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Biomedical subjects

G Liu

Publications and source records attributed to G Liu.

At least 595 records · Page 33Linked to original sources
PubMed1993

Regulation of collagen synthesis and messenger RNA levels in normal and hypertrophic scar fibroblasts in vitro by interferon alfa-2b.

Hypertrophic scars, which commonly occur after thermal and traumatic injury of the skin, are a fibroproliferative disorder of the dermal matrix wherein components of the inflammatory process, including the fibrotic growth factor, transforming growth factor-beta, appear to activate dormant fibroblasts leading to cellular proliferation and excessive matrix synthesis. To investigate the potential beneficial role and mechanism of interferon alfa-2b in controlling excessive collagen production in hypertrophic scar, we measured dose response, time of onset, and duration of action in hypertrophic scar fibroblasts in vitro and compared them with those of site-matched normal fibroblasts obtained from four patients after thermal injury. Interferon alfa-2b reduced collagen protein synthesis and type I messenger RNA levels in both hypertrophic scar and normal fibroblasts after treatment, but these changes were apparent only after approximately 72 hours. Significant reductions in collagen synthesis occurred in four pairs of normal and hypertrophic scar fibroblasts (p < 0.05), accompanied by significant reductions in type I (p < 0.05) but not type III procollagen messenger RNA. Hypertrophic scar fibroblasts recovered completely from the effects of interferon alfa-2b on procollagen type I messenger RNA within 48 hours of cessation of treatment in contrast to normal skin fibroblasts, in which the reduction in type I procollagen messenger RNA by interferon alfa-2b persisted beyond 72 hours after treatment. These data suggest that interferon alfa-2b reduces collagen synthesis in both normal and hypertrophic fibroblasts but the hypertrophic fibroblast may remain less sensitive to its effects.

Journal Article↗
PubMed1993

New aspects on heparin and lipoprotein metabolism.

Lipoprotein lipase (LPL) and hepatic lipase (HL) are two enzymes which participate in metabolism of plasma lipoproteins. The enzymes are located at vascular surfaces and are released from their binding sites on injection of heparin. In this paper we give a short overview of the structure of the lipases and their role in lipoprotein metabolism. Earlier studies had shown that low molecular weight (LMW) heparin preparations result in lower LPL activities in blood than do corresponding amounts of conventional heparin. Studies with organ perfusion in rats show that the two types of heparin have similar ability to release the lipases from their binding sites in extrahepatic tissues, but that LMW heparin is less effective than conventional heparin in preventing rapid uptake and degradation of LPL by the liver. After injection of heparin the metabolism of triglyceride-rich lipoproteins is initially accelerated, presumably as a result of the high levels of circulating LPL. Then follows a phase when lipoprotein metabolism is slower than normal, perhaps because endothelial LPL has been depleted by accelerated transport to and degradation in the liver.

Animals↗
PubMed1993

Body composition and muscle strength in healthy men receiving testosterone enanthate for contraception.

To determine the effect of androgens on body composition and muscle strength, we measured fat-free mass (kg), fat mass (kg), and bone density (g/cm2) by dual x-ray absorptiometry, and muscle strength (Newton meters) by dynamometry in a controlled, prospective study involving 13 nonathletic men receiving testosterone enanthate 200 mg/week in for 6 months and 8 healthy controls. Biochemical markers of bone turnover were measured in the treated subjects at baseline and 6 months. In the treated subjects at 6 months, fat-free mass (mean +/- SEM) increased by 9.6 +/- 1.0% (P < or = 0.01) whereas fat mass decreased by 16.2 +/- 6.7% (P < or = 0.05). Changes in muscle strength ranged from -1.6-19.2%. Only hip adduction increased 19.2 +/- 9.5% (P < 0.05). Changes in bone density ranged from -1.3-5.2%, decreasing significantly at one site and increasing significantly at four of the nine sites measured (P < 0.05). Serum testosterone increased by 91.1 +/- 7.5% (P < 0.01), and testicular volume decreased by 24.0 +/- 3.2% (P < 0.01). Serum osteocalcin increased by 35.7 +/- 17.3% (P < 0.05), serum immunoreactive PTH (iPTH) increased by 41.4 +/- 15.1% (P < 0.05), serum calcium decreased by 2.3 +/- 1.0% (P < 0.05), and serum albumin decreased by 4.5 +/- 1.7% (P < 0.05). There were no detectable changes in fat-free mass, fat mass, muscle strength, or bone density in controls. The administration of testosterone enanthate in pharmacological doses for 6 months resulted in a modest reduction in fat mass and small increases in fat-free mass, muscle strength, and bone density. These changes do not support the use of androgens for enhancing athletic performance.

Absorptiometry, Photon↗
PubMed1993

The role of cyclic GMP in regulating myosin during chemotaxis of Dictyostelium: evidence from a mutant lacking the normal cyclic GMP response to cyclic AMP.

Evidence has previously been reported that, during chemotaxis of the cellular slime mould Dictyostelium discoideum, cyclic GMP regulates the association of myosin II with the cytoskeleton and that this regulation is effected by inhibiting myosin II heavy chain phosphorylation (Liu and Newell, J. Cell Sci., 90, 123-129, 1988; 98, 483-490, 1991). Here we provide further evidence in support of this hypothesis using a mutant (KI-10) that is defective in chemotaxis and lacks the normal cyclic AMP-induced cyclic GMP response. We found that the cyclic AMP-induced cytoskeletal actin response was similar to that of the parental strain in this mutant (although showing a slight displacement in the dose-response curve) but the cytoskeletal myosin II heavy chain response was abolished. Moreover, the mutant showed no phosphorylation of myosin II heavy chain in response to cyclic AMP. Compared to the parental strain XP55, the mutant cells contained approximately 40% more protein and their doubling time was 30% longer. These differences could be due to differences in the efficiency of cell division, a process in which the proper regulation of myosin function is essential and in which cyclic GMP may therefore play a role.

Actins↗
PubMed1993

Epidemiological study on poliovirus isolates from patients with acute flaccid paralysis in Shandong province in China.

In five years from 1988 to 1992, 51 polioviruses were isolated from patients with acute flaccid paralysis in Shandong province in China. Of the 51 poliovirus isolates, 17 were type 1, 18 type 2 and 16 type 3. Twelve type 1 viruses isolated during the period from 1988 to 1990 were shown to be wild strains by serology and the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. These wild strains were classified into three groups by PCR-RFLP. The other type 1 isolates were Sabin-like strains. No wild strain was isolated in 1991 or 1992. All isolates of types 2 and 3 during the five years were Sabin-like strains. These data suggest that wild strains of polioviruses will soon be eradicated in Shandong province.

Acute Disease↗
PubMed1993

Repair of large bone defect by transplanting xenografts implanted with autovessels.

This paper reports on the role of autovessels implanted into an organic xenograft (AX) from the vertebrae of pigs in repairing fibular defect (2 cm long) in rabbits. The incorporation rate and mechanical strength of AX implanted with autovessels (AXV) and AX with combined autologous red marrow and autovessels implanted (AXMV) were determined at 2-week intervals up to 12 weeks after operation by roentgenograms, histological investigations and mechanical strength measurement. The results of AXV and AXMV were compared with those of AX impregnated with autologous red marrow (AXM), simple AX and xenografts treated with alcohol (XTA). The results indicated that the incorporation rates of AXV and AXMV were higher than those of AXM and AX (90.9% and 88.9% vs 66.7% and 62.5%, respectively). In contrast, XTA showed no sign of bone incorporation at 12 weeks after operation.

Animals↗
PubMed1993

Role of cyclic GMP in signal transduction to cytoskeletal myosin.

Evidence is presented for cyclic GMP having a role as a secondary messenger connecting the cell surface cyclic AMP receptors and cytoskeletal myosin II involved in chemotaxis of amoebae of Dictyostelium. Studies were conducted using mutants whose primary defect is in the structural gene for the cyclic GMP-specific phosphodiesterase (streamer F mutants). These mutants show abnormally prolonged accumulation of cyclic GMP in response to stimulation with the chemoattractant cyclic AMP. Investigation of signal transduction in these mutants indicated that, while events associated with production and relay of cyclic AMP signals were normal, certain events associated with movement were (like the cyclic GMP response) abnormally prolonged and these included myosin II association with the cytoskeleton and inhibition of myosin heavy and light chain phosphorylation. These events can be correlated with the amoebae becoming elongated and transiently decreasing their locomotive speed after chemotactic stimulation. Other mutants studied in which the accumulation of cyclic GMP was reduced or absent produced correspondingly reduced or absent myosin responses. We propose a model in which cyclic GMP (transiently accumulated intracellularly in response to stimulation with extracellular cyclic AMP) induces accumulation of myosin II on the cytoskeleton by inhibiting phosphorylation of the myosin heavy chain. As a consequence, bending of the myosin tail and its dissociation from the cytoskeleton are inhibited.

Actins↗
PubMed1993

Long-term safety and efficacy of programmable implantable insulin delivery systems.

OBJECTIVES: Since only short-term studies of continuous intraperitoneal insulin infusion (CIPII) therapy using implantable programmable insulin delivery systems have been performed to show this method of diabetes therapy to be safe and efficacious, we have performed long-term studies to assess its safety and efficacy. RESEARCH DESIGN AND METHODS: For 78 patient-years of follow-up, we have longitudinally studied the incidence of diabetic ketoacidosis and severe hypoglycemia in 25 type 1 diabetic patients treated with CIPII. We also compared, cross-sectionally, the long-term safety and efficacy of CIPII to intensive subcutaneous insulin therapy using intermittent injections or continuous subcutaneous insulin infusion. Finally, we examined the relationship between glycated hemoglobin levels and the standard deviation of daily blood glucose excursion. RESULTS: Cross-sectional analysis revealed similar degrees of metabolic control accompanied by significantly decreased rates of both ketoacidosis (0.013 events/patient/year) and severe hypoglycemia (0.05 events/patient/year) during CIPII compared to intermittent injections and continuous subcutaneous insulin infusion therapy. A four-fold decrease in the rate of severe hypoglycemia was observed during longitudinal comparison of pre- and post-implantation complication rates. A relationship was also shown between decreased levels of mean glycated hemoglobin and the standard deviation of blood glucose excursions during CIPII therapy. CONCLUSIONS: Our data demonstrate that long-term therapy with CIPII is as effective as other methods in achieving near-normal levels of glycated hemoglobin, which in CIPII is associated with a decreased standard deviation of blood glucose excursions. Further, CIPII using implantable programmable insulin delivery systems is the safest method described for intensive insulin therapy in home blood glucose monitoring type 1 diabetic patients.

Adolescent↗
PubMed1993

Effects of extracorporeal circulation on blood ketone body ratio reflecting hepatic energy metabolism during cardiac operation.

To examine the effects of extracorporeal circulation using an artificial heart and lung machine on hepatic energy metabolism in patients with cardiac operation using hypothermia, the arterial blood ketone body ratio (AKBR) reflecting the hepatic mitochondrial redox state was determined in 12 patients who had undergone cardiac operation using extracorporeal circulation from March to August 1991. Changes in AKBR were compared with those before and after extracorporeal circulation. AKBR decreased significantly after the beginning of extracorporeal circulation (p < 0.001) and remained at a lower level throughout extracorporeal circulation. On termination of extracorporeal circulation, the initial level was immediately resumed. The extent of decrease in ketone body ratio at ten minutes before termination of extracorporeal circulation was correlated with short term postoperative hepatic insufficiency. The patients whose ratio decreased below 0.4 showed increased levels in glutamic-pyruvic transaminase at the end of the first and second week after operation. Changes in AKBR were significantly associated with those in blood pressure (r = 0.433; p < 0.005) and body temperature (r = 0.472; p < 0.005). It was concluded that blood pressure and body temperature influence the blood ketone body ratio during extracorporeal circulation.

Adolescent↗
PubMed1993

Duration and dose-related effects of an orally administered, partially lipophilic polyaminocarboxylic acid on the decorporation of plutonium and americium.

A recently developed, orally administered, partially lipophilic polyaminocarboxylic acid-based chelator, docosyl-triethylenetetraminepentaacetic acid (C22TT), was tested for its ability to promote decorporation of 239Pu and 241Am. The effects of dose and duration of treatment were determined in rats injected with 239Pu or 239Pu/241Am 2 weeks before the initiation of C22TT treatment and compared with untreated controls. In the dose-effects study, significant reductions in total body Am content were seen within 3 days after the initiation of C22TT treatment. After 30 days of treatment, there were dose-related reductions in the Pu and Am content of soft tissues and bones. All doses of C22TT resulted in substantial reductions in Pu and Am content of the liver. In the time-response study, there were rapid reductions in total body Am content in the C22TT-treated animals. The greatest reductions occurred within the first 30 days of treatment. Significant decreases in Pu content of soft and hard tissue were observed in the treated animals at 30, 60 or 90 days compared with untreated controls. The greatest reductions in organ Pu content occurred within the first 30 days of treatment, particularly in the liver, but it continued throughout the experiment. Neutron-induced autoradiography showed that C22TT greatly reduced the incorporation of Pu into new bone and substantially reduced the Pu content of the bone marrow. There was no evidence of overt toxicity in either experiment. This study demonstrates that orally administered C22TT is effective in reducing soft and hard tissue content of internally deposited Pu and Am.

Acetates↗
PubMed1993

[Gas chromatographic analysis of nicotine in indoor air].

An analytical method for the determination of nicotine in indoor air was developed. Air sample was collected in absorption solution of 1% NaHSO4. After alkalization and heptance extraction, the content of nicotine in the sample was determined by gas chromatography with FID. The average sampling efficiency was 93.6%. The recovery rate was 89.3%-105.5% (mean = 98.4%). The coefficient of variation was 1.7-4.1%. Under the sampling condition the detection limit was 0.01 microgram/m3. After discussing the stability and extraction efficiency of the sample, we found the air sample collected in the absorption solution was stable for at least 7 days in refrigerator. The field experimental results show that the method is simple, reliable and suitable for collecting and determining trace nicotine in indoor air.

Air Pollution, Indoor↗