Histopathological changes in gills of the estuarine crab Chasmagnathus granulata (Crustacea-Decapoda) following acute exposure to ammonia

Histopathological effects of ammonia on the gills of the estuarine crab Chasmagnathus granulata (Dana, 1851) were evaluated after acute exposure to ammonia concentrations around LC₅₀ value (17.85 Mm). Disruption of pilaster cells and a subsequent collapse of gill lamellae were the main effects observed. Ephitelial necrosis and hyperplasia were also detected. Significant (P<0.05) increases in pCO₂ and lactate, and significant decreases of pO₂ were detected in the haemolymph of ammonia-exposed crabs. These changes suggest that the observed histopathological damage affected gas exchange, possibly leading to death.     

Proteomic changes in the crucian carp brain during exposure to anoxia

During exposure to anoxia, the crucian carp brain is able to maintain normal overall protein synthesis rates. However, it is not known if there are alterations in the synthesis or expression of specific proteins. This investigation addresses this issue by comparing the normoxic and anoxic brain proteome. Nine proteins were found to be reduced by anoxia. Reductions in the glycolytic pathway proteins creatine kinase, fructose biphosphate aldolase, glyceraldehyde‐3‐phosphate dehydrogenase, triosephosphate isomerase and lactate dehydrogenase reflect the reduced production and requirement for adenosine tri‐phosphate during anoxia. In terms of neural protection, voltage‐dependent anion channel, a protein associated with neuronal apoptosis, was reduced, along with gefiltin, a protein associated with the subsequent need for neuronal repair. Additionally the expression of proteins associated with neural degeneration and impaired cognitive function also declined; dihydropyrimidinase‐like protein‐3 and vesicle amine transport protein‐1. One protein was found to be increased by anoxia; pre‐proependymin, the precursor to ependymin. Ependymin fulfils multiple roles in neural plasticity, memory formation and learning, neuron growth and regeneration, and is able to reverse the possibility of apoptosis, thus further protecting the anoxic brain.     

Proteomic analysis of wild-type Sinorhizobium meliloti responses to N-acyl homoserine lactone quorum-sensing signals and the transition to stationary phase

Proteome analysis revealed that two long-chain N-acyl homoserine lactones (AHLs) produced by Sinorhizobium meliloti 1021 induced significant differences in the accumulation of more than 100 polypeptides in early-log-phase cultures of the wild type. Fifty-six of the corresponding proteins have been identified by peptide mass fingerprinting. The proteins affected by addition of these two AHLs had diverse functions in carbon and nitrogen metabolism, energy cycles, metabolite transport, DNA synthesis, and protein turnover. Two hours of exposure to 3-oxo-C(16:1)-homoserine lactone (3-oxo-C(16:1)-HL) affected the accumulation of 40 of the 56 identified proteins, whereas comparable exposure to C(14)-HL affected 13 of the 56 proteins. Levels of four proteins were affected by both AHLs. Exposure to 3-oxo-C(16:1)-HL for 8 h affected the accumulation of 17 proteins, 12 of which had reduced accumulation. Of the 80 proteins identified as differing in accumulation between early-log- and early-stationary-phase cultures, only 13 were affected by exposure to 3-oxo-C(16:1)-HL or C(14)-HL. These results provide a foundation for future studies of the functions regulated by AHL quorum sensing in S. meliloti and help to establish proteomic analysis as a powerful global approach to the identification of quorum-sensing regulatory patterns in wild-type bacteria.     

Defect of the cerebellar vermis induced by prenatal gamma-ray irradiation in radiosensitive BALB/c mice

The developing fetal brain is one of the most susceptible organs to irradiation insult. Prenatal irradiation-induced abnormalities in the cerebrum have been well examined in mouse fetuses. However, little information on abnormalities in the cerebellum caused by irradiation is available. Moreover, few reports have examined the chronological changes of the brain from the prenatal to the postnatal period. To analyze the chronological changes induced by irradiation, we exposed pregnant mice to gamma-ray irradiation on embryonic day 13.5 (E13.5) and investigated the histopathology of the cerebellum at several time points from E14.5 to postnatal day 28. BALB/cA mice were used, which is a radiosensitive strain, and C57BL/6J, which is a radioresistant strain. The irradiated BALB/c showed a remarkable vermis deficit after birth, and histological analysis demonstrated that there were severe losses of the external germinal layer (EGL) and Purkinke cell layer. TUNEL analysis shoed that apoptosis was strongly induce in the cerebellar anlage of the irradiated BALB/c compared to the C57BL/6J at E14.5. Immunohistochemical analysis revealed a significant decrease of phospho-histone H3 positive EGL cells in the irradiated BALB/c at E18.5 and E0, indicating that irradiation causes a decrease in the number of mitotic cells. The results suggest that the strong induction of apoptosis in radiosensitive BALB/c led to a decrease of proliferation activity in the cerebellar anlage during embryonic development, and consequently, severe cerebellar abnormality was evoked.     

Morphological and morphometrical changes in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water

Summary Fathead minnows, Pimephales promelas, were exposed for 129 days to Lake Superior water acidified with sulfuric acid by means of a flow-through toxicant injection system. The effects of chronic acid stress (pH 6.5, 6.0, 5.5, 5.0) on gill histology were examined. Most of the histological effects were seen at pH 5.5 and 5.0 and were confined primarily to changes in numbers, distribution, and morphology of chloride cells. At low pH levels there tend to be more chloride cells in the gill epithelium and an increased percentage of these cells in the secondary lamellae. In contrast to normal chloride cells, chloride cells from fish exposed to low pH frequently had apical pits while some had bulbous apical evaginations. The occurrence of structural changes in chloride cells during exposure to acid water suggests that chloride cells may be involved in acclimation to acid stress.     

Liquid holding recovery kinetics in wild-type and radiosensitive mutants of the yeast Saccharomyces exposed to low- and high-LET radiations

Three wild-type diploid yeast strains Saccharomyces ellipsoideus and Saccharomyces cerevisiae and five radiosensitive mutants of S. cerevisiae in the diploid state were irradiated with gamma-rays from 60Co and alpha-particles from 239Pu in the stationary phase of growth. Survival curves and the kinetics of the liquid holding recovery were measured. It was shown that the irreversible component was enhanced for the densely ionizing radiation in comparison to the low-LET radiation while the probability of the recovery was identical for both the low- and high-LET radiations for all the strains investigated. It means that the recovery process itself is not damaged after densely ionizing radiation and the enhanced RBE of the high-LET radiation may be caused by the increased yield of the irreversible damage. A parent diploid strain and all its radiosensitive mutants showed the same probability for recovery from radiation damage. Thus, the mechanism of the enhanced radiosensitivity of the mutant cells might not be related to the damage of the repair systems themselves but with the production of some kind of radiation damage from which cells are incapable to recover.     

Increased mitochondrial mass in cells with functionally compromised mitochondria after exposure to both direct gamma radiation and bystander factors

The bystander effect describes radiation-like damage in unirradiated cells either in the vicinity of irradiated cells or exposed to medium from irradiated cells. This study aimed to further characterize the poorly understood mitochondrial response to both direct irradiation and bystander factor(s) in human keratinocytes (HPV-G) and Chinese hamster ovarian cells (CHO-K1). Oxygen consumption rates were determined during periods of state 4, state 3 and uncoupled respiration. Mitochondrial mass was determined using MitoTracker FM. CHO-K1 cells showed significantly reduced oxygen consumption rates 4 h after exposure to 5 Gy direct radiation and irradiated cell conditioned medium (ICCM) and an apparent recovery 12-24 h later. The apparent recovery was likely due to the substantial increase in mitochondrial mass observed in these cells as soon as 4 h after exposure. HPV-G cells, on the other hand, showed a sustained increase in oxygen consumption rates after ICCM exposure and a transient increase 4 h after exposure to 5 Gy direct radiation. A significant increase in mitochondrial mass per HPV-G cell was observed after exposure to both direct radiation and ICCM. These findings are indicative of a stress response to mitochondrial dysfunction that increases the number of mitochondria per cell.     

Histological changes in spleens of radio-sensitive and radio-resistant mice exposed to low-dose X-ray irradiation

We have previously determined by using immune-assay or bio-assay methods that low-dose irradiation enhances immune and anti-oxidation functions. In this study, we examined histological changes of lymphatic follicles at 4, 24, or 48 hrs after sham, 0.25, 0.5, or 15 Gy irradiation in the spleens of BALB/c mice, which are sensitive to radiation compared with other strains, and C57BL/6J mice, which are resistant to radiation, using hematoxylin-eosin staining for lymphatic follicles or methylgreen pyronin staining for plasma cells. Results show that the lymphatic follicles in the spleens of the two mouse strains decreased at 24 or 48 hrs after 15 Gy irradiation. The number of plasma cells in the spleens of sham irradiated BALB/c mice was greater than that of sham irradiated C57BL/6J mice. At 4 hrs after 0.25 Gy irradiation, plasma cells increased in the spleens of the two mouse strains. These findings suggest, by histology, that low-dose irradiation activates the plasma cells and enhances the immune function. Although those two mouse strains have different sensitivities to radiation, the above changes were similar in both time course and degree of response. Therefore, the phenomena observed may be common in mice.     

Rhythmicity in the structure-functional changes in hepatocytes following exposure to pesticides]

The processes of dursban biotransformation during the liver perfusion in rats exposed to CCl4 and milbex for 4, 8 and 15 days (microsomal enzyme inhibitor and inducer, respectively) were studied. The ultrastructure of hepatocytes was examined in the animals treated with the mentioned poisons. Three stages of the structural and functional changes were revealed. Reconstruction of the dursban biotransformation ways occurred from the 8th day, i.e. the dialkylation processes were intensified, resulting in production of less toxic metabolites.     

Radiation induced bystander signals are independent of DNA damage and DNA repair capacity of the irradiated cells

Evidence is accumulating that irradiated cells produce signals, which interact with non-exposed cells in the same population. Here, we analysed the mechanism for bystander signal arising in wild-type CHO cells and repair deficient varients, focussing on the relationship between DNA repair capacity and bystander signal arising in irradiated cells. In order to investigate the bystander effect, we carried out medium transfer experiments after X-irradiation where micronuclei were scored in non-targeted DSB repair deficient xrs5 cells. When conditioned medium from irradiated cells was transferred to unirradiated xrs5 cells, the level of induction was independent of whether the medium came from irradiated wild-type, ssb or dsb repair deficient cells. This result suggests that the activation of a bystander signal is independent of the DNA repair capacity of the irradiated cells. Also, pre-treatment of the irradiated cells with 0.5% DMSO, which suppresses micronuclei induction in CHO but not in xrs5 cells, suppressed bystander effects completely in both conditioned media, suggesting that DMSO is effective for suppression of bystander signal arising independently of DNA damage in irradiated cells. Overall the work presented here adds to the understanding that it is the repair phenotype of the cells receiving bystander signals, which determines overall response rather than that of the cell producing the bystander signal.     

DNA base changes induced following in vivo exposure of unadapted, adapted or ada- Escherichia coli to N-methyl-N'-nitro-N-nitrosoguanidine

The adaptive response is one of the major repair pathways in Escherichia coli that removes DNA alkylation damage. To investigate the role of the adaptive response in mutagenesis, the E. coli gpt forward mutation assay system was used to determine the mutation spectrum of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in MNNG-adapted and unadapted GP120 (wild-type) and unadapted PJ5 (ada-5) cells. We observed that 34/37 mutations in the unadapted GP120 cells, 38/40 mutations in the adapted GP120 cells, and 10/10 mutations in the PJ5 cells were GC----AT transitions. The remaining 3/37 mutations in the unadapted GP120 cells were large insertions. The remaining 2/40 mutations in the adapted GP120 cells were transversions with one a GC----CG and the other an AT----CG. A surrounding sequence specificity of mutagenesis was observed for the GC----AT transitions in both the unadapted (GP120 and PJ5) and adapted (GP120) cells, with 70% of the unadapted PJ5, 68% of the unadapted GP120, and 61% of the adapted GP120 mutations occurring at the middle G of the sequence 5'--GG(A or T)--3'. Both strains also displayed a statistically significant preference for mutagenesis at guanine bases in the non-transcribed strand. The overall distribution of mutated sites in the gpt gene in adapted and unadapted cells was similar, although the rate of mutations at certain sites appeared different. These minor differences could result from either non-uniform repair of alkylation damage at different sites on the DNA, or altered processing of the alkylated bases to mutations in the adapted state.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neural and behavioral changes in rats following continuous exposure to an odor

Summary Continuous exposure of young rats to the almond-like odor of acetophenone or cyclohexanone for up to 4 months, resulted in distinct but similar patterns of degenerating mitral cells in their olfactory bulbs. Rats favored their exposure odor in olfactory preference tests (Fig. 2) and their acuity for it was not altered (Fig. 3). However, they appeared to exhibit a deficit in detecting a similar but novel odor. The results suggest that the remaining normal mitral cells in the bulbs of these animals are those stimulated by the exposure odor. Cells which show signs of degeneration (Fig. 4) may receive little or no input from the periphery. Controls exposed to a similar but non-odorous environment showed evidence of non-selective mitral cell degeneration. In addition they had a lower acuity for acetophenone and cyclohexanone than animals reared in a normal rat colony (Fig. 3). Anatomical and behavioral data from odor exposed and control groups, suggest that partial regeneration of altered mitral cells may have occurred during a 5 month period following exposure. Overall the results provide further evidence for a topographical projection of the olfactory receptor epithelium onto the olfactory bulb and spatial coding of different odors in the bulb.     

辐射过程中耐辐射奇球菌蛋白酶变化的检测与分析

采用明胶和酪蛋白底物酶谱法以及荧光酪蛋白底物对紫外线以及γ射线辐射后恢复期耐辐射奇球菌R1(Deinococcus radiodurans R1,DRR1)的蛋白酶变化进行了检测。结果发现,DRR1存在高活性大分子量组成性表达蛋白酶,与Karlin等［16］提出的DRR1蛋白酶为预测高表达蛋白(PHX)的设想一致。DRR1包含大量分子量大于140kD 的明胶降解酶和分子量大于120kD的酪蛋白降解酶,其中活性最高的174kD明胶酶在经SDS变性处理后仍有较高活性,该蛋白酶在DRR1受紫外线辐射和电离辐射后恢复期的表达模式存在差异,在γ射线电离辐射过程中以及电离辐射后恢复的晚期活性较高。此外,还发现一些蛋白酶特异性由辐射所诱导,表明这些蛋白酶可能参与细胞信号通路中蛋白的顺序降解,也提示DRR1损伤修复过程中细胞内存在一个精确的蛋白酶系统。这些蛋白酶的表达与细胞的营养状态相关。同时对一株由本实验室从北京地区土壤中分离到的杆状耐辐射菌RR533.2的明胶和酪蛋白蛋白酶谱进行了测定,结果发现其蛋白酶谱与DRR1相类似。     

Susceptibility of male and female medaka (Oryzias latipes) fish to spontaneous and X-ray induced micronucleus formation in gill cells

The frequency of micronucleated cells (MNCs) was measured in acridine-orange (AO) stained RNA-rich gill cells from male and female medaka (Oryzias latipes) fish of known body weight. Spontaneous MNC frequencies were not significantly correlated with body weight, despite the fact that the heaviest of the 30 fish used outweighed the lightest by a factor of 3. Average MNC frequencies were identical in males and females at 0.8 per thousand. An X-ray dose of 4 Gy increased the frequency of MNCs over the spontaneous level in all 30 of the fish used, reaching a level of 7.2 per thousand on average when assayed 24 h after exposure. In X-ray treated fish, MNC frequency and body weight were not significantly correlated, nor was there any difference between the sexes. These and other results support our primary conclusion that AO-staining is suitable for the medaka micronucleus assay in gill cells, and indicate that male and female medaka fish are similarly and size-independently susceptible to both spontaneous and X-ray induced micronucleus formation in gill cells.     

Proteomic changes in the brain of the western painted turtle (Chrysemys picta bellii) during exposure to anoxia

During anoxia, overall protein synthesis is almost undetectable in the brain of the western painted turtle. The aim of this investigation was to address the question of whether there are alterations to specific proteins by comparing the normoxic and anoxic brain proteomes. Reductions in creatine kinase, hexokinase, glyceraldehyde‐3‐phosphate dehydrogenase, and pyruvate kinase reflected the reduced production of adenosine triphosphate (ATP) during anoxia while the reduction in transitional endoplasmic reticulum ATPase reflected the conservation of ATP or possibly a decrease in intracellular Ca²⁺. In terms of neural protection programed cell death 6 interacting protein (PDCD6IP; a protein associated with apoptosis), dihydropyrimidinase‐like protein, t‐complex protein, and guanine nucleotide protein G_(o) subunit alpha (G_o alpha; proteins associated with neural degradation and impaired cognitive function) also declined. A decline in actin, gelsolin, and PDCD6IP, together with an increase in tubulin, also provided evidence for the induction of a neurological repair response. Although these proteomic alterations show some similarities with the crucian carp (another anoxia‐tolerant species), there are species‐specific responses, which supports the theory of no single strategy for anoxia tolerance. These findings also suggest the anoxic turtle brain could be an etiological model for investigating mammalian hypoxic damage and clinical neurological disorders.