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G Papanikolaou

Publications and source records attributed to G Papanikolaou.

9 recordsLinked to original sources
PubMed2006

Long-term signal detection, segmentation and summarization using wavelets and fractal dimension: a bioacoustics application in gastrointestinal-motility monitoring.

The current paper describes a wavelet-based method for long-term processing and analysis of gastrointestinal sounds (GIS). Windowing techniques are used to select sequential blocks of the prolonged multi-channel recordings and proceed to various wavelet-domain processing stages. De-noising, significant-activity detection, automated segmentation and extraction of summary curves are applied in an integrated mode, allowing for enhanced content manipulation and analysis. The proposed analysis scheme combines flexible long-term graphical representation tools, while maintaining the ability of quick browsing via visualization and auralization of the detected short-term events. This work is part of a project aiming to implement non-invasive diagnosis over gastrointestinal-motility (GIM) physiology. However, the proposed techniques might be applied to any study of long-term bioacoustics time series.

Algorithms↗
PubMed2005

Iron metabolism and toxicity.

Iron is an essential nutrient with limited bioavailability. When present in excess, iron poses a threat to cells and tissues, and therefore iron homeostasis has to be tightly controlled. Iron's toxicity is largely based on its ability to catalyze the generation of radicals, which attack and damage cellular macromolecules and promote cell death and tissue injury. This is lucidly illustrated in diseases of iron overload, such as hereditary hemochromatosis or transfusional siderosis, where excessive iron accumulation results in tissue damage and organ failure. Pathological iron accumulation in the liver has also been linked to the development of hepatocellular cancer. Here we provide a background on the biology and toxicity of iron and the basic concepts of iron homeostasis at the cellular and systemic level. In addition, we provide an overview of the various disorders of iron overload, which are directly linked to iron's toxicity. Finally, we discuss the potential role of iron in malignant transformation and cancer.

Animals↗
PubMed2000

Hereditary hemochromatosis: HFE mutation analysis in Greeks reveals genetic heterogeneity.

Hereditary hemochromatosis (HH) is common among Caucasians; reported disease frequencies vary from 0.3 to 0.8%. Identification of a candidate HFE gene in 1996 was soon followed by the description of two ancestral mutations, i.e., c.845G-->A (C282Y) and c.187C-->G (H63D). To these was recently added the mutation S65C, which may represent a simple polymorphism. The incidence of HH in Greece is unknown but clinical cases are rare. Also unknown is the carrier frequency of the two mutant alleles. A first estimate of the latter is given in the present report. It is based on data from the genetic analysis of 10 unrelated patients of Greek origin who were referred to our center for genotyping and 158 unselected male blood donors. The allele frequencies for the C282Y and H63D mutations were 0.003 and 0.145, respectively. The C282Y allele was detected in 50% of HH patients. This is considerably lower than the frequencies reported for HH patients in the U.S.A. (82%) and France (91 %) and closer to that reported in Italy (64%). Five patients did not carry any known HFE mutation; three may represent cases of juvenile hemochromatosis, given their early onset with iron overload, hypogonadism, and heart disease. We suggest that genetic heterogeneity is more prominent in Southern Europe. It is also possible that the penetrance of the responsible genes is different across the Mediterranean.

Adult↗
PubMed2000

Micrococcus luteus: a putative cause of hepatic abscess?

Micrococcus luteus was repeatedly isolated in blood cultures during a prolonged feverish syndrome in a patient who presented with multiple hepatic abscesses as well. In contrast to the literature, this case is not related to prosthetic devices; an untreated limb wound may have been the site of microbial entry.

Gram-Positive Bacterial Infections↗
PubMed1995

Tamm-Horsfall protein in reflux nephropathy.

The distribution of Tamm-Horsfall protein, the main protein in normal urine, was studied immunohistologically in the kidneys of 70 pigs with unilateral vesico-ureteric reflux but without outflow obstruction. Strains of Escherichia coli were inoculated in the bladder. Inflammatory changes of reflux nephropathy (chronic pyelonephritis) were found in 52 pigs. There were extra-tubular deposits of Tamm-Horsfall protein in the kidneys of only 26 pigs. These deposits were small, increased in prevalence as the size of inflamed areas increased, and were not associated with deposits of the protein in glomeruli. These findings suggest that escape of Tamm-Horsfall protein from tubules and backwash into glomeruli are not major features of low pressure reflux nephropathy, unlike the findings in outflow obstruction of the lower urinary tract. There was no evidence that a reaction to Tamm-Horsfall protein was important in the pathogenesis of reflux nephropathy.

Animals↗
PubMed1978

Cannabis interferes with nest-building behavior in mice.

Nest-building, a behavioral model shown to be disrupted by hallucinogens, has never been used to answer questions concerning the psychotomimetic effects of delta9-THC. Several fractions of cannabis and tobacco pyrolysis products were tested consecutively in the same procedure. The following drugs were injected i.p. under a saline-drug-saline schedule: d-amphetamine (6 mg/kg), pentobarbital (25 mg/kg), delta9-THC (10 mg/kg, 5 mg/kg, 2.5 mg/kg), the cannabis fractions designated Is (water soluble products), IIs (nonsoluble, nonvolatile products, IIIs (it comprises what is inhaled by a common hashish smoker), and analogous fractions of tobacco pyrolysis products designated IIIB (what is inhaled by a common tobacco smoker), IIB and IB. The effects of delta9-THC (10 mg/kg), IIs, and IIIs were quite similar as far as the disruption of the normal behavioral pattern is concerned. d-Amphetamine, delta9-THC (5 mg/kg), and IIB disrupted the normal behavioral pattern as well. The similarity of the effects of IIs and IIIs was unexpected in view of the different contents of cannabinoids in these fractions. Also unexpected was the similarity of the effects of delta9-THC (10 mg/kg) and IIIs (40 mg/kg containing 7% delta9-THC) as well as the activity of fraction IIIB.

Animals↗
PubMedDate not supplied

Linkage to chromosome 1q in Greek families with juvenile hemochromatosis.

Hereditary hemochromatosis (HH) is a genetically heterogeneous disease. The HFE gene resides on chromosome 6 and its mutations account for the majority of HH cases in populations of northern European ancestry. Recently, two new types of hemochromatosis have been identified: Juvenile hemochromatosis (JH or HFE2), which maps to chromosome 1q21, and an adult form defined as HFE 3, which results from mutations of the TFR 2 gene, located at 7q22. We have performed a linkage study in five unrelated families of Greek origin with non-HFE hemochromatosis. Linkage at the chromosome 1q21 JH locus was detected in affected members with the use of polymorphic markers. Comparison of haplotypes between Greek and Italian JH patients revealed the presence of a common haplotype. However, the fact that many other haplotypes carrying the JH defect were observed in the two populations indicates that the respective mutations may have occurred in different genetic backgrounds. We suggest that hemochromatosis patients without HFE mutations should be evaluated for other possible types of hemochromatosis since hemochromatosis type 3 (HFE3) has a clinical appearance similar to HFE 1, and JH may have a late onset in some cases.

Adult↗
PubMedDate not supplied

Genetic heterogeneity underlies juvenile hemochromatosis phenotype: analysis of three families of northern Greek origin.

Hereditary hemochromatosis is a genetically heterogeneous disease. Common HFE mutations (C282Y and H63D) are related to the majority of hereditary hemochromatosis cases in populations of Northern European ancestry (HFE1). Juvenile hemochromatosis (JH) is a more severe iron overload disorder, usually presenting at the second decade of life. The gene responsible for JH lies on a genetic locus at chromosome 1q. We have performed a genetic linkage study in three families of Northern Greek origin with typical clinical features of JH. In two families results were in accordance with linkage to chromosome 1q. In one family linkage of the disease to the genetic loci at 1q21, 7q22, and 6p22 was excluded. We suggest that more than one gene may underlie the JH phenotype. This genetic type of hemochromatosis may be designated 1q unlinked juvenile hemochromatosis. Family studies are necessary to establish the genetic diagnosis of JH.

Adult↗