The downregulation of Tapasin in dendritic cell regulates CD8+ T cell autophagy to hamper hepatitis B viral clearance in the induced pluripotent stem cell-derived hepatocyte organoid

Tapasin, a crucial molecular chaperone involved viral antigen processing and presentation, plays an important role in antivirus immunity. However, its impact on T cell differentiation in the context of virus clearance remains unclear. In this study, we employed induced pluripotent stem cells to differentiate into hepatocyte-like cell, which were subsequently inserted to the inverted colloidal crystal scaffolds, thus establishing a hepatocyte organoid (HO). By inoculating hepatitis B virus (HBV) particles in the system, we successfully engineered a robust in vitro HBV infection model for at least 3 weeks. Furthermore, we aimed to explore the effects of lentivirus-mediated short hairpin RNA (shRNA) targeting human Tapasin on the differentiation and antiviral function of CD8+ T cells. Specifically, we transfected dendritic cells (DCs) with Tapasin-shRNA and cocultured with T cells. The results demonstrated that Tapasin-shRNA transfected DCs effectively suppressed T cell proliferation and impeded HBV-specific cytotoxic T lymphocyte responses. Our investigation also revealed the role of mTOR pathway activation in reducing autophagy activity within CD8+ T cells. Expressions of autophagy-related proteins, beclin-1, LC3II/LC3I were decreased and PI3K/AKT/mTOR activity was increased in Tapasin-shRNA group. Collectively, our findings elucidate that shRNA targeting the Tapasin gene within DCs inhibits T cell differentiation by reducing autophagy activity to hamper viral clearance in the HBV-infected HO.

RGD density along with substrate stiffness regulate hPSC hepatocyte functionality through YAP signalling

Human pluripotent stem cell-derived hepatocytes (hPSC-Heps) may be suitable for treating liver diseases, but differentiation protocols often fail to yield adult-like cells. We hypothesised that replicating healthy liver niche biochemical and biophysical cues would produce hepatocytes with desired metabolic functionality. Using 2D synthetic hydrogels which independently control mechanical properties and biochemical cues, we found that culturing hPSC-Heps on surfaces matching the stiffness of fibrotic liver tissue upregulated expression of genes for RGD-binding integrins, and increased expression of YAP/TAZ and their transcriptional targets. Alternatively, culture on soft, healthy liver-like substrates drove increases in cytochrome p450 activity and ureagenesis. Knockdown of ITGB1 or reducing RGD-motif-containing peptide concentration in stiff hydrogels reduced YAP activity and improved metabolic functionality; however, on soft substrates, reducing RGD concentration had the opposite effect. Furthermore, targeting YAP activity with verteporfin or forskolin increased cytochrome p450 activity, with forskolin dramatically enhancing urea synthesis. hPSC-Heps could also be successfully encapsulated within RGD peptide-containing hydrogels without negatively impacting hepatic functionality, and compared to 2D cultures, 3D cultured hPSC-Heps secreted significantly less fetal liver-associated alpha-fetoprotein, suggesting furthered differentiation. Our platform overcomes technical hurdles in replicating the liver niche, and allowed us to identify a role for YAP/TAZ-mediated mechanosensing in hPSC-Hep differentiation.

Liver RBFOX2 regulates cholesterol homeostasis via Scarb1 alternative splicing in mice

RNA alternative splicing (AS) expands the regulatory potential of eukaryotic genomes. The mechanisms regulating liver-specific AS profiles and their contribution to liver function are poorly understood. Here, we identify a key role for the splicing factor RNA-binding Fox protein 2 (RBFOX2) in maintaining cholesterol homeostasis in a lipogenic environment in the liver. Using enhanced individual-nucleotide-resolution ultra-violet cross-linking and immunoprecipitation, we identify physiologically relevant targets of RBFOX2 in mouse liver, including the scavenger receptor class B type I (Scarb1). RBFOX2 function is decreased in the liver in diet-induced obesity, causing a Scarb1 isoform switch and alteration of hepatocyte lipid homeostasis. Our findings demonstrate that specific AS programmes actively maintain liver physiology, and underlie the lipotoxic effects of obesogenic diets when dysregulated. Splice-switching oligonucleotides targeting this network alleviate obesity-induced inflammation in the liver and promote an anti-atherogenic lipoprotein profile in the blood, underscoring the potential of isoform-specific RNA therapeutics for treating metabolism-associated diseases.

Human iPSC-derived hepatocyte system models cholestasis with tight junction protein 2 deficiency

Background & Aims

The truncating mutations in tight junction protein 2 (TJP2) cause progressive cholestasis, liver failure, and hepatocyte carcinogenesis. Due to the lack of effective model systems, there are no targeted medications for the liver pathology with TJP2 deficiency. We leveraged the technologies of patient-specific induced pluripotent stem cells (iPSC) and CRISPR genome-editing, and we aim to establish a disease model which recapitulates phenotypes of patients with TJP2 deficiency.

Methods

We differentiated iPSC to hepatocyte-like cells (iHep) on the Transwell membrane in a polarized monolayer. Immunofluorescent staining of polarity markers was detected by a confocal microscope. The epithelial barrier function and bile acid transport of bile canaliculi were quantified between the two chambers of Transwell. The morphology of bile canaliculi was measured in iHep cultured in the Matrigel sandwich system using a fluorescent probe and live-confocal imaging.

Results

The iHep differentiated from iPSC with TJP2 mutations exhibited intracellular inclusions of disrupted apical membrane structures, distorted canalicular networks, altered distribution of apical and basolateral markers/transporters. The directional bile acid transport of bile canaliculi was compromised in the mutant hepatocytes, resembling the disease phenotypes observed in the liver of patients.

Conclusions

Our iPSC-derived in vitro hepatocyte system revealed canalicular membrane disruption in TJP2 deficient hepatocytes and demonstrated the ability to model cholestatic disease with TJP2 deficiency to serve as a platform for further pathophysiologic study and drug discovery.

Lay summary

We investigated a genetic liver disease, progressive familial intrahepatic cholestasis (PFIC), which causes severe liver disease in newborns and infants due to a lack of gene called TJP2. By using cutting-edge stem cell technology and genome editing methods, we established a novel disease modeling system in cell culture experiments. Our experiments demonstrated that the lack of TJP2 induced abnormal cell polarity and disrupted bile acid transport. These findings will lead to the subsequent investigation to further understand disease mechanisms and develop an effective treatment.

Sulfated Alginate Reduces Pericapsular Fibrotic Overgrowth on Encapsulated cGMP-Compliant hPSC-Hepatocytes in Mice

Intra-peritoneal placement of alginate encapsulated human induced pluripotent stem cell-derived hepatocytes (hPSC-Heps) represents a potential new bridging therapy for acute liver failure. One of the rate-limiting steps that needs to be overcome to make such a procedure more efficacious and safer is to reduce the accumulation of fibrotic tissue around the encapsulated cells to allow the free passage of relevant molecules in and out for metabolism. Novel chemical compositions of alginate afford the possibility of achieving this aim. We accordingly used sulfated alginate and demonstrated that this material reduced fibrotic overgrowth whilst not impeding the process of encapsulation nor cell function. Cumulatively, this suggests sulfated alginate could be a more suitable material to encapsulate hPSC-hepatocyte prior to human use.

Advances in 3D cell culture for liver preclinical studies

The 3D cell culture model is an indispensable tool in the study of liver biology in the field of health and disease and the development of clinically relevant products for liver therapies. The 3D culture model captures critical factors of the microenvironmental niche required by hepatocytes for exhibiting optimal phenotypes, thus enabling the pursuit of a range of preclinical studies that are not entirely feasible in conventional 2D cell models. In this review, we highlight the major attributes associated with and the components needed for the development of a functional 3D liver culture model for a range of applications.

Wnt-modified materials mediate asymmetric stem cell division to direct human osteogenic tissue formation for bone repair

The maintenance of human skeletal stem cells (hSSCs) and their progeny in bone defects is a major challenge. Here, we report on a transplantable bandage containing a three-dimensional Wnt-induced osteogenic tissue model (WIOTM). This bandage facilitates the long-term viability of hSSCs (8 weeks) and their progeny, and enables bone repair in an in vivo mouse model of critical-sized calvarial defects. The newly forming bone is structurally comparable to mature cortical bone and consists of human and murine cells. Furthermore, we show that the mechanism of WIOTM formation is governed by Wnt-mediated asymmetric cell division of hSSCs. Covalently immobilizing Wnts onto synthetic materials can polarize single dividing hSSCs, orient the spindle and simultaneously generate a Wnt-proximal hSSC and a differentiation-prone Wnt-distal cell. Our results provide insight into the regulation of human osteogenesis and represent a promising approach to deliver human osteogenic constructs that can survive in vivo and contribute to bone repair.

Biomimetic niches reveal the minimal cues to trigger apical lumen formation in single hepatocytes

The symmetry breaking of protein distribution and cytoskeleton organization is an essential aspect for the development of apicobasal polarity. In embryonic cells this process is largely cell autonomous, while differentiated epithelial cells collectively polarize during epithelium formation. Here, we demonstrate that the de novo polarization of mature hepatocytes does not require the synchronized development of apical poles on neighbouring cells. De novo polarization at the single-cell level by mere contact with the extracellular matrix and immobilized cadherin defining a polarizing axis. The creation of these single-cell liver hemi-canaliculi allows unprecedented imaging resolution and control and over the lumenogenesis process. We show that the density and localization of cadherins along the initial cell-cell contact act as key triggers of the reorganization from lateral to apical actin cortex. The minimal cues necessary to trigger the polarization of hepatocytes enable them to develop asymmetric lumens with ectopic epithelial cells originating from the kidney, breast or colon.

What is the Quality of Life of Transtibial Amputees in Brunei Darussalam?

Introduction:

Lower limb amputations have a profound impact on the quality of life (QoL) of the patients. This study was done to assess the QoL of patients with transtibial (below-the-knee) amputations (TTA) and transtibial amputees fitted with prosthesis.

Material and Methods:

A case-control study of patients who had undergone TTA from 2015 to 2018 was conducted in Raja Isteri Pengiran Anak Saleha Hospital (RIPAS). Complete data was available for 30 subjects and it was compared with 30 diabetic, non-amputee patients matched for age and gender. QoL was assessed using the RAND 36-Item Health Survey (SF-36) and the functional outcome of prosthesis-fitted transtibial amputees was assessed using the Houghton Scale.

Results:

Almost all cases of TTA were a result of vascular problems related to diabetes and chronic renal disease (n=29; 97%). Eighteen (60%) participants were fitted with prosthesis and 15 (50%) reported having phantom pain. QoL of participants was found to be significantly lower than that of age and sex-matched diabetic non-amputees with regards to physical functioning, role limitation due to physical health, emotional well-being, social functioning, and bodily pain. The mean Houghton Score for participants fitted with prosthesis was 4.89 (SD= 2.83) suggesting low functional outcome.

Conclusion:

TTA has a negative impact on the QoL of patients, especially in terms of functionality. The availability of prosthesis does not significantly improve the quality of life except in the physical functioning domain. Emotional well-being should be emphasised more in the rehabilitation process as this study found poor emotional well-being among participants.

Validation of Current Good Manufacturing Practice Compliant Human Pluripotent Stem Cell-Derived Hepatocytes for Cell-Based Therapy

Recent advancements in the production of hepatocytes from human pluripotent stem cells (hPSC-Heps) afford tremendous possibilities for treatment of patients with liver disease. Validated current good manufacturing practice (cGMP) lines are an essential prerequisite for such applications but have only recently been established. Whether such cGMP lines are capable of hepatic differentiation is not known. To address this knowledge gap, we examined the proficiency of three recently derived cGMP lines (two hiPSC and one hESC) to differentiate into hepatocytes and their suitability for therapy. hPSC-Heps generated using a chemically defined four-step hepatic differentiation protocol uniformly demonstrated highly reproducible phenotypes and functionality. Seeding into a 3D poly(ethylene glycol)-diacrylate fabricated inverted colloid crystal scaffold converted these immature progenitors into more advanced hepatic tissue structures. Hepatic constructs could also be successfully encapsulated into the immune-privileged material alginate and remained viable as well as functional upon transplantation into immune competent mice. This is the first report we are aware of demonstrating cGMP-compliant hPSCs can generate cells with advanced hepatic function potentially suitable for future therapeutic applications. Stem Cells Translational Medicine 2019;8:124&14.

Human iPS derived progenitors bioengineered into liver organoids using an inverted colloidal crystal poly (ethylene glycol) scaffold

Generation of human organoids from induced pluripotent stem cells (iPSCs) offers exciting possibilities for developmental biology, disease modelling and cell therapy. Significant advances towards those goals have been hampered by dependence on animal derived matrices (e.g. Matrigel), immortalized cell lines and resultant structures that are difficult to control or scale. To address these challenges, we aimed to develop a fully defined liver organoid platform using inverted colloid crystal (ICC) whose 3-dimensional mechanical properties could be engineered to recapitulate the extracellular niche sensed by hepatic progenitors during human development. iPSC derived hepatic progenitors (IH) formed organoids most optimally in ICC scaffolds constructed with 140 μm diameter pores coated with type I collagen in a two-step process mimicking liver bud formation. The resultant organoids were closer to adult tissue, compared to 2D and 3D controls, with respect to morphology, gene expression, protein secretion, drug metabolism and viral infection and could integrate, vascularise and function following implantation into livers of immune-deficient mice. Preliminary interrogation of the underpinning mechanisms highlighted the importance of TGFβ and hedgehog signalling pathways. The combination of functional relevance with tuneable mechanical properties leads us to propose this bioengineered platform to be ideally suited for a range of future mechanistic and clinical organoid related applications.

Imaging-Based Screen Identifies Laminin 411 as a Physiologically Relevant Niche Factor with Importance for i-Hep Applications

Use of hepatocytes derived from induced pluripotent stem cells (i-Heps) is limited by their functional differences in comparison with primary cells. Extracellular niche factors likely play a critical role in bridging this gap. Using image-based characterization (high content analysis; HCA) of freshly isolated hepatocytes from 17 human donors, we devised and validated an algorithm (Hepatocyte Likeness Index; HLI) for comparing the hepatic properties of cells against a physiological gold standard. The HLI was then applied in a targeted screen of extracellular niche factors to identify substrates driving i-Heps closer to the standard. Laminin 411, the top hit, was validated in two additional induced pluripotent stem cell (iPSC) lines, primary tissue, and an in vitro model of α1-antitrypsin deficiency. Cumulatively, these data provide a reference method to control and screen for i-Hep differentiation, identify Laminin 411 as a key niche protein, and underscore the importance of combining substrates, soluble factors, and HCA when developing iPSC applications.

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iPSC-derived hepatocytes (i-Heps) are functionally limited compared with primary cells

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Factors within the extracellular niche likely play a role in bridging this gap

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Laminin 411 was shown to be an important niche factor for i-Heps

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High content image analysis (HCA) can help development of i-Hep applications

Long-term culture of human liver tissue with advanced hepatic functions

A major challenge for studying authentic liver cell function and cell replacement therapies is that primary human hepatocytes rapidly lose their advanced function in conventional, 2-dimensional culture platforms. Here, we describe the fabrication of 3-dimensional hexagonally arrayed lobular human liver tissues inspired by the liver's natural architecture. The engineered liver tissues exhibit key features of advanced differentiation, such as human-specific cytochrome P450-mediated drug metabolism and the ability to support efficient infection with patient-derived inoculums of hepatitis C virus. The tissues permit the assessment of antiviral agents and maintain their advanced functions for over 5 months in culture. This extended functionality enabled the prediction of a fatal human-specific hepatotoxicity caused by fialuridine (FIAU), which had escaped detection by preclinical models and short-term clinical studies. The results obtained with the engineered human liver tissue in this study provide proof-of-concept determination of human-specific drug metabolism, demonstrate the ability to support infection with human hepatitis virus derived from an infected patient and subsequent antiviral drug testing against said infection, and facilitate detection of human-specific drug hepatotoxicity associated with late-onset liver failure. Looking forward, the scalability and biocompatibility of the scaffold are also ideal for future cell replacement therapeutic strategies.

Fabrication of Inverted Colloidal Crystal Poly(ethylene glycol) Scaffold: A Three-dimensional Cell Culture Platform for Liver Tissue Engineering

The ability to maintain hepatocyte function in vitro, for the purpose of testing xenobiotics' cytotoxicity, studying virus infection and developing drugs targeted at the liver, requires a platform in which cells receive proper biochemical and mechanical cues. Recent liver tissue engineering systems have employed three-dimensional (3D) scaffolds composed of synthetic or natural hydrogels, given their high water retention and their ability to provide the mechanical stimuli needed by the cells. There has been growing interest in the inverted colloidal crystal (ICC) scaffold, a recent development, which allows high spatial organization, homotypic and heterotypic cell interaction, as well as cell-extracellular matrix (ECM) interaction. Herein, we describe a protocol to fabricate the ICC scaffold using poly (ethylene glycol) diacrylate (PEGDA) and the particle leaching method. Briefly, a lattice is made from microsphere particles, after which a pre-polymer solution is added, properly polymerized, and the particles are then removed, or leached, using an organic solvent (e.g., tetrahydrofuran). The dissolution of the lattice results in a highly porous scaffold with controlled pore sizes and interconnectivities that allow media to reach cells more easily. This unique structure allows high surface area for the cells to adhere to as well as easy communication between pores, and the ability to coat the PEGDA ICC scaffold with proteins also shows a marked effect on cell performance. We analyze the morphology of the scaffold as well as the hepatocarcinoma cell (Huh-7.5) behavior in terms of viability and function to explore the effect of ICC structure and ECM coatings. Overall, this paper provides a detailed protocol of an emerging scaffold that has wide applications in tissue engineering, especially liver tissue engineering.

Collective cell traction force analysis on aligned smooth muscle cell sheet between three-dimensional microwalls

During the past two decades, novel biomaterial scaffold for cell attachment and culture has been developed for applications in tissue engineering, biosensing and regeneration medicine. Tissue engineering of blood vessels remains a challenge owing to the complex three-layer histology involved. In order to engineer functional blood vessels, it is essential to recapitulate the characteristics of vascular smooth muscle cells (SMCs) inside the tunica media, which is known to be critical for vasoconstriction and vasodilation of the circulatory system. Until now, there has been a lack of understanding on the mechanotransduction of the SMC layer during the transformation from viable synthetic to quiescent contractile phenotypes. In this study, microfabricated arrays of discontinuous microwalls coated with fluorescence microbeads were developed to probe the mechanotransduction of the SMC layer. First, the system was exploited for stimulating the formation of a highly aligned orientation of SMCs in native tunica medium. Second, atomic force microscopy in combination with regression analysis was applied to measure the elastic modulus of a polyacrylamide gel layer coated on the discontinuous microwall arrays. Third, the conventional traction force assay for single cell measurement was extended for applications in three-dimensional cell aggregates. Then, the biophysical effects of discontinuous microwalls on the mechanotransduction of the SMC layer undergoing cell alignment were probed. Generally, the cooperative multiple cell-cell and cell-microwall interactions were accessed quantitatively by the newly developed assay with the aid of finite-element modelling. The results show that the traction forces of highly aligned cells lying in the middle region between two opposing microwalls were significantly lower than those lying adjacent to the microwalls. Moreover, the spatial distributions of Von Mises stress during the cell alignment process were dependent on the collective cell layer orientation. Immunostaining of the SMC sheet further demonstrated that the collective mechanotransduction induced by three-dimensional topographic cues was correlated with the reduction of actin and vinculin expression. In addition, the online two-dimensional LC-MS/MS analysis verified the modulation of focal adhesion formation under the influence of microwalls through the regulation in the expression of three key cytoskeletal proteins.

Effect of adhesive ligand on cell deadhesion kinetics on poly(N-isopropylacrylamide)

Thermo-responsive poly(N-isopropylacrylamide) (PIPAAm) with a particular lower critical solution temperature (LCST) have been applied for the non-invasive harvesting of confluent cell layer. Until now, the effect of adhesive ligand on the biophysical responses of cells during cell layer harvesting from PIPAAm has not been elucidated. In this study, the deadhesion kinetics of smooth muscle cells (SMC) on various adhesive ligands immobilized on PIPAAm were investigated. Firstly, the formation of elastin (EL), laminin (LA), hyaluronic acid (HA) and collagen (CL) coating on PIPAAm surfaces were validated with XPS, microBCA assay and AFM. It was shown that EL was most effective in driving cell retraction on PIPAAm surface. Moreover, the highest rate of initial SMC deadhesion on EL-PIPAAm was driven by the formation of stress fibers. Interestingly, HA was most effective in preventing initial SMC detachment from PIPAAm surface in comparison with EL, LA and CL. Also, the adhesion energy of SMC on HA-PIPAAm remained constant, which was two times and six times higher than that on CL-PIPAAm and EL-PIPAAm, respectively from 20 min onward. Overall, the results reported herein pave the way for the engineering of the invasive regeneration/recovery of cells/tissue with adhesive ligand.

Biomechanical study of the edge outgrowth phenomenon of encapsulated chondrocytic isogenous groups in the surface layer of hydrogel scaffolds for cartilage tissue engineering

In cartilage tissue engineering, hydrogel is widely used as the scaffold for hosting and culturing chondrocyte suspension during neo-tissue formation. In order to develop cultured chondrocytes into a functional cartilage equivalent, the hydrogel must provide an ideal microenvironment for the rapidly proliferating chondrocytes. At the same time, the essential functions of chondrocytes, such as the secretion of type II collagen and glycosaminoglycans, must be maintained. In these studies, we quantitatively characterize the mechanobiology underlying a newly discovered "edge flourish" phenomenon of cultured chondrocytes within a three-dimensional agarose hydrogel, which may ultimately nurture scaffold-free cartilaginous tissue regeneration. First, real-time microscopy was used to track the spatiotemporal distributions of chondrocytes at different focal planes. The chondrocytes were observed to exhibit abundant neo-tissue outgrowth and significant cartilaginous phenotype at the edge of the hydrogel compared to those inside the hydrogel bulk. Secondly, the hydrogel surface stresses induced by the encapsulated chondrocytes were characterized quantitatively in real time using the finite-element method. Finally, the real-time three-dimensional matrix deformations of agarose hydrogel under the influence of chondrocytes were measured using a multiple-particle tracking assay. Our results indicate that the mechanism of the "edge flourish" phenomenon is induced by the oriented outgrowth of chondrocytic isogenous groups located at the edge of hydrogel. These isogenous groups exhibit directed outgrowth towards the surface of the hydrogel and eventually generate substantial surface tension on the interface of hydrogel and medium. Ultimately, the encapsulated chondrocytes closest to the hydrogel/medium interface will spontaneously sprout out of the hydrogel and form a layer of rich proliferative and chondrocytic extracellular matrix secreting chondrocytes at the surface of the hydrogel.

Experimental and numerical determination of cellular traction force on polymeric hydrogels

Anchorage-dependent cells such as smooth muscle cells (SMCs) rely on the transmission of actomyosin-generated traction forces to adhere and migrate on the extracellular matrix. The cellular traction forces exerted by SMCs on substrate can be measured from the deformation of substrate with embedded fluorescent markers. With the synchronous use of phase-contrast and fluorescent microscopy, the deformation of polyacrylamide (PAM) gel substrate can be quantitatively determined using particle image velocimetry. This displacement map is then input as boundary conditions for the stress analysis on PAM gel by the finite-element method. In addition to optical microscopy, atomic force microscopy was also used to characterize the PAM substrate using the contact mode, from which the elasticity of PAM can be quantified using Hertzian theory. This provides baseline information for the stress analysis of PAM gel deformation. The material model introduced for the computational part is the Mooney-Rivlin constitutive law because of its long proven usefulness in predicting polymers' mechanical behaviour. Numerical results showed that adhesive stresses are high around the cell edges, which is in accordance with the general phenomena of cellular focal adhesion. Further calculations on the total traction forces indicate a slightly contact-dominated regime for a broad range of Mooney-Rivlin stiffnesses.

Epigallocatechin-3-gallate induced modulation of cell deadhesion and migration on thermosensitive poly(N-isopropylacrylamide)

Epigallocatechin-3-gallate (EGCG), which is the main polyphenolic constituent of green tea, has emerged as a promising candidate for potential applications in selected anticancer therapeutics. Generally, tumor metastasis is known to be correlated with the alterations in cell adhesion and migration of normal cells. Nevertheless, the effect of EGCG on the biophysical responses of tumor cell adhering on extracellular matrix remains obscure. In this study, a thermosenstive poly(N-isopropylacrylamide) (PIPAAm) system was developed to elucidate the potential anti-tumor effect of EGCG on the deadhesion and migration of HepG2 cells. First, both XPS and ELISA validated the coating of laminin (LA) on PIPAAm. Second, a change of nanotopology of LA layer on PIPAAm across the lower solution critical temperature (LCST) was detected with AFM. HepG2 cells seeded on LA-coated PIPAAm surface was shown to go through deadhesion by lowering the temperature below the LCST. Interestingly, EGCG was shown to decelerate the thermally triggered deadhesion of HepG2 cell on LA coated PIPAAm. Moreover, the inhibition of cell deadhesion in EGCG treated cells was shown to be driven by actin remodeling. Interestingly, the modulation of cell deadhesion on LA coated PIPAAm by EGCG leads to the reduction of cell motility as shown by real-time cell migration assay. Overall, the use of PIPAAm system demonstrated the promise of EGCG as anticancer therapy through the suppression of cell deadhesion and migration.

Surface phonon polariton characteristics of In(0.04)Al(0.06)Ga(0.90)N/AlN/Al(2)O(3) heterostructure

Surface phonon polariton (SPP) characteristics of In(0.04)Al(0.06)Ga(0.90)N/AlN/Al(2)O(3) heterostructure are investigated by means of p-polarized infrared (IR) attenuated total reflection spectroscopy. Two absorption dips corresponding to In(0.04)Al(0.06)Ga(0.90)N SPP modes are observed. In addition, two prominent dips and one relatively weak and broad dip corresponding to the Al(2)O(3) SPP mode, In(0.04)Al(0.06)Ga(0.90)N/Al(2)O(3) interface mode, and Al(2)O(3) bulk polariton mode, respectively, are clearly seen. No surface mode feature originating from the AlN layer is observed because it is too thin. Overall, the observations are in good agreement with the theoretical predictions.

Prognostic significance of thymidylate synthase, dihydropyrimidine dehydrogenase and thymidine phosphorylase protein expression in colorectal cancer patients treated with or without 5-fluorouracil-based chemotherapy

BACKGROUND

Low tumour expression levels of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP) have been linked with improved outcome for colorectal cancer (CRC) patients treated with 5-fluorouracil (5-FU). It is unclear whether this occurs because such tumours have better prognosis or they are more sensitive to 5-FU treatment.

PATIENTS AND METHODS

Associations between TS, DPD and TP levels, determined by tissue microarrays and immunohistochemistry, and survival was evaluated in 945 CRC patients according to treatment status.

RESULTS

Low TS and DPD expression associated with worse prognosis in stage II [hazard ratio (HR) = 1.69, 95% confidence interval (CI) (1.09-2.63) and HR = 1.92 (95% CI 1.23-2.94), respectively] and stage III CRC patients treated by surgery alone [HR = 1.39 (95% CI 0.92-2.13) and HR = 1.49 (95% CI 1.02-2.17), respectively]. Low TS, DPD and TP associated with trends for better outcome in stage III patients treated with 5-FU [HR = 0.81 (95% CI 0.49-1.33), HR = 0.70 (95% CI 0.42-1.15) and HR = 0.66 (95% CI 0.39-1.12), respectively].

CONCLUSION

Low TS and DPD expression are prognostic for worse outcome in CRC patients treated by surgery alone, whereas low TS, DPD and TP expression are prognostic for better outcome in patients treated with 5-FU chemotherapy. These results provide indirect evidence that low TS, DPD and TP protein expression are predictive of good response to 5-FU chemotherapy.

Tissue microarrays characterise the clinical significance of a VEGF-A protein expression signature in gastrointestinal stromal tumours

A tissue microarray analysis of 22 proteins in gastrointestinal stromal tumours (GIST), followed by an unsupervised, hierarchical monothetic cluster statistical analysis of the results, allowed us to detect a vascular endothelial growth factor (VEGF) protein overexpression signature discriminator of prognosis in GIST, and discover novel VEGF-A DNA variants that may have functional significance.

Quantitative and qualitative evaluation of sural nerve graft donor site

This study is designed to evaluate twenty patients after sural nerve harvest using the single longitudinal incision method. The area of sensory loss to pin prick was assessed by the authors at different intervals. Donor site factors, scar cosmesis, functional status and complications were assessed using a questionnaire. The mean area of anaesthesia at one month was 65 cm2 and it had reduced by 77% to 15 cm2 at one and a half years. The mean area of reduced sensation was 49 cm2 at one month and it increased by 18% to 58 cm2 over the same period. Therefore, the total area of sensory deficit was reduced by 36% from 114 cm2 at one month to 73 cm2 at one and a half years. Subjective patient evaluation indicated moderate level of pain during immediate post surgical period, which reduced significantly at one month. A low level of neuroma symptoms was recorded throughout the study period. At a mean follow-up period of two years, there was no area of anaesthesia in 50% of the patients. Mean area of anaesthesia for all patients was 12 cm2 and mean area of reduced sensation was 55 cm2. Subjective patient evaluation indicated a low level of pain, neuroma symptoms and numbness over the sural nerve sensory distribution. Twenty five percent of the patients were not satisfied with the scar appearance. Function and daily activities were not affected significantly. No surgical complications were observed.

Package plant of extended aeration membrane bioreactors: a study on aeration intensity and biofouling control

Biofouling control is important for effective process of membrane bioreactor (MBR). In this study, phenomena of biofouling for immersed type extended aeration MBR with two different anti-fouling aeration intensities were studied through a laboratory set up. The objectives of this study were (a) to observe biofouling phenomena of MBR that operates under different anti-fouling bubbling intensity, and simultaneously monitors performance of the MBR in organic carbon and nutrients removal; (b) to compare effectiveness of detergent and detergent-enzyme cleaning solutions in recovering biofouled membranes that operated in the extended aeration MBR. For MBR, which operated under continuous anti-fouling aeration, deposition and accumulation of suspended biomass on membrane surface were prohibited. However, flux loss was inescapable that biofilm layer was the main problem. Membrane cleaning was successfully carried out with detergent-enzyme mixture solutions and its effectiveness was compared with result from cleaning with just detergent solution.

Wortmannin inhibits pkb/akt phosphorylation and promotes gemcitabine antitumor activity in orthotopic human pancreatic cancer xenografts in immunodeficient mice

Pancreatic cancer is resistant to almost all classes of cytotoxic agents. Gemcitabine seems to be the current drug of choice. We have recently reported that inhibition of the phosphatidylinositide 3-kinase-protein kinase B (PKB/Akt) cell survival pathway by wortmannin enhances gemcitabine-induced apoptosis in cultured human pancreatic cancer cells (1). The present study investigated the effects of wortmannin on orthotopic human pancreatic cancer xenografts implanted in severe combined immunodeficient mice. Animals were given single i.v. bolus injections of 0.175, 0.35, or 0.7 mg/kg of wortmannin and killed at 0.5, 1, 2, or 4 h after treatment. Phosphorylated PKB/Akt levels in tumor tissues were measured by fluorescence image analysis. Wortmannin was found to inhibit PKB/Akt phosphorylation in a time- and dose-dependent manner, reaching a plateau at 4 h and at 0.7 mg/kg. The levels of phosphorylated PKB/Akt were maximally decreased by approximately 50% relative to the vehicle control. Subsequently, the extent of apoptosis in tumors treated with gemcitabine or wortmannin alone or in combination was determined using terminal deoxynucleotidyl transferase-mediated nick end labeling assay and computerized image analysis. Orthotopic tumors exposed to 80 mg/kg gemcitabine for 48 h and then 0.7 mg/kg wortmannin for 4 h showed a 5-fold increase (P = 0.002) in apoptosis compared with those treated with each agent alone and with the vehicle control. The combination treatment also significantly (P < 0.001) inhibited tumor growth. Taken together, our findings support the potential of phosphatidylinositide 3-kinase inhibitors as adjuncts to conventional chemotherapy in the treatment of pancreatic cancer.

Secretin facilitates GABA transmission in the cerebellum

Secretin was the first hormone discovered in human history, and yet, its function as a neuropeptide has been overlooked in the past. The recent discovery of the potential use of secretin in treating autistic patients, together with the conflicting reports on its effectiveness, urges an in-depth investigation of this issue. We show here that in the rat cerebellar cortex, mRNAs encoding secretin are localized in the Purkinje cells, whereas those of its receptor are found in both Purkinje cells and GABAergic interneurons. Immunoreactivity for secretin is localized in the soma and dendrites of Purkinje cells. In addition, secretin facilitates evoked, spontaneous, and miniature IPSCs recorded from Purkinje cells. We propose that secretin is released from the somatodendritic region of Purkinje cells and serves as a retrograde messenger modulating GABAergic afferent activity.

mik1(+) G1-S transcription regulates mitotic entry in fission yeast

In the fission yeast Schizosaccharomyces pombe Mik1p, in combination with Wee1p, is an important inhibitor of mitosis through direct phosphorylation of Cdc2p. Here we present the observation that mik1(+) is transcribed during G1- and S-phase in normally dividing cells. mik1(+) transcription is regulated by the MCB-DSC1 system, which controls expression of other genes at the G1-S interval. mik1(+) is shown to be an important target of MCB-DSC1 as it is epistatic for the mitotic delay phenotype displayed in cdc10-C4 cells, which are mutated in a component of DSC1. The mitotic delay in cdc10-C4 cells is bypassed by cdc2-1w, suggesting that mik1(+) acts directly on cdc2(+), with no checkpoint function involved. Thus, mik1(+) represents a new type of MCB-DSC1 regulated gene in fission yeast, whose gene product is exclusively expressed during G1- and S-phase to prevent premature mitosis during this cell cycle stage.

Real-time analysis of the activities of GnRH and GnRH analogs in alphaT3-1 cells by the Cytosensor microphysiometer

Gonadotropin-releasing hormone (GnRH), acting via the GnRH receptor, elicited rapid extracellular acidification responses in mouse gonadotrope-derived alphaT3-1 cells as measured by the Cytosensor microphysiometer, which indirectly monitors cellular metabolic rates. GnRH increased the extracellular acidification rate of the cells in a dose-dependent manner (EC(50) = 1.81 +/- 0.24 nM). The GnRH-stimulated acidification rate could be attenuated by protein kinase C (PKC) down-regulation, extracellular Ca2+ depletion, and the voltage-sensitive Ca2+ channel (VSCC) blocker nifedipine, indicating that the acidification response is activated by both Ca2+ and PKC-mediated pathways. Upon continuous exposure to 100 nM GnRH or periodic stimulation by 10 nM GnRH at 40 min intervals, homologous desensitization was more pronounced in the absence of extracellular Ca2+, suggesting that desensitization of GnRH activity may be mediated via depletion of intracellular Ca2+ stores. We have also compared the potency of eight GnRH analogs on alphaT3-1 cells. No acidification response was detected for GnRH free acid, consistent with the idea that the C-terminal amide is a critical structural determinant for GnRH activity. Replacement of Gly-NH(2) at the C-terminus by N-ethylamide dramatically reduced the EC(50) value, suggesting that substitution of the Gly-NH(2) moiety by N-ethylamide increases the potency of GnRH analogs. Substitution of Gly at position 6 by D-Trp significantly reduced the EC(50) value, whereas D-Lys at the same position slightly increased the EC(50) value, implying that either an aromatic amino acid or a non-basic amino acid at position 6 may be essential for potent GnRH agonists. In summary, our results demonstrate that the Cytosensor microphysiometer can be used to evaluate the actions of GnRH and GnRH analogs in alphaT3-1 cells in a real-time and noninvasive manner. This silicon-based microphysiometric system should provide new information on the structure-function studies of GnRH and is an invaluable tool for the screening of new GnRH agonists and antagonists in the future.

Predicting mortality and morbidity of patients operated on for perforated peptic ulcers

HYPOTHESIS

Since the early 1990s, the laparoscopic technique has been increasingly used for the treatment of perforated peptic ulcer. It is important to validate a risk scoring system that can stratify patients into various risk groups before comparing the treatment outcome of laparoscopic repair against that of conventional open surgery. The scoring system should be able to predict the likelihood of mortality and morbidity. Boey score and APACHE II (Acute Physiology and Chronic Health Evaluation II) score may be of use in patient stratification.

DESIGN

Retrospective review of relevant case notes by one reviewer.

SETTING

A teaching hospital treating 0. 5 million to 1 million patients during the study period.

PATIENTS

Patients operated on for perforated peptic ulcer between January 1989 and December 1998. Patients treated conservatively were excluded.

MAIN OUTCOME MEASURES

Mortality and postoperative complications (morbidity).

RESULTS

A total of 436 patients (365 male and 71 female) with a mean +/- SD age of 51.5 +/- 18.3 years (range, 14-92 years) were studied. Duodenal perforation accounted for 344 (78.9%) of 436 cases. The mortality rate was 7.8% (34/436), and 89 patients had postoperative complications. Multivariate analysis demonstrated that only the APACHE II score predicted both mortality and morbidity. Although the Boey score predicted mortality, it failed to predict morbidity. However, the Boey score predicted the chance of conversion in patients undergoing laparoscopic repair.

CONCLUSIONS

The APACHE II score may be a useful tool for stratifying patients into various risk groups, and the Boey score might select appropriate patients for laparoscopic repair.

Role of N-linked glycosylation on the function and expression of the human secretin receptor

Secretin is a 27-amino acid long peptide hormone that regulates pancreatic water, bicarbonate, enzymes, and potassium ion secretion. The human secretin receptor (hSR) is a glycoprotein consisting of 440 amino acids, of which there are 5 putative N-linked glycosylation sites at positions Asn72, Asn100, Asn106, Asn128 (N-terminal ectodomain), and Asn291 (second exoloop). Through functional analysis of the hSR-transfected cells cultured in the presence of various glycosylation inhibitors, it was found that tunicamycin and castanospermine were able to significantly reduce the secretin-stimulated cAMP response. On the other hand, the effects of other inhibitors, swainsonine and deoxymannojirimycin, were much lower, suggesting that the high mannose-type carbohydrate side-chain is essential to the expression of a fully functional hSR. The role of individual N-linked glycosylation sites was studied by mutation analysis (Asn to Leu or Ser to Ala) coupled to measurements of cAMP accumulation and extracellular acidification rate. The ED50 values of the wild-type receptor in these two assay systems were 0.25 and 0.11 nM, respectively, and mutation at position 100, 106, or 291 did not affect either the ED50 values or the maximal responses in the two assays. However, the Asn72Leu and Ser74Ala mutations reduced the maximal responses and increased the ED50 values in both assays, suggesting that this site is a true glycosylation signal. This hypothesis was further supported by competitive binding studies, the same mutants were found to be defective in binding with [125I]secretin. To evaluate whether the change in receptor function of the mutants is caused by the change in the process of presenting the receptor to the cell surface, the mutants and the wild-type receptor were tagged with a c-Myc epitope at the C-termini. Using an anti-c-Myc monoclonal antibody and confocal microscopy, all of the mutant receptors were found to be expressed and delivered to the plasma membrane.

Real-time evaluation of human secretin receptor activity using cytosensor microphysiometry

Human secretin receptor is a G protein-coupled receptor that is functionally linked to the cAMP second messenger system by stimulation of adenylate cyclase. To functionally characterize the receptor and evaluate its signal transduction pathway, the full-length human secretin receptor cDNA was subcloned into the mammalian expression vector pRc/CMV and expressed in cultured CHO cells. Intracellular cAMP accumulation of the stably transfected cells was measured by a radioimmunoassay (RIA), while the extracellular acidification rate was measured by the Cytosensor microphysiometer. Human secretin and biotinylated human secretin were equipotent in both assays in a dose-dependent manner. The EC50 values of stimulating the intracellular cAMP accumulation and the extracellular acidification rate were 0.2-0.5 nM and 0.1 nM, respectively, indicating that microphysiometry is more sensitive than the cAMP assay in monitoring ligand stimulation of the human secretin receptor. The secretin-stimulated response could be mimicked by forskolin and augmented by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, indicating that the extracellular acidification response is positively correlated with intracellular cAMP level. The response could be abolished by the protein kinase A inhibitor H-89, suggesting that protein kinase A plays an essential role in the intracellular signaling of the receptor. Upon repeated stimulation by the ligand, the peak acidification responses did not change significantly at both physiological (0.03 nM and 3 nM) and pharmacological (0.3 microM) concentrations of human secretin, suggesting that the human secretin receptor did not exhibit robust homologous desensitization.

Venous versus arterial actions of diethylamine/nitric oxide (DEA/NO) complex and S-nitroso-N-acetylpenicillamine (SNAP) in vivo

We studied the effects of diethylamine/NO complex (DEA/NO) and S-nitroso-N-acetylpenicillamine (SNAP), relative to those of sodium nitroprusside (SNP) and nitroglycerin (NTG), on mean arterial pressure (MAP), mean circulatory filling pressure (MCFP), arterial resistance (Ra), venous resistance (Rv), heart rate (HR), cardiac output (CO) and stroke volume (SV) in groups of Inactin-anaesthetized rats pre-treated with i.v. mecamylamine (3.7 micromol kg(-1)) and noradrenaline (6.8 nmol kg(-1) min(-1)). Doses of each that reduced MAP by 30%, 80% and the lowest dose that maximally reduced MAP were examined to allow a comparison of the compounds' dilator actions at equivalent effective depressor doses. DEA/NO (4, 32 and 256 microg kg(-1) min(-1)), SNAP (4, 32 and 256 microg kg(-1) min(-1)) and SNP (8, 32 and 128 microg kg(-1) min(-1)) caused similar dose-dependent reductions in MAP and Ra, and increases in CO and SV. NTG (0.2, 0.8 and 6.4 microg kg(-1) min(-1)) dose-dependently reduced Ra, and increased CO and SV, but lowered MAP only at the highest dose. DEA/NO, SNAP and SNP but not NTG lowered MCFP with efficacy: DEA/NO > SNAP > SNP. All four drugs reduced Rv with efficacy: DEA/NO approximately equal to SNAP > SNP approximately equal to NTG. Therefore, all compounds lowered Ra and Rv. DEA/NO, SNAP and SNP but not NTG reduced MCFP. The pharmacological profiles of DEA/NO and SNAP resemble SNP more than NTG.

Zaprinast, a type V phosphodiesterase inhibitor, dilates capacitance vessels in anaesthetised rats

The effects of zaprinast (a type V phosphodiesterase inhibitor) on mean arterial pressure, heart rate, cardiac output, mean circulatory filling pressure, arterial and venous resistances were compared to those of sodium nitroprusside in three groups, each of intact or ganglion-blocked, Inactin-anaesthetised rats. In intact rats, zaprinast (1.5, 3.0 mg kg(-1) min(-1)) and sodium nitroprusside (8.0, 64.0,microg kg(-1) min(-1)) dose-dependently reduced mean arterial pressure and arterial resistance, but did not alter cardiac output and venous resistance. Both increased heart rate, with the effect of zaprinast less than that of sodium nitroprusside. Mean circulatory filling pressure was elevated by both doses of zaprinast but only the high dose of sodium nitroprusside. In rats given mecamylamine (3.7 micromol kg(-1), i.v. bolus) and noradrenaline (7.3 nmol kg(-l) min(-1)), zaprinast and sodium nitroprusside elicited dose-dependent reductions in mean arterial pressure, arterial and venous resistances, and mean circulatory filling pressure. Both increased cardiac output, with the effect of zaprinast greater than that of sodium nitroprusside at the low dose. Zaprinast but not sodium nitroprusside reduced heart rate. Our results indicate that zaprinast, similar to sodium nitroprusside, dilates both resistance and capacitance vessels in ganglion-blocked rats infused with noradrenaline to restore vasomotor tone. Zaprinast but not sodium nitroprusside has a direct, negative chronotropic effect on the heart.

Transgene-encoded antiphosphorylcholine (T15+) antibodies protect CBA/N (xid) mice against infection with Streptococcus pneumoniae but not Trichinella spiralis

Immunodeficient CBA/N (xid) mice are highly susceptible to Streptococcus pneumoniae infection. Previous studies indicated that this susceptibility may be attributed to the lack of antibodies to phosphorylcholine (PC) in the circulation of these animals. We now provide direct proof that when these mice are genetically manipulated to produce significant amounts of circulating anti-PC immunoglobulin G antibodies of the T15 idiotype, they can be protected against a lethal challenge with S. pneumoniae. Transgenic mice were also used to investigate whether the transgene-encoded antibodies could protect the animals against another PC-bearing microorganism, Trichinella spiralis; in this case, there was no protection. These results were further supported by experiments with CFW mice which had been immunized to produce high levels of anti-PC antibodies but which were found to be just as susceptible to T. spiralis infection as nonimmunized animals.

Production of anti-phosphorylcholine antibodies of the T15 idiotype in CBA/N xid mice: investigation of the defect using a T15 immunoglobulin transgene

A notable defect in CBA/N xid mice is their relative inability to make antibodies to phosphorylcholine (PC), particularly those of the T15 idiotype which predominate in the anti-PC responses of immunologically normal mice. To investigate the basis of this defect, we introduced functionally rearranged genes encoding a T15+ PC-binding immunoglobulin G antibody into the germline of these animals. Expression of these genes in the xid cells was observed, shown by the existence of a distinct population of T15+ cells (3 x 10(6)) in the spleen of the transgenic animals, and the presence of PC-binding T15+ IgG antibodies (1-15 micrograms/ml) in the serum. Mixed antibody molecules were also found, however, which were composed of both transgene-encoded and endogenously-derived chains. Existence of the T15+ cells in these animals seemed normal, since these were not depleted (to any great extent) and were immunocompetent as well. The latter was shown by the increased T15+ antibody production in the transgenic animals when stimulated with a PC-associated thymus-independent type 1 (TI-1) antigen and anti-idiotype antibodies, but not with the pneumococcal TI-2 antigen. This is similar to the PC-specific (T15-) responsiveness of normal CBA/N xid mice. Based on these results, we argue that a reason why T15+ antibodies are not normally made by CBA/N xid animals is because T15+ genes are not utilized or, as with any T15+ precursors present, selected for in these animals, in contrast to normal mice where the Lyb-5 or CD5 cells (which are absent in CBA/N xid animals) are known to be specially endowed to make such antibodies.

Anti-arrhythmic surgery for atrioventricular junctional and atrioventricular re-entrant tachycardia--a report of six cases

Since 15th March 1989, six patients with recurrent supraventricular tachycardia (SVT) had antiarrhythmic surgery performed. There were 4 males and 2 females, ages ranged from 23 to 62 years (mean 41 years). Two of these patients with the Wolff Parkinson White (WPW) syndrome also had syncope. Five of these patients had atrioventricular re-entrant tachycardia (AVRT) involving the bypass tracts. Two patients with the WPW syndrome had persistent antegrade conduction, two had intermittent conduction and the last patient had no antegrade conduction via the bypass tract. The bypass tracts were localised at the left free wall in all the five patients. Only one patient had atrioventricular junctional re-entrant tachycardia (AVJRT) of the slow-fast type. The indications for surgery for these patients include failed medical therapy, "dangerous" arrhythmias and patient's preference. All the patients had surgery performed using the endocardial dissection technique on the cardioplegic heart. There were no perioperative mortality and morbidity. All the patients were discharged within 2 weeks. To date, none of the patients had clinical recurrence of SVT and only one patient remained in atrial fibrillation and is on digoxin. In conclusion, antiarrhythmic surgery should be considered for patients with "symptomatic" palpitations as it is curative with a resumption to normal life.

Hospitalization of adolescents in a new Children's Hospital

The amalgamation of two provincial pediatric referral centers into a single new Children's Hospital is examined from the perspective of the pattern of adolescent hospitalization in each. Ministry of Health hospital records for 11-19-year-olds discharged from the two pediatric referral centers during the period 1971-1978 were studied. Patients were divided into five arbitrary groups, based on their length of stay and discharge diagnosis. Level A patients accounted for 43.9% of discharges and were short-stay, uncomplicated, and primarily surgical cases. Level D patients were a much smaller group (16.3%) but accounted for 56.9% of bed days. Violence and pregnancy accounted for 37.8% of all discharges and were the most frequent reason for hospitalization. The present pattern of bed utilization by 11-19-year-olds admitted to these two centers requires an estimated 100 hospital beds per day. If this pattern were to be transposed, unmodified, to the new Children's Hospital, adolescents would use 50% of its 200-bed complement. Planning options to modify this requirement and the impact of changing patterns of hospital utilization are presented.

Sialyltransferases in young rat brain

1. There are more glycolipid acceptor sites for NeuNAc than for glycoproteins in 11--15 day old rat cerebra. 2. The glycolipid acceptors appear to be almost exclusively Cer-Glc-Gal and GM1 ganglioside and each is a substrate for a different sialyltransferase. 3. The sialyltransferase(s) that acted on glycoprotein could be differentiated from the ones that acted on the glycolipids. 4. The apparent Km for CMP-NeuNAc was the same for all four of the sialyltransferase reactions studied. 5. Electron microscopic examination and marker enzyme studies on continuous sucrose gradient fractions found that most of the sialyltransferase activities appeared to be localized in smooth microsomal membrane and the Golgi complex derivatives and not associated with the synaptosomes.