Rebound activation of 5-HT neurons following SSRI discontinuation

Cessation of therapy with a selective serotonin (5-HT) reuptake inhibitor (SSRI) is often associated with an early onset and disabling discontinuation syndrome, the mechanism of which is surprisingly little investigated. Here we determined the effect on 5-HT neurochemistry of discontinuation from the SSRI paroxetine. Paroxetine was administered repeatedly to mice (once daily, 12 days versus saline controls) and then either continued or discontinued for up to 5 days. Whereas brain tissue levels of 5-HT and/or its metabolite 5-HIAA tended to decrease during continuous paroxetine, levels increased above controls after discontinuation, notably in hippocampus. In microdialysis experiments continuous paroxetine elevated hippocampal extracellular 5-HT and this effect fell to saline control levels on discontinuation. However, depolarisation (high potassium)-evoked 5-HT release was reduced by continuous paroxetine but increased above controls post-discontinuation. Extracellular hippocampal 5-HIAA also decreased during continuous paroxetine and increased above controls post-discontinuation. Next, immunohistochemistry experiments found that paroxetine discontinuation increased c-Fos expression in midbrain 5-HT (TPH2 positive) neurons, adding further evidence for a hyperexcitable 5-HT system. The latter effect was recapitulated by 5-HT1A receptor antagonist administration although gene expression analysis could not confirm altered expression of 5-HT1A autoreceptors following paroxetine discontinuation. Finally, in behavioural experiments paroxetine discontinuation increased anxiety-like behaviour, which partially correlated in time with the measures of increased 5-HT function. In summary, this study reports evidence that, across a range of experiments, SSRI discontinuation triggers a rebound activation of 5-HT neurons. This effect is reminiscent of neural changes associated with various psychotropic drug withdrawal states, suggesting a common unifying mechanism.

Evidence for a Role of 5-HT-glutamate Co-releasing Neurons in Acute Stress Mechanisms

A major subpopulation of midbrain 5-hydroxytryptamine (5-HT) neurons expresses the vesicular glutamate transporter 3 (VGLUT3) and co-releases 5-HT and glutamate, but the function of this co-release is unclear. Given the strong links between 5-HT and uncontrollable stress, we used a combination of c-Fos immunohistochemistry and conditional gene knockout mice to test the hypothesis that glutamate co-releasing 5-HT neurons are activated by stress and involved in stress coping. Acute, uncontrollable swim stress increased c-Fos immunoreactivity in neurons co-expressing VGLUT3 and the 5-HT marker tryptophan hydroxylase 2 (TPH2) in the dorsal raphe nucleus (DRN). This effect was localized in the ventral DRN subregion and prevented by the antidepressant fluoxetine. In contrast, a more controllable stressor, acute social defeat, had no effect on c-Fos immunoreactivity in VGLUT3-TPH2 co-expressing neurons in the DRN. To test whether activation of glutamate co-releasing 5-HT neurons was causally linked to stress coping, mice with a specific deletion of VGLUT3 in 5-HT neurons were exposed to acute swim stress. Compared to wildtype controls, the mutant mice showed increased climbing behavior, a measure of active coping. Wildtype mice also showed increased climbing when administered fluoxetine, revealing an interesting parallel between the behavioral effects of genetic loss of VGLUT3 in 5-HT neurons and 5-HT reuptake inhibition. We conclude that 5-HT-glutamate co-releasing neurons are recruited by exposure to uncontrollable stress. Furthermore, natural variation in the balance of 5-HT and glutamate co-released at the 5-HT synapse may impact stress susceptibility.

Continuous home cage monitoring of activity and sleep in mice during repeated paroxetine treatment and discontinuation

RATIONALE

Non-invasive home cage monitoring is emerging as a valuable tool to assess the effects of experimental interventions on mouse behaviour. A field in which these techniques may prove useful is the study of repeated selective serotonin reuptake inhibitor (SSRI) treatment and discontinuation. SSRI discontinuation syndrome is an under-researched condition that includes the emergence of sleep disturbances following treatment cessation.

OBJECTIVES

We used passive infrared (PIR) monitoring to investigate changes in activity, sleep, and circadian rhythms during repeated treatment with the SSRI paroxetine and its discontinuation in mice.

METHODS

Male mice received paroxetine (10 mg/kg/day, s.c.) for 12 days, then were swapped to saline injections for a 13 day discontinuation period and compared to mice that received saline injections throughout. Mice were continuously tracked using the Continuous Open Mouse Phenotyping of Activity and Sleep Status (COMPASS) system.

RESULTS

Repeated paroxetine treatment reduced activity and increased behaviourally-defined sleep in the dark phase. These effects recovered to saline-control levels within 24 h of paroxetine cessation, yet there was also evidence of a lengthening of sleep bouts in the dark phase for up to a week following discontinuation.

CONCLUSIONS

This study provides the first example of how continuous non-invasive home cage monitoring can be used to detect objective behavioural changes in activity and sleep during and after drug treatment in mice. These data suggest that effects of paroxetine administration reversed soon after its discontinuation but identified an emergent change in sleep bout duration, which could be used as a biomarker in future preclinical studies to prevent or minimise SSRI discontinuation symptoms.

Effect of selective serotonin reuptake inhibitor discontinuation on anxiety-like behaviours in mice

BACKGROUND

Abrupt cessation of therapy with a selective serotonin reuptake inhibitor (SSRI) is associated with a discontinuation syndrome, typified by numerous disabling symptoms, including anxiety. Surprisingly, little is known of the behavioural effect of SSRI discontinuation in animals.

AIM

Here, the effect of SSRI discontinuation on anxiety-like behaviour was systematically investigated in mice.

METHODS

Experiments were based on a three-arm experimental design comprising saline, continued SSRI and discontinued SSRI. Mice were assessed 2 days after SSRI discontinuation over a 5-day period using the elevated plus maze (EPM) and other anxiety tests.

RESULTS

An exploratory experiment found cessation of paroxetine (12 days) was associated with decreased open-arm exploration and reduced total distance travelled, in male but not female mice. Follow-up studies confirmed a discontinuation effect on the EPM in male mice after paroxetine (12 days) and also citalopram (12 days). Mice receiving continued paroxetine (but not citalopram) also showed decreased open-arm exploration but this was dissociable from the effects of discontinuation. The discontinuation response to paroxetine did not strengthen after 28 days of treatment but was absent after 7 days of treatment. A discontinuation response was not discernible in other anxiety and fear-learning tests applied 3-5 days after treatment cessation. Finally, discontinuation effects on the EPM were typically associated with decreased locomotion on the test. However, separate locomotor testing implicated anxiety-provoked behavioural inhibition rather than a general reduction in motor activity.

CONCLUSION

Overall, this study provides evidence for a short-lasting behavioural discontinuation response to cessation of SSRI treatment in mice.

The impact of resistance training on strength and correlates of physical activity in youth

Resistance training (RT) may have a positive impact on specific correlates of physical activity (PA) in inactive and/or obese youth, with strength as a possible underlying mechanism. The aim of this study was to investigate this. Twelve participants (aged 8.9 ± 1.0 years) were assigned to an experimental group (EG) or control group (CG). Pre and post intervention assessments for strength, physical self-perceptions (PSPs), weight status, fundamental movement skills (FMS), and PA levels were completed. The EG participated in a twice-weekly 10-week RT programme. There were significant group x time interactions for FMS (CAMSA total P = 0.016, CAMSA skill score P = 0.036) and stretch stature (P = 0.002) (EG larges changes than the CG). Large effect sizes for the differences in change scores between the EG and CG were evident for CAMSA total score (Hedges' g = 0.830, P = 0.138), CAMSA skill score (Hedges' g = 0.895, P = 0.112) and relative strength (Hedges' g = 0.825, P = 0.140). This study demonstrated that a 10-week RT intervention has a positive effect on strength and FMS, and may also benefit weight status and PSPs. This study supports the development of RT interventions to develop these correlates, and increase PA levels.

Identification and spatio-temporal expression analysis of barley genes that encode putative modular xylanolytic enzymes

Arabinoxylans are cell wall polysaccharides whose re-modelling and degradation during plant development are mediated by several classes of xylanolytic enzymes. Here, we present the identification and new annotation of twelve putative (1,4)-β-xylanase and six β-xylosidase genes, and their spatio-temporal expression patterns during vegetative and reproductive growth of barley (Hordeum vulgare cv. Navigator). The encoded xylanase proteins are all predicted to contain a conserved carbohydrate-binding module (CBM) and a catalytic glycoside hydrolase (GH) 10 domain. Additional domains in some xylanases define three discrete phylogenetic clades: one clade contains proteins with an additional N-terminal signal sequence, while another clade contains proteins with multiple CBMs. Homology modelling revealed that all fifteen xylanases likely contain a third domain, a β-sandwich folded from two non-contiguous sequence segments that bracket the catalytic GH domain, which may explain why the full length protein is required for correct folding of the active enzyme. Similarly, predicted xylosidase proteins share a highly conserved domain structure, each with an N-terminal signal peptide, a split GH 3 domain, and a C-terminal fibronectin-like domain. Several genes appear to be ubiquitously expressed during barley growth and development, while four newly annotated xylanase and xylosidase genes are expressed at extremely high levels, which may be of broader interest for industrial applications where cell wall degradation is necessary.

Genes That Mediate Starch Metabolism in Developing and Germinated Barley Grain

Starch is synthesized in the endosperm of developing barley grain, where it functions as the primary source of stored carbohydrate. In germinated grain these starch reserves are hydrolyzed to small oligosaccharides and glucose, which are transported to the embryo to support the growth of the developing seedling. Some of the mobilized glucose is transiently stored as starch in the scutellum of germinated grain. These processes are crucial for early seedling vigor, which is a key determinant of crop productivity and global food security. Several starch synthases (SS), starch-branching enzymes (SBEs), and starch debranching enzymes (isoamylases, ISA), together with a limit dextrinase (LD), have been implicated in starch synthesis from nucleotide-sugar precursors. Starch synthesis occurs both in the developing endosperm and in the scutellum of germinated grain. For the complete depolymerization of starch to glucose, α-amylase (Amy), β-amylase (Bmy), isoamylase (ISA), limit dextrinase (LD), and α-glucosidase (AGL) are required. Most of these enzymes are encoded by gene families of up to 10 or more members. Here RNA-seq transcription data from isolated tissues of intact developing and germinated barley grain have allowed us to identify the most important, specific gene family members for each of these processes in vivo and, at the same time, we have defined in detail the spatio-temporal coordination of gene expression in different tissues of the grain. A transcript dataset for 81,280 genes is publicly available as a resource for investigations into other cellular and biochemical processes that occur in the developing grain from 6 days after pollination.

Transcriptional and biochemical analyses of gibberellin expression and content in germinated barley grain

Mobilization of reserves in germinated cereal grains is critical for early seedling vigour, global crop productivity, and hence food security. Gibberellins (GAs) are central to this process. We have developed a spatio-temporal model that describes the multifaceted mechanisms of GA regulation in germinated barley grain. The model was generated using RNA sequencing transcript data from tissues dissected from intact, germinated grain, which closely match measurements of GA hormones and their metabolites in those tissues. The data show that successful grain germination is underpinned by high concentrations of GA precursors in ungerminated grain, the use of independent metabolic pathways for the synthesis of several bioactive GAs during germination, and a capacity to abort bioactive GA biosynthesis. The most abundant bioactive form is GA1, which is synthesized in the scutellum as a glycosyl conjugate that diffuses to the aleurone, where it stimulates de novo synthesis of a GA3 conjugate and GA4. Synthesis of bioactive GAs in the aleurone provides a mechanism that ensures the hormonal signal is relayed from the scutellum to the distal tip of the grain. The transcript data set of 33 421 genes used to define GA metabolism is available as a resource to analyse other physiological processes in germinated grain.

Overexpression of HvCslF6 in barley grain alters carbohydrate partitioning plus transfer tissue and endosperm development

In cereal grain, sucrose is converted into storage carbohydrates: mainly starch, fructan, and mixed-linkage (1,3;1,4)-β-glucan (MLG). Previously, endosperm-specific overexpression of the HvCslF6 gene in hull-less barley was shown to result in high MLG and low starch content in mature grains. Morphological changes included inwardly elongated aleurone cells, irregular cell shapes of peripheral endosperm, and smaller starch granules of starchy endosperm. Here we explored the physiological basis for these defects by investigating how changes in carbohydrate composition of developing grain impact mature grain morphology. Augmented MLG coincided with increased levels of soluble carbohydrates in the cavity and endosperm at the storage phase. Transcript levels of genes relating to cell wall, starch, sucrose, and fructan metabolism were perturbed in all tissues. The cell walls of endosperm transfer cells (ETCs) in transgenic grain were thinner and showed reduced mannan labelling relative to the wild type. At the early storage phase, ruptures of the non-uniformly developed ETCs and disorganization of adjacent endosperm cells were observed. Soluble sugars accumulated in the developing grain cavity, suggesting a disturbance of carbohydrate flow from the cavity towards the endosperm, resulting in a shrunken mature grain phenotype. Our findings demonstrate the importance of regulating carbohydrate partitioning in maintenance of grain cellularization and filling processes.

Revised Phylogeny of the Cellulose Synthase Gene Superfamily: Insights into Cell Wall Evolution

Cell walls are crucial for the integrity and function of all land plants and are of central importance in human health, livestock production, and as a source of renewable bioenergy. Many enzymes that mediate the biosynthesis of cell wall polysaccharides are encoded by members of the large cellulose synthase (CesA) gene superfamily. Here, we analyzed 29 sequenced genomes and 17 transcriptomes to revise the phylogeny of the CesA gene superfamily in angiosperms. Our results identify ancestral gene clusters that predate the monocot-eudicot divergence and reveal several novel evolutionary observations, including the expansion of the Poaceae-specific cellulose synthase-like CslF family to the graminids and restiids and the characterization of a previously unreported eudicot lineage, CslM, that forms a reciprocally monophyletic eudicot-monocot grouping with the CslJ clade. The CslM lineage is widely distributed in eudicots, and the CslJ clade, which was thought previously to be restricted to the Poales, is widely distributed in monocots. Our analyses show that some members of the CslJ lineage, but not the newly identified CslM genes, are capable of directing (1,3;1,4)-β-glucan biosynthesis, which, contrary to current dogma, is not restricted to Poaceae.

Method for hull-less barley transformation and manipulation of grain mixed-linkage beta-glucan

Hull-less barley is increasingly offering scope for breeding grains with improved characteristics for human nutrition; however, recalcitrance of hull-less cultivars to transformation has limited the use of these varieties. To overcome this limitation, we sought to develop an effective transformation system for hull-less barley using the cultivar Torrens. Torrens yielded a transformation efficiency of 1.8%, using a modified Agrobacterium transformation method. This method was used to over-express genes encoding synthases for the important dietary fiber component, (1,3;1,4)-β-glucan (mixed-linkage glucan), primarily present in starchy endosperm cell walls. Over-expression of the HvCslF6 gene, driven by an endosperm-specific promoter, produced lines where mixed-linkage glucan content increased on average by 45%, peaking at 70% in some lines, with smaller increases in transgenic HvCslH1 grain. Transgenic HvCslF6 lines displayed alterations where grain had a darker color, were more easily crushed than wild type and were smaller. This was associated with an enlarged cavity in the central endosperm and changes in cell morphology, including aleurone and sub-aleurone cells. This work provides proof-of-concept evidence that mixed-linkage glucan content in hull-less barley grain can be increased by over-expression of the HvCslF6 gene, but also indicates that hull-less cultivars may be more sensitive to attempts to modify cell wall composition.

Morphology, Carbohydrate Distribution, Gene Expression, and Enzymatic Activities Related to Cell Wall Hydrolysis in Four Barley Varieties during Simulated Malting

Many biological processes, such as cell wall hydrolysis and the mobilisation of nutrient reserves from the starchy endosperm, require stringent regulation to successfully malt barley (Hordeum vulgare) grain in an industrial context. Much of the accumulated knowledge defining these events has been collected from individual, unrelated experiments, and data have often been extrapolated from Petri dish germination, rather than malting, experiments. Here, we present comprehensive morphological, biochemical, and transcript data from a simulated malt batch of the three elite malting cultivars Admiral, Navigator, and Flagship, and the feed cultivar Keel. Activities of lytic enzymes implicated in cell wall and starch depolymerisation in germinated grain have been measured, and transcript data for published cell wall hydrolytic genes have been provided. It was notable that Flagship and Keel exhibited generally similar patterns of enzyme and transcript expression, but exhibited a few key differences that may partially explain Flagship's superior malting qualities. Admiral and Navigator also showed matching expression patterns for these genes and enzymes, but the patterns differed from those of Flagship and Keel, despite Admiral and Navigator having Keel as a common ancestor. Overall (1,3;1,4)-β-glucanase activity differed between cultivars, with lower enzyme levels and concomitantly higher amounts of (1,3;1,4)-β-glucan in the feed variety, Keel, at the end of malting. Transcript levels of the gene encoding (1,3;1,4)-β-glucanase isoenzyme EI were almost three times higher than those encoding isoenzyme EII, suggesting a previously unrecognised importance for isoenzyme EI during malting. Careful morphological examination showed that scutellum epithelial cells in mature dry grain are elongated but expand no further as malting progresses, in contrast to equivalent cells in other cereals, perhaps demonstrating a morphological change in this critical organ over generations of breeding selection. Fluorescent immuno-histochemical labelling revealed the presence of pectin in the nucellus and, for the first time, significant amounts of callose throughout the starchy endosperm of mature grain.

Isolation of tissues and preservation of RNA from intact, germinated barley grain

Isolated barley (Hordeum vulgare L.) aleurone layers have been widely used as a model system for studying gene expression and hormonal regulation in germinating cereal grains. A serious technological limitation of this approach has been the inability to confidently extrapolate conclusions obtained from isolated tissues back to the whole grain, where the co-location of several living and non-living tissues results in complex tissue-tissue interactions and regulatory pathways coordinated across the multiple tissues. Here we have developed methods for isolating fragments of aleurone, starchy endosperm, embryo, scutellum, pericarp-testa, husk and crushed cell layers from germinated grain. An important step in the procedure involves the rapid fixation of the intact grain to freeze the transcriptional activity of individual tissues while dissection is effected for subsequent transcriptomic analyses. The developmental profiles of 19 611 gene transcripts were precisely defined in the purified tissues and in whole grain during the first 24 h of germination by RNA sequencing. Spatial and temporal patterns of transcription were validated against well-defined data on enzyme activities in both whole grain and isolated tissues. Transcript profiles of genes involved in mitochondrial assembly and function were used to validate the very early stages of germination, while the profiles of genes involved in starch and cell wall mobilisation matched existing data on activities of corresponding enzymes. The data will be broadly applicable for the interrogation of co-expression and differential expression patterns and for the identification of transcription factors that are important in the early stages of grain and seed germination.

Water uptake in barley grain: Physiology; genetics and industrial applications

Water uptake by mature barley grains initiates germination and is the first stage in the malting process. Here we have investigated the effects of starchy endosperm cell wall thickness on water uptake, together with the effects of varying amounts of the wall polysaccharide, (1,3;1,4)-β-glucan. In the latter case, we examined mutant barley lines from a mutant library and transgenic barley lines in which the (1,3;1,4)-β-glucan synthase gene, HvCslF6, was down-regulated by RNA interference. Neither cell wall thickness nor the levels of grain (1,3;1,4)-β-glucan were significantly correlated with water uptake but are likely to influence modification during malting. However, when a barley mapping population was phenotyped for rate of water uptake into grain, quantitative trait locus (QTL) analysis identified specific regions of chromosomes 4H, 5H and 7H that accounted for approximately 17%, 18% and 11%, respectively, of the phenotypic variation. These data indicate that variation in water uptake rates by elite malting cultivars of barley is genetically controlled and a number of candidate genes that might control the trait were identified under the QTL. The genomics data raise the possibility that the genetic variation in water uptake rates might be exploited by breeders for the benefit of the malting and brewing industries.

Genetics and physiology of cell wall polysaccharides in the model C4 grass, Setaria viridis spp

BACKGROUND

Setaria viridis has emerged as a model species for the larger C4 grasses. Here the cellulose synthase (CesA) superfamily has been defined, with an emphasis on the amounts and distribution of (1,3;1,4)-β-glucan, a cell wall polysaccharide that is characteristic of the grasses and is of considerable value for human health.

METHODS

Orthologous relationship of the CesA and Poales-specific cellulose synthase-like (Csl) genes among Setaria italica (Si), Sorghum bicolor (Sb), Oryza sativa (Os), Brachypodium distachyon (Bradi) and Hordeum vulgare (Hv) were compared using bioinformatics analysis. Transcription profiling of Csl gene families, which are involved in (1,3;1,4)-β-glucan synthesis, was performed using real-time quantitative PCR (Q-PCR). The amount of (1,3;1,4)-β-glucan was measured using a modified Megazyme assay. The fine structures of the (1,3;1,4)-β-glucan, as denoted by the ratio of cellotriosyl to cellotetraosyl residues (DP3:DP4 ratio) was assessed by chromatography (HPLC and HPAEC-PAD). The distribution and deposition of the MLG was examined using the specific antibody BG-1 and captured using fluorescence and transmission electron microscopy (TEM).

RESULTS

The cellulose synthase gene superfamily contains 13 CesA and 35 Csl genes in Setaria. Transcript profiling of CslF, CslH and CslJ gene families across a vegetative tissue series indicated that SvCslF6 transcripts were the most abundant relative to all other Csl transcripts. The amounts of (1,3;1,4)-β-glucan in Setaria vegetative tissues ranged from 0.2% to 2.9% w/w with much smaller amounts in developing grain (0.003% to 0.013% w/w). In general, the amount of (1,3;1,4)-β-glucan was greater in younger than in older tissues. The DP3:DP4 ratios varied between tissue types and across developmental stages, and ranged from 2.4 to 3.0:1. The DP3:DP4 ratios in developing grain ranged from 2.5 to 2.8:1. Micrographs revealing the distribution of (1,3;1,4)-β-glucan in walls of different cell types and the data were consistent with the quantitative (1,3;1,4)-β-glucan assays.

CONCLUSION

The characteristics of the cellulose synthase gene superfamily and the accumulation and distribution of (1,3;1,4)-β-glucans in Setaria are similar to those in other C4 grasses, including sorghum. This suggests that Setaria is a suitable model plant for cell wall polysaccharide biology in C4 grasses.

Distribution, structure and biosynthetic gene families of (1,3;1,4)-β-glucan in Sorghum bicolor

In cereals, the presence of soluble polysaccharides including (1,3;1,4)-β-glucan has downstream implications for human health, animal feed and biofuel applications. Sorghum bicolor (L.) Moench is a versatile crop, but there are limited reports regarding the content of such soluble polysaccharides. Here, the amount of (1,3;1,4)-β-glucan present in sorghum tissues was measured using a Megazyme assay. Very low amounts were present in the grain, ranging from 0.16%-0.27% (w/w), while there was a greater quantity in vegetative tissues at 0.12-1.71% (w/w). The fine structure of (1,3;1,4)-β-glucan, as denoted by the ratio of cellotriosyl and cellotetraosyl residues, was assessed by high performance liquid chromatography (HPLC) and ranged from 2.6-3:1 in the grain, while ratios in vegetative tissues were lower at 2.1-2.6:1. The distribution of (1,3;1,4)-β-glucan was examined using a specific antibody and observed with fluorescence and transmission electron microscopy. Micrographs showed a variable distribution of (1,3;1,4)-β-glucan influenced by temporal and spatial factors. The sorghum orthologs of genes implicated in the synthesis of (1,3;1,4)-β-glucan in other cereals, such as the Cellulose synthase-like (Csl) F and H gene families were defined. Transcript profiling of these genes across sorghum tissues was carried out using real-time quantitative polymerase chain reaction, indicating that, as in other cereals, CslF6 transcripts dominated.

Pattern of deposition of cell wall polysaccharides and transcript abundance of related cell wall synthesis genes during differentiation in barley endosperm

Immunolabeling, combined with chemical analyses and transcript profiling, have provided a comprehensive temporal and spatial picture of the deposition and modification of cell wall polysaccharides during barley (Hordeum vulgare) grain development, from endosperm cellularization at 3 d after pollination (DAP) through differentiation to the mature grain at 38 DAP. (1→3)-β-D-Glucan appears transiently during cellularization but reappears in patches in the subaleurone cell walls around 20 DAP. (1→3, 1→4)-β-Glucan, the most abundant polysaccharide of the mature barley grain, accumulates throughout development. Arabino-(1-4)-β-D-xylan is deposited significantly earlier than we previously reported. This was attributable to the initial deposition of the polysaccharide in a highly substituted form that was not recognized by antibodies commonly used to detect arabino-(1-4)-β-D-xylans in sections of plant material. The epitopes needed for antibody recognition were exposed by pretreatment of sections with α-L-arabinofuranosidase; this procedure showed that arabino-(1-4)-β-D-xylans were deposited as early as 5 DAP and highlighted their changing structures during endosperm development. By 28 DAP labeling of hetero-(1→4)-β-D-mannan is observed in the walls of the starchy endosperm but not in the aleurone walls. Although absent in mature endosperm cell walls we now show that xyloglucan is present transiently from 3 until about 6 DAP and disappears by 8 DAP. Quantitative reverse transcription-polymerase chain reaction of transcripts for GLUCAN SYNTHASE-LIKE, Cellulose Synthase, and CELLULOSE SYNTHASE-LIKE genes were consistent with the patterns of polysaccharide deposition. Transcript profiling of some members from the Carbohydrate-Active Enzymes database glycosyl transferase families GT61, GT47, and GT43, previously implicated in arabino-(1-4)-β-d-xylan biosynthesis, confirms their presence during grain development.

Over-expression of specific HvCslF cellulose synthase-like genes in transgenic barley increases the levels of cell wall (1,3;1,4)-β-d-glucans and alters their fine structure

Cell walls in commercially important cereals and grasses are characterized by the presence of (1,3;1,4)-β-d-glucans. These polysaccharides are beneficial constituents of human diets, where they can reduce the risk of hypercholesterolemia, type II diabetes, obesity and colorectal cancer. The biosynthesis of cell wall (1,3;1,4)-β-d-glucans in the Poaceae is mediated, in part at least, by the cellulose synthase-like CslF family of genes. Over-expression of the barley CslF6 gene under the control of an endosperm-specific oat globulin promoter results in increases of more than 80% in (1,3;1,4)-β-d-glucan content in grain of transgenic barley. Analyses of (1,3;1,4)-β-d-glucan fine structure indicate that individual CslF enzymes might direct the synthesis of (1,3;1,4)-β-d-glucans with different structures. When expression of the CslF6 transgene is driven by the Pro35S promoter, the transgenic lines have up to sixfold higher levels of (1,3;1,4)-β-d-glucan in leaves, but similar levels as controls in the grain. Some transgenic lines of Pro35S:CslF4 also show increased levels of (1,3;1,4)-β-d-glucans in grain, but not in leaves. Thus, the effects of CslF genes on (1,3;1,4)-β-d-glucan levels are dependent not only on the promoter used, but also on the specific member of the CslF gene family that is inserted into the transgenic barley lines. Altering (1,3;1,4)-β-d-glucan levels in grain and vegetative tissues will have potential applications in human health, where (1,3;1,4)-β-d-glucans contribute to dietary fibre, and in tailoring the composition of biomass cell walls for the production of bioethanol from cereal crop residues and grasses.

Helicobacter pylori upregulates matrilysin (MMP-7) in epithelial cells in vivo and in vitro in a Cag dependent manner

BACKGROUND AND AIMS

Matrix metalloproteinase-7 (MMP-7) is important in normal and pathological remodelling of epithelial-matrix interactions, and is upregulated in gastric cancer. Helicobacter pylori infection is the first stage in gastric carcinogenesis, and therefore our aim was to determine if H pylori upregulated gastric MMP-7 expression and if this was affected by strain virulence.

METHODS

We took gastric biopsy specimens at endoscopy from H pylori infected (n = 17) and uninfected (n = 18) patients and assessed MMP-7 expression by ELISA, real time polymerase chain reaction (PCR), and immunohistochemistry (concentrating on epithelial cells in the proliferative zone). We PCR typed H pylori for cagE and vacA. We performed H pylori/cell line coculture studies with wild-type pathogenic and non-pathogenic H pylori strains and with CagE(-) and VacA(-) isogenic mutants.

RESULTS

Gastric biopsy specimens from H pylori+ patients expressed higher levels of MMP-7 at the protein and mRNA levels in the antrum and corpus (for example, by ELISA: H pylori+ 0.182 OD units vH pylori- 0.059; p = 0.009 antrum). Epithelial cells from H pylori+ patients stained more intensely for MMP-7 than those from uninfected patients, including in the proliferative zone containing pluripotent cells (p<0.03 antrum, p<0.04 body). Upregulation of MMP-7 in epithelial cells was confirmed at the protein and mRNA levels by H pylori/cell line coculture. These experiments also showed that MMP-7 upregulation was dependent on an intact H pyloricag pathogenicity island but not on the vacuolating cytotoxin.

CONCLUSION

We speculate that increased expression of MMP-7 in H pylori gastritis may contribute to gastric carcinogenesis.

Matrix metalloproteinases 2 and 9 in otitis media with effusion

A qualitative and quantitative study of the presence of matrix metalloproteinase 2 (MMP 2) and matrix metalloproteinase 9 (MMP 9), in the effusions of otitis media with effusion (OME), was performed. The activity of the above enzymes was compared in thick and thin effusions, and concentrations compared in samples from children with one, two, three and four sets of ventilation tubes. The activity of both MMP 2 and MMP 9 was higher in thick than thin effusions, P = 0.07 and P = 0.04, respectively. The concentrations of MMP 9 did not vary with the number of tube insertions but those of MMP 2 did (ANOVA P < 0.05). MMPs may be involved in tympanic membrane damage and prognosis of OME.

Spectrum of matrix metalloproteinase expression in primary and metastatic colon cancer: relationship to the tissue inhibitors of metalloproteinases and membrane type-1-matrix metalloproteinase

The matrix metalloproteinases, MMP-2 and MMP-9, are capable of degrading components of the basement membrane, a vital barrier breached during the progression of colorectal cancer. The regulation of MMP-2 activation and subsequent targets is vital to understanding the metastatic process. MMP-2 was not expressed by colorectal cancer cells (C170 and C170HM(2)) in vitro but by stromal fibroblasts (46BR.1GI). There was induction of this MMP upon transwell co-cultivation of the colon cancer cells with the fibroblasts but in vivo growth did not lead to a similar increase in the metastatic tumour cells (C170HM(2)), MMP-2 again being attributed to the stromal cells. MMP-2 mRNA was overexpressed in human colorectal tumours compared to normal colorectal tissue, which correlated with Dukes' stage and immunolocalized to the stromal compartment of the tumour tissue. The active form of the MMP-2 enzyme was also present in the colorectal tumour tissue (7/8) but essentially absent in all normal colon samples examined (1/8). MMP-2 activation was not related to an increase in MT-1-MMP mRNA or a decrease in the specific inhibitor TIMP-2 in human tissue. There was however an increase in MMP-2/TIMP-2 ratio in tumour compared to normal. MMP-9, a target of active MMP-2, was present in the metastatic cell line but expression was down-regulated in the tumour cells in vivo, gelatin analysis revealed that MMP-9 was almost entirely attributable to the murine host, confirmed by PCR. There was no increase in mRNA for MMP-9 or its specific inhibitor TIMP-1 in colorectal tumour tissue compared to normal, MMP-9 protein localized to the inflammatory infiltrate. Fibroblast cells may provide malignant epithelial cells with a ready source of enzyme which is crucial to the metastatic process.

Increased type-IV collagenase (MMP-2 and MMP-9) activity following preoperative radiotherapy in rectal cancer

The aim of this study was to investigate the effect of preoperative high-dose radiotherapy (25 Gy in 5 fractions over 5 days) on the type-IV collagenase protein profile, in patients with resectable rectal cancer, by gelatin zymography. Biopsy samples of tumour and distant normal mucosa from 12 patients with resectable rectal cancer were obtained pre- and post-radiotherapy. Expression of type-IV collagenases (both pro- and active forms) was studied using gelatin zymography. Enzyme levels were normalized for total protein content of each sample. Rectal cancer specimens expressed both pro (72 kDa) and active (62 kDa) forms of MMP-2 but only the pro form of MMP-9 (92 kDa). Normal mucosa showed expression of the pro forms of MMP-2 and MMP-9 while no active form of either enzyme was detected in any of the samples. A significant three- to fourfold increase (P < 0.01) of active matrix metalloproteinases (MMP)-2 (62 kDa) was seen in malignant rectal mucosa after radiotherapy. The effect of radiotherapy also led to a twofold increase (P = 0.047) of pro MMP-2 (72 kDa) and a two- to threefold increase (P = 0.03) of the precursor form of MMP-9 (92 kDa). In contrast, in normal mucosa expression of the precursor form of MMP-9 (92 kDa) did not change after radiation, and no significant effect on the levels of pro MMP-2 (72 kDa) was observed. Preoperative high-dose radiotherapy leads to an increase in activity of type-IV collagenases in patients with resectable rectal cancer. Type-IV collagenase inhibition may be a useful therapeutic adjunct to radiotherapy in rectal cancer.

Inhibition of tumour growth by marimastat in a human xenograft model of gastric cancer: relationship with levels of circulating CEA

Inhibition of matrix metalloproteinases (MMPs) is an attractive approach to adjuvant therapy in the treatment of cancer. Marimastat is the first orally administered, synthetic MMP inhibitor to be evaluated, in this capacity, in the clinic. Measurement of the rate of change of circulating tumour antigens was used for evaluating biological activity and defining optimum dosage in the early clinical trials of marimastat. Although tumour antigen levels have been used in the clinical management of cancer for many years, they have not been validated as markers of disease progression. In order to investigate the relationship between the effects of marimastat on tumour growth and circulating tumour antigen levels, mice bearing the human gastric tumour, MGLVA1, were treated with marimastat. The MMP inhibitor exerted a significant therapeutic effect, reducing tumour growth rate by 48% (P = 0.0005), and increasing median survival from 19 to 30 days (P = 0.0001). In addition, carcinoembryonic antigen (CEA) levels were measured in serum samples from animals sacrificed at regular intervals, and correlated with excised tumour weight. It was shown that the natural log of the CEA concentration was linearly related to the natural log of the tumour weight and that treatment was not a significant factor in this relationship (P = 0.7). In conclusion, circulating CEA levels were not directly affected by marimastat, but did reflect tumour size. These results support the use of cancer antigens as markers of biological activity in early phase trials of non-cytotoxic anticancer agents.

Experimental studies with Stronglyloides papillosus in goats

Unusual clinical and pathological observations in the field in goats and sheep suffering from Strongyloides papillosus infection prompted experimental work on this parasite. Goats were infected percutaneously with either single or multiple, low or high levels of S. papillosus. Young goats up to 12 months of age were found to be the most susceptible. Some animals, however, showed substantial resistance to infective doses. Clinical signs included transient diarrhoea, misshapen, elongated faecal pellets terminally, dehydration, anorexia, cachexia, gnashing of teeth, foaming at the mouth, anaemia and nervous signs such as ataxia, a wide-based stance, stupor and nystagmus. A 'pushing syndrome' was seen in 22% of the animals. The pathological changes are described and included enteritis, status spongiosus in the brain, hepatosis leading to rupture of the liver, nephrosis, pulmonary oedema, interstitial pneumonia and pneumonia. About 6% of the goats died acutely from fatal hepatic rupture. The development of an acquired immunity was determined. The immunity elicited an allergic skin reaction at the application site of larvae or injection sites of larval metabolites. This immunity, however, could be breached by large doses of larvae. The most profound clinicopathological changes induced by the parasites were an anaemia (most pronounced in the young goats) and hypophosphataemia. Trace element analyses provided evidence of Cu, Mn and possibly Se deficiencies in some goats.

Gelatinase (MMP-2 and -9) expression in gastrointestinal malignancy

The aim of the study was to investigate expression of the active and inactive gelatinases (MMP-2 and -9) in colorectal neoplasia and gastric cancer compared with normal mucosa. A total of 53 colorectal cancers and corresponding normal mucosa were studied using gelatin zymography as well as 15 colorectal adenomas and 13 gastric cancers with corresponding normal mucosa. Overexpression of all the gelatinases occurs in both colorectal and gastric cancer, with activation of MMP-2 appearing to be a feature of the malignant phenotype. Overexpression of MMP-9 occurs in colorectal adenomas. The gelatinases are overexpressed in gastrointestinal neoplasia, suggesting that these enzymes may have an important role in tumour invasion and metastasis.

Matrix metalloproteinases

BACKGROUND

The matrix metalloproteinases (MMPs) have a role in gastrointestinal malignancy. This role is reviewed, with particular reference to the gelatinase subgroup of enzymes.

METHODS

All relevant papers derived from the Medline and Enbase databases between 1984 and early 1996 were reviewed.

RESULT AND CONCLUSION

There is now strong evidence that MMPs play a major role in tumour invasion and metastasis. The development of MMP inhibitors may lead to important new treatment for the control of malignant disease.