Tamoxifen induced multinucleated cells (symplasts) and distortion of seminiferous tubules in rat testis

Aim: To evaluate the effect of tamoxifen citrate on male reproductive system of rat. Methods: Groups of male rats were gavaged with tamoxifen at doses of 200 mg·kg-1·d-1, 400 mg·kg-1·d-1 or 800 mg·kg-1·d-1 in 0.1 mL olive oil for 10 consecutive days. Controls were treated with 0.1 mL olive oil. Rats were anesthetized and killed on d 3, d 15 or d 35 after the last dose. Testes were collected, processed for paraffin embedding, sectioned at 5 μm thickness, stained with H&E and analyzed microscopically. Results: There was a dose-dependent increase in the occurrence of seminiferous tubular distortion with germinal cell sloughing. The highest dose increased the number of multinucleated giant cells on d 3 and d 15. Conclusion: Tamoxifen citrate induces multinucleated giant cells and germinal epithelial sloughing in a dose-dependent manner and these changes are detrimental to male fertility.

EFFECT OF DENTIN TUBULES TO THE MECHANICAL PROPERTIES OF DENTIN.PART Ⅱ:EXPERIMENTAL STUDY

To verify the theoretical models of varying transversely isotropic stress-strain relations of dentin established in the preceding work(Part Ⅰ),we per- form a set of experiments.Because of the very fine tooth size,it usually seems to be difficult to directly measure the inhomogeneous and anisotropic parameters of dentin.In this paper,by the digital speckle correlation method,tensile experiments are made on the small dentin samples either parallel or perpendicular to the dentin tubules.With the theoretically predicted elastic stress-strain relations,an optimiza- tion method is proposed to fit the strain curve adapted to the experimental data. The results show that the theoretical elastic stress-strain relations coincides very well with the experimental observations.The determined Young's modulus and Poisson's ratio of dentin matrix are 29.5GPa and 0.44,respectively,in the optimization sense.

EFFECT OF DENTIN TUBULES ON THE MECHANICAL PROPERTIES OF DENTIN. PART Ⅰ: STRESS-STRAIN RELATIONS AND STRENGTH CRITERION

As known, there is a large number of dentin tubules in dentin. These tubules have varying radii and are shaped into radially parallel pattern. The anisotropy of microstructure of dentin shows that dentin should be treated as a ma- terial of varying transverse isotropy. In this Part, the elastic stress-strain relations and the quadratic strength criterion are established in the form of having varying transverse isotropy, in the framework of micromechanics to take into account of the effect of the microstructures-dentin tubules. Simplified forms for isotropic and ho- mogeneous cases, as well as the corresponding plane stress form of the stress-strain relations are also given. These theoretical models are very well supported by the experiments shown later in the continued paper (Part Ⅱ).

Actin phosphorylation correlates with actin sequestration in ATP-depleted rabbit renal proximal tubules

Objective: To demonstrate the relation sh ip between actin phosphorylation and actin sequestration in ATP-depleted rabbi t renal proximal tubules. Methods: Using two-dimensional electr ophoreses and Western blotting to analyze the phosphorylation state of the seque stered actin in rabbit renal proximal tubules. Results: The anal ytical result of the sequestered actin indicated that nearly half of the actin w as phosphorylated on serine residue(s). Conclusion: Result sugge sted a close correlation between actin sequestration and actin phosphorylation i n ATP-depleted rabbit renal proximal tubules.

Effect of Different Irradiation Times on the Occlusion of Dentinal Tubules When Using a Nd:YAG Laser: An <i>in Vitro</i>SEM Study

Objective: To evaluate the effect of different irradiation times on the occlusion of dentinal tubules when using Nd:YAG laser. Background data: Dentin hypersensitivity is a frequent problem that has limited treatment success despite many chemical and physical therapies. Methods: Four coronal dentin disks 2 mm thick were cut with a low-speed diamond saw from four freshly extracted intact first molars. The coronal dentin surface of each disk was divided into four regions, each approximately 2 mm × 3 mm. The dentin surfaces were treated with 27% EDTA then the four regions irradiated separately in a randomized pattern with a Nd:YAG laser (120 mJ, 5 Hz), using irradiation times of 0 s, 20 s, 40 s and 60 s, representing laser energies of 0 J/cm2, 200 J/cm2, 400 J/cm2 and 600 J/cm2, respectively. SEM photomicro-graphs were taken at 1500× and 3000× to calculate the dentinal tubule orifice occlusion rates and to measure the tubule diameters, respectively. Results: For the laser irradiation times of 0 s, 20 s, 40 s and 60 s, the corresponding dentinal tubule occlusion rates were 2.05 (SD 0.29)%, 10.01 (1.71)%, 23.58 (2.51)% and 90.23 (2.24)%, respectively;and the tubule diameters were 4.18 (0.32) μm, 3.46 (0.24) μm, 1.69 (0.32) μm and 0.12 (0.02) μm, respectively. There were significant differences among all groups for both measured variables (p ≤ 0.005). Conclusions: Within the limitations of this in Vitro study, when using a Nd:YAG laser at 120 mJ and 5 Hz, an irradiation time of 60 s achieved the best sealing of the coronal dentinal tubule orifices.

Different modes of renal proximal tubule regeneration in health and disease

Tissues are equipped with reasonable strategies for re-pair and regeneration and the renal proximal tubule （PT）is no exception. New information has become availableon the mode of PT regeneration in mammals. Unlikethe intestinal epithelium with a high rate of turnovermaintained by the stem cell system, the kidney has lowturnover under normal physiological conditions. The PTseems to be maintained physiologically by hyperplasia,a regenerating system with self-renewal of mature tu-bular cells. This mode of regeneration is advantageousfor effective replenishment of randomly isolated andeliminated tubular cells by self-renewal of adjacentcells. On the other hand, it has been suggested thatdedifferentiation of mature tubular cells plays a role inregeneration after acute kidney injury. Recent studiesemploying genetic labeling and DNA-labeling tech-niques have confrmed that the proliferation of preex-isting injured mature tubular cells contributes mainlyto PT regeneration in ischemic reperfusion injury. Thismode of regeneration is beneficial with regard to therapid reparation of focally injured tubules often inducedby ischemic reperfusion injury. What happens, howeverwhen the PT is homogeneously injured with almost noremaining surviving cells？ Is the PT equipped with another backup regeneration system, e.g., the stem cell system？ Is it possible that certain types of renal injuries evoke a stem cell response whereas others do not？ This review focuses on all three possible modes of tis-sue regeneration （compensatory hyperplasia, dediffer-entiation and stem cell system） in mammals and their involvement in PT regeneration in health and disease.

Observation of the effect of cleaning the smear layer and tubule plugs with SEM

To clean out the smear layer on teeth surface, and protect the teeth medulla, the experiment applied the study observing the cleanup of six groups of surface smear layer of dental caries and the tubule plugs reserving effect after using of different cavity cleansers with the help of SEM. The result implied that both the acidic preparations and chelator could clean out the smear layer on teeth surface in some way, but the later one could also reserve partial tubule plugs, which reduce the stimulation to the teeth medulla. So the chelator is better cleansers in clinical use.

Cycloheximide prevents production of arresting,a fraction of 30-50 kDa obtained from seminiferous tubule conditioned medium

Aim: To evaluate the effect of a protein synthesis inhibitor cycloheximide on arresting activity in spermato-genesis and sperm count in male rats. Methods: The study used seminiferous tubule (ST) segments from adult rats cultured in vitro with or without cycloheximide to condition culture media, which have been concentrated, size fractioned (30-50 kDa) and administered 7 days to adult rats by intraperitoneal injections. The effects on testicular and epididymal weights, spermatogenesis and epididymal sperm count were determined. Results: The fraction (30-50 kDa), named arresting, obtained from the culture without cycloheximide decreased testicular and epididymal weights (P<0.01) and reduced the epididymal sperm count significantly. Study of the spermatogenic cycle by transillumination showed spermatogenic arrest at stage VII in rats treated with arresting compared to that observed in controls. The length of stage VII in the group receiving the seminiferous tubules culture media with cycloheximide (30-50 KDa CHX-STCM fraction) was similar to control. Conclusion: The difference in the effect may be the result of the presence or absence of arresting, a protein secreted by the tubules.

MORPHOLOGICAL TRANSITION BETWEEN VESICLES AND TUBULES FOR A GLYCOPOLYMER-CONTAINING AMPHIPHILIC DIBLOCK COPOLYMER IN AQUEOUS SOLUTIONS

The morphological transition of molecular assemblies in aqueous solutions for a new amphiphilic diblock copolymer induced by changing the initial solvent conditions was studied by transmission electron microscopy (TEM). The copolymer was polystyrene(77)-b-poly[2-(beta -D-glucopyranosyloxy)ethyl acrylate (6)] (PSt(77)-b-PGEA(6)) and the solvent was a mixture of DMF and THF. PSt(77)-b-PGEA(6) yields vesicles and tubules when it is initially dissolved in THF and DMF respectively. The morphological transition between vesicles and tubules can be achieved by simply varying the amounts of THF and DMF, or changing the temperature at which the aggregates were prepared.

Construction of Bioartificial Renal Tubule Assist Device In Vitro and Its Function of Transporting Sodium and Glucose

To explore a new way of constructing bioartificial renal tubule assist device （RAD） in vitro and its function of transporting sodium （Na^＋） and glucose and to evaluate the application of atomic force microscope in the RAD construction, rat renal tubular epithelial cell line NRK-52E was cultured in vitro, seeded onto the outer surfaces of hollow fibers in a bioreactor, and then cultured for two weeks to construct RAD. Bioreactor hollow fibers without NRK-52E cells were used as control. The morphologies of attached cells were observed with scanning electron microscope, and the junctions of cells and polysulfone membrane were observed with atomic force microscope. Transportation of Na＋ and glucose was measured. Oubaine and phlorizin were used to inhibit the transporting property. The results showed that NRK-52E cells and polysulfone membrane were closely linked, as observed under atomic force microscope. After exposure to oubaine and phlorizin, transporting rates of Na^＋ and glucose were decreased significantly in the RAD group as compared with that in the control group （P〈0.01）. Furthermore, when the inhibitors were removed, transportation of Na^＋ and glucose was restored. It is concluded that a new RAD was constructed successfully in vitro, and it is able to selectively transport Na^＋ and glucose.

EFFECT OF DENTIN TUBULES ON THE MECHANICAL PROPERTIES OF DENTIN PART Ⅲ: NUMERICAL ANALYSIS

Imitating a real tooth and the periodontal supporting tissues, we have established a 2D finite element model and carried out a numerical analysis based on the inhomogeneous and anisotropic (IA) stress-strain relation and strength model of dentin proposed in the preceding Parts Ⅰ and Ⅱ, and the conventional homogeneous and isotropic (HI) model, respectively. Quite a few cases of loadings for a non-defected and a defected tooth are considered. The numerical results show that the stress level predicted by the IA model is remarkably higher than that by the HI model, revealing that the effect of the dentin tubules should be taken into a serious consideration from the viewpoint of biomechanics.

Impact of Dentinal Tubule Orientation on Dentin Bond Strength

This study aimed to determine the impact of dentinal tubule orientation on dentin bond strength to provide a reference for clinical cavity preparation in resin-bonded restoration. Patients aged 13-16 years were selected, including 18 males and 21 females. Forty-eight human maxillary first premolars from orthodontic extractions were chosen to prepare the test models with the dentinal tubule orientations perpendicular and parallel to the bonding substrate. The test models in the vertical and parallel groups were divided into three groups： total-etching with 20% phosphoric acid, total-etching with 35% phosphoric acid and self-etching, with the dentinal tubule surfaces bonded with composite resin blocks in each group. After the standard test models of dentinal tubule-composite resin blocks were placed in distilled water and stored at 37℃ for 24 h, shearing tests were performed using a universal material testing machine at a crosshead speed of 0.5 mm/min. The bond strength values in the vertical group were 19.33＋1.59 MPa for the 20% phosphoric acid group, 21.39±2.34 MPa for the 35% phosphoric acid group, and 16.88±1.54 MPa for the self-etching group. The bond strength values in the parallel group were 24.53±1.99 MPa for the 20% phosphoric acid group, 25.16＋2.88 MPa for the 35% phosphoric acid group, and 20.83±1.99 for the self-etching group. After using same total-etching adhesive, the shear bond strength of the parallel group was higher than that of the vertical group, and the difference was statistically significant （P〈0.05）. Regardless of vertical group or parallel group, the difference in the bond strength value between the total-etching groups and the self-etching group was statistically significant （P〈0.05）. It was concluded that the dentin bonding substrate which was parallel to the direction of the dentin tubule achieved an improved bond strength; the total-etching adhesives achieved higher bond strengths in dentin bond than the self-etching adhesives.

Association of Acid-Base Balance in the Renal Proximal Tubule and Blood Pressure Alterations: Potential Role of Local Mediators

Disturbances in acid-base balance leading to the development of hypertension are currently gaining increased attention among researchers. Perturb acid-base balance characterized by metabolic acidosis has been demonstrated in hypertensive animals and humans. Research suggests that acid-base changes are not only the consequences of elevated blood pressure but can precede the development of hypertension. However, no exact mechanism has been identified to link acid-base imbalance with alterations in blood pressure. The kidney proximal tubule is the major site for maintaining normal bicarbonate concentrations which is an important component of acid-base balance. Acid-base transporter proteins in the renal proximal tubule such as Na+/HCO-3?cotransporters, Na+/H+ exchangers, and anion-exchangers play important roles in controlling acid secretion, ammonia production and bicarbonate reabsorption for maintaining acid-base balance. It is well known that sodium retention in the renal tubules leads to increase in blood volume and consequently increases in blood pressure. Therefore, it is the purpose of this review to discuss the role of sodium-coupled acid-base transporters in regulating proximal tubular sodium retention and controlling blood pressure homeostasis. We will also focus on the capacity of local mediators;angiotensin II, cortisol, prosta-glandin and aldosterone, to regulate acid-base and blood pressure homeostasis.

The Effects of Insulin Resistance and Inflammation on Renal Proximal Tubule Sodium Transport and Hypertension

Insulin resistance, closely linked to inflammation, is recognized as a key factor in the onset and aggravation of diabetes, cardio-renal syndrome, hypertension, and obesity. In the renal proximal tubule, insulin resistance may increase renal sodium reabsorption, leading to hypertension, edema and sometimes heart failure. Recently some anti-diabetic agents have been shown to have effects on the transporters in renal proximal tubule. Because renal proximal tubule mediates about 70% of sodium reabsorption, it is quite important to clarify the function of renal proximal tubule under insulin resistance and inflammation.

Species differences in regulation of renal proximal tubule transport by certain molecules

Renal proximal tubules （PTs） play important roles in the regulation of acid/base, plasma volume and blood pressure. Recent studies suggest that there are substantial species differences in the regulation of PT transport. For example, thiazolidinediones （TZDs） are widely used for the treatment of type 2 diabetes mellitus, but the use of TZDs is associated with fluid overload. In addition to the transcriptional enhancement of sodium transport in distal nephrons, TZDs rapidly stimulate PT sodium transport via a non-genomic mechanism depending onperoxisome proliferator activated receptor g/Src/epidermal growth factor receptor （EGFR）/MEK/ERK. In mouse PTs, however, TZDs fail to stimulate PT transport probably due to constitutive activation of Src/EGFR/ERK pathway. This unique activation of Src/ERK may also affect the effect of high concentrations of insulin on mouse PT transport. On the other hand, the effect of angiotensin Ⅱ （Ang Ⅱ） on PT transport is known to be biphasic in rabbits, rats, and mice. However, Ang Ⅱ induces a concentration-dependent, monophasic transport stimulation in human PTs. The contrasting responses to nitric oxide/guanosine 3’,5’-cyclic monophosphate pathway may largely explain these different effects of Ang Ⅱ on PT transport. In this review, we focus on the recent fndings on the species differences in the regulation of PT transport, which may help understand the species-specific mechanisms underlying edema formation and/or hypertension occurrence.

Effect of Calcium Phosphate Glass on Dentinal Tubule Sealing after Irradiation with the Carbon Dioxide Laser

The aim of this study was to evaluate the dentinal tubule sealing and acid resistance of dentin specimens following the application of calcium phosphate glass powder prior to irradiation with a CO2(carbon dioxide)laser.Dentin models simulating open dentinal tubules were divided into two groups:experimental(calcium phosphate glass slurry applied to the dentin surface)and control(no slurry applied to the surface).All specimens in the experimental group and five specimens in the control group were irradiated with a CO2 laser.The defocused laser beams(0.5 and 1 W)were applied(spot size,5 mm in diameter)from a distance of 20 mm for 10 s.The surfaces and cross-sectional areas of the specimens were examined using an SEM(scanning electron microscope).In addition,the resistance to acid was evaluated in these specimens.The open dentinal tubules in the control groups were sealed following irradiation with the CO2 laser at 0.5 W and 1.0 W.Likewise,sealing of open dentinal tubules was observed in the experimental group after CO2 laser irradiation.The acid resistance of the dentin surface was improved after CO2 laser irradiation;specimens in the experimental group presented with significantly lower amounts of Ca ion release compared to those in the control group.These findings indicate that CO2 laser irradiation alone or after the application of calcium phosphate glass powder can effectively seal the dentinal tubules and alleviate dentin hypersensitivity.

F-Actin Distribution Changes Provoked by Acetaminophen in the Proximal Tubule in Kidney of Adult Male Rat

Acetaminophen is a drug used to treat many conditions as headache, muscle aches, arthritis, backache, toothache, and fever between others, but collateral effects of this drug are not well known yet. Here is tested its effect on proximal tubule epithelium. Acetaminophen (APAP) at doses of 200, 500, 1000 and 1500 mg/Kg i.p. caused cell damage and changes in F-actin distribution in the proximal tubule of male Wistar rats. After 48 hours of treatment, the proximal tubule epithelium showed tumefaction and necrosis. Dose of 200 mg/kg decreased the F-actin and was observed a structure in patches in the basal cytoplasm of epithelial cells of the proximal tubule. This effect was increased depending on the administered dose. Dose of 1000 mg/kg produced the highest histological damage and changes in the actin cytoskeleton. Results of this study suggested that nephrotoxic damage produced by high doses of APAP included breakdown of cytoskeleton in proximal tubule epithelium.

The mechanism by which exosomes derived from bone marrow mesenchymal stem cells promote the regeneration of renal tubules in acute kidney injury through the regulation of the PTEN signaling pathway by miR-21

Acute kidney injury(AKI)is a significant global health issue with limited current treatment options.This study focused on the mechanism by which exosomes derived from bone marrow mesenchymal stem cells(BMSCs)promote renal tubule regeneration in AKI through the regulation of the PTEN signaling pathway by miR-21.BMSCs were isolated and characterized,and their exosomes were purified.In vitro,renal tubular epithelial cell injury models were established,and the co-culture of exosomes and cells demonstrated enhanced cell proliferation and reduced apoptosis.In vivo,AKI animal models showed improved renal function and histopathological changes after exosome treatment.miR-21 was found to be upregulated in exosomes and recipient cells,targeting PTEN and activating the PI3K/AKT pathway.The signaling network also interacted with other pathways related to renal tubule regeneration.The study highlights the potential of exosome therapy for AKI and provides insights into the underlying molecular mechanisms,although further research is needed to address remaining challenges and translate these findings into clinical applications.

The mechanism of dentine hypersensitivity:Stimuli-induced directional cation transport through dentinal tubules

Dentine hypersensitivity is an annoying worldwide disease,yet its mechanism remains unclear.The long-used hydrodynamic theory,a stimuli-induced fluid-flow process,describes the pain processes.However,no experimental evidence supports the statements.Here,we demonstrate that stimuli-induced directional cation transport,rather than fluid-flow,through dentinal tubules actually leads to dentine hypersensitivity.The in vitro/in vivo electro-chemical and electro-neurophysiological approaches reveal the cation current through the nanoconfined negatively charged dentinal tubules coming from external stimuli(pressure,pH,and temperature)on dentin surface and further triggering the nerve impulses causing the dentine hypersensitivity.Furthermore,the cationic-hydrogels blocked dentinal tubules could significantly reduce the stimuli-triggered nerve action potentials and the anionhydrogels counterpart enhances those,supporting the cation-flow transducing dentine hypersensitivity.Therefore,the inspired ion-blocking desensitizing therapies have achieved remarkable pain relief in clinical applications.The proposed mechanism would enrich the basic knowledge of dentistry and further foster breakthrough initiatives in hypersensitivity mitigation and cure.

Effect of D_(4)Dopamine Receptor on Na^(+)-K^(+)-ATPase Activity in Renal Proximal Tubule Cells

Objective:Dopamine,via its receptors,plays a vital role in the maintenance of blood pressure by modulating renal sodium transport.However,the role of the D_(4)dopamine receptor(D_(4)receptor)in renal proximal tubules(PRTs)is still unclear.This study aimed to verify the hypothesis that activation of D_(4)receptor directly inhibits the activity of the Na+-K+-ATPase(NKA)in RPT cells.Methods:NKA activity,nitric oxide(NO)and cyclic guanosine monophosphate(cGMP)levels were measured in RPT cells treated with the D_(4)receptor agonist PD168077 and/or the D_(4)receptor antagonist L745870,the NO synthase inhibitor NG-nitro-L-arginine-methyl ester(L-NAME)or the soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one(ODQ).Total D_(4)receptor expression and its expression in the plasma membrane were investigated by immunoblotting in RPT cells from Wistar-Kyoto(WKY)rats and spontaneously hypertensive rats(SHRs).Results:Activation of D_(4)receptors with PD168077,inhibited NKA activity in RPT cells from WKY rats in a concentration-and time-dependent manner.The inhibitory effect of PD168077 on NKA activity was prevented by the addition of the D_(4)receptor antagonist L745870,which by itself had no effect.The NO synthase inhibitor L-NAME and the soluble guanylyl cyclase inhibitor ODQ,which by themselves had no effect on NKA activity,eliminated the inhibitory effect of PD168077 on NKA activity.Activation of D_(4)receptors also increased NO levels in the culture medium and cGMP levels in RPT cells.However,the inhibitory effect of D_(4)receptors on NKA activity was absent in RPT cells from SHRs,which could be related to decreased plasma membrane expression of D_(4)receptors in SHR RPT cells.Conclusions:Activation of D_(4)receptors directly inhibits NKA activity via the NO/cGMP signaling pathway in RPT cells from WKY rats but not SHRs.Aberrant regulation of NKA activity in RPT cells may be involved in the pathogenesis of hypertension.