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Biomedical subjects

A Gajewska

Publications and source records attributed to A Gajewska.

At least 19 recordsLinked to original sources
PubMed2006

Leptin and long form of leptin receptor genes expression in the hypothalamus and pituitary during the luteal phase and early pregnancy in pigs.

Leptin is a polypeptide that plays a key role in the regulation of energy homeostasis and is also linked, among others, to mechanisms controlling reproductive processes. Data concerning the involvement of leptin in controlling reproductive functions at the level of hypothalamus and pituitary in the pig are limited. Therefore, in the present study, an expression of genes coding for leptin and long-form leptin receptor (Ob-Rb) was determined by a semiquantitative reverse transcription polymerase chain reaction (RT-PCR) in the discrete areas of porcine hypothalamus (medial basal hypothalamus - MBH, preoptic area - POA, stalk median eminence - SME) and pituitary (anterior - AP and posterior/neural - NP parts) during the luteal phase of the cycle (days 10-12 and 14-16) and two early stages of pregnancy (days 14-16 and 30-32). Leptin gene expression in MBH was found to be higher in the mid- than in the late-luteal phase, whereas in other structures studied it remained unchanged during these periods. More pronounced differences were noted in expression of Ob-Rb gene, which was increased in MBH, AP and NP during the late-luteal phase in comparison to the mid-luteal one, whilst the relationship in the POA was reversed. In turn, during pregnancy, leptin gene expression in all tested areas of hypothalamus as well as Ob-Rb mRNA content in MBH were higher on days 30-32 than on days 14-16. In contrast, in the anterior pituitary, Ob-Rb gene expression was more pronounced on days 14-16 than during later stage of pregnancy. Comparison of leptin and Ob-Rb mRNA content in studied structures between the mid-luteal phase and days 14-16 of pregnancy revealed inhibition of leptin gene expression in almost all examined tissues (MBH, POA, SME, NP) during early pregnancy whereas Ob-Rb gene expression was inhibited in POA but stimulated in both parts of the pituitary during this stage. In summary, obtained results suggest an involvement of leptin in the regulation of hypothalamic-pituitary axis activity during both the luteal phase of the cycle and early pregnancy in pigs.

Animals↗
PubMed2004

Stimulation of luteinizing hormone subunit gene expression by pulsatile intracerebroventricular microinjection of galanin in female rats.

Although galanin, which exerts its effects both at the hypothalamic and pituitary level, has been implicated as an important neuroendocrine regulator of hypothalamic-pituitary-gonadal axis activity, there is a lack of data concerning its involvement in the regulation of gonadotropin subunit gene expression. To elucidate whether galanin can influence luteinizing hormone (LH) subunit mRNA content, as well as affect gonadotropin-releasing hormone (GnRH) receptor activity, a model based on pulsatile (one pulse per hour over 5 h) galanin (1 nM) microinjections directly into the third cerebral ventricle of ovariectomized (OVX) and/or oestrogen/progesterone-pretreated rats was used. Furthermore, to determine galanin effects on GnRH-induced LH subunit mRNA synthesis, a cocktail of 1 nM GnRH and 1 nM galanin was coadministered in a pulsatile manner to OVX/steroid primed rats. Subsequently, to obtain data concerning the role of galanin receptors in the regulation of pituitary alpha (common to LH, follicle-stimulating hormone, thyroid-stimulating hormone) and LHbeta subunit gene expression, OVX/oestrogen/progesterone rats received microinjections of 1 nM of the receptor antagonist galantide and 1 nM of galanin. In this case, both substances were administered separately, with a 30 min lag, according to which each galantide pulse always preceded a galanin pulse. Northern-blot analysis revealed that intracerebroventricular pulsatile galanin injections were effective in stimulation of both alpha and LHbeta subunit mRNA levels and that this effect was apparently steroid-dependent. Moreover, galanin also up-regulated GnRH receptor functional parameters (affinity and maximum binding capacity) but was ineffective in potentiating GnRH-induced accumulation of both subunit mRNAs. The results from the study also indicate that galanin acts through its own receptor(s) because a receptor antagonist, galantide, significantly reduced the stimulatory effect exerted by galanin on the expression of both LH subunit genes in vivo.

Animals↗
PubMed2001

Daily GnRH and LH secretion in ewes is not modified by exogenous melatonin during seasonal anestrus.

The effect of central, short-term melatonin administration on daily GnRH and LH secretion was studied in ewes during seasonal anestrus. Melatonin, in a total dose of 32 micrograms and the vehicle were perfused for 4 hours into the mediobasal hypothalamus/median eminence (MBH/ME). The mean GnRH concentration during perfusion with melatonin decreased significantly (P < 0.05), as compared to the concentration during the preceding perfusion with the vehicle only. This change resulted from high variations in GnRH concentration noted during the initial phase of perfusion rather than from an action of melatonin. Melatonin perfused into the MBH/ME did not significantly affect LH secretion. A higher dose of melatonin and vehicle were also infused intracerebroventricularly (icv.) in either intact (300 micrograms for 3 hours) or ovariectomized (OVX) ewes (400 micrograms for 4 hours, 100 micrograms/100 microliters/h). In the intact animals, melatonin did not significantly affect LH secretion. Interestingly, melatonin significantly decreased (P < 0.05) the number of LH peaks in OVX ewes. These results demonstrate that melatonin delivered for a few hours directly into the central nervous system did not affect either daily hypothalamic GnRH release or pituitary LH secretion in intact ewes during seasonal anestrus, but did modify pulsatile LH secretion in ewes deprived of the negative feedback of estradiol.

Anestrus↗
PubMed2001

GnRH pulsality and the differential activation of the rat luteinizing hormone subunit genes in the anterior pituitary gland.

Detailed studies have been focused on the mechanisms by which the rat alpha and LHbeta genes are differentially regulated by GnRH and indicate that differential sensitivity to the second messenger exists in a physiological context. Differential signaling from the GnRH receptor may be a mechanism for preferential regulation of luteinizing hormone subunit gene transcription; however which of these genes are specifically regulated by PKC or calcium and how GnRH pulsatility could preferentially activate individual pathways of second messengers within gonadotrope cells remain unclear. Several transcription factors that have profound effects on basal and/or GnRH-stimulated LHbeta gene promoter activity have been identified: SF-1, Egr-1, Sp-1. A model explaining possible interactions among them in mediating GnRH responsiveness of the LHbeta gene has been proposed: Sp1, SF-1 and Egr-1 form a tripartite GnRH response element which is sensitive to the spacing changes between the upstream Sp1 binding sites and the downstream SF-1/Egr-1 binding elements and SF-1 plays a critical role in integrating the effects of Sp1 and Egr-1. GnRH responsive element located on LHbeta gene promoter in position between -495 to -342 has been identified. At 3'-end of the promoter three Sp-1 binding sites have been identified: position -416, sequence: GGGGGCTGGG and two sites almost completely overlapping, position -403, sequence; GGGGCGGCGCCCA while at the 5'region of the promoter one Sp-1 binding site exists: position -450, sequence: ACCACACCCATTTTTGG. The 5'Sp1 site overlaps a CArG box (at -443 to -434, sequence: CCATTTTTGG) which seems to be essential in LHbeta gene sensitivity for pulsatile GnRH stimulation.

Animals↗
PubMed2000

Modulation of luteinizing hormone subunit gene expression by intracerebroventricular microinjection of gonadotropin-releasing hormone or beta-endorphin in female rats.

The effects of gonadotropin-releasing hormone (GnRH), beta-endorphin and its antagonist naloxone on the expression of luteinizing hormone (LH) subunit genes and LH secretion were examined in ovariectomized and/or cycling female rats through their direct microinjection into the third cerebral ventricle, in the proximity of the hypothalamus-pituitary complex. GnRH (1 nM) induced a significant augmentation of the pituitary content of alpha mRNA when administered 15, 30 or 60 min intervals over 5 h to ovariectomized rats whereas only the 30 and 60 min intervals were effective in increasing LHbeta mRNA, and the 60 min intervals for LH release. This was in agreement with the established concept of a pulse-dependent regulation of gonadotropin synthesis and release. Hourly pulses of GnRH also increased alpha and LHbeta mRNA levels when microinjected in female cycling rats during proestrus or diestrus II. Using this model we observed a marked negative influence of hourly intracerebral microinjections of beta-endorphin on LH mRNA content and LH release in ovariectomized rats while naloxone had no effect. This suggests that endogenous beta-endorphin was unable to exert its negative action on beta-endorphin receptors that were present and responded to the ligand. The present approach would be valuable for the exploration of the mechanisms of action of beta-endorphin or other substances on the functions of the gonadotrophs.

Animals↗
PubMed1997

In vivo effect of growth hormone on DNA synthesis and expression of milk protein genes in the rabbit mammary gland.

The aim of this work was to show whether growth hormone (GH) is able to directly induce growth and functional differentiation of the mammary gland. We have shown that i.m. injections of prolactin and to lesser extent injections of growth hormone increased DNA synthesis in the mammary gland of pregnant rabbits. Injections of pituitary and recombinant bovine growth hormone (GH), similarly to prolactin, could also induce the expression of milk protein genes--caseins alpha S1 and beta and whey acidic protein (WAP). However, in contrast to prolactin, growth hormone failed to induce the synthesis of casein proteins. Lactogenic hormones act through binding to receptors in target tissues. Prolactin receptors were shown to be abundant in the rabbit mammary glands but no specific binding sites for 125I-labelled GH have been found in membranes isolated from mammary glands of pregnant or lactating rabbits. The specificity of hormone binding was examined using unlabelled hormones as competitive inhibitors of 125I-labelled prolactin. Bovine and recombinant bovine growth hormone did not displace prolactin from its receptors, thus excluding the possibility of action of GH through lactogenic receptors. Our results support the hypothesis that GH may act directly on the mammary gland and independently from prolactin; however, the mechanism of its action is still unknown.

Animals↗
PubMed1996

Biosynthesis of gonadotropins in vivo.

GnRH is potent stimulator of gonadotropin's alpha and beta chains synthesis in vivo. Stimulation of LH beta gene transcription requires pulsatile GnRH administration but the transcription of alpha subunit can be stimulated independently of GnRH mode of administration. Castration increases whereas in vivo estradiol and testosterone replacement decreases the rate of gene transcription of pituitary gonadotropin subunits. Thyroid hormones can enhance or diminish the pituitary levels of LH beta and FSH beta subunit mRNAs in female rats. Inhibin, activin and follistatin were shown to be potent regulators of FSH beta gene expression.

Animals↗
PubMed1994

Ovarian LH/hCG receptors and plasma level of LH,17-beta estradiol and progesterone in gonadotropin--induced PCO syndrome in rats.

The aim of this work was to investigate the morphologic changes, LH/hCG receptor content in the ovaries and plasma levels of LH, progesterone and estradiol of hypo--and hyperthyroid rats injected with PMSG and hCG. The hypothyroid state was induced by thyreoidectomy (Tr-X) and the hyperthyroid condition by injections of 40 micrograms L-thyroxine daily during 21 days (T4). Gonadotropins were injected during 14 days in daily doses: PMSG--5 i.u. and hCG--10 i.u. The following 8 groups (n = 10-20) were established: control (euthyroid, no treatment), Tr-X, PMSG + hCG, Tr-X + hCG, Tr-X + PMSG, Tr-X + PMSG + hCG, T4 and T4 + PMSG. At the end of experiments rats were sacrificed, ovaries weighed, macroscopically inspected and concentration of LH/hCG receptors was estimated. In blood plasma the level of LH, progesterone and 17-beta estradiol was also analysed. The experiments showed that injections of PMSG alone, or PMSG + hCG in eu-or hypothyroid rats, appear the most effective in induction of PCO syndrome in rats. Low levels of thyroid hormones sensitized the ovaries to gonadotropin action, but a hyperthyroid status diminished or inhibited this response. Thyroid function is also essential in production of LH/hCG receptors in the ovaries. In hypothyroid animals the amount of these receptors was greatly increased, while in hyperthyroid animals they decreased. The level of plasma LH, progesterone, and estradiol showed insignificantly differences and various inconsiderable deviations from norm. These differences were not dependent on large doses of gonadotropins, altered thyroid function, or on cystic or luteinizing changes in the ovary.

Animals↗
PubMed1992

Increased LH and FSH release from the anterior pituitary of ovariectomized rat, in vivo, by copper-, nickel-, and zinc-LHRH complexes.

The effect of Cu2+, Ni2+, Zn2+ and their complexes with LHRH on the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH) was estimated in in vivo experiments with the use of the method proposed by Ramirez and McCann. Ovariectomized, estradiol, and progesterone pretreated rats were injected intravenously either with LHRH alone, a metal ion alone, a mixture of metal and hormone, or a metal-LHRH complex. A metal alone or a mixture of it with LHRH did not affect gonadotropin release at all or no more than LHRH alone. However, the complex of Cu2+ with LHRH brought about a high release of LH and even higher release of FSH. This indicates that copper complex is more effective than metal-free LHRH. The nickel complex showed a similar although lesser effect. The zinc complex had similar potency to free LHRH though higher FSH-releasing ability was noticed. We conclude that copper-, nickel-, and zinc-LHRH complexes were more potent than the peptide hormone itself and promoted the FSH release in the ovariectomized, estradiol, and progesterone pretreated rats.

Animals↗
PubMed1991

Release of luteinizing hormone-releasing hormone, beta-endorphin and noradrenaline by the nucleus infundibularis/median eminence during periovulatory period in the sheep.

The relationships between the release of LHRH, beta-endorphin (beta-END) and noradrenaline (NA) from the hypothalamic infundibular nuclei/median eminence (NI/ME) during the periovulatory period in the ewe was studied. Neurohormone release was assayed in perfusates collected from the NI/ME via push-pull cannulae. LHRH concentrations in perfusates ranged from below detectable values (5 pg) to 50 pg and from 15 to 240 pg/20 min perfusate on the days of proestrus and estrus, respectively. beta-END concentrations in perfusates ranged from 320 to 6,000 pg on the day of proestrus and fell to a range between 100 and 380 pg/20 min perfusate on the day of estrus. The NA content of perfusates ranged from an undetectable level to 0.9 x 10(4) pg/perfusate during proestrus, and rose from 1.0 x 10(4) to 6.6 x 10(4) pg/perfusate shortly before the preovulatory release of LHRH and LH. On the basis of the present observations, the following sequence of events leading to the massive LH ovulatory surge in the sheep is suggested: (1) increased secretion of beta-END in the NI/ME on the day of proestrus generates an increase in the releasable pool of LHRH through inhibition of LHRH release; (2) on the day of estrus a decreased release of beta-END allows the expression of NA activity in the NI/ME and the augmentation of NA tone facilitates the release of newly accumulated LHRH; (3) the resultant intensified LHRH output with its significantly changing pattern of release triggers the preovulatory surge of LH.

Animals↗
PubMed1991

[Prognostic value of measuring serum angiotensin I-converting enzyme (ACE) in patients with sarcoidosis].

Serum ACE (s-ACE) activity were determined in 112 sarcoid patients and 60 healthy volunteers. The mean s-ACE activity in sarcoid patients were 39.5 +/- 14.1 U. and in healthy volunteers 22.1 +/- 3.6, U. Significant increase of s-ACE was seen in active sarcoidosis 51.2 +/- 13.7 U. Serum ACE activity increased twice or more in comparison with control values imply activity of the process. Serum-ACE determination may be of use as a prognostic factor in sarcoidosis.

Adolescent↗
PubMed1990

Activation of potassium efflux from Escherichia coli by glutathione metabolites.

The mechanism by which N-ethylmaleimide (NEM) elicits potassium efflux from Escherichia coli has been investigated. The critical factor is the formation of specific glutathione metabolites that activate transport systems encoded by the kefB and kefC gene products. Formation of N-ethyl-succinimido-S-glutathione (ESG) leads to the activation of potassium efflux via these transport systems. The addition of dithiothreitol and other reducing agents to cells reverses this process by causing the breakdown of ESG and thus removing the activator of the systems. Chlorodinitrobenzene, p-chloromercuribenzoate and phenylmaleimide provoke similar effects to NEM. lodoacetate, which leads to the formation of S-carboxymethyl-glutathione, does not activate the systems but does prevent the action of NEM. It is concluded that the KefB and KefC systems are gated by glutathione metabolites and that the degree to which they are activated is dependent upon the nature of the substituent on the sulphydryl group.

Biological Transport↗
PubMed1990

[Post-traumatic chylothorax].

A case of post-traumatic chylothorax in a 84 year old man with ILD is presented. The chylothorax was successfully treated after 6 months, which was confirmed at post-mortem, during which a solitary plasmocytoma of the left kidney was also diagnosed.

Accidental Falls↗
PubMed1987

Evidence for multiple K+ export systems in Escherichia coli.

The role of the K+ transport systems encoded by the kefB (formerly trkB) and kefC (formerly trkC) genes of Escherichia coli in K+ efflux has been investigated. The rate of efflux produced by N-ethylmaleimide (NEM), increased turgor pressure, alkalinization of the cytoplasm, or 2,4-dinitrophenol in a mutant with null mutations in both kef genes was compared with the rate of efflux in a wild-type strain for kef. The results show that these two genes encode the major paths for NEM-stimulated efflux. However, neither efflux system appears to be a significant path of K+ efflux produced by high turgor pressure, by alkalinization of the cytoplasm, or by addition of high concentrations of 2,4-dinitrophenol. Therefore, this species must have at least one other system, besides those encoded by kefB and kefC, capable of mediating a high rate of K+ efflux. The high, spontaneous rate of K+ efflux characteristic of the kefC121 mutation increases further when the strain is treated with NEM. Therefore, the mutational defect that leads to spontaneous efflux in this strain does not abolish the site(s) responsible for the action of NEM.

2,4-Dinitrophenol↗
PubMed1987

Pharmacokinetics of ciprofloxacin in the elderly.

The pharmacokinetics of ciprofloxacin, administered orally as a 250-mg tablet were compared in 10 young (age 20-30 years) and 10 elderly (age 60-73 years) healthy volunteers. The time to peak serum concentrations was about 80 min in both age groups, although the maximum concentration attained was significantly greater in the old (1.7 mg/l) than the young (1.2 mg/l). Area under the plasma concentration-time curve, corrected for body weight, was on average 48% greater in the elderly, but the mean terminal elimination half-life was not significantly different, averaging 4.3 h in the old and 3.7 h in the young. Overall 24-hour urinary recovery in both age groups was comparable. The differences may be explained by a reduced volume of distribution of ciprofloxacin in old age and do not suggest a general need for significant dose alteration in the elderly.

Administration, Oral↗