Context-specific stress causes compartmentalized SARM1 activation and local degeneration in cortical neurons

SARM1 is an inducible NADase that localizes to mitochondria throughout neurons and senses metabolic changes that occur after injury. Minimal proteomic changes are observed upon either SARM1 depletion or activation, suggesting that SARM1 does not exert broad effects on neuronal protein homeostasis. However, whether SARM1 activation occurs throughout the neuron in response to injury and cell stress remains largely unknown. Using a semi-automated imaging pipeline and a custom-built deep learning scoring algorithm, we studied degeneration in both mixed sex mouse primary cortical neurons and male human iPSC derived cortical neurons in response to a number of different stressors. We show that SARM1 activation is differentially restricted to specific neuronal compartments depending on the stressor. Cortical neurons undergo SARM1-dependent axon degeneration after mechanical transection and SARM1 activation is limited to the axonal compartment distal of the injury site. However, global SARM1 activation following vacor treatment causes both cell body and axon degeneration. Context-specific stressors, such as microtubule dysfunction and mitochondrial stress, induce axonal SARM1 activation leading to SARM1-dependent axon degeneration and SARM1-independent cell body death. Our data reveal that compartment-specific SARM1-mediated death signaling is dependent on the type of injury and cellular stressor.Significance Statement SARM1 is an important regulator of active axon degeneration after injury in the peripheral nervous system. Here we show that SARM1 can also be activated by a number of different cellular stressors in cortical neurons of the central nervous system. Loss or activation of SARM1 does not cause large scale changes in global protein homeostasis. However, context-dependent SARM1 activation is localized to specific neuronal compartments and results in localized degeneration of axons. Understanding which cell stress pathways are responsible for driving degeneration of distinct neuronal compartments under what cellular stress conditions and in which neuronal subtypes, will inform development of neurodegenerative disease therapeutics.

PROTACs Targeting BRM (SMARCA2) Afford Selective In Vivo Degradation over BRG1 (SMARCA4) and Are Active in BRG1 Mutant Xenograft Tumor Models

The identification of VHL-binding proteolysis targeting chimeras (PROTACs) that potently degrade the BRM protein (also known as SMARCA2) in SW1573 cell-based experiments is described. These molecules exhibit between 10- and 100-fold degradation selectivity for BRM over the closely related paralog protein BRG1 (SMARCA4). They also selectively impair the proliferation of the H1944 "BRG1-mutant" NSCLC cell line, which lacks functional BRG1 protein and is thus highly dependent on BRM for growth, relative to the wild-type Calu6 line. In vivo experiments performed with a subset of compounds identified PROTACs that potently and selectively degraded BRM in the Calu6 and/or the HCC2302 BRG1 mutant NSCLC xenograft models and also afforded antitumor efficacy in the latter system. Subsequent PK/PD analysis established a need to achieve strong BRM degradation (>95%) in order to trigger meaningful antitumor activity in vivo. Intratumor quantitation of mRNA associated with two genes whose transcription was controlled by BRM (PLAU and KRT80) also supported this conclusion.

Argonaute3-SF3B3 complex controls pre-mRNA splicing to restrain type 2 immunity

Argonaute (AGO) proteins execute microRNA (miRNA)-mediated gene silencing. However, it is unclear whether all 4 mammalian AGO proteins (AGO1, AGO2, AGO3, and AGO4) are required for miRNA activity. We generate Ago1, Ago3, and Ago4-deficient mice (Ago134Δ) and find AGO1/3/4 to be redundant for miRNA biogenesis, homeostasis, or function, a role that is carried out by AGO2. Instead, AGO1/3/4 regulate the expansion of type 2 immunity via precursor mRNA splicing in CD4+ T helper (Th) lymphocytes. Gain- and loss-of-function experiments demonstrate that nuclear AGO3 interacts directly with SF3B3, a component of the U2 spliceosome complex, to aid global mRNA splicing, and in particular the isoforms of the gene Nisch, resulting in a dysregulated Nisch isoform ratio. This work uncouples AGO1, AGO3, and AGO4 from miRNA-mediated RNA interference, identifies an AGO3:SF3B3 complex in the nucleus, and reveals a mechanism by which AGO proteins regulate inflammatory diseases.

Consensus recommendations for the screening, diagnosis, and management of Helicobacter pylori infection in Hong Kong

Helicobacter pylori infection causes chronic gastric inflammation that contributes to various gastroduodenal diseases, including peptic ulcer and gastric cancer. Despite broad regional variations, the prevalence of resistance to antibiotics used to manage H pylori infection is increasing worldwide; this trend could hinder the success of eradication therapy. To increase awareness of H pylori and improve the diagnosis and treatment of its infection in Hong Kong, our consensus panel proposed a set of guidance statements for disease management. We conducted a comprehensive review of literature published during 2011 and 2021, with a focus on articles from Hong Kong or other regions of China. We evaluated the evidence using the Oxford Centre for Evidence-Based Medicine's 2011 Levels of Evidence and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system and sought consensus through online voting and a subsequent face-to-face meeting, which enabled us to develop and refine the guidance statements. This report consists of 24 statements regarding the epidemiology and burden, screening and diagnosis, and treatment of H pylori. Key guidance statements include a recommendation to use the test-and-treat approach for high-risk individuals, as well as the confirmation that triple therapy with a proton pump inhibitor, amoxicillin, and clarithromycin remains a valid first-line option for adults and children in Hong Kong.

Polarized microtubule remodeling transforms the morphology of reactive microglia and drives cytokine release

Microglial reactivity is a pathological hallmark in many neurodegenerative diseases. During stimulation, microglia undergo complex morphological changes, including loss of their characteristic ramified morphology, which is routinely used to detect and quantify inflammation in the brain. However, the underlying molecular mechanisms and the relation between microglial morphology and their pathophysiological function are unknown. Here, proteomic profiling of lipopolysaccharide (LPS)-reactive microglia identifies microtubule remodeling pathways as an early factor that drives the morphological change and subsequently controls cytokine responses. We find that LPS-reactive microglia reorganize their microtubules to form a stable and centrosomally-anchored array to facilitate efficient cytokine trafficking and release. We identify cyclin-dependent kinase 1 (Cdk-1) as a critical upstream regulator of microtubule remodeling and morphological change in-vitro and in-situ. Cdk-1 inhibition also rescues tau and amyloid fibril-induced morphology changes. These results demonstrate a critical role for microtubule dynamics and reorganization in microglial reactivity and modulating cytokine-mediated inflammatory responses.

Selective PROTAC-mediated degradation of SMARCA2 is efficacious in SMARCA4 mutant cancers

The mammalian SWItch/Sucrose Non-Fermentable (SWI/SNF) helicase SMARCA4 is frequently mutated in cancer and inactivation results in a cellular dependence on its paralog, SMARCA2, thus making SMARCA2 an attractive synthetic lethal target. However, published data indicates that achieving a high degree of selective SMARCA2 inhibition is likely essential to afford an acceptable therapeutic index, and realizing this objective is challenging due to the homology with the SMARCA4 paralog. Herein we report the discovery of a potent and selective SMARCA2 proteolysis-targeting chimera molecule (PROTAC), A947. Selective SMARCA2 degradation is achieved in the absence of selective SMARCA2/4 PROTAC binding and translates to potent in vitro growth inhibition and in vivo efficacy in SMARCA4 mutant models, compared to wild type models. Global ubiquitin mapping and proteome profiling reveal no unexpected off-target degradation related to A947 treatment. Our study thus highlights the ability to transform a non-selective SMARCA2/4-binding ligand into a selective and efficacious in vivo SMARCA2-targeting PROTAC, and thereby provides a potential new therapeutic opportunity for patients whose tumors contain SMARCA4 mutations.

Shigella ubiquitin ligase IpaH7.8 targets gasdermin D for degradation to prevent pyroptosis and enable infection

The pore-forming protein gasdermin D (GSDMD) executes lytic cell death called pyroptosis to eliminate the replicative niche of intracellular pathogens. Evolution favors pathogens that circumvent this host defense mechanism. Here, we show that the Shigella ubiquitin ligase IpaH7.8 functions as an inhibitor of GSDMD. Shigella is an enteroinvasive bacterium that causes hemorrhagic gastroenteritis in primates, but not rodents. IpaH7.8 contributes to species specificity by ubiquitinating human, but not mouse, GSDMD and targeting it for proteasomal degradation. Accordingly, infection of human epithelial cells with IpaH7.8-deficient Shigella flexneri results in increased GSDMD-dependent cell death compared with wild type. Consistent with pyroptosis contributing to murine disease resistance, eliminating GSDMD from NLRC4-deficient mice, which are already sensitized to oral infection with Shigella flexneri, leads to further enhanced bacterial replication and increased disease severity. This work highlights a species-specific pathogen arms race focused on maintenance of host cell viability.

The current treatment landscape of irritable bowel syndrome in adults in Hong Kong: consensus statements

OBJECTIVE

The estimated prevalence of irritable bowel syndrome in Hong Kong is 6.6%. With the increasing availability of pharmacological and non-pharmacological treatments, the Hong Kong Advisory Council on Irritable Bowel Syndrome has developed a set of consensus statements intended to serve as local recommendations for clinicians about diagnosis and management of irritable bowel syndrome.

PARTICIPANTS

A multidisciplinary group of clinicians constituting the Hong Kong Advisory Council on Irritable Bowel Syndrome-seven gastroenterologists, one clinical psychologist, one psychiatrist, and one nutritionist-convened on 20 April 2017 in Hong Kong.

EVIDENCE

Published primary research articles, meta-analyses, and guidelines and consensus statements issued by different regional and international societies on the diagnosis and management of irritable bowel syndrome were reviewed.

CONSENSUS PROCESS

An outline of consensus statements was drafted prior to the meeting. All consensus statements were finalised by the participants during the meeting, with 100% consensus.

CONCLUSIONS

Twenty-four consensus statements were generated at the meeting. The statements were divided into four parts covering: (1) patient assessment; (2) patient's psychological distress; (3) dietary and alternative approaches to managing irritable bowel syndrome; and (4) evidence to support pharmacological management of irritable bowel syndrome. It is recommended that primary care physicians assume the role of principal care provider for patients with irritable bowel syndrome. The current statements are intended to guide primary care physicians in diagnosing and managing patients with irritable bowel syndrome in Hong Kong.

Willingness for deceased organ donation under different legislative systems in Hong Kong: population-based cross-sectional survey

INTRODUCTION

Under the current opt-in system, the deceased organ donation rate remains low in Hong Kong. An opt-out system and an opt-in system combined with organ allocation priority (ie, priority to donors as transplant recipients) have been proposed to encourage willingness among the general population towards deceased organ donation. This study aimed to compare willingness, and its determinants, across these three legislative systems.

METHODS

A random telephone survey of Hong Kong permanent residents aged ≥18 years was conducted between August and October 2016 using an anonymous questionnaire. Willingness towards deceased organ donation was compared between the legislative systems with McNemar's test. Determinants of willingness were tested by logistic regression.

RESULTS

The proportion of those willing to consider deceased organ donation under the current opt-in system would significantly increase after combining it with allocation priority (64.5% vs 73.4%; P=0.018). "Fairness or reciprocity" was the major reported reason underlying the increase. In contrast, willingness would decrease after introducing the opt-out system (60.1%), although not significantly (P=0.336). The reduction might be attributable to a "belief of being forced to donate". Under the allocation priority system, reduced willingness to donate was associated with advanced age, lower educational attainment, and lower monthly household income. Under the opt-out system, reduced willingness was associated with being married, having a lower household income, and distrust of local government.

CONCLUSIONS

An opt-in system with allocation priority could induce willingness to donate, whereas an opt-out system may reduce willingness. The findings have implications for policy-making and promotion of organ donation.

A KDM5 Inhibitor Increases Global H3K4 Trimethylation Occupancy and Enhances the Biological Efficacy of 5-Aza-2'-Deoxycytidine

The H3K4 demethylase KDM5B is amplified and overexpressed in luminal breast cancer, suggesting it might constitute a potential cancer therapy target. Here, we characterize, in breast cancer cells, the molecular effects of a recently developed small-molecule inhibitor of the KDM5 family of proteins (KDM5i), either alone or in combination with the DNA-demethylating agent 5-aza-2'-deoxycytidine (DAC). KDM5i treatment alone increased expression of a small number of genes, whereas combined treatment with DAC enhanced the effects of the latter for increasing expression of hundreds of DAC-responsive genes. ChIP-seq studies revealed that KDM5i resulted in the broadening of existing H3K4me3 peaks. Furthermore, cells treated with the drug combination exhibited increased promoter and gene body H3K4me3 occupancy at DAC-responsive genes compared with DAC alone. Importantly, treatment with either DAC or DAC+KDM5i induced a dramatic increase in H3K27ac at enhancers with an associated significant increase in target gene expression, suggesting a previously unappreciated effect of DAC on transcriptional regulation. KDM5i synergized with DAC to reduce the viability of luminal breast cancer cells in in vitro assays. Our study provides the first look into the molecular effects of a novel KDM5i compound and suggests that combinatorial inhibition along with DAC represents a new area to explore in translational epigenetics.Significance: This study offers a first look into the molecular effects of a novel KDM5 inhibitory compound, suggesting how its use in combination with DNA methylation inhibitors presents new opportunities to explore in translational cancer epigenetics. Cancer Res; 78(5); 1127-39. ©2017 AACR.

Silencing of retrotransposons by SETDB1 inhibits the interferon response in acute myeloid leukemia

Cancer cells can rewire genetic and epigenetic regulatory networks to promote cell proliferation and evade the immune system. Using a focused CRISPR/Cas9 genetic screen, Cuellar et al. identify a novel role for the SETDB1 histone methyltransferase in regulating the antiviral response in AML cells via the suppression of transposable elements.

A propensity for rewiring genetic and epigenetic regulatory networks, thus enabling sustained cell proliferation, suppression of apoptosis, and the ability to evade the immune system, is vital to cancer cell propagation. An increased understanding of how this is achieved is critical for identifying or improving therapeutic interventions. In this study, using acute myeloid leukemia (AML) human cell lines and a custom CRISPR/Cas9 screening platform, we identify the H3K9 methyltransferase SETDB1 as a novel, negative regulator of innate immunity. SETDB1 is overexpressed in many cancers, and loss of this gene in AML cells triggers desilencing of retrotransposable elements that leads to the production of double-stranded RNAs (dsRNAs). This is coincident with induction of a type I interferon response and apoptosis through the dsRNA-sensing pathway. Collectively, our findings establish a unique gene regulatory axis that cancer cells can exploit to circumvent the immune system.

The Staphylococcus aureus ABC-Type Manganese Transporter MntABC Is Critical for Reinitiation of Bacterial Replication Following Exposure to Phagocytic Oxidative Burst

Manganese plays a central role in cellular detoxification of reactive oxygen species (ROS). Therefore, manganese acquisition is considered to be important for bacterial pathogenesis by counteracting the oxidative burst of phagocytic cells during host infection. However, detailed analysis of the interplay between bacterial manganese acquisition and phagocytic cells and its impact on bacterial pathogenesis has remained elusive for Staphylococcus aureus, a major human pathogen. Here, we show that a mntC mutant, which lacks the functional manganese transporter MntABC, was more sensitive to killing by human neutrophils but not murine macrophages, unless the mntC mutant was pre-exposed to oxidative stress. Notably, the mntC mutant formed strikingly small colonies when recovered from both type of phagocytic cells. We show that this phenotype is a direct consequence of the inability of the mntC mutant to reinitiate growth after exposure to phagocytic oxidative burst. Transcript and quantitative proteomics analyses revealed that the manganese-dependent ribonucleotide reductase complex NrdEF, which is essential for DNA synthesis and repair, was highly induced in the mntC mutant under oxidative stress conditions including after phagocytosis. Since NrdEF proteins are essential for S. aureus viability we hypothesize that cells lacking MntABC might attempt to compensate for the impaired function of NrdEF by increasing their expression. Our data suggest that besides ROS detoxification, functional manganese acquisition is likely crucial for S. aureus pathogenesis by repairing oxidative damages, thereby ensuring efficient bacterial growth after phagocytic oxidative burst, which is an attribute critical for disseminating and establishing infection in the host.

Abstract A160: Recognition of UbcH5c and the nucleosome by the Bmi1/Ring1b ubiquitin ligase complex

Background and Objectives: The Polycomb repressive complex 1 (PRC1) mediates gene silencing, in part by monoubiquitination of histone H2A on lysine 119 (uH2A). Bmi1 and Ring1b are critical components of PRC1 that heterodimerize via their N-terminal RING domains to form an active E3 ubiquitin ligase. A longstanding question in this field is how a single lysine residue in the nucleosome is singled out for ubiquitin modification and why only one ubiquitin is added rather than a chain of ubiquitins. To better understand how Bmi1/Ring1b controls monoubiquitination of H2A, we structurally characterized the E2 and nucleosome interaction sites on Bmi1/Ring1b.

Methods: X-ray crystallography was used to determine the structure of a complex between Bmi1/Ring1b and UbcH5c, its cognate E2 enzyme. Fluorescence-polarization assays were used to measure the binding of Bmi1/Ring1b to a synthetic DNA duplex. Site-directed mutagenesis was used to assess the importance of residues at the potential Bmi1/Ring1b-DNA interface, and in vitro ubiquitin ligase assays were used to measure the catalytic activity of mutant complexes. Molecular modeling studies were performed using HADDOCK v2.0.

Results: We have determined the crystal structure of a complex between the Bmi1/Ring1b RING-RING heterodimer and the E2 enzyme UbcH5c and find that UbcH5c interacts with Ring1b only, in a manner fairly typical of E2-E3 interactions. However, we further show that the Bmi1/Ring1b RING domains bind directly to duplex DNA through a basic surface patch unique to the Bmi1/Ring1b RING-RING dimer. Mutation of residues on this interaction surface leads to a loss of H2A ubiquitination activity. Through site-directed mutagenesis we have been able to uncouple the E2 binding and the DNA binding activities of Bmi1/Ring1b, indicating that Bmi1/Ring1b uses distinct binding surfaces to recognize E2 and the nucleosomal substrate. Computational modeling of the interface between Bmi1/Ring1b-UbcH5c and the nucleosome suggests that Bmi1/Ring1b interacts with both nucleosomal DNA and an acidic patch on histone H4 to achieve specific mono-ubiquitination of H2A.

Conclusions: Our data show that the direct interaction of the RING domains with nucleosomal DNA is crucial for the ubiquitin ligase activity of Bmi1/Ring1b. To our knowledge, this is the first example of a RING-domain E3 ligase binding directly to its substrate via the RING domain. Our results point to a novel mechanism of substrate recognition, and control of product formation, by Bmi1/Ring1b.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A160.

Decreasing trend of esophageal adenocarcinoma in Hong Kong

BACKGROUND

The incidence of esophageal adenocarcinoma was increasing in the Western Europe and United States, but not in East Asian countries. Population based study on the trend of esophageal adenocarcinoma in Hong Kong was not available.

MATERIALS AND METHODS

Population-based data of Hong Kong Cancer Registry from 1984 to 2003 were used. Cases were grouped into four 5-year periods. Average age standardized rate (WSR) of each period was calculated by averaging the WSR of the 5 years in each period, basing on the world standard population, with adjustment made for cases with missing histology.

RESULTS

10,751 new cases of esophageal neoplasm were studied (8,637 males and 2,114 females). Esophageal adenocarcinoma declined among both males and females, with the total number decreased from 224 in 1984 to 1988 to 131 in 1998 to 2003. WSR decreased from 1.10 of 100,000 in 1984 to 1988 to 0.34 of 100,000 in 1998 to 2003. The decline was faster than that for esophageal squamous cell carcinoma so that the relative ratio of esophageal adenocarcinoma decreased from 11.7% in 1984 to 1988 to 6.4% in 1998 to 2003.

CONCLUSIONS

The incidence of esophageal adenocarcinoma and ratio of esophageal adenocarcinoma versus esophageal squamous cell carcinoma decreased in Hong Kong.

Clinical trial: levofloxacin-based quadruple therapy was inferior to traditional quadruple therapy in the treatment of resistant Helicobacter pylori infection

BACKGROUND

The efficacy of levofloxacin-based quadruple therapy in resistant Helicobacter pylori infection is not known.

AIM

To test the efficacy of levofloxacin-based quadruple therapy and traditional quadruple therapy in resistant H. pylori infection.

METHODS

One hundred and two patients with resistant H. pylori infection were randomized to 1 week of either EBAL (esomeprazole 40 mg b.d., bismuth subcitrate 240 mg b.d., amoxicillin 1 g b.d. and levofloxacin 500 mg b.d.) or EBMT (esomeprazole 40 mg b.d., bismuth subcitrate 240 mg b.d., metronidazole 400 mg t.d.s. and tetracycline 500 mg q.d.s.). (13)C-urea breath test was performed at week 12 to assess post-treatment H. pylori status.

RESULTS

In intention-to-treat analysis H. pylori eradication was achieved in 37 of 51 (73%) subjects in EBAL and 45 of 51 (88%) subjects in EBMT groups, respectively (P = 0.046). Per-protocol eradication rates of EBAL and EMBT groups were 78% and 94%, respectively (P = 0.030). The intention-to-treat eradication rate was statistically lower for EBAL than EMBT (56% vs. 90%, P = 0.013) among those who had failed more than one course of eradication therapy. Previous levofloxacin triple therapy did not affect the efficacy of either protocol significantly.

CONCLUSIONS

Levofloxacin-based quadruple therapy was inferior to traditional quadruple therapy for resistant H. pylori infection.

The view of gastroenterologists on non-cardiac chest pain in Asia

BACKGROUND

Non-cardiac chest pain is an important disorder in Asia. The practice and views of gastroenterologists on non-cardiac chest pain in this region are not known.

AIMS

To determine the current understanding, diagnostic practice and treatment strategies among gastroenterologists on the management of non-cardiac chest pain in Asia.

METHODS

A 24-item questionnaire was sent to gastroenterologists in Mainland China, Hong Kong, Malaysia, Indonesia, Philippines, Singapore, Taiwan and Thailand.

RESULTS

186 gastroenterologists participated with a response rate of 74%. 98% of gastroenterologists managed patients with non-cardiac chest pain over the last 6 months. 64% felt that the number of non-cardiac chest pain patients was increasing and 85% believed that the most common cause of non-cardiac chest pain was GERD. 94% of the gastroenterologists believed that they should manage non-cardiac chest pain patients, but only 41% were comfortable in diagnosing non-cardiac chest pain. The average number of investigations performed was four in non-cardiac chest pain patients, and oesophago-gastro-duodenoscopy was the most commonly used initial test. A proton pump inhibitor was considered the first-line treatment in non-cardiac chest pain and was reported as the most effective treatment by the gastroenterologists.

CONCLUSION

Most gastroenterologists were practicing evidence-based medicine, but frequent use of investigations and a lack of awareness of the role of visceral hypersensitivity in non-cardiac chest pain patients were noted.

Positive association between gastro-oesophageal reflux disease and irritable bowel syndrome in a Chinese population

BACKGROUND

Gastro-oesophageal reflux disease and irritable bowel syndrome are common diseases which may be related.

AIM

To examine the association between gastro-oesophageal reflux disease and irritable bowel syndrome in Chinese population in Hong Kong.

METHODS

Randomly selected ethnic Chinese were invited to participate in a telephone survey in 1996. Gastro-oesophageal reflux disease was defined as subjects having heartburn and/or acid regurgitation once weekly or more. Irritable bowel syndrome was diagnosed according to the Rome I criteria. The association between gastro-oesophageal reflux disease and irritable bowel syndrome was calculated using a statistical model which allows the odds ratio to be measured.

RESULTS

One thousand six hundred and forty-nine subjects completed the interview (response rate 62%). The population prevalence of gastro-oesophageal reflux disease and irritable bowel syndrome were 5% and 4%, respectively. Thirteen per cent of subjects with gastro-oesophageal reflux disease and 11% with irritable bowel syndrome suffered from both gastro-oesophageal reflux disease and irritable bowel syndrome. The OR of having gastro-oesophageal reflux disease and irritable bowel syndrome together was estimated to be 3 (95% CI: 1.05, 6.27) indicating a positive association between the two diseases. This association occurred predominantly in male subjects [OR = 9.3, (95% CI: 2.3, 26.2)] but not as strong in females [OR = 1.5, (95% CI: 0.3, 4.3)]. Younger subjects were statistically more prone to the two diseases.

CONCLUSIONS

There is a positive association between gastro-oesophageal reflux disease and irritable bowel syndrome, and their association occurs predominantly in male subjects.

Expression of divalent metal transporter 1 (DMT1) isoforms in first trimester human placenta and embryonic tissues

BACKGROUND

Divalent metal transporter 1 (DMT1) is a transmembrane glycoprotein which mediates the proton-coupled transport of a variety of divalent metal ions. Two isoforms, which differ by the presence (DMT1-IRE) or absence (DMT1-nonIRE) of an iron-responsive element (IRE) in their 3' untranslated region, are implicated in apical iron transport and endosomal iron transport respectively. Although the expression pattern of DMT1 isoforms is tissue specific in adult, data regarding its expression in embryonic tissues are lacking.

METHODS

Semiquantitative RT-PCR and immunohistochemistry were used to study the mRNA and protein expression of both DMT1 isoforms in embryonic tissues between 8 and 14 weeks gestational age.

RESULTS

DMT1-IRE and DMT1-nonIRE expressions were ubiquitous in embryonic tissues examined. In the lung, statistically significant correlations were found between the levels of DMT1 isoform expression and gestational age. In the placenta, DMT1-IRE was the predominantly expressed isoform. Both isoform proteins were localized in embryonic epithelial cellular membrane.

CONCLUSION

Both DMT1 isoforms are ubiquitously expressed in embryonic tissues in the first trimester. Predominant DMT1-IRE isoform expression in placenta suggests an iron-regulatory mechanism reminiscent of that in the adult duodenum. Epithelial distributions of both DMT1 isoforms are associated with the absorptive or excretory functions of the expressed tissues.

Fluoroquinolone resistance among Streptococcus pneumoniae in Hong Kong linked to the Spanish 23F clone

Serotypes 6A/B, 19F, and 23F accounted for 73% of 140 mucosal isolates of Streptococcus pneumoniae from Hong Kong. In pulsed-field gel electrophoresis analysis, a group of related patterns was shared by 14 of 15 ciprofloxacin-resistant and 12 of 16 ciprofloxacin-susceptible isolates. These strains exhibited capsular switching and were highly similar to the Spanish 23F clone.

A three-dimensional, six-segment chain analysis of forceful overarm throwing

A three-dimensional, six-segment model was applied to the pitching motion of three professional pitchers to analyze the kinematics and kinetics of the hips, upper trunk, humerus and forearm plus hand of both the upper limbs. Subjects were filmed at 250 frames per second. An inverse dynamics approach and angular momentum principle with respect to the proximal endpoint of a rigid segment were employed in the analysis. Results showed considerable similarities between subjects in the kinetic control of trunk rotation about the spine's longitudinal axis, but variability in the control of trunk lean both to the side and forward. The kinetics of the throwing shoulder and elbow joint were comparable between subjects, but the contribution of the non-throwing upper limb was minimal and variable. The upper trunk rotators played a key role in accelerating the ball to an early, low velocity near stride foot contact. After a brief pause they resumed acting strongly in a positive direction, though not enough to prevent trunk angular velocity slowing, as the musculature of the arm applied a load at the throwing shoulder. The interaction moment from the proximal segments assisted the forearm extensor in slowing flexion and producing rapid elbow extension near ball release. The temporal onset of muscular torques was not in a strictly successive proximal-to-distal sequence.

A crossover study of triptorelin and leuprorelin acetate

OBJECTIVE

To compare the potency, side effects, and duration of action of triptorelin and leuprorelin acetate after i.m. injections.

DESIGN

Prospective, double-blind crossover clinical study.

SETTING

A teaching hospital.

PATIENT(S)

Fifty-four patients with pelvic endometriosis.

INTERVENTION(S)

Twenty-seven patients had three doses of i.m. triptorelin (3.75 mg) followed by three doses of i.m. leuprorelin acetate at 4-week intervals. Twenty-one patients had three doses of i.m. leuprorelin acetate (3.75 mg) followed by three doses of i.m. triptorelin, also at 4-week intervals.

MAIN OUTCOME MEASURE(S)

Menopausal symptoms, time taken for menstruation to return, serum E(2), FSH, LH levels, lipid profiles, and liver function tests.

RESULT(S)

The potencies of triptorelin and leuprorelin acetate in lowering the serum E(2), FSH, and LH levels were comparable. The severity of menopausal symptoms, changes in the lipid profile and liver function parameters were similar after triptorelin and leuprorelin acetate. The resurgence of ovarian activities and the spontaneous return of menstruation occurred significantly earlier after leuprorelin acetate than triptorelin.

CONCLUSION(S)

Both drugs are equally potent in down-regulating the pituitary-ovarian function, and their side effects are similar. Triptorelin has a longer duration of drug action and can be administered over a longer interval period.

Electromyographic activity of the long digital extensor muscle in the exercising Thoroughbred horse

Surface electrodes were used to record electromyographic (EMG) activity of the long digital extensor muscle on the right hindlimb of 8 Thoroughbred horses for 8 s at the walk and 8 s at the trot before (unfatigued) and after (fatigued) an exercise test. The exercise test was performed on a motorised treadmill set on a 10% grade. Each test started at a speed of 6 m/s which was increased by 1 m/s each minute until the horse fatigued as indicated by its inability to keep pace with the treadmill with minimal encouragement. Observations were made on the horses prior to conditioning (untrained state) and after 8 weeks of regular exercise (trained state). The mean root-mean-square (rms) values of EMG bursts collected in each experimental trial were determined for each horse and group means were derived from the mean of independent subjects. Statistical comparisons for differences in rmsEMG were related to gait, fatigue and training. Mean rmsEMG at the trot was consistently higher than at the walk (P<0.05). At the walk, mean fatigued rmsEMG tended to be higher than the mean unfatigued rmsEMG in the untrained state and was significantly higher in the trained state (P<0.05). At the trot, mean fatigued rmsEMG was higher (P<0.05) than mean unfatigued rmsEMG in both the untrained and trained states. Training did not have an effect on mean rmsEMG of unfatigued muscles at the walk or the trot (P>0.05). However, fatigued muscles experienced higher EMG activity in the trained state at the walk (P<0.05). A similar tendency was observed at the trot. Results of this study suggest that surface EMG measurement may be useful for evaluating fatigue in exercising horses.

Detection of p53 antigen expression in cytologic preparations of ovarian carcinomas

We explored the value of p53 immunostaining in detection of malignant cells in cytologic analyses in ovarian cancer patients. Ninety-six percent of 23 tumor touch preparations had nuclear staining with PAb240: 44% had nuclear only, 26% had both nuclear and cytoplasmic staining, and 26% had cytoplasmic staining alone. Eight of 20 cytospins of peritoneal washings from ovarian cancer patients were PAb240 positive, 6 had cytoplasmic, and two had nuclear staining. Cytospins of fluid from 3/15 patients with no malignancy revealed cytoplasmic staining of mesothelial cells. The lack of concordance between staining of primary tumors and cytospins of peritoneal washings and the apparent reactivity in some benign samples may limit the utility of immunohistochemical detection of malignant cells in the peritoneal fluid of ovarian cancer patients.

Intracytoplasmic barium salts in pleural fluid

Cytological examination of the pleural effusion fluid obtained from a 66-yr-old Chinese lady showed numerous intra- and extracytoplasmic colourless refractile non-birefringent crystals. X-ray analysis of the crystals identified barium salts. On further inquiry, it was learnt that the fluid obtained had been placed in a specimen bottle provided by the x-ray department. This container was presumably contaminated with barium salts. The case highlights an unusual aspect of specimen contamination and the usefulness of x-ray analysis in the identification of crystals/substances.

Do heart valve bioprostheses degenerate for metabolic or mechanical reasons?

Although heart valve bioprostheses provide a normal quality of life, their durability is still of great concern. Their durability failure is defined as "degeneration," which is considered to be a consequence of metabolic factors. In this study, we demonstrate that mechanical and design factors can also be responsible for bioprosthesis failure. Large numbers of porcine and pericardial bioprostheses were tested in a fatigue-testing system in which the test conditions were proved to be reproducible and accurate by a laser Doppler anemometer. The results have allowed us to define causes of failure, previously insufficiently stressed, in each type of valve tested. There is a clear difference in factors influencing tissue disruption between porcine and pericardial valves. We have compared these in vitro results with in vivo clinical findings. The main inferences are as follows: (1) Bioprostheses rupture and fail in the same fashion in both in vitro and in vivo studies. (2) Mechanical and design factors are involved in tissue failure. (3) The in vitro/in vivo durability ratio is not 1:1. This ratio depends on the test conditions. (4) Pericardial valves fail because of damage during closure, whereas porcine valves are damaged during both opening and closing (mostly opening) because of design features. (5) Once one cusp fails and prolapses, the other cusps will fail in an accelerated fashion. (6) In vitro durability of 100 X 10(6) cycles can be considered excellent and is an achievable goal. (7) Variability is the key impediment to predicting the durability of bioprostheses. Valves can fail within 2 to 3 million cycles or can last more than 100 million cycles. Similarly, bioprostheses may require explantation within a few months or can last 10 to 13 years in patients. (8) Fatigue testing is an excellent and valuable tool to elucidate the mechanical factors responsible for this variability.

Effect of selection on heritability and genetic correlation of two quantitative traits in mice

The effects of different intensities of single trait directional selection on the heritability and genetic correlation of two quantitative traits in random mating populations of mice were observed during 14 generations. The initial population was divided at random into five groups (A, B, C, D and E). Group A and Group B were under 30% and 60% mass selection for large 6-week body weight, respectively. Group C and Group D were under 30% and 60% mass selection for long 6-week tail length, respectively. Group E acted as control group with no selection applied. In all groups, the parent population consisted of 15 males and 30 females each generation, mated at random.Direct selection had no apparent effect on the heritability of either the trait under selection or the correlated trait over the 14 generations. Heritability of 6-wk tail length was higher than the heritability of 6-wk body weight. Estimates of heritability of 6-wk tail length ranged from 0.15 ± 0.22 to 0.68 ± 0.24, while estimates of heritability of 6-wk body weight ranged from 0.05 ± 0.17 to 0.33 ± 0.09. There was no significant difference among the estimates of genetic correlation between the two traits in the five selection groups. Estimates of realized genetic correlation between 6-wk body weight and 6-wk tail length seemed to indicate that more intense selection led to some decrease in genetic correlation between the two traits.