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S Song

Publications and source records attributed to S Song.

At least 235 records · Page 13Linked to original sources
PubMed1993

Heme-heme interactions in a homodimeric cooperative hemoglobin. Evidence from transient Raman scattering.

The comparison of the resonance Raman spectrum of the deoxy dimeric hemoglobin (HbI) from the Arcid clam, Scapharca inaequivalvis, to its CO photoproduct at 10 ns reveals several significant differences in the low frequency vibrational modes including those involving motions of the peripheral substituents on the heme such as the propionates. This finding reflects the involvement of the propionates in a hydrogen bonding network which connects the two heme groups across the subunit interface and is sensitive to ligand binding. A frequency difference in the iron-histidine stretching mode of 6 cm-1 in this invertebrate hemoglobin is substantially smaller than that detected in tetrameric vertebrate hemoglobins under similar conditions. Time evolution studies of the vibrational modes from the photoproduct demonstrate that the transient form relaxes to the deoxy structure concertedly with a half-life of 1 microseconds, the time scale in which tertiary relaxations of tetrameric hemoglobins occur. These data establish that the tertiary and quaternary structural changes take place on the same time scale and confirm a mechanism of cooperativity involving direct interaction between the two heme groups through the peripheral substituents. This direct structural communication provides a very tight linkage between the heme groups prohibiting modulation of the oxygen affinity by factors in the physiological milieu.

Animals↗
PubMed1993

Lower motor neuron dysfunction associated with human immunodeficiency virus infection.

OBJECTIVE: The association of human immunodeficiency virus with a clinical picture of motor neuron disease is uncommon, with three cases reported to date. This case represents an additional case of a human immunodeficiency virus-infected patient with apparent motor neuron disease. DESIGN: Single patient case report. SETTING: Large urban public hospital. PATIENT: A 45-year-old human immunodeficiency virus-positive Hispanic man who presented with muscle wasting, fasciculations, areflexia, cranial nerve deficits, and weakness progressing to a complete quadriplegia. RESULTS: Electrophysiologic data showed evidence of diffuse denervation with normal sensory and motor nerve conductions and no evidence of demyelination. Electromyography showed diffuse sharp waves and fibrillation. CONCLUSIONS: This case demonstrates a progressive motor neuron dysfunction in a patient positive for the human immunodeficiency virus and provides additional evidence that infection with the human immunodeficiency virus should be considered in the differential diagnosis of apparent motor neuron disease.

HIV Infections↗
PubMed1993

Effects of different doses of norethisterone on ovarian function, serum sex hormone binding globulin and high density lipoprotein-cholesterol.

The ovarian effects of different doses of norethisterone (NET) were compared in 45 normally menstruating women in order to find the lowest effective dose of the Chinese NET "visiting pill". Subjects were randomly divided into 3 groups. Each subject in each group was taking 0.5, 1.5 or 3.0 mg per day from days 5 to day 18 of the cycle. Blood samples were taken on days 5, 8, 11, 14, 17, 20, 23, 26 and 29 of the cycle. Serum oestradiol (E2), progesterone (P), sex hormone binding globulin (SHBG), high density-lipoprotein cholesterol (HDL-C), and NET concentrations were measured. Ovulation, delayed ovulation, ovulation inhibition and follicular activity were classified by the analysis of the peripheral serum levels of sex hormones. Ovulation occurred in 7 women in the 0.5 mg group, in 2 women in the 1.5 mg group and in none of the 3.0 mg group. Mean serum SHBG levels were reduced progressively by 6.6% (Group 0.5), 15.5% (Group 1.5) and 23.4% (Group 3.0). There were no significant changes in HDL-C levels in any group. There was a significant correlation of mean serum NET concentrations with dose. The lack of complete inhibition of ovulation in most women in the 1.5 mg and 0.5 mg groups might suggest that the dose of NET required when used as a visiting pill could not be reduced below 3.0 mg.

Adult↗
PubMed1993

Metastable CO binding sites in the photoproduct of a novel cooperative dimeric hemoglobin.

The infrared absorption spectrum of the CO-photoproduct from Scapharca inaequivalvis hemoglobin (Hbl) at 10 K yields only a single line in the "B" state region at 2132 cm-1. This is the same frequency as the B1 line observed in photodissociated vertebrate HbCO and MbCO. No evidence was found for the B2 line detected in vertebrate hemoglobins and myoglobin in the 2118-2120 cm-1 region. These data demonstrate that the protein does not have the same conformationally accessible ligand-binding sites as do vertebrate hemoglobins and myoglobins. The absence of the B2 line indicates that only a single weak site is accessible to the photolyzed CO molecule. These results are in accord with geminate rebinding experiments and ligand escape pathway calculations which have shown that the distal properties of Hbl are distinct from those of tetrameric hemoglobins and vertebrate myoglobins.

Animals↗
PubMed1993

The Bilitch Registry.

Explore the source record for details and available documents.

Defibrillators, Implantable↗
PubMed1993

Transformation of Escherichia coli with foreign DNA by electroporation.

Electroporation has been widely applied in molecular biology in recent years. In this study, successful transformation of plasmid DNA and transfection of phage DNA into E. coli were described by using intense electrical field of exponential decay waveform (electroporation) generated by a Gene Pulsar LN-101 (made in Tianjin, Tianjin Institute of Technology and Nankai University). We have obtained 10(9)-10(10) transformants/micrograms with strain DH5 alpha and plasmid pUC18, by a single voltage pulse at 1.0-2.5 kV (initial electric field strength = 2.8-16 kV/cm) with 5-20 microF capacitor. The efficiency of electroporation depends on various parameters: the electric field strength, capacitance, the pulse length (RC time constant), etc. The frequency of transformation was a linear function of the DNA concentration, as well as the density of recipient cell. The incubation time of before or after electroporation has no significant effect on transformation. The high transfection efficiency was also achieved with strain JM109 and M13mp19RF by electroporation. The method was easier, more time-saving and more efficient than Ca(2+)-dependent transformation (transfection) method. The results obtained by Gene-Pulsar LN-101 was similar to that by the Bio-Rad Gene-Pulsar apparatus.

Calcium↗
PubMed1992

Isolation of a Drosophila gene encoding glutathione S-transferase.

We have isolated a Drosophila gene, DmGST-2, that encodes glutathione S-transferase, a homo- or heterodimeric enzyme thought to be involved in detoxification of xenobiotics, including known carcinogens. The encoded protein has a primary sequence that is more similar to mammalian placental and nematode GSTs than that of a previously described Drosophila GST gene, herein referred to as DmGST-1. We provide a physical map of the gene and show that it specifies at least two mRNAs, measuring 1.9 and 1.6 kb, which differ only in the lengths of their 3' untranslated regions. Both of the mRNAs are present during all developmental stages. In situ hybridization of the DmGST-2 gene to larval polytene chromosomes places it within the 53F subdivision of chromosome 2, and Southern blotting to chromosomal DNA indicates that the gene has no close relatives within the Drosophila genome. Our results make possible molecular genetic approaches for further elaborating the function of glutathione S-transferases in insect development and physiology, in the metabolism of plant toxins, and in conferring insecticide resistance.

Amino Acid Sequence↗
PubMed1992

A cross-over study of three oral contraceptives containing ethinyloestradiol and either desogestrel or levonorgestrel.

A randomised cross-over trial was performed to compare the pharmacodynamic actions of three low-dose oral contraceptives (OCs): Marvelon (150 micrograms desogestrel (DSG)+ 30 micrograms ethinyloestradiol (EE)), Mercilon (150 micrograms DSG + 20 micrograms EE) and Microgynon (150 micrograms levonorgestrel (LNG) + 30 micrograms EE). None of the OCs produced any significant changes in serum cholesterol, LDL-C and apoprotein B. Triglycerides were increased by the desogestrel OCs but not by Microgynon. The latter however increased the glucose and insulin responses to a glucose tolerance test whereas Marvelon and Mercilon had no effect. HDL-C increased with Marvelon, was unchanged with Mercilon and was decreased with Microgynon. Apoprotein AII was increased by all three OCs but only the DSG OCs increased apoprotein AI. All OCs produced similar increases in caeruloplasmin but the increase in SHBG was much greater with Marvelon and Mercilon than with Microgynon. Testosterone was reduced more with Microgynon than with the DSG OCs. Many of the changes reflect the strong anti-oestrogenic action of LNG on metabolic parameters compared to DSG. Except for the effect on HDL-C, there was little difference between Marvelon and Mercilon on metabolic parameters and this complements the findings from large-scale clinical trials of the two OCs. Mercilon, therefore provides a very satisfactory alternative to Marvelon.

Adult↗
PubMed1992

21-aminosteroids interact with the dopamine transporter to protect against 1-methyl-4-phenylpyridinium-induced neurotoxicity.

U-78518F, a 21-aminosteroid from the novel family of lipid peroxidation inhibitors (lazaroids), increased survival of dopamine (DA) neurons in mesencephalic cell cultures incubated with the neurotoxin 1-methyl-4-phenylpyridinium (MPP+). Protection against DA neuron death occurred with increasing concentrations of U-78518F up to 30 microM. Non-specific toxicity produced with higher concentrations of MPP+ was not affected by the lazaroid. U-78518F inhibited cellular uptake of [3H]MPP+ and [3H]DA, but not that of gamma-[3H]aminobutyric acid. In human striatal membrane preparations, U-78518F competed with [3H]mazindol for binding to the DA transporter, with a calculated Ki value of 10 microM. Two of four lazaroids tested inhibited [3H]DA uptake in the cell culture system. The protective effects of 21-aminosteroids in MPP(+)-induced neurotoxicity are, in part, a function of the interaction of these agents with the DA transporter.

1-Methyl-4-phenylpyridinium↗
PubMed1992

The use of implantable sensors for the control of pacemaker mediated tachycardias: a comparative evaluation between minute ventilation sensing and acceleration sensing dual chamber rate adaptive pacemakers.

The role of implantable sensors to control pacemaker mediated tachycardias was investigated in 16 patients with two different dual chamber rate adaptive (DDDR) pacemakers, which sensed eiter minute ventilation (DDDR-Meta, nine patients) or body acceleration (Relay, seven patients). Successive atrial sensed events beyond a programmable rate occurring in the absence of detection of exercise by the sensors were considered to represent retrograde conduction or atrial arrhythmias, and the pacemakers responded by either a mode shift from DDDR to ventricular rate adaptive (VVIR) pacing (DDDR-Meta) or by tracking at an interim rate, the so-called conditional ventricular tracking limit (CVTL, Relay). In the unipolar atrial sensing mode, myopotential sensing (MPI) and external chest wall stimulations (CWS) at 250 beats/min were induced to be preferentially sensed by the atrial channel to simulate the conditions of atrial arrhythmias. In the DDD mode, these maneuvers resulted in ventricular responses of 88 +/- 3 beats/min and 110 +/- 3 beats/min for MPI and CWS, respectively. The pacing rate was significantly reduced in the DDDR mode with the sensors correctly detecting and responding to the sensed abnormal atrial signals (68 +/- 5 beats/min during MPI and 71 +/- 5 beats/min during CWS, P less than 0.005 compared with the corresponding DDD rate). One patient with a Relay pacemaker developed spontaneous atrial flutter and the ventricular tracking responses were 140 and 85 beats/min in the DDD and DDDR pacing modes, respectively. Thus MPI and CWS are useful bedside testing methods to assess pacemaker response during atrial arrhythmias. The use of implantable sensors to judge the appropriateness of atrial rate is a new approach to the management of pacemaker mediated tachycardias.

Adult↗
PubMed1992

Clinical experience with an activity sensing DDDR pacemaker using an accelerometer sensor.

The rate adaptive characteristics and pacemaker mediated tachycardia protection algorithm of an accelerometer based DDDR pacemaker were evaluated in 11 patients with bradycardia (seven atrioventricular block, four sick sinus syndrome). Rate adaptive programming was effected by collecting the acceleration level during a 3-minute moderate exercise ("tailoring" of sensor). In comparison with an externally attached piezoelectric sensor, the accelerometer sensor showed lower rate changes during external tapping of the pacemaker (16 +/- 3 vs 29 +/- 4 ppm, P less than 0.02) and applied direct pressure (1 +/- 1 vs 40 +/- 3 beats/min, P less than 0.001) on the pacemaker. At nominal setting, the accelerometer sensor showed improved rate stability and higher rate response to jogging and standing, although responses to other daily activities and treadmill exercise were similar. Apart from changing the rate responsive slope, rate response could be improved by repeat "tailoring" of the sensor at a lower exercise level, resulting in better overall rate response characteristics. The ability of the rate monitoring software to collect acceleration levels for an activity and profile the projected rate response at different rate responsive settings allowed programming to be effected with the minimum amount of exercise testing. The pacemaker also discriminated atrial tachyarrhythmias from normal sinus response using the sensor to judge the appropriateness of the atrial rate, which correctly identified and prevented rapid ventricular tracking in two patients during atrial flutter/fibrillation.

Adult↗
PubMed1992

[Isolation and characterization of prolactin messenger RNA from bovine anterior pituitary glands].

The messenger RNA was extracted from bovine anterior pituitary glands and was purified by oligo(dT)-cellulose chromatography. The length of the mRNA was 1,200 nucleotides measured by agarose gel electrophoresis containing methylmercury hydroxide. The bovine prolactin (PRL) mRNA was confirmed by Northern blot analysis of the mRNA with gamma-32P labelled synthetic oligonucleotide probes based on the partial amino acid sequences of bovine PRL and could stimulate the incorporation of 35S-methionine into protein in the rabbit reticulocyte cell-free system. The translation product of bovine PRL mRNA was immunoprecipitable by rabbit anti-ovine PRL anti-antibodies. The molecular weight of the translation product corresponding to the bovine PRL precursor was estimated to be approximately 25,000 by SDS polyacrylamide gel electrophoresis and autoradiograph.

Amino Acid Sequence↗
PubMed1992

[Cloning and sequence analysis of salmon growth hormone cDNA].

cDNA clones encoding Chinook Salmon, Oncorhynchus tschawytscha, growth hormone (sGH) have been isolated from a cDNA library prepared from Chinook Salmon pituitary gland poly(A)+ RNA. Synthetic oligodeoxynucleotide mixtures based on amino acid residues 1-7 of sGH and 166-172 of sGH were used as hybridization probes to select recombinant plasmids carrying the sGH coding sequence. The complete nucleotide sequence of sGH cDNA has been determined. The cDNA sequence codes for a polypeptide of 210 amino acids including a putative signal sequence of 22 amino acids. The 5' and 3' untranslated regions of the message were 70 and 446 bases long, respectively. Comparison of the nucleotide sequence and amino acid sequence between Chum sGH and Chinook sGH indicated that there were 97% and 99% homology respectively.

Amino Acid Sequence↗
PubMed1990

A pharmacodynamic and pharmacokinetic study of the Chinese No. 1 pill.

A pharmacodynamic and pharmacokinetic study of the Chinese No. 1 pill, a combined oral contraceptive containing 35 micrograms ethynyloestradiol (EE) and 600 micrograms norethisterone (NET), was performed in 29 women over a period of six months. Blood samples for analysis were taken during a pretreatment cycle, the first and 6th treatment cycles and post-treatment. Minor changes in carbohydrate metabolism occurred and these were particularly noticeable when the incremental areas under the serum concentration-time curves for both glucose and insulin in response to a glucose tolerance test were calculated. No changes occurred in the serum glycosylated haemoglobin levels. The serum concentrations of all the lipids measured (total cholesterol, triglycerides, LDL-C, HDL-C and apolipoproteins AI, AII and B) were significantly increased on treatment as were levels of Factor X, SHBG and caeruloplasmin whereas antithrombin III decreased. In 38 of the 40 treatment cycles, ovulation was suppressed. In one cycle serum oestradiol and progesterone levels showed a typical ovulatory pattern and in another there was evidence of follicular activity without ovulation. Serum EE concentrations showed a similar pattern in both treatment cycles showing that co-administration of NET did not affect EE metabolism. Serum NET levels were higher in the 6th than in the first treatment cycles. On comparing pharmacodynamic and pharmacokinetic parameters, the only statistically significant correlations were between the percentage change in triglycerides and SHBG and serum NET, but not EE concentrations, and between apolipoproteins AI and serum EE.

Adult↗