Expression of MAGE genes in ocular melanoma during progression from primary to metastatic disease

Primary melanomas that form within the eye have a unique pattern of disease progression as compared with melanomas that form within the skin. A high percentage of patients (approximately 50%) develop metastatic tumors that occur predominately in the liver. An unusual characteristic of ocular melanomas is the prolonged disease-free interval that extends for many years between the development of primary and metastatic tumors. It is estimated that the shortest interval between dissemination of tumor cells from the eye and the appearance of clinically detectable metastases is 6 years. A recent report indicated that fresh uveal melanoma tissue and metastatic tumor biopsies failed to express melanoma antigen gene (MAGE)-1, MAGE-2, or MAGE-3. In the present study, we examined the expression of MAGE genes on fresh and cultured tumor cells obtained from an ocular melanoma patient during different stages of progressive disease. MAGE gene expression was determined by reverse transcription-polymerase chain reaction using MAGE-1, MAGE-2 and MAGE-3 specific primers. Our results demonstrate that primary ocular tumor tissue and cultured tumor cells both express significant levels of MAGE-1, 2, and 3 at the time of enucleation. A high percentage of tumor cells within the primary tumor appear to express MAGE as demonstrated by consistent MAGE expression in 16 tumor cell clones. Metastatic liver tumors that developed 3 years after enucleation and 18 years after the initial formation of the primary tumor also expressed high levels of MAGE-1, -2, and -3. MAGE was expressed on fresh tumor tissue from a single biopsy and cultured tumor cells obtained from three of four different metastatic tumor nodules. When the MAGE-negative metastatic tumor cells were treated with the demethylating agent 5-Aza-2-Deoxycytidine (5-Aza-dC), transcription of MAGE-1 was restored, indicating the MAGE genes were not deleted. Our results demonstrate that in some patients, MAGE genes are expressed on primary and metastatic ocular melanomas.

Formation of 2',3'-cyclic phosphates at the 3' end of human U6 small nuclear RNA in vitro. Identification of 2',3'-cyclic phosphates at the 3' ends of human signal recognition particle and mitochondrial RNA processing RNAs

Approximately 90% of human U6 small nuclear RNA (snRNA) contains uridine cyclic phosphate (U>p) at its 3'-end (Lund, E., and Dahlberg, J. E. (1992) Science 255, 327-330). We studied the formation of U>p at the 3' end of human U6 snRNA using an in vitro system where uridylic acid residues are added from UTP precursor and U>p is formed. Analysis of U6 snRNAs with varying number of uridylic acid residues showed that each of these species contains U>p where the phosphate originated from alpha-phosphate of UTP precursor. The cyclic phosphate formation occurred on U6 snRNA in extracts where essential spliceosomal snRNAs were specifically degraded, thereby indicating that U>p formation is not coupled to pre-mRNA splicing. A subpopulation of human signal recognition particle and mitochondrial RNA processing RNAs isolated from HeLa cells also contained cyclic phosphates at their 3' ends. These data suggest that U>p in U6 snRNA is unlikely to be related to its participation in splicing of pre-mRNAs. It appears that cyclic phosphate is an intermediate product in the metabolism of these small RNAs.

Triple quantum sodium imaging of articular cartilage

Triple quantum (TQ) sodium imaging of bovine articular cartilage is presented. True triple quantum imaging sequence was modified to incorporate asymmetric echo acquisition. Triple quantum signal expression in the presence of residual quadrupolar interaction is presented. The filtering capability of the sequence is first demonstrated on an agarose phantom. Both single and triple quantum images of articular cartilage are compared. The TQ image shows non-zero signal intensity solely from cartilage, indicating complete suppression of signals from bone marrow and saline. The advantages of TQ imaging of articular cartilage, its feasibility in in vivo situations and further improvements in SNR are described.

Collaboration Technology for Rural Health-care

Health-care is a collaborative endeavor involving a number of individuals and organizations with diverse perspectives. Computer-supported collaboration technologies have great potential to enable health-care providers to improve the quality of care provided to their patients. Such technologies have the potential to overcome barriers to quality health-care in the small, scattered populations of rural areas. Rapid changes in technology are making it more and more possible for collaborative telemedicine to be a part of the practice of medicine. The World Wide Web has amply demonstrated that the globe has shrunk and information from afar is a mere mouse click away. However, the ease with which information is accessed along with the potential disclosure and misuse of personal information has raised serious concerns about the ability to restrict such information to legitimate accesses by duly authorized health-care providers. The authors present their experience in developing a health-care collaboration facility, ARTEMIS, which enabled Web-based access to electronic medical records, and provide a vision of their experiment to provide secure telemedicine for rural health-care practitioners.

In vivo sodium multiple quantum spectroscopy of human articular cartilage

The authors report, for the first time, sodium properties of human articular cartilage in vivo using sodium multiple-quantum-filtered methods with a surface coil. A flip angle-independent, phase-cycled pulse sequence was used to obtain triple-quantum-filtered spectra as a function of preparation time. Biexponential relaxation rates were calculated by fitting the triple-quantum-filtered spectral amplitudes to a theoretical expression. Theoretical analysis of the flip angle dependence of even rank two-quantum coherence (T2[2]), odd rank two-quantum coherence (T2[3]), and triple-quantum coherence are presented and verified against experimental results on a cartilage specimen. Sodium multiple-quantum-filtered spectral lineshapes obtained in vivo correlate well with those observed on in vitro specimens. Relaxation rates obtained from asymptomatic volunteers were found to be: T(2rise) = 1.0 + 0.12 ms, T(2decay) = 12.0 +/- 0.75 ms (mean +/- SD). The diagnostic potential of this method in detecting early changes in articular cartilage is described.

Point mutations in the 23S rRNA gene of Helicobacter pylori associated with different levels of clarithromycin resistance

Fifty-four of 59 (91.5%) clarithromycin-resistant isolates of Helicobacter pylori from different patients possessed either the A2143G (formerly A2058G) or the A2144G (formerly A2059G) mutation in the gene encoding 23S rRNA. The A2143G mutation was significantly more likely to occur in isolates with MICs exceeding 64 mg/L (65% versus 30% with the A2144G mutation; P = 0.01). The majority (26 of 31; 83.9%) of isolates with the A2143G mutation had MICs exceeding 64 mg/L. Peptic ulcer disease recurred in a substantial proportion of patients infected with H. pylori strains containing either the A2143G or the A2144G mutation.

Laparoscopic evaluation of liver disease in chronic renal failure prior to renal transplantation

BACKGROUND

Diagnostic laparoscopy with liver biopsy has been shown to be safe and effective in the evaluation of patients with chronic liver disease. Patients with end-stage renal disease may be more prone to bleeding complications secondary to liver biopsy as a result of multiple factors directly related to their underlying renal condition.

METHODS AND PATIENTS

From January 1994 to June 1996, 16 patients with end-stage renal disease and hepatic dysfunction (6 women and 10 men) underwent diagnostic laparoscopy with liver biopsy prior to renal transplantation at the University of Miami School of Medicine. Laparoscopy was performed using a 5 mm video laparoscope with a left paramedian approach. The mean patient age was 46 years. Fourteen patients had chronic hepatitis C with a reactive anti-HCV by ELISA; one patient had chronic hepatitis B with reactive HBsAg, and one patient was co-infected with both hepatitis B and C viruses.

RESULTS

Two patients developed hypotension related to the procedure and one patient developed an intra-abdominal hemorrhage 5 days after laparoscopy that did not require surgical intervention. Biopsy findings were as follows: 13 patients had mild chronic hepatitis; 2 patients had chronic hepatitis with bridging fibrosis; and 1 patient was cirrhotic. Prior kidney transplantation or peritoneal dialysis did not preclude the performance of laparoscopy.

CONCLUSION

Diagnostic laparoscopy can be safety performed in patients with end-stage renal disease with acceptable morbidity and mortality.

Reproducibility of exercise-induced modulation of cardiovascular responses to cold stress

The modulation of cardiovascular responses to the cold pressor test (CPT) as produced by exercise was studied in 13 volunteers. The reproducibility of the measurements selected for the study, i.e. heart rate (HR), blood pressure (BP), blood flow (BF) and skin temperature (ST), was investigated through repeat experiments in the fall of 1994 and the winter of 1995. HR was monitored before, during and after a 10-min period of bicycling at 70% of reserve HR. BP, cutaneous BF and ST were measured before and after exercise. Two CPTs (hand into ice-cold water for 1 min) were performed: one preceding exercise and another at 3 min after exercise. The results obtained allow us to conclude that in non-hypertensive volunteers (1) the pronounced cardiovascular responses (ST, BF and BP) induced by CPT are reproducible (p > 0.2) when compared to basal level values and (2) cardiovascular responses to cold stress are significantly attenuated by exercise (p < 0.03). Our study, therefore, supports and validates the use of our coupled exercise-CPT method in ongoing epidemiological studies attempting to identify individuals at risk for the development of hypertension as well as those most likely to benefit from preventative exercise programs.

17O-decoupled proton MR spectroscopy and imaging in a tissue model

17O-decoupled proton MR spectroscopy and imaging were implemented at 2 T. Their sensitivity and accuracy in vitro were examined using semisolid tissue phantoms doped with H2(17)O. A double-tuned solenoidal coil was used to irradiate the same volume of 17O and 1H nuclei, as well as to facilitate direct calibration of the decoupling power. Decoupling efficiency was optimized as was 17O detection sensitivity. Decoupling was most efficient at RF amplitudes below 2.5 kHz (expressed as gamma [17O] x H1), which is within the limits of the acceptable specific absorption rate. Propagation of error analysis demonstrated that 17O detection sensitivity is optimal at a TE equal to the T2 of 17O-depleted water protons. Based on Meiboom's work, a simple theory was formulated for estimating the transverse relaxivity of H2(17)O and the proton signal enhancement produced by decoupling. There was excellent agreement between theory and experiment. Overall, 17O-decoupled spectroscopy and imaging were highly sensitive and accurate in quantifying H2(17)O in vitro.

Collaboration Technology for Rural Health-care

Health-care is a collaborative endeavor involving a number of individuals and organizations with diverse perspectives. Computer-supported collaboration technologies have great potential to enable health-care providers to improve the quality of care provided to their patients. Such technologies have the potential to overcome barriers to quality health-care in the small, scattered populations of rural areas. Rapid changes in technology are making it more and more possible for collaborative telemedicine to be a part of the practice of medicine. The World Wide Web has amply demonstrated that the globe has shrunk and information from afar is a mere mouse click away. However, the ease with which information is accessed along with the potential disclosure and misuse of personal information has raised serious concerns about the ability to restrict such information to legitimate accesses by duly authorized health-care providers. The authors present their experience in developing a health-care collaboration facility, ARTEMIS, which enabled Web-based access to electronic medical records, and provide a vision of their experiment to provide secure telemedicine for rural health-care practitioners.

Small RNA database

The small RNA database is a compilation of all the small size RNA sequences available to date, including nuclear, nucleolar, cytoplasmic and mitochondrial small RNAs from eukaryotic organisms and small RNAs from prokaryotic cells as well as viruses. Currently, about 600 small RNA sequences are in our database. It also gives the sources of individual RNAs and their GenBank accession numbers. The small RNA database can be accessed through WWW(World Wide Web). Our WWW URL address is: http://mbcr.bcm.tmc.edu/smallRNA/smallrna. html . The new small RNA sequences published since our last compilation are listed in this paper.

A strategy for the development of secure telemedicine applications

Healthcare applications based on computer-supported collaboration technologies have the potential to improve the quality of care delivered to patients. Such applications can help overcome barriers to quality healthcare in the small, scattered populations of rural areas enabling telemedicine to be a part of the practice of medicine. However the growing concern about the potential for abuse through disclosure of personal health information to unauthorized parties has restricted the deployment and adoption of these potentially valuable tools. The authors, who built ARTEMIS--an Intranet healthcare collaboration facility, now describe their approach to develop secure telemedicine applications for rural healthcare practitioners.

Malignant sustained ventricular tachyarrhythmias in women: characteristics and outcome of treatment with an implantable cardioverter defibrillator

Clinical rhythm, heart disease, ejection fraction, defibrillation threshold, recurrent arrhythmias, and mortality were compared in 268 consecutive recipients (213 men and 55 women) of their first implantable cardioverter defibrillator for life-threatening ventricular tachycardia or fibrillation. Women were younger than men, less likely to have structural heart disease, and more likely to have clinical ventricular fibrillation, a higher ejection fraction, and a lower defibrillation threshold. Complications of defibrillator placement were similar in both sexes. Unadjusted survival tended to be higher in women than in men (97% vs 90%, respectively, at 2 years, P = 0.08), largely due to fewer deaths from noncardiac causes or cardiac causes other than arrhythmia (P = 0.04). Women also tended to be at lower, albeit still substantial, risk for recurrent arrhythmias during follow-up (37% vs 52% in men at 2 years, P = 0.11). After adjustment for baseline differences, overall survival, arrhythmia death-free survival, nonarrhythmia death-free survival, and frequency of recurrent arrhythmias were not found to be gender related. Despite their apparent "lower risk" status on initial presentation, women remained at substantial risk for recurrent arrhythmias. This underscores the need to avoid being unduly biased by the "appearance" of health in managing women with malignant arrhythmias. That survival and other clinical endpoints were all ultimately independent of gender emphasizes the importance of other clinical variables in assessing risk from ventricular tachyarrhythmias.

Changes in adenine nucleotides during hemorrhagic shock and reperfusion

Certain tissues are known to be susceptible to shock-induced damage: liver, small bowel mucosa, and small bowel wall. This study was done to assess the changes in adenine nucleotides induced by hemorrhagic shock. Male Sprague-Dawley rats (n = 21; 300-350 g) were anesthetized with sodium pentobarbital (50 mg/kg, ip) and mechanically ventilated. The external jugular vein and common carotid artery were cannulated. Laparotomy was done. Hemorrhagic shock was induced by withdrawing blood into a heparinized syringe until a mean arterial blood pressure of 40 mm Hg was obtained and was maintained for 30 min by continued withdrawals. Shed blood was then reinfused through the venous catheter. No additional fluid was administered. The animals were observed for another 60 min. Throughout the procedure, biopsies were taken of liver and small bowel. The small bowel biopsies were separated into mucosal and wall fractions. Nucleotides were extracted. ATP, ADP, AMP, adenosine, inosine, xanthine, and hypoxanthine were measured with gradient HPLC. Cellular ATP concentrations decreased significantly during shock (P < 0.05). Liver ATP dropped from 8.93 +/- 0.55 to 2.91 +/- 0.16 micromol/g dry tissue (mean +/- SEM) (33%), small bowel mucosal ATP from 9.40 +/- 1.04 to 3.26 +/- 0.21 (35%), and small bowel wall ATP from 5.47 +/- 0.36 to 2.74 +/- 0.18 (50%). The nucleotide response to shock in small bowel mucosa was closer to that of liver than to that of small bowel wall. After reperfusion, ATP levels were partially restored in liver, small bowel mucosa, and small bowel wall, but not to preshock values. All of the metabolites (adenosine, inosine, hypoxanthine, and xanthine) increased during shock (P < 0.05), and did not return to preshock levels after reperfusion. The abnormalities in ATP and its metabolites, and their persistence after reperfusion, suggest a possible mechanism for the production of postshock damage.

Multicenter comparison of truncated biphasic shocks and standard damped sine wave monophasic shocks for transthoracic ventricular defibrillation. Transthoracic Investigators

BACKGROUND

The most important factor for improving out-of-hospital ventricular fibrillation survival rates is early defibrillation. This can be achieved if small, lightweight, inexpensive automatic external defibrillators are widely disseminated. Because automatic external defibrillator size and cost are directly affected by defibrillation waveform shape and because of the favorable experience with truncated biphasic waveforms in implantable cardioverter-defibrillators, we compared the efficacy of a truncated biphasic waveform with that of a standard damped sine monophasic waveform for transthoracic defibrillation.

METHODS AND RESULTS

The principal goal of this multicenter, prospective, randomized, blinded study was to compare the first-shock transthoracic defibrillation efficacy of a 130-J truncated biphasic waveform with that of a standard 200-J monophasic damped sine wave pulse using anterior thoracic pads in the course of implantable cardioverter-defibrillator testing. Pad-pad ECGs were also examined after transthoracic defibrillation. After the elimination of data for 24 patients who did not meet all protocol criteria, the results from 294 patients were analyzed. The 130-J truncated biphasic pulse and the 200-J damped sine wave monophasic pulse resulted in first-shock efficacy rates of 86% and 86%, respectively (P = .97). ST-segment levels measured 10 seconds after the shock in 151 patients in sinus rhythm were -0.26 +/- 1.58 and -1.86 +/- 1.93 mm for the 130- and 200-J shocks, respectively (P < .0001).

CONCLUSIONS

We found that 130-J biphasic truncated transthoracic shocks defibrillate as well as the 200-J monophasic damped sine wave shocks that are traditionally used in standard transthoracic defibrillators and result in fewer ECG abnormalities after the shock.

Bronchodilatation and the inspiratory flow volume curve

The inspiratory flow volume curve is included in the spirometric tracing provided by most pulmonary function laboratories and is useful in assessing upper airway abnormalities. We analyzed the changes in peak inspiratory flow (PIF), forced inspiratory flow at 50% (FIF50), and forced inspiratory vital capacity (FIVC) that occur with bronchodilator challenge testing (3 puffs of a beta-agonist by metered-dose inhaler without a spacer device) in 145 consecutive patients. Fifty-five patients responded to bronchodilators with either a 12% or 200-mL change in FEV1 or FVC. All of these subjects produced forced expiratory maneuvers that fulfilled American Thoracic Society criteria or acceptability. The FIVC was the only inspiratory parameter that consistently showed a similar correlation to the bronchodilator responsiveness demonstrated by the FEV1 or FVC. With the reduction in air trapping, a 12% or 200-mL change in the FIVC is additional confirmatory evidence of bronchodilator responsiveness.

Helicobacter pylori does not migrate from the antrum to the corpus in response to omeprazole

BACKGROUND

Omeprazole is known to have an effect on Helicobacter pylori in vivo. One opinion is that H. pylori "migrates" from the antrum to the corpus in response to omeprazole therapy.

METHODS

To determine whether H. pylori migrates in response to omeprazole, we assessed the presence of H. pylori in the antrum and corpus in duodenal ulcer patients receiving omeprazole for 4 wk. Culture and histological examination of antral biopsies (Genta stain) were performed before patients received omeprazole, at the end of therapy, and 4-6 wk later. The end points were presence or absence of H. pylori and the number of H. pylori colonies per biopsy.

RESULTS

Seventy-two patients had H. pylori in both the antrum and corpus at entry and 4-6 wk after ending therapy. Three general patterns were prevalent at the end of omeprazole therapy: antrum- and corpus-positive (54%), antrum-negative and corpus-positive (24%), both antrum- and corpus-negative (21%), and one patient had antrum-positive with corpus-negative (1%). Evaluation of the number of colonies per biopsy in those who remained H. pylori-positive in both the antrum and corpus throughout showed that the number of H. pylori decreased in both the antrum and corpus during therapy (507 +/- 60 vs. 225 +/- 51, p < 0.01 and 415 +/- 58 vs. 290 +/- 46 0.1) for antrum and corpus, respectively, and tended to return to pre-therapy levels 4-6 wk later. The number of H. pylori in the corpus also decreased in the antrum-negative and corpus-positive group during therapy with omeprazole (433 +/- 87 vs. 185 +/- 61, p < 0.05). In most of the patients studied, the number of H. pylori in the corpus was less posttreatment than it was pretreatment. The decrease in H. pylori load was also reflected in the development of false-negative urea breath tests.

CONCLUSIONS

Omeprazole is detrimental to H. pylori in both the antrum and the corpus; migration from the antrum to the corpus in response to omeprazole is a myth.

Direct activity of recombinant human lactoferrin against Helicobacter pylori

We report the activity of recombinant human lactoferrin against Helicobacter pylori. Lactoferrin exerted a time- and dose-dependent action against 8 of the 13 clinical isolates of H. pylori tested in vitro. These results highlight a potential therapeutic use for lactoferrin against H.pylori infection.

Localization of modified nucleotides in Schizosaccharomyces pombe spliceosomal small nuclear RNAs: modified nucleotides are clustered in functionally important regions

The specific and dynamic RNA:RNA interactions between pre-mRNA and small nuclear RNAs (snRNAs), especially U2, U5, and U6 snRNAs, form the catalytic core and are at the heart of the spliceosome formation. The functionally important regions in the snRNAs correspond to the highly modified regions in snRNAs from human, rat, and plant cells. To better understand the importance of the modifications of snRNAs, we identified and localized the modified nucleotides in the five spliceosomal snRNAs of Schizosaccharomyces pombe cells. Twenty-two modified nucleotides, including base methylations, 2'-O-methylations, and pseudouridines, were found in the five spliceosomal snRNAs. The conservation of modified nucleotides between human and S. pombe snRNAs is striking. In addition, most of the modified nucleotides are in or around positions that form hydrogen bonds with the pre-mRNA or with other snRNAs. The results are consistent with the suggestion that modified nucleotides are clustered around functionally important regions of the spliceosomal snRNAs. These data provide the basis for further functional studies on posttranscriptional modifications in spliceosomal snRNAs.

Is antrum or corpus the best site for culture of Helicobacter pylori?

BACKGROUND

Isolating Helicobacter pylori on culture media and performing antibiotic susceptibility testing is potentially the most useful tool for guiding antibiotic therapy, especially when antimicrobial resistance is suspected. The aim of this study was to determine whether the yield of H. pylori culture was related to the site from which the gastric specimen was obtained either before or after therapy.

METHODS

Gastric mucosal biopsies from the antrum and the corpus of the stomach were cultured. H. pylori status was determined by histological assessment using the Genta stain.

RESULTS

Fifty-two patients with documented H. pylori infection were studied: Twenty-three were tested before antibiotic therapy and 29 after therapy had failed. In 47 patients (90%), both antral and corpus culture specimens were positive. In 5 patients (10%), only one site was positive, with three false-negative antral and two false negative corpus cultures. The overall sensitivity of culture in detecting H. pylori infection was 95% (95% confidence interval = 89-98%) and was not significantly different for the antrum or corpus, either before or after therapy.

CONCLUSION

Culture of gastric biopsies from either the antrum or the corpus has an excellent diagnostic yield even in patients who failed antimicrobial therapy.

Early graft loss secondary to massive hemorrhagic necrosis following orthotopic liver transplantation. Evidence for cytokine-mediated univisceral Shwartzman reaction

Massive hemorrhagic necrosis (MHN) of the liver following orthotopic liver transplantation (OLT) occurs infrequently during an otherwise uneventful recovery 1 week after OLT. It is characterized by fever and sudden deterioration of allograft function leading to failure in the absence of vascular thrombosis. The etiology is unknown, although it is usually preceded by some degree of allograft rejection. Between 6 and 8 days after OLT, four patients (out of 150) became febrile, hypotensive, and experienced a rapid rise in transaminases within 48 hr. Two patients had evidence of mild rejection; the other two had moderate to severe acute cellular rejection. All patients were ABO identical, crossmatch negative. Bolus steroids were given followed by OKT3 in the two patients with severe rejection. Although sepsis was suspected, antibiotic therapy did not ameliorate the clinical course. Each patient progressed to MHN with severe centrilobular necrosis and variable portal infiltrate. High levels of interferon-gamma and tumor necrosis factor-alpha occurred prior to the rise in transaminases in each MHN patient (155 +/- 39 pg/ml and 414 +/- 201 pg/ml, respectively) compared with levels in OLT patients with severe rejection (14 +/- 4 pg/ml and 26 +/- 5 pg/ml, respectively, P < 0.05). These data support the concept of a cytokine-mediated inflammatory response leading to a univisceral Shwartzman reaction in the transplanted liver. Early recognition of this syndrome and retransplantation are critical for survival.

Protein engineering studies of A-chain loop 47-56 of Escherichia coli heat-labile enterotoxin point to a prominent role of this loop for cytotoxicity

Heat-labile enterotoxin (LT), produced by enterotoxigenic Escherichia coli, is a close relative of cholera toxin (CT). These two toxins share approximately 80% sequence identity, and consists of one 240-residue A chain and five 103-residue B subunits. The B pentamer is responsible for GM1 receptor recognition, whereas the A subunit carries out an ADP-ribosylation of an arginine residue in the G protein, Gs alpha, in the epithelial target cell. This paper explores the importance of specific amino acids in loop 47-56 of the A subunit. This loop was observed to be highly mobile in the inactive R7K mutant of the A subunit. The position of the loop in wild-type protein is such that it might require considerable reorganization during substrate binding and is likely to have a crucial role in substrate binding. Five single-site substitutions have been made in the LT-A subunit 47-56 loop to investigate its possible role in the enzymatic activity and toxicity of LT and CT. The wild-type residues Thr-50 and Val-53 were replaced either by a glycine or by a proline. The glycine substitutions were intended to increase the mobility of this active-site loop, and the proline substitutions were intended to decrease the mobility of this same loop by restricting the accessible conformational space. Under the hypothesis that mobility of the loop is important for catalysis, the glycine-substitution mutants T50G and V53G would be expected to exhibit activity equal to or greater than that of the wild-type A subunit, while the proline substitution mutants T50P and T53P would be less active. Cytotoxicity assays showed, however, that all four of these mutants were considerably less active than wild-type LT. These results lend support for assignment of a prominent role to loop 47-56 in catalysis by LT and CT.

Culture of Helicobacter pylori: effect of preimmersion of biopsy forceps in formalin

BACKGROUND

Treatment of antibiotic-resistant Helicobacter pylori should be based on bacterial sensitivity testing that requires the ability to isolate the bacterium from gastric mucosal biopsies. The aim of this study was to determine whether the yield for detecting H. pylori infection by culture is reduced by immersion of biopsy forceps in formalin prior to obtaining the specimen.

MATERIALS AND METHODS

Gastric antral mucosal biopsies (100 specimens) from 50 patients were obtained for culture of H. pylori. An antral biopsy was taken for culture, and with the same forceps a biopsy was taken for histological examination. The biopsy specimen was removed by shaking, whereas the forceps was immersed in 10% buffered formalin for the histological investigation. The forceps was then used without rinsing to obtain a second specimen for culture from an area adjacent to the first site. H. pylori status was determined by histological assessment with the Genta stain and a rapid urease test.

RESULTS

Fifty patients with H. pylori infection documented by histological inquiry and positive rapid urease testing entered the study; 29 had duodenal ulcers, 5 had gastric ulcers, 1 had mucosal associated lymphoid tissue (MALT) lymphoma, and 15 were without ulcer disease. The results of culture both before and after immersion in formalin were identical. One patient had both cultures negative; the sensitivity of culture for detection of H. pylori infection was 98% (95% confidence interval = 93%-100%).

CONCLUSION

Preimmersion of biopsy forceps in formalin does not adversely affect the ability to culture H. pylori.