Growing and differentiating characterization of aortic smooth muscle cell line, p53LMAC01 obtained from p53 knock out mice

Recently we have established an aortic smooth muscle cell line, p53LMAC01 obtained from p53 knockout mice. This cell line showed some differentiated properties which were accelerated by 5-azacytidine treatment [1]. In this study, further characterization of p53LMAC01 cell line was investigated according to cell growth and differentiation, and especially focused into the changes of cell feature, actin filaments' formation, and changes of intracellular calcium concentrations to sympathetic nerve transmitter, norepinephrine. While the cell feature was changed from flattened shape to extended form during 4 days, actin filaments were developing, arranging in parallel to longitudinal direction, and gathering under the surface membrane. In 11 days many cells died and detached from substrate, while actin filaments became poor except for the surface membrane in the remained cells. Appearance of calcium response to noradrenalin needed several days after passage as well as a morphological change of the cells for the extended form and development of actin filaments. The calcium response was maintained on 11 days, which coincided with the result that the cells hold actin filaments under the surface membrane. These results suggest that p53LMAC01 cell line maintains several differentiated characters of adult smooth muscle cell and that their expression needs several days after passage.

Dynamic regulation of intracellular calcium signals through calcium release channels

After the seminal work of Ebashi and coworkers which established the essential role of the intracellular Ca2+ concentration ([Ca2+]i) in the regulation of skeletal muscle contraction, we have witnessed an explosive elongation of the list of cell functions that are controlled by the [Ca2+]i. In numerous instances, release of intracellular Ca2+ stores plays important roles in Ca2+ signalling which displays significant variation in spatio-temporal pattern. There are two families of Ca2+ release channels, ryanodine receptors and inositol 1,4,5-trisphosphate (IP3) receptors. These Ca2+ release channels are structurally and functionally similar. In particular, the activity of both types of channels is regulated by the [Ca2+]i. The [Ca2+]i dependence of the Ca2+ release channel activity provides both types of channels with properties of a Ca2+ signal amplifier. This function of the ryanodine receptor is important in striated muscle excitation-contraction coupling, whereas that of the IP3 receptor seems to be the basis of the generation of Ca2+ waves. Thus the wide variety of Ca2+ signalling patterns seem to be critically dependent on the [Ca2+]i dependence of the Ca2+ release channels.

Gravitropism and phototropism of oat coleoptiles: post-tropic autostraightening and tissue shrinkage during tropism

We measured changes in length on the two opposite sides of the red-light-grown oat (Avena sativa L.) coleoptiles subjected to either gravitropic or phototropic stimulation and subsequently rotated on a horizontal clinostat. The length measurement was conducted using three 5 mm-long zones delimited by ink markers from the tip. Curvature of each zone was analyzed from the length difference between the two sides. Gravitropism was induced by displacing the seedling from the vertical by 30 degrees or 90 degrees for 25 min. Phototropism was induced by exposing the coleoptile to unilateral blue light for 30 s, which provided a fluence (1.0 micromoles m-2) optimal for the pulse-induced positive phototropism or a lower, suboptimal fluence (0.03 micromoles m-2). After negatively gravitropic bending, the upper two zones straightened rapidly at either displacement angle. After positively phototropic bending, straightening occurred, but only in the top zone and at the lower fluence. The upper two zones straightened rapidly, however, when bilateral blue light (30 s; 15 micromoles m-2 from either direction) was applied 25 min after unilateral stimulation at the higher fluence. Bilateral blue light alone induced no curvature. These results confirm that the straightening of gravitropically bent coleoptiles is autonomic, and suggest that a similar autonomic response participates in the straightening of phototropically bent coleoptiles. Suppression of elongation on the concave side of the coleoptile mainly accounted for gravitropic and phototropic curvatures. The concave side of the top zone shrank during both tropisms. This shrinkage progressed at a high rate from the beginning of curvature response, suggesting that a drop in turgor pressure is the main and direct cause of the shrinkage.

Morphological abnormalities of adrenal gland and hypertrophy of liver in mutant mice lacking ryanodine receptors

Ryanodine receptors (RyRs), which form Ca2+ channels in the membrane of the endoplasmic reticulum, consist of three subtypes (RyR1, RyR2, and RyR3). The RyRs release Ca2+ from the endoplasmic reticulum into the cytoplasm and thus play an important role, especially in the contraction of skeletal and cardiac muscle cells. The genes of these RyRs are also expressed in many non-muscle tissues, but the role played by RyRs in non-muscle cells is not fully understood. In the present study, we examined the morphological changes in such cells caused by a deficiency of RyRs genes using three mutant mice lacking RyR1, RyR3, or both RyR1 and RyR3. The results showed morphological abnormalities in the adrenal cortical cells in all three mutant mice. In addition, an excessive accumulation of glycogen granules in hepatic cells, and a hypertrophy of the liver were both present in those mutant mice lacking both RyR1 and RyR3. We discuss the relationship between the morphological abnormalities of the adrenal cortex and liver induced by a deficiency of RyRs, and the possible causes of these abnormalities.

Effect of calmodulin on Ca2+-induced Ca2+ release of skeletal muscle from mutant mice expressing either ryanodine receptor type 1 or type 3

We analyzed the effects of calmodulin (CaM) on Ca2+-induced Ca2+ release (CICR) in mouse skeletal muscle cells expressing only ryanodine receptor type 1 (RyR-1) or type 3 (RyR-3) following targeted disruption of one of the RyR genes. Under Mg2+-free conditions, CaM potentiated CICR via RyR-3 at low Ca2+ concentrations (pCa>/=6) but inhibited CICR at high Ca2+ concentrations (pCa</=5). On the other hand, CaM potentiated CICR via RyR-1 between pCa 7 and pCa 5. Greater concentrations of CaM were required for potentiation of CICR at pCa 6 than for the inhibition at pCa 5 in the RyR-3-expressing cells. Similarly, higher concentrations of CaM were required for the potentiation of CICR via RyR-1 at pCa 6 than potentiation at pCa 5. In the presence of Mg2+ and beta,gamma-methyleneadenosine 5'-trisphosphate (AMPOPCP), the same differential effects of CaM on the CICR via the different subtypes of RyR were observed. These data suggest that multiple CaM-binding sites are involved in the differential effects on RyR-1 and RyR-3. These effects of CaM are important for the evaluation of the physiological roles of RyRs.

Role of the inositol phosphatase SHIP in B cell receptor-induced Ca2+ oscillatory response

Src homology-2 domain-containing inositol polyphosphate 5'-phosphatase (SHIP) is a recently identified protein that has been implicated as an important signaling molecule. Although SHIP has been shown to participate in the FcgammaRIIB-mediated inhibitory signal, the functional role of SHIP in activation responses by immunoreceptor tyrosine-based activation motif-bearing receptors such as B cell receptor (BCR) remains unclear. Indeed, it has been proposed that SHIP serves as a linking molecule for the regulation of the extracellular signal-regulated kinase pathway in BCR signaling, because SHIP associates with Shc. We now report that SHIP-deficient DT40 B cells display enhanced Ca2+ mobilization in response to BCR ligation, whereas extracellular signal-regulated kinase activation is unaffected. This Ca2+ enhancement is due to a sustained intracellular Ca2+ increase or to long-lasting Ca2+ oscillations by loss of SHIP, as revealed by single-cell Ca2+ imaging analysis. These results demonstrate the importance of SHIP in B cell activation by the modulation of Ca2+ mobilization.

Newly synthesized dihydropyridine derivatives as modulators of P-glycoprotein-mediated multidrug resistance

Newly synthesized 1,4-dihydropyridine derivatives possessing alkyl chains at the 4-position screened whether they could overcome P-glycoprotein-mediated multidrug resistance in cultured cancer cells and also leukemia-bearing animals. Of these derivatives, some could overcome drug resistance to doxorubicin and vincristine in multidrug resistant human cancer cell lines. Combined administration of vincristine and some of the derivatives significantly increased the life span of P-glycoprotein overexpressing multidrug-resistant P388 leukemia-bearing mice. The calcium antagonistic activities, an undesirable effects, were weaker than that of verapamil. These results suggested that the introduction of alkyl groups at the 4-position were effective for both overcoming multidrug resistance and reducing the calcium antagonistic activity.

[Incidence of prolonged distal motor latency of the median nerve augments with the progression of diabetic polyneuropathy]

We investigated 303 diabetic patients in order to clarify the relationship between progression of diabetic polyneuropathy and conduction delay across the carpal tunnel. Distal latency ratio (DLR) was determined by comparison of distal motor latency of the median nerve with that of the ulnar nerve. Lower extremity polyneuropathy index (LPNI), expressed as a mean percentage of the normal for six indices over two nerves obtained by motor nerve conduction studies, was 82.9% on the average in the patients. Their DLR (1.44 +/- 0.24) was larger than the normal value (1.29 +/- 0.10). About 30% of the diabetics had abnormal DLR, especially in women its incidence was as high as 39%. The lower the LPNI level, the larger the incidence of abnormal DLR. In diabetic polyneuropathy patients peripheral nerves will become fragile, which might increase the incidence of conduction delay across the carpal tunnel. This phenomenon might also be called as 'double crush syndrome'.

Mitsugumin23, a novel transmembrane protein on endoplasmic reticulum and nuclear membranes

We report the identification using monoclonal antibody and the primary structure by cDNA cloning of mitsugumin23, a novel transmembrane protein with a molecular mass of approximately 23 kDa from skeletal muscle sarcoplasmic reticulum. Mitsugumin23 possesses three putative transmembrane segments, and its carboxy-terminal hydrophilic region exhibits sequence similarity with the tail-end portion of the myosin heavy chain. Immunochemical analysis showed that this protein is distributed throughout the outer nuclear membrane and the sarcoplasmic reticulum including the terminal cisternae at the triad junction in skeletal muscle cells. Furthermore, RNA blotting and immunohistochemical experiments demonstrated that mitsugumin23 is distributed among a wide variety of cell types in various tissues. The distribution and primary structure indicate the possibility that mitsugumin23 interacts with cytoplasmic protein(s) and participates in a housekeeping function on the intracellular organelle membranes.

Interaction of cryptochrome 1, phytochrome, and ion fluxes in blue-light-induced shrinking of Arabidopsis hypocotyl protoplasts

Protoplasts isolated from red-light-adapted Arabidopsis hypocotyls and incubated under red light exhibited rapid and transient shrinking within a period of 20 min in response to a blue-light pulse and following the onset of continuous blue light. Long-persisting shrinkage was also observed during continuous stimulation. Protoplasts from a hy4 mutant and the phytochrome-deficient phyA/phyB double mutant of Arabidopsis showed little response, whereas those from phyA and phyB mutants showed a partial response. It is concluded that the shrinking response itself is mediated by the HY4 gene product, cryptochrome 1, whereas the blue-light responsiveness is strictly controlled by phytochromes A and B, with a greater contribution by phytochrome B. It is shown further that the far-red-absorbing form of phytochrome (Pfr) was not required during or after, but was required before blue-light perception. Furthermore, a component that directly determines the blue-light responsiveness was generated by Pfr after a lag of 15 min over a 15-min period and decayed with similar kinetics after removal of Pfr by far-red light. The anion-channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoic acid prevented the shrinking response. This result, together with those in the literature and the kinetic features of shrinking, suggests that anion channels are activated first, and outward-rectifying cation channels are subsequently activated, resulting in continued net effluxes of Cl- and K+. The postshrinking volume recovery is achieved by K+ and Cl- influxes, with contribution by the proton motive force. External Ca2+ has no role in shrinking and the recovery. The gradual swelling of protoplasts that prevails under background red light is shown to be a phytochrome-mediated response in which phytochrome A contributes more than phytochrome B.

Auxin-growth relationships in maize coleoptiles and pea internodes and control by auxin of the tissue sensitivity to auxin

Growth of a zone of maize (Zea mays L.) coleoptiles and pea (Pisum sativum L.) internodes was greatly suppressed when the organ was decapitated or ringed at an upper position with the auxin transport inhibitor N-1-naphthylphthalamic acid (NPA) mixed with lanolin. The transport of apically applied 3H-labeled indole-3-acetic acid (IAA) was similarly inhibited by NPA. The growth suppressed by NPA or decapitation was restored by the IAA mixed with lanolin and applied directly to the zone, and the maximal capacity to respond to IAA did not change after NPA treatment, although it declined slightly after decapitation. The growth rate at IAA saturation was greater than the rate in intact, nontreated plants. It was concluded that growth is limited and controlled by auxin supplied from the apical region. In maize coleoptiles the sensitivity to IAA increased more than 3 times when the auxin level was reduced over a few hours with NPA treatment. This result, together with our previous result that the maximal capacity to respond to IAA declines in pea internodes when the IAA level is enhanced for a few hours, indicates that the IAA concentration-response relationship is subject to relatively slow adaptive regulation by IAA itself. The spontaneous growth recovery observed in decapitated maize coleoptiles was prevented by an NPA ring placed at an upper position of the stump, supporting the view that recovery is due to regenerated auxin-producing activity. The sensitivity increase also appeared to participate in an early recovery phase, causing a growth rate greater than in intact plants.

Structure and expression of mitsugumin29 gene

Recently mitsugumin29 unique to the triad junction in skeletal muscle was identified as a novel member of the synaptophysin family; the members of this family have four transmembrane segments and are distributed on intracellular vesicles. In this study, we isolated and analyzed mouse mitsugumin29 cDNA and genomic DNA containing the gene. The mitsugumin29 gene mapped to the mouse chromosome 3 F3-H2 is closely related to the synaptophysin gene in exon-intron organization, which indicates their intimate relationship in molecular evolution. RNA blot hybridization and immunoblot analysis revealed that mitsugumin29 is expressed abundantly in skeletal muscle and at lower levels in the kidney. Immunofluorescence microscopy demonstrated that mitsugumin29 exists specifically in cytoplasmic regions of the proximal and distal tubule cells in the kidney. The results obtained may suggest that mitsugumin29 is involved in the formation of specialized endoplasmic reticulum systems in skeletal muscle and renal tubule cells.

Surgical repositioning of the premaxilla in combination with two-stage alveolar bone grafting in bilateral cleft lip and palate

OBJECTIVE

This paper introduces a surgical technique for premaxillary repositioning in combination with two-stage alveolar bone grafting for the correction of the premaxillary deformity of patients with bilateral cleft lip and palate (BCLP). The paper also reports on two patients with BCLP who underwent this surgical management.

SURGICAL PROCEDURE

The operation is usually performed when the patient is 8 to 14 years of age. In the first stage of surgery, the side more accessible to the septo-premaxillary junction is selected, and an osteotomy of the premaxilla and unilateral alveolar bone grafting are performed. Approximately 4 to 12 months after the first stage of surgery, contralateral alveolar bone grafting is carried out.

CONCLUSION

We have found that this surgical procedure is highly effective, because it ensures the blood supply to the premaxilla and minimizes the potential for surgical failure. Moreover, it affords wide exposure of the premaxillary bone surface, facilitating sufficient boney bridging and allowing for orthodontic tooth movement.

Embryonic lethality and abnormal cardiac myocytes in mice lacking ryanodine receptor type 2

The ryanodine receptor type 2 (RyR-2) functions as a Ca2+-induced Ca2+ release (CICR) channel on intracellular Ca2+ stores and is distributed in most excitable cells with the exception of skeletal muscle cells. RyR-2 is abundantly expressed in cardiac muscle cells and is thought to mediate Ca2+ release triggered by Ca2+ influx through the voltage-gated Ca2+ channel to constitute the cardiac type of excitation-contraction (E-C) coupling. Here we report on mutant mice lacking RyR-2. The mutant mice died at approximately embryonic day (E) 10 with morphological abnormalities in the heart tube. Prior to embryonic death, large vacuolate sarcoplasmic reticulum (SR) and structurally abnormal mitochondria began to develop in the mutant cardiac myocytes, and the vacuolate SR appeared to contain high concentrations of Ca2+. Fluorometric Ca2+ measurements showed that a Ca2+ transient evoked by caffeine, an activator of RyRs, was abolished in the mutant cardiac myocytes. However, both mutant and control hearts showed spontaneous rhythmic contractions at E9.5. Moreover, treatment with ryanodine, which locks RyR channels in their open state, did not exert a major effect on spontaneous Ca2+ transients in control cardiac myocytes at E9.5-11.5. These results suggest no essential contribution of the RyR-2 to E-C coupling in cardiac myocytes during early embryonic stages. Our results from the mutant mice indicate that the major role of RyR-2 is not in E-C coupling as the CICR channel in embryonic cardiac myocytes but it is absolutely required for cellular Ca2+ homeostasis most probably as a major Ca2+ leak channel to maintain the developing SR.

Functional consequences of mutations in Ser-52 and Ser-60 in human blood coagulation factor VII

Human blood coagulation factor VII has unique carbohydrate moieties O-glycosidically linked to serine 52 and serine 60 residues in its first epidermal growth factor-like domain. To study the functional role of these glycosyl moieties in factor VII, we constructed, expressed, and purified site-specific recombinant mutants of human factor VII in which serine 52 and serine 60 were conservatively replaced with alanine residues. S52A factor VIIa (Ser-52-->Ala), S60A factor VIIa (Ser-60-->Ala), and S52,60A factor VIIa (Ser-52, Ser-60-->Ala) exhibited 56, 73, and 44%, respectively, of the clotting activity of wild-type factor VIIa using human brain thromboplastin as a source of tissue factor/phospholipids and 32, 43, and 14% of wild-type factor VIIa using a mixture of recombinant soluble tissue factor and mixed brain phospholipids. The tissue factor-dependent and -independent amidolytic activities of these mutants were essentially indistinguishable from that of wild-type factor VIIa. In addition, equilibrium dialysis experiments indicated that the profiles of 45Ca2+ binding to these mutants were identical with that of wild-type factor VII. In the presence of either Ca2+ or EGTA, the Kd values for the interaction of the three factor VIIa mutants to full-length tissue factor were 2- to 5-fold higher than that of wild-type factor VIIa, while the Kd values for the interaction of these mutants to soluble tissue factor were 4- to 15-fold higher than that of wild-type factor VIIa. Measurement of the association and dissociation rate constants for factor VIIa binding to relipidated tissue factor apoprotein revealed that the association rate constants of the three factor VII mutants were decreased in comparison with that of wild-type factor VIIa, while the dissociation rate constants of these three mutants were virtually identical to that of wild-type factor VIIa. These findings strongly suggest that glycosyl moieties attached to Ser-52 and Ser-60 in factor VII/VIIa provide unique structural elements that are important for the rapid association of factor VII/VIIa with its cellular receptor and cofactor.

Mitsugumin29, a novel synaptophysin family member from the triad junction in skeletal muscle

In skeletal muscle, excitation-contraction (E-C) coupling requires the conversion of the depolarization signal of the invaginated surface membrane, namely the transverse (T-) tubule, to Ca2+ release from the sarcoplasmic reticulum (SR). Signal transduction occurs at the junctional complex between the T-tubule and SR, designated as the triad junction, which contains two components essential for E-C coupling, namely the dihydropyridine receptor as the T-tubular voltage sensor and the ryanodine receptor as the SR Ca2+-release channel. However, functional expression of the two receptors seemed to constitute neither the signal-transduction system nor the junction between the surface and intracellular membranes in cultured cells, suggesting that some as-yet-unidentified molecules participate in both the machinery. In addition, the molecular basis of the formation of the triad junction is totally unknown. It is therefore important to examine the components localized to the triad junction. Here we report the identification using monoclonal antibody and primary structure by cDNA cloning of mitsugumin29, a novel transmembrane protein from the triad junction in skeletal muscle. This protein is homologous in amino acid sequence and shares characteristic structural features with the members of the synaptophysin family. The subcellular distribution and protein structure suggest that mitsugumin29 is involved in communication between the T-tubular and junctional SR membranes.

Photochemical identification of transmembrane segment IVS6 as the binding region of semotiadil, a new modulator for the L-type voltage-dependent Ca2+ channel

To identify the binding domain of a new Ca2+ antagonist semotiadil on L-type Ca2+ channels from skeletal muscle, photolabeling was carried out by using an azidophenyl derivative of [3H]semotiadil. Photoincorporation was observed in several polypeptides of membrane triad preparations; the only specific photoincorporation was in the alpha1 subunit of the Ca2+ channel. After solubilization and purification, the photolabeled alpha1 subunit was subjected to proteolytic and CNBr cleavage followed by antibody mapping. Specific labeling was associated solely with the region of transmembrane segment S6 in repeat IV. Quantitative immunoprecipitation was found in the tryptic and the Lys-C/Glu-C fragments of 6.6 and 6.1 kDa, respectively. Further CNBr cleavage of the Lys-C digests produced two smaller fragments of 3.4 and 1.8 kDa that were included in the tryptic and Lys-C/Glu-C fragments. The smallest labeled fragments were: Tyr1350-Met1366 and Leu1367-Met1381 containing IVS6, a possible pore-forming region. The data suggest that semotiadil binds to a region that is overlapped with but not identical to those for phenylalkylamines, dihydropyridines and benzothiazepines. The present study also provides evidence that region IV represents an important component of a binding pocket for Ca2+ antagonists.

In vitro neuronal and glial production and differentiation of human central neurocytoma cells

Human central neurocytoma cells were cultured and characterized immunophenotypically and electrophysiologically to clarify their developmental potential. We conducted systematic in vitro studies utilizing fresh tissues from three patients. Initially small homogeneous cell clusters settled down onto the bottom of the culture flasks, and, after 2 weeks from plating, mature neuron-like cells developed from these clusters and expressed neurofilament proteins (NF: specific neuronal markers). On the other hand, approximately 80% of small round cell clusters and flat glial-like cells from which these clusters developed were positively stained for glial fibrillary acidic protein (GFAP: a specific glial marker). Furthermore these neuronal and glial cells showed distinct morphology, and dual-label, indirect immunohistochemistry for GFAP and NF-200 kD disclosed that the two antigens were not found co-localized in the same cells. In single-cell clonal analysis, neuronal, glial, and mixed neuronal and glial clones were generated. Electrophysiologically, the cells of neuronal morphology possessed sodium channels, and also L-type calcium channels in whole-cell voltage clamp. The sodium channels were of a characteristic neuronal phenotype which appears in neurons. These findings suggest that small round human central neurocytoma cells exhibit both neuronal and glial differentiations and have the properties reminiscent of precursor cells derived from subventricular matrix; thus, these cultured cells may be a potential source for investigations of human CNS neuronal and glial development and differentiation.

Allosteric regulation by cytoplasmic Ca2+ and IP3 of the gating of IP3 receptors in permeabilized guinea-pig vascular smooth muscle cells

1. The potentiation by Ca2+ of inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release was studied by measuring luminal Ca2+ concentrations of the Ca2+ stores using a fluorescent Ca2+ indicator, furaptra, in permeabilized smooth muscle cells. 2. Ca2+ release at 10 microM IP3 was potentiated by an increase in the cytoplasmic Ca2+ concentration in the presence of 10 mM EGTA. This effect was not due to the pharmacological effect of EGTA, because changes in the EGTA concentration at a constant Ca2+ concentration had no effect on the Ca2+ release rate. 3. With an increase in the cytoplasmic Ca2+ concentration from 30 to 630 nM, the Ca2+ release rate at a saturating IP3 concentration increased 110-fold and the EC50 for IP3 increased from 0.07 to 1.0 microM. It was also indicated that the relationship between Ca2+ concentration and Ca2+ release rate was shifted towards higher Ca2+ concentrations at higher IP3 concentrations. 4. These results suggest that IP3 and submicromolar concentrations of Ca2+ allosterically lower the affinity of the IP3 receptor for each other and are both required for IP3 receptor activation. These properties enable the IP3 receptors to detect simultaneous increases in IP3 and Ca2+ concentrations.

Quantification and characterization of human endothelial cell-derived tissue factor pathway inhibitor-2

Tissue factor pathway inhibitor-2 (TFPI-2), also known as placental protein 5, is a serine protease inhibitor consisting of three tandemly-arranged Kunitz-type protease inhibitor domains. While TFPI-2 is a potent inhibitor of trypsin, plasmin, kallikrein, and factor XIa in the test tube, the function of this inhibitor in vivo remains unclear. In the present study, we investigated the synthesis and secretion of TFPI-2 by cultured endothelial cells derived from human umbilical vein, aorta, saphenous vein, and dermal microvessels to gain insight into its biological function. While all endothelial cells examined synthesized and secreted TFPI-2, dermal microvascular endothelial cells synthesized threefold to sevenfold higher levels of TFPI-2. Approximately 60% to 90% of the TFPI-2 secreted by endothelial cells was directed to the subendothelial extracellular matrix (ECM). When cultured human umbilical vein endothelial cells were stimulated with inflammatory mediators such as phorbol 12-myristate,13-acetate; endotoxin; and tumor necrosis factor-alpha, TFPI-2 synthesis by these cells increased twofold to 14-fold. Recombinant TFPI-2 bound to dermal microvascular endothelial cell monolayers and its ECM in a specific, dose-dependent, and saturable manner with Kd values of 21 and 24 nmol/L, respectively. TFPI-2 interacted with 4.5 X 10(10) sites/cm2 (3 X 10[5] sites/cell) and 2.3 X 10(11) sites/cm2 on endothelial cells and ECM, respectively. In the presence of rabbit anti-TFPI-2 IgG, but not preimmune IgG, endothelial cells dissociated from the culture flask in a time- and IgG concentration-dependent manner. Our findings provide evidence that endothelial cell-derived TFPI-2 is primarily secreted into the abluminal space and presumably plays an important role in maintaining the integrity of the ECM essential for cell attachment.

Gravitropism of oat and wheat coleoptiles: dependence on the stimulation angle and involvement of autotropic straightening

Gravitropism of oat (Avena sativa L.) and wheat (Triticum aestivum L.) coleoptiles was investigated in relation to the displacement angle or to the initially set stimulation angle (SA). We measured curvature rates at the early phase of curvature, before it was affected by the drop in SA resulting from the curvature response itself. The plot of the rates against the sines of initial SAs revealed similar curves for oats and wheat, which approached saturation as the sine increased to unity. The two species and previously analyzed rice [Iino et al. (1996) Plant Cell Environ. 19: 1160] appeared to have similar gravisensitivities. Initial SAs below and over 90 degrees yielded comparable rates when the sine values were the same, indicating that the extent of gravitropism is determined by the gravity component perpendicular to the organ's long axis. Long-term curvature kinetics at different SAs indicated that the net curvature rate dropped sharply before the tip reached the vertical position and then the tip approached the vertical slowly, with clear oscillatory movements in the case of wheat. During this late curvature phase, the coleoptile straightened gradually, although none of its parts had yet reached the vertical. When rotated on horizontal clinostats or displaced upwards to reduce SA in the late curvature phase, coleoptiles bent in the opposite direction. These results demonstrated that autotropism counteracts gravitropism to straighten coleoptiles.