Biomedical subjects

Anna Lorenc

Publications and source records attributed to Anna Lorenc.

8 recordsLinked to original sources

PubMed2006

Daily oscillation in melatonin synthesis in the Turkey pineal gland and retina: diurnal and circadian rhythms.

The aim of the present study was to examine arylalkylamine N-acetyltransferase (AANAT) activity and melatonin content in the pineal gland and retina as well as the melatonin concentration in plasma of the turkey (Meleagris gallopavo), an avian species in which several physiological processes, including reproduction, are controlled by day length. In order to investigate whether the analyzed parameters display diurnal or circadian rhythmicity, we measured these variables in tissues isolated at regular time intervals from birds kept either under a regular light-dark (LD) cycle or under constant darkness (DD). The pineal gland and retina of the turkey rhythmically produced melatonin. In birds kept under a daily LD cycle, melatonin levels in the pineal gland and retina were high during the dark phase and low during the light phase. Rhythmic oscillations in melatonin, with high night-time concentrations, were also found in the plasma. The pineal and retinal melatonin rhythms mirrored oscillations in the activity of AANAT, the penultimate enzyme in the melatonin biosynthetic pathway. Rhythmic oscillations in AANAT activity in the turkey pineal gland and retina were circadian in nature, as they persisted under conditions of constant darkness (DD). Transferring birds from LD into DD, however, resulted in a potent decline in the amplitude of the AANAT rhythm from the first day of DD. On the sixth day of DD, pineal AANAT activity was still markedly higher during the subjective dark than during the subjective light phase; whereas, AANAT activity in the retina did not exhibit significant oscillations. The results indicate that melatonin rhythmicity in the turkey pineal gland and retina is regulated both by light and the endogenous circadian clock. The findings suggest that environmental light may be of primary importance in the maintenance of the high-amplitude melatonin rhythms in the turkey.

Animals↗

PubMed2006

Clinicoprognostical features of endometrial cancer patients with somatic mtDNA mutations.

Somatic mitochondrial DNA (mtDNA) mutations have been found in a subset of endometrial cancers (EC) from different populations. We have investigated the relationship between mtDNA changes and clinical and pathological variables of women affected by EC. mtDNA mutations were detected both in early (3/32; 9%) and in advanced (1/8; 12%) stages of uterine tumors. However, patients carrying the mtDNA mutations or the normal mtDNA sequence had indistinguishable clinicopathological data, including age, clinical stage, histological grade and type or depth of myometrial invasion. It is noteworthy that mtDNA mutations were not detected in hyperplastic endometrial tissues or in ECs coexisting with hyperplasia, nor in a single case of endometrial stromal sarcoma. LOH at the tumor suppressor genes RB1 and TP53 as well as p16INK4A alterations (LOH, gene deletion) were found in tumors carrying mtDNA mutations. These results suggest that somatic mtDNA mutations are detected in a subset of ECs, although they are unrelated to clinicopathological variables of cancer.

Adult↗

PubMed2005

Diurnal and circadian rhythms in melatonin synthesis in the turkey pineal gland and retina.

The pineal gland and retina of the turkey rhythmically produce melatonin. In birds kept under a daily light-dark (LD) illumination cycle melatonin concentrations in the pineal gland and retina were low during the light phase and high during the dark phase. A similar melatonin rhythm with high night-time values was also observed in the plasma. The pineal and retinal melatonin rhythms mirror oscillations in the activity of serotonin N-acetyltransferase (AANAT; the penultimate enzyme in the melatonin biosynthetic pathway). In contrast, in both the pineal gland and retina the activity of the enzyme hydroxyindole-O-methyltransferase (HIOMT) did not exhibit significant changes throughout the 24-h period. Acute exposure of turkeys to light at night dramatically decreased melatonin levels in the pineal gland, retina and plasma. The rhythms in AANAT activity and melatonin concentrations in the turkey pineal gland and retina were circadian in nature as they persisted under conditions of constant darkness (DD). Under DD, however, the amplitudes of AANAT and melatonin rhythms were significantly lower (by 50-80%) than those found under the LD cycle. The findings indicate that melatonin rhythmicity in the turkey pineal gland and retina is regulated both by light and the endogenous circadian clock. The rapid dampening of the rhythms under DD suggests that of these two regulatory factors, environmental light may be the primary stimulus in the maintenance of the high amplitude melatonin rhythms in the turkey.

Acetylserotonin O-Methyltransferase↗

PubMed2005

Posthatching developmental changes in noradrenaline content in the chicken pineal gland.

Noradrenaline (NA) levels in pineal gland of chickens at various posthatching stages (P2, P4, P8, P15, P30 and P57) were determined by high-performance liquid chromatography with electrochemical detection. Pineal NA content markedly increased between P2 and P30. P30 and P57 chickens, kept from the day of hatching under a 12:12 hr light-dark (LD) illumination cycle, exhibited rhythmic changes in pineal NA, with levels in the dark period being markedly higher than in the light period. In younger birds pineal NA concentrations did not show pronounced daily variations. In 4-wk-old chickens (P28-30) kept under constant darkness (DD), the rhythmic pattern of pineal NA persisted for 1 day (with higher values during the subjective dark phase than during the subjective light phase), but this disappeared 24 hr after the introduction of DD. In contrast, NA content in pineal glands isolated from birds maintained for 2 days under continuous light was similar to that found during the light phase of the LD cycle, and did not exhibit significant rhythmicity. In P30 chickens, pretreated with alpha-methyl-p-tyrosine (AMPT, an inhibitor of tyrosine hydroxylase, the key regulatory enzyme in the biosynthesis of catecholamines), pineal NA content declined slowly and monophasically during the light phase. During the dark phase the AMPT-induced decay of NA was biphasic--namely an initial rapid decline over the first 15 min which was followed by a slow-rate decline--an observation indicating that NA turnover was higher in the dark. Acute exposure of the dark-adapted P30 and P57 chickens to light significantly decreased pineal NA content, but did not affect pineal NA concentrations in younger birds. Our results suggest that the NA rhythm in the chicken pineal gland and its sensitivity to light regulation progressively develop during the first month of life.

Aging↗

PubMed2004

Retinal illumination phase shifts the circadian rhythm of serotonin N-acetyltransferase activity in the chicken pineal gland.

The pineal gland of birds, in contrast to its mammalian counterpart, is a directly photosensitive organ. It has recently been demonstrated that light also acting via the retina acutely suppresses melatonin synthesis in the chicken pineal gland. The present study was aimed to investigate whether retinal illumination alone was capable of resetting the biological oscillator generating the circadian rhythm of pineal serotonin N-acetyltransferase (AA-NAT) activity in the chicken. Ocular exposure of chickens to 6 h low intensity white light (4 lux) potently suppressed AA-NAT activity (the penultimate and key regulatory enzyme in the melatonin biosynthetic pathway) in the pineal gland. In addition, this light pulse produced phase-dependent shifts in the circadian AA-NAT rhythm. Exposure to light early in the subjective night (circadian time (CT) 12-18) caused a phase delay in the circadian rhythm of pineal AA-NAT activity by 3.5+/-0.4 h compared to non-exposed controls. When the light pulse was applied during the second half of the subjective night (CT18-24), it produced a large phase advance of the circadian rhythm of pineal AA-NAT activity by 10.9+/-0.4 h. The advancing effect of light was more pronounced than the phase-delaying effect. Our results suggest that in the chicken retinally perceived light provides a powerful and important signal for synchronization of circadian rhythmicity in the pineal gland.

Adaptation, Biological↗

PubMed2004

Comparison between the Polish population and European populations on the basis of mitochondrial morphs and haplogroups.

Polymorphisms in mitochondrial DNA (mtDNA) were analyzed in 152 samples from the Polish population using restriction enzymes AvaI, BamHI, HaeII, HpaI and PstI. Additionally, each sample was classified into the appropriate haplogroup. When required, appropriate fragments were sequenced to establish the exact polymorphic sites. We found one new morph for PstI and six new morphs for AvaII. Some detected morphs have previously been described as population specific morphs in different regions of the world. All polymorphisms were classified into 31 different haplotypes. 21 of them were detected in single individuals. The Polish population was compared with other populations from different regions. Moreover, we have obtained evidence for mutation hot spots in the mtDNA coding region. Our results indicate that AvaII morph and haplogroup composition of the Polish population is similar to other European populations and has a distribution typical for this part of the world. However, statistically significant differences in haplogroup composition were found between the Polish population and Italian and Finnish populations.

DNA, Mitochondrial↗

PubMed2003

Homoplasmic MELAS A3243G mtDNA mutation in a colon cancer sample.

We have analyzed mtDNA variation in various cancer samples, comparing them with normal tissue controls, and identified mutations and polymorphisms, both known and novel, in mitochondrial tRNA, rRNA and protein genes. Most remarkably, in a colon cancer sample we have found the A3243G mutation in the homoplasmic state. This mutation is known to cause severe mitochondrial dysfunction and, until now, has not been found in cancer cells, nor in the homoplasmic state in living subjects. The mutation was absent from normal tissue, suggesting that mtDNA mutation and resulting respiratory deficiency played a role in carcinogenesis.

Journal Article↗

PubMed2003

Transposable elements and vertebrate protein diversity.

Interspersed repetitive sequences are major components of eukaryotic genomes. Repetitive elements comprise about 50% of the mammalian genome. They interact with the whole genome and influence its evolution. Repetitive elements may serve as recombination hot spots or acquire specific cellular functions such as RNA transcription control or become part of protein coding regions. The latter is a subject of presented analysis. We searched all currently available vertebrate protein sequences, including human proteome complement for the presence of transposable elements. It appears that insertion of TE-cassettes into open reading frames is a general phenomena. They can be found in all vertebrate lineages and originate in all types of transposable elements. It seems that genomes use those cassettes as 'ready to use' motifs in their evolutionary experiments. Most of TE-cassettes are used to create alternative forms of a message and usually the other form, without TE-cassette, is expressed in a cell. Tables listing vertebrate messages with TE-cassettes are available at http://warta.bio.psu.edu/ScrapYard/.

Animals↗