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X Sun

Publications and source records attributed to X Sun.

At least 253 records · Page 14Linked to original sources

Decreased responsiveness of vascular postjunctional alpha1-, alpha2-adrenoceptors and neuropeptide Y1 receptors in rats with heart failure.

Heart failure is associated with increased sympathetic nerve activity. We hypothesized that chronic sympathetic stimulation in heart failure resulted in decreased vascular sympathetic responsiveness. A pithed rat model was employed to evaluate peripheral vascular alpha-adrenoceptor and neuropeptide Y (NPY) receptor responsiveness. Heart failure was induced in Sprague-Dawley rats by coronary artery ligation. Sham operated rats (Sham) served as controls. Two months after this surgical procedure, both heart failure (n = 30) and Sham (n = 30) rats underwent standard pithing procedure. Pressor responses to preganglionic sympathetic nerve stimulation (PNS) and activation of postjunctional alpha1- and alpha2-adrenoceptors as well as Y1 receptors were studied. In response to PNS, cardiac index was similar between heart failure and sham rats (P = n.s.). Mean arterial pressure (MAP) increased in a frequency-dependent fashion after PNS in heart failure rats as well as in control rats. All the agonists used, i.e. the alpha1-adrenoceptor agonist phenylephrine, the alpha2-adrenoceptor agonists clonidine and BHT933 as well as NPY, induced dose-dependent increases in MAP in heart failure and in sham rats. However, in rats with heart failure, the response to all the agonists studied was significantly decreased and the dose response curves were shifted to the right (P < 0.01). We conclude that in vivo vascular response to postjunctional alpha1- and alpha2-adrenoceptors as well as Y1 receptors are decreased in rats with heart failure.

Adrenergic alpha-Agonists↗

Lipocortin-1 preserves myocardial responsiveness to beta-adrenergic stimulation in rat papillary muscle.

1. During septic shock, myocardial contractile dysfunction is accompanied by the release of cytokines and enhanced production of nitric oxide, and the contractile dysfunction is prevented by glucocorticoids. 2. Myocardial dysfunction was induced in vitro by incubation of rat papillary muscle for 15 h with endotoxin (lipopolysaccharide, LPS) and interferon-gamma (IFN-gamma). 3. Both baseline contractile function and inotropic responsiveness to isoprenaline were markedly reduced by the combination of LPS plus IFN-gamma. 4. Lipocortin-1 (LC-1) is induced by glucocorticoids, and LC-1(2-26), its N-terminal fragment, protected the papillary muscle inotropic responsiveness to isoprenaline, but did not affect the decline in baseline contractile function induced by LPS plus IFN-gamma. 5. The mechanisms of this protective action need to be explored further, but LC-1 may prove to be a novel cardioprotective agent for the management of septic shock.

Adrenergic beta-Agonists↗

Axonal cytoskeletal responses to nondisruptive axonal injury and the short-term effects of posttraumatic hypothermia.

In human diffuse axonal injury (DAI), axons are exposed to transient tensile strain. Over the ensuing several hours, injured axons enter a "pathological cascade" of events that lead to secondary axotomy. Use of animal models of traumatic axonal injury (TAI) has allowed description of a number of pathological changes before axotomy occurs, including structural and functional changes in the axolemma, disorientation, and/or loss of microtubules, either compaction and/or dispersion of neurofilaments together with focal compaction at sites where continuity of the axolemma is lost. Recent literature suggests that use of hypothermia may improve behavioral outcomes or reduce the number/density of injured axons in which axonal transport is altered after TAI. But there is presently no ultrastructural, pathological explanation as to how hypothermia may act at the level of the axon to reduce posttraumatic loss of axoplasmic transport. In this study, we tested the hypothesis that posttraumatic hypothermia may ameliorate (a) alteration of axonal transport and (b) early pathological changes in the axonal cytoskeleton prior to secondary axotomy. We have undertaken a pilot study within 4 h of stretch injury to adult guinea pig optic nerve axons as a model of TAI and applied stereological techniques to assess differences in pathology in animals either maintained at 37.5 degrees C or cooled to 32-32.5 degrees C for 2 or 4 h after injury. We provide quantitative evidence that posttraumatic hypothermia significantly reduces the number of axons labelled for beta-APP, a marker for disruption of fast axonal transport, and reduces the loss of microtubules and compaction of neurofilaments, which occurs in normothermic animals over the first 4 h after injury.

Amyloid beta-Protein Precursor↗

Sepsis stimulates release of myofilaments in skeletal muscle by a calcium-dependent mechanism.

Sepsis is associated with a pronounced catabolic response in skeletal muscle, mainly reflecting degradation of the myofibrillar proteins actin and myosin. Recent studies suggest that sepsis-induced muscle proteolysis may reflect ubiquitin-proteasome-dependent protein breakdown. An apparently conflicting observation is that the ubiquitin-proteasome pathway does not degrade intact myofibrils. Thus, it is possible that actin and myosin need to be released from the myofibrils before they can be ubiquitinated and degraded by the proteasome. We tested the hypothesis that sepsis results in disruption of Z-bands, increased expression of calpains, and calcium-dependent release of myofilaments in skeletal muscle. Sepsis induced in rats by cecal ligation and puncture resulted in increased gene expression of micro-calpain, m-calpain, and p94 and in Z-band disintegration in the extensor digitorum longus muscle. The release of myofilaments from myofibrillar proteins was increased in septic muscle. This response to sepsis was blocked by treating the rats with dantrolene, a substance that inhibits the release of calcium from intracellular stores to the cytoplasm. The present results provide evidence that sepsis is associated with Z-band disintegration and a calcium-dependent release of myofilaments in skeletal muscle. Release of myofilaments may be an initial and perhaps rate-limiting component of sepsis-induced muscle breakdown.

Actin Cytoskeleton↗

Roles of nitric oxide synthases in platelet-activating factor-induced intestinal necrosis in rats.

OBJECTIVE: To examine the role of constitutive and inducible nitric oxide synthases (cNOS and iNOS) in platelet-activating factor (PAF)-induced shock and intestinal injury. DESIGN: Prospective, randomized, controlled experimental study. SETTING: Hospital research laboratory. SUBJECTS: Young adult male Sprague-Dawley rats were anesthetized and studied. INTERVENTIONS: Rats were injected with PAF, either alone or after the following pretreatments: a) selective iNOS inhibitors aminoguanidine or S-methylisothiourea; b) 3-morpholinosydnonimine, a NO donor; c) S-methylisothiourea + 3-morpholinosydnonimine; and d) antineutrophil antibody (to deplete neutrophils). MEASUREMENTS AND MAIN RESULTS: Blood pressure, hematocrit, white blood cell counts, intestinal injury, and intestinal cNOS and iNOS activities were assessed. We found that: a) cNOS is the predominant NOS in the intestine and its activity is inversely correlated to the level of tissue injury; b) there is a time-dependent increase in cNOS activity in sham-operated animals, which was abolished by PAF; c) Western blotting and immunohistochemistry showed iNOS present in the normal intestine, localizing mainly in crypt cells; d) iNOS inhibitors attenuated PAF-induced injury in animals with high cNOS activity, but had no protective effect in animals with low cNOS activity; e) 3-morpholinosydnonimine, alone or together with S-methylisothiourea, alleviated PAF-induced injury; and f) neutrophil depletion blocked the suppressive effect of PAF on cNOS and prevented injury. CONCLUSIONS: We conclude that cNOS and iNOS play different roles in PAF-induced intestinal injury. Caution should be exerted concerning potential therapeutic uses of iNOS inhibitors.

Animals↗

Perflubron emulsion improves tolerance to low-flow ischemia in isolated rabbit hearts.

The efficacy of the temporary oxygen carrier perflubron emulsion (PFC) in maintaining oxygen delivery, tissue oxygenation, high-energy phosphates (HEPs), and myocardial function was investigated during low-flow ischemia. Perfusion rate, oxygen tensions, and cardiac function were measured during stabilization (5 min), controlled-flow (22 ml/min x 20 min), and low-flow (0.22 ml/min x 120 min) periods in isolated rabbit hearts. Hearts were perfused with Krebs-Henseleit (KH) solution (Control), or 10 or 20% PFC (vol/vol; n = 8 per group) 5 min before and throughout the low-flow period. Myocardial tissue was then frozen for biochemical and metabolic measurements. Myocardial oxygenation was measured at incremental flow rates by using 20% PFC (n = 4) or KH (n = 6). In PFC hearts, oxygen delivery and intramyocardial tissue Po2 were improved at all evaluated time points and flow rates, respectively (p < 0.05). In Control hearts, left ventricular end-diastolic pressure was elevated at 60, 90, and 120 min of low-flow ischemia (p < 0.05). Tissue lactate was higher (p < 0.05) and HEPs lower (p < 0.05) in Control hearts during low-flow ischemia. These results indicate that PFC treatment improves myocardial oxygenation, maintains HEPs, prevents ischemic contracture, and may increase the margin of safety during low-flow ischemia in isolated rabbit hearts.

Adenosine Diphosphate↗

Sepsis is associated with increased ubiquitinconjugating enzyme E214k mRNA in skeletal muscle.

Previous studies provided evidence that sepsis is associated with increased ubiquitin-proteasome-dependent protein breakdown in skeletal muscle. The 14-kDa ubiquitin-conjugating enzyme (E214k) has been proposed to be a key regulator of the ubiquitin proteolytic pathway. We tested the hypothesis that E214k message and protein levels are increased in skeletal muscle during sepsis. Sepsis was induced in rats by cecal ligation and puncture (CLP). Control rats were sham operated. E214k mRNA and protein levels were quantitated after Northern and Western blot analysis, respectively, 16 h after CLP or sham operation. Sepsis resulted in a 70% increase in the 1. 2-kb E214k transcript in the fast-twitch extensor digitorum longus muscle, whereas no changes were seen in the slow-twitch soleus muscle. E214k protein levels were not influenced by sepsis in any of the muscles studied. Although the changes in the expression of the E214k 1.2-kb transcript paralleled the differential effect of sepsis on protein breakdown in fast- and slow-twitch muscle, the potential role of E214k in the regulation of sepsis-induced muscle proteolysis needs to be interpreted with caution, because the results demonstrated that increased message levels were not associated with increased E214k protein levels.

Animals↗

Activity and expression of the 20S proteasome are increased in skeletal muscle during sepsis.

Recent studies suggest that sepsis stimulates ubiquitin-dependent protein breakdown in skeletal muscle. In this proteolytic pathway, ubiquitinated proteins are recognized, unfolded, and degraded by the multicatalytic 26S protease complex. The 20S proteasome is the catalytic core of the 26S protease complex. The role of the 20S proteasome in the regulation of sepsis-induced muscle proteolysis is not known. We tested the hypothesis that sepsis increases 20S proteasome activity and the expression of mRNA for various subunits of this complex. Proteolytic activity of isolated 20S proteasomes, assessed as activity against fluorogenic peptide substrates, was increased in extensor digitorum longus muscles from septic rats. The proteolytic activity was inhibited by specific proteasome blockers. Northern blot analysis revealed an approximately twofold increase in the relative abundance of mRNA for the 20S alpha-subunits RC3 and RC9 and the beta-subunit RC7. However, Western blot analysis did not show any difference in RC9 protein content between sham-operated and septic rats. The increased activity and expression of the 20S proteasome in muscles from septic rats lend further support for a role of the ubiquitin-proteasome-pathway in the regulation of sepsis-induced muscle proteolysis.

Animals↗

Age-associated differential expression of Na(+)-K(+)-ATPase subunit isoforms in skeletal muscles of F-344/BN rats.

Skeletal muscle expresses multiple isoforms of the Na(+)-K(+)-ATPase. Their expression has been shown to be differentially regulated under pathophysiological conditions. In addition, previous studies suggest possible age-dependent alterations in Na(+)-K(+) pump function. The present study tests the hypothesis that advancing age is associated with altered Na(+)-K(+)-ATPase enzyme activity and isoform-specific changes in expression of the enzyme subunits. Red and white gastrocnemius (Gast) as well as soleus muscles of male Fischer 344/Brown Norway (F-344/BN) rats at 6, 18, and 30 mo of age were examined. Na(+)-K(+)-ATPase activity, measured by K(+)-stimulated 3-O-methylfluorescein phosphatase activity, increased by approximately 50% in a mixed Gast homogenate from 30-mo-old compared with 6- and 18-mo-old rats. Advancing age was associated with markedly increased alpha(1)- and beta(1)-subunit, and decreased alpha(2)- and beta(2)-subunit in red and white Gast. In soleus, there were similar changes in expression of alpha(1)- and alpha(2)-subunits, but levels of beta(1)-subunit were unchanged. Functional Na(+)-K(+)-ATPase units, measured by [(3)H]ouabain binding, undergo muscle-type specific changes. In red Gast, high-affinity ouabain-binding sites, which are a measure of alpha(2)-isozyme, increased in 30-mo-old rats despite decreased levels of alpha(2)-subunit. In white Gast, by contrast, decreased levels of alpha(2)-subunit were accompanied by decreased high-affinity ouabain-binding sites. Finally, patterns of expression of the four myosin heavy chain (MHC) isoforms (type I, IIA, IIX, and IIB) in these muscles were similar in the three age groups examined. We conclude that, in the skeletal muscles of F-344/BN rats, advancing age is associated with muscle type-specific alterations in Na(+)-K(+)-ATPase activity and patterns of expression of alpha- and beta-subunit isoforms. These changes apparently occurred without obvious shift in muscle fiber types, since expression of MHC isoforms remained unchanged. Some of the alterations occurred between middle-age (18 mo) and senescence (30 mo), and, therefore, may be attributed to aging of skeletal muscle.

Aging↗

Impaired physiological responses to chronic hypoxia in mice partially deficient for hypoxia-inducible factor 1alpha.

Chronic hypoxia induces polycythemia, pulmonary hypertension, right ventricular hypertrophy, and weight loss. Hypoxia-inducible factor 1 (HIF-1) activates transcription of genes encoding proteins that mediate adaptive responses to hypoxia, including erythropoietin, vascular endothelial growth factor, and glycolytic enzymes. Expression of the HIF-1alpha subunit increases exponentially as O2 concentration is decreased. Hif1a-/- mouse embryos with complete deficiency of HIF-1alpha due to homozygosity for a null allele at the Hif1a locus die at midgestation, with multiple cardiovascular malformations and mesenchymal cell death. Hif1a+/- heterozygotes develop normally and are indistinguishable from Hif1a+/+ wild-type littermates when maintained under normoxic conditions. In this study, the physiological responses of Hif1a+/- and Hif1a+/+ mice exposed to 10% O2 for one to six weeks were analyzed. Hif1a+/- mice demonstrated significantly delayed development of polycythemia, right ventricular hypertrophy, pulmonary hypertension, and pulmonary vascular remodeling and significantly greater weight loss compared with wild-type littermates. These results indicate that partial HIF-1alpha deficiency has significant effects on multiple systemic responses to chronic hypoxia.

Animals↗

Vertebrate Sprouty genes are induced by FGF signaling and can cause chondrodysplasia when overexpressed.

The Drosophila sprouty gene encodes an antagonist of FGF and EGF signaling whose expression is induced by the signaling pathways that it inhibits. Here we describe a family of vertebrate Sprouty homologs and demonstrate that the regulatory relationship with FGF pathways has been conserved. In both mouse and chick embryos, Sprouty genes are expressed in intimate association with FGF signaling centers. Gain- and loss-of-function experiments demonstrate that FGF signaling induces Sprouty gene expression in various tissues. Sprouty overexpression obtained by infecting the prospective wing territory of the chick embryo with a retrovirus containing a mouse Sprouty gene causes a reduction in limb bud outgrowth and other effects consistent with reduced FGF signaling from the apical ectodermal ridge. At later stages of development in the infected limbs there was a dramatic reduction in skeletal element length due to an inhibition of chondrocyte differentiation. The results provide evidence that vertebrate Sprouty proteins function as FGF-induced feedback inhibitors, and suggest a possible role for Sprouty genes in the pathogenesis of specific human chondrodysplasias caused by activating mutations in Fgfr3.

Amino Acid Sequence↗

Changes in lectin binding patterns of mouse male germ cells (gonocytes) during prespermatogenesis.

The distribution of sugar residues in gonocytes of the differentiating mouse testis was examined by light microscopy using 22 different kinds of lectins. Characteristic binding patterns of sWGA, VVA, and LEA in gonocytes were observed during prespermatogenesis. sWGA preferentially bound to the cytoplasm and plasma membrane of gonocytes on 16.5 days post coitus (dpc). Its reaction decreased thereafter and almost disappeared on 1.5 days post partum (dpp), but reaction reappeared on 4.5 dpp and continued until 6.5 dpp. The VVA reaction was recognized in a few gonocytes on 0.5 dpp, and remained strong until 6.5 dpp. LEA reacted strongly in the plasma membrane and cytoplasm of gonocytes from 0.5 dpp to 6.5 dpp. The present study indicates that sWGA, VVA, and LEA are useful markers for gonocytes, and the appearance or disappearance of sWGA and VVA may be related to the differentiation of gonocytes during prespermatogenesis.

Aging↗

Clinicopathological and genetic characteristics of mucinous carcinomas in the colorectum.

We investigated the clinicopathological and genetic characteristics including patients' gender, age, tumour location, growth pattern, Dukes' stage, DNA ploidy, S-phase fraction, PCNA, apoptosis, c-erbB-2, bcl-2, K-ras, p53, DCC and heat shock protein in 32 mucinous carcinomas versus 261 non-mucinous carcinomas in the colorectum. Sixty percent of mucinous carcinomas were located in the right colon, 13% in the left colon and 27% in the rectum (p=0.01). More mucinous carcinomas grew in expanding pattern than non-mucinous carcinomas (66% vs 39%, p=0.005). Compared with non-mucinous carcinoma, mucinous carcinoma had more K-ras mutations (50% vs 25%, p=0.02), but less p53 expression (72% vs 49%, p=0.02) and less apoptotic activity (19% vs 51%, p=0.01). We further confirm that the mucinous carcinoma in the colorectum represents a distinct clinicopathologic and genetic features as compared to non-mucinous tumour, and may have a different biological behaviour.

Adenocarcinoma, Mucinous↗

[A comparative study of HLA-A locus in northern and southern Chinese bymeans of PCR/SSOP typing].

OBJECTIVE: To compare the HLA-A locus in a population selected from Beijing (northern group) with that in a population selected from Guangzhou (southern group). METHODS: HLA typing was performed by using PCR/SSOP method. A pair of primer and 54 probes were used. RESULTS: In 18 alleles identified, the differences in gene frequency between northern and southern Chinese were found. In northern group, A*0205, 0210 and 2901 were absent, and the frequencies of A*2601, 3001 and 3101 were higher than those of southern group; while in southern group, A*3103, 3201 and 6801 were absent, the frequencies of A*0203 and 1101 were higher than those of northern group; and in addition, six subtypes of A2 serological specificity, namely A*0201, 0203, 0205, 0206, 0207 and 0210, were found, in which A*0201 predominated. CONCLUSION: There are some differences in the genetic background of northern and southern Chinese. A2 subtypes have important implications for unrelated-donor transplantation.

Alleles↗

Efficacy of recombinant methioninase in combination with cisplatin on human colon tumors in nude mice.

The present treatment of colon cancer is based on 5-fluorouracil (5-FU). Despite promising results of combining leucovorin or levamisole with 5-FU, the 5-year survival rate of patients with advanced colon cancer has not increased significantly. Colon tumors in vitro have been shown previously to have an elevated requirement for methionine, suggesting a new therapeutic target. In this study, targeting the methionine dependence of colon tumors is effected by recombinant methioninase (rMETase), alone and in combination with cisplatin (CDDP). In vitro results demonstrated that CDDP and rMETase act synergistically on the human colon cancer cell line SW 620, with a combination index (CI) of 0.45, as well as on the human colon cancer cell line Colo 205 with a CI of 0.7. Human colon cancer lines HCT 15, HT 29, Colo 205, and SW 620 growing in nude mice were treated with rMETase to determine an effective dose for depletion of tumor methionine. rMETase at 15 units/g/day for 5 days depleted tumor methionine in all four tumor types to approximately 30% of untreated control. rMETase alone arrested growth of HCT 15 and HT29 in nude mice for 1 week after treatment termination. Colo 205 and SW 620 were partially arrested by rMETase. However, CDDP in combination with rMETase resulted in tumor regression of Colo 205 and growth arrest of SW 620 in nude mice. The ratio of the treated:control group (T:C) tumor weights for Colo 205 was 8% when CDDP was given on day-5, followed by treatment on days 5-9 with rMETase. This treatment schedule resulted in two of the six animals having no detectable tumor when the experiment was terminated on day 16. SW620 was resistant to CDDP alone and only partially sensitive to rMETase alone. However, when SW 620 was treated with rMETase from days-5 to -9 and CDDP on day-5, tumor growth was arrested. The results demonstrate that rMETase used simultaneously in combination with CDDP had significant antitumor efficacy in colon cancer in vitro and in vivo. The data suggest a novel and promising therapeutic approach by targeting the elevated methionine dependence of colon cancer.

Animals↗

The expression of genes in the ubiquitin-proteasome proteolytic pathway is increased in skeletal muscle from patients with cancer.

BACKGROUND: The intracellular mechanisms of muscle cachexia in patients with cancer are not known. To assess the role of the ubiquitin-proteasome proteolytic pathway in cancer-induced muscle breakdown, we determined messenger RNA levels for ubiquitin and several 20S proteasome subunits in muscle from patients undergoing surgery for cancer METHODS: A biopsy specimen was obtained from the rectus abdominis muscle in patients undergoing laparotomy for cancer (n = 6) or noncancer disease (n = 6). Tissue levels of mRNA for ubiquitin and the 20S proteasome subunits HC3, HC5, HC7, and HC9 were determined by dot blot analysis. RESULTS: The mRNA levels for ubiquitin and the 20S proteasome subunits were 2 to 4 times higher in muscle from patients with cancer than in muscle from control patients. CONCLUSION: This is the first report of increased expression of genes in the ubiquitin-proteasome proteolytic pathway in muscle tissue from patients with cancer. Cancer-induced muscle catabolism may at least in part reflect ubiquitin-proteasome-dependent protein breakdown.

Adult↗

[Seroepidemiological study on Helicobactor pylori infection in rural adult residents].

OBJECTIVE: To study the prevalence of Helicobactor pylori (Hp) infection in rural adult residents of China and its relation to serum levels of pepsinogen I (PG I), pepsinogen II (PG II) and gastrin (GAS). METHODS: Serum levels of antibodies against Hp were determined with enzyme-liked immunosorbent assay (ELISA) in 1,504 residents aged over 30 in Zanhuang County of Hebei Province, and their serum levels of PG I, PG II and GAS, as well as PG I/PG II ratio, were analyzed quantitatively, with radioimmunoassay (RIA). RESULTS: Positivity for serum Hp antibody accounted for 66.4% of the rural adults in Zanhuang County, without significant sex difference. There was no significant difference in positivity for serum Hp antibody between residents in the high and low prevalent areas of gastric cancer. Serum levels of PG I, PG II and GAS were significantly higher in those with positive serum IgG anti-Hp (62.3 micrograms/L, 15.45 micrograms/L and 74.00 pg/ml, respectively) than those negative (42.1 micrograms/L, 6.40 micrograms/L and 66.00 pg/ml, respectively), all with a P-value less than 0.005, and the ratio of serum PG I to PG II levels was significantly lower in the former (4.0) than that in the latter (6.6), with P < 0.005. CONCLUSION: More than two thirds of the adult residents in Zanhuang County had infected with Hp, which could affect their serum levels of PG and GAS.

Adult↗

[Application of fluorescence insitu hybridization technique for prenatal diagnosis of chromosome abnormality in amniotic cells].

OBJECTIVE: To study the technique and diagnostic value of fluorescence in situ hybridization (FISH) in chromosome abnormality for prenatal diagnosis. METHODS: Amniocenteses were performed in 34 pregnant women of 16-23 gestational weeks with indications for prenatal diagnosis. The amniotic fluid samples were cultured in Chang's medium. The metaphase chromosomes were hybridized in situ with the human centromere probes, alpha-satellites DNA probes of X, Y, 13, 21, 18 chromosomes and all primer chromosome probes. These probes were conjugated by Biotin and Dioxin then. The treated slides were examined and taken photos under the fluoromicroscope. RESULTS: By FISH technique, normal karyotypes were shown in 31 cases: 16 cases of 46, XY, 15 cases of 46, XX. Abnormalities were found in 3 patients which were 47, XY + 21; 47, XY + 18 and 45, X/46, X, r (X) respectively. CONCLUSION: Using FISH technique to detect chromosome abnormalities in amniotic fluid for prenatal diagnosis is a reliable method which is rapid and accurate. It has higher sensitivity and specificity in finding chromosome structure abnormalities and marking chromosome DNA sequences.

Adult↗