Translocation (8;12;21)(q22.1;q24.1;q22.1): a new masked type of t(8;21)(q22;q22) in a patient with acute myeloid leukemia

The translocation t(8;21)(q22;q22) is found in 40% of cases of acute myeloid leukemia (AML) designated as the subtype M2 in the French-American-British (FAB) classification. The 8;21 translocation is clinically of interest because patients with this subtype have a good prognosis. We describe a masked type of the translocation, t(8;12;21)(q22.1;q24.1;q22.1). The translocation was first interpreted as t(8;12)(q22;q24) based on cytogenetics, but was reevaluated as a result of Southern blot and fluorescence in situ hybridization (FISH) analyses.

Displacement of the double-lumen endobronchial tube can be detected by bronchial cuff pressure change

We measured the bronchial cuff pressure of left-sided double-lumen endobronchial tubes (DLTs) in 54 patients to confirm the effect of DLT displacement on cuff pressure. After positioning the cephalad surface of the bronchial cuff of the DLT 2.5 cm distal to the carina (23 patients in the first part of the study) or just below the carina (23 patients in the second part), the cuff was withdrawn in 0.5-cm steps during right-sided, one-lung ventilation. The bronchial cuff pressure was measured, and the capnogram and pressure-volume loop, displayed by a side-stream spirometer, was evaluated. After positioning the cephalad surface of the bronchial cuff just below the carina (eight patients in the third part), bronchial cuff pressure was measured while confirming the position of the bronchial cuff during the 30 min of the operative procedure. The bronchial cuff pressure decreased significantly by 28.4 cm H2O (P < 0.01) and 21.3 cm H2O (P < 0.01) in the first and second parts, respectively, before the pressure-volume loop or the capnogram changed. The bronchial cuff pressure in the third part showed no significant change. We conclude that bronchial cuff pressure monitoring was very helpful in detecting displacement of the DLT during right-sided, one-lung ventilation.

Increased levels of IL-13 mRNA, but not IL-4 mRNA, are found in vivo in peripheral blood mononuclear cells (PBMC) of patients with atopic dermatitis (AD)

Previous studies using in vitro systems with various stimuli have shown that PBMC from patients with AD show increased levels of IL-4 but decreased levels of interferon-gamma (IFN-gamma) compared with PBMC from normal controls. However, in vitro conditions do not always mimic the in vivo condition. We therefore believe that it is important to quantify the expression of these cytokines in freshly isolated PBMC. This study examines the expression of IFN-gamma, IL-4 and IL- 13 mRNA in freshly isolated PBMC from adult patients with AD, from patients with psoriasis vulgaris and from healthy adults, using the semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method. Levels of IFN-gamma mRNA were significantly lower in PBMC of patients with AD than in controls. IL-4 mRNA levels did not differ significantly between groups. Conversely, levels of mRNA for IL-13 were significantly greater in PBMC of patients with AD than in controls. An increase in IL-13 expression may regulate the in vivo synthesis of IgE in patients with AD.

Volatile anaesthetics attenuate hypocapnia-induced constriction in isolated dog cerebral arteries

PURPOSE

Hypocapnia causes cerebral arterial constriction, whereas volatile anaesthetics cause dilatation. The purpose of this study was to compare the direct effects of halothane, isoflurane and sevoflurane on hypocapnia-induced constriction of isolated cerebral arteries in vitro.

METHODS

Basilar and middle cerebral arteries of mongrel dogs (n = 11) were cut into rings and mounted for isometric tension recording in organ baths containing Krebs' bicarbonate solution, aerated with CO2 5% and O2 95% at 37 degrees C. After constriction with 20 mM KCl, hypocapnia was induced by replacing the aerating gas with CO2 2.5% and O2 97.5% in the presence or absence of anaesthetics.

RESULTS

Exposure of cerebroarterial rings to the hypocapnic gas produced sustained vasoconstriction (418 +/- 19 mg), reaching a plateau within 10 to 15 min. Halothane (0.5, 1, 2 MAC) attenuated the hypocapnia-induced constriction (P < 0.05). In contrast, isoflurane and sevoflurane attenuated this constriction only at 2 MAC (P < 0.05). Attenuation by halothane was greater than that by isoflurane or sevoflurane at each concentration (P < 0.05). NG-nitro-L-arginine (3 x 10(-5) M) did not alter the contractile response to hypocapnia. When a similar degree of constriction was induced by addition of 10 mM KCl, halothane (1 and 2 MAC) preferentially attenuated the constriction induced by hypocapnia to a greater extent than that induced by 10 mM KCl (P < 0.01).

CONCLUSION

Hypocapnia-induced vasoconstriction of isolated dog cerebral arteries precontracted with KCl is more susceptible to halothane than isoflurane or sevoflurane. This may account for the greater increase in cerebral blood flow during halothane than isoflurane or sevoflurane anaesthesia.

Different effects of halothane, isoflurane and sevoflurane on sarcoplasmic reticulum of vascular smooth muscle in dog mesenteric artery

BACKGROUND

The direct effect of halothane on vascular smooth muscle is mediated in part via its effects on the sarcoplasmic reticulum (SR). Little information is available concerning the effects of other volatile anesthetics including isoflurane and sevoflurane, whose vascular effects differ from those of halothane. The aim of the present study was to compare the effects of halothane, isoflurane and sevoflurane on the SR by testing the contraction induced by caffeine in vascular smooth muscle.

METHODS

Rings without endothelium from isolated canine mesenteric artery were mounted in physiological saline solution (PSS) for isometric tension recording. After complete depletion of Ca2+ from the SR by adding 35 mM caffeine, the rings were exposed to normal Ca2+ containing PSS (Ca2+ loading), to Ca(2+)-free PSS for 10 min, and then to 15 mM caffeine to induce contraction. Anesthetics were administered during Ca2+ loading, the Ca(2+)-free phase and simultaneously with caffeine administration.

RESULTS

Halothane (0.5-2%) attenuated the caffeine-induced contraction of canine mesenteric artery when administered during Ca2+ loading in the SR (P < 0.001), whereas isoflurane and sevoflurane (1-4%) failed to affect the contraction. When given simultaneously with caffeine, halothane (1-2%) potentiated the caffeine-induced contraction (P < 0.05), but isoflurane and sevoflurane had no effect. When given before caffeine administration, halothane (0.5-2%), isoflurane (2-4%) and sevoflurane (4%) all potentiated the caffeine-induced contraction (P < 0.05).

CONCLUSION

It has been shown that halothane not only potentiates caffeine-induced Ca2+ release from the SR, but also induces contraction by releasing Ca2+ from the SR. We conclude that halothane decreases Ca2+ accumulation in the SR while exerting facilitative and additive effects on caffeine-induced Ca2+ release from the SR when applied before caffeine administration and simultaneously with caffeine, respectively, whereas isoflurane and sevoflurane lack both the ability to decrease Ca2+ accumulation and an additive effect on caffeine-induced Ca2+ release from the SR, but are able to facilitate Ca2+ release by caffeine.

[Antiemetic efficacy of granisetron in repeated CAF chemotherapy after breast cancer operation]

The antiemetic efficacy of granisetron in repeated CAF chemotherapy after breast cancer operation was investigated. Twenty-three patients who were treated with repeated CAF chemotherapy after breast cancer operation received drip-infused granisetron (3 mg/body) to prevent nausea and vomiting. Antiemetic efficacy was evaluated by means of the severity of nausea and the frequency of vomiting. The antiemetic efficacy rate of the drug was 74.4%. However, the average rate of antiemetic efficacy was 86.9% on the first through the sixth administration of the chemotherapy (first period). 75.9% on the seventh through the twelfth (second period), 48.4% on the thirteenth through the eighteenth (third period), and 31.8% on the nineteenth through the twenty-fourth (fourth period). There were significant differences in the antiemetic efficacy rate among the first, second and third periods. The antiemetic efficacy of granisetron decreased significantly by repeated CAF chemotherapy.

Sevoflurane inhibits human platelet aggregation and thromboxane A2 formation, possibly by suppression of cyclooxygenase activity

BACKGROUND

Halothane increases bleeding time and suppresses platelet aggregation in vivo and in vitro. A previous study by the authors suggests that halothane inhibits platelet aggregation by reducing thromboxane (TX) A2 receptor-binding affinity. However, no studies of the effects of sevoflurane on platelet aggregation have been published.

METHODS

The effects of sevoflurane, halothane, and isoflurane were examined at doses of 0.13-1.4 mM. Human platelet aggregation was induced by adenosine diphosphate, epinephrine, arachidonic acid, prostaglandin G2, and a TXA2 agonist ([+]-9, 11-epithia-11, 12-methano-TXA2, STA2) and measured by aggregometry. Platelet TXB2 levels were measured by radioimmunoassay, and the ligand-binding characteristics of the TXA2 receptors were examined by Scatchard analysis using a [3H]-labeled TXA2 receptor antagonist (5Z-7-(3-endo-([ring-4-[3H] phenyl) sulphonylamino-[2.2.1.] bicyclohept-2-exo-yl) heptenoic acid, [3H]S145).

RESULTS

Isoflurane (0.28-0.84 mM) did not significantly affect platelet aggregation induced by adenosine diphosphate and epinephrine. Sevoflurane (0.13-0.91 mM) and halothane (0.49-1.25 mM) inhibited secondary platelet aggregation induced by adenosine diphosphate (1-10 microM) and epinephrine (1-10 microM) without altering primary aggregation. Sevoflurane (0.13 mM) also inhibited arachidonic acid-induced aggregation, but not that induced by prostaglandin G2 or STA2, although halothane (0.49 mM) inhibited the latter. Sevoflurane (3 mM) did not affect the binding of [3H]S145 to platelets, whereas halothane (3.3 mM) suppressed it strongly. Sevoflurane (0.26 mM) and halothane (0.98 mM) strongly suppressed TXB2 formation by arachidonic acid-stimulated platelets.

CONCLUSIONS

The findings that sevoflurane suppressed the effects of arachidonic acid, but not those of prostaglandin G2 and STA2, suggest strongly that sevoflurane inhibited TXA2 formation by suppressing cyclooxygenase activity. Halothane appeared to suppress both TXA2 formation and binding to its receptors. Sevoflurane has strong antiaggregatory effects at subanesthetic concentrations (greater than 0.13 mM; i.e., approximately 0.5 vol/%), whereas halothane has similar effects at somewhat greater anesthetic concentrations (0.49 mM; i.e., approximately 0.54 vol/%). Isoflurane at clinical concentration (0.84 mM; i.e., approximately 1.82 vol/%) does not affect platelet aggregation significantly.

A beta-adrenoceptor agonist evokes a nitric oxide-cGMP relaxation mechanism modulated by adenylyl cyclase in rat aorta. Halothane does not inhibit this mechanism

BACKGROUND

The objective of this study was to characterize the effects of halothane on the agonist-induced nitric oxide-cyclic GMP (NO-cGMP) mechanisms by comparing the intracellular signal transduction mediating isoproterenol- and acetylcholine-induced nitric oxide formation.

METHODS

Isoproterenol-induced relaxations of rat aortic rings with and without endothelia were examined in the absence and presence of halothane. Studies were also done in the presence of inhibitors of nitric oxide-synthase, adenylyl cyclase, calmodulin, protein kinase A, and intracellular Ca2+ release mechanism. The relaxations under some of these conditions were compared with those induced by acetylcholine. Cyclic nucleotide contents of the rings were also measured.

RESULTS

Isoproterenol relaxed aortic rings via the endothelium-dependent nitric oxide-cyclic GMP mechanism. Inhibition of adenylyl cyclase or of protein kinase A attenuated the isoproterenol-induced relaxations significantly but did not affect those induced by acetylcholine. Inhibition of intracellular Ca2+ release abolished the acetylcholine-induced relaxations but did not affect those induced by isoproterenol. Calmodulin inhibition attenuated both agonist-induced relaxations significantly. Unlike acetylcholine-induced relaxation, that induced by isoproterenol was not affected by halothane. Isoproterenol increased both the cyclic adenosine monophosphate and cGMP contents of rings significantly when endothelia were intact. Inhibition of nitric oxide synthase attenuated the isoproterenol-induced cGMP content increases significantly but did not affect the cyclic adenosine monophosphate content increases. Halothane (2%) did not affect isoproterenol-induced increases in nucleotide content.

CONCLUSIONS

Isoproterenol-induced nitric oxide formation requires the activation of constitutive nitric oxide synthase, but the Ca2+ release mechanism is not involved in activating this enzyme. Halothane can inhibit the nitric oxide-cyclic GMP mechanism only when Ca2+ release is greatly involved in the activation of constitutive nitric oxide synthase.

Protective effects of human urinary trypsin inhibitor against trypsin-induced relaxation in rat aorta

OBJECTIVES

To investigate the vasodilatory responses induced by trypsin, and to determine the antitrypsin effects of human urinary trypsin inhibitor on blood vessels.

DESIGN

Prospective, randomized, controlled study, with repeated measurements.

SETTING

University research laboratory.

INTERVENTIONS

The isometric tension of the aortic rings isolated from male Wistar rats was recorded. The vasodilatory responses to varying amounts of trypsin (0.01 to 10 U/mL) were examined under pretreatment with human urinary trypsin inhibitor (1 to 10 U/mL), chicken-egg-white trypsin inhibitor (0.1 to 10 mg/mL), N infinity-nitro-L-arginine (3 x 10(-5) M), and denudation of the endothelium. In addition, with the scanning electron microscopy, the endothelium of aorta was examined under treatment with trypsin alone (10 U/mL), and with trypsin plus human urinary trypsin inhibitor (10 U/mL each).4

MEASUREMENTS AND MAIN RESULTS

The addition of trypsin produced dose-dependent relaxation in aortic rings with an intact endothelium, which was abolished by denudation and treatment with N infinity-Nitro-L-arginine. Pretreatment with human urinary trypsin inhibitor and with chicken-egg-white trypsin inhibitor caused dose-dependent inhibition against trypsin-induced vasorelaxation. On the repeated trials of the response to trypsin, the responses gradually developed tachyphylaxis in control aortic rings, whereas no tachyphylaxis developed in rings pretreated with human urinary trypsin inhibitor (10 U/mL). Scanning electron microscopy demonstrated endothelial disruption in aorta exposed to trypsin alone, whereas the endothelium was intact in strips treated with trypsin plus human urinary trypsin inhibitor.

CONCLUSIONS

The data indicate that relaxation induced by trypsin is attributable to nitric oxide released from the endothelium, and that human urinary trypsin inhibitor protects vessels against trypsin-induced endothelial injury. It appears that the clinical antishock effect of human urinary trypsin inhibitor is ascribable in part to its antitrypsin activity on the endothelium of vascular smooth muscle.

Electron microscopic observations of aberrant capsids of pseudorabies virus

Interactions between four strains of pseudorabies virus (PrV) and seven kinds of cell lines were examined. Three kinds of cells (SKL, CPK and PK-15) were especially infected with PrV at an MOI of about 10 PFC/cell. At sequential intervals after infection, cells of these types were collected for electron microscopic observations and the infectious doses of culture fluids were assayed. Developmental features of PrV were found to be very similar to those of herpes simplex virus (HSV), with the slight difference that PrV developed a little earlier and more vigorously than did HSV. At the late stage of infection, aberrant capsids of PrV were observed frequently in the nucleus of SKL but rarely in the nuclei of CPK and PK-15. The titer of infectious virus produced by SKL was much larger than that produced by CPK and PK-15. Immuno-electron microscopic examination using a monoclonal antibody against the major capsid protein of PrV clearly demonstrated that the complete and aberrant capsids have a common epitope. The mechanism of the formation of aberrant capsids is discussed.

Translocation (9;11;22)(p22;q23;q11). A new type of complex variant translocation of t(9;11)(p22;q23) with MLL rearrangement

We describe a patient with acute monocytic leukemia (M5a, FAB classification) associated with a new type of variant translocation (9;11). Southern blot analysis showed the rearrangement of the MLL (ALL-1/HRX) gene at 11q23. Fluorescence in situ hybridization (FISH) with painting probes of chromosomes 9, 11, and 22 revealed the translocation as t(9;11;22) (p22;q23;q11). This is more evidence that the production of chimeric mRNA following the translocation of the LTG9 (MLLT3/AF9) gene at 9p22 to 11q is a critical event in this leukemia subtype.

Adenomyoepithelioma of the Breast: A Case Reprot and a Review of Literature

A 74-year-old woman complained of a small nodule in the outer lower quadrant of her left breast. On physical examination, a 0.9 x 0.8 cm, round-shaped and firmly elastic nodule was palpated. Excisional biopsy was performed. Histologically, the tumor was separated into, with a bicellular pattern, containing both numerous glandular structures and numerous spindle-shaped cells. Immunohistochemical staining for EMA and cytokeratin showed strongly positive immunoreactivity for epithelial cells. Staining for &aipha;-SMA showed strongly positive immunoreactivity for myoepithelial components. Staining for keratin and S-100 protein showed weakly positive immunoreactivity for myoepithelial cells. Microscopically, the tumor was diagnosed as adenomyoepithelioma of the breast. Immunohistochemical examination is needed to distinguish epithelial cell proliferation from myoepithelial cell proliferation. Immunohistochemical examination using antibodies against EMA, alpha-SMA, Keratin, cytokeratin and S-100 protein, is indispensable.

Nicergorine-induced lichen planus-like eruption

A case of a lichen planus-like eruption due to nicergorine on the lower legs of an 84-year-old woman is reported. She presented with slightly pruritic, erythematous plaques of six months' duration. She had taken eight kinds of drugs, including nicregorine for cerebral arteriosclerosis, for two years. After nicergorine was discontinued, the eruption gradually disappeared. Readministration of nicergorine induced a similar eruption within two months. Histologic findings were identical in the two biopsy specimens obtained at the first visit and from the recurrent lesion. To our knowledge, this is the first report on nicergorine-induced lichen planus-like eruptions.

Combined dorsal forearm and lateral arm flap

The free latissimus dorsi musculocutaneous flap and the free groin flap have been used for the coverage of medium- to large-sized soft-tissue defects in the hand. However, these are often too bulky for the hand, requiring secondary operation for thinning. We have used the dorsal forearm flap combined with the lateral arm flap for the coverage of large soft-tissue defects in the hand. This flap is based on the reversed vascular pedicle of the posterior interosseous artery. The posterior radial collateral branch of the profunda brachii artery is then anastomosed to the recipient vessel to augment the vascular supply to the lateral arm flap. We have used this combination flap in two clinical cases and achieved one-stage soft-tissue reconstruction of the hand.

Endothelium-dependent and -independent vasodilation of isolated rat aorta induced by caffeine

Caffeine (10(-4)-10(-3) M) induced concentration-dependent relaxations of phenylephrine-precontracted rat aortic rings with endothelium. Endothelial denudation significantly, but only partially, attenuated caffeine-induced relaxation. Pretreatment with NG-nitro-L-arginine, oxyhemoglobin, and methylene blue attenuated the relaxations to an extent similar to endothelial denudation. Guanosine 3',5'-cyclic monophosphate (cGMP) and adenosine 3',5'-cyclic monophosphate (cAMP) contents of aortic strips with endothelium increased significantly after exposure to caffeine (10(-3) M). Endothelial denudation attenuated caffeine-induced cGMP increase. Pretreatment with ryanodine (2 x 10(-5) M), which has been shown to combine with receptors on endoplasmic reticulum (ER) of endothelium, attenuated caffeine-induced relaxation and cGMP content increase of rings with endothelium. Pretreatment with caffeine potentiated sodium nitroprusside-induced relaxations and cGMP increase of rings without endothelium. These results demonstrated that caffeine-induced relaxation comprises two components. In the endothelium-dependent mechanism, caffeine promotes nitric oxide synthesis in endothelium by release of Ca2+ from ER through a ryanodine-sensitive Ca2+ channel, and the suppression of cGMP degradation also contributes to the relaxation. In the endothelium-independent mechanism, caffeine acts as a 3',5'-cyclic-nucleotide phosphodiesterase inhibitor.

Granulocyte colony-stimulating factor downregulates allogeneic immune responses by posttranscriptional inhibition of tumor necrosis factor-alpha production

We report downregulatory effects of granulocyte colony-stimulating factor (G-CSF) on allogeneic immune responses in vitro. G-CSF did not affect the proliferative response of peripheral blood mononuclear cells (PBMC) against allogeneic Daudi cells but did inhibit tumor necrosis factor (TNF)-alpha secretion. In contrast with G-CSF, granulocyte-macrophage (GM)-CSF and interleukin (IL)-3 enhanced alloactivation-induced TNF-alpha production. G-CSF-mediated suppression of TNF-alpha production was not affected by fixation of stimulators. G-CSF did not inhibit TNF-alpha mRNA expression or accelerate mRNA degradation, whereas pentoxifylline inhibited the expression of TNF-alpha mRNA. These results indicate that G-CSF acts directly on responder cells and modulates TNF-alpha production at posttranscriptional levels. Suppression of TNF-alpha secretion was accompanied by an increase of intracellular cyclic adenosine monophosphate (cAMP) concentration in alloactivated PBMC. The cell-permeable cAMP analogue, dibutyryl cAMP, suppressed TNF-alpha secretion without affecting TNF-alpha mRNA expression. G-CSF showed an inhibitory effect on the development of cytotoxic effector cells against allogeneic Daudi cells. Anti-TNF-alpha monoclonal antibody (MoAb) also inhibited the induction of cytolytic activity, and the inhibitory effects of G-CSF and anti-TNF-alpha MoAb on killer activity generation were overcome by adding exogenous TNF-alpha. Hence, impaired generation of cytolytic effector cells by G-CSF is believed to be the result of reduced TNF-alpha production. Collectively, the results described above suggest that G-CSF downregulates allogeneic immune responses by posttranscriptionally inhibiting TNF-alpha production.

Analysis of molluscum contagiosum virus genomes isolated in Japan

The genomes of 477 Japanese strains of molluscum contagiosum virus (MCV) were analyzed using an in-gel digestion method with the restriction enzyme BamHI, and classified into four types, including a newly detected type (MCV type 4). All type 1 (MCV-1) genomes examined so far in Japan showed a common difference from the genome of the MCV-1 prototype (MCV-1p), the type reported to be most prevalent in Europe. The common markers of the variants of MCV-1 were 24-kbp fusion fragments generated by the loss of a BamHI site between the D2 and F fragments of MCV-1p. These variants of MCV-1 were classified into three groups (MCV-1va, MCV-1vb, MCV-1vc), with the variability among them being due to additions and losses of BamHI sites located in the right terminus and around the E and I fragments of MCV-1va. The restriction map of MCV-4 was generated and lined up with those of the other types. Cross-hybridization analysis revealed that the organization of all types of MCV genomes were essentially colinear. Considerable numbers of BamHI restriction sites were conserved between MCV-2 and 4, indicating a close analogy between them. The overall prevalence of MCV, as shown by the ratios of MCV-1 (MCV-1p):MCV-2:MCV-3:MCV-4, was 436(0):13:24:4. Thus, the molecular epidemiology of MCV in Japan is characterized by the absence of the European prototype of MCV-1, the exclusive occurrence and abundance of variants of MCV-1, a greater prevalence of MCV-3 over MCV-2, and the presence of MCV-4.

The effect of inhaled anesthetics on the platelet aggregation and the ligand-binding affinity of the platelet thromboxane A2 receptor

The mechanism by which anesthetics suppress platelet aggregation has not been elucidated. We determined the effects of halothane, enflurane, and isoflurane on human platelet aggregation induced by adenosine diphosphate (ADP), epinephrine, and a thromboxane A2 (TXA2) analog, and on ligand binding to the platelet TXA2 receptor. Halothane (2.6 mM) strongly suppressed ADP- and epinephrine-induced secondary aggregation of platelets, without significant alteration of primary aggregation. Platelet aggregation induced by a specific TXA2 agonist, (+)-9,11-epithia-11,12-methano-TXA2 (STA2), was suppressed by halothane, enflurane, and isoflurane in a concentration-dependent manner; the concentration of halothane, enflurane, and isoflurane which induced 50% inhibition (IC50) were 3.2, 12.3, and 15.7 mM, respectively (or 4.7, 9.8, and 24 minimum alveolar anesthetic concentration [MAC], respectively). The binding of a specific TXA2 receptor antagonist, 3H-S145, was significantly reduced by halothane (14-28 mM), but not by enflurane (20 mM) and isoflurane (20 mM). Scatchard analysis revealed that halothane (14 mM) increased Kd from 0.53 nM to 14.3 nM but did not alter Bmax significantly. These results indicate that halothane has a stronger suppressive effect on platelet aggregation than enflurane and isoflurane, and that the effect of halothane on platelet aggregation is due to reduction of the ligand-binding affinity of the platelet TXA2 receptor.

cDNA cloning of BR gamma, a novel brain-specific isoform of the B regulatory subunit of type-2A protein phosphatase

A cDNA clone for a novel isoform of the B regulatory subunit of type 2A protein phosphatase (BR) was isolated from a rat brain cDNA library by hybridization under low-stringency conditions with the BR beta cDNA fragment as a probe. The novel cDNA encodes a protein of 447 amino acids. The identities of amino acid sequences of the novel isoform with those of rat BR alpha and BR beta were 80% and 85%, respectively, with a unique sequence at the C-terminal. Since this isoform is thought to be encoded by a third gene for the B regulatory subunit, it was named BR gamma. The mRNA for BR gamma was 4.2 kb. The expression level of BR gamma was high in the brain and spinal cord of rats, and its expression was also detected in mouse and human brains, but in contrast to BR beta, it was not detected in the testes of rats or mice. Thus BR gamma is though to be a brain-specific isoform of the B regulatory subunit.