Roles of the three transcriptional attenuators of the Bacillus subtilis pyrimidine biosynthetic operon in the regulation of its expression

Expression of the Bacillus subtilis pyr operon is regulated by exogenous pyrimidines and the protein product of the first gene of the operon, PyrR. It has been proposed that PyrR mediates transcriptional attenuation at three untranslated segments of the operon (R.J. Turner, Y. Lu, and R.L. Switzer, J. Bacteriol., 176:3708-3722, 1994). In this study, transcriptional fusions of the pyr promoter followed by the pyr attenuation sequences, either individually or in tandem to a lacZ reporter gene, were used to examine the physiological functions of all three attenuators through their ability to affect beta-galactosidase expression. These fusions were studied as chromosomal integrants in various B. subtilis strains to examine the entire range of control by pyrimidines, PyrR dependence, amd developmental control of pyr gene expression. The nutritional regulation of each attenuator separately was roughly equivalent to that of the other two and was totally dependent upon PyrR, and that of tandem attenuators was cumulative. The regulation of a fusion of the spac promoter followed by the pyrP:pyrB intercistronic region to lacZ produced results similar to those obtained with the corresponding fusion containing the pyr promoter, demonstrating that attenuator-dependent regulation is independent of the promoter. Extreme pyrimidine starvation gave rise to two- to threefold-higher levels of expression of a pyr-lacZ fusion that lacked attenuators, independent of PyrR, than were obtained with cells that were not starved. Increased expression of a similar spac-lacZ fusion during pyrimidine starvation was also observed, however, indicating that attenuator-independent regulation is not a specific property of the pyr operon. Conversion of the initiator AUG codon in a small open reading frame in the pyrP:pyrB intercistronic region to UAG reduced expression by about half but did not alter regulation by pyrimidines, which excludes the possibility of a coupled transcription-translation attenuation mechanism. Developmental regulation of pyr expression during early stationary phase was found to be dependent upon the attenuators and PyrR, and the participation of SpoOA was excluded.

Immunoglobulin E levels in relationship to HIV-1 disease, route of infection, and vitamin E status

Our recent studies have demonstrated that in early HIV-1 infection, elevation of plasma immunoglobulin E (IgE) levels precedes the decline of CD4 cell count and is influenced by vitamin E status. In order to further investigate the role of IgE elevation in HIV-1 infection, we determined IgE levels in HIV-1-seropositive and -seronegative intravenous drug users (IDUs) (n = 38), in relationship to cellular and humoral immune function, liver enzymes, and vitamin E status. To examine the possible impact of the route of HIV-1 infection on IgE levels, comparisons between the cohorts of the HIV-1-seropositive and -seronegative IDUs and homosexual men (n = 45) were also conducted. All HIV-1-seropositive participants had significantly higher (P = 0.003) IgE levels than the HIV-1-seronegative subjects. The HIV-1-seropositive IDUs, moreover, demonstrated significantly higher (P = 0.01) IgE levels than HIV-1-seropositive homosexual men, despite similar CD4 cell counts. Stepwise regression analysis was used to evaluate the possible variables contributing to the IgE variation. HIV-1 status (P = 0.0009), intravenous drug use (P = 0.014), CD8 cell counts (P = 0.0001), plasma level of vitamin E (P = 0.006), and alcohol intake (P = 0.047) were significant, accounting for 71% of the IgE elevation. These findings suggest that IgE may serve as a sensitive marker to reflect the evolution of HIV-1 disease in individuals from different risk groups.

Phosphatidylinositol 3-kinase activity is not essential for CD28 costimulatory activity in Jurkat T cells: studies with a selective inhibitor, wortmannin

The interaction of CD28 with its counter-receptor, B7-1 (CD 80), on antigen-presenting cells induces a co-signal in T cells required to promote antigen-dependent interleukin-2 (IL-2) production and to prevent clonal anergy. CD28 stimulation causes both protein-tyrosine kinase and phosphatidylinositol3-kinase (PI3-K) activation, suggesting a possible role for these enzyme activities in CD28 co-signal transduction. Here, we investigate the effect of wortmannin, a selective and irreversible PI3-K inhibitor on CD28 co-signaling events in the Jurkat T cell line. Wortmannin added to cell cultures partially inhibits CD28-induced tyrosine phosphorylation of the putative p110 catalytic subunit of PI3-K, but does not block CD28-induced association of the p85 PI3-K regulatory subunit with the CD28 receptor. Wortmannin inhibits in a dose-dependent manner both total cellular PI3-K activity and CD28-induced receptor-associated PI3-K activity. Wortmannin (1 microM) inhibits cellular PI3-K activity by 90% with complete inhibition achieved at 10 microM. The inhibitory effect of wortmannin on cellular PI3-K activity is prolonged ( > 18 h), suggesting that the drug is not readily metabolized by Jurkat T cells. Wortmannin, at concentrations that blocked PI3-K activity, fails to inhibit the synergistic effect of CD28 on IL-2 secretion in the presence of phorbol 12-myristate 13-acetate and ionomycin. These data demonstrate that CD28-induced signaling events other than the activation of PI3-K catalytic activity contribute to the control of IL-2 secretion.

Spinal bone mineral assessment in postmenopausal women: a comparison between dual X-ray absorptiometry and quantitative computed tomography

We compared quantitative computed tomography (QCT) and dual X-ray absorptiometry (DXA) with respect to their ability to discriminate subjects with and without prevalent vertebral fractures. In 240 post-menopausal women (mean age 63.7 +/- 6.9 years) lateral spine radiographs (T4-L4) were reviewed for the presence of vertebral fracture. Using a semiquantitative technique to grade the severity of vertebral deformities, we classified fractures as mild, moderate or severe (grade 1 to 3, respectively). Postero-anterior DXA (PA-DXA) and lateral DXA (L-DXA) measurements (L2-4) as well as QCT measurements of the lumbar spine (T12-L3 or L1-14) were obtained in all women. Seventy-two women were diagnosed with at least one fracture, and of these 40 were graded as mild. Comparing normal women with fractured women, we found the area under the receiver operating characteristics (ROC) curves to be greatest for QCT (0.81), followed by L-DXA (0.72) and PA-DXA (0.65). The differences among all three techniques were significant. Comparing the normal women with women having only mild fractures, the areas under the ROC curves were 0.79, 0.73 and 0.63 for QCT, L-DXA and PA-DXA, respectively. Significant differences existed between QCT and PA-DXA as well as between L-DXA and PA-DXA. Logistic regression analysis also revealed the highest age-adjusted odds ratios for QCT (3.67; 2.25-5.97) while L-DXA and PA-DXA showed substantially lower odds ratios (2.00; 1.39-2.87, and 1.54; 1.11-2.15, respectively). We conclude that low bone density as measured by QCT, PA-DXA or L-DXA is significantly associated with the prevalence of vertebral fractures. Of the methods studied, QCT of trabecular bone offered the best discriminatory capability. L-DXA proved to be superior to PA-DXA in its diagnostic sensitivity, particularly in women with mild fracture. Mild vertebral fractures are associated with decreased spinal bone density and may be regarded as osteoporotic deformities.

[Effect of streptomycin placing in the fenestra of semicircular canals on the function and morphology of the normal and hydropic ears in guinea pigs]

The effect of streptomycin placed in the fenestra of lateral semicircular canal (LSC) on the function and morphology of the normal and artificial hydropic inner ears in guinea pigs was studied in order to explore the method and possibility of treating Meniere's disease by using aminoglycosides. After placing the drug in the fenestra of LSC, no change in AP threshold of ECochG in normal ears but an increase of that in hydropic ears were found caloric induced nystagmus in both groups were disappeared. Under light microscope, severe damage of vestibular epithelium of three canal cristae and utricular macula was noted, while no insult of cochlear hair cells was found in normal ears. More severe damage of vestibular epithelium with part of them degenerated and atrophied and lesions of cochlear hair cells in basal turns and part of second turns occurred in hydropic ears. These demonstrated that the ototoxicity of streptomycin was higher in hydropic ears than in normal ears. In order to destroy vestibular function and preserve cochlear function, further study for adequate dosage of streptomycin and correct route of administration is needed.

[Mental status and personality of infertile women]

Mental status and personality were investigated in 130 infertile women from November 1992 to May 1993 in the infertility clinic of The Second Hospital of Hunan Medical University. Causes of their infertility attributed to female (n = 65), male (n = 53), unexplained infertility (n = 12). Fifty four fertile women were recruited as normal control. A women consulting questionnaire, Eysenck personality questionnaire (EPQ), symptom checklist-90 (SCL-90), self-rating anxiety scale (SAS) and Hamilton depressive scale (HDS) were used in this study. The result showed that any level of mental pressure were found in 83.8% of infertile women, and moderate and severe in 52%. In comparison with the control, the prevalence of psychiatric symptoms were significantly higher in infertile than fertile women (P < 0.01). Infertile women were more likely to suffer from severe depression and anxiety. Their mental status were more unstable than fertile women and correlated with their personality traits. Authors emphasized that not only the somatic treatment, but also the psychological consultation and mental support should be provided in the program of the infertility management.

Accurate assessment of precision errors: how to measure the reproducibility of bone densitometry techniques

Assessment of precision errors in bone mineral densitometry is important for characterization of a technique's ability to detect longitudinal skeletal changes. Short-term and long-term precision errors should be calculated as root-mean-square (RMS) averages of standard deviations of repeated measurements (SD) and standard errors of the estimate of changes in bone density with time (SEE), respectively. Inadequate adjustment for degrees of freedom and use of arithmetic means instead of RMS averages may cause underestimation of true imprecision by up to 41% and 25% (for duplicate measurements), respectively. Calculation of confidence intervals of precision errors based on the number of repeated measurements and the number of subjects assessed serves to characterize limitations of precision error assessments. Provided that precision error are comparable across subjects, examinations with a total of 27 degrees of freedom result in an upper 90% confidence limit of +30% of the mean precision error, a level considered sufficient for characterizing technique imprecision. We recommend three (or four) repeated measurements per individual in a subject group of at least 14 individuals to characterize short-term (or long-term) precision of a technique.

3D laser scanning for image guided stereotactic neurosurgery

While this work is in its very early stages, the 3D laser scanner shows significant promise as a surgical localization device with advantages over other sensing methods. Accurate 3D surface extraction and matching, a central problem in computer vision, is the key to frameless stereotaxic neurosurgery using this technique.

Retinoblastoma protein regulation of surface CD74 (invariant chain) expression in breast carcinoma cells

The HLA class II genes encode heterodimeric cell surface proteins which bind peptide antigen recognized by T-cell receptors on CD4+ T-cells. The class II proteins are inducible by IFN-gamma, and this induction requires, or is strongly enhanced, by retinoblastoma protein (RB) in a series of breast carcinoma cell lines. Loading of peptide onto the class II protein appears to be regulated by CD74, which associates with class II during their transition to the endosomal compartment, where class II binds peptide. Class II proteins and CD74 are largely regulated in concert, provoking the question, is CD74 induction by IFN-gamma affected by RB? Results described here indicate that IFN-gamma induction of CD74 surface expression in a series of breast carcinoma lines is enhanced by RB, while RB has no effect on CD74 mRNA induction. Also, neither the class II nor the CD74 promoter regions are activated by RB in cotransfection experiments where RB activates the SV40 promoter.

Antibody-induced epidermal growth factor receptor dimerization mediates inhibition of autocrine proliferation of A431 squamous carcinoma cells

We previously reported that anti-epidermal growth factor (EGF) receptor monoclonal antibody (mAb) 225 can block receptor activation and inhibit proliferation of tumor cells bearing EGF receptors. To further explore the mechanism of mAb-mediated growth inhibition, we compared the capacities of bivalent 225 mAb and 225 F(ab')2, and monovalent 225 Fab' fragment to block ligand binding to EGF receptors, inhibit activation of receptor tyrosine kinase by exogenous and endogenous ligand, produce receptor dimerization, down-regulate receptors, and inhibit proliferation of cultured A431 squamous carcinoma cells. Unlike 225 mAb and 225 F(ab')2, 225 Fab' fragment was a poor inhibitor of A431 cell proliferation. The weak antiproliferative capacity of 225 Fab' was not due to depletion of active fragment from cultures. When cells were exposed to exogenous EGF, monovalent 225 Fab' remaining in conditioned culture medium could act as well as the bivalent forms of mAb to block binding and tyrosine kinase activation by exogenous EGF. However, unlike the bivalent forms, 225 Fab' fragment was unable to induce receptor dimerization and down-regulation, and it lacked the capacity to block autocrine activation of EGF receptors by endogenous ligand. These deficiencies were corrected by addition of rabbit anti-mouse IgG antibody, which also enabled 225 Fab' fragment to inhibit cell proliferation. We conclude that in A431 cells, inhibition of autocrine-stimulated proliferation by anti-EGF receptor mAbs requires antibody bivalency, which provides the capacity to produce EGF receptor dimerization accompanied by receptor down-regulation. These properties may explain the greater efficacy of bivalent mAb and F(ab')2, compared with monovalent Fab' fragment, in inhibiting proliferation of a variety of malignant and nonmalignant cultured cell lines.

CD28 signal transduction: tyrosine phosphorylation and receptor association of phosphoinositide-3 kinase correlate with Ca(2+)-independent costimulatory activity

The interaction of CD28 with its counter-receptor, B7, induces a cosignal in T cells required to prevent clonal anergy and to promote antigen-dependent interleukin-2 production. The molecular basis of the CD28 cosignal is not well understood but involves the activation of protein tyrosine kinase(s) (PTK). In this report we demonstrate that CD28 cross-linking on Jurkat T leukemic cells causes the activation of at least two PTK pathways. A CD28-induced, p56lck kinase-independent pathway causes tyrosine-phosphorylation of a 110-kDa substrate while recruitment of p56lck kinase activity is apparently required for CD28-induced tyrosine-phosphorylation of 97- and 68-kDa substrates as well as CD28-induced increases in intracellular calcium. The tyrosine phosphorylation of p110, but not p97 or p68, correlated with CD28 calcium-independent costimulatory activity. The pp110 molecule was tentatively identified as the catalytic subunit of phosphoinositide (PI)-3 kinase based upon its coimmunoprecipitation with the p85 regulatory subunit of PI-3 kinase. PI-3 kinase protein and catalytic activity were found complexed with the CD28 receptor if the receptor was "activated" by cross-linking on the surface of intact cells prior to detergent solubilization. The kinetics of association of PI-3 kinase with the "activated" CD28 receptor was rapid, occurring within 30 s of receptor cross-linking and was stable for at least 30 min. Analysis of the CD28 cytoplasmic peptide sequence revealed a putative PI-3 kinase src homology 2 binding motif and CD28 tyrosine phosphorylation site, DYMNM. Tyrosine phosphorylation of CD28 was detected in pervanadate-treated Jurkat B2.7 cells, but not untreated cells. Pervanadate-induced tyrosine phosphorylation of CD28 correlated with receptor association of PI-3 kinase in the absence of CD28 cross-linking, suggesting that CD28 association with PI-3 kinase uses a tyrosine phosphorylation-dependent mechanism. These data provide a model for CD28 signal transduction and support a role for PI-3 kinase in mediating the CD28 calcium-independent, cyclosporin A-insensitive costimulatory signal.

[Detection on BCR-ABL fusion gene in Ph1 chromosome positive leukemia by "nested" retrotranscriptase/polymerase chain reaction]

By using "nested" retrotranscriptase/polymerase chain reaction (RT/PCR) technique, we determined the expression patterns of the BCR-ABL fusion gene resulting from the chromosomal translocation t (9; 22) in leukemias with Ph1 chromosome. Three distinct isoforms of fusion gene transcripts were discovered: ela2, b2a2 and b3a2. In 10 cases of chronic myelogenous leukemia (CML), only two types (b2a2 and b3a2) were observed. However, in 8 cases of Ph1 chromosome positive acute lymphoblastic leukemia (Ph1 + ALL), all three types were detected, including two cases characterized by the coexistence of ela2 and b2a2 or b3a2 types. Moreover, the RT/PCR procedure established in the present study proved to be a very sensitive method, allowing the detection of one leukemic cell among 10(5)-10(6) normal cells. Thus, a positive RT/PCR result was obtained in two Ph1 + ALL cases just after chemotherapy-induced clinical remission (CR), suggesting the presence of residual disease. One case remained RT/PCR positive four months after achieving CR and relapsed in the fifth month, while the other case converted to RT/PCR negative eight months later and is now in CR for 18 months. Therefore the detection of BCR-ABL fusion gene is of importance not only in the study of the pathogenesis of Ph1 + leukemias but also in their diagnosis and monitoring of minimal residual disease during CR.

Mutagenic effects of heavy ion radiation in plants

Genetic and developmental effects of heavy ions in maize and rice were investigated. Heavy particles with various charges and energies were accelerated at the BEVALAC. The frequency of occurrence of white-yellow stripes on leaves of plants developed from irradiated maize seeds increased linearly with dose, and high-LET heavy charged particles, e.g., neon, argon, and iron, were 2-12 times as effective as gamma rays in inducing this type of mutation. The effectiveness of high-LET heavy ion in (1) inhibiting rice seedling growth, (2) reducing plant fertility, (3) inducing chromosome aberration and micronuclei in root tip cells and pollen mother cells of the first generation plants developed from exposed seeds, and (4) inducing mutation in the second generation, were greater than that of low-LET gamma rays. All effects observed were dose-dependent; however, there appeared to be an optimal range of doses for inducing certain types of mutation, for example, for argon ions (400 MeV/u) at 90-100 Gy, several valuable mutant lines with favorable characters, such as semidwarf, early maturity and high yield ability, were obtained. Experimental results suggest that the potential application of heavy ions in crop improvement is promising. RFLP analysis of two semidwarf mutants induced by argon particles revealed that large DNA alterations might be involved in these mutants.

Reconstruction of limb defects with the free posterior tibial artery fasciocutaneous flap

There are few reports on the use of free posterior tibial artery free flaps. We present four cases of reconstruction of a limb defect with a free posterior tibial artery fasciocutaneous flap.

Particle assembly and Vpr expression in human immunodeficiency virus type 1-infected cells demonstrated by immunoelectron microscopy

The 96 amino acid viral protein R (Vpr) of human immunodeficiency virus type 1 (HIV-1) was detected during virus assembly in intracellular vacuoles and at the plasma membrane on peripheral blood mononuclear cells. In both immature and mature virus particles, Vpr was located immediately beneath the viral envelope, colocalizing with the core structural protein, Gag p24. Vpr was present in intracellular HIV-1 wild-type virions at 50% of the level found in extracellular HIV-1 particles. Cells infected with HIV-1 strains with C-terminal truncations of Vpr manifested a different pattern of Vpr expression. A mutant with an alteration of amino acids 79 to 85 exhibited a 23% reduction in total levels of Vpr expression, but a marked accumulation of Vpr in intracellular rather than extracellular virions. A mutant with the last 17 amino acids of Vpr deleted expressed only 10% of wild-type levels of Vpr. These observations indicate that Vpr is incorporated into virions from the cytoplasmic aspect of either the vacuolar or plasma membrane. Furthermore, the proportion of Vpr on intracellular compared to extracellular virions is affected by a specific locus within the protein.

Far less frequent mutations in ras genes than in the p53 gene in skin tumors of xeroderma pigmentosum patients

Mutations in Ha-ras, Ki-ras, and N-ras genes in squamous and basal cell carcinomas in patients with xeroderma pigmentosum (XP) were examined by the polymerase chain reaction followed by single-strand conformation polymorphism analysis and direct base sequencing. No mutation was detected in codons 12, 13, and 61 of the ras genes in XP skin tumors. This was in contrast with previous findings of a high frequency of mutation in the p53 gene in skin tumors in XP patients. A novel mutation in codon 6 of the Ki-ras gene was detected in a squamous cell carcinoma. The mutation was a C-->T transition at a dipyrimidine (5'-CT) sequence and could have been produced by solar ultraviolet light. The mutated ras gene did not have the ability to transform NIH/3T3 cells. In three tumors, multiple base substitutions were detected in exon 1 of the Ki-ras and N-ras genes. These results and our previous work on p53 gene mutations suggest that mutations in ras genes are far less frequent than in the p53 gene in the skin tumors in XP patients and that ras genes are less important in skin tumorigenesis in XP patients than is the p53 gene.

GM-CSF and M-CSF expression is associated with macrophage proliferation in progressing and regressing rabbit atheromatous lesions

Recent studies have documented that macrophages are a significant cell component of atherosclerotic lesions and may play a significant role in the pathogenesis of these lesions. It has also been documented that markers of cell proliferation (e.g., the proliferating cell nuclear antigen) can be expressed by macrophage subpopulations in atherosclerotic lesions, and there is great interest in identifying cell mediated factors which might be instrumental in macrophage proliferation in this context, perhaps accounting for the persistence of macrophages within this context. Important candidates for this function include granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF); the latter has been previously demonstrated to be expressed in human and rabbit atherosclerotic lesions. We have extended these studies by studying immunocytochemical localization of GM-CSF and M-CSF in progressing and regressing lesions of cholesterol-fed rabbits, documenting expression of these factors predominantly in macrophages, but also in some smooth muscle-cells and endothelial cells. The simultaneous documentation of macrophage subpopulations expressing the proliferating cell nuclear antigen in the same lesions provides evidence to support the hypothesis that macrophage GM-CSF and M-CSF production represents a factor underlying macrophage proliferation and accumulation in atherosclerotic lesions.

Effects of denervation upon receptor cell survival and basal cell proliferation in tuberous electroreceptor organs of a weakly electric fish

Weakly electric fish generate electric fields for the purposes of electrolocation and communication. These fields are detected by specialized receptor organs: the tuberous organs. In the present study we investigated the effects of denervation upon receptor cell survival and progenitor (basal) cell proliferation rate. The left, infraorbital, anterior lateral line nerve of brown ghosts (Apteronotus leptorhynchus) was sectioned, and the proximal stump was dipped in ricin to prevent regrowth. In groups of four, the animals were given two daily injections of the cell proliferation marker bromodeoxyuridine (BrdU) for 2 days at 1, 2, 3, or 4 weeks following denervation. At the completion of the BrdU injection schedule, a piece of cheek skin, rostroventral to the eye, was removed from the left (denervated) and the right (intact) sides and processed for light microscopy or immunocytochemistry. Our results show: (1) there is progressive receptor cell death and tuberous organ degeneration following denervation; (2) basal cell proliferation increases steadily with time after denervation and tuberous organ degeneration; and (3) despite denervation, some proliferating basal cells differentiate into receptor cells, but these new receptor cells eventually die. These results suggest that innervation is essential for tuberous electroreceptor cell survival and that the rate at which basal cells proliferate is regulated by receptor cell health, locally released factors, or both.

Effect of norfloxacin and clonidine on human trabecular meshwork cells in vitro

We evaluated the effect of norfloxacin and clonidine on the morphology, DNA synthesis and phagocytic activity of cultured human trabecular meshwork cells in the 3rd-5th generations. Exposure to norfloxacin at a concentration of 1.5 x 10(-4) g ml-1 for 6 h led to retraction of cytoplasmic processes and rounding of cell profile, and exposure for 48 h caused cell death. Exposure to clonidine at 1.0 x 10(-3) g ml-1 for 12 h caused cell degeneration, and exposure for 72 h led to cell death. The morphologic changes were dose-time dependent. Tritiated thymidine incorporation was determined as an index of DNA synthesis, which was significantly inhibited by 1.5 x 10(-5) g ml-1 norfloxacin or 1.0 x 10(-3) g ml-1 clonidine, but obviously enhanced by 1.0 x 10(-4) and 1.0 x 10(-5) g ml-1 clonidine. Both drugs inhibited phagocytosis of latex microspheres in a dose-dependent mode. According to the presented results and the pharmacokinetic data reported in the literature, we suggest that the topical use of norfloxacin should not be too frequent or continued too long, especially when the corneal epithelium was not intact; clonidine has no deleterious effect on trabecular cells in its conventional use.

Evidence that the activation of an inactive pool of membrane-associated protein kinase C is linked to the IL-2-dependent survival of T lymphocytes

The activation of protein kinase C (PKC) is believed to result from the translocation of inactive cytosolic enzyme to the lipid environment of membranes. However, by using a novel method for measuring PKC activity directly in isolated membranes, we have previously shown that a significant proportion of the PKC present in a variety of cells associates with membranes in an inactive state, and that this pool of inactive PKC can be stimulated specifically in cells in the absence of translocation. IL-2 did not stimulate the translocation of PKC to membranes in the IL-2-dependent mouse T cell line, CTLL-2. Nevertheless, a transient, two approximately threefold increase in membrane PKC activity was observed within 10 min of IL-2 addition to these cells. This increase was entirely caused by the activation of a pool of inactive membrane PKC previously associated with the membrane. The inhibition of PKC activity by the specific inhibitors bisindolylmaleimide (BIS) and 1-O-hexadecyl-2-O-methyl-rac-glycerol (AMG) blocked the ability of IL-2 to suppress the onset of apoptosis in IL-2 and serum-deprived CTLL-2 cells. The inhibition of this important function of IL-2 was most pronounced when the PKC inhibitors were added to the medium within 2 h of stimulating the cells with IL-2. The results suggest that transient activation of inactive membrane PKC is linked to the IL-2 receptor signaling, and may be an important step in the mechanism(s) by which the cytokine suppresses cell death in T lymphocytes.

Evidence that the activation of an inactive pool of membrane-associated protein kinase C is linked to the IL-2-dependent survival of T lymphocytes

The activation of protein kinase C (PKC) is believed to result from the translocation of inactive cytosolic enzyme to the lipid environment of membranes. However, by using a novel method for measuring PKC activity directly in isolated membranes, we have previously shown that a significant proportion of the PKC present in a variety of cells associates with membranes in an inactive state, and that this pool of inactive PKC can be stimulated specifically in cells in the absence of translocation. IL-2 did not stimulate the translocation of PKC to membranes in the IL-2-dependent mouse T cell line, CTLL-2. Nevertheless, a transient, two approximately threefold increase in membrane PKC activity was observed within 10 min of IL-2 addition to these cells. This increase was entirely caused by the activation of a pool of inactive membrane PKC previously associated with the membrane. The inhibition of PKC activity by the specific inhibitors bisindolylmaleimide (BIS) and 1-O-hexadecyl-2-O-methyl-rac-glycerol (AMG) blocked the ability of IL-2 to suppress the onset of apoptosis in IL-2 and serum-deprived CTLL-2 cells. The inhibition of this important function of IL-2 was most pronounced when the PKC inhibitors were added to the medium within 2 h of stimulating the cells with IL-2. The results suggest that transient activation of inactive membrane PKC is linked to the IL-2 receptor signaling, and may be an important step in the mechanism(s) by which the cytokine suppresses cell death in T lymphocytes.

The human DNA-binding protein, PO-GA, is homologous to the large subunit of mouse replication factor C: regulation by alternate 3' processing of mRNA

We have previously cloned a human gene encoding a 128-kDa protein which we termed PO-GA [Lu et al., Biochem. Biophys. Res. Commun. 193 (1993) 779-786]. In the present report, we compared PO-GA to recent DNA database entries and determined that PO-GA was 80% identical, at the amino-acid level, to the large subunit of replication factor C (activator 1) cloned from mouse [Burbelo et al., Proc. Natl. Acad. Sci. USA 91 (1994) in press]. This indicates that PO-GA probably represents the corresponding subunit of human replication factor C. In addition, PO-GA has high homology to a putative Drosophila transcription factor. All three proteins contain a nuclear translocation signal and an ATP/ADP-binding motif, and are highly conserved in regions with homology to Escherichia coli and yeast DNA ligases. We determined that PO-GA mRNA species of 5.3 and 4.5 kb can be detected in most human tissues, but levels are especially high in ovary. Analysis of the sequence of a new PO-GA cDNA clone that we obtained reveals a previously undetected 650-bp 3'-UTR extension. This region contains several A+U-rich regions potentially involved in regulation of mRNA stability. This fragment only hybridizes to the larger 5.3-kb mRNA. Comparison of cDNA sequences revealed that the two mRNA species arise as a result of alternate use of poly(A)-addition sites. Since the ratio of the two mRNA species is variable in different tissues, we speculate that alternative 3' processing of the PO-GA mRNA is utilized as a mechanism of regulating cellular levels of mRNA.

The influenza virus NS1 protein: a novel inhibitor of pre-mRNA splicing

We have shown previously that the influenza virus NS1 protein inhibits the nuclear export of mRNAs. Here we demonstrate that the NS1 protein also regulates another post-transcriptional step: It inhibits pre-mRNA splicing both in vivo and in vitro. The mode by which the NS1 protein inhibits pre-mRNA splicing is novel. The pre-mRNA forms spliceosomes, but subsequent catalytic steps in splicing are inhibited. Affinity selection experiments establish that the NS1 protein is associated with the spliceosomes that are formed. The RNA-binding domain of the NS1 protein is required for the inhibition of splicing and for the interaction of the protein with spliceosomes. Because the NS1 protein is associated with U6 snRNA in influenza virus-infected cells as well as in splicing extracts from uninfected cells, it is likely that the NS1 protein also inhibits pre-mRNA splicing in infected cells. Surprisingly, the splicing of the viral ns1 mRNA, the very mRNA that encodes the NS1 protein, was resistant to inhibition by the NS1 protein. This resistance is conferred by sequences in ns1 mRNA.

Interactions of intestinal mediators in the mode of action of cholera toxin

Cholera toxin (CT) and prostaglandin E2 (PGE2) increased the synthesis of 3',5'-cyclic adenosine monophosphate (cAMP) in rabbit intestinal mucosa, which appeared to be responsible for inducing the release of 5-hydroxytryptamine (5-HT) from enterochromaffin cells into the intestinal lumen. With isolated intestinal cells, CT induced the synthesis of PGE2 more efficiently from epithelial cells than from lamina propria cells; however, the basal amount of this eicosanoid produced by lamina propria cells was approximately six-fold more than that formed by the epithelial cells. The CT-induced stimulation of arachidonate metabolism appeared to be generalised in nature, as PGF2 alpha and leukotrienes were synthesised in addition to PGE2. Injection of dibutyryl cAMP into the intestinal lumen in vivo markedly reduced both basal levels of PGE2, as well as CT-induced levels of PGE2, released into the luminal fluid. Similarly, when biopsy samples of tissue from rabbit intestinal loops, challenged in vivo with dibutyryl cAMP, were washed and incubated in vitro, the amount of PGE2 synthesis remained below basal levels. In contrast, when biopsy samples of normal small intestinal tissue were exposed in vitro to dibutyryl cAMP, PGE2 synthesis increased. Thus, cAMP appeared to down-regulate the levels of intestinal eicosanoids in vivo, despite its innate capacity to evoke PGE2 synthesis from mucosal tissue in vitro. Thus, the data indicate that CT-induced mediators exhibit interactive effects that alter their cellular concentrations, that in turn could affect the biological responses.

Using Markov processes to describe the prognosis of HIV-1 infection

In 1989, Turner and colleagues proposed a new method for automated classification and prediction of outcomes for hospitalized patients with AIDS, based on severity of illness. The authors have confirmed this system, which includes three main stages and 20 substages, in a cohort of HIV-1-infected symptomatic patients admitted to the Miami Veteran's Affairs Medical Center (VAMC) since 1988. They propose a new model of Markov illness-and-death processes and use it to describe the disease progression of the patient cohort. The new Markov model also measures transitions between stages, including risk factors associated with the speed of transitions. Significant differences in survival experiences were found from the different disease stages. The estimated mean (median) survival times were: from stage 1, 21.0 (17.8) months; from stage 2, 10.5 (8.4) months; and from stage 3, 6.7 (4.7) months. In addition, age at HIV-1 diagnosis and homosexual behavior were significant prognostic factors for disease progression and survival. The results indicate that the combination of a severity-of-illness clinical staging system with Markov illness-and-death process modeling is particularly useful for the evaluation of prognostic factors influencing the course of HIV-1 disease progression.

Estimating multiple tumor transition rates based on data from survival-sacrifice experiments

The development of two types of tumors in an animal survival-sacrifice experiment can be described by a Markov illness-and-death process with four unknown tumor transition rates and four unknown death rates. Due to the occult nature of tumors, these transition rates cannot be identified through the use of a completely nonparametric model. We propose a semiparametric model that assumes that the four tumor transition rates are proportional to each other and can be described by a known parametric function. We show that these tumor transition rates can be estimated using an ECM algorithm and that inferences about these parameters can be drawn using the likelihood ratio test. We illustrate this model and the algorithm with data from the ED01 study.

Interaction of 2,3,7,8-tetrachlorodibenzo-p-dioxin and retinoic acid in MCF-7 human breast cancer cells

Both retinoic acid (RA) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) elicit a number of common biochemical and toxic responses including teratogenic effects in mice and inhibition of cell proliferation of numerous cell lines. In mice, RA plus TCDD interact synergistically as teratogens, suggesting a link between the RA and aryl hydrocarbon receptor signal transduction pathways. In this study, it was shown that both RA and TCDD elicit a number of common responses in MCF-7 human breast cancer cells, including inhibition of estrogen-induced cell proliferation and [3H]thymidine uptake, inhibition of nuclear estrogen receptor (ER) ligand binding, and interactions with a consensus [32]estrogen-responsive element in a gel mobility shift assay. RA and TCDD also decrease steady-state ER mRNA levels in a time-dependent manner. Moreover, interactive studies in which cells were treated with both RA plus TCDD also resulted in decreased responses.

A strand bias occurs in point mutations associated with variant surface glycoprotein gene conversion in Trypanosoma rhodesiense

We previously described a bloodstream Trypansoma rhodesiense clone, MVAT5-Rx2, whose isolation was based on its cross-reactivity with a monoclonal antibody (MAb) directed against a metacyclic variant surface glycoprotein (VSG). When the duplicated, expressed VSG gene in MVAT5-Rx2 was compared with its donor (basic copy) gene, 11 nucleotide differences were found in the respective 1.5-kb coding regions (Y. Lu, T. Hall, L. S. Gay, and J. E. Donelson, Cell 72:397-406, 1993). Here we describe a characterization of two additional bloodstream trypanosome clones, MVAT5-Rx1 and MVAT5-Rx3, whose VSGs are expressed from duplicated copies of the same donor VSG gene. The three trypanosome clones each react with the MVAT5-specific MAb, but they have different cross-reactivities with a panel of other MAbs, suggesting that their surface epitopes are similar but nonidentical. Each of the three gene duplication events occurs at a different 5' crossover site within a 76-bp repeat and is associated with a different set of point mutations. The 35, 11, and 28 point mutations in the duplicated VSG coding regions of Rx1, Rx2, and Rx3, respectively, exhibit a strand bias. In the sense strand, of the 74 total mutations generated in the three duplications, 54% are A-to-G or G-to-A (A:G) transitions and 7% are C:T transitions, while 26% are C:A transversions and 13% are C:G transversions. No T:G or T:A transversions occurred. Possible models for the generation of these point mutations are discussed.

Regulation of the Bacillus subtilis pyrimidine biosynthetic (pyr) gene cluster by an autogenous transcriptional attenuation mechanism

A complete transcript of the Bacillus subtilis pyr operon contains the following elements in 5' to 3' order: a 151-nucleotide (nt) untranslated leader; pyrR, encoding a 20-kDa protein; a 173-nt intercistronic region; pyrP, encoding a 46-kDa protein; a 145-nt intercistronic region; and eight overlapping cistrons encoding all of the six enzymes for de novo pyrimidine biosynthesis. Transcription is controlled by the availability of pyrimidines via an attenuation mechanism. There are three transcription terminators within the operon, each of which is preceded by another stem-loop structure, the antiterminator, whose formation would prevent formation of the terminator stem-loop. These are located in the leader, the pyrR-pyrP intercistronic region, and the pyrP-pyrB intercistronic region. Northern (RNA) blot analysis has identified transcripts of lengths which coincide with termination at these proposed attenuation sites and whose relative abundances vary in the expected pyrimidine-dependent manner. Each antiterminator contains a 50-base conserved sequence in its promoter-proximal half. Various transcriptional fusions of the pyr promoter and surrounding sequences to promoterless reporter genes support an attenuation mechanism whereby when pyrimidines are abundant, the PyrR protein binds to the conserved sequence in the pyr mRNA and disrupts the antiterminator, permitting terminator hairpin formation and promoting transcription termination. Deletion of pyrR from the chromosome resulted in the constitutive, elevated expression of aspartate transcarbamylase, which is encoded by pyrB, the third gene in the operon. Complementation of an E. coli upp mutant, as well as direct enzymatic assay, has demonstrated that pyrR also confers uracil phosphoribosyltransferase activity. Analysis of pyrR and upp deletion mutants demonstrated that upp, not pyrR, encodes the quantitatively important uracil phosphoribosyltransferase activity. The pyrP gene probably encodes an integral membrane uracil permease.

A clinical study on the postoperative prognosis of 168 cases of surgical hyperbilirubinemia

It's universally acknowledged that the mortality rate of postoperative patients with obstructive jaundice is higher than that of the non-icteric. Opinions, however, differ as to whether the mortality rate goes up with the worsening of jaundice. Some even regard hyperbilirubinemia as a contraindication in operation. The present article through a clinical research of 168 cases suggested that postoperative mortality registered no increase because of bilirubin level in plasma and the degree of severity of bilirubinemia was not a major factor affecting the postoperative prognosis. The 4 preoperative complications: hypoproteinemia, hepatocirrhosis, portal hypertension and acute cholangitis were responsible for postoperative prognosis, the conclusion is hyperbilirubinemia is not a contraindication in operation. A great portion of the patients should be given active operation to intercept persistent injury on liver and prevent the occurrence of acute cholangitis. To reduce the postoperative mortality, the treatment to be adopted is not to arrange biliary drainage before operation but to improve the patients general conditions by eliminating the complications mentioned above.

Carrier deficit from the nominal threshold density and mode-suppression ratio of an above-threshold biased semiconductor laser

An analytical expression for the carrier deficit DeltaN from the nominal threshold carrier density N(t) of an above-threshold biased semiconductor laser has been deduced. As a result, both the mode spectra and the mode-suppression ratio of a semiconductor laser can be studied analytically. The measured dependence of the mode-suppression ratio on the wavelength difference between the gain peak and its nearest cavity mode of the semiconductor laser confirms the theoretical predictions.

The invariant arginine in motif 2 of Escherichia coli alanyl-tRNA synthetase is important for catalysis but not for substrate binding

Structural motifs 2 and 3, located in the active site of class II aminoacyl-tRNA synthetases, each contain an invariant arginine thought to participate in interactions with ATP. For Escherichia coli alanyl-tRNA synthetase (AlaRS), sequence comparisons indicate that Arg-69 should be aligned with the invariant arginine in motif 2 of other class II synthetases. Site-directed random mutagenesis has been employed to generate a set of proteins containing amino acid substitutions in a portion of motif 2 of AlaRS. In this set, only mutations at position 69 caused the enzyme to lose ability to complement growth of an alaS deletion strain, and proteins containing substitutions at position 69 alone are undetectable in a Western blot assay. A mutant protein containing the transposition of Arg-69 with Gly-71 does not complement growth but does accumulate in vivo and has thus been purified. Michaelis and dissociation constants for the interaction of this protein with ATP are indistinguishable from those of the wild-type enzyme. However, this two-position displacement of the arginine causes a decrease in the kcat for the ATP-PPi exchange reaction by 2 orders of magnitude. These data suggest a role for the invariant arginine of motif 2 in stabilization of the transition state during alanyladenylate synthesis.

Limits of the capacity and density of holographic storage

Previous research assessing planar holographic storage and cross talk between volume multiplexed holograms is reviewed. Using these results, we derive equations for volume holographic storage density and capacity. These equations permit us to identify and to calculate the trade-off between storage density and input-output parallelism and the dependence of capacity on both the parallelism and the resolution of the input-output path.

Evidence for retinoblastoma protein (RB) dependent and independent IFN-gamma responses: RB coordinately rescues IFN-gamma induction of MHC class II gene transcription in noninducible breast carcinoma cells

The class II major histocompatibility (MHC) genes encode cell surface heterodimers that present processed antigen to CD4 positive T-cells. The class II genes are expressed constitutively on B-cells and can be induced by IFN-gamma on a variety of other cell types. Because the class II genes are aberrantly expressed on many mesenchymal tumors, which are frequently defective for the retinoblastoma tumor suppressor protein (RB), we investigated the role of RB in the regulation of HLA-DR and -DP. The RB defective breast carcinomas cell line, MDA-468-S4 (S4), as well as S4 subclones reconstituted with RB coding sequences under the control of a zinc inducible promoter, were treated with IFN-gamma and examined for DR and DP expression. Surface DR is not inducible in S4 cells, but inducibility is rescued by RB. DP is only slightly inducible in S4, but inducible to a much higher level in the RB positive subclones of S4. IFN-gamma induction of DR and DP mRNAs are correspondingly dependent on RB. IFN-gamma receptors are present on S4 cells, and the guanylate binding protein and ICAM-1 genes respond to IFN-gamma, ruling out the possibility that all IFN-gamma signal transduction pathways are defective in S4 cells. These data indicate RB regulates the coordinate response of class II genes to IFN-gamma. Possible roles for RB in this process are discussed, as well as the role of the class II-noninducible phenotype in tumor rejection.

Results of radical cystectomy for transitional cell carcinoma of the bladder and the effect of chemotherapy

BACKGROUND

Radical cystectomy continues to be one of the primary modalities of treatment for locally advanced bladder cancer. However, long-term survival after cystectomy has improved only marginally in the last decade, and still, nearly half of the patients die from the disease within 5 years. Adjuvant treatments such as radiation therapy and chemotherapy have been used, but a clear advantage has not been demonstrated.

METHODS

The authors reviewed 130 patients who underwent radical cystectomy by the same surgeon as treatment for transitional cell carcinoma of the bladder. Morbidity, postoperative mortality, overall survival time, and accuracy of clinical staging as well as the effect of perioperative chemotherapy were evaluated.

RESULTS

The overall actuarial survival rate at 2, 5, and 10 years was 80%, 53%, and 45%, respectively. The survival rate based on T-classification at 5 years was 82%, 65%, and 28% for less than pT2, pT2, and greater than pT2, respectively. Regional lymph node status had a significant effect on survival. The 5-year survival rate for all patients with negative nodes was 65%, whereas patients with positive nodes had a 18% 5-year survival rate. The overall clinical staging error was 61.5%, with 41.5% of the cancers understaged. Of the patients with cTis, 60% were found to be of greater extent than pT1 tumors. No apparent survival advantage was noted for those patients who received perioperative chemotherapy when compared with patients who were followed conservatively or received chemotherapy upon relapse. These results, however, are not conclusive because this was an observation study and the number of patients was limited.

CONCLUSIONS

Only a modest improvement in survival time after radical cystectomy has been observed in the last decade, despite the use of adjuvant treatments such as radiation and chemotherapy. The pathologic (pT) classification is the most accurate prognostic indicator. Clinical errors in classification are common and impair the evaluation of neoadjuvant treatments. A high incidence of invasive tumors of greater extent than pT1 was found among patients with clinical cTis; this supports an aggressive approach when these patients do not respond promptly to intravesical chemotherapy. Prospective randomized studies are needed to evaluate objectively the benefit of perioperative adjuvant treatment in locally advanced transitional cell carcinoma of the bladder.

[Studies on the constituents of the roots of Acorus calamus L]

A new tricyclic sesquiterpene, named calamenone (1), and two known sesquiterpenes, calamendiol (2) and isocalamendiol (3), were isolated from the roots of Acorus calamus L. The structure of the new compound was elucidated on the basis of spectral and X-ray diffraction data.

Prediction of pain center treatment outcome for geriatric chronic pain patients

OBJECTIVE

Geriatric chronic pain patients (age 65 and over) form an increasing percentage of the pain center treatment population. It is therefore important to be able to predict pain center treatment success or failure for these patients; this is the first study to address this concern.

DESIGN

Chronic pain patients rated themselves at pain center admission and discharge on 43 rating scales for the areas of pain, functional status, behavioral variables, and other pain center modification categories. The 43 scores at admission were used as potential predictors, while the 43 change scores (from admission to discharge) were the outcome measures to be predicted. Additional possible predictors were 16 other variables that are considered prognostic of treatment outcome, including age, number of surgeries, and prior occupational level. The statistical analysis consisted of a five-step procedure: (a) mathematical techniques were used to remove redundant outcome measures; (b) each of the remaining outcome variables was correlated with the full set of predictor variables; (c) regression techniques were used to predict the outcome variables; (d) these outcome variables were combined into independent factors using factor analysis; and (e) regression techniques were used to predict the factors.

RESULTS

The variable-reduction technique was successful in removing 26 of the 43 outcome variables. Factor analysis of change scores of the remaining variables resulted in four factors, which were identified as change in activity, change in pain and behavior, change in constant pain, and change in attitude to pain center goals. The analysis showed that the best predictor of a variable's change score was the initial level of that variable. Regression analysis, using all variables as predictors except initial level, found a number of statistically significant predictors. However, no predictor variable, alone or in combination, was able to account for > 30% of the variance of any outcome measure.

CONCLUSION

These results indicate that we cannot as yet predict geriatric pain center treatment outcome. Potential reasons for these results are discussed.

Activation of oncogene c-Ha-ras in gastric cancer of Chinese patients

A transforming gene was cloned from a focus of rat fibroblast cell line Rat 1 transfected with DNA of a gastrocarcinoma cell line. The transforming gene is the activated form of oncogene c-Ha-ras, and the lesion was identified as a single nucleotide substitution at codon 12 by sequencing. We further used polymerase chain reaction (PCR)-restriction analysis to detect the mutations at codon 12 of c-Ha-ras. By using this method, 11 cases out of 24 solid tumors and 3 cell lines of gastric cancer were shown to contain mutations, and there was a strong correlation between mutations and metastasis and survival of the patients. The role of the activated c-Ha-ras in tumorigenesis of stomach cancer was further proved through the assay in which the malignant phenotypes of the c-Ha-ras-transformed cells were partially inhibited by blocking the c-Ha-ras expression with antisense oligonucleotides or exogenous plasmid expressing antisense RNA.