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Biomedical subjects

J K Li

Publications and source records attributed to J K Li.

At least 91 records · Page 5Linked to original sources
PubMed1990

Chromatographic purification and characterization of EBV DNase from chemically induced lymphoid cells.

Epstein-Barr virus-associated deoxyribonuclease (EBV-DNase) was purified to homogeneity, as determined by silver staining, sequential column chromatography, and FPLC from Raji and P3HR-1 cells treated with 12-O-tetradecanoyl-phorbol-13-acetate and sodium butyrate. This viral protein was immunogenic and elicited high neutralization titer sera in rabbits. By silver staining of SDS-PAGE, Western immunoblot, and radioimmunoprecipitation using NPC patient sera and both polyclonal and monoclonal antibodies, the EBV DNase was identified as a 58K protein. The potential presence of two EBV DNases was also discussed.

Butyrates↗
PubMed1990

Mapping of two immunodominant antigenic epitopes conserved among the major inner capsid protein, VP7 of five bluetongue viruses.

A combination of polyclonal, monoclonal, and oligoclonal antibodies was used in Western blot to analyze intact VP7 proteins and their proteolytic peptide fragments of five bluetongue viruses found in the United States. Two linear immunodominant antigenic determinants were located and identified on this major inner capsid protein. One of the antigenic epitopes, which consisted of 11 residues (LTRAIARAAYV), was mapped by polyclonal antibody to the carboxyl terminus of the viral protein (residues 339 through 349). The second epitope (ARQPYGFFLETEEVYQPG) was located by both monoclonal and oligoclonal antibodies and mapped between residues 122 through 139. The exact locations of these two linear and continuous epitopes were also confirmed by competition with sequence-specific synthetic peptides. These epitopes were highly conserved among the VP7 proteins of all five U.S. bluetongue viruses.

Amino Acid Sequence↗
PubMed1990

Molecular cloning and comparative sequence analyses of bluetongue virus S1 segments by selective synthesis of specific full-length DNA copies of dsRNA genes.

Using primers complementary to the conserved sequences of the 3' ends of bluetongue virus genomic dsRNA segments, full-length DNA clones of all 10 dsRNA genes from the five U.S. BTV serotypes were synthesized and amplified by a novel method (ClampR). This amounts to nearly 100,000 base pairs of dsRNA cloned as unique full-length DNA copies. This continuous one-tube procedure combined cloning of the denatured dsRNA with reverse transcriptase and the selective amplification of full-length DNA by the polymerase chain reaction. ClampR-derived clones of the genomic segment S1 of BTV-11 encoding the serogroup antigen, VP7, were sequenced and shown to be complete copy, containing a total of 1156 bp and a long open reading frame of 349 amino acids. Comparative sequence analyses of BTV-11 S1 with those of the other U.S. serotypes show that 95.2% of the nucleotides are conserved between BTV-11 and -10, while only 79.0% of the bases are identical between BTV-11 and -13. Comparison of the VP7 proteins demonstrates that 100% of the amino acids are conserved between BTV-11 and -10 and 93.7% of these residues are identical between VP7 of BTV-11 and -13. The adaptation of the polymerase chain reaction to the full-length cloning and amplification of dsRNA (ClampR) should greatly facilitate molecular studies within the Reoviridae family.

Amino Acid Sequence↗
PubMed1990

Lymphocytic orchitis: a case report.

A young man with a unilateral testicular mass of short duration was found on histopathologic examination of the orchiectomy specimen to have a nongranulomatous, lymphocytic orchitis. No evidence of any infectious agent, autoimmune disease, or lymphoma could be found. We believe that this case represents an example of a nonspecific or idiopathic lymphocytic orchitis that is distinct from the hitherto recognized granulomatous orchitis.

Adult↗
PubMed1990

A closed-loop control scheme for intraaortic balloon pumping.

The beneficial hemodynamic effects of IABP are critically dependent on balloon timing relative to the diastolic phase of the cardiac cycle. A microprocessor-based controller has been developed to implement real-time automation of IABP using P-R intervals to regulate balloon deflation and systolic time intervals to trigger balloon inflation in a semi-automatic fashion. Experiments were performed on anesthetized open-chest dogs. Simultaneous measurement of aortic pressure and flow, coronary flow, and left ventricular pressure were recorded. Muscle segment lengths in normal and ischemic border zones were also measured from implanted pairs of endocardial ultrasonic dimension gages. P-waves were obtained from atrial cardiograms, and heart sounds were detected using a special filtering circuit. Both signals were input together with ECG to automate IABP timing. Systolic time intervals were calculated in real-time. IABP efficacy was assessed from changes in aortic flow, coronary flow, tension time index, end diastolic pressure, and the endocardial viability ratio. Comparisons were made between automated and manual timing set by a certified technician. Results indicate that automated timing yielded equivalent hemodynamic enhancement with greater ease of adjustment. A closed-loop control scheme is proposed which allows complete automatic device operation and the capability to rapidly achieve the optimum of any directly measurable hemodynamic variable.

Animals↗
PubMed1990

A nonlinear model of the arterial system incorporating a pressure-dependent compliance.

The three-element modified Windkessel model has been widely used to study the characteristics of the systemic arterial system. This model provides most of the features of the systemic input impedance, but does not describe the nonlinear effect of the pressure dependence of arterial compliance. The current investigation examines the hemodynamic consequences of such an inclusion. Simultaneous aortic pressure and flow during control and brief descending aortic occlusion were measured in open chest anesthetized experimental dogs. A numerical procedure was implemented to compute constant compliance linear and nonlinear compliance model-predicted pressure waveforms with flow as the input. Results show that the nonlinear compliance model in general can more accurately predict the measured pressure waveforms during control and during acute pressure loading. The difference between the predicted waveforms is more pronounced when blood pressure is high and when the pulse pressure is large.

Animals↗
PubMed1990

Effect of naloxone on spectral shifts of the diaphragm EMG during inspiratory loading.

Shifts in the power spectrum of the diaphragm EMG to lower frequencies may occur in the presence of fatiguing inspiratory flow-resistive loads (IRL). However, such a shift of the centroid frequency (fc) could follow a reduction in central output through a differential reduction in end-inspiratory high-frequency power (HFP). In unanesthetized goats, we tested the hypothesis that activation of the endogenous opioid system by IRL would differentially reduce central respiratory output, causing a reduction in fc. IRL was imposed for 180 min after which naloxone (0.1 mg/kg, NLX) was given. fc was computed from the power spectral density estimated by the Welch method. IRL reduced fc from 148.0 +/- 9.8 (SE) Hz at base line to 141.1 +/- 8.9 Hz or to 95.5 +/- 1.3% of base line by 180 min (both P less than 0.05). NLX increased fc to 148.9 +/- 9.9 Hz or to 100.6 +/- 1.1% of base line (both P less than 0.05). The decline in fc during IRL was found to be the result of a reduction in HFP, predominantly toward the end of inspiration. The reversibility of this fc shift with NLX suggests a central mechanism consequent to elaboration of endogenous opioids and not a peripheral (muscular) event consequent to muscle fatigue.

Animals↗
PubMed1989

Limb deficiency in an infant with Smith-Lemli-Opitz syndrome.

We describe a 46,XY newborn infant with Smith-Lemli-Opitz syndrome (SLOS) with multiple congenital anomalies including female external genitalia, a testis palpable in each labium majus, a cone-shaped cervix, and normal vagina. Additional anomalies included cleft palate, total anomalous pulmonary venous return, and striking limb defects (ectrodactyly of the left upper limb, radial aplasia, and monodactyly of the right upper limb). To our knowledge, this is the first report of SLOS associated with limb deficiency and the third associated with total anomalous pulmonary venous return. Our patient demonstrates that limb deficiencies may be a rare component manifestation in this syndrome of multiple congenital anomalies.

Abnormalities, Multiple↗
PubMed1989

Effect of propranolol on the myocardial contractility of normotensive and spontaneously hypertensive rabbits: relationship of pharmacokinetics and pharmacodynamics.

Myocardial contractility of normotensive and spontaneously hypertensive rabbits was determined following an iv bolus injection of propranolol HCl. Left ventricular pressure and dimension were used to calculate the contractility parameters of (dP/dt)max, maximum fiber shortening velocity (Vcf), and the slope of the end systolic pressure-end systolic volume line (ESP-ESV line). Hypertension was induced by a methoxamine HCl iv infusion which mimicked the cardiac effects seen in essential hypertension. Propranolol caused a significant decrease in all contractility parameters (p less than 0.05) within 15 min after administration, with a peak effect occurring after 30-35 mins. The pharmacokinetics and pharmacodynamics of propranolol were fit using Hill's equation in conjunction with the concentration of drug in the theoretical effect compartment. The normotensive group of rabbits had a calculated EC(50) of 12.7 ng/ml, while the hypertensive group had an EC(50) of 6.9 ng/ml, indicating that the hypertensive rabbits were much more sensitive to the propranolol than the normotensive group. In addition, the normotensive group of rabbits demonstrated a much different pharmacokinetic-pharmacodynamic relationship than that of the hypertensive group, indicating that the hypertensive state of the animal has a significant effect upon the concentration-effect relationship.

Animals↗
PubMed1989

Sequence analyses and structural predictions of double-stranded RNA segment S1 and VP7 from United States prototype bluetongue virus serotypes 13 and 10.

The nucleotide sequence of segment S1 and the deduced amino acid sequence of VP7 from bluetongue virus (BTV) serotype 13 was determined. Sequences were obtained by use of standard dideoxy DNA sequencing and by direct sequencing of genomic double-stranded RNA (dsRNA). The dsRNA was sequenced with a new dideoxy protocol that produces 300 to 350 bases per set of reactions. Segment S1 is 1156 bp long and contains one long open reading frame capable of coding for 349 amino acids. The protein, VP7, is rather hydrophobic, and has a calculated molecular weight of 38,619 and a net charge of +1.5 at pH 7.0. Segment S1 of BTV-13 has 79.6% of its nucleotides conserved when compared with segment S1 of BTV-10. While most of these differences occur at the third codon position of the open reading frame, the differences between the 89-base-long, 3' noncoding regions occur predominantly in pockets at positions 1092-1098, 1112-1114, and 1125-1129. Potential stem-loop structures encompassing the stop codon of the open reading frame are proposed for both serotypes. Comparisons of VP7 from BTV-13 and BTV-10 indicate that 93.7% of the amino acid residues are conserved, including a single lysine at position 255. Secondary structure predictions infer an eight-stranded beta-barrel structure between residues 150 and 250. This putative beta-barrel may serve as a target for the development of drugs to combat bluetongue disease. Comparable structures detected in the core proteins of single-stranded RNA viruses from both plants and animals suggest that these viruses and BTV had a common origin.

Amino Acid Sequence↗
PubMed1989

Selective separation of virus proteins and double-stranded RNAs by SDS-KCl precipitation.

The total viral structural polypeptides and the double-stranded genomic RNAs of bluetongue virus can be selectively separated by a single SDS-KCl precipitation step. This simple, rapid and highly reproducible method enables greater than 95% recovery and purity of both viral proteins and dsRNAs within 30 min. The serotypic identity of the separated dsRNAs can be analyzed by SDS-PAGE electrophorogram immediately. After a single phenol/chloroform extraction, the dsRNA can also be used as hybridization probes, templates for molecular cloning and direct RNA sequencing. The SDS-KCl-precipitated viral proteins could be used readily for peptide mapping and as immunogens. Polyclonal and monoclonal antibodies raised against SDS-KCl-precipitated viral structural polypeptides were useful in Western immunoblots.

Blotting, Northern↗
PubMed1989

Ultrasonic treatment of varicose veins.

Varicose veins and venous ailments are common among adult Americans. Treatment procedures vary but are mostly invasive. The current investigation utilizes focused high-intensity ultrasound for producing destruction of the venous wall in experimental dogs and in patients with varicose veins. Results are encouraging and suggest that focused ultrasonic irradiation can be an efficacious means of treating varicose veins and other venous disorders.

Animals↗
PubMed1989

Increased arterial pulse wave reflections and pulsatile energy loss in acute hypertension.

Increased afterload is normally associated with hypertension. The work of the heart increases to overcome this load, but whether this is beneficial for pulse transmission has not been examined. Experimental measurements were obtained in induced acute hypertension in dogs. Results show that increased pulse wave reflections compound the increase in arterial blood pressure, and the increased work output by the left ventricle is compromised by the reduced efficiency of pulsatile energy transmission to organ vascular beds.

Animals↗
PubMed1989

DNA polymorphism analysis of hereditary multiple exostoses in horses.

Genomic DNA polymorphisms obtained by restriction fragment-length polymorphism from healthy horses and horses with hereditary multiple exostoses were analyzed. These DNA were digested by 12 restriction enzymes and were hybridized against 6 isotopically labeled oncogene probes. Hybridization was not detected with the viral oncogene, v-ras, which indicated this oncogene was absent in the equine genome. Oncogenes (c-raf-1, c-fes, c-myb, c-myc, and c-sis) were present and had similar hybridization patterns and signal intensities in DNA from healthy horses and horses with hereditary multiple exostoses. Unique and distinct restriction fragment-length polymorphisms were detected with the c-raf-1 probe only in BamHI- and PstI-digested equine DNA.

Animals↗
PubMed1988

Laminar and turbulent flow in the mammalian aorta: Reynolds number.

Laminar to turbulent flow transition in the mammalian aorta is generally characterized by Reynolds number. When dimensional analysis is applied to obtain the Reynolds number in allometric form, it is found that this number is not invariant of body weight but is approximately proportional to body length dimensions. This implies that flow in the aorta of large mammals is turbulent and laminar in smaller mammals during most of ventricular ejection. Since Reynolds number is defined for steady flow through rigid tubes, it may not reflect the actual fluid behavior of pulsatile flow in compliant vessels such as the aorta. In addition, turbulence is frequency dependent. The larger compliance of the aorta and the slower heart rate in larger mammals and the shorter entrance length and higher heart rate in smaller mammals lead to equal prevalence of turbulence. The consequence is that the aortic flow waveforms remain similar in all mammals.

Anatomy, Comparative↗
PubMed1988

Multiple uses of liquepipets in Southern, northern, and western blots.

Individually wrapped, sterile disposable transfer pipets can be used in the isolation of ds-DNA and ds-RNA fragments from gels as well as in the screening of multiple samples in Southern, Northern, and Western blots without potential contamination by exogenous nucleases and proteases. The sensitivity and results obtained by this method are comparable to those obtained by conventional methods. All the prehybridization, blocking, hybridization, and detection processes can be performed within the transfer pipet. The isotopically labeled probes used in hybridization can easily be recovered, stored for reuse, or disposed of as waste with no potential contamination of personnel or laboratory equipment. Strip blots are stable in appropriate buffers within the liquepipets which can be shipped easily worldwide for comparative analyses by collaborative investigators. This method is simple, time saving, and inexpensive and is particularly suitable for multiple sample screening. Other potential applications of this procedure are discussed.

Blotting, Northern↗
PubMed1988

Proximal humeral defects in Gaucher's disease.

Defects in the medial aspect of the proximal humeral metaphysis of two patients with Gaucher's disease are reported and their aetiology discussed. Similar cortical irregularities have been described as a normal variant in children and their presence in patients with an infiltrative disorder suggested as being coincidental. The two reported cases indicate that there is a causal association in Gaucher's disease since the defect persisted post-skeletal maturity in one case and progressed to bilateral pathological fractures of the proximal humeri in the other case. A review of the radiographs of 50 patients, pre-skeletal maturity, presenting with idiopathic scoliosis revealed a defect of the proximal humeral metaphysis in only one case, to give an estimated incidence of this anomaly in the "normal" population of 2%. It is suggested that the presence of this defect is non-specific with a spectrum of occurrence from the normal variant to the clearly pathological. The presence, however, of subtle abnormalities in the underlying bone tend to indicate a pathological entity.

Adolescent↗