Nucleotide sequences of the rabbit alpha-smooth-muscle and beta-non-muscle actin mRNAs

Expression and characterization of functional recombinant bovine follicle-stimulating hormone (boFSHalpha/beta) produced in the milk of transgenic rabbits

Bovine follicle-stimulating hormone (boFSH) is a heterodimeric glycoprotein that belongs to the pituitary gonadotropins. Bioactive FSH is composed of alpha and beta subunits which require extensive N-glycosylation and sialylation. The mammary gland of transgenic livestock is an attractive source for the synthesis of post-translationally modified proteins. Two mammary gland-specific gene constructs with the cDNA for the boFSH alpha (boFSHalpha) and beta (boFSHbeta) subunits controlled by bovine alpha-s1 casein regulatory sequences were co-microinjected into fertilized rabbit oocytes. Two FSHalpha/FSHbeta double transgenic rabbit lines were established. The transgene expression was strictly lactation and mammary gland specific. Protein analysis revealed the presence of the boFSH heterodimer in the milk of transgenic rabbits showing a molecular weight similar to that of purified pituitary gland derived boFSH (boFSH-P). Subunit specific antibodies detected both polypeptides with the expected molecular sizes. Biochemical characterization demonstrated the expected isoelectric points of the recombinant boFSH. The presence of the post-translationally added terminal sialic acid residues was indicated by wheat germ agglutinin (WGA) lectin Western blotting. The biological activity of the recombinant mammary gland produced boFSH was determined using a FSH-dependent reporter cell line. The bioactivity of the recombinant boFSH was comparable to that of purified boFSH-P.

Cytokines and oxygen radicals after hyperoxia in preterm and term alveolar macrophages

To determine if the alveolar macrophage inflammatory cytokine response to oxygen differs in premature cells, macrophages were obtained from litters of premature (27 days) and term (31 days) rabbits. The majority of these cells were nonspecific esterase positive and actively phagocytosed latex particles. The cells that expressed cytokines also reacted with a monoclonal antibody against rabbit macrophages. After incubation overnight in 5 or 95% oxygen, the amount of interleukin (IL)-1beta and IL-8 mRNA was assessed by RT-PCR and the amount of cytokine protein by quantitative immunofluorescence microscopy. The preterm macrophage showed a significant increase in cytokine mRNA and protein after overnight incubation in 95% oxygen. This response was not seen in the term cells. Only premature macrophages had a significant increase in intracellular oxygen radical content, measured by 2',7'-dichlorofluorescin analysis, after incubation in 95% oxygen. This enhanced inflammatory cytokine response to oxygen may be one mechanism involved in the early development of chronic lung disease in premature infants.

Collar-induced elevation of mRNA and functional activity of 5-HT(1B) receptor in the rabbit carotid artery

Hypersensitivity to serotonin (5-HT) develops in rabbit collared carotid arteries. Previous data demonstrated the involvement of 5-HT(1)-like receptors which are not active in normal carotid arteries. This study investigated the interaction in the rabbit carotid artery between 5-HT and a moderate tone as this can uncover functional 5-HT(1)-like receptors. Furthermore, the expression of messenger RNA (mRNA) and protein of 5-HT(1B), 5-HT(1D) and 5-HT(2A) receptors was addressed. Silicone collars were placed around the carotid arteries of male New Zealand White rabbits for 1 week. Rings from inside (=collar) and outside (=sham) the collar were either mounted in isolated organ baths for isometric force measurements or frozen in liquid nitrogen to isolate total RNA or proteins which were subsequently analysed by respectively reverse transcriptase-polymerase chain reaction and Western blot analysis. In sham and collared rings concentration-response curves (CRC's) to 5-HT were monophasic. Only in collared segments the presence of a 5-HT(2A) antagonist (spiperone or ketanserin, 0.1 microM) revealed a biphasic CRC which was even more pronounced when a moderate tone was induced by KCl pointing to functional 5-HT(1)-like receptors. The rabbit carotid artery constitutively expressed 5-HT(1B) and 5-HT(2A) mRNA, not 5-HT(1D) mRNA. Manipulation of the carotid artery increased the 5-HT(1B) mRNA level. Collar placement raised it even further. The 5-HT(2A) mRNA level remained unchanged. All the anti-5-HT receptor antibodies tested resulted in variable, non specific patterns with multiple bands. In conclusion, collar placement elevates mRNA expression and activity of the 5-HT(1B) receptor in the rabbit carotid artery.

Periadventitial inducible nitric oxide synthase expression and intimal thickening

Positioning a silicone collar around the rabbit carotid artery induces a smooth muscle cell-rich intimal thickening. We investigated the localization of inducible nitric oxide synthase (iNOS) during thickening of the intima, the effect of iNOS inhibition on intimal thickness, and the effect of oxidized LDL (ox-LDL) on iNOS expression in the vessel wall. Collars were positioned for 18 hours or for 3, 7, or 14 days. Arterial cross sections were immunostained for iNOS, including naïve, sham-operated, and carotid arteries in which ox-LDL had been infused locally for 14 days. Furthermore, collars were connected to osmotic minipumps for local delivery (5 microL. h(-1), 14 days, n=12) of saline or the iNOS inhibitor L-N(6)-(1-iminoethyl)-lysine-HCl (L-NIL, 10 mmol/L). In the adventitia and the periadventitial granulation tissue of collared arteries, iNOS-positive macrophages and T lymphocytes were present from 18 hours onward. The media and intima were negative for iNOS. Reverse transcription-polymerase chain reaction revealed iNOS mRNA in collared but not in sham-operated arteries. Local inhibition of iNOS doubled the intimal thickness and decreased nitrotyrosine staining. Ox-LDL-treated arteries, which had a thicker intima, showed a pronounced influx of macrophages and T lymphocytes in all layers of the vessel wall, accompanied by iNOS expression in a subpopulation of these cells. Our study indicates that iNOS was not induced in intimal thickenings predominantly consisting of smooth muscle cells. However, iNOS was expressed in (peri)adventitial tissue and counteracted the progression of intimal thickening. Ox-LDL treatment was accompanied by an abundant influx of iNOS-positive macrophages and T lymphocytes in the vessel, but this could not prevent the progression of intimal thickening.

Increased interleukin-1 (IL-1) and imbalance between IL-1 and IL-1 receptor antagonist during acute inflammation in experimental Shigellosis

Infection by the enteric bacterial pathogen Shigella results in intense mucosal inflammation and destruction of the colonic and rectal epithelium in infected humans. Initial bacterial translocation occurs through the follicle-associated epithelium. Previous experiments suggest that interleukin-1 (IL-1) is crucial to trigger inflammation, particularly in the follicular zones. During the first 4 hours of infection in a rabbit ligated-loop model of intestinal invasion, there are two salient characteristics: (i) a high concentration of IL-1alpha and IL-1beta, both in infected Peyer's patch tissue and in the corresponding efferent mesenteric blood, and (ii) a very low level of expression of IL-1 receptor antagonist (IL-1ra). These may reflect a combination of regulation of expression and secretion of IL-1alpha, IL-1beta, and IL-1ra by both resident and recruited phagocytes and the induction of mononuclear phagocyte apoptosis by Shigella. This low IL-1ra/IL-1 ratio likely accounts for the rapid, uncontrolled inflammation characteristic of shigellosis.

Intimal deposition of functional von Willebrand factor in atherogenesis

During the formation of intimal thickening in normocholesterolemic rabbits, von Willebrand factor (vWF) is increased in the endothelial cells (ECs) and deposited in the intima. We investigated whether this also occurs during cholesterol-induced plaque formation, whether the synthesis of vWF increases, and whether this influences platelet adhesion. Rabbits were fed a cholesterol-rich (0.3%) diet for 26 weeks. Thereafter, half of the animals received a normal diet for another 26 weeks (cholesterol withdrawal). To induce intimal thickening in normocholesterolemic rabbits, collars were positioned around the carotid artery. Arterial segments were studied using immunohistochemistry, reverse transcription-polymerase chain reaction, electron microscopy, and platelet adhesion tests. Cholesterol treatment induced plaque formation in the aorta. The ECs had a cuboidal aspect, showed a dense immunoreactivity for vWF, a pronounced rough endoplasmic reticulum, and numerous Weibel-Palade bodies. There were subendothelial vWF deposits in the plaques and vWF mRNA was significantly increased as compared with controls. Similar changes were seen after collar-induced intimal thickening. After cholesterol withdrawal, both vWF mRNA and the ultrastructural morphology of the ECs normalized, and the vWF deposits disappeared from the plaque. Perfusion studies with anticoagulated rabbit blood over cross-sections of atherosclerotic aortas revealed increased vWF-mediated platelet adhesion in the subendothelial plaque region. Whereas rabbit platelets perfused through the lumen adhered to the same extent to de-endothelialized aortas of normocholesterolemic and atherosclerotic rabbits, vWF mediated platelet adhesion to endothelium was observed in atherosclerotic but not in normal aortas. Our results show an increased synthesis and (sub)endothelial presence of vWF after vascular injury, with functional consequences for platelet deposition on the vessel wall.

The Presence of Novel Amino Acids in the Cytoplasmic Domain of Stem Cell Factor Results in Hematopoietic Defects inSteel17H Mice

Stem cell factor (SCF) is expressed as an integral membrane growth factor that may be differentially processed to produce predominantly soluble (S) (SCF248) or membrane-associated (MA) (SCF220) protein. A critical role for membrane presentation of SCF in the hematopoietic microenvironment (HM) has been suggested from the phenotype of the Steel-dickie(Sld) mice, which lack MA SCF, and by studies performed in our laboratory (and by others) using long-term bone marrow cultures and transgenic mice expressing different SCF isoforms.Steel17H (Sl17H) is an SCF mutant that demonstrates melanocyte defects and sterility in males but not in females. The Sl17H allele contains a intronic mutation resulting in the substitution of 36 amino acids (aa’s) in the SCF cytoplasmic domain with 28 novel aa’s. This mutation, which affects virtually the entire cytoplasmic domain of SCF, could be expected to alter membrane SCF presentation. To investigate this possibility, we examined the biochemical and biologic properties of the Sl17H-encoded protein and its impact in vivo and in vitro on hematopoiesis and on c-Kit signaling. We demonstrate that compound heterozygous Sl/Sl17H mice manifest multiple hematopoietic abnormalities in vivo, including red blood cell deficiency, bone marrow hypoplasia, and defective thymopoiesis. In vitro, both S and MA Sl17H isoforms of SCF exhibit reduced cell surface expression on stromal cells and diminished biological activity in comparison to wild-type (wt) SCF isoforms. These alterations in presentation and biological activity are associated with a significant reduction in the proliferation of an SCF-responsive erythroid progenitor cell line and in the activation of phosphatidylinositol 3-Kinase/Akt and mitogen-activated protein-Kinase signaling pathways. In vivo, transgene expression of the membrane-restricted (MR) (SCFX9/D3) SCF in Sl/Sl17H mutants results in a significant improvement in peripheral red blood cell counts in comparison toSl/Sl17H mice.

The Presence of Novel Amino Acids in the Cytoplasmic Domain of Stem Cell Factor Results in Hematopoietic Defects inSteel17H Mice

Stem cell factor (SCF) is expressed as an integral membrane growth factor that may be differentially processed to produce predominantly soluble (S) (SCF248) or membrane-associated (MA) (SCF220) protein. A critical role for membrane presentation of SCF in the hematopoietic microenvironment (HM) has been suggested from the phenotype of the Steel-dickie(Sld) mice, which lack MA SCF, and by studies performed in our laboratory (and by others) using long-term bone marrow cultures and transgenic mice expressing different SCF isoforms.Steel17H (Sl17H) is an SCF mutant that demonstrates melanocyte defects and sterility in males but not in females. The Sl17H allele contains a intronic mutation resulting in the substitution of 36 amino acids (aa’s) in the SCF cytoplasmic domain with 28 novel aa’s. This mutation, which affects virtually the entire cytoplasmic domain of SCF, could be expected to alter membrane SCF presentation. To investigate this possibility, we examined the biochemical and biologic properties of the Sl17H-encoded protein and its impact in vivo and in vitro on hematopoiesis and on c-Kit signaling. We demonstrate that compound heterozygous Sl/Sl17H mice manifest multiple hematopoietic abnormalities in vivo, including red blood cell deficiency, bone marrow hypoplasia, and defective thymopoiesis. In vitro, both S and MA Sl17H isoforms of SCF exhibit reduced cell surface expression on stromal cells and diminished biological activity in comparison to wild-type (wt) SCF isoforms. These alterations in presentation and biological activity are associated with a significant reduction in the proliferation of an SCF-responsive erythroid progenitor cell line and in the activation of phosphatidylinositol 3-Kinase/Akt and mitogen-activated protein-Kinase signaling pathways. In vivo, transgene expression of the membrane-restricted (MR) (SCFX9/D3) SCF in Sl/Sl17H mutants results in a significant improvement in peripheral red blood cell counts in comparison toSl/Sl17H mice.

Scavenger receptor activity is increased in macrophages from rabbits with low atherosclerotic response: studies in normocholesterolemic high and low atherosclerotic response rabbits

We have previously described 2 strains of New Zealand White rabbits with a high (HAR) or low (LAR) atherosclerotic response to hypercholesterolemia. In the present study, we focused on class A scavenger receptor (SR-A) activity and ApoE expression in macrophages from both rabbit strains. These parameters play a crucial role in maintaining cholesterol homeostasis in the arterial wall and may be involved in the development of atherosclerosis. SR activity, as measured by uptake of DiI-labeled acetylated LDL, was significantly higher in macrophages from LAR rabbits (2177+/-253 ng/mg cell protein) than in macrophages from HAR rabbits (1153+/-200 ng/mg cell protein). The higher SR activity was caused by a greater number of SRs (apparent Vmax, 4100 ng/mg in LAR and 1980 ng/mg in HAR rabbits). The high SR activity in macrophages from LAR rabbits was associated with a significantly higher expression of SR-A mRNA compared with macrophages from HAR rabbits. However, the latter finding could not be explained by differences in the activity of transcription factor-activating protein 1 (AP-1), which was comparable in macrophages from both strains of rabbits. Because under certain circumstances SR-A mRNA expression is regulated in parallel with ApoE expression, we also evaluated this parameter. Although ApoE mRNA was 74% higher in macrophages from LAR rabbits, the difference did not reach statistical significance. In conclusion, the increased expression of SR-A in macrophages in the presence of adequate amounts of ApoE may play a role in attenuating atherosclerosis in LAR rabbits.

Expression of insulin growth factor-1 splice variants and structural genes in rabbit skeletal muscle induced by stretch and stimulation

1. Skeletal muscle is a major source of circulating insulin growth factor-1 (IGF-1), particularly during exercise. It expresses two main isoforms. One of the muscle IGF-1 isoforms (muscle L.IGF-1) is similar to the main liver IGF-1 and presumably has an endocrine action. The other muscle isoform as a result of alternative splicing has a different 3' exon sequence and is apparently designed for an autocrine/paracrine action (mechano-growth factor, MGF). Using RNase protection assays with a probe that distinguishes these differently spliced forms of IGF-1, their expression and also the expression of two structural genes was measured in rabbit extensor digitorum longus muscles subjected to different mechanical signals. 2. Within 4 days, stretch using plaster cast immobilization with the limb in the plantar flexed position resulted in marked upregulation of both forms of IGF-1 mRNA. Electrical stimulation at 10 Hz combined with stretch (overload) resulted in an even greater increase of both types of IGF-1 transcript, whereas electrical stimulation alone, i.e. without stretch, resulted in no significant increase over muscle from sham-operated controls. Previously, it was shown that stretch combined with electrical stimulation of the dorsiflexor muscles in the adult rabbit results in a marked increase in muscle mass involving increases in both length and girth, within a few days. The expression of both systemic and autocrine IGF-1 growth factors provides a link between the mechanical signal and the marked increase in the structural gene expression involved in tissue remodelling and repair. 3. The expression of the beta actin gene was seen to be markedly upregulated in the stretched and stretched/stimulated muscles. It was concluded that the increased expression of this cytoskeletal protein gene is an indication that the production of IGF-1 may initially be a response to local damage. 4. Switches in muscle fibre phenotype were studied using a specific gene probe for the 2X myosin heavy chain gene. Type 2X expression was found to decrease markedly with stimulation alone and when electrical stimulation was combined with stretch. Unlike the induction of IGF-1 and beta actin, the decreased expression of the 2X myosin mRNA was less marked in the 'stretch only' muscles. This indicates that the interconversion of fibre type 2X to 2A may in some situations be commensurate with, but not under the control of IGF-1.

Expression of myosin isoforms in smooth muscle cells in the corpus cavernosum penis

Corpus cavernosum smooth muscle (CCSM) in the penis is unique in that it exhibits a high resting tone and, on stimulation, the muscle cells relax, allowing cavernous spaces to fill with blood, which results in an erection (tumescence). During detumescence, the muscle cells contract and return to the state of high resting tone. This study was undertaken to determine whether CCSM with these unique properties contains myosin isoforms typical of aorta or bladder smooth muscles, muscles that exhibit tonic and phasic characteristics, respectively. RT-PCR revealed that normal CCSM contains an SM2/SM1 mRNA ratio of 1.2:1 (similar to the rabbit aorta). Approximately 31% of the myosin heavy chain transcripts possess a 21-nt insert (predominant in bladder smooth muscle but not expressed in aorta) that encodes the seven-amino acid insert near the NH2-terminal ATP binding region in the head portion of the myosin molecule found in SMB, with the remaining mRNA being noninserted (SMA). Quantitative competitive RT-PCR revealed that the CCSM possesses approximately 4.5-fold less SMB than the bladder smooth muscle. Western blot analysis using an antibody specific for the seven-amino acid insert reveals that both SM1 and SM2 in the CCSM contain the seven-amino acid insert. Furthermore, SMB containing the seven-amino acid insert was localized in the CCSM by immunofluorescence microscopy using this highly specific antibody. The analysis of the expression of LC17 isoforms a and b in the CCSM revealed that it is similar to that of bladder smooth muscle. Thus the CCSM possesses an overall myosin isoform composition intermediate between aorta and bladder smooth muscles, which generally express tonic- and phasiclike characteristics, respectively. Two-dimensional gel electrophoresis showed a relatively low level (approximately 10%) of Ca2+-dependent light-chain (LC20) phosphorylation at the basal tone, which reaches approximately 23% in response to maximal stimulation. The presence of noninserted and inserted myosin isoforms with low and high levels of actin-activated ATPase activities, respectively, in the CCSM may contribute to the ability of the CCSM to remain in a state of high resting tone and to relax rapidly for normal penile function.

Expression of LDL receptor, VLDL receptor, LDL receptor-related protein, and scavenger receptor in rabbit atherosclerotic lesions: marked induction of scavenger receptor and VLDL receptor expression during lesion development

BACKGROUND

Atherosclerotic lesions contain foam cells that arise from monocyte-macrophages and smooth muscle cells (SMCs) by excessive uptake of lipoproteins. There are many candidate receptors for the lipid accumulation, such as LDL receptor (LDLR), VLDL receptor (VLDLR), LDL receptor-related protein (LRP), and scavenger receptors (SRs). However, little quantitative information exists on the expression of these receptors in normal and atherosclerotic arteries.

METHODS AND RESULTS

Competitive reverse transcription-polymerase chain reaction and in situ hybridization were used for the studies in New Zealand White (NZW) and Watanabe heritable hyperlipidemic (WHHL) rabbit aortic intima-medias. NZW rabbits were fed a 1% cholesterol diet for 0 (control group), 3, 6, or 14 weeks. LDLR mRNA expression was low in aortic intima-medias of all groups. Of the analyzed receptors, LRP had the highest expression in the control group, and its mRNA was induced threefold in the 14-week group, the aortas of which had extensive lesions. SR expression was low and VLDLR expression moderate in the control group. Both receptors were highly induced during cholesterol feeding (SRs, 3-fold and 270-fold induction; VLDLR, 15-fold and 100-fold induction in the 3-week and 14-week groups, respectively). Comparable results were obtained from WHHL rabbits: high basal LRP mRNA in normal intima-medias; moderate induction of LRP and marked induction of SRs and VLDLR in fatty streaks and fatty plaques. In situ hybridization indicated that LRP and VLDLR were expressed in SMCs and macrophages. VLDLR expression was also observed in endothelial cells. SR expression was detected only in macrophages.

CONCLUSIONS

SR and VLDLR mRNAs were highly induced in atherosclerotic lesions. VLDLR and LRP may be involved in the formation of both SMC-and macrophage-derived foam cells, whereas SRs play an important role in lipid uptake in macrophages.

Signaling Through the Interaction of Membrane-Restricted Stem Cell Factor and c-kit Receptor Tyrosine Kinase: Genetic Evidence for a Differential Role in Erythropoiesis

Mutations of the receptor tyrosine kinase c-kit or its ligand stem cell factor (SCF), which is encoded as a soluble and membrane-associated protein by the Steel gene in mice, lead to deficiencies of germ cells, melanocytes, and hematopoiesis, including the erythroid lineage. In the present study, we have used genetic methods to study the role of membrane or soluble presentation of SCF in hematopoiesis. Bone marrow–derived stromal cells expressing only a membrane-restricted (MR) isoform of SCF induced an elevated and sustained tyrosine phosphorylation of both c-kit and erythropoietin receptor (EPO-R) and significantly greater proliferation of an erythrocytic progenitor cell line compared with stromal cells expressing soluble SCF. Transgene expression of MR-SCF inSteel-dickie (Sld) mutants resulted in a significant improvement in the production of red blood cells, bone marrow hypoplasia, and runting. In contrast, overexpression of the full-length soluble form of SCF transgene had no effect on either red blood cell production or runting but corrected the myeloid progenitor cell deficiency seen in these mutants. These data provide the first evidence of differential functions of SCF isoforms in vivo and suggest an abnormal signaling mechanism as the cause of the severe anemia seen in mutants of the Sl gene.

Signaling Through the Interaction of Membrane-Restricted Stem Cell Factor and c-kit Receptor Tyrosine Kinase: Genetic Evidence for a Differential Role in Erythropoiesis

Mutations of the receptor tyrosine kinase c-kit or its ligand stem cell factor (SCF), which is encoded as a soluble and membrane-associated protein by the Steel gene in mice, lead to deficiencies of germ cells, melanocytes, and hematopoiesis, including the erythroid lineage. In the present study, we have used genetic methods to study the role of membrane or soluble presentation of SCF in hematopoiesis. Bone marrow–derived stromal cells expressing only a membrane-restricted (MR) isoform of SCF induced an elevated and sustained tyrosine phosphorylation of both c-kit and erythropoietin receptor (EPO-R) and significantly greater proliferation of an erythrocytic progenitor cell line compared with stromal cells expressing soluble SCF. Transgene expression of MR-SCF inSteel-dickie (Sld) mutants resulted in a significant improvement in the production of red blood cells, bone marrow hypoplasia, and runting. In contrast, overexpression of the full-length soluble form of SCF transgene had no effect on either red blood cell production or runting but corrected the myeloid progenitor cell deficiency seen in these mutants. These data provide the first evidence of differential functions of SCF isoforms in vivo and suggest an abnormal signaling mechanism as the cause of the severe anemia seen in mutants of the Sl gene.

In vivo role of B lymphocytes in somatic transgene immunization

Immunity generated by in vivo inoculation of plasmid DNA is a straightforward and potentially valuable new approach to immunization. Little is known about the type of cells involved, the various immunological aspects, and the destiny of the transgene. In this report, we describe a system in which immunity is the result of in vivo targeting of B lymphocytes. This was accomplished using plasmid DNA encoding an immunoglobulin heavy-chain gene under the control of immunoglobulin promoter and enhancer elements. We show persistence of the transgene in splenic B lymphocytes for at least 3 months, i.e., the average life span of long-lived B lymphocytes in the mouse. The transgene could not be detected in any other lymphoid or nonlymphoid organs over a period of 6 months. We also established that the transgene is integrated in the host DNA. These studies bring new understanding to the events underlying the in vivo use of plasmid DNA. Moreover, the characteristics of this new approach make somatic transgene immunization a model system to study the immunogenicity of endogenous antigens in adult animals.

NH2-terminal-inserted myosin II heavy chain is expressed in smooth muscle of small muscular arteries

We demonstrate, using reverse transcriptase-polymerase chain reaction, that, whereas abdominal aorta from rabbit consists almost entirely of myosin heavy chain (MHC) mRNA with no insert at the 5'-terminal coding region, the distributing arteries (femoral and saphenous) begin to show MHC mRNA with the 21-nucleotide insert that encodes seven amino acids in the ATP-binding region located in the myosin head. The femoral/iliac artery contains > 50% inserted mRNA, whereas the more distal saphenous artery contains > 80% inserted mRNA. This insert is also present in the smooth muscle from rat tail artery but is absent in the smooth muscle from rat aorta. The actin-activated ATPase activity of myosin from the rabbit femoral/saphenous artery is 1.7-fold higher than that of the myosin from the aorta. A concomitant increase (about twofold) in the maximum shortening velocity of the saphenous artery, compared with that of the aorta, indicates that the preponderance of the inserted myosin is associated with both an increase in the actin-activated ATPase activity and a larger maximum velocity of shortening. Furthermore, analysis of the 17-kDa essential light chain from the aorta reveals near equal quantities of the 17-kDa light chain isoforms a and b, whereas the myosin from the femoral/ saphenous artery contains predominantly the 17-kDa light chain a isoform. Together, these data indicate that the smooth muscle cells from the small distributing arteries are similar to those of visceral smooth muscle with respect to the expression of myosin isoforms, actin-activated myosin ATPase activity and contractility.

Cloning and sequence analysis of a Bothrops jararaca cDNA encoding a precursor of seven bradykinin-potentiating peptides and a C-type natriuretic peptide

A 1.8-kb cDNA clone was isolated from a Bothrops jararaca venom gland cDNA library that encodes a 256-aa precursor for bradykinin-potentiating peptides (angiotensin-converting enzyme inhibitors) and a C-type natriuretic peptide (CNP). The seven bradykinin-potentiating peptides are aligned tandemly after the hydrophobic signal peptide sequence, followed by a putative intervening sequence and a CNP at the C terminus. Northern blot analysis indicated the predominant expression of a 1.8-kb mRNA in the venom glands as well as in the spleen and the brain. Two lower intensity mRNA bands of 3.5 kb and 5.7 kb also hybridized to the cDNA clone. Radioimmunoassay for the CNP was performed using the antiserum against rat CNP. The presence of CNP immunoreactivity was detected in the low molecular weight fraction of the Bothrops jararaca venom.

Effects of gemfibrozil administration on very low density lipoprotein receptor mRNA levels in rabbits

To elucidate the regulation of very low density lipoprotein (VLDL) receptor gene expression, we administered to rabbits for 14 days gemfibrozil, a fabric acid derivative and a lipid lowering drug that is also included among peroxisome proliferators. VLDL receptor mRNA levels were examined by Northern blot analysis. The VLDL receptor mRNA levels in retroperitoneal adipose tissue and in gastrocnemius muscle were increased 6.9-fold and 3.7-fold, respectively, with gemfibrozil treatment, but no marked changes were observed in the heart, the organ in which VLDL receptor is most highly expressed. In the liver, VLDL receptor mRNA was not detected either before or after gemfibrozil administration. Lipoprotein lipase (LPL) and long-chain acyl coenzyme A synthetase (ACS) mRNA levels were also increased in parallel in adipose tissue. The enhanced expression of VLDL receptor mRNA may contribute to the increase of triglyceride-rich lipoprotein catabolism in peripheral tissues such as adipose tissue and muscles.

Induction of 15-lipoxygenase mRNA and protein in early atherosclerotic lesions

BACKGROUND

15-Lipoxygenase (15-LO) may be involved in atherogenesis and in oxidative modification of LDL. In this study, we investigated 15-LO expression in developing atherosclerotic lesions and verified the exact type of the atherosclerosis-associated LO at the nucleotide level.

METHODS AND RESULTS

Quantitative reverse transcription-polymerase chain reaction, in situ hybridization, and immunocytochemistry were used in two models of experimental atherosclerosis. New Zealand White rabbits were given a 1% cholesterol diet for 0 (control group), 3, 6, or 14 weeks. 15-LO mRNA was undetectable in the aortic intima-medias of the control group, whereas it was clearly induced as early as after 3 weeks. 15-LO expression increased further in the 6- and 14-week groups. According to in situ hybridization and immunocytochemical studies, 15-LO was localized to macrophagerich areas. In Watanabe heritable hyperlipidemic rabbits, 15-LO mRNA was undetectable in normal aortic intima-medias. 15-LO mRNA was markedly induced in fatty streaks but less so in more advanced lesions. Identification of the induced LO as reticulocyte-type 15-LO was done by cloning and sequencing. We also observed a distinct basal expression of copper-zinc and extracellular superoxide dismutases in normal aortic intima-medias, but no clear induction of these mRNAs was detected in atherosclerotic aortas.

CONCLUSIONS

The results show that, in contrast to copper-zinc and extracellular superoxide dismutases, the expression of reticulocyte-type 15-LO is markedly induced in rabbit fatty streaks. This may lead to an increase in the oxidative potential during the early phase of atherogenesis and contribute to the development of atherosclerotic lesions.

Cloning and pharmacological characterization of a rabbit bradykinin B1 receptor

A rabbit B1 bradykinin receptor cDNA was isolated from a rabbit aorta smooth muscle cell library. The 1223 bp cDNA clone encodes a protein of 352 amino acids which is 78% identical to the human bradykinin B1(3) receptor protein. Heterologous expression of the rabbit B1 receptor cDNA in COS-7 cells imparts a high affinity specific binding for 3H-labeled [des-Arg10,Leu9]kallidin. Scatchard analysis indicates that the receptor binds the radiolabeled ligand with a Kd of 0.5 nM. The ability of kallidin (Lys-bradykinin) and bradykinin analogues to compete with binding of 3H-labeled [des-Arg10,Leu9]kallidin was determined and defined a rank order of potency: [des-Arg10,Leu9]kallidin = [des-Arg10]kallidin > [des- Arg9]bradykinin = kallidin >> bradykinin. This receptor exhibits the classical B1 pharmacological property of preferentially binding to kinin analogues which lack the C-terminal arginine. In addition, the affinities for [des-Arg10]kallidin and [des-Arg10,Leu9]kallidin are 100-fold higher than those for the corresponding bradykinin analogues [des-Arg9]bradykinin and [des-Arg9,Leu8]bradykinin which lack the N-terminal lysine. This pharmacological profile is characteristic of the B1 receptor subtype.

A cytoplasmic actin gene from the silkworm Bombyx mori is expressed in tissues of endodermal origin and previtellogenic germ cells of transgenic Drosophila

A cytoplasmic actin gene from Bombyx mori introduced into Drosophila melanogaster by P-element mediated transformation, is efficiently transcribed in larvae, pupae and adults of the host. The exogenous mRNA has the same size as the one observed in the Bombyx cells and the intron located within the coding region is properly excised, indicating a correct recognition of the exogenous sequences by the Drosophila transcriptional and splicing machineries. The expression of the Bombyx gene in Drosophila tissues was determined by transforming flies with a hybrid gene in which a large part of the Bombyx actin coding sequences was replaced by those of the bacterial lac Z gene. This chimaeric gene is specifically and highly expressed, from the embryo to the adult of the transgenic lines, in tissues of endodermal origin, the midgut and its derivatives, i.e. gastric caeca, the outer layer of the proventriculus, and in the Malpighian tubules. This gene is also expressed, at a lower level, in germ cells but restricted to the sixteen cell cysts during previtellogenesis. The expression of the Bombyx gene during development of transgenic flies was compared to that of the two Drosophila endogenous cytoplasmic actin genes and the results are discussed.