Nonsurgical treatment of a sublingual ranula in a ten-month-old baby.
A clinical case of nonsurgical treatment of a sublingual ranula in a ten-month-old baby is presented.
Humans↗
Biomedical subjects
G Marra
Publications and source records attributed to G Marra.
Mismatch repair deficiency associated with overexpression of the MSH3 gene.
We tested the ability of recombinant hMutSalpha (hMSH2/hMSH6) and hMutSbeta (hMSH2/hMSH3) heterodimers to complement the mismatch repair defect of HEC59, a human cancer cell line whose extracts lack all three MutS homologues. Although repair of both base/base mispairs and insertion-deletion loops was restored by hMutSalpha, only the latter substrates were addressed in extracts supplemented with hMutSbeta. hMutSalpha was also able to complement a defect in the repair of base/base mispairs in CHO R and HL60R cell extracts. In these cells, methotrexate-induced amplification of the dihydrofolate reductase (DHFR) locus, which also contains the MSH3 gene, led to an overexpression of MSH3 and thus to a dramatic change in the relative levels of MutSalpha and MutSbeta. As a rule, MSH2 is primarily complexed with MSH6. MutSalpha is thus relatively abundant in mammalian cell extracts, whereas MutSbeta levels are generally low. In contrast, in cells that overexpress MSH3, the available MSH2 protein is sequestered predominantly into MutSbeta. This leads to degradation of the partnerless MSH6 and depletion of MutSalpha. CHO R and HL60R cells therefore lack correction of base/base mispairs, whereas loop repair is maintained by MutSbeta. Consequently, frameshift mutations in CHO R are rare, whereas transitions and transversions are acquired at a rate two orders of magnitude above background. Our data thus support and extend the findings of Drummond et al. [Drummond, J. T., Genschel, J., Wolf, E. & Modrich, P. (1997) Proc. Natl. Acad. Sci. USA 94, 10144-10149] and demonstrate that mismatch repair deficiency can arise not only through mutation or transcriptional silencing of a mismatch repair gene, but also as a result of imbalance in the relative amounts of the MSH3 and MSH6 proteins.
Animals↗
hMSH2 and hMSH6 play distinct roles in mismatch binding and contribute differently to the ATPase activity of hMutSalpha.
In extracts of human cells, base-base mismatches and small insertion/deletion loops are bound primarily by hMutSalpha, a heterodimer of hMSH2 and hMSH6 (also known as GTBP or p160). Recombinant hMutSalpha bound a G/T mismatch-containing oligonucleotide with an apparent dissociation constant Kd = 2.6 nM, while its affinity for a homoduplex substrate was >20-fold lower. In the presence of ATP, hMutSalpha dissociated from mismatched oligonucleotide substrates, and this reaction was attenuated by mutating the conserved lysine in the ATP-binding domains of hMSH6, hMSH2 or both to arginine. Surprisingly, this reaction required only ATP binding, not hydrolysis. The ATPase activity of hMutSalpha variants carrying the Lys-->Arg mutation in hMSH2 or in hMSH6 was severely affected, but these mutants were still proficient in mismatch binding and were able to complement, albeit to different extents, mismatch repair-deficient cell extracts. The mismatch binding-proficient, ATPase-deficient double mutant was inactive in the complementation assay and its presence in repair-proficient extracts was inhibitory. We conclude that although the ATPase activity of hMutSalpha is dispensible for mismatch binding, it is required for mismatch correction.
Adenosine Triphosphatases↗
Hemiarthroplasty for glenohumeral arthritis with massive rotator cuff tears.
Rotator cuff deficiency with associated glenohumeral arthritis poses a formidable clinical challenge. Humeral head replacement with maintenance of the coracoacromial arch is the current treatment of choice. Properly performed arthroplasty can provide pain relief and modest gains in motion.
Acromion↗
Congenital reflux nephropathy: a follow-up of 108 cases diagnosed perinatally.
OBJECTIVE: To determine: (i) the proportion of vesicoureteric reflux (VUR) associated with congenital renal damage and whether it can be severe enough to cause renal impairment from birth: (ii) to evaluate the distribution of males and females affected; and (iii) to describe the course of congenital damage in the first years of life. PATIENTS AND METHODS: A total of 108 children (76 male and 32 female, M:F 2.3:1), whose VUR was diagnosed before any infection, were followed from birth for a mean (range) of 4.3 (1-10) years. Renal damage was defined by serum creatinine concentration, creatinine clearance and renal imaging (ultrasonography and renal scintigraphy) performed within the first month of life and periodically thereafter. RESULTS: Of the 108 children, 58 had bilateral and 50 unilateral reflux (total number of refluxing units, 166). High-grade VUR (grade > or = 4) was found in 96 (58%) refluxing renal units (RRUs). Males had a prevalence of bilateral severe (> or = grade 4) reflux (M:F 5.2:1), while in those wit unilateral VUR, the M:F ration was 1.5:1. At birth, mild to moderate damage was present in 56 (36%) RRUs and only associated with VUR of grade > or = 3. Bilateral reflux of grade > or = 4 was associated with congenital moderate/severe renal failure in nine neonates (seven males). In infants with grade > or = 4 VUR who underwent surgical correction, VUR resolved in 92% of cases. In infants with VUR of grade > or = 4 followed medically, the reflux spontaneously resolved in 42% and ameliorated in 16% after 18 months. Serial renal scans during the follow-up showed no progression of renal damage. CONCLUSIONS: VUR diagnosed at birth on prenatal ultrasonography is associated with congenital damage, with males affected more often than females. The damage involves both kidneys in a consistent proportion and is an important cause of chronic renal impairment from birth. It does not progress in the first years of life if infections are prevented. It is suggested that males with this condition may constitute a major group at risk of developing chronic renal failure in later life.
Child↗
Genetic instability and chromosomal aberrations in colorectal cancer: a review of the current models.
Our understanding of the pathogenesis of cancer has undergone a revolution over the past decade. Tumors develop by the accumulation of damage to genes that regulate cell growth. Many of the genes responsible for disregulation of cell growth have been identified, as have the processes that lead to the genetic damage. One of the most important concepts that has facilitated our understanding of carcinogenesis is that of genetic or "genomic" instability, which is required to permit a sufficient amount of genetic damage to accumulate to permit the neoplastic phenotype to emerge and evolve. Two mechanisms that lead to genomic instability--one of which involves the loss of chromosomal fragments from the nucleus, and a second which is characterized by microsatellite instability--are discussed.
Chromosome Aberrations↗
Mutation of the mismatch repair gene hMSH2 and hMSH6 in a human T-cell leukemia line tolerant to methylating agents.
Cell killing by monofunctional methylating agents is due mainly to the formation of adducts at the O6 position of guanine. These methyl adducts are removed from DNA by the O6-alkylguanine DNA alkyltransferase (OGAT). The mechanism by which O6-methylguanine (O6meG) induces cell death in OGAT-deficient cells requires a functional mismatch repair system (MRS). We have previously reported that depletion of OGAT activity in the human T-cell leukemic urkat line does not sensitize these cells to the cytotoxic and apoptotic effects of the methylating triazene temozolomide (Tentori et al., 1995). We therefore decided to establish whether the tolerance of Jurkat cells to O6meG could be associated with a defect in MRS. The results of mismatch repair complementation studies indicated that Jurkat cells are defective in hMutSalpha, a heterodimer of the hMSH2 and hMSH6 proteins. Cytogenetic analysis of two Jurkat clones revealed a deletion in the short arm of chromosome region 2p15-21, indicating an allelic loss of both hMSH2 and hMSH6 genes. DNA sequencing revealed that exon 13 of the second hMSH2 allele contains a base substitution at codon 711, which changes an arginine to a termination codon (CGA-->TGA). In addition, a (C)8-->(C)7 frameshift mutation in codon 1085-1087 of the hMSH6 gene was also found. Although both hMSH2 and hMSH6 transcripts could be detected in Jurkat clones, the respective polypeptides were absent. Taken together, these data indicate that tolerance of Jurkat cells to methylation damage is linked to a loss of functional hMutSalpha.
Base Pair Mismatch↗
Rapid identification of RT-PCR clones containing translation-terminating mutations.
The technique of in vitro transcription/translation (IVTT) has become an important method of detecting mutations that result in a prematurely terminated protein. Subsequent characterization of the mutations by cloning and sequencing the RT-PCR products, however, is often difficult and time consuming. This is due in large part to the altered metabolism to which transcripts containing translation terminating mutations are subject. Recent data has shown that mRNAs with nonsense or frame shift mutations are often selectively degraded, so that mutation bearing transcripts are significantly less abundant that wild-type transcripts and, after cloning, mutant clones are correspondingly scarce. We have developed a reliable method of identifying the cDNA clones containing translation terminating mutations by a 'second round' of IVTT. Clones are subjected to PCR and IVTT using similar conditions as in the initial IVTT reaction and are identified unequivocally as either wild-type or mutant prior to sequencing. Wasteful 'blind' sequencing is thus avoided as well as possible misidentification of taq polymerase errors as the mutation of interest.
Adaptor Proteins, Signal Transducing↗
Defective plasma antioxidant defenses and enhanced susceptibility to lipid peroxidation in uncomplicated IDDM.
Oxidative stress is postulated to be increased in patients with IDDM. Accumulating evidence suggests that oxidative cell injury caused by free radicals contributes to the development of IDDM complications. On the other side, a decreased efficiency of antioxidant defenses (both enzymatic and nonenzymatic) seems to correlate with the severity of pathological tissue changes in IDDM. Thus, we determined plasma antioxidant defenses, measuring the total radical-trapping antioxidant capacity (TRAP) and the two markers of oxidative stress, lipid hydroperoxides (ROOHs) and conjugated dienes, in 72 patients with well-controlled IDDM and without evident complications, compared with 45 nondiabetic subjects. Compared with control subjects, IDDM patients showed significantly reduced plasma TRAP (669 +/- 131 vs. 955 +/- 104 micromol/l, P < 0.001) and significantly increased levels of ROOHs (7.13 +/- 2.11 vs. 2.10 +/- 0.71 micromol/l, P < 0.001) and conjugated dienes (0.0368 +/- 0.0027 vs. 0.0328 +/- 0.0023 arbitrary units [AU], P < 0.01), especially in the trans-trans conformation (0.0340 +/- 0.0028 vs. 0.0259 +/- 0.0022 AU, P < 0.001), with a concurrent reduction of conjugated dienes in the cis-trans conformation (0.0028 +/- 0.0011 vs. 0.0069 +/- 0.0012 AU, P < 0.001). The oxidative parameters studied did not appear to be correlated with metabolic control (HbA1c levels) and lipid profile (cholesterol or triglyceride levels). The reduced TRAP and the increased ROOH and conjugated diene plasma levels, together with the decreased ratio of cis-trans/trans-trans conjugated dienes, which reflects an altered redox status of plasma, indicate that in IDDM patients, oxidative stress is enhanced and antioxidant defenses are defective, regardless of diabetes duration, metabolic control, or presence of complications.
Adult↗
Modulating effect of omega-3 fatty acids on the proliferative pattern of human colorectal mucosa.
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Adenomatous Polyposis Coli↗
Expression of human MutS homolog 2 (hMSH2) protein in resting and proliferating cells.
The hMSH2 protein plays an important role in the DNA mismatch repair system. Since this system is involved in the correction of errors that occur during DNA replication, we studied the expression of hMSH2 protein in resting and DNA-replicating cells, as well as through the cell cycle in cell types with different growth characteristics. Using Western blot analysis, we showed that hMSH2 protein was detectable in resting peripheral blood lymphocytes and thymocytes. However, when these cells were induced to proliferate, the protein level increased at least 12-fold. In cell-cycle dependent expression studies we chose two DNA mismatch repair proficient cell lines (HEL and HeLa-S3), and flow cytometry was used to monitor cell-cycle progression. At every phase in the cell cycle, the steady-state level of hMSH2 was higher than in resting lymphocytes or thymocytes, and only minor variations of expression level were observed through the cell cycle. In particular, a two to fourfold decrease in hMSH2 expression occurred at G1 in HEL and at early S phase in HeLa-S3, but higher expression levels resumed during the replicative and postreplicative phases of the cell cycle. Interestingly, hMSH2 protein expression decreased fourfold when HEL cells were induced to differentiate along the megakaryocyte lineage, when continuous DNA replication occurs without mitosis. These results suggest that a basal level of hMSH2 protein expression is necessary for resting and differentiated cells, and that increased hMSH2 protein expression is required when DNA replication is activated and followed by mitosis.
Cell Cycle↗
Competency in mismatch repair prohibits clonal expansion of cancer cells treated with N-methyl-N'-nitro-N-nitrosoguanidine.
The phenomenon of alkylation tolerance has been observed in cells that are deficient in some component of the DNA mismatch repair (MMR) system. An alkylation-induced cell cycle arrest had been reported previously in one MMR-proficient cell line, whereas a MMR-defective clone derived from this line escapes from this arrest. We examined human cancer cell lines to determine if the cell cycle arrest were dependent upon the MMR system. Growth characteristics and cell cycle analysis after MNNG treatment were ascertained in seven MMR-deficient and proficient cell lines, with and without confirmed mutations in hMLH1 or hMSH2 by an in vitro transcription/translation assay. MMR-proficient cells underwent growth arrest in the G2 phase of the cell cycle after the first S phase, whereas MMR-deficient cells escaped an initial G2 delay and resumed a normal growth pattern. In the HCT116 line corrected for defective MMR by chromosome 3 transfer, the G2 phase arrest lasted more than five days. In another MMR-proficient colon cancer cell line, SW480, cell death occurred five days after MNNG treatment. A competent MMR system appears to be necessary for G2 arrest or cell death after alkylation damage, and this cell cycle checkpoint may allow the cell to repair damaged DNA, or prevent the replication of mutated DNA by prohibiting clonal expansion.
Alkylating Agents↗
Nephrotic syndrome in a mother and her infant: relationship with cytomegalovirus infection.
This case report describes infantile nephrotic syndrome (NS) in a baby girl with a clinically severe cytomegalovirus (CMV) infection. Culture of the baby's urine was positive for CMV and IgM anti-CMV antibodies were detected. After an unsuccessful course of corticosteroids, gancyclovir treatment was started and a remission of cutaneous, pulmonary, and renal symptoms was achieved. As the mother also developed NS at the end of pregnancy, a common etiology could be postulated, although there were no signs of recent CMV infection in the mother, only anti-CMV IgG. The relationship between CMV infection and glomerular disease is still unclear; NS may represent another manifestation of CMV disease.
Adrenal Cortex Hormones↗
DNA repair and colorectal cancer.
The mismatch repair system plays a major role in the processing of recombination intermediates and in the repair of errors made during DNA replication or resulting from chemical damage to DNA. Human homologues of the bacterial and yeast mismatch repair genes have been recently identified, and mutations in these genes have been found to show risk for tumor development in hereditary nonpolyposis colorectal cancer syndrome (HNPCC). Colorectal tumors bearing homozygous mutations in these mismatch repair genes show a hypermutable phenotype, mainly at microsatellite regions of DNA. The temporal relationship between the loss of mismatch repair activity and the cascades of mutations in critical genes involved in the carcinogenesis of HNPCC tumors is unknown.
Animals↗
n-3 fatty acids induce oxidative modifications in human erythrocytes depending on dose and duration of dietary supplementation.
The present work was performed to study an optimal dose and duration of dietary n-3 polyunsaturated fatty acid (PUFA) supplementation that would not result in harmful modifications of oxidative cell metabolism. Forty healthy subjects were divided into four groups that received 2.5 g/d eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA), 5.1 g EPA + DHA/d, 7.7 g EPA + DHA/d, or placebo. Fatty acid composition, tocopherol status, and susceptibility to lipid peroxidation induced in vitro by 2,2'-azobis-(2-amidinopropane) (AAPH) were evaluated in human red blood cell (RBC) membranes on days 30 and 180. n-3 PUFA treatment increased EPA and DHA concentrations in RBC membranes in a time-dependent manner in all of the n-3 PUFA groups. These modifications occurred with concomitant dose- and time-dependent increases in the membrane unsaturation index. After 30 d of treatment with n-3 PUFAs, alpha-to-copherol significantly increased in RBC membranes of the intermediate- and high-dose groups. Because of the higher concentration of this antioxidant in these groups, the susceptibility of RBC membranes to peroxidation was decreased. However, after 180 d of treatment, alpha-tocopherol decreased to baseline values and AAPH-induced lipid peroxidation increased in a dose-dependent manner. These results show that high doses of dietary n-3 PUFAs, as well as long-time treatments, affect human RBC susceptibility to lipid peroxidation by changes in fatty acid composition and tocopherol content.
Adult↗
NA+/K+ ATPase impairment and experimental glycation: the role of glucose autoxidation.
Non enzymatic glycation could be involved in the early impairment of Na+/K+ ATPase that occurs in sciatic nerve of diabetic rats. In fact, decrease of Na+/K+ ATPase activity is one of the first alterations showed in experimental diabetic neuropathy. In this respect, it is known that in the presence of transition metals under physiological conditions, glucose can autoxidize yielding hydrogen peroxide (H2O2) and free radical intermediates, which, in turn, inhibit the cation pump. Our experiments were designed to determine if glucose autoxidation has any relevance in the early steps of Na+/K+ ATPase experimental glycation. Compared experiments with and without the sodium borohydride (NaBH4) reduction step demonstrated that incubation of brain Na+/K+ ATPase with glucose 6-phosphate (G 6-P) and trace metals induced a significant decrease in enzyme activity dramatically enhanced by addition of copper (Cu2+). A concomitant production of H2O2 was noticed. The presence of diethylenetriaminepentaacetic acid (DTPA), a strong metal chelator, completely prevented Na+/K+ ATPase impairment and hydrogen-peroxide formation. No gross structural and conformational alterations of the enzyme can be demonstrated by intrinsic and extrinsic fluorescence measurements. Our results suggest that during the exposure of brain NA+/K+ ATPase to glucose 6-phosphate in vitro (experimental glycation), the decrease in activity can be correlated, at lease in the early phases, to metal-catalyzed production of oxidative species, such as H2O2, through the glucose autoxidation process, and not to glucose attachment to the enzyme. Since plasma hydroperoxides and copper appear to be elevated in diabetic patients with complications, our data suggest a critical role for oxidative reactions in the pathophysiology of the chronic complications of diabetes like neuropathy.
Animals↗
Evidence for a connection between the mismatch repair system and the G2 cell cycle checkpoint.
The human colon tumor cell line HCT116 is deficient in wild-type hMLH1, is defective in mismatch repair (MMR), exhibits microsatellite instability, and is tolerant to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Transferring a normal copy of hMLH1 on chromosome 3 into the cell line restores MMR activity, stabilizes microsatellite loci, and increases the sensitivity of the cell to MNNG. Previous studies in other cell lines tolerant to alkylating agents such as MNNG or N-methylnitrosourea have shown cross-tolerance to 6-thioguanine (6TG), leading to a hypothesis that tolerance to MNNG or 6TG may be the result of MMR deficiency. To test this hypothesis, we studied the effects of 6TG on the MNNG-tolerant, MMR-deficient HCT116 cell line and its MNNG-sensitive, MMR-proficient, MNNG-tolerant, and MMR-deficient derivatives. Continuous exposure to low doses of 6TG (0.31-1.25 micrograms/ml) had no apparent effect on colony-forming ability (CFA) in MNNG-tolerant, MMR-deficient cells, whereas MNNG-sensitive, MMR-proficient cells exhibited a dose-dependent decrease in CFA. Growth kinetics and cell cycle analysis revealed that the growth of 6TG-treated HCT116 + chr3 cells was arrested at G2 after exposure to low dose of 6TG. In contrast, the same exposure to 6TG did not induce G2 arrest but rather a G1 delay in HCT116 and HCT116 + chr2. To obtain further evidence for the role of MMR on 6TG and MNNG toxicity, we isolated an MNNG-resistant revertant clone, M2, from the MNNG-sensitive, MMR-proficient HCT116 + chr3 cell line and characterized the MMR activity, hMLH1 status, and 6TG response. The results showed that M2 cells lost MMR activity as well as the previously introduced normal hMLH1 gene. Restoration of the CFA of M2 and an absence of G2 arrest were observed after treatment with low doses of 6TG. These results suggest that the mismatch repair system interacts with the G2 checkpoint in response to 6TG or MNNG-induced DNA lesions. The results further suggest that any agent that induces DNA mispairs will cause G2 arrest in MMR-proficient cells but not in MMR-deficient cells.
Azaguanine↗
Hereditary nonpolyposis colorectal cancer: the syndrome, the genes, and historical perspectives.
Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant disorder characterized by the occurrence within a family of multiple cases of colorectal cancer in the absence of gastrointestinal polyposis. The prevalence of this syndrome is not yet clear, but it may account for 1%-5% of all colorectal cancers. Prior to the identification of the genetic basis of this syndrome, the disease was recognized by the familial aggregation of colorectal cancers that had an early age of onset, an excess of proximally located, and often multiple, primary tumors, and an excess occurrence of cancers in certain other organs. The recent description of an abnormality called "microsatellite instability," present in almost all cancers from HNPCC patients and in about 12%-15% of sporadic cases, led to a series of discoveries that linked this type of genomic instability to a defect in the DNA mismatch repair (MMR) system. Independent investigators have identified four HNPCC genes: hMSH2 (a homologue of the prokaryotic DNA MMR gene MutS) and hMLH1, hPMS1, and hPMS2 (all homologues of the prokaryotic DNA MMR gene MutL). Mutations in each of the four genes have been found in the germline cells of HNPCC families. A major target for research in this area is the development of clinically practical screening tests for the genetic carrier state of HNPCC.
Colorectal Neoplasms, Hereditary Nonpolyposis↗