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Biomedical subjects

Y J Kim

Publications and source records attributed to Y J Kim.

At least 73 records · Page 4Linked to original sources

Resonant inelastic x-ray scattering study of charge excitations in La(2)CuO(4).

We report a resonant inelastic x-ray scattering study of the dispersion relations of charge-transfer excitations in insulating La(2)CuO(4).. These data reveal two peaks, both of which show two-dimensional characteristics. The lowest energy excitation has a gap energy of approximately 2.2 eV at the zone enter, and a dispersion of approximately 1 eV. The spectral weight of this mode becomes dramatically smaller around (pi, pi). The second peak shows a smaller dispersion ( approximately 0.5 eV) with a zone-center energy of approximately 3.9 eV. We argue that these are both highly dispersive exciton modes damped by the presence of the electron-hole continuum.

Journal Article↗

Root canal length measurement in teeth with electrolyte compensation.

Electronic root canal length measurement devices have made it easier and faster to measure the root canal length of a tooth compared with the conventional radiographic method. Of these electronic apex locators, the frequency-dependent type features greater accuracy and convenience in operation. However, its accuracy is still influenced by the presence of blood and/or the various electrolytes used in root canal therapy. This study describes the development of a new frequency-dependent electronic apex locator featuring electrolyte compensation, utilising an impedance ratio and voltage difference technique to minimise the influence of electrolytes on the accuracy of root canal length measurement. The errors for distances from file tips to apical constrictions were determined in vivo with the device operating with electrolyte compensation. The measured lengths were compared with the true lengths of the extracted teeth determined using a microscope. The mean error was +0.14+/-0.27mm, and 95.2% of the measurements were within the clinical tolerance of +/-0.5mm. It was also found that the degree of accuracy was not dependent on the size of the apical foramen (p = 0.74).

Dental Pulp Cavity↗

The enrichment of a ruminal bacterium (Megasphaera elsdenii YJ-4) that produces the trans-10, cis-12 isomer of conjugated linoleic acid.

AIMS: To isolate predominant ruminal bacteria that produce trans-10, cis-12 conjugated linoleic acid (CLA) from linoleic acid (LA). METHODS AND RESULTS: Mixed bacteria from ruminal contents of a cow fed grain were enriched with DL-lactate and trypticase. They produced more trans-10, cis-12 CLA than those that were not enriched (7 vs 2 microg mg protein(-1), P < 0.05). Enrichments had an abundance of large cocci that produced trans-10, cis-12 CLA from LA. Strain YJ-4 produced the most trans-10, cis-12 CLA (approx. 7 microg mg protein(-1)) and 16S rDNA sequencing indicated that YJ-4 was a strain of Megasphaera elsdenii. Megasphaera elsdenii T81 produced approx. 4 microg trans-10, cis-12 CLA mg protein(-1) while strains B159, AW106 and JL1 produced < 0.5 microg mg protein(-1). The trans-10, cis-12 CLA production of YJ-4 was first order with respect to cell concentration (0-800 microg protein ml(-1)), but kinetics were not first order with respect to substrate concentration. CONCLUSIONS: Some M. elsdenii strains produce significant amounts of trans-10, cis-12 CLA. SIGNIFICANCE AND IMPACT OF THE STUDY: Trans-10, cis-12 CLA appears to cause milk fat depression in cattle fed diets supplemented with grain and polyunsaturated fatty acids, but predominant ruminal bacteria that produced trans-10, cis-12 CLA from LA had not previously been isolated.

Animals↗

Effects of hydrogen peroxide on the light reflectance and morphology of bovine enamel.

The purpose of this study was to examine the effects of a bleaching agent (30% hydrogen peroxide) on the surface of bovine enamel using a scanning electron microscope and a UV-VIS-NIR spectrophotometer. Five non-carious bovine incisors were bleached for 0, 1, 2 and 3 days using 30% hydrogen peroxide. The light reflectance spectrum was measured using a spectrophotometer with diffuse reflectance mode. Colour values and colour differences in the teeth were evaluated from the reflectance measurements with the CIE L*a*b* colour coordinate system. Surface alterations in the bleached and unbleached teeth were studied using a scanning electron microscope. The change of reflectance in the teeth was related to the change of colour. Most reflectance change occurred within a 1-day bleaching, and this result was confirmed by a CIE L*a*b* colour coordinate system. The colour differences in the bleached teeth were significant enough to be perceived by the observer's eye. The comparison of bleached to unbleached bovine enamel revealed that the bleached surface showed non-uniform slight morphological alterations, and it developed varying degrees of surface porosity. This study indicates that the bleached bovine teeth showed apparent colour differences as well as slight morphological alterations after bleaching.

Animals↗

The value of maximum jaw motion measurements for distinguishing between common temporomandibular disorder subgroups.

OBJECTIVE: The purpose of this study was to determine if mandibular motion measurements could be used to distinguish between common temporomandibular disorder (TMD) subgroups that were established on the basis of only clinical signs and symptoms. STUDY DESIGN: Patients were 41 consecutive TMD clinic patients (31 women and 10 men). These patients were divided into 6 typical TMD subgroups. The subgroups were patients with (1) arthromyalgia, (2) arthromyalgia with disk condyle incoordination, (3) disk condyle incoordination only, (4) osteoarthritis, (5) suspected disk displacement without reduction, or (6) other diagnoses. RESULTS: There were no subjects in the other-diagnosis subgroup and only 1 subject with suspected disk displacement without reduction who was dropped without further consideration. The data for mean age showed that the osteoarthritis subgroup (n = 12) was statistically older (17 years) than the disk-condyle-incoordination-only subgroup (n = 11). The mean age of the other 2 groups, arthromyalgia (n = 11) and arthromyalgia with disk condyle incoordination (n = 6), was between the osteoarthritis and the disk-condyle-incoordination-only subgroups. For the 4 TMD subgroups whose data were analyzed, the mean differences between similar jaw opening measurements ranged from 6 to 8 mm with a standard deviation of approximately 8 to 10 mm. The mean left lateral motions were 0.5 to 1.3 mm larger than observed on the right. The widest mean jaw opening (56 mm) occurred in the disk-condyle-incoordination-only group. These differences were not found to be statistically significant. CONCLUSION: Analysis of opening, lateral and protrusive jaw motion data showed these measurements could not reliably differentiate between patients with osteoarthritis, arthromyalgia, arthromyalgia with disk condyle incoordination and disk condyle incoordination only.

Adult↗

Biofiltration of ammonia gas with sponge cubes coated with mixtures of activated carbon and zeolite.

Removal of ammonia gas was investigated using a biofilter system packed with small cubes of polyurethane sponge that were coated with a powder mixture of activated carbon and natural zeolite. Experimental tests and measurements include removal efficiency, pH, metabolic products of ammonia and kinetic analysis. A removal efficiency over 90% can be obtained with ammonia concentrations below 150 ppm and at contact times above 23 sec.The ammonia adsorbing power of the present biocarrier can protect the biofilter system from a high ammonia shock loading in the feed. The maximum removal rate, Vm, obtained from the kinetic analysis is 8.47 g N (kg carrier)(-1) day(-1) and the saturation constant Ks is 50.36 ppm. Nitrite is produced dominantly during the entire experiments. The cell number of nitrifying bacteria is 1.58 x 10( cell (g carrier)(-1). The present synthetic bio-carrier is considered to be one of the best among bio-carriers that have been used for the biofiltration of ammonia.

Ammonia↗

Acidogenic fermentation: utilization of wasted sludge as a carbon source in the denitrification process.

Laboratory scale batch experiments were conducted at 20 degrees C to investigate the acidogenic fermentation for the conversion of wasted sludge into short chain fatty acids (SCFA) to be utilized as a carbon source in the denitrification process. Hydraulic retention time (HRT), volatile solid (VS) loading rate and pH were studied as these are the important parameters governing the production of volatile fatty acids (VFA). Four different phases were investigated by varying these parameters. HRT was varied from 2.7 to 8.2 days whereas VS loading rate was varied from 1.2 to 3.6 g d(-1). VFA production decreased with the increase in HRT above 2.7 days. 538.37+/-19.39 mg VFA(produced) x d(-1) (0.176+/-0.010 mg VFA(produced) mg(-1) VS(feed) was found as the maximum value of VFA at 2.7 days. The present results based on wasted sludge showed that almost 0.0483+/-0.0016 mg VFA (as COD mg(-1) initial COD) and about 5% of soluble COD production were achieved, which are slightly less than the results reported for primary sludges. The rates of VFA production increased with the increase in VS, however, opposite results were obtained when pH was increased in the reactor. SCFA/FA ratios during fermentation were found in the range of 67-73%. The specific denitrification rates (SDNR) of methanol (2.20+/-0.44 mg NO3-N g(-1) MLVSS x h(-1)) and the fermenter supernatant (2.00+/-0.45 mg NO3-N g(-1) MLVSS x h(-1)) were found to be comparable. Fermenter supernatant, therefore, has the potential to be utilized as a carbon source. However, the results need to be investigated further on a larger scale to ascertain their validity.

Biodegradation, Environmental↗

Synthesis of 188 Re-labelled long chain alkyl diaminedithiol for therapy of liver cancer.

Radioisotope-labelled lipiodol has been used in the therapy of liver cancer. Recently a lipiodol solution of 188Re-labelled diaminedithiol (DD) has been reported to show a high uptake in the liver cancer. We synthesized long-chain alkyl DD derivatives to improve their uptake and retention in tissue. As the length of the alkyl chain increased, tissue uptake and retention also increased due to hydrophobic interaction with lipiodol. Among the synthesized compounds, the lipiodol solution of 188Re-HDD, the DD derivative with the longest side chain (C16), is a promising agent for therapy of liver cancer.

Animals↗

Effect of load alterations on the effective regurgitant orifice area in chronic aortic regurgitation.

OBJECTIVE: To evaluate the load dependence of effective regurgitant orifice area (ROA) in an animal model of chronic aortic regurgitation. METHODS: Eight sheep were studied 10-20 weeks after the surgical creation of aortic regurgitation. After baseline studies, 500 ml of blood, angiotensin II, and nitroprusside were infused sequentially. Electromagnetic flow meters were used as reference standards to determine aortic regurgitation volume. The time-velocity integral was acquired using the continuous wave Doppler method. RESULTS: Baseline aortic regurgitant volume varied from 8 ml (regurgitant fraction 28%) to 29 ml (59%), with a mean (SD) value of 17 (8) ml; mean ROA was 0.15 (0.05) cm2. During angiotensin II infusion, aortic regurgitation volume (20 (8) ml) and mean diastolic aortoventricular pressure gradient (62 (18) mm Hg) increased by 26 (16)% and 48 (64)%, respectively (p < 0.01 for both). ROA did not change (0.16 (0.06) cm(2), p = 0.15). During nitroprusside infusion, aortic regurgitant volume (13 (7) ml, p = 0.05) and diastolic pressure gradient (25 (13) mm Hg, p < 0.05) decreased. ROA did not change (0.15 (0.05) cm2). When analysing 32 stages together, aortic regurgitant volume (r = 0.78, p < 0.01) and regurgitant fraction (r = 0.55, p < 0.01) correlated well with ROA. However, diastolic pressure gradient (r = 0.28) was not significantly correlated with ROA. CONCLUSIONS: In an animal model of chronic aortic regurgitation, ROA did not change with load alterations.

Angiotensin II↗

Clinicopathologic features of mucinous gastric carcinoma.

BACKGROUND/AIMS: Mucinous gastric carcinoma (MGC) is a histopathologic subtype of gastric carcinoma with a poor prognosis. The purpose of this study was to compare the disease course of MGC with non-mucinous gastric carcinoma (NMGC) and study the clinicopathologic features that influence the prognosis of MGC patients. METHODS: We reviewed the records of 2,383 patients with a confirmed histologic diagnosis of gastric carcinoma. There were 157 patients with MGC compared to 2,226 with NMGC. RESULTS: A depth of invasion greater than T3 was more frequently found in MGC than in NMGC. The mean number of lymph nodes with metastases was 2.78 in MGC and 2.28 in NMGC (p < 0.001). There were more MGC patients with TNM stages II through IV (UICC classification). The overall survival rate was lower for the MGC group (46.5%) than for the NMGC group (64.0%; p < 0.05). Depth of invasion, lymph node metastases, and stage at diagnosis were significant factors affecting the outcome. CONCLUSION: The factors influencing the poorer prognosis (lower 5-year survival rate) of MGC are the advanced stage at the time of diagnosis, lymph node metastases, and a higher TNM status. Mucinous histologic type itself was not an independent predictive factor in survival.

Adenocarcinoma, Mucinous↗

Staurosporine mobilizes Ca(2+) from secretory granules by inhibiting protein kinase C in rat submandibular acinar cells.

Staurosporine was previously shown to mobilize Ca(2+) from the thapsigargin-insensitive Ca(2+) store in rat submandibular acinar cells. However, the nature of the store is not yet known. Therefore, in the present study, the staurosporine-releasable intracellular Ca(2+) store was characterized. Staurosporine increased the cytosolic Ca(2+) concentration ([Ca(2+)](c)) after the inositol 1,4,5-trisphosphate (IP(3))-sensitive Ca(2+) store was depleted. Ionomycin caused only small increases in [Ca(2+)](c) after the depletion of the IP(3)-sensitive Ca(2+) store, whereas ionomycin+monensin caused large increases. However, ionomycin+monensin did not increase [Ca(2+)](c) when added after [Ca(2+)](c) was increased by staurosporine, indicating that the acidic Ca(2+) store was the main source of Ca(2+). The acidic Ca(2+) store appeared to be associated with secretory granules, since ionomycin+monensin- and staurosporine-induced [Ca(2+)](c) increases were significantly reduced when the acinar cells were degranulated. The effect of staurosporine on [Ca(2+)](c) was mimicked by other protein kinase C inhibitors. Therefore, we conclude that staurosporine mobilizes Ca(2+) from secretory granules, probably through the inhibition of protein kinase C in rat submandibular acinar cells.

Animals↗

Lack of bioequivalence of two oxytetracycline formulations in the rabbit.

Oxytetracycline (OTC) has been used for over 40 years in veterinary medical field. Various forms of oxytetracycline preparations have been marketed, but little information is available on the bioequivalence of OTC preparations. This study was conducted to evaluate the bioequivalence of two OTC powder preparations available in Korea. Fourteen rabbits were randomly allocated into two groups. During the first period, a dose (200 mg/kg) of reference product was orally administered to the rabbits in Group A and test product to those in Group B. After 7-day washout period the reference and test products were given in group B and A, respectively. Blood samples were drawn at 17 points during 48 hours after administration and plasma OTC concentrations were measured by using HPLC. The solution concentrations of OTC dissolved from two products were not significantly different in the dissolution test. The mean area under the curve (AUC0- infinity ) and peak plasma concentration (C(max)) values for test and reference OTCs were 7.22 +/- 3.90 and 11.04 +/- 7.37 microg h/ml, 1.11 +/- 0.65 and 1.85 +/- 1.15 microg/ml, respectively. The relative bioavailability and C(max) of test product to those of reference product was 65.4% and 60.0%, respectively. The ranges of AUC and C(max) of test drug compared to those of reference drug under 90% confidence limits were 27 104% and 28 91.5%, respectively. The results of statistical analysis indicate that the two pivotal pharmacokinetic parameters, AUC and C(max) of test product are not within the 20% of those of the reference, suggesting that the test OTC is not bioequivalent to the reference OTC.

Analysis of Variance↗

Targeted hsp70.1 disruption increases infarction volume after focal cerebral ischemia in mice.

BACKGROUND AND PURPOSE: Heat-shock proteins (HSPs) are highly conserved proteins that are induced by a variety of stresses. HSP70 is a 70-kDa HSP family known to have cytoprotective effects against various insults. The role of HSP70 in cerebral ischemia remains to be elucidated in vivo. METHODS: To investigate the effect of reduced HSP70 levels on cerebral ischemia, focal cerebral ischemia by intraluminal occlusion of the middle cerebral artery was induced in hsp70.1 knockout mice. The expressions of hsp70.1 and hsp70.3 mRNAs and HSP70 protein were determined, and infarction volumes were measured and compared. RESULTS: Northern blots confirmed the absence of hsp70.1 mRNA expression in the knockout mice. The mean infarction volume was significantly larger in hsp70.1 knockout mice (92.5+/-8.3 mm(3)) than in the wild-type mice (59.3+/-8.9 mm,(3) P<0.001). Western blots showed increased HSP70 expression in the ischemic hemisphere in both knockout and wild-type mice, but HSP70 expression levels in knockout mice were significantly lower than those in their wild-type littermates. Immunohistochemistry did not show any significant differences between the knockout and wild-type animals and showed increased HSP70 immunoreactivity in the ischemic hemisphere, with predominance in the cerebral cortex, especially in the penumbra. CONCLUSIONS: Our results suggest that hsp70.1 plays an important role in the early protection of the brain, at least after acute focal cerebral ischemia in mice.

Animals↗

Xenobiotic response in humanized double transgenic mice expressing tetracycline-controlled transactivator and human CYP1B1.

The cytochrome P450 enzymes (P450s or CYPs) are a superfamily of hemeproteins that catalyze the monooxygenation of a wide range of endobiotic and xenobiotic substrates. A typical strategy in toxicological research and testing involves applying a toxicant at high doses for a short period to homogeneous animals under controlled conditions. However, the conditions of this approach have very little in common with actual human exposure. Transgenic (Tg) mice carrying human genes encoding a drug-metabolizing enzyme (CYP) offer a solution to many of the difficulties in the evaluation of chemical toxicity. It has been demonstrated that the expression of human CYP transgenes under the control of mammalian-inducible promoters exhibits relatively poor fold increases after induction. In this study, we used the tetracycline-regulated (tet) promoter system to increase the expression of the human CYP1B1 (hCYP1B1) gene in the tissues of transgenic mice. By mating two lineages of transgenic mice, double transgenic (dTg) mice expressing both tTA and hCYP1B1 genes under the control of the tet promoter were successfully produced, into which the two transgenes were introduced in an embryo. The expression pattern of tTA-driven hCYP1B1 transgene featured a fold induction of more than 3 to 12 in the brain, heart, and lung and 2- to 4-fold induction in the liver, kidney, and intestine upon doxycycline removal. Immunohistochemical staining with hCYP1B1 antibody was also increased by the removal of doxycycline. In addition, the activities of CYP liver microsomes in the dTg mice without doxycycline showed an increase compared to that in the dTg mice treated with doxycycline. The level of activities correspond to the levels of human CYP1B1 protein expression in the Tg mice (-dox) that was increased by 2-fold induction as compared to that of the dTg mice with doxycycline. Thus, overproduction in Tg can be purified and the activity of purified human CYP1B1 can be characterized by alterations to the coding sequence in order to solve the physiological function of this enzyme in a humanized in vivo system. It is also possible to examine the activity of purified human CYP1B1 using several environmental toxicants such as procarcinogens.

Animals↗

Caspase 3-cleaved N-terminal fragments of wild-type and mutant huntingtin are present in normal and Huntington's disease brains, associate with membranes, and undergo calpain-dependent proteolysis.

The Huntington's disease (HD) mutation is a polyglutamine expansion in the N-terminal region of huntingtin (N-htt). How neurons die in HD is unclear. Mutant N-htt aggregates in neurons in the HD brain; expression of mutant N-htt in vitro causes cell death. Other in vitro studies show that proteolysis by caspase 3 could be important in regulating mutant N-htt function, but there has been no direct evidence for caspase 3-cleaved N-htt fragments in brain. Here, we show that N-htt fragments consistent with the size produced by caspase 3 cleavage in vitro are resident in the cortex, striatum, and cerebellum of normal and adult onset HD brain and are similar in size to the fragments seen after exogenous expression of human huntingtin in mouse clonal striatal neurons. HD brain extracts treated with active caspase 3 had increased levels of N-htt fragments. Compared with the full-length huntingtin, the caspase 3-cleaved N-htt fragments, especially the mutant fragment, preferentially segregated with the membrane fraction. Partial proteolysis of the human caspase 3-cleaved N-htt fragment by calpain occurred in vitro and resulted in smaller N-terminal products; products of similar size appeared when mouse brain protein extracts were treated with calpain. Results support the idea that sequential proteolysis by caspase 3 and calpain may regulate huntingtin function at membranes and produce N-terminal mutant fragments that aggregate and cause cellular dysfunction in HD.

Adult↗

Cerebral activation and distribution of inducible hsp110 and hsp70 mRNAs following focal ischemia in rat.

A potential function for inducible heat shock protein 70 (hsp70i) expression in the pathophysiology of ischemic brain has been well documented. The recently cloned hsp70 superfamily member, hsp110, was shown to be highly expressed in the brain and suggested to have a similar functional property as members of the hsp70 family. In this study, as an initial step to probe for its physiological significance in the ischemic brain, cerebral activation and distribution of hsp110 mRNA was comparatively evaluated with that of hsp70i mRNA by in situ hybridization. A rat focal cerebral ischemia model was employed to examine the distribution and localization of hsp110 and hsp70i mRNAs in both affected (ipsilateral) and unaffected (contralateral) hemispheres of the same animal. Our results demonstrated a significant accumulation of hsp110 as well as hsp70i mRNAs following ischemia; although the magnitude and kinetics of induction differ slightly, spatial expression profiles of hsp110 and hsp70i mRNAs were highly correlated in the affected region. In control brain, limited hybridization signal was observed with 3'-untranslated region (UTR) containing hsp110 probe, suggesting a possible existence of inducible hsp110 and a selective recognition of our 3'-UTR containing probe for the inducible hsp110 mRNA species. Subsequent 2D western analysis with Hsp110 specific Ab was consistent with our view, which resolved constitutive and inducible immunostained spots in rat ischemic brain. Considering a regulatory similarity as well as previously documented structural and functional similarities between hsp110 and hsp70i, we propose that coordinated cerebral activation of hsp110 and hsp70i is likely to be of significant relevance in the context of pathophysiology of ischemic brain. Further study is required to characterize the genetic and biochemical nature of rat inducible hsp110 identified in the current study.

Animals↗

Surgical treatment of congenital kyphosis.

STUDY DESIGN: In this study, 26 cases of congenital kyphosis and kyphoscoliosis treated surgically were retrospectively reviewed. OBJECTIVE: To assess the clinical outcomes and surgical indications for posterior only versus anteroposterior surgery in the child. SUMMARY OF BACKGROUND DATA: Congenital kyphosis usually is progressive without surgical intervention. Current recommended treatment includes posterior arthrodesis for deformities of less than 50 degrees to 60 degrees, and anterior release or decompression, anterior fusion, and posterior instrumented arthrodesis for large deformities and cord compression. METHODS: Cases involving myelodysplasia, spinal dysgenesis, and skeletal dysplasia were excluded from the study. Kyphoscoliosis was included if the kyphotic deformity was greater than the scoliotic deformity. Patients were grouped by age and surgical technique. The patients in group P1 underwent posterior arthrodesis at an age younger than 3 years, and those in group P2 underwent the procedure at an age older than 3 years. The patients in group AP1 underwent anterior and posterior procedures at an age younger than 3 years, and those in group AP2 underwent the procedures at an age older than 3 years. The preoperative deformity, complications, and postoperative deformity correction were analyzed. There were nine Type 1 (failure of formation), nine Type 2 (failure of segmentation), and eight Type 3 (mixed) deformities. Four patients had associated spinal dysraphism. Three patients with Type 1 deformities had clinical or radiographic evidence of cord compression. RESULTS: In Group P1, five patients at an average age of 16 months underwent posterior arthrodesis alone for an average kyphotic deformity of 49 degrees. The immediate postoperative correction improved over a period of 6 years and 9 months by an additional 10 degrees, resulting in a final deformity of 26 degrees. Pseudarthrosis developed in two patients, requiring fusion mass augmentation or anterior arthrodesis. Neither patient was instrumented. In Group P2, five patients at an average age of 13 years and 7 months underwent posterior arthrodesis with instrumentation for kyphotic deformity of 59 degrees. Approximately 30 degrees of intraoperative correction was achieved safely using compression instrumentation and positioning. No further correction occurred with growth. The final residual kyphotic deformity was 29 degrees after a follow-up period of 4 years and 5 months. In Group AP1, seven patients underwent anterior release or vertebra resection for deformity correction and posterior arthrodesis for an average kyphotic deformity of 48 degrees at the age of 16 months. There were no iatrogenic neurologic injuries. The final residual kyphotic deformity was 22 degrees after a follow-up period of 6 years and 3 months. In Group AP2, nine patients underwent anterior release or decompression with posterior arthrodesis for kyphotic deformity of 77 degrees at the age of 11 years and 6 months. The deformity was corrected to 37 degrees, with no significant loss over a follow-up period of 5 years and 2 months. There were two postoperative neurologic complications. CONCLUSIONS: After reviewing their experience, the authors made the following observations: 1) The pseudarthrosis rate was low even without routine augmentation of fusion mass if instrumentation was used; 2) gradual correction of kyphosis may occur with growth in patients younger than 3 years with Types 2 and 3 deformities after posterior fusion, but appears to be unpredictable; 3) the risk of neurologic injury with anterior and posterior fusion for kyphotic deformity was associated with greater age, more severe deformity, and preexisting spinal cord compromise.

Adolescent↗

Mechanistic insight into the inactivation of carboxypeptidase A by alpha-benzyl-2-oxo-1,3-oxazolidine-4-acetic acid, a novel type of irreversible inhibitor for carboxypeptidase A with no stereospecificity.

On the basis of the active site topology and enzymic catalytic mechanism of carboxypeptidase A (CPA), a prototypical zinc-containing proteolytic enzyme, alpha-benzyl-2-oxo-1,3-oxazolidine-4-acetic acid (1), was designed as a novel type of mechanism-based inactivator of the enzyme. All four possible stereoisomers of the inhibitor were synthesized in an enantiomerically pure form starting with optically active aspartic acid, and their CPA inhibitory activities were evaluated to find that surprisingly all of the four stereoisomers inhibit CPA in a time dependent manner. The inhibited enzyme did not regain its enzymic activity upon dialysis. The inactivations were prevented by 2-benzylsuccinic acid, a competitive inhibitor that is known to bind the active site of the enzyme. These kinetic results strongly support that the inactivators attach covalently to the enzyme at the active site. The analysis of ESI mass spectral data of the inactivated CPA ascertained the conclusion from the kinetic results. The values of second-order inhibitory rate constants (k(obs)/[I](o)) fall in the range of 1.7-3.6 M(-1) min(-1). The lack of stereospecificity shown in the inactivation led us to propose that the ring cleavage occurs by the nucleophilic attack at the 2-position rather than at the 5-position and the ring opening takes place in an addition-elimination mechanism. The tetrahedral transition state that would be generated in this pathway is thought to be stabilized by the active site zinc ion, which was supported by the PM3 semiemprical calculations. In addition, alpha-benzyl-2-oxo-1,3-oxazolidine-5-acetic acid (18), a structural isomer of 1 was also found to inactivate CPA in an irreversible manner, reinforcing the nucleophilic addition-elimination mechanism. The present study demonstrates that the transition state for the inactivation pathway plays a critical role in determining stereochemistry of the inactivation.

Carboxypeptidases↗