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PubMed1995

Reversible structural changes of octacalcium phosphate and labile acid phosphate.

Acid phosphate is one of the major impurities incorporated into bioapatites, and its quantity and environment in forming mineral have been used as diagnostic probes to pursue acidic precursor(s). Currently, little is known about the structural feature of nonstoichiometric octacalcium phosphate (OCP), which has been advocated to be, most plausibly, mineral salt initially formed during amelogenesis. In the present report, we attempt to define the state of acid phosphate in OCP crystals which were Ca-deficient and contained 40% total phosphate as acid phosphate. We assessed fractions of acid phosphate in discrete environments by extracting the crystals in either deionized water, 10 mmol/L NaOH solution (initial pH 11), or 150 mmol/L Tris buffer at pH 7.4. Solid samples before and after the treatments were examined by chemical analyses and x-ray diffraction. The results indicated that successive extractions with use of the alkaline solution brought about a reversible change (not hydrolysis) in the interior structure of OCP, which accompanied a marked decrease in acid phosphate. A substantial part of the lost acid phosphate was restored during subsequent treatments at neutral pH, and, intriguingly, this restoration accompanied a re-ordering of OCP structure. The data suggested that the acid phosphate in OCP is separated into three pools: (a) a stable pool corresponding to roughly 50 to 60% of the total acid phosphate, (b) a reversibly exchangeable pool corresponding to 25 to 30% of the acid phosphate which may exist either in the water layer or on crystal surfaces, and (c) an unstable (or irreversibly lost) pool corresponding to 15 to 20% of the acid phosphate, a part of which might be explained by the presence of excess hydrogen in OCP. The present work supports the concept that protons and, to a lesser magnitude, phosphate species can diffuse into and out of the OCP lattice prior to initiation of its hydrolytic transition into apatite.

Apatites↗
PubMed1992

Tomographic assessment of alterations of the temporomandibular joint after orthognathic surgery.

The aims of the study were: (1) to identify absolute condylar displacements and glenoid fossa changes; (2) to assess alterations in the condyle-fossa relationships following orthognathic surgery, by means of linear temporomandibular joint tomography. The sample consisted of 44 adults who received pre- and post-operative orthodontic therapy and management of their dentofacial deformities with various osteotomies (maxillary: 10; mandibular: 24; combined: 10). The material consisted of the tomograms of the right temporomandibular joints taken within 1 week pre-operatively, immediately post-surgery, and 6 months postoperatively. The X-rays were taken with the mouth closed. Tracing, superimposition, and interpretation of the tomograms were made according to a new method. The findings of the study regarding the groups which received mandibular or combined osteotomies indicated that immediately post-operatively there was a tendency for the condyle to be distracted downward and anteriorly from its original position in the fossa. However, in the 6 months follow-up the condyle showed a tendency to re-establish its initial position. Large variation in posterior space was observed among the patients of the mandibular osteotomy group who were also examined individually. In the maxillary osteotomy group no significant post-operative changes were observed on the average. Remodelling was noticed in both condylar and fossa surfaces of all groups.

Adolescent↗
PubMed1996

Study on early re-rupture of intracranial aneurysms.

The prognosis of patients with early re-ruptured intracranial aneurysms is discouraging. We compared the data on patients suffering re-rupture before the onset of late vasospasm (Early-Re) with those suffering rebleeding thereafter (Late-Re). The operability in the Early-Re group was lower (p < 0.05) and the outcome less satisfactory than that of Late-Re group. Of the Early-Re patients, 83% had a re-rupture within 24 hours of the initial subarachnoid haemorrhage; moreover 46% of these experienced rebleeding within three hours of the initial bleeding. Cases in the Early-Re group tended to belong to Hunt-Hess grade III or IV on admission, of wide spread subarachnoid haemorrhage on CT and of "bump" type aneurysms on angiograms. Based on our experience we propose that early re-rupture may be attributable to the following factors: a gradual and progressive thinning of the wall of bump type aneurysms results in such a large laceration through the fundus of the aneurysm. Re-rupture may occur within a short period after the first rupture because the fibrin net covering the wide laceration cannot tolerate the slight increase in internal pressure within the aneurysmal dome. Therefore, in the patients of Hunt-Hess grade III or IV, conventional angiography, tight holding during CT examination and lumbar puncture, should be avoided during the first three hours after the first bleed. Although early direct operations on patients with high Hunt-Hess grades tend to produce an unsatisfactory outcome, we cannot help these patients with Early-Re without surgical treatment. Not only early direct operation but also first conservative treatment to control systolic blood pressure are very important in patients with Early-Re.

Adult↗
PubMed1994

Using computed tomography/discography and enhanced magnetic resonance imaging to distinguish between scar tissue and recurrent lumbar disc herniation.

STUDY DESIGN: Patients who had lumbar spine surgeries and experienced residual symptoms were prospectively studied using computed tomography/discography and enhanced magnetic resonance imaging. OBJECTIVES: Determining the sensitivity and specificity of gadolinium-enhanced magnetic resonance imaging versus computed tomography/discography in distinguishing scarring from recurrent disc herniation was the first objective. The second goal was to determine if there were any imaging characteristics unique to either scar or recurrent disc herniation. SUMMARY OF BACKGROUND DATA: The results of reoperation for recurrent disc herniation are uniformly good, whereas the results of reoperation for scar tissue are poor. There have been no studies comparing the ability of enhanced magnetic resonance imaging and computed tomography/discography to distinguish between scar and herniation material. METHODS: Two neuroradiologists who were blinded to the surgical findings in 33 patients independently reviewed the imaging studies and labeled abnormalities as disc herniation or scar tissue. Their responses were compared with surgical findings to determine the accuracy, sensitivity, and specificity of each test. Also, imaging studies were used to determine if disc material or scar tissue had specific imaging characteristics. RESULTS: Computed tomography/discography was more sensitive and specific in distinguishing between scar tissue and recurrent disc herniation. Information from both studies improved the sensitivity over either test alone. Characteristics associated with recurrent disc herniation included nonenhanced or rim-enhanced abnormality surrounding a low signal intensity lesion on magnetic resonance imaging and extension of contrast into the epidural space and an enhancing abnormality on computed tomography/discography. CONCLUSIONS: Using computed tomography/discography alone or with enhanced magnetic resonance imaging enables surgeons to distinguish between scarring and recurrent disc herniation so they can determine the need to re-enter the spinal canal.

Adult↗
PubMed2005

Frequency of goldmann applanation tonometer calibration error checks.

PURPOSE: To investigate how quickly Goldmann applanation tonometers used in clinical practice develop calibration errors, and to determine the frequency of checks required to detect these errors. MATERIALS AND METHODS: Prospective check of the calibration error of all Haag-Streit Goldmann applanation tonometers in the department at month zero, month one, and month four. The tonometers were checked according to the Haag-Streit method using a standard calibration check weight bar by two independent observers. Calibration errors were classed as +/-0.5 to 2.5 mm Hg, +/-3 to 4 mm Hg, or >+/-4 mm Hg. Tonometers with a calibration error greater than +/-2.5 mm Hg were returned to the manufacturer for re-calibration. RESULTS: At month zero 2 of 34 (5.9%), at month one 3 of 29 (10.3%), and at month four 0 of 33 (0.0%) tonometers fell within the manufacturer's recommended calibration range of +/-0.5 mm Hg. A total of 14 of 34 (41.2%) tonometers at month zero, 10 of 29 (34.5%) tonometers at month one, and 17 of 33 (51.5%) tonometers at month four were identified to have calibration errors greater than +/-2.5 mm Hg. CONCLUSIONS: Goldmann applanation tonometers are not as accurate as the manufacturer's recommended calibration error tolerance of +/-0.5 mm Hg would suggest. Calibration error of less than +/-2.5 mm Hg is clinically acceptable. Calibration error checks should be carried out once monthly and tonometers with calibration error greater than +/-2.5 mm Hg returned to the manufacturer for re-calibration. Additional checks should be made if tonometers suffer specific damage. Ideally individual ophthalmologists should check calibration before each session.

Calibration↗
PubMed1992

Further characterization of monoclonal antibody indicates specificity for (6-4)-dipyrimidine photoproducts.

Monoclonal antibody aUVssDNA-1 is produced by hybridoma cell line 25JF.C3B6 originally selected from cell fusions using spleen cells from mice immunized with UV-irradiated polydeoxynucleotides (Strickland and Boyle, Photochem. Photobiol. 34, 595-601, 1981). Original and subsequent studies of the binding characteristics of aUVssDNA-1 indicated that it was specific for cyclobuta-dithymidine photoproducts. Those investigations examined action spectrum, short-wavelength photo-reversal, nucleotide sequence effects, and photoreactivation using E. coli photolyase and incandescent light. However, the more recent studies reported here examined acetophenone-UV-B photosensitization, UV-B photoisomerization, and photoreactivation using cloned E. coli photolyase and filtered incandescent light. The results indicate that aUVssDNA-1 recognizes photoproducts with characteristics of (6-4)-dipyrimidines. Thus, previous studies in which relatively rapid repair of cyclobuta-dithymidine photoproducts was inferred using this antibody, require re-interpretation in light of these new findings.

Animals↗
PubMedDate not supplied

Dapsone-induced eosinophilic pneumonitis in a leprosy patient.

A leprosy patient with no prior history of respiratory complaints, developed symptoms of dry cough, fever and dyspnea after six weeks of therapy. Peripheral eosinophilia and radiological evidence of pulmonary interstitial infiltrates pointed towards the possibility of drug-induced eosinophilic pneumonitis. The results of relevant tests for other possible pathologies were normal. The resolution of symptoms without any intervention other than withdrawal of the drug and subsequent re-challenge proved dapsone to be the cause.

Dapsone↗
PubMed1996

Inflammatory disease of the ureter.

This article examines how the spectrum of responses of the ureter to inflammation is manifested in conventional radiography and to some extent in newer modalities, such as ultrasound, CT scan, and MR imaging. Common clinical entities are highlighted. The re-emergence of tuberculosis in the urinary tract and current information on infection with organisms are also discussed.

Female↗
PubMed2000

The x-ray structure of D-amino acid oxidase at very high resolution identifies the chemical mechanism of flavin-dependent substrate dehydrogenation.

Flavin is one of the most versatile redox cofactors in nature and is used by many enzymes to perform a multitude of chemical reactions. d-Amino acid oxidase (DAAO), a member of the flavoprotein oxidase family, is regarded as a key enzyme for the understanding of the mechanism underlying flavin catalysis. The very high-resolution structures of yeast DAAO complexed with d-alanine, d-trifluoroalanine, and l-lactate (1.20, 1.47, and 1.72 A) provide strong evidence for hydride transfer as the mechanism of dehydrogenation. This is inconsistent with the alternative carbanion mechanism originally favored for this type of enzymatic reaction. The step of hydride transfer can proceed without involvement of amino acid functional groups. These structures, together with results from site-directed mutagenesis, point to orbital orientation/steering as the major factor in catalysis. A diatomic species, proposed to be a peroxide, is found at the active center and on the Re-side of the flavin. These results are of general relevance for the mechanisms of flavoproteins and lead to the proposal of a common dehydrogenation mechanism for oxidases and dehydrogenases.

Binding Sites↗
PubMed2006

Arthroscopic collagen meniscus implant results at 6 to 8 years follow up.

Meniscal substitution is a fundamental procedure to prevent osteoarthritis of the knee after massive meniscectomy. Stone, Steadman and Rodkey have developed a bioreadsorbable collagen matrix (CMI) which acts as a scaffold to restore the original medial meniscal. The objective of this study was to prospectively evaluate the results of CMI implantation at a follow up from a minimum of 6 to a maximum of 8 years. Eight patients (mean age 25) were evaluated at a final observation point from 6 to 8 years after CMI implantation. Inclusion criteria were an irreparable meniscal tear or a previous meniscectomy involving the medial meniscus. Follow up evaluation included Cincinnati Knee Rating Scale (CKRS), IKDC, subjective evaluation and X-ray and MRI control. There were no complications related to the device. All patients were able to return to day activities without limitations 3 months after surgery. Both subjective CKRS score and objective IKDC score showed improvement in all cases except one patient with an ACL re-injury. In two cases scores were slightly worse from 2 years after surgery to the final observation point. The other five cases obtained maximum score at final follow-up. In four cases the absence of pain remained until the final observation point, while in four cases a low entity of pain was described at long term follow-up. MRI showed in five cases mixoid degeneration signal, two had normal signal with reduced size, while one patient had no recognizable implant. Six patients had preserved cartilage and articular space, with no changes respect to pre-op control. Arthroscopic second look evaluation has been performed in three cases, revealing in two cases the presence of the implant, although with a reduced size respect to the original one, while in one case the CMI was almost disappeared. Our small series of eight patients prospectively followed from 6 to 8 years of follow-up has shown highly satisfactory results. Although the aspect of the implant was mostly abnormal, the implant may have helped reduce the deterioration of the knee joint at final observation time.

Absorbable Implants↗
PubMed2005

Reversible thermoresponsive aggregation/deaggregation of water-dispersed polymeric nanospheres exhibiting structural transformation.

Crystalline polymeric nanospheres composed of poly{stearyl methacrylate (SMA)-co-poly(ethylene glycol) monomethacrylate (PEGm)}s were prepared by the dispersion radical polymerization of SMA and PEGm in an ethanol/water solution. Scanning electron microscopy showed that the nanospheres were highly spherical, and had a narrow size distribution. Electron spectroscopy for chemical analysis and X-ray diffraction studies of the nanospheres suggested a core-corona-type structure; the hydrophilic PEGm corona accumulated on the nanosphere surface, while the hydrophobic SMA core formed a layered structure. Heat treatment caused a melting of the SMA layers, but successive cooling allowed it to re-form. Accompanying this reversible order-disorder transition, the nanospheres also showed a reversible aggregation/deaggregation behavior in their water-dispersion state.

Journal Article↗
PubMed2001

[Use of a portable CT scanner for monitoring ventilated patients in an intensive care unit].

PURPOSE: Evaluation of postoperative pulmonary atelectasis using a portable computed tomography (CT) unit. MATERIAL AND METHODS: 5 spiral CT-examinations in low-dose technique were performed on each of 10 patients with partial pulmonary atelectasis after coronary bypass surgery. The patients were artificially ventilated using different levels (0 to +15 cm H2O) of positive end-exspiratory pressure (PEEP). The changes in atelectatic volumes were determined for each side. RESULTS: In 6 patients the primary volume of atelectasis was larger on the left side than on the right. Atelectatic volumes decreased with increasing PEEP. Re-expansion of atelectases was significantly (p < 0.01) better with a PEEP of +15 cm H2O. CONCLUSION: Computed tomography allows visualisation of postoperative atelectasis reliably, even in the low-dose technique. Concordantly, additional therapeutically relevant side findings can be detected compared to conventional chest X-ray. Risky patient transport becomes unnecessary.

Coronary Artery Bypass↗
PubMed2000

[Value of the 'non-diagnostic' lung scan--further classification as to the risk of pulmonary embolism not reliable].

OBJECTIVE: To determine to what extent the 'non-diagnostic' lung scans made because of a clinical suspicion of pulmonary embolism enable further determination of the risk of pulmonary embolism. DESIGN: Retrospective. METHOD: All non-diagnostic lung perfusion ventilation scans made in the Academic Medical Centre of Amsterdam in 1997 of 114 patients in succession (55 males and 59 females aged 27-85 years) were subjected to blind and independent re-evaluation by three observers (an experienced nuclear medicine expert, an experienced and an inexperienced intern) who, using a lung segment chart, estimated the risk of embolism as < 25%, 25-50%, 50-75% and > 75%. They did this first without and then with the chest X-ray. The findings were grouped on the basis of accordance or non-accordance with the pulmonary angiogram. The interobserver agreement was calculated by means of kappa statistics. RESULTS: Of 58 patients the lung scan could be compared with a chest X-ray and a pulmonary angiogram. In 43 patients with a normal angiogram the observers in an average of 50% of the scans estimated the risk of pulmonary embolism as < 25%, as against 25-50% in 27%, 50-75% in 9% and > 75% in 5%. In 15 patients with a deviant pulmonary angiogram, these figures were 22%, 38%, 20%, and 12%, respectively. The interobserver kappa for evaluation without chest X-ray was < or = 0.16, as against < or = 0.41% with the chest X-ray. CONCLUSIONS: A reliable classification of the risk of pulmonary embolism was not possible on the basis of non-diagnostic lung scans, regardless of whether the patient did or did not have pulmonary embolism. The interobserver variability was less when the lung scan was evaluated together with the chest X-ray, but even so it was unacceptably high.

Adult↗
PubMed1998

[A case of spontaneous hemopneumothorax occurred after thoracic drainage].

A 21-year-old man; complaining of left chest pain and dyspnea, was admitted to our hospital with a diagnosis of spontaneous pneumothorax. Though chest X-ray on admission did not show hemothorax, chest drainage revealed intrapleural bleeding. As chest X-ray on the following day showed evident fluid level, emergency operation was carried out with a diagnosis of spontaneous hemopneumothorax. Bleeding point was a ruptured vessel between parietal pleura and bulla in apex of lung. The bulla was resected following hemostasis. After improvement of complicating postoperative re-expansive pulmonary edema, the patient was discharged on the 18th postoperative day. On treatment of spontaneous hemopneumothorax, existence of such a case as ours should be taken into account.

Adult↗