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Biomedical subjects

L Liu

Publications and source records attributed to L Liu.

At least 1,207 records · Page 67Linked to original sources
PubMed1991

Basic fibroblast growth factor in cultured cardiac myocytes.

Distribution of basic-fibroblast-growth-factor-like peptides in immature cultured cardiac myocytes was investigated using specific antisera and immunolocalization. Basic FGF was detected in association with the external surface of the cell membrane, with specialized intercellular junctions and with the myofibril Z lines in the cytoplasm. Intense, punctate nuclear anti-bFGF labeling was observed in a fraction of interphase myocytes of near-confluent, proliferating cultures. This staining pattern persisted even after the dissolution of the nuclear envelope in prophase myocytes. The pattern of cellular localization of bFGF indicates a continuous participation of this factor in myocyte physiology as well as a role in the cell cycle. Furthermore, the identification of bFGF not only in cell lysates but also in culture media after gentle mechanical disruption suggests that cardiac myocytes may release bFGF in vivo following tissue damage.

Animals↗
PubMed1991

A functional leuABCD operon is required for leucine synthesis by the tyrosine-repressible transaminase in Escherichia coli K-12.

In Escherichia coli K-12, two enzymes, encoded by ilvE and tyrB, catalyze the amination of 2-ketoisocaproate (2-KIC) to form leucine. Although leucine-requiring derivatives of an ilvE strain that are unable to grow on 2-KIC were expected to have mutations only in tyrB, mapping studies showed that one such mutation was tightly linked to the leu operon (at 1.5 min), not to tyrB (at 92 min). Chromosomal fragments cloned because they complemented this mutation were found to complement leu mutations, and vice versa, but none of these fragments complemented a tyrB mutation. The Tn5 insertion and flanking host DNA from this anomalous mutant was cloned in vivo, using Mu dII4042, and an in vivo procedure was developed to isolate deletion derivatives of Tn5-containing plasmids. These deletion plasmids were used to determine the DNA sequences flanking the transposon. The data showed that Tn5 was inserted between bp 122 and 132 in the leu leader. In addition, other ilvE leu double mutants were found to be unable to grow on 2-KIC in place of leucine. The accumulation of 2-ketoisovalerate in ilvE leu double mutants was shown to interfere with 2-KIC amination by the tyrB-encoded transaminase and also by the aspC- and avtA-encoded transaminases (which are able to catalyze this reaction in vivo when the corresponding genes are present on multicopy plasmids).

Bacteriophages↗
PubMed1991

Growth hormone (GH) responses to the hexapeptide GH-releasing peptide and GH-releasing hormone (GHRH) in the cynomolgus macaque: evidence for non-GHRH-mediated responses.

GH-releasing peptide (GHRP; His-D-Trp-Ala-Trp-D-Phe-Lys-NH2), a hexapeptide derived from enkephalin, has been shown to have GH-releasing activity in man and several animal species. To characterize the GHRP dose-response curve and compare it with that of GH-releasing hormone [GHRH-(1-44)NH2], six unanesthetized young adult cynomolgus macaques were tested with a range of iv doses of GHRP or GHRH in random order. Animals were fitted with vests and tethers. Blood samples were obtained before and at 15-min intervals after the administration of drugs. Doses ranged from 0.03-3 mg/kg for GHRP and from 1-30 micrograms/kg for GHRH. The dose-response curves for the two peptides were not parallel. GHRP had lower potency, but evoked a much higher peak GH response than GHRH (greater than 55 vs. 12 micrograms/L). Because one of the proposed mechanisms of action of GHRP is the inhibition of somatostatin (SS), we tested the effects of propranolol, which inhibits SS, on the GH responses to GHRH and GHRP. Propranolol was given at a dose of 14 micrograms/kg, iv, 10 min before the injection of saline, GHRH (10 micrograms/kg), or GHRP (1 mg/kg). GH responses to propranolol alone did not differ from those to placebo (peak, 6 +/- 2 vs. 8 +/- 2 micrograms/L). However, propranolol pretreatment doubled the GH responses to both GHRH and GHRP compared with those to GHRH or GHRP alone 28 +/- 5 micrograms/L vs. 14 +/- 5 (P less than 0.05) and 54 +/- 2 vs. 25 +/- 6 micrograms/L (P less than 0.001), respectively]. These results show that GHRP causes a potent dose-dependent release of GH in this primate species. Since GHRP can produce a greater maximal GH response than GHRH, mechanisms other than release of endogenous GHRH must be involved.

Animals↗
PubMed1991

Effects of pituitary-testicular axis suppression in utero and during the early neonatal period with a long-acting luteinizing hormone-releasing hormone analog on genital development, somatic growth, and bone density in male cynomolgus monkeys in the first 6 months of life.

The specific role of late fetal and early neonatal gonadotropins and/or sex steroids on genital development, linear growth, and bone mass accretion remains unclear. To investigate this, we attempted to selectively suppress pituitary-testicular activation from midgestation through early infancy with a long-acting LHRH agonist (LHRHA), D-Trp6,Pro9-NEt-LHRH, in microspheres. The agonist was injected sc on days 72-81 in utero, on day 1 of life, and 3 months postnatally in male cynomolgus monkeys. Control animals were treated with placebo. We then examined the consequences of such an intervention in the first 6 months of life. In the LHRHA-treated animals, marked suppression of plasma testosterone and gonadotropin levels were evident in the first 3 months of life compared to control values. The mean testicular volumes of the LHRHA group were significantly lower at birth and in the first 2 months of life than those of the placebo group (P less than 0.05). However, by 4 months of age, the mean testicular volumes of the two groups were comparable. Similarly, the mean stretched phallic lengths of the LHRH approximately A group were significantly lower than those of the placebo group throughout the first 6 months of life (P less than 0.05). By contrast, LHRHA treatment had no effect on somatic growth, as mean body weights, total body lengths, and trunk lengths of the two groups were similar over the first 6 months of life. Mean bone widths and densities of the distal third of the left radius and the left midfemur were similar in the two groups at 1 and 6 months of life. We conclude that pituitary-testicular axis suppression with a long-acting LHRHA in utero and during early infancy results in markedly stunted penile and testicular growth without affecting general somatic growth and bone density of appendicular cortical bone in the cynomolgus monkey in the first 6 months of life. Thus, an intact fetal and neonatal pituitary-testicular axis is critical for normal genital growth. However, the sex steroid requirement for maintenance of bone mineral content of appendicular cortical bone may be lower than that necessary for normal genital development.

Aging↗
PubMed1991

Spatial disorientation in persons with early senile dementia of the Alzheimer type.

Although spatial disorientation is frequently observed in persons with Alzheimer disease, it is not well understood. A descriptive study was conducted to examine spatial skills associated with spatial orientation. Spatial tasks were selected and grouped into three types of spatial skills: perceptual, cognitive, and functional. These spatial tasks were administered to a group of 15 persons with senile dementia of the Alzheimer type (SDAT) (early Alzheimer disease) and a group of 15 control subjects. The results indicated that the subjects with SDAT were impaired on half of the perceptual spatial tasks and all of the cognitive spatial tasks. On the functional spatial tasks, however, the subjects with SDAT showed impaired skills in the new environment but intact skills in familiar environments. Spatial disorientation poses a danger and limits a person's ability to independently perform daily activities that require navigation outside of the home. Occupational therapy should therefore include the assessment of spatial orientation skills in persons who are in the early stages of dementia.

Activities of Daily Living↗
PubMed1991

[Respiratory effects of microinjection of three kinds of neurotransmitters in ventromedial region of nucleus facialis].

The effects of microinjection of three kinds of neurotransmitters in ventromedial region of nucleus facialis (VMNF) on respiration were observed in vagotomized, spontaneously breathing rabbits anesthetized with urethane. Microinjection of adrenaline in VMNF induced a marked increase in respiratory rate and amplitude of integrated phrenic activity associated with an increase in the initial rate of rise of inspiratory activity. However, alpha-receptor antagonist tolazoline elicited marked decreases in respiratory rate accompanied by little or no changes in amplitude of integrated phrenic activity and initial rate of rise of inspiratory activity. The respiratory effects of microinjection of adrenaline were blocked by previous injection of tolazoline. Microinjection of GABA and glycine resulted in a decrease of respiratory frequency. These results suggest that adrenaline, GABA and glycine may modulate respiration by acting on VMNF neurons as neurotransmitters.

Animals↗
PubMed1991

[The relationship between hepatitis B and renin-angiotensin-aldosterone system].

The angiotensin II (AT II) levels in plasma were measured 68 times by using radio-immunoassay in 30 patients with viral hepatitis B (HB) and in 35 healthy persons as the control group. The results showed that the AT II levels of patients with HB were much higher than those of the control group (P less than 0.001). They were 219.25 +/- 91.31 ng/L and 60.70 +/- 10.73 ng/L, respectively. These indicated that the renin-angiotensin-aldosterone system (RAAS) of the patients was in exciting state. The levels of 8 cases of severe chronic active hepatitis (SCAH) (AT II = 270.40 +/- 106.55 ng/L, 6 cases of subacute fulminant hepatitis (SFH) (AT II = 332.80 +/- 140.12 ng/L), and 4 cases of hepatocirrhosis (HC) (AT II = 218.50 +/- 97.64 pg/ml) were all higher than those of 8 cases of chronic active hepatitis (CAH) (100.50 +/- 83.81 ng/L) and those of 4 cases of acute icteric hepatitis (A1H) (123.33 +/- 64.97 ng/L). These findings showed that the levels of AT II were directly related with the severity of the illness. The AT II levels of 8 cases of HRS (270.50 +/- 66.31 ng/L) were higher that those without HRS (174.50 +/- 78.48 ng/L). After treatment with captopril (CPT), the renal function of the patients returned to normal and the patients got better, while the AT II levels decreased greatly. The results suggested that high AT II levels in plasma may be one of the causes aggressing the HRS. The CPT may inhibit the produce of AT II and there are some therapeutic effects for the HRS.

Adult↗
PubMed1991

[Logistic regression analysis of risk factors influencing the occurrence of category III pneumoconiosis in the coal mine].

Using 1:4 matched method, we have selected 40 cases of category III pneumoconiosis and 160 controls in a coal mine, and analyzed the factors which influenced the occurrence of category III pneumoconiosis by Multiple Logistic Regression Model. The results were as follows: Tuberculous infection and the type of radiographic appearance manifested mainly as small round opacities were positively correlated with the attack of category III pneumoconiosis. The time of starting exposure to dust, the years and the kinds of work were not led into regression model as significant factors.

Case-Control Studies↗
PubMed1991

[Effects on respiratory rhythmicity by lesion or focal block in ventromedial region of nucleus facialis].

Experiments were performed on 42 urethane-anesthetized rabbits of both sexes. The rabbits were either spontaneously breathing or gallamine paralyzed and artificially ventilated. Efferent phrenic nerve activity was recorded with bipolar silver electrodes. The experiment results were as follows: Unilateral mechanical lesion of focal block by microinjection of lidocaine (2%, 1 microliter) in the ventromedial region of nucleus facialis (VMNF) consistently caused apneustic-type breathing associated with no significant changes in the rate of rise of inspiratory activity. The expiratory time (Te) was only slightly affected or not changed at all. Some increase in Te was present only when a very strong apneustic effect was evoked. Respiratory effects of focal block by lidocaine in the region of VMNF were not accompanied by changes in blood pressure. No significant changes in respiratory rhythm were observed when lidocaine is microinjected in the nearby regions of VMNF. The results suggest that VMNF appears to be involved in an inspiratory off-switch mechanism.

Animals↗
PubMed1991

Evaluation of second-look laparotomy for ovarian cancer: second-look vs. serum CA125.

Thirty patients with ovarian cancers underwent second-look operations in our hospital between 1981 and 1989, and the results were compared with serum CA125 values. The over-all positive rate determined by second-look laparotomy in the present series was 56.7% (17/30)-40% as gross and 17% an microscopic tumors. The result of the second-look was related to the staging and size of the residual tumor after the previous operation: 1/3 of stage I and II lesions and 16/27 of stage III and recurrent lesions were positive on second-look. The positive rates of those patients who were free from residual tumor and those with residual tumors less than or equal to 2 cm or greater than 2 cm were 28.6% (2/7), 60% (9/15) and 75% (6/8), respectively. Among the 23 patients assayed as to serum CA125 level before the second-look, 18 (78%) were within normal limits (less than 65 U/ml), including 12 patients (66.6%) who were second-look positive and 6 who were negative. Five patients with microscopic tumors and 3 patients with gross tumors less than or equal to 2 cm all had normal CA125 levels before the second-look. Among the 5 of 9 patients with gross tumors greater than 2 cm who had elevated CA125 levels, not one was found to be negative on second-look. This may imply that the elevated CA125 levels indicate recurrence, though a normal CA125 assay certainly does not preclude recurrence.

Adult↗
PubMed1991

[Computerized image analysis of normal optic discs].

A self-designed computer system was used for image analysis of 172 normal optic discs, with Littmann's correction of photographic magnification. The mean disc area was found to be 2.40 +/- 0.50mm2, and the mean rim area 1.77 +/- 0.32mm2. The rim area was significantly correlated to disc area (r = 0.67, P = 0), but not to age, sex or refraction.

Adolescent↗
PubMed1991

[Effects of AMG-1 on energy metabolism and neuronal damage of ischemic brain in mice and rats].

The effect of AMG-1 [6(5-hydroxy-2-methylpyridylamino)-9 ribofranosylpurine] on mouse brain energy metabolism in complete brain ischemia induced by decapitation and on neurological deficit and histopathological changes after occlusion of the middle cerebral artery (MCAO) in rats were studied. The results indicate that AMG-1 has an effect of improving the status of energy metabolism in complete brain ischemia in mice. Lactate concentration was greatly reduced and the ATP and phosphocreatine levels were significantly elevated. Treatment with AMG-1 or nimodipine was performed before and after MCAO. The score of neurological deficit was significantly decreased as compared with the vehicle treated group. The extent of ischemic neuronal injury was determined by histopathological examination. AMG-1 and nimodipine seemed to attenuate the MCAO-induced neuronal damage. In as much as AMG-1 can improve the status of brain energy metabolism, neurological deficit and neuronal damage after ischemic insult, AMG-1 may have a beneficial effect for the treatment of cerebral ischemic damage.

Adenosine↗
PubMed1991

[Radioimmunoimaging of nude mice bearing human lung adenocarcinoma xenografts after injecting 131I-McAbs].

Monoclonal antibodies (Lc86a-C5, Lc86a-H8) directed against human lung adenocarcinoma cell line LTEP-a-2 and normal BALB/c IgG were labelled with iodine-131 by chloramine T. The 131I-McAbs and 131I-IgG were respectively injected into the peritoneal cavities of nude mice bearing transplanted human lung adenocarcinoma cell line LTEP-a-2. After 72 h, the tumor tissue in nude mice injected with 131I-McAbs was distinguishable from normal tissues as a very clear image obtained during gamma scintigraphy. No difference was found between tumor and normal tissues in the nude mice injected with 131I-IgG. The tumor: blood ratio was 3.1:1 in nude mice injected with 131I-McAb(H8) and 0.9:1 in nude mice injected with 131I-IgG respectively. This indicates that the tumor tissue image was the result of specific binding of the 131I-McAbs, which have high specificity and affinity both in vitro and in vivo, to tumor cells, and these monoclonal antibodies may serve as potential agents in tumor diagnosis and treatment.

Adenocarcinoma↗
PubMed1991

Analysis of the role of hormones and growth factors in growth control and tissue differentiation using transplanted mammalian embryos and fetal structures.

Results obtained from our analyses of the role of hormones and growth factors in rat embryonic and fetal development are reviewed. Whole 10-day embryos or structures from 14-16-day fetuses (paws, intestines, reproductive tracts) were transplanted under the kidney capsule of syngeneic host rats of different age, sex, physiological state or level of nutrition. In intact hosts, fetal transplants grew almost as much as they would have if left in situ in the fetuses, and tissue differentiation in them was essentially normal. By contrast, growth of embryo transplants was severely depressed relative to their growth in utero, but tissue differentiation was only slightly retarded. Fetal paws grew equally well in female hosts widely diverging in age and growth rate. Thus, in such hosts growth of the fetal paw was highly independent of the growth rate of the hosts. In hosts in which growth was arrested or reduced by diabetes, hypophysectomy or food restriction, growth of paw transplants was impaired, but not as severely as that of the hosts themselves. Fetal skeletal structures were relatively independent of thyroid hormones (TH) for growth; TH dependence developed progressively postnatally. In pregnant hosts, fetal paw transplants grew as well during the first half of gestation as they did in virgin females. By contrast, during the second half of pregnancy and during both halves of the lactational period, growth of the transplants was significantly reduced. Host skeletal growth was also inhibited during late pregnancy and throughout lactation. The impaired growth during the second half of gestation was associated with a large reduction in serum IGF-I concentration and a resistance to the growth-promoting actions of GH. In the lactating hosts, serum IGF-I concentration returned almost to prepregnancy levels and the resistance to GH persisted, but at a reduced level. The direct effects of hormones, growth factors, and antibodies to them on growth and tissue differentiation in the transplants were assessed using infusion methods. Substances were infused into the renal artery of transplant-bearing kidneys via catheters attached to osmotic minipumps. The direct effects of insulin, GH, IGFs, basic FGF and EGF on transplant growth and tissue differentiation were evaluated. Insulin directly stimulated growth of transplants in diabetic hosts but GH did not have a direct effect in hypophysectomized rats. The growth-restorative effects of GH observed in hypophysectomized hosts were apparently mediated indirectly via IGF-I. Infused rat IGF-II (MSA) was more effective at stimulating growth of embryo transplants than was recombinant human IGF-I.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗