Biomedical subjects

S G Chen

Publications and source records attributed to S G Chen.

At least 19 recordsLinked to original sources

PubMed2002

Insomnia associated with thalamic involvement in E200K Creutzfeldt-Jakob disease.

BACKGROUND: Insomnia with predominant thalamic involvement and minor cortical and cerebellar pathologic changes is not characteristic of familial Creutzfeldt-Jakob disease (CJD) but is a hallmark of fatal familial insomnia. OBJECTIVE: To report a 53-year-old woman with intractable insomnia as her initial symptom of disease. METHODS: The authors characterized clinical, pathologic, and molecular features of the disease using EEG, polysomnography, neurohistology, Western blotting, protein sequencing, and prion protein (PrP) gene (PRNP) analysis. RESULTS: The patient developed dysgraphia, dysarthria, bulimia, myoclonus, memory loss, visual hallucinations, and opisthotonos, as well as pyramidal, extrapyramidal, and cerebellar signs. Polysomnographic studies showed an absence of stages 3 and 4, and REM. She died 8 months after onset. On neuropathologic examination, there was major thalamic involvement characterized by neuronal loss, spongiform changes, and prominent gliosis. The inferior olivary nuclei exhibited chromatolysis, neuronal loss, and gliosis. Spongiform changes were mild in the neocortex and not evident in the cerebellum. PrP immunopositivity was present in these areas as well as in the thalamus. PRNP analysis showed the haplotype E200K-129M. Western blot analysis showed the presence of proteinase K (PK)-resistant PrP (PrP(sc)) with the nonglycosylated isoform of approximately 21 kd, corresponding in size to that of type 1 PrP(sc). N-terminal protein sequencing demonstrated PK cleavage sites at glycine (G) 82 and G78, as previously reported in CJD with the E200K-129 M haplotype. CONCLUSIONS: Insomnia may be a prominent early symptom in cases of CJD linked to the E200K-129M haplotype in which the thalamus is severely affected.

Amino Acid Sequence↗

PubMed2001

Absence of protease-resistant prion protein in the cerebrospinal fluid of Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease (CJD), believed to be caused by a protease-resistant isoform of prion protein (PrP(Sc)), usually manifests itself as a clinically distinctive age-related dementia because of its rapid progression, occasionally accompanied by cerebellar ataxia. Recently, a variant CJD (vCJD) has been described, which has prominent early psychiatric symptoms and an earlier age of death. Although cerebrospinal fluid (CSF) is part of the extracellular fluid of the central nervous system (CNS), the bulk of its proteins are derived from the plasma and there is increasing concern about possible transmission of prion disease by blood. As investigation of CSF has played a significant role in the diagnosis and management of several neurological diseases, it was decided to characterize PrP present in the CSF of CJD individuals. Significant variation was observed in the level of PrP in the CSF from both non-CJD and CJD (including vCJD) patients, and the detected PrP forms are protease-sensitive. Using a conformation-dependent immunoassay, it was further demonstrated that the PrP detected in the CSF from CJD patients was broadly similar in conformation to that found in non-CJD patients. Taken together, the results of this study fail to demonstrate any correlation between the presence of protease-resistant PrP isoform (PrP(Sc)) in the CSF and disease manifestation.

Creutzfeldt-Jakob Syndrome↗

PubMed2001

Induction of HO-1 and NOS in doppel-expressing mice devoid of PrP: implications for doppel function.

Ectopic expression of the doppel (Dpl) protein, a homologue of the prion protein (PrP), was recently associated with cerebellar Purkinje cell degeneration observed in two aging prion protein knock-out (Prnp(0/0)) mouse lines. We investigated the possible role of Dpl in oxidative metabolism. Two Prnp(0/0) mouse lines of similar genetic background were studied. One line expresses Dpl in the brain and displays Dpl-associated cerebellar abnormalities. The other has no elevated expression of Dpl and no cerebellar abnormalities. We observed a correlation between Dpl expression and the induction of both heme oxygenase 1 (HO-1) and nitric oxide synthase systems (nNOS and iNOS). These responses are suggestive of increased oxidative stress in the brains of the Dpl-expressing Prnp(0/0) mice. No induction was observed with Hsp-60, indicating a specific response by the HO/NOS system. We proposed that Dpl expression exacerbates oxidative damage that is antagonistic to the protective function of wild-type PrP.

Animals↗

PubMed2001

The management of white phosphorus burns.

Phosphorus burns are a rarely encountered chemical burn, typically occurring in battle, industrial accidents, or from fireworks. Death may result even with minimal burn areas. Early recognition of affected areas and adequate resuscitation is crucial. Amongst our 2765 admissions between 1984 and 1998, 326 patients had chemical burns. Seven admissions were the result of phosphorus burns. Our treatment protocol comprises 1% copper sulfate solution for neutralization and identification of phosphorus particles, copious normal saline irrigation, keeping wounds moist with saline-soaked thick pads even during transportation, prompt debridement of affected areas, porcine skin coverage or skin grafts for acute wound management, as well as intensive monitoring of electrolytes and cardiac function in our burns center. Intravenous calcium gluconate is mandatory for correction of hypocalcemia. Of the seven, one patient died from inhalation injury and the others were scheduled for sequential surgical procedures for functional and cosmetic recovery. Cooling affected areas with tap water or normal saline, prompt removal of phosphorus particles with mechanical debridement, intensive monitoring, and maintenance of electrolyte balance are critical steps in initial management. Fluid resuscitation can be adjusted according to urine output. Early excision and skin autografts summarize our phosphorus burn treatment protocol.

Adolescent↗

PubMed2001

Aberrant metal binding by prion protein in human prion disease.

Human prion diseases are characterized by the conversion of the normal prion protein (PrP(C)) into a pathogenic isomer (PrP(Sc)). Distinct PrP(Sc) conformers are associated with different subtypes of prion diseases. PrP(C) binds copper and has antioxidation activity. Changes in metal-ion occupancy can lead to significant decline of the antioxidation activity and changes in conformation of the protein. We studied the trace element status of brains from patients with sporadic Creutzfeldt-Jakob disease (sCJD). We found a decrease of up to 50% of copper and an increase in manganese of approximately 10-fold in the brain tissues from sCJD subjects. We have also studied the metal occupancy of PrP in sCJD patients. We observed striking elevation of manganese and, to a lesser extent, of zinc accompanied by significant reduction of copper bound to purified PrP in all sCJD variants, determined by the PrP genotype and PrP(Sc) type, combined. Both zinc and manganese were undetectable in PrP(C) preparations from controls. Copper and manganese changes were pronounced in sCJD subjects homozygous for methionine at codon 129 and carrying PrP(Sc) type-1. Anti-oxidation activity of purified PrP was dramatically reduced by up to 85% in the sCJD variants, and correlated with increased in oxidative stress markers in sCJD brains. These results suggest that altered metal-ion occupancy of PrP plays a pivotal role in the pathogenesis of prion diseases. Since the metal changes differed in each sCJD variants, they may contribute to the diversity of PrP(Sc) and disease phenotype in sCJD. Finally, this study also presented two potential approaches in the diagnosis of CJD; the significant increase in brain manganese makes it potentially detectable by MRI, and the binding of manganese by PrP in sCJD might represent a novel diagnostic marker.

Antioxidants↗

PubMed2001

Reconstruction of burn scar of the upper extremities with artificial skin.

The management of upper-extremity burn contractures is a major challenge for plastic surgeons. After approval by the Food and Drug Administration, artificial skin (Integra) has been available in Taiwan since 1997. From January of 1997 to July of 1999, the authors applied artificial skin to 13 severely burned patients for the reconstruction of their upper extremities, resulting in an increased range of motion in the upper-extremity joints and improved skin quality. An additional benefit was the rapid reepithelialization of the donor sites. There were no complications of infection throughout the therapeutic course, and the overall results were satisfactory. During the 2-year study, scar condition was monitored between 8 and 24 months, and a good appearance and pliable skin were obtained according to the Vancouver Scar Scale. According to this evaluation of Oriental skin turgor, normal pigmentation was restored about 6 months after the resurfacing procedure. For patients with severe burns in whom there is insufficient available skin for a full-thickness skin graft or another appropriate flap for scar revision, Integra is an alternative. The two major concerns in dealing with artificial skin are (1) a 10- to 14-day waiting period for maturation of the neo-dermis, necessitating a two-stage operation, and (2) prevention of infection with antibiotics and meticulous wound care.

Adolescent↗

PubMed2000

Expression and structural characterization of the recombinant human doppel protein.

The doppel protein (Dpl) is a newly recognized prion protein (PrP)-like molecule encoded by a novel gene locus, prnd, located on the same chromosome as the PrP gene. To study the structural features of Dpl, we have expressed recombinant human Dpl corresponding to the putative mature protein domain (residues 24-152) in Escherichia coli. The primary structure of the recombinant Dpl 24-152 was characterized using gel electrophoresis, N-terminal Edman sequencing, matrix-assisted laser desorption ionization mass spectrometry, and electrospray ionization mass spectrometry. Dpl 24-152 was shown to contain two disulfide bonds (Cys94-Cys145 and Cys108-Cys140). The secondary structure of Dpl was analyzed using far-UV circular dichroism spectroscopy. Dpl 24-152 was found to be an alpha-helical protein having a high helical content (40%). Dpl 24-152 exhibited characteristics of a thermodynamically stable protein that undergoes reversible and cooperative thermal denaturation. In addition, Dpl was found to be soluble and sensitive to proteinase K digestion. Therefore, Dpl 24-152 possesses biochemical properties similar to those of recombinant PrP. This study provides knowledge about the molecular features of human Dpl that will be useful in further investigation into its normal function and the role it may play in neurodegenerative diseases.

Amino Acid Sequence↗

PubMed2000

Genetic influence on the structural variations of the abnormal prion protein.

Prion diseases are characterized by the presence of the abnormal prion protein PrP(Sc), which is believed to be generated by the conversion of the alpha-helical structure that predominates in the normal PrP isoform into a beta-sheet structure resistant to proteinase K (PK). In human prion diseases, two major types of PrP(Sc), type 1 and 2, can be distinguished based on the difference in electrophoretic migration of the PK-resistant core fragment. In this study, protein sequencing was used to identify the PK cleavage sites of PrP(Sc) in 36 cases of prion diseases. We demonstrated two primary cleavage sites at residue 82 and residue 97 for type 1 and type 2 PrP(Sc), respectively, and numerous secondary cleavages distributed along the region spanning residues 74-102. Accordingly, we identify three regions in PrP(Sc): one N-terminal (residues 23-73) that is invariably PK-sensitive, one C-terminal (residues 103-231) that is invariably PK-resistant, and a third variable region (residues 74-102) where the site of the PK cleavage, likely reflecting the extent of the beta-sheet structure, varies mostly as a function of the PrP genotype at codon 129.

Brain Chemistry↗

PubMed2000

Cloning of amadoriase I isoenzyme from Aspergillus sp.: evidence of FAD covalently linked to Cys342.

Amadoriases are a novel class of FAD enzymes which catalyze the oxidative deglycation of glycated amino acids to yield corresponding amino acids, glucosone, and H(2)O(2). We previously reported the purification and characterization of two amadoriase isoenzymes from Aspergillus fumigatus and the molecular cloning of amadoriase II. To identify the primary structure of amadoriase I, we prepared a cDNA library from Aspergillus fumigatus and isolated a clone using a probe amplified by polymerase chain reaction with primers designed according to the partial amino acid sequences from peptide mapping. The primary structure of the enzyme deduced from the nucleotide sequence comprises 445 amino acid residues. The enzyme contains 1 mol of FAD as a cofactor, which is covalently linked to Cys342, as determined by mutagenesis analysis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and electrospray ionization-collisional-activated dissociation tandem mass spectrometry. Sequence alignment studies show that amadoriase I has 22% homology with monomeric sarcosine oxidase in which FAD is also linked to a homologous Cys residue. Amadoriases are of potential importance as tools for uncoupling hyperglycemia and glycation reactions that are thought to play a role in diabetic complications.

Amino Acid Oxidoreductases↗

PubMed2000

Aggregation and fibrillization of the recombinant human prion protein huPrP90-231.

According to the "protein-only" hypothesis, the critical step in the pathogenesis of prion diseases is the conformational transition between the normal (PrP(C)) and pathological (PrP(Sc)) isoforms of prion protein. To gain insight into the mechanism of this transition, we have characterized the biophysical properties of the recombinant protein corresponding to residues 90-231 of the human prion protein (huPrP90-231). Incubation of the protein under acidic conditions (pH 3.6-5) in the presence of 1 M guanidine-HCl resulted in a time-dependent transition from an alpha-helical conformation to a beta-sheet structure and oligomerization of huPrP90-231 into large molecular weight aggregates. No stable monomeric beta-sheet-rich folding intermediate of the protein could be detected in the present experiments. Kinetic analysis of the data indicates that the formation of beta-sheet structure and protein oligomerization likely occur concomitantly. The beta-sheet-rich oligomers were characterized by a markedly increased resistance to proteinase K digestion and a fibrillar morphology (i.e., they had the essential physicochemical properties of PrP(Sc)). Contrary to previous suggestions, the conversion of the recombinant prion protein into a PrP(Sc)-like form could be accomplished under nonreducing conditions, without the need to disrupt the disulfide bond. Experiments in urea indicate that, in addition to acidic pH, another critical factor controlling the transition of huPrP90-231 to an oligomeric beta-sheet structure is the presence of salt.

Chromatography, Gel↗

PubMed2000

Free vascularized fibular bone flap in the rat.

Free vascularized fibula bone flap has been widely used in reconstruction of the mandible, long segment defect, congenital pseudarthroses, and osteomyelitis. Such applications stirred an interest in basic studies of bone biology, bone healing process, and incorporation of recipient bone defect. An experimental free vascularized fibula rat model is presented here for such investigations. We performed 16 angiograms and anatomic dissections in eight rats for collecting data on fibular length, blood supply, and the caliber of significant vessels. The fibula was harvested with part of the flexor hallucis longus muscle with an average length of 28 mm. The pedicle can be taken in continuity with the popliteal vessels (average diameter of 0.8 mm and 0.9 mm of artery and vein, respectively, with an average pedicle length of 14 mm). This vascularized fibula bone was harvested and transferred to the groin area of the same rat and anastomosed to the saphenous vessels. Twelve transplantations were performed, with a 7-day flap survival rate of 100%. The free fibula vascularized bone flap in the rat is a reliable model for further investigations.

Animals↗

PubMed2000

Free microvascular transfer of the acromiotrapezius osteomuscular flap in rats.

The acromiotrapezius-scapular spine osteomuscular flap is a new osteomuscular research model for use in microvascular free tissue transfer in rats. We performed anatomical studies to collect data on muscle weight, dimension, vessel calibre and bone size in 20 flaps. This flap has a triangular shape with an average size of 38 x 39 x 32 mm and an average weight of 1.25 g; the scapular spine of 20 mm in average length can be harvested with the flap. The pedicle can be taken in continuity with the cervical trunk (average diameter of artery and vein were 0.5 mm and 0.6mm, respectively, with an average pedicle length of 12 mm). The flap was harvested and transferred to the groin area of the same rat and anastomosed to the superficial epigastric vessels. Fifteen transplantations were performed and the 7-day flap survival was 93.3%. The acromiotrapezius flap is believed to be a new and reliable osteomuscular model in the rat.

Animals↗

PubMed2000

The boomerang flap in managing injuries of the dorsum of the distal phalanx.

Finding an appropriate soft-tissue grafting material to close a wound located over the dorsum of a finger, especially the distal phalanx, can be a difficult task. The boomerang flap mobilized from the dorsum of the proximal phalanx of an adjacent digit can be useful when applied as an island pedicle skin flap. The vascular supply to the skin flap is derived from the retrograde perfusion of the dorsal digital artery. Mobilization and lengthening of the vascular pedicle are achieved by dividing the distal end of the dorsal metacarpal artery at the bifurcation and incorporating two adjacent dorsal digital arteries into one. The boomerang flap was used in seven individuals with injuries involving the dorsal aspect of the distal phalanx over the past year. Skin defects in all patients were combined with bone,joint, or tendon exposure. The authors found that the flap was reliable and technically simple to design and execute. This one-step procedure preserves the proper palmar digital artery to the fingertip and has proven valuable for the coverage of wide and distal defects because it has the advantages of an extended skin paddle and a lengthened vascular pedicle. When conventional local flaps are inadequate, the boomerang flap should be considered for its reliability and low associated morbidity.

Arteries↗

PubMed2000

PrP(Sc) typing by N-terminal sequencing and mass spectrometry.

The heterogeneity of the clinicopathological phenotype in human prion diseases is associated with the presence of the different forms of the abnormal prion protein, PrP(Sc). We have previously shown that PrP(Sc) in FFI and a subtype of familial CJD linked to the D178N mutation can be distinguished by their difference in gel mobility following proteinase K (PK) treatment. To further characterize the structural difference of PrP(Sc) in familial prion diseases, N-terminal sequencing and mass spectrometry were used to identify the protease cleavage sites in PrP(Sc) extracted from affected brains. We found that the main PK cleavage sites of PrP(Sc) are located at residue 97 in FFI, and residue 82 in both CJD178 and a GSS subtype linked to the P102L mutation. The differential accessibility to protease in the native PrP(Sc) suggests that PrP(Sc) exist as distinct conformers in different disease states.

Brain↗

PubMed1999

Tau gene mutation in familial progressive subcortical gliosis.

Familial forms of frontotemporal dementias are associated with mutations in the tau gene. A kindred affected by progressive subcortical gliosis (PSG), a rare form of presenile dementia, has genetic linkage to chromosome 17q21-22. This kindred (PSG-1) is included in the 'frontotemporal dementias and Parkinsonism linked to chromosome 17' group along with kindreds affected by apparently different forms of atypical dementias. Some of these kindreds have mutations in the tau gene. We report here that PSG-1 has a tau mutation at position +16 of the intron after exon 10. The mutation destabilizes a predicted stem-loop structure and leads to an over-representation of the soluble four-repeat tau isoforms, which assemble into wide, twisted, ribbon-like filaments and ultimately result in abundant neuronal and glial tau pathology. The mutations associated with PSG and other atypical dementias can be subdivided into three groups according to their tau gene locations and effects on tau. The existence of tau mutations with distinct pathogenetic mechanisms may explain the phenotypic heterogeneity of atypical dementias that previously led to their classification into separate disease entities.

Cerebral Cortex↗

PubMed1999

Prolonged perivascular use of verapamil or lidocaine decreases skin flap necrosis.

During this experiment the authors investigated whether prolonged local use of verapamil or lidocaine prevents vasoconstriction and establishes better blood supply to the rat epigastric skin flap, hence reducing the necrosis that occurs otherwise. Abdominal wall skin flaps of 45 Sprague-Dawley rats, based on a single pedicle of the femoral vessels, were elevated. A subcutaneous pocket for the microport valve was created, and the adjacent catheter tip was sewn next to the femoral vessels. In the control and the two treatment groups, 0.5 ml saline or vasodilator solution respectively was injected through the microport every 12 hours for 5 days. On postoperative day 5 there was no statistical difference between the flap surfaces in all groups. The area of flap necrosis was significantly lower in the verapamil- (p = 0.001) and the lidocaine-treated (p = 0.012) groups vs. the control group as determined by analysis of variance with Bonferroni's post hoc test. In conclusion, topical application of verapamil and lidocaine solutions for 5 postoperative days decreased flap marginal necrosis significantly. Prolonged injection of vasodilators in the vicinity of the vascular pedicle prevents vasospasm and improves blood supply to the flap.

Administration, Topical↗

PubMed1999

Patterns of flap loss related to arterial and venous insufficiency in the rat pedicled TRAM flap.

Vascular supply to the contralateral portion of the conventional transverse rectus abdominis musculocutaneous (TRAM) flap (zone IV) may become compromised, resulting in partial flap loss and requiring segmental excision. The etiology of this necrosis is not clear. This study determines skin necrosis patterns on a superiorly pedicled caudal TRAM flap during conditions of venous and arterial insufficiency, and determines whether cutaneous venous outflow can sustain a flap with venous insufficiency. Twenty-eight adult male Sprague-Dawley rats underwent superior pedicled TRAM flap elevation, and the zones were marked on the skin paddle. The animals were divided into four groups: control (group A, N = 6), arterial ligation (group B, N = 6), venous ligation (group C, N = 8), and venous ligation with cutaneous venous outflow (group D, N = 8). After 10 days, the skin paddle was photographed and the areas of necrotic skin were measured. Results showed that group B (selective arterial ligation) had 51.7 +/- 2.8% and 40.0 +/- 2.0% skin necrosis in zones I and II respectively. Zone I necrosis was significantly greater in group B compared with the control (p < 0.05). Group C (selective venous ligation) resulted in 73.8 +/- 16.4% and 93.8 +/- 33.4% skin necrosis in zones III and IV respectively. This necrosis was significantly greater compared with the control (p < 0.001). Group D rats' lateral skin necrosis compared significantly less with group C (p < 0.001). These results demonstrate that the patterns of flap necrosis in rat TRAM flaps with poor arterial inflow differ from those with venous stasis. Necrosis of the contralateral portion (zone IV) of human TRAM flaps may be related to problems with venous stasis; thus, a cutaneous venous outflow may prevent this problem.

Animals↗

PubMed1998

Different patterns of truncated prion protein fragments correlate with distinct phenotypes in P102L Gerstmann-Sträussler-Scheinker disease.

The clinicopathological phenotype of the Gerstmann-Sträussler-Scheinker disease (GSS) variant linked to the codon 102 mutation in the prion protein (PrP) gene (GSS P102L) shows a high heterogeneity. This variability also is observed in subjects with the same prion protein gene PRNP haplotype and is independent from the duration of the disease. Immunoblot analysis of brain homogenates from GSS P102L patients showed two major protease-resistant PrP fragments (PrP-res) with molecular masses of approximately 21 and 8 kDa, respectively. The 21-kDa fragment, similar to the PrP-res type 1 described in Creutzfeldt-Jakob disease, was found in five of the seven subjects and correlated with the presence of spongiform degeneration and "synaptic" pattern of PrP deposition whereas the 8-kDa fragment, similar to those described in other variants of GSS, was found in all subjects in brain regions showing PrP-positive multicentric amyloid deposits. These data further indicate that the neuropathology of prion diseases largely depends on the type of PrP-res fragment that forms in vivo. Because the formation of PrP-res fragments of 7-8 kDa with ragged N and C termini is not a feature of Creutzfeldt-Jakob disease or fatal familial insomnia but appears to be shared by most GSS subtypes, it may represent a molecular marker for this disorder.

Adult↗