Changes of connexin43 expression in non-pregnant porcine myometrium correlate with progesterone concentration during oestrous cycle.

Connexin43 (Cx43) is a major protein of myometrial gap junctions. The number of Cx43 gap junctions increase dramatically with the onset of labour in association with development of synchronized uterine contractions. The formation of myometrial gap junctions follows an increase in the oestrogen to progesterone ratio indicating an important role of steroid hormones in regulating Cx43 expression at term. However, no relationship has been established between the expression of Cx43 in the non-pregnant myometrium and concentration of steroid hormones during the oestrous cycle. Here, we used immunofluorescence and Western blotting to analyse the expression of Cx43 gap junctions in the myometrium of pre-pubertal pigs (n = 7) and mature pigs at pre-ovulatory (n = 7), luteal (n = 5) and late luteal (n = 3) stages of the oestrous cycle. The number of Cx43 gap junctions calculated per 1 mm(2) of the myometrial section was low in pre-pubertal pigs and significantly higher (p < 0.022) in pre-ovulatory animals. In relation to pre-ovulatory animals the number of myometrial gap junctions was significantly lower (p < 0.019) at the luteal phase and correlated with significantly higher (p < 0.005) concentration of endogenous progesterone. Phosphorylated isoforms of Cx43 protein were expressed in the myometrium of pre-pubertal pigs and mature animals at pre-ovulatory and late luteal phases, while they were down regulated at the luteal stage. These results indicate that changes of Cx43 expression in the porcine myometrium during the oestrous cycle may be regulated by progesterone concentration and may contribute to the modulation of uterine motility.

Capillary density and capillary-to-fibre ratio in vastus lateralis muscle of untrained and trained men.

Muscle fibre profile area (Af), volume density (Vv), capillary-to-fibre ratio (CF) and number of capillaries per fibre square millimetre (CD) were determined from needle biopsies of vastus lateralis of twenty-four male volunteers (mean +/- SD: age 25.4+/-5.8 years, height 178.6+/-5.5 cm, body mass 72.1+/-7.7 kg) of different training background. Seven subjects were untrained students (group A), nine were national and sub-national level endurance athletes (group B) with the background of 7.8+/-2.9 years of specialised training, and eight subjects were sprint-power athletes (group C) with 12.8+/-8.7 years of specialised training. Muscle biopsies of vastus lateralis were analysed histochemically for mATPase. Capillaries were visualized and counted using CD31 antibodies against endothelial cells. There were significant differences in the Vv of type I and type II muscle fibres in both trained groups, B (51.8%; 25.6%) and C (50.5%; 26.4%). However, in untrained group A that was treated as a reference group, the difference between Vv of type I and type II fibres was less prominent, nevertheless statistically significant (42.1%; 35.1%). There was also a significant difference in CF: 1.9 in group A and 2.1 in groups B and C. The number of capillaries per mm2 (CD) was 245 (group A), 308 (group B) and 325 (group C). Significant differences (P<0.05) in CF and CD, were found only between group A (1.9; 245) and both groups of trained men, B and C (2.1; 308 and 325). However, endurance athletes (group B), such as long-distance runners, cyclists and cross country skiers, did not differ from the athletes representing short term, high power output sports (group C) such as ice hockey, karate, ski-jumping, volleyball, soccer and modern dance.

Characteristics of myosin profile in human vastus lateralis muscle in relation to training background.

Twenty-four male volunteers (mean +/- SD: age 25.4+/-5.8 years, height 178.6+/-5.5 cm, body mass 72.1+/-7.7 kg) of different training background were investigated and classified into three groups according to their physical activity and sport discipline: untrained students (group A), national and sub-national level endurance athletes (group B, 7.8+/-2.9 years of specialised training) and sprint-power athletes (group C, 12.8+/-8.7 years of specialised training). Muscle biopsies of vastus lateralis were analysed histochemically for mATPase and SDH activities, immunohistochemically for fast and slow myosin, and electrophoretically followed by Western immunoblotting for myosin heavy chain (MyHC) composition. Significant differences (P<0.05) regarding composition of muscle fibre types and myosin heavy chains were found only between groups A (41.7+/-1.6% of MyHCI, 40.8+/-4.0% of MyHCIIA and 17.5+/-4.0% of MyHCIIX) and B (64.3+/-0.8% of MyHCI, 34.0+/-1.4% of MyHCIIA and 1.7+/-1.4% of MyHCIIX) and groups A and C (59.6+/-1.6% of MyHCI, 37.2+/-1.3% of MyHCIIA and 3.2+/-1.3% of MyHCIIX). Unexpectedly, endurance athletes (group B) such as long-distance runners, cyclists and cross country skiers, did not differ from the athletes representing short term, high power output sports (group C) such as ice hockey, karate, ski-jumping, volleyball, soccer and modern dance. Furthermore, the relative amount of the fastest MyHCIIX isoform in vastus lateralis muscle was significantly lower in the athletes from group C than in students (group A). We conclude that the myosin profile in the athletes belonging to group C was unfavourable for their sport disciplines. This could be the reason why those athletes did not reach international level despite of several years of training.

Connexin43 in porcine myocardium and non-pregnant myometrium.

It is generally accepted that connexin43 (Cx43) is a major constituent of heart and myometrial gap junctions. However, the presence of Cx43 gap junctions in non-pregnant myometrium is still poorly documented. Tissue sections of porcine heart and non-pregnant uterus and myometrial smooth muscle cell cultures were immunostained with monoclonal antibody against Cx43. In the heart, intensive immunostaining was confined to the intercalated discs as previously reported. In the non-pregnant uterus, punctuate immunostaining of Cx43 was seen throughout the myometrium along cell interfaces between myocytes. The expression of Cx43 was sustained in cultured smooth muscle cells isolated from non-pregnant myometrium. Western blotting has detected single isoform of Cx43 in both, cardiac and myometrial tissues. The electrophoretic mobility of porcine heart Cx43 was similar to that of myometrial isoform but different from the pattern of mobility of Cx43 of the rat heart. Hence, porcine myometrium may provide attractive model for studying cellular mechanisms triggering expression of gap junction protein in normal (non-pregnant) uterus.

Effect of progesterone and oestradiol on expression of connexin43 in cultured human myometrium cells.

In human myometrium, the formation of gap junctions at various stages of labour and in correlation with the concentration of progesterone and oestradiol in maternal blood was described previously by electron microscopy and laser confocal microscopy of immunohistochemically stained myometrial sections. The present investigation focused on the effect of continuous exposure of isolated myometrial tissue to progesterone and oestradiol on the number of gap junction plaques in human myometrium cells in vitro. The presence of gap junctions was evaluated by immunocytochemistry with antibodies against gap junction protein, connexin43 (Cx43). Human myometrial cells were isolated from biopsies obtained from term pregnant women who had an elective caesarean operation in the 37th or 40th week of pregnancy. The dispersed myometrial cells that were obtained by limited enzymatic digestion of the myometrial samples were maintained in monolayer culture for 1, 3 and 6 days in the presence of medium that contained foetal bovine serum and the steroids at different concentration. In primary culture, as well as after several passages, the characteristics of these cells were morphologically and biochemically similar to those of smooth muscle cells and myometrial tissue. The obtained results showed that the cells in culture responded synchronously to the increased concentrations of oestradiol/progesterone mixtures. The number of gap junctions increased significantly on days 1, 3 and 6 in culture and showed positive correlation (p < 0.05) with the cell number when the concentration of oestradiol was raised to 1 microgram/mL in the progesterone ratio (1.0 microgram/0.5 microgram/mL). No significant correlation, however, in connexin43 gap junction number versus cell number was observed between the six experimental groups treated with progesterone only.

Immunohistochemical analysis of connexin26 and 43 expression in the mouse alimentary tract.

The spatial pattern of connexins26 (Cx26) and 43 (Cx43) expressions were investigated in the mouse digestive tract by immunocytochemistry. High levels of connexin43 in the epithelium of the oesophagus, non-glandular part of the stomach, and the circular layer of duodenal and ilea muscularis externa were detected. Cx26 was expressed in stratum granulosum of oesophagal folds and in the non-glandular part of the stomach. A low level of immunoreactivity of Cx43 was observed in the circular, and very low in the longitudinal layer of the muscularis externa in the stomach and colon. No immunoreactivity for Cx26 and Cx43 was found in the entire muscularis externa of the oesophagus or in the longitudinal muscle layers of the duodenum and ileum.

Antiserum against connexin32 fragment reacts with a 32-kD protein localised in gap junctions of mouse and rat liver, endometrium and in the fish heart.

The expression of various connexins so far identified is metabolically and developmentally regulated. Examples include uterine endometrium where the expression of gap junction protein, connexin32 (Cx32) is regulated by steroid hormones. In this study we attempted to synthesise a short peptide which matches the portion of the amino acid sequence of the Cx32. Cx32 has primary structure predicted from the nucleotide sequence of cDNA clone. A fragment of Cx32 molecule was synthesised to produce anti-peptide antibody for detecting gap junction protein in mouse and rat liver and endometrium. The 12-peptide, plus Abu residue that corresponds to residues 108-119 (LEGHGDPLHLEE-Abu) of the rat Cx32 (283-mer) was synthesised by the solid phase method. Antibodies against this peptide were raised in rabbits, screened for reactivity and specificity using dot blot assays [15] and used for immunocytochemical staining at the light and at electron microscope levels. The antibodies also reacted with fish heart myocardium.

Scanning electron microscopy of the egg surface of the common toad, Bufo bufo, following fertilization and during first cleavage.

Scanning electron microscopy was applied for surface analysis of unfertilized and fertilized eggs of the common toad, Bufo bufo. In unfertilized eggs two types of surface protrusions were found: microvilli and microfolds. 5 min post fertilization (pf), at the place of sperm entrance, a fertilization body appears, surrounded by a group of small depressions, which gradually spread over the whole egg surface. This phenomenon is considered to reflect structural changes of the egg membrane, occurring in response to cortical granule breakdown. Another process which follows fertilization is the disappearance of microfolds and the formation of microvilli. Shortly before the first cleavage, the egg surface smooths out and a zone of spherical microvilli becomes visible at the presumptive furrow region. While the cleavage furrow penetrates into the egg, microvilli appear at the surface of the newly forming blastomeres.

Comparison of reactions to skin grafts in green frogs: Rana lessonae cam., R. esculenta L. and R. ridibunda pall.

Adult, field-collected green frogs, Rana lessonae and R. ridibunda, and their interspecific hybrid R. esculenta were tested with skin grafts at 22 +/- 2 degrees C. Two types of reactions to grafts were observed. 1) Median survival time (MST) was about 25 days, which was observed in R. lessonae hosts in response to allogeneic stimuli and to skin grafts from R. esculenta, and R. esculenta hybrids given grafts from the parental species. 2) MST was equal to or longer than 30 days, which was observed in the case of grafts among R. esculenta, and in R. ridibunda hosts given grafts from R. esculenta and R. lessonae. It seems that a high histocompatibility allele polymorphism occurs in R. lessonae even within one population, whereas lower polymorphism and/or reduced immunological reactivity occurs in R. ridibunda.

Rejection of skin allo- and xenografts in the grass frog, Rana temporaria and the edible frog, Rana esculenta.

The fate of orthotopic dorsal skin allo- and xenografts at 22 +!- 2 degrees C in the grass frog, Rana tempororai (Rt) and in the edible frog, R. esculenta (Re) which is an interspecific hybrid of R. ridibunda and R. lessonae. Median survival times (MSTs) in experimental groups Rt in equilibrium Rt, Re in equilibrium Re and Rt comes from Re were 28, 26 and 25 days, respectively. In R. tempororia hosts the significantly shorter viability of xenografts than allogeneic grafts may be caused by the broader spectrum of transplantation antigens of the hybrid donors. In the experimental group Re comes from Rt similar surviva times of sensitizing, second set and third set grafts were observed (24, 22, and 22 days, respectively). The first symptoms of destruction in the grafts of dorsal skin of R. temporaria were visible earlier than in the grafts of dorsal skin of R. esculenta independently of the species of the hosts. Hypotheses which could explain the differences observed are discussed.