Urinary uric acid/creatinine ratio as an additional marker of perinatal asphyxia

PURPOSE

To study the validity of urinary uric acid (UA) as a marker of perinatal asphyxia in term and premature infants.

METHODS

The urinary ratio of UA to creatinine (Cr) was obtained within 24 hours after birth in four groups of infants: 17 term infants and 18 premature infants with perinatal asphyxia, and 22 healthy term infants and 20 premature infants without perinatal asphyxia. Perinatal asphyxia was defined as an Apgar score of 3 or less at 1 minute or 5 or less at 5 minutes, and/or a first blood gas pH of less than 7.25 and a base deficit of at least 12 mmol/L.

RESULTS

The urinary ratio of UA to Cr was significantly higher in term infants with perinatal asphyxia than in term infants without asphyxia (1.53 +/- 0.71 vs 0.73 +/- 0.45; p < 0.005). The same result was found between premature infants with and without perinatal asphyxia (3.89 +/- 1.84 vs 2.45 +/- 0.88; p < 0.01). The urinary ratio of UA to Cr in premature infants was significantly higher than in term infants. When the urinary ratio of UA to Cr was greater than 0.95, perinatal asphyxia was identified with a sensitivity of 80% and a specificity of 71% in term infants. In premature infants, a cut-off value of UA/Cr for perinatal asphyxia of 2.9 had a sensitivity of 71% and a specificity of 70%.

CONCLUSIONS

The results of this study indicate that the urinary ratio of UA to Cr may be used as an additional marker of perinatal asphyxia in term and premature infants. In comparison with other markers such as xanthine, hypoxanthine, and ascorbic acid, it is a simple, quick, and inexpensive way to detect hypoxic episodes in a neonatal intensive care unit within 24 hours after birth.

Classification of some active compounds and their inactive analogues using two three-dimensional molecular descriptors derived from computation of three-dimensional convex hulls for structures theoretically generated for them

Two three-dimensional (3D) molecular descriptors are used to classify 73 protease inhibitors against the human immunodeficiency virus type 1 (HIV-1). X-ray structures of these HIV-1 protease bound inhibitors are used as templates to generate the most probable bioactive conformations of the inhibitors. A convex hull computation algorithm is applied to each structure generated. The frequency of atoms lying on the vertexes of each hull is counted. Vertexes of the same atomic charge state are then gathered together as a set of commonly exposed groups for all the structures generated. The first 3D descriptor is computed as the maximum molecular path length among any three distinct commonly exposed groups, while the second 3D one is computed as the maximum molecular path length among any three atoms of nonconvex hull vertexes. We find that the 73 HIV-1 protease inhibitors can be classified by the first 3D descriptor into two groups, which agrees with the result of visual classification using the activity data as a criterion for these compounds. The classification scheme is then used to classify a database of 427 active trypsin inhibitors and their inactive analogues. The structures of these compounds are generated theoretically from steps of energy minimization and molecular dynamics. Classification for all these compounds is performed using the SYBYL hierarchical clustering method on the first 3D descriptor and then the second 3D one computed. It is found that some inactive analogues are completely separated from the active inhibitors at the first stage of classification using the first 3D descriptor. Most of the highly active inhibitors are classified into a cluster at the second stage of classification using the second 3D descriptor. Finally, most of these highly active inhibitors are separated from all the accompanying inactive analogues in the cluster through a structural alignment process using a set of commonly exposed groups determined for them.

Amniotic membrane transplantation for severe neurotrophic corneal ulcers

AIMS

To evaluate whether amniotic membrane transplantation can be an effective alternative treatment for neurotrophic corneal ulcers.

METHODS

Amniotic membrane transplantation was performed in 16 eyes of 15 patients with neurotrophic corneal ulcers and vision equal to or worse than 20/200. The neurotrophic state was developed following keratoplasty (four eyes), herpes zoster ophthalmicus (four eyes), diabetes mellitus (four eyes), radiation (two eyes), removal of acoustic neuroma with neuroparalysis (one eye), and herpes simplex keratitis (one eye).

RESULTS

During a mean follow up period of 18.8 (SD 13.0) months, one to three layers of amniotic membrane with or without additional membrane as a patch were used for 17 procedures in 16 eyes for persistent neurotrophic corneal ulcers. All but four (76.4%) instances of amniotic membrane transplantation achieved rapid epithelialisation in 16.6 (9.0) days. Of the four eyes showing delayed healing, three eyes healed by tarsorrhaphy, and the remaining one eye with corneal perforation required penetrating keratoplasty and tarsorrhaphy. Two eyes gained vision better than 20/200. The healed corneal surface was accompanied by reduced inflammation.

CONCLUSION

Amniotic membrane transplantation can be considered an effective alternative for treating severe neurotrophic corneal ulcers.

Total synthesis and antifungal evaluation of cyclic aminohexapeptides

The need for new therapies to treat systemic fungal infections continues to rise. Naturally occurring hexapeptide echinocandin B (1) has shown potent antifungal activity via its inhibition of the synthesis of beta-1,3 glucan, a key fungal cell wall component. Although this series of agents has been limited thus far based on their physicochemical characteristics, we have found that the synthesis of analogues bearing an aminoproline residue in the 'northwest' position imparts greatly improved water solubility (> 5 mg/mL). The synthesis and structure-activity relationships (SAR) based on whole cell and upon in vivo activity of the series of compounds are reported.

Delayed apnea in patients with mid- to lower cervical spinal cord injury

STUDY DESIGN

A retrospective study of 36 patients with mid- to lower cervical spinal cord injury (CSCI) divided into two groups based on whether delayed apnea developed.

OBJECTIVES

To determine nonpulmonary risk factors associated with the development of delayed apnea in mid- to lower cervical spinal cord injury.

SUMMARY OF BACKGROUND DATA

Patients with mid- to lower cervical spinal cord injury are generally at lower risk of developing respiratory failure than those with high cervical spinal cord injury. Respiratory failure manifesting as sudden apnea may occur days or even weeks after injury without any pulmonary complications in such patients.

METHODS

An index group of eight patients with complete mid- to lower cervical spinal cord injury in whom delayed catastrophic apnea occurred were reviewed. Another group of 28 patients with cervical spinal cord injury of identical magnitude and presentation but without respiratory failure served as the control group. Six parameters presumed to be related to the delayed apnea were analyzed.

RESULTS

The extent of cord lesions was significantly different, being diffuse in most of the index patients, but focal in the majority of the control patients (P<0.001). Involvement of the C4 segment of cord appeared to be more frequent in the index group; however, the difference was not statistically significant (P = 0.091). The incidence of transient bradycardia (P<0.01) and dyspnea (P<0.001) in the index group was significantly higher than in the control group. Paralytic ileus was a much rarer event and found to be unrelated to the occurrence of apnea. In five of the eight index patients, the apnea occurred during sleep. Six of the eight index patients died of it.

CONCLUSIONS

Delayed but devastating apnea may develop in patients with mid- to lower cervical cervical spinal cord injury, even when they are clinically stable and free from any pulmonary complications. The presence of diffuse, extensive cord lesions, respiratory distress, or bradycardia with or without associated hypotension, however transient and self-limited, should be regarded as warning signs. Sleep was found to be a risky period of time.

Scanning laser polarimetry in evaluation of retinal nerve fiber layer thickness for normal Taiwanese

Scanning laser polarimetry has been used recently for the measurement of retinal nerve fiber layer (RNFL) thickness, taking advantage of the birefrigence of the RNFL. We observe the RNFL with the instrument and try to find out a set of normal basic values of the RNFL thickness for clinical comparison. One hundred normal volunteers of different age groups were recruited for this study. There are 44 males and 56 females with a mean (1SD) age of 36.17(14.77) years. Three consecutive 15-degree polarimetric maps were acquired for each subject. RNFL thickness measurements were obtained at 1.75 disc diameters ring from the optic nerve. Four 90-degree quadrants were identified. As a result, the average of RNFL thickness is 90.69 (20.20) microns in the superior quadrant, 80.45 (17.4) microns in the inferior quadrant, 59.28 (15.37) microns in the nasal quadrant, and 48.98 (15.72) microns in the temporal quadrant with a mean thickness value of 69.86 (13.97) microns. Superior and inferior quadrants showed a comparatively thicker nerve fiber layer than nasal and temporal quadrants. The temporal quadrant was always the lowest. The axial length does not affect the RNFL thickness and no significant difference between males and females exists. However, an obvious inverse linear correlation between age and the RNFL thickness in all quadrants is found. The average RNFL thickness decreased with age by 0.26 micron per year. (R2 = 0.081, p-value = 0.004). When compared with the normal range, age-match would be necessary.

Angiogenically active vascular endothelial growth factor is over-expressed in malignant human and rat prostate carcinoma cells

Vascular endothelial growth factor (VEGF) is one of the most potent factors for stimulating angiogenesis, an essential process required for expansion of primary tumour and dissemination of malignant cells. To investigate the possible role of VEGF in facilitating metastasis of prostate cancer via stimulating angiogenesis, we have used Northern and slot blotting, reverse transcription polymerase chain reaction, nucleotide sequence analysis and enzyme-linked immunosorbent assay to compare the VEGF expression in series of human and rat cell lines with either benign or malignant characteristics. We have also employed the chick chorioallantoic membrane (CAM) assay to measure the angiogenic activity of the VEGF derived from both benign and malignant cells. The level of VEGF mRNA expressed in the seven malignant human and rat cell lines is 3.5- to 10-fold higher than that expressed in the benign cell lines. The three metastatic variants, generated by transfection of a benign cell line with DNA extracted from prostate carcinoma cells, expressed 2.5 to 5 times more VEGF mRNA than their parental benign cells. While VEGF 121 and 165 were predominantly expressed by both the benign and malignant cells, the transcript representing VEGF 189 isoform was only detected in the malignant cells. At protein level, three human malignant cell lines produced more VEGF (2.7-7.9 ng ml(-1)) than the benign cell line (1.3 ng ml(-1)). CAM assay detected a VEGF-dependent angiogenic activity in the medium from malignant cells, but only a relatively weak VEGF-independent activity in the medium from benign cells. These results demonstrated that malignant cells did over-express VEGF and only the VEGF derived from malignant cells was angiogenically active. Thus, we suggest that the VEGF produced by malignant cells might play an important role in facilitating metastasis of prostatic cancer.

Degradation of DNA topoisomerase I by a novel trypsin-like serine protease in proliferating human T lymphocytes

DNA topoisomerase I (Topo I) contributes to various important biological functions, and its activity is therefore likely regulated in response to different physiological conditions. Increases in both the synthesis and degradation of Topo I were previously shown to accompany phytohemagglutinin stimulation of proliferation in human peripheral T lymphocytes. The mechanism of this degradation of Topo I has now been investigated with both in vivo and in vitro assays. The activity of a nuclear protease that specifically degrades Topo I was induced in proliferating T lymphocytes. The full-length Topo I protein (100 kDa) was sequentially degraded to 97- and 82-kDa fragments both in vivo and in vitro. The initial site of proteolytic cleavage was mapped to the NH(2)-terminal region of the enzyme. The degradation of Topo I in vitro was inhibited by aprotinin or soybean trypsin inhibitor, suggesting that the enzyme responsible is a trypsin-like serine protease. Furthermore, Topo I degradation by this protease was Mg(2+)-dependent. The Topo I-specific protease activity induced during T lymphocytes proliferation was not detected in Jurkat (human T cell leukemia) cells and various other tested human cancer cell lines, possibly explaining why the abundance of Topo I is increased in tumor cells.

Transcriptional repression of p21((Waf1/Cip1/Sdi1)) gene by c-jun through Sp1 site

Previously, we found that c-jun represses the tumor suppressor p21((Waf1/Cip1/Sdi1)) (p21) gene expression. In this study, we further investigated the mechanism of the inhibitory effect of c-jun on p21. After analysis of a series of deletion and point mutants of p21 promoter, we found that Sp1-3 site (-77 and -83) relative to the transcription start site played an important role for c-jun-repressing-responsive element in the p21 promoter. Both Sp1 and Sp3 transcription factors were the key factors for this event. However, the data from electrophoretic mobility shift assay indicated that c-jun did not change the Sp1 DNA-binding affinity, suggesting that additional factors may be involved in the repression of p21 by c-jun. Furthermore, c-jun could inhibit butyrate-inducing p21 gene expression through Sp1, indicating at least one common pathway whereby p21 expression is affected by c-jun and butyrate in opposing actions. Moreover, the hyperphosphorylated retinoblastoma protein (Rb) increased in c-jun expressing cells, indicating that phosphorylated Rb may play a role in regulating Sp1 to repress p21 expression. This is the first demonstration of how housekeeping factors and oncogene product counteract the function of tumor suppressor genes to control cell cycle progression.

Atopic cataracts in a child with atopic dermatitis: a case report and review of the literature

Cataracts induced by atopic dermatitis rarely occur in adolescent and young adult patients suffering from this problem. Lenticular opacity is an important ocular complication in atopic dermatitis. Although the cause of atopic dermatitis and its ocular complications are unknown, cataracts have been observed to develop and progress during periods of exacerbation of the dermatitis. We report the case of a 16-year-old boy with atopic dermatitis who abruptly developed cataracts in both eyes while suffering from severe skin itching which began 2 months before the initial examination. His peroxidation test result was very high, and we postulate the retinal peroxidation might play a key role in cataractogenesis. Lens aspiration and intraocular artificial lens implantation were performed smoothly with restoration of visual acuity in both eyes.

Ptosis surgery on chronic myasthenia gravis

We report three cases of long-standing, early onset myasthenia gravis. The eyes of all three patients eventually became disabled, and the patients were almost unable to move their eyes in any direction. We termed this condition as "frozen eyes" appearance. We discuss the unique clinical condition and follow the electromyographic and neuro-ophthalmological characteristics. The patients all suffered from ptosis, mild to moderate exotropia, and facial and oropharyngeal weakness. All of the patients responded to the neostigmine test positively at the early stage. Two of them were seropositive. The results of electromyography for two of these three cases were abnormal. The average duration of follow-up was 5 years. The treatments included conventional recession and resection procedures with adjustable sutures for strabismus and frontalis suspension for blepharoptosis. The patients achieved stable satisfactory results in over one-and-a-half years of postoperative follow up.

Changes of bilateral palmar skin temperature in transthoracic endoscopic T-2 sympathectomy

OBJECT

Transthoracic endoscopic T-2 sympathectomy is currently the treatment of choice for palmar hyperhidrosis (PH). Intraoperative monitoring of palmar skin temperature (PST) is often used to assess the adequacy of sympathetic ablation. The aim of this study was to investigate the time course of PST changes during the operation and to determine factors involved in the sympathetic modulation of the palmar skin blood flow.

METHODS

Eighty-one patients with PH underwent bilateral transthoracic endoscopic sympathectomy of T-2 in which continuous intraoperative PST monitoring was used. Palmar skin temperature data, recorded every 30 seconds throughout the operation, were plotted against time, and a graph of two PST curves was obtained in each case. A multiphasic curve pattern of great similarity was observed in nearly 70% of cases. Specific PST readings at different operative stages were collected and averaged for all cases. The trend of PST changes in response to different procedures during the operation was analyzed. It was found that unilateral procedures caused simultaneous bilateral PST alterations. In almost all cases, bilateral PST was dramatically lowered when unilateral skin incision and intercostal muscle dissection were performed. The temperature remained low until the T-2 sympathectomy was finished on one side. In addition, unilateral T-2 sympathectomy induced synchronous elevation of bilateral PST. However, the ipsilateral response was significantly stronger than that on the contralateral side.

CONCLUSIONS

Although intraoperative monitoring of PST is a reliable guide for surgeons performing endoscopic transthoracic sympathectomy, it is important to realize that PST fluctuates at different stages during the operation and that surgical procedures themselves can significantly influence PST readings. The PST data recorded at specific time points, therefore, can be misleading in terms of accuracy and the completeness of ablation of the target sympathetic ganglia, especially when the sympathetic trunk or ganglia are anatomically aberrant.

Favorable clinical outcome of cervical cancers infected with human papilloma virus type 58 and related types

To determine whether the status of human-papillomavirus (HPV) infection affects the clinical outcome of cervical carcinoma (CC), HPV genotype was prospectively determined in 94 consecutive CC cases subsequently followed for a median duration of 37.5 months. With a consensus PCR-RFLP method of HPV genotyping, 81 (86.2%) cancers were positive for HPV DNA. They were classified, according to the phylogenic similarities, into HPV-16-related (type 16, n = 45; type 31, n = 2), HPV-58-related (type 58, n = 17; type 33, n = 3; type 52, n = 2) and HPV-18-related (type 18, n = 8; type 68, n = 1) groups, and analyzed in relation to clinical outcome. The following results were observed: (i) Type-58-related HPVs were more prevalent in the old age (older than the median age of 52) group than in the young age group (41% vs. 14.6%, p = 0.045); (ii) 63% (5/8) of patients with advanced stages (III and IV) were HPV-negative, a figure much higher than that (9.3%, 8/84) of patients with early stages (stage I and II) (p = 0.002); (iii) the occurrence of adenocarcinoma or adenosquamous carcinoma was higher in the HPV-18-related group (50%) than in the HPV-16-related (33.3%) or the HPV-58-related (16.7%) groups (p = 0.024); (iv) the status of lymph-node metastasis and tumor grade did not correlate with HPV status; (v) 5-year survival rates were 90.2%, 80% and 74% for HPV-58-, HPV-16- and HPV-18-related groups, respectively (p = 0.03, after adjustment for tumor stage); (vi) in comparison with the HPV-16-related group, the relative risk of death in the HPV-58- and the HPV-18-related groups were 0.32 [95% CI, 0.07-1.49] and 1.87 [0.36-14.9] respectively. HPV genotype appears to affect the clinical behavior and outcome of cervical cancer. HPV-58-related types are prevalent in the older population, and appear to confer a favorable prognosis. Int. J. Cancer (Pred. Oncol.) 84:553-557, 1999.

Detection and quantification of 1,N(6)-ethenoadenine in human placental DNA by mass spectrometry

Exocyclic DNA adducts have been reported to derive from various exogenous as well as endogenous sources, such as lipid peroxidation. Among them, 1,N(6)-ethenoadenine (epsilonAde) has previously been detected in tissue DNA of untreated rodents and humans by an immunoaffinity/(32)P-postlabeling method. This study reports detection and quantification of the endogenous epsilonAde adduct in the same human placental DNA by three independent assays, namely, GC/MS, LC/MS, and HPLC/fluorescence. Using a recently reported gas chromatography/negative ion chemical ionization/mass spectrometry (GC/NICI/MS) method [Chen, H.-J. C., et al. (1998) Chem. Res. Toxicol. 11, 1474], the level of epsilonAde in human placental DNA from a commercial source was found to be 2.3 adducts per 10(6) Ade bases. To confirm these findings, a liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS) method was developed for epsilondAdo. With this LC/MS assay, epsilondAdo was detected at the level of 2.5 adducts per 10(6) dAdo nucleosides in the same human placental DNA. The stable isotopes of epsilonAde and epsilondAdo were added as internal standards in both GC/MS and LC/ESI/MS/MS assays, respectively, and thus provided high specificity, reproducibility, and accurate quantification. The relatively high levels of epsilonAde in this human placental DNA detected by mass spectrometry were further verified by HPLC/fluorescence analysis. The GC/MS method was validated by the HPLC/fluorescence assay using calf thymus DNA treated with chloroacetaldehyde or by the LC/MS method with 2, 3-epoxy-4-hydroxynonanal-modified calf thymus DNA. The epsilonAde level in human placental DNA freshly isolated in the presence of an antioxidant was similar to that in DNA from the commercial source. Since epsilonAde is a potential mutagenic lesion, analysis of epsilonAde by the specific and sensitive GC/NICI/MS method may provide a useful biomarker in cancer risk assessment.

Porous balloon delivery of S-dC28 does not prevent restenosis in the porcine coronary artery model of balloon injury

Phosphorothioate (PS) oligodeoxynucleotides (ODN) inhibit vascular smooth muscle cell proliferation through antisense and G-quartet aptameric mechanisms. PS-ODN such as the cytidine homopolymers, have been demonstrated to have non-G-quartet, nonsequence-specific inhibitory effects in a rat carotid balloon injury model of neointimal proliferation. We sought to test the efficacy of S-dC28, a cytidine homopolymer lacking G-quartets, on neointimal proliferation in the porcine coronary artery model of balloon injury. A total of 23 animals (11 controls, 12 treated) were subjected to balloon injury in a coronary artery, followed by infusion of control solution or S-dC28 via porous balloon, the Scimed Dispatch Coronary Infusion Catheter. After a mean interval of 49 days, the animals were killed, and the target coronary segments were examined histologically. S-dC28 did not significantly inhibit neointimal formation. Fluorescein isothiocyanate (FITC)-labeled S-dC28 was present in the intima and media immediately after administration but was present mainly within the adventitia 3 hours after administration. S-dC28, when delivered by a Scimed Dispatch Coronary Infusion Catheter (Maple Grove, MN), did not significantly affect neointimal proliferation after balloon injury in a porcine coronary artery model.

Aerodynamic measurements of patients with Parkinson's disease

Patients with Parkinson's disease commonly complain of voice dysfunction. Most of these complaints can be attributed to the known muscular control disorders that occur with Parkinson's disease. However, the manifestations of Parkinson's disease muscular dysfunction on parameters of phonation such as airflow, laryngeal resistance, and subglottal pressure necessary to sustain phonation have not been reported. The purpose of this study was to examine the aerodynamic characteristics of flow, laryngeal resistance, and phonation pressure threshold in a heterogeneous population of patients with Parkinson's disease who had varying voice complaints and to compare the data to similar studies for human subjects who have no voice complaints. The studies used a noninvasive method of detecting flow and acoustic signal from the lips, oral cavity and nose during phonation and used an external flow interruption technique to estimate subglottal pressure and phonation threshold pressure. About one third of the patients could not produce phonation at regular and loud intensities that were comfortable for normal subjects. The mean subglottal pressure (SGP) of patients with Parkinson disease who could produce 3 levels of intensity comparable to normal subjects was significantly higher than the mean SGPs for normal subjects for the same intensities of vocal production. The mean flow rates measured from patients with Parkinson's disease at the same 3 intensities of phonation was not significantly greater than in normal subjects. This indicated that the mean laryngeal resistance calculated for patients with Parkinson's disease was notably and significantly greater than mean laryngeal resistance calculated for normal subjects at the same intensity levels. The mean vocal efficiency (VE) for normal subjects was not significantly different than the mean VE for patients with Parkinson's disease, because greater pressure was used to generate similar flow and acoustic energy. These findings correlate with the perception of patients with Parkinson's disease that they are working harder to produce phonation. The observation of notably greater laryngeal resistance and phonation threshold pressure in patients with Parkinson's disease suggests that further studies of the glottic aperture in patients with Parkinson' disease may be useful for understanding how this common motor disorder disturbs phonation.

Development of a prefabricated treatment plant for diluted pig wastewater

In order to develop a prefabricated treatment and reuse plant for diluted pig wastewater, an entrapped-mixed-microbial-cell (EMMC) process was evaluated for its process performance and economic analysis. At the hydraulic retention time (HRT) of 30 hrs (loading rate of 1.0 g TCOD/L/d) and intermittent aeration of 1 hr of aeration and 1 hr of non-aeration, it was found that, by using the pretreatment of the ammonium crystallization, both the medium and large carriers were able to reduce TCOD, SCOD, and T-N by 83.51, 84.11, and 95.10%, respectively. The EMMC unit and lime post-treatment followed by ammonium crystallization can reduce BOD5, TCOD, SCOD, TSS, T-N, and T-P, respectively by 99.22, 93.85, 92.67, 97.73, 96.43, and 97.27%. The treated wastewater, after disinfection, is able to meet the requirements of the standards issued by the USEPA for reuse of food crops. The economic analysis indicates that based on the process performance of the EMMC unit, a prefabricated wastewater treatment plant for 2000 pigs has comparable net present worth (NPW) comparing intermittent aerated biological systems and less operation and maintenance and land requirement than conventional biological processes for removal carbon and nitrogen. A farm operation of more than 2000 pigs meets the unit cost of US$4.91/pig/yr. This will minimize the problems pertaining to technical factors or considerations that heavily influence planning, construction and operation of a pig wastewater treatment system.

Binding of ATP to human DNA topoisomerase I resulting in an alteration of the conformation of the enzyme

It has been known for some time that ATP inhibits the DNA relaxation activity of human DNA topoisomerase I. However, the underlying mechanism of this inhibitory effect remains largely unknown. Using filter binding assays, the binding of human DNA topoisomerase I to DNA was decreased in the presence of ATP. This result suggests that the inhibition of DNA relaxation activity of human DNA topoisomerase I by ATP is at the binding step rather than at the nicking or resealing step. DNA topoisomerase I cleavage assay further supports this notion. ATP-agarose binding and UV cross-linking assays also demonstrate that ATP directly and specifically binds human DNA topoisomerase I. To address whether the ATP binding results in conformational changes in human DNA topoisomerase I, various proteases were employed for detecting potential protein conformational changes. Our results indicated that the proteolytic susceptibilities of trypsin and chymotrypsin were altered in the presence of ATP. The result suggests that the conformation of human DNA topoisomerase I was altered upon ATP binding. In addition, the binding between ATP and human DNA topoisomerase I was also reduced by increasing concentrations of DNA. Our data suggests that human DNA topoisomerase I exhibits at least two incompatible conformations. One conformation is in the form of a topoisomerase I-ATP complex, which inhibits DNA relaxation activity of human DNA topoisomerase I, and the other, a topoisomerase I-DNA complex, which exerts DNA relaxation activity. Our studies identify the role of ATP in the regulation of human DNA topoisomerase I and provide a substantial implication of how human DNA topoisomerase I compromises its versatile functions.

Neuroimages of disseminated neurotuberculosis: report of one case

We report a 38-year-old male patient with rare concurrent intracranial and intramedullary tuberculoma demonstrated by serial magnetic resonance image (MRI) and confirmed by a pathological study. The involvement of the middle cerebral artery is also shown by magnetic resonance angiography. These findings have a good correlation with the clinical features including cranial nerve involvement, stroke-like symptoms, and paraplegia.

Mechanisms of Surface Precipitation and Dissolution of Barite: A Morphology Approach

Barite (BaSO4) was synthesized at normal pressure and room temperature by mixing sodium sulfate and barium chloride solutions by gentle flow (0.5 ml/min.). The well-formed rectangular and rhombohedral crystals with smooth faces formed from solutions with low degrees of supersaturation. Most precipitates became single crystals. We employed the scanning electron microscope (SEM) to observe barite dissolution by chemical agent diethylenetrinitrilopentaacetic acid. Molecular modeling was used to assist the interpretation of the surface reaction. A kinetic model for the pit growth (initial dissolution) on the surface was evaluated. With SEM microanalysis of barite and kinetic model of pit growth, important surface phenomena and mechanisms of dissolution can be hypothesized. Surface phenomena and composition are very important in barite dissolution. Experimental results suggest that the initial dissolution starts on the two lowest energy surfaces: (001) and (210), and that the etch pits are elongated in one direction on the (210) surface and formed cavities on the (001) surface. The simulated surface structures by molecular modeling can aid the interpretation the pit formation on those selected surfaces. Copyright 1999 Academic Press.