Zinc Finger Binding Motifs Do Not Explain Recombination Rate Variation within or between Species of Drosophila

In humans and mice, the Cys₂His₂ zinc finger protein PRDM9 binds to a DNA sequence motif enriched in hotspots of recombination, possibly modifying nucleosomes, and recruiting recombination machinery to initiate Double Strand Breaks (DSBs). However, since its discovery, some researchers have suggested that the recombinational effect of PRDM9 is lineage or species specific. To test for a conserved role of PRDM9-like proteins across taxa, we use the Drosophila pseudoobscura species group in an attempt to identify recombination associated zinc finger proteins and motifs. We leveraged the conserved amino acid motifs in Cys₂His₂ zinc fingers to predict nucleotide binding motifs for all Cys₂His₂ zinc finger proteins in Drosophila pseudoobscura and identified associations with empirical measures of recombination rate. Additionally, we utilized recombination maps from D. pseudoobscura and D. miranda to explore whether changes in the binding motifs between species can account for changes in the recombination landscape, analogous to the effect observed in PRDM9 among human populations. We identified a handful of potential recombination-associated sequence motifs, but the associations are generally tenuous and their biological relevance remains uncertain. Furthermore, we found no evidence that changes in zinc finger DNA binding explains variation in recombination rate between species. We therefore conclude that there is no protein with a DNA sequence specific human-PRDM9-like function in Drosophila. We suggest these findings could be explained by the existence of a different recombination initiation system in Drosophila.     

Troglitazone‐Induced Changes in Adiponectin Do Not Affect Endothelial Function in Diabetes

Objective: Adiponectin has been proposed to be related to endothelial function. We have examined the relationship between the increase in adiponectin levels that is associated with troglitazone treatment and endothelium‐dependent vasodilation in type 2 diabetic patients. Research Methods and Procedures: Seventy‐two patients participated in this randomized, placebo‐controlled, double‐blinded study. High‐resolution ultrasound images were used to measure the flow‐mediated dilation (endothelium‐dependent) and nitroglycerin‐induced dilation (endothelium‐independent) of the brachial artery. Laser Doppler perfusion imaging was employed to measure the vascular reactivity in the forearm skin. Results: Troglitazone treatment resulted in an average 75% increase in the adiponectin levels, but no changes were observed in the endothelium‐dependent vasodilation, any other measurement of vascular reactivity, or any other markers of endothelial activation. Also, no changes were observed in the expression of the receptor for advanced glycation end‐products in skin biopsies taken from the forearm. Significant correlations were observed during troglitazone treatment between the changes in the adiponectin levels and the changes in fasting plasma glucose (r = ?0.29, p < 0.05), hemoglobin A_1c (r = ?0.30, p < 0.05), total cholesterol (r = 0.25, p < 0.05), and low‐density lipoprotein‐cholesterol (r = 0.34, p < 0.01). Discussion: The increase in adiponectin levels after troglitazone treatment is not associated with an improvement in the endothelium‐dependent vasodilation, indicating that adiponectin is not a major determinant of endothelial function. In addition, receptor for advanced glycation end‐products expression in the skin microcirculation is not affected by troglitazone treatment.     

Repeated Recent Aggressive Encounters Do Not Affect Behavioral Consistency in Male Siamese Fighting Fish

Consistent individual differences in behavior suggest that individuals respond in a predictable and repeatable manner in a specific situation while differing from other individuals. Male Siamese fighting fish exhibit consistent individual differences in decision‐making strategies when they encounter a receptive female and a rival male simultaneously. However, whether these differences are altered by recent experience is unknown. We examined the influence of repeated aggressive encounters on behavioral consistency and decision‐making. Males were presented with paired female–male dummies prior to any aggressive experiences to obtain a baseline measure. Next, males either won or lost three consecutive contests against rivals and then received the paired female–male dummies after each of these encounters. Overall levels of highly aggressive behaviors were affected by contest outcome, while levels of female‐directed were not. Not surprisingly, winning a fight led to an increase in male‐directed bites, an overtly aggressive behavior that only occurs after fights have escalated. Fighting a male before encountering the dummies caused males to perform more tail beats to the dummy male, perhaps as a result of increased motivation. Males exhibited similar levels of repeatability and used the same strategies when faced with conflicting stimuli regardless of fighting experience. Thus, while winning or losing a fight impacts overall aggression, it does not influence behavioral consistency. This study demonstrates that consistent individual differences and decision‐making strategies may be resistant to recent aggressive experiences, even over a period of days.     

Pulsed High-Peak Power Microwaves at 9.4 GHz Do Not Affect Basic Endpoints in Caenorhabditis elegans

Because of the extensive application of electromagnetic technology, its health impact on humans has attracted widespread attention. Due to the lack of a model organism with a stable response to electromagnetic waves, the research conclusions on the biological effects of electromagnetic waves have been vague. Therefore, the aim of this study was to investigate the effects of irradiation by pulsed 9.4 GHz high-power microwaves with a peak power density of 2126 W/cm² using Caenorhabditis elegans. The development, movement, egg production, ROS, and lifespan of C. elegans were detected at different times after irradiation with different repetitive frequencies of 10, 20, and 50 Hz for 30 min. The results indicated that no obvious changes in basic life indices were induced compared with the sham radiation group, but the survival rate of positive control was significantly decreased compared with other groups, which is of interest for microwave protection research based on C. elegans and provides data for updating safety standards with respect to pulsed high-peak power microwave. © 2021 Bioelectromagnetics Society.     

Mutations of Phosphorylation Sites in MSL1 Protein Do Not Affect Dosage Compensation in Drosophila melanogaster

Doklady Biochemistry and Biophysics - Proteins MSL1 and MSL2 form the core of the Drosophila dosage compensation complex, which specifically binds to the X chromosome of males. Phosphorylation of...     

Moderate-Intensity Rotating Magnetic Fields Do Not Affect Bone Quality and Bone Remodeling in Hindlimb Suspended Rats

Abundant evidence has substantiated the positive effects of pulsed electromagnetic fields (PEMF) and static magnetic fields (SMF) on inhibiting osteopenia and promoting fracture healing. However, the osteogenic potential of rotating magnetic fields (RMF), another common electromagnetic application modality, remains poorly characterized thus far, although numerous commercial RMF treatment devices have been available on the market. Herein the impacts of RMF on osteoporotic bone microarchitecture, bone strength and bone metabolism were systematically investigated in hindlimb-unloaded (HU) rats. Thirty two 3-month-old male Sprague-Dawley rats were randomly assigned to the Control (n = 10), HU (n = 10) and HU with RMF exposure (HU+RMF, n = 12) groups. Rats in the HU+RMF group were subjected to daily 2-hour exposure to moderate-intensity RMF (ranging from 0.60 T to 0.38 T) at 7 Hz for 4 weeks. HU caused significant decreases in body mass and soleus muscle mass of rats, which were not obviously altered by RMF. Three-point bending test showed that the mechanical properties of femurs in HU rats, including maximum load, stiffness, energy absorption and elastic modulus were not markedly affected by RMF. µCT analysis demonstrated that 4-week RMF did not significantly prevent HU-induced deterioration of femoral trabecular and cortical bone microarchitecture. Serum biochemical analysis showed that RMF did not significantly change HU-induced decrease in serum bone formation markers and increase in bone resorption markers. Bone histomorphometric analysis further confirmed that RMF showed no impacts on bone remodeling in HU rats, as evidenced by unchanged mineral apposition rate, bone formation rate, osteoblast numbers and osteoclast numbers in cancellous bone. Together, our findings reveal that RMF do not significantly affect bone microstructure, bone mechanical strength and bone remodeling in HU-induced disuse osteoporotic rats. Our study indicates potentially obvious waveform-dependent effects of electromagnetic fields-stimulated osteogenesis, suggesting that RMF, at least in the present form, might not be an optimal modality for inhibiting disuse osteopenia/osteoporosis.     

X Chromosome Duplications Affect a Region of the Chromosome They Do Not Duplicate in Caenorhabditis Elegans

X chromosome duplications have been used previously to vary the dose of specific regions of the X chromosome to study dosage compensation and sex determination in Caenorhabditis elegans. We show here that duplications suppress and X-linked hypomorphic mutation and elevate the level of activity of an X-linked enzyme, although these two genes are located in a region of the X chromosome that is not duplicated. The effects do not depend on the region of the X chromosome duplicated and is stronger in strains with two doses of a duplication than in strains with one dose. This is evidence for a general elevation of X-linked gene expression in strains carrying X-chromosome duplications, consistent with the hypothesis that the duplications titrate a repressor acting on many X-linked genes.     

Osmotic Swelling-Induced Changes in Cytosolic Calcium Do Not Affect Regulatory Volume Decrease in Rat Cultured Suspended Cerebellar Astrocytes

Abstract: Hyposmotic swelling-induced changes in intracellular Ca²⁺ concentration ([Ca²⁺]_i) and their influence on regulatory volume decrease (RVD) were examined in rat cultured suspended cerebellar astrocytes. Hyposmotic media (50 or 30%) evoked an immediate rise in [Ca²⁺]_i from 117 nM to a mean peak increase of 386 (50%) and 220 nM (30%), followed by a maintained plateau phase. Ca²⁺ influx through the plasmalemma as well as release from internal stores contributed to this osmosensitive [Ca²⁺]_i elevation. Omission of external Ca²⁺ or addition of Cd²⁺, Mn²⁺, or Gd³⁺ did not reduce RVD, although it was decreased by La³⁺ (0.1–1 mM). Verapamil did not affect either the swelling-evoked [Ca²⁺]_i or RVD. Maneuvers that deplete endoplasmic reticulum (ER) Ca²⁺ stores, such as treatment (in Ca²⁺-free medium) with 0.2 µM thapsigargin (Tg), 10 µM 2,5-di-tert-butylhydroquinone, 1 µM ionomycin, or 100 µM ATP abolished the increase in [Ca²⁺]_i but did not affect RVD. However, prolonged exposure to 1 µM Tg blocked RVD regardless of ER Ca²⁺ content or cytosolic Ca²⁺ levels. Ryanodine (up to 100 µM) and caffeine (10 mM) did not modify [Ca²⁺]_i or RVD. BAPTA-acetoxymethyl ester (20 µM) abolished [Ca²⁺]_i elevation without affecting RVD, but at higher concentrations BAPTA prevented cell swelling and blocked RVD. We conclude that the osmosensitive [Ca²⁺]_i rise occurs as a consequence of increased Ca²⁺ permeability of plasma and organelle membranes, but it appears not relevant as a transduction signal for RVD in rat cultured cerebellar astrocytes.     

Androgens Increase Persistence But Do Not Affect Neophobia in a Problem‐Solving Context in a Songbird

Gonadal steroid hormones enhance cognitive performance, particularly spatial and vocal learning, in mammals and birds. However, it is unknown whether problem‐solving ability is similarly regulated. We propose that androgens, such as testosterone and 5α‐dihydrotestosterone, play a role in mediating problem‐solving behavior as well. As a test, male white‐crowned sparrows (Zonotrichia leucophrys gambelii) were either castrated and administered a blank (Blank‐castrate) or testosterone‐filled implant (T‐castrate) or were sham operated and were exposed to a novel feeder, which they had to open to receive a food reward, in two trials. Testosterone treatment affected neither a neophobic response nor problem‐solving performance. However, T‐castrates were more persistent in manipulating the feeder than Blank‐castrates or Shams. Furthermore, their persistence correlated positively with circulating levels of both testosterone and 5α‐dihydrotestosterone. We suggest that a positive correlation between sex steroids and persistence in foraging and problem‐solving contexts may lead to an adaptive increase in resource acquisition in the breeding season. Given the overall low success on the problem‐solving test, we cannot confidently conclude that androgens do not play a role in mediating problem‐solving behavior. However, unlike in mammals, it seems these hormones do not significantly influence neophobia in foraging contexts in birds.     

Secretory Antibodies Do Not Affect the Composition of the Bacterial Microbiota in the Terminal Ileum of 10-Week-Old Mice

Terminal restriction fragment length polymorphism (T-RFLP) analysis was conducted on the 16S rRNA genes of the bacterial communities colonizing the epithelial surfaces of the terminal ilea of open conventionally housed mice in an institutional small-animal facility. Polymeric-immunoglobulin-receptor-deficient (pIgR^−/−) mice that were unable to secrete antibodies across mucosal surfaces were cohoused with normal and otherwise genetically identical wild-type (C57BL/6) mice for 4 weeks. If secretory antibodies played a role in modeling the gastrointestinal microbiota, C57BL/6 mice would have had a more distinct and uniform microbiota than their pIgR^−/− cage mates. The T-RFLP profiles of the bacterial communities were compared by using Sorensen's pairwise similarity coefficient, a newly developed weighted pairwise similarity coefficient, and on the basis of Shannon's and Simpson's diversity indices. No systematic differences were observed between the dominant components of the mucosa-associated bacterial communities of the terminal ileal walls of the two types of mice, indicating that secretory antibodies do not control the composition of this microbiota. Similar analyses of experiments conducted at two different times, between which the bacterial community composition of the mouse colony in the small-animal facility appeared to have changed, showed that differences could have been detected, had they existed.     

Nitric Oxide Synthase Inhibitors Do Not Attenuate Diacylglycerol or Monoacylglycerol Lipase Activities in Synaptoneurosomes

Neuron-enriched cultures and synaptoneurosomal fractions from 10 day-old rat brain contain diacylglycerol and monoacylglycerol lipase activities. Glutamate and its analogs stimulate the activities of diacylglycerol and monoacylglycerol lipases in a time-and dose-dependent manner. Stimulation of diacylglycerol and monoacylglycerol lipases by glutamate or NMDA can be blocked by MK-801 (non-competitive antagonist). Nitro L-arginine methyl ester and L-methylarginine have no effect on glutamate stimulated activities of diacylglycerol and monoacylglycerol lipases. Our studies suggest that synaptoneurosomal preparations from young rat brain are useful for obtaining important information on signal transduction.     

Video-Games Do Not Negatively Impact Adolescent Academic Performance in Science,Mathematics or Reading

Video-gaming is a common pastime among adolescents, particularly adolescent males in industrialized nations. Despite widespread suggestions that video-gaming negatively affects academic achievement, the evidence is inconclusive. We reanalyzed data from over 192,000 students in 22 countries involved in the 2009 Programme for International Student Assessment (PISA) to estimate the true effect size of frequency of videogame use on adolescent academic achievement in science, mathematics and reading. Contrary to claims that increased video-gaming can impair academic performance, differences in academic performance were negligible across the relative frequencies of videogame use. Videogame use had little impact on adolescent academic achievement.     

Statins Do Not Alter the Incidence of Mesothelioma in Asbestos Exposed Mice or Humans

Mesothelioma is principally caused by asbestos and may be preventable because there is a long latent period between exposure and disease development. The most at-risk are a relatively well-defined population who were exposed as a consequence of their occupations. Although preventative agents investigated so far have not been promising, discovery of such an agent would have a significant benefit world-wide on healthcare costs and personal suffering. Statins are widely used for management of hypercholesterolemia and cardiovascular risk; they can induce apoptosis in mesothelioma cells and epidemiological data has linked their use to a lower incidence of cancer. We hypothesised that statins would inhibit the development of asbestos-induced mesothelioma in mice and humans. An autochthonous murine model of asbestos-induced mesothelioma was used to test this by providing atorvastatin daily in the feed at 100 mg/kg, 200 mg/kg and 400 mg/kg. Continuous administration of atorvastatin did not alter the rate of disease development nor increase the length of time that mice survived. Latency to first symptoms of disease and disease progression were also unaffected. In a parallel study, the relationship between the use of statins and development of mesothelioma was investigated in asbestos-exposed humans. In a cohort of 1,738 asbestos exposed people living or working at a crocidolite mine site in Wittenoom, Western Australia, individuals who reported use of statins did not have a lower incidence of mesothelioma (HR = 1.01; 95% CI = 0.44–2.29, p = 0.99). Some individuals reported use of both statins and non-steroidal anti-inflammatory drugs or COX-2 inhibitors, and these people also did not have an altered risk of mesothelioma development (HR = 1.01; 95% CI = 0.61–1.67, p = 0.97). We conclude that statins do not moderate the rate of development of mesothelioma in either a mouse model or a human cohort exposed to asbestos.     

Separation-of-Function Mutations in Saccharomyces cerevisiae MSH2 That Confer Mismatch Repair Defects but Do Not Affect Nonhomologous-Tail Removal during Recombination

Yeast Msh2p forms complexes with Msh3p and Msh6p to repair DNA mispairs that arise during DNA replication. In addition to their role in mismatch repair (MMR), the MSH2 and MSH3 gene products are required to remove 3' nonhomologous DNA tails during genetic recombination. The mismatch repair genes MSH6, MLH1, and PMS1, whose products interact with Msh2p, are not required in this process. We have identified mutations in MSH2 that do not disrupt genetic recombination but confer a strong defect in mismatch repair. Twenty-four msh2 mutations that conferred a dominant negative phenotype for mismatch repair were isolated. A subset of these mutations mapped to residues in Msh2p that were analogous to mutations identified in human nonpolyposis colorectal cancer msh2 kindreds. Approximately half of the these MMR-defective mutations retained wild-type or nearly wild-type activity for the removal of nonhomologous DNA tails during genetic recombination. The identification of mutations in MSH2 that disrupt mismatch repair without affecting recombination provides a first step in dissecting the Msh-effector protein complexes that are thought to play different roles during DNA repair and genetic recombination.     

Experimental Shifts in Intraclutch Egg Color Variation Do Not Affect Egg Rejection in a Host of a Non-Egg-Mimetic Avian Brood Parasite

Avian brood parasites lay their eggs in the nests of other birds, and impose the costs associated with rearing parasitic young onto these hosts. Many hosts of brood parasites defend against parasitism by removing foreign eggs from the nest. In systems where parasitic eggs mimic host eggs in coloration and patterning, extensive intraclutch variation in egg appearances may impair the host’s ability to recognize and reject parasitic eggs, but experimental investigation of this effect has produced conflicting results. The cognitive mechanism by which hosts recognize parasitic eggs may vary across brood parasite hosts, and this may explain variation in experimental outcome across studies investigating egg rejection in hosts of egg-mimicking brood parasites. In contrast, for hosts of non-egg-mimetic parasites, intraclutch egg color variation is not predicted to co-vary with foreign egg rejection, irrespective of cognitive mechanism. Here we tested for effects of intraclutch egg color variation in a host of nonmimetic brood parasite by manipulating egg color in American robins (Turdus migratorius), hosts of brown-headed cowbirds (Molothrus ater). We recorded robins’ behavioral responses to simulated cowbird parasitism in nests where color variation was artificially enhanced or reduced. We also quantified egg color variation within and between unmanipulated robin clutches as perceived by robins themselves using spectrophotometric measures and avian visual modeling. In unmanipulated nests, egg color varied more between than within robin clutches. As predicted, however, manipulation of color variation did not affect rejection rates. Overall, our results best support the scenario wherein egg rejection is the outcome of selective pressure by a nonmimetic brood parasite, because robins are efficient rejecters of foreign eggs, irrespective of the color variation within their own clutch.     

Blood Clot Formation Does Not Affect Metastasis Formation or Tumor Growth in a Murine Model of Breast Cancer

Cancer is associated with increased fracture risk, due either to metastasis or associated osteoporosis. After a fracture, blood clots form. Because proteins of the coagulation cascade and activated platelets promote cancer development, a fracture in patients with cancer often raises the question whether it is a pathologic fracture or whether the fracture itself might promote the formation of metastatic lesions. We therefore examined whether blood clot formation results in increased metastasis in a murine model of experimental breast cancer metastasis.For this purpose, a clot was surgically induced in the bone marrow of the left tibia of immundeficient mice. Either one minute prior to or five minutes after clot induction, human cancer cells were introduced in the circulation by intracardiac injection. The number of cancer cells that homed to the intervention site was determined by quantitative real-time PCR and flow cytometry. Metastasis formation and longitudinal growth were evaluated by bioluminescence imaging.The number of cancer cells that homed to the intervention site after 24 hours was similar to the number of cells in the opposite tibia that did not undergo clot induction. This effect was confirmed using two more cancer cell lines. Furthermore, no difference in the number of macroscopic lesions or their growth could be detected. In the control group 72% developed a lesion in the left tibia. In the experimental groups with clot formation 79% and 65% developed lesions in the left tibia (p = ns when comparing each experimental group with the controls). Survival was similar too.In summary, the growth factors accumulating in a clot/hematoma are neither enough to promote cancer cell homing nor support growth in an experimental model of breast cancer bone metastasis. This suggests that blood clot formation, as occurs in traumatic fractures, surgical interventions, and bruises, does not increase the risk of metastasis formation.     

Arginine Depletion by Arginine Deiminase Does Not Affect Whole Protein Metabolism or Muscle Fractional Protein Synthesis Rate in Mice

Due to the absolute need for arginine that certain cancer cells have, arginine depletion is a therapy in clinical trials to treat several types of cancers. Arginine is an amino acids utilized not only as a precursor for other important molecules, but also for protein synthesis. Because arginine depletion can potentially exacerbate the progressive loss of body weight, and especially lean body mass, in cancer patients we determined the effect of arginine depletion by pegylated arginine deiminase (ADI-PEG 20) on whole body protein synthesis and fractional protein synthesis rate in multiple tissues of mice. ADI-PEG 20 successfully depleted circulating arginine (<1 μmol/L), and increased citrulline concentration more than tenfold. Body weight and body composition, however, were not affected by ADI-PEG 20. Despite the depletion of arginine, whole body protein synthesis and breakdown were maintained in the ADI-PEG 20 treated mice. The fractional protein synthesis rate of muscle was also not affected by arginine depletion. Most tissues (liver, kidney, spleen, heart, lungs, stomach, small and large intestine, pancreas) were able to maintain their fractional protein synthesis rate; however, the fractional protein synthesis rate of brain, thymus and testicles was reduced due to the ADI-PEG 20 treatment. Furthermore, these results were confirmed by the incorporation of ureido [¹⁴C]citrulline, which indicate the local conversion into arginine, into protein. In conclusion, the intracellular recycling pathway of citrulline is able to provide enough arginine to maintain protein synthesis rate and prevent the loss of lean body mass and body weight.     

Transcranial Direct Current Stimulation of Right Dorsolateral Prefrontal Cortex Does Not Affect Model-Based or Model-Free Reinforcement Learning in Humans

There is broad consensus that the prefrontal cortex supports goal-directed, model-based decision-making. Consistent with this, we have recently shown that model-based control can be impaired through transcranial magnetic stimulation of right dorsolateral prefrontal cortex in humans. We hypothesized that an enhancement of model-based control might be achieved by anodal transcranial direct current stimulation of the same region. We tested 22 healthy adult human participants in a within-subject, double-blind design in which participants were given Active or Sham stimulation over two sessions. We show Active stimulation had no effect on model-based control or on model-free (‘habitual’) control compared to Sham stimulation. These null effects are substantiated by a power analysis, which suggests that our study had at least 60% power to detect a true effect, and by a Bayesian model comparison, which favors a model of the data that assumes stimulation had no effect over models that assume stimulation had an effect on behavioral control. Although we cannot entirely exclude more trivial explanations for our null effect, for example related to (faults in) our experimental setup, these data suggest that anodal transcranial direct current stimulation over right dorsolateral prefrontal cortex does not improve model-based control, despite existing evidence that transcranial magnetic stimulation can disrupt such control in the same brain region.