Disposable FFP2 and Type IIR Medical-Grade Face Masks: An Exhaustive Analysis into the Leaching of Micro- and Nanoparticles and Chemical Pollutants Linked to the COVID-19 Pandemic.

The COVID-19 pandemic has increased the worldwide production and use of disposable plastic face masks (DPFMs). The release of micro- and nanopollutants into the environment is one of the impacts derived from regulated and unregulated disposal of DPFMs. This study focuses on the emission of pollutants from medical-grade DPFMs when submerged in deionized water, simulating regulated and unregulated disposal of these masks. Three brands of FFP2 and three brands of Type IIR medical masks, produced in various countries (UK, EU, and non-EU), were investigated. Field emission gun scanning electron microscopy (FEG-SEM) was used to obtain high-resolution images of the micro- and nanoparticles, and 0.02 µm pore size inorganic membranes were used to retain and subsequently analyze smaller particle size nanoparticles (>20 nm) released from the DPFMs. Particles and fibers in the micro- and nanoscale were found in all six DPFM brands. SEM with energy-dispersive spectroscopy analysis revealed the presence of particles containing different heavy metals like lead, mercury, and arsenic. Inductively coupled plasma mass spectrometry analysis confirmed the leaching of trace heavy metals to water (antimony up to 2.41 µg/L and copper up to 4.68 µg/L). Liquid chromatography-mass spectrometry analysis identified polar organic species related to plastic additives and contaminants such as polyamide-66 monomers and oligomers.

The genetics and evolution of obligate reproductive parasitism in Trichogramma pretiosum infected with parthenogenesis-inducing Wolbachia.

Parthenogenesis-inducing (PI) Wolbachia belong to a class of intracellular symbionts that distort the offspring sex ratio of their hosts toward a female bias. In many PI Wolbachia-infected species sex ratio distortion has reached its ultimate expression-fixation of infection and all-female populations. This is only possible with thelytokous PI symbionts as they provide an alternative form of reproduction and remove the requirement for males and sexual reproduction. Many populations fixed for PI Wolbachia infection have lost the ability to reproduce sexually, even when cured of the infection. We examine one such population in the species Trichogramma pretiosum. Through a series of backcrossing experiments with an uninfected Trichogramma pretiosum population we were able to show that the genetic basis for the loss of female sexual function could be explained by a dominant nuclear effect. Male sexual function had not been completely lost, though some deterioration of male sexual function was also evident when males from the infected population (created through antibiotic curing of infected females) were mated to uninfected females. We discuss the dynamics of sex ratio selection in PI Wolbachia-infected populations and the evolution of non-fertilizing mutations.

Host control over infection and proliferation of a cheater symbiont.

Host control mechanisms are thought to be critical for selecting against cheater mutants in symbiont populations. Here, we provide the first experimental test of a legume host's ability to constrain the infection and proliferation of a native-occurring rhizobial cheater. Lotus strigosus hosts were experimentally inoculated with pairs of Bradyrhizobium strains that naturally vary in symbiotic benefit, including a cheater strain that proliferates in the roots of singly infected hosts, yet provides zero growth benefits. Within co-infected hosts, the cheater exhibited lower infection rates than competing beneficial strains and grew to smaller population sizes within those nodules. In vitro assays revealed that infection-rate differences among competing strains were not caused by variation in rhizobial growth rate or interstrain toxicity. These results can explain how a rapidly growing cheater symbiont--that exhibits a massive fitness advantage in single infections--can be prevented from sweeping through a beneficial population of symbionts.

Effect of experimental chronic renal insufficiency on bone mineral and collagen maturation.

The effect of chronic renal disease on bone matrix and mineral maturation was evaluated in rats with experimental renal insufficiency of 2-11 wk duration utilizing bromoform-toluene gradient fractionation of bone powder, pulse labeling experiments with (45)Ca and proline-(3)H differential extraction, and X-ray diffraction techniques.Maturation defects in both collagen and mineral ((45)Ca) metabolism were documented as early as 2 wk after the induction of uremia, when total bone calcium, inorganic phosphate, and hydroxyproline content were unchanged. The maturational defect progressed with advancing uremia despite insignificant changes in plasma pH and calcium, and normal bone carbonate levels. Although circulating levels of 25-hydroxycholecalciferol were significantly lower than normal in the uremic animals, pretreatment with either this vitamin D metabolite or vitamin D(3) itself failed to alter the observed changes in skeletal maturation.

25-hydroxycholecalciferol-enhanced bone maturation in the parathyroprivic state.

In vitro evidence presently favors a direct osteolytic effect of biologically active vitamin D metabolites. Studies were designed to evaluate the effect of 25-hydroxycholecalciferol (25OHD3) on bone collagen and mineral maturation in vivo and its dependence on parathyroid hormone (PTH). After treatment of sham-operated control and parathyroidectomized (PTX) mature rats with either 25OHD3 or an oil vehicle for 2 wk, tibial bone mineral-collagen maturation was quantitated by bromoform-toluene density gradient fractionation techniques. Intestinal calcium absorption was measured by in vivo 45Ca transport procedures. In contrast to the control group, the response to 25OHD3 of PTX rats was dramatic. Bone mineral and matrix maturation were both accelerated by 25OHD3 treatment without concomitant reduction in total bone mineral or collagen content or changes in the intestinal calcium absorption. These observations support the premise that biologically active vitamin D metabolites stimulate bone tissue maturation, and that PTH is not required in this regard.

Abnormal bone mineral maturation in the chronic uremic state.

X-ray diffraction analysis of bone from chronically uremic but nonacidotic rats with normocalcemia and hyperphosphatemia revealed smaller apatite crystals and an increase in the X-ray amorphous mineral fraction when compared to age-matched, pair-fed control animals, indicating less advanced mineral maturation in the uremic animals. Studies in animals with varied degrees of chronic renal insufficiency revealed a progression of the bone crystal maturational defect with advancing uremia.

Experimental renal osteodystrophy. The response to 25-hydroxycholecalciferol and dicholomethylene diphosphate therapy.

Bone mineral and matrix maturation in chronically uremic, nonacidotic rats were investigated after 25-hydroxcholecalciferol (25OHD) and/or dichloromethylene diphosphonate (C12MDP) therapy utilizing bromoform-toluene density gradient fractionation and X-ray diffraction analyses. The bromoform-toluene density gradient analyses demonstrated that the progressive accumulation of less dense, more immature bone characteristic of progressive uremia was reversed by 25OHD and/or C12MDP therapy for a 2-wk period, and that after 4 wk of therapy the maturational profile of bones from chronically uremic animals treated with 250HD and/or C12MDP was comparable to that from nonuremic littermates. X-ray diffraction analysis revealed that by the 4th wk of therapy with 25OHD and C12MDP both the degree of crystallinity and the crystal size/perfection parameters in the uremic bones were comparable to those of nonuremic, pair-fed control littermates. Treatment for 4 wk with 25OHD resulted in enlarged and/or more perfect apatite crystallites, while C12MDP alone slightly inhibited crystal growth and/or perfection after 2 wk of treatment. Soft tissue calcification was diminished in uremic animals treated for 4 wk with C12MDP or a combined C2MDP/25OHD regimen, the latter being much more effective in this regard. The accumulated data in this study support the premise that the attendant accelerated bone resorption, soft tissue calcification, and abnormal mineralization and maturation of the skeletal tissue, well documented to characterize experimental ranal insufficiency, may be alleviated with therapeutic dosages of 25OHD and/or C12MDP.

Bone deficit in ovariectomized rats. Functional contribution of the marrow stromal cell population and the effect of oral dihydrotachysterol treatment.

This study investigates the proliferative and osteogenic role of marrow stromal/osteoprogenitor cells in the development of the cortical bone deficit in ovariectomized (OVX) female rats. In vitro, clonal growth of marrow stromal cells from OVX rats was significantly impaired (vs. sham-operated controls). Yet in vivo, cells from sham-operated and OVX rats had equal osteogenic potential in several in vivo experimental situations, such as in intraperitoneally implanted millipore diffusion chambers and in intramuscular implants of marrow plus osteoinductive bone matrix (composite grafts). Long-term (6 mo) dihydrotachysterol (DHT) treatment of OVX rats enhanced their in vitro proliferative potential and clonal growth, as well as their osteogenic expression in composite grafts. The observation that the in vivo osteogenic performance of OVX rat marrow stromal cells was normal at extraosseous sites suggests that the mechanisms leading to osteopenia may involve an abnormality in cell-matrix interactions.

Structural and functional analysis of an mRNP complex that mediates the high stability of human beta-globin mRNA.

Human globins are encoded by mRNAs exhibiting high stabilities in transcriptionally silenced erythrocyte progenitors. Unlike alpha-globin mRNA, whose stability is enhanced by assembly of a specific messenger RNP (mRNP) alpha complex on its 3' untranslated region (UTR), neither the structure(s) nor the mechanism(s) that effects the high-level stability of human beta-globin mRNA has been identified. The present work describes an mRNP complex assembling on the 3' UTR of the beta-globin mRNA that exhibits many of the properties of the stability-enhancing alpha complex. The beta-globin mRNP complex is shown to contain one or more factors homologous to alphaCP, a 39-kDa RNA-binding protein that is integral to alpha-complex assembly. Sequence analysis implicates a specific 14-nucleotide pyrimidine-rich track within its 3' UTR as the site of beta-globin mRNP assembly. The importance of this track to mRNA stability is subsequently verified in vivo using mice expressing human beta-globin transgenes that contain informative mutations in this region. In combination, the in vitro and in vivo analyses indicate that the high stabilities of the alpha- and beta-globin mRNAs are maintained through related mRNP complexes that may share a common regulatory pathway.

Developmental silencing of the embryonic zeta-globin gene: concerted action of the promoter and the 3'-flanking region combined with stage-specific silencing by the transcribed segment.

Globin gene switching is a well-described model of eucaryotic developmental control. In the case of the human alpha-globin gene cluster, migration of erythropoietic activity from the embryonic yolk sac to the fetal liver is parallaled by the zeta-globin gene silencing and enhanced expression of the alpha-globin genes. To map critical cis determinants of this switch, the human zeta-globin gene, the alpha-globin gene, and chimeric recombinants were introduced into the mouse genome. Consistent with previous studies, expression of the individual alpha- and zeta-globin transgenes was found to be developmentally appropriate. Contrary to current models, however, the alpha- and zeta-globin gene promoters were not sufficient to establish this control. Instead, full silencing of the zeta-globin gene required the combined activities of this promoter, transcribed region, and 3'-flanking sequences. Individually, the silencing activities of the zeta-globin gene promoter and 3'-flanking region were minimal but increased markedly when both regions were present. The zeta-globin transcribed region appeared to contribute to gene silencing by a mechanism specifically activated in definitive erythroblasts in the fetal liver. These data demonstrate that a complex set of controls, requiring at least three determinants and involving at least two independent mechanisms, is necessary for full developmental silencing of the human zeta-globin gene.

Sequence divergence in the 3' untranslated regions of human zeta- and alpha-globin mRNAs mediates a difference in their stabilities and contributes to efficient alpha-to-zeta gene development switching.

The developmental stage-specific expression of human globin proteins is characterized by a switch from the coexpression of zeta- and alpha-globin in the embryonic yolk sac to exclusive expression of alpha-globin during fetal and adult life. Recent studies with transgenic mice demonstrate that in addition to transcriptional control elements, full developmental silencing of the human zeta-globin gene requires elements encoded within the transcribed region. In the current work, we establish that these latter elements operate posttranscriptionally by reducing the relative stability of zeta-globin mRNA. Using a transgenic mouse model system, we demonstrate that human zeta-globin mRNA is unstable in adult erythroid cells relative to the highly stable human alpha-globin mRNA. A critical determinant of the difference between alpha- and zeta-globin mRNA stability is mapped by in vivo expression studies to their respective 3' untranslated regions (3'UTRs). In vitro messenger ribonucleoprotein (mRNP) assembly assays demonstrate that the alpha- and zeta-globin 3'UTRs assemble a previously described mRNP stability-determining complex, the alpha-complex, with distinctly different affinities. The diminished efficiency of alpha-complex assembly on the zeta 3'UTR results from a single C-->G nucleotide substitution in a crucial polypyrimidine tract contained by both the human alpha- and zeta-globin mRNA 3'UTRs. A potential pathway for accelerated zeta-globin mRNA decay is suggested by the observation that its 3'UTR encodes a shortened poly(A) tail. Based upon these data, we propose a model for zeta-globin gene silencing in fetal and adult erythroid cells in which posttranscriptional controls play a central role by providing for accelerated clearance of zeta-globin transcripts.

A microsatellite genetic linkage map for Xiphophorus.

Interspecies hybrids between distinct species of the genus Xiphophorus are often used in varied research investigations to identify genomic regions associated with the inheritance of complex traits. There are 24 described Xiphophorus species and a greater number of pedigreed strains; thus, the number of potential interspecies hybrid cross combinations is quite large. Previously, select Xiphophorus experimental crosses have been shown to exhibit differing characteristics between parental species and among the hybrid fishes derived from crossing them, such as widely differing susceptibilities to chemical or physical agents. For instance, genomic regions harboring tumor suppressor and oncogenes have been identified via linkage association of these loci with a small set of established genetic markers. The power of this experimental strategy is related to the number of genetic markers available in the Xiphophorus interspecies cross of interest. Thus, we have undertaken the task of expanding the suite of easily scored markers by characterization of Xiphophorus microsatellite sequences. Using a cross between Xiphophorus maculatus and X. andersi, we report a linkage map predominantly composed of microsatellite markers. All 24 acrocentric chromosome sets of Xiphophorus are represented in the assembled linkage map with an average intergenomic distance of 7.5 cM. Since both male and female F1 hybrids were used to produce backcross progeny, these recombination rates were compared between "male" and "female" maps. Although several genomic regions exhibit differences in map length, male- and female-derived maps are similar. Thus Xiphophorus, in contrast to zebrafish, Danio rerio, and several other vertebrate species, does not show sex-specific differences in recombination. The microsatellite markers we report can be easily adapted to any Xiphophorus interspecies and some intraspecies crosses, and thus provide a means to directly compare results derived from independent experiments.

Effects of age and estrogen on calcium absorption in the rat.

In order to differentiate the relative effects of age and estrogen on rates of calcium absorption and serum levels of parathyroid hormone and calcitonin, the effect of oophorectomy with and without estrogen replacement (2 weeks) was studied in rats for 30- or 120-day periods. Whereas oophorectomy for 30 days resulted in a significant decrease in serum calcium and an increase in serum phosphate, no change in either calcium or phosphate was observed in the 120-day oophorectomized animals. iPTH decreased in both the 30- and 120-day oophorectomized animals although these changes were not significant at the .05 level. Whereas no significant change in basal circulating calcitonin occurred in the 30-day oophorectomized rats, it decreased significantly in the older animals following the ablative procedure. Forty-five days following estrogen deprivation, calcitonin release to a calcium secretagogue was significantly blunted. Intestinal calcium absorption decreased with age, and unlike the increments in calcium absorption observed in the younger estrogen-repleted, 30-day oophorectomized rat, no change in calcium absorption was observed when estrogens were administered to the older, 120-day oophorectomized rat. The accumulated data suggest that the effects of estrogen loss on the hormonal control of bone metabolism and calcium absorption are age dependent, and that estrogen contributes significantly to changes in calcium homeostasis observed in the maturing rat.

Meal timing as a Zeitgeber for skeletal deoxyribonucleic acid and collagen synthesis rhythms.

Meal timing protocols were used to probe the circadian regulation of DNA and protein synthesis in the rat tibia. Two groups of 4-week-old rats were entrained to 12-h light, 12-h dark cycles (light, 0800-2000 h; darkness, 2000-0800 h) for 4 weeks. One group was fed for 4 h at the onset of the light span (EL). The other group was fed for 4 h at the onset of the dark span (ED). Forty-eight hours before death, the rats were injected ip with 0.015 microCi/g BW [14C]proline [collagen and noncollagen protein (NCP) synthesis], and they received 0.25 microCi/g BW [3H] thymidine (DNA synthesis) 1 h before death. Groups of 10-12 rats were bled from the abdominal aorta at 4-h intervals under light ether anesthesia (1-2 min/rat) during 2 consecutive 24-h periods, and the tibias were then biopsied and frozen in liquid N2. Serum samples were analyzed for calcium, inorganic phosphorus, and immunoassayable levels of corticosterone (CS), PTH, and calcitonin. Epiphyseal cartilage and metaphyseal and diaphyseal bone were analyzed for DNA and acidic pepsin-digestible collagen. Chronograms indicated that DNA synthesis in cartilage and bone, along with serum CS, showed two approximately equal and positively correlated peaks, with the cycles for rats fed EL vs. ED being in approximate antiphase. The fit of a 12-h cosine curve was statistically significant in all cases (P less than 0.01). The acrophase peaks were: EL, 0800 and 2000 h; and ED, 1600 and 0400 h. These patterns were unrelated to those for NCP and collagen synthesis. EL and ED relationships for NCP synthesis were also antiphasal. A statistically significant circadian rhythm of collagen synthesis was detected in cartilage and bone of ED-fed rats (peak, 0800 h; nadir, 2400 h). In EL-fed rats, the 0800 h peak alone was muted. No consistent correlations were observed between serum calcium and phosphorus chronograms and those of cartilage and bone collagen and DNA synthesis. The results suggest that physiological alterations of CS in vivo serve to modulate cartilage and bone cell proliferation, but they do not seem to regulate the phasing of the net collagen synthetic rhythm.

Adrenal/parathyroid regulation of DNA, collagen and protein synthesis in rat epiphysial cartilage and bone.

Young, growing rats which had been chronically (2 weeks) adrenalectomized or parathyroidectomized were used to define the roles of the adrenal and parathyroid glands on the maintenance of normal circadian rhythms of DNA, collagen and non-collagen protein synthesis in the skeleton. The animals were conditioned to food being available ad libitum and to 12 h light: 12 h darkness (lights on from 08.00 to 20.00 h). The pace of DNA, collagen and non-collagen protein synthesis in different regions of the tibia (tibial growth cartilage, metaphysial bone and diaphysial bone) was measured by the in-vivo incorporation of tritiated thymidine (1 h) and radioactive proline (48 h). In intact rats there were no regional differences in the phasing of the circadian profiles; peak DNA and non-collagen protein synthesis occurred at the onset of the dark period while peak collagen synthesis occurred during the middle of the period of light. Adrenalectomy selectively abolished the regional DNA synthesis rhythms without altering the phases of the serum Ca and phosphorus (P) rhythms, which peak at mid-day and at the onset of darkness respectively. Parathyroidectomy abolished the regional rhythms for collagen and non-collagen protein synthesis and serum Ca rhythms, without altering the phase of the serum P and corticosterone rhythms. Dietary Ca-lactate supplements, which raised serum Ca levels towards normal in parathyroidectomized rats, were able to correct serum corticosterone values but did not normalize bone collagen and non-collagen protein synthesis values. These data indicate that the adrenal rhythm governs the proliferative activities of bone and cartilage cells, and that parathyroid hormone is essential to maintain normal collagen and non-collagen protein synthesis rhythms.

Effect of an adrenocorticotropin analogue, ACTH 1-17, on DNA synthesis in murine metaphyseal bone.

The effects of injections of a synthetic adrenocorticotropin (ACTH 1-17, Synchrodyn) on the rate of DNA labeling in the metaphyseal bone of CD2F1 mice were tested on a chronopharmacological dosing schedule. Groups of mice that had been conditioned to a 12-hr light/12-hr dark schedule were injected at one of six different timepoints, 4 hr apart, during a single 24-hr span with either a low (0.02 I.U./kg) or a high (20 I.U./kg) dose of ACTH 1-17. Control groups received injections of a placebo at corresponding timepoints. Subgroups of mice were injected with [3H]thymidine ([3H]Tdr) to follow the changes in DNA labeling in the proximal tibial metaphysis at 15 min and 2, 4, 8, 12 and 24 hr after ACTH 1-17 or placebo treatment. All mice were injected with the isotope 30 min before killing, except for those killed 15 min after Rx administration where the isotope had been injected 14 min before killing. The data were analyzed both by analysis of variance and by the cosinor method, the latter of which tests the fit of a 24-hr cosine curve to the data. The effect of ACTH 1-17 on the target cell population was dependent not only upon the dose but upon the time of administration. Both doses exerted time-dependent action, ranging from stimulation to inhibition of DNA labeling. Inhibition was noted when the ACTH 1-17 was administered at 2 hr after the beginning of the daily dark span when nocturnal animals become active. When administered at this circadian stage, the larger dose in particular was associated with an inhibition of DNA labeling lasting for 24 hr. The inhibitory effect was much shorter when the same dose was injected 4 hr earlier. Moreover, the large ACTH 1-17 dose had a stimulatory effect lasting for 24 hr when it was administered 2 hr after the onset of the daily light span, with a much shorter stimulation following administration of the large dose at 6 hr after the beginning of the daily dark span. A circadian stage-dependent stimulation or inhibition of DNA labeling at 2 or 14 hr after light onset, respectively, was thus complemented by an initial inhibition followed by stimulation and vice versa at 10 and 18 hr after light onset respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

A new method for measurement of airway occlusion pressure.

Airway occlusion pressure correlates with central respiratory drive. The airway occlusion pressure (P0.1) may be an excellent predictor of the ability of patients with obstructive lung disease to wean from mechanical ventilation. We describe a new method for measuring P0.1 using digitized signals generated from standard respiratory equipment and a computer program to automatically determine P0.1 values. The accuracy of this new method was tested by comparison with standard analog recorder methods using a mechanical lung model, in ventilated patients in an intensive care unit, and in normal volunteers. In all settings, excellent correlation was obtained between P0.1 measurements by the digital Servo and standard analog methods (r = 0.99). This new method permits accurate and automatic determination of P0.1 in ventilated patients using standard respiratory equipment. The rapid response and ease of use of this method should enable evaluation of a number of physiologic variables involved in respiratory control in ventilated and nonventilated patients.

Myeloperoxidase-positive acute megakaryoblastic leukemia.

Acute megakaryoblastic leukemia (FABM7) is an unusual but well recognized form of acute myelogenous leukemia in which the bone marrow blast cells are phenotypically recognized by the demonstration of cytoplasmic platelet peroxidase or surface staining for the IIb/IIIa platelet-specific glycoprotein. Herein, the authors report a case of acute megakaryoblastic leukemia that satisfies the accepted French-American-British criteria and in which the blast cells also exhibit evidence of myeloid differentiation, including surface MY7 (CD13) by flow cytometry and immunocytochemical positivity for myeloperoxidase. These findings suggest that megakaryoblasts may be closely related to myelomonoblasts, that they have the potential to partially differentiate along multiple phenotypic lines, and that aberrant phenotypes can occur that do not correspond to known stages of normal maturation. The authors illustrate the difficulty in classification of these aberrant phenotypes by standard cytochemical and morphologic criteria.

Expression and developmental control of the human alpha-globin gene cluster.

The human alpha-globin gene cluster contains three functional genes zeta, alpha 2 and alpha 1. The zeta-globin gene is expressed exclusively in the primitive erythroblasts of the embryonic yolk sac and is selectively silenced during the transition from primitive to definitive erythropoesis. The two alpha-globin genes are expressed through development; they are expressed at equivalent levels in embryonic cells at a 2.6:1 ratio of alpha 2:alpha 1 in fetal and adult cells. The dominant contribution of the alpha 2-globin locus to overall expression of adult alpha-globin is reflected in the more severe phenotype resulting from mutations that affect this locus. Developmental silencing of the zeta-globin gene reflects both transcriptional and posttranscriptional mechanisms. Transcriptional silencing is mediated by an interaction between the zeta-globin gene promoter and a silencer located in the 3' flanking region. This transcriptional silencing is only partial, and residual levels of zeta-globin mRNA are subject to subsequent degredation. This instability of zeta-globin mRNA relative to that of alpha-globin mRNA reflects differences in their respective 3'UTR segments; the zeta-globin mRNA 3'UTR has a lower affinity for a sequence-specific mRNP stability complex which assembles at this site. The alpha-globin mRNA assembles this complex at a higher efficiency and mutations which interfere with 3'UTR function result in corresponding loss of alpha-globin gene expression. These data outline a developmental pathway for the alpha-globin gene cluster which reflects transcriptional and posttranscriptional controls.