Isolation and molecular cloning of prostacyclin synthase from bovine endothelial cells

Prostacyclin synthase catalyzes the conversion of prostaglandin H2 to prostacyclin, which is a powerful vasodilator and the most potent natural occurring inhibitor of platelet aggregation. In the present study, we determined the amino acid sequence of bovine prostacyclin synthase by combined protein chemical and molecular cloning techniques. The enzyme was purified and characterized from bovine aorta microsomes, and the partial amino acid sequences were determined with the native enzyme and endoproteinase Lys-C-cleaved peptides. Using primers synthesized according to the amino acid sequences, cDNA coding for prostacyclin synthase was amplified by polymerase chain reaction with bovine endothelial cell poly(A)+ RNA and cloned into pBluescript II. Nucleotide sequence analyses of the cloned cDNA inserts revealed that cDNA for this enzyme contained a 1500-base pair open reading frame coding for a 500-amino acid polypeptide with a M(r) of 56,628. COS-7 cells transfected with an expression plasmid harboring this cDNA clone expressed prostacyclin synthase activity. The primary structure of the enzyme showed structural characteristics of cytochrome P450 and exhibited a 32% identity to that of human cholesterol 7 alpha-hydroxylase. However, the identity between the amino acid sequences of bovine prostacyclin synthase and human thromboxane synthase was only 16%, and no P450 showed an identity higher than 40%, suggesting that prostacyclin synthase represents a new family in the P450 superfamily. RNA blot analysis indicated that the mRNA for prostacyclin synthase from bovine endothelial cells showed a size of approximately 2.7 kilobases and that the mRNA level increased about 3-fold by treatment of tumor necrosis factor-alpha.

Restoration of junctional tetrads in dysgenic myotubes by dihydropyridine receptor cDNA

Excitation-contraction coupling was restored in primary cultures of dysgenic myotubes by transfecting the cells with an expression plasmid encoding the rabbit skeletal muscle dihydropyridine receptor. Dishes containing normal, dysgenic, and transfected myotubes were fixed, freeze-fractured, and replicated for electron microscopy. Numerous small domains in the surface membrane of normal myotubes contain ordered arrays of intramembrane particles in groups of four (tetrads). The disposition of tetrads in the arrays is consistent with alternate positioning of tetrads relative to the underlying feet of the sarcoplasmic reticulum. Dysgenic myotubes have no arrays of tetrads. Some myotubes from successfully transfected cultures have arrays of tetrads with spacings equal to those found in normal myotubes. Thus the dihydropyridine receptor appears to be needed for the formation of tetrads and their association with the sarcoplasmic reticulum feet. This result is consistent with the hypothesis that each tetrad is composed of four dihydropyridine receptors.

Cloning and expression of the gene for hydroxypyruvate reductase (D-glycerate dehydrogenase from an obligate methylotroph Hyphomicrobium methylovorum GM2

The gene encoding hydroxypyruvate reductase, catalyzing the asymmetric reduction of hydroxypyruvate to D-glycerate, and its flanking regions were isolated from a methylotrophic bacterium, Hyphomicrobium methylovorum GM2. Nucleotide sequencing of the recombinant plasmids revealed that the hydroxypyruvate-reductase gene codes for the 322-amino-acid protein with calculated molecular mass 35,726 Da. The sequence was confirmed by sequencing the intact enzyme and peptides obtained by digestion of the enzyme with Achromobacter proteinase I. The amino acid sequence of the enzyme showed similarity to members of the D-isomer-specific 2-hydroxyacid dehydrogenase family. The recombinant plasmid, which was constructed by ligation of the cloned gene and an expression vector pKK223-3, was introduced into Escherichia coli HB101. The recombinant enzyme purified from the transformed E. coli cells was indistinguishable from the enzyme isolated from H. methylovorum GM2 by immunological and enzymological analyses.

[Intractable vasculitis syndromes--incidence and epidemiology]

Incidence and epidemiology of various diseases related to vasculitis were mainly reviewed from recent studies carried out in the Research Committee of Intractable Vasculitis Syndrome supported by the Ministry of Health and Welfare of Japan. A relative higher proportion of patients with aortitis syndrome (Takayasu's arteritis), Buerger's disease was reported in Asia compared to Europe and the United States. Today, the incidence of these diseases is considered to indicate a trend to decrease in Japan. However, the number of patients studied by the Committee remained almost unchanged. The patients are reported from all districts of Japan, though the incidences varied with the prefecture. The Research Committee is continuing further careful epidemiological investigations by established diagnostic criteria from year to year.

Mass screening for hepatocellular carcinoma: experience in Hokkaido, Japan

Mass screening for liver cancer based mainly on abdominal ultrasound was begun in major cities of Hokkaido, Japan, in November 1981, to enable early detection and treatment of hepatocellular carcinoma (HCC). Serum alpha-fetoprotein levels were also measured to minimize false negative studies. Examinees included those who sought liver disease screening as well as high risk individuals: hepatitis B surface antigen carriers and those with a past or current liver disease, history of blood transfusion, family history of liver cancer, and more recently those with positive anti-hepatitis C antibodies. The examination was carried out on each Saturday and Sunday as one round, and by February 1992 48 rounds had been performed. A total of 8090 individuals were investigated, and HCC was detected in 91 with a detection rate of 1.12%. This rate was 1.6% among 5684 individuals who were selected for high risk. Cumulative rates of survival among these patients were 79.0% at 1 year, 43.8% at 3 years, 19.3% at 5 years and 15.4% at 7 years. These survival rates were comparable with those for the patients with HCC diagnosed during follow-up of chronic liver disease and treated at our hospital. The cost for detecting one HCC patient in this programme was 2,660,000 yen (approximately US$25,000), which was less than those for some other types of cancer in a similar setting. Considering the high detection rate in this programme, we feel that similar programmes should be encouraged and supported.

Molecular determinants of calcium-dependent inactivation in cardiac L-type calcium channels

We investigated the nature and structural requirements for Ca(2+)-dependent inactivation of cardiac L-type Ca2+ channel. Investigation of subunit requirements indicates that the interaction of alpha 1 subunit with ancillary subunits, especially beta subunit, is important for this property. Replacement of the putative cytoplasmic regions of the cardiac alpha 1 subunit with skeletal muscle counterparts eliminates Ca(2+)-dependent inactivation, indicating that the site regulated by Ca2+ resides in the cytoplasmic region of the alpha 1 subunit. Deletion of the carboxy-terminal region of the cardiac alpha 1 subunit does not eliminate this property, suggesting that the modulation by protein kinase A may not be involved in this mechanism. Single amino acid substitution that strongly reduces Ca2+ selectivity of Ca2+ channels also eliminates Ca(2+)-dependent inactivation, suggesting the close link between the ion selectivity and Ca(2+)-dependent inactivation.

Clinical application of evoked spinal cord potentials elicited by direct stimulation of the cord during temporary occlusion of the thoracic aorta

Evoked spinal cord potentials elicited by direct stimulation of the cord were used to monitor spinal cord ischemia in 68 patients undergoing temporary occlusion of the thoracic aorta (29 thoracic nondissecting aortic aneurysms, 9 nondissecting thoracoabdominal aneurysms, and 30 dissecting aneurysms). "Immediate" postoperative paraplegia developed in three patients and "immediate" paraparesis developed in one, whereas "delayed" paraplegia developed in two others. During aortic crossclamping, four response patterns of the spinal cord potentials were obtained: (1) no change (n = 53), (2) change with return (n = 10), (3) change with inconsistent return (n = 2), and (4) change without return (n = 3). Neurologic complications occurred in 2%, 0%, 100% of these groups, respectively. Delayed paraplegia developed on the second postoperative day in only one patient with a false-negative result, and the potentials correlated well with this patient's clinical neurologic recovery. The aortic crossclamp time was significantly longer in the patients with "change with inconsistent return" and "change without return" than in the other two groups (p < 0.01). Femoral artery pressure and the cardiopulmonary bypass flow rate were also significantly lower in these groups than in the other two groups (p < 0.02 and p < 0.01, respectively). We conclude that intraoperative monitoring of direct spinal cord responses is useful for the early detection of spinal cord ischemia for assessing the efficacy of surgical countermeasures.

N-(4-hydroxyphenyl) retinamide induces cell cycle specific growth inhibition in PC3 cells

The synthetic retinoid N-(4-hydroxyphenyl) retinamide (4-HPR) has been demonstrated to inhibit the development of primary and metastatic neoplasms in several animal models. In order to investigate the effect of 4-HPR on human prostate adenocarcinoma, we designed a series of in vitro experiments with the PC3 cell line to evaluate effects on proliferation, cell cycle kinetics, and c-myc mRNA expression. 4-HPR demonstrated cytotoxicity only at the supraphysiologic concentration of 10.0 microM. However, asynchronously growing cells exposed to 1 microM 4-HPR demonstrated a 51% reduction in proliferation rate, associated with an accumulation of cells in the G0/G1 phase of the cell cycle. PC3 cells synchronized with serum deprivation or aphidicolin exhibited significant decreases in DNA synthesis when treated with 1 microM 4-HPR. Additionally, these cells were found to accumulate in G0/G1 and S phase. Northern blots indicated a significant decrease in c-myc mRNA expression in asynchronously growing cells with continuous administration of 1 microM 4-HPR for 6 days. These data suggest that 4-HPR can inhibit growth of PC3 cells as a consequence of a block in cell cycle transition from G1 to S phase at a concentration of 1 microM, and that this inhibition is associated with a suppression of c-myc gene expression.

Molecular cloning and expression of human prostacyclin synthase

The cDNA for human prostacyclin synthase was cloned by polymerase chain reaction using poly(A)+ RNA from human aortic endothelial cells according to the partial nucleotide sequence of prostacyclin synthase gene. The cloned cDNA with a size of 1977 base pairs contained a 1500 base pairs open reading frame which encoded a 500 amino acid protein sharing an 88% identity with bovine prostacyclin synthase. RNA blot analysis indicated that the size of major prostacyclin synthase mRNA of human aortic endothelial cells was approximately 6 kilobases and that its mRNA level was increased by interleukin 1 or interleukin 6 treatment. Moreover, tissue distribution study demonstrated that prostacyclin synthase mRNA is widely expressed in human tissues and is particularly abundant in ovary, heart, skeletal muscle, lung, and prostate. These results suggest a variety of physiological roles of prostacyclin in addition to the implications in the cardiovascular system.

Characterization of the human gene (PTGS2) encoding prostaglandin-endoperoxide synthase 2

The human gene (PTGS2) encoding an inducible isozyme of prostaglandin-endoperoxide synthase (prostaglandin-endoperoxide synthase 2) that is distinct from the well-characterized and constitutive isozyme (prostaglandin-endoperoxide synthase 1), was isolated using a polymerase-chain reaction-generated cDNA fragment probe for human prostaglandin-endoperoxide synthase 2. Nucleotide sequence analysis of the entire human prostaglandin-endoperoxide-synthase-2 gene demonstrated that it is more than 8.3 kb in size and consists of ten exons; this gene is very similar to the murine and chicken prostaglandin-endoperoxide-synthase-2 genes. The structures of exons in the human prostaglandin-endoperoxide-synthase-2 gene were also similar to those of the human prostaglandin-endoperoxide-synthase-1 gene (PTGS1). However, the sizes of introns in the human prostaglandin-endoperoxide-synthase-2 gene were generally smaller than those of the human prostaglandin-endoperoxide-synthase-1 gene. Primer-extension analysis indicated that the transcriptional-start site is 134 bases upstream of the translational-initiation site. The sequence of the 1.69-kb region of nucleotides preceding the transcriptional-start site and the first 0.8-kb intron contained a canonical TATA box and various transcriptional-regulatory elements (CArG box, NF-IL6, PEA-1, myb, GATA-1, xenobiotic-response element, cAMP-response element, NF-kappa B, PEA-3, Sp-1 and 12-O-tetradecanoyl-phorbol-13-acetate-response element). The nucleotide sequence of the 5'-flanking region (275 bp) of the human prostaglandin-endoperoxide-synthase-2 gene showed 63% similarity to the sequence of murine prostaglandin-endoperoxide-synthase-2/TIS10 gene, but essentially no homology to the chicken prostaglandin-endoperoxide-synthase-2 gene, and human and murine prostaglandin-endoperoxide-synthase-1 genes. A fluorescence in situ hybridization study showed that the human genes coding for prostaglandin-endoperoxide synthase 1 (PTGS1) and prostaglandin-endoperoxidase synthase 2 (PTGS2) were mapped to distinct chromosomes 9q32-q33.3 and 1q25.2-q25.3, respectively, indicating that these genes are not genetically linked.

Eicosanoid biosynthetic enzymes in placental and decidual tissues from preeclamptic pregnancies: increased expression of thromboxane-A2 synthase gene

Preeclampsia is a disease of late pregnancy characterized by hypertension, edema, and proteinuria, in which vasoconstriction, platelet aggregation, and reduced uteroplacental blood flow contribute to preterm delivery, perinatal morbidity, and mortality. Increased thromboxane-A2 (TXA2) and/or decreased prostacyclin (PGI2) have been implicated as causative factors of this disease. The present studies investigated the expression of TXA2 synthase gene along with those of TXA2 receptors, PGI2 synthase, cyclooxygenase-1 (COX-1), and COX-2 in placental and decidual tissue from preeclamptic and normal pregnancies. In situ hybridization and immunocytochemistry showed that primarily trophoblast layer and decidual cells express TXA2 synthase, COX-1, and COX-2 enzymes. Immunocytochemistry for PGI2 synthase and in situ hybridization for TXA2 receptors showed similar results. Trophoblast layer and decidua from preeclamptic pregnancies contained a greater abundance of mRNA and protein of TXA2 synthase than the matched normal pregnancies. In summary, our findings suggest that an increased local expression of TXA2 synthase could be responsible for local and/or peripheral vascular changes in preeclampsia.

[Clinical study on reoperation for recurrent pulmonary metastasis]

Ninety seven patients with metastatic lung tumors were treated surgically in our department. Second pulmonary resections were performed in 13 patients. They consists of 9 males and 4 females, their age ranged from 12 to 75 years old (average 54.4 years old). Tumors originate from sarcoma in 5 cases, laryngeal cancer, colorectal cancer, renal cell cancer in 2 cases respectively, oral cavity cancer and transitional cell cancer in 1 case respectively. No second pulmonary resection was performed in patients with metastatic lung tumors originating from lung cancer or breast cancer, because they metastatize not only lung but also general organs. No second pulmonary resection was required in patients with testicular tumor and choriocarcinoma, because chemotherapy take good effect on them.

Endoscopic laser surgery for subglottic and tracheal stenosis

Seventeen patients with subglottic and tracheal stenosis were treated with laser surgery. Six patients had airway stenosis caused by malignant tumors. Out of 16 patients who required emergency endolaryngeal laser surgery, satisfactory results were achieved in 12, obtaining a sufficient lumen for ventilation. Five cases with airway tumors underwent laser surgery to increase the airway lumen, however, only one patient showed excellent results, with a sufficient airway lumen not being obtained in the others. Airway obstructions due to tumor can be treated satisfactorily by laser surgery, though long-term postoperative follow-up confirmed recurrence of tumor in some cases, which is a problem that must be overcome in the future.

Positive effect of tamoxifen as part of adjuvant chemo-endocrine therapy for breast cancer. Hokkaido Adjuvant Chemo-Endocrine Therapy for Breast Cancer Study Group

A prospective randomised multicentre clinical study was undertaken for 2 years and 3 months from November 1982, with the aim of examining the significance of using a combination of ftorafur (FT) and tamoxifen (TAM) for post-operative adjuvant therapy of breast cancer. Patients had either stage II or stage IIIa disease, were age 75 or below and had undergone radical mastectomy. Patients were divided into two groups and received one of the following treatment protocols: treatment A, intravenous administration of doxorubicin (DOX), 20 mg on the day of surgery and 10 mg the next day, followed by oral FT 50 mg day-1 for 2 years from the 14th day; treatment B, the same pattern of DOX administration for the first 2 days, followed by a combined therapy of FT and TAM 20 mg day-1 for 2 years. The number of patients was 546 (treatment A 274 and treatment B 272), of whom 34 (6%) were ineligible. The remaining 512 patients (treatment A 254 and treatment B 258) were followed up for 5 years for analysis. Significantly higher 5 year disease-free rate and 5 year survival rates were observed with treatment B compared with treatment A. When seen in terms of background factors, node-positive patients appeared to derive more benefit from tamoxifen than node-negative patients, but the oestrogen receptor-negative and premenopausal subgroups appeared to derive about the same benefit as those who were oestrogen receptor positive and post-menopausal. Indeed, survival in the premenopausal group was significantly better with tamoxifen (P = 0.04). No increase in side-effects was seen by combining TAM with FT. The study results demonstrate that concomitant administration of FT and TAM is better than FT alone for post-operative adjuvant therapy for breast cancer.

Awake evoked electromyography recording from the chronically implanted rat

Investigation of the effects of various factors on nerve regeneration has been compromised by the lack of an accurate and objective technique which can monitor dynamic changes in the status of nerve-muscle innervation over the entire course of regeneration. The approach of evoked electromyography (EEMG) was adopted to obtain temporal and quantitative data during nerve regeneration. Initially, transcutaneous nerve stimulation and percutaneous muscle recording was performed, but the approach was abandoned because of the high interest variability (20% average deviation) and requirement for anesthesia during testing. A new approach using chronically implanted stimulation and recording electrodes was adopted in an attempt to circumvent these problems. Initial acute studies performed in the hindlimb of the anesthetized rat identified stable EEMG recording sites with sciatic nerve stimulation. In a second study conducted in chronically implanted unanesthetized unrestrained animals, EEMG recording from these sites demonstrated remarkable stability with an average interest variability of only 5%. Preliminary results have been obtained with this technique in monitoring the progression of hindlimb reinnervation following crush and transection nerve injuries.

Degradation of enamelins by proteinases found in porcine secretory enamel in vitro

The action of proteinases obtained from porcine secretory enamel on the porcine 89-kDa enamelin was examined in vitro. The results of sodium dodecyl sulphate-acrylamide gel electrophoresis of the reaction products indicated the following. (1) The 76- and 78-kDa proteinases localized in the outermost layer of the secretory enamel not only convert the 25-kDa amelogenin to the 20-kDa amelogenin, but also split the 89-kDa enamelin, which is the major enamelin component in the enamel in the very early secretory stage, into large fragments such as 25-, 41- and 56-kDa enamelins. (2) The serine proteinases localized in the inner layer of secretory enamel further degrade not only amelogenins but also enamelins.

Abundant expression of thromboxane synthase in rat macrophages

The cloned cDNA for rat thromboxane (TX) synthase with a size of 1851 bp contained a 1599-bp open reading frame which encoded a 533-amino acid protein sharing 79.7% identity with human TX synthase. RNA blot analysis was carried out with rat cells and tissues. Rat peritoneal macrophages most abundantly expressed mRNA for TX synthase, and its level was not changed by in vivo stimulation of casein. Bone marrow, spleen, lung and thymus also expressed the TX synthase gene. These findings suggest the possibility that TXA2 plays a role in the immune system.

Calcium channel beta-subunit binds to a conserved motif in the I-II cytoplasmic linker of the alpha 1-subunit

The beta-subunit is an integral component of purified voltage-sensitive Ca2+ channels. Modulation of Ca2+ channel activity by the beta-subunit, which includes significant increases in transmembrane current and/or changes in kinetics, is observed on coexpression of six alpha 1-subunit genes with four beta-subunit genes in all alpha 1-beta combinations tested. Recent reports suggest that this regulation is not due to targeting of the alpha 1-subunit to the plasma membrane but is probably a result of a conformational change induced by the beta-subunit. Here we report that the beta-subunit binds to the cytoplasmic linker between repeats I and II of the dihydropyridine-sensitive alpha 1-subunits from skeletal (alpha 1S) and cardiac muscles (alpha 1C-a), and also with the more distantly related neuronal alpha 1A and omega-conotoxin GVIA-sensitive alpha 1B-subunits. Sequence analysis of the beta-subunit binding site identifies a conserved motif (QQ-E--L-GY--WI--E) positioned 24 amino acids from the IS6 transmembrane domain in each alpha 1-subunit. Mutations within this motif reduce the stimulation of peak currents by the beta-subunit and alter inactivation kinetics and voltage-dependence of activation. Conservation of the beta-subunit binding motif in these functionally distinct calcium channels suggests a critical role for the I-II cytoplasmic linker of the alpha 1-subunit in channel modulation by the beta-subunit.

High levels of nm23 expression are related to cell proliferation in human prostate cancer

Reduced expression of the nm23 gene has been correlated with high metastatic potential in rodent mammary tumors and human breast cancer. The expression of this gene was studied in human prostate cancer tissue from 43 patients by immunohistochemistry using anti-nm23-H1 antibodies. Intense immunostaining was observed in 71.4% of the patients with clinical stage D disease as compared to 23.1% in clinical stage B and 18.7% in stage C disease (P < 0.05). Similarly intense immunostaining was present in 75% of poorly differentiated cancers versus only 28.6% in men with moderately differentiated cancer. nm23-H1 mRNA expression was measured by Northern blot analysis during phases of the cell cycle in DU 145, PC-3, LNCaP, and TSU-Prl human prostate cancer cell lines. Cells were synchronized in G0-G1 phases by serum deprivation and at the G1-S boundary by aphidicolin. nm23-H1 mRNA levels declined during serum deprivation and increased rapidly following serum addition. Although nm23-H1 was expressed continuously throughout the cell cycle, higher expression was observed in late G1, early S, and G2-M phases. These results indicate that nm23-H1 gene expression is related to the proliferative phase of cell growth.

Site-directed mutagenesis studies on the iron-binding domain and the determinant for the substrate oxygenation site of porcine leukocyte arachidonate 12-lipoxygenase

cDNA for arachidonate 12-lipoxygenase of porcine leukocytes was expressed in Escherichia coli. The recombinant 12-lipoxygenase was purified by immunoaffinity chromatography to near homogeneity with a specific activity of about 1.5 mumol/min per mg protein. Each of eight histidine residues, which were well-conserved among various mammalian lipoxygenases and presumed as ligands for non-heme iron, was substituted with leucine by site-directed mutagenesis. Each mutant enzyme was immunoaffinity-purified to near homogeneity. Mutations of His-361, -366 and -541 caused a total loss of enzyme activity, and the iron content was much lower (0.10, 0.06 and 0.06 g atom/mol protein) than that of the wild-type enzyme (0.53). Mutations of His-128 and -356 gave 159% and 162% specific activity of the wild-type enzyme, and the iron contents were 0.55 and 0.52 g atom/mol protein. Substitution of His-426 decreased the activity to 5%, but the iron content was 0.4 g atom/mol protein. The expression level of mutants at His-384 and -393 was too low to precisely determine the iron content. Taken together, His-361, -366 and -541 may play important roles for iron-binding in catalytically active 12-lipoxygenase. Since a high homology of amino acid sequence was known between porcine leukocyte 12-lipoxygenase and mammalian 15-lipoxygenases, we attempted to convert the 12-lipoxygenase to a 15-lipoxygenase. A double mutation of Val-418 and -419 to Ile and Met increased the ratio of 15- and 12-lipoxygenase activities from 0.1 to 5.7.

Relationship of calcium transients to calcium currents and charge movements in myotubes expressing skeletal and cardiac dihydropyridine receptors

In both skeletal and cardiac muscle, the dihydropyridine (DHP) receptor is a critical element in excitation-contraction (e-c) coupling. However, the mechanism for calcium release is completely different in these muscles. In cardiac muscle the DHP receptor functions as a rapidly-activated calcium channel and the influx of calcium through this channel induces calcium release from the sarcoplasmic reticulum (SR). In contrast, in skeletal muscle the DHP receptor functions as a voltage sensor and as a slowly-activating calcium channel; in this case, the voltage sensor controls SR calcium release. It has been previously demonstrated that injection of dysgenic myotubes with cDNA (pCAC6) encoding the skeletal muscle DHP receptor restores the slow calcium current and skeletal type e-c coupling that does not require entry of external calcium (Tanabe, Beam, Powell, and Numa. 1988. Nature. 336:134-139). Furthermore, injection of cDNA (pCARD1) encoding the cardiac DHP receptor produces rapidly activating calcium current and cardiac type e-c coupling that does require calcium entry (Tanabe, Mikami, Numa, and Beam. 1990. Nature. 344:451-453). In this paper, we have studied the voltage dependence of, and the relationship between, charge movement, calcium transients, and calcium current in normal skeletal muscle cells in culture. In addition, we injected pCAC6 or pCARD1 into the nuclei of dysgenic myotubes and studied the relationship between the restored events and compared them with those of the normal cells. Charge movement and calcium currents were recorded with the whole cell patch-clamp technique. Calcium transients were measured with Fluo-3 introduced through the patch pipette. The kinetics and voltage dependence of the charge movement, calcium transients, and calcium current in dysgenic myotubes expressing pCAC6 were qualitatively similar to the ones elicited in normal myotubes: the calcium transient displayed a sigmoidal dependence on voltage and was still present after the addition of 0.5 mM Cd2+ + 0.1 mM La3+. In contrast, the calcium transient in dysgenic myotubes expressing pCARD1 followed the amplitude of the calcium current and thus showed a bell shaped dependence on voltage. In addition, the transient had a slower rate of rise than in pCAC6-injected myotubes and was abolished completely by the addition of Cd2+ + La3+.

Porcine amelogenins

Amelogenins were extracted from the thin outer layer of porcine secretory enamel and purified by gel filtration and reverse-phase HPLC. The results of amino acid sequencing of the purified porcine amelogenins indicated the presence of at least four prototype amelogenins translated from alternatively spliced transcripts. The results of mass spectroscopy of the CNBr-cleaved peptides derived from the 25 kDa amelogenin indicated that porcine 25 kDa amelogenin is neither phosphorylated nor glycosylated.