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Biomedical subjects

G Liu

Publications and source records attributed to G Liu.

At least 667 records · Page 37Linked to original sources
PubMed1990

[Mosquito-net spraying with deltamethrin for malaria control].

Mosquito-nets were sprayed with 9.6mg deltamethrin per square meter for control of malaria vectors in Yibin County, Sichuan Province in 1986. In the study area, the relative population indices of Anopheles anthropophagus and An. sinensis in 35 mosquito-nets were 0.6 and 1.4 respectively; the man biting rates of these two vectors dropped by 97.8 and 90.8% respectively. The residual toxic effect of sprayed mosquito-nets, up to 104 days after spray, caused a mortality of 93.1-100% of An. anthropophagus and 87.1-100% of An. sinensis. The multiparous mosquito rate dropped by 48.4 and 51.3%. Indoor-intruding An. anthropophagus and An. sinensis were reduced by 76% and 78.3% respectively. The incidence of malaria decreased by 94.4%, the positive rate in school children declined by 77.5%. Both entomological and epidemiological indices indicated that mosquito-nets sprayed with deltamethrin could effectively control the malaria prevalence. This measure is economical and practical for control of malaria.

Animals↗
PubMed1990

[Further observation on the ultrastructural characteristics of Trichomonas vaginalis].

In longitudinal sections, T. vaginalis visualized by TEM was round or ovoid with an ovoid nucleus situated close to the anterior one-third of the body. There was an independent and well-developed Golgi complex dorsal to the nucleus and parabasal filaments. The anterior end of the cell had a blepharoplast complex which consisted of three parts, i.e., periflagellar canal, C-shaped structure of the pelta in the wall of periflagellar canal and five blepharoplasts. Four anterior flagella and one posterior flagellum were extended respectively from each of the blepharoplasts, simultaneously with one costa and two parabasal filaments. The axostyle was divided into three parts, i.e., capitulum, trunk and caudal. The spoon-shaped axostylar capitulum originated from the peltar-axostylar junction was composed of many microtubules and extended around the side of the nucleus posteriorly and turned itself at the end of the nucleus forming an axostylar trunk which projected externally in the form of a spicule.

Animals↗
PubMed1989

Physiological role during export for the retardation of folding by the leader peptide of maltose-binding protein.

It has been shown that folding of precursor maltose-binding protein of Escherichia coli in vitro is retarded by the leader peptide. We now present evidence that this modulation of folding plays a role during the export of maltose-binding protein in vivo. Maltose-binding protein synthesized in vivo without a leader sequence did not engage the cellular export apparatus. However, the requirement for the leader in at least one step, that of binding the export factor SecB, could be overcome by an amino acid substitution in the mature portion of maltose-binding protein. This substitution retarded the folding of the polypeptide even in the absence of a leader. Investigations using purified proteins in vitro demonstrated that SecB would stably bind to species of maltose-binding protein devoid of a leader when the folding of the binding proteins was sufficiently slow. Thus, we conclude that one of the roles of the leader is to retard folding and expose the binding site for SecB.

ATP-Binding Cassette Transporters↗
PubMed1988

Intracellular recording from phrenic motoneurons receiving respiratory drive in vitro.

Stable, long-term (2-4 h) intracellular recordings were obtained from phrenic motoneurons receiving respiratory drive in an in vitro neonatal rat brainstem-spinal cord preparation. Several passive and active phrenic motoneuron properties in vitro, including resting membrane potential, inspiratory drive potentials, and threshold depolarization levels, are similar to those in the adult mammal in vivo. Manipulations of the extracellular fluid environment by the addition or washout of chemicals affecting motoneuronal activity and spinal synaptic transmission of respiratory drive did not affect the quality of the intracellular recordings. These results establish the feasibility of long-term intracellular recording from the in vitro brainstem-spinal cord preparation for studies of cellular and synaptic mechanisms underlying control of respiratory movements.

Action Potentials↗
PubMed1988

Modulation of folding pathways of exported proteins by the leader sequence.

Leader peptides that function to direct export of proteins through membranes have some common features but exhibit a remarkable sequence diversity. Thus there is some question whether leader peptides exert their function through conventional stereospecific protein-protein interaction. Here it is shown that the leader peptides retarded the folding of precursor maltose-binding protein and ribose-binding protein from Escherichia coli. This kinetic effect may be crucial in allowing precursors to enter the export pathway.

ATP-Binding Cassette Transporters↗
PubMed1988

Evidence that cyclic GMP regulates myosin interaction with the cytoskeleton during chemotaxis of Dictyostelium.

Amoebae of Dictyostelium discoideum respond to a chemotactic cyclic AMP stimulus within 10 s by the formation of an intracellular peak of cyclic GMP. In wild-type cells the cyclic GMP is rapidly degraded by a cyclic GMP-specific phosphodiesterase. In "streamer F" mutants this enzyme structural gene, and the cyclic GMP persists several times longer than the normal period, an effect that is correlated with a persistence in cell elongation during the chemotactic movement phase. In this study we have used the streamer mutants NP368 and NP377 and their parental strain XP55, to study changes in cytoskeletal proteins during the chemotactic response. We have studied three proteins that change their association with the cytoskeleton after stimulation of amoebae with the chemoattractant cyclic AMP: (1) actin, (2) a protein with an apparent Mr of 190 x 10(3) and (3) myosin heavy chain. Both actin and the 190 x 10(3) Mr protein were found to accumulate rapidly int he cytoskeleton after cyclic AMP stimulation, with a sharp peak at 5 s, and showed similar changes in the parental and streamer mutants. However, the cytoskeletal level of myosin heavy chain showed different pattern of changes, which also compared with the parental strain XP55. In XP55 myosin heavy chain showed an initial drop after cyclic AMP stimulation, with a trough at 3-10 s followed by a rapid rise to a sharp peak at 20-25 s. In contrast, the myosin heavy chain in the streamer mutants produced a broad peak that persisted several times longer than the parental strain. We conclude that in the streamer mutants the defect in cyclic GMP phosphodiesterase that produces the broad peak of cyclic GMP is casually correlated with the broad peak of cytoskeletal myosin, and we suggest that this is connected with the observed phenotype of prolonged cell elongation during chemotaxis in these mutants.

3',5'-Cyclic-GMP Phosphodiesterases↗