PubMed Health⌕ Search

Biomedical subjects

Yan Liang

Publications and source records attributed to Yan Liang.

At least 37 records · Page 2Linked to original sources
PubMed2006

[Fifteen short tandem repeat polymorphisms in Han race of North China].

OBJECTIVE: To research on the genetic polymorphism distributions of 15 short tandem repeat (STR) loci in Han race of North China and the genetic data of population genetics. METHODS: The capillary electrophoresis and five-color fluorescent multi-amplifying were applied to detect the genotypes of 15 STR loci in 597 unrelated Chinese Han individuals. RESULTS: No significant deviation from the Hardy-Weinberg Equilibrium was observed. High polymorphism was detected in the loci. Statistical analysis was carried out to obtain some parameters of forensic medicine. The heterozygosity of 15 loci was above 0.62. The values of discrimination power (DP) at 15 STRs ranged from 0.802 to 0.967. The values of excluding probability of paternity (EP) ranged from 0.320 to 0.697. The values of probability matching (Pm) ranged from 0.033 to 0.198. The fifteen loci showed an accumulated total discrimination power (TDP) more than 0.999999, a cumulative excluding probability of paternity (CEP) as 0.99999571, and total probability matching to be 8.93 x 10(-18). CONCLUSION: The data indicated that detecting combined 15 STRs is sensitive and reliable, and can be used to forensic and individual identification cases in Chinese group.

Asian People↗
PubMed2006

[Study on Meta analysis regarding the acceptability of medical abortion compared with surgical abortion].

OBJECTIVE: To analyze and evaluate the acceptability of mifepristone compatible with misoprostone versus conventional surgical abortion among women under unwanted early pregnancy, so as to help the unexpected pregnant women to choose the satisfactory abortion, and to provide the evidence for clinicians to make a proper clinical decision. METHODS: Six medical databases were searched, including MEDLINE, EMBASE, Cochrane library, CBMdisc, CNKI and VIP, together with twelve journals hand-searched, and references of included studies additionally searched. Two qualified reviewers reviewed the original articles, evaluating qualities of articles, and extracting data independently. After heterogeneity test, the data was pooled using Revman software if capable, or descriptive analysis was applied. RESULTS: In total, nine original clinical controlled trials were included, containing 3565 cases. Before abortion, more unwanted pregnant women chose the medical abortion because they believed medical abortion was less painful than surgical abortion (OR = 466.51, 95% CI: 91.37 - 2381.88), but medical abortion was less time-consuming than surgical abortion (OR = 0.02, 95% CI: 0.01 - 0.06). After abortion, satisfaction with medical abortion was similar to that with surgical abortion, with insignificant difference (P = 0.89). However, second choice and recommendation rates of medical abortion were much higher than those of surgical abortion with OR and 95% CI as 2.72, 2.13 - 3.47 and 4.19, 2.16 - 11.16, respectively. CONCLUSIONS: Medical abortion was less painful than surgical abortion and the rate of second choice and recommendation to others were all also higher than those of surgical abortion. However, the process of medical abortion was not as quick as surgical abortion but the satifacation of both methods seemed similar. Therefore, the two artificial abortion methods were not recommended to replace each other at the present time.

Abortifacient Agents↗
PubMed2006

[The significance of soluble vascular cell adhesion molecule-1 and its relationship with tumor necrosis factor-alpha and interferon-gamma in patients with pulmonary tuberculosis].

OBJECTIVE: To explore the clinical significance and the possible role of soluble vascular cell adhesion molecule-1 (sVCAM-1) in the pathogenesis of pulmonary tuberculosis in terms of its relationship with tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). METHODS: Blood samples were taken from 35 patients with pulmonary tuberculosis before therapy, including military pulmonary tuberculosis (type II) in 15 cases and secondary pulmonary tuberculosis (type III) in 20 cases. After 2 month therapy, samples were taken from 20 cases with type III tuberculosis again. Twenty healthy volunteers served as controls. Serum concentrations of sVCAM-1 and IFN-gamma were detected by ELISA method and TNF-alpha by radioimmunoassay. RESULTS: The serum concentrations of sVCAM-1, TNF-alpha and IFN-gamma in patients with pulmonary tuberculosis were (822 +/- 206) microg/L, (1.5 +/- 1.1) microg/L, and (23 +/- 13) microg/L, respectively; all were significantly higher than those in healthy controls [(428 +/- 73), (0.2 +/- 0.1), and (16 +/- 10) microg/L; P < 0. 01, P < 0.01, and P < 0.05, respectively]. In the subgroup of patients with military pulmonary tuberculosis, the concentrations of sVCAM-1 and TNF-alpha were (897 +/- 144) microg/L and (2.0 +/- 1.4) microg/L, respectively, which were higher than those in patients with secondary pulmonary tuberculosis [(765 +/- 230) microg/L and (1.2 +/- 0.6) microg/L, respectively, both P < 0.05]. The difference in the concentrations of IFN-gamma between type II and type III was not significant (P = 0.222). The levels of sVCAM-1 and TNF-alpha were lower after therapy [(532 +/- 103) and (0.8 +/- 0.8) microg/L, respectively] than those before therapy (both P < 0.01), but the levels of sVCAM-1 and TNF-alpha after therapy were still higher than those in healthy controls (both P < 0.01). The level of IFN-gamma was higher after therapy than that before therapy (P < 0.05), and the difference between the level after therapy and that of the controls was significant. There were significant correlations between VCAM-1 and TNF-alpha and IFN-gamma respectively in untreated pulmonary tuberculosis (r = 0.669 and 0.560, respectively both P < 0.01). CONCLUSION: The measurement of serum sVCAM-1 is useful to evaluate the severity of disease and to monitor activity of the disease during chemotherapy.

Adolescent↗
PubMed2006

[Analysis of X ba I polymorphism of FVIII gene and its application on prenatal diagnosis for hemophilia A].

OBJECTIVE: To establish the linkage methods of X ba I polymorphisms specific for FVIII gene intron 22, and to find a rapid and simple system for haemophilia A (HA) carrier detection and prenatal diagnosis. METHODS: A long PCR to amplify FVIII gene intron 22 followed by X ba I digestion was used to assay the gene rate and heterozygosity rate of 206 unrelated people. Detection of intron 22 inversion by long distance PCR (LD-PCR) and XbaI, BclI, Hind III, DXS52, STR polymorphism within intron 13 and 22 by hereditary linkage analysis were assays in 20 HA pedigrees. RESULTS: The gene rate and polymorphism information contents of 206 people were 0.5475 and 0.4955 respectively, 7 of 20 HA families were diagnosed as intron 22 inversion, 6 of 13 non-inversion HA families were diagnosed by X ba I linkage analysis, 8 of 13 non-inversion HA families were diagnosed by two or more linkage analysis. CONCLUSIONS: The improved X ba I linkage analysis is a specific and useful molecular diagnosis marker. LD-PCR and five-linkage analysis can be used in prenatal HA gene diagnosis.

Factor VIII↗
PubMed2006

[Research development of chemistry and bioactive activity of plant peptides].

As the technologies of separation, purification and determination develop rapidly, more and more peptide compounds, which have special bioactive and medical value, have been separated from natural plants, such as oligopeptides and cyclopeptides. The chemical structures and function of these plant peptides have been researched profoundly. This paper mainly reviews the composition, structure, bioactive function and medicine value of representative plant peptides in recent years, and can give some references about research and application of plant bioactive peptides.

Animals↗
PubMed2005

Simple, sensitive and rapid LC-ESI-MS method for the quantitation of lafutidine in human plasma--application to pharmacokinetic studies.

A sensitive and specific liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed and validated for the identification and quantification of lafutidine in human plasma. Lafutidine and internal standard were isolated from plasma samples by liquid-liquid extraction with diethyl ether. The chromatographic separation was accomplished on a stainless-steel column (C18 Shim-pack 5 microm 150 mm x 2.0 mm i.d. Shimadzu) at a flow rate of 0.2 ml/min by a gradient elution. Detection was performed on a single quadrupole mass spectrometer by selected ion monitoring (SIM) mode via electrospray ionization (ESI) source. The method was proved to be sensitive and specific by testing six different plasma batches. Linearity was established for the range of concentrations 1.0-400.0 ng/ml with a coefficient of determination (r) of 0.9998 and good back-calculated accuracy and precision. The intra- and inter-day precision (R.S.D.%) was lower than 10% and accuracy ranged from 85 to 115%. The lower limit of quantification was identifiable and reproducible at 0.5 ng/ml with 0.2 ml plasma. The proposed method enables the unambiguous identification and quantification of lafutidine for pharmacokinetic, bioavailability or bioequivalence studies.

Acetamides↗
PubMed2005

Simultaneous determination of berberine and palmatine in rat plasma by HPLC-ESI-MS after oral administration of traditional Chinese medicinal preparation Huang-Lian-Jie-Du decoction and the pharmacokinetic application of the method.

A sensitive and specific liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method has been developed and validated for the identification and quantification of berberine and palmatine in rat plasma. After the addition of the internal standard (IS) and alkalization with 0.5M sodium hydroxide solution, plasma samples were extracted by ethyl ether and separated by HPLC on a Shim-pack ODS (4.6 microm, 150 mm x 2.0mm i.d.) column using a mobile phase composed of A (0.08% formic acid and 2 mmol/l ammonium acetate) and B (acetonitrile) with linear gradient elution. Analysis was performed on a Shimadzu LC/MS-2,010A in selected ion monitoring (SIM) mode with a positive electrospray ionization (ESI) interface. [M](+)=336 for berberine; 352 for palmatine and [M+H](+)=340 for IS were selected as detecting ions, respectively. The method was validated over the concentration range of 0.31-20 ng/ml for berberine and palmatine. Inter- and intra-CV precision (R.S.D.%) were all within 15% and accuracy (%bias) ranged from -5 to 5%. The lower limits of quantification were 0.31 ng/ml for both analytes. The extraction recovery was on average 68.6% for berberine, 64.2% for palmatine. The validated method was used to study the pharmacokinetic profile of berberine and palmatine in rat plasma after oral administration of Huang-Lian-Jie-Du decoction.

Animals↗
PubMed2005

Localization of NGF and TrkA at mitotic apparatus in human glioma cell line U251.

It has previously been implicated that nerve growth factor (NGF) with its high-affinity receptor tyrosine kinase A (TrkA) could play an important role in the growth modulation of human tumor cells, such as glioblastoma multiform cell lines and human breast cancer cell lines. However, the direct mitogenic effects of NGF and TrkA in these tumor cells still remain to be elucidated. Herein we show, by immunofluorescence staining, that NGF was colocalized with gamma-tubulin at the centrosomes or the spindle poles throughout the cell cycle and phosphorylated TrkA was colocalized with alpha-tubulin at mitotic spindle in the glioma cell line U251. The results suggest that NGF concentrated to centrosome can recruit its receptor TrkA there and cause phosphorylation of the latter. The phosphorylated TrkA with the tyrosine kinase activity may phosphorylate the tubulin and promote the mitotic spindle assembly. By these mechanisms, NGF can modulate the mitosis of human glioma cells.

Cell Line, Tumor↗
PubMed2005

Association studies of cholesterol metabolism genes (CH25H, ABCA1 and CH24H) in Alzheimer's disease.

Recent studies have demonstrated that cholesterol metabolism has an important role in Alzheimer's disease (AD) pathogenesis, suggesting that cholesterol-related genes may be significant genetic risk factors for AD. Based on the results of genome-wide screens, along with biological studies, we selected three genes as candidates for AD risk factors: ATP-binding cassette transporter A1 (ABCA1), cholesterol 25-hydroxylase (CH25H) and cholesterol 24-hydroxylase (CH24H). Case-control of North American Caucasians and AD families of Caribbean Hispanic origin were examined. Although excellent biological candidates, the case-control dataset did not support the hypothesis that these three genes were associated with susceptibility to AD. Similarly, no association was found in the Caribbean Hispanic families for CH25H. However, we did observe a possible interaction between ABCA1 and APOE in the Hispanics.

ATP Binding Cassette Transporter 1↗
PubMed2005

[Clinical characteristics and management of patients with ST segment elevation myocardial infarction in China: survey of 7510 cases].

OBJECTIVE: To analyze the clinical characteristics and management of the patients with ST segment elevation myocardial infarction (STEMI) in China. METHODS: As part of the international multicentre CREATE Study, the clinical data of 7510 patients with STEMI presenting their symptoms within 12 hours of onset who were hospitalized in 274 centers throughout China from July 2001 through July 2004, aged 62.7, were collected to be analyzed. RESULTS: 99.3% of these patients had STEMI, and 0.7% had new left bundle-branch block. 11.5% of them underwent percutaneous coronary intervention (PCI), 52.5% underwent thrombolytic therapy, and 0.1% coronary artery bypass grafting. All types of reperfusion therapy were carried out to 62.4% of the patients during the hospitalization. The medication therapy used was similar to those in the previous Registry report. The composite of all-cause mortality, re-infarction, and stroke within the first 7 days was 10.3% and the all-cause mortality within 30 days was 11.1%. CONCLUSION: The clinical characteristics and management of the STEMI patients in China have been described. The age of onset of STEMI is 62 years on average. The most common complication is hypertension, and diabetes mellitus is relatively rare. rt-PA was used rarely mainly because of the expensive price. A large proportion of patients in China receive reperfusion, which is worth recommendation. Active intervention should be carried out in the early stage after infarction.

Adult↗
PubMed2005

Four viral proteins of white spot syndrome virus (WSSV) that attach to shrimp cell membranes.

White spot syndrome virus (WSSV) is a major shrimp pathogen that has a widespread negative affect on shrimp production in Asia and the Americas. It is known that WSSV infects shrimp cells through viral attachment proteins (VAP) that bind with shrimp cell receptors. However, the identity of both WSSV VAP and shrimp cell receptors remains unclear. We used digoxigenin (DIG)-labeled shrimp hemocyte and gill cell membranes to bind to WSSV proteins immobilized on nitrocellulose membranes, and 4 putative WSSV VAP (37 kDa, 39 kDa and 2 above 97 kDa) were identified. Mass spectrometric analysis identified the 37 kDa putative VAP as the product of WSSV gene VP281.

Amino Acid Sequence↗
PubMed2005

Determination of limonin in rat plasma by liquid chromatography-electrospray mass spectrometry.

A simple, sensitive and selective liquid chromatography coupled with electrospray ionization mass spectrometry (LC/ESI/MS) method for determination of limonin (LM) in rat plasma has been developed and validated. The method had advantages of a single liquid-liquid extraction with ether and high sensitivity. Analyses were conducted at a flow rate of 0.2 ml/min by a gradient elution. The detection utilized selected ion monitoring in the negative ion mode at m/z 460.00 and 423.15 for the deprotonated molecular ions of LM and the internal standard, respectively. The quantitation limit for LM in rat plasma was 1.0 ng/ml. The linearity was also excellent over the concentration range of 1.9-500 ng/ml of LM. The intra- and inter-day precision (relative standard deviation (R.S.D.%)) was lower than 10% and accuracy ranged from 90 to 110%, showing a good reproducibility. This developed method was successfully applied to analysis of LM in biological fluids.

Animals↗
PubMed2005

[The influencing factors of surviving time of patients with non-ST elevation acute coronary syndromes in China].

OBJECTIVE: To identify the influencing factors of surviving time of patients with non-ST elevation acute coronary syndromes in China. METHODS: The data of patients with non-ST elevation acute coronary syndromes hospitalized in 38 hospitals in China, including clinical characteristics, therapeutic procedure, and major events at hospitalization and two years' follow-up period, were collected and analyzed as part of an international multicentre registry--OASIS. No particular intervention was needed in patients' therapy. The needed data were recorded by filling in the Case Report Forms offered by Canadian Cardiovascular Collaboration according to the protocol. Cox regression model was used to analyze the association with survival and multiple factors recorded. RESULTS: From April 1999 to December 2001, 2294 patients with non-ST elevation acute coronary syndromes were enrolled in 38 Chinese hospitals nationwide, two years' follow-up had been finished among 2188 of which with a mean age of 62.8 +/- 8.3 and 62.3% being male. The clinical diagnosis at admission was unstable angina in 88.5% of the patients and was non Q-wave myocardial infarction in the remaining 11.5%. The number of death totaled up to 174 with a mortality of 7.6% by the end of the two years' follow-up. The most common cause of death was severe arrhythmia or sudden death (92 cases, 52.9%). More than 70 factors had been analyzed by Cox regression model in order to determine which might influence survival. Risk factors that reduced lifetime were: frequencies of myocardial infarction during follow-up period, stroke during hospitalization, thrombolysis during hospitalization, frequencies of heart failure during follow-up period, heart failure during hospitalization, frequencies of stroke during follow-up period, history of myocardial infarction, times of hospitalization because of non-cardiovascular disease during follow-up period, history of diabetes mellitus, duration of the first hospitalization, and age by the first hospitalization. Protective factors that prolonged lifetime were the frequencies of using oral anticoagulant, anti-platelet medicine, nitrate, and lipid lowering agents during follow-up period. CONCLUSION: The most common cause of death in patients with non-ST elevation acute coronary syndromes is severe arrhythmias or sudden death in China. Several factors influence the survival of patients. The effects of most factors in this study are similar to those founded by previous evidence based medical study.

Acute Disease↗
PubMed2005

[Transforming growth factor-beta1 stimulates matrix metalloproteinase-9 production through ERK activation pathway and upregulation of Ets-1 protein].

OBJECTIVE: To investigate the molecular mechanism of transforming growth factor-beta1 (TGF-beta1) in regulating the production of matrix metalloproteinase-9 (MMP-9) protein. METHODS: Mouse immortal podocyte cells were cultured. Different concentrations (1, 2, and 5 ng/l) of TGF-beta1 were added into the culture medium. Cell culture without TGF-beta1 stimulation was used as control group. The activity of MMP-9 in the supernatant of the culture medion was assayed by gelatin zymography, expression of MMP-9 mRNA was assessed by RT-PCR; the activation of ERK pathway and the level of a transcriptional factor Ets-1 protein was analyzed by Western blotting. PD98059, a specific inhibitor of ERK1/2 activation, was added into the culture fluid of the podocytes for 30 minutes, than 2 ng/ml TGF-beta1 was added. The above mentioned tested were conducted to observe the influence of the inhibitor of ERK1/2 activation. RESULTS: The MMP-9 activity was very week in the supernatant of culture fluid of the control group and was increased in the TGF-beta1 groups dose-dependently. After the podocytes were co-incubated with 1 ng/ml TGF-beta1 for 24 hours, the MMP-9 activity was 26.86 times that of the control group (P < 0.01). Since the 12th hour after co-incubation with 2 ng/ml TGF-beta1 the MMP-9 activity in the supernatant of culture fluid began to be significantly increased and remained at high level till the 48 th hour. RT-PCR showed that low-level MMP-9 mRNA expression in the control group. After stimulation of 2 ng/ml TGF-beta1 for 6 hours the MMP-9 mRNA expression was 2.71 times that of the control group (P < 0.01) and the high-level expression lasted 24 hours. Western blotting showed low-level Ets-1 protein in the control group. At the time point of 12 th hour after stimulation of TGF-beta1 the Ets-1 protein expression was increased in all the three TGF-beta1 groups. After stimulation with 2 ng/ml TGF-beta1 for 4 hours the Ets-1 protein expression was 2.71 times that of the control group (P <0.01). After pretreatment of the podocyte with PD98059 for 30 minutes, the added 2 ng/ml TGF-beta1 failed to increase the MMP-9 activity and up-regulate the MMP-9 mRNA expression. CONCLUSION: TGF-beta1 stimulates the production of MMP-9 by activation of cytoplasmic ERK signaling pathway and upregulation of Ets-1 expression.

Animals↗
PubMed2005

[Two year follow-up of acute ischemic syndrome without ST elevation].

OBJECTIVE: To analyze the characteristics, treatment, and natural course during two years of the patients with acute coronary ischemic syndrome (ACS) without ST elevation in China as a part of the international multicentre registry of acute ischemic syndrome, Organization to Assess Strategies for Ischemic Syndromes (OASIS). METHODS: 2294 patients with ACS without ST elevation, including unstable angina pectoris and non-Q-wave myocardial infarction, aged 63 +/- 8, 62.3% being males, were registered and observed for 2 years based on informed consent in the northwest, north, and northeast China. The specific clinical protocols for patients were decided by the attending physicians without outside intervention. The patients' clinical characteristics, treatments, major events in hospital, and natural course of disease during the period of two years were recorded by filling in Case Report Forms offered by Canadian Cardiovascular Collaboration. RESULTS: 89.8% of the patients showed abnormal ECG. The most probable clinical diagnosis on admission was unstable angina in 88.5% of the patients and non-Q-wave myocardial infarction in the other 11.5%. 56.2% of the patients had past history of coronary artery disease, and nearly half of them had myocardial infarction. 57.4%, 18.3%, 47.6%, and 7.1% of them had the prior history of hypertension, diabetes, cigarette smoking and stroke respectively. During hospitalization, anti-platelet therapy and nitrate were used in 94.5% and 96.6% of the cases respectively, and 67.5%, 57.4%, and 59.1%t of them took beta-blockers, calcium antagonists and angiotensin-converting enzyme inhibitor (ACEI) respectively simultaneously. The medication rate dropped by 20.2% approximately 50.2% after discharge from hospital. During the two-year follow up the therapeutic rates of anti-platelets, nitrates, beta-blockers, calcium antagonists, and ACEI were 73.8%, 69.4%, 43.9%, 35.8%, and 31.6% respectively. During the 2 years 43.1%, 23.1%, and 8.2% of the patients underwent coronary angiography, percutaneous coronary intervention (PCI), and coronary artery bypass graft surgery (CABG) respectively. The two-year total mortality was 8.0%. The most common causes of death were severe arrhythmias or sudden death with an incidence of 4.3%. The major events were refractory angina, heart failure, new MI, stroke, and major bleeding with incidence rates of 29.4%, 15.4%, 7.9%, 4.8%, and 0.3%, respectively. CONCLUSION: Most patients with acute ischemic syndrome without ST elevation in China are diagnosed as unstable angina. The patients with acute ischemic syndrome are diagnosed as unstable angina mostly in China. More than half of the patients are treated with anti-platelets, nitrates, beta-blockers, calcium antagonists, and ACEI during hospitalization. The medication rate gradually decreases after discharge. The two-year mortality is 8.0%. The most common causes of death include severe arrhythmias and sudden death.

Adult↗
PubMed2005

The LATD gene of Medicago truncatula is required for both nodule and root development.

The evolutionary origins of legume root nodules are largely unknown. We have identified a gene, LATD, of the model legume Medicago truncatula, that is required for both nodule and root development, suggesting that these two developmental processes may share a common evolutionary origin. The latd mutant plants initiate nodule formation but do not complete it, resulting in immature, non-nitrogen-fixing nodules. Similarly, lateral roots initiate, but remain short stumps. The primary root, which initially appears to be wild type, gradually ceases growth and forms an abnormal tip that resembles that of the mutant lateral roots. Infection by the rhizobial partner, Sinorhizobium meliloti, can occur, although infection is rarely completed. Once inside latd mutant nodules, S. meliloti fails to express rhizobial genes associated with the developmental transition from free-living bacterium to endosymbiont, such as bacA and nex38. The infecting rhizobia also fail to express nifH and fix nitrogen. Thus, both plant and bacterial development are blocked in latd mutant roots. Based on the latd mutant phenotype, we propose that the wild-type function of the LATD gene is to maintain root meristems. The strong requirement of both nodules and lateral roots for wild-type LATD gene function supports lateral roots as a possible evolutionary origin for legume nodules.

Chromosome Mapping↗
PubMed2005

Yellow fever virus NS2B-NS3 protease: characterization of charged-to-alanine mutant and revertant viruses and analysis of polyprotein-cleavage activities.

A series of 46 charged-to-alanine mutations in the yellow fever virus NS2B-NS3 protease, previously characterized in cell-free and transient cellular expression systems, was tested for their effects on virus recovery. Four distinct plaque phenotypes were observed in cell culture: parental plaque-size (13 mutants), reduced plaque-size (17 mutants), small plaque-size (8 mutants) and no plaque-formation (8 mutants). No mutants displayed any temperature sensitivity based on recovery of virus after RNA transfection at 32 versus 37 degrees C. Most small plaque-mutants were defective in growth efficiency compared with parental virus. However not all small plaque-mutants had defective 2B/3 cleavage, with some showing selective defects at other non-structural protein cleavage sites. Revertant viruses were recovered for six mutations that caused reduced plaque sizes. Same-site and second-site mutations occurred in NS2B, and one second-site mutation occurred in the NS3 protease domain. Some reversion mutations ameliorated defects in cleavage activity and plaque size caused by the original mutation. These data indicate that certain mutations that reduce NS2B-NS3 protease cleavage activity cause growth restriction of yellow fever virus in cell culture. However, for at least two mutations, processing defects other than impaired cleavage activity at the 2B/3 site may account for the mutant phenotype. The existence of reversion mutations primarily in NS2B rather than NS3, suggests that the protease domain is less tolerant of structural perturbation compared with the NS2B protein.

Amino Acid Substitution↗