[Multiple bioimaging modalities in evaluation of an experimental osteonecrosis model induced by a combination of lipopolysaccharide and methylprednisolone]

OBJECTIVE

The present study employed both static and dynamic imaging modalities to study both intra- and extravascular events attributing to steroid-associated osteonecrosis (ON) using an experimental protocol with a single low-dose lippolysaccharide (LPS) injection and subsequently three injections of high-dose methylprednisolone (MPS).

METHODS

Fourteen 28-week-old male New Zealand white rabbits received one intravenous injection of LPS (10 microg/kg). After 24 hours, three injections of 20 mg/kg of MPS were given intramuscularly at a time interval of 24 hours. Additional 6 rabbits were used as controls. Dynamic MRI was performed on bilateral femora for local intraosseous perfusion before and after LPS injection. Blood samples were collected for haematological examinations before and after LPS injection. Bilateral femora were dissected and decalcified for microCT-based microangiography. ON lesion, intravascular thrombus and extravascular marrow fat cell size were examined histopathologically.

RESULTS

Intravascular thrombus was observed in all ON rabbits. Extravascular marrow fat cell size was significantly increased in ON rabbits than that of the controls (P < 0.05). Compared to baseline, a significant decrease in ratio of tissue-type-plasminogen-activator/plasminogen-activator inhibitor 1, activated-partial- thromboplatin-time, and a significant increase in ratio of low-density-lipoprotein/high-density-lipoprotein were only found in ON rabbits (P < 0.05). Dynamic MRI showed a significant decrease in the perfusion index 'maximum enhancement' in the ON rabbits (P < 0.05) and microCT-based microangiography showed blocked stem vessels in ON samples. Overall, 93% of the rabbits (13/14) developed ON and no rabbits died throughout the experiment period.

CONCLUSION

Both intra- and extravascular events were found attributing to the steroid-associated ON based on our experimental protocol with a single low-dose LPS injection and subsequent three injections of high-dose MPS. Both high ON incidence and no mortality in rabbits treated with this inductive protocol suggested its effectiveness for future studies on evaluation of therapeutic efficacy of interventions developed for prevention of steroid-associated ON.

Open access colonoscopy in the training setting: which factors affect patient satisfaction and pain?

BACKGROUND AND STUDY AIM

Patient satisfaction with colonoscopy is important for quality assurance; it may be affected by various factors, including patient characteristics, physician training level, and procedural or organizational features. We aimed to analyze how these factors influenced patient satisfaction and pain in an outpatient training setting.

METHODS

Consecutive patients for open access colonoscopy (OAC) were enrolled in a prospective, single-blinded, controlled study. Primary and secondary outcomes were satisfaction and pain scores with and without trainee participation. A multivariate analysis was designed to achieve an 80 % power with an alpha value of 0.05.

RESULTS

368 patients were enrolled. Satisfaction with the procedure was high (mean score 1.36; 1 = best to 5 = worst). In the multivariate analysis only waiting time in the endoscopy suite was significantly associated with lower satisfaction scores ( P = 0.024). Satisfaction was unaffected by patient factors (gender, American Society of Anesthesiologists' [ASA] score, anxiety, etc). Higher pain scores were associated with higher anxiety levels ( P = 0.02), female gender ( P = 0.02), longer procedure ( P< 0.001), and lower sedation levels ( P = 0.001); trainee involvement (49 % of procedures) did not adversely affect satisfaction or pain scores.

CONCLUSIONS

Patient satisfaction with OAC using sedation appears to depend primarily on organizational factors (waiting time beforehand). In contrast, pain is associated with patient characteristics (female gender, anxiety) and procedural factors (lower sedation, longer procedure). Trainee participation did not affect satisfaction or pain scores, a finding which may help to reassure patients undergoing OAC with trainee participation.

Neuropathogenesis of chimeric simian/human immunodeficiency virus infection in pig-tailed and rhesus macaques

We recently reported that a chimeric simian/human immunodeficiency virus (SHIVKU-1) developed in our laboratory caused progressive depletion of CD4+ T lymphocytes and AIDS within 6 months of inoculation into pig-tailed macaques (M. nemestrina). None of the pig-tailed macaques showed productive SHIV infection in the central nervous system (CNS). In this report, we show that by further passage of the pathogenic virus in rhesus macaques [M. mulatta], we have derived a new strain of SHIV (SHIVKU-2) that has caused AIDS and productive CNS infection in 3 of 5 rhesus macaques infected with the virus. Productive replication of SHIV in the CNS was clearly shown by high infectivity titers and p27 protein levels in brain homogenates, and in 2 of the 3 rhesus macaques this was associated with disseminated, nodular, demyelinating lesions, including focal multinucleated giant cell reaction, largely confined to the white matter. These findings were reminiscent of HIV-1 associated neurological disease, and our immunohistochemical and in situ hybridization data indicated that the neuropathological lesions were associated with the presence of SHIV-specific viral antigens and nucleic acid respectively. However, the concomitant reactivation of opportunistic infections in these macaques suggested that such pathogens may have influenced the replication of SHIV in the CNS, or modified the neuropathological sequelae of SHIV infection in the rhesus species, but not in pig-tailed macaques. Our findings in the two species of macaques highlight the complexities of lentiviral neuropathogenesis, the precise mechanisms of which are still elusive.

Changes of microstructure and mineralized tissue in the middle and late phase of osteoporotic fracture healing in rats

BACKGROUND

With osteoporosis emerged as one of the most important health issues, more and more investigations are focusing on osteoporotic fracture healing. However, there are few studies on the changes of microstructure and mineralized tissue of newly formed callus.

OBJECTIVE

We established an osteoporotic fracture rat model to evaluate the changes of microstructure and mineralized tissue during osteoporotic fracture healing.

MATERIALS AND METHODS

A mid-shaft femur fracture model was established 12 weeks after ovariectomy as an osteoporotic fracture group (OPF group). Femurs were then harvested at 4 weeks, 8 weeks and 12 weeks after fracture for peripheral quantitative computed tomography (pQCT), micro-computed tomography (MicroCT), histology and biomechanical test. A sham-operated group was used for comparison, i.e. the normal fracture group (NF group).

RESULTS

The pQCT-derived total external callus area in the OPF group was smaller than that in the NF group at 4 weeks after fracture (P<0.05), whereas it was 21% larger in the OPF group than that in the NF group at 12 weeks after fracture (P<0.01). The pQCT-derived bone mineral density in the OPF group was significantly inferior to the NF group at all the time points (P<0.05 for all the time points, respectively). MicroCT data, at 12 weeks after fracture, showed the total callus, bony callus, and newly formed bone was approximately 20% lower in the OPF group than that in the NP group, and the total connectivity was 56% lower in the OPF group as compared to the NF group. Biomechanical test data, at 12 weeks after fracture, showed that the failure load of the left femur of OPF group was 17% less compared to that of the NF group (P<0.01), and 15% lower bending stiffness (P<0.05), 20% lower bending stress (P<0.01), and 28% lower energy at failure (P<0.01) were observed in the OPF group as compared to the NF group.

CONCLUSION

The decrease in mineralized tissue and the not well connected microstructure in newly formed callus may explain the decline of mechanical impairment of fracture healing in the ovariectomized rats.

Treatment of hepatitis B with lamivudine and tenofovir in HIV/HBV-coinfected patients: factors associated with response

As therapy for human immunodeficiency virus (HIV) infection evolves, optimizing hepatitis B virus (HBV) treatment and identifying factors that impact its response in the HIV/HBV-coinfected population is critical. We identified retrospectively 45 HBV/HIV-coinfected patients with detectable HBV DNA by the Bayer VERSANT HBV 3.0 bDNA assay (limit of quantification 2000 copies/mL) at baseline and/or year 1 of therapy. Patients were divided into three groups based on the active HBV agent in their antiretroviral regimen: group 1 (n = 15) received lamivudine; group 2 (n = 10), lamivudine plus tenofovir and group 3 (n = 20), lamivudine followed by lamivudine plus tenofovir. HBV genotypes and resistance profiles were determined by the Bayer Trugene HBV 1.0 assay. More patients in group 2 achieved HBV DNA suppression below 2000 copies/mL (80%), loss of HBe antigen (HBeAg) (40%) and loss of HBeAg and gain of anti-HBe (20%) than did patients in group 1 or 3. More patients with HBV genotype A, achieved HBV DNA suppression <2000 copies/mL than did patients with non-A genotypes [74% (26/35) vs 20% (2/10)], respectively (P = 0.003). Risk for virological nonresponse was significant in those with non-A genotypes [odds ratio (OR) 11.1; 95% CI: 2.0-50], previous HIV therapy (OR 6.5; 95% CI: 1.2-35) and <90% compliance (OR 3.7; 95% CI: 0.99-14.3). Simultaneous therapy with lamivudine/tenofovir suppresses HBV DNA more effectively than lamivudine or tenofovir added to lamivudine. More patients infected with HBV genotype A responded than the non-A patients, regardless of therapeutic regimen, compliance or prior HIV therapy.

Low-intensity pulsed ultrasound accelerates osteogenesis at bone-tendon healing junction

This study was designed to evaluate low-intensity pulsed ultrasound (LIPUS) in acceleration of mineralization and remodeling of the new bone formed at the healing interface of bone-tendon junction. Thirty-two mature New Zealand white rabbits underwent partial patellectomy and direct repair of the patellar tendon and proximal patella. Animals were then divided into LIPUS treatment group (20 min/d, 5 times/wk) and placebo control group and were euthanized at week 8 and 16 postoperatively (n = 8, for each group and time point). The main outcome measures included new bone size and its bone mineral density (BMD). Results showed that the size of new bone was found to be 2.6 and 3.0 times significantly greater in the LIPUS group compared with that of the control group at weeks 8 and 16, respectively. In addition, the LIPUS group showed significantly higher BMD at week 8 than controls, but not at week 16. In conclusion, this was the first experimental study to show that LIPUS was able to enhance osteogenesis at the healing bone-tendon junction, especially before the postoperative week 8. Findings of this study formed a scientific basis for future clinical trials and establishment of indication of LIPUS for enhancing bone-tendon junction repair.

Low-intensity pulsed ultrasound accelerates bone-tendon junction healing: a partial patellectomy model in rabbits

BACKGROUND

Low-intensity pulsed ultrasound has been demonstrated to be beneficial for accelerating fracture healing, delayed union, nonunion, and soft tissue repair.

HYPOTHESIS

Low-intensity pulsed ultrasound accelerates healing of bone-to-tendon junction repair by promoting osteogenesis and tissue remodeling at the healing junction.

STUDY DESIGN

Controlled laboratory study.

METHODS

Standard partial patellectomy was conducted in forty-eight 18-week-old rabbits divided into an ultrasound treatment and control group. Daily ultrasound was delivered 3 days after surgery onto the patellar tendon-patella healing junction and continuously up to weeks 2, 4, 8, and 16 postoperatively, when the patella-patellar tendon complexes were harvested for radiographic, histologic, and biomechanical evaluations.

RESULTS

Radiographic measurements showed significantly more newly formed bone at the patellar tendon-patella healing junction in the ultrasound group compared with the controls at week 8 (4.91 +/- 2.74 mm(2) vs 2.50 +/- 1.83 mm(2), P < .05) and week 16 (7.22 +/- 2.34 mm(2) vs 4.61 +/- 2.22 mm(2), P < .05) after partial patellectomy. Histologically, the ultrasound group at weeks 8 and 16 showed improved tissue integration, characterized by trabecular bone expansion from the remaining patella and regeneration of fibrocartilage layer at the patellar tendon-patella healing junction. Fluorescence microscopy revealed earlier bone formation in the ultrasound group when compared with the controls at week 8 (1.78 +/- 0.32 vs 1.23 +/- 0.43, P < .01) and week 16 (2.10 +/- 0.67 vs 1.29 +/- 0.35, P < .01). Mechanical testing showed significantly higher failure load and ultimate strength in the ultrasound group (300.2 +/- 61.7 N and 7.10 +/- 1.29 MPa, respectively) as compared with controls (222.3 +/- 65.1 N and 5.26 +/- 1.36 MPa, respectively) at week 16 (P < .05 for both).

CONCLUSION

Low-intensity pulsed ultrasound was able to accelerate bone-to-tendon junction repair.

CLINICAL RELEVANCE

These results may help establish treatment efficacy for accelerating bone-to-tendon junction repair and facilitating earlier rehabilitation.

Low intensity pulsed ultrasound increases the matrix hardness of the healing tissues at bone-tendon insertion-a partial patellectomy model in rabbits

BACKGROUND

This study evaluated the low intensity pulsed ultrasound enhancement on matrix hardness of the healing tissues at the bone-tendon junction.

METHODS

Sixteen 18 week-old mature female rabbits were used. An established transverse partial patellectomy was performed at the distal one-third of the patella. Animals were then divided according to their body weight into ultrasound group (n = 8) with daily treatment of low intensity pulsed ultrasound and control group (n = 8) without ultrasound treatment. Animals were euthanized at week 8 and 16 postoperatively to evaluate the radiographic new bone formation and the Vickers hardness of the matrix of the healing tissues at the bone-tendon junction.

FINDINGS

(1) Comparing with the control group, the anterior-posterior area of the new bone in the ultrasound treated group was found on average to be 3.0 and 3.1 times greater at week 8 and 16, respectively (P < 0.01). (2) The Vickers hardness of the new bone in ultrasound group was 11.3% (P < 0.05) significantly lower at week 8 but 20.0% (P < 0.05) significantly higher at week 16 as compared with that of the control group. (3) The Vickers hardness of the newly regenerated fibrocartilage zone, healing tendon, and cartilaginous metaplasia in ultrasound group was found higher than the control group at both week 8 and 16, but the difference was significant at week 16 only, being 44.1% (P < 0.05), 20.1% (P < 0.01), and 46.4% (P < 0.01) higher, respectively.

INTERPRETATION

The preliminary findings suggested for the first time that low intensity pulsed ultrasound treatment resulted in the enhancement of the matrix hardness in new bone, fibrocartilage, cartilaginous metaplasia, and healing tendon at the healing bone-tendon junction. These findings can be extrapolated into clinical practice, i.e. the more rapid healing induced by low intensity pulsed ultrasound, the earlier mobilization of the affected joint. The beneficial effects on prevention of the musculoskeletal deterioration resulting from the prolonged immobilization would be therefore expected.

A comparative study between axial compression and lateral fall configuration tested in a rat proximal femur model

BACKGROUND

Conventional testing method for evaluation of rat hip failure force is based on an axial compression approach. However, as the most osteoporotic hip fractures are a result of a lateral fall, it is necessary to establish mechanical testing methods more close to clinical conditions. This study was therefore designed to evaluate the differences in hip mechanical failure force to be tested between 'axial compression' and 'lateral fall configuration' in a rat proximal femur model.

METHODS

Eighteen 10-month-old female Wistar rats were body-weight matched and divided into ovariectomized group (n = 9) and sham group (n = 9). All rats were euthanized 3 months after surgery. The bilateral proximal femora of each rat were excised. The left femur served for testing to failure in a fall configuration fashion while the right femur was tested using axial compression approach. After mechanical testing, the anterior-posterior radiographs were taken to identify the fracture mode and measure the Pauwel's angle between the fracture line and the line perpendicular to the femoral shaft long axis.

FINDINGS

The failure force in fall configuration was significantly correlated with but lower than that tested in axial compression. A comparison between the ovariectomized and sham group showed that the failure force in both fall configuration and axial compression was found significantly higher in the sham group than that in the ovariectomized group. However, the logistic regression analysis revealed that the fall configuration approach had larger discrimination power. Radiographs showed that almost all samples fractured at the base of the femur neck. The Pauwel's angle in fall configuration group was significantly larger than that in axial compression group.

INTERPRETATION

In comparison with the characteristics of axial compression test, the fall configuration approach generated higher shearing stress with larger bending moment to the bone and induced susceptibility to fracture at lower mechanical load. Although the failure force obtained from the two testing configurations revealed significant correlation, the mechanical testing in fall configuration demonstrated higher sensitivity in identifying the estrogen-deficiency induced deterioration of hip mechanical failure force as compared with that in axial compression. These findings suggested the potential application of lateral fall configuration in evaluation of improvement effects of intervention stratagems on hip mechanical failure force involving an ovariectomized rat model.

Treatment of atrophic vaginitis with topical conjugated equine estrogens in postmenopausal Asian women

OBJECTIVE

We investigated the effects of 2 months of treatment with topical estrogens on atrophic vaginitis and gynecological health in Asian women.

STUDY DESIGN

Multicenter, open-label trial of 150 postmenopausal women age <70 years with atrophic vaginitis. Women applied conjugated equine estrogens (CEE) vaginal cream (0.625 mg/g) once daily on days 1-21 of two 28-day cycles. Changes in the vaginal maturation index (VMI) from baseline to days 21 (month 1) and 49 (month 2) were the primary outcome. Physiological changes were assessed by the Genital Health Clinical Examination (GHCE).

RESULTS

The VMI was significantly improved (p < 0.001) from baseline at each assessment period. The significant improvement in GHCE from baseline after 1 month (p < 0.001) was maintained at 2 months.

CONCLUSIONS

Vaginal treatment with CEE cream for 21 days of two consecutive 28-day cycles resulted in beneficial changes in the vaginal tissues and induced an overall genital health pattern more characteristic of the premenopausal state.

Beneficial effects of regular Tai Chi exercise on musculoskeletal system

This study was performed to evaluate the potential benefits of regular Tai Chi Chun (TCC) exercise on bone mineral density (BMD) and neuromuscular function in postmenopausal women. In this cross-sectional study, 99 healthy postmenopausal women, with a mean age of 55.9+/-3.1 years and within 10 years after the menopause, were recruited; including 48 subjects who had been regularly practicing TCC exercise for more than 3 h/week and 51 age- and sex-matched sedentary controls (CON). BMD was measured in the lumbar spine and proximal femur of the non-dominant leg (femoral neck, greater trochanter, and Ward's triangle), using dual-energy X-ray absorptiometry (DXA). Neuromuscular function was evaluated, including magnitude of trunk bend-and-reach, quadriceps muscle strength, and single-stance time on the nondominant leg. The TCC group showed overall higher BMD at all measurement sites, with a significant difference found at the spine (7.1%), greater trochanter (7.2%), and Ward's triangle (7.1%) of the proximal femur (all; P<0.05). Functional tests revealed an average 43.3% significantly greater quadriceps strength (P<0.01), and 67.8% significantly longer single-stance time in the TCC group as compared with the CON group (P<0.05), as well as a greater magnitude of trunk bend-and-reach in the TCC group (P=0.08). Bivariate linear correlation analysis showed that quadriceps muscle strength was significantly correlated with the single-stance time (r=0.41; P<0.01). This study revealed that regular TCC exercise may have an association with higher BMD and better neuromuscular function in early postmenopausal women.

Phytoestrogen-rich herb formula "XLGB" prevents OVX-induced deterioration of musculoskeletal tissues at the hip in old rats

This study investigated a phytoestrogen-rich herb formula, Xianlinggubao (XLGB) (including genistein 510 microg/g and daidzein 2500 microg/g), concerning prevention of OVX-induced deterioration of musculoskeletal tissues in 11-month-old female Wistar rats, which were randomized into Sham, OVX, and XLGB groups. Daily oral administration of XLGB (250 mg/kg/day) started after OVX for 3 months. mRNA of MHC-I IIa IIb of abductor muscle was determined by RT-PCR. The proximal femoral BMD and geometry, microarchitecture, and mechanical strength were evaluated by pQCT, micro-CT, and compressive testing, respectively. The bone turnover biochemical markers serum osteocalcin (OC) and urinary deoxypyridinoline (DPD) were evaluated. The results showed that (1) XLGB-treated OVX rats showed no difference compared to the Sham group, whereas OVX induced significant deterioration in variables related to bone density, microarchitecture, and mechanical strength (P < 0.05); (2) biochemical markers showed no difference between sham and XLGB groups as compared with higher bone turnover in OVX rats (P < 0.05); (3) mRNA expression of MHC-I IIa IIb was downregulated in OVX rats but upregulated after XLGB treatment (P < 0.05); and (4) as compared with the OVX group, no uterine hypertrophy was found in XLGB-treated rats. In conclusion, findings of this study suggested that the herbal preparation XLGB was able to prevent OVX-induced deterioration of musculoskeletal tissues at the hip without causing uterine stimulation.

Correlation study of scanning acoustic microscope reflection coefficients and image brightness intensities of micrographed osteons

Scanning acoustic microscopy (SAM) of Haversian bone at high frequency clearly shows differences in the brightness (gray) levels of individual osteons, which were observed to correspond to the differences in reflection coefficients measured with the SAM technique: the darker the bony regions on the SAM micrographs, the lower the SAM reflection coefficient values, and vice versa. We studied the correlation between differences in brightness and the related reflection coefficients of osteons on undecalcified transverse sections of goat tibial diaphysis using a 400-MHz burst mode lens on the Olympus UH3 SAM. Results showed that there was a strong linear correlation between brightness intensities and the corresponding reflection coefficients, with a correlation coefficient r = 0.99 ( P << 0.001) using gray level 210 as cutoff. This result suggested that the image brightness intensity of osteonic bone could be measured retrospectively to provide information on the stiffness of the corresponding bone matrix.

Personality in cultural context: methodological issues

Methodological issues in cultural and cross-cultural personality research are described. A taxonomy of these studies is presented, based on whether a study is exploratory or tests hypotheses, and whether or not contextual information is measured. Core methodological issues are bias and equivalence: a taxonomy and a brief overview of statistical procedures to examine equivalence are presented, with a focus on procedures for assessing structural equivalence (i.e., similarity of meaning of an instrument across cultures). Examples are given of studies in which cultural and cross-cultural approaches, often seen as antithetical, have been fruitfully integrated. Finally, multilevel models are described in which personality characteristics are examined at individual and cultural level.

Identification of Arcobacter cryaerophilus isolated from a traffic accident victim with bacteremia by 16S ribosomal RNA gene sequencing

Traditional ways of identifying slow growing bacteria is slow and often difficult. In this study, a small, Gram-negative, facultative anaerobic, slow growing bacillus was isolated from the blood culture of a 7-year old traffic accident victim. The bacterium was non-hemolytic, catalase and oxidase positive. An attempt to use the Vitek system (GNI+) and the API system (20NE) to identify the strain was unsuccessful as the growth controls showed negative results. 16S ribosomal RNA gene sequencing showed that there was 1 base difference between the isolate and Arcobacter cryaerophilus (GenBank Accession no. U25805), 1 base difference between the isolate and A. cryaerophilus (GenBank Accession no. U34387), 10 base differences between the isolate and A. cryaerophilus (GenBank Accession no. L14624), 34 base differences between the isolate and A. butzleri (GenBank Accession no. U34386), 34 base differences between the isolate and A. butzleri (GenBank Accession no. U34387), and 38 base differences between the isolate and A. butzleri (GenBank Accession no. L14626), indicating that the isolate most closely resembled a strain of A. cryaerophilus. Identification of the isolate in our case by conventional methods was difficult, as the absence of a curved morphology has made it confused with other Gram-negative non-fermentative bacteria, and the slow growth rate has made it unidentifiable by both the Vitek and API systems. Although the exact source of infection and route of transmission in our case remains elusive, we speculate that the bacteria were transmitted through the respiratory tract while the boy was suffocated in the mud. The present report represents an example of showing the usefulness of 16S rRNA gene sequencing for identification of slow growing bacteria.

Identification by 16S ribosomal RNA gene sequencing of an Enterobacteriaceae species with ambiguous biochemical profile from a renal transplant recipient

Traditional ways of identification of bacteria by phenotypic characteristics cannot be used for non-cultivable organisms and organisms with unusual biochemical profiles. In this study, an Enterobacteriaceae was isolated in pure growth from the mid-stream urine of a 67-year old renal transplant recipient with urinary tract infection. Conventional biochemical tests did not reveal a pattern resembling any known member of the Enterobacteriaceae family. The Vitek system (GNI+) showed that it was 18% Leclercia adecarboxylata and 55% Klebsiella ozaenae; whereas the API system (20E) showed that it was 99.8% Rahnella aquatilis. 16S ribosomal RNA gene sequencing showed that there was 7 base differences between the isolate and Enterobacter cloacae, 18 base differences between the isolate and Enterobacter asburiae, 17 base differences between the isolate and Enterobacter cancerogenus, 35 base differences between the isolate and K. ozaenae, 27 base differences between the isolate and L. adecarboxylata, and 72 base differences between the isolate and R. aquatilis, indicating that the isolate most closely resembled a strain of E. cloacae. Identification of the organism in this study is important, as the choice of antibiotics would be radically different. In this case, cephalosporins should be avoided regardless of in-vitro susceptibility as cephalosporins are well-known to select for AmpC derepressed mutants in Enterobacter, and previous administration of third-generation cephalosporins is more likely to be associated with multidrug resistant Enterobacter isolates than is administration of antibiotics that do not include a third-generation cephalosporin.

Inhibitory effects of nitric oxide on estrogen production and cAMP levels in rat granulosa cell cultures

Previous studies demonstrated inhibitory effects of nitric oxide (NO) and cGMP on ovarian steroidogenesis. This study examined the effects of NO on estrogen levels and cAMP accumulation from immature cultured rat granulosa cells. Granulosa cells were incubated with media alone (control), FSH or FSH plus increasing concentrations of the NO generator, (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA/NO). While FSH increased estrogen levels 15-fold compared with controls, DETA/NO inhibited FSH-stimulated aromatase activity in a dose-dependent manner. Time-course studies revealed that the inhibitory effects of DETA/NO on aromatase activity persisted throughout the 72 h culture period. Treatment with DETA/NO also inhibited the stimulatory effects of forskolin on estrogen production, indicating that NO can influence steroidogenesis by actions downstream of the FSH receptor. Incubation of cells with FSH plus DETA/NO increased cGMP accumulation over 100-fold, compared with cells treated with media or FSH alone. In this regard, a cGMP analog mimicked the inhibitory effects of NO on FSH- and forskolin-stimulated estrogen production, indicating a potential mechanism of NO action. NO also decreased FSH-stimulated (cAMP) accumulation from cultured cells, indicating an antagonistic effect of NO on the second messenger mediating FSH actions. These findings demonstrate that NO inhibits estrogen production from rat granulosa cells, potentially reflecting actions on the second messengers cGMP and cAMP.

Studies on the metabolism of troglitazone to reactive intermediates in vitro and in vivo. Evidence for novel biotransformation pathways involving quinone methide formation and thiazolidinedione ring scission

Therapy with the oral antidiabetic agent troglitazone (Rezulin) has been associated with cases of severe hepatotoxicity and drug-induced liver failure, which led to the recent withdrawal of the product from the U.S. market. While the mechanism of this toxicity remains unknown, it is possible that chemically reactive metabolites of the drug play a causative role. In an effort to address this possibility, this study was undertaken to determine whether troglitazone undergoes metabolism in human liver microsomal preparations to electrophilic intermediates. Following incubation of troglitazone with human liver microsomes and with cDNA-expressed cytochrome P450 isoforms in the presence of glutathione (GSH), a total of five GSH conjugates (M1-M5) were detected and identified tentatively by LC-MS/MS analysis. In two cases (M1 and M5), the structures of the adducts were confirmed by NMR spectroscopy and/or by comparison with an authentic standard prepared by synthesis. The formation of GSH conjugates M1-M5 revealed the operation of two distinct metabolic activation pathways for troglitazone, one of which involves oxidation of the substituted chromane ring system to a reactive o-quinone methide derivative, while the second involves a novel oxidative cleavage of the thiazolidinedione (TZD) ring, potentially generating highly electrophilic alpha-ketoisocyanate and sulfenic acid intermediates. When troglitazone was administered orally to a rat, samples of bile were found to contain GSH conjugates which reflected the operation of these same metabolic pathways in vivo. The finding that metabolism of the TZD ring of troglitazone was catalyzed selectively by P450 3A enzymes is significant in light of the recent report that troglitazone is an inducer of this isoform in human hepatocytes. The implications of these results are discussed in the context of the potential for troglitazone to covalently modify hepatic proteins and to cause oxidative stress through redox cycling processes, either of which may play a role in drug-induced liver injury.