Biomedical subjects

A Bogdan

Publications and source records attributed to A Bogdan.

At least 19 recordsLinked to original sources

PubMed2002

Effect of a short photoperiod on circadian rhythms of body temperature and motor activity in old rats.

Circadian rhythms of body temperature and motor activity were documented in young and old rats (four 8-week-old and five 22-month-old male Wistars, implanted with telemetric probes and housed in a chronobiological facility) under two different photoperiod conditions. The animals were maintained in a light:dark (LD) cycle of 12 h each (LD 12:12) for 4 weeks and then exposed to a LD 6:18 cycle for 7 weeks to assess the effect of age on the desynchronization of the temporal structure of the rhythms. In old rats under LD 12:12, the power of the 24-h component and the circadian amplitude of body temperature and motor activity were markedly lower than in the young and both rhythms were phase-advanced. After the shift to LD 6:18, the circadian rhythmicity was maintained for both variables and the same phase delay (+5+/-1 h) was observed in both age groups, as was a gradual expansion of the patterns of both functions with the longer night. The photoperiod reduction (6 weeks under LD 6:18) did not modify the power of the 24-h component of body temperature and motor activity in old rats. In young rats, however, the power and amplitude of the 24-h component of motor activity rhythm fell to the levels of those in old rats, while the power of the 24-h component of body temperature rhythm and the amplitude did not change. Our data show that the circadian rhythm of motor activity, but not of body temperature, responds age dependently to a photoperiod reduction.

Aging↗

PubMed2001

Circadian rhythms of body temperature and motor activity in rodents their relationships with the light-dark cycle.

In rodents, the alternation of light and dark is the main synchronizer of circadian rhythms. The entrainment abilities of the LD cycle could be estimated by experimental modifications of the photoperiod and by following the subsequent temporal distribution of a circadian rhythm. The rate of reentrainment of a rhythm is determined by the nature of the studied variable, by the direction (advance or delay) and the magnitude (or value) of the phase shift. In rodents, core body temperature and motor activity are known to be well synchronized with each other under L:D 12:12 and under constant conditions (LL or DD). There are clear evidences that the circadian pattern of motor activity is generated by two oscillators, one from dusk signal and the other from dawn signal. Whether the circadian rhythms of body temperature and motor activity are generated by a common circadian mechanism or controlled by separate ones still remains unknown. The purpose of this review is to summarize the results obtained on the circadian rhythms of body temperature and motor activity throughout the daily cycle in order to clarify the relationships between these two functions.

Animals↗

PubMed2001

Ramadan fasting alters endocrine and neuroendocrine circadian patterns. Meal-time as a synchronizer in humans?

Muslims must refrain from eating, drinking, smoking, and sexual relations from sunrise to sunset during the month of Ramadan. Serum concentrations of melatonin, steroid hormones (cortisol, testosterone), pituitary hormones (prolactin, LH, FSH, GH, TSH) and thyroid hormones (free thyroxin and free triiodothyronine) were documented around the clock at six 4-hourly intervals before Ramadan began and on the twenty-third day of Ramadan (daytime fasting). Time series were analysed with repeated measures ANOVA. Statistically significant differences were found in some variables: the nocturnal peak of melatonin was diminished and may have been delayed; there was a shift in the onset of cortisol and testosterone secretion; the evening peak of prolactin was enhanced, FSH and GH rhythmic patterns were affected little or not at all by Ramadan fasting and only the serum TSH rhythm was blunted over the test time span. These data show that daytime fasting, modifications in sleep schedule and psychological and social habits during Ramadan induce changes in the rhythmic pattern of a number of hormonal variables.

Adult↗

PubMed2001

Automatic differentiation of melanoma from melanocytic nevi with multispectral digital dermoscopy: a feasibility study.

BACKGROUND: Differentiation of melanoma from melanocytic nevi is difficult even for skin cancer specialists. This motivates interest in computer-assisted analysis of lesion images. OBJECTIVE: Our purpose was to offer fully automatic differentiation of melanoma from dysplastic and other melanocytic nevi through multispectral digital dermoscopy. METHOD: At 4 clinical centers, images were taken of pigmented lesions suspected of being melanoma before biopsy. Ten gray-level (MelaFind) images of each lesion were acquired, each in a different portion of the visible and near-infrared spectrum. The images of 63 melanomas (33 invasive, 30 in situ) and 183 melanocytic nevi (of which 111 were dysplastic) were processed automatically through a computer expert system to separate melanomas from nevi. The expert system used either a linear or a nonlinear classifier. The "gold standard" for training and testing these classifiers was concordant diagnosis by two dermatopathologists. RESULTS: On resubstitution, 100% sensitivity was achieved at 85% specificity with a 13-parameter linear classifier and 100%/73% with a 12-parameter nonlinear classifier. Under leave-one-out cross-validation, the linear classifier gave 100%/84% (sensitivity/specificity), whereas the nonlinear classifier gave 95%/68%. Infrared image features were significant, as were features based on wavelet analysis. CONCLUSION: Automatic differentiation of invasive and in situ melanomas from melanocytic nevi is feasible, through multispectral digital dermoscopy.

Diagnosis, Differential↗

PubMed2001

Reduction of ultraviolet transmission through cotton T-shirt fabrics with low ultraviolet protection by various laundering methods and dyeing: clinical implications.

BACKGROUND: The public has long been instructed to wear protective clothing against ultraviolet (UV) damage. OBJECTIVE: Our purpose was to determine the UV protection factor (UPF) of two cotton fabrics used in the manufacture of summer T-shirts and to explore methods that could improve the UPF of these fabrics. METHODS: Each of the two types of white cotton fabrics (cotton T-shirt and mercerized cotton print cloth) used in this study was divided into 4 treatment groups: (1) water-only (machine washed with water), (2) detergent-only (washed with detergent), (3) detergent-UV absorber (washed with detergent and a UV absorber), and (4) dyes (dyed fabrics). Ultraviolet transmission through the fabrics was measured with a spectrophotometer before and after laundry and dyeing treatments. Based on UV transmission through these fabrics, the UPF values were calculated. RESULTS: Before any treatments, the mean UPFs were 4.94 for the T-shirt fabric and 3.13 for the print cloth. There was greater UVA (320-400 nm) than UVB (280-320 nm) transmission through these fabrics. After 5 washings with water alone and with detergent alone, UPF increased by 51% and 17%, respectively, for the cotton T-shirt fabric. Washing the T-shirt fabrics with detergent plus the UV-absorbing agent increased the UPF by 407% after 5 treatments. Dyeing the fabric blue or yellow increased the UPF by 544% and 212%, respectively. Similar changes in UPFs were observed for the print cloth fabric. CONCLUSION: The two cotton fabrics used in this study offered limited protection against UV radiation as determined by spectrophotometric analysis. Laundering with detergent and water improves UPF slightly by causing fabric shrinkage. Dyeing fabrics or adding a UV-absorbing agent during laundering substantially reduces UV transmission and increases UPF. More UVA is transmitted through the fabrics than UVB.

Coloring Agents↗

PubMed2001

Is melatonin circadian rhythm a physiological feature associated with healthy longevity? A study of long-living subjects and their progeny.

The study investigates the circadian rhythm (CR) of urinary 6-sulphatoxy-melatonin (aMT6s) in long-living (longevous) subjects and their progeny. The aim is to detect whether or not the melatonin CR is a physiological feature associated with healthy longevity. The aMT6s CR was investigated in 10 longevous subjects, 8 of their children and 9 of their grandchildren, all in good health. Control data were obtained respectively from 13 adult subjects and 9 young subjects, in good health, but characterized by a negative family history for longevity. All the subjects were born and living in the same city. The study was performed in the summer of 1996. The aMT6s CR was found to persist in longevous subjects, being characterized by a lower mesor and amplitude. The aMT6s CR was found not to show properties consistently different in children and grandchildren as compared respectively to their adult and young controls. Because of its preservation in longevous subjects, it can be argued that the melatonin CR is a physiological feature associated with healthy longevity. Because of the comparability of aMT6s CR in children and grandchildren, with respect to their controls without a positive family history of longevity, it can be argued that the melatonin CR is not a marker that can be used for an earlier identification of the candidates for longevity.

Adult↗

PubMed2000

Evidence of prooxidant and antioxidant action of melatonin on human liver cell line HepG2.

The aim of this study was to evaluate melatonin cytotoxicity by measuring its effects on various cellular targets. Cell viability, intracellular reduced glutathione (GSH) level, and reactive oxygen species (ROS) production were assessed in the human liver cell line (HepG2), after incubation with increasing melatonin concentrations (0.1-10,000 microM). The incubation times tested were 24, 72, and 96 h for cell viability and intracellular GSH level, and 15 and 45 minutes for ROS production. Cellular target evaluations were possible in living cells by means of a new microplate cytofluorimeter. This technology was suitable for the assessment of cell viability, GSH level, and ROS overproduction with, respectively, neutral red, monochlorobimane (mBCl), and 2',7'-dichlorofluorescin diacetate (DCFH-DA) fluorescent probes. At the lowest melatonin concentrations (0.1-10 microM) and for a relatively short incubation time (24 h), the antioxidant effect of melatonin was revealed by an increased intracellular GSH level, associated to cell viability improvement. In contrast, after longer incubation (96 h), cell viability significantly decreased with these lowest melatonin concentrations (0.1-10 microM). Moreover, high melatonin concentrations (1,000-10,000 microM) induced GSH depletion. This oxidative stress is associated with ROS overproduction from 10 microM after only 15 minutes of incubation. This dual effect is strong evidence that, in vitro, melatonin can be both antioxidant and prooxidant on the human liver cell line, depending on the concentration and incubation time.

Antioxidants↗

PubMed2000

Genetically modified Vibrio harveyi strains as potential bioindicators of mutagenic pollution of marine environments.

For biodetection of mutagenic pollution of marine environments, an organism naturally occurring in these habitats should be used. We found that marine bacterium Vibrio harveyi may be an appropriate bioindicator of mutagenic pollution. For positive selection of mutants, we developed a simple method for isolation of V. harveyi mutants resistant to neomycin. We constructed genetically modified V. harveyi strains that produce significantly more neomycin-resistant mutants upon treatment with low concentrations of mutagens than the wild-type counterpart. The sensitivity of the mutagenicity test with the V. harveyi strains is at least comparable to (if not higher than) that of the commonly used Ames test, which uses Salmonella enterica serovar Typhimurium strains. Therefore, we consider that the V. harveyi strains described in this report could be used as potential bioindicators of mutagenic pollution of marine environments.

Anti-Bacterial Agents↗

PubMed2000

Marked 24-h rest/activity rhythms are associated with better quality of life, better response, and longer survival in patients with metastatic colorectal cancer and good performance status.

The rest/activity circadian cycle has been used as a reference for chemotherapy administration at specific times to improve tolerability and efficacy. Because cancer processes may be associated with alterations of circadian rhythms, the rest/activity cycle was monitored noninvasively to assess its relationship with tumor response, survival, and quality of life in 200 patients with metastatic colorectal cancer. Patients wore an actigraph, a wristwatch that records the number of accelerations per minute, for 3 days before receiving chronomodulated chemotherapy. The circadian rhythms in activity were estimated by two robust parameters: the autocorrelation coefficient at 24 h (r24), and the dichotomy index (I<O) for comparing amounts of activity when in bed and out of bed. Accurate data for inclusion, quality of life, response, and survival were available for 192 patients. Survival at 2 years was 5-fold higher (P = 10(-4)) in patients with marked activity rhythm (I<O in upper quartile) than in those with rhythm alteration (I<O in lower quartile). These results were supported by the multivariate Cox analysis. Multivariate regression analysis showed that circadian rhythms in activity (I<O; P = 3 x 10(-4)) and in WBCs (P = 0.03) as well as performance status (P = 0.02) were jointly prognostic of response. Patients with marked rest/activity rhythms also had better quality of life and reported significantly less fatigue. The individual rest/activity cycle provides a novel independent prognostic factor for cancer patients' survival and tumor response as well as a quantitative indicator for quality of life.

Adult↗

PubMed1999

Obsessive-compulsive disorder: evaluation of clinical and biological circadian parameters during fluoxetine treatment.

RATIONALE: Many biological abnormalities have been found in obsessive-compulsive disorder (OCD). The circadian rhythm investigations of different clinical and biological parameters may provide a comparison with depression. Fluoxetine is one of the efficient drugs in alleviating symptoms of OCD. The effect of fluoxetine can highlight some clues to the neurotransmitter alterations in the disorder. OBJECTIVE: The present study investigated clinical and biological circadian modifications in OCD patients during a fluoxetine treatment. METHODS: Daily clinical symptoms, and circadian rhythms of axillary temperature, plasma cortisol and plasma melatonin were assessed in eight patients suffering from OCD. These parameters were compared in the same patients, before and after an 8-week fluoxetine treatment period. RESULTS: A therapeutic effect of fluoxetine was obtained. No significant differences were observed either in daily clinical variations or in biological circadian rhythms measured before and after treatment. CONCLUSION: The therapeutic efficacy of fluoxetine was not related to the biological parameters assessed.

Adult↗

PubMed1999

Body temperature and locomotor activity as marker rhythms of aging of the circadian system in rodents.

Most biological functions present rhythmic variations. These rhythms are distinguished by their period and concern all the levels of biological life. Circadian rhythms follow a periodicity close to 24-h, they allow individuals to survive via adaptation to the periodic variations of environment. Throughout the aging process, modifications in circadian rhythms of endocrinological, metabolical and behavioural fields have been found in many animal species. This review updates the body of knowledge on aging-related alterations of the circadian rhythms of body temperature and locomotor activity: modifications in circadian profiles, modifications in the period of free-running rhythms, internal desynchronisations and modifications in entrainment ability of these rhythms.

Aging↗

PubMed1998

Non-invasive estimation of the circadian rhythm in serum cortisol in patients with ovarian or colorectal cancer.

The variability in toxicity or efficacy of cancer chronotherapy among patients may be due to differences in circadian rhythm. Adequate assessment of circadian rhythm often requires repeated blood sampling over at least a 24-hr period; this cannot be a routine procedure. We attempted to assess the reliability of a 2-timepoint estimate of the 24-hr rhythm of serum cortisol in 19 healthy subjects, 19 women with ovarian cancer and 18 patients with metastatic colorectal cancer. The difference between daily maximum and minimum values (MAX-MIN) was compared with that observed between values at 08.00 and at 16.00 (H8-H16). As significant correlations were found between both variables in all groups, we conclude that the magnitude of circadian changes in serum cortisol may be estimated from blood samples collected at 08.00 and at 16.00. The clinical relevance and the prognostic value of this method of assessment are currently under evaluation in a larger-scale clinical trial.

Adult↗

PubMed1998

Plasma melatonin and cortisol in patients with obsessive-compulsive disorder: relationship with axillary temperature, physical activity, and clinical symptoms.

BACKGROUND: Many studies have found biological abnormalities in obsessive-compulsive disorder (OCD), although most of them have not been replicated. The investigation of melatonin rhythm may thus provide an indirect clue to neurotransmitter alterations, and allow a biological comparison with depression. METHODS: The circadian variations of plasma melatonin, plasma cortisol, axillary temperature, motor activity, and obsessive-compulsive symptoms have been documented on a circadian basis in 8 patients with OCD compared to 8 paired healthy volunteers. RESULTS: The circadian pattern of axillary temperature was slightly different in OCD patients when compared to control subjects. No significant difference between the two groups could be observed for any other variable studied. CONCLUSIONS: The discrepancies with previous studies are discussed on the basis of the methods used (patients and control subjects samples, biological measurement procedures). An alteration of temperature circadian rhythm hypothesis is suggested.

Adult↗

PubMed1997

Serum thymidine kinase levels are elevated and exhibit diurnal variations in patients with advanced ovarian cancer.

Deoxythymidine kinase (TK) is an enzyme involved in DNA synthesis whose serum activity reflects the proliferative activity of tumors and correlates with prognosis in various malignancies. In ovarian cancer, the value of s-TK has not been studied so far. Therefore the serum levels of TK were investigated in patients with advanced ovarian cancer. Because considerable diurnal fluctuations of s-TK levels were reported previously, repeated determinations were performed over a 48-h time span. Fourteen patients (mean age +/- S.D., 56.1 +/- 8.0 years) with advanced ovarian cancer and five healthy volunteers (30.2 +/- 3.5 years) were studied. Serial determinations of s-TK and serum CA 125 (s-CA 125) levels were performed over a 48-h time period. S-TK and s-CA 125 were elevated (> 4.7 U/l and > 35 U/ml) in 10 patients at least once over the 48-h period, respectively. Linear regression analysis showed a strong correlation between s-TK and s-CA 125. However, three patients with consistently normal s-CA 125 values (< or = 35 U/ml) had elevated s-TK levels, indicating that these two parameters may be independent in some patients. Both s-TK and s-CA 125 levels showed considerable diurnal changes over the 24-h period in individual patients, in marked contrast to normal subjects. Individual peak-trough differences ranged from 0.1-8.5 U/l or 5-268% for s-TK, and from 4-75 U/ml or 15-100% for s-CA 125. Peak-trough differences of s-TK > or = 100% were found in five patients. The circadian fluctuations of s-TK and CA 125 did not show a regular circadian pattern nor any temporal covariation. This study demonstrates for the first time that s-TK levels may be elevated in ovarian cancer. In some patients, s-TK levels may exhibit considerable, irregular diurnal fluctuations. Repeated determinations should therefore be performed in situations where this marker is relevant for patient monitoring.

Adult↗

PubMed1997

Effect of Acids on Water Vapor Uptake by Pyrogenic Silica

Effect of gaseous HCl and HNO3 on the water vapor uptake by pyrogenic silica was studied at different relative humidities (RH) for pure water and different compositions of binary and ternary vapor mixtures. Experiments showed that the ability of silica to uptake water strongly depends on RH and on the type of acids and their concentration in the vapor mixtures. At low acid concentration in the binary mixtures the influence of acids is probably small. Water uptake by silica does not change monotonically with acid concentration: at first it decreases and then starts to grow. However, the presence of acids promotes water uptake, and the effect is very significant at low RH. HCl seems to be more effective acid to enhance water uptake than HNO3 . In the case of ternary mixtures the adsorbed weight of water is a bit larger than that adsorbed from the binary mixtures. Acids are accumulated by silica surface, and the accumulation is larger for nitric acid.

Journal Article↗

PubMed1997

Ramadan diet restrictions modify the circadian time structure in humans. A study on plasma gastrin, insulin, glucose, and calcium and on gastric pH.

The rule of Ramadan (1 month of food and water intakes restricted to night hours) is followed by the majority of the Moslem fraction of the human population, but the possible consequences of this long-lasting modification of food intake schedule on public health have not yet been extensively documented. Therefore, a group of healthy control subjects and a group of healed duodenal ulcer patients were studied before (controls), during (both groups), and after (both groups) the month of Ramadan. The time-restricted food and water intakes were associated with variations of gastric pH, plasma gastrin, insulin, glucose, and calcium documented on a circadian basis. All of the studied biological variables, except insulin, underwent changes in their 24-h mean concentration (e.g. decrease in gastric pH, increase in plasma gastrin), some of which were still present 1 month after the end of Ramadan. The circadian patterns of all the studied variables were altered during the month of Ramadan. Some differences between the group of healthy control subjects and the group of healed duodenal ulcer patients may suggest a greater susceptibility of the latter to the modifications of feeding and sleeping schedule, which could possibly be a risk factor for the disease.

Adult↗

PubMed1996

NMR Study of Phase Transitions in Pure Water and Binary H(2)O/HNO(3) Films Adsorbed on Surface of Pyrogenic Silica.

Pyrogenic silica (aerosil) was employed as host within which the phase transitions in the adsorbed pure water and binary H(2)O/HNO(3) films have been studied with NMR spectroscopy. The median freezing temperature and freezing temperature region were shown to be highly sensitive both to the average thickness of the adsorbed films and to the amount of adsorbed nitric acid. The molar concentration of nitric acid in the adsorbed films was found to be very small, on the order of 10(-3)-10(-2) (M/liter). The concentration was found to be greater in the layers adjacent to the surface of silica and sharply decreases with distance from the surface. The difference between the median freezing temperatures for adsorbed pure water and for the binary system was found to be about 9 K for films of equal thickness. This is about 150 times greater than the difference between the freezing temperatures of bulk pure water and a solution with the same concentration of nitric acid.

Journal Article↗

PubMed1996

Increased delta aminolevulinic acid and decreased pineal melatonin production. A common event in acute porphyria studies in the rat.

Tryptophan (TRP) is the precursor of melatonin, the primary secretory product of the pineal gland. Hepatic heme deficiency decreases the activity of liver tryptophan pyrrolase, leading to increased plasma TRP and serotonin. As a paradox, patients with attacks of acute intermittent porphyria (AIP), exhibit low nocturnal plasma melatonin levels. This study using a rat experimental model was designed to produce a pattern of TRP and melatonin production similar to that in AIP patients. Pineal melatonin production was measured in response to: (a) a heme synthesis inhibitor, succinylacetone, (b) a heme precursor, delta-aminolevulinic acid (Ala), (c) a structural analogue of Ala, gamma-aminobutyric acid. Studies were performed in intact rats, perifused pineal glands, and pinealocyte cultures. Ala, succinylacetone, and gamma-aminobutyric acid significantly decreased plasma melatonin levels independently of blood TRP concentration. In the pineal gland, the key enzyme activities of melatonin synthesis were unchanged for hydroxyindole-O-methyltransferase and decreased for N-acetyltransferase. Our results strongly suggest that Ala overproduced by the liver acts by mimicking the effect of gamma-aminobutyric acid on pineal melatonin in AIP. They also support the view that Ala acts as a toxic element in the pathophysiology of AIP.

Acetylserotonin O-Methyltransferase↗