,各组间进行单因素方差分析,差异有统计学意义的指标与C-P水平进行Pearson相关分析,同时记录用药情况进行行×列x^2检验。结果各组间IMT的差异有统计学意义（P〈0．05）,B组和C组高于A组（P〈0．05）;同时腰围、体质指数、尿酸、甘油三酯存在差异且与C-P呈正相关;三组间高密度脂蛋白胆固醇差异有统计学意义（P〈0．05）,C组明显低于A组（P〈0．05）,B组与A组无明显统计学差异（P〉0．05）,且HDL-C与C-P呈负相关。结论随着C-P水平的升高IMT增加,在胰岛素抵抗及病程小于5年的2型糖尿病中升高的C-P可能反映动脉粥样硬化的发生。     

Plasma C-peptide and serum insulin antibodies in diabetic patients receiving pancreatic transplants

Summary Plasma C-peptide and serum insulin antibody levels were determined in 5 diabetic patients undergoing vascularized pancreatic transplantation. The grafts functioned well at first and exogenous insulin could be withdrawn, but one to 7 weeks later the grafts were rejected. After the transplantation there was an increase in the fasting plasma C-peptide level, and B-cell stimulation with glucose or glucagon evoked a C-peptide response. Healing of ischaemic damage was reflected in an increase in the C-peptide level. During graft rejection the C-peptide level fell. Measurement of plasma C-peptide levels provides a direct index of the B-cell function of the pancreatic graft. After transplantation the insulin antibody level fell exponentially, with an apparent half life of 10–11 days, whereas the level of total IgG was variable. The results indicate that formation of insulin antibodies ceases immediately on removal of the immunogenic stimulus, that is, on withdrawal of xenogeneic insulin.