Utilization of bloodfed females of Aedes aegypti as a vehicle for the transfer of the insect growth regulator pyriproxyfen to larval habitats

Bloodfed female Aedes aegypti were exposed to a surface treated with pyriproxyfen at 1.0 g m2 for 30 min and then allowed to lay eggs in cups of water containing 4th-instar larvae. Adult emergence from the immatures was highly inhibited, and transmission of pyriproxyfen from the females to the water was revealed. The transfer of the chemical to the water decreased with time before the blood meal. Chemical analysis for pyriproxyfen on the exoskeleton of treated females demonstrated the rapid disappearance of the compound. Pyriproxyfen obviously affected egg maturation of females treated before blood meals, as the number of eggs deposited decreased concurrently with the number of days before the blood meals.

Stimulation of in vitro hematopoiesis by a murine fetal hepatocyte clone through cell-cell contact

We have previously shown that a fetal liver-derived epithelial cell clone, FHC-4D2, could support hematopoiesis in vitro through its colony-stimulating factor (CSF) activities in a short-term culture. In this study, since FHC-4D2 cells were found capable of maintaining hematopoietic progenitors in the coculture for a long time, we examined how FHC-4D2 could exert hematopoietic supporting activity in a long-term culture by coculturing adult bone marrow (BM) cells or fetal liver (FL) cells on a monolayer of FHC-4D2 cells. This clone could maintain the colony-forming unit of granulocytes and macrophages (CFU-GM) of BM for > or = 12 weeks under the coculture condition, but the fibroblastic cell clone from the fetal liver, FHC-4A3, could not support the survival of CFU-GM, even for 1 week. In addition to BM CFU-GM, the FHC-4D2 clone also supported the survival of FL CFU-GM, burst-forming unit of erythroid cells (BFUe), and colony-forming unit of mixed progenitors (CFU-Mix) for longer than 4 weeks. When BM cells were separated by a membrane filter from the FHC-4D2 cells in the coculture, the comparable number of CFU-GM was maintained at day 3, but virtually no hematopoietic progenitors were detected at the end of the first week. CFU-GM were present in both nonadherent and adherent cells to the FHC-4D2 cells at day 3 of the coculture, but at day 7, the adherent population contained greater number of CFU-GM. CFU-GM derived from the adherent cells formed larger colonies and contained more bipotential CFU-GM than the nonadherent population. When BM cells from mice given 5-fluorouracil were cocultured with FHC-4D2 cells under the limiting dilution condition, interleukin-3 (IL-3)-responsive CFU-GM were induced from immature hematopoietic progenitor cells that were otherwise unresponsive to IL-3. From these data we conclude that the FHC-4D2 clone could generate and maintain IL-3-responsive hematopoietic progenitors via close contact and that, in the fetal liver, the contact between hepatocytes and hematopoietic cells may be critically important in inducing the differentiation of resting, IL-3-unresponsive immature hematopoietic cells into CFU-GM (progenitors responsive to IL-3) and in triggering the self-renewal of CFU-GM.

The effect of estrogen and androgen on androgen receptors and mRNA levels in uterine leiomyoma, myometrium and endometrium of human subjects

This study was designed to show the effect of estrogen and androgen on the level of testosterone and dihydrotestosterone specific binding sites (TBS and DHTBS, respectively) and to clarify the implication of androgen receptor mRNA expression to TBS and DHTBS in human uterine tissues. Estrogen mainly induces the increase of TBS and androgen receptor mRNA in uterine endometrium and leiomyoma. TBS increased by estrogen are downregulated when testosterone is given along with estrogen, while androgen receptor mRNA increased by estrogen was not significantly altered by testosterone with estrogen in endometrium and leiomyoma. These results suggest that the androgen receptor mRNA determined might encode TBS and that testosterone may stimulate the metabolic rate of TBS, or inhibit the translation rate of androgen receptor mRNA to TBS. Furthermore, the biological character of leiomyoma is considered to be an endometrial type.

Cytotoxic effect of extracellular ATP on L1210 leukemic cells and normal hemopoietic stem cells

The cytotoxic effect of extracellular adenosine triphosphate (ATP) was examined on normal murine hemopoietic stem cells and a representative leukemic cell line (L1210). After L1210 cells were incubated with 4 mM ATP for 3 h, 3H-thymidine incorporation was almost completely inhibited. The number of viable L1210 cells was also significantly decreased and L1210 colony formation was suppressed to approximately 30% of the control level after treatment. The CFU-GM survival rate was reduced to 70%, however, CFU-S and marrow nucleated cell numbers were not changed after the same treatment with ATP. All mice that were injected with the untreated mixture of normal marrow cells (3.3 x 10(4)) and L1210 cells (3.3 x 10(3)) died of leukemia within 18 days. On the contrary, 85% of the recipients given ATP-treated grafts survived more than 70 days. These findings indicate that ATP extra vivo treatment is useful for purging the residual leukemic cells in autologous bone marrow transplantation.

Isolated iliac artery aneurysm and its management

The records of 16 patients with 44 aneurysms of the iliac artery during a 12-year period (1981 to 1992) were retrospectively reviewed. The mean age was 71.2 (range 53-81) years; the male/female ratio was 7:1. An extremely high incidence of isolated iliac artery aneurysm was noted relative to abdominal aortic aneurysm (11.7%) during the same period. Aneurysms ranged in size from 2 to 12 cm. Rupture occurred in four patients (25%). Six patients presented urologic complications of ureteral stenosis, with hydronephrosis caused by perianeurysmal fibrosis in five. Thirteen patients underwent surgical treatment with emergency operation performed in four with rupture and one with impending rupture. The mortality rate for ruptured aneurysm was high (50%). The operative procedures for common iliac aneurysms were open resection in 18, aneurysmectomy in two, and thromboexclusion in three. For internal iliac aneurysms, the procedures were aneurysmorrhaphy (partial resection) in five, obliterative endoaneurysmorrhaphy in seven, aneurysmectomy in two, and thromboexclusion in two, with appropriate graft replacement. Endarterectomy and reimplantation of the inferior mesenteric artery, and internal iliac artery graft interposition were performed to prevent colon ischaemia in three and two patients, respectively. Ureterolysis was performed in three patients with ureteral stenosis caused by perianeurysmal fibrosis, which improved hydronephrosis and renal function in two. Early diagnosis and elective surgery before rupture is the treatment of choice for saving the patient's life. The importance of preventing colon ischaemia for bilateral internal iliac aneurysms and ureterolysis for ureter entrapped within perianeurysmal fibrosis is emphasized.

Partial purification of murine tumor-associated peptide epitopes common to histologically distinct tumors, melanoma and sarcoma, that are presented by H-2Kb molecules and recognized by CD8+ tumor-infiltrating lymphocytes

The B16/BL6 melanoma is a relatively nonimmunogenic tumor expressing low levels of MHC class I molecules. BL6 clones expressing transfected H-2Kb class I molecules were, by contrast, highly immunogenic in immunocompetent mice. Tumor-infiltrating lymphocytes (TILs) generated from the H-2Kb+ BL6 lesions (Thy 1.2+, CD8+, CD4-) efficiently lysed H-2Kb+ melanoma (CL8-1 and 2Kb38) and the H-2Kb+ nonrelated 3-methylcholanthrene (MCA)-105 sarcoma, but not the H-2Kb- parental melanoma BL6-8. This strongly suggests that CL8-1, 2Kb38, and MCA-105 express identical or cross-reactive T cell epitopes recognized by CL8-1 TILs in the context of the H-2Kb class I allele. To identify the T cell epitopes, peptides were acid-eluted from various cells, and fractionated by HPLC. Five HPLC fractions (F1mel-F5mel) of 70 tested contained peptides derived from H-2Kb+ CL8-1 melanoma (but not H-2Kb- melanomas) that were capable of conferring susceptibility to CL8-1 TIL lysis on H-2b-expressing target cells (EL4, C1R.Kb), but not on H-2d-expressing P815 target cells. CL8-1 TILs failed to recognize peptides derived from H-2Kb+ nonmelanoma targets such as EL4 or normal B6 splenocytes. Interestingly, CL8-1 TILs appeared to recognize peptide species contained in two HPLC fractions derived from the MCA-105 sarcoma (F1sar and F5sar). Conversely, TILs derived from MCA-105 lesions recognized MCA-105 and CL8-1 tumor cells, as well as F5mel and F5sar peptides presented by EL4 targets. These data support common murine tumor-associated peptide epitopes presented by H-2Kb and recognized by CD8+ CTLs derived from histologically distinct tumors, melanoma and sarcoma.

[Successful mitral valve replacement in multiple organ failure due to mechanical hemolytic anemia after mitral valve repair: a case report]

An 18-year-old man suffered multiple organ failure due to hemolytic anemia after mitral valve repair. He was admitted with mitral regurgitation (MR) and mitral valve repair was performed. However, after 3 days of the operation, he developed hemolytic anemia and heart murmur. A reoperation of mitral valve replacement was performed because of progressing heart failure with renal and liver dysfunction. The operative findings revealed a rupture in the choldae with dislocation of the C-E ring. The MR flow and dislocated ring are suspected to be the cause of the hemolysis. After the reoperation, the hemolysis and general condition were immediately improved. The indication of this reoperation should be carefully decided. In this case of multiple organ failure following mitral valve repair, reoperation of mitral valve replacement was successful.

Partial purification of murine tumor-associated peptide epitopes common to histologically distinct tumors, melanoma and sarcoma, that are presented by H-2Kb molecules and recognized by CD8+ tumor-infiltrating lymphocytes

The B16/BL6 melanoma is a relatively nonimmunogenic tumor expressing low levels of MHC class I molecules. BL6 clones expressing transfected H-2Kb class I molecules were, by contrast, highly immunogenic in immunocompetent mice. Tumor-infiltrating lymphocytes (TILs) generated from the H-2Kb+ BL6 lesions (Thy 1.2+, CD8+, CD4-) efficiently lysed H-2Kb+ melanoma (CL8-1 and 2Kb38) and the H-2Kb+ nonrelated 3-methylcholanthrene (MCA)-105 sarcoma, but not the H-2Kb- parental melanoma BL6-8. This strongly suggests that CL8-1, 2Kb38, and MCA-105 express identical or cross-reactive T cell epitopes recognized by CL8-1 TILs in the context of the H-2Kb class I allele. To identify the T cell epitopes, peptides were acid-eluted from various cells, and fractionated by HPLC. Five HPLC fractions (F1mel-F5mel) of 70 tested contained peptides derived from H-2Kb+ CL8-1 melanoma (but not H-2Kb- melanomas) that were capable of conferring susceptibility to CL8-1 TIL lysis on H-2b-expressing target cells (EL4, C1R.Kb), but not on H-2d-expressing P815 target cells. CL8-1 TILs failed to recognize peptides derived from H-2Kb+ nonmelanoma targets such as EL4 or normal B6 splenocytes. Interestingly, CL8-1 TILs appeared to recognize peptide species contained in two HPLC fractions derived from the MCA-105 sarcoma (F1sar and F5sar). Conversely, TILs derived from MCA-105 lesions recognized MCA-105 and CL8-1 tumor cells, as well as F5mel and F5sar peptides presented by EL4 targets. These data support common murine tumor-associated peptide epitopes presented by H-2Kb and recognized by CD8+ CTLs derived from histologically distinct tumors, melanoma and sarcoma.

Autoreactive T cell-dependent polyclonal hypergammaglobulinemia in mantle cell lymphoma

We investigated the mechanism of polyclonal B cell differentiation in mantle cell lymphoma (MCL) using peripheral blood mononuclear cells (PBMC) from a patient with MCL in leukemic stage presenting polyclonal hypergammaglobulinemia. Patient T cells not only responded to autologous non-T cells but induced polyclonal production of IgG in vitro. Flow cytometric analysis of PBMC showed the increased conversion of CD4+ T cells from the naive to the memory state. We propose the possible mechanism that autoreactive T cells may be involved in polyclonal B cell differentiation in this monoclonal B cell disorder.

Expression of mRNA encoding IFN alpha in macrophages stimulated with Lactobacillus gasseri

The ability of Lactobacillus gasseri, a dairy lactic acid bacterium, to induce interferon (IFN) was investigated in murine macrophage cultures. IFN alpha was substantially induced by some strains of L. gasseri and the titers were the highest at a concentration of 100 micrograms ml-1 of L. gasseri DSM20243T. The expression of mRNA encoding IFN alpha was detected in spleen-macrophages (SP-M phi) and Peyer's patch-adherent cells stimulated with L. gasseri DSM20243T. Actinomycin D and cycloheximide added to SP-M phi cultures showed that the mRNA was synthesized by 0.5 h, and that IFN alpha was produced within 3 to 6 h after the stimulation with L. gasseri DSM20243T. The results support the notion that dairy products containing L. gasseri can be 'physiologically functional foods'.

Control of ColE2 plasmid replication: negative regulation of the expression of the plasmid-specified initiator protein, Rep, at a posttranscriptional step

The incA gene of ColE2 is involved in the copy number control and incompatibility. Two promoters were identified around the incA gene. Transcription of the mRNA for the essential plasmid-coded initiator protein (Rep) mainly starts at a site about 140 bp upstream of the initiation codon of the Rep protein. The second transcript (RNA I) of about 115 nucleotides with two stem-and-loop structures is entirely complementary to the 5' untranslated region of the Rep mRNA. By using translational and transcriptional fusions of the rep gene of ColE2 and the lacZ gene of Escherichia coli, the incA gene product was shown to regulate expression of the rep gene at a posttranscriptional step. The results also suggest that the target of the incA gene product is the 5' untranslated region of the Rep mRNA. Deletion analyses reported here show that a region(s) about 17 to 70 bp upstream of the initiation codon of the Rep protein and another region inside the coding frame are important for efficient production of the Rep protein. This suggests that some additional sequence elements other than the initiation codon and the Shine-Dalgarno region and/or a secondary structure of the Rep mRNA are required for efficient production of the Rep protein. These results show that RNA I is an antisense RNA for the Rep mRNA and imply that it might regulate expression of the rep gene at the initiation step of translation by sequestering such additional sequence elements and/or by disrupting RNA secondary structure. We propose that RNA I represents the incA gene product.

Control of ColE2 plasmid replication: regulation of Rep expression by a plasmid-coded antisense RNA

We isolated and characterized mutants of ColE2 with increased copy number (cop) and those with reduced sensitivity to the wild-type incA gene (inc). Both types of mutations were single-base substitutions in the incA region and simultaneously increased the plasmid copy number and reduced the inhibitory activity of the incA gene on ColE2 DNA replication. Most of the cop mutations also reduced sensitivity to the wild-type incA gene. These mutations were located in the region specifying the large stem-and-loop structures of RNA I and the 5' portion of the Rep mRNA. All these results indicate that RNA I interacts with the Rep mRNA and thereby inhibits expression of the Rep protein at a post-transcriptional step and that this is probably the only mechanism that controls the ColE2 Rep protein expression. It is suggested that only portions of the nucleotides in the loop region are involved in initial (kissing) interaction of these RNAs. The total level of rep gene expression in the host cells appears to be kept constant (at a level characteristic for each cop allele) irrespective of the actual plasmid copy number above a certain level, when rep gene expression is regulated by the incA gene on the same plasmid. These seem to be the basic mechanisms for the replication control of ColE2.

Comparison of polymerase chain reaction and culture methods for detection of Mycoplasma pulmonis from nasal, tracheal and oral swab samples of rats

The polymerase chain reaction (PCR) and culture methods were used to detect Mycoplasma pulmonis in nasal, tracheal and oral swab samples of rats derived from 5 mycoplasma-contaminated and 2 mycoplasma-free facilities, and the results of both methods were compared. Thirty-four/54 and 30/54 in nasal samples, 31/54 and 28/54 in tracheal samples, and 12/39 and 30/39 in oral samples were positive in PCR and cultures, respectively. Agreements in the results of both tests were 48/54 (88.9%) in nasal samples and 49/54 (90.7%) in tracheal samples. This indicates that nasal and tracheal samples are useful for detecting M. pulmonis by PCR. The detection number for M. pulmonis from the oral cavity by PCR was remarkably lower than those of nasal and tracheal sites. These results show that the PCR method has significant potential as a rapid and sensitive method for detecting M. pulmonis in clinical samples collected from the nasal cavity and trachea.

Detection of Bacillus piliformis by specific amplification of ribosomal sequences

In an effort to explore a sensitive species-specific detection system using the polymerase chain reaction (PCR) for B. piliformis, we sequenced 16S ribosomal DNA (rDNA) of the organism (MSK strain) isolated from the mouse and compared it with known rDNA sequences of the RJ strain isolated from the rat. Sequence homology between the MSK strain and the RJ strain was over 97%, but homology between the MSK strain and other bacterial species was less (70-83%). The results indicated that the sequences included B. piliformis species-specific regions. On the basis of the sequences, we designed a PCR primer set which amplifies B. piliformis rDNA specifically. The PCR with the primer set detected not only these two strains but also an HN strain of hamster origin, although it did not detect other organisms. Therefore, this primer set was considered to be specific for B. piliformis species. More than one organism (RJ strain) could be detected by the PCR method. Nine Jcl:Wistar rats were infected perorally with 2x10(4) RJ strain organisms, and three rats each were sacrificed on days 1, 3 and 5 postinoculation (p.i.) to investigate the presence of the organism in the liver, heart, cecum, spleen and mesenteric lymph nodes by PCR and the immunofluorescence test. On days 1 and 3 p.i., B. piliformis was not detected in any tissues of the six rats, but B. piliformis was detected in two of the three rats sacrificed on day 5 p.i. The presence of the pathogen was seen in both liver and heart (1/3), or in the cecum (1/3) by both methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of dephosphate bromofenofos in milk by liquid chromatography with electrochemical detection

A sensitive, specific method for the determination of dephosphate bromofenofos (DBFF) in milk by liquid chromatography (LC) with electrochemical detection is described. DBFF, the only metabolite of bromofenofos (BFF, a fasciolicide), was extracted from milk by liquid-liquid partition with acetone, acetonitrile, and dichloromethane and purified by using a C18 cartridge. The compound was separated from the matrix peaks by reversed-phase LC and detected by dual-electrode coulometric detection on a Kaseisorb LC ODS-300-5 (250 x 4.6 mm id, 5 microns) column. The mobile phase was acetonitrile-0.05M potassium dihydrogen phosphate (55 + 45, v/v) at pH 3.0. The flow rate was 1 mL/min at 40 degrees C. The applied potentials of detectors 1 and 2 were maintained at 0.30 and 0.45 V, respectively. Average recoveries (n = 5) of DBFF from milk spiked at 1 and 10 ng/mL were 73.1 and 82.7%, respectively; and coefficients of variation were 8.4 and 2.8%, respectively. The detection limit of DBFF in milk was 0.2 ng/mL. Fifty-nine raw and 181 commercial milks were analyzed. DBFF was detected in 4 raw milks (0.2-1.5 ng/mL; average, 0.6 ng/mL) and in 3 normal liquid commercial milks (0.3-0.7 ng/mL; average, 0.5 ng/mL). The identity of DBFF from milk was confirmed by gas chromatography/mass spectrometry.

Spinal cord protection: development of a paraplegia-preventive solution

We present a clinically available method to protect the spinal cord against ischemic or reperfusion injury and to prevent paraplegia after cross-clamping of the aorta. We separated 35 rabbits into five equal groups and clamped each animal's abdominal aorta distal to the left renal artery. We also occluded the aortas 2 cm above the iliac bifurcation for 45 minutes with inflated 5F balloon catheters. Through the catheter port distal to each balloon one of four different solutions was infused at 3 degrees C for 3 minutes at a rate of 5 mL/min (group I, uninfused control; group II, lactated Ringer's solution; group III, lactated Ringer's solution + 30 mg/kg of methylprednisolone; group IV, lactated Ringer's solution+methylprednisolone + 3 mL of 20% mannitol; group V, lactated Ringer's solution+methylprednisolone+mannitol + 10 mg/kg of vitamins E and C). We assessed the neurologic status of the hind limbs on the second postoperative day using Tarlov's criteria. The neurologic status in groups III, IV, and V was significantly superior to that of group I (p < 0.05, groups III versus I; p < 0.01, groups IV and V versus I). Spastic paraplegia occurred in 71% of group I, in 43% of group II, in 29% of group III, in 14% of group IV, and not at all in group V. The infusion of our specially blended solution with several spinal cord neuroprotective properties (hypothermia, methylprednisolone, mannitol, and vitamins E and C) achieved the best spinal cord protection against ischemic or reperfusion injury and prevented postoperative paraplegia.

Isolation and characterization of a highly hydrophobic new bacteriocin (gassericin A) from Lactobacillus gasseri LA39

A new bacteriocin, gassericin A, was purified from the culture fluid of Lactobacillus gasseri LA39 mainly by reverse-phase (RP) chromatography. The purification of gassericin A from a modified MRS broth, in which Tween 80 had been replaced by oleic acid, resulted in a 4500-fold increase in specific activity with a 6% recovery. Gassericin A was eluted as a single peak on the chromatogram from RP-HPLC and migrated by SDS-PAGE as a single band with a molecular weight of ca. 3.8 kDa. Gassericin A, a highly hydrophobic bacteriocin, was slightly soluble in water, but its solubility was increased by adding alcohol and acetonitrile. An amino acid analysis revealed that it was composed of 45.7% hydrophobic amino acids in the total residues of 35 amino acids. Gassericin A produced in the MRS broth associated strongly with Tween 80, although several further trials of dissociation were unsuccessful.

Nucleolar organizer regions in tongue carcinomas induced in rats: comparison with DNA cytofluorometric analysis

Eleven papillomas and 25 carcinomas were induced in rat tongues by oral administration of 0.001% 4-nitroquinoline 1-oxide (4NQO) in drinking water, and the biological characteristics and proliferative activity of the tumors were investigated by both DNA cytofluorometry and the argyrophilic nucleolar organizer region (AgNOR) staining method. The histopathological characteristics, the mean number of AgNORs per cell and DNA ploidy patterns were compared. The mean AgNOR number was lowest in normal epithelium (1.65 +/- 0.10), and highest in squamous cell carcinomas (2.97 +/- 0.70) and intermediate in papillomas (1.87 +/- 0.28). The differences were statistically significant. All normal epithelium and all papillomas showed a diploid pattern. Eighteen (72%) of 25 squamous cell carcinomas showed a diploid pattern, while 7 (28%) showed a diploid plus tetraploid pattern. There was a significant difference in the mean AgNOR number between the two ploidy groups of squamous cell carcinomas. These results suggest that the mean AgNOR number may reflect the histological grade in the process of carcinogenesis and polyploidization of carcinomas.

Different modes of interaction of two peptide fragments from subdomain 4 of rabbit skeletal muscle actin with actin promoters

Previously, we reported that the 2.6 kDa peptide fragment extending from Arg-177 to Tyr-198 in rabbit skeletal muscle actin bound to actin itself and inhibited its polymerization, while the 9.1 kDa peptide extending from Ser-199 to Tyr-279 in actin did not. The 2.6 kDa segment of actin was reported to contain one of the important actin-actin contacts (Hori, K. and Morita, F. (1992) J. Biochem. 112, 401-408). In this paper, we show additional evidence that the rate of salt-induced increase in the fluorescence of pyrene-labeled actin was decreased in the presence of the 2.6 kDa peptide. Conventional actin filaments were only scarcely observed in the presence of the 2.6 kDa peptide under an electron microscope with a steady state of fluorescence increase. Furthermore, the 2.6 kDa peptide was found to sever F-actin into short filament fragments. The 9.1 kDa peptide, on the other hand, neither inhibited the fluorescence increment of pyrene-actin nor severed actin filaments. However, the 9.1 kDa peptide was found to increase the viscosity and fluorescence intensity of pyrene-G-actin and to form short actin filaments in the absence of salts. Contact sites in the 9.1 kDa segment in actin may have a different mode of interaction with adjacent actin promoters in actin filaments from that of the 2.6 kDa segment.

New modification of a mammary artery retractor

A new accessory instrument to the self-retaining internal mammary artery retractor was developed. This instrument presses the chest wall inward, relieves the concavity of the inner surface of the chest wall, and provides good exposure of the internal mammary artery.

Effects of exogenously applied calponin on Ca(2+)-regulated force in skinned smooth muscle of the rabbit mesenteric artery

To help elucidate the physiological role of calponin (a thin-filament-linked regulatory protein) in smooth muscle contraction, the effects of its exogenous application were investigated on actin-activated MgAT-Pase activity in crude actomyosin from chicken gizzard, and on contraction induced by Ca(2+)-dependent and -independent means in arterial smooth muscle strips skinned by saponin or beta-escin. Calponin concentration dependently inhibited actin-activated MgATPase activity with a proportional increase in its binding to actomyosin and also attenuated Ca(2+)-induced contractions, in the presence or absence of calmodulin, in skinned arterial strips. Calponin, when phosphorylated by protein kinase C, reduced both its ability to bind to actomyosin and its inhibitory action on actomyosin MgATPase. The phosphorylated calponin also had no effect on the maximum Ca(2+)-induced contraction in skinned smooth muscle, suggesting that these actions of calponin are not nonspecific. Calponin attenuated the Ca(2+)-independent contraction observed in myosin light chain thio-phosphorylated strips, or on application of trypsin-treated myosin light chain kinase. However, calponin had no effect on maintained rigor contraction. These results suggest that in vascular smooth muscle, calponin may play a physiological role in the inhibition of Ca(2+)-regulated force, possibly through a direct action on active actin-myosin interactions.

Mechanisms of vasoconstriction induced by endothelin-1 in smooth muscle of rabbit mesenteric artery

1. The mechanism underlying the vasoconstriction induced by endothelin-1 (ET-1) was investigated by measuring the intracellular concentration of Ca2+ ([Ca2+]i), isometric force and phosphorylation of the myosin light chain (MLC) in endothelium-denuded unskinned and beta-escin-treated skinned smooth muscle from resistance vessels of the rabbit mesentery. The role of protein kinase C (PKC) in the action of ET-1 was studied in skinned smooth muscle using a synthetic peptide, PKC19-36, which corresponds to the autoinhibitory domain of PKC. 2. ET-1 (> 0.1 nM) induced slowly developing, maintained increases in [Ca2+]i and force. Nicardipine completely blocked the ET-1-induced increase in [Ca2+]i. BQ-123 (an inhibitor of the ETA receptor) blocked the ET-1-induced contraction but IRL 1620 (Suc-[Glu9,Ala11,15]-ET-1(8-21), an agonist of the ETB receptor) failed to induce contraction. 3. In ionomycin- and 70 mM K(+)-treated strips, ET-1 shifted the [Ca2+]i-force relationship to the left and enhanced the maximum amplitude of contraction induced by 2.6 mM Ca2+. In skinned smooth muscle treated with ionomycin, Ca2+ (0.1-3 microM) increased both force and MLC phosphorylation, in a concentration-dependent manner. ET-1 with GTP shifted both the Ca(2+)-force and Ca(2+)-MLC phosphorylation relationships to the left without significant changes in the maximum responses. ET-1 with GTP did not change the relationship between force and MLC phosphorylation. Similar effects were observed with phorbol 12,13-dibutyrate (PDBu, an activator of PKC). These results indicate that the sensitivity of MLC phosphorylation to Ca2+ is enhanced both by ET-1 with GTP and by PDBu. 4. PKC19-36 (an inhibitor of PKC) modified neither the contraction nor MLC phosphorylation induced by 0.3 microM Ca2+ but blocked the PDBu-induced enhancement of both these Ca(2+)-induced responses. However, PKC19-36 only partly inhibited the enhancement produced by ET-1 with GTP on the Ca(2+)-induced responses. PKC19-36 did not modify the relationship between force and MLC phosphorylation in the presence either of ET-1 with GTP or of PDBu. By contrast, BQ-123, neomycin and guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) each abolished the ET-1-induced enhancement of the contraction induced by 0.3 microM Ca2+. 5. These results suggest that ET-1 acts on the ETA receptor and increases Ca2+ influxes through an activation of the dihydropyridine-sensitive Ca2+ channel, causing a long-lasting and maintained contraction in resistance vessels of the rabbit mesentery.(ABSTRACT TRUNCATED AT 400 WORDS)