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Biomedical subjects

J G Liu

Publications and source records attributed to J G Liu.

At least 55 records · Page 3Linked to original sources
PubMed1995

Rapid cDNA sequencing in combination with RNA expression studies in mice identifies a large number of male germ cell-specific sequence tags.

A large number of cDNA clones were isolated from an adult mouse testis cDNA library and partially sequenced. Sequence comparisons revealed that many of them displayed similarities to genes previously identified only in invertebrates and lower eukaryotes, including, e.g., one cDNA clone related to the Drosophila melanogaster suppressor of forked gene. Other cDNA clones were found to be related, but not identical, to rodent genes involved in a variety of cellular activities, e.g., signal transduction and tumor development. The RNA expression patterns of 258 cDNA clones were analyzed through use of Northern blot methodology. Forty-two novel cDNA clones were found to be expressed only in male germ cells, the majority of them during spermiogenesis. One male germ cell-specific mouse cDNA clone was found to be similar to tektin A1, a protein known to interact with the flagellar microtubules of sea urchin sperm.

Amino Acid Sequence↗
PubMed1995

[Minocycline potentiates the antimetastatic effect of boanmycin].

Boanmycin (bleomycin A6, BAM) was found to markedly inhibit the spontaneous pulmonary metastasis of Lewis carcinoma in mice. Compared at equitoxic doses (1/9 LD50), BAM was more effective than mitomycin. Minocycline (MNO) at 5 mg.kg-1 showed no inhibition on the growth of sc transplanted Lewis primary tumor; however, it markedly potentiated the antimetastatic effect of BAM. Treated with BAM (5 mg.kg-1) alone, the number of total metastatic foci and that of large foci (> 2 mm in diameter) in the lung were suppressed by 67% and 85%, respectively. When BAM was used in combination with MNO, the number of those foci was further reduced by 88% and 100%, respectively. By NAG enzyme assay, MNO was not cytotoxic and showed no synergism with BAM against PG cells, a cell line derived from a highly metastatic human giant cell carcinoma of the lung. Determined by ELISA with a monoclonal antibody, the expression of type IV collagenase in PG cells was remarkably inhibited by MNO. The intracellular free Ca2+ level in PG cells was reduced from 76.7 nmol.L-1 to 42.2 nmol.L-1 by MNO treatment. The study suggests that the combination of boanmycin and minocycline may be useful for control of tumor metastasis and the inhibition of type IV collagenase expression may be involved in the mechanism of minocycline potentiation.

Animals↗
PubMed1994

[Stress shielding and fracture healing].

The influence of stress shielding after fracture fixation with plate on fracture healing was studied. The results of animal and biomechanical experiments as well as the clinical observations demonstrated that rigidity of the plate was not the only factor causing stress redistribution and stress shielding effects of bone. Either the internal fixation with different implants or external fixation with fixators all might lead to physical and chemical characteristic changes of bone tissue. In the early stage, the disturbance of blood supply and the bone structure remodeling may be the main reasons. Reaction to the implant was another cause in the middle stage. If the affected limb can take weight-bearing normally at late stage, the influences of plate on fracture healing mechanical properties of bone and the osteoporosis cause by stress shielding effects will become much less. The tissue of the affected limb was the most important factor which may cause osteoporosis and refracture. Osteoporosis, bone atrophy and immobilization syndrome of bone and joint can be prevented and treated by taking normal weight-bearing and overcoming infection and implant reaction.

Animals↗
PubMed1993

Stress analyses after femoral shaft osteotomy fixed by various plates with different rigidities in simulation test.

Three pairs of human cadaver femora were used for strain measurement under a weight-bearing simulation test, which was performed on intact bone and osteotomized bone fixed by 3 types of plates with different rigidities respectively. The plates with uniform thickness did not adhere to the uniform stress distribution along the plate. The stress between both central screw holes was significantly great. However, the device of trapezoidal plate conformed to the uniform stress distribution along it, and the safety factors of 3 different types of the plates were proposed. The osteotomy site was mainly subjected to compression stress in standing phase with load on both femora, but subjected to bending stress mostly with load on the single femur. The total compression strain at the osteotomy site was greater than that on intact bone while the load was adding over twice body weight with load on both legs, and nearly normal with load on one leg. We believe that the bone structural changes caused by stress shielding and limb disuse etc can be overcome by using optimal plate and normal weight bearing.

Bone Plates↗
PubMed1992

Evaluation of penetrating keratoplasties with long-term cryopreserved corneas using simplified method.

Since March 1986, the authors have studied and simplified the corneal cryopreservation technique using a self-made QL Bio-freezer. On the basis of successful animal experiments, penetrating keratoplasties with human cadaver corneas cryopreserved 9 to 571 days (averaging 131 days) were performed in 60 patients (61 eyes). The patients were followed up for 1.5 to 50 months. 41 of the corneal grafts remained clear, 9 became translucent and 11 cloudy. A total of 46 eyes had their visual acuity improved significantly. The results show that clinical use of corneal cryopreservation by the simplified two-step method is noteworthy.

Adolescent↗
PubMed1991

Blood supply and structural changes of canine intact tibia following plate fixation with different rigidities.

To study the causes of osteopenia after plate fixation in the treatment of fractures and bone diseases, intact tibiae of 26 dogs were fixed by 3 different plates at various rigidities. The dogs were killed at 24 hours 3, 6, 12, 20 weeks. Disulphine blue was injected intravenously before killing. The results showed that in addition to stress shielding the disturbance of blood supply was the main cause of osteopenia in the early stage. Reaction to the implant might be another cause in the middle stage. The disuse of the affected limb was the most important factor in the late stage. Osteopenia can be treated by active exercises and normal weight-bearing before plate removal.

Animals↗
PubMed1989

Roussin red methyl ester, a tumor promoter isolated from pickled vegetables.

Roussin red methyl ester [RRME; Fe2(SMe)2(NO)4], has recently been isolated from pickled vegetables consumed in Linxian, China. In the present studies, the tumor-promoting effect of RRME was found in rats treated first with nitrosodiethylamine. A two-stage experiment was also carried out by application of RRME on BALB/c mouse skin subsequent to 7,12-dimethylbenz[a]anthracene treatment, and induction of ornithine decarboxylase (ODC) activity was observed in epidermal cells. After 37-week treatments with 150, 300 or 450 nmol of RRME, the skin developed precancerous lesions and squamous cell carcinomas. The epidermal ODC activity was increased rapidly following a single application of RRME, and the level of its activation was in proportion to the doses used, although the promoting effect of RRME was weaker than that of 12-O-tetradecanoyl-phorbol-13-acetate. Since pickled vegetables are staple food in high-risk areas for esophageal cancer, RRME, as a tumor promoter, may therefore play a role in the development of this malignant disease.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

[Analysis of urinary citrate and oxalate in 42 diabetics].

Among 42 diabetics, there were 32 with the disease remaining uncontrolled after treatment. Their fasting blood glucose was 15.24 +/- 5.37 mmol/L (mean +/- S), urinary glucose 42.6 +/- 47.83 g/24 hr, urinary oxalate 0.43 +/- 0.16 mmol/24 hr and urinary citrate 3.60 +/- 2.28 mmol/24 hr All of these levels were higher than those in a control group (P less than 0.001). Urinary citrate level was significantly positively correlated with fasting blood glucose level (gamma = 0.3954, P less than 0.001). In the remaining 10 diabetics with the disease controlled after treatment the fasting blood glucose was 7.04 +/- 0.92 mmol/L, urinary citrate 1.92 +/- 0.96 mmol/24 hr and urinary oxalate 0.37 +/- 0.11 mmol/24 hr. All of these levels were significantly lower than those before treatment (P less than 0.01) and were not different from those in the control group (P greater than 0.05). This explains that urinary citrate and oxalate increased when diabetes is uncontrolled as a result of accelerated decomposition due to increased metabolism. Urinary oxalate level is correlated positively with that of urinary citrate (gamma = 0.3773, P less than 0.05). Urinary oxalate and citrate are good index reflecting diabetic metabolic changes. Analysis of urinary oxalate with ion-chromatography is accurate and rapid method worthy to be used clinically.

Adult↗
PubMed1989

[Risk factors for the formation of urinary calcium-containing stones in diabetics].

Levels of 24-hour urinary calcium, magnesium, oxalate, citrate, uric acid, phosphorus and creatinine as well as urinary volume were determined in 85 patients and 81 normal subjects. Among the patients, 43 were diabetics without stone, 5 diabetics with stone and 37 with idiopathic calcium stone formation in the urinary tract. It is shown that the main risk factors involved in urinary calcium-containing stone formation are the levels of calcium, oxalate, uric acid and citrate and the volume of 24-hour urine. With the data obtained, the authors calculated the ion-activity products index of calcium oxalate and the relative probability of stone formation in the three groups of patients and the control group of normal subjects. The index in normal subjects, diabetics without stone, diabetics with stone and patients with idiopathic urinary calcium stone was 3.07 +/- 0.16, 2.90 +/- 0.25, 3.90 +/- 0.58 and 5.11 +/- 0.38 respectively. The upper limit of the relative probability in normal subjects was 0.54. Most of the patients with idiopathic urinary calcium stone (32/37) and all the 5 diabetics with stone had higher probability value than this, while most of the normal subjects (73/81) and of the diabetics without stone (39/43) had value lower than this. The results indicate that though the diabetics have higher level of urinary calcium and higher value of the product of calcium x oxalate x uric acid, they have also inhibitive factors for stone formation, such as increased level of urinary citrate. As a result, urinary stone formation will not be a frequent occurrence.

Adult↗
PubMed1989

[Culture conditions for uricase formation of Candida utilis].

A uricase producing strain, Candida utilis AS 2.117, was screened out and the uricase-forming conditions have been investigated. The results are obtained as follows: uric acid, xanthine and guanine were found to be effective inducers for enzyme formation. Corn steep liquor was essential for enzyme formation and cell growth. Sucrose, glucose, D-mannose and D-fructose were the suitable carbon sources for enzyme formation. To the medium containing corn steep liquor, addition of inorganic nitrogen sources was harmful to the enzyme formation, however, addition of organic nitrogen sources enhanced enzyme activity slightly. The suitable medium for uricase formation was consisted of sucrose 5%, corn steep liquor 3%, uric acid 0.1%, proteose-peptone 0.1%, biotin 0.05%, KCl 0.1%, NaCl 0.1% at pH 6.2. When the yeast was grown in 250 ml conic flask containing 30 ml of the medium mentioned above on the rotary shaker (200 r/min) at 25 degrees C for 21 h, uricase with 0.6 u/ml activity was obtained.

Candida↗
PubMed1987

Alpha-2 adrenergic modulation of norepinephrine secretion in the perfused rabbit iris-ciliary body.

Clonidine and other selective alpha-2 adrenergic agonists have been found to lower intraocular pressure in the eyes of rabbits and primates, including humans. It has been suggested that the ocular hypotensive response to alpha-2 agonists may be mediated, in part, by prejunctional inhibition of norepinephrine secretion at intraocular synapses. In this study, we have investigated the effects of adrenergic agonists and antagonists on field-stimulated, Ca++-dependent release of 3H-norepinephrine (3H-NE) from isolated, perfused rabbit iris-ciliary bodies and have utilized radioligand binding methods to identify prejunctional adrenoceptors in this tissue. Clonidine (10(-9)-10(-5) M) produced a dosage-dependent inhibition of stimulation-evoked 3H-NE secretion (EC50 approximately equal to 3 X 10(-8) M), but did not alter basal secretion. Other adrenergic agonists capable of activating alpha-2 adrenoceptors (e.g., epinephrine, norepinephrine and xylazine) also significantly depressed 3H-NE secretion, whereas selective alpha-1 adrenergic or beta adrenergic agonists were without effect. Clonidine-mediated inhibition of 3H-NE release was reversed by the selective alpha-2 antagonist yohimbine (10(-7) M), but was unaffected by prazosin or timolol. Yohimbine alone markedly enhanced 3H-NE secretion, indicating tonic activation of prejunctional alpha-2 adrenoceptors by endogenous released norepinephrine. Forskolin or 8-bromo-cAMP, which alone enhanced norepinephrine secretion, failed to attenuate the inhibitory responses to alpha-2 agonists. 3H-rauwolscine binding measurements showed a small decrease in alpha-2 receptor sites in iris-ciliary body membranes following surgical sympathetic denervation. It is concluded that the rabbit iris-ciliary body contains functional, prejunctional alpha-2 adrenoceptors which may play an autoregulatory role in vivo and contribute to the ocular effects of adrenergic drugs.

Animals↗
PubMed1986

A rapid assessment of percentage hemoglobin-S in whole blood.

In an effort to bridge the gap between the rapid Sickledex screening test (Ortho Diagnostics, Raritan, NJ) and the slow but quantitative hemoglobin electrophoresis, the authors developed a rapid method for quantification of the percentage of hemoglobin S (%Hgb-S) in whole blood. The method involves quantification of the hemoglobin before and after removal of sodium dithionite-induced sickled cells for calculation of the %Hgb-S. Test results were within a +10% range of hemoglobin electrophoresis, with 67% of results within a +5% range. The method, taking 30-45 minutes to perform, offers a rapid assessment of %Hgb-S in acute care situations.

Hemoglobin, Sickle↗