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Biomedical subjects

L Hu

Publications and source records attributed to L Hu.

At least 127 records · Page 7Linked to original sources
PubMed1996

Raccoon poxvirus feline panleukopenia virus VP2 recombinant protects cats against FPV challenge.

An infectious raccoon poxvirus (RCNV) was used to express the feline panleukopenia virus (FPV) open reading frame VP2. The recombinant, RCNV/FPV, was constructed by homologous recombination with a chimeric plasmid for inserting the expression cassette into the thymidine kinase (TK) locus of RCNV. Expression of the VP2 DNA was regulated by the vaccinia virus late promoter P11. Southern blot and polymerase chain reaction (PCR) analyses confirmed the cassette was in the TK gene of the RCNV genome. An immunofluorescent antibody assay using feline anti-FPV polyclonal serum showed the expressed viral antigen in the cytoplasm of infected cells. Radioimmunoprecipitation with the same antiserum detected a 67-kDa VP2 protein which exactly matched the migration of the authentic FPV VP2 protein by SDS-polyacrylamide gel electrophoresis. Nine five-month-old cats were vaccinated and 21 days later were boosted with the recombinant virus. Peroral FPV challenge 2 weeks after the booster showed that the cats were fully protected as measured by examining clinical signs and total white blood cell counts in peripheral blood. Cats not immunized developed low to very low leukocyte counts following peroral FPV challenge. The nine vaccinated cats showed high FPV neutralization antibody prior to challenge, whereas nonvaccinated cats formed anti-FPV antibodies only after challenge.

Animals↗
PubMed1996

Substrate specificity of the Escherichia coli 4-aminobutyrate carrier encoded by gabP. Uptake and counterflow of structurally diverse molecules.

Transport of 4-aminobutyrate into Escherichia coli is catalyzed by gab permease (GabP). Although published studies show that GabP is relatively specific, recognizing the common alpha-amino acids with low affinity, recent work from this laboratory indicates that a number of synthetic compounds are high affinity transport inhibitors (50% inhibition at 5-100 microM). Here we present evidence that many of these structurally heterogeneous compounds not only inhibit transport but also function as alternative GabP substrates (i.e. a set of observations inconsistent with the idea that the core of the GabP transport channel exhibits rigid structural specificity for the native substrate, 4-aminobutyrate.

Aminobutyrates↗
PubMed1996

Nuclear accumulation of multiple protein kinases during prolactin-induced proliferation of Nb2 rat lymphoma cells.

Intracellular kinases play important roles in signal transduction and are involved in the surface receptor-mediated regulation of cellular functions, including mitogenesis. In the present study, we examined the possible involvement of various protein kinases in the passage of a mitogenic signal from the cell surface to the nucleus of Nb2 cells, a rat nodal lymphoma cell line in which prolactin is a mitogen. Following a prolactin challenge, various kinase activities were monitored at short intervals in different cellular fractions over a 60 min period. Protein kinase C (PKC) activity in the cytosolic fraction rapidly declined to 50% of its original activity within the first 30 min, while PKC activity in the nuclear fractions increased sharply, reaching its highest level by 30 min following a prolactin challenge. There were also increases in both casein kinase and protein tyrosine kinase (PTK) activities in the nuclear fractions during the first 30 min following a prolactin challenge that paralleled PKC activity. The activities of all three kinases declined thereafter, reaching levels close to their respective basal values by 60 min following initiation of prolactin treatment. These observations suggest the possibility that multiple protein kinases may be involved in mitogenic signal transduction for prolactin in Nb2 cells.

5'-Nucleotidase↗
PubMed1996

In vitro prolactin release from pituitaries of ovariectomized, estradiol-treated Holtzman rats: a direct comparison of dispersed cells and tissue explants.

In this study we compared prolactin (PRL) release from pituitary explants with that from dispersed cells from two regions of anterior pituitaries obtained from ovariectomized rats treated for 7 days with estradiol. Pituitaries were cut horizontally into dorsal (or inner) and ventral (or outer) zones. One half of each these regions was enzymatically dispersed to cells; the other half was bisected and examined as tissue explants. The dispersed cells and explants were perifused in parallel over a 2 hour period with dopamine (1 microM) present for the first hour and absent during the second hour. Prolactin released into the perifusion medium was measured by radioimmunoassay. Tissue explants secreted more total prolactin than did cells in the presence or absence of dopamine and the pattern of release was sustained compared to the more transient release observed in dispersed cells. However, the response to dopamine withdrawal was not different between cells and explants when expressed as a percent change from respective controls. The results suggest that organization and architecture of the rat anterior pituitary may be important factors for overall prolactin production, but in terms of relative responsiveness to dopamine and its withdrawal, dispersed cells and tissue explants appear equivalent.

Animals↗
PubMed1996

X-linked myotubular myopathy: refinement of the critical gene region.

X-linked recessive myotubular myopathy (XLMTM) is a severe neonatal neuro-muscular disease characterized by muscle weakness, hypotonia, and respiratory problems. The locus for the XLMTM gene (MTM1) has previously been mapped to Xq28 between the markers DXS304 and DXS497 by linkage analyses and by determining the breakpoints of deletion patients. We report linkage analysis data or 20 XLMTM families who were tested using the DNA markers DXS1113, DXS304, DXS455, DXS1684, DXS305 and DXS52 and present two families showing recombination between MTM1 and either DXS304, DXS334 or DXS305. We found each of the families to be informative for at least three markers. Based on these findings we excluded 30 women from being carriers, the carrier status of 17 obligate carrier mothers could be confirmed and eight mothers and sisters were identified as to be at high risk of carrying a MTM1 mutation. By combining recently published data with the results of our recombinant families, we suggest that the MTM1 locus maps between DXS334 and DXS497 narrowing the region of interest from 600 kb to an estimated < 500 kb interval. This additional refinement in the localization of MTM1 means a further step towards the isolation of the gene in the near future, and allows more reliable and efficient carrier detection and prenatal diagnosis.

Chromosome Mapping↗
PubMed1996

NGF prevents further atrophy of cholinergic cells of the nucleus basalis due to cortical infarction in adult post-hypothyroid rats but does not restore cell size compared to euthyroid [correction of euthroid] rats.

We have tested the hypotheses that nerve growth factor treatment in adult post-hypothyroid rats can: (1) restore cross-sectional area of cholinergic cells of the nucleus basalis and (2) prevent further atrophy of these neurons following cortical infarction. In addition, we assessed the expression of p75NGFR and p140trkA mRNAs in the nucleus basalis cells of post-hypothyroid rats. Rats were rendered hypothyroid by the addition of propylthiouracil to their diet beginning on embryonic day 19 until the age of 1 month. At this time both the pups and their dams continued to receive 0.05% propylthiouracil in their diet and the pups were thyroidectomized. At 60 days, propylthiouracil treatment was interrupted and thyroxine levels were restored to normal by daily subcutaneous administration of physiological levels of thyroxine. Morphometric analysis identified atrophied nucleus basalis magnocellularis cholinergic cells at two ages, days 75 and 105, identified by in situ hybridization for p75NGFR and p140trkA mRNAs in methylene blue stained cells (day 75) and choline acetyltransferase immunostaining (day 105). The mean number of silver grains (pixels) per microns2 (mean +/- S.E.M.) of cell body cross-sectional area for p75NGFR mRNA in the nucleus basalis magnocellularis of euthyroid rats was 3.43 +/- 0.89, which was not statistically different from post-hypothyroid animals (4.02 +/- 1.07). A similar finding was noted for p140trkA mRNA: mean number of grains in the euthyroid group was 5.54 +/- 0.96 and was not statistically different from the post-hypothyroid group (6.32 +/- 1.45). Nerve growth factor treatment in adulthood (between days 75 and 82) did not restore cross-sectional area from early thyroid deprivation. However, it prevented further atrophy of nucleus basalis magnocellularis neurons following cortical devascularization inflicted in adulthood (day 75).

Acetylcholine↗
PubMed1996

Transcription-modulating drugs: mechanism and selectivity.

Transcription-modulating drugs achieve their therapeutic effects through the modulation of gene transcription. To understand how selectivity is achieved, four groups of such drugs - including immunosuppressants, estrogen analogs, the antidiabetic thiazolidinediones, and the anti-inflammatory salicylates - will be discussed. The immunosuppressants cyclosporin A and FK506, when complexed with immunophilins, inactivate the protein phosphatase calcineurin, resulting in the inhibition of interleukin-2 gene activation. Another immunosuppressant, rapamycin, binds to the same immunophilin as FK506 but inactivates a protein kinase p70(s6k). Estrogen analogs tamoxifen and rolaxifene antagonize one estrogen receptor transactivation function (AF-2) and agonize another (AF-1). They modulate expression of a wide variety of genes, including transforming growth factor-alpha, insulin-like growth factor-1, and transforming growth factor-beta3, which are important for breast and endometrial cancer proliferation and bone maintenance respectively. The antidiabetic drugs thiazolidinediones bind and activate peroxisome proliferator-activated receptor gamma and suppress insulin resistance mediated by tumor necrosis factor-alpha. Salicylates inhibit transcription factor NFkappaB, which is important for immune and inflammatory responses. Continuing understanding of molecular mechanisms of such drugs not only helps to identify better drugs for these targets but should also provide an insight into developing future transcription-modulating drugs with better selectivity and reduced toxicity.

Animals↗
PubMed1996

New triterpenoid saponins from Gynostemma pentaphyllum.

Three new triterpenoidal saponins (1-3), together with the known compound 4, were isolated from a MeOH extract of the aerial parts of Gynostemma pentaphyllum. Their structures were elucidated on the basis of chemical and spectral methods, such as 1H-1H DQFCOSY, HMQC, HMBC, and TOCSY NMR spectra. The aglycon moiety of 1 and 2 is a new dammarane-type triterpene 12-oxo-2 alpha, 3 beta, 20 (S)-trihydroxydammar- 24-ene.

Carbohydrate Sequence↗
PubMed1996

Development of an expert system for amino acid sequence identification.

An expert system for amino acid sequence identification has been developed. The algorithm uses heuristic rules developed by human experts in protein sequencing. The system is applied to the chromatographic data of phenylthiohydantoin-amino acids acquired from an automated sequencer. The peak intensities in the current cycle are compared with those in the previous cycle, while the calibration and succeeding cycles are used as ancillary identification criteria when necessary. The retention time for each chromatographic peak in each cycle is corrected by the corresponding peak in the calibration cycle at the same run. The main improvement of our system compared with the onboard software used by the Applied Biosystems 477A Protein/Peptide Sequencer is that each peak in each cycle is assigned an identification name according to the corrected retention time to be used for the comparison with different cycles. The system was developed from analyses of ribonuclease A and evaluated by runs of four other protein samples that were not used in rule development. This paper demonstrates that rules developed by human experts can be automatically applied to sequence assignment. The expert system performed more accurately than the onboard software of the protein sequencer, in that the misidentification rates for the expert system were around 7%, whereas those for the onboard software were between 13 and 21%.

Algorithms↗
PubMed1996

Effects of deferoxamine on ischemia/reperfusion injury after peripheral nerve compression.

We have demonstrated previously that acute nerve compression produces ischemia/reperfusion injury in rat sciatic nerve. In this study, we evaluated the effects of deferoxamine, an antioxidant, on recovery from ischemia/reperfusion injury after nerve compression. The sciatic nerves of male Sprague-Dawley rats, 370 to 430 g, were subjected to 24 hours of compression with Silastic tubing. The control group received intravenous saline solution at the time of decompression. The therapeutic group received intravenous deferoxamine (50 mg per kilogram) at the time of removal of the Silastic tubing. Nerve tissues within and distal to the compression site were assayed for malondialdehyde (MDA) levels and for growth-associated protein 43 (GAP-43) expression, as markers of ischemia/reperfusion injury and nerve regeneration, respectively. In the control group (injury alone), the MDA levels were three times higher than normal during the initial 10 days and returned to normal by 14 days. In contrast, the deferoxamine treatment group had MDA levels that were not significantly different from precompression levels. In the control group, enhanced GAP-43 expression persisted until late in the recovery period. In the deferoxamine treatment group, the increased GAP-43 expression subsided early. The results suggest that the treatment of compressed peripheral nerve with deferoxamine at the time of surgical decompression reduces ischemia/reperfusion injury.

Animals↗
PubMed1996

Cardiac hypertrophy and telemetered blood pressure 6 wk after baroreceptor denervation in normotensive rats.

We investigated cardiac morphometry 6 wk after sinoaortic baroreceptor denervation (SAD) in Long-Evans rats. SAD (n = 19) was associated with an 11% increase in the weight of the left ventricle (LV) plus septum (P < 0.001) and a 39% increase in that of the right ventricular (RV) free wall (P < 0.001), relative to sham-operated rats (n = 18). RV wall thickness was significantly increased in SAD animals, but there was no difference in the LV wall thickness and volumes of the RV and LV between groups. Constrictor responses to methoxamine and dilation responses to acetylcholine were assessed in an in vitro perfused mesenteric circulation preparation, but neither response was affected by SAD. Baroreceptor denervation was associated with marked and significant increases in the variability (2.8-fold) and daily peak (39 mmHg) levels of telemetered mean arterial pressure (MAP) and small (5%) but significant increases in the daily mean MAP level. Our results are consistent with an effect of increased MAP variability on ventricular weight but cannot rule out possible contributions from other mechanisms.

Animals↗
PubMed1996

Hypocalcemia, morbidity, and mortality in end-stage renal disease.

BACKGROUND: Hypocalcemia and hyperphosphatemia with secondary hyper-parathyroidism are characteristic of end-stage renal disease (ESRD). Although calcium levels critically affect almost all cellular processes, the impact of chronic hypocalcemia and other abnormalities of calcium-phosphate homeostasis on the prognosis of ESRD patients is unknown. METHODS: An inception cohort of 433 patients starting ESRD therapy was followed prospectively for an average of 41 months. Serum calcium and other parameters were measured monthly. The mean calcium levels were 9.4 +/- 0.7 mg/dl. 23% of the patients had mean calcium levels < 8.8 mg/dl. After adjusting for baseline age, diabetes mellitus, ischemic heart disease, smoking and cholesterol levels, as well as serial albumin, hemoglobin, mean arterial blood pressure, phosphate and alkaline phosphatase levels, chronic hypocalcemia was strongly associated with mortality (RR 2.10, p = 0.006 for a mean calcium level < 8.8 mg/dl). The association with mortality was similar in hemodialysis (RR 2.10, p = 0.006) and peritoneal dialysis patients (2.67, p = 0.034). Using similar covariate adjustment, chronic hypocalcemia was associated with de novo ischemic heart disease (RR 5.23, p < 0.001), recurrent ischemic heart disease (RR 2.46, p = 0.006), de novo cardiac failure (RR 2.64, p < 0.001), and recurrent cardiac failure (RR 3.30, p < 0.001). Hypocalcemia retained its independent impact on morbidity and mortality when analyzed as a time-dependent covariate. CONCLUSIONS: Chronic hypocalcemia, a very common, reversible feature of chronic uremia, is independently associated with morbidity and mortality in ESRD patients.

Alkaline Phosphatase↗
PubMed1996

Prolactin release from subpopulations of rat lactotrophs in the presence and absence of dopamine.

In this study we examined the effects of dopamine (DA) and its withdrawal on in vitro prolactin (PRL) release from subpopulations of lactotrophs from two regions of the anterior pituitary obtained from untreated ovariectomized (OVX) rats or OVX rats treated with estrogen, progesterone or a combination of the two. Anterior pituitaries were cut horizontally into an inner (dorsal) zone and an outer (ventral) zone. Each of these regions was enzymatically dispersed and the resulting cells were otherwise untreated (unseparated) or centrifuged through a discontinuous Percoll gradient to separate the cells into two subpopulations (light and heavy cells). Each of these types of cells was perifused for 1 h with culture medium containing 1 microM DA followed by medium devoid of DA for 1 h. Prolactin released into the perifusion medium, collected as 5-min fractions, was measured by radioimmunoassay and normalized to the number of lactotrophs in the cellular pools as determined by immunocytochemistry. In the presence of DA, PRL release from unseparated cells of the outer zone was significantly increased by estradiol treatment compared with the release from similar cells from OVX rats. (Differences were considered significant where P < 0.05.) However, no effect of estradiol treatment was observed with unseparated cells of the inner zone or light or heavy cells from either zone. Progesterone had no effect on any cell type when administered alone. However, when progesterone was given following estradiol, PRL release from unseparated cells of the inner zone was increased significantly compared with similar cells from the other steroid-treated groups. Similar significant increases were observed with light and heavy cells of the outer zone, but there was no effect of the combined steroid treatment on light or heavy cells from the inner zone. When DA was withdrawn, prolactin release was significantly increased from all cells except unseparated cells of the outer zone of OVX rat pituitaries. However, when the cells of the outer zone from OVX rats were separated into light and heavy cells, they responded to the withdrawal of DA with significant and equivalent increases in prolactin release. Light cells of the inner zone of pituitaries from OVX rats were more responsive to DA withdrawal than were heavy cells. Estradiol increased the response to the withdrawal of DA by light and heavy cells of the outer zone and heavy cells of the inner zone. Progesterone significantly reversed these effects of estradiol on separated cells. These results suggest that lactotrophs in two regions of rat pituitaries respond differently to dopamine and to its withdrawal, that subpopulations of lactotrophs within these regions also respond differently and that steroids modulate these responses.

Animals↗
PubMed1996

[Experiment study on biological and immunological characteristics of modified DNL of oral squamous cell carcinoma with TNF-alpha gene]

Growing characteristic of gene-transduced and nontransduced DNL in medium of containing rIL-2 was compared,and growing characteristic of gene-transduced DNL in medium of non containing rIL-2 was analyzed.DNA index (DI),cell cycle and immunologic phenotypes of gene-transduced and nontransduced DNL were analyzed with FACS.The results revealed interfered with growth,DL,cell cycle and immunologic phenotypes of DNL,and gene-transduced DNL couldn't growing infinitely.

Journal Article↗
PubMed1996

[Overexpression of c-Fos induces apoptosis of CD43+ pro-B cells].

The proto-oncogene product c-Fos, a component of the transcription factor AP-1, is induced in early B lineage cells. In order to investigate a role of the c-Fos in early B cell development, fetal liver (FL) cells from transgenic mice carrying an IFN-inducible c-fos gene (Mx-c-fos) were cultured on a stromal cell layer with IL-7. The development was perturbed by the addition of IFN at the beginning of culture. When IFN was added in the FL culture after B lineage cells developed, pro-B (B220+, CD43+) cells were selectively dying by apoptosis within 48 h after IFN stimulation. These results suggest that c-Fos plays a causal role in deletion of pro-B cells.

Animals↗
PubMed1996

Study on the column process of adsorption decolorization for monosodium glutamate solution in fluidized beds.

The adsorption decolorization of monosodium glutamate solution employed in multiple column fluidized beds in a series is studied. The equilibrium data, the mass transfer kinetics, and fluid flow parameters are determined. A mathematics model taking into account the effects of particle size classification, particle size distribution, external and internal diffusions, and axial mixing in the liquid and solid phases is proposed, and the simulated results are in good agreement with the experimental data.

Adsorption↗