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Biomedical subjects

C C Yang

Publications and source records attributed to C C Yang.

At least 19 recordsLinked to original sources
PubMed1992

Nonidentical DNA-binding sites of endonuclease NaeI recognize different families of sequences flanking the recognition site.

NaeI endonuclease uses a two-site binding mechanism to cleave substrate DNA: reaction-rate studies imply that occupancy of the second DNA site causes an allosteric change in the protein that enables DNA cleavage at the first site [Conrad, M., & Topal, M. D. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 9707-9711]. Measurements of relative binding affinities for 14-base-pair DNA fragments containing the NaeI recognition sequence GCCGGC and various flanking sequences showed that the two DNA-binding sites are not identical. G.C-rich flanking sequences were preferred by the activator binding site, whereas A.T-rich flanking sequences were preferred by the substrate binding site: GGGTGCCGGCAGGG was preferred 8-fold more by the activator site but 14-fold less by the substrate site than TTTCGCCGGCGTTT. Substitution of pyrimidine or 7-deazapurine for purine immediately 3' to GCCGGC reduced DNA affinity for only the activator site by up to 26-fold, implying that the activator DNA-binding site requires N-7 base contacts immediately flanking GCCGGC. The implications of nonidentical DNA-binding sites, one of which binds a specific DNA site to allosterically activate the other, are discussed.

Allosteric Regulation↗
PubMed1992

Inhibition of lymphocyte proliferation by liver arginase.

The activities of thymidine kinase and uridine kinase (enzymes for pyrimidine salvage pathway) in phytohemagglutinin (PHA)--prestimulated lymphocytes were inhibited by arginase in a similar pattern to the inhibition on thymidine incorporation. Further study revealed that arginase did not directly affect the activities of these enzymes in the cell-free system. Thymidine kinase and uridine kinase activities of PHA-prestimulated lymphocytes were inhibited by arginase making their activities as low as that cultured in arginine-free RPMI-1640 medium. These results suggest that arginine-depletion in the culture medium is the primary mode of action of arginase on the inhibition of mitogen-stimulated lymphocyte proliferation.

Animals↗
PubMed1992

Immunochemical properties of Naja naja atra (Taiwan cobra) phospholipase A2 using polyclonal and monoclonal antibodies.

The immuno-chemical properties of Naja naja atra phospholipase A2 (NNA-PLA2) were studied by using the chemically modified PLA2 derivatives and the PLA2 homologues toward anti-NNA-PLA2 polyclonal and monoclonal antibodies. Anti-NNA-PLA2 polyclonal antibodies inhibited the enzymatic activity of NNA-PLA2 and Hemachatus haemachatus DE-I by 87% and 68%, respectively. However, the enzymatic activities of Naja nigricollis CMS-9 and notexin were not significantly affected by the polyclonal antibodies. Competitive enzyme immunoassay revealed that the affinity of NNA-PLA2 for polyclonal antibodies was 330-fold higher than that of Hemachatus haemachatus DE-I. Naja nigricollis CMS-9 and notexin failed to inhibit the binding of NNA-PLA2 to polyclonal antibodies. This implies that the epitope(s) of NNA-PLA2 might comprise some substituted residues in the sequence of PLA2 homologues. Three monoclonal antibodies against NNA-PLA2 were prepared by a hybridoma technique. Two of these monoclonal antibodies inhibited the enzymatic activity of NNA-PLA2, but the other did not. Removal of the N-terminal octapeptide affected the epitope interacting with these monoclonal antibodies. Selective modification of tyrosine residues at positions 3 and 63 or lysine residues at positions 6 and 65 induced a substantial reduction in affinity of NNA-PLA2 for polyclonal and monoclonal antibodies. The three monoclonal antibodies failed to recognize PLA2 homologues. The comparison of the sequence of NNA-PLA2 to those of PLA2 homologues showed that most of the amino acid substitutions of PLA2 homologues occur in the spatially nearby region of the N-terminal region and residues at positions 63 and 65.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Native American mitochondrial DNA analysis indicates that the Amerind and the Nadene populations were founded by two independent migrations.

Mitochondrial DNAs (mtDNAs) from 167 American Indians including 87 Amerind-speakers (Amerinds) and 80 Nadene-speakers (Nadene) were surveyed for sequence variation by detailed restriction analysis. All Native American mtDNAs clustered into one of four distinct lineages, defined by the restriction site variants: HincII site loss at np 13,259, AluI site loss at np 5,176, 9-base pair (9-bp) COII-tRNA(Lys) intergenic deletion and HaeIII site gain at np 663. The HincII np 13,259 and AluI np 5,176 lineages were observed exclusively in Amerinds and were shared by all such tribal groups analyzed, thus demonstrating that North, Central and South American Amerinds originated from a common ancestral genetic stock. The 9-bp deletion and HaeIII np 663 lineages were found in both the Amerinds and Nadene but the Nadene HaeIII np 663 lineage had a unique sublineage defined by an RsaI site loss at np 16,329. The amount of sequence variation accumulated in the Amerind HincII np 13,259 and AluI np 5,176 lineages and that in the Amerind portion of the HaeIII np 663 lineage all gave divergence times in the order of 20,000 years before present. The divergence time for the Nadene portion of the HaeIII np 663 lineage was about 6,000-10,000 years. Hence, the ancestral Nadene migrated from Asia independently and considerably more recently than the progenitors of the Amerinds. The divergence times of both the Amerind and Nadene branches of the COII-tRNA(Lys) deletion lineage were intermediate between the Amerind and Nadene specific lineages, raising the possibility of a third source of mtDNA in American Indians.

Asian People↗
PubMed1992

Mitochondrial DNA complex I and III mutations associated with Leber's hereditary optic neuropathy.

Four new missense mutations have been identified through restriction analysis and sequencing of the mitochondrial DNAs (mtDNA) from Leber's hereditary optic neuropathy (LHON) patients who lacked the previously identified 11778 mutation. Each altered a conserved amino acid and correlated with the LHON phenotype in population and phylogenetic analyses. The nucleotide pair (np) 13708 mutation (G to A, ND5 gene) changed an alanine to a threonine and was found in 6/25 (24%) of non-11778 LHON pedigrees and in 5.0% of controls, the np 15257 mutation (G to A, cytochrome b gene) changed an aspartate to an asparagine and was found in 4 of the 13708-positive pedigrees and 0.3% of controls, the np 15812 mutation (G to A, cytochrome b gene) changed a valine to a methionine and was detected in two of the 15257-positive pedigrees and 0.1% of controls and the np 5244 mutation (G to A, ND2 gene) changed a glycine to a serine and was found in one of the 15812-positive patients and none of 2103 controls. The 15257 mutation altered a highly conserved amino acid in an extramembrane domain of cytochrome b that is associated with the ligation of the low potential b566 heme and the 5244 mutation altered a strongly evolutionarily conserved region of the ND2 polypeptide. The 13708 and 15812 mutations changed moderately conserved amino acids. Haplotype and phylogenetic analysis of the four np 15257 mtDNAs revealed that all harbored the same rare Caucasian haplotype and that the np 13708, np 15257, np 15812 and np 5244 mutations were added sequentially along this mtDNA lineage. Since the percentage of sighted controls decreases as these mutations accumulate, it appears that they interact synergistically, each increasing the probability of blindness. The involvement of both mitochondrial complex I (np 5244, 11778, 13708) and complex III (np 15257, 15812) mutations in LHON indicates that the clinical manifestations of this disease are the product of an overall decrease in mitochondrial energy production rather than a defect in a specific mitochondrial enzyme.

Base Sequence↗
PubMed1992

The adipofascial turnover flap for elbow coverage.

Closure of soft tissue defects in the vicinity of the elbow with exposed bone or joint remains a difficult problem. Local adipofascial turnover flaps covered by a skin graft were successfully used to reconstruct two elbow defects. The flap's base was placed 1.5 to 2.0 cm from the wound edge. The flap-to-base area ratio, which is an important index of flap survival, in addition to the traditional length-to-width ratio were 3.25 and 3.3, respectively. The undermined skin of the flap donor site was preserved rather than discarded as in the conventional deepithelialized turnover flap. The primary benefits of this flap are that it is an easy and rapid one-stage procedure, it requires limited immobilization of the involved joint, and it leaves an inconspicuous donor site scar. The motion of the elbow joint was not impeded because the adiposal component of the flap faced the exposed vital structures. The padding is not thick, but is sufficient to cover and protect the elbow. The flap is especially indicated for small- to medium-sized, complicated elbow wounds.

Accidents, Traffic↗
PubMed1992

[Dipyridamole Tc-99m MIBI myocardial perfusion scintigraphy in patients with post-infarction chest pain symptom].

To evaluate the efficacy of stress Tc-99m MIBI myocardial perfusion imaging using intravenous dipyridamole in detecting coronary artery disease (CAD) and to determine if chest pain symptom is a proper index for detection of myocardial ischemia in post-infarction patients, we observed 73 cases (65 men, 8 women, 38-79 years old) between Sept. 1990 and May 1992. All patients were suffered from old myocardial infarction (MI) evidenced by history and ECG and were divided into two groups: group I involving 41 patients with post-infarction chest pain symptom and group II including 32 patients without post-infarction chest pain symptom. Among them, 19 (group IA) of group I and 11 (group IIA) of group II received coronary arteriography (CAG) for comparison. Of the 41 group I post-infarction chest pain patients, 17 suffered from old anterior or antero-septal wall (AW) MI, 21 from old inferior wall (IW) MI, 1 from old lateral wall (LW) MI and 2 from combined old AW and IW (AIW) MI by ECG. All 17 patients with AWMI suffered from AW perfusion defect (7 were MI, 10 were MI with ischemia) but 7 of them from multivessel disease (MVD) by Tc-99m MIBI. All 21 patients with IWMI suffered from IW perfusion defect (9 were MI, 12 were MI with ischemia) but 13 of them from MVD by Tc-99m MIBI. Of the patient with LWMI and 2 patients with AIWMI suffered from MVD by Tc-99m MIBI. Of the 32 group II post-infarction patients without chest pain symptom, 12 suffered from old AWMI, 14 from old IWMI, 2 from old LWMI, 3 from AIWMI and 1 from ALWMI by ECG. Of the 12 patients with AWMI, 11 suffered from AW perfusion defect (6 were MI, 5 were MI with ischemia) but 1 of them from MVD by TC-99m MIBI. All 14 patients with IWMI suffered from IW perfusion defect (12 were MI, 2 were MI with ischemia) but 4 of them from MVD by Tc-99m MIBI. Of the 2 patients with LWMI suffered from LW infarction by Tc-99m MIBI. Of the 3 patients with AIWMI and 1 with ALWMI suffered from MVD by Tc-99m MIBI. Of the 11 patients in group IA and 5 patients in group IIA with AWMI, CAG revealed the incidence of infarct-related recanalization of LAD was 9/11(82%) and 4/5(80%) respectively and the respective incidence of MVD was 6/11(55%) and 0/5(0%).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

A mitochondrial DNA variant, identified in Leber hereditary optic neuropathy patients, which extends the amino acid sequence of cytochrome c oxidase subunit I.

A G-to-A transition at nucleotide pair (np) 7444 in the mtDNA was found to correlate with Leber hereditary optic neuropathy (LHON). The mutation eliminates the termination codon of the cytochrome c oxidase subunit I (COI) gene, extending the COI polypeptide by three amino acids. The mutation was discovered as an XbaI restriction-endonuclease-site loss present in 2 (9.1%) of 22 LHON patients who lacked the np 11778 LHON mutation and in 6 (1.1%) of 545 unaffected controls. The mutant polypeptide has an altered mobility on SDS-PAGE, suggesting a structural alteration, and the cytochrome c oxidase enzyme activity of patient lymphocytes is reduced approximately 40% relative to that in controls. These data suggest that the np 7444 mutation results in partial respiratory deficiency and thus contributes to the onset of LHON.

Amino Acid Sequence↗
PubMed1992

Intravenous dipyridamole technetium-99m MMI myocardial perfusion scintigraphy for detection of coronary artery disease.

To evaluate the efficacy of stress technetium-99m MMI (N-2-methoxy-2-methyl propyl isonitrile) myocardial perfusion scintigraphy (Tc-99m MMI) using intravenous dipyridamole for detection of coronary artery disease (CAD), we collected 66 cases (53 men, 13 women, aged 40-79 years old) between Sept. 1990 and Oct. 1991. The cases were divided into two groups: group I involving 44 patients received coronary arteriography (CAG) examination without previous percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass graft (CABG); group II embracing 22 patients received no CAG examination but all were suffering from old myocardial infarction (MI) evidenced by history and electrocardiography (ECG). All cases underwent Tc-99m MMI planar and single photon emission computed tomography (SPECT) both on intravenous dipyridamole stress and separate day rest tests. Of the 44 group I patients receiving both Tc-99m MMI and CAG, 35 (79.5%) were positive and 7 (16%) were negative by both tests and another 2 (4.5%) were positive by CAG only. Of those positive by both tests, 21 (60%) suffered from identical coronary arterial involvement, including 13 one-vessel disease, 5 double-vessel disease and 3 triple-vessel disease. Of group II patients, 14 suffered from old inferior wall (IW) MI, 6 from old anterior or anteroseptal wall (AW) MI, 1 from old lateral wall (LW) MI and another 1 from combined old anterior and lateral wall (ALW) MI by ECG. Of the 14 patients with IWMI by ECG, all suffered from right coronary artery (RCA) disease but 7 (50%) of them from multivessel disease (MVD) by Tc-99m MMI. 5 of the 6 patients with AWMI by ECG suffered from left anterior descending coronary artery (LAD) disease, but 3 of them from MVD by Tc-99m MMI. Both patients with LWMI and ALWMI by ECG suffered from triple-vessel disease by Tc-99m MMI. The sensitivity of Tc-99m MMI in detecting CAD in group I was 95%, the specificity was 100%. The sensitivity for detection of individual coronary artery disease in LAD, left circumflex coronary artery (LCX) and RCA was 96%, 45% and 89% in this order and the respective specificity was 94%, 100% and 88%. In group II the sensitivity was 95%. The overall sensitivity of intravenous dipyridamole Tc-99m MMI for detection of CAD in groups I and II was 95%; specificity was 100% and accuracy was 95%. In conclusion, stress Tc-99m MMI using intravenous dipyridamole is a valuable method for evaluation and detection of CAD.

Adult↗
PubMed1992

[The detection of an early glomerular filtration rate change of spinal cord injury patients by renal scan].

A Technetium-99m DTPA computer-assisted renal scan and CCR studies were performed on 35 spinal cord injured patients who had been hospitalized in the rehabilitation ward of Kaohsiung Medical College Hospital for less than 6 months during the period of August 1988 to March 1990. For each patient, the glomerular filtration rate (GFR), the effective renal plasma flow (ERPF), and the filtration fraction (FF) were obtained by a renal scan. CCR was measured by conventional procedure and was corrected with body length, body weight and body surface. Least square fit linear regression analysis revealed the best correlation between GFR and CCR. Based on GFR values the renal function was classified into four grades from normal to severe damage and the change of renal function was analyzed using four corresponding factors. The results showed that the ratio of GFR impairment in early spinal injury is 48.6% (mostly mild impairment). There are not significant differences between levels of lesion, severity of injury or successfulness of bladder training by Fisher's exact test. Renal function deteriorated proportionally with age and most of those patients having the worst renal function belonged to an old age group. Thus age is also one of the major factors in renal function impairment. Single kidney function impairment was noted in two patients whose total GFR or CCR were in the normal range, which implied the characteristic of early detection of renal dysfunction by renal scan.

Adult↗
PubMed1992

[Detection of open processus vaginalis by radionuclide scintigraphy].

The processus vaginalis usually obliterates spontaneously from the inguinal ring to the scrotum after the descent of testis has been completed. Under certain conditions, it can be reopened. In present reports, 3 cases with open processus vaginalis were described. The first one is a case of uremia due to chronic glomerulonephritis, suddenly suffering from right scrotal and penile swelling, following continuous ambulatory peritoneal dialysis (CAPD) for 4 months. The second one is a case of uremia, due to unknown etiology, suddenly developing right scrotal and penile swelling after 5 months of CAPD. The third one is a case with uremia of uncertain etiology, suffering from bilateral scrotal and penile swelling in the first month of CAPD, following a wrong procedure, by adding some 200cc more dialysate. Three mCi of Tc-99m phytate or pertechnetate, added into the bag of peritoneal dialysate for each patient, allowed us to visualize a peritoneo-vaginal communication. After surgery one of the patients who had been given followup treatment by radionuclide scintigraphy showed no passage of the labeled infusion in the swollen side of the scrotum. A previous postmortem study of adults dying without clinically apparent inguinal hernia demonstrated an open processus vaginalis in 20% of groins examined. Thus, this study suggests that in placement of catheters for CAPD or ventriculo-peritoneal shunt, Tc-99m pertechnetate/phytate may be given through intraperitoneal injection to detect a subclinical open processus vaginalis.

Adult↗
PubMed1992

[Treatment of large skin defect with 6:1 meshed skin autograft and 1.5:1 meshed fresh porcine skin overlay].

The use of expanded mesh skin graft from limited donor sites has greatly increased wound coverage. However, grafts with an expansion size of 6:1 or greater often heal slowly or are lost because of local infection. Three patients with large skin defects in lower extremity have been treated with 6:1 mesh autograft overlayed by 1.5:1 fresh porcine skin mesh graft. Epithelium grown from both grafts could be found. The autografts continuously expanded under the xenografts. The outer xenografts gradually separated and desquamated, on an average, in 14 days. This technique enables resurfacing of a large area of skin defect from smaller donor sites.

Aged↗
PubMed1992

Microsurgical replantation of avulsed scalp--two cases report.

Two female patients with scalp avulsion were treated successfully by microsurgical replantation. The first patient suffered an avulsion of the right half of scalp and which survived fully after replantation. The second patient suffered avulsion of the entire scalp as well as the forehead skin and nape of the neck. Almost all of the avulsed part survived except partial skin loss in the posterior neck and left occipital area. Only one temporal artery and one vein was anastomosed in each case. Near normal hair growth recurred in both cases.

Adult↗
PubMed1992

Reconstruction of children's scalp defects with the Orticochea flap.

From January 1985 to February 1990, 4 children with scalp defects were selected for use of the Orticochea flap technique for reconstruction. The ages ranged from 15 months (the youngest in the literature) to 7 years. The defects ranged from 6 x 7 to 11 x 13 cm. Three defects were traumatic and 1 was acute lymphocytic leukemia septic emboli in cause. All these children got satisfactory results with follow-up periods ranging from 5 months to more than 5 years. With these preliminary experiences, we have verified that the Orticochea flap scalp reconstruction surgery described 20 years ago can be performed safely even in children, especially when tissue expansion is not suitable or readily available.

Child↗
PubMed1991

Dissociation of lethal toxicity and enzymic activity of notexin from Notechis scutatus scutatus (Australian-tiger-snake) venom by modification of tyrosine residues.

Notexin from Notechis scutatus scutatus snake venom was subjected to tyrosine modification with p-nitrobenzenesulphonyl fluoride (NBSF), and four modified derivatives were separated by h.p.l.c. The results of amino acid analysis and sequence determination revealed that only Tyr-7, Tyr-70 and Tyr-77 were modified in notexin. Modification of Tyr-7 resulted in decreases in lethal toxicity and enzymic activity by 70.2% and 22.7% respectively. Conversely, modification of Tyr-77 caused a 1.8-fold increase in enzymic activity, in contrast with the loss of 52.5% of lethality. A drastic decrease in lethal toxicity was observed when both Tyr-7 and Tyr-70 were modified, whereas the enzymic activity decreased by only 35.8%. Likewise, the derivative in which Tyr-7 and Tyr-77 were modified retained 44.4% of enzymic activity, but showed a marked decrease in lethal toxicity. It is obvious that modification of tyrosine residues causes a decrease in lethal toxicity of notexin, which does not directly correlate with the change in enzymic activity. On the other hand, the antigenicity of NBS derivatives remained unchanged. The modified derivatives retained their affinity for Ca2+, indicating that the modified tyrosine residues did not participate in Ca2+ binding. These results indicate that modification of tyrosine residues can differentially influence the enzymic activity and lethal toxicity of notexin, and suggest that notexin might possess two functional sites, one being responsible for the catalytic activity and the other associated with its lethal effect.

Amino Acid Sequence↗
PubMed1991

Adipofascial turn-over flap for reconstruction of the dorsum of the foot.

Local adipofascial turn-over flaps with skin grafts were successfully used to reconstruct complicated skin defects over the dorsum of the foot in 7 patients. The blood supply of the flap comes from perforators in the base and from the surrounding subcutaneous and fascial plexuses. A new concept of base-to-flap area ratio is proposed to predict the survival of the turn-over flaps in addition to the conventional base-to-length ratio. This appears to be a valuable technique for difficult wounds of the dorsum of the foot.

Adult↗
PubMed1991

Venom constituents of Notechis scutatus scutatus (Australian tiger snake) from differing geographic regions.

Column chromatography and polyacrylamide gel electrophoresis of Notechis scutatus scutatus venom showed that the venoms from different geographical locations had variations in their constituents. The venom collected from South Australia region contained both notexin and notechis II-5. The relative quantity of notechis II-5 was about three times that of notexin. On the other hand, the venom from Victoria region contained large amounts of notexin, but lacked notechis II-5. Instead, an unknown nontoxic protein, designated as notechis II-5b, exhibiting weak phospholipase A2 activity appeared in the position of notechis II-5 elution. This protein had an N-terminal sequence of N-L-I-Q-L-S-N-M-I-K-C-A-I-P-G-S-Q-P-L-F, sharing 45% homology with notexin and notechis II-5 and 60% homology with notechis II-1. The antibodies raised against Trp-modified notexin inhibited the enzymatic activities of notexin and notechis II-5 by 88 and 68%, respectively. However, the affinity of notexin for the antibodies was nine-fold greater than that of notechis II-5. This result is contrary to the previous finding (Mollier et al., FEBS Lett. 250, 479-482, 1989) in which notexin and notechis II-5 had similar binding affinities for antibodies raised against native notexin. This observation suggests that the antibodies prepared in this study could differentiate between isoforms of notexin.

Amino Acid Sequence↗