Vapor pressure response to denaturant and water in E10 blends

On December 16, 1993, the U.S. Environmental Protection Agency (EPA) released the final rule on reformulated gasoline (RFG). This rule will affect the composition of as much as 45% of the gasoline used in the United States by the summer of 1995. The acceptance of any gasoline component lies in its ability to contribute to the RFG program's environmental goals. This study was conducted to determine the effect of water and ethanol denaturant on gasoline Reid vapor pressure (RVP) for which little quantitative data are available. This paper addresses two new areas where environmental goals may be achieved while maintaining the use of ethanol-blended gasolines within ozone nonattainment areas.

Effects of oxygen on wound responses to growth factors: Kaposi's FGF, but not basic FGF stimulates repair in ischemic wounds

Kaposi's fibroblast growth factor (K-FGF, FGF-4) is a newer member of FGF family with uncharacterized wound healing properties. Basic fibroblast growth factor (bFGF, FGF-2) has been well studied and accelerates repair in normal and impaired wound healing models. K-FGF and bFGF are known to have similar biological effects in tissue culture, and both stimulate fibroblast and endothelial cell proliferation. The rabbit dermal ulcer model was used to examine the effects of bFGF and K-FGF under ischemic and nonischemic conditions. We found bFGF was ineffective in stimulating healing under ischemic conditions even at high doses (30 micrograms/wound). However, when the ischemic wounds were treated with bFGF (5 micrograms/wound) plus hyperbaric oxygen therapy, it was highly effective again as previously found under nonischemic conditions (P < 0.05). In contrast K-FGF stimulated repair in both nonischemic and ischemic wounds (P < 0.05). These results suggest that wound oxygen content differentially regulates responsiveness to bFGF and that K-FGF is biologically active in hypoxic wounds.

Alternatively spliced forms in the carboxy-terminal domain of the p53 protein regulate its ability to promote annealing of complementary single strands of nucleic acids

The carboxy-terminal domain of the p53 protein comprising amino acid residues 311 to 393 is able to promote the reassociation of single-stranded RNA or DNA into duplex hybrids. This domain is as efficient as the intact p53 protein in both the rate and the extent of the double-stranded product produced in this reaction. Both wild-type and mutant p53 proteins from cancerous cells carry out this reaction. The monoclonal antibody PAb421, which detects an epitope between residues 370 and 378, blocks the ability of p53 to reassociate single strands of RNA or DNA. Similarly, the alternative splice form of the murine p53 protein, which removes amino acid residues 364 to 390 and replaces them with 17 new amino acids, does not carry out the reassociation reaction with RNA or DNA. This is the first indication of functionally distinct properties of the alternative splice forms of p53. These results suggest that this splice alternative can regulate a p53-mediated reaction that may be related to the functions of this protein.

The phosphodiesterase secreted by prestalk cells is necessary for Dictyostelium morphogenesis

Dictyostelium discoideum secretes a cyclic nucleotide phosphodiesterase to control cAMP levels during development. Three promoters control expression of the gene--one during vegetative growth, one during aggregation, and one which constrains phosphodiesterase synthesis to prestalk cells. In this report we show that the expression of phosphodiesterase (PDE) in prestalk cells is necessary for morphogenesis. A gene that codes for a specific glycoprotein inhibitor of the phosphodiesterase (Kd = 0.1 nM) was fused to the prestalk-specific promoter of the PDE gene. Transformants carrying multiple copies of this construct secreted inhibitor in 100-fold excess after the aggregation process had occurred. The first effect seen was an elongated tip, followed by a block in slug formation and an inability to culminate. Stalk and spores cells are produced but morphogenesis is uncoupled from cellular differentiation. Overproduction of inhibitor during earlier stages delayed aggregation, but did not affect fruiting body formation. A phosphodiesterase mutant was transformed with a plasmid that expresses PDE only during aggregation and not in prestalk cells. The defect in aggregation was rescued, but the defect in later development was not. The combined results indicate that PDE expression in prestalk cells is critical to morphogenesis. To ask whether the inhibitor gene under its normal regulation had a role in aggregation or later morphogenesis, it was destroyed by homologous recombination. The loss of the gene did not prevent development under the conditions used.

Purified murine long-term in vivo hematopoietic repopulating cells are not prothymocytes

Analysis of kinetics of thymic repopulation by Rh123low, Lin-, Ly6A/E+, c-kit+ (Rh123low) cells, highly enriched for long-term in vivo hematopoietic repopulating cells, reveals that this population is deficient in thymic repopulation at week 3 after intravenous transplantation when compared to normal bone marrow cells. This suggests that the marrow prothymocytes have been depleted from this population, and analysis of thymic repopulation at week 3 can therefore be used to differentiate prothymocytes and their precursors. Using this short-term assay, the Rh123high, Lin-, Ly6A/E+, c-kit+ (Rh123high) population has been found to be relatively more efficient at early thymic repopulation, suggesting that this population contains the prothymocytes. In addition, the differentiation potential and reconstitution behavior of the Rh123high population observed after intravenous and intrathymic transfer strongly indicates that this population is at the transitional stage between the marrow primitive pluripotential and thymic more mature lymphoid restricted stem cells. We propose that the thymic repopulating ability of the Rh123low population is through generation of the more mature Rh123high progeny, presumably in the marrow.

The Cys(X)5Arg catalytic motif in phosphoester hydrolysis

The Yersinia protein tyrosine phosphatase (PTPase) was identified in the genus of bacteria responsible for the plague or the Black Death and was shown to be essential for pathogenesis. The three-dimensional structure of the catalytic domain of the Yersinia PTPase has been solved, and this information along with a detailed kinetic analysis has led to a better understanding of the catalytic mechanism of the PTPase. Mutational and chemical modification experiments have established that an invariant Cys residue (Cys403) is directly involved in formation of a covalent phosphoenzyme intermediate. We have shown that Arg409 plays a critical role in PTPase action and that the Cys(X)5Arg active site motif forms a phosphate-binding loop which appears to represent the essential features necessary for catalysis by the PTPases, the dual specific phosphatases, and the low molecular weight acid phosphatases.

[The study of metaphasic chromosome pellicle]

Among 12 antichromosome antisera from scleroderma patients, four were found to be the antisera against the pellicle of metaphase chromosomes. Western blotting with these sera were achieved on the protein bands resolved by SDS-PAGE of the whole cell lysate and nuclear lysate of the ascites cells. The result showed 11 bands of the nuclear lysate reacted with antisera. Moreover, additional 8 were obtained in the whole cell lysate.

Ultrastructural observation on macrophage-lymphocyte interactions in semen from Tripterygium wilfordii Hook.f. takers

Sixty-nine specimens from Tripterygium Wilfordii Hook.f. (TWH) users were investigated by electron microscopy. No macrophages were demonstrated in the 21 specimens collected prior to the administration of TWH. However, it was found in 23 out of the 48 semen specimens obtained following the TWH administration. The macrophages were functionally active as shown by the presence of a large number of cytoplasmic processes and pseudopodia on the surface, and primary and secondary lysosomes in the cytoplasm. The macrophages phagocytized sperm debris and degenerated or dead spermatids with formation of specific phagosomes. Around those macrophages, lymphocytes were commonly noted. The cytoplasmic processes of the two cell types could come into contact or even fuse with each other, leading to tight junction-like structure; in some of the contacts, the plasma membranes were found dissolved so as to form direct cytoplasmic linkage.

The catalytic role of Cys124 in the dual specificity phosphatase VHR

The recombinant human Vaccinia virus H1-related protein tyrosine phosphatase, (VHR PTPase) possesses intrinsic Tyr and Thr/Ser phosphatase activities. Both activities were abolished by a single amino acid substitution, C124S. When VHR was incubated with a 32P-labeled phosphotyrosine-containing substrate and then rapidly denatured, enzyme-associated 32P was evident following SDS-polyacrylamide gel electrophoresis. The formation of 32P-labeled protein could be blocked in the presence of an unlabeled substrate. VHR-associated 32P was sensitive to iodine but insensitive to pyridine and hydroxylamine. The catalytically inactive C124S mutant would not form a 32P-labeled enzyme. Furthermore, VHR phosphatase could be selectively inactivated by the alkylating agent iodoacetate. The inactivation resulted from the specific covalent modification of Cys124. Collectively these results suggest that a thiol-phosphate enzyme intermediate is formed when Cys124 of VHR accepts a phosphate from the substrate. Our results also demonstrate that the dual specificity phosphatases and the tyrosine-specific PTPases employ similar catalytic mechanisms.

Specificity of the complement resistance and cell association phenotypes encoded by the outer membrane protein genes rck from Salmonella typhimurium and ail from Yersinia enterocolitica

Virulence-associated phenotypes of an outer membrane protein gene family of members of the family Enterobacteriaceae were compared by means of pBR322 constructs transformed into Escherichia coli HB101.rck (Salmonella typhimurium) and ail (Yersinia enterocolitica) promote serum resistance and eukaryotic cell invasion, properties not shared by other members of the gene family, pagC, ompX, and lom.

Effects of copper concentration on mineral nutrient uptake and copper accumulation in protein of copper-tolerant and nontolerant Lotus purshianus L

One copper-tolerant and one copper-sensitive inbred line of Lotus purshianus L. derived from a copper mine waste site in Northern California and one inbred line of the same species derived from a pasture next to the mine waste were examined for the effects of excessive copper concentrations on mineral nutrient uptake and accumulation of copper in protein fractions. Plants were grown from seeds for a period of 24 days in a modified Hoagland nutrient solution culture supplemented with 3, 6, and 10 microM copper as copper sulfate. The basal nutrient solution without copper amendment was used as the control treatment. The uptake of Cu found in the roots was 100 times or more than that in the leaves. The root tissue copper concentrations reached a plateau under 6 microM copper treatment. The leaf tissue copper concentrations increased with the increase of copper concentration in the solution culture. No difference in pattern of copper uptake was detected between the copper-tolerant and nontolerant plants. The effects of excessive copper concentrations caused reduction of Ca uptake in the leaf tissue and P uptake in both the root and leaf tissues, and no difference was found between the copper-tolerant and nontolerant plants. Increased tissue copper concentration caused greater reduction of Fe, Mn, and Zn uptake in the nontolerant plants than in the tolerant plants; this difference may be important for the growth of the tolerant plants under conditions of excessive copper concentrations. Protein extracted from the roots and leaves of both the copper tolerant and nontolerant plants was subjected to Sephadex G-75 column separation. Two major peaks of protein fractions were detected. Under low (normal level) copper concentration treatment, the copper-tolerant and nontolerant plants had similar Cu/protein ratios. However, under high copper concentration challenged conditions the copper-tolerant plant had a considerably greater Cu/protein ratio (peak II protein) than the nontolerant plants. The amino acid composition of the copper-rich protein fraction (peak II) extracted from both the tolerant and nontolerant plants demonstrated a high asparate (about 25%) content. The contents of glutamate, cystine, and glycine were about 11, 2.5, and 10%, respectively, and the rest of the amino acids were in a range of 2 to 6%. This pattern of amino acid composition is different from the amino acid composition of the phytochelatin metallothionein-like proteins found in copper-tolerant plants which are very high in cysteine.(ABSTRACT TRUNCATED AT 400 WORDS)

Coexpression of glucose transporters and glucokinase in Xenopus oocytes indicates that both glucose transport and phosphorylation determine glucose utilization

A Xenopus oocyte expression system was used to examine how glucose transporters (GLUT 2 and GLUT 3) and glucokinase (GK) activity affect glucose utilization. Uninjected oocytes and low rates of both glucose transport and phosphorylation; expression of GLUT 2 or GLUT 3 increased glucose phosphorylation approximately 20-fold by a low Km, endogenous hexokinase at glucose concentrations < or = 1 mM, but not at higher glucose concentrations. Coexpression of functional GK isoforms with GLUT 2 or 3 increased glucose utilization approximately an additional two- to threefold primarily at the physiologic glucose concentrations of 5-20 mM. The Km for glucose of both the hepatic and beta cell isoforms of GK, determined in situ, was approximately 5-10 mM when coexpressed with either GLUT 2 or GLUT 3. The increase in glucose utilization by coexpression of GLUT 3 and GK was dependent upon glucose phosphorylation since two missense GK mutations linked with maturity-onset diabetes, 182: Val-->Met and 228:Thr-->Met, did not increase glucose utilization despite accumulation of both a similar amount of immunoreactive GK protein and glucose inside the cell. Coexpression of a mutant GK and a normal GK isoform did not interfere with the function of the normal GK enzyme. Since the coexpression of GK and a glucose transporter in oocytes resembles conditions in the hepatocyte and pancreatic beta cell, these results indicate that increases in glucose utilization at glucose concentrations > 1 mM depend upon both a functional glucose transporter and GK.

Identification, assay, and purification of a Cdc2-activating threonine-161 protein kinase from human cells

The biological activities of cyclin-dependent, proline-directed protein kinases (PDPKs) are highly regulated by a complex series of protein phosphorylation/dephosphorylation reactions involving both catalytic and regulatory subunits. In this paper we report on the enzymatic activation of p34cdc2/p58Cyclin A PDPK by a protein kinase present in human cells that targets threonine-161 of Cdc2. An assay for this Cdc2 kinase-kinase (PK161) was developed and specific enzyme activity was detected in a variety of mammalian cells and tissues. PK161 activity was rapidly stimulated by epidermal growth factor in human A431 epidermoid carcinoma cells. The development of an assay selective for PK161 phosphotransferase activity afforded the partial purification of the enzyme from human Wilms' tumors. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining of highly purified enzyme preparations revealed the presence of phosphoproteins migrating at approximately 42-44 and approximately 95 kDa, respectively, which correlated with enzyme activity upon fast-protein liquid chromatography gel permeation chromatography. Further purification was accomplished by immobilized peptide substrate affinity chromatography. The ability of PK161 to phosphorylate and activate p34cdc2/p58Cyclin A PDPK was confirmed by the use of purified recombinant subunits. Polyclonal antibodies directed against the Xenopus MO15 gene product (a putative Cdc2-activating kinase) cross-reacted with the purified 42- to 44-kDa phosphoprotein, thus identifying the catalytic subunit of human PK161 as a human homologue of Xenopus p40MO15. Subsequent immunoprecipitation experiments with metabolically labeled A431 cells identified a approximately 95-kDa phosphoprotein that coprecipitated with the approximately 42-kDa catalytic subunit. Taken together, these findings identify a human Cdc2-activating kinase as a growth factor-responsive enzyme system that may participate in the acute activation of cyclin-dependent protein kinases observed in mammalian somatic cells.

Sequence and spatial requirements for the tissue- and species-independent 3'-end processing mechanism of plant mRNA

Two cis-regulatory regions are required for efficient mRNA 3'-end processing of the maize 27-kDa zein mRNA: a region containing a duplicated AAUGAA poly(A) signal and a region that is present upstream from it. Strict spatial positioning of these two regions is required for efficient mRNA 3'-end processing. Insertion of a stuffer sequence as short as 17 or 18 bp either between the upstream region and the two AAUGAA motifs or between the two AAUGAA motifs drastically reduced the efficiency of 3'-end processing. Mutational analyses of the nucleotide preference at the fourth position of the AAUGAA motif revealed the preference order G > A >> C or U, suggesting that AAUAAA is neither a defective nor an optimal poly(A) signal for the 27-kDa zein mRNA. As for the 3' control region of the cauliflower mosaic virus (CaMV) transcription unit, the mRNA 3'-end processing mechanism mediated by the 27-kDa zein 3' control sequence is neither tissue nor species specific. The 3' upstream sequence of the 27-kDa zein gene can functionally replace that of the CaMV transcription unit. Conversely, the CaMV upstream sequence can mediate mRNA polyadenylation in the presence of a duplicated 27-kDa zein poly(A) signal. However, instead of the proximal poly(A) signal normally used in the 27-kDa zein mRNA, the distal signal is utilized. These results suggest that a general mechanism controls the 3'-end processing of plant mRNAs and that the cis-regulatory functions mediated by their upstream regions are interchangeable.

[Histochemical study of dopamine on rat substantia nigra--ventral tegmental area during status epilepticus]

We studied the amount of dopamine on the substantia nigra-ventral tegmental area during status epilepticus of male Wistar rats induced by coriaria lactone with fluorescence histochemical technique and autoexposuremeter of microscope. The intensity of dopamine fluorescence in the climax epileptic seizure group (10 rats) and postepileptic seizure group (8 rats) decreased significantly as compared with the control (10 rats), but the intensity of dopamine fluorescence in the pre-eileptic seizure group (10 rats) was not significantly different from that of the control group. The result indicated that epileptic seizure induces a decrease of the inhibitory neurotransmitter-dopamine. Therefore dopamine plays an important role in regulating the epileptic seizures.

[Morphometric study of motor cortex in acute focal epilepsy rat induced by coriaria lactone]

Twenty adult male Wistar rats were divided randomly into two groups (10 rats for LM, 10 rats for EM). The experimental rats were injected with convulsive dosage 3.8 microliters (19 micrograms) of coriaria lactone (CL) in the left cerebral motor cortex of the fore limb to induce acute focal epilepsy. The control rats were injected with normal saline of the same volume and at the same location. Motor cortex was cut coronally 2 hours after seizure and the layer V was studied morphometrically. Under x400 and x7000, take photos of focus, parafocus areas respectively for morphometric study. The number of neurons and neuroglias of layer V was counted in the LM photos. The number of presynaptic terminals of the neuropil was counted in the x7000 EM photos and the area fraction of each constitute in the neuropil was measured. The positive results demonstrated that the number of neurons and neuroglias in the focus and parafocus areas of the experimental animals was significantly lower than that in the control group, the side injected was lower than the other side and it was the lowest in the focus. The number and area fraction of the presynaptic terminals of the experimental rats at the focus neuropil decreased significantly, but the area fraction of neuroglial components increased significantly. The authors suggest that the convulsive dosage of CL may have toxic effect on some neurons and neuroglias and therefore to decrease the number of both types of cells and the number and area fraction of presynaptic terminals in the neuropil.(ABSTRACT TRUNCATED AT 250 WORDS)

Levels of messenger-RNA coding for DNA topoisomerase-ii isoforms do not correlate with in-vitro drug-sensitivity

The relationship between cellular levels of mRNA coding for DNA topoisomerase II, both the alpha and beta isoforms, and in vitro sensitivity to anticancer drugs were evaluated. Using a sensitive RNA-polymerase chain reaction technique, the levels of mRNA coding for the alpha and beta isoforms of topoisomerase II were estimated relative to beta-actin mRNA. A relatively narrow range of expression was observed across a broad range of approximately 60 human tumor cell lines representing eight major histological types which have been characterized in detail with respect to their in vitro sensitivity to standard anticancer drugs. No significant correlations were observed between mRNA level and cellular response to drugs thought to inhibit topoisomerase II or any of the other drugs studied. These results suggest that predictive tests for response to topoisomerase II-related drugs can not be based on estimation of levels of mRNA.

A method of developing and weighting explicit process of care criteria for quality assessment

The use of explicit criteria to evaluate how well processes of care conform to accepted standards is a key method of quality assessment. Synthesizing four decades of literature, we devised an inexpensive, 6-step method of developing reliable, content-valid, explicit process criteria. This paper describes the method using a set of congestive heart failure criteria. In step 1 of the Criteria Development Method, criteria are derived from state-of-the-art clinical literature. In step 2, criteria are refined by expert panels. In this study, panelists refined the items by mail in a three-round Delphi process. In step 3, decisions about unit-or differential item weighting are made; we derived differential item weights from the panelists' third-round ratings. Step 4 consists of flagging items which may yield little information, i.e., consensus items of low import, and nonconsensus items. Numeric flags were computed using third-round median ratings and their interquartile ranges. Selection of a scoring method to summarize scores and communicate results is done in step 5. In step 6, chart reviewers are trained, inter-rater reliability is measured, and items with poor reliability are culled. This straightforward developmental method can be used to devise explicit process criteria for use in ambulatory or hospital settings and to evaluate care delivered by different types of providers. The method yields reliable criteria representing accepted standards of current clinical practice. This high content validity is a sine qua non for convergent and predictive validity, both of which must be demonstrated in empirical studies in which the criteria are compared against external yardsticks.

Platelet-derived growth factor-BB accelerates wound closure in a new mesentery culture model without macrophages

Platelet-derived growth factor-BB has multiple effects in vitro and has been demonstrated to accelerate wound healing in several animal models, but its precise mechanisms of action in vivo have not been fully explained. A rat mesentery culture model was developed, and platelet-derived growth factor-BB (100 ng/ml) was added to the medium containing 2% fetal calf serum for examining its closure effects. The mesentery specimens were stained by routine hematoxylin and eosin and immunohistochemical staining for macrophages. A significant improvement in closure rate and complete closure rate was seen when platelet-derived growth factor-BB was added to the medium compared with the controls (p < 0.05). There are significantly fewer macrophages in the in vitro specimen than in the in vivo specimen. In conclusion, platelet-derived growth factor-BB can contribute to wound closure of a mesenteric defect even without macrophages, suggesting a second mechanism in which it can act directly on mesenchymal cells during wound healing. This tissue-culture model is useful for gaining further insights into growth factor interactions and wound healing.

[Histopathologic and ultrastructural studies of the iris in acute angle-closure glaucoma]

By light and transmission electron microscopy, iris specimens from 40 eyes of 24 patients with acute angle-closure glaucoma were investigated and compared with those of healthy eyes in the same patients. During an acute attack, the anterior border layer of the iris became thickened, and stromal cells and collagen fibrils greatly proliferated. The endothelial cells swelled and muscle fibers showed vacuolization, depigmentation or atrophy. During the stage of remission, the iris was structurally disrupted and the stromal cells degenerated markedly. In the absolute stage, the stromal cells were atrophic and the fibers resolved, while the mast cells increased in large numbers. The significance of these findings were discussed.

Molecular cloning of the human CAK1 gene encoding a cyclin-dependent kinase-activating kinase

Cyclin-dependent, proline-directed protein kinases normally function to execute critical cell cycle transitions; abnormal expression and/or viral subversion of the positive (cyclins) and negative (Pic1) regulatory subunits may contribute to neoplastic transformation and tumorigenesis. In addition to the binding of regulatory subunits, the enzymatic activities of the cyclin-dependent kinases, Cdc2 and Cdk2, are tightly regulated by site-specific protein phosphorylation events. Recent studies have identified a critical phosphorylation site (Thr-161) located within kinase Subdomain VIII that is necessary for Cdc2 activation, and enzymatic activities capable of carrying out this heterologous phosphorylation event have been detected in both Xenopus oocytes and human somatic cells. In this report, we characterize by molecular cloning a human homologue of the Xenopus Cdk-activating kinase (Cak, encoded by MO15); the novel human gene is designated (HS)CAK1. While only 75% identity is observed at the nucleotide level, the deduced amino acid sequence encoded by (HS)CAK1 is approximately 87% identical to that of the Xenopus MO15 gene in corresponding regions. The catalytic domain of (HS)Cak1, defined by conserved kinase Subdomains I through XI, exhibits considerable homology with (HS)Cdc2, suggesting that this kinase cascade involves closely related enzymes. Immunological studies with anti-Cak antibodies confirm the presence of specific immunoreactivity in highly purified preparations of the human Cdc2-activating kinase. The molecular characterization of (HS)CAK1 should facilitate studies of its physiological regulation, as well as its potential utility as a target for therapeutic intervention in the treatment of proliferative disorders.

The selenium metabolite selenodiglutathione induces p53 and apoptosis: relevance to the chemopreventive effects of selenium?

Selenodiglutathione (SDG), the initial metabolite of selenite, is shown to be a more powerful inhibitor of cell growth in vitro than selenite itself. This has been established both with mouse erythroleukaemia (MEL) cells and an ovarian cell line (A2780) which is known to contain wild-type p53. Other seleno-compounds, such as selenomethyl selenocysteine (SMS) and dimethyl selenoxide (DMS), which are potent chemopreventive agents and are known to be metabolized to methylated selenium derivatives directly rather than via SDG, are also growth inhibitory to both MEL and A2780 cells, although less so than SDG or selenite. However, cells growth-inhibited by DMS are more viable than cells growth-inhibited to the same extent by SDG or selenite, suggesting that the methylated seleno-compounds may inhibit cell growth in a different manner from that of SDG or selenite. Our studies of the mechanism of growth inhibition by SDG, have established two facts. First, SDG induces p53 protein levels in cells that contain wild-type p53 (A2780 cells), suggesting that SDG induces the DNA damage-recognition pathway. Secondly, SDG induces apoptosis in MEL cells, as judged by flow cytometry and formation of nucleosomal DNA ladders. However, since p53 mutations have been found to be targetted events in all MEL cells examined, our evidence suggests that induction of apoptosis by SDG is not absolutely dependent on the p53 response pathway.

Thymic stem cells in mouse bone marrow

There is still controversy concerning the nature of the stem cells from bone marrow that colonize the thymus during embryogenesis and continually throughout life. To identify the bone marrow stem cells that home to and populate the thymus, we screened murine bone marrow cells for the presence of a population of surface phenotype similar to the earliest known intrathymic precursor. We have identified a population characterized by expression of an intermediate level of heat stable antigen, a very low level of Thy-1, and high levels of CD44 and class I major histocompatibility complex antigens. It is negative for B-cell, granulocyte, macrophage, and erythrocyte markers (B220, Gr-1, Mac-1, and TER 119). All these markers are common to the intrathymic precursors and bone marrow stem cells. However, this new bone marrow population is Sca-2+, similar to the intrathymic precursor, which makes a clear distinction from the Sca-2- bone marrow hematopoietic stem cells previously characterized. The frequency of the new population in the normal mouse bone marrow is about 0.25%. When transferred intrathymically or intravenously to lethally irradiated mice, it has a higher expansion potential (2 x 10(5)) than has been found for the intrathymic precursors (10(3)), but less than was found for the Sca-2- multipotent stem cell (10(7)). These transfer studies also showed that it was pluripotent, in that its precursor activity was not restricted to the production of T or B lymphocytes. However, it gave a reduced spleen colony number and smaller colonies (day-12 colony-forming unit spleen) when compared with multipotent stem cells. Thus, the cell we have identified appears to be the latest pluripotent cells so far identified in bone marrow and is therefore a good candidate for a bone marrow prothymocyte, but it appears not to be T-cell-committed.

Cloning and targeted mutations of G alpha 7 and G alpha 8, two developmentally regulated G protein alpha-subunit genes in Dictyostelium

GTP-binding protein (G protein)-mediated signal transduction pathways play essential roles during the aggregation and differentiation process of Dictyostelium. In addition to the five known G protein alpha-subunit genes, we recently identified three novel alpha-subunit genes, G alpha 6, G alpha 7, and G alpha 8, using the polymerase chain reaction technique. We present here a more complete analysis of G alpha 7 and G alpha 8. The cDNAs of these two genes were cloned, and their complete nucleotide sequences were determined. Sequence analyses indicate that G alpha 8 possesses some unusual features. It lacks the "TCATDT" motif, a sequence of amino acids highly conserved among G alpha subunits, and has an additional 50 amino acids at its C-terminus consisting of long stretches of asparagine. Moreover, G alpha 8 is unusually resistant to protease digestion, which may indicate a slow GTP hydrolysis rate. The possible functions of these alpha-subunits were assessed by generating mutants lacking G alpha 7 or G alpha 8 by gene targeting through homologous recombination and by overexpressing G alpha 7 or G alpha 8 protein. Overexpression of G alpha 7 resulted in abnormal morphogenesis starting at the slug stage, whereas analysis of the other strains failed to reveal any obvious growth or developmental defects under either normal or stressful conditions. The implications of these results are discussed.

Herpes simplex virus type 1 replication and IL-1 beta gene expression in mouse peritoneal macrophages activated in vivo by an attenuated Salmonella typhimurium vaccine or Corynebacterium parvum

Activated macrophages (M phi) from mice given Salmonella typhimurium or Corynebacterium parvum were compared with resident peritoneal macrophages at the molecular level for permissiveness for herpes simplex virus type 1 (HSV-1) replication and for expression of interleukin-1 beta (IL-1 beta). Peritoneal macrophages were harvested from mice injected 7 days previously with live, avirulent S. typhimurium (Sal-PM phi) or heat-killed C. parvum (CP-PM phi) and infected with HSV-1 in vitro. Both Sal-PM phi and CP-PM phi were activated as evidenced by characteristic changes in an ectoenzyme, by increased permissiveness for infectious virus production and viral cytopathic effect, and by induction of IL-1 beta mRNA. Analysis at the molecular level revealed that both types of activated M phi demonstrated increased patterns of HSV-1 immediate-early gene expression and viral DNA replication as compared with resident cells. A novel finding was that viral infection reduced IL-1 beta mRNA in both types of activated M beta. This observation has implications for the efficacy of Salmonella vaccines given in proximity to HSV-1 infection and for potential deleterious effects of HSV-1 infection in immunosuppressed patients receiving immunotherapy.

Adenovirus-mediated gene transfer in the transplant setting. II. Successful expression of transferred cDNA in syngeneic liver grafts

These experiments establish a model for gene transfer to transplanted liver grafts ex vivo using adenoviral vectors. Rat liver grafts (n = 8) were harvested, and preserved in UW or lactated Ringer's. The grafts were infected ex-vivo via portal vein perfusion with replication-defective Ad vectors encoding the beta-galactosidase (beta-gal) gene diluted in UW solution. The infected grafts were stored at 4 degrees C for 1 hr, then transplanted into syngeneic hosts. Liver biopsies were taken at 1, 7, and 15 days after transplantation. Infection rate was assessed by histochemical staining for beta-gal. Liver DNA and RNA were assayed for the beta-gal sequences, and recombinant protein production measured at 24 hr and 7 days after transplantation. Under conditions mimicking liver graft cold storage, efficient gene transfer was achieved with an infection rate of 10-15%, as assessed by X-gal staining. Viral DNA and RNA presence in the graft was confirmed; gene expression with protein production were verified by western blots and a functional protein assay. All studies were negative in control livers. Gene expression persisted for at least 2 weeks after transplantation. We conclude that efficient adenovirus-mediated gene insertion and expression of gene products can be accomplished in whole-liver grafts under hypothermic preservation conditions currently used in clinical transplantation.

Regulation of expression of the cyclic nucleotide phosphodiesterase gene in phosphodiesterase inhibitor-negative mutants of Dictyostelium discoideum

During early development of Dictyostelium discoideum, the enzyme cyclic nucleotide phosphodiesterase (PD) is produced at a low rate during the period its specific inhibitor (PDI) is being synthesized. In addition, PD gene expression is derepressed in the aggregation-deficient (Agg-), Pdi- mutant HC35. These observations suggest that the PDI might function to regulate PD gene expression, as well as modulate its activity. To explore this idea further, five new Agg-, Pdi- mutants were isolated and analyzed. All of the mutants produced high PD activity and overexpressed PD mRNA; four exhibited elevated levels of the 2400-nucleotide aggregation transcript and one overproduced the 1900-nucleotide vegetative transcript. In contrast, PD transcripts were not elevated in two Agg-, Pdi+ mutants. To determine if PDI production regulates PD expression, HC35 cells were transformed with plasmids carrying the PDI structural gene under the control of either the vegetative or aggregative PD promoter. Neither expression of PDI by the transformants nor addition of partially purified PDI to HC35 cells affected PD transcription. These results suggest that PD overexpression in the Pdi- mutants is not a direct consequence of the inability of these cells to produce inhibitor.

Oedipism in a patient with frontal lobe encephalomalacia

There is a growing recognition of the role of the frontal lobes in the aetiology of severe behavioural aberrations. The authors describe a case of Oedipism in a patient who had MRI evidence of frontal lobe encephalomalacia. After discussing the function of the frontal lobes in modulating behaviour the authors suggest that the structural lesion seen on the MRI was in part responsible for the patient's self-destructive act. Treatment issues and the importance of recognizing underlying structural lesions in instances of extreme self-mutilation are discussed.

Male pseudohermaphroditism caused by mutations of testicular 17 beta-hydroxysteroid dehydrogenase 3

Defects in the conversion of androstenedione to testosterone in the fetal testes by the enzyme 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) give rise to genetic males with female external genitalia. We have used expression cloning to isolate cDNAs encoding a microsomal 17 beta-HSD type 3 isozyme that shares 23% sequence identity with other 17 beta-HSD enzymes, uses NADPh as a cofactor, and is expressed predominantly in the testes. The 17 beta HSD3 gene on chromosome 9q22 contains 11 exons. Four substitution and two splice junction mutations were identified in the 17 beta HSD3 genes of five unrelated male pseudohermaphrodites. The substitution mutations severely compromised the activity of the 17 beta-HSD type 3 isozyme.

Functional analysis of Mel-14+ and Mel-14- early precursor cells in the adult mouse thymus

The earliest T-cell precursor population in the adult mouse thymus (low CD4 precursors) may be divided into 85% of cells expressing surface Mel-14 (LECAM-1, the lymphocyte homing receptor) and 15% of cells which are Mel-14. To date, this is the only surface marker for which we have found this population to be heterogeneous. The precursor activity of the Mel-14+ and Mel-14- subpopulation was assessed by both intrathymic and intravenous transfer of sorted cells into Ly5 congenic irradiated recipient mice. On both a cell-for-cell and a total activity basis, almost all precursor activity was associated with the Mel-14+ cells. No segregation was seen between T-cell, B-cell and dendritic cell precursor activity of the low CD4 population, all activities being concentrated in the Mel-14+ fraction. This strengthens the hypothesis that one precursor cell has the potential to form all three lineages.

Assessment of CD4 expression by early T precursor cells and by dendritic cells in the human thymus

The adult mouse thymus contains a minute population of early lymphoid precursor cells that express moderate levels of CD4. We searched for a corresponding population of early T precursors in the infant human thymus, by first depleting the majority of more mature thymocytes, then using immunofluorescence and flow cytometry to analyze cells bearing a range of early T lineage markers. No discrete population of early T precursors expressing CD4 was observed, in contrast to the murine thymus. Most putative very early human thymocytes were CD4-8-3-1-2lo44+34+7hi class I MHChi class II MHC-. However, a distinct population of human thymic dendritic cells expressing high levels of CD4 was isolated. These were CD4hi8-3-1-2-44+34-7- class I MHChi class II MHChi, and lacked markers of B cells, NK cells, or myeloid cells. They were large cells that exhibited dendritic morphology after brief periods of culture, and they were efficient stimulators of allogeneic T cells. The biologic implications of CD4 expression by thymic dendritic cells are discussed.

Assessment of CD4 expression by early T precursor cells and by dendritic cells in the human thymus

The adult mouse thymus contains a minute population of early lymphoid precursor cells that express moderate levels of CD4. We searched for a corresponding population of early T precursors in the infant human thymus, by first depleting the majority of more mature thymocytes, then using immunofluorescence and flow cytometry to analyze cells bearing a range of early T lineage markers. No discrete population of early T precursors expressing CD4 was observed, in contrast to the murine thymus. Most putative very early human thymocytes were CD4-8-3-1-2lo44+34+7hi class I MHChi class II MHC-. However, a distinct population of human thymic dendritic cells expressing high levels of CD4 was isolated. These were CD4hi8-3-1-2-44+34-7- class I MHChi class II MHChi, and lacked markers of B cells, NK cells, or myeloid cells. They were large cells that exhibited dendritic morphology after brief periods of culture, and they were efficient stimulators of allogeneic T cells. The biologic implications of CD4 expression by thymic dendritic cells are discussed.

Inositol 1,4,5-trisphosphate-, GTP-, arachidonic acid- and thapsigargin-mediated intracellular calcium movement in PANC-1 microsomes

Inositol 1,4,5-trisphosphate (IP3)-, GTP-, arachidonic acid- and thapsigargin-mediated Ca2+ release from endoplasmic reticulum (ER)-enriched microsomes was studied in a PANC-1 cell line. IP3 maximally caused an approximately 20% release of actively accumulated Ca2+. This effect was completely blocked by heparin. In the presence of 3% polyethylene glycol (PEG), GTP maximally discharged about 60% of Ca2+ from the microsomes. This effect involved a GTP hydrolytic process, not the IP3-activated Ca2+ channel. Arachidonic acid maximally released approximately 80% of Ca2+ from PANC-1 microsomes. Metabolites of arachidonic acid did not appear to be involved in arachidonic acid-mediated Ca2+ release. However, other fatty acids also induced similar releasing effects suggesting that arachidonic acid-induced Ca2+ release appeared to be non-specific. Thapsigargin was shown to inhibit Ca2+ accumulation into and induce Ca2+ release from PANC-1 microsomes. The thapsigargin-releasable Ca2+ pool included the IP3- or arachidonic acid-sensitive pool. Studies on liposomes suggested that both arachidonic acid and thapsigargin did not exert either a Ca2+ ionophore-like or a membrane detergent-like effect. The present results have provided evidence for the existence of multiple non-mitochondrial Ca2+ pools in PANC-1 cells. These Ca2+ pools could be released by various Ca2+ mediators via different mechanisms.

Granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor: differential action on incisional wound healing

BACKGROUND

Granulocyte-macrophage colony-stimulating factor (GM-CSF) specifically stimulates granulocyte, macrophage, and eosinophil colonies; granulocyte colony-stimulating factor (G-CSF) acts directly on neutrophil-restricted progenitor cells in their proliferation. Those cells have been implicated in the process of wound healing.

METHODS

Paired 6 cm incisions were made on rats; GM-CSF or G-CSF was given systemically (100 micrograms/kg/dose) or locally (30 micrograms/wound). The controls received vehicle alone. Impaired healing was induced by injection of methylprednisolone (30 mg/kg). White blood cells (WBC) were counted at day 2 after treatment. Tissue strips were evaluated for tensiometry and histologic features at days 7 and 14 after wounding.

RESULTS

For local GM-CSF treated incisions, the breaking strength was 25% stronger than controls at day 7 (p = 0.004), 36% at day 14 (p < 0.0001), and 42% at day 7 (p = 0.012) in impaired animals. Local G-CSF and systemic GM-CSF and G-CSF increased circulating WBC (p < 0.05), but they had no effects on healing. Histologic studies revealed an increase of wound cellulity at day 7 and day 14 in topical GM-CSF treated wounds.

CONCLUSIONS

These results suggest GM-CSF is an activator of tissue macrophages and that increasing circulating WBC did not affect wound healing.

[Quantitative study on cerebral motor cortex structure of kindling rat induced by coriaria lactone]

Ten male Wistar rats were divided into two groups. The experimental rats were injected with subconvulsive dosage of coriaria lactone (1 mg/kg) intramuscularly every 3.5 days to induce kindling seizures. The controls were injected with normal saline. Cerebral motor cortex of kindling rats was taken at the time between seizures and layer V was compared morphologically with that of the control. The number of neurons and neuroglias was counted from light micrographs. The numerical density and length fraction of boutons on the surface of pyramidal somata were measured from electron micrographs with MIAS 300 type image analyser. The number of synapses in neuropil was counted directly and the areal fraction of various constitute in neuropil was measured stereologically from EM photos. In the experimental rats, the number of neurons remained unchanged and the numerical density and length fraction of boutons on the surface of pyramidal somata showed no change, either. The number of synapses (or presynaptic terminals) decreased significantly in neuropil, but the areal fraction of synaptic terminals had no change and the areal fraction of dendrites and unmyelinated fibers decreased. The areal fraction of myelinated fibers increased significantly. The number of neuroglias and the areal fraction of neuroglial processes increased significantly in the experimental rats. The data suggest that the major morphological changes are manifested as a decline in the pyramidal dendritic components, especially dendritic spines, and the axons with its terminals from superficial neurons in motor cortex layer V of the kindling rats induced by coriaria lactone, besides the neurogliosis which is similar to that occurring in other long-term seizures.

The inhibition of silica-induced lung inflammation by dexamethasone as measured by bronchoalveolar lavage fluid parameters and peroxynitrite-dependent chemiluminescence

The inhalation of silica has been shown to produce a dramatic inflammatory and toxic response within the lungs of humans and laboratory animals. Currently, no effective treatment exists for workers who may have been exposed to the inhalation of silica. The objective of this study was to develop an animal model in which we could evaluate the effect that anti-inflammatory steroids have on the acute silica-induced pulmonary inflammatory response. Male Fischer 344 rats were pretreated with either dexamethasone (2 mg/kg) or saline vehicle (i.p.) on days 1, 3, and 5. On day 6, the animals from the two groups were then intratracheally instilled with either silica (20 mg/0.5 ml saline vehicle) or saline vehicle (0.5 ml). Twenty-four hours after the instillations in the non-steroid group, significant increases occurred in total protein, total number of cells, neutrophils, and lymphocytes recovered from the lungs of animals treated with silica compared to saline controls. Silica also caused dramatic increases in the luminol-dependent chemiluminescence (LDCL) of lung tissue and bronchoalveolar lavage (BAL) cells. The LDCL reaction was markedly decreased by either superoxide dismutase (SOD) or N-nitro-L-arginine methyl ester hydrochloride (L-NAME). SOD is involved in the enzymatic breakdown of superoxide anion, while L-NAME, a nitric oxide (NO) synthase inhibitor, prevents the formation of NO. When the superoxide anion and NO react, they form the highly oxidizing substance peroxynitrite. This study then implicates peroxynitrite as an agent which may be involved in the silica-induced oxidant lung injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of elevated selenium concentration on selenium accumulation and nitrogen fixation symbiotic activity of Melilotus indica L

Biological and soil factors which contribute to the successful colonization of an annual legume species. Melilotus indica L., in soils with elevated selenium (Se) were studied. This species was introduced into the Kesterson Reservoir in the fresh top soil that was brought in under the Kesterson Cleanup Action to fill lowering pond sites and prevent the formation of ephemeral pools containing hazardous levels of Se. In 4 years since its introduction, it has expanded its range of colonization from the fresh soil fill sites to the native soil sites and contributed 10 to 50% of biomass to the grassland communities. The plant and nodule tissue Se concentrations of the field grown plants were found to be negatively correlated with the soil sulfate concentration. Nutrient solution culture studies discovered that M. indica was able to accumulate 500 micrograms Se g-1 dry weight without a reduction of growth rate. Plants without nodulation were found to accumulate a greater amount of Se and more vulnerable to Se toxicity. Acetylene reduction rate measurements indicate that the nitrogen fixation symbiotic activity appears to be more susceptible to an elevated Se concentration than its host plant. M. indica is a winter weed, and it occurs naturally in the Se-rich soils. It grows actively over the winter and spring and complete its life cycle in May. If the root nodules and root tissues are incorporated into the soil, the rate of soil Se volatilization may be accelerated over the warm summer months. For disposal of the Se-rich plant materials the plant shoot tissues may be harvested for Se-deficient forage supplementation. Therefore, this species may be useful for field management and reclamation of Se-contaminated soils.

Safety of one 52-mumol (50,000 IU) oral dose of vitamin A administered to neonates

A placebo-controlled trial was carried out among 2067 Indonesian neonates to assess the safety of administering one oral 52-mumol (50,000 IU) dose of vitamin A. Infants were assessed for potential acute side-effects before and throughout 48 hours after the dose. The first 965 infants were examined by cranial ultrasound before and at 24 hours after dosing to rule out intracranial haemorrhage and determine the resistive index (RI) of the anterior cerebral artery using duplex Doppler. Groups were comparable at the baseline. A bulging fontanelle occurred in the control and vitamin A groups, respectively, among 2.7% and 4.6% of the infants at 24 hours, and 2.4% and 4.5% of the infants at 48 hours. The groups did not differ in any other sign or symptom assessed. No infant developed intracranial haemorrhage. Mean RI values were normal and not different between groups at baseline or at 24 hours. Mean RI fell during the 24 hours, as normally occurs; the mean decrease was nearly identical in the two groups. A bulging fontanelle was not associated with increased rates of any sign or symptom or with an increase in RI. The 52-mumol dose of oral vitamin A may cause a small increase in intracranial volume in a small proportion of infants, but no increase in intracranial pressure. Acute side-effects following this intervention were rare and mild.

Enhanced calcium influx by parathyroid hormone in identified Helisoma trivolvis snail neurons

The modulation of [Ca2+]i by parathyroid hormone (PTH) has been extensively studied in vertebrates. The present study examined the effects of PTH on [Ca2+]i in isolated invertebrate neurons B5 from buccal ganglia of the pond snail, Helisoma trivolvis, utilizing the Fura-2 fluorescence technique. Bovine PTH, bPTH-(1-84), induced a slow and sustained increase in [Ca2+]i in neurons B5. In contrast, the elevation of extracellular K+ concentration from 1.7 mM to 15 mM induced a rapid and transient increase in [Ca2+]i. Simultaneous application of 15 mM KCl and bPTH-(1-84), or application of 15 mM KCl in the presence of bPTH-(1-84) additively increased [Ca2+]i in neurons B5. An increase in [Ca2+]i in neurons B5 was also induced by a PTH agonist [bPTH-(1-34)], but not by a PTH antagonist [bPTH-(3-34)]. The absence of calcium, or the presence of lanthanum (2 mM) or omega-conotoxin (10 microM), in the bath solution abolished the effect of bPTH-(1-84) on [Ca2+]i. Furthermore, our results demonstrated that the effect of PTH on [Ca2+]i in neurons B5 was not due to the hormonal modulation of voltage-dependent Na+ or K+ channels or a Na+/Ca2+ exchanger. The results from this study show that PTH can modulate [Ca2+]i in an identified invertebrate neuron mainly by promoting extracellular calcium influx via the N-like voltage-dependent calcium channel.

Intrathymic lymphoid precursor cells during fetal thymus development

Our previous studies have demonstrated the presence, in the adult mouse thymus, of a population of early precursor cells able to give rise to T and B lymphocytes but not myeloid cells. This population of cells expresses low levels of CD4 and has been termed the "low CD4 precursors." All these precursors were found to be c-kit positive, and they precede the better known CD4-CD8- precursor stage. In this study, embryonic and neonatal thymuses were examined to see whether a similar low CD4 precursor was part of the pathway of T cell development during ontogeny. A population with the phenotypic characteristics of the adult low CD4 precursor was found from day 15 of embryonic development, although the expression of low levels of CD4 was apparent only from embryonic day 17. Functional tests of these putative precursors showed they had no thymus-reconstituting ability when isolated from thymuses at any time during embryonic life, and very low reconstituting ability even 24 days after birth. These results raise questions about the adult low CD4 precursor as an obligatory stage in the development of T cells in the thymus.

Intrathymic lymphoid precursor cells during fetal thymus development

Our previous studies have demonstrated the presence, in the adult mouse thymus, of a population of early precursor cells able to give rise to T and B lymphocytes but not myeloid cells. This population of cells expresses low levels of CD4 and has been termed the "low CD4 precursors." All these precursors were found to be c-kit positive, and they precede the better known CD4-CD8- precursor stage. In this study, embryonic and neonatal thymuses were examined to see whether a similar low CD4 precursor was part of the pathway of T cell development during ontogeny. A population with the phenotypic characteristics of the adult low CD4 precursor was found from day 15 of embryonic development, although the expression of low levels of CD4 was apparent only from embryonic day 17. Functional tests of these putative precursors showed they had no thymus-reconstituting ability when isolated from thymuses at any time during embryonic life, and very low reconstituting ability even 24 days after birth. These results raise questions about the adult low CD4 precursor as an obligatory stage in the development of T cells in the thymus.

Reconstitution of the Raf-1-MEK-ERK signal transduction pathway in vitro

Raf-1 is a serine/threonine kinase which is essential in cell growth and differentiation. Tyrosine kinase oncogenes and receptors and p21ras can activate Raf-1, and recent studies have suggested that Raf-1 functions upstream of MEK (MAP/ERK kinase), which phosphorylates and activates ERK. To determine whether or not Raf-1 directly activates MEK, we developed an in vitro assay with purified recombinant proteins. Epitope-tagged versions of Raf-1 and MEK and kinase-inactive mutants of each protein were expressed in Sf9 cells, and ERK1 was purified as a glutathione S-transferase fusion protein from bacteria. Raf-1 purified from Sf9 cells which had been coinfected with v-src or v-ras was able to phosphorylate kinase-active and kinase-inactive MEK. A kinase-inactive version of Raf-1 purified from cells that had been coinfected with v-src or v-ras was not able to phosphorylate MEK. Raf-1 phosphorylation of MEK activated it, as judged by its ability to stimulate the phosphorylation of myelin basic protein by glutathione S-transferase-ERK1. We conclude that MEK is a direct substrate of Raf-1 and that the activation of MEK by Raf-1 is due to phosphorylation by Raf-1, which is sufficient for MEK activation. We also tested the ability of protein kinase C to activate Raf-1 and found that, although protein kinase C phosphorylation of Raf-1 was able to stimulate its autokinase activity, it did not stimulate its ability to phosphorylate MEK.

Comparison of four methods in the diagnosis of Clostridium difficile disease

Nine hundred forty-five stool specimens from patients suspected of having Clostridium difficile disease were examined using a cell culture cytotoxicity assay (CTA), two enzyme immunoassay (EIA) kits (Cytoclone for toxins A and B; VIDAS for toxin A) and a latex agglutination assay (CDT). One hundred nineteen specimens had positive titers (> or = 90) in the CTA; clinical review of 16 discordant samples and 49 controls supported the significance of 90 as the positive cut-off titer. The performance of the two EIAs and the latex assay was assessed relative to CTA titers of the samples. Sensitivity was < or = 50% for all three assays for the 24 specimens with CTA titers of 90, but it reached 97-100% for the two EIAs and 84% for the latex assay at titers of > or = 2,250. The Cytoclone EIA exhibited higher sensitivity at the lower positive titers. Overall, specificity of the methods ranged from 96.7% (CDT latex assay) to 99.1% (Cytoclone EIA).

TCR beta and TCR alpha gene enhancers confer tissue- and stage-specificity on V(D)J recombination events

We describe transgenic mice carrying germline variable gene segments associated with either the T cell receptor (TCR) beta or alpha gene enhancers (E beta or E alpha). Transgenic constructs underwent high rates of site-specific rearrangements predominantly in T cells from independent mice. Rearrangements of the E beta-containing transgenes began at different stages of T cell differentiation in embryonic and adult thymus than did the E alpha-containing ones, with a pattern superimposable upon the patterns of TCR beta or TCR alpha gene expression, respectively. We demonstrate that sequences within the TCR beta and TCR alpha gene enhancers confer tissue- and stage-specificity upon the V(D)J recombination events affecting adjacent gene segments. The patterns of transgene expression also gave information on developmental events and lineage relationships (gamma delta versus alpha beta) during T cell development.

Sequence-dependent differences in DNA structure influence the affinity of P22 operator for P22 repressor

Although the central bases of the P22 operator are not contacted by P22 repressor, the affinity of repressor for operator varies with the sequence of these bases. The KMnO4 and .OH radical susceptibilities of the central bases of the operator vary with their sequence, whether or not the operator is complexed with protein or free in solution. These data show that the minor groove of a lower affinity operator which bears central C-G bases (9C) is more open than that of the higher affinity 9T operator, which bears central T-A bases. This difference in minor groove width is seen both in the absence and presence of repressor. Results of ring closure studies show that, in the absence of repressor, an operator bearing central C.G base pairs operator is overtwisted relative to an operator which contains central T.A base pairs. The binding of P22 repressor unwinds the two operators to similar extents, thereby preserving the relative differences in twists of these DNAs. Although repressor alters the twist of the operator DNA, our results show that differences in DNA torsional flexibility have no role in determining the affinity of operator for protein. Instead, the results indicate that central sequences affect operator affinity for protein by limiting the degree to which the operator can be deformed in the protein-DNA complex. The stability of the complex is apparently modulated, in a central sequence-dependent manner, by alterations in the number and/or geometry of protein-DNA contacts.