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H Schatz

Publications and source records attributed to H Schatz.

At least 73 records · Page 4Linked to original sources
PubMed2000

Effect of estradiol on insulin secreting INS-1 cells overexpressing estrogen receptors.

BACKGROUND: Estrogen has been shown to have profound effects on insulin and glucose metabolism in vivo. Indeed, estrogens were recently shown to modulate ion channel and secretory activities in endocrine cells. DESIGN AND METHODS: To investigate whether estrogenic influences are caused by direct effects on pancreatic beta-cells, we equipped INS-1 insulinoma cells with estrogen receptors and monitored insulin content and Ca(2+) fluxes as well as basal and stimulated insulin secretion upon different stimuli including glucose, the Ca(2+) ionophore ionomycin, the Ca(2+) channel agonist BayK8644, the protein kinase C activator TPA, and the adenylate cyclase activator forskolin. RESULTS AND CONCLUSION: Our data reveal that estradiol has no significant direct effect on proliferation rate, insulin content, basal and stimulated insulin output as well as Ca(2+) fluxes of insulin secreting cells in vitro, indicating that in vivo responses to estrogen on insulin and glucose metabolism result from indirect betacytotropic effects.

Calcium↗
PubMed1999

Anti-proliferative activity of protein kinase C in apical compartments of human colonic crypts: evidence for a less activated protein kinase C in small adenomas.

The protein-kinase-C (PKC) family of iso-enzymes regulates mitogenic signal transduction in colorectal-cell lines. Its function in human colonic mucosal proliferation is controversial. Our study investigated the role of PKC with regard to proliferation and changes of PKC iso-enzyme expression in colonic biopsies compared with small adenomas. In short-term tissue-culture experiments of colonic mucosal biopsies, we found reduced S-phase labeling in the 2 apical compartments of longitudinally sectioned crypts when PKC was activated by 200 nM of the phorbol ester TPA (n = 8). Thus, PKC inhibited growth of differentiated colonocytes which may influence cell homeostasis in colonic crypts. Furthermore, we have determined the expression of PKC alpha, -beta1, -beta2, -delta and -epsilon in colonic adenomas smaller than 1 cm in diameter of 18 patients and found a significant increase of PKC alpha in the cytosolic fraction and decreased membrane levels of PKC beta2 in adenomas compared to normal, neighboring mucosa while protein levels of PKC beta1, -delta and -epsilon were not altered. Moreover PKC delta but not PKC alpha mRNA expression was significantly lowered in adenoma tissue in 7 patients, as determined by ribonuclease-protection analysis. Changes in the regulation patterns of PKC isoforms suggest a decreased activation state of PKC even in small adenomas. This is compatible with an anti-proliferative function of PKC serving to protect mucosa from expanding mutated cells.

Adenoma↗
PubMed1999

Insulin resistance and impaired insulin secretion due to phosphofructo-1-kinase-deficiency in humans.

UNLABELLED: The etiology of non-insulin-dependent diabetes mellitus (NIDDM) is usually explained as a combination of peripheral insulin resistance and impaired beta-cell function. Phosphofructo-1-kinase (PFK1) is a rate limiting enzyme in glycolysis, and its muscle subtype (PFK1-M) deficiency leads to an autosomal recessively inherited disorder known as glycogenosis type VII or Tarui's disease. It was evaluated whether PFK1-M deficiency leads to NIDDM in humans. A core family of four was evaluated for PFK1-M deficiency by DNA- and enzyme-activity-analyses. All members underwent oral and intravenous glucose tolerance test (oGTT/ivgtt), as well as an insulin sensitivity test (IST) using octreotide. RESULTS: Father (46 years, BMI 22.4 kg/m2) and older son (19 years, BMI 17.8 kg/m5) showed homozygous PFK1-M deficiency, while mother (47 years, BMI 28.4 kg/m5) and younger son (13 years, BMI 16.5 kg/m5) were shown to be heterozygously PFK1-M-deficient on enzyme activity levels. DNA analysis revealed an exon 5-missense-mutation at one allele of all four members, and an exon 22-frameshift-mutation at the other allele of the two homozygously affected individuals. By oGTT the father showed impaired glucose tolerance, and the mother clinical diabetes. By ivGTT both parents and the older son had a decreased first phase insulin secretion, and a diminished glucose disappearance rate. The IST showed marked insulin resistance in both parents and the older son, and moderate resistance in the younger son, previously not described. CONCLUSION: PFK1-M-deficiency leads to a metabolic state typical for early NIDDM in homozygously affected humans, especially concerning insulin resistance and loss of first phase beta-cell insulin secretion, and may contribute to the manifestation of NIDDM in a subgroup of patients.

Adult↗
PubMed1999

Deficient activation and different expression of transforming growth factor-beta isoforms in active proliferative diabetic retinopathy and neovascular eye disease.

An increased expression and secretion of angiogenic growth factors was proposed to occur in proliferative diabetic retinopathy and other neovascularizing retinal diseases. However, a loss of anti-angiogenic factors also might promote retinal neovascularization. Therefore we investigated the active and latent vitreous levels of the subtypes of the endothelial anti-mitogen transforming growth factor-beta in vitreous of 58 patients. Four groups of patients were compared: Controls without retinal hypoxia, patients with quiescent and active proliferative diabetic retinopathy (PDR), and patients with severe retinal hypoxia resulting in rubeosis iridis. Whereas the amount of total TGF-beta in the four groups did not differ significantly, latent TGF-beta isoform expression showed complex alterations in ocular vitreous. Levels of active TGF-beta of patients with active PDR (79.5 +/- 28 pg/ml; n = 8) were decreased to 20% of the control levels (378 +/- 55 pg/ml; n = 12; p = 0.0005) and 25% of the mean concentration in quiescent PDR (346 +/- 64 pg/ml; n = 9; p = 0.0021). Levels in rubeosis (52 +/- 10 pg/ml; n = 10) did not differ significantly from those found in active PDR but were decreased to 15% of those in patients with quiescent PDR (p = 0.0004). Furthermore a highly significant inverse correlation between active TGF-beta and alpha2-antiplasmin, a liver produced inhibitor of the activation of TGF-beta by plasmin was noted (r = -0.59; n = 28; p = 0.001). We conclude that deficient activation of TGF-beta occurs in active proliferative diabetic retinopathy and in hypoxic angiogenesis most likely as a consequence of a blood retina barrier breakdown and influx of alpha2-antiplasmin from serum. The disinhibition of endothelial cell proliferation may be a central component in the process of neovascularization.

Aged↗
PubMed1999

Preclinical and clinical studies on safety and tolerability of repaglinide.

Repaglinide, an insulinotropic benzoic acid derivative, has been tested extensively in the preclinical and clinical setting for safety and tolerability. In preclinical safety trials, no clinically relevant laboratory or histopathological changes were found and repaglinide was not found to be genotoxic, immunogenic, teratogenic or tumorigenic at levels 50 times greater than the exposure in humans. In an ascending-dose tolerability study in Type 2 diabetic patients, no clinically relevant changes in liver enzymes or ECG occurred during the trial. A total of five active-controlled, long-term trials of identical design have been carried out (with 12 months of maintenance on a fixed, pretitrated dose), including 1228 patients on repaglinide and 597 on sulphonylureas, 417 of whom were on glibenclamide. The most common adverse event in the phase II studies was hypoglycaemia. The frequency of hypoglycaemia was identical for repaglinide and sulphonylureas; however, fewer nocturnal hypoglycaemic events were observed with repaglinide and no increase in the frequency of hypoglycaemic events occurred in elderly patients (> 65 years) compared with younger patients. Severe reactions (assistance required) were approximately twice as frequent in the comparator group. During these studies, two serious hypoglycaemic reactions were reported (coma, seizure or hospitalization), both occurring in patients on glibenclamide. The frequency of serious adverse events and serious cardiovascular events was comparable between repaglinide and sulphonylureas.

Aged↗
PubMed1998

[Continuous blood glucose monitoring: the acute effect of acarbose on blood glucose variations].

BACKGROUND: Acarbose, a pseudo-tetrasaccharid, inhibits intestinal alpha-glucosidases, effects a reduction of postprandial hyperglycemia and is particularly used in the treatment of patients with type-2 diabetes mellitus. The aim of the study is to analyse by a continuous blood glucose measurement the acute effect of acarbose after a carbohydrate loading and during a 12 hours period. PATIENTS AND METHODS: We examined 10 patients with type-2 diabetes mellitus (mean age 59.2 +/- 3.79, HbA1 9.2 +/- 0.26%) treated with sulfonylureas and/or insulin after a carbohydrate meal and 12 hours during daytime, to test whether the first application of acarbose influences the mean blood glucose or the blood glucose amplitudes. Four measurements were enrolled using a portable continuous blood glucose sensor (Glucosensor, unitec Ulm). A measurement after a carbohydrate loading (Fresubin, 500 kcal, 69 g carbohydrate) with 100 mg acarbose (Glucobay) was followed by a 12-hour measurement during daytime with 3 x 100 mg acarbose and standard diet. These measurements were repeated without acarbose. RESULTS: After a carbohydrate loading, the mean blood glucose level (AUC 44,320 +/- 10,660 with acarbose vs. 61,390 +/- 12,590 without acarbose; mean + SD; p = 0.004) decreased by 28%. During daytime blood glucose levels were not significantly decreased (165.7 +/- 50.3 mg/dl vs 183.7 + 67.4 mg/dl; p = 0.1) although the postprandial blood glucose amplitudes after the 3 meals were reduced significantly (85.90 +/- 24.6 mg/dl vs 106.5 +/- 20.5 mg/dl; p = 0.02). CONCLUSIONS: Continuous blood glucose monitoring indicated that acarbose diminished mean blood glucose levels after a carbohydrate loading in patients with type-2 diabetes mellitus, but not during 12 hours of standard diet, although blood glucose amplitudes decreased. Long-term improvements of metabolism by acarbose may therefore be related to the reduction of blood glucose amplitudes which is likely to reduce toxic effects of glucose on islet cell function.

Acarbose↗
PubMed1998

Purification and characterization of a Ca2+/calmodulin-dependent protein kinase II from hog gastric mucosa using a protein-protein affinity chromatographic technique.

A peripheral member of the Ca2+/calmodulin-dependent protein kinase II (CaMkinase II) group has been purified from hog gastric mucosa with the use of a novel affinity-chromatographic step. For the well known neural isotypes of CaMkinase II, it is proposed that the subunits form holoenzymes through a specific domain at the C-terminus called the 'association domain'. We immobilized a bacterially expressed association domain from CaMkinase II-delta-2 and used it as an affinity column. This matrix was used as the last step in a sequential enzyme purification procedure from hog gastric mucosa and yielded a homogeneous CaMkinase II which showed the typical physical and enzymatic properties of CaMkinase II. The enzyme activity showed a dependence on Ca2+ and calmodulin (apparent K0.5 = 2.7 microM and K0.5 = 0.02 microM, respectively). We found a subunit molecular mass of 61 kDa. An apparent native molecular mass of 310 kDa was calculated. The Stokes radius and the sedimentation coefficient were 6.7 nm and 11.2 S, respectively. Moreover, the isolated CaMkinase II was very well inhibited by the CaMkinase-II-specific inhibitors KN-62 (Ki = 0.52 nM) and KT5926 (Ki = 0.79 nM). The phosphorylation of several substrates revealed its multifunctionality. The purified CaMkinase II had an apparent Km for Mg-ATP of 24.0 microM and for autocamtide-II of 0.62 microM. CaMkinase II is considered as a strong candidate for regulating vesicle released quanta such as acid, neurotransmitters or insulin.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

Epidermal-growth-factor receptor correlates negatively with cell density in cervical squamous epithelium and is down-regulated in cancers of the human uterus.

The role of the epidermal-growth-factor receptor (EGFR) in cervical cancer is controversial, due to technical difficulties in localizing or in quantifying EGFR by homogenate assays or immunohistochemistry. Our autoradiographic approach, in combination with morphometry, allowed cell-type-specific quantification of EGFR, leading to the following observations: (i) In normal cervical epithelium, EGFR levels per cell were high in non-dividing squamous cells of the upper layers of normal epithelium, where a mitogenic function of these EGFRs can be excluded. (ii) In contrast to earlier findings in tissue homogenates, but consistent with our observation in normal cervical epithelium that cells of the proliferating strata (basal and parabasal cells) express intermediate and comparatively reduced levels of EGFR per cell, cervical cancers displayed a significant reduction both of specific EGF binding and of EGFR levels per cell as compared with normal epithelium. (iii) A significant negative correlation of cell density and EGFR number per cell was obtained. In normal cervical epithelium, cervical intra-epithelial neoplasia and invasive cervical cancer (p = 0.002). This negative correlation was most evident in normal epithelium, where large changes of cell density occur within one slide (p < 0.001). (iv) Specific EGF-binding was also significantly reduced in endometrial cancers when compared with normal endometrium. It is proposed that in uterine tissues low or intermediate levels of EGFR do not exclude their function as mediators of cell proliferation.

Autoradiography↗
PubMed1998

Crystalline retinopathy associated with chronic retinal detachment.

OBJECTIVE: To describe the presence of crystalline opacities located at the level of the inner retina in patients with chronic retinal detachment. METHODS: We reviewed the clinical records, fundus photographs, and fluorescein angiograms of patients with superficial retinal crystals in the presence of a chronic retinal detachment. RESULTS: Eleven eyes in 11 patients with chronic retinal detachment were found to have these peculiar crystalline opacities on the inner retinal surface. In 5 patients, the crystalline opacities were noted on initial assessment prior to surgery and persisted without change in appearance or number after surgical repair. In 6 eyes, the crystals were not appreciated until after surgical repair of the retinal detachment. The crystals appeared similar in all 11 eyes, were highly refractile, and were located in the posterior pole. Eight of the eyes had retinal detachment associated with retinal dialysis and 6 of these had a history of trauma. There was a definite history of vitreous hemorrhage in 2 eyes. The crystals did not seem to be associated with any visual deficit. CONCLUSIONS: Chronic retinal detachment can be associated with crystals on the inner retinal surface. The cause and composition of these crystals are unknown. They seem to be visually inconsequential and unchanging.

Adult↗
PubMed1998

Thyroid nodules in recurrent multinodular goiters are predominantly polyclonal.

Not only thyroid adenomas and carcinomas, but also the majority of single and well delimited goiter nodules, even if morphologically heterogeneous, are of clonal origin. However, it is still unknown whether the nodules of rapidly growing, recurrent goiters are clonal or polyclonal. We investigated by PCR-based analysis of exon 1 of the human androgen receptor gene clonality of nodules grown in recurrent multinodular goiters (MNG) of 14 female patients. The total goiter volume varied widely between 15 ml and 170 ml. The mean age of patients undergoing surgery for recurrent goiter at the time of their first operation was significantly lower with 34.6 +/- 10.9 yr in comparison to 50 consecutive patients who were operated for MNG for the first time (53.7 +/- 13.5 yr). The interval between first and recurrent operation was 18 +/- 8.5 yr. The mean volume of well circumscribed nodules selected for the present investigation was 3.8 +/- 1.4 ml. Assessment of clonality in at least 2 samples of each lesion revealed a polyclonal pattern in 10 out of 14 nodules, whereas only 3 nodules were clonal and in one case the result remained unclear. The unexpected finding that most nodules within MNG, that had re-grown after a first subtotal thyroidectomy, were of polyclonal rather than clonal composition, suggests that these lesions are generated by de novo-proliferation of cohorts of differing thyrocytes sharing the common trait of an exceedingly high intrinsic growth rate or alternatively, by unknown growth stimulating molecular events acting focally on clusters of cells derived from different ancestors. In addition, the relatively young age of patients with recurrent MNG at the time of their first surgery and the comparatively short interval between first and second operation point to a genetic element in the occurrence of growth-prone thyrocytes.

Adult↗
PubMed1998

Enhanced G protein activation in IDDM patients with diabetic nephropathy.

Genetic susceptibility contributes significantly to the risk of developing nephropathy in insulin-dependent diabetes mellitus (IDDM). The cellular substrate for this has remained enigmatic. We investigated whether afflicted IDDM patients display an enhanced activation of pertussis toxin (PTX)-sensitive G proteins, a phenomenon which has been demonstrated in patients with essential hypertension. We established immortalised B lymphoblast cell lines from 10 IDDM patients without nephropathy (DC) and 15 IDDM patients with nephropathy (DN). Nephropathy was defined as a persistent albumin excretion rate of more than 20 microg/min (DC 3.9 +/- 5.8, DN 562.3 +/- 539.0 microg/min, respectively). Subjects were matched with regard to age (DC 28.9 +/- 6.5, DN 35.9 +/- 9.9 years), diabetes duration (DC 19.3 +/- 6.9, DN 22.7 +/- 5.8 years) and HbA1c values (DC 8.5 +/- 1.4, DN 8.8 +/- 1.6%). Reactivity of PTX-sensitive G proteins was quantified by measuring platelet-activating factor (PAF)-induced Ca2+ mobilisation (fura 2 method) and by mastoparan-stimulated [35S]GTPgammaS binding. Expression of Galphai proteins was quantified by Western blot analysis. PAF-evoked Ca2+ increases above baseline averaged 77.0 +/- 52.5 nmol/l in DC and 150.7 +/- 61.5 nmol/l in DN (p = 0.005). PAF-evoked Ca2+ increases correlated with stimulated [35S]GTPgammaS binding (r2 = 0.42, p = 0.012). From Western blot analysis an overexpression of Galphai proteins could be excluded in DN. A consequence of the altered metabolic milieu in diabetes is the increased release of vasoactive and proliferative agonists which promote glomerular hyperfiltration, hypertrophy, enhanced matrix deposition, and, finally, glomerulosclerosis. Many of these auto- and paracrine agonists bind to G protein-coupled receptors. Therefore, their cellular effects are reinforced by the enhanced G protein reactivity and increase the propensity to nephropathy in IDDM.

Adult↗
PubMed1998

Rash, fever, and chills after intravenous fluorescein angiography.

PURPOSE: To report a previously unreported complication associated with intravenous injection of fluorescein dye. METHOD: Case report. A 75-year-old man developed a unique complication after intravenous injection of fluorescein dye for angiography. RESULTS: Two hours after receiving an intravenous injection of fluorescein for angiography, the patient developed a fever, rash, and chills. Admission to a hospital and careful systemic evaluation determined that this reaction was a noninfectious allergic response to intravenous fluorescein dye injection. CONCLUSION: A delayed allergic response to intravenous fluorescein dye injection can occur.

Aged↗
PubMed1998

Influence of metabolic control and duration of disease on microvascular dysfunction in diabetes assessed by laser Doppler anemometry.

A reduced and delayed postocclusive reactive hyperaemia has been demonstrated in diabetic patients using videophotometric capillaroscopy and laser Doppler fluxmetry. The aim of the present study was to examine by means of the new technique of laser Doppler anemometry whether impairment of skin microcirculation differs between type 1 and type 2 diabetic patients especially with regard to metabolic control and duration of diabetes. Sixteen type 1 and 19 type 2 diabetic patients were investigated and subdivided in patients with "good" (HbA1c < 7.5%) or "bad" (HbA1c > 7.5%) metabolic control and in patients with a diabetes duration of less or more than 10 years. Two age- and sex-matched groups comprising 16 and 19 non-diabetic subjects served as controls. The capillary blood cell velocity (CBV) was measured in the dorsal middle phalangeal area during rest and after 3-min arterial occlusion. In type 1 diabetic patients we found a reduced peak CBV (0.69 +/- 0.08 mm/s vs. 0.96 +/- 0.07 mm/s, p < 0.05) and a prolonged time to peak CBV (33.8 +/- 4.8 s vs. 13.6 +/- 1.9 s, p < 0.001). The delay of the postocclusive reactive hyperaemia was shown not only in patients with a diabetes duration of more than 10 years and HbA1c values above 7.5% but also in patients with a shorter disease duration and better metabolic control. In type 2 diabetes time to peak CBV (46.8 +/- 8.5 s vs. 16.4 +/- 2.2 s, p < 0.001) was also prolonged already in the first 10 years of the disease. However with regard to metabolic control a reduced peak CBV (0.54 +/- 0.04 mm/ s vs. 0.70 +/- 0.04 mm/s, p < 0.05) and a prolonged time to peak CBV (56.6 +/- 14.8 s vs. 13.7 +/- 2.7 s, p < 0.01) was found in type 2 diabetes only in the group of patients with HbA1c > 7.5%. The results indicate that in type 2 diabetes actual metabolic control might be of greater importance for the microvascular dysfunction than in type 1 diabetes and that the skin capillary circulation is impaired already in the first 10 years of both diabetes types.

Adolescent↗