Glycosylation in health and disease

The glycome describes the complete repertoire of glycoconjugates composed of carbohydrate chains, or glycans, that are covalently linked to lipid or protein molecules. Glycoconjugates are formed through a process called glycosylation and can differ in their glycan sequences, the connections between them and their length. Glycoconjugate synthesis is a dynamic process that depends on the local milieu of enzymes, sugar precursors and organelle structures as well as the cell types involved and cellular signals. Studies of rare genetic disorders that affect glycosylation first highlighted the biological importance of the glycome, and technological advances have improved our understanding of its heterogeneity and complexity. Researchers can now routinely assess how the secreted and cell-surface glycomes reflect overall cellular status in health and disease. In fact, changes in glycosylation can modulate inflammatory responses, enable viral immune escape, promote cancer cell metastasis or regulate apoptosis; the composition of the glycome also affects kidney function in health and disease. New insights into the structure and function of the glycome can now be applied to therapy development and could improve our ability to fine-tune immunological responses and inflammation, optimize the performance of therapeutic antibodies and boost immune responses to cancer. These examples illustrate the potential of the emerging field of 'glycomedicine'.

Embryonic stem cells differentiate into oligodendrocytes and myelinate in culture and after spinal cord transplantation

Demyelination contributes to the loss of function consequent to central nervous system (CNS) injury. Enhanced remyelination through transplantation of myelin-producing cells may offer a pragmatic approach to restoring meaningful neurological function. An unlimited source of cells suitable for such transplantation therapy can be derived from embryonic stem (ES) cells, which are both pluripotent and genetically flexible. In this paper we show that oligodendrocyte cultures can be reliably produced from retinoic acid-induced ES cells and that these oligodendrocytes can myelinate axons in vitro. Methods were further developed for generating highly enriched cultures of oligodendrocytes through an additional culturing step, producing an intermediate "oligosphere" stage. To test whether ES cells can survive, migrate, and differentiate into mature myelin-producing cells in areas of demyelination in the adult CNS, ES cells were transplanted into the dorsal columns of adult rat spinal cord 3 days after chemical demyelination. In the demyelination site, large numbers of ES cells survived and differentiated primarily into mature oligodendrocytes that were capable of myelinating axons. Furthermore, when oligosphere cells were transplanted into the spinal cords of myelin-deficient shiverer (shi/shi) mutant mice, the ES cell-derived oligodendrocytes migrated into the host tissue, produced myelin and myelinated host axons. These studies demonstrate the ability of ES cell-derived oligodendrocytes to myelinate axons in culture and to replace lost myelin in the injured adult CNS. Transplantation of ES cells may be a practical approach to treatment of primary and secondary demyelinating diseases in the adult CNS.

Occult schwannomas of the vestibular nerve

Five small occult schwannomas of the vestibular nerve were discovered on routine examination of 893 serially sectioned temporal bones of 517 individuals. Three arose from the superior division, one from the inferior division, and the other had a multicentric origin from both divisions of the nerve. Location and size of these tumors indicate that clinical diagnosis would have been difficult or impossible by any method of study. The finding of vestibular schwannomas in 0.9% of individuals in this series, indicates the high incidence of this tumor in the general population. The much lower incidence of diagnosed symptomatic tumors in the general population can only be explained by the conclusion that this neoplasm exhibits considerable variation in growth characteristics. Usually the tumor enlarges so slowly as to be of no health importance, but occasionally it grows more rapidly to become symptomatic and require surgical removal.

Effects of garlic on lipid metabolism in rats fed cholesterol or lard

Effects of garlic on lipid metabolism were studied in three experiments using different aged male rats fed a diet containing 1% cholesterol or 15% lard. Lyophilized garlic was supplemented at 2% and 4% of the diet. Plasma glucose was not changed by dietary treatments. Rats fed cholesterol and lard diets increased plasma cholesterol and triglycerides compared to controls. Garlic decreased plasma cholesterol in cholesterol- and lard-fed rats, but decreased plasma triglycerides only in the lard-fed group. Garlic supplementation decreased very low density lipoprotein cholesterol and increased high density lipoprotein cholesterol. The liver weight, total liver lipid and cholesterol were increased in rats fed the cholesterol diet but a supplementation of garlic decreased those parameters by about 30%. Dietary cholesterol and lard decreased hepatic glucose-6-phosphate dehydrogenase and malic enzyme activities: the garlic supplementation further decreased these enzyme activities. Garlic feeding increased the excretion of the neutral steroids in both 16-week and 10-week-old rats and bile acids in only 16-week-old pair-fed rats. Garlic at the 2% level was similarly effective on lipid metabolism as at 4%. These results demonstrate that garlic increases the excretion of neutral and acidic steroids and exerts hypocholesterolemic effects in cholesterol-fed rats.

Infection with Pneumocystis carinii is prevalent in healthy Gambian children

Pneumocystis pneumonia is rarely identified in the many immunosuppressed individuals with acquired immune deficiency syndrome (AIDS) and malnutrition in Africa. To test whether infection with Pneumocystis carinii occurs in the continent we conducted a comparative serological study, measuring by enzyme-linked immunosorbent assay antibodies to the parasite in 150 healthy young individuals from both Britain and the Gambian savanna. The prevalence of significant titres of antibody to P. carinii steadily increased with age and included more than 70% of both populations by 8 years of age. Infection with P. carinii is, therefore, common in the Gambia. Thus opportunistic pneumocystis pneumonia may be an important but largely unrecognized disease in the continent, though its impact is probably diminished by the prevalence of fatal tuberculous infection, particularly in the AIDS population.

Human IgE response to the Schistosoma haematobium 22.6 kDa antigen

In Schistosoma mansoni and S. japonicum infection, the 22.6 kDa tegumental antigens Sm22.6 and Sj22.6 are principal targets for the human IgE response, and levels of IgE to Sm22.6 have been correlated with resistance to re-infection after chemotherapy. S. haematobium is arguably a more important species in terms of human infection, and in this report we describe for the first time the molecular characterization of a cDNA from S. haematobium (Sh22.6) that is closely homologous to Sm22.6 and Sj22.6. As a member of the tegument-associated antigen family, Sh22.6 possesses EF-hand domains and regions homologous to the dynein light chain domains. We have expressed recombinant Sh22.6 and studied the IgE responses to the antigen in a group of 99 infected individuals (68 children and 31 adults) from an endemic area of Gabon who donated blood before and 5 weeks after praziquantel treatment. IgE to Sh22.6 was detected by ELISA in 18 subjects (18%), and in the majority of responders levels rose between pre- and post-treatment. Interestingly, the proportion of adults expressing IgE to Sh22.6 was 35.5%, significantly higher than the 10.3% seen in children. IgE from at least 10 of the 18 ELISA responders recognized Sh22.6 on Western blots of adult worm extract and recombinant antigen. These results demonstrate that like related molecules in other species, Sh22.6 is a target for the human IgE response. The data also indicate that changes in the IgE response occur with age or with progressive exposure to key antigens.

Surgical anatomy and pathology of the round window

A study of the surgical anatomy and pathology of the round window was performed on a total of 292 serially sectioned temporal bones. The surgical approach to the round window is discussed with consideration of the anatomical findings. In the pathological study obliteration of the round window niche occurred as a congenital anomaly, in otosclerosis, chronic otitis media and as an end result in suppurative labyrinthitis. Clinical reports seem to indicate that obliteration of the window is associated with significant hearing loss, contrary to the findings in experimental animals. In chronic otitis media the round window is a pathway for spread of infection to the labyrinth, but also the finding of perilymphatic precipitates to the window in some ears suggests that certain inflammatory products may enter the scala tympani through the round window and so lead to high tone sensorineural hearing loss.

Vaccine-induced Th1-type responses are dominant over Th2-type responses in the short term whereas pre-existing Th2 responses are dominant in the longer term

The effect of adjuvant on induction of human papillomavirus type 16 E7 protein-specific cytotoxic T lymphocytes (CTL) and immunoglobulin G (IgG)2a antibody was studied in C57BL/6 J mice immunized with various adjuvants and E7 protein. Quil-A adjuvant, but not complete Freund's adjuvant (CFA) or Algammulin, induced a T-helper 1 (Th1)-type response to E7, which was characterized by CTL activity against a tumour cell line transfected with E7 protein and by E7-specific IgG2a. All tested adjuvants elicited comparable levels of E7-specific IgG1. The longest duration and greatest magnitude of CTL response was seen following two immunizations with the highest dose of E7 and Quil-A. Simultaneous immunization with a Th1 and a T helper 2 (Th2)-promoting adjuvant gave a Th1-type response. However, E7 and Quil-A were unable to induce a Th1-type response (as measured by the inability to generate anti-E7 IgG2a antibody) in animals with a pre-existing Th2-type response to E7. These results suggest that saponin adjuvants may be suitable for immunotherapy in humans where a Th1-type response is sought, provided that there is no pre-existing Th2-type response to the antigen.

Somatic Mutations Modulate Autoantibodies against Galactose-Deficient IgA1 in IgA Nephropathy

Autoantibodies against galactose-deficient IgA1 drive formation of pathogenic immune complexes in IgA nephropathy. IgG autoantibodies against galactose-deficient IgA1 in patients with IgA nephropathy have a specific amino-acid sequence, Y₁CS₃, in the complementarity-determining region 3 of the heavy chain variable region compared with a Y₁CA₃ sequence in similar isotype-matched IgG from healthy controls. We previously found that the S₃ residue is critical for binding galactose-deficient IgA1. To determine whether this difference is due to a rare germline sequence, we amplified and sequenced the corresponding germline variable region genes from peripheral blood mononuclear cells of seven patients with IgA nephropathy and six healthy controls from whom we had cloned single-cell lines secreting monoclonal IgG specific for galactose-deficient IgA1. Sanger DNA sequencing revealed that complementarity-determining region 3 in the variable region of the germline genes encoded the Y₁C(A/V)₃ amino-acid sequence. Thus, the A/V>S substitution in the complementarity-determining region 3 of anti-galactose-deficient-IgA1 autoantibodies of the patients with IgA nephropathy is not a rare germline gene variant. Modeling analyses indicated that the S₃ hydroxyl group spans the complementarity-determining region 3 loop stem, stabilizing the adjacent β-sheet and stem structure, important features for effective binding to galactose-deficient IgA1. Understanding processes leading to production of the autoantibodies may offer new approaches to treat IgA nephropathy.

N-acetylgalactosaminide α2,6-sialyltransferase II is a candidate enzyme for sialylation of galactose-deficient IgA1, the key autoantigen in IgA nephropathy

BACKGROUND

Galactose-deficient O-glycans in the hinge region (HR) of immunoglobulin A1 (IgA1) play a key role in the pathogenesis of IgA nephropathy (IgAN). O-Glycans of circulatory IgA1 consist of N-acetylgalactosamine (GalNAc) with a β1,3-linked galactose; both sugars may be sialylated. In patients with IgAN, α2,6-sialylated GalNAc is a frequent form of the galactose-deficient O-glycans. Prior analyses of IgA1-producing cells had indicated that α2,6-sialyltransferase II (ST6GalNAc-II) is likely responsible for sialylation of GalNAc of galactose-deficient IgA1, but direct evidence is missing.

METHODS

We produced a secreted variant of recombinant human ST6GalNAc-II and an IgA1 fragment comprised of Cα1-HR-Cα2. This IgA1 fragment and a synthetic HR peptide with enzymatically attached GalNAc residues served as acceptors. ST6GalNAc-II activity was assessed in vitro and the attachment of sialic acid to these acceptors was detected by lectin blot and mass spectrometry.

RESULTS

ST6GalNAc-II was active with both acceptors. High-resolution mass spectrometry analysis revealed that up to three sialic acid residues were added to the GalNAc residues of the HR glycopeptide.

CONCLUSIONS

Our data provide direct evidence that ST6GalNAc-II can sialylate GalNAc of galactose-deficient IgA1. As serum levels of galactose-deficient IgA1 with sialylated glycoforms are increased in IgAN patients, our data explain the corresponding part of the biosynthetic pathway.

Pathologocal changes in the middle ear joints

A histological study was made of the middle ear joints in association with several middle ear disorders, including congenital anomalies, acute and chronic otitis media, congenital syphilis, otosclerosis, Paget's disease, and primary and secondary neoplasms. Although the numbers of cases are small, the data suggest that the degenerative changes in the joints are more severe and in higher incidence than expected as a function of aging. Whereas advanced changes may be present, including fusion of the articular surfaces, it seems improbable that the joint changes contribute to the conductive hearing losses existing in these ears.

Surgical treatment of glossopharyngeal neuralgia via the pharyngeal approach

Idiopathic glossopharyngeal neuralgia is an uncommon disorder which often fails to respond to medical treatment. Surgical treatment most commonly consists of intracranial section of the glossopharyngeal nerve and upper vagal rootlets. We present three cases treated by the much simpler pharyngeal approach and argue that in appropriately selected patients this approach should receive more serious consideration.

Tonsil flora in the very young tonsillectomy patient

The tonsil flora of 20 children below the age of 4 years undergoing tonsillectomy, and a control group of 18 children were studied using tonsil swabs and core specimens. The study group had a significantly higher culture rate of anaerobic organisms, whereas there was no significant difference between the groups in respect of aerobic pathogens. Since most anaerobic organisms are relatively resistant to the antibiotics usually prescribed for recurring tonsillitis, the use of more appropriate antimicrobial therapy may be helpful in the prevention of early tonsillectomy.

Fetal heart rate changes associated with general anesthesia

Decreased fetal heart rate variability was noted 90 seconds after the induction of general anesthesia with sodium thiopentone and fentanyl in a patient undergoing basket extraction of a renal calculus at 30 weeks' gestation. The fetal sleep pattern lasted for 105 minutes after the anesthetic was discontinued, 45 minutes after the mother was fully awake.

Analysis of the complete sequence of a muscle calcium-binding protein of Schistosoma mansoni

The complete sequence of the cDNA encoding a 20 kDa calcium-binding protein of Schistosoma mansoni (Sm20) has been determined. The predicted amino acid sequence contains 4 EF hand domains but examination of the predicted secondary structure of Sm20, together with the specific residues in each calcium-binding domain, suggests that only 1 EF hand (domain IV) is functional. Sm20 is most homologous to calmodulin, troponin C and the regulatory light-chain of myosin, particularly those of invertebrates. However, troponin C and the regulatory light-chain of myosin can be distinguished from Sm20 by size and by their differential levels of expression during the life-cycle. Sm20 also appears to be distinct from calmodulin but may be functionally equivalent to the soluble sarcoplasmic calcium-binding proteins of molluscs and crustacea which may act as a reservoir for calcium in muscle. Sm20 is encoded by a small multi-gene family whose members are clustered within a 15 kb region of the genome. A 20 kDa antigen, cross-reactive with Sm20, is expressed in Schistosoma haematobium, Fasciola hepatica and Paragonomus mexicanus.

IgA1 hinge-region clustered glycan fidelity is established early during semi-ordered glycosylation by GalNAc-T2

GalNAc-type O-glycans are often added to proteins post-translationally in a clustered manner in repeat regions of proteins, such as mucins and IgA1. Observed IgA1 glycosylation patterns show that glycans occur at similar sites with similar structures. It is not clear how the sites and number of glycans added to IgA1, or other proteins, can follow a conservative process. GalNAc-transferases initiate GalNAc-type glycosylation. In IgA nephropathy, an autoimmune disease, the sites and O-glycan structures of IgA1 hinge-region are altered, giving rise to a glycan autoantigen. To better understand how GalNAc-transferases determine sites and densities of clustered O-glycans, we used IgA1 hinge-region (HR) segment as a probe. Using LC-MS, we demonstrated a semi-ordered process of glycosylation by GalNAc-T2 towards the IgA1 HR. The catalytic domain was responsible for selection of four initial sites based on amino-acid sequence recognition. Both catalytic and lectin domains were involved in multiple second site-selections, each dependent on initial site-selection. Our data demonstrated that multiple start-sites and follow-up pathways were key to increasing the number of glycans added. The lectin domain predominately enhanced IgA1 HR glycan density by increasing synthesis pathway exploration by GalNAc-T2. Our data indicated a link between site-specific glycan addition and clustered glycan density that defines a mechanism of how conserved clustered O-glycosylation patterns and glycoform populations of IgA1 can be controlled by GalNAc-T2. Together, these findings characterized a correlation between glycosylation pathway diversity and glycosylation density, revealing mechanisms by which a single GalNAc-T isozyme can limit and define glycan heterogeneity in a disease-relevant context.

Quantitative assessment of successive carbohydrate additions to the clustered O-glycosylation sites of IgA1 by glycosyltransferases

Mucin-type O-glycosylation occurs on many proteins that transit the Golgi apparatus. These glycans impact structure and function of many proteins and have important roles in cellular biosynthetic processes, signaling and differentiation. Although recent technological advances have enhanced our ability to profile glycosylation of glycoproteins, limitations in the understanding of the biosynthesis of these glycan structures remain. Some of these limitations stem from the difficulty to track the biosynthetic process of mucin-type O-glycosylation, especially when glycans occur in dense clusters in repeat regions of proteins, such as the mucins or immunoglobulin A1 (IgA1). Here, we describe a series of nano-liquid chromatography (LC)-mass spectrometry (MS) analyses that demonstrate the range of glycosyltransferase enzymatic activities involved in the biosynthesis of clustered O-glycans on IgA1. By utilizing nano-LC-MS relative quantitation of in vitro reaction products, our results provide unique insights into the biosynthesis of clustered IgA1 O-glycans. We have developed a workflow to determine glycoform-specific apparent rates of a human UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltrasnfersase (GalNAc-T EC 2.4.1.41) and demonstrated how pre-existing glycans affect subsequent activity of glycosyltransferases, such as core 1 galactosyltransferase and α2,3- and α2,6-specific sialyltransferases, in successive additions in the biosynthesis of clustered O-glycans. In the context of IgA1, these results have potential to provide insight into the molecular mechanisms implicated in the pathogenesis of IgA nephropathy, an autoimmune renal disease involving aberrant IgA1 O-glycosylation. In a broader sense, these methods and workflows are applicable to the studies of the concerted and competing functions of other glycosyltransferases that initiate and extend mucin-type core 1 clustered O-glycosylation.

A field test of the use of pop-off data storage tags in freshwater fishes

In the present study, pop-off data storage tags (pDST) without any transmitting capabilities were attached to 118 adult salmonids in a 19 000 km² freshwater system (Lake Ontario). The 9·3 cm long cylindrical tags were externally attached to fishes using a backpack-style harness, set to record pressure (dBar ≈ depth in m) and temperature every 70 s (and at some key times, every 5 s) and programmed to release from the harness and float to the surface after c. 1 year. Recapture of the bright-orange tags for data retrieval relied on members of the public finding tags on shore, or on anglers capturing fishes with tags attached and using the contact information displayed on each tag to mail tags to the research team in exchange for a monetary reward. Thirty-seven tags were found and returned from the 118 released (31%), while 26 of the 118 tags (22%) remained scheduled to pop-off in summer 2017. Of the 37 tags returned, 23 were from wild-caught fishes (out of 88 wild-caught and tagged fishes; 26%) and yielded useful data whereas 14 were from hatchery-reared fishes that were opportunistically tagged and appear to have been unable to acclimate to life in the wild and died days to weeks after release. The field study described here thus demonstrated that pDSTs can be a viable option for collecting large amounts of high-resolution depth and temperature data for salmonids in freshwater systems. Technical challenges, limitations and unknowns related to the use of pDSTs with freshwater fishes are discussed. In addition, pDSTs are compared with alternate electronic tagging technologies and assessed for their potential as a more widespread tool in research on freshwater fishes.

An unusual presentation of oat cell carcinoma

A case is reported of oat cell carcinoma of the lung presenting with unusual sites of metastasis to the orofacial region. Distant metastases are common in oat cell carcinoma but a literature review did not reveal any reports of metastases either to the hard palate or to medial canthus of the eye.

Tracking the Temporal Dynamics of Intracellular Lead Speciation in a Green Alga

Organisms have developed metal regulatory mechanisms in response to changes in the bioavailability of trace metals. Just as metal bioavailability dictates cellular uptake, intracellular metal speciation determines the availability of metals to exert biological effects. However, the missing link in understanding the relationship between metal uptake and biological responses is the ability to accurately measure intracellular metal speciation. We conducted Pb exposure studies on the well-characterized model green alga Chlamydomonas reinhardtii and identified temporal changes in intracellular Pb speciation under conditions relevant for fresh water ecosystems using resonant X-ray emission spectroscopy (RXES), which possesses enhanced sensitivity to functional group chemistry relative to X-ray absorption spectroscopy (XAS). Analysis of RXES maps show that only a small fraction of total intracellular Pb was complexed by thiol groups. Initial sequestration of Pb in oxides and inorganic phosphate was followed by binding of Pb to organic phosphate, suggesting potential interference in vital cellular functions. These results contrast proposed detoxification responses involving complexation by thiol groups from peptides.