Anti-CD3 activation of human CD4+ T cells increases expression of the intracellular beta-endorphin endopeptidase (IDE/gamma-EpGE)

In this study, increased expression of an endopeptidase hydrolyzing beta-endorphin (beta-Ep) to gamma-endorphin (gamma-Ep, beta-Ep1-17) was observed upon immobilized anti-CD3 stimulated activation of human peripheral blood CD4+ T cells (hCD4+ T cells). Although freshly isolated hCD4+ T cells are devoid of significant beta-Ep endopeptidase activity ( < 0.1 nmol h(-1) 10(6) cells (-1)), activation of these cells with immobilized anti-CD3 results in a time dependent appearance of beta-Ep endopeptidase activity which reaches a maximal value of 17.4+/-0.48 nmol h(-1) 10(6) cells(-1) after 48 h of culture. Significant up-regulation of both mRNA encoding IDE/gamma-EpGE and immunoreactive protein are observed in anti-CD3 stimulated hCD4+ T cells, indicating transcription and translation of IDE/gamma-EpGE may be elevated. No significant hydrolysis of exogenous beta-Ep is observed with intact hCD4+ T cells whether quiescent or activated or from preparations of hCD4+ T cell membranes. Therefore, this activity appears to be intracellular. Immunoreactive IDE/gamma-EpGE is detected inside activated hCD4+ T cells. Analysis of metabolites generated upon hydrolysis of beta-Ep with lysed activated hCD4+ T cell preparations identified the presence of: beta-Ep1-18, beta-Ep2-18, beta-Ep1-17, beta-Ep2-17, beta-Ep18-31, beta-Ep19-31, beta-Ep1-13, beta-Ep2-13, beta-Ep18-26, and beta-Ep20-31 as major metabolites and the majority of these are consistent with beta-Ep hydrolytic activity attributable to IDE/gamma-EpGE.

Unusual association of intractable temporal lobe seizures and intracranial aneurysms in an adolescent: is it a coincidence?

Intracranial aneurysms in the pediatric age group are rare occurrences. They usually present with subarachnoid hemorrhage or mass effect. Their association with epilepsy has rarely been reported; such concurrence may not be a coincidence. We present a 16-year-old girl with a 5-year history of medically intractable complex partial seizures. Preoperative electrophysiological and neuroimaging studies demonstrated an epileptogenic focus and atrophy in the right mesial temporal lobe, and ipsilateral incidental aneurysm at the carotid artery bifurcation. The patient underwent a complete right anterior temporal lobectomy, followed by clipping of the aneurysm. We concluded that the epilepsy management in association with cerebral aneurysms is controversial, but when surgery is indicated, clipping of the aneurysm and resection of the epileptogenic focus may provide the optimal outcome. The relevant literature is reviewed and the possible mechanisms of production of epilepsy by intracranial aneurysms are discussed.

[Formation of neutralizing antibodies in therapy of multiple sclerosis with interferon beta-1b. Practical procedure in suspected therapeutic failure]

Interferon beta-1b has been shown to reduce the frequency and severity of exacerbations in relapsing-remitting multiple sclerosis (MS). In the North American study, however, approximately 35% of patients developed neutralizing antibodies leading to a diminution of therapeutic efficacy according to current investigations. In contrast, antibody-negative patients showed a 50% reduction in the annual relapse rate compared to patients receiving placebo. Here we provide practical guidelines for neutralizing antibody testing if treatment failure is suspected.

Increased expression of an endopeptidase (gamma-EGE/IDE) hydrolyzing beta-endorphin during differentiation and maturation of bone marrow macrophages

The presence and regulated expression of peptidase activity is a powerful mechanism with the potential to terminate or alter receptor recognition, cell membrane signal transduction, and physiological responses of immune cells to exogenous opioid peptides. In this study, the expression of an endopeptidase that hydrolyzes beta-endorphin to gamma-endorphin and other peptide products was investigated during in vitro differentiation and maturation of recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) -derived, bone marrow-derived macrophages. In freshly isolated intact isolated mouse bone marrow cells the rate of beta-endorphin hydrolysis is undetectable (<0.1 nmol beta-endorphin hydrolyzed/h/10[6] cells). However, total intracellular beta-endorphin hydrolytic activity was increased significantly to 20.0 +/- 1.7 nmol/h/10(6) cells in the mature mouse macrophages derived in vitro by culture with rGM-CSF. rGM-CSF-derived macrophages expressed significantly higher levels of both protein and mRNA for the major beta-endorphin endopeptidase, gamma-endorphin-generating enzyme/insulin-degrading enzyme (gamma-EGE/IDE). Moreover, this enzymatic activity appears to be responsible for cleavage of exogenous beta-endorphin by intact rGM-CSF-derived macrophages or peritoneal macrophages to generate gamma-endorphin and other peptide products.

Effect of the presence of transgenic H and L chain genes on B cell development and allelic exclusion

The expression of various components of the antigen receptor is closely associated with the developmental progression of B lymphocytes. For this reason, introduction of rearranged Ig transgenes exerts profound effects on B cell development. In these studies we show that the presence of transgenes for both mu and delta H as well as L chains accelerates the rate of B cell maturation resulting in the appearance of large numbers of IgD-expressing B lymphocytes in vitro that are otherwise undetectable. In addition, allelic exclusion, normally exerted very effectively by these particular transgenes (carried in the MD-3 strain), was lost in the long-term bone marrow cultures. These findings can be recapitulated in vivo by serial adoptive transfers of bone marrow cells from the transgenic animals into lethally irradiated recipients. We conclude from these studies that allelic exclusion is not necessarily mediated by any one event but may be a result of the integrated occurrence of Ig H chain gene rearrangement, accumulation of transcription factors, along with the ordered progression of B cell differentiation under the influence of the appropriate inductive microenvironment. These findings may account for at least some of the observed cases of allelic inclusion in transgenic animals.

Nup93, a vertebrate homologue of yeast Nic96p, forms a complex with a novel 205-kDa protein and is required for correct nuclear pore assembly

Yeast and vertebrate nuclear pores display significant morphological similarity by electron microscopy, but sequence similarity between the respective proteins has been more difficult to observe. Herein we have identified a vertebrate nucleoporin, Nup93, in both human and Xenopus that has proved to be an evolutionarily related homologue of the yeast nucleoporin Nic96p. Polyclonal antiserum to human Nup93 detects corresponding proteins in human, rat, and Xenopus cells. Immunofluorescence and immunoelectron microscopy localize vertebrate Nup93 at the nuclear basket and at or near the nuclear entry to the gated channel of the pore. Immunoprecipitation from both mammalian and Xenopus cell extracts indicates that a small fraction of Nup93 physically interacts with the nucleoporin p62, just as yeast Nic96p interacts with the yeast p62 homologue. However, a large fraction of vertebrate Nup93 is extracted from pores and is also present in Xenopus egg extracts in complex with a newly discovered 205-kDa protein. Mass spectrometric sequencing of the human 205-kDa protein reveals that this protein is encoded by an open reading frame, KIAAO225, present in the human database. The putative human nucleoporin of 205 kDa has related sequence homologues in Caenorhabditis elegans and Saccharomyces cerevisiae. The analyze the role of the Nup93 complex in the pore, nuclei were assembled that lack the Nup93 complex after immunodepletion of a Xenopus nuclear reconstitution extract. The Nup93-complex-depleted nuclei are clearly defective for correct nuclear pore assembly. From these experiments, we conclude that the vertebrate and yeast pore have significant homology in their functionally important cores and that, with the identification of Nup93 and the 205-kDa protein, we have extended the knowledge of the nearest-neighbor interactions of this core in both yeast and vertebrates.

Soma-germ cell interactions in Caenorhabditis elegans: multiple events of hermaphrodite germline development require the somatic sheath and spermathecal lineages

Germ cells complete multiple events to form functional oocytes and sperm. In the Caenorhabditis elegans hermaphrodite, germ cells develop in proximity to the somatic gonad sheath and spermathecal cells. We present evidence from cellular laser ablation studies indicating that cells of the somatic sheath and spermathecal lineages play critical roles in four events of hermaphrodite germline development. (1) Cells of the sheath and spermathecal lineage support germline proliferation; ablation of sheath/spermathecal precursor cells reduces mitotic proliferation. (2) These cells also play a role in the exit of germ cells from the pachytene stage of meiotic prophase and/or gamete differentiation; ablation can result in undifferentiated germ cells arrested in pachytene. (3) Proximal sheath and distal spermatheca cells are required for ovulation of the oocyte. During wild-type ovulation, the mature oocyte is expelled from the gonad arm by contraction of the proximal myoepithelial sheath and dilation of the distal spermatheca. Ablation of these cells traps mature oocytes in the gonad arm where they endomitotically replicate their DNA (the Emo phenotype). (4) Cells of the sheath and spermathecal lineage also appear to promote the male germ cell fate since ablation of one sheath/spermathecal precursor cell can feminize the hermaphrodite germ line. These somatic ablation-induced germline phenotypes demonstrate that the somatic gonad is required for multiple events in C. elegans germline development. Further, these results suggest that soma to germline cell-cell interactions in C. elegans are physiological in character (i.e., contraction during ovulation) as well as regulatory.

Role of the autonomic nervous system in the acute blood pressure elevation during repetitive hypoxic and hypercapnic breathing in rats

Acute intermittent repetitive hypoxia simulating sleep apnoea syndrome is responsible for acute rises in blood pressure (BP). In the rat, the BP rises are enhanced by added hypercapnia. To investigate the role of the autonomic nervous system (ANS) in acute hypertension during repetitive hypoxia alone, FiO2 (inspiratory fractional concentration of oxygen) 2 to 5%, or combined with hypercapnia FiCO2 (inspiratory fractional concentration of carbon dioxide) 2 to 5%, we used autonomic blockade by atropine (1 mg kg-1) + propranolol (1 mg kg-1)-phentolamine (1 mg kg-1). Seven Wistar male rats were chronically instrumented with two aortic and venous catheters. Repetitive administration of N2 and N2 + CO2 for 10s followed by 20s compressed air was repeated for 4-5 min before (control) and after autonomic blockade. After autonomic blockade there was no significant difference in mean blood pressure (MBP) during severe hypoxia (SHO) (14.9 +/- 0.5 mmHg) compared to control (10.5 +/- 0.9 mmHg), while MBP was significantly decreased in severe hypoxia + hypercapnia (SHOHC) (14.1 +/- 0.4 mmHg) compared to control (26.8 +/- 0.3 mmHg) (p < 0.001). We conclude that the acute BP rise observed during hypoxic breathing is not due to the activation of ANS, but when hypercapnia is added to the hypoxic stimulus about half of pressor response is caused by ANS.

Regulation of IgM and IgD heavy chain gene expression: effect of abrogation of intergenic transcriptional termination

Early IgM+ B cells express little or no membrane IgD due to the low abundance of delta mRNA. Extensive transcriptional termination regulated by sequences in the intronic region between mu and delta heavy chain genes may be the primary reason for the lack of delta gene transcription. We have examined the effect of deletion of these sequences on the regulation of IgM and IgD heavy chain gene expression in transfectants as well as mice carrying this otherwise intact transgene. By run-on transcriptional measurement, we show that the delta exons are transcribed in bone marrow B cells from these transgenic mice. However, in spite of the induced premature synthesis of the full-length mu-delta transcript in pre-B cells, processing to delta mRNA does not occur until the lymphocytes express cell surface IgM. Therefore, during B cell development, synthesis of the full-length transcript is a necessary but not sufficient condition for initiation of delta mRNA synthesis. Furthermore, unexpectedly, the abrogation of transcriptional termination was found to also affect the processing of the primary transcript to microM mRNA. These results show that expression of IgD in primary B cells is stringently regulated and closely linked to IgM expression.

Regulation of IgM and IgD heavy chain gene expression: effect of abrogation of intergenic transcriptional termination

Early IgM+ B cells express little or no membrane IgD due to the low abundance of delta mRNA. Extensive transcriptional termination regulated by sequences in the intronic region between mu and delta heavy chain genes may be the primary reason for the lack of delta gene transcription. We have examined the effect of deletion of these sequences on the regulation of IgM and IgD heavy chain gene expression in transfectants as well as mice carrying this otherwise intact transgene. By run-on transcriptional measurement, we show that the delta exons are transcribed in bone marrow B cells from these transgenic mice. However, in spite of the induced premature synthesis of the full-length mu-delta transcript in pre-B cells, processing to delta mRNA does not occur until the lymphocytes express cell surface IgM. Therefore, during B cell development, synthesis of the full-length transcript is a necessary but not sufficient condition for initiation of delta mRNA synthesis. Furthermore, unexpectedly, the abrogation of transcriptional termination was found to also affect the processing of the primary transcript to microM mRNA. These results show that expression of IgD in primary B cells is stringently regulated and closely linked to IgM expression.

Chronic treatments with 5-HT1A agonists attenuate posthypoxic myoclonus in rats

Following 10 min cardiac arrest and resuscitation, male Sprague-Dawley rats developed posthypoxic myoclonus. This phenomenon peaked at 14 days and disappeared by 60 days after cardiac arrest. From previous results, the 5-hydroxytryptamine (5-HT) system was implicated in the pathogenesis of the disease. In the present study, we investigated the involvement of 5-HT1A receptors in posthypoxic myoclonus in rats. Single injections of 5-HT1A agonists, buspirone (5 and 10 mg/kg body wt.) or 8-OH-DPAT (1, 2, and 4 mg/kg), had no effect on either the intensity or time course of the disease. In contrast, multiple injections (twice a day for 7 or more days) of buspirone (10 mg/kg) or 8-OH-DPAT (4 mg/kg) significantly attenuated the myoclonus scores of animals (p < 0.05). The results indicate that chronic stimulation of 5-HT1A receptors in the brain may accelerate endogenous compensatory mechanisms and shorten the time course of the disease.

Role of the OCTA site in regulation of IgH chain gene transcription during B cell activation

We have evaluated the importance of the OCTA site in both the promoter and enhancer regions for the induction of enhancement of IgH chain gene transcription after B cell activation. These studies show that although occupancy of the OCTA site in the promoter is critical for basal transcription of the mu gene, it is not necessary for the increase in transcription induced by in vivo activation. On the other hand, the OCTA site in the enhancer is necessary for neither basal transcription nor in vivo activation of transcription; however, occupancy of this site is required for further up-regulation in transcription of the mu gene in pre-activated cells. These results indicate that different mechanisms may be involved in the activation of resting versus in vivo stimulated B lymphocytes. The findings are discussed in relation to the phenotype described for Oct-2-deficient mice.

Rates of local cerebral protein synthesis in the rat during normal postnatal development

The degree of recycling of leucine derived from protein breakdown into the precursor pool for protein synthesis was measured in rat brain at different postnatal ages, and age-specific values were used in the calculation of regional (local) rates of cerebral leucine incorporation into protein (lCPSleu) in 44 brain regions and the brain as a whole. Early in development, a greater fraction of the precursor leucine pool is derived from protein breakdown, indicating that protein degradation is higher in young rats compared with adults. In whole brain and in most regions, values for lCPSleu were highest at 10 days and gradually decreased with age. By 60 days of age, values in cortex were approximately 60% of those at 10 days of age. In the paraventricular and supraoptic nuclei of the hypothalamus, however, lCPSleu increased during development, reaching peak values in adults. In white matter of the cerebellum and the cerebrum, peaks of lCPSleu were reached at 14 and 21 days, respectively, approximately at the times of maximum rates of myelination.

Effects of chronic dietary aluminum on local cerebral glucose utilization in rats

Beginning at 4 weeks of age normal, male, Sprague-Dawley rats were reared on Purina Laboratory Chow and drinking water containing 100 microM AlCl3. After 2 years, local rates of cerebral glucose utilization were determined with the autoradiographic [14C] deoxyglucose method in the brain as a whole and in 25 brain regions in 6 treated rats and 4 age-matched controls. The results indicate that any effects of chronic aluminum in the diet on rates of cerebral glucose utilization are small. In the brain as a whole, the mean rate of glucose utilization in the aluminum-treated rats was 6% lower than that of the controls (p = 0.09). In 21 of the 25 brain regions examined mean rates of glucose utilization were generally lower in the aluminum-treated rats but in none of the region were the effects statistically significant.

A stapling instrument for placement of right atrial pursestrings

The right atrial pursestring was placed in 12 patients undergoing cardiac operations utilizing a commercially available stapling instrument. Our initial experience indicates that this device can be used for rapid, simple, and safe application of the right atrial pursestring.

Role of maturation-promoting factor (p34cdc2-cyclin B) in differential expression of the Xenopus oocyte and somatic-type 5S RNA genes

Transcription of 5S rRNA and tRNA genes by RNA polymerase III (pol III) in cytosolic extracts of unfertilized Xenopus eggs and in a reconstituted system derived from Xenopus oocytes is repressed by the action of one or more mitotic protein kinases. Repression is due to the phosphorylation of a component of the pol III transcription apparatus. We find that the maturation/mitosis-promoting factor kinase (MPF, p34cdc2-cyclin B) can directly mediate this repression in vitro. Affinity-purified MPF and immune complexes formed with antibodies to the protein subunits of MPF (p34cdc2 and cyclin B) retain both histone H1 kinase activity and the capacity to repress transcription in the reconstituted transcription system. Transcription complexes of oocyte-type 5S RNA genes and tRNA genes are quantitatively more sensitive to MPF repression than the corresponding transcription complexes of the somatic-type 5S RNA gene. The differential transcription of oocyte- and somatic-type genes observed during early Xenopus embryogenesis has been reproduced with the reconstituted transcription system and affinity-purified MPF. This differential transcription may be due to the instability of transcription complexes on the oocyte-type genes and the heightened sensitivity of soluble transcription factors to inactivation by mitotic phosphorylation. Our results suggest that MPF may play a role in vivo in the establishment of the embryonic pattern of pol III gene expression.

Role of differential mRNA stability in the regulated expression of IgM and IgD

The expression of IgM and IgD heavy chain mRNA in resting vs activated B cells offers a unique tool for the assessment of the effect of translation on mRNA stability because mu and delta mRNA have identical VDJ sequences but differ substantially in the rest of the molecule. We have shown that despite the 5' UTR identity that allows equal access to the translation machinery, mu mRNA has a significantly higher turnover rate than delta mRNA. However, the short t1/2 of mu mRNA increases significantly after B cell activation. Furthermore, the induction of microS mRNA after B cell activation provides yet another related molecule for comparison. Thus, despite the fact that microS and microM mRNA differ at their 3' ends, they have identical turnover rates in activated B cells. In addition, because the turnover rates of delta mRNA and beta 2 and GAPDH mRNA remain unchanged, these experiments suggest that B cell activation results in the induction of regulatory factor(s) that target specific sequences within mRNA-mu to confer greater stability. They also argue against a more passive regulation of mRNA stability that is a consequence of alterations in the secretory machinery.

Role of differential mRNA stability in the regulated expression of IgM and IgD

The expression of IgM and IgD heavy chain mRNA in resting vs activated B cells offers a unique tool for the assessment of the effect of translation on mRNA stability because mu and delta mRNA have identical VDJ sequences but differ substantially in the rest of the molecule. We have shown that despite the 5' UTR identity that allows equal access to the translation machinery, mu mRNA has a significantly higher turnover rate than delta mRNA. However, the short t1/2 of mu mRNA increases significantly after B cell activation. Furthermore, the induction of microS mRNA after B cell activation provides yet another related molecule for comparison. Thus, despite the fact that microS and microM mRNA differ at their 3' ends, they have identical turnover rates in activated B cells. In addition, because the turnover rates of delta mRNA and beta 2 and GAPDH mRNA remain unchanged, these experiments suggest that B cell activation results in the induction of regulatory factor(s) that target specific sequences within mRNA-mu to confer greater stability. They also argue against a more passive regulation of mRNA stability that is a consequence of alterations in the secretory machinery.

Nuclear assembly with lambda DNA in fractionated Xenopus egg extracts: an unexpected role for glycogen in formation of a higher order chromatin intermediate

Crude extracts of Xenopus eggs are capable of nuclear assembly around chromatin templates or even around protein-free, naked DNA templates. Here the requirements for nuclear assembly around a naked DNA template were investigated. Extracts were separated by ultracentrifugation into cytosol, membrane, and gelatinous pellet fractions. It was found that, in addition to the cytosolic and membrane fractions, a component of the gelatinous pellet fraction was required for the assembly of functional nuclei around a naked DNA template. In the absence of this component, membrane-bound but functionally inert spheres of lambda DNA were formed. Purification of the active pellet factor unexpectedly demonstrated the component to be glycogen. The assembly of functionally active nuclei, as assayed by DNA replication and nuclear transport, required that glycogen be pre-incubated with the lambda DNA and cytosol during the period of chromatin and higher order intermediate formation, before the addition of membranes. Hydrolysis of glycogen with alpha-amylase in the extract blocked nuclear formation. Upon analysis, chromatin formed in the presence of cytosol and glycogen alone appeared highly condensed, reminiscent of the nuclear assembly intermediate described by Newport in crude extracts (Newport, J. 1987. Cell. 48:205-217). In contrast, chromatin formed from phage lambda DNA in cytosol lacking glycogen formed "fluffy chromatin-like" structures. Using sucrose gradient centrifugation, the highly condensed intermediates formed in the presence of glycogen could be isolated and were now able to serve as nuclear assembly templates in extracts lacking glycogen, arguing that the requirement for glycogen is temporally restricted to the time of intermediate formation and function. Glycogen does not act simply by inducing condensation of the chromatin, since similarly isolated mitotically condensed chromatin intermediates do not form functional nuclei. However, both mitotic and fluffy interphase chromatin intermediates formed in the absence of glycogen can be rescued to form functional nuclei when added to a second extract which contains glycogen. This study presents a novel role for a carbohydrate in nuclear assembly, a role which involves the formation of a particular chromatin intermediate. Potential models for the role of glycogen are discussed.

Mitotic repression of RNA polymerase III transcription in vitro mediated by phosphorylation of a TFIIIB component

Interphase cytosol extracts prepared from Xenopus laevis eggs are active in RNA polymerase III (Pol III) transcription. Addition of recombinant B1 cyclin to these extracts activates mitotic protein kinases that repress transcription. Affinity-purified p34cdc2-cyclin B kinase (mitosis-promoting factor) is sufficient to effect this repression in a simplified Pol III transcription system. This mitotic repression involves the direct phosphorylation of a component of the Pol III transcription initiation factor TFIIIB, which consists of the TATA box-binding protein (TBP) and associated Pol III-specific factors. The transcriptional activity of the TFIIIB-TBP fraction can be modulated in vitro by phosphorylation with mitotic kinases and by dephosphorylation with immobilized alkaline phosphatase.

People movements between Australia and Asian-Pacific nations: trends, issues and prospects

"This article examines the growth and diversification of...permanent, long and short-term movements of people from Asia and the Pacific and the growth in immigrant and local-born Australians departing Australia to live and work in Asia. The occasional controversies surrounding the growth of Asian arrivals and Australia's current push to integrate with the booming Asian economies are examined. The article concludes with a general discussion of the economic, social, cultural, and international consequences of the two-way movements of people between Australia and its Asian and Pacific neighbors."

Activation of B lymphocytes by NK cells

The ability of NK cells to induce differentiation of B lymphocytes to IgM secretion in vitro has been investigated. Homogeneous preparations of NK cells obtained from IL-2 propagated splenocytes from SCID mice were found to have the ability to induce resting B lymphocytes to proliferate and secrete significant amounts of IgM. The induction is greatly enhanced by the presence of both IL-2 and IL-5 and does not require T lymphocytes or adherent cells in the responding population. Cell contact between the two populations is not necessary suggesting that the effect is mediated by soluble factor(s) which can be produced even by irradiated NK cells. Because the activity cannot be replaced by either r-tau-IFN or tumor necrosis factor-alpha or inhibited by antibodies to these lymphokines, a novel NK cell-derived factor(s) may be involved. The implications of this interaction between NK cells and B lymphocytes are discussed.

Mechanism of lipopolysaccharide-mediated transcriptional enhancement of the mu gene

LPS induces both B cell proliferation and differentiation to Ig secretion. By treating stimulated cells for a brief period with staurosporine, and inhibitor of protein kinase C, it is possible to allow continued proliferation but partially inhibit differentiation. Analysis of the molecular basis for the decrease in IgM production shows that the increased transcription of the Ig-H chain gene induced by LPS is abrogated by staurosporine treatment whereas alteration of 3' end processing is not affected. These experiments indicate that LPS continues to mediate its effect on some of the more distal differentiative events through protein kinase C even after initial cell activation.

Mechanism of lipopolysaccharide-mediated transcriptional enhancement of the mu gene

LPS induces both B cell proliferation and differentiation to Ig secretion. By treating stimulated cells for a brief period with staurosporine, and inhibitor of protein kinase C, it is possible to allow continued proliferation but partially inhibit differentiation. Analysis of the molecular basis for the decrease in IgM production shows that the increased transcription of the Ig-H chain gene induced by LPS is abrogated by staurosporine treatment whereas alteration of 3' end processing is not affected. These experiments indicate that LPS continues to mediate its effect on some of the more distal differentiative events through protein kinase C even after initial cell activation.

Overexpression of amyloid precursor protein alters its normal processing and is associated with neurotoxicity

The recent discovery that point mutations in the beta/A4 amyloid precursor protein may be the cause of certain forms of familial Alzheimer's disease provides strong support for the view that a thorough understanding of the metabolism of this protein may elucidate the pathogenesis of most forms of the disease and thus serve as a basis for rational prevention and therapy. Here we show that overexpression of a portion of the amyloid precursor protein molecule produces at least four distinct fragments of the COOH-terminus of amyloid precursor protein, suggesting altered proteolysis of amyloid precursor protein, and that such overexpression is associated with cytotoxicity. The degree of toxicity in the P19 cell culture model (differentiating mouse embryonal carcinoma cells) is shown to be related to the two larger novel COOH-terminal protein fragments (16 and 14 kilodalton), as well as to levels of expression of these two fragments. The toxicity is manifested in several differentiated cell lineages, including neuronal cells.