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Biomedical subjects

Wei Sun

Publications and source records attributed to Wei Sun.

At least 127 records · Page 7Linked to original sources

Response of heterograft heart valve biomaterials to moderate cyclic loading.

We have recently demonstrated that noncalcific tissue damage can lead to significant collagen degradation in clinically explanted bioprosthetic heart valves (BHVs). In the present study we quantified the early response of glutaraldehyde treated bovine pericardium (GLBP) to cyclic tensile loading to begin to elucidate the mechanisms of noncalcific tissue degeneration in BHV biomaterials. GLBP specimens were cycled at 30 Hz to a maximum uniaxial strain of 16% (corresponding to approximately 1-MPa peak stress), with the loading direction parallel to the preferred collagen fiber (PD) direction. After 30 x 10(6) cycles, specimens were subjected to biaxial mechanical testing, then cycled until 65 x 10(6) cycles. The results indicated a permanent change in the unloaded tissue dimensions of +7.1% strain in the PD direction and -7.7% strain in the cross fiber direction (XD) after 65 x 10(6) cycles and an increase of the collagen crimp period from 40.6 to 45.2 microm by 65 x 10(6) cycles (p = 0.05). Fourier transform IR spectroscopy analysis indicated that cyclic fatigue of GLBP leads to both collagen conformational changes and early denaturation. Furthermore, no significant changes in areal strain were found under 1-MPa equibiaxial stress, indicating that cyclic loading changed the collagen fiber orientation but not the overall tissue compliance. These observations suggest that while deterioration of collagen begins immediately, fiber straightening and reorientation dominates the changes in the mechanical behavior up to 65 x 10(6) cycles. The present study underscores the complexity of the response of biologically derived biomaterials to cyclic mechanical loading. Improved understanding of these phenomena can potentially guide the development of novel chemical treatment methods that seek to improve BHV durability by minimizing these degenerative processes.

Animals↗

Characteristics of T-cell receptor repertoire and myelin-reactive T cells reconstituted from autologous haematopoietic stem-cell grafts in multiple sclerosis.

Multiple sclerosis is thought to involve aberrant immune responses to myelin autoantigens. Haematopoietic stem-cell transplantation (HSCT) is in clinical trials for progressive multiple sclerosis based on the rationale that it destroys aberrant immune system, while recapitulation of lymphocyte ontogeny might alter the immune system and slow down disease progression. This study was undertaken to analyse characteristics of the T-cell receptor (TCR) repertoire, serum cytokine profile and the T-cell responses to myelin basic protein (MBP) in the reconstituted immune system in progressive multiple sclerosis. The study revealed that, following autologous HSCT, the T-cell immunity recovered in two distinctive phases. The first phase was characterized by limited T-cell immunity as a result of selective expansion of pre-existing T cells commonly expressing the TCR beta chain variable region (TCR BV) 20 and increased serum cytokine production during the first several months. The second phase of T-cell reconstitution coincided with increased thymic T-cell output 9-12 months after HSCT. T cells reconstituted from stem-cell grafts had the distinctive properties of comprehensive T-cell immunity and a broad TCR repertoire. T cells recognizing MBP were initially depleted by immunoablation and rapidly expanded from the reconstituted T-cell repertoire in 12 months. The reconstituted MBP-reactive T cells exhibited a broader epitope recognition repertoire while maintaining the same skewed reactivity pattern compared with that seen at baseline. The findings have important implications in the understanding of the role of HSCT as a potential treatment for multiple sclerosis.

Autoantigens↗

Alpha-adrenoceptor-mediated coronary vasoconstriction is augmented during exercise in experimental diabetes mellitus.

This study tested whether alpha-adrenoceptor-mediated coronary vasoconstriction is augmented during exercise in diabetes mellitus. Experiments were conducted in dogs instrumented with catheters in the aorta and coronary sinus and with a flow transducer around the circumflex coronary artery. Diabetes was induced with alloxan monohydrate (n = 8, 40 mg/kg i.v.). Arterial plasma glucose concentration increased from 4.7 +/- 0.2 mM in nondiabetic, control dogs (n = 8) to 21.4 +/- 1.9 mM 1 wk after alloxan injection. Coronary blood flow, myocardial oxygen consumption (MVo(2)), aortic pressure, and heart rate were measured at rest and during graded treadmill exercise before and after infusion of the alpha-adrenoceptor antagonist phentolamine (1 mg/kg iv). In untreated diabetic dogs, exercise increased MVo(2) 2.7-fold, coronary blood flow 2.2-fold, and heart rate 2.3-fold. Coronary venous Po(2) fell as MVo(2) increased during exercise. After alpha-adrenoceptor blockade, exercise increased MVo(2) 3.1-fold, coronary blood flow 2.7-fold, and heart rate 2.1-fold. Relative to untreated diabetic dogs, alpha-adrenoceptor blockade significantly decreased the slope of the relationship between coronary venous Po(2) and MVo(2). The difference between the untreated and phentolamine-treated slopes was greater in the diabetic dogs than in the nondiabetic dogs. In addition, the decrease in coronary blood flow to intracoronary norepinephrine infusion was significantly augmented in anesthetized, open-chest, beta-adrenoceptor-blocked diabetic dogs compared with the nondiabetic dogs. These findings demonstrate that alpha-adrenoceptor-mediated coronary vasoconstriction is augmented in alloxan-induced diabetic dogs during physiological increases in MVo(2).

Adrenergic alpha-Agonists↗

Ca2+ and N-ethylmaleimide-sensitive factor differentially regulate disassembly of SNARE complexes on early endosomes.

The endosome-associated protein Hrs inhibits the homotypic fusion of early endosomes. A helical region of Hrs containing a Q-SNARE motif mediates this effect as well as its endosomal membrane association via SNAP-25, an endosomal receptor for Hrs. Hrs inhibits formation of an early endosomal SNARE complex by displacing VAMP-2 from the complex, suggesting a mechanism by which Hrs inhibits early endosome fusion. We examined the regulation of endosomal SNARE complexes to probe how Hrs may function as a negative regulator. We show that although NSF dissociates the VAMP-2.SNAP-25.syntaxin 13 complex, it has no effect on the Hrs-containing complex. Whereas Ca(2+) dissociates the Hrs-containing complex but not the VAMP-2-containing SNARE complex. This is the first demonstration of differential regulation of R/Q-SNARE and all Q-SNARE-containing SNARE complexes. Ca(2+) also reverses the Hrs-induced inhibition of early endosome fusion in a tetanus toxin-sensitive manner and removes Hrs from early endosomal membranes. Moreover, Hrs inhibition of endosome fusion and its endosomal localization are sensitive to bafilomycin, implying a role for luminal Ca(2+). Thus, Hrs may bind a SNARE protein on early endosomal membranes negatively regulating trans-SNARE pairing and endosomal fusion. The release of Ca(2+) from the endosome lumen dissociates Hrs, allowing a VAMP-2-containing complex to form enabling fusion.

Calcium↗

Proteomic analysis on structural proteins of Severe Acute Respiratory Syndrome coronavirus.

Recently, a new coronavirus was isolated from the lung tissue of autopsy sample and nasal/throat swabs of the patients with Severe Acute Respiratory Syndrome (SARS) and the causative association with SARS was determined. To reveal further the characteristics of the virus and to provide insight about the molecular mechanism of SARS etiology, a proteomic strategy was utilized to identify the structural proteins of SARS coronavirus (SARS-CoV) isolated from Vero E6 cells infected with the BJ-01 strain of the virus. At first, Western blotting with the convalescent sera from SARS patients demonstrated that there were various structural proteins of SARS-CoV in the cultured supernatant of virus infected-Vero E6 cells and that nucleocaspid (N) protein had a prominent immunogenicity to the convalescent sera from the patients with SARS, while the immune response of spike (S) protein probably binding with membrane (M) glycoprotein was much weaker. Then, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to separate the complex protein constituents, and the strategy of continuous slicing from loading well to the bottom of the gels was utilized to search thoroughly the structural proteins of the virus. The proteins in sliced slots were trypsinized in-gel and identified by mass spectrometry. Three structural proteins named S, N and M proteins of SARS-CoV were uncovered with the sequence coverage of 38.9, 93.1 and 28.1% respectively. Glycosylation modification in S protein was also analyzed and four glycosylation sites were discovered by comparing the mass spectra before and after deglycosylation of the peptides with PNGase F digestion. Matrix-assisted laser desorption/ionization-mass spectrometry determination showed that relative molecular weight of intact N protein is 45 929 Da, which is very close to its theoretically calculated molecular weight 45 935 Da based on the amino acid sequence deduced from the genome with the first amino acid methionine at the N-terminus depleted and second, serine, acetylated, indicating that phosphorylation does not happen at all in the predicted phosphorylation sites within infected cells nor in virus particles. Intriguingly, a series of shorter isoforms of N protein was observed by SDS-PAGE and identified by mass spectrometry characterization. For further confirmation of this phenomenon and its related mechanism, recombinant N protein of SARS-CoV was cleaved in vitro by caspase-3 and -6 respectively. The results demonstrated that these shorter isoforms could be the products from cleavage of caspase-3 rather than that of caspase-6. Further, the relationship between the caspase cleavage and the viral infection to the host cell is discussed.

Amino Acid Sequence↗

RScore: a peptide randomicity score for evaluating tandem mass spectra.

RScore, a new criterion of randomicity for evaluating tandem mass (MS/MS) spectra, is described. RScore is defined as the relative quality in cross-correlation and matched intensity percentage of a potentially positive peptide to those of other possible candidates for the same spectrum. By utilizing RScore combined with less stringent SEQUEST score filters, the number of true positive peptides can be increased and the number of false positives in datasets from a known protein mixture can be reduced compared with current SEQUEST parameters used alone. This algorithm is simple and adds little overheads to SEQUEST computation.

Algorithms↗

E-cadherin expression in invasive urothelial carcinoma.

E-cadherin (E-CD) is a transmembrane glycoprotein involved in intercellular adhesion. A loss or reduction in E-CD expression has been linked to the invasive phenotype of a wide variety of human neoplasms, including bladder tumors. The objective of this study was to compare the E-CD expression at different depths of tumor invasion below the bladder's basement membrane in high- and low-grade urothelial carcinomas to investigate whether deeper tumor invasion and higher-grade invasive urothelial carcinomas are associated with decreased E-CD expression. E-cadherin staining was performed on 29 formalin-fixed, paraffin-embedded sections from high- and low-grade urothelial carcinoma specimens using an automatic immunohistochemical stainer. The sections were divided into three categories according to the depth of invasion below the basement membrane: upper, middle, and lower. The percentage and intensity of E-CD cell membrane staining for the three categories were calculated using a quantitative automated cellular imaging system. The percentage of cells that stained for E-CD was 82.6% +/- 1.4% (mean +/- SD) in the upper layer, 59.6% +/- 2.2% in the middle layer, and 29.4% +/- 2.7% in the lower layer. The intensity of E-CD expression was 64.7 +/- 3.2 units in the upper layer, 43.3 +/- 2.9 units in the middle layer, and 26.1 +/- 3.1 units in the lower layer. There were significant differences between the three layers in both the percentage and intensity of cellular E-CD staining (P<.05). Normal urothelium, high-grade urothelial dysplasia/carcinoma in situ, and superficial noninvasive papillary urothelial carcinoma maintained E-CD expression. However, once malignant cells infiltrated through the basement membrane, E-CD expression decreased. The more poorly differentiated urothelial carcinoma, the deeper the nests, and the smaller the clusters of neoplastic cells within the tumor were, and the more decrease in E-CD expression noted. The degree of decreased E-CD expression was directly proportional to the degree of tumor differentiation and depth of infiltration in invasive urothelial carcinoma. Down-regulation of E-CD may be one of the pathways responsible for tumor differentiation and may promote deeper invasion in urothelial carcinomas.

Biomarkers, Tumor↗

A novel behavioral paradigm for assessing tinnitus using schedule-induced polydipsia avoidance conditioning (SIP-AC).

A behavioral technique was developed that allowed the onset and recovery of tinnitus to be measured in individual rats treated with different doses of salicylate. Food-restricted rats were self-trained to lick for water during the time between scheduled delivery of food pellets, i.e., schedule-induced polydipsia (SIP). SIP-induced licking was placed under stimulus control by administering foot shock if licks occurred when sound (one of six stimuli, 40 dB SPL) was present; rats were allowed to lick during quiet. After the number of licks-in-quiet (correct response) exceeded 90% of total licks, rats were treated with saline and four different doses of salicylate (50, 100, 150 and 350 mg/kg, intraperitoneally (i.p.); 2 days). Performance was assessed before, during and after treatment. Licks-in-sound remained extremely low with saline and all four salicylate doses indicating that the sounds were audible under all treatment conditions. Licks-in-quiet remained high during the saline control and 50 mg/kg dose of salicylate, behavior consistent with the absence of tinnitus. However, licks-in-quiet showed a statistically significant decline with the 150 and 350 mg/kg dose, behavior consistent with the presence of tinnitus. Licks-in-quiet gradually recovered to baseline level 2-3 days following high-dose salicylate treatments, behavior consistent with the gradual disappearance of tinnitus. The salicylate dose needed to induce tinnitus and the length of recovery are consistent with previous reports, providing support for the method. The ability to obtain sequential estimates of tinnitus-like behavior in an animal after administering a tinnitus-inducing agent could aid in understanding the underlying neural mechanisms and assessing potential treatments.

Animals↗

A systematical analysis of tryptic peptide identification with reverse phase liquid chromatography and electrospray ion trap mass spectrometry.

In this study we systematically analyzed the elution condition of tryptic peptides and the characteristics of identified peptides in reverse phase liquid chromatography and electrospray tandem mass spectrometry (RPLC-MS/MS) analysis. Following protein digestion with trypsin, the peptide mixture was analyzed by on-line RPLC-MS/MS. Bovine serum albumin (BSA) was used to optimize acetonitrile (ACN) elution gradient for tryptic peptides, and Cytochrome C was used to retest the gradient and the sensitivity of LC-MS/MS. The characteristics of identified peptides were also analyzed. In our experiments, the suitable ACN gradient is 5% to 30% for tryptic peptide elution and the sensitivity of LC-MS/MS is 50 fmol. Analysis of the tryptic peptides demonstrated that longer (more than 10 amino acids) and multi-charge state (+2, +3) peptides are likely to be identified, and the hydropathicity of the peptides might not be related to whether it is more likely to be identified or not. The number of identified peptides for a protein might be used to estimate its loading amount under the same sample background. Moreover, in this study the identified peptides present three types of redundancy, namely identification, charge, and sequence redundancy, which may repress low abundance protein identification.

Acetonitriles↗

Computer-aided tissue engineering: overview, scope and challenges.

Advances in computer-aided technology and its application with biology, engineering and information science to tissue engineering have evolved a new field of computer-aided tissue engineering (CATE). This emerging field encompasses computer-aided design (CAD), image processing, manufacturing and solid free-form fabrication (SFF) for modelling, designing, simulation and manufacturing of biological tissue and organ substitutes. The present Review describes some salient advances in this field, particularly in computer-aided tissue modeling, computer-aided tissue informatics and computer-aided tissue scaffold design and fabrication. Methodologies of development of CATE modelling from high-resolution non-invasive imaging and image-based three-dimensional reconstruction, and various reconstructive techniques for CAD-based tissue modelling generation will be described. The latest development in SFF to tissue engineering and a framework of bio-blueprint modelling for three-dimensional cell and organ printing will also be introduced.

Animals↗

Computer-aided tissue engineering: application to biomimetic modelling and design of tissue scaffolds.

Computer-aided tissue engineering (CATE) enables many novel approaches in modelling, design and fabrication of complex tissue substitutes with enhanced functionality and improved cell-matrix interactions. Central to CATE is its bio-tissue informatics model that represents tissue biological, biomechanical and biochemical information that serves as a central repository to interface design, simulation and tissue fabrication. The present paper discusses the application of a CATE approach to the biomimetic design of bone tissue scaffold. A general CATE-based process for biomimetic modelling, anatomic reconstruction, computer-assisted-design of tissue scaffold, quantitative-computed-tomography characterization, finite element analysis and freeform extruding deposition for fabrication of scaffold is presented.

Biocompatible Materials↗

The 40-mg dose of eletriptan: comparative efficacy and tolerability versus sumatriptan 100 mg.

Meta-analysis provides valuable information regarding relative efficacies of triptans, but head-to-head comparator studies remain the gold standard. Three similar head-to-head trials comparing eletriptan 40 mg (E40) with sumatriptan 100 mg (S100) provide a rare opportunity and sufficient power, for robust comparisons of efficacy. Data were combined from three double-blind, placebo-controlled, first-dose, first-attack acute migraine treatment studies comparing E40 (n=1132), S100 (n=1129), and placebo (n=645). The primary outcome was headache response at 2 h. Secondary outcomes included headache response at 1 h, pain-free and functional responses, and sustained headache and pain-free responses. Odds ratios were calculated for summary estimates of probability of response. There were higher headache response rates with eletriptan versus sumatriptan at 2 h (67% vs. 57%; P<0.0001) and 1 h (34% vs. 26%; P<0.0001). Eletriptan also had higher 2 h pain-free (35% vs. 25%; P<0.0001) and functional responses (67% vs. 58%; P<0.0001). Sustained headache (42%) and pain-free (22%) response rates were higher for eletriptan versus sumatriptan (34%, P<0.0001; 15%, P<0.0001). The probability of response for eletriptan versus sumatriptan ranged from 36% higher (relief of nausea) to 64% higher (sustained pain-free rate). Combined analysis demonstrates that E40 has superior efficacy versus S100 across all clinically relevant outcomes.

Adolescent↗

Neuronal gene expression and function in the growth-stimulated R28 retinal precursor cell line.

PURPOSE: Proliferative retinal progenitor cells that express neuronal characteristics are potentially useful for developmental studies and as experimental graft material. The continuously-growing R28 retinal cell line has been distributed to over 60 laboratories for a variety of studies, yet has not been fully characterized. In this study, we tested the hypothesis that the proliferative R28 retinal cell line contains subpopulations of cells that express neuronal mRNAs and proteins characteristic of CNS neurons. METHODS: To this end, we sought to determine the potential retinal, neuronal, and growth-related characteristics of this retinal cell line through gene expression profiling, coupled with confirmatory immunocytochemistry and electrophysiology. RESULTS: Despite expression of growth-stimulatory oncogenes and growth-promoting factors, subpopulations of R28 cells express abundant retinal and neuronal markers, as well as the functional capacity to respond to specific neurotransmitters such as dopamine, acetylcholine, serotonin, and glycine. CONCLUSION: Proliferative R28 cells retain functional neuronal properties that may prove useful in future studies of neuronal differentiation and development.

Animals↗

Intramuscular gene transfer of CGRP inhibits neointimal hyperplasia after balloon injury in the rat abdominal aorta.

CGRP is a well-known neuropeptide that has various protective effects on cardiovascular system. Our previous studies have shown that CGRP inhibits vascular smooth muscle cell (VSMC) proliferation in vitro. The present study aimed to explore the role of the CGRP in neointimal formation after balloon injury in the rat aortic wall and the underlying mechanism. Gene transfer of CGRP was performed with the use of intramuscular electroporation in a balloon-injured rat aorta model. Apoptosis in VSMCs was determined by electrophoresis assessment of DNA fragmentation and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay. Overexpression of the CGRP gene significantly inhibited the neointimal formation after balloon injury compared with the mock transfer, as assessed by the intima-to-media ratio 14 days after balloon injury (29.2 +/- 3.7% vs. 52.7 +/- 5.4%; n = 9-12, P < 0.05). In addition, CGRP gene expression increased the number of apoptotic cells in the neointima in vivo 14 days after balloon injury. Similarly, the addition of bioactive CGRP and the nitric oxide donor induced similar apoptosis in cultured VSMCs. The antagonist of the CGRP(1) receptor and inhibitors of cAMP-PKA and nitric oxide blocked CGRP-mediated apoptosis. Furthermore, CGRP gene transfer increased inducible nitric oxide synthase and p53 but decreased PCNA and Bcl-2 protein levels in balloon-injured rat aorta. Our data demonstrated that CGRP potently inhibited neointimal thickening in the rat aorta, at least in part through its distinct effects on apoptosis and proliferation of VSMCs both in vivo and in vitro. Therefore, delivery of the CGRP gene may have therapeutic implications in limiting vascular restenosis.

Animals↗

Alpha-adrenergic vasoconstrictor tone limits right coronary blood flow in exercising dogs.

In exercising dogs, increased myocardial O2 consumption (MVO2) of the left ventricle is met primarily by hyperemia, whereas increased O2 extraction makes a greater contribution to right ventricular (RV) O2 supply. We hypothesized that alpha-adrenergic vasoconstrictor tone limits right coronary (RC) blood flow during exercise, forcing increased O2 extraction. This tone might also contribute to lesser RC vascular conductance at rest. Accordingly, RV O2 balance was examined at rest and during graded treadmill exercise before and during alpha-adrenergic blockade with phentolamine (1 mg/kg, i.v., n=6). The transmural distribution of RC flow was measured with radiolabeled microspheres in 4 additional dogs. At rest, alpha-adrenergic receptor blockade did not significantly increase RC flow or conductance. During exercise, alpha-adrenergic blockade increased RC flow and conductance responses to increased RV MVO2 by 25% and 60%, respectively. The transmural distribution of RC flow was not altered by exercise or by alpha-adrenergic blockade. Before alpha-adrenergic blockade, hyperemia provided 39%-66% of the additional O2 consumed by the right ventricle during graded exercise; after alpha-adrenergic blockade, hyperemia contributed 74%-85%. After alpha-adrenergic blockade, the slope of the relationship between RC venous PO2 and RV MVO2 became less steep, reflecting less O2 extraction due to enhanced hyperemia. Additional experiments were conducted on 5 anesthetized, open-chest dogs with constant RC perfusion pressure and beta-adrenergic blockade. The RC flow response to intracoronary norepinephrine was shifted to the left compared with that measured in the left coronary circulation, consistent with observations in the conscious exercising dogs. In conclusion, alpha-adrenergic vasoconstrictor tone does not restrict resting RC blood flow, but during exercise, this tone transmurally blunts RC hyperemia and forces the right ventricle to mobilize its O2 extraction reserve. This effect is more pronounced than has been reported for the left ventricle.

Adrenergic alpha-Agonists↗

Intermittent hypoxic training protects canine myocardium from infarction.

This investigation examined cardiac protective effects of normobaric intermittent hypoxia training. Six dogs underwent intermittent hypoxic training for 20 consecutive days in a normobaric chamber ventilated intermittently with N2 to reduce fraction of inspired oxygen (FiO2) to 9.5%-10%. Hypoxic periods, initially 5 mins and increasing to 10 mins, were followed by 4-min normoxic periods. This hypoxia-normoxia protocol was repeated, initially 5 times and increasing to 8 times. The dogs showed no discomfort during intermittent hypoxic training. After 20 days of hypoxic training, the resistance of ventricular myocardium to infarction was assessed in an acute experiment. The left anterior descending (LAD) coronary artery was occluded for 60 mins and then reperfused for 5 hrs. At 30 mins of LAD occlusion, radioactive microspheres were injected through a left atrial catheter to assess coronary collateral blood flow into the ischemic region. After 5 hrs reperfusion, the heart was dyed to delineate the area at risk (AAR) of infarction and stained with triphenyl tetrazolium chloride to identify infarcted myocardium. During LAD occlusion and reperfusion, systemic hemodynamics and global left ventricular function were stable. Infarction was not detected in 4 hearts and was 1.6% of AAR in the other 2 hearts. In contrast, 6 dogs sham-trained in a chamber ventilated with compressed air and 5 untrained dogs subjected to the same LAD occlusion/reperfusion protocol had infarcts of 36.8% +/- 5.8% and 35.2% +/- 9.5% of the AAR, respectively. The reduction in infarct size of four of the six hypoxia-trained dogs could not be explained by enhanced collateral blood flow to the AAR. Hypoxia-trained dogs had no ventricular tachycardia or ventricular fibrillation. Three sham-trained dogs had ventricular tachycardia and two had ventricular fibrillation. Three untrained dogs had ventricular fibrillation. In conclusion, intermittent hypoxic training protects canine myocardium from infarction and life-threatening arrhythmias during coronary artery occlusion and reperfusion. The mechanism responsible for this potent cardioprotection merits further study.

Animals↗

Applications of proteomics in hepatic diseases research.

Proteomics has become an important part in the leading research area and been widely used in the disease-associated study. In hepatic research field, proteomics could be applied in study of hepatic diseases including liver cancer, cirrhosis and hepatotoxicities, etc. Significant proteins could be identified as biomarkers, drug targets and clues for pathogenesis illumination.

Animals↗