GD2 ganglioside-specific monoclonal antibody reacts with murine cytotoxic T lymphocytes reactive with FBL-3N erythroleukaemia

Ganglioside expression on cytotoxic T lymphocytes induced against the mouse erythroleukaemia line FBL-3N, was analysed, compared with that of naive T lymphocytes in the thymus, lymph nodes and spleen. Although normal uncultured and cultured T lymphocytes expressed no GD2, GD3 or GM2 gangliosides, cytotoxic T cells with CD4+CD8-, CD4-CD8+, and CD4-CD8- phenotypes reacted with anti-GD2 monoclonal antibody with various intensities. The reactivity with anti-GD2 was associated with the intensity of cytotoxic activity as analysed using cytotoxic T lymphocyte (CTL) clones established from the bulk CTLs of each phenotype. An increase of the mRNA expression of GM2/GD2 synthase gene was demonstrated by Northern blot hybridization using RNA extracted from thymocytes, spleen cells, Con A-treated spleen cells and various types of CTL cells. These results indicated that GD2 ganglioside expression might be associated with the functional differentiation of murine T lymphocytes.

Flow cytometric analysis on cytotoxic action of amyloid beta protein fragment 25-35 on brain neurons dissociated from the rats

Effects of amyloid beta protein fragment 25-35, A beta P(25-35), on membrane permeability and cell viability were examined in the brain neurons dissociated from the rats using a flow cytometer and two fluorescent dyes, fluo-3 to monitor intracellular Ca2+ concentration ([Ca2+]i) of neurons and ethidium which is impermeant to membranes of intact neurons to stain dead and dying neurons. A beta P(25-35) augmented fluo-3 fluorescence of some neurons at concentrations greater than 1 microM, indicating an increase in [Ca2+]i although other neurons (about 80% of total neurons) did not respond to A beta P(25-35) even at 10 microM. A beta P(25-35) at 1 microM or greater increased dose-dependently the number of ethidium-stained neurons, suggesting a dose-dependent increase in number of dead and dying neurons. Results suggest that A beta P(25-35) increases the membrane permeability of brain neurons, resulting in a destabilized intracellular homeostasis that leads to neuonal death.

Amyloid beta protein-induced irreversible current in rat cortical neurones

The effect of amyloid beta protein (A beta P) was examined in neurones dissociated from rat cortex using the nystatin perforated patch-clamp technique. A beta P at concentrations > 10 nM induced an irreversible slow inward current associated with an increase in membrane conductance. The time lag until the appearance of the effect of A beta P shortened in a concentration-dependent manner. When extracellular Na+ and Cl-, and intracellular K+ were replaced by equimolar N-methyl glucamine, isothionate- and Cs+, respectively, the membrane conductance and the reversal potential were not affected. Even when an internal solution including 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (20 mM) was used, the effect of A beta P did not alter. It is suggested that A beta P binds to the neuronal membrane and opens non-selective ion channels, resulting in neuronal degeneration.

Isolation of GD3 synthase gene by expression cloning of GM3 alpha-2,8-sialyltransferase cDNA using anti-GD2 monoclonal antibody

For the isolation of ganglioside GD3 synthase (EC 2.4.99.8) cDNA, we developed an expression cloning approach that used an anti-GD2 monoclonal antibody for selection. A host recipient cell line that we have named KF3027-Hyg5 was also utilized. This cell line expresses high levels of GM2 as well as GM3 but no GD3 or GD2 and was constructed from mouse B16 melanoma cells transfected with the polyoma large tumor antigen gene (KF3027) and the previously cloned beta-1,4-N-acetylgalactosaminyltransferase (EC 2.4.1.92) cDNA. Four rounds of transfection, monoclonal antibody 3F8 panning, and Hirt extraction resulted in the isolation of two cDNA clones, transfection of which directed the expression of GD3 in KF3027 and B16 melanoma cells and GD3 and GD2 in KF3027-Hyg5 cells. The cDNA contained a 1650-bp insert and a single open reading frame. The deduced amino acid predicted a type II membrane topology consisting of cytoplasmic (14 aa), transmembrane (18 aa), and catalytic (309 aa) domains. The sequence also predicted the presence of a sialyl motif similar to that found in the other sialyltransferases cloned so far. As expected, mRNA of this gene (2.6 kb) was strongly expressed in human melanoma lines.

Methylmercury-induced augmentation of oxidative metabolism in cerebellar neurons dissociated from the rats: its dependence on intracellular Ca2+

Effect of methylmercury chloride on oxidative metabolism of cerebellar neurons dissociated from the rats was examined using 2',7'-dichlorofluorescin (DCFH) which is oxidized by cellular hydrogen peroxide to be a fluorescent compound (DCF) and fluo-3, an indicator for intracellular Ca2+ concentration ([Ca2+]i). Methylmercury at 1 microM or less did not affect DCF fluorescence of cerebellar neurons. Further increase in concentration of methylmercury (up to 30 microM) induced changes in DCF fluorescence. Thus, DCF fluorescence was slightly attenuated during 5 min after applying methylmercury to the neurons, indicating a decrease in oxidation of DCFH. Thereafter, DCF fluorescence was time-dependently augmented in continued presence of methylmercury, indicating an increase in DCFH oxidation. Although methylmercury-induced augmentation of DCF fluorescence was greatly suppressed under external Ca(2+)-free condition, it was not the case for methylmercury-induced attenuation of DCF fluorescence. Methylmercury at 3 microM or more dose-dependently increased the [Ca2+]i. Results suggest that methylmercury increases intracellular Ca2+ in cerebellar neurons, resulting in an increase in formation of reactive oxygen species that may contribute to cell injury.

Effect of N,N-diethyldithiocarbamate on ionomycin-induced increase in oxidation of cellular 2',7'-dichlorofluorescin in dissociated cerebellar neurons

Effect of N,N-diethyldithiocarbamate (DDC), an inhibitor for cytosolic superoxide dismutase, on an ionomycin-induced increase in oxidative metabolism was examined in cerebellar neurons dissociated from the rats, using a flow cytometer and 2',7'-dichlorofluorescin diacetate and fluo-3-AM, fluorescent dyes for intracellular hydrogen peroxide and Ca2+, respectively. DDC reduced the ionomycin-induced augmentation of 2',7'-dichlorofluorescin fluorescence in a dose-dependent manner. DDC did not affect cellular content of 2',7'-dichlorofluorescin and ionomycin-induced increase in intracellular Ca2+ concentration. Results indicate that ionomycin increases the formation of superoxide anion in brain neuron.

Video-assisted thoracoscopic resection of a mediastinal cyst: report of a case

Video-assisted endoscopic surgery has recently been expanding its potential, which is shown by our report herein describing the case of a 23-year-old woman for whom successful thoracoscopic resection of a mediastinal cystic lesion was carried out. The patient's postoperative course was uneventful with minimal pain and a prompt recovery. Histological examination confirmed that the lesion was a benign cystic teratoma. We believe that video-assisted thoracoscopic surgery will become the standard procedure for most mediastinal cystic lesions in the future.

[Study on development of linear-traction type skeletal muscle powered pump]

We successfully developed Linear-Traction Type Skeletal Muscle Powered Pump (LSMPP). Unlike the Insertion-Type SMPP (ISMPP), previously used by us, in which a polyurethane chamber is inserted between skeletal muscle and chest wall, this pump can utilize the traction of muscle fiber in a linear direction. This pump also enabled us to obtain a sufficient flow with a low preload by the use of a spring for the filling of the pump. Comparison was made between the measurement of flow using the origin side of Latissimus Dorsi Muscle (o-group) (n = 6) and that using the upper arm side (i-group) (n = 6), both measured with the Linear-Traction Type equipment, and the result obtained with the ISMPP (s-group) (n = 6). Under a rate of 60 beat/min and a preload of 40 mmHg, the flows (ml/min) of o-group, i-group and s-group were 668.0 +/- 108.0, 1202 +/- 478.6 and 620.0 +/- 188.0, respectively. In i-group (n = 6), different rate, preload and spring constant were given to examine how the flow would vary with them. Mean flow (Mean +/- Std ml/min) was 815.0 +/- 378.0 at 60 beat/min, significantly different in comparison with that of 80 beat/min and that of 100 beat/min. For 40, 30 and 20 mmHg of preloads, mean flows were 877.0 +/- 366.0, 625.0 +/- 311.0 and 422.0 +/- 270.0, respectively. This showed that, as far as the rate remains low, even low preload can provide some 30% of the cardiac output of a dog as compensate cardiac flow. In contrast, there were no significant differences in mean flow with spring constants such as 0, 80, 160, 240 and 320 g/cm.

The surgical treatment of aortic dissection in a patient with Turner's syndrome: report of a case

We report herein the successful surgical management of a 42-year-old patient with Turner's syndrome (TS) complicated by Stanford type B aortic dissection. The patient had a single entry in the proximal descending aorta with dissection extending from the entry point to the abdominal aorto-left iliac bifurcation. A patch plasty using felt reinforcement was performed through a left 4th intercostal space thoracotomy. Her postoperative course was uneventful and she has been well during the 3 years since her operation. There have been only nine reports of patients with TS complicated by aortic dissection for whom operations were performed; however, the details of surgical treatment have not been well documented. This paper reports the course of aortic dissection and the surgical methods employed in the treatment of our patient.

Glycine response in acutely dissociated ventromedial hypothalamic neuron of the rat: new approach with gramicidin perforated patch-clamp technique

1. We investigated the glycine-induced response in ventromedial hypothalamic (VMH) neurons freshly dissociated from 8- to 12-day-old rats using the nystatin and gramicidin perforated patch recording modes. The nystatin-formed pores in the plasma membrane are permeable for both monovalent cations and anions, whereas those formed by gramicidin are permeable only to monovalent cations. Therefore, when the patch-pipette contains 150 mM Cl- and gramicidin, the physiological intracellular Cl- concentration ([Cl-]i) is undisturbed in the cell-attached condition of the pipette. 2. At holding potentials of -40 to -60 mV, glycine induced inward currents and outward currents in the nystatin and gramicidin perforated patch recording modes, respectively. The values of the half-maximum effective concentration (EC50) and the Hill coefficient in the concentration-response relationships of the glycine responses were 2.9 x 10(-5) M, 1.1, and 4.2 x 10(-5) M, 1.4, respectively. These values were quite similar in both recording modes. 3. The reversal potentials of the glycine responses (EGly) were -1.5 mV in the nystatin perforated patch recording and -75.0 to -24.8 mV in the gramicidin perforated patch recording. 4. Strychnine (3 x 10(-8) M) inhibited the glycine-induced outward currents in a competitive manner and the half-inhibition concentration (IC50) of strychnine on the 10(-4) M glycine-induced response was 1.9 x 10(-8) M. 5. The physiological [Cl-]i in the VMH neurons calculated from the EGly obtained by the gramicidin perforated patch mode ranged from 6.0 to 43.8 mM (n = 28).

Nicotinic and muscarinic acetylcholine responses in the embryo chick ciliary ganglion cells

Nicotinic and muscarinic acetylcholine (ACh) responses were investigated in acutely dissociated chick ciliary ganglion neurons using the nystatin perforated patch clamp technique. ACh-induced a rapid transient inward current in 100% of the neurons at a holding potential of -60 mV. This rapid inward current was mimicked by nicotine but not by muscarine. The reversal potential of the rapid inward current was +10.5 mV and the current was inhibited by d-tubocurarine and hexamethonium in a dose-dependent manner. In 57.6% of neurons, a slow inward current was also induced by ACh at a holding potential of -20 mV. This slow inward current was mimicked by muscarine but not by nicotine. The slow inward current became smaller at a hyperpolarized potential but not reversed, being consistent with the fact that this current was elicited by the inhibition of M-current. p-Fluorohexa-hydrosiladifenidol (P-F-HHSiD) strongly inhibited the slow inward current, suggesting that the current was elicited by the activation of M3 receptors.

Alteration of nm23 gene expression during the induced differentiation of human leukemia cell lines

The nm23-H1 gene is regarded as a human homologue of the mouse nm23 gene, which was expressed in a non-metastatic subline of mouse melanoma K-1735. The expression levels of nm23-H1 mRNA and the levels of protein during induced differentiation of human leukemia cell lines were analysed. mRNA levels of the megakaryoblastic leukemia line MEG-01, which were induced to differentiate into megakaryocyte by TPA, decreased rapidly from 2 days after the start of treatment and became almost undetectable at day 4. Similar down-regulation of nm23-H1 mRNA was also observed in the induced differentiation of the promyelocytic leukemia line HL-60 by TPA, or DMSO into monocyte-macrophage lineage or granulocytes, respectively. The amount of Nm23-H1 protein was analysed by Western immuno-blot analysis using mouse antiserum raised against a recombinant fusion protein with glutathione S-transferase. The amount of Nm23-H1 protein also decreased during the induced differentiation of these leukemia cell lines. On the other hand, in the differentiation of the erythroleukemia line K562 by hemin, levels of both mRNA and protein of Nm23-H1 elevated transiently, then reduced to the original level. When MEG-01 and K562 were stably transfected with nm23-H1 cDNA, MEG-01 transfectants showed reduced sensitivity to the induction of differentiation, whereas K562 transfectants were better induced to synthesize hemoglobin than controls. These findings suggest the possibility that Nm23-H1 protein plays an important role to maintain the proliferation of immature leukemic cells in MEG-01 and HL-60, but it may also play a role in the early stage of K562 differentiation, possibly in the different manner.

Ca2+ release induced by myotoxin alpha, a radio-labellable probe having novel Ca2+ release properties in sarcoplasmic reticulum

1. Myotoxin alpha (MYTX), a polypeptide toxin purified from the venom of prairie rattlesnakes (Crotalus viridis viridis) induced Ca2+ release from the heavy fraction (HSR) but not the light fraction of skeletal sarcoplasmic reticulum at concentrations higher than 1 microM, followed by spontaneous Ca2+ reuptake by measuring extravesicular Ca2+ concentrations using the Ca2+ electrode. 2. The rate of 45Ca2+ release from HSR vesicles was markedly accelerated by MYTX in a concentration-dependent manner in the range of concentrations between 30 nM and 10 microM, indicating the most potent Ca2+ releaser in HSR. 3. The Ca2+ dependency of MYTX-induced 45Ca2+ release has a bell-shaped profile but it was quite different from that of caffeine, an inducer of Ca(2+)-induced Ca2+ release. 4. 45Ca2+ release induced by MYTX was remarkable in the range of pCa between 8 and 3, whereas that by caffeine was prominent in the range of pCa, i.e., between 7 and 5.5. 5. MYTX-induced 45Ca2+ release consists of both early and late components. The early component caused by MYTX at low concentrations (30-300 nM) completed within 20 s, while the late component induced by it at higher concentrations (> 0.3 microM) was maintained for at least 1 min. 6. Both the components were almost completely inhibited by inhibitors of Ca2+ such as Mg2+, ruthenium red and spermine. 7. 45Ca2+ release induced by caffeine or beta,gamma-methyleneadenosine 5'-triphosphate (AMP-PCP) was completely inhibited by high concentrations of procaine. Procaine abolished the early component but not the late one, suggesting that at least the early component is mediated through Ca(2+)-induced Ca2+ release channels. 8. On the basis of these results, the character of Ca2+ release induced by MYTX was quite different from that caused by caffeine or AMP-PCP, suggesting that MYTX induces Ca2+ release having novel properties in HSR. MYTX is the first polypeptide Ca2+ inducer and has become a useful pharmacological tool for clarifying the mechanism of Ca2+ release from skeletal muscle SR.

O-gene detection by allele specific amplification in the ABO blood group system

We have constructed a fast and easy method for the detection of O-gene in the ABO blood group system. Our method included allele specific amplification using polymerase chain reaction (PCR) and subsequent analysis with polyacrylamide gel electrophoresis (PAGE) and silver staining. O-gene product was observed on the gel in 25 DNA samples from group O phenotype and 20 DNA samples from group A or B (genotype AO or BO) persons. No product was found in 10 DNA samples from group AB phenotype.

Oligoclonal expansion of cd8+ T-lymphocytes in cultured peripheral lymphocytes derived from asymptomatic HTLV-I carriers

Peripheral blood mononulear cells (PBMC) derived from 10 asymptomatic human T lymphotropic virus type I (HTLV-I) carriers were cultured for a short term (10-14 days) in the absence of exogenous antigens. In 5 carriers, when compared with 5 HTLV-I non-carriers an apparent increase in the proportion of CD8+ DR+ cells was observed. The clonality of cultured lymphocytes was then examined by analyzing the usage of Vbeta families of T cell receptor genes. In three of the 5 carriers with an increased CD8+ population, two to four Vbeta genes were dominant in the CD8+ population but not in the CD4+ population. No dominance of Vbeta gene usage was observed in lymphocytes derived from the 5 noncarriers. The sequence of cDNA from Vbeta families which were especially dominant revealed their oligoclonal characteristics. These results were quite similar to our previous findings from HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients in whom the same oligoclonal CD8+ cells were expanded cytotoxic T lymphocyte clones for HTLV-I genome products. We posed the question of whether the dominance of TCR Vbeta usage in cultured PBMC was associated with the HTLV-I genome dose in the PBMC or with anti-HTLV-I antibody titers. The three carriers who showed an increased CD8+ population mentioned above all showed a rather high HTLV-I genome dose, which again was similar to HAM/TSP patients. These three carriers however, did not necessarily show high anti-HTLV-I antibody titers in contrast with HAM/TSP patients, who generally do.

Gastric carcinoma resected 95 months after being diagnosed: report of a case

It is usually assumed that patients with gastric carcinoma will almost certainly die within 5 years if they do not receive treatment. We report herein a rare case of curative gastrectomy being performed 95 months after gastric carcinoma was diagnosed. A 37-year-old Japanese man had an upper gastrointestinal endoscopy with biopsy which revealed moderately differentiated adenocarcinoma of the stomach. This was diagnosed as type IIc early gastric carcinoma with ulceration but he refused surgery. At 45 years of age, 95 months later, he presented to our hospital with melena, at which time lesions in an identical location had enlarged to Borrmann type 3 advanced gastric carcinoma. Thus, a total gastrectomy with regional lymph node dissection was performed. Although there was no liver or peritoneal metastasis, the regional lymph nodes were involved; however, the patient recovered well and is still alive without any further recurrence roughly 4 years postoperatively. The natural history of gastric carcinoma and the malignant cycle are discussed following the presentation of this case.

Isolation of human nm23 genomes and analysis of loss of heterozygosity in primary colorectal carcinomas using a specific genomic probe

Genomic clones of nm23-H1 and -H2 were isolated. The nm23-H1 and -H2 genes were located in a tandem array 4 kilobases apart. Each genome contained 5 exons and most of the splicing sites in the exon-intron junctions of two isotypes were essentially identical. A probe derived from intron 4 of nm23-H1 was used to examine the loss of heterozygosity (LOH) in primary colorectal carcinomas. Twenty-nine of 42 samples were informative and LOH was found in 3 of these 29. In all three samples with LOH, cancer tissues expressed lower levels of nm23-H1 mRNA when compared with those without LOH.

[Buerger's disease]

Diagnostic criteria and therapeutic strategies for Buerger's disease have been established recently. However, there are many unknown factors concerning its etiology and exacerbation. Further studies are necessary for the better understanding of these factors and it is important to establish therapeutic modalities matching the pathology. Although drug therapy is the basic approach to treatment of the disease, aggressive surgical treatment also can prove to be effective in many cases.

Gonadotropin-releasing hormones of terminal nerve origin are not essential to ovarian development and ovulation in goldfish

The involvement of gonadotropin-releasing hormones (GnRHs) from the terminal nerve (TN) in ovarian development and ovulation was examined by olfactory tract section (OTX) in goldfish. After OTX, brain contents of salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II) were measured by specific radioimmunoassays. Olfactory tracts of sexually maturing females were sectioned prior to the spawning season and were kept under natural conditions. Two months later, brain sGnRH contents markedly decreased in all brain areas (telencephalon, hypothalamus, optic tectum-thalamus, cerebellum, medulla oblongata) except in the olfactory bulbs, whereas cGnRH-II contents did not obviously change. Despite the large decreases in brain sGnRH contents, OTX and sham-operated female fish underwent vitellogenesis. Sexually mature OTX females could be stimulated to ovulate by increased water temperatures during spawning season. Brain sGnRH contents of these OTX fish also markedly decreased with no changes in cGnRH-II. It appears that sGnRH of TN origin, which comprises most of the brain sGnRH in the goldfish, is not a prerequisite for basal gonadotropin secretion and ovarian development, and is not likely to be related to the preovulatory gonadotropin surge which stimulates ovulation in goldfish.

Amino acid-induced responses in CNS neurons of normal mouse and Wriggle Mouse Sagami

Amino acid-induced responses and their regional heterogeneities in the motor cortical and hippocampal (CA1) neurons of normal mouse and Wriggle Mouse Sagami (WMS) were studied by conventional patch-clamp techniques. There were no differences in the current densities and EC50s of glutamate-, gamma-amino butyric acid (GABA)-, and glycine-induced responses between the two groups of mice. In both types of mice, the GABA-induced current density of cortical neurones was higher and EC50 was lower than in hippocampal neurones, whereas the responses induced by glycine and glutamate did not show any differences.

3',3",5',5"-Tetraiodophenolsulfonephthalein is a selective inhibitor of Ca(2+)-pumping ATPase in intracellular Ca2+ store

3',3",5',5"-Tetraiodophenolsulfonephthalein (I4PSP) stimulated both Ca2+ transient levels and aggregation in response to thrombin in platelets. Ca2+ uptake into skeletal sarcoplasmic reticulum (SR) was inhibited by I4PSP (IC50, 1.8 microM) whereas that of red blood cell ghosts was not affected by it. Furthermore, I4PSP inhibited the SR Ca(2+)-ATPase activity (IC50, 1.1 microM). Kinetic analysis of the inhibitory effects of I4PSP reveals that I4PSP shows an inhibition of noncompetitive and competitive type with respect to low and high concentrations of ATP, respectively. The mode of inhibition by I4PSP is an uncompetitive type with respect to Ca2+. I4PSP decreased the decomposition rate of the phosphorylated enzyme intermediate (EP). The change in the tryptophan fluorescence of SR Ca(2+)-ATPase induced by ATP was reduced by I4PSP indicating inhibition of the EP transition from Ca2E1P to E2P. The concentration-inhibitory response curves for I4PSP in Ca(2+)-ATPase activities and fluorescence changes were closely correlated. These results suggest that I4PSP slows down the structure transition from Ca2E1P to E2P, resulting in inhibition of the Ca(2+)-ATPase activity. On the basis of these results, it is suggested that the stimulation of Ca2+ transient levels in platelets and their aggregation in response to thrombin are due to the inhibition of Ca2+ pump in intracellular Ca2+ stores by I4PSP.

Spinal cord protection: development of a paraplegia-preventive solution

We present a clinically available method to protect the spinal cord against ischemic or reperfusion injury and to prevent paraplegia after cross-clamping of the aorta. We separated 35 rabbits into five equal groups and clamped each animal's abdominal aorta distal to the left renal artery. We also occluded the aortas 2 cm above the iliac bifurcation for 45 minutes with inflated 5F balloon catheters. Through the catheter port distal to each balloon one of four different solutions was infused at 3 degrees C for 3 minutes at a rate of 5 mL/min (group I, uninfused control; group II, lactated Ringer's solution; group III, lactated Ringer's solution + 30 mg/kg of methylprednisolone; group IV, lactated Ringer's solution+methylprednisolone + 3 mL of 20% mannitol; group V, lactated Ringer's solution+methylprednisolone+mannitol + 10 mg/kg of vitamins E and C). We assessed the neurologic status of the hind limbs on the second postoperative day using Tarlov's criteria. The neurologic status in groups III, IV, and V was significantly superior to that of group I (p < 0.05, groups III versus I; p < 0.01, groups IV and V versus I). Spastic paraplegia occurred in 71% of group I, in 43% of group II, in 29% of group III, in 14% of group IV, and not at all in group V. The infusion of our specially blended solution with several spinal cord neuroprotective properties (hypothermia, methylprednisolone, mannitol, and vitamins E and C) achieved the best spinal cord protection against ischemic or reperfusion injury and prevented postoperative paraplegia.

Calsequestrin is a major binding protein of myotoxin alpha and an endogenous Ca2+ releaser in sarcoplasmic reticulum

Myotoxin alpha from prairie rattlesnakes induced Ca2+ release from the heavy fraction of sarcoplasmic reticulum at submicromolar concentrations. 125I-Labeled myotoxin alpha (125I-myotoxin alpha) specifically bound to the heavy fraction. Fractionation of the solubilized heavy fraction with a spermine-agarose column gave purified calsequestrin as a major binding protein of 125I-myotoxin alpha. We have first indicated that calsequestrin is a target protein for Ca(2+)-releasing action of myotoxin alpha. Calsequestrin probably plays a key role in physiological Ca2+ release from sarcoplasmic reticulum.

Identification and cloning of an mRNA coding for a germ cell-specific A-type lamin in mice

The nuclear lamins are karyoskeletal proteins which have important functions, such as maintaining nuclear envelope integrity and organizing high order nuclear structure during mitosis in higher eukaryotes. In somatic mammalian cells, the A-type and B-type lamins, composed of lamins A and C and lamins B1 and B2, are major components of the nuclear lamina. However, A-type lamins have as yet not been identified in germ cells and undifferentiated embryonic cells. Here we report the cloning of a new 52-kDa A-type lamin from mouse pachytene spermatocytes, termed lamin C2 because of its similarities with lamin C. It has a sequence identical to that of lamin C except that the N-terminal segment, containing the head and the alpha-helical coil 1A domains, is replaced with a short non-alpha-helical stretch of amino acids. In mice, lamin C2 was found to be specifically expressed in germ cells. This specific expression and unique structure suggests a role for lamin C2 in determining the organization of nuclear and chromosomal structures during spermatogenesis.