Exploring Internal Conflicts and Collaboration of a Hospital Home Healthcare Team: A Grounded Theory Approach

An aging society is on the rise, leading to a variety of caregiving issues. The Taiwanese government has been implementing a home healthcare integration plan since 2015, aimed at integrating and forming interdisciplinary care teams with medical institutions. This study explores the internal conflict factors among hospital home healthcare team members at a district teaching hospital in Taichung, Taiwan, and it seeks a better collaboration model between them. Semi-structured in-depth interviews were conducted with seven hospital home healthcare team members. Data analysis was based on grounded theory, with research quality relying on the triangulation and consistency analysis methods. The results show that "work overload", "resource overuse", "inconsistent assessment", "limited resources", "communication cost", and "lack of incentives" are the major conflicts among the team. This study proposed the following collaboration model, including "identifying the internal stakeholders of a home healthcare team" and "the key stakeholders as referral coordinators", "patient-centered resource allocation", and "teamwork orientation". The study recommends that within a teamwork-oriented home healthcare team, its members should proactively demonstrate their role responsibilities and actively provide support to one another. Only through patient-centered resource allocation and mutual respect can the goal of seamless home healthcare be achieved. The content of the research and samples were approved by the hospital ethics committee (REC108-18).

Exacerbation of Pre-existing Epilepsy by Mild Head Injury: a Five Patient Series

Objective:

While the risk of developing seizures following a mild head injury has been reported and is thought to be low, the effect of mild head injury on patients with a pre-existing seizure disorder has not been reported. We present a series of cases where a strong temporal relationship between mild head injury and worsening of seizure frequency was observed.

Methods:

Five cases were identified and reviewed in detail. Information was derived from clinic and hospital charts with attention to the degree of injury, pre- and postinjury seizure patterns and frequency.

Results:

One patient has primary generalized epilepsy and four have localization related epilepsy. Prior to the head injury, three of the patients were seizure free (range: two to 24 years). The patients suffered from mild head injuries with no or transient loss of consciousness and no focal neurological deficits. In all cases, the patients experienced a worsening of seizure control within days of the injury. In one case, the patient's seizure pattern returned to baseline one year after the accident, while in the remaining four cases, the patients continue to have medically refractory seizures.

Conclusion:

A close temporal relationship between mild head injury and a worsening of seizure control was observed in five patients with epilepsy. Although further study is required, this observation suggests that a head injury that would be considered benign in the general population can have serious consequences such as recurrence of seizures and medical intractability in patients with epilepsy.

Quantification of glyceryl trinitrate effect through analysis of the synthesised ascending aortic pressure waveform

OBJECTIVE

To establish through analysis of the radial pressure pulse waveform the dose dependent effects of glyceryl trinitrate (GTN) on properties of different blood vessels.

DESIGN

Radial pulse waveform was measured in randomised order before, during a five hour application of a GTN patch delivering 0.104-0.625 mg/h, and for two hours after patch removal. The radial pressure waveform (Millar applanation tonometer) was convolved into an ascending aortic wave using a generalised transfer function (SphygmoCor process) enabling measurement of aortic systolic, diastolic, pulse, mean, and augmented pressure and left ventricular ejection duration in addition to standard brachial cuff pressures.

SETTING

Fu Wai and Ren Ming hospitals in Beijing, China.

PATIENTS

46 recumbent hospitalised patients aged 56 (9) years, awaiting electrophysiological or other diagnostic studies, fasting, and with other treatments suspended.

MAJOR OUTCOME MEASURES

Conventional brachial pressure measures and data from the synthesised aortic pulse.

RESULTS

There was no consistent change in heart rate or brachial pressures except for a decrease in systolic and pulse pressures (p < 0.01) at dose > 0.416 mg/h. In contrast, there were substantial and significant (p < 0.0001) decreases in aortic systolic, pulse, and augmented pressures at all doses, mean pressure (p < 0.001) at doses > 0.416 mg/h, and ejection duration (p < 0.001) at doses > 0.208 mg/h.

CONCLUSIONS

Pulse waveform analysis exposes dose dependent effects of GTN on the aortic waveform, suggesting muscular conduit arterial dilatation with reduced wave reflection at the lowest dose, arteriolar dilatation and decreased peripheral resistance at the highest dose, and venous dilatation at the intermediate dose.

A CUB-serine protease in the olfactory organ of the spiny lobster Panulirus argus

csp, a gene encoding a protein with high sequence identity to trypsinlike serine protease and CUB domains, was identified from a cDNA library from the olfactory organ (antennular lateral flagellum) of the spiny lobster Panulirus argus. The full-length cDNA sequence of csp is 1801 bp, encoding a protein of 50.25 kD, with three domains: signal peptide, trypsinlike serine protease, and CUB (named for a class of compounds including Complement subcomponents Clr/Cls, Uegf, and Bone morphogenic protein-1). RT-PCR, Northern blots, and immunoblots showed that csp is predominantly expressed in the lateral flagellum and eyestalk. Immunocytochemistry showed that Csp is present in olfactory (aesthetasc) sensilla around auxiliary cells (glia that surround the inner dendrites of olfactory receptor neurons, ORNs) and ORN outer dendrites. We propose that Csp is expressed and secreted by auxiliary cells, associates with ORN cell membranes or extracellular matrix via the CUB domain, and has trypsinlike activity. In the eyestalk, Csp is associated with cells surrounding axons between neuropils of the eyestalk ganglia. Possible functions in the olfactory organ and eyestalk are discussed. To our knowledge, this is the first report from any olfactory system of a gene encoding a protein with serine protease and CUB domains.

Functional signal peptides bind a soluble N-terminal fragment of SecA and inhibit its ATPase activity

The selective recognition of pre-secretory proteins by SecA is essential to the process of protein export from Escherichia coli, yet very little is known about the requirements for recognition and the mode of binding of precursors to SecA. The major reason for this is the lack of a soluble system suitable for biophysical study of the SecA-precursor complex. Complicating the development of such a system is the likelihood that SecA interacts with the precursor in a high affinity, productive manner only when it is activated by binding to membrane and SecYEG. A critical aspect of the precursor/SecA interaction is that it is regulated by various SecA ligands (nucleotide, lipid, SecYEG) to facilitate the release of the precursor, most likely in a stepwise fashion, for translocation. Several recent reports show that functions of SecA can be studied using separated domains. Using this approach, we have isolated a proteolytically generated N-terminal fragment of SecA, which is stably folded, has high ATPase activity, and represents an activated version of SecA. We report here that this fragment, termed SecA64, binds signal peptides with significantly higher affinity than does SecA. Moreover, the ATPase activity of SecA64 is inhibited by signal peptides to an extent that correlates with the ability of these signal peptides to inhibit either SecA translocation ATPase or in vitro protein translocation, arguing that the interaction with SecA64 is functionally significant. Thus, SecA64 offers a soluble, well defined system to study the mode of recognition of signal peptides by SecA and the regulation of signal peptide release.

Subtype-independent immature secretion and subtype-dependent replication deficiency of a highly frequent, naturally occurring mutation of human hepatitis B virus core antigen

The most frequent mutation of the human hepatitis B virus (HBV) core antigen occurs at amino acid 97. Recently, a phenylalanine (F)-to-leucine (L) mutation at this position (mutant F97L) in HBV surface antigen subtype ayw has been shown to result in an immature secretion phenotype, which is characterized by the nonselective export of an excessive amount of virions containing minus-strand, single-stranded HBV DNA. While subtype ayw mutant F97L has been found in Europe, the major reservoir of HBV resides in Asia and Africa. We report here that the immature secretion phenotype indeed can be found in an HBV strain (subtype adr) prevalent in Asia, changing from an isoleucine (I) to a leucine (mutant I97L). Despite its immature secretion phenotype, the adr variant I97L replicates as well as its parental adr wild-type I97I, supporting the conclusion that the extracellular phenotype of immature secretion is not a consequence of the intracellular HBV DNA replication defect. Further studies demonstrated that it is the acquisition of a leucine, rather than the loss of a wild-type amino acid at codon 97, that is important for immature secretion. We conclude that immature secretion is a subtype-independent phenotype and deficiency in intracellular DNA synthesis is a subtype-dependent phenotype. The former is caused by the trans-acting effect of a mutant core protein, while the latter by a cis-acting effect of a mutated nucleotide on the ayw genome. These immature secretion variants provide an important tool for studying the regulation of HBV virion assembly and secretion.

Mutational analysis of CvaA in the highly conserved domain of the membrane fusion protein family

The antibacterial peptide toxin colicin V (ColV) uses a dedicated signal sequence-independent export system for its secretion in Escherichia coli that involves the products of three genes, cvaA, cvaB, and tolC in this process. As a member of the membrane fusion protein (MFP) family, the CvaA protein has been proposed to interact with an outer membrane protein TolC via its C-terminal hydrophobic domain. The importance of this domain, which is highly conserved throughout the members of MFP family, was analyzed by use of site-directed mutagenesis of missense or nonsense mutations with suppressors. All the nonsense mutations tested resulted in the loss of ColV secretion, indicating the importance of the C-terminus of CvaA, including the last 100 residue-hydrophilic domain. The missense mutations of several conserved amino acids have no drastic effects. On the other hand, when Glu-248, Ala-262, Thr-274, Leu-285, Gly-313, Ala-322, or Val-335 of CvaA protein was mutated, the secretion of ColV was greatly reduced in certain mutants. While some mutations resulted in structural instability, Glu-248 to Lys and Ala-322 to Gly proteins were relatively stable, but were not functional in ColV secretion. The results indicate that these conserved amino acids are important for the structure and functions of CvaA in the secretion of ColV.

Catabolic repression of secB expression is positively controlled by cyclic AMP (cAMP) receptor protein-cAMP complexes at the transcriptional level

SecB, a protein export-specific chaperone, enhances the export of a subset of proteins across cytoplasmic membranes of Escherichia coli. Previous studies showed that the synthesis of SecB is repressed by the presence of glucose in the medium. The derepression of SecB requires the products of both the cya and crp genes, indicating that secB expression is under the control of catabolic repression. In this study, two secB-specific promoters were identified. In addition, 5' transcription initiation sites from these two promoters were determined by means of secB-lacZ fusions and primer extension. The distal P1 promoter appeared to be independent of carbon sources, whereas the proximal P2 promoter was shown to be subject to control by the cyclic AMP (cAMP) receptor protein (CRP)-cAMP complexes. Gel-mobility shift studies showed that this regulation results from direct interaction between the secB P2 promoter region and the CRP-cAMP complex. Moreover, the CRP binding site on the secB gene was determined by DNase I footprinting and further substantiated by mutational analysis. The identified secB CRP binding region is centered at the -61.5 region of the secB gene and differed from the putative binding sites predicted by computer analysis.

Characterization of the cvaA and cvi promoters of the colicin V export system: iron-dependent transcription of cvaA is modulated by downstream sequences

Secretion of the Escherichia coli toxin colicin V was previously determined to be iron regulated via the Fur (ferric uptake regulator) protein, based on studies in fur mutants. The iron dependence of transcription and expression of cvaA, which encodes a transporter accessory protein, and cvi, encoding the colicin V immunity protein, was assessed under conditions of iron excess or depletion. Immunoblots showed that production of both Cvi and CvaA is iron dependent. The iron-dependent transcriptional start for cvaA identified by primer extension and S1 nuclease analysis, P1, lies 320 bp upstream of the translational start and is associated with a newly identified Fur binding site. Beta-galactosidase activity in transcriptional lacZ fusions with the P1 promoter alone is higher than with downstream sequences present and is induced 10-fold by iron depletion. Including immediate downstream regions with P1 enhances activity from P1 even more but reduces the induction by iron depletion fivefold. Including subsequent downstream sequences, however, down-modulates overall transcription from P1 almost fourfold. Deletion of a long stem-loop structure in this region alleviates the down-modulation by increasing transcription, indicating that the sequences or structure of this element may contribute to this down-regulation. Characterization of the cvi promoter by primer extension showed that it resides where predicted, about 50 bp upstream of cvi associated with a previously identified Fur binding site. The cvi promoter is also inducible by iron depletion. The modulating sequences from cvaA were placed downstream of the cvi promoter to test their effects in transcriptional fusions of the cvi promoter to lacZ. The fusion results showed that these sequences also modulate transcription of the cvi promoter in a manner similar to that of the cvaA promoter. The potential for up- and down-regulation within the long untranslated region downstream of the cvaA promoter suggests a novel mechanism that fine-tunes expression of the colicin V secretion genes.

When an ATPase is not an ATPase: at low temperatures the C-terminal domain of the ABC transporter CvaB is a GTPase

The ATP-binding cassette (ABC) transporters belong to a large superfamily of proteins which share a common function and a common nucleotide-binding domain. The CvaB protein from Escherichia coli is a member of the bacterial ABC exporter subfamily and is essential for the export of the peptide antibiotic colicin V. Here we report that, surprisingly, the CvaB carboxyl-terminal nucleotide-binding domain (BCTD) can be preferentially cross-linked to GTP but not to ATP at low temperatures. The cross-linking is Mg2+ and Mn2+ dependent. However, BCTD possesses similar GTPase and ATPase activities at 37 degrees C, with the same kinetic parameters and with similar responses to inhibitors. Moreover, a point mutation (D654H) in CvaB that completely abolishes colicin V secretion severely impairs both GTPase and ATPase activities in the corresponding BCTD, indicating that the two activities are from the same enzyme. Interestingly, hydrolysis activity of ATP is much more cold sensitive than that of GTP: BCTD possesses mainly GTP hydrolysis activity at 10 degrees C, consistent with the cross-linking results. These findings suggest a novel mechanism for an ABC protein-mediated transport with specificity for GTP hydrolysis.

Identification and characterization of protease-resistant SecA fragments: secA has two membrane-integral forms

We have identified and characterized the protease-resistant SecA fragments (X. Chen, H. Xu, and P. C. Tai, J. Biol. Chem. 271:29698-29706, 1996) through immunodetection with region-specific antibodies, chemical extraction, and sequencing analysis. The 66-, 36-, and 27-kDa proteolytic fragments in the membranes all start at Met1, whereas the 48-kDa fragment starts at Glu361. The overlapping of the sequences of the 66- and 48-kDa fragments indicates that they are derived from different SecA molecules. These two fragments were generated differently in response to ATP hydrolysis and protein translocation. Furthermore, the presence of membrane is required for the generation of the 48-kDa fragment but not for that of the 66-kDa fragment. These data suggest that there are two different integral forms of SecA in the membrane: SecA(S) and SecA(M). The combination of these two forms of SecA has several membrane-interacting domains. Both forms of SecA are integrated in the membrane, since both the 48- and 66-kDa fragments could be derived from urea- or Na2CO3-washed membranes. Moreover, all fragments are resistant to extraction with a high concentration of salt or with heparin, but the membrane-specific 48-kDa SecA domain is more sensitive to Na2CO3 or urea extraction. This suggests that this domain may interact with other membrane proteins in an aqueous microenvironment and therefore may form a part of the protein-conducting channel.

Differential translocation of protein precursors across SecY-deficient membranes of Escherichia coli: SecY is not obligatorily required for translocation of certain secretory proteins in vitro

SecY, a component of the protein translocation system in Escherichia coli, was depleted at a nonpermissive temperature in a strain which had a temperature-sensitive polar effect on the expression of its secY. Membrane vesicles prepared from these cells, when grown at the nonpermissive temperature, contained about 5% SecY and similarly low levels of SecG. As expected, translocation of alkaline phosphatase precursors across these SecY-deficient membranes was severely impaired and appeared to be directly related to the decrease of SecY amounts. However, despite such a dramatic reduction in SecY and SecG levels, these membranes exhibited 50 to 70% of the wild-type translocation activity, including the processing of the signal peptide, of OmpA precursor (proOmpA). This translocation activity in SecY-deficient membranes was still SecA and ATP dependent and was not unique to proOmpA, as lipoprotein and lambda receptor protein precursors were also transported efficiently. Membranes that were reconstituted from these SecY-depleted membranes contained undetectable amounts of SecY yet were also shown to possess substantial translocation activity for proOmpA. These results indicate that the requirement of SecY for translocation is not obligatory for all secretory proteins and may depend on the nature of precursors. Consequently, it is unlikely that SecY is the essential core channel through which all precursors traverse across membranes; rather, SecY probably contributes to efficiency and specificity.

Interactions of dedicated export membrane proteins of the colicin V secretion system: CvaA, a member of the membrane fusion protein family, interacts with CvaB and TolC

The antibacterial peptide toxin colicin V uses a dedicated signal sequence-independent system for its secretion in Escherichia coli and requires the products of three genes, cvaA, cvaB, and tolC. As a member of the membrane fusion protein family, CvaA is supposed to form a bridge that connects the inner and outer membranes via interaction with CvaB and TolC, respectively. In this study, we investigated the possible interaction of these proteins. When CvaA or CvaB was absent, the corresponding amount of CvaB or CvaA, respectively, was decreased, and the amounts of both proteins were reduced when TolC was depleted. Translational lacZ fusions showed that TolC did not affect the synthesis of either CvaA-beta-galactosidase or CvaB-beta-galactosidase, and CvaA or CvaB did not affect the synthesis of CvaB-beta-galactosidase or CvaA-beta-galactosidase, respectively. However, the stabilities of CvaA and CvaB proteins were affected by the absence of one another and by that of TolC. The instability of CvaA was more severe in TolC-depleted cells than in CvaB-depleted cells. On the other hand, CvaB was less stable in the absence of CvaA than in the absence of TolC. In addition, using a cross-linking reagent, we showed that CvaA directly interacts with both CvaB and TolC proteins. Taken together, these data support the hypothesized structural role of CvaA in connecting CvaB and TolC.

Novel and frequent mutations of hepatitis B virus coincide with a major histocompatibility complex class I-restricted T-cell epitope of the surface antigen

We examined the full-length hepatitis B virus (HBV) envelope (surface antigen or HBV small surface antigen [HBsAg]) sequences of 12 different liver samples from 10 different hepatoma-containing chronic carriers. Surprisingly, novel and frequent mutations occurred predominantly at amino acids 40 and 47 of HBsAg, in addition to within a known protective B-cell epitope (so-called group a determinant of HBsAg 124-148). Approximately 58% of chronic carriers contain mutations at the group a determinant. The mutation frequency at the hotspot codons 40 and 47 is approximately 83%, 1 order of magnitude higher than at the known polymorphic sites of subtype-specific determinants at codons 122 and 160, which is approximately 4%. This new mutational domain is found to coincide with a major histocompatibility complex class I-restricted T-cell epitope. The potential biological significance of this novel mutation in the immunopathogenesis of HBV chronic carriers is discussed.

SecE-depleted membranes of Escherichia coli are active. SecE is not obligatorily required for the in vitro translocation of certain protein precursors

Membrane vesicles were prepared from Escherichia coli cells in which SecE was depleted to 2% of wild-type membranes. SecE depletion had pleiotropic effects; SecD, SecF, SecG, and SecY were decreased 4-6-fold, whereas SecA was increased about 16-fold over that of wild-type membranes. These membranes were substantially active in the in vitro translocation of proOmpA, which was mediated by the SecA pathway since it was inhibited by azide. Similar substantial translocation activities were observed for proLamB and proLpp in the SecE-depleted membranes. However, the translocation of proPhoA was more severely impaired. These data indicate that SecE may enhance but is not obligatorily required for the translocation of at least certain precursors, and suggest that the effects of the SecE depletion on protein translocation may be precursor-dependent.

Carbon source-dependent synthesis of SecB, a cytosolic chaperone involved in protein translocation across Escherichia coli membranes

SecB is a cytosolic chaperone involved in protein translocation across cytoplasmic membranes in Escherichia coli. It has been shown to be required for efficient translocation of a subset of precursor proteins but is not essential for cell viability. This study investigated whether synthesis of SecB is growth rate dependent. Interestingly, the total amount of SecB synthesized in the cells was relatively small. Moreover, the levels of SecB were found to be carbon source dependent since more SecB was produced in cells grown in glycerol media than in cells grown in glucose media, regardless of the growth rate. This is in contrast to the other Sec proteins, whose synthesis is growth rate dependent and not related to glucose as a carbon source. In addition, cyclic AMP (cAMP) partially relieves the lower levels of SecB observed in glucose medium, a compensatory effect that depends on the presence of both cya and crp gene products. Thus, the glucose-dependent synthesis of SecB may be related to the cAMP-cAMP receptor protein complex-mediated activation.

Characterization of in-frame proteins encoded by cvaA, an essential gene in the colicin V secretion system: CvaA* stabilizes CvaA to enhance secretion

Colicin V (ColV), an antibacterial peptide toxin, uses a dedicated signal sequence-independent export system for its extracellular secretion in Escherichia coli. The products of at least three genes (a chromosomal tolC gene and two plasmid-born cvaA and cvaB genes) are involved in this process. To characterize the gene products, the cvaA gene was subcloned and expressed under the control of T7 RNA polymerase promoter. Two in-frame proteins, CvaA and CvaA*, were expressed and identified. DNA sequences predicted that both proteins have two potential translational initiation sites. N-terminal peptide sequencing showed that the translation of CvaA starts from a TTG, 11 amino acids upstream of the previously proposed ATG initiation site. CvaA* is translated from an upstream ATG. Expression of both CvaA and CvaA* was induced by the iron chelator 2,2'-dipyridyl, indicating that cvaA is negatively regulated at least partially by Fur. CvaA*-depleted cells were found to secrete less ColV, based on reduced activity in the supernatant, than did wild type, which was recovered by the addition of a plasmid producing CvaA*. Interestingly, CvaA*-depleted and wild-type cells had similar levels of intracellular ColV activity. Translational fusions showed that the syntheses of ColV and CvaA are not affected by CvaA* depletion. However, CvaA in CvaA*-depleted cells was less stable than that in wild-type cells, indicating that CvaA* may directly or indirectly affect the stability of CvaA. We conclude that CvaA* is not essential for ColV secretion but that it enhances the ColV secretion by stabilizing the CvaA protein.

A significant fraction of functional SecA is permanently embedded in the membrane. SecA cycling on and off the membrane is not essential during protein translocation

SecA has been suggested to cycle on and off the cytoplasmic membrane of Escherichia coli during protein translocation. We have reconstituted 35S-SecA onto SecA-depleted membrane vesicles and followed the fate of the membrane-associated 35S-SecA during protein translocation. Some 35S-SecA was released from the membranes in a translocation-independent manner. However, a significant fraction of 35S-SecA remained on the membranes even after incubation with excess SecA. This fraction of 35S-SecA was shown to be integrated into the membrane and was active in protein translocation, indicating that SecA cycling on and off membrane is not required for protein translocation. Proteolysis experiments did not support the model of SecA insertion and deinsertion during protein translocation; instead, a major 48-kDa domain was found persistently embedded in the membrane regardless of translocation status. Thus, in addition to catalyzing ATP hydrolysis, certain domains of SecA probably play an important structural role in the translocation machinery, perhaps forming part of the protein-conducting channels.

Processing of colicin V-1, a secretable marker protein of a bacterial ATP binding cassette export system, requires membrane integrity, energy, and cytosolic factors

Extracellular secretion of the peptide antibiotic colicin V (ColV) in Escherichia coli is mediated by a dedicated exporter system consisting of host TolC protein and the products of two specific genes, cvaA and cvaB, the latter being a member of the ATP binding cassette (ABC) superfamily. An amino-terminal export signal of ColV is specific for the CvaA-CvaB-TolC exporter and is processed concomitant with secretion. In this study, we attempt to characterize this processing with a secretable marker protein, ColV-1, using a newly developed in vitro assay. Processing is found to be dependent on both CvaA-CvaB transporters and the TolC protein and to require membrane integrity. An additional cytoplasmic soluble factor(s) is also necessary for the processing. Although the sequence of the cleavage site suggests it could be a substrate, ColV-1 cannot be processed in vitro by the purified leader peptidase I. Moreover, ColV-1 processing is inhibited by antipain and N-ethylmaleimide. Furthermore, the processing requires energy in the form of nucleotide hydrolysis. These results indicate that the processing of ColV-1 is specific and more complex than expected, requiring the CvaA-CvaB-TolC transporter intact in the membrane, energy, and cytosolic factors for rapid cleavage.

Core antigen mutations of human hepatitis B virus in hepatomas accumulate in MHC class II-restricted T cell epitopes

Despite the extensive molecular information on serum-derived human hepatitis B viruses (HBV), liver-derived replicative HBV genomes have remained largely uninvestigated. We have examined the sequences of the entire core antigen (nucleocapsid) of liver-derived HBVs in 15 different hepatoma patients. Bona fide mutations, rather than subtype polymorphism, have been identified based on the high-frequency occurrence of structural differences from wild type at the highly evolutionarily conserved positions, instead of at the positions known to contain genetic heterogeneity among different isolates from different geographic locations. The distribution of these naturally occurring mutations of HBV core gene appears to be nonrandom and is found predominantly within three major (I, IV, and V) and four minor domains (II, III, VI, and VII). In general, domain IV mutations correlate with domain V mutations. The replicative HBV DNAs tend to accumulate a higher number of mutated core domains than the integrated HBV DNAs. At the domain level, there is no significant difference in HBV core mutation frequencies between the liver tumors and the adjacent nontumorous livers. Strikingly, domains I, III, and V coincide with three major known T cell epitopes within the core protein in acute and chronic hepatitis B patients. Furthermore, these domains coincide with HLA class II-restricted T cell epitopes, rather than with the conventional HLA class I-restricted epitopes of cytotoxic T lymphocytes. Our results support the hypothesis that HBV core antigen variants can accomplish immunoevasion via accumulated escape mutations. In addition, they also provide a potential molecular explanation for the maintenance of persistent infection of human hepatitis B virus in chronic carriers.

Genetic analysis of the colicin V secretion pathway

Colicin V (ColV) is peptide antibiotic secreted by Escherichia coli through a dedicated exporter composed of three proteins, CvaA, CvaB, and TolC. ColV secretion is independent of the E. coli general secretory pathway (Sec) but requires an N-terminal export signal specific for the CvaAB/TolC exporter. ColV secretion was characterized using genetic and biochemical methods. When the ColV N-terminal extension is replaced with the OmpA signal sequence, the Sec system can localize ColV to the periplasm. Periplasmic ColV is lethal to cells lacking the ColV immunity protein, Cvi. Based on this result, a genetic assay was designed to monitor for the presence of periplasmic ColV during normal CvaAB/TolC mediated secretion. Results indicate that low levels of ColV may be present in the periplasm during secretion. Precursor and mature ColV were also characterized from the wild-type system and in various exporter mutant backgrounds using immunoprecipitation. ColV processing is rapid in wild-type cells, and CvaA and CvaB are critical for processing to occur. In contrast, processing occurs normally, albeit more slowly, in a TolC mutant.

Activation of the respiratory burst in eosinophil leucocytes--a transduction sequence decoupled from cytosolic Ca2+ rise

The activation of the respiratory burst by complement factor 5a (C5a), platelet-activating factor (PAF), formyl-Met-Leu-Phe (fMLP) and neutrophil-activating peptide IL-8 was explored in eosinophils from patients with the hypereosinophilic syndrome. The amplitude of the response increased with increasing concentrations of C5a and PAF, but the time for its induction was unaffected by the amount of stimulus applied. Respiratory burst activity resulting from phorbol 12-myristate, 13-acetate (PMA)-mediated activation of protein kinase C (PKC) produced longer onset times, which shortened with increasing PMA concentrations. Total inhibition of the C5a- and PMA-mediated burst could be achieved with the PKC inhibitor staurosporine at concentrations of 100 and 5nM, respectively. Calcium depletion abolished agonist-induced rises in cytosolic free calcium ([Ca2+]i) and respiratory burst activity, but not PMA-mediated NADPH-oxidase activation. While PMA reduced elevations in [Ca2+]i, it restored the burst response to agonists in Ca(2+)-depleted eosinophils. These results agree with the agonist-induced activation of the NADPH-oxidase via PKC, but suggest a parallel, Ca(2+)-, phospholipase C- and PKC-independent signal transduction pathway. Data obtained with B. pertussis toxin showed that the respiratory burst in eosinophils is blocked by ADP-ribosylation of G(i)-proteins, but that in the presence of PMA portions of the agonist response could be recovered.

Circulating histamine and eosinophil cationic protein levels in nocturnal asthma

1. To investigate the role of mast cells and eosinophils in the pathogenesis of nocturnal asthma, the plasma methylhistamine concentration, serum eosinophil cationic protein level and peak expiratory flow rate were measured 2-hourly for 24 h in 10 patients with nocturnal asthma and in 10 healthy control subjects. Nocturnal asthma was defined as at least one nocturnal awakening per week due to cough, wheeze or breathlessness with an average overnight fall in peak expiratory flow rate of at least 15% during a 2-week run-in period. 2. The lowest peak expiratory flow rate occurred at 02.00-04.00 hours in the group with nocturnal asthma, whose overnight fall in peak expiratory flow rate was 29 +/- 5% in comparison with 5 +/- 1% (means +/- SEM) in the normal subjects. 3. Plasma methylhistamine levels at night (0.200-04.00 hours) were lower than during the day (10.00-20.00 hours) in both asthmatic patients and normal subjects (asthmatic patients: day, median 0.22 ng/ml, 95% confidence intervals 0.18-0.34 ng/ml; night, 0.17 ng/ml, 0.13-0.24 ng/ml; P < 0.01; normal subjects: day, 0.31 ng/ml, 0.24-0.41 ng/ml; night, 0.24 ng/ml, 0.21-0.33 ng/ml; P < 0.01). 4. The serum eosinophil cationic protein level was higher by day (30 ng/ml, 8-47 ng/ml) than by night (21 ng/ml, 5-34 ng/ml; P < 0.04) in the group with nocturnal asthma, but did not change significantly with the time of day in the normal subjects (day: 8 ng/ml, 4-14 ng/ml; night: 8 ng/ml, 5-21 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Release of granule proteins by eosinophils from allergic and nonallergic patients with eosinophilia on immunoglobulin-dependent activation

The release of eosinophil peroxidase (EPO) and eosinophil cationic protein (ECP) was evaluated after incubation of eosinophils (EOSs) from allergic subjects with the specific allergen or with anti-IgE monoclonal antibodies (MAbs). High levels of EPO could be released after addition of the specific allergen (and not unrelated ones) or anti-IgE MAb. Moreover, EPO release with the two stimuli was significantly correlated both in allergic and in nonallergic patients. In the same supernatants, another granule protein, ECP, could not be detected, suggesting a lack of correlation between EPO and ECP release after IgE-dependent stimulation. However, when EOSs with surface-IgA antibodies were incubated with anti-IgA MAb, both EPO and ECP were released. In contrast, incubation of EOSs with anti-IgG MAb induced mainly the release of ECP and not EPO. These results indicate that pharmacologically active mediators can be released by EOSs from allergic and nonallergic patients on immunoglobulin-dependent activation. The results also confirm the hypothesis of a selective release of the various granule proteins and raise the question of transduction signals delivered by the three Fc receptors (Fc epsilon R, FC alpha R, and FC gamma R) present on human EOSs.

Dilated cardiomyopathy and myocarditis: monoclonal antibodies to diseased heart tissues

This study looked for the presence of abnormal contractile protein antigens and alterations in contractile protein expression in dilated cardiomyopathy (DCM). Monoclonal antibodies were raised to extracts from hearts removed at cardiac transplantation from two patients with dilated cardiomyopathy (DCM), and one with myocarditis. The specificities of the antibodies were assessed on cryostat sections from eight hearts with DCM. Although an extensive search was made for DCM-specific antibodies among over 1500 clones, none were found. However, a panel of antibodies was prepared and characterized, including antibodies to human adult myosin heavy chain beta, actin and troponin-I, which were selected for their value as reagents for immunocytochemical studies on cardiac, skeletal and smooth muscle. No significant alteration in the distribution of the epitopes recognized by these antibodies was found in DCM although more atrial myocytes in patients with DCM contained myosin adult heavy chain-beta. As a similar increase was found in atria from patients with other diseases who had a normal filling pressure, it was concluded that this alteration was unrelated to filling pressure, and was not specific for DCM. Further work with well defined monoclonal antibodies to other cardiac components in DCM could be useful in defining the alterations which lead to the functional defects in DCM and other cardiac diseases of unknown cause.

Effects of IL-5, granulocyte/macrophage colony-stimulating factor (GM-CSF) and IL-3 on the survival of human blood eosinophils in vitro

The mechanisms that could affect the lifespan of eosinophils after they have left the bone marrow, and their capacity to respond to activation factors were studied by examining the effects of IL-5, GM-CSF and IL-3 on purified human blood eosinophils in culture. All three cytokines prolonged the lifespan of the majority of blood eosinophils. This effect was dose-dependent: IL-5 greater than GM-CSF greater than IL-3. Light density eosinophils from most patients had a longer lifespan in culture than did normal density eosinophils, with or without the three cytokines. Eosinophil death in the absence of these cytokines occurred by apoptosis. Eosinophils from two patients did not survive when cultured with IL-5, although they survived in the presence of IL-3 or GM-CSF. IL-5, GM-CSF and IL-3 induced the expression of the activation epitope on the eosinophil ribonucleases recognized by monoclonal antibody EG2. We conclude that small amounts of IL-5, GM-CSF and IL-3 prevented programmed cell death in human blood eosinophils and induced the expression of the activation forms of eosinophil ribonucleases. We suggest that differences in the capacity of normal and light density eosinophils to survive in culture, and in the ability of eosinophils from some patients to respond to IL-5 could account for variations in the severity of disease seen in patients with persistent eosinophilia.

Shape changes, exocytosis, and cytosolic free calcium changes in stimulated human eosinophils

Essentially pure preparations of normal density eosinophils obtained from patients with hypereosinophilic syndrome (HES) were stimulated with complement factor 5a (C5a), platelet-activating factor (PAF), FMLP and neutrophil-activating peptide (NAP-1/IL-8). Three responses were studied, the transient rise in cytosolic free calcium concentration ([Ca2+]i) (derived from indo-1 fluorescence), shape changes (measured by laser turbidimetry), and exocytosis of eosinophil peroxidase (EPO) (assessed by H2O2/luminol-dependent chemiluminescence). Responses were obtained with all four agonists, but C5a and PAF were by far more potent than FMLP and NAP-1/IL-8, which induced only minor effects. Pretreatment of the cells with pertussis toxin attenuated [Ca2+]i changes, EPO release and, to a lesser extent, shape changes, indicating that GTP-binding proteins of Gi-type are involved in receptor-dependent signal transduction processes leading to these responses. A clear dissociation was observed in the control of the shape change response and EPO exocytosis. The shape change was not affected by Ca2+ depletion or treatment with the protein kinase inhibitor staurosporine, but exocytosis was prevented by Ca2+ depletion and markedly enhanced by staurosporine. The activation of the contractile system, leading to shape changes and motility, thus appears to be independent of the classical signal transduction pathway involving phospholipase C, a [Ca2+]i rise and protein kinase C activation. Exocytosis is, as expected, Ca2+ dependent and appears to be under a negative control involving protein phosphorylations.

The effects of recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 on the secretory capacity of human blood eosinophils

The effects of recombinant human GM-CSF and interleukin-3 (IL-3) on human blood eosinophil survival, activation, and secretion were studied. Purified normal density eosinophils from patients with the idiopathic hypereosinophilic syndrome (HES) survived in culture for 7 days (50% viable) in the presence of 50 nM GM-CSF or 50 nM IL-3. Neutrophils did not survive after 4 days. No eosinophils survived in the absence of GM-CSF or IL-3. In two out of five patients studied, the cultured eosinophils became elongated with numerous processes. In all five patients the cells became adherent, but there were no morphological signs of degranulation. Both GM-CSF and IL-3 activated eosinophils, transforming the storage form of eosinophil cationic protein (ECP) into the secreted form. The proportion of activated cells increased from less than 20% to over 50% after 4 days in culture. However, GM-CSF and IL-3 did not induce secretion on their own. On the other hand, when GM-CSF/IL-3-activated eosinophils were exposed to known secretory stimuli, there was a six-fold increase in the amount of ECP released when the cells were stimulated with sepharose coated with C3b, and a two-fold increase when they were stimulated with sepharose-activated whole autologous serum. Eosinophils from patients taking steroids were unable to secrete their granule contents, even though they became activated by GM-CSF and IL-3. A novel finding was that sepharose-activated whole serum was an extremely potent secretory signal for ECP, releasing up to 50% of the total ECP content. These studies showed that GM-CSF and IL-3 prime eosinophil effector function by initiating granule solubilization which is the first step in the secretory event, without affecting the subsequent extracellular release of granule proteins.

Protein translocation in vitro: biochemical characterization of genetically defined translocation components

Recent years have seen the convergence of both genetic and biochemical approaches in the study of protein translocation in E. coli. The powerful combination of these approaches is exemplified in the use of an in vitro protein synthesis-protein translocation system to analyze the role of genetically defined components of the protein translocation machinery. We describe in this review recent results focusing on the function of the secA, secB, and secY gene products and the demonstration of their requirement for in vitro protein translocation. The SecA protein was recently shown to possess ATPase activity and was proposed to be a component of the translocation ATPase. We present a speculative working model whereby the translocator complex is composed of the integral membrane proteins SecY, SecD, SecE, and SecF, forming an aqueous channel in the cytoplasmic membrane, and the tightly associated peripheral membrane protein SecA functioning as the catalytic subunit of the translocator or "protein-ATPase."

Effects of inhibitors of membrane signal peptide peptidase on protein translocation into membrane vesicles

The effect of the removal of signal peptides after cleavage of precursor molecules by the signal peptidase I was examined in an in vitro translocation system with Escherichia coli membrane vesicles. The translocation of periplasmic alkaline phosphatase precursors was significantly inhibited by the protease inhibitors antipain, elastatinal and leupeptin. Antipain and leupeptin enhanced the translocation of precursors of outer membrane protein OmpA, but inhibited the processing. However, antipain did not inhibit the processing of precursors mediated by signal peptidase I in the soluble form. Moreover, the inhibition by antipain was not due to the disruption of membrane integrity, but occurred during the process of protein translocation. Since these small peptide inhibitors are known to inhibit membrane protease IV, a signal peptide peptidase, these results suggest that the hydrolysis of signal peptides is an important step in the recycles of the overall translocation process, and that the prevention of degradation of signal peptides feedback inhibits the preceding steps in the translocation pathway.

Temperature-dependent insertion of prolipoprotein into Escherichia coli membrane vesicles and requirements for ATP, soluble factors, and functional SecY protein for the overall translocation process

The requirements for the translocation of prolipoprotein into membrane vesicles were examined in an in vitro system. As measured by the eventual modification and processing of the prolipoprotein to form mature lipoprotein, the overall translocation process was found to require ATP hydrolysis, the presence of some heat-labile soluble cytoplasmic translocation factors, and the function of a cytoplasmic membrane protein, SecY/PrlA. However, the initial step of complete insertion of prolipoprotein into the membrane vesicles occurred without apparent requirements of a nucleotide, cytoplasmic translocation factors, or a functional SecY/PrlA membrane protein. Immunopurified prolipoprotein spontaneously inserted into membrane vesicles at elevated temperatures and required ATP and cytoplasmic translocation factors to form mature lipoprotein. The prolipoprotein inserted most efficiently into liposomes made of negatively charged phospholipids, indicating the importance of phospholipids in protein translocation. These results suggest that ATP hydrolysis and the actions of both cytoplasmic translocation factors and a functional SecY/PrlA membrane protein occur at a step(s) after the insertion of the precursors into membrane vesicles. The initial step of spontaneous insertion of prolipoprotein into membranes is in good agreement with membrane trigger hypothesis proposed by W. Wickner (Annu. Rev. Biochem. 48:23-45, 1979) and the helical hairpin hypothesis proposed by D. M. Engleman and T. A. Steitz (Cell 23:411-422, 1981).

Activation of eosinophils in cancer patients treated with IL-2 and IL-2-generated lymphokine-activated killer cells

Of 16 patients, a total of 13 who received IL-2 and autologous IL-2-generated lymphokine-activated killer LAK cells developed eosinophilia late during the course of treatment. To understand the direct or indirect effects of IL-2 on eosinophils, the physical and functional characteristics of the late-treatment eosinophils were compared to those of early-treatment and control eosinophils. Late-treatment eosinophils differed from early-treatment and control eosinophils in the following respects: they had somewhat reduced density, hypersegmented nuclei, eosinophil cationic protein converted from the storage form to the secretory form, and a greater than 200% increased ability to kill larvae of Schistosoma mansoni by an antibody-dependent mechanism (cytotoxic function). In vitro, IL-2 (1000 U/ml in medium as used to culture LAK cells) did not affect the cytotoxic function of eosinophils from cancer patients or from control subjects. However, LAK cell-conditioned medium enhanced the cytotoxic function of eosinophils from early-treatment cancer patients and from normal subjects by greater than 150%. Thus, eosinophils late in the course of IL-2/LAK cell treatment undergo physical changes and become functionally activated. The involvement of IL-2 in these changes is probably indirect, as an inducer of factors that enhance eosinophil function.

Activation of eosinophils in cancer patients treated with IL-2 and IL-2-generated lymphokine-activated killer cells

Of 16 patients, a total of 13 who received IL-2 and autologous IL-2-generated lymphokine-activated killer LAK cells developed eosinophilia late during the course of treatment. To understand the direct or indirect effects of IL-2 on eosinophils, the physical and functional characteristics of the late-treatment eosinophils were compared to those of early-treatment and control eosinophils. Late-treatment eosinophils differed from early-treatment and control eosinophils in the following respects: they had somewhat reduced density, hypersegmented nuclei, eosinophil cationic protein converted from the storage form to the secretory form, and a greater than 200% increased ability to kill larvae of Schistosoma mansoni by an antibody-dependent mechanism (cytotoxic function). In vitro, IL-2 (1000 U/ml in medium as used to culture LAK cells) did not affect the cytotoxic function of eosinophils from cancer patients or from control subjects. However, LAK cell-conditioned medium enhanced the cytotoxic function of eosinophils from early-treatment cancer patients and from normal subjects by greater than 150%. Thus, eosinophils late in the course of IL-2/LAK cell treatment undergo physical changes and become functionally activated. The involvement of IL-2 in these changes is probably indirect, as an inducer of factors that enhance eosinophil function.

Purification of the Escherichia coli secB gene product and demonstration of its activity in an in vitro protein translocation system

Mutations in the Escherichia coli secB gene lead to protein export defects in vivo (Kumamoto, C.A., and Beckwith, J. (1985) J. Bacteriol. 163, 267-274). To demonstrate directly the participation of the secB gene product (SecB) in protein export, SecB was purified, and its effects on in vitro protein translocation were analyzed. SecB was purified from soluble extracts of a strain that overproduced it, by ammonium sulfate precipitation, DEAE-cellulose chromatography, and differential precipitation at acid pH. The chromatographic behavior on gel filtration columns indicated apparent molecular masses of approximately 90 kDa for both purified SecB and SecB in cytosolic extracts of wild type cells. When added to a translocation mixture, purified SecB stimulated pro-OmpA translocation into membrane vesicles. SecB also suppressed the thermoinduced defect in translocating activity of membranes derived from a secY24 mutant. The results of these in vitro studies and of previous in vivo studies demonstrate that SecB plays a direct role in normal protein export in E. coli.

SecA suppresses the temperature-sensitive SecY24 defect in protein translocation in Escherichia coli membrane vesicles

Genetic analysis of protein secretion in Escherichia coli has identified secY/prlA and secA as components of the secretory apparatus. We have examined the roles of the secY(prlA) gene product (an integral membrane protein) and the soluble secA gene product in translocation of OmpA and alkaline phosphatase precursors in an in vitro system. The protein translocation defect of the secY24 mutation was recently demonstrated in vitro as was its suppression by an S300 extract. We show here that the extract was essentially inactive in SecY24 suppression when SecA protein was removed from it by immunoaffinity chromatography. Furthermore, purified SecA protein suppressed the SecY24 defect. Preincubation of the inactivated SecY24 membrane vesicles either with S300 containing SecA or with purified SecA protein reconstituted the membranes and restored the translocation activity when assayed in the absence of additional soluble proteins. These results suggest that the SecY24 translocation defect is suppressed by SecA interacting, directly or indirectly, with SecY24 on the cytoplasmic membrane.

SecA protein is required for secretory protein translocation into E. coli membrane vesicles

The soluble and membrane components of an E. coli in vitro protein translocation system prepared from a secA amber mutant, secA13[Am], contain reduced levels of SecA and are markedly defective in both the cotranslational and posttranslational translocation of OmpA and alkaline phosphatase into membrane vesicles. Moreover, the removal of SecA from soluble components prepared from a wild-type strain by passage through an anti-SecA antibody column similarly abolishes protein translocation. Translocation activity is completely restored by addition of submicrogram amounts of purified SecA protein, implying that the observed defects are solely related to loss of SecA function. Interestingly, the translocation defect can be overcome by reconstitution of SecA into SecA-depleted membranes, suggesting that SecA is an essential, membrane-associated translocation factor.

Requirement of heat-labile cytoplasmic protein factors for posttranslational translocation of OmpA protein precursors into Escherichia coli membrane vesicles

The involvement of possible cytoplasmic factors in ATP-dependent postttranslational translocation of proteins into Escherichia coli membrane vesicles was examined. The precursor of OmpA protein was partially purified by DEAE-cellulose chromatography, and its translocation was found to require material from the soluble cytoplasmic fraction. The fractionated active cytoplasmic translocation factor (CTF) was protease sensitive, micrococcal nuclease insensitive, N-ethylmaleimide resistant, and heat labile. The heat sensitivity of the CTF allowed its specific and preferential inactivation in the crude-precursor synthesis mixture, which provided a simple and rapid assay procedure for the factor during purification. Two active fractions were detected upon further fractionation: the major one was about 8S in sucrose gradient centrifugation and 120 kilodaltons by Sephadex filtration, whereas the other was about 4S and 60 kilodaltons in sucrose gradient centrifugation and by Sephadex filtration, respectively. The active fractions could also be fractionated by DEAE-Sepharose chromatography. These CTFs are apparently different from the previously reported 12S export factor (M. Muller and G. Blobel, Proc. Natl. Acad. Sci. USA 81:7737-7741, 1984).

Biochemical evidence for the secY24 defect in Escherichia coli protein translocation and its suppression by soluble cytoplasmic factors

The secY (prlA) gene product is an integral membrane protein that has been identified genetically as one of the central components of the Escherichia coli protein translocation machinery. We have examined the effect of the secY24 (temperature-sensitive) mutation on the protein translocation activity of E. coli inverted membrane vesicles. Vesicles isolated from cells carrying this allele and grown at the nonpermissive temperature (42 degrees C) were less than 1% as active in translocation as vesicles isolated from an isogenic secY+ strain under the same conditions. Vesicles from the mutant strain grown at the permissive temperature (32 degrees C) were partially active, but those vesicles preincubated at 40 degrees C lost 90% of their activity. Moreover, the secY24 translocation defect on in vivo- or in vitro-inactivated vesicles was suppressed, or compensated, by an S300 soluble fraction from wild-type cells or from secY24 cells grown at nonpermissive temperature. The suppressing factor(s) was heat-labile and sensitive to proteinase K. These results provide biochemical evidence for the essential role of SecY in the translocation process and indicate that the translocation defect of SecY24 membranes can be compensated for by supplementing with additional soluble cytoplasmic proteins.

Nucleotide sequences and expression in Escherichia coli of the in-phase overlapping Pseudomonas aeruginosa plcR genes

The translation products of chromosomal DNAs of Pseudomonas aeruginosa encoding phospholipase C (heat-labile hemolysin) have been examined in T7 promoter plasmid vectors and expressed in Escherichia coli cells. A plasmid carrying a 4.7-kilobase (kb) DNA fragment was found to encode the 80-kilodalton (kDa) phospholipase C as well as two more proteins with an apparent molecular mass of 26 and 19 kDa. Expression directed by this DNA fragment with various deletions suggested that the coding region for the two smaller proteins was contained in a 1-kb DNA region. Moreover, the size of both proteins was reduced by the same amount by an internal BglII-BglII DNA deletion, suggesting that they were translated from overlapping genes. Similar results were obtained with another independently cloned 6.1-kb Pseudomonas DNA, which in addition coded for a 31-kDa protein of opposite orientation. The nucleotide sequence of the 1-kb region above revealed an open reading frame with a signal sequence typical of secretory proteins and a potential in-phase internal translation initiation site. Pulse-chase and localization studies in E. coli showed that the 26-kDa protein was a precursor of a secreted periplasmic 23-kDa protein (PlcR1) while the 19-kDa protein (PlcR2) was mostly cytoplasmic. These results indicate the expression of Pseudomonas in-phase overlapping genes in E. coli.

Evidence for the involvement of ATP in co-translational protein translocation

Identification of the source of energy for protein translocation across biological membranes is important in understanding the mechanism of this process. In eukaryotic cells, the tight coupling between translation and translocation and firm attachment of the secreting ribosomes to membranes, as well as theoretical calculations, have led to the suggestion that energy derived from protein synthesis is sufficient for protein translocation. On the other hand, in bacterial systems neither the attachment of ribosomes to membrane (other than nascent chains) nor tight coupling of translocation to translocation has been observed. Moreover, certain proteins can be translocated across membranes either at the time of, or after, translation. The separation of protein translocation from translation has made possible the demonstration that ATP hydrolysis is essential for post-translational protein translocation across bacterial membranes and, more recently, also across canine and yeast endoplasmic reticulum membranes. Here we report that certain ATP analogues inhibit co-translational protein translocation at concentrations that do not interfere with protein synthesis, suggesting that ATP is also required for co-translational protein translocation.

Effects of antibiotics and other inhibitors on ATP-dependent protein translocation into membrane vesicles

The effects of several membrane antibiotics and other agents on ATP-dependent protein translocation were examined in membrane vesicles under conditions where no significant proton motive force was present. The membrane perturbants ethanol and procaine abolished ATP-dependent protein translocation. Phenethyl alcohol at low concentrations abolished translocation, whereas at high concentrations it allowed precursors to be translocated but inhibited their processing. Translocation of precursors promoted by phenethyl alcohol was temperature dependent and occurred without an added energy source but was enhanced by ATP. However, such precursors could not be further processed to mature forms upon removal of the alcohol. The membrane-active antibiotics polymyxin B and gramicidin S were strong inhibitors of translocation, whereas gramicidin D, cerulenin, and mycobacillin had no effect even at higher concentrations, indicating some specificity in interference with protein translocation. Duramycin, an antibiotic previously shown to affect protein-lipid interaction, severely impaired protein translocation. These results showed that membrane structures play important roles, either directly or indirectly, in protein translocation. Chelating agents 1,10-phenanthroline and EDTA, but not EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid], also abolished protein translocation.

Synergism between eosinophil cationic protein and oxygen metabolites in killing of schistosomula of Schistosoma mansoni

To study the cytotoxic reactions responsible for mediating eosinophil damage to schistosomula of Schistosoma mansoni, we have used cytoplasts (eosinophil or neutrophil vesicles devoid of granules and nuclei, with an intact oxidase in their plasma membrane) in combination with purified eosinophil cationic protein (ECP) or major basic protein (MBP) in a cytotoxicity test toward schistosomula. Suboptimal concentrations of ECP (10(-6) M) or MBP (10(-6) M) resulting in less than 10% killing were used in combination with cytoplasts. Cytoplasts alone in the presence of immune serum tested over a wide range of cytoplast:schistosomula ratios generated superoxide and hydrogen peroxide, but were unable to damage schistosomula. However, when a suboptimal ECP concentration (10(-6) M) was combined with neutroplasts or eosinoplasts, 43.9% +/- 8.5 (n = 7) and 24.7% +/- 9.8 (n = 3), respectively, of the schistosomula were killed. Oxygen metabolites were responsible for the synergism, because cytoplasts from a patient with chronic granulomatous disease were unable to act in synergy with ECP. In contrast to ECP, no synergism was found between cytoplasts and MBP (10(-6) to 2 X 10(-5)M). These results show that oxygen metabolites are important for the killing of schistosomula by lowering the concentration of ECP needed to inflict damage.

Synergism between eosinophil cationic protein and oxygen metabolites in killing of schistosomula of Schistosoma mansoni

To study the cytotoxic reactions responsible for mediating eosinophil damage to schistosomula of Schistosoma mansoni, we have used cytoplasts (eosinophil or neutrophil vesicles devoid of granules and nuclei, with an intact oxidase in their plasma membrane) in combination with purified eosinophil cationic protein (ECP) or major basic protein (MBP) in a cytotoxicity test toward schistosomula. Suboptimal concentrations of ECP (10(-6) M) or MBP (10(-6) M) resulting in less than 10% killing were used in combination with cytoplasts. Cytoplasts alone in the presence of immune serum tested over a wide range of cytoplast:schistosomula ratios generated superoxide and hydrogen peroxide, but were unable to damage schistosomula. However, when a suboptimal ECP concentration (10(-6) M) was combined with neutroplasts or eosinoplasts, 43.9% +/- 8.5 (n = 7) and 24.7% +/- 9.8 (n = 3), respectively, of the schistosomula were killed. Oxygen metabolites were responsible for the synergism, because cytoplasts from a patient with chronic granulomatous disease were unable to act in synergy with ECP. In contrast to ECP, no synergism was found between cytoplasts and MBP (10(-6) to 2 X 10(-5)M). These results show that oxygen metabolites are important for the killing of schistosomula by lowering the concentration of ECP needed to inflict damage.

Killing of Plasmodium falciparum by eosinophil secretory products

The multiplication of two strains of Plasmodium falciparum in culture, as measured by [3H]hypoxanthine incorporation, was inhibited in a dose-dependent manner by granule proteins secreted by purified eosinophils obtained from patients with the hypereosinophilic syndrome. Morphological examination revealed the presence of abnormal parasites inside erythrocytes, indicating that they were killed in situ, and the later stages of the developmental cycle were found to be most susceptible to these toxic effects. A monoclonal antibody against eosinophil cationic protein partially blocked the inhibitory effect, suggesting that it was caused by more than one of the eosinophil granule proteins. Thus some of the antimalarial effects of molecules such as the tumor necrosis factor, which activates eosinophils, may be mediated through the enhanced production of eosinophil secretion products.

Deposits of eosinophil granule proteins in cardiac tissues of patients with eosinophilic endomyocardial disease

Eosinophilic endomyocardial disease is a complication of the hypereosinophilic syndrome and of several other disorders associated with high blood eosinophil counts. Eosinophil granule proteins may be involved in the development of these lesions. This multi-centre study investigated whether these proteins could be demonstrated within the cardiac tissues of eighteen patients with eosinophilic endomyocardial disease. Serial sections of tissue taken at necropsy or at cardiac biopsy were stained for eosinophil major basic protein by indirect immunofluorescence and for eosinophil cationic protein, eosinophil protein-X, and activated eosinophils by means of alkaline-phosphatase-linked monoclonal antibodies. Activated eosinophils and secreted eosinophil granule proteins were most evident within the necrotic and later stage thrombotic lesions and were found mainly within the areas of acute tissue damage in the endocardium and in the walls of small blood vessels. These findings suggest that eosinophil granule proteins are involved in cardiac injury, producing muscle damage and vascular injury which lead to the development of endomyocardial fibrosis.