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Biomedical subjects

G Hou

Publications and source records attributed to G Hou.

28 records · Page 2Linked to original sources
PubMed1995

Pyrido[2,3-d]pyrimidin-4(3H)-one derivatives and 1,2,3,4-tetrahydro- pyrido[2,3-d]pyrimidine derivatives: synthesis and in vitro study of their activity against platelet aggregation.

Some new derivatives of pyrido[2,3-d]pyrimidin-4(3H)-one A and 1,2,3,4-tetrahydro-pyrido[2,3-d]pyrimidines B were prepared. The study of their in vitro antiaggregating activity showed that the compounds A possessed an inhibitory potency when aggregation was induced with ADP. Their reduction to derivatives of 1,2,3,4-tetrahydro-pyrido[2,3-d]pyrimidine B led to a new series of molecules possessing a greater antiaggregating power. When compared to that of acetylsalicylic acid under the same conditions, this activity was weaker with collagen, the same with arachidonic acid-induced aggregation, but greater when aggregation was induced by ADP. However, they inhibited serotonin release only slightly. Compared to ginkgolide they remained weaker with PAF-induced aggregation.

Arachidonic Acid↗
PubMed1994

Induction of arsenite tolerance and thermotolerance by arsenite occur by different mechanisms.

Both V79 and As/R28A cells (an arsenite-resistant Chinese hamster V79 cell variant) show increased resistance to toxic concentrations of arsenite after pretreatment with a nontoxic concentration. The induced tolerance can be completely inhibited by actinomycin D or cycloheximide. Pretreatment with a nontoxic heat shock (45 degrees C, 10 min) resulted in a clear increased thermotolerance in both cell lines but failed to induce arsenite tolerance in either cell line. Pretreatment with arsenite induced a thermotolerance in V79 cells but not in As/R28A cells. These results are consistent with a model whereby the signal for induction of arsenite tolerance involves binding of arsenite to a protein effector which is amplified in the As/R28A line, thereby preventing action of arsenite in the regulation of heat shock factor which induces the heat shock response.

Animals↗
PubMed1993

[CT scan in 52 cases of retinoblastoma].

The results of CT scan in 52 patients (61 eyes) with retinoblastoma (Rb) managed and confirmed by clinical and pathological examination are reported. The features and value of imaging of CT scan are described and discussed. In this series, 96.72% of cases revealed Rb and 90.16% of the cases with Rb tumor showed evidence of calcification on CT scan. The contrast enhancement of the tumor was slight. 19.67% of the cases with Rb tumor showed retrobulbar extension and invaded intracranium (including 3 cases of intracranical tumor extension and one case of trilateral Rb). We think it is important to perform CT scan in suspected cases of Rb, and in patients with Rb invading the orbit or intracranium as well as in bilateral Rb. Some problems in the diagnosis and differential diagnosis are briefly discussed.

Child↗
PubMed1992

Thieno[2,3-d]pyrimidin-4(3H)-one derivatives and 1,2-dihydrogenated homologues: synthesis, enhanced in vitro antiaggregant activity for reduced compounds.

Some derivatives of thieno[2,3-d]pyrimidin-4(3 H)-one A and their 1,2-dihydrogenated homologues B were synthesized. The study of their in vitro antiaggregating activity showed that the first compounds exhibited significant inhibiting power when aggregation was induced with ADP. Their reduction to derivatives of 1,2-dihydrothieno[2,3-d]pyrimidin-4(3 H)-one led to a new series of molecules possessing a large antiaggregant activity. When compared to that of acetylsalicylic acid under the same conditions, this activity was the same with collagen or arachidonic acid-induced aggregation, but greater when aggregation was induced by ADP. Serotonin release was also inhibited.

Adenosine Diphosphate↗
PubMed1992

Synthesis and in vitro study of platelet antiaggregant activity of some 4-quinazolinone derivatives.

Some new 4-quinazolinones were prepared. Their antiplatelet activity was evaluated in vitro with respect to aggregation induced by ADP, collagen, arachidonic acid and the platelet serotonin release reaction. Most molecules showed an inhibiting power similar to that of acetylsalicylic acid under the same conditions, and even greater when aggregation was induced by ADP. Reduction of the 4-quinazolinone derivatives to their 1,2,3,4-tetrahydroquinazoline homologues produced an increase in platelet inhibitory action except when ADP is the inductor.

Blood Platelets↗
PubMed1991

Action of some salicylate derivatives on in vitro platelet aggregation. Inhibitory and inhibition antagonistic effects.

Twenty salicylate derivatives were tested for their antagonistic activity on the inhibitory effect of aspirin on platelet aggregation. The blocking effect was not limited to the salicylate but also characterised some of its substituted compounds. The substituant influence did not seem to be related to electronic or size parameters. This antagonistic activity of these derivatives decreased as concentrations increased, owing to the emergence of their own inhibitory activity: several salicylate derivatives showed dual inhibitory and inhibition antagonistic activity, with both properties present at the same concentration. A mechanism involving dissociated activities on the two enzymatic sites of cyclooxygenase is proposed.

Arachidonic Acid↗
PubMed1987

In vitro neuronal differentiation of Drosophila embryo cells.

Early gastrula-stage Drosophila embryo cells will differentiate in vitro to form several cell types, including neurons. We report here the morphological appearance of cultured embryo cells, the pattern of DNA synthesis, and the expression of neurotransmitter-metabolizing macromolecules. The cells initially exhibit no overt morphological differentiation, and all cells incorporate 3H-thymidine following a 1 hr pulse-labeling period. As cells undergo morphological differentiation, fewer total cells as well as qualitatively different cell types incorporate label. By the time cells are 8 or 9 hr old, no myocytes or myotubes are labeled. In contrast, some neurons are labeled with a thymidine pulse as late as 18 hr. We have also stained cultured cells of various developmental ages with the insect neuron-specific antibody: anti-HRP. Some positive cells can be detected as early as 5 hr, when no overt morphological differentiation is apparent. As the cells differentiate, the staining is limited to the small, round neuronal type and its processes. These findings suggest that this neuron-specific cell marker is expressed very early in cultured gastrula-stage cells and may be used to identify neuronal precursor cells. We have studied the patterns of expression of several macromolecules involved in acetylcholine metabolism using these cultures. The appearance of choline acetyltransferase (ChAT), the biosynthetic enzyme for ACh production, is first detected in 5-hr-old cells. There is an initial phase of low-level expression, followed by a rapid rise in activity shortly after the differentiating neuron clusters make contact with one another. ChAT activity reaches a plateau in 36-48-hr-old cells. Acetylcholinesterase activity can be detected several hours before ChAT and also shows a period of low-level expression followed by a rapidly increasing phase, reaching a plateau at around 36-48 hr. 125I-alpha-bungarotoxin binding appears in cells about 4 hr old and rapidly approaches maximum levels by about 36 hr. The in vitro expression pattern for ChAT and AChE is similar to that seen in vivo. AChE activity has been localized histochemically to the neurons and their processes in vitro. The normal in vitro expression pattern for ChAT and AChE can be altered by adding various cholinergic drugs to the culture medium during cell differentiation. Medium conditioned by older cultures can also result in lower levels of ChAT and AChE expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗