PubMed Health⌕ Search

Biomedical subjects

L Peng

Publications and source records attributed to L Peng.

At least 145 records · Page 8Linked to original sources
PubMed1992

Long-lasting abolishment of noradrenaline induced stimulation of oxidative metabolism after chronic exposure of developing mouse astrocytes to cocaine.

Rate of 14CO2 production from [l-14C]glutamate was determined as a measurement of oxidative metabolism in developing primary cultures of astrocytes, obtained from the neonatal mouse brain and grown in the absence (control) or presence of cocaine. From the age of 3 days, the drug-exposed cultures were grown in a tissue culture medium containing either 1 or 3 microM cocaine. After 2 months of chronic exposure to cocaine the metabolic rate showed an increase of approximately 50%, but there was a long lag period (several weeks) before this response occurred. In contrast to a marked stimulation of CO2 production when noradrenaline was added to untreated cultures of the same age, there was no similar effect of noradrenaline on cultures treated with cocaine. After exposure to cocaine for 21 days (24-day-old cultures), both the enhanced CO2 production and the abolishment of the normal response to noradrenaline persisted during 'withdrawal' (cessation of drug exposure) throughout the total period investigated, i.e. to an age of 60 days (corresponding to a withdrawal period of 36 days). The correlation of these findings with in vivo data is discussed.

Animals↗
PubMed1992

Energy metabolism at the cellular level of the CNS.

Evidence is accumulating that interactions between different cell types are of paramount importance for CNS function, for example, release of the excitatory transmitter glutamate from neurons and its preferential uptake into astrocytes. Some information is also available about energy metabolism in different cell types, or more often in models of different cell types (e.g., synaptosomes, cultured neurons, cultured astrocytes). In this review an attempt is made not only to correlate information obtained with different cell models but also to integrate this information with in vivo data, with histochemical observations, and with results obtained using brain slices. The emerging patterns indicate that neurons, synaptosomes, and astrocytes are all capable of complete glycolysis and oxidation of glucose. Elevated extracellular concentrations of potassium, known to occur in vivo, enhance energy metabolism by mechanisms that differ between neurons and astrocytes and to a large extent serve to reaccumulate extracellular potassium ions into adjacent cells. Monoaminergic agonists also stimulate energy metabolism, but mainly or exclusively in astrocytes. Profound differences are found between the effects of excess potassium and of aminergic transmitters, suggesting that high potassium concentrations enhance neuronal-astrocytic interactions, whereas the monoamines may tend to dissociate metabolic events in neurons and in astrocytes.

Animals↗
PubMed1992

Context rules of rightward overlapping reading.

We have investigated the mechanism and sequence context rules governing ribosome frameshifting promoted by aminoacyl-tRNA limitation. In the case of one shifty sequence, frameshifting promoted by lysyl-tRNA limitation occurs at the sequence AAG C and is due to rightward movement of the ribosome so as to read the AGC triplet overlapping the hungry codon from the right. The frequency of this event is unaffected by sequence elements more than three bases to the left (upstream) or two bases to the right (downstream) of the hungry codon, and only slightly affected by the identity of the base two bases to the right. It is strongly affected by the base immediately to the right of the hungry codon, which becomes the wobble base of the shifted triplet; and by the third base of the hungry codon, even though the two synonyms (AAG and AAA) call for the same aminoacyl-tRNA; and by the identity of the base immediately to the left of the hungry codon. The latter result suggests that the aminoacyl-tRNA in the P site affects the maintenance of reading frame at the adjacent A site of the ribosome. However, the DNA sequence makes it seem unlikely that the P-site tRNA shifts to the right in concert with the A-site tRNA, a mechanism that can account for leftward frameshifting (in the opposite direction) in retroviral translation. The specificity of sequence determinants of leftwing versus rightwing frameshifting is discussed.

Amino Acid Sequence↗
PubMed1991

Effects of indomethacin on demineralized bone-induced heterotopic ossification in the rat.

Indomethacin inhibits bone formation when treatment is initiated before the implantation of demineralized bone matrix (DBM). For the inhibition of bone induction to occur, indomethacin treatment had to be initiated 6 h or more before implantation of DBM. Initiating the drug treatment at or after the time of DBM implantation had no effects on the amounts of new bone formed. The inhibition by indomethacin is dose related over a range between 0.04 and 4 mg/kg body weight. Recovered day-1 DBM implants, transplanted into indomethacin pre- and posttreated syngeneic rats, formed bone at the same rate as controls did. However, recovered day-1 DBM implants lyophilized before transplantation showed decreased bone formation but significant dystrophic calcification as judged by a lower alkaline phosphatase activity and an elevated calcium content.

Alkaline Phosphatase↗
PubMed1991

Numerical simulation of heating from an acrylic implant in bone.

Heat transfer in an acrylic cement-bone system during hyperthermia has been has been simulated by using a spectral element method, using a 2-D linear model which combines the geometric flexibility of low-order finite element methods and high accuracy of spectral methods. The work is directed at obtaining a fundamental understanding of factors affecting hyperthermia therapy applied to giant cell tumors of bone in a two-dimensional model at a cross-section of the distal femur. Results suggest the heating may be significant within approximately 4 mm to 7 mm of the interface of the acrylic and the cancellous bone. Computational results are compared with published experimental results.

Bone Cements↗
PubMed1990

Immobilization of enzymes with polyaziridines.

A novel method of enzyme immobilization using a low molecular weight prepolymer of tri-functional aziridines which can immobilize enzymes both by covalent attachment and entrapment within a gel matrix is described. The enzymes are immobilized on a solid support and exhibit an excellent retention of enzymatic activity. The immobilization procedure is essentially a single step process which can be easily performed at room temperature or 4 degrees C in either aqueous solution or in an inert organic solvent. The polyaziridines used in the immobilization are nontoxic, available in bulk at low cost and completely miscible with water and many organic solvents, thus providing one of the most satisfactory methods of immobilization available.

Biotechnology↗
PubMed1990

Alteration of collagen composition and cross-linking in keloid tissues.

Collagen composition and cross-linking in human keloid and normal skin tissues were analyzed biochemically. CNBr peptides were separated by 2-dimensional (2-D) mapping and high performance liquid chromatography (HPLC). The amounts of type I and type III collagen was quantified by 2-D scanning densitometry of fluorographs of 2-D maps derived from samples radioactively labelled in vitro by [3H]-NaBH4 in dimethylformamide. Keloid tissues contained 31.6 +/- 2.2 percent type III collagen as compared to 21.4 +/- 2.7 percent type III present in normal human skin dermis. HPLC profiles of CNBr peptides showed that approximately 5 percent of the high molecular weight material in keloids is mercaptoethanol reducible, compared to insignificant amounts in normal skin. 2-D maps derived from CNBr peptides of keloid collagen demonstrated thiol reduction sensitive alpha 1(III)-CB9 dimer as well as 24,000- and 32,000-dalton CNBr peptides, which were not mercaptoethanol reduction sensitive in normal skin due to cross-linking via the lysyl oxidase pathway. Also, a group of 20,000- to 25,000-dalton CNBr peptides, in the alpha 1(I)-CB6 cross-linking region were prominent in keloid tissues.

Adult↗
PubMed1990

Automated sulfur hexafluoride washout functional residual capacity measurement system for any mode of mechanical ventilation as well as spontaneous respiration.

A new sulfur hexafluoride (SF6) washout functional residual capacity (FRC) measurement system has been developed which will work with any mode of mechanical ventilation, as well as with spontaneous respiration. This system was evaluated in three different human studies. In the first two studies, the accuracy of the system was compared with He dilution and body plethysmography in 12 spontaneously breathing normal volunteers and in 12 spontaneously breathing chronic obstructive pulmonary disease (COPD) patients. In the third study, the reproducibility and efficacy of using the system in the ICU was tested in 12 adult respiratory distress syndrome (ARDS) patients who were mechanically ventilated with PEEP. In the normal volunteers, there was no significant difference between the three measurement techniques. In the COPD group, there was an overall significant difference between measurement techniques (F[2,28] = 17.18, p less than .0001) and the rank of the magnitude of the FRC measurements from lowest to highest was SF6 washout, He dilution, and body plethysmography. There was a significant difference in accuracy between the COPD and normal volunteer groups (F[2,28] = 12.24, p less than .0002). There were a total of 1,227 FRC measurements made on the 12 ARDS patients. The number of FRC measurements per patient was 102 +/- 13 (SEM). The "stable" periods were 14 +/- 2 h long and ranged from 60 min to 63.5 h. The reproducibility for all 12 patients was 188 +/- 17 ml or 11.7 +/- 0.7%. This automated SF6 washout system should make routine FRC measurements in patients who are being mechanically ventilated simple and easy to do.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Development of monoamine oxidase activity and monoamine effects on glutamate release in cerebellar neurons and astrocytes.

Activities of monoamine oxidase (MAO) A and B were measured during the first month of postnatal development in mouse cerebellum and in primary cultures of either cerebellar granule cells or cerebellar astrocytes, derived from 7-day-old cerebella. In addition, effects of the two monoamines, serotonin (a MAO A substrate) and phenylethylamine (a MAO B substrate) on the release of glutamate under resting conditions and in a transmitter related fashion (i.e., potassium-induced, calcium-dependent glutamate release) were studied during the same period. Both MAO A and MAO B activities increased during in vivo development (beginning around postnatal day 14) and in cultured astrocytes (during a comparable time period and to a similar extent), but remained constant at a low level in granule cells. In 4-day-old cerebellar granule cell cultures there was no potassium-induced glutamate release but serotonin as well as phenylethylamine reduced the release in both the presence and absence of excess potassium. In 8- and 12-day-old granule cell cultures and in 8- and 18-day old astrocyte cultures there was a pronounced glutamate release during superfusion with 50 mM K+. In both neurons and astrocytes this response was inhibited by 1 nM of either serotonin or phenylethylamine. In the astrocytes the inhibition was followed by an increased release of glutamate in both the presence and absence of the high potassium concentration, whereas the 8-day-old neurons showed only a slight increase in glutamate release after the withdrawal of the monoamine and only in the absence of excess potassium. The response was almost identical in 8- and 18-day-old astrocytes in spite of the marked difference in MAO activities.

Animals↗
PubMed1989

[Dermatoglyphics parameters and cluster analysis of seven minority nationalities].

This paper reports the normal values of dermatoglyphics parameters of seven minority nationalities in Yunnan Province which are Bai, Blang, Yi, Hui, Lisu, Nu and Jinuo. The test of difference signification and cluster analysis show different parameters in several nationalities and the greatest most remarkable difference between Jinou and other nationalities. Han is very different from several nationalities. In each nationality, the symmetry pattern of same name finger or area is highly unanimous, the symmetry between left and right does not show random combination.

China↗
PubMed1987

Sister chromatid exchanges in lymphocytes of early cases of nasopharyngeal carcinoma and in 100 healthy subjects.

Sister chromatid exchange rate was studied in 12 early diagnosed cases of nasopharyngeal carcinoma and in their paired controls. Exchange frequencies were also analyzed in 100 healthy subjects distributed in four regions of Hunan Province and correlated to nationality, age and sex. The incidence of sister chromatid exchange was significantly higher in the cancer patients than in the normal controls. No correlation was found between the frequency of sister chromatid exchange and region, nationality, age or sex.

Adult↗
PubMed1987

Effect of borohydride reduction on antibodies.

The effect of borohydride reducing reagents on monoclonal and polyclonal antibodies was examined by enzyme-linked immunosorbent assay (ELISA). Each antibody showed different stability characteristics to the reducing reagents. Sodium cyanoborohydride was at least five times milder toward immunological activity than sodium borohydride, however, sodium cyanoborohydride with a catalytic amount of metal ion (Zn2+ or Al3+) can be as harsh as sodium borohydride. Activated hydrophobic borohydrides, 9BBN-pyridine, did not have any advantages in respect to the stabilities of antibodies. Antibodies to be used for immunosorbent purification must be evaluated individually to determine whether their structure is stable to immobilization reagents and conditions prior to their linkage to the column support.

Antibodies↗
PubMed1986

[Experience in the surgical treatment of 748 patients with lung cancer].

A series of 748 patients with lung cancer as treated by surgery from 1961 to 1984 is reported. Regular lobectomy was done in 445 (74%) patients, bronchoplastic lobectomy in 67 (11.2%), segmental or wedge excision in 15 (2.5%) and pneumonectomy in 74 (12.3%) in which the ratio of left to right pneumonectomy was 2.9:1. Overall resection rate was 80.4% (601/748) and resection mortality was 1.2% (7/601) (death within 30 days of operation). Overall 5 year survival rate was 42% (169/402). The 5 year survival rate was 35.3% for pneumonectomy, 54.1% for bronchoplastic lobectomy, 42.3% for regular lobectomy and 16.7% for segmental or wedge excision. In this analysis, emphasis is laid to the therapeutic validity of the different modes of surgery. Statistical data show that only when the indication of different surgical interventions are strictly adhered to and the reasonable procedures are carried out, could better results be obtained. In surgical treatment of lung cancer, it is an important principle to eradicate the tumor and its metastatic foci as thorough as possible and to conserve the respiratory function as much as possible. Regular lobectomy has now become the "standard" and first choice operation. Pneumonectomy should be reserved for the patients with absolute necessity due to the extent of the lesion, adequate cardiopulmonary function and possibility of a permanent cure. Pneumonectomy is substituted by bronchoplastic lobectomy to a certain degree, preserving more of the lung function and improving the living quality after operation and long term results. Extensive practice of this surgical modality is advised.

Adenocarcinoma↗
PubMed1985

A study of dynamic development in radiolesion and cell death of eukaryotes after exposure to ionizing radiation--the visualization of the dynamic reaction by means of cytochemical method with lactate dehydrogenase (LDH) as a nuclear marker and radiation-induced nuclear anomalization by an ultramicrostructural manifestation: a dynamic explanation.

The present work deals with the radiation effect on adult rats suffering from acute, whole-body irradiation with cobalt-60 gamma rays of dosages 100R and 300R respectively. The morphological alteration of the lymphocytic nucleus and exhibition of cytochemical reaction of LDH in intra- or extra-nuclear region has been observed at the end of predetermined time intervals after irradiation. A close relationship between the percentage of damage of the lymphocytic nucleus and that of positivity of LDH reaction is seen from their variations with time parallel. From technical color microphotographs which exhibit cytochemical reactions, the existence of enzyme LDH in the nucleus so far obscure has been visually recognized. The events happening in enzymic reaction and the leakage of enzyme across the nuclear envelope reflect the dynamic nature. The ultrastructural alteration of nuclear anomalization confirms the dynamic development of inducing radiolesion. The experimental facts inspire us to attempt an explanation of cellular radiolesion and cell death owing to ionization radiation in light of the dynamic concept.

Animals↗