A possible mitochondrial gene in the early-branching amitochondriate protist Trichomonas vaginalis

Trichomonads are anaerobic flagellated protists that, based on analyses of ribosomal RNA sequences, represent one of the earliest branching lineages among the eukaryotes. The absence of mitochondria in these organisms coupled with their deep phylogenetic position has prompted several authors to suggest that trichomonads, along with other deeply-branching amitochondriate protist groups, diverged from the main eukaryotic lineage prior to the endosymbiotic origin of mitochondria. In this report we describe the presence of a gene in Trichomonas vaginalis specifically related to mitochondrial chaperonin 60 (cpn60). A recent study indicates that a protein immunologically related to cpn60 is located in trichomonad hydrogenosomes. Together, these data provide evidence that ancestors of trichomonads perhaps harbored the endosymbiotic progenitors of mitochondria, but that these evolved into hydrogenosomes early in trichomonad evolution.

Salmonella typhimurium InvA expression probed with a monoclonal antibody to the C-terminal peptide of InvA

The Salmonella typhimurium InvA protein is a component of a sec-independent secretion apparatus necessary for full virulence of the bacteria. We generated a monoclonal antibody to the C-terminal portion of the InvA protein that recognized proteins in S. typhimurium and weakly in Y. enterocolitica, but not in several other species of bacteria, including S. flexneri. S. typhimurium grown without agitation produced relatively constant amounts of membrane InvA throughout the growth cycle, whereas bacteria grown with agitation had a sharp increase in the amount of membrane InvA at late exponential phase. Levels of InvA present in Salmonella membranes under some growth conditions do not appear to correlate with levels of invasion under the same conditions.

Further characterisation of a monoclonal antibody reactive with Escherichia coli O157:H7

Monoclonal antibody (MAb) 4E8C12 has been previously reported to recognise low mol. wt proteins from enterohaemorrhagic Escherichia coli (EHEC) serotypes O157:H7 and O26:H11. Crude lipopolysaccharide (LPS) preparations from proteinase K-digested bacterial suspensions reacted in Western blots with MAb 4E8C12, as did highly purified LPS from O157:H7 strains. The material recognised by this antibody was, therefore, LPS. The LPS epitope was identified by a whole-cell ELISA in several EHEC, verotoxin producing E. coli (VTEC) and verotoxin-negative strains in addition to E. coli serotypes O157:H7 and O26:H11. Acriflavine and bile salts enhanced the production or availability of the epitope at the cell surface and in culture supernates. These data indicate that the presence of the epitope did not correlate with the virulence of these organisms.

Axenic cultivation of Entamoeba dispar Brumpt 1925, Entamoeba insolita Geiman and Wichterman 1937 and Entamoeba ranarum Grassi 1879

Three species of Entamoeba have been grown in axenic culture for the first time. In two cases, novel methods for adapting the organisms to growth without bacteria were employed. While E. ranarum was axenized by the classic technique of Diamond, from a monoxenic culture with Trypanosoma cruzi as the associate, both E. dispar and E. insolita were first grown in axenic culture medium supplemented with lethally irradiated bacteria. From there, E. insolita was axenized directly, but E. dispar initially required the presence of fixed bacteria. After prolonged culture under this technically axenic but unwieldy culture system, E. dispar was eventually adapted to growth in the absence of added bacteria.

Direct evidence for secondary loss of mitochondria in Entamoeba histolytica

Archezoan protists are though to represent lineages that diverged from other eukaryotes before acquisition of the mitochondrion and other organelles. The parasite Entamoeba histolytica was originally included in this group. Ribosomal RNA based phylogenies, however, place E. histolytica on a comparatively recent branch of the eukaryotic tree, implying that its ancestors had these structures. In this study, direct evidence for secondary loss of mitochondrial function was obtained by isolating two E. histolytica genes encoding proteins that in other eukaryotes are localized in the mitochondrion: the enzyme pyridine nucleotide transhydrogenase and the chaperonin cpn60. Phylogenetic analysis of the E. histolytica homolog of cpn60 confirmed that it is specifically related to the mitochondrial lineage. The data suggest that a mitochondrial relic may persist in this organism. Similar studies are needed in archezoan protists to ascertain which, if any, eukaryotic lineages primitively lack mitochondria.

YI-S, a casein-free medium for axenic cultivation of Entamoeba histolytica, related Entamoeba, Giardia intestinalis and Trichomonas vaginalis

Pancreatic digests of casein are major ingredients of media used in the axenic cultivation of lumen-dwelling parasitic protozoa, especially Entamoeba, Giardia, and trichomonads. The digest used almost exclusively in the development of these media, Medo-Peptone (Trypticase BBL), has not been available since 1981. Moreover, none of dozens of similar type digests tested since then in our laboratory has proved equal to Medo-Peptone, and in the last two years it has become increasingly difficult to obtain new batches which will support even modest growth of Entamoeba histolytica. In response to this problem we have developed a casein-free medium, YI-S, consisting of a nutrient broth, vitamin mixture and serum. We recommend it as a replacement for the casein-dependent medium TYI-S-33, currently the most widely used for axenic culture of Entamoeba histolytica and other lumen-dwellers.

Phylogenetic relationships among anuran trypanosomes as revealed by riboprinting

Twenty trypanosome isolates from Anura (frogs and toads) assigned to several species were characterized by riboprinting-restriction enzyme digestion of polymerase chain reaction amplified small subunit ribosomal RNA genes. Restriction site polymorphisms allowed distinction of all the recognized species and no intraspecific variation in riboprint patterns was detected. Phylogenetic reconstruction using parsimony and distance estimates based on restriction fragment comigration showed Trypanosoma chattoni to be only distantly related to the other species, while T. ranarum and T. fallisi appear to be sister taxa despite showing non-overlapping host specificities.

The 70-kilodalton pertussis toxin-binding protein in Jurkat cells

125I-ASD photoaffinity-labeling derivatives of pertussis toxin (125I-ASD-PT) or lipopolysaccharide (125I-ASD-LPS) labeled similar 70-kDa proteins in Jurkat cells, a cell line derived from human CD4+ T lymphocytes. Labeling of this 70-kDa protein by 125I-ASD-PT was inhibited by underivatized PT but not by underivatized LPS. However, an immunoglobulin M monoclonal antibody with specificity for the p73 LPS receptor in murine splenocytes (S. W. Bright, T.-Y. Chen, L. M. Flebbe, M.-G. Lei, and D. C. Morrison, J. Immunol. 145:1-7, 1990) inhibited 125I-ASD-PT labeling of the 70-kDa species in Jurkat cells. Our results suggested that PT may bind to the same 70-kDa protein as LPS does in Jurkat cells but that PT and LPS bind to different sites on this receptor candidate. 125I-ASD-PT photoaffinity labeling of the 70-kDa protein was also inhibited by underivatized glycoproteins to which PT has been shown to bind, and this inhibition correlated with the relative binding affinities of the glycoproteins for PT. 125I-ASD derivatives of two sialic acid-specific plant lectins, Maackia amurensis leukoagglutinin and Sambucus nigra agglutinin, with oligosaccharide binding specificities similar to those of PT also labeled a 70-kDa protein in Jurkat cells. This suggests that the 70-kDa PT receptor candidate in Jurkat cells likely contains sialooligosaccharide sequences to which PT, M. amurensis leukoagglutinin, and S. nigra agglutinin bind. The cross-reacting epitope recognized by monoclonal antibody 5D3 in this 70-kDa species might overlap the PT- and LPS-binding sites.

Host-parasite relationships in amebiasis: conference report

Entamoeba histolytica has been redescribed as the separate species E. histolytica and Entamoeba dispar. E. dispar is apparently never invasive in humans, while E. histolytica is the etiologic agent of amebic colitis and liver abscess. Virulence factors that may enable E. histolytica to invade include a galactose-specific adhesin, secreted proteases, extracellular matrix receptors, and a cell surface lipophosphoglycan. Progress in vaccine development includes the identification of the cysteine-rich domain of the adhesin and the serine-rich surface protein as protective antigens.

Entamoeba histolytica: a method for isolate identification

The ability to identify individual isolates of Entamoeba histolytica Schaudinn 1903 (Emend. Walker 1911) is necessary before several important epidemiological questions can be answered. We have developed such a method based on our discovery of extensive polymorphism in two E. histolytica genes--the serine-rich antigen gene and the "strain specific gene"--each of which has an internal tandemly repeated structure. Using the polymerase chain reaction we detected both size and restriction site polymorphisms in the repetitive regions. When the two genes were used in combination we obtained 16 distinct DNA patterns out of 18 isolates examined. Moreover, these patterns proved to be stable under a variety of conditions--long-term culture, axenization, cell cloning, and animal passage.

Entamoeba histolytica: an explanation for the reported conversion of "nonpathogenic" amebae to the "pathogenic" form

The reported conversion of "nonpathogenic" Entamoeba histolytica isolates to the "pathogenic" form during attempted axenization of the amebae is highly controversial. After failing to obtain conversions ourselves we concluded that the simplest explanation for the published observations would be contamination of nonpathogenic cultures with pathogenic amebae. To address this possibility we used a method based on analysis of stable DNA polymorphisms that allows the positive identification of individual pathogenic isolates. The DNA patterns obtained using the "converted" amebae proved to be identical to those of reference isolates present in the laboratories at the time of conversion. We also found that very few cells need be transferred for a pathogenic contaminant to become established in a nonpathogenic culture. Cross-contamination fully explains the conversion phenomenon and thus recognition of nonpathogenic and pathogenic amebae as the distinct species Entamoeba dispar Brumpt 1925 and E. histolytica Schaudinn 1903 (Emend. Walker 1911), respectively, is upheld.

Expression and characterization of the eaeA gene product of Escherichia coli serotype O157:H7

In enteropathogenic Escherichia coli, the eaeA gene produces a 94-kDa outer membrane protein called intimin which has been shown to be necessary but not sufficient to produce the attaching-and-effacing lesion. The purpose of this study was to characterize the intimin specified by the eaeA allele of the enterohemorrhagic E. coli (EHEC) serotype O157:H7 strain CL8 and to determine its role in adherence. The carboxyl-terminal 266 amino acids of the CL8 intimin were expressed as a protein fusion with glutathione S-transferase, which was used to raise antiserum in rabbits. The antiserum reacted in Western immunoblots with a 97-kDa outer membrane protein of EHEC strains of serogroups O5, O26, O111, and O157 and enteropathogenic E. coli strains of serogroups O55 and O127. Surface labelling of CL8 with 125I showed that intimin was surface exposed. An eaeA insertional inactivation mutant of CL8 was produced and was designated CL8-KO1. Total adherence of CL8-KO1 to HEp-2 cells was not significantly different from that of CL8, but CL8-KO1 gave a negative result in the fluorescent actin staining test. The eaeA gene expressed alone in E. coli HB101 also gave a negative fluorescent actin staining test result. The eaeA gene of CL8 was able to complement the eaeA deletion mutation in CVD206. We conclude that the product of the EHEC eaeA gene is a 97-kDa surface-exposed protein and propose that it be designated intiminO157. Sherman et al. described a 94-kDa outer membrane protein which played an important role in adherence of E. coli O157:H7 (Infect. Immun. 59:890-899, 1991). Western immunoblotting and indirect fluorescent antibody studies showed that the protein described by Sherman et al. is not intimin.

Hydrophobic binding of pertussis toxin is enhanced by oligosaccharide receptors

Pertussis toxin is one of several virulence factors produced by Bordetella pertussis, the etiologic agent of whooping cough. Pertussis toxin is an oligomeric A-B class toxin composed of an ADP-ribosyltransferase S1 (A) subunit and a B oligomer containing lectin-like binding domains. The carbohydrate binding specificity of the B oligomer is for sialooligosaccharide sequences expressed on target cell receptors and asparagine-linked glycans found in many serum glycoproteins. Pertussis toxin also has the ability to bind to the inert surfaces of culture tubes. In this report we present data showing that pertussis toxin binding to polypropylene microcentrifuge tubes was enhanced in a time- and concentration-dependent manner by the addition of soluble glycoprotein or oligosaccharide receptor analogs. Evidence obtained using the hydrophilic and hydrophobic surfaces of Gel Bond electrophoresis casting film indicated that receptor-enhanced binding was likely due to hydrophobic interactions. Hydrophobic binding of the isolated B oligomer of pertussis toxin was enhanced only in the presence of high concentrations of glycoproteins. Therefore, the S1 (A) subunit of pertussis holotoxin appears to play a role in receptor-enhanced hydrophobic binding. We propose, therefore, that pertussis toxin binding to its receptors may expose or preferentially orient hydrophobic residues that may contribute to the functional association of the toxin with host cell plasma membranes and delivery of the S1 subunit to its intracellular target.

A redescription of Entamoeba histolytica Schaudinn, 1903 (Emended Walker, 1911) separating it from Entamoeba dispar Brumpt, 1925

Explaining the low incidence of invasive disease (10%) in humans infected with Entamoeba histolytica has occupied the attention of generations of both clinical and nonclinical investigators. One possible explanation would be the existence of two morphologically identical species-one an invasive pathogen, the other noninvasive. This was first proposed by Brumpt in 1925, but his explanation was virtually ignored until 1978 when the first of several publications appeared suggesting that E. histolytica did indeed consist of two species. We have reexamined Brumpt's claim in light of recent biochemical, immunological and genetic studies and conclude that the data derived from these investigations provide unequivocal evidence supporting his hypothesis. With this in mind, we redescribe the invasive parasite retaining the name Entamoeba histolytica Schaudinn, 1903 (Emended Walker, 1911), and set it apart from the noninvasive parasite described by Brumpt, Entamoeba dispar Brumpt, 1925.

Entamoeba histolytica: is conversion of "nonpathogenic" amebae to the "pathogenic" form a real phenomenon?

Entamoeba histolytica isolates have been shown to fall into two groups based on isoenzyme analysis. These groupings ("pathogenic" and "nonpathogenic") correlate well with the clinical course of the infection. A controversy exists over whether isoenzyme patterns are stable or whether under certain circumstances an isolate can convert from one form to the other. Resolution of this uncertainty is of importance since the nonpathogenic pattern has never been observed in amebae isolated from cases of active disease. This implies that, if the patterns are stable, carriers of amebae with this nonpathogenic pattern may never develop invasive disease. Although we set out to study isoenzyme conversion, we have been unable to replicate the two published accounts of this phenomenon. We have examined all of the variables proposed to be involved in the triggering of conversion, both individually and in combination. In none of the experiments was an alteration in the isoenzyme pattern observed. We now believe that isoenzyme patterns are stable and that all available evidence, other than the reported conversions, points to pathogenic and nonpathogenic E. histolytica being distinct species.

Colonization of the uterus by the oral protozoan Entamoeba gingivalis

Pap smears occasionally reveal protozoa of the genus Entamoeba in the uterus of intrauterine device (IUD) users, but definitive identification of the species involved has not been possible. Using riboprinting, a technique that compares ribosomal RNA gene sequences, we present evidence that the organism is Entamoeba gingivalis, an inhabitant of the mouth. Colonization most likely occurs via orogenital contact and requires the presence of an IUD and a concomitant bacterial infection.

Differentiation of pathogenic Entamoeba histolytica from other intestinal protozoa by riboprinting

Differentiation of the pathogen Entamoeba histolytica from the variety of other amebas that can infect the human intestinal tract is vital for accurate diagnosis and treatment. Morphology and serology alone are not adequate for positive identification to be achieved. We have developed methods using the polymerase chain reaction to amplify amebal ribosomal RNA genes that allow either specific detection of E. histolytica or species identification.

Ribosomal RNA genes of 'pathogenic' and 'nonpathogenic' Entamoeba histolytica are distinct

Most infections with Entamoeba histolytica are asymptomatic. Two forms of the organism can be distinguished biochemically, and this finding has been explained by two distinct hypotheses: (1) there are two morphologically indistinguishable species, one of which causes disease; (2) there is one species which exists in two interconvertible forms, one of which causes disease. Knowledge of which hypothesis is correct has major implications for evaluation and treatment of carriers. We have studied the ribosomal RNA genes of the two forms hypothesizing that, if E. histolytica is one species, there should be no differences between them. We have found that the ribosomal RNA genes of the two forms are quite distinct, which supports the hypothesis that E. histolytica is two species.

Synthesis and characterization of a Pertussis toxin-biotin conjugate

We prepared a Pertussis toxin-biotin conjugate and found its biological properties to be similar to those of native Pertussis toxin with respect to the hemagglutination, Chinese hamster ovary cell, and lymphocyte proliferation assays. Direct binding to Chinese hamster ovary and Jurkat cells was observed using fluorescence microscopy. Pertussis toxin-biotin was also found to possess similar glycoconjugate binding specificities as those of 125I-labeled Pertussis toxin.

The Laredo strain and other 'Entamoeba histolytica-like' amoebae are Entamoeba moshkovskii

A small number of Entamoeba isolates from humans, the best known of which is the 'Laredo' strain, have the ability to grow at room temperature. This peculiarity, along with other characteristics, distinguishes the strains from the human pathogen E. histolytica despite their being morphologically inseparable. In contrast, these 'E. histolytica-like' strains share several features with E. moshkovskii, which is most frequently isolated from polluted water. To examine the taxonomic relationships among these morphologically similar organisms, we have used polymerase chain reaction amplification of the small subunit ribosomal RNA gene combined with restriction fragment length polymorphism analysis, 'riboprinting'. The results clearly show that the 'E. histolytica-like' amoebae are indeed strains of E. moshkovskii, and not closely related to E. histolytica.

Technique for continuous stride analysis of horses exercising on a treadmill

A technique for continuous computerised recording and analysis of the stride of horses on a treadmill is described. Advantages of the system are low cost, the use of normal shoes and the calculation of stride parameters in real time.

Lymphocyte receptors for pertussis toxin

We have investigated human T-lymphocyte receptors for pertussis toxin by affinity isolation and photoaffinity labeling procedures. T lymphocytes were obtained from peripheral human blood, surface iodinated, and solubilized in Triton X-100. The iodinated mixture was then passed through pertussis toxin-agarose, and the fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoradiography of the fixed, dried gels revealed several bands in the pertussis toxin-bound fraction that were not observed in fractions obtained from histone or fetuin-agarose. Further investigations employed a photoaffinity labeling reagent, sulfosuccinimidyl 2-(p-azido-salicylamido)-1,3'-dithiopropionate, to identify pertussis toxin receptors in freshly isolated peripheral blood monocytic cells, T lymphocytes, and Jurkat cells. In all three cell systems, the pertussis toxin affinity probe specifically labeled a single protein species with an apparent molecular weight of 70,000 that was not observed when the procedure was performed in the presence of excess unmodified pertussis toxin. A protein comparable in molecular weight to the one detected by the photoaffinity labeling technique was also observed among the species that bound to pertussis toxin-agarose. The results suggest that pertussis toxin may bind to a 70,000-Da receptor in human T lymphocytes.

Electrophoretic karyotype and linkage groups of the amoeboflagellate Naegleria gruberi

We have constructed a molecular karyotype for two strains of Naegleria gruberi using pulsed field gel electrophoresis. Each strain has about 23 chromosomes, considerably more than any previous estimate. These chromosomes range in size from 400 kilobasepairs to over 2,000 kilobasepairs. In Naegleria, construction of the DNA karyotype depends on assessment of the anomalous electrophoretic mobility of the circular ribosomal RNA genes. We have determined the chromosomal locations of an identified unique gene (flagellar calmodulin) and four identified multigene families (alpha- and beta-tubulin, actin, ubiquitin), as well as three differentially expressed genes of unknown functions. The ca. 12 actin genes are dispersed over at least seven chromosomes, whereas the majority of the more than eight alpha-tubulin genes are confined to a single chromosome. The ubiquitin genes are found on five chromosomes in one strain and seven in the other and the beta-tubulin genes are on three or four. Our observations provide a foundation for molecular genetic studies in this organism.

Genome structure and evolution of Naegleria and its relatives

In the 4 yr since the molecular biology of DNA in Naegleria was last reviewed several major advances have been made, and these are reviewed here: isolation and characterization of mitochondrial and ribosomal DNAs; enumeration of chromosomal DNAs by pulsed field gel electrophoresis; sequence analysis of differentially expressed genes; phylogenetic placement of the genus Naegleria among the eukaryotes and Naegleria species within the genus.

Immunoscintigraphy of colorectal cancer with an antibody to epithelial membrane antigen (EMA)

Immunoperoxidase staining of LICR-LON M8, a mouse monoclonal antibody reactive with epithelial membrane antigen, showed a strong reaction with colorectal cancer. This finding prompted an immunoscintigraphic study of colorectal cancer patients using this antibody. Sixteen patients had external gamma scintigraphy after intravenous injection of indium 111-labeled M8. Positive scans were obtained in 11 of the 13 patients with primary colorectal cancers, and 2 of the 3 patients with recurrent tumors. The high indium 111 background in the liver prevented the detection of hepatic metastases in 5 patients. Twelve patients had samples taken of tumor, normal colon, and venous blood at the time of surgery. The ratio of labeled antibody uptake in tumor to that of blood was 5.1 (+/- 3.6 S.D.), which was significantly different (P = 0.001) to that of the similar ratio for normal colon (2.0 +/- 1.6 S.D.). The tumor to normal colon uptake ratio was 2.6 (+/- 1.3 S.D.). These results suggest a specific uptake of indium 111-labeled M8 by colorectal cancer.

Vertical banded gastroplasty in the treatment of morbid obesity: results of three year follow up

Vertical banded gastroplasty has replaced jejunoileal bypass in the surgical treatment of morbid obesity. Although this procedure carries a low incidence of early postoperative complications there is little information on either longer term follow up or the impact on nutritional status. The present study describes the outcome in 42 patients with morbid obesity who underwent vertical banded gastroplasty and were followed up in a special nutrition clinic between nine and 36 months postoperatively. Body mass index (BMI) fell from a preoperative value of 47.4 (6.7) kg/m2 (mean (SD] to 37.5 (5.8), 35 (6.2), 33.9 (6.1), and 33.1 (5.7) kg/m2 at 6, 12, 24, and 36 months respectively. Immediate postoperative complications were minimal but during follow up four patients developed stenosis of the gastroplasty stoma and required reoperation. Plasma albumen concentrations were maintained but three patients developed iron deficiency anaemia. Most patients were able to eat a normal diet in reduced quantities and noted a marked improvement in the quality of life. The benefits and safety of vertical banded gastroplasty suggest an important role for this operation in the management of morbid obesity.

Differences in mucosal appearances and in relapse rates in duodenal ulceration treated with sucralfate or cimetidine

A total of 46 patients with duodenal ulcer were randomly assigned, without the knowledge of the investigators, to treatment with cimetidine 200 mg three times daily and 400 mg at night or sucralfate 1 g four times daily followed by one year of maintenance treatment with cimetidine 400 mg at night or sucralfate 1 g twice daily, respectively, in those patients with healed ulcers. The endoscopic healing rates and relapse rates during the maintenance period were similar, four relapses occurring in each group. All four relapses in the sucralfate group occurred at 12 months and only two were symptomatic. All the cimetidine relapses were symptomatic, two occurring at six months, one at nine months, and one at 12 months. Following the one year maintenance period, 13 cimetidine patients and 11 sucralfate patients were followed up for 36 months. During the first two years, nine of 13 (69 percent) cimetidine-treated and two of 11 (18 percent) sucralfate-treated patients had relapses. During the third year, three more sucralfate-treated patients and one more cimetidine-treated patient had relapses, making a total of 10 of 13 (77 percent) and five of 11 (45 percent) in the cimetidine and sucralfate groups, respectively. Duodenal biopsy specimens obtained before and after healing and after one year of maintenance were examined by light and electron microscopy. The sucralfate group showed greater improvement after one year of maintenance therapy than did the cimetidine group, although the appearances in either group were not predictive of subsequent relapse. The results show that relapses are less frequent and occur later after sucralfate therapy and also that the morphologic appearances are more normal after treatment with sucralfate than after treatment with cimetidine.

Lectinlike properties of pertussis toxin

We have examined the lectinlike properties of pertussis toxin by binding-inhibition assays and affinity chromatography of goose erythrocyte membranes. Although pertussis toxin and wheat germ agglutinin apparently recognize similar sugar sequences on glycoproteins, the binding activities of the two lectins are not identical.

Evaluation of evolutionary divergence in the genus Naegleria by analysis of ribosomal DNA plasmid restriction patterns

Ribosomal DNA (rDNA) plasmid restriction maps of 10 strains and rDNA hybridisation patterns of 61 additional strains have been used to assess inter- and intra-specific diversity and phylogenetic relationships in the genus Naegleria. The results obtained by this method largely confirm those of previous studies based on a variety of other criteria. They indicate that very little variation exists within the pathogenic species Naegleria fowleri despite its worldwide distribution and that it is closely related to the nonpathogenic Naegleria lovaniensis. Naegleria gruberi is most likely a polyphyletic grouping and care should be taken when using one strain as a reference point for this species. In addition, the two subspecies of the pathogenic Naegleria australiensis arose separately from within the range of variability encompassed by N. gruberi, as did the species Adelphamoeba galeacystis which should probably be assigned to the genus Naegleria. The species Naegleria jadini and Naegleria andersoni are not closely related to any other in the genus based on their rDNA patterns.

Comparison of relapse rates and of mucosal abnormalities after healing of duodenal ulceration and after one year's maintenance with cimetidine or sucralfate: a light and electron microscopy study

Forty six patients with endoscopically diagnosed duodenal ulceration were randomly allocated to treatment with either sucralfate 1 g qds (n = 24) or cimetidine 200 mg tds and 400 mg nocte (n = 22). When the ulcers healed, a maintenance dose of sucralfate 1 g bd or cimetidine 400 mg nocte was given for one year (or until relapse if earlier). Biopsies of duodenal mucosa adjacent to ulcer sites for light and electron microscopy were obtained before and after healing and again after one year's maintenance if the ulcer remained healed. Duodenal biopsies were also taken from 20 age and sex matched controls. Rates of healing and relapse during maintenance did not differ between the two treatments, although relapses occurred earlier with cimetidine. In the three year post-maintenance follow up period 10/13 cimetidine patients relapsed compared with four of 11 sucralfate patients (p less than 0.05), the relapses occurring significantly earlier in the cimetidine treated patients (p less than 0.05). Mucosal biopsies from both treatment groups still showed considerable abnormalities after healing. During maintenance, however, the sucralfate scores fell significantly (p less than 0.02) to near control levels unlike the cimetidine scores which remained raised at pretreatment values. The histological and ultrastructural changes were not predictive of later relapse. These findings favour the use of sucralfate in preference to cimetidine for maintenance treatment in the prevention of relapse of healed duodenal ulcers.

Leucine kinetics in surgical patients. II: A study of the effect of malignant disease and tumour burden

Isotope studies of protein turnover have given conflicting evidence about the effects of a malignant tumour on the protein metabolism of the host. Leucine kinetics have been studied, as an index of protein turnover, using a well established methodology. Twenty patients were studied, five with benign disease of the colon, ten with localized malignant tumours of the large bowel, and five in whom there was evidence of metastatic disease from a colonic primary. No effect was observed on the leucine turnover of the patients that might be attributable to the presence or size of the tumour burden. It is suggested that some of the previously conflicting results may be attributable to variability in the experimental design, the heterogeneous patient groups studied and the methods used to express the results obtained.

Leucine kinetics in surgical patients. I: A study of the effect of surgical 'stress'

At present there is no consensus about the effect of surgical and accidental trauma on protein metabolism. Leucine kinetics, an index of protein turnover, have been studied in ten patients before intra-abdominal surgery and on either the third (n = 5) or seventh (n = 5) postoperative day. Only small changes in leucine kinetics were noted in the early postoperative study but, by the seventh day, there was evidence of increased synthesis as part of an overall elevation of turnover rates. It is suggested that the previously expressed opinion that protein synthesis is reduced after surgery must be re-examined.

Duodenal and antral mucosal prostaglandin E2 synthesis in a study of normal subjects and all stages of duodenal ulcer disease treated by H2 receptor antagonists

We tested the hypothesis that the production of prostaglandin E2 (PGE2) is impaired in duodenal ulcer disease and affected by treatment and healing. This was investigated by a study of maximal PGE2 synthesis rates in duodenal and antral mucosal biopsies obtained at endoscopy. The patients were divided into three groups. Group (a): endoscopically normal controls (n = 56); group (b): treatment controls (non-DU disease: gastric ulcer or oesophagitis treated by histamine H2 receptor antagonists) (n = 41); and group (c): patients with DU disease (n = 183) further subdivided into group (c1) active ulcer not on treatment (n = 47), (c2) treated active ulcer (n = 35), (c3) healed ulcer on treatment (n = 86), and (c4) healed ulcer not on treatment (n = 15). Group (a) synthesised (mean (SD] 106.6 (39.0) pg PGE2/mg wt of tissue from the duodenal bulb and 129.9 (56.9) from the second part of the duodenum. No difference was found between group (a) and (b) at either site. Group (c1) ulcer rim made 49.8 (22.7) and at all stages ulcer rim and scar made less than the control duodenal bulb (p less than 0.02). Uninvolved duodenal bulb form groups (c1) (63.4 (31.0], (c2) (83.6 (38.5], and (c3) (81.5 (31.1], however, also made significantly less than controls (p less than 0.02) and a similar though non-significant trend was seen in group (c4). Biopsies from the second part of the duodenum did not synthesise significantly less than the control group but a similar trend was noticed at each stage of ulcer treatment. Biopsies of control antrum synthesised 124.5 (32.2) but only 93.7 (44.2) in group (cl) (p < 0.005). All stages of duodenal ulcer healing were associated with a decreased capacity to synthesise the major prostaglandin PGE2 at the ulcer site and the uninvolved duodenal bulb and, in acute untreated duodenal ulcer, the uninvolved antrum. This decreased capacity may be the consequence of the disease process itself and not secondary to the treatment, indicating a basic pathophysiological abnormality which may explain the characteristic tendency of the disease to relapse.

Small-subunit ribosomal RNA sequence from Naegleria gruberi supports the polyphyletic origin of amoebas

We have sequenced the small-subunit ribosomal RNA gene of the amoebo-flagellate protozoan Naegleria gruberi. Comparison of this sequence with the rRNA sequences of other eukaryotes resulted in a phylogenetic tree that supports the suggested polyphyletic origin of amoebas and suggests a flagellate ancestry for Naegleria.

Circular ribosomal RNA genes are a general feature of schizopyrenid amoebae

We have recently shown that the ribosomal RNA genes of the amoebo-flagellate Naegleria gruberi Schardinger, 1899, strain NEG-M are carried exclusively on a 14 kilobasepair plasmid. To explore the distribution of this unique gene arrangement, we have examined another strain of N. gruberi and four other species from the order Schizopyrenida. All have this unusual gene arrangement although the size of the plasmid varies widely. Species groups based on morphological criteria do not agree with those resulting from comparison of plasmid restriction enzyme patterns.

The protective effect of Meciadanol (O-methyl-3(+)-catechin) on experimental ulceration

Meciadanol, (O-methyl-3(+)-catechin), a histidine decarboxylase inhibitor was shown to have a marked protective action against experimental peptic ulceration in three rat models. The three methods used to induce ulceration were the instillation of absolute alcohol, pyloric ligation following an ulcerogenic South Indian diet and the instillation of rice bran oil into the stomach after pyloric ligation. Meciadanol was shown to reduce incidence, numbers and areas of ulceration and protected mast cells against degranulation and to preserve a normal vascular patterns. Furthermore, Meciadanol reduced gastric acid output and concentration in the pylorus ligation model. These results indicate that Meciadanol may be useful for the treatment of peptic ulcers in humans.

The strength, contractile properties and radiological density of skeletal muscle before and 1 year after gastroplasty

1. Skeletal muscle strength, contractile properties and radiological composition have been studied in seven morbidly obese adults (six female) before and 1 year after gastroplasty operations. The mean body weight fell from 138.3 kg (SD 25.2) to 99.7 kg (SD 23.0) (P less than 0.001). 2. The strength and contractile properties (force/frequency, relaxation rate and fatiguability) of both the adductor pollicis and quadriceps muscles were unaffected by the weight loss. 3. Computerized axial tomography scans obtained 1 year after surgery showed that the quadriceps contained an abnormally high proportion of fat. The mean fat content was 10.8% (range 3.0-30.1%) compared with 1.6% (range 0-5%) for normal muscle. Two individuals were scanned before and after surgery and the fat content of their quadriceps fell from 12.6% and 6.9% to 3.1% and 3.0%, respectively. 4. It is concluded that in obese individuals large amounts of weight can be lost, from both subcutaneous and intramuscular fat stores, without compromising either the strength or contractile properties of skeletal muscles. These results do not support the claim that skeletal muscle contractility is a sensitive indicator of changes in nutritional status.

A comparison of carcinoembryonic antigen (CEA) and epithelial membrane antigen (EMA) in human colorectal cancer

The development of monoclonal antibodies (MAbs) to tumour-associated antigens has allowed the successful radioimmunolocalization of a variety of tumours and has provided a basis for targeted therapy. In patients with colorectal cancer, antibodies to CEA have been the most widely used for imaging, but their role in targeted therapy may be inhibited by their reaction with normal tissues and with circulating CEA. Epithelial-membrane antigen (EMA) is expressed by most epithelial tumours, including colorectal cancers, and antibodies to EMA may provide a satisfactory alternative. We therefore compared two high-affinity MAbs, one to CEA (C46) and one to EMA (ICR2), in tissues obtained from 31 patients with cancer (18 primary colonic, 6 nodal metastases and 7 liver metastases), 14 patients with adenomatous polyps and 17 with normal colon. The indirect immunoperoxidase staining reaction was used and the results classified as either positive or negative. A heterogeneous pattern of staining was found for both antibodies. ICR2, the anti-EMA, reacted with slightly fewer colonic cancers than C46, the anti-CEA antibody (83% vs. 100%) and a similar number of metastases. Most noticeable was the minimal reaction of anti-EMA with normal colon (12% vs. 71%) and benign polyps (7% vs. 79%) in comparison to anti-CEA. This would suggest a possible role for ICR2 in the radioimmunolocalization and targeting of colorectal cancer.

Skeletal muscle function after major abdominal surgery

The contractile properties of the adductor pollicis and quadriceps muscles have been studied before and 4 and 10 d after major abdominal surgery in 15 patients. Eight patients were considered well nourished and 7 malnourished on the grounds of body mass index, recent weight loss and serum albumin. There were no significant changes in the contractility of the adductor pollicis at 4 and 10 d post-operatively compared to pre-operative values. The only change in the quadriceps was seen in the malnourished patients and was a potentiation of the force:frequency relationship at day 4, affecting force generation at 1 Hz. There was a tendency for the malnourished patients to generate higher forces at low stimulation frequencies and to have slower relaxation rates, but there was no significant difference between the two groups. Pre-operative contractile properties of those patients who developed post-operative complications were not different from those who were free of complications, nor did the post-operative results of the two groups of patients differ. The patients generated higher forces at lower stimulation frequencies than is usually found in young normal subjects. This may be due to age, disease or nutritional factors, but it is not possible to determine the relative contributions of these factors from this study.

rRNA genes of Naegleria gruberi are carried exclusively on a 14-kilobase-pair plasmid

An extrachromosomal DNA was discovered in Naegleria gruberi. The 3,000 to 5,000 copies per cell of this 14-kilobase-pair circular plasmid carry all the 18S, 28S, and 5.8S rRNA genes. The presence of the ribosomal DNA of an organism exclusively on a circular extrachromosomal element is without precedent, and Naegleria is only the third eucaryotic genus in which a nuclear plasmid DNA has been found.

Photodynamic therapy in the normal rat colon with phthalocyanine sensitisation

Photodynamic therapy (PDT) involves the interaction of light with an administered photosensitising agent to produce cellular destruction. It has promising potential for the local and endoscopic treatment of gastrointestinal cancer. There is however little data on the response of normal intestine to PDT. We have investigated the use of a new photosensitiser chloro aluminum sulphonated phthalocyanine (AlSPc) for colonic PDT. The peak concentration of AlSPc in the colon measured by alkali extraction occurred 1 h after i.v. injection. The cellular uptake demonstrated by laser fluorescence microscopy was greater in the mucosa than in the muscle. AlSPc was activated in the tissues by light from an argon ion pumped dye laser at 675 nm. The laser power was set at 100 mW and the fibre placed touching the mucosa. In control animals no macroscopic damage was seen. Temperature measurement using a microthermocouple array showed no temperature rise during light exposure. The energy (fluence), dose of sensitiser and time from sensitisation to phototherapy were altered and the area of necrosis measured. The geometry of the colon made theoretical analysis of the correlation between laser energy and size of lesion difficult. However, following direct measurement of the relative light intensity (fluence rate) in the colon we were able to confirm that there was a threshold fluence for colonic necrosis. The area of photodynamic damage seen 72 h after phototherapy fell with the fall in tissue concentration of AlSPc from 1 h to 1 month after i.v. injection. However, maximum tissue necrosis occurred when treatment was performed immediately after i.v. injection. In this situation, intense vascular spasm was seen and any light transmitted through the colon which fell on the small bowel mesentery caused a lethal ischaemic necrosis. The initial histological changes after PDT were vascular, followed by full thickness necrosis at 72 h. Healing by regeneration was complete by 2-3 weeks. Despite full thickness necrosis there was no reduction in the colonic bursting pressure at any time. Colon treated by hyperthermia had a reduced bursting pressure. Specific collagen stains showed that PDT did not alter the submucosal collagen architecture whereas hyperthermia did.