Biomedical subjects

X M Liu

Publications and source records attributed to X M Liu.

At least 73 records · Page 4Linked to original sources

PubMed1991

Persistent reversal of diabetes by transplantation of fetal pig proislets into nude mice.

Facing the limited availability of human adult and fetal pancreases, fetal pig proislets (pancreatic islet precursors) were investigated in view of several inherent advantages. Six litters of fetuses of mean +/- SE gestational age 75 +/- 3 days were obtained from commercially available farm pigs. Pancreatic tissue was gently digested with collagenase, then a 10-day culture was performed. During culture, fetal proislets showed no insulin response to glucose alone but a significant response to glucose plus theophylline. The insulin content per microgram of DNA in the cultured proislets continuously increased. Histological examination by immunoperoxidase staining showed that, apart from single insulin- and glucagon-positive cells, there were no discrete islets in the pancreatic tissue and the cultured proislets. Diabetes was induced with streptozocin (STZ) in eight nude mice 3-4 wk after proislet transplantation and in another eight nude mice without transplantation. During the initial week, blood glucose levels of mice in both groups increased rapidly. The mean +/- SE peak value of blood glucose levels in the transplanted group was 20.4 +/- 2.0 mM and was 20.1 +/- 1.3 mM in the group without transplantation. Simultaneously, body weight decreased from 29.5 +/- 0.7 to 21.5 +/- 0.9 g and from 27.9 +/- 0.7 to 19 +/- 1 g in the groups, respectively. Afterward, blood glucose levels of mice in the transplanted group gradually decreased, and normoglycemia was achieved in all mice within 50 +/- 13 days after injection of STZ, i.e., 74 +/- 13 days after transplantation. The group without transplantation persistently maintained blood glucose levels greater than 16.7 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Determination of DNA topoisomerase II activity from L1210 cells--a target for screening antitumor agents.

DNA topoisomerase II was isolated from mouse leukemia L1210 cells and the activity was determined by using P4 phage knotted DNA and pBR 322 DNA as the substrates. Based on these results, a method for screening antitumor agents by using DNA topoisomerase II as a target was established. The experiments showed that DNA topoisomerase II catalyzed pBR 322 DNA breaking and relaxing which were reversible and dependent on ATP. The activity was increased 2-4 times in the presence of ATP 1 mmol.L-1. In contrast with type II enzyme, the activity of DNA topoisomerase I was completely inhibited in the presence of ATP 1 mmol.L-1 and had full activity in the absence of ATP. Type II enzyme also showed the unknotting activity by using p4 phage knotted DNA as a substrate. DNA cleavage and relaxing reaction induced by type II enzyme increased 5-fold in the presence of Doxorubicin (Dox) 1 microgram.ml-1 or daunorubicin (Dau). Etoposide (Eto) and aclarubicin B (Acl B) also stimulated the reaction at 100 micrograms.ml-1. The cleavage reaction resulted from topoisomerase II was inhibited by other agents, such as frankincense extracts, terpenic compounds (BC series).

Animals↗

PubMed1991

Pharmacological studies of meisoindigo: absorption and mechanism of action.

Meisoindigo, an indirubin derivative, is a new type of cancer chemotherapeutic agent. It exhibited higher activity against rodent tumors than indirubin itself. Experiments have shown the improved absorption of meisoindigo, compared to indirubin to be one of the major reasons for the enhancement of antitumor activity. Studies on the mechanism of meisoindigo action indicate that it strongly inhibits DNA biosynthesis in tumor cells. Strong inhibition of the drug on assembly of microtubule protein was also obtained. By means of FCM technique the effects of meisoindigo on mouse leukemia L1210 cell cycle were examined. Experimental results showed that under the action of meisoindigo the S phase cells accumulated and the traverse of the cells in G2 + M phase to G1 phase may also be blocked to some extent.

Animals↗

PubMed1991

[Depletion of O6-alkylguanine alkyltransferase and chromosome damage induced by cisplatin, ning xin platin and carboplatin].

O6-Alkylguanine-DNA-alkyltransferase (O6-AGT) is a very important DNA repair protein known to carry out the transfer of alkyl groups from the O6 position of guanine in alkylated DNA to a cysteine acceptor site contained within its own protein sequence. In this work, the activity of O6-AGT in different cell lines and the relationship between the depletion of the enzyme and the frequency of micronuclei induced by cisplatin (DDP), Ning Xin platin (camphoramine chloroacetic platinum, CCP) or carboplatin (JM-8) in KB and CHL cells were studied. Experiments indicate that KB cells showed higher O6-AGT activity (greater than 400 dpm/300 micrograms protein extracts) which belonged to Mer+ cells, but CHL, HL-60 and L1210 cells showed very low O6-AGT activity (less than 50 dpm/300 micrograms protein extracts) which can be considered to be Mer- cells. Cytotoxicity studies indicated that no mer- selection was observed in these platinum complexes for KB, HL-60, CHL and L1210 cells. However, a good relationship between the depletion of O6-AGT and the frequency of micronuclei induced by the platinum complexes was obtained. CCP caused the highest depletion of the enzyme and exhibited highest potency in damaging chromosome.

Animals↗

PubMed1990

Epidemic non-A, non-B hepatitis in Xinjiang. Clinical and pathologic observations.

131 cases of epidemic hepatitis from two villages in Xinjiang, were admitted to the provisional infectious diseases hospital from February to April 1987. In 125 (95%) patients neither anti-HAV IgM nor anti-HBc IgM were positive. 118 (90%) were drinking water from a local stream of the Hotan River. The study was conducted on 125 patients aged from 5 to 90 years, with a mean of 26.4 years. There were slightly more males than females, a ratio of 1.5 to 1. The incubation period was roughly estimated to be 17 to 37 days (mean 24.8 days). All subjects were jaundiced. 12 patients (including 6 pregnant women) had cholestatic symptoms. Except one woman who died of postpartum bleeding, all patients ran a benign course without fulminant hepatic failure. Pathologic changes of liver biopsies from 35 cases included lobular damage and inflammation, ballooned hepatocytes with clear cytoplasm and delineated cell membrane which were named "clear cell". There were cholestasis of different degrees in the acute icteric stage and fatty changes in the convalescent stage. It was seen under the electron microscope that the livers of 8 cases had neither tubular structure nor sponge-like inclusions, but had nuclear changes including curled edge of nuclear membrane and nuclear heterochromatin condensed in masses. Liver biopsies were repeated in 7 cases followed up for 6-13 months, and hepatohistology was normal in 5. Of the other two cases there was one of each.

Adolescent↗

PubMed1990

Effect of acute water loading on plasma levels of antidiuretic hormone AVP aldosterone, ANP fractional excretion of sodium and plasma and urine osmolalities in myxedema.

We monitored the plasma and urine osmolalities, fractional excretion of sodium, fractional excretion of chloride, plasma levels of antidiuretic hormone (ADH, AVP), aldosterone and atrial natriuretic peptide (ANP) before and after acute water ingestion in 12 patients with overt hypothyroidism. The ability of the patients to dilute and concentrate urine was found impaired and the ability of excretion of water load decreased and delayed. Acute water load test was proved to be effective in evaluating the urinary excreting function for the patients. We hypothesize that inappropriate secretion of anti-diuretic hormone and elevated plasma ANP may be homeostatic factors for abnormal urinary excretion in patients with hypothyroidism.

Adolescent↗

PubMed1990

[Study on urinary function and metabolism of water and electrolytes in primary hypothyroidism].

Water excretion in 16 patients with primary hypothyroidism was lower in amount and more delayed (P less than 0.05) than that in 5 normal controls after acute water ingestion. The mean plasma osmolality of the patients was lower than that of normal controls both before and after water loading. However, the mean urine osmolality was not decreased but rather elevated. The clearance of free water in the patients was lower than that in normal controls before loading, Although the clearance of osmolality in the patients was higher than that in the controls, the difference was insignificant. These two clearance rates were lower than those in the controls after loading. The fractional excretion of sodium (P less than 0.05) and chloride (P less than 0.01) in the patients was significantly higher than that in the controls before loading and both of them remained elevated after loading. Most of the parameters mentioned above improved in 9 patients after treatment with desiccated thyroid.

Adolescent↗

PubMed1989

Scanning electron microscopic observation on the surface ultrastructure of leucocytes in CSF.

Using scanning electron microscope (SEM), The CSF leucocytes from 3 healthy subjects and 12 patients with various NS diseases were observed. The findings were used to compare with those by optical microscope (OM) and those of human peripheral blood cells by SEM. Five types of CSF cells with particular surface structures, are emphasized in relation to both optical microscopic findings and the involved diseases.

Cell Membrane↗

PubMed1988