Deltamethrin-Mediated Toxicity and Cytomorphological Changes in the Midgut and Nervous System of the Mayfly Callibaetis radiatus

Immature instars of mayflies are important constituents of the food web in aquatic ecosystems (especially in Neotropical regions) and they are among the most susceptible arthropods to pyrethroid insecticides. These insecticides have been recognized as important stressors of freshwater ecosystems, but their cellular effects in aquatic insects have been neglected. Here, we assessed the susceptibility to deltamethrin (a typical type II pyrethroid) as well as the deltamethrin-mediated cytomorphological changes in the central nervous system and midgut of the mayfly Callibaetis radiatus. While the deltamethrin LC₅₀ for 24h of exposure was of 0.60 (0.46–0.78) μg of a.i/L, the survival of C. radiatus was significantly reduced in deltamethrin concentrations ≥ 0.25 μg a.i/L at 96h of exposure. Sub-lethal deltamethrin exposure severely affected the cytomorphology of C. radiatus midgut (e.g., muscle layer retraction, cytoplasm vacuolation, nucleus and striated border disorganization) and also induced slight cytomorphological changes in the brain (e.g., presence of pyknotic nuclei) and in the thoracic ganglia (e.g., vacuolation of neurons and presence of pyknotic nuclei) of these insects. However, DNA damage was absent in all of these organs, suggesting that the sublethal cellular stress induced by deltamethrin might disrupt physiological processes (e.g., metabolism or electrical signal transmission) rather than cause cell death (e.g., apoptosis) in C. radiatus. Thus, our findings indicated that deltamethrin actions at cellular levels represent a clear indication of sublethal effects on the C. radiatus survival abilities.     

The capacity of the fourth chromosome of Drosophila melanogaster to establish end-to-end contacts with the other chromosomes in salivary-gland cells

When the fourth chromosome of Drosophila melanogaster is attached, as the result of an induced translocation, to 21A in 2L or 60E in 2R, its tip exhibits a marked capacity to pair end-to-end with the tips of the other chromosomes. In each of the translocations, about 59 per cent of the contacts involving the tip of 4 were with the tip of X. If this pairing preference reflects structural similarity, the tip of 4 is much more like the tip of X than that of any other chromosome. The significance of this phenomenon is discussed with respect to the standard pattern of end-to-end association in the Oregon-R wild-type stock that provided the control preparations. In the 4-2L rearrangement, the interaction of chromosome 4 with the tip of 2L (101E with 21A) led to pronounced puffing in subdivisions 21A and B, as was most strikingly manifested when the distal segments of 2L failed to synapse and the homologue of paternal origin showed a large puff whereas that of maternal origin (not carrying the fourth chromosome) remained unpuffed.This study was supported in part by a Research Grant (GM-10499) from the National Institutes of Health, U.S. Public Health Service.     

In Vivo Interaction Proteomics Reveal a Novel p38 Mitogen-Activated Protein Kinase/Rack1 Pathway Regulating Proteostasis in Drosophila Muscle

Several recent studies suggest that systemic aging in metazoans is differentially affected by functional decline in specific tissues, such as skeletal muscle. In Drosophila, longevity appears to be tightly linked to myoproteostasis, and the formation of misfolded protein aggregates is a hallmark of senescence in aging muscle. Similarly, defective myoproteostasis is described as an important contributor to the pathology of several age-related degenerative muscle diseases in humans, e.g., inclusion body myositis. p38 mitogen-activated protein kinase (MAPK) plays a central role in a conserved signaling pathway activated by a variety of stressful stimuli. Aging p38 MAPK mutant flies display accelerated motor function decline, concomitant with an enhanced accumulation of detergent-insoluble protein aggregates in thoracic muscles. Chemical genetic experiments suggest that p38-mediated regulation of myoproteostasis is not limited to the control of reactive oxygen species production or the protein degradation pathways but also involves upstream turnover pathways, e.g., translation. Using affinity purification and mass spectrometry, we identified Rack1 as a novel substrate of p38 MAPK in aging muscle and showed that the genetic interaction between p38b and Rack1 controls muscle aggregate formation, locomotor function, and longevity. Biochemical analyses of Rack1 in aging and stressed muscle suggest a model whereby p38 MAPK signaling causes a redistribution of Rack1 between a ribosome-bound pool and a putative translational repressor complex.     

B-CHROMOSOMES,THEIR ORIGIN AND RELATION TO MEIOSIS IN INTERSPECIFIC LOLIUM HYBRIDS

The following Lolium species were shown to have 14 chromosomes: L. canariensis Steud. (= L. gracile Parl.), L. loliaceum (Bory and Chaub.) Hand.-Mazz., L. multiflorum Lam., L. perenne L., and L. temulentum L. B-chromosomes in addition to the normal complement were observed during metaphase I and anaphase I for L. persicum Boiss. and Hohen., L. remotum Schrank, L. rigidum Gaud., L. strictum Presl. (= L. rigidum?), and for several synthesized interspecific hybrids. General absence of B-chromosomes in diakinesis suggested that they originated by misdivision of A-chromosomes during prometaphase I. The B-chromosomes reached a maximum of eight but the number varied for microsporocytes of the same plant. B-chromosomes appeared spontaneously in progenies from sibbing of hybrid plants without supernumeraries but were also eliminated in the F₂ from other sibbings. Degree of chromosome pairing during meiosis was unrelated to the subsequent presence of B-chromosomes. Normal pairing of seven bivalents was typical for L. perenne × L. multiflorum, L. perenne × L. rigidum, L. multiflorum × L. loliaceum, and L. rigidum × L. loliaceum. Between five and seven bivalents were recorded for L. multiflorum × L. persicum, L. multflorum × L. remotum, L. multiflorum × L. strictum, L. rigidum × L. persicum, L. rigidum × L. remotum, L. rigidum × L. strictum, and L. rigidum × L. temulentum. The results indicated that these Lolium species have a common and generally undifferentiated genome suggesting relatively recent speciation.     

Malnutrition Has No Effect on the Timing of Human Tooth Formation

The effect of nutrition on the timing of human tooth formation is poorly understood. Delays and advancements in dental maturation have all been reported as well as no effect. We investigated the effect of severe malnutrition on the timing of human tooth formation in a large representative sample of North Sudanese children. The sample (1102 males, 1013 females) consisted of stratified randomly selected healthy individuals in Khartoum, Sudan, aged 2-22 years using a cross-sectional design following the STROBE statement. Nutritional status was defined using WHO criteria of height and weight. Body mass index Z-scores and height for age Z-scores of ≤−2 (cut-off) were used to identify the malnourished group (N = 474) while the normal was defined by Z-scores of ≥0 (N = 799). Clinical and radiographic examination of individuals, with known ages of birth was performed including height and weight measurements. Mandibular left permanent teeth were assessed using eight crown and seven root established tooth formation stages. Mean age at entry and mean age within tooth stages were calculated for each available tooth stage in each group and compared using a t-test. Results show the mean age at entry and mean age within tooth stages were not significantly different between groups affected by severe malnutrition and normal children (p>0.05). This remarkable finding was evident across the span of dental development. We demonstrate that there is little measurable effect of sustained malnutrition on the average timing of tooth formation. This noteworthy finding supports the notion that teeth have substantial biological stability and are insulated from extreme nutritional conditions compared to other maturing body systems.     

The association between arthritis and the weather

 Despite the pervasiveness of the idea that arthritis is influenced by the weather, scientific evidence on the matter is sparse and non-conclusive. This study, conducted in the Australian inland city of Bendigo, sought to establish a possible relationship between the pain and rigidity of arthritis and the weather variables of temperature, relative humidity, barometric pressure, wind speed and precipitation. Pain and rigidity levels were scored by 25 participants with osteoarthritis and/or rheumatoid arthritis four times per day for 1 month from each season. Mean pain and rigidity scores for each time of each day were found to be correlated with the meteorological data. Correlations between mean symptoms and temperature and relative humidity were significant (P <0.001). Time of day was included in the analysis. Stepwise multiple regression analysis indicated that meteorological variables and time of day accounted for 38% of the variance in mean pain and 20% of the variance in mean rigidity when data of all months were considered. A post-study telephone questionnaire indicated 92% of participants perceived their symptoms to be influenced by the weather, while 48% claimed to be able to predict the weather according to their symptoms. Hence, the results suggest (1) decreased temperature is associated with both increased pain and increased rigidity and (2) increased relative himidity is associated with increased pain and rigidity in arthritis sufferers. Received: 3 October 1996/Accepted: 10 December 1996     

The antigenic anatomy of SARS-CoV-2 receptor binding domain

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Increased Serum and Musculotendinous Fibrogenic Proteins following Persistent Low-Grade Inflammation in a Rat Model of Long-Term Upper Extremity Overuse

We examined the relationship between grip strength declines and muscle-tendon responses induced by long-term performance of a high-repetition, low-force (HRLF) reaching task in rats. We hypothesized that grip strength declines would correlate with inflammation, fibrosis and degradation in flexor digitorum muscles and tendons. Grip strength declined after training, and further in weeks 18 and 24, in reach limbs of HRLF rats. Flexor digitorum tissues of reach limbs showed low-grade increases in inflammatory cytokines: IL-1β after training and in week 18, IL-1α in week 18, TNF-α and IL-6 after training and in week 24, and IL-10 in week 24, with greater increases in tendons than muscles. Similar cytokine increases were detected in serum with HRLF: IL-1α and IL-10 in week 18, and TNF-α and IL-6 in week 24. Grip strength correlated inversely with IL-6 in muscles, tendons and serum, and TNF-α in muscles and serum. Four fibrogenic proteins, TGFB1, CTGF, PDGFab and PDGFbb, and hydroxyproline, a marker of collagen synthesis, increased in serum in HRLF weeks 18 or 24, concomitant with epitendon thickening, increased muscle and tendon TGFB1 and CTGF. A collagenolytic gelatinase, MMP2, increased by week 18 in serum, tendons and muscles of HRLF rats. Grip strength correlated inversely with TGFB1 in muscles, tendons and serum; with CTGF-immunoreactive fibroblasts in tendons; and with MMP2 in tendons and serum. Thus, motor declines correlated with low-grade systemic and musculotendinous inflammation throughout task performance, and increased fibrogenic and degradative proteins with prolonged task performance. Serum TNF-α, IL-6, TGFB1, CTGF and MMP2 may serve as serum biomarkers of work-related musculoskeletal disorders, although further studies in humans are needed.