Development of early-stage embryos of the Japanese field vole, Microtus montebelli, in vivo and in vitro

Although ovulation could be easily induced in the Japanese field vole by administering pregnant mares' serum gonadotrophin and hCG, the number of embryos obtained varied from 1 to 47 (mean, 9.6). One-cell embryos were small (57.8-63.3 microns in diameter; mean, 61.0 microns) compared with those in other mammals. Development of the preimplantation vole embryos in vivo was similar to that of mouse embryos. The first cleavage occurred between 24 and 26 h after mating. The second cleavage was between 46 and 52 h after mating, and subsequent cleavages occurred at about 12 h intervals. Blastocysts were clearly observed in the uterus 4 days after mating. Vole embryos could be cultured in vitro from the late two-cell to the blastocyst stage in M16 medium. However, development of one-cell and early two-cell embryos in vitro was limited, and few cleaved beyond the four-cell stage. Eliminating sodium pyruvate from M16 medium significantly improved the development of early two-cell embryos into blastocysts (P < 0.05). The Japanese field vole may be a useful experimental animal for reproductive biology, comparable with the mouse.

Depressed contractile state and increased myocardial consumption for non-mechanical work in patients with heart failure due to old myocardial infarction

OBJECTIVE

The aim was to characterise the impaired myocardial mechanoenergetics in patients with heart failure due to old myocardial infarction by using the oxygen consumption versus left ventricular pressure--volume area (PVA) relationship.

METHODS

The VO2-PVA relationship was assessed in 15 patients: group N consisted of seven patients with vasospastic angina pectoris whose left ventricular ejection fractions were normal [72 (SD 8)%], and group F consisted of eight patients with old myocardial infarction whose left ventricular ejection fractions were reduced [45(11)%]. Left ventricular volume and pressure were measured by the conductance catheter method. VO2 was measured by thermodilution.

RESULTS

Linear VO2-PVA relationships with dextran infusions were obtained in both groups (median r = 0.92 v 0.90). There was no difference in the slope between the two groups. There was a positive correlation between Emax and VO2 at median PVA (VO2,PVA0.8) in group N. Emax, an index of left ventricular contractility, was significantly smaller in group F than in group N, at 5.1(2.1) v 3.2(1.1) mm Hg.ml-1.m2; p < 0.05). On the other hand, the VO2 intercept in group F was comparable to that in group N, at 0.71(0.63) v 0.40(0.29) J x beat-1.100 g LV-1; NS). In addition, the ratio of VO2,PVA0.8 to Emax was significantly larger in group F than in group N: 0.55(0.14) v 0.89(0.37) J x beat-1.100 g LV-1.mm Hg-1.ml.m-2 (p < 0.05).

CONCLUSIONS

These results suggest that the VO2 for non-mechanical work in group F is disproportionately high relative to the reduced contractility. An abnormality of excitation-contraction coupling rather than of crossbridge cycling may be responsible for the impaired mechanoenergetics in patients with heart failure due to old myocardial infarction.

Changes in the immunoreactivity of follistatin within preovulatory follicles after the primary gonadotrophin surge in rats

Cyclic changes in follistatin localization and the role of the primary gonadotrophin surge in regulating follistatin expression were studied in rat ovaries by immunohistochemistry. Two different polyclonal antisera were raised against synthetic peptides corresponding to amino acids 123-134 and 300-315 of human follistatin. Immunoreactive follistatin was detected in granulosa cells of secondary and mature follicles. Although immunoreactions with anti-follistatin (300-315) occurred in preovulatory follicles until immediately before ovulation (23:00 h on the day of pro-oestrus), follistatin was not immunodetected in newly formed corpora lutea (11:00 h on the day of oestrus). Granule-like immunoreactions with anti-follistatin (123-134) serum in preovulatory follicles markedly decreased in intensity on the evening of pro-oestrus, indicating the loss of follistatin production. Blocking the primary gonadotrophin surge by a pentobarbitone injection (40 mg kg-1) at 13:30 h on the day of pro-oestrus sustained the immunoreactivity with anti-follistatin (123-134) in preovulatory follicles up to 23:00 h on the day of pro-oestrus. Injection of pentobarbitone-treated animals with exogenous LH (100 micrograms kg-1) or FSH (50 micrograms kg-1) at 15:30 h on the day of pro-oestrus eliminated the immunoreactions. These results indicate that the expression of follistatin in preovulatory follicles is suppressed by the primary gonadotrophin surge during pro-oestrus. Hence, it is conceivable that the cessation of follistatin production in preovulatory follicles may occur before ovulation, and that it may be caused by the primary gonadotrophin surge.

Treatment of postoperative chylothorax by pleurodesis with the streptococcal preparation OK-432

Of the 2877 patients who underwent chest surgery at our department during the 20-year period between 1973 and 1992, 9 (0.3%) developed postoperative chylothorax. The underlying disease included primary lung cancer in 5 patients, pulmonary metastasis in 1, invasive thymoma in 2, and neuroblastoma of the posterior mediastinum in 1. For the treatment of chylothorax, the thoracic duct was ligated in 2 patients with a high volume of chylous leakage. In 6 patients treated conservatively, early pleurodesis was attained by injecting 1 to 5 doses (mean: 2.2 doses) of the streptoccal preparation OK-432 intrathoracically; favorable results were achieved. In 1 patient, the diagnosis of chylothorax was delayed because of postoperative pyothorax. This patient developed nutritional deficiency, compromised immunity, and disseminated intravascular coagulation (DIC), which led to death before the chylothorax could be treated. In principle, postoperative chylothorax should be treated conservatively. Favorable results can be expected with the intrathoracic injection of OK-432 beginning at the early postoperative period to achieve pleurodesis, combined with the prevention of nutritional deficiency, electrolyte imbalance, and infection.

Nerve growth factor and epidermal growth factor rescue PC12 cells from programmed cell death induced by etoposide: distinct modes of protection against cell death by growth factors and a protein-synthesis inhibitor

A rat pheochromocytoma cell line (PC12 cells) died within 24 h in the presence of etoposide (1-40 micrograms/ml), an inhibitor of topoisomerase II. This cytotoxic effect was prevented by either nerve growth (NGF) or epidermal growth factor (EGF). Cycloheximide and actinomycin D also suppressed the cell death as well. Furthermore, a difference among protective modes against etoposide-induced death by growth factors and a protein-synthesis inhibitor was observed: the protective effect of either NGF or EGF remained rather constant as a function of incubation time with etoposide whereas that of cycloheximide declined. These results indicate that etoposide induces programmed death in PC12 cells and that prevention of the programmed cell death by both NGF and EGF is mainly due to inactivation of molecules involved in the death processes rather than suppression of specific protein and/or mRNA synthesis.

Effect of NKH477, a new water-soluble forskolin derivative, on arterial-ventricular coupling and mechanical energy transduction in patients with left ventricular systolic dysfunction: comparison with dobutamine

We examined the effects of a novel water-soluble forskolin derivative, NKH477 (0.5 microgram/kg/min), on arterial-ventricular (A-V) coupling and mechanical energy transduction from heart to circulatory bed in comparison with those of dobutamine (3 micrograms/kg/min) in 8 patients with left ventricular (LV) systolic dysfunction using a conductance catheter method. A-V coupling was assessed as the ratio of the effective arterial elastance (E(a)) to the slope of the end-systolic pressure-volume relation (ESPVR) (E(max), left ventricular contractility index), and the ratio of mechanical energy transduction was obtained as the fraction of PV area (PVA) comprised of stroke work (SW). E(max) (2.59 mm Hg/ml/m2), E(a)/E(max) (1.62), and SW/PVA (0.58) were impaired in control contractile state. NKH477 increased Emax to the same extent as dobutamine. E(a) decreased with NKH477 but not with dobutamine. As a consequence, the decrease in E(a)/E(max) with NKH477 was greater than that with dobutamine (52 vs. 47%, p < 0.05); the increase in SW/PVA with NKH477 was also greater than that with dobutamine (28 vs. 21%, p < 0.05). These findings suggest that NKH477 may be a superior alternative to dobutamine in A-V coupling and mechanical energy transduction in patients with LV systolic dysfunction.

Prophylactic efficacy of milbemycin oxime against multiple infection of dogs with Dirofilaria immitis

In order to examine the prophylactic effects of milbemycin oxime (MO) against Dirofilaria immitis infection, experiments were carried out under multiple infection with D. immitis. Ten filaria-free beagles of age 4 to 8 months were each inoculated with a total number of 480 larvae 12 times at intervals of 15 days over a period of 6 months, and MO was given monthly for the 6 months at a dose of 0.25 mg/kg. The infection rate in the medicated group of dogs was nil, this suggesting complete protection of the infection, while in the non-medicated control group it ranged from 6.5 to 14.8% (mean, 11.4%).

An identical missense mutation in the albumin gene results in familial dysalbuminemic hyperthyroxinemia in 8 unrelated families

Familial dysalbuminemic hyperthyroxinemia (FDH) is the most common form of inherited increase of serum thyroxine in Caucasians. It is the result of increased thyroxine-binding to serum proteins and is inherited as a dominant trait. The entire coding region of the albumin gene of a subject with FDH was sequenced. A single nucleotide substitution, G to A transition in codon 218, was found in one of the two alleles, resulting in the replacement of the normal Arg with His. This mutation was found in 9 affected family members but not in 8 unaffected relatives and 18 unrelated normal individuals. The same missense mutation was found in 12 other subjects with FDH belonging to 7 unrelated families. In every individual with FDH, the mutation was associated with the Sac I+ polymorphism in the albumin gene, strongly suggesting a founder effect.

Induction of an olfactory memory by the activation of a metabotropic glutamate receptor

Female mice form an olfactory memory of male pheromones at mating; exposure to the pheromones of a strange male after that mating will block pregnancy. The formation of this memory is mediated by the accessory olfactory system, in which an increase in norepinephrine after mating reduces inhibitory transmission of gamma-aminobutyric acid from the granule cells to the mitral cells. This study shows that the activation of mGluR2, a metabotropic glutamate receptor that suppresses the gamma-aminobutyric acid inhibition of the mitral cells, permits the formation of a specific olfactory memory without the occurrence of mating by infusion of mGluR2 agonists into the female's accessory olfactory bulb. This memory faithfully reflects the memory formed at mating.

[Atypical Guillain-Barré syndrome associated with ophthalmoplegia and visual impairment following herpes simplex virus type 1 infection]

Two weeks after a flu-like illness, a 59-year-old woman developed double vision, muscle weakness and sensory discomfort in the proximal portions of her limbs. On admission, there was complete external ophthalmoplegia with bilateral ptosis. The pupils were dilated and did not react to light. Swallowing and elevation of the soft palate were also limited. There was severe muscle weakness in all limbs. Deep tendon reflexes were absent. Superficial and deep sensations were impaired in the proximal portions of the extremities. Neuro-ophthalmological examinations revealed an acquired color disorder with no scotoma and normal discs. P100 latencies of flashed visual evoked potentials were prolonged on day 41, and returned to normal on day 87. Herpes simplex virus type 1 (HSV-1) infection was confirmed by isolation of the virus from her sputum and the detection of anti-HSV-1 antibody in the acute phase serum.

Primary thymic carcinoma: a clinicopathological and immunohistochemical study

During the treatment of five cases of thymic carcinoma, we conducted a clinicopathological and immunohistochemical study. The patients included four males and one female, whose ages ranged from 50 to 69 years. The histologic breakdown was squamous cell carcinoma in four and small cell carcinoma in one. Immunohistochemically, the squamous cell carcinomas were positive for cytokeratin (intermediate molecular weight) and keratin. However, staining was negative for Leu-7 and chromogranin. A complete resection was achieved in only one case. In all four of the remaining cases, the resection was incomplete due to invasion into adjacent organs and disseminated lesions. Thymic carcinoma is a tumor for which a higher response rate can be expected from multidisciplinary therapy than that for lung cancer. Therefore, it is desirable, from the clinical view, to determine clinical staging and to establish standard operative procedures comprising mediastinal lymph node dissection as well as effective chemotherapy. With respect to pathology, it is hoped that an improved histologic classification will be developed.

Peroxisome proliferation of hepatocytes in rats by a microbial degradation product of cholic acid, 4-(decahydro-6-methyl-3-oxocyclopenta(f)quinoline-7-yl)valeric acid

Three-week oral administration of 4-(decahydro-6-methyl-3-oxo-cyclopenta(f)quinoline-7-yl)valeric acid (32-1328) in the diet supplemented at concentrations of 0.1% or 0.3% was associated with hepatomegaly and hypotriglyceridemia in male F344 rats. Electron microscopic examination of the liver revealed a remarkable increase of peroxisomes in hepatocytes both in number and size. Biochemically, there were increased activities of peroxisomal marker enzymes including the heat-labile enoyl-CoA hydratase and catalase while the mitochondrial enoyl-CoA hydratase activity was unchanged after feeding of 32-1328. These findings indicate that 32-1328 can exert peroxisome-proliferating activity to rat liver in a manner similar to typical peroxisome proliferators such as clofibrate or di(2-ethylhexyl)phthalate.

Endodontic treatment in taurodontism

This case report presents the successful endodontic treatment of a taurodontic mandibular second molar with five root canals (four in the mesial root, one in the distal root).

Dose-dependent promoting effects of sodium chloride (NaCl) on rat glandular stomach carcinogenesis initiated with N-methyl-N'-nitro-N-nitrosoguanidine

The influence of different doses of sodium chloride (NaCl) on glandular stomach carcinogenesis was examined in male outbred Wistar rats after initiation with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Rats were given 100 p.p.m. MNNG in their drinking water for 8 weeks and then fed a diet supplemented with NaCl at doses of 10, 5, 2.5 or 0% for the next 82 weeks. The administration of 10% and 5% NaCl significantly enhanced the development of gastric adenocarcinomas and adenomas in a dose-dependent manner. Similar but non-significant tendencies for increase were also seen in the group given 2.5% NaCl compared to the MNNG-alone group values. Clear linear correlations between incidences of adenocarcinomas and/or adenomas and the concentration of supplemented NaCl were found. Mesenchymal tumors were also induced in the stomach of rats given MNNG, although the incidence was not statistically different between groups. Independent of the MNNG treatment, urinary lipid peroxidation levels were significantly increased in the NaCl-treated groups as compared to the control values. Thus, the results in the present study indicate that NaCl exerts dose-dependent tumor promoting activity on gastric carcinogenesis in rats, even at doses as low as 2.5%, when given after MNNG initiation.

Epstein-Barr virus-associated gastric carcinoma and Epstein-Barr virus infection of the stomach

BACKGROUND

Epstein-Barr virus (EBV) has been found to be associated with a type of gastric carcinoma (EBVaGC). However, many questions remain unanswered, such as epidemiology, and pathologic features of EBVaGC and the significance of EBV in the genesis of EBVaGC.

EXPERIMENTAL DESIGN

Gastric carcinoma and non-neoplastic mucosa were evaluated to reveal the following issues: the incidence of EBVaGC in Japanese population, pathologic features and EBV genotype, clonality, and gene-expression in EBVaGC, localization of EBV in non-neoplastic stomach, and serum titer of anti-EBV antibodies in EBVaGC-carrying patients.

RESULTS

Using PCR and EBER1 in situ hybridization, EBVaGC (definitely amplifiable EBV-DNA and positive EBER1-signal in the nuclei of carcinoma cells) was found in 8 of 72 gastric carcinomas (11%). The dominant genotype of EBV was type A (7/8), with type C (6/8), and F (8/8) restriction enzyme polymorphism, which are the predominant type of EBV found in throat washing of the general population in Japan. EBVaGC was found in the cardia (4/8) or body (4/8) of the stomach, and consisted of 7 advanced and 1 intramucosal carcinoma. By Southern blot analysis of EBVaGC hybridized with right- and left-side probe adjacent to the terminal repeats, EBV was present in a monoclonal episomal form in all of the EBVaGC. EBVaGC lacked expression of EBNA2 (0/8) and LMP1 (0/8) by immunocytochemistry. In non-neoplastic mucosa, EBER1 signal was identified in the infiltrating lymphocytes and shedding epithelial cells predominantly in fundic gland mucosa of patients with EBVaGC (8/8). Patients with EBVaGC showed high titers of anti-VCA IgG (8/8), anti-VCA IgA (2/8) and anti-EA IgG (7/8) antibodies just before surgery.

CONCLUSIONS

EBV may infect the surface epithelium of the stomach through the reactivated EBV-carrying lymphocytes. EBV may be a factor initiating EBVaGC. Anti-EBV antibodies or EBER1 in situ hybridization may help to identify patients at high risk for EBVaGC.

Synergistic effects of phenobarbital and thiourea on proliferative lesions in the rat liver

To evaluate the effects of phenobarbital (PB) and thiourea (TU), alone or in combination, on proliferative lesions of the liver, thyroid and lung, male F344 rats initiated with 2000 mg/kg body weight N-bis(2-hydroxypropyl) nitrosamine (DHPN) were given diet and/or drinking water containing 0% PB/TU (group 1), 1000 ppm PB (group 2), 0.1% TU (group 3) and 500 ppm PB and 0.05% TU (group 4), from weeks 2 to 20 for 19 weeks. Group 4 showed remarkable increases in the number of hepatocellular altered foci per animal, the values being superior to the averages of groups 2 and 3. The number of thyroid proliferative lesions per animal was highest in group 3 and lowest in group 2. Lung proliferative lesions were induced in all groups, but no modifying influence on their development was evident in the combined group. The present results indicate that combined administration of PB and TU exerts synergistic enhancing effects on hepatocarcinogenesis.

An RNA-binding protein gene, TLS/FUS, is fused to ERG in human myeloid leukemia with t(16;21) chromosomal translocation

The t(16;21)(p11;q22) translocation is a recurrent chromosomal abnormality found in several types of myeloid leukemia. We have previously demonstrated that the breakpoints of this translocation are clustered in a specific intron of the ERG gene on chromosome 21, which has recently been reported to be involved in Ewing's sarcoma. We show here that the TLS/FUS gene on chromosome 16 is fused with the ERG gene to produce the TLS/FUS-ERG chimeric transcript by this translocation. The TLS/FUS gene has been identified as a translocated gene in myxoid liposarcoma by the t(12;16)(q13;p11) translocation and encodes an RNA-binding protein that is highly homologous to the product of the EWS gene involved in Ewing's sarcoma. Thus, the TLS/FUS-ERG gene fusion in t(16;21) leukemia is predicted to produce a protein that is very similar to the EWS-ERG chimeric protein responsible for Ewing's sarcoma.

[A female case of adenocarcinoma of the lung producing human chorionic gonadotropin]

A 72-year-old female was admitted with complaints of cough and sputum. The chest X-ray film revealed a solitary round mass and pleural effusion in the left lower lung field. Laboratory tests demonstrated elevated levels of serum HCG and beta-HCG. Left lower lobectomy with parietal pleurectomy was performed under the diagnosis of primary lung cancer with malignant effusion. The serum HCG level decreased after the operation. Histologically, the tumor was diagnosed as moderately differentiated papillo-tubular adenocarcinoma of the lung. In the HCG staining using an immunohistochemical method, the tumor cells showed a positive reaction. Thus, this tumor was definitively diagnosed to be HCG-producing adenocarcinoma of the lung.

Stage-synchronization of the seminiferous tubules after vitamin A replacement in vitamin A deficient golden hamsters

The effect of vitamin A deficiency and vitamin A replacement on spermatogenesis in golden hamsters was studied using a light microscope. Male golden hamsters were fed a vitamin A deficient (VAD) diet from 3 weeks of age. Hamsters with a VAD diet reached maximum body weight at about 13 weeks. After 17 weeks, the body weight of the hamsters began to decrease. When their body weight decreased to 70 g, only Sertoli cells, spermatogonia, and a few spermatocytes were present within the seminiferous tubules. Administering retinol acetate (vitamin A) combined with a conventional diet to the VAD hamsters induced a reinitiation of spermatogenesis with stage-synchronization. At 9, 10, and 11 weeks after vitamin A replacement, the testes with active spermatogenesis possessed only a few successive stages of the seminiferous epithelial cycle.

Clinical application of energy dispersive x-ray microanalysis for nondestructively confirming dental metal allergens

Dental metal restorations contain and release allergens that cause metal allergy. Until now it has been a general treatment for dental metal allergy to remove all suspected metal restorations without confirming their chemical composition. This study describes the procedures to examine nondestructively the chemical composition of metal restorations by the use of an energy dispersive x-ray microanalysis system. The present results indicate that this new application of energy dispersive x-ray microanalysis could identify the dental metal restorations that contain elements positive in skin tests for the patient in whom a metal allergy is suspected and that the potential for the clinical use of energy dispersive x-ray microanalysis exists.

The evidence of carotid body in the carotid rete of the shiba goat

The carotid body was found in/on the cavernous sinus of the carotid rete of the Japanese miniature Shiba goat by light and electron microscopies. The carotid body-like aggregated cell group consisted of two types of cells arranged in the lobule. The first type contained membrane-bound granular vesicles; these cells resembled to the type-I cells in the carotid body. The second type contained no cytoplasmic vesicles, and were located in the periphery, investing the type-I cells. These features appear to be consistent with those of the type-II cells in the carotid body. The nerve ending showed two peculiar features in the intercellular space of type-I cells. The clear vesicle-containing nerve ending showed a structural feature indicative of efferent synapsis. The small granular vesicle-containing nerve ending has been described as a baroreceptor-like ending by VERNA (1979). All of these features are typical characteristics of the carotid body.

Age-related changes in cytoskeletal components of the BDF1 mouse Sertoli cell

Age-related changes in mouse Sertoli cell cytoskeletal components (F-actin, vimentin and cytokeratin) were investigated by light and transmission electron microscopy and immunofluorescence using BDF1 mice from 3-33 months of age. In old mice (30 and 33 months of age), the testicular seminiferous epithelia were extremely thin, containing scarce round spermatids and spermatocytes with no elongated spermatids. In these epithelia, the Sertoli cells had lost their polarity and had become flattened. F-actin was detectable at the junction between adjoining Sertoli cells and around the spermatid head in young mice. In old mice, F-actin was distributed at the junction between adjacent Sertoli cells, around the spermatid head, and at the luminal side of the Sertoli cell cytoplasm. Vimentin was detected around the Sertoli cell nucleus and extended into the Sertoli cell trunk towards the tubular lumen in young mice. In old mice testes, however, vimentin was recognized around the Sertoli cell nucleus, but not in the Sertoli cell trunk. Additionally, sheet-like reactions of vimentin, running parallel to the basement membrane, were detected near the luminal surface. Although cytokeratin was not detected in the Sertoli cells of mice until 27 months of age, it was obvious in the extremely thin seminiferous epithelia of older mice. Cytokeratin was randomly distributed within the Sertoli cell cytoplasm. In these Sertoli cells, the expression of vimentin was concurrently detected. Detection of cytokeratin in the extremely thin seminiferous epithelia is one of the most characteristic phenomena of age-related testicular changes in Sertoli cells of older mice.

Detection of new paternal dystrophin gene mutations in isolated cases of dystrophinopathy in females

Duchenne muscular dystrophy is one of the most common lethal monogenic disorders and is caused by dystrophin deficiency. The disease is transmitted as an X-linked recessive trait; however, recent biochemical and clinical studies have shown that many girls and women with a primary myopathy have an underlying dystrophinopathy, despite a negative family history for Duchenne dystrophy. These isolated female dystrophinopathy patients carried ambiguous diagnoses with presumed autosomal recessive inheritance (limb-girdle muscular dystrophy) prior to biochemical detection of dystrophin abnormalities in their muscle biopsy. It has been assumed that these female dystrophinopathy patients are heterozygous carriers who show preferential inactivation of the X chromosome harboring the normal dystrophin gene, although this has been shown for only a few X:autosome translocations and for two cases of discordant monozygotic twin female carriers. Here we study X-inactivation patterns of 13 female dystrophinopathy patients--10 isolated cases and 3 cases with a positive family history for Duchenne dystrophy in males. We show that all cases have skewed X-inactivation patterns in peripheral blood DNA. Of the nine isolated cases informative in our assay, eight showed inheritance of the dystrophin gene mutation from the paternal germ line. Only a single case showed maternal inheritance. The 10-fold higher incidence of paternal transmission of dystrophin gene mutations in these cases is at 30-fold variance with Bayesian predictions and gene mutation rates. Thus, our results suggest some mechanistic interaction between new dystrophin gene mutations, paternal inheritance, and skewed X inactivation. Our results provide both empirical risk data and a molecular diagnostic test method, which permit genetic counseling and prenatal diagnosis of this new category of patients.

Molecular cloning and sequencing of calnexin-t. An abundant male germ cell-specific calcium-binding protein of the endoplasmic reticulum

A mouse testis cDNA expression library was screened using a monoclonal antibody (1C9) that recognized an abundant testis-specific 101-kDa endoplasmic reticulum-associated protein. The screening resulted in the isolation of a 2.3-kilobase cDNA clone (A2/6). The sequence encoded 611 amino acids with a calculated mass of 69,454 Da, that was 60% similar to mouse calnexin. A high affinity calcium binding domain, present in both calnexin and calreticulin, and one transmembrane domain similar to that of calnexin were found in the A2/6 protein domain. Northern blot analysis of total RNA from seven different tissues showed hybridization only to testis RNA. Southern blot analysis indicated that A2/6 was a single copy gene. The calculated molecular mass for A2/6 was unexpectedly lower than the 101-kDa protein recognized by 1C9 on Western blot analysis of total testis protein. However, Escherichia coli and in vitro translation products of A2/6 cDNA yielded a similar 100-kDa protein. Finally, using the recombinant protein, calcium binding activity was detected by a 45Ca2+ overlay assay. These results suggest that spermatogenic cell endoplasmic reticulum has a unique calcium binding protein, calnexin-t, which appears to be a calnexin variant.