bluuebunny/crossref_metadata_2025 huggingface dataset:
Age‐Related Alteration in Hepatic Disposition of the Neurotoxin 1‐Methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine and Pesticides
Authors: Yang Maria C. , McLean Allan J. , Le Couteur David G.
Published: March 2003

Abstract: Idiopathic Parkinson's disease may be caused by environmental neurotoxins such as pesticides, however the major risk factor is old age. We postulated that the high incidence of Parkinson's disease in older people is secondary to age‐related impairment of the hepatic detoxification of xenobiotics. Previously, we have shown that there are significant differences between the hepatic disposition of the neurotoxin 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) and pesticides. Here, we investigated whether there are age‐related differences in the hepatic disposition of MPTP and pesticides, putatively associated with the pathogenesis of Parkinson's disease. We measured the hepatic disposition of paraquat, dichlorodiphenyltrichloroethane (DDT), malathion and MPTP using the multiple indicator dilution technique in the perfused livers of Fischer F344 rats aged 3 and 18 months. The recoveries of MPTP, DDT and malathion were increased from the livers of the older rats (by 258%, 253% and 134% compared with young rats, respectively). The hepatic transport of DDT and malathion into hepatocytes was reduced with age suggesting that part of the impaired uptake of neurotoxins may be secondary to an age‐related barrier to influx. Ageing may increase risk of Parkinson's disease by altering hepatic detoxification and increasing systemic bioavailability of neurotoxins.
Effects of Carbamazepine and Novel 10,11‐Dihydro‐5H‐Dibenz[b,f]Azepine‐5‐Carboxamide Derivatives on Synaptic Transmission in Rat Hippocampal Slices
Authors: Cunha Rodrigo A. , Coelho Joana E. , Costenla Ana Rita , Lopes Luísa V. , Parada António , De Mendonça Alexandre , Sebastião Ana M. , Ribeiro J. A.
Published: March 2003

Abstract: The effects of carbamazepine on synaptic transmission in rat hippocampal slices were compared with those of two novel analogues (BIA2–093 and BIA2–024) with equivalent anticonvulsant efficacy but with fewer side effects. Carbamazepine (10–1000 μM) inhibited in a concentration‐dependent manner the field excitatory postsynaptic potential (fPSP) response, with an EC50 of 263 μM, and also attenuated the presynaptic volley with a similar EC50 value. Carbamazepine was more potent to inhibit the NMDA receptor component of the fPSP (fPSPNMDA), with an EC50 of 160 μM. BIA2–093 and BIA2–024 were nearly equipotent with carbamazepine to inhibit synaptic transmission, and displayed similar potency to inhibit the fPSP (EC50 of 145 μM and 205 μM) and fPSPNMDA responses (EC50 of 198 μM and 206 μM). As with carbamazepine, BIA2–093 and BIA2–024 also attenuated the presynaptic volley with EC50 values ranging from 142 to 322 μM. These results indicate that carbamazepine and its analogues mostly inhibit synaptic transmission through inhibition of conduction, although carbamazepine, but not BIA2–093 and BIA2–024, may also depress NMDA receptor‐mediated responses.
Ebselen Protects against the Reduction in Levels of Drug‐Metabolizing Enzymes in Livers of Rats with Deoxycholic Acid‐Induced Liver Injury
Authors: Tanaka Masami , Takezawa Nahomi , Kumai Toshio , Watanabe Minoru , Matsumoto Naoki , Nakaya Sachiko , Kobayashi Shinichi
Published: March 2003

Abstract: Ebselen is a seleno‐organic compound that inhibits oxidative stress by lipid peroxidation through a glutathione peroxidase‐like activity. We studied the effect of ebselen on the expression of hepatic drug‐metabolizing enzymes in rats with deoxycholic acid‐induced liver injury. Hydrophobic bile acids, such as deoxycholic acid, are known to cause cholestatic liver injury, and it was reported that expression of hepatic cytochrome P‐450 (CYP) was reduced by deoxycholic acid administration in rats. Hydrophobic bile acids induce lipid peroxidation in the liver, and this may be one mechanism of the development of liver injury. In the present study, we investigated the effect of ebselen (30 mg/kg/day for 10 days) on rats ingesting deoxycholic acid (1% of diet for 10 days). Deoxycholic acid decreased levels of CYP1A1, 2B1, 2E1 and 3A2 to 34, 58, 62 and 37% of control values, respectively, and increased serum alkaline phosphatase (ALP) and alanine aminotransferase (ALT) activities to 1.8 and 8.6 times the levels of controls, respectively. Administration of ebselen with deoxycholic acid prevented the decreases in levels of CYP1A1 and 3A2 (86 and 65% of control, respectively) and the increases in serum ALP and ALT activities (1.4 and 1.9 times of control, respectively) caused by deoxycholic acid. These results indicate that ebselen may have a protective effect against hydrophobic bile acid‐induced liver injury.
Molecular Models for Cholecystokinin‐A Receptor
Authors: Dawson Eric S. , Henne Randel M. , Miller Laurence J. , Lybrand Terry P.
Published: March 2003

Abstract: Numerous techniques have been used to elucidate the structural basis for interaction of cholecystokinin (CCK)‐related peptides with their hormone‐binding receptor, the CCK‐A receptor (CCK‐AR), including structure‐activity relationship studies, site‐directed mutagenesis, photoaffinity‐labeling, and solution NMR analysis of both CCK peptide ligands and peptide fragments derived from the CCK‐A receptor. Different structural models have been developed for the peptide‐receptor complexes using various subsets of the available experimental data (Giragossian & Mierke 2001; Ding et al. 2002; Escrieut et al. 2002). Here, we review details of the various models and evaluate the impact of selected experimental data sets on model development.
Does smoking influence the efficacy of bath‐PUVA therapy in chronic palmoplantar eczema?
Authors: Douwes K. E. , Karrer S. , Abels C. , Landthaler M. , Szeimies R.‐M.
Published: March 2003

Bath‐PUVA therapy has been described as successful treatment for palmoplantar eczema. However, our own observations showed that patients with palmoplantar eczema of the dyshidrotic or hyperkeratotic type responded only partially to bath‐PUVA therapy. In order to evaluate environmental influences possibly having an impact on the efficacy of this therapy, smokers and non‐smokers suffering from palmoplantar eczema treated with bath‐PUVA therapy were compared. A retrospective study was conducted involving 62 patients, 39 non‐smokers and 23 smokers, with palmar and/or plantar eczema resistant to local corticosteroids. Bath‐PUVA therapy was performed according to the European standard regimen for oral PUVA therapy. The total number of treatments and the cumulative UVA‐dose were similar in smokers and non‐smokers (smokers 24±17.7 (mean±SD) and 67.6±51.3 J/cm2 vs. non‐smokers 25.7±16.3 and 68.5±49.3 J/cm2). In the group of non‐smokers, 31% showed complete remission (CR; 100% clearance), 33% partial remission (PR; more than 50% clearance) and 36% no change after treatment (NC; less than 50% clearance). In contrast, the group of smokers showed only 13% CR and 22% PR, whereas 65% exhibited NC. The differences regarding complete or partial remission between the groups were statistically significant (Student t‐test for paired samples; P<0.05). Regarding the different type of eczema, bath‐PUVA proved to be more successful in the dyshidrotic type of eczema as compared to the hyperkeratotic type in non‐smokers (P<0.05). In the group of smokers no CR was achieved in patients suffering from the dyshidrotic form of eczema. Smoking is likely to be a reason for the failure of bath‐PUVA therapy in the treatment of chronic palmoplantar eczema, in particular regarding smokers with eczema of the dyshidrotic type where no complete remission was achieved.
Usage of real‐time ultraviolet radiation data to modify the daily erythemal exposure of primary schoolchildren
Authors: Kimlin Michael , Parisi Alfio
Published: March 2003

Background/Aims: Primary schoolchildren in their everyday school life are exposed to solar ultraviolet radiation. This may be through time spent outdoors whilst having meal breaks, physical education classes and other class orientated outdoor activities.

Methods: This research investigates the UV exposure of primary schoolchildren and the effect real‐time UV irradiances data and an associated software package, UVGUIDE, have on UV exposure. This software utilises scientifically collected data, such as facial distribution of UV, as well as accessing real‐time on‐line UV irradiances data to estimate the UV distribution to the head region. The students can also enter other parameters such as hat usage and hat type to show the effect of using such a UV protective device on their facial UV distribution.

Conclusions: The results from this study found that the average 3‐day erythemal UV exposure in late summer and early autumn to the left shoulder was 33% higher for the students not having access to the on‐line UV data and software package.
Psoralen plus ultraviolet‐A‐bath photochemotherapy as an adjunct treatment modality in cutaneous chronic graft versus host disease
Authors: Leiter Ulrike , Kaskel Peter , Krähn Gertraud , Gottlöber Petra , Bunjes Donald , Peter Ralf‐Uwe , Kerscher Martina
Published: March 2003

Background: Cutaneous chronic graft versus host disease (GVHD) is a severe complication following allogeneic stem cell (PBSCT) and bone marrow transplantation (BMT). Immunosuppressive therapy consists of prednisone, cyclosporine‐A, azathioprine or mycophenolate mofetil (MMF). Treatment of patients refractory to immunosuppression represents a major problem.

Methods: We report six patients suffering from severe chronic GVHD of the skin who did not respond to immunosuppressive therapy or relapsed after reduction of glucocorticosteroids. Patients were treated with psoralen plus ultraviolet (PUVA)‐bath photochemotherapy three times weekly following a standardized treatment protocol under continued treatment with prednisone and/or MMF. One patient was additionally pretreated with ultraviolet‐A1 (UV‐Al).

Results: After a median of 14, 5 treatment sessions, skin lesions improved. Out of six patients, three showed a complete remission. In all patients, systemic immunosuppressive therapy could be reduced. In sclerodermic lesions, skin thickness returned to the levels of normal skin after 25 treatments confirmed by 20 MHz ultrasound evaluation. In a follow‐up ranging from 2 to 21 months (median 10, 3 months), skin conditions remained stable.

Conclusion: Psoralen plus ultraviolet‐A‐bath represents an effective adjunct treatment option for extensive chronic and sclerodermic cutaneous GVHD offered by dermatologists. This is of high interest in patients suffering from cutaneous GVHD resistant to conventional immunosuppressive therapy and should be included to the menu of topical treatment options for chronic cutaneous GVHD.
The mutagenic effect of ultraviolet‐A1 on human skin demonstrated by sequencing the p53 gene in single keratinocytes
Authors: Persson Åsa E. , Edström Desiree W. , Bäckvall Helena , Lundeberg Joakim , Pontén Fredrik , Ros Anne‐Marie , Williams Cecilia
Published: March 2003

Background:  Sun exposure is accepted as the major risk factor for developing skin cancer, the most common cancer in the western world. Ultraviolet‐B (UV‐B) radiation is considered the causative agent, but recently several findings suggest a role also for ultraviolet‐A (UV‐A) radiation. Repeated suberythemal doses of ultraviolet‐A1 (UV‐A1) on healthy human skin induce an increase of p53 immunoreactive cells in epidermis, which may indicate cell cycle arrest and/or occurrence of p53 mutations.

Methods:
 We have investigated the possible mutagenic effect of UV‐A1 on skin by sequencing exons 4–11 and adjacent intron sequence of the p53 gene in immunoreactive single cells from three healthy individuals. Previously unexposed buttock skin was irradiated three times a week for 2 weeks with physiological fluences (40 J/cm2) of UV‐A1. Punch biopsies were taken before and at different time‐points after the exposure, and from these single p53 immunoreactive cells were isolated by using laser‐assisted microdissection.

Results:  Three mutations – all being indicative of oxidative damage and most likely related to UV‐A exposure – were found among the 37 single cells from exposed skin, whereas no mutations were found in the 22 single cells taken before exposure.

Conclusions:  The findings indicate a mutagenic effect of low‐dose UV‐A1 on healthy human skin, which further demonstrates the importance of considering UV‐A when taking protective measures against skin cancer.
Morning urinary assessment of nocturnal melatonin secretion in older women
Authors: Cook Mary R. , Graham Charles , Kavet Robert , Stevens Richard G. , Davis Scott , Kheifets Leeka
Published: March 2003

We evaluated the feasibility of using morning urine samples in epidemiological studies aimed at clarifying the relationship between nocturnal melatonin levels and breast cancer risk. Initially, a laboratory‐based study of 29 women (40–70 yr old) was performed to examine the correlation between plasma melatonin levels in hourly nocturnal blood samples and both melatonin and its major enzymatic metabolite, 6‐hydroxymelatonin‐sulfate (6‐OHMS) in morning urine samples. In a companion field study, morning urine samples were collected from 203 healthy women to assess similarities and differences in laboratory versus field measures. Taken together, our results indicate: 1) levels of melatonin and of creatinine‐corrected 6‐OHMS in the first morning void urine are strongly correlated with total nocturnal plasma melatonin output (P<0.001) and also with peak nocturnal melatonin values
(P<0.001); 2) similar ranges for 6‐OHMS were found in the laboratory and the field; and 3) neither menopausal status nor hormonal replacement therapy altered 6‐OHMS values in morning void urine. The inclusion of morning urine samples in epidemiological studies of cancer could allow cost‐effective, widespread testing of the role played by melatonin in human health and disease.
Influence of melatonin on free radical‐induced changes in rat pancreatic beta‐cells in vitro
Authors: Ebelt Henning , Peschke Dorothee , Brömme Hans‐Jürgen , Mörke Wolfgang , Blume Rudolf , Peschke Elmar
Published: March 2003

Free radicals may produce cytotoxicity to pancreatic islets under pathophysiological conditions. The aim of our in vitro investigations was to compare functional and morphological changes in pancreatic beta‐cells induced by reactive oxygen species (ROS) generated by alloxan or xanthine oxidase/hypoxanthine (XO/HX), respectively. We demonstrate that short‐term exposure to alloxan or to XO/HX leads to a temporarily elevated insulin release from isolated pancreatic islets. On application of alloxan, this effect is caused by beta‐cell necrosis and can be prevented by administration of melatonin, while in contrast, XO/HX did not lead to long‐term morphological changes in the majority of the cells. Among the cells destroyed by alloxan, only necrosis could be detected, while in contrast, some apoptotic cells were identified by the terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end labeling (TUNEL) reaction and electron microscopic examinations of cells treated with XO/HX. Melatonin was able to prevent the changes caused by alloxan, but failed to influence the alterations caused by XO/HX. Using electron spin resonance and lipid peroxidation assay, respectively, it was confirmed that melatonin effectively detoxifies hydroxyl radicals. Therefore, we believe that hydroxyl radicals are the toxic principle of alloxan, but not of XO/HX toxicity.
Evidence for a direct effect of melatonin on mitochondrial genome expression of Siberian hamster brown adipocytes
Authors: Prunet‐Marcassus Bénédicte , Ambid Louis , Viguerie‐Bascands Nathalie , Pénicaud Luc , Casteilla Louis
Published: March 2003

Photoperiod variations are known to participate in the regulation of energy balance in different rodent species via melatonin, a neurosecretory product synthesized by the pineal gland during the night. A direct effect of melatonin on adipose tissue has been suggested since binding sites for the indole have been described on brown adipocytes. The aim of this study was to investigate a genetic effect of melatonin on isolated Siberian hamster brown adipocytes using differential display RT‐PCR (DDRT‐PCR). Brown adipose cells were isolated from brown adipose tissue and treated for 3 hr with 0.1 and 10 μM melatonin. Total RNA was extracted and DDRT‐PCR experiments were performed. A differential band, which disappeared after melatonin treatment, was detected. After confirmation and cloning, the corresponding cDNA fragment B18 was sequenced. B18 had 85 and 81% similarity with a portion of rat and mouse cytochrome b mRNA, respectively, suggesting that B18 corresponds to hamster cytochrome b. This hypothesis was confirmed by the close parallel between the changes in mRNA content, detected by B18, and by cytochrome b mRNA content, detected by a rat probe. Cytochrome b mRNA is encoded by the mitochondrial genome, suggesting a similar effect of melatonin on the whole mitochondrial transcripts. Indeed, 3 hr of treatment with melatonin (10 nM and 0.1 μM) decreased by 44% mitochondrial transcript contents. This work constitutes the first evidence of a direct biological effect of melatonin on Siberian hamster brown adipocytes.
Increased pineal Fdopa uptake is related to severity of Parkinson's disease – A PET study
Authors: Ghaemi Mehran , Rudolf Jobst , Hilker Rüdiger , Herholz Karl , Heiss Wolf‐Dieter
Published: March 2003

We investigated regional L‐3,4‐dihydroxy‐6‐[18F]fluoro‐phenylalanine (Fdopa) uptake within the pineal gland using co‐registration of Fdopa PET and MRI images. Data from 12 early Parkinson's disease (PD) and 9 advanced PD patients were compared with those from 13 age‐matched healthy controls. We found a significant increase of Fdopa influx constants (Ki) and relative Fdopa tracer activity in the pineal gland of PD patients. Additionally, significant correlations were found between Ki and the Hoehn and Yahr (H&Y) scores, and between the relative Fdopa activity and the parameters disease duration, H&Y disease score and Unified Parkinson's Disease Rating Scale (UPDRS). Our studies in patients with PD indicate a participation of extrastriatal dopaminergic structures within the scope of pathophysiological processes in PD. The result may be explained as a compensatory upregulation of monoaminergic transmitter systems outside the basal ganglia. Increased Fdopa uptake in the pineal gland may reflect pineal dysfunction in PD patients.
Gene expression of the key enzymes of melatonin synthesis in extrapineal tissues of the rat
Authors: Stefulj Jasminka , Hörtner Michael , Ghosh Meenakshi , Schauenstein Konrad , Rinner Ingo , Wölfler Albert , Semmler Johann , Liebmann Peter M.
Published: March 2003

Besides the pineal gland, melatonin is reported to be produced in a number of extrapineal sites, where it could act as an intracellular mediator or paracrine signal in addition to its endocrine effects. In view of the suggested immunoregulatory role of melatonin, we compared lymphoid organs and several other tissues of the rat for their potential to synthesize melatonin. Using the reverse transcription‐polymerase chain reaction (RT‐PCR) method, we determined the tissue‐specific expression of mRNAs encoding two key enzymes of the melatonin biosynthesis: serotonin‐N‐acetyltransferase (NAT) and hydroxyindole‐O‐methyltransferase (HIOMT). The minimal number of PCR cycles required to obtain a positive signal served as a measure for the abundance of a given mRNA. NAT and HIOMT mRNAs were detected in all tested tissues at high numbers of PCR cycles (40 and 45, respectively). At 35 cycles, only gut, testis, spinal cord, raphe nuclei, stomach fundus and striatum yielded positive signals for both enzymes. In conclusion, the presence of NAT and HIOMT mRNAs in a wide range of tissues corroborates and extends the notion of extrapineal melatonin synthesis. Comparatively low levels of the HIOMT messages in lymphoid organs, however, indicate a limited significance of melatonin synthesis within the immune system.
Putative regulatory molecules in plants: evaluating melatonin
Authors: Van Tassel David L. , O'Neill Sharman D.
Published: March 2003

Numerous classes of chemicals have been considered as regulators of various aspects of plant growth and development. In evaluating these putative regulatory molecules, plant biologists have encountered a number of challenges, including: the problem of quantifying substances present at trace levels in extremely complex mixtures; difficulty in obtaining and interpreting phenotypic responses to exogenous applications; and, until recently, the inability to selectively alter endogenous levels of these substances. Melatonin (N‐acetyl 5‐methoxytryptamine), a methoxylated indoleamine, is a potential regulatory molecule found in plants. Although no specific phenotype is currently associated with melatonin or its analogs in higher plants, it has important and unique biological activity in many other taxa, from algae to primates. In these organisms, melatonin functions as a night signal, coordinating responses to diurnal and photoperiodic environmental cues. We assess the process by which melatonin has been evaluated in plants so far and find that many of the methods for melatonin analysis, which have been adopted from animal studies, are inappropriate for use with plant materials. Thus, despite some interesting preliminary reports, research supporting the case for melatonin as a plant regulator is still in its infancy.
Daily variation in the concentration of 5‐methoxytryptophol and melatonin in the duck pineal gland and plasma
Authors: Zawilska Jolanta B. , Rosiak Jolanta , Vivien‐Roels Berthe , Skene Debra J. , Pévet Paul , Nowak Jerzy Z.
Published: March 2003

The duck pineal gland rhythmically produces two 5‐methoxyindole compounds, i.e. 5‐methoxytryptophol and melatonin. 5‐Methoxytryptophol levels are low at night and high during the day, while melatonin concentrations are high at night and low during the day. The melatonin rhythm reflects oscillations in the activity of serotonin N‐acetyltransferase (AA‐NAT; a penultimate and key regulatory enzyme in the melatonin biosynthetic pathway). The activity of hydroxyindole‐O‐methyltransferase (HIOMT; an enzyme involved in the synthesis of both 5‐methoxytryptophol and melatonin) does not exhibit any significant rhythmic changes throughout the 24‐hr period. Plasma levels of melatonin exhibited daily changes that were parallel to fluctuations in pineal melatonin content. Although plasma concentrations of 5‐methoxytryptophol were low in ducks, they showed daily variations. The mean 5‐methoxytryptophol concentration between zeitgeber time 9 (ZT9) and ZT15 was 2.4‐times higher than the mean value for samples collected between ZT18 and ZT3. These findings indicate that in the duck the pineal production of 5‐methoxytryptophol and melatonin may be inversely correlated.
Acute modifications in the levels of daytime melatonin do not influence leptin in postmenopausal women
Authors: Cagnacci Angelo , Malmusi Stefania , Zanni Annalisa , Arangino Serenella , Cagnacci Paolo , Volpe Annibale
Published: March 2003

Melatonin shows a clear circadian rhythm with peak values at night, and may act directly with fat cells. Leptin, the anorexic hormone synthesized mainly by adipocytes, is produced in a circadian fashion, similar to that of melatonin. Accordingly, in the present study, we investigated whether melatonin may contribute to the rise in circulating leptin. The study was performed in postmenopausal women with 2 months of treatment with placebo or estradiol (50 μg/day). Melatonin was administered in doses of 1 mg by mouth versus placebo. In experiment 1, melatonin was administered at 08:30 hr. In experiment 2, at 08:30 hr and 10:30 hr, and in experiment 3 at 15:30 hr. Three blood samples, one every 15 min, were collected prior to the administration of melatonin and 2 hr after the administration of the single melatonin dose or the second melatonin administration (experiment 2). Following its administration, circulating melatonin reached pharmacological levels. In the three experiments, levels of leptin were not modified by the daytime administration of melatonin. These data indicate that, at least in daytime hours, acute modifications in daytime melatonin levels do not influence levels of leptin of postmenopausal women either without or with estradiol replacement. Accordingly, the metabolic, endocrine, reproductive and biological modifications induced by acute daytime melatonin in women do not seem to be mediated by modifications in circulating leptin.
Melatonin suppresses NO‐induced apoptosis via induction of Bcl‐2 expression in PGT‐β immortalized pineal cells
Authors: Yoo Yeong‐Min , Yim Sung‐Vin , Kim Sung‐Soo , Jang Hyun Yong , Lea Ho Zoo , Hwang Geun‐Cheal , Kim Jong‐Woo , Kim Soon‐Ae , Lee Hee Jae , Kim Chang‐Ju , Chung Joo‐Ho , Leem Kang‐Hyun
Published: March 2003

Abstract: In the present study, we investigated whether melatonin would prevent nitric oxide (NO)‐induced apoptotic death of PGT‐β immortalized pineal cells. To examine the protective effect of melatonin, cytotoxicity assay, DNA fragmentation analysis, caspase‐3 activity assay, and Western blotting for caspase‐3 and poly(ADP‐ribose) polymerase (PARP) were performed. Treatment of cells with S‐nitroso‐N‐acetylpenicillamine (SNAP), an NO donor, was shown to induce apoptotic cell death in a dose‐dependent manner, and pretreatment with melatonin (0.1 mm) attenuated the occurrence of NO‐induced apoptotic cell death. DNA fragmentation in response to NO was also arrested by melatonin. Caspase‐3 activity induced by NO was decreased with melatonin treatment. Furthermore, the active fragments of caspase‐3 and PARP were almost completely absent following exposure to melatonin. To elucidate the protective mechanisms of action of melatonin, Western blot analyses for Bcl‐2 expression and cytochrome c release were carried out. Pretreatment with melatonin (0.1 mm) induced the expression of Bcl‐2 and suppressed the release of cytochrome c into the cytosol, thereby arresting NO‐induced apoptotic cell death. These results suggest that the antiapoptotic effect of melatonin is associated with induction of Bcl‐2 expression in PGT‐β cells, which in turn blocks caspase‐3 activation and inhibits cytochrome c release into the cytosol.
Long‐term melatonin administration reduces hyperinsulinemia and improves the altered fatty‐acid compositions in type 2 diabetic rats via the restoration of Δ‐5 desaturase activity
Authors: Nishida Shigeru , Segawa Toshiko , Murai Ichiro , Nakagawa Shigeki
Published: March 2003

The objective of this study was to investigate the effect of long‐term melatonin administration on plasma levels of triglycerides, insulin and leptin, and on the fatty‐acid metabolism of plasma and hepatic lipids in type 2 diabetic rats. Otsuka Long‐Evans Tokushima Fatty (OLETF) rats, an animal model of type 2 diabetes mellitus, were divided into two groups: one untreated (n=6), and one implanted with time‐releasing melatonin pellets (1.1 mg/day for 30 wk) under the abdominal skin (n=6). Age‐matched Long‐Evans Tokushima Otsuka (LETO) rats (n=6) were used as healthy controls. The untreated diabetic rats had the increased plasma levels of triglycerides, cholesterol, insulin and leptin at 35 wk, as compared with the healthy control rats (n=6). The diabetic rats also had augmented ratios of 20:3n‐6/20:4n‐6 fatty acids, owing to diminished activity of Δ‐5 desaturase, an insulin‐permissive enzyme, in the liver. Melatonin administration to OLETF rats reduced the hypertriglyceridemia (−39%, P < 0.05), hyperinsulinemia (−33%, P < 0.01) and hyperleptinemia (–43%, P < 0.01), and restored hepatic Δ‐5 desaturase activity (148%, P < 0.005). This resulted in a return to normal ratios of 20:3n‐6/20:4n‐6 fatty acids in plasma and hepatic lipids. There was a significant correlation (r=0.64, P < 0.005) between plasma levels of insulin and the ratios of 20:3n‐6/20:4n‐6 in plasma phospholipids of all rats in the three groups. Thus, subcutaneous implantation of a melatonin‐releasing pellet thus resulted in improved lipid metabolism in diabetic rats, probably through restored insulin resistance.ALP, alkaline phosphataseGOT, glutamic oxalacetic transaminaseGPT, glutamic pyruvic transaminaseHPLC, high performance liquid chromatographyLETO rats, Long‐Evans Tokushima Otsuka ratsMUFA, monounsaturated fatty acidOLETF rats, Otsuka Long‐Evans Tokushima Fatty ratsPUFA, polyunsaturated fatty acidVLDL, very low density lipoprotein
The protective effects of melatonin from oxidative damage induced by amyloid beta‐peptide 25–35 in middle‐aged rats
Authors: Shen Y. X. , Xu S. Y. , Wei W. , Sun X. X. , Liu L. H. , Yang J. , Dong C.
Published: March 2003

This work investigated the ability of melatonin to prevent oxidative damage in brain tissue induced by injection of beta‐amyloid peptide 25–35 (Aβ25–35) in middle‐aged rats. The Morris water maze was used to evaluate the cognitive function of the rats. Thiobarbituric acid‐reactive substances and antioxidative enzymes (superoxide dismutase and glutathione peroxidase) activities were measured. It was found that injection of (Aβ25–35) (20 μg) into the rat hippocampus caused an increase in the latency (the time to find the platform), the total swimming distance to the platform, and the starting angles in (Aβ25–35)‐treated rats. Furthermore, a significant rise in lipid peroxidation and decrease in antioxidative enzyme activities in brain tissue were found. Melatonin (0.1, 1, and 10 mg/kg, i.g. × 10 days) improved the spatial resolution of amnesic rats in the Morris water maze test. Meanwhile, melatonin antagonized the lipid peroxidation in both the mitochondria (P < 0.01) at the doses of 0.1, 1.0, and 10 mg/kg and in the cytoplasm at the doses of 0.1 and 1.0 mg/kg. Also in the amnesic rats, melatonin (0.1, 1.0, and 10 mg/kg, i.g. × 10 days) stimulated the antioxidative enzyme activities. The results show that melatonin effectively reduced lipid peroxidation and enhanced the antioxidative enzyme activities in Aβ25–35‐treated rats, which may contribute to the improvement of rats' learning and memory impaired by Aβ25–35.
Modulation of intracellular calcium and calmodulin by melatonin in MCF‐7 human breast cancer cells
Authors: Dai Jun , Inscho Edward W. , Yuan Lin , Hill Steven M.
Published: March 2003

The pineal hormone, melatonin, has been shown to inhibit the proliferation of the estrogen receptor alpha (ERα)‐positive macrophage chemotactic factor (MCF)‐7 human breast cancer cells. Previous studies from other systems indicate that melatonin modulates the calcium (Ca2+)/calmodulin (CaM) signaling pathway either by changing intracellular calcium concentration ([Ca2+]i) via activation of its G‐protein coupled membrane receptors, or through a direct interaction with CaM. In this study, although melatonin alone had no effect on basal [Ca2+]i in MCF‐7 cells, it significantly enhanced the elevation of [Ca2+]i induction by extracellular adenosine triphosphate (ATP), which increases [Ca2+]i via the G protein‐coupled P2y‐purinoceptor and the phospholipase C (PLC) pathway. Pretreatment of MCF‐7 cells with 10–7 M melatonin increased the 10–5 M ATP‐induced [Ca2+]i peak change from 79.4 ± 11.6 nM to 146.2 ± 22.3 nM. Furthermore, without changing total cellular CaM levels, melatonin markedly increased the amount of membrane‐bound CaM to 237 and 162% of control levels after 1 and 6 hr of treatment, respectively. Cytosolic CaM levels were also elevated to 172% of control after 6 hr of melatonin treatment. Correlative growth studies demonstrated that ATP (10−5 M) can stimulate MCF‐7 cell growth, that melatonin can suppress MCF‐7 cell proliferation, but that pretreatment of MCF‐7 cells with melatonin followed by ATP(10–5 M), like 10–4 M ATP can further suppress MCF‐7 cell proliferation; this indicates that melatonin's potentiation of ATP induced [Ca2+]i may be above the threshold for cell growth. Given the important role of [Ca2+]i and CaM in tumor cell homeostasis and proliferation and melatonin's modulation of [Ca2+]i, melatonin's effects on the Ca2+/CaM signaling pathway may play an important role in mediating the growth‐inhibitory effect of melatonin on MCF‐7 human breast cancer cells.
Characterization of melatonin high‐affinity binding sites in purified cell nuclei of the hamster (Mesocricetus auratus) harderian gland
Authors: Coto‐Montes Ana , Tomás‐Zapico Cristina , Germaine Escames  , León Josefa , Tolivia Delio , JosefaRodríguez‐Colunga Mª , Acuña‐Castroviejo Darío
Published: March 2003

Abstract:  In the present paper, binding of melatonin to purified cell nuclei from harderian glands of male and female hamsters was assessed. Binding of 125I‐melatonin to cell nuclei fulfills the criteria for binding to a receptor site. Binding kinetics exhibit properties such as dependence on time and temperature as well as reversibility, saturability, high affinity and specificity. The dissociation constants (KD) and the number of binding sites (Bmax) for the binding of 125I‐melatonin to harderian gland nuclei were 260 ± 56 pm and 12.2 ± 0.8 fmol/mg protein in male glands, and 280 ± 43 pm and 9.8 ± 0.6 fmol/mg protein in female glands, respectively. Competition experiments showed IC50 values for melatonin of 250 ± 45 pm and 290 ± 68 pm in male and female glands, respectively. Other indoleamines such as N‐acetylserotonine and 5‐metoxytryptamine showed IC50 values in the micromolar range, suggesting that the binding sites are specific for melatonin. Hill analyses of the data show nH values of 0.96–0.98, suggesting the existence of a single class of binding sites. These data indicate that specific 125I‐melatonin binding sites exist in the cell nuclei of Harderian glands in male as well as in female hamsters, without significant differences between them. The KD and Bmax values obtained from the binding in both sexes correlates well with the concentration of melatonin described in these respective Harderian glands. It is hypothesized that the nuclear binding sites of melatonin here described could be a physiological melatonin receptor, which may be involved in the genomic‐dependent antioxidant effects of melatonin on hamster Harderian glands elsewhere reported.
Maternal transfer of photoperiodic information in Siberian hamsters. vi. effects of time‐dependent 1‐hr melatonin infusions in the mother on photoperiod‐induced testicular development of her offspring
Authors: Gündüz Bülent , Stetson Milton H.
Published: March 2003

Abstract: We tested in Siberian hamsters the nature of the maternal signal that relays photoperiodic information to the developing fetuses. As previous investigations have identified maternal hormonal and circadian components in this process, the specific goal of this presentation is to determine quality of the signal that connotes daylength when it is imparted to the fetus. Does the function of the signal received by the fetus best support the coincidence or duration hypotheses of photoperiodic induction? Pregnant hamsters received 1 or 8 hr melatonin or vehicle infusions everyday. Juveniles of intact mothers gestated on 16 hr of light per day (16L) experienced maximal suppression of testicular development when reared on 14L. However, when intact mothers gestated on 10L received a 1‐hr melatonin infusion daily at 20:00–21:00 hr, their young responded to 14L with greatly accelerated testicular development. In the absence of the maternal pineal gland (and, therefore, the maternal melatonin signal), the effects of maternal melatonin infusions were reversed. Here, only the juveniles of 16L‐gestated females infused at 20:00–21:00 hr daily responded to 14L with enhanced testicular development. All other groups showed the same extent of gonadal development, independent of the time or type of infusion their mothers received. Testicular development on 14L of all juveniles from pinealectomized mothers gestated on 10L was of the same magnitude, regardless of the type and time of infusion their mothers received during pregnancy. The results suggest that the maternal signal transferred to the fetuses during gestation consists not only of the daily melatonin signal, but also some circadian‐based component that greatly affects the effect of the former. The timing, and not the duration, of the maternal melatonin signal with respect to the animals’ (mother and fetus) circadian day is of crucial importance in the transfer of photoperiodic information from mother to fetus.
The validity and feasibility of saliva melatonin assessment in the elderly
Authors: Gooneratne Nalaka S. , Metlay Joshua P. , Guo Wensheng , Pack Frances M. , Kapoor Shiv , Pack Allan I.
Published: March 2003

Abstract: Recent work in young and middle‐aged subjects suggests that melatonin levels in saliva may represent a viable alternative to serum melatonin measurement. We hypothesized that it may be a valid measure of melatonin levels in older adults as well, but features unique to the elderly may limit its utility. To study this, subjects were admitted to an academic medical center where saliva and serum specimens were collected concurrently in dim light conditions during a 14‐hr overnight study period and analyzed for melatonin levels with radioimmunoassays (RIAs). Eighty‐five subjects over the age of 65 with a broad range of medical conditions participated in the study. Subjects with dementia, depression and anemia were excluded. We found that saliva volume was inadequate for analysis (<200 μL) in 23.6% of specimens, with the majority of inadequate volume specimens occurring after midnight and inadequate specimens occurring more frequently in females than in males. The correlation coefficient for saliva melatonin and serum melatonin was r = 0.659 (Spearman, P < 0.001), and r = 0.466 for saliva dim light melatonin onset (DLMO) and serum DLMO. Saliva melatonin levels were 30.9% of serum melatonin levels, with a wide range of ratios noted between subjects. Overall melatonin levels influenced both the correlation and ratio of saliva melatonin to serum melatonin; higher correlations and lower ratios were noted when melatonin levels were high. Saliva specimens provide an economical and practical method for melatonin assessment, however, in older adults, issues such as hyposalivation and low melatonin levels limit the feasibility and validity, respectively, of saliva melatonin.
Pineal melatonin synthesis and release are not altered throughout the estrous cycle in female rats
Authors: Skorupa Ana‐Lucia , Garidou Marie‐Laure , Bothorel Béatrice , Saboureau Michel , Pévet Paul , Neto José Cipolla , Simonneaux Valérie
Published: March 2003

Abstract: Melatonin times reproduction with seasons in many photoperiodic mammalian species. Whether sexual hormones reflect on melatonin synthesis is still debated. The aim of this work was to study, using a large panel of technical approaches, whether the daily profile of pineal melatonin synthesis and release varies with the estrous cycle in the female rat. The mRNA levels and enzyme activities of the melatonin synthesizing enzymes, arylalkylamine N‐acetyltransferase and hydroxyindole‐O‐methyltransferase were similar at the four stages of the rat estrous cycle. The endogenous release of melatonin, followed by transpineal microdialysis during six consecutive days in cycling female rats, displayed no significant variation during this interval. Taken together, the present results demonstrate that there is no regular fluctuation in the pineal metabolism leading to melatonin synthesis and release throughout the estrous cycle in female rats.
Patellar tendinopathy in junior basketball players: a controlled clinical and ultrasonographic study of 268 patellar tendons in players aged 14–18 years
Authors: Cook J. L. , Khan K. M. , Kiss Z. S. , Griffiths L.
Published: March 2003

Anterior knee pain is a common presenting complaint amongst adolescent athletes. We hypothesised that patellar tendinopathy may occur at a younger age than is generally recognised. Thus, we studied the patellar tendons in 134 elite 14‐ to 18‐year‐old female (n=64) and male (n=70) basketball players and 29 control swimmers (17 female, 12 male) clinically and with ultrasonography. We found that of 268 tendons, 19 (7%) had current patellar tendinopathy on clinical grounds (11% in males, 2% in females). Twenty‐six percent of the basketball players’ patellar tendons contained an ultrasonographic hypoechoic region. Ultrasonographic abnormality was more prevalent in the oldest tertile of players (17–18 years) than the youngest tertile (14–15.9 years). Of tendons categorised clinically as ‘Never patellar tendinopathy’, 22% had an ultrasonographic hypoechoic region nevertheless. This study indicates that patellar tendinopathy can occur in 14‐ to 18‐year‐old basketball players. Ultrasonographic tendon abnormality is 3 times as common as clinical symptoms.
Tenascin‐C in the pathobiology and healing process of musculoskeletal tissue injury
Authors: Järvinen T. A. H. , Kannus P. , Järvinen T. L. N. , Jozsa L. , Kalimo H. , Järvinen M.
Published: March 2003

Tenascin‐C (TN‐C) is a hexabrachion‐shaped extracellular matrix (ECM) protein which has very restricted expression in normal musculoskeletal tissues, but is expressed in large quantities in these tissues during embryogenesis as well as during regenerative and healing processes. TN‐C is an elastic protein which has a number of binding sites for other extracellular matrix proteins as well as for cell membrane adhesion receptors. In addition, it can be stretched to several times its resting length, the ability of which is attributed to the stretch‐induced unfolding of its fibronectin type III domains. In the musculoskeletal tissues, TN‐C is present in the regions where high mechanical forces are transmitted from one tissue component to another, such as the myotendinous and osteotendinous junctions. Not surprisingly, it was recently presented that the expression of TN‐C in the musculoskeletal tissues is regulated by the mechanical strain applied to their cells. Thus, taking into account the flexible structure of the TN‐C and its site‐specific expression pattern at sites exposed to heavy mechanical loads, TN‐C is likely to play an important role in providing elasticity to the musculoskeletal tissues. This feature has a special significance in the degenerative and regenerative processes where the normal biomechanical environment of the musculoskeletal tissue is temporarily interrupted by injury. The rapidly increasing understanding of the structure and function of the ECM protein TN‐C may well bring important insights into the clinical treatment of sports injuries in the future.
Histopathology in rabbit Achilles tendon after operative tenolysis (longitudinal fiber incisions)
Authors: Friedrich TH. , Schmidt W. , Jungmichel D. , Horn L.‐C. , Josten CH.
Published: March 2003

The surgical treatment (tenolysis) of chronic Achilles tendinopathy is often successful. However, little is known about the postoperative intratendinous changes after this procedure. The study group consisted of 21 rabbits. Operative tenolysis was done in each case on one Achilles tendon (AT). The ATs of both legs were studied histologically and immunohistochemically using antibodies against collagen types I and III 2, 4 and 6 weeks postoperatively. Nine rabbits without operation served as controls. A significant uniform hypervascularization was noted in the entire operated tendon postoperatively, and this concurred with the contralateral nonoperated AT, but neither side showed changes in collagen fiber structure as judged by immunohistochemistry. We conclude that the tenolysis procedure triggers neoangiogenesis at the AT followed by increased blood flow and improved nutrition in the same. These changes could, at least partly, explain the often seen clinical success in surgically treated tendinopathy.
Fluoroscopic validation of electrogoniometrically measured femorotibial translation in healthy and ACL deficient subjects
Authors: Vergis A. , Hammarby S. , Gillquist J.
Published: March 2003

Equipment which measure femorotibial motions indirectly by using a patellar pad are reported to have errors caused by deformation of soft tissues and slippage of the device. For the purpose of validation, the tibial translation in relation to the femur per degree of knee extension was estimated from the slope coefficients of the flexion‐displacement curve, obtained by both fluoroscopic and electrogoniometric tests, in the knee of the dominant limb in healthy subjects and in both knees of patients with unilateral anterior cruciate ligament (ACL) deficiency. In addition, the anterior and posterior static knee laxity limits and the tibial resting position were evaluated. Within all knee groups, the tibia moved posteriorly in relation to the femur during extension. The measured movement was similar both with the electrogoniometer and with fluoroscopy thereby indicating that sagittal plane knee translation measurements with the CA‐4000 electrogoniometer are reliable and in good agreement with the X‐ray measurements, even though the measurements were made separately. The ACL injured knees showed approximately 20% smaller posterior movement of tibia in relation to femur per degree change of knee extension than the non‐injured or control knees (p < 0.05) and a more anterior resting position of the tibia relative to femur as compared to the contralateral healthy knee during knee laxity testing (p = 0.002).
Muscle strength before and mortality after a bone fracture in older people
Authors: Rantanen T. , Sakari‐Rantala R. , Heikkinen E.
Published: March 2003

We studied whether muscle strength measured before a bone fracture predicts mortality following the fracture. The participants were a sub‐cohort of 82 people of a total of 493 Evergreen project participants initially aged 75‐ and 80 years, who had participated in knee extension strength tests as part of the baseline examinations, and who subsequently suffered at least one bone fracture. Maximal isometric knee extension strength was measured at baseline using an adjustable dynamometer chair. Fracture surveillance was carried out from patient records for 5 years, and mortality surveillance from population register for 10 years after baseline examinations. Average time till a fracture occurred after the baseline was 878 days (SD 576). Subsequent to the fracture, 32 deaths occurred. Using gender‐specific cut‐offs, three equal distribution‐based groups were formed. A gradient risk of mortality was found according to baseline strength. The crude mortality rate per 1000 person‐months was 15.2 in the lowest 4.9 in the middle and 1.7 in the highest third of baseline knee extension strength. The adjusted relative risk (RR) of death was 4.40 (95% confidence interval, CI 1.40–13.80) in the lowest and 2.39 (95% CI 0.68–8.4) in the middle tertile vs the highest tertile of muscle strength. Poor muscle strength measured before a fracture occurred was a powerful predictor of increased mortality after the fracture. Poor muscle strength may be a good indicator of overall vulnerability and frailty in old age, and strength testing could be helpful in targeting older people for preventive interventions.