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Biomedical subjects

J Rosiak

Publications and source records attributed to J Rosiak.

At least 19 recordsLinked to original sources
PubMed2003

L-745,870 suppresses the nighttime serotonin N-acetyltransferase activity in chick retina: in vivo evidence for agonist activity at D4-dopamine receptors.

This study examined the in vivo activity of L-745,870 at dopamine (DA) D(4) receptors, using the chick retina as a model system. In dark-adapted retinas of various vertebrates, including hen, DA acting via D(4) receptors suppresses melatonin content and activity of serotonin N-acetyltransferase (AA-NAT, a key regulatory enzyme in melatonin synthesis). Systemic administration to chicks of quinpirole (0.1 mg/kg), a high affinity agonist of D(3)/D(4)-DA receptors, potently decreased the nighttime AA-NAT activity of the retina. The quinpirole-evoked decline in the enzyme activity was attenuated by L-745,870 (0.1-10 nmol/eye). In addition to this action, L-745,870 given to chicks either directly into the eye (0.03-10 nmol/eye) or intraperitoneally (0.5-5 mg/kg) decreased the nighttime AA-NAT activity of the retina in a dose-dependent manner. The suppressive effect of L-745,870 on retinal AA-NAT activity was blocked by 2-chloro-11-(4-methylpiperazino)dibenz[ b, f]oxepin, an antagonist of D(4)-DA receptors, but was not affected by raclopride, an antagonist of D(2)/D(3)-DA receptors. Altogether these results indicate that in chicks L-745,870, the potent putative D(4)-DA receptor antagonist, behaves in vivo as a partial D(4) agonist.

Animals↗
PubMed2000

Near-ultraviolet radiation suppresses melatonin synthesis in the chicken retina: a role of dopamine.

Effects of near-ultraviolet radiation (UV-A; 325-390 nm, peak at 365 nm) on melatonin content and activity of serotonin N-acetyltransferase (AA-NAT; a key regulatory enzyme in melatonin biosynthesis) were examined in the retina of chickens. Acute exposure of dark-adapted animals to UV-A light produced a marked decline in melatonin content and AA-NAT activity of the retina. The magnitude of the observed changes was dependent upon duration of the light pulse and age of chickens, with 1-2-week old birds being more sensitive to UV-A action than 6-7-week old ones. The decrease in the nocturnal AA-NAT activity evoked by a 5-min UV-A pulse gradually deepened during the first 30 min after the return of chickens to constant darkness, then the enzyme activity began to rise, reaching nearly complete restoration within 2.5 hr. Systemic administration to chickens of alpha-methyl-p-tyrosine (an inhibitor of catecholamine synthesis; 0.3 g/kg) blocked the suppressive effect of UV-A light on retinal AA-NAT activity. Haloperidol, sulpiride (blockers of D2-family of dopamine (DA) receptors) and 2-chloro-11-(4-methylpiperazino)dibenz[b,f]oxepin (an antagonist of D4-DA receptors), given intraocularly (1-100 nmol/eye) prevented the UV-A light-evoked decrease in AA-NAT activity in the chicken retina in a dose-dependent manner, while raclopride (300 nmol/eye), an antagonist of D2/D3-DA receptors, was ineffective. In dark-adapted chickens exposure to UV-A light increased the DA content of the retina. It is concluded that UV-A radiation, similar to visible light, potently suppresses melatonin biosynthesis in the retina of chicken, with a D4-dopaminergic signal playing the role of an intermediate in this action.

Animals↗
PubMed2000

Effects of cycloheximide and aminophylline on 5-methoxytryptophol and melatonin contents in the chick pineal gland.

The chick pineal gland rhythmically synthesizes two 5-methoxyindoles, melatonin and 5-methoxytryptophol. These rhythms are circadian in nature and have opposite phases. The aim of this study was to determine the effects of cycloheximide, a protein synthesis inhibitor, and aminophylline, an inhibitor of phosphodiesterase, on 5-methoxytryptophol content in the chick pineal gland and to compare this with the drugs' action on pineal melatonin production. Inhibition of melatonin biosynthesis by cycloheximide (1 mg/kg, i.p. ), revealed by a marked reduction in the nighttime activity of serotonin N-acetyltransferase (AA-NAT; a key regulatory enzyme in melatonin synthesis) and melatonin concentrations, was accompanied by a significant increase in 5-methoxytryptophol content. In contrast, administration of aminophylline (100 mg/kg, i.p.) to light-exposed chicks significantly increased pineal AA-NAT activity and melatonin levels and decreased 5-methoxytryptophol concentrations. It is concluded that in the chick the production of pineal 5-methoxytryptophol and melatonin is inversely correlated.

Acetylserotonin O-Methyltransferase↗
PubMed1999

The effects of near-ultraviolet light on serotonin N-acetyltransferase activity in the chick pineal gland.

Effects of near-ultraviolet light (UV-A; 325-390 nm, peak at 365 nm) on the activity of the pineal serotonin N-acetyltransferase (NAT; a key regulatory enzyme in melatonin biosynthesis) were examined in chicks. Acute exposure of dark-adapted animals to UV-A radiation produced a marked decline in NAT activity of the pineal gland. The magnitude of this suppression was dependent upon duration of the light pulse and the age of the animals. The decrease in the nighttime NAT activity evoked by a 5 min pulse of UV-A light applied during the fourth hour of the dark phase of the 12 hr light:12 hr dark cycle (LD) gradually deepened during the first 40 min after the return of animals to constant darkness, then the enzyme activity began to rise, reaching control values by 2 hr. Exposure of chicks to a 5 min pulse of UV-A light during the ninth hour of the dark phase produced a marked decline in pineal NAT activity, which was reversible after 15 min of darkness. Pretreatment of animals with an inhibitor of catecholamine synthesis, alpha-methyl-p-tyrosine (300 mg/kg, i.p.), or with a blocker of alpha2-adrenergic receptors, yohimbine (2 mg/kg, i.p.), antagonized the suppressive effect of UV-A light on nighttime NAT activity of the chick pineal gland. It is concluded that UV-A irradiation, similar to visible light, potently suppresses melatonin biosynthesis in the chick pineal gland, with an alpha2-noradrenergic signal playing the role of an intermediate in this action.

Animals↗
PubMed1999

[Cascade of biochemical events triggered by stimulation of adrenergic receptors in the rat pineal gland--from cell membrane to nucleus].

Pineal glands of various vertebrate species synthesize melatonin in a circadian rhythm generated by an endogenous pacemaker. The levels of melatonin and activity of serotonin N-acetyltransferase (AA-NAT: a penultimate and key regulatory enzyme in melatonin biosynthesis) are low during the light phase and high during the dark phase of any natural or imposed light-dark illumination cycle. The expression of AA-NAT gene in rat pineal gland is regulated by a photoneural system that acts through the adrenergic-cAMP-related mechanisms in pinealocytes. Concomitant stimulation by noradrenaline of beta 1- and alpha 1-adrenergic receptors, in a mechanism of "AND gate" activation, results in a large, 60-100-fold increase in intrapinealocyte cAMP level. The role of cAMP-dependent transcription factors CREB, ICER and Fra-2 in turning on and off the AA-NAT gene expression is discussed.

Animals↗
PubMed1998

Effects of near-ultraviolet light on the nocturnal serotonin N-acetyltransferase activity of rat pineal gland.

Effects of near-ultraviolet (UV-A; 325-390 nm, peak at 365 nm) light on the activity of the pineal serotonin N-acetyltransferase (NAT; a penultimate and key regulatory enzyme in melatonin biosynthesis) were examined in rats. Acute exposure of dark-adapted animals to UV-A radiation produced a marked suppression of NAT activity of the pineal gland, the effect being dependent on exposure time. The decrease in the night-time NAT activity evoked by a 1-min pulse of UV-A light (as well as by a 15-s pulse of broad-band visible light) gradually deepened during the first 40 min of treatment of animals with constant darkness, then the enzyme activity began to rise reaching control values by 3 h. Treatment of rats with a protein synthesis inhibitor, cycloheximide, attenuated this night-driven reactivation of the pineal NAT activity. The presented results provide evidence that UV-A light is a powerful signal capable of controlling melatonin biosynthesis in rat pineal gland.

Animals↗
PubMed1995

[Analysis of seven year prophylactic examinations of uterine cervix carcinoma in women living in the town of Kielce].

The authors are presenting an analysis of the prophylactic examinations carried out within the period of seven years among women under the care of the Municipal Health Care Center in Kielce. They are also trying to evaluate the influence such examinations have in forming up the detectability of preneoplastic states and cancer of the uterine cervix. The studies were carried out from 1982-1988. A rule was adopted to repeat the examinations every two years. Owing to organizing difficulties, the first stage of the examinations took three years. The basis of the prophylactic examinations was cytologic examination. The detectability of intraepithelial neoplasm of the uterine cervix (CIN) in the three stages was 0.26%, 0.16%, and 0.07%. It was observed therefore, the gradual drop in the number of the detectable CIN among the population in the duration of the studies. A "shift" of detectable neoplasma changes in the uterine cervix in the direction of a higher percentage of preinvasive cancers and with an early invasion was observed. This shift, beside the stable decrement of the absolute number of detectable cancers is a favourable phenomenon and testifies the great usefulness and the effectiveness of the studies.

Adolescent↗
PubMed1994

[Hydrogels in medicine. Origin and clinical use].

Hydrogels are a new revolutionary method used to dress wounds without using gauzes and cotton wool. Our hydrogels were produced by irradiation and are perfectly sterile and biocompatible. The innovation of this topical treatment permits direct contact of hydrogels on wounds and results in complete repair of wounds and ulcers that do not heal easily. The fundamental advantage are: disappearance of local pain, very good protection of wounds, easy removal of necrotic tissue, total adhesion on wounds and simple removal without pain, faster tissue repair.

Administration, Topical↗
PubMed1994

[Polymeric materials for biomedical purposes obtained by radiation methods. V. hybrid artificial pancreas].

The authors present a review of works done on the elaboration of a hybrid-type artificial pancreas. The article discusses construction designs, applied polymeric materials as well as biocompatibility problems of polymeric membranes that encapsulate the Langerhans islets. On example of hydrogel membranes prepared by radiation crosslinking of poly(vinyl alcohol) (PVA) the dependence of the diffusion coefficients of glucose, insulin and immunoglobulin G on the crosslinking degree of hydrogels has been shown.

Animals↗
PubMed1992

Studies on dressings for dental surgery use. Part 3: Effect of gamma-radiation and of formaldehyde on properties of gelatinous dental dressings.

Gelatinous dressings were exposed to gamma-radiation or treated with formaldehyde to improve their resistance to the proteolytic effects of trypsin. After aging of the preparations, both gamma-irradiated and blank samples of gelatinous dressings were etched at a constant rate. Etching rate of the formaldehyde treated dressings decreases during storage.

Cross-Linking Reagents↗
PubMed1989

[Polymer materials for biomedical use obtained by radiation methods. III. Radiation cross-linking of acrylamide and N-vinylpyrrolidone].

The course of the radiation formation of hydrogels in aqueous solutions of acrylamide and N-vinylpyrrolidone was investigated on the base of gel-sol analysis. Using relations from Inokuti's equation as a test of crosslinking mechanism it was pointed out that creation of gels takes place according to classical mechanism e.g. through four-functional joining points. In the systems containing oxygen gel formation results from simultaneous crosslinking and degradation. On the base of swelling measurements of gels (ROCH method) the yields of radiation processes were calculated. Using a method of pulse radiolysis the absorption spectra of macroradicals were recorded, their structures discussed and the rate constants of crosslinking estimated.

Acrylamides↗
PubMed1989

[Polymer materials for biomedical use obtained by radiation methods. IV. The therapeutic system for local release of prostaglandins].

The suitability of a radiation crosslinked polyvinylpyrrolidone++ as a therapeutical system for local prostaglandin monitoring has been studied. The effect of the dose and dose rate of ionizing radiation and of the time of heating the matrix on the content of gel fraction and the degree of hydrogel swelling was determined. The dimensions of a polymer network as dependent on the parameters of the process were calculated. For a chosen way of obtaining the therapeutical system, the release of prostaglandin F2 alpha in vitro was also estimated.

Abortifacient Agents, Steroidal↗