Targeted disruption of the Stat1 gene in mice reveals unexpected physiologic specificity in the JAK-STAT signaling pathway

The JAK-STAT signaling pathway has been implicated in mediating biological responses induced by many cytokines. However, cytokines that promote distinct cellular responses often activate identical STAT proteins, thereby raising the question of how specificity is manifest within this signaling pathway. Here we report the generation and characterization of mice deficient in STAT1. STAT1-deficient mice show no overt developmental abnormalities, but display a complete lack of responsiveness to either IFN alpha or IFN gamma and are highly sensitive to infection by microbial pathogens and viruses. In contrast, these mice respond normally to several other cytokines that activate STAT1 in vitro. These observations document that STAT1 plays an obligate and dedicated role in mediating IFN-dependent biologic responses and reveal an unexpected level of physiologic specificity for STAT1 action.

Two forms of the Photosystem II D1 protein alter energy dissipation and state transitions in the cyanobacterium Synechococcus sp. PCC 7942

Synechococcus sp. PCC 7942 (Anacystis nidulans R2) contains two forms of the Photosystem II reaction centre protein D1, which differ in 25 of 360 amino acids. D1: 1 predominates under low light but is transiently replaced by D1:2 upon shifts to higher light. Mutant cells containing only D1:1 have lower photochemical energy capture efficiency and decreased resistance to photoinhibition, compared to cells containing D1:2. We show that when dark-adapted or under low to moderate light, cells with D1:1 have higher non-photochemical quenching of PS II fluorescence (higher qN) than do cells with D1:2. This is reflected in the 77 K chlorophyll emission spectra, with lower Photosystem II fluorescence at 697-698 nm in cells containing D1:1 than in cells with D1:2. This difference in quenching of Photosystem II fluorescence occurs upon excitation of both chlorophyll at 435 nm and phycobilisomes at 570 nm. Measurement of time-resolved room temperature fluorescence shows that Photosystem II fluorescence related to charge stabilization is quenched more rapidly in cells containing D1:1 than in those with D1:2. Cells containing D1:1 appear generally shifted towards State II, with PS II down-regulated, while cells with D1:2 tend towards State I. In these cyanobacteria electron transport away from PS II remains non-saturated even under photoinhibitory levels of light. Therefore, the higher activity of D1:2 Photosystem II centres may allow more rapid photochemical dissipation of excess energy into the electron transport chain. D1:1 confers capacity for extreme State II which may be of benefit under low and variable light.

flk2/flt3 ligand is a potent cofactor for the growth of primitive B cell progenitors

We have investigated the role of flk2/flt3 ligand (FL) in B cell lymphopoiesis. The ability of FL to stimulate the growth of immature B cells was assessed using distinct populations: CD43lowB220+ pre-B cells, CD43+B220+ pro-B cells, and CD43+B220low progenitors. FL failed to affect the growth of the pro-B or pre-B cells whether used alone or in combination with stem cell factor (SCF) or IL-7. In striking contrast, FL was a potent cofactor for the CD43+B220low progenitor cells, interacting with either IL-7 and/or SCF to stimulate their growth. The combination of FL with IL-7 plus SCF stimulated maximum expansion of these cells, albeit, less than that stimulated in stromal cell cultures. When the CD43+B220low progenitors were divided based on expression of heat stable Ag (CD24) into a CD24- and a CD24+ subset, the FL-responsive cells were contained only within the CD24- subset. FL interacted with SCF or with IL-7 to stimulate their growth resulting in a 20- and 50-fold increase in cellularity, respectively. Since the CD24- subset was the most immature of the B cell populations studied, our data suggest that FL costimulates the expansion of very primitive B cell progenitors.

flk2/flt3 ligand is a potent cofactor for the growth of primitive B cell progenitors

We have investigated the role of flk2/flt3 ligand (FL) in B cell lymphopoiesis. The ability of FL to stimulate the growth of immature B cells was assessed using distinct populations: CD43lowB220+ pre-B cells, CD43+B220+ pro-B cells, and CD43+B220low progenitors. FL failed to affect the growth of the pro-B or pre-B cells whether used alone or in combination with stem cell factor (SCF) or IL-7. In striking contrast, FL was a potent cofactor for the CD43+B220low progenitor cells, interacting with either IL-7 and/or SCF to stimulate their growth. The combination of FL with IL-7 plus SCF stimulated maximum expansion of these cells, albeit, less than that stimulated in stromal cell cultures. When the CD43+B220low progenitors were divided based on expression of heat stable Ag (CD24) into a CD24- and a CD24+ subset, the FL-responsive cells were contained only within the CD24- subset. FL interacted with SCF or with IL-7 to stimulate their growth resulting in a 20- and 50-fold increase in cellularity, respectively. Since the CD24- subset was the most immature of the B cell populations studied, our data suggest that FL costimulates the expansion of very primitive B cell progenitors.

Identification of polymorphism at the glutathione S-transferase, GSTM3 locus: evidence for linkage with GSTM1*A

Allelism in the glutathione S-transferase, GSTM3 gene has been identified using PCR with specific primers to exon 6/exon 7. Sequencing showed the mutant GSTM3*B allele to have a three-base deletion in intron 6 with a frequency of 0.158. The mutation generates a recognition sequence, 5'-AAGATA-3', for the negative transcription factor YY1. GSTM3*B was significantly associated with GSTM1*A.

Electron transport regulates exchange of two forms of photosystem II D1 protein in the cyanobacterium Synechococcus

Synechococcus sp. PCC 7942 modulates photosynthetic function by transiently replacing the constitutive D1 photosystem II protein, D1:1, with an alternate form, D1:2, to help counteract photoinhibition under excess light. We show that a temperature drop from 37 to 25 degrees C also drives D1:1/D1:2 exchange under constant, moderate light. Chilling or light-induced D1 exchange results from rapid loss of psbAI message coding for D1:1 and accumulation of psbAII and psbAIII messages coding for D1:2. During chilling, a large pool of a novel form, D1:2*, transiently accumulates, distinguishable from normal D1 by an increase in apparent molecular mass. D1:2* is not phosphorylated and is probably a functionally inactive, incompletely processed precursor. After acclimation to 25 degrees C, D1:2* disappears and D1:1 again predominates, although substantial D1:2 remains. Partial inhibition of electron transport under constant, moderate light also triggers the D1 exchange process. These treatments all increase excitation pressure on photosystem II relative to electron transport. Therefore, information from photosynthetic electron transport regulates D1 exchange without any requirement for a change in light intensity or quality, possibly via a redox sensing mechanism proximal to photosystem II.

Tissue-specific targeting of cytokine unresponsiveness in transgenic mice

The ubiquitous cellular distribution of certain cytokine receptors has hampered attempts to define the physiologically important cell-specific functions of cytokines in vivo. Herein, we report the generation of transgenic mice that express a dominant-negative IFN gamma receptor alpha chain mutant under the control of either the human lysozyme promoter or the murine lck proximal promoter, which display tissue-specific unresponsiveness in the macrophage or T cell compartments, respectively, to the pleiotropic cytokine, IFN gamma. We utilize these mice to identify previously undefined cellular targets of IFN gamma action in the development of a murine antimicrobial response and the mixed lymphocyte reaction. Moreover, we identify the macrophage as a critical responsive cell in manifesting the effects of IFN gamma in regulating CD4+ T helper subset development. These studies thus represent a novel approach to studying the cell-specific actions of an endogenously produced pleiotropic cytokine in vivo.

The cyanobacterium Synechococcus modulates Photosystem II function in response to excitation stress through D1 exchange

In this minireview we discuss effects of excitation stress on the molecular organization and function of PS II as induced by high light or low temperature in the cyanobacterium Synechococcus sp. PCC 7942. Synechococcus displays PS II plasticity by transiently replacing the constitutive D1 form (D1:1) with another form (D1:2) upon exposure to excitation stress. The cells thereby counteract photoinhibition by increasing D1 turn over and modulating PS II function. A comparison between the cyanobacterium Synechococcus and plants shows that in cyanobacteria, with their large phycobilisomes, resistance to photoinhibition is mainly through the dynamic properties (D1 turnover and quenching) of the reaction centre. In contrast, plants use antenna quenching in the light-harvesting complex as an important means to protect the reaction center from excessive excitation.

Susceptibility to astrocytoma and meningioma: influence of allelism at glutathione S-transferase (GSTT1 and GSTM1) and cytochrome P-450 (CYP2D6) loci

We describe a case-control study to identify associations between polymorphism at the cytochrome P-450 (CYP2D6) and glutathione S-transferase (GSTT1 and GSTM1) loci and susceptibility to astrocytoma and meningioma. Accordingly, genotype frequencies in 112 astrocytoma and 50 meningioma patients were compared with frequencies in 577 controls. GSTM1 genotype frequencies in these groups were not different. Logistic regression analysis showed GSTT1 null and CYP2D6 poor metabolizer were risk factors in astrocytoma (odds ratio = 2.67 P = 0.0005 and odds ratio = 4.17 P = 0.0043, respectively) and meningioma (odds ratio = 4.52, P = 0.0001 and odds ratio = 4.90, P = 0.0132, respectively) when corrected for the other variables. No interactive effects between genotypes were identified. The data suggest polymorphism at loci encoding carcinogen-metabolizing enzymes influences susceptibility to astrocytoma and meningioma, possibly by determining effectiveness in the detoxification of environmental carcinogens.

Non-response in a population study after an environmental disaster

After the grounding of the tanker MV Braer off the coast of Shetland an epidemiological study was rapidly instigated to determine any immediate or long-term health effects on the exposed resident population. The study was carried out in two phases, at the time of the grounding and five months later. The objective of this study is to determine the reasons for non-response in both phases of the Shetland Health Study. A telephone survey was performed on a systematic sample of non-responders from the exposed population in both phases of the study. The setting was the south mainland of Shetland. Fifty-nine of the 215 non-responders in the first phase of the study and 16 of the 86 non-responders in the second phase were surveyed. The main reasons for non-response were attitudinal rather than situational or organisational. Non-responders did not feel their health was affected, were not interested in the study or did not think the study was useful. Some were put off by the biological tests involved and some had difficulties with appointment times. Practical issues such as flexible appointment systems are easier to address than client characteristics but factors relating to distrust and indifference must be addressed if non-response rates are to be minimised.

NFATx, a novel member of the nuclear factor of activated T cells family that is expressed predominantly in the thymus

The nuclear factor of activated T cells (NFAT) regulates cytokine gene expression in T cells through cis-acting elements located in the promoters of cytokine genes. Here, we report the cDNA cloning, chromosomal localization, and initial characterization of a transcription factor related to NFATp and NFATc. The novel molecule, designated NFATx, exhibits in its middle a region very similar to the Rel homology domain in NFATc and NFATp. The amino-terminal region of NFATx also shows significant similarities to corresponding sequences in NFATc and NFATp and contains three copies of a conspicuous 17-residue motif of unknown function. We provide evidence showing that NFATx can reconstitute binding to the NFAT-binding site from the interleukin 2 promoter when combined with AP1 (c-Fos/c-Jun) polypeptides and that NFATx is capable of activating transcription of the interleukin 2 promoter in COS-7 cells when stimulated with phorbol ester and calcium ionophore. NFATx mRNA is preferentially and remarkably found in the thymus and at lower levels in peripheral blood leukocytes. The expression pattern of NFATx, together with its functional activity, strongly suggests that NFATx plays a role in the regulation of gene expression in T cells and immature thymocytes.

The role of the father in a pre-suicide state

In the self-examination that followed a patient's suicide attempt, the author was worried by three features which he had observed in an earlier suicide attempt by another patient: (1) the father had not featured in the analysis as much as would have been expected, (2) the suicide attempt occurred during a period when the time and place boundaries of the analytic setting were in jeopardy, e.g. the patient was absent from sessions; and (3) this coincided with the author having temporarily underestimated the suicidal risk. These three features were illuminated by a transference to a father who did not claim his child for himself and offer an alternative to fusion with a dangerous mother. Although the patient's suicide fantasies were based on a pathological bond with his mother, during the pre-suicide state the internalised father who had failed to protect his son from mother was evoked in the countertransference to function as a sanction for the suicidal act.

Enhancing critical-thinking skills: faculty-student partnerships in community health nursing

The enhancement of critical-thinking skills empowers students to participate in the building of healthy environments in a variety of settings. The authors describe the development and implementation of unique classroom strategies emphasizing the use of critical thinking by students, the forging of faculty-student partnerships in community health nursing, and the potential impact of these strategies on the expanding horizons of practice.

The MAP kinase signal transduction pathway is activated by the endogenous cannabinoid anandamide

Anandamide is an endogenous ligand for delta 9-tetrahydrocannabinol (THC) receptors. Incubation of cultured cells with anandamide or THC causes increased arachidonic acid release and eicosanoid biosynthesis. Here we demonstrate that the MAP kinase signal transduction pathway contributes to this response. Treatment of WI-38 fibroblasts with anandamide causes increased MAP kinase activity and increased phosphorylation of the arachidonate-specific cytoplasmic phospholipase A2 (cPLA2). Significantly, MAP kinase phosphorylates and activates cPLA2 [Lin, et al., Cell, 72 (1993) 269-278]. The MAP kinase signal transduction pathway may therefore mediate the effects of anadamide on cPLA2 activation and arachidonic acid release.

Smoking-related beliefs and behaviour among adults with asthma in a representative population sample

BACKGROUND

Smoking and exposure to environmental tobacco smoke are inadvisable for adults with asthma.

AIMS

To determine the smoking prevalence and daily smoking rate of asthmatics and compare smoking-related beliefs and behaviours among smokers with and without asthma. To compare beliefs of asthmatics about passive smoking and asthma, how many are exposed at home and what they do when they are exposed, with people who do not have asthma.

METHODS

A representative population survey of 3019 South Australian adults aged 15 years and older interviewed in their own homes in late 1992.

RESULTS

Twenty-eight per cent of asthmatics were smokers; mean daily smoking rate was 17.6. Asthmatics had similar patterns of smoking, readiness to quit and quit attempt histories as people without asthma. More than 40% of smokers with asthma did not perceive that smoking had greatly affected their health, over half did not believe they were at risk in future and two-thirds did not think future health problems would be serious. Among non-smokers, despite being more convinced of the effects of passive smoking on asthma, and being more concerned about exposure, those with asthma were no more likely to take protective action in response to actual or imminent exposure than those without asthma. One in ten non-smokers with asthma were exposed to smoking at home.

CONCLUSIONS

The smoking habits of adults with asthma are cause for concern, with many asthmatic smokers perceiving they are not personally at risk from their smoking. Health education principles should be used by health professionals caring for asthmatic smokers to guide the selection and delivery of smoking cessation strategies. Prevailing restrictions on indoor smoking play an important role in protecting the respiratory health of non-smokers with asthma.

Transcription factor ATF2 regulation by the JNK signal transduction pathway

Treatment of cells with pro-inflammatory cytokines or ultraviolet radiation causes activation of the c-Jun NH2-terminal protein kinase (JNK). Activating transcription factor-2 (ATF2) was found to be a target of the JNK signal transduction pathway. ATF2 was phosphorylated by JNK on two closely spaced threonine residues within the NH2-terminal activation domain. The replacement of these phosphorylation sites with alanine inhibited the transcriptional activity of ATF2. These mutations also inhibited ATF2-stimulated gene expression mediated by the retinoblastoma (Rb) tumor suppressor and the adenovirus early region 1A (E1A) oncoprotein. Furthermore, expression of dominant-negative JNK inhibited ATF2 transcriptional activity. Together, these data demonstrate a role for the JNK signal transduction pathway in transcriptional responses mediated by ATF2.

A functional factor X deficiency

A functional factor X deficiency is described which caused pronounced reduction in the in vitro activation of the extrinsic system while marginally affecting the in vitro activation of the intrinsic pathway. All studies were normal with the exception of a prolonged PT, an elevated factor X antigen, and low factor X activity. Western blot analysis revealed the presence of two factor X species. The abnormal molecule was of higher molecular weight. Interestingly, there was no bleeding associated with this deficiency. The biochemical basis of this defect is currently under investigation.

Pseudothrombocytopenia in plateletpheresis donors

BACKGROUND

EDTA pseudothrombocytopenia (PTCP) is an in vitro artifact in which the anticoagulation of blood with EDTA is associated with in vitro agglutination of platelets, resulting in a spuriously low platelet count. In apheresis donors, whole-blood samples for complete blood counts are routinely drawn into tubes anti-coagulated with EDTA.

STUDY DESIGN AND METHODS

Records of apheresis donors were examined to identify persons in whom the postdonation counts were less than 100 x 10(9) per L. Identified donors were studied to confirm the presence of PTCP by drawing blood samples into EDTA, heparin, and trisodium citrate for serial platelet counts at room-temperature incubation. Platelet counts in citrated plasma were measured before and after the addition of EDTA. A single HLA-matched component from an identified PTCP donor was monitored for response by corrected count increment in the recipient.

RESULTS

A total of nine donations were identified, involving 2 donors from a population of 945 donors (prevalence 0.2%). On testing, both donors were confirmed to have PTCP. The addition of EDTA to citrated plasma did not affect the platelet count. Response in a recipient to an HLA-matched component showed an acceptable corrected count increment.

CONCLUSION

PTCP may occur in plateletpheresis donors and result in needless medical referral or donor deferral. PTCP does not appear to alter the yield content of the component or to be passively transferred to a recipient.