Larval development and post-settlement metamorphosis of the barnacle Balanus albicostatus Pilsbry and the serpulid polychaete Pomatoleios kraussii Baird: Impact of a commonly used antifouling biocide,Irgarol 1051

Abstract

The impact of a commonly-used antifouling algicide, Irgarol 1051, on the larval development and post-settlement metamorphosis of the barnacle, Balanus albicostatus Pilsbry (Crustacea: Cirripedia), and the larval metamorphosis of a serpulid polycheate, Pomatoleios kraussii Baird, was evaluated. In the case of B. albicostatus, larval mortality increased with an increase in the concentration of Irgarol 1051, and there was a shift in the larval stage targeted from advanced instars to early instars. Nauplii that survived to the cyprid instar stage when reared in the presence of Irgarol 1051 showed prolonged instar and total naupliar duration when compared to the controls. The post-settlement metamorphosis of cyprids significantly varied with Irgarol concentration and also with biofilm age. One and 2-d-old untreated biofilms showed higher metamorphosis when compared to 5-d-old biofilms. However, when the biofilms that promoted cyprid metamorphosis were treated with Irgarol 1051 at low concentrations, metamorphosis rates decreased. Cyprids were prevented from metamorphosing completely by biofilms treated at the highest concentration of Irgarol 1051. Inhibition of metamorphosis was also observed in the case of competent polychaete larvae when exposed to Irgarol 1051 compared to those exposed to metamorphosis inducers such as 3-iso-butyl-1-methylxanthine (IBMX) and natural biofilms. Identification of the pathway(s) that caused the promotory biofilms to become toxic when exposed to Irgarol 1051 is discussed.     

Degradation of barnacle nauplii: implications to chitin regulation in the marine environment

The exoskeleton of most invertebrate larval forms is made of chitin, which is a linear polysaccharide of β (1→4)-linked N-acetylglucosamine (GlcNAc) residues. These larval forms offer extensive body surface for bacterial attachment and colonization. In nature, degradation of chitin involves a cascade of processes brought about by chitinases produced by specific bacteria in the marine environment. Microbial decomposition of larval carcasses serves as an alternate mechanism for nutrient regeneration, elemental cycling and microbial production. The present study was undertaken to assess the influence of chitinase enzyme on the degradation of the nauplii of barnacle, Balanus amphitrite. The survival and abundance of bacteria during the degradation process under different experimental conditions was monitored. To the best of our knowledge, no such study is conducted to understand the degradation of larval exoskeleton using chitinase and its influence on bacteria. An increase in the chitinase activity with increase in temperature was observed. Scanning electron micrographs of chitinase treated nauplii showed scars on the surface of the barnacle nauplii initially and further disruption of the exoskeleton was observed with the increase in the treatment time. Bacterial abundance of the chitinase treated nauplii increased with the increase in enzyme concentration. Pathogenic bacteria such as Vibrio cholerae, V. alginolyticus, V. parahaemolyticus which were initially associated with the exoskeleton were absent after chitinase treatment, however, Bacillus spp. dominated subsequent to chitinase treatment and this might have important implications to marine ecosystem functioning.     

Enhancing the evaluation of PI3K inhibitors through 3D melanoma models

Targeted therapies for mutant BRAF metastatic melanoma are effective but not curative due to acquisition of resistance. PI3K signaling is a common mediator of therapy resistance in melanoma; thus, the need for effective PI3K inhibitors is critical. However, testing PI3K inhibitors in adherent cultures is not always reflective of their potential in vivo. To emphasize this, we compared PI3K inhibitors of different specificity in two‐ and three‐dimensional (2D, 3D) melanoma models and show that drug response predictions gain from evaluation using 3D models. Our results in 3D demonstrate the anti‐invasive potential of PI3K inhibitors and that drugs such as PX‐866 have beneficial activity in physiological models alone and when combined with BRAF inhibition. These assays finally help highlight pathway effectors that could be involved in drug response in different environments (e.g. p4E‐BP1). Our findings show the advantages of 3D melanoma models to enhance our understanding of PI3K inhibitors.     

Sequential and compartmentalized action of Rabs,SNAREs, and MAL in the apical delivery of fusiform vesicles in urothelial umbrella cells

Uroplakins (UPs) are major differentiation products of urothelial umbrella cells and play important roles in forming the permeability barrier and in the expansion/stabilization of the apical membrane. Further, UPIa serves as a uropathogenic Escherichia coli receptor. Although it is understood that UPs are delivered to the apical membrane via fusiform vesicles (FVs), the mechanisms that regulate this exocytic pathway remain poorly understood. Immunomicroscopy of normal and mutant mouse urothelia show that the UP-delivering FVs contained Rab8/11 and Rab27b/Slac2-a, which mediate apical transport along actin filaments. Subsequently a Rab27b/Slp2-a complex mediated FV–membrane anchorage before SNARE-mediated and MAL-facilitated apical fusion. We also show that keratin 20 (K20), which forms a chicken-wire network ∼200 nm below the apical membrane and has hole sizes allowing FV passage, defines a subapical compartment containing FVs primed and strategically located for fusion. Finally, we show that Rab8/11 and Rab27b function in the same pathway, Rab27b knockout leads to uroplakin and Slp2-a destabilization, and Rab27b works upstream from MAL. These data support a unifying model in which UP cargoes are targeted for apical insertion via sequential interactions with Rabs and their effectors, SNAREs and MAL, and in which K20 plays a key role in regulating vesicular trafficking.     

Lymphoplasmacytic sclerosing pancreato-cholangitis: a case report and review of the literature

Autoimmune pancreatitis is a rare but important cause of pancreatitis that is becoming increasingly recognized in the West. Lymphoplasmacytic sclerosing pancreatitis (LPSP) is a benign form of chronic pancreatitis characterized clinically by infrequent attacks of abdominal pain, jaundice, and weight loss, and pathologically by focal or diffuse chronic or lymphoplasmacytic inflammatory infiltrates centered around pancreatic ducts and ductules, accompanied by obliterative phlebitis, acinar atrophy, and interstitial fibrosis. It has been described alone or as a part of the spectrum of autoimmune gallbladder and biliary tract disease, with clinical, radiological, and pathological overlap reported with primary sclerosing cholangitis. It has been described as "primary sclerosing pancreatitis," "sclerosing cholangitis," "non-alcoholic duct destructive chronic pancreatitis," and "autoimmune pancreatitis." We report a case of LPSP that mimicked pancreatic adenocarcinoma and was subsequently treated with a pylorus-preserving Whipple procedure. This may point towards a primary biliary autoimmune process involving the pancreatic duct, causing a benign form of chronic pancreatitis that may be difficult to characterize pre-operatively to avoid surgery. This case typifies the growing awareness of this relatively recently characterized clinical entity, its similar presentation to pancreatic carcinoma, and the importance for LPSP to be included in the differential diagnosis of pancreaticobiliary disease. Finally, we review the literature.     

Changes in cellular levels of inositol polyphosphates during apoptosis

Accumulations of higher inositol polyphosphates, diphosphoinositol polyphosphates or pyrophosphates, have been implicated to mediate cellular apoptosis. Whether cellular levels of lower inositol phosphates (lower than inositol hexakisphosphates) change during apoptosis is not known, although these inositol phosphates are known to play crucial roles in a number of cellular signaling processes including calcium mobilization. Therefore, in this study, we have examined changes in cellular levels of inositol phosphates following metabolic labeling of these compounds by [³H]myo-inositol and induction of apoptosis. The levels of inositol mono- and bis-phosphates were increased, whereas the levels of inositol tris- and tetrakis-phosphates decreased significantly with an increasing rate of apoptosis induced by etoposide in a dose-dependent manner. NaF treatment, which increased the rate of apoptosis in a time- and dose-dependent manner, also increased the levels of inositol mono- and bis-phosphates and drastically reduced the levels of inositol tris- and tetrakis-phosphates. Prior treatment with antimycin A, a strategy used to reverse the NaF-induced accumulations of higher InsPs, partially reduced the effects of NaF on apoptosis as well as the levels of lower InsPs. Taken together, our results suggest that cellular levels of lower InsPs are altered during apoptosis.     

Larval development and post-settlement metamorphosis of the barnacle Balanus albicostatus Pilsbry and the serpulid polychaete Pomatoleios kraussii Baird: Impact of a commonly used antifouling biocide, Irgarol 1051

AbstractThe impact of a commonly-used antifouling algicide, Irgarol 1051, on the larval development and post-settlement metamorphosis of the barnacle, Balanus albicostatus Pilsbry (Crustacea: Cirripedia), and the larval metamorphosis of a serpulid polycheate, Pomatoleios kraussii Baird, was evaluated. In the case of B. albicostatus, larval mortality increased with an increase in the concentration of Irgarol 1051, and there was a shift in the larval stage targeted from advanced instars to early instars. Nauplii that survived to the cyprid instar stage when reared in the presence of Irgarol 1051 showed prolonged instar and total naupliar duration when compared to the controls. The post-settlement metamorphosis of cyprids significantly varied with Irgarol concentration and also with biofilm age. One and 2-d-old untreated biofilms showed higher metamorphosis when compared to 5-d-old biofilms. However, when the biofilms that promoted cyprid metamorphosis were treated with Irgarol 1051 at low concentrations, metamorphosis rates decreased. Cyprids were prevented from metamorphosing completely by biofilms treated at the highest concentration of Irgarol 1051. Inhibition of metamorphosis was also observed in the case of competent polychaete larvae when exposed to Irgarol 1051 compared to those exposed to metamorphosis inducers such as 3-iso-butyl-1-methylxanthine (IBMX) and natural biofilms. Identification of the pathway(s) that caused the promotory biofilms to become toxic when exposed to Irgarol 1051 is discussed.     

Activation of Glucose-6-phosphate Dehydrogenase Promotes Acute Hypoxic Pulmonary Artery Contraction

Hypoxic pulmonary vasoconstriction (HPV) is a physiological response to a decrease in airway O₂ tension, but the underlying mechanism is incompletely understood. We studied the contribution of glucose-6-phosphate dehydrogenase (Glc-6-PD), an important regulator of NADPH redox and production of reactive oxygen species, to the development of HPV. We found that hypoxia (95% N₂, 5% CO₂) increased contraction of bovine pulmonary artery (PA) precontracted with KCl or serotonin. Depletion of extracellular glucose reduced NADPH, NADH, and HPV, substantiating the idea that glucose metabolism and Glc-6-PD play roles in the response of PA to hypoxia. Our data also show that inhibition of glycolysis and mitochondrial respiration (indicated by an increase in NAD⁺ and decrease in the ATP-to-ADP ratio) by hypoxia, or by inhibitors of pyruvate dehydrogenase or electron transport chain complexes I or III, increased generation of reactive oxygen species, which in turn activated Glc-6-PD. Inhibition of Glc-6-PD decreased Ca²⁺ sensitivity to the myofilaments and diminished Ca²⁺-independent and -dependent myosin light chain phosphorylation otherwise increased by hypoxia. Silencing Glc-6-PD expression in PA using a targeted small interfering RNA abolished HPV and decreased extracellular Ca²⁺-dependent PA contraction increased by hypoxia. Similarly, Glc-6-PD expression and activity were significantly reduced in lungs from Glc-6-PD^mut(−/−) mice, and there was a corresponding reduction in HPV. Finally, regression analysis relating Glc-6-PD activity and the NADPH-to-NADP⁺ ratio to the HPV response clearly indicated a positive linear relationship between Glc-6-PD activity and HPV. Based on these findings, we propose that Glc-6-PD and NADPH redox are crucially involved in the mechanism of HPV and, in turn, may play a key role in increasing pulmonary arterial pressure, which is involved in the development of pulmonary hypertension.