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PubMed2026

Early hepatic protein responses to dietary restriction-refeeding in Japanese quail: A proteomic investigation.

Feed intake and refeeding after nutrient scarcity induce rapid metabolic adaptations in the poultry liver; however, hepatic proteomic recovery pathways in the early hours post-refeeding remain poorly defined. This study aimed to characterize early liver protein signatures in Japanese quail (Coturnix japonica) recovering from nutritional stress under two refeeding conditions. Eighteen 12-week-old male quails (245.20 ± 0.213 g) were assigned to three groups (n = 6): control fed ad libitum (12.13 MJ/kg), 24 h feed deprivation followed by 6 h refeeding, and 24 h low metabolizable energy (6.30 MJ/kg) diet followed by 6 h refeeding. In total, 854 proteins were identified, of which 515 met the filtering criteria. The low metabolizable energy refeeding showed higher abundance of proteins linked to ATP binding and carbohydrate/carboxylic acid metabolism, alongside detoxification-related proteins, while suppressing translation/RNA-binding machinery and antioxidant pathways. Feed-deprived refeeding enriched in oxidative phosphorylation and mitochondrial complex I assembly with reduced cytoplasmic translation, NMD-related components, and sulfur compound metabolism. A direct comparison indicated divergent recovery strategies: low metabolizable energy refeeding mainly reflected oxidoreductase activity and translation initiation, whereas feed-deprived refeeding potentially enriched mitochondrial ATP production and glutathione-based defenses. Our analysis indicate that 6 h of refeeding initiates an early, incomplete recovery toward hepatic homeostasis, with the severity of prior nutritional restriction dictating distinct liver metabolic priorities. Collectively, these findings might provide a preliminary understanding of the hepatic mechanisms involved in recovery from nutrient deprivation and may help in the development of feeding strategies for managing metabolic recovery in poultry. However, these findings should be considered hypothesis-generating pending further validation.

Animals↗

PubMed2026

Pesticide occurrence, transformation, and transport from wastewater treatment plants into stream networks with diverse land uses.

Neonicotinoid insecticides and strobilurin fungicides are detected in many environmental compartments and have been associated with negative environmental and human health implications. Wastewater treatment plants (WWTPs) are often hotspots for introducing such contaminants into the environment. Therefore, the occurrence of strobilurin fungicides, neonicotinoids, and their metabolites at two WWTPs with varying land uses and population sizes was investigated. Polar organic chemical integrative samplers were deployed in WWTP influent and effluent and placed upstream and downstream of the effluent mixing zone for 2 weeks in April and July 2022. Biosolids were also collected at each time point. Neonicotinoids were detected with the highest frequency (68%), followed by strobilurin fungicides (49%) and neonicotinoid metabolites (31%). Time-weighted average concentrations for influent/effluent ranged from 85.2 ± 87.8 to 409.4 ± 74.5 ng/L. Pesticide concentrations, specifically the metabolites, typically increased from influent to effluent, resulting in effluent having higher pesticide loads than influent. Pesticide concentrations varied between the upstream and downstream monitoring locations by analyte, with WWTP samples in the highly developed region having significantly higher concentrations of pesticides and less variation by monitoring period. Chronic ecotoxicity benchmarks for freshwater invertebrates for imidacloprid were surpassed in treated effluent at both WWTPs in July and in the downstream monitoring location in the heavily developed area. Findings support the need for further exploration of pesticide contributions from WWTPs to river systems, specifically related to metabolite contributions to downstream streams and their effects on aquatic environments.

Water Pollutants, Chemical↗

PubMed2026

Distinct functions of mammalian RAD51 paralogs in genome maintenance.

RAD51 paralogs (RAD51B, RAD51C, RAD51D, XRCC2, and XRCC3) are evolutionarily conserved essential proteins for cell survival and genome maintenance. RAD51 paralogs were originally identified to play a role in homologous recombination-mediated repair of DNA double-strand breaks (DSBs). However, investigations over the last decade have uncovered new roles of RAD51 paralogs beyond DSB repair in replication stress responses, including replication fork progression, fork stability, and its restart. Recent structural studies have not only uncovered the molecular architecture of previously known RAD51 paralog complexes but also identified novel paralog complex assemblies, providing mechanistic insights into their various genome-maintenance functions. Additionally, a role for RAD51 paralogs in resolving R-loops has been identified, and studies with cancer-associated variants suggest that RAD51 paralogs are potential determinants of cancer susceptibility and therapeutic responses. In the present review, we highlight the recently deciphered structures and novel functions of RAD51 paralog complexes and discuss the clinical and therapeutic implications.

Rad51 Recombinase↗

PubMed2026

Transcriptomic analysis reveals the molecular mechanisms underlying the inhibition of Mytilus edulis attachment by biofouling control agents.

This study combined acute toxicity assays, phenotypic quantification, and transcriptomic profiling to systematically investigate the inhibitory effects and molecular regulatory mechanisms of a novel alkylamine-based antifouling agent on survival, byssus secretion, and attachment behavior of juvenile Mytilus edulis. The 96 h-LC50 of the agent to juvenile M. edulis was 8.84 mg/L, and 10 mg/L of the agent completely inhibited mussel attachment within 24 h, significantly reducing byssal thread number, length, and diameter while increasing detachment frequency, resulting in irreversible attachment failure. Transcriptomic analysis identified 2746 differentially expressed genes, which were mainly enriched in pathways including signal transduction, immune defense, stress response, cytoskeleton organization, and protein binding. KEGG and GSEA enrichment revealed that the antifouling agent activated the MAPK stress signaling pathway, disturbed transcriptional regulation, and impaired intracellular homeostasis and cytoskeletal stability, thereby synergistically suppressing the expression of key byssal protein genes including mfp-1 and mfp-3 and ultimately blocking byssus synthesis and adhesion. This study clarifies the multi-pathway molecular mechanism underlying antifouling agent-induced attachment inhibition in M. edulis, and provides core molecular targets and theoretical support for developing efficient, specific antifouling activity, and potentially applicable marine antifouling technologies.

Animals↗

PubMed2026

Association between prenatal exposure to tetrachloroethylene and adverse birth outcomes: Systematic review and meta-analysis.

BACKGROUND: Tetrachloroethylene (PCE) is a ubiquitous chlorinated solvent with documented placental transfer. Despite widespread environmental and occupational exposure, no prior systematic review has synthesized evidence on prenatal PCE exposure and adverse birth outcomes. METHODS: We conducted a systematic review and meta-analysis of observational studies. PubMed, Web of Science, PsycINFO, EMBASE, and CINAHL were searched from inception to July 13, 2026. Eligible studies reported associations between prenatal PCE exposure (drinking water or inhalation) and adverse birth outcomes. Study quality was assessed using the Newcastle-Ottawa Scale (NOS) and Agency for Healthcare Research and Quality (AHRQ) criteria. Random-effects meta-analyses were performed using risk ratios (RRs) with 95% confidence intervals (CIs), with Knapp-Hartung adjustments and Paule-Mandel τ2 estimation. RESULTS: Twenty one studies (1987-2023) met inclusion criteria. Prenatal PCE exposure was associated with spontaneous abortion (8 studies; RR = 1.28, 95% CI 1.00-1.63; I2 = 64.2%). Analyses of stillbirth, central nervous system defects, oral clefts, neural tube defects, preterm birth, low birthweight, and small-for-gestational-age (SGA) yielded positive but statistically non-significant pooled estimates. The certainty of evidence ranged from very low to low across outcomes (GRADE). CONCLUSIONS: Prenatal PCE exposure may be associated with spontaneous abortion, particularly at higher exposure levels, and with SGA. Findings support ongoing regulatory efforts to limit PCE in occupational and environmental settings, particularly for pregnant individuals. Future prospective studies with biological monitoring and confounder-adjusted designs are needed.

Tetrachloroethylene↗

PubMed2026

Genomic and One Health insights into Vibrio parahaemolyticus from environmental, seafood and clinical sources.

Vibrio parahaemolyticus is a leading cause of seafood-borne gastroenteritis worldwide, with climate warming facilitating its spread to high-latitude areas. In this study, we analyzed 212 genomes of environmental and seafood-associated isolates collected from seven cities in Zhejiang Province, China (2019-2024), alongside 228 clinical genomes from public databases. The 212 isolates were assigned to 172 sequence types (STs), with ST490 being the most frequent (5/212, 2.36%). Forty-four serotypes were identified, dominated by OL3:KUT (12.68%). High ST and serotype diversity were observed across different sample types and sources, with median pairwise single nucleotide polymorphisms (SNPs) ranging from 57,431 to 58,378, indicating comparable genetic diversity across groups. All isolates carried tlh and T3SS1 but lacked tdh and T3SS2. Resistance rates against ampicillin and cefazolin were 54.72% (116/212) and 44.34% (94/212), respectively, with multidrug resistance (MDR) detected in nine isolates, predominantly from seafood (7/9). A total of 63 distinct antimicrobial resistance genes (ARGs) spanning seven classes were identified. Isolates from aquaculture farms and wet markets exhibited greater resistance category diversity and higher ARG carriage than those from coastal or riverine sites. In contrast, the 228 clinical isolates harbored only 25 ARGs across two classes, with a significantly lower proportion of isolates carrying multiple ARG classes (0.44% vs. 6.13%, P < 0.001). Human isolates formed tighter phylogenetic clusters, although a minority were closely related to environmental/foodborne strains. Overall, our findings demonstrate the genetic diversity and resistance potential of V. parahaemolyticus across environmental, seafood, and clinical sources, highlighting the importance of the One Health approach to comprehensive public health risk assessment.

Vibrio parahaemolyticus↗

PubMed2026

Comprehensive source-risk assessment of organophosphate esters in surface water of the Dianchi Lake Basin, Yunnan, China.

Organophosphate esters (OPEs), widely used as flame retardants and plasticizers, have been increasingly detected in aquatic environments. However, investigations of their distribution in high-altitude plateau lakes remain scarce. Identifying and quantifying the sources and associated risks of OPEs are crucial for subsequent water environment management. In this study, an integrated source-risk analysis approach was employed by combining the Positive Matrix Factorization (PMF) model, the Geodetector (GD) model, and risk quotient (RQ). Analysis of 14 OPEs in surface waters of the Dianchi Lake Basin (DLB) revealed 12 detectable compounds, with total OPEs concentrations (ΣOPEs) ranging from not detected (ND)-64.6 ng/L during the wet season and ND-35.8 ng/L during the dry season. Elevated ΣOPEs were primarily observed at inflow sites in the northern part of the lake and in urban rivers. Source apportionment indicated four major contributing sources: agricultural films containing flame-retardant and plasticizer additives, traffic-related particulate emissions, releases from household and personal care products, and industrial production and applications of flame retardants in plastics, electronics, and related products (the predominant source). The ecological impact caused by OPEs ranges from no risk to low risk, with tris(2-chloroethyl) phosphate emitted from industrial source being the primary driver of potential environmental risk. These findings highlight the necessity of prioritizing industrial sources in future management strategies. Overall, this study provides a methodological framework for source apportionment and risk assessment of OPEs and offers scientific evidence to support environmental management of OPEs in the DLB.

Environmental Monitoring↗

PubMed2026

The spatial and temporal distribution of Staphylococcus aureus along a tropical Hawaiian watershed.

Staphylococcus aureus is a leading cause of community-acquired skin and soft-tissue infections worldwide. One major route of exposure is recreating in marine waters, but knowledge is limited regarding the drivers of S. aureus in surface waters that discharge into marine environments. This study explores spatial and temporal distributions of S. aureus, including antimicrobial-resistant and virulence genes, using both culture-dependent and molecular techniques across a tropical Hawaiian watershed with a gradient of human influence. Negative binomial generalized linear mixed models revealed that the interaction between spatial and temporal factors was the strongest predictor of S. aureus and associated genes. Cultured S. aureus was highest at mid-watershed sites in summer, which included a popular swimming hole, suggesting human shedding as a significant source. Molecular detection of S. aureus (femA gene) yielded concentrations two orders of magnitude higher than cultured concentrations and peaked at estuarine sites with the greatest nutrients and water residence times. In the winter at upstream sites with no public access, staphylococci antibiotic-resistant (mecA) and S. aureus virulence gene (etb) were elevated, indicating highly pathogenic S. aureus strains in surface waters may originate from zoonotic sources. Our findings indicate that human and zoonotic sources contribute antibiotic-resistant and virulent S. aureus to watersheds, with streams facilitating environmental transmission to marine waters. This watershed-scale assessment enables the prediction of spatial and temporal conditions associated with elevated S. aureus concentrations, thereby reducing exposure and infections.

Staphylococcus aureus↗

PubMed2026

Oxidative potential of fresh vs. O₃-aged PM2.5 across urban and rural sources in China.

Fine particulate matter (PM2.5) is a major health risk, yet its impacts are still largely assessed using mass concentration, which does not capture toxicity. Recently, oxidative potential (OP) has emerged as a more relevant metric, reflecting the ability of particles to generate reactive oxygen species. A current challenge, especially in China, is understanding how emission sources and ozone (O3) aging affect PM2.5 toxicity, given that O3 is an increasingly important pollutant there. A work by Ma and co-workers published in J. Environ. Sci. (doi.org/10.1016/j.jes.2024.04.023) addressed this by evaluating the OP of fresh and O3-aged PM2.5 from multiple sources in China using the dithiothreitol (DTT) assay. Biomass burning particles exhibited the highest OP, up to 35 times greater than suburban PM2.5, driven by water-soluble organics and transition metals. While O3 aging generally reduced OP, it also induced complex chemical transformations. These findings highlight that PM2.5 toxicity is dynamic and source-dependent, underscoring the need to move beyond mass-based air quality metrics.

Particulate Matter↗

PubMed2026

Longitudinal Relations among Perceived Economic Stress, Teacher-Student Relationships, and Cybervictimization: Exploring Within-Person Links.

Family economic hardship has been identified as a risk factor for adolescents' cybervictimization. Nevertheless, existing studies have primarily focused on objective economic conditions, and little is known about the within-person association between perceived economic stress and adolescents' cybervictimization and the mediating mechanisms underlying this association. To fill these gaps, the random intercept cross-lagged model was employed to examine the dynamic relations among perceived economic stress, teacher-student relationships, and cybervictimization. The data were obtained from a sample of 2407 Chinese adolescents (Mage = 12.75, SD = 0.58, 50.23% girls at baseline) recruited from seven schools and assessed at three time points over one year. At the between-person level, there were no significant associations among perceived economic stress, teacher-student relationships, and cybervictimization. At the within-person level, perceived economic stress positively predicted later cybervictimization over time, and this effect was unidirectional. The bidirectional relations between perceived economic stress and teacher-student relationships remained stable over time. Cybervictimization significantly and negatively predicted subsequent teacher-student relationships across time, indicating a unidirectional predictive effect. Additionally, perceived economic stress indirectly predicted cybervictimization through teacher-student relationships. The findings highlight the importance of distinguishing within-person from between-person processes and shed light on the longitudinal role of teacher-student relationships in the association between perceived economic stress and cybervictimization.

Humans↗

PubMed2026

Watershed-scale risk assessment of cadmium contamination in Chinese cropland soils: Dual pathways of irrigation input and flood-driven transport.

Irrigation and flood events serve as critical pathways for the transport of cadmium (Cd) from industrial sources into cropland soils at the watershed scale, constituting a major driver of widespread Cd contamination in China's cropland soil. This study evaluated the risk of Cd contamination in cropland soils across China's nine major river basins at the watershed scale, focusing on the contributions of irrigation and flood events, and conducted a sensitivity analysis of key risk factors. The assessment was conducted within a framework that considered factors including hazard, exposure, and vulnerability. The results revealed that numerous watersheds in southeastern China are exposed to dual pressures of Cd contamination risks in cropland soils, driven by both irrigation practices and flood events. Watersheds categorized as High-High, High-Moderate, or Moderate-High risk, reflecting combined Cd contamination risks from irrigation and flood, are vital to China's grain production, contributing 67.1 % of the national cropland area and 66.4 % of the grain yield. The study suggests localized strategies for managing cropland soils Cd contamination risks from irrigation and flood at the watershed scale in China, alongside strengthened cross-regional collaboration in southeastern China.

Cadmium↗

PubMed2026

The global potential of freshwater microbes for plastic degradation.

Plastic pollution is becoming increasingly severe on a global scale, and the potential for biodegradation as a treatment method that is environmentally friendly merits greater attention. A significant number of genes that associated the degradation of plastic (PDAGs) have been identified, however, the distribution of these genes among microorganisms in global inland waters remains to be elucidated. A global-scale meta-analysis was conducted, incorporating approximately 1000 metagenome datasets of inland waters across seven continents. A total of 13,109 metagenome-assembled genomes (MAGs) were obtained by means of metagenomics binning, and 22,621 PDAGs were identified from these. Among these recognized PDAGs, phenylacetaldehyde dehydrogenase (PAD) was the most dominant (n = 16,664), followed by catalase (n = 5931). The predominant hosts for PAD and catalase were identified as Gamma-proteobacteria and Bacteroidia, respectively. The largest number of both PAD and catalase was found in MAGs from North America, while the average gene number in single MAG was highest in MAGs from Oceania. In accordance with the prediction of traits, PDAG-carrying MAGs from Europe demonstrated the fastest growth rate and the lowest optimal growth rate. Furthermore, 25 styrene monooxygenase (StyA) enzymes were identified, which were found to cluster into two distinct groups hosted by Alpha-proteobacteria and Gamma-proteobacteria, respectively. Moreover, 11 MAGs were observed to possess the complete pathway of polystyrene degradation. These results explored the potential of inland water microorganisms as a biological resource for plastic degradation and provided valuable microbial reference information that can be used to develop biological treatment technologies for mitigating plastics.

Plastics↗

PubMed2026

Testing How Mindfulness Skills Change for Novice Meditators Using Headspace: Examining Trait Mindfulness and Perceived Stress as Moderators.

Mindfulness-based interventions are found to effectively reduce stress and improve mental health outcomes. Yet, it is not always clear how the mindfulness skills of attention and acceptance develop throughout the intervention. This knowledge gap is especially pertinent for novice meditators learning these skills for the first time, including whether some individuals are more prone to learning them. Using a randomized waitlist-controlled trial, we tested the effect of the app Headspace on changes in attention and acceptance over 8 weeks among participants new to mindfulness meditation. Further, we tested the moderating effects of trait mindfulness and perceived stress. Non-faculty university employees were randomized to a Headspace or waitlist control condition. Trait mindfulness and perceived stress were measured at baseline. Ecological momentary assessment survey data for attention and acceptance were collected five times a day in 4-day bursts at baseline and 2, 5, and 8 weeks post-randomisation. Attention and acceptance were significantly higher at Week 8 compared to baseline for the Headspace group, but not the control group. For the Headspace group, both skills showed significant change by Week 2. Trait mindfulness moderated this effect with those who were lower in trait mindfulness displaying greater increases in attention, but not acceptance. Perceived stress also moderated this effect with those who were lower in perceived stress displaying greater increases in attention and acceptance. Our discussion draws attention to implications for matching intervention content to individual needs to ensure participants reporting different levels of characteristics benefit from mindfulness training.

Humans↗

PubMed2026

Mapping Wastewater Pathogens and Their Associated Environmental and Public Health Risk Factors: A Systematic Review and Meta-Analysis.

BACKGROUND: Wastewater-based epidemiology (WBE) has emerged as a critical tool for public health surveillance, yet its application across diverse pathogens and geographical settings remains inconsistent. This systematic review synthesizes global evidence on wastewater surveillance to identify associated risk factors. METHODS: Following PRISMA 2020 guidelines (PROSPERO: CRD420261297382), a systematic search was conducted across PubMed, Scopus, Google Scholar, and Web of Science for studies published between 2000 and 2025. RESULTS: Thirty-nine peer-reviewed studies were included. The evidence base is geographically skewed toward the European Region (48.7%) and the Americas (23.1%), with significant underrepresentation in LMICs. Viruses were the primary biological target (89.7%), followed by bacteria (7.7%) and parasites (2.6%). A proportion meta-analysis of 31 eligible studies demonstrated a pooled wastewater pathogen detection prevalence of 62% (95% CI: 47.5-74.6%), with the European Region yielding the highest regional estimate (73%) and the African Region the lowest (8.3%). Conventional PCR and sequencing methods showed higher pooled detection rates (92.4% and 90.1%, respectively) than RT-qPCR (47.9%). CONCLUSION: WBE provides a robust early-warning system indicating a need for broader pathogen diversity, incorporating bacterial and parasitic surveillance and expansion into rural and resource-limited regions.

Contamination↗

PubMed2026

Genome-wide identification and functional validation of asparagine synthetase genes (NtASNs) in Nicotiana tabacum.

Asparagine (Asn) is pivotal for plant nitrogen (N) metabolism and plays indispensable roles in plant growth, development, and stress tolerance. However, the systematic characteristics and core functions of asparagine synthetase genes (NtASNs) in tobacco remain unclear. Through a comprehensive genome-wide investigation, nine members of the NtASN gene family were identified. Subsequent CRISPR/Cas9-mediated knockout and overexpression assays of these NtASN genes revealed that NtASN1e, NtASN2a, and NtASN2b are the core genes responsible for Asn biosynthesis in tobacco. Their knockout reduced asparagine synthetase activity and Asn content, delayed seed germination by 2-3 days, and displayed elevated oxidative injury when exposed to salinity conditions. In contrast, overexpression of these genes elevated Asn accumulation. Subcellular localization analysis indicated that NtASN1e was localized to both the cytoplasm and chloroplasts, whereas NtASN2a exhibited dual localization in the cytoplasm and endoplasmic reticulum, and NtASN2b was mainly localized in the cytoplasm. This study systematically clarifies the evolutionary characteristics and core functions of the NtASN gene family and provides candidate genes for optimizing nitrogen metabolism and improving salt-stress adaptation in tobacco. These findings hold important practical significance for molecular breeding and product quality improvement in industrial crops.

Nicotiana↗

PubMed2026

Systematic review of machine learning approaches for predicting sickle cell crisis and mortality risk at the climate-health nexus.

BACKGROUND: Sickle cell anemia (SCA) is a severe genetic blood disorder characterized by recurrent vaso-occlusive crises and increased mortality, with the greatest burden occurring in low- and middle-income countries. Climatic and environmental conditions, including temperature variability, humidity, rainfall, air pollution, and seasonal changes, have been associated with disease exacerbation. However, the extent to which these factors have been incorporated into predictive models remains unclear. This study systematically reviews the application of machine learning (ML) models for predicting SCA crises and mortality in relation to climate and environmental factors. METHODOLOGY: The PRISMA guidelines were used, and 34 peer-reviewed studies published between 2005 and 2026 were analyzed to identify the climate variables, ML approaches employed, and predictive performance. The reviewed studies applied a range of ML techniques, including artificial neural networks, random forests, support vector machines, decision trees, logistic regression, and deep learning models. Temperature, humidity, rainfall, wind speed, air quality indicators, and seasonal patterns were the most frequently examined environmental variables. RESULTS: The findings indicate that most existing models rely predominantly on clinical and demographic data, with limited integration of climate information and inadequate representation of high-burden regions, especially Sub-Saharan Africa. Studies incorporating environmental variables reported improved predictive performance and highlighted the potential of climate-informed early warning systems for SCA management. CONCLUSION: The review recommends development of interdisciplinary, climate-aware ML frameworks, expansion of longitudinal environmental datasets, and increased research in underrepresented regions to support climate-resilient and patient-centered SCA care.

Humans↗

PubMed2025

Application of causal discovery of factors driving dissolved oxygen in estuarine environments.

Dissolved oxygen (DO) concentrations in estuarine bottom waters are a manifestation of multiple, interacting physical and biogeochemical processes, yet identifying their independent contributions remains challenging. Here, we analyze monthly water quality monitoring data from eight stations across Long Island Sound from 1994 to 2022 using a causal discovery framework (PCMCI+) and transformation of forcing variables. Our goal is to identify and isolate variables that causally influence bottom DO and improve predictive models by minimizing overfitting and multicollinearity. PCMCI+ reveals surface-layer temperature as the most important and consistent negative driver of bottom DO, followed by stratification. Wind events exhibit only brief relief by advection and mixing, while river discharge shows no direct causal link to DO, making it less influential than previously thought. Biogeochemical variables, including chlorophyll-a (Chl-a), nitrate and nitrite, and particulate carbon, influence DO through both contemporaneous and time-lagged pathways, often with signs that shift depending on the process. The derived models were evaluated by comparing skill scores, mean squared error, and Akaike Information Criterion. Both model types perform well, with coefficient of determination values exceeding 0.90 at multiple stations using only 3-5 predictors. Our analysis reveals that the best causal predictors are surface-layer temperature, stratification, Chl-a, and particle carbon. This approach provides a scalable framework for improving prediction models and understanding the mechanistic links that control the seasonal variability of DO in estuarine systems.

Estuaries↗

PubMed2026

Spermidine and melatonin ameliorate heat stress-induced decline in sheep semen quality.

Heat stress impairs reproductive performance in sheep through endocrine disruption and oxidative stress. This study evaluated the protective effects of spermidine (SPD) and melatonin (MT) supplementation on semen quality in Dorper rams during summer. Twenty-four rams were randomly assigned to a control group, an SPD group (5 mg/kg, dietary supplementation), or an MT group (60 mg, subcutaneous implantation) and treated for 60 days. The temperature-humidity index (THI) was monitored throughout the experimental period. Compared with the control group, MT significantly reduced serum cortisol concentration on day 30 (P < 0.05), whereas no significant differences were observed at the other sampling time points. Serum testosterone, spermidine, and melatonin concentrations remained unchanged throughout the study (P > 0.05). SPD supplementation significantly increased ejaculate volume on day 35 and sperm motility on day 42 (P < 0.05), whereas MT did not significantly affect these parameters. Neither treatment reduced the overall sperm abnormality rate. However, both SPD and MT significantly decreased the proportion of acephalic and decaudated sperm on day 56 (P < 0.05). Neither treatment significantly affected pregnancy rate, delivery rate, or the expression of PMFBP1 and SUN5 proteins in semen (P > 0.05). Regarding oxidative stress, MT significantly downregulated CAT protein expression (P < 0.05), whereas SPD significantly reduced MDA content and SOD1 protein expression (P < 0.05); MT showed similar but non-significant trends for these two markers (P > 0.05). Collectively, these findings demonstrate that SPD and MT exert distinct protective effects against heat stress, with SPD improving selected semen quality traits and both treatments reducing sperm head-tail separation, although these benefits did not translate into improved reproductive performance.

Animals↗