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Biomedical subjects

M H Chung

Publications and source records attributed to M H Chung.

At least 19 recordsLinked to original sources
PubMed2006

Emerging invasive liver abscess caused by K1 serotype Klebsiella pneumoniae in Korea.

OBJECTIVES: The high incidence of invasive liver abscess caused by Klebsiella pneumoniae in Taiwan, contrasted with the rareness of this disease in Western countries, has aroused special interest. There have been few detailed reports from other Asian countries. To investigate a current epidemiology of K. pneumoniae liver abscess in Korea and to determine K serotype distribution in K. pneumoniae strains causing liver abscess, we performed a nationwide prospective study. METHODS: Community-acquired, culture-proven liver abscess cases were enrolled between 2004 and 2005. Etiologies and clinical features were analyzed. K. pneumoniae isolates were serotyped according to K antigen. Meta-analysis was done to determine the time trend of the etiologies of liver abscess in Korea. RESULTS: Out of 371 cases collected prospectively, 290 (78.2%) were caused by K. pneumoniae. Most K. pneumoniae liver abscesses were monomicrobial. Diabetes mellitus was the most common underlying disease (39.9%). Distant metastatic infections were frequently observed (8.7%). magA PCR revealed that 95 (59.4%) out of 160 K. pneumoniae isolates belonged to the K1 serotype. CONCLUSIONS: Our study indicates that K. pneumoniae has emerged as a major etiologic agent of liver abscess in Korea, and these emerging infections seem to be attributable to invasive K. pneumoniae strains with capsular K1 serotype.

Aged↗
PubMed2004

A laparoscopic approach to the surgical management of enterocutaneous fistula in a wound healing by secondary intention.

Traditional surgical management of a chronic enterocutaneous fistula requires laparotomy, but the optimal site of incision is unclear. Laparoscopy and adhesiolysis may offer an alternative approach. Two cases of non-healing enterocutaneous fistula within chronic, granulating wounds are described. The laparoscope was placed subcostally using the Hasson technique with additional ports placed under direct vision. After clearing the anterior abdominal wall of all but the fistula-containing bowel, an incision was made circumferentially around the granulation bed. Resection and primary anastomosis was performed in standard fashion. Lateral component separation allowed primary wound closure. Both patients were discharged without sequelae and doing well at last follow-up (mean 12 months). A laparoscopic approach to non-healing enterocutaneous fistulas seems safe and technically feasible. When combined with lateral component separation, it may result in reduction of inadvertent enterotomies and optimal management of the wound without the use of prosthetic mesh.

Abdominal Wall↗
PubMed2003

Laparoscopic repair of a right paraduodenal hernia.

BACKGROUND: Laparoscopic repair of a right paraduodenal hernia has never been described in the literature. A 24-year-old woman was admitted after 2 weeks of intermittent abdominal pain associated with nausea and vomiting. Physical examination was normal. Laboratory studies and upper endoscopy were normal. Computed tomography revealed that the small bowel was on the right side of the abdomen and the colon on the left, suspicious for malrotation. Subsequent upper gastrointestinal series with small bowel follow-through revealed the ligament of Treitz on the right with the small bowel encased within a probable hernia sac. A presumptive diagnosis of a right paraduodenal hernia was made. METHODS AND RESULTS: Initial access was obtained with a 10-mm infraumbilical port followed by placement of 5-mm ports in the right and left upper and lower quadrants. The duodenum was identified and the small bowel was found encased within a hernia sac, which was opened widely from the duodenum to the pelvis. The hernia sac was opened laterally to avoid injury to the superior mesenteric vessels. The small bowel was then released from the sac into the peritoneal cavity. The entire bowel was inspected and no other abnormalities were noted. The patient had resolution of her abdominal pain and her postoperative course was uncomplicated. She was discharged home on postoperative day 3 and has since done exceptionally well. CONCLUSIONS: Paraduodenal hernia, a rare cause of small bowel obstruction, can present a diagnostic challenge. However, when the diagnosis is made preoperatively, a laparoscopic repair is a feasible and practical option.

Abdominal Pain↗
PubMed2002

Effect of rebamipide in treatment of Helicobacter pylori-associated duodenal ulcer: attenuation of chemokine expression and nitrosative damage.

Production of cytokines along with increased activity of nitric oxide synthase has been implicated as one of the contributing mechanisms of Helicobacter pylori-mediated gastroduodenal diseases. We aimed to evaluate the effect of rebamipide in treating Helicobacter pylori-associated duodenal ulcers in terms of cytokine production and nitrosative damage of the gastric mucosa. In patients with duodenal ulcers, rebamipide or placebo were given randomly after eradication. Mucosal cytokine production was measured by enzyme linked immunoassay, and nitrotyrosine immunoexpression was measured by immunohistochemistry. The inflammatory activity and degree of neutrophil infiltration were graded accordingly. The mucosal production of RANTES, interleukin-8, and TNF-alpha showed a significant decrease after eradication in patients with rebamipide after-treatment. The nitrotyrosine immunoreactivity of gastric epithelium was significantly decreased in the rebamipide group. Rebamipide treatment after eradication resulted in a significant reduction in chemokine production along with nitrotyrosine immunoexpression in Helicobacter pylori-associated duodenal ulcers.

Adult↗
PubMed2001

Ntg2 of Saccharomyces cerevisiae repairs the oxidation products of 8-hydroxyguanine.

In Escherichia coli, endonuclease III (endo III) repairs the oxidation products of 8-OHGua. However, the corresponding repair enzymes in eukaryotes have not been identified. Here we report that 8-hydroxyguanine (8-OHGua) is highly sensitive to further oxidation. We also show that Ntg2, a functional homolog of endo III in Saccharomyces cerevisiae, is capable of nicking the irradiated duplex DNA containing 8-OHGua. Moreover, Ntg2 formed a stable complex with the DNA upon incubation with NaBH(4). In contrast, Ntg1, another functional homolog of endo III, showed no such activities. These findings indicate that Ntg2 is, at least in part, responsible for repairing the oxidation products of 8-OHGua in eukaryotic cells.

Borohydrides↗
PubMed2001

Laparoscopic radiofrequency ablation of unresectable hepatic malignancies. A phase 2 trial.

BACKGROUND: Radiofrequency ablation (RFA) of hepatic malignancies has been performed successfully via a percutaneous route or at laparotomy. We analyzed the efficacy and utility of laparoscopic intraoperative ultrasound and RFA in patients with unresectable hepatic malignancies. METHODS: Between November 1997 and November 1999, 27 patients with unresectable hepatic malignancies and no evidence of extrahepatic disease were entered in a phase 2 trial of laparoscopic intraoperative ultrasound and RFA. Real-time ultrasonography was used to guide RFA, and lesions were ablated at a temperature of 100 degrees C for 10 min. Overlapping ablations were performed for larger lesions. RESULTS: Additional tumors were identified in 10 (37%) of the 27 study patients by laparoscopy and laparoscopic intraoperative ultrasound despite extensive preoperative imaging. Radiofrequency ablation of 85 hepatic tumors yielded no mortality and only one case of postoperative bleeding. During a mean follow-up period of 14 months, four tumors (4.7%) locally recurred. Of the 27 patients, 11 (41%) remain free of disease at this writing; (22%) are alive with disease; and 10 (37%) have died with disease. CONCLUSION: Laparoscopic RFA and intraoperative ultrasound constitute a safe and accurate method for ablation of unresectable hepatic tumors.

Adult↗
PubMed2001

Diagnostic laparoscopy and laparoscopic ultrasonography optimize the staging and resectability of intraabdominal neoplasms.

BACKGROUND: Despite technical improvements, preoperative imaging studies often fail to predict intraoperative findings. We investigated the potential use of diagnostic laparoscopy (DL) and laparoscopic ultrasonography (LUS) for the assessment of disease in patients with abdominal neoplasms. METHODS: Fifty consecutive patients with abdominal neoplasms underwent spiral computed tomography with oral and intravenous contrast using 5-mm contiguous sections. In addition, eight patients underwent ultrasonography, six underwent magnetic resonance imaging, and eight underwent positron emission tomography. All patients then underwent DL and LUS using a 7.5-MHz ultrasound probe. RESULTS: There were 29 men and 21 women with a mean age of 63 years (range, 35-84). Most had a diagnosis of colorectal cancer (19 cases), melanoma (12 cases), or hepatoma (five cases). In nine cases (18%), DL revealed peritoneal metastatic implants not shown on preoperative images. In 18 cases (36%), LUS was more accurate than preoperative imaging. Combined DL and LUS findings radically changed the operative management in 16 patients (32%). CONCLUSION: As compared with preoperative imaging, the combination of DL and LUS provides more accurate information regarding staging and resectability. Moreover, it helps to determine the extent of operation and reduces the number of unnecessary laparotomies. DL and LUS should be used as an adjunct to preoperative imaging studies in patients with primary or metastatic intraabdominal neoplasms.

Abdominal Neoplasms↗
PubMed2001

The antioxidant effect of rebamipide on oxygen free radical production by H. pylori-activated human neutrophils: in comparison with N-acetylcysteine, ascorbic acid and glutathione.

Helicobacter pylori(H. pylori)-activated neutrophils produce the oxygen-derived free radicals (OFRs) which play an important role in gastric mucosal cell damage. Rebamipide (2-(4-chlorobenzoylamino)-3-[2-(1H)-quinolinon-4-yl] propionic acid) is an antiulcer compound, which protects gastric mucosa against OFR-mediated injury. In order to investigate the effects of rebamipide on OFR production and to compare the antioxidant activity of rebamipide with those of three known antioxidants, N-acetylcysteine (AC), ascorbic acid (Vit C) and glutathione (GSH), the antioxidant activities were determined by luminol-dependent chemiluminescence (ChL) assay and pyrogallol autoxidation assay. The ChL value was markedly elevated immediately after the addition of H. pylori into the medium containing neutrophils. The antioxidant activity of 1.0 mM rebamipide was greater than that of 0.1 mM rebamipide in the luminol-dependent ChL assay, while in the pyrogallol autoxidation assay, the antioxidant activity of 1.0 mM rebamipide was similar to that of 0.1 mM rebamipide. Rebamipide inhibited OFR generation in the pyrogallol autoxidation assay, with the potency being in the order of GSH > Vit C > rebamipide > AC. In the luminol-dependent ChL assay, the antioxidant activity of rebamipide was the greatest among them. These results indicate that rebamipide is a potent antioxidant and scavenges OFRs produced by H. pylori effectively in luminol-dependent ChL assays.

Acetylcysteine↗
PubMed2001

Role for sentinel lymph node dissection in the management of large (> or = 5 cm) invasive breast cancer.

BACKGROUND: Sentinel lymph node dissection (SLND) for small, early-stage breast cancer is well accepted. However, the role of SLND for large primary breast cancer is controversial. We investigated the feasibility and clinical applicability of SLND in patients with large (> or = 5 cm) breast cancers and clinically negative axillae. METHODS: A prospectively entered database was used to identify all patients who underwent surgical management of histopathologically confirmed primary breast carcinomas > or = 5 cm in diameter between September 1991 and August 2000. Patients who had clinically negative axillae and underwent SLND followed by completion axillary lymph node dissection (ALND) were selected for the study. The positivity rate, accuracy rate, and false-negative rate of SLND were determined. RESULTS: Of the 41 patients selected for the study, 24 had infiltrating ductal carcinoma and 17 had infiltrating lobular carcinoma. Mean tumor size was 7.12 cm (range, 5-23 cm). At least one sentinel lymph node (SLN) was identified in all cases. Thirty patients had tumor-positive SLNs. Axillary metastasis was also identified in one patient who did not have a positive SLN. Thus, SLN status accurately predicted regional nodal status in 98% (40 of 41) of cases. The false-negative rate of SLND was 3% (1 of 31). None of the three patients with SLN micrometastasis, defined as a tumor focus < or = 2 mm, had tumor deposits in nonsentinel axillary lymph nodes. Only SLN macrometastasis (> 2-mm tumor deposit) and primary tumor size > or = 7 cm predicted nonsentinel axillary metastasis with significance on multivariate analysis (P = .008 and P = .046, respectively). CONCLUSIONS: SLND is feasible and accurate in patients with large breast cancers and clinically negative axillae. Axillary lymph node dissection can be avoided in nearly one third of patients by focused examination of the SLN.

Adult↗
PubMed2001

Genetic changes of hOGG1 and the activity of oh8Gua glycosylase in colon cancer.

oh8Gua glycosylase repairs DNA by removing oh8Gua, a highly mutagenic oxidative DNA adduct. Recently, the gene for human oh8Gua glycosylase (hOGG1) was cloned and several mutational types have been reported. However, the implications of such mutations in human cancer have not been clearly demonstrated. To test the involvement of hOGG1 mutation in colon carcinogenesis, we analysed the genetic changes of hOGG1 and the activity of oh8Gua glycosylase in 15 paired normal and tumorous colon specimens. The activity of antioxidant enzymes (catalase and superoxide dismutase (SOD)) and extent of oxidative cellular damage (oh8Gua and malondialdehyde) were also assessed to compare the oxidative status of normal and tumour tissues. An Arg 154 to His mutation was detected in two tumour samples, but not in the corresponding normal tissues. A Ser 326 to Cys mutation (polymorphism) was found in both the normal and tumour tissues of 3 patients. However, neither the Arg 154 to His mutation nor the polymorphism at codon 326 significantly decreased the oh8Gua glycosylase activity. The mean activity of oh8Gua glycosylase was significantly higher in the tumours than in normal tissues (P=0.022). Antioxidant enzyme activities were decreased (catalase; P=0.004 and SOD; P=0.002), and the extent of oxidative damage correspondingly increased in the tumour tissues (oh8Gua; P=0.007 and malondialdehyde; P=0.046). Although the sample size was limited, these results suggest that the somatic mutation or the polymorphism of hOGG1 is less likely to be involved in colon carcinogenesis. Nevertheless, the greater oxidative DNA damage in the tumour tissues, as a possible result of impaired antioxidant activity, implies an important role for oxygen free-radicals in colon carcinogenesis.

Adult↗
PubMed2001

Expression and characterization of monocot rice cytosolic CuZnSOD protein in dicot Arabidopsis.

Cytosolic CuZnSOD removes deleterious superoxides from plant cells. In order to understand its function better, we sought to express a monocot CuZnSOD gene in transgenic Arabidopsis. We constructed a transgene using the CaMV 35S promoter to express a rice cytosolic CuZnSOD gene in Arabidopsis and generated over 200 transformants. A 16 kD polypeptide, the same size as the native rice CuZnSOD polypeptide, was detected in the transgenic Arabidopsis. Interestingly, two forms of rice CuZnSOD, rSODI and rSODII, having the same dimeric size, were detected in the transgenic plants. rSODII protein was relatively abundant but had low specific activity. In contrast, rSODI protein was relatively rare and had high specific activity. Inter-conversion of rSODI and rSODII could be achieved by the addition and removal of copper ions into the purified recombinant SOD and to the leaf extract of transgenic plants. Our analysis indicates that rSODI most likely corresponds to native rice CuZnSOD that has incorporated the Cu and Zn ions required for full activity, whereas the less active rSODII form may not have properly incorporated the necessary copper ions.

Arabidopsis↗
PubMed2001

The wound-healing effect of a glycoprotein fraction isolated from aloe vera.

BACKGROUND: Aloe vera has been used as a family medicine for promoting wound healing, but it is not known which component of the plant is effective for this purpose. OBJECTIVES: To isolate and characterize the component effective in wound healing. METHODS: Chromatography, electrophoresis and spectroscopic methods were used. The cell-proliferation activity of each component isolated was measured by a [3H]thymidine uptake assay. The cell-proliferation activity of the effective component was tested on a three-dimensional raft culture (cell culture technique by which artificial epidermis is made from keratinocytes). The effect of the active component on cell migration and wound healing was observed on a monolayer of human keratinocytes and in hairless mice. RESULTS: A glycoprotein fraction was isolated and named G1G1M1DI2. It showed a single band on sodium dodecyl sulphate-polyacrylamide gel electrophoresis, with an apparent molecular weight of about 5.5 kDa. It exhibited significant [3H]thymidine uptake in squamous cell carcinoma cells. The effect of G1G1M1DI2 on cell migration was confirmed by accelerated wound healing on a monolayer of human keratinocytes. When this fraction was tested on a raft culture, it stimulated the formation of epidermal tissue. Furthermore, proliferation markers (epidermal growth factor receptor, fibronectin receptor, fibronectin, keratin 5/14 and keratin 1/10) were markedly expressed at the immunohistochemical level. The glycoprotein fraction enhanced wound healing in hairless mice by day 8 after injury, with significant cell proliferation. CONCLUSIONS: It is considered that this glycoprotein fraction is involved in the wound-healing effect of aloe vera via cell proliferation and migration.

Aloe↗
PubMed2001

Vitamin C prevents radiation-induced endothelium-dependent vasomotor dysfunction and de-endothelialization by inhibiting oxidative damage in the rat.

1. The present study was undertaken to determine whether endothelial function or morphology was altered in aortic rings of rats after irradiation, to investigate the mechanism of radiation effects on the endothelium and to examine the effect of vitamin C treatment against radiation-induced damage of the endothelium. 2. Female Sprague-Dawley rats were randomized into four groups (control, radiation, radiation + vitamin C, radiation + vitamin C + NG-nitro-L-arginine methyl ester (L-NAME); n = 10 for each group and n = 7 for the control group) and were irradiated with 10 Gy of 137Cs as a radiation source. Segments of the thoracic aorta were obtained and isometric tension, levels of 8-hydroxydeoxyguanosine (OH-dG) and immunohistochemical staining were measured. 3. Irradiation significantly impaired the acetylcholine-induced vasodilation of aortic segments, an effect that could be prevented by pretreatment with vitamin C (500 mg/kg per day). This beneficial effect of vitamin C was abolished by the addition of L-NAME (100 microg/kg per day), an inhibitor of nitric oxide (NO) synthesis. Irradiation significantly increased the level of OH-dG in the aorta (1.02 +/- 0.27 vs 2.61 +/- 0.78 OH-dG/105 deoxyguanosine (dG) for control and irradiated tissues, respectively; P < 0.01), an increase that was prevented by vitamin C treatment (1.59 +/- 0.23 OH-dG/105 dG; P < 0.01). Irradiation caused significant de-endothelialization (von Willebrand factor (vWF) staining was 93 +/- 7 vs 100% in irradiated and control tissues, respectively; P < 0.05) and this was prevented by vitamin C treatment (vWF staining 98 +/- 3%; P < 0.05). 4. Radiation caused endothelial damage and impaired NO production through oxidative injury, resulting in a selective impairment of endothelial-dependent vasodilation that could be prevented by vitamin C, partly through anti-oxidant mechanisms.

Acetylcholine↗
PubMed2001

Hepatic cytoreduction followed by a novel long-acting somatostatin analog: a paradigm for intractable neuroendocrine tumors metastatic to the liver.

BACKGROUND: Optimal management of symptomatic neuroendocrine tumors that metastasize to the liver is controversial. We investigated aggressive hepatic cytoreduction and postoperative administration of octreotide long-acting release (LAR), a long-acting somatostatin analog. METHODS: Between December 1992 and August 2000, 31 patients underwent hepatic surgical cytoreduction (20 carcinoid, 10 islet cell, and 1 medullary). All patients had progressive symptoms refractory to conventional therapy. RESULTS: Hepatic cytoreduction (resection, cryosurgery, and/or radiofrequency ablation) eliminated symptoms in 27 patients (87%) and decreased secretion of hormones by an overall mean of 59%. When minor symptoms returned and/or hormonal levels increased during follow-up, adjuvant therapy was started. Ten patients received adjuvant octreotide LAR once a month, and 21 received other adjuvants. At a median postoperative follow-up of 26 months, 16 patients had progressive/recurrent disease, 13 had died of their disease, and 2 remained free of disease. Median symptom-free interval was 60 months (95% confidence interval, 48-72) with octreotide LAR and 16 months (95% confidence interval, 10-29) with other adjuvants (P = .0007). Two-year symptom-free survival rate was 100% with octreotide LAR and 33% with other adjuvants. CONCLUSIONS: Hepatic surgical cytoreduction can palliate progressive symptoms associated with liver metastases from intractable neuroendocrine tumors. Postoperative adjuvant therapy with octreotide LAR can prolong symptom-free survival.

Adult↗
PubMed2001

Mixed infiltrative and obstructive disease on high-resolution CT: differential diagnosis and functional correlates in a consecutive series.

Fourteen of 400 consecutive patients having high-resolution computed tomography (HRCT) with expiratory images showed findings of infiltrative lung disease on inspiratory HRCT and air trapping on expiratory CT. Diagnoses included hypersensitivity pneumonitis, sarcoidosis, atypical infection, and pulmonary edema. The extent of infiltrative abnormalities and air trapping were correlated with pulmonary function tests (PFT) in 11 patients. PFT indicated a mixed pattern in five, an obstructive pattern in three, and a restrictive pattern in three. Forced expiratory volume (FEV) in 1 second/forced vital capacity (FVC) correlated significantly with the extent of air-trapping (r = 0.60; p = 0.05). The extent of infiltrative abnormalities correlated significantly and negatively with forced vital capacity (r = -0.82, p = 0.002), FEV1 (r = -0.59, p = 0.05), total lung capacity (TLC) (r = -0.67, p = 0.05), and DLCO (r = -0.75, p = 0.02). Findings of lung infiltration on inspiratory HRCT scans and air trapping on expiratory CT correlated respectively with PFT measures of restrictive and obstructive lung disease.

Adult↗
PubMed2001

CT differentiation of pneumonic-type bronchioloalveolar cell carcinoma and infectious pneumonia.

The objective was to analyse the potential of CT to distinguish pneumonic-type bronchioloalveolar cell carcinoma (BAC) from infectious pneumonia. The study consisted of 21 patients with pathologically proven BAC and 30 patients with infectious pneumonia. Both groups of patients had patchy or diffuse consolidation of more than half the area of a lobe or lobes on CT. CT findings in these two groups were compared with regard to morphological appearance, including CT angiogram, air bronchogram, mucous bronchogram, contrast enhancement pattern, pseudocavitation, cavity with air-fluid level, location, satellite lesion, ground-glass opacity and bulging of the interlobar fissure. Air-filled bronchi were morphologically analysed as dilatation, stretching, sweeping, widening of the branching angle, squeezing and crowding. Lymphadenopathy and pleural effusion were also analysed. CT findings favouring the diagnosis of BAC included an air-filled bronchus within the consolidation with stretching, squeezing, sweeping, widening of the branching angle and bulging of the interlobar fissure (p<0.05). It is concluded that CT may be helpful in differentiating pneumonic-type BAC from infectious pneumonia if the air-filled bronchus within the consolidation shows stretching, squeezing, widening of the branching angle or bulging of the interlobar fissure.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed2001

Effects of insulin and antioxidant on plasma 8-hydroxyguanine and tissue 8-hydroxydeoxyguanosine in streptozotocin-induced diabetic rats.

Cumulating evidence suggests that enhanced oxidative stress may contribute to diabetic angiopathy. The levels of 8-hydroxydeoxyguanosine (8-OHdG) and 8-hydroxyguanine (8-OHG), indicators of oxidative DNA damage, in tissue or body fluid are increased in diabetic patients. However, it is unclear whether plasma 8-OHG correlates with tissue 8-OHdG and whether insulin or antioxidant treatment reduces plasma 8-OHG in diabetic state. In this study, we measured the 8-OHG levels in plasma as well as the 8-OHdG levels in liver and kidney in streptozotocin-induced diabetic rats (DR) treated with insulin (DR+I), insulin and probucol (DR+I/P), or insulin and vitamin E (DR+I/E). There was a correlation between plasma 8-OHG levels and tissue 8-OHdG levels (plasma 8-OHG vs. liver 8-OHdG: r = 0.64, P < 0.001; plasma 8-OHG vs. kidney 8-OHdG: r = 0.38, P = 0.06). DR had levels of plasma 8-OHG that were three times higher than control rats (CR), whereas they had levels of tissue 8-OHdG that were approximately 1.5-2 times higher. Plasma 8-OHG levels in DR were almost normalized by insulin treatment, although insulin partially corrected hyperglycemia (plasma 8-OHG: CR 3.3 +/- 2.7 pmol/ml; DR 10.4 +/- 2.3 pmol/ml, P < 0.05 vs. CR; DR with insulin 3.6 +/- 1.0 pmol/ml, P < 0.05 vs. DR). However, tissue 8-OHdG levels in DR were significantly decreased by combined treatment with insulin and antioxidant (probucol or vitamin E), but not by insulin treatment alone. This data suggests that plasma 8-OHG could be a useful biomarker of oxidative DNA damage in diabetic subjects. The mechanism of differential response of plasma 8-OHG and tissue 8-OHdG to insulin and antioxidant treatment remains to be elucidated.

8-Hydroxy-2'-Deoxyguanosine↗