Predictors of permanent stoma creation in patients with mid or low rectal cancer: results of a multicentre cohort study with preoperative evaluation of anal function.

AIM: Preoperative factors predictive of permanent stoma creation were investigated in a long-term follow-up of patients with mid or low rectal cancer. METHOD: We included patients who underwent radical resection for mid or low rectal cancer with available data for preoperative anal function measured by manometry and Faecal Incontinence Severity Index questionnaire between January 2005 and December 2015 in three tertiary referral hospitals. A permanent stoma was defined as a stoma present until the patient's last follow-up visit or death. Preoperative factors that predicted permanent stoma creation were analysed. RESULTS: Over a median follow-up of 57.4 months (range 12-143 months), a permanent stoma was created in 144/577 (25.0%) patients, including 89 (15.4%) who underwent abdominoperineal resection, one (0.2%) who underwent Hartmann's operation without reversal, 15 (2.6%) with a diverting ileostomy at the time of initial sphincter-preserving surgery without undergoing stoma reversal, and 39 (6.8%) who underwent permanent ileostomy formation after sphincter-preserving surgery. Patients with permanent stoma creation had a shorter tumour distance from the anal verge (P < 0.001), larger tumour size (P = 0.020) and higher preoperative Faecal Incontinence Severity Index score (P = 0.020). On multivariable analysis, tumour distance from the anal verge predicted permanent stoma formation (relative risk 0.53 per centimetre increase; 95% confidence interval 0.46-0.60; P < 0.001) but preoperative anal function did not. CONCLUSION: Tumour distance from the anal verge was the only preoperative determinant of permanent stoma creation in rectal cancer patients. These data may help mid and low rectal cancer patients understand the need for permanent stoma.

The impact of social media on citation rates in coloproctology.

AIM: This study aimed to investigate the association between Twitter exposure and the number of citations for coloproctology articles. METHOD: Original articles from journals using Twitter between June 2015 and May 2016 were evaluated for the following characteristics: publishing journal; article subject; study design; nationality, speciality and affiliation of the author(s); and reference on Twitter. Citation data for these articles were retrieved from Google Scholar (https://scholar.google.com) in January 2018. We performed a univariate analysis using these data followed by a multivariate, logistic regression analysis to search for factors associated with a high citation level, which was defined as accrual of more than five citations. RESULTS: Out of six coloproctology journals listed on the InCites JCR database, three (Diseases of the Colon & Rectum, Colorectal Disease and Techniques in Coloproctology) used Twitter, where 200 (49.5%) out of a total of 404 articles had been featured. Citation rates of articles that featured on Twitter were significantly higher than those that did not (11.4 ± 9.2 vs 4.1 ± 3.1, P < 0.001). In multivariate analysis, Twitter exposure (OR 8.6, P = 0.001), European Union nationality (OR 2.4, P = 0.004), Colorectal Disease journal (OR 3.3, P = 0.005) and systematic review articles (OR 3.4, P = 0.009) were associated with higher citation levels. CONCLUSION: Article exposure on Twitter was strongly associated with a high citation level. Medical communities should encourage journals as well as physicians to actively utilize social media to expedite the spread of new ideas and ultimately benefit medical society as a whole.

Elevated Microsatellite Alterations at Selected Tetranucleotide Repeats (EMAST) and Microsatellite Instability in Patients with Colorectal Cancer and Its Clinical Features.

PURPOSE: Recently, a different type of microsatellite instability (MSI) instability designated 'elevated microsatellite alterations at selected tetranucleotide repeats' (EMAST) has been reported in several neoplasms, but its clinical implications remain unclear. We aimed to determine the relationships among EMAST, MSI and clinicopathologic characteristics, including oncologic outcomes, in colorectal cancer (CRC). MATERIALS AND METHODS: We evaluated 100 sporadic CRC cases subjected to surgery using five markers (MYCL1, D9S242, D20S85, D8S321, and D20S82) for EMAST and the Bethesda panel for MSI status. Immunohistochemical detection of hMSH3, c-erbB2, EGFR and thymidylate synthase was performed. Clinical characteristics and prognostic relevance were assessed. RESULTS: We identified 22 EMAST-positive tumors (22.0%) and 32 MSI-high (MSI-H) tumors (32.0%). EMAST was more frequent in colon cancer than rectal cancer (p=0.033), and associated with MSI-H phenotype (p<0.001), low expression of hMSH3 (p=0.004), and overexpression of thymidylate synthase (p=0.006). Among the 38 MSI-L tumors, only one (4.5%) showed EMAST. Long-term oncologic results in terms of overall and disease-free survival were similar between EMAST and non-EMAST tumors. CONCLUSION: EMAST is more closely related to MSI-H than MSI-L or MSS status. The clinical and molecular characteristics of EMAST were distinct in terms of tumor location, thymidylate synthase expression, MSI status and hMSH3 expression. Our preliminary findings support the utility of EMAST as a new potential classifier in CRC.

Scaffold protein FHL2 facilitates MDM2-mediated degradation of IER3 to regulate proliferation of cervical cancer cells.

The expression of immediate early response 3 (IER3), a protein with a short half-life, is rapidly induced by various cellular stimuli. We recently reported that IER3 induces the apoptosis of cervical cancer cells and that its expression is downregulated in patients with cervical cancer. However, the molecular mechanism involved in the rapid degradation of IER3 remains unknown. Here, we demonstrate that MDM2 is an E3 ligase that interacts with IER3 and promotes its ubiquitination, followed by proteasomal degradation. Polyubiquitination of the conserved lysine 60 of IER3 is essential for its degradation. In addition, four and a half LIM domains protein 2 (FHL2) binds to both IER3 and MDM2, allowing for efficient MDM2-mediated IER3 degradation by facilitating an association between MDM2 and IER3. Moreover, IER3 induces cell cycle arrest in cervical cancer cells and its activity is further enhanced in cells in which FHL2 or MDM2 was silenced, thereby preventing IER3 degradation. The E6 and E7 oncoproteins of human papilloma virus 18 regulated IER3 expression. FHL2 expression was significantly higher in the squamous epithelium of cervical carcinoma tissues than in non-cancerous cervical tissues, whereas cervical carcinoma expression of IER3 was downregulated in this region. Thus, we determined the molecular mechanism responsible for IER3 degradation, involving a ternary complex of IER3, MDM2 and FHL2, which may contribute to cervical tumor growth. Furthermore, we demonstrated that FHL2 serves as a scaffold for E3 ligase and its substrate during the ubiquitination reaction, a function that has not been previously reported for this protein.

Comparison between a new electronic bidet and conventional sitz baths: a manometric evaluation of the anal resting pressure in normal healthy volunteers.

BACKGROUND: A bidet has been proposed as a replacement for the sitz bath. Like a sitz bath, it brings water into contact with the perineum. However, the high force of water from commercially used electronic bidets may harm the anus. We developed a new electronic bidet and evaluated its effects on anal resting pressure compared with a warm sitz bath. METHODS: Forty volunteers used the electronic bidet and sitz bath on separate days. The electronic bidet was newly designed with warm (38 °C) water and very low force (10 mN) with a fountain type of flow. Anal resting pressure at the high-pressure zone was measured before (control) and after the electronic bidet and sitz bath. Pressure changes after bidet or sitz bath were expressed as percentages compared with control. Water temperatures and rectal temperatures were also recorded. RESULTS: The anal resting pressures before the electronic bidet and sitz bath were 90.2 ± 24.6 and 88.1 ± 16.8 mmHg, respectively. At 3 min after the electronic bidet and sitz bath, the anal resting pressures were 71.3 ± 23.4 and 69.6 ± 19.8 mmHg, respectively. The pressure changes compared with the control were 78.2 ± 12.9 and 78.1 ± 12.5%, respectively, which were not significantly different. The maximal increase and minimal decrease were not significantly different. The rectal temperature was not elevated, and the water temperature decreased significantly with the sitz bath (p < 0.001). CONCLUSIONS: Our new electronic bidet may reduce the anal resting pressure much like a warm sitz bath does.

The submuscular sliding plate technique for acetabular posterior wall fractures extending to the acetabular roof.

There is extension of the Kocher-Langenbeck approach using trochanteric osteotomy for posterior wall fracture extending to acetabular roof, but it exposes to complications such as nonunion, breakage, and heterotopic ossification. The current study introduces a submuscular sliding plate technique. We retrospectively analyzed 13 patients treated with this technique. It is based on conventional method for posterior wall fracture. After reduction of roof fragment with direct visualization, a pre-contoured plate was passed through a submuscular tunnel under the gluteus medius and minimus. A small split incision was performed on the muscles, and screws were inserted with a triple trocar complex safely under fluoroscopic imaging. All patients had fracture union without complications. X-rays results showed anatomical reduction in 10 cases and imperfect reduction in 3 cases. Our results were satisfactory, particularly without heterotopic ossifications despite no prophylactic regimen of NSAID was applied and no neurological complications, so we believe that this technique is a good option for posterior wall fractures extending to the acetabular roof.

Effects of dietary protein levels for gestating gilts on reproductive performance, blood metabolites and milk composition.

This experiment was conducted to evaluate the effects of dietary CP levels in gestation under equal lysine content on reproductive performance, blood metabolites and milk composition of gilts. A total of 25 gilts (F1, Yorkshire×Landrace) were allotted to 4 dietary treatments at breeding in a completely randomized design, and fed 1 of 4 experimental diets containing different CP levels (11%, 13%, 15%, or 17%) at 2.0 kg/d throughout the gestation. Body weight of gilts at 24 h postpartum tended to increase linearly (p = 0.09) as dietary CP level increased. In lactation, backfat thickness, ADFI, litter size and weaning to estrus interval (WEI) did not differ among dietary treatments. There were linear increases in litter and piglet weight at 21 d of lactation (p<0.05) and weight gain of litter (p<0.01) and piglet (p<0.05) throughout the lactation as dietary CP level increased. Plasma urea nitrogen levels of gilts in gestation and at 24 h postpartum were linearly elevated as dietary CP level increased (p<0.05). Free fatty acid (FFA) levels in plasma of gestating gilts increased as dietary CP level increased up to 15%, and then decreased with quadratic effects (15 d, p<0.01; 90 d, p<0.05), and a quadratic trend (70 d, p = 0.06). There were no differences in plasma FFA, glucose levels and milk composition in lactation. These results indicate that increasing dietary CP level under equal lysine content in gestation increases BW of gilts and litter performance but does not affect litter size and milk composition. Feeding over 13% CP diet for gestating gilts could be recommended to improve litter growth.

Factors affecting accurate drill sleeve insertion in locking compression plates.

BACKGROUND: Accurate positioning of locking screws depends on accurate insertion of the drill sleeve into the locking compression plate (LCP). The purpose of the present study was to determine factors affecting accurate drill sleeve insertion. HYPOTHESIS: Tilting and shallow locking screw holes and combination-type holes make it difficult to insert the drill sleeve in the LCP. MATERIALS AND METHODS: Twenty-seven 3.5mm LCP metaphyseal insertion holes were selected (Philos(®), LPHP(®), DMTP(®), low-band DMTP(®) [Synthes, Solothurn, Switzerland]). Two orthopedic surgeons checked the time taken for accurate insertion of the drill sleeve into the plate. Variables relating to LCP drill sleeve insertion time were analyzed. RESULTS: It took an average 6.6seconds to insert the drill sleeve accurately in the holes. Insertion time increased with the tilt of the screw hole but not with shallowness. Insertion time in combination-type holes was longer (8.8seconds) than in single locking holes (5.6seconds). DISCUSSION: Tilted screw holes and combination-type holes affect the insertion of the drill sleeve into 3.5mm LCPs. LEVEL OF EVIDENCE: Level IV, experimental study.

Assessment of Intellectual and Visuo Spatial Abilities in Children and Adults with Williams Syndrome / Evaluación de habilidades intelectuales y visuoespaciales de niños y adultos con Síndrome de Williams

The Williams-Beuren syndrome (SWB), also known as Williams syndrome, is a contiguous gene deletion of the region 7q.11.23. The main clinical characteristics are typical faces, supravalvular aortic stenosis, failure to thrive, short stature, transient neonatal hypercalcemia, delayed language, friendly personality, hyperacusis and intellectual disability. The diagnosis of SWB is confirmed by the detection of micro deletion by different techniques of molecular cytogenetics, FISH, MLPA or polymorphic markers. This study assessed the verbal intelligence quotient (IQ) and performance and visuo-spatial skills in children and adults with WBS. The composed group was of 31 WBS patients (19 M and 12 F), whose ages ranged from 9 to 26 years (M 14.45 y). All patients had the diagnosis confirmed molecularly. The tests used were the WISC-III, WAIS-III and Rey-Osterrieth Complex Figure Test. The results indicated a total IQ ranged from 51 to 86 (M 63): 22 with mild intellectual disability, 4 with moderate intellectual disability, 4 borderlines and 1 below the normal media. All patients had marked visual-spatial deficits. The results suggest nonverbal reasoning, visuo-spatial perception, spatial representation, working memory, motor planning and executive functions are very affected in this group.

El síndrome de Williams-Beuren (SWB), también conocido como síndrome de Williams, es un síndrome de deleción de genes contiguos de la región 7q.11.23. Se caracteriza por dimorfismo facial típico asociado a anomalías cardiovasculares, personalidad amigable, hiperacusia y deficiencia intelectual. El diagnóstico del SWB es confirmado por la detección de microdeleción a partir de las diferentes técnicas de citogenética molecular: FISH, marcadores polimórficos o MLPA. Este estudio evaluó el cociente intelectual verbal y manipulativo, así como las habilidades visuoespaciales en niños y adultos con SWB. El grupo estuvo formado por 31 pacientes con SWB (19 de sexo masculino y 12 de sexo femenino), cuyas edades variaron entre 9 y 26 años (media 14.45 años). Todos los pacientes tenían el diagnóstico confirmado molecularmente. Los test utilizados fueron las escalas WISC-III, WAIS-III y el Test Figuras Complejas Rey-Osterrieth. Los resultados indicaron un cociente intelectual que osciló de 51 a 86 (media 63), distribuido así: 22 con deficiencia intelectual leve, 4 con deficiencia intelectual moderada, 4 limítrofes, 1 en la media inferior. Todos los pacientes presentaron déficit visuoespacial. Los resultados sugieren que el razonamiento no verbal, la percepción visuoespacial, la representación espacial, la memoria de trabajo, la planificación motora y las funciones ejecutivas están muy comprometidos en el grupo estudiado.

Effects of alendronate on a disintegrin and metalloproteinase with thrombospondin motifs expression in the developing epiphyseal cartilage in rats.

A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) have been reported to play a role in the degradation of aggrecan, a major component of cartilage. This study was performed to examine the effects of alendronate on the expression of ADAMTS in developing femoral epiphyseal cartilage. Primary cultured chondrocytes from this cartilage were treated with alendronate in vitro and postnatal day 1 rats were injected subcutaneously with alendronate (1 mg/kg) every second day in vivo. The number of cultured chondrocytes and their aggrecan mRNA levels were unaffected by the alendronate treatment at 10(-6) to 10(-4) M concentrations. The mRNA levels of ADAMTS-1, -2 and -9 in chondrocytes were also unaffected. However, the levels of ADAMTS-5 and -4 were reduced significantly by the same treatment. The thickness of the proliferating chondrocyte layers and the aggrecan mRNA levels in the epiphysis were unaffected by the alendronate treatment in vivo. However, the hypertrophied chondrocyte layers became significantly thicker, and the size of the secondary ossification centre was reduced significantly by the same treatment (P < 0.05). Both ADAMTS-4 and -5 mRNA expressions were also reduced significantly in vivo. The immunoreactivity against ADAMTS-4 was seen in hypertrophied chondrocytes and reduced significantly by the alendronate treatment. These results suggested that alendronate can inhibit the degradation of aggrecan in the articular cartilage by downregulating the expression of matrix enzymes such as ADAMTS-4 and -5.

Systemic herpes simplex virus infection following cadaveric renal transplantation: a case report.

Herpes simplex virus (HSV) infection usually occurs in immunocompromised or severely debilitated patients. It is not so common in patients with renal transplants. The diagnosis can only be made histologically. It usually occurs during or shortly after treatment of graft rejection with high-dose steroids. We have recently experienced a case of HSV esophagitis and nephropathy in the renal allograft biopsy, which was identified by histology, immunostaining, and electron microscopy. A 43-year-old woman underwent cadaveric renal transplantation with cyclosporine and prednisolone treatment. Twelve months later, she developed renal insufficiency and proteinuria. Allograft renal biopsy showed some evidence of acute rejection. She was treated with 3 successive days of methylprednisolone (1.0 g/d) intravenously and continued tapering of steroids. Three weeks after steroid pulse therapy, she had throat pain, oral cavity ulcer, dysphagia, and febrile sensation. Esophagoscopy revealed multiple confluent ulcers in the whole esophagus, and biopsy showed enlarged epithelial cells with prominent nuclei. Immunohistochemically, the epithelial cells were positive with a monoclonal antibody to HSV type 1. She was started on acyclovir intravenously, which was continued for a week. After a week, her symptoms began to improve and repeat endoscopy showed no residual esophagitis. A renal allograft infection with HSV can persist in heavily immunosuppressed patients with recurrent rejection episodes. HSV mainly affects tubular cells causing necrosis, a major reason for functional deterioration. A biopsy is required for diagnosis.

KNT-artificial neural network model for flux prediction of ultrafiltration membrane producing drinking water.

This paper describes the prediction of flux behavior in an ultrafiltration (UF) membrane system using a Kalman neuro training (KNT) network model. The experimental data was obtained from operating a pilot plant of hollow fiber UF membrane with groundwater for 7 months. The network was trained using operating conditions such as inlet pressure, filtration duration, and feed water quality parameters including turbidity, temperature and UV254. Pre-processing of raw data allowed the normalized input data to be used in sigmoid activation functions. A neural network architecture was structured by modifying the number of hidden layers, neurons and learning iterations. The structure of KNT-neural network with 3 layers and 5 neurons allowed a good prediction of permeate flux by 0.997 of correlation coefficient during the learning phase. Also the validity of the designed model was evaluated with other experimental data not used during the training phase and nonlinear flux behavior was accurately estimated with 0.999 of correlation coefficient and a lower error of prediction in the testing phase. This good flux prediction can provide preliminary criteria in membrane design and set up the proper cleaning cycle in membrane operation. The KNT-artificial neural network is also expected to predict the variation of transmembrane pressure during filtration cycles and can be applied to automation and control of full scale treatment plants.

Purification of recombinant human B-domain-deleted factor VIII using anti-factor VIII monoclonal antibody selected by the surface plasmon resonance biosensor.

The surface plasmon resonance (SPR) biosensor measures the real-time kinetics of noncovalent interaction between a receptor and its ligand. Monoclonal antibodies (mAbs) against recombinant factor VIII (rFVIII) were screened from 127 mAb candidates using the SPR biosensor for the purpose of affinity purification of rFVIII. Each mAb showed a different association and dissociation capacity for rFVIII at each buffer condition. One mAb, F8-38, was selected for immunopurification of rFVIII. To characterize the selected mAb F8-38, the immunopurification results on the anti-FVIII mAb F8-38 affinity gel and the anti-von Willebrand factor (vWF) mAb affinity gel were studied. Immunopurification by the anti-vWF affinity gel showed a lower binding capacity of rFVIII and resulted in low purification efficiency. On the other hand, immunopurification by the anti-FVIII affinity gel exhibited a 3.5-fold binding capacity and a 2-fold purification efficiency compared to those of the anti-vWF affinity gel. The amounts of proteins and DNAs derived from host cells and mouse IgGs derived from the affinity matrix in the affinity eluate were similar to those of the anti-vWF affinity gel. In conclusion, the SPR method of immunopurification is a useful technology in the screening of mAbs aimed at the development of an affinity purification procedure, and the mAb F8-38 was selected using this technology on the basis of the purification procedure of rFVIII.

Management of advanced mandibular osteoradionecrosis with free flap reconstruction.

BACKGROUND: The purpose of this study was to assess the effectiveness of free tissue transfer for treatment of advanced mandibular osteoradionecrosis (ORN) in head and neck cancer patients. METHODS: We reviewed 29 patients who were treated for advanced mandibular ORN by radical resection and reconstruction with free flaps at our institution. All patients had either failed to respond to conservative treatment, including hyperbaric oxygen therapy and debridement or had pathological fracture due to ORN. RESULTS: Twenty-four vascularized bone (17 fibula, five iliac, and two scapula), four rectus abdominis myocutaneous, and one radial forearm fasciocutaneous free flaps were used. The complications occurred in 6 of 29 patients (21%). A total of four flaps (14%) were lost. The mean follow-up was 2 years 9 months. All patients had complete resolution of ORN symptoms. No evidence of ORN recurrence was observed in any patient. CONCLUSION: For advanced osteoradionecrosis of the mandible, radical resection followed by reconstruction using free flap provides a reliable means of obtaining good wound healing with acceptable aesthetic and functional results.

The modified human DNA repair enzyme O(6)-methylguanine-DNA methyltransferase is a negative regulator of estrogen receptor-mediated transcription upon alkylation DNA damage.

Cell proliferation requires precise control to prevent mutations from replication of (unrepaired) damaged DNA in cells exposed spontaneously to mutagens. Here we show that the modified human DNA repair enzyme O(6)-methylguanine-DNA methyltransferase (R-MGMT), formed from the suicidal repair of the mutagenic O(6)-alkylguanine (6RG) lesions by MGMT in the cells exposed to alkylating carcinogens, functions in such control by preventing the estrogen receptor (ER) from transcription activation that mediates cell proliferation. This function is in contrast to the phosphotriester repair domain of bacterial ADA protein, which acts merely as a transcription activator for its own synthesis upon repair of phosphotriester lesions. First, MGMT, which is constitutively present at active transcription sites, coprecipitates with the transcription integrator CREB-binding protein CBP/p300 but not R-MGMT. Second, R-MGMT, which adopts an altered conformation, utilizes its exposed VLWKLLKVV peptide domain (codons 98 to 106) to bind ER. This binding blocks ER from association with the LXXLL motif of its coactivator, steroid receptor coactivator-1, and thus represses ER effectively from carrying out transcription that regulates cell growth. Thus, through a change in conformation upon repair of the 6RG lesion, MGMT switches from a DNA repair factor to a transcription regulator (R-MGMT), enabling the cell to sense as well as respond to mutagens. These results have implications in chemotherapy and provide insights into the mechanisms for linking transcription suppression with transcription-coupled DNA repair.

Insulin allergy resolution following pancreas transplantation alone.

Clinically significant immunological reactions to exogenous insulin are classified as local or generalized. Most of the insulin allergies are local reactions which usually improve or resolve spontaneously. Generalized allergic reactions to insulin range in severity from simple urticaria to life-threatening anaphylaxis. Most of the allergic reactions to exogenous insulin are antibody-mediated reactions to antigens such as zinc, protamine, non-insulin proteins, and aggregates of insulin molecules as well as animal antigens. Immunologic reactions to endogenous insulin usually result in insulin resistance. Herein, we report a case in which systemic insulin allergy was intractable, thus requiring a pancreas transplantation which is the first of its case according to the International Pancreas Transplant Registry/United Network for Organ Sharing (IPTR/UNOS) Registry.

Two low-dose OKT3 induction regimens following renal transplantation--clinical experience at a single center.

Experience with quadruple-drug induction therapy with two regimens of low-dose OKT3 in renal transplant patients was evaluated. Group I received 5.0 mg OKT3 in the operating room and on day 1, followed by 2.5 mg/d for a total dose and duration of 40 mg and 14 d, respectively, and group II received 14 d of OKT3 2.5 mg/d (a total dose of 35 mg). Rejection episodes developed in 21% of patients: 29% of group I vs. 17% of group II. In groups I and II, the mean number of days until first rejection was 134 and 119 d, respectively, and delayed graft function was observed in 24 vs. 13% of patients, respectively. Cytokine release syndrome was noted in 95% of group I patients and in 78% of group II patients. The overall incidence of infections did not differ significantly between the two groups; however, the incidence of oral candidiasis was higher in group II (30 vs. 11% in group I, p = 0.021) and the incidence of herpes simplex virus infection was higher in group I (13 vs. 1% in group II, p = 0.015). The average length of hospital stay was 6.7 d in group I and 6.2 d in group II. The current pharmacy charge for a 2.5-mg vial of OKT3 is 28% lower for a 5.0-mg vial. Our study suggests that by using either low-dose OKT3 regimen renal transplant patients can be safely treated with shortened hospital stays, lower pharmacy costs, and without increased incidence of graft loss or patient morbidity.

Implication of localization of human DNA repair enzyme O6-methylguanine-DNA methyltransferase at active transcription sites in transcription-repair coupling of the mutagenic O6-methylguanine lesion.

DNA lesions that halt RNA polymerase during transcription are preferentially repaired by the nucleotide excision repair pathway. This transcription-coupled repair is initiated by the arrested RNA polymerase at the DNA lesion. However, the mutagenic O6-methylguanine (6MG) lesion which is bypassed by RNA polymerase is also preferentially repaired at the transcriptionally active DNA. We report here a plausible explanation for this observation: the human 6MG repair enzyme O6-methylguanine-DNA methyltransferase (MGMT) is present as speckles concentrated at active transcription sites (as revealed by polyclonal antibodies specific for its N and C termini). Upon treatment of cells with low dosages of N-methylnitrosourea, which produces 6MG lesions in the DNA, these speckles rapidly disappear, accompanied by the formation of active-site methylated MGMT (the repair product of 6MG by MGMT). The ability of MGMT to target itself to active transcription sites, thus providing an effective means of repairing 6MG lesions, possibly at transcriptionally active DNA, indicates its crucial role in human cancer and chemotherapy by alkylating agents.

Fibrillary glomerulonephritis in a renal allograft.

Fibrillary glomerulonephritis is an uncommon disease seen in approximately 1% of all native kidney biopsy specimens. We present here a case of a 40-year-old white woman with the rapid loss of graft function secondary to fibrillary glomerulonephritis within 7 days of receiving a living-related renal allograft. This case emphasizes the values of combining urinalysis with prompt allograft kidney biopsy in recipients with an elevated serum creatinine posttransplantation. When one encounters rapidly progressing glomerulonephritis or a pulmonary-renal syndrome in the immediate posttransplantation period, fibrillary glomerulonephritis must be considered in the differential diagnosis. Because of a high recurrence rate and no available treatment to modify a potentially malignant course of this disease, we recommend caution when considering these patients for transplantation.

Conformational change in human DNA repair enzyme O6-methylguanine-DNA methyltransferase upon alkylation of its active site by SN1 (indirect-acting) and SN2 (direct-acting) alkylating agents: breaking a "salt-link".

Human O6-methylguanine-DNA methyltransferase (MGMT) repairs DNA by transferring alkyl (R-) adducts from O6-alkylguanine (6RG) in DNA to its own cysteine residue at codon 145 (formation of R-MGMT). We show here that R-MGMT in cell extracts, which is sensitive to protease V8 cleavage at the glutamic acid residues at codons 30 (E30) and 172 (E172), can be specifically immunoprecipitated with an MGMT monoclonal antibody, Mab.3C7. This Mab recognizes an epitope of human MGMT including the lysine 107 (K107) which is within the most basic region that is highly conserved among mammalian MGMTs. Surprisingly, the K107L mutant protein is repair-deficient and readily cleaved by protease V8 similar to R-MGMT. We propose that R-MGMT adopted an altered conformation which exposed the Mab.3C7 epitope and rendered that protein sensitive to protease V8 attack. This proposal could be explained by the disruption of a structural "salt-link" within the molecule based on the available structural and biochemical data. The specific binding of Mab.3C7 to R-MGMT has been compared with the protease V8 method in the detection of R-MGMT in extracts of cells treated with low dosages of methyliodide (SN2) and O6-benzylguanine. Their identical behaviors in producing protease V8 sensitive R-MGMT and Mab.3C7 immunoprecipitates suggest that probably methyl iodide (an ineffective agent in producing 6RG in DNA) can directly alkylate the active site of cellular MGMT similar to O6-benzylguanine. The effectiveness of MeI in producing R-MGMT, i.e., inactivation of cellular MGMT, indicates that this agent can increase the effectiveness of environmental and endogenously produced alkylating carcinogens in producing the mutagenic O6-alkylguanine residues in DNA in vivo.