Characterization of mouse Dach2, a homologue of Drosophila dachshund

The Drosophila genes eyeless, eyes absent, sine oculis and dachshund cooperate as components of a network to control retinal determination. Vertebrate homologues of these genes have been identified and implicated in the control of cell fate. We present the cloning and characterization of mouse Dach2, a homologue of dachshund. In situ hybridization studies demonstrate Dach2 expression in embryonic nervous tissues, sensory organs and limbs. This pattern is similar to mouse Dach1, suggesting a partially redundant role for these genes during development. In addition, we determine that Dach2 expression in the forebrain of Pax6 mutants and dermamyotome of Pax3 mutants is not detectably altered. Finally, genetic mapping experiments place mouse Dach2 on the X chromosome between Xist and Esx1. The identification of human DACH2 sequences at Xq21 suggests a possible role for this gene in Allan-Herndon syndrome, Miles-Carpenter syndrome, X-linked cleft palate and/or Megalocornea.

Spinal muscular atrophy disrupts the interaction of ZPR1 with the SMN protein

The survival motor neurons (smn) gene in mice is essential for embryonic viability. In humans, mutation of the telomeric copy of the SMN1 gene causes spinal muscular atrophy, an autosomal recessive disease. Here we report that the SMN protein interacts with the zinc-finger protein ZPR1 and that these proteins colocalize in small subnuclear structures, including gems and Cajal bodies. SMN and ZPR1 redistribute from the cytoplasm to the nucleus in response to serum. This process is disrupted in cells from patients with Werdnig-Hoffman syndrome (spinal muscular atrophy type I) that have SMN1 mutations. Similarly, decreased ZPR1 expression prevents SMN localization to nuclear bodies. Our data show that ZPR1 is required for the localization of SMN in nuclear bodies.

Dach1 mutant mice bear no gross abnormalities in eye, limb, and brain development and exhibit postnatal lethality

Drosophila dachshund is necessary and sufficient for compound eye development and is required for normal leg and brain development. A mouse homologue of dachshund, Dach1, is expressed in the developing retina and limbs, suggesting functional conservation of this gene. We have generated a loss-of-function mutation in Dach1 that results in the abrogation of the wild-type RNA and protein expression pattern in embryos. Homozygous mutants survive to birth but exhibit postnatal lethality associated with a failure to suckle, cyanosis, and respiratory distress. The heart, lungs, kidneys, liver, and skeleton were examined to identify factors involved in postnatal lethality, but these organs appeared to be normal. In addition, blood chemistry tests failed to reveal differences that might explain the lethal phenotype. Gross examination and histological analyses of newborn eyes, limbs, and brains revealed no detectable abnormalities. Since Dach1 mutants die shortly after birth, it remains possible that Dach1 is required for postnatal development of these structures. Alternatively, an additional Dach homologue may functionally compensate for Dach1 loss of function.

Reproductive disease and congenital malformations caused by Menangle virus in pigs

OBJECTIVE

To describe a new syndrome characterised by embryonic mortalities, stillbirths, mummified foetuses and congenital malformations in a herd of intensively farmed pigs.

DESIGN

Field observations, laboratory investigations and examination of breeding records.

PROCEDURE

Pathology examinations were performed on mummified and congenitally deformed piglets during an outbreak of reproductive disease at a 2600 sow intensive piggery in New South Wales from April to October 1997. Reproductive performance was monitored during the outbreak and breeding records were examined retrospectively. Serum and tissue samples from pigs were tested for evidence of infection with known porcine pathogens and for a new virus, Menangle virus, isolated from stillborn piglets with deformities from the affected piggery in August 1997.

RESULTS

Reproductive disease occurred sequentially in all four breeding units at the affected piggery over a period of 21 weeks. The farrowing percentages in each unit decreased from 80 to 82% before the outbreak to 63 to 78% during the outbreak and the number of live piglets per litter declined from a mean of 9.6 to 9.8 before the outbreak to 7.2 to 8.9 during the outbreak. The proportion of affected litters (litters with less than six liveborn piglets) was highest (64%) in the sixth week of the outbreak. Mummified foetuses, stillborn piglets with arthrogryposis, craniofacial deformities and degeneration of the brain and spinal cord, were observed along with occasional abortions. Sera from sows that produced affected litters contained neutralising antibodies against Menangle virus and there was evidence that this virus had been introduced to the piggery in February 1997.

CONCLUSIONS

Reproductive disease in pigs due to Menangle virus was characterised by stillbirths, mummification, embryonic death and infertility, along with abortions, skeletal deformities and degeneration of the brain and spinal cord in affected foetuses and stillborn piglets.

Epidemiology and control of Menangle virus in pigs

OBJECTIVE

To describe the epidemiology and eradication of Menangle virus infection in pigs.

DESIGN

Field observations and interventions, structured and unstructured serological surveys, prospective and cross-sectional serological studies and laboratory investigations.

PROCEDURE

Serum samples were collected from pigs at a 2600-sow intensive piggery in New South Wales that experienced an outbreak of reproductive disease in 1997. Serum samples were also collected from piggeries that received pigs from or supplied pigs to the affected piggery and from other piggeries in Australia. Serum and tissue samples were collected from pigs at piggeries experiencing reproductive disease in New South Wales. Sera and faeces were collected from grey-headed flying foxes (Pteropus poliocephalus) in the region of the affected piggery. Serum samples were tested for neutralising antibodies against Menangle virus. Virus isolation was attempted from faeces.

RESULTS

Following the outbreak of reproductive disease, sera from 96% of adult pigs at the affected piggery, including sows that produced affected litters, contained neutralising antibodies against Menangle virus. Neutralising antibodies were also detected in sera from 88% of finisher pigs at two piggeries receiving weaned pigs from the affected piggery. No evidence of Menangle virus infection was found in other piggeries in Australia. In cross-sectional studies at the affected piggery, colostral antibodies were undetectable in most pigs by 14 to 15 weeks of age. By slaughter age or entry to the breeding herd, 95% of pigs developed high antibody titres (> or = 128) against Menangle virus in the virus neutralisation test. Menangle virus was eradicated from the affected piggery following a program of serological testing and segregation. Neutralising antibodies against Menangle virus were also detected in P poliocephalus from two colonies in the vicinity of the affected piggery. Two piggery workers were infected with Menangle virus. There was no evidence of infection in cattle, sheep, birds, rodents, feral cats and a dog at the affected piggery.

CONCLUSIONS

Serological evidence of infection with Menangle virus was detected in pigs at a piggery that had experienced reproductive disease, in pigs at two associated piggeries and in fruit bats in the region of the piggery. Two humans were infected. The mode of transmission between pigs is unknown, but spread by faecal or urinary excretion is postulated. This virus can be eradicated by the segregation of pigs into discrete age groups.

Control of tumor size and disease activity during cotreatment with octreotide and the growth hormone receptor antagonist pegvisomant in an acromegalic patient

We describe the case of an acromegalic subject, who was the first patient ever treated with the GH receptor antagonist pegvisomant. Furthermore, in this particular patient, progression in tumor size was encountered during treatment with pegvisomant. The patient described did benefit from cotreatment with pegvisomant and octreotide, including decreased GH levels, normalization of serum insulin-like growth factor I concentrations, and improvement of visual field defects.

Metabolic and behavioral responses in pre-weanling rats following alteration of maternal diet

In rat pups, blockade of fatty acid oxidation by administration of 2-mercaptoacetate (MA) produces an increase in independent ingestion by 12 days of age. In contrast, administration of methyl palmoxirate (MP) fails to increase intake or to alter oxidation of fatty acids in young rats due to the high proportion of medium chain triglycerides (MCT) in rat milk. In the present experiments, the composition of rat milk was altered by placing dams on a high fat (HF) diet to examine the development of ingestive responding in rat pups following administration of MP. Following delivery of MP (0.5--10 mg/kg), pups were placed in a cage inside an incubator for 1, 3, or 6 h, and then received an intake test consuming a commercial half-and-half milk diet from the floor of test containers. Blood was collected from additional groups of pups for measurement of beta-hydroxybutyrate (beta HBA) and glucose levels. The results demonstrated that administration of MP produced significant reductions in beta HBA levels after 3 h in 12- and 15-day-old pups, but behavioral responses were noted only in pups aged 15 days. Similar results were obtained following administration of MA to pups reared by dams on HF diets; physiological responses were observed at 12 and 15 days of age, but behavioral responses were not observed after administration of MA until 15 days of age. Taken together, these results suggest that (1) changes in fatty acid oxidation may represent an early metabolic signal that can influence intake in rat pups and (2) alteration of the dam's diet produces physiological and behavioral changes in the pups.

Growth regulation via p38 mitogen-activated protein kinase in developing liver

During normal development in the rat, hepatocytes undergo marked changes in the rate of proliferation. We have previously observed transient G(1) growth arrest at term, re-activation of proliferation immediately after birth, and a gradual transition to the quiescent adult hepatocyte phenotype after postnatal day 4. We hypothesized that these changes in proliferation are due in part to growth inhibitory effects mediated by the p38 mitogen-activated protein kinase pathway. p38 kinase activity measurements showed an inverse relationship with hepatocyte proliferation during the perinatal and postnatal transitions, whereas p38 content remained constant. Anisomycin activated the p38 pathway in fetal hepatocyte cultures while inducing growth inhibition that was sensitive to the p38 inhibitor, SB203580. Activation of p38 in these cultures, via transient transfection with a constitutively active form of its upstream kinase MKK6, also inhibited DNA synthesis as well as reducing cyclin D1 content. Transfection with inactive MKK6 did neither. Furthermore, MKK6-induced growth arrest was sensitive to SB203580. Finally, administration of SB203580 to near-term fetal rats in utero abrogated the transient hepatocyte growth arrest that occurs at term. These findings indicate a role for the p38 mitogen-activated protein kinase pathway in the physiological regulation of hepatocyte proliferation during normal development in the rat.

Beta-arrestin 2: a receptor-regulated MAPK scaffold for the activation of JNK3

beta-Arrestins, originally discovered in the context of heterotrimeric guanine nucleotide binding protein-coupled receptor (GPCR) desensitization, also function in internalization and signaling of these receptors. We identified c-Jun amino-terminal kinase 3 (JNK3) as a binding partner of beta-arrestin 2 using a yeast two-hybrid screen and by coimmunoprecipitation from mouse brain extracts or cotransfected COS-7 cells. The upstream JNK activators apoptosis signal-regulating kinase 1 (ASK1) and mitogen-activated protein kinase (MAPK) kinase 4 were also found in complex with beta-arrestin 2. Cellular transfection of beta-arrestin 2 caused cytosolic retention of JNK3 and enhanced JNK3 phosphorylation stimulated by ASK1. Moreover, stimulation of the angiotensin II type 1A receptor activated JNK3 and triggered the colocalization of beta-arrestin 2 and active JNK3 to intracellular vesicles. Thus, beta-arrestin 2 acts as a scaffold protein, which brings the spatial distribution and activity of this MAPK module under the control of a GPCR.

Dual roles for c-Jun N-terminal kinase in developmental and stress responses in cerebellar granule neurons

c-Jun N-terminal kinases (JNKs) typically respond strongly to stress, are implicated in brain development, and are believed to mediate neuronal apoptosis. Surprisingly, however, JNK does not respond characteristically to stress in cultured cerebellar granule (CBG) neurons, a widely exploited CNS model for studies of death and development, despite the regulation of its substrate c-Jun. To understand this anomaly, we characterized JNK regulation in CBG neurons. We find that the specific activity of CBG JNK is elevated considerably above that from neuron-like cell lines (SH-SY5Y, PC12); however, similar elevated activities are found in brain extracts. This activity does not result from cellular stress because the stress-activated protein kinase p38 is not activated. We identify a minor stress-sensitive pool of JNK that translocates with mitogen-activated protein kinase kinase-4 (MKK4) into the nucleus. However, the major pool of total activity is cytoplasmic, residing largely in the neurites, suggesting a non-nuclear role for JNK in neurons. A third JNK pool is colocalized with MKK7 in the nucleus, and specific activities of both increase during neuritogenesis, nuclear JNK activity increasing 10-fold, whereas c-Jun expression and activity decrease. A role for JNK during differentiation is supported by modulation of neuritic architecture after expression of dominant inhibitory regulators of the JNK pathway. Channeling of JNK signaling away from c-Jun during differentiation is consistent with the presence in the nucleus of the JNK/MKK7 scaffold protein JNK-interacting protein, which inhibits JNK-c-Jun interaction. We propose a model in which distinct pools of JNK serve different functions, providing a basis for understanding multifunctional JNK signaling in differentiating neurons.

JNK1 is required for T cell-mediated immunity against Leishmania major infection

c-Jun N-terminal kinase (JNK) is a mitogen-activated protein kinase that plays important regulatory roles in helper T cell differentiation. In the current study, we used Jnk1-deficient mice to examine the function of JNK during an in vivo pathogenic infection, leishmaniasis, which is strongly influenced by Th1/Th2 effector mechanisms. The data show that Jnk1-deficient mice, despite their usually genetically resistant background, were unable to resolve Leishmania infections. Jnk1-/- mice displayed reduced delayed-type hypersensitivity in response to the pathogen, which was associated with a T cell defect. We found that, although these mice can direct an apparent Th1-response, there is also simultaneous generation of Leishmania-specific Th2 responses, which possibly down-modulate protective Th1-mediated immune function. These findings demonstrate that the negative regulation of Th2 cytokine production by the JNK1 signaling pathway is essential for generating Th1-polarized immunity against intracellular pathogens, such as Leishmania major.

Differential requirement for the stress-activated protein kinase/c-Jun NH(2)-terminal kinase in RNAdamage-induced apoptosis in primary and in immortalized fibroblasts

Onconase, an anticancer ribonuclease, damages cellular tRNA and causes caspase-dependent apoptosis in targeted cells (M. S. Iordanov, O. P. Ryabinina, J. Wong, T. H. Dinh, D. L. Newton, S. M. Rybak, and B. E. Magun. Cancer Res. 60, 1983-1994, 2000). The proapoptotic action of onconase depends on its RNase activity, but the molecular mechanisms leading to RNA damage-induced caspase activation are completely unknown. In this study, we have investigated whether onconase activates two signal-transduction pathways commonly stimulated by conventional chemo- and radiotherapy, namely the stress-activated protein kinase (SAPK) cascade and the pathway leading to the activation of nuclear factor-kappa B (NF-kappaB). We found that, in all cell types tested, onconase is a potent activator of SAPK1 (JNK1 and JNK2) and SAPK2 (p38 MAP kinase), but that it is incapable of activating NF-kappaB. Inhibition of p38 MAP kinase activity with a pharmacological inhibitor, SB203580, demonstrated that p38 MAP kinase is not required for onconase cytotoxicity. Using explanted fibroblasts from mice that contain targeted disruption of both jnk1 and jnk2 alleles, we found that JNKs are important mediators of onconase-induced cytotoxicity. Surprisingly, following the immortalization of these same cells with human papilloma virus (HPV16) gene products E6 and E7, additional proapoptotic pathways (exclusive of JNK) were provoked by onconase. Our results demonstrate that onconase may activate proapoptotic pathways in tumor cells that are not able to be accessed in normal cells. These results present the possibility that the cytotoxic activity of onconase in normal cells may be reduced by blocking the activity of JNKs.

c-Jun NH(2)-terminal kinase inhibits targeting of the protein phosphatase calcineurin to NFATc1

The protein phosphatase calcineurin is a critical mediator of calcium signals during T-cell activation. One substrate of calcineurin is the transcription factor NFATc1, which is retained in the cytoplasm of quiescent cells. NFATc1 activation requires the translocation of the transcription factor into the nucleus, a process that is mediated by calcineurin. This interaction with calcineurin requires a targeting domain (PxIxIT motif) located in the NH(2)-terminal region of NFATc1. Here we demonstrate that the calcineurin targeting domain of NFATc1 is phosphorylated and inactivated by the c-Jun NH(2)-terminal kinase (JNK). This disruption of calcineurin targeting inhibits the nuclear accumulation and transcription activity of NFATc1 and accounts for the observation that Jnk1(-/-) T cells exhibit greatly increased NFATc1-dependent nuclear responses.

Role of the guanosine triphosphatase Rac2 in T helper 1 cell differentiation

T helper 1 (TH1) cells mediate cellular immunity, whereas TH2 cells potentiate antiparasite and humoral immunity. We used a complementary DNA subtraction method, representational display analysis, to show that the small guanosine triphosphatase Rac2 is expressed selectively in murine TH1 cells. Rac induces the interferon-gamma (IFN-gamma) promoter through cooperative activation of the nuclear factor kappa B and p38 mitogen-activated protein kinase pathways. Tetracycline-regulated transgenic mice expressing constitutively active Rac2 in T cells exhibited enhanced IFN-gamma production. Dominant-negative Rac inhibited IFN-gamma production in murine T cells. Moreover, T cells from Rac2-/- mice showed decreased IFN-gamma production under TH1 conditions in vitro. Thus, Rac2 activates TH1-specific signaling and IFN-gamma gene expression.

Activation of p38 MAP kinase in T cells facilitates the immune response to the influenza virus

Activation of p38 MAP kinase in T cells leads to increased interferon-gamma production in CD4+ and CD8+ T cells, and the selective cell death of CD8+ T cells. To address the role of p38 MAP kinase activation in T cells during an in vivo immune response, we examined the response against the influenza virus in transgenic mice expressing a constitutively activated MKK6 (MKK6(Glu)), an upstream activator of p38 MAP kinase. Activated CD4+ T cells accumulate in the lung and mediastinal lymph node of both wild-type and MKK6(Glu) transgenic mice upon intranasal inoculation with the influenza virus. MKK6(Glu) CD8+ T cells, however, disappear rapidly from the mediastinal lymph node but accumulate in the lung tissue. We demonstrate that interleukin-6, a cytokine produced by lung epithelial cells, partially protects CD8+ T cells from the cell death induced by p38 MAP kinase activation. During the influenza infection in MKK6(Glu) transgenic mice, reduced virus titers were also observed despite a normal B-cell antibody response. These results indicate that the activation of p38 MAP kinase in T cells affects the in vivo antiviral immune response.

Requirement of JNK for stress-induced activation of the cytochrome c-mediated death pathway

The c-Jun NH2-terminal kinase (JNK) is activated when cells are exposed to ultraviolet (UV) radiation. However, the functional consequence of JNK activation in UV-irradiated cells has not been established. It is shown here that JNK is required for UV-induced apoptosis in primary murine embryonic fibroblasts. Fibroblasts with simultaneous targeted disruptions of all the functional Jnk genes were protected against UV-stimulated apoptosis. The absence of JNK caused a defect in the mitochondrial death signaling pathway, including the failure to release cytochrome c. These data indicate that mitochondria are influenced by proapoptotic signal transduction through the JNK pathway.

JNK is required for effector T-cell function but not for T-cell activation

The hallmark of T-cell activation is the production of interleukin 2 (IL-2). c-Jun amino-terminal kinase (JNK), a MAP kinase that phosphorylates c-Jun and other components of the AP-1 group of transcription factors, has been implicated in the activation of IL-2 expression. Previously, we found that T cells from mice deficient in the Jnk1 or Jnk2 gene can be activated and produce IL-2 normally, but are deficient in functional differentiation into Th1 or Th2 subsets. However, studies of mice with compound mutations indicate that JNK1 and JNK2 are redundant during mouse development. Here we use three new mouse models in which peripheral T cells completely lack JNK proteins or signalling, to test whether the JNK signalling pathway is crucial for IL-2 expression and T-cell activation. Unexpectedly, these T cells made more IL-2 and proliferated better than wild-type cells. However, production of effector T-cell cytokines did require JNK. Thus, JNK is necessary for T-cell differentiation but not for naive T-cell activation.

Treatment of acromegaly with the growth hormone-receptor antagonist pegvisomant

BACKGROUND

Patients with acromegaly are currently treated with surgery, radiation therapy, and drugs to reduce hypersecretion of growth hormone, but the treatments may be ineffective and have adverse effects. Pegvisomant is a genetically engineered growth hormone-receptor antagonist that blocks the action of growth hormone.

METHODS

We conducted a 12-week, randomized, double-blind study of three daily doses of pegvisomant (10 mg, 15 mg, and 20 mg) and placebo, given subcutaneously, in 112 patients with acromegaly.

RESULTS

The mean (+/-SD) serum concentration of insulin-like growth factor I (IGF-I) decreased from base line by 4.0+/-16.8 percent in the placebo group, 26.7+/-27.9 percent in the group that received 10 mg of pegvisomant per day, 50.1+/-26.7 percent in the group that received 15 mg of pegvisomant per day, and 62.5+/-21.3 percent in the group that received 20 mg of pegvisomant per day (P<0.001 for the comparison of each pegvisomant group with placebo), and the concentrations became normal in 10 percent, 54 percent, 81 percent, and 89 percent of patients, respectively (P<0.001 for each comparison with placebo). Among patients treated with 15 mg or 20 mg of pegvisomant per day, there were significant decreases in ring size, soft-tissue swelling, the degree of excessive perspiration, and fatigue. The score fortotal symptoms and signs of acromegaly decreased significantly in all groups receiving pegvisomant (P< or =0.05). The incidence of adverse effects was similar in all groups.

CONCLUSIONS

On the basis of these preliminary results, treatment of patients who have acromegaly with a growth hormone-receptor antagonist results in a reduction in serum IGF-I concentrations and in clinical improvement.

Conference highlight: do T cells care about the mitogen-activated protein kinase signalling pathways?

Mitogen-activated protein (MAP) kinases, which include the extracellular response kinases, p38 and c-Jun amino terminal kinases (JNK), play a significant role in mediating signals triggered by cytokines, growth factors and environmental stress. The JNK and p38 MAP kinases have been involved in growth, differentiation and cell death in different cell types. In the present paper, we describe how the JNK and p38 MAP kinase signalling pathways are regulated and their role during thymocyte development and the activation and differentiation of T cells in the peripheral immune system. The results from these studies demonstrate that the JNK and p38 MAP kinase signalling pathways regulate different aspects of T-cell mediated immune responses.

Carbon monoxide has anti-inflammatory effects involving the mitogen-activated protein kinase pathway

The stress-inducible protein heme oxygenase-1 provides protection against oxidative stress. The anti-inflammatory properties of heme oxygenase-1 may serve as a basis for this cytoprotection. We demonstrate here that carbon monoxide, a by-product of heme catabolism by heme oxygenase, mediates potent anti-inflammatory effects. Both in vivo and in vitro, carbon monoxide at low concentrations differentially and selectively inhibited the expression of lipopolysaccharide-induced pro-inflammatory cytokines tumor necrosis factor-alpha, interleukin-1beta, and macrophage inflammatory protein-1beta and increased the lipopolysaccharide-induced expression of the anti-inflammatory cytokine interleukin-10. Carbon monoxide mediated these anti-inflammatory effects not through a guanylyl cyclase-cGMP or nitric oxide pathway, but instead through a pathway involving the mitogen-activated protein kinases. These data indicate the possibility that carbon monoxide may have an important protective function in inflammatory disease states and thus has potential therapeutic uses.

Molecular determinants that mediate selective activation of p38 MAP kinase isoforms

The p38 mitogen-activated protein kinase (MAPK) group is represented by four isoforms in mammals (p38alpha, p38beta2, p38gamma and p38delta). These p38 MAPK isoforms appear to mediate distinct functions in vivo due, in part, to differences in substrate phosphorylation by individual p38 MAPKs and also to selective activation by MAPK kinases (MAPKKs). Here we report the identification of two factors that contribute to the specificity of p38 MAPK activation. One mechanism of specificity is the selective formation of functional complexes between MAPKK and different p38 MAPKs. The formation of these complexes requires the presence of a MAPK docking site in the N-terminus of the MAPKK. The second mechanism that confers signaling specificity is the selective recognition of the activation loop (T-loop) of p38 MAPK isoforms. Together, these processes provide a mechanism that enables the selective activation of p38 MAPK in response to activated MAPKK.

Laboratory and field studies of an antigen capture ELISA for bluetongue virus

An improved bluetongue antigen capture ELISA (BTACE) technique was evaluated for its ability to detect the full range of 24 bluetongue (BLU) serotypes. The BTACE detected all 24 serotypes in cell culture fluids, including eight serotypes where the representative strains originated from both Australia and also from the South African reference collection. The amount of infectious virus required to obtain a positive BTACE result varied between 100-1000 TCID50. This was approximately 10-fold more sensitive than the antigen capture test described previously (Hosseini, M., Hawkes, R.A., Kirkland, P.D., Dixon, R., 1998. J. Virol. Methods 75, 39-46.). The BTACE method was compared with conventional passage in cell culture to detect the presence of virus in the tissues of embryonated chicken eggs (ECEs) which had been inoculated intravenously with the blood of sheep and cattle infected experimentally with the eight Australian serotypes of BLU (1, 3, 9, 15, 16, 20, 21, and 23). The BTACE method was at least as sensitive as the conventional cell culture detecting virus in ECEs, obviating the need for prolonged cell culture passage to detect the virus. A comparison of the amount of antigen detected in different embryo tissues indicated that liver homogenates gave the highest positive to negative ratios in the BTACE and were selected as the specimen of choice. In studies of sheep infected with all 24 South African reference BLU serotypes this new BTACE was able to detect viraemia with all serotypes. Finally, the BTACE was validated in surveillance programs for BLU in both New South Wales, Australia and in Yunnan Province, People's Republic of China. Blood samples from sentinel cattle were inoculated into ECEs. Homogenised ECE livers were tested by BTACE and those positive were passaged subsequently in cell culture for virus isolation and identification. This protocol led to the efficient isolation of field isolates of many serotypes. The high sensitivity and broad reactivity of the method indicates that it should be valuable for BLU diagnosis and surveillance programs.

Activation of p38 mitogen-activated protein kinase in vivo selectively induces apoptosis of CD8(+) but not CD4(+) T cells

CD4(+) and CD8(+) T cells play specific roles during an immune response. Different molecular mechanisms could regulate the proliferation, death, and effector functions of these two subsets of T cells. The p38 mitogen-activated protein (MAP) kinase pathway is induced by cytokines and environmental stress and has been associated with cell death and cytokine expression. Here we report that activation of the p38 MAP kinase pathway in vivo causes a selective loss of CD8(+) T cells due to the induction of apoptosis. In contrast, activation of p38 MAP kinase does not induce CD4(+) T-cell death. The apoptosis of CD8(+) T cells is associated with decreased expression of the antiapoptotic protein Bcl-2. Regulation of the p38 MAP kinase pathway in T cells is therefore essential for the maintenance of CD4/CD8 homeostasis in the peripheral immune system. Unlike cell death, gamma interferon production is regulated by the p38 MAP kinase pathway in both CD4(+) and CD8(+) T cells. Thus, specific aspects of CD4(+) and CD8(+) T-cell function are differentially controlled by the p38 MAP kinase signaling pathway.