Male Hartley Guinea Pigs Research Articles

Evaluation of the skin phototoxicity and photosensitivity of honeybee venom.

Bee (Apis mellifera L.) venom (BV) has been used as a cosmetic ingredient owing to its anti-aging, anti-inflammatory, and antibacterial effects. The aim of this study was to assess the skin safety of BV. For this purpose, skin phototoxicity and sensitization tests were conducted in healthy male Hartley guinea pigs. The animals were divided into three groups (n=5) for the phototoxicity test: G1 (negative control), G2 (BV gel treatment), and G3 (positive control). After specified treatments, the animals were irradiated with ultraviolet A (15 J/cm2 ). The photosensitivity test was also performed in three groups: G4 (negative control, n=5), G5 (BV gel treatment, n=10), and G6 (positive control, n=5). Erythema and edema were observed after 24, 48, and 72 hours in the positive control group, but not in the negative control and BV gel groups. Application of BV to the guinea pig skin had no toxic effects on any clinical signs, body weight, or mortality. In addition, it did not evoke a skin reaction in both either the skin phototoxicity and skin photosensitization tests. Therefore, it can be concluded that BV has the potential to be developed as a drug ingredient for topical uses.

Fingolimod (Gilenya® ) in multiple sclerosis: bradycardia, atrioventricular blocks, and mild effect on the QTc interval. Something to do with the L-type calcium channel?

Cardiac arrhythmias and ECG abnormalities including bradycardia, prolongation of the QT interval, and atrioventricular (AV) conduction blocks have been extensively observed with fingolimod, the first marketed oral drug for treating the relapsing-remitting form of multiple sclerosis. This study was aiming to further elucidate the effects of fingolimod on cardiac electrophysiology at three different levels: (i) in vitro, (ii) ex vivo, and (iii) in vivo. (i) Patch-clamp experiments in whole cell configuration were performed on Cav 1.2-transfected tsA201 cells exposed to fingolimod-phosphate 100 or 500 nmol/L (n = 27 cells, total) to measure drug effect on L-type calcium current (ICaL ). (ii) Langendorff perfusion experiments were undertaken on male Hartley guinea-pigs isolated hearts (n = 4) exposed to fingolimod 10 and 100 nmol/L to evaluate drug-induced effects on monophasic action potential duration measured at 90% repolarization (MAPD90 ). (iii) Implanted cardiac telemeters were used to record ECGs in guinea-pigs (n = 7) treated with a single dose of fingolimod 0.0625 mg/kg suspension, administered as an oral gavage. (i) In vitro cellular experiments showed that fingolimod-phosphate causes a concentration-dependent reduction in ICaL . (ii) Ex vivo Langendorff experiments revealed that fingolimod had no significant effect on MAPD90 . (iii) Fingolimod caused significant prolongations of the RR, PR, QT, and QTcF intervals in vivo. Reversible AV blocks were also observed in 7/7 animals. Fingolimod possesses ICaL -blocking properties, further contributing to its AV conduction-slowing effects. These properties are also consistent with its mitigated effect on the QT interval in humans, despite previously shown HERG-blocking effect.

Moringa leaf powder modulate reverse cholesterol transport without changing plasma lipids in guinea

Leaves from the plant Moringa Oleifera have been found to improve insulin resistance, reduce inflammation and lower plasma lipids in several animal models. The polyphenols/flavonoids present in Moringa leaves (ML) appear to be the bioactive components responsible of these beneficial effects. In this study we hypothesized that Moringa leaves (ML) would improve lipid profile by modulating the size and number of lipoprotein subfractions (large, medium or small) and affect reverse cholesterol transport (RCT) in guinea pigs. Twenty four 3‐month old male Hartley guinea pigs, were given a hypercholesterolemic diet with 0.25% cholesterol and were randomly allocated to either one of three Moringa groups (n=8/group): control (0% ML), Low Moringa (10% ML) or High Moringa (15% ML), corresponding to a daily intake of 0, 3 or 4.5 g ML/day. Animals consumed these diets for 6 weeks. Macro and micronutrients were adjusted for all diets, the only difference being the flavonoids and polyphenols present in ML. After sacrifice, blood was collected and plasma was obtained by centrifugation. Plasma was aliquoted to measure total, LDL and HDL cholesterol, triglycerides, glucose, and insulin. VLDL, LDL and HDL subfractions concentrations and size were measured by nuclear magnetic resonance. Lecithin cholesterol acyltransferase (LCAT) and cholesteryl ester protein (CETP) activities, major regulators of RCT, were also measured by fluorometric methods. Unexpectedly, no changes in plasma lipids, glucose or insulin were observed among groups. However both ML groups had lower concentrations of the medium HDL, which has been postulated to be pro‐atherogenic. Values were: 0.56 μmol/L for control, 0.11 ± 0.21 μmol/L for 10% ML and 0.21 ± 0.13 μmol/L for 15% ML groups. Further LCAT activity was increased by 55% (p< 0.05) by ML intake while CETP activity was not different among groups. These results suggest a potential role of ML in modulating RCTSupport or Funding InformationTaif University, Saudi Arabia

Acotiamide improves stress-induced impaired gastric accommodation.

Gastric accommodation is a reflex reaction related to gastric reservoir function. Psychological stress, such as anxiety, inhibits gastric accommodation in humans. Acotiamide enhances the effect of acetylcholine in the enteric nervous system, enhances gastric contractility, and accelerates delayed gastric emptying. However, the effect of acotiamide on stress-induced impaired gastric accommodation remains unclear. Therefore, we examined the effect of acotiamide on gastric accommodation and stress-induced impaired gastric accommodation using a conscious guinea pig model. A polyethylene bag was inserted through the distal region of the gastric body into the proximal stomach of 5-week-old male Hartley guinea pigs. Gastric accommodation was evaluated by measuring the intrabag pressure in the proximal stomach after oral administration of a liquid meal. In the stress model, animals were subjected to water-avoidance stress. Acotiamide (Z-338) or nizatidine was administered subcutaneously. Fecal output was determined as the number of fecal pellets. Administration of the liquid meal significantly decreased intrabag pressure, indicating induction of gastric accommodation. Acotiamide treatment prolonged liquid meal-induced gastric accommodation and significantly increased the number of fecal pellets compared to controls. Water-avoidance stress significantly inhibited liquid meal-induced gastric accommodation. Pretreatment with acotiamide significantly improved stress-induced impaired gastric accommodation. The number of fecal pellets in the acotiamide group increased significantly compared to controls. Acotiamide, but not nizatidine, significantly decreased gastric emptying. Acotiamide prolongs gastric accommodation and improves stress-induced impaired gastric accommodation, indicating a potential role for acotiamide in the treatment of functional dyspepsia through its effects on gastric accommodation reactions.

Compared with Powdered Lutein, a Lutein Nanoemulsion Increases Plasma and Liver Lutein, Protects against Hepatic Steatosis, and Affects Lipoprotein Metabolism in Guinea Pigs

Background: It is not clear how oil-in-water nanoemulsions of lutein may affect bioavailability and consequently alter lipoprotein metabolism, oxidative stress, and inflammation.Objective: The bioavailability as well as effects of a powdered lutein (PL) and an oil-in-water lutein nanoemulsion (NANO; particle size: 254.2 nm; polydispersity index: 0.29; and ζ-potential: −65 mV) on metabolic variables in liver, plasma, and adipose tissue in a guinea pig model of hepatic steatosis were evaluated.Methods: Twenty-four 2-mo-old male Hartley guinea pigs, weighing 200–300 g (n = 8/group), were fed diets containing 0.25 g cholesterol/100 g to induce liver injury for the duration of the study. They were allocated to control (0 mg lutein), PL (3.5 mg/d), or NANO (3.5 mg/d) groups. After 6 wk, plasma, liver, and adipose tissue were collected for determination of lutein, plasma lipids, tissue cholesterol, and inflammatory cytokines.Results: The NANO group had 2-fold higher concentrations of lutein in plasma (P < 0.001) and 1.6-fold higher concentrations in liver (P < 0.001) than did the PL group, indicating greater bioavailability of this carotenoid. The NANO group also had 24% lower hepatic steatosis scores (P < 0.05), 31% lower hepatic cholesterol accumulation (P < 0.05), and 64% lower plasma alanine aminotransferase (P < 0.05) than did the control group. Hepatic oxidized LDL was 55% lower in both the PL and NANO groups than in the control group (P < 0.05). In plasma, the NANO group had 2-fold higher concentrations of LDL and HDL cholesterol as well as a 2-fold higher number of VLDL, LDL, and HDL particles than did the other 2 groups as evaluated by nuclear magnetic resonance. Furthermore, the NANO group had 15% higher concentrations of free cholesterol in adipose tissue, resulting in higher concentrations of inflammatory markers, than did the other 2 groups.Conclusions: These results indicate that, although this lutein nanoemulsion exerted protective effects against hepatic steatosis, plasma lipoproteins and adipose tissue cholesterol were increased. These data suggest that the metabolic effects of this particular nanoemulsion might not be protective in all tissues in guinea pigs.

Abnormal Mechanical Loading Induces Cartilage Degeneration by Accelerating Meniscus Hypertrophy and Mineralization After ACL Injuries In Vivo

Background: Although patients with an anterior cruciate ligament (ACL) injury have a high risk of developing posttraumatic osteoarthritis (PTOA), the role of meniscus hypertrophy and mineralization in PTOA after an ACL injury remains unknown. Purpose/Hypothesis: The purpose of this study was to determine if menisci respond to abnormal loading and if an ACL injury results in meniscus hypertrophy and calcification. The hypotheses were that (1) abnormal mechanical loading after an ACL injury induces meniscus hypertrophy and mineralization, which correlates to articular cartilage damage in vivo, and (2) abnormal mechanical loading on bovine meniscus explants induces the overexpression of hypertrophic and mineralization markers in vitro. Study Design: Controlled laboratory study. Methods: In vivo guinea pig study (hypothesis 1): Three-month-old male Hartley guinea pigs (n = 9) underwent ACL transection (ACLT) on the right knee; the left knee served as the control. Calcification in the menisci was evaluated by calcein labeling 1 and 5 days before knee harvesting at 5.5 months. Cartilage and meniscus damage and mineralization were quantified by the Osteoarthritis Research Society International score and meniscus grade, respectively. Indian hedgehog (Ihh), matrix metalloproteinase–13 (MMP-13), collagen type X (Col X), progressive ankylosis homolog (ANKH), ectonucleotide pyrophosphatase/phosphodiesterase–1 (ENPP1), alkaline phosphatase (ALP), inorganic pyrophosphate (PPi), and inorganic phosphate (Pi) concentrations were evaluated by immunohistochemistry and enzyme-linked immunosorbent assay. In vitro bovine meniscus explant study (hypothesis 2): Bovine meniscus explants were subjected to 25% strain at 0.3 Hz for 1, 2, and 3 hours. Cell viability was determined using live/dead staining. The levels of mRNA expression and protein levels were measured using real-time quantitative reverse transcription polymerase chain reaction and Western blot after 24, 48, and 72 hours in culture. The conditioned medium was collected for sulfated glycosaminoglycan (GAG) release and Pi/PPi assay. Results: In vivo guinea pig study: Meniscus size and area as well as intensity of meniscus calcification were significantly increased in the ACLT group compared with the control group. Both calcified area and intensity were correlated with cartilage damage in the ACLT group (meniscus calcified area: r = 0.925, P < .0001; meniscus calcified intensity: r = 0.944, P < .0001). Ihh, MMP-13, Col X, ANKH, ENPP1, and ALP expression were increased in the ACLT group compared with the control group. The Pi level and Pi/PPi ratio increased by 63% and 42%, respectively, in the ACLT group compared with the control group. In vitro bovine meniscus explant study: Cell death was found in the superficial zone of the bovine meniscus explants after loading for 3 hours. The mRNA expression and protein levels of MMP-13, ANKH, ENPP1, and ALP were up-regulated in all 3-hour loaded samples. The Pi/PPi ratio and sulfated GAG content in the culture medium were increased in the 3-hour loaded group. Conclusion: Meniscus hypertrophy and mineralization correlated to cartilage degeneration after ACL injuries. Clinical Relevance: The study data suggest that the suppression of meniscus hypertrophy and calcification may decrease the risk of PTOA after ACL injuries.

Establishment of a rat and guinea pig aortic interposition graft model reveals model-specific patterns of intimal hyperplasia

Although the aortic interposition bypass model has been widely used to evaluate biomaterials for bypass grafting, there is no comprehensive description of the procedure or of the distribution of intimal hyperplasia that results. The objectives of this study were to (1) review and summarize approaches of aortic interposition grafting in animal models, (2) determine the pertinent anatomy for this procedure, (3) validate this model in the rat and guinea pig, and (4) compare the distribution of intimal hyperplasia that develops in each species. A literature search was performed in PubMed from 1980 to the present to analyze the use of anesthesia, anticoagulation, antiplatelet agents, graft material, suture, and anastomotic techniques. Using 10-week-old male Sprague-Dawley rats and Hartley guinea pigs, we established pertinent aortic anatomy, developed comparable models, and assessed complications for each model. At 30days, the graft and associated aorta were explanted, intimal formation was assessed morphometrically, and cellularity was assessed via nuclear counting. We reviewed 30 articles and summarized the pertinent procedural findings. Upon establishing both animal models, key anatomic differences between the species that affect this model were noted. Guinea pigs have a much larger cecum, increased retroperitoneal fat, and lack the iliolumbar vessels compared with the rat. Surgical outcomes for the rat model included a 53% technical success rate and a 32% technical error rate. Surgical outcomes for the guinea pig model included a 69% technical success rate and a 31% technical error rate. These two species demonstrated unique distribution of intimal hyperplasia at 30days. Intimal hyperplasia in the rat model was greatest at two areas, the proximal graft (5400 μm2; P< .001) and distal graft (2800 μm2; P< .04), whereas the guinea pig model developed similar intimal hyperplasia throughout the graft (4500-5100 μm2; P< .01). In this report, we summarize the literature on the aortic interposition graft model, present a detailed description of the anatomy and aortic interposition graft procedure in the rat and guinea pig, and describe a unique distribution of intimal formation that results in both species. This information will be helpful when designing studies to evaluate novel graft materials in the future.

Effects of sphincter of Oddi motility on the formation of cholesterol gallstones.

To investigate the mechanisms and effects of sphincter of Oddi (SO) motility on cholesterol gallbladder stone formation in guinea pigs. Thirty-four adult male Hartley guinea pigs were divided randomly into two groups, the control group (n = 10) and the cholesterol gallstone group (n = 24), which was sequentially divided into four subgroups with six guinea pigs each according to time of sacrifice. The guinea pigs in the cholesterol gallstone group were fed a cholesterol lithogenic diet and sacrificed after 3, 6, 9, and 12 wk. SO manometry and recording of myoelectric activity were obtained by a multifunctional physiograph at each stage. Cholecystokinin-A receptor (CCKAR) expression levels in SO smooth muscle were detected by quantitative real-time PCR (qRT-PCR) and serum vasoactive intestinal peptide (VIP), gastrin, and cholecystokinin octapeptide (CCK-8) were detected by enzyme-linked immunosorbent assay at each stage in the process of cholesterol gallstone formation. The gallstone formation rate was 0%, 0%, 16.7%, and 83.3% in the 3, 6, 9, and 12 wk groups, respectively. The frequency of myoelectric activity in the 9 wk group, the amplitude of myoelectric activity in the 9 and 12 wk groups, and the amplitude and the frequency of SO in the 9 wk group were all significantly decreased compared to the control group. The SO basal pressure and common bile duct pressure increased markedly in the 12 wk group, and the CCKAR expression levels increased in the 6 and 12 wk groups compared to the control group. Serum VIP was elevated significantly in the 9 and 12 wk groups and gastrin decreased significantly in the 3 and 9 wk groups. There was no difference in serum CCK-8 between the groups. A cholesterol gallstone-causing diet can induce SO dysfunction. The increasing tension of the SO along with its decreasing activity may play an important role in cholesterol gallstone formation. Expression changes of CCKAR in SO smooth muscle and serum VIP and CCK-8 may be important causes of SO dysfunction.

Cartilage Degeneration, Subchondral Mineral and Meniscal Mineral Densities in Hartley and Strain 13 Guinea Pigs.

Osteoarthritis is a joint disease involved in articular cartilage, subchondral bone, meniscus and synovial membrane. This study sought to examine cartilage degeneration, subchondral bone mineral density (BMD) and meniscal mineral density (MD) in male Hartley, female Hartley and female strain 13 guinea pigs to determine the association of cartilage degeneration with subchondral BMD and meniscal MD. Cartilage degeneration, subchondral BMD and meniscal MD in 12 months old guinea pigs were examined with histochemistry, X-ray densitometry and calcium analysis. We found that male Hartley guinea pigs had more severe cartilage degeneration, subchondral BMD and meniscal MD than female Hartley guinea pigs, but not female strain 13 guinea pigs. Female strain 13 guinea pigs had more severe cartilage degeneration and higher subchondral BMD, but not meniscal MD, than female Hartley guinea pigs. These findings indicate that higher subchondral BMD, not meniscal MD, is associated with more severe cartilage degeneration in the guinea pigs and suggest that abnormal subchondral BMD may be a therapeutic target for OA treatment. These findings also indicate that the pathogenesis of OA in the male guinea pigs and female guinea pigs are different. Female strain 13 guinea pig may be used to study female gender-specific pathogenesis of OA.

Blocking Dopaminergic Signaling Soon after Learning Impairs Memory Consolidation in Guinea Pigs.

Formation of episodic memories (i.e. remembered experiences) requires a process called consolidation which involves communication between the neocortex and hippocampus. However, the neuromodulatory mechanisms underlying this neocortico-hippocampal communication are poorly understood. Here, we examined the involvement of dopamine D1 receptors (D1R) and D2 receptors (D2R) mediated signaling on memory consolidation using the Novel Object Recognition (NOR) test. We conducted the tests in male Hartley guinea pigs and cognitive behaviors were assessed in customized Phenotyper home cages utilizing Ethovision XT software from Noldus enabled for the 3-point detection system (nose, center of the body, and rear). We found that acute intraperitoneal injections of either 0.25 mg/kg SCH23390 to block D1Rs or 1.0 mg/kg sulpiride to block D2Rs soon after acquisition (which involved familiarization to two similar objects) attenuated subsequent discrimination for novel objects when tested after 5-hours in the NOR test. By contrast guinea pigs treated with saline showed robust discrimination for novel objects indicating normal operational processes undergirding memory consolidation. The data suggests that involvement of dopaminergic signaling is a key post-acquisition factor in modulating memory consolidation in guinea pigs.

Effect of intratympanic application of efinaconazole 10 % solution in the guinea pig.

Efinaconazole 10 % solution is a new triazole antifungal agent developed for the topical treatment of fungal infections of the nails. The current study examined the effect of intratympanic application of efinaconazole 10 % solution in the guinea pig ear. Sixteen male Hartley guinea pigs (weight 501-620 g) were divided into 3 groups to be treated with efinaconazole 10 % solution, gentamicin (50 mg/mL), or saline solution. Topical solutions of 0.2 mL were applied through a small hole made at the tympanic bulla once daily for 7 consecutive days. Post-intervention auditory brainstem responses were obtained 7 days after the last treatment. The extent of middle ear damage and hair cell loss was investigated. The efinaconazole- and gentamicin-treated groups showed severe deterioration in auditory brainstem response threshold. Middle ear examination revealed extensive changes in the efinaconazole-treated group and medium changes in the gentamicin-treated group. Hair cells were preserved in the efinaconazole- and saline-treated groups, but severe damage was seen in the gentamicin group. In conclusion, efinaconazole 10 % solution applied intratympanically to the guinea pig middle ear caused significant middle ear inflammation and hearing impairment.

Phosphocitrate reduced cartilage degeneration in non-calcification induced osteoarthritis

Purpose: It was believed that phosphocitrate (PC) exerted its disease modifying effect on calcification-induced osteoarthritis (OA) by inhibiting the formation of calcium crystals within the joints. However, recent studies suggest that PC exerts its disease modifying effect on OA, at least in part, through a crystal-independent mechanism. This study sought to investigate the disease-modifying effect of PC on partial-meniscectomy induced OA or non-calcification induced OA and test the hypothesis that PC is not only potentially a disease modifying drug for calcification-induced OA therapy but also potentially a disease-modifying drug for non-calcification-inducted OA therapy. Methods: Male Hartley guinea pigs of 4 weeks old were subjected to intraperitoneal injections of PC and physiological saline respectively. Two months later, partial medial meniscectomy was performed on the right knee of all guinea pigs to remove the anterior horn (calcification site) of the medical meniscus. After the surgery, injections of PC and saline were resumed. Five months later, these guinea pigs were euthanized and hind limbs were collected. Meniscal calcification and cartilage degeneration was examined with digital x-ray, Indian ink and safranin O staining. Matrix metaloproteinse-13 (MMP-13), ADAM metallopeptidase with thrombospondin type 1 motif 5 (ADAMTS5), chemokine (C-C motif) ligand 5 (CCL5), cyclooxygenase 2 (Cox-2) and type X collagen were examined with immunostaining. Results were are expressed as the mean ± standard deviation. The differences between PC-treated and untreated groups were analyzed using Student’s t test or Wilcoxon rank sum test. Results: Meniscal calcification in the medial meniscus was absent in the partial-meniscectomy performed right knees. PC treatment significantly reduced the severity of cartilage degeneration and cartilage thinning in the partial-meniscectomy induced OA or non-calcification-induced OA. The reductions in cartilage degeneration and cartilage thinning were accompanied with significantly decreased protein levels of MMP-13, ADAMTS5 and CCL5. Conclusions: PC is not only potentially a disease modifying drug for calcification-induced OA therapy but also potentially a disease-modifying drug for non-calcification-inducted OA therapy. PC exerts its disease modifying activity on non-calcification-induced OA mainly by targeting the production of extracellular matrix-degrading enzymes through a crystal-independent mechanism. These findings provide further support for the development of PC or its analogues as disease-modifying drugs for human OA therapy.Figure 2. Mean histological scores of the tibia plateaus. Left bar group: Mean histological scores of the medial tibia plateaus of the rights knees in the untreated and PC-treated guinea pigs. Right bar group: Mean histological scores of the lateral tibia plateaus of the right knees in the untreated and PC-treated guinea pigs. * = P < 0.05 PC-treated versus the untreated guinea pigs.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3. Cartilage thickness. Left: thickness of the medial tibia cartilage in the untreated guinea pigs. Right: thickness of the medial tibia cartilage in the PC-treated guinea pigs.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 4. Immunostaining scores. Left bar group: MMP-15 immunostaining. Middle bar group: ADAMTS5 immunostaining. Right bar group: CCL-5 immunostaining.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

A comprehensive evaluation of the efficacy of leading oxime therapies in guinea pigs exposed to organophosphorus chemical warfare agents or pesticides

The currently fielded pre-hospital therapeutic regimen for the treatment of organophosphorus (OP) poisoning in the United States (U.S.) is the administration of atropine in combination with an oxime antidote (2-PAM Cl) to reactivate inhibited acetylcholinesterase (AChE). Depending on clinical symptoms, an anticonvulsant, e.g., diazepam, may also be administered. Unfortunately, 2-PAM Cl does not offer sufficient protection across the range of OP threat agents, and there is some question as to whether it is the most effective oxime compound available. The objective of the present study is to identify an oxime antidote, under standardized and comparable conditions, that offers protection at the FDA approved human equivalent dose (HED) of 2-PAM Cl against tabun (GA), sarin (GB), soman (GD), cyclosarin (GF), and VX, and the pesticides paraoxon, chlorpyrifos oxon, and phorate oxon. Male Hartley guinea pigs were subcutaneously challenged with a lethal level of OP and treated at approximately 1min post challenge with atropine followed by equimolar oxime therapy (2-PAM Cl, HI-6 DMS, obidoxime Cl2, TMB-4, MMB4-DMS, HLö-7 DMS, MINA, and RS194B) or therapeutic-index (TI) level therapy (HI-6 DMS, MMB4-DMS, MINA, and RS194B). Clinical signs of toxicity were observed for 24h post challenge and blood cholinesterase [AChE and butyrylcholinesterase (BChE)] activity was analyzed utilizing a modified Ellman's method. When the oxime is standardized against the HED of 2-PAM Cl for guinea pigs, the evidence from clinical observations, lethality, quality of life (QOL) scores, and cholinesterase reactivation rates across all OPs indicated that MMB4 DMS and HLö-7 DMS were the two most consistently efficacious oximes.

Diagnostic Exercise: Metastatic Calcification in Guinea Pigs.

Seven male Hartley guinea pigs, 3 to 18 months old, died or had to be euthanized because of nonspecific clinical signs unresponsive to supportive treatment. Gross necropsy and histopathology findings in all animals included severe soft tissue calcification affecting the myocardium, kidneys, and occasionally the liver.

Ototoxic Effect of Anti‐fog Solution Applied to the Guinea Pig Middle Ear

Objectives: Recent advances in endoscopic technology have allowed an application to middle ear surgery. Anti-fog agent is necessary for endoscopy because moisture and blood may cause obscured vision. Ultrastop is one of the most commonly used anti-fog agents. The current study examined the ototoxic effect of topical application of Ultrastop in the guinea pig ear. Methods: A preliminary experimental animal study. in a university hospital. Eighteen male Hartley guinea pigs (weight, 480-620 g) were divided into 3 groups to be treated with Ultrastop, gentamicin (50 mg/mL, positive control), or saline solution (negative control). After auditory brainstem responses were measured, topical solutions of 0.2 mL were applied through a small hole made at the tympanic bulla. Posttreatment auditory brainstem responses were obtained 14 days after the treatment. The extent of middle ear damage was investigated and scored. Results: The saline-treated group showed no deterioration in auditory brainstem response threshold. The anti-fog-treated and gentamicin-treated groups showed severe deterioration in auditory brainstem response threshold. Middle ear examination revealed extensive changes in the anti-fog-treated group and medium changes in the gentamicin-treated group. Conclusions: Anti-fog solution (Ultrastop) applied topically to the guinea pig middle ear caused significant middle ear inflammation and hearing impairment. Great care must be taken to prevent anti-fog solution reaching the middle ear.

Ototoxic effect of daptomycin applied to the guinea pig middle ear

Conclusion: Daptomycin applied topically at a concentration of 50 mg/ml caused mild but statistically significant hearing impairment. Outer hair cells were not damaged by daptomycin. Great care must be taken when there is a chance that daptomycin can reach the middle ear. Objective: Ototopic antibiotic eardrops are frequently used to treat external and middle ear infections. Daptomycin is a new anti-methicillin-resistant Staphylococccus aureus (MRSA) drug with unknown ototoxicity. The current study examined the ototoxic effect of daptomycin in topical applications to guinea pig ears. Methods: Twenty-three male Hartley guinea pigs (weight, 250–640 g) were divided into three groups receiving daptomycin (50 mg/ml), gentamicin (50 mg/ml, positive control), or saline solution (negative control). After insertion of a pressure-equalizing tube, pretreatment auditory brainstem responses (ABRs) were obtained. Topical solutions of 0.1 ml were applied through the tube into the middle ear twice a day for 7 days. Post-treatment ABRs were obtained 7 days after the last treatment. Hair cell loss was investigated with whole-mount cochlear surface preparations. Results: The saline-treated (negative control) group showed no deterioration of ABR threshold. The daptomycin-treated group showed mild deterioration and the gentamicin-treated group showed severe deterioration in ABR threshold. Hair cells were preserved in the daptomycin- and saline-treated groups but severely damaged in the gentamicin group.

Roles of sphincter of Oddi motility and serum vasoactive intestinal peptide, gastrin and cholecystokinin octapeptide.

To investigate roles of sphincter of Oddi (SO) motility played in pigment gallbladder stone formation in model of guinea pigs. Thirty-four adult male Hartley guinea pigs were divided randomly into two groups: the control group and pigment stone group. The pigment stone group was divided into 4 subgroups with 6 guinea pigs each according to time of sacrifice, and were fed a pigment lithogenic diet and sacrificed after 3, 6, 9 and 12 wk. SO manometry and recording of myoelectric activity of the guinea pigs were obtained by multifunctional physiograph at each stage. Serum vasoactive intestinal peptide (VIP), gastrin and cholecystokinin octapeptide (CCK-8) were detected at each stage in the process of pigment gallbladder stone formation by enzyme-linked immunosorbent assay. The incidence of pigment gallstone formation was 0%, 0%, 16.7% and 66.7% in the 3-, 6-, 9- and 12-wk group, respectively. The frequency of myoelectric activity decreased in the 3-wk group. The amplitude of myoelectric activity had a tendency to decrease but not significantly. The frequency of the SO decreased significantly in the 9-wk group. The SO basal pressure and common bile duct pressure increased in the 12-wk group (25.19 ± 7.77 mmHg vs 40.56 ± 11.81 mmHg, 22.35 ± 7.60 mmHg vs 38.51 ± 11.57 mmHg, P < 0.05). Serum VIP was significantly elevated in the 6- and 12-wk groups and serum CCK-8 was decreased significantly in the 12-wk group. Pigment gallstone-causing diet may induce SO dysfunction. The tension of the SO increased. The disturbance in SO motility may play a role in pigment gallstone formation, and changes in serum VIP and CCK-8 may be important causes of SO dysfunction.

Efficacy and Pharmacokinetic/Pharmacodynamic Study of 1,1′-Methylenebis{4-[(hydroxyimino)methyl] pyridinium} Dimethanesulfonate in Guinea Pigs and Rhesus Macaques Exposed to Cyclosarin

Male Hartley guinea pigs and male rhesus macaques were used to determine an efficacious dose of 1,1'-methylenebis{4-[(hydroxyimino)methyl] pyridinium} dimethanesulfonate (MMB4 DMS) that would result in 80% survival, 24 hours following a single exposure to cyclosarin (GF). The pharmacokinetic/pharmacodynamic relationship between acetylcholinesterase activity and MMB4 plasma concentrations relative to survival was evaluated. Guinea pigs and non-human primates (NHPs) were concurrently administered MMB4 DMS (guinea pigs: 0, 10, 30, or 40 mg/kg, intramuscular [IM] and NHPs: 0.1, 1, 5, 10, or 20 mg/kg, IM), atropine, and diazepam following a 3 × median lethal dose (LD50) GF challenge. Clinical observations were evaluated using a quality-of-life (QOL) scoring system. All GF-exposed animals exhibited typical signs of nerve agent poisoning immediately following challenge. In guinea pigs, 24-hour survival was 0%, 50%, 90%, and 90% for 0, 10, 30, and 40 mg/kg MMB4 DMS groups, respectively. In addition, nearly all animals surviving to 24 hours were clinically normal, with many in the 30 and 40 mg/kg MMB4 DMS dose group observed as normal by 4 hours post-challenge. In NHPs, survival was 100% for all treatment groups, with all animals noted as clinically normal by 48 hours. Following treatment with atropine/MMB4 DMS/diazepam, NHPs exhibited dose- and temporal-related decreases in incidence and duration of the clinical signs of toxicity. The QOL scores improved with increasing MMB4 DMS dose in both species. The estimated ED80s were 25.5 mg/kg MMB4 DMS (human equivalent dose [HED] of 5.5 mg/kg) and ≤ 0.1 mg/kg (HED of 0.03 mg/kg) in guinea pigs and NHPs, respectively.

Su2058 Chronic Homotypic Stress May Affect GI Functions Through Upregulation of Oxytocin Within PVN-DVC Neurocircuits

Background and Aims: Gastric accommodation is a reflex reaction related to gastric reservoir function by which the gastric fundus is relaxed when food enters the stomach. Gastric fundus relaxation induced by accommodation is mediated by nitric oxide (NO), produced by NO neurons. Depletion of NO thus inhibits gastric accommodation. Serotonin (5-HT) 2B receptors exist at the gastric fundus and 5-HT2B receptor activation induces contraction of smoothmuscle. However, the relationship between 5-HT2B receptor and gastric accommodation has not been elucidated. This study investigated the involvement of 5-HT2B receptors and the relationship to NO in gastric accommodation using a conscious guinea pig model. Methods: A polyethylene bag was inserted through the distal part of the gastric body and placed in the proximal stomach of 5-week-old male Hartley guinea pigs. Measurement of gastric accommodation was performed as follows: air (6 mL) was injected into the polyethylene bag at a rate of 2 mL/min, and intrabag pressure at baseline was recorded for 1 min. Immediately after oral administration of a liquid meal (4 mL, 1.7 kcal), air (6 mL) was again injected into the bag, and intrabag pressure was recorded 6 times, for 1 min each time at intervals of 5 min. NG-nitro-L-arginine (L-NNA) (a NO synthase inhibitor; 1-10 mg/kg) or BW723C86 (a 5-HT2B receptor agonist; 5 mg/kg) were administered orally 60 or 20 min before the liquid meal. SB215505 (a 5-HT2B receptor antagonist; 6 mg/kg), rikkunshito (traditional Japanese medicine; 250-1,000 mg/kg), or isoliquiritigenin (component of rikkunshito with 5-HT2B receptor antagonism; 0.125-4 mg/kg) were administered orally 30 min before the liquid meal. Results: Intrabag pressure was significantly decreased 5-25 min after liquid meal administration compared to baseline levels. SB215505 (6 mg/kg) did not affect liquid meal-induced decreases in intrabag pressure. Conversely, BW723C86 (5 mg/kg) significantly inhibited liquid meal-induced decreases in intrabag pressure. The effect of BW723C86 was abolished by co-administration of SB215505 (6 mg/kg). L-NNA dosedependently inhibited liquid meal-induced decreases in intrabag pressure and completely blocked the decrease at a dose of 10 mg/kg (-1.91 ± 0.83 vs. 0.05 ± 1.01 mmHg; p , 0.01). SB215505 (6 mg/kg), rikkunshito (1000 mg/kg), and isoliquiritigenin (4 mg/kg) significantly ameliorated L-NNA (10 mg/kg)-induced inhibition of decreases in intrabag pressure (0.03 ± 1.01 vs. -1.77 ± 0.62 mmHg, p , 0.01; -0.16 ± 0.46 vs. -1.79 ± 0.74 mmHg, p , 0.001; -0.38 ± 0.76 vs. -1.82 ± 0.58 mmHg, p , 0.01). Conclusions: The activation of 5-HT2B receptor inhibits gastric accommodation and may be regulated in part by NO neurons.

Su2057 5-HT2B Receptor Is Involved in the Regulation of Gastric Accommodation: A Lesson From a Model of Gastric Accommodation Using Conscious Guinea Pigs

Background and Aims: Gastric accommodation is a reflex reaction related to gastric reservoir function by which the gastric fundus is relaxed when food enters the stomach. Gastric fundus relaxation induced by accommodation is mediated by nitric oxide (NO), produced by NO neurons. Depletion of NO thus inhibits gastric accommodation. Serotonin (5-HT) 2B receptors exist at the gastric fundus and 5-HT2B receptor activation induces contraction of smoothmuscle. However, the relationship between 5-HT2B receptor and gastric accommodation has not been elucidated. This study investigated the involvement of 5-HT2B receptors and the relationship to NO in gastric accommodation using a conscious guinea pig model. Methods: A polyethylene bag was inserted through the distal part of the gastric body and placed in the proximal stomach of 5-week-old male Hartley guinea pigs. Measurement of gastric accommodation was performed as follows: air (6 mL) was injected into the polyethylene bag at a rate of 2 mL/min, and intrabag pressure at baseline was recorded for 1 min. Immediately after oral administration of a liquid meal (4 mL, 1.7 kcal), air (6 mL) was again injected into the bag, and intrabag pressure was recorded 6 times, for 1 min each time at intervals of 5 min. NG-nitro-L-arginine (L-NNA) (a NO synthase inhibitor; 1-10 mg/kg) or BW723C86 (a 5-HT2B receptor agonist; 5 mg/kg) were administered orally 60 or 20 min before the liquid meal. SB215505 (a 5-HT2B receptor antagonist; 6 mg/kg), rikkunshito (traditional Japanese medicine; 250-1,000 mg/kg), or isoliquiritigenin (component of rikkunshito with 5-HT2B receptor antagonism; 0.125-4 mg/kg) were administered orally 30 min before the liquid meal. Results: Intrabag pressure was significantly decreased 5-25 min after liquid meal administration compared to baseline levels. SB215505 (6 mg/kg) did not affect liquid meal-induced decreases in intrabag pressure. Conversely, BW723C86 (5 mg/kg) significantly inhibited liquid meal-induced decreases in intrabag pressure. The effect of BW723C86 was abolished by co-administration of SB215505 (6 mg/kg). L-NNA dosedependently inhibited liquid meal-induced decreases in intrabag pressure and completely blocked the decrease at a dose of 10 mg/kg (-1.91 ± 0.83 vs. 0.05 ± 1.01 mmHg; p , 0.01). SB215505 (6 mg/kg), rikkunshito (1000 mg/kg), and isoliquiritigenin (4 mg/kg) significantly ameliorated L-NNA (10 mg/kg)-induced inhibition of decreases in intrabag pressure (0.03 ± 1.01 vs. -1.77 ± 0.62 mmHg, p , 0.01; -0.16 ± 0.46 vs. -1.79 ± 0.74 mmHg, p , 0.001; -0.38 ± 0.76 vs. -1.82 ± 0.58 mmHg, p , 0.01). Conclusions: The activation of 5-HT2B receptor inhibits gastric accommodation and may be regulated in part by NO neurons.