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Biomedical subjects

L Song

Publications and source records attributed to L Song.

At least 217 records · Page 12Linked to original sources
PubMed1992

Infection of cord blood monocyte-derived macrophages with human immunodeficiency virus type 1.

We have investigated the susceptibility of cord blood monocyte-derived macrophages to human immunodeficiency virus type 1 (HIV-1) infection in vitro. Cord blood monocytes were maintained in vitro for 10 to 15 days and then infected with HIV-1. Syncytia were observed 14 days after infection by light microscopy. Viral proteins were detected by immunofluorescence assay. Electron microscopic examination demonstrated typical lentivirus particles within cytoplasmic vacuoles. The supernatants from the HIV-1-infected cultures also contained significant reverse transcriptase activity and p24 antigen. Like adult monocyte/macrophages, cord-derived monocyte/macrophages expressed the CD4 receptor molecule. Pretreatment with blocking antibody prior to infection with HIV-1 Bal significantly reduced or blocked infection of cord monocyte/macrophages. When cord and adult monocyte/macrophages were infected with HIV-1 Bal or Ada-M and directly compared, higher reverse transcriptase activities and p24 antigen expression were obtained with cord monocyte/macrophages. However, no significant difference was found between adult and cord monocyte/macrophages infected with HIV-1 IIIB. These observations suggest that cord monocyte-derived macrophages may be important in the pathogenesis of pediatric AIDS and that the increased susceptibility of cord monocyte/macrophages to HIV-1 infection in vitro may be relevant to the enhanced susceptibility of neonates to HIV-1 diseases in vivo.

Adult↗
PubMed1992

Problems in deterrence: a comparison of the driving histories of DUII and non-DUII drivers.

Driving records of subjects arrested for driving under the influence of intoxicants (DUII), both recidivists and nonrecidivists, were compared with records of an age- and sex-matched random sample of non-DUII drivers. Major differences were found between DUII and non-DUII groups in the incidence of traffic violations but some differences also existed between nonrecidivist and recidivist DUII subjects. Rehabilitative diversion programs for first-time DUII offenders did not affect recidivism rates in the study population. Findings in this study suggest that general deterrence directed at the non-DUII population should receive emphasis equal to specific deterrence directed at DUII offenders.

Accidents, Traffic↗
PubMed1992

Seizures selectively impair agonist-stimulated phosphoinositide hydrolysis without affecting protein kinase C activity in rat brain.

The influence of seizures on phosphoinositide hydrolysis and protein kinase C activity was measured in rat hippocampus and cerebral cortex, primarily using a model in which generalized convulsive status epilepticus was induced by administration of LiCl (3 mmole/kg) 20 hr prior to pilocarpine (30 mg/kg). A short (5 min) period of seizures reduced phosphoinositide hydrolysis in hippocampal slices stimulated by norepinephrine or ibotenate, but did not alter the responses to carbachol, 50 mM K+, or NaF. Induction of seizures with diisopropylfluorophosphate caused a similar reduction in the response to norepinephrine without altering carbachol-stimulated phosphoinositide hydrolysis. The inhibition of norepinephrine-stimulated phosphoinositide hydrolysis after seizures generated by lithium plus pilocarpine administration was apparently not due to inhibitory influences of quisqualate or activation of protein kinase C since both of these treatments caused similar inhibitions in slices from control and treated rats. Seizures induced by lithium plus pilocarpine or by kainate did not alter the activity of protein kinase C or the distribution of protein kinase C between membrane and cytosolic fractions. Thus, seizures cause a neurotransmitter-selective impairment of phosphoinositide hydrolysis, and this response may play a role in the severity or duration of seizure activity.

Animals↗
PubMed1992

[Effect of electroacupuncture on myocardial oxygen metabolism and pH of coronary sinus blood during experimental angina pectoris].

The experiments were performed on 30 healthy mongrel dogs, intubation was taken in the left anterior descending coronary (LAD), the blood in carotid was transported to LAD through a peristalic pump, the blood flow was reduced to 3-5 ml/min, thus acute myocardial ischemia was produced. Basing on this condition, 0.1-0.16 ml bradykinin (2 ug/ml) was given into LAD coronary before recording to produce angina pectoris. The effects of electroacupuncture (EA) at "Neiguan" area on myocardial oxygen metabolism, pH of coronary sinus blood and myocardial contractile force were observed (EA intensity 5 volts, frequency 1-20 Hz). The results are as follows: 1. EA could reduce obviously A-V difference of blood oxygen capacity (Ca-vO2) and the rate of myocardium extracting oxygen (O2E), thus reduced obviously oxygen consumption of ischemic myocardium. 2. EA could reduce V-A difference of carbon dioxide partial pressure (Pv-aCO2), prevent the decrease of pH of coronary sinus blood (PHv), this indicated that EA could prevent accumulation of acidic metabolic products. 3. EA could increase myocardial developed tension (DT) of ischemic area, strengthen myocardial contractile force of ischemic area. Above results indicated that EA could reduce oxygen consumption of ischemic myocardium, prevent the decrease of pH of coronary sinus blood, thus myocardial cell acidosis was prevented, myocardial contractile force was strengthened. It might be the mechanism of acupuncture treating coronary heart disease.

Angina Pectoris↗
PubMed1992

Selection of strains capable of utilizing D-xylose and cellobiose to produce ethanol by electric field-induced protoplast fusion.

The protoplast fusion between Candida guilliermondii S208 (Arg-) and Saccharomyces cerevisiae 314 was induced by three pulses (18kV/cm, 10 microseconds duration) applied at an interval of 1 s with the model GH-401 Electric Induced Gene Transfer/Cell Fusion System. The frequency of appearance of prototrophic hybrids was 3.6 x 10(-3). Stable fusion products were obtained after continual subculture over 20 times on selected and unselected media. Comparative studies showed that the fusion products were real hybrids of both parents. Two fustants, F-106 and F-308, could ferment both D-xylose and cellobiose to ethanol. The ethanol production of F-106 in the media containing 2% D-xylose or 2% cellobiose were 3.1g/l and 1.05g/l, respectively. The ethanol production of F-308 in the above media were 0.2g/l and 2.8g/l, respectively.

Candida↗
PubMed1991

Dynamic light scattering from weakly bending rods: estimation of the dynamic bending rigidity of the M13 virus.

A theory is presented for the dynamic structure factor [S(K,t]) of weakly bending rods. This treatment is based on a discrete bead model for the Brownian dynamics in which all bead motions associated with bending are constrained to occur in a plane perpendicular to the end-to-end vector, thus prohibiting extension or contraction along that axis. Preset hydrodynamic interactions are incorporated in a numerically exact manner. The predicted normalized dynamic structure factor S(K,t)/S(K,0) should be valid for short times t such that the rms rotation of the end-to-end vector around any transverse axis is much less than 1.0 radian. With geometrical parameters appropriate for the M13 virus, the intensity autocorrelation function G(2) (K,t) = 1 + magnitude of S(K,t)/S(K,0)2 is calculated over a range of times and scattering vectors K for selected values of the persistence length P. The calculated G(2) (K,t) are fitted to a single exponential with unit baseline over the same range of times as the experimental photon correlation functions, and the apparent diffusion coefficients Dapp (K) are obtained from the best-fit relaxation times. For the sake of completeness, an exact expression is derived for the apparent diffusion coefficient obtained from the initial slope of the dynamic structure factor. However, this does not reduce to the known correct result in the rigid rod limit. To obtain the correct result, the limit of infinite bending rigidity must be taken before the limit of zero time. For this and other reasons, the initial slope value of Dapp (K) is not useful for weakly bending rods. Photon correlation functions are measured for the M13 virus, which is virtually identical to the often-studied fd virus. The experimental photon correlation functions are fitted over 8 relaxation times to a single-exponential plus baseline, and the Dapp (K) are calculated from the best-fit relaxation times. Theoretical curves of Dapp (K) vs K2 for selected values of P are compared with the experimental data, which are satisfactorily reproduced when P = 22000 +/- 2000 A. This dynamic value is close to the static value, P = 20000 +/- 2000 A, reported for the very similar fd virus. The most recent theories of Maeda and Fujime and their dynamic light scattering studies of fd virus are compared with the present results in some detail. Their optimum value of P is in surprisingly good agreement with the present value.

Bacteriophages↗
PubMed1991

Analysis of the convulsant-potentiating effects of lithium in rats.

Lithium pretreatment of rats has previously been shown to potentiate the convulsant effects of cholinomimetic drugs, such as pilocarpine. The first objective of this project was to determine if lithium also potentiates seizures induced by other classes of drugs. Lithium pretreatment of rats did not affect seizure activity induced by administration of N-methyl-D-aspartate, kainic acid, bicuculline, or pentylenetetrazole. This suggests that the proconvulsant effect of lithium is largely selective for cholinomimetics. A second series of experiments investigated possible mechanisms of the lithium potentiation of pilocarpine-induced seizures. The alpha 2-adrenergic receptor agonist clonidine suppressed seizure development, and the antagonist idazoxan enhanced the onset of seizures, suggesting that endogenous norepinephrine provides anticonvulsant properties. Administration of the norepinephrine depleter DSP-4 potentiated pilocarpine-induced seizures. These results suggest that the previously reported impairment of noradrenergic function by lithium may play a role in its potentiation of cholinomimetic-induced seizures.

Animals↗
PubMed1991

Effect of ethidium on the torsion constants of linear and supercoiled DNAs.

The torsion elastic constants (alpha) of linear pBR322 (4363 bp) and pUC8 (2717 bp) DNAs and supercoiled pBR322 and pJMSII (4375 bp) DNAs are measured in 0.1 M NaCl as a function of added ethidium/base-pair (EB/BP) ratio by studying the fluorescence polarization anisotropy (FPA) of the intercalated ethidium. The time-resolved FPA is measured by using a picosecond dye laser for excitation and time-correlated single photon counting detection. Previously developed theory for the emission anisotropy is generalized to incorporate rotations of the transition dipole due to excitation transfer. The excitation transfers are simulated by a Monte Carlo procedure (Genest et al., Biophys. Chem. 1 (1974) 266-278) and the consequent rotations of the transition dipole are superposed on the Brownian rotations. After accounting for excitation transfer, the torsion constants of the linear DNAs are found to be essentially independent of intercalated ethidium up to a binding ratio r = 0.10 dye/bp. Dynamic light scattering measurements on linear pUC8 DNA confirm that the torsion constant is independent of binding ratio up to r = 0.20 dye/bp. If alpha d denotes the torsion constant between ethidium and a base-pair, and alpha 0 that between two base-pairs, then our data imply that alpha d/alpha 0 lies in the range 0.65 to 1.64 with a most probable value of 1.0. The torsion constants of supercoiled DNAs decrease substantially with increasing binding ratio even after accounting for excitation transfer. At the binding ratio r* = 0.064, where the superhelix density vanishes and superhelical strain is completely relaxed, the torsion constant of the supercoiled pBR322 DNA/dye complex lies below that of the corresponding linear DNA/dye complex by about 30%. This contradicts the conventional view according to which linear, nicked circular, and supercoiled DNA/dye complexes with r = r* should coexist with the same concentration of free dye, display the same distribution of bound dye, and exhibit identical secondary structures, twisting and bending rigidities, and FPA dynamics. These and other observations imply the existence of metastable secondary structure in freshly relaxed supercoiled DNAs. A tentative explanation is presented for these and other unexpected observations on supercoiled DNAs.

DNA↗
PubMed1991

Unhooking dynamics of U-shaped DNA molecule undergoing gel electrophoresis.

It has been found that DNA molecules are often hooked around obstacles in a U-shaped configuration in gel electrophoresis. To understand the dynamics of the unhooking of U-shaped DNA molecules undergoing gel electrophoresis, we have examined the length changes of the longer and shorter arms of the U-shape as a function of time. Two types of unhooking have been found. In one type, the length changes of both arms are expontential in time but with different time constants. In another type, the length changes of the shorter arm is exponential and that of the longer one is linear with time. The interpretation is that the extent of stretch of the spring-like DNA chain decreases as the length difference between the two arms increases during the unhooking processes, and that the frictions at the pivot point can be relatively large depending upon the local structure of the gel. The friction coefficient at the pivot point is estimated to be nu 0 = (2.98 +/- 1.42)x10(-5) g/sec.

DNA, Viral↗
PubMed1991

Observation of DNA molecules undergoing capillary electrophoresis.

This paper presents a method to observe the motions and configurations of large DNA molecules undergoing capillary electrophoresis (CE). A simple device to perform CE horizontally under microscopic observation is designed and images of single DNA molecules inside the capillary are obtained using an epi-fluorescence microscope. DNA molecules moved towards the negative electrode when an electric field was applied. The mobilities of three types of DNA (T4 and lambda bacteriophage DNA and PBR322 plasmid DNA) were measured at different electric field strength. The mobility vs. electric field strength curves of these three large DNAs showed that the mobility remained constant at high electric field strength (200-600 Volt/cm) and increased significantly at low electric field strength (less than or equal to 50 Volt/cm.). The apparent mobilities of the large DNA molecules were independent of molecular weight. At electric field strengths greater than or equal to 400 Volt/cm., big aggregates (snowballs) of DNA molecules formed and moved upstream towards the positive electrode. When the field was turned off, the aggregates dissociated into a cloud of single DNA molecules, and diffused into the solution.

DNA↗
PubMed1991

Do women with premenstrual symptoms self-medicate with caffeine?

Recent investigations have suggested that caffeine consumption is related to the occurrence and severity of premenstrual symptoms. Phillis has proposed that not only the total amount of caffeine consumed but also the pattern of consumption over the menstrual cycle may be important. This study explored whether women who experience moderate or severe premenstrual symptoms differ from other women in their pattern of caffeine intake throughout the menstrual cycle. Analysis of data for 96 complete menstrual cycles from 47 women demonstrated that caffeine intake during the menstrual cycle differed between women who experience moderate or severe premenstrual symptoms and other women. Furthermore, the monthly pattern of caffeine consumption for women with moderate or severe premenstrual symptoms, but not for other women, differed substantially from Phillis's proposed beneficial pattern. Women with premenstrual symptoms may self-mediate with caffeine in response to premenstrual symptoms, thereby exacerbating their symptoms.

Adolescent↗
PubMed1991

Human cytomegalovirus infection and trans-activation of HIV-1 LTR in human brain-derived cells.

In order to investigate the hypothesis that human cytomegalovirus (HCMV) influences HIV-1 infection of brain cells, we studied primary astrocytes derived from human fetal brains and a neuronal cell line (SK-N-MC). Infection of these cells with two strains of HCMV resulted in expression of immediate early, early, and late antigens and production of infectious virus. HCMV infection of primary astrocytes also led to cytopathic effects and cell death. SK-N-MC cells were infected with HIV-1 strains with or without HCMV. HIV LTR-directed CAT activities and the expression of HIV p24 antigen from the SK-N-MC culture coinfected with both HIV-1 and HCMV were higher than those from the cells infected with HIV-1 alone. The primary astrocytes were cotransfected with HIV-1 proviral DNAs and HIV LTR-CAT with or without HCMV infection. HCMV-infected astrocytes produced greater amounts of CAT activity and higher p24 than the cells transfected with HIV-1 proviral DNAs alone. When both primary astrocytes and SK-N-MC cells were transfected with (a) HIV LTR-CAT alone, (b) HIV LTR-CAT plus HCMV-IE gene, or (c) HIV LTR-CAT plus HCMV infection 2 days before the transfection, both HCMV infection and its IE gene trans-activated the HIV LTR promoter. HCMV-IE gene 2 may play a critical role in trans-activation of HIV-1 LTR.

Acquired Immunodeficiency Syndrome↗
PubMed1991

[Toxic principles of Oxytropis glabra DC].

Eight alkaloids were isolated from Oxytropis glabra and identified as anagirine, thermopsine, N-methylcytisine, sparteine, baptifoline, adenine, dictamnine and ethyl allophanate respectively by spectral analysis and physicochemical methods. All these alkaloids were isolated from this genus for the first time and ethyl allophanate was found in nature for the first time.

Alkaloids↗
PubMed1990

Reduction of Na+ enhances phosphoinositide hydrolysis and differentiates the stimulatory and inhibitory responses to quisqualate in rat brain slices.

The concentration of Na+ in the incubation medium significantly influenced phosphoinositide hydrolysis induced by some, but not all, agonists in rat cerebral cortical slices. Reductions of the Na+ concentration below 120 mM resulted in incremental increases in basal and norepinephrine-stimulated accumulation of [3H]inositol monophosphate in cortical slices that had been prelabelled with [3H]inositol, and maximal responses were obtained with 0 and 5 mM Na+. In contrast, the responses to carbachol and ibotenate were similar in medium containing 120 or 5 mM Na+. In medium with 120 mM Na+, quisqualate has two effects on phosphoinositide hydrolysis in cortical slices, including a relatively weak stimulatory effect and an inhibitory modulation of the stimulation induced by norepinephrine. These two responses to quisqualate were differentially modulated by Na+; in 5 mM compared with 120 mM Na+ the stimulatory response was greatly increased and the inhibitory effect was mostly eliminated. That these were two separate events was confirmed by the use of L-BOAA (beta-N-oxalyl-L-alpha, beta-diaminopropionic acid), which reproduces the inhibitory, but not the stimulatory effect of quisqualate on phosphoinositide hydrolysis. In 5 mM Na+, inhibition by L-BOAA of norepinephrine-stimulated phosphoinositide hydrolysis was completely eliminated. These results demonstrate that a physiological concentration of Na+ maintains phosphoinositide hydrolysis at a submaximal level of sensitivity to some, but not all, agonists. The differential effects of Na+ on the stimulatory and inhibitory effects of quisqualate further substantiate the suggestion that these are two separate processes and indicate that alterations of the Na+ concentration may influence the effects of quisqualate, and other agonists, on phosphoinositide hydrolysis.

Animals↗
PubMed1990

Evidence for allosteric transitions in secondary structure induced by superhelical stress.

Previous studies suggest that the global secondary structures of native supercoiled and equilibrium linear DNAs may differ somewhat. Recent evidence also indicates that metastable secondary structure commonly persists following complete relaxation of the superhelical stress by intercalating dyes or by the action of topoisomerase I. In this work, the torsion constants (alpha) of pBR322, pUC8 and M13mp7 (replicative form) DNAs are determined by time-resolved fluorescence polarization anisotropy at various times subsequent to linearization. In all three cases, the torsion constants are relatively low immediately after linearization, and evolve for eight to ten weeks before reaching their apparent equilibrium values. It is shown in detail how the persistence of metastable secondary structure, subsequent to relaxation of superhelical stress, necessarily implies that one or more transitions in equilibrium secondary structure are induced as the superhelix density is varied from zero to native, or vice versa. Samples of pUC8 dimer (5434 base-pairs) with different superhelix densities are prepared by the action of topoisomerase I in the presence of various amounts of ethidium. Their median linking number differences are determined by standard band counting methods. The translational diffusion coefficient (Do) and the plateau diffusion coefficient (Dplat) characterizing internal motions over short distances (225 A) are determined by dynamic light-scattering. The torsion constant (alpha) between base-pairs and the circular dichroism spectrum are also measured for each sample. Curves of Dplat, Do, alpha and molar ellipticity ([theta]) (at the minimum near 250 nm) versus superhelix density (sigma) are constructed. The curve of Do versus sigma is very similar to that for sedimentation coefficient versus sigma for simian virus 40 (SV40) and polyoma DNAs. The curves of Dplat, Do, alpha and [theta] versus sigma show that, with increasing negative superhelix density, a structural transition occurs near sigma = -0.020 to an intermediate state with low torsion constant, and a second structural transition occurs near sigma = -0.035 to a state that exhibits more normal properties by sigma = -0.048. These data are consistent with the hypothesis that supercoiling induces two successive allosteric transitions to alternative global secondary structures. The data are much less consistent with the hypothesis that supercoiling induces some radical secondary structure at one or a few sites of small extent at sigma = -0.020, and at other sites at sigma = -0.035, or with hypotheses based on changes in tertiary structure alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Circular Dichroism↗
PubMed1990

Dynamic bending rigidity of DNA.

Rapidly relaxing components in the decay of the transient electric dichroism of DNA restriction fragments were reported by Diekmann et al. [(1982) Biophys. Chem. 15, 263-270] and Pörschke et al. [(1987) Biopolymers 26, 1971-1974]. These are analyzed using a new normal mode theory for weakly bending rods and assigned to bending. The longest bending relaxation times for fragments with 95-250 base pairs coincide with the theoretical curve calculated for a dynamic bending rigidity corresponding to a dynamic persistence length Pd = 2100 A. Analysis of the relative amplitudes of fast and slow components following weak orienting pulses is also consistent with a rather large dynamic persistence length. The enhancement of the relative amplitude of the fast component in large electric fields is attributed to steady-state bending of initially perpendicular DNAs by the field. Several reasons are proposed why the dynamic bending rigidity is 4 times larger than the apparent static bending rigidity inferred from equilibrium persistence length measurements on the same fragments.

Chemical Phenomena↗