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Biomedical subjects

L Lu

Publications and source records attributed to L Lu.

At least 451 records · Page 25Linked to original sources
PubMed1994

Molecular genealogy of some nematode taxa as based on cytochrome c and globin amino acid sequences.

We have begun to reconstruct the ancient history of the nematode phylum based on cytochrome c and globin amino acid sequences. The data suggest that the nematode ancestor diverged from a line leading to mammals about 1 billion years ago and that the most recent common ancestor of the extant species Caenorhabditis elegans, Trichostrongylus colubriformis, Nippostrongylus brasiliensis, Ascaris suum, and Pseudoterranova decipiens lived about 550 MY ago. The rhabditids and strongylids emerged as one offshoot of this ancestor, the ascarids as another. Rhabditids and strongylids diverged some 400 MY ago, whereas the genera Trichostrongylus and Nippostrongylus diverged slightly over 200 MY ago. A gene duplication event in the strongylid branch is predicted to have occurred around 250-335 MY ago. There are two globin genes in Nippostrongylus, expressed in anatomically distinct compartments (body and cuticle), and the single sequence from Trichostrongylus is most like the Nippostrongylus body globin gene. A strikingly different duplication event occurred within the same period in the line leading to the extant ascarid genera, creating a single polypeptide containing two globin domains. The genera Ascaris and Pseudoterranova diverged some 150-250 MY ago. Interestingly, the second globin repeat evolved at a faster rate in both species examined. This is possibly related to the acquisition of an unusual carboxyterminal extension, composed of alternating positively and negatively charged residues, that is necessary for the assembly of several monomers into the native polymeric molecules.

Amino Acid Sequence↗
PubMed1994

Protein kinase A-regulated Cl- channel in ML-1 human hematopoietic myeloblasts.

Using the inside-out patch clamp technique, we identified a Cl- channel in patches from the membrane of cultured human hematopoietic myeloblastic leukemia ML-1 cells. The Cl- channel was not seen at negative membrane potentials in excised patches until the membrane potential was depolarized to greater than +40 mV. The channel was also activated by addition of cAMP-dependent protein kinase (PKA) catalytic subunit at physiological membrane potential (-40 mV). Biophysical studies of the Cl- channel revealed that the current-voltage (I-V) relationship of the Cl- channel was outwardly rectifying in symmetrical 142 mM Cl- solutions. Single channel conductances were 48 pS for the outward current measured at +60 mV and 27 pS for the inward current at -60 mV. The open time constant of the channel was dependent on the membrane potential and was significantly prolonged at positive membrane potentials. Channels activated by cAMP-dependent protein kinase spent a significantly longer time in the open state compared to those channels activated by depolarization pulses. Pharmacological properties of the Cl- channel were also studied. Two anion transport inhibitors, anthracene-9-carboxylic acid (9-AC) and 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS) caused a flickering block of the channel. Half-inhibitory concentrations (IC50) for 9-AC and DIDS were 174 +/- 20 and 70 +/- 16 microM, respectively. Blockade of the Cl- channel by 9-AC or DIDS was completely reversible. Our findings suggest that outwardly rectifying Cl- channels (ORCC) are present in human hematopoietic myeloblasts. The function of ORCC may be involved in hormone-regulated cell growth, cell volume regulation and immune responses.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1994

University transition: major and minor life stressors, personality characteristics and mental health.

One hundred and two first-year students at an independent college in Taiwan participated in a questionnaire study. Measurements of stressors (major life events, minor daily hassles and perceived university stress), personality (locus of control, extraversion and neuroticism) and mental health (depression, anxiety and somatic symptoms) were taken. Using multivariate analyses, we found that: (1) life events predicted anxiety, while daily hassles predicted depression; (2) locus of control and extraversion correlated negatively, while neuroticism correlated positively with university stress; and (3) neuroticism had a main effect on symptom reportings across the board, while extraversion had a vulnerability effect on somatic symptoms. Relationships between life events and daily hassles, and the roles of personality in the stress process, are discussed.

Adaptation, Psychological↗
PubMed1994

Multi-frequency imaging and modelling of respiratory related electrical impedance changes.

Two studies concerning multi-frequency impedance measurements are presented. The first uses tetrapolar measurements made on the thorax and the second electrical impedance tomography images, also made from the thorax. The way in which the impedance and the changes in impedance with ventilation depend upon frequency are investigated using Cole-Cole modelling and also a physiological model of lung tissue. There is an excellent fit to the Cole-Cole model, and the results show that it should be possible to identify tissue on the basis of the impedance spectrum and the spectrum of the changes in impedance during breathing.

Cardiography, Impedance↗
PubMed1994

Noise equalization within EIT images.

We first describe experiments designed to measure the spatial distribution of noise within an electrical impedance tomographic image of a saline-filled tank. These experiments show that the noise increases by a factor of up to 30 from the periphery towards the centre of the image. We then propose a method of noise equalization that depends upon spending longer collecting the smaller potentials than the larger potentials. The method is tested and shown to give an improvement in noise uniformity of about 16 dB.

Algorithms↗
PubMed1994

Apoptosis and macrophage-mediated cell deletion in the regulation of B lymphopoiesis in mouse bone marrow.

Studies of cell population dynamics and microenvironmental organization of B lymphopoiesis in the bone marrow of normal mice and in various genetically modified states have shown that cell loss, involving processes of apoptosis and macrophage-mediated cell deletion, is a prominent feature of the primary genesis of B lymphocytes. Balanced against the influence of proliferative stimulants, the programmed death of precursor B cells provides a quantitative control, determining the magnitude of the final output of functional B lymphocytes to the peripheral immune system. The cell loss mechanisms can be readily set in motion by external or systemic influences, making the B-cell output particularly vulnerable to suppression by ionizing irradiation, stress or other systemic mediators. In addition, however, cell loss exerts an important quality control in the formation of the primary B-cell repertoire. The combination of apoptosis and macrophage-mediated deletion, acting at successive stages of B-cell differentiation, efficiently eliminates many precursors having non-productive Ig gene rearrangements, cell cycle dysregulations, and certain autoreactive Ig specificities. Outstanding areas of further work abound. Important questions concern the nature of mechanisms which underlie the processes of B-cell apoptosis and macrophage deletion in bone marrow, the microenvironmental signals involved in B-cell life or death decisions and genetic factors which may override these B-cell culling mechanisms. The answers will be relevant to problems of autoimmune disease, humoral immunodeficiency and B-cell neoplasia.

Animals↗
PubMed1994

Insulin-like growth factor-binding protein-3 (IGFBP-3) concentration in rat Sertoli cell-conditioned medium is regulated by a pathway involving association of IGFBP-3 with cell surface proteoglycans.

Rat Sertoli cells in culture produce insulin-like growth factor-I (IGF-I), and IGF-binding protein-3 (IGFBP-3) is the predominant IGFBP. Previous studies suggested that the concentration of IGFBP-3 in Sertoli cell-conditioned medium is regulated by a clearance pathway involving association of IGFBP-3 with the Sertoli cell surface. The purpose of these studies was to characterize further the nature of the interaction of IGFBP-3 with the cell surface and to examine how this interaction might be regulating IGFBP-3 concentrations in conditioned medium. Recombinant nonglycosylated human IGFBP-3 was added to cultured Sertoli cells derived from 15-day-old rats, and the change in concentration over time in the medium was measured by [125I]IGF-I ligand blot analysis and Western blot analysis using an antiserum specific for human IGFBP-3. Chloroquine, an inhibitor of lysosomal enzymes involved in internalization of proteins and reduction of temperature, inhibited IGFBP-3 reduction in Sertoli cell medium. Soluble heparin, at a half-maximal concentration of approximately 5 microgram/ml, inhibited the decrease in IGFBP-3 in the medium. In addition, soluble heparin decreased the amount of IGFBP-3 detectable on the cell surface, as determined by performing ligand blots on plasma membrane preparations. Finally, pretreatment of Sertoli cells with sodium chlorate, an inhibitor of cell surface proteoglycan sulfation, also retarded the decrease in recombinant IGFBP-3. Taken together, these data suggest that an important mechanism influencing the concentration of IGFBP-3 3 in Sertoli cell-conditioned medium is a pathway involving IGFBP-3 interaction with the cell surface proteoglycans.

Animals↗
PubMed1994

Extensive proliferative capacity of single isolated CD34 human cord blood cells in suspension culture.

Nonadherent, low-density T-lymphocyte-depleted (NALT-) CD34 cells from normal human cord blood were assessed in suspension culture for the effects of recombinant cytokines on their proliferation, differentiation, and generation of myeloid progenitor cells. In this cell population, 82% of cells expressed c-kit protein as assessed by in situ hybridization, and their cloning efficiency was 85% when cells were plated at low cell numbers with combinations of growth factors. CD34 cells were sorted as 1, 5, or 10 cell(s) per well and also at 5000 cells per dish to initiate stromal-free suspension cultures in the presence of steel factor (SLF), interleukin (IL)-1 alpha, and IL-3. Forty-eight percent of the wells started with a single CD34 cell were positive for growth after 14 days, and the wells contained greater than 5 x 10(3) cells by 21-28 days. Progenitors were assayed weekly with cultures initiated with 1 or 5000 cells. While the fold expansion of nucleated cells was greater in cultures initiated with one cell per well (> 5000 compared to 791-fold expansion for 5000 cells), the fold expansion of progenitors was greater than 5000 cells were used to initiate cultures. Under optimal conditions, there was, respectively, a 160-, 164-, and 57-fold output of high proliferative potential colony-forming cells, granulocyte-macrophage colony-forming units, and erythroid burst-forming units/granulocyte erythroid macrophage megakaryocyte colony-forming units within 1-3 weeks for cultures initiated with 5000 CD34 cells compared with respective fold increases of 29, 16, and 1, for single-initiated cultures. These results demonstrate the expansion capacity of single CD34 cord blood cells and demonstrate that factors in addition to SLF, IL-1 alpha, and IL-3 are necessary for optimal expansion of progenitors from single isolated CD34 cells.

Antigens, CD↗
PubMed1994

Comparative analysis of retroviral-mediated gene transduction into CD34+ cord blood hematopoietic progenitors in the presence and absence of growth factors.

Hematopoietic stem and progenitor cells present in umbilical cord blood at the birth of a child are efficiently transduced ex vivo by genes using retroviral vectors in combination with exposure of these cells to combinations of growth factors. Because retroviral-mediated gene transduction of adult bone marrow and blood hematopoietic stem and progenitor cells is greatly enhanced by growth factors, we evaluated the possibility that cord blood progenitors, which have extensive proliferative and replating capacity, could be efficiently transduced with a TK neo gene in a retroviral vector in the absence of growth factors, and also determined the influence of exogenously added growth factors on this transduction. Highly purified CD34+ (62% pure) cord blood cells isolated by magnetic bead separation were cultured in suspension for 72 hours with viral supernatant in the absence and presence of interleukin-3 (IL-3), IL-6, and steel factor. Evaluation of progenitor cell-derived colonies and polymerase chain reaction (PCR)/Southern analysis of the TK neo gene in resultant colony cells demonstrated that some gene transduction was apparent in the absence of growth factors (12.8-14.3% by PCR), but that this was greatly enhanced (40.0-44.4%) by addition of growth factors. Reverse transcription PCR analysis of the expression of IL-3, IL-6, and granulocyte-macrophage colony-stimulating factor genes in this population of cells suggested that the transduction, although at a lower efficiency, in the absence of added growth factors might in part be due to "constitutive" and viral supernatant-induced expression of these cytokine genes in the CD34(+)-enriched cell population.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, CD↗
PubMed1994

Evaluating for vitreous surgery used in proliferative vitreoretinopathy grade D3.

Proliferative vitreoretinopathy (PVR) is one of the main failure causes of retinal detachment repair. In this paper, 25 cases of vitreous surgery used in the PVR D3 are analyzed. The diagnosis of PVR depended on the classification of the American Retina Society Terminology Committee. Vitrectomy and peeling were carried out in all of the patients. Intraocular tamponade included silicone oil and gas tamponade. Follow-up is more than 3 months. The anatomic successful rate was 68% and 11 cases arrived 20/400 or better. The complications included vitreous hemorrhage, cataract, silicone oil into anterior chamber, PVR recurrent and so on. The authors suggest that vitrectomy combined with peeling and intraocular tamponade be key for the treatment of PVR D3. Silicone oil tamponade may improve the patients' prognosis. PVR formation is connected with the operative irritation, giant tear, trauma and vitreous hemorrhage. Adaptation and time of the vitreous surgery are discussed in this paper, too.

Adolescent↗
PubMed1994

Stable integration of retrovirally transduced genes into human umbilical cord blood high-proliferative potential colony-forming cells (HPP-CFC) as assessed after multiple HPP-CFC colony replatings in vitro.

We previously demonstrated stable integration of a transduced thymidine kinase (TK)-neo gene into immature and replatable stem and progenitor cells, as assessed by the presence of the gene in second-generation colonies. To evaluate whether this integration was still present in third- and fourth-generation colonies, nonadherent low-density T-lymphocyte-depleted (NALT-) cells from human umbilical cord blood were prestimulated with recombinant human (rhu) erythropoietin (Epo), steel factor (SLF), interleukin-3 (IL-3), granulocyte-macrophage (GM) colony-stimulating factor (CSF), and granulocyte (G)-CSF. Prestimulated NALT- cells were incubated with retroviral-containing supernatant obtained from TK-neo vector-producing cells, washed, and assayed for colony formation in the presence of Epo, SLF, IL-3, GM-CSF, and G-CSF -/+ G418. The results confirmed that the TK-neo gene could be efficiently introduced into hematopoietic progenitor cells without stromal cells as a source of virus. As previously reported, proviral integration was detected in primary G418R-colonies, and in second-generation replated colonies derived from G418R granulocyte erythroid macrophage megakaryocyte colony-forming units and high-proliferative potential colony-forming cells (HPP-CFCs). Moreover, we now document that proviral integration was apparent in cells from colonies derived from third- and fourth-generation replated HPP-CFC, suggesting a high degree of stable integration of the transduced gene.

Cells, Cultured↗
PubMed1994

[The relationship between opportune administration of antibiotics and infection after burn injury: an experimental study].

45 male rabbits with 15% III degree burn were infected with Pseudomonas aeruginosa. They were divided into three groups: the prevention group, in which cpz (cefoperazone) was immediately administered after the scald at the dose of 25 mg/kg with an interval of 1/12 h for a total of 4 doses; the treatment group, in which cpz was administered 48 th after the scald with the dosage same as above; control group in which cpz was not administered. The findings were as follows: In the prevention group, gross observation showed dessication and crustation of the surface of the wound within 1 week after the scald. By employing immunofluorescent antibody it was found that P. A existed only in the superficial layer. However, ulceration and exudation were found in the control and treatment group within 3 or 4 days after the scald, and P. A was shown to have invaded the deep muscular tissue to cause intermuscular septal abscess. The positive rate of blood culture of bacteria in the prevention group (10/81) was significantly lower than that of the treatment (15/57) and the control groups (21/76, P < 0.05). The death rate of the prevention group (2/15) was significantly lower than that of the treatment (10/15) and the control groups (9/15, P < 0.05). The above finding showed that antibiotics specific to the infectious organism of the wound in extensive burn patients should be given in the early exudation stage in order to ward off invasive infection.

Animals↗
PubMed1994

[Application of silicone oil in management of complicated retinal detachment surgery].

60 eyes of 60 cases with complicated retinal detachment were treated by vitrectomy combined with silicone oil tamponade, including grade D of proliferative vitreoretinopathy (PVR) in 27, giant retinal tears with posterior flaps folded up in 15, posterior polar or macular holes in 13 and traumatic PVR in 5 eyes. After 3-24 months of follow-up, it is shown that 48 eyes obtained anatomic reattachment, the success rate being 80%, and the post-operative visual acuities improved in 43 eyes of which 32 eyes achieved > 0.05. The authors consider that vitrectomy and membrane peeling create a situation for silicone oil tamponade to play its role fully, vitrectomy is perfected by the combination of silicone oil tamponade and the rate of success of the retinal detachment operation is increased. The theory, indications, advantages and disadvantages of silicone oil tamponade were briefly discussed.

Adolescent↗
PubMed1994

[Using 3 primer pairs to detect HBV DNA in liver tissues from hepatocellular carcinomas with PCR technique].

PCR technique was used to detect HBV DNA in liver tissue samples for study of the prevalence of HBV DNA in tumorous and nearby nontumorous liver tissues from 16 hepatocellular carcinoma (HCC) patients. Three primer pairs, S1/S2, C1/C2 and X1/X2, used in this study were selected from S region, pre C and C region, and X region of HBV DNA, respectively. The detection limit with agarose gel electrophoresis and ethidium bromide staining (PCR-EB) was 10(-2) pg, and with Southern blot hybridization was 10(-6) pg. The positive rates in amplification of HBV DNA by S, C and X regions primer pairs in liver samples were 43.8% (14/32), 71.9% (23/32) and 71.9% (23/32), respectively. There was significant difference between the positive rates in amplification with S primer and with C primer (P < 0.05), but no significant difference between the C primer and the X primer (P > 0.05), and between the S primer and the X primer (0.10 > P > 0.05). HBV DNA fragments were detected in the livers from all 16 cases. The results indicated that x gene integration which induces hepatocellular carcinogensis and arrest of C gene expression which evades host immune surveillance are the possible mechanisms of HCC development in patients with persistent HBV infection.

Base Sequence↗
PubMed1994

Stressors, personality and mental health: a follow-up study.

One hundred and two Taiwanese subjects participated in a questionnaire follow-up study. Measurements of stressors (major life events, minor daily hassles and perceived stress of university life), personality (locus of control, extraversion and neuroticism) and mental health (depression, anxiety and somatic symptoms) were taken at Time 1; mental health was measured again at Time 2 eight months later. Using multivariate analyses, we found that (1) depressive, anxiety and somatic symptoms were all quite stable over an 8-month period; (2) daily hassles could still predict somatic symptoms at Time 2; and (3) locus of control could also predict anxiety symptoms at Time 2. Impacts of life events and daily hassles and the roles of personality in the stress process are discussed.

Adolescent↗
PubMed1994

Leisure satisfaction and happiness as a function of leisure activity.

114 subjects rated their happiness, leisure satisfaction, and several dimensions of leisure activity at two points in time. Some personality differences were found between those choosing different kinds of leisure, e.g. self-esteem and voluntary work, cooperativeness and clubs, neuroticism and hobbies rather than sports. Sixty-eight percent of respondents reported being committed to a leisure activity; they found their leisure to be more absorbing, more under control, and more challenging as well as more stressful than those who were not committed to a leisure activity; and they also had greater leisure satisfaction. Leisure satisfaction correlated with happiness, and social aspects of leisure satisfaction predicted happiness in longitudinal analysis.

Adolescent↗