Search PubMed⌕ Search

Biomedical subjects

L Liu

Publications and source records attributed to L Liu.

At least 937 records · Page 52Linked to original sources
PubMed1996

Ontogeny and hormonal basis of female-dominant rat hepatic sulfotransferases.

Female-dominant sulfotransferases (ST) are a group of enzymes catalyzing sulfation of steroid hormones, bile acids and exogenous carcinogens. To understand the regulation of these enzymes, developmental and hormonal regulation of three female-dominant ST was studied. The three ST, ST-20/21, ST-40/41 and ST-60, were differentiated by specific oligonucleotide probes, and their gene expression was examined by Northern-blot analyses. The three ST have different developmental patterns, as ST-20/21 and ST-60 were increased after puberty in female rats, although ST-40/41 was higher in immature rats. In addition, ST-20/21 and ST-60 expression reached a peak at 30 days of age in male rats, although ST-40/41 reached its highest value in male rats at 15 days of age. Estrogens and androgens did not appear to be major determinants of the developmental profiles. However, ST-20/21 was decreased in both male and female rats by hypophysectomy, and reversed by continuous infusion (female pattern) of growth hormone (GH). In contrast, hypophysectomy elevated ST-40/41 and ST-60 expression in males. The elevation in males was reversed by GH injection (male pattern). This study demonstrates that the three female-dominant sulfotransferases display two ontogenic patterns and are regulated by different mechanisms. Female GH secretory pattern appears to determine the high expression of ST-20/21 in postpubertal female rats, although male GH secretory pattern results in the low expression of ST-40/41 and ST-60 in mature male rats.

Animals↗
PubMed1996

Regulation of hepatic sulfotransferases by steroidal chemicals in rats.

Pregnenolone-16 alpha-carbonitrile (PCN) has previously been shown to increase sulfotransferase (ST) activity in rats. It was of interest to determine whether other steroids, such as dexamethasone (DEX), similarly affect ST activity, and whether they alter ST gene expression. The modulation of rat liver STs by the two steroidal compounds was examined at both the enzyme activity and mRNA levels. PCN (75 mg/kg daily for 4 days) increased liver phenol ST activity toward 1-naphthol and estrone, and hydroxysteroid ST activities toward dehydroepiandrosterone (DHEA) and bile acids; but, PCN had no effects on ST activities toward dopamine and N-hydroxy-2-acetylaminofluorene (N-OH-2AAF). DEX (50 mg/kg daily for 4 days) had similar effects on ST activities toward 1-naphthol, estrone, and DHEA, but DEX markedly increased ST activity toward dopamine and suppressed the N-OH-2AAF ST activity. Northern-blot analysis showed that PCN (75 mg/kg, single injection) had no effects on mRNA levels of phenol ST (ST1A1), N-OH-2AAF ST (ST1C1), and estrogen ST (ST1E2), but PCN significantly increased mRNA levels of hydroxysteroid ST (ST-20/21, ST-40/41, and ST-60). DEX (50 mg/kg, single injection), in contrast, increased the mRNA levels of ST1A1 and tended to suppress ST1C1, which corresponds to changes in encoded ST activity. Although DEX increased ST activity toward DHEA, as did PCN, DEX had less effect on hydroxysteroid ST mRNA levels. These results suggest that STs are regulated by steroids, but DEX and PCN regulate the STs differently. The change in ST enzyme activity seems to be partially caused by alteration in mRNA levels.

Animals↗
PubMed1996

YAC cloning and identification of rice (Oriza sativa L.) genomic DNA.

Construction of the genomic library by using yeast artificial chromosomes (YAC) has been an approach to a map-based gene cloning strategy. We have obtained more than 2000 YAC clones for the construction of a rice (Oriza sativa L.) genomic library through a procedure that could be summarized as follows: a fractionate by the pulsed-field gel electrophoresis (PFGE), the rice nucleic high molecular weight (HMW) DNA which is partially digested with EcoRI, and recovered fragments larger than 200 kb; ligate the fragments to the EcoRI digested YAC vector pairs pJS97 and pJS98; transform competent spheroplasts prepared from yeast strain YPH252; and select transformants directly on Ura-Trp-double selective media. Southern hybridization results indicated that the sizes of inserts were in the range of 200-820 kb.

Chromosomes, Artificial, Yeast↗
PubMed1996

Nematode spliced leaders--ubiquity, evolution and utility.

Most nematode messenger RNAs (mRNAs) have at their 5' end a common 22 nucleotide leader sequence, the trans-spliced leader or SL1. The presence of this leader on some but not all mRNAs raises several questions: What is the role of the spliced leader in mRNA maturation, stability and translation? Why do some genes have a spliced leader and others not? What is the evolutionary origin of this trans-splicing mechanism? Recently, additional trans-spliced leaders (SL2, 3, 4, 5) have been described. What role do these variants play in nematode gene expression? While definitive answers to these questions remain elusive, it is clear that the spliced leader will significantly facilitate the cloning and sequence analysis of most nematode mRNAs.

Animals↗
PubMed1996

Long-term blood pressure control in older Chinese patients with isolated systolic hypertension: a progress report on the Syst-China trial.

This report on the ongoing double-blind placebo-controlled Syst-China trial investigated whether antihypertensive drug treatment based mainly on a calcium entry blocker and a converting enzyme inhibitor, would be suitable for maintaining long-term blood pressure (BP) control in older Chinese patients (average age: 67 years) with isolated systolic hypertension (systolic pressure 160-219 mm Hg and diastolic pressure < 95 mm Hg). Active treatment consisted of nitrendipine (10- 40 mg/day) with the possible addition of captopril (12.5- 50 mg/day) and hydrochlorothiazide (12.5-50 mg/day), as necessary to reduce systolic pressure to a level of 150 mm Hg or lower and by at least 20 mm Hg. Matching placebos were used in the control group. This progress analysis was restricted to BP control up to 3 years of follow-up. The placebo (n = 1134) and active treatment n = 1245) groups had similar characteristics at enrolment. The sitting BP averaged 170/86 mm Hg. Systolic pressure fell (P < 0.001) on average 8 mm Hg more on active treatment than on placebo and diastolic pressure 3 mm Hg more. Fewer patients remained on monotherapy in the placebo than in the active treatment group (P < 0.001); on placebo the second and third line medications were started more frequently (P < 0.001). This progress report showed that significant BP reduction can be achieved and maintained in older Chinese patients treated with a calcium antagonist, associated with a converting-enzyme inhibitor and a thiazide, as necessary. Whether this BP reduction would result in a clinically meaningful decrease of cardiovascular complications is still under investigation.

Aged↗
PubMed1996

Endothelial binding sites for lipoprotein lipase are not diminished in perfused hearts from diabetic rats.

The possibility that diabetes reduces functional, heparin-releasable lipoprotein lipase (HR-LPL) activity on the coronary vasculature of perfused hearts by altering endothelial binding sites for the enzyme was examined by measuring the binding and subsequent heparin-induced release of exogenous lipoprotein lipase purified from bovine milk (mLPL). Rat hearts were first perfused with heparin (5 U/mL) for 5 min to displace endogenous HR-LPL into the perfusate. The subsequent perfusion of control hearts with 0.05-2 micrograms/mL mLPL resulted in a progressive increase in bound exogenous enzyme that could be released by a second heparin perfusion. Induction of an acute, insulin-deficient model of diabetes (100 mg/kg streptozotocin 4-5 days prior to heart perfusions) reduced endogenous HR-LPL activity, but the binding and heparin-induced release of mLPL (0.5 microgram/mL) were the same as measured in control hearts. Therefore, diabetes does not alter low-affinity, high-capacity proteoglycan binding sites for mLPL on the endothelium of perfused hearts.

Animals↗
PubMed1996

[Packing of the chromatin fibers and the distribution of RNP in BK chromosomes].

The packing of the chromatin fibers and the distribution of RNP in bovine kidney (BK) chromosomes were studied by the combination of transmission, scanning electronic microscopy (TEM, SEM) and cytochemical electronic microscopy (CCEM). The results showed that BK chromosomes reveal a multiple double strand helical structure. The central axial area of each chromatid is a low electronic density region or chromatin free compartment, in which there are lots of RNP. In the peripheral chromatin region the RNP is distributed among the chromatin fibers and continued with that of the central region. The density of the central RNP is more than that of the peripheral RNP, which indicates that RNP is not uniformly distributed in chromosome.

Animals↗
PubMed1996

[Studies on prematurely condensed chromosomes and induced condensed chromosomes with SEM].

The ultrastructure of prematurely condensed chromosomes (PCC) in BK cells and the CHO metaphase chromosomes (the PCC inducer) were studied with cell fusion technique and SEM. The methods for preparing complete specimens for SEM, were used to eliminate artifact as complete as possible, so the natural states of PCC ultrastructure, especially the ultrastructure of the early, mid, and late S-PCC, were observed for the first time. In the three phases of S-PCC multiple double strand helical structure were revealed, on the chromosome segments of BK cells. On the surface of CHO metaphase chromosomes which may induce PCC may regularly arrayed short hair-like loop-protrusions consisting of helical chromatin fibers were observed.

Animals↗
PubMed1996

Detection of bovine fetal Y-specific Sry sequence from maternal blood.

Two pairs of primers were designed based on the sequence of bovine Sry and applied to the assay of Sry sequence from maternal blood using the polymerase chain reaction. Of the total twenty DNA samples from peripheral blood of late pregnant cow, nine appeared positive with male-specific Sry sequence. The fetal sex predicted by the PCR analysis of maternal blood DNA accorded with the sex of babies on delivery in 16 cows (the remaining four were false negative). Our methods showed that bovine Sry sequence can be directly detected from the maternal blood for identifying fetal sex.

Animals↗
PubMed1996

[Investigation of urinary fibrinopeptide A level in pregnancy induced hypertension and its clinical significance].

OBJECTIVE: To investigate the changes of urinary fibrinopeptide A (FPA) level in pregnancy induced hypertension (PIH) and its clinical significance. METHODS: High performance liquid chromatography (HPLC) was employed in determination. Urinary FPA was measured in 96 cases of normal pregnancy and 49 cases with PIH. RESULTS: The urinary FPA levels in mild and moderate PIH groups were significantly higher than that in normal pregnancy (71.65 +/- 18.53 micrograms/L vs 40.17 +/- 20.26 micrograms/L, P < 0.01). The levels of urinary FPA in patients with preeclampsia increased significantly (146.65 +/- 32.53 micrograms/L) when compared with the mild and moderate PIH groups (P < 0.001). The levels of urinary FPA in patients with eclampsia (422.93 +/- 81.46 micrograms/L) were much higher than that in group of preeclampsia (P < 0.001). CONCLUSIONS: It showed that the assay of urinary FPA might be helpful for earlier diagnosis, classification, treatment and judgement of prognosis in PIH.

Adult↗
PubMed1996

[A study of neuroretinal rim morphology in physiologic large cups and early glaucoma].

OBJECTIVE: To find the differences of the physiologic large cups from the optic cup of early glaucoma. METHODS: The morphology of neuroretinal rim was studied. The subjects were divided into two groups: (1) 54 cases 88 eyes with physiologic large cups defined by cup/disk (C/D) ratio more than 0.6, optic disk areas more than 2.8 mm2, without neuroretinal rim loss within 3-6 years of follow-up, normal intraocular pressure and visual field. (2) 68 cases 89 eyes with early glaucoma defined by visual field defects, neuroretinal rim loss in follow-up and C/D ratio less than 0.8. The indexes of neuroretinal rim related to morphology are a series of rim widths and a parameter of cupping morphology which is a ratio of the vertical C/D over the horizontal C/D. RESULTS: The characteristics of a physiologic large cup are a large optic disk, a horizontal elliptic cupping and the widest neuroretinal rim at the inferior, followed by superior, nasal and temporal, while the characteristics of optic nerve head of glaucoma are normal size of optic disk, vertical elliptic cupping and the widest rim not at the inferior, since the inferior rim is subject to glaucomatous damage. CONCLUSION: To differentiate a physiologic large cup from a glaucomatous one, the most effective way is to apply the parameter of cupping morphology in combination with neuroretinal rim area and optic disk area in the multivariate discrimination.

Adult↗
PubMed1996

[A double column double pH solid phase extraction and capillary GC/FID method for rapid simultaneous determination of acidic and basic drugs in human plasma].

A capillary gas chromatographic method for the rapid simultaneous identification and quantitation of acidic and basic drugs in human plasma is presented. A special double column solid phase extraction device was designed, in which two X-5 resin columns can extract drugs at different pH. The detection limits for acidic and basic drugs can reach 0.5 microgram.ml-1, while the time needed is only half of that when using commercial solid phase extraction cartridges.

Anesthetics, Local↗
PubMed1996

[Urine level of trans, trans-muconic acid used as an index of internal dose of exposure to benzene].

Urine trans, trans-muconic acid (TTMA) in population exposed to benzene was determined with a high performance liquid chromatography-ultra violet detection system. Result showed urine TTMA increased significantly with increasing of air benzene levels, showing a good correlationship between them (r = 0.940, P < 0.05). Even in relatively low air benzene levels (with an average of 2.46 mg/m3), urine TTMA in exposed group was higher, as compared with that in controls, and their difference reached statistically significant level. It suggests that urine TTMA level can be used as a sensitive and specific indicator for biological monitoring, especially for low exposure to benzene. There was no significant difference in urine TTMA between males and females exposed. Urine TTMA formation can be inhibited by toluene, and confounding of toluene can be roughly adjusted by analysis of covariance.

Adult↗
PubMed1996

[Systematic analysis of basic drugs in plasma using X-5 solid-phase extraction GC-FID and GC-MS].

A systematic determination method for 34 basic drugs in human plasma is described. Drugs were extracted from plasma at pH 10 using X-5 resin as adsorbent, then identified and quantitated by capillary GC-FID and GC-MS. The detection limits for most drugs are in the range of 0.5-2.0 micrograms.ml-1. Precision and linearity of the method are satisfactory for clinical toxicological applications.

Analgesics, Opioid↗
PubMed1996

[Preoperative intraluminal 5-FU osmosis chemotherapy as an adjuvant to radical resection for rectal cancer].

Patients with rectal cancer of stage dukes B and C were randomized into two groups. In osmosis chemotherapy group 86 patients were treated by radical resection plus adjuvent preoperative intraluminal 5-FU osmosis chemotherapy at the area of tumor. In control group 74 patients were treated by radical resection alone. There were high concentration of 5-FU in the cancer, mucosa and lymph node around the cancer and mesenterica inferior venae, and the lower in a round venae. After the chemotherapy the symptoms were improved without side-effects, the II-III grade at pathological change was 83%, the cancer regression more than 50 was 38%. Compared the two groups osmosis chemotherapy raised 14% at radical resection and reduced 22%, 11%, 22% at local recurrence and metastasis of lymph nodes and liver. The 3-, 5-year survival rates (81.1%, 69.6%) were higher than 19.2%, 26.7% in the control group.

Adenocarcinoma↗
PubMed1996

[Primary malignant melanoma of the vagina: a report of 22 cases].

In this paper, 22 patients from 1973 through 1994 with primary malignant melanoma are retrospectively analyzed. Vaginal bleeding, discharge and a tumor mass were the chief complaints. The most common site of the tumor origin was the lower third of the anterior and postrior vaginal wall. The 5-year survival rate of 18 previously untreated patients was 11% (2/18). Of the 18 patients, 9 in stage I treated by surgery and postoperative chemothreoapy and/or radiotherapy survived for an average of 33 months. Two of the 9 patients receiving radical surgery survived for more than 5 years. None of the remaining 9 patients in stage II-IV treated with chemotherapy and/or radiotherapy survived longer than 2 years. The survival time differed significantly in patients with and without pelvic lymph node metastasis (7 versus 41 months) and in those with and without vascular tumor thrombi (13 versus 43 months). Mitotic index of tumor cells and lymphocytic infiltration were of no prognostic value.

Adult↗