Triiodothyronine rapidly alters the TSH content and the secretory granules distribution in male rat thyrotrophs by a cytoskeleton rearrangement-independent mechanism

Rapid actions of T3 on TSH synthesis in posttranscriptional steps, such as polyadenylation and translation rate, have already been described. The focus of this paper was to characterize rapid actions of T3 on TSH secretion and the involvement of actin and microtubule cytoskeleton in this process. For that, sham-operated (SO) and thyroidectomized (Tx) rats were subjected to acute or chronic treatment with T3. We observed a disarrangement in microtubule and actin cytoskeletons and an increase in Tshb mRNA levels in Tx rats, whereas the total TSH protein content was reduced in the pituitary gland as a whole, but increased in the secretory granules close to the plasma membrane of thyrotrophs, as well as in the extracellular space. The acute T3 dose promoted a rapid increase and redistribution of TSH secretory granules throughout the cytoplasm, as well as a rearrangement in actin and microtubule cytoskeletons. The T3 chronic treatment outcome reinforces the acute effects observed and, additionally, evinces an increase in the α-tubulin content and a rearrangement in microtubule cytoskeleton. Thus, T3 is able to rapidly suppress TSH secretion and, in parallel, to promote a rearrangement in actin and microtubules assembly throughout the pituitary gland, effects that seem to be independent from each other.

Maternal diabetes affects cell proliferation in developing rat placenta

Placentation starts with the formation of a spheroidal trophoblastic shell surrounding the embryo, thus facilitating both implantation into the uterine stroma and contact with maternal blood. Although it is known that diabetes increases the placental size and weight, the mechanisms responsible for this alteration are still poorly understood. In mammals, cellular proliferation occurs in parallel to placental development and it is possible that diabetes induces abnormal uncontrolled cell proliferation in the placenta similar to that seen in other organs (e.g. retina). To test this hypothesis, the objective of this work was to determine cell proliferation in different regions of the placenta during its development in a diabetic rat model. Accordingly, diabetes was induced on day 2 of pregnancy in Wistar rats by a single injection of alloxan (40 mg/kg i.v.). Placentas were collected on days 14, 17, and 20 postcoitum. Immunoperoxidase was used to identify Ki67 nuclear antigen in placental sections. The number of proliferating cells was determined in the total placental area as well as in the labyrinth, spongiotrophoblast and giant trophoblast cell regions. During the course of pregnancy, the number of Ki67 positive cells decreased in both control and diabetic rat placentas. However, starting from day 17 of pregnancy, the number of Ki67 positive cells in the labyrinth and spongiotrophoblast regions was higher in diabetic rat placentas as compared to control. The present results demonstrate that placentas from the diabetic rat model have a significantly higher number of proliferating cells in specific regions of the placenta and at defined developmental stages. It is possible that this increased cell proliferation promotes thickness of the placental barrier consequently affecting the normal maternal-fetal exchanges.

Mechanisms involved in the reduced leukocyte migration in intrauterine undernourishment

OBJECTIVE

We investigated factors that may be involved in the reduced leukocyte migration observed in intrauterine undernourished rats.

METHODS

Male Wistar rat offspring (8-9 wk of age) of dams fed during pregnancy with 50% less food than control dams were used to measure L-selectin expression (by flow cytometry), bone marrow cell count, blood cell count, laminin and type IV collagen in the basal membrane of venules of the spermatic fascia (by immunohistochemistry), total protein level and serum albumin, and the production of leukotriene B4 after stimulation with tumor necrosis factor-alpha and corticosterone plasma levels (by enzyme-linked immunosorbent assay).

RESULTS

Hypocellularity in bone marrow and peripheral blood and reduced L-selectin expression were found in the undernourished rat offspring (UR) compared with nourished offspring (NR; P < 0.05). Type IV collagen in the basal membrane of the venules of the spermatic fascia was less in UR than in NR (P < 0.05). The total protein levels and serum albumin did not differ between the two groups. Leukotriene B4 production after stimulation with tumor necrosis factor-alpha was lower in UR (P < 0.05). These differences could not be attributed to circulating glucocorticoids levels, which were not different in the NR and UR groups.

CONCLUSION

Our data suggest that all observed differences contribute to reduced leukocyte migration in undernourishment.

Collagen birefringence in skin repair in response to red polarized-laser therapy

We use the optical path difference (OPD) technique to quantify the organization of collagen fibers during skin repair of full-thickness burns following low-intensity polarized laser therapy with two different polarization incidence vectors. Three burns are cryogenerated on the back of rats. Lesion L(parallel) is irradiated using the electric field vector of the polarized laser radiation aligned in parallel with the rat's occipital-caudal direction. Lesion L(perpendicular) is irradiated using the electric field vector of the polarized laser radiation aligned perpendicularly to the aforementioned orientation. Lesion C is untreated. A healthy area labeled H is also evaluated. The tissue samples are collected and processed for polarized light microscopy. The overall finding is that the OPD for collagen fibers depends on the electric field vector of the incident polarized laser radiation. No significant differences in OPDs are observed between L(parallel) and H in the center, sides, and edges of the lesion. Lesions irradiated using the electric field vector of the polarized laser radiation aligned in parallel with the rat's occipital-caudal direction show higher birefringence, indicating that collagen bundles in these lesions are more organized.

Collagen types I, III, and V constitute the thick collagen fibrils of the mouse decidua

A mammal's endometrium is deeply remodeled while receiving and implanting an embryo. In addition to cell proliferation and growth, endometrial remodeling also comprises synthesis and degradation of several molecular components of the extracellular matrix. All of these events are orchestrated by a precise sequence of ovarian hormones and influenced by several types of cytokines. As we have previously reported, an intriguing and rapid increase in collagen fibril diameter occurs in the decidualized areas of the endometrium, surrounding the implantation crypt, whereas collagen fibrils situated far from the embryo remain unchanged. Collagen fibrilogenesis is a complex molecular process coordinated by a number of factors, such as the types and amounts of glycosaminoglycans and proteoglycans associated with collagen molecules. Collagen genetic type, mechanical stress, aging, and other factors not yet identified also contribute to this development. A recent study suggests that thick fibrils from mouse decidua are formed, at least in part, by aggregation of thin fibrils existing in the stroma before the onset of decidualization. In the present ultrastructural study using single and double immunogold localization, we showed that both thin and thick collagen fibrils present in the mouse pregnant endometrium endometrium are heterotypic structures formed at least by type I, type III, and type V collagens. However, type V collagen predominates in the thick collagen fibrils, whereas it is almost absent of the thin collagen fibrils. The putative role of type V homotrimer in the rapid increase of the diameter of collagen fibrils of the mouse decidua is discussed.

Endothelin-1 contributes to the sexual differences in renal damage in DOCA-salt rats

We investigated whether gender differences in renal damage in DOCA-salt hypertension are associated with effects of ovarian hormones and/or endothelin-1 (ET-1). Renal injuries and renal pre-pro-ET-1 mRNA expression were enhanced in male and female ovariectomized (OVX) DOCA rats versus female DOCA rats. Treatment with estrogen plus progesterone or progesterone, but not estrogen alone, attenuated renal damage and pre-pro-ET-1 mRNA expression in OVX DOCA rats. The ETA antagonist BMS182874 greatly ameliorated renal damage in male and OVX DOCA rats. In conclusion, the ovarian hormones have a protective role on the renal structural alterations in female DOCA rats by modulating effects of ET-1, via ETA receptors.

Repercussions of digoxin, digitoxin and estradiol on the endometrial histomorphometry of oophorectomized mice

The digitalics (digoxin and digitoxin) have an estrogenic action, confirmed by the presence of gynecomastia observed in men who are users of steroids, and it is also confirmed by the increase of vaginal trophism in postmenopausal female users, although little is known about the endometrium. These effects might result from the similarity of the chemical structures between the digitalics and estrogens. This study evaluated 27 female mice. Twenty-four mice were oophorectomized and in three of them the ovaries were manipulated, but they were not extirpated. Forty days after the surgery each group of three animals received a medication with a specific drug (digoxin, digitoxin or estradiol) for 2 weeks. Twenty-four hours after the last medication, all the animals were hysterectomized and the wombs were processed, cut and put on laminae. By histomorphometry, we analysed the area of the transverse sections of the endometrium, the area of the endometrial glands and the height of the uterine epithelium. The respective averages and the standard deviations were calculated. The results showed that digoxin neither presented an estrogenic action (p > 0.05) nor raised the power of the estradiol action (p > 0.05). Digitoxin promoted an estrogenic action on the glandular area (p < 0.05), and also raised the power of the estradiol action on the transverse section of the endometrium and on the glandular area (p < 0.05).

Perlecan and Syndecan-4 in Uterine Tissues during the Early Pregnancy in Mice

PROBLEM

During early pregnancy in mice, there is recruitment of specific immune cells, remodeling of the endometrium, cell differentiation and synthesis of new molecules.

METHOD OF STUDY

Immunohistochemistry was used to determine the distribution of perlecan and syndecan-4 in the uteri before and after embryo implantation.

RESULTS

During pre-implantation, perlecan was identified in basement membranes and extracellular spaces of the endometrial stroma. In contrast, expression of syndecan-4 was quite weak. In the peri-implantation period, perlecan remained in the basement membranes, and it was no longer observed in the stroma and it was identified in the embryonic cells. On day 4 of pregnancy, syndecan-4 increased in the fibroblasts of the subepithelial stroma. After implantation, syndecan-4 was pronounced in pre-decidual and mature decidual cells.

CONCLUSIONS

The coordinate balance between the pre- and post-implantation periods suggests a role of these two molecules in the adaptive modification of the uterine microenvironment to receive and implant the embryo.

Increase of interstitial collagen in the mouse endometrium during decidualization

Decidualization in the mouse consists of an extensive remodeling of the endometrial extracellular matrix, resulting in a reduction of the extracellular spaces, an increase in the diameter of collagen fibrils, and changes in the relative ratio of different types of glycosaminoglycans. To assess the dynamic changes of the endometrial extracellular matrix during decidualization, collagen was analyzed biochemically and immunochemically in the endometrium of nulliparous and day 5 to day 8 pregnant mice. The amount of collagen per gram dry weight was higher in the endometrium of implantation sites than in interimplantation sites. Collagen types I, III, and V were the main components of the endometrium of nulliparous and pregnant animals. The amount of collagen type V was higher in the endometrium of pregnant animals than in nulliparous ones. A relative unusual homotrimeric form of collagen type V, probably formed by [alpha1(V)](3), was detected in pregnant endometrium by gel eletrophoresis and immunoblotting.

Effects of Low-Intensity Polarized Visible Laser Radiation on Skin Burns: A Light Microscopy Study

OBJECTIVE

This study was carried out to investigate the influence of low-intensity polarized visible laser radiation on the acceleration of skin wound healing.

BACKGROUND DATA

Low-level laser therapy (LLLT) at adequate wavelength, intensity, and dose can accelerate tissue repair. However, there is still unclear information about light characteristics, such as coherence and polarization. Some studies indicate that linearly polarized light can survive through long propagation distance in biological tissue.

MATERIALS AND METHODS

Three burns about 6 mm in diameter were created on the back of rats with liquid N(2). Lesion "L(//)" was irradiated by He-Ne laser (lambda = 632.8 nm), D= 1.0 J/cm(2), with linear polarization parallel to the spinal column of the rat. Lesion "L(inverted v)" was irradiated using the same laser and dose, but the light polarization was aligned perpendicularly to the relative orientation. Lesion "C" was not irradiated in order to be considered as control. The animals were sacrificed at day 3-17 after lesion creation. Samples were collected and prepared for histological analysis.

RESULTS

Histological analysis showed that the healing of irradiated wounds was faster than that of non-irradiated wounds. Moreover, it was observed that skin wound repair is dependent on polarization orientation with respect to a referential axis as the animal's spinal column. Consequently, "L(//)" was completely healed after 17 days, whereas "L (perpendicular) " showed a moderate degree of healing after the same period.

CONCLUSIONS

These results indicate that the relative direction of the laser polarization plays an important role in the wound healing process when highly coherent He-Ne laser is used.

Distribution of biglycan and decorin in rat dental tissue

Biglycan and decorin are small leucine-rich proteoglycans that play several biological and structural roles in different tissues and organs. Several reports have indicated that biglycan participates in odontoblast and ameloblast differentiation and in the calcification process. In the present study we show that the expression of biglycan changes from within the ameloblasts and odontoblasts to the extracellular space according to the stage of animal development. In predentin and in the pulp space, however, biglycan was continually expressed throughout the period of investigation. In contrast, decorin was absent in odontoblasts and in ameloblasts and was exclusively expressed in predentin throughout the period of observation. In young rats, however, decorin was expressed in the extracellular spaces of the pulp, where it was concentrated mainly in the peripheral pulp.

Distribution of versican and hyaluronan in the mouse uterus during decidualization

Preparation for embryo implantation requires extensive adaptation of the uterine microenvironment. This process consists of cell proliferation and cell differentiation resulting in the transformation of endometrial fibroblasts into a new type of cell called decidual cell. In the present study, we followed the space-time distribution of versican and hyaluronan (HA) in different tissues of the uterus before and after embryo implantation. Fragments of mouse uteri obtained on the fourth, fifth, sixth and seventh days of pregnancy were fixed in Methacarn, embedded in Paraplast and cut into 5-microm thick sections. HA was detected using a biotinylated fragment of the proteoglycan aggrecan, which binds to this glycosaminoglycan with high affinity and specificity. Versican was detected by a polyclonal antibody. Both reactions were developed by peroxidase methods. Before embryo implantation, both HA and versican were present in the endometrial stroma. However, after embryo implantation, HA disappeared from the decidual region immediately surrounding the implantation chamber, whereas versican accumulated in the same region. The differences observed in the expression of HA and versican suggest that both molecules may participate in the process of endometrial decidualization and/or embryo implantation.

The small proteoglycan biglycan is associated with thick collagen fibrils in the mouse decidua

In mice, embryo implantation induces profound changes in the endometrium. These changes include redifferentiation of endometrial fibroblasts and extensive remodeling of extracellular matrix components. We have previously shown that, during this process, there is an impressive increase in the thickness of collagen fibrils present in decidualised areas that surround the implantation site, while collagen fibrils in non-decidualised areas and in the interimplantation site remain thin. In vitro and in vivo experiments have identified small leucine rich proteoglycans (SLRPs) as regulators of collagen fibrillogenesis. In a previous study, we demonstrated a difference between the pre-implantation and the post-implantation expression and distribution of four SLRPs types in uterine tissues. The present study, utilising immunocytochemical electron microscopy, shows that biglycan is associated with the presence of thick collagen fibrils in decidualised regions of the endometrium and that decorin is associated exclusively with thin collagen fibrils in non-decidualised endometrial areas. These results strongly indicate that biglycan plays a role in collagen fibrillogenesis and probably participates in the determination of collagen fibril thickness in the mouse decidua.

Small leucine-rich proteoglycans (SLRPs) in uterine tissues during pregnancy in mice

Remodelling of the extracellular matrix (ECM) occurs during decidualization of the endometrium in mice. Previously we have documented the appearance of large-diameter collagen fibrils around mature decidual cells between day 5 and day 7 of pregnancy. Proteoglycans are important in the regulation of collagen fibrillogenesis, and the present study analysed four members (decorin, biglycan, lumican and fibromodulin) of the family of small leucine-rich proteoglycans (SLRPs) in the uterus from day 1 to day 7 of pregnancy. Decorin was present together with lesser amounts of lumican in the stroma before the onset of decidualization, whereas biglycan and fibromodulin were almost absent. Biglycan and, less significantly, lumican were expressed in decidualized regions of the endometrium, but decorin was absent. Fibromodulin was weakly expressed in the non-decidualized stroma, but only after implantation. Decorin and lumican were strongly expressed in the undifferentiated interimplantation site stroma, whereas biglycan and fibromodulin were expressed only weakly. These results indicate that the SLRP profile of the uterine ECM alters with differentiation of endometrial stromal cells. The large decidual collagen fibrils are thought to arise by lateral association of smaller diameter fibrils. As decorin has been shown to inhibit lateral association of collagen fibrils, its disappearance between day 2 and day 5 of pregnancy may be a prerequisite for the formation of large fibrils in decidua in mice.