Chemical synthesis and hepatic biotransformation of 3 alpha,7 alpha-dihydroxy-7 beta-methyl-24-nor-5 beta-cholan-23-oic acid, a 7-methyl derivative of norchenodeoxycholic acid: studies in the hamster.

A new bile acid analogue, 3 alpha,7 alpha-dihydroxy-7 beta-methyl-24-nor-5 beta-cholan-23-oic acid (7-Me-norCDCA) was synthesized from the methyl ester of norursodeoxycholic acid, and its hepatic biotransformation was defined in the hamster. To synthesize 7-Me-norCDCA, the 3 alpha-hydroxyl group of methyl norursodeoxycholate was protected as the hemisuccinate, and the 7 beta-hydroxyl group was oxidized with CrO3 to form the 7-ketone. A Grigard reaction with methyl magnesium iodide followed by alkaline hydrolysis gave 7-Me-norCDCA (greater than 70% yield). The structure of the new compound was confirmed by proton magnetic resonance and mass spectrometry. After intraduodenal administration of the 14C-labeled compound into the anesthetized biliary fistula hamster, it was rapidly and efficiently secreted into the bile; 80% of radioactivity was recovered in 2 h. After intravenous infusion, the compound was efficiently extracted by the liver and secreted into the bile (greater than 75% in 3 h). Most (93%) of the biliary radioactivity was present in biotransformation products. The major biotransformation product (48.7 +/- 6.0%) was a new compound, assigned the structure of 3 alpha,5 beta,7 alpha- trihydroxy-7 beta-methyl-24-nor-5 beta-cholan-23-oic acid (5 beta-hydroxy-7- Me-norCDCA). In addition, conjugates of 7-Me-norCDCA with taurine (13.7 +/- 5.0%), sulfate (10.3 +/- 3.0%), or glucuronide (5.1 +/- 1.7%) were formed. 7-Me-norCDCA was strongly choleretic in the hamster; during its intravenous infusion, bile flow increased 2 to 3 times above the basal level, and the calculated choleretic activity of the compound (and its metabolic products) was much greater than that of many natural bile acids, indicating that the compound induced hypercholeresis. It is concluded that the biotransformation and physiological properties of 7-Me-norCDCA closely resemble those of norCDCA. Based on previous studies, the major biological effect of the 7-methyl group in 7-Me-norCDCA is to prevent its bacterial 7-dehydroxylation in the distal intestine.     

Effects of irradiation on RNA synthesis primed by calf thymus deoxyribonucleoprotein treated with salt and salt-urea.

1. The effects of ionizing radiation on the activity of calf thymus templates were examined in a Escherichia coli RNA polymerase system. 2. The template activity of native and 2 M NaCl-5M urea-treated deoxyribonucleoproteins was enhanced by relatively low doses of irradiation, while that of 2 M NaCl-treated deoxyribonucleoprotein was not enhanced by irradiation. 3. The template activity of purified DNA was markedly decreased by irradiation, while that of native deoxyribonucleoprotein, 2 M NaCl-treated, and 2 M NaCl-5 M urea-treated ones were slightly decreased at a higher dose range. The doses for 50% inactivation of these templates were 1.3, 210, 140, and approximately 200 krad, respectively.     

The autophagy gene Wdr45/Wipi4 regulates learning and memory function and axonal homeostasis

WDR45/WIPI4, encoding a WD40 repeat-containing PtdIns(3)P binding protein, is essential for the basal autophagy pathway. Mutations in WDR45 cause the neurodegenerative disease β-propeller protein-associated neurodegeneration (BPAN), a subtype of NBIA. We generated CNS-specific Wdr45 knockout mice, which exhibit poor motor coordination, greatly impaired learning and memory, and extensive axon swelling with numerous axon spheroids. Autophagic flux is defective and SQSTM1 (sequestosome-1)/p62 and ubiquitin-positive protein aggregates accumulate in neurons and swollen axons. Nes-Wdr45^fl/Y mice recapitulate some hallmarks of BPAN, including cognitive impairment and defective axonal homeostasis, providing a model for revealing the disease pathogenesis of BPAN and also for investigating the possible role of autophagy in axon maintenance.     

The dual-oscillator system of Drosophila melanogaster under natural-like temperature cycles

Dual-oscillator systems that control morning and evening activities can be found in a wide range of animals. The two coupled oscillators track dawn and dusk and flexibly adapt their phase relationship to seasonal changes. This is also true for the fruit fly Drosophila melanogaster that serves as model organism to understand the molecular and anatomical bases of the dual-oscillator system. In the present study, the authors investigated which temperature parameters are crucial for timing morning and evening activity peaks by applying natural-like temperature cycles with different daylengths. The authors found that the morning peak synchronizes to the temperature increase in the morning and the evening peak to the temperature decrease in the afternoon. The two peaks did not occur at fixed absolute temperatures, but responded flexibly to daylength and overall temperature level. Especially, the phase of the evening peak clearly depended on the absolute temperature level: it was delayed at high temperatures, whereas the phase of the M peak was less influenced. This suggests that the two oscillators have different temperature sensitivities. The bimodal activity rhythm was absent in the circadian clock mutants Clk(Jrk) and cyc(01) and reduced in per(01) and tim(01) mutants. Whereas the activity of Clk(Jrk) mutants just followed the temperature cycles, that of per(01) and tim(01) mutants did not, suggesting that these mutants are not completely clockless. This study revealed new characteristics of the dual-oscillator system in Drosophila that were not detected under different photoperiods.     

Comparison of PCR-RFLP and PFGE for determining the clonality of enterohemorrhagic Escherichia coli strains

We report here on a comparative evaluation of PCR-restriction fragment length polymorphism (PCR-RFLP) and pulsed-field gel electrophoresis (PFGE) assays, and ascertain the clonal relationship between 13 enterohemorrhagic Escherichia coli O157 : H7 strains isolated from fecal samples collected from three cows over a period of 2 months. PCR-RFLP analysis was carried out with either BglI or EcoRV digested LA-PCR amplicons, generated by targeting region V of the Stx-phage. While PCR-RFLP analysis placed these 13 strains into a single clonal type, pulsotyping analysis, as reported earlier, grouped these strains into four different PFGE subtypes of which three were closely related, while the other appeared to be different. The comparative analysis was extended further using two clonally different wild-type (3-0 and Sakai 215) strains and 17 derivative strains which had passed through an animal's gastrointestinal tract. The PCR-RFLP assay, which was not only able to differentiate the wild-type strains, but also placed the passaged derivative strains into their respective parental group, although PFGE patterns of the same set of strains resulted from different PFGE subtypes. These data indicate that PCR-RFLP is the more reliable and useful assay for a molecular epidemiological survey of enterohemorrhagic E. coli strains.     

Quantitative measures of femoral fracture repair in rats derived by micro-computed tomography

Although fracture healing is frequently studied in pre-clinical models of long bone fractures using rodents, there is a dearth of objective quantitative techniques to assess successful healing. Biomechanical testing is possibly the most quantitative and relevant to a successful clinical outcome, but it is a destructive technique providing little insight into the cellular mechanisms associated with healing. The advent of X-ray computed tomography (CT) has provided the opportunity to quantitatively and non-destructively assess bone structure and density, but it is unknown how measurements derived using this technology relate to successful healing. To examine possible relationships, we used a pre-clinical model to test for statistically significant correlations between quantitative characteristics of the callus by micro-CT (μCT) and the bending strength, stiffness, and energy-to-failure of the callus as assessed by three-point bending of excised bones. A closed, transverse fracture was generated in the mid-shaft of rat femurs by impact loading. Shortly thereafter, the rats received a one-time, local injection of either the vehicle or one of four doses of lovastatin. Following sacrifice after 4 weeks of healing, fractured femurs were extracted for μCT analysis and then three-point bending. Setting the region of interest to be 3.2 mm above and below the fracture line, we acquired standard and new μCT-derived measurements. The mineralized callus volume and the mineral density of the callus correlated positively with callus strength (r_xy=?0.315, p=0.016 and r_xy=0.444, p<0.0005, respectively) and stiffness (r_xy=?0.271, p=0.040 and r_xy=0.325, p=0.013, respectively), but the fraction of the callus that mineralized and the moment of inertia of the callus did not. This fraction did correlate with energy-to-failure (r_xy=?0.343, p=0.0085). Of the μCT-derived measurements, quantifying defects within the outer bridging cortices of the callus produced the strongest correlation with both callus strength (r_xy=0.557, p<0.0001) and stiffness (r_xy=0.468, p=0.0002). By both reducing structural defects and increasing mineralization, lovastatin appears to increase the callus strength.