Asymptomatic HIV patient with cardiomyopathy and nephropathy: case report and literature review

We report a previously asymptomatic HIV patient with high CD4 lymphocyte count and low HIV1 viral load who developed cardiac and renal disease. Management with ACE inhibitor, diuretics and triple antiretroviral combination therapy yielded a rapid clinical response. An understanding of the spectrum of renal and cardiac derangements is essential for clinicians in managing patients with HIV disease.

Dynamical fluctuation of the mesoscopic structure in ternary C12E5-water-n-octane amphiphilic system

Dynamical fluctuations of the bicontinuous microemulsion and lamellar structures in ternary C12E5-water-n-octane amphiphilic system are studied by means of neutron spin echo (NSE) spectrometry. The decay rates of the time correlation of the concentration were analyzed in terms of three theories: (1) A. G. Zilman and R. Granek, Phys. Rev. Lett. 77, 4788 (1996), (2) M. Nonomura and T. Ohta, J. Chem. Phys. 110, 7516 (1999), and (3) R. Granek and M. E. Cates, Phys. Rev. A 46, 3319 (1992), in the first of which a Langevin equation for membrane plaquettes and in the latter two of which time-dependent Ginzburg-Landau equations for the order parameters are considered. The result shows that the intermediate correlation functions I(q,t) for the ranges of 0<t<15 ns and 0<q<0.2 A (-1) are well fitted to a stretched exponential function in time, I(q,t)=exp[-(Gammat)(2/3)], for the bicontinuous microemulsion and the lamellar phases of the same systems with the relaxation rate Gamma increasing as q(3) in agreement with theory (1) from which the bending modulus of the membrane kappa was estimated. For more restricted ranges of 0<t<5 ns and 0.05<q<0.15 A (-1) the NSE result can be expressed by an exponential function in time in agreement with theory (2) determined exclusively by hydrodynamic interactions and for extended range of 0<t<10 ns and 0.03<q<0.15 A (-1) by a nonexponential function in agreement with theory (3), from both of which the effective viscosities eta(0) and eta(eff) of the system were estimated. The effective viscosity from the nonexponential eta(eff) is five times greater than that from the simple exponential eta(0) that is almost the same as the literature value. The implication of this result is discussed in terms of the effective viscosity eta(eff) that takes into account the renormalization of the bending modulus of the membrane.

The IML3/MCM19 gene of Saccharomyces cerevisiae is required for a kinetochore-related process during chromosome segregation

The mcm19 mutation in budding yeast affects minichromosome maintenance. In this work we have shown that this mutation leads to defects in the segregation of minichromosomes and chromosomes. The mutant cells show defective kinetochore function as judged by three criteria-- relaxation of the transcriptional block normally associated with a CEN box, stable maintenance of a dicentric plasmid in mutant cells, and mild sensitivity to the antimicrotubule drug benomyl. The MCM19 gene has been cloned and found to be the same as IML3, which codes for the ORF YBR107C. Deletion of the gene was not lethal, nor did it confer any growth defects on the mutant cells. However, the mcm19 null mutation conferred growth defects in the presence of a mutation in the TUB1 gene coding for alpha-tubulin. Two-hybrid experiments showed an interaction between Im13p/Mcm19p and the kinetochore protein Ch14, indicating that the Im13/Mcm19 protein has a role in kinetochore function.

Effects of T-lymphocyte-dependent and -independent immunity on cholinergic enzyme activity in mouse lacrimal gland

The nature of the immune response following ocular immunization with a protein and a polysaccharide and the effects such immunization have on the activities of cholinergic enzymes in the lacrimal glands of BALB/c mice were examined. Lacrimal glands are highly innervated by sympathetic and parasympathetic nerve fibres and are involved in mucosal immunity and therefore are excellent sites to study neuro-immune interactions. In this report, a T-lymphocyte-dependent protein antigen, keyhole limpet haemocyanin (KLH) and a T-lymphocyte-independent polysaccharide antigen, dextran (DEX) were administered topically to the eyes or intraperitoneally injected. Both routes of immunization produced a strong serum antibody response when KLH was the antigen. DEX, however, evoked a serum antibody response only after intraperitoneal administration. Eosin-haematoxylin staining indicated no histological abnormality or inflammatory changes in any immunized lacrimal glands, but immuno-staining revealed that only in the KLH-treated tissues were IgG-producing plasma cells discernible. Furthermore, KLH-specific antibody was also detectable using an immuno-blot assay in lacrimal glands. Polymerase chain reaction analysis with cytokine-specific primers revealed induction of interleukin-4 (lL-4) in KLH-treated lacrimal glands, but not in DEX or unimmunized tissues. Thus, the nature of the antigen seems important in the induction of the immune response in lacrimal glands. To delineate the effects that immunogenic differences might have on the activities of the cholinergic enzymes, choline acetyl-transferase (ChAT) and acetylcholinesterase (AChE) were assayed using radiolabelled substrates and measuring labelled products. Both ChAT and AChE activities were influenced following KLH immunization, while DEX had only transient effects on ChAT. This is possibly due to the fact that KLH, a protein antigen, is the effective inducer of the specific immune response in the lacrimal gland, while DEX is not. Experimental Physiology (2001) 86.2, 169-176.

The effect of glutathione upon chaperone activity of alpha-crystallin is probably mediated through target modulation

We studied the effect of the presence of glutathione, both reduced (GSH) and oxidized (GSSG), on the chaperone activity of alpha-crystallin towards thermal aggregation of gamma 2-crystallin. Results showed that while GSH enhanced the chaperone activity of alpha-crystallin, GSSG appeared to diminish it to some extent. When, however, the effect of the presence of glutathione was studied in the absence of alpha-crystallin, the nature of their action was found to be almost similar to that observed in its presence. These results suggest that glutathiones probably modulate the target protein which ultimately influences the chaperone activity of alpha-crystallin.

Long terminal repeat regions from exogenous but not endogenous feline leukemia viruses transactivate cellular gene expression

We have previously reported that the long terminal repeat (LTR) region of feline leukemia viruses (FeLVs) can enhance expression of certain cellular genes such as the collagenase IV gene and MCP-1 in trans (S. K. Ghosh and D. V. Faller, J. Virol. 73:4931-4940, 1999). Genomic DNA of all healthy feline species also contains LTR-like sequences that are related to exogenous FeLV LTRs. In this study, we evaluated the cellular gene transactivational potential of these endogenous FeLV LTR sequences. Unlike their exogenous FeLV counterparts, neither nearly full-length endogenous FeLV molecular clones (CFE-6 and CFE-16) nor their isolated LTRs were able to activate collagenase IV gene or MCP-1 expression in transient transfection assays. We had also demonstrated previously that production of an RNA transcript from exogenous FeLV LTRs correlates with their transactivational activity. In the present study, we demonstrate that the endogenous FeLV LTRs do not generate LTR-specific RNA transcripts in the feline embryo fibroblast cell line AH927. Furthermore, infection of AH927 cells by an exogenous FeLV subgroup A virus did not induce production of such LTR-specific transcripts from the endogenous proviral genomes, although the LTR-specific transcripts from the exogenous virus were readily detected. Finally, LTR-specific transcripts were not generated in BALB/3T3 cells transiently transfected with isolated CFE-6 LTR, in contrast to transfections with LTRs from exogenous viruses. Our data thus suggest that the inability of endogenous FeLV LTRs in gene transactivation is not due to cell line specificity or presence of any upstream inhibitory cis-acting element. Endogenous, nonleukemogenic FeLV LTRs, therefore, do not transactivate cellular gene expression, and this property appears to be specific to exogenous, leukemogenic FeLVs.

Template/primer requirements and single nucleotide incorporation by hepatitis C virus nonstructural protein 5B polymerase

Nonstructural protein 5B (NS5B) of hepatitis C virus (HCV) possesses an RNA-dependent RNA polymerase activity responsible for viral genome RNA replication. Despite several reports on the characterization of this essential viral enzyme, little is known about the reaction pathway of NS5B-catalyzed nucleotide incorporation due to the lack of a kinetic system offering efficient assembly of a catalytically competent polymerase/template/primer/nucleotide quaternary complex. In this report, specific template/primer requirements for efficient RNA synthesis by HCV NS5B were investigated. For intramolecular copy-back RNA synthesis, NS5B utilizes templates with an unstable stem-loop at the 3' terminus which exists as a single-stranded molecule in solution. A template with a stable tetraloop at the 3' terminus failed to support RNA synthesis by HCV NS5B. Based on these observations, a number of single-stranded RNA templates were synthesized and tested along with short RNA primers ranging from two to five nucleotides. It was found that HCV NS5B utilized di- or trinucleotides efficiently to initiate RNA replication. Furthermore, the polymerase, template, and primer assembled initiation-competent complexes at the 3' terminus of the template RNA where the template and primer base paired within the active site cavity of the polymerase. The minimum length of the template is five nucleotides, consistent with a structural model of the NS5B/RNA complex in which a pentanucleotide single-stranded RNA template occupies a groove located along the fingers subdomain of the polymerase. This observation suggests that the initial docking of RNA on NS5B polymerase requires a single-stranded RNA molecule. A unique beta-hairpin loop in the thumb subdomain may play an important role in properly positioning the single-stranded template for initiation of RNA synthesis. Identification of the template/primer requirements will facilitate the mechanistic characterization of HCV NS5B and its inhibitors.

Responses of Entamoeba invadens to heat shock and encystation are related

An Entamoeba invadens gene encoding a homologue of BiP/GRP78, a 70-kDa heat shock protein or chaperonin was cloned. The predicted E. invadens BiP contained an ATP-binding site, a substrate-recognition domain, and a carboxy-terminal KDEL-peptide. Messenger RNAs of E. invadens for BiP, for a 70-kDa heat shock cognate, for a cyst wall glycoprotein (Jacob), and for chitinase were all induced by heat shock and by encystation medium. The presence of Jacob in heat-shocked amebae was confirmed by confocal microscopy and suggests that heat shock and encystation responses in E. invadens are related.

Can cosmic strangelets reach the earth?

The mechanism for the propagation of strangelets with low baryon number through the atmosphere of the Earth has been explored. It has been shown that, under suitable initial conditions, such strangelets may indeed reach depths near mountain altitudes with mass numbers and charges close to the observed values in cosmic ray experiments.

The most abundant glycoprotein of amebic cyst walls (Jacob) is a lectin with five Cys-rich, chitin-binding domains

The infectious stage of amebae is the chitin-walled cyst, which is resistant to stomach acids. In this study an extraordinarily abundant, encystation-specific glycoprotein (Jacob) was identified on two-dimensional protein gels of cyst walls purified from Entamoeba invadens. Jacob, which was acidic and had an apparent molecular mass of approximately 100 kDa, contained sugars that bound to concanavalin A and ricin. The jacob gene encoded a 45-kDa protein with a ladder-like series of five Cys-rich domains. These Cys-rich domains were reminiscent of but not homologous to the Cys-rich chitin-binding domains of insect chitinases and peritrophic matrix proteins that surround the food bolus in the insect gut. Jacob bound purified chitin and chitin remaining in sodium dodecyl sulfate-treated cyst walls. Conversely, the E. histolytica plasma membrane Gal/GalNAc lectin bound sugars of intact cyst walls and purified Jacob. In the presence of galactose, E. invadens formed wall-less cysts, which were quadranucleate and contained Jacob and chitinase (another encystation-specific protein) in secretory vesicles. A galactose lectin was found to be present on the surface of wall-less cysts, which phagocytosed bacteria and mucin-coated beads. These results suggest that the E. invadens cyst wall forms when the plasma membrane galactose lectin binds sugars on Jacob, which in turn binds chitin via its five chitin-binding domains.

Cytogenetic toxicity of methotrexate in mouse bone marrow

Methotrexate (MTX), a widely used anticancer drug, was tested for its cytogenetic toxicity in mouse bone marrow after a single intraperitoneal treatment with three different doses i.e. at the rate of 2, 10 and 20 mg/kg b.w. of mice. The end points selected were chromosomal aberrations and mitotic index study at 24-h post-treatment and micronucleus (MN) test at 30-h post-treatment. The induction of statistically significant number of chromosomal aberrations, percentage of aberrant metaphases and highly significant number of MN per thousand polychromatic erythrocytes by all the doses of MTX indicated it as highly clastogenic. MTX was found more clastogenic in male mice than the females and the intermediate dose tested (10 mg/kg) was found more effective than the other doses. In mitotic index study, none of the doses of MTX inhibited cell proliferation during the first post-treated cell cycle. The results were compared with the earlier reports on the clastogenicity and cell proliferation inhibition of MTX only after multiple treatments. The possible mechanism of the cytogenetic effects of MTX has been discussed.

IL-12 gene-deficient C57BL/6 mice are susceptible to Leishmania donovani but have diminished hepatic immunopathology

To determine the in vivo role of IL-12 in the development of protective immunity in visceral leishmaniasis caused by Leishmania donovani, we examined the course of L. donovani infection in IL-12-deficient C57BL/6 (IL-12-/-) mice. IL-12-/- mice displayed significantly higher parasite burdens in their livers and spleens than wild-type C57BL/6 mice throughout the course of infection. Despite high parasite burdens, the onset of hepatosplenomegaly was significantly delayed in L. donovani-infected IL-12-/-. Moreover, livers and spleens from IL-12-/- mice displayed significantly less inflammation and poorly formed granulomatous lesions than those from IL-12+/+ mice throughout the course of infection. Antigen-stimulated splenocytes from IL-12-/- mice produced significantly less IFN-gamma but more IL-4 than IL-12+/+ mice. These findings indicate that although endogenous IL-12 is critical for the development of protective immunity to L. donovani, it is also responsible for inducing the significant immunopathology associated with visceral leishmaniasis.

Green tea polyphenols induce apoptosis in vitro in peripheral blood T lymphocytes of adult T-cell leukemia patients

Green tea polyphenols (TEA) are known to exhibit antioxidative activity as well as tumor-suppressing activity. In order to examine the tumor-suppressing activity of TEA against adult T-cell leukemia (ATL), we cultivated peripheral blood T lymphocytes of ATL patients (ATL PBLs), an HTLV-I-infected T-cell line (KODV) and healthy controls (normal PBLs) for 3 days in the presence of TEA and its main constituent, epigallocatechin-3-gallate (EGCg), to measure cell proliferation and apoptosis, and to quantitate mRNAs of HTLV-I pX and beta-actin genes of the cultured cells. Growth of ATL PBLs was significantly inhibited by 9-27 microg/ml of TEA and EGCg, in contrast to minimal growth inhibition of T cells of normal PBLs. Inhibition of KODV was intermediate between ATL PBLs and normal PBLs. The ATL PBLs and KODV treated with 27 microg/ml of either TEA or EGCg induced apoptotic DNA fragmentation, producing terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells, while the normal PBLs treated with the same concentration of TEA or EGCg produced a negligibly small number of TUNEL-positive cells, in which apoptotic DNA fragmentation was not detectable. Expression of HTLV-I pX mRNA was suppressed more than 90% in ATL PBLs by treatment with 3-27 microg/ml of either TEA or EGCg, while expression of beta-actin mRNA was much less suppressed by treatment with the same concentration of TEA or EGCg. These results indicate that TEA and EGCg inhibit growth of ATL PBLs, as well as HTLV-I-infected T-cells, by suppressing HTLV-I pX gene expression and inducing apoptotic cell death.

A graph-theoretic approach for studying the convergence of fractal encoding algorithm

In this paper, we present a graph-theoretic interpretation of convergence of fractal encoding based on partial iterated function system (PIFS). First we have considered a special circumstance, where no spatial contraction has been allowed in the encoding process. The concept leads to the development of a linear time fast decoding algorithm from the compressed image. This concept is extended for the general scheme of fractal compression allowing spatial contraction (on averaging) from larger domains to smaller ranges. A linear time fast decoding algorithm is also proposed in this situation, which produces a decoded image very close to the result obtained by an ordinary iterative decompression algorithm.

Poliovirus RNA-dependent RNA polymerase (3D(pol)). Divalent cation modulation of primer, template, and nucleotide selection

We have analyzed the divalent cation specificity of poliovirus RNA-dependent RNA polymerase, 3D(pol). The following preference was observed: Mn(2+) > Co(2+) > Ni(2+) > Fe(2+) > Mg(2+) > Ca(2+) > Cu(2+), and Zn(2+) was incapable of supporting 3D(pol)-catalyzed nucleotide incorporation. In the presence of Mn(2+), 3D(pol) activity was increased by greater than 10-fold relative to that in the presence of Mg(2+). Steady-state kinetic analysis revealed that the increased activity observed in the presence of Mn(2+) was due, primarily, to a reduction in the K(M) value for 3D(pol) binding to primer/template, without any significant effect on the K(M) value for nucleotide. The ability of 3D(pol) to catalyze RNA synthesis de novo was also stimulated approximately 10-fold by using Mn(2+), and the enzyme was now capable of also utilizing a DNA template for primer-independent RNA synthesis. Interestingly, the use of Mn(2+) as divalent cation permitted 3D(pol) activity to be monitored by following extension of 5'-(32)P-end-labeled, heteropolymeric RNA primer/templates. The kinetics of primer extension were biphasic because of the enzyme binding to primer/template in both possible orientations. When bound in the incorrect orientation, 3D(pol) was capable of efficient addition of nucleotides to the blunt-ended duplex; this activity was also apparent in the presence of Mg(2+). In the presence of Mn(2+), 3D(pol) efficiently utilized dNTPs, ddNTPs, and incorrect NTPs. On average, three incorrect nucleotides could be incorporated by 3D(pol). The ability of 3D(pol) to incorporate the correct dNTP, but not the correct ddNTP, was also observed in the presence of Mg(2+). Taken together, these results provide the first glimpse into the nucleotide specificity and fidelity of the poliovirus polymerase and suggest novel alternatives for the design of primer/templates to study the mechanism of 3D(pol)-catalyzed nucleotide incorporation.

Cytotoxic effector T cells elicited by the killed tumor vaccine differ significantly from the effectors generated during active growth of a murine B-cell lymphoma

Active specific immunotherapy of neoplastic diseases is an elusive goal. Using a murine B lymphoma 2C3, we showed that vaccination with the killed tumor cells effectively induces protective immunity and a cytotoxic T cell (CTL) response. Similar protection, however, is rarely observed in mice bearing live tumor cells. These animals usually succumb to the progressively growing tumor. In this study, we inquired whether the splenic CTL induced during tumor progression in mice differ from those evoked by the killed tumor cells. Here we demonstrate that the CTL generated following vaccination are significantly different from those induced in the tumor-bearing hosts. Adding to the complexity, the CTL from the early tumor bearers also differ significantly from those induced at the late stages. These differences are based on their cytotoxic activity, MHC allele specificity, mitogen responsiveness, cytokine secretion profile and T cell receptor Vbeta gene expression. The results clearly indicate that passive immunization with killed tumor is most effective, possibly because the CTL induced are not subject to the same regulatory pressure as those induced during active tumor growth. This decreasing effectiveness of CTL could be due to greater variability in antigenic stimulus, less involvement of innate immunity, changes in cytokine milieu and/or costimulatory factors.

Acetylation of alpha-crystallin with N-acetylimidazole and its influence upon the native aggregate and subunit reassembly

PURPOSE

An attempt has been made to investigate the involvement and importance of some of the hydrogen bond forming amino acid side chains in intra and inter subunit interactions in alpha-crystallin assembly.

METHODS

For this, alpha-crystallin has been acetylated, partially or completely, using N-acetylimidazole. The apparent molecular size, electrophoretic mobility, conformational properties, surface hydrophobicity and chaperone activity of the modified proteins have been determined and compared with those of unmodified native protein as well as of the aggregates reassembled from the modified subunits.

RESULTS

Acetylation of the surface-exposed tyrosine side chains has been found to destabilize the integrity of the native assembly with the formation of a somewhat smaller aggregate. This acetylated aggregate appears to adopt a molten globule-like conformation as evidenced from its almost unaltered secondary structure with some detectable alterations in its tertiary structure as well as from its enhanced chaper-one activity exhibited by the reduction assay compared to the native alpha-crystallin. Reassociation studies from either partially or completely acetylated subunits indicate that acetylation perturbs the information needed for native refolding of the subunits from their unfolded state as well as that needed for the normal mode of subunit reassembly. Acetylated subunits exhibit abnormal gel electrophoretic band pattern with distinctly retarded migration compared to the unmodified subunits. However, in spite of the partial/complete acetylation of the subunits or their reassociation from the denatured state, the tryptophan fluorescence emission maxima of the modified proteins and also that of the reassociated aggregates appear to remain unaffected.

CONCLUSIONS

Results tend to indicate that the unperturbed hydrogen bonding capability of the relevant side chains in alpha-crystallin is needed for the integrity of the native alpha-crystallin assembly, for the normal refolding of its denatured subunits and also for the correct mode of subunit reassembly.

STAT-4 mediated IL-12 signaling pathway is critical for the development of protective immunity in cutaneous leishmaniasis

Recent studies have demonstrated that two IL-12 signaling pathways, a STAT 4 - dependent and STAT4 - independent, are involved in the development of a Th1-like response. To determine their roles in the development of protective immunity against Leishmania major, we monitored progression of cutaneous Leishmania major infection in STAT4-deficient mice (STAT4-/-) compared to similarly infected wild-type (STAT4+/+) mice. Although the onset of lesion growth was delayed in STAT4-/- mice during the early phase of infection, these mice eventually developed large, non-healing lesions, whereas STAT4+/+ mice resolved their lesions. As infection progressed, both STAT4+/+ and STAT4-/- mice infected with L. major displayed similar titers of Leishmania-specific IgG1 and IgE but later produced lower IgG2a. On days 20 and 40 post-infection, Leishmania antigen-stimulated lymphnode cells from STAT4-/- mice produced significantly lower amounts of IFN-gamma than those from STAT4+/+ mice as measured by enzyme-linked immunosorbent assay. There was no significant difference, however, in IL-4 and IL-12 production between the two groups. These results indicate that STAT4-mediated IL-12 signaling is critical for the development of protective Th1 response following L. major infection in genetically resistant mice. Additionally, they demonstrate that, although genetically resistant mice lacking STAT4 signaling pathway develop large, non-healing lesions, they do not default towards a Th2-like response.

Feline leukemia virus long terminal repeat activates collagenase IV gene expression through AP-1

Leukemia and lymphoma induced by feline leukemia viruses (FeLVs) are the commonest forms of illness in domestic cats. These viruses do not contain oncogenes, and the source of their pathogenic activity is not clearly understood. Mechanisms involving proto-oncogene activation subsequent to proviral integration and/or development of recombinant viruses with enhanced replication properties are thought to play an important role in their disease pathogenesis. In addition, the long terminal repeat (LTR) regions of these viruses have been shown to be important determinants for pathogenicity and tissue specificity, by virtue of their ability to interact with various transcription factors. Previously, we have shown that, in the case of Moloney murine leukemia virus, the U3 region of the LTR independently induces transcriptional activation of specific cellular genes through an LTR-generated RNA transcript (S. Y. Choi and D. V. Faller, J. Biol. Chem. 269:19691-19694, 1994; S.-Y. Choi and D. V. Faller, J. Virol. 69:7054-7060, 1995). In this report, we show that the U3 region of exogenous FeLV LTRs can induce transcription from collagenase IV (matrix metalloproteinase 9) and monocyte chemotactic protein 1 (MCP-1) promoters up to 12-fold. We also show that AP-1 DNA-binding activity and transcriptional activity are strongly induced in cells expressing FeLV LTRs and that LTR-specific RNA transcripts are generated in those cells. Activation of mitogen-activated protein kinase kinases 1 and 2 (MEK1 and -2) by the LTR is an intermediate step in the FeLV LTR-mediated induction of AP-1 activity. These findings thus suggest that the LTRs of FeLVs can independently activate transcription of specific cellular genes. This LTR-mediated cellular gene transactivation may play an important role in tumorigenesis or preleukemic states and may be a generalizable activity of leukemia-inducing retroviruses.

Chitinase secretion by encysting Entamoeba invadens and transfected Entamoeba histolytica trophozoites: localization of secretory vesicles, endoplasmic reticulum, and Golgi apparatus

Entamoeba histolytica, the protozoan parasite that phagocytoses bacteria and host cells, has a vesicle/vacuole-filled cytosol like that of macrophages. In contrast, the infectious cyst form has four nuclei and a chitin wall. Here, anti-chitinase antibodies identified hundreds of small secretory vesicles in encysting E. invadens parasites and in E. histolytica trophozoites overexpressing chitinase under an actin gene promoter. Abundant small secretory vesicles were also identified with antibodies to the surface antigen Ariel and with a fluorescent substrate of cysteine proteinases. Removal of an N-terminal signal sequence directed chitinase to the cytosol. Addition of a C-terminal KDEL peptide, identified on amebic BiP, retained chitinase in a putative endoplasmic reticulum, which was composed of a few vesicles of mixed sizes. A putative Golgi apparatus, which was Brefeldin A sensitive and composed of a few large, perinuclear vesicles, was identified with antibodies to ADP-ribosylating factor and to epsilon-COP. We conclude that the amebic secretory pathway is similar to those of other eukaryotic cells, even if its appearance is somewhat different.

Bayesian analysis and model selection for interval-censored survival data

Interval-censored data occur in survival analysis when the survival time of each patient is only known to be within an interval and these censoring intervals differ from patient to patient. For such data, we present some Bayesian discretized semiparametric models, incorporating proportional and nonproportional hazards structures, along with associated statistical analyses and tools for model selection using sampling-based methods. The scope of these methodologies is illustrated through a reanalysis of a breast cancer data set (Finkelstein, 1986, Biometrics 42, 845-854) to test whether the effect of covariate on survival changes over time.