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Biomedical subjects

L Liu

Publications and source records attributed to L Liu.

At least 1,261 records · Page 70Linked to original sources
PubMed1989

Effects of insulin-like growth factors I and II on growth and differentiation of transplanted rat embryos and fetal tissues.

The objective of our study was to obtain comparative information on the roles of insulin-like growth factors (IGFs) I and II in the growth and differentiation of rat embryos and fetuses in an in vivo experimental system. Ten-day-old rat embryos or 16-day-old fetal rat paws were transplanted under the capsule of both kidneys of syngeneic hosts, where they grew rapidly, and tissue differentiation occurred in an essentially normal manner. Infusion of a rabbit antiserum to human (h) IGF-I for 6 days into the renal artery of one kidney caused only a slight inhibition (approximately 20%) of growth of transplanted embryos on that kidney. However, 9 days of treatment with the antiserum caused highly significant growth retardation of transplanted embryos by 40-45%. Exposure of fetal paws to the same antiserum for 9 days inhibited their growth by 27%. Infusion of synthetic hIGF-II or partially purified rat IGF-II [(MSA)multiplication-stimulating activity], for 6 days stimulated the growth of embryo transplants directly, and MSA was more effective than hIGF-II. By contrast, infusion of purified natural hIGF-I did not promote their growth. Growth of fetal paw transplants in hypophysectomized (HX) hosts was reduced by 70% compared to that in intact hosts. In the HX hosts infusion of the MSA was more effective than the hIGF-I at promoting the growth of paw transplants. Both MSA and IGF-I promoted ossification in the fetal paws in the HX hosts. These results suggest that both IGFs could be involved in regulating the growth and differentiation in prenatal rats, and IGF-II may be the more effective of the two factors as a growth-promoting agent in utero.

Animals↗
PubMed1989

Kappa opiate receptor multiplicity: evidence for two U50,488-sensitive kappa 1 subtypes and a novel kappa 3 subtype.

Kappa receptor multiplicity is a complex area. We now present evidence from binding studies suggesting the existence of four kappa receptor subtypes. The guinea pig cerebellum contains high levels of U50,488-sensitive, or kappa 1, receptors. Kappa opiates (U50,488, tifluadom, Mr2034, Mr2266 and Win44,441) compete [3H]ethylketocyclazocine binding to kappa 1 receptors with kappa, values under 10 nM and Hill coefficients of approximately one, as does dynorphin A (kappa 1, 0.27 +/- 0.05 nM; Hill coefficient, 0.83 +/- 0.20, n = 4). However, competition studies with dynorphin B yield a Hill coefficient of 0.46 +/- 0.03 (n = 5) and nonlinear regression analysis of the competition curve is best fit by two sites. alpha-Neoendorphin Neoendorphin competition curves (Hill coefficient, 0.46 +/- 0.07; n = 3) also were best fit with two components. Competition studies with both alpha-neoendorphin and dynorphin B together suggest that both compounds label the same site with high affinity. Similar results were obtained using [3H]U69,593. Dynorphin B and alpha-neoendorphin competed binding with Hill coefficients of 0.45 +/- 0.04 (n = 3) and 0.59 +/- 0.09 (n = 3), respectively. These data suggest two subtypes of kappa 1 receptors in the guinea pig cerebellum: kappa 1a and kappa 1b. Classical kappa opiates and dynorphin A have high affinity for both subtypes whereas dynorphin B and alpha-neoendorphin label kappa 1b over 50-fold more potently than kappa 1a sites. [3H]Naloxone benzoylhydrazone [( 3H]NalBzoH) labels a novel, U50,488-insensitive kappa receptor subtype, kappa 3, in membranes from calf striatum, rat and mouse brain. We now have developed a relatively selective assay in calf striatum.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1989

[Development and application of hybridoma secreting monoclonal antibody against poly-human serum albumin].

Two hybridomas which secrete monoclonal antibody (McAb) against polymerized human serum albumin (PHSA) were obtained by the fusion of SP2/0 myeloma cell with immune murine spleen cells. One of the McAb was identified as mouse IgG1, the other was IgM. The titers of these purified McAb was 1:16 364 with passive hemagglutination assay (PHA). After labelling with 125I by chloramine-T method, a solid phase radioimmune assay for detecting the PHSA has yielded in 21 positive results, out of 126 HBsAg positive sera, but 53 HBsAg negative sera were all negative. At present we have not seen any report of PHSA present in circulation. PHSA may be as a bridge bind receptor between HBV and hepatocytes and then initiate infection. The appearance of PHSA in HBsAg positive sera could be the result of the damage of the liver during virus infection. More work should be done for this explanation.

Animals↗
PubMed1989

[Relationship between HBcAg in the liver and mechanisms of chronic type B hepatitis HBVM in serum].

We detected the presence and distribution of HBcAg in the liver by immunohistochemistry (ABC method) and the presence of HBV-DNA in serum (spot hybridization) and anti-HBe in serum (ELISA) from 59 cases of hepatitis B hospitalized in our hospital, including 47 cases of CAH, 5 cases of CPH, and 7 cases of subacute fulminant hepatitis. 1. HBcAg in the liver was detected in 25 out of 47 cases (53%) of CAH, in 2 out of 5 cases of CPH and in 4 out of 7 cases of subacute fulminant hepatitis. The total percentage was 53% (31/59). 2. There was no positive correlation between HBV replication activity and liver disease activity (P greater than 0.05). Our results did not support the hypothesis that suggests a direct cytopathic effect of HBV. Oppositely, the fact was that the presence, the amount and the patterns of HBcAg in the liver, and the presence of HBV-DNA in serum were predominant in mild CAH compared with those in severe CAH, predominant in CAH without cirrhosis compared with those in CAH with cirrhosis. There was a tendency of inverse correlation between HBV replication activity and liver disease activity. The results above were in line with the concept that HBcAg expressed on the surface of infected hepatocytes may be relevant target for T lymphocyte cytotoxicity. The results have suggested that an immune response to HBV is present, leading to the destruction of most infected cells. 3. There was a positive correlation between HBV-DNA in serum and HBcAg in the liver (P less than 0.005), indicating that HBV-DNA in serum can represent HBV replication.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA, Viral↗
PubMed1989

[Comparison of effect in the change of respiration by stimulating three trigeminal subnucleus].

Experiments were performed on 31 rabbits. After recovery from surgical anesthesia the change of respiration were observed in various experimental conditions, under which original nucleus of trigemini (ONT), terminal nucleus of trigemini (TNT), spinal tractus nucleus of trigemini (SNT) were respectively stimulated by an electrical current (EC) or monosodium glutamate (MSG) or lidocaine (LID). Because SNT had a longitudinal long shape, three different sections of SNT were selected as stimulating points respectively, namely rostral point (A2.33 mm), middle point (AP0 mm) and caudal point P1.9 mm). Phrenic nerve discharge and its integrated curve, PCO2 and blood pressure were recorded by a RM-6000 polygraph. The results indicated that the stimulations of EC and MSG to SNT and TNT enhanced respiratory activity obviously. Stimulation of EC and MSG to ONT caused much less enhancement of respiration. Microinjection of LID to TNT and ONT decreased respiratory activity, but microinjection of LID to SNT increased. The present experiment concluded that stimulation of SNT and TNT could cause significant change in respiration.

Animals↗
PubMed1989

[Neodymium YAG laser iridotomy].

130 eyes with primary angle-closure glaucoma were performed iridotomy successfully with Nd: YAG laser. The iris perforations remained open in follow-ups of 1 week to 8 months, and pupil block was relieved. The technique involved was described. The common complications included slight local opacity in the peripheral cornea, mild iris hemorrhage, and postoperative hypertensive response in IOP, all of which did not affect the visual acuity.

Adult↗
PubMed1988

Acquisition of new metabolic capabilities: multicopy suppression by cloned transaminase genes in Escherichia coli K-12.

The four general transaminases of Escherichia coli K-12 have overlapping, but discrete, substrate specificities and participate in the final step in the synthesis of at least seven different amino acids. Through the use of strains that have mutations in one or more transaminase genes and carry a different wild-type (wt) gene on a multicopy plasmid, it was possible to detect instances in which an amplified wt gene suppressed nonallelic mutations. In these cases, overproduction of the enzyme permitted a broader range of substrates to be used at physiologically significant levels, either because a low catalytic efficiency (in the case analyzed here) or a low affinity of the enzyme towards the substrate prevented its effective utilization under normal conditions. Consequently, by compensating for a low catalytic reaction rate, enzyme overproduction circumvents the original lesion and restores biosynthetic activity to the mutant strain. The suppression of a mutation in one gene by amplified copies of a different wt gene is termed 'multicopy suppression'. This phenomenon is useful for detecting poorly expressed genes, for detecting duplicate genes, for identifying secondary functions of the products of known genes, and for elucidating the metabolic role of the product of the suppressed gene.

Cloning, Molecular↗
PubMed1988

The pigmented epithelium sustains cell growth and tissue differentiation of chicken retinal explants in vitro.

Embryonic retinae from 5-6-day-old chicks (E5-E6) were cut into stripes either in close contact with (RPE stripes) or in absence of the neighboring retinal pigmented epithelium (R stripes). The stripes were explanted and cultivated in vitro for up to 6 days, during which time they show the following differences in their characteristics of growth and differentiation. Compared with R stripes, RPE stripes morphologically showed a significant increase in size during the first 2 days in culture. Using E5 tissue, this is also demonstrated by a higher rate of cell proliferation (as measured by uptake of radioactive thymidine as well as by DNA contents). In contrast, R stripes after two days in culture show a much stronger neurite growth. After longer periods of culturing (5-6 days) we can show by cholinesterase histochemistry (AChE and BChE) and by PNA-lectin binding that the RPE stripes have started to form all major layers of the in vivo retina, whereas R stripes remain unstratified and start to degenerate earlier. We conclude that the pigment epithelium might exert a specific stimulus on growth and tissue differentiation of the neural retina not only during in vitro, but possibly also during in vivo development. The in vitro methods introduced here could become useful model systems to further investigate the significance of the RPE for developmental, regenerative and even adult processes of the neural retina. Their future applicability in ophthalmologic research is briefly discussed.

Animals↗
PubMed1988

Comparison of pulsatile subcutaneous gonadotropin-releasing hormone and exogenous gonadotropins in the treatment of men with isolated hypogonadotropic hypogonadism.

Eight men with isolated hypogonadotropic hypogonadism were treated with pulsatile gonadotropin-releasing hormone (GnRH) after maximal testicular growth and function had already been achieved with human chorionic gonadotropin (hCG) and human menopausal gonadotropin (hMG). Only four subjects could normalize plasma testosterone (T) levels (group A). After 18 months of GnRH therapy, testicular size of group A increased by 53% (P less than 0.01) over that previously attained with exogenous gonadotropins. However, despite further testicular growth, two men who were previously azoospermic on hCG/hMG remained so on GnRH. In the other two patients, total sperm count increased minimally. Thus, pulsatile gonadotropin levels achieved with GnRH are more effective in stimulating testicular growth, but not necessarily sperm output, than are stable gonadotropin concentrations obtained with hCG/hMG.

Adult↗
PubMed1988

Rapid identification of bacterial genes that are lethal when cloned on multicopy plasmids.

A procedure to identify genes that are lethal when cloned on multicopy plasmids was developed. It depends on the ability of mini-Mu plasmid elements to be used for both in vivo cloning and generalized transduction of enterobacterial genes. The feasibility of this procedure was demonstrated by using the tetA gene of Tn10, which is lethal when in multiple copies in the presence of 25 micrograms of tetracycline per ml.

Cloning, Molecular↗
PubMed1988

Effects of pyrethroid insecticides on subjects engaged in packaging pyrethroids.

A health survey was conducted on 199 workers engaged in dividing and packaging pyrethroids. The subjects were exposed to fenvalerate at 0.012-0.055 mg/m3 and deltamethrin at 0.005-0.012 mg/m3 in the air with simultaneous skin contact for 0.5-4.5 months. Burning sensations and tightness or numbness on the face appeared in two thirds of the subjects and one third had sniffs and sneezes. Abnormal facial sensations, dizziness, fatigue, and miliary red papules on the skin were more evident in summer than in winter. Neither abnormalities in other organs or systems nor symptoms or signs of acute pyrethroid poisoning were found by interviews, examinations, and laboratory tests. There was no significant difference in plasma levels of NA, cAMP, and cGMP between the examined subjects and the control group. The urine concentration of fenvalerate in the study group ranged from 1.02 to 18.6 micrograms/l; deltamethrin in the urine was present in trace amounts.

Adolescent↗
PubMed1988

Two-year comparison of testicular responses to pulsatile gonadotropin-releasing hormone and exogenous gonadotropins from the inception of therapy in men with isolated hypogonadotropic hypogonadism.

Men with the complete form of isolated hypogonadotropic hypogonadism (initial mean testes volume less than 4 mL) require 2 or more yr of exogenous gonadotropin therapy combining hCG and human menopausal gonadotropin (hMG) to achieve maximal, but subnormal, testis size and sperm output. To test whether pulsatile GnRH therapy, which more closely mimics normal hormonal stimulation, would accelerate or further augment testicular growth, hasten the onset of sperm production, and/or increase sperm output more than occurs during conventional exogenous gonadotropin therapy, we administered either hCG/hMG or GnRH from the inception of therapy to 2 comparable groups of men with complete IHH (initial testicular volume, less than 4 mL) and compared their testicular responses during the first 2 hr of therapy. Five men were treated with pulsatile GnRH in doses of 143-714 ng/kg every 2 h, sc, while 11 other men received hCG (2000 IU) and hMG (75 IU FSH and 75 IU LH) im 3 times/week. In the GnRH-treated men, the mean plasma total and free testosterone levels during therapy rose to within the normal range, but were significantly lower (P less than 0.01 and P less than 0.02, respectively) than those in the hCG/hMG-treated men. The mean plasma estradiol concentrations during therapy were within the high normal range and were similar in the two groups. The mean plasma FSH levels achieved in the GnRH-treated men were significantly (P less than 0.01) and 1.3- to 3.2-fold higher than those in the hCG/hMG-treated men. The mean testicular size achieved in the GnRH-treated men was not significantly different from that in the hCG/hMG-treated men (P = 0.08); the mean testicular volumes after 2 yr were 4.8- and 4.3-fold the pretreatment values in the GnRH and hCG/hMG groups, respectively. After 12 months of therapy, sperm production had occurred in one man in the GnRH group and in no subject in the hCG/hMG group. After 24 months, two men in the GnRH group and eight men in the hCG/hMG group produced sperm. Thus, 40% of the GnRH-treated men and 80% of the hCG/hMG-treated men (P = NS) produced sperm after 2 yr of therapy. The sperm concentrations in all men were below 5 million/mL and were comparable in the two groups (P = NS). These results suggest that pulsatile sc GnRH therapy for the first 2 yr does not accelerate or enhance testicular growth, hasten the onset of sperm production, or increase sperm output significantly compared to hCG/hMG.

Adult↗
PubMed1988

Regulation of vasopressin and oxytocin synthesis in anterior pituitary and peripheral tissues.

Recent studies have demonstrated the presence of immunoreactive oxytocin (OT) and vasopressin (VP), OT and VP receptors and physiological functions for these two hormones in a variety of peripheral tissues, including anterior pituitary gland. The objectives of this study were to determine if (i) OT and VP genes are expressed in rat testis and anterior pituitary gland and (ii) if osmotic stimulation known to modify the regulation of OT and VP genes in hypothalamus, would modify the expression of these genes in rat testis and anterior pituitary gland. Using oligonucleotide probes (courtesy of Drs. M. Brownstein and W. Scott Young, NIMH) corresponding to the VP gene or OT gene and specific fractions of human OT and VP genes (courtesy of Dr. J. Battey, NCI) subcloned in the pGEM-3 riboprobe system, and Northern blot and slot blot techniques, OT and VP mRNAs were found in rat testis and anterior pituitary gland. When adult male rats (SD) were either deprived of drinking water or offered 2% salt solution as a sole source of drinking fluid for 72 hrs, both OT and VP mRNA levels were increased in hypothalamus, anterior pituitary gland and testis. Our data suggest that testis and anterior pituitary gland could also be sites of synthesis of OT and VP and that the same stimulus may regulate these genes in various tissues.

Animals↗