Morphological effects of mercury exposure on windowpane flounder gills as observed by scanning electron microscopy

Windowpane flounder, Scophthalmus aquosus Mitchill, were exposed for 60 days to 5 or 10 μg 1⁻¹ mercury and gill samples were examined by scanning electron microscopy. The response of the gill epithelium was different at the two levels of mercury exposure. The number of chloride cell apical pits and gill filaments bearing 'cratered' epithelial cells increased at the 5-μg 1⁻¹ level and decreased at the higher exposure level.
Focal swellings demonstrated a dose-dependent relationship, their numbers being greatest at the higher exposure level. Marked fragmentation of pavement cell microridge patterns and swelling of the respiratory epithelial cells was evident at the 10-μg 1⁻¹ exposure level.     

Ultrastructure and distribution of the taste buds in the buccal cavity in relation to the food and feeding habit of a herbivorous fish: Oreochromis niloticus

The buccal cavity of an herbivorous fish Oreochromis niloticus was investigated by means of scanning electron microscopy. The buccal cavity distinguished into the roof and the floor. Three different types of taste buds (type I, II and III) are distributed in the buccal cavity. The proximal part of the buccal cavity bears relatively high epidermal papillae in which type I TBs was found. The middle region of the buccal cavity is mostly occupied by low epidermal papillae containing type II TBs. Type III TBs which are present within the metabranchial buccal cavity; never rise above the normal level of the epithelium.The different types of TBs are useful for ensuring full utilization of the gustatory ability of the fish. It is postulated that the TBs serve different functions: TBs type I and II may act as chemoreceptors and mechanoreceptors. TBs type III acts predominantly as a chemoreceptors. TBs of each type show two kinds of receptor villi within their receptor areas: tall villi and small villi. The surface of the lining epithelial cells shows a delicate microridge system. These structures protect against physical abrasion potentially caused during food maneuvering and swallowing. Furthermore, protection of the epithelium from abrasion is enhanced with goblet cells secretion.     

Morphological and ultrastructural changes induced by sublethal concentrations of an anionic detergent on Ictalurus species barbel taste buds.

Morphological and ultrastructural changes were studied in Ictalurus sp. barbel taste buds (TBs), exposed to sublethal concentrations (3 ppm) of sodium alkylbenzene sulphonate for periods varying from 3 to 15 days. No significant alterations were noted after 3 days while, after just 6 days damage began to appear. The blood vessels were dilated and larger, more numerous intercellular spaces were observed between the light and dark TB cells than were to be found in the controls, but the basal portion of the TB was unaltered. After 9-12 days the most prominent features were the rupture of the plasma membranes, loss of microvillar organization of the light and dark cells as well as an increase in cytoplasmatic vacuolization. The skin was damaged and the germinative layer of the epidermis appeared activated and its height had increased. About 30% of the TBs were affected, and after 15 days they were severely damaged, whilst the feeding behaviour changed from day 6 onwards.     

Histological changes in relation to accumulation and elimination of inorganic and methyl mercury in gills of Labeo rohita Hamilton

L. rohita was exposed to identical concentrations of inorganic and methyl mercury (HgCl2 and CH3HgCl) and the gills were studied for mercury bioaccumulation and histological changes. In methyl mercury exposed group the mercury level in the gills continuously increased til the end of the exposure period whereas the level started decreasing from the day 30 onwards in the other group even though the exposure was continued for 60 days. Histological changes were similar in inorganic and methyl mercury treated fish except the higher intensity observed in the latter treatment. Under depuration for 15 days the clearance rate of accumulated mercury and subsequent histological recovery in the gills were less prominent in fish pretreated with methyl mercury.     

Cytological response of hemocytes in the European flat oyster, Ostrea edulis, experimentally exposed to mercury

Molluscs bivalves have been widely used as bioindicators to monitor contamination levels in coastal waters. In addition, many studies have attempted to analyze bivalve organs, considered pollutant-targets, to understand the bio-accumulation process and to characterize the effects of pollutants on the organisms. Here we analyzed the effects of mercury exposure on flat oyster hemocytes. Optical and electronic microscope procedures were used to characterize hemocyte morphology. In addition, cell solutions treated with acridine orange were analyzed by flow cytometry and laser scanning cytometry in order to evaluate the variations of cytoplasmic granules (red fluorescence, ARF) and cell size (green fluorescence, AGF) of hemocyte populations over time. Light and electron microscopical studies enabled us to differentiate four hemocyte subpopulations, agranulocytes (Types I and II) and granulocytes (Types I and II). Slight morphological differences were observed between control and Hg-exposed cells only in granulocytes exposed to Hg for 30 days, where condensed chromatin and partially lysed cytoplasmic regions were detected. Flow and laser scanning cytometry studies allowed us to differentiate three hemocyte populations, agranulocytes (R1) and granulocytes (R2 and R3). The exposure time to Hg increased the average red fluorescence (ARF) of agranulocytes and small granulocytes, while there was no change in large granulocytes, which showed a loss of membrane integrity. In control oysters, the three hemocyte populations showed an increase of ARF after 19 days of exposure although initial values were restored after 30 days. The average green fluorescence (AGF) was more stable than the ARF throughout the experiment. In Hg-exposed oysters, the values of AGF of agranulocytes showed an increase at half Hg-exposure period while the AGF values of large granulocytes decreased throughout the experiment, confirming the instability of these types of cells. The relative percentage of small granulocytes and granulocytes showed time variations in both control and exposed oysters. However, the values of small granulocytes remained constant during the whole experiment. The fact that there were only changes in agranulocytes and large granulocytes suggested a possible relationship between these two types of cells. In a quantitative study, we found a significant linear relationship between the agranulocytes and large granulocytes.     

Ultrastructural localization of mercury in adrenals from rats exposed to methyl mercury

Accumulations of mercury have been demonstrated in adrenal glands by light and electron microscopy with a highly sensitive histochemical technique. Rats were exposed to methyl mercury in drinking water (20 mg/l) for 7-180 days, or were given intraperitoneal injections of methyl mercury (daily dose 100 or 200 micrograms). The amount and location of the mercury deposits were dependent upon the exposure time, the method of administration and the amount administered. In rats exposed to methyl mercury in drinking water, accumulations were often observed in both the zona glomerulosa and reticularis. They appeared first in the zona glomerulosa of animals treated for 1 week. In the zona fasciculata, deposits were observed only in the animals treated for 50 to 180 days. In animals treated for 180 days the cytoplasm of the cells in the zona fasciculata was heavily vacuolated and distinct necrotic cells were observed in other cortical zones. In the chromaffin cells, a slight increase in the amount of deposits was observed with increasing exposure time. Both epinephrenic and norepinephrenic cells contained deposits. Only a few deposits were observed in the cortical and chromaffin cells of animals treated with intraperitoneal injections. Ultrastructural deposits were observed in the lysosomes of cortical cells and in both lysosomes and secretory granules of chromaffin cells.     

A study on the potential reprotoxic effects of thimerosal in male albino rats

Thimerosal is ethyl mercury based compound which is being used as a preservative in vaccines since decades. Pharmaceutical products and vaccines that contain thimerosal are among the potential source of mercury exposure. Current research was intended to ascertain the reprotoxic effects of thimerosal on rat testes. Twenty-four adult male albino rats were sorted into four groups (n = 6). The first group was a control group. Rats of experimental Group 2, 3 and 4 were treated with various dosages of thimerosal (0.5, 10, 50 mg/kg) respectively. Rats were decapitated after thirty days of trial and different parameters were analyzed. Thimerosal exposure resulted in a significant decrease in antioxidant enzyme activities including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), glutathione reductase (GSR) and increased levels of thiobarbituric acid reactive substances (TBARS). Different doses of thimerosal significantly decreased (p < 0.05) the concentration of plasma testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH). Additionally, Daily sperm production (DSP) and efficiency of daily sperm production were significantly reduced followed by thimerosal exposure. Moreover, thimerosal significantly (p < 0.05) decreased the primary spermatocytes, secondary spermatocytes, number of spermatogonia along with spermatids. Thimerosal induced adverse histopathological and morphological changes in testicular tissues such as decreased Leydig cells, diameter of seminiferous tubules, tunica albuginea height and epithelial height. On the other hand, the increase in tubular lumen and interstitial spaces was observed due to thimerosal. These outcomes indicated that thimerosal has potential reprotoxic effects in male albino rats.     

Effects of 60 Hz electric and magnetic fields on maturation of the rat neopallium

This study was undertaken to determine the effects of extremely low frequency (ELF; 60 Hz) electromagnetic (EM) fields on somatic growth and cortical development, as well as biochemical and morphological maturation, of the rat neopallium. On the fifth day of pregnancy, female rats were put in pairs into plastic cages that were housed in a specially constructed apparatus for irradiation under three separate sets of combination and intensity: 1) 1 kV/m and 10 gauss; 2) 100 kV/m and 1 gauss; and 3) 100 kV/m and 10 gauss. The dams were exposed for 23 h daily, from days 5 through 19 postconception after which they were returned to cages outside the exposure apparatus until they littered. The neonates were culled to eight pups per litter. At 0 (birth), 5, 12, and 19 days postnatally, they were killed for biochemical and morphological studies. Another group of pregnant rats was sham-exposed in an identical apparatus, which was not energized, and the pups were used as controls. The irradiated rats exhibited no physical abnormalities, nor did they show brain deformities such as swelling or herniation following exposure to ELF-EM fields. There was no difference in somatic growth between control and exposed rats, but a small reduction in cortical weight was observed in rats exposed at 1 kV/m and 10 gauss, and 100 kV/m and 1 gauss, respectively. Biochemical measurements of DNA. RNA, protein, and cerebroside concentrations indicated that among the three separate exposures, only the neopallium of rats exposed at 1 kV/m and 10 gauss showed a small reduction in DNA level, as well as small reductions in RNA and protein levels. No changes were noticed in cerebroside levels in any exposed animals, and there were no differences in protein/DNA and cerebroside/DNA ratios between control and exposed rats. Morphological observations did not reveal any detectable alterations in the irradiated rats. These results indicate that exposure to ELF-EM fields caused minimal or no changes in somatic growth and cerebral development of the rat. © 1993 Wiley-Liss, Inc.     

Ultrastructural alterations in branchial chloride cells of Atlantic salmon, Salmo salar, during parr-smolt transformation and early development in sea water

The ultrastructure of the gill primary lamellae of juvenile Atlantic salmon was examined during the parr-smolt transformation and for 42 days after smolts were exposed to sea water. Scanning electron microscopy indicated that primary lamellae were characterized by rough convoluted surfaces that became rougher throughout the experimental period and that crypts did begin to form in freshwater fish. Crypt formation increased in sea water.
Transmission electron microscopy indicated that parr preadapt for life in sea water in part by changes in chloride cells. Chloride cells show an elaboration of rough endoplasmic reticulum in fresh water and a decline of rough endoplasmic reticulum after 42 days of sea water exposure. The tubular membrane system becomes well developed in fresh water, and apical vesicles become abundant only after seawater exposure. Mitochondria are both spherical and elongate through the period and contain well developed cristae. No evidence of mitochondrial rupture was observed. The junctions between chloride cells and adjacent cells were characterized in fresh water by long tight junctions with desmosomes. This type of junction continued in sea water and was the norm between chloride cells and accessory cells after 42 days of seawater exposure. While leaky junctions appeared to be forming, no evidence was found of membrane interdigitation between accessory cells and chloride cells after 42 days of seawater exposure. It also appeared that seawater exposure influenced the number of chloride cells exposed to the external milieu.
Pavement cells showed an elaboration in fresh water of free ribosomes and rough endoplasmic reticulum and these elements became less prominent after seawater exposure.     

Effect of c-myc on the ultrastructural structure of cochleae in guinea pigs with noise induced hearing loss

Noise over-stimulation may induce hair cells loss and hearing deficit. The c-myc oncogene is a major regulator for cell proliferation, growth, and apoptosis. However, the role of this gene in the mammalian cochlea is still unclear. The study was designed to firstly investigate its function under noise condition, from the aspect of cochlear ultrastructural changes. We had established the adenoviral vector of c-myc gene and delivered the adenovirus suspension into the scala tympani of guinea pigs 4 days before noise exposure. The empty adenoviral vectors were injected as control. Then, all subjects were exposed to 4-kHz octave-band noise at 110 dB SPL for 8 h/day, 3 days consecutively. Auditory thresholds were assessed by auditory brainstem response, prior to and 7 days following noise exposure. On the seventh days after noise exposure, the cochlear sensory epithelia surface was observed microscopically and the cochleae were taken to study the ultrastructural changes. The results indicated that auditory threshold shift after noise exposure was higher in the ears treated with Ad.EGFP than that treated with Ad.c-myc-EGFP. Stereocilia loss and the disarrangement of outer hair cells were observed, with greater changes found in the Ad.EGFP group. Also, the ultrastructure changes were severe in the Ad.EGFP group, but not obvious in the Ad.c-myc-EGFP group. Therefore, c-myc gene might play an unexpected role in hearing functional and morphological protection from acoustic trauma.     

Histological and electron microscopical observations on the effects of different salinities and heavy metal Ions,on the gills of Jaera nordmanni (Rathke) (Crustacea,Isopoda)

Summary The effects of different salinities and concentrations of copper, mercury and cadmium ions on the gills of Jaera nordmanni are investigated by means of light and electron microscopy. After exposure to 10% and 50% sea water the gill epithelium cells show a marked uniformity in appearance, possessing characteristically large, sub-cuticular spaces which are prominent between microvilli. With exposure to the heavy metal ions a similar sequence of histological and ultrastructural changes occur in all the gill epithelial cells, culminating in cell breakdown. The ultrastructural changes include distended microvilli, dilated endoplasmic reticulum, dissociated ribosomes, diffuse (swollen) cytoplasm, swollen mitochondria and a basal membrane withdrawn from the basal lamina. An increase in the number of haemocytes is also commonly observed in the haemolymph spaces during heavy metal ion exposure. The significance of the morphological changes undergone by the gill epithelial cells after exposure to different salinities and heavy metal ion concentration, are discussed in relation to the physiological functioning of the gill.The author wishes to thank Dr. M.B. Jones and Mr. R.H. Moore for setting up the experiments and to Professor E. Naylor for providing laboratory facilities at the Department of Marine Biology, University of Liverpool, Port Erin, Isle of Man. This work was supported by a Ministry of Defence (Navy) Contract No. AT/2198/010/CDL.     

Bath exposure of Atlantic halibut (Hippoglossus hippoglossus L.) yolk sac larvae to bacterial lipopolysaccharide (LPS): absorption and distribution of the LPS and effect on fish survival

Radiolabelled bacterial lipopolysaccharide (3H-LPS) obtained from Aeromonas salmonicida subsp. salmonicida was added to the petri dishes containing yolk sac larvae of Atlantic halibut (Hippoglossus hippoglossus L.). The larvae were exposed either to 6.25, 12.5, 25, 50 or 100 micrograms 3H-LPS ml-1. The uptake was both dependent on the LPS concentration and the time of exposure. After 5 days of exposure, each larva contained 1.8-7.4 ng 3H-LPS dependent on the initial concentration. After 10 days of exposure each larva contained 7.0-12.4 ng LPS and after 15 days they contained 18.3-34.9 ng 3H-LPS. Fluorescence microscopic analysis of sections obtained from larvae exposed to FITC-LPS (25, 50 and 100 micrograms ml-1) for 5, 10 and 15 days, revealed fluorescence in intestinal epithelial cells, cells in the connective tissue adjacent to the intestine, in cells located between the integumental layer and yolk sac, and in some epithelial cells in the integument. By use of immunohistochemical techniques, LPS was confined to intestinal epithelial cells, lumen of excretory duct and in numerous cells in the epidermal layer. Control specimens did not contain fluorescence or were immunohistochemically negative for LPS. In groups of larvae exposed to 12.5, 25, 50 and 100 micrograms LPS ml-1, the survival was significantly increased after exposure to 50 and 100 micrograms LPS ml-1 from day 20 (96 d degree) and throughout the yolk sac period compared to untreated larvae.     

Effects of γ-interferon on the growth, morphology, and membrane and cytoskeletal proteins expression of LAN-1 cells

The effects of gamma-interferon (gamma-IFN) on the growth, morphology, and phenotypic expression of the human neuroblastoma (NB) cell line, LAN-1, have been extensively tested. Low doses of gamma-IFN allowing more than 90% cell viability induce morphological differentiation and growth inhibition. Cells exposed to gamma-IFN significantly decreased their growth rate, became smaller and poligonal, and sprouted long cellular processes with varicosities along their course, typical of the neurites seen in differentiated NB cells; morphological changes appeared within 48 h of culture with 1,000 U/ml gamma-IFN. The new morphological aspect reached the maximum expression after 6 days of culture, becoming more evident when fresh drug was added after 2 days of culture. A decrease in [3H]thymidine incorporation was also observed within 24 h; cell growth was completely inhibited at the 6th day. Membrane immunofluorescence showed several changes in NB-specific antigen expression after 6 days of treatment with gamma-IFN. At the same time gamma-IFN also modulated cytoskeletal proteins. These findings suggest that noncytotoxic doses of gamma-IFN do promote the differentiation of LAN-1 neuroblastoma cells which is associated with the reduced expression of the malignant phenotype.     

Biological and morphological effects on the brain after exposure of rats to a 1439 MHz TDMA field

We investigated the effects of exposure to a 1439 MHz TDMA (Time Division Multiple Access) field, as used in cellular phones, on the permeability of the blood-brain barrier (BBB), on the morphological changes of the brain, and on body-mass fluctuations. Male Sprague-Dawley (SD) rats were divided into three groups of eight rats each. The rats in the EM(+) group, which had their heads arrayed in a circle near the central antenna of an exposure system, were exposed to a 1439 MHz field for one hour a day. The rats in EM(-) group were also in the exposure system, however, without high-frequency electromagnetic wave (HF-EMW) exposure. The animals in the control group were neither placed in the system nor exposed to HF-EMWs. The exposure period was two or four weeks. The energy dose rate peaked at 2 W/kg in the brain; the average over the whole body was 0.25 W/kg. The changes in the permeability of BBB were investigated by Evans blue injection method and by immunostaining of serum albumin. HF-EMWs had no effect on the permeability of BBB. The morphological changes in the cerebellum were investigated by assessing the degeneration of Purkinje cells and the cell concentration in the granular layer. No significant changes were observed in the groups of rats exposed to HF-EMWs for two or four weeks. Averaged body masses were not affected by HF-EMWs exposure. In conclusion, a 1439 MHz TDMA field did not induce observable changes in the permeability of the BBB, morphological changes in the cerebellums, or body mass changes in rats, as evaluated by the conventional methods.     

Time course of IL1 and IL6 synthesis and release in human bronchial epithelial cell cultures exposed to toluene diisocyanate.

We have previously demonstrated that human bronchial epithelial cells release appreciable amounts of interleukin 1 (IL1) and interleukin 6 (IL6) when exposed to toluene diisocyanate (TDI) in vitro. TDI is an inflammatory and asthmogenic stimulus presumed to act at least in part through immunological mechanisms. The epithelial cell-derived IL1 and IL6 can promote T cell activation and proliferation in culture, and if this also happens in vivo they may contribute to the persistence of the inflammatory response of the bronchial mucosa observed in TDI-sensitive asthmatics. In this study, we confirmed the release of biologically active IL1 beta and IL6-like substances from bronchial epithelial cells exposed to isocyanates in vitro, and related the rate and the magnitude of the cytokine secretion with the pattern of IL1 beta and IL6 gene expression and the extent of epithelial cell injury. In the epithelial cell cultures exposed to TDI, there was a parallel, progressive increase in the expression of IL6 mRNA and in the secretion of IL6 protein between 48 hours and 6 days after exposure. By contrast, although increasing amounts of biologically active IL1 beta were detected in the supernatants of TDI-exposed epithelial cells throughout the 6-day period following exposure, augmented levels of IL1 beta mRNA were only evident 6 days after exposure, suggesting that TDI exposure might have initially affected the enzymatic cleavage of the intracellular IL1 beta precursor and the mechanisms which regulate the secretion of mature IL1 beta.     

A localised decrease of GA1 in shoot tips of Salix pentandra seedings precedes cessation of shoot elongation under short photoperiod

By application of a recently developed method allowing analysis of gibberellins (GAs) in mg amounts of tissue, the effect of photoperiod on levels of GAs in shoot tips of individual seedlings of the woody species Salix pentandra was studied. In elongating long day-grown seedlings, maximum levels of GA₁ were found 5–20 mm below the apex, approximately twice the levels in other segments. After exposure of plants to 5 or 15 short days, the levels of GA₁ were about 50% lower within this specific region of the stem, as compared with seedlings grown under long days. Short day-induced cessation of shoot elongation also correlated with overall declines in the levels of GA₅₃, GA₁₉, GA₂₀ and GA₈, Within each photoperiodic treatment the levels of these GAs were generally relatively similar throughout the upper 35 mm of stems. No differences in internode lengths or in lengths of pith or epidermal cells were found in plants grown under long days compared with those exposed to 5 short days. In both cases, cells in mitosis were observed in the subapical stem tissues of shoot tips. After 15 short days, stem elongation was completed, and dividing cells were generally not found in the subapical part of the stem. However, short day exposure did not prevent elongation of internodes and cells differentiated before the treatment was started. Thus, the localised decrease in level of GA₁ in shoot tips under short days precedes the morphological and anatomical changes connected with the short day-induced cessation of elongation growth. This supports the hypothesised role for GA₁ in photoperiodic control of shoot elongation in S. pentandra .     

兔机械性角膜上皮损伤后伤口愈合的形态学动态变化

目的观察兔机械性角膜上皮损伤后伤口愈合的形态学动态变化。方法选取新西兰大白兔12只,随机分为A、B两组,均建立机械性角膜上皮损伤模型（刮除直径为8mm的角膜中央上皮）,术后给予盐酸林可霉素滴眼液滴眼,3次/日,1滴/次。A组在建模后第0、1、4、7天共4个时间点采用前节裂隙灯照相系统进行眼表照相,并计算损伤面积。B组在建模后第1、4、7天,按随机数字表法取2只兔的实验眼角膜,行透射电镜及病理检查。结果前节裂隙灯照相系统记录了不同观察时间点损伤范围（伤口愈合面积）的动态变化。造模后第1天,角膜上皮全层缺如,损伤边缘处上皮细胞胞膜向损伤区内伸出褶皱的伪足;造模后第4天,上皮自周边向缺损区域爬行生长,覆盖整个角膜,可见2～3层细胞,主要为基底细胞和多角细胞,细胞连接松驰;造模后第7天,再生上皮分化较完全,约5～6层细胞,极向齐,连接较紧密,可见均匀分布的半桥粒结构。结论兔机械性角膜上皮损伤后伤口愈合的动态形态学变化包括上皮细胞向心性移行、增殖,以及随后的分化,连接。     

Delayed consequences of the influence of simulated geomagnetic storms on roach Rutilus rutilus embryos

This study presents data collected over a 3 year period on the effects of simulated geomagnetic storms (SGMS) on Eurasian roach Rutilus rutilus embryos. Effects were studied during different stages of early development. Rutilis rutilus were raised in ponds for 4 months after exposure to SGMS. The mass, standard length and morphological characteristics of under-yearlings exposed as embryos were recorded. A decrease in length–mass indices in under-yearlings was noted after they had been exposed to SGMS during the first 2 days or during the third and fourth days of early development. Near the time point of 48 h post fertilisation, either no effect or an increased size was observed. In addition, exposure to SGMS led to a redistribution of the vertebral number between the sections of the vertebral column as well as changes in the number of seismosensory system openings in the mandibular and praeoperculum bones of under-yearlings. Observed effects are similar to previously published data on the influence of anthropogenic magnetic fields on roach, namely changes in linear-mass indices, number of vertebrae and number of seismosensory system openings in the mandibular bones of under-yearlings exposed as embryos. Possible mechanisms of magnetic influence on early development of fish are discussed.     

A Highlights from MBoC Selection: Stochastic contraction of myosin minifilaments drives evolution of microridge protrusion patterns in epithelial cells

Actin-based protrusions vary in morphology, stability, and arrangement on cell surfaces. Microridges are laterally elongated protrusions on mucosal epithelial cells, where they form evenly spaced, mazelike patterns that dynamically remodel by fission and fusion. To characterize how microridges form their highly ordered, subcellular patterns and investigate the mechanisms driving fission and fusion, we imaged microridges in the maturing skin of zebrafish larvae. After their initial development, microridge spacing and alignment became increasingly well ordered. Imaging F-actin and non-muscle myosin II (NMII) revealed that microridge fission and fusion were associated with local NMII activity in the apical cortex. Inhibiting NMII blocked fission and fusion rearrangements, reduced microridge density, and altered microridge spacing. High-resolution imaging allowed us to image individual NMII minifilaments in the apical cortex of cells in live animals, revealing that minifilaments are tethered to protrusions and often connect adjacent microridges. NMII minifilaments connecting the ends of two microridges fused them together, whereas minifilaments oriented perpendicular to microridges severed them or pulled them closer together. These findings demonstrate that as cells mature, cortical NMII activity orchestrates a remodeling process that creates an increasingly orderly microridge arrangement.     

The effects of cadmium exposure on the cytology and function of primary cultures from rainbow trout

Cultured epidermal cells from explants of skin of rainbow trout were used to study the cytological and functional changes following sublethal exposure to cadmium stress. The aim was to develop diagnostic markers for ecotoxicology. Cultures were exposed to the pollutant for 48 h. Cell structural and cytological changes were established by light and electron microscopy. Metabolic alterations were detected by immunohistochemistry. The relation between the initiation of cellular alterations and cadmium concentrations was compared in cultures exposed in commercially-available serum-free and serum-containing medium. The expression of stress proteins (metallothionein and heat shock protein) was also studied. Rainbow trout epithelial cells exposed to cadmium showed typical morphological changes indicative of cell death by apoptosis. Sublethal exposure also resulted in cellular metabolic disturbances with increased deposits of glycogen. Increased melanization was also observed. These changes appeared at lower concentrations of cadmium when cells were exposed in serum-free media than in serum-containing media. Cadmium induced the expression of heat shock proteins but not of metallothioneins. The results broadly confirm in vivo findings for cadmium toxicity and suggest that this in vitro technique may have applications in aquatic toxicology. © 1998 John Wiley & Sons, Ltd.