Skeletal muscle regeneration induced by chorio-allantoic grafting

To examine whether the expression pattern of fast-muscle type troponin-T (TnT) isoforms was fixed in cell lineage, breast muscle pieces (pectoralis major) from chick embryos and young and adult chickens were grafted on to chorio-allantoic membrane of 9-day-old chick embryos and cultured until the host embryos hatched out. Muscle fibre formation of the grafts was investigated by histological and immunohistochemical methods with anti-fast-muscle type and anti-slow-muscle type TnT sera, and the expression of fast-muscle type TnT in the grafts from chick embryos and young chickens was studied by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional SDS-PAGE, and immunoblotting. In the chorio-allantoic grafting, the breast muscle initially degenerated forming pyknotic nuclei and hyaline cytoplasm. The surviving cells, which were supposed to be satellite cells, regenerated new muscle fibres of the same type as those of the grafted muscle in respect of TnT isoform expression. Therefore, we considered that the ability to express specific isoforms of TnT was fixed in the satellite cells, and that chorio-allantoic grafting was a useful technique for studying muscle differentiation.

Heterogeneous smooth muscle cell population derived from small and larger arteries

Vascular lesion formations in such disease states as hypertension and atherosclerosis occur in a district-specific manner. Large conduit and small resistance arteries play district-specific roles in the regulation of organ perfusion. Using a culture method, we studied the morphology and growth of smooth muscle cells derived from small arteries (S-SMCs, less than 90 microm in internal diameter) and from larger arteries (L-SMCs, ranging from 800 to 900 microm) of the rat mesenteric arterial bed. S-SMCs showed a hill-and-valley pattern, whereas L-SMCs showed sheet or whorl formation. The majority of S-SMCs were smaller, bipolar-shaped; in contrast, the majority of L-SMCs were larger, polygonal-shaped. Actin fibers within S-SMCs were oriented in a bipolar manner from the nuclei, whereas those within L-SMCs had a radial appearance. [3H]Thymidine incorporation induced by serum, platelet-derived growth factor-AB (PDGF), or mechanical stretch was greater in S- vs L-SMCs. The population doubling time measured after the addition of serum or PDGF was shorter in S- vs L-SMCs. Thus, distinct morphological and growth phenotypes of SMCs exist in small and larger arteries of the same vascular bed.

A repressor function for telomerase activity in telomerase-negative immortal cells

Human telomerase, a ribonucleoprotein that adds TTAGGG repeats onto telomeres and compensates for their shortening, is repressed in most normal human somatic cells. Human somatic cells are considered to have a limited proliferation capacity because of the telomere shortening. Although immortalization of somatic cells is often associated with telomerase reactivation, there are some immortal cells in which telomerase activity is undetectable. In these cells, telomeres may be maintained by an unknown mechanism other than telomerase reactivation. To examine the genetic regulation of telomerase activity, we constructed hybrids between immortal cells with (HepG2) and without (KMST6) telomerase activity. These two cell lines had relatively short and long telomeres, respectively. The hybrid cells continued to proliferate without detectable telomerase activity even after 100 population doublings. Telomerase-positive subpopulations occasionally appeared after serial passages. Southern blot analysis revealed that the hybrids had long terminal restriction fragments similar to that of KMST6, regardless of telomerase activity, and fluorescence in situ hybridization with a telomeric probe showed high-intensity hybridization signals on telomeres, indicating relatively long telomeric repeats. These results suggest that the telomerase-negative immortal cells contain a gene or genes functioning as a telomerase repressor and maintain telomere length by a dominant mechanism other than telomerase reactivation.

Identification of soluble type of membrane-type matrix metalloproteinase-3 formed by alternatively spliced mRNA

Homology screening for human membrane-type MMP (MT-MMP) was carried out, and cDNA encoding a soluble type of MT3-MMP (SM3), which is considered to be an alternatively spliced variant of MT3-MMP, was obtained. SM3 had a novel sequence consisting of 50 amino acids after Lys407 instead of amino acids containing the transmembrane domain of MT3-MMP. When SM3 tagged with a FLAG epitope (SM3-flag) was expressed in COS-7 cells, SM3-flag was present in the conditioned medium in its activated form. The enzymatic activity of SM3 was studied using a recombinant enzyme expressed in E. coli (SM3-e). The fluorogenic peptide substrate hydrolyzing activity of SM3-e was inhibited by EDTA and by the tissue inhibitor of metalloproteinase-2 (TIMP-2), whereas TIMP-1 had only relatively weak inhibitory ability. SM3-e was able to activate proMMP-2, and this activity was also inhibited by TIMP-2 but not by TIMP-1. SM3-e was able to cleave type III collagen, and also digested fibronectin. In view of the homology of the primary structures, MT3-MMP was considered to have the same catalytic activity as SM3. The results of studies of SM3's activity on extracellular matrix (ECM) protein suggests that MT3-MMP plays a role in ECM turnover not only by activating proMMP-2 but also by acting directly on ECM macromolecules.

Four-week repeated inhalation study of HCFC 225ca and HCFC 225cb in the common marmoset

Four male and three female marmosets in each group were exposed to air only, 1000 ppm of HCFC 225ca or 5000 ppm of HCFC 225cb, for 6 h per day for 28 consecutive days. HCFC 225ca caused a slight reduction in body weight. HCFC 225cb occasionally caused somnolence during exposure and vomiting on the first day of exposure. Clinical chemistry findings included a mild reduction of triglyceride, cholesterol and phospholipid levels and increased GOT level in the HCFC 225ca exposure group. HCFC 225cb also caused a reduction of triglyceride levels in some animals. HCFC 225ca caused a slight increase of hepatic carnitine palmitoyltransferase (CPT) activity while HCFC 225cb slightly increased cyanide-insensitive palmitoyl CoA beta-oxidation (FAOS) activity. In the HCFC 225cb exposure group, an increase in cytochrome P-450 content was also observed. HCFC 225ca caused a fatty change in the hepatic cells. Increased incidence of lipid droplets in the hepatic cells and myelin-like bodies in hepatic cells, Kupffer's cells and hepatic blood vessels were observed electron microscopically in the HCFC 225ca exposure group. A proliferation of smooth endoplasmic reticulum was observed in the HCFC 225cb exposure group. Decreased peroxisome volume density in the HCFC 225ca group, and increased volume density in the HCFC 225cb exposed females were seen. However, organ weight measurement and histopathological examination did not reveal hepatomegaly or hypertrophy with either substance. Although slight changes were noticed in peroxisome volume density and in some of the peroxisomal enzyme activities, the changes related to peroxisome proliferation with HCFC 225ca and 225cb were minimal in marmosets compared to those seen in rats. Histopathological examination and hormonal analysis did not reveal any abnormalities in the pancreas or testes.

Collagen degradation induced by the combination of IL-1alpha and plasminogen in rabbit articular cartilage explant culture

To investigate the effect of plasminogen on cartilage catabolism, we assessed collagen degradation in rabbit articular cartilage explants treated with or without plasminogen and interleukin-1alpha (IL-1alpha). The combination of IL-1 alpha and plasminogen induced rapid collagen degradation, amounting to more than 60% of the total collagen by day 7, while neither IL-1alpha nor plasminogen alone had any effect. To examine the mechanism of collagen degradation induced by IL-1alpha and plasminogen, the matrix metalloproteinases (MMPs) in the culture supernatants were examined by ELISA, Western blotting and gelatin zymography. We found that the treatment with IL-1alpha induced MMP-1, MMP-3, and MMP-9. In addition, plasminogen converted the pro form of MMPs into the active form. Both a tissue inhibitor of metalloproteinases-1 (TIMP-1) and a synthetic hydroxamate MMP inhibitor prevented this collagen release. These results suggest that plasminogen causes collagen degradation via activation of MMPs induced by IL-1alpha.

[Combined deficiency in neutrophil functions after bone marrow transplantation and the in vitro effect of granulocyte colony-stimulating factor]

In order to investigate the mechanism of susceptibility to bacterial infection after bone marrow transplantation (BMT), we evaluated the neutrophil functions at 1, 3, 6, and 12 months after hematological reconstitution in a 29-year-old AML patient who received allogeneic bone marrow transplantation. Acute graft-versus-host disease (GVHD) was grade I, and chronic GVHD was not present. The patient exhibited complications of upper and lower respiratory infections several times after BMT, all of which subsided within a month. Chemotactic responses toward all three chemotactic factors, random mobility, phagocytosis, superoxide (O2-) release and bactericidal activity were severely impaired early after reconstitution. These neutrophil functions gradually improved with time after BMT, and all normalized at 12 months after reconstitution of transplanted bone marrow. Both O2- release and bactericidal activity of neutrophils were significantly enhanced at 6 and 12 months after marrow reconstitution following pretreatment of 50 ng/ml of granulocyte colony-stimulating factor (G-CSF) in vitro. These findings suggest that the combined disorders in neutrophil functions in early phase after BMT may play an important role in susceptibility to bacterial infections until one year after BMT. Administration of G-CSF, which potentiates the bactericidal activity of neutrophils, is recommended for preventing infectious complications and for treating prolonged and unmanageable infections after BMT.

MST/MLK2, a member of the mixed lineage kinase family, directly phosphorylates and activates SEK1, an activator of c-Jun N-terminal kinase/stress-activated protein kinase

c-Jun N-terminal kinases/stress-activated protein kinases (JNKs/SAPKs) are mitogen-activated protein kinase (MAPK)-related protein kinases that are involved in several cellular events, including growth, differentiation, and apoptosis. Mixed lineage kinases (MLKs) form a family of protein kinases sharing two leucine zipper-like motifs and a kinase domain whose primary structure is similar to both the tyrosine-specific and the serine/threonine-specific kinase classes. We have reported that a member of the MLK family, MUK/DLK/ZPK, can activate JNK/SAPK in vivo, and here we show that another member of the MLK family, MST/MLK2, activates JNK/SAPK. Both MUK/DLK/ZPK and MST/MLK2 cause a slight activation of p38/Mpk2 when overexpressed in COS-1 cells, whereas MST/MLK2, but not MUK/DLK/ZPK, activates extracellular response kinase (ERK) to a certain degree. The activity of SEK1/MKK4/JNKK, a MAPK kinase class protein kinase designated as a direct activator of JNK/SAPK, is also induced by MUK/DLK/ZPK or MST/MLK2 overexpression. Furthermore, recombinant MST/MLK2 produced in bacteria directly phosphorylates and activates SEK1/MKK4/JNKK in vitro, showing that MST/MLK2 acts like a MAPK kinase kinase. Taken together, these results suggest that MLK family members are MAPK kinase kinases preferentially acting on the JNK/SAPK pathway.

Behavioral and electroencephalographic studies of beagles with an Eck's fistula: suitability as a model of hepatic encephalopathy

Behavioral manifestations, electroencephalograms (EEGs) and visually evoked potentials (VEPs) were studied in beagles with Eck's fistula (portacaval shunt [PCS]), an established model of hyperammonemia, to determine whether they developed CNS disorders characteristic of hepatic encephalopathy. After PCS, behavioral changes occurred in the form of listlessness, sluggishness (altered gait, snapping and transient catatonia-like symptoms) and apparent blindness, which appeared in that order and progressed to coma and death in some animals. The EEGs from the frontal cortex showed a gradual decrease in voltage and frequency. Development of snapping and catatonia-like symptoms coincided with the occurrence of high voltage fast waves in the EEGs from the occipital cortex. In comatose Eck's fistula dogs. flattening of the EEGs was recorded from the frontal cortex and a lowered voltage was noted in the EEGs from the occipital cortex. After PCS, the latencies and amplitudes of the components of VEP were increased. The snapping and catatonia-like symptoms were markedly ameliorated by carbamazepine and the coma by flumazenil and thyrotropin-releasing hormone. These findings indicate that Eck's fistula dogs provide a useful model of hepatic encephalopathy.

[Single stage excision for an intractable brain abscess and free rectus abdominis flap for reconstruction of the anterior skull base]

A case is presented of the frontal brain abscess following resection of squamous cell carcinoma of the maxillary sinus who had undergone reconstruction of the anterior skull base using a free rectus abdominis muscle flap. Local flap, ex. galeal flap, can be used for separating the cranial space from the paranasal sinuses and the nasopharynx, but it cannot provide reliable separation and protection of the brain from bacterial flora of the upper airway and it is too weak to support the brain in cases where orbital exenteration has been performed. The distant flaps such as the pectoralis major musculocutaneous flap, on the other hand, can provide a good alternative for reconstruction of the anterior skull base in such difficult cases, but frequently requires a secondary division of the pedicle. The free flap can circumvent such problems. We used the free rectus abdominis muscle flap and the postoperative course was uneventful. A bone graft was not necessary to reconstruct the anterior skull base.

Cloning of human bone morphogenetic protein type IB receptor (BMPR-IB) and its expression in prostate cancer in comparison with other BMPRs

Bone metastasis is a common event in prostate cancer, and it is known that some of the bone morphogenetic proteins (BMPs) are expressed in prostate cancer cells, while no study on the expression of their receptors, BMPRs, has been reported. Here we report cloning and sequence analysis of the human BMPR-IB cDNA. We also analysed the expression of transcripts of three types of the BMPR genes in human tissues and prostate cancer cell lines. The BMPR-IB mRNA was present in various organs, but the highest level was found in the prostate. Moreover, the amount of BMPR-IB mRNA was significantly low in prostate cancer tissues after androgen withdrawal and was also low in prostate cancer cell lines. RT-PCR analysis showed that the BMPR-IB message was upregulated by androgen stimulation in the LNCaP cell line which expresses the androgen receptor. By contrast, the mRNA levels of BMPR-IA and BMPR-II were not significantly different among non-cancerous and cancerous prostate tissues. It was also suggested that human BMPR-IA and BMPR-IB might have different biological functions in the prostate, although their sequences were 85.3% identical in the serine-threonine kinase domain.

Role of myocyte nitric oxide in beta-adrenergic hyporesponsiveness in heart failure

BACKGROUND

The positive inotropic response to beta-adrenergic stimulation is attenuated at the isolated myocyte level in heart failure. Nitric oxide (NO) has a negative inotropic effect and attenuates the response to isoproterenol. It has been suggested that NO synthesis is increased in failing myocytes. However, the pathophysiological consequences after induction of NO in myocyte contractility are less clear in the setting of heart failure.

METHODS AND RESULTS

We examined the effects of an NO synthase (NOS) inhibitor on contractile function in myocytes isolated from 11 dogs with rapid pacing-induced heart failure (ejection fraction, 29 +/- 2%) and 8 control dogs (ejection fraction, 74 +/- 3%). Sarcomere shortening velocity was measured as an index of contractility under four experimental conditions: at baseline, after adding isoproterenol (ISO; 1 nmol/L), after an NOS inhibitor (N pi-nitro-L-arginine methyl ester [L-NAME], 0.1 nmol/L), and after L-NAME plus ISO. L-NAME alone had no effects on basal sarcomere shortening velocity in either control or heart failure myocytes. However, L-NAME significantly augmented the inotropic response to isoproterenol in heart failure myocytes (107.1 +/- 7.3% [ISO alone] versus 140.6 +/- 10.7% [ISO plus L-NAME] increase from baseline; P < .05) but not in control myocytes (135.5 +/- 9.9% [ISO alone] versus 137.1 +/- 11.4% [ISO plus L-NAME]; P = NS). Myocardial NOS activity measured by the conversion of arginine to citrulline was significantly increased in dogs with heart failure compared with that in control dogs.

CONCLUSIONS

The increased NO induction in failing myocytes does not alter baseline sarcomere mechanics but attenuates the positive inotropic response to isoproterenol. Thus, myocyte NO plays an important role in the autocrine regulation of the contractile function of myocytes in congestive heart failure.

Mutations induced in male germ cells after treatment of transgenic mice with ethylnitrosourea

The present study was undertaken to clarify whether the transgenic mouse mutagenesis assay system can be used instead of dominant lethals or specific locus test after treatment of male germ cells in mouse with ethylnitrosourea (ENU). Male Big Blue transgenic mice (BB) carrying a lacI target gene were given a single intraperitoneal injection of 150 mg/kg ENU. Vasa deferential sperm, caudal epididymal sperm or whole testes were assayed for mutation at 3, 14, 22 and 93 days after treatment with ENU. The average of background lacI- mutant frequencies was 2.05 x 10(-5). The MF observed in post spermatogonial stage after treatment with ENU were slightly increased over background. On the other hand, ENU induced high MF in the spermatogonial stage. MF detected after treatment of BB male germ cells with ENU were lower than those detected in the mouse visible specific-locus mutations in previous reports. Nevertheless, it is clear that this assay is a practical alternative to the specific locus test for detecting mutations induced in spermatogonial stage.

Comb-type polycations effectively stabilize DNA triplex

DNA triplex formation has been studied as a potential strategy for regulation of gene expression. The triplex is, however, unstable under physiological conditions, so that an effective stabilizer for the triplex formation is needed. Here is shown a novel strategy to stabilize the triplex based on the molecular design of a comb-type polycation. Linear polycations, such as poly(L-lysine) and poly(L-arginine), thermally stabilize DNA duplexes (and triplexes). The complexes between DNA and the polycation are irreversible and are liable to precipitate out of aqueous media. The irreversibility and phase separating properties of the complex impede association of single-stranded (ss) DNAs in the complex to form duplexes and triplexes. A comb-type polycation consisting of a poly(L-lysine) backbone and grafted chains of hydrophilic polymers was prepared. The comb-type copolymers increased solubility of their complex with DNA and suppressed conformational changes of DNA. Thermal melting curve analyses revealed that the comb-type copolymer markedly stabilized DNA triplexes and did not disturb ssDNAs in forming duplexes and triplexes. Reversible and one-step melting/reassociation transitions of poly(dA).2poly(dT) triplex were shown in the pressure of the copolymers. The stabilizing effect of the copolymer was larger than that of spermine, a polyamine considered effective in stabilizing triplexes. These results indicated that molecular design of polycations with a comb-type structure is a novel strategy to create efficient triplex stabilizers. Such comb-type copolymer consisting of various types of polycation backbones and hydrophilic graft chains may have many applications in which specific and precise interactions of polynucleotides are involved.

[Study on the surgical treatment for pulmonary metastasis from renal cell carcinoma]

BACKGROUND

Pulmonary resection for metastatic renal cell carcinoma were studied to assess the indication of surgical management.

METHODS

Between January, 1981 and December 1994, 17 consecutive patients (14 men and 3 women) underwent complete pulmonary resection for metastatic renal carcinoma. Median age was 61 years (range, 45 to 73 years). Eleven were appeared lung metastasis after resection of primary tumor. Median time between nephrectomy and pulmonary resection was 32 months (range, 0 to 127 months).

RESULTS

There were no operative deaths. One patient had solitary metastasis, 4 had two, 2 had three, 2 had four, one had seven, one had eight and 6 had more than twenty-two. Segmental resection was performed in 12 patients, lobectomy in 2, lobectomy and segmentectomy in 3 and segmentectomy for total lobes in 3. Four patients had another site operation of renal metastasis, brain tumor resection, chest wall and ribs resection, contra-lateral adrenalectomy and contralateral partial nephrectomy. Median follow-up was 44 months (range, 10 to 129 months). The cause specific survival rate and disease free survival after pulmonary resection was 55 and 48 percent at 5 years and 27 and 14 percent at 10 years, respectively.

CONCLUSION

Pulmonary resection for metastatic renal cell carcinoma was considered effective in some selected slow-growing cases. Multiple and both lungs metastases is not contraindication and the patients under 10 metastatic focuses had good prognosis.

Analysis of vascular anatomy and lymph node metastases warrants radical segmental bowel resection for colon cancer

To determine the indications for limited colon cancer surgery in each location, we reviewed the arterial branching patterns and lymph node metastases along the course of specific vascular trunks in 344 colon cancer patients who had undergone preoperative angiography and colectomy with lymph node dissection. Our conclusions are follows: Because the ileocecal artery always arises from the superior mesenteric artery and lymph node metastases of cecum cancer were limited to nodes along the ileocolic artery, cecum cancer can be cured by ileocecal resection. The right colic artery has various origins, and ascending colon cancer shows various patterns of lymph node metastases. Therefore a right hemicolectomy should be performed for ascending colon cancer. The middle colic artery forks into right and left branches, and each branch has different branching variations. If the right colic and middle colic arteries have a common trunk, a right hemicolectomy should be performed for transverse colon cancer on the right side. If the left branch of the middle colic artery has an independent replaced origin, lymph node dissection should be modified according to the variant origin. If the left colic artery and the first sigmoidal artery have a common trunk, the lymph nodes along the common trunk should be removed for sigmoid colon cancer and for descending colon cancer. Of the patients with sigmoid colon cancer, 6.3% also had lymph node metastases along the superior rectal artery. Given that the lymph nodes along the superior rectal artery are skeletonized, sigmoid colon cancer can be also cured by partial sigmoidectomy.

Teratology study of erythritol in rabbits

The effect of maternal ingestion of the reduced energy sweetener erythritol was investigated in KBL:JW strain pregnant rabbits. Animals received 1.0, 2.24, or 5.0 g/kg intravenously once daily from Days 6 to 18 of gestation. Maternal effects (auricular edema, and bradypragia) were observed in the high-dose group. No deaths or significant abnormalities occurred in animals given 1.0 or 2.24 g/kg. No effect was observed in the reproductive performance of the dams or in fetal development from ingestion at any of the treatment levels.

Cloning, expression and chromosomal localization of Wnt-13, a novel member of the Wnt gene family

The Wnt genes, encoding structurally-related secreted glycoproteins, are implicated in mammary carcinogenesis induced by mouse mammary tumor virus. In search of the Wnt gene(s) expressed in human gastric cancer, a WTGC1 cDNA fragment sharing 66.9% amino-acid homology with human and mouse Wnt-2 was isolated by degenerate polymerase chain reaction. The human gene corresponding to WTGC1 was designated as Wnt-13 and overlapping Wnt-13 cDNAs were cloned. Nucleotide sequence analysis indicated that the Wnt-13 gene encodes the protein of 372 amino acids, including a signal peptide, two potential N-glycosylation sites and 24 cystein residues highly conserved among members of the Wnt gene family. The Wnt-13 mRNA of 2.5 kb in size was detected in heart, brain, placenta, lung, prostate, testis, ovary, small intestine and colon of adult human and also in brain, lung and kidney of fetal human. Among various cancer cell lines, the Wnt-13 mRNA was detected in HeLa (cervical cancer), MKN28 and MKN74 (gastric cancer). The Wnt-13 gene has been mapped to human chromosome 1p13. These results suggest that the Wnt-13 gene may be involved in normal human development or differentiation as well as in human carcinogenesis.

Tetrahymena nuclear proteins that bind to a micronucleus-specific sequence during vegetative growth

Tetrahymena thermophila has two nuclei: a micronucleus is transcriptionally silent during vegetative growth and a macronucleus is active. Extensive programmed DNA rearrangement is known to occur during the development of the somatic macronucleus from the germ-line micronucleus. We previously found a 1.4 kb micronucleus-specific sequence, C-element, which was located upstream of the micronuclear calmodulin gene and was eliminated from the macronuclear genome during macronuclear development. Here, using gel mobility shift assays, we show that C-element binding factors, CBFs, are present in the nuclear extract prepared from vegetative cells. Competition experiments demonstrate that CBFs bind to two regions within the C-element. A sequence motif common to these regions is 5'-ATAGATTT-3'.

[Chemotherapy for two patients with non-Hodgkin's lymphoma in hemodialysis]

There are few reports on chemotherapy of non-Hodgkin's lymphoma (NHL) in patients with chronic renal failure. Two long-term hemodialysis patients were treated for NHL with modified CHOP therapy. The plasma pharmacokinetics of adriamycin (ADR) and etoposide (VP-16) were investigated in these patients. In the first case, NHL was diagnosed in a 37-year-old male (diffuse pleomorphic, T cell type, stage I E). After 4 courses of chemotherapy, he achieved complete remission. The second case, was a 56-year-old male who was admitted to our hospital with melena and abdominal pain. A diagnosis of NHL (diffuse mixed, B cell type, stage III E) was made. Complete remission was achieved with 2 courses of chemotherapy. Levels of hematological and neurological toxicity were moderately severe but tolerable. Pharmacokinetics of ADR and VP-16 in these patients were similar to those in patients with normal renal function. These results suggested that ADR and VP-16 were effective drugs for hemodialysis patients with NHL.

Molecular cloning of rabbit matrix metalloproteinase-2 and its broad expression at several tissues

We have cloned cDNA encoding rabbit matrix metalloproteinase-2 (MMP-2, 72 kDa type IV collagenase) by a combination of conventional library screening, the 'single strand ligation to single-stranded cDNA (SLIC)' method and 'long and accurate PCR (LA-PCR)'. Deduced amino acid sequence was highly conserved through mammalian species. Northern blot analysis revealed that rabbit MMP-2 had 2 species of mRNA, 2.8 kbp and 3.5 kbp, and were expressed constitutively in all the tissues tested. This was totally different from mRNA expression of rabbit MMP-1, -3 and -9.

Determination of the allele-specific antigen-binding site on I-Ak and I-Ab molecules

Residues 46 and 54 on a pigeon cytochrome c 43-58 analog, 50E, function as major histocompatibility complex class II contact sites. A peptide, 46F50E54A, with phenylalanine (F) at position 46 and alanine (A) at 54 on 50E bound to Ab and a peptide, 46D50E54A, with aspartic acid (D) at 46 and alanine at 54, bound to Ak. To determine the allele-specific peptide contact sites on I-A molecules corresponding to the I-A contact sites of the peptides, we analyzed responses of Ak- and/or Ab-restricted T cell hybridomas to 46F50E54A or 46D50E54A using L cell transfectants expressing recombinant I-A molecules between Ak and Ab or point mutants of Ak as antigen presenting cells. It was shown that the N-terminal half of the alpha helix of the A alpha chain determined the allele-specific T cell responses. Furthermore, with arginine (k type amino acid) or alanine (b type amino acid) at position 56 of the Ak alpha chain, these T cell hybridomas were stimulated predominantly by 46D50E54A (Ak binding peptide) or 46F50E54A (Ab binding peptide), respectively. Thus, the amino acid at position 56 of the A alpha chain determines allele-specific antigen presentation. This postulate was confirmed by direct binding analysis of 50E analogs of various I-A molecules. A single amino acid change (arginine to alanine) at position 56 of the Ak alpha chain altered the peptide binding specificity (46D50E54A to 46F50E54A).

A promiscuous T cell hybridoma restricted to various I-A molecules

In a previous study, we identified T cell receptor and major histocompatibility complex (MHC) contact sites on the pigeon cytochrome c p43-58 peptide. Positions 46 and 54 of p43-58 were shown to be the MHC-binding sites. Specific amino acids were identified on the MHC-binding sites which bound to the relevant I-A molecule. In the present study, using NOD (I-Ag7) mice, we established a T cell hybridoma specific for a p43-58 analog 46R50E54A with arginine (R) and alanine (A) at positions 46 and 54, respectively. Interestingly, NOE 33-1-2 recognized 46R50E54A in the presence of not only I-Ag7, but also I-Ad, s, u and v. In contrast to previous reports that promiscuous T cells were able to recognize peptide antigens with various HLA-DR or I-E molecules consist of monomorphic alpha and polymorphic beta chains, the promiscuous T cell clone NOE33-1-2 recognized peptides with various I-A molecules lacking the monomorphic chain.