Wyniki wyszukiwania - Biblioteka Nauki

1

Morphological investigations of the winter coat in white-tailed deer: Differences in skin, glands and hair structure of various body regions

100%

Bubenik G. A.

Acta Theriologica

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1996

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tom 41

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nr 1

EN

Skin and hair samples taken from seven body areas of a winter hair coat of a male and a female yearling white-tailed deer Odocoileus virginianus Zimmerman, 1780 were investigated morphologically. The color, length, diameter, density and relative proportion of guard and wooly hair was determined from the histological sections. In addition, the epidermal thickness, and the shape, density, location and structure of sebaceous and sudoriferous glands were also determined .A reciprocal relationship was found between the insulation values of the pelage, the epidermal thickness and the amount of either gland. The areas known to provide the best insulation (the tail and the belly) exhibited the thinnest epidermis, the highest density of hair and the highest concentration of sebaceous glands. In reverse, the region with the lowest insulation capacity (the leg) exhibits the thickest epidermis, the lowest hair density and the highest amount of sudoriferous glands.

2

Thirty four years since the discovery of gastrointestinal melatonin

100%

Bubenik G. A.

Journal of Physiology and Pharmacology. Supplement

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2008

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tom 59

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nr 2

EN

After the discovery of melatonin in the pineal gland by Lerner and co-workers in 1958, melatonin was also detected in the retina and the human appendix. Later, melatonin was confirmed immunohistologically in all segments of the gastrointestinal tract (GIT), in the guts of bovine embryos and in the GIT of low vertebrates. Melatonin was also confirmed in the pancreas and the hepatobilliary system. Melatonin is produced in the enteroendocrine cells of the GIT mucosa. The concentrations of melatonin in the GIT are 10-100x higher than in the plasma and the total amount of melatonin in the GIT is around 400x higher than the amount of melatonin in the pineal gland. Similar to pineal melatonin, GIT melatonin is a multifunctional compound which exhibits some general as well as some specific effects, depending on the organ and the location of GIT tissue. In the GIT, melatonin exhibits endocrine, paracrine, autocrine and luminal actions. Generally, the episodic secretion of melatonin from the GIT is related to the intake and digestion of food and to the prevention of tissue damage caused by hydrochloric acid and digestive enzymes. Some actions, such as the scavenging of hydroxyl free radicals, immunoenhancement and antioxidant effects are of general nature, whereas others, such as an increase of mucosal blood flow, the reduction of peristalsis and the regulation of fecal water content, are specific to the tubular GIT. Generally, melatonin actions oppose those of serotonin. Laboratory and clinical studies indicate that the utilization of melatonin can prevent or treat pathological conditions such as esophageal and gastric ulcers, pancreatitis, colitis, irritable bowel disease, and colon cancer.

3

Melatonin and aging: prospects for human treatment

63%

Bubenik G. A. , Konturek S. J.

Journal of Physiology and Pharmacology

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2011

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tom 62

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nr 1

EN

Human life span, with or without modern medicine is around 85-95 years. All living creatures have their inner clock that measures their daily (circadian) and their seasonal (circannual) time. These time changes are mediated by the alteration of levels of melatonin, an evolutionary ancient hormone, which is produced in many body tissues, including the pineal gland, retina and the gastrointestinal tract (GIT). Light is blocking the production of melatonin in the pineal gland, darkness is stimulating it. So, the diurnal changes of light intensity of melatonin, provide a "daily clock" and the seasonal changes provide a "seasonal clock". Finally, the reduction of melatonin observed with aging, may indicate the presence of an "age clock". Melatonin is a strong antioxidant (often it is called scavenger of free radicals), which protects the body from the effects of noxious compounds. Therefore it was hypothesized that the reduction of melatonin levels with age contributes to the aging process. So far, the only remedy to extend the life span was a 40% reduction in caloric intake, which prolonged the life in mice, rats, dogs and monkeys by 30-50%. A large group of people imitate these experiments performed on animals, but the results of these experiments will not be known for several decades. How is being hungry prolonging the life span? There is a connection between caloric reduction and melatonin levels in GIT. Several experiments indicate that fasting in animals substantially increased their production of GIT melatonin. Therefore, instead of being permanently hungry, a prolongation of human life could be achieved by a replacement melatonin therapy. A daily intake of melatonin before bed time might achieve the same effect as fasting e.g. an increase of body melatonin levels, which will protect the individual from the ravages of old age. That includes Parkinson's disease and Alzheimer's disease. There is a large group of people taking melatonin daily who believe that melatonin is the "fountain of youth". Those are the subjects which will one day provide an experimental evidence of the efficacy of melatonin.

4

Role of melatonin in upper gastrointestinal tract

51%

Konturek S. J. , Konturek P. C. , Brzozowski T. , Bubenik G. A.

Journal of Physiology and Pharmacology. Supplement

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2007

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tom 58

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nr 6

5

Seasonal changes of testicular parameters in southern pudu Pudu puda in relationship to circannual variation of its reproductive hormones

44%

Reyes E. , Bubenik G. A. , Schams D. , Lobos A. , Enriquez R.

Acta Theriologica

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1997

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tom 42

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nr 1

EN

Seasonal variation of testicular and epididymal parameters in the smallest deer, the southern pudu Pudu puda Molina, 1782 were related to the circannual fluctuation of plasma levels of its reproductive hormones. The diameter and the length of testes, the diameter of epididymis as well as the diameter and the heights of epithelium of seminiferous and epididymal tubules were measured, Morphological evaluation of spermatogenesis were performed on histological sections of testicular and epididymal tissues. Most of these gonadal parameters exhibit a seasonal variation which is in accordance with the reproductive pattern as well as the variation of reproductive hormones. Seasonal fluctuations of LH and testosterone indicate two seasonal activations of the reproductive system, one in the spring (antler mineralization), the other in the fall (rut), FSH exhibit one prolonged peak (summer to fall) whereas prolactin follows the expected, photoperiodically-dependant time course with peak levels around the summer solstice, The measurements of testicular parameters indicate a prolonged period of gonadal activity in southern pudu but the period of maximal reproductive stimulation is limited to the time around the rut.

6

Localization and biological activities of melatonin in intact and diseased gastrointestinal tract (GIT)

32%

Konturek S. J. , Konturek P. C. , Brzozowska I. , Pawlik M. , Sliwowski Z. , Czesnikiewicz-Guzik M. , Kwiecien S. , Brzozowski T. , Bubenik G. A. , Pawlik W. W.

Journal of Physiology and Pharmacology

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2007

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tom 58

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nr 3

EN

Melatonin (MT), an indole formed enzymatically from L-trytophan (Trp), was first discovered in the bovine pineal gland in 1958 by Lerner et al. Melatonin is the most versatile and ubiquitous hormonal molecule produced not only in the pineal gland but also in various other tissues of invertebrates and vertebrates, particularly in the gastrointestinal tract (GIT). This review focuses on the localization, production, metabolism and the functions of MT in GIT and the duodenal unit (liver, biliary routes and pancreas), where multi-step biosynthetic pathways of this indole, similar to those in pinealocytes, have been identified. These biosynthetic steps of MT, including two major rate limiting enzymes; arylalkylamine-N-acetyltransferase (AA-NAT) and hydroxyindole-O-methyltransferase (HIOMT), transforming L-tryptophan (Trp), originally identified in pinealocytes, have been also detected in entero-endocrine (EE) cells of GIT, where this indole appears to act in endocrine, paracrine and/or luminal pathway directly or through G-protein coupled MT receptors. Studies of the distribution of MT in GIT mucosa showed that this indole is generated in GIT in much larger amounts than it is produced in the pineal gland. Melatonin acts in GIT, partly locally in paracrine fashion and is partly released into portal circulation, to be taken up by the liver. It is then metabolized and excreted with the bile to small bowel and finally returns to liver through entero-hepatic circulation. The production of MT by the pineal gland shows circadian rhythm with high night-time surge, especially at younger age, followed by the fall during the day-light time. As a highly lipophylic substance, MT reaches all body cells within minutes, thus, serving as a convenient circadian timing signal. Following pinealectomy, the light/dark cycle of plasma MT levels disappears, while its day-time blood concentration is maintained mainly due to its release from the GIT. According to our experience, after oral application of Trp, the plasma MT increases in dose-dependent manner both in intact and pinealectomized animals and humans, indicating that GIT but not the pineal gland is a source of this indole. In GIT MT exhibits a wide spectrum of activities such as circadian entrainment, antioxidant and free radicals scavenging activity, cytoprotective, anti-inflammatory and healing efficacy of various GIT lesions such as esophagitis, gastritis, peptic ulcer, pancreatitis and colitis. This review concentrates on the generation and pathophysiological implication of MT in GIT and related organs.