Study of the Effect of Different Breast Implant Surfaces on Capsule Formation and Host Inflammatory Response in an Animal Model.

BACKGROUND: Breast implants are biomaterials eliciting a physiological and mandatory foreign body response. OBJECTIVES: The authors designed an animal study to investigate the impact of different implant surfaces on the formation of the periprosthetic capsule, the inflammatory response, and the cellular composition. METHODS: The authors implanted 1 scaled-down version of breast implants by different manufactures on 70 female Sprague Dawley rats. Animals were divided into 5 groups of 14 animals. Group A received a smooth implant (Ra ≈ 0.5 µm) according to the ISO 14607-2018 classification, Group B a smooth implant (Ra ≈ 3.2 µm), Group C a smooth implant (Ra ≈ 5 µm), Group D a macrotextured implant (Ra ≈ 62 µm), and Group E a macrotextured implant (Ra ≈ 75 µm). At 60 days, all animals received a magnetic resonance imaging (MRI), and 35 animals were killed and their capsules sent for histology (capsule thickness, inflammatory infiltrate) and immunohistochemistry analysis (cellular characterization). The remaining animals repeated the MRI at 120 days and were killed following the same protocol. RESULTS: MRI showed a thinner capsule in the smooth implants (Groups A-C) at 60 days (P < .001) but not at 120 days (P = .039), confirmed with histology both at 60 days (P = .005) and 120 days (P < .001). Smooth implants (Groups A-C) presented a mild inflammatory response at 60 days that was maintained at 120 days and a high M2-Macrophage concentration (anti-inflammatory). CONCLUSIONS: Our study confirms that smooth implants form a thinner capsule, inferior inflammatory infiltrate, and a cellular composition that indicates a mild host inflammatory response. A new host inflammatory response classification is elaborated classifying breast implants into mild, moderate, and high.

Detection and whole genome sequencing of murine norovirus in animal facility in Italy.

Viruses belonging to the genus Norovirus (NoV) of the family Caliciviridae are the major cause of acute viral gastroenteritis worldwide. NoVs are classified into 10 genogroups (GI-GX), and those belonging to the genogroup GV are able to infect several species of rodents. To evaluate the circulation of MNV among mice housed in an Italian facility, sampling was performed over two separate periods, in 2011, and 3 years later in 2014. During the two samplings, 75 fecal samples were collected from healthy mice housed in the animal facility and subjected to RT-PCR for viral detection. After the analysis, 41/75 animals (54.6%) resulted positive for the presence of MNV in feces. Nucleotide sequencing revealed the presence of two MNV variants co-circulating in both 2011 and 2014. One MNV strain was isolated on RAW264.7 cell line, and subjected to full genome sequencing. Our study showed that the murine noroviruses are widespread in the investigated animal facility, despite guidelines for animal care and maintenance. Full genome sequence analysis of the MNV strain described in this study showed a correlation with other strains circulating in Europe. Understanding the molecular epidemiology of this virus should give insight into its natural history and evolution in mice.

Amorphous silica nanoparticles induced spleen and liver toxicity after acute intravenous exposure in male and female rats.

Synthetic amorphous silica (SAS) nanomaterial - consisting of aggregates and agglomerates of primary silicon dioxide (SiO2) particles in the nanorange (<100 nm) - is commonly used as excipient in pharmaceuticals, in cosmetics and as food additive (E551). The available data suggest that SAS nanoparticles (NP) after intravenous (IV) exposure persist in liver and spleen; however, insufficient data exist to verify whether SAS may also induce adverse effects. The aim of the present study was to verify the potential long-term effects of SAS NP (NM-203) on spleen and liver as target organs following short-term exposure. Adult male and female Sprague-Dawley rats were treated by IV injection in the tail vein with a single (1-day) dose (SD) and repeated (5-day) doses (RD) of 20 mg/kg bw per day of SAS dispersed in sterile saline solution as vehicle. Histopathological examinations of target organs were performed after 90 days. Tissue biodistribution and full characterization of NM-203, primary particle size 13-45 nm, was performed within the framework of the Nanogenotox project. No mortality or general toxicity occurred; histopathological analysis showed splenomegaly in the RD group accompanied by inflammatory granulomas in both sexes. Granulomas were also present in liver parenchyma in the RD (both sexes) and SD groups (male only). The histopathological results indicated that SAS NP have the potential to persist and induce sex-specific chronic inflammatory lesions in spleen and liver upon short-term treatment. Overall, the data showed that the widespread use of silica in drugs might elicit chronic reactions in spleen and liver prompting to the need of further investigations on the safety of SAS NP.[Formula: see text].

Sex-Specific Effects of Short-Term Oral Administration of Food-Grade Titanium Dioxide Nanoparticles in the Liver and Kidneys of Adult Rats.

Titanium dioxide (TiO2) nanomaterial is used in several items (implant materials, pills composition, cosmetics, etc.). Although TiO2 is no longer considered safe as a food additive, the general population is exposed daily through different routes, and information is lacking on some aspects of animal and human health. This study evaluated liver and kidney toxicity of food-grade TiO2 nanoparticles (NPs) (primary size < 25 nm) in male and female rats that were orally exposed for 5 days to 0, 1, and 2 mg/kg body weight per day (comparable with daily E171 consumption). Selected liver and kidney toxicity endpoints included serum biomarkers, histopathological analysis and expression of osteopontin (SPP1), vascular endothelial growth factor (VEGF), interleukin 6 (IL-6), and neuropeptide Y (NPY). Although TiO2 NPs are known to affect the gastric mucosa, short-term exposure induced sex-specific effects: general toxicity parameters were predominantly altered in female rats, whereas the liver appeared to be more affected than the kidneys in male rats, which also showed overexpression of NPY and SPP1. In the kidneys, the TiO2 NP effects were quantitatively similar but qualitatively different in the two sexes. In conclusion, careful consideration should be paid to the presence of TiO2 NPs in other items that can lead to human exposure.

Single cell analysis of the localization of the hematopoietic stem cells within the bone marrow architecture identifies niche-specific proliferation dynamics.

Introduction: Hematopoietic stem cells (HSC) reside in the bone marrow (BM) in specialized niches which provide support for their self-replication and differentiation into the blood cells. Recently, numerous studies using sophisticated molecular and microscopic technology have provided snap-shots information on the identity of the BM niches in mice. In adults, HSC are localized around arterioles and sinusoids/venules whereas in juvenile mice they are in close to the osteoblasts. However, although it is well recognized that in mice the nature of the hematopoietic niche change with age or after exposure to inflammatory insults, much work remains to be done to identify changes occurring under these conditions. The dynamic changes occurring in niche/HSC interactions as HSC enter into cycle are also poorly defined. Methods: We exploit mice harboring the hCD34tTA/Tet-O-H2BGFP transgene to establish the feasibility to assess interactions of the HSC with their niche as they cycle. In this model, H2BGFP expression is driven by the TET trans-activator under the control of the human CD34 promoter which in mice is active only in the HSC. Since Doxycycline inhibits TET, HSC exposed to this drug no longer express H2BGFP and loose half of their label every division allowing establishing the dynamics of their first 1-3 divisions. To this aim, we first validated user-friendly confocal microscopy methods to determine HSC divisions by hemi-decrement changes in levels of GFP expression. We then tracked the interaction occurring in old mice between the HSC and their niche during the first HSC divisions. Results: We determined that in old mice, most of the HSC are located around vessels, both arterioles which sustain quiescence and self-replication, and venules/sinusoids, which sustain differentiation. After just 1 week of exposure to Doxycycline, great numbers of the HSC around the venules lost most of their GFP label, indicating that they had cycled. By contrast, the few HSC surrounding the arterioles retained maximal levels of GFP expression, indicating that they are either dormant or cycle at very low rates. Conclusion: These results reveal that in old mice, HSC cycle very dynamically and are biased toward interactions with the niche that instructs them to differentiate.

Inhibition of CXCR1/2 reduces the emperipolesis between neutrophils and megakaryocytes in the Gata1low model of myelofibrosis.

Emperipolesis between neutrophils and megakaryocytes was first identified by transmission electron microscopy. Although rare under steady-state conditions, its frequency greatly increases in myelofibrosis, the most severe of myeloproliferative neoplasms, in which it is believed to contribute to increasing the transforming growth factor (TGF)-ß microenvironmental bioavailability responsible for fibrosis. To date, the challenge of performing studies by transmission electron microscopy has hampered the study of factors that drive the pathological emperipolesis observed in myelofibrosis. We established a user-friendly confocal microscopy method that detects emperipolesis by staining with CD42b, specifically expressed on megakaryocytes, coupled with antibodies that recognize the neutrophils (Ly6b or neutrophil elastase antibody). With such an approach, we first confirmed that the bone marrow from patients with myelofibrosis and from Gata1low mice, a model of myelofibrosis, contains great numbers of neutrophils and megakaryocytes in emperipolesis. Both in patients and Gata1low mice, the emperipolesed megakaryocytes were surrounded by high numbers of neutrophils, suggesting that neutrophil chemotaxis precedes the actual emperipolesis event. Because neutrophil chemotaxis is driven by CXCL1, the murine equivalent of human interleukin 8 that is expressed at high levels by malignant megakaryocytes, we tested the hypothesis that neutrophil/megakaryocyte emperipolesis could be reduced by reparixin, an inhibitor of CXCR1/CXCR2. Indeed, the treatment greatly reduced both neutrophil chemotaxis and their emperipolesis with the megakaryocytes in treated mice. Because treatment with reparixin was previously reported to reduce both TGF-ß content and marrow fibrosis, these results identify neutrophil/megakaryocyte emperipolesis as the cellular interaction that links interleukin 8 to TGF-ß abnormalities in the pathobiology of marrow fibrosis.

Antiviral effect of SARS-CoV-2 N-specific CD8+ T cells induced in lungs by engineered extracellular vesicles.

Induction of effective immunity in the lungs should be a requisite for any vaccine designed to control the severe pathogenic effects generated by respiratory infectious agents. We recently provided evidence that the generation of endogenous extracellular vesicles (EVs) engineered for the incorporation of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)-2 Nucleocapsid (N) protein induced immunity in the lungs of K18-hACE2 transgenic mice, which then can survive the lethal virus infection. However, nothing is known about the ability of the N-specific CD8+ T cell immunity in controlling viral replication in the lungs, a major pathogenic signature of severe disease in humans. To fill the gap, we investigated the immunity generated in the lungs by N-engineered EVs in terms of induction of N-specific effectors and resident memory CD8+ T lymphocytes before and after virus challenge carried out three weeks and three months after boosting. At the same time points, viral replication extents in the lungs were evaluated. Three weeks after the second immunization, virus replication was reduced in mice best responding to vaccination by more than 3-logs compared to the control group. The impaired viral replication matched with a reduced induction of Spike-specific CD8+ T lymphocytes. The antiviral effect appeared similarly strong when the viral challenge was carried out 3 months after boosting, and associated with the persistence of N-specific CD8+ T-resident memory lymphocytes. In view of the quite low mutation rate of the N protein, the present vaccine strategy has the potential to control the replication of all emerging variants.

SARS-CoV-2-Specific CD8+ T-Cells in Blood but Not in the Lungs of Vaccinated K18-hACE2 Mice after Infection.

Severe acute respiratory syndrome coronavirus (SARS-CoV)-2 enters the host by infecting nasal ciliated cells. Then, the virus can spread towards the oropharyngeal cavity and the pulmonary tissues. The antiviral adaptive immunity is promptly induced in response to the virus's detection, with virus-specific T-lymphocytes appearing before antiviral antibodies. Both the breadth and potency of antiviral CD8+ T-cell immunity have a key role in containing viral spread and disease severity. Current anti-SARS-CoV-2 vaccines do not impede the virus's replication in the upper respiratory tract, and there is consensus on the fact that the best potency of the antiviral immune response in both blood and the upper respiratory tract can be reached upon infection in vaccinees (i.e., breakthrough infection). However, whether the antiviral CD8+ T-cells developing in response to the breakthrough infection in the upper respiratory tract diffuse to the lungs is also still largely unknown. To fill the gap, we checked the CD8+ T-cell immunity elicited after infection of K18-hACE2 transgenic mice both at 3 weeks and 3 months after anti-spike vaccination. Virus-specific CD8+ T-cell immunity was monitored in both blood and the lungs before and after infection. By investigating the de novo generation of the CD8+ T-cells specific for SARS-CoV-2 viral proteins, we found that both membrane (M) and/or nucleocapsid (N)-specific CD8+ T-cells were induced at comparable levels in the blood of both unvaccinated and vaccinated mice. Conversely, N-specific CD8+ T-cells were readily found in the lungs of the control mice but were either rare or absent in those of vaccinated mice. These results support the idea that the hybrid cell immunity developing after asymptomatic/mild breakthrough infection strengthens the antiviral cell immunity in the lungs only marginally, implying that the direct exposition of viral antigens is required for the induction of an efficient antiviral cell immunity in the lungs.

Resident Self-Tissue of Proinflammatory Cytokines Rather Than Their Systemic Levels Correlates with Development of Myelofibrosis in Gata1low Mice.

Serum levels of inflammatory cytokines are currently investigated as prognosis markers in myelofibrosis, the most severe Philadelphia-negative myeloproliferative neoplasm. We tested this hypothesis in the Gata1low model of myelofibrosis. Gata1low mice, and age-matched wild-type littermates, were analyzed before and after disease onset. We assessed cytokine serum levels by Luminex-bead-assay and ELISA, frequency and cytokine content of stromal cells by flow cytometry, and immunohistochemistry and bone marrow (BM) localization of GFP-tagged hematopoietic stem cells (HSC) by confocal microscopy. Differences in serum levels of 32 inflammatory-cytokines between prefibrotic and fibrotic Gata1low mice and their wild-type littermates were modest. However, BM from fibrotic Gata1low mice contained higher levels of lipocalin-2, CXCL1, and TGF-ß1 than wild-type BM. Although frequencies of endothelial cells, mesenchymal cells, osteoblasts, and megakaryocytes were higher than normal in Gata1low BM, the cells which expressed these cytokines the most were malignant megakaryocytes. This increased bioavailability of proinflammatory cytokines was associated with altered HSC localization: Gata1low HSC were localized in the femur diaphysis in areas surrounded by microvessels, neo-bones, and megakaryocytes, while wild-type HSC were localized in the femur epiphysis around adipocytes. In conclusion, bioavailability of inflammatory cytokines in BM, rather than blood levels, possibly by reshaping the HSC niche, correlates with myelofibrosis in Gata1low mice.

Gata1 expression driven by the alternative HS2 enhancer in the spleen rescues the hematopoietic failure induced by the hypomorphic Gata1low mutation.

Rigorously defined reconstitution assays developed in recent years have allowed recognition of the delicate relationship that exists between hematopoietic stem cells and their niches. This balance ensures that hematopoiesis occurs in the marrow under steady-state conditions. However, during development, recovery from hematopoietic stress and in myeloproliferative disorders, hematopoiesis occurs in extramedullary sites whose microenvironments are still poorly defined. The hypomorphic Gata1(low) mutation deletes the regulatory sequences of the gene necessary for its expression in hematopoietic cells generated in the marrow. By analyzing the mechanism that rescues hematopoiesis in mice carrying this mutation, we provide evidence that extramedullary microenvironments sustain maturation of stem cells that would be otherwise incapable of maturing in the marrow.

Toxicological Assessment of Oral Co-Exposure to Bisphenol A (BPA) and Bis(2-ethylhexyl) Phthalate (DEHP) in Juvenile Rats at Environmentally Relevant Dose Levels: Evaluation of the Synergic, Additive or Antagonistic Effects.

BACKGROUND: The general population (including children) is exposed to chemical mixtures. Plasticizers such as Bisphenol A (BPA) and Phthalates (mainly Bis(2-ethylhexyl) phthalate-DEHP) are widespread contaminants classified as endocrine disrupters which share some toxicological profiles and coexist in food and environment. METHODS: To identify hazards of DEHP and BPA mixtures, the juvenile toxicity test-where rodents are in peripubertal phase of development, resembling childhood-was selected using exposure data from biomonitoring study in children. Biological activity and potential enhanced and/or reduced toxicological effects of mixtures due to common mechanisms were studied, considering endpoints of metabolic, endocrine and reproductive systems. The degree of synergy or antagonism was evaluated by synergy score calculation, using present data and results from the single compound individually administered. RESULTS: In metabolic system, synergic interaction predominates in female and additive in male rats; in the reproductive and endocrine systems, the co-exposure of BPA and DEHP showed interactions mainly of antagonism type. CONCLUSIONS: The present approach allows to evaluate, for all the endpoints considered, the type of interaction between contaminants relevant for human health. Although the mode of action and biological activities of the mixtures are not completely addressed, it can be of paramount usefulness to support a more reliable risk assessment.

Metabolic, reproductive and thyroid effects of bis(2-ethylhexyl) phthalate (DEHP) orally administered to male and female juvenile rats at dose levels derived from children biomonitoring study.

Bis(2-ethylhexyl) phthalate (DEHP) is a plasticizer used in several items, non-covalently bound to plastics and easily released, since metabolites were found in human matrices. DEHP is an endocrine disrupter and children are particularly vulnerable and susceptible to DEHP effects due to higher exposure levels and developmental stage. A juvenile toxicity study was performed to identify DEHP hazard and mode of action in Sprague-Dawley rats of both sexes during peri-pubertal period - corresponding to childhood phase - from weaning, post-natal day (PND) 23, to full sexual maturity (PND60); the dose levels of 0, 9, 21 and 48 mg/kg bw/day were derived from LIFE PERSUADED biomonitoring study in children. DEHP was administered by gavage for 28 days (5 days/week); timing of preputial separation and vaginal opening was observed during treatment. Histopathological analysis was performed on: adrenals, spleen, liver, thyroid and reproductive organs. The following serum biomarkers were assessed: estradiol, testosterone, anti-Mullerian hormone, tetraiodothyronine, thyroid stimulating hormone, adiponectin and leptin. Gene expression on hypothalamic-pituitary area was focused on follicle stimulating, luteinizing, and thyroid stimulating hormones. The results showed that main targets of DEHP during juvenile period were liver and metabolic system in both sexes, while sex-specific effects were recorded in reproductive system (male rats) and in thyroid (female rats). DEHP exposure during peri-pubertal period at dose levels derived from biomonitoring study in children can induce sex-specific imbalances identifying the juvenile animal model as a sound tool to identify hazards for a reliable risk assessment targeted to children.

Effects of sub-chronic oral exposure to pyrogenic synthetic amorphous silica (NM-203) in male and female Sprague-Dawley rats: focus on reproductive systems.

Synthetic amorphous silica (SAS) consists of agglomerates and aggregates of primary particles in the nanorange (<100 nm) and it is the E551 authorized food additive. The potential risks for human health associated to dietary exposure to SAS are not completely assessed; in particular, data on male and female reproductive systems are lacking. A 90-day oral toxicity study with pyrogenic SAS nanomaterial NM-203 was carried out on the basis of the OECD test guideline 408 in the frame of the NANoREG project. Adult Sprague-Dawley rats of both sexes were orally treated for 90 days with 0, 2, 5, 10, 20 and 50 mg SAS/kg bw per day. Dose levels were selected to be as close as possible to the expected human exposure to food additive E551. The present paper provides specific information on potential effects on male and female reproductive systems, through the evaluation of serum biomarkers, sperm count, histopathological analysis of testis, epididymis, ovary and uterus and real-time PCR on uterus; potential genotoxic alterations were evaluated by comet assay on testis, sperm and ovary. NM-203 did not induce histophatological and genotoxic effects in male reproductive system. In female rats, ovary is not target of NM-203 and only tissue-specific effects on uterus were recorded up to 10 mg/kg bw per day. To our best knowledge, this is the first study providing data on male and female reproductive systems after long-term, repeated oral exposure at dose levels close to dietary human exposure, which identifies a limited concern only for female reproductive health.

Quantum key distribution with entangled photons generated on demand by a quantum dot.

Quantum key distribution-exchanging a random secret key relying on a quantum mechanical resource-is the core feature of secure quantum networks. Entanglement-based protocols offer additional layers of security and scale favorably with quantum repeaters, but the stringent requirements set on the photon source have made their use situational so far. Semiconductor-based quantum emitters are a promising solution in this scenario, ensuring on-demand generation of near-unity-fidelity entangled photons with record-low multiphoton emission, the latter feature countering some of the best eavesdropping attacks. Here, we use a coherently driven quantum dot to experimentally demonstrate a modified Ekert quantum key distribution protocol with two quantum channel approaches: both a 250-m-long single-mode fiber and in free space, connecting two buildings within the campus of Sapienza University in Rome. Our field study highlights that quantum-dot entangled photon sources are ready to go beyond laboratory experiments, thus opening the way to real-life quantum communication.

Experimental violation of n-locality in a star quantum network.

The launch of a satellite capable of distributing entanglement through long distances and the first loophole-free violation of Bell inequalities are milestones indicating a clear path for the establishment of quantum networks. However, nonlocality in networks with independent entanglement sources has only been experimentally verified in simple tripartite networks, via the violation of bilocality inequalities. Here, by using a scalable photonic platform, we implement star-shaped quantum networks consisting of up to five distant nodes and four independent entanglement sources. We exploit this platform to violate the chained n-locality inequality and thus witness, in a device-independent way, the emergence of nonlocal correlations among the nodes of the implemented networks. These results open new perspectives for quantum information processing applications in the relevant regime where the observed correlations are compatible with standard local hidden variable models but are non-classical if the independence of the sources is taken into account.

Hazard identification of pyrogenic synthetic amorphous silica (NM-203) after sub-chronic oral exposure in rat: A multitarget approach.

Food additive E551 consists of synthetic amorphous silica (SAS), comprising agglomerates and aggregates of primary particles in the nanorange (<100 nm), which potential nanospecific risks for humans associated to dietary exposure are not yet completely assessed. In NANoREG project, aim of the study was to identify potential hazards of pyrogenic SAS nanomaterial NM-203 by a 90-day oral toxicity study (OECD test guideline 408). Adult Sprague-Dawley rats of both sexes were orally treated with 0, 2, 5, 10, 20 and 50 mg SAS/kg bw per day; dose levels were selected to be as close as possible to E551 dietary exposure. Several endpoints were investigated, the whole integrative study is presented here along with the results of dispersion characterization, tissue distribution, general toxicity, blood/serum biomarkers, histopathological and immunotoxicity endpoints. No mortality, general toxicity and limited deposition in target tissues were observed. NM-203 affected liver and spleen in both sexes. Proposed NOAEL 5 mg/kg bw per day in male rats for enlarged sinusoids in liver. In female rats, TSH and creatinine levels were affected, proposed LOAEL 2 mg/kg bw per day. Overall, these data provide new insight for a comprehensive risk assessment of SAS exposure by the oral route.

Evaluation of five elements in lenses and aqueous humour of experimental rabbits after induced opacity.

We evaluated the presence of Ca, Na, K, Cu and Zn in the lenses and aqueous humour of rabbits treated with an Nd:YAG laser to induce opacity of the crystalline. The mean concentrations of the elements found in control lenses were: Ca: 15.8+/-5.2 mg/kg; Na: 1.2+/-0.6 g/kg; K: 10.3+/-3.3 g/kg; Cu: 0.19+/-0.06 mg/kg; Zn: 20.6+/-3.0 mg/kg. With the exception of K and Zn, the values found in the lenses of treated eyes (Ca: 135+/-24 mg/kg; Na: 4.3+/-1.5 g/kg; K: 10.1 +/- 3.2 g/kg; Cu: 0.47+/-0.17 mg/kg; Zn: 21.8+/-4.2 mg/kg) were significantly higher than in the controls. On the other hand, the concentrations found in the aqueous humour of treated eyes (Ca: 21.7+/-4.5 mg/l; Na: 0.66+/-0.21 g/l; K: 0.29+/-0.10 g/l; Cu: 0.035+/-0.009 mg/l; Zn: 0.079+/-0.01 mg/l) were significantly lower than those of the controls. The greatest difference was observed for Na (-68.6%) and Cu (-52.7%), followed by Ca and Zn (-35.0% and -35.2%, respectively). A positive correlation was found between Ca and Na in treated lenses (r2 = 0.9226, p < 0.0001) whereas inverse correlations were found for both Ca (r2 = 0.9788, p<0.0001) and Na (r2 = 0.9491, p<0.0001) between the concentrations found in the lenses and in the aqueous humour of treated eyes.

Oral, short-term exposure to titanium dioxide nanoparticles in Sprague-Dawley rat: focus on reproductive and endocrine systems and spleen.

The study explored possible reproductive and endocrine effects of short-term (5 days) oral exposure to anatase TiO2 nanoparticles (0, 1, 2 mg/kg body weight per day) in rat. Nanoparticles were characterised by scanning electron microscopy (SEM) and transmission electron microscopy, and their presence in spleen, a target organ for bioaccumulation, was investigated by single-particle inductively coupled plasma mass spectrometry and SEM/energy-dispersive X-ray. Analyses included serum hormone levels (testosterone, 17-ß-estradiol and triiodothyronine) and histopathology of thyroid, adrenals, ovary, uterus, testis and spleen. Increased total Ti tissue levels were found in spleen and ovaries. Sex-related histological alterations were observed at both dose levels in thyroid, adrenal medulla, adrenal cortex (females) and ovarian granulosa, without general toxicity. Altered thyroid function was indicated by reduced T3 (males). Testosterone levels increased in high-dose males and decreased in females. In the spleen of treated animals TiO2 aggregates and increased white pulp (high-dose females) were detected, even though Ti tissue levels remained low reflecting the low doses and the short exposure time. Our findings prompt to comprehensively assess endocrine and reproductive effects in the safety evaluation of nanomaterials.

Differential amplification of murine bipotent megakaryocytic/erythroid progenitor and precursor cells during recovery from acute and chronic erythroid stress.

Two murine bipotent erythroid/megakaryocytic cells, the progenitor (MEP) and precursor (PEM) cells, recently have been identified on the basis of the phenotypes of linnegc-kitposSca-1neg CD16/CD32lowCD34low and TER119pos4A5pos or 2D5pos, respectively. However, the functional relationship between these two subpopulations and their placement in the hemopoietic hierarchy is incompletely understood. We compared the biological properties of these subpopulations in marrow and spleen of mice with and without acute or chronic erythroid stress. MEP cells, but not PEM cells, express c-kit, respond to stem cell factor in vitro, and form spleen colonies in vivo. PEM cells comprise up to 50%-70% of the cells in BFU-E-derived colonies but are not present among the progeny of purified MEP cells cultured under erythroid and megakaryocytic permissive conditions. PEM cells increase 10- to 20-fold under acute and chronic stress, whereas MEP cell increases (21%-84%) are observed only in acutely stressed animals. These data suggest that MEP and PEM cells represent distinct cell populations that may exist in an upstream-downstream differentiation relationship under conditions of stress. Whereas the dynamics of both populations are altered by stress induction, the differential response to acute and chronic stress suggests different regulatory mechanisms. A model describing the relationship between MEP, PEM, and common myeloid progenitor cells is presented.