The composition of the mucus gel of the tear film reflects the competing needs for transparency, stability, hydration, and protection of the ocular surface. Mucins form the macromolecular scaffolding of this hydrated gel, and glycans decorating these glycoproteins represent a rich source of binding ligands that may both modulate microbial binding and regulate the physicochemical characteristics of the gel. This study compares the structure of O-linked glycans derived from the ocular mucins of three species, to determine whether the ocular surface microenvironment dictates the need for a common pattern of O-linked carbohydrate structures. Ocular mucus aspirates were collected from healthy humans, rabbits and dogs. Mucins were purified using standard protocols. O-glycans were released by hydrazinoloysis and subsequently analysed by a combination of HPLC, exoglycosidase digestions and LC-MS/MS. A total of 12 different O-glycans were identified. In human ocular mucin, the majority were negatively charged and terminated in sialic acid, whilst those from rabbit or dog were mainly neutral and terminated in alpha 1-2 fucose and/or alpha 1-3 N-acetylgalactosamine. The glycans were short: the most common structures being tetra-, tri- or disaccharides. Less elaborate glycan structures are encountered at the ocular surface than at many other mucosal surfaces. Species-specific glycan expression is a feature of ocular surface mucins, and has implications for their defensive properties where different microbial and environmental challenges are encountered.

The aim of this study was to describe metabolism of early-lactation dairy cows by clustering cows based on glucose, insulin-like growth factor I (IGF-I), free fatty acid, and β-hydroxybutyrate (BHB) using the k-means

S_ry We have shown that addition of exogenous A-aminolaevulinic acid (ALA) to rat pancreatoma AR4-2J cells in culture leads to the increased production of porphobilinogen (PBG) and the accmulation of photoactive protoporphyrin IX (PPix) in these cells. Exposure to light (A> 400 mm) at an intensity of 0.2 mW cm-2 for 8 min resulted in an ALA dose-dependent cytolysis of the cells, with an EC50 of 6.6 ± 0.7 LM.This cytolytic effect was light intensity dependent, with greater cell destruction after exposure to light at an intensity of 0.47 mW cm-2 than at 0.2 mW cm-'; it was also dependent on the duration of illumination, cell survival decreasing with increasing illumination times. (van Hillegersberg et al., 1992). The biosynthesis of PPix can be enhanced by the exogenous administration of the amino acid 6-aminolaevulinic acid (ALA), especially in tumour cells, a pathway that offers promise for exploitation in photodynamic therapy (Pottier et al., 1986;Malik and Lugaci, 1987).The purpose of the present investigation was to determine whether endogenous PPix produced from exogenous ALA in rat pancreatoma AR4-2J cells can achieve a sufficient concentration to serve as a cytolytic agent following photoactivation. Light-activated PPix exerts its tumonrcidal effect presumably by the generation of singlet oxygen (102), a short-lived excited state of molecular oxygen which reacts with membranous structures, lipids and proteins (Weishaupt et al., 1976). The present study verifies the generation of 102 by PPix and also shows that ALA does not itself contribute directly to 102 production, thus confiuming that it is the endogenously generated PPix, not the ALA, that mediates the cellular phototoxicity.Recently, it has been proposed that the physiological dicarboxylic porphyrins, notably PPix, are endogenous ligands for the mitochondrial benzodiazepine receptor (MBR), an 18 kDa protein located on the outer mitochondrial membrane and mediating a wide range of physiological effects (Verma et al., 1987), including modulation of mitochondrial respiratory control (Hirsch et al., 1988), inhibition of cellular proliferation (Stepien et al., 1991) and induction of cellular differentiation (Wang et al., 1984a). The MBR has been implicated in the translocation of PPix and haem across mitochondrial membranes, presumably by way of the anion channel, porin, an integral part of the MBR (Anholt, 1986). Centrally acting benzodiazepine compounds such as clonazepam and flumazenil have minimal affinities for the MBR, but the peripherally active ligands Ro5-4864 and PK1195 will bind to the MBR with high affinity, and both will displace the endogenous ligand PPix (Verma et al., 1987). In the present investigation the abilities of these MBR ligands to interfere with phototoxicity elicted by exogenous ALA in the AR4 2J cells were compared with the effects of those centrally acting benzodiazepine ligands possessing a low affinity at the MBR. A role for the MBR in ALA/PPix-mediated phototoxicity is proposed from the findings of this study, some of whi...

Both blood- and milk-based biomarkers have been analysed for decades in research settings, although often only in one herd, and without focus on the variation in the biomarkers that are specifically related to herd or diet. Biomarkers can be used to detect physiological imbalance and disease risk and may have a role in precision livestock farming (PLF). For use in PLF, it is important to quantify normal variation in specific biomarkers and the source of this variation. The objective of this study was to estimate the between- and within-herd variation in a number of blood metabolites (β-hydroxybutyrate (BHB), non-esterified fatty acids, glucose and serum IGF-1), milk metabolites (free glucose, glucose-6-phosphate, urea, isocitrate, BHB and uric acid), milk enzymes (lactate dehydrogenase and N-acetyl-β-D-glucosaminidase (NAGase)) and composite indicators for metabolic imbalances (Physiological Imbalance-index and energy balance), to help facilitate their adoption within PLF. Blood and milk were sampled from 234 Holstein dairy cows from 6 experimental herds, each in a different European country, and offered a total of 10 different diets. Blood was sampled on 2 occasions at approximately 14 days-in-milk (DIM) and 35 DIM. Milk samples were collected twice weekly (in total 2750 samples) from DIM 1 to 50. Multilevel random regression models were used to estimate the variance components and to calculate the intraclass correlations (ICCs). The ICCs for the milk metabolites, when adjusted for parity and DIM at sampling, demonstrated that between 12% (glucose-6-phosphate) and 46% (urea) of the variation in the metabolites’ levels could be associated with the herd-diet combination. Intraclass Correlations related to the herd-diet combination were generally higher for blood metabolites, from 17% (cholesterol) to approximately 46% (BHB and urea). The high ICCs for urea suggest that this biomarker can be used for monitoring on herd level. The low variance within cow for NAGase indicates that few samples would be needed to describe the status and potentially a general reference value could be used. The low ICC for most of the biomarkers and larger within cow variation emphasises that multiple samples would be needed - most likely on the individual cows - for making the biomarkers useful for monitoring. The majority of biomarkers were influenced by parity and DIM which indicate that these should be accounted for if the biomarker should be used for monitoring.

Fasciola hepatica secretes proteolytic enzymes and other molecules that are essential for host penetration and migration. This mixture may include enzymes required for the degradation of supramucosal gels, which defend epithelial surfaces against pathogen entry. These contain hydrated mucins that are heavily glycosylated. Excretory-secretory products (ES) from F. hepatica were examined for a range of glycosidase activities, using synthetic 4-methylumbelliferyl glycosides as substrates. The ES product contained at least 8 different glycosidase activities, the most abundant of which were beta-N-acetylhexosaminidase, beta-galactosidase and beta-glucosidase. Alpha-fucosidase, beta-glucuronidase, alpha-galactosidase, alpha-mannosidase and neuraminidase were also present. Beta-N-acetylhexosaminidase and beta-galactosidase were present in multiple isoforms (at least 4), whereas beta-glucosidase appeared to exist as one isoenzyme with a pI < 3.8. All three enzymes had acidic pH optima (4.5-5.0). Ovine small intestinal mucin was degraded by ES at pH 4.5 or 7.0, with or without active cathepsin L, the major protease found in F. hepatica ES. The ability of F. hepatica ES to degrade mucin in the presence or absence of active cathepsin L suggests that cathepsin L is not essential for mucin degradation. The abundance of beta-galactosidase and beta-hexosaminidase in ES supports a role for these enzymes in mucin degradation.