Venlafaxine-induced adrenergic signaling stimulates Leydig cells steroidogenesis via Nur77 overexpression: a possible role of EGF

Venlafaxine, a norepinephrine and serotonin reuptake inhibitor, impairs rat sperm parameters, spermatogenesis and causes high intratesticular estrogen and testosterone levels, indicating that Leydig cells (LCs) may be a venlafaxine target. We evaluated the effect of venlafaxine treatment on LCs in vivo, focusing on adrenergic signaling, EGF immunoexpression and steroidogenesis. Germ cells mitotic/meiotic activity and UCHL1 levels were also evaluated in the seminiferous epithelium. Adult male rats received venlafaxine (30 mg/kg) or distilled water. In testicular sections, the seminiferous tubules, epithelium and the LCs nuclear areas were measured, and the immunoexpression of Ki-67, UCHL1, StAR, EGF, c-Kit and 17β-HSD was evaluated. UCHL1, StAR and EGF protein levels and Adra1a, Nur77 and Ndrg2 expression were analyzed. MDA and nitrite testicular levels, and serum estrogen and testosterone levels were measured. Venlafaxine induced LCs hypertrophy and Ndrg2 upregulation, in parallel to increased number of Ki-67, c-Kit- and 17β-HSD-positive interstitial cells, indicating that this antidepressant stimulates LCs lineage proliferation and differentiation. Upregulation of Adra1a and Nur77 could explain the high levels of StAR and testosterone levels, as well as aromatization. Enhanced EGF immunoexpresion in LCs suggests that this growth fact is involved in adrenergically-induced steroidogenesis, likely via upregulation of Nur77. Slight tubular atrophy and weak Ki-67 immunoexpression in germ cells, in association with high UCHL1 levels, indicate that spermatogenesis is likely impaired by this enzyme under supraphysiological estrogen levels. These data corroborate the unchanged MDA and nitrite levels. Therefore, venlafaxine stimulates LCs steroidogenesis via adrenergic signaling, and EGF may be involved in this process.

Comparison of Bio-C Pulpo and MTA Repair HP with White MTA: effect on liver parameters and evaluation of biocompatibility and bioactivity in rats

AIM

To evaluate the tissue response promoted by Bio-C Pulpo (Bio), MTA Repair HP (MTA-HP) and White MTA (WMTA) and whether these materials cause liver changes in a rat experimental model.

METHODOLOGY

Polyethylene tubes filled with Bio, MTA-HP and WMTA, and empty tubes (control group, CG) were implanted into the subcutaneous tissues of rats for 7, 15, 30 and 60 days. Inflammatory reaction score (IRS), capsule thickness, number of inflammatory cells (IC), von Kossa reaction, interleukin-6 (IL-6) and alkaline phosphatase (ALP) immunohistochemistry reactions were performed. Combined methods, von Kossa followed by immunohistochemistry for detection of ALP, were performed. At 60 days, the serum glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) levels were measured and liver fragments were collected for histological analysis; the data were assessed by one-way ANOVA analysis followed by Sidak's post-test. The biocompatibility and bioactivity data were subjected to the two-way ANOVA analysis followed by Tukey post hoc test, except the IRS. The IRS data were subjected to the Kruskal-Wallis ANOVA non-parametric test followed by Dunn's test (p ≤ .05).

RESULTS

No significant difference was detected in serum GOT and GPT concentrations and in the number of hepatocytes among the experimental and CG samples. Although Bio-C Pulpo had the highest IC and IL-6-immunolabelled cells (p < 0.0001) at all periods, no significant difference was observed in the IRS among the materials, except at 60 days. In this period, the WMTA had lower IRS. All groups had a significant reduction in the capsule thickness and in the number of IC and IL-6-immunolabelled cells over time. Bio-C Pulpo, MTA-HP and WMTA specimens had greater immunoexpression of ALP than CG (p < .0001). At all periods, von Kossa-positive and birefringent structures were observed in the capsules around the materials. ALP-immunolabelled cells were also seen near von Kossa-positive structures.

CONCLUSIONS

Bio-C Pulpo, MTA-HP and WMTA materials did not cause morphological changes in the liver and no significant alteration in the serum GOT and GPT levels. Moreover, these bioceramic materials were biocompatible and exhibited bioactive potential. However, Bio-C Pulpo induced greater inflammatory infiltrate than MTA-HP and WMTA at all periods.

Phytocystatin CsinCPI-2 Reduces Osteoclastogenesis and Alveolar Bone Loss

Periodontal disease (PD) is a polymicrobial chronic inflammatory condition of the supporting tissues around the teeth, leading to the destruction of surrounding connective tissue. During the progression of PD, osteoclasts play a crucial role in the resorption of alveolar bone that eventually leads to the loss of teeth if the PD is left untreated. Therefore, the development of antiresorptive therapies targeting bone-resorbing cells will significantly benefit the treatment of PD. Here, we demonstrate the inhibitory effect of CsinCPI-2, a novel cysteine peptidase inhibitor from the orange tree, on periodontitis-induced inflammation, alveolar bone loss, and osteoclast differentiation. Using the ligature-induced periodontitis model in mice, we show that treatment with CsinCPI-2 (0.8 µg/g of body weight) significantly reduced inflammatory cell infiltrate in the connective tissue and prevented the loss of alveolar bone mass (BV/TV) caused by PD, effects associated with diminished numbers of TRAP-positive multinucleated cells. Furthermore, CsinCPI-2 significantly downregulated the numbers of inflammatory cells expressing CD3, CD45, MAC387, and IL-1β. In vitro, CsinCPI-2 inhibited RANKL-induced TRAP+ multinucleated osteoclast formation in mouse bone marrow macrophage cultures in a concentration-dependent manner. This effect was not due to cytotoxicity, as demonstrated by the MTT assay. CsinCPI-2 inhibited RANKL-induced mRNA expression of Acp5, Calcr, and Ctsk, as well as the RANKL-induced upregulation of Nfatc1, a crucial transcription factor for osteoclast differentiation. Based on our findings, CsinCPI-2 prevents bone loss induced by PD by controlling the inflammatory process and acting directly on osteoclastogenesis, suggesting an interesting potential for CsinCPI-2 in the strategy for PD treatment.

Experimental models of orthodontic tooth movement and their effects on periodontal tissues remodelling

OBJECTIVES

The present study aimed to compare two different models of orthodontic tooth movement (OTM) in rats by evaluating tooth movement efficiency and periodontal tissues remodelling.

DESIGN

Fifteen animals were randomly distributed into 3 groups: control group (untreated); ligature appliance (LA) as experimental OTM using a closed coil spring fixed around maxillary first molar by steel ligature; occlusal appliance (OA) as experimental OTM using a closed coil spring attached on the occlusal surface of the maxillary first molar. After 15 days, all animals were euthanized, and the maxilla of each animal was collected for qPCR, micro-computed tomography, and histological analyses.

RESULTS

Interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha gene expressions were significantly upregulated in the animals of the LA group as compared to the other groups. No significant difference was observed in tooth displacement between both methods. The LA group presented higher linear bone loss and lower values of bone volume fraction, bone mineral density, trabecular number and increased values of trabecular separation compared to the other groups. The birefringent collagen content in the tension side of the periodontal ligament contained significantly lower collagen content in the LA group than in the control group. Furthermore, on the pressure side, the collagen content was significantly lower in the LA and OA groups than in the control group.

CONCLUSIONS

The OA group presented little or no deleterious effect on periodontal tissues compared to the LA group, suggesting its use may be more reliable for OTM induction in rats for 15 days.

Cimetidine-induced androgenic failure causes cell death and changes in actin, EGF and V-ATPase immunoexpression in rat submandibular glands

Submandibular gland (SMG) is responsive to androgens via androgen receptor (AR). We verified whether cimetidine induces androgenic dysfunction in SMG, and evaluated the structural integrity, cell death and immunoexpression of actin, EGF and V-ATPase in androgen-deficient SMG. Male rats received cimetidine (CMTG) and control animals (CG) received saline. Granular convoluted tubules (GCTs) diameter and number of acinar cell nuclei were evaluated. TUNEL and immunofluorescence reactions for detection of AR, testosterone, actin, EGF and V-ATPase were quantitatively analysed. In CG, testosterone immunolabelling was detected in acinar and ductal cells cytoplasm. AR-immunolabelled nuclei were observed in acinar cells whereas ductal cells showed AR-immunostained cytoplasm, indicating a non-genomic AR action. In CMTG, the weak testosterone and AR immunoexpression confirmed cimetidine-induced androgenic failure. A high cell death index was correlated with decreased number of acinar cells, GCTs diameter and EGF immunoexpression under androgenic dysfunction. Actin immunofluorescence decreased in the SMG cells, but an increased and diffuse cytoplasmic V-ATPase immunolabelling was observed in striated ducts, suggesting a disruption in the actin-dependent V-ATPase recycling due to androgenic failure. Our findings reinforce the androgenic role in the maintenance of SMG histophysiology, and point to a potential clinical use of cimetidine against androgen-dependent glandular tumour cells.

Histomorphometric and immunohistochemical study shows that tricalcium silicate cement associated with zirconium oxide or niobium oxide is a promising material in the periodontal tissue repair of rat molars with perforated pulp chamber floors

AIM

To evaluate the periodontium response to tricalcium silicate (TCS) with zirconium oxide (ZrO₂ ) or niobium oxide (Nb₂ O₅ ) used in the sealing of perforated pulp chamber floors in rat maxillary molars.

METHODOLOGY

In eighty rats, the perforations in right maxillary molars were filled with either TCS + ZrO₂ , TCS + Nb₂ O₅ , White MTA (used as a gold standard material) or no repair material was placed (Sham Group, SG); the left molars of SG, were used as controls (CG). Sections of maxillary fragments following 7, 15, 30 and 60 days were used to evaluate the volume densities of inflammatory cells (VvIC) and fibroblasts (VvFb), width of the periodontal space, amount of collagen, number of osteoclasts and number of IL-6-immunostained cells. The data were subjected to two-way ANOVA followed by Tukey's test (P ≤ 0.05).

RESULTS

At all periods, significant differences in VvIC were not detected among TCS + ZrO_2, TCS + Nb₂ O₅ and MTA groups, which had values significantly lower (P < 0.05) than the SG. Significant differences in the number of IL-6-immunolabelled cells were not observed among TCS + ZrO₂ , TCS + Nb₂ O₅ and MTA groups (P > 0.05) at 15, 30 and 60 days. At 7, 15 and 30 days, the number of osteoclast was significantly greater in TCS + ZrO_2, TCS + Nb₂ O₅ and MTA (P < 0.05) than in the CG; no significant difference was detected after 60 days (P > 0.05). The width of the periodontal space and amount of collagen in TCS + ZrO₂ and TCS + Nb₂ O₅ groups were similar to the CG at 30 and 60 days while SG specimens had a significant reduction (P < 0.05) in the amount of collagen and significant increase (P < 0.05) in the width of the periodontal space.

CONCLUSIONS

TCS + ZrO₂ and TCS + Nb₂ O₅ were associated with periodontium repair since these materials allowed the reestablishment of periodontal space width and collagen formation when used in the filling of uninfected perforations in the pulp chamber floor of maxillary rat molars. Furthermore, the significant reduction in the periodontal space of TCS + ZrO₂ and TCS + Nb₂ O₅ specimens after 60 days confirmed that the experimental materials were associated with a more rapid recovery of the injured tissues than MTA.

Venlafaxine-induced damage to seminiferous epithelium, spermiation, and sperm parameters in rats: A correlation with high estrogen levels

BACKGROUND

Venlafaxine (selective serotonin and norepinephrine reuptake inhibitor) use has increased worldwide. However, the impact of venlafaxine on testes and sperm parameters has not been investigated.

OBJECTIVES

We evaluated venlafaxine impact on testicular and sperm parameters and verified whether the changes are reversible.

METHODS

Animals from venlafaxine-35 days and venlafaxine-65 days groups received 30 mg/kg of venlafaxine for 35 days. Control-35 days and control-65 days received distilled water. In control-65 days and venlafaxine-65 days, the treatment was interrupted for 30 days. Sperm concentration, morphology, motility, and mitochondrial activity were analyzed. Number of step 19 spermatids (NLS), frequency of tubules with spermiation failure, Sertoli cells number, and TUNEL-positive germ cells were quantified. Testicular aromatase, connexin 43 (Cx43) immunoexpression, Cx43 protein levels, and Cx43 expression were evaluated. Either intratesticular testosterone or estrogen levels were measured.

RESULTS

Venlafaxine impaired sperm morphology, reduced sperm concentration, mitochondrial activity, and sperm motility. The frequency of tubules with spermiation failure and NLS increased in parallel to increased Cx43 immunoexpression; mRNA and protein levels; and aromatase, testosterone, and estrogen levels. An increase in germ cell death and decreased Sertoli cells number were observed. In venlafaxine-65 days, except for sperm motility, mitochondrial activity, Sertoli cells number, and germ cell death, all other parameters were partially or totally recovered.

CONCLUSION

Venlafaxine increases testosterone aromatization and Cx43. This drug, via high estrogen levels, disturbs Sertoli cells, induces germ cell death, and impairs spermiation and sperm parameters. The restoration of spermiation associated with the decreased Cx43 and hormonal levels in venlafaxine-65 days reinforces that high estrogen levels are related to venlafaxine-induced changes. The presence of damaged Sertoli cells, germ cell death, and low sperm motility in venlafaxine-65 days indicates that interruption of treatment for 30 days was insufficient for testicular recovery and points to a long-term estrogen impact on the seminiferous epithelium.

Evaluation of the biological properties of two experimental calcium silicate sealers: an in vivo study in rats

AIM

To evaluate the biological properties of experimental sealers based on tricalcium silicate and dicalcium silicate, manipulated with polyethylene glycol (CE-1) and with the addition of calcium hypochlorite (CE-2) compared to AH Plus (AHP) and TotalFill BC Sealer (TBC).

METHODOLOGY

The tissue reaction caused by the materials in the subcutaneous tissue of rats was evaluated after implantation of polyethylene tubes filled with the materials at 7, 15, 30 and 60 days. Sections were stained with haematoxylin and eosin (HE) for morphological analysis and to evaluated number of inflammatory cells/mm² (ICs). Sections were used for immunohistochemical detection of interleukin-6 (IL-6) and osteocalcin (OC). The von Kossa method was used to identify calcium precipitation in the capsules. The data were submitted to anova and Tukey's tests, with 5% significance level.

RESULTS

At 7 days, CE-1, CE-2 and AHP had higher numbers of ICs. AHP presented higher immunolabelling for IL-6. After 15 days, regarding IL-6, there was no difference between CE-2 and the control group. At 30 days, AHP exhibited the highest number of IC (P < 0.05) and CE-2 and the control group presented the lowest ICs and IL-6-positive cells. After 60 days, all materials exhibited decreases in ICs. CE-2, TBC and the control had the lowest values (P < 0.05). No significant difference was detected between CE-1 and TBC, and between CE-2 and control considering the immunoexpression of IL-6. In this period, AHP had the greatest number of IC and IL-6 (P < 0.05). In all periods, CE-1, CE-2 and TBC sealers had von Kossa-positive structures and OC-immunolabelled cells. CE-2 had higher number of OC-positive cells than the CE-1 and TBC sealers (P < 0.05), in all periods. OC immunolabelling was not observed in the capsules of AH Plus and the control groups.

CONCLUSIONS

The experimental sealer and its association with calcium hypochlorite, in addition to TotalFill BC Sealer, were biocompatible and had bioactive potential.

Fluoxetine-induced androgenic failure impairs the seminiferous tubules integrity and increases ubiquitin carboxyl-terminal hydrolase L1 (UCHL1): Possible androgenic control of UCHL1 in germ cell death?

The selective serotonin reuptake inhibitor fluoxetine has been used for the treatment of depression. Although sexual disorders have been reported in male patients, few studies have demonstrated the fluoxetine effect on the reproductive histophysiology, and the target of this antidepressant in testes is unknown. We evaluated the impact of short-term treatment with fluoxetine on the adult rat testes, focusing on steroidogenesis by Leydig cells (LC) and androgen-dependent testicular parameters, including Sertoli cells (SC) and peritubular myoid cells (PMC). Since UCHL1 (ubiquitincarboxyl-terminal hydrolase L1) seems to control spermatogenesis, the immunoexpression of this hydrolase was also analyzed. Adult male rats received 20 mg/kg BW of fluoxetine (FG) or saline (CG) for eleven days. In historesin-embedded testis sections, the seminiferous tubule (ST) and epithelial (Ep) areas, and the LC nuclear diameter (LCnu) were measured. The number of abnormal ST, androgen-dependent ST, SC and PMC was quantified. Testicular β-tubulin levels and peritubular actin immunofluorescence were evaluated. Serum testosterone levels (STL) and steroidogenesis by 17β-HSD6 immunofluorescence were analyzed, and either UCHL1-immunolabeled or TUNEL-positive germ cells were quantified. In FG, abnormal ST frequency increased whereas ST and Ep areas, androgen-dependent ST number, LCnu, 17β-HSD6 activity and STL reduced significantly. TUNEL-positive PMC and SC was related to decreased number of these cells and reduction in peritubular actin and β-tubulin levels. In FG, uncommon UCHL1-immunoexpression was found in spermatocytes and spermatids, and the number of UCHL1-immunolabeled and TUNEL-positive germ cells increased in this group. These findings indicate that LC may be a fluoxetine target in testes, impairing PMC-SC integrity and disturbing spermatogenesis. The increase of UCHL1 in the damaged tubules associated with high incidence of cell death confirms that this hydrolase regulates germ cell death and may be controlled by androgens. The fertility in association with the androgenic status of patients treated with fluoxetine should be carefully evaluated.

Biocompatibility of mineral trioxide aggregate flow and biodentine

AIM

To evaluate the influence of powder-to-gel ratio (0.19 g powder to 50 μL of gel, thick MTA Flow, and 0.06 g powder to 50 μL of gel, fluid MTA Flow) on biocompatibility of MTA Flow (Ultradent Products Inc., South Jordan, UT, USA, lot: 2015122901) and compare it with Biodentine (Septodont Inc., Saint-Maur-des-Fossés, France, lot: B18542A).

METHODOLOGY

The materials were manipulated and inserted into polyethylene tubes for implantation in twenty rats. After 7, 15, 30 and 60 days, the specimens were removed and embedded in paraffin. Haematoxylin and eosin sections were used to count the number of inflammatory cells (IC) and fibroblasts mm^-2 (Fb). In the Masson's trichrome-stained sections, the fibrous capsule thickness was measured; picrosirius red-stained sections were used for birefringent collagen quantification. The data were submitted to two-way ANOVA and Tukey test (P ≤ 0.05).

RESULTS

A significantly lower number of IC and consequently higher number of Fb were observed in the capsules adjacent to thick MTA Flow at all periods, in comparison with other materials (P ≤ 0.05). At 60 days, the quantity of birefringent collagen was significantly greater in the tissue in contact with thick MTA Flow, when compared with fluid MTA Flow and Biodentine.

CONCLUSIONS

Although thick MTA Flow induced a less intense inflammatory response, all evaluated materials are biocompatible because they allowed regression of this process after 60 days.

Reduced levels of stromal sex hormone-binding globulin and androgen receptor dysfunction in the sperm storage region of the rat epididymis

The cauda epididymidis is the major sperm storage region whose androgenic supply, essential for the sperm viability, is provided by the vasculature and is dependent upon testosterone diffusion through the stromal tissue to reach the epithelial cells. We have focused our efforts on examining the regulation of this important epididymal region by evaluating the impact of the androgen disrupter cimetidine on the epithelial–stromal androgenic microenvironment. Male rats received 100 mg/kg cimetidine (CMTG) or saline (CG) for 50 days, serum testosterone levels were measured and the epididymal cauda region was processed for light and transmission electron microscopy. In the proximal cauda region, the duct diameter was measured and birefringent collagen in the stroma was quantified. TUNEL-labeled epithelial cells were quantified, and androgen receptor (AR), karyopherin alpha (KPNA) and sex hormone-binding globulin (SHBG) levels were analyzed by immunofluorescence and Western blot. CMTG showed reduced duct diameter and high number of apoptotic epithelial cells. In the epithelium, the total AR concentration and the KPNA immunoreactivity were reduced, and a weak/absent AR nuclear immunofluorescence was observed in contrast to the enhanced AR immunolabeling observed in the cytoplasm of the epithelial cells. A significant reduction of collagen and SHBG levels in the stroma was also observed. Cimetidine treatment impairs AR nuclear import in the epithelium, causing androgenic dysfunction and subsequent epithelial cell apoptosis and duct atrophy. The connective tissue atrophy and reduction of SHBG stromal levels associated with epithelial androgenic dysfunction indicate a possible role of stromal SHBG in the androgenic supply of the sperm storage region of the epididymis.

Effects of estrogen status in osteocyte autophagy and its relation to osteocyte viability in alveolar process of ovariectomized rats

Estrogen maintains osteocyte viability, whereas its deficiency induces osteocyte apoptosis. As autophagy is important for osteocyte viability, we hypothesized whether the anti-apoptotic effect of estrogen is related to autophagy in osteocytes. Thirty adult female rats were sham-operated (SHAM) or ovariectomized (OVX). After three weeks, twelve rats of SHAM and OVX groups were killed before treatment (basal period), whereas the remaining rats received estrogen (OVXE) or vehicle (OVX) for 45 days. Fragments of maxilla containing alveolar process of the first molars were embedded in paraffin or Araldite. Paraffin-sections were stained with hematoxylin/eosin for histomorphometry, or subjected to the silver impregnation method for morphological analysis of osteocyte cytoplasmic processes. Autophagy was analyzed by immunohistochemical detections of beclin-1, MAP-LC3α and p62, whereas apoptosis was evaluated by immunohistochemical detections of cleaved caspase-3 and BAX, TUNEL (Terminal deoxynucleotidyl transferase dUTP nick end labeling) method and by ultrastructural analysis. Araldite-semithin sections were subjected to the Sudan-black method for detection of lipids. OVX-basal group showed high frequency of caspase-3-, TUNEL- and p62-positive osteocytes accompanied with low frequency of beclin-1- and MAP-LC3α-positive osteocytes. At 45 days, OVXE group exhibited higher number of osteocytes, higher frequency of beclin-1- and MAP-LC3α-positive osteocytes, and lower frequency of caspase-3, BAX-, TUNEL- and p62-positive osteocytes than OVX group. Significant reduction in bone area was observed in the OVX compared to OVXE and SHAM groups. The highest frequency of Sudan-Black-positive osteocytes and osteocytes with scarce cytoplasmic processes, or showing apoptotic features were mainly observed in OVX groups. Our results indicate that estrogen deficiency decreases autophagy and increases apoptosis, whereas estrogen replacement enhances osteocyte viability by inhibiting apoptosis and maintaining autophagy in alveolar process osteocytes. These results suggest that the anti-apoptotic effect of estrogen may be, at least in part, related to autophagy regulation in osteocytes.

The antineoplastic busulphan impairs peritubular and Leydig cells, and vitamin B12 stimulates spermatogonia proliferation and prevents busulphan-induced germ cell death

Busulphan (Bu), an alkylating agent used for bone marrow and spermatogonial stem cell transplantation (SSCT), impairs Sertoli (SC) cells, which are necessary for the spermatogonial stem cell (SSC) homing during transplantation. As Leydig (LC) and peritubular myoid (PMC) cells are essential for SC support and maintenance of spermatogonial niche, we evaluated the impact of Bu on the LC and PMC structural integrity. Vitamin B₁₂ (B₁₂) has demonstrated beneficial effects against drug-induced testicular changes; thus, we also examined whether this vitamin is able to stimulate spermatogonia mitotic activity and prevent Bu-induced germ cell death. Rats received 10mg/kg of Bu in the 1st and 4th days, and daily B₁₂ supplementation during Bu treatment and for 6days after the last injection of Bu (Bu-6d), totaling 10days of treatment. Other animals received the same treatment as Bu-6d, and B₁₂ supplementation (Bu+7dB₁₂) or saline (Bu+7dS) for 7 more days, totaling 17days of treatment. Serum testosterone levels were measured. In the historesin-embedded testis sections, the seminiferous tubule and epithelial areas were measured, and the number of spermatogonia and PMC was quantified. Actin and 17β-HSD6 immunofluorescence was detected, and the number of TUNEL-positive LC and germ cells was computed. In Bu-6d, PMC number reduced, and a weak actin immunoexpression and death in these cells was observed. The testosterone levels reduced, and the interstitial tissue showed a weak 17β-HSD6 immunoexpression and increased number of TUNEL-positive LC. In Bu+7dB₁₂, the number of spermatogonia was higher than in Bu-6d and Bu+7dS, and the number of TUNEL-positive germ cells was significantly lower than in Bu+7dS. Bu exerts a harmful impact on PMC and LC, reducing the testosterone levels. Vitamin B₁₂ prevents significantly Bu-induced germ cell death and stimulates spermatogonia proliferation, being a useful strategy for the enrichment of SSC in vitro and an adjuvant therapy for spermatogenesis recovery in oncologic patients.

Microparticulated and nanoparticulated zirconium oxide added to calcium silicate cement: Evaluation of physicochemical and biological properties

The physicochemical and biological properties of calcium silicate-based cement (CS) associated to microparticulated (micro) or nanoparticulated (nano) zirconium oxide (ZrO2 ) were compared with CS and bismuth oxide (BO) with CS. The pH, release of calcium ions, radiopacity, setting time, and compression strength of the materials were evaluated. The tissue reaction promoted by these materials in the subcutaneous was also investigated by morphological, immunohistochemical, and quantitative analyses. For this purpose, polyethylene tubes filled with materials were implanted into rat subcutaneous. After 7, 15, 30, and 60 days, the tubes surrounded by capsules were fixed and embedded in paraffin. In the H&E-stained sections, the number of inflammatory cells (ICs) in the capsule was obtained. Moreover, detection of interleukin-6 (IL-6) by immunohistochemistry and number of IL-6 immunolabeled cells were carried out. von Kossa method was also performed. The differences among the groups were subjected to Tukey test (p ≤ 0.05). The solutions containing the materials presented an alkaline pH and released calcium ions. The addition of radiopacifiers increased setting time and radiopacity of CS. A higher compressive strength in the CS + ZrO2 (micro and nano) was found compared with CS + BO. The number of IC and IL-6 positive cells in the materials with ZrO2 was significantly reduced in comparison with CS + BO. von Kossa-positive structures were observed adjacent to implanted materials. The ZrO2 associated to the CS provides satisfactory physicochemical properties and better biological response than BO. Thus, ZrO2 may be a good alternative for use as radiopacifying agent in substitution to BO.

NF-kB overexpression and decreased immunoexpression of AR in the muscular layer is related to structural damages and apoptosis in cimetidine-treated rat vas deferens

BACKGROUND

Cimetidine, histamine H2 receptors antagonist, has caused adverse effects on the male hormones and reproductive tract due to its antiandrogenic effect. In the testes, peritubular myoid cells and muscle vascular cells death has been associated to seminiferous tubules and testicular microvascularization damages, respectively. Either androgen or histamine H2 receptors have been detected in the mucosa and smooth muscular layer of vas deferens. Thus, the effect of cimetidine on this androgen and histamine-dependent muscular duct was morphologically evaluated.

METHODS

The animals from cimetidine group (CMTG; n=5) received intraperitoneal injections of 100 mg/kg b.w. of cimetidine for 50 days; the control group (CG) received saline solution. The distal portions of vas deferens were fixed in formaldehyde and embedded in paraffin. Masson´s trichrome-stained sections were subjected to morphological and the following morphometrical analyzes: epithelial perimeter and area of the smooth muscular layer. TUNEL (Terminal deoxynucleotidyl-transferase mediated dUTP Nick End Labeling) method, NF-kB (nuclear factor kappa B) and AR (androgen receptors) immunohistochemical detection were also carried out. The birefringent collagen of the muscular layer was quantified in picrosirius red-stained sections under polarized light. The muscular layer was also evaluated under Transmission Electron Microscopy (TEM).

RESULTS

In CMTG, the mucosa of vas deferens was intensely folded; the epithelial cells showed numerous pyknotic nuclei and the epithelial perimeter and the area of the muscular layer decreased significantly. Numerous TUNEL-labeled nuclei were found either in the epithelial cells, mainly basal cells, or in the smooth muscle cells which also showed typical features of apoptosis under TEM. While an enhanced NF-kB immunoexpression was found in the cytoplasm of muscle cells, a weak AR immunolabeling was detected in these cells. In CMTG, no significant difference was observed in the birefringent collagen content of the muscular layer in comparison to CG.

CONCLUSIONS

Cimetidine induces significant damages in the epithelium; a possible antiandrogenic effect on the basal cells turnover should be considered. The cimetidine-induced muscle cells apoptosis confirms the susceptibility of these cells to this drug. The parallelism between enhanced cytoplasmic NF-kB immunolabeling in the damaged muscular tissue and muscle cell apoptosis suggests that this drug may avoid the translocation of NF-kB to the nucleus and interfere in the control of NF-kB-mediated smooth muscle cell apoptosis. The decreased immunoexpression of ARs verified in the damaged muscular tissue reinforces this possibility.

Cimetidine-induced vascular cell apoptosis impairs testicular microvasculature in adult rats

Cimetidine, an H₂ receptor antagonist used for treatment of gastric ulcers, exerts antiandrogenic and antiangiogenic effects. In the testes cimetidine impairs spermatogenesis, Sertoli cells and peritubular tissue, inducing apoptosis in the myoid cells. Regarding the importance of histamine and androgens for vascular maintenance, the effect of cimetidine on the structural integrity of the testicular vasculature was evaluated. Adult male rats received cimetidine (CMTG) and saline (CG) for 50 days. The testes were fixed in buffered 4% formaldehyde and embedded in historesin and paraffin. In the PAS-stained sections, the microvascular density (MVD) and the vascular luminal area (VLA) were obtained. TUNEL method was performed for detection of cell death. Testicular fragments embedded in Araldite were analyzed under transmission electron microscopy. A significant decrease in the MVD and VLA and a high number of collapsed blood vessel profiles were observed in CMTG. Endothelial cells and vascular muscle cells were TUNEL-positive and showed ultrastructural features of apoptosis. These results indicate that cimetidine induces apoptosis in vascular cells, leading to testicular vascular atrophy. A possible antagonist effect of cimetidine on the H₂ receptors and/or androgen receptors in the vascular cells may be responsible for the impairment of the testicular microvasculature.

Immunosuppressant prograf® (tacrolimus) induces histopathological disorders in the peritubular tissue of rat testes

Treatment with tacrolimus (FK-506) has been shown to induce a significant decrease in the number of spermatocytes, spermatids, and Sertoli cells. Regarding the importance of the peritubular tissue for the maintenance of Sertoli cells, the integrity of the cellular and extracellular components of the peritubular tissue was evaluated in adult rats that were treated with 1 mg/kg/day of FK-506 for 30 and 60 days. Testicular sections were used for a quantitative analysis of the peritubular cells (PCs) and were submitted to the PAS method. Paraffin sections were submitted to the TUNEL method and to immunohistochemistry for the detection of caspase-3. Several testicular fragments were analyzed under a transmission electron microscope (TEM). A weak PAS reaction was noted in the peritubular tissue of the tacrolimus-treated animals. Next to the damaged peritubular tissue, the Sertoli cell nuclei were absent or dislocated from the basement membrane. In the treated animals, the number of PCs decreased significantly compared to the control animals, and these cells showed apoptotic features, were TUNEL positive, and were caspase-3 immunolabeled. Using the TEM, apoptosis was confirmed in myoid cells; moreover, the thickness and undulation of the basal laminae and an enlargement of the collagen I layer adjacent to the myoid cells was observed. Long-term treatment with the immunosuppressor induced peritubular myoid cell death by apoptosis and disarrangement of the peritubular extracellular layers. Future studies are necessary to confirm whether the structural alterations in the seminiferous epithelium are related to the effect of FK-506 on peritubular tissue.

Jaw and long bone marrows have a different osteoclastogenic potential

Osteoclasts, the multinucleated bone-resorbing cells, arise through fusion of precursors from the myeloid lineage. However, not all osteoclasts are alike; osteoclasts at different bone sites appear to differ in numerous respects. We investigated whether bone marrow cells obtained from jaw and long bone differed in their osteoclastogenic potential. Bone marrow cells from murine mandible and tibiae were isolated and cultured for 4 and 6 days on plastic or 6 and 10 days on dentin. Osteoclastogenesis was assessed by counting the number of TRAP(+) multinucleated cells. Bone marrow cell composition was analyzed by FACS. The expression of osteoclast- and osteoclastogenesis-related genes was studied by qPCR. TRAP activity and resorptive activity of osteoclasts were measured by absorbance and morphometric analyses, respectively. At day 4 more osteoclasts were formed in long bone cultures than in jaw cultures. At day 6 the difference in number was no longer observed. The jaw cultures, however, contained more large osteoclasts on plastic and on dentin. Long bone marrow contained more osteoclast precursors, in particular the myeloid blasts, and qPCR revealed that the RANKL:OPG ratio was higher in long bone cultures. TRAP expression was higher for the long bone cultures on dentin. Although jaw osteoclasts were larger than long bone osteoclasts, no differences were found between their resorptive activities. In conclusion, bone marrow cells from different skeletal locations (jaw and long bone) have different dynamics of osteoclastogenesis. We propose that this is primarily due to differences in the cellular composition of the bone site-specific marrow.

Immunohistochemical detection of estrogen receptor beta in alveolar bone cells of estradiol-treated female rats: possible direct action of estrogen on osteoclast life span

The role of estrogen in bone resorption has been specifically related to the effect of estrogen on the signalling pathway that inhibits the formation of osteoclasts. However, osteoclast apoptosis and a significant reduction in the number of these cells have been observed in the alveolar bone of female rats treated with estradiol. In the present study, the expression of estrogen receptor beta (ERbeta) in the cells of alveolar bone was evaluated in estradiol-treated and -untreated female rats. In order to test the possible direct action of estrogen on osteoclasts, the relationship between apoptosis and ERbeta expression in these cells was also analysed. The animals received estradiol for 14 days and the alveolar bone fragments were embedded in paraffin for the quantification of tartrate-resistant acid phosphatase-positive osteoclasts. The expression of ERbeta and apoptosis in the osteoclasts were evaluated by ERbeta immunohistochemistry and Terminal deoxynucleotidyl transferase-mediated dUTP Nick-End Labelling (TUNEL) methods, respectively. To confirm osteoclast death by apoptosis, these cells were analysed under transmission electron microscopy. Some osteoclasts from estradiol-treated animals were found to be undergoing apoptosis and the number of tartrate-resistant acid phosphatase-positive osteoclasts was significantly reduced. ERbeta immunolabelling was observed in the cytoplasm and nuclei of active osteoblasts, osteocytes and osteoclasts in both groups, suggesting a direct participation of estrogen on alveolar bone cells. However, following estradiol treatment, a strong ERbeta immunolabelling was often observed in the TUNEL-positive osteoclasts. Therefore, these results indicate that, in addition to the other signalling pathway, the reduction of alveolar bone resorption is also related to a direct action of estrogen on osteoclasts, promoting apoptosis in these cells, via ERbeta.

Structural alterations in the seminiferous tubules of rats treated with immunosuppressor tacrolimus

BACKGROUND

Tacrolimus (FK-506) is an immunosuppressant that binds to a specific immunophilin, resulting in the suppression of the cellular immune response during transplant rejection. Except for some alterations in the spermatozoa, testicular morphological alterations have not been described in rats treated with tacrolimus. In the present study, we purpose to evaluate if the treatment with tacrolimus at long term of follow-up interferes in the integrity of the seminiferous tubules.

METHODS

Rats aging 42-day-old received daily subcutaneous injections of 1 mg/kg/day of tacrolimus during 30 (T-30) and 60 (T-60) days; the rats from control groups (C-30 and C-60) received saline solution. The left testes were fixed in 4% formaldehyde and embedded in glycol methacrylate for morphological and morphometric analyses while right testes were fixed in Bouin's liquid and embedded in paraffin for detection of cell death by the TUNEL method. The epithelial and total tubular areas as well as the stages of the seminiferous epithelium and the number of spermatocytes, spermatids and Sertoli cells (SC) per tubule were obtained.

RESULTS

In the treated groups, seminiferous tubules irregularly outlined showed disarranged cellular layers and loss of germ cells probably due to cell death, which was revealed by TUNEL method. In addition to germ cells, structural alterations in the SC and folding of the peritubular tissue were usually observed. The morphometric results revealed significant decrease in the number of SC, spermatocytes, spermatids and significant reduction in the epithelial and total tubular areas.

CONCLUSION

Tacrolimus induces significant histopathological disorders in the seminiferous tubules, resulting in spermatogenic damage and reduction in the number of Sertoli cells. A careful evaluation of the peritubular components will be necessary to clarify if these alterations are related to the effect of FK-506 on the peritubular tissue.

Treatment with tacrolimus enhances alveolar bone formation and decreases osteoclast number in the maxillae: a histomorphometric and ultrastructural study in rats

Recent studies have suggested that tacrolimus monotherapy is a beneficial therapeutic alternative for the normalization of cyclosporin-induced bone loss in animal models and humans. The mechanism accounting for this action is unclear at present. In the present study, we attempted to determine the effect of tacrolimus monotherapy on alveolar bone using histological, histomorphometric and transmission electron microscopy (TEM). Groups of rats (n=10 each) were treated with either tacrolimus (1mg/kg/day, s.c.) or drug vehicle for 60 days. Fragments containing maxillary molars were processed for light microscopy to investigate the alveolar bone volume, trabecular separation, number of osteoclasts and osteoblasts, and transmission electron microscopy to investigate their ultrastructural basic phenotype. Treatment with tacrolimus monotherapy during 60 days may induce increases in alveolar bone volume (BV/TV,%; P<0.05) and a non-significant decrease in trabecular separation (Tb.Sp,mm; P>0.05), represented by a decrease in osteoclast number (N.Oc/BS; P<0.05) and maintenance of osteoblast number (N.Ob/BS; P>0.05). Osteoblasts were often observed as a continuous layer of active cells on the bone surface. Osteoclasts appeared to be detached from the resorbed bone surface, which was often filled by active osteoblasts and collagen-rich matrix. Moreover, osteoclasts in the treated group were frequently observed as inactive cells (without ruffled border, clear zone and detached from the bone surface). Within the limits of the present study, we conclude that tacrolimus leads to an increase in alveolar bone formation, which probably exerts action on osteoclasts. Tacrolimus could, therefore, play a crucial role in the control of both early osteoclast differentiations from precursors, as well as in functional activation.

Morphological evidences indicate that the interference of cimetidine on the peritubular components is responsible for detachment and apoptosis of Sertoli cells

Cimetidine, referred as antiandrogenic agent, has caused alterations in the seminiferous tubules, including alterations in the peritubular tissue and death of myoid cells by apoptosis. Regarding the structural and functional importance of the peritubular tissue for the maintenance of Sertoli cells (SC), we purpose to investigate the SC-basement membrane interface, focusing the morphological features of SC and their interaction with the basement membrane in the affected tubules by cimetidine. Ten animals were distributed into two groups, control (CG) and cimetidine (CmG) which received saline solution and 50 mg of cimetidine per kg of body weight, respectively, for 52 days. The testes were fixed, dehydrated and embedded for analyses under light and transmission electron microscopy. Paraffin sections were submitted to the TUNEL method; sections of testes embedded in glycol methacrylate were submitted to PAS method and stained by H&E for morphological and quantitative analyses of Sertoli Cells. In the CmG, the SC nuclei were positive to the TUNEL method and showed typical morphological alterations of cell death by apoptosis (from early to advanced stages). A significant reduction in the number of Sertoli Cells was probably due to death of these cells by apoptosis. A close relationship between SC nuclear alterations (including a high frequency of dislocated nuclei from the basal portion) and damage in the peritubular tissue was observed. The ultrastructural analysis showed a parallelism between the gradual advancement of apoptotic process in SC and detachment of the anchoring sites (hemidesmosomes) of SC plasma membrane from the lamina densa. The presence of portions of lamina densa underlying the detached hemidesmosomes indicates a continuous deposition of lamina densa, resulting in the thickening of the basal lamina. The results indicate a possible disarrangement of the SC cytoskeleton, including the focal adhesion structure. These alterations are related to SC apoptosis and probably result from disturbs induced by cimetidine on the peritubular tissue.

Decrease in the number and apoptosis of alveolar bone osteoclasts in estrogen-treated rats

BACKGROUND AND OBJECTIVE

Bone is a mineralized tissue that is under the influence of several systemic, local and environmental factors. Among systemic factors, estrogen is a hormone well known for its inhibitory function on bone resorption. As alveolar bone of young rats undergoes continuous and intense remodeling to accommodate the growing and erupting tooth, it is a suitable in vivo model for using to study the possible action of estrogen on bone. Thus, in an attempt to investigate the possibility that estrogen may induce the death of osteoclasts, we examined the alveolar bone of estrogen-treated rats.

MATERIAL AND METHODS

Fifteen, 22-d-old female rats were divided into estrogen, sham and control groups. The estrogen group received estrogen and the sham group received corn oil used as the dilution vehicle. After 8 d, fragments containing alveolar bone were removed and processed for light microscopy and transmission electron microscopy. Sections were stained with hematoxylin and eosin and tartrate-resistant acid phosphatase (TRAP)-an osteoclast marker. Quantitative analysis of the number of TRAP-positive osteoclasts per mm of bone surface was carried out. For detecting apoptosis, sections were analyzed by the Terminal deoxynucleotidyl transferase-mediated dUTP Nick-End Labeling (TUNEL) method; TUNEL/TRAP combined methods were also used.

RESULTS

The number of TRAP-positive osteoclasts per mm of bone surface was significantly reduced in the estrogen group compared with the sham and control groups. TRAP-positive osteoclasts exhibiting TUNEL-positive nuclei were observed only in the estrogen group. In addition, in the estrogen group the ultrastructural images revealed shrunken osteoclasts exhibiting nuclei with conspicuous and tortuous masses of condensed chromatin, typical of apoptosis.

CONCLUSION

Our results reinforce the idea that estrogen inhibits bone resorption by promoting a reduction in the number of osteoclasts, thus indicating that this reduction may be, at least in part, a consequence of osteoclast apoptosis.

Apoptosis in the epithelial cells of the rests of Malassez of the periodontium of rat molars

BACKGROUND AND OBJECTIVES

Epithelial rests of Malassez are clusters of cells derived from Hertwig's root sheath that remain in the periodontal ligament throughout life. Although it is known that the cells of Malassez proliferate, there are no studies showing that they undergo programmed cell death, i.e. apoptosis. In most tissues, proliferation is balanced by apoptosis. Thus we examined regions of the periodontium of young and adult rat molars in the hope of detecting apoptosis.

METHODS

Wistar rats aged 29, 45 and 120 days were killed with chloral hydrate (600 mg/kg). Fragments containing maxillary molars were removed and fixed in formaldehyde, decalcified, and embedded in paraffin and glycol methacrylate. Sections were stained with hematoxylin/eosin and the Terminal deoxynucleotidyl transferase-mediated dUTP Nick End Labeling (TUNEL) method for detection of apoptosis. Specimens were also fixed in glutaraldehyde-formaldehyde, decalcified and processed for transmission electron microscopy.

RESULTS

Epithelial rests of Malassez containing round/ovoid basophilic dense bodies and TUNEL-positive structures were found in all specimens examined. Ultrastructural examination revealed that some cells of Malassez contained masses of condensed peripheral chromatin and a shrunken cytoplasm exhibiting intact organelles--images typical of apoptosis. Moreover, round/ovoid electron-opaque structures appeared to be in the process of being engulfed by neighboring epithelial cells of Malassez.

CONCLUSIONS

Our results demonstrate that epithelial cells of Malassez's rests undergo apoptosis in the developing and adult periodontium. Apoptosis may, together with proliferation, be part of the mechanism of turnover/remodelling of the cells of Malassez.

Staining methods applied to glycol methacrylate embedded tissue sections

The use of glycol methacrylate (GMA) avoids some technical artifacts, which are usually observed in paraffin-embedded sections, providing good morphological resolution. On the other hand, weak staining have been mentioned during the use of different methods in plastic sections. In the present study, changes in the histological staining procedures have been assayed during the use of staining and histochemical methods in different GMA-embedded tissues. Samples of tongue, submandibular and sublingual glands, cartilage, portions of respiratory tract and nervous ganglion were fixed in 4% formaldehyde and embedded in glycol methacrylate. The sections of tongue and nervous ganglion were stained by H&E. Picrosirius, Toluidine Blue and Sudan Black B methods were applied, respectively, for identification of collagen fibers in submandibular gland, sulfated glycosaminoglycans in cartilage (metachromasia) and myelin lipids in nervous ganglion. Periodic Acid-Schiff (PAS) method was used for detection of glycoconjugates in submandibular gland and cartilage while AB/PAS combined methods were applied for detection of mucins in the respiratory tract. In addition, a combination of Alcian Blue (AB) and Picrosirius methods was also assayed in the sublingual gland sections. The GMA-embedded tissue sections showed an optimal morphological integrity and were favorable to the staining methods employed in the present study. In the sections of tongue and nervous ganglion, a good contrast of basophilic and acidophilic structures was obtained by H&E. An intense eosinophilia was observed either in the striated muscle fibers or in the myelin sheaths in which the lipids were preserved and revealed by Sudan Black B. In the cartilage matrix, a strong metachromasia was revealed by Toluidine Blue in the negatively-charged glycosaminoglycans. In the chondrocytes, glycogen granules were intensely positive to PAS method. Extracellular glycoproteins were also PAS positive in the basal membrane and in the region occupied by the lamina externa and reticular fibers surrounding each smooth muscle cells of the blood vessels. In the epithelial cells of the respiratory tract, acid and neutral mucins were histochemically detected by AB and PAS methods, respectively. Moreover, granules containing acid and neutral mucins were revealed in purple by AB and PAS concomitantly. In the sublingual gland sections, a distinct affinity of acid mucins by AB (in turquoise-blue) and collagen fibers by Picrosirius (in red) was obtained when these methods were combined. Although some routine dyes used in paraffin sections have showed a weak stain in historesin sections, our results showed that different dyes could be applied in GMA sections if modified staining procedures were assayed. Therefore, appropriate staining contrast and, thus, detection of one or different substances in a same section can be acquired in association to the good morphological resolution provided by GMA.

Combined TUNEL and TRAP methods suggest that apoptotic bone cells are inside vacuoles of alveolar bone osteoclasts in young rats

Although it is generally accepted that osteoclasts breakdown and resorb bone matrix, the possibility that they may also be able to engulf apoptotic osteoblasts/lining cells and/or osteocytes remains controversial. Apoptosis of osteoblasts/ lining cells and/or osteocytes and interactions between these cells and osteoclasts are extremely rapid events that are difficult to observe in vivo. A suitable in vivo model for studying these events is the alveolar bone of young rats because it is continuously undergoing intense resorption/remodeling. Thus, sections of aldehyde fixed alveolar bone of young rats were stained by the combined terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method and the tartrate-resistant acid phosphatase (TRAP) method for the simultaneous visualization of apoptotic cells and osteoclasts in the same section. The combined TUNEL and TRAP reactions, in the same section, greatly facilitated visualization of relationship between osteoclasts and apoptotic bone cells during alveolar bone remodeling. Our results showed that several TRAP-positive osteoclasts exhibited large vacuoles containing TUNEL positive apoptotic structures, probably derived from osteoblasts/lining cells and/or osteocytes. These results support the idea that alveolar bone osteoclasts are able to internalize dying apoptotic bone cells.

Apoptotic bone cells may be engulfed by osteoclasts during alveolar bone resorption in young rats

The alveolar bone is a suitable in vivo physiological model for the study of apoptosis and interactions of bone cells because it undergoes continuous, rapid and intense resorption/remodelling, during a long period of time, to accommodate the growing tooth germs. The intensity of alveolar bone resorption greatly enhances the chances of observing images of the extremely rapid events of apoptosis of bone cells and also of images of interactions between osteoclasts and osteocytes/osteoblasts/bone lining cells. To find such images, we have therefore examined the alveolar bone of young rats using light microscopy, the TUNEL method for apoptosis, and electron microscopy. Fragments of alveolar bone from young rats were fixed in Bouin and formaldehyde for morphology and for the TUNEL method. Glutaraldehyde-formaldehyde fixed specimens were processed for transmission electron microscopy. Results showed TUNEL positive round/ovoid structures on the bone surface and inside osteocytic lacunae. These structures--also stained by hematoxylin--were therefore interpreted, respectively, as osteoblasts/lining cells and osteocytes undergoing apoptosis. Osteoclasts also exhibited TUNEL positive apoptotic bodies inside large vacuoles; the nuclei of osteoclasts, however, were always TUNEL negative. Ultrathin sections revealed typical apoptotic images--round/ ovoid bodies with dense crescent-like chromatin--on the bone surface, corresponding therefore to apoptotic osteoblasts/lining cells. Osteocytes also showed images compatible with apoptosis. Large osteoclast vacuoles often contained fragmented cellular material. Our results provide further support for the idea that osteoclasts internalize dying bone cells; we were however, unable to find images of osteoclasts in apoptosis.

Apoptosis in the early developing periodontium of rat molars

Development of the periodontium involves a series of complex steps that result in the formation of root dentine, cementum, bone and fibres of the ligament. These precisely controlled and timed events require the participation of the enamel organ derived epithelial cells of Hertwig's (HRS) and ectomesenchymal cells of the dental follicle. These events involve rapid turnover of the tissues and cells, including disappearance of epithelial cells of HRS. Thus, it seemed likely to us that programmed cell death (apoptosis) may play a role in the development of the periodontium. Fragments of first molars, obtained from 14- and 29-day-old rats, were fixed in glutaraldehyde-formaldehyde and processed for light and electron microscopy. For the TUNEL method for detection of apoptosis, specimens were fixed in 4% formaldehyde and embedded in paraffin. Results confirmed that epithelial cells of HRS maintain a close relationship with the forming dentine root, and that they may become trapped in the dentino-cemental junction. Some of the epithelial cells exhibited ultrastructural features which are consistent with the interpretation that they were undergoing programmed cell death, i.e. apoptosis. Periodontal fibroblast-like cells showed typical images of apoptosis and engulfed apoptotic bodies. TUNEL positive structures were present in all corresponding regions. It seems therefore that apoptosis of epithelial cells of HRS and fibroblast-like cells of the periodontal ligament constitutes an integral part of the developmental process of the tissues of the periodontium.

Effect of ibotenate lesions of the ventromedial hypothalamus on the water and salt intake induced by activation of the median preoptic nucleus in sodium-depleted rats

In this study we investigated the influence of a ventromedial hypothalamus (VMH) lesion with ibotenic acid on water and sodium intake and pressor responses induced by combined treatment of the median preoptic nucleus (MnPO) with angiotensin II (ANG II) and adrenergic agonists (phenylephrine, norepinephrine, isoproterenol and clonidine). Male Holtzman rats with a stainless steel cannula implanted into the MnPO and bilateral sham (vehicle) or VMH lesions with ibotenic acid were used. The ingestion of water and sodium and mean arterial pressure (MAP) were determined in separate groups submitted to sodium depletion with the diuretic furosemide (20 mg/rat). ANG II (10 pmol) injection into the MnPO of sham-lesioned rats induced water and sodium intake and pressor responses. VMH-lesion reduced ANG II-induced water intake and increased saline intake. In sham rats phenylephrine (80 nmol) into MnPO increased, whereas norepinephrine (80 nmol) and clonidine (40 nmol) reduced ANG II-induced water intake while sodium intake was reduced only by clonidine into MnPO. In VMH-lesioned rats, phenylephrine reduced, noradrenaline increased and clonidine produced no effect on ANG II-induced water intake. In lesioned rats ANG II-induced sodium intake was reduced by phenylephrine and noradrenaline, whereas clonidine produced no change. ANG II-induced pressor response was reduced in VMH-lesioned rats, but the pressor response combining ANG II and phenylephrine or noradrenaline in VMH-lesioned rats was bigger than sham rats. These results show that the VMH is important for the changes in water and sodium intake and cardiovascular responses induced by angiotensinergic and adrenergic activation of the MnPO.

Light and electron microscopic study of autologous implants of dental roots in the subcutaneous tissue of rats

Maxillary first molars of rats were extracted. The roots were separated and subsequently implanted in the dorsal subcutaneous tissue of the same animal. In Experiment 1, the roots were implanted immediately after removal; in Experiment 2, the roots were subjected to freeze-thawing (devitalized) before implantation. After 4, 8, and 15 weeks of implantation, the roots were removed and processed for light and transmission electron microscopy. Roots of Experiment 1 showed an amorphous clear material filling depressions on the irregular surface of the cementum. This material consisted predominantly of collagen fibrils. Cells adjacent to the amorphous clear material exhibited numerous cytoplasmic processes surrounded by collagen fibrils. Globular structures with an electron-opacity similar to that of neighbouring cementum were observed within the bundles of collagen fibrils. Multinucleated cells with features of osteo/odontoclasts were often closely apposed to deep depressions of the cementum. In Experiment 2, only large multinucleated giant cells appeared around the surfaces of the roots. It seems therefore that, in Experiment 1, precementum formation and osteo/odontoclast mediated destruction occurred. It is likely that these activities may have originated from periodontal ligament cells carried to the implantation site. This conclusion is supported by the observation that such activities were absent in Experiment 2. Devitalized roots were unable to form precementum and were surrounded by foreign body giant cells.