SEARCH · PubMed Health

Results for “ASC”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources

PubMed1993

Ascorbic acid phosphate ester and wound healing in rabbit corneal alkali burns: epithelial basement membrane and stroma.

We examined the effect of L-ascorbic acid 2-phosphate (P-Asc) on the healing of alkali-burned corneas in rabbits. Round filter paper containing 1 N NaOH was applied to the central cornea for 60 or 120 s to produce the alkali burn. Animals were treated with topical saline, 10% ascorbate, or 6.5% P-Asc applied on the cornea. The corneas were then examined histologically. Burned stroma showed no toluidine blue staining, indicating a loss of glycosaminoglycan. In the 60-s burn group, P-Asc reduced the size of the unstained area as compared with the control. Transmission electron microscopy showed basal lamina under new epithelia in the corneas treated with ascorbate or P-Asc, but not in controls. These observations support the theory that P-Asc may have a therapeutic role in the repair of corneal alkali burns.

Administration, Topical↗

PubMed2003

Increase in tartrate-resistant acid phosphatase of bone at the early stage of ascorbic acid deficiency in the ascorbate-requiring Osteogenic Disorder Shionogi (ODS) rat.

The effect of ascorbic acid deficiency on bone metabolism was evaluated using the ascorbate-requiring Osteogenic Disorder Shionogi (ODS) rat model. Ascorbic acid (Asc)-deficient rats gained body weight in a manner similar to Asc-supplemented rats (control) during 3 weeks, but began to lose weight during the 4th week of Asc deficiency. The tartrate-resistant acid phosphatase (TRAP) activity in serum increased to about 2-fold the control value in the rats fed the Asc-free diet for 2, 3, and 4 weeks (AscD2, AscD3, and AscD4), while a decrease in the alkaline phosphatase (ALP) activity was observed only in AscD4 rats. The serum pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) level significantly increased to 1.3-, 1.4-, and 1.9-fold of that in the controls in AscD2, D3, and D4, respectively. The ALP activity in the distal femur was unchanged in AscD1, D2, and D3, but decreased to 50% of the control level in AscD4 rats. The TRAP activity in the distal femur increased to about 2-fold of that in the controls in the AscD2 and D3 and decreased to the control level in the AscD4 rats. The amount of hydroxyproline in the distal femur significantly decreased to about 80%, 70%, and 60% of the control in AscD2, D3, and D4 rats, respectively. These decreases were associated with a similar reduction in the calcium content of the distal femur. Histochemical analysis of the distal femur showed an increase in TRAP-positive cells in AscD2 and AscD3 rats and a decrease in the trabecular bone in AscD2, D3, and D4 rats. These results suggested that a deficiency of Asc stimulated bone resorption at an early stage, followed by a decrease in bone formation in mature ODS rats which already had a well-developed collagen matrix and fully differentiated osteoblasts.

Acid Phosphatase↗

PubMed1996

Expressed human hippocampal ASCT1 amino acid transporter exhibits a pH-dependent change in substrate specificity.

In mammalian cells, the basal Na+-dependent uptake for many of the neutral amino acids is mediated by a transport activity designated System ASC. A cloned human brain cDNA sequence, ASCT1, encodes a Na+-dependent neutral amino acid transport activity that exhibits a substrate specificity similar to that commonly associated with System ASC. However, the characteristics of ASC activity varies significantly between cell types and not all tissues contain detectable levels of ASCT1 mRNA. A unique property of System ASC activity is an altered substrate selectivity such that at pH values below 7.4 anionic amino acids function as inhibitors and substrates. The experiments in this report were designed to determine if the cloned ASCT1 transporter exhibited this pH-dependent anionic transport. Following transfection of HeLa cells with the ASCT1 cDNA, transport strongly favored neutral zwitterionic) amino acids when uptake was measured at a physiologic pH value of 7.5. However, lowering the assay pH to 5.5 significantly enhanced the interaction of the ASCT1 carrier with anionic amino acids such as cysteate, in a pH-dependent manner. The apparent pK for the titratable group was in the range of 6.5-7.0. These results provide evidence that the human brain ASCT1 transporter exhibits the most distinguishing characteristic known for System ASC and provides a model system to investigate the molecular basis for this shift in substrate acceptance.

Amino Acid Transport Systems↗

PubMed1983

Inhibition of transplantable melanoma tumor development in mice by prophylactic administration of Ca-ascorbate.

Hemicalcium ascorbate (Ca-Asc, 51 mM, 1% wt/vol), added to the drinking water, had the following effects in DBA/2 mice inoculated with 10(5) S91 (Cloudman) melanoma cells: 1) it delayed the appearance of visible tumors by 2-4 weeks; 2) it increased the survival rate at three months after tumor challenge by 12-50%; 3) it had no significant effect on the rate of tumor growth once the size of the tumors had reached 10 mm3; 4) the inhibition was maximal when the treatment with Ca-Asc was started at least one week prior to the inoculation of cells 5) when free ascorbic acid was used instead of Ca-Asc, the animals consumed 50% less water, they became dehydrated and the treatment was less effective; 6) Ca++ (51 mM) alone had no significant inhibitory effect.--Since Ca Asc (1 mM) was not toxic to S91 melanoma cells in vitro, we suggest that prophylactic treatment of the animals with Ca-Asc inhibited tumor development by increasing the resistance of the host.

Animals↗

PubMed1996

Systemic and pulmonary immune response to intrabronchial administration of ovalbumin in calves.

Local immunization of the respiratory tract may be the best way to achieve protection against respiratory pathogens. In order to do so successfully, it is important to fully understand how the immune response to antigen administered via the respiratory route develops. We studied the respiratory and systemic immune response after subcutaneous (SC) and intrabronchial (IB) inoculation of calves with ovalbumin (OVA). Eight calves received two SC inoculations of OVA and eight other calves received two SC and three additional IB inoculations of OVA. The occurrence of OVA-specific antibodies and antibody-secreting cells (ASC) was measured over time using isotype-specific enzyme linked immunosorbent assay (ELISA) and ELISPOT. SC immunization of calves did not result in OVA-specific IgA in bronchoalveolar lavage (BAL) fluid. Subcutaneous priming followed by intrabronchial challenge caused an initial IgG1 response in the bronchoalveolar lavage fluid, followed by a large IgA response. The presence of IgG1-ASCs indicated that the IgG1 was at least partially locally produced. Most of the OVA-specific IgA in the BAL fluid was secreted by pulmonary ASCs as indicated by the large number of IgA-ASCs in BAL samples and the low serum level of OVA-specific IgA. Antigen-specific IgG1 ASCs were detectable among peripheral mononuclear cells after culture with OVA.

Animals↗

PubMed1996

Peripheral blood antibody-secreting cells in the evaluation of the immune response to an oral vaccine.

Specific antibody-secreting cells (ASC) appear in the blood as a response to oral vaccination in humans. Based on information from animal experiments, these cells are believed to be migrating to the mucosa. This review summarizes a series of studies aimed at a detailed characterization of the ASC response to a prototype oral vaccine Salmonella typhi Ty21a, with respect to its kinetics, Ig-class distribution, antigen specificity, influence of the administration route and nature of the antigen, and the corresponding antibody responses in serum. Different vaccine formulations as well as dosage schedules are compared, and the response to booster immunization is described. The response manifested by ASC in blood is shown to be independent from serum antibody responses. Moreover, it is shown to parallel with the results obtained for protection in field trials. Finally, some data on the homing receptor expression of these cells are presented, giving further evidence for the mucosal homing of these cells. The ASC assay offers a practical means for assessing immune response to oral vaccines in humans. It can be used as a laboratory parameter correlated with protection conferred by an oral typhoid vaccine. It can even be applied to measure active mucosal immunity, i.e., protective immunity by showing the relative reduction of the ASC response to an oral dose of live vaccine.

Administration, Oral↗

PubMed1995

Effects of methylene blue and ascorbate on transmembrane potential in frog skeletal muscle.

1. The effects of methylene blue (MB, 10(-4) M) and ascorbate (ASC, 10(-4) M) on the resting membrane potential of frog skeletal muscle fibers were studied in Cl(-)-free medium at various external K+ concentrations. 2. Muscle fibers formed two distinct populations according to their resting potentials (hyperpolarized to -104 mV or depolarized to -31 mV) after a 90 min period of K+ withdrawal. ASC increased the relative contribution of hyperpolarized fibers, while in the presence of MB, all fibers depolarized during the 90 min of K+ withdrawal. 3. In the presence of 2.5 mM K+, ASC had no significant effect on the resting potential, while MB moved half of the fibers into the depolarized pool. Elevation of [K+]0 to 10 mM caused repolarization of all previously depolarized fibers (to -63 mV) in spite of the continuous presence of MB. 4. Ionic currents were measured during a 60 mV depolarization step using the double sucrose-gap technique. MB significantly increased the peak inward current, while ASC had no effect. The steady-state outward current was not affected by MB or ASC. 5. The results suggest that ionic conductances may be under redox control in frog skeletal muscle.

Animals↗

PubMed2005

Computer-aided diagnosis via model-based shape analysis: automated classification of wall motion abnormalities in echocardiograms.

RATIONALE AND OBJECTIVE: Shape analysis of endocardial contour sequences from echocardiograms can provide classification of wall motion abnormalities (WMA). MATERIALS AND METHODS: We previously reported on active appearance motion models (AAMM) for automated detection of endocardial contours in sequences of echocardiograms. The shape analysis of AAMM renders eigenvariations of shape/motion, including typical normal and pathologic endocardial contraction patterns. A set of stress echocardiograms (single-beat four-chamber and two-chamber sequences with expert-verified endocardial contours) of 129 infarct patients was split randomly into training (n = 65) and testing (n = 64) sets. AAMMs were generated from the training set and AAMM shape coefficients (ASCs) were extracted for all sequences and statistically related to regional/global visual wall motion scoring (VWMS) and volumetric parameters. RESULTS: Linear regression showed clear correlations between ASCs and VWMS. Discriminant analysis showed good prediction by ASCs of both segmental (74% correctness) and global WMA (90% correctness). Volumetric parameters correlated poorly to regional VWMS. CONCLUSION: 1) ASCs show promising accuracy for automated WMA classification. 2) VWMS and endocardial border motion are closely related; with accurate automated border detection, automated WMA classification should be feasible. 3) ASC shape analysis allows contour set evaluation by direct comparison to clinical parameters.

Cardiac Volume↗

PubMed2004

Effects of ascorbic acid and ascorbic acid 2-phosphate, a long-acting vitamin C derivative, on the proliferation and differentiation of human osteoblast-like cells.

In order to investigate the effect of ascorbic acid (AsA) and ascorbic acid 2-phosphate (Asc 2-P), a long-acting vitamin C derivative, on the growth and differentiation of human osteoblast-like cells, we supplemented the culture medium of MG-63 cells with various concentrations (0.25 to 1 mM) of these factors. Asc 2-P significantly stimulated nascent cell growth at all concentrations in the presence of fetal bovine serum (FBS). On the other hand, AsA showed a growth repressive effect depending on its concentration, and that of FBS. Asc 2-P also increased expression of osteoblast differentiation markers, such as collagen synthesis and alkaline phosphatase (ALP) activity. These stimulative activities of Asc 2-P were attenuated by inhibitors of collagen synthesis, indicating that these effects were dependent on collagen synthesis. Electron micrographs of the cells showed the formation of a three-dimensional tissue-like structure endowed with a mature extracellular matrix in the presence of Asc 2-P.

Alkaline Phosphatase↗

PubMed2005

Specific antibody secreting cells from chickens can be detected by three days and memory B cells by three weeks post-infection with the avian respiratory coronavirus.

Infectious bronchitis virus (IBV), the first coronavirus described, has been a continuing problem in poultry for more than 70 years. IBV, causing a highly contagious respiratory disease in chickens, resembles the recently described severe acute respiratory syndrome virus in pathogenesis and genome organization. While previous studies demonstrated that effector and memory CD8(+) T lymphocytes are critical in controlling acute IBV infection and disease in chickens, here chicken anti-IBV antibody (IgG) secreting cells (ASC) in both peripheral blood mononuclear cells (PBMC) and spleens collected following IBV Gray infection were evaluated using an ELISPOT assay. The ASC in peripheral blood and spleens can be detected from 3 to 7 days post-infection (p.i.), which is 3-7 days earlier than anti-IBV IgG detected in the serum. The ASC frequency reached a maximum at 7-10 days p.i., and decreased more than 90% in the spleen and 70% in PBMC by 14 days p.i. The ASC levels in the PBMC then decreased gradually to 0.5 ASC/10(6) over the next 8 weeks. The higher concentration of about 20 ASC/10(6) cells in spleens may, at least partially, account for the presence of antibody in the serum although bone marrow ASC were not determined. In vitro stimulation of PBMC and splenocytes with IBV antigen demonstrated that memory B cells can be activated to secrete antibody by 3 weeks p.i. ELISPOT detection of primary B cells could be useful in the early detection of infection following infection with respiratory coronaviruses.

Animals↗

PubMed2006

Migration of mouse antibody-secreting hybridoma cells from blood to genital tract and its regulation by sex hormones are associated with the differential expression patterns of adhesion molecules and chemokines in the tract rather than in the antibody-secreting cells.

To understand better the molecular mechanisms of differential migration of antibody-secreting cells (ASCs) into mouse genital tracts, and regulation by sex hormones, surface markers, hormone receptors and adhesion molecules in mouse SG2 and PA4 hybridoma cells, respectively, secreting IgG2b and polymeric IgA antibody were detected by flow cytometry or RT-PCR. Semi-quantitative RT-PCR was also used for measuring mRNA expression of adhesion molecules and chemokines (VCAM-1, ICAM-1, P-selectin, JAM-1 and CXCL12) in genital tracts of various adult mouse groups. The mRNAs of androgen receptor, estrogen receptor beta and CXCR4 were expressed in the ASCs. Sex hormones had no effect on expression of these molecules in ASCs. Except for VCAM-1, mRNA of all examined genes was expressed in normal mouse genital tracts. The mean of relative amounts of ICAM-1 and CXCL12 mRNA in all examined organs of females were higher (2.1- and 1.9-fold) than those in males. After orchiectomy or ovariectomy, the expression of ICAM-1, CXCL12 and P-selectin mRNA in the examined organs increased, except JAM-1 in male and CXCL12 in female. Sex hormone treatment recovered the changes to normal levels of mRNA expression in many examined genital tissues. In combination with our previous work, preferential migration of ASCs into female genital tract and regulation of migration by sex hormones are associated with expression patterns of adhesion molecules and chemokines in genital tract rather than in ASCs.

Animals↗

PubMed2006

Home anticoagulation testing: predictors of rural patient interest.

BACKGROUND: Home anticoagulation testing (HAT) may be useful for rural patients who cannot attend an anticoagulation service clinic (ASC). Interest in HAT is unknown and was the focus of this study. MATERIALS AND METHODS: Anticoagulated patients from two clinics, the ASC and vascular surgery clinic (VSC) were surveyed and compared for demographics, anticoagulation knowledge and opinions, and HAT interest. Logistic regression was performed, using the entire patient cohort, to identify factors associated with HAT interest. RESULTS: There were 211 (141 ASC, 70 VSC) patients surveyed. Differences between the ASC and VSC patients included education level (13.2 versus 12.1 years; P = 0.02), time spent testing (60.5 +/- 33.5 versus 46.4 +/- 20.7 min; P = 0.001), use of fingerstick testing (90% versus 2.9%; P < 0.001), and knowledge of the potential interaction of warfarin with medications or diet (79% versus 59% P = 0.003). HAT interest was similar (62.1% ASC versus 50% VSC; P = 0.14). Factors associated with HAT interest included employment [odds ratio (OR) 2.9, 95% confidence interval (CI) 1.2-6.7], knowledge of potential interactions between medications and warfarin (OR 3.9, 95% CI 1.9-8.1), and a willingness to check international normalized ratio values more frequently if recommended (OR 2.4, 95% CI 1.2-4.6). Patients who received family help with medications appeared less interested in HAT (OR 0.29, 95% CI 0.12-0.68). CONCLUSIONS: A slight majority of surveyed rural patients conveyed interest in HAT. Working patients and those assuming more responsibility for international normalized ratio control may be more interested in HAT. A possible association between anticoagulation knowledge and increased HAT interest was seen and should be further studied.

Aged↗

PubMed2002

Interplay between ascorbic acid and lipophilic antioxidant defences in chloroplasts of water-stressed Arabidopsis plants.

The effects of low ascorbic acid (Asc) on lipophilic antioxidant defences and lipid peroxidation in chloroplasts were evaluated in the vtc-1 mutant of Arabidopsis thaliana, which had an Asc deficiency in chloroplasts of ca. 60%. Although low Asc did not cause oxidative stress in optimal growth conditions, it increased malondialdehyde levels in chloroplasts by ca. 60%, and reduced alpha-tocopherol and beta-carotene by ca. 85% and 40%, respectively, in water-stressed (WS) mutants. These results are indicative of the interplay between Asc and lipophilic antioxidants in chloroplasts of WS plants in vivo, and show that Asc contributes to the protection of thylakoid membrane lipids from oxidation in stressed plants.

Antioxidants↗

PubMed1998

Carrier mediated uptake of dehydroascorbate into higher plant plasma membrane vesicles shows trans-stimulation.

The activity of the ascorbate (Asc) carrier of purified Phaseolus plasma membranes is demonstrated to be highly stimulated when membrane vesicles are preloaded with Asc. Asc transport is inhibited by DTT but is not affected by glutathione or ferricyanide, indicating that dehydroascorbate (DHA) is the preferred species for uptake. Asc transport in the loaded vesicles showed saturable kinetics with an apparent affinity constant of 24 microM and maximal uptake rate of 94 pmol/mg/min. Addition of DHA stimulated the efflux of Asc molecules from the loaded vesicles. Together these results suggest the presence of an Asc/DHA exchange mechanism in higher plant plasma membranes.

Biological Transport↗

PubMed1994

High-performance liquid chromatography-electrochemical detection of antioxidants in vertebrate lens: glutathione, tocopherol, and ascorbate.

The HPLC-EC method has good specificity for the analysis of glutathione, tocopherol, and ascorbate. The same HPLC system can be used for all three analysis with changes of mobile phase and the electrode cell to match the procedure required. The same C18 reversed-phase column has been used with a refillable guard column for 3 years with no noticeable loss of resolving power. The main advantage of the glutathione procedure was the ability to monitor both GSH and GSSG, which allowed us to confirm that loss of GSH in the diabetic rat lens does not result in the appearance of GSSG. The main benefit of the tocopherol procedure was the ability to measure the tocopherol content of a single rat lens. Our previous experience with UV or fluorescence detection showed those methods to be not sensitive enough for a single lens determination. The mammalian lens has the lowest tocopherol content of the tissues of the eye, 10 to 40 times less than most body tissues as measured by gas chromatography-mass spectrometry (GC-MS). The better sensitivity of electrochemical detection has allowed for a single lens determination, keeping the number of experimental animals to a minimum. An advantage of the ASC analysis procedure was the extra specificity imparted by both the chromatography and the detector as well as the ability to estimate the total ascorbate (ASC plus DHAA) and DHAA content. Other reducing agents such as GSH and uric acid can interfere in colorimetric methods that rely on the reducing action of ASC. The very high GSH content of the mammalian lens was a concern when choosing a procedure. GSH levels exceeding 10 times the level of lens samples were found to yield no response using the HPLC-EC procedure for ASC. The only disadvantage with electrochemical detection was that the electrode response could drift with time, requiring more frequent calibration with standards. We continue to utilize these methods to examine the prevacuole loss of ASC and GSH in the diabetic rat lens model of cataract.

Animals↗

PubMed2002

Mucosal and systemic isotype-specific antibody responses and protection in conventional pigs exposed to virulent or attenuated porcine epidemic diarrhoea virus.

Eleven-day-old conventionally reared piglets were inoculated orally with two different doses of the cell-culture adapted strain CV-777 of the porcine epidemic diarrhoea virus (PEDV) or the virulent isolate of the same strain and challenged with the same virulent PEDV 3 weeks later. Pigs inoculated with the two doses of the attenuated virus did not show any typical sign of the disease, and virus shedding was not frequent. In contrast, 31% of pigs exposed to the virulent PEDV developed diarrhoea and virus shedding was demonstrated in 100%. At different postinoculation day (PID) and postchallenge day (PCD) virus-specific antibody-secreting cells (ASC) in gut associated lymphoid tissues (duodenum and ileum lamina propria and mesenteric lymph nodes) and systemic locations (blood and spleen) were assessed by enzyme-linked immunospot (ELISPOT). Only a small response was detected in the groups inoculated with attenuated PEDV, whereas in the group previously exposed to the virulent virus on PID 21 a large number of IgG and IgA ASC was detected. Isotype-specific antibody responses in serum were investigated by ELISA. IgG responses were detected in all groups, although the highest response corresponded to the group inoculated with virulent virus and only this group showed an IgA response. The pigs exposed to virulent PEDV were completely protected against the challenge with a higher dose of the same virulent virus on PID 21 and none of them shed the virus. The pigs inoculated with the attenuated strain were partially protected against the challenge, and 25% of the low dose- and 50% of the high dose-exposed pigs did not shed virus after challenge. All the pigs from a control group, not previously exposed to the virus, excreted the virus in faeces. A strong positive correlation was established between protection and the ASC responses detected in gut associated lymphoid tissues and blood at the challenge day and also between protection and serum isotype-specific antibody titers on that day. In addition, the IgA and IgG ASC responses detected in the blood on PID 21 also correlated with the responses found in the gut associated lymphoid tissues. The ASC and serum antibody responses after the challenge corresponded to a secondary immune response in the groups inoculated with attenuated virus, whereas a primary response was evident in the control group. No increase was seen in any of the parameters studied in the pigs inoculated with virulent PEDV.

Animals↗

PubMed1996

Restricted B-cell responses to microbial challenge of the respiratory tract.

The local B-cell response in the respiratory tract to infectious challenge has been analyzed in pigs and calves using two techniques: flow cytometry and antibody secreting cell (ASC) probes. Pneumonia in pigs caused by experimental infection with Mycoplasma hyopneumoniae resulted in a 25-fold increase in the B-cell population in BAL and lung parenchyma 28 days post infection. ASC probes revealed that the B-cell response of immune pigs to a large challenge infection was localized to lung parenchyma and tracheobronchal lymph nodes. Naive calves infected with Pasteurella multocida had a 5-fold increase in the B-cell blast population in lung parenchyma and BAL, and a greater than 60-fold increase in the draining lymph node at 9 days post infection. The ASC probes prepared post challenge from immune calves showed the response to be localized to the draining lymph nodes, with little response in lung parenchyma. A major finding was that ASC probes prepared from lung parenchyma and from pulmonary lymph nodes of both calves and pigs recognized a restricted range of bacterial antigens, particularly compared to the range of antigens recognized by concurrently circulating sera. The use of ASC probes demonstrates that there is a restricted B-cell repertoire in the respiratory tract.

Animals↗

PubMedDate not supplied

Glutamine transport in C6 glioma cells.

Glutamine transport across the cell membranes of a variety of mammalian tissues is mediated by at least four transport systems: a sodium-independent system L, and sodium-dependent systems A, ASC and N, the latter occurring in different tissue-specific variants. In this study we assessed the contribution of these systems to the uptake of [(3)H]glutamine in C6 rat glioma cells. The sodium-dependent uptake, which accounted for more than 80% of the total uptake, was not inhibited by 2-methylaminoisobutyric acid (MeAIB), indicating that system A was inactive, possibly being depressed by glutamine present in the culture medium. About 80% of the sodium-dependent uptake was mediated by system ASC, which differed from system ASC common to other CNS- and non-CNS tissues by its pH-dependence and partial lithium tolerance. The residual 20% of sodium-dependent uptake appeared to be mediated by system N, which was identified as a component resistant to inhibition by MeAIB+threonine. The system N in C6 cells appeared to be neither fully compatible with the neuronal system Nb, nor with the N system described in astrocytes: it differed from the former in being strongly inhibited by histidine and showing fair tolerance for lithium, and from the latter in its pH-insensitivity and strong inhibition by glutamate. The sodium-independent glutamine uptake differed from the astrocytic or neuronal uptake in its relatively weak inhibition by system L substrates and a strong inhibition by system ASC substrates, indicating a possible contribution of a variant of the ASC system.

Animals↗