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Biomedical subjects

C Maravelias

Publications and source records attributed to C Maravelias.

At least 19 recordsLinked to original sources
PubMed2005

Zinc: a multipurpose trace element.

Zinc (Zn) is one of the most important trace elements in the body and it is essential as a catalytic, structural and regulatory ion. It is involved in homeostasis, in immune responses, in oxidative stress, in apoptosis and in ageing. Zinc-binding proteins (metallothioneins, MTs), are protective in situations of stress and in situations of exposure to toxic metals, infections and low Zn nutrition. Metallothioneins play a key role in Zn-related cell homeostasis due to their high affinity for Zn, which is in turn relevant against oxidative stress and immune responses, including natural killer (NK) cell activity and ageing, since NK activity and Zn ion bioavailability decrease in ageing. Physiological supplementation of Zn in ageing and in age-related degenerative diseases corrects immune defects, reduces infection relapse and prevents ageing. Zinc is not stored in the body and excess intakes result in reduced absorption and increased excretion. Nevertheless, there are cases of acute and chronic Zn poisoning.

Aging↗
PubMed2005

Adverse effects of anabolic steroids in athletes. A constant threat.

Anabolic-androgenic steroids (AAS) are used as ergogenic aids by athletes and non-athletes to enhance performance by augmenting muscular development and strength. AAS administration is often associated with various adverse effects that are generally dose related. High and multi-doses of AAS used for athletic enhancement can lead to serious and irreversible organ damage. Among the most common adverse effects of AAS are some degree of reduced fertility and gynecomastia in males and masculinization in women and children. Other adverse effects include hypertension and atherosclerosis, blood clotting, jaundice, hepatic neoplasms and carcinoma, tendon damage, psychiatric and behavioral disorders. More specifically, this article reviews the reproductive, hepatic, cardiovascular, hematological, cerebrovascular, musculoskeletal, endocrine, renal, immunologic and psychologic effects. Drug-prevention counseling to athletes is highlighted and the use of anabolic steroids is must be avoided, emphasizing that sports goals may be met within the framework of honest competition, free of doping substances.

Aggression↗
PubMed2002

Dynamic characteristics of Prochlorococcus and Synechococcus consumption by bacterivorous nanoflagellates.

We compared the characteristics of ingestion of Prochlorococcus and Synechococcus by the marine heterotrophic nanoflagellate Pseudobodo sp. and by a mixed nanoflagellate culture (around 3 microm in size) obtained from an open sea oligotrophic area. Maximum ingestion rate on Synechococcus (2.7 Syn flagellate(-1) h(-1)) was reached at concentrations of 5 x 10(5) Syn mL(-1) and decreased between 6 x 10(5) and 1.5 x 10(6) Syn mL(-1). In order to validate laboratory data, one set of data on Synechococcus grazing was obtained during a field study in the oligotrophic northeastern Mediterranean Sea. Ingestion rates by heterotrophic nanoflagellates were related to Synechococcus abundance in the water, and the feeding rate showed a clear diel rhythm with consumption being highest during the night, declining during the day hours, and being lowest at dusk. Ingestion rates on Prochlorococcus increased linearly for the whole range of prey density used (i.e., from 1 x 10(3) to 3 x 10(6) Proc mL(-1)), with maximum ingestion of 6.7 Proc flagellate(-1) h(-1). However, for prey concentrations in the range of 10(3)-10(5), which are usually encountered in aquatic systems, ingestion rates were significantly less than on Synechococcus. In our experiments, both Prochlorococcus and Synechococcus proved to be poor food items for support of nanoflagellate growth.

Animals↗
PubMed2001

Immunomodulative effects of aflatoxins and selenium on human natural killer cells.

The possible immunomodulative effects of aflatoxin B1 and selenium (as sodium selenite) at concentrations lower than 5.10(-11) M or 0.05ppb and 10(-5) M, respectively on natural killer (NK) cells from healthy volunteers were evaluated by a 51Cr release natural killer assay. Aflatoxin B1 and selenium separately had an immunosuppressive effect on NK cell activity. When they were studied in combination, they caused a statistically significant increase of the cytotoxic activity of NK cells in the presence of the lowest concentrations of aflatoxin B1 (0.005ppb) and of sodium selenite (10(-8)M).

Adjuvants, Immunologic↗
PubMed2000

Cytotoxic and immunomodulative effects of flunitrazepam, zipeprol and trihexyphenidyl on human peripheral blood lymphocytes.

The cytotoxic effects of flunitrazepam, zipeprol and trihexyphenidyl on cell viability of peripheral blood mononuclear cells from healthy volunteers were studied at concentrations from 10(-2) to 10(-8) M by 2 colorimetric in vitro assays: the neutral red uptake assay and thiazolyl blue tetrazolium bromide assay. All tested drugs of abuse were non-cytotoxic at concentrations lower than 10(-5) M. Possible immunomodulative effects of these substances were evaluated through phytohemagglutinin induced lymphocyte proliferation ([3H]-thymidine DNA incorporation assay) and by a 51Cr release natural killer assay. The 3 drugs studied produced statistically significant immunomodulative alterations on both immunological parameters.

Adjuvants, Immunologic↗
PubMed2000

The importance of performing in vitro cytotoxicity testing before immunomodulation evaluation.

This study uses the well known sensitive and reproducible human peripheral blood lymphocyte (PBL) assay as a model for the possible discrimination between cytotoxic and/or immunomodulative properties of 5 reference compounds: cadmium chloride (CdCl2): didodecyl-dimethyl ammonium bromide (DDAB); cyclosporin (CsA); dexamethasone (DEXA); and theophylline. Two colorimetric cytotoxicity assays were employed, the thiazolyl blue tetrazolium bromide and neutral red, and the H-thymidine DNA incorporation assay on phytohemagglutinin stimulated or non-stimulated PBL was used, as a parameter of cell mediated immunity. This study demonstrated the importance of performing colorimetric or other cytotoxicity assays before any investigation of mechanisms of action of different substances on immunomodulation and relative human risk assessment. This study showed that CdCl2 and DDAB have a cytotoxic rather than immunomodulative effect on PBL and that CsA, DEXA and to a lesser extent theophylline have immunomodulative rather than cytotoxic effects on PBL within the range of the concentrations studied.

Antineoplastic Agents, Hormonal↗
PubMed1999

The use of alcohol and other psychoactive substances by victims of traffic accidents in Greece.

Alcohol is one of the main causes of traffic accidents worldwide. Its use decreases significantly the driving ability of an individual as well as the reflexes of a pedestrian increasing in this way the possibilities of their involvement in motor-vehicle accidents. The above possibilities are increased when a psychoactive substance has been taken in combination with alcohol due to their synergistic effect. The Laboratory of Forensic Medicine and Toxicology of the University of Athens is authorized to perform the toxicological investigation of traffic accidents that happen in the major part of Greece. The findings of the toxicological analyses that were performed in our laboratory during the years 1995 to 1997 are classified according to the alcohol concentration and the kind of psychoactive substance detected as well as to the gender and the age of the victims, drivers or pedestrians. The results of the above classification are evaluated and the conclusions regarding alcohol, drugs and traffic accidents in Greece are discussed thoroughly.

Accidents, Traffic↗
PubMed1999

Flour contamination as a source of lead intoxication.

CASE REPORT: A 43-year-old man was hospitalized because of severe anemia and recurrent bouts of abdominal pain over 20 days. There was no known occupational exposure to toxins. Concomitantly, the patient's father complained of having the same symptoms. Familial lead poisoning was diagnosed when all 6 family members tested had high blood leads (31-64 micrograms/dL). RESULTS: Following detailed examination of the potential sources common to all members of the household, the cause of poisoning was determined to be corn flour containing 38.7 mg/g lead. Physicians are reminded to consider lead poisoning in the differential diagnosis of individuals with unexplained symptoms, particularly those of abdominal discomfort and anemia.

Abdominal Pain↗
PubMed1999

Immunomodulative effects of some drugs of abuse on human peripheral blood lymphocytes.

The cytotoxic effects of opiates, cocaine and their metabolites on peripheral blood mononuclear cells from healthy volunteers, concerning cell viability, were studied in a wide range of concentrations (ranging from 10-(2) to 10-(8) M), by 2 colorimetric in vitro assays, the neutral red uptake assay and thiazolyl blue tetrazolium bromide assay. All tested drugs of abuse and their metabolites were non-cytotoxic at concentrations lower than 10-(5) M. The possible immunomodulative effects of these substances were evaluated through phytohemagglutinin-induced lymphocyte proliferation ([3H]-thymidine DNA incorporation assay) as well as by a 51Cr release natural killer assay. The results showed immunomodulative effects of all the opiates tested. Cocaine, freebase cocaine and benzoylecgonine produced a statistically non-significant decrease of phytohemagglutinin proliferation. Cocaine induced a statistically non-significant increase, whereas freebase cocaine and benzoylecgonine showed a non-significant decrease of natural killer cell activity.

Adult↗
PubMed1998

Immunological aspects of the common food colorants, amaranth and tartrazine.

We describe a sensitive and reproducible microassay model using human peripheral blood lymphocytes (PBL) for discrimination between the cytotoxic and immunosuppressive effects of food colorants such as amaranth and tartrazine. The cytotoxic effects of a wide range of concentrations of these substances were studied on human PBL by the colorimetric in vitro cytotoxicity assays, neutral red uptake (NR) and thiazolyl blue tetrazolium bromide (MTT). The immunotoxic properties of these 2 substances were determined by a [3H]-thymidine DNA incorporation assay on phytohemagglutinin stimulated or non-stimulated lymphocytes, as well as by a Cr51 release Natural Killer assays. The results showed clear immunosuppressive effects from the 2 substances tested, although the concentrations chosen for this study proved to be non-cytotoxic by NR and MTT cytotoxic endpoints.

Adult↗
PubMed1998

[Determination of amphetamine derivatives in urine with solid phase micro-extraction (SPME)].

Amphetamine derivatives (amphetamine A, methamphetamine MA, 3,4-methylene-dioxy-methamphetamine MDMA, 3,4-methylene-dioxy-amphetamine MDA and 3,4-methylene-dioxy-N-ethyl-amphetamine MDE) are the first most frequently group of abused illegal drugs in Hungary. This experimental work deals with in the determination of amphetamines in connection with the forensic toxicological applicability of a relatively new isolation process, the SPME using by GC-NPD analysis. The paper demonstrates 14 types of amphetamine investigation from spiked urine samples and reports two typical amphetamine cases for SPME isolation method.

Amphetamine↗
PubMed1996

Immunomodulative effects of aflatoxins and selenium on human peripheral blood lymphocytes.

We investigated the antagonist immunomodulative properties of aflatoxin B1 and selenium on human peripheral blood lymphocytes by 2 colorimetric in vitro cytotoxicity assays, the neutral red uptake and the thiazolyl blue tetrazolium bromide assay. Immunotoxic properties of these substances were determined by a (3H)-thymidine DNA incorporation assay on phytohemagglutinin (PHA) stimulated and non-stimulated lymphocytes. Aflatoxin B1 and selenium, when studied separately, had an immunosuppressive effect on PHA stimulated and non-stimulated human peripheral blood lymphocytes. When they were studied together, they had an antagonistic effect on this immunological parameter.

Adjuvants, Immunologic↗
PubMed1994

Lead exposure of the child population in Greece.

Lead exposure of the child population was studied in three different areas in Greece: Kalamata which is a rural area of Southern Greece; Tavros, a district of Athens with a considerable industrial activity; and Lavrion, a small city near Athens where a lead-zinc mining and smelting industrial complex has existed for more than 90 years. The results were evaluated with respect to a number of individual, social and environmental variables (i.e. smelter, occupation of the father) especially those concerning the area of Lavrion which is the most heavily polluted area in Greece. The results of this study can be considered as an index for the extent of the lead pollution problem in the named areas of Greece.

Analysis of Variance↗
PubMed1989

Exposure to lead and cadmium of children living near a lead smelter at Lavrion, Greece.

Exposure of children of the Greek town of Lavrion to lead and cadmium has been evaluated by determination of the levels of lead (PbB) and cadmium (CdB) in the blood of 514 children living in the town. The Lavrion area is heavily polluted by lead owing to the presence of a large lead-zinc mining and smelting industrial complex. The industrial PbB level (geometric mean) was 21.7 micrograms dl-1 (range 7.4-79.8 micrograms dl-1). The CdB levels were, on average, 0.36 micrograms l-1 (range 0.1-3.1 micrograms l-1). The results were evaluated with respect to a number of constitutional, social and environmental variables, such as age, gender, distance of the school from the lead-zinc mining and smelting complex, and occupation and education of the father.

Age Factors↗
PubMed1985

Changes of HDL-lipid composition as related to delta 9-THC action.

An attempt was made to investigate the possible action of delta 9-THC on HDL-Lipid composition. Significant changes were observed in the serum total lipids, triglycerides and HDL subfractions after hashish smoking. The results are discussed in relation to the possible alterations of some enzymatic mechanisms regulating lipid metabolism in hashish users.

Adult↗
PubMed1984

Zinc deficiency in mild hypertensive patients treated with diuretics.

Mean hair zinc was found to be significantly lower in 20 mild hypertensive patients treated with thiazides for 6-36 months than in 19 mild hypertensive patients who had not been given diuretics for at least six months before study. Mean serum zinc did not differ significantly between the two groups. Chronic diuretic treatment can result in zinc deficiency through enhanced urinary excretion of zinc.

Adrenergic beta-Antagonists↗