[Quantitative analysis of the gustatory evoked potentials in the guinea pig]

Gustatory evoked potentials were studied in anesthetized guinea pigs to develop an objective and quantitative taste examination for patients with taste disorders. A positive wave was recorded by the application of NaCl, HCl or quinine hydrochloride solution. There was little difference in latency, duration and waveform among these three solutions. No apparent change in activity was seen after the application of sucrose solution or distilled water. The gustatory evoked potentials that excluded the influence of the trigeminal nerve innervating the tongue surface were able to be reproducibly recorded on either the cortical surface or the skull surface. There was a linear relationship between logarithmic values of potential amplitude and those of taste solution concentration. Therefore, it is suspected that the quantitative evaluation of taste detection is possible by measuring the taste solution concentration-potential amplitude relationship.

Intracranial calcifications, epilepsy, and optic atrophy associated with metaphyseal dysplasia: a case report

A 15-year-old boy presenting with epilepsy, optic atrophy and intracranial calcifications was diagnosed as having metaphyseal dysplasia by bone X-ray examinations. The patient had no laboratory data suggesting other metabolic or endocrinologic disorders. In addition, CT scans showed unique intracranial calcifications of the corpus callosum and periventricular and subcortical white matter, which were distinct from those of previously reported disorders. This case may represent a unique subset or a new type of metaphyseal dysplasia associated with intracranial calcifications and central nervous system symptoms.

Regulation of tissue inhibitor of metalloproteinase-1 in fibroblasts and acute phase proteins in hepatocytes in vitro by mouse oncostatin M, cardiotrophin-1, and IL-6

Mouse oncostatin M (mOSM) has been recently cloned; however, its full spectrum of biologic functions has not been defined. To assess its potential role in inflammation, we have tested the activity of mOSM in vitro in regulation of fibroblasts and hepatic cells. At concentrations of 10 and 20 ng/ml, mOSM stimulates tissue inhibitor of metalloproteinase-1 (TIMP-1) mRNA in NIH-3T3 mouse embryonic fibroblasts, rat lung fibroblasts, and rat synovial fibroblasts, whereas mouse cardiotrophin-1 (mCT-1) or human OSM (hOSM) did not. Similarly, only mOSM was able to induce transcription of chloramphenicol acetyl-transferase (CAT) in NIH-3T3 cells transfected with a minimal TIMP-1 promoter/CAT construct. Mouse OSM had strong action inducing primary rat hepatocyte cultures to produce acute phase proteins; however, mOSM was very weak in its ability to stimulate acute phase protein synthesis in rat H35 cells or human HepG2 cells, which was consistent with weak STAT activation in H35 cells and HepG2 cells. Binding studies showed that NIH-3T3 cells possessed high affinity binding sites for mOSM, but rat H35 cells did not. On the other hand, mCT-1 and mouse IL-6 induced strong STAT activation as well as marked increases in acute phase protein production by H35 cells. These results indicate that mOSM does not share a functional receptor with mCT-1 or hOSM in mouse and rat cells and that hOSM does not activate the putatively specific OSM receptor on mouse or rat cells. These results also suggest that mOSM is an important cytokine in inflammation, through modulation of fibroblast function as well as hepatocyte responses.

Abnormal expansion of peripheral gamma delta T cells in patients with neurologic disorders

The proportions and the variable region usages of peripheral gamma delta T cells were investigated in 205 patients with various neurologic disorders. Flow cytometric analysis was performed with monoclonal antibodies against C delta, V delta 1, V delta 2. V delta 1-J delta 1/J delta 2, and V gamma II (9) epitopes. Further analysis was carried out with reverse transcription-polymerase chain reaction (RT-PCR) using variable region-specific primers. The proportion of gamma delta T cells in 33 patients with cerebral palsy (CP) (mean +/- SD; 11.1 +/- 11.0%) was significantly higher than that in 35 normal controls (5.6 +/- 2.6%) (p < .01). Of 205 patients, persistent gamma delta T cell expansion over 15% was observed in 15 patients (M/F = 13/2). Nine of these 15 were patients with CP. Six of the 9 with CP had neither perinatal nor postnatal events related to the neurologic abnormalities. None of the 9 with CP had active infections or autoimmune disorders that could induce gamma delta T cell expansion. Of the 15, 13 had V gamma II/V delta 2-dominant expansion and 2 showed V delta 1-dominant expansion. Unusual expansions of V delta 4 and V delta 6, which were not usually found in peripheral blood, were detected by RT-PCR in one case with CP and V delta 1-dominant expansion. This study showed subclinical immunologic abnormalities with marked and persistent gamma delta T cell expansion in patients with neurologic disorders, especially CP. These results might indicate the existence of neuroimmunologic disorder(s).

Nucleotide sequence divergence in the A+T-rich region of mitochondrial DNA in Drosophila simulans and Drosophila mauritiana

We have determined the nucleotide sequences of two regions within the A+T-rich region of mitochondrial DNA (mtDNA) in the siIII type of Drosophila simulans and the maI type of D. mauritiana. The sequences of the two regions in siIII and maI are almost identical. The sequences include elements corresponding to the type I and type II repeats elements and the T-stretches as reported in D. melanogaster; an approximately 340-bp region (A region) adjacent to the tRNA(Ile) gene includes a part of the type II repeat element, and an approximately 440-bp region (B region) includes a central portion of the A+T-rich region between the type I and type II repeat arrays. Each sequence of the two species was compared with those of D. melanogaster and D. yakuba. The sequences of the A region are relatively well conserved among the four species. The alignment of the two sequences of the B region with those of D. melanogaster and D. yakuba requires numerous insertions/deletions. For both regions, nucleotide differences between D. simulans or D. mauritiana and D. melanogaster are similar to those between the two and D. yakuba. The tendency is obvious in a subregion within the type II repeat element in the A region. These findings suggest that the rate of nucleotide substitution in the subregion is accelerated in the lineage leading to D. melanogaster. Loss of functional constraint in the stem-loop-forming sequence is proposed for this acceleration.

Wegener's granulomatosis with dural involvement as the initial clinical manifestation

We treated a patient with an atypical presentation of Wegener's granulomatosis (WG) with dural involvement as the initial clinical manifestation. A 37-year-old man had a dural lesion without lower respiratory tract or renal manifestations in the initial clinical course. His only initial symptom was headache, and at disease onset computed tomography (CT) and magnetic resonance imaging (MRI) of the head revealed bilateral abnormal subdural masses. The diagnosis of WG was made based on the results of needle biopsy of the nasal polyps and the finding of positive circulating antineutrophil cytoplasmic antibodies (c-ANCA). He achieved remission on daily prednisone and cyclophosphamide with the later addition of sulfamethoxazole-trimethoprim.

Oncostatin M and leukemia inhibitory factor do not use the same functional receptor in mice

Oncostatin M (OSM) and leukemia inhibitory factor (LIF) are members of the interleukin-6 (IL-6) subfamily of cytokines that use a common signal transducer gp130. Human OSM (hOSM) and LIF share a functional high-affinity receptor that is composed of gp130 and LIF receptor beta subunit (LIFRbeta). A second high-affinity receptor for hOSM was recently found to be formed by gp130 and the hOSM receptor beta subunit. However, the nature of murine OSM (mOSM) and its receptors has remained unknown. Using the recently cloned mOSM cDNA, we produced recombinant mOSM and studied its biological activity and receptor structure. Murine hematopoietic cell lines M1 and DA1.a, an embryonic stem cell line CCE, and Ba/F3 transfectants expressing gp130 and LIFRbeta responded to murine LIF (mLIF) and hOSM equally well, while these cells responded to mOSM only at a 30-fold to 100-fold higher concentration than those of mLIF and hOSM. In contrast, NIH3T3 cells responded to mOSM, but not to mLIF and hOSM. Scatchard plot analyses showed that mOSM bound to gp130 with low-affinity (kd = 2.8 to 4.2 nmol/L) and that the binding affinity did not increase in the presence of LIFRbeta. However, mOSM bound to NIH3T3 cells with high-affinity (kd = 660 pmol/L), whereas mLIF did not bind to NIH3T3 cells at all. These results indicate that unlike hOSM, mOSM and mLIF do not share the same functional receptor, and mOSM delivers signals only through its specific receptor complex. Further studies in mice will define the physiological roles of OSM.

Hydroxyapatite-coating on titanium arc sprayed titanium implants

We developed a new titanium spray technique using an inert gas shielded arc spray (titanium arc spray). Hydroxyapatite (HA)-coating can be applied to the implant without any surface pore obstruction after the rough surface is made by this technique. Scanning electron microscopy (SEM) of various porous implant surfaces after HA-coating revealed that the bead and fiber metal-coated implants had either a pore obstruction or an uneven HA-coating. On the other hand, the titanium arc sprayed implant demonstrated an even HA-coating all the way to the bottom of the surface pore. In the first set of animal experiments (Exp. 1), the interfacial shear strength to bone of four kinds of cylindrical Ti-6A1-4V (Ti) implants were compared using a canine transcortical push-out model 4 and 12 weeks after implantation. The implant surfaces were roughened by titanium arc spray (group A-C) and sand blasting (group D) to four different degrees (roughness average, Ra = group A: 56.1, B: 44.9, C: 28.3, D: 3.7 microns). The interfacial shear strength increased in a surface roughness-dependent manner at both time periods. However, the roughest implants (group A) showed some failed regions in the sprayed layers after pushout test. In the second set of animal experiments (Exp. 2), four kinds of Ti implants; HA-coated smooth Ti (sHA) with Ra of 3.4 microns, bead-coated Ti (Beads), titanium arc sprayed Ti (Ti-spray) with Ra of 38.1 microns and HA-coated Ti-spray (HA + Ti-spray) with Ra of 28.3 microns were compared using the same model as that in Exp. 1. The interfacial shear strength of HA + Ti-spray was significantly greater than that of sHA and Beads at both time periods, and that of Ti-spray at 4 weeks. Although a histological examination revealed that HA-coating enhanced bone ingrowth, sHA showed the lowest shear strength at both time periods. SEM after pushout test showed that sHA consistently demonstrated some regional failure at the HA-implant substrate interface. HA + Ti-spray had many failed regions either at the HA-bone interface or within the bone tissue rather than at the HA-implant substrate interface. These results suggested that the HA-coated smooth surfaced implants had a mechanical weakness at the HA-substrate interface. Therefore, HA should be coated on the rough surfaced implants to avoid a detachment of the HA-coating layer from the substrate and thus obtain a mechanical anchoring strength to bone. HA-coating on this new type of surface morphology may thus lead to a solution to the problems of conventional HA-coated and porous-coated implants.

Enhancement by morphine of radiographic contrast media-induced histamine release in rat peritoneal mast cells

In intravascular application of radiographic contrast media causes hypersensitivity reactions, in which histamine release may play a major role. We examined the interaction between contrast medium and morphine. Among the four nonionic contrast media examined, iopamidol showed the most marked histamine release from rat peritoneal mast cells in vitro. Although iopamidol and morphine themselves did not induce histamine release at concentrations up to 65 mgI/ml and 3 mM, respectively, their combination resulted in a significant histamine release. These findings suggest that patients with exposure to medicines that induce histamine release may have a higher incidence and severity of hypersensitivity reactions to radiographic contrast media.

Catecholamine and renin-angiotensin response during controlled hypotension induced by prostaglandin E1 combined with hemodilution during isoflurane anesthesia

STUDY OBJECTIVE

To evaluate the catecholamine and renin-angiotensin response during controlled hypotension combined with hemodilution in the clinical setting.

DESIGN

Randomized, prospective study.

SETTING

Inpatient surgery at Nagasaki Rosai Hospital.

PATIENTS

30 ASA physical status I and II female patients scheduled for total hip arthroplasty.

INTERVENTIONS

Patients were randomly divided into three groups. Group A (N = 10) received hemodilution alone. Group B (N = 10) received controlled hypotension alone. Group C (N = 10) received hemodilution plus controlled hypotension. Hemodilution was carried out after induction of anesthesia, in which drawn blood was replaced with 6% hydroxyethyl starch, and the final hematocrit value was approximately 22%. Controlled hypotension was induced with prostaglandin E1 (PGE1) to maintain mean arterial blood pressure at 55 mmHg for 80 minutes.

MEASUREMENTS AND MAIN RESULTS

Measurements included plasma renin activity (RA) and plasma concentrations of angiotensin-II (AG-II), aldosterone (AS), norepinephrine (NE), and epinephrine (EP). These indices were measured before hemodilution, after hemodilution, 80 minutes after starting hypotension, and 60 minutes after recovery from hypotension. Hemodilution alone caused no significant change in the values throughout the time course. Controlled hypotension alone caused significant increases in plasma concentrations of NE (+295%) and EP (+203%) at 80 minutes after starting hypotension, whereas it caused no change in plasma RA and plasma concentrations of AG-II and AS. Hemodilution plus controlled hypotension caused significant increases in plasma RA (+271%) and plasma concentrations of AG-II (+188%), AS (+199%), NE (+279%), and EP (+184%) at 80 minutes after starting hypotension.

CONCLUSION

The combination of hemodilution and PGE1 induced controlled hypotension causes significant responses, especially in a renin-angiotensin-aldosterone system under isoflurane anesthesia.

Time resolved study of effect of chlorpromazine on mobility of cytochrome P-450 and phospholipids in the inner membrane of adrenocortical mitochondria

The effects of chlorpromazine on the mobility of cytochrome P-450 and the fluidity of lipid membranes have been investigated in bovine adrenocortical submitochondrial particles (SMP). Rotational diffusion of the cytochrome was measured by observing the decay of absorption anisotropy, ra(t), after photolysis of the heme.CO complex by a vertically polarized laser flash. Analysis of ra(t) was based on a 'rotation-about-membrane-normal' model. The anisotropy decayed within 2 ms to a time independent value r3. The presence of chlorpromazine decreased the mobile population of cytochrome P-450 from 28 to 23%. The rotational relaxation time phi a of the mobile population (approximately 1100 microseconds) was, however, not significantly changed by chlorpromazine. The lipid fluidity was examined by observing time-resolved fluorescence anisotropy, rf(t), of 1,6-diphenyl 1,3,5-hexatriene (DPH). The anisotropy rf(t) decayed within 70 ns to a time independent value r infinity. The motion of DPH was analyzed based on a 'wobbling-in-cone' model. The presence of chlorpromazine decreased the cone angle from 42 degrees to 39 degrees, while the rotational relaxation time phi f (approximately 2 ns) was not significantly changed by the presence of chlorpromazine. These results demonstrate that chlorpromazine decreased the mobility of not only lipids but also membrane proteins.

[Surgical revision of failed filtering bleb with mitomycin C]

The revision of a failed filtering bleb using mitomycin C was performed in 40 eyes (28 eyes with primary open angle glaucoma and 12 eyes with secondary open angle glaucoma) in which the previous trabeculectomy using 5-fluorouracil had failed to control intraocular pressure (IOP). Presurgical IOP ranged from 21 approximately 36 mm Hg (average: 24.7 mmHg) with the maximum tolerable antiglaucoma medication. The follow-up period was at least 2 years (24 approximately 60, mean: 39.8 months). Mitomycin C (0.04%, 5 ml, 5 min) was applied under the subconjunctival space. After rinsing, the wall of the scarred bleb was incised in cases with a localized bleb, or the margin of the scleral flap was incised in cases without a filtering bleb. The conjunctival wound was closed with 10-0 Nylon sutures. IOP control under 21 mmHg was achieved in 53.4% without medication and in 60.2% with or without medication at 60 months. After repeating the same procedure, IOP control was obtained in 82.2% with or without medication at 60 months. The success rate in secondary open angle glaucoma was less than in primary open angle glaucoma. Complications such as flattening of the anterior chamber requiring reformation (8%), choroidal detachment (8%), hyphema (5%), and hypotonic maculopathy (5%) were less than after trabeculectomy but conjunctival wound separation (5%) occurred little more frequently.

PET imaging of brain tumor with [methyl-11C]choline

This article describes a new method of [11C]choline synthesis for intravenous injection. We aimed at the utilization of this compound for brain tumor imaging with PET.

METHODS

After [11C]carbon dioxide production in a cyclotron and the subsequent [11C]methyl iodide synthesis, [methyl-11C]choline was synthesized by the reaction of [11C]methyl iodide with "neat" dimethylaminoethanol at 120 degrees C for 5 min. Purification was achieved by evaporation of the reactants followed by passage of the aqueous solution of the product through a cation-exchange resin cartridge. The time required for overall chemical processing, excluding the cyclotron operation, was 15 min. Radiochemical yield was > 98%. Radiochemical purity was > 98%. Chemical purity was > 90% (dimethylaminoethanol was the only possible impurity). Specific radioactivity of the product was > 133 GBq/mumol. The whole body distribution was examined in rabbits with PET. Clinical studies were performed in patients with brain tumor using PET after intravenous injection of 370 MBq of [11C]choline.

RESULTS

In rabbits,[11C]choline was taken up from blood by various tissues very rapidly, and the radioactivity remaining in blood became almost negligible 5 min after intravenous injection. Taking advantage of this characteristic, we obtained stable tissue distribution images of human brain using PET. In patients with brain tumor, PET produced clearly delineated positive images of the tumors.

CONCLUSION

Carbon-11-choline can be used for obtaining clear images of brain tumor in PET.

[A case of the tuberculous abscess in the abdominal wall]

A case of the tuberculous abscess in the abdominal wall is reported. A 84-year-old female was admitted to our hospital with evaluation of soft tumor at the left lower abdomen. She has a mass in the abdominal wall measuring 4 cm in diameter, and abscess in the abdominal wall was detected by ultrasonogram and CT. The confirmed diagnosis of abdominal wall tuberculosis was made by means of bacterial culture and polymerase chain reaction (PCR method) of the aspirated fluid from a mass. Multiple calcified lesions on the abdominal X-ray were seen, which were thought to past history of tuberculous peritonitis. Antituberculosis therapy of three-drug regimens was not effective. Four month later, resection of the abscess was then performed. Adhesion was demonstrated between greater omentum and peritoneum, therefore the abscess in the abdominal wall was considered to arise and advance directly from the abdominal cavity.

Effect of an aldose reductase inhibitor on abnormalities of electroretinogram and vascular factors in diabetic rats

The effect of an aldose reductase inhibitor, [5-(3-thienyl) tetrazol-1-yl] acetic acid (TAT), on the electroretinogram was determined in rats with streptozotocin-induced diabetes. Laboratory chow containing 0.05% TAT was given to rats for 2 months, while other diabetic rats were untreated. Groups of TAT-treated and untreated normal rats were also studied. Treatment with TAT produced significant improvement of the electroretinogram. TAT shortened the peak latencies of the b-wave oscillatory potentials, which were significantly prolonged in untreated diabetic rats (P < 0.0001 vs. untreated normal rats). This was accompanied by a significant decrease in the retinal sorbitol and fructose concentrations (by 46.5% and 25.7%, respectively). TAT treatment of diabetic rats also markedly reduced ADP-induced platelet aggregation and significantly increased the red blood cell 2,3-diphosphoglycerate level, accompanied by a marked reduction in sorbitol and fructose concentrations of platelet and red blood cells. There were significant correlations between the summed b-wave peak latencies and platelet aggregation or the 2,3-diphosphoglycerate level in diabetic rats. These findings suggest that an aldose reductase inhibitor, TAT, has therapeutic value for diabetic retinopathy.

[The essential region of CD40 cytoplasmic domain for signal transduction in WEHI231 cells]

Ligation of surface immunoglobulin M (IgM) induced cell death and this was blocked by CD40-mediated signal in a mouse B cell line, WEHI231. In order to define which region of CD40 and how CD40-mediated signal are involved in the blocking of IgM-induced cell death, we generated several human CD40 transfectants. We demonstrated that a 10-amino acid segment in the conserved cytoplasmic region of CD40-mediated rescue from IgM-induced cell death and was involved in the activation of c-Jun aminoterminal kinase (JNK). In addition, the same segment was also important for CD40-mediated activation of extracellular signal-regulated protein kinase 2 (ERK2). Moreover, tumor necrosis factor receptor-associated factor (TRAF) 2 and 3 could bind to the same segment of CD40.

Intraocular lens durability after a mean of 10.9 years' implantation in humans

AIMS/BACKGROUND

To clarify whether intraocular lens (IOL) implantation in the human eye affects the durability of polymethylmethacrylate over an average period of 10.9 years.

METHODS

Shearing stress and extent of damage following neodymium (Nd):YAG laser application to 18 study and 12 control optics were examined.

RESULTS

No significant difference was found between the study and the control IOLs in shearing stress and extent of damage following Nd:YAG.

CONCLUSION

An average 10.9 years' implantation in humans does not affect either the shearing stress or extent of damage following Nd:YAG shots of polymethylmethacrylate.

Binding mode of CA074, a specific irreversible inhibitor, to bovine cathepsin B as determined by X-ray crystal analysis of the complex

The binding mode of CA074 [N-(L-3-trans-propylcarbamoyl-oxirane-2-carbonyl)-L-isoleucyl-L-pr oline], a specific irreversible inhibitor, to bovine spleen cathepsin B was elucidated by X-ray crystal structure analysis of the complex at 2.2 A resolution (conventional R=0.185). Inconsistently with our model used for the development of CA074, the L-isoleucyl-L-proline and propylcarbamoyl moieties are located at the S' and S subsites, respectively. This unexpected binding is primarily due to (i) similar extended chain conformations (due to the same S configurations) at the oxirane C2 and C3 atoms of CA074 and (ii) the just fit formation of double hydrogen bonds between the carboxyl oxygens of L-proline and the imidazole nitrogens of His-110 and His-111 residues (these residues are missing in papain, the tertiary structure of which was used for the design of CA074). The oxirane C3 atom possessing the P' substituent is covalently bound to the Cys-29 Sgamma atom (C3-Sgamma=1.79 A) and the S configuration is maintained. The present result will provide useful information for characterizing the substrate-specificity of cathepsin B.

Nasal lesions induced by intranasal administration of benzaikonium chloride in rats

We investigated the lesions of nasal cavity mucous membrane caused by administration of 0.01, 0.05 and 0.10 w/v% Benzalkonium chloride (BZC) solutions in the nasal cavity of rats. No BZC-induced symptoms or nasal lesions were seen in the 0.01 w/v% BZC-treated group. On the other hand, BZC-induced symptoms such as nasal sound and rubbing the nose with forelegs were observed in the 0.05 and 0.10 w/v% BZC-treated groups. Additionally, BZC-induced lesions, including epithelial desquamation, inflammation and edema, occurred in the anterior nasal cavity in the 0.05 and 0.10 w/v% BZC-treated groups, but these lesions were confined to the dorsal meatus and the adjacent nasal septum. These results indicate that 0.01 w/v% BZC solution has no effect on the nasal cavity mucous membrane. However, 0.05 and 0.10 w/v% BZC solutions induce lesions in the nasal cavity mucous membrane due to their irritating effect.

IgA and IgG2 deficiency associated with zonisamide therapy: a case report

PURPOSE

To report a previously undescribed adverse effect, IgA/IgG subclass deficiency associated with zonisamide (ZNS) therapy.

METHODS

Serum IgA and IgG subclass levels were determined by the turbidimetric immunoassay and enzyme-linked immunosorbent assay, respectively, in a 2-year-old boy with postmeningitis sequelae who was treated by ZNS.

RESULTS

Four months after initiation of ZNS, combined deficiency of IgA and IgG2 was noted. After cessation of ZNS, serum IgA level was promptly increased. IgG2 level was gradually increased, but remained subnormal after 7 months.

CONCLUSIONS

This case documents, for the first time, the action of ZNS on IgG immune system as well as IgA system. If patients with ZNS therapy showed IgA deficiency and recurrent infections, it is preferable to check serum IgG subclass concentrations as well.

[A case of primary malignant melanoma of the esophagus]

A case of primary and malignant melanoma of the esophagus was reported. A 64-year-old male complaining of discomfort of anterior chest pain was admitted to our hospital for operation. Findings of upper G-1 X-ray and endoscopic examination revealed suspiciously malignant melanoma. Subtotal thoracic esophagectomy with R III dissection was performed. Operative findings included A0 N2 Pl0 M0 Stage III. Macroscopically it showed black-grayish colored polypoid tumors, 7 cm in size. The typical finding of junctional activity adjacent to the tumor mass and melanocytes were microscopically found. The patient received postoperative systemic chemotherapy, but was died of multiple liver and bone metastases 125 days after surgery. Malignant melanoma of the esophagus has extremely poor prognosis and none of effective therapies has been reported.

An experimental study of a combination method using a pedicle screw and laminar hook for the osteoporotic spine

STUDY DESIGN

Using human cadaver spines, the authors compared the effect of using a combination of pedicle screw and laminar hook on the same vertebra with that of using a pedicle screw alone in reference to bone mineral density of the vertebra under nondestructive cyclic loading.

OBJECTIVES

To quantify stiffness obtained by pedicle screw alone and by the combination method and to clarify a relationship between stiffness obtained by each instrumentation method and bone mineral density of the vertebra.

SUMMARY OF BACKGROUND DATA

The use of pedicle screws apparently improves the union rate of spinal fusion. Instrumentation failures sometimes occur, however, such as loosening or loss of correction of the spine, especially in patients with osteoporosis. Some augmentation method in instrumentation is necessary to overcome bone fragility in the osteoporotic spine.

METHODS

Thirteen cadaver lumbar vertebrae were used for this study. Bone mineral density was measured by dual-energy X-ray absorptiometer. After separating each vertebrae, the pedicle screw was screwed into a vertebra. Five cycles of cephalocaudal loading were performed to the shank of the screw with a cross-head speed of 3 mm/min under a maximum load control of 29.4 N using an Instron type testing machine, and the stiffness obtained with the pedicle screw (Kj) was calculated from the load-deformation curve. Then, a laminar hook was set and connected to the screw via a rod. Mechanical testing was performed in the same way, and the stiffness obtained with the combination method (Kf) was determined. Kj and Kf were compared using the paired t test. The relationship between Kj, Kf, or the stiffness improvement ratio ([Kf-Kj]/Kj) by the combination method and bone mineral density was analyzed by linear regression analysis.

RESULTS

Stiffness obtained by the combination method was significantly greater than that obtained by pedicle screw alone (89.8 +/- 35.0 N/mm by the combination method, 60.2 +/- 19.6 N/mm by pedicle screwing alone; P < 0.0001). Stiffness, whether obtained by pedicle screw alone or by the combination method, was positively correlated with bone mineral density (with pedicle screw alone, R2 = 0.614, P < 0.0001; with the combination method, R2 = 0.645, P < 0.0001). However, there was no significant correlation between stiffness improvement ratio and bone mineral density.

CONCLUSION

Instrumentation stiffness obtained by the combination method was significantly greater than that obtained by the use of pedicle screw alone. There was no significant correlation between the improvement ratio by the combination method and bone mineral density. These results suggest that the combination method is valuable irrespective of the presence of spinal osteoporosis.

Site-directed mutagenesis of active site contact residues in a hydrolytic abzyme: evidence for an essential histidine involved in transition state stabilization

Specific molecular interactions involved in catalysis by antibody 6D9 were investigated by site-directed mutagenesis. The catalytic antibody 6D9, which was generated against a transition state analog (III), hydrolyzes a non-bioactive chloramphenicol monoester derivative (I) to produce chloramphenicol (II). Construction of a three-dimensional molecular model of 6D9 and sequence comparison within a panel of related antibodies suggested candidates for catalytic residues, His (L27d), Tyr (L32), Tyr (H58) and Arg (H100b); these were targeted for the site-directed mutagenesis study. The Y-H58-F and R-H100b-A mutants possessed catalytic activities comparable to that of the wild-type, and the Y-H58-H and Y-L32-F mutant displayed an approximately fivefold decrease in k(cat)/Km. In the transition state analysis, the plots of logK(TSA) versus log(k(cat)/Km) for the mutants are linear, with a slope of approximately 1.0, indicating that the entire hapten-binding energy in the mutants is also utilized to bind the transition state and to accelerate the catalysis. In addition, a dramatic change in the catalytic activity was observed when the histidine residue (27d) in the CDR1 light chain was replaced with alanine. The H-L27d-A mutant had no detectable catalytic activity. This mutation led to a large, 40-fold reduction in transition state binding, with no change in substrate binding. Coupled with the previous kinetic studies and chemical modifications of the intact 6D9 antibody, this mutagenesis study has demonstrated that His L27d plays an essential role in stabilization of the transition state, the mechanism of catalysis by the 6D9 antibody.