Search PubMed⌕ Search

Biomedical subjects

L Liu

Publications and source records attributed to L Liu.

At least 1,243 records · Page 69Linked to original sources
PubMed1990

[The study of effect of pain in the change of respiration by stimulating "renzhong" acupoint].

UNLABELLED: It had been reported that the stimulation of the "Renzhong" starts respiratory activity in rabbits whose respiration has been suspended. This action was caused by stimulating Renzhong. Those signals transmit to the nucleus of trigeminal spinal, and go to influence the nucleus of respiration. Those signals include of pain and other sense. This study investigated whether this stimulation of "Renzhong" is caused by pain or another stimulus. Phrenic nerve discharges and respiratory rates of 7 anesthetized rabbits, each weighing 1.5 to 2.0 kg were recorded. Stimulation of the "Renzhong" by electrical impulses (10 ms pulse, 20 Hz, 0.4-4 mA, duration 3-5 seconds). RESULTS: 1. Stimulating the "Renzhong", resulted in an 83 +/- 16% increase in the amplitude of phrenic nerve discharges, and a 31 +/- 6% decrease in respiratory rate. 2. morphine was then injected into the rabbits (5 mg/kg). After 8 minutes, the amplitude of phrenic nerve discharges had decreased by 22 +/- 9% and the respiratory rate had decreased by 16 +/- 6%. 3. At this acupoint, stimulation of the "Renzhong" resulted in a 43 +/- 8% increase of the amplitude of phrenic nerve discharges and a 20 +/- 6% decrease in respiratory rate. These results suggest that in the effect of the stimulation of "Renzhong" on the respiration pain sensation is one factor among the rest.

Acupuncture Points↗
PubMed1990

[A population-based study on types of viral hepatitis].

The epidemiological features of various types of acute viral hepatitis in 5 regions of Sichuan Province (211,639) population) form Feb.16, 1987 to Feb 15, 1988 were studied. One-year surveillance was carried out and the results showed an incidence rate of 167.74 per 100,000 for acute viral hepatitis. The proportional distribution of HA,HB,non-A,non-B Hepatitis (HNANB), Hepatitis with EBV (HEB), Hepatitis with CMV (HCM) and Mixed infection in all the patients being 24.51%, 38.31%, 24.51%, 3.38%, 3.38% and 5.92%, respectively. There was a proportion of 14.93% for superinfection. The incidence differences in these regions ranged from 110.30 per 100,000 to 299.95 per 100,000. The incidence of hepatitis peaked in spring, and the sex ratio (male:female) for acute viral hepatitis was 1.75:1 (P less than 0.001). There was a peak of attack rate for HA in 0-19 age group. The incidence of HB in 20-39 age group was obviously higher than that in other age groups. For HNANB, a relatively high attack rate was noticed in 5-19 age group, but no significant age-differences were noted for HEB,HCM and Mixed. Of 355 patients with acute viral hepatitis, 43.94% had a history of contact, and 36.62% a history of injection.

Adolescent↗
PubMed1990

[Ultrastructural study of the megakaryocytes in megaloblastic anemia].

The ultrastructure of the megakaryocytes in the bone marrow from 14 cases of megaloblastic anemia was studied. The commonest change observed was that the development of the nucleus lagged behind that of the cytoplasm. There were some evidences supporting the theory of ineffective thrombocytopoiesis. The mechanism of the relationship between the changes of morphology and function based on the impaired DNA synthesis and methylation due to folate and vitamin B12 deficiency were also discussed.

Anemia, Megaloblastic↗
PubMed1990

[Effects of stimulation of dorso-medial area of nucleus facialis on respiration related units in ventro-lateral region of nucleus tractus solitaris in rabbits].

In urethane-anesthetized, vagotomized and paralyzed rabbits, effects of electrical stimulation of the dorso-medial area of the nucleus facialis (DMNF) on the respiration-related units (RRUs) in ventro-lateral region of nucleus tractus solitaris (VLNTS) were observed. The experimental results showed that during electrical stimulation of DMNF the majority of the inspiratory (I) neurons (64.4%) were increased in frequency and duration of discharge, some to a marked extent. During electrical stimulation of DMNF the expiratory neurons (35%) were decreased in their frequency and duration of discharge, some to a marked extent too. The responses of RRUs in ipsilateral and contralateral VLNTS to stimulation of DMNF was not statistically significant (P greater than 0.05). It is suggested that DMNF may have a facilitating effect on the inspiratory neurons and an inhibiting effect on the expiratory neurons in VLNTS.

Animals↗
PubMed1990

[Effect of pigmented epithelium from different developmental stages of chick embryo on cell growth of retinal explants].

The model system to investigate the effect of retinal pigmented epithelium (PE) on the retinal development in vitro has been established in this laboratory. Chick retina separated from 5-day-old embryo (E 5) were cut into strips and explanted on the collagen substratum either in close contact with retinal PE (RPE), or without PE (R). The rates of cell proliferation of retinal strips cultured for 48 hr were measured by the uptake of radioactive thymidine and DNA contents. Both parameters in RPE were increased to values ranging from 137 to 167% when PE was taken from E5 and E6. However PE taken from E7, E8 and E9 had no effect on cell proliferation. The rate of cell proliferation of retina were increased both when separated retina and PE of E5 either from same or from an other eye closely contact again and when retina and PE of E5 were explanted together without separation. However the rates of cell proliferation were remained without much change when a millipore filter existed between retina and PE of E5 as well as the retina was inverted, the ganglion cell layer contacted with PE. The neurite outgrowth from retina explant with and without PE of E5 or E6 were also different. After culture for 24 hr the fiber length of neurite growing in RPE was only 36-39% of that in R. After 48 hr it was about 70% of that in R. This results suggested that the developmental stage of PE and the direct cell-to-cell contact of PE from E5 with photoreceptor layer of retina was important for the retinal cell proliferation. But PE had negative influence on neurite growth of retina in culture.

Animals↗
PubMed1990

[Immuno-electron microscopical studies on the retinal basement membrane of chick embryo].

Retinal basement membrane (RBM), also called inner limiting membrane of retina, is constituted by extracellular matrix. It was reported that neurite outgrowth of a neuron was closely related to extracellular matrix, particularly the laminin. In this laboratory RBM was used as the optimal substrate for retinal cells in culture. We have studied the surface of RBM and its relation to neurite outgrowth by scanning electronmicroscopy and immunogold transmission electronmicroscopy. RBM could be separated by mechanical disruption of the retina mounted between 2 adhesive substrata (membrane filter and poly-L-lysine coated glass). The surface of RBM studied was the side of RBM facing the optic fiber layer and ganglion cell layer. Small particles densely distributed on surface of RBM (Plate I, Fig. 1 and 2) were shown to be chrysanthemum-like structures with radiative arms under the scanning electronmicroscopy (Plate I, Fig. 3 and 4). The radiative arms of RBM of 12-day old chick embryo (E 12) were more in number and longer in length than that of the 6-day old chick embryo (E 6). The axons of ganglion cell from E 6 retinal strip extended out very well on RBM (Plate I, Fig. 5). Growth cone was active with filopodia. The chrysanthemum-like structures changed to ball-particles when the RBM was cultured for 24 hr. Some of ball-particles lay over the growth cone, and some beside it. Over and beside the nerve fiber could also be seen some ball-particles. When many neurites grew on RBM, a lot of ball-particles were shown to be displaced and piled up (Plate I, Fig. 6). The whole amount RBM labeled by indirect immunogold staining of Müller glial cell could be observed by transmission electronmicroscopy. The gold particles wer located at the chrysanthemum-like structure of E 6 RBM (Plate II, Fig. 7) and E 12 RBM (Plate II, Fig. 8). It was suggested that those structures were the end foot of Müller glial cells. Staining of PBS control or mouse serum control was negative (Plate II, Fig. 9 and 10).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

A method of neuronal spike train study based on autoregressive analysis.

The method of autoregressive (AR) analysis for neuronal spike trains (NST) is proposed in the paper. The AR model and the Green's function as well as the power spectral density function are used to process and analyse the neuronal interspike interval (ISI) sequences of cat's first somatosensory area of cortex (SI area) under various situations. With these methods the characteristics of the ISI sequence such as the AR order and parameters, memory property, correlativity and periodicity etc. can be extracted.

Animals↗
PubMed1989

Clinical manifestations and diagnosis of acute pyrethroid poisoning.

This article reviews 573 cases of acute pyrethroid poisoning reported in the Chinese medical literatures during 1983-1988. There were 325 cases of acute deltamethrin poisoning (occupational 158, accidental 167), 196 patients of acute fenvalerate poisoning (occupational 63, accidental 133, including 2 cases of ingestive fenvalerate-organophosphate mixture poisoning), 45 cases of acute cypermethrin poisoning (occupational 6, accidental 39) and 7 cases of other pyrethroid poisoning (occupational 2, accidental 5). The clinical manifestations have been reviewed and analysed. The diagnosis, gradation and differential diagnosis of occupational acute pyrethroid poisoning have been discussed.

Adult↗
PubMed1989

Purification and immunochemical characterization of ascitic fluid glycoproteins containing certain tumor-associated and blood group antigen markers.

Ascitic fluids from patients with various types of cancer were screened for the CA 19-9 and CA 125 tumor-associated antigenic activities. Two fluids exhibiting the highest activities were tested for their binding to various lectin-Sepharose columns resulting in both being bound best to wheat germ agglutinin (WGA) Sepharose. The WGA column eluate of one fluid was further chromatographed by HPLC and three peaks were obtained with approximate molecular weights of 3.65 MDa, 664 kDa and 330 kDa, of which only the largest fraction contained the CA 19-9 activity. The fluids were also fractionated on a Sephacryl S-400 column with most of the activity being present in or near the void volume. Monoclonal antibodies were used to demonstrate that the purified glycoproteins also contained the blood group A determinant, the four Lewis determinants Le(a), Le(b), Le(x) and Le(y), and the sialylated-Le(x) determinant, while other antibody analyses failed to detect other blood group and/or carbohydrate sequence determinants. Some of the blood group expressions could be separated from the CA 19-9 and CA 125 active glycoproteins by adsorption with various lectins other than the WGA.

Antibodies, Monoclonal↗
PubMed1989

An exponential ESS model and its application to frequency-dependent selection.

A nonlinear ESS model is put forward, that is, a nonnegative exponential ESS model. For a simple case, we discuss the existence, uniqueness, and stability of an ESS. As an application of the model, we give a quantitative analysis of frequency-dependent selection in population genetics when the rare type has an advantage.

Animals↗
PubMed1989

Site-directed mutagenesis of the phosphocarrier protein. IIIGlc, a major signal-transducing protein in Escherichia coli.

The glucose-specific phosphocarrier protein (IIIGlc) of the bacterial phosphoenolpyruvate:glycose phosphotransferase system (PTS) is a major signal transducer that mediates the intricate interplay among extracellular signals (PTS and non-PTS sugars), cytoplasmic and membrane proteins (PTS and non-PTS transporters), and adenylate cyclase. To further define the central role of IIIGlc in these multiplex signaling mechanisms, we have used site-directed mutagenesis to construct three mutant IIIGlc proteins containing single amino acid changes; Phe-3 was replaced with tryptophan [( Trp3]IIIGlc), and His-75 and the active-site His-90 were replaced with glutamine [( Gln75]IIIGlc and [Gln90]IIIGlc, respectively). [Trp3]IIIGlc resembles the wild-type protein in most properties and should be valuable for spectrophotometric experiments. In contrast, clear differences between mutant and wild-type proteins were observed with both [Gln75]IIIGlc and [Gln90]IIIGlc in in vitro sugar phosphorylation assays. As predicted, [Gln90]IIIGlc with a modified active site cannot be phosphorylated. Unexpectedly, [Gln75]IIIGlc accepts but cannot transfer phosphoryl groups, suggesting His-75 may also be a critical amino acid for IIIGlc-mediated signaling mechanisms. The physiological effects of these mutations are briefly described.

Escherichia coli↗
PubMed1989

Liver-tumor boundary detection: human observer vs computer edge detection.

As a preliminary step in computing tumor volume, we developed a computer edge detection program to define the liver-tumor interface in computed tomography (CT) images. Computer program performance was tested using CT images from a lucite liver/tumor phantom; from normal livers containing computer-generated pseudotumors of known size, object contrast, and liver-tumor edge gradients; and from 12 abdominal livers containing 19 focal tumors, eight with well-defined and 11 with ill-defined borders. Calculated sizes of the tumor phantom and pseudo-tumors were compared with measured volumes and predetermined cross-sectional areas, respectively. In the absence of a truth standard for the size of the focal hepatic tumors, computer-calculated cross-sectional areas of the tumors were compared with the measurements made by an experienced interpreter of CT images using the trackball cursor at the CT console. The console measurements were made five times on separate days during a one-week period. The variability in the measured areas of these tumors averaged 7.1% for the well-defined tumors and 14.0% for the poorly defined tumors (P = 0.05). The edge-linking algorithm systematically overestimated the volumes of individual slices of the hemispherical tumors in the lucite phantom. Nevertheless, because of algorithm failure in the slices containing the poles of the hemispheres, errors in total tumor volumes were -2.1% for the 5.1 cm radius tumor, +1.2% for the 2.7 cm radius tumor, and +15% for the 1.8 cm radius tumor. The edge-linking algorithm was reasonably successful in calculating areas of pseudotumors with object contrast of 3.0% or greater and steep edge gradients.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1989

Methods for assessing the linkage between pulsatile hormone profiles.

Although the different anterior pituitary hormones are generally considered to be regulated independently, examination of their patterns in blood suggests that pulsatile secretion of several of these hormones may be synchronized. Traditional methods of cross-correlation analysis may not be adequate for quantifying this linkage. Since some simultaneity may arise by chance, expected rates of random coincidences must also be estimated to determine if apparent concordance rates significantly exceed those due to chance. A method of estimating linkage by counting simultaneous and near-simultaneous events within temporal 'windows' of varying width is proposed and tested against 11 series of luteinizing hormone (LH) and prolactin measurements from normal men. Rates of concordance in series drawn from different subjects rather than the same subject, or series scrambled in time, do not contain meaningful simultaneous events and so can be used to estimate the rate of random synchrony. By these standards, a clear excess of concordant prolactin and luteinizing hormone (LH) peaks was observed in normal men, suggesting significant physiological synchrony between these pulses of secretion. This method can be applied to a variety of hormonal systems.

Circadian Rhythm↗
PubMed1989

Structure-kinetic relationships of choriogonadotropin and related molecules.

To assess how profound differences in carbohydrate and/or polypeptide structures affect parameters of plasma disappearance of glycoprotein hormones, we calculated and compared the initial volume of distribution, rate constants, and metabolic clearance rates of several highly purified human choriogonadotropin (hCG) analogues in monkeys. hCG, deglycosylated hCG, desialylated hCG, or core fragment of hCG-beta purified from pregnancy urine (beta-core) was administered as a rapid intravenous injection to adult male cynomolgus monkeys (n = 3/group). The metabolic clearance rates of deglycosylated hCG, beta-core fragment, and desialylated hCG were increased 15-, 47-, and 152-fold, respectively, over that of hCG. Their corresponding initial volumes of distribution, however, remained essentially unchanged compared with that of hCG and approximated the estimated plasma volume. In contrast, the fast and slow rate constants of plasma disappearance of the hCG analogues were increased as much as 18- and 23-fold, respectively, relative to those of hCG. These studies of structure-kinetic relationships in primates show that major carbohydrate and polypeptide modifications of a glycoprotein hormone cause profound changes in the rate constants of the disappearance curves without changes in the initial volume of distribution.

Animals↗
PubMed1989

Stimulation of testosterone production in the cynomolgus monkey in vivo by deglycosylated and desialylated human choriogonadotropin.

Modifications of carbohydrate structures of hCG, such as deglycosylation or desialylation, have been shown to reduce the biological activity of the hormone derivatives in vivo. We posed the question of whether deglycosylated hCG (dg-hCG) and desialylated hCG (ds-hCG) would behave as agonists at the LH/CG receptor in the primate in vivo, as this would bear on their potential clinical utility as LH/CG agonists or antagonists. Thus, we administered large doses (approximately 3 nmol) of highly purified dg-hCG, ds-hCG, hCG, or normal saline as a rapid iv injection to adult male cynomolgus monkeys (n = 3/group). Mean areas under the curves of plasma T over the first 6 h achieved with dg-hCG and ds-hCG were about 5-fold, significantly (P less than 0.05) greater than that in the saline controls and not significantly (P greater than 0.05) different from that in hCG-injected animals. Despite comparable plasma T responses in the first 6 h, mean plasma concentrations of ds-hCG, dg-hCG, and hCG differed dramatically among the groups. Plasma ds-hCG and dg-hCG levels were undetectable by 15 and 180 min, respectively, while the mean plasma hCG level was more than 2.10 nmol/L at 360 min. These data indicate that 1) dg-hCG is a full agonist at the LH/CG receptor in the primate in vivo, despite having minimal intrinsic activity in the rat Leydig cell adenyl cyclase assay and being able to near-completely antagonize hCG action therein; and 2) ds-hCG is a full agonist in the monkey in vivo, capable of stimulating a full testicular response over 6 h, despite being cleared from the circulation in 15 min. We conclude that the signal transduction system at the monkey LH/CG receptor is capable of achieving full steroidogenesis despite dramatically shortened exposure to stimulus or exposure to a stimulus with markedly reduced adenyl cyclase-stimulating activity in vitro.

Animals↗