A VARIATIONAL MODEL FOR DENOISING HIGH ANGULAR RESOLUTION DIFFUSION IMAGING

The presence of noise in High Angular Resolution Diffusion Imaging (HARDI) data of the brain can limit the accuracy with which fiber pathways of the brain can be extracted. In this work, we present a variational model to denoise HARDI data corrupted by Rician noise. Numerical experiments are performed on three types of data: 2D synthetic data, 3D diffusion-weighted Magnetic Resonance Imaging (DW-MRI) data of a hardware phantom containing synthetic fibers, and 3D real HARDI brain data. Experiments show that our model is effective for denoising HARDI-type data while preserving important aspects of the fiber pathways such as fractional anisotropy and the orientation distribution functions.

Precision-cut slice culture method for rat placenta

Primary trophoblasts, placental explants, and cell line cultures are commonly used to investigate placental development, physiology, and pathology, particularly in relation to pregnancy outcomes. Organotypic slice cultures are increasingly used in other systems because they maintain the normal three-dimensional tissue architecture and have all cell types represented. Herein, we demonstrate the utility of the precision-cut placental slice culture model for studying trophoblastic diseases.

The constitutional t(11;22): implications for a novel mechanism responsible for gross chromosomal rearrangements

The constitutional t(11;22)(q23;q11) is the most common recurrent non-Robertsonian translocation in humans. The breakpoint sequences of both chromosomes are characterized by several hundred base pairs of palindromic AT-rich repeats (PATRRs). Similar PATRRs have also been identified at the breakpoints of other nonrecurrent translocations, suggesting that PATRR-mediated chromosomal translocation represents one of the universal pathways for gross chromosomal rearrangement in the human genome. We propose that PATRRs have the potential to form cruciform structures through intrastrand-base pairing in single-stranded DNA, creating a source of genomic instability and leading to translocations. Indeed, de novo examples of the t(11;22) are detected at a high frequency in sperm from normal healthy males. This review synthesizes recent data illustrating a novel paradigm for an apparent spermatogenesis-specific translocation mechanism. This observation has important implications pertaining to the predominantly paternal origin of de novo gross chromosomal rearrangements in humans.

Gastric emptying of enterally administered liquid meal in conscious rats and during sustained anaesthesia

BACKGROUND

Gastric motility studies are frequently conducted with anaesthetized animal models. Some studies on the same animal species have reported differences in vagal control of the stomach that could not be explained solely by slightly different experimental conditions. A possible limitation in the comparison between similar studies relates to the use of different anaesthetic agents. Furthermore, anaesthetic effects may also limit generalizations between mechanistic studies of gastric function and the gastric function of conscious animals. In the present study, we used the [(13)C]-breath test following a liquid mixed-nutrient test meal (Ensure), 1 ml) with the aim to investigate the rate of gastric emptying in animals that were either conscious or anaesthetized with either Inactin or urethane.

METHODS

One week after determining the maximum (13)CO(2) concentration, time to peak [(13)C] recovery and gastric half emptying time in control, conscious rats, we repeated the experiment in the same rats anaesthetized with Inactin or urethane.

KEY RESULTS

Our data show that Inactin anaesthesia prolonged the time to peak [(13)C] recovery but did not significantly reduce the maximum (13)CO(2) concentration nor delay gastric half emptying time. Conversely, urethane anaesthesia resulted in a significant slowing of all parameters of gastric emptying as measured by the maximum (13)CO(2) concentration, time to peak [(13)C] recovery and half emptying time.

CONCLUSIONS & INFERENCES

Our data indicate that Inactin(R) anaesthesia does not significantly affect gastric emptying while urethane anaesthesia profoundly impairs gastric emptying. We suggest that Inactin(R), not urethane, is the more suitable anaesthetic for gastrointestinal research.

Time-course of recovery of gastric emptying and motility in rats with experimental spinal cord injury

We have shown recently that spinal cord injury (SCI) decreases basal gastric contractions 3 days after injury. In the present study we used the [(13)C]-octanoic acid breath test and gastric strain gauges with the aim to investigate the time-course of recovery from postinjury gastric stasis in rats that underwent experimental SCI at the level of the third thoracic (T3) vertebra. Following verification of the [(13)C]-breath test sensitivity in uninjured rats, we conducted our experiments in rats that underwent T3-spinal contusion injury (T3-CI), T3-spinal transection (T3-TX) or laminectomy (control) surgery at 3 days, 1, 3 or 6 weeks postinjury. Our data show that compared to rats that underwent laminectomy, rats that received SCI showed a significant reduction in the cumulative per cent [(13)C] recovery. Although more marked in T3-TX rats, the delayed gastric emptying in T3-CI and T3-TX rats was comparable in the 3 days to 3 weeks period postinjury. At 6 weeks postinjury, the gastric emptying in T3-CI rats recovered to baseline values. Conversely animals in the T3-TX group still show a significantly reduced gastric emptying. Interestingly, the almost complete functional recovery observed in T3-CI rats using the [(13)C]-breath test was not reflected by analysis of spontaneous gastric contractions after SCI. These data indicate that T3-SCI produces a significant reduction in gastric emptying independent of injury severity (T3-CI vs T3-TX) that persists for at least 3 weeks after injury. However, 6 weeks postinjury T3-CI, but not T3-TX, rats begin to demonstrate functional recovery of gastric emptying.

Gastric dysreflexia after acute experimental spinal cord injury in rats

Gastric reflexes are mediated mainly by vago-vagal reflex circuits in the caudal medulla. Despite the fact that brainstem vago-vagal circuitry remains intact after spinal cord injury (SCI), patients with SCI at the cervical level most often present gastric stasis with an increased risk of reflux and aspiration of gastric contents. Using a miniature strain gauge sutured to the gastric surface; we tested gastric motility and reflexive gastric relaxation following oesophageal distension (oesophageal-gastric relaxation reflex) in animals 3 days after a severe spinal contusion at either the third or ninth thoracic spinal segment (acute T3- or T9 SCI, respectively). Both basal gastric motility and the oesophageal-gastric relaxation reflex were significantly diminished in animals with T3 SCI. Conversely, both basal gastric motility and the oesophageal-gastric relaxation reflex were not significantly reduced in T9 SCI animals compared to controls. The reduced gastric motility and oesophageal-gastric reflex in T3 SCI rats was not ameliorated by celiac sympathectomy. Our results show that gastric stasis following acute SCI is independent of altered spinal sympathetic input to the stomach caudal to the lesion. Our data suggest that SCI may alter the sensitivity of vagal reflex function, perhaps by interrupting ascending spinosolitary input to brainstem vagal nuclei.

Ultrafast response of surface electromagnetic waves in an aluminum film perforated with subwavelength hole arrays

The ultrafast dynamics of surface electromagnetic waves photogenerated on aluminum film perforated with subwavelength arrays of holes was studied in the visible spectral range by the technique of transient photomodulation with approximately 100 fs time resolution. We observed a pronounced blueshift of the resonant transmission band that reveals the important role of plasma attenuation in the optical response of nanohole arrays. The blueshift is inconsistent with plasmonic mechanism of extraordinary transmission and points to the crucial role of interference in the formation of transmission bands. The transient photomodulation spectra were successfully modeled within the Boltzmann equation approach for the electron-phonon relaxation dynamics, involving nonequilibrium hot electrons and quasiequilibrium phonons.

Elasticity indices of large and small arteries in relation to the metabolic syndrome in Chinese

BACKGROUND

The purpose of this study was to investigate the elasticity of large and small arteries in relation to the components of the metabolic syndrome in a Chinese population.

METHODS

Arterial elasticity indices were derived from pulse wave analysis based on a modified Windkessel model in 688 subjects, aged 33-65 years, who volunteered to participate in our study.

RESULTS

The study population included 420 (61.0%) men and 433 (62.9%) hypertensive patients, of whom 197 (28.6%) took antihypertensive medication. Overall, the presence of the metabolic syndrome was 20.5%. In univariate analysis, both large artery elasticity index (C1) and small artery elasticity index (C2) were higher in men than in women (P < or = 0.008) and were inversely (P < or = 0.05) correlated with age, systolic and diastolic blood pressure (BP), pulse pressure, pulse rate, and plasma glucose concentration, and positively (P < 0.0001) correlated with body height and body weight. In men, smokers, compared with nonsmokers, had significantly lower C2 (P = 0.007), but they had similar C1 (P = 0.33). In adjusted analysis, patients with the metabolic syndrome, compared with those without, had significantly (P < 0.01) lower C1 and C2. In continuous adjusted analysis, both C1 and C2 were significantly (P < 0.0001) associated with systolic and diastolic BP, whereas in addition, C1 was also significantly associated with plasma glucose concentration (P = 0.007), and C2 with serum high-density lipoprotein (HDL) cholesterol (P = 0.02).

CONCLUSIONS

The metabolic syndrome is indeed a risk factor for reduced arterial elasticity.

Impaired placentation in fetal alcohol syndrome

Intrauterine growth restriction (IUGR) is one of the key features of fetal alcohol syndrome (FAS), and IUGR can be mediated by impaired placentation. Insulin-like growth factors (IGF) regulate placentation due to stimulatory effects on extravillous trophoblasts, which are highly motile and invasive. Previous studies demonstrated that extravillous trophoblasts express high levels of aspartyl-(asparaginyl) beta-hydroxylase (AAH), a gene that is regulated by IGF and has a critical role in cell motility and invasion. The present study examines the hypothesis that ethanol impaired placentation is associated with inhibition of AAH expression in trophoblasts. Pregnant Long Evans rats were fed isocaloric liquid diets containing 0% or 37% ethanol by caloric content. Placentas harvested on gestation day 16 were used for histopathological, mRNA, and protein studies to examine AAH expression in relation to the integrity of placentation and ethanol exposure. Chronic ethanol feeding prevented or impaired the physiological conversion of uterine vessels required for expansion of maternal circulation into placenta, a crucial process for adequate placentation. Real-time quantitative RT-PCR analysis demonstrated significant reductions in IRS-1, IRS-2, and significant increases in IGF-II and IGF-II receptor mRNA levels in ethanol-exposed placentas. These abnormalities were associated with significantly reduced levels of AAH expression in trophoblastic cells, particularly within the mesometrial triangle (deep placental bed) as demonstrated by real time quantitative RT-PCR, Western blot analysis, ELISA, and immunohistochemical staining. Ethanol-impaired placentation is associated with inhibition of AAH expression in trophoblasts. This effect of chronic gestational exposure to ethanol may contribute to IUGR in FAS.

Clinical trial: effects of adefovir dipivoxil therapy in Asian and Caucasian patients with chronic hepatitis B

BACKGROUND

Two-thirds of the 350 million people infected with chronic hepatitis B virus live in the Asia-Pacific region. AIM To compare the effects of adefovir dipivoxil therapy between Asian and Caucasian patients with chronic hepatitis B.

METHODS

The safety and efficacy of 10 mg of adefovir dipivoxil was compared to placebo in 501 Asian (n = 259) or Caucasian (n = 242) HBeAg+ and HBeAg- chronic hepatitis B virus patients treated for 48 weeks in two randomized, double-blind, placebo-controlled studies.

RESULTS

At week 48, histological improvement was observed in 60% and 56% of Caucasian and Asian patients, respectively. Change in serum hepatitis B virus DNA from baseline to week 48 for the adefovir dipivoxil-treated patients was -3.89 and -3.70 log(10) copies/mL in Caucasian and Asian patients, respectively, while 34 per cent of Caucasian patients and 39 per cent of Asian patients had undetectable serum hepatitis B virus DNA (<400 copies/mL) at week 48. The percentage of patients achieving alanine aminotransferase (ALT) normalization at week 48 was similar in both groups (Caucasian 64 per cent, Asian 63 per cent). No patients developed resistance through week 48. No differences in adverse events or grade 3 or 4 laboratory abnormalities were observed between groups.

CONCLUSIONS

There were no significant differences in treatment response between Asians and Caucasians. Adefovir dipivoxil was well tolerated and no resistance developed up to week 48 in both racial groups.

Cloacal Gland Growth Differences in High and Low Plasma Corticosterone Stress Response Line Male Quail Reared Under Short Daylengths

Mail quail selected (generation 32) for reduced [low stress (LS)] or exaggerated [high stress (HS)] plasma corticosterone stress response to brief mechanical restraint (5 min of immobilization) were studied for differences in the growth of their cloacal glands when reared essentially lifelong on short day lengths of 8L:16D. Post-brooding, at 4 wk of age, 96 quail (48 LS+48 HS) were housed in cages (1 LS and 1 HS male/cage), and the short day light treatment was instigated. Using a digital caliper, cloacal gland (CG) size measurements (length and width, mm) were made biweekly beginning at 42 d of age and ending at 196 d of age (28 wk old). The CG volume (CVOL) was calculated from these measurements using a literature-proposed formula. The CVOL in both lines increased similarly with increasing age from 6 to 12 wk of age. However, beginning at 14 wk of age and thereafter, LS males showed greater (P<0.05) CVOL than HS ones. No further increases in CVOL were observed in either line at 24 wk of age beyond that seen at 22 wk. This study demonstrated that although both lines show CG development under short days, eventually CG growth becomes comparatively stymied in the HS males. Furthermore, the maintenance of similarly lower CVOL in HS than LS males, CVOL that showed no further increase from 22 to 24 wk of age, suggests that holding these quail lifelong on short days results in, comparatively, yet another permanent negative reproductive consequence in quail selected for exaggerated plasma corticosterone stress responsiveness.

NAD+-linked 15-hydroxyprostaglandin dehydrogenase: structure and biological functions

NAD(+)-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes the oxidation of 15(S)-hydroxyl group of prostaglandins and lipoxins resulting in the formation of 15-keto metabolites which exhibit greatly reduced biological activities. Therefore, this enzyme has been considered the key enzyme responsible for the inactivation of prostaglandins and lipoxins. Both the cDNA and the genomic DNA of the 15-PGDH gene have been cloned. Structural characterization, transcriptional regulation and biological functions of this enzyme have been investigated. Molecular modeling corroborated with site-directed mutagenesis has identified key residues and domains involved in coenzyme and substrate binding. Catalytic mechanism has been proposed. Studies on the regulation of enzyme expression and activity by physiological and pharmacological agents have begun to uncover its significant roles in cancer, inflammation and reproduction. Apparently, 15-PGDH works with cyclooxygenase-2 to control the cellular levels of prostaglandins. Their reciprocal regulation within the same cells appears to determine the fate of the cells. Because of its ability to inactivate both prostaglandins and lipoxins of two opposite biological activities, the roles of 15-PGDH in cancer and inflammation are particularly intriguing and challenging. Future investigations in these areas are warranted.

Chronic gestational exposure to ethanol causes insulin and IGF resistance and impairs acetylcholine homeostasis in the brain

In fetal alcohol syndrome (FAS), cerebellar hypoplasia is associated with impaired insulin-stimulated survival signaling. This study characterizes ethanol dose-effects on cerebellar development, expression of genes required for insulin and insulin-like growth factor (IGF) signaling, and the upstream mechanisms and downstream consequences of impaired signaling in relation to acetylcholine (ACh) homeostasis. Pregnant Long Evans rats were fed isocaloric liquid diets containing 0%, 2%, 4.5%, 6.5%, or 9.25% ethanol from gestation day 6. Ethanol caused dose-dependent increases in severity of cerebellar hypoplasia, neuronal loss, proliferation of astrocytes and microglia, and DNA damage. Ethanol also reduced insulin, IGF-I, and IGF-II receptor binding, insulin and IGF-I receptor tyrosine kinase activities, ATP, membrane cholesterol, and choline acetyltransferase (ChAT) expression. In vitro studies linked membrane cholesterol depletion to impaired insulin receptor binding and insulin-stimulated ChAT. In conclusion, cerebellar hypoplasia in FAS is mediated by insulin/IGF resistance with attendant impairments in energy production and ACh homeostasis.

15-Hydroxyprostaglandin dehydrogenase (PGDH) is an aberrant tumor suppressor in human breast cancer

10550

Background: Prostaglandin E2 plays a growth stimulatory role in breast cancer; and the rate-limiting enzyme in its synthesis, cyclooxygenase-2 (COX-2), is over-expressed in breast cancers. However, little is known about the expression pattern and activities of the key prostaglandin catabolic enzyme PGDH, in breast cancer pathogenesis. Methods: 5-aza-2’-deoxycytidine and suberoyl anilide bishydroxamide (SAHA) were used to unmask epigenetically silenced genes. DNA and RNA were extracted from tumors and cell lines using standard methods, and bisulfite sequencing was used for methylation analysis. Western blotting and real time PCR were used for expression analysis, and PGDH expression vector and PGDH-directed siRNA were used for overexpression and downregulation of PGDH, respectively. Athymic mice were utilized for xenograft models. Results: Using a pharmacologically based, genome-wide screen for epigenetically silenced genes, we found low levels of PGDH in MDA-MB-231 cells (estrogen receptor- (ER) and HER2-negative), but high levels in MCF-7 cells (ER-positive, HER2-negative), and observed upregulation of this enzyme following demethylation treatment. Methylation analysis revealed methylation of the PGDH promoter in one breast cancer cell line and in 3 of 10 primary tumors. Analysis of PGDH expression demonstrated low levels in 40% of primary breast tumors and identified a correlation between PGDH and ER expression. Upregulation of PGDH levels in MDA-MB-231 cells decreased their clonal growth and reduced their ability to form tumors in athymic mice. In contrast, silencing of PGDH in MCF-7 cells increased proliferation and enhanced in-vivo tumorigenicity. Further analysis revealed upregulation of aromatase following silencing of PGDH and inhibition of the ER pathway by forced expression of the enzyme. PGDH levels were downregulated by estrogen but upregulated by the tumor suppressor gene C/EBPα. Conclusions: Our results identify for the first time, that PGDH, the COX-2 antagonist, is aberrantly silenced in breast cancer. Activation of this enzyme, particularly in ER- and HER2-negative tumors, now becomes an interesting target for clinical studies.

No significant financial relationships to disclose.