Synapse formation in dissociated cell cultures of embryonic chick cerebral neurons

The development of synapses was confirmed in the primary cultures of dissociated cerebral cortex neurons from chick embryos. Whole-cell patch clamp recording applied to dissociated neurons from 6- to 12-day-old embryos revealed that these neurons form functional synapses. In these cultures, both excitatory and inhibitory postsynaptic responses were observed. Synaptogenesis in our cultures seemed to be in proportion to the embryonic equivalent days, which are the sum of the days in incubation and culture.

Vitrification of mouse oocytes and embryos at various stages of development in an ethylene glycol-based solution by a simple method

Mouse oocytes and embryos at various developmental stages were exposed directly to an ethylene glycol-based vitrification solution (EFS) for 2 or 5 minutes at 20 degrees C. They were then vitrified at -196 degrees C and were warmed rapidly. At the germinal vesicle stage, the proportion of morphologically normal oocytes was 36 to 39% if they had cumulus cells, whereas in cumulus-removed immature oocytes and in ovulated oocytes it was only 2 to 4%. This low survival was attributed to the harmful action of ethylene glycol. After fertilization, on the other hand, the post-warming survival rate of 1-cell zygotes, as assessed by cleavage to the 2-cell stage, increased markedly (62%). As the developmental stage proceeded, higher proportions of vitrified embryos developed to expanded blastocysts; the rates increased up to 77 and 80% in 2-cell and 4-cell embryos, respectively. For embryos at the 8-cell, morula and early blastocyst stages, the proportion of embryos developed after vitrification (90 to 95%) was not significantly different from that of the untreated embryos (95 to 100%) when the period of exposure to EFS solution was 2 minutes. As the blastocoel began to enlarge, however, survival began to decrease again, with rates of 79 and 57% in blastocysts and expanded blastocysts, respectively. After the cryopreserved 2-cell, 4-cell and 8-cell embryos as well as morulae and blastocysts were transferred to recipients, 43 to 57% of the recipients became pregnant, and 48 to 60% of these various stage embryos developed into live young.

Membrane properties of identified guinea-pig paraventricular neurons and their response to an opioid mu-receptor agonist: evidence for an increase in K+ conductance

Intracellular recordings were obtained from neurons in the paraventricular nucleus (PVN) of guinea-pig hypothalamic slices. Passive and active properties of the neurons were determined, and when possible, recorded neurons were injected with biocytin. The effects of a mu-receptor opioid agonist [D-Ala2, Nme-Phe4, Gly5-ol]enkephalin (DAGO) were studied in order to determine which types of cells have mu receptors and to test the hypothesis that an increase in K+ conductance causes mu-receptor-mediated inhibition in the PVN. The recorded cells inside the PVN were divided into two groups, primarily on the basis of the presence or absence of a low threshold Ca2+ spike (LTS). In one group of neurons, LTS potentials could not be evoked (non-LTS cells, n = 42). In another group of neurons (n = 35), LTS potentials with one or two Na+ spikes could be initiated with depolarizing pulses superimposed on steady hyperpolarizing currents; however, these neurons did not fire robust bursts (i.e. non-bursting LTS cells). The mean time constant of non-LTS cells (19.9 +/- 1.6 ms; mean +/- SEM) was significantly shorter than that of non-bursting LTS cells (26.7 +/- 2.1 ms). There were no differences in the mean resting membrane potential, spike amplitude, spike duration, input resistance, spike threshold and pattern of synaptic inputs between the two groups. Intracellular labeling with biocytin combined with cresyl violet counter-staining demonstrated that the two types of cells were located in the PVN.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone marrow transplantation for hematological diseases in Hokkaido--June 1985 to December 1991

Bone marrow transplantation (BMT) was started in Hokkaido in 1985. In the present report we have reviewed the clinical outcome of patients treated with BMT for hematological diseases in Hokkaido. Fifty-eight allogeneic and 19 autologous transplants were registered by December 1991. The underlying diseases consisted of 47 leukemias, 14 lymphomas, 10 aplastic anemias and six myelodysplastic syndromes. Among the allogeneic BMT cases, 55 were human leucocyte antigen (HLA) identical and three were mismatched. Among the autologous BMT patients, two received their marrow purged with 4-hydroperoxycyclophosphamide and five, with monoclonal antibodies and complements. The conditioning regimens used for malignancies were chiefly cyclophosphamide (CY) plus total body irradiation, or busulfan plus CY. In many cases, cytokines were used for rapid recovery of decreased leukocytes. Engraftment was observed in 50 out of 52 evaluated allogeneic and 18 out of 19 autologous transplants. Ten allogeneic patients suffered from severe acute graft-versus-host diseases (GVHD), and extensive chronic GVHD appeared in 16 patients. Relapses were observed in four cases of allogeneic BMT and six of autologous BMT. The major complications were interstitial pneumonitis (IP) and severe infections. Long-term survival rates were almost 60% in both allogeneic and autologous transplants. Mild acute GVHD and limited chronic GVHD increased the survival rates. The results indicated that substantial problems such as GVHD, IP and relapses must be controlled in the near future for an improved outcome to be made possible.

Cryopreservation of expanded mouse blastocysts by vitrification in ethylene glycol-based solutions

Experiments were conducted to find optimal conditions for obtaining high survival of expanded mouse blastocysts after vitrification. The vitrification solutions used were designated EFS20, EFS30 and EFS40, and contained 20%, 30% and 40% ethylene glycol, respectively, diluted in PB1 medium containing 30% Ficoll plus 0.5 mol sucrose l-1. In the toxicity test of the solutions and each cryoprotectant, ethylene glycol was found to be toxic to embryos. For vitrification, expanded blastocysts were exposed to the vitrification solutions at 10, 20 or 25 degrees C for various periods; they were then cooled rapidly in liquid nitrogen, after which they were warmed rapidly. When the embryos were directly exposed to EFS40 at 20 degrees C for 2 min before vitrification, 66% of them re-expanded during 48 h of post-warming culture. The re-expansion rates decreased when exposure time was shortened (0.5 min), when exposure temperature was lowered (10 degrees C), or when embryos were vitrified in EFS20 and EFS30, although these conditions should be less toxic. When embryos had been pretreated in a dilute (10-20%) ethylene glycol solution for 5 min, followed by short exposure (0.5 min) to EFS40 at 20 degrees C, post-vitrification survival rate increased to 83-84%; furthermore, the rate reached 94% when the temperature was increased to 25 degrees C. Expanded blastocysts cryopreserved by this two-step method developed into live young as well as control embryos after transfer.(ABSTRACT TRUNCATED AT 250 WORDS)

Channel opening process is responsible for the slow component in the flux measurement of membrane vesicles

The time course of tracer ion efflux from vesicles of uniform size, each of which contains an ion channel was theoretically analyzed. It is shown that the apparent flux rate reflects the opening rate of the channel when the flux rate is much higher than the channel gating rates. The theory was also developed for the system of vesicles whose volume is changed by an osmotic pressure jump with permeable solutes. The theory was applied to analyze the results obtained from ion flux measurements with sarcoplasmic reticulum vesicles, where ion fluxes through anion and cation channels have been observed by the tracer method, the volume change-light scattering method and the fluorescence quenching method. The results were successfully interpreted with the present model referring to the results from the electrical single channel recordings.

[Detection of point mutation of K-ras gene codon 12 in biliary tract and ampullary carcinoma by modified two-step polymerase chain reaction]

The point mutation of K-ras gene at codon 12 was investigated in 11 cases of gall bladder carcinoma, 10 cases of extrahepatic bile duct carcinoma, 2 cases of intrahepatic bile duct carcinoma, and 4 cases of ampullary carcinoma by modified two-step polymerase chain reaction which employed paraffin embedded materials. The results revealed that there were point mutations in 6/11, 10/10, 2/2, and 4/4, respectively. Judging from the ratio of density of wild and mutant band, not all cancer cells in the tissue section contained the mutation. So it was suggested that the normal cells were initiated for the malignant transformation by ras gene mutations and then, selection might occur against cells containing ras mutations during progression of the tumor. Modified two-step polymerase chain reaction was markedly useful for detecting mutation even at low frequency among tumor cells.

Characterization of a Cl(-)-channel from rabbit transverse tubules in the planar lipid bilayer system

A Cl(-)-channel of the transverse tubule(TT) was incorporated into artificial planar lipid bilayers and its properties were investigated. The channel was found to have the following properties. (1) The single-channel conductance is 40 pS in choline-Cl solution. (2) The rate of gating of the channel does not depend on the membrane voltage. (3) The channel is blocked by stilbene derivatives (DIDS and SITS), which are known as inhibitors of voltage-dependent Cl(-)-channels of the Torpedo electric organ, from both sides of the membrane. (4) An inhibitor of voltage-dependent Cl(-)-channels of skeletal muscle, 9-anthracene carboxylic acid(9-AC), inhibits Cl(-)-current from the cis-side to which the TT vesicles were added.

Tolerance induction by clonal deletion of CD4+8+ thymocytes in vitro does not require dedicated antigen-presenting cells

The cellular requirements of T cell tolerance induction in the thymus by clonal deletion was investigated by using an in vitro assay: thymocytes from mice expressing a transgenic TcR specific for lymphocytic choriomeningitis virus (LCMV) and H-2Db were co-cultured with various H-2b cell types as antigen-presenting cells in the presence of the antigenic LCMV peptide. The results revealed that all cell lines examined including embryonic and transformed fibroblasts, melanoma cells, cortical thymic epithelial cells, lymphomas and neuronal cells induced an antigen dose-dependent deletion of CD4+8+ thymocytes. Similarly, highly enriched accessory cell populations from thymus and spleen (macrophages, dendritic and cortical epithelial cells, i.e. thymic nurse cells) could induce antigen-specific depletion of immature CD4+8+ thymocytes. Depending on the cell type examined micromolar to picomolar concentration of LCMV peptide were required to induce deletion. The effectiveness of deletion by the different cell types did not correlate with their major histocompatibility class I expression level; it was, however, influenced by the presence of ICAM-1 adhesion molecules.

Successful vitrification of bovine blastocysts, derived by in vitro maturation and fertilization

Bovine blastocysts were produced through maturation, fertilization, and development in vitro. For vitrification, solutions designated EFS, GFS, and PFS were prepared; these were 40% ethylene glycol, 40% glycerol, and 40% propylene glycol, respectively, diluted in modified phosphate-buffered saline (PBS) containing 30% Ficoll + 0.5 M sucrose. The embryos were exposed to the solutions in one step at room temperature, kept in the solutions for various times, vitrified in liquid nitrogen, and warmed rapidly. When the embryos were vitrified in EFS solution after 1 or 2 min exposure, the postwarming survival rate, assessed by the reexpansion of the blastocoel, was 74-77%. However, when the exposure time was extended to 3 min or longer, this rate dropped to 7-0%. This reduction was attributed to the toxicity of ethylene glycol. Of the embryos vitrified in GFS solution, 53% survived when they were cooled after 1 min exposure; as the duration of the exposure increased, the survival rate increased, reaching a peak (72%) at 4 min. The rate then decreased gradually with exposure time. In PFS solution, embryos surviving after vitrification were recovered only with 1 min exposure (33%), reflecting the high toxicity of propylene glycol. After vitrification in EFS or GFS solution, two embryos were nonsurgically transferred into each of 14 recipient animals. Of the 14 recipients, ten (71%) became pregnant; two resulted in early stillbirths, four recipients delivered twins (four alive and four stillborn), and two delivered single live calves, demonstrating the effectiveness of this simple vitrification method for the cryopreservation of in-vitro-produced bovine blastocysts.

Effects of ryanodine on permeability of choline and glucose through calcium channels in sarcoplasmic reticulum vesicles

The effect of ryanodine on the permeation of glucose, choline, and Ca2+ through the Ca2+ channel in sarcoplasmic reticulum vesicles was studied by means of the light scattering and/or the tracer method. Ryanodine had the same effect on the permeabilities of choline and Ca2+; low concentrations of ryanodine (10 microM) locked the channel in the open state, and high concentrations (100 microM) opened the channel transiently, which closed finally. Glucose became permeable on the ryanodine treatment even in the absence of KCl, although it was not permeable before the treatment when the channel was open. Submolar concentrations of KCl enhanced the glucose and choline permeability of the ryanodine-treated channel as well as the untreated one. Activators such as ATP and caffeine did not enhance the permeability of the treated channel in the open locked state, but inhibitors such as Mg2+ and ruthenium red closed the channel, although much higher concentrations were required than for the untreated channel. The maximal rates of choline and glucose permeation of the ryanodine-treated channel were lower than those of the untreated one attained in the presence of ATP and/or caffeine. This result is consistent with the fact that the single channel conductance after the ryanodine treatment decreased to 40-50% of the maximal conductance of the untreated one. This result suggests that the conformation of the channel opened by ryanodine was different from that with ATP or caffeine.

[Primary Waldenström's macroglobulinemia associated with pure red cell aplasia in which Ts/c lymphocytes inhibiting erythroid precursors were detected]

Waldenström's macroglobulinemia (WMG) is a malignancy of B lymphocytes manifesting heavy accumulation of monoclonal IgM in the plasma. In about 80% cases of WMG, Normocytic normochronic anemia (NNA) is complicated. A case of WMG complicated with pure red cell aplasia (PRCA) and the results of in vitro CFU-E colony assay of bone marrow mononuclear cells (BMMNC) cultured with the patient's serum and/or peripheral lymphocytes were described. A 59-year-old male was admitted with serum total protein Level of 9.7g/dl and 48.2% of gamma globulin. The diagnosis of WMG was made by monoclonal IgM in immunoelectrophoresis. Severe NNA was initially demonstrated on admission and gradually deteriorated further. Both reticulocytes in peripheral blood and erythroid precursors in bone marrow were markedly decreased. Erythropoietin showed high values in plasma. Complication by PRCA was considered to be present in vitro study of a CFU-E colony formation of BMMNC from a normal volunteer showed significant suppression on addition of the patient's peripheral lymphocytes and adverse enhancement by adding the patient's serum. This inhibition of CFU-E colony formation was most prominent by the addition of suppressor/cytotoxic T lymphocytes (Ts/c) and was dose dependent. This result showed the existence of inhibitory Ts/c against proliferation of allogeneic erythroid precursors.

Comparison of uptake of mitomycin C and KW-2149 by murine P388 leukemia cells sensitive or resistant to mitomycin C

KW-2149, a new mitomycin C (MMC) derivative, inhibited the growth of murine P388 leukemia in vitro at 20-fold lower concentrations than those of MMC. KW-2149 was also effective in inhibiting the growth of MMC-resistant P388 (P388/MMC) cells. To elucidate these characteristics of KW-2149, its uptake and efflux were compared with those of MMC in MMC-sensitive and -resistant P388 cells. Both MMC and KW-2149 accumulated rapidly in P388 cells after incubation at the concentration of 0.47 and 0.024 microM, respectively, which were the IC50 values at 1-h exposure. Although this concentration of KW-2149 was 20 times lower than that of MMC, its intracellular concentration was little more than that of MMC, suggesting that KW-2149 accumulated in the cells quite efficiently. The accumulated KW-2149 in the cells after 1-h treatment remained for as long as 24 h after the incubation of the cells in drug-free medium, suggesting that most of the intracellular KW-2149 or MMC was bound to cellular components. The ratios of resistance of P388/MMC cells to MMC and KW-2149 were 34 and 8.8, respectively, at 1-h exposure, suggesting that P388/MMC cells were partially resistant to KW-2149 in vitro. P388/MMC cells also showed partial resistance to cisplatin, Adriamycin, m-AMSA, and etoposide. The accumulation of MMC in P388/MMC cells was lower than that in P388 cells, although the size of the former cells was almost equal to that of the latter. As a result, the amount of DNA-bound MMC was lower in P388/MMC cells than in P388 cells, suggesting its involvement in the mechanisms of MMC resistance in P388/MMC cells.

[Immunological study on Alzheimer's disease using anti-beta-protein monoclonal antibodies]

Monoclonal antibodies (TB1 & TB2), which were obtained by immunization of 24 amino acids in BALB/c mice, bound specifically to the amyloid senile plaque and amyloid-angiopathic lesions of brain tissues of patients with Alzheimer's disease (AD) or with senile dementia of Alzheimer type (SDAT), and strongly reacted with the 1st part (Asp-Ala-Glu-Phe-Arg-His-Asp) of beta-protein. Western blotting and two-dimensional immunoelectrophoresis of cerebrospinal fluid (CSF) and serum revealed bands of 125 and 20 kilodaltons. The positive frequency of 125 and 20 KD bands detected by two-dimensional immunoelectrophoresis was higher in the serum of AD and SDAT patients (12 cases) than in that of normal control patients. ELISA employing various anti-amyloid precursor protein (APP) antibodies was performed using the extract of the human neuroblastoma cell line (NB39) which produces APP. In the near future, we hope to measure APP in CSF and sera from patients with Alzheimer's disease.

[A case of ALL complicated with acute pancreatitis and pancreatic pseudocyst caused by L-asparaginase ]

We reported a case of ALL complicated with acute pancreatitis caused by L-asparaginase (L-Asp). The patient was a 42-year-old man, who showed eosinophilia in peripheral blood and an increase of lymphoblast in bone marrow. He was diagnosed as ALL (L2) and treated by JALSG '87 protocol. Remission induction chemotherapy including L-Asp was administered by 5,000 IU i.v. for 10 days. The day after giving all dose of L-Asp, slight epigastralgia developed and then became severe. After two days, s-amylase was markedly elevated, and the patient was diagnosed as acute pancreatitis caused by L-Asp. He was treated conservatively, but hyperglycemia occurred. The epigastrial tumor was palpable and gradually grew in size. CT-scan and abdominal ultrasonography revealed pancreatic pseudocyst, so he was treated by percutaneous cyst drainage. The patient died of a relapse of ALL. The prophylaxis and early diagnosis of the pancreatitis and hyperglycemia caused by L-Asp are very difficult. We have to examine more cases and pay greater attention to the chemotherapy, including L-Asp.

[Large scale outbreak of Yersinia pseudotuberculosis serotype 5a infection at Noheji-machi in Aomori Prefecture]

In June 1991, there were large scale outbreaks of Yersinia pseudotuberculosis at 4 primary schools and 1 junior high-school in Noheji-machi in Aomori Prefecture. A total of 732 patients (725 pupils and school children, 7 teachers and personnel) were affected and 134 were hospitalized. Sex ratio of incidence was 1.1:1.0 without appreciable difference. Clinical symptoms (478 patients) were represented frequently by pyrexia (86.4%), eruption (73.8%), abdominal pain (66.7%), vomiting nausea (63.4%), etc., and were characterized by a strawberry tongue, pharyngeal redness, membranous desquamation of the fingers and arthralgia during convalescence. Yersinia pseudotuberculosis was isolated from 27 (81.8%) of 33 patients stool specimens, 1 waste water specimen and 2 (11.7%) of cooking employees' stool specimens. The isolates were confirmed serotype 5a, and positive for calcium-dependency and autoagglutination, and harboring 40-50 megadalton virulent plasmid. Restrictive endonuclease digestive pattern of plasmid proved to be identical. In many cases, patients' serum antibody titer showed a significant increase ratio to the isolated strain. In term of drug susceptibility, all the strains were sensitive to cefem, penicillin and amino-glycoside series and resistant to macrolide and sulfa series. The infectious source was limited to the school feeding, but the responsible food remained unknown. Mean latency and exposure day were presumed to be 6.5 days and May 30, respectively.

Disposition and metabolism of KW-2149, a novel anticancer agent

KW-2149 is a new derivative of mitomycin C (MMC). The plasma concentrations, distribution, metabolism, and excretion of [3H]-KW-2149 in normal and tumor-bearing mice after i.v. administration of 16.6 mg/kg were investigated. The plasma radioactivity decreased biexponentially after i.v. administration in normal mice. However, the unchanged drug disappeared rapidly, showing a half-life (t1/2) of 9.7 min, which was shorter than MMC's (18 min). The radioactivity was excreted in mouse urine (33%) and feces (58%) within 144 h. High radioactivity was distributed in the gallbladder, liver, kidney, pancreas, and lung at 1 h after i.v. administration to normal mice. The tumor concentration was lower than the plasma or blood concentration. The lowest radioactivity was observed in the brain. The metabolic rate of KW-2149 was very rapid. The methyl sulfide form (M-16), the symmetrical disulfide dimer (M-18), and the albumin conjugate were detected in plasma, which possessed anticellular activity. The specific anticellular activity of these compounds against uterine carcinoma (HeLa S3) was 1/100, 1, and 1/20 respectively, as compared with that of KW-2149.

Survival of mouse morulae vitrified in an ethylene glycol-based solution after exposure to the solution at various temperatures

Mouse morulae were exposed in one step to a vitrification solution (EFS, a modified PBS containing 40% ethylene glycol, 18% Ficoll, and 0.3-M sucrose) at various temperatures, then cooled rapidly in liquid nitrogen, and then warmed rapidly. All of the embryos exposed to the EFS solution for 0.5 min at 25 degrees C before vitrification developed in culture. However, survival rates were lower if the duration of exposure was prolonged to 2, 5, or 10 min. At lower ambient temperatures (20, 10, and 5 degrees C), high survival rates were associated with longer exposure to the EFS solution. The toxicity of the EFS solution was also lower at lower temperatures. The toxic injury of morulae was manifested as decompaction of the blastomeres. Among the three additives in the EFS solution, ethylene glycol, which can cross cell membranes, was responsible for the toxicity. The results show that the optimum time for exposure of the embryos to the EFS solution before rapid cooling varies with the ambient temperature, i.e., 0.5 min at 25 degrees C, 0.5-5 min at 20 degrees C, 2-5 min at 10 degrees C, and 2-10 min at 5 degrees C. If they are exposed for an optimum period, almost all mouse morulae can survive vitrification (94-100%).

Differentiation of HL-60 cells by phorbol ester is correlated with up-regulation of protein kinase C-alpha

To clarify the mechanism of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced macrophage-like differentiation of HL-60 cells, we investigated the correlation between the effects of protein kinase C (PKC) inhibitors on the induction of markers of TPA-induced differentiation and those on suggested critical steps of the differentiation. H-7, sphingosine, and trifluoroperazine significantly suppressed TPA-induced cell adhesion but their effects on the induction of acid phosphatase and nonspecific esterase differed among the inhibitors. The three inhibitors failed to affect on TPA-induced annexin I expression. In contrast, staurosporine markedly suppressed the induction of all these markers. The effects of the inhibitors on some suggested critical steps of the differentiation, a rapid phosphorylation of specific proteins, a rapid membrane association of PKC, and down-regulation of PKC at 18 h after addition of TPA, were not correlated with those on the differentiation marker induction. Only the effect of the inhibitors on up-regulation of PKC-alpha was closely correlated with TPA-induced annexin I expression; staurosporine inhibited up-regulation of PKC-alpha but other inhibitors did not similarly affect the induction of annexin I expression. These results suggest that PKC-alpha is intimately related to macrophage-like differentiation of HL-60 cells by TPA.

Ion channels on synaptic vesicle membranes studied by planar lipid bilayer method

An anion selective channel and three types of cation selective channels were found in planar lipid bilayers incorporating synaptic vesicles from rat brains. In asymmetric KCl solutions (cis: 300 mM/trans: 150 mM), the anion selective channel showed a single-channel conductance of 94 pS and was inactivated by negative voltages and by 4-acetoamido-4'-isothiocyanostilbene-2,2'-disulfonic acid disodium salt (SITS). In the same solution, single-channel conductances of three types of cation selective channels were 250 pS (Type 1), 248 pS (Type 2), and 213 pS (Type 3), respectively. These channels resembled one another in single-channel conductances but were different in gating behaviors. Type 1 channel, which was most frequently observed, had a remarkable subconducting state (175 pS). Type 2 channel had a flickering state that increased as the potential became more positive, and a long inactive state that increased as the potentials were more negative. Type 3 channel, which was also sensitive to the potentials, had the open-channel probability increased as the potential became more positive.

Immunological identification of a Cl- channel protein in electric organs of Narke japonica

A Cl- channel in electric organs of Narke japonica was reconfirmed, using a polyclonal antibody, to be a 180k protein composed of two identical 90k units. The specific antibody against the 180k protein from electric organs reduced, when added in the cis side solution, the open probability of the Cl- channel in a planar bilayer membrane without affecting the single channel conductance, ion selectivity nor voltage dependency. Furthermore, the antibody added in the trans side also affected the channel to increase the open probability. The eluate of the immuno-affinity chromatography was found to contain only the 180k protein. These results indicate that 180k protein to be an integral membrane protein and to form the Cl- channel.

Molecular involvement of the pvt-1 locus in a gamma/delta T-cell leukemia bearing a variant t(8;14)(q24;q11) translocation

A highly malignant human T-cell receptor (TCR) gamma/delta+ T-cell leukemia was shown to have a productive rearrangement of the TCR delta locus on one chromosome 14 and a novel t(8;14)(q24;q11) rearrangement involving the J delta 1 gene segment on the other chromosome 14. Chromosome walking coupled with pulsed-field gel electrophoretic (PFGE) analysis determined that the TCR J delta 1 gene fragment of the involved chromosome was relocated approximately 280 kb downstream of the c-myc proto-oncogene locus found on chromosome band 8q24. This rearrangement was reminiscent of the Burkitt's lymphoma variants that translocate to a region identified as the pvt-1 locus. Sequence comparison of the breakpoint junctions of interchromosomal rearrangements in T-cell leukemias involving the TCR delta-chain locus revealed novel signal-like sequence motifs, GCAGA(A/T)C and CCCA(C/G)GAC. These sequences were found on chromosome 8 at the 5' flanking site of the breakpoint junction of chromosome 8 in the TCR gamma/delta leukemic cells reported here and also on chromosome 1 in T-cell acute lymphocytic leukemia patients carrying the t(1;14)(p32;q11) rearrangement. These results suggest that (i) during early stages of gamma delta T-cell ontogeny, the region 280 kb 3' of the c-myc proto-oncogene on chromosome 8 is fragile and accessible to the lymphoid recombination machinery and (ii) rearrangements to both 8q24 and 1p32 may be governed by novel sequence motifs and be subject to common enzymatic mechanisms.