Improvement of immune dysregulation in individuals with long COVID at 24-months following SARS-CoV-2 infection

This study investigates the humoral and cellular immune responses and health-related quality of life measures in individuals with mild to moderate long COVID (LC) compared to age and gender matched recovered COVID-19 controls (MC) over 24 months. LC participants show elevated nucleocapsid IgG levels at 3 months, and higher neutralizing capacity up to 8 months post-infection. Increased spike-specific and nucleocapsid-specific CD4+ T cells, PD-1, and TIM-3 expression on CD4+ and CD8+ T cells were observed at 3 and 8 months, but these differences do not persist at 24 months. Some LC participants had detectable IFN-γ and IFN-β, that was attributed to reinfection and antigen re-exposure. Single-cell RNA sequencing at the 24 month timepoint shows similar immune cell proportions and reconstitution of naïve T and B cell subsets in LC and MC. No significant differences in exhaustion scores or antigen-specific T cell clones are observed. These findings suggest resolution of immune activation in LC and return to comparable immune responses between LC and MC over time. Improvement in self-reported health-related quality of life at 24 months was also evident in the majority of LC (62%). PTX3, CRP levels and platelet count are associated with improvements in health-related quality of life.

Immunological dysfunction persists for 8 months following initial mild-to-moderate SARS-CoV-2 infection

A proportion of patients surviving acute coronavirus disease 2019 (COVID-19) infection develop post-acute COVID syndrome (long COVID (LC)) lasting longer than 12 weeks. Here, we studied individuals with LC compared to age- and gender-matched recovered individuals without LC, unexposed donors and individuals infected with other coronaviruses. Patients with LC had highly activated innate immune cells, lacked naive T and B cells and showed elevated expression of type I IFN (IFN-β) and type III IFN (IFN-λ1) that remained persistently high at 8 months after infection. Using a log-linear classification model, we defined an optimal set of analytes that had the strongest association with LC among the 28 analytes measured. Combinations of the inflammatory mediators IFN-β, PTX3, IFN-γ, IFN-λ2/3 and IL-6 associated with LC with 78.5-81.6% accuracy. This work defines immunological parameters associated with LC and suggests future opportunities for prevention and treatment.

The discriminatory power of the T cell receptor

T cells use their T cell receptors (TCRs) to discriminate between lower-affinity self and higher-affinity non-self peptides presented on major histocompatibility complex (pMHC) antigens. Although the discriminatory power of the TCR is widely believed to be near-perfect, technical difficulties have hampered efforts to precisely quantify it. Here, we describe a method for measuring very low TCR/pMHC affinities and use it to measure the discriminatory power of the TCR and the factors affecting it. We find that TCR discrimination, although enhanced compared with conventional cell-surface receptors, is imperfect: primary human T cells can respond to pMHC with affinities as low as K_D ∼ 1 mM. The kinetic proofreading mechanism fit our data, providing the first estimates of both the time delay (2.8 s) and number of biochemical steps (2.67) that are consistent with the extraordinary sensitivity of antigen recognition. Our findings explain why self pMHC frequently induce autoimmune diseases and anti-tumour responses, and suggest ways to modify TCR discrimination.

Multi-resolution dimer models in heat baths with short-range and long-range interactions

This work investigates multi-resolution methodologies for simulating dimer models. The solvent particles which make up the heat bath interact with the monomers of the dimer either through direct collisions (short-range) or through harmonic springs (long-range). Two types of multi-resolution methodologies are considered in detail: (a) describing parts of the solvent far away from the dimer by a coarser approach; (b) describing each monomer of the dimer by using a model with different level of resolution. These methodologies are then used to investigate the effect of a shared heat bath versus two uncoupled heat baths, one for each monomer. Furthermore, the validity of the multi-resolution methods is discussed by comparison to dynamics of macroscopic Langevin equations.

Scalable population-level modelling of biological cells incorporating mechanics and kinetics in continuous time

The processes taking place inside the living cell are now understood to the point where predictive computational models can be used to gain detailed understanding of important biological phenomena. A key challenge is to extrapolate this detailed knowledge of the individual cell to be able to explain at the population level how cells interact and respond with each other and their environment. In particular, the goal is to understand how organisms develop, maintain and repair functional tissues and organs. In this paper, we propose a novel computational framework for modelling populations of interacting cells. Our framework incorporates mechanistic, constitutive descriptions of biomechanical properties of the cell population, and uses a coarse-graining approach to derive individual rate laws that enable propagation of the population through time. Thanks to its multiscale nature, the resulting simulation algorithm is extremely scalable and highly efficient. As highlighted in our computational examples, the framework is also very flexible and may straightforwardly be coupled with continuous-time descriptions of biochemical signalling within, and between, individual cells.

Topology-dependent density optima for efficient simultaneous network exploration

A random search process in a networked environment is governed by the time it takes to visit every node, termed the cover time. Often, a networked process does not proceed in isolation but competes with many instances of itself within the same environment. A key unanswered question is how to optimize this process: How many concurrent searchers can a topology support before the benefits of parallelism are outweighed by competition for space? Here, we introduce the searcher-averaged parallel cover time (APCT) to quantify these economies of scale. We show that the APCT of the networked symmetric exclusion process is optimized at a searcher density that is well predicted by the spectral gap. Furthermore, we find that nonequilibrium processes, realized through the addition of bias, can support significantly increased density optima. Our results suggest alternative hybrid strategies of serial and parallel search for efficient information gathering in social interaction and biological transport networks.

Reactions, diffusion, and volume exclusion in a conserved system of interacting particles

Complex biological and physical transport processes are often described through systems of interacting particles. The effect of excluded volume on these transport processes has been well studied; however, the interplay between volume exclusion and reactions between heterogenous particles is less well studied. In this paper we develop a framework for modeling reaction-diffusion processes which directly incorporates volume exclusion. We consider simple reactions (unimolecular and bimolecular) that conserve the total number of particles. From an off-lattice microscopic individual-based model we use the Fokker-Planck equation and the method of matched asymptotic expansions to derive a low-dimensional macroscopic system of nonlinear partial differential equations describing the evolution of the particles. A biologically motivated, hybrid model of chemotaxis with volume exclusion is explored, where reactions occur at rates dependent upon the chemotactic environment. Further, we show that for reactions that require particle contact the appropriate reaction term in the macroscopic model is of lower order in the asymptotic expansion than the nonlinear diffusion term. However, we find that the next reaction term in the expansion is needed to ensure good agreement with simulations of the microscopic model. Our macroscopic model allows for more direct parametrization to experimental data than existing models.

Racial Differences in Selection of Ideal Body Size by Adolescent Females

Cultural differences may partially account for the fact that more black women than white women are overweight in the United States. This study measured perceptions of ideal body size among 93 black and 80 white females, 14-17 years old, who were randomly selected from three public high schools in a southeastern state. The subjects' height and weight were measured along with their estimates of their mother's body size, weight control attitudes, and demographic variables. Blacks preferred a significantly larger body size than whites when asked to select ideal body size (p = 0.045). Subjects who estimated their mother's size to be larger, also selected a larger ideal body size (p = .047). Those who perceived themselves as too fat were more likely to skip meals to help control their weight, compared with those who perceived themselves as normal or too thin (p = .003). Approximately 30% of the sample was overweight or obese. There were not significant racial differences in weight or BMI. These results suggest that overweight is more acceptable among black females than among white females and may help explain why more black females are obese.

Kinetics of Cellulose Digestion by Fibrobacter succinogenes S85

Growing cultures of Fibrobacter succinogenes S85 digested cellulose at a rapid rate, but nongrowing cells and cell extracts did not have detectable crystalline cellulase activity. Cells that had been growing exponentially on cellobiose initiated cellulose digestion and succinate production immediately, and cellulose-dependent succinate production could be used as an index of enzyme activity against crystalline cellulose. Cells incubated with cellulose never produced detectable cellobiose, and cells that were preincubated for a short time with thiocellobiose lost their ability to digest cellulose (competitive inhibition [K(infi)] of only 0.2 mg/ml or 0.56 mM). Based on these results, the crystalline cellulases of F. succinogenes were very sensitive to feedback inhibition. Different cellulose sources bound different amounts of Congo red, and the binding capacity was HCl-regenerated cellulose > ball-milled cellulose > Sigmacel > Avicel > filter paper. Congo red binding capacity was highly correlated with the maximum rates of metabolism of cellulose digestion and inversely related to K(infm). Congo red (250 (mu)g/ml) did not inhibit the growth of F. succinogenes S85 on cellobiose, but this concentration of Congo red inhibited the rate of ball-milled cellulose digestion. A Lineweaver-Burk plot of ball-milled cellulose digestion rate versus the amount of cellulose indicated that Congo red was a competitive inhibitor of cellulose digestion (K(infi) was 250 (mu)g/ml).

Regulation of beta-1,4-Endoglucanase Synthesis in Thermomonospora fusca

In Thermomonospora fusca YX, endocellulase synthesis varies over a 100-fold range depending on the carbon source used. This study shows that the variation is caused by two regulatory mechanisms: an induction mechanism that increases the rate of endocellulase synthesis about 20-fold and a growth rate-dependent repression mechanism that changes the rate of synthesis over a 6-fold range in both induced and noninduced cells. In T. fusca, endocellulase synthesis can be induced by cellulose, cellobiose, or cellodextrin. Cellulase is involved in inducer generation from cellulose. Growth rate-dependent repression can be reversed by limiting cultures for carbon, nitrogen, or, to a lesser extent, phosphorus. Further evidence for two separate regulatory mechanisms is provided by the isolation of mutants (CC-1 and CC-2) whose endocellulases are synthesized constitutively but are still sensitive to growth rate-dependent repression. These conclusions about total endocellulase synthesis were extended to the individual endocellulases by showing that three T. fusca endocellulases are coordinately regulated.

QUANTITATIVE STUDIES ON THE BEHAVIOR OF SENSITIZED LYMPHOCYTES IN VITRO : I. RELATIONSHIP OF THE DEGREE OF DESTRUCTION OF HOMOLOGOUS TARGET CELLS TO THE NUMBER OF LYMPHOCYTES AND TO THE TIME OF CONTACT IN CULTURE AND CONSIDERATION OF THE EFFECTS OF ISOIMMUNE SERUM

When lymphoid cells, derived from rats immunized with respect to homologous skin, were cultured with target cells originally of donor origin, cytocidal and cytostatic activities of the attacking lymphocytes became evident. By application of a sensitive and reproducible quantitative assay system, various aspects of the mechanism of this destructive interaction between target cells and lymphocytes were examined with the following results. 1. The degree of survival of target cells was inversely related to the number of sensitized lymphocytes. Graphic plots of the data indicated that this relationship was an exponential one similar to "single-hit" inactivation phenomena. One interpretation which could be placed on these results is that a single lymphocyte, if immunologically active, was sufficient to destroy or at least have a detectably adverse effect on one target cell. Furthermore, from such a model it could be computed that, of the lymphocytes derived from an immunized animal, approximately 1 to 2 per cent of the cells were immunologically active; i.e., capable of demonstrable destructive activities against homologous target cells in vitro. 2. Morphological studies on the effect of sensitized lymphoid cells on homologous target cells, aftervarious lengths of time in culture, showed that by 7 hours of incubation, the attacking lymphocytes firmly adhered to the target cells. The cytotoxic effect of these lymphocytes generally occurred after the 20th hour. Quantitative studies supported this conclusion; the latent period, i.e., the time required for detectable degrees of target cell destruction to occur, was approximately 20 hours. 3. A consequence of the incubation of target cells with normal lymphoid cells or even with small numbers of sensitized lymphoid cells was an increase in the rate of division of the target cells. As might be expected, this was reflected in a shorter doubling time of these cells. 4. Extracts prepared from sonically disrupted sensitized lymphocytes proved to be no more deleterious to target cells than similar preparations from normal lymphoid cells. Furthermore, no evidence could be obtained that sensitized lymphoid cells, separated from target cells by a Millipore membrane, were cytocidally effective. These data indicated that if a cell-bound substance is involved in the destruction of homologous cells, either it is not toxic by itself, or it cannot be detached from the sensitized cells. In any case, close apposition of the lymphocytes to the target cells is apparently required for the destruction of the latter in vitro. 5. Serum obtained from immunized animals, if heat-inactivated, did not adversely affect homologous target cells; if employed fresh, slight degrees of toxicity resulted. Specific isoimmune sera did not impart any detectable degrees of immunological reactivity upon otherwise normal lymphoid cells. Immune sera, even in high concentrations, did not augment the effect of sensitized lymphoid cells upon homologous target cells; rather a slight inhibitory effect of these sera was detected. 6. Attempts to detect the presence of complement activity, which might have been provided by the lymphoid cells in culture, were unsuccessful. On the basis of these results, it was suggested that the destruction of homologous target cells by sensitized lymphoid cells occurs as a two step process. First, the attacking lymphocytes attach to their targets via a non-toxic cell-bound substance having an immunologic specificity, and then, destruction of the target cells follows the result of some process dependent on the metabolic activity of the attacking lymphoid cells.

Review paper: origin and molecular pathology of adrenocortical neoplasms

Neoplastic adrenocortical lesions are common in humans and several species of domestic animals. Although there are unanswered questions about the origin and evolution of adrenocortical neoplasms, analysis of human tumor specimens and animal models indicates that adrenocortical tumorigenesis involves both genetic and epigenetic alterations. Chromosomal changes accumulate during tumor progression, and aberrant telomere function is one of the key mechanisms underlying chromosome instability during this process. Epigenetic changes serve to expand the size of the uncommitted adrenal progenitor population, modulate their phenotypic plasticity (i.e., responsiveness to extracellular signals), and increase the likelihood of subsequent genetic alterations. Analyses of heritable and spontaneous types of human adrenocortical tumors documented alterations in either cell surface receptors or their downstream effectors that impact neoplastic transformation. Many of the mutations associated with benign human adrenocortical tumors result in dysregulated cyclic adenosine monophosphate signaling, whereas key factors and/or signaling pathways associated with adrenocortical carcinomas include dysregulated expression of the IGF2 gene cluster, activation of the Wnt/beta-catenin pathway, and inactivation of the p53 tumor suppressor. A better understanding of the factors and signaling pathways involved in adrenal tumorigenesis is necessary to develop targeted pharmacologic and genetic therapies.

Cytochrome b5 expression in gonadectomy-induced adrenocortical neoplasms of the domestic ferret (Mustela putorius furo)

Whereas the adrenal glands of healthy ferrets produce only limited amounts of androgenic steroids, adrenocortical neoplasms that arise in neutered ferrets typically secrete androgens or their derivative, estrogen. The 17,20-lyase activity of cytochrome P450 17alpha-hydroxylase/17,20-lyase (P450c17) must increase to permit androgen biosynthesis in neoplastic adrenal tissue. We screened ferret adrenocortical tumor specimens for expression of cytochrome b(5) (cyt b(5)), an allosteric regulator that selectively enhances the 17,20-lyase activity of P450c17. Cyt b(5) immunoreactivity was evident in 24 of 25 (96%) adrenocortical adenomas/carcinomas from ferrets with signs of ectopic sex steroid production. Normal adrenocortical cells lacked cyt b(5), which may account for the low production of adrenal androgens in healthy ferrets. Other markers characteristic of gonadal somatic cells, such as luteinizing hormone receptor, aromatase, and GATA4, were coexpressed with cyt b(5) in some of the tumors. We concluded that cyt b(5) is upregulated during gonadectomy-induced adrenocortical neoplasia and is a marker of androgen synthetic potential in these tumors.

Molecular cloning, characterization, and expression studies of water buffalo (Bubalus bubalis) somatotropin

Cloning, high-level expression, and characterization of the somatotropin (ST) gene of an indigenous Nili-Ravi breed of water buffalo Bubalus bubalis (BbST) are described. Coding, non-coding, and promoter regions of BbST were amplified and sequenced. Sequence analysis revealed several silent and two interesting point mutations on comparison with STs of other vertebrate species. One interesting variation in the BbST sequence was the replacement of a conserved glutamine residue by arginine. A plasmid was also constructed for the production of BbST in Escherichia coli BL21 (RIPL) CodonPlus, under the control of IPTG-inducible T7-lac promoter. High-level expression could be obtained by synthesizing a codon-optimized ST gene and expressing it in the form of inclusion bodies. The inclusion bodies represented over 20% of the E. coli cellular proteins. The biologically active conformation of purified BbST was confirmed by its efficient growth promoting activity in Nb2 cell proliferation assay. The expression system and purification strategy employed promise to be a useful approach to produce BbST for further use in structure-function studies and livestock industry.

Modelling nitrogen saturation and carbon accumulation in heathland soils under elevated nitrogen deposition

A simple model of nitrogen (N) saturation, based on an extension of the biogeochemical model MAGIC, has been tested at two long-running heathland N manipulation experiments. The model simulates N immobilisation as a function of organic soil C/N ratio, but permits a proportion of immobilised N to be accompanied by accumulation of soil carbon (C), slowing the rate of C/N ratio change and subsequent N saturation. The model successfully reproduced observed treatment effects on soil C and N, and inorganic N leaching, for both sites. At the C-rich upland site, N addition led to relatively small reductions in soil C/N, low inorganic N leaching, and a substantial increase in organic soil C. At the C-poor lowland site, soil C/N ratio decreases and N leaching increases were much more dramatic, and soil C accumulation predicted to be smaller. The study suggests that (i) a simple model can effectively simulate observed changes in soil and leachate N; (ii) previous model predictions based on a constant soil C pool may overpredict future N leaching; (iii) N saturation may develop most rapidly in dry, organic-poor, high-decomposition systems; and (iv) N deposition may lead to significantly enhanced soil C sequestration, particularly in wet, nutrient-poor, organic-rich systems.

GATA-4 is a granulosa cell factor employed in inhibin-alpha activation by the TGF-beta pathway

Part of heterodimeric inhibin, inhibin-alpha is crucial for mammalian ovarian function. Regulation of inhibin-alpha expression in granulosa cells is both endocrine, primarily by follicle-stimulating hormone (FSH), and paracrine, primarily by members of the transforming growth factor beta (TGF-beta) superfamily. Smad proteins transmit TGF-beta signals to the nucleus, but the cooperating transcription factors involved in inhibin-alpha promoter activation remain unknown. Transcription factor GATA-4 regulates inhibin-alpha in gonadal cells, and the FSH cascade activates GATA-4. We hypothesized that the TGF-beta signalling cascade and GATA-4 also cooperate to regulate inhibin-alpha expression. In KK-1 granulosa tumour cells, which resemble normal granulosa cells and express inhibin-alpha, we found that TGF-beta upregulated GATA-4 expression. Transient transfection experiments in KK-1 cells demonstrated that dominant negative GATA-4 variants or mutations of GATA-binding sites in the inhibin-alpha promoter attenuated TGF-beta-induced gene activation. In GATA-4-deficient COS-7 cells, TGF-beta enhanced the expression of the inhibin-alpha promoter only in the presence of exogenous GATA-4. Smad3, but not Smad2, cooperated with GATA-4 in the transcriptional activation of the inhibin-alpha promoter, and immunoprecipitation experiments in KK-1 cells revealed a physical Smad3:GATA-4 interaction. Our data suggest that GATA-4, interacting with Smad3, is a cofactor for TGF-beta signalling to activate inhibin-alpha in granulosa cells.

Gonadectomy-induced adrenocortical neoplasia in the domestic ferret (Mustela putorius furo) and laboratory mouse

Sex steroid-producing adrenocortical adenomas and carcinomas occur frequently in neutered ferrets, but the molecular events underlying tumor development are not well understood. Prepubertal gonadectomy elicits similar tumors in certain inbred or genetically engineered strains of mice, and these mouse models shed light on tumorigenesis in ferrets. In mice and ferrets, the neoplastic adrenocortical cells, which functionally resemble gonadal steroidogenic cells, arise from progenitors in the subcapsular or juxtamedullary region. Tumorigenesis in mice is influenced by the inherent susceptibility of adrenal tissue to gonadectomy-induced hormonal changes. The chronic elevation in circulating luteinizing hormone that follows ovariectomy or orchiectomy is a prerequisite for neoplastic transformation. Gonadectomy alters the plasma or local concentrations of steroid hormones and other factors that affect adrenocortical tumor development, including inhibins, activins, and Müllerian inhibiting substance. GATA-4 immunoreactivity is a hallmark of neoplastic transformation, and this transcription factor might serve to integrate intracellular signals evoked by different hormones. Synergistic interactions among GATA-4, steroidogenic factor-1, and other transcription factors enhance expression of inhibin-alpha and genes critical for ectopic sex steroid production, such as cytochrome P450 17alpha-hydroxylase/17,20 lyase and aromatase. Cases of human adrenocortical neoplasia have been linked to precocious expression of hormone receptors and to mutations that alter the activity of G-proteins or downstream effectors. Whether such genetic changes contribute to tissue susceptibility to neoplasia in neutered ferrets and mice awaits further study.

Dyskeratosis congenita -- a disease of dysfunctional telomere maintenance

Dyskeratosis congenita (DC) is a rare inherited bone marrow failure syndrome associated with abnormalities of the skin, fingernails, and tongue. Other clinical manifestations may include epiphora, lung fibrosis, liver cirrhosis, osteoporosis, and a predisposition to develop a variety of malignancies. The clinical picture often resembles that of a premature aging syndrome and tissues affected are those with a high cell turnover. DC has been linked to mutations in at least four distinct genes, three of which have been identified. The product of these genes, dyskerin, the telomerase RNA (TERC), and the catalytic unit of telomerase (TERT) are part of a ribonucleoprotein complex, the telomerase enzyme, that is essential for the elongation and maintenance of chromosome ends or telomeres. All patients with DC have excessively short telomeres, indicating that the underlying defect in these individuals is an inability to maintain the telomeres. The purpose of the current review is to highlight recent insights into the molecular pathogenesis of DC. We discuss the impact these findings have on our current understanding of telomere function and maintenance, and on the diagnosis, management, and treatment of patients with conditions caused by dysfunctional telomeres.

Nude mice as a model for gonadotropin-induced adrenocortical neoplasia

Certain inbred mice (e.g., DBA/2J, CE) develop sex steroid producing adrenocortical tumors following gonadectomy. This adrenal response is thought to result from an unopposed increase in circulating gonadotropins and/or a decrease in factor(s) of gonadal origin. To differentiate between these two possibilities, we utilized the NU/J strain of nude mice, which are immunologically compromised and therefore permissive to xenografts. One group of female nude mice was gonadectomized, while another group of females received xenografts of CHO cells stably transfected with human chorionic gonadotropin (hCG). After 1-2 months, subcapsular adrenocortical neoplasms containing sex steroid-producing cells were observed in both groups. We conclude that high levels of circulating gonadotropins are sufficient to induce adrenocortical tumorigenesis, even in the presence of intact gonads.

Transcription factor GATA-4 is a marker of anaplasia in adrenocortical neoplasms of the domestic ferret (Mustela putorius furo)

Adrenocortical neoplasms are a common cause of morbidity in neutered ferrets. Recently we showed that gonadectomized DBA/2J mice develop adrenocortical tumors that express transcription factor GATA-4. Therefore, we screened archival specimens of adrenocortical neoplasms from neutered ferrets to determine whether GATA-4 could be used as a tumor marker in this species. Nuclear immunoreactivity for GATA-4 was evident in 19/22 (86%) of ferret adrenocortical carcinomas and was prominent in areas exhibiting myxoid differentiation. Normal adrenocortical cells lacked GATA-4 expression. Two other markers of adrenocortical tumors in gonadectomized mice, inhibin-alpha and luteinizing hormone receptor, were coexpressed with GATA-4 in some of the ferret tumors. No GATA-4 expression was observed in three cases of nodular hyperplasia, but patches of anaplastic cells expressing GATA-4 were evident in 7/14 (50%) of tumors classified as adenomas. We conclude that GATA-4 can function as a marker of anaplasia in ferret adrenocortical tumors.

Corn fiber hydrolysis by Thermobifida fusca extracellular enzymes

Thermobifida fusca was grown on cellulose (Solka-Floc), xylan or corn fiber and the supernatant extracellular enzymes were concentrated. SDS gels showed markedly different protein patterns for the three different carbon sources. Activity assays on a variety of synthetic and natural substrates showed major differences in the concentrated extracellular enzyme activities. These crude enzyme preparations were used to hydrolyze corn fiber, a low-value biomass byproduct of the wet milling of corn. Approximately 180 mg of reducing sugar were produced per gram of untreated corn fiber. When corn fiber was pretreated with alkaline hydrogen peroxide, up to 429 mg of reducing sugars were released per gram of corn fiber. Saccharification was enhanced by the addition of beta-glucosidase or by the addition of a crude xylanase preparation from Aureobasidium sp.

Computational and experimental studies of the catalytic mechanism of Thermobifida fusca cellulase Cel6A (E2)

Mutagenesis experiments suggest that Asp79 in cellulase Cel6A (E2) from Thermobifida fusca has a catalytic role, in spite of the fact that this residue is more than 13 A from the scissile bond in models of the enzyme-substrate complex built upon the crystal structure of the protein. This suggests that there is a substantial conformational shift in the protein upon substrate binding. Molecular mechanics simulations were used to investigate possible alternate conformations of the protein bound to a tetrasaccharide substrate, primarily involving shifts of the loop containing Asp79, and to model the role of water in the active site complex for both the native conformation and alternative low-energy conformations. Several alternative conformations of reasonable energy have been identified, including one in which the overall energy of the enzyme-substrate complex in solution is lower than that of the conformation in the crystal structure. This conformation was found to be stable in molecular dynamics simulations with a cellotetraose substrate and water. In simulations of the substrate complexed with the native protein conformation, the sugar ring in the -1 binding site was observed to make a spontaneous transition from the (4)C(1) conformation to a twist-boat conformer, consistent with generally accepted glycosidase mechanisms. Also, from these simulations Tyr73 and Arg78 were found to have important roles in the active site. Based on the results of these various MD simulations, a new catalytic mechanism is proposed. Using this mechanism, predictions about the effects of changes in Arg78 were made which were confirmed by site-directed mutagenesis.

Transcription factors GATA-4 and GATA-6 during mouse and human adrenocortical development

Our earlier work implicates transcription factors GATA-4 and GATA-6 in the murine adrenal. We have now studied their expression during mouse and human adrenal development in detail. GATA-4 and GATA-6 mRNAs are readily detectable from embryonic day 15 in mouse and gestational week 19 in human adrenal cortex. In postnatal adrenal, GATA-4 expression is down-regulated, whereas GATA-6 mRNA and protein continue to be abundantly present. In a human adrenocortical cell line NCI-H295R, GATA-6 mRNA is up-regulated by cAMP. This cell line does not express GATA-4. Our findings suggest that GATA-6 expression is hormonally controlled, and required throughout adrenal development from fetal to adult age. GATA-4, on the other hand, may serve a role in fetal adrenal gene regulation.

A meta-analytic inquiry into the relationship between selected risk factors and problem behavior

Identifying the predictors of problem behavior is essential both for understanding the causes of such behavior and for preventing it. Although a great deal of research has sought to identify the factors predictive of problem behavior, much of the research to date has been correlational and tells us little about causality. This study attempts to improve on the correlational research by applying meta-analytic techniques to existing experimental and quasi-experimental studies of school-based prevention. The following 3 risk factors were examined: academic performance, bonding to school, and social competency skills. The most convincing evidence of a relationship between risk and problem behavior was found for bonding to school. Positive changes in attachment and commitment to school resulting from the preventive interventions were consistently accompanied by positive changes in problem behavior. Preventive interventions that produced improvements in academic performance produced moderate improvements in problem behavior. With regard to social competence, the association depended in large part on the type of measure used to assess social competency skills. Changes in self-report measures of social competency were unrelated to changes in problem behavior, whereas a strong positive correlation was observed between changes in ratings and observations of social competency by others and improvements in problem behavior.

The role of method in treatment effectiveness research: evidence from meta-analysis

A synthesis of 319 meta-analyses of psychological, behavioral, and educational treatment research was conducted to assess the influence of study method on observed effect sizes relative to that of substantive features of the interventions. An index was used to estimate the proportion of effect size variance associated with various study features. Study methods accounted for nearly as much variability in study outcomes as characteristics of the interventions. Type of research design and operationalization of the dependent variable were the method features associated with the largest proportion of variance. The variance as a result of sampling error was about as large as that associated with the features of the interventions studied. These results underscore the difficulty of detecting treatment outcomes, the importance of cautiously interpreting findings from a single study, and the importance of meta-analysis in summarizing results across studies.

A selective inhibitor of Escherichia coli prephenate dehydratase

To identify selective prephenate dehydratase (PDT) inhibitors, a series of substituted biphenic acid derivatives was synthesized using the Ullmann reaction. Screening experiments identified 18 as a promising new PDT inhibitor.

The way in which intervention studies have "personality" and why it is important to meta-analysis

Intervention studies represent webs of interrelated substantive and methodological characteristics that take on different patterns in different studies and different intervention areas. All too often, meta-analysts do not give close attention to the possibility that these interrelated differences among studies are related in complex ways to study effect sizes and, consequently, run considerable risk of reporting results that are misleading or flatly wrong. To remedy this situation, improvements are needed in both the method and practice of meta-analysis so that greater attention can be given to effect size variation, the generalizability of study results, and the systematic multivariate relationships between study characteristics and the effect sizes reported in those studies.

Adrenocortical tumorigenesis in transgenic mice: the role of luteinizing hormone receptor and transcription factors GATA-4 and GATA-61

Transgenic (TG) mice, bearing the Simian Virus 40 T-antigen (Tag) under a 6-kb fragment of the murine inhibin alpha-subunit promoter (inhalpha), develop gonadal tumors of granulosa or Leydig cell origin with 100% penetrance by the age of 5-7 months. When these TG mice were gonadectomized prepubertally, between 21-25 days of life, adrenal gland tumors were observed in each mouse by the age of 5-7 months. No adrenal tumors were detected in any intact TG, gonadectomized or intact or control non-TG littermates. The adrenocortical tumors appeared to originate from the X-zone of the adrenal cortex. If functional gonadectomy was induced by GnRH antagonist treatment or by cross-breeding of the TG mice into hypogonadotropic hpg genetic background, neither gonadal nor adrenal tumorigenesis appeared. This prompted a hypothesis that adrenal tumor development in inhalpha/Tag TG mice is related to elevated gonadotropin secretion, which is the most obvious difference between the surgical and functional gonadectomy models. The adrenal tumors and a cell line (Calpha1) derived from them, was found to express luteinizing hormone receptor (LHR), but no FSHR, and hCG treatment stimulated their proliferation. No FSHR was found in the adrenal glands. On the basis of this it was suggested that expression of the potent oncogene T-antigen, allow LH in adrenocortical cells to function as a tumor promoter, and induction of high level functional LHR expression in adrenal tumors. Given the induction of expression and regulation of the GATA-4 and GATA-6 zinc finger family of transcription factors in the gonads by gonadotropins, it was in our interest to explore their expression in the adrenals. We utilized the inalpha/Tag TG mouse model and pathological human adrenal samples to explore the role of GATA-4 and GATA-6 in adrenocortical tumorigenesis. Abundant GATA-6 mRNA expression was found in normal control adrenal cortex during mouse development, whereas GATA-4 mRNA was undetectable. In striking contrast to this, GATA-6 was absent from murine adrenocortical tumors, while GATA-4 mRNA expression was dramatically upregulated in the murine adrenal tumors as well as in human adrenocortical carcinomas. Taken together, these results suggest different roles for GATA-4 and GATA-6 in the adrenal gland, and implicate GATA-4 in adrenal LHR expression and tumorigenesis. Immunohistochemical detection of GATA-4 may serve as a useful marker in differential diagnosis of human adrenal tumors. In addition, the inhalpha/Tag TG model will be helpful for exploring the molecular mechanisms underlying adrenocortical tumorigenesis, ectopic LHR expression in adrenals and the GATA-4/LHR interaction that is related to adrenal tumorigenesis in TG mice.

Bioaccumulation of mercury from wastewater by genetically engineered Escherichia coli

Genetically engineered E. coli, which express both a Hg2+ transport system and metallothionein, were tested for their ability to remove mercury from wastewater. The wastewater contained more than ten different ions, including 2.58 mg/l mercury, and its pH was 9.6. Mercury uptake was faster from the wastewater than from distilled water, probably because of the higher ionic strength, as the high pH had little effect on mercury accumulation. EDTA also stimulated mercury uptake rather than inhibiting it. A hollow-fiber bioreactor was used to retain induced cells for continuous mercury uptake. The cells removed more than 99% of the mercury in the wastewater and the final amount of mercury accumulated was 26.8 mg/g cell dry weight, while none of the other ions were removed from the water. These results indicated that the induced cells had a high affinity and specificity for mercury.

Cloning and biochemical characterization of BglC, a beta-glucosidase from the cellulolytic actinomycete Thermobifida fusca

An operon, bglABC, that encodes two sugar permeases and a beta-glucosidase was cloned from a cellulolytic actinomycete, Thermobifida fusca, into Escherichia coli and sequenced. The bglC gene encoding an intracellular beta-glucosidase (beta-d-glucoside glucohydrolase, EC 3.2.1.21) belonging to glycosyl hydrolase family 1 was subcloned and expressed in E. coli. The purified enzyme (MW 53,407 Da; pI 4.69) hydrolyzed substrates containing both beta 1 --> 4 and beta 1 --> 2 glycosidic bonds, and was most active against cellobiose (Vmax = 29, Km = 0.34 mm), cellotriose, cellotetraose, and sophorose. The enzyme also showed aryl-beta-glucosidase activity on p-nitrophenyl-beta-d-glucopyranoside and p-nitrophenyl-beta-d-cellobioside. BglC had a pH optimum of 7.0 and a temperature optimum of 50 degrees C. The enzyme was stable at 60 degrees C, but was rapidly inactivated at 65 degrees C. BglC was inhibited by low concentrations of gluconolactone, but was insensitive to end-product inhibition by glucose and was not affected by Ca or Mg ions or EDTA. Its properties are well suited for use in a process to hydrolyze biomass cellulose to glucose.

Identification of MHC class II-restricted peptide ligands, including a glutamic acid decarboxylase 65 sequence, that stimulate diabetogenic T cells from transgenic BDC2.5 nonobese diabetic mice

Nonobese diabetic (NOD) mice spontaneously develop insulitis and destruction of pancreatic islet beta cells similar to type 1 diabetes mellitis in humans. Insulitis also occurs in the BDC2.5 TCR transgenic line of NOD mice that express the rearranged TCR alpha- and beta-chain genes of a diabetogenic NOD CD4 T cell clone. When activated with syngeneic islet cells in culture, BDC2.5 T cells adoptively transfer disease to NOD recipients, but the identity of the islet cell Ag responsible for pathogenicity is not known. To characterize the autoantigen(s) involved, BDC2.5 T cells were used to screen a combinatorial peptide library arranged in a positional scanning format. We identified more than 100 decapeptides that stimulate these T cells at nanomolar concentrations; they are then capable of transferring disease to NOD-scid mice. Surprisingly, some of the peptides include sequences similar (8 of 10 residues) to those found within the 528-539 fragment of glutamic acid decarboxylase 65. Although this 12-mer glutamic acid decarboxylase 65 fragment is only slightly stimulatory for BDC2.5 T cells (EC(50) > 100 microM), a larger 16-mer fragment, 526-541, shows activity in the low micromolar range (EC(50) = 2.3 microM). Finally, T cells from prediabetic NOD mice respond spontaneously to these peptide analogs in culture; this finding validates them as being related to a critical autoantigen involved in the etiology of spontaneous diabetes and indicates that their further characterization is important for a better understanding of underlying disease mechanisms.

Use of remifentanil in a patient with peripartum cardiomyopathy requiring Caesarean section

We describe a case of a 26 yr old primigravida at 39 weeks' gestation, with a diagnosis of peripartum cardiomyopathy, requiring urgent Caesarean section. The patient presented in severe heart failure and active labour. A general anaesthetic, using a target-controlled infusion of propofol and an intravenous infusion of remifentanil, was used to provide stable anaesthesia and analgesia for a successful delivery. The unusual diagnosis of peripartum cardiomyopathy and the potential benefits of the use of remifentanil in high-risk obstetric surgery are discussed.

Construction and characterization of an Escherichia coli strain genetically engineered for Ni(II) bioaccumulation

An Escherichia coli strain that accumulated Ni(II) was constructed by introducing the nixA gene (coding for a nickel transport system) from Helicobacter pylori into JM109 cells that expressed a glutathione S-transferase-pea metallothionein fusion protein. The resulting strain accumulated 15 micromol of Ni(II) per g (dry weight) from a 10 microM Ni(II) solution, four times the level taken up by JM109 cells. Ni(II) accumulation did not require an energy source, was inhibited by only 50% by 0.1 M NaCl, and occurred over the pH range from 3 to 9.

Meta-analyses in alcohol and other drug abuse treatment research

Meta-analysis is a quantitative method of synthesizing empirical evidence across a collection of related studies and addresses many of the weaknesses of traditional narrative forms of reviewing. This paper describes the basic methods for conducting a state-of-the-art meta-analysis and criticizes 11 extant meta-analyses of alcohol and other drug abuse treatment programs. Eight of these 11 meta-analyses used questionable methods and contributed little to our understanding of the effects of these programs. The paper concludes with a proposal for an archive of alcohol and other drug services research to facilitate and improve the quality of future meta-analyses.

A randomized, crossover comparison of warfarin products in the treatment of chronic atrial fibrillation

OBJECTIVE

To compare the dosing requirements and international normalized ratios (INRs) associated with two bioequivalent crystalline warfarin sodium products in patients with chronic atrial fibrillation.

METHODS

A multicenter, single-blind (prescriber), randomized, crossover evaluation of Apothecon warfarin and DuPont warfarin (Coumadin) was conducted in consenting adults with chronic or paroxysmal atrial fibrillation who had been receiving DuPont warfarin chronically for the prevention of thromboembolism. Patients were randomly assigned to initially either continue DuPont warfarin or receive Apothecon warfarin for four weeks, with weekly evaluation of dosage and INR changes, safety, and efficacy. Subsequently, patients crossed over and received the other product for four weeks.

RESULTS

There were 113 patients randomized to receive study treatment. Neither the propensity for a dosage change or an INR change nor the magnitude of a dosage change or INR change appeared related to a particular warfarin product (NS for each variable after each study period). After four weeks of treatment, the same number of patients (n = 7) experienced a > or = 20% change in warfarin dosage from the respective baseline with each product. The number of patients with INRs outside the desired protocol range after four weeks of treatment was similar for both groups (< 1.8, n = 9 for both products, or > 3.2, n = 9 for DuPont, n = 10 for Apothecon). No major hemorrhagic or thromboemoblic events occurred.

CONCLUSIONS

The results of this study show that Apothecon warfarin and DuPont warfarin provide equivalent anticoagulation in patients with chronic or paroxysmal atrial fibrillation.

Transcription factors GATA-4 and GATA-6 and a GATA family cofactor, FOG-2, are expressed in human ovary and sex cord-derived ovarian tumors

Previous studies have implicated transcription factors GATA-4 and GATA-6 in the regulation of murine ovarian development and function. In rodents, GATA-4 is expressed in granulosa cells of primary and early antral follicles, whereas GATA-6 is expressed in granulosa cells of late antral follicles and luteal glands. Both transcription factors can be detected in lesser amounts in theca cells and interstitial cells. We have now examined the expression of GATA-4 and GATA-6 in human ovaries, human granulosa-luteal (GL) cells and sex cord-derived tumors. We show by in situ hybridization and immunohistochemistry that GATA-4 and GATA-6 messenger RNA (mRNA) and GATA-4 protein are present in granulosa and theca cells in both preantral and antral follicles. Both human ovarian tissue samples and freshly isolated GL cells derived from preovulatory follicles of gonadotropin-treated women express GATA-4, GATA-6, and FOG-2 transcripts, and GATA-6 mRNA expression in GL cell cultures is stimulated by human CG and 8-bromo-cAMP. The vast majority of granulosa and theca cell tumors examined expressed GATA-4 and GATA-6. We also found that mRNA for FOG-2, a recently discovered regulator of GATA-4, is coexpressed with GATA-4 in human ovary samples, normal granulosa cells, and in sex cord-derived tumors. Our results demonstrate that GATA-4, GATA-6, and FOG-2 are expressed in human ovary and in granulosa and theca cell tumors. Our findings support a role for GATA-binding proteins in human ovarian folliculogenesis. Moreover, these data suggest that GATA factors may contribute to the phenotypes of sex cord-derived ovarian tumors.

Cloning, expression and characterization of a family 48 exocellulase, Cel48A, from Thermobifida fusca

The gene for a 104-kDa exocellulase, Cel48A, formerly E6, was cloned from Thermobifida fusca into Escherichia coli and Streptomyces lividans. The DNA sequence revealed a type II cellulose-binding domain at the N-terminus, followed by a FNIII-like domain and ending with a glycosyl hydrolase Family 48 catalytic domain. The enzyme and catalytic domain alone were each expressed in and purified from S. lividans and had very low catalytic activity on swollen cellulose, carboxymethyl cellulose, bacterial microcrystalline cellulose and filter paper. However, in synergistic assays on filter paper, the addition of Cel48A to a balanced mixture of T. fusca endocellulase and exocellulase increased the specific activity from 7.9 to 11.7 micromol cellobiose.min-1.mL-1, more than 15-fold higher than any single enzyme alone. Cel48A retained > 50% of its maximum activity from pH 5 to 9 and from 40 to 60 degrees C. Using SWISSMODEL, the amino-acid sequence of the Cel48Acd was modeled to the known structure of Clostridium cellulolyticum CelF. Family 48 enzymes are remarkably homologous at 35% identity for all their catalytic domains and some of the properties of the 10 members are discussed.

Prevention education and evaluation in U.S. medical schools: a status report

The Prevention Curriculum Assistance Program (PCAP) was initiated to help U.S. medical schools examine the extent to which they are evaluating the learning of medical students about disease prevention/health promotion. A survey was sent to all 144 allopathic and osteopathic medical schools, with an overall response rate of 68%. The results revealed more emphasis on teaching and evaluating the learning of medical students in the areas of clinical preventive services and quantitative methods, and less emphasis on the community dimensions of medical practice and health services organization and delivery. Written tests and unstructured observation are the most common methods of evaluation. Fewer than half of all respondents were satisfied with the quality of their assessment of student achievement in any of the four domains of prevention education. More than 30% expressed a desire to receive assistance with designing curricula and/ or evaluation methods in each of the four content areas examined. Several indicated their willingness to assist colleagues who want to improve their prevention curricula and/or measurement strategies. This study identified a need for more attention and support for prevention education and evaluation programs. Curriculum leaders can help by designating prevention a priority area and appointing faculty to be responsible for monitoring the content and quality of prevention teaching throughout the curriculum. Resources such as the Internet can be utilized to establish a network whereby medical schools can collaborate to improve their educational programs and evaluation methods in prevention.

Site-directed mutation of noncatalytic residues of Thermobifida fusca exocellulase Cel6B

Fifteen mutant genes in six loop residues and eight mutant genes in five conserved noncatalytic active site residues of Thermobifida fusca Cel6B were constructed, cloned and expressed in Escherichia coli or Streptomyces lividans. The mutant enzymes were assayed for catalytic activity on carboxymethyl cellulose (CMC), swollen cellulose (SC), filter paper (FP), and bacterial microcrystalline cellulose (BMCC) as well as cellotetraose, cellopentaose, and 2, 4-dinitrophenyl-beta-D-cellobioside. They were also assayed for ligand binding, enzyme processivity, thermostability, and cellobiose feedback inhibition. Two double Cys mutations that formed disulfide bonds across two tunnel forming loops were found to significantly weaken binding to ligands, lower all activities, and processivity, demonstrating that the movement of these loops is important but not essential for Cel6B function. Two single mutant enzymes, G234S and G284P, had higher activity on SC and FP, and the double mutant enzyme had threefold and twofold higher activity on these substrates, respectively. However, synergism with endocellulase T. fusca Cel5A was not increased with these mutant enzymes. All mutant enzymes with lower activity on filter paper, BMCC, and SC had lower processivity. This trend was not true for CMC, suggesting that processivity in Cel6B is a key factor in the hydrolysis of insoluble and crystalline cellulose. Three mutations (E495D, H326A and W329C) located near putative glycosyl substrate subsites -2, +1 and +2, were found to significantly increase resistance to cellobiose feedback inhibition. Both the A229V and L230C mutations specifically decreased activity on BMCC, suggesting that BMCC hydrolysis has a different rate limiting step than the other substrates. Most of the mutant enzymes had reduced thermostability although Cel6B G234S maintained wild-type thermostability. The properties of the different mutant enzymes provide insight into the catalytic mechanism of Cel6B.

Probing the catalytic mechanism of prephenate dehydratase by site-directed mutagenesis of the Escherichia coli P-protein dehydratase domain

The Escherichia coli bifunctional P-protein, which plays a central role in L-phenylalanine (Phe) biosynthesis, contains distinct chorismate mutase (CM) and prephenate dehydratase (PDT) domains as well as a regulatory (R) domain for feedback control by Phe. To elucidate the catalytic mechanism of PDT in the P-protein, 24 mutations of 15 conserved residues in the PDT domain were created, expressed in the pheA(-)E. coli strain NK6024, and studied for their effect on PDT activity. Fourteen mutant enzymes were purified to homogeneity, tested for feedback inhibition by Phe, and characterized by kinetic analysis and circular dichroism spectroscopy. Selected mutant enzymes were further studied by gel filtration, fluorescence emission, and microcalorimetry. In addition, a monofunctional PDT domain (PDT20, residues 101-285) was cloned and overexpressed in plasmid pET with expression levels up to 200-250 mg/L. PDT20 retained full PDT activity, lacked CM activity, and was insensitive to feedback inhibition by Phe. Four residues (T278, N160, Q215, and S208) were shown to be important for PDT catalysis. The values of k(cat)/K(m) for the S208A/C and T278S mutant enzymes were 100-fold lower, and 500-fold lower for the N160A and Q215A mutant enzymes than the wild-type (WT) protein. The T278A and T278V mutant enzymes displayed no measurable catalytic activity, yet bound both prephenate and a competitive inhibitor (S-DNBA) comparably to the WT protein. These data, taken together with the normal CD spectra of the mutant enzymes, strongly suggested that T278 was involved in the catalytic mechanism. To establish whether acidic residues were involved in catalysis, all the conserved Glu and Asp residues in the PDT domain were mutated to Ala. None of these mutations significantly reduced PDT activity, indicating that the acidic residues of the PDT domain are not directly involved in catalysis. However, two mutant enzymes (E159A and E232A) displayed higher levels of PDT activity (2.2- and 3.5-fold, respectively), which was due to enhanced substrate binding. For the double mutant enzyme (E159A-E232A), k(cat)/K(m) was ca. 7-fold higher than for the WT enzyme, while its K(m) was 4.6-fold lower.

Faculty perspectives of health promotion in allied health curricula: results of a national survey

More knowledge and skills related to health promotion/disease prevention are being required of health professionals. Allied health graduates entering the workforce will need academic preparation in these areas. This study assessed faculty perspectives on the status of health promotion content in allied health programs by a survey of 524 program directors. A questionnaire gathered information about perception of importance, level of representation, and method of delivery of health promotion content. Response rate was 41%. The majority of participants thought this content area was important for their programs and was highly or moderately represented in their curricula. Level of representation was significantly associated with requirement for accreditation. Programs in the Northeast were more likely to think health promotion was important and those in the West were more likely to have it integrated into their curricula. The most common delivery modality was guest lecture. Allied health is adopting health promotion curricular content, but further study is needed to assess programs and faculty expertise and identify strategies to ensure greater consistency of delivering material.

Effects of noncatalytic residue mutations on substrate specificity and ligand binding of Thermobifida fusca endocellulase cel6A

The availability of a high-resolution structure of the Thermobifida fusca endocellulase Cel6A catalytic domain makes this enzyme ideal for structure-based efforts to engineer cellulases with high activity on native cellulose. In order to determine the role of conserved, noncatalytic residues in cellulose hydrolysis, 14 mutations of six conserved residues in or near the Cel6A active-site cleft were studied for their effects on catalytic activity, substrate specificity, processivity and ligand-binding affinity. Eleven mutations were generated by site-directed mutagenesis using PCR, while three were from previous studies. All the CD spectra of the mutant enzymes were indistinguishable from that of Cel6A indicating that the mutations did not dramatically change protein conformation. Seven mutations in four residues (H159, R237, K259 and E263) increased activity on carboxymethyl cellulose (CM-cellulose), with K259H (in glucosyl subsite -2) creating the highest activity (370%). Interestingly, the other mutations in these residues reduced CM-cellulose activity. Only the K259H enzyme retained more activity on acid-swollen cellulose than on filter paper, suggesting that this mutation affected the rate-limiting step in crystalline cellulose hydrolysis. All the mutations lowered activity on cellotriose and cellotetraose, but two mutations, both in subsite +1 (H159S and N190A), had higher kcat/Km values (6.6-fold and 5.0-fold, respectively) than Cel6A on 2,4-dinitrophenyl-beta-D-cellobioside. Measurement of enzyme : ligand dissociation constants for three methylumbelliferyl oligosaccharides and cellotriose showed that all mutant enzymes bound these ligands either to the same extent as or more weakly than Cel6A. These results show that conserved noncatalytic residues can profoundly affect Cel6A activity and specificity.

A celR mutation affecting transcription of cellulase genes in Thermobifida fusca

Biosynthesis of extracellular cellulases in the cellulose-degrading actinomycete Thermobifida fusca is controlled by a transcriptional regulator, CelR, and cellobiose, which acts as an inducer interfering with the CelR-DNA interaction. We report the identification and characterization of a mutation in the celR gene that changes Ala(55) in the hinge helix of CelR to Thr. The wild-type and mutant celR genes were cloned in Escherichia coli, and their protein products were characterized. The CelR mutant protein bound DNA more weakly than the wild-type protein and formed a less stable complex with DNA in the presence of cellobiose. The results of Western analysis and gel retardation experiments suggest that CelR is produced constitutively and its DNA-binding activity is regulated through posttranslational modification.

Immunogenicity. I. Use of peptide libraries to identify epitopes that activate clonotypic CD4+ T cells and induce T cell responses to native peptide ligands

Recent studies have demonstrated the utility of synthetic combinatorial libraries for the rapid identification of peptide ligands that stimulate clonotypic populations of T cells. Here we screen a decapeptide combinatorial library arranged in a positional scanning format with two different clonotypic populations of CD4+ T cells to identify peptide epitopes that stimulate proliferative responses by these T cells in vitro. An extensive collection of mimic peptide sequences was synthesized and used to explore the fine specificity of TCR/peptide/MHC interactions. We also demonstrate that many of these deduced ligands are not only effective immunogens in vivo, but are capable of inducing T cell responses to the original native ligands used to generate the clones. These results have significant implications for considerations of T cell specificity and the design of peptide vaccines for infectious disease and cancer using clinically relevant T cell clones of unknown specificity.

Substrate heterogeneity causes the nonlinear kinetics of insoluble cellulose hydrolysis

Nonlinear kinetics are commonly observed in the enzymatic hydrolysis of cellulose. This nonlinearity could be explained by any or all of the following three factors: enzyme inactivation, product inhibition, or substrate heterogeneity. In this study, four different approaches were applied to test the above hypotheses using two Thermomonospora fusca endocellulases, E2 and E5. The lack of stimulation of cellulase activity by beta-glucosidase rules out the possibility of product inhibition as a cause of the observed nonlinearity. The results from the other three approaches all provide strong evidence against enzyme inactivation and strong evidence for substrate heterogeneity as the cause of the nonlinear kinetics. The most direct evidence for substrate heterogeneity is that pretreatment of swollen cellulose with either E2cd or E5cd gave a product that was hydrolyzed at a much (3- to 4-fold) slower rate than untreated swollen cellulose even though the initial treatment degraded only 15-18% of the substrate. Furthermore, the activation energy of E2 catalyzed hydrolysis of swollen cellulose increased from 10 kcal/mol for the initial rate to 29 kcal/mol for hydrolysis after 24% digestion.

Regulatory T cells in experimental allergic encephalomyelitis. II. T cells functionally antagonistic to encephalitogenic MBP-specific T cells show persistent expression of fasL

Naive LEW rats and animals that have recovered from active or adoptive EAE contain a subset of T cells that inhibit EAE in secondary recipients and are lytic for MBP-reactive T cell lines in culture. Here we explore various features of these regulatory T cell populations (RTC) with respect to (1) their frequency in animals following immunization with syngeneic MBP-reactive cell lines, (2) their ability to inhibit proliferative responses by MBP-reactive cell lines in culture, (3) their ability to lyse MBP-specific target cells, and especially (4) their prolonged expression of high levels of FasL following activation in culture correlating with their lytic effects on A20, a FasL-sensitive mouse lymphoma cell line. Inhibition studies indicate that mAbs specific for MHC class I and MHC class II molecules inhibit lysis of syngeneic MBP-reactive target T cells, soluble Fas protein shows some inhibition, but none of these agents inhibits the lytic effects of activated RTC on the A20 cell line.

Characterization of cadmium uptake in Lactobacillus plantarum and isolation of cadmium and manganese uptake mutants

Two different Cd(2+) uptake systems were identified in Lactobacillus plantarum. One is a high-affinity, high-velocity Mn(2+) uptake system which also takes up Cd(2+) and is induced by Mn(2+) starvation. The calculated K(m) and V(max) are 0.26 microM and 3.6 micromol g of dry cell(-1) min(-1), respectively. Unlike Mn(2+) uptake, which is facilitated by citrate and related tricarboxylic acids, Cd(2+) uptake is weakly inhibited by citrate. Cd(2+) and Mn(2+) are competitive inhibitors of each other, and the affinity of the system for Cd(2+) is higher than that for Mn(2+). The other Cd(2+) uptake system is expressed in Mn(2+)-sufficient cells, and no K(m) can be calculated for it because uptake is nonsaturable. Mn(2+) does not compete for transport through this system, nor does any other tested cation, i.e., Zn(2+), Cu(2+), Co(2+), Mg(2+), Ca(2+), Fe(2+), or Ni(2+). Both systems require energy, since uncouplers completely inhibit their activities. Two Mn(2+)-dependent L. plantarum mutants were isolated by chemical mutagenesis and ampicillin enrichment. They required more than 5,000 times as much Mn(2+) for growth as the parental strain. Mn(2+) starvation-induced Cd(2+) uptake in both mutants was less than 5% the wild-type rate. The low level of long-term Mn(2+) or Cd(2+) accumulation by the mutant strains also shows that the mutations eliminate the high-affinity Mn(2+) and Cd(2+) uptake system.