Biomedical subjects

C Streli

Publications and source records attributed to C Streli.

8 recordsLinked to original sources

PubMed2006

Lead accumulation in tidemark of articular cartilage.

OBJECTIVE: Determination of the spatial distribution of the toxic element lead (Pb) and other trace elements in normal articular cartilage and subchondral bone from adult humans with no history of work-related exposure to Pb. METHODS: Four macroscopically normal femoral heads and three patellas were harvested from randomly selected forensic autopsies. All subjects died of acute illnesses, had no history of work-related exposure to Pb and had no metabolic bone disease. The elemental distribution of lead (Pb) together with zinc (Zn), strontium (Sr) and calcium (Ca) in the chondral and subchondral region was detected using high resolution synchrotron radiation induced micro X-ray fluorescence (SR mu-XRF) analysis. SR mu-XRF line scans in conventional and SR mu-XRF area scans in confocal geometry were correlated to backscattered electron (BE) images visualizing the mineralized tissue. RESULTS: In all samples, we found a highly specific accumulation of Pb in the tidemark, the transition zone between calcified and non-calcified articular cartilage. Pb fluorescence intensities in the tidemark, which is thought to be a metabolically active mineralization front, were 13-fold higher when compared to subchondral bone. Pb intensities in the subchondral region were strongly correlated with Zn, but were distinctly different from Ca and Sr. CONCLUSIONS: The finding of the highly specific accumulation of lead in the tidemark of human articular cartilage is novel. However at this point, the exact mechanisms of the local Pb accumulation as well as its clinical implications are unknown.

Calcium↗

PubMed2005

Laser technology: source of coherent kiloelectronvolt X-rays.

Generating X-rays that have the properties of laser light has been a long-standing goal for experimental science. Here we describe the emission of highly collimated, spatially coherent X-rays, at a wavelength of about 1 nanometre and at photon energies extending to 1.3 kiloelectronvolts, from atoms that have been ionized by a 5-femtosecond laser pulse. This means that a laboratory source of laser-like, kiloelectronvolt X-rays, which will operate on timescales relevant to many chemical, biological and materials problems, is now within reach.

Journal Article↗

PubMed2000

Femtosecond X-Ray fluorescence

Using few-cycle-driven coherent laser harmonics, K-shell vacancies have been created in light elements, such as boron (E(B) = 188 eV) and carbon (E(B) = 284 eV), on a time scale of a few femtoseconds for the first time. The capability of detecting x-ray fluorescence excited by few-femtosecond radiation with an accuracy of the order of 1 eV paves the way for probing the evolution of the microscopic environment of selected atoms in chemical and biochemical reactions on previously inaccessible time scales (<100 fs) by tracing the temporal evolution of the "chemical shift" of peaks associated with inner-shell electronic transitions in time-resolved x-ray fluorescence and photoelectron spectra.

Journal Article↗

PubMed1997

Pronounced insulin resistance and inadequate beta-cell secretion characterize lean gestational diabetes during and after pregnancy.

OBJECTIVE: To evaluate beta-cell secretion and glucose metabolism in lean subjects with gestational diabetes mellitus (GDM) compared with that in subjects with normal pregnancy and obesity. RESEARCH DESIGN AND METHODS: Insulin secretion, insulin sensitivity (S1), and hepatic insulin extraction were assessed in pregnant women with GDM before and after delivery and in those with normal glucose tolerance (NGT) in comparison to healthy nonpregnant lean and obese women. Kinetic analysis of glucose, insulin, and C-peptide plasma concentrations during oral and intravenous glucose tolerance tests was performed by mathematical modeling. RESULTS: S1 was blunted in pregnant women with GDM by 84% and in those with NGT by 66% compared with lean nonpregnant women (P < 0.005 vs. healthy nonpregnant lean control subjects; P < 0.05, GDM vs. pregnant women with NGT), whereas glucose effectiveness was decreased by 33% in both pregnant groups (P < 0.05 vs. healthy nonpregnant lean control subjects). Insulin secretion was 30% higher (P < 0.05) in subjects with GDM than in pregnant women with NGT or in nonpregnant lean women, but decreased (P < 0.005) when compared with obese women with a comparable degree of insulin resistance. Fractional hepatic insulin extraction was similar in both pregnant groups, being lower (P < 0.0001) by 30% versus nonpregnant females. beta-cell sensitivity to glucose for insulin release was decreased in subjects with GDM versus pregnant women with NGT as well as nonpregnant women by 40-50% (P < 0.01). Twelve weeks after delivery, GDM returned to normal glucose tolerance, but S1 remained 50% lower than that in lean nonpregnant women, while beta-cell sensitivity to glucose did not change (P < 0.01 vs. healthy nonpregnant lean control subjects). CONCLUSIONS: Pregnancy is characterized by insulin resistance, diminished hepatic insulin extraction, and glucose effectiveness. Lean subjects with GDM are additionally characterized by having more pronounced insulin resistance and inadequate insulin secretion, which persist after delivery. Compared with other insulin-resistant prediabetic states like impaired glucose tolerance (IGT), defective insulin secretion seems to be a predominant defect in lean GDM subjects, indicating that it might represent a specific prediabetic condition.

Adult↗

PubMed1996

Elevated concentrations of circulating adhesion molecules and their association with microvascular complications in insulin-dependent diabetes mellitus.

To better understand potential associations of circulating adhesion molecules (cAMs) with diabetic microangiopathy, circulating serum concentrations of intercellular adhesion molecule-1 (cICAM-1), vascular cell adhesion molecule-1 (cVCAM-1), and endothelial leukocyte adhesion molecule-1 (cELAM-1) were determined in patients with insulin-dependent diabetes mellitus (IDDM) (n = 70) presenting with varying degree of metabolic control and status of diabetic late complications, and were compared with age-matched healthy subjects (n = 70) in a cross-sectional study. Concentrations of cICAM-1 and cVCAM-1 were elevated in IDDM vs. age-matched controls (cICAM-1: 276 +/- 71 vs. 212 +/- 57 ng/mL; P < 0.0001; cVCAM-1: 781 +/- 245 vs. 615 +/- 151 ng/mL; P < 0.0001), whereas cELAM-1 did not differ between the groups (cELAM-1: 50 +/- 25 vs. 46 +/- 23 ng/mL, P = 0.31). The levels of cVCAM-1 were more markedly elevated in IDDM patients with diabetic retinopathy (n = 32) than in those without (n = 38) (cVCAM-1: 848 +/- 281 vs. 724 +/- 197 ng/mL, P < 0.05), as well as in patients with micro- or macroalbuminuria (n = 10) vs. those without (n = 60) (cVCAM-1: 947 +/- 256 ng/mL vs. 753 +/- 234 ng/mL, P < 0.05), whereas no difference in cICAM-1 and cELAM-1 was apparent regarding the clinical status of diabetic microangiopathy. No correlations were found between hemoglobin A1e and cAMs in the individual subgroups of patients and healthy subjects. Interestingly, however, low density lipoprotein cholesterol correlated with cVCAM-1 (r = 0.38, P = 0.03) in IDDM patients with diabetic microangiopathy (n = 33), but not in healthy controls or patients without microangiopathy (n = 37). Analyzing the pooled data of diabetic patients and healthy subjects (n = 140), concentrations of cICAM-1 were markedly related to cVCAM-1 (r = 0.45, P < 0.0001) and cELAM-1 (r = 0.31, P < 0.0002), whereas cVCAM-1 was related less to cELAM-1 (r = 0.19, P = 0.03), respectively. We conclude that, irrespective of actual metabolic control, serum concentrations of cICAM-1 and cVCAM-1 but not cELAM-1 are elevated in patients with IDDM, reflecting ongoing endothelial cell stimulation and leukocyte activation. More specifically, more marked elevation of cVCAM-1 may even hint at clinically manifest diabetic microangiopathy.

Adolescent↗

PubMed1995

Intravenous calcitriol normalizes insulin sensitivity in uremic patients.

Recent studies suggest that secondary hyperparathyroidism and/or vitamin D deficiency are responsible for the insulin resistance in chronic renal failure. We investigated the effect of a 12-week intravenous treatment with 1,25 dihydroxycholecalciferol on glucose metabolism in 10 hemodialysis patients compared with 10 healthy control subjects by the frequently-sampled intravenous glucose tolerance test, analyzed with the minimal model technique. Compared to control subjects, the uremic patients featured elevated levels of parathyroid hormone (432 +/- 60 vs. 41 +/- 4 ng/liter, P < 0.001), insulin resistance (insulin sensitivity index, SI: 4.9 +/- 0.8 vs. 9.5 +/- 0.9 min-1/(microU/ml), P < 0.002), increased posthepatic insulin delivery (6.48 +/- 2.48 vs. 2.73 +/- 3.14 nmol/liter in 4 hr, P < 0.001) and a reduced C-peptide fractional clearance (0.033 +/- 0.004 vs. 0.085 +/- 0.009 min-1, P < 0.0002). Following treatment with 1,25 dihydroxycholecalciferol, the parathyroid hormone levels decreased significantly to 237 +/- 30 ng/liter (P < 0.05), the insulin sensitivity index (SI: 9.6 +/- 2.2, P < 0.05) reached a value similar to that of control subjects, and posthepatic insulin delivery decreased to 4.63 +/- 0.83 nmol/liter in 4 hr (P < 0.01), while all the other parameters remained unchanged. In summary, uremic patients with secondary hyperparathyroidism were found to be severely insulin resistant and hyperinsulinemic. Intravenous vitamin D treatment led to a significant reduction of parathyroid hormone levels and to a complete normalization of insulin sensitivity in the hemodialysis patients. Thus, intravenous 1,25 dihydroxycholecalciferol improves insulin resistance in uremic patients, acting per se or by reducing secondary hyperparathyroidism.

Adult↗

PubMed1994

Role of islet amyloid polypeptide secretion in insulin-resistant humans.

Although it is generally accepted that islet amyloid polypeptide is cosecreted with insulin, relatively few data on its kinetics are available. We therefore studied the dynamics of islet amyloid polypeptide release following oral and frequently sampled intravenous glucose tolerance tests in comparison to insulin and C-peptide using mathematical model techniques in 14 control subjects, 10 obese and 11 hypertensive patients. The fractional clearance rate of islet amyloid polypeptide (0.034 +/- 0.004 min-1 in control subjects, 0.058 +/- 0.008 in the obese and 0.050 +/- 0.008 in the hypertensive patients) was significantly different (p < 0.01) in each group compared with that of insulin (0.14 +/- 0.03 min-1) and similar to that of C-peptide (0.061 +/- 0.007 min-1), at least in the insulin-resistant subjects. Based on the insulin sensitivity index derived from the minimal model analysis of intravenous glucose tolerance test data, both the hypertensive (2.4 +/- 0.4 min-1/(microU/ml); p < 0.0005) and the obese (2.7 +/- 0.5; p < 0.001) patients demonstrated severe insulin resistance compared to control subjects (8.1 +/- 1.3). Marked insulin hypersecretion was found in the hypertensive (57.6 +/- 5.2 nmol.l-1 in 180 min; p < 0.001) and obese (60.8 +/- 10.1; p < 0.003) patients in comparison with control subjects (32.4 +/- 3.2). The release of islet amyloid polypeptide was significantly higher in the hypertensive (83.1 +/- 16.6 pmol/l in 180 min; p < 0.02) and obese (78.6 +/- 13.1; p < 0.005) patients than in control subjects (40.5 +/- 6.4). No correlation was found between islet amyloid polypeptide release and the insulin sensitivity index in any group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

[Diabetes and sports].

Through better understanding of the physiology of physical exercise in normal and diabetic subjects we can more closely define the significance of regular physical exercise in the treatment of diabetes. Although patients with type I and type II diabetes can obtain different advantages from regular physical exercise, this activity is in turn connected with different risks. The introduction of self-monitoring of blood glucose has though considerably eased management in relation to physical activity by type I diabetics. Essentially the risk to type I diabetics is that of developing hypoglycemia during or after exercise as well as the danger of a worsening of metabolic levels with the development of ketoacidosis. In type II diabetics the risk of hypoglycemia is less pronounced and in patients treated solely by dietary means the regulation of blood glucose presents no great problem. With these individuals regular physical activity can be implemented as a further therapeutic tool towards the normalisation of body weight and an improvement in insulin sensitivity. With appropriate training and self-control the potential hypoglycemia in type I diabetic patients can easily be avoided. For this reason regular physical exercise can be recommended as a cornerstone of therapy, both in the management of type I as well as type II diabetes. The positive effect of exercise is significantly better defined in regard to type II diabetics than with type I diabetics. In particular, regular physical exercise can be implemented as a supplement to caloric restriction for weight reduction and as a means to improve insulin sensitivity in the obese insulin-resistant individual.

Blood Glucose↗