Renal Functional Reserve in Naïve HIV Patients.

Introduction. Renal functional reserve (RFR) is the kidney capability of increasing its basal glomerular filtration rate (GFR) at least 20% after an adequate stimulus. Renal disorders have been reported in seropositive HIV patients, particularly the decrease in glomerular filtration rate (eGFR), nephrotic syndrome, and proximal tubular deficiency associated with the disease itself or the use of some anti-retroviral treatments. Thus, it was decided to carry out a prospective study in order to evaluate if RFR test was preserved in naive HIV patients. Material and Method. GFR was measured by using cimetidine-aided creatinine clearance (CACC), and RFR as described Hellerstein et al. in seropositive naive HIV patients and healthy volunteers. Results. RFR was evaluated in 12 naïve HIV patients who showed positive RFR (24.8±2%), but significantly lower compared to RFR in 9 control individuals (90.3 ± 5%). Conclusion. In this study was found that renal functional reserve was positive in naïve HIV patients, but significantly lower compared to renal functional reserve achieved by seronegative healthy individuals.

Evaluation of Gastroprotective Activity of the Methanolic Extract of Justicia pectoralis Jacq. (Acanthaceae).

INTRODUCTION: Justicia pectoralis Jacq. is traditionally applied in folk medicine in Brazil and in several Latin American countries. The leaves are used in tea form, especially in the treatment of respiratory disorders, acting as an expectorant. It also has activity in gastrointestinal disorders, and it is anti-inflammatory, antioxidant, sedative, and estrogenic, among others. AIMS: To investigate the gastroprotective activity of the methanol extract of the leaves of Justicia pectoralis Jacq. (MEJP) in different experimental models of gastric ulcers. MATERIALS AND METHODS: The adult leaves of Justicia pectoralis Jacq. were collected and cultivated in beds, with an approximate spacing of 40 × 40 cm, organic fertilization, irrigation with potable water and without shelter from light. The MEJP was prepared from the dried and pulverized leaves and concentrated under reduced pressure in a rotary evaporator. For the experimental model of gastric ulcer, Swiss male albino mice were used. The inputs used in the experiment were MEJP at three different concentrations (250, 500 and 1000 mg/kg p.o.), cimetidine (50 mg/kg p.o.), indomethacin (50 mg/kg s.c.) and vehicle (10 mL/kg p.o.). RESULTS: MEJP (250, 500 and 1000 mg/kg p.o.) demonstrated gastroprotective activity, with levels of protection of 45.65%, 44.80% and 40.22%, respectively, compared to the control (vehicle). Compared with cimetidine (48.29%), MEJP showed similar gastroprotective activity. CONCLUSIONS: This study demonstrated the gastroprotective activity of MEJP and contributes to validate the traditional use the species for gastric disorders and provides a pharmacological basis for its clinical potential.

Influence of Topography and Composition of Commercial Titanium Dental Implants on Cell Adhesion of Human Gingiva-Derived Mesenchymal Stem Cells: An In Vitro Study.

The topography and composition of dental implant surfaces directly impact mesenchymal cell adhesion, proliferation, and differentiation, crucial aspects of achieving osseointegration. However, cell adhesion to biomaterials is considered a key step that drives cell proliferation and differentiation. The aim of this study was to characterize characterize the topography and composition of commercial titanium dental implants manufactured with different surface treatments (two sandblasted/acid-etched (SLA) (INNO Implants, Busan, Republic of Korea; BioHorizonsTM, Oceanside, CA, USA) and two calcium phosphate (CaP) treated (Biounite®, Berazategui, Argentina; Zimmer Biomet, Inc., Warsaw, IN, USA)) and to investigate their influence on the process of cell adhesion in vitro. A smooth surface implant (Zimmer Biomet, Inc.) was used as a control. For that, high-resolution methodologies such as scanning electron microscopy (SEM), X-ray dispersive spectroscopy (EDX), laser scanning confocal microscopy (LSCM), and atomic force microscopy (AFM) were employed. Protein adsorption and retromolar gingival mesenchymal stem cells (GMSCs) adhesion to the implant surfaces were evaluated after 48 h. The adherent cells were examined by SEM and LSCM for morphologic and quantitative analyses. ANOVA and Tukey tests (α = 0.05) were employed to determine statistical significance. SEM revealed that INNO, BioHorizonsTM, and Zimmer implants have an irregular surface, whereas Biounite® has a regular topography consisting of an ordered pattern. EDX confirmed a calcium and phosphate layer on the Biounite® and Zimmer surfaces, and AFM exhibited different roughness parameters. Protein adsorption and cell adhesion were detected on all the implant surfaces studied. However, the Biounite® implant with CaP and regular topography showed the highest protein adsorption capacity and density of adherent GMSCs. Although the Zimmer implant also had a CaP treatment, protein and cell adhesion levels were lower than those observed with Biounite®. Our findings indicated that the surface regularity of the implants is a more determinant factor in the cell adhesion process than the CaP treatment. A regular, nanostructured, hydrophilic, and moderately rough topography generates a higher protein adsorption capacity and thus promotes more efficient cell adhesion.

Sarcoide em equinos - tratamento com associação de Aciclovir e excisão cirúrgica / Equine sarcoids - treatment with a combination of Acyclovir and surgical excision

Background: Sarcoids are the most frequent skin tumors among horses, causing serious lesions due to their different shapes, sizes, degree of invasiveness and distribution on the body. The pathogenesis of sarcoids is multifactorial, with genetic, viral and environmental involvement, making their treatment complex. The aggressiveness and high rate of recurrence of sarcoids makes it difficult to use an effective treatment, which is why there are several therapeutic routes described in the literature. Aiming to describe and expand sarcoid treatments, this paper reports on the use of acyclovir in the treatment of this type of tumor. Cases: Four horses sent to the Large Animal Veterinary Hospital of the Federal University of Lavras - UFLA were diagnosed and treated for sarcoids. Case 1. Lesions on the right ear, region of the masseter muscle of the right side of the face, neck, vulva and medial aspect of the left pelvic limb. Case 2. Lesion in the left groin region. Case 3. Lesions on the face, masseter muscle region on the left side, mandibular region and right ear pinna. Case 4. Lesion in the lateral region of the left pelvic limb, close to the tarsometatarsal joint. All horses had a diagnosis of sarcoid, which was confirmed by histopathological examination of material collected after surgical excision. Macroscopically, the neoplastic lesions were classified as fibroblastic, verrucous and nodular. The tumors exhibited irregular surfaces, keratinization, and a firm consistency. Their surfaces were alopecic, slightly rough, some of them were ulcerated, and their color ranged from greyish to rosy and reddish. All the tumor masses were surgically excised from the 4 horses, and one sarcoid was treated by thermal cauterization with liquid nitrogen due to the lesion's depth and size. In most cases, the sarcoid removal sites were closed with sutures. Only 2 lesions were not sutured due to the impossibility of bringing the edges of tissue close together, or due to proximity to the tarsometatarsal joint. The surgical wounds were cleaned twice a day with sterile saline solution followed by the topical application of Acyclovir. One of the animals received complementary therapy with Cimetidine. Discussion: The equines recovered completely from their sarcoid treatment, and no recurrences were reported a year later. Thus, the combination of treatments employed for the extirpation of sarcoids proved to have greater chances of success. First, all the tumors were surgically removed with the largest possible margins of safety in order to ensure the elimination of neoplastic cells. In the postoperative period, all the animals received topical treatment of the lesions with acyclovir after surgical resection of the tumors. The drug aided the complete healing of post-surgical wounds, and healing time varied according to the size and depth of the lesion. One tumor was treated with liquid nitrogen after surgical excision of the sarcoid. Another horse was treated with cimetidine over a 3-month period after surgical excision of the neoplasm in order to reduce the sarcoid and prevent its evolution. Surgical excision of the sarcoid associated with topical application of acyclovir ointment showed satisfactory results. Moreover, the combination of surgical excision and administration of liquid nitrogen on the lesion and topical application of acyclovir ointment in the postoperative period also provided good results. Given the complexity of sarcoid treatment and the high recurrence rate of these tumors, the use of combined treatments should be taken into account.

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.

Muscular atrophy, impaired epithelial autophagy and UCHL1 increase in androgen-deficient cauda epididymis.

In epididymis, cimetidine induces androgenic failure due to reduced sex hormone-binding globulin stromal levels and blockade of androgen receptor (AR) nuclear import. UCHL1, a hydrolase of ubiquitin-proteasome system (UPS), seems to play a role in autophagy and apoptotic pathway. However, the role of UPS and autophagy in epididymis has not been clarified. We evaluated UCHL1 and autophagy in epididymal cauda epithelium under androgenic deficiency induced by cimetidine, focusing on the interplay among these processes and apoptosis. The integrity of epididymal muscular layer was also evaluated. Male rats received cimetidine (CMTG) or saline (CG). Seminal vesicles were weighed, the expression of androgen-responsive genes Crisp1 and connexin 43 (Cx43) in cauda epididymis was evaluated, and cauda fragments were processed for light and transmission electron microscopy. The epithelium height and muscular thickness were measured. TUNEL, immunohistochemistry for caspase-3 and Cx43, and immunofluorescence for AR, Bcl-2, UCHL1, MAP LC3A, and p62/SQSTM1 (autophagic markers) were performed. Bcl-2, UCHL1, and Cx43 were detected by Western blot. In CMTG, the reduction in seminal vesicles weight accompanied by downregulation of Crisp1 and Cx43 confirmed epididymal androgenic failure. These results were associated with muscular atrophy, apoptosis and weak Cx43 and AR immunoexpression, supporting the androgenic dependence of muscular integrity. The high UCHL1 levels and reduction in Bcl-2 reinforce UCHL1 role in epithelial cells death. The intense immunoexpression of LC3A and p62/SQSTM1 indicates autophagic disturb, which in association with high UCHL1 levels, points to a role of UPS and autophagy in the regulation of epididymal epithelial cells viability under androgenic control.

TCTP from Loxosceles Intermedia (Brown Spider) Venom Contributes to the Allergic and Inflammatory Response of Cutaneous Loxoscelism.

LiTCTP is a toxin from the Translationally Controlled Tumor Protein (TCTP) family identified in Loxosceles brown spider venoms. These proteins are known as histamine-releasing factors (HRF). TCTPs participate in allergic and anaphylactic reactions, which suggest their potential role as therapeutic targets. The histaminergic effect of TCTP is related to its pro-inflammatory functions. An initial characterization of LiTCTP in animal models showed that this toxin can increase the microvascular permeability of skin vessels and induce paw edema in a dose-dependent manner. We evaluated the role of LiTCTP in vitro and in vivo in the inflammatory and allergic aspects that undergo the biological responses observed in Loxoscelism, the clinical condition after an accident with Loxosceles spiders. Our results showed LiTCTP recombinant toxin (LiRecTCTP) as an essential synergistic factor for the dermonecrotic toxin actions (LiRecDT1, known as the main toxin in the pathophysiology of Loxoscelism), revealing its contribution to the exacerbated inflammatory response clinically observed in envenomated patients.

Prolactin Induces IL-2 Associated TRAIL Expression on Natural Killer Cells from Chronic Hepatitis C Patients In vivo and In vitro.

BACKGROUND: Natural killer cells (NKC) are a major component of the innate immune response to HCV, mediating their effects through TRAIL and IFN-γ. However, their function is diminished in chronic HCV patients (HCVp). Prolactin is an immunomodulatory hormone capable of activating NKC. OBJECTIVE: The study aims to explore if hyperprolactinemia can activate NKC in HCVp. METHODS: We treated twelve chronic HCVp (confidence level =95%, power =80%) for 15 days with Levosulpiride plus Cimetidine to induce mild hyperprolactinemia. Before and after treatment, we determined TRAIL and NKG2D expression on peripheral blood NKC, along with cytokine profiles, viral loads and liver function. We also evaluated in vitro effects of prolactin and/or IL-2 on NKC TRAIL or NKG2D expression and IFN-γ levels on cultured blood mononuclear cells from 8 HCVp and 7 healthy controls. RESULTS: The treatment induced mild hyperprolactinemia and increased TRAIL expression on NKC as well as the secretion of IL-1ra, IL-2, PDGF and IFN-γ. Viral loads decreased in six HCVp. IL-2 and TRAIL together explained the viral load decrease. In vitro, prolactin plus IL-2 synergized to increase TRAIL and NKG2D expression on NKC from HCVp but not in controls. CONCLUSION: Levosulpiride/Cimetidine treatment induced mild hyperprolactinaemia that was associated with NKC activation and Th1-type cytokine profile. Also, an increase in TRAIL and IL-2 was associated with viral load decrease. This treatment could potentially be used to reactivate NKC in HCVp.

Fiebre periódica con estomatitis aftosa, faringitis, y adenitis / Periodical fever with aphthous stomatitis, pharyngitis, and adenitis (PFAPA syndrome)

RESUMEN Se presenta un caso de fiebre periódica con estomatitis aftosa, faringitis, y adenitis síndrome de fiebre periódica con estomatitis aftosa, faringitis, y adenitis, entidad aparentemente infrecuente de la cual no se recoge reporte en el país. La etiología no es todavía bien comprendida, se observa con mayor frecuencia entre los 2 y 5 años, aunque se han descrito casos en adultos. Se caracteriza por fiebre periódica con estomatitis aftosa, faringitis, y adenitis de carácter periódica con una dramática respuesta al uso de esteroide en la mayoría de los casos. El caso que se presenta es un paciente de 5 años de edad, sexo masculino, con cuadros de fiebre periódica asociado a amigdalitis con exudado, adenitis y lesiones aftosas, con respuesta en la fase aguda a la prednisona y con respuesta al tratamiento de mantenimiento con cimetidina. En la actualidad lleva 11 meses en remisión (AU).

ABSTRACT We present a case of periodical fever with aphthous stomatitis, pharyngitis and adenitis (PFAPA syndrome), entity that is apparently infrequent and its report in the country was not found. Its etiology is not still clearly understood. It appears with higher frequency in the ages between 2 and 5 years, though it has been described in adult population. It is characterized by periodical fever with aphthous stomatitis, pharyngitis and adenitis of periodical character, with a dramatic answer to the use of steroids in most of the cases. The case that is presented is the one of a male patient aged 5 years with reiterative periodical fever associated to tonsillitis with exudate, adenitis and aphthous lesions, with answer, in the acute phase, to prednisone, and to cimetidine at the maintenance therapy. Nowadays, he is already 11 months in remission (AU).

Fiebre periódica con estomatitis aftosa, faringitis, y adenitis / Periodical fever with aphthous stomatitis, pharyngitis, and adenitis (PFAPA syndrome)

RESUMEN Se presenta un caso de fiebre periódica con estomatitis aftosa, faringitis, y adenitis síndrome de fiebre periódica con estomatitis aftosa, faringitis, y adenitis, entidad aparentemente infrecuente de la cual no se recoge reporte en el país. La etiología no es todavía bien comprendida, se observa con mayor frecuencia entre los 2 y 5 años, aunque se han descrito casos en adultos. Se caracteriza por fiebre periódica con estomatitis aftosa, faringitis, y adenitis de carácter periódica con una dramática respuesta al uso de esteroide en la mayoría de los casos. El caso que se presenta es un paciente de 5 años de edad, sexo masculino, con cuadros de fiebre periódica asociado a amigdalitis con exudado, adenitis y lesiones aftosas, con respuesta en la fase aguda a la prednisona y con respuesta al tratamiento de mantenimiento con cimetidina. En la actualidad lleva 11 meses en remisión (AU).

ABSTRACT We present a case of periodical fever with aphthous stomatitis, pharyngitis and adenitis (PFAPA syndrome), entity that is apparently infrequent and its report in the country was not found. Its etiology is not still clearly understood. It appears with higher frequency in the ages between 2 and 5 years, though it has been described in adult population. It is characterized by periodical fever with aphthous stomatitis, pharyngitis and adenitis of periodical character, with a dramatic answer to the use of steroids in most of the cases. The case that is presented is the one of a male patient aged 5 years with reiterative periodical fever associated to tonsillitis with exudate, adenitis and aphthous lesions, with answer, in the acute phase, to prednisone, and to cimetidine at the maintenance therapy. Nowadays, he is already 11 months in remission (AU).

The role of organic cation transporter 2 inhibitor cimetidine, experimental diabetes mellitus and metformin on gabapentin pharmacokinetics in rats.

PURPOSE: We investigated the influence of diabetes mellitus (DM), glycemic control with insulin, cimetidine (Oct2 inhibitor) and metformin (Oct2 substrate) on the kinetic disposition of GAB in rats. MAIN METHODS: Male Wistar rats were divided in five groups and all animals received an oral dose of 50 mg/kg GAB: (vehicle + GAB), cimetidine + GAB (single dose of cimetidine [100 mg/kg] intraperitoneally 1 h before GAB), metformin + GAB (single dose of metformin 100 mg/kg by gavage concomitantly with GAB), DM + GAB (single dose of 40 mg/kg streptozotocin (STZ) intravenously) and DM + GAB + insulin (single dose 40 mg/kg STZ intravenously and 2 IU insulin twice daily for 15 days). Pharmacokinetic analysis was based on plasma and urine data concentrations. KEY FINDINGS: No differences in pharmacokinetic parameters were observed between vehicle + GAB × cimetidine + GAB and vehicle + GAB × metformin + GAB groups. Diabetes increased the fraction of GAB excreted unchanged in urine (vehicle + GAB: 0.48 [0.38-0.58]; DM + GAB: 0.83 [0.62-1.04]; DM + GAB + insulin: 0.88 [0.77-0.93]) (mean [95% confidence interval]) without any changes in GAB exposure. Insulin treated diabetic animals showed higher renal clearance compared to control (vehicle + GAB: 0.25 [0.18-0.30] L/h·kg; DM + GAB + insulin: 0.55 [0.45-1.43] L/h·kg), which was attributed to the diabetes-induced glomerular hyperfiltration. SIGNIFICANCE: Glomerular filtration is the main mechanism of renal excretion of GAB without significant contribution of Oct2 active transport.

Effect of mutation of Phe 2436.44 of the histamine H2 receptor on cimetidine and ranitidine mechanism of action.

Despite the pivotal role GPCRs play in cellular signaling, it is only in the recent years that structural biology has begun to elucidate how GPCRs function and to provide a platform for structure-based drug design. It is postulated that GPCR activation involves the movement of transmembrane helices. The finding that many residues, which have been shown to be critical for receptor activation and are highly conserved among different GPCRs, are clustered in particular positions of transmembrane helices suggests that activation of GPCRs may involve common molecular mechanisms. In particular, phenylalanine 6.44, located in the upper half of TMVI, is highly conserved among almost all GPCRs. We generated Phe 2436.44 Ala/Ser mutants of histamine H2 receptor and found that while the substitutions do not affect receptor expression or ligand signaling, are able to specifically alter cimetidine and ranitidine mechanisms of action from simply inactivating the receptor to produce a ligand-induced G-protein sequestering conformation, that interferes with the signaling of ß2-adrenoceptor. Taking advantage of the cubic ternary complex model, and mathematically modeling our results, we hypothesize that this alteration in ligand mechanism of action is consequence of a change in ligand-induced conformational rearrangement of receptor and its effect on G-protein coupling. Our results show that receptor point mutations can not only alter receptor behavior, as shown for activating/inactivating mutations, but also can have more subtle effects changing ligand mechanism of action.

Cimetidine Reduces Interleukin-6, Matrix Metalloproteinases-1 and -9 Immunoexpression in the Gingival Mucosa of Rat Molars With Induced Periodontal Disease.

BACKGROUND: Histamine seems to act, via H2 receptor, on inflammatory processes by stimulating interleukin (IL)-6 and matrix metalloproteinase (MMP) release. As cimetidine is an H2 receptor antagonist, the authors hypothesize that this antiulcer drug reduces IL-6, MMP-1, and MMP-9 immunoexpression in gingiva with induced periodontal disease (PD). To confirm a possible modulatory role of IL-6 on MMPs, the relationship between IL-6/MMP-1 and IL-6/MMP-9 immunoexpression was evaluated. METHODS: Forty-six male rats were distributed into the cimetidine group (CimG: received daily intraperitoneal injections of 100 mg/kg of body weight of cimetidine) or the saline group (SG). PD was induced by cotton ligature around the maxillary left first molars (PDSG and PDCimG). The right molars were used as controls (SG and CimG). After 7, 15, 30, and 50 days, maxillary fragments were processed for paraffin embedding or for transmission electron microscopy. Tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts in the alveolar process surface and number of IL-6, MMP-1, and MMP-9-immunolabeled cells in the gingival mucosa were quantified. Statistical analyses were performed (P ≤0.05). RESULTS: In PDSG and PDCimG, gingival mucosa exhibited few collagen fibers among numerous inflammatory cells. In PDCimG, the number of TRAP-positive osteoclasts and IL-6, MMP-1, and MMP-9-immunolabeled cells was significantly lower than in PDSG at all periods. A positive correlation between IL-6/MMP-1 and IL-6/MMP-9 was detected in PDSG and PDCimG. CONCLUSION: Cimetidine decreases bone loss through reduction of osteoclast number and induces reduction of IL-6, MMP-1, and MMP-9 immunoexpression, reinforcing the idea that the beneficial effect of cimetidine in PD may be due to reduction of IL-6 immunolabeling in the inflamed gingival mucosa.

Vitamin B12-induced spermatogenesis recovery in cimetidine-treated rats: effect on the spermatogonia number and sperm concentration.

The H2-receptor antagonist cimetidine is an antiulcer drug also used for the treatment of cancer due to its antiangiogenic effect. However, this drug has caused structural changes in the seminiferous tubules. Vitamin B12 has been used as a therapeutic agent for the treatment of male infertility. The supplementation of rats with vitamin B12 during cimetidine treatment has recovered the damaged seminiferous tubules, but how this vitamin restores the seminiferous epithelium has not been clarified. In this study, we evaluated whether vitamin B12 improves the number of spermatogonia, spermatocytes, and sperm concentration in cimetidine-treated rats. Adult male rats were treated for 50 days as follows: cimetidine group received 100 mg kg-1 b.w. of cimetidine, cimetidine-B12 group received cimetidine and 3 µg of vitamin B12-hydroxocobalamin, B12 group received only 3 µg of vitamin, and control group received saline. Sperm concentration was calculated and historesin-embedded testes sections were used for the quantitative analyses of spermatogonia (A; In/B) and spermatocytes. TUNEL method and PCNA immunofluorescence were performed. Cimetidine caused a significant reduction in sperm concentration. TUNEL-positive spermatogonia and spermatocytes were correlated to a significant reduction in the number of these cells. In cimetidine-B12 group, sperm concentration was higher than cimetidine group and a significant increase in the number of spermatogonia (stages II-VI) was correlated to a high incidence of PCNA-immunolabeled spermatogonia and spermatocytes. The results show that the supplementation of rats with vitamin B12 during cimetidine treatment increases sperm concentration and exerts a potential effect in the recovery of spermatogonia and spermatocytes.

Cimetidine-induced Leydig cell apoptosis and reduced EG-VEGF (PK-1) immunoexpression in rats: Evidence for the testicular vasculature atrophy.

The antiulcer drug cimetidine has shown to cause changes in the testicular microvasculature of adult rats. Since Leydig cells (LCs) produce the pro-angiogenic factor, EG-VEGF (endocrine gland-derived vascular endothelial growth factor), also known as prokineticin 1 (PK-1), this study examined the effect that cimetidine might have on LCs in testes with damaged vasculature. Rats received intraperitoneal injections of 100mg/kg of cimetidine (cimetidine group) or saline vehicle (control group) for 50 days. Serum testosterone levels were measured by chemiluminescence immunoassay and testicular sections were subjected to TUNEL and immunohistochemical reactions for caspase-3, 17ß-HSD6, CD163 (ED2 macrophage), PK-1 and androgen receptor (AR). LCs in the cimetidine group showed TUNEL and caspase-3 positive labeling and apoptotic ultrastructural features. Moreover, the presence of 17ß-HSD6-positive inclusions inside macrophages and the reduced number of LCs, AR immunoreactivity and serum testosterone levels correlated with a decrease in either the number of PK-1-immunostained LCs or PK-1 immunoreactivity. Although it is not clear which cell type is the primary target of cimetidine in the testicular interstitial compartment, these findings support a direct link between cimetidine-induced testicular vascular atrophy and LCs damage.

Thermally induced solid-state transformation of cimetidine. A multi-spectroscopic/chemometrics determination of the kinetics of the process and structural elucidation of one of the products as a stable N3-enamino tautomer.

Exposure of cimetidine (CIM) to dry heat (160-180°C) afforded, upon cooling, a glassy solid containing new and hitherto unknown products. The kinetics of this process was studied by a second order chemometrics-assisted multi-spectroscopic approach. Proton and carbon-13 nuclear magnetic resonance (NMR), as well as ultraviolet and infrared spectroscopic data were jointly used, whereas multivariate curve resolution with alternating least squares (MCR-ALS) was employed as the chemometrics method to extract process information. It was established that drug degradation follows a first order kinetics. One of the products was structurally characterized by mono- and bi-dimensional NMR experiments. It was found to be the N3-enamino tautomer (TAU) of CIM, resulting from the thermal isomerization of the double bond of the cyanoguanidine moiety of the drug, from the imine form to its N3-enamine state. The thus generated tautomer demonstrated to be stable for months in the glassy solid and in methanolic solutions. A theoretical study of CIM and TAU revealed that the latter is less stable; however, the energy barrier for tautomer interconversion is high enough, precluding the process to proceed rapidly at room temperature.

A PCA-based chemometrics-assisted ATR-FTIR approach for the classification of polymorphs of cimetidine: application to physical mixtures and tablets.

The identity of the polymorphic form of an active pharmaceutical ingredient is an important parameter that may affect the performance of the drug formulation. This calls for special techniques, able to classify crystal forms or assign the polymorphic identity to a given solid in a mixture. In order to develop a method to determine which of the relevant polymorphs of Cimetidine (CIM) is present in commercial tablet samples, authentic forms A, B, D and M1 of the drug were prepared, structurally characterized and employed as standards. Thus, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was coupled to Principal Component Analysis (PCA) and used for the classification of physical mixtures of CIM and excipients, as well as laboratory-made and commercial tablets, according to their polymorphic composition. It was demonstrated that two principal components (PCs) suffice to classify the samples of the four forms of CIM into distinct groups, and that method performance is optimum when the second and third PCs are used for the classification process. The application of the method to commercial tablets of CIM also gave good results, confirming they were prepared employing the correct polymorph (form A).

Modulatory effects of taurine on jejunal contractility

Taurine (2-aminoethanesulfonic acid) is widely distributed in animal tissues and has diverse pharmacological effects. However, the role of taurine in modulating smooth muscle contractility is still controversial. We propose that taurine (5-80 mM) can exert bidirectional modulation on the contractility of isolated rat jejunal segments. Different low and high contractile states were induced in isolated jejunal segments of rats to observe the effects of taurine and the associated mechanisms. Taurine induced stimulatory effects on the contractility of isolated rat jejunal segments at 3 different low contractile states, and inhibitory effects at 3 different high contractile states. Bidirectional modulation was not observed in the presence of verapamil or tetrodotoxin, suggesting that taurine-induced bidirectional modulation is Ca2+ dependent and requires the presence of the enteric nervous system. The stimulatory effects of taurine on the contractility of isolated jejunal segments was blocked by atropine but not by diphenhydramine or by cimetidine, suggesting that muscarinic-linked activation was involved in the stimulatory effects when isolated jejunal segments were in a low contractile state. The inhibitory effects of taurine on the contractility of isolated jejunal segments were blocked by propranolol and L-NG-nitroarginine but not by phentolamine, suggesting that adrenergic β receptors and a nitric oxide relaxing mechanism were involved when isolated jejunal segments were in high contractile states. No bidirectional effects of taurine on myosin phosphorylation were observed. The contractile states of jejunal segments determine taurine-induced stimulatory or inhibitory effects, which are associated with muscarinic receptors and adrenergic β receptors, and a nitric oxide associated relaxing mechanism.

Modulatory effects of taurine on jejunal contractility.

Taurine (2-aminoethanesulfonic acid) is widely distributed in animal tissues and has diverse pharmacological effects. However, the role of taurine in modulating smooth muscle contractility is still controversial. We propose that taurine (5-80 mM) can exert bidirectional modulation on the contractility of isolated rat jejunal segments. Different low and high contractile states were induced in isolated jejunal segments of rats to observe the effects of taurine and the associated mechanisms. Taurine induced stimulatory effects on the contractility of isolated rat jejunal segments at 3 different low contractile states, and inhibitory effects at 3 different high contractile states. Bidirectional modulation was not observed in the presence of verapamil or tetrodotoxin, suggesting that taurine-induced bidirectional modulation is Ca(2+) dependent and requires the presence of the enteric nervous system. The stimulatory effects of taurine on the contractility of isolated jejunal segments was blocked by atropine but not by diphenhydramine or by cimetidine, suggesting that muscarinic-linked activation was involved in the stimulatory effects when isolated jejunal segments were in a low contractile state. The inhibitory effects of taurine on the contractility of isolated jejunal segments were blocked by propranolol and L-NG-nitroarginine but not by phentolamine, suggesting that adrenergic ß receptors and a nitric oxide relaxing mechanism were involved when isolated jejunal segments were in high contractile states. No bidirectional effects of taurine on myosin phosphorylation were observed. The contractile states of jejunal segments determine taurine-induced stimulatory or inhibitory effects, which are associated with muscarinic receptors and adrenergic ß receptors, and a nitric oxide associated relaxing mechanism.