Synergistic stimulatory effects of tumour necrosis factor alpha and interferon gamma on replication of human immunodeficiency virus type 1 and on apoptosis of HIV-1-infected host cells

Differential and sometimes contradictory effects have been described for tumour necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) on replication of human immunodeficiency virus type 1 (HIV-1). The authors examined individual and coordinate action of these cytokines on HIV-1 expression, and on apoptosis of HIV-1-infected host cells by determination of reverse transcriptase activity in cell culture supernatant, expression of HIV-1-RNA and production of p24 antigen in the promonocytic cell line U937 and its persistently HIV-1-infected clone U1. Apoptosis was demonstrated by typical cleavage of cellular DNA at internucleosomal regions in promonocytic and T-lymphocytic cell lines. TNF-alpha alone markedly stimulated HIV-1 replication in U1 cells at the transcriptional and on the translational level. Exclusive application of IFN-gamma only slightly enhanced HIV-1 expression, whereas it synergistically potentiated stimulatory effects of TNF-alpha. Both cytokines also synergistically induced apoptosis in HIV-1-infected host cells. Co-ordinate action of TNF-alpha and IFN-gamma is suggested to represent an important mechanism for disease progression in HIV infection. These findings demonstrate that cytokine effects on viral expression may vary depending on their single or combined application.

Characterization of the sphingomyelin content of isolated pancreatic islets. Evaluation of the role of sphingomyelin hydrolysis in the action of interleukin-1 to induce islet overproduction of nitric oxide

Inflammatory cytokines may participate in the destruction of pancreatic islets during the pathogenesis of insulin-dependent diabetes mellitus, and the cytokine interleukin-1 (IL-1) strongly inhibits insulin secretion from rat pancreatic islets by a process which involves induction of expression of the inducible isoform of nitric oxide synthase and the overproduction of nitric oxide. The signaling events between IL-1 receptor occupancy and induction of nitric oxide synthase in rat islets involve activation of the transcriptional activator NFkappa B. Because sphingomyelin hydrolysis has been implicated as a signaling process both in NFkappa B activation and in IL-1 action in some cells, we have examined the potential involvement of sphingomyelin hydrolysis in the induction of islet nitric oxide overproduction by IL-1. Rat islet sphingomyelin pools were radiolabeled with [3H]choline, and sphingomyelin was then isolated by normal phase HPLC. Electrospray ionization-mass spectrometric analysis revealed islet sphingomyelin consists of at least 4 distinct molecular species, and the most abundant of them contained sphingosine as the long chain base and a residue of palmitic acid as the fatty acid substituent. Molecular species containing residues of stearic acid and arachidic acid were also observed. Neither interleukin-1 nor tumor necrosis factor-alpha was found to induce hydrolysis of islet sphingomyelin species, and neither an exogenous, cell-permeant ceramide species (N-acetyl-D-sphingosine) nor exogenous sphingomyelinase mimicked or potentiated the effect of IL-1 to increase rat islet nitric oxide generation, as reflected by nitrite production. Similar findings were obtained with RINm5F insulinoma cells and with mouse pancreatic islets. These findings provide the first information on the molecular species of sphingomyelin in pancreatic islets and suggest that sphingomyelin hydrolysis is not involved in the signaling pathway whereby IL-1 induces the overproduction of nitric oxide by pancreatic islets.

Relationship between chondroitin sulfate proteoglycan and coronary atherosclerosis in the youth

OBJECTIVE

To study the relationship between chondroitin sulfate proteoglycan (CSPG) and coronary atherosclerosis in youth.

MATERIAL AND METHODS

Immunohistochemistry of chondroitin sulfate proteoglycan and SM-alpha-actin was performed on 39 human coronary arteries, including normal vessels and vessels with fatty streaks, intermediate lesions and plaques. Some of the lesional vessels were taken for beta-lipoprotein immunohistochemical study. CSPG contents were quantitated by image analyzer and the coronary arteries from one heart were processed for immunoelectron microscopy.

RESULTS

The range of CSPG distribution was extensive and CSPG area density was increased significantly in the intima with atherosclerotic lesions. The increase of CSPG was parallel to the numbers of smooth muscle cell (SMC) with positive SM-alpha-actin reaction and was likely related to the phenotype transformation of SMC. Similar distribution of beta-lipoprotein and CSPG were found within the lesional regions.

CONCLUSIONS

The increase of CSPG in atherosclerotic lesion may be an important factor resulting in the deposition of lipids in the vascular wall so as to promote the formation and development of atherosclerosis.

Identification and properties of an ATP-sensitive K+ current in rabbit sino-atrial node pacemaker cells

1. Single myocytes were isolated from rabbit sino-atrial (SA) node by enzymatic dissociation. Spontaneous pacemaker activity, whole-cell and single-channel currents were recorded under conditions known to modulate ATP-sensitive K+ (KATP) channels. 2. The KATP channel openers, cromakalim and pinacidil, slowed or abolished the pacemaker activity, and caused hyperpolarization of the maximum diastolic potential (MDP). Glibenclamide, a KATP channel blocker, reversed these effects. Cromakalim- and pinacidil-activated currents reversed near the potassium equilibrium potential, EK. Glibenclamide had no effect on the L-type calcium current, ICa(L), the hyperpolarization-activated inward current, If, or the delayed rectifier potassium current, IK. 3. Sodium cyanide, which inhibits mitochondrial ATP production, induced a macroscopic current that reversed near EK and was blocked by glibenclamide. 4. In excised, inside-out patches from SA node cells, single KATP channels showed a slope conductance of 52 +/- 8 pS (mean +/- S.D.) when measurements were made at negative voltages in symmetric, 140 mM K+. Channels from ventricular myocytes showed a somewhat larger slope conductance (70 +/- 5 pS). 5. Raising the intracellular ATP concentration caused a concentration-dependent reduction in the open probability of the KATP channels (IC50, 16 microM; Hill coefficient, approximately 1; at both pH 7.4 and 6.8). 6. In excised inside-out patches, cromakalim or pinacidil induced significant increases in KATP channel activity in the presence of 50 microM or 1 mM intracellular ATP. This channel activity was blocked by glibenclamide. 7. Our results suggest that sino-atrial node cells express a distinct isoform of KATP channel which may play an important role in pharmacological and pathophysiological modulation of pacemaker activity.

Regulation of expression of taurine transport in two continuous renal epithelial cell lines and inhibition of taurine transporter by a site-directed antibody

The renal tubular epithelium adapts to changes in the sulfur amino acid composition of the diet, particularly in terms of reabsorption of taurine. The adaptive response is expressed by enhanced or decreased NaCl-dependent taurine transport by rat renal brush border membrane vesicles (BBMV). Taurine transport activity in two cultured renal epithelial cell lines (MDCK and LLC-PK1) is up- or down-regulated by extracellular taurine concentration as the result of reciprocal changes in the Vmax of the transporter. In MDCK cells, abundance of taurine transporter mRNA (pNCT mRNA) was up- or down-regulated after incubation in media containing 0, 50, or 500 microM taurine. Decreased mRNA was observed in both cell lines after 12 h, and it was appreciably reduced after 72 h exposure to 500 microM taurine. Northern blot analysis of mRNA from LLC-PK1 cells using pNCT cDNA as a riboprobe showed that two transcripts, 9.6 kb and 7.2 kb, were expressed; the abundance of mRNA was increased or decreased after incubation in taurine-free or high taurine medium, respectively. Down-regulation was observed primarily in the 7.2 kb transcript after 24 h incubation. Rapid up-regulation occurred in the 9.6 kb transcript within 12 h of transfer from high to low taurine. Nuclear run-off assays showed that the gene for pNCT is induced at the transcriptional level by taurine. Regulation of expression of the taurine transporter was also studied by injection of pNCT cRNA into Xenopus laevis oocytes. Expression of transport activity was significantly reduced (64%) when oocytes were incubated in 50 microM taurine as compared to 0 microM taurine. Transport activity was totally blocked when pNCT cRNA-injected oocytes were exposed to an active phorbol ester, PMA (10(-6) M). Inhibition of uptake was reversed by staurosporine, an inhibitor of protein kinase C activity. An inactive phorbol ester, 4 alpha-phorbol, had no effect on taurine transport. A polyclonal antibody directed a highly conserved intracellular segment between homologous transmembrane domains VI and VII inhibited taurine transport activity in both pNCT cRNA-injected oocytes and BBMV. Incubation of oocytes with 10 micrograms/ml antibody (Ab) reduced taurine uptake to 46% of control, and 20-80 micrograms/ml Ab reduced uptake to 20% of control. In BBMV, active taurine uptake (10 microM) was inhibited approximately 30% by 10 pg Ab/mg protein, whereas none specific IgG had no significant effect. Proline uptake (20 microM) by BBMV was not inhibited by the Ab, nor was GABA uptake (50 microM). Two pNCT proteins, approximately 70 kD and approximately 30 kD, were detected by Western blot, and the abundance of both was regulated by medium taurine.

IN CONCLUSION

(i) regulation of taurine transport activity in LLC-PK1 cells by medium taurine occurs at a level of mRNA transcription; (ii) regulation of pNCT occurs at both transcriptional and translational levels; (iii) pNCT expression is regulated by protein kinase C-dependent phosphorylation; and (iv) the intracellular segment between domains VI and VII may be required for activation of the taurine transporter; this segment may function as a gate in taurine transport.

Clinical neuroimmunology

Clinical research has focused on autoimmune disease (AID) for a couple of decades. More sensitive and specific methods have been developed for neuroimmunological research. Gamma fraction bands (bands separated by electrophoresis and visualized by amino black staining) and IgG fraction bands (bands separated by iso-electric focusing and visualized by immunostaining) are used instead of oligoclonal bands. Myasthenia gravis (MG) mainly involves acetylcholine receptors of the postsynaptic membrane at the neuromuscular junction. Myasthenia gravis has been considered to be a generalized AID, because 7% of patients with myasthenia gravis associate with other AIDs and more than one autoimmune antibody is detected in 52.5% patients with myasthenia gravis. Pyramidal signs in myasthenia gravis patients are described; the possible mechanism may at least be partly due to the acetylcholine receptor antibody. P2 protein and its antibody are studied in patients with acute and chronic inflammatory demyelinating polyneuropathy.

SR8--the establishment and characterisation of a new ovarian carcinoma cell line and xenograft model

A new cell line, SR8, and xenograft model of ovarian carcinoma has been established in this laboratory over the past 20 months from a patient with advanced ovarian cancer. Electron microscopic examination of SR8 cells demonstrated the presence of desmosomes and tonofilaments; SR8 cells expressed epithelial membrane antigen (EMA) and glandular associated cytokeratin, all of these confirmed the epithelial origin of this cell line. In addition, SR8 cells expressed CA125, as did the original ovarian tumour. EGF-R and TP53 expression was identified by immunocytochemistry (ICC) in this line. Nearly all the SR8 cells (93%) expressed HLA-class I antigen while 13.5% expressed HLA-DR. SR8 cells showed near-diploid and -triploid chromosome populations with several clonal and non-clonal rearrangements. Subcutaneous and intraperitoneal xenografting of SR8 cells resulted in invasive tumour production at both sites in 3/4 and 4/4 female nude mice, respectively. These xenografts exhibited similar morphology as that of original tumour and were found to express EMA, cytokeratin, CA125 and TP53. The potential research applications of this cell line are discussed.

Tubular gelatinase A (MMP-2) and its tissue inhibitors in polycystic kidney disease in the Han:SPRD rat

Thickening of the tubular basement membrane is one of the hallmarks of the polycystic kidney disease (PKD). The present study was conducted to investigate the potential role of the matrix metalloproteinase-2 (MMP-2) and its specific tissue inhibitors (TIMP-1 and TIMP-2) in the accumulation of matrix components in PKD. As a model of PKD, two-month-old heterozygous Han:SPRD rats, which are at an early stage of cystogenesis, were used. MMP-2, but not MMP-9 (gelatinase B) nor MMP-3 (stromelysin) could be detected in proximal tubules of the normal rat kidney. The presence of the inhibitors TIMP-1 and TIMP-2 was confirmed on the mRNA level. In tubules from PKD rats MMP-2 activity was lower (31 +/- 8 vs. 58 +/- 7 U/prep., N = 9, P < 0.05), mRNA of MMP-2 was reduced 4.2 +/- 0.6-fold (N = 4, P < 0.05) and enzyme protein was depressed 3.8 +/- 0.8-fold (N = 4, P < 0.05). By contrast, TIMP-1 mRNA was 9.0 +/- 1.1-fold and TIMP-2 mRNA 3.8 +/- 0.7-fold (N = 4, P < 0.05) elevated over controls. Cyst fluid from homozygous rats contained MMP-2 protein and activity. These findings indicate that tubular MMP-2 activity is reduced in PKD, due to down-regulation of MMP-2, up-regulation of TIMP-1 and TIMP-2, and luminal secretion of the enzyme. It is conceivable that these alterations relate to the enhanced matrix accumulation observed in the evolution of PKD.

Pre- and post-translational regulation of lysyl oxidase by transforming growth factor-beta 1 in osteoblastic MC3T3-E1 cells

The final enzymatic step required for collagen cross-linking is the extracellular oxidative deamination of peptidyl-lysine and -hydroxylysine residues by lysyl oxidase. A cross-linked collagenous extracellular matrix is required for bone formation. The goals of this study were to compare the transforming growth factor (TGF)-beta 1 regulation of lysyl oxidase enzyme activity and steady state mRNA levels to changes in COL1A1 mRNA levels in MC3T3-E1 osteoblastic cells. TGF-beta 1 increased steady state lysyl oxidase and COL1A1 mRNA levels in a dose- and time-dependent manner. The increase in lysyl oxidase mRNA levels was transient, peaking at 12 h and 8.8 times controls in cells treated with 400 pM TGF-beta 1. COL1A1 steady state mRNA levels increased maximally to 3.5-fold of controls. Development of increased lysyl oxidase enzyme activity was delayed and was of slightly lower magnitude than the increase in its mRNA levels. This suggested limiting post-translational processing of lysyl oxidase proenzyme. Pulse-labeling/immunoprecipitation studies demonstrated slow proenzyme secretion and proteolytic processing. Development and application of an independent assay for lysyl oxidase proenzyme proteolytic processing activity verified its proportionately lower stimulation by 400 pM TGF-beta 1. Thus, lysyl oxidase regulation by TGF-beta 1 in osteoblastic cell cultures occurs at both pre- and post-translational levels. This regulation is consistent with increased production of a collagenous extracellular matrix.

Structural determination of picomole amounts of phospholipids via electrospray ionization tandem mass spectrometry

The remarkable sensitivity of electrospray ionization was exploited to achieve great increases in the sensitivity of tandem mass spectrometric analyses of phospholipids derived from both synthetic and biologic sources. Herein, we demonstrate that (1) product-ion spectra after electrospray ionization can be obtained easily by utilizing ≤ 5 pmol of phospholipid with a mass-selected window of less than 2 mass units, (2) the low energy inherent in the electrospray ionization method facilitates analysis of labile molecular ions that are not easily detected with the relatively high energy employed during fast-atom bombardment desorption, and (3) collision-induced dissociation of precursor ions generated from electrospray ionization often resulted in novel product-ion patterns. Collectively, these results underscore the utility of electrospray ionization tandem mass spectroscopy for the structural determination of diminutive amounts of phospholipids.

[Effect of cholecystokinin on prolactin release and its action mechanism in the rats]

The effect of cholecystokinin octapeptide (CCK-8) on the release of prolactin (PRL) in male rats were studied in vivo and in vitro. CCK-8 at the concentrations (microgram) of 0.05 and 0.5 was injected into the third cerebral ventricle (3rd, V. I) of conscious rats, outfitted with chronic 3rd. V. and jugular cannulae, a significant increase in resting secretion and restraint stress-induced release of PRL were observed. The effects of CCK-8 at the concentration of 0.05 microgram were stronger than those of 0.5 microgram. To determine if CCK-8 would exert any direct action on anterior pituitary, CCK-8 of 0.05, 0.5, 1.00 microgram were added to the medium of dispersed anterior pituitary cell, and caused dose-dependent increase of PRL secretion. To study a mechanism of intracellular signal transduction in the action of CCK-8, the levels of cAMP and [Ca2+] in the medium were measured. Intracellular Ca2+ concentration of disperse anterior pituitary cell was significantly elevated by CCK-8 (2 x 10(-4) mol/L), but CCK-8 (10(-8)-10(-6) mol/L) did not change intracellular cAMP content. The results indicate that CCK-8 stimulate prolactin release at both sites of hypothalamic and anterior pituitary and the mechanism of stimulating effects of CCK-8 might be mediated by [Ca2+] but not cAMP.

Ligand-directed retroviral targeting of human breast cancer cells

We explored the feasibility of designing retroviral vectors that can target human breast cancer cells with characteristic receptors via ligand-receptor interaction. The ecotropic Moloney murine leukemia virus envelope was modified by insertion of sequences encoding human heregulin. Ecotropic virus, which normally does not infect human cells, when pseudotyped with the modified envelope protein now crosses species to infect human breast cancer cell lines that overexpress HER-2 (human epidermal growth factor receptor; also called ERBB2) and HER-4 (also called ERBB4), while human breast cancer cell lines expressing low levels of these receptors remain resistant to infection. Since about 20% of human breast cancers overexpress HER-2 and some of breast cancer cell lines overexpress both HER-2 and HER-4, cell-specific targeting of retroviral vectors may provide a different approach for in vivo gene therapy of this type of breast cancer.

Microsome-mediated 8-hydroxylation of guanine bases of DNA by steroid estrogens: correlation of DNA damage by free radicals with metabolic activation to quinones

Free radical generation by metabolic redox cycling between catechol estrogens and their quinones and subsequent hydroxyl radical damage to DNA have been proposed to mediate estrogen-induced renal carcinogenesis in the hamster. In this study the content of 8-hydroxy-2'-deoxy-guanosine (8-OHdG), a marker product of hydroxyl radical action, was examined in DNA incubated with a liver microsomal activating system and with catechol estrogens, equilenin-3,4-quinone or with parent estrogens. Equilenin-3,4-quinone increased the formation of 8-OHdG by 50% over control levels. 4-Hydroxyestrone and 4-hydroxy-estradiol raised 8-OHdG contents significantly, to 1.61 +/- 0.79 and 1.27 +/- 0.31 8-OHdG/10(5) deoxyguanosine (dG) respectively over controls (0.68 +/- 0.25 8-OHdG/10(5) dG). The corresponding 2-hydroxylated estrogens and the parent hormones estrone, estradiol and equilenin did not affect 8-hydroxylation of guanine bases of DNA. In incubations of catechol estrogens with microsomes and cumene hydroperoxide the 4-hydroxyestrogens were oxidized to quinones more rapidly than the 2-hydroxyestrogens. Our data support a mechanism of hydroxyl radical generation from estrogens by redox cycling between 4-hydroxylated metabolites and their quinones. The rapid oxidation of 4-hydroxylated estrogens to quinones, their redox cycling and hydroxyl radical damage to DNA is consistent with the previously reported carcinogenic activities of 4-hydroxylated, but not of 2-hydroxylated, catechol estrogens.

Clinical application of modified Anyang type 2 esophageal intubation instrument--a new esophageal intubation method

The preliminary experience in the clinical use of Anyang Type 2 esophageal intubation instrument, designed by ourselves, in 11 patients with severe esophageal obstruction due to advanced carcinoma of the esophageal was reported. The diagnosis of all 11 cases was confirmed by barium-meal roentgenography. After intubation, all the patients could take liquid or soft diet by mouth. There was no operative mortality and the patients survived 2 to 14 months (mean 5.7 months). All of them could take food by mouth before death. The clinical application proved that the intubation has been a safe and suitable management.

Localisation of 15-hydroxy prostaglandin dehydrogenase (PGDH) and steroidogenic enzymes in the equine placenta

15-hydroxy prostaglandin dehydrogenase (PGDH) is the critical enzyme that determines metabolism of primary prostaglandins. Its expression is determined in part by steroid hormones, particularly progesterone, formed from delta(5) steroids through 3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity. To assess whether the regulation of PGDH might occur in a paracrine, autocrine or intracrine fashion, we used immunohistochemistry (IHC) to determine the localisation of key steroidogenic enzymes in the equine placenta and compared these patterns to the distribution of immunoreactive (IR-) PGDH. Placental tissue was obtained from pony or Thoroughbred mares at about Days 150, 250-280 and >300 of pregnancy (term 320 to 360 days; n=5-8 each group). IR-PGDH, 3beta-HSD, cholesterol side chain cleavage enzyme (P450(scc)) and 17-hydroxylase/lyase (P450(C17)) were localised using specific antibodies and the avidin-biotin peroxidase technique and visualised using diaminobenzidine as substrate. IR-P450(scc) was present in trophoblast cells, but not in maternal tissues of the microcotyledons. In contrast, at Days 150 and 280, IR-PGDH was present in maternal epithelial and interstitial cells in the microcotyledons, but was not detected in trophoblast epithelium, chorioallantois or endometrial glands. After Day 300, IR-PGDH was present in the maternal epithelium and interstitial cells of the placenta and it was also present in trophoblast cells in some specimens.

Effects of streptozotocin-induced diabetes, physical training and their combination on collagen biosynthesis in rat skeletal muscle

The effects of streptozotocin-induced diabetes, physical training and their combination on the activities of prolyl 4-hydroxylase (PH) and galactosylhydroxylysyl glucosyl-transferase (GGT), both marker enzymes of collagen biosynthesis, and on the concentration of hydroxyproline (Hyp) were studied in vastus lateralis, rectus femoris and gastrocnemius muscles in rats. The experimental period was 12-16 weeks. Diabetes had an overall decreasing effect on specific PH activity in all muscles studied, whereas specific GGT activity remained at control level. Total PH and GGT activities decreased in all three muscles in the diabetic animals (P < 0.001). Training caused an increase in PH and GGT activities in gastrocnemius in non-diabetic rats, whereas training in combination with diabetes did not change specific PH or GGT activity. Diabetes increased specific Hyp concentration in vastus lateralis and gastrocnemius in trained diabetic rats (P < 0.05), whereas training decreased Hyp level significantly (P < 0.05) in vastus lateralis in non-diabetic rats, but not in diabetic animals. The results suggest that in streptozotocin-induced diabetes the decrease in collagen synthesis rate exceeds the negative total protein balance in the muscle. Although physical training may have an increasing effect on muscular collagen synthesis in non-diabetic rats, it is unable to prevent the decreasing effect of diabetes on collagen synthesis.

Effect of diet on insulin- and contraction-mediated glucose transport and uptake in rat muscle

A diet rich in fat diminishes insulin-mediated glucose uptake in muscle. This study explored whether contraction-mediated glucose uptake is also affected. Rats were fed a diet rich in fat (FAT, 73% of energy) or carbohydrate (CHO, 66%) for 5 wk. Hindquarters were perfused, and either glucose uptake or glucose transport capacity (uptake of 3-O-[14C]-methyl-D-glucose (40 mM)) was measured. Amounts of glucose transporter isoform GLUT-1 and GLUT-4 glucose-transporting proteins were determined by Western blot. Glucose uptake was lower (P < 0.05) in hindlegs from FAT than from CHO rats at submaximum and maximum insulin [4 +/- 0.4 vs. 5 +/- 0.3 (SE) mumol.min-1.leg-1 at 150 microU/ml insulin] as well as during prolonged stimulation of the sciatic nerve (4.4 +/- 0.4 vs. 5.6 +/- 0.6 mumol.min-1.leg-1). Maximum glucose transport elicited by insulin (soleus: 1.7 +/- 0.2 vs. 2.6 +/- 0.2 mumol.g-1.5 min-1, P < 0.05) or contractions (soleus: 1.8 +/- 0.2 vs. 2.6 +/- 0.3, P < 0.05) in red muscle was decreased in parallel in FAT compared with CHO rats. GLUT-4 content was decreased by 13-29% (P < 0.05) in the various fiber types, whereas GLUT-1 content was identical in FAT compared with CHO rats. It is concluded that a FAT diet reduces both insulin and contraction stimulation of glucose uptake in muscle and that these effects are associated with diminished skeletal muscle glucose transport capacities and GLUT-4 contents.

A cellular mechanism for nitric oxide-mediated cholinergic control of mammalian heart rate

The biochemical signaling pathways involved in nitric oxide (NO)-mediated cholinergic inhibition of L-type Ca2+ current (ICa[L]) were investigated in isolated primary pacemaker cells from the rabbit sinoatrial node (SAN) using the nystatin-perforated whole-cell voltage clamp technique. Carbamylcholine (CCh; 1 microM), a stable analogue of acetylcholine, significantly inhibited ICa(L) after it had been augmented by isoproterenol (ISO; 1 microM). CCh also activated an outward K+ current, IK(ACh). Both of these effects of CCh were blocked completely by atropine. Preincubation of the SAN cells with L-nitro-arginine methyl ester (L-NAME; 0.2-1 mM), which inhibits NO synthase (NOS), abolished the CCh-induced attenuation of ICa(L) but had no effect on IK(ACh). Coincubation of cells with both L-NAME and the endogenous substrate of NOS, L-arginine (1 nM), restored the CCh-induced attenuation of ICa(L), indicating that L-NAME did not directly interfere with the muscarinic action of CCh on ICa(L). In the presence of ISO the CCh-induced inhibition of ICa(L) could be mimicked by the NO donor 3-morpholino-sydnonimine (SIN-1; 0.1 mM). SIN-1 had no effect on its own or after a maximal effect of CCh had developed, indicating that it does not inhibit ICa(L) directly. SIN-1 failed to activate IK(ACh), demonstrating that it did not activate muscarinic receptors. Both CCh and NO are known to activate guanylyl cyclase and elevate intracellular cGMP. External application of methylene blue (10 microM), which interferes with the ability of NO to activate guanylyl cyclase, blocked the CCh-induced attenuation of ICa(L). However, it also blocked the activation of IK(ACh), suggesting an additional effect on muscarinic receptors or G proteins. To address this, a separate series of experiments was performed using conventional whole-cell recordings with methylene blue in the pipette. Under these conditions, the CCh-induced attenuation of ICa(L) was blocked, but the activation of IK(ACh) was still observed. Methylene blue also blocked the SIN-1-induced decrease in ICa(L). 6-anilino-5,8-quinolinedione (LY83583; 30 microM), an agent known to decrease both basal and CCh-stimulated cGMP levels, prevented the inhibitory effects of both CCh and SIN-1 on ICa(L), but had no effect on the activation of IK(ACh) by CCh. In combination, these results show that CCh- and NO-induced inhibition of ICa(L) is mediated by cGMP.(ABSTRACT TRUNCATED AT 400 WORDS)

Nitric oxide-dependent parasympathetic signaling is due to activation of constitutive endothelial (type III) nitric oxide synthase in cardiac myocytes

Nitric oxide synthase (NOS) isoforms are discovered in an increasing variety of cell types with different roles in signaling. The inducible NOS (i.e. iNOS or NOS II) is expressed in cardiac myocytes in response to specific cytokines. Independent of iNOS induction, however, receptor-dependent signaling is modulated by a constitutive nitric oxide (NO) synthase isoform in these cells (Balligand, J. L., Kelly, R.A., Marsden, P.A., Smith, T. W., and Michel, T. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 347-351). We now show that cardiac myocytes constitutively express the endothelial isoform of NO synthase (ecNOS or NOS III). Transcripts for NOS III were detected by Northern blot in myocyte extracts using as a probe a polymerase chain reaction-generated cDNA amplified with isoform and species-specific primers. In subcellular fractionation experiments, a calcium-sensitive NO synthase activity was present primarily in the particulate fraction, coinciding with the distribution of NOS III analyzed by protein immunoblotting. The localization of NOS III within cardiac myocytes was further demonstrated by immunohistochemistry. The functional role of NOS III was explored by analyzing the effects of NOS inhibitors on single myocyte L-type calcium current and contractility. Inhibition of NOS blocked the attenuation by carbamylcholine of the increases in both parameters induced by beta-adrenergic stimulation. We conclude that NO-dependent parasympathetic signaling is mediated by NOS III in cardiac myocytes.

Induction of immunocellular resistance to IL-2-activated lymphocytes within ovarian carcinoma cells

The development of resistance within ovarian carcinoma cells to activated cytotoxic lymphocytes was the objective of this study. Primary ovarian carcinoma cells were obtained from the ascites of a patient. These cells were cocultured with IL-2-activated autologous tumor-associated lymphocytes (TALs) for 1 week. The resulting selected cells underwent a second coculture for 3 days with IL-2-activated autologous TALs or tumor-infiltrating lymphocytes (TILs). Phenotype analysis of the lymphocytes was performed prior to selection and 4-hr chromium release assays were used to detect resistance induction. Resistance to all effector cells could be demonstrated for the selected cells. However, selected cells maintained in culture demonstrated no difference in cytotoxic susceptibility from unselected cells. The following conclusions were made: (i) rapid immunoselection can occur for ovarian carcinoma in vitro; (ii) the resistance induced is not MHC-restricted; (iii) resistance induced by one type of cytotoxic cell results in general resistance to other types of cell from the same patient; and (iv) this resistance is not maintained during in vitro culture. These results may have direct implications on the future immunotherapy for this condition.

Contribution of Na(+)-Ca2+ exchange to stimulation of transient inward current by isoproterenol in rabbit cardiac Purkinje fibers

Cellular mechanisms underlying beta-adrenergic stimulation of the arrhythmogenic transient inward current (TI) were investigated by using a two-microelectrode voltage-clamp technique in rabbit cardiac Purkinje fibers. TI induced by elevating [Ca2+]o to 30 mmol/L and substituting [Na+]o with N-methyl-D-glucamine (NMG) chloride had a distinct reversal potential (EREV) of -25 mV, suggesting that Na(+)-Ca2+ exchange was not the charge carrier for TI. In the absence of [Na+]o, isoproterenol (ISO, 0.01 to 5.0 mumol/L) had no effect on either inward or outward TI or on the current-voltage relation of TI. However, ISO (0.1 mumol/L) significantly increased both inward and outward TIs without affecting the EREV of TI, if [Na+]o was present. Pretreatment with propranolol (0.2 mumol/L) or atenolol (0.2 mumol/L) abolished the stimulatory effects of ISO. Addition of propranolol (0.2 to 0.5 mumol/L) after the effects of ISO had developed caused only partial reversal of TI stimulation. This indicates persistence of stimulatory effects downstream from the initial agonist-receptor interaction. Forskolin (1 mumol/L), a direct adenylate cyclase activator, also strongly increased both inward and outward TI in the presence of [Na+]o. These effects also were abolished when [Na+]o was substituted by NMG. Inward and outward TIs enhanced by either ISO or forskolin were reversed by two putative Na(+)-Ca2+ exchange blockers, dodecylamine (20 mumol/L) and quinacrine (20 mumol/L). These results suggest that beta-adrenergic stimulation of TI is mediated by the Na(+)-Ca2+ exchange; stimulation likely involves phosphorylation of the exchanger or some factor that modulates exchanger activity.

Induction of a DNA adduct detectable by 32P-postlabeling in the dorsolateral prostate of NBL/Cr rats treated with estradiol-17 beta and testosterone

Treatment with estradiol-17 beta and testosterone induces epithelial dysplasia and, subsequently, adenocarcinoma in the dorsolateral prostate of NBL rats. The purpose of this study was to determine whether this carcinogenic effect is mediated by genotoxicity. Analogous to adducts produced by estrogens in the male hamster kidney, a target of estrogen carcinogenicity, induction of DNA adducts detectable by 32P-postlabeling was investigated in the prostate target tissue. NBL rats were treated with separate Silastic tubing implants containing testosterone and estradiol-17 beta. Control animals received empty implants. Animals were killed at 8, 16 and 24 weeks after initiation of treatment, and accessory sex glands were sampled for adduct analysis. DNA of the dorsolateral and ventral prostate and the coagulating gland (= anterior prostate) was isolated and analyzed by nuclease P1-enhancement of the 32P-post-labeling assay. DNA adducts were quantitated by Cerenkov counting. An adduct occurred selectively in DNA of the dorsolateral prostate of rats treated with estradiol plus testosterone for 16 or 24 weeks with relative adduct level values of approximately 10 x 10(9), but not in DNA of the ventral or anterior prostate. The adduct was not present in DNA of prostate tissue of rats treated for 8 weeks or in DNA of control tissues. This adduct was unique with respect to chromatographic location and has not been observed before in any tissue of control or hormone-treated animals. Neither the structure of the treatment-induced adduct nor the mechanism of its formation is known. However, the selective occurrence of this adduct in the tissue of origin of the carcinomas and its appearance coinciding with putative preneoplastic lesions and preceding carcinoma development suggests a causal relation between adduct formation and prostate cancer development in testosterone plus estradiol-17 beta-treated rats.

Immunohistochemical localisation of steroidogenic enzymes and phenylethanolamine-N-methyl-transferase (PNMT) in the adrenal gland of the fetal and newborn foal

An increase in fetal adrenal cortisol output signals the onset of parturition in many animal species but, in the fetal horse, plasma concentrations of cortisol remain low for much of late pregnancy, with a rise occurring only very close to the time of birth (term 320-360 days). Immunohistochemistry was used to determine the localisation and changes in distribution of key steroidogenic enzymes for cortisol production; P450scc, P450C17 and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in adrenal tissue from fetal and newborn horses and these findings were correlated with the appearance of immunoreactive (IR)-phenylethanolamine-N-methyl-transferase (PNMT), a cortisol-dependent enzyme. Five micron sections of adrenal tissue from fetuses at Day 100-156 (n = 5), Day 244-295 (n = 8), greater than Day 300 (n = 4) and from newborn foals (n = 6), were stained using specific antibodies and the avidin-biotin-peroxidase technique. All 3 steroidogenic enzymes were present by Day 150, but in less than 20% of the cortical cells. By late gestation the steroidogenic enzymes were present in approximately 30% of the cells, but the distribution varied. P450SCC and P450C17 predominated in cortical cells proximal to the medulla; 3 beta HSD was present throughout the cortex, but more in the zona fasciculata. In foals after birth, IR-3 beta HSD and IR-P450SCC had increased substantially throughout the adrenal cortex, and IR-P450C17 was present in most cells of the presumptive zonae fasciculata and reticularis. IR-PMNT was localised to nuclei of scattered medullary cells at the medullary-cortical interface by Day 150.(ABSTRACT TRUNCATED AT 250 WORDS)