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Biomedical subjects

J K Li

Publications and source records attributed to J K Li.

At least 109 records · Page 6Linked to original sources
PubMed1987

Beta-adrenoceptor stimulation and blockade during myocardial ischemia in dogs: effect on cardiac O2 supply and consumption.

The effect of beta-adrenoceptor blockade and activation on ischemic regional and microregional myocardial O2 supply/consumption parameters was assessed in 28 open chest, anesthetized dogs. Ten minutes after LAD occlusion, dogs were given i.v. saline, 2 mg/kg propranolol, 0.2 mg/kg pindolol, or 1 microgram/kg per min isoproterenol. Coronary blood flow was determined using radioactive microspheres before and 2 h after LAD occlusion while O2 supply/consumption parameters were determined using microspectrophotometry. Ischemia resulted in a 66% reduction in subendocardial flow in controls in the ischemic zone and no experimental treatment significantly altered this flow. Pindolol resulted in a significant improvement in the ischemic regional subendocardial/subepicardial flow ratio (from 0.69 in the control ischemic region to 0.88 during pindolol treatment). O2 extractions were significantly increased and O2 consumptions were significantly depressed in the ischemic regions of all groups. O2 extractions were increased to a lesser degree in the ischemic region with the use of pindolol and propranolol. Propranolol and pindolol both significantly decreased the proportion of veins with low (0-20%) O2 saturations in the ischemic region indicating an improved microregional distribution of blood flow and/or O2 consumption within the ischemic region.

Adrenergic beta-Agonists↗
PubMed1987

Rapid alkaline blot-transfer of viral dsRNAs.

The double-stranded genomic RNAs of reovirus and bluetongue virus can be transferred very efficiently from either sodium dodecyl sulfate-polyacrylamide gels or NuSieve agarose gels onto several nylon membranes. After a brief acid depurination treatment, viral dsRNAs from the gels are transferred at room temperature using 0.2 N NaOH as the transfer medium. Four blots can be obtained within 1 h and each blot contains 15-20% of the input RNA sample. These blots can be used immediately without baking in vacuo. Less than 5% of the "fixed" dsRNAs are removed after repeated washings of the membrane blots. As little as 10 pg of the genomic dsRNA segment can be detected in this alkaline Northern blot. A 20- to 50-fold increase in resolution and sensitivity over traditional Northern blots is routinely achieved. These alkaline blots can be reused 6-10 times after appropriate strip washing and proper handling.

Bluetongue virus↗
PubMed1987

Thymic hypoplasia associated with isotretinoin embryopathy.

A newborn had isotretinoin embryopathy, including thymic hypoplasia. Evaluation of her immune functions demonstrated progressive attrition of T cells over the nine weeks until her death due to pneumonia. These studies strongly suggest an insult by isotretinoin to the immune system. Immune abnormalities may predispose infants with isotretinoin embryopathy to infection and contribute to their high mortality.

Abnormalities, Drug-Induced↗
PubMed1987

The genetic relatedness of United States prototype bluetongue viruses by RNA/RNA hybridization.

The genetic relatedness of the prototype bluetongue viruses isolated in the United States was examined by RNA/RNA hybridization. Genomic dsRNAs of bluetongue viruses were separated by either SDS-PAGE or NuSieve agarose gel electrophoresis and were blotted by both standard Northern technique and the recently developed rapid alkali-blotting method of Li, Kowalik, and Parker (submitted for publication) to positively charged nylon membranes. The blotted RNA was then probed with 3'-end-labeled dsRNA of each serotype. Initially, single segments were individually hybridized to identify cognate genes. Total genomic dsRNAs were then probed to determine genetic relatedness. The genes coding for the nonstructural proteins NS1 and NS2 were the most conserved. Most of the RNA segments coding for the core proteins were also well conserved, with segment S1 showing some diversity among the five serotypes. The outer capsid protein-coding segments demonstrated a wide degree of sequence divergence with segment L2 having little or no cross-hybridization among the five serotypes.

Bluetongue virus↗
PubMed1987

Chromatographic purification and immunological analysis of viral polypeptides of mouse mammary tumor virus.

The seven mouse mammary tumor virus (MMTV) structural polypeptides (GP52, GP36, P28, P23, P14, P12, and P10) were purified to apparent homogeneity. An improved and reproducible chromatographic method was used to obtain high yields of viral proteins from the same batch of isopycnically purified MMTV. The viral structural proteins were first extracted repeatedly with a high salt and high pH buffer in the presence of 1% Triton X-100. Loss of the minor viral proteins during column purification was minimized by first purifying the smaller molecular weight viral proteins (P14, P12 and P10) by oligo-d(T) column chromatography from the dissociated virions. The other four major viral polypeptides (GP52, GP36, P28 and P23) were then fractionated by affinity and ion-exchange columns. High titer polyclonal antibodies were produced against all of the seven structural proteins except P12 and P10. These antisera were monospecific and showed no cross-reactivity in radioimmunoassay towards other MMTV proteins. With minor modifications, this method has also been applied to purify other structural proteins from several different C-type retroviruses.

Animals↗
PubMed1986

Comparative cardiac mechanics: Laplace's Law.

The pumping ability of the heart is determined by mechanical and geometrical factors. These latter are governed by Laplace's Law. The extent of the applicability of this law across mammalian species is examined utilizing allometric relations and dimensional analysis. Results show that Laplace's Law plays an important role in linking the anatomical design to the functional capability of mammalian hearts.

Animals↗
PubMed1986

Pressure pulse transmission into vascular beds.

Observations at the microcirculatory level have revealed that (a) the pressure pulse reaches the smallest vessel, and (b) the pulse wave velocity alters from a value in the order of meters/second in large arteries to a value in the order of centimeters/second in the microvessels. We investigate, herein, whether these experimental findings are consonant with linear pulse wave transmission theory in a branching system of vessels. Our computations, utilizing available data, show that this is indeed the case. For low frequency (1 Hz), cumulative attenuation is such that about one-third of the pulse, originating at the heart, reaches the capillary. A 10-Hz pulse, however, is virtually completely attenuated by the time the capillary is reached. Transmission time for a pulse, from heart to capillary, is also frequency dependent, with higher frequencies propagating more rapidly. Vasoconstriction, at the arteriolar level in the absence of reflection, can also strongly attenuate the pulse remnant at that site.

Blood Pressure↗
PubMed1985

Demonstration of a stimulatory protein for virus-specified DNA polymerase in phorbol ester-treated Epstein-Barr virus-carrying cells.

A heat-labile Epstein-Barr virus-specific DNA polymerase stimulatory protein having a molecular mass of 45 kDa was purified from phorbol 12-myristate 13-acetate-treated P3HR-1 cells by column chromatography. The virus DNA polymerase stimulatory protein was precipitated by sera from patients with nasopharyngeal carcinoma but not by sera from healthy donors. The interaction of the stimulatory protein with DNA polymerase was stoichiometric. Furthermore, this protein stimulated Epstein-Barr virus DNA polymerase but not herpes simplex virus type 1 or type 2 or human DNA polymerase alpha. The stimulatory protein did not alter the Km value of dTTP or DNA but did increase the Vmax of DNA polymerase. Salt concentrations between 100 mM and 150 mM KCl were optimal for this protein-induced stimulation of Epstein-Barr virus DNA polymerase activity. The presence of the stimulatory protein in the reaction mixture enhanced the sensitivity of virus DNA polymerase to phosphonoformate.

Carcinoma↗
PubMed1985

Pulse wave reflections at the aorto-iliac junction.

For pressure pulses to be transmitted to vital organ vascular beds, minimum loss through vascular branching junctions is necessary. Experimental measurements of pulse wave velocities and cross-sectional areas allowed branching reflections to be quantified. Wave reflections at normal aorto-iliac junction is minimal. Increased reflection occurs when the branch vessel is either narrowed or occluded. Also, geometric factors dominate over elastic factors in determining the amount of pulse wave reflections at the aorto-iliac junction.

Animals↗
PubMed1984

Directional disparity of pulse reflection in the dog.

Local reflection coefficients were experimentally determined in the dog for the first time at the aortoiliac junction using characteristic impedances derived from phase velocity, fluid density, and the vessels' cross-sectional areas. Reflection coefficients were determined for both the normal trifurcation and with the segment of aorta between external and internal iliacs occluded. For the normal case the coefficients were as follows: antegrade, 0.7; retrograde, -0.74. For the occlusion case the coefficients were as follows: antegrade, 0.33; retrograde, -0.67. These results provide experimental support for the concept that the vascular system, at least in this region, favors antegrade and suppresses retrograde pulse transmission. In addition, global reflection coefficients were determined in the femoral artery using a three-point pressure technique. Coefficient magnitudes varied from low (1.6 Hz) to high (9.6 Hz) frequencies, i.e., control, 0.42-0.22; vasoconstriction, 0.65-0.33; vasodilation, less than 0.1 for all frequencies. Discrepancies between results appearing in the literature are evaluated and shown to be associated with the method utilized as well as with system nonlinearities enhanced by tying branches.

Animals↗
PubMed1983

Hemodynamic significance of metabolic turn-over rate.

Method in establishing mammalian hemodynamic similarity criteria via the classical allometric approach was examined. Metabolic rate (MR) per unit body weight (w), termed the metabolic turn-over rate (MTR), was found to be linearly related to mammalian resting heart rate (fh). The external ventricular work (EW) per unit body weight was found to be constant among mammalian species. The ratio of (EW/w)/(MTR/fh) is dimensionless, and is about 1/70. This latter qualifies as a new similarity principle. It states that the external ventricular work intensity during each cardiac cycle is directly proportional to the metabolic turn-over rate.

Animals↗