Biomedical subjects

V Grill

Publications and source records attributed to V Grill.

At least 37 records · Page 2Linked to original sources

PubMed2002

Local secretion of parathyroid hormone-related protein by an osteoblastic osteosarcoma (UMR 106-01) cell line results in growth inhibition.

Parathyroid hormone-related protein (PTHrP) has been implicated as being important in the growth of tumor cells responsive to the peptide. We utilized a rat osteoblastic osteosarcoma cell line, UMR 106-01, which has PTHrP receptors and a PTHrP-responsive adenylate cyclase/cAMP messenger system, to produce a modified cell line that overexpresses PTHrP. The human PTHrP cDNA sequence was transfected by electroporation into UMR 106-01 cells and the stable cell lines UMR-36 and UMR-34 were established. The modified cell line, UMR-36, had increased levels of PTHrP mRNA compared with control cell lines and secreted PTHrP into the culture medium at levels of 0.01-0.1 pmol/10(7) cells in 12 h. The secreted peptide was biologically active as indicated by its ability to activate adenylate cyclase. The number of UMR-36 cells following 9 days in culture was reduced by up to 80% compared with control lines, which was associated with decreased (3)H-thymidine incorporation into genomic DNA. Addition of 1000-fold excess of the PTHrP antagonist, PTHrP(7-34), to UMR-36 cells resulted in the escape of growth inhibition and increased rate of growth. In vivo, tumors derived from UMR-36 cells were smaller in size compared with tumors derived from control cells. In conclusion, increased autocrine secretion of, and responsiveness to, PTHrP results in inhibited growth kinetics of an osteoblast-like bone tumor cell line in vitro and in vivo.

Animals↗

PubMed2002

A rapid increase in beta-cell function by multiple insulin injections in type 2 diabetic patients is not further enhanced by prolonging treatment.

OBJECTIVE: Intensive insulin treatment in type 2 diabetes can improve beta-cell function. It is not known which duration of treatment achieves maximal improvement. We addressed this question in type 2 diabetic patients who displayed features of 'secondary failure'. RESEARCH DESIGN AND METHOD: Ten patients were randomized to multiple insulin injection (MI) therapy for 9 weeks. Another 10 patients started with bedtime insulin (BTI) and continued their peroral medication. Following 9 weeks of treatment, patients on MI switched to BTI and glibenclamide. RESULTS: Three days of MI led to a decrease in fasting proinsulin/insulin ratio, 0.43 +/- 0.20 vs. 0.29 +/- 0.11, P=0.01 and an increase in glucagon-stimulated C-peptide over baseline, 0.77 +/- 0.43 vs. 1.28 +/- 0.44 nmol L-1, P 0.02. Nine weeks of MI treatment successively decreased fasting and nonfasting blood glucose in parallel with increasing insulin dosage. Initial improvements in secretion parameters were upheld but not further enhanced, the 9 week proinsulin/insulin ratio being 99 +/- 23% and that of glucagon-stimulated C-peptide being 95 +/- 24% of the values obtained after 3 days of treatment. Eight weeks after termination of MI there persisted a total weight gain that tended to be larger than after continuous peroral medication with BTI. CONCLUSION: Improvement of insulin secretion by intensive insulin treatment is rapidly gained with no further effect obtained after a longer treatment period. This finding, as well as undesirable effects of MI on body weight, argues against prolonged MI treatment as a prelude to other therapeutic regimens in type 2 diabetic patients.

Blood Glucose↗

PubMed2002

Effects of long-term fasting on insulin responses to fatty acids in man.

OBJECTIVE: To investigate whether the prolonged physiological elevation of nonesterified fatty acids (NEFA) seen in man during fasting associates with an altered acute insulin response to NEFA. SUBJECTS AND METHODS: Fourteen non-diabetic subjects, age 18-25 years, BMI 23.2 +/- 0.8 kg/m2 underwent hyperglycemic clamps (blood glucose 11 mM) for 120 min, during which either saline or Intralipid was administered in the last 60 min. Subjects were tested after an overnight as well as after a 58 h fast. RESULTS: After the overnight fast, insulin levels increased during Intralipid infusion, at min 120 reaching an increment of 33.0 +/- 8.5 microU/ml vs. 9.5 +/- 4.4 microU/ml during saline; p<0.05 for difference. Conversely, after the 58 h fast. Intralipid failed to promote a successive increase of insulin levels (increment during Intralipid at min 120: 0.5 +/- 5.8 microU/ml vs. -4.3 +/- 2.5 microU/ml during saline, NS). Insulin sensitivity as assessed by the amount of infused glucose and its ratio to insulin was enhanced by Intralipid after an overnight fast, but was decreased after a 58 h fast. CONCLUSION: Long-term elevated NEFA during fasting associates with diminished beta cell responsiveness to an acute elevation of fatty acids in conjunction with negative effects on insulin sensitivity.

Adolescent↗

PubMed2002

Effect of acute hyperketonemia on the cerebral uptake of ketone bodies in nondiabetic subjects and IDDM patients.

Using R-beta-[1-(11)C]hydroxybutyrate and positron emission tomography, we studied the effect of acute hyperketonemia (range 0.7-1.7 micromol/ml) on cerebral ketone body utilization in six nondiabetic subjects and six insulin-dependent diabetes mellitus (IDDM) patients with average metabolic control (HbA(1c) = 8.1 +/- 1.7%). An infusion of unlabeled R-beta-hydroxybutyrate was started 1 h before the bolus injection of R-beta-[1-(11)C]hydroxybutyrate. The time course of the radioactivity in the brain was measured during 10 min. For both groups, the utilization rate of ketone bodies was found to increase nearly proportionally with the plasma concentration of ketone bodies (1.0 +/- 0.3 micromol/ml for nondiabetic subjects and 1.3 +/- 0.3 micromol/ml for IDDM patients). No transport of ketone bodies from the brain could be detected. This result, together with a recent study of the tissue concentration of R-beta-hydroxybutyrate in the brain by magnetic resonance spectroscopy, indicate that, also at acute hyperketonemia, the rate-limiting step for ketone body utilization is the transport into the brain. No significant difference in transport and utilization of ketone bodies could be detected between the nondiabetic subjects and the IDDM patients.

3-Hydroxybutyric Acid↗

PubMed2002

Improved beta cell function after short-term treatment with diazoxide in obese subjects with type 2 diabetes.

OBJECTIVE: Our aim was to distinguish beneficial effects of B-cell rest from other effects of correction of hyperglycaemia. For this purpose we used diazoxide which reversibly blocks insulin secretion. MATERIAL AND METHODS: Eight obese (age 53 +/- 1 yr: BMI 33 +/- 2 kg/m2: 4 females) type 2 diabetic patients with poor metabolic control (HbA1c 8.7 +/- 0.9% ref.<5.2%) were studied twice after a randomly ordered treatment period of five days of intensive i.v. insulin treatment alone or i.v. insulin with peroral diazoxide (300 mg/day, divided into 3 doses). The glycaemic control was not altered between the two treatment periods. Insulin secretion was measured in response to i.v. glucose and arginine. RESULTS: Insulin infusion was used to achieve close to identical degrees of glycaemia during the two treatment periods. Previous treatment with diazoxide was associated with a moderate 1.9 +/- 0.6 fold rise in insulin response to intravenous glucose (p=0.04) and 1.6 +/- 0.4 fold increased glucose potentiation of arginine-induced insulin secretion (GPAIS) (p=0.04). Conversely, after insulin alone there was no response to i.v. glucose and no change in GPAIS. CONCLUSIONS: Short-term diazoxide treatment improved important parameters of B-cell function and these effects could be dissociated from confounding effects of changes in glycaemia. Consequently, the results indicate beneficial effects of B-cell rest.

Antihypertensive Agents↗

PubMed2001

Uncoupling protein-2 participates in cellular defense against oxidative stress in clonal beta-cells.

The role of uncoupling protein-2 (UCP-2) in beta-cells is presently unclear. We have tested the notion that UCP-2 participates in beta-cell defense against oxidants. Expression of the UCP-2 gene in clonal beta-cells (INS-1) was decreased by 45% after 48 h of culture with vitamin E and selenite. When INS-1 cells were exposed to 200 microM H(2)O(2) for 5 min, the cell viability (MTT assay) decreased to 85 +/- 1, 61 +/- 1, 40 +/- 2, and 39 +/- 2% of control when measured respectively 30 min, 2 h, 6 h, and 16 h after H(2)O(2) exposure. At corresponding time points UCP-2 mRNA levels were 1.01 +/- 0.09, 1.53 +/- 0.15 (P < 0.05), 1.44 +/- 0.18 (P = 0.06), and 1.12 +/- 0.09 fold of control, i.e., transiently increased. We next tested whether overexpression of UCP-2 could enhance resistance of beta-cells toward H(2)O(2) toxicity. A cotransfection method using EGFP as a suitable marker and a human cDNA UCP-2 construct was used for transient overexpression of UCP-2. Transfected cells expressed the gene about 30-fold more than normal cells. After exposure to H(2)O(2) (200 micrometer, 5 min), the survival of UCP-2 overexpressing cells was measured 30-45 min later by flow cytometry. Survival was 13 +/- 0.05% higher than control (EGFP only) cells, P < 0.004 for difference. The results indicate that oxidative stress induces UCP-2 expression in beta-cells, and that UCP-2 serves a role in beta-cell defense against oxidative stress.

Cell Survival↗

PubMed2001

Operating principle of an electron monochromator in an axial magnetic field.

Electron monochromators which are operated within an axial magnetic (guiding) field are especially suitable for the production of monochromatic electrons at low energies. Although in principle the technology of such devices has an appreciable historic background, we have discovered experimentally important new features, which cannot be understood using the previously published theories of operation. An in-depth study of the electron trajectories in a crossed electric and magnetic field using Simion1 showed a number of possible pitfalls, which have to be avoided in construction and operation. From our simulations we derived a novel design and operational method, which is currently under evaluation. We have already demonstrated that using this novel design an electron energy resolution of about 50 meV is realistic.

Electromagnetic Fields↗

PubMed2001

Hypocalcemic and normocalcemic hyperparathyroidism in patients with advanced prostatic cancer.

PTH and ionized calcium levels were measured in 131 patients with advanced prostate cancer, all of whom had received at least first-line hormone therapy. Patients were classified into those in remission, those with stable disease, or those with progressive disease according to their prostate-specific antigen response and their clinical status. Thirty-four percent of all patients had PTH levels above the upper level of normal for controls of similar age (7.0 pmol/liter), and in 44% of these patients this was associated with a normal ionized calcium. Patients with proven bone metastases had significantly higher PTH levels than those without. (7.3 +/- 0.5 vs. 4.3 +/- 0.4 pmol/liter, P < 0.0005). There was evidence for a difference in the PTH levels between the three response groups. The PTH levels tended to be higher in patients with progressive disease. Thirty-seven of 65 patients (57%) with both progressive disease and proven bone metastases had elevated PTH levels. Mean levels of urinary deoxypyridinoline and cAMP were significantly greater in patients with high PTH than in those with a normal PTH. Treatment with oral calcium supplements in 32 patients with a high PTH seemed to have only a transient effect on elevated PTH or low ionized calcium levels. These data show that secondary hyperparathyroidism occurs frequently in patients with advanced prostate cancer, particularly in those with both progressive disease and bone metastases. The increased PTH levels are associated with an increase in bone resorption markers. These findings raise important questions about the role of PTH in progression of prostatic cancer in bone and the potential limitations of the use of bisphosphonates in patients with a raised PTH or low serum calcium.

Aged↗

PubMed2001

Influence of a high-fat diet during chronic hyperglycemia on beta-cell function in pancreatic islet transplants to streptozotocin-diabetic rats.

Chronically elevated non-esterified fatty acids (NEFAs) can exert negative effects on beta-cell function both in vitro and in vivo. Negative effects of fatty acids have been difficult to evaluate in overt diabetes because of the attendant hyperglycemia that gives rise to the confounding influence of 'glucotoxicity'. In this work, we tested for the effects of NEFAs in diabetes by (i) taking into account potential effects of prevailing levels of hyperglycemia, and (ii) focusing on lingering (and therefore possibly more serious) effects. A diabetic transplantation model was used in which two islet grafts with 200 and 20 rat islets respectively were transplanted under the kidney capsule of syngeneic recipients previously made diabetic by streptozotocin injection. Rats were then fed either a high-fat or a low-fat diet for 7 weeks, followed by 1 week of normal laboratory chow. During dietary intervention, food was consumed ad libitum in one protocol, but was restricted in the low-fat group in a second protocol (in order to match blood-glucose levels). A high-fat diet did not affect body weight. At the end of the protocols, graft-bearing kidneys were isolated and perfused. Insulin responses to 27.8 mM glucose in perfusion were uniformly absent, in keeping with previously documented effects of chronic hyperglycemia. In contrast, 10 mM arginine induced a marked increase in insulin secretion after a low-fat diet, an effect that was significantly reduced after a high-fat diet (109 +/- 39 vs 13 +/- 15 fmol/min (P < 0.05) and 95 +/- 18 vs 32 +/- 5 fmol/min (P < 0.05) in the 2 protocols respectively). Regardless of protocol, no effect of diet could be detected on graft contents of insulin or preproinsulin mRNA. Thus, under conditions in which influences of chronic hyperglycemia could be accounted for, a previous high-fat diet with elevated NEFAs inhibited arginine-induced insulin secretion; however, the results indicate that insulin biosynthesis and/or beta-cell mass were not affected.

Animals↗

PubMed2001

Overstimulation and beta-cell function.

Previous and present evidence ascribes an important role to overstimulation of beta-cells for the secretory abnormalities associated with type 2 diabetes. The abnormality most clearly linked to overstimulation is the elevated ratio of circulating proinsulin to insulin. Evidence obtained in human pancreatic islets suggests that aberrations in insulin oscillations that occur in type 2 diabetes could at least in part be linked to abnormalities in cytoplasmic Ca2+ oscillations induced by overstimulation. Furthermore, in a transplantation model, we have obtained evidence for long-lasting, perhaps irreversible, effects of overstimulation, implying that this is a causative factor for the well-recognized deterioration of insulin secretion with increasing duration of type 2 diabetes. The mechanisms behind the effects of overstimulation are only partly clarified, but it is clear that reduced insulin secretion after overstimulation is only partly explained by decreased insulin stores. In cultured human pancreatic islets, overstimulation by high glucose leads to a rise in cytoplasmic Ca2+ levels, which persists after normalization of the glucose levels. Persistent elevation of cytoplasmic Ca2+ may trigger apoptosis, thus participating in long-term irreversible deterioration of beta-cell function. These data provide sufficient rationale for clinical studies to test the beneficial effects of relative beta-cell rest in type 2 diabetic patients.

Apoptosis↗

PubMed2000

Biocompatibility evaluation of dental metal alloys in vitro: expression of extracellular matrix molecules and its relationship to cell proliferation rates.

The biocompatibility in vitro of dental biomaterials has been widely studied, with consideration of cell viability and cell proliferation rates. In the present study we evaluated the biocompatibility in vitro of three single-phase dental metal alloys, all provided by the same manufacturer. To this aim, we considered the percentage of proliferating cells revealed by 5-bromodeoxyuridine incorporation in human fibroblast cultures in the presence of these biomaterials, performing a short time test (72 h). These data were correlated with immunocytochemical expression of four molecules of the extracellular matrix, i.e., fibronectin, type I collagen, beta(1)-integrin subunit, and chondroitin sulfate, because the capability of cells to adhere to substrata is widely related to cell proliferation rates. Alloys presenting higher amounts of noble elements were more biocompatible even when they contained significant amount of both Ag and Cu. As regards the expression of the extracellular matrix molecules, the organization level of fibronectin in fibrils was correlated with higher cell proliferation rates, whereas no difference was detected for the expression of the other antigens. On these bases, we assume that expression of fibronectin could be a useful parameter in evaluation of biocompatibility in addition to cell proliferation capability.

Bromodeoxyuridine↗

PubMed2000

[Why is insulin release from beta cells insufficient in type 2 diabetes?].

Insulin secretion is finely tuned to tissue requirements by tight links to prevailing blood glucose levels. The normal regulation of insulin secretion is linked to glucose metabolism in the pancreatic beta-cell, a major but not exclusive signal for secretion being closure of K+ ATP-dependent channels in the cell membrane through an increase in the cytosolic ATP/ADP. Insulin secretion in type 2 diabetes is abnormal in several respects, due to genetic causes, but also due to the metabolic environment of the pancreatic beta-cells. This environment may be particularly important for the deterioration of insulin secretion, which occurs with increasing duration of diabetes. Factors of the environment with potential importance include over-stimulation, a negative effect of hyperglycaemia per se ("glucotoxicity"), and adverse effects of elevated fatty acids ("lipotoxicity"). A better understanding of the mechanisms behind these factors and of their clinical importance will pave the way for treatment which could preserve beta-cell function in type 2 diabetic patients.

Diabetes Mellitus, Type 2↗

PubMed2000

[Increased cardiovascular risk in patients with type 2 diabetes treated with sulfonylurea?].

BACKGROUND: The use of sulphonylureas for type 2 diabetes has been debated since 1970, when the University Group Diabetes Program (UGDP) reported increased cardiovascular mortality with tolbutamide treatment. MATERIAL AND METHODS: We try to present a balanced review of the current knowledge of the possible cardiovascular side effects of sulphonylureas. RESULTS: Recent studies on the molecular actions of sulphonylureas show that sulphonylureas, in addition to closing K+ ATP channels in insulin producing cells, also do so in the myocard and in vascular smooth muscle. This action could theoretically have adverse effects during ischaemia. Experimental studies show effects on cardiac parameters and also differences in such effects between sulphonylureas, but leave the net effect of sulphonylureas during ischaemia uncertain. The United Kingdom Prospective Diabetes Study (UKPDS), published in September 1998, found no increase in cardiovascular mortality with the use of sulphonylureas. One possible explanation for the difference in relation to the UGDP is the exclusion of cardiovascular patients in the UKPDS. INTERPRETATION: Our interpretation is that sulphonylureas are without clinically important cardiovascular side effects in type 2 diabetic patients without cardiovascular disease. Clinical studies focusing on the effects of sulphonylurea in cardiovascular patients are, however, lacking. More studies are also needed on the effect of newly developed and possibly more selective sulphonylureas as well as related compounds.

Adenosine Triphosphate↗

PubMed2000

Improvement by aminoguanidine of insulin secretion from pancreatic islets grafted to syngeneic diabetic rats.

Prolonged hyperglycemia inhibits B-cell function by mechanisms that are largely unclarified. We investigated the involvement of advanced glycation end products (AGEs), using aminoguanidine as well as the AGE-breaking compound ALT-711 in a transplantation model. Islets from Wistar-Furth rats were transplanted under the kidney capsule of syngeneic streptozocin-diabetic recipients. Aminoguanidine was administered as 1 g/L in the drinking water. Graft-bearing kidneys were isolated and perfused to investigate insulin secretion, and grafts were excised to measure preproinsulin mRNA contents. In all transplants to diabetic rats, insulin responses to 27.8 mM glucose were abolished and aminoguanidine failed to correct this abnormality. However, aminoguanidine treatment for 8 weeks following transplantation increased preproinsulin mRNA contents of the grafts (P < 0.05). In addition, treatment with aminoguanidine enhanced the insulin secretory response to arginine (P < 0.05). Arginine-induced insulin secretion was also enhanced when aminoguanidine treatment was started after an initial 2-week implantation period rather than immediately after transplantation. On the other hand, treatment with ALT-711 (0.1 mg/kg by gavage) for 8 weeks completely failed to affect B-cell function of grafts, and ALT-711 was also ineffective under in vitro conditions. Our findings indicate that aminoguanidine effects in vivo are to a major extent not coupled to AGEs or nitric oxide synthetase inhibition, but possibly to oxidative modifications accomplished by the guanidine compound.

Animals↗

PubMed2000

[New diagnostic criteria for diabetes mellitus--why?].

In 1997, the diagnostic criteria for diabetes mellitus were changed in the USA; the WHO has also proposed changes in its criteria. The main difference from the previous set of WHo criteria is a lowering of the cut-off level of fasting plasma glucose to > or = 7.0 mmol/l. This article discusses the implications of new diagnostic criteria and recommends that the level of fasting plasma glucose for diagnosing diabetes is decreased to > or = 7.0 mmol/l in Norway as well.

Blood Glucose↗

PubMed2000

Enhanced nuclear diacylglycerol kinase activity in response to a mitogenic stimulation of quiescent Swiss 3T3 cells with insulin-like growth factor I.

Results from several laboratories have established the existence in the nucleus of an autonomous polyphosphoinositide cycle, which is involved in both cell proliferation and differentiation. A key step of intranuclear polyphosphoinositide metabolism is the phospholipase C-mediated generation of diacylglycerol (DAG). In insulin-like growth factor (IGF)-I-stimulated Swiss 3T3 cells, a transient elevation of intranuclear DAG levels is essential for attracting the alpha isoform of protein kinase C (PKC) to the nucleus. Previous evidence has shown that the nucleus also contains DAG kinase, i.e., the enzyme that yields phosphatidic acid from DAG, thus terminating PKC-mediated signaling events. Here we show that IGF-I treatment of quiescent Swiss 3T3 cells results in the stimulation of nuclear DAG kinase activity. Time course analysis showed an inverse relationship between nuclear DAG mass and DAG kinase activity levels. After IGF-I treatment, maximal enhancement of DAG kinase activity was measured in the internal matrix domain of the nucleus. PKC-alpha remained within the nuclear compartment, even when nuclear DAG mass returned to basal levels. This was conceivably due to interactions with specific nuclear PKC-binding proteins, some of which were identified as lamins A, B, and C and protein C23/nucleolin. Treatment of cells with two DAG kinase inhibitors, R59022 and R59949, blocked the IGF-I-dependent rise in nuclear DAG kinase activity and maintained elevated intranuclear levels of DAG. The two inhibitors also markedly potentiated the mitogenic effect of IGF-I. These results suggest that nuclear DAG kinase plays a key role in regulating the levels of DAG present in the nucleus and that DAG is a key molecule for the mitogenic effect that IGF-I exerts on Swiss 3T3 cells.

3T3 Cells↗

PubMed2000

Assessment of cellular expression of parathyroid hormone-related protein mRNA and protein in multiple myeloma.

The capacity of multiple myeloma cells to generate parathyroid hormone-related protein (PTHrP) has been examined by in situ assessment of PTHrP mRNA and PTHrP protein in myeloma cells of patients in whom the disease was associated with the development of hypercalcaemia. The presence of PTHrP mRNA was evaluated by in situ hybridization using an antisense riboprobe, and PTHrP by immunohistochemistry using a monoclonal antibody, in archival bone marrow trephine specimens from 17 patients. PTHrP mRNA was detected in myeloma cells in 16 of the 17 patients, indicating a high frequency of PTHrP gene expression in myeloma cells in these subjects. PTHrP protein was, on the other hand, detected in the myeloma cells of only five of these patients. The impact of the mercury-based fixation and decalcification procedure used for processing the bone marrow trephine specimens was assessed to determine the influence of this process on the outcome of the immunohistochemical assay for PTHrP. It was shown that this preparative procedure resulted in a marked reduction of immunohistochemically detectable PTHrP, which provides a possible explanation for the lower frequency of positivity for PTHrP in myeloma cells in the bone marrow specimens. The present findings are consistent with the view that PTHrP can be generated in myeloma cells in vivo, and could contribute to osteolysis and hypercalcaemia, as in patients with cancer.

Aged↗

PubMed2000

Experimental urethane anaesthesia prevents digoxin intoxication: electrocardiographic and histological study in rabbit.

An electrocardiographic and histological study was performed in rabbit to detect the effects of urethane (ethyl carbamate) intraperitoneal (i.p.) anaesthesia in digoxin intoxication, since it has been previously shown that this anaesthetic and digitalis glycosides exert specific peripheral effects on the cardiovascular system involving central structures of the autonomic nervous system. We observed that i.p. urethane anaesthesia prevented the onset of the electrocardiographic signs of digitalis intoxication, as well as inhibiting the appearance of histological myocardial alterations after treatment with toxic digoxin doses. On the other hand, lethal arrhythmias and severe myocardial damage were observed in animals that had not undergone preliminary urethane anaesthesia. These results indicate that the effect exerted by urethane in preventing the toxic action of digoxin is probably due to a decrease of sympathetic activity in anaesthetized animals by centrally mediated sympathetic inhibition.

Anesthesia↗