Decrease In Cellular Density Research Articles

Argentic staining reveals changes in cerebellar tissue organisation by prenatal glucocorticoid administration in rats.

It was almost 150 years ago that Golgi revolutionised histology with silver-based stains. Major advances in knowledge of the nervous system became possible because of silver impregnations. Silver staining combined with classical histological staining, cytochemistry methods, and electron microscopy is useful for studying mechanisms and components at subcellular, cellular, and tissue levels. Despite the advantages of silver staining, its use has decreased over time. The aim of this work was to use argentic staining to study the cerebellar effects of controversial prenatal glucocorticoid (GC) therapy. At postnatal day 12 (P12), the cerebellum of corticosterone (CC)-treated rats impregnated with AgNOR staining exhibited diminished thickness of the external granule layer (EGL) and irregular Purkinje cell arrangement. There was a greater number of nucleoli and nucleolar organiser regions (NORs) in 24% of Purkinje cells. Cerebellar granule neuron progenitor (CGNP) cells of the EGL showed a decrease in cellular density (confirmed by proliferating cell nuclear antigen [PCNA] immunolocalization) and NORs. At postnatal day 6 (P6), the Golgi-Kopsch technique allowed us to observe disturbances in the distribution pattern of CGNP cells (during proliferation, migration, and differentiation) and premature growth of the Bergmann glia. Our findings reveal disturbances in the cerebellar development program with early cellular and tissue changes.

Bioimpedance Vector Patterns Changes in Response to Swimming Training: An Ecological Approach.

Background and aim: Monitoring bioelectric phase angle (PhA) provides important information on the health and the condition of the athlete. Together with the vector length, PhA constitutes the bioimpedance vector analysis (BIVA) patterns, and their joint interpretation exceeds the limits of the evaluation of the PhA alone. The present investigation aimed to monitor changes in the BIVA patterns during a training macrocycle in swimmers, trying to ascertain if these parameters are sensitive to training load changes across a 13-week training period. Methods: Twelve national and international level swimmers (four females; eight males; 20.9 ± 1.9 years; with a competitive swimming background of 11.3 ± 1.8 years; undertaking 16–20 h of pool training and 4–5 h of dry-land training per week and 822.0 ± 59.0 International Swimming Federation (FINA) points) were evaluated for resistance (R) and reactance (Xc) using a single frequency phase sensitive bioimpedance device at the beginning of the macrocycle (M1), just before the beginning of the taper period (M2), and just before the main competition of the macrocycle (M3). At the three-time assessment points, swimmers also performed a 50 m all-out first stroke sprint with track start (T50 m) while time was recorded. Results: The results of the Hotelling T2 test showed a significant vector displacement due to simultaneous R and Xc changes (p < 0.001), where shifting from top to bottom along the major axis of the R-Xc graph from M1 to M2 was observed. From M2 to M3, a vector displacement up and left along the minor axis of the tolerance ellipses resulted in an increase in PhA (p < 0.01). The results suggest a gain in fluid with a decrease in cellular density from M1 to M2 due to decrements in R and Xc. Nevertheless, the reduced training load characterizing taper seemed to allow for an increase in PhA and, most importantly, an increase of Xc, thus demonstrating improved cellular health and physical condition, which was concomitant with a significant increase in the T50 m performance (p < 0.01). Conclusions: PhA, obtained by bioelectrical R and Xc, can be useful in monitoring the condition of swimmers preparing for competition. Monitoring BIVA patterns allows for an ecological approach to the swimmers’ health and condition assessment without resorting to equations to predict the related body composition variables.

Diffusion weighted magnetic resonance imaging (DW-MRI) as a non-invasive, tissue cellularity marker to monitor cancer treatment response

BackgroundDiffusion weighted magnetic resonance imaging (DW-MRI) holds great potential for monitoring treatment response in cancer patients shortly after initiation of radiotherapy. It is hypothesized that a decrease in cellular density of irradiated cancerous tissue will lead to an increase in quantitative apparent diffusion coefficient (ADC) values. DW-MRI can therefore serve as a non-invasive marker of cell death and apoptosis in response to treatment. In the present study, we aimed to investigate the applicability of DW-MRI in preclinical models to monitor radiation-induced treatment response. In addition, we compared DW-MRI with ex vivo measures of cell density, cell death and apoptosis.MethodsDW-MRI was tested in two different syngeneic mouse models, a colorectal cancer (CT26) and a breast cancer (4 T1). ADC values were compared with quantitative determinations of apoptosis and cell death by flow cytometry. Furthermore, ADC-values were also compared to histological measurement of cell density on tumor sections.ResultsWe found a significant correlation between ADC-values and apoptotic state in the CT26 model (P = 0.0031). A strong correlation between the two measurements of ADC-value and apoptotic state was found in both models, which were also present when comparing ADC-values to cell densities.ConclusionsOur findings demonstrate that DW-MRI can be used for non-invasive monitoring of radiation-induced changes in cell state during cancer therapy. ADC values reflect ex vivo cell density and correlates well with apoptotic state, and can hereby be described as a marker for the cell state after therapy and used as a non-invasive response marker.

A Pilot Study on Ocular Safety and Efficacy of Infliximab as an Antifibrotic Agent After Experimental Glaucoma Filtration Surgery

IntroductionTumor necrosis factor-α (TNF-α) is a multifunctional, proinflammatory cytokine that mediates pleiotropic biological functions, especially inflammation and immunoregulation. We hypothesized that blocking TNF-α with a monoclonal antibody would decrease inflammation and subconjunctival scarring in an animal model of experimental filtration surgery.MethodsIn a randomized, prospective, masked-observer study, 30 New Zealand albino rabbits underwent glaucoma filtration surgery. The animals were allocated to receive either intraoperative application of infliximab (group A) or mitomycin C (MMC) at a concentration of 0.2 mg/ml (group B) or balanced salt solution (BSS, control) (group C). Different infliximab doses, namely 1.0, 2.0, 3.0, 4.0, 5.0 mg in 0.1 ml, were applied. Bleb survival and characteristics were evaluated over a 30-day period. The animals were killed on postoperative day 15 or 30. Histology of the operated eyes was performed to evaluate and grade the amount of scarring in each group. Cellular density was evaluated in each case.ResultsInfliximab did not appear to improve outcomes in this model of glaucoma filtration surgery. Bleb survival was significantly higher in the MMC group compared to the other groups (p < 0.001 for both comparisons). Vascularity was also significantly lower in the MMC group compared to the other groups (p = 0.018 for both comparisons). There was a significant decrease in cellular density in the MMC group compared to the control (p = 0.0352) and the infliximab group (p < 001).ConclusionOur results have shown that trabeculectomies in the infliximab group failed faster and displayed more scarring, compared to the control and MMC groups. This outcome suggests that the infliximab doses used in this pilot study resulted in a subconjunctival TNF-α concentration, which acted as a stimulator to fibroblasts.

Efecto de metales pesados en el crecimiento de la microalga tropical Tetraselmis chuii (Prasinophyceae)

We determined the toxic effect of four metals, cadmium (Cd), copper (Cu), mercury (Hg) and lead (Pb), on the tropical microalga Tetraselmis Chuii (Butcher, 1959). We exposed 50 ml of cultivated microalgae (f/2 Guillard) in the exponential growth phase, with three replicates, to concentrations of 0 (control). 0.1, 1.0, 5.0, 10.0 and 20.0 mgxl(-1) with each metal for 96 hr. We evaluated the lethal effect daily, through the cellular count. In the control treatment (not exposed to any metal) we observed an increase in cellular density. In all treatments exposed to metals, we observed a decrease in cellular density, which accelerated in 48 h, after which it became less pronounced. There were exceptions with low concentrations of Cd and Cu at 24 h, as there was no significant decrease, probably due to their use as micronutrients at these low concentrations. The metal that caused the most lethal effect was Pb, which killed 50% of the microalgal population at a concentration of 0.40 mg x l(-1). This concentration was 3 times lower than that of mercury and 13 times lower than those of cadmium and copper. The microalga Tetraselmis chuii is recommended as a model species to estimate the toxic effects of xenobiotics on tropical seawater environments.

Dose‐dependent inhibitory effects of proton pump inhibitors on human osteoclastic and osteoblastic cell activity

Proton pump inhibitors (PPIs), a class of molecules that are used to decrease gastric acid production, might have adverse effects on bone metabolism. The aim of this study was to characterize the concentration-dependent and time-dependent effects of three PPIs (omeprazole, esomeprazole, and lansoprazole) on human osteoclast precursor cells isolated from peripheral blood, and on human mesenchymal stem cells (osteoblast precursors). Cell cultures were characterized for total protein content, apoptosis, and several osteoclastic/osteoblastic features, and also for the involvement of some intracellular signaling pathways. PPIs caused a dose-dependent decrease in cellular density, which correlated with an increase in the apoptosis rate, effects that became statistically significant at concentrations ≥ 10(-5) m. They also inhibited phenotype-related gene expression and functional parameters. For both cell types, cellular function, i.e. osteoclastic resorption and the formation of mineralized deposits by osteoblastic cells, was more affected than proliferation-related parameters. The three PPIs showed similar qualitative and quantitative effects, but displayed some differences in the underlying intracellular signaling pathways. These results suggest that PPIs might have a direct deleterious effect on bone cells, with the possibility of decreased bone turnover.

Abstract A44: The Pi3K inhibitor GSK2126458 is highly toxic in ovarian dysgerminoma

Abstract Introduction: Mutations in PI3K/PTEN/Akt/mTOR have been implicated in the pathogenesis of numerous human carcinomas. Moreover, inhibitors of the phosphatidylinositol 3-kinase (PI3K) pathway are shown to be potent in several tumors, including ovarian adenocarcinomas. The effect of this class of agents on ovarian germ cell tumors, however, has not been previously studied. The aim of this work was to investigate cytotoxicity of the PI3K inhibitor GSK2126458 (a highly potent and selective compound) in ovarian dysgerminoma from a patient. Methods: The studied ovarian dysgerminoma was collected immediately following resection. Tumor sections (0.5×0.5×0.1 cm) were immersed in ice-cold RPMI medium gassed with 95% O2:5% CO2. The samples were then incubated at 37°C in RPMI (continuously gassed as above) with and without 50 nM GSK2126458 (Selleck Chemicals, cat. #S2658) for 150 min. At the end of the incubation period, specimens were processed for hematoxylin and eosin histologic stain. Results: Sections from untreated tissue revealed variable-sized tumor nests separated by fibrous stromal bands. Neoplastic cells were characterized by uniformly round central nuclei, clear-to-eosinophilic cytoplasm and prominent single nucleoli. Mitotic figures were abundant. Sections from treated tissue revealed a decrease in cellular density. Neoplastic cells demonstrated cytoplasmic disintegration, vacuolar degeneration and nuclear basophilia. Apoptotic bodies were numerous. Conclusions: GSK2126458 induced remarkable necrosis in the ovarian dysgerminoma. This preliminarily observation suggests sensitivity of this tumor to PI3K inhibition. The described in vitro methodology provides rapid assessment of the cytotoxicity of PI3K/PTEN/Akt/mTOR inhibitors.

Radiation-induced blood–brain barrier damages: An in vitro study

A radiation-induced blood–brain barrier (BBB) breakdown has been supposed to explain the acute radiation syndrome and the delayed brain radiation injury, but it has been clearly demonstrated only at high doses. In a previous study (Diserbo et al., 2002), we showed that non-lethal total body irradiation produced an early transient increase in BBB permeability in rats but the underlying mechanisms of radiation-induced BBB breakdown remain unclear. In the present work, the effects of ionizing radiation were studied on an in vitro BBB model. Gamma irradiation induced an increase in [ 14C]-sucrose BBB permeability that can be detected 72 h after exposure at doses up to 4 Gy. This increase was more important 8 days after irradiation and could be limited by dexamethasone treatment. An increase in fluorescein and FITC-dextrans (4 kDa/70 kDa) permeability was also observed, which can be related to a substantial opening of endothelial cell tight-junctions but without massive modification of tight-junction protein (ZO-1, ZO-2, claudin-5, occludin) immunolabeling even 8 days after 25 Gy exposure. Formation of actin stress fibers occurred in endothelial cells 8 days after 25 Gy exposure. A progressive decrease in cellular density associated with a simultaneous spreading of the endothelial cells was also observed after irradiation. Anti-γH2AX immunolabeling was used to investigate both DNA double-strand break induction and repair rates in endothelial cells. It revealed long-lasting DNA double-strand breaks after gamma irradiation. A better understanding and awareness of these phenomena are essential for designing appropriate pharmacotherapy in radiation-therapy and treatment of accidental overexposure.

Reduced platelet concentration does not harm PRP effectiveness for ACL repair in a porcine in vivo model

Enhanced primary repair of the ACL using a collagen scaffold loaded with platelets has been shown to improve the functional healing of suture repair in animal models. In this study, our objectives were to determine if lowering the platelet concentration would reduce the structural properties of the repaired ACL and increase postoperative knee laxity. Eight Yucatan mini-pigs underwent bilateral suture repair. In one knee, the repair was augmented with a collagen scaffold saturated with platelet-rich plasma (PRP) containing five times the systemic baseline of platelets (5×) while the contralateral knee had a collagen scaffold saturated with PRP containing three times the systemic baseline of platelets (3×). After 13 weeks of healing, knee joint laxity and the structural properties of the ACL were measured. The 3× platelet concentration resulted in a 24.1% decrease in cellular density of the repair tissue (p < 0.05), but did not significantly decrease the structural properties [3× vs. 5×: 362 N vs. 291 N (p = 0.242) and 70 N/mm vs. 53 N/mm (p = 0.189) for the yield load and linear stiffness, respectively]. The 3× platelet concentration also did not significantly change the mean anteroposterior knee laxity at 30° and 90° of flexion [5× vs. 3×: 3.5 mm vs. 5.1 mm (p = 0.140), and 6.1 mm vs. 6.3 mm (p = 0.764)] but did result in a lower AP laxity at 60° [5× vs. 3×: 8.6 mm vs. 7.3 mm (p = 0.012)]. The decrease in platelet concentration from 5× to 3× to enhance suture repair of the ACL did not significantly harm the mechanical outcomes in this animal model.

Higher Molecular Weight Polyethylene Glycol Increases Cell Proliferation While Improving Barrier Function in an In Vitro Colon Cancer Model

Polyethylene glycol (PEG) has been previously shown to protect against enteric pathogens and prevent colon cancer invasion. To determine if PEG could indeed protect against previously observed pro-invasive effects of commensal E. coli and EPEC, Caco-2 cells grown in an in vitro model of colon cancer were infected with strains of human commensal E. coli or EPEC and treated with 10% PEG 3350, PEG 8000, and PEG 20,000, respectively. At 24 hours after infection, MMP-1 and MMP-13 activities, cell cluster thickness, depth of invasion, and proliferation were determined using standard molecular biology techniques and advanced imaging. We found that higher molecular weight PEG, especially PEG 8000 and 20,000, regardless of bacterial infection, increased proliferation and depth of invasion although a decrease in cellular density and MMP-1 activity was also noted. Maximum proliferation and depth of invasion of Caco-2 cells was observed in scaffolds treated with a combination of commensal E. coli strain, HS4 and PEG 8000. In conclusion, we found that PEG 8000 increased cell proliferation and led to the preservation of cell density in cells treated with commensal bacteria. This is important, because the preservation of a proliferative response in colon cancer results in a more chemo-responsive tumor.

Immunoreactive vasoactive intestinal polypeptide and vasopressin cells after a protein malnutrition diet in the suprachiasmatic nucleus of the rat

The aim of the present study was to evaluate the effects of prenatal and postnatal protein deprivation on the morphology and density of vasopressin (VP) and vasoactive intestinal polypeptide (VIP) immunoreactive neurons in the suprachiasmatic nucleus (SCN) of young rats. Female Wistar rats were fed either 6% (malnourished group) or 25% (control group) casein diet five weeks before conception, during gestation and lactation. After weaning, the pups were maintained on the same diet until sacrificed at 30 days of age. The major and minor axes, somatic area and the density of VP- and VIP-immunoreactive neurons were evaluated in the middle sections of the SCN. The present study shows that chronic protein malnutrition (ChPM) in VP neurons induces a significant decrease in number of cells (-31%,) and a significant increase in major and minor axes and somatic area (+12.2%, +21.1% and +15.0%, respectively). The VIP cells showed a significant decrease in cellular density (-41.5%) and a significant increase in minor axis (+13.5%) and somatic area (+10.1%). Our findings suggest that ChPM induces abnormalities in the density and morphology of the soma of VP and VIP neurons. These alterations may be a morphological substrate underlying circadian alterations previously observed in malnourished rats.

Ex vivo transfer of Smad7 decreases damage to the corneal endothelium after penetrating keratoplasty

To determine whether transient gene transfer and expression of the intracellular antagonist of transforming growth factor beta (TGF-beta), Smad7, to corneal endothelial cells decreases corneal endothelial cell damage after penetrating keratoplasty in a rabbit model. Rabbit corneas were transfected ex vivo with replication-deficient adenoviruses encoding Flag-tagged Smad7, Flag-tagged Smad3, or LacZ (termed AdCMV-Smad7, AdCMV-Smad3, AdCMV-LacZ) and then transplanted to normal rabbits. Expression of the exogenous Smads and phosphorylation of endogenous Smad2 in the transplanted corneal endothelium were examined by immunoblotting and immunohistochemistry with anti-Flag or anti-phosphorylated Smad2 antibodies. Cellular density and morphological changes in the corneal endothelium of the transplanted cornea were evaluated by scanning electron microscopy after transplantation of the Smad-transfected corneas. Transplanted AdCMV-Smad7-transfected corneas significantly inhibited the decrease in cellular density and accelerated wound healing at the host-graft junction when compared with transplanted AdCMV-LacZ-transfected corneas. Transplanted AdCMV-Smad3-transfected corneas showed decreased cellular density and delayed wound healing at the host-graft junction. Ex vivo gene transfer of Smad7 to corneal endothelial cells inhibits the decrease in cellular density and accelerates wound healing after penetrating keratoplasty in rabbits. Thus, modulation of Smad7 expression in corneal endothelial cells may decrease corneal endothelial cell damage after penetrating keratoplasty.

Proteomic analysis and quantification of cytokines and chemokines from biomaterial surface‐adherent macrophages and foreign body giant cells

Implantation of biomaterial devices results in the well-known foreign body reaction consisting of monocytes, macrophages, and foreign body giant cells (FBGCs) at the material/tissue interface. We continue to address the hypothesis that material surface chemistry modulates the phenotypic expression of these cells. Utilizing our human monocyte culture system, we have used surface-modified polymers displaying hydrophobic, hydrophilic, and/or ionic chemistries to determine the cytokines/chemokines released from biomaterial-adherent macrophages/FBGCs. This study broadens our approach by using proteomic analysis to identify important factors expressed by these cells and further quantifies these molecules with ELISAs. Proteomic profiles changed over time suggesting that the adherent macrophages underwent a phenotypic switch. Macrophage/FBGC-derived proinflammatory cytokines, IL-1beta and IL-6, decreased with time, while the anti-inflammatory cytokine, IL-10, gradually increased with time. Resolution of the inflammatory response was also demonstrated by a decrease in chemoattractant IL-8 and MIP-1beta production with time. Material-dependent macrophage/FBGC activation was analyzed using cytokine/chemokine production and cellular adhesion. Monocyte/macrophage adhesion was similar on all surfaces, except for the hydrophilic/neutral surfaces that showed a significant decrease in cellular density and minimal FBGC formation. Normalizing the ELISA data based on the adherent cell population provided cytokine/chemokine concentrations produced per cell. This analysis showed that although there were fewer cells on the hydrophilic/neutral surface, these adherent cells were further activated to produce significantly greater amounts of each cytokine/chemokine tested than the other surfaces. This study clearly presents evidence that material surface chemistry can differentially affect monocyte/macrophage/FBGC adhesion and cytokine/chemokine profiles derived from activated macrophages/FBGCs adherent to biomaterial surfaces.

Induction of Multiple Programmed Cell Death Pathways by IFN-β in Human Non-Small-Cell Lung Cancer Cell Lines

Tissue transglutaminase (tTG) and keratinocyte transglutaminase (kTG), as well as the cross-linked envelopes (CLE) that they form, have been associated with squamous differentiation and programmed cell death in epithelial cells. When interferon-β (IFN-β) was used to stimulate differentiation and programmed cell death in the human lung cancer cell lines NCI-H596 and NCI-H226, the cells underwent a decrease in cellular density. In NCI-H596 IFN-β caused an increase in kTG activity and DNA fragmentation in the lower density cells, which were significantly slower growing than control cells. However, in the higher density cells, which were only slightly slower growing than control cells, IFN-β caused an increase in tTG activity and CLE competence. Dual-parameter flow cytometry demonstrated that IFN-β-induced squamous differentiation preceded programmed cell death. Treatment of NCI-H596 cells with monodansylcadaverine, a transglutaminase inhibitor, prevented the increase in CLE competence, but did not inhibit DNA fragmentation. These results suggest that IFN-β can induce NCI-H596 cells to enter multiple cell death pathways and that these pathways are not only differentiation related, but may also be growth driven.

Phenotypic and Immunohistological Analyses of the Human Adult Thymus: Evidence for an Active Thymus during Adult Life

We analyzed cellular content of thymic samples from 26 human healthy donors, ranging from 1 week postnatal to 49 years old. Our results showed that there was an overall decrease in cellular density, beginning early during life, but with two peaks of cellular density, at 9 months and 10 years of age. Histological and immunohistological analyses showed that variations in cellular density were correlated with the morphological changes observed during thymic involution, namely the enlargement of interlobular trabeculae and the development of adipocytic tissue. However, the adult thymus still contained thymocytes, up to 49 years. Phenotypic analysis showed no significant variations according to the age of donors in the distribution of the main thymocyte subsets, both precursors and more mature cells. These results suggest that the human thymus remains active during adult life.

Effect of progesterone on the non-genomic response to oestrogen in the rat.

Different effects of oestrogen are mediated separately, by independent mechanisms of action. Accordingly, it has been shown that it is possible to dissociate these effects under various conditions which stimulate or inhibit responses selectively. The present study describes the action of progesterone on non-genomic responses to oestrogen stimulation which, it has been suggested, are mediated by eosinophils. Oestrogen induced an increase in the number of eosinophils in the rat uterus, an increase in uterine wet weight and oedema of deep endometrial stroma (measured as decrease in cellular density). Progesterone induced a slight oedematous reaction in superficial endometrial stroma but did not induce uterine eosinophilia. Progesterone pretreatment of oestrogen-treated rats did not block oestrogen-induced uterine eosinophilia and oedema but induced an increase in the degranulation of uterine eosinophils. Therefore the number of eosinophils decreased without any change in the uterine oedema induced after 6h of oestrogen action. The results corroborate previously published evidence of a dissociation of the action of oestrogen in independent groups of responses. Progesterone, a known blocker of some oestrogenic responses, did not block the effects mediated by eosinophils at 6h after oestrogen administration; any change in these effects at later times can be explained by an earlier eosinophil degranulation under the action of progesterone.

The development of the amoebocyte-producing organ in Lymnaea truncatula Müller infected by Fasciola hepatica L.

The amoebocyte-producing organ in Lymnaea truncatula is located between the pericardium and the kidney. In control snails bred at 20 degrees C, the organ only has fibroblast-like cells and type I amoebocytes; its growth is associated with a decrease in cellular density. The organ in infected snails bred at 20 degrees enlarges from day 1 to day 21 after exposure (phase 1) with a rapid increase in the number of type I amoebocytes. Then a gradual cellular rarefaction occurs in this organ from day 21 to day 70 after exposure (phase 2) with a fall in the number of type I amoebocytes and a correlated increase in the number of type II amoebocytes. The connective septae become "fibrous" with thickening from day 42 to day 70 after exposure. The breeding temperature only affects the timing and the dates when the different developmental phases begin in this organ. At a given temperature, the body volume of the snail affects only the cellular density. The amoebocytic rarefaction in the organ is uninterrupted if the snail begins its fast on day 49 after exposure (phase 2, 20 degrees C); the organ becomes "fibrous" if the fast begins on day 14 after exposure (phase 1, 20 degrees C). The significance of these observations is discussed.

Accumulation of water during transformation of cells by an avian sarcoma virus

Chick embryo (CE) cells transformed by the Bryan “high titer” strain of Rous sarcoma virus (RSV-BH) are larger than nontransformed CE cells, as determined by direct measurements of diameter and volume. An observed general increase in cell mass is insufficient to fully account for the larger size. However, RSV-BH-transformed cells contain a greater proportion of water, which is reflected in a decrease in cellular density. These changes in size, water content, and density were not found in cells infected with the Schmidt-Ruppin strain of avian sarcoma virus. CE cells infected with a mutant of RSV-BH are morphologically transformed at 37°C but not at 41°C, and after shifting from 41°C to 37°C they become larger, accumulate more water, and band higher in density gradients. These changes occur without a requirement for new RNA or protein synthesis. The noted increase in cellular water may be an early event leading to changes in transcription and translation, culminating in malignancy in cells transformed by RSV-BH.