Integrating metagenomic and isolation strategies revealed high contamination of pathogenies and resistome in market shrimps

This study employs a comprehensive approach combining metagenomic analysis and bacterial isolation to elucidate the microbial composition, antibiotic resistance genes (ARGs), and virulence factors (VFGs) present in shrimps from market and supermarket. Metagenomic analysis of shrimps revealed a dominance of Proteobacteria and Bacteroidetes with Firmicutes notably enriched in some samples. On the other hand, the dominant bacteria isolated included Citrobacter portucalensis, Escherichia coli, Salmonella enterica, Vibrio species and Klebsiella pneumonaie. Metagenomic analysis unveiled a diverse spectrum of 23 main types and 380 subtypes of ARGs in shrimp samples including many clinical significant ARGs such as blaKPC, blaNDM, mcr, tet(X4) etc. Genomic analysis of isolated bacterial strains identified 14 ARG types with 109 subtype genes, which complemented the metagenomic data. Genomic analysis also allowed us to identify a rich amount of MDR plasmids, which provided further insights into the dissemination of resistance genes in different species of bacteria in the same samples. Examination of VFGs and mobile genetic elements (MGEs) in both metagenomic and bacterial genomes revealed a complex landscape of factors contributing to bacterial virulence and genetic mobility. Potential co-occurrence patterns of ARGs and VFGs within human pathogenic bacteria underlined the intricate interplay between antibiotic resistance and virulence. In conclusion, this integrated analysis for the first time provides a comprehensive view and sheds new light on the potential hazards associated with shrimp products in the markets. The findings underscore the necessity of ongoing surveillance and intervention strategies to mitigate risks posed by antibiotic-resistant bacteria in the food supply chain using the novel comprehensive approaches.

Early detection of OXA-232-producing Klebsiella pneumoniae in China predating its global emergence

Antibiotic resistance is a global health issue, with Klebsiella pneumoniae (KP) posing a particular threat due to its ability to acquire resistance to multiple drug classes rapidly. OXA-232 is a carbapenemase that confers resistance to carbapenems, a class of antibiotics often used as a last resort for treating severe bacterial infections. The study reports the earliest known identification of six OXA-232-producing KP strains that were isolated in Zhejiang, China, in 2008 and 2009 within a hospital, two years prior to the first reported identification of OXA-232 in France. The four KP strains carry the OXA-232 gene and exhibit hypervirulent loci, suggesting a broader temporal and geographical spread and integration of this resistance and virulence than previously recognized with implications for public health. Global analysis of all OXA-232-bearing KP strains revealed that OXA-232-encoding plasmids are conservative, while the strains were very diverse suggesting the plasmid mediated transmission of this carbapenemase genes. Importantly, a large proportion of the OXA-232-bearing KP strains also carried virulence plasmids, in particular the recent emergence of ST15 type of KP that carried both OXA-232-encoding plasmids and hypervirulent (hv) plasmids in China since 2019, highlighting the importance of the emergence of this type of KP strains in clinical setting. The early detection and investigations of OXA-232 in these strains warrants the retrospective studies to uncover the true timeline of antibiotic resistance spread, which could provide valuable insights for shaping future strategies to tackle the global health crisis.

Molecular epidemiology and clinical impact of Klebsiella spp. causing bloodstream infections in Hong Kong

BACKGROUND

The epidemiological features of the Klebsiella pneumoniae causing bloodstream infections in Hong Kong and their potential threats to human health remained unknown.

METHODS

K. pneumoniae strains collected from four hospitals in Hong Kong during the period of 2009-2018 were subjected to molecular typing, string test, antimicrobial susceptibility testing, whole genome sequencing and analysis. Clinical data of patients from whom these strains were isolated were analyzed retrospectively using univariate and multivariate logistic regression approaches.

FINDINGS

The 240 Klebsiella spp. strains belonged to 123 different STs and 63 different capsule loci (KLs), with KL1 and KL2 being the major type. 86 out of 212 BSI-KP (40.6%) carried at least one of the virulence genes iuc, iro, rmpA or rmpA2. Virulence plasmid correlated well with the string test positive result, yet 8 strains without rmp genes were also hypermucoviscous, which was due to wzc mutation. The mortality rate of bloodstream infection patients was 43.0%. Univariant analysis showed that factors including renal replacement therapy (FDR adjusted p = 0.0007), mechanical ventilation (FDR adjusted p < 0.0001) and respiratory sepsis (FDR adjusted p < 0.0001) were found to pose the highest risk of death upon infection by Klebsiella spp.

INTERPRETATION

This study revealed the high mortality rate and risk factors associated with bloodstream infections caused by K. pneumoniae in Hong Kong, which warrants immediate action to develop effective solution to tackle this problem.

FUNDING

Theme Based Research Scheme (T11-104/22-R), Research Impact Fund (R5011-18 F) and Postdoctoral Fellowship (PDFS2223-1S09).

Discovery of a Monoclonal Antibody That Targets Cell-Surface Pseudaminic Acid of Acinetobacter baumannii with Direct Bactericidal Effect

The therapeutic effects of antibodies include neutralization of pathogens, activation of the host complement system, and facilitation of phagocytosis of pathogens. However, antibody alone has never been shown to exhibit bactericidal activity. In this study, we developed a monoclonal antibody that targets the bacterial cell surface component Pseudaminic acid (Pse). This monoclonal antibody, Pse-MAB1, exhibited direct bactericidal activity on Acinetobacter baumannii strains, even in the absence of the host complements or other immune factors, and was able to confer a protective effect against A. baumannii infections in mice. This study provides new insight into the potential of developing monoclonal antibody-based antimicrobial therapy of multidrug resistant bacterial infections, especially those which occurred among immunocompromised patients.

Global genomic profiling of Klebsiella pneumoniae: A spatio-temporal population structure analysis

Klebsiella pneumoniae is an important clinical bacterial pathogen that has hypervirulent and multidrug-resistant variants. Uniform Manifold Approximation and Projection (UMAP) was used to cluster genomes of 16 797 K. pneumoniae strains collected, based on core genome distance, in over 100 countries during the period 1937 to 2021. A total of 60 high-density genetic clusters of strains representing the major epidemic strains were identified among these strains. Using UMAP bedding, the relationship between genetic cluster, capsular polysaccharide (KL) types and sequence type (ST) of the strains was clearly demonstrated, with some important STs, such as ST11 and ST258, found to contain multiple clusters. Strains within the same cluster often exhibited significant diverse features, such as originating from different areas and being isolated in different years, as well as carriage of different resistance and virulence genes. These data enable the routes of evolution of the globally prevalent K. pneumoniae strains to be traced. Alarmingly, carbapenem-resistant K. pneumoniae strains accounted for 51.7% of the test strains and worldwide transmission was observed. Carbapenem-resistant and hypervirulent K. pneumoniae strains are mainly reported in China; however, these strains are increasingly reported in other parts of the world. Also identified in this study were several key genetic loci that facilitate development of a new K. pneumoniae typing method to differentiate between high- and low-risk strains. In particular, the acrR, ompK35 and hha genes were predicted to play a key role in expression of the resistance and virulence phenotypes.

Prevalence and genetic basis of tetracycline resistance in Vibrioparahaemolyticus isolates recovered from food products in Shenzhen, China during 2013 to 2021

Understanding tetracycline resistance in Vibrio parahaemolyticus from food products is crucial for effective control measures against this foodborne pathogen. This study aimed to investigate the prevalence, evolution routes, and mechanism of transmission of tetracycline resistance in Vibrio parahaemolyticus isolates collected from food products in Shenzhen, China. A total of 2342 non-duplicate Vibrio parahaemolyticus were isolated from 3509 food samples during the period 2013-2021. Among these 2342 Vibrio parahaemolyticus strains, 530 (21.37 %) were resistant to tetracycline. These tetracycline-resistant Vibrio parahaemolyticus strains were mainly isolated from shrimp samples, with the highest resistance rate (46.9 %) observed in 2019. Phylogenetic and genomic analyses of 387 isolates carrying the tet genes revealed that five different types of tet genes (tet(34), tet(A), tet(B), tet(M), and tet(E)) were present. The tet(A) gene was the most common (65 % of isolates), while tet(E) and tet(M) genes were only detected in specific years. Although tet(A) is the most commonly detected gene, it only encodes resistance in a low percentage of strains (47/129). On the other hand, the resistance rate is highest in isolates carrying tet(B) (41/55). Interestingly, V. parahaemolyticus carrying the tet genes were not necessarily tetracycline-resistant, and vice versa. A total of six different types of plasmids and two transposable units were found to carry the tet genes. V. parahaemolyticus strains that harbored these plasmids were often resistant to multiple antibiotics, indicating that horizontal transfer of antibiotic resistance genes is common among V. parahaemolyticus strains. Our findings suggest a high prevalence of tetracycline resistance in Vibrio parahaemolyticus strains recovered from food products in Shenzhen, China. These results provide valuable insight into the evolution and transmission of tetracycline resistance in foodborne Vibrio parahaemolyticus isolates and highlight the need for effective control measures to prevent the spread of antibiotic resistance.

Prevalence and molecular characterization of cefotaxime-resistant Salmonella strains recovered from retail meat samples in Shenzhen, China, during 2014-2017

In this work, we collected foodborne Salmonella strains in Shenzhen, China, during 2014-2017 and investigated the genetic profile of all cefotaxime-resistant isolates in the collection. The strains were subjected to antimicrobial susceptibility tests, whole-genome sequencing, bioinformatics analysis, and conjugation studies. A total of 79 cefotaxime-resistant Salmonella were identified and found to exhibit multidrug resistance. Resistance rate recorded during the study period increased from 1.9% to 9.1%. Salmonella Typhimurium was the predominant serovar, and CTX-M family genes were dominant among the ESBLs genes detected. Notably, CTX-M-bearing plasmids or transposons often contain other drug resistance genes. Furthermore, a combination of CTX-M-55 and CTX-M-65 genes was detected for the first time in foodborne Salmonella strains. Our findings reveal the prevalence and molecular characteristics of cefotaxime-resistant foodborne Salmonella strains in southern China. IMPORTANCE Cefotaxime-resistant Salmonella strains pose an increasing threat to human health by causing infections with limited treatment options. It is therefore necessary to undertake a surveillance on the prevalence of such strains and investigate the resistance and transmission mechanisms. In this work, various ESBL genes flanked by different IS located in different mobile genetic elements were detectable among cefotaxime-resistant Salmonella strains. These data show that the high prevalence and genotypic diversity of cefotaxime-resistant foodborne Salmonella strains in China are possibly attributed to the evolution and transmission of a wide range of multidrug resistance-encoding mobile genetic elements.

Genetic and drug susceptibility profiles of mcr-1-bearing foodborne Salmonella strains collected in Shenzhen, China during the period 2014-2017

Colistin resistance mediated by mcr-1-bearing plasmids poses a new challenge to treatment of Salmonella infections. To probe the scale of the problem that colistin resistance mediated by mcr-1 plasmids among Salmonella, the prevalence of mcr-1 in foodborne Salmonella recovered from 2014 to 2017 in Shenzhen, China and genetic profile of mcr-1 positive isolates were investigated. All mcr-1 positives Salmonella strains were collected from food products, characterized by PCR and MALDI-TOF, and subjected to antimicrobial susceptibility testing, whole-genome sequencing, bioinformatics analysis, and conjugation. Twenty-eight mcr-1-positive Salmonella strains were recovered from pork. The rate of recovery displayed an increasing trend and was often accompanied by multidrug resistance. Salmonella Typhimurium was the most prevalent serotypes. Comparative genomic analysis indicated that the mcr-1 gene was located on the transferable IncX4 plasmids, as well as the IncHI2 plasmids, in which the gene was associated with ISApl1. All two types of plasmids were often detected in zoonotic pathogen. Transferable 251K mcr-1-bearing IncHI2 type plasmids were frequently reported in human and food-producing animals, but this is first time to detect a certain number in food. These findings show that dissemination of these two types of plasmids is responsible for the increase in the prevalence of colistin resistance in Salmonella strains in recent years, leading to rapid emergence of MDR Salmonella upon acquisition of these two mcr-1-bearing plasmids. Transmission of IncX4 and IncHI2 plasmids in Salmonella would cause huge public health concerns in controlling foodborne infections caused by Salmonella.

High-Resolution Metagenomics of Human Gut Microbiota Generated by Nanopore and Illumina Hybrid Metagenome Assembly

Metagenome assembly is a core yet methodologically challenging step for taxonomic classification and functional annotation of a microbiome. This study aims to generate the high-resolution human gut metagenome using both Illumina and Nanopore platforms. Assembly was achieved using four assemblers, including Flye (Nanopore), metaSPAdes (Illumina), hybridSPAdes (Illumina and Nanopore), and OPERA-MS (Illumina and Nanopore). Hybrid metagenome assembly was shown to generate contigs with almost same sizes comparable to those produced using Illumina reads alone, but was more contiguous, informative, and longer compared with those assembled with Illumina reads only. In addition, hybrid metagenome assembly enables us to obtain complete plasmid sequences and much more AMR gene-encoding contigs than the Illumina method. Most importantly, using our workflow, 58 novel high-quality metagenome bins were obtained from four assembly algorithms, particularly hybrid assembly (47/58), although metaSPAdes could provide 11 high-quality bins independently. Among them, 29 bins were currently uncultured bacterial metagenome-assembled genomes. These findings were highly consistent and supported by mock community data tested. In the analysis of biosynthetic gene clusters (BGCs), the number of BGCs in the contigs from hybridSPAdes (241) is higher than that of contigs from metaSPAdes (233). In conclusion, hybrid metagenome assembly could significantly enhance the efficiency of contig assembly, taxonomic binning, and genome construction compared with procedures using Illumina short-read data alone, indicating that nanopore long reads are highly useful in metagenomic applications. This technique could be used to create high-resolution references for future human metagenome studies.

From DNA structure to gene expression: mediators of nuclear compartmentalization and dynamics

Eukaryotic genomes are functionally compartmentalized into chromatin domains by their attachment to a supporting structure that has traditionally been termed the nuclear matrix. Present evidence indicates the dynamics of this entity, which requires particular properties of the elements that mediate this kind of interaction. Above all, this is enabled by the so-called 'mass binding phenomenon' by which scaffold/matrix-attachment regions (S/MARs) reversibly associate with ubiquitous factors. Recent investigations and novel techniques have shown that these contacts can be altered by modulators as well as by specific interactions with the components of enhancers and locus control regions.

Association of deletions and translocation of the reduced folate carrier gene with profound loss of gene expression in methotrexate-resistant K562 human erythroleukemia cells

Severe impairment of methotrexate membrane transport in methotrexate-resistant K562 (K500E) cells was characterized by a nearly complete loss of reduced folate carrier (RFC) transcripts and RFC protein. As determined by 5'-rapid amplification of cDNA ends (5'-RACE), approximately 93% of the RFC transcripts in wild-type cells contained the KS43 5'-untranslated region transcribed from the RFC-B promoter. KS43 transcripts decreased > 90% in K500E cells. The basal and full-length RFC-B promoters were more active (3- and 2-fold, respectively) in directing transcription of a luciferase reporter gene in K500E than in wild-type cells. Treatment with a demethylating agent, 5-aza-2'-deoxycytidine, or with a histone deacetylase inhibitor, trichostatin A, did not increase the levels of RFC transcripts in K500E cells. No differences in RFC gene structure were detected between the lines on Southern blots; however, the RFC signals were decreased approximately 60% in K500E cells. DNA sequences were identical between the lines for the RFC coding region and the two 5'-non-coding exons and their respective promoters. Spectral karyotype analysis and fluorescence in situ hybridization in wild-type cells showed two normal chromosome 21 copies and one or two marker chromosomes, each with an RFC signal. In K500E cells, the RFC gene locus was no longer localized to a normal chromosome 21 (at 21q22.2), and a single RFC signal was associated with a small metacentric chromosome, characterized by a 21/22 translocation. Our results suggest that loss of RFC transcripts in K500E cells is unrelated to changes in the levels of critical transcription factors, or to differences in the extent of RFC promoter methylation or core histone deacetylation. Rather, this phenotype is due to the loss of one or more RFC alleles, and to a translocation of the remaining RFC allele with the formation of a 21/22 fusion chromosome.

Overlapping and non-overlapping Ptch2 expression with Shh during mouse embryogenesis

In Drosophila, patched encodes a negative regulator of Hedgehog signaling. Biochemical experiments have demonstrated that vertebrate patched homologues might function as a Sonic hedgehog (Shh) receptor. In mice, two patched homologues, Ptch and Ptch2, have been identified. Sequence comparison have suggested that they might possess distinct properties in Shh signaling. In the developing tooth, hair and whisker, Shh and Ptch2 are co-expressed in the epithelium while Ptch is strongly expressed in the mesenchymal cells. We report here the chromosomal localization of Ptch2 and further analysis of Ptch2 expression. Throughout mouse development, the level of Ptch2 expression is significantly lower than that of Ptch. In early mouse embryos, Ptch and Ptch2 were found to be co-expressed in regions adjacent to Shh-expressing cells in the developing CNS. Similar to other epidermal structures, Shh and Ptch2 also show overlapping expression in the developing nasal gland and eyelids. Thus, during mouse development, Ptch2 is expressed in both Shh-producing and -nonproducing cells.

Aquarius, a novel gene isolated by gene trapping with an RNA-dependent RNA polymerase motif

In a retinoic acid (RA) gene trap screen of mouse embryonic stem (ES) cells, a novel gene, named Aquarius (Aqr), was identified and characterized. The promoterless lacZ marker was used to trap the genomic locus and to determine the expression pattern of the gene. Aqr transcripts are strongly induced in response to RA in vitro. During embryogenesis, Aqr is expressed in mesoderm, in the neural crest and its target tissues, and in neuroepithelium. Expression was first detected at 8.5 days postcoitum, when neural crest cells are visible at the lateral ridges of the neural plate. The gene-trapped Aqr locus was transmitted through the mouse germ line in three genetic backgrounds. In the F2 generation, the expected mendelian ratio of 1:2:1 was observed in all backgrounds, indicating that homozygous mice are viable. Homozygotes are normal in size and weight and breed normally. The gene trap insertion, however, does not seem to generate a null mutation, because Aqr transcripts are still present in the homozygous mutant animals. The Aqr open reading frame has weak homology to RNA-dependent RNA polymerases (RRPs) of the murine hepatitis viruses and contains an RRP motif. Aqr was mapped to mouse chromosome 2 between regions E5 through F2 by using fluorescence in situ hybridization analysis.

Genomic organization and functional analysis of the murine protein phosphatase 1c gamma (Ppp1cc) gene

Protein phosphatase 1 holoenzymes are composed of catalytic subunits in combination with various regulatory subunits. In rodents, four different catalytic isoforms are known, PP1c alpha, -delta, -gamma 1, and -gamma 2. Here we describe the genomic organization of the murine Ppp1cc gene that encodes the PP1c gamma 1 and PP1c gamma 2 isoforms. We determined that Ppp1cc maps to F1.2-G1.2 on chromosome 5 by FISH mapping. Southern hybridization and analysis of cross-hybridizing genomic clones revealed four Ppp1cc-related pseudogenes in the mouse genome. The authentic Ppp1cc gene encodes two isoforms, PP1c gamma 1 and PP1c gamma 2, that arise from alternative splicing and differ by retention of the last intron. The introns of Ppp1cc are flanked by short direct repeats, the significance of which is not clear. Both isoforms retain phosphatase function since they are able to complement the cold-sensitive PP1 defect caused by the dis2-11 mutation in the fission yeast Schizosaccharomyces pombe.

Tissue distribution, genomic structure, and chromosome mapping of mouse and human eukaryotic initiation factor 4E-binding proteins 1 and 2

Two related eukaryotic initiation factor-4E binding proteins (4E-BP1 and 4E-BP2) were recently characterized for their capacity to bind specifically to eIF4E and inhibit its function. Here, we determined the cDNA sequence, tissue distribution, genomic structure, and chromosome localization of murine and human 4E-BP1 and 4E-BP2. Mouse 4E-BP1 and 4E-BP2 consist of 117 and 120 amino acids and exhibit 91. 5 and 95.0% identity, respectively, to their human homologues. 4E-BP1 mRNA is expressed in most tissues, but is most abundant in adipose tissue, pancreas, and skeletal muscle, while 4E-BP2 mRNA is ubiquitously expressed. The structures of the mouse 4E-BP1 and 4E-BP2 were determined. The 4E-BP1 gene consists of three exons and spans approximately 16 kb. In addition, two 4E-BP1 pseudogenes exist in the mouse genome. The 4E-BP2 gene spans approximately 20 kb and exhibits an identical genomic organization to that of 4E-BP1, with the protein coding portion of the gene divided into three exons. There are no pseudogenes for 4E-BP2. The chromosomal locations of 4E-BP1 and 4E-BP2 were determined in both mice and humans by fluorescence in situ hybridization analysis. Mouse 4E-BP1 and 4E-BP2 map to chromosomes 8 (A4-B1) and 10 (B4-B5), respectively, and human 4E-BP1 and 4E-BP2 localize to chromosomes 8p12 and 10q21-q22, respectively.

A novel family of repeat sequences in the mouse genome responsive to retinoic acid

Repetitive DNA sequences form a substantial portion of eukaryotic genomes and exist as members of families that differ in copy number, length, and sequence. Various functions, including chromosomal integrity, gene regulation, and gene rearrangement have been ascribed to repetitive DNA. Although there is evidence that some repetitive sequences may participate in gene regulation, little is known about how their own expression may be regulated. During the course of gene trapping experiments with embryonic stem (ES) cells, we identified a novel class of expressed repetitive sequences in the mouse, using 5' rapid amplification of cDNA ends-polymerase chain reaction (5' RACE-PCR) to clone fusion transcripts from these lines. The expression of these repeats was induced by retinoic acid (RA) in cultured ES cells examined by Northern blot analyses. In vivo, their expression was spatially restricted in embryos and in the adult brain as determined by RNA in situ hybridization. We designated this family of sequences as Dr (developmentally regulated) repeats. The members of the Dr family, identified by cDNA cloning and through database search, are highly similar in sequence and show peculiar structural features. Our results suggest the expression of Dr-containing transcripts may be part of an ES cell differentiation program triggered by RA.

The effects of ozone on lung, heart, and liver superoxide dismutase and glutathione peroxidase activities in the protein-deficient rat

The effects of protein deficiency or food restriction and ozone exposure on lung, heart and liver superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were studied in weanling and adult rats. Two groups of rats were fed diets containing 4 or 16% protein. A third group was fed the 16% protein diet, but at the level consumed by the rats fed the 4% protein diet. After 3 weeks (weanling) or 5 weeks (adult), one-half of the rats in each group were exposed continuously to 0.64 ppm ozone for 7 days. In adult rat lung, O3 exposure typically stimulated Cu,Zn-SOD and GPx activities in all groups, but in weanling rats only GPx activity was elevated and only in rats fed the 16% protein diet. Liver Cu,Zn-SOD activity was also influenced by diet; in adult rats, liver Mn-SOD and GPx activities were often depressed following O3 exposure. Heart SOD and GPx, however, were not affected by ozone or diet. The pulmonary and hepatic effects due to diet and O3 further illustrate the importance of nutritional status when assessing the health effects of O3 exposure.

Cell number and size in selected organs of fetuses of rats malnourished and exposed to nitrofen

The effects of maternal exposure to nitrofen or protein-energy malnutrition on the number and sizes of cells in selected organs of the fetal rat have been studied. Pregnant rats were fed either an adequate (CON) or protein-energy deficient diet (PEM) throughout gestation. Each diet group was divided into two subgroups. One subgroup was gavaged with 25 mg nitrofen/kg body weight on gestational days 7-21 and the other, with corn oil carrier only. Fetal liver, kidneys, intestine, heart, lung, and brain were weighed and assayed for DNA, RNA, and protein. Maternal protein deficiency resulted in a reduction in organ weight and total DNA, RNA, and protein in all six organs. Maternal nitrofen exposure resulted in reduced weight and reduced protein in all organs except the brain. Total DNA and RNA were reduced in intestine, heart, and lung, and total RNA was also reduced in the liver following maternal nitrofen exposure. An interaction between diet and toxin affected lung weight, DNA, RNA, and protein, intestinal total protein, and heart DNA. Protein/DNA ratios were reduced in liver, intestine, and brain in the group fed the inadequate diet and in intestine only following nitrofen exposure. The deficient diet resulted in increased RNA/DNA ratio in the fetal liver and heart and a decreased ratio in the kidney and brain. Nitrofen exposure resulted in a lower RNA/DNA ratio in the liver. The data indicate that maternal protein-energy malnutrition results in smaller organs in the fetuses with fewer cells and containing less protein and RNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of protein deficiency and food restriction on lung ascorbic acid and glutathione in rats exposed to ozone

Weanling (52 +/- 4 g) or adult (259 +/- 16 g) male Sprague-Dawley rats were fed ad libitum casein-based diets containing 4 or 16% protein. A third group (food restricted) was fed daily the 16% protein diet, but at the food intake level of the 4% protein group. After 3 wk (weanling) or 5 wk (adults), half of the rats in each group were continuously exposed to 0.64 ppm ozone for 7 d. Ascorbic acid and reduced glutathione levels were then measured. In the heart and liver from weanling rats, ascorbic acid concentrations were lower in the protein-deficient group than in either control group. In the liver from weanling rats glutathione concentrations were also reduced in response to protein deficiency. Exposure to ozone produced no additional response. For adult rats the response for liver glutathione was similar to that of the weanlings. The liver ascorbate concentration, however, was consistently lower in adult rats compared to weanlings exposed to ozone. In lungs from adult rats, the ascorbic acid concentration was lower in the protein-deficient group than in either control group. On a whole-organ basis, both ascorbic acid and glutathione were usually higher in lungs from rats exposed to ozone than from those exposed to air. Interestingly, protein deficiency did not appear to compromise the lung's ability to maintain, in relative terms, the ascorbic acid or glutathione concentration in response to ozone.

Elastin accumulation in the chick aorta: effect of 6-hydroxydopamine and deoxycorticosterone acetate

The net accumulation of aorta elastin in the chick was estimated from day 1 to 14, post-hatching. Increased elastin accumulation was coincident with the elevation in blood pressure observed for this period. Further deoxycorticosterone acetate plus dietary NaCl also caused stimulation of protein synthesis in aorta. In contrast, aorta protein synthesis and net elastin accumulation appeared to be decreased in chicks given 6-hydroxydopamine.

Dietary cadmium, zinc and copper: effects on chick lung morphology and elastin cross-linking

Day-old White Leghorn cockerels were divided into seven dietary groups and fed one of the following diets: 1) a casein-based basal diet; 2) a casein-based diet supplemented with 10 mg/kg cadmium, 3) 100 mg/kg cadmium, 4) or 800 mg/kg zinc; 5) a casein-based diet pair-fed to the 100 mg/kg Cd group; 6) a spray-dried nonfat milk-based diet with no added copper, or 7) a spray-dried nonfat milk-based diet supplemented with 5 mg/kg copper. At termination (5 weeks), the birds were killed, and the effects of the diets on selected features of lung composition and morphology were assessed. Body weights were reduced in the 100 mg/kg Cd, pair-fed, and Cu-deficient groups when compared to their controls (casein-based or milk-based copper-supplemented diets). There were no differences in lung weights (expressed relative to metabolic body size) among the groups, although copper deficiency did result in a slight decrease in the dry to wet weight ratio of lung. Lung elastin content and the desmosine content in elastin were significantly lower in the Cu-deficient group and tended to be lower in the group fed 800 ppm Zn. Significant alterations (enlargement of the tertiary bronchial lumen) in morphology were also observed in lungs from both the 100 mg/kg Cd and Cu-deficient groups. Alteration in lung morphology observed in the 100 mg/kg Cd group could not be explained by changes in the elastin content of lung.