Competitive binding of alpha-actinin and calmodulin to the NMDA receptor

The mechanisms by which neurotransmitter receptors are immobilized at postsynaptic sites in neurons are largely unknown. The activity of NMDA (N-methyl-D-aspartate) receptors is mechanosensitive and dependent on the integrity of actin, suggesting a functionally important interaction between NMDA receptors and the postsynaptic cytoskeleton. alpha-Actinin-2, a member of the spectrin/dystrophin family of actin-binding proteins, is identified here as a brain postsynaptic density protein that colocalizes in dendritic spines with NMDA receptors and the putative NMDA receptor-clustering molecule PSD-95. alpha-Actinin-2 binds by its central rod domain to the cytoplasmic tail of both NR1 and NR2B subunits of the NMDA receptor, and can be immunoprecipitated with NMDA receptors and PSD-95 from rat brain. Intriguingly, NR1-alpha-actinin binding is directly antagonized by Ca2+/calmodulin. Thus alpha-actinin may play a role in both the localization of NMDA receptors and their modulation by Ca2+.

Idiopathic hyperplasia of the adrenal gland behaving like an aldosterone producing adenoma

Primary hyperaldosteronism (adrenal adenoma and idiopathic hyperplasia) is a disorder with hypertension, hypokalemia, elevated serum aldosterone and suppressed plasma renin activity. Hyperplasia is managed medically whereas adenomas are treated surgically. Selective adrenal venous catheterization and aldosterone measurement is a useful tool in making the distinction in 95% of cases. We report a case of bilateral idiopathic hyperplasia of the adrenal glands adequately treated with medications for 6 years followed by worsening. Selective catheterization was consistent with a right sided adenoma. Surgical removal of the right adrenal gland alleviated her symptoms. Pathological examination showed focal nodular hyperplasia. We propose that in the course of the disease the focal hyperplastic nodule became autonomous and behaved like an adenoma. Monitoring of patients with adrenal hyperplasia for recurrence of symptoms is prudent as surgery is beneficial in patients who develop an autonomous nodule.

GH, GH-releasing factor and somatostatin in the growing lamb: sex differences and mechanisms for sex differences

Factors contributing to sex differences in the somatotrophic axis were investigated in growing lambs. In the first experiment, circulating patterns of GH in venous blood, pituitary content of GH and GH mRNA, and median eminence (ME) contents of GH-releasing factor (GRF) and somatostatin (SRIF) were characterized in prepubertal ram and ewe lambs which were pair-fed to remove sex differences in feed intake. Mean and baseline plasma GH concentrations, GH pulse amplitude, and integrated plasma GH were greater in ram lambs than in ewe lambs, but GH interpulse interval did not differ between sexes. The pituitary GH content and ME contents of GRF and SRIF were greater in rams than in ewes, but steady-state levels of mRNA for GH in the pituitary gland did not differ between sexes. A second experiment investigated sex effects on the levels of SRIF in hypophysial portal blood, and found that these did not differ between sexes. We concluded that the presence of sexually dimorphic patterns of GH secretion in the growing lamb is independent of feed-intake differences between sexes. The lack of sex differences in circulating patterns of SRIF in portal plasma implies that there may be a difference in GRF secretion which may produce sexually dimorphic patterns of GH secretion in lamb.

Transcription factors of the NFAT family: regulation and function

As targets for the immunosuppressive drugs cyclosporin A and FK506, transcription factors of the NFAT (nuclear factor of activated T cells) family have been the focus of much attention. NFAT proteins, which are expressed in most immune-system cells, play a pivotal role in the transcription of cytokine genes and other genes critical for the immune response. The activity of NFAT proteins is tightly regulated by the calcium/calmodulin-dependent phosphatase calcineurin, a primary target for inhibition by cyclosporin A and FK506. Calcineurin controls the translocation of NFAT proteins from the cytoplasm to the nucleus of activated cells by interacting with an N-terminal regulatory domain conserved in the NFAT family. The DNA-binding domains of NFAT proteins resemble those of Rel-family proteins, and Rel and NFAT proteins show some overlap in their ability to bind to certain regulatory elements in cytokine genes. NFAT is also notable for its ability to bind cooperatively with transcription factors of the AP-1 (Fos/Jun) family to composite NFAT:AP-1 sites, found in the regulatory regions of many genes that are inducibly transcribed by immune-system cells. This review discusses recent data on the diversity of the NFAT family of transcription factors, the regulation of NFAT proteins within cells, and the cooperation of NFAT proteins with other transcription factors to regulate the expression of inducible genes.

Evolution of B2 repeats: the muroid explosion

B2 repeats are a group of short interspersed elements (SINEs) specific for rodent genomes. Copy numbers were determined for different rodent genera. All the Muroid (rat, mouse, deer mouse, hamster, gerbil) rodent genomes analyzed exhibited 80,000-100,000 copies per haploid genome, whereas the squirrel genome contains only 2,500 copies, and fewer than 100 (if any) copies were observed for the Hystricognath rodents (guinea pig and nutria). These findings demonstrate that there was an 'explosion' of amplification of B2 elements within muroid rodents. The similar copy number of B2 elements within the different muroid species could be explained by formation of a high proportion of the B2 elements prior to the divergence of the different muroid species. However, the 3'-end of the B2 sequence is unique between murid and cricetid rodents suggesting that the majority of elements amplified after the divergence of these species. Also consistent with recent amplification of these elements in parallel within the muroid genomes is the finding that within mouse and rat there are distinct subfamilies of B2 repeats. The pattern of consistent parallel amplification of B2 elements in muroid species contrasts with the sporadic nature of ID repeat amplification in the same genomes. The consensus of the young mouse subfamily of elements corresponds to the B2 RNA that is preferentially transcribed in embryonic, tumor, and normal liver cells. The subfamily is young based on both its low divergence from the subfamily consensus sequence and the finding that the most recent B2 element insertions in the mouse genome are members of this subfamily.

Clinical trials and projected future of liver xenotransplantation

The trial and error of the pioneering xenotransplant trials over the past three decades has defined the limitation of the species used. Success was tantalizingly close with the chimpanzee, baboon, and other primates. The use of more disparate species has been frustrated by the xenoantibody barrier. Future attempts at clinical xenotransplantation will be hampered by the consideration of the species of animals and the nature of the organs to be transplanted. On one hand, primate donors have the advantage of genetic similarity (and therefore potential compatibility) and less risk of immunologic loss. On the other hand, pig donors are more easily raised, are not sentient animals, and may be less likely to harbor transmissible disease. It is recognized that the success of xenotransplantation may very with different organs. Because it is relatively resistant to antibody-mediated rejection, the liver is the organ for which there is the greatest chance of long-term success. Consideration of using xenotransplants on a temporary basis, or as a "bridge" to permanent human transplantation, may allow clinical trials utilizing hearts or kidney xenografts. Issues on metabolic compatibility and infection risks cannot be accurately determined until routine success in clinical xenotransplantation occurs. Based on a limited experience, the conventional approaches to allotransplantation are unlikely to be successful in xenotransplantation. The avoidance of immediate xenograft destruction by hyperacute rejection, achieved using transgenic animals bearing human complement regulatory proteins or modulating the antigenic target on the donor organ, is the first step to successful xenotransplantation. The ability to achieve tolerance by establishing a state of bone marrow chimerism is the key to overcoming the long-term immunologic insults and avoiding the necessarily high doses of nonspecific immunosuppression that would otherwise be required and associated with a high risk of infections complications. Xenotransplantation faces criticism that is strongly reminiscent of that leveled against human-to-human transplantation during the late 1960s and early 1970s. Yet with persistence, the field of human-to-human transplantation has proved highly successful. This success was the result of a stepwise increase in our understanding of the biology of rejection, improvements in drug management, and experience. It is possible that xenotransplantation may not be universally successful until further technologic advances occur; yet cautions exploration of xenotransplantation appears warranted to identify those areas that require further study.

Immunophenotypic characterization of tumor infiltrating lymphocytes and peripheral blood lymphocytes isolated from melanomatous and non-melanomatous Sinclair miniature swine

Selectively-bred Sinclair miniature swine exhibit a high incidence of congenital malignant melanoma which either proves fatal (10-15% of tumor-bearing piglets) or spontaneously regresses with a biphasic immunological phenomenon (85-90%) and no recurrence of malignancy. Mononuclear leukocytes were isolated from cutaneous melanomas and peripheral blood specimens collected from melanomatous (tumor-bearing) Sinclair swine during second-phase regression, and from peripheral blood specimens collected from non-melanomatous (tumor-free) Sinclair swine and control Hanford swine. Leukocyte identities were determined with single- and dual-parameter indirect immunofluorescence assays via flow cytometry. Assays for the specific surface antigens CD45, CD2, CD4, CD8, CD1, MHC class II, and N1 were employed to develop immunophenotypic profiles within the gated lymphocyte clusters from each TIL and PBL suspension. Significantly more CD8+ T-lymphocytes were identified in TIL suspensions than in peripheral blood leukocyte (PBL) suspensions (P < and = 0.05), regardless of breed or tumor status. Conversely, PBL suspensions contained significantly higher percentages of CD4+ T-lymphocytes than the levels found in TIL suspensions (P < and = 0.05). Virtually all TIL were MHC class II+, whereas the percentages of PBL expressing this antigen were markedly lower (P < and = 0.05). The percentages of T-lymphocytes co-expressing CD4 and CD8, a normal subset unique to swine, were generally consistent in all TIL and PBL suspensions examined. The results of this study have firmly established the immunophenotypic identities of cells associated with the second-phase regression phenomenon of this melanoma and have identified specific variations in the leukocyte profiles of the respective TIL and PBL suspensions.

Normal function of the transcription factor NFAT1 in wasted mice. Chromosome localization of NFAT1 gene

NFAT1 (NFATp), a cytosolic component of the nuclear factor of activated T cells (NFAT), is encoded by a single gene which was mapped to mouse chromosome 2 in the vicinity of the wasted (wst) locus. Although wasted mice display a severe immune disorder, they express normal levels of NFAT1 protein. The NFAT1 protein in wasted mice is properly regulated and possesses comparable DNA binding activity as that in their littermate controls. Therefore, the wasted phenotype is not due to a defect in the expression or early regulation of the NFAT1 protein.

Imaging of physiologically evoked responses by electrical impedance tomography with cortical electrodes in the anaesthetized rabbit

The purpose of this study was to determine if electrical impedance tomography (EIT) could be used to image impedance changes of several per cent over tens of seconds, known to occur during evoked activity of the cerebral cortex. A ring of 16 electrodes was placed on the exposed superior surface of the brain of anaesthetized rabbits. EIT images were acquired every 15 s using a Sheffield Mark 1 EIT system. During periods of 2.5-3 min of intense photic stimulation of both eyes or electrical stimulation of a forepaw, reproducible impedance decreases of 4.5 +/- 2.7% and 2.7 +/- 2.4% (mean +/- SD) respectively occurred in appropriate cortical areas, with a time course similar to the period of stimulation. They were accompanied by adjacent smaller impedance increases. The decreases are probably due to increased blood flow and temperature; the cause of the adjacent increases may be a shadowing artefact of the reconstruction algorithm or due to physiological shrinkage of the extracellular space. This demonstrated, for the first time, that such small changes may be imaged under optimal conditions. These results are encouraging to the prospect that EIT may eventually be suitable for imaging evoked responses or epilepsy in human subjects.

Some practical biological phantoms for calibrating multifrequency electrical impedance tomography

Three groups of materials have been assessed with a Hewlett-Packard 4284A impedance analyser and Sheffield Mark 1 electrical impedance tomography (EIT) system for suitability for calibration of multifrequency EIT systems. They were required to be easy to use, stable over several hours, and have complex impedance similar to biological tissue. The groups were: (i) inorganic materials including barium titanate, polystyrene microspheres and fumed silica, all in aqueous suspension; these had phase angles below 1 degrees and so were unsuitable. (ii) Cucumber in KCl solution. Cucumber cortex had a phase angle of 40 degrees at a centre frequency of 50 kHz. Contrast between the cucumber and bathing solution could be selected by varying the KCl concentration. (iii) Polyurethane sponge immersed in packed red cells. The phase angle of packed cells was about 25 degrees at 1 MHz. Sponge resistivities and permittivities when immersed in packed cells were 5-20% higher than the bathing solution itself, for densities of 2-6.2% w/v. Both the biological materials appear suitable for the intended purpose; system (iii) is inherently more stable, and has capacitance in both bathing medium and test object. If an initial accuracy of greater than about +/- 15% is required, direct measurement with an impedance analyser is recommended prior to imaging studies.

Interaction of calcineurin with a domain of the transcription factor NFAT1 that controls nuclear import

The nuclear import of the nuclear factor of activated T cells (NFAT)-family transcription factors is initiated by the protein phosphatase calcineurin. Here we identify a regulatory region of NFAT1, N terminal to the DNA-binding domain, that controls nuclear import of NFAT1. The regulatory region of NFAT1 binds directly to calcineurin, is a substrate for calcineurin in vitro, and shows regulated subcellular localization identical to that of full-length NFAT1. The corresponding region of NFATc likewise binds calcineurin, suggesting that the efficient activation of NFAT1 and NFATc by calcineurin reflects a specific targeting of the phosphatase to these proteins. The presence in other NFAT-family transcription factors of several sequence motifs from the regulatory region of NFAT1, including its probable nuclear localization sequence, indicates that a conserved protein domain may control nuclear import of all NFAT proteins.

Direct actions of the luteinizing hormone-releasing hormone agonist, deslorelin, on anterior pituitary contents of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), LH and FSH subunit messenger ribonucleic acid, and plasma concentrations of LH and FSH in castrated male cattle

The objective in this study was to characterize direct effects of the LHRH agonist, deslorelin, on anterior pituitary gland function in male cattle in the absence of gonadal feedback. Castrated bulls (steers), 30 mo old, were allocated to four groups: group 1, control, no treatment (n = 8); group 2, five deslorelin implants (approximately 250 micrograms total deslorelin/day) for 42 days (n = 8); group 3, control+ LHRH (50 micrograms i.m.) at weekly intervals (n = 3); group 4, five deslorelin implants+LHRH as for group 3 (n = 3). Plasma LH was similar (p > 0.05) for steers in groups 1 and 2 on Day 0 and lower (p < 0.05) for steers in group 2 on Day 4, and continued to decrease to Day 41 (group 1, 1.71 +/- 0.20 ng/ml [mean +/- SEM]; group 2, 0.38 +/- 0.03 ng/ml [p < 0.001]). Mean plasma concentrations of FSH were similar (p > 0.05) for steers in groups 1 and 2 on Day 0 and lower (p < 0.05) for steers in group 2 on Day 7, and declined to Day 41 (group 1, 43.5 +/- 3.9 ng/ml; group 2, 17.5 +/- 1.5 ng/ml [p < 0.001]). Steers in group 3 showed increases in plasma LH after injection of LHRH on all occasions, while steers in group 4 did not show increases in plasma LH from Day 14 onward. Mean relative pituitary contents (arbitrary units) of LH beta- and FSH beta-subunit mRNAs were reduced on Day 42 in steers treated with deslorelin (LH beta: groups 1 and 3, 1.56 +/- 0.27; groups 2 and 4, 0.08 +/- 0.01 [p < 0.001]; FSH beta: groups 1 and 3, 1.01 +/- 0.08; groups 2 and 4, 0.34 +/- 0.07 [p < 0.001]). However, alpha-subunit mRNA was similar for control steers and steers treated with deslorelin (groups 1 and 3, 1.00 +/- 0.11; groups 2 and 4, 0.86 +/- 0.12 [p > 0.1]). Pituitary content of LH, but not FSH, was reduced in steers treated with deslorelin. In summary, steers treated with deslorelin showed desensitization to natural LHRH, and this was associated with reduced pituitary contents of LH and FSH beta-subunit mRNAs, a reduction in pituitary content of LH, and decreases in plasma concentrations of LH and FSH. This demonstrated, for the first time, a direct action of LHRH agonist on LH and FSH beta-subunit gene expression in cattle, independent of gonadal feedback. Also, there was a differential effect of treatment with deslorelin on gonadotropin alpha- and beta-subunit mRNA contents in the anterior pituitary.

Recombinant NFAT1 (NFATp) is regulated by calcineurin in T cells and mediates transcription of several cytokine genes

Transcription factors of the NFAT family play a key role in the transcription of cytokine genes and other genes during the immune response. We have identified two new isoforms of the transcription factor NFAT1 (previously termed NFATp) that are the predominant isoforms expressed in murine and human T cells. When expressed in Jurkat T cells, recombinant NFAT1 is regulated, as expected, by the calmodulin-dependent phosphatase calcineurin, and its function is inhibited by the immunosuppressive agent cyclosporin A (CsA). Transactivation by recombinant NFAT1 in Jurkat T cells requires dual stimulation with ionomycin and phorbol 12-myristate 13-acetate; this activity is potentiated by coexpression of constitutively active calcineurin and is inhibited by CsA. Immunocytochemical analysis indicates that recombinant NFAT1 localizes in the cytoplasm of transiently transfected T cells and translocates into the nucleus in a CsA-sensitive manner following ionomycin stimulation. When expressed in COS cells, however, NFAT1 is capable of transactivation, but it is not regulated correctly: its subcellular localization and transcriptional function are not affected by stimulation of the COS cells with ionomycin and phorbol 12-myristate 13-acetate. Recombinant NFAT1 can mediate transcription of the interleukin-2, interleukin-4, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor promoters in T cells, suggesting that NFAT1 contributes to the CsA-sensitive transcription of these genes during the immune response.

T-cell receptor stimulation elicits an early phase of activation and a later phase of deactivation of the transcription factor NFAT1

We show here that NFAT1 is rapidly activated, then slowly deactivated, by stimulation of T cells through their antigen receptor. Within minutes of T-cell receptor stimulation, NFAT1 is dephosphorylated, translocates from the cytoplasm into the nucleus, and shows an increase in its ability to bind to DNA. These changes are dependent on calcium mobilization and calcineurin activation, since they are also elicited by ionomycin and are blocked by the immunosuppressive drug cyclosporin A. After several hours of T-cell receptor stimulation, the majority of the NFAT1 in the cell reverts to its original phosphorylated form, reappears in the cytoplasm, and again displays a low affinity for DNA. Deactivation of NFAT1 is facilitated by phorbol 12-myristate 13-acetate and inhibitors of capacitative calcium entry and most likely reflects the slow return of intracellular free calcium concentrations towards resting levels. Our results suggest that calcineurin-dependent signalling pathways mediate the early activation of NFAT1, while phorbol 12-myristate 13-acetate-dependent feedback pathways contribute to the late deactivation. Persistent NFAT-dependent cytokine gene transcription in activated T cells may be mediated by other NFAT family proteins in addition to NFAT1 during the immune response.

Mechanisms of transactivation by nuclear factor of activated T cells-1

Nuclear factor of activated T cells-family proteins (NFAT1/NFATp, NFATc, NFAT3, and NFAT4/NFATx/NFATc3) play a key role in the transcription of cytokine genes and other genes during the immune response. We have defined the mechanisms of transactivation by NFAT1. NFAT1 possesses two transactivation domains whose sequences are not conserved in the other NFAT-family proteins, and a conserved DNA-binding domain that mediates the recruitment of cooperating nuclear transcription factors even when it is expressed in the absence of other regions of the protein. The activity of the NH2-terminal transactivation domain is modulated by an adjacent regulatory region that contains several conserved sequence motifs represented only in the NFAT family. Our results emphasize the multiple levels at which NFAT-dependent transactivation is regulated, and predict significant differences in the architecture of cooperative transcription complexes containing different NFAT-family proteins.

Towards a texture naming system: identifying relevant dimensions of texture

Recently, researchers have started using texture for data visualization. The rationale behind this is to exploit the sensitivity of the human visual system to texture in order to overcome the limitations inherent in the display of multidimensional data. A fundamental issue that must be addressed is what textural features are important in texture perception, and how they are used. We designed an experiment to help identify the relevant higher order features of texture perceived by humans. We used twenty subjects, who were asked to rate 56 pictures from Brodatz's album on 12 nine-point Likert scales. Each subject was also asked to group these pictures into as many classes as desired. We applied the techniques of hierarchical cluster analysis and non-parametric multidimensional scaling (MDS) to the pooled similarity matrix generated from the subjects' groupings. We used Classification and Regression Tree Analysis (CART), discriminant analysis, and principal component analysis on the data from the scale ratings. The clusters generated from hierarchical cluster analysis remained intact in the MDS plots. We found that the MDS solutions fit the data well. The stress in the three-dimensional case is 0.12. The CART and discriminant analyses provided further justification for our interpretation. The three orthogonal dimensions we identified for texture are repetitive vs non-repetitive; high-contrast and non-directional vs low-contrast and directional; granular, coarse and low-complexity vs non-granular, fine and high-complexity.

An enhanced immune response in mice lacking the transcription factor NFAT1

Transcription factors of the NFAT family are thought to play a major role in regulating the expression of cytokine genes and other inducible genes during the immune response. The role of NFAT1 was investigated by targeted disruption of the NFAT1 gene. Unexpectedly, cells from NFAT1 -/- mice showed increased primary responses to Leishmania major and mounted increased secondary responses to ovalbumin in vitro. In an in vivo model of allergic inflammation, the accumulation of eosinophils and levels of serum immunoglobulin E were increased in NFAT1 -/- mice. These results suggest that NFAT1 exerts a negative regulatory influence on the immune response.

Calcineurin binds the transcription factor NFAT1 and reversibly regulates its activity

NFAT1 (previously termed NFATp) is a cytoplasmic transcription factor involved in the induction of cytokine genes. We have previously shown that the dephosphorylation of NFAT1, accompanied by its nuclear translocation and increased DNA binding activity, is regulated by calcium- and calcineurin-dependent mechanisms, as each of these hallmarks of NFAT1 activation is elicited by ionomycin and blocked by the immunosuppressive drugs cyclosporin A and FK506 (Shaw, K.T.-Y., Ho, A.M., Raghavan, A., Kim, J., Jain, J., Park, J., Sharma, S., Rao, A., and Hogan, P.G. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 11205-11209). Here we show that the activation state of NFAT1 in T cells is remarkably sensitive to the level of calcineurin activity. Addition of cyclosporin A, even in the presence of ongoing ionomycin stimulation, results in rephosphorylation of NFAT1, its reappearance in the cytoplasm, and a return of its DNA binding activity to low levels. Similar effects are observed upon removal of ionomycin or addition of EGTA. We also demonstrate a direct interaction between calcineurin and NFAT1 that is consistent with a direct enzyme-substrate relation between these two proteins and that may underlie the sensitivity of NFAT1 activation to the level of calcineurin activity. The NFAT1-calcineurin interaction, which involves an N-terminal region of NFAT1 conserved in other NFAT family proteins, may provide a target for the design of novel immunosuppressive drugs.

Tumor necrosis factor alpha gene regulation in activated T cells involves ATF-2/Jun and NFATp

The human tumor necrosis factor alpha (TNF-alpha) gene is one of the earliest genes expressed upon the activation of a T or B cell through its antigen receptor. Previous experiments have demonstrated that in stimulated T cells, a TNF-alpha promoter element, kappa 3, which binds NFATp, is required for the cyclosporin A-sensitive transcriptional activation of the gene. Here, we demonstrate that a cyclic AMP response element (CRE), which lies immediately upstream of the kappa 3 site, is also required for induction of TNF-alpha gene transcription in T cells stimulated by calcium ionophore or T-cell receptor ligands. The CRE binds ATF-2 and Jun proteins in association with NFATp bound to kappa 3. These proteins bind noncooperatively in vitro; however, the transcriptional activity of the CRE/kappa 3 composite site is dramatically higher than the activity of the kappa 3 site alone, indicating that the two sites cooperate in vivo. This study is the first demonstration of a role for ATF-2 in TNF-alpha gene transcription and of a functional interaction between ATF-2/Jun and NFATp. This novel pairing of NFATp with ATF-2/Jun may account for the specific and immediate pattern of TNF-alpha gene transcription in stimulated T cells.

Synthesis and antitumor activity evaluation of Delta2-1,2,4-oxadiazoline derivatives

4-Adamantyl-5-aryl-3-phenyl-Delta2-1,2,4-oxadiazolines were synthesized and evaluated in vitro as antitumor agents against 60 human tumor cell lines. Some derivatives exhibit both cell selectivity and tumor growth inhibition activity. In particular, 2,6-dichlorophenyl derivative (2q), the most active of the series, possesses significant activity on 26 cell lines at 10(-5) M.