mlsa-iai-msu-lab/ru_sci_bench_zho_cite_reranking huggingface dataset:
Error model identification of inertial navigation platform based on errors-in-variables model

Because the real input acceleration cannot be obtained during the error model identification of inertial navigation platform, both the input and output data contain noises. In this case, the conventional regression model and the least squares (LS) method will result in bias. Based on the models of inertial navigation platform error and observation error, the errors-in-variables (EV) model and the total least squares (TLS) method are proposed to identify the error model of the inertial navigation platform. The estimation precision is improved and the result is better than the conventional regression model based LS method. The simulation results illustrate the effectiveness of the proposed method.
Multislice behavioral modeling based on envelope domain for power amplifiers

An envelope domain multislice behavioral modeling is introduced. The tradition AM-AM and AM-PM characteristics of power amplifiers are extended to envelope domain and base-band filter is applied to distortion complex envelope signal for description of the envelope memory effect. Using traditional one and two-tone tests, the coefficients of nonlinear model and the FIR filter can be extracted. At last the model has been applied to a 10 W WCDMA power amplifier to predict its output signal. And simulation results show that the model output conforms very well to the traditional transistor level simulation results.
Ponseti方法治疗先天性马蹄内翻足研究进展

1948年Iowa大学的Ponseti教授通过对先天性马蹄内翻足(congenital talipes equinovarus)功能性解剖学的深入研究,逐渐发展了先天性马蹄内翻足的Ponseti系列手法矫正加石膏固定的治疗方法,在过去50年全世界很多研究文献报道Ponseti疗法出色的长期与短期治疗效果,有超过70%的患儿经过至少30年的随访具有较好的效果.充分证实了Ponseti疗法是一种简单、有效、损伤小、经济的方法.
交叉V形皮瓣在臀部联体儿分离手术中的应用

联体儿分离造成皮肤缺损的覆盖是分离手术中面临的主要挑战之一 [1].最近,我们成功地使用交叉"V"形皮瓣完成了1例臀部联体儿分离手术的皮肤覆盖,现报告如下.
前庭大腺癌一例并文献复习

外阴癌的发生率极低,约占女性全身恶性肿瘤的1%,占女性生殖道恶性肿瘤的3%～5%.外阴癌以鳞状细胞癌最多见,占8O%～89%,前庭大腺癌仅占4%～7%~([1-4]),治疗方案参照外阴癌,但尚存在一定的争论.
水稻灌浆期冠-气温差与土壤水分和气象因子的关系

在水稻灌浆结实期进行不同梯度水分胁迫处理,研究该时期水稻冠-气温差(冠层-空气温差)与土壤水分及气象因子间的关系.结果表明,灌浆期水稻冠-气温差与土壤水分含量关系密切,总体来说,土壤含水量越低,冠层温度越高,冠-气温差的算术值越大,而且冠层温度一般来说都低于气温,灌浆前期表现得尤为明显.冠层温度与气象因子中的大气温度、太阳辐射呈极显著正相关,与空气湿度呈极显著负相关,与风速呈负相关但不显著.一天中,不同水分处理间冠-气温差差别最大的时间在各灌浆时期表现不同,但基本集中于12:00～15:00.
大豆分离蛋白涂膜保鲜大蒜米技术研究

采用大豆分离蛋白作为涂膜保鲜材料,在常温条件下研究不同浓度的保鲜膜材料对大蒜米贮藏期间主要理化特性变化的影响.结果表明,5.0%和7.0%浓度的大豆分离蛋白膜都可有效抑制大蒜米的呼吸强度,保持大蒜米的水分含量、可溶性固形物含量、总糖含量和还原糖含量.实际应用中采用5.0%的大豆分离蛋白涂膜大蒜米,可达到较为理想的保鲜效果.
长期有机无机肥配施对红壤稻田土壤重金属的影响

以中国科学院桃源农业生态试验站的长期定位试验为依托,分析了施用纯化肥(CK、N、NP、NPK)和有机无机肥配施(C、N+C、NP+C、NPK+C) 8个处理对稻田土壤Zn、Cu、Cd、Pb全量、有效态含量以及有机质(TOC)和活性有机质(热水可提取碳,HWC)的影响,并探讨了其相关性.结果表明:(1)与纯化肥处理相比,配施有机肥对Zn、Cu、Pb全量的影响不明显,但全Cd含量显著降低,Zn、Cu、Cd有效态含量显著提高(P<0.05);(2)化肥配施程度对重金属全量和有效态含量无明显影响;(3)施用有机肥使土壤TOC和HWC显著增加(P<0.05).相关分析表明,TOC和HWC与Zn、Cu、Cd有效态含量呈显著(P<0.05)或极显著(P<0.01)正相关,与全Cd含量呈显著负相关.土壤有机质对重金属有明显的"活化作用",因此在重金属本底值较高的稻田中应慎用有机肥.
KI和I_2对红提葡萄贮藏过程中SO_2伤害的防止效果

红提葡萄采前分别喷淋0.5% KI、0.5% KI与0.5% I_2混合物,入贮时在包装袋内放入7袋SO_2类保鲜剂CT_2(处理T1、T2);葡萄采前不作处理,入贮时在包装袋内放入1gI_2和7袋CT_2,I_2装入密闭的塑料小袋内,在袋上扎1个直径为1 mm的透眼(处理T3).以上每个处理5 kg果穗.处理T1、T2和T3,在温度为-1 ℃、相对湿度为90%～95%条件下贮藏180 d,和对照CK1(采前不作处理,7袋CT_2)、CK2(采前喷淋蒸馏水,7袋CT_2)相比较:漂白指数分别比对照CK1和CK2低44.16%和43.44%、66.24%和65.80%、58.88%和58.35%.SO_2配合以上药剂并没有削弱它的防腐效果,I_2还增强了它的防腐效果;KI增强了SO_2的防褐变效果,I_2削弱SO_2的防褐变效果.
NaCl胁迫对葛藤生长和生理指标的影响

以葛藤盆栽幼苗为试验材料,研究了NaCl胁迫对葛藤生长和生理指标的影响.结果表明:NaCl胁迫显著抑制了葛藤幼苗的生长,随着NaCl浓度的升高,葛藤生长量呈下降趋势,但低盐浓度(<0.6%)间差异不明显;叶绿素含量在高盐浓度(>0.6%)下显著下降;叶片细胞膜透性、丙二醛(MDA)以及游离脯氨酸(Pro)含量都随NaCl浓度升高而上升;葛藤的耐盐上限为1.0%～1.2%.
套袋对梨果实生长及品质的影响

以绿皮梨品种西子绿和褐皮梨品种丰水为试材,研究套袋对梨果实生长及品质的影响.结果表明:花后10 d套袋,至花后60 d,套袋果鲜重高于未套袋果;花后60 d至果实成熟,未套袋果鲜重增加较快,高于套袋果;果实干物质重,只有品种丰水花后27 d套袋果实干物质重高于未套袋果,干物重变化趋势与鲜重基本一致;果实套袋后,果皮叶绿素a含量急剧下降,远低于未套袋果,叶绿素b含量下降缓慢,后期高于未套袋果,套袋后,改变了叶绿素含量,对幼果光合作用造成一定影响,但果重变化动态表明,并不是造成单果重差异的主要原因;套袋后,果实可溶性固形物和还原糖含量下降,可滴定酸含量和果实硬度增加.
NaCl和pH值对北美海蓬子种子萌发的影响

研究了NaCl、pH值、TDZ和光照对北美海蓬子种子发芽的影响,结果表明:北美海蓬子的种子在150 mmol/L的NaCl浓度时发芽率最高,随NaCl浓度增加发芽率呈下降的趋势,NaCl浓度至400 mmol/L(相当于全海水中的NaCl浓度)时,仍有21.67%的发芽率;pH值7.0最适于北美海蓬子的种子发芽,pH值高于7.0时,随pH值升高,发芽率呈下降趋势,海蓬子根系和幼苗生长受到抑制;此外,光照有利于北美海蓬子种子萌发;在光照条件下TDZ对北美海蓬子种子的萌发无明显的促进作用,在黑暗的条件下,可以促进北美海蓬子种子萌发.
正交设计优化番茄基因组DNA SSR-PCR反应体系

以21份番茄品种为材料,应用正交试验设计对影响番茄SSR-PCR的主要参数进行优化,建立适于番茄的SSR反应体系和扩增程序.在15 μl 体系中各反应的最适合含量为: 2.5 μlddH_2O,1 μl40 ng模板DNA,3 μl200 μmol/L dNTP,3 μl0.8 μmol/L SSR引物,0.1 μl0.5 U/μlTaq DNA聚合酶,1.5 μl 10×PCR Buffer,0.9 μl1.5 mmol/L MgCl_2.PCR适宜扩增程序为: 94 ℃预变性2 min;94 ℃变性1 min,45 ℃退火25 s,共35个循环;68 ℃延伸25 s,68 ℃延伸10 min,然后4 ℃保存.利用此反应体系对21个番茄品种进行PCR扩增并电泳检测,扩增结果清晰且有较高的多态性,表明该体系适合番茄的遗传多样性研究.
From the Gla domain to a novel small-molecule detector of apoptosis

Apoptosis plays a pivotal role in the etiology or pathogenesis of numerous medical disorders, and thus, targeting of apoptotic cells may substantially advance patient care. In our quest for novel low-molecular-weight probes for apoptosis, we focused on the uncommon amino acid γ-carboxyglutamic acid (Gla), which plays a vital role in the binding of clotting factors to negatively charged phosphofipid surfaces. Based on the aikyl-malonic acid motif of Gia, we have developed and now present ML-10 (2-(5-fluoro-pentyl)-2-methyl-malonic acid, MW=206 Da), the prototypical member of a novel family of small-molecule detectors of apoptosis. ML-10 was found to perform selective uptake and accumulation in apoptotic cells, while being excluded from either viable or necrotic cells. ML-10 uptake correlates with the apoptotic hallmarks of caspase activation, Annexin-V binding and disruption of mitochondrial membrane potential. The malonate moiety was found to be crucial for ML-10 function in apoptosis detection. ML-10 responds to a unique complex of features of the cell in early apoptosis, comprising irreversible loss of membrane potential, permanent acidification of cell membrane and cytoplasm, and preservation of membrane integrity. ML-10 is therefore the most compact apoptosis probe known to date. Due to its fluorine atom, ML-10 is amenable to radiolabeling with the 18SF isotope, towards its potential future use for clinical positron emission tomography imaging of apoptosis.
Extramedullary plasmocytoma associated with a massive deposit of amyloid in the duodenum

We report a rare case of extramedullary plasmocytoma associated with a massive deposit of amyloid in the duodenum. A 72-year-old Japanese man was admitted to our hospital presenting with a 3-mo history of epigastric pain, vomiting and weight loss. On computed tomography (CT) a wall thickening of the fourth part of the duodenum was observed. Multiple biopsies obtained from the lesion showed infiltration of plasma cells and lymphocytes, but they were not conclusive. The patient underwent resection of the lesion and, on histopathological examination, the lesion consisted of a dense and diffuse infiltrate of plasma cells and a few admixed lymphocytes with reactive follicles extending to the muscular propria. An extensive deposition of amyloid was also observed. Immunohistochemical stains revealed that a few plasmacytoid cells showed λ light chain staining, though most were κ light chain positive. These cells also were positive for CD138 and CD56 but negative for CD20 and CD79. The findings were consistent with extramedullary plasmocytoma associated with a massive deposit of amyloid in duodenum. A subsequent workup for multiple myeloma was completely negative. The patient showed no signs of local recurrence or dissemination of the disease after 12 mo follow-up. Because of the association of plasmocytoma and amyloidosis, the patient must be followed up because of the possible systemic involvement of the neoplasm and amyloidosis in future.
Prophylaxis with carnosol attenuates liver injury induced by intestinal ischemia/reperfusion

AIM: To investigate the possible protective effects of carnosol on liver injury induced by intestinal ischemia reperfusion (I/R).METHODS: Rats were divided randomly into three experimental groups: sham, intestinal I/R and carnosol treatment ( n = 18 each). The intestinal I/R model was established by clamping the superior mesenteric artery for 1 h. In the carnosol treatment group, surgery was performed as in the intestinal I/R group, with intraperitoneal administration of 3 mg/kg carnosol 1 h before the operation. At 2, 4 and 6 h after reperfusion, rats were killed and blood, intestine and liver tissue samples were obtained. Intestine and liver histology was investigated. Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and interleukin (IL)-6 were measured. Liver tissue superoxide dismutase (SOD) and myeloperoxidase (MPO) activity were assayed. The liver intercellular adhesion molecule-1 (ICAM-1) and nuclear factor κB (NF-κB) were determined by immunohistochemical analysis and western blot analysis.RESULTS: Intestinal I/R induced intestine and liver injury, characterized by histological changes, as well as a significant increase in serum AST and ALT levels. The activity of SOD in the liver tissue decreased after I/R, which was enhanced by carnosol pretreatment. In addition, compared with the control group, carnosol markedly reduced liver tissue MPO activity and serum IL-6 level, which was in parallel with the decreased level of liver ICAM-1 and NF-κB expression. CONCLUSION: Our results indicate that carnosol pretreatment attenuates liver injury induced by intestinal I/R, attributable to the antioxidant effect and inhibition of the NF-κB pathway.
Characterization of clarithromycin resistance in Malaysian isolates of Helicobacterpylori

AIM: To characterize the types of mutations present in the 23S rRNA genes of Malaysian isolates of clarithromycin-resistant Helicobacter pylori (H pylori).METHODS: Clarithromycin susceptibility of H pylori isolates was determined by E test. Analyses for point mutations in the domain V of 23S rRNA genes in clarithromycin-resistant and -sensitive strains were performed by sequence analysis of amplified polymerase chain reaction products. Restriction fragment length polymorphism was performed using BsaⅠ and Mbo Ⅱ enzymes to detect restriction sites that correspond to the mutations in the clarithromycin-resistant strains.RESULTS: Of 187 isolates from 120 patients, four were resistant to clarithromycin, while 183 were sensitive. The MIC of the resistant strains ranged from 1.5 to 24 μg/mL. Two isolates had an A2142G mutation and another two had A2143G mutations. A T2182C mutation was detected in two out of four clarithromycin-resistant isolates and in 13 of 14 clarithromycin-sensitive isolates. Restriction enzyme analyses with Bsa I and Mbo n were able to detect the mutations.CONCLUSION: Clarithromycin resistance is an un-common occurrence among Malaysian isolates of Hpylori strains and the mutations A2142G and A2143G detected were associated with low-level resistance.
Human papilloma virus and esophageal carcinoma in a Latin-American region

AIM: To investigate the presence of high-risk human papilloma virus (HPV) in esophageal squamous cell carcinomas (ESCCs) in a non-selected Mexican population.METHODS: Cases with a pathological diagnosis of squamous cell carcinoma of the esophagus were obtained from Department of Pathology files, at the National Cancer Institute in Mexico City during the period between 2000 and 2008. Slides from each case were reviewed and cases with sufficient neoplastic tissue were selected for molecular analysis. DNA was extracted from paraffin-embedded tissue samples for polymerase chain reaction analysis to detect HPV DNA sequences. Demographic and clinical data of each patient were retrieved from corresponding clinical records.RESULTS: HPV was detected in 15 (25%) of ESCCs. HPV-16 was the most frequently observed genotype, followed by HPV-18; HPV-59 was also detected inone case. Unfortunately, HPV genotype could not be established in three cases due to lack of material for direct sequencing, although universal primers detected the presence of HPV generic sequences. No low-risk HPV genotypes were found nor was HPV-16/18 co-infection. HPV presence in ESCC was not significantly associated with gender, age, alcohol consumption, smoking, anatomic location, or histologic grade. All patients belonged to low and very low socioeconomic strata, and were diagnosed at advanced disease stage. Male patients were most commonly affected and the male:female ratio in HPV-positive ESCC increased twofold in comparison with HPV-negative cases (6.5:1 vs 3.1:1).CONCLUSION: High prevalence of high-risk HPV in ESCC in Mexico does not support the hypothesis that HPV-associated ESCC is more common in areas with higher ESCC incidence rates.
Anti-Helicobacter pylori therapy followed by celecoxib on progression of gastric precancerous lesions

AIM:To evaluate whether celecoxib,a selective cyclooxygenase 2 (COX-2) inhibitor,could reduce the severity of gastric precancerous lesions following Helicobacter pylori (H pylori) eradication.METHODS:H pylori-eradicated patients with gastric precancerous lesions randomly received either celecoxib (n=30) or placebo (n=30) for up to 3 mo.COX-2 expression and activity was determined by immunostaining and prostaglandin E_2 (PGE_2) assay,cell proliferation by Ki-67 immunostaining,apoptosis by TUNEL staining and angiogenesis by microvascular density (MVD) assay using CD31 staining.RESULTS:COX-2 protein expression was significantly increased in gastric precancerous lesions (atrophy,intestinal metaplasia and dysplasia,respectively) compared with chronic gastritis,and was concomitant with an increase in cell proliferation and angiogenesis.A significant improvement in precancerous lesions was observed in patients who received celecoxib compared with those who received placebo (P<0.001).Of these three changes,84.6% of sites with dysplasia regressed in patients treated with celecoxib (P=0.002) compared with 60% in the placebo group,suggesting that celecoxib was effective on the regression of dysplasia.COX-2 protein expression (P<0.001) and COX-2 activity (P<0.001) in the gastric tissues were consistently lower in celecoxib-treated patients compared with the placebo-treated subjects.Moreover,it was also shown that celecoxib suppressed cell proliferation (P<0.01),induced cell apoptosis (P<0.01) and inhibited angiogenesis with decreased MVD (P<0.001).However,all of these effects were not seen in placebo-treated subjects.Furthermore,COX-2 inhibition resulted in the up-regulation of PPARγ expression,a protective molecule with anti-neoplastic effects.CONCLUSION:H pylori eradication therapy followed by celecoxib treatment improves gastric precancerous lesions by inhibiting COX-2 activity,inducing apoptosis,and suppressing cell proliferation and angiogenesis.
Size does not determine the grade of malignancy of early invasive colorectal cancer

AIM:To clarify the clinicopathological characteristics of small and large early invasive colorectal cancers (EICRCs),and to determine whether malignancy grade depends on size.METHODS:A total of 583 consecutive EI-CRCs treated by endoscopic mucosal resection or surgery at the National Cancer Center Hospital between 1980 and 2004 were enrolled in this study.Lesions were classified into two groups based on size:small (≤10 mm) and large (> 10 mm).Clinicopathological features,incidence of lymph node metastasis (LNM) and risk factors for LNM,such as depth of invasion,lymphovascular invasion (LVI) and poorly differentiated adenocarcinoma (PDA) were analyzed in all resected specimens.RESULTS:There were 120 (21%) small and 463 (79%) large lesions.Histopathological analysis of the small lesion group revealed submucosal deep cancer (sm:≥1000 μm) in 90 (75%) cases,LVI in 26 (22%) cases,and PDA in 12 (10%) cases.Similarly,the large lesion group exhibited submucosal deep cancer in 380 (82%) cases,LVI in 125 (27%) cases,and PDA in 79 (17%) cases.The rate of LNM was 11.2% and 12.1% in the small and large lesion groups,respectively.CONCLUSION:Small EI-CRC demonstrated the same aggressiveness and malignant potential as large cancer.
Diet, ageing and genetic factors in the pathogenesis of diverticular disease

Diverticular disease (DD) is an age-related disorder of the large bowel which may affect half of the population over the age of 65 in the UK. This high prevalence ranks it as one of the most common bowel disorders in western nations. The majority of patients remain asymptomatic but there are sociated life-threatening co-morbidities, which, given the large numbers of people with DD, translates into a considerable number of deaths per annum. Despite this public health burden, relatively little seems to be known about either the mechanisms of development or causality. In the 1970s, a model of DD formulated the concept that diverticula occur as a onsequence of pressureinduced damage to the colon wall amongst those with a low intake of dietary fiber. In this review, we have examined the evidence regarding the influence of ageing, diet, inflammation and genetics on DD development. We argue that the evidence supporting the barotrauma hypothesis is largely anecdotal. We have also identified several gaps in the knowledge base which need to be filled before we can complete a model for the etiology of diverticular disease.
Sclerosing cholangitis associated with autoimmune pancreatitis differs from primary sclerosing cholangitis

AIM: To clarify the characteristic features of biliary lesions in patients with autoimmune pancreatitis (AIP) and compare them with those of primary sclerosing cholangitis (PSC). METHODS: The clinicopathological characteristics of 34 patients with sclerosing cholangitis (SC) associated with AIP were compared with those of 4 patients with PSC. RESULTS: SC with AIP occurred predominantly in elderly men. Obstructive jaundice was the most frequent initial symptom in SC with AIP. Only SC patients with AIP had elevated serum IgG4 levels, and sclerosing diseases were more frequent in these patients. SC patients with AIP responded well to steroid therapy. Segmental stenosis of the lower bile duct was observed only in SC patients with AIP, but a beaded and prunedtree appearance was detected only in PSC patients. Dense infiltration of IgG4-positive plasma cells was detected in the bile duct wall and the periportal area, as well as in the pancreas, of SC patients with AIP. CONCLUSION: SC with AIP is distinctly different from PSC. The two diseases can be discriminated based on cholangiopancreatographic findings and serum IgG4 levels.
Repair of a mal-repaired biliary injury: A case report

Iat rogenic bi le-duct injury pos t- laparoscopi c cholecystectomy remains a major serious complication with unpredictable long-term results. We present a patient who underwent laparoscopic cholecystectomy for gal lstones, in which the biliary injury was recognized intraoperatively. The surgical procedure was converted to an open one. The first surgeon repaired the injury over a T-tube without recognizing the anatomy and type of the biliary lesion, which led to an unusual biliary mal-repair. Immediately postoperatively, the abdominal drain brought a large amount of bile. A T-tube cholangiogram was performed. Despite the contrast medium leaking through the abdominal drain, the mal-repair was unrecognized. The patient was referred to our hospital for biliary leak. Ultrasound and cholangiography was repeated, which showed an unanatomical repair (right to left hepatic duct anastomosis over the T-tube), with evidence of contrast medium coming out through the abdominal drain. Eventually the patient was subjected to a definitive surgical treatment. The biliary continuity was re-established by a Roux-en-Y hepaticojejunostomy, over transanastomotic external biliary stents. The patient is now doing well 4 years after the second surgical procedure. In reviewing the literature, we found a similar type of injury but we did not find a similar surgical mal-repair. We propose an algorithm for the treatment of early and late biliary injuries.
No association between cyclooxygenase-2 and uridine diphosphate glucuronosyltransferase 1A6 genetic polymorphisms and colon cancer risk

AIM: To investigate the association of variations in the cyclooxygenase-2 (COX2) and uridine diphosphate glucuronosyltransferase 1A6 (UGT1A6) genes and nonsteroidal anti-inflammatory drugs (NSAIDs) use with risk of colon cancer. METHODS: NSAIDs, which are known to reduce the risk of colon cancer, act directly on COX2 and reduce its activity. Epidemiological studies have associated variations in the COX2 gene with colon cancer risk, but others were unable to replicate this finding. Similarly, enzymes in the UGT1A6 gene have been demonstrated to modify the therapeutic effect of NSAIDs on colon adenomas. Polymorphisms in the UGT1A6 gene have been statistically shown to interact with NSAID intake to influence risk of developing colon adenomas, but not colon cancer. Here we examined the association of tagging single nucleotide polymorphisms (SNPs) in the COX2 and UGT1A6 genes, and their interaction with NSAID consumption, on risk of colon cancer in a population of 422 colon cancer cases and 481 population controls. RESULTS: No SNP in either gene was individually statistically significantly associated with colon cancer, nor did they statistically significantly change the protective effect of NSAID consumption in our sample. Like others, we were unable to replicate the association of variants in the COX2 gene with colon cancer risk ( P > 0.05), and we did not observe that these variants modify the protective effect of NSAIDs ( P > 0.05). We were able to confirm the lack of association of variants in UGT1A6 with colon cancer risk, although further studies will have to be conducted to confirm the association of these variants with colon adenomas.CONCLUSION: Our study does not support a role of COX2 and UGT1A6 genetic variations in the development of colon cancer.
Embolization of an unusual metastatic site of hepatocellular carcinoma in the humerus

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world. This case documents an unusual metastatic presentation of HCC in the humerus. Preoperative palliative arterial embolization of the tumor was performed to arrest severe tumor bleeding caused by the biopsy. Embolization turned out to be useful also in limiting/preventing potential uncontrolled bleeding during subsequent amputation.
Pneumocystis jiroveci pneumonia and pneumomediastinum in an anti-TNFα naive patient with ulcerative colitis

We report the case of a 21-year-old man who was noted to have pneumomediast inum dur ing an admission for an acute flare of ulcerative colitis. At that time, he was on maintenance treatment with azathioprine at a dose of 1.25 mg/kg per day, and had not received supplementary steroids for 9 mo. He had never received anti-tumor necrosis factor (TNF)α therapy. Shortly after apparently effective treatment with intravenous steroids and an increased dose of azathioprine, he developed worsening colitic and new respiratory symptoms, and was diagnosed with Pneumocystis jiroveci ( carinii) pneumonia (PCP). Pneumomediastinum is rare in immunocompetent hosts, but is a recognized complication of PCP in human immunodeficiency virus (HIV) patients, although our patient 's HIV test was negative. Treatment of PCP with co-trimoxazole resulted in resolution of both respiratory and gastrointestinal symptoms, without the need to increase the steroid dose. There is increasing vigilance for opportunistic infections in patients with inflammatory bowel disease following the advent of anti-TNFα therapy. This case emphasizes the importance of considering the possibility of such infections in all patients with inflammatory bowel disease, irrespective of the immunosuppressants they receive, and highlights the potential of steroid-responsive opportunistic infections to mimic worsening colitic symptoms in patients with ulcerative colitis.