The subcellular localization of glutamate dehydrogenase (GDH): is GDH a marker for mitochondria in brain?

Glutamate dehydrogenase (GDH, EC 1.4.1.2) has long been used as a marker for mitochondria in brain and other tissues, despite reports indicating that GDH is also present in nuclei of liver and dorsal root ganglia. To examine whether GDH can be used as a marker to differentiate between mitochondria and nuclei in the brain, we have measured GDH by enzymatic activity and on immunoblots in rat brain mitochondria and nuclei which were highly enriched by density-gradient centrifugation methods. The activity of GDH was enriched in the nuclear fraction as well as in the mitochondrial faction, while the activities of other mitochondrial enzymes (fumarase, NAD-isocitrate dehydrogenase and pyruvate dehydrogenase complex) were enriched only in the mitochondrial fraction. Immunoblots using polyclonal antibodies against bovine liver GDH confirmed the presence of GDH in the rat brain nuclear and mitochondrial fractions. The GDH in these two subcellular fractions had a very similar molecular weight of 56,000 daltons. The mitochondrial and nuclear GDH differed, however, in their susceptibility to solubilization by detergents and salts. The mitochondrial GDH could be solubilized by extraction with low concentrations of detergents (0.1% Triton X-100 and 0.1% Lubrol PX), while the nuclear GDH could be solubizeded only by elevated concentrations of detergents (0.3% each) plus KCl (>150mM). Our results indicate that GDH is present in both nuclei and mitochondria in rat brain. The notion that GDH may serve as a marker for mitochondria needs to be re-evaluated.     

Histological assessment of cerebellar granule cell layer in postmortem brain; a useful marker of tissue integrity?

Tissue quality control measures are routinely performed in brain banks with the assessment of brain pH being the most common measure. In some brain banks the assessment of the RNA integrity number is also performed, although this requires access to specialised equipment and is more expensive. The aim of this study is to determine if there is a correlation between the visual assessment of cerebellar granule cell integrity and brain pH or RIN. One hundred and five consecutive cases from the NSW Tissue Resource Centre, Sydney, Australia were accessed. The cerebrum was hemisected and one hemisphere sliced parasagittally at approximately 1–2?cm intervals and frozen. The other hemisphere was fixed in 15% buffered formalin for 2–3?weeks. The contralateral cerebellar hemisphere was preserved in the same manner as the cerebral hemisphere. Samples of fixed tissue were embedded in paraffin, 7?μm sections cut and stained routinely with hematoxylin and eosin. The granular cell layer (GCL) was assessed microscopically to determine the degree of autolytic degradation. Degradation was graded as nil, mild, moderate or severe. Brain tissue pH and RIN were measured using standardised protocols. This study showed that both brain pH and RIN significantly correlated with the severity of the degradation of the cerebellar granule cell layer. This additional screening tool can be performed during routine histological review of the cerebellar tissue to assess the suitability for further investigation of tissue quality.     

Wilms' tumor 1 (WT1) gene in hematopoiesis: a surrogate marker of cell proliferation as a possible mechanism of action?

BACKGROUND: Wilms' tumor 1 (WT1) gene expression is seen in a significant number of cases of human neoplasia; however, the mechanism of action remains to be clarified. We hypothesized that WT1 gene is a surrogate marker of proliferation in normal hematopoietic cells and leukemias. While we and others have recognized its value as a tool for the detection of minimal residual disease (MRD), the objective of this study was to confirm our hypothesis regarding normal. METHODS: Samples from healthy donors (n=16) and UC blood (n=9) were cultured in Methocult for 21 days. Colonies were analyzed on days 7, 14 and 21 by RT-PCR for WT1 gene expression. Our positive controls were samples from patients with leukemia (n=91). Negative controls were from normal volunteers without stimulation (n=26). RESULTS: Results showed a statistically significant difference (P<0.0001) between cultured groups, with the highest level of WT1 gene expression in the positive controls and on day 14, when cells are at their maximal proliferation. DISCUSSION: In conclusion, WT1 gene expression in the proliferating colonies was highest on day 14, although less than in leukemia samples, confirming our hypothesis that WT1 gene is a surrogate marker of proliferation, not only in leukemogenesis but also, to a lesser degree, in normal cell proliferation.     

The pink-blue spot syndrome in Acropora eurystoma (Eilat, Red Sea): a possible marker of stress?

The appearance of pink-blue spots (termed here as pink-blue spot syndrome - PBSS) in the branching coral Acropora eurystoma from the Gulf of Eilat, Red Sea, is described. We monitored 18 transects (10 x 1 m2 each) in front of the H. Steinitz Marine Laboratory (Eilat), at 3, 6 and 9 m depth, during March and August in 2001 and 2002. Transect measurements revealed high frequencies of colonies with PBSS (up to 100% of colonies) between 3 and 9 m depth. Ten PBSS-affected colonies of A. eurystoma were labelled and monitored for the development of spots. From March to August 2001, the number of spots per colony increased and remained constantly high at both sampling dates in 2002. Spot size ranged between 7 and 149 mm2. Spots were primarily recorded in areas where coral tissues contacted foreign biological matter, either around regenerative wounds or when surrounded by encrusting organisms, in fast-growing areas and in allogeneic interactions. A preliminary biochemical examination suggested that the pink-blue pigment in A. eurystoma is part of a family of compounds (pocilloporin) responsible for the pink-blue colours in pocilloporid and acroporid corals. Pink-blue colour could be experimentally induced in A. eurystoma by tissue-to-tissue contacts between distressed and non-distressed allogeneic branches. PBSS was also induced in healthy coral tissue by contact with inert objects, e.g., by bandaging a branch with plastic strips. Any specific pink-blue colour spots faded within 1-3 months from onset. These results suggest that PBSS in A. eurystoma may not be considered a regular coral disease, but rather a locally induced syndrome caused by restricted environmental and/or biological stress conditions.     

Glycogen metabolism loss: a common marker of parasitic behaviour in bacteria?

We searched 55 completely sequenced bacterial genomes for glycogen synthesis and degradation enzymes. A significant proportion of these bacteria appears to lack glycogen metabolism capability. Interestingly, these bacteria are parasitic, symbiotic or fastidious (i.e. difficult to culture outside their normal environment). It is suggested that the lack of bacterial glycogen metabolism is a trait associated with parasitic behaviour in bacteria.     

Heritability of cellular radiosensitivity: a marker of low-penetrance predisposition genes in breast cancer?

Many inherited cancer-prone conditions show an elevated sensitivity to the induction of chromosome damage in cells exposed to ionizing radiation, indicative of defects in the processing of DNA damage. We earlier found that 40% of patients with breast cancer and 5%-10% of controls showed evidence of enhanced chromosomal radiosensitivity and that this sensitivity was not age related. We suggested that this could be a marker of cancer-predisposing genes of low penetrance. To further test this hypothesis, we have studied the heritability of radiosensitivity in families of patients with breast cancer. Of 37 first-degree relatives of 16 sensitive patients, 23 (62%) were themselves sensitive, compared with 1 (7%) of 15 first-degree relatives of four patients with normal responses. The distribution of radiosensitivities among the family members showed a trimodal distribution, suggesting the presence of a limited number of major genes determining radiosensitivity. Segregation analysis of 95 family members showed clear evidence of heritability of radiosensitivity, with a single major gene accounting for 82% of the variance between family members. The two alleles combine in an additive (codominant) manner, giving complete heterozygote expression. A better fit was obtained to a model that includes a second, rarer gene with a similar, additive effect on radiosensitivity, but the data are clearly consistent with a range of models. Novel genes involved in predisposition to breast cancer can now be sought through linkage studies using this quantitative trait.     

Is a biology of rarity in primates yet possible?

If we lack data on the biology of rare species, then understanding of the biology of rarity will be incomplete at best, biased at worst. However, the extent of potential under-study is mostly unknown. We therefore ask for primates, one of the better known orders of mammals, whether data are lacking on rare species. The measure used is published data on a crucial aspect of biology, namely density. Rare species are here defined as those with both geographic range sizes and habitat breadths less than the median for primates; common species are at or above the median for those two measures. Globally, nearly half, 47%, of the 32 rare species lack data on their density, compared to only 10% of the 83 common species (²corr. = 17.1, p < 0.001). Within realms, Asia and Madagascar show a particularly strong bias, missing density data for over 50% of their rare species. Thus, rare species are indeed severely under-studied compared to common species, even in this well-studied mammalian taxon.     

Malondialdehyde in benign prostate hypertrophy: a useful marker?

Benign prostate hypertrophy (BPH) is the most common benign tumor in men due to obstruction of the urethra and, finally, uremia. Malondialdehyde (MDA) is a product derived from peroxidation of polyunsaturated fatty acids and related esters. Evaluation of MDA in serum represents a non-invasive biomarker of oxidative stress. Prostate-specific antigen (PSA) is a sensitive marker for prostatic hypertrophy and cancer. We analyzed MDA serum levels to evaluate the oxidative stress in BPH. To this end, 22 BPH patients and 22 healthy donors were enrolled. Data show an increase of MDA level in BPH patients and a positive correlation between PSA and MDA levels. In conclusion, we describe a previously unknown relationship between PSA and MDA as an index of inflammation and oxidative stress in BPH.     

Oxidation of uric acid in rheumatoid arthritis: is allantoin a marker of oxidative stress?

Free radicals are implicated in many diseases including atherosclerosis, cancer and also in rheumatoid arthritis. Reaction of uric acid with free radicals, such as hydroxyl radical and hypochlorous acid (HOCl) results in allantoin production. In this study, we measured the serum allantoin levels, oxidation products of uric acid, as a marker of free radical generation in rheumatoid arthritis. Fasting blood samples were obtained from 21 rheumatoid patients and 15 healthy controls. In this study, the serum allantoin and uric acid levels were measured by a gas chromatography-mass spectrometry method and the ratios were calculated. The mean allantoin and uric acid levels and ratios in the patient group were 22.1±11.3, 280.5±65.0 and 8.0±3.7 μM, while in the control group they were 13.6±6.3, 278.3±53.6 and 4.9±2.1 μM, respectively. The effects of gender, age, menopausal status, duration of disease and medications on serum allantoin and uric acid levels of the patient and control groups were studied. Our results suggest that uric acid acts as a free radical scavenger and thus is converted to allantoin. Increased allantoin levels suggest the possible involvement of free radicals in rheumatoid arthritis.     

Bromine patterns in Norwegian coastal Cod otoliths—a possible marker for distinguishing stocks?

Bromine was found to accumulate in otoliths of Norwegian coastal Cod Gadus morhua that were reared under known conditions. Despite the fact that the Cod were moved from one rearing environment to another, causing marked changes in some otolith elemental concentrations, bromine appeared to accumulate continuously along certain growth axes as revealed by 2-D elemental mapping. In contrast, North Sea and Baltic Sea Cod showed little to no patterning in Br. We suggest that Br uptake in otoliths may be under physiological and genetic control, and as such, may prove useful as a stock identification tool.     

Attentional weighting: a possible account of visual field asymmetries in visual search?

Several previous visual search studies measuring reaction times have demonstrated scanning biases across the visual field (i.e. a tendency to begin a serial search in a particular region of space). In the present study, we measured visual discrimination thresholds for a target presented amongst distractors using displays that were short enough to greatly reduce the potential for serial (i.e. scanning) search. For both a motion and orientation task, subjects' performance was significantly better when the target appeared in the inferior, as compared to the superior, visual field (no differences were observed between left and right visual fields). These findings suggest that subjects may divide attention unevenly across the visual field when searching for a target amongst distractors, a phenomenon we refer to as 'attentional weighting'. To rule out the possibility that these visual field asymmetries were sensory in nature, thresholds were also measured for conditions in which subjects' attention was directed to the location of the target stimulus, either because it was presented alone in the display or because a spatial cue directed subjects' attention to the location of that target presented amongst distractors. Under these conditions, visual field asymmetries were smaller (or non-existent), suggesting that sensory factors (such as crowding) are unlikely to account for our results. In addition, analyses of set-size effects (obtained by comparing thresholds for a single target vs. the target presented amongst distractors) could be accounted for by an unlimited capacity model, suggesting that multiple stimuli can be processed simultaneously without any limitations at an early stage of sensory processing. Taken together, these findings suggest the possible existence of biases in attentional weighting at a late stage of processing. The bias appears to favor the inferior visual field, which may arise from the fact that there is more ecologically-relevant information in this region of space.     

Is beta-galactosidase staining a marker of senescence in vitro and in vivo?

Cytochemically detectable beta-galactosidase (beta-gal) at pH 6.0 has been reported to increase during the replicative senescence of fibroblast cultures and has been used widely as a marker of cellular senescence in vivo and in vitro. In this study, we have characterized changes in senescence-associated (SA) beta-gal staining in early and late passage cultures, cultures established from donors of different ages, virally immortalized cells, and tissue slices obtained from donors of different ages. The effects of different culture conditions were also examined. While we confirm the previous report that SA beta-gal staining increased in low-density cultures of proliferatively senescent cells, we were unable to demonstrate that it is a specific marker for aging in vitro. Cultures established from donors of different ages stained for SA beta-gal activity as a function of in vitro replicative age, not donor age. We also failed to observe any differences in SA beta-gal staining in skin cells in situ as a marker of aging in vivo. The level of cytochemically detectable SA beta-gal was elevated in confluent nontransformed fibroblast cultures, in immortal fibroblast cultures that had reached a high cell density, and in low-density, young, normal cultures oxidatively challenged by treatment with H2O2. Although we clearly demonstrate that SA beta-gal staining in cells is increased under a variety of different conditions, the interpretation of increased staining remains unclear, as does the question of whether the same mechanisms are responsible for the increased SA beta-gal staining observed in senescent cells and changes observed in cells under other conditions.     

Adoptive transfer of NK 1.1+ lymphocytes in immune-mediated colitis: a pro-inflammatory or a tolerizing subgroup of cells?

T lymphocytes expressing NK1.1 marker (NKT) have been suggested to play crucial roles in immune modulation. AIM: To determine the role of NK1.1+ cells in induction and maintenance of pro-inflammatory and/or tolerizing responses. METHODS: Colitis was induced in C57/B6 donor mice by intracolonic instillation of trinitrobenzenesulfonic acid (TNBS). Donor mice received five oral doses of colonic proteins extracted from TNBS-colitis colonic wall. Depletion of NK1.1+ lymphocytes was performed before lymphocyte harvesting. Splenocytes were harvested and separated into T-cell subpopulations, and transplanted into recipient mice before intracolonic instillation of TNBS. Standard clinical, macroscopic, and microscopic scores, and intracellular staining, flow cytometry, and cytotoxicity assays were performed. RESULTS: The adoptive transfer of CD4+ and NK1.1+ cells harvested from tolerized mice markedly ameliorated the colitis in recipient mice. In contrast, the adoptive transfer of CD8+ and double negative lymphocytes failed to transfer the tolerance. Recipients of splenocytes from tolerized mice exhibited an increase in CD4+ IL4+/CD4+ IFNgamma+ ratio. In contrast, recipients of splenocytes from NK1.1-depleted-tolerized mice exhibited severe colitis with a significant decrease of the CD4+ IL4+/CD4+ IFNgamma+ ratio. However adoptive transfer of splenocytes from non-tolerized NKT-depleted mice led to an alleviation of colitis with a relative increase of the CD4+ IL4+/CD4+ IFNgamma+ ratio. CONCLUSIONS: NK1.1+ lymphocytes play a critical role in immune regulation. They may be accountable for an alteration of the inflammatory response and the CD4+ IL4+/CD4+ IFNgamma ratio immune-mediated colitis and in peripheral tolerance induction.     

Gastrulation in Xenopus laevis: involution—a current view

In this article, we describe some of the morphogenetic movements reshaping the Xenopus laevis embryo during gastrulation. We have learned a great deal about these movements in recent years through advances made in explant culture techniques. Here, we will focus on involution, the process by which mesoderm is internalized and placed in between ectoderm and endoderm. Our aim is to present our current view of how involution takes place in the dorsal involuting marginal zone of the Xenopus embryos.