Liming effects of poultry litter derived biochar on soil acidity amelioration and maize growth.

Crop production in acid soils is facing enormous challenges due to low soil quality associated with an increase in the acidification rate and aluminum toxicity. Despite comprehensive prior work with biochar application on nutrient availability and crop productivity in acid soils, little information is available about the recommendation or standardization of biochar application rates that are more suitable for soil fertility improvement under different soil environments (physico-chemical properties) for maximizing the benefits of biochar applications and minimizing the potential environmental risk. Thus, the objective of this study was to investigate the effectiveness of poultry litter (PL) and poultry litter biochar (PLB) in ameliorating the fertility of acid soils through incubation and pot experiments. The soil was amended with different materials as follows; lime (1 g kg-1), PL (5, 10 and 15 g kg-1) and PLB (5, 10 and 15 g kg-1) along with control (non-amended). A pot experiment was also conducted using similar treatments to observe the responses of maize crop to the different amendments. The results indicated an increase in the pH and a decrease in exchangeable acidity in lime, PL and PLB amended soils. Lower soil pH, base cations and soil available phosphorus (P), and higher exchangeable acidity were found in control than the amended soils. Compared to PL and lime, PLB achieved greater increase rate in soil pH and reduction rate in soil exchangeable acidity with increased soil exchangeable base cations. An increase in soil available calcium (Ca) was observed in the lime treatment, while in PL and PLB treatments, there was an increase in soil available Ca, magnesium (Mg), potassium (K) and P. Application of the amendments increased availability of nitrogen (N), P, K, Ca and Mg relative to the control for maize in the pot experiment. When PL and PLB amendments were compared, it was found that the PLB was the best choice for the amelioration of acid soils as well as nutrient uptake by maize plants. It is suggested that application of PLB at the rate of 15 g kg-1 is suitable for maize growth in acid soils.

Profiling of Brevibacillus borstelensis transcriptome exposed to high temperature shock.

To understand the molecular mechanisms underlying the ability of the bacteria to survive at high temperature, gene expression profile of Brevibacillusborstelensis at 55°C during 5 and 10min heat shock period was carried out by high-throughput sequencing technology. A total of 2555 non-redundant transcripts were annotated. A total of 575 genes at 5min and 400 genes at 10min exhibited significant differential expression in response to temperature upshift from 50 to 55°C. Genes up-regulated under heat shock were associated with metabolism (mtnE), membrane transport, signal transduction, transcriptional regulation (ycxD, codY) and folding and sorting (hsp90). A larger number of genes encoding hypothetical proteins were identified. RT-PCR experimental results carried out on genes expressed under heat shock were found to be consistent with transcriptome data. The results enhance our understanding of adaptation strategy of thermophilic bacteria thereby providing a strong background for in depth research in thermophiles.

A review on host-pathogen interactions: classification and prediction.

The research on host-pathogen interactions is an ever-emerging and evolving field. Every other day a new pathogen gets discovered, along with comes the challenge of its prevention and cure. As the intelligent human always vies for prevention, which is better than cure, understanding the mechanisms of host-pathogen interactions gets prior importance. There are many mechanisms involved from the pathogen as well as the host sides while an interaction happens. It is a vis-a-vis fight of the counter genes and proteins from both sides. Who wins depends on whether a host gets an infection or not. Moreover, a higher level of complexity arises when the pathogens evolve and become resistant to a host's defense mechanisms. Such pathogens pose serious challenges for treatment. The entire human population is in danger of such long-lasting persistent infections. Some of these infections even increase the rate of mortality. Hence there is an immediate emergency to understand how the pathogens interact with their host for successful invasion. It may lead to discovery of appropriate preventive measures, and the development of rational therapeutic measures and medication against such infections and diseases. This review, a state-of-the-art updated scenario of host-pathogen interaction research, has been done by keeping in mind this urgency. It covers the biological and computational aspects of host-pathogen interactions, classification of the methods by which the pathogens interact with their hosts, different machine learning techniques for prediction of host-pathogen interactions, and future scopes of this research field.

Rationally designed donor-acceptor scheme based molecules for applications in opto-electronic devices.

Several donor (D)-acceptor (A) based molecules are rationally designed by adopting three different schemes in which the conjugation length, strength of the donor and acceptor moieties, and planarity of the molecules are varied. These variations are made by introducing a π-conjugated linkage unit, terminating the ends of the moieties by different electron donating and accepting functional groups, and fusing the donor and acceptor moieties, respectively. Our DFT and TDDFT based calculations reveal that using the above-mentioned design schemes, the electronic and optical properties of the D-A based molecules can be largely tuned. While introduction of a linkage and fusing of moieties enhance the π-π interaction, addition of electron donating groups (-CH3, -OH, and -NH2) and electron accepting groups (-CF3, -CN, -NO2, and -NH3(+)) varies the strength of the donor and acceptor moieties. These factors lead to modulation of the HOMO and LUMO energy levels and facilitate the engineering of the HOMO-LUMO gap and the optical gap over a wide range of ∼0.7-3.7 eV. Moreover, on the basis of calculated ionization potential and reorganization energy, most of the investigated molecules are predicted to be air stable and to exhibit high electron mobility, with the possibility of the presence of ambipolar characteristics in a few of them. The results of our calculations not only demonstrate the examined molecules to be the potential materials for organic opto-electronic devices, but also establish an understanding of the composition-structure-property correlation, which will provide guidelines for designing and synthesizing new materials of choice.

Upregulation of transcripts for metabolism in diverse environments is a shared response associated with survival and adaptation of Klebsiella pneumoniae in response to temperature extremes.

Klebsiella pneumoniae being ubiquitous in nature encounters wide differences in environmental condition. The organism's abundance in natural water reservoirs exposed to temperature variation forms the basis of its persistence and spread in the soil and other farm produce. In order to investigate the effect of temperature changes on the survival and adaptation of the bacteria, the transcriptional response of K. pneumoniae subjected to low (20 °C) and high (50 °C) temperature shock were executed using Applied Biosystems SOLiD platform. Approximately, 33 and 34% of protein coding genes expressed in response to 20 and 50 °C, respectively, displayed significant up- or downregulation (p < 0.01). Most of the significantly expressed transcripts mapped to metabolism, membrane transport, and cell motility were downregulated at 50 °C, except for protein folding, sorting, and degradation, suggesting that heat stress causes general downregulation of gene expression together with induction of heat shock proteins. While at 20 °C, the transcripts of carbohydrate, lipid, and amino acid metabolism were highly upregulated. Hypothetical proteins as well as canonical heat and cold shock proteins, viz. grpE, clpX, recA, and deaD were upregulated commonly in response to 20 and 50 °C. Significant upregulation of genes encoding ribosomal proteins at 20 and 50 °C possibly suggest their role in the survival of K. pneumoniae cells under low- and high-temperature stress.

Sequence polymorphism of GroEL gene in natural population of Bacillus and Brevibacillus spp. that showed variation in thermal tolerance capacity and mRNA expression.

GroEL, a class I chaperonin, plays an important role in the thermal adaptation of the cell and helps to maintain the viability of the cell under heat shock condition. Function of groEL in vivo depends on the maintenance of proper structure of the protein which in turn depends on the nucleotide and amino acid sequence of the gene. In this study, we investigated the changes in nucleotide and amino acid sequences of the partial groEL gene that may affect the thermotolerance capacity as well as mRNA expression of bacterial isolates. Sequences among the same species having differences in the amino acid level were identified as different alleles. The effect of allelic variation on the groEL gene expression was analyzed by comparison and relative quantification in each allele under thermal shock condition by RT-PCR. Evaluation of K a/K s ratio among the strains of same species showed that the groEL gene of all the species had undergone similar functional constrain during evolution. The strains showing similar thermotolerance capacity was found to carry same allele of groEL gene. The isolates carrying allele having amino acid substitution inside the highly ATP/ADP or Mg(2+)-binding region could not tolerate thermal stress and showed lower expression of the groEL gene. Our results indicate that during evolution of these bacterial species the groEL gene has undergone the process of natural selection, and the isolates have evolved with the groEL allelic sequences that help them to withstand the thermal stress during their interaction with the environment.

Role of local application of autologous platelet-rich plasma in the management of pressure ulcers in spinal cord injury patients.

STUDY DESIGN: Prospective clinical case series. OBJECTIVES: The objective of this study is to evaluate the local application of platelet-rich plasma (PRP) in relation to pressure ulcers (PrUs) healing on one PrU (case) versus saline dressing on another PrU (control) in the same patient. SETTING: Tertiary Level Care Centre, India. METHODS: Twenty-five spinal cord injury patients with at least two PrUs were included. All 25 PrUs (case) were grade IV, and PrUs (control) were grade II (n=11), grade IV (n=10) and grade III in 4 patients. Evaluation of PrU healing was done by measuring wound surface area, Pressure Ulcer Scale for Healing (PUSH), biopsy and clinical examination. RESULTS: Statistically significant decrease in mean PUSH scores of PrUs (case) (t=6.13, P<0.000) and PrUs (control) (t=3.98, P=0.000) was observed after 5 weeks. The wound surface area of PrU (case) decreased significantly (t=4.98, P=0.000); however, the decrease was not significant (t=0.095, P=0.924) in PrUs (control). Majority of histopathological pictures of PrUs (case) showed necrosis and suppuration (56%) at the time of enrollment and well-formed granulation tissue and epithelialization (60%) at the 5th week. Twenty-four (96%) PrUs (case) improved and only 1 deteriorated with PRP therapy, whereas in control group 17 (68%) PrUs improved, 7 (28%) deteriorated and 1 wound showed no change. CONCLUSIONS: Advanced wound therapy using local applications of PRP seems to be a promising alternative to standard saline dressings in PrU healing. With the advantages of simple preparation, biocompatible safety, low cost and significant clinical effectiveness, it may be beneficial to study the effects of PRP in large-scale trials to validate it as an ideal therapy for enhanced wound healing in PrUs.

Comparative metatranscriptomic signatures of wood and paper feeding in the gut of the termite Reticulitermes flavipes (Isoptera: Rhinotermitidae).

Termites are highly eusocial insects that thrive on recalcitrant materials like wood and soil and thus play important roles in global carbon recycling and also in damaging wooden structures. Termites, such as Reticulitermes flavipes (Rhinotermitidae), owe their success to their ability to extract nutrients from lignocellulose (a major component of wood) with the help of gut-dwelling symbionts. With the aim to gain new insights into this enzymatic process we provided R. flavipes with a complex lignocellulose (wood) or pure cellulose (paper) diet and followed the resulting differential gene expression on a custom oligonucleotide-microarray platform. We identified a set of expressed sequence tags (ESTs) with differential abundance between the two diet treatments and demonstrated the source (host/symbiont) of these genes, providing novel information on termite nutritional symbiosis. Our results reveal: (1) the majority of responsive wood- and paper-abundant ESTs are from host and symbionts, respectively; (2) distinct pathways are associated with lignocellulose and cellulose feeding in both host and symbionts; and (3) sets of diet-responsive ESTs encode putative digestive and wood-related detoxification enzymes. Thus, this study illuminates the dynamics of termite nutritional symbiosis and reveals a pool of genes as potential targets for termite control and functional studies of termite-symbiont interactions.

Co-evolutionary patterns and diversification of ant-fungus associations in the asexual fungus-farming ant Mycocepurus smithii in Panama.

Partner fidelity through vertical symbiont transmission is thought to be the primary mechanism stabilizing cooperation in the mutualism between fungus-farming (attine) ants and their cultivated fungal symbionts. An alternate or additional mechanism could be adaptive partner or symbiont choice mediating horizontal cultivar transmission or de novo domestication of free-living fungi. Using microsatellite genotyping for the attine ant Mycocepurus smithii and ITS rDNA sequencing for fungal cultivars, we provide the first detailed population genetic analysis of local ant-fungus associations to test for the relative importance of vertical vs. horizontal transmission in a single attine species. M. smithii is the only known asexual attine ant, and it is furthermore exceptional because it cultivates a far greater cultivar diversity than any other attine ant. Cultivar switching could permit the ants to re-acquire cultivars after garden loss, to purge inferior cultivars that are locally mal-adapted or that accumulated deleterious mutations under long-term asexuality. Compared to other attine ants, symbiont choice and local adaptation of ant-fungus combinations may play a more important role than partner-fidelity feedback in the co-evolutionary process of M. smithii and its fungal symbionts.

Sensitive detection of CO2 implementing tunable thulium-doped all-fiber laser.

In this paper a compact, yet sensitive gas detection system based on a modulated, tunable thulium-doped fiber laser in the 2 µm wavelength region is reported. The laser operating wavelength range centered at a wavelength of 1.995 µm has been selected to access the R(50) transition (ν1+2ν2+ν3) of CO2 based on its line strength and to achieve isolation from interfering high-temperature water absorption features. The laser linewidth and tuning range are optimized accordingly. The modulation of the fiber laser, achieved through pump source modulation and a locking detection mechanism, has been utilized to stabilize the laser system and therefore to create a compact gas sensor with high sensitivity. The absorption spectrum, as well as the line strength and the concentration level of CO2, have been monitored through absorption spectroscopy techniques. The measured minimum detectable concentration of CO2 obtained using the system shows that it is quite capable of detecting trace gas at the ppm (parts in 10(6)) level. The stable laser performance achieved in the sensor system illustrates its potential for the development of practical, compact, yet sensitive fiber-laser-based gas sensor systems.

Luminescence properties of dual valence Eu doped nano-crystalline BaF2 embedded glass-ceramics and observation of Eu2+ → Eu3+ energy transfer.

Europium doped glass-ceramics containing BaF(2) nano-crystals have been prepared by using the controlled crystallization of melt-quenched glasses. X-ray diffraction and transmission electron microscopy have confirmed the presence of cubic BaF(2) nano-crystalline phase in glass matrix in the ceramized samples. Incorporation of rare earth ions into the formed crystalline phase having low phonon energy of 346 cm(-1) has been demonstrated from the emission spectra of Eu(3+) ions showing the transitions from upper excitation states (5)D(J) (J = 1, 2, and 3) to ground states for the glass-ceramics samples. The presence of divalent europium ions in glass and glass-ceramics samples is confirmed from the dominant blue emission corresponding to its 5d-4f transition under an excitation of 300 nm. Increase in the reduction of trivalent europium (Eu(3+)) ions to divalent (Eu(2+)) with the extent of ceramization is explained by charge compensation model based on substitution defect mechanisms. Further, the phenomenon of energy transfer from Eu(2+) to Eu(3+) ion by radiative trapping or re-absorption is evidenced which increases with the degree of ceramization. For the first time, the reduction of Eu(3+) to Eu(2+) under normal air atmospheric condition has been observed in a BaF(2) containing oxyfluoride glass-ceramics system.

Composition analysis and material characterization of an emulsifying extracellular polysaccharide (EPS) produced by Bacillus megaterium RB-05: a hydrodynamic sediment-attached isolate of freshwater origin.

AIMS: This work was aimed to isolate, purify and characterize an extracellular polysaccharide (EPS) produced by a freshwater dynamic sediment-attached micro-organism, Bacillus megaterium RB-05, and study its emulsifying potential in different hydrocarbon media. METHODS AND RESULTS: Bacillus megaterium RB-05 was found to produce EPSs in glucose mineral salts medium, and maximum yield (0.864 g l(-1) ) was achieved after 24-h incubation. The recovery rates of the polysaccharide material by ion-exchange and gel filtration chromatography were around 67 and 93%, respectively. As evident from HPLC and FT-IR analyses, the polysaccharide was found to be a heteropolymer-containing glucose, galactose, mannose, arabinose, fucose and N-acetyl glucosamine. Different oligosaccharide combinations namely hexose(3), hexose(4), hexose(5) deoxyhexose(1) and hexose(5) deoxyhexose(1) pentose(3) were obtained after partial hydrolysis of the polymer using MALDI-ToF-MS. The polysaccharide with an average molecular weight of 170 kDa and thermal stability up to 180°C showed pseudoplastic rheology and significant emulsifying activity in hydrocarbon media. CONCLUSIONS: Isolated polysaccharide was found to be of high molecular weight and thermally stable. The purified EPS fraction was composed of hexose, pentose and deoxyhexose sugar residues, which is a rare combination for bacterial polysaccharides. Emulsifying property was either better or comparable to that of other commercially available natural gums and polysaccharides. SIGNIFICANCE AND IMPACT OF THE STUDY: This is probably one of the few reports about characterizing an emulsifying EPS produced by a freshwater sediment-attached bacterium. The results of this study contribute to understand the influence of chemical composition and material properties of a new microbial polysaccharide on its application in industrial biotechnology. Furthermore, this work reconfirms freshwater dynamic sediment as a potential habitat for bioprospecting extracellular polymer-producing bacteria. This study will improve our knowledge on the exploitation of a nonconventional renewable resource, which also seems to be ecologically significant.

Purification and partial elucidation of the structure of an antioxidant carbohydrate biopolymer from the probiotic bacterium Bacillus coagulans RK-02.

An exopolysaccharide (EPS) was isolated from Bacillus coagulans RK-02 and purified by size exclusion chromatography. The purified, homogeneous EPS had an average molecular weight of ∼3 × 104 Da by comparison with FITC-labeled dextran standards. In vivo evaluations showed that, like other reported polysaccharides, this EPS displayed significant antioxidant activity. FTIR spectroscopy analysis showed the presence of hydroxy, carboxy, and α-glycosidic linkages and a mannose residue. GC analysis indicated that the EPS was a heteropolymer composed of glucose, mannose, galactose, glucosamine, and fucose as monomeric constituent units. Partial elucidation of the structure of the carbohydrate biopolymer based on GC-MS and NMR analysis showed the presence of two unique sets of tetrasaccharide repeating units that have 1→3 and 1→6 glycosidic linkages. This is also the first report of a Gram-positive bacterial polysaccharide with both fucose as a sugar monomer and 1→3 and 1→6 glycosidic linkages in the molecular backbone.

Fibrous dysplasia & McCune-Albright syndrome: an experience from a tertiary care centre in north India.

BACKGROUND & OBJECTIVES: Fibrous dysplasia (FD) is a rare metabolic bone disease and information available from India is limited to only anecdotal case reports. We describe the clinical profile and therapeutic outcome of 25 patients with FD observed over a period of 14 yr in a tertiary care centre from north India. METHODS: In this retrospective study patients (n = 25) with diagnosis of fibrous dysplasia based on either classical radiological features and/or histological evidence on bone biopsy, were analyzed. Associated endocrinopathies if any, were evaluated. The diagnosis of McCune Albright syndrome (MAS) was considered when fibrous dysplasia was accompanied by either café-au-lait macules and/or endocrinopathies. The clinical presentation, biochemical parameters and imaging were analysed. Seven patients received bisphosphonate therapy. The final outcome and side effects were noted. RESULTS: Age of the patients ranged from 7 to 48 yr (mean ± SD, 24.2 ± 11.4 yr) with a lag time between onset of symptoms and presentation ranging from 1 to 20 yr (mean ± SD, 6.6 ± 6.2 yr). The mean duration of follow up was 3.5 ± 2.1 yr. Eighteen (72%) patients had polyostotic disease while the remaining had monostotic FD. Eight patients had endocrinopathies: five had acromegaly, one each had gonadotropin independent precocious puberty (GIPP), hyperthyroidism and hypophosphatemic rickets. One child with GIPP later developed hyperthyroidism. McCune Albright syndrome was observed in 10 (40%) patients. A majority of the patients underwent various minor or major surgical procedures and seven patients received bisphosphonates for recurrent pathological fractures. Bone pain was reduced in all bisphosphonate treated patients with a decrease in subsequent fractures. INTERPRETATION & CONCLUSIONS: This series of FD patients from north India shows the varying presentations of this rare disease. Medical treatment with bisphosphonates appears to be potentially rewarding.

Identification of a functional NF-kappa B binding site in the murine T cell receptor beta 2 locus.

We have identified a sequence in the TCR beta 2 locus that is homologous to the kappa B site in the Ig kappa light chain enhancer. This element, TCR beta-B, is located in the vicinity of previously identified T cell-specific DNase1 hypersensitive sites. Transfection analysis shows that a 60-bp fragment encompassing this site is preferentially active in T cells stimulated with phorbol esters or the HTLV-1 tax gene product compared with a B cell line that constitutively expresses NF-kappa B. Our results provide the first evidence for transcriptional regulatory sequences residing within the J beta 2-C beta 2 intron and suggest the possible involvement of these sequences in modulation of TCR beta gene expression upon cellular activation.

Functional GATA-3 binding sites within murine CD8 alpha upstream regulatory sequences.

Genes encoding the accessory molecules CD8 and CD4 are activated early in thymocyte development, generating CD4+8+ double positive intermediates, which give rise to two functionally distinct mature T cell subsets that express either CD4 or CD8. The mechanisms that govern the activation or suppression of the CD8 gene are likely to be central to the T cell development program. To identify the key regulatory factors, we have initiated an analysis of the transcriptional regulation of the murine CD8 alpha gene. We have identified three CD8+ cell-specific DNAase I hypersensitive sites (HSS) located upstream of the murine CD8 alpha gene. In vitro mobility shift analysis of the -4.0-kb HSS region has revealed multiple binding sites for the T cell-restricted transcription factor GATA-3. In vitro translated murine GATA-3 binds specifically to both CD8 GATA sites, and coexpression of this factor in transient transfection assays transactivates a reporter construct containing these sequences. These results provide the first evidence for the role of a T cell-restricted factor in the regulation of either CD8 or CD4 genes.

FK506 inhibits antigen receptor-mediated induction of c-rel in B and T lymphoid cells.

Stimulation of B and T cells via the antigen receptor, by phorbol ester or by phorbol ester and ionomycin, leads to nuclear translocation of the inducible transcription factor NF-kappa B, comprising the p50 and p65 rel-related polypeptides. In this report we show that c-rel is a component of the antigen receptor-induced kappa B binding proteins in both B and T cells. Whereas NF-kappa B can be induced by phorbol ester alone, optimal induction of c-rel requires stimulation by both phorbol ester and ionomycin, the dual signal that is necessary for proliferation of untransformed lymphocytes. Furthermore, c-rel induction is blocked by the immunosuppressive drug FK506 that is known to inhibit B and T cell activation. c-rel-dependent transactivation of the interleukin-2 receptor alpha chain (IL-2R alpha) promoter is augmented by coexpression of calcineurin, suggesting the involvement of a calcineurin-dependent intracellular pathway. Our results identify c-rel as a target of immunosuppressive agents and illustrate the similarity of activation pathways in both B and T cells.

Switch recombination breakpoints are strictly correlated with DNA recognition motifs for immunoglobulin S gamma 3 DNA-binding proteins.

The deletion looping out model of switch (S) recombination predicts that the intervening DNA between switch regions will be excised as a circle. Circular excision products of immunoglobulin switch recombination have been recently isolated from lipopolysaccharide (LPS)-stimulated spleen cells. The recombination breakpoints in these large circles were found to fall within switch regions. Since switch recombination is clearly focused on switch regions, we hypothesized that some DNA-binding protein factor might be involved in specifically recognizing and facilitating the alignment of switch regions before recombination. Two DNA-binding proteins that specifically interact with two discrete regions of the S gamma 3 tandem repeat have been identified in crude and partially purified nuclear extracts derived from LPS- and dextran sulfate (DxS)-activated splenic B cells. The first factor has been found indistinguishable from NF-kappa B by mobility shift assays, methylation interference, competition binding studies, and supershift analysis using an antiserum specific for the p50 component. The second appears to be composed of two closely traveling mobilities that do not separate upon partial purification. This second complex is unique and specific for S gamma 3 by methylation interference assays and competition-binding analysis. The sites at which recombination occurs in the S gamma 3 switch region have been analyzed and found to strictly correlate with the binding sites of the S gamma 3 switch binding proteins.

Bruton's tyrosine kinase links the B cell receptor to nuclear factor kappaB activation.

The recognition of antigen by membrane immunoglobulin M (mIgM) results in a complex series of signaling events in the cytoplasm leading to gene activation. Bruton's tyrosine kinase (BTK), a member of the Tec family of tyrosine kinases, is essential for the full repertoire of IgM signals to be transduced. We examined the ability of BTK to regulate the nuclear factor (NF)-kappaB/Rel family of transcription factors, as the activation of these factors is required for a B cell response to mIgM. We found greatly diminished IgM- but not CD40-mediated NF-kappaB/Rel nuclear translocation and DNA binding in B cells from X-linked immunodeficient (xid) mice that harbor an R28C mutation in btk, a mutation that produces a functionally inactive kinase. The defect was due, in part, to a failure to fully degrade the inhibitory protein of NF-kappaB, IkappaBalpha. Using a BTK-deficient variant of DT40 chicken B cells, we found that expression of wild-type or gain-of-function mutant BTK, but not the R28C mutant, reconstituted NF-kappaB activity. Thus, BTK is essential for activation of NF-kappaB via the B cell receptor.

Nuclear factors that mediate intrathymic signals are developmentally regulated.

Thymocytes mature through several stages of development, defined by cell surface markers such as CD3, CD4, and CD8, in response to environmental cues. Signal transduction resulting from lymphocyte-stromal cell interactions is likely to activate inducible transcription factors which in turn govern stage-specific gene expression. In this report we show that inducible transcription factors such as AP-1 and NF-AT are constitutively nuclear, in response to intrathymic signals, in freshly isolated thymocytes at all stages of maturation. In CD4+CD8+ double positive (DP), but not in the more immature CD4-CD8- double negative (DN) thymocytes, constant stimulus from the thymic environment is required to maintain nuclear AP-1. Thus, disruption of the thymus and incubation of thymocytes at 37 degrees C downregulates DNA binding by nuclear factors AP-1 and NF-AT. Similar treatment of thymocytes has previously been shown to downregulate CD3 zeta chain phosphorylation and increase T cell receptor CD3 expression on DP thymocytes, which is a feature of repertoire selection. Since mature T cells maintain inducible nuclear factors in an inactive form until an encounter with antigen, we propose that downregulation of nuclear DNA binding proteins may reflect another feature of this stage of T cell maturation.