A strategy for selective anti-cancer drug concentration increase in rat glioma tissue with Ca(2+)-channel blocker co-administration: calcium kinetics in intra-glioma arteriolar smooth muscle cells

A rat glioma model was employed to estimate the Ca2+ kinetics in the tumor arteriolar smooth muscle cells. Electron microcytochemistry revealed that the density of intracellular Ca2+ deposits in the intra-tumor arteriolar smooth muscle cells was significantly greater, with slightly higher membrane Ca(2+)-adenosine triphosphatase (ATPase) activity, compared to the contralateral cerebral arterioles. Furthermore, the administration of tyrphostin, a tyrosine kinase inhibitor, specifically increased only the intra-tumor blood flow. These findings suggest that the condition of the intra-tumor arteriole alters the susceptibility to contraction by the accelerated Ca2+ influx into the cytoplasm mediated through the tyrosine kinase pathway. After the administration of diltiazem, which also has a blocking effect on the Ca(2+)-channel mediated through this pathway, the local intra-tumor blood flow showed an increase of 39% with a marked decrease of intracellular Ca2+ concentration of the arteriolar smooth muscle cells in the tumor, while the blood flow in the basal ganglia increased by only 8%. The intra-tumor concentration of Nimustine-HCl (ACNU) with co-administration of diltiazem was significantly increased compared to that without the co-administration. Co-administration of diltiazem may be a valuable strategy in chemotherapy for glioma in affording the selective increase of intra-tumor concentration of the anti-cancer drug.

[A case of systemic sclerosis associated with interstitial pneumonia with various autoantibodies: improvement by intravenous cyclophosphamide therapy]

A 41-year-old woman was admitted to Tokyo Women's Medical College Aoyama Hospital in January 1994. She presented cough and dyspnea in September 1991. The diagnosis of interstitial pneumonia was made based on TBLB. Interstitial pneumonia was responsive to initial prednisolone of 40 mg daily. When dose of prednisolone was reduced to 15 mg daily, she complained of cough and dyspnea again. She was referred to Institute of Rheumatology, Tokyo Women's Maedical College in November 1993. She was diagnosed as systemic sclerosis associated with interstitial pneumonia based on proximal scleroderma and digital pitting scar. Double immunodiffusion and immunoprecipitation assay revealed the presence of anti-Ki, anti-Wa, and anti-RNA polymerases antibodies in the serum. On admission in March 1994, she was treated with intravenous cyclophosphamide therapy at 500 mg/day once a mouth. After the third infusion, respiratory symptoms, pulmonary function test values, findings of chest X-ray and CT scan were improved without adverse drug effects. Intravenous cyclophosphamide therapy seems to be useful in this case. The efficacy of Intravenous cyclophosphamide therapy in the treatment of the interstitial pneumonia associated with systemic sclerosis was discussed.

Induction of apoptosis in androgen-independent mouse mammary cell line by 1, 25-dihydroxyvitamin D3

Androgen-dependent tumors eventually progress to independent tumors after androgen withdrawal. Effective treatment for hormone-independent tumors is therefore needed. Androgen-independent CS-2 cells could grow in serum-free culture whether androgen is present in the medium or not. In the present study, the mechanism of cell death in CS-2 cells was examined after 1, 25-dihydroxyvitamin D3[1, 25(OH)2D3] treatment. 1, 25(OH)2D3 has been examined as an anti-tumor agent, but its role in promoting cell death is poorly understood. Based upon the temporal sequence of DNA fragmentation, morphologic changes and loss of cell viability, the cells underwent apoptosis with 1, 25(OH)2D3 treatment. Northern-blot analysis was used to identify a series of genes whose expression per cell is enhanced during the apoptotic pathway. In the apoptotic process induced by 1, 25(OH)2D3, mRNA expression of testosterone-repressed prostatic message 2, transforming growth factor beta1, glucose-regulated 78-kDa protein and calmodulin increased. Flow-cytometric analysis showed that 1, 25(OH)2D3 treatment resulted in a block in G0/G1 of the cell cycle. These results demonstrate that androgen-independent CS-2 cells retain the ability to undergo apoptosis by 1, 25(OH)2D3. This system appears to be a good model for investigating apoptosis of hormone-independent cancer.

Reversal of adriamycin resistance with chimeric anti-ganglioside GM2 antibody

Ganglioside GM2 is one of the major cell-surface gangliosides expressed in human tumors. We earlier established a mouse/human IgG1 chimeric anti-GM2 antibody, KM966, which displayed anti-tumor activity in human tumor cells both in vitro and in vivo. In this study, we have screened for changes in ganglioside expressions in several drug-resistant human cancer cell lines to examine the modulation of drug resistance by immunotherapy with anti-ganglioside antibodies. Increased GM2 expression, detected by flow cytometry and thin-layer chromatography, was observed in the SBC-3/ADM and AdrR MCF7 adriamycin-resistant cell lines, in contrast with their parental lines. In other related gangliosides, ganglioside GD2 levels in AdrR MCF7 were higher than those in MCF7 cells. We confirmed increased N-acetylgalactosaminyltransferase mRNA in adriamycin-resistant cell lines, as compared with the parental cells, by Northern-blot analysis. Moreover, to investigate the possibility of exploiting the anti-tumor activity of KM966 in order to overcome resistance to adriamycin, we investigated the antibody-dependent cell-mediated cytotoxity of human peripheral mononuclear blood cells and the complement-dependent cytotoxity of human serum with KM966 against SBC-3, SBC-3/ADM, MCF7 and AdrR MCF7. Significantly higher killing via KM966 was observed in SBC-3/ADM and AdrR MCF7 cells as compared with the parental cells. This suggests that passive immunotherapy using KM966 against human adriamycin-resistant cancer may be useful for overcoming resistance to adriamycin.

Cerebral [15O]water clearance in humans determined by PET: I. Theory and normal values

When used to measure blood flow in the brain, water leaves a residue in the vascular bed that influences the estimation of blood flow by current methods. To assess the magnitude of this influence, we developed a two-compartment model of blood flow with separate parameters for transport and vascular distribution of brain water. Maps of the water clearance, K1 into brain tissue, separated from the circulation by a measurably resistant blood-brain barrier (BBB), were generated by time-weighted integration. Depending on the validity of the assumptions underlying the two-compartment model presented here, the maps revealed a significant overestimation of the clearance of water when the vascular residue was ignored. Maps of Vo, the estimate of the apparent vascular distribution volume of tracer H2(15)O, clearly revealed major cerebral arteries. Thus, we claim that the accumulation of radioactive water in brain tissue also reflects the volume of the arterial vascular bed of the brain.

Different distribution of dihydrolipoamide succinyltransferase, dihydrolipoamide acetyltransferase and ATP synthase beta-subunit in monkey brain

The distribution of three mitochondrial enzymes: dihydrolipoamide succinyltransferase, dihydrolipoamide acetyltransferase, and beta-subunit of ATP synthase, were examined in the nucleus basalis of Meynert, substantia nigra, locus coeruleus, hippocampus, and cerebral cortex of monkey brain by immunocytochemical staining. Dihydrolipoamide succinyltransferase and dihydrolipoamide acetyltransferase had parallel distribution in the substantia nigra, but dihydrolipoamide acetyltransferase was rich in the locus coeruleus, nucleus basalis of Meynert, and especially in the hippocampus in comparison with dihydrolipoamide succinyltransferase. The ATP synthase beta-subunit was strikingly rich in many neurons of the locus coeruleus and cerebral cortex in comparison with dihydrolipoamide acetyltransferase and dihydrolipoamide succinyltransferase. These results show that these mitochondrial enzymes are not expressed synchronously in the neurons of brain, suggesting the differential regulation of mitochondrial enzymes and the heterogeneity of mitochondria.

Expression of the apoptosis-mediator Fas is enhanced by dysfunctional mitochondria

We applied an antibody against an apoptosis mediator, Fas/APO-1/CD95, to HeLa-derived cells that completely lack mitochondrial DNA (mtDNA) or have mutant mtDNAs. The anti-Fas antibody killed the cells completely lacking mtDNA (EB8), at concentrations as low as 1 ng/ml, but not control cells harboring wild-type mtDNA (Ft2-11). TUNEL (terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end-labeling) and analysis of fragmented DNA indicated that the cell death of EB8 was due to apoptosis. The antibody was cytotoxic to other two cell lines harboring mutant mtDNA with a point mutation or a large-scale deletion. RT-PCR (reverse transcriptase-polymerase chain reaction) showed that the mRNA content of the Fas gene was 2 to 19-fold higher in the cells with deficient mtDNA than in the control cells. In addition, the expressed Fas protein was detected by immunohistochemical staining in the cells without mtDNA but not in the control cells. Incubating the cells containing wild-type mtDNA with the respiratory inhibitors rotenone and antimycin A enhanced the content of mRNA of the Fas gene 2 to 4-fold and sensitized cells to the antibody. Thus, defects in mitochondria caused apoptotic cell death by anti-Fas antibody and enhanced Fas gene expression.

Calcium movement in ischemia-tolerant hippocampal CA1 neurons after transient forebrain ischemia in gerbils

Hippocampal CA1 neurons exposed to a nonlethal period (2 min) of ischemia, acquired tolerance to a subsequent lethal 5-min period of ischemia, which usually causes delayed-type neuronal death. Intracellular Ca2+ movements before and after the 5 min of forebrain ischemia were evaluated in gerbil hippocampal CA1 pyramidal neurons, had acquired tolerance in comparison with nonischemia-tolerant CA1 neurons. Evaluation was performed by observing the ultrastructural intracellular Ca2+ distribution and the Ca2+ adenosine triphosphatase (Ca(2+)-ATPase) activity using electron microscopic cytochemistry. In comparison with nonischemia-tolerant CA1 neurons, mitochondria of ischemia-tolerant CA1 neurons sequestered more Ca2+ from the cytosomal fraction 15 min after the 5-min period of ischemia, and Ca2+ deposits in these mitochondria were rapidly decreased. Plasma membrane Ca(2+)-ATPase activities were already significantly elevated before the 5 min of ischemia, and remained at a higher level subsequently compared to nonischemia-tolerant CA1 neurons. Changes in the mitochondrial Ca2+ distribution and Ca(2+)-ATPase activities in ischemia-tolerant CA1 neurons after the 5-min period of ischemia showed a strong resemblance to those in CA3 neurons, which originally possess resistance to such periods of ischemia. These findings suggest that enhanced or maintained activities of mitochondrial Ca2+ sequenstration and plasma membrane Ca(2+)-ATPase reduced Ca2+ toxicity following 5-min ischemia in terms of time, resulting in escape from delayed neuronal death.

[A 63 year-old man with progressive gait disturbance and dysarthria]

We report a 63-year-old man with progressive gait disturbance and dysarthria. The patient was apparently well until the age of 62 (February, 1990) when he noted unsteadiness of gait. Two months later, dysarthria appeared. He was admitted to Juntendo Izunagaoka Hospital on April 23, 1990. Neurologic examination revealed a mentally sound man with normal higher cerebral functions. Cranial nerves were unremarkable except for scanning speech. His gait was ataxic with positive Romberg sign. No motor weakness was noted, however, he had hypotonia and cerebellar ataxia. Deep tendon reflexes were retained and the plantar response was flexor. Pain, touch and vibration senses were diminished in the distal parts of the lower extremities. Laboratory examination revealed a 2.5 cm mass in the left lung field. Cranial MRI revealed a small T1-low and T2-high signal intensity lesion in the left temporal lobe. Abdominal CT scan revealed multiple low density lesions in the liver. His subsequent course was complicated by progressive deterioration in his gait and loss of deep tendon reflexes. He expired on November 24, 1990. The patient was discussed in the neurological CPC and the chief discussant arrived at the conclusion that the patient had anti-Hu associated paraneoplastic encephalomyelitis and sensory neuropathy. Some other participants thought that the patient had carcinomatous cerebellar degeneration. Postmortem examination revealed a 4x4 cm mass lesion involving the left S4-S5 segments. Histologic examination of the tumor was small cell carcinoma. Many metastatic foci were found in the liver. The cerebral hemispheres were unremarkable except for a small wedge-shaped tissue defect in the left temporal lobe which appeared to have been caused by old head trauma which the patient had received. The cerebellar vermis showed slight enlargement of cortical sulci, however, the cerebellar hemispheres appeared unremarkable. Upon histologic examination, marked loss of Purkinje cells was noted, particularly in the cerebellar anterior lobe. The dentate nucleus showed slight cell loss with increase in fat granule cells. The inferior olive was normal. The histologic characteristics were consistent with the pathologic diagnosis of carcinomatous cerebellar degeneration. No evidence of limbic encephalitis was seen. The peripheral nerve was not examined.

Effects of new endogenous nonprotein amino acids, 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives, on behavior of mice

Several 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acids were synthesized and found to have a transiently increasing effect on the locomotor activity of mice after peripheral injection. Three of the active compounds were detected in the brain after intraperitoneal administration. Two of them, the 7-hydroxy and 7-hydroxy-6-methoxy derivatives, were found as endogenous compounds in untreated rat brain and may play a physiological role. The effects of some of these compounds on the level of various endogenous amines, amino acids and metabolites were examined.

Structural characterization of a novel glycoinositolphospholipid from the parasitic nematode, Ascaris suum

A novel glycosphingolipid containing inositol phosphate as an acidic group has been demonstrated in whole tissues of the porcine roundworm, Ascaris suum. The thin layer chromatographic pattern of the total acidic glycolipid revealed the presence of several components, of which a major component (named AGL) with positive reactions toward both orcinol-sulfuric acid (sugar) and molybdate (phosphate) spray reagents was isolated and purified by the use of successive column chromatography on DEAE-Sephadex and silicic acid (latrobeads). From structural studies including compositional sugar analysis, hydrogen fluoride degradation, methylation analysis, periodate oxidation, proton magnetic resonance spectroscopy and fast atom bombardment mass spectrometry, the structure of AGL was deduced to be Gal alpha 1-2Ins(1-->)-P-Cer. Aliphatic constituents were lignoceric acid and its 2-hydroxy homologue as the principal fatty acids, and octadecasphinganine and branched heptadecasphinganine as the major sphingoids.

[A case of alpha-fetoprotein producing mediastinal germ cell tumor treated with preoperative chemotherapy]

A 20-year-old male was treated with 3 courses of cisplatin combined chemotherapy, with a clinical diagnosis of mediastinal germ cell tumor. Although alpha-fetoprotein (AFP), which alone had been high (893 ng/ml on admission) among tumor markers examined, normalized after chemotherapy, the size of the tumor remained unchanged. The patient underwent total resection of the tumor and has been followed with no evidence of recurrence for 18 months. Pathological examination suggested that the tumor was an immature teratoma with extensive proliferation of fibrous element. Neither other elements of germ cell tumor nor AFP producing cells were found. Preoperative chemotherapy is usually effective in treatment of germ cell tumors. However, it is important to recall that measurements of tumor volume occasionally do not provide information on the tumor's response.

Histamine enhanced the TNF-alpha-induced expression of E-selectin and ICAM-1 on vascular endothelial cells

Cell adhesion molecules are expressed on endothelial cells by various proinflammatory cytokines. Tumor necrosis factor-alpha (TNF-alpha) induces the expression of E-selectin and intercellular adhesion molecule-1 (ICAM-1) on human umbilical vein endothelial cells (HUVEC). Although histamine is a potent vasoactive mediator, it does not induce the expression of E-selectin and ICAM-1. In this report, we show that histamine concentration-dependently enhances the TNF-alpha-induced expression of E-selectin and ICAM-1 on HUVEC. The histamine-enhanced expression of E-selectin and ICAM-1 was inhibited by the histamine H1 receptor antagonists, mepyramine and diphenhydramine. KW-4679 and ketotifen, antiallergic drugs with histamine H1 receptor antagonistic activity, potently inhibit the expression of E-selectin and ICAM-1. A histamine H2 receptor antagonist, ranitidine, did not affect the histamine-induced expression of cell adhesion molecules. These data indicate that histamine induces the expression of E-selectin and ICAM-1 synergistically with TNF-alpha through histamine H1 receptors.

Nonsurgical management of patients with blunt splenic injury: efficacy of transcatheter arterial embolization

OBJECTIVE

We evaluated the efficacy of nonsurgical management of patients with blunt splenic injury using detailed angiographic examinations and transcatheter arterial embolization.

SUBJECTS AND METHODS

We prospectively studied 228 patients who had blunt abdominal injury and for whom CT was performed. When splenic injury was revealed by CT, angiography was performed in all patients except those requiring emergency surgery. Transcatheter arterial embolization was performed when patients had the following angiographic criteria: (1) extravasation of contrast material extending beyond or within the splenic parenchyma, (2) arterial disruption or major arteriovenous fistula, or (3) both. Splenic function was subsequently estimated by 99mTc-sulfur colloid scintigraphy and repeat angiography.

RESULTS

Of 228 patients with blunt trauma, 31 patients had CT evidence of splenic injury. In three of these 31 patients, emergency laparotomy was performed before angiography because of an associated injury or unstable circulatory status. In 13 of the 28 remaining patients, transcatheter arterial embolization was not required as these patients did not meet the necessary criteria. They were treated with bed rest. Transcatheter arterial embolization was performed in the remaining 15 patients and was completely successful in 13. Because one of these 13 patients died of a brain contusion, follow-up angiography and scintigraphy were performed in the remaining 12 patients and showed preservation of splenic function. Nonsurgical treatment of splenic injury with angiography was successful in 93% of patients.

CONCLUSION

Our success rate for nonsurgical management of patients with blunt splenic injury should encourage more extensive evaluation and use of angiography for splenic injury and the subsequent management of splenic injury without surgery.

[Changes in the production of reactive oxygen species from neutrophils following a 100-km marathon]

Recently, the numbers of city marathon runners and joggers have increased. They believe that exercise can enhance their fitness level and health maintenance. However, many researchers have suggested that exhausting exercise may increase the risk of infection and free radical generation. In this study, eight male and ten female city marathon runners who participated in the Akita Nairiku Resort Cup 100-km Challenge Marathon Race were studied using luminol-dependent chemiluminescence (LDCL) to examine the ability of their neutrophils to produce reactive oxygen species. Furthermore, serum opsonic activity using LDCL, serum concentrations of the third and fourth components of the complement (C3, C4), the total number of leukocytes, and proportion of leukocytes were also determined. Evaluation of LDCL was undertaken using the maximum light emission (peak height) and the time to reach the maximum light emission (peak time) in the response curve of LDCL. Following the race, the peak time was prolonged by 11% in males and 15% in females, and the peak height increased by 68% in males and 48% in females. These results suggest that exhausting exercise stimulates neutrophils to produce reactive oxygen species. The total number of leukocytes increased about twofold, whereas the number of neutrophils increased about threefold after the race as compared to before. The rate of the increase in leukocytes was closely associated with that of neutrophils (r = 0.96, P < 0.01). Therefore, the leukocytosis observed in this study was dependent on neutrophilia. Serum opsonic activity and serum concentrations of C3 and C4 were not changed following the race. The increase in the ability of neutrophils to produce reactive oxygen species and neutrophilia after the race, suggests that a large quantity of reactive oxygen species may be produced in vivo following exhausting exercise.

Usefulness of thallium-201 single photon emission computed tomography to quantify the malignancy grade of brain tumors

Preoperative thallium-201 (201Tl) single photon emission computed tomography (SPECT) was used to evaluate the histological malignancy in 24 patients with brain tumors. A corrected L/E ratio was calculated based on the ratio of thallium uptake in the tumor on early images versus the tumor in the delayed images (L/E ratio) corrected for thallium uptake in the contralateral cerebral hemisphere. The corrected L/E ratio in benign brain tumors was 0.79 +/- 0.23, significantly different to 1.32 +/- 0.25 in high grade astrocytomas (p < 0.01) and 1.19 +/- 0.05 in metastatic brain tumors (p < 0.01), respectively. The corrected L/E ratio in low grade astrocytomas was 0.64 +/- 0.32, significantly lower than that in high grade astrocytomas (p < 0.01) and metastatic brain tumors (p < 0.05). There was one false positive result among 24 patients using a threshold of 1.0 to separate malignant and benign tumors. 201Tl SPECT using the corrected L/E ratio is effective for determining the malignant viability of tumors.

[Limited operation and simple lobectomy for primary lung cancer in poor risk patients]

During the years 1990 to 1994, 54 poor risk patients were performed relative noncurative operation for primary lung cancer, such as limited operation or lobectomy without mediastinal lymphnodal dissection. The indication for lesser resection were mainly cardiopulmonary diseases and the elderly over 75 years old. 3 were bilobectomies, 32 were lobectomies, 1 was lobectomy and segmentectomy, 10 were segmentectomies, 8 were wedge resections. The number of cases with stage I were 41 (75.9%). Postoperative complications occurred in 13 patients (24.1%). The overall 5-year survival rate was 63.5%. The 5-year survial rate of p 0 approximately p 1, pN 0 cases was 73.9%. Relative noncurative cases undergoing lesser resection showed relatively good result compared to standard lobectomy. It was considered that lesser resection for such poor risk patients with stage I can be a beneficial therapeutic modality.

Successful percutaneous transluminal angioplasty for basilar artery stenosis: technical case report

OBJECTIVE

We report our experience with low-pressure submaximal percutaneous transluminal angioplasty (PTA) for basilar artery stenosis of > 90%. This treatment resulted in a favorable clinical course and satisfactory improvement of posterior cerebral circulation.

CLINICAL PRESENTATION

This technique was applied to two patients with repeated basilar arterial ischemic symptoms that were resistant to medical treatment.

INTERVENTION

Low-pressure submaximal PTA was performed with use of a smaller balloon (2.0-mm diameter) and lower inflation pressure (< or = 303,975 Pa) than previously reported.

RESULTS

Despite basilar arteries with 50 and 60% residual stenosis, the clinical symptoms and hemodynamics in the basilar arterial territory as assessed using single photon emission tomography were markedly improved after PTA. Follow-up angiographic evaluation demonstrated the absence of restenosis, and improved cerebral blood flow was maintained. Neither patient has developed any new neurological deficits 10 and 13 months after the PTA, respectively.

CONCLUSION

Submaximal PTA may have reduced the high risk associated with this procedure, and cerebral blood flow measurement may be a useful tool to assess whether this technique will produce adequate results.

Biochemical characterization of a Pseudomonas fluorescens strain isolated from a benzalkonium chloride solution

A bacterium isolated as the contaminant of a batch of commercial benzalkonium chloride (BAC) solution (10% (w/v)) stored in a loosely capped bottle in the Department of Pharmacy Shinshu University Hospital was identified as Pseudomonas fluorescens belonging to biotype G of Stanier, et al. The strain was highly resistant to BAC, and the lowest concentration of BAC that inhibited visible growth of the strain as measured on nutrient agar plates was > or = 5000 micrograms/ml. BAC is a typical quaternary ammonium detergent. Thus we examined the tolerable growth concentration of various strains on surfactants. We were able to confirm growth of P. fluorescens of BAC resistance strain (PFRB) in 5% concentration, but the other strains were not able to grow in 0.1% concentration. We investigated the relationship between biotype and resistance to BAC. PFRB and three clinical isolated strains were found to be the same biotype G. However, no apparent correlation was found between the same biotypes and minimum inhibitory concentration (MIC) of disinfectant or growth permissible concentration on surfactants. The strain was unable to decompose BAC, as no growth occurred in the minimum medium containing BAC as the sole source of carbon, nitrogen or both. Our finding caused us to realize that P. fluorescens might also be a contaminant of disinfectants, as we have seen in Pseudomonas cepacia.

High efficiency transformation of maize (Zea mays L.) mediated by Agrobacterium tumefaciens

Transformants of maize inbred A188 were efficiently produced from immature embryos cocultivated with Agrobacterium tumefaciens that carried "super-binary" vectors. Frequencies of transformation (independent transgenic plants/embryos) were between 5% and 30%. Almost all transformants were normal in morphology, and more than 70% were fertile. Stable integration, expression, and inheritance of the transgenes were confirmed by molecular and genetic analysis. Between one and three copies of the transgenes were integrated with little rearrangement, and the boundaries of T-DNA were similar to those in transgenic dicotyledons and rice. F1 hybrids between A188 and five other inbreds were transformed at low frequencies.

An additional form of rat Bcl-x, Bcl-xbeta, generated by an unspliced RNA, promotes apoptosis in promyeloid cells

The bcl-2 oncogene product delays apoptotic cell death and prolongs the cell survival. We cloned two bcl-2-related cDNAs from a rat thymus cDNA library by low stringency hybridization with a rat bcl-2 fragment as a probe. One of these, designated bcl-xalpha, was a counterpart of the human bcl-xL reported previously as a bcl-2-related gene (Boise, L. H., Gonzalez-Garcia, M., Postema, C. E. , Ding, L., Lindsten, T., Turka, L. A., Mao, M., Nunez, G., and Thompson, C. B. (1993) Cell 74, 597-608). The other, designated bcl-xbeta, was novel and found to be generated by an unspliced mRNA, whereas bcl-xalpha was generated from a spliced transcript. The splice junction exactly corresponded to that found in the bcl-2 gene. bcl-xbeta was specifically expressed in cerebellum, heart, and thymus. When bcl-xbeta directed by a strong promoter was introduced into an interleukin-3-dependent promyeloid cell line, FDC-P1, DNA fragmentation was observed even in the growing state in the presence of interleukin-3 although not in the control transfectants. This finding suggests that the rat bcl-xbeta gene product promotes apoptosis in the promyeloid cells.