bluuebunny/crossref_metadata_2025 huggingface dataset:
High resolution ultrastructural reevaluation of dental cuticle in monkey tooth
Authors: Sawada Takashi , Inoue Sadayuki
Published: March 2003

In this study the detailed ultrastructure of the dental cuticle at the dentogingival border in monkeys (macaques) was observed. The deciduous molars and permanent premolars with associated gingiva were prepared for thin section electron microscopy. The dental cuticle, seen as a dense amorphous, usually unlaminated layer, was localized between the tooth enamel and the junctional epithelium of the gingiva in close association with the internal basement membrane of the junctional epithelium. High resolution electron microscopy showed that its basic structure was a fine network of irregular anastomosing strands identified as the cord network of the basement membrane which was continuous with that of the lamina densa of the internal basement membrane of the junctional epithelium. In the cuticle, openings of most of the network were filled with a dark amorphous material. These observations suggest that an additional layer of a cord network formed from the basement membrane components, which is probably secreted by the cells of the junctional epithelium during formation of the cuticle, is added to the cord network of the lamina densa of the basement membrane. In addition, a dark amorphous material is deposited within the newly added cord network at the enamel side of the basement membrane. The origin of this dark material still remains to be clarified, but the possibility is that it originates, as has previously been suggested, from either serum protein in gingival exudate or from hemoglobin produced by the degradation of red blood cells.
Enamel matrix derivative (EMDOGAIN®) rapidly stimulates phosphorylation of the MAP kinase family and nuclear accumulation of smad2 in both oral epithelial and fibroblastic human cells
Authors: Kawase Tomoyuki , Okuda Kazuhiro , Momose Manabu , Kato Yumi , Yoshie Hiromasa , Burns Douglas M.
Published: March 2003

In our previous study, we demonstrated that porcine enamel matrix derivative (EMD) induces p21WAF1/cip1 within 8 hours and subsequently arrests the cell cycle of human oral epithelial cells in G1 phase. In contrast, EMD markedly stimulates the proliferation of gingival fibroblasts without inducing p21WAF1/cip1. To investigate the mechanism of how EMD produces these differential effects, we have focused on the initial response of these two cell types to EMD. In epithelial cell cultures, EMD stimulated cytoskeletal actin polymerization within 30 min and promoted cell adhesion within 3 hours, but EMD had no substantial effects on fibroblastic cell adhesion in our experimental system. EMD failed to stimulate either intracellular Ca2+ mobilization or cAMP production in either cell type. In both epithelial and fibroblastic cells, EMD (25–100 μg/ml) rapidly produced dose‐dependent phosphorylation of the mitogen‐activated protein kinase (MAPK) family: extracellular signal response kinase (ERK), p38‐MAPK (p38‐K), and c‐Jun–terminal kinase/stress‐activated protein kinase (JNK). However, neither inhibitors of MEK (ERK kinase) nor p38‐K could block EMD’s anti‐proliferative action on epithelial cells. On the other hand, EMD rapidly stimulated translocation of smad2 into the nucleus in both cell types. Spurred by this finding, we assayed for TGF‐β1, a ligand for one receptor associated with smad2 activation, and detected significant levels in EMD preparations. The sum of these pharmacological findings indicates that EMD contains at least one bioactive factor, which is most probably TGF‐β1 (or TGF‐β‐like substances). In conjunction with the similarities in the differential growth‐modulating actions between EMD and what is known for TGF‐β, we suggest that TGF‐β might act as the principal growth regulating agent of oral fibroblastic and epithelial cell types in EMD despite being present in only low levels.
The volatile fraction of cigarette smoke induces alterations in the human gingival fibroblast cytoskeleton
Authors: Poggi P. , Rota M. T. , Boratto R.
Published: March 2003

Several in vitro investigations have indicated that the particulate phase of cigarette smoke, such as nicotine, affects many cell types, including gingival fibroblasts. However, few studies have been performed on the effects of the volatile fraction on the cellular structures that are involved in cell functions, such as adhesion and proliferation. Since the survival and reproduction of gingival fibroblasts are fundamental in maintaining the integrity of the oral connective tissue, as well as in wound healing, the effects on the cytoskeleton of acrolein and acetaldehyde, which are the volatile fractions of cigarette smoke, were examined in vitro for human gingival fibroblasts (HGFs). HGF strains that were taken from healthy subjects with non‐inflamed‐gingiva were utilized in this investigation. The cells were incubated in the presence of different concentrations of acrolein and acetaldehyde. Cell adhesion and viability were evaluated after incubation for 3 h and 5 days, respectively. The influence on cytoskeletal structures (tubulin, actin and vimentin intermediate filaments) was investigated with the indirect immunofluorescence technique. The results show that both substances produced similar effects, which resulted in a dose‐dependent inhibition of HGF adhesion and viability. Disturbance of the HGF cytoskeleton consisted of disruption of the microtubules, actin filaments and vimentin microfilaments, which was accompanied by alterations to cell shape. Our experimental findings suggest that the volatile fractions of cigarette smoke, such as acrolein and acetaldehyde, have a cytotoxic effect on HGFs, with the result that they lose their capacity for adhesion and proliferation. The consequences of this could be impairment of the maintenance, integrity and remodelling of the oral connective tissue. According to our morphological evidence, these findings show that cigarette smoke can lead to the development and progression of periodontal disease, and indicate the need for appropriate therapy.
Effects of ovariectomy on trabecular structures of rat alveolar bone
Authors: Tanaka M. , Ejiri S. , Toyooka E. , Kohno S. , Ozawa H.
Published: March 2003

An association between postmenopausal osteoporosis and tooth loss has been proposed. However, histomorphometrical changes in alveolar bone following estrogen deficiency are rarely reported with data on microtrabecular structural changes. To clarify the relationship between estrogen deficiency and tooth loss, we histomorphometrically analyzed the trabecular structural changes of mandibular alveolar bone in ovariectomized rats. Twenty‐four adult female Fischer rats were used. Eight rats were sacrificed on day 0 (baseline). The remaining 16 rats were divided into two groups. One group was ovariectomized bilaterally (OVX) and the other group was subjected to sham surgery (Sham). After administration of tetracycline and calcein, the animals were sacrificed 60 days after surgery. Bone histomorphometry, node‐strut analysis and measurement of thickness of alveolar bone proper were performed on the interradicular septum of the first molar on the sagittal surface. The trabecular bone volume and trabecular number of the OVX group were significantly lower than those of the baseline and Sham groups. All of the bone resorptive and formative parameters of the OVX group were significantly higher (about one‐and‐a‐half times) than those of the Sham group. Several osteoclasts were seen lining the irregular, eroded surface facing the bone marrow in the OVX group. Furthermore, the OVX group tended to have low microtrabecular stiffness and showed significantly thinner distal alveolar bone proper than in the baseline and Sham groups. In summary, estrogen deficiency caused osteoporotic changes and thin alveolar bone proper in the interradicular septum of rat first molar. This phenomenon might accelerate destruction of alveolar bone and tooth loss, especially in elderly women affected by periodontal disease.
Hard tissue formation on dentin surfaces applied with recombinant human bone morphogenetic protein‐2 in the connective tissue of the palate
Authors: Miyaji Hirofumi , Sugaya Tsutomu , Miyamoto Tetsuro , Kato Katsuya , Kato Hiroshi
Published: March 2003

The purpose of this study was to evaluate whether hard tissue might be formed on dentin surfaces applied with recombinant human bone morphogenetic protein‐2 (rhBMP‐2) in palatal connective tissue. Fifty‐eight dentin blocks were prepared from rat roots, demineralized with 24% EDTA (pH 7.0), applied with 0, 50 and 100 μg/ml rhBMP‐2, and labeled as groups 0, 50 and 100. The dentin blocks were then transplanted into palatal connective tissue of rats, and specimens were prepared at two and four weeks after surgery for histologic and histomorphometric examinations. The results showed that the percentage of newly formed hard tissue in relation to the total dentin block surface length in groups 0, 50 and 100 was 0.0%, 2.8% and 4.4% at two weeks, and 0.0%, 1.6% and 12.8% at four weeks, respectively. New hard tissue formation in groups 50 and 100 was significantly promoted as compared to group 0 (p < 0.01). These findings thus indicate that rhBMP‐2 application to dentin enhanced new hard tissue formation on dentin surfaces in the connective tissue of the palate.
Molecular size distribution analysis of human gingival glycosaminoglycans in cyclosporin‐ and nifedipine‐induced overgrowths
Authors: Martins Rita C. L. , Werneck Claudio C. , Rocha Lia A. G. , Feres‐Filho Eduardo J. , Silva Luiz‐Claudio F.
Published: March 2003

Glycosaminoglycans are thought to accumulate in formative lesions like drug‐induced gingival overgrowth. Recent evidences, however, suggest that the amounts of glycosaminoglycans are comparable in overgrown and healthy gingiva. Besides, alterations in the size distribution of glycosaminoglycan molecules isolated from phenytoin‐induced overgrown samples have also been suggested. Therefore, we sought to determine possible differences in molecular size distribution of gingival glycosaminoglycans in other types of drug‐induced overgrowths. Purified gingival glycosaminoglycans from healthy and cyclosporin‐ and nifedipine‐induced overgrown gingival tissues were analyzed by agarose gel electrophoresis and their molecular‐size distribution was evaluated by both gel filtration chromatography and polyacrylamide gel electrophoresis. Our results on the gingival glycosaminoglycan composition showed presence of chondroitin sulfate, dermatan sulfate, heparan sulfate and hyaluronic acid in all types of gingival tissues examined. In addition, hyaluronic acid was predominantly of a large size eluting near to the void volume of a Superose‐6 column, while the sulfated glycosaminoglycans were mainly composed of low molecular size glycosaminoglycans. Our results show no differences in the molecular‐size distribution of hyaluronic acid and sulfated glycosaminoglycans among healthy and drug‐induced overgrown gingival tissues.
Treatment of Distal Colitis with Local Anaesthetic Agents
Authors: Björck Stellan , Dahlström Annica , Ahlman Håkan
Published: March 2003

Abstract: The results of clinical and experimental studies on topical treatment of distal colitis with local anaesthetic agents are summarized. The original observation was an adrenergic hyperinnervation of the inflamed mucosa (hyperinnervation hypothesis). In order to silence local nervous reflexes, the mucosa was treated topically with 2% lidocaine gel. The clinical results are promising and no side effects have been observed. The relapse rate is relatively high and related to the duration of treatment. In studies of experimental colitis a potential antagonism between harmful adrenergic nerves (vasoconstrictor substances and proinflammatory cytokines) and mucosa‐protective visceral afferents (antiinflammatory cytokines) in the pathogenesis of colitis is intriguing. Other studies have emphasized the importance of neutrophils for causing damage to the colon epithelium (neutrophil hypothesis) and local anaesthetics have potent effects on several steps of the inflammatory response in addition to the nervous blockade.
Bioavailability of Reduced Nicotinamide‐adenin‐dinucleotide (NADH) in the Central Nervous System of the Anaesthetized Rat Measured by Laser‐Induced Fluorescence Spectroscopy
Authors: Rex André , Hentschke Mike‐Percy , Fink Heidrun
Published: March 2003

Abstract: Drugs intended to increase wellness or quality of life (“lifestyle drugs“) have gained popularity and/or importance over recent years. Biogenic substances like nicotinamide adenine dinucleotide (NADH) are supposed to increase the physical and intellectual performance without side‐effects. NADH is an energy‐delivering co‐substrate in the respiratory chain. Clinical studies showed positive effects of peripherally given NADH in Morbus Parkinson and major depression. NADH can be measured by its fluorescence. In this study a pulsed N2‐laser combined with a fibre‐optic probe and photomultipliers was used to induce and measure NADH fluorescence in the rat cortex. The aims of the study were to assess the suitability of the laser‐induced spectroscopy for in vivo and on‐line measurement of NADH in neuroscience and the assessment of the central availability of NADH after peripheral administration. NADH (50 mg/kg) but not the precursor nicotinamide caused a significant rise of the NADH fluorescence intensity indicating an increase of the NADH concentration in the rat cortex. In conclusion, the results suggest that NADH given orally or intraperitoneally increases the amounts of NADH in the brain. The results may thus help to explain the clinical effects reported.
Influence of Chloramphenicol on Rat Hepatic Microsomal Components and Biomarkers of Oxidative Stress: Protective Role of Antioxidants
Authors: Farombi E. Olatunde , Adaramoye Oluwatosin A. , Emerole Godwin O.
Published: March 2003

Abstract:The effects of chloramphenicol and antioxidant vitamins onin vivoandin vitroindices of microsomal drug oxidizing system were examined in rats. Chloramphenicol at doses of 28 mg/kg, 57 mg/kg and 86 mg/kg body weight administered for 10 consecutive days resulted in a dose‐dependent decrease in body weight, liver weight, relative liver weight and protein content compared to control. Chloramphenicol treatment also resulted in a dose‐dependent decrease in microsomal phospholipid and a significant increase in cholesterol content causing an increase in cholesterol/phospholipid molar ratio. The drug produced a significant reduction in the activity of aniline hydroxylase, aminopyrineN‐demethylase, p‐nitroanisoleO‐demethylase and ethoxyresorufinO‐deethylase. Activity of ethoxyresorufinO‐deethylase was little affected by the drug. Chloramphenicol ranging from 10−4–10−6M similarly produced a concentration dependent inhibition in the activities of the enzymes. Kinetic studies revealed that chloramphenicol inhibited the enzymes non‐competitively. α‐Tocopherol, β‐carotene and ascorbic acid decreased the chloramphenicol inhibition of the enzymes within the range of 70 to 81%, 45–63% and 55 to 75% respectively. Also, the antioxidant vitamins attenuated the chloramphenicol‐induced formation of malondialdehyde by 60%, 53% and 56% and lipid hydroperoxide by 60%, 54%, and 54% respectively The results indicate that the effect of chloramphenicol on cytochrome P450 drug oxidizing enzyme components is related to the action of the drug presumably, via free radical mechanism and that co‐administration with antioxidant vitamins can attenuate its toxic action.
Cholecystokinin Activates a Variety of Intracellular Signal Transduction Mechanisms in Rodent Pancreatic Acinar Cells
Authors: Williams John A. , Dolors Sans M. , Tashiro Mitsuo , Schäfer Claus , Bragado M. Julia , Dabrowski Andrzej
Published: March 2003

Abstract: Cholecystokinin (CCK) acting through its G protein‐coupled receptor is now known to activate a variety of intracellular signaling mechanisms and thereby regulate a complex array of cellular functions in pancreatic acinar cells. The best studied mechanism is the coupling through heterotrimeric G proteins of the Gq family to activate a phospholipase C leading to an increase in inositol trisphosphate and release of intracellular Ca2+. This pathway along with protein kinase C activation in response to the increase in diacylglycerol stimulates the secretion of digestive enzymes by the process of exocytosis. CCK also activates signaling pathways in acini more related to other processes. The three mitogen activated protein kinase cascades leading to ERKs, JNKs and p38 MAPK are all activated by CCK. CCK activates the ERK cascade by PKC activation of Raf which in turn activates MEK and ERKs. JNKs are activated by a distinct mechanism whish requires higher concentrations of CCK. Both ERKs and JNKs are presumed to regulate gene expression. CCK activation of p38 MAPK also plays a role in regulating the actin cytoskeleton through phosphorylation of the small heat shock protein HSP27. The PI3K‐PKB‐mTOR pathway is activated by CCK and plays a major role in regulating protein synthesis at the translational level. This includes both activation of p70 S6K leading to phosphorylation of ribosomal protein S6 and the phosphorylation of the binding protein for initiation factor 4E leading to formation of the mRNA cap binding complex. Other signaling pathways activated by CCK receptors include NF‐κB and a variety of tyrosine kinases. Further work is needed to understand how CCK receptors activate most of the above pathways and to better understand the biological events regulated by these diverse signaling pathways.
Some Aspects on the Anatomy and Function of Central Cholecystokinin Systems
Authors: Hökfelt Tomas , Blacker David , Broberger Christian , Herrera‐Marschitz Mario , Snyder Gretchen , Fisone Gilberto , Cortés Roser , Morino Patrizia , You Zhi‐Bing , Ögren Sven Ove
Published: March 2003

Abstract:The distribution of some cholecystokinin (CCK) systems in the rat brain is reviewed focusing on mesencephalic dopamine neurones which coexpress CCK and, in particular, on cortico‐striatal CCK neurones which probably have glutamate as their co‐transmitter. Functional studies based on the effect of several CCKBantagonists on phencyclidine‐induced motility suggest that CCK is involved in locomotor behaviour causing inhibition in phencyclidine‐treated habituated rats. In contrast, in unhabituated rats CCK stimulates exploratory behaviour. These effects may be related to the cortico‐striatal CCK/glutamatergic pathway. Moreover, these studies provide evidence for endogenous release of a neuropeptide with behavioural consequences.
The Involvement of P‐Glycoprotein in Berberine Absorption
Authors: Pan Guo‐yu , Wang Guang‐Ji , Liu Xiao‐Dong , Fawcett J. Paul , Xie Yuan‐Yuan
Published: March 2003

Abstract: Berberine is an important ingredient in a number of traditional Chinese medicines but has been shown to have poor bioavailability in the dog. The aim of this study was to use the P‐glycoprotein (P‐glycoprotein) inhibitors cyclosporin A, verapamil and the monoclonal antibody C219 in in vivo and in vitro models of intestinal absorption to determine the role of P‐glycoprotein in berberine absorption. In the rat recirculating perfusion model, berberine absorption was improved 6‐times by P‐glycoprotein inhibitors. In the rat everted intestinal sac model, berberine serosal‐to‐mucosal transport was significantly decreased by cyclosporin A. In Ussing‐type chambers, the rate of serosal‐to‐mucosal transport across rat ileum was 3‐times greater than in the reverse direction and was significantly decreased by cyclosporin A. In Caco‐2 cells, berberine uptake was significantly increased by P‐glycoprotein inhibitors and by monoclonal antibody C219. P‐glycoprotein appears to contribute to the poor intestinal absorption of berberine which suggests P‐glycoprotein inhibitors could be of therapeutic value by improving its bioavailability.
Molecular mechanisms of UV‐induced apoptosis
Authors: Kulms D. , Schwarz T.
Published: March 2003

Sunburn cells, single standing cells with typical morphologic features occurring in UV‐exposed skin, have been recognized as keratinocytes undergoing apoptosis following UV irradiation. Induction of apoptosis following UV exposure appears to be a protective mechanism, getting rid off severely damaged cells that bear the risk of malignant transformation. UV‐mediated apoptosis is a highly complex process in which different molecular pathways are involved. These include DNA damage, activation of the tumor suppressor gene p53, triggering of cell death receptors either directly by UV or by autocrine release of death ligands, mitochondrial damage and cytochrome C release. Detailed knowledge about the interplay between these pathways will increase our understanding of photocarcinogenesis. This review briefly discusses recent findings concerning the molecular mechanisms underlying UV‐induced apoptosis.
Successful treatment of solar urticaria by extracorporeal photochemotherapy (photopheresis) – a case report
Authors: Mang R. , Stege H. , Budde M.‐A. , Ruzicka T. , Krutmann J.
Published: March 2003

Abstract: Solar urticaria is characterized by erythema and whealing immediately after exposure to ultraviolet radiation and/or visible light. We report about a patient with severe solar urticaria, who was highly sensitive to both UVA radiation and visible light with a Minimal Urticaria Dose (MUD) of 7 J/cm2 UVA. Management of this patient was extremely difficult because standard treatment with oral antihistamines, hardening with UVA, UVB, visible light or oral PUVA and even oral cyclosporin A were completely ineffective. We therefore decided to perform extracorporeal photochemotherapy (photopheresis, ECP). After nine treatment cycles with photopheresis the MUD increased from 7 J/cm2 UVA before treatment to 22 J/cm2 UVA. This hardening effect was associated with a significant decrease of the frequency and severity of whealing and the accompanying symptoms (pain, fatigue, pruritus).

Conclusion: Photopheresis might be of some benefit in selected patients with otherwise intractable solar urticaria.
Changes of photosensitivity and action spectrum with time in solar urticaria
Authors: Ng Jonathan C. H. , Foley Peter A , Crouch Rohan B , S. Baker Christopher
Published: March 2003

Background: Solar urticaria is a rare photosensitivity disorder characterized by the rapid onset of a pruritic, erythematous and urticarial rash following sun‐exposure. The action spectrum and degree of photosensitivity have been observed to change over time in several isolated reports.

Methods: Monochromator phototesting was performed on multiple occasions on 12 patients with solar urticaria.

Results: Six patients demonstrated normal responses in the initial phototest. They remained normal in five patients upon subsequent testing. Seven patients demonstrated abnormal immediate responses, most frequently at UVA wavelengths. Within some individuals, variations in action spectrum and/or degree of photosensitivity were observed over the years, but not over days.

Conclusion: Significant changes in action spectrum and degree of photosensitivity may occur over years in solar urticaria. However, changes over shorter periods of time are likely to be minor and not have clinical significance.
002 Multiple exposures to blue light does not improve psoriasis in patients with elevated endogenous levels of protoporphyrin IX
Authors: Maari C. , Bissonnette R.
Published: March 2003

Endogenous levels of protoporphyrin IX (PpIX) are known to be elevated in psoriatic plaques. Activation of PpIX by visible light after topical application of aminolevulinic acid has been shown to improve psoriasis. This study was designed to determine whether multiple exposures to blue light alone could improve psoriasis in patients exhibiting elevated endogenous PpIX levels.

Patients and methods: Seventeen patients with at least two psoriatic plaques of 4 × 4 cm exhibiting elevated endogenous PpIX levels (as detected by in vivo fluorescence spectroscopy) were included in the study. Patients were required to discontinue all topical therapies for at least 2 weeks and systemic therapy for at least 8 weeks before treatment. One of the two plaques on each patient was exposed to 10 J/cm2 Of blue light from a fluorescence panel three times per week for 4 consecutive weeks. The other plaque was used as a non‐exposed control. Blinded clinical evaluations were performed at baseline and every week during the 4‐week treatment period as well as at 1 and 3 weeks after the last exposure. Psoriasis severity was assessed by evaluating on a scale of 0–4 the presence of erythema, induration, and desquamation. PpIX levels were measured before and after light exposure by in vivo fluorescence spectroscopy at week 1 and 4.

Results: All patients completed the study without presenting treatment related side‐effects. In vivo fluorescence spectroscopy demonstrated an almost complete photobleaching of PpIX in exposed plaques immediately after light exposure (P = 0.005). There was no significant difference between the mean psoriasis severity score of the exposed or control plaques before and after 12 exposures to blue light.

Conclusion: Under the current conditions multiple exposures to blue light did not improve psoriasis.
Ototoxicity caused by cisplatin is ameliorated by melatonin and other antioxidants
Authors: Lopez‐Gonzalez Miguel A. , Guerrero Juan M. , Rojas Francisco , Delgado Francisco
Published: March 2003

The mechanism of the ototoxicity caused by cisplatin is based in the generation of reactive oxygen species, which interferes with the antioxidant protection of the organ of Corti. Conversely, the protection of the cochlea with antioxidants ameliorates the ototoxicity by cisplatin. The ototoxicity produced by cisplatin can be reversible or persistent, depending on the age of the patient, cumulative doses, number of chemotherapy cycles, history of noise exposure, and deteriorating renal function. We have obtained in rats an ototoxic chart utilizing cisplatin (10 mg/kg body weight injected intraperitoneally, once only). Together with this treatment, the animals were treated with melatonin in the drinking water (10 mg/L) or injected subcutaneously (250 μg), and with an antioxidant mixture, injected subcutaneously, composed of 0.25 mg alpha‐tocopherol acid succinate, 3 mg ascorbic acid, 1 mg glutathione, and 60 mg N‐acetylcysteine. The distortion product otoacoustic emissions were determined for a prolonged period of time for each animal. The ototoxicity produced by cisplatin was maximal from days 7 to 10 post‐treatment, returning to normal values in a month. When melatonin and the antioxidant mixture were present, the recovery was between days 10 and 15 post‐treatment, independent of the means of administration of the pineal product. We conclude that the ototoxicity caused by cisplatin is ameliorated by melatonin and other antioxidants.
Changes in nocturnal melatonin secretion in perimenopausal women: Correlation with endogenous estrogen concentrations
Authors: Okatani Yuji , Morioka Nobuyuki , Wakatsuki Akihiko
Published: March 2003

Although age‐related decrease in melatonin secretion in humans and animals is well documented, there is a paucity of data on the precise changes in melatonin secretion that occur during the perimenopausal period. The present study was designed to measure changes in nocturnal melatonin and to characterize the role played by estrogen in controlling nocturnal melatonin secretion in perimenopausal women. Nocturnal serum melatonin concentrations were determined every 2 hr in 46 premenopausal women, 44 postmenopausal women, and 11 premenopausal women with uterine leiomyoma scheduled for hysterectomy and bilateral salpingo‐oophorectomy. Nocturnal serum melatonin secretion in premenopausal women declined moderately from 17 to 45 years of age, and increased during the period from 46 to 50 years of age. Among postmenopausal women, a steep, age‐related decline in nocturnal melatonin secretion was found for up to 15 years postmenopause, followed by an extremely gradual decline thereafter. A significant negative correlation was observed between the peak serum melatonin concentration and the serum 17 β‐estradiol concentration in premenopausal women aged 40–50 years (r=−0.661, P<0.0005). Daily oral administration of
conjugated estrogen (0.625 mg) to postmenopausal women suppressed
nocturnal melatonin secretion (P<0.005). A low estrogen state,
induced by oophorectomy of premenopausal women with uterine leiomyoma led
to an increase in nocturnal melatonin secretion (P<0.0001). Our findings suggest that transient elevated nocturnal melatonin secretion during menopause may be related to the existence of a low estrogen environment. The age‐related decrease in melatonin secretion observed in other conditions is most likely attributable to other age‐related factors.
Melatonin stimulates glutathione peroxidase activity in human chorion
Authors: Okatani Yuji , Wakatsuki Akihiko , Shinohara Koichi , Kaneda Chitose , Fukaya Takao
Published: March 2003

In preeclampsia, placental production of lipid peroxides is abnormally increased, while placental glutathione peroxidase (GSH‐Px) and superoxide dismutase (SOD) activities are decreased. Administration of melatonin, a powerful scavenger of oxygen free radicals, also may protect the placenta from free radical‐induced damage by increasing the activity of antioxidant enzymes. To test this hypothesis we administered melatonin to pregnant women before they underwent voluntary interruption of pregnancy between 7 and 9 wk of gestation. Melatonin (6 mg) was administered orally at 12:00 hr, and samples of chorion and maternal blood were obtained at the time of the procedure, 1, 2 or 3 hr later. We measured the melatonin concentration in maternal serum and activities of GSH‐Px and SOD and levels of melatonin in chorionic homogenates. Melatonin administration was reflected by markedly increased melatonin concentrations in maternal serum and in chorion, with peak levels achieved 1 hr after melatonin administration (serum, 46.87±10.87 nM/L; chorionic homogenate, 4.36±1.56 pmol/mg protein). Between 1 and 3 hr after melatonin administration, GSH‐Px activity in chorionic homogenates increased significantly (P<0.001), with peak levels occurring at 3 hr (51.68±3.22 mU/mg protein per min, 137.3% of GSH‐Px activity in untreated control subjects). No significant changes in chorionic SOD activity occurred during the 3‐hr post‐administration period. These results indicate that exogenous melatonin increases GSH‐Px activity in the chorion and thereby may protect indirectly against free radical injury. Melatonin could be useful in treating preeclampsia and possibly other clinical states involving excessive free radical production, such as intrauterine fetal growth retardation and fetal hypoxia.
Endogenous rhythms of melatonin, total antioxidant status and superoxide dismutase activity in several tissues of chick and their inhibition by light
Authors: Albarrán M.T. , López‐Burillo S. , Pablos M.I. , Reiter R.J. , Agapito M.T.
Published: March 2003

Melatonin was recently shown to be a component of the antioxidative defense system of organisms due to its free radical scavenging ability and to its capacity to stimulate several antioxidant enzymes. In this report, we studied the endogenous rhythm of the antioxidant enzyme superoxide dismutase (SOD) in three different tissues (cerebral cortex, liver and lung) of chick (Gallus domesticus) (three weeks, at age and sacrificed every 2 hr). During the study the chicks were under a light:dark cycle of 12:12. Total antioxidant status of the plasma was correlated with physiological blood melatonin concentrations. Superoxide dismutase activity exhibited a marked 24 hr rhythm in cerebral cortex, lung and liver, with peak activity coincident with the melatonin and total antioxidant status peaks. The exposure of chicks to constant light for 7 days eliminated the melatonin rhythm as well as the peaks in superoxide dismutase activity and the total antioxidant status. These findings suggest that the melatonin rhythm may be related to the nighttime increase in the superoxide dismutase activity and to total antioxidant capacity of the blood.
Melatonin inhibits lipid peroxidation and stimulates the antioxidant status of diabetic rats
Authors: Vural Hüseyin , Sabuncu Tevfik , Arslan S. Oktay , Aksoy Nurten
Published: March 2003

Although melatonin has been established as a free radical scavenger and antioxidant, its effects in diabetes have not been thoroughly investigated. The purpose of this study, therefore, was to investigate the effects of melatonin administration on lipid peroxidation and antioxidant status in streptozotocin (STZ)‐induced diabetes in rats. Concentrations of malondialdehyde (MDA) and reduced glutathione (GSH) in erythrocytes and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH‐Px) were compared in 3 groups of 10 rats each [control non‐diabetic rats (group I), untreated diabetic rats (group II) and diabetic rats treated with melatonin (group III)]. In the study groups, diabetes developed 3 days after intraperitoneal (i.p.) administration of a single 60‐mg/kg dose of STZ. Thereafter, while the rats in group II received no treatment, the rats in group III began to receive a 10‐mg/kg i.p. dose of melatonin per day. After 6 wk, the rats in groups II and III had significantly lower body weights and significantly higher blood glucose levels than the rats of group I (P<0.001 and P<0.001, respectively). There were no significant differences in body weight or blood glucose levels between groups II and III. MDA levels in untreated diabetic rats were higher than those in control group rats and in diabetic rats treated with melatonin (P<0.01 and P<0.05, respectively). However, MDA levels in diabetic rats treated with melatonin were not different from those of the control group. The GSH, GSH‐Px and SOD levels of untreated diabetic rats were significantly lower than those of the control group (P<0.02, P<0.002 and P<0.05, respectively). In group III, however, melatonin prevented decreases in the thiol antioxidant and the associated enzymes, and so these levels were not significantly different from those in the control group. These results confirm the presence of oxidative stress in STZ‐induced experimental diabetes and indicate the beneficial free radical‐scavenging and antioxidant properties of melatonin.
Potentiation of antiproliferative effects of tamoxifen and ethanol on mouse hepatoma cells by melatonin: possible involvement of mitogen‐activated protein kinase and induction of apoptosis
Authors: Hermann R. , Podhajsky S. , Jungnickel S. , Lerchl A.
Published: March 2003

Melatonin, the major secretory product of the pineal gland, is in focus of many research areas because of its ability to scavenge free oxygen radicals and thereby protect cells and tissues from radical damage. Some studies suggest melatonin may be a possible therapeutic agent with potential clinical applications against pathological states due to reactive oxygen species. Here, we investigated the effects of melatonin on the mouse hepatoma cell line HEPA 1–6, coincubated with ethanol, and tamoxifen, respectively. Cell proliferation rates were detected by the 3‐[4,5 dimethylthiazol‐2‐y1]‐2,5‐diphenyltetrazolium bromide (MTT) proliferation assay. A dose‐dependent inhibition of the proliferative activity by melatonin was observed from 640 μMto 3 mM, which was significantly higher (P < 0.01) than with the solvent (ethanol) alone. Concentrations of 320 μMand less had no effect on cell proliferation. This antiproliferative effect might be because of the prolonged activation of mitogen‐activated protein kinase which was activated by phosphorylation 15 min after the induction with melatonin. Furthermore, apoptosis was found to be enhanced by melatonin (75% more than with the solvent alone,P < 0.001). Finally, we show that the inhibitory effect of tamoxifen (25 μM) is markedly enhanced by the coincubation with melatonin (1.3 mM) up to 75% (P < 0.001). These data show that the antiproliferative effects of tamoxifen and ethanol, respectively, on mouse hepatoma cell line HEPA 1–6 are enhanced by melatonin. Although at the conditions described here the antiproliferative effects of melatonin occur at supraphysiological concentrations, these data may help to support clinical studies where melatonin is given simultaneously with tamoxifen or other standard chemotherapeutica.
Comparative analysis of the protective effects of melatonin and vitamin E on streptozocin‐induced diabetes mellitus
Authors: Baydas Giyasettin , Canatan Halit , Turkoglu Abdulbaki
Published: March 2003

There is a clearly documented link between diabetic complications and lipid peroxidation. Hyperglycemia causes a reduction in levels of protective endogenous antioxidants and increases generation of free radicals. The present study was carried out to compare the protective effects of melatonin and vitamin E against streptozocin (STZ)‐induced diabetes in rats. Melatonin was administered s.c. (100 μg/kg) whereas vitamin E was given i.p. (100 mg/kg) after induction of diabetes with STZ (60 mg/kg). Plasma total cholesterol, triglyceride and low density lipoprotein (LDL) levels were increased in STZ group while both melatonin and vitamin E injection caused a significant decrease in the levels of all these parameters. The lipid lowering effect of melatonin was greater than that of vitamin E. Melatonin caused a significant decrease in brain, liver and kidney tissue malondialdehyde (MDA) levels which were increased because of STZ‐induced diabetes. Vitamin E also reduced elevated MDA concentrations in diabetic rat tissues, but the effect of melatonin was more potent than that of vitamin E. Furthermore, treatment of diabetic rats with melatonin increased brain and kidney glutathione peroxidase (GSH‐Px) activity to the levels below that of control rats. Vitamin E was found to be less effective on GSH‐Px activity levels in brain and kidney than melatonin whereas it was more potent than melatonin in liver. In summary, melatonin prevents many diabetic complications by reducing oxidative stress and protects organisms from oxidative damage and dyslipidemia. Considering the much lower molar concentration of melatonin compared with vitamin E, melatonin seems to be a more potent antioxidant, especially in the brain and kidney.
Physiological and pharmacological concentrations of melatonin protect against cisplatin‐induced acute renal injury
Authors: Parlakpinar Hakan , Sahna Engin , Ozer M. K. , Ozugurlu Fikret , Vardi Nigar , Acet Ahmet
Published: March 2003

Abstract: Abstract: Cisplatin [cis‐diaminedichloroplatinum(II), CDDP] is a widely used antineoplastic drug. However, it has major side‐effects such as acute tubular necrosis (ATN). There are a number of studies concerning the role of reactive oxygen radical species in the pathophysiology of CDDP‐dependent ATN. Several antioxidant agents have been reported to prevent this side‐effect but there is no study regarding the protective action of either physiological or pharmacological concentrations of melatonin. Melatonin, the chief secretory product of the pineal gland, is a direct free radical scavenger and indirect antioxidant. We investigated the effects of melatonin on CDDP‐induced changes of renal malondialdehyde (MDA), a lipid peroxidation product, and blood urea nitrogen (BUN) and serum creatine (Cr). The morphological changes in kidney were also examined using light microscopy. The rats were divided into two groups: pinealectomized (Px) and sham‐operated (non‐Px). Both CDDP and melatonin were administered to all groups. MDA levels were found to be higher in Px than non‐Px animals. CDDP administration to Px or non‐Px rats increased renal MDA levels and melatonin administration either before or after CDDP injection caused significant decreases in MDA in kidney compared with those in rats treated with CDDP alone. Serum levels of BUN and Cr did not change as a result of any treatment. Morphological tubule damage because of CDDP was more severe in the renal cortex than in the medulla. The damage to the kidney induced by CDDP was reversed by melatonin. The results show that pharmacological and physiological concentrations of melatonin reduce CDDP‐induced renal injury.
Melatonin receptors in human fetal brain: 2‐[125I]iodomelatonin binding and MT1 gene expression
Authors: Thomas Louise , Purvis Cheryl C. , Drew Janice E. , Abramovich David R. , Williams Lynda M.
Published: March 2003

Abstract: The purpose of this study was to identify sites of action of melatonin in the human fetal brain by in vitro autoradiography and in situ hybridization. Specific, guanosine triphosphate (GTP) sensitive, binding of 2‐[125I]iodomelatonin was localized to the leptomeninges, cerebellum, thalamus, hypothalamus, and brainstem. In the hypothalalmus, specific binding was present in the suprachiasmatic nuclei (SCN) as well as the arcuate, ventromedial and mammillary nuclei. In the brainstem specific binding was present in the cranial nerve nuclei including the oculomotor nuclei, the trochlear nuclei, the motor and sensory trigeminal nuclei, the facial nuclei, and the cochlear nuclei. The localization of MT1 receptor subtype gene expression as determined by in situ hybridization matched the localization of 2‐[125I]iodomelatonin binding. No MT2 receptor subtype gene expression was detected using this technique. Thus, melatonin may act on the human fetus via the MT1 receptor subtype at a number of discrete brain sites. A major site of action of melatonin in both fetal and adult mammals is the pars tuberalis of the pituitary gland. However, no 2‐[125I]iodomelatonin binding or melatonin receptor gene expression was detected in the pituitary gland in the present study, indicating that the pituitary, particularly the pars tuberalis, is not a site of action of melatonin in the human fetus.
Influence of light intensity, spectrum and orientation on sea bass plasma and ocular melatonin
Authors: Bayarri M.J , Madrid J.A , Sánchez‐Vázquez F.J
Published: March 2003

Melatonin is involved in the transduction of light information and the photoperiodic control of many important physiological functions in fish. Although artificial photoperiods have been used to improve fish growth and manipulate reproduction, there is little information about the characteristics of light `quality'. In this paper we describe the effects of a light pulse in the middle of the dark phase on plasma and ocular melatonin in European sea bass. We first determined the light intensity necessary to elicit a melatonin response using white light of varying intensities (0.6–600 μW/cm2, experiment 1). Secondly, we tested the effect of the light spectrum on melatonin production using three differently coloured lights (half‐peak bandwidth=434–477, 498–575 and 610–687 nm for the blue, green and red lamp, respectively, experiment 2) and, finally, we determined the effect of light orientation (downwards directed versus upwards directed, experiment 3). The results show that the minimum light intensity needed to inhibit or stimulate melatonin levels in both plasma and the eye was 6.0 μW/cm2. A linear correlation was found between the logarithm of light intensity and the relative inhibition. In addition, the blue wavelength was more effective in decreasing melatonin levels in the former and increasing the levels in the latter. Nevertheless, red light at sufficient intensity proved effective at significantly suppressing circulating melatonin. Downwards light had a greater effect than upward‐directed illumination in suppressing plasma melatonin. In conclusion, the results point to the importance of giving proper consideration to the characteristics of light, to adequately control melatonin production and its related physiological processes.
On the in vitro antioxidative properties of melatonin
Authors: Gulcin Ilhami , Buyukokuroglu Mehmet E. , Oktay Munir , Kufrevioglu O. Irfan
Published: March 2003

Abstract:The aim of this study is to examine possible in vitro antioxidant effects of melatonin. Thus, the total in vitro antioxidant activity of melatonin was studied using a thiocyanate method. Additionally, the reducing power, the superoxide anion scavenging activity and free radical scavenging activity of melatonin were determined. Melatonin exhibited potent antioxidant activity in a linoleic acid emulsion system. The antioxidant activity increased with increasing concentrations of melatonin (50–500 μg). The 50, 100, 250 and 500 μg melatonin doses showed 41, 60, 86 and 99% inhibition of peroxidation of linoleic acid, respectively. On the other hand, a 500‐μg dose of α‐tocopherol showed 34% inhibition of peroxidation of linoleic acid. Like the total antioxidant activity, the reducing power of melatonin increased in a dose‐dependent manner. The reducing power of melatonin was statistically significant versus control, but lower than butylated hydroxytoluene (BHT) or quercetin. Additionally, melatonin had potent superoxide radical scavenging activity and exhibited a higher superoxide radical scavenging activity than quercetin or BHT but lower than butylated hydroxyanisole (BHA). Melatonin's direct free radical scavenging actions may account, at least in part, for its ability to reduce lipid peroxidation. Melatonin may have utility in protecting stored foods from free radical‐induced deterioration.
Melatonin exerts a therapeutic effect on cholestatic liver injury in rats with bile duct ligation
Authors: Ohta Yoshiji , Kongo Mutsumi , Kishikawa Teruaki
Published: March 2003

Abstract: We examined whether melatonin exerts a therapeutic effect on cholestatic liver injury in rats treated with bile duct ligation (BDL). Cholestatic liver injury was induced in male Wistar rats aged 4 wk by ligating the bile duct. Cholestatic liver injury developed 5 days after BDL and continued to 13 days, judging from the levels of serum hepatobiliary injury markers. The serum concentration of thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation, and the hepatic level of TBARS and the activity of hepatic myeloperoxidase, an index of tissue neutrophil infiltration, increased 5 days after BDL, and these increases were enhanced at 13 days. A similar increase in the serum total cholesterol concentration occurred 5 and 13 days after BDL, while the hepatic cholesterol concentration tended to increase at 13 days. When melatonin [10 or 100 mg/kg body weight (BW)] was orally administered to BDL‐treated rats everyday for 8 days, starting 5 days after BDL, the indoleamine attenuated cholestatic liver injury observed at 13 days after BDL was more effective at the higher dose than at the lower dose. The administered melatonin (10 or 100 mg/kg BW) reduced the increases in serum and hepatic TBARS concentrations and hepatic myeloperoxidase activity observed at 13 days after BDL and the higher dose of indoleamine was more effective than the lower dose. Neither dose of melatonin affected the increased serum total cholesterol concentration or the hepatic cholesterol concentration observed at 13 days after BDL. These results indicate that orally administered melatonin at pharmacological doses exerts a therapeutic effect on cholestatic liver injury in rats with BDL possibly through its antioxidant and anti‐inflammatory actions.