Diagnostic challenges of focal nodular hyperplasia: interobserver variability, accuracy, and the utility of glutamine synthetase immunohistochemistry.

AIMS: The diagnosis of focal nodular hyperplasia (FNH) and the interpretation of glutamine synthetase (GS) staining can be challenging on biopsies. We aimed to evaluate the reproducibility of needle biopsy diagnosis of FNH, the effect of GS immunohistochemistry on FNH diagnosis, and which histological features are most useful for the diagnosis of FNH. METHODS AND RESULTS: The study included virtual needle biopsies generated from 75 resection specimens (30 FNHs, 15 hepatocellular adenomas, 15 hepatocellular carcinomas, and 15 non-lesional liver specimens). Pathologists were reasonably accurate (83.1%) in the diagnosis of FNH with haematoxylin and eosin alone. Ductular reaction and nodularity had the highest sensitivity for a diagnosis of FNH (88.1% and 82.2%, respectively), whereas central scar was the most specific feature (90.6%). The presence of two or more of the classic histological features had 89.6% sensitivity and 86.2% specificity for a diagnosis of FNH. Diagnostic accuracy was significantly higher with the addition of a GS stain. A map-like GS staining pattern was highly specific (99.3%) for FNH. However, GS staining was interpreted as non-map-like in 14.4% of reviews of true FNH cases, and overall interobserver agreement for interpretation of the GS staining pattern was only moderate (kappa = 0.42). CONCLUSIONS: Pathologists are reasonably accurate in the diagnosis of FNH on virtual biopsies, and GS staining improves accuracy. However, a subset of FNH cases remain challenging. Steatosis and a pseudo-map-like GS staining pattern were associated with increased difficulty. Therefore, although a map-like GS staining pattern is useful for confirmation of a diagnosis, the lack of a map-like GS staining pattern on needle biopsy does not necessarily exclude a diagnosis of FNH.

Utility of glutamine synthetase immunohistochemistry in identifying features of regressed cirrhosis.

The prevailing view that cirrhosis is irreversible has been challenged. It has been proposed that varying degrees of fibrosis regression can be achieved if the injurious agent is removed. In the normal liver, glutamine synthetase immunostaining is present around central veins. In regressed cirrhosis, although fibrous bands between portal tracts and central veins may largely be resorbed, the abnormal portal tract-central vein adherence often remains. Hence, we hypothesized that aberrant glutamine synthetase positivity adjacent to portal tracts would help identify regressed cirrhosis. We performed glutamine synthetase immunohistochemistry on 49 liver specimens (16 regressed cirrhosis, 18 cirrhotic, and 15 normal livers). Qualification for regressed cirrhosis required the following histologic features: curved, delicate incomplete septa, portal tract-central vein adhesions, and portal tract "remnants" (portal tracts with no venous branch). Out of 16, 14 regressed cirrhosis cases had baseline cirrhosis established based on previous biopsy or signs of cirrhosis based on physical exam, laboratory, and radiological findings. All regressed cirrhosis cases (100%) had areas of aberrant glutamine synthetase positivity adjacent to portal tracts, indicating that portal tract-central vein approximation had occurred (p < 0.001 compared to all other categories). No normal cases had glutamine synthetase positivity adjacent to portal tracts, and half of cirrhosis cases had areas showing features of regression, with focal glutamine synthetase positivity adjacent to portal tracts. Overall, glutamine synthetase expression showed highly significant differences among the three categories (p < 0.001). This study shows that aberrant glutamine synthetase positivity adjacent to portal tracts is present in regressed cirrhosis and can be useful in identifying regressed cirrhosis when it is histologically suspected.

Genomic profiling of well-differentiated hepatocellular neoplasms with diffuse glutamine synthetase staining reveals similar genetics across the adenoma to carcinoma spectrum.

Well-differentiated hepatocellular neoplasms are currently classified in the World Health Organization scheme as hepatocellular adenoma or hepatocellular carcinoma. There is no recognized diagnostic category for atypical cases with borderline features, and we have designated these as atypical hepatocellular neoplasms. Diffuse glutamine synthetase staining is used as a surrogate marker to detect ß-catenin activation, a well-recognized high risk feature in hepatocellular tumors. This study examined 27 well-differentiated hepatocellular neoplasms with diffuse glutamine synthetase staining, including 7 atypical hepatocellular neoplasms with no cytoarchitectural atypia, 6 atypical hepatocellular neoplasms with focal cytoarchitectural atypia, and 14 well-differentiated hepatocellular carcinomas. Capture-based next-generation sequencing was performed, and alterations in WNT pathway genes (CTNNB1, APC, AXIN1) were seen in 81% of cases (10/13 atypical hepatocellular neoplasms and 12/14 of hepatocellular carcinomas), while the molecular basis of diffuse glutamine synthetase staining was unclear in the remaining 19% of cases. Additional non-WNT pathway mutations (TP53, TSC1, DNMT3A, CREBBP) or copy number alterations were present in 56% of atypical hepatocellular neoplasms, with no significant difference in cases with or without focal cytoarchitectural atypia, supporting that all cases with ß-catenin activation should be classified as atypical irrespective of atypia. Atypical hepatocellular neoplasm and hepatocellular carcinoma also demonstrated largely similar genomic profiles, but TERT promoter mutations were restricted to hepatocellular carcinoma (21%) and copy number alterations were more common in hepatocellular carcinoma (64 vs 31%). Mutational and copy number analysis may be helpful in characterization and risk stratification of atypical hepatocellular neoplasms when morphology and glutamine synthetase staining yield ambiguous results.

Urea cycle dysregulation in non-alcoholic fatty liver disease.

BACKGROUND & AIMS: In non-alcoholic steatohepatitis (NASH), the function of urea cycle enzymes (UCEs) may be affected, resulting in hyperammonemia and the risk of disease progression. We aimed to determine whether the expression and function of UCEs are altered in an animal model of NASH and in patients with non-alcoholic fatty liver disease (NAFLD), and whether this process is reversible. METHODS: Rats were first fed a high-fat, high-cholesterol diet for 10 months to induce NASH, before being switched onto a normal chow diet to recover. In humans, we obtained liver biopsies from 20 patients with steatosis and 15 with NASH. Primary rat hepatocytes were isolated and cultured with free fatty acids. We measured the gene and protein expression of ornithine transcarbamylase (OTC) and carbamoylphosphate synthetase (CPS1), as well as OTC activity, and ammonia concentrations. Moreover, we assessed the promoter methylation status of OTC and CPS1 in rats, humans and steatotic hepatocytes. RESULTS: In NASH animals, gene and protein expression of OTC and CPS1, and the activity of OTC, were reversibly reduced. Hypermethylation of Otc promoter genes was also observed. Additionally, in patients with NAFLD, OTC enzyme concentration and activity were reduced and ammonia concentrations were increased, which was further exacerbated in those with NASH. Furthermore, OTC and CPS1 promoter regions were hypermethylated. In primary hepatocytes, induction of steatosis was associated with Otc promoter hypermethylation, a reduction in the gene expression of Otc and Cps1, and an increase in ammonia concentration in the supernatant. CONCLUSION: NASH is associated with a reduction in the gene and protein expression, and activity, of UCEs. This results in hyperammonemia, possibly through hypermethylation of UCE genes and impairment of urea synthesis. Our investigations are the first to describe a link between NASH, the function of UCEs, and hyperammonemia, providing a novel therapeutic target. LAY SUMMARY: In patients with fatty liver disease, the enzymes that convert nitrogen waste into urea may be affected, leading to the accumulation of ammonia, which is toxic. This accumulation of ammonia can lead to scar tissue development, increasing the risk of disease progression. In this study, we show that fat accumulation in the liver produces a reversible reduction in the function of the enzymes that are involved in detoxification of ammonia. These data provide potential new targets for the treatment of fatty liver disease.

From large to small: the immunohistochemical panel in the diagnosis of early hepatocellular carcinoma.

AIMS: The aims of this study were to: validate the use of the immunohistochemical (IHC) markers glutamine synthetase (GS), glypican-3 (GPC3), heat shock protein-70 (HSP70) and enhancer of zeste homologue 2 (EZH2) in liver biopsies for the differential diagnosis between small hepatocellular carcinoma (HCC) and non-neoplastic liver nodules, with special attention to <10-mm nodules; and assess the actual sensitivity and specificity of the single markers, and their combination, in needle biopsies. METHODS AND RESULTS: One hundred liver nodules, i.e. 66 HCCs and 34 non-neoplastic nodules, were prospectively collected from 43 consecutive orthotopic liver transplantation patients, and subjected to 'backtable' needle biopsies directly on surgical specimens. IHC evaluation was semi-automatically performed with a Benchmark Ultra immunostainer. The morphological and IHC diagnosis in surgical specimens was considered to be the gold standard. GS, GPC3, HSP70 and EZH2 showed 16.6%, 10.7%, 28.8% and 62.1% decreases in sensitivity, respectively, from surgical specimen to needle biopsy. Higher decreases were observed in <10-mm nodules. In 18 HCCs with no morphological diagnostic features of malignancy in biopsies, GPC3 or GS were positive in 16; in seven HCCs, neither morphology nor IHC evaluation ruled out the differential diagnosis made on the basis of needle biopsy. CONCLUSIONS: We present for the first time a direct comparison between surgical specimens and needle biopsies to confirm the usefulness and reproducibility of the most widely used antibodies for the diagnosis of small liver nodules. Our results support the use of IHC evaluation in biopsies for the diagnosis of small liver lesions, although the IHC panel could also give negative results in the presence of obvious HCC, and the possibility of false positives should always be considered.

Glutamine synthetase gene knockout-human embryonic kidney 293E cells for stable production of monoclonal antibodies.

Previously, it was inferred that a high glutamine synthetase (GS) activity in human embryonic kidney (HEK) 293E cells results in elevated resistance to methionine sulfoximine (MSX) and consequently hampers GS-mediated gene amplification and selection by MSX. To overcome this MSX resistance in HEK293E cells, a GS-knockout HEK293E cell line was generated using the CRISPR/Cas9 system to target the endogenous human GS gene. The GS-knockout in the HEK293E cell line (RK8) was confirmed by Western blot analysis of GS and by observation of glutamine-dependent growth. Unlike the wild type HEK293E cells, the RK8 cells were successfully used as host cells to generate a recombinant HEK293E cell line (rHEK293E) producing a monoclonal antibody (mAb). When the RK8 cells were transfected with the GS expression vector containing the mAb gene, rHEK293E cells producing the mAb could be selected in the absence as well as in the presence of MSX. The gene copies and mRNA expression levels of the mAb in rHEK293E cells were also quantified using qRT-PCR. Taken together, the GS-knockout HEK293E cell line can be used as host cells to generate stable rHEK293E cells producing a mAb through GS-mediated gene selection in the absence as well as in the presence of MSX.

Complementary roles of ß-catenin and glutamine synthetase immunostaining in diagnosis of chemotherapy-treated and untreated hepatoblastoma.

BACKGROUND/PURPOSE: This study aimed to evaluate the expression of ß-catenin and its downstream target glutamine synthetase (GS) in hepatoblastoma (HB), and to evaluate the use of these two markers for diagnosing HB. METHODS: Eighteen untreated HBs and 22 HBs resected after neoadjuvant chemotherapy were analyzed using ß-catenin and GS immunostaining. RESULTS: We detected nuclear ß-catenin immunostaining in nearly all untreated HBs, including in fetal and embryonal epithelial components and in mesenchymal elements. We also observed diffuse GS expression in the epithelial component; however, it was frequently absent in embryonal and mesenchymal areas. In HBs resected after neoadjuvant chemotherapy, we recognized four histological patterns: fetal, hepatocellular-carcinoma-like, clear-cell, and normal-liver-like. All these patterns displayed diffuse GS expression. Fetal pattern showed diffuse nuclear ß-catenin immunostaining. Nuclear ß-catenin immunostaining was weak in the hepatocellular-carcinoma-like and clear-cell patterns. In normal-liver-like area, ß-catenin expression was only located in the cell membrane. CONCLUSION: The results suggest that nuclear ß-catenin expression and diffuse GS immunostaining are the hallmarks of HB. Although epithelial and mesenchymal components of HB display nuclear ß-catenin staining, this expression is attenuated following chemotherapy-induced cell maturation. GS immunostaining is especially useful for the assessment of section margins after neoadjuvant chemotherapy.

Combined use of heat-shock protein 70 and glutamine synthetase is useful in the distinction of typical hepatocellular adenoma from atypical hepatocellular neoplasms and well-differentiated hepatocellular carcinoma.

Well-differentiated hepatocellular carcinoma can mimic high-grade dysplastic nodule in cirrhotic liver and hepatocellular adenoma in non-cirrhotic liver. This study evaluates the efficacy of combined use of heat-shock protein 70 (HSP70), glutamine synthetase (GS) and glypican-3 in this setting. Immunohistochemistry for these three markers was done in 17 typical hepatocellular adenoma, 15 high-grade dysplastic nodules, 20 atypical hepatocellular neoplasms (14 clinically atypical and 6 pathologically atypical), 14 very well-differentiated hepatocellular carcinoma, and 43 well-differentiated hepatocellular carcinoma. All three markers were negative in typical adenomas. HSP70 was positive in 10, 71, and 67% of atypical neoplasms, very well-differentiated and well-differentiated HCC, respectively, while GS was positive in 60, 50, and 60% of atypical neoplasms, very well-differentiated and well-differentiated hepatocellular carcinoma, respectively. Glypican-3 was negative in all atypical neoplasms and very well-differentiated hepatocellular carcinoma, and was positive in 27% of well-differentiated hepatocellular carcinoma. Positive staining with at least one marker (HSP70 and/or GS) was seen in 85% of very well-differentiated hepatocellular carcinoma, which was similar to well-differentiated hepatocellular carcinoma (78%, P=0.4), and pathologically atypical cases (100%, P=0.5), but significantly higher compared with clinically atypical cases (43%. P=0.03) and none of typical adenomas (P<0.001). Positive staining with both GS and HSP70 was seen significantly more often in hepatocellular carcinoma compared with atypical neoplasms (45 vs 10%, P=0.004). Both these markers were also more often expressed in very well-differentiated hepatocellular carcinoma compared with atypical cases (38 vs 10%, P=0.06). In conclusion, the combined use of GS and HSP70 can be useful in the diagnosis of very well-differentiated hepatocellular carcinoma. These stains can also help in the distinction of typical adenoma from atypical hepatocellular neoplasms. Glypican-3 has low sensitivity and is not useful in this setting.

Remodeling of glial coverage of glutamatergic synapses in the rat nucleus tractus solitarii after ozone inhalation.

Besides the well-described inflammatory and dysfunction effects on the respiratory tract, accumulating evidence indicates that ozone (O3 ) exposure also affects central nervous system functions. However, the mechanisms through which O3 exerts toxic effects on the brain remain poorly understood. We previously showed that O3 exposure caused a neuronal activation in regions of the rat nucleus tractus solitarii (NTS) overlapping terminal fields of vagal lung afferents. Knowing that O3 exposure can impact astrocytic protein expression, we decided to investigate whether it may induce astroglial cellular alterations in the NTS. Using electron microscopy and immunoblot techniques, we showed that in O3 -exposed animals, the astrocytic coverage of NTS glutamatergic synapses was 19% increased while the astrocyte volume fraction and membrane density were not modified. Moreover, the expression of glial fibrillary acidic protein and S100ß, which are known to be increased in reactive astroglia, did not change. These results indicate that O3 inhalation induces a glial plasticity that is restricted to the peri-synaptic coverage without overall astroglial activation. Taken together, these findings, along with our previous observations, support the conclusion that O3 -induced pulmonary inflammation results in a specific activation of vagal lung afferents rather than non-specific overall brain alterations mediated by blood-borne agents. Exposure to ozone, a major atmospheric pollutant, induces an increase in the glial coverage of neurons that is restricted to peri-synaptic compartments. This observation does not support the view that the ozone-induced neuronal disorders are related to non-specific overall brain alterations. It rather argues for a specific activation of the vagus nerve in response to pulmonary inflammation.

Expression of glutamine synthetase in balloon cells: a basis of their antiepileptic role?

Glutamine synthetase is an enzyme involved in the clearance of glutamate, the most potent excitatory neurotransmitter. We studied the immunohistochemical expression of glutamine synthetase in neocortical samples from 5 children who underwent surgery for pharmacoresistant epilepsy and a histological diagnosis of focal cortical dysplasia IIb. In all cases, balloon cells, but not dysmorphic neurons, were immunopositive for glutamine synthetase. This finding suggests that balloon cells can be involved in the neutralization of glutamate and play a protective anti-seizure role.

Metabolic and phylogenetic analyses based on nitrogen in a new poly-γ-glutamic acid-producing strain of Bacillus subtilis.

OBJECTIVES: Nitrogen metabolism was investigated during poly-γ-glutamic acid (γ-PGA) synthesis and phylogenetic analyses was used to explore glutamate dependency in Bacillus subtilis HSF1410. RESULTS: Bacillus subtilis HSF1410 was cultured with (15)NH4+ in the medium, and the γ-PGA synthesized was then analyzed using (15)N-NMR. The γ-PGA framework was partially labeled with (15)N, indicating that γ-PGA was synthesized from inorganic nitrogen and carbohydrate. Assay of glutamate synthetase and glutamine synthetase activities also revealed that ammonium can be used to synthesize γ-PGA in HSF1410. Phylogenetic trees based on γ-PGA synthesis genes (pgsBCA) and 16S rRNA showed that HSF1410 falls within a cluster of glutamate-dependent strains, versus glutamate-independent strains, which is confirmed by HSF1410 being unable to produce γ-PGA without glutamate in its medium CONCLUSION: we classify B. subtilis HSF1410 as a glutamate-dependent strain that can use exogenous inorganic nitrogen sources to synthesize γ-PGA.

Diagnostic utility and limitations of glutamine synthetase and serum amyloid-associated protein immunohistochemistry in the distinction of focal nodular hyperplasia and inflammatory hepatocellular adenoma.

Inflammatory hepatocellular adenoma can show overlapping histological features with focal nodular hyperplasia, including inflammation, fibrous stroma, and ductular reaction. Expression of serum amyloid-associated protein in inflammatory hepatocellular adenoma and map-like pattern of glutamine synthetase in focal nodular hyperplasia can be helpful in this distinction, but the pitfalls and limitations of these markers have not been established. Morphology and immunohistochemistry were analyzed in 54 inflammatory hepatocellular adenomas, 40 focal nodular hyperplasia, and 3 indeterminate lesions. Morphological analysis demonstrated that nodularity, fibrous stroma, dystrophic blood vessels, and ductular reaction were more common in focal nodular hyperplasia, while telangiectasia, hemorrhage, and steatosis were more common in inflammatory hepatocellular adenoma, but there was frequent overlap of morphological features. The majority of inflammatory hepatocellular adenomas demonstrated perivascular and/or patchy glutamine synthetase staining (73.6%), while the remaining cases had diffuse (7.5%), negative (3.8%), or patchy pattern of staining (15%) that showed subtle differences from the classic map-like staining pattern and was designated as pseudo map-like staining. Positive staining for serum amyloid-associated protein was seen in the majority of inflammatory hepatocellular adenomas (92.6%) and in the minority of focal nodular hyperplasia (17.5%). The glutamine synthetase staining pattern was map-like in 90% of focal nodular hyperplasia cases, with the remaining 10% of cases showing pseudo map-like staining. Three cases were labeled as indeterminate and showed focal nodular hyperplasia-like morphology but lacked map-like glutamine synthetase staining pattern; these cases demonstrated a patchy pseudo map-like glutamine synthetase pattern along with the expression of serum amyloid-associated protein. Our results highlight the diagnostic errors that can be caused by variant patterns of staining with glutamine synthetase and serum amyloid-associated protein in inflammatory hepatocellular adenoma and focal nodular hyperplasia.

Hepatocellular carcinoma arising in adenoma: similar immunohistochemical and cytogenetic features in adenoma and hepatocellular carcinoma portions of the tumor.

Well-differentiated hepatocellular carcinoma in non-cirrhotic liver can show morphological features similar to hepatocellular adenoma. In rare instances, hepatocellular carcinoma can arise in the setting of hepatocellular adenoma. This study compares the immunohistochemical and cytogenetic features of the hepatocellular adenoma-like and hepatocellular carcinoma portions of these tumors. Immunohistochemistry for ß-catenin, glutamine synthetase, serum amyloid A protein, glypican-3, and heat-shock protein 70 was done in 11 cases of hepatocellular carcinoma arising in hepatocellular adenoma in non-cirrhotic liver. Tumors with nuclear ß-catenin and/or diffuse glutamine synthetase were considered ß-catenin activated. Fluorescence in situ hybridization (FISH) was done in nine cases for gains of chromosomes 1, 8 and MYC. There were seven men (33-75 years) and four women (29-65 years). Focal atypical morphological features were seen in hepatocellular adenoma-like areas in 7 (64%) cases. Hepatocellular adenoma-like areas showed features of inflammatory hepatocellular adenoma in 7 (64%) cases; 4 of these were also serum amyloid A-positive in the hepatocellular carcinoma portion. ß-Catenin activation, heat-shock protein 70 positivity, and chromosomal gains on FISH were seen in the hepatocellular adenoma portion in 55%, 40%, and 56% of cases, and 73%, 60%, and 78% of cases in the hepatocellular carcinoma portion, respectively. In conclusion, the hepatocellular adenoma-like portion of most cases of hepatocellular carcinoma arising in hepatocellular adenoma shows features typically seen in hepatocellular carcinoma such as focal morphological abnormalities, ß-catenin activation, heat-shock protein 70 expression, and chromosomal gains. Hepatocellular adenoma-like areas in these tumors, especially in men and older women, may represent an extremely well-differentiated variant of hepatocellular carcinoma, whereas the morphologically recognizable hepatocellular carcinoma portion represents a relatively higher grade component of the tumor.

Evaluation of the histologic and immunohistochemical (CD34, glutamine synthetase) findings in idiopathic non-cirrhotic portal hypertension (INCPH).

AIM: Idiopathic non-cirrhotic portal hypertension (INCPH) is a vascular disorder of uncertain origin. Diagnosis can be challenging on liver biopsy. Despite diverse histomorphologic findings documented in literature, studies on the frequency of these findings are lacking. This study aims to assess both the histomorphologic features and the immunoexpression patterns of CD34 and glutamine synthetase (GS) in liver biopsies and searched for their contribution to the pathologic diagnosis of INCPH. MATERIALS AND METHODS: Hematoxylin-eosin, CD34, and GS-stained liver needle biopsy sections of 16 patients clinically diagnosed with INCPH were retrospectively analyzed. Histologic findings such as portal vein narrowing, obliteration, or loss were grouped as major findings, while portal vein herniation, hypervascularized portal tracts, and periportal abnormal vessels were grouped as minor findings, and their frequency were evaluated. Periportal endothelial CD34 stained areas were measured via ocular micrometer. The distribution of GS immunoexpression was evaluated. Eighteen healthy liver donor biopsies were evaluated as controls. RESULTS: In INCPH cases, 58% of portal tracts showed major findings, compared to 15% in the control group (p < 0.001). Minor findings were observed in 16% of INCPH cases and 7% of controls (p = 0.014). The number of portal tracts with histologic findings is significantly higher in INCPH than in control liver biopsies. Abnormal portal tract distribution, like being close to each other, was seen in 75% of INCPH cases but not in controls (p < 0.001). Nodular regenerative hyperplasia (NRH) was present in 31% of cases. Periportal CD34 expression was higher in INCPH, and affected areas were larger than in controls (p < 0.001). Irregular GS staining, i.e. GS staining with patchy distribution in zone 3, and/or periportal and zone 2 hepatocytes, was found in 62% of INCPH cases, while controls showed the usual pattern (p < 0.001). CONCLUSION: In the biopsy diagnosis of INCPH, in addition to the presence of major histologic findings and the amount of portal tracts displaying these features, the expression of endothelial CD34 in periportal areas, and irregular hepatocellular GS expression can also be considered as supporting feature.

Absence of post-lesion reactive gliosis in elasmobranchs and turtles and its bearing on the evolution of astroglia.

In the mature mammalian and avian central nervous systems, neuronal destructions are followed by reactive gliosis, but data on other vertebrates are rather controversial. Mammals and birds belong to different amniote groups (Synapsida and Diapsida, respectively), but exhibit common general features in their glial architecture, mainly the predominance of astrocytes. Two vertebrate groups seem to be in special positions of glial evolution: turtles (Testudiniformes) and skates and rays (Batoidea). The purely ependymoglial system of turtles seems to be the simplest one among the extant amniotes. In skates and rays, true astrocytes are preponderant glial elements, in contrast to the other "anamniotes" (and even to reptiles). We investigated stab wounds by the immunohistochemical detection of GFAP in turtles (Trachemys-formerly Pseudemys-scripta elegans), a skate (Raja clavata) and rays (Dasyatis akajei and Torpedo marmorata). Sharks (Scyliorhinus canicula) as ependymoglia-predominated chondrichthyans, and-for positive controls-rats were also studied. In the elasmobranchs, other astroglial markers: glutamine synthetase and S100 protein were also applied. Neither turtles nor elasmobranchs presented considerable astroglial reactions. Critically surveying the former reports on different vertebrates, these results complete the picture that typical post-lesion reactive gliosis is confined to mammals and birds. Analysis of the astroglial systems from phylogenetic perspective suggests that the capability of forming glial demarcation and scar formation evolved independently in mammals and birds. Predominance of astrocytes is a necessary condition but not sufficient for reactive gliosis. The intense glial reactivity of mammals and birds may be attributed to their complex cerebralization.

Peritumoral hyperplasia of the liver: a response to portal vein invasion by hypervascular neoplasms.

AIMS: Several cases of focal nodular hyperplasia (FNH) or similar hyperplastic lesions have been reported adjacent to hepatic neoplasms, including hepatocellular carcinoma, epithelioid haemangioendothelioma and hepatoblastoma. We refer to this hyperplastic response as peritumoral hyperplasia (PTH). Here, we report eight cases of PTH adjacent to primary hepatocellular carcinomas (two) and metastatic neuroendocrine tumours (three), gastrointestinal stromal tumour (one) and colon carcinomas (two). METHODS AND RESULTS: Sections were stained with H&E and trichrome, and for glutamine synthetase, CD34 and cytokeratin 7. PTH was composed of a peritumoral rim of hyperplastic hepatocytes up to 7.0 mm wide, delimited by adjacent hepatocellular atrophy. PTH had altered plate architecture, strong glutamine synthetase expression and variable sinusoidal endothelial cell CD34 expression. The central tumour deposit typically invaded portal veins and was markedly hypervascular with CD34-positive capillaries. CONCLUSIONS: We suggest that PTH is a hyperplastic response to increased blood flow in the peritumoral parenchyma. The increased flow occurs when portal vein invasion by a hypervascular tumour causes arterio-portal shunting. While PTH shares some morphological features with FNH, it lacks the defining nodular architecture, central scar and bile ductules. PTH may be related pathophysiologically to FNH, but should be classified as a separate entity because of its distinct morphology and peritumoral location.

Glutamine synthetase expression in activated hepatocyte progenitor cells and loss of hepatocellular expression in congestion and cirrhosis.

BACKGROUND & AIMS: In normal human liver, glutamine synthetase (GS) is expressed in a rim of hepatocytes surrounding hepatic veins. GS expression is decreased in cirrhosis and increased in chronic hepatitis, focal nodular hyperplasia, peritumoural hyperplasia and some hepatocellular neoplasms. For the non-neoplastic conditions, there is limited information available on histological pattern of altered GS expression and the mechanisms of these changes. METHODS: We examined GS expression in 58 large specimens and 45 needle biopsies with a variety of non-neoplastic human liver conditions and in 12 normal control livers. Expression was correlated with clinical and histological disease states. RESULTS: We identified four patterns of GS expression: (i) Loss of normal perivenular expression was seen in states of chronic congestion, severe cirrhosis and zone 3 necrosis. (ii) Diffuse expression was seen in states with active hepatocellular injury and correlated with Ki-67 expression. (iii) Interface expression was seen in feathery degeneration of chronic cholestasis. (iv) GS expression in activated hepatocyte progenitor cells (HPCs) associated with small ducts and ductules was seen in fulminant hepatic failure and in early and late chronic liver disease and rarely in normal livers. CONCLUSIONS: Glutamine synthetase expression is increased in regenerating hepatocytes and in early HPCs prior to morphological evidence of hepatocellular differentiation. This may be the earliest marker of HPCs yet demonstrated. Loss of expression may be a reflection of disrupted endothelium-hepatocyte contact in hepatic vein walls caused by congestive injury as found in congestive heart failure and advanced cirrhosis.

Biochemical and proteomic analyses reveal that Populus cathayana males and females have different metabolic activities under chilling stress.

Male and female poplars (Populus cathayana Rehd.) respond differently to environmental stresses. However, little is known about sex-dependent responses to chilling at the proteome level. To better understand these differences, a comparative proteomics investigation combined with a biochemical approach was used in the current study. Three-month-old poplar cuttings were treated at 25 or 4 °C for 14 days. Results revealed significant sexual differences in nitrogen metabolic enzymes and free amino acid components in response to chilling. The chilling-treated males showed higher activities of nitrate reductase and glutamine synthetase and higher contents of reduced glutathione, serine, arginine, leucine, glycine, proline and methionine than chilling-treated females. A total of 65 chilling-responsive spots were found, of which 48 showed significant sexual differences. These proteins are involved in photosynthesis, carbon and energy metabolism, metabolic processes of proteins, lipid metabolism, vitamin metabolism, stress defense, and gene expression regulation. The study shows that males have more effective metabolic processes and protective systems to chilling than females.

A rapid method to improve protein detection by indirect ELISA.

The enzyme-linked immunosorbant assay (ELISA) is a rapid, high-throughput, quantitative immunoassay for the selective detection of target antigens. The general principle behind an ELISA is antibody mediated capture and detection of an antigen with a measurable substrate. Numerous incarnations of the ELISA have resulted in its commercialization for sensitive diagnostic applications using a variety of detection platforms. Many of these applications require a pair of antibodies necessary for the capture and detection of a specific antigen (cELISA) in defined substrates. However, the availability of cELISA for target antigens is limited and thus restricts the use of this technique for quantitative measure of antigens during discovery. Alternatively, the indirect ELISA (iELISA) requires only a single antibody directed against a target antigen that has been immobilized to a surface. Unlike the cELISA, which uses an immobilized capture antibody that can bind a native antigen in solution followed by a detector antibody that binds captured antigen, the iELISA uses an antibody the binds directly to an immobilized antigen for detection. Although the iELISA may lack the sensitivity of a cELISA, its requirement of only a single antigen specific antibody makes it a simple technique for evaluating the relative difference in the level of target protein expression between samples. However, many antibodies that work effectively to detect protein antigens in other immunoassays such as Western blotting or immunohistochemistry fail to work in microplate based iELISA. Although these alternate immunoassay methods are useful for qualitative determination of target antigens, they provide limited quantitative information, limiting the assessment of sample specific differences in protein expression. We hypothesized that protein conformation following adsorption on the plastic surface of microplates impedes antibody epitope binding and this restriction could be overcome by a short chemical denaturation step. In this report we define a rapid method to assess the utility of an antibody for iELISA application and demonstrate a significant improvement in both qualitative and quantitative protein detection after chemical denaturation using defined assay conditions.

Oxidative stress markers in the brain of patients with cirrhosis and hepatic encephalopathy.

UNLABELLED: Cell culture studies and animal models point to an important role of oxidative/nitrosative stress in the pathogenesis of cerebral ammonia toxicity. However, it is unknown whether oxidative/nitrosative stress in the brain is also characteristic of hepatic encephalopathy (HE) in humans. We therefore analyzed post mortem cortical brain tissue samples from patients with cirrhosis dying with or without HE in comparison with brains from patients without liver disease. Significantly elevated levels of protein tyrosine-nitrated proteins, heat shock protein-27, and 8-hydroxyguanosine as a marker for RNA oxidation were found in the cerebral cortex of HE patients, but not of patients with cirrhosis but without HE. Glutamine synthetase (GS) activity was significantly decreased, whereas GS protein expression was not significantly affected. Protein expression of the glutamate/aspartate cotransporter was up-regulated in HE, whereas protein expression of neuronal and inducible nitric oxide synthases, manganese-dependent and copper/zinc-dependent superoxide dismutase, and glial glutamate transporter-1 were not significantly increased. CONCLUSION: These data indicate that HE in patients with cirrhosis is associated with oxidative/nitrosative stress, protein tyrosine nitration, and RNA oxidation, suggesting a role of oxidative stress in the pathogenesis of HE in patients with cirrhosis.