Treatment with succinic anhydride improves the immunogenicity of Shigella flexneri type 2a O-specific polysaccharide-protein conjugates in mice

Seroepidemiological data and a clinical trial with a Shigella sonnei O-specific polysaccharide (O-SP)-Pseudomonas aeruginosa recombinant exoprotein A (rEPA) conjugate provide evidence that a critical level of immunoglobulin G (IgG) lipopolysaccharide (LPS) antibodies in serum confers protection against shigellosis. We evaluated the immunogenicity of conjugates whose carrier proteins and O-SPs were treated with succinic anhydride (SA), which reacts with amino groups at neutral pH to form amide-linked carboxyls (succinylation). Conjugates were synthesized with either of two genetically inactivated medically useful toxins, the diphtheria protein CRM9 or rEPA, bound to the O-SP of Shigella flexneri type 2a. Conjugates composed of the succinylated protein, succinylated O-SP, or both succinylated components were administered to mice by a clinically relevant scheme, and their levels of serum IgG anti-LPS and anti-proteins were assayed 7 days after the second and third injections. CRM9 served as a more immunogenic carrier than rEPA. Conjugates composed of succinylated components were more immunogenic than the conjugates composed of the native components. SA treatment of both the carrier protein and the O-SP did not confer an advantage over the succinylated protein alone. Conjugates prepared with native proteins, in general, elicited slightly higher levels of IgG protein antibodies than conjugates composed of the SA-treated proteins.

Comparative physical and genetic maps of the virulence plasmids of Salmonella enterica serovars typhimurium, enteritidis, choleraesuis, and dublin

Using fragment profiling, PCR, and Southern hybridization, we found that Salmonella enterica serovar Choleraesuis harbored virulence plasmids of various sizes, whereas serovars Typhimurium, Enteritidis, and Dublin carried a plasmid of a unique size. Also, the virulence plasmid of Typhimurium contained genes in the same order detected in the other three plasmids, all of which contained deletions.

Protein conjugates of synthetic saccharides elicit higher levels of serum IgG lipopolysaccharide antibodies in mice than do those of the O-specific polysaccharide from Shigella dysenteriae type 1

Our development of vaccines to prevent shigellosis is based on the hypothesis that a critical (protective) level of serum IgG to the O-specific polysaccharide (O-SP) domain of Shigella lipopolysaccharide (LPS) confers immunity. The O-SP is a hapten and must be conjugated to a protein to induce serum antibodies. The O-SP of Shigella dysenteriae type 1 (approximately 27 tetrasaccharide repeat units), prepared by acid hydrolysis of the LPS, was bound to human serum albumin (HSA) by multiple point attachment (O-SP-HSA): The molar ratio of HSA to O-SP was 1.0. Synthetic saccharides, composed of one or multiples of the O-SP tetrasaccharide, equipped with a spacer at their reducing end, were bound to HSA by a single point attachment: The average molar ratios of the saccharides to HSA ranged from 4 to 24. Serum IgG anti-LPS, elicited in mice by O-SP-HSA or synthetic tetra-, octa-, dodeca-, and hexadecasaccharide fragments, was measured by ELISA. Outbred 6-week-old female mice were injected s.c. three times at biweekly intervals with 2.5 micrograms of saccharide as a conjugate and were bled 7 days after the second and third injections. Excepting the tetramer, conjugates of the octamer, dodecamer and hexadecamer elicited IgG LPS antibodies after the second injection, a statistically significant rise (booster) after the third injection, and higher levels than those vaccinated with O-SP-HSA (P = 0.0001). The highest geometric mean levels of IgG anti-LPS were elicited by the hexadecamer with 9 chains or 9 moles of saccharide/HSA (15.5 ELISA units) followed by the octamer with 20 chains (11.1 ELISA units) and the dodecamer with 10 chains (9.52 ELISA units). Clinical evaluation of these synthetic saccharides bound to a medically useful carrier is planned.

Prognostic value of plasma HIV RNA in the natural history of Pneumocystis carinii pneumonia, cytomegalovirus and Mycobacterium avium complex. Multicenter AIDS Cohort Study

OBJECTIVES

To use follow-up on untreated HIV-positive men to assess the prognostic information provided by baseline data on plasma HIV RNA, CD4 cell count, age, and HIV-related symptom status, separately for three specific AIDS-defining illnesses: Pneumocystis carinii pneumonia (PCP), cytomegalovirus (CMV), and Mycobacterium avium complex (MAC).

METHODS

The study population were 734 HIV-positive homosexual men enrolled in the Multicenter AIDS Cohort Study, with follow-up (1984-1985 through mid-1988) restricted to the antiretroviral treatment-free and prophylaxis-free era. Baseline marker values were categorized and assessed as predictor variables in separate time-to-event analyses for each of the three specific outcomes.

RESULTS

A total of 138 cases of PCP, 25 cases of CMV, and 25 cases of MAC were observed. For PCP and CMV, higher categories of HIV RNA and lower categories of CD4 cell count were associated with increased risk relative to the respective reference groups. For MAC, oral candidiasis or fever and elevated HIV RNA at baseline were the primary risk factors. Further analysis highlighted the importance of monitoring HIV RNA levels in addition to CD4 cell counts when evaluating patients' risk of developing PCP.

CONCLUSIONS

In the absence of treatment, plasma HIV RNA levels provide prognostic information about the risk of these three specific AIDS-defining illnesses, independently of the CD4 cell count. These data provide a useful reference as researchers investigate changing patterns in the incidence and predictors of opportunistic infections in the era of increasingly active antiretroviral therapies.

Myocardial oxygenation during high work states in hearts with postinfarction remodeling

BACKGROUND

Postinfarction left ventricular remodeling (LVR) is associated with reductions in myocardial high-energy phosphate (HEP) levels, which are more severe in animals that develop overt congestive heart failure (CHF). During high work states, further HEP loss occurs, which suggests demand-induced ischemia. This study tested the hypothesis that inadequate myocyte oxygen availability is the basis for these HEP abnormalities.

METHODS AND RESULTS

Myocardial infarction was produced by left circumflex coronary artery ligation in swine. Studies were performed in 20 normal animals, 14 animals with compensated LVR, and 9 animals with CHF. Phosphocreatine (PCr)/ATP was determined with 31P NMR and deoxymyoglobin (Mb-delta) with 1H NMR in myocardium remote from the infarct. Basal PCr/ATP tended to be decreased in postinfarct hearts, and this was significant in animals with CHF. Infusion of dobutamine (20 microg x kg-1 x min-1 IV) caused doubling of the rate-pressure product in both normal and LVR hearts and resulted in comparable significant decreases of PCr/ATP in both groups. This decrease in PCr/ATP was not associated with detectable Mb-delta. In CHF hearts, rate-pressure product increased only 40% in response to dobutamine; this attenuated response also was not associated with detectable Mb-delta.

CONCLUSIONS

Thus, the decrease of PCr/ATP during dobutamine infusion is not the result of insufficient myocardial oxygen availability. Furthermore, in CHF hearts, the low basal PCr/ATP and the attenuated response to dobutamine occurred in the absence of myocardial hypoxia, indicating that the HEP and contractile abnormalities were not the result of insufficient oxygen availability.

Epitopic overload at the site of injection may result in suppression of the immune response to combined capsular polysaccharide conjugate vaccines

Capsular polysaccharide (CP) conjugate vaccines targeting a variety of bacterial infections are currently under development and clinical evaluation. The inclusion of multiple CP serotypes combined in a single injection is an important maneuver being evaluated. The combination of CP conjugate vaccines into a single multivalent injection may result in competition among the different components and adversely affect the immunogenicity of any individual conjugate. We observed a reduction of 30-90% in antibody responses to several serotypes in mice when immunogenicity of a 12-valent Escherichia coli (E. coli) lipopolysaccharide (LPS) conjugate vaccine was compared to the immunogenicity of each monovalent vaccine evaluated separately. A reduction of 30% was observed in the Staphylococcus aureus (S. aureus) type 8 CP antibodies when a type 8-rEPA conjugate was combined with a type 5-rEPA conjugate. S. aureus types 5 and 8-rEPA conjugates were combined with 100 micrograms of either rEPA (homologous) or diphtheria toxoid (DT) (heterologous) carrier proteins, and evaluated in rEPA or DT primed mice. The addition of the homologous protein resulted in a 64% reduction in type 5 CP antibodies. The heterologous protein did not affect the immunogenicity of the type 5. We postulate that the free protein competed with the conjugate and recruited most of the rEPA primed T cells. In the case of the DT conjugates, the DT targeted different populations of the T cells, thus interference was not observed. These data suggested that the epitopic load rather than the antigenic load at the site of injection caused reduced immunogenicity of the conjugates. We theorize that individual components of multivalent CP vaccines conjugated to the same carrier proteins would compete for a limited number of specific carrier protein primed T cells. This would result in one or more components being unavailable in eliciting a sufficient immune response. The use of multiple carrier proteins should be considered as an approach to reduce interference when multivalent conjugate vaccines are to be formulated into a single injection.

Molecular identification of a role for tyrosine 167 in the function of the human intestinal proton- coupled dipeptide transporter (hPepT1)

hPepT1 is a proton-coupled peptide transporter that mediates the absorption of di- and tripeptides. Here we show that tyrosine 167 (Y167) in transmembrane domain 5 (TMD5) of this 12-transmembrane spanning protein contributes to its transport function. We identified this particular amino acid by a computer model of the arrangement of the TMDs of hPepT1 and investigated its role by site-directed mutagenesis and dipeptide uptake studies. [3H]Gly-sar uptake in cells transiently transfected with Y167A-hPepT1 was abolished completely, even though the level of Y167A-hPepT1 expression by Western blot analysis and cell surface expression by immunofluorescence microscopy was similar to those of the wild type. Therefore, mutation affected transport function, but apparently not the steady-state protein level or trafficking of the transporter to the plasma membrane. Moreover, mutation of Y167 into phenylalanine, serine, or histidine all abolished gly-sar uptake in transfected HEK 293 cells. Taken together, these findings suggest that Y167 plays an essential role in hPepT1 function, perhaps due to the unique chemistry of its phenolic side chain.

Decline in total T cell count is associated with onset of AIDS, independent of CD4(+) lymphocyte count: implications for AIDS pathogenesis

We previously reported that blind T cell homeostasis, in which the total T cell count is maintained but the CD4(+) and CD8(+) subset composition of the T cells can vary, fails approximately 1.5 to 2.5 years before the onset of AIDS. The present study was premised on the hypothesis that if failure of T cell homeostasis (i.e., a decline in total T cell counts) is important in the pathogenesis of AIDS, it should be a significant predictor of AIDS after controlling for the CD4(+) lymphocyte count. Data from 1556 homosexual men with sufficient sequential T cell subset measurements were evaluated, representing 11,988 person-visits in men with known clinical outcomes over a period of more than 10 years. Using regression models that incorporated CD4(+) lymphocyte count and HIV-related symptoms (fever, thrush), it was determined that a yearly decline of more than 300 T cells/microliter of peripheral blood was an independent predictor of the onset of AIDS for subjects with CD4(+) lymphocyte counts of <500 cells/microliter. The results support an important role for failure of T cell homeostasis in the pathogenesis of AIDS.

Caveolin-mediated regulation of signaling along the p42/44 MAP kinase cascade in vivo. A role for the caveolin-scaffolding domain

The p42/44 mitogen-activated protein (MAP)-kinase cascade is a well-established signal transduction pathway that is initiated at the cell surface and terminates within the nucleus. More specifically, receptor tyrosine kinases can indirectly activate Raf, which in turn leads to activation of MEK and ERK and ultimately phosphorylation of Elk, a nuclear transcription factor. Recent reports have suggested that some members of p42/44 MAP kinase cascade can be sequestered within plasmalemmal caveolae in vivo. For example, morphological studies have directly shown that ERK-1/2 is concentrated in plasma membrane caveolae in vivo using immunoelectron microscopy. In addition, constitutive activation of the p42/44 MAP kinase cascade is sufficient to reversibly down-regulate caveolin-1 mRNA and protein expression. However, the functional relationship between the p42/44 MAP kinase cascade and caveolins remains unknown. Here, we examine the in vivo role of caveolins in regulating signaling along the MAP kinase cascade. We find that co-expression with caveolin 1 dramatically inhibits signaling from EGF-R, Raf, MEK-1 and ERK-2 to the nucleus. Using a variety of caveolin-1 deletion mutants, we mapped this in vivo inhibitory activity to caveolin-1 residues 32-95. Peptides derived from this region of caveolin 1 also inhibit the in vitro kinase activity of purified MEK-1 and ERK-2. Thus, we show here that caveolin-1 expression can inhibit signal transduction from the p42/44 MAP kinase cascade both in vitro and in vivo. Taken together with previous data, our results also suggest that a novel form of reciprocal negative regulation exists between p42/44 MAP kinase activation and caveolin-1 protein expression, i.e. up-regulation of caveolin-1 protein expression down-modulates p42/44 MAP kinase activity (this report) and up-regulation of p42/44 MAP kinase activity down-regulates caveolin-1 mRNA and protein expression.

Equilibration of air temperature inside the thimble of a Farmer-type ion chamber

Ionization chambers are frequently moved from one environment to another, sometimes with significant differences in temperature between the chamber and measurement phantom. To obtain reliable ionization data, the temperature of the air in the chamber must be allowed to equilibrate with the measuring phantom. The air temperature inside a thimble of a Farmer-type ion chamber was measured as a function of time for various phantom materials (air, water, and plastic). Equilibration rates for the various conditions are presented. Heat-diffusion theory is presented to explain the characteristics of the measured data. Waiting times for temperature equilibration down to 10% of the initial temperature difference ranges from 1 to 18 min, depending on the phantom material and use of bare or covered thimble. Radiation measurements confirm the temperature data.

Cross-cultural health issues in contemporary Australia

In recent decades, Australia has rapidly become one of the more ethnically diverse societies with over 120 different languages groups and 41.9% of the population having at least one parent born overseas. This presents a great challenge for decision-makers and service providers to plan and provide effective and responsive health services for communities with such diverse languages, cultural backgrounds, migration circumstances and socioeconomic status. In order to offer equitable, culturally sensitive and appropriate health services, there is a pressing need to identify and manage cross-cultural health issues. This paper will first clarify concepts fundamental to the understanding of cross-cultural phenomena. It will then discuss several priority migrant health issues including communication breakdown, reproductive health, mental health, workplace health and safety, and doubly disadvantaged groups. Finally it will recommend measures to address the above issues and to promote equity, access and quality in health care for migrants.

Effect of delayed intervention with ACE-inhibitor therapy on myocyte hypertrophy and growth of the cardiac interstitium in the rat model of myocardial infarction

The effectiveness of angiotensin-converting enzyme (ACE)-inhibitor therapy in attenuating ventricular remodeling when initiated immediately following myocardial damage is clearly established. Less information, however, is available on the impact of late therapy on the remodeling process, especially its influence on the cellular components of these structural changes. The purpose of this study was to examine the effects of converting enzyme inhibitor therapy commenced 28 days following infarction in the rat on changes in cardiac myocyte dimension and the interstitium. At 28 days following infarction, myocyte cell length (153.9+/-7.3 v 131.1+/-5.9 micron, P=0.0002) and cell volume in the free wall of the left ventricle (38. 5+/-5.0 x 10(3) v31.4+/-3.1 x 10(3), P=0.009) had increased compared with sham-operated rats. Similar changes were noted in the septum and right ventricle. Captopril therapy administered between 28 and 56 days attenuated a further increase in cell length noted in an untreated group in the left ventricle (153.5+/-15.3 v 167.3+/-13.7 micron, P=0.02), right ventricle (153.8+/-20.5 v 173.8+/-2.3 micron, P=0.01) and septum (158.0+/-20.2 v 179.1+/-16.6 micron, P=0.004). There was an increase in hydroxyproline content in the right ventricle and a similar trend in the left ventricle in the untreated myocardial infarction groups. These changes were not altered by captopril therapy. In summary, even late therapy with captopril attenuates progressive myocyte remodeling, which may contribute to the ability of ACE-inhibitor therapy to slow progressive chamber enlargement following infarction.

The effect of delayed reperfusion following infarction in the rat on structural changes in viable myocardium

OBJECTIVE

Evidence indicates that patency of the infarct related artery following the completion of myocardial necrosis can attenuate ventricular remodeling. Data have also demonstrated that inhibition of infarct expansion contributes to the anti-remodeling effect of delayed reperfusion. However, the influence of a patent artery on components of the remodeling process in the viable myocardium is poorly understood.

METHODS

Myocyte morphometrics (isolated cell technique) and collagen content (hydroxyproline analysis) were assessed 28 days following experimental myocardial infarction from rats with permanently ligated left coronary vessels (NRP; n = 10) compared with rats who underwent reperfusion 150 minutes after ligation (RP; n = 11) and a sham-operated group (n = 10).

RESULTS

Analysis of infarct size (planimetry) in a separate group of rats demonstrated that reperfusion at this late time point did not reduce infarct size (NRP: 33 +/- 3 vs. RP: 35 +/- 5%). Myocyte length in RP rats was less than in NRP rats in viable, non-infarcted left ventricular tissue (155 +/- 3 vs. 167 +/- 4 microns, p = 0.02), in the right ventricle (154 +/- 4 vs. 167 +/- 3 microns, p = 0.02) and in the septum (158 +/- 4 vs. 169 +/- 4 microns, p = 0.05). Reperfusion also attenuated the expected increase in cell volume compared with NRP rats (left ventricle 39.4 +/- 1.7 x 10(3) vs. 44.1 +/- 1.6 x 10(3) micron 3, p = 0.06; right ventricle 36.7 +/- 1.6 x 10(3) vs. 42.7 +/- 2.0 x 10(3) micron 3, p = 0.02; septum 41.0 +/- 1.6 x 10(3) vs. 44.2 +/- 1.8 x 10(3) micron 3, p = 0.19). Hydroxyproline content increased in the viable left ventricular tissue in both the reperfused and non-reperfused groups.

CONCLUSION

Reperfusion without myocardial salvage attenuates the increase in myocyte length and volume that occurs in remodeling myocardium following infarction in the rat, with no effect on the increase in collagen content. These data indicate that patency of the infarct vessel, which is known to have an inhibitory effect on infarct expansion, also has an anti-remodeling effect remote from the area perfused by this artery.

Identification of functioning cortex using cortical optical imaging

OBJECTIVE

The purpose of this study was to evaluate the technique of cortical optical imaging (COI) of intrinsic cortical optical signals related to neuronal activation. The specific goals of the study were to evaluate some of the technical aspects of COI and thus maximize the intensity of the image of this intrinsic signaling process and to determine the physiological reliability of COI in a well-defined animal system.

METHODS

The intrinsic optical signal of activated whisker barrel cortex of rat was imaged using a computer-based technique for rapid acquisition of enhanced images. Single-unit microelectrode recordings of cortical neuronal responses to whisker movement were used to confirm the locations of the whisker barrels.

RESULTS

Narrow band incident light at 600- to 610-nm wavelength was most effective for producing optical images. Images could be obtained during activation by a single long (40 s) stimulus or by averaging the signal generated by repeated shorter (1-8 s) stimuli. Focusing slightly below the cortical surface, minimizing movement, and abolishing extraneous light were all important in increasing the signal-to-noise ratio. The locations of whisker movement-evoked cortical activity determined using COI are consistent with the known functional anatomy of rat whisker barrel cortex. The images obtained with this experimental arrangement are shown to be accurate predictors of the location of neuronal activity determined by comparing the locations of active sites identified with COI with locations of areas of neuronal activity determined using single-cell recording techniques.

CONCLUSIONS

COI is able to rapidly identify areas of cortex containing elicited neuronal activity. The technique allows cortical activation maps to be made rapidly with a very high degree of spatial resolution. COI is reliable and consistent over time. COI, if used carefully, holds promise as an intraoperative technique to study both human and experimental animal cortical function.

The health-promoting workplace: an integrative perspective

The workplace is an important setting, affecting the physical, mental, economic and social wellbeing of workers, and, in turn, their families. Health of workers has many determinants, and a multidisciplinary, integrated approach is important. An overview of trends in workplace health promotion shows that current thinking has changed from a narrowly based risk-factors approach aimed at individual behaviour changes, to an integrative approach aimed at creating health-promoting workplaces. The health-promoting workplace has 'an all-encompassing approach that empowers workers and employers to improve all facets of their health'. There are gaps in knowledge, at the state and national levels, relevant to the planning and assessment of workplace health. A national information network is needed to facilitate better links between public health practitioners and researchers in advancing the health of working Australians.

Delayed reperfusion alters matrix metalloproteinase activity and fibronectin mRNA expression in the infarct zone of the ligated rat heart

Delayed reperfusion has a beneficial effect on prognosis, independent of infarct size. One potential mechanism to explain this observation may be an effect on infarct healing. In this study, the impact of delayed reperfusion on two aspects of the healing process was examined, the activity of matrix metalloproteinase (MMP) enzymes and the expression of fibronectin (FN) mRNA. The rat model of coronary artery ligation was used and rats were randomly assigned to delayed reperfusion (150 min following coronary ligation) or permanent ligation. Animals were subsequently killed 1, 2, 3 and 7 days following infarction. Infarct tissue was harvested for MMP activity (zymography), FN mRNA (RNase protection analysis) and protein (immunofluorescence microscopy and Western analysis), and collagen content (hydroxyproline concentration). Infarction produced marked activation of MMP-1, -2, and -9. Reperfusion significantly attenuated the activity of these enzymes (approximately 50% reduction in MMP-1, P=0.03 and ;60% reduction in MMP-2 at 7 days, P=0.001; approximately 55% reduction in MMP-9 at 24 h and 84% reduction at 48 h, P=0.01 and 0.002, respectively). Delayed reperfusion also produced a trend toward a greater increase in FN mRNA 24 h following infarction and immunofluorescent staining suggested the presence of more FN protein at this point. These data demonstrate that delayed reperfusion alters matrix metalloproteinase activity and fibronectin mRNA expression in the infarct zone. The impact of these changes on infarct healing and their association with the improved prognosis of a patent infarct vessel following infarction will require further study.

Detection of infection with human immunodeficiency virus type 1 before seroconversion: correlation with clinical symptoms and outcome

Early (pre-seroconversion) infection with human immunodeficiency virus type 1 (HIV-1) was identified in 50 of 267 participants in the Multicenter AIDS Cohort Study. These 50 men had a positive EIA result, which detected IgM antibody (n = 35), p24 antigen, or serum HIV RNA (n = 15) at their last "seronegative" visit. At that visit, the mean CD4 lymphocyte number (890/mm3 vs. 1038/mm3) was significantly lower than in men who subsequently seroconverted but had no evidence of early infection. The decline in CD4 cells was slower and the duration of AIDS-free time longer in the 19 men who were symptomatic in comparison to the 31 asymptomatic men with early infection, but differences were not significant.

MyoD functions as a transcriptional repressor in proliferating myoblasts

The myogenic basic helix-loop-helix (myo-bHLH) proteins are a family of transcriptional regulators expressed in myoblasts and differentiated skeletal muscle. Ectopic expression of myo-bHLH regulators transdetermines some fibroblast cell lines into myoblasts, which exit the cell cycle and differentiate into skeletal muscle when cultured in low mitogen medium. While members of the myo-bHLH family have been shown to function as transcriptional activators in differentiating muscle, the molecular basis of their function in proliferating myoblasts has not been elucidated. In this report, we present evidence that MyoD functions as a transcriptional repressor in myoblasts. We show that transcription from a cyclin B1 promoter construct is repressed in proliferating myoblasts and that repression is mediated by a pair of MyoD binding sites. We also show that transcription from the cyclin B1 promoter is repressed in proliferating C3H10T1/2 cells by ectopic expression of MyoD. These results demonstrate that MyoD can repress transcription of specific genes in proliferating cells, a novel function that may be important to maintenance of the myogenic phenotype and to cell cycle regulation in myoblasts.

Safety and immunogenicity of investigational Shigella conjugate vaccines in Israeli volunteers

The safety and immunogenicity of investigational conjugates, composed of the O-specific polysaccharides of Shigella sonnei and Shigella flexneri type 2a covalently bound to Pseudomonas aeruginosa recombinant exoprotein A (rEPA), were evaluated in 192 Israeli soldiers. None had significant local reactions or fever. Fourteen days after injection, 90% of S. sonnei-rEPA recipients and 73 to 77% of S. flexneri-rEPA recipients had a fourfold or greater increase in serum immunoglobulin G (IgG) and IgA anti-lipopolysaccharide (anti-LPS) levels; at 2 years, these remained higher than at prevaccination (P < 0.01). There was a fourfold or greater increase in IgM anti-LPS in 20% of vaccinees at 2 weeks, but levels returned to prevaccination values at 6 to 12 months. IgG was the highest and most sustained class of LPS antibodies. Reinjection at day 42 did not boost antibody levels. Eighteen of 23 (78%) who received S. sonnei-rEPA and 13 of 19 (68%) who received S. flexneri-rEPA. had significant IgA-secreting cell responses. Significant IgG antibody-secreting cell responses were detected in 19 of 23 (83%) and 11 of 19 (58%) volunteers following vaccination with S. sonnei-rEPA and S. flexneri 2a-rEPA, respectively. On the basis of these data, further evaluation of the Shigella conjugates for protective efficacy in field trials in Israel was started.

Oral clonidine reduces postoperative PCA morphine requirements

PURPOSE

The purpose of this study was to evaluate the effect of perioperative oral clonidine on postoperative analgesia and PCA morphine requirements in adult patients after major orthopaedic knee surgery.

METHODS

In this prospective, double blind, placebo-controlled study 44 patients undergoing either total knee replacement or hemiarthroplasty of the knee were randomly assigned to receive oral placebo or clonidine (5 micrograms . kg-1) 1.5 hr before surgery, and at 12 hr, and 24 hr after the initial dose. Five patients were subsequently withdrawn from study. No other preoperative drugs were given. Preoperative sedation score was recorded. A standardized general anaesthetic was administered to all patients. Postoperative blood pressure, heart rate, PCA morphine use, visual analogue score (VAS) for pain, sedation, nausea, and pruritus were recorded for 36 hr postoperatively.

RESULTS

The cumulative PCA morphine used was 37% lower after clonidine 57.3 +/- 26.8 mg (mean +/- SD) compared with placebo 91 +/- 31.6 mg (P = 0.031). There was no difference in pain or sedation scores postoperatively but patients who received clonidine were more sedated preoperatively (P < 0.001) and had a lower mean arterial blood pressure throughout the period of study by 10 to 26 mmHg (P < 0.0001). Clonidine reduced the incidence of postoperative nausea (25% vs 74%) (P < 0.01) and vomiting compared with placebo (10% vs 53%) (P < 0.01) and required less antiemetic (dimenhydrinate 37.5 +/- 20.9 mg vs 82.1 +/- 49.4 mg) but not statistically significant (P = 0.065).

CONCLUSIONS

Oral clonidine is a useful component to postoperative balanced analgesia as it decreases PCA morphine requirements and decreases the incidence of nausea and vomiting.

Imaging of orbital floor fractures

The aim of this study was to compare the efficacy of plain films and computed tomography (CT) in defining inferior orbital fractures and any muscle involvement. Forty-four patients with final diagnosis of orbital floor fractures in the period 1990-94 were retrospectively studied. Computed tomography was performed in 28 patients, 20 being direct coronal acquisitions and eight being fine axial acquisitions with coronal reconstructions. Water's view radiographs were performed in 34 patients. Fourteen fractures on plain films were associated with soft tissue opacities to suggest inferior rectus (IR) muscle involvement, but only two required surgical elevation of the orbital floor. The remaining patients were successfully treated conservatively. Three patients had IR entrapment on direct coronal CT, all requiring surgical elevation of the orbital floor. Seven patients had IR muscle displacement on direct coronal CT and all had conservative management. In four patients with axial acquisition and coronal reconstructions, the CT images were of inadequate quality to determine the presence or absence of a fracture. One patient who had no IR muscle involvement identified on reconstructed coronal CT required surgical elevation of the orbital floor on clinical grounds. We conclude that: (i) soft tissue opacities on plain films are not an accurate indicator of clinically significant IR involvement; (ii) axial CT is not efficacious in detection of fractures or IR involvement; and (iii) direct coronal CT is the most efficacious imaging modality.

Expression of caveolin-3 in skeletal, cardiac, and smooth muscle cells. Caveolin-3 is a component of the sarcolemma and co-fractionates with dystrophin and dystrophin-associated glycoproteins

Caveolae are microdomains of the plasma membrane that have been implicated in signal transduction. Caveolin, a 21-24-kDa integral membrane protein, is a principal component of the caveolae membrane. Recently, we and others have identified a family of caveolin-related proteins; caveolin has been retermed caveolin-1. Caveolin-3 is most closely related to caveolin-1, but caveolin-3 mRNA is expressed only in muscle tissue types. Here, we examine (i) the expression of caveolin-3 protein in muscle tissue types and (ii) its localization within skeletal muscle fibers by immunofluorescence microscopy and subcellular fractionation. For this purpose, we generated a novel monoclonal antibody (mAb) probe that recognizes the unique N-terminal region of caveolin-3, but not other members of the caveolin gene family. A survey of tissues and muscle cell types by Western blot analysis reveals that the caveolin-3 protein is selectively expressed only in heart and skeletal muscle tissues, cardiac myocytes, and smooth muscle cells. Immunolocalization of caveolin-3 in skeletal muscle fibers demonstrates that caveolin-3 is localized to the sarcolemma (muscle cell plasma membrane) and coincides with the distribution of another muscle-specific plasma membrane marker protein, dystrophin. In addition, caveolin-3 protein expression is dramatically induced during the differentiation of C2C12 skeletal myoblasts in culture. Using differentiated C2C12 skeletal myoblasts as a model system, we observe that caveolin-3 co-fractionates with cytoplasmic signaling molecules (G-proteins and Src-like kinases) and members of the dystrophin complex (dystrophin, alpha-sarcoglycan, and beta-dystroglycan), but is clearly separated from the bulk of cellular proteins. Caveolin-3 co-immunoprecipitates with antibodies directed against dystrophin, suggesting that they are physically associated as a discrete complex. These results are consistent with previous immunoelectron microscopic studies demonstrating that dystrophin is localized to plasma membrane caveolae in smooth muscle cells.

Lack of IL-4-induced Th2 response and IgE class switching in mice with disrupted Stat6 gene

Signal transducers and activators of transcription (Stats) are activated by tyrosine phosphorylation in response to cytokines, and are thought to mediate many of their functional responses. Stat6 is activated in response to interleukin (IL)-4 and may contribute to various functions including mitogenesis, T-helper cell differentiation and immunoglobulin isotype switching. To evaluate the role of Stat6, we generated Stat6-null mice (Stat6 -/-) by gene disruption in embryonic stem cells. The mice were viable, indicating the lack of a non-redundant function in normal development. Although naive lymphoid cell development was normal, Stat6 -/- mice were deficient in IL-4-mediated functions including Th2 helper T-cell differentiation, expression of cell surface markers, and immunoglobulin class switching to IgE. In contrast, IL-4-mediated proliferation was only partly affected.

Molecular cloning of caveolin-3, a novel member of the caveolin gene family expressed predominantly in muscle

Caveolin, a 21-24-kDa integral membrane protein, is a principal component of caveolar membranes in vivo. Caveolin interacts directly with heterotrimeric G-proteins and can functionally regulate their activity. Recently, a second caveolin gene has been identified and termed caveolin-2. Here, we report the molecular cloning and expression of a third member of the caveolin gene gamily, caveolin-3. Caveolin-3 is most closely related to caveolin-1 based on protein sequence homology; caveolin-1 and caveolin-3 are approximately 65% identical and approximately 85% similar. A single stretch of eight amino acids (FED-VIAEP) is identical in caveolin-1, -2, and -3. This conserved region may represent a "caveolin signature sequence" that is characteristic of members of the caveolin gene family. Caveolin-3 mRNA is expressed predominantly in muscle tissue-types (skeletal muscle, diaphragm, and heart) and is selectively induced during the differentiation of skeletal C2C12 myoblasts in culture. In many respects, caveolin-3 is similar to caveolin-1: (i) caveolin-3 migrates in velocity gradients as a high molecular mass complex; (ii) caveolin-3 colocalizes with caveolin-1 by immunofluorescence microscopy and cell fractionation studies; and (iii) a caveolin-3-derived polypeptide functionally suppresses the basal GTPase activity of purified heterotrimeric G-proteins. Identification of a muscle-specific member of the caveolin gene family may have implications for understanding the role of caveolin in different muscle cell types (smooth, cardiac, and skeletal) as previous morphological studies have demonstrated that caveolae are abundant in these cells. Our results also suggest that other as yet unknown caveolin family members are likely to exist and may be expressed in a regulated or tissue-specific fashion.

Post-infarction myocardial remodelling: why does it happen?

Myocardial remodelling is currently the subject of intense investigative interest. The question "Why does it happen?' is not clearly answerable by today's methods; however, the work of many basic scientists and clinicians has allowed an improved understanding of the process. Multiple mechanisms are probably operative in the cardiac remodelling process, including cell drop-out, myocyte slippage, collagen replacement and growth, and myocyte hypertrophy. The concept of heart failure as primarily a structural problem rather than the result of a specific biochemical "defect' is advanced. There is now direct evidence that cardiac myocytes are enlarged in both experimental and clinical left ventricular remodelling. Possible signal processing cascades are potential pathways to myocyte remodelling. Although not proven, the enlarged and elongated cardiac myocyte may be at a structural disadvantage, thus contributing functionally to the clinical syndrome of heart failure. Reversal of established cardiomegaly--regression of myocardial remodelling--is an unusual but occasional event in patients with cardiomyopathy that can be observed experimentally.

Peroxisomes contain delta 3,5,delta 2,4-dienoyl-CoA isomerase and thus possess all enzymes required for the beta-oxidation of unsaturated fatty acids by a novel reductase-dependent pathway

The presence of delta 3,5,delta 2,4-dienoyl-CoA isomerase in peroxisomes was demonstrated by determining the subcellular distribution of this enzyme in rat liver. The peroxisomal and mitochondrial forms of the isomerase exhibit similar chain length specificities and they are homologous as indicated by the recognition of the peroxisomal 66-kDa enzyme by an antiserum raised against the mitochondrial 32-kDa isomerase. This report demonstrates that peroxisomes contain all enzymes required for the beta oxidation of unsaturated fatty acids with odd-numbered double bonds by a novel pathway in which double bonds are reductively removed by the NADPH-dependent 2,4-dienoyl-CoA reductase.

Mitochondrial beta-oxidation of 2-methyl fatty acids in rat liver

The mitochondrial beta-oxidation of 2-methyl fatty acids was studied with coupled rat liver mitochondria and purified enzymes. Measurements of mitochondrial respiration supported by 2-methyl fatty acids, straight chain fatty acids, or their coenzyme A (CoA) thioesters revealed that free short-chain and medium-chain 2-methyl fatty acids are oxidized nearly or as efficiently as are their straight chain analogs. Long-chain 2-methyl hexadecanoyl-CoA is also oxidized, although more slowly than its unbranched counterpart. However, medium-chain 2-methyldecanoyl-CoA, in contrast to its unbranched analog, is not oxidized at all. Of all acyl-CoA dehydrogenases only long-chain acyl-CoA dehydrogenase acts on medium-chain and long-chain 2-methylacyl-CoA thioesters. The resultant 2-methyl-2-enoyl-CoA thioesters are substrates of the mitochondrial trifunctional beta-oxidation complex which catalyzes the sequential hydration, dehydrogenation, and thiolytic cleavage of 2-methyl-substituted substrates to yield chain-shortened acyl-CoA thioesters and propionyl-CoA. The matrix enzymes L-3-hydroxyacyl-CoA dehydrogenase and 3-ketoacyl-CoA thiolase, in contrast to enoyl-CoA hydratase, are inactive with medium-chain and long-chain 2-methyl-substituted chain substrates. The specificity of the beta-oxidation enzymes toward 2-methyl-branched substrates forms the basis for assays of long-chain acyl-CoA dehydrogenase and the trifunctional beta-oxidation complex in the presence of their mitochondrial isozymes. It is concluded that rat liver mitochondria can oxidize 2-methyl fatty acids, but does so most effectively with medium-chain and short-chain ones that can enter mitochondria directly in a carnitine-independent manner.

Compensatory and maladaptive responses to cardiac dysfunction

The field of congestive heart failure continues to be vigorously investigated at both the basic science level and in the clinic. As we move from the "hemodynamic" to the "neurohormonal" model of heart failure, more emphasis is being placed on interruption of neurohormone activity as a therapeutic strategy. A number of important clinical trials have been reported in the past year that underscore the potential of using drugs to inhibit neuroendocrine activity. The ultimate neuroendocrine inhibitors are perhaps the beta-adrenergic blocking drugs. They have yet to be adequately studied in a statistically powerful, randomized, placebo-controlled multicenter trial. Such a trial is about to begin in North America. In the meantime, numerous studies continue to confirm manifestations of neurohormone imbalance in clinical heart failure. Reduced heart rate variation has been under intensive investigation. A great variety of animal models of heart failure are also currently being studied. Perhaps more important advances have been made in the treatment of patients with heart failure than in any other field in internal medicine in recent years. However, improved patient survival tends to further increase the overall cost of patient care. Perhaps we are simply shifting the patient population, extending survival by 9 to 18 months. More advanced heart failure is more expensive to care for. It is only through understanding the basic biology and pathophysiology of heart failure that fresh new ideas will emerge leading to earlier therapy and, ultimately, prevention of this important disorder.

Pathophysiologic aspects of end-stage heart failure

Heart failure is not a distinct disease, but rather a complex clinical syndrome that can result from virtually any form of heart disease. The so-called "end stages" of heart failure do not respect etiologic boundaries. Patients are characterized clinically by extreme cardiomegaly, breathlessness, and fluid retention. Despite recent advances in the pharmacologic management of congestive heart failure, it remains a highly lethal and disabling disorder. Only through an improved understanding of the basic biology of the early stages of the syndrome can heart failure be prevented or at least forestalled. There is now intense interest in understanding the mechanisms operative in early left ventricular remodeling, which has the potential to culminate in end-stage heart failure. The study of animal models has been particularly useful in this regard, as have clinical studies performed in the early stages of acute myocardial infarction. The remodeling process is characterized by myocyte loss and segmental scarring, interstitial fibrosis, myocardial slippage, and myocyte hypertrophy. Although the mechanisms responsible for these topographic changes are as yet unclear, the net result is progressive enlargement of the heart, culminating in severe left ventricular dysfunction. A long-held view that cardiomegaly is a necessary adaptive process that maintains stroke volume in the presence of a falling ejection fraction has been challenged, although undoubtedly the early responses to myocardial injury in the form of myocyte hypertrophy and maintenance of wall stress are useful adaptations. However, as the left ventricle continues to dilate and hypertrophy over time, a form of overadjustment occurs that perhaps is an important contributory factor toward end-stage failure.

Resource intensity weighing and case mix grouping: assumptions and implications for health service performance evaluation

The use of Resource Intensity Weights (RIWs*) for equity funding and utilization management assumes validity of the cost estimates, reliability of the patient categorization scheme, equivalence of the bases for cost comparison, and equity of the subsequent resource distribution. This paper examines these assumptions, and concludes that caution must be taken when using the current RIWs and Case Mix Groups (CMGs*) for resource allocation and performance evaluation purposes. RIW has represented a milestone in the history of Canadian health care product costing and management. It would be prudent for health care professionals at the operational level to provide structured and continuing feedback that can contribute to the validation and refinement of these valuable management tools.

Inflammatory intermediates produced by tissues encasing silicone breast prostheses

Silicone prostheses, when implanted within the soft tissues of the breast, evoke an inflammatory reaction. In response to silicone exposure, inflammatory mediator production by individual cells has been observed in various experimental studies. In this study, inflammatory mediator production by periprosthetic tissues (whole organ) was measured. The mediator levels were correlated with both the tissue histopathology of the periprosthetic capsules and the clinical symptoms noted by each patient. Tissue surrounding breast implants removed at surgery from ten women (average age and implant duration 40 and 7 years respectively) was cultured in vitro for 24 hours. Control tissues consisting of (a) augmentation mammaplasty skin scars from eight additional patients and (b) knee synovium from seven orthopedic surgery patients with arthritis undergoing primary joint arthroplasty were similarly cultured. The mediators [interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and prostaglandin E2 (PGE2)] liberated into the culture media were measured by an enzyme linked immunosorbent assay. When compared to controls, the mediator levels of IL-6 and TNF-alpha were substantially greater, although IL-2 and PGE2 were lower. Levels varied greatly from patient to patient: in pg/ml per 10 g tissue, IL-2 ranged from 10 to over 1,000; TNF-alpha from 100 to 1,000; IL-6 from 100 to 1,000,000; and PGE2 from 100 to 10,000. The correlation between TNF-alpha and PGE2 levels was .5 between IL-6 and PGE2 was .6, and between IL-6 and TNF-alpha was .77. The correlation between TNF-alpha and IL-6 was statistically significant at a p-value less than .01. Elevated levels of TNF-alpha production were associated with an increased number of macrophages and overall tissue cellularity (p < .05). No significant relationship was observed between mediator production and clinical symptoms. We conclude that overall cellularity, specifically macrophages, in the periprosthetic capsule may lead to TNF-alpha production but that cytokine production by periprosthetic tissues alone is not a predictor of clinical symptomatology in patients with silicone breast prostheses.

Adjuvant activity of QS-21 for experimental E. coli 018 polysaccharide vaccines

Three types of experimental vaccines containing O-side-chain polysaccharide from the enterotoxigenic strain Escherichia coli 018 were evaluated. The immunogenicity of free O-polysaccharide (PS), a polysaccharide-diphtheria toxoid conjugate (PS-conj), and detoxified lipopolysaccharide (dLPS) was tested in female ICR mice, either alone or in combination with QS-21, a purified saponin adjuvant derived from the bark of the tree Quillaja saponaria Molina. Both the number of individual mice responding and the titres of O-polysaccharide specific antibodies in pools of sera were increased by the addition of QS-21. The immune response to both O-specific polysaccharide and carrier was primarily IgM and IgG1. The addition of QS-21 not only increased the level of IgG1, but also had a significant adjuvant effect on antigen-specific IgG2a, IgG2b and IgG3.

Estimation of peroxisomal beta-oxidation in rat heart by a direct assay of acyl-CoA oxidase

The contribution of peroxisomes to palmitate beta-oxidation in rat heart was estimated by either inhibiting mitochondrial beta-oxidation or measuring the activity of acyl-CoA oxidase. When respiratory inhibitors such as KCN or antimycin plus rotenone, or inhibitors of mitochondrial fatty acid uptake such as 2-tetradecylglycidic acid or 2-bromopalmitate, were used, degrees of inhibitions ranging from 24% to 87% were observed for palmitate beta-oxidation by a rat heart homogenate. Although the oxidation of palmitoyl-L-carnitine by coupled rat heart mitochondria was almost completely (94%) inhibited by KCN, the inhibition by antimycin plus rotenone was incomplete (77%) and was stimulated by L-carnitine. A direct assay of acyl-CoA oxidase, based on the spectrophotometric measurement at 300 nm of 2,4-decadienoyl-CoA formation from 4-trans-decenoyl-CoA, was evaluated with the aim of obtaining reliable values for the activity of this enzyme, which is presumed to catalyse the rate-limiting step of peroxisomal beta-oxidation. Activities determined by use of this assay were much higher than activities obtained by a coupled assay [Small, Burdett and Connock (1985) Biochem. J. 227, 205-210] commonly used to measure the activity of acyl-CoA oxidase. However, both methods yielded the same relative activities with different tissue homogenates. Based on an estimated palmitoyl-CoA oxidase activity of 0.3 nmol/min per mg of protein, the contribution of peroxisomes to palmitate beta-oxidation in a rat heart homogenate would optimally be 4%, and most likely is several-fold lower.

Ectopic expression of cyclin D1 prevents activation of gene transcription by myogenic basic helix-loop-helix regulators

Activation of muscle gene transcription in differentiating skeletal myoblasts requires their withdrawal from the cell cycle. The effects of ectopic cyclin expression on activation of muscle gene transcription by myogenic basic helix-loop-helix (bHLH) regulators were investigated. Ectopic expression of cyclin D1, but not cyclins A, B1, B2, C, D3, and E, inhibited transcriptional activation of muscle gene reporter constructs by myogenic bHLH regulators in a dose-dependent manner. Ectopic expression of cyclin D1 inhibited the activity of a myogenic bHLH regulator mutant lacking the basic region protein kinase C site, indicating that phosphorylation of this site is not relevant to the mechanism of inhibition. Analysis of cyclin D1 mutants revealed that the C-terminal acidic region was required for inhibition of myogenic bHLH regulator activity, whereas an intact N-terminal pRb binding motif was not essential. Together, these results implicate expression of cyclin D1 as a central determinant of a putatively novel mechanism that links positive control of cell cycle progression to negative regulation of genes expressed in differentiated myocytes.

Reproductive health research in China: the Ford Foundation initiatives

Increasing demographic and epidemiological evidence shows that maternal health problems are widespread and are linked to social, cultural, and economic factors, in particular, to women's status in society. Thus, there is an urgent need to expand existing knowledge about these influences on reproductive health and to empower women to gain control over them. To this end, there is a need for a comprehensive, interdisciplinary approach with an emphasis on social science research and training. The Ford Foundation, after an extensive review of its work in population and development, embarked on a new, ten-year, comprehensive reproductive health program for the 1990s. This paper describes one component of that program, a partnership with the All China Women's Federation to sponsor a series of reproductive health research activities. It examines the development and evaluates the positive and negative outcomes of the project, which commenced in 1991, from the perspective of a consultant involved in the process. So far, the project has generated interest in reproductive health in at least twenty-one Chinese provinces and has fostered a real partnership between the sponsoring and the collaborating agency. Based on the immediate outcomes of a research competition designed to identify research projects and investigators, of participant evaluation of the methodology training course, and of the strategies aimed at building capabilities and strengthening institutions in order to ensure future success, I conclude that the Ford Foundation's reproductive health initiative in China is a worthwhile and sustainable project.

Compensatory and maladaptive responses to cardiac dysfunction

The past few years have witnessed an extraordinary number of important developments in the study of compensatory and maladaptive responses to cardiac dysfunction. It now seems clear that the process whereby the heart remodels in response to left ventricular injury is of paramount importance in the expression of clinical heart failure. There have been parallel attempts by basic scientists and clinical investigators to understand better the fundamental biologic processes that underlie remodeling and to assess numerous new treatments--especially angiotensin-converting enzyme inhibitors. A general consensus seems to be emerging that holds that the response of the heart to acute injury includes a number of highly compensatory and adaptive mechanisms that ultimately become maladaptive and contribute to cardiomegaly and severe congestive heart failure. Such mechanisms undoubtedly include local and systemic release of cytokines, peptides, and neurohormones, and altered loading conditions leading to unusual mechanical forces on cardiac myocytes and other cells of the heart. At the organ level there is hypertrophy, dilatation and growth of the interstitium. Preliminary evidence also suggests there may be some "remodeling" at the cardiac myocyte level. Reduction in peripheral vasodilator reserve is seen in experimental animal models of heart failure. Patients with heart failure also develop an endothelial-dependent form of peripheral vascular dysfunction expressed clinically as an attenuated ability to dilate in response to such stimuli as acetylcholine. The transition point whereby these myocardial and peripheral vascular abnormalities become clearly dysfunctional and contribute toward the full clinical expression of heart failure remains to be further investigated.

Clonal proliferation of Langerhans cells in Langerhans cell histiocytosis

X-chromosome-inactivation assays can be used to assess clonality. We used such an assay at the human androgen-receptor gene locus in three female patients with histologically proven Langerhans cell histiocytosis. All patients were heterozygous for this locus. Cells bearing the Langerhans cell phenotype were purified from involved tissue after fluorescence-activated cell sorting with monoclonal antibodies against the CD1a complex. After HhaI digestion of DNA, these CD1a positive cells demonstrated a non-random X-chromosome-inactivation pattern, whereas CD1a negative cells in the same tissue showed a random pattern. Our data suggest that Langerhans cell histiocytosis represents a clonal proliferation of cells bearing the Langerhans cell phenotype.

Hepatic beta-oxidation of 3-phenylpropionic acid and the stereospecific dehydration of (R)- and (S)-3-hydroxy-3-phenylpropionyl-CoA by different enoyl-CoA hydratases

The hepatic beta-oxidation of 3-phenylpropionic acid (PPA) was studied by the use of subcellular fractions and purified enzymes with the aim of characterizing intermediates and the subcellular location of this pathway. Respiration measurements with coupled rat liver mitochondria indicate that PPA is efficiently metabolized by mitochondrial beta-oxidation. In contrast, the peroxisomal beta-oxidation of this compound is at best a very slow process, as evidenced by the low activity of peroxisomal acyl-CoA oxidase toward 3-phenylpropionyl-CoA. In mitochondria, 3-phenylpropionyl-CoA is effectively dehydrogenated to cinnamoyl-CoA, which is only slowly converted to benzoylacetyl-CoA due to the unfavorable equilibrium of the hydration of cinnamoyl-CoA to 3-hydroxy-3-phenylpropionyl-CoA. Benzoylacetyl-CoA is a substrate of 3-ketoacyl-CoA thiolase. The dehydration of 3-hydroxy-3-phenylpropionyl-CoA to cinnamoyl-CoA forms the basis for a sensitive and stereospecific assay of enoyl-CoA hydratases. The progress of this reaction, which proceeds to near completion, can be measured spectrophotometrically at 308 nm. Soluble mitochondrial and peroxisomal enoyl-CoA hydratases only act on the (R,L) isomer, whereas the peroxisomal D-3-hydroxyacyl-CoA dehydratase is specific for the (S,D) isomer. Both substrates can be easily prepared from the commercially available enantiomeric acids. It is concluded that PPA, a key compound in Knopp's classical study that led him to formulate the principle of beta-oxidation, is overwhelmingly, if not completely, degraded by mitochondrial beta-oxidation.

Comparison of geniposide and its acetylated derivative for the inhibition of aflatoxin b1-induced DNA-repair synthesis in rat primary hepatocyte

Our previous studies showed that geniposide (GP) inhibits aflatoxin B1 (AFB1)-induced hepatoxicity in rats, and that DNA repair synthesis in vitro and penta-acetyl geniposide ((Ac)5-GP) inhibits AFB1-induced genotoxicity in C3H10T1/2 cells. One possible mechanism for GP is the enhancement of the enzyme activity of glutathione S-transferase (GST) and GSH-peroxidase (GSH-Px) in AFB1-treated hepatocyte culture. But the mechanism is unknown for (Ac)5-GP. The present study demonstrated that (Ac)5-GP was more potent in inhibiting AFB1-induced unscheduled DNA synthesis in rat primary hepatocyte. The action of GP and (Ac)S-GP may be related to their ability to induce the activity of phase II enzymes.

Binding of the O-antigen of Shigella dysenteriae type 1 and 26 related synthetic fragments to a monoclonal IgM antibody

Shigella dysenteriae type 1 possesses an O-antigen whose repeating unit is -->3)-alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->2)-alpha-D-Galp -(1-->3)-alpha-D- GlcpNAc-(1-->, where Rhap is rhamnopyranosyl, Galp is galactopyranosyl, and Glcp is glucopyranosyl. Using ligand-induced protein fluorescence change, we have measured the affinities of a monoclonal murine IgM for 26 fragments of, or related to, the structure of the O-polysaccharide and of the IgM Fab for the intact O-specific bacterial polysaccharide. Synthetic saccharides used were methyl glycosides to ensure an anomerically defined pyranosyl ring conformation. The galactosyl residue is the only monosaccharide of the antigenic epitope that shows quantifiable binding: approximately 3.0 kcal/mol of binding free energy, depending on the structure and conformation of the fragment it is a part of. Addition of an alpha-(1-->2)-linked rhamnosyl residue increases the free energy of binding significantly. We propose this rhamnopyranosyl-alpha-(1-->2)-galactopyranosyl disaccharide to be the basic determinant of the Shigella O-polysaccharide. Further extension (by linkages as in the natural antigen) of this oligosaccharidic ligand toward the upstream end (in an oligo- (or poly-)saccharide, such as A-->B-->C-->D-->E-->m, where A, B, C, D, and E are sugars and m is any moiety, such as methyl, we define A as the glycosyl- or upstream terminus, and E as the glycoside- or downstream terminus) by rhamnosyl and N-acetylglucosaminyl moieties improves the binding only minimally. The antibody is quite specific for the rhamnosyl-alpha-(1-->2)-galactosyl sequence but less so for the nature of the attachment to the galactosyl residue on the downstream side. Measurements using IgM Fab and the intact O-specific polysaccharide show that the antibody can bind internal segments on the antigen chain. The free energy of binding of this antibody for the disaccharide determinant varies from -delta G of 4.7 to 5.1 kcal/mol, depending on its flanking residues.

Synthesis, characterization, and clinical evaluation of conjugate vaccines composed of the O-specific polysaccharides of Shigella dysenteriae type 1, Shigella flexneri type 2a, and Shigella sonnei (Plesiomonas shigelloides) bound to bacterial toxoids

The theoretic basis for developing conjugate vaccines, to induce immunoglobulin G (IgG) lipopolysaccharide (LPS) antibodies for the prevention of shigellosis, has been described (J. B. Robbins, C.-Y. Chu, and R. Schneerson, Clin. Infect. Dis. 15:346-361, 1992). The O-specific polysaccharides (O-SPs) of Shigella dysenteriae type 1, S. flexneri type 2a, and S. sonnei were covalently bound to carrier proteins. Alone, the O-SPs were not immunogenic in mice. Conjugates of these O-SPs, injected into young outbred mice subcutaneously as saline solutions containing 2.5 micrograms of saccharide, elicited serum IgG and IgM antibodies with booster responses; adsorption onto alum enhanced their immunogenicity. Injection of 25 micrograms of these conjugates into adult volunteers elicited mild local reactions only. Each conjugate induced a significant rise of the geometric mean serum IgG, IgM, and IgA LPS antibody levels. A second injection 6 weeks later did not elicit booster responses, and adsorption of the conjugates onto alum did not enhance their immunogenicity. Conjugate-induced levels of IgA, but not IgG or IgM, declined to preimmunization levels at day 56. The levels of postimmunization antibodies of the three immunoglobulin classes were similar to or higher than those of recruits in the Israel Defense Force following shigellosis caused by S. flexneri type 2a or S. sonnei. These data provide the basis for evaluating these conjugates to prevent shigellosis.