Biomedical subjects

L Huynh

Publications and source records attributed to L Huynh.

16 recordsLinked to original sources

PubMed2000

Regional cerebral cortical activation in monoamine oxidase A-deficient mice: differential effects of chronic versus acute elevations in serotonin and norepinephrine.

Mice deficient in monoamine oxidase A have previously been shown to demonstrate a chronic elevation of serotonin and norepinephrine in the brain. Using the autoradiographic [14C]iodo-antipyrine method, we examined cerebral cortical blood flow in conscious, restrained four- to five-month-old knock-out and wild-type animals following the intraperitoneal administration of either saline or D-fenfluramine. Knock-out animals administered saline, compared to their wild-type counterparts, demonstrated a significantly higher regional cortical blood flow in somatosensory and barrel field neocortex, an area which previous histological studies have shown to be characterized by abnormal serotonergic projection fibers and absent barrel formation. Regional cortical blood flow was significantly lower in knock-out than in wild-type mice in the entorhinal and midline motor cortex, with non-significant decreases noted in the olfactory, piriform and retrosplenial cortices and the amygdala. We compared the above findings to those obtained in response to D-fenfluramine which, in conjunction with its metabolite D-norfenfluramine, results in acute elevations of brain levels of serotonin and norepinephrine. Administration of D-fenfluramine (21. 2mg/kg) resulted in changes in regional cortical perfusion in most brain regions of both knock-out and wild-type mice that were opposite to the genotypic differences seen in perfusion in response to saline. Fenfluramine significantly increased regional cortical blood flow in the allocortex (olfactory, piriform, entorhinal) and the amygdala, and significantly decreased regional cortical blood flow in the somatosensory, barrel field, midline motor and retrosplenial cortices. Changes in regional perfusion in response to fenfluramine were topographically equivalent in knock-out and wild-type mice, although in knock-out mice such changes were of greater magnitude. Our study suggests that the effects on regional cortical blood flow of a lifelong absence of monoamine oxidase A, and the consequent chronic increase in serotonin and norepinephrine, differ from those attributable to acute increases in these neurotransmitters following fenfluramine administration. Such a differential response may reflect neurodevelopmental abnormalities and/or effects of a chronic physiological adaptation on the regulation of cortical activation.

Animals↗

PubMed2000

Hypertension in beta-adducin-deficient mice.

Polymorphic variants of the cytoskeletal protein adducin have been associated with hypertension in humans and rats. However, the direct role of this protein in modulating arterial blood pressure has never been demonstrated. To assess the effect of beta-adducin on blood pressure, a beta-adducin-deficient mouse strain (-/-) was studied and compared with wild-type controls (+/+). Aortic blood pressure was measured in nonanesthetized, freely moving animals with the use of telemetry implants. It is important to note that these mice have at least 98% of C57Bl/6 genetic background, with the only difference from wild-type animals being the beta-adducin mutation. We found statistically significant higher levels of systolic blood pressure (mm Hg) (mean+/-SE values: -/-: 126.94+/-1.14, n=5; +/+: 108.06+/-2. 34, n=6; P:</=0.0001), diastolic blood pressure (-/-: 83.54+/-1.07; +/+: 74.87+/-2.23; P:</=0.005), and pulse blood pressure (-/-: 43. 32+/-1.10; +/+: 33.19+/-1.96; P:</=0.001) in beta-adducin-deficient mice. Western blot analysis showed that as a result of the introduced genetic modification, beta-adducin was not present in heart protein extracts from -/- mice. Consequently, this deficiency produced a sharp decrease of alpha-adducin and a lesser reduction in gamma-adducin levels. However, we found neither cardiac remodeling nor modification of the heart function in these animals. This is the first report showing direct evidence that hypertension is triggered by a mutation in the adducin gene family.

Animals↗

PubMed1999

Lack of protection from ischemic injury of monoamine oxidase B-deficient mice following middle cerebral artery occlusion.

Adult male wild-type mice received intraperitoneal (i.p.) administration of saline (n = 9) or 10 mg/kg L-deprenyl (n = 9) three times a week for 3 weeks. Mice with targeted inactivation of the monoamine oxidase B (MAO-B) gene received i.p. administration of saline (n = 8). Animals underwent ligation of the left common and external carotid arteries, followed by cauterization of the ipsilateral middle cerebral artery. Twenty-four hours post-surgery, all groups showed right torsion of the torso but no evidence of limb weakness, lateral instability, or circling. Ischemic changes were assessed from digitized video-images of serial sections of the brain stained with Hematoxylin/Eosin. No significant group differences were detected in infarct volume (14-18% of ipsilateral cortex) or in the extent of brain edema (4-7% increase in ipsilateral hemispheric swelling with respect to contralateral side). Our results suggest that absence of the MAO-B gene or inhibition of the enzyme with L-deprenyl are not protective or detrimental in an animal model of acute cortical infarction.

Animals↗

PubMed1999

Transport of uterine PGF2 alpha to the ovaries by systemic circulation and local lymphovenous-arterial diffusion during luteolysis in sheep.

The theory of countercurrent vascular transfer of PGF2 alpha during luteolysis was examined. In the first experiment, pulmonary clearance of PGF2 alpha was determined to re-examine whether the total amount of PGF2 alpha was degraded in the lungs after one passage. Cardiac output was measured by the Fick method and PGF2 alpha by radio-immunoassay before and after vascular lung supply, using pulmonary catheterization and the interventional radiology method in ten anaesthetized ewes on day 16 of the oestrous cycle. Cardiac output remained stable (7156 +/- 439 ml min-1). Infusion of 5 iu oxytocin resulted in an increase in plasma PGF2 alpha concentrations at 30 min in the uterine vein and the pulmonary and femoral arteries (3811 +/- 806, 224 +/- 55 and 18 +/- 4 pg ml-1, respectively). The PGF2 alpha concentrations decreased exponentially and the half-time decreases were 27 (r = 0.99), 16 (r = 0.99) and 18 (r = 0.98) min, respectively. Pulmonary clearance of PGF2 alpha was estimated at 6338 +/- 451 ml min-1. In a second experiment, an arterio-arterial gradient of plasma PGF2 alpha concentrations was analysed between the proximal and distal segments of the ovarian artery to verify whether the total amount of PGF2 alpha flowing to the ovary was from the local venous-arterial countercurrent pathway. Surgical catheterization techniques were performed on 11 ewes on day 16 of the oestrous cycle. The ovarian arterial blood flow was measured by the implantable Doppler method (8 +/- 1 ml min-1). The maximum plasma PGF2 alpha concentrations in the femoral and distal ovarian arteries were 23 +/- 6 and 42 +/- 11 pg ml-1 (P < 0.05), respectively. Plasma PGF2 alpha decreased exponentially in the femoral artery and the half-time decrease was 26 min (r = 0.98), and in the distal ovarian artery close to the ovary PGF2 alpha decreased linearly and the half-time decrease was 108 min (r = 0.96). Consequently, the arterio-arterial diffusion gradient of PGF2 alpha concentrations was extended to 3 h. These experiments showed that the PGF2 alpha flow rate in the pulmonary artery was 42.275 +/- 10.793 micrograms per 150 min (n = 10) and the systemic arterial PGF2 alpha flow rate was 5.359 +/- 1.658 micrograms per 150 min (n = 10). Therefore, 12% of the PGF2 alpha was not oxidized by the lungs. The proximal ovarian PGF2 alpha flow rate was 6.909 +/- 2.341 ng per 150 min, while the distal flow rate was 21.003 +/- 5.703 ng per 150 min (n = 11). Thus, 33% of the PGF2 alpha was transported rapidly to the ovary via the systemic route, while 67% was transported by slow local countercurrent diffusion, which extended the duration of luteolytic activity to four times that of the PGF2 alpha surge. These results indicate both rapid systemic transport of PGF2 alpha to the ovaries and a slower buffer mechanism involving a local diffusion pathway, rather than a direct countercurrent system.

Animals↗

PubMed1997

Subunit interactions in the Na,K-ATPase explored with the yeast two-hybrid system.

Subunit interactions of the alpha1- and beta1-subunits of the chicken Na,K-ATPase were explored with the yeast two-hybrid system. Gal4-fusion proteins containing domains of the alpha1- and beta1-subunits were designed for examining both intersubunit and intrasubunit protein-protein interactions. Regions of the alpha- and beta-subunits known to be involved in alpha-beta-subunit assembly were positive in two-hybrid assay, supporting the validity of the assays. A library of beta-subunit ectodomains with C-terminal truncations was screened to find the maximal truncation retaining an interaction with the alpha-subunit extracellular H7H8 loop (where H7 refers to the seventh membrane span, and so on). The maximal truncation removed all the cysteines involved in disulfide bridges, leaving only 63 amino acids of the beta-subunit ectodomain. Scanning alanine mutagenesis led to identification of an evolutionarily conserved sequence of four amino acids (SYGQ) in the extracellular H7H8 loop of the alpha-subunit that is crucial to alpha-beta-intersubunit interactions. Oligomerization studies with single domains failed to detect self-association of either of the two large cytosolic loops (H2H3 and H4H5) within the alpha-subunit. However, evidence was found for an interaction between these two cytoplasmic loops.

Amino Acid Sequence↗

PubMed1997

The Drosophila Na,K-ATPase alpha-subunit gene: gene structure, promoter function and analysis of a cold-sensitive recessive-lethal mutation.

The Drosophila Na,K-ATPase (or sodium pump) alpha-subunit gene was found to contain 10 exons and span approx. 25 kb. Two nearly adjacent transcriptional initiation sites were identified, and the 2085-nucleotide sequence upstream of the first transcriptional start was analysed for promoter activity in transfected Drosophila SL2 cells. This region was found to contain many cis-acting elements that influence promoter activity, including elements that confer 2- to 3-fold higher activity in SL2 cells cultured at 30 degrees C versus 22 degrees C. Temperature-sensitive transcriptional regulation of the Na,K-ATPase alpha-subunit in Drosophila is a plausible mechanistic candidate for the factor driving temperature-dependent up-regulation of the Na,K-ATPase alpha-subunit described here for fly strains homozygous for single P-element insertions in the alpha-subunit gene. Four new P-element insertion strains were identified in this study, each insertion site lying within the first intron of the Na,K-ATPase alpha-subunit gene. The insertion in strain 0462 resulted in cold-sensitive recessive lethality; flies homozygous for the 0462 mutation could be rescued by growth at 29-30 degrees C, a condition that partially corrected a deficiency in the level of Na,K-ATPase alpha-subunit. The high-temperature rescue of homozygous 0462 flies appeared to result primarily from improved Na,K-ATPase expression rather than an increase in the rate of ion transport per Na,K-ATPase molecule. These observations point to a role for sodium-pump activity in determining the range of temperature tolerance in Drosophila and demonstrate that relatively subtle changes in sodium-pump expression can have major consequences in whole organisms.

Adaptation, Physiological↗

PubMed1997

Recent developments and potentialities for reducing embryo mortality in ruminants: the role of IFN-tau and other cytokines in early pregnancy.

This review considers the potential reduction of embryo mortality in vitro and in vivo in ruminants. Data on cytokines provided by different fields of reproductive immunology and biology were collated. Because of the crucial importance of the local interactions between the embryo and its dam, the expression of growth-factor and cytokine genes was analysed in the embryo proper, trophoblast, oviduct and endometrium by reverse transcriptase polymerase chain reaction in sheep and in cattle during the pre- and periimplantation periods. Many deleterious cytokines, such as tumour necrosis factor-alpha, interferon-gamma (IFN-gamma), interleukin-2 (IL-2), and beneficial cytokines, such as transforming growth factor-beta, leukaemia inhibiting factor, colony-stimulating factor-1 (CSF-1), granulocyte-macrophage CSF, IL-1, IL-3, IL-4, IL-6, IL-10 and IFN-tau appeared to be involved in embryo survival in ruminants and other species. Their administration is efficient in a murine experimental model (CBA/J x DBA/2) of embryonic and fetal mortality. For instance, recombinant ovine IFN-tau (roIFN-tau) injected at the moment of implantation drastically reduces embryonic mortality in this model. In ruminants, roIFN-tau and recombinant bovine IFN-tau are very efficient in maintaining progesterone luteal secretion in cyclic animals. The involvement of IFN-tau in the mechanisms of maternal pregnancy recognition are particularly detailed in relation to inhibition of 13,14 dihydro-15-keto-prostaglandin F2 alpha (PGFM) pulses and oxytocin uterine receptivity. A synthetic model of the anti-luteolytic effects of IFN-tau on the endometrial cell is proposed. Finally, the particular potential of serum pregnancy-specific proteins (PSPs: PSPB, PSP60, pregnancy-associated glycoprotein) for monitoring embryo survival, with examples given for cattle and sheep is underlined.

Amino Acid Sequence↗

PubMed1996

Rapid debulking and CD34 enrichment of filgrastim-mobilized peripheral blood stem cells by semiautomated density gradient centrifugation in a closed system.

Filgrastim-mobilized peripheral blood progenitor cells (PBPC) are used for hematopoietic reconstitution after myeloablative therapy for malignancies, but the large number of cells collected in a single apheresis frequently presents a problem for storage or further processing. We have evaluated the use of CD34 Buoyant Density Solution-PBPC, an ultralight-density colloidal silica suspension, for debulking and enrichment of CD34+ cells in PBPC preparations in a semiautomated system. Cells were collected from four filgrastim-treated normal donors using the COBE Spectra. The separation procedure was carried out with Plasma-Lyte A and DNase 5 U/ml using the COBE 2991. Following processing and washing, there was a 26% recovery of nucleated cells, 2.6-fold enrichment of CD34+ cells, 68% recovery of CD34+ cells, 88% recovery of CFU-GM, 73% recovery of BFU-E, 1 log depletion of CD3+ cells, 0.5 log depletion of CD56+ cells, and 1 log depletion of CD19+ cells. These results were not significantly different from those obtained when PBPC were separated over CD34 Buoyant Density Solution-PBPC by centrifugation in tubes. Using CD34 Buoyant Density Solution-PBPC, mononuclear preparations of PBPC can be enriched rapidly for CD34+ cells and depleted of lymphocytes in a semiautomated closed system using reagents produced according to good manufacturing practice (GMP).

Antigens, CD34↗

PubMed1995

A single intrauterine infusion of sustained recombinant ovine interferon-tau extends corpus luteum lifespan in cyclic ewes.

Delivery carriers were developed to permit sustained release of recombinant ovine tau-interferon (roIFN-tau) to increase corpus luteum (CL) lifespan in cyclic ewes following a single intrauterine administration on Day 10 post estrus. A single infusion with 1.7 mg roIFN-tau covalently bound to carboxymethyl biogel agarose (carbodiimide coupling) significantly increased the interestrus interval (P < 0.01) in treated (n = 4) versus control animals (n = 6), whereas liposomally encapsulated roIFN-tau administered to experimental ewes (n = 8) versus control ewes (n = 6) was less effective (P < 0.05). RoIFN-tau covalently bound to trisacryl (glutaraldehyde coupling) was also effective in cyclic ewes (n = 6), but covalent binding to Eupergit C through oxirane bonds yielded ineffective preparations. Ewes that were given 1.7 mg soluble roIFN-tau (n = 8) displayed slight extension of the CL lifespan compared with ewes that were given 1.7 mg soluble BSA (n = 6), but this extension lacked significance in the Mann-Whitney U-test (P > 0.05). These results are consistent with previous data from experiments performed with daily intrauterine infusion of soluble, native or recombinant oIFN-tau. In addition, because CL maintenance requires only a single administration, these methods are efficient and simple to use since they avoid animal catheterization and allow for reduced injection frequency. Moreover, they may permit the use of smaller amounts of IFN. It is concluded that the use of oIFN-tau sustained in some delivery systems may allow for the development of an experimental sheep pseudopregnancy model.

Journal Article↗

PubMed1995

Alprazolam for tinnitus.

There is insufficient evidence to support the use of alprazolam in the treatment of tinnitus. The Johnson trial is the only study to date assessing the role of alprazolam, and at best it is an open-label trial demonstrating activity. There is a need for definitive double-blind, controlled, crossover studies of sufficient statistical power to resolve the issue. Furthermore, once efficacy is demonstrated, further studies are needed to determine the appropriate length of therapy, the necessity for maintenance therapy, the role of "drug holidays," appropriate dose tapering schedules, and a more careful delineation of which populations of patients are more likely to respond to alprazolam.

Alprazolam↗

PubMed1995

[Trophoblastic interferons and embryonal immune tolerance].

Current evidence support the hypothesis that trophoblast interferons play a key role in preventing maternal immunologal rejection of the embryonic semi-allograft. The information of this review is divided in two sections. In the first section we described molecular and biological characteristics of type I (alpha, beta, omega, tau and spl) and type II (gamma) interferons. In the second section we emphasize studies on immunoendocrine functions of IFN-tau (oTP-1 or trophoblastins) in the network of cytokines and hormonal environment at the uterine embryonic interface.

Animals↗

PubMed1994

Large-scale preparation of highly purified, frozen/thawed CD34+, HLA-DR- hematopoietic progenitor cells by sequential immunoadsorption (CEPRATE SC) and fluorescence-activated cell sorting: implications for gene transduction and/or transplantation.

The purification of early hematopoietic progenitor cells for autologous transplantation is based on two rationales: (1) elimination of clonogenic tumor cells, and/or (2) gene transfer into indefinitely self-replicating hematopoietic stem cells. Primitive CD34+ stem cells can be separated from more mature stem cells, or probably from clonogenic tumor cells, by differences in HLA-DR surface antigen expression. The objective of this study was to establish a large-scale technique for purification of CD34+, DR- progenitor cells from a large volume marrow harvest. In five different experiments, CD34+ cells were purified to between 76% and 91% by avidin-biotin immunoadsorption (CEPRATE SC) as a first step. This was followed by fluorescence-activated cell sorting to separate DR+ and DR- cells, which resulted in the generation of between 1.75 and 11.3 x 10(5) CD34+, DR- cells. The purity of DR- cells increased from between 0.5% and 4.3% in the immuno-adsorbed fraction up to 99% in the DR- sorted fraction. As shown in a single experiment, the purity of CD34+, DR- cells immediately after thawing increased from 0.01% to 94.3% while losing 99% of those early progenitor cells during the multistep purification procedure. We were able to physically separate one CD34+, DR- cell from up to 8000 nucleated cells in the prepurified cell suspension. One million highly purified CD34+, DR- progenitor cells is potentially an adequate cell dose for autologous transplantation equivalent to what is contained in an unselected and functioning marrow autograft.

Antigens, CD↗

PubMed1994

[Cytokines and the corpus luteum].

This minireview present main findings concerning the contribution of cytokines to the regulation of some key processes of luteal functions. Data concerning the preovulatory follicles invasion by white blood cells and the migration of macrophages, granulocytes and T lymphocytes into corpus luteum suggest that local secretion of regulatory cytokines may be involved in regulating corpus luteum formation and demise as well its maintenance in early pregnancy. Several lines of evidence indicate that the pro-inflammatory cytokines such as IL-1, IL-6 and TNF-alpha modulate the steroidogenic changes which take place during luteinization. For instance, an inhibition of E2 biosynthesis is evidenced in granulosa cells in human or porcine species with IL-1, in rat with TNF-a and in bovine with IL-6. Moreover, IL-1 stimulates P4 production but to a much lower extent than LH, and PGE2 synthesis by rat thecal cells. The potential relevance of pro-inflammatory cytokines in the mechanisms controlling luteolysis is suggested by the ability of IL-1 and TNF-alpha to decrease both P4 production and the survival of bovine luteal cells. As opposed to ruminants, TNF-alpha has no effect in human luteal cells but potentiates the decrease of P4 secretion induced by IFN-gamma. Finally, data regarding the participation of trophoblast interferons in the mechanisms for maintaining the corpus luteum at the establishment of pregnancy are now available in ruminants. From these observations and others, we can consider that cytokines are involved in the regulation of the corpus luteum function.

Animals↗

PubMed1985

Effect of pretreatment with cyclophosphamide on high-dose toxicity of melphalan in mice.

This study was undertaken to evaluate the effect of pretreatment (or priming) with cyclophosphamide (CY) on lethal toxicity of high-dose melphalan (MELPH) in mice. In C57BL/6 X DBA/2 F1 (hereafter called B6D2F1) mice given an injection of a single dose of CY, 50 mg/kg, 1-5 days before MELPH, 20 mg/kg, improved survival was noted in only one of five experiments. Reducing the challenge dose of MELPH to 17 mg/kg did not improve survival consistently. Priming with CY, 50 mg/kg, 3 days before a dose of MELPH, 20 mg/kg, did not improve survival in CBA/J or C57BL/6 mice. These results indicate that CY is an inconsistent priming agent for abrogating high-dose MELPH toxicity in mice. A slightly earlier recovery of regenerating hemopoietic and of jejunal crypt cells was noted in CY-primed B6D2F1 mice given injections of a low dose of MELPH, 15 mg/kg. The occasional improved animal survival noted in CY-primed B6D2F1 mice might be related to this earlier cell recovery.

Animals↗

PubMed1981

Piperazinedione (NSC 135758) and total body irradiation as an ablative bone marrow transplantation regimen in mice.

Piperazinedione, an antitumor antibiotic with activity against leukemia, has been incorporated into a regimen for clinical bone marrow transplantations. Studies were conducted to evaluate the effect of piperazinedione on hemopoietic stem cells and the recovery of hemopoiesis after syngeneic transplantation. The effect of piperazinedione on hemopoietic stem cells is short in duration (nadir day 1). Myelosuppression does not appear to be its limiting toxicity, since mice could not be rescued by syngeneic bone marrow at increased doses of piperazinedione. Piperazinedione given prior to total body irradiation has an enhancing effect on colony-forming unit culture (CFUC) and colony-forming unit spleen (CFUS) recovery from day 7 to day 90 post transplantation when compared with total body irradiation alone.

Animals↗

PubMed1980

Enhancement of hemopoietic recovery after bone marrow transplantation with the addition of nucleated blood cells in mice.

Recovery of bone marrow cellularity, CFU-C, and CFU-S were studied sequentially over 90 days time after syngeneic bone marrow transplantation in mice. A minimal cell dose of 2 X 10(5) bone marrow cells was given. At day 28 after transplantation, CFU-C reached more than 50% of the normal range whereas the CFU-S concentration was less than 15%. Normalization of CFU-S occurred at day 90. The effect of the addition of peripheral blood nucleated cells on bone marrow hemopoietic recovery was studied at day 28. The augmentation of CFU-C and CFU-S recoverey were dose dependent. Optimal enhancement was seen with bone marrow to blood ratios of 1:1 and 1:2.5. This enhancement effect was lost when nucleated blood cells in a ratio of 1:10 were administered.

Animals↗