• The korean journal of orthodontics
• /
• v.31 no.1 s.84
• /
• pp.85-95
• /
• 2001

The purpose of this study was to evaluate the material for fixed type retainer, allowing physiologic tooth movement. and proper remodeling or periodontal tissue during retention period. The Present study was Performed to observe the histologic changes of periodontal tissue after application of different types of fixed type retainer after orthodontic tooth movement in young adult dogs. For this study, 4 young adult dogs were used as a experimental animal and experimental group was divided into three groups : experimental group 1 contained right side maxillayy third incisors and canines, experimental group 2 contained contralateral teeth of same animals, and control group contained mandibular premolars. And each dogs were applied the 4 different types of fixed type retainer to experimental group 1. The experimental teeth were ligated on the Sentalloy closed coil $spring^{\circledR}$(Tomy Co., Japan) from maxillary third incisors and canines and applied orthodontic force at initial 200gm-forced during 1 week. All the experimental animals were sacrificed on the 3rd week after the orthodontic teeth movement and then the specimens were taken, fixed in formalin, embeded in parafin, sectioned $6-8{\mu}m$ in thickness and stained with Hematoxylin-Eosin staining, and Masson's trichrome staining method. Examined under the light microscopy The following results were observed. 1. There were observed that decreased infiltration of giant tells in pressure side and increased the new bone forming in tension side on the specimen of 6-stranded 0.0195' $Respond^{\circledR}$(G&H Co., U.S.A.) group. Periodontal ligament fibers were much compressed or elongated in 3-stranded 0.018', 0.020' $Dentaflex^{\circledR}$(Dentarum Co., Germany), and Superbond $C&B^{\circledR}$(Sun Medical Co., Japan) groups. 2. In experimental group 1, necrotic bone inside the alveolar bone of pressure side, forming of the sharpey's fiber in osteoid tissue, and remodeling of the periodontal ligament were observed in all animals. 3. In experimental group 2, it was observed that the amount of bone resorption was equal or decreased in pressure side, and increased new bone forming and significantly decreased infiltration of giant cell than the experimental group 1. By this results, it considered that 6-stranded $Respond^{\circledR}$(G&H Co., U.S.A.) wire was the most useful material allowing early periodontal tissue remodeling.

• The korean journal of orthodontics
• /
• v.27 no.4 s.63
• /
• pp.559-568
• /
• 1997

For orthodontic tooth movement, optimal orthodontic force should be maintained without periodontal breakdown and alveolar bone should be remodeled physiologically Therefore, To obtain proper occlusion through tooth movement within alveolar bone, we should know the biomechanics of teeth and supporting 4issues. The present study was performed to observe histologic changes of periodontal tissue immediately after application of orthodontic force and during the retention period in growing young adult dogs. In this study, experimental group contained between mandibular left canine and 1st molar and control group contained contralateral teeth of same animal. The .018'x.022' stainless steel closed coil spring(Dentaurum Co.) was ligated on the experimental teeth at initial 200gm-force from mandibular canine to 1st molar The animals(4 to 6 months aged young adult dogs) were sacrificed on 0, 14, 28 days after the finish of appliance activation, and then tissue samples were divided into hematoxylin-eosin(HE) staining section, ground section, alkaline phosphatase(ALP) staining section, and tartrate-resistant acid phosphatase(TRAP) staining section. Thereafter, the preparations were examined under light microscopy The following results were obtained: 1. Immediately after the finish of appliance activation, the periodontal space was increased in tension side, but decreased in pressure side compared to that of control. The hyalinized zone was also observed in the periodontium. 2. After the 14-day retention, peridontal space was decreased in tension side and slightly increased in pressure side compared to that of immediately after the finish of appliance activation. The hyalinized zone was repaired and a few osteoblasts showing slightly new bone formation were seen. Osteoblasts were scarcely observed along the alveolar bone. 3. Aftter the 28-day retention, the periodontal fibers are normally repaired. A lot of TRAP(+) osteoclasts md increased alveolar bone resorption were observed in pressure side, and AP(+) osteoblast and increased new bone formation were observed in tension side.

• Proceedings of the Ginseng society Conference
• /
• 2007.12a
• /
• pp.57-58
• /
• 2007

Purpose: Ginseng is a well-known medical plant used in traditional Oriental medicine. Korean red ginseng (KRG) has been known to have potent biological activities such as radical scavenging, vasodilating, anti-tumor and anti-diabetic activities. However, the mechanism of the beneficial effects of KRG on diabetes is yet to be elucidated. The present study was designed to investigate the anti-diabetic effect and mechanism of KRG extract in C57BL/KsJ db/db mice. Methods: The db/db mice were randomly divided into six groups: diabetic control group (DC), red ginseng extract low dose group (RGL, 100 mg/kg), red ginseng extract high dose group (RGH, 200 mg/kg), metformin group (MET, 300 mg/kg), glipizide group (GPZ, 15 mg/kg) and pioglitazone group (PIO, 30 mg/kg), and treated with drugs once per day for 10 weeks. During the experiment, body weight and blood glucose levels were measured once every week. At the end of treatment, we measured Hemoglobin A1c (HbA1c), blood glucose, insulin, triglyceride (TG), adiponectin, leptin, non-esterified fatty acid (NEFA). Morphological analyses of liver, pancreas and white adipose tissue were done by histological observation through hematoxylin-eosin staining. Pancreatic islet insulin and glucagon levels were detected by double-immunofluorescence staining. To elucidate an action of mechanism of KRG, DNA microarray analyses were performed, and western blot and RT-PCR were conducted for validation. Results: Compared to the DC group mice, body weight gain of PIO treated group mice showed 15.2% increase, but the other group mice did not showed significant differences. Compared to the DC group, fasting blood glucose levels were decreased by 19.8% in RGL, 18.3% in RGH, 67.7% in MET, 52.3% in GPZ, 56.9% in PIO-treated group. With decreased plasma glucose levels, the insulin resistance index of the RGL-treated group was reduced by 27.7% compared to the DC group. Insulin resistance values for positive drugs were all markedly decreased by 80.8%, 41.1% and 68.9%, compared to that of DC group. HbA1c levels in RGL, RGH, MET, GPZ and PIO-treated groups were also decreased by 11.0%, 6.4%, 18.9%, 16.1% and 27.9% compared to that of DC group, and these figure revealed a similar trend shown in plasma glucose levels. Plasma TG and NEFA levels were decreased by 18.8% and 16.8%, respectively, and plasma adiponectin and leptin levels were increased by 20.6% and 12.1%, respectively, in the RGL-treated group compared to those in DC group. Histological analysis of the liver of mice treated with KRG revealed a significantly decreased number of lipid droplets compared to the DC group. The control mice exhibited definitive loss and degeneration of islet, whereas mice treated with KRG preserved islet architecture. Compared to the DC group mice, KRG resulted in significant reduction of adipocytes. From the pancreatic islet double-immunofluorescence staining, we observed KRG has increased insulin production, but decreased glucagon production. KRG treatment resulted in stimulation of AMP-activated protein kinase (AMPK) phosphorylation in the db/db mice liver. To elucidate mechanism of action of KRG extract, microarray analysis was conducted in the liver tissue of mice treated with KRG extract, and results suggest that red ginseng affects on hepatic expression of genes responsible for glycolysis, gluconeogenesis and fatty acid oxidation. In summary, multiple administration of KRG showed the hypoglycemic activity and improved glucose tolerance. In addition, KRG increased glucose utilization and improved insulin sensitivity through inhibition of lipogenesis and activation of fatty acid $\beta$-oxidation in the liver tissue. In view of our present data, we may suggest that KRG could provide a solid basis for the development of new anti-diabetic drug.

• Clinical and Experimental Reproductive Medicine
• /
• v.26 no.1
• /
• pp.55-65
• /
• 1999

There have been many reports to date regarding the role of GnRH as a local regulatory factor of ovarian function as studies of human and rat ovaries revealed GnRH and its receptor. In recent studies it has been shown that GnRH directly causes apoptosis in the granulosa cells of the rat ovary, and such results leads to the suggestion that the use of GnRH agonist for more stable long term ovarian hyperstimulation in human IVF-ET programs causes granulosa cell apoptosis which may lead to follicular atresia. Therefore this study attempts to determine if granulosa-luteal cell apoptosis occurs in patients during IVF-ET programs in which GnRH agonist is employed for ovarian hyperstimulation. The quality of oocyte-cumulus complexes obtained during ovum pickup procedures were assessed morphologically and then the fertilization rate and developmental rate was determined. Apoptotic cells among the granulosa-luteal cells obtained during the same procedure were observed after staining with Hematoxylin-eosin. The fragmentation degree of DNA extracted from granulosa-luteal cells was determined and comparatively analyzed. There was no difference in the average age of the patients, the number of oocytes retrieved, and fertilization and developmental rates between the FSH/hMG group and GnRH-long group. There was also no difference in the apoptosis rate and pyknosis rate in the granulosa-luteal cells between the two groups. However, when the oocyte-cumulus complexes were morphoogically divided into the healthy group and atretic group without regard for the method of hyperstimulation, the results showed that the number of oocytes obtained averaged $11.09{\pm}8.75\;and\;10.33{\pm}4.53$ per cycle, respectively, showing no significant difference, but the fertilization rate (77.05%, 56.99%, respectively, p<0.01) and developmental rate (65.96%, 41.51%, respectively, p<0.01) was significantly increased in the healthy group when compared to the atretic group. The degree of apoptosis in the granulosa-luteal cells showed that in the healthy group it was 2.25% which was not significantly different from the atretic group (2.77%), but the pyknosis rate in the atretic group (27.81%) was significantly higher compared to the healthy group (11.35%, p<0.01). The quantity of DNA fragmentation in the FSH/hMG group was 32.22%, while in the GnRH-long group it was 34.27%, showing no significant difference. On the other hand the degree of DNA fragmentation was 39.05% and 11.83% in the healthy group and atretic group, respectively, showing significantly higher increase in the atretic group (p<0.01). The above results suggest that death of granulosa-luteal cells according to the state of the oocyte-cumulus complex is more related to pyknosis rather than apoptosis. Also, the GnRH agonist used in ovarian hyperstimulation does not seem to directly affect the apoptosis of retrieved oocytes and granulosa-luteal cells, and which is thought to be due to the suppression of the apoptogenic effect of GnRH agonist as a result of the high doses of FSH administered.

• Tuberculosis and Respiratory Diseases
• /
• v.48 no.1
• /
• pp.33-44
• /
• 2000

Background: To evaluate airway responses and inflammation to antigen in Sprague-Dawley rat asthma model, we examined airway responses, serial histologic changes of the lung, and the relationship between airway responses and airway inflammation after antigen airway challenge. Methods: Sprague-Dawley rats were sensitized with subcutaneous injection of 10 ${\mu}g$ ovalbumin(OA). Antigen airway challenges were done 14~16 days after sensitization and the sensitized rats were sacrificed 1h($A_E$), 6~8h($A_L$) and 1day($A_D$) after airway challenge, to examine the histologic changes of the lung. Airway responses were measured by body plethysmograph and recorded by enhanced pause(Penh) as an index of airway obstruction 6~8h after antigen challenges. Nonsensitized controls(10 rats) were also challenged with antigen and sacrificed 1 day later. Histopathologic examination of two trachea, large bronchi, small bronchi, and vessels was performed to evaluate the severity of inflammation and eosinophilic infiltration with H&E stain. Results: In 17 of 20 rats(85%) in both groups, we observed airway responses. Among them, an early response(ER) in 15 rats(75%), an dual response in 5(25%), and an late response(LR) only in 2 rats(10%) displayed. There were no significant differences in the severity of inflammation among the trachea, large bronchi, small bronchi and vessels in all groups after antigen challenge(p>0.05) and between early and late responders. The significant eosinophil infiltration was observed in 5 rats(50%) of AL(p<0.05) compared with in AE and controls. Also, eosinophil infiltration was observed in higher trend in LR(57.1%) compared to ER(40%)(p>0.05). Conclusion: Sprague-Dawley rats sensitized with subcutaneous injection of OA showed a significant airway responses to antigen challenge. But antigen challenges caused a little eosinophil infiltration and no significant airway inflammation. Asthma model of Sprague-Dawley rats could be useful for antigen-induced airway responses, but this model has a limitation for the study of human asthma because of no significant pathologic change.

• Journal of Sasang Constitutional Medicine
• /
• v.27 no.2
• /
• pp.270-287
• /
• 2015

Objectives To evaluate the neuroprotective effects of modified Yuldahanso-tang (MYH) in a Parkinson's disease mouse model. Methods 1) Four groups (each of 8 rats per group) were used in this study. 2) The neuroprotective effect of MYH was examined in a Parkinson's disease mouse model. C57BL/6 mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 30 mg/kg/day), intraperitoneal (i.p.) for 5 days. 3) The brains of 2 mice per group were removed and frozen at $-20^{\circ}C$, and the striatum-substantia nigra part was seperated. The protein volume was measured by Bradford method following Bio-Rad protein analyzing kit. Using mouse/Rat Dopamine ELISA Assay Kit. 4) The brains of 2 mice per group were separated and removed. TH-immunohistochemical was examined in the MPTP-induced Parkinson's disease mice to evaluate the neuroprotective effects of MYH on ST and SNpc. 5) Two mice out of each group were anesthetized and skulls were opened from occipital to frontal direction to take out the brains. The brains added TTC solution for 20 minutes for staining. 6) The water tank used for morris water maze test was filled with $28^{\circ}C$ water, and a round platform of 10cm in diameter was installed for mice to step on. The study was carried out once a day within 30 seconds, keep exercising to step on the platform in the pool. 7) The brains of two mice out of each group were fixed in 10% formaldehyde solution and paraphillin substance was infiltrated. They were fragmented by microtome, and observed under an optical microscope after Hematoxylin & Eosin staining. 8) A round acrylic cylinder with its upper side open was filled with clean water and depressive mouse models were forced to swim for 15 minutes. After 24 hours the animals were put in the same equipment for 5 minutes and were forced to swim. 9) The convenient, simple, and accurate high-performance liquid chromatography (HPLC) method was established for simultaneous determination of Neurotransmitters in MPTP-MYH group. Results 1) MYH possess Dopamine cell protective effect on MPTP-induced injury in striatum and substantia nigra pars compacta. 2) MYH inhibits the loss of tyrosine hydroxylase-immunoreacitive (TH-IR) cells in the striatum and substantia nigra pars compacta on MPTP-induced injury in C57BL/6 mice. 3) MYH possesses improvement effect on MPTP-induced memory deterioration in C57BL/6 mice through the reduction of prolongated Sort of lost time by MPTP injection using the Morris water maze test. 4) MYH possesses hippocampal neuron protective effect on MPTP-induced injury in C57BL/6 mice. 5) MYH possesses improvement effect on MPTP-induced motor behaviour deficits and depression in C57BL/6 mice through the reduction of prolongated losing motion by MPTP injection using the Forced swimming test. 6) MYH increases serotonin product amount on MPTP-induced injury in C57BL/6 mice. Conclusions This experiment suggests that the neuroprotective effect of MYH is mediated by the increase in Dopamin, TH-ir cell, Hippocampus and Serotonin. Furthermore, MYH essential oil may serve as a potential preventive or therapeutic agent regarding Parkinson's disease.

• Applied Microscopy
• /
• v.15 no.2
• /
• pp.31-68
• /
• 1985

Authors are trying to unveil the ultrastructural organization of olfactory bulb, which has been summerized under light microscopic level or communicated only in some detail in different view point until now. For the critical point of view, since the phylogenetical approach will give the ultimate value in the correlative study between structural and functional bases (Brodal, 1969), the present study was carried out light and electron microscopic analyses of the structures of the neurons and synaptic organizations in olfactory bulbs from different animals in phylogenetical scale. We selected each one species from five animal classes: the house rabbit(Oryctolagus cuniculus var. domesticus [Gmelin]) from Mammalia, the domestic fowl (Gallus gallus domesticus Brisson) from Aves, the viper (Agkistrodon hylys [G.P. Pallas]) from Reptilia, a frog (Bombiana orientalis Boulenger) from Amphibia and the crussian carp (Carassius carassius [Linne]) from Pisces. For light microscopic study, samples were fixed in 10% formalin and paraffin sections were stained with hematoxylin-eosin. For the electron microscopic study, the tissues were fixed by perfusion through the heart or immersion with 1% paraform-aldehyde-glutaraldehyde mixture (phosphate buffer, pH 7.4), and final tissue block trimmed under dissecting microscope were osmicated (1% OsO4), they were embedded in Araldite or Epon 812, and ultrathin sections were made by LKB-V ultratome following the inspection of semi-thin sections stained with toluidine blue-borax solution. Ultra-thin sections contrasted with uranyl acetate and lead citrate were observed with JEM 100CX electron microscope. We have summerized our morphological analyses as follows: 1. The olfactory bulb of rabbit, viper and frog shows the eight layers of fila olfactoria, glomerular, external granular, external plexiform, mitral cell, internal plexiform, internal granular, medullary but domestic fowl shows the five layers of glomerular, fibrillar, mitral, granular and medullary and the three layers of fibrilla, glomerular and medullary in crussian carp. The sharpness of demarcation between the layers shows deferential tendency according to phylogenetical order. 2. Mitral cells of vertebrate have large triangular or oval shape with spherical nuclei which contain not so much chromatin. The cytoplasm contains numerous cell organelles, of which Nissl's bodies or granular endoplasmic reticula arranged as parallel strands. Development of granular endoplasmic reticula were declined as the phylogentical grade is going lower. 3. Tufted cells of all animal are mostly spindle or polygonal contour and contain oval nuclei which located in periphery of cytoplasm. The nuclei of rabbit, fowl, viper and frog has relatively space chromatin, but a nucleus of crussian carp contain irregularly aggregated chromatin in karyoplasm. Their cytoplasmic volume and cell organelle contents are in between those of mitral cell and granular cell. They contain moderate amount of mitochondria, granular endoplasmic reticula, a few Golgi complex, polysomes, lysosome, etc. 4. Granule of cells of all the vertebrate amimals studied exhibit similar features; cells and their dense nuclei show spherical or oval contour, and they have the thin rim of cytoplasm which contain only a few cell organelles. 5. In rabbit, the soma of mitral cells were in contact with boutons with two types of synaptic vesicles, that is, round and flat vesicles, especially flat vesicles in boutons were showing reciprocal synapses. However, in domestic fowls, vipers, frogs and crussian carps, there were found boutons showing only spherical synaptic vesicles. 6. The boutons containing round synaptic vesicles were made contact with the some of tufted cell of olfactory bulb in the rabbits, fowls, vipers and frogs, but no synaptic boutons were observed in soma of tufted cells in crussian carps. In the frogs, there were observed dendrites were contact with the soma of tufted cells. 7. In the neuropils of plexiform, granular and glomerular layers olfactory bulbs in the vertebrate, the synapses were axo-large dendrites, axo-median and small dendrites, dendrodendritic, and axo-axonal contacts. However, in the neuropil of crussian carps, synapses were observed only in glomerular layer.

• Applied Microscopy
• /
• v.39 no.3
• /
• pp.205-218
• /
• 2009

This experiment was performed to evaluate the morphological responses of the gastric epithelial cells of the mouse, inoculated with Ehrlich carcinoma cells in the inguinal area, following administration of BCG. Healthy adult ICR mice weighing 25 gm each were divided into normal and experimental groups (tumor control group and BCG-treated group). In the experimental groups, each mouse was inoculated with $1{\times}10^7$ Ehrlich carcinoma cells subcutaneously in the inguinal area. From next day after inoculations, 0.2 mL of saline or BCG (0.5 mL/25 g B.W.: $0.03{\times}10^8{\sim}0.32{\times}10^8$ CFU) were injected subcutaneously to the animals every other day, respectively. The day following the 7th injection of saline or BCG, each mouse was injected with a single dose of 0.7 ${\mu}Ci/g$ of methyl-$^3H$-thymidine (25 Ci/mmol, Amersham Lab., England) through tail vein. Seventy minutes after the thymidine injection, animals were sacrificed, and gastric tissues were taken and fixed in 10% neutral formalin. Deparaffinized sections were coated with autoradiographic emulsion EM-1 (Amersham Lab., England) in a dark room. The number of labeled epithelial cells in the gastric mucosae (mean number of labeled epithelial cells per 3.5 mm length of mucosa) were observed and calculated. And for electron microscopic observation, gastric tissues were prefixed with 2.5% glutaraldehyde-1.5% paraformaldehyde solution, followed by post-fixation with 1% osmium tetroxide solution. On the light microscopic study, gastric mucosae had no morphological changes following the injection of BCG. On the electron microscopic study, in the BCG-treated mice, myelin figures and multivesicular bodies within the gastric epithelial cells were observed more frequently than in those of the normal control ones. On the autoradiographic study, number of the labeled cells of normal control, tumor control and BCG-treated mice were 380.2 (${\pm}31.35$), 426.1 (${\pm}28.43$) and 301.8 (${\pm}34.63$), respectively. In the BCG-treated mice, poorly-labeled cells containing only a few silver grains of 3H-thymidine were observed more frequently as compared in those of the normal control and tumor control ones. From the above results, BCG may suppress the DNA synthesis of the gastric epithelial cells, but does not results severe fine structural defect on the gastric epithelial cells. These results suggest that BCG is expected as one of the effective supplemental anticancer drugs.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.5 no.1
• /
• pp.19-25
• /
• 2002

Purpose: The triple therapy with proton pump inhibitor (PPI) has been recognized as the treatment of choice in Helicobacter pylori (H. pylori) infection in adults. However, the effect of triple therapy with omeprazole, amoxicillin and clarithromycin (OAC) on eradication of H. pylori infection in children has not been established yet. This study was performed to evaluate the efficacy of OAC triple therapy and to compare the effect of one-week with two-week therapy on H. pylori eradication. Methods: From July 1998 to July 2000, 34 children with upper gastrointestinal symptoms, who underwent upper gastrointestinal endoscopy with biopsy at entry and 4 or more weeks after therapy, were enrolled in this study. H. pylori infection was assessed by CLO test and histologic examination (Hematoxylin-Eosin stain or Alcian yellow stain) with biopsy specimens. The regimen consisted of omeprazole (0.7 mg/kg/day), amoxicillin (50 mg/kg/day), and clarithromycin (25 mg/kg/day) for 1 week (n=21) or 2 weeks (n=13). Eradication of H. pylori was determined after the termination of treatment by the CLO test and histologic examination. Results: One-week treatment group consisted of 21 children (11 male, 10 female) with a mean age of $9.5{\pm}3.0$ years. Two-week group consisted of 13 children (4 male, 9 female) with a mean age of $9.9{\pm}4.0$ years. The endoscopic diagnoses included nodular gastritis in 19 cases, superficial gastritis in 7 cases, gastric ulcer in 4 cases, purpuric duodenitis in 2 cases, and normal in 2 cases. H. pylori was eradicated in 28 of total 34 children (82.4%). In 1-week group, H. pylori was eradicated in 17 of 21 children (81%). In 2-week group, H. pylori was eradicated in 11 of 13 children (84.6%). In remaining 6 cases in whom H. pylori had not been eradicated with OAC regimen, H. pylori infection persisted despite of the treatment with additional drugs such as colloidal bismuth subcitrate ($Denol^{(R)}$) and metronidazole. Conclusion: In this study, eradication rate of H. pylori with OAC regimen was 82.4%, and the triple therapy would be highly effective as primary treatment. However, there was no significant difference in the eradication rate between the 1-week and 2-week treatment group (P=0.785).

• Korean Journal of Dental Materials
• /
• v.44 no.2
• /
• pp.187-195
• /
• 2017

TheraCal LC, a new light-cured, resin-modified calcium silicate-filled base/liner material, has been introduced as a pulpotomy agent. The aim of this study was to evaluate the capacity of hard tissue formation and pulpal response after pulpotomy with TheraCal LC. Twenty-two 9-week-old male rats were anesthetized, cavities were prepared in maxillary first molars and pulps were capped with formocresol (FC), mineral trioxide aggregate (MTA), and TheraCal LC. Specimens obtained from rats were scanned using a high-resolution micro CT system. The specimens were prepared and evaluated histologically, and immunofluorescence assay was performed to assess the dentin matrix protein-1 (DMP-1) expression. On micro CT analysis, the MTA and TheraCal LC groups showed thicker hard tissue formation than the FC group. On hematoxylin and eosin (H&E) staining, MTA and TheraCal LC groups showed dentine bridge formation with vital pulp beneath the materials. On immunofluorescence analysis, DMP-1 was highly expressed in the TheraCal LC group compared to the FC group. TheraCal LC showed similar capacity to form hard tissue as MTA when it was used as a pulpotomy agent. Because of its good manipulation and faster setting time compared to MTA, TheraCal LC could be considered as a good alternative to MTA.