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1.
Gruber R 《Plastic and reconstructive surgery》2001,107(3):856-863
Alar disharmony is one of the most common abnormalities observed after a rhinoplasty. This article describes three classes in addition to Gunter's classifications of alar/columella deformities, which include concave ala, convex ala caused by convex lateral crus, and convex ala caused by thick alar tissues. These deformities are best visualized from the basilar view. The different surgical techniques for correction of true alar abnormalities are presented. The alar convexity, when it is the result of a misshapen cartilage, is corrected using a lateral crura spanning suture, posterior transection of the lateral crura, or transdomal suture. A thick ala, resulting in convexity, can be thinned through either a direct incision on the ala or an incision in the alar base. A lateral crura strut, an onlay graft, or a rim graft eliminates the concavity. For a slight retraction, an alar rim cartilage graft is an optimal choice. For significant alar retractions, the author's preferred technique is an internal V-to-Y advancement, which is described in detail. An elliptical excision of the alar lining will effectively correct the hanging ala. These techniques have been used to correct alar disharmonies on 58 patients. One patient from the V-Y advancement group exhibited a small area of alar necrosis, and two early patients demonstrated an overcorrection; all were easily resolved with revision surgery. By carefully identifying nasal base and alar abnormalities, harmony can be established to correct an undesirable appearance. 相似文献
2.
Dynamics of rhinoplasty 总被引:2,自引:0,他引:2
B Guyuron 《Plastic and reconstructive surgery》1991,88(6):970-8; discussion 979
Nasal dynamics were studied on 87 patients undergoing rhinoplasty of one zone or two distant nasal zones. Statistical analysis of the result revealed that reduction of the nasion area, besides setting the soft tissue back, gave the appearance of increased intercanthal distance and lengthened the nose. Reduction of the nasal bridge resulted in a wider appearance on front view and a cephalically rotated tip on profile. Augmentation of the bridge affected the nose reversely. Tip cephalad rotation was achieved by resecting one of the three areas: the cephalad portion of the lower lateral cartilages (affecting the rims more), the caudal septum (affecting the central portion more), and the caudal portion of the medial crura of the lower lateral cartilages (affecting the central portion only). Resection of the alar base not only narrowed the nostrils but also moved the alar rim caudally. Furthermore, it reduced tip projection when a large alar base reduction was done. Reduction of the nasal spine increased the upper lip length on profile and reduced tip projection when a large reduction took place. Significant reduction in caudal nose projection resulted in widening of the alar base. 相似文献
3.
Dynamics in rhinoplasty 总被引:6,自引:0,他引:6
Guyuron B 《Plastic and reconstructive surgery》2000,105(6):2257-2259
Nasal dynamics were studied on 87 patients undergoing rhinoplasty of one zone or two distant nasal zones. Statistical analysis of the results revealed that reduction of the nasion area, besides setting the soft tissue back, gave the appearance of increased intercanthal distance and lengthened the nose. Reduction of the nasal bridge resulted in a wider appearance on frontal view and a cephalically rotated tip on profile. Augmentation of the bridge affected the nose reversely. Tip cephalad rotation was achieved by resecting one of the three areas: the cephalad portion of the lower lateral cartilages (affecting the rims more), the caudal septum (affecting the central portion more), and the caudal portion of the medial crura of the lower lateral cartilages (affecting the central portion only). Resection of the alar base not only narrowed the nostrils but also moved the alar rim caudally. Furthermore, it reduced tip projection when a large alar base reduction was done. Reduction of the nasal spine increased the upper lip length on profile and reduced tip projection when a large reduction took place. Significant reduction in caudal nose projection resulted in widening of the alar base. 相似文献
4.
S I Shehadi 《Plastic and reconstructive surgery》1984,74(6):771-777
Two hundred and forty patients who underwent a corrective rhinoplasty have been presented. Of these, 224 patients (93.3 percent) had a cartilage repositioning procedure in which the alar cartilages were only undermined and repositioned, and 16 patients (6.7 percent) had a cartilage resection procedure. The techniques and indications for both procedures are described and discussed. The results obtained in this series of patients indicate that cartilage repositioning is an effective and reliable procedure to refine and reshape the nasal tip. Cartilage resection is less reliable and should be reserved for a few selected patients with specific indications. Indiscriminate resection of the lower alar cartilage is neither warranted nor wise. 相似文献
5.
Valvular nasal obstruction may occur in the postoperative rhinoplasty patient. One may anticipate a dropping of the tip, from residual redundant or inelastic skin, in some older patients with long noses. Measures to correct (or avoid) this may be undertaken at the time of the primary rhinoplasty. However, an overcorrection may be necessary if there is much redundant skin. Discretion may indicate the need for a secondary procedure. Lateral wall valving is unusual-but it may occur in the long, high, thin nose (where a suggestion of this action may be observed preoperatively). Maintenance of continuous cartilage along the alar rim, at the time of alar cartilage resection, appears to be important in prevention of postoperative valvular obstruction in these few patients. 相似文献
6.
The onlay cartilage grafting technique is described for treatment of unilateral or bilateral cleft lip nasal deformities. The alar cartilage is exposed through rim and intercartilagenous incisions. The cephalic half of the alar cartilage is excised, similar to the technique of traditional tip rhinoplasty. The harvested cartilage is applied to the intact caudal cartilage in layered fashion and secured with absorbable sutures. If necessary, successive layers may be added. These grafts provide a sturdy, yet delicate framework for a more normal appearing alar rim. We have performed this procedure on 16 patients, ages 10 to 41. Follow-up intervals range from 13 to 40 months, with a mean of 19 months. Results have been rated good-to-excellent by patients and surgeons. There has been no recurrence of the deformity. The only complication has been one nasal vestibule synechia. 相似文献
7.
C B Cutting J Bardach R Pang 《Plastic and reconstructive surgery》1989,84(3):409-17; discussion 418-9
The secondary nasal skin envelope asymmetries were studied after unilateral cleft lip repair using the original (obsolete) rotation-advancement (Millard I) and the triangular flap techniques (Bardach's modification). Secondary correction of the nasal deformity was not performed in either group. Our findings indicated that in both groups, vertical asymmetries of the nasal skin envelope were similar. The alar dome on the cleft side was depressed, the columella was shorter on the cleft side, and there was hooding at the nostril apex. The principal difference between the two lip repairs was observed in the horizontal dimension of the nasal skin envelope. The position of the alar base was more normal following the Millard I repair, while the triangular flap repair left the alar base laterally displaced. When considered together with flattening of the cleft alar dome, a horizontal skin-envelope deficiency from middome to lateral alar crease was produced in the Millard I group. More lateral positioning of the alar base after the triangular flap technique minimized this horizontal skin deficiency. The triangular flap technique produced a secondary nasal deformity that looked worse but was easier to correct. The clinical implications of these findings are discussed. 相似文献
8.
Constantian MB 《Plastic and reconstructive surgery》2002,110(4):1116-1133
The fragile alar rims are complex structures whose specialized and supportive skin ensures the competence of the external valves and the patency of the inlets to the nasal airways. A chart review was performed of 100 consecutive secondary or tertiary rhinoplasty patients in whom the author had placed composite grafts before February 1999. Follow-up continued for at least 12 months. In 94 percent of the patients, composite grafts were harvested from the cymba conchae by removing the cartilage with its adherent anterior skin. In 6 percent of the patients, independently indicated alar wedges supplied the grafts. Six patients required secondary procedures to thin the alar rims, but such revisions have not been necessary since primary contouring of the cartilaginous graft component was instituted. Three auricular donor-site complications (one keloid, two thickened graft contours) were successfully revised through office procedures. Prior cosmetic rhinoplasty in a patient with normal alar cartilage anatomy exceeded all other etiologies as the cause of the deformity for which composite grafts were indicated (50 percent). The second most common etiology was deformity from prior rhinoplasty in a patient with alar cartilage malposition (33 percent of patients). Congenital deformities (7 percent of patients), trauma (6 percent), and prior tumor ablation (4 percent) comprised the remaining etiologies. Composite grafts were used most frequently to correct alar notching or asymmetry in rim height (43 percent of patients) or to provide an increase in apparent or real nasal length (28 percent). External valvular incompetence (14 percent of patients), nostril or vestibular stenosis (11 percent), or combined vestibular stenosis and lateral alar wall collapse (4 percent) were less common indications. Most composite grafts were oriented in the coronal plane (parallel to the alar rims). However, nostril or vestibular stenosis was corrected by sagittally placed composite grafts, and a third orientation (axial plane), to the author's knowledge not described previously, was used in patients with combined nostril stenoses and flattening of the alar walls. In this secondary rhinoplasty series, iatrogenic alar rim deformities or stenoses following cosmetic rhinoplasty dominated other causes requiring composite graft reconstruction (83 percent of patients). Of these 83 patients, 39.7 percent had preexisting alar cartilage malpositions, further supporting the importance of making accurate anatomical diagnosis part of every preoperative rhinoplasty plan. 相似文献
9.
The alar contour graft: correction and prevention of alar rim deformities in rhinoplasty 总被引:5,自引:0,他引:5
Rohrich RJ Raniere J Ha RY 《Plastic and reconstructive surgery》2002,109(7):2495-505; discussion 2506-8
One of the most common problems affecting both the primary and secondary rhinoplasty patient is deformity of the alar rim. Typically, this deformity is caused by congenital malpositioning, hypoplasia, or surgical weakening of the lateral crura, with the potential for both functional and aesthetic ramifications. Successful correction and prevention of alar rim deformities requires precise preoperative diagnosis and planning. Multiple techniques of varying complexity have been described to treat this common and challenging problem.Over the past 6 years (1994 through 2000), the authors have employed a simple technique in 123 patients for alar retraction that involves the nonanatomic insertion of an autogenous cartilage buttress into an alar-vestibular pocket. Among the 53 patients who underwent primary rhinoplasty in this study, 91 percent experienced correction or prevention of alar notching or collapse. However, correction was achieved for only 73 percent of the patients who underwent secondary rhinoplasty; many of whom had alar retraction secondary to scarring or lining loss. In patients with moderate or significant lining loss or scarring, a lateral crural strut graft is recommended. The alar contour graft provides the foundation in the patient undergoing primary or secondary rhinoplasty for the reestablishment of a normally functioning external nasal valve and an aesthetically pleasing alar contour. This article discusses the anatomic and aesthetic considerations of alar rim deformities and the indications and the surgical technique for the alar contour graft. 相似文献
10.
K E Salyer 《Plastic and reconstructive surgery》1986,77(4):558-568
This paper reviews a 15-year personal experience based on 400 unilateral cleft nasal deformities that were reconstructed using a method that repositions the alar cartilage by freeing it from the skin and lining and shifts it to a new position. The rotation-advancement lip procedure facilitates the exposure and approach to the nasal reconstruction. The nasal soft tissues are transected from the skeletal base, reshaped, repositioned, and secured by using temporary stent sutures that readapt the alar cartilage, skin, and lining. The nasal floor is closed and the ala base is positioned to match the normal side. Good subsequent growth with maintenance of the reconstruction has been noted in this series. The repair does not directly expose or suture the alar cartilage. Improvement in the cleft nasal deformity is noted in 80 percent of the cases. Twenty percent require additional techniques to achieve the desired symmetry. This method has been used by the author as his primary unilateral cleft nasal repair and has been taught to residents and fellows under his direction with good results. This technique eliminates the severe cleft nasal deformity seen in many secondary cases. 相似文献
11.
Neu BR 《Plastic and reconstructive surgery》2002,109(2):768-79; discussion 780-2
Alar cartilage losses and alar length discrepancies present problems in nasal tip support, contour, and symmetry. The true extent of the cartilage defect is often not apparent until the time of surgery. This article examines a problem-oriented and segmental open approach to such deformities. It is based on the size of the defect, its location within the dome and lateral crus, and the presence or absence of alar collapse. The defects are classified as major when there is a total or near total loss of the lateral crus, moderate when more than 5 mm is involved, and minor when less than 5 mm is affected. In major defects, a segmental reconstruction of the nasal tip cartilages is undertaken. It consists of a septal graft for columellar support and a conchal shield graft and umbrella graft for nasal tip contour. The whole length of the lateral crus is not reconstructed unless alar collapse is present. In moderate cartilage defects, usually seen laterally in secondary rhinoplasties, the remaining central dome segments are remodeled with shaping sutures. Moderate cartilage length discrepancies, as seen in unilateral cleft lip noses, are equalized through reversed alar rotations. The short crus is rotated laterally, taking length from the medial crus, and the long crus is rotated medially, with the excess advanced into the medial crural footplate. Additional shortening of the long crus can be achieved through cartilage division and advancement. The balanced alar units are then raised with tip projection-vector sutures, and onlay grafts are added if required. In minor cartilage losses, symmetry is usually obtained by shortening the opposite uninjured crus. A total of 33 patients are examined in this review. The average follow-up is 14 months. An improvement in nasal tip shape and support was achieved in all patients. 相似文献
12.
Primary repair of the unilateral cleft lip nose in the Oriental: a 20-year follow-up 总被引:2,自引:0,他引:2
K Boo-Chai 《Plastic and reconstructive surgery》1987,80(2):185-194
The unilateral cleft lip nasal deformity is corrected as a primary procedure with the lip repair. The abnormal attachment of the alar base is first released by an incision along the superior buccal sulcus and piriform margin. There is no intercartilaginous incision. Basically, we use the Brown-McDowell technique with the addition of an alar rim incision. Undermining of the ala between the two incisions is carefully and adequately done, splitting it into two layers. The first is a skin and the second, a chondrocutaneous (vestibular skin) layer, which is handled as a single unit, thus enhancing its vascularity. This second layer is a bipedicle flap with a broad medial pedicle and a narrow lateral pedicle at the alar base. When the alar base is rolled into its normal position, the chondrocutaneous unit hinging on its two pedicles counterrotates, correcting the subluxation of the ala, a major component of the cleft lip nasal deformity. We depend on the normal position of the alar base, the postoperative scar tissue, and the inherently thick nostril wall in the Oriental to keep the alar dome up. No transfixion sutures are used. Ten consecutive patients are shown 20 years after surgery. All had one operation only. None showed any disturbance of nasal growth. 相似文献
13.
A one-stage repair procedure is described for the reconstruction of small to medium-sized full-thickness alar rim defects with a hinged medially based nasolabial island flap. The operation is performed under local anesthesia as an office procedure and is indicated particularly in older patients. The hinged flap provides both the inner and outer layers of the alar rim. The donor site is closed primarily with no need to mobilize a large skin flap. The procedure leaves no conspicuous scars on the face. This method was found to be simple and safe, providing excellent tissue viability and yielding good color and texture match. 相似文献
14.
Recessive constitutive mutant Chinese hamster ovary cells (CHO-K1) with an altered A system for amino acid transport and the mechanism of gene regulation of the A system. 总被引:6,自引:0,他引:6
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Chinese hamster ovary cells (CHO-K1) starved for 24 h for amino acids show a severalfold increase in velocity of proline transport through the A system (Vmax is five times that of unstarved cells). This increase is inhibited by cycloheximide, actinomycin D, N-methyl-alpha-amino isobutyric acid (MeAIB, a non-metabolizable specific A system amino acid analog), and by other amino acids that are generally transported by the A system. However, transport by the A system is not a prerequisite for this repression, and all compounds that have affinity for the A system do not necessarily act as "co-repressors." The addition of proline, MeAIB, or other amino acids, as described above, to derepressed cells results in a rapid decrease in A system activity. As shown with proline and MeAIB, this decrease in activity is in part due to a rapid trans-inhibition and a slow, irreversible inactivation of the A system. Neither process is inhibited by cycloheximide or actinomycin D. Alanine antagonizes the growth of CHO-K1 pro cells by preventing proline transport, and alanine-resistant mutants (alar) have been isolated (Moffett et al., Somatic Cell Genet. 9:189-213, 1983). alar2 and alar4 are partial and full constitutive mutants for the A system and have two and six times the Vmax for proline uptake by the A system, respectively. The A system in alar4 is also immune to the co-repressor-induced inactivation. Both alar2 and alar4 phenotypes are recessive. Alar3 shows an increase in Vmax and Km for proline transport through the A system, and this phenotype is codominant. All three mutants have a pleiotropic effect, producing increases in activity of the ASC and P systems of amino acid transport. This increase is not due to an increase in the Na+ gradient. The ASC and P phenotypes behave similarly to the A system in hybrids. A model has been proposed incorporating these results. 相似文献
15.
The nasolabial flap remains the favored technique for alar and lateral nasal reconstruction. Results with currently popular techniques tend to be inartistic and aesthetically disappointing. Improved results can be achieved, however, by a technique using a medially based nasolabial turnover flap for lining with a distal extension providing the cover. Reconstruction of the ala begins by designing a nasolabial flap with its base as close as possible to the site of the proposed ala. The flap is incised to the required margins, carrying 2 to 3 mm of underlying fat; then, hinged on its base, the flap is flipped over medially like the page of a book. As the proximal flap is sutured to the lining side of the defect, the distal flap gracefully twists 90 degrees and is then folded on itself to form the external surface of the ala. The donor site is closed primarily. With this procedure, a natural-appearing and appropriately positioned ala may be reconstructed in one step, although a second procedure may be helpful to sculpture the margin or precisely position the alar base. 相似文献
16.
Radical correction of secondary nasal deformity in unilateral cleft lip patients presenting late 总被引:6,自引:0,他引:6
Ahuja RB 《Plastic and reconstructive surgery》2001,108(5):1127-1135
It is universally acknowledged that correction of a cleft lip nasal deformity continues to be a difficult problem. In developing countries, it is common for patients with cleft lip deformities to present in their early or late teens for correction of severe secondary lip and nasal deformities retained after the initial repairs were carried out in infancy or early childhood. Such patients have never had the benefit of primary nasal correction, orthodontic management, or alveolar bone grafting at an appropriate age. Along with a severe nasal deformity, they present with alveolar arch malalignments and anterior fistulae. In the study presented here, a strategy involving a complete single-stage correction of the nasal and secondary lip deformity was used.In this study, 26 patients (nine male and 17 female) ranging in age from 13 to 24 years presented for the first time between June of 1996 and December of 1999 with unilateral cleft lip nasal deformity. Eight patients had an anterior fistula (diameter, 2 to 4 mm) and 12 patients had a secondary lip deformity. An external rhinoplasty approach was used for all patients. The corrective procedures carried out in a single stage in these patients included lip revision; columellar lengthening; repair of anterior fistula; augmentation along the pyriform margin, nasal floor, and alveolus by bone grafts; submucous resection of the nasal septum; repositioning of lower lateral cartilages; fixation of the alar cartilage complex to the septum and the upper lateral cartilages; augmentation of nasal dorsum by bone graft; and alar base wedge resections. Medial and lateral nasal osteotomies were performed only if absolutely indicated. The median follow-up period was 11 months, although it ranged from 5 to 25 months. Overall results have been extremely pleasing, satisfactory, and stable.In this age group (13 years of age or older), it is not fruitful to use a technique for nasal correction that corrects only one facet of the deformity, because no result of nasal correction can be satisfactory until septal deviations and maxillary deficiencies are addressed along with any alar repositioning. The results of complete remodeling of the nasal pyramid are also stable in these patients because the patients' growth was nearly complete, and all the deformities could be corrected at the same time, leaving no active deforming vector. These results would indicate that aesthetically good results are achievable even if no primary nasal correction or orthodontic management had been previously attempted. 相似文献
17.
In a prospective study, 15 consecutive patients who underwent simultaneous open rhinoplasty and alar base excision were included to investigate whether there is a problem with the blood supply of the nasal tip and columellar skin. During the surgical procedure in these patients, there was transection of the columellar arteries and external nasal arteries, and frequently of the alar branches of the angular artery. Yet, none of the patients had any evidence of ischemia of the nasal tip or columellar skin, and there was primary wound healing with a thin-line transcolumellar scar in all patients. Techniques to avoid injury to the lateral nasal artery and nasal tip plexus are discussed. It was concluded that simultaneous open rhinoplasty and alar base excision is safe as long as certain surgical principles are applied. 相似文献
18.
Anatomic reconstruction of the nasal tip cartilages in secondary and reconstructive rhinoplasty 总被引:4,自引:0,他引:4
Menick FJ 《Plastic and reconstructive surgery》1999,104(7):2187-98; discussion 2199-2201
Most techniques for secondary rhinoplasty assume that useful residual remnants of the tip cartilages remain, but frequently the alar cartilages are missing--unilaterally, bilaterally, completely, or incompletely--with loss of the lateral crura, middle crura, and parts of the medial crura. In such severe cases, excision of scar tissue and the residual alar remnants and their replacement with nonanatomic tip grafts have been recommended. Multiple solid, bruised, or crushed cartilage fragments are positioned in a closed pocket or solid shield-shaped grafts are fixed with sutures during an open rhinoplasty. These onlay filler grafts only increase tip projection and definition. Associated tip abnormalities (alar rim notching, columellar retraction, nostril distortion) are not addressed. Problems with graft visibility, an unnatural appearance, or malposition have been noted. Fortunately, techniques useful in reconstructive rhinoplasty can be applied to severe cosmetic secondary deformities. Anatomic cartilage replacements similar in shape, bulk, and position to normal alar cartilages can be fashioned from septal, ear, and rib cartilage, fixed to the residual medial crura and/or a columellar strut, and bent backward to restore the normal skeletal framework of the tip. During an open rhinoplasty, a fabricated and rigid framework is designed to replace the missing medial, middle, or lateral crus of one or both alar cartilages. The entire alar tripod is recreated. These anatomic alar cartilage reconstructive grafts create tip definition and projection, fill the lobule and restore the expected lateral convexity, position the columella and establish columellar length, secure and position the alar rim, and brace the external valve against collapse, support the vestibular lining, and restore a nostril shape. The anatomic form and function of the nasal tip is restored. This technique is recommended when alar cartilages are significantly destroyed or absent in secondary or reconstructive rhinoplasty and the alar remnants are insufficient for repair. Anatomically designed alar cartilage replacements allow an aesthetically structured skeleton to contour the overlying skin envelope. Problems with displacement are minimized by graft fixation. Graft visibility is used to the surgeon's advantage. A rigidly supported framework with a nasal shape can mold a covering forehead flap or the scarred tip skin of a secondary rhinoplasty and create a result that may approach normal. Anatomic alar cartilage reconstructions were used in eight reconstructive and eight secondary rhinoplasties in the last 5 years. Their use in the repair of postrhinoplasty deformities is emphasized. 相似文献
19.
Arregui JS Elejalde MV Regalado J Ezquerra F Berrazueta M 《Plastic and reconstructive surgery》2000,106(7):1624-1629
To achieve permanent results for the correction of a drooping nasal tip, it is important to understand the mechanism responsible for the caudal rotation of the tip when a person speaks or smiles. This mechanism can be considered to depend on a "functional unity" formed by three components: (1) the cartilaginous framework (alar cartilages and accessories acting as a single structure); (2) muscular motors (m. levator labii superioris alaeque nasi and depressor septi nasi); and (3) gliding areas (apertura piriformis, the valvular mechanism between the upper lateral cartilages and alar cartilages, the lax tissue of the nasal dorsum, and the membranous septum). We describe a new anatomical and functional concept responsible for the plunging of the nasal tip. When a person smiles, the functional unit is activated by a combination of two forces acting simultaneously in opposite directions that rotate the tip caudally and elevate the nasal base. The levator moves the alar base upward and the depressor pulls the tip caudally. To correct the drooping tip, the transcartilaginous incision is extended laterally, and the lateral portion of the alar arch is dissected free from the skin and the mucosa, thus exposing the accessory cartilages. The arch is then severed at the level of the accessories to allow the cephalad rotation of the domes. The muscle insertions are dissected free from the accessories and a section of the muscle and, if necessary, the accessory cartilages, is removed. From January of 1991 onward, 312 patients have had this ancillary procedure performed in addition to the basic rhinoplasty technique. 相似文献
20.
Amino acid transport in membrane vesicles from CHO-K1 and alanine-resistant transport mutants 总被引:4,自引:0,他引:4
Membrane vesicles were prepared from CHO-K1 and alanine-resistant transport mutants, alar4 and alar4-H3.9. Alar4 is a constitutive mutant of the A system, and alar4-H3.9, derived from alar4, may be the result of amplification of a gene coding for an A-system transporter. Under conditions in which the same membrane potential (interior negative) and Na+ gradient were employed, the mutant vesicles show increases in the A system over that of the parental CHO-K1 cell line, paralleling, but not equivalent to, that found in whole cells. L-system and 5'-nucleotidase activities of these vesicles were similar, indicating that the increased A-system activity of the mutant vesicles is not due to the differential enrichment of the A system in these vesicles. The membrane potential was produced by a K+ diffusion gradient (internal greater than external) in the presence of valinomycin or by the addition of a Na+ salt of a highly permeant anion such as SCN-. Monensin was employed to study the effect of the Na+ gradient on transport and membrane potential. The latter was determined by measuring the uptake of tetraphenylphosphonium ion. A negative membrane potential determines the concentrative ability and the initial velocity of the A system in these vesicles. The concentration of external Na+ has a stimulatory effect on the initial velocity of this system. However, the Na+ gradient (external greater than internal) has no effect on the initial velocity or the membrane potential when the potential is set by valinomycin and high internal K+. Little if any ASC system could be detected in vesicles from CHO-K1. 相似文献