Changes in Sagittal Spinopelvic Parameters according to Pelvic Incidence in Asymptomatic Old Korean Men

STUDY DESIGN: A radiographic study of normal subjects. OBJECTIVES: To analyze sagittal spinal parameters according to the size of pelvic incidence (PI). SUMMARY OF LITERATURE REVIEW: There has been no previous study about the classification of spinopelvic parameters that has used a large cohort of asymptomatic older men with the same ethnic background as those in the current study. MATERIALS AND METHODS: We examined 160 males aged over 50 without disease, trauma, or history of operation on spine or lower extremities. Sagittal standing radiographs of the whole spine on 36-inch film were taken. Group 1 (n=30) had a PI of less than 40degrees. Group 2 (n=71) had PI between 40degrees and 50degrees, and group 3 (n=59) had a PI greater than 50degrees. Thoracic kyphosis, thoracolumbar kyphosis, lumbar lordosis, the vertebral slope of T12, sacral slope, and pelvic incidence were measured. The distances from the plumb line of C7, T12, and the lumbar apex to the posterosuperior corner of the sacrum were also measured. RESULTS: Subjects' average age was 64.1(53~83).Lumbar lordosis, sacral slope and pelvic tilt were all significantly increased in group 3. Thoracic kyphosis and the vertebral slope of T12 were not different between groups. The distances from the plumb line of C7, T12, and the lumbar apex to the posterosuperior corner of the sacrum were significantly translated anteriorly in group 3. CONCLUSIONS: Group 3, who had the largest PI, demonstrated the largest lumbar lordosis and the most forward transition of trunk. However there were no differences in thoracic kyphosis and the vertebral slope of T12 among the three groups.

Incomplete Anterior Interosseous Nerve Palsy That Accompanied a Monteggia Fracture / 대한정형외과학회잡지

The anterior interosseous nerve innervates the flexor pollicis longus, the flexor digitorum profundus and the pronator quadratus. There are no sensory fibers from the anterior interosseous nerve leading to the skin. Paralysis of the anterior interosseous nerve that accompanies a Monteggia fracture has rarely been reported, and incomplete paralysis of the anterior interosseous nerve has almost not been reported. We experienced a patient with incomplete anterior interosseous nerve palsy involving the flexor pollicis longus as a complication of a Monteggia fracture. The paralysis of the flexor pollicis longus recovered 4 months after the surgery for the Monteggia fracture.

Variations in Sagittal Spinopelvic Parameters According to the Lumbar Spinal Morphology in Healthy Korean Young Men

STUDY DESIGN: This is a prospective radiographic study. OBJECTIVES: We wanted to describe and quantify the common variations in the sagittal lumbar spine. SUMMARY OF THE LITERATURE REVIEW: No previous study of the spinopelvic parameters with a large cohort of asymptomatic young men was performed on subjects with the same ethnic background. MATERIALS AND METHODS: 166 young males without disease, trauma or a history of operation on the spine or lower extremities were included. The sagittal standing radiographs of the whole spine on 36 inch film were taken. The distances from the plumb line of C7, T12, the lumbar apex and the bicoxofemoral head to the posterosuperior corner of the sacrum were measured. Thoracic kyphosis, thoracolumbar kyphosis, lumbar lordosis, the segmental vertebral slopes, the sacral slope and the pelvic incidence were measured. Groups 1 and 2 were classified by having a sacral slope less than 35degrees (group 1: apex below L4, group 2: above L4). Group 3 had a sacral slope between 35degrees and 45degrees, and group 4 had a sacral slope greater than 45degrees. RESULTS: The average age was 21.8 years (range: 19~26 years). Group 1 contained 37 cases, group 2 had 44, group 3 had 62 and group 4 had 23. Thoracolumbar kyphosis was significantly increased in group 1 and lumbar lordosis and pelvic incidence were increased in groups 3 and 4. Thoracic kyphosis and the vertebral slope of T12 did not demonstrate any difference between the groups. CONCLUSION: The sagittal spinopelvic parameters showed significant changes according to the morphology of the lower lumbar spine. Understanding the patterns of variation in the spinopelvic parameters may help surgeons to plan treatment for various spinal lesions.

Acromioclavicular Separation with the Fracture of the Coracoid Process: 2 Cases report

The acromioclavicular separation (AC separation) is a common injury, which is often accompanied by the rupture of the coracoclavicular ligament (CC ligament) in severe occasions. In rare forms of AC separation, the fracture of the coracoid process would occur rather than the rupture of the CC ligament. Only 31 cases of such injury have been reported in the English literature. We present 2 additional cases with literature review. The fracture of the coracoid process is not readily seen on anteroposterior shoulder radiograms. Severe AC separation without widening of CC distance on anteroposterior shoulder radiogram heralds the fracture of the coracoid process.

Anterior Neck Approach for 4-vessel Occlusion in Rats: A Study for Immunohistological Changes and the Effects of Aminoguanidine on Neuronal Cell Death in the Hippocampus

BACKGROUND: Clinically relevant cerebral ischemia is encountered most frequently as a cardiac arrest or as single or multiple occlusions of the intracranial or extracranial cerebral arteries. Yamaguchi et al. has introduced a one-stage anterior approach to occlude the common carotid arteries (CCAs) and vertebral arteries (VAs). METHODS: We used a 2-stage anterior approach for producing transient global ischemia by 4-vessel occlusion (4-VO). Four to five days after electrocauterization of two VAs using the anterior neck approach, two CCAs were clipped for 10 min under anesthesia. Aminoguanidine (100 mg/kg) was administered intraperitoneally immediately after 4-VO, and then twice a day for three consecutive days. Cresyl violet staining and immunohistochemical analysis for the expression of GFAP, CD11b, nitrotyrosine, iNOS, and Bax were performed, using brain slices obtained from the rats that were sacrificed 1, 3, 5 and 7 days after reperfusion. RESULTS: Aminoguanidine reduced neuronal cell death in the CA1 region of the hippocampus. Expression of GFAP, CD11b, nitrotyrosine, iNOS, and Bax were significantly increased in the CA1 region of the hippocampus three days after 4-VO. CONCLUSIONS: We believe that modified 4-VO is a good method to study transient forebrain ischemia as it is simple and inexpensive to perform and can be utilized without stereotaxis, a pivoting dissection microscope, EEG, a laser flowmeter or the use of Mongolian gerbils.

Nicotinamide Reduces the Infarct Volume in a Rat Model of Transient Middle Cerebral Artery Occlusion

BACKGROUND: Cerebral ischemia depletes ATP and causes irreversible tissue injury. Nicotinamide is a precursor of NAD+ and it is also a poly (ADP-ribose) polymerase (PARP) inhibitor that increases the neuronal ATP concentration and so protects against stroke. Therefore we examined whether nicotinamide could protect against cerebral ischemia by using a model of transient middle cerebral artery occlusion (MCAO) (reperfusion 2 h post ischemia) in Sprague-Dawley rats. METHODS: Nicotinamide (500 mg/kg) or normal saline was administered intraperitoneally 24 and 0 h before and after MCAO, respectively. The infarction volumes were determined with triphenyltetrazolium chloride staining 24 h after reperfusion. The nitrotyrosine, PAR polymer and PARP-1 expressions were examined by immunohistochemistry with using brain slices obtained from the rats that were sacrificed at 0, 15, 30, 60 and 120 min after reperfusion. RESULTS: The infarction volumes were significantly attenuated (21.8%, p<0.05). The nitrotyrosine expressions were increased at 0, 15 and 30 min, and those expressions for PARP polymer and PARP-1 were increased at 60 and 120 min, respectively. Nicotinamide partly reduced the expressions for nitrotyrosine and PAR polymer except for PARP-1. CONCLUSIONS: These results suggest that nicotinamide may attenuate ischemic brain injury through its antioxidant activity and the inhibition of PARP-1.

Late Complications after Excisional Operation for Choledochal Cyst

PURPOSE: Even after excision of choledochal cyst, late postoperative complications can develop. This study was conducted to examine the long-term outcome of cyst excision. METHODS: Of 50 choledochal cysts treated over a 10-year period (1991~2000), excluding cancer and rare types, 39 patients (type I: 21, IVa: 18) who underwent cyst excision were reviewed to evaluate the late outcome. RESULTS: Median follow-up period was 24 months after surgery. Late complications (5 intrahepatic duct stone, 4 cholangitis, 4 pancreatitis, and 1 malignancy) developed in 14 (35.9%) patients. Of the 5 patients with intrahepatic duct stone, 2 underwent choledochoscopic stone removal, one of whom additionally underwent balloon dilatation for anastomotic stricture. The remaining 3 patients were free of symptoms and didn't need further management. Of the 4 patients with cholangitis, one underwent left lateral sectionectomy for remaining intrahe patic cyst in type IVa and another patient balloon dilatation for anastomotic stricture. The remaining 2 patients developed cholangitis because of incomplete excision and ascending cholangitis, and they were conservatively managed. Of the 4 patients with pancreatitis, 2 developed pancreatitis because of pancreas divisum and probably residual distal cyst. The symptoms of all four patients with pancreatitis were mild and treated with conservative management. Periampullary cancer developed 18 months after cyst excision in one patient. CONCLUSION: To minimize hepatopancreatobiliary complications and malignancy after cyst excision, complete excision of the extrahepatic bile duct should be performed. Moreover, long-term follow-up is necessary because of these late complications.

Minocycline Attenuates the Development of Allodynia: An Immunohistochemical Study on CD11b, GFAP and c-Fos in the Spinal Dorsal Horn in SD Rat

BACKGROUND: Minocycline, a semisynthetic second-generation tetracycline, is an antibiotic that has excellent ability to penetration into the CNS via the brain-blood barrier. Minocycline has emerged as a potent inhibitor of microglial activation, and it is an effective neuroprotective agent in experimental brain ischemia. Glial cell activation and proliferation are known to be associated with neuropathic pain in the peripheral nerve injuries. METHODS: The fifty percent threshold of withdrawal responses was measured in the hindpaws of SD rats following tight ligation of left fifth lumbar spinal nerve. Rats were sacrificed at 1, 3, 5, and 7 days and at 0.5, 1, 2, and 4 h post ligation (n=5/group/time point). Immunohistochemistry for GFAP, CD11b and c-Fos was done on the spinal cord at the level of the fifth lumbar nerve. Minocycline (45 mg/kg) and normal saline (300-400 microL) were administered intraperitoneally, 1 day and 1 h before the operations, and every day postoperatively until the rats were sacrificed. RESULTS: Treatment with minocycline reduced allodynia and the expressions of CD11b at 5 days and c-Fos at 1 and 2 h post operation compared with the saline treatment (control). CONCLUSIONS: It was thought that minocycline reduced the allodynia induced by tight ligation of the fifth lumbar spinal nerve in rats through the inhibition of microglial activation and c-Fos expression.

The Explanation of Postoperative Change of Vertebral Rotation and Rib Hump Using 3 Dimensional Finite Element Scoliosis Model / 대한척추외과학회지

STUDY DESIGN: An analytical study using a mathematical 3-D finite element model for thoracic scoliosis. OBJECTIVE: To find the important kinematics and post-operative changes of the spine and rib cage, in the corrective surgery for scoliosis, using the rod derotation method. SUMMARY OF LITERATURE REVIEW: A conventional corrective surgery for scoliosis was performed, based on empirical knowledge, and an increase in the secondary postoperative change in the rib hump, and a shoulder level imbalance, were reported. However, no analytical data exists for the kinematics and optimal correction method. MATERIALS AND METHODS: A mathematical finite element model of a normal spine, including the rib cage, sternum, both clavicles and pelvis, was developed. Using geometric mapping, with standing radiographs and CT images, a 3-D FEM of scoliosis was reconstructed, after translating and rotating the 3-D FEM of a normal spine, with the amounts analyzed from 12 built-in digitized coordinate axes for each vertebral image. With this model, three elements; distraction, translation and derotation, in operative kinematics, were investigated by analyzing the Cobb angle, apical vertebrae axial rotation (AVAR) and thoracic kyphosis. A simulation of a segmental pedicle screw fixation, with rod derotation for scoliosis, was performed. The changes in the Cobb angle, kyphotic angle, AVAR and rib hump were compared after 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees and 90 degrees rod derotations. RESULTS: In kinematics, the vertebral rod derotation of a major curve, without rod deformation, is less influential in the correction of scoliosis, simply causing an increase in the rib hump. During the simulation, the co-action of distraction and translation, during rod insertion, has a major impact on the decrease in the Cobb angle and in the maintenance of the kyphotic angle. However, after a 30 degrees rod derotation, a decrease in the kyphosis, and increases in the rib hump and AVAR were observed. CONCLUSIONS: The distraction and translation factors were more important in operative kinematics than the rod derotation. With excessive rod derotation, the Cobb angle progressively decreased, but increases in the secondary change in the rib hump and rotation of the apical vertebrae were found.

The Prevalence and Associated Factors of Constipation in the School-aged Children / 대한소아소화기영양학회지

PURPOSE: Constipation in childhood is a significant problem, however, understanding of its epidemiology has been limited in Korea. The aim of this study was to investigate the prevalence and risk factors of constipation in school-aged children, helping to manage and prevent it. METHODS: This cross-sectional, descripsive observational prevalence study included children (2 grade, 1st and 6th grade) who were attending two elementary schools in Gwangju. The prevalence of constipation, associated symptoms, and risk factors were evaluated by questionnaire. A child was considered to be constipated when he or she defecated two or less times per week. RESULTS: The prevalence of constipation was 15.4%. There is no significant difference between both sexes and grades. Of the causes of constipation, there was statistically significant difference in exercise deficiency, frequent intake of convenience food, long-time watching TV, unbalanced diet and enuresis history between constipation and normal group. Especially, long-time watching TV, exercise deficiency, and enuresis history were risk factors for development of constipation. Only 27.1% of children with constipation were treated by laxative and enema. CONCLUSION: Even though the prevalence of constipation was high, more than half of them was not treated at all. We should endeavor to educate the children and their parents to prevent constipation by evaluating the feeding and behavioral habit completely, and treating them properly.

The Expression of Bcl-2, Bax, Cytochrome C and Caspase-3 in Camptothecin-Induced Apoptosis of Mouse 3T3 Fibroblasts

BACKGROUND: Camptothecin (CPT), which has been used for cancer treatment and apoptosis as an inhibitor of DNA topoisomerase I. We investigated the possibility that camptothecin induces anti-appoptotic bcl-2 and pro-apoptotic bax, cytochrome c and caspase-3. METHODS: We performed immunocytochemical stains for bcl-2, bax and cytochrome c, and also performed westem blots for caspase-3 and the three proteins above using mouse 3T3 fibroblasts treated with CPT (0.5 microgram/mL). The immunostain for bcl-2 was done 12 hours after a microinjection of antisense oligomer to bcl-2 in the nuclei of the cells. RESULTS: On immunocytochemistry, bcl-2 showed no expressions regardless of CPT treatment and microinjection of the antisense oligomer. The expression of cytochrome c was not changed before and after CPT treatment, and bax demonstrated weak or moderate expressions at 36 and 48 hours afte the treatment. There were no expressions at 0, 12, and 24 hours after CPT treatment. On westem blot, bcl-2 exhibited no expressions before and after CPT treatment. Expressions of ctyochrome c and caspase-3 increased after CPT treatment, and expressions of bax decreased 24 hours after CPT treatment followed by a tendency of increased expressions as time went by. CONCLUSIONS: In the CPT-induced apoptosis of mouse 3T3 fibroblasts, CPT induced increased expressions of bax, cytochrome c and caspase-3 with no expressions of bcl-2, which are associated with the apoptosis pathway.

Spiral CT of Hepatocellular Carcinoma: Value of Dynamic Fast Infusion of Contrast Material

PURPOSE: To assess the value of dynamic fast infusion of contrast material in the detection and diagnosis of hepatocellular carcinoma(HCC) with spiral CT. MATERIALS AND METHODS: Two-phase dynamic spiral CT was performed in 59 patients with 104 HCCs. 150ml of nonionic contrast material was injected with an automatic injector at the rateof 5 ml/sec. Two-phase images were obtained at 20-45 sec(arterial dominant phase) and 2-5 min(equilibrium phase)after the initiation of bolus injection of contrast material. The tumors were divided into three groups(5cm) according to the size and the enhancement patterns on two-phase images were compared. RESULTS: Inthe arterial phase, HCCs showed total or partial hyperattenuation in 79% of cases(82/104), isoattenuation in 12%,and hypoattenuation in 9%. In the equilibrium phase, HCCs showed hypoattenuation in 86%(89/104) and isoattenuationin 14%. The most common and characteristic enhancement patterns of HCCs were hyperattenuation in the arterialphase and hypoattenuataion in the equilibrium phase ; in the latter, capsules were demonstrated in 45% of cases. Invasions of the portal and/or hepatic vein were demonstrated in 34% of cases. CONCLUSION: Dynamic fastinfusion(5ml/sec) of contrast material(150ml) is useful in the detection and diagnosis of HCCs with spiral CT.

Detection of Liver Metastases: Usefulness of Dynamic Spiral CT during the Portal Phase with a Higher IV Injection Rate of Contrast Material

PURPOSE: To evaluate the usefulness of dynamic spiral computed tomography(CT) during the portal phase with ahigher IV injection rate of contrast material in detecting hepatic metastases. MATERIALS AND METHODS: We reviewed two-phase dynamic spiral CT in 44 patients with hepatic metastases of pathologically proven primary malignancy. One hundred and fifty ml. of non-ionic contrast material was administered with a power injector at a rate of 5ml/sec., and two-phase images at 55-80 sec.(portal phase) and 2-5 min.(equilibrium phase) were obtained after thestart of bolus injection. Two phase images were compared for detectability of hepatic metastases according tosize, number and enhancement pattern. RESULTS: In cases of metastases less than 1cm, 113 lesions(100%) that showed clearly defined hypodense lesions were detected in the portal phase of dynamic CT. However, the equilibriumphase images showed hypodense lesions in 58 cases(51%) and isodense lesions in 55cases(49%). In cases of metastases 1-2cm in size, the portal phase images detected 70 hypodense lesions(92%) and six hyperdense lesions(8%). In the equilibrium phase, however, the lesions were hypodense in 54 cases(71%), hyperdense infour(5%), and isodense in 18(24%). In cases of metastases larger than 2 cm, portal phase images showed 29 hypodense lesions(97%) and one hyperdense lesion(3%). In the equilibrium phase, however, the lesions were hypodense in 25 cases(83%), hyperdense in two(7%), and mixed in three(10%). As compared with the portal phase, most metastatic lesions were detected as poorly defined hypodense or isodense lesions in the equilibrium phase and decrease in size due to peripheral enhancement. CONCLUSION: Dynamic spiral CT during the portal phase with a higher IV injection rate(5 ml/sec) of contrast material is a useful method for detecting hepatic metastases, especially small lesions less than 1cm.

MRI Findings of Miliary Tuberculosis of the Brain

PURPOSE: To evaluate MRI(Magnetic Resonance Imaging) findings of miliary tuberculosis of the brain. MATERIALS AND METHODS: Six patients with miliary tuberculosis of the brain diagnosed by characteristic clinical or laboratory findings were studied with spin echo MRI before and after contrast enhancement. We retrospectively evaluated MRI findings acording to the appearance, distribution, location, and enhancement pattern of the granulomas as well as associated other abnormalities. RESULTS: In six patients, contrast-enhanced MRI of thebrain showed numerous punctate, contrast enhancing lesions scattered throughout the brain. Unenhanced MRI failed to demonstrate small granulomas except a few small foci of high signal intensity on T2-weighted images. The shapes of enhancing granulomas were homogeneous nodular enhancement in 86% of cases and small ring enhancement in 14%.98% of granulomas were smaller than 3-mm and 2% were larger. Although several lesions were located in the basalganglia, thalamus, and brain stem, the majority were located in the subpial and subarachnoid space. There was no significant difference in distribution of granulomas between the supratentorial and the infratentorial areas. Other associated abnormalities were focal meningitis in five cases and focal cerebritis in one. On chest radiograph, all patients had miliary tuberculosis in the lungs. CONCLUSION: Contrast-enhanced T1-weighted MRimaging showed numerous round, very small enhancing lesions scattered throughout the brain. The majority of lesions were located in the subpial and subarachnoid space. Contrast-enhanced T1-weighted images are helpful inthe detection and diagnosis of miliary disseminated tuberculous granulomas and meningitis.

Value of Axial 3-D Fourier Transformation GRASS MR Images in Diagnosis of Meniscal Tears of the Knee

PURPOSE: The purpose of this study is to compare the sensitivity and specificity of axial 3-D imaging with those of conventional 2-D imaging in the diagnosis of meniscal injuries. MATERIALS AND METHODS: Twenty-nine kneesof 27 patients with clinically suspected meniscal tears were imaged at a 1.5 T MR system. Conventional 2-D imagesand axial 3-D GRASS images were obtained in all cases. Arthroscopic or surgical confirmation was available in allcases and was used as the gold standard. RESULTS: Among the 29 knee-joints evaluated, 21 of 23 meniscal tears and 33 of 35 normal menisci were correctly identified with axial 3-D imaging, yielding a sensitivity of 91.3% and specificity of 94.3%. Conversely, the sensitivity was 82.6% and the specificity was 97.1% for the conventional 2-Dtechnique. A combination of both techniques yielded 95.7% sensitivity and 100% specificity in the diagnosis of meniscal tears. Of the 23 meniscal tears proven at arthroscopy or surgery, there were four discrepancies between the two techniques ; three of the four represented false-negative 2-D images and one was a false-negative axial3-D image. Of 35 normal menisci, two false-positives occurred with axial 3-D imaging and one with 2-D imaging. CONCLUSION: Despite the lack of a statistically significant difference between the efficacy of the two techniques, these results suggest that the sensitivity in the diagnosis of meniscal tears can be improved by adding thin-sliced axial 3-D GRASS imaging to conventional 2-D imaging in the limited cases with clinically suspected meniscal tears.

Percutaneous Balloon Dilatation of Benign Biliary Strictures and Stone Extraction of Residual Intrahepatic Stones

PURPOSE: The residual intrahepatic stones with biliary strictures are difficult to remove percutaneously via T-tube tract after surgery in patients with recurrent pyogenic cholangitis. We evaluated the effectiveness of percutaneous balloon dilatation of benign biliary strictures. MATERIALS AND METHODS: The balloon dilatations with 6-12mm angioplasty balloon catheter and stone extractions were performed via a T-tube tract after surgical treatment in 15 patients with recurrent pyogenic cholangitis. The balloons were inflated for 3-4minutes under 5 atm. until disappearance of waist of the stricture site, from one to seven session. After balloon dilatation, residual stones were extracted with saline irrigation or stone basket. RESULTS: Among total 42 strictures, the balloon dilatation was succesful in 27 strictures(64.3%), partially successful in 12 strictures(28.6%), and failed in three strictures(7.1%). Single or central biliary strictures were dilated easily rather than multiple ductal strictures. Of 26 sites with residual intrahepatic stones, stone extraction was complete in 17 sites(65.4%), incomplete in seven sites(26.9%) due to impacted or large stone and acute ductal angulation, and failed in two sites(7.7%). CONCLUSION: Percutaneous balloon dilatation of benign biliary strictures is an effective procedure for extraction of residual intrahepatic stones associated with recurrent pyogenic cholangitis.

The Role of Endorectal Ultrasonography in the Follow-up Evaluation of the Uterine Cervical Carcinomas in Intra-arterial Cisplatin Chemotherapy

PURPOSE: lntra-arterial cisplatin infusion chemotherapy delivers higher concentration of this therapeutic agent to the limited area of cervical carcinoma. We evaluated the role of endorectal ultrasonography (ERUS) in the analysis of the tumor response to this chemotherapy. MATERIALS AND METHODS: ERUS was done in 20 patients of cervical carcinomas limited to the pelvis by rotating the 5 UHz linear arraytransducer along the reference sagittal plane in the middle of uterine cervix and vagina. We examined and compared the change of tumor size and morphology on ER US, before, during and after intra-arterial cisplatin (50 mg/m2) chemotherapy through internal lilac artery near uterine arterial branching. Colposcopy and radical hysterectomy with pelvic lymphadenectomy were performed in all patients, and ERUS findingswere compared with those findings. RESULTS: ERUS correlated well with surgery in the estimation of preoperative tumor size and morphology. Tumor reduction rate on ERUS (100-the largest area of the preoperative tumor/the largest area of the initial tumor) was as follows: more than 75% decrease of the original size in 3 patients, 75% -50% in 6 patients, 50%-25% in 8 patients, and less than 25% in 3 patients. Hyperechoic reflecting areas were noted in 4 patients, which corresponded to gaseous necrosis on postoperative pathology. CONCLUSION: ERUS is helpful to evaluate the morphologic change of cervical carcinoma limited tothe pelvis in intra-arterial cisplatin chemotherapy.