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Biomedical subjects

M Lõhmus

Publications and source records attributed to M Lõhmus.

8 recordsLinked to original sources
PubMed2004

Leptin increases T-cell immune response in birds.

Leptin is a 16 kDa protein hormone that besides being a satiety factor also functions as a pleiotropic molecule regulating endocrine and immune functions. The aim of this study was to investigate the role of leptin on mitogen stimulated T-lymphocyte proliferation in birds. In the first experiment (in vitro), peripheral blood was collected from turkeys and lymphocytes were isolated from samples. Recombinant chicken leptin was added at concentrations of 0, 10(-9), 10(-8), 10(-7), and 10(-6) M prior to mitogen stimulation with Concavalin A. BrdU incorporation allowed us to detect T-cell proliferation using intracellular labeling of nucleic acids. Mitogen activation induced with Concavalin A caused a proliferation of T-cells that was positively correlated with the concentration of leptin. In the second experiment (in vivo), asian blue quail were fitted with osmotic pumps releasing leptin and injected with phytohemagglutinin (PHA) in their wing-webs before, during, and after leptin administration. The response to mitogen was greater in leptin treated birds during the leptin administration, but not before or after. These findings demonstrate that leptin enhances mitogen stimulated T-cell proliferation in birds. The results correspond with previous reports on mammals.

Animals↗
PubMed2004

Effects of egg yolk testosterone on growth and immunity in a precocial bird.

In oviparous vertebrates, maternal steroid allocation to eggs can have important fitness consequences for the offspring. However, elevated testosterone levels are not only associated with beneficial postnatal effects, such as enhanced growth and high social status, but may also entail costs by suppressing the immune system. In this study, testosterone levels in eggs of Chinese painted quail (Coturnix chinensis) were experimentally manipulated to evaluate its effects on growth and immunocompetence. Testosterone did not affect embryonic development, body size or growth during the first 20 days. However, elevated testosterone levels during embryonic development were immunosuppressive for chicks with inherently higher growth rate. Adaptive scenarios where only beneficial effects of increased testosterone levels are considered may therefore need to be re-evaluated.

Analysis of Variance↗
PubMed2000

Magnetic information calibrates celestial cues during migration.

Migratory birds use celestial and geomagnetic directional information to orient on their way between breeding and wintering areas. Cue-conflict experiments involving these two orientation cue systems have shown that directional information can be transferred from one system to the other by calibration. We designed experiments with four species of North American songbirds to: (1) examine whether these species calibrate orientation information from one system to the other; and (2) determine whether there are species-specific differences in calibration. Migratory orientation was recorded with two different techniques, cage tests and free-flight release tests, during autumn migration. Cage tests at dusk in the local geomagnetic field revealed species-specific differences: red-eyed vireo, Vireo olivaceus, and northern waterthrush, Seiurus noveboracensis, selected seasonally appropriate southerly directions whereas indigo bunting, Passerina cyanea, and grey catbird, Dumetella carolinensis, oriented towards the sunset direction. When tested in deflected magnetic fields, vireos and waterthrushes responded by shifting their orientation according to the deflection of the magnetic field, but buntings and catbirds failed to show any response to the treatment. In release tests, all four species showed that they had recalibrated their star compass on the basis of the magnetic field they had just experienced in the cage tests. Since release tests were done in the local geomagnetic field it seems clear that once the migratory direction is determined, most likely during the twilight period, the birds use their recalibrated star compass for orientation at departure. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1997

Modulatory effect of 8-iso-PGE2 on platelets.

1. 8-Iso-PGE2 induced either reversible or irreversible aggregation of platelets in human platelet-rich plasma (PRP) or in the suspension of washed platelets (WP). The values of EC50 for irreversible aggregation in PRP and WP were 4 and 2 microM, respectively. 2. In rabbit PRP, 8-iso-PGE2 (0.1-100 microM) itself did not induce or induced only reversible aggregation. 3. 8-Iso-PGE2 (0.1-20 microM) potentiated adenosine diphosphate-(ADP) induced platelet aggregation in both human and rabbit. The same effect also was found for adrenaline-induced platelet aggregation in rabbit. 4. The lower concentrations (0.2-0.5 microM) of 8-iso-PGE2 decreased, and higher concentrations (1-2 microM) increased platelet aggregating factor- (PAF) induced aggregation in human PRP. In rabbit PRP, 8-iso-PGE2 (0.02-200 microM) had only a decreasing effect on PAF-induced aggregation. 5. The results suggest that low concentrations of 8-iso-PGE2 can amplify or weaken platelet aggregation induced by various aggregatory agents.

Adenosine Diphosphate↗
PubMed1993

Comparison of the inhibitory effect of E-prostaglandins in human and rabbit platelet-rich plasma and washed platelets.

1. The anti-aggregatory potency of a number of E-type PGs was compared in human and rabbit platelet-rich plasma (PRP) and washed platelets. The potency of 13,14-dihydro-PGE1 and 5,6-dihydro-PGE3 is significantly higher in human than in rabbit washed platelets, while the potency of 15-keto-13,14-dihydro-PGE1 is higher in rabbit. 2. The potency of PGEs in rabbit PRP is very similar to that of washed platelets, with the exception of 1a,1b-dihomo-PGE2, which is of a significantly lower potency in PRR. 3. In human, 5,6-trans-PGE2, PGE3, and 15-keto-13,14-dihydro-PGE1 are more potent in PRP than in washed platelets. 4. The results indicate that the potency of E-type PGs in human and rabbit platelets is different and plasma can essentially influence the anti-aggregatory effect of PGEs; plasma can either decrease or increase potency.

Adenosine Diphosphate↗
PubMed1988

Solvent selectivity in the resolution of some regioisomeric and diastereomeric prostaglandin intermediates on silica.

The possibilities of predicting the selectivity in the resolution of regioisomeric and diastereomeric prostaglandin intermediates on silica gel was investigated. A satisfactory correlation between log alpha and the solvent localization parameters m and m0 was obtained, confirming the importance of solvent-solute localization in determining alpha values. The results will be useful in developing further the theory of the selectivity of resolution.

Chemical Phenomena↗
PubMed1987

Identification and biological activity of a novel natural prostaglandin, 5,6-dihydro-prostaglandin E3.

A novel natural E-prostaglandin was detected by HPLC among the endogenous prostaglandins extracted from ram seminal vesicles. The corresponding precursor - all-cis-eicosa-8, 11, 14, 17-tetraenoic acid was isolated from bovine liver lipids and the preparative biosynthesis with the microsomal fraction of ram seminal vesicles was performed. The isolated product was purified by HPLC and identified by GC-MS as 5,6-dihydro-PGE3. The results of in vitro tests demonstrate that 5,6-dihydro-PGE3 is 14 times less active uterine stimulant than PGE1, at the same time retaining 75% of the anti-aggregatory potency of PGE1. Thus, 5,6-dihydro-PGE3 meets the requirements of a selective antithrombotic agent more than PGE1.

Alprostadil↗