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Biomedical subjects

M Yang

Publications and source records attributed to M Yang.

At least 397 records · Page 22Linked to original sources
PubMed1995

Oxygen transport and hemodynamics during retrograde whole-body perfusion.

The changes in oxygen transport and hemodynamics during retrograde whole-body extracorporeal perfusion (retro-ECC) were studied in six mongrel dogs. Oxygen consumption during retro-ECC, in which the blood flow rate was set at 25% and 50% of the flow during antegrade extracorporeal perfusion (ante-ECC), respectively, was relatively high compared with that during ante-ECC. These changes were caused by an increase in the oxygen extraction ratio to 71.5% +/- 8.2% and 51.2% +/- 12.4% during retro-ECC/25% and retro-ECC/50%, respectively. Thus, tissue perfusion was apparently well maintained by retrograde perfusion on the basis of the oxygen transport data. However, central venous pressure increased markedly to 29.5 +/- 11.6 mmHg and 56.2 +/- 24.5 mmHg during retro-ECC/25% and retro-ECC/50%, respectively, because of massive venous congestion caused by insufficient arterial return of perfused blood. The great venous compliance and increased systemic vascular resistance were the main causes of circulatory failure during retro-ECC. The risk of serious complications owing to the venous congestion must be considered during retrograde perfusion, especially during the clinical application of retrograde cerebral perfusion.

Animals↗
PubMed1995

Fucosidosis with dystonia.

Fucosidosis, a progressive neurodegenerative disease, evident in early childhood, is associated with progressive loss of mental and motor function and increasing spasticity and hyperreflexia. We report a Canadian male, with clinical features similar to previously reported fucosidosis patients, however, since age 5 he has exhibited progressive dystonic posturing, initially unilateral, but recently involving both lower limbs. Extensive study of his cultured lymphoblasts demonstrated that alpha-fucosidase activity and immunoreactive alpha-fucosidase protein were absent. He is homozygous for the Q422X mutation, a C to T transition within exon 8 of the alpha-fucosidase gene which results in loss of an EcoR1 restriction enzyme cut site. Even among the 4 other reported fucosidosis families having one or more individuals homozygous for this same (Q422X) mutation there was no previous report of dystonia.

Child, Preschool↗
PubMed1995

Disseminated toxoplasmosis as a cause of diarrhea.

Disseminated toxoplasmosis in patients with acquired immunodeficiency syndrome is often a central nervous system disease but may be seen as myocarditis or pneumonitis. Toxoplasmic colitis is a rarity. We report a case of toxoplasma colitis in a patient with diarrhea and hypokalemia. The microorganisms were identified in the colonic mucosa on H&E sections and confirmed by immunoperoxidase study.

Adult↗
PubMed1995

The too many mouths and four lips mutations affect stomatal production in Arabidopsis.

Stomata regulate gas exchange through the aerial plant epidermis by controlling the width of a pore bordered by two guard cells. Little is known about the genes that regulate stomatal development. We screened cotyledons from ethyl methanesulfonate-mutagenized seeds of Arabidopsis by light microscopy to identify mutants with altered stomatal morphology. Two mutants, designated too many mouths (tmm) and four lips (flp), were isolated with extra adjacent stomata. The tmm mutation results in stomatal clustering and increased precursor cell formation in cotyledons and a virtual absence of stomata in the inflorescence stem. The flp mutation results in many paired stomata and a small percentage of unpaired guard cells in cotyledons. The double mutant (tmm flp) exhibits aspects of both parental phenotypes. Both mutations appear to affect stomatal production more than patterning or differentiation. tmm regulates stomatal production by controlling the formation, and probably the activity, of the stomatal precursor cell.

Arabidopsis↗
PubMed1995

Recombinant PDGF enhances megakaryocytopoiesis in vitro.

The effect of recombinant platelet-derived growth factor (PDGF) on both murine and human megakaryocyte colony formation was studied in the plasma clot culture system. PDGF significantly stimulates megakaryocyte colony formation in a dose-dependent manner. The minimum concentration which had a significant stimulating effect on colony forming unit megakaryocyte (CFU-MK) was 10 ng/ml and maximum stimulation occurred at 50 ng/ml. The effect of PDGF was compared with that of interleukin (IL)-3, IL-6, granulocyte-macrophage colony stimulating factor (GM-CSF), erythropoietin (EPO) and acid fibroblast growth factor (aFGF) on megakaryocyte colony formation. The results showed that megakaryocyte colony stimulating activity of PDGF was slightly higher than those of GM-CSF and aFGF, but lower than those of IL-3, IL-6 and EPO. The effect of PDGF in combination with IL-3 or IL-6 on megakaryocyte colony formation was also investigated. No synergistic action was found between PDGF and IL-3 or IL-6, but an additive effect was observed with IL-3 plus IL-6. We also studied the effects of PDGF in combination with anti-IL6, anti-IL-3 or anti-GM-CSF antibody. The increase of megakaryocyte colony formation induced by PDGF was partially inhibited by anti-IL-6 or anti-GM-CSF antibody but not by anti-IL-3 antibody. These results indicate that PDGF is a positive regulator for megakaryocytopoiesis in vitro and IL-6 and GM-CSF may play a role in the mechanism whereby PDGF stimulates megakaryocytopoiesis.

Animals↗
PubMed1995

Translation of trpG in Bacillus subtilis is regulated by the trp RNA-binding attenuation protein (TRAP).

trpG of Bacillus subtilis encodes a glutamine amidotransferase subunit that is involved in the synthesis of both folic acid and L-tryptophan. Expression of trpG is negatively regulated by tryptophan even though this gene is located within a folic acid biosynthetic operon. Examination of both transcriptional and translational gene fusions to lacZ involving trpG and direct measurements of trpG mRNA levels and TrpG polypeptide accumulation demonstrated that translation of trpG is regulated by tryptophan whereas transcription is not. these studies also show that this regulation is mediated by the trp RNA-binding attenuation protein. Deletion and point mutations indicated that regulation is dependent on a series of G/UAG trinucleotide repeats surrounding the putative ribosome-binding site for trpG. Our results are consistent with a model in which the tryptophan-activated trp RNA-binding attenuation protein and ribosomes compete for binding to trpG mRNA.

Amino Acid Sequence↗
PubMed1995

Dynamics of sensory afferent synaptic transmission in aortic baroreceptor regions on nucleus tractus solitarius.

1. Synaptic responses of medial nucleus tractus solitarius (mNTS) neurons to solitary tract (ST) activation were studied in a horizontal brain slice preparation of the rat medulla. Slices included sections of ST sufficiently long that the ST could be electrically activated several millimeters from the recording site of cell bodies in mNTS. 2. Three types of synaptic events were evoked in response to ST stimulation: simple excitatory postsynaptic potentials (EPSPs), simple inhibitory postsynaptic potentials (IPSPs), and complex EPSP-IPSP sequences. Simple EPSPs had substantially shorter latencies than IPSPs (3.39 +/- 0.65 ms, mean +/- SE, n = 42, vs. 5.86 +/- 0.71 ms, n = 6, respectively). 3. EPSP amplitude increased linearly with increasing hyperpolarization, with an extrapolated reversal potential near 0 mV. 4. EPSPs were maximal at < 0.5 Hz of sustained, constant-frequency ST stimulation (n = 14). EPSP amplitude declined to an average of 57.5% of control at 10 Hz after 2 s of sustained stimulation. With 1 min of sustained, 100-Hz stimulation, EPSP amplitude declined to near zero. 5. With stimuli intermittently delivered as 100-ms bursts every 300 ms, generally comparable average EPSPs were evoked during constant and burst patterns of ST stimulation. The amplitude of the initial EPSP in each burst was very well maintained even at intraburst stimulation rates of 100 Hz. 6. At resting membrane potentials, low constant frequencies of ST stimulation (< 5 Hz) reliably elicited action potentials and suppressed spontaneous spiking, but higher frequencies led to spike failures (> 85% at 100 Hz). Between 5 and 10 Hz, this periodic stimulation-suppression cycle clearly entrained action potential activity to the ST stimuli. Similar patterns of current pulses (5 ms) reliably evoked action potentials with each pulse to higher frequencies (50 Hz) without failures, and entrainment was similar to ST stimulation. 7. In a subset of nucleus tractus solitarius (NTS) neurons (3 of 9 studied), bursts of ST stimuli were as much as 50% more effective at transmitting high frequencies (> 10 Hz) of ST stimulation than the equivalent constant frequencies (P < 0.0001). 8. The long-latency simple IPSPs with no preceding EPSPs reversed to become depolarizing at potentials more negative than -62.9 +/- 7.0 mV (n = 5) and were blocked by the non-N-methyl-D-aspartate antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (n = 3). The ST stimulation frequency-response relation of these IPSPs was similar to that for the short-latency EPSP response excited by ST synapses. Thus these IPSPs appear to be activated polysynaptically via a glutamatergic-GABAergic sequence in response to ST activation. 9. The results suggest that sensory afferent synapses in mNTS have limited transmission of high-frequency inputs. Both synaptic transmission and the characteristics of the postsynaptic neuron importantly contribute to the action potential transmission from afferent to NTS neuron and beyond. This overall frequency response limitation may contribute to the accommodation of reflex responses from sensory afferent inputs such as arterial baroreceptors within their physiological discharge frequency range.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1995

Evaluation of new catheter systems for intrauterine pressure measurement.

To verify the reliability of intrauterine pressure recordings by a newly available intrauterine catheter. In five women in labor the tips of the two newly available catheters (Hewlett Packard HP 13975 A) were tied together and placed in the same amniotic fluid pocket. In three other women the tip of the new catheter (HP) and tip of an established catheter system (Intran II) were tied and placed in the uterine cavity above the fetal head. The difference in active pressure recorded by the two catheters for each contraction in all 8 women was calculated. The total active pressure recorded for each patient for the whole labor by the two catheter was calculated. The active pressure difference for individual contractions was less than 5 mm Hg in 95% of contractions (n = 222) with the two new catheters (HP versus HP) and 99% when the new catheter was compared with the established catheter system (HP versus Intran II) (n = 222). The total active pressure in each labor differed by 0.4% to 5.4% (n = 5) and 1.4% to 4.1% (n = 3) respectively when similar (new HP versus new HP) and different catheter systems (new HP versus established Intran II) were used. The new transducer tip catheter gives reliable pressure readings in-vivo. (n = 3) respectively when similar (new HP versus new HP) and different catheter systems (new HP versus established Intran II) were used. The new transducer tip catheter gives reliable pressure readings in-vivo.

Catheterization↗
PubMed1995

[Antidepressant active constituents in the roots of Morinda officinalis How].

Five compounds having antidepressant activities have been isolated from the roots of Morinda officinalis, a Chinese traditional Yang-tonic drug. These compounds were identified as succinic acid (1), nystose (2), 1F-fructofuranosylnystose (3), inulin-type hexasaccharide (4) and heptasaccharide (5) by chemical and spectroscopic methods. All of the compounds are isolated from the species of genus Morinda for the first time.

Animals↗
PubMed1995

[Secondary and tertiary hyperparathyroidism].

Secondary hyperparathyroidism following various causes except for end stage renal disease was reviewed. Chronic low serum ionic calcium status such as osteomalacia and ricket or its negative balance may cause the stimulation for the parathyroids glands, which results in over excretion of PTH. Serum calcium levels are compensated to normal and low phosphate is prominent because of phosphate diuresis by PTH. Vitamin D treatment may be effective. In autonomous (tertiary) hyperparathyroidism, the parathyroidectomy is necessary.

Humans↗
PubMed1995

Measurement of mosquito Aedes vexans salivary gland-specific IgE and IgG antibodies and the distribution of these antibodies in human sera.

BACKGROUND: Lack of sensitive, reproducible, and specific immunoassays has hampered the evaluation and immunotherapy of mosquito allergy. OBJECTIVE: We wanted to develop ELISAs for measurement of mosquito-specific IgE and IgG using salivary glands from the mosquito Aedes vexans. METHODS: Microplates coated with the salivary gland antigen were sequentially incubated with serum samples or reference serum, goat antibody to human IgE or IgG, and enzyme-conjugated rabbit anti-goat IgG. RESULTS: The specificity of the assays was demonstrated by the successful inhibition of the ELISA reactions with the mosquito antigens. Reproducible results were obtained; mean coefficients of variation between assays were 0.200 +/- 0.002 for the IgE measurement and 0.114 +/- 0.001 for the IgG measurement. The sensitivity of each assay was 0.39 U/mL. Using these assays, sera from 50 subjects with skin reactions to mosquito bites ranging from negative to strongly positive were analyzed for mosquito-specific IgE and IgG. The mean mosquito-specific IgE and IgG were significantly higher in subjects with skin reactions to mosquito bites than in those without skin reactions (P < .005), higher in females than males (P < .031), and slightly higher in atopics than nonatopics (P > .05). Also, there was a significant correlation between mosquito-specific IgE and IgG levels (r = .77, P < .001). CONCLUSIONS: Specific, reproducible, and sensitive ELISAs have been developed for measurement of antibodies to Aedes vexans. Mosquito-specific IgE and IgG may involved in the development of sensitivity to mosquito bites.

Aedes↗
PubMed1995

DNA content and morphological parameters in synovial sarcoma and synovioma.

By using image analysis technique with 6 normal synovial tissue specimens as controls, nuclear DNA content and morphological parameters in specimens from 51 synovial sarcomas and 15 synovioma were examined quantitatively. The DNA content in synovial sarcoma and synovioma was significantly different (P < 0.01), and that of synovioma and normal synovial tissue was also different (P < 0.05). Morphological parameters including nuclear areas and perimeters differed significantly among the above three groups (P < 0.01). There was no correlation between the DNA content of synovial sarcoma and its histologic type (P > 0.05), but the DNA content greatly differed between its higher and lower differentiated grade in each type (P < 0.01). The DNA content in synovial sarcoma IIA stage, according to Enneking's staging system was lower than that in IIB, IIIA and IIIB (P < 0.05). The 5-year survival rate of synovial sarcoma with diploid/nearly diploid (D/ND) pattern was higher than that of aneuploid (AN) pattern (P = 0.028). The study suggests that analysis of the DNA content and morphological parameters of tumor cells is helpful in the diagnosis and pathologic grading of synovial sarcoma. It also provides a guide to clinical operation and estimation of the prognosis. Although synovioma is usually a well-differentiated and benign lesion, this investigation also suggested that increased DNA content may be an indication of poor prognosis for this neoplasm.

Adolescent↗
PubMed1995

Adolescent sexuality and its problems.

Adolescent sexual activity is increasing globally. Abstinence and a delay in the start of sexual intercourse may be the most effective methods in preventing the consequences of teenage sexual activity. However, these goals are seldom met. With the change in social norms, peer pressure and media influences; teenagers are engaging in premarital sex earlier. Family life education in countries like Sweden and Finland reduces teenage pregnancy and abortion. It is unrealistic to expect sexually active adolescents to stop their sexual activity. An effective contraceptive method will provide an alternative to prevent teenage pregnancy. Issues on compliance of contraceptive use, especially at the very outset of sexual activity should be addressed. Most of the problems associated with teenage pregnancy are now thought to be related to the social circumstances of the mother, the poor nutritional status before pregnancy and poor attendance at antenatal clinics. Risk-taking behaviour in this age group will also make them more prone to contracting sexually transmitted diseases. High risk groups should be screened and treated early. Contraceptive methods with protection against sexually transmitted diseases should be advised.

Adolescent↗
PubMed1995

Interaction of the 11-subunit trp RNA-binding attenuation protein (TRAP) with its RNA target.

The trp RNA-binding attenuation protein (TRAP) regulates expression of the B. subtilis trp operon by binding to an RNA target composed of 11 G/UAG repeats in the trp leader transcript. TRAP contains 11 identical subunits arranged in a ring. The binding of 11 molecules of L-tryptophan to sites formed between adjacent subunits activates TRAP to bind trp leader RNA. We propose that the trp leader RNA forms a matching circle on the surface of TRAP when it binds. RNA binding is relatively insensitive to changes in ionic strength and pH, and is apparently driven by changes in entropy. Two lysine residues on the surface of TRAP have been shown to be important for RNA binding.

Bacillus subtilis↗
PubMed1995

Synergistic gene expressions of cyclin E, cdk2, cdk5 and E2F-1 during the prolactin-induced G1/S transition in rat Nb2 pre-T lymphoma cells.

G1 cyclins and some cyclin-dependent kinases (cdks) have been implicated in the G1/S transition during the eukaryotic cell cycle initiation. The present study demonstrates that the genes of cyclin E, cdk2, cdk5 and the transcriptional factor E2F-1 are expressed during the prolactin (PRL)-induced G1/S transition in rat Nb2 pre-T lymphoma cells. The mRNAs for these four cell cycle regulators were synergistically synthesized and degraded after the stimulation by PRL. The maximal levels of these mRNAs were observed at 8 to 12 h after the PRL addition, while DNA replication reached to the maximum between 12 and 16 h. These results suggest that cyclin E, cdk2, cdk5 and E2F-1 play the roles in the G1/S transition being expressed by a common cellular mechanism(s) in the PRL-stimulated pre-T lymphoma cells.

Animals↗
PubMed1994

Direct measurement of thermodynamic and kinetic parameters of DNA triple helix formation by fluorescence spectroscopy.

Direct measurement of thermodynamic and kinetic parameters of oligonucleotide-directed DNA triple helix formation has been achieved by fluorescence spectroscopic methods. Fluorescence resonance energy transfer (FRET) was used to study the binding of an acceptor-labeled single-stranded oligonucleotide to a donor-labeled DNA duplex. Equilibrium binding constants and association rate constants for triplex formation between 5'-tetramethylrhodamine-labeled 11-mer, 13-mer, and 15-mer homopyrimidine oligonucleotides and a 5'-fluorescein-labeled, 25-bp DNA duplex containing a 15-bp homopurine site were determined by FRET measurements, and the values were in close agreement with those determined by established methods. The thermal dissociation profile of the triplex-to-duplex transition was also directly observed by FRET and was consistent with the triplex melting curves obtained by UV absorbance measurements. In addition, a homogeneous fluorescence anisotropy assay is described which enables determination of the binding constants between 5'-tetramethylrhodamine-labeled 11-mer and 13-mer homopyrimidine oligonucleotides and unlabeled 25-, 30-, and 50-bp double-stranded DNA containing a homopurine target site. These results demonstrate the utility of nonradioactive fluorescence measurements as an efficient method for studying triple helix formation under homogeneous solution conditions and highlight the uniqueness of the FRET method for obtaining equilibrium, kinetic, and thermal dissociation data in a straightforward manner.

Base Sequence↗
PubMed1994

Contribution of potassium channels to the discharge properties of rat aortic baroreceptor sensory endings.

The expression of several types of membrane potassium channel at the cell body and central synaptic terminal of the rat aortic arch baroreceptor has been reported by others. It is not known if any of the same channels function at the peripheral sensory terminal of these afferent nerves. Our study examined the effect of three potassium channel blocking agents on the pressure-evoked discharge of such baroreceptors. Thirty-one single unit, regularly discharging baroreceptors were studied using an in vitro aortic arch-aortic nerve preparation. Discharge thresholds and suprathreshold pressure sensitivities were derived from responses of receptors to slowly rising ramps of pressure applied to the aortic arch. Vessel diameter was recorded along with receptor discharge to assess any drug-induced changes in vascular smooth muscle. The blocking agents tested have a range of specificities for classes of potassium channels: tetraethylammonium (TEA), 4-aminopyridine (4-AP) and charybdotoxin. TEA depressed the pressure sensitivity of all baroreceptors tested (n = 3) in a dose-dependent manner. Baroreceptor responses to 4-AP were complex (n = 22) and varied widely across individuals. Three were unaffected by 5 mM 4-AP. Most baroreceptors were generally depressed by 4-AP. Some of the 4-AP effects appeared to be related to actions at vascular smooth muscle. None of the baroreceptors tested (n = 6) was affected by charybdotoxin. The results of selective potassium channel blockade are generally consistent with what would be expected from a sustained depolarization of baroreceptor endings such as has been reported with raising extracellular potassium and probably includes effects of inactivation of other voltage-dependent channels.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Aminopyridine↗