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Biomedical subjects

S A Syed

Publications and source records attributed to S A Syed.

At least 19 recordsLinked to original sources

Early passive mobilization after digital nerve repair and grafting in a fresh cadaver.

In the clinical management of combined tendon and nerve injuries, there are competing treatment strategies. Isolated tendon injuries should be rapidly mobilized after repair to prevent adhesion formation, whereas isolated nerve repairs are usually immobilized to prevent disruption and to allow axon regrowth. Recommendations in the published literature for the management of combined tendon and nerve injuries are vague and advise up to 3 weeks of immobilization. The goals of this study were to determine which length of nerve gap resulted in rupture of a repair following postoperative mobilization with the modified Duran protocol and with unrestricted motion and to determine whether nerve grafts are at risk of rupture after mobilization. A total of 100 digital nerves from 10 cadaver hands were tested with the modified Duran and the unsplinted protocols. Each digital nerve on each hand was sequentially resected and repaired at five progressively larger gap lengths after testing with both protocols. The mean nerve gaps at which disruption occurred were significantly different between the splinted (9.7 +/- 0.8 mm, n = 100) and unsplinted (7.3 +/- 1.9 mm, n = 100) protocols (t test, p < 0.001). One hundred percent of repairs remained intact, with up to 5 mm of resection with the modified Duran protocol (n = 100) and with up to 2.5 mm of resection with the unsplinted protocol (n = 100). All nerve grafts remained intact after mobilization within a dorsal-blocking splint (n = 100). Considering mechanical integrity of the nerve repair only, these data suggest that early mobilization with tendon protocols may be considered after a nerve injury to avoid the detrimental tendon sequelae that result from immobilization. The adequacy of functional recovery of mobilized nerves is yet to be determined.

Cadaver↗

Chromosome 11q13 and atopic asthma.

Asthma is a complex syndrome in which bronchial inflammation and smooth muscle hyperactivity lead to labile airflow obstruction. The commonest form of asthma is that due to atopy, which is an immune disorder where production of IgE to inhaled antigens leads to bronchial mucosal inflammation. The ultimate origins of asthma are interactive environmental and genetic factors. The genetics is acknowledged to be heterogeneous, and one chromosomal region of interest and controversy has been 11q13. To clarify the nature of the chromosome 11q13 effect in atopy and asthma, we conducted a genetic association study in subjects with marked atopic asthma and matched controls, which incorporated the study of 13 genetic variants over a distance of 10-12 cM and which took account of detailed immune and clinical phenotyping. Association with high IgE levels was limited to the interval flanked by D11S1335 and CD20 in a 0.8-Mb interval and was greatest for variants of Fc epsilonRIbeta and HTm4; these variants also associated with asthma (recurrent wheeze with labile airflow obstruction and need for regular inhaler treatment). At the more telomeric marker, D11S480, variants associated with asthma, but not with high IgE levels. The data might support the possibility of multiple loci relevant to atopic asthma on chromosome 11q13.

Alleles↗

Effects of nerve growth factor on nerve regeneration through a vein graft across a gap.

The limited availability of donor sites for nerve grafts and their inherent associated morbidity continue to stimulate research toward finding suitable alternatives. In the following study, the effect of direct administration of nerve growth factor (NGF) into a nerve conduit across a gap was tested in a rat sciatic nerve model. A 1-cm segment of the right sciatic nerve in Sprague-Dawley rats was resected, and the gap was then bridged using one of three methods: group I (NGF-treated group, n = 12), a vein graft filled with NGF (100 ng in 0.3-ml phosphate buffered saline); group II (control group, n = 12), a vein graft filled with phosphate buffered saline only; group III (standard nerve graft, n = 11), a resected segment of the sciatic nerve. All animals were evaluated at 3 and 5 weeks by behavioral testing and at 5 weeks by electrophysiologic testing. At 3 weeks, sensory testing showed that the latency to a noxious stimulus in group I animals (8.0 +/- 5.4 sec, mean +/- SD) was significantly lower than that of group II animals (13.2 +/- 6.5 sec), indicating that sensory recovery was superior in the animals receiving NGF. The mean latency of animals in group III was 12.9 +/- 6.5 sec, but the difference between the latencies of group I and group III did not reach statistical significance. At 5 weeks, there was no difference in sensory testing between groups. Motor function in groups I and III as measured by walk pattern analysis was superior to that of group II at 5 weeks (toe spread ratios 0.66 +/- 0.09, 0.48 +/- 0.07, and 0.69 +/- 0.09 for groups I, II, and III, respectively). Mean motor conduction velocities across the 1-cm gap were 8.6 +/- 4.7 m/sec, 2.5 +/- 0.7 m/sec, and 6.9 +/- 2.9 m/sec in groups I, II, and III respectively. The difference between groups I and III was not statistically significant, but the motor conduction velocity of group II was significantly slower than that of either group I or III (p < 0.002). The positive effects of NGF on regeneration of nerves across a gap seen in this study suggest that it may be useful for treating peripheral nerve injuries in combination with autogenous vein grafts.

Animals↗

Comparison of the effects of ischemic preconditioning and surgical delay on pedicled musculocutaneous flap survival in a rat model.

Both surgical delay (SD) and ischemic preconditioning (IP) have been shown to be effective in improving the survival of pedicled musculocutaneous flaps. The goal of our study was to determine the effects of IP and SD, separately and together, on the survival of pedicled transverse rectus abdominis musculocutaneous (TRAM) flaps in a rat model. Thirty-two male Sprague-Dawley rats were divided into four groups of 8 rats each: (1) control, (2) 2-week SD, (3) IP, and (4) SD plus IP. A TRAM flap was elevated in each rat. Flap viability was assessed on the fifth postoperative day by computerized video planimetry. Mean area of flap survival was compared between the control, IP, SD, and SD plus IP groups using analysis of variance and Student's t-test. Improvement in surface area survival was seen in musculocutaneous flaps subjected to IP, SD, and SD plus IP compared with the control. IP and SD improved survival 1.3 and 1.4 times the control area respectively. Differences between treatment and control flaps were statistically significant (p < 0.04). In addition, the combination of SD plus IP improved survival by 1.8 times, which is statistically different from controls and from either technique individually (p < 0.002). IP and SD have similar efficacy in improving survival in this musculocutaneous flap model. The effects of IP and SD appear to be additive. The advantage of IP over SD is that IP can be performed during the same operative session as the flap elevation and only adds 1 hour to the surgical procedure.

Animals↗

Ischemic preconditioning of musculocutaneous flaps: effects of ischemia cycle length and number of cycles.

Previous work in our laboratory has indicated that ischemic preconditioning improves musculocutaneous flap survival 2.5 times that of the control flap area when the flaps are subsequently subjected to 4 hours of global ischemia. The preconditioning protocol used in this study was arbitrarily designed to be 10 minutes of pedicle clamping followed by 10 minutes of reperfusion. This sequence was repeated for three cycles with a total preconditioning time of 1 hour. There are no published works comparing different preconditioning protocols in musculocutaneous flaps. The goal of this study was to determine if the ischemic cycle time and the number of cycles influenced the effectiveness of ischemic preconditioning. Fifty-one male Sprague-Dawley rats were divided into one control and six treatment groups of 6 to 10 animals in each group. A transverse rectus abdominis musculocutaneous flap based on the inferior epigastric vessels was elevated in each animal. Flaps were preconditioned by pedicle clamping and reperfusion for either 5 or 10 minutes per cycle. This was repeated for one, two, or three cycles. Controls were simply perfused for 30 minutes. Each flap was then subjected to 4 hours of global ischemia. Flap surface survival area was calculated on the fifth postoperative day by computerized video planimetry. Differences in survival areas between control and preconditioned flaps were compared using analysis of variance and t-tests. There was an overall statistical significance in the comparison of flap survival of preconditioned flaps with that of controls. A single 5-minute cycle improved flap survival 2.5 times the mean control area. Two and three 5-minute cycles resulted in a reduction of the preconditioning effect, with flap survival no different than controls. Ten-minute preconditioning cycles increased flap survival 1.5 to 3 times the mean control area. Flap survival was improved by increasing the number of 10-minute cycles. Cycle time and number of cycles have definite effects on the survival areas of preconditioned musculocutaneous flaps. Ischemic preconditioning with 10-minute cycles is superior to 5-minute cycles. Three cycles of 10-minute preconditioning is statistically superior to one or two cycles. Future studies are planned to study four or more cycles and longer cycle times.

Animals↗

The effect of prolonged clamping and vascular stasis on the patency of arterial and venous microanastomoses.

During free tissue transfer, an artery and one or two veins must be sutured. Either the artery or the vein can be repaired first, but the optimal order of vascular repair has not been established. Maintaining a clamp on a vessel is associated with vessel injury, and releasing the clamp may cause bleeding and vascular stasis. The purpose of this study was to determine if the order of vessel repair and the length of vascular clamping affects surgical outcome. Free flaps were created on Sprague-Dawley rats (400-450 g) as follows: Bilateral abdominal skin flaps (3 x 3 cm) based on the superficial inferior epigastric vessels were elevated. The femoral artery and vein were tied and divided distal to the branching of the inferior epigastric vessels. Proximal to the branching, the artery and vein were divided. The animals were then randomized into four groups as follows: In group I (N=16), the artery was repaired and then the clamps were released to revascularize the flap. Venous stasis occurred as the vein was being repaired because of the venous clamp. In group II (N=15), the artery was repaired, but the clamp was maintained to prevent blood from coming in contact with the fresh arterial anastomosis and to prevent venous stasis. The vein was then repaired. In group III (N=15), the vein was repaired first but the venous clamp was not released until the artery was repaired. In group IV (N=15), the vein was repaired first and the clamps were released, allowing venous blood to contact the fresh anastomosis while the artery was being repaired. After final clamp removal, all anastomoses were assessed immediately for evidence of thrombosis. Five days postoperatively the skin flap was evaluated for evidence of necrosis and the anastomosis was inspected for evidence of late thrombosis. The anastomoses were resected for histopathological evaluation. Flap success was compared between groups using chi-squared analysis. Eleven of 16 flaps failed (69%) in group I, and 3 of 15 flaps failed (20%) in each of groups II, III, and IV. Statistical significance was reached in comparing group I with the other three groups (p < 0.01). All failures in group I were caused by immediate venous thrombosis. The other failures were secondary to arterial thrombosis. Histopathological analysis failed to demonstrate any differences between the groups. According to these results, arterial repair followed by clamp release prior to the completion of the venous repair results in a low success rate, probably secondary to venous stasis within the draining vein while the venous anastomosis is being completed. If the arterial repair is performed first, then it is recommended that the arterial clamp be maintained until the venous repair is completed. If the vein is repaired first, then it can be clamped or unclamped with similar results.

Anastomosis, Surgical↗

Ischemic preconditioning improves the survival of skin and myocutaneous flaps in a rat model.

Inadequate blood supply of pedicle flaps results in partial necrosis, and prolonged ischemia during free-tissue transfer can result in partial or complete flap necrosis. Recent research in the field of cardiovascular surgery has shown that ischemic preconditioning (repeated brief episodes of coronary artery occlusion followed by reperfusion) improves myocardial muscle survival when the heart is subsequently subjected to prolonged ischemia. Preconditioning of skin or myocutaneous flaps as either pedicle or free flap models has never been studied. The goal of this investigation was to measure the effect of ischemic preconditioning on myocutaneous and skin flap survival areas and total necrosis rates after variable periods of global ischemia. In 220 rats, 100 transverse rectus abdominis myocutaneous flaps and 120 dorsal cutaneous flaps were randomized into treatment and control groups. The treatment flaps underwent preconditioning by three cycles of 10 minutes of pedicle clamping followed by 10 minutes of reperfusion for a total preconditioning period of 1 hour. The control flaps were perfused without clamping for 1 hour. Both control and treatment flaps then underwent global ischemia for 0, 2, 4, 6, 10, or 14 hours by pedicle clamping. Flap survival area was measured on the fifth postoperative day. Statistical analysis was performed with analysis of variance, student's t tests, and probit analysis. Preconditioning improved survival areas of pedicle myocutaneous flaps (0-hour group) from 47 +/- 16 percent (mean percent area surviving +/- SD) to 63 +/- 5 percent. This difference was statistically significant (t test, p < 0.04). There was no statistically significant improvement in pedicle skin flap survival. For free flap models (flaps undergoing global ischemia), preconditioning increased the survival areas of skin and myocutaneous flaps (analysis of variance, p < 10(-5)). For the skin flap model, statistical significance of the survival area difference was reached at 6, 10, and 14 hours of ischemia (t test, p < 10(-4)). The magnitude of this effect was higher in the myocutaneous flap model and reached statistical significance at 2, 4, 6, and 10 hours of ischemia (p < 10(-3)). Preconditioned flap survival areas were increased by two to five times that of non-preconditioned flaps at these ischemia times. Preconditioning lowered total necrosis rates at all ischemia times for both flap models. The critical ischemia time when 50 percent of skin flaps became totally necrotic (CIT50) improved from 6.9 to 12.4 hours by preconditioning. Similarly, preconditioning improved the CIT50 of myocutaneous flaps from 3.6 to 9.2 hours. For the first time, statistically significant improvements of partial necrosis areas and total necrosis rates have been demonstrated through intraoperative ischemic preconditioning of skin and myocutaneous flaps. In clinical practice, application of this technique may lead to improved survival during pedicled or free transfer of myocutaneous flaps and free transfer of skin flaps.

Analysis of Variance↗

Surgical delay in TRAM flap breast reconstruction: a comparison of 7- and 14-day delay periods.

Thirty-one transverse rectus abdominis musculocutaneous (TRAM) flap breast reconstructions were performed after a delay period either of 1 week (group I, N = 15) or 2 weeks (group II, N = 16). The preliminary delay procedure consisted of bilateral deep inferior epigastric and superficial inferior epigastric artery and vein ligation. In group I the diameter and flow in the superior epigastric artery increased from baseline values of 1.3 +/- 0.3 mm and 7.25 +/- 0.8 ml per minute to 1.8 +/- 0.3 mm and 18.2 +/- 2.7 ml per minute at 1 week. In group II the diameter and flow in the superior epigastric artery increased from baseline values of 1.2 +/- 0.3 mm and 5.85 +/- 1.5 ml per minute to 1.7 +/- 0.4 mm and 23.4 +/- 6.2 ml per minute at 2 weeks. The differences between 1 and 2 weeks were not statistically significant. The complication rate in either group was similar. We conclude that a preliminary delay procedure is highly effective at augmenting TRAM flap vascularity and may be implemented between 1 and 2 weeks prior to TRAM flap breast reconstruction in high-risk patients.

Blood Flow Velocity↗

Transferring vascular territories from one axial pattern flap to another: a comparison of delay procedures.

The delay technique is an established method of enhancing flap survival. This investigation attempts to determine which of two delay techniques results in the best delay effect by measuring their relative abilities to capture adjacent vascular territories in a rat model. A dorsal flap based on the iliac branch of the iliolumbar artery with a captured random zone corresponding to the axial territory of the lateral thoracic artery was used in the evaluation. Sprague-Dawley rats (350-400 g) were randomly assigned into three groups. Group I was the control group. In group II, the circumferential borders of the animal's dorsum were incised without undermining and the dominant pedicle of the lateral thoracic flap was divided. In group III, the medial and lateral borders of the flap were incised and undermined as a bipedicled flap, violating the musculocutaneous perforators. The dominant pedicle of the lateral thoracic artery was also divided. Group III had the greatest survival with only 9% of flap area necrosis compared to 28% and 21% for groups I and II, respectively. These differences were statistically significant. The results suggest that musculocutaneous perforators provide a substantial vascular source to the tissue at risk and should be considered in selecting a delay technique.

Animals↗

Distal dorsal forearm flap.

The goal of this study was to investigate the vascular supply of the distal dorsal forearm and the feasibility of using a local skin flap based on perforating vessels of the anterior interosseous artery (AIA) to reconstruct the dorsal aspect of the hand. The results of anatomic studies on 71 adult, fresh-frozen cadaveric upper extremities indicate that a new flap can be designed based on a cutaneous branch of the AIA. The AIA runs along the volar surface of the anterior interosseous membrane. At the proximal border of the pronator quadratus muscle it gives off a dorsal septocutaneous branch (DSCB) that pierces the interosseous membrane and supplies the extensor muscles of the thumb and the skin of the distal two-thirds of the dorsal forearm. The average artery diameter at the origin of the DSCB was 1.1 +/- 0.2 mm (mean +/- standard error of mean). The mean pedicle length was 3.1 +/- 0.6 cm. The pedicle could be extended to 12.4 +/- 0.9 cm if the entire AIA was included. Based on dye injection studies, the smallest skin paddle that could be supported by this vessel ranged from 5 x 9 cm to 8 x 15 cm. The flap can be configured as an island vascular flap based on the DSCB or AIA, a distally based flap, a free flap, a fascial flap, or a composite flap including muscle, bone, nerve, and skin.

Adult↗

Amniotic fluid embolism: emergency management.

A case of successful outcome is described in a patient with amniotic fluid embolism presenting to the accident and emergency department. Diagnostic features and guidelines for management are outlined.

Adult↗

Purification and general properties of an oligopeptidase from Treponema denticola ATCC 35405--a human oral spirochete.

An endo-acting oligopeptidase (OPase) was purified to homogeneity from the cells of Treponema denticola ATCC 35405--a human oral spirochete--by a procedure that comprised a mild Triton X-100 extraction (which disintegrates the outer membrane but leaves the cells morphologically intact) and four successive fast protein liquid chromatographic steps of the extract. The activity of this oligopeptidase (formerly named "trypsin-like" enzyme and "BANA-peptidase") together with the proteinase activities of T. denticola and Porphyromonas gingivalis is utilized in a diagnostic test for human periodontal infections, but the enzyme's chemical nature has not been studied. The enzyme is a cell-associated 78-kDa protein with an isoelectric point of 6.1, and its estimated minimum peptide length was 688 amino acid residues. The OPase does not hydrolyze proteins, but hydrolyzes -X-Arg-p-nitroaniline peptides between arginine and the chromogen, the optimum pH of hydrolysis covering a broad pH range (7 to 9). The OPase is not a metalloenzyme, although 1.0 mmol/liter Ca(II) increases the rate of the hydrolysis of all substrates. Ca(II) did not affect the values of the Michaelis constant. The OPase activity is not dependent on reactive SH-groups, but is suggested to depend on the catalytic triad COOH. . .His. . .Ser. The N-terminal sequence for the first 29 amino acid residues is MKQSDFEKPPIAEIKETRFEKFGKTRIDN. The purified enzyme is very sensitive to chlorhexidine acetate (mixed inhibition; Ki = 0.85 microM) and somewhat less sensitive to bacitracin (Ki(app) = 27.5 microM). The present OPase is considered to belong to the serine peptidases, functionally resembling trypsin except that the OPase does not hydrolyze proteins. The OPase may be regarded as an oligopeptidase, the substrate specificity profile of which resembles to a certain extent that of some members of the coagulation cascade.

Amino Acid Sequence↗

Anatomic study of a new axial skin flap based on the cutaneous branch of the medial plantar artery.

A new axial skin flap based on the middle cutaneous branch of the medial plantar artery was evaluated in 33 fresh cadaver legs. The vascular pedicle of the skin flap is based on the middle cutaneous artery, its venae comitantes, and segments of the great saphenous vein, if necessary. The middle cutaneous artery is the largest cutaneous branch, arising from the medial plantar artery 2.5 cm distal to its origin. The diameter of its origin is 1.2 mm, and its pedicle is 2 cm long. The midline of the flap runs from the first web space to the heel tip. The upper and lower borders of the flap are 3 to 4 cm on either side of this line. The upper border is medial to the extensor hallucis tendon, and the lower border is medial to the abductor hallucis. Distally, the border begins 2 cm proximal to the metatarsalphalangeal joint; proximally, the border is at the middle of the medial malleolus. The flap diameter can be up to 8 x 12 cm. The middle cutaneous branch of the medial plantar artery was found in all cadaver specimens, except for one with a common trunk. The new flap design leaves the major blood supply to the foot and the plantar aponeurosis intact. It is easy to harvest and may be used either as an island flap or free flap.

Arteries↗

A new technique for endoscopic carpal tunnel decompression.

A new one-portal technique for endoscopic carpal tunnel release (ECTR) is introduced with its clinical results. The incision is made at the palmar aspect of the hand. A custom-made glass tube with a groove is inserted, and under endoscope observation, a meniscus knife is pushed forward along the groove to release the flexor retinaculum. This new technique has been studied in ten fresh cadaver hands and used in 123 patients' hands. Results of the cadaver study showed that the flexor retinaculum was released completely in all ten hands. No injuries to tendons, nerves, or arteries were noted. In one case the cotton tip was lost from the stick. All clinical releases were performed uneventfully except for three cases of neuropraxia of the digital nerve of the radial side of the ring finger, one laceration of the motor branch of the median nerve, one mild infection, one loss of cotton tip from the cotton swab stick, and one case of chipping of the glass tube. The case with the laceration of the motor branch of the median nerve occurred early in the series and required the conventional open incision to repair the nerve. The cases with loss of cotton from the stick and chipping of the tube also required a conventional incision to remove the cotton and glass chip. Advantages of this one-portal technique with the glass tube include less scar tenderness than with two-portal techniques, decreased risk of injury to the superficial palmar arch and ulnar nerve because of the distal approach, a view of pathology in the carpal tunnel through the glass tube, and confirmation of release of the flexor retinaculum.

Carpal Tunnel Syndrome↗

Role of the chymotrypsin-like membrane-associated proteinase from Treponema denticola ATCC 35405 in inactivation of bioactive peptides.

The ability of washed whole cells of Treponema denticola ATCC 35405 to hydrolyze (inactivate) substance P, bradykinin, and angiotensin I was studied. Substance P was attacked primarily at the Phe-8-Gly-9 bond by a chymotrypsin-like proteinase (CTLP), at Pro-4-Gln-5 by an endo-acting prolyl oligopeptidase (POPase), and at Gln-5-Gln-6 by an endopeptidase (FALGPA-peptidase). Bradykinin was cleaved at Phe-5-Ser-6 by the FALGPA-peptidase and at Pro-7-Phe-8 by the POPase. Angiotensin I was rapidly converted to angiotensin II by the CTLP, and both angiotensin I and angiotensin II were further hydrolyzed at Pro-7-Phe-8 by the POPase. All these enzymes were assumed to be cell associated and were easily extracted with a mild (0.05 to 0.1%) Triton X-100 treatment. Because it was conceivable that the hydrolysis of substance P at the Phe-8-Gly-9 bond was catalyzed by a CTLP described earlier (V.-J. Uitto, D. Grenier, E. C. S. Chan, and B. C. McBride, Infect. Immun. 56:2717-2722, 1988), the enzyme was purified to homogeneity by means of conventional fast protein liquid chromatography procedures. For kinetic studies, Phe-8(4-nitro)-substance P (NSP) (absorption maximum at 309.2 nm, epsilon = 545 M-1 cm-1) was synthesized to replace substance P as a substrate in kinetic studies. In reversed-phase chromatography, both NSP and substance P gave identical results with both whole cells and the purified enzyme. The CTLP has a mass of 95 kDa, and its activity is suggested to be based on an active seryl residue, on an active imidazole group, and on an active carboxyl group but not on metal cations. The enzyme hydrolyzes N-succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroaniline (SAAPFNA, a typical chymotrypsin substrate) at a high rate and several proteins, such as calf thymus histone, human plasma fibrinogen, milk caseins, and gelatin. Among the substrates tested, substance P showed the highest affinity (Km = 0.22 mM) for the purified enzyme. Depending on conditions, clinically applicable chlorhexidine levels (3.2 mmol/liter, or 0.2%) strongly activated (up to fourfold) the hydrolysis of SAAPFNA by whole cells and the purified CTLP. The hydrolysis of NSP by whole cells and purified CTLP was slightly inhibited by chlorhexidine. The results demonstrated the versatility and the effectiveness of the outer membrane of T. denticola in occasioning a rapid breakdown and inactivation of human bioactive peptides and other peptidolytic catalyses.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

A new operative technique: cubital tunnel decompression with endoscopic assistance.

The final outcome of a surgical decompression of the ulnar nerve depends on the precise release of all potential entrapment points. Careful attention must be given to all anatomic structures around the ulnar nerve and elbow area to ensure adequate dissection and surgical accuracy. In the authors' new endoscopic technique, glass tubes have been specially designed to house an endoscope and guide a meniscus knife, allowing for the release of all involved structures up to 10 cm both proximally and distally through a 3-cm skin incision. The authors present their experience in a cadaver trial and with 26 patients with follow-up of at least 6 months.

Adult↗