Biomedical subjects

M Wasa

Publications and source records attributed to M Wasa.

At least 37 records · Page 2Linked to original sources

PubMed1997

Regulation of glutamine synthetase in human breast carcinoma cells and experimental tumors.

BACKGROUND: Acute deprivation of extracellular glutamine causes up-regulation of glutamine synthetase (GS) expression by a mechanism involving an increase in GS protein stability. This study examines GS expression in a highly glutamine-dependent and tumorigenic human breast cancer cell line, TSE cells, in response to acute and chronic glutamine deprivation in culture and during tumor formation. METHODS: TSE cells were subjected to acute glutamine deprivation, adapted to growth in low glutamine concentrations, and subcutaneously injected into nude mice. GS protein and mRNA levels were assayed by Western and Northern blotting, and intracellular glutamine levels were evaluated by using a colorimetric assay. RESULTS: GS protein levels increased, but GS mRNA levels were unchanged in response to acute glutamine deprivation. Chronic glutamine deprivation in vitro and tumor growth in vivo caused an increase in both GS protein and mRNA levels. Large tumors exhibited lower intracellular glutamine, higher GS protein, and relatively unchanged GS mRNA levels relative to small tumors. CONCLUSIONS: TSE tumors exhibit up-regulation of GS protein and mRNA levels and declines in intracellular glutamine content, suggesting that growth in vivo causes a chronic and progressive glutamine deprivation. Up-regulation of GS expression may contribute to adaptation to a nutrient-poor intratumor environment.

Animals↗

PubMed1997

Beneficial effects of growth hormone combined with parenteral nutrition in the management of inflammatory bowel disease: an experimental study.

BACKGROUND: Growth hormone (GH) improves net protein anabolism and stimulates wound healing. Although GH is also known to exert the trophic effect on the intestinal tract, its role in the healing of intestinal ulceration is not known. The aim of this study was to evaluate the effects of exogenous GH coinfused with parenteral nutrition (PN) in an experimental model of inflammatory bowel disease in rats. METHODS: All rats underwent central venous cannulation and were randomized to two groups after induction of small intestinal ulceration with indomethacin. Both groups received the same PN formula. In addition, the GH group (n = 10) received subcutaneous injections of human GH at a dose of 1.0 IU/kg daily for 4 days, whereas the control group (n = 10) received injections of normal saline solution. Nitrogen balance, macroscopic inflammation score, intestinal myeloperoxidase activity, DNA content, and mucosal permeability were determined for each rat. Insulin-like growth factor-I (IGF-I) mRNA was detected by reverse transcription and polymerase chain reaction. RESULTS: Administration of GH significantly improved the cumulative nitrogen balance, ameliorated the gross inflammation score, and decreased intestinal myeloperoxidase activity. Similarly, intestinal permeability was significantly decreased in the GH group as compared with the control group. GH treatment resulted in increased plasma concentration of IGF-I and IGF-I mRNA expressions in both the liver and the small intestine compared with those in the control group. CONCLUSIONS: Exogenous GH plays an important role in accelerating intestinal healing in an experimental model of small bowel ulceration in rats. The mechanisms may include the stimulated IGF-I production, which thereafter augments intestinal epithelial cell growth.

Animals↗

PubMed1997

Induction of nitric oxide synthase in rat intestine by interleukin-1alpha may explain diarrhea associated with zinc deficiency.

Synthesis of inducible nitric oxide synthase (iNOS) in the intestine may result in local tissue damage. We investigated whether a challenge with interleukin-1alpha could give rise to intestinal iNOS expression and diarrhea in rats of differing zinc status. Weaning male rats were fed a zinc-deficient (ZD) diet (2 mg zinc/kg) for 4 wk to induce zinc deficiency or a zinc-supplemented diet [50.8 mg zinc/kg; controls, including pair-fed (PF ) and ad libitum (AL) consumption groups], and then subcutaneously injected with interleukin-1alpha (2 x 10(7) units/kg body wt). Without the interleukin-1alpha challenge, ZD rats had significantly lower plasma zinc concentration than the other groups. Intestinal metallothionein-1 mRNA abundance was lower in ZD rats than in AL rats. iNOS was expressed in the intestine of ZD rats but not in the others. None of the rats experienced diarrhea during the feeding period. Interleukin-1alpha led to a reduction in plasma zinc concentration, enhancement in intestinal metallothionein-1 mRNA levels, and expression of the intestinal iNOS gene in all groups. However, the abundance of iNOS mRNA was significantly higher in ZD rats than in the other groups. The presence of iNOS protein was demonstrated by immunohistochemical staining in the intestine of ZD rats that had been treated with interleukin-1alpha 12 h earlier. In addition, diarrhea occurred in most of the ZD rats and some of the PF rats but not in AL rats after interleukin-1alpha treatment. We conclude that ZD rats respond to interleukin-1alpha challenge more severely than controls, reflected by a more marked and prolonged iNOS expression and a greater incidence of diarrhea.

Animals↗

PubMed1997

[Home parenteral nutrition in the elderly].

The number of elderly patients receiving home parenteral nutrition (HPN) has been increasing. This could result from several factors such as advances in HPN therapy and the natural aging of long-term older patients on HPN. Our experience shows that elderly patients receiving HPN are likely to be highly dependent on family members to supervise their HPN therapy. Therefore, indepth education of family members is essential before HPN is initiated. The important points to manage the elderly HPN patients are as follows: 1) It takes a long time for the elderly to learn the technique. 2) They often make technical mistakes. 3) In many cases, patients are not living with their children. Therefore, it is often difficult for them to support the patient's HPN therapy. 4) Nurses play an important role in giving instructions on catheter care and HPN techniques to the patient or family members.

Aged↗

PubMed1996

Adaptive regulation of amino acid transport in nutrient-deprived human hepatomas.

BACKGROUND: Malignant cells require increased amounts of amino acids, in particular glutamine and leucine, to support DNA and protein biosynthesis. Although plasma concentrations in the center of solid tumors can be much lower than normal circulating levels, it is still unknown how tumor cells can survive despite low amino acid levels. We examined the effects of glutamine or leucine deprivation on cell growth and amino acid transport activity in two human hepatoma cell lines, SK-Hep and HepG2. METHODS: We studied the transport of glutamine, leucine, alanine, and arginine. The carrier-mediated uptake of 3H-amino acids was determined in cells cultured in normal and amino acid-deprived media. RESULTS: The growth of both cell lines was dependent on the concentration of glutamine and leucine. In SK-Hep, there was a significant increase in initial rate glutamine transport activity in the glutamine-deprived group, attributable to an increase in transporter affinity (Km; 0.6 mmol/L [control], 385 +/- 43 mumol/L; 0.1 mmol/L, 221 +/- 11 mumol/L; P < 0.01). At low glutamine concentration, the saturable Na(+)-independent uptake of leucine and arginine as well as the Na(+)-dependent uptake of alanine increased significantly in both SK-Hep and HepG2. Similarly, in leucine-deprived SK-Hep cells, leucine uptake increased twofold, but the change was attributable to an enhanced transporter capacity (Vmax; 0.2 mmol/L [control], 38,900 +/- 700; 0.0 mmol/L, 75,900 +/- 4,900 pmol/mg protein per minute; P < 0.001). CONCLUSIONS: Adaptive increases in initial rate amino acid transport activities were elicited by glutamine and leucine deprivation in these two human hepatoma cell lines. Decreased extracellular amino acid levels encountered by tumors in vivo may elicit similar adaptive responses that contribute to the maintenance of cytoplasmic levels of amino acids essential for growth.

Adaptation, Physiological↗

PubMed1996

Glutamine as a regulator of DNA and protein biosynthesis in human solid tumor cell lines.

OBJECTIVE: The transport of glutamine by six different human solid tumor-derived cell lines (e.g., breast, colon, liver) was characterized and the impact of glutamine deprivation on rates of tumor cell proliferation and DNA and protein synthesis was assayed. SUMMARY BACKGROUND DATA: Glutamine is added routinely to cell culture media and its importance for cellular growth has been established. However, carrier-mediated glutamine transport by solid tumors has not been studied extensively, and the mechanisms by which glutamine contributes to cell growth regulation require further investigation. METHODS: In a panel of different human solid tumor-derived cells, sodium-dependent glutamine transport was characterized in vitro and rates of cell proliferation, protein and DNA synthesis, as well as thymidine transport, were correlated with glutamine concentrations in the culture media. RESULTS: In all cells, regardless of tissue origin, sodium-dependent glutamine transport was mediated almost exclusively by a single carrier. There was a range of Michaelis constants (Km) and maximal transport velocities (Vmax) for the glutamine transporter in each cell type, but the amino acid inhibition profiles were nearly identical, consistent with uptake by the System ASC family of transporters. Rates of cell growth, DNA and protein synthesis, and thymidine transport correlated with the glutamine concentration in the culture media, indicating the central role of this amino acid in regulating cellular proliferation. CONCLUSIONS: These data indicate that glutamine transport by all solid tumors is mediated by the System ASC family of transporters. The variation in Km values suggests that some cancers may be better suited to survive in a low glutamine environment than others. The mechanism by which glutamine supports cell proliferation and regulates cell cycle kinetics involves its modulation of DNA and protein biosynthetic rates.

Cell Division↗

PubMed1995

Protein kinase C activation inhibits glutamate transport by endothelial cells.

The role of protein kinase C (PKC) in regulating endothelial cell glutamate transport was investigated. Glutamate transport studies were performed in confluent human umbilical vein endothelial cells which were treated with the phorbol ester 12-myristate 13-acetate (TPA, 0-1000 nM), a compound which directly activates PKC. TPA inhibited Na(+)-independent System xAG- glutamate transport by 70% but only slightly reduced Na(+)-dependent activity. The TPA-mediated reduction in transport activity was dose-dependent, beginning at 5 min and lasting for at least 24 hr. TPA inhibition of glutamate transport had two distinctive phases: an acute phase (< 1 hr, not affected by either cycloheximide or actinomycin D) in which TPA decreased System xAG- glutamate transporter affinity (TPA Km = 522 +/- 25 microM vs control Km = 329 +/- 85 microM, P < 0.01) but did not alter transporter capacity (TPA Vmax = 4426 +/- 230 pmole/mg/min vs control Vmax = 4535 +/- 750 pmole/mg/min, P = NS) and a chronic phase (4-24 hr) in which TPA inhibition of glutamate transport was due to a reduced transporter capacity (Vmax = 2895 +/- 570 pmole/mg/min) without altering transporter affinity (Km = 370 +/- 60 microM glutamate) and was abrogated by cycloheximide or actinomycin D. The protein kinase C inhibitor chelerythrine chloride abrogated TPA's inhibition effect in both the acute and chronic phases. These data indicate that protein kinase C activation decreases glutamate transport in human umbilical vein endothelial cells via protein synthesis dependent and independent mechanisms.

Biological Transport↗

PubMed1995

Tumor necrosis factor stimulates system XAG- transport activity in human endothelium.

System xAG- is responsible for the carrier-mediated Na(+)-independent transport of anionic amino acids such as glutamate and aspartate across the plasma membrane of cells. In order to examine a possible role for cytokines in regulating System xAG- activity, the effect of TNF on [3H]glutamate transport in cultured human umbilical vein endothelial cells (HUVECs) was studied. Carrier-mediated glutamate uptake was accomplished by two high-affinity carriers, predominantly by a Na(+)-independent carrier (System xAG-, 75% of total glutamate uptake) and, to a lesser extent by a Na(+)-dependent carrier (System XAG-, 24% of total uptake). TNF treatment (10 ng/ml for 10 hr) resulted in an 80% increase in Na(+)-independent glutamate transport activity with no change in System XAG- activity. The TNF stimulatory effect was blocked by actinomycin D and cycloheximide. TNF treatment increased System xAG- glutamate transporter Vmax by 51% (control Vmax = 2359 +/- 345 pmole/mg protein/min vs TNF Vmax = 3569 +/- 436 pmole/mg protein/min, P < 0.01) without altering transporter affinity (control Km, 229 +/- 40 microM glutamate vs TNF Km = 224 +/- 60 microM glutamate, P = NS). The protein kinase C (PKC) inhibitor chelerythrine chloride had no effect on the TNF-stimulated glutamate transport, indicating that the augmented glutamate transport was not mediated by PKC activation. These data indicate that the TNF-stimulated glutamate transport in HUVECs requires do novo protein synthesis, possibly of the System xAG- transporter protein itself. Accelerated glutamate transport provides a precursor for the biosynthesis of macromolecules and glutamine.

Biological Transport↗

PubMed1995

Bronchial reconstruction for bronchopulmonary foregut malformation: a case report.

In this case of bronchopulmonary foregut malformation (BPFM), the bronchus of the anomalous pulmonary tissue was reconstructed and tracheoplasty for associated congenital tracheal stenosis was performed at 5 days of age. After reconstruction the right lung was ventilated, which was followed by improved blood gas data. However, the persistent fatal circulation developed, and the patient died of respiratory insufficiency on postoperative day 5. The autopsy showed that both lungs were hypoplastic. This is the first case of bronchial reconstruction of BPFM.

Bronchi↗

PubMed1995

TNF-stimulated arginine transport by human vascular endothelium requires activation of protein kinase C.

OBJECTIVE: The authors determined the endothelial arginine transport mechanism and the potential role of a tumor necrosis factor (TNF)-alpha-mediated signal transduction pathway involving protein kinase C (PKC) in regulating this transport in cultured endothelial cells. SUMMARY BACKGROUND DATA: The vascular endothelium metabolizes arginine to generate nitric oxide (NO), and an increase in NO production can be stimulated by several cytokines. The mechanism(s) responsible for the accelerated arginine transport are poorly understood. METHODS: Arginine transport was assayed in confluent human umbilical vein endothelial cells in the presence of TNF +/- the PKC inhibitor chelerythrine chloride. RESULTS: Carrier-mediated arginine transport was accomplished by two Na(+)-independent transporters, System y+ (80% of total transport) and System b0,+ (20% of transport). Tumor necrosis factor (0.1-2 ng/mL) increased System y(+)-mediated arginine transport in a time- and dose-dependent manner by augmenting System y+ transport maximal capacity (control Vmax = 1325 +/- 60 pmol/mg protein/minute vs. TNF Vmax = 3015 +/- 110 pmol/mg protein/minute, p < 0.01) without affecting transporter affinity (control Km = 30 +/- 1.4 microM vs. 34 +/- 1.3 microM arginine, p = NS). Stimulation was maximal at the 8-hour time point and was inhibited by both actinomycin D and cycloheximide. In addition, inhibition of PKC with chelerythrine abrogated the TNF-augmented arginine transport. Similarly, incubation of cells with the direct PKC activator TPA (phorbol ester 12-myristate 13-acetate) stimulated System y(+)-mediated arginine transport nearly fivefold, secondary to an increase in transporter Vmax (TPA Vmax = 5349 +/- 310 pmol/mg protein/minute, p < 0.001 vs. control), with no change in Km. This TPA-induced stimulation of arginine transport also was blocked by chelerythrine CI, actinomycin D, and cycloheximide. Incubation of TNF-stimulated cells with two NO synthase inhibitors did not reduce transport activity, suggesting that the arginine transporter and the NO synthase enzyme may, in part, be independently regulated.

Alkaloids↗

PubMed1995

Amino acid metabolism and the vascular endothelium: regulation and disease implications.

Amino acid metabolism by the vascular endothelium is a complex process that often begins with the carrier-mediated uptake of circulating amino acids into the endothelial cytoplasm. Amino acids are essential for maintaining intact endothelial functions, which include cell proliferation, regulation of blood flow and vascular tone, coagulation and fibrinolysis, and metabolism of a variety of macromolecules. The disturbances in endothelial amino acid transport and metabolism that occur during infection and inflammation are due, in part, to changes in substrate availability and to the local and/or systemic elaboration of specific mediators. An improved understanding of endothelial amino acid metabolism will not only provide new knowledge regarding disease mechanisms and regulation, but may also lead to new treatment strategies that may include the clinical use of specific nutritional formulas.

Amino Acid Sequence↗

PubMed1991