NADP+-Dependent internalization of recombinant CD38 in CHO cells

CD38 is a 46-kDa type II transmembrane glycoprotein that catalyses the synthesis of cyclic ADP-ribose (cADPR) from NAD+. cADPR is a second messenger known to regulate intracellular Ca2+-induced Ca2+-release (CICR). A recent study has revealed that CD38 in Namalwa B cells undergoes internalization upon exposure to external NAD+. In this study, recombinant rat CD38 was expressed in Chinese hamster ovary (CHO) cells and the possibility of the protein to undergo internalization upon exposure to a substrate analog NADP+ was examined. It was found that such treatment of CHO cells resulted in a decrease of ADP-ribosyl cyclase activity, as well as immunofluorescence of CD38 on the cell surface. The same treatment of CHO cells also resulted in intracellular clustering of CD38 molecules as revealed by confocal microscopic analysis. The internalized CD38 was purified using a streptavidin/biotin-based method and was found to exhibit both ADP-ribosyl cyclase and cADPR hydrolase activities. On immunoblot, the internalized CD38 appeared as a monomer of 46 kDa under reducing condition of SDS-PAGE. Our data demonstrate that NADP+ can efficiently induce internalization of CD38, a process that may be important in the production of cADPR intracellularly to regulate CICR.

Characterization and localization of CD38 in the vertebrate eye

CD38 is a 42-kDa type II transmembrane glycoprotein that has been shown to catalyze the synthesis and hydrolysis of cyclic ADP-ribose, a metabolite with well-known calcium mobilizing properties independent of IP3. In this report, characterization and localization of CD38 in the porcine and rat eyes were carried out. Western blot analysis of a purified microsomal eye extract detected a single 42-kDa protein band characteristic of CD38. Subcellular fractionation studies indicate the presence of ADP-ribosyl cyclase and NADase activities in the nuclear, membrane and microsomal fractions. Immunohistochemical staining of the rat retina showed the expression of CD38 in three distinct layers: the ganglion cell layer, inner nuclear layer and the pigmented epithelium. In the lens, the lenticular epithelium and lens cells were also immunoreactive for CD38 while in the ciliary body, both the pigmented and non-pigmented epithelium also showed the presence of CD38. For the first time, the presence of CD38/ADP-ribosyl cyclase was detected in the vertebrate eye.

Influence of endoscopic variceal ligation on oesophageal motility

BACKGROUND

To determine the change of oesophageal manometry in patients with oesophageal varices before and after oesophageal variceal ligation (EVL).

METHODS

Forty-five patients who had liver cirrhosis and oesophageal varices with high risk of bleeding were managed by EVL. Oesophageal manometry was performed just prior to the ligation and 4-6 weeks after obliteration of varices. Another 45 age- and sex-matched patients without hepatic, oesophageal or systemic disease served as the control group.

RESULTS

At 5 cm above the lower oesophageal sphincter (LES), the amplitude of the contractive wave was significantly lower in patients before EVL (56.9 +/- 31.8 vs 80.1 +/- 30.1, P< 1.05) and returned to the level of control subjects after EVL (76.5 +/- 37.0 vs 80.1 +/- 30.1, P> 0.05). At 10 cm above LES, the amplitude of the contractive wave was significantly lower in patients before and after EVL than the control group (54.3 +/- 29.2 vs 68.1 +/- 29.5, 54.2 +/- 26.0 vs 68.1 +/- 29.5, respectively, P< 0.05). The percentage of tertiary waves was significantly higher in patients before and after EVL than in the control group (31.4 +/- 36.6 vs 5.8 +/- 15.1, 26.9 +/- 32.9 vs 5.8 +/- 15.1, respectively, P< 0.05). However, no significant swallowing disturbance was noted in patients after EVL. There was significantly greater LES length in patients before EVL (4.0 +/- 0.9 vs 3.4 +/- 0.7, P<0.05) but there was no significant difference in the LES length after EVL as compared with the control group. Eighty-six per cent (39/45) of patients developed paraoesophageal varices and 31% (14/45) developed new varices 6 months after variceal obliteration. However, there was no significant difference in manometry at the time of variceal obliteration between patients with variceal recurrence and those without.

CONCLUSIONS

The presence of varices affected oesophageal motility. However, such abnormality had little clinical significance. Endoscopic variceal ligation normalized oesophageal motility and may not induce abnormal oesophageal motility. The manometric change can not be used to predict the recurrence of varices in cirrhotic patients after variceal obliteration.

Inhibition of phenolic acid metabolism results in precocious cell death and altered cell morphology in leaves of transgenic tobacco plants

Several complex phenotypic changes are induced when the transcription factor AmMYB308 is overexpressed in transgenic tobacco plants. We have previously shown that the primary effect of this transcription factor is to inhibit phenolic acid metabolism. In the plants that we produced, two morphological features were prominent: abnormal leaf palisade development and induction of premature cell death in mature leaves. Evidence from the analysis of these transgenic plants suggests that both changes resulted from the lack of phenolic intermediates. These results emphasize the importance of phenolic secondary metabolites in the normal growth and development of tobacco. We suggest that phenolic acid derivatives are important signaling molecules in the final stages of leaf palisade formation and that phenolic acid derivatives also play a prominent role in tissue senescence.

Inhibition of phenolic acid metabolism results in precocious cell death and altered cell morphology in leaves of transgenic tobacco plants

Several complex phenotypic changes are induced when the transcription factor AmMYB308 is overexpressed in transgenic tobacco plants. We have previously shown that the primary effect of this transcription factor is to inhibit phenolic acid metabolism. In the plants that we produced, two morphological features were prominent: abnormal leaf palisade development and induction of premature cell death in mature leaves. Evidence from the analysis of these transgenic plants suggests that both changes resulted from the lack of phenolic intermediates. These results emphasize the importance of phenolic secondary metabolites in the normal growth and development of tobacco. We suggest that phenolic acid derivatives are important signaling molecules in the final stages of leaf palisade formation and that phenolic acid derivatives also play a prominent role in tissue senescence.

The solution structure of a cytotoxic ribonuclease from the oocytes of Rana catesbeiana (bullfrog)

RC-RNase is a pyrimidine-guanine sequence-specific ribonuclease and a lectin possessing potent cell cytotoxicity. It was isolated from the oocytes of Rana catesbeiana (bull frog). From analysis of an extensive set of 1H homonuclear 2D NMR spectra we have completed the resonance assignments. Determination of the three-dimensional structure was carried out with the program X-PLOR using a total of 951 restraints including 814 NMR-derived distances, 61 torsion angles, and 76 hydrogen bond restraints. In the resultant family of 15 best structures, selected from a total of 150 calculated structures, the root-mean-square deviation from the average structure for the backbone heavy-atoms involved in well-defined secondary structure is 0.48 A, while that for all backbone heavy-atoms is 0.91 A. The structure of RC-RNase consists of three alpha-helices and two triple-stranded anti-parallel beta-sheets and folds in a kidney-shape, very similar to the X-ray crystal structure of a homolo gous protein, onconase isolated from Rana pipiens. We have also investigated the interaction between RC-RNase and two inhibitors, cytidylyl(2'-->5')guanosine (2',5'-CpG) and 2'-deoxycytidylyl(3'-->5')-2'-deoxyguanosine (3',5'-dCpdG). Based on the ligand-induced chemical shift changes in RC-RNase and the NOE cross-peaks between RC-RNase and the inhibitors, the key residues involved in protein-inhibitor interaction have been identified. The inhibitors were found to bind in a "retro-binding" mode, with the guanine base bonded to the B1 subsite. The His103 residue was found to occupy the B state with the imidazole ring pointing away from the active site. The structure coordinates and the NMR restraints have been deposited in the Brookhaven Protein Data Bank (1bc4 and 1bc4mr, respectively).

Effects of backbone modification on helical peptides: the reduced carbonyl modification

Reducing a CO to a CH2 moiety in a peptide bond destroys the ability of the peptide link to act as a proton acceptor in a hydrogen-bonded structure. Here, this modification is introduced into different positions of the helical peptide, acetyl-WGG(RAAAA)4R-amide, and the melting of these peptides is followed using CD. Effects of this modification on helical peptides are compared to our previous N-methylation studies [C. F. Chang and M. H. Zehfus (1996) Biopolymers, Vol. 40, pp. 609-616]. While the experiments were designed to remove the same hydrogen bond from the peptide, no consistent results are obtained between these two modifications. This result suggests that these modifications not only break the backbone hydrogen bonds, but also involve other destabilizing effects. When our data is analyzed using different helix-coil transition models, the results show that as the models increase in complexity the energy associated with a single residue modification increases. Unfortunately, the most detailed dichroic model, which should best describe this system, works for only one peptide. Apparently, the models need to be further improved to better mimic our system.

T-antigen-dependent transcriptional initiation and its role in the regulation of human neurotropic JC virus late gene expression

The multifunctional protein of papovaviruses, T-antigen, regulates the virus lytic cycle partly by exerting transcriptional control over viral and cellular gene expression. In this study, the ability of the T-antigen of human neurotropic JC virus (JCV) to enhance expression from the virus late promoter has been further examined. By deletion analysis, a T-antigen-responsive region was mapped within the JCV 98 bp enhancer/promoter between nucleotides 139 and 168. Interestingly, T-antigen appears to mediate transactivation by increasing expression from a basal transcriptional initiation site and through a novel T-antigen-dependent initiation site (TADI). The TADI element contains a region homologous to initiator (Inr) sequences and is sufficient to confer T-antigen responsiveness to a heterologous minimal promoter. Electrophoretic mobility shift and UV crosslinking analyses demonstrate that multiple cellular proteins interact with both single- and double-stranded forms of this sequence. Mutations within the TADI element which abolish T-antigen-mediated transcriptional activation also prevent the formation of specific nucleoprotein complexes. These data suggest that the ability of JCV T-antigen to regulate JCV late gene expression may be partly due to the formation of specific nucleoprotein complexes and transcriptional initiation from the TADI site on the viral promoter.

Functional role of glycosylation on the recombinant CD38/ADP-ribosyl cyclase in CHO cells

Current evidence suggests that CD38, a lymphocyte differentiation antigen, has been found to be functionally indistinguishable from the native form when it was expressed as a soluble and non-glycosylated protein in yeast. Studies were conducted to evaluate the functional role of glycosylation on the membrane-bound CD38 in mammalian cells. The stable transformants of CHO cells were established with pXJ41-CD38 construct and the recombinant CD38 was detected at the surface of CHO cells using a polyclonal antibody to rat CD38 by immunocytochemistry. The recombinant protein displaying ADP-ribosyl cyclase activity was purified from CHO cells, which appeared as 42 and 46 kDa bands on immunoblot under non-reducing and reducing conditions, respectively. The recombinant CD38 was then subjected to deglycosylation with N-glycosidase F that resulted in a 33 kDa band on immunoblot under reducing condition. Further the partial deglycosylation of the recombinant CD38, performed at various time intervals, resulted in a series of bands (33-46 kDa) on immunoblot. Kinetic analysis indicated that deglycosylation of the recombinant CD38 showed a considerable decrease in Vmax and an increase in K(m) of ADP-ribosyl cyclase activity. These observations clearly suggest that glycosylation plays an important role to maintain the enzymatic activity and substrate affinity of CD38/ADP-ribosyl cyclase for mediating the signalling events in mammalian cells.

Experimental infection of the human granulocytic ehrlichiosis agent in horses

Human blood collected from two patients from Westchester County, New York with human granulocytic ehrlichia (HGE) infection was inoculated into two ponies. Inoculated ponies developed clinical signs similar to a previous report (Madigan et al., 1995). Histopathological changes involved follicular hyperplasia of lymphoid tissues. HGE DNA was detected by PCR in muscle, fascia, peritoneum, and adrenal gland after the ponies produced a high level of antibodies to HGE. We suggest that HGE may reside in poorly vascularized connective tissues, where the antibodies may have some difficulties to penetrate, resulting in persistent infection. Since HGE and E. equi cause very similar diseases in both humans and horses, they may be the same organism with minor genetic differences.

Differential oligomerization of membrane-bound CD38/ADP-ribosyl cyclase in porcine heart microsomes

A protein fraction displaying ADP-ribosyl cyclase activity was purified from porcine heart microsomes which appeared as a major band of 45 kDa on Coomassie blue stained SDS-PAGE gel under reducing condition. Protein immunoblot analysis with antiserum to recombinant rat CD38 showed a series of bands (45-285 kDa) under nonreducing condition, while only the 45 kDa monomer under reducing condition. The high molecular weight oligomers of CD38 were found to be stable even upon treatment with various concentrations of SDS in the sample buffer and also upon incubation at lower temperature. These oligomers of CD38 also displayed higher ADP-ribosyl cyclase activity than that of the monomer.

Purification and characterization of CD38/ADP-ribosyl cyclase from rat lung

Purification and characterization of CD38/ADP-ribosyl cyclase in the rat lung tissue was performed with microsomes solubilized in Triton X-100 and the ADP-ribosyl cyclase was then purified using sequential column chromatography. Partially purified rat lung ADP-ribosyl cyclase was analyzed by immunoblotting using an antibody raised against a recombinant rat CD38 and showed the presence of monomer (42 kDa) and dimer (85 kDa) under non-reducing conditions but under reducing conditions, only the monomer was detected. Both the monomer and dimer could be eluted out in a stable manner from SDS-PAGE and the enzymatic activity was retained by the two different forms of CD38/ADP-ribosyl cyclase. Immunohistochemical staining showed the presence of CD38 on the bronchial epithelium and the alveoli.

Tennessee's failed managed care program for mental health and substance abuse services

In July 1996, Tennessee initiated a managed mental health and substance abuse program called TennCare Partners. This publicly funded "carve-out" experiment started chaotically and soon deteriorated into a crisis. Many patients did not receive care or lost continuity of care, and the traditional "safety net" mental health system nearly disintegrated. This qualitative case study sought to ascertain the impact of the TennCare Partners program. It points out that the program's difficulties stemmed directly from a flawed design that spread funds previously earmarked for severely mentally ill patients across the entire Medicaid population. States contemplating similar reforms should strive to protect vulnerable patients by risk-adjusting capitation payments and by focusing resources on care for severely mentally ill persons. States should also minimize program complexity and ensure the accountability of managed care networks for their patients' behavioral health care needs.

Suspected malignant hyperthermia during isoflurane anesthesia--a case report

We present a patient with thyroid cancer, who developed respiratory acidosis, tachycardia and hyperthermia during isoflurane anesthesia. Malignant hyperthermia was suspected on the basis of clinical manifestation and laboratory finding. With early diagnosis and treatment the patient survived the episode.

Functional expression of secreted mouse BST-1 in yeast

BST-1, a bone marrow stromal cell surface antigen, is a glycosyl phosphotidylinositol-anchored protein that stimulates pre-B-cell growth and has adenosine diphosphate (ADP)-ribosyl cyclase and cyclic ADP-ribose (cADPR) hydrolase activity. The two enzymatic activities are responsible for the synthesis and hydrolysis of cADPR, a novel second messenger of calcium release from intracellular calcium stores. The expression and characterization of human BST-1 in certain mammalian cell lines have been reported. We have expressed the murine BST-1 in yeast as a 6 x His-tagged secreted protein. The recombinant protein has been purified and subjected to structural and functional characterization. It has an apparent molecular mass of 38.5 kDa on SDS-PAGE gel stained with Coomassie blue and is recognized on Western blots by a rabbit polyclonal antibody against BST-1. Deglycosylation of the protein with N-glycanase produces a ladder of bands with molecular sizes ranging from 32 to 39 kDa. The protein possesses the ADP-ribosyl cyclase activity as measured using nicotinamide guanine dinucleotide as substrate.

Relative success of state-managed behavioral health care: does the financing structure play any role?

Federal Section 1915(b) and Section 1115 waivers, through the Health Care Financing Administration, are the primary modes for implementing Medicaid-managed mental health and chemical dependency services. This paper focuses on three distinct case studies of managed mental health programs in Tennessee, Massachusetts, and Hawaii. The purpose is to determine, among other design factors (such as carve-in, carve-out, and covered services) the specific roles that differences in the financing structure play in the relative success of these programs. Findings from the three distinct models should provide lessons for the impending mental health programs of other states, including those in the varying stages of implementation.

Detection of human granulocytic ehrlichiosis agent and Borrelia burgdorferi in ticks by polymerase chain reaction

Adult ixodid ticks were collected from Westchester County, New York, and Ipswich, Massachusetts, to determine the presence of infection with a human granulocytic ehrlichiosis (HGE) agent by using the polymerase chain reaction (PCR). The presence of Borrelia burgdorferi in ticks collected from New York was also determined by PCR. Of the 229 ticks from New York and 47 ticks from Massachusetts, 9% (22/229) and 25% (12/47) of ticks contained HGE agent, respectively. Fifty-four percent (123/229) of the ticks collected from New York were B. burgdorferi positive; 4% (9/229) of these ticks contained both HGE agent and B. burgdorferi. This finding indicates that animals with Lyme borreliosis may be also exposed to the etiologic agent of HGE. More extensive laboratory diagnosis may be necessary when multiple tick-borne diseases are suspected in animals.

The endocrine mechanism of sex reversal in the protandrous black porgy, Acanthopagrus schlegeli: a review

Black porgy, Acanthopagrus schlegeli Bleeker, a marine protandrous hermaphrodite, is a functional male for the first 2 years of life but begin to sexually reverse to female after the third year. This sex pattern provides a very good model to study the mechanism of sex reversal in fish. The gonad at 5 month of age consisted of testicular tissue with few primary oocytes at 5 month of age. The ovarian tissue became dominant at 18 months of age during the non-spawning season. Testicular and ovarian tissues were separated by connective tissue. Plasma estradiol-17 beta(E2), vitellogenin and 11-ketotestosterone (11-KT) profiles in males were significantly different from those in the 3-year-old reversing females. Peak levels of plasma E2 in the reversing females occurred during the early prespawning season (in October). Lower levels of plasma E2 were, however, observed in the males. Plasma 11-KT levels significant decreased but no changes of plasma testosterone were detected in the reversing females. Exogenous E2 suppressed the testicular development but induced the gonadal aromatase activity, ovarian development and sex reversal in 2-year-old black porgy. Exogenous T and LHRH analog did not have effects on the sex reversal. Higher concentrations of pituitary GtH II and mRNA of GtH II-beta subunit were detected in the reversed females. These data suggested that E2 and gonadal aromatase closely associated to the occurrence of sex reversal. A working model of the sex reversal in black porgy is proposed.

Isolation and characterization of the female-specific protein (vitellogenin) in mature female hemolymph of the freshwater prawn, Macrobrachium rosenbergii: comparison with ovarian vitellin

Purification and characterization of the female-specific protein (vitellogenin) from the hemolymph of mature female prawn, Macrobrachium rosenbergii, were the objectives of this study. The comparison of biochemical characteristics between vitellogenin and ovarian vitellin was also conducted. Hemolymph vitellogenin was purified with DEAE, hydroxylapatite, and another DEAE chromatographic column. The specific protein (vitellogenin) was shown in the fractions of chromatographic columns on the basis of ELISA, Western blotting, and immunoprecipitation. A purified vitellogenin was obtained with an apparent molecular weight of 700 kDa as determined by PAGE. The purified vitellogenin was considered as a lipoglycoprotein on the basis of staining data. Three subunits (170, 100, and 89 kDa) in purified vitellogenin and two subunits (100 and 89 kDa) in vitellin were detected with SDS-PAGE. Nondisulfide bonds were found in the binding of polypeptide subunits. Only the 89-kDa subunit was a glycopolypeptide in both vitellogenin and vitellin. The amino acid composition of vitellogenin differed from that of vitellin in a few amino acids. Eight amino acid sequences from the N-terminal end of 89- and 100-kDa subunits were determined and they were identical between vitellogenin and vitellin. Seven amino acid sequence from the N-terminal end of the 170-kDa subunit were also identical to the 100-kDa subunit. Purified vitellogenin was more susceptible to precipitation in a solution with low ionic strength than vitellin. This study suggests a close relationship between vitellogenin and vitellin in M. rosenbergii in their biochemical characteristics.

Androgens stimulate gonadotropin-II beta-subunit in eel pituitary cells in vitro

Primary cultures of juvenile eel (Anguilla anguilla) pituitary cells were used to study the direct effects of sex steroids on gonadotropin (GtH-II) cell content and release (radioimmunoassay) as well as on mRNAs levels for alpha and GtH-II beta-subunits (dot-blot). Testosterone stimulated GtH-II production in a dose- and time-dependent manner by selectively increasing mRNAs for GtH-II beta-subunit but not alpha-subunit. This positive effect was also induced by non-aromatizable androgens (androstanediol and dihydrotestosterone) but not by estradiol, indicating an androgen-specific effect in the eel. The androgen-specific stimulation of eel GtH-II beta appears closer to the regulation of mammalian follicle stimulating hormone-beta (FSHbeta) than that of salmonid GtH-II beta or mammalian luteinizing hormone-beta (LHbeta)-subunits. Comparison with previous in vivo experiments suggests multiple sites of action of sex steroids on the brain-pituitary gonadotropic axis for the positive feedback on GtH-II synthesis in this juvenile fish.

The concentrations of vitellogenin (vitellin) and protein in hemolymph, ovary and hepatopancreas in different ovarian stages of the freshwater prawn, Macrobrachium rosenbergii

The objectives were to measure the concentrations of vitellogenin (vitellin) and protein in hemolymph, ovary, and hepatopancreas of the freshwater prawn, Macrobrachium rosenbergii, in different stages of ovarian development. The ovarian development of M. rosenbergii was classified into five developmental stages (Stages I-V). Vitellogenin concentrations increased in the hemolymph of prawns in the early stages of ovarian development (Stage I or II) and were maintained at high levels until Stage V. There was no close association between ovarian development and the concentrations of circulating vitellogenin. Concentrations of protein in hemolymph and hepatopancreas remained constant during various stages of ovarian development. The ovarian stages closely correlated with the gonadosomatic index, the concentrations of ovarian vitellin and protein, respectively. Vitellogenin levels in hepatopancreas remained very low in different stages of the prawn although the highest levels were observed in Stage IV. No close association between hemolymph vitellogenin and ovarian vitellin was observed. The increase of vitellogenin concentration in hemolymph occurred earlier than vitellin content in ovary.

Pterin and folate reduction by the Leishmania tarentolae H locus short-chain dehydrogenase/reductase PTR1

Overproduction of the short-chain dehydrogenase/reductase PTR1 confers resistance to the dihydrofolate reductase inhibitor methotrexate in the protozoan parasite Leishmania. Genetic analysis has previously implicated PTR1 in pterin and folate metabolism. PTR1 was purified from a fusion protein expressed in Escherichia coli. Purified PTR1 exhibits NADPH-dependent biopterin, dihydrobiopterin, folate, and dihydrofolate reductase activities. The highest activity was found with the most oxidized pterins. The active protein was found to be a tetramer as demonstrated by gel-filtration chromatography. Kinetic constants (K(m)), as determined by double-reciprocal plots, were calculated for NADPH and for several of PTR1's substrates. The PTR1 of Leishmania tarentolae had a K(m) of 16.9 microM for the cofactor NADPH and K(m) values ranging from 3.5 to 85 microM for the various substrates. The dissociation constant (KD), as determined by fluorescence titration, for NADPH was estimated to be 130 microM. The biochemical characterization of this important and novel enzyme involved in folate and pterin metabolism of Leishmania should be useful for structure-function analysis and for developing specific inhibitors against this putative important chemotherapeutic target.