Reshuffling of Rhs components to create a new element

RhsF has been identified as the fourth member of the RhsABCF subfamily of genetic elements. This new element is found in Escherichia coli ECOR-50 and several other strains but not in strain K-12. A novel feature of RhsF is that it represents a new arrangement of components previously uniquely associated with RhsA and RhsC of strain K-12.

Identification of candidate vaccine antigens of bovine hemoparasites Theileria parva and Babesia bovis by use of helper T cell clones

Current vaccines for bovine hemoparasites utilize live attenuated organisms or virulent organisms administered concurrently with antiparasitic drugs. Although such vaccines can be effective, for most hemoparasites the mechanisms of acquired resistance to challenge infection with heterologous parasite isolates have not been clearly defined. Selection of potentially protective antigens has traditionally made use of antibodies to identify immunodominant proteins. However, numerous studies have indicated that induction of high antibody titers neither predicts the ability of an antigen to confer protective immunity nor correlates with protection. Because successful parasites have evolved antibody evasion tactics, alternative strategies to identify protective immunogens should be used. Through the elaboration of cytokines, T helper 1-(Th1)-like T cells and macrophages mediate protective immunity against many intracellular parasites, and therefore most likely play an important role in protective immunity against bovine hemoparasites. CD4+ T cell clones specific for soluble or membrane antigens of either Theileria parva schizonts or Babesia bovis merozoites were therefore employed to identify parasite antigens that elicit strong Th cell responses in vitro. Soluble cytosolic parasite antigen was fractionated by gel filtration, anion exchange chromatography or hydroxylapatite chromatography, or a combination thereof, and fractions were tested for the ability to induce proliferation of Th cell clones. This procedure enabled the identification of stimulatory fractions containing T. parva proteins of approximately 10 and 24 kDa. Antisera raised against the purified 24 kDa band reacted with a native schizont protein of approximately 30 kDa. Babesia bovis-specific Th cell clones tested against fractionated soluble Babesia bovis merozoite antigen revealed the presence of at least five distinct antigenic epitopes. Proteins separated by gel filtration revealed four patterns of reactivity, and proteins separated by anion exchange revealed two patterns of reactivity when selected T cell clones were assayed for stimulation by antigenic fractions. Studies using a continuous-flow electrophoresis apparatus have indicated the feasibility of identifying T cell-stimulatory proteins from parasite membranes as well as from the cytosolic fraction of B. bovis merozoites. The Th cell clones reactive with these different hemoparasites expressed either unrestricted or Th1 cytokine profiles, and were generally characterized by the production of high levels of IFN-gamma. A comprehensive study of T cell and macrophage responses to defined parasite antigens will help elucidate the reasons for vaccine failure or success, and provide clues to the mechanisms of acquired immunity that are needed for vaccine development.

[Determination of primaquine and hepatic targeting neoglycoalbumin-primaquine in whole blood and liver of mouse by normalphase high-performance liquid chromatography]

We have developed a method to estimate primaquine (PQ) and hepatic targeting antimalarial agent neoglycoalbumin-primaquine (NGA PQ) in whole blood and liver of mice by sensitive and selective high-performance liquid chromatography. The primaquine was extracted out with ether from the basified biological samples in the PQ diphosphate group or from the samples which were acidic hydrolyzed then basified in NGA-PQ group. The extracts were evaporated under N2 then dissolved in the mobile phase. A linear chain analogue of primaquine was used as the internal standard. The samples were injected into the normal phase silica column with chloroform: methanol:ammonia solution (86.8:12.5:0.7,V/V/V) as mobile phase and detected at 254 nm. The average recovery of the method was 100.09 +/- 3.46 (mean +/- s)%; the CV of within-day and between-day were 2.7%-6.13% (n = 5) and 8.32%-13.56% (n = 9) respectively; in PQ group and NGA-PQ group, the PQ concentrations ranged from 10-20,000 ng/ml blood or 1g. liver respectively, and they all yielded a good linear relationship with the peak height ratios. No endogeneous interference was found in chromatograms of biological samples.

Expression of MDR1 by normal bone marrow cells and its implication for leukemic hematopoiesis

Expression of MDR1 is a well-characterized mechanism leading to resistance of tumor cells to drugs like vinca-alkaloids, anthracyclines, and epipodophyllotoxins. In hematopoiesis, recent data indicate that not only leukemic cells, but also some populations of normal hematopoietic cells, particularly CD34+ progenitor cells as well as peripheral blood lymphocytes, express a functional multidrug-resistant phenotype. Among CD34+ cells, we found evidence that myeloid committed precursor cells (CD34+/CD33+) have lower levels of MDR1 expression than earlier CD34+ cell populations, but there was no difference in MDR1 expression between CD34+/HLA-DR- and CD34+/HLA-DR+ subpopulations. During normal myeloid differentiation, MDR1 expression is down-regulated, which is similar to our observations in acute myelogenous leukemia (AML): MDR1 expression was only rarely detected in acute promyelocytic leukemia, which was in contrast to other subtypes of AML; also, within leukemic subpopulations of the same patient, higher MDR1 levels were correlated with a more immature immunophenotype. Regarding regulation of MDR1 expression, we did not observe changes of MDR1 expression in normal CD34+ cells in response to various cytokines. However, in 2 patients with AML treated with interleukin-3 and granulocyte-colony stimulating factor, respectively, a significant down-regulation of MDR1 expression was found after 24 hours. In conclusion, there is evidence that the pattern of MDR1 expression observed in leukemias reflects the distribution of MDR1 in normal hematopoiesis. In contrast to normal CD34+ cells, leukemic cells from some AML patients can respond to cytokines with a down-regulation of MDR1, which may contribute to response to cytokine/chemotherapy combinations.

[Detection of hypermethylation in affected males with fragile X syndrome by PCR assay]

PCR technique was applied to detect hypermethylation at BssH II recognition sites within CpG island of FMR-1 gene in normal, affected, and clinically suspected males with fragile X syndrome. Hypermethylation was found to occur in all 7 affected and 5 of 26 suspected, but none of 15 normal males. The results of PCR assay are in good coincidence with those of Southern blot and cytogenetic assays. This PCR assay will be a promising method in the diagnosis of fragile X syndrome in males with mental retardation.

[Rectal administration of ash bark]

A TLC-densitometric method was applied to determine aesculin in rabbit blood. The best way for ash bark rectal administration was found by orthogonal design [L4(2(3))]. The two routes of administration (per rectal, P.O.) were compared by bioavailabilities and the result indicated that per rectal was better than P.O. Modified isolated rectum-bag method was applied successfully to finding the best way for rectal administration of ash bark.

[Research on rectal administration of bark of official Magnolia]

Fluorescence assay was applied to the determination of magnolol in rabbit blood, and the best way to administer the bark of official magnolia per rectal was established by orthogonal test. Then the two routes of administration were compared by AUC of magnolol and per rectal was found better than P.O. In addition, the modified isolated rectum-bag method was applied successfully to the research on rectal administration of bark of official magnolia.

Granulocyte-colony stimulating factor, granulocyte-macrophage colony stimulating factor, PIXY-321, stem cell factor, interleukin-3, and interleukin-7: receptor binding and effects on clonogenic proliferation in acute lymphoblastic leukemia

Cytokines are frequently used after chemotherapy of leukemias and solid tumors to augment recovery of normal hematopoiesis. While the regulation of normal and leukemic myelopoiesis is well investigated, little is known about effects of cytokines on growth and differentiation of lymphoblastic leukemia. In this study, we investigated the expression of receptors for G-CSF, GM-CSF, SCF, IL-3, and IL-7 on acute lymphoblastic leukemia (ALL) blasts and the effects of these growth factors (GF) on ALL blast colony formation. The binding of fluorescence-tagged cytokines to receptors on ALL blasts was studied by flow-cytometry in 27 cases of ALL (24 precursor B-ALL, 3 T-ALL). Receptor-binding for myeloid-associated GF was observed in the majority of precursor B-ALL (G-CSF = 100%, GM-CSF = 65%, IL-3 = 83%, SCF = 74%), but not in T-ALL. Binding of labelled IL-7 was detected in both precursor B- (92%) and T-ALL (100%). The presence of receptors for SCF in ALL was confirmed by polymerase chain reaction for c-kit mRNA in 19/21 cases tested. Expression of receptors for G-CSF, GM-CSF, IL-3, and SCF was not associated with expression of myeloid antigens, or with specific cytogenetic abnormalities. The effects of these GF on clonogenic cells were tested in the ALL blast colony assay and varied between samples, but all cytokines were able to increase clonogenic growth. The GM-CSF/IL-3 fusion molecule PIXY-321 was most effective in promoting colony growth. In some cases inhibition of colony formation was found. We conclude that ALL blast cells have receptors not only for IL-7, but also for G-CSF, GM-CSF, SCF, and IL-3. ALL precursors can respond to these GF with changes in their clonogenic growth indicating the presence of functional receptors. Results may have implications for therapeutic approaches combining cytokines and chemotherapy.

Epitope mapping of the branched chain alpha-ketoacid dehydrogenase dihydrolipoyl transacylase (BCKD-E2) protein that reacts with sera from patients with idiopathic dilated cardiomyopathy

Sera from 29 of 48 patients with idiopathic dilated cardiomyopathy (IDCM) and six of six patients with dilated cardiomyopathy (DCM) secondary to suspected viral myocarditis were shown to react with the branched chain alpha-ketoacid dehydrogenase (BCKD) complex mitochondrial proteins. Whereas sera from only 1 of 26 patients with ischemic heart disease showed reactivity against the BCKD complex protein, 0 of 30 sera from normal human volunteers, 0 of 64 sera from patients with lupus, and 0 of 34 sera from patients with rheumatoid arthritis showed detectable reactivity, denoting an element of specificity for the reactivity of sera from IDCM patients. The major reactivity was localized to the dihydrolipoyl transacylase (E2) component of BCKD complex. By using recombinant techniques, the immunodominant BCKD-E2 epitope recognized by sera from IDCM patients was localized to amino acid (aa) sequences 116 to 134. Each of the IDCM sera that reacted with the native BCKD complex was shown to react with the immunodominant peptide, as defined by a peptide inhibition ELISA and by an ELISA using the reactive peptide conjugated to BSA. Sera from IDCM patients that reacted with the native BCKD complex and the reactive peptide also showed inhibition of BCKD enzyme activity. The possible mechanisms for the induction of the Abs and the implications of these findings for the pathogenesis of IDCM are discussed.

Epitope mapping of the branched chain alpha-ketoacid dehydrogenase dihydrolipoyl transacylase (BCKD-E2) protein that reacts with sera from patients with idiopathic dilated cardiomyopathy

Sera from 29 of 48 patients with idiopathic dilated cardiomyopathy (IDCM) and six of six patients with dilated cardiomyopathy (DCM) secondary to suspected viral myocarditis were shown to react with the branched chain alpha-ketoacid dehydrogenase (BCKD) complex mitochondrial proteins. Whereas sera from only 1 of 26 patients with ischemic heart disease showed reactivity against the BCKD complex protein, 0 of 30 sera from normal human volunteers, 0 of 64 sera from patients with lupus, and 0 of 34 sera from patients with rheumatoid arthritis showed detectable reactivity, denoting an element of specificity for the reactivity of sera from IDCM patients. The major reactivity was localized to the dihydrolipoyl transacylase (E2) component of BCKD complex. By using recombinant techniques, the immunodominant BCKD-E2 epitope recognized by sera from IDCM patients was localized to amino acid (aa) sequences 116 to 134. Each of the IDCM sera that reacted with the native BCKD complex was shown to react with the immunodominant peptide, as defined by a peptide inhibition ELISA and by an ELISA using the reactive peptide conjugated to BSA. Sera from IDCM patients that reacted with the native BCKD complex and the reactive peptide also showed inhibition of BCKD enzyme activity. The possible mechanisms for the induction of the Abs and the implications of these findings for the pathogenesis of IDCM are discussed.

Comparison of the enzymatic activities of native and recombinant protein phosphatase-1 toward histone

The activities of native and recombinant rabbit muscle protein phosphatase-1 toward phosphorylated lysine-rich histone and phosphorylase a were compared. The activity of rabbit muscle protein phosphatase-1 toward histone is strongly stimulated by Mn++. In the case of the recombinant enzyme, both phosphorylase phosphatase and histone phosphatase activities exhibit a dependence on Mn++. Examination of the activities of both enzymes assayed under optimal conditions show that they exhibit similar substrate specificities toward histone and phosphorylase, contrary to previous claims (Alessi et al., Eur. J. Biochem. 213, 1055-1066, 1993).

The reductive acetyl coenzyme A pathway: sequence and heterologous expression of active methyltetrahydrofolate:corrinoid/iron-sulfur protein methyltransferase from Clostridium thermoaceticum

The methyltransferase (MeTr) from Clostridium thermoaceticum transfers the N5-methyl group of (6S)-methyltetrahydrofolate to the cobalt center of a corrinoid/iron-sulfur protein in the acetyl coenzyme A pathway. MeTr was purified to homogeneity and shown to lack metals. The acsE gene encoding MeTr was sequenced and actively expressed in Escherichia coli at a level of 9% of cell protein. Regions in the sequence of MeTr and the E. coli cobalamin-dependent methionine synthase were found to share significant homology, suggesting that they may represent tetrahydrofolate-binding domains.

Markedly enhanced cytochrome P450 2E1 induction and lipid peroxidation is associated with severe liver injury in fish oil-ethanol-fed rats

We evaluated the role of changes in cytochrome P-450 2E1 (CYP 2E1) and lipid peroxidation in relation to development of severe liver injury in fish oil-ethanol-fed rats. The experimental animals (male Wistar rats) were divided into 5 rats/group and were fed the following diets for 1 month: corn oil and ethanol (CO+E) or corn oil and dextrose (CO+D), and fish oil and ethanol (FO+E) or fish oil and dextrose (FO+D). For each animal, microsomal analysis of CYP 2E1 protein, aniline hydroxylase activity, fatty acid composition, and conjugated dienes was conducted. Also, evaluation of severity of pathology was done for each rat. The mean +/- SD of the pathology score was significantly higher (p < 0.01) in the FO+E (6.0 +/- 1.3) group than in the CO+E group (3.0 +/- 0.5). No pathological changes were evident in the dextrose-fed controls. The CYP 2E1 protein levels (mean +/- SD) were significantly higher (p < 0.01) in the FO+E group (13.1 +/- 2.0) compared with the CO+E (4.7 +/- 1.2) and FO+D (1.8 +/- 0.5) groups. Higher levels of eicosapentaenoic and docosahexaenoic acids and lower levels of arachidonic acid were detected in liver microsomes from rats fed fish oil compared with corn oil. A significant correlation was obtained between CYP 2E1 protein and conjugated diene levels (r = 0.78, p < 0.01). Our results showing markedly increased CYP 2E1 induction and lipid peroxidation in the FO+E group provides one possible explanation for the greater severity of liver injury in this group.

The STL1 gene of Saccharomyces cerevisiae is predicted to encode a sugar transporter-like protein

A gene has been cloned from the yeast Saccharomyces cerevisiae which, on the basis of the deduced translation product, encodes a sugar transporter-like protein. This gene, STL1, was identified as an open reading frame (ORF) closely linked to the cinnamic-acid-resistance gene POF1 on chromosome IV. The putative translation product of STL1 (STL1) contains 536 amino acids, with a M(r) of 60,507. Hydropathy analysis of STL1 suggests that it contains the twelve transmembrane (TM) domains characteristic of a family of sugar transporters from S. cerevisiae and other organisms. STL1 displays greatest homology (28% identity) to the products of the yeast HXT2 (hexose transporter) and GAL2 (galactose transporter) genes. Disruption of STL1 had no detectable effect on yeast growth on glucose, galactose, mannose, maltose or glycerol as sole carbon source. The transport function of the gene product remains unknown at present.

Changes in cytochromes P-450, 2E1, 2B1, and 4A, and phospholipases A and C in the intragastric feeding rat model for alcoholic liver disease: relationship to dietary fats and pathologic liver injury

The influence of dietary fat and alcohol on hepatic microsomal levels of cytochromes P-450 2E1, 2B, and 4A; phospholipases A and C; and UDP-glucuronosyltransferase was studied in the intragastric feeding rat model for alcoholic liver injury. Eight groups of animals were evaluated. Control and ethanol fed rats received either saturated fat or corn oil and were killed after 2 weeks and 1 month of feeding. All animals were pair-fed by continuous infusion of liquid diet through permanently implanted gastric cannulas. Alcoholic liver injury developed only in the corn oil-ethanol-fed groups and was manifest by 1 month. Livers were subjected to the following analyses: pathologic evaluation of liver injury; levels of cytochromes P-450 2E1, 2B, and 4A protein and mRNA; aniline hydroxylase activity; and phospholipase A and C and UDP-glucuronosyltransferase activities. Ethanol-induced increases in cytochromes P-450 2E1 and 2B protein determined by Western blotting were greatest in the corn oil-ethanol-fed group, which developed pathologic changes in the liver. Cytochromes P-450 2E1 and 2B1 mRNA levels were unaffected, suggesting that posttranscriptional mechanisms are responsible for the increase in the corresponding P-450 proteins. In contrast, cytochrome P-450 4A levels were higher in the saturated fat-ethanol groups compared with the corn oil-ethanol groups. Phospholipase A and phospholipase C levels were higher in the corn oil-ethanol groups compared with pair-fed dextrose controls and the saturated fat-ethanol groups. UDP-glucuronosyltransferase levels declined with time in the ethanol-fed groups.(ABSTRACT TRUNCATED AT 250 WORDS)

A device for subjecting vascular endothelial cells to both fluid shear stress and circumferential cyclic stretch

The proposal of the role of mechanical forces as a localizing factor of atherosclerosis has led many researchers to investigate their effects on vascular endothelial cells. Most previous efforts have concentrated on either the fluid shear stress, which results from the flow of blood, or the circumferential "hoop" stretch, which results from the expansion of the artery during the cardiac cycle. In fact, arterial endothelial cells are subjected to both fluid shear stress and cyclic hoop stretch in vivo. Therefore, a more complete investigation of mechanical phenomena on endothelial cell behavior should include both kinds of mechanical stimuli. This study was undertaken to design an experimental apparatus that could subject cultured vascular endothelial cells to simultaneous physiologic levels of both shear stress and cyclic hoop stretch. The experimental apparatus consists of four cylindrical elastic tubes so that the following conditions may be studied: (a) static conditions: (b) shear stress only; (c) hoop stretch only; and (d) shear stress and hoop stretch. In order to establish the functional capabilities of the apparatus, bovine pulmonary artery endothelial cells were cultured in the tubes, and their morphology and f-actin structure were observed with confocal microscopy. The cells remained healthy and attached to the walls throughout the 24 hr experiment. Preliminary results indicated that the alignment of endothelial cells subjected to shear stress was significantly enhanced by the addition of hoop strain.

rDlx, a novel distal-less-like homeoprotein is expressed in developing cartilages and discrete neuronal tissues

From a rat chondrosarcoma we isolated a cDNA that encodes a novel homeoprotein rDlx. The homeodomain of rDlx shows a high degree of sequence identity with those of Drosophila Distal-less, mouse Dlx, and Xenopus Xdll proteins. Northern hybridization of rDlx revealed a 1.4- to 1.6-kb RNA species in a rat chondrosarcoma and a cell line derived from this tumor and in mouse C3H10T1/2 cells, but no rDlx RNA was detected in mouse NIH3T3 fibroblasts, rat skin fibroblasts, mouse C2 myoblasts, mouse myeloma S194 cells, human B-cell lymphoma Daudi cells, or human acute myelocytic leukemia cells. RNase protection assays showed that rDlx transcripts were present at high levels in 14-day-old rat embryos, 18-day-old rat embryo skeletal tissues, and adult rat brain. rDlx RNAs were present at lower levels in newborn rat rib cartilage, 18-day-old rat embryo soft tissues, newborn rat skin, and adult rat heart. rDlx transcripts were not detected in adult rat liver, spleen, lung, kidney, testis, or skeletal muscle. In situ hybridization of rat embryos at different stages revealed that rDlx transcripts were present in otic vesicle, branchial arches, apical ectodermal ridge of limb bud, developing cartilages, perichondria of mature cartilages, mesenchymal cells of developing membranous bones, developing teeth, ganglionic eminence of the telencephalon, diencephalon, olfactory epithelia, and epidermis of the skin. rDlx RNAs were also detected in the developing parasympathetic mesenteric ganglia of the gastrointestinal tract. Hence, rDlx RNAs are mainly expressed in several neuronal tissues and developing skeletal tissues.

A mutant of protein phosphatase-1 that exhibits altered toxin sensitivity

A chimeric mutant was constructed in which a 4-amino acid region (GEFD, residues 274-277) of rabbit muscle protein phosphatase-1 was replaced with the sequence YRCG corresponding to residues 267-270 of rabbit protein phosphatase-2A. This was based on the findings of a gene mutation in okadaic acid-resistant cells which results in a Cys-->Gly conversion in protein phosphatase-2A. The YRCG mutant of protein phosphatase-1 was expressed and purified. The properties of the mutant enzyme were investigated in terms of its sensitivity toward several toxin inhibitors (okadaic acid, microcystin, nodularin, calyculin A, and cantharidic acid), as well as inhibitor-2. The mutant enzyme exhibited a gain of function in the form of a 10-fold increased sensitivity toward okadaic acid that suggests this region is involved in toxin binding. Significant changes in sensitivity to inhibitor-2 and several of the other toxins were also observed, indicating that these may have a common binding region.

[Preliminary investigation on acute flaccid paralysis (AFP) cases in Jinan area]

Eighty AFP cases under 12 years old from 6 hospitals in Jinan were investigated. Among them, there were 17 (21.25%) cases with poliomyelitis (POLIO), 40 (50.00%) cases with Guillian-Barre syndrome (GBS) and 23 (28.75%) cases with other AFP diseases. Most AFP cases occurred from May to October and no significant seasonal difference was found for each kind of AFP cases (P > 0.05), but the average age for POLIO cases (1.55 +/- 1.24) was significantly lower than that for non-POLIO AFP cases (3.76 +/- 2.58) (P < 0.01). The reporting rate from hospitals to each level of epidemic prevention station (EPS) for POLIO, GBS and other AFP cases were 100%, 12.50% and 43.75%, respectively (P < 0.01). Sixty-five AFP cases occurred in 6 prefectures around Jinan city. The average incidence rate (per 100,000) for total AFP, non-POLIO AFP and GBS cases among children under 12 years old were 1.11, 0.89 and 0.53, respectively. The results are helpful to estimate the incidence of AFP cases among children in north provinces of China and also indicate that the POLIO surveillance system in Shandong Province at the present is not sensitive enough, so the AFP cases reporting work of hospitals and the surveillance at each level of EPS should be enhanced.

Use of reverse transcription-polymerase chain reaction to evaluate in vivo cytokine gene expression in rats fed ethanol for long periods

We evaluated the expression of interleukin-1 alpha, interleukin-1 beta, tumor necrosis factor-alpha and transforming growth factor-beta mRNAs in the intragastric-feeding rat model of alcoholic liver disease. Rats were fed different diets for periods of 2 or 4 wk. Animals fed saturated fat and ethanol and the corn oil-dextrose control group had no liver injury, whereas animals fed corn oil and ethanol showed pathologic changes. RNA was extracted from the livers at the time of killing, reverse-transcribed and amplified; polymerase chain reaction products were subjected to electrophoresis on agarose gel. Interleukin-1 alpha mRNA was present in all groups at 2 and 4 wk; interleukin-1 beta and transforming growth factor-beta mRNAs were present in all groups at 4 wk. Tumor necrosis factor-alpha mRNA was absent in all groups at 2 wk but was present in the corn oil-ethanol group only at 4 wk. Because pathological liver injury was evident in the corn oil-ethanol group by 4 wk, the presence of tumor necrosis factor-alpha mRNA at this time suggests a pathogenetic role for tumor necrosis factor-alpha in alcohol-induced liver injury.

Characterization of deletion mutants of the catalytic subunit of protein phosphatase-1

Deletion mutagenesis was used to define the core region of the catalytic subunit of rabbit muscle protein phosphatase-1. Deletions in the N terminus were found to lead to loss of expression. Deletions of up to 33 residues from the C-terminal region were tolerated, and the truncated enzymes were fully active. Deletion of an additional 21 residues led to loss of expression. Mutants which had had 33 and 25 residues deleted maintained specific activities that were comparable to those of the wild type enzyme. The response of these two deletion mutants to okadaic acid, microcystin, and inhibitor-2 was determined. Only slightly lower IC50 values were observed in all cases, showing that the C terminus itself does not play a major role in the binding of these inhibitors. The deletion mutants formed stable complexes with inhibitor-2 as shown by gel filtration. These studies provide unambiguous evidence that the extreme C-terminal region of protein phosphatase-1 is not directly involved in catalytic function or in the binding of inhibitor-2, microcystin, or okadaic acid, and they also establish that the first approximately 300 residues of the sequence constitute a sufficient core for protein phosphatase-1 catalytic functions.

Cimetidine prevents alcoholic hepatic injury in the intragastric feeding rat model

Cytochrome P450 induction is believed to be important in the pathogenesis of alcoholic hepatic disease. Because cimetidine is a general inhibitor of cytochrome P450 enzymes, it was hypothesized that it could be useful in preventing alcoholic hepatic injury. An intragastric feeding model was used these studies. Experimental animals were divided into groups of four to five rats/group and fed the following diets: corn oil+dextrose, corn oil+ethanol (CE) and corn oil+ethanol+cimetidine (250 mg kg-1 day-1) (CEC). The rats in each group were sacrificed at the following time intervals: 2 weeks, 1 month and 2 months. For each animal, the severity of the pathologic findings and relative protein levels of cytochromes P450 2E1, 2B and 4A were measured. In addition, plasma levels of thromboxane B2, 6-ketoprostaglandin F1 alpha and 8-isoprostane were also measured. The most significant finding was that cimetidine completely prevented alcoholic hepatic injury in this model system. The pathologic scores (an indication of the severity of injury) were significantly lower in the CEC groups compared with the CE group. There was however, no significant difference in cytochrome P450 2E1, 2B or 4A protein levels between CE and CEC groups. Thromboxane B2 and 8-isoprostane levels were significantly lower and 6-ketoprostaglandin F1 alpha, significantly higher in the CEC group than in the CE group. These results indicate that possible mechanisms involved in the protective action of cimetidine include inhibition of thromboxane production and lipid peroxidation.

DSM-III-R generalized anxiety disorder in the National Comorbidity Survey

BACKGROUND

Nationally representative general population data are presented on the current, 12-month, and lifetime prevalence of DSM-III-R generalized anxiety disorder (GAD) as well as on risk factors, comorbidity, and related impairments.

METHODS

The data are from the National Comorbidity Survey, a large general population survey of persons aged 15 to 54 years in the noninstitutionalized civilian population of the United States. DSM-III-R GAD was assessed by lay interviewers using a revised version of the Composite International Diagnostic Interview.

RESULTS

Generalized anxiety disorder was found to be a relatively rare current disorder with a current prevalence of 1.6% but was found to be a more frequent lifetime disorder affecting 5.1% of the US population aged 15 to 45 years. Generalized anxiety disorder was twice as common among women as among men. Multivariate logistic regression analysis showed that being older than 24 years, separated, widowed, divorced, unemployed, and a homemaker are significant correlates of GAD. Consistent with studies in treatment samples, we found that GAD was frequently associated with a wide spectrum of other mental disorders, with a lifetime comorbidity among 90.4% of the people who had a history of GAD.

CONCLUSION

Contrary to the traditional view that GAD is a mild disorder, we found that the majority of people with GAD, whether they were comorbid or not, reported substantial interference with their life, a high degree of professional help seeking, and a high use of medication because of their GAD symptoms. Although lifetime GAD is highly comorbid, the proportion of current GAD that is not accompanied by any other current diagnosis is high enough to indicate that GAD should be considered an independent disorder rather than exclusively a residual or prodrome of other disorders.

Cloning, sequencing, and structural analysis of the DNA encoding inosine monophosphate dehydrogenase (EC 1.1.1.205) from Tritrichomonas foetus

The inosine monophosphate dehydrogenase (IMPDH) of the parasitic protozoan Tritrichomonas foetus is a purine salvage enzyme with a subunit molecular weight of 58,000. The enzyme has been purified to homogeneity by Verham et al. (Molecular and Biochemical Parasitology 24, 1-12, 1987) and characterized in more detail by Hedstrom and Wang (Biochemistry 29, 849-854, 1990). We used a polyclonal antibody directed against the purified enzyme to identify three cDNA clones from T. foetus. These clones were sequenced and found to contain an open reading frame encoding 497 amino acids. By complementation studies on an Escherichia coli mutant with its IMPDH gene deleted, the cDNA clones were able to transform the bacterial cells to grow on minimal medium without guanine. One of the cDNA clones, 2aa1, was used to identify two genomic clones, 2d1c and 3m4b, both containing a 4.1-kb HindIII fragment. The fragment was subcloned into the Bluescript KS+ plasmid, sequenced, and found to contain the same open reading frame as the cDNA clone except that it encodes six additional amino acid residues at the N-terminus. Its sequence has a 34% identity with that of the human IMPDH, 32% with that of E. coli IMPDH, and 31% with that of Leishmania donovani IMPDH. The molecular weight of the deduced protein is 55,534. Two segments of polypeptide that are conserved in all other IMPDHs, containing the putative NAD+ and IMP binding sites, are also relatively conserved in T. foetus. Since the parasite enzyme differs from the bacterial and mammalian IMPDHs by a very high Km value for NAD+ and an even higher KI value for mycophenolic acid (MPA) (Verham et al. 1987; Hedstrom and Wang 1990), the sequence of the parasite enzyme may provide information on the mechanism of MPA binding and the chance for other specific inhibitor design.

Analysis of protein binding to receptor-doped lipid monolayers by Monte Carlo simulation

This paper presents a Monte Carlo simulation (MCS) method for estimating the parameters that characterize ligand-receptor binding directly from experimentally derived binding isotherms. Binding parameters are estimated by incorporating an MCS algorithm for ligand binding to a two-dimensional receptor array into a nonlinear regression program. The MCS method was tested by analyzing experimental isotherms of avidin binding to biotinylated lipid in Langmuir-Blodgett (LB) monolayers. The MCS-derived cooperativity coefficients and intrinsic association constants for avidin-biotin binding to LB films are correlated strongly (R2 > 0.93) with the binding parameters determined from the same experimental data by a thermodynamic equilibrium binding model (Zhao et al. 1993. Langmuir. 9:3166-3173). This result shows MCS to be an accurate and potentially more versatile method for characterizing biomolecular interactions at surfaces.

G1/S-regulated E2F-containing protein complexes bind to the mouse thymidine kinase gene promoter

By performing DNase I footprint analysis, we had identified three distinct protein binding sequences (MT1, MT2, and MT3) located on the mouse thymidine kinase (TK) upstream promoter (Dou, Q.-P., Fridovich-Keil, J. L., and Pardee, A.B. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 1157-1161). Here we report that MT2 includes an E2F-like binding site (GTTCGCGGGCAAA), as shown by the following evidence. (i) MT2 bound specifically to an affinity-purified fusion human E2F protein. (ii) Both MT2 and an authentic E2F site (TTTCGCGCGCTTT) bound specifically to similar or identical nuclear protein complexes. (iii) Formation of both these DNA-protein complexes were cell cycle-dependent: a G0/G1 phase-specific complex (E2F.G0/G1) was replaced by an S phase-specific complex(es) (E2F.S), whereas "free" E2F increased after the G1/S transition. (iv) Pulse inhibition of protein synthesis with cycloheximide interchanged these complexes with similar kinetics. (v) When MT2-shifted E2F.G0/G1, E2F.S, and free E2F were eluted and analyzed by Western blot assay using a specific antiserum to human E2F-1, two forms of murine E2F (62 and 66 kDa) were observed from all three complexes. The compositions of these MT2-bound complexes were also investigated. Studies using specific antibodies revealed that p107, a retinoblastoma-like protein, was present in both E2F-G0/G1 and E2F.S, whereas cyclin E.cyclin A.cdk2 were only present in E2F.S complex(es). These data suggest that removal of the p107-containing E2F.G0/G1 complex, a candidate repressor, from the MT2 site in late G1 may be essential for S phase-dependent transcription of the mouse TK gene.

Lifetime and 12-month prevalence of DSM-III-R psychiatric disorders in the United States. Results from the National Comorbidity Survey

BACKGROUND

This study presents estimates of lifetime and 12-month prevalence of 14 DSM-III-R psychiatric disorders from the National Comorbidity Survey, the first survey to administer a structured psychiatric interview to a national probability sample in the United States.

METHODS

The DSM-III-R psychiatric disorders among persons aged 15 to 54 years in the noninstitutionalized civilian population of the United States were assessed with data collected by lay interviewers using a revised version of the Composite International Diagnostic Interview.

RESULTS

Nearly 50% of respondents reported at least one lifetime disorder, and close to 30% reported at least one 12-month disorder. The most common disorders were major depressive episode, alcohol dependence, social phobia, and simple phobia. More than half of all lifetime disorders occurred in the 14% of the population who had a history of three or more comorbid disorders. These highly comorbid people also included the vast majority of people with severe disorders. Less than 40% of those with a lifetime disorder had ever received professional treatment, and less than 20% of those with a recent disorder had been in treatment during the past 12 months. Consistent with previous risk factor research, it was found that women had elevated rates of affective disorders and anxiety disorders, that men had elevated rates of substance use disorders and antisocial personality disorder, and that most disorders declined with age and with higher socioeconomic status.

CONCLUSIONS

The prevalence of psychiatric disorders is greater than previously thought to be the case. Furthermore, this morbidity is more highly concentrated than previously recognized in roughly one sixth of the population who have a history of three or more comorbid disorders. This suggests that the causes and consequences of high comorbidity should be the focus of research attention. The majority of people with psychiatric disorders fail to obtain professional treatment. Even among people with a lifetime history of three or more comorbid disorders, the proportion who ever obtain specialty sector mental health treatment is less than 50%. These results argue for the importance of more outreach and more research on barriers to professional help-seeking.

Optical imaging of human breast cancer

Since an increasing number of breast cancers have been reported in recent years, there is a need for improving techniques for early detection of the breast cancer. Here we tested a time gated optical imaging technique as a tool for imaging human breast. Pulsed laser light at wavelengths of 780 and 830 nm are transmitted through human breast tissues and time spectra of the diffused light through the tissue are recorded over nanoseconds. Data from different locations are acquired and used to reconstruct a two dimensional image as a set of spectra in pixel form. The imaging consists of absorption and scattering coefficients, and the absorption coefficients at the two wavelengths are related to oxygen concentration and blood volume. The analysis of these coefficients is based upon the early arrival photons, therefore allowing construction of a better image than those from the current diaphanography. We demonstrate images of breast cancer, cysts created after lumpectomy, and consequences of radiation therapy. Results show that time gated optical imaging can image oxygen concentration in the cancerous and fibrotic breasts. Resolution of the imaging for smaller tumor size needs to be improved.

Expression of recombinant inhibitor-2 in E. coli and its utilization for the affinity chromatography of protein phosphatase-1

The coding sequence for rabbit muscle protein phosphatase inhibitor-2 was inserted into the pET3a expression vector. This vector allowed the expression of recombinant inhibitor-2 at levels of ca. 1.5% of the soluble protein. A simple procedure allowed the purification of inhibitor-2 from Escherichia coli lysates. This involved heat-treatment, followed by chromatography on Blue-Sepharose and Q-Sepharose. Recombinant inhibitor-2 inhibited rabbit muscle protein phosphatase-1 with a potency similar to that reported for the wild type protein. The recombinant protein was coupled to CH-Sepharose and this support was found to bind the catalytic subunit of protein phosphatase-1 with high efficiency. A procedure for a single-step affinity purification of recombinant ppase-1 from E. coli lysates was shown to be feasible.

Somatosensory evoked potentials induced by stimulating a variable number of nerve fibers in rat

Somatosensory evoked potentials (SEPs) were recorded from rat spinal cord (sSEPs) and cerebral cortex (cSEPs). Stimulus sites included either one or both sural nerve branches having different fiber populations (group A), or distal to a lesion of controlled size of the sural nerve made 1 week earlier (group B). In the two groups of animals, amplitudes of SEPs correlated with the quantity of large myelinated nerve fibers. Peak latencies of sSEPs in group A related to the ratio of sizes of transmitting fibers. sSEPs and cSEPs in both groups A and B could be recorded in a reproducible fashion by stimulating sural nerve branches or lesioned nerve trunks containing only 100 or less nerve fibers greater than 4 microns in size. Thus, presence of sSEPs or cSEPs after stimulation distal to a lesion site does not insure that many nerve fibers have continuity with the central nervous system (CNS).

Mutagenesis of the catalytic subunit of rabbit muscle protein phosphatase-1

We have generated site-directed mutants of the catalytic subunit of rabbit muscle ppase-1. Since it is known that ppase-1 and ppase-2A are highly susceptible to inactivation by sulfhydryl reagents, we have mutagenized the six cysteine residues conserved between these two enzymes to serines. The six mutants were purified to near homogeneity by affinity chromatography on inhibitor-2-Sepharose and characterized. All six exhibited enzymatic activity. These results indicate that the catalytic mechanism of ppase-1 is different from that of the protein tyrosine phosphatases which involve a cysteinyl phosphate intermediate.

Comparison of macropore, semipermeable, and nonpermeable collagen conduits in nerve repair

Twelve rabbits were used to study functional nerve regeneration through macropore, semipermeable, and nonpermeable collagen conduits. Each animal underwent a 10-mm bilateral resection of posterior tibial nerve. Lesions were repaired with a macropore collagen tube in one leg, and with a semipermeable or a nonpermeable collagen tube contralaterally. Functional nerve regeneration was evaluated at 6 and 12 weeks post-repair periods. Functional recovery was assessed by electrophysiologic analysis of nerve conduction velocity, amplitude of nerve action potential, amplitude and area of muscle action potential, and by quantitative and qualitative histologic analysis of myelinated nerve fibers from the distal nerve stumps. The macropore-collagen-tube group showed significantly greater functional recoveries than semipermeable or nonpermeable collagen-tube groups, based on electrophysiologic and histologic analyses.

Plasma norepinephrine changes after arousal and exercise were enhanced in conscious pigs with perinephritic hypertension

This study found that pigs in the early stages of perinephritic hypertension had enhanced plasma norepinephrine (NE) and heart rate (HR) responses to behaviorally arousing stimuli (lifting in a canvas sling) and exercise. In the hypertensive animals, the increase in plasma NE in response to behavioral arousal caused by lifting was double that of the intact group, and the HR response was 50% greater. The increase in plasma NE in response to exercise was six times greater in hypertensive pigs. By contrast, mean arterial pressure changes were not enhanced in the hypertensive group. Exaggerated catecholamine responses in plasma to lifting and exercise stimulation were present when hemodynamic responses were not exaggerated.

Rapid induction of CD38 antigen on myeloid leukemia cells by all trans-retinoic acid

The CD38 or T10 molecule is one of the least understood differentiation antigens. Virtually no information is available on the regulation and functions of CD38 antigen in hematopoietic cells. Using human promyelocytic leukemia cells, we demonstrate that all trans-retinoic acid is a potent and specific inducer of CD38 expression in myeloid lineage. At physiological doses, all trans-retinoic acid induces significant levels (8 to 10-fold) of CD38. Similarly, in patients with promyelocytic leukemia, a significant increase (3 to 6-fold) in CD38 expression was observed in vivo following single oral dose administration of all trans-retinoic acid. The induction of CD38 is a specific response of myeloid cells to retinoic acid and is not seen with other agents that induce differentiation. We believe that the induction of CD38 antigen is an early event in retinoid-regulated gene expression in normal and transformed myeloid cells.

Electrochemical preparation of 1,1'-dimethylferricinium from a water-soluble 1,1'-dimethylferrocene-2-hydroxypropyl-beta-cyclodextrin complex and its applications in enzyme assay

Water-soluble 2-hydroxypropyl-beta-cyclodextrin (hp-beta-CyD), a cyclic and nonreducing oligosaccharide, was used to enclose the hydrophobic guest molecules ferrocene (FeCp2) and 1,1'-dimethylferrocene (DMFeCp2) to form a water-soluble complex. At high concentrations (300 mM), hp-beta-CyD enclosed up to 100 mM FeCp2 or DMFeCp2. The yellow complexes were electrochemically oxidized (platinum vs Ag/AgCl poised at +450 mV) to form the blue dyes ferricinium (FeCp2+) and 1,1'-dimethylferricinium (DMFeCp2+). This is a one-electron transfer process and the ferricinium cations formed exhibited absorption peaks at 620 and 650 nm, respectively. The concentrated DMFeCp2+ was much more stable (4 months) than the FeCp2+ (2 days) and both oxidized dyes were insensitive to a wide pH variation (pH 2-11). The DMFeCp2+ was reduced easily by various reducing agents such as ascorbic acid, uric acid, and sulfite and exhibited an absorption coefficient of 325 cm-1 M-1. Application of the novel DMFeCp2+ complex as a colorimetric dye for the enzymatic oxidation of glucose, glutamate, lactate, phenylalanine, xanthine, and hypoxanthine was successfully demonstrated. When applied to real samples the results obtained agreed well with those of standard enzymatic assays. The DMFeCp2+ complex could also be utilized to monitor activity of oxidases under saturating substrate concentrations.

Detection of Mycoplasma meleagridis by polymerase chain reaction

A pair of 32 base primers was synthesized based on the DNA sequence data of a Mycoplasma meleagridis (MM) species-specific recombinant, pMM-2. The primers were used in a MM-polymerase chain reaction (PCR) to amplify a target DNA of approximately 850 bp. Annealing temperatures ranging from 58 degrees C to 61 degrees C could be used for the MM-PCR without loss of specificity. The primers amplified 1 ng of DNA from 17 strains of MM, but not 10 ng of DNA from 16 heterologous species of avian mycoplasma, pUC8 plasmid, lambda phage or calf thymus DNA. The minimum amount of target DNA detected by MM-PCR was 10 fg, which indicated that this procedure was 100000 times more sensitive than dot blot methodology using an MM recombinant DNA probe.

Expression and characterization of rat protein phosphatases-1 alpha, -1 gamma 1, -1 gamma 2, and -1 delta

Four distinct cDNAs for rat protein phosphatase-1 have been isolated from rat tissues (Sasaki et al., Jpn. J. Cancer Res. 81, 1272-1280, 1990). These cDNAs encode proteins of highly similar sequence, the major differences being located at their N and C termini. In order to demonstrate that these cDNAs encode functional proteins and to investigate their enzymatic properties, it would be desirable to obtain purified preparations of these proteins. Using a system that was developed for the expression of rabbit muscle protein phosphatase-1 (Zhang et al., J. Biol. Chem. 267, 1484-1490, 1992) we have expressed these isoforms in Escherichia coli. The four recombinant isoforms were purified to near homogeneity and their properties were examined in terms of substrate specificity and sensitivity to okadaic acid and inhibitor-2.

Changes in microsomal phospholipases and arachidonic acid in experimental alcoholic liver injury: relationship to cytochrome P-450 2E1 induction and conjugated diene formation

We evaluated the role of changes in microsomal phospholipases (A and C) and arachidonic acid in the intragastric rat feeding model. The experimental animals (male Wistar rats), divided into 4-5 rats/group, were fed the following diets: corn oil and ethanol and corn oil plus dextrose. One set of groups was killed after 2 weeks of feeding, and the second set was killed after 1 month. For each animal, microsomal analysis of cytochrome P-450 2E1 (CYP 2E1) and fatty acids was done. Fourteen animals had analyses of phospholipase C (PLC) and phospholipase A (PLA), and 10 animals had measurements of conjugated dienes. A significant correlation was obtained between the level of CYP 2E1 and the decrease in arachidonic acid (AA) from baseline levels (r = 0.69, p < 0.01). The decrease in AA also correlated with the increase in conjugated dienes (r = 0.70, p < 0.05). PLA and PLC activities were both significantly increased in the corn oil and ethanol groups. The activity of PLC correlated with the decline in AA (r = 0.69, p < 0.01). The correlations noted between the decrease in microsomal AA and CYP 2E1 induction and conjugated diene formation suggest that these processes may be interlinked especially in regard to generation of lipid peroxides that may play a role in alcoholic liver injury.

Mycetomas in northern Yemen: identification of causative organisms and epidemiologic considerations

Fifteen cases of mycetomas from four locations in northern Yemen were studied. On the basis of morphologic characteristics and staining properties of the granules in discharges from the draining sinus tracts (a narrow elongated cavity that extends from a focus of suppuration or other inflammatory softening to a free surface and through which pus discharges) in the affected appendages and in tissue sections, three causative organisms were identified: Streptomyces somaliensis, Actinomadura madurae, and Madurella mycetomatis. Because of the similarity in the climate and the causative organisms, northern Yemen can be considered as being in the same endemic area for mycetomas as eastern Africa.

Molecular and biochemical reprogramming of oncogenesis through the activity of prooxidants and antioxidants

The antioxidant alpha-tocopherol and the weaker antioxidant and prooxidant chemopreventative, beta-carotene have been shown to inhibit tumor cell growth in vivo and in vitro. In some epidemiologic studies their serum levels were demonstrated to be inversely related to the incidence of malignant tumor. We hypothesized two basic pathways triggered by antioxidants and prooxidants, which resulted in the control of tumor cell growth. These included changes in phosphorylation and ultimately transcription. Specifically, the prooxidant beta-carotene treatment produced an oxidative stress resulting in the selective induction of heat shock proteins (hsps). These proteins and other proteins that were possibly oxidized were associated with the increased expression of cyclins (A and D) and increased cdc2 kinase expression. An increase in expression of phosphoproteins, such as p53 (tumor suppressor form) was also discerned. The level of expression for the transcription factor c-fos was reduced. Growth factors that contribute to tumor cell growth were also reduced. Increased DNA fragmentation, depression of proliferation and intracellular calcium levels, the accumulation of tumor cells in G0-->G1, and morphologic changes, were consistent with programmed cell death. Antioxidants such as alpha-tocopherol bound to membrane-associated proteins could inhibit the development of peroxidation products (hydroxyl radicals (.OH)), which attack proteins and modify their function and promote their degradation. Some kinases such as, cdc2 may be increased in activity, which would explain the observed increased expression of tumor suppressor p53, the accumulation of the tumor cells in G1 of the cell cycle and the inhibition of tumor cell proliferation. A reduction in oxidant radicals could also reduce transcription factor products, such as c-myb. Indirectly this result may occur through changes in nuclear translocation (signaling) NF-AT or the Rel-related family of transcription factors, including NF-kB (p50 or p65) or inhibition of immunophilin-calmodulin activity. Although the data remains fragmentary there are common points for control for tumor cell growth resulting from the effects of alpha-tocopherol or beta-carotene treatment. These changes involve phosphorylation and protein expression. Ultimately there is a reduction of important transcription factor protein products, a reduction in response to growth factors, and suppression of cell proliferation, resulting in increased control of the cell cycle.

Species-specific recombinant DNA probes for Mycoplasma meleagridis

Two recombinant DNA probes (pMM-2 and pMM-13) were isolated from a Mycoplasma meleagridis strain 17529 genomic library prepared in plasmid pUC8, and Escherichia coli strain JM83. In dot blot assays, 32P-labeled pMM-13 with a DNA insert of 3.5 kbp, hybridized with 18 isolates of M. meleagridis but not with 16 other known species of avian mycoplasmas. Except for weaker signals on hybridization with the M. meleagridis cultures, pMM-2 with an DNA insert of 0.85 kbp, showed a similar reaction pattern. The minimal concentration of M. meleagridis strain 17529 chromosomal DNA that pMM-13 and pMM-2 detected were 1 and 8 ng, respectively. Neither probe hybridized with chromosomal DNA of M. gallisepticum strain S6, M. synoviae strain WVU-1853, or M. iowae strain I-695 at concentration of 256 ng.

Rhs elements of Escherichia coli K-12: complex composites of shared and unique components that have different evolutionary histories

The complete sequences of the RhsB and RhsC elements of Escherichia coli K-12 have been determined. These sequence data reveal a new repeated sequence, called H-rpt (Hinc repeat), which is distinct from the Rhs core repetition that is found in all five Rhs elements. H-rpt is found in RhsB, RhsC, and RhsE. Characterization of H-rpt supports the view that the Rhs elements are composite structures assembled from components with very different evolutionary histories and that their incorporation into the E. coli genome is relatively recent. In each case, H-rpt is found downstream from the Rhs core and is separated from the core by a segment of DNA that is unique to the individual element. The H-rpt's of RhsB and RhsE are very similar, diverging by only 2.1%. They are 1,291 bp in length, and each contains an 1,134-bp open reading frame (ORF). RhsC has three tandem copies of H-rpt, all of which appear defective in that they are large deletions and/or have the reading frame interrupted. Features of H-rpt are analogous to features typical of insertion sequences; however, no associated transposition activity has been detected. A 291-bp fragment of H-rpt is found near min 5 of the E. coli K-12 map and is not associated with any Rhs core homology. The complete core sequences of RhsB and RhsC have been compared with that of RhsA. As anticipated, the three core sequences are closely related, all having identical lengths of 3,714 bp each. Like RhsA, the RhsB and RhsC cores constitute single ORFs that begin with the first core base. In each case, the core ORF extends beyond the core into the unique sequence. Of the three cores, RhsB and RhsA are the most similar, showing only 0.9% sequence divergence, while RhsB and RhsC are the least similar, diverging by 2.9%. All three cores conserve the 28 repetitions of a peptide motif noted originally for RhsA. A secondary structure is proposed for this motif, and the possibility of its having an extracellular binding function is discussed. RhsB contains one additional unique ORF, and RhsC contains two additional unique ORFs. One of these ORFs includes a signal peptide that is functional when fused to TnphoA.