Contamination Status and Risk Assessment of Paralytic Shellfish Toxins in Shellfish along the Coastal Areas of China.

Paralytic shellfish toxins (PSTs) are widely distributed in shellfish along the coast of China, causing a serious threat to consumer health; however, there is still a lack of large-scale systematic investigations and risk assessments. Herein, 641 shellfish samples were collected from March to November 2020, and the PSTs' toxicity was detected via liquid chromatography-tandem mass spectrometry. Furthermore, the contamination status and potential dietary risks of PSTs were discussed. PSTs were detected in 241 shellfish samples with a detection rate of 37.60%. The average PST toxicities in mussels and ark shells were considerably higher than those in other shellfish. The PSTs mainly included N-sulfonylcarbamoyl toxins (class C) and carbamoyl toxins (class GTX), and the highest PST toxicity was 546.09 µg STX eq. kg-1. The PST toxicity in spring was significantly higher than those in summer and autumn (p < 0.05). Hebei Province had the highest average PST toxicity in spring. An acute exposure assessment showed that consumers in Hebei Province had a higher dietary risk, with mussels posing a significantly higher dietary risk to consumers. This research provides reference for the green and sustainable development of the shellfish industry and the establishment of a shellfish toxin prevention and control system.

Transcriptional and translational landscape fine-tune genome annotation and explores translation control in cotton.

INTRODUCTION: The unavailability of intergenic region annotation in whole genome sequencing and pan-genomics hinders efforts to enhance crop improvement. OBJECTIVES: Despite advances in research, the impact of post-transcriptional regulation on fiber development and translatome profiling at different stages of fiber growth in cotton (G. hirsutum) remains unexplored. METHODS: We utilized a combination of reference-guided de novo transcriptome assembly and ribosome profiling techniques to uncover the hidden mechanisms of translational control in eight distinct tissues of upland cotton. RESULTS: Our study identified P-site distribution at three-nucleotide periodicity and dominant ribosome footprint at 27 nucleotides. Specifically, we have detected 1,589 small open reading frames (sORFs), including 1,376 upstream ORFs (uORFs) and 213 downstream ORFs (dORFs), as well as 552 long non-coding RNAs (lncRNAs) with potential coding functions, which fine-tune the annotation of the cotton genome. Further, we have identified novel genes and lncRNAs with strong translation efficiency (TE), while sORFs were found to affect mRNA transcription levels during fiber elongation. The reliability of these findings was confirmed by the high consistency in correlation and synergetic fold change between RNA-sequencing (RNA-seq) and Ribosome-sequencing (Ribo-seq) analyses. Additionally, integrated omics analysis of the normal fiber ZM24 and short fiber pag1 cotton mutant revealed several differentially expressed genes (DEGs), and fiber-specific expressed (high/low) genes associated with sORFs (uORFs and dORFs). These findings were further supported by the overexpression and knockdown of GhKCS6, a gene associated with sORFs in cotton, and demonstrated the potential regulation of the mechanism governing fiber elongation on both the transcriptional and post-transcriptional levels. CONCLUSION: Reference-guided transcriptome assembly and the identification of novel transcripts fine-tune the annotation of the cotton genome and predicted the landscape of fiber development. Our approach provided a high-throughput method, based on multi-omics, for discovering unannotated ORFs, hidden translational control, and complex regulatory mechanisms in crop plants.

Characterization and fine mapping of a yellow leaf gene regulating chlorophyll biosynthesis and chloroplast development in cotton (Gossypium arboreum).

Chlorophyll biosynthesis and chloroplast development are essential for photosynthesis and plant growth. Gossypium arboreum, a valuable source of genetic variation for cotton improvement, remains poorly studied for the mechanisms regulating chlorophyll biosynthesis and chloroplast development. Here we created a G. arboreum etiolated leaf and stuntedness (els) mutant that displayed a distinct yellow color of leaves, bracts and stems throughout the whole growth, where chlorophyll accumulation in leaves was reduced and chloroplast development was delayed. The GaCHLH gene, which encodes the H subunit of magnesium chelatase (Mg-chelatase), was screened by MutMap and KASP analysis. Compared to GaCHLH, the gene Gachlh of the mutant had a single nucleotide transition (G to A) at 1549 bp, which causes the substitution of a glycine (G) by a serine (S) at the 517th amino acid, resulting in an abnormal secondary structure of the Gachlh protein. GaCHLH-silenced SXY1 and ZM24 plants exhibited a lower GaCHLH expression level, a lower chlorophyll content, and the yellow-leaf phenotype. Gachlh expression affected the expression of key genes in the tetrapyrrole pathway. GaCHLH and Gachlh were located in the chloroplasts and that alteration of the mutation site did not affect the final target position. The BiFC assay result indicated that Gachlh could not bind to GaCHLD properly, which prevented the assembly of Mg-chelatase and thus led to the failure of chlorophyll synthesis. In this study, the Gachlh gene of G. arboreum els was finely localized and identified for the first time, providing new insights into the chlorophyll biosynthesis pathway in cotton.

Bioconversion of chitin into chitin oligosaccharides using a novel chitinase with high chitin-binding capacity.

Chitin is the second largest renewable biomass resource in nature, it can be enzymatically degraded into high-value chitin oligosaccharides (CHOSs) by chitinases. In this study, a chitinase (ChiC8-1) was purified and biochemically characterized, its structure was analyzed by molecular modeling. ChiC8-1 had a molecular mass of approximately 96 kDa, exhibited its optimal activity at pH 6.0 and 50 °C. The Km and Vmax values of ChiC8-1 towards colloidal chitin were 10.17 mgmL-1 and 13.32 U/mg, respectively. Notably, ChiC8-1 showed high chitin-binding capacity, which may be related to the two chitin binding domains in the N-terminal. Based on the unique properties of ChiC8-1, a modified affinity chromatography method, which combines protein purification with chitin hydrolysis process, was developed to purify ChiC8-1 while hydrolyzing chitin. In this way, 9.36 ± 0.18 g CHOSs powder was directly obtained by hydrolyzing 10 g colloidal chitin with crude enzyme solution. The CHOSs were composed of 14.77-2.83 % GlcNAc and 85.23-97.17 % (GlcNAc)2 at different enzyme-substrate ratio. This process simplifies the tedious purification and separation steps, and may enable its potential application in the field of green production of chitin oligosaccharides.

High-quality genome assembly of Verticillium dahliae VD991 allows for screening and validation of pathogenic genes.

Verticillium dahliae (V. dahliae) is a notorious soil-borne pathogen causing Verticillium wilt in more than 400 dicotyledonous plants, including a wide range of economically important crops, such as cotton, tomato, lettuce, potato, and romaine lettuce, which can result in extensive economic losses. In the last decade, several studies have been conducted on the physiological and molecular mechanisms of plant resistance to V. dahliae. However, the lack of a complete genome sequence with a high-quality assembly and complete genomic annotations for V. dahliae has limited these studies. In this study, we produced a full genomic assembly for V. dahliae VD991 using Nanopore sequencing technology, consisting of 35.77 Mb across eight pseudochromosomes and with a GC content of 53.41%. Analysis of the genome completeness assessment (BUSCO alignment: 98.62%; Illumina reads alignment: 99.17%) indicated that our efforts resulted in a nearly complete and high-quality genomic assembly. We selected 25 species closely related to V. dahliae for evolutionary analysis, confirming the evolutionary relationship between V. dahliae and related species, and the identification of a possible whole genome duplication event in V. dahliae. The interaction between cotton and V. dahliae was investigated by transcriptome sequencing resulting in the identification of many genes and pathways associated with cotton disease resistance and V. dahliae pathogenesis. These results will provide new insights into the pathogenic mechanisms of V. dahliae and contribute to the cultivation of cotton varieties resistant to Verticillium wilt.

De novo biosynthesis of 2'-fucosyllactose in engineered Pichia pastoris.

PURPOSE: Pichia pastoris is well known for its ability to produce short and low-immunogenic humanized glycosyl chains onto recombinant glycoproteins, it was thus speculated to be applicable to synthesize oligosaccharides. In this study, generally recognized as safe (GRAS) microorganism Pichia pastoris GS115 was tested for its potential to be used as a new synthetic chassis to produce the most abundant human milk oligosaccharide 2'-fucosyllactose (2'-FL). METHODS: To enable the de novo synthesis of 2'-FL, lactose transporter lac12, two enzymes of gmd, gmer, and fucosyltransferases futC were integrated into the genome of P. pastoris, under the control of constitutive PGAP promoter. RESULTS: The resulting recombinant yeasts yielded up to 0.276 g/L through culture optimization in a 5 L bioreactor. CONCLUSION: To our knowledge, this is the first report of 2'-FL production in engineered Pichia pastoris. This work is a good starting point to produce 2'-FL using Pichia pastoris as a viable chassis.

The Capparis spinosa var. herbacea genome provides the first genomic instrument for a diversity and evolution study of the Capparaceae family.

BACKGROUND: The caper bush Capparis spinosa L., one of the most economically important species of Capparaceae, is a xerophytic shrub that is well adapted to drought and harsh environments. However, genetic studies on this species are limited because of the lack of its reference genome. FINDINGS: We sequenced and assembled the Capparis spinosa var. herbacea (Willd.) genome using data obtained from the combination of PacBio circular consensus sequencing and high-throughput chromosome conformation capture. The final genome assembly was approximately 274.53 Mb (contig N50 length of 9.36 Mb, scaffold N50 of 15.15 Mb), 99.23% of which was assigned to 21 chromosomes. In the whole-genome sequence, tandem repeats accounted for 19.28%, and transposable element sequences accounted for 43.98%. The proportion of tandem repeats in the C. spinosa var. herbacea genome was much higher than the average of 8.55% in plant genomes. A total of 21,577 protein-coding genes were predicted, with 98.82% being functionally annotated. The result of species divergence times showed that C. spinosa var. herbacea and Tarenaya hassleriana separated from a common ancestor 43.31 million years ago. CONCLUSIONS: This study reported a high-quality reference genome assembly and genome features for the Capparaceae family. The assembled C. spinosa var. herbacea genome might provide a system for studying the diversity, speciation, and evolution of this family and serve as an important resource for understanding the mechanism of drought and high-temperature resistance.

Functional divergence of GLP genes between G. barbadense and G. hirsutum in response to Verticillium dahliae infection.

Germin-like proteins (GLPs) play important roles in plant disease resistance but are rarely reported in cotton. We compared the expression of GLPs in Verticillium dahliae inoculate G. hirsutum (susceptible) and G. barbadense (resistant) and enriched 11 differentially expressed GLPs. 2741 GLP proteins identified from 53 species determined that GLP probably originated from algae and could be classified into 7 clades according to phylogenetic analysis, among which Clade I is likely the most ancient. Cotton GLP (two allopolyploids and two diploids) genes within a shared clade were highly conserved. Intriguingly, clade VII genes were mainly located in gene clusters that derived from the expansion of LTR transposons. Clade VII members expressed mainly in root which is the first battle against Verticillium dahlia and could be induced more intensely in G. barbadense than G. hirsutum. The GLP genes are resistant to Verticillium dahliae, which can be further investigated against Verticillium wilt.

GRAND: An Integrated Genome, Transcriptome Resources, and Gene Network Database for Gossypium.

With the increasing amount of cotton omics data, breeding scientists are confronted with the question of how to use massive cotton data to mine effective breeding information. Here, we construct a Gossypium Resource And Network Database (GRAND), which integrates 18 cotton genome sequences, genome annotations, two cotton genome variations information, and also four transcriptomes for Gossypium species. GRAND allows to explore and mine this data with the help of a toolbox that comprises a flexible search system, BLAST and BLAT suite, orthologous gene ID, networks of co-expressed genes, primer design, Gbrowse and Jbrowse, and drawing instruments. GRAND provides important information regarding Gossypium resources and hopefully can accelerate the progress of cultivating cotton varieties.

Genome sequence and transcriptome of Sorbus pohuashanensis provide insights into population evolution and leaf sunburn response.

Sorbus pohuashanensis (Hance) Hedl. is a potential horticulture and medicinal plant, but its genomic and genetic backgrounds remain unknown. Here, we sequence and assemble the S. pohuashanensis reference genome using PacBio long reads. Based on the new reference genome, we resequence a core collection of 22 Sorbus spp. samples, which are divided into 2 groups (G1 and G2) based on phylogenetic and PCA analyses. These phylogenetic clusters are highly consistent with their classification based on leaf shape. Natural hybridization between the G1 and G2 groups is evidenced by a sample (R21) with a highly heterozygous genotype. Nucleotide diversity (π) analysis shows that G1 has a higher diversity than G2 and that G2 originated from G1. During the evolution process, the gene families involved in photosynthesis pathways expanded and the gene families involved in energy consumption contracted. RNA-seq data suggests that flavonoid biosynthesis and heat-shock protein (HSP)-heat-shock factor (HSF) pathways play important roles in protection against sunburn. This study provides new insights into the evolution of Sorbus spp. genomes. In addition, the genomic resources, and the identified genetic variations, especially those related to stress resistance, will help future efforts to produce and breed Sorbus spp.

The involvement of oxidative stress, neuronal lesions, neurotransmission impairment, and neuroinflammation in acrylamide-induced neurotoxicity in C57/BL6 mice.

Acrylamide (ACR) is a typical environmental contaminant, presenting potential health hazards that have been attracting increasing attention. Its neurotoxicity is known to cause significant damage to health. However, the mechanisms of ACR-induced neurotoxicity require further clarification. This study uses a mouse model to explore how ACR-induced oxidative stress, neuronal lesions, neurotransmission impairment, and neuroinflammation mutually contribute to neurotoxicity. A distinct increase in the cellular reactive oxygen species (ROS) levels, malondialdehyde (MDA), and 8-hydroxy-2-deoxyguanosine (8-OHdG) content and a significant decrease in the glutathione (GSH) content after ACR exposure were indicative of oxidative stress. Moreover, ACR caused neurological defects associated with gait abnormality and neuronal loss while suppressing the acetylcholine (ACh) and dopamine (DA) levels and increasing the protein expression of α-synuclein (α-syn), further inhibiting cholinergic and dopaminergic neuronal function. Additionally, ACR treatment caused an inflammatory response via nuclear factor-kappa B (NF-κB) activation and increased the protein expression of NOD-like receptor protein-3 (NLRP3), consequently activating the NLRP3 inflammasome constituents, including cysteinyl aspartate specific proteinase 1 (Caspase-1), apoptosis-associated speck-like protein containing CARD (ASC), N domain gasdermin D (N-GSDMD), interleukin-1ß (IL-1ß), and IL-18. The results revealed the underlying molecular mechanism of ACR-induced neurotoxicity via oxidative stress, neurotransmission impairment, and neuroinflammation-related signal cascade. This information will further improve the development of an alternative pathway strategy for investigating the risk posed by ACR. The hypothetical mechanism of ACR-induced neurotoxicity in vivo.

Suppression of GOLM1 by EGCG through HGF/HGFR/AKT/GSK-3ß/ß-catenin/c-Myc signaling pathway inhibits cell migration of MDA-MB-231.

Golgi Membrane Protein 1 (GOLM1) has been identified as a prime target for cancer therapy because it overexpresses in many solid tumors, increases tumor growth and metastasis and leads to unfavorable survival. Though various approaches including siRNA interference and antibody targeting have been attempted, GOLM1 has remained an un-targetable molecule because of its mainly intracellular location and the lack of domains that could possibly be interfered with by small molecules. Numerous natural anti-tumoral plant substances have been identified, while their possible function on GOLM1 has never been revealed. This is the first report to study the relationship between GOLM1 downregulation and natural anti-tumoral plant substances and the possible mechanism. Among three tested possible migration-inhibiting natural substances (Epigallocatechin gallate (EGCG), Betulinic acid (BA) and Lupeol), EGCG showed the most potent inhibition effect on GOLM1 expression and MDA-MB-231 cell migration. Knocking down GOLM1 expression further increased the EGCG treatment effect. Molecular docking prediction and following experiments suggested that EGCG may inhibit GOLM1 expression and MDA-MB-231 cells migration through HGF/HGFR/AKT/GSK-3/ß-catenin/c-Myc signaling pathway. In all, EGCG is the first identified GOLM1 downregulation natural product. Silencing GOLM1 may be a novel mechanism of potentiated anti-cancer migration effects and cytotoxic effect of EGCG. In addition, this study shed a new way for cancer therapy by combination of GOLM1 silencing and EGCG treatment in the future.

Co-expression network and comparative transcriptome analysis for fiber initiation and elongation reveal genetic differences in two lines from upland cotton CCRI70 RIL population.

Upland cotton is the most widely planted for natural fiber around the world, and either lint percentage (LP) or fiber length (FL) is the crucial component tremendously affecting cotton yield and fiber quality, respectively. In this study, two lines MBZ70-053 and MBZ70-236 derived from G. hirsutum CCRI70 recombinant inbred line (RIL) population presenting different phenotypes in LP and FL traits were chosen to conduct RNA sequencing on ovule and fiber samples, aiming at exploring the differences of molecular and genetic mechanisms during cotton fiber initiation and elongation stages. As a result, 249/128, 369/206, 4296/1198 and 3547/2129 up-/down- regulated differentially expressed genes (DGEs) in L2 were obtained at -3, 0, 5 and 10 days post-anthesis (DPA), respectively. Seven gene expression profiles were discriminated using Short Time-series Expression Miner (STEM) analysis; seven modules and hub genes were identified using weighted gene co-expression network analysis. The DEGs were mainly enriched into energetic metabolism and accumulating as well as auxin signaling pathway in initiation and elongation stages, respectively. Meanwhile, 29 hub genes were identified as 14-3-3ω , TBL35, GhACS, PME3, GAMMA-TIP, PUM-7, etc., where the DEGs and hub genes revealed the genetic and molecular mechanisms and differences during cotton fiber development.

A Novel GH Family 20 ß-N-acetylhexosaminidase With Both Chitosanase and Chitinase Activity From Aspergillus oryzae.

Aminooligosaccharides possess various biological activities and can exploit wide applications in food, pharmaceutical and cosmetic industries. Commercial aminooligosaccharides are often prepared by the hydrolysis of chitin and chitosan. In this study, a novel GH family 20 ß-N-acetylhexosaminidases gene named AoNagase was cloned from Aspergillus oryzae and expressed in Pichia pastoris. The purified AoNagase had maximal activity at pH 5.5 and 65°C. It exhibited good pH stability in the range of pH 6.0-7.5 and at temperatures below 50°C. AoNagase was capable of hydrolyzing not only colloidal chitosan (508.26 U/mg) but also chitin (29.78 U/mg). The kinetic parameters (K m and V max ) of AoNagase were 1.51 mM, 1106.02 U/mg for chitosan and 0.41 mM, 40.31 U/mg for colloidal chitin. To our knowledge, AoNagase is the first GH family 20 ß-N-acetylhexosaminidase capable of hydrolyzing both chitosan and chitin. AoNagase is an endo-type ß-N-acetylhexosaminidases and can potentially be used for the manufacturing of aminooligosaccharides.

Ultrasound-microbubble cavitation facilitates adeno-associated virus mediated cochlear gene transfection across the round-window membrane.

The round window of the cochlea provides an ideal route for delivering medicines and gene therapy reagents that can cross the round window membrane (RWM) into the inner ear. Recombinant adeno-associated viruses (rAAVs) have several advantages and are recommended as viral vectors for gene transfection. However, rAAVs cannot cross an intact RWM. Consequently, ultrasound-mediated microbubble (USMB) cavitation is potentially useful, because it can sonoporate the cell membranes, and increase their permeability to large molecules. The use of USMB cavitation for drug delivery across the RWM has been tested in a few animal studies but has not been used in the context of AAV-mediated gene transfection. The currently available large size of the ultrasound probe appears to be a limiting factor in the application of this method to the RWM. In this study, we used home-made ultrasound probe with a decreased diameter to 1.5 mm, which enabled the easy positioning of the probe close to the RWM. In guinea pigs, we used this probe to determine that (1) USMB cavitation caused limited damage to the outer surface layer or the RWM, (2) an eGFP-gene carrying rAAV could effectively pass the USMB-treated RWM and reliably transfect cochlear cells, and (3) the hearing function of the cochlea remained unchanged. Our results suggest that USMB cavitation of the RWM is a good method for rAAV-mediated cochlear gene transfection with clear potential for clinical translation. We additionally discuss several advantages of the small probe size.

Chitopentaose inhibits hepatocellular carcinoma by inducing mitochondrial mediated apoptosis and suppressing protective autophagy.

Hepatocellular carcinoma (HCC) is one of the most prevalent and deadliest cancers. In this study, the anti-tumor effect of singular degree of polymerization (DP) chitooligosaccharides (COS) (DP 2-5) and the underlay molecular mechanisms were investigated on HCC cell line HepG2. MTT assay showed that (GlcN)5 have the best anti-proliferation effect among the different DP of COS (DP2-5). Furthermore, the administration of (GlcN)5 could decrease mitochondrial membrane potential, release cytochrome c into cytoplasm, activate the cleavage of Caspases9/3, thus inducing mitochondrial-mediated apoptosis in HepG2 cells (accounting for 24.57 ± 2.25%). In addition, (GlcN)5 treatment could increase the accumulation of autophagosomes. Further investigation showed that (GlcN)5 suppressed protective autophagy at the fusion of autophagosomes and lysosomes. Moreover, the inhibition of protective autophagy flux by (GlcN)5 could further decrease cell viability and increase the apoptosis rate. Our findings suggested that (GlcN)5 suppressed HepG2 proliferation through inducing apoptosis via the intrinsic pathway and impairing cell-protective autophagy. COS might have the potential to be an agent for lowering the risk of HCC.

Structure-function analysis of Gynuella sunshinyii chitosanase uncovers the mechanism of substrate binding in GH family 46 members.

Chitooligosaccharides (COS) is a kind of functional carbohydrates with great application potential as its various biological functions in food, cosmetics, and pharmaceutical fields. Exploring the relationship between structure and function of chitosanase is essential for the controllable preparation of chitooligosaccharides with the specific degree of polymerization (DP). GsCsn46A is a cold-adapted glycosyl hydrolase (GH) family 46 chitosanase with application potential for the controllable preparation of chitooligosaccharides. Here, we present two complex structures with substrate chitopentaose and chitotetraose of GsCsn46A, respectively. The overall structure of GsCsn46A contains nine α-helices and two ß-strands that folds into two globular domains with the substrate between them. The unique binding positions of both chitopentaose and chitotetraose revealed two novel sugar residues in the negatively-numbered subsites of GH family 46 chitosanases. The structure-function analysis of GsCsn46A uncovers the substrate binding and catalysis mechanism of GH family 46 chitosanases. Structural basis mutagenesis in GsCsn46A indicated that altering interactions near +3 subsite would help produce hydrolysis products with higher DP. Specifically, the mutant N21W of GsCsn46A nearly eliminated the ability of hydrolyzing chitotetraose after long-time degradation.

Pre-exposure to Lower-Level Noise Mitigates Cochlear Synaptic Loss Induced by High-Level Noise.

The auditory sensory organs appear to be less damaged by exposure to high-level noise that is presented after exposure to non-traumatizing low-level noise. This phenomenon is known as the toughening or conditioning effect. Functionally, it is manifested by a reduced threshold shift, and morphologically by a reduced hair cell loss. However, it remains unclear whether prior exposure to toughening noise can mitigate the synaptic loss induced by exposure to damaging noise. Since the cochlear afferent synapse between the inner hair cells and primary auditory neurons has been identified as a novel site involved in noise-induced cochlear damage, we were interested in assessing whether this synapse can be toughened. In the present study, the synaptic loss was induced by a damaging noise exposure (106 dB SPL) and compared across Guinea pigs who had and had not been previously exposed to a toughening noise (85 dB SPL). Results revealed that the toughening noise heavily reduced the synaptic loss observed 1 day after exposure to the damaging noise. Although it was significant, the protective effect of the toughening noise on permanent synaptic loss was much smaller. Compared with cases in the control group without noise exposure, coding deficits were seen in both toughened groups, as reflected in the compound action potential (CAP) by signals with amplitude modulation. In general, the pre-exposure to the toughening noise resulted in a significantly reduced synaptic loss by the high-level noise. However, this morphological protection was not accompanied by a robust functional benefit.

Temporary Versus Permanent Synaptic Loss from Repeated Noise Exposure in Guinea Pigs and C57 Mice.

A single brief noise exposure can cause a significant loss of cochlear afferent synapses without causing permanent threshold shift. Previously we reported that the initial synaptic loss is partially reversible in Guinea pigs, indicating that synaptic loss can be categorized as either temporary or permanent. Since synaptic loss is biased to innervating auditory nerve fibers (ANFs) with low spontaneous spike rates (SSR), which are critical to the coding of in-background noise, coding-in-noise deficits (CIND) have been predicted to result from noise-induced synaptic damage. However, recent study of the noise masking of amplitude-modulation (AM) evoked compound action potentials (CAP) tailed to find evidence for such deficits in either mice or Guinea pigs. The present study sought to determine the effects of repeated noise exposure on temporary and permanent synaptic loss in Guinea pigs and C57 mice, whether such effects were additive, and whether repeated noise exposure induced CIND in Guinea pigs. The results show that the second noise exposure caused much less temporary synaptic loss and no additional permanent loss in Guinea pigs; however, an additional permanent loss was seen after the second noise was in the mice, although it was not significant. In Guinea pigs, the observed increased masking of the AM CAP provides evidence for CIND after repeated noise exposure.