Feline leukemia virus variants in experimentally induced thymic lymphosarcomas

This study was initiated to evaluate the in vivo infectivity and pathogenicity of a group of recombinant feline leukemia viruses (rFeLVs) previously generated by in vitro forced recombination between a FeLV subgroup A virus (FeLV-A) and an endogenous FeLV (enFeLV) envelope (env) element (Sheets et al., 1992, Virology 190, 849-855). To determine infectivity of rFeLVs, neonatal cats were inoculated with rFeLVs alone or in combination with FeLV-A. The recombinant viruses were able to replicate efficiently in vivo only when administered along with FeLV-A. Of six co-infected cats, three developed thymic lymphosarcomas, one severe aplastic anemia, and two cachexia and depression; all were viremic and seroconverted shortly after inoculation. While both virus types were detected in virtually all tissues examined from these tumor-bearing cats, there was a particularly noteworthy sequence reversion in the rFeLVs. It is known that exogenous FeLV isolates carry a conserved neutralizing MGPNL epitope in the middle of the surface glycoprotein domain of the env gene. In contrast, the parental recombinant viruses used to inoculate these cats harbored the enFeLV-derived MGPNP sequence at this position. However, all in vivo-propagated recombinants displayed the MGPNL sequence, while the env-encoded backbone flanking the MGPNL sequence was that of the parental recombinant virus. These results suggest that viruses with the MGPNL epitope have an in vivo proliferative advantage. The data also provide an explanation for the conservation of this epitope in exogenous FeLVs despite the existence of variant forms in enFeLV proviral elements with which they can recombine.

[Responses of somatostatin, beta-endorphin and dynorphin A to A glucose load in two groups of women with polycystic ovarian syndrome]

OBJECTIVES

To investigate the relationship between elevated luteinizing hormone (LH), hyperinsulinemia and neuropeptides in patients with polycystic ovarian syndrome (PCOS).

METHODS

An oral glucose (100g) tolerance test (OGTT) was performed in 15 normally menstruating women (control) and 30 PCOS women with LH/follicle stimulating hormone (FSH) ratio greater than 3 (group 1) and 25 PCOS subjects with the ratio < 3 (group 2). The responses of insulin, somatostatin (SS), beta-endorphin (beta-EP) and dynorphin A (Dyn A) during OGTT were measured by RIA.

RESULTS

In basal state, significant negative correlations were found between LH and SS (r = -0.51, P < 0.05) in group 1 and between LH and beta-EP (r = -0.49, P < 0.05) in group 2. During OGTT, PCOS women had a greater beta-EP and Dyn A responses in group 1 and an impaired SS response in group 2 as compared with the control.

CONCLUSION

These data suggested lower endogenous SS, higher beta-EP and Dyn A may lead to elevation of LH and insulin secretions in patients with PCOS.

Hypoxia inhibits L-arginine synthesis from L-citrulline in porcine pulmonary artery endothelial cells

Both non-arginine-depleted and arginine-depleted pulmonary artery endothelial cells (PAEC) actively convert citrulline into arginine. Exposure to hypoxia for 4-24 h inhibited arginine synthesis from citrulline in intact cells and in cell homogenates. The conversion of L-citrulline to L-argininosuccinate by argininosuccinate synthetase (AS) was inhibited by exposure to hypoxia for 4, 12, or 24 h. The conversion of argininosuccinate to arginine by argininosuccinate lyase was inhibited by exposure to hypoxia for 24 h but not for 4-12 h. The decrease of L-arginine biosynthesis during hypoxia coincided with the increase of intracellular glutamine content and was abrogated by preventing an increase in intracellular glutamine. In addition, AS activity was inversely related to glutamine content in the medium. These results indicate that hypoxia inhibited the L-arginine biosynthetic pathway via decreased activity of AS. The latter is related to increased glutamine content. Hypoxic inhibition of arginine synthesis from citrulline did not result in a decrease of arginine content, suggesting that PAEC are able to maintain intracellular arginine for up to 24 h despite reduction in the L-arginine biosynthetic pathway.

Ultrastructural cytochemistry of human gastric cancer: electron microscopic observations of five organellae marker enzymes

The distribution of ALPase, ACPase, G6Pase TPPase and CCOase of gastric cancer and normal gastric epithelium were studied ultrastructurally. The results showed that normal gastric epithelium had no ALPase reaction. The reactions of ACPase, G6Pase, TPPase and CCOase were found in the corresponding organellae which were consistent with their functions. In tubular adenocarcinoma cells, their reactions were more apparent in the corresponding organellae. Some cells of tubular adenocarcinomas showed ALPase reaction. The mucinous adenocarcinoma cells had higher ACPase and TPPase reactions. In poorly differentiated adenocarcinoma cells, the five marker enzymes showed negative or faint reactions. The biological significance and mechanisms of distribution of the five marker enzymes were discussed.

The formation of nitric oxide donors from peroxynitrite

1. Administration of peroxynitrite (ONOO-, 30-300 microM) caused relaxation of rabbit aortic strips superfused in series in a cascade. The compound responsible for this effect had a half-life greater than 20 s and could not therefore be either nitric oxide (NO) or ONOO- which have half-lives in the order of 1-2 s under these conditions. However the relaxation was inhibited by oxyhaemoglobin, suggesting the compound could be converted to NO in the vascular tissues or in the superfusate. 2. The products of the reactions between ONOO- and Krebs buffer containing 11 mM glucose, but not glucose-free Krebs buffer, caused relaxation of the bioassay tissues. These data suggest that stable NO donor(s) were formed from the reaction of ONOO- with glucose. We therefore prepared these NO donor(s) by the reaction of glucose solutions with ONOO- in order to characterize their ability to release NO. 3. These reaction product(s) caused relaxation in the cascade and inhibition of platelet aggregation. Both effects were dependent on the concentration of D-glucose, were equally effective if L-glucose was used as a reactant and were reversed by oxyhaemoglobin. 3. The products of the reaction between ONOO- and glucose or other biological molecules containing an alcohol functional group, such as fructose, glycerol, or glyceraldehyde, released NO in the presence of Cu2+and L-cysteine. 5. These results indicate that ONOO- reacts with sugars or other compounds containing an alcohol functional group(s) to form NO donors with the characteristics of organic nitrate/nitrites. This may represent a further detoxification pathway for ONOO- in vivo.

Growth inhibition and apoptosis in human neuroblastoma SK-N-SH cells induced by hypericin, a potent inhibitor of protein kinase C

The effect of hypericin, an antiviral agent and inhibitor of protein kinase C (PKC), on cell proliferation and programmed death was investigated in the human neuroblastoma cell line SK-N-SH. Hypericin induced significant growth inhibition in a dose-dependent manner demonstrated by a microculture tetrazolium (MTT) assay. DNA isolated from cells treated with hypericin at concentrations over 1 microM exhibited a 'ladder' pattern of oligonucleosome-sized fragments characteristic of apoptosis. Similarly, treatment of the cells with the PKC inhibitors staurosporine, tamoxifen or phorbol ester PMA for 72 h also resulted in apoptosis, suggesting that hypericin may be triggering an apoptotic signal in neuroblastoma cells, which at least in part may be mediated by the inhibition of PKC.

[Preliminary study on multi-resistant gene location of 20 strains of Pseudomonas aeruginosa]

20 strains of Pseudomonas aeruginosa were isolated from burn patients of Xijing Hospital in Xi'an. These 20 strains which showed resistance to multiple antibiotics were selected to be studied regarding the location of multi-resistant gene. According to the sensitivity tests before and after plasmid removal, we found that in 70% of the bacteria resistance to multiple antibiotics was mediated by the plasmid. In 30% the bacteria remained resistant to antibiotics after plasmids were removed. Two explanations were postulated. (1) plasmids were not removed completely; (2) resistance gene was encoded by the chromosomes.

Regulatory subunit of protein kinase A: structure of deletion mutant with cAMP binding domains

In the molecular scheme of living organisms, adenosine 3',5'-monophosphate (cyclic AMP or cAMP) has been a universal second messenger. In eukaryotic cells, the primary receptors for cAMP are the regulatory subunits of cAMP-dependent protein kinase. The crystal structure of a 1-91 deletion mutant of the type I alpha regulatory subunit was refined to 2.8 A resolution. Each of the two tandem cAMP binding domains provides an extensive network of hydrogen bonds that buries the cyclic phosphate and the ribose between two beta strands that are linked by a short alpha helix. Each adenine base stacks against an aromatic ring that lies outside the beta barrel. This structure provides a molecular basis for understanding how cAMP binds cooperatively to its receptor protein, thus mediating activation of the kinase.

Rapid dephosphorylation of tau in heat-shocked fetal rat cerebral explants: prevention and hyperphosphorylation by inhibitors of protein phosphatases PP1 and PP2A

We heat shocked 21- and 35-day-old fetal rat cerebral explants at 45 degrees C for 18 min and performed immunocytochemistry and immunoblot analysis of sodium dodecyl sulfate extracts using the monoclonal anti-tau antibodies Tau-1, Tau-5, Tau-46, and PHF-1 and the peroxidase-antiperoxidase technique or 125I-labeled protein A. Tau-1 and PHF-1 recognize nonphosphorylated and phosphorylated epitopes, respectively, and both Tau-5 and Tau-46 recognize phosphate-independent epitopes. tau immunoreactivity was confined to neurons and increased in heat-shocked perikarya but not axons. At 0 h after heat shocking, there was dephosphorylation of tau exemplified by (1) faster migration of tau isoforms with resultant loss or attenuation of the 60- and 52-kDa tau isoforms recognized by all four anti-tau antibodies and concomitant accentuation of the fastest moving 50-kDa tau isoform recognized by Tau-1, Tau-5, and Tau-46; and (2) significant increase in the nonphosphorylated Tau-1 epitope with resultant decreases in the ratio of total (phosphorylated plus nonphosphorylated) tau to nonphosphorylated tau and the difference of total tau minus nonphosphorylated tau. tau was phosphorylated back to the control level by 12 h and remained so at 24 and 48 h after heat shocking. Treatment of explants with cycloheximide, a protein synthesis inhibitor, did not prevent the heat shocking-induced dephosphorylation of tau. Treatment of explants with the inhibitors of protein phosphatases PP1 and PP2A, okadaic acid or calyculin A, produced hyperphosphorylated tau polypeptides, prevented the heat shocking-induced dephosphorylation of tau, and intensified the immunoreactivity of the neurofilament subunit H with the only antiphosphoneurofilament antibody that reacts with intraneuronal neurofibrillary tangles. In 35-day-old explants, in addition to the three 50-, 52-, and 60-kDa tau isoforms seen in 21-day-old explants, a 66-kDa tau polypeptide was also present.

The role of calcium influx in cellular proliferation induced by interaction of endogenous ganglioside GM1 with the B subunit of cholera toxin

The B subunit of cholera toxin, which binds specifically to ganglioside GM1, is mitogenic for quiescent Swiss 3T3 fibroblasts. It was previously shown that the B subunit had no effect on cAMP, protein kinase C or phosphoinositide turnover, but did cause an increase in the influx of calcium from extracellular sources (Spiegel, S. and Panagiotopoulos, C. (1988) Exp. Cell Res. 177, 414-427). In contrast to the action of known growth factors, the B subunit induced significant DNA synthesis after only a 1-3 h treatment. We utilized this unique property to determine whether the increase in calcium influx plays a role in B subunit-induced mitogenicity. Cells were briefly treated with the B subunit in the presence of calcium channel blockers, followed by removal of the blockers and further incubation in B subunit-free medium for the remaining time required to measure DNA synthesis. When 1 mM cobalt was only present during the first 3 h incubation. DNA synthesis induced by either the B subunit or fetal bovine serum was completely abolished. However, both nickel (1 mM) adn the L-type voltage-gated calcium channel inhibitor nicardipin (10 microM) inhibited B subunit-induced cell proliferation without abrogating the response to fetal bovine serum. Using a gel retardation assay, we found that the B subunit markedly stimulated specific DNA-binding activity of the transcription factor, activator protein-1 (AP-1), which functions as a major convergence point coupling early events induced by a variety of mitogens to long term growth responses. Presence of c-Fos protein in the AP-1 complex was demonstrated as a supershift band in the gel mobility assay using c-Fos polyclonal antibody. Cobalt, which markedly inhibited B subunit-induced DNA synthesis, also completely abolished AP-1 DNA-binding activity stimulated by the B subunit. In sharp contrast, cobalt had no effect on DNA-binding activity of AP-1 induced by the tumor promoter, 12-O-tetradecanoylphorbol 13-acetate. Our results suggest that calcium influx is a key element for both DNA-binding activity of AP-1 and cell proliferation induced by binding of the B subunit of cholera toxin to cell surface ganglioside GM1.

Variation in membrane properties from the action of laminin on membrane receptors

Biophysical studies were conducted on the action of laminin through membrane receptors of cancer cells. The results showed that variations occurred in the thermodynamic properties of membrane proteins, the mobility of hydrocarbon chains of membrane lipids, and the permeability and transportation pathways of the membrane.

A new salicylate ISFET for the determination of salicylic and acetylsalicylic acid in drugs

A salicylate ISFET for the analysis of salicylic and acetylsalicylic acid in drugs is described. It is based on a salicylate ion selective membrane coated on the surface of the Si3N4 gate of the FET. The sensitive membrane consists of tetra-dodecylammonium salicylate, polyvinyl chloride and a proper plasticizer. The linearity range of the sensor is 5 x 10(-5)-1.5 x 10(-2) M for the salicylic acid, and 7 x 10(-5)-1.5 x 10(-2) M for the acetylsalicylic acid, respectively. The detection limit for the two compounds is 5 x 10(-5) M while the response time is < or = 20 s. The effect of pH and different interfering ions was also studied. The sensor was used to analyse the content of acetylsalicylic and salicylic acid in some drugs, and the accuracy of the method was evaluated through recovery tests. The results obtained with this method are well correlated either with those obtained with a classical ISE employing the same sensitive membrane or with the classical volumetric method.

Inhibition of human immunodeficiency virus type 1 replication by a Tat-activated, transduced interferon gene: targeted expression to human immunodeficiency virus type 1-infected cells

We have examined the feasibility of using interferon (IFN) gene transfer as a novel approach to anti-human immunodeficiency virus type 1 (HIV-1) therapy in this study. To limit expression of a transduced HIV-1 long terminal repeat (LTR)-IFNA2 (the new approved nomenclature for IFN genes is used throughout this article) hybrid gene to the HIV-1-infected cells, HIV-1 LTR was modified. Deletion of the NF-kappa B elements of the HIV-1 LTR significantly inhibited Tat-mediated transactivation in T-cell lines, as well as in a monocyte line, U937. Replacement of the NF-kappa B elements in the HIV-1 LTR by a DNA fragment derived from the 5'-flanking region of IFN-stimulated gene 15 (ISG15), containing the IFN-stimulated response element, partially restored Tat-mediated activation of LTR in T cells as well as in monocytes. Insertion of this chimeric promoter (ISG15 LTR) upstream of the human IFNA2 gene directed high levels of IFN synthesis in Tat-expressing cells, while this promoter was not responsive to tumor necrosis factor alpha-mediated activation. ISG15-LTR-IFN hybrid gene inserted into the retrovirus vector was transduced into Jurkat and U937 cells. Selected transfected clones produced low levels of IFN A (IFNA) constitutively, and their abilities to express interleukin-2 and interleukin-2 receptor upon stimulation with phytohemagglutinin and phorbol myristate acetate were retained. Enhancement of IFNA synthesis observed upon HIV-1 infection resulted in significant inhibition of HIV-1 replication for a period of at least 30 days. Virus isolated from IFNA-producing cells was able to replicate in the U937 cells but did not replicate efficiently in U937 cells transduced with the IFNA gene. These results suggest that targeting IFN synthesis to HIV-1-infected cells is an attainable goal and that autocrine IFN synthesis results in a long-lasting and permanent suppression of HIV-1 replication.

Lovastatin induces growth inhibition and apoptosis in human malignant glioma cells

The competitive HMG-CoA reductase inhibitor lovastatin has been shown to suppress growth and induce morphological changes in a variety of non-glioma tumor cell lines. This study assesses the effects of this agent on the growth and survival of the human malignant glioma cell lines A172 and U87-MG. The response to the drug was investigated using a cell proliferation assay which revealed significant dose-dependent growth inhibition. Treatment with as little as 100 nM lovastatin over a period of 72 hours led to DNA degradation into nucleosome-sized fragments characteristic of apoptosis. Our data suggest that HMG-CoA reductase inhibitors such as lovastatin merit further investigation as potential therapeutic agents for the treatment of malignant gliomas.

A new staging system for nasopharyngeal carcinoma in China

PURPOSE

An accurate and rational nasopharyngeal carcinoma (NPC) stage based on images is proposed.

METHODS AND MATERIALS

Four hundred and twenty-one cases of NPC, treated in the Cancer Hospital, Sun Yat-sen University of Medical Sciences (SUMS), with computed tomography scanning before initial radiotherapy, are analyzed. Important prognostic factors that form the basis of the new staging system are screened out by means of Cox model and clinical experiences. Survival curves of various kinds of T and N stages are compared by computer simulation. A new staging system is proposed by studying the traditional staging systems such as the AJC, UICC, Ho's and Changsha systems.

RESULTS

According to the new staging criteria, the 5-year survival rates for Stages I-IV are 89.7%, 75.9%, 51.3%, and 22.2%, respectively.

CONCLUSION

This new clinical staging for NPC based on a large amount of cases multivariate analysis is satisfactory and widely used in China.

[Clinical research on the treatment of acute leukemia with autologous bone marrow transplantation]

38 cases of acute leukemia were treated with autologous bone marrow transplantation (ABMT). The marrow was purged with hyperthermia of 42 degrees C in vitro for one hour in microwave. Twenty-two among them were AML (CR1). Sixteen were ALL (CR1). The mean age was 26 (10-43) years. All the patients were engrafted successfully after ABMT. Mean DFS was 21 (3-69) months. Four cases relapsed at 3 to 8 months after ABMT. Two patients with ALL developed central nervous system leukemia at 12 and 15 months respectively after ABMT. The DFS and probability of relapse at 5 years were 67.8% and 16.8% respectively for all patients.

Crystal structure of a monoclinic form of dihydropteridine reductase from rat liver

A binary complex of dihydropteridine reductase and NADH crystallizes in the space group C2, with a = 222.2, b = 46.5, c = 95.3 A and beta = 101.1 degrees. There are two dimers in the asymmetric unit. The structure was solved by molecular-replacement techniques and refined with 2.6 A data to a crystallographic R factor of 16.8%. Each dimer has twofold non-crystallographic symmetry and the four individual monomers in the asymmetric unit have the same overall molecular conformation.

Transgenic hepatocarcinogenesis in the rat

Although transgenic hepatocarcinogenesis has been accomplished in the mouse with a number of genetic constructs targeting the oncogene to expression primarily in the liver, no example of this process has yet been developed in the rat. Because our understanding of the multistage nature of hepatocarcinogenesis is most advanced in the rat, we have developed a strain of transgenic rats carrying the promoter-enhancer sequences of the mouse albumin gene linked 5' to the simian virus-40 T antigen gene. A line of transgenic rats bearing this transgene has been developed from a single founder female. Five to six copies of the transgene, possibly in tandem, occur within the genome of the transgenic animals, which are maintained by heterozygous matings. Livers of transgenic animals are histologically normal after weaning; at 2 months of age, small foci of vacuolated cells appear in this organ. By 4 months of age, all animals exhibit focal lesions and nodules consisting primarily of small basophilic cells, many of which exhibit considerable cytoplasmic vacuolization. Mating of animals each bearing the transgene results in rats with a demyelinating condition that develops acutely in pregnant females and more chronically in males. Ultrastructural studies of these cells indicate that the vacuoles contain substantial amounts of glycogen, with the cells resembling hepatoblasts. Malignant neoplasms with both a glandular and a hepatoblastoma/hepatocellular carcinoma pattern arise from the nodules. Enzyme and immunohistochemical studies of all lesions reveal many similarities in gene expression to comparable lesions in rats subjected to chemically induced hepatocarcinogenesis, with certain exceptions. The placental form of glutathione-S-transferase is absent from all lesions in the transgenic animal, as is the expression of connexin 32. A significant number of lesions express serum albumin, and many, but not all, exhibit the T antigen. Lesions expressing the T antigen also contain stainable amounts of the p53 gene product; by contrast, normal hepatocytes express only very low levels of the T antigen within their nuclei and no demonstrable p53. All of the animals develop hepatic lesions, and approximately one-third also develop adenomas and carcinomas derived from the islet cells of the pancreas. Although there are differences in the morphology, biology, and genetic expression in early and late hepatic lesions in this strain of transgenic rat, many similarities also occur, making this a potential model system with which to study the interactions of environmental factors with a genetic program for hepatocarcinogenesis.

Sphingosine 1-phosphate, a novel signaling molecule, stimulates DNA binding activity of AP-1 in quiescent Swiss 3T3 fibroblasts

Sphingosine and sphingosine 1-phosphate, metabolites of sphingolipids, stimulate cell proliferation in quiescent Swiss 3T3 fibroblasts and induce transient increases in intracellular free calcium (Zhang, H., Desai, N. N., Olivera, A., Seki, T., Brooker, G., and Spiegel, S. (1991) J. Cell Biol. 114, 155-167). However, little is yet known of the nuclear events that follow the early responses induced by sphingolipid metabolites. Using a gel retardation assay, we found that specific DNA binding activity of activator protein-1 (AP-1) was markedly increased after treatment of quiescent Swiss 3T3 fibroblasts with sphingosine 1-phosphate and sphingosine. The DNA binding specificity of AP-1 was confirmed with competing probes containing consensus sequences of AP-1, AP-2, AP-3, SP-1, and NF1/CTF. The c-fos gene product was detected in the AP-1 complex using anti-c-Fos antibody. The dose response for stimulation of DNA binding activity of AP-1 by sphingosine 1-phosphate correlated closely with its effect on DNA synthesis. Furthermore, an inhibitor of sphingosine kinase, DL-threo-dihydrosphingosine, which inhibits sphingosine-induced DNA synthesis and the formation of sphingosine 1-phosphate, also inhibited sphingosine-stimulated AP-1 DNA binding activity. This result further supports our proposal that sphingosine 1-phosphate mediates the mitogenic effect of sphingosine. Our results indicate that sphingosine 1-phosphate-induced DNA synthesis and cell division may result from activation of AP-1 protein, linking signal transduction by sphingolipid metabolites to gene expression.

[A murine model of mammary adenocarcinoma (VI TA2MA-891) with high rate of spontaneous metastases in the lungs]

The primary donor tumor was a spontaneous mammary tumor which arose in a 348-day-old female TA2 mouse. The pedigree number of that mouse was 0901-1423. The mouse was sacrificed for serial s.c. transplantation with 3 isogeneic hosts on January 19, 1989 and a total of 27 generations succeeded by the end of April, 1992. The primary donor tumor was diagnosed pathologically as a type B mouse mammary adenocarcinoma (Dunn 1959). The incidence of this serial s.c. transplantation tumor is 100% after inoculation. The latency period is 4-7 days and the lifetime of tumorbearing mice is about 47 days. The spontaneous metastatic rates in the lungs was 100% after the 11th generations. The earliest metastasis seen in the lung under light microscopy was on the 10th day after inoculation, and the earliest seen by gross examination was on about the 35th day. The transplanted tumor grew slowly from the 4th day to the 21st day after inoculation and then grew rather fast from the 22nd to the 47th day. The average size of the transplanted tumor obtained from 10 recipient mice on the 47th day after inoculation was 4.93cm3. Seven anticancer drugs were administered respectively for a sensitivity test. The taking rates of the transplanted tumor using 4 of the 7 drugs were as follows: 5-fluorouracil 29.27% (P < 0.05); thio-tepa 44.80% (P < 0.01); cyclophosphamide 95.31% (P < 0.01); and bleomycin 96.27% (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

GFAP promoter directs astrocyte-specific expression in transgenic mice

Glial fibrillary acidic protein (GFAP) is an intermediate-filament protein expressed abundantly and almost exclusively in astrocytes of the CNS. We are studying transcriptional regulation of the GFAP gene to gain insight into astrocyte function and also to develop an astrocyte-specific expression system for manipulating brain physiology. In this work, we have produced transgenic mice carrying the bacterial lacZ reporter gene linked to a 2.2 kilobase 5'-flanking sequence derived from the human GFAP gene that previously was shown to direct astrocyte-specific transcription in cultured cells. We report that this promoter directs expression to astrocytes in the CNS. In addition, the upregulation of GFAP gene activity that follows injury to the brain was mimicked by the transgene. One of the transgenes was found to be X-linked and appeared to undergo the usual random inactivation that achieves gene dosage compensation in females. The brains of hemizygous females stained uniformly rather than displaying mosaic patches, indicating that astrocytes intermingle following their formation. The specific expression of the GFAP-lacZ transgene means that it is now possible to target expression of other heterologous genes to astrocytes in vivo, and to study the mechanisms for reactive gliosis at the DNA level.

Design of a scanning ellipsometer by synchronous rotation of the polarizer and analyzer

We have designed and constructed a new type of spectroscopic ellipsometer to study the optical properties of materials in the 3500-8000-Å wavelength range. In the system, the analyzer and polarizer are driven 10(4) steps/revolution by two stepping motors that have hollow shafts and rotate synchronously with a speed ratio of 2:1, i.e., A = 2P. Both the polarizer and analyzer are mounted directly on the shafts to avoid mechanical transmission and vibration problems entirely and make the system simple and reliable. An additional source polarizer was placed in the optical path to reduce the slight polarization effects of the light source. The light intensity finally received by the detector contained five components, one dc and four ac, with frequencies of ω(0), 2ω(0), 3ω(0), and 4ω(0), respectively. One can independently obtain the ellipsometric parameters of ψ and Δ as well as the optical constants by calculating any one of the two sets of ac signals, with a raw data self-consistency of better than 0.5%. The incident angle, aligned precisely by a laser beam, was continuously variable through a mechanical system with a computercontrolled resolution of 0.001° or a visual resolution of 0.005°. The system operations, including data acquisition and reduction, high-voltage control of the photomultiplier, incident angle, as well as wavelength setting and scanning, were fully and automatically controlled by a 386-based microcomputer. We self-calibrated the system by adjusting and setting precisely the initial azimuthal angles of the prisms. The results from the measured spectra of the complex refractive index for a gold-film sample are presented, and we show that the data obtained at three different incident angles of 65°, 70°, and 75° are remarkably consistent with one another. A comparison of the two results from the ellipsometry and reflectance measurements is given. The experimental skills and system error reduction are discussed in detail.

Sphingosine-1-phosphate, a novel second messenger involved in cell growth regulation and signal transduction, affects growth and invasiveness of human breast cancer cells

This review will focus on the role of sphingosine and its phosphorylated derivative sphingosine-1-phosphate (SPP) in cell growth regulation and signal transduction. We will show that many of the effects attributed to sphingosine in quiescent Swiss 3T3 fibroblasts are mediated via its conversion to SPP. We propose that SPP has appropriate properties to function as an intracellular second messenger based on the following: it elicits diverse cellular responses; it is rapidly produced from sphingosine by a specific kinase and rapidly degraded by a specific lyase; its concentration is low in quiescent cells but increases rapidly and transiently in response to the growth factors, fetal calf serum (FCS) and platelet derived growth factor (PDGF); it releases Ca2+ from internal sources in an InsP3-independent manner; and finally, it may link sphingolipid signaling pathways to cellular ras-mediated signaling pathways by elevating phosphatidic acid levels. The effects of this novel second messenger on growth, differentiation and invasion of human breast cancer cells will be discussed.

The crystallographic structure of a human dihydropteridine reductase NADH binary complex expressed in Escherichia coli by a cDNA constructed from its rat homologue

A human dihydropteridine reductase (EC 1.6.99.10) has been created from a rat cDNA clone by a single five-oligonucleotide mutagenesis reaction and expressed in good yield in Escherichia coli. The enzyme has been purified to homogeneity, and kinetic identity to the naturally occurring enzyme has been proven. Crystallization has also been achieved, and the crystal structure was solved using 2.5 A data that was refined to an R value of 16.9%. The structure described in this report represents the first complete structural characterization of this important human enzyme.

(Pro)collagenase (matrix metalloproteinase-1) is present in rodent osteoclasts and in the underlying bone-resorbing compartment

Osteoclasts resorb the extracellular matrix of bone by secreting enzymes and acid into a sealed-off compartment that they form upon attachment to the bone surface. Although the lysosomal cysteine proteinases can degrade collagen after the demineralization of bone at low pH, several lines of evidence suggest that collagenase (matrix metalloproteinase-1, EC 3.4.24.7) may also be involved in this process. The question of whether collagenase is present in the osteoclast and/or in the bone-resorbing compartment has however not been resolved. We have prepared an anti-mouse collagenase antiserum and affinity-purified an IgG fraction that specifically immunoblots and immunoprecipitates (pro)collagenase. Using these antibodies, we demonstrate by immunolocalization the presence of (pro)collagenase both in the osteoclasts and in the extracellular subosteoclastic bone-resorbing compartment. These specific localizations were observed not only in mice but also in rat and rabbit osteoclasts and using not only the antibody we have prepared but also antibodies raised in other laboratories against rat (Jeffrey et al., J. Cell. Physiol. 143, 396–403, 1990) and rabbit (Brinckerhoff et al., J. Biol. Chem. 265, 22262–22269, 1990) collagenase. Intracellular collagenase was observed in the osteoclasts whether the cells were plated on bone or cultured on glass coverslips. It is proposed that osteoclastic collagenase is secreted in the resorbing compartment where it may cooperate with the lysosomal cysteine proteinases in the degradation of the collagen component of the matrix during the resorption of bone.

Possibility of signal transduction through microfilaments below the membrane following ligand-receptor interaction

In this paper, we describe the changes of microfilament assembly and 3H-TdR incorporation in mouse ascites liver cancer cells under the action of concanavalin A (ConA) and laminin (LN). We have also studied the variation of 3H-TdR incorporation induced by destroying microfilaments with cytochalasin B (CB) following ConA and LN binding with their membrane receptors. It was found that ConA and LN interactions with their membrane receptors could induce the assembly of microfilaments below the membrane and promote DNA synthesis in these cells, but this effect was inhibited when microfilaments were destroyed by CB treatment. These results suggest that microfilaments might play a role in transferring signals from the membrane to the nucleus.

Myelin protein zero gene mutated in Charcot-Marie-tooth type 1B patients

Autosomal dominant of Charcot-Marie-Tooth disease (CMT), whose gene is type 1B (CMT1B), has slow nerve conduction with demyelinated Schwann cells. In this study the abundant peripheral myelin protein zero (MPZ) gene, MPZ, was mapped 130 kb centromeric to the Fc receptor immunoglobulin gene cluster in band 1q22, and a major MPZ point mutation was found to cosegregate with CMT1B in one large CMT1B family. The MPZ point mutation in 18 of 18 related CMT1B pedigree 1 patients converts a positively charged lysine in codon 96 to a negatively charged glutamate. The same MPZ locus cosegregates with the CMT1B disease gene in a second CMT1B family [total multipoint logarithm of odds (lod) = 11.4 at theta = 0.00] with a splice junction mutation. Both mutations occur in MPZ protein regions otherwise conserved identically in human, rat, and cow since these species diverged 100 million years ago. MPZ protein, expressed exclusively in myelinated peripheral nerve Schwann cells, constitutes > 50% of myelin protein. These mutations are anticipated to disrupt homophilic MPZ binding and result in CMT1B peripheral nerve demyelination.

Virus-mediated induction of interferon A gene requires cooperation between multiple binding factors in the interferon alpha promoter region

Transcriptional activation of interferon A (IFNA) gene in virus-infected cells is controlled by a 35-nucleotide inducible element that is cell type specific. Within this region, two elements, alpha F1 and IRF-1 binding sites, were shown by mutation analysis to play a crucial role in the expression of inducible element. In this study, we have analyzed the binding of nuclear proteins to the alpha F1 sequence and have shown that the induction is associated with the formation of a novel complex alpha F1/B, which contains at least two DNA binding proteins of 68 and 96 kDa. In contrast, no binding of the purified interferon regulatory factor 1 (IRF-1) either to the alpha F1 or IRF-1 binding sites could be detected in vitro. However, the oligonucleotides corresponding to alpha F1 or IRF-1 binding sites competed efficiently for the induction of IFNA4 promoter region in a transient transfection assay. We suggest that the induction of IFNA promoter region requires cooperation between alpha F1 binding proteins and IRF-1. Interestingly, our data also show that the inability of IFNA6 promoter to be expressed in infected L-cells may be a result of a viral-induced repressor, which could act by binding and inactivating alpha F1 or by competing for the IRF-1 binding site. These results suggest that cell-specific expression of IFNA genes results from core-cruitment of trans-acting factors that bind to alpha F1 and the IRF-1 binding site with the cell-specific virus-induced activator or repressor.

Prenatal diagnosis of Charcot-Marie-Tooth disease type 1A by multicolor in situ hybridization

Genetic heterogeneity within the most common genetic neuropathy, Charcot-Marie-Tooth disease (CMT) results in about 70% slow nerve conduction CMT1 and 30% normal nerve conduction CMT2. Autosomal dominant CMT1A on chromosome 17p11.2 represents about 70% of CMT1 cases and about 50% of all CMT cases. Three different size CMT1A duplications with variable flanking breakpoints were characterized by multicolor in situ hybridization and confirmed by pulsed field gel electrophoresis and quantitative polymerase chain reaction (PCR) amplification. These different size duplications result in the same CMT1A phenotype confirming that trisomy of a normal gene region results in CMT1A. The smallest duplication does not include the 409 locus used previously to screen for CMT1A duplications. Direct analysis of interphase nuclei from fetuses and at-risk patients by multicolor in situ hybridization to a commonly duplicated CMT1A probe is informative more often than polymorphic PCR analysis, faster than pulsed field gel electrophoresis (PFGE), and faster, more informative, and more reliable than restriction enzyme analysis. CMT1B restriction enzyme analysis of CMT pedigrees without CMT1A is expected to diagnose another 8% of at-risk CMT1 patients (total: 78%).

Analysis of a segment of the human glial fibrillary acidic protein gene that directs astrocyte-specific transcription

To understand astrocyte-specific transcription, we have been studying the human gfa gene. This gene encodes glial fibrillary acidic protein (GFAP), an intermediate filament protein expressed primarily in astrocytes. A survey of the gfa 5' flanking region showed it to contain several segments that contribute to expression of a chloramphenicol acetyltransferase reporter gene in transfected cells. The most active of these was the 124-bp B region, which spans bp -1612 to -1489. We have now used site-directed mutagenesis to analyze this region in greater detail, and show that the B region itself contains several important elements. The most crucial of these is a consensus AP-1 sequence, the binding site for the Fos and Jun families of transcription factors. The presence of members of both these families in the glial fibrillary acidic protein-expressing U251 cell line used for our transfection studies was verified by gel mobility-shift experiments. This is the first demonstration of the functioning of a specific transcription factor site for astrocytes, and provides a focus for future studies of glial fibrillary acidic protein regulation during development and reactive gliosis.

The effect of laminin on molecular motion in the cell membrane and on cell motility

We have studied the variation of lateral diffusion of proteins in the cell membrane, of membrane lipid fluidity and of the electrophoretic motility (EPM) of macrophages after treatment with extrinsic laminin. The results showed that the lateral diffusion coefficient D value of membrane proteins, the fluidity of membrane lipids and the EPM of macrophages were decreased after laminin had bound to its membrane receptor on the macrophages. These results are important for developing an understanding of the early reaction of plasma membranes and cells in the presence of laminin.

Crystallization of a deletion mutant of the R-subunit of cAMP dependent protein kinase

A single deletion (delta 1 to 91) mutant of the regulatory subunit of the cAMP dependent protein kinase was crystallized. The crystals are hexagonal P6(1)22 (P6(5)22) with a = b = 88.7 A and c = 179.9 A. The crystals diffract to 3 A resolution. There is one molecule per asymmetric unit.

Cerebral amino acid, norepinephrine and nitric oxide metabolism in CNS oxygen toxicity

CNS oxygen (O2) toxicity is complex, and the etiology of its most severe manifestation, O2 convulsions, is yet to be determined. A role for depletion of the brain GABA pool has been proposed, although recent data have implicated production of reactive O2 species, e.g. H2O2, in this process. We hypothesized that the production of H2O2 and NH3 produced by monoamine oxidase (MAO) would lead to depletion of GABA and production of nitric oxide (NO.) respectively, and thereby enhance CNS O2 toxicity. In this study, rats treated with an MAO inhibitor (pargyline) or a nitric oxide synthase inhibitor (LNNA) were protected against O2-induced convulsions. Selected cerebral amino acids including arginine were measured in control and O2 treated rats (6 ATA, 20 min) with or without drug pretreatment. After O2 exposure, the cerebral pools of glutamate, aspartate, and GABA decreased significantly while glutamine content increased relative to control (P < 0.05). After treatment with either enzyme inhibitor, glutamine, glutamate and aspartate concentrations were maintained near control levels. Remarkably, GABA depletion by O2 was not prevented despite protection from seizures by both pargyline and LNNA. The NO. precursor, arginine, was increased significantly in the brain by toxic O2 exposure, but both pargyline and LNNA inhibited this effect. Simultaneous norepinephrine measurements indicated that its storage substantially decreased during hyperoxia (P < 0.05), but this effect too was blocked by either pargyline or LNNA. These data indicate that protection against O2 by these inhibitors is not related to preservation of the GABA pool. More importantly, O2 dependent norepinephrine metabolism and NO. synthesis appear to be interactive during CNS O2 toxicity.

Exclusion of linkage between schizophrenia and the D2 dopamine receptor gene region of chromosome 11q in 112 Irish multiplex families

A leading theory hypothesizes that schizophrenia arises from dysregulation of the dopamine system in certain brain regions. As this dysregulation could arise from abnormal expression of D2 dopamine receptors, the D2 receptor gene (DRD2) on chromosome 11q is a candidate locus for schizophrenia. We tested whether allelic variation at DRD2 and five surrounding loci cosegregated with schizophrenia in 112 small- to moderate-size Irish families containing two or more members affected with schizophrenia or schizoaffective disorder, defined by DSM-III-R. Evidence of linkage was assessed using varying definitions of illness and modes of transmission. Assuming genetic homogeneity, linkage between schizophrenia and large regions of 11q around DRD2 could be strongly excluded. Assuming genetic heterogeneity, variation at the DRD2 locus could be rejected as a major risk factor for schizophrenia in more than 50% of these families for all models tested and in as few as 25% of the families for certain models. The DRD2 linkage in fewer than 25% of these families could not be excluded under any of the models tested. Our results suggest that the major component of genetic susceptibility to schizophrenia is not due to allelic variation at the DRD2 locus or other genes in the surrounding chromosomal region.

Molecular characterization of human prorenin isoelectric forms

OBJECTIVE

Mammalian renins and prorenins can be fractionated by isoelectric focusing into multiple species, the individual production and decay rates of which vary with certain physiological and pharmacological stimuli. The relative abundance of renin isoelectric species varies in certain pathological states, and the individual species have been reported to differ in their biological function. The present study was undertaken to clarify further the biochemical basis for isoelectric heterogeneity in human renin.

DESIGN

Previous data have suggested that differences in glycosylation contribute to isoelectric heterogeneity in human renin. To determine whether glycosylation was solely responsible for the observed isoelectric heterogeneity, the isoelectric focusing patterns of either native or non-glycosylated human prorenin were compared. The specific activities of the three most abundant isoelectric species of human prorenin were also compared.

METHODS

Tissue culture supernatants from transfected cells expressing either native recombinant human prorenin or human prorenin in which both glycosylation sites were eliminated were fractionated by isoelectric focusing. The expressed prorenins were detected in various fractions by trypsin activation and the angiotensin I generation assay. Specific activities of the various prorenins were estimated by direct comparison of immunoprecipitable radiolabeled prorenin and trypsin-activatable renin activity in the three most abundant fractions.

RESULTS

Native human recombinant prorenin was fractionated into at least five isoelectric species, whereas non-glycosylated human recombinant prorenin migrated as a single isoelectric species, the migration of which was unaffected by forskolin treatment. There was a direct correlation between immunoprecipitable and enzymatically determined prorenin in the three major isoelectric species of native prorenin.

CONCLUSIONS

The results suggest that isoelectric heterogeneity of human renin is due solely to differential glycosylation of the protein. The proposed different biological functions of the various isoelectric forms is not directly correlated with variations in their specific activities.

Biocompatibilities of organic solvents with Lactobacillus delbrueckii

In the search for biocompatible extractants for extractive fermentation of lactic acid, the effect of twelve organic solvents on the activity of L. delbrueckii were studied at different concentration levels. On this basis, the compatibilities of twelve solvents with L. delbrueckii were summarized into four classes: completely compatible, compatible at molecular level, partially compatible and non-compatible. The characteristics were described qualitatively for each class in terms of relative values between the solubility of organic solvent in water (Cs) and the toxicity of organic solvent, which is indicated by a newly defined concentration parameter (Cm). The classification was helpful for the selection of extractant in extractive fermentation.

Phosphofructokinase from white muscle of the rainbow trout, Oncorhynchus mykiss: purification and properties

Phosphofructokinase was purified and characterized from the white skeletal muscle of rainbow trout Oncorhynchus mykiss. Purification involved three steps: ion-exchange chromatography on hydroxyapatite and affinity chromatography on phosphocellulose and ATP-agarose. A final specific activity of 75 units per mg of protein at 22 degrees C and pH 7.2 with 40% recovery was obtained. The purified enzyme gave a single band on SDS-PAGE with a subunit molecular mass of 76.5 +/- 0.6 kDa. Based on gel filtration analysis, the active form of the enzyme was found to be composed of six identical subunits. A high isoelectric point (7.1) was found for this enzyme. Arrhenius plots of the enzyme activity showed a sharp transition at 15-16 degrees C. The pH optimum of the enzyme was 8.0-8.5 at physiological level of ATP and positive modulators shifted the optimum to lower pH values. Amino-acid analysis revealed a lower content of the aromatic residues Phe, Tyr and Trp and higher level of Ser residue than in the rabbit muscle enzyme.