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Biomedical subjects

A Moran

Publications and source records attributed to A Moran.

At least 109 records · Page 6Linked to original sources
PubMed1991

Effects of IGF-I and glucose on protein and proteoglycan synthesis by human fetal mesangial cells in culture.

Abnormalities in proteoglycan metabolism have been implicated in the pathogenesis of diabetic nephropathy. Whether hyperglycemia plays a direct role in these events is unknown. To evaluate the effects of high glucose concentrations and insulinlike growth factor I (IGF-I) on kidney proteoglycan and protein metabolism, we incubated quiescent, subconfluent human fetal mesangial cells for 24 h in serum-free media containing either physiological (5.6-mM) or elevated (25-mM) glucose concentrations with or without 1.3 x 10(-9) M IGF-I. In the presence of physiological glucose concentrations, IGF-I stimulated incorporation of [3H]leucine into protein and [35S]sulfate or [3H]glucosamine into proteoglycans. High glucose concentrations significantly amplified IGF-I-mediated stimulation of protein synthesis but totally abolished IGF-I-induced proteoglycan synthesis. The hydrodynamic size and proportions of heparan-35SO4 and chondroitin/dermatan-35SO4 proteoglycans in all experimental media were the same. However, high glucose concentrations decreased the iduronic acid content of dermatan-35SO4. In separate experiments, quiescent cells were cultured for 7 days in media supplemented with 2% fetal calf serum. IGF-I had no effect on mesangial cell proliferation, but as cells reached confluence, high glucose concentrations significantly inhibited cell proliferation. This inhibition was not mimicked by isosmolar concentrations of mannitol. After 7 days, uptake of radioactive precursors into proteoglycans and proteins over 24 h was similar under all culture conditions. However, IGF-I decreased the ratio of [35S]sulfate to [3H]glucosamine in proteoglycans and their glycosaminoglycan side chains. This difference persisted in disaccharides derived by chondroitin ABC lyase digestion of dermatan-35SO4.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Division↗
PubMed1990

Glucagon, catecholamine and pancreatic polypeptide secretion in type I diabetic recipients of pancreas allografts.

Successful pancreas transplantation in type I diabetic patients restores normal fasting glucose levels and biphasic insulin responses to glucose. However, virtually no data from pancreas recipients are available relative to other islet hormonal responses or hormonal counterregulation of hypoglycemia. Consequently, glucose, glucagon, catecholamine, and pancreatic polypeptide responses to insulin-induced hypoglycemia and to stimulation with arginine and secretin were examined in 38 diabetic pancreas recipients, 54 type I diabetic nonrecipients, and 26 nondiabetic normal control subjects. Glucose recovery after insulin-induced hypoglycemia in pancreas recipients was significantly improved. Basal glucagon levels were significantly higher in recipients compared with nonrecipients and normal subjects. Glucagon responses to insulin-induced hypoglycemia were significantly greater in the pancreas recipients compared with nonrecipients and similar to that observed in control subjects. Glucagon responses to intravenous arginine were significantly greater in pancreas recipients than that observed in both the nonrecipients and normal subjects. No differences were observed in epinephrine responses during insulin-induced hypoglycemia. No differences in pancreatic polypeptide responses to hypoglycemia were observed when comparing the recipient and nonrecipient groups, both of which were less than that observed in the control subjects. Our data demonstrate significant improvement in glucose recovery after hypoglycemia which was associated with improved glucagon secretion in type I diabetic recipients of pancreas transplantation.

Arginine↗
PubMed1990

Hexose uptake and transport in polymorphonuclear leukocytes from patients with glycogen storage disease Ib.

Neutrophil functions and glucose metabolism are known to be impaired in glycogen storage disease (GSD) Ib patients. The uptake of nonmetabolizing glucose analogues into polymorphonuclear leukocytes (PMN) of GSD Ib patients was studied. 2-Deoxyglucose (2-DOG) and 3-O-methylglucose are transported across the cell membrane by facilitated diffusion mediated by the glucose transporter. Because 2-DOG is phosphorylated within the cell, its uptake rate reflects hexose transport as long as phosphorylation is not rate-limiting. These conditions prevail only at low 2-DOG concentrations. Transport of 5 microM DOG into GSD Ib patient PMN was found to be similar to controls (4.3 +/- 0.5 and 4.65 +/- 1.77 pmol/min X 10(6), respectively). In contrast, 2-DOG uptake at high concentrations (2 mM) decreased by 70% in patient PMN compared with control cells (0.17 +/- 0.06 and 0.51 +/- 0.11 nmol/min X 10(6), for patients and controls, respectively). Transport of 3-O-methylglucose (a glucose analogue that does not undergo intracellular phosphorylation) was not different in patient PMN compared with controls (1.86 +/- 0.53 and 2.19 +/- 0.30 nmol/min X 10(6), respectively). Hexose monophosphate shunt activity in PMN of GSD Ib patients at a glucose concentration of 2 mM was 43% of control values, whereas at 10 microM it was similar to controls. Taken together, these results suggest that the defect in glucose uptake and metabolism found in GSD Ib patient PMN is due to an impairment in hexose phosphorylation rather than in a reduction in the transmembrane glucose transport activity.

3-O-Methylglucose↗
PubMed1990

Salvage therapy with methyl-gag, high-dose Ara-C, M-Amsa, and ifosfamide (MAMI) for recurrent or refractory lymphoma.

Thirty adult patients with relapsed or refractory malignant lymphoma underwent a Phase I-II trial of salvage chemotherapy combining methyl-gag, high-dose Ara-C, M-Amsa, and ifosfamide (MAMI protocol). All patients had been extensively pretreated. At the time of salvage therapy, 21 patients had visceral involvement and 23 patients were refractory. The overall response rate was 50% (11 patients in complete remission and 3 patients in partial remission). The main toxicity was myelosuppression; 4 treatment-related deaths occurred and 17 patients died of tumor progression with a median of 5 months. The MAMI protocol showed similar antitumoral efficacy to that of other salvage chemotherapy regimens used for poor prognosis malignant lymphoma but was more toxic. However, a response rate of 45% in refractory patients should be taken into account and this drug association deserves further investigation with regard to the selection of patients for bone marrow transplants.

Adolescent↗
PubMed1989

Sodium-hydrogen exchange system in brush border membranes from cortical and medullary regions of the proximal tubule.

The Na+/H+ exchange system was studied in brush border membrane vesicles isolated from cortical and medullary regions of the proximal tubule of rabbit kidney. The activity of the exchanger was assessed by measuring hydrogen influx (monitored by acridine orange fluorescence), 22 Na influx and the sensitivity of these fluxes to amiloride and its analogue ethylisopropyl amiloride. In contrast to previously published data (indicating the absence of pH-gradient driven and amiloride sensitive 22Na-influx in medullary site vesicles (13, 15], Na+/H+ exchange activity could be detected in both membrane preparations by sodium tracer and fluorescence detection of hydrogen influx. Amiloride inhibition of 22Na influx was more effectively protected by increasing sodium concentration in cortical than in medullary vesicles, suggesting differences in the action of amiloride in these preparations.

Amiloride↗
PubMed1989

Kinetic properties of derepressible acid phosphatase from the yeast from of Yarrowia lipolytica.

(1) An acid phosphatase from depressed cells of the yeast form of Yarrowia lipolytica has been characterized kinetically by studies on specificity, inhibition, rate equation forms and modelling of the enzyme mechanisms. (2) The study on specificity revealed that the acid phosphatase is a rather unspecific phosphohydrolase that has similar activity on several different phosphate esters. A very weak transphosphorylating activity was also detected. (3) Among the reversible inhibitors, phosphate and vanadate were outstanding, whereas EDTA behaved as an activator. (4) v vs. [S] studies with o-carboxyphenyl phosphate as substrate show that the acid phosphatase of Y. lipolytica exhibits non-Michaelian behaviour, a minimum degree of 2:2 being detected for the rate equation in [S]. (5) The inhibition by phosphate and vanadate seems to have the same pattern of partial inhibition with a certain non-competitive nature, 1:1 being the minimum degree of the rate equation detected in (I).

Acid Phosphatase↗
PubMed1989

Involvement of intracellular pH elevation in the effect of 1,25-dihydroxyvitamin D3 on HL-60 cells.

Besides its effect in inhibiting proliferation and inducing differentiation of HL-60 to monocyte-like cells, 1,25-dihydroxyvitamin D3 also causes a rise in intracellular pH (pHi) from 7.17 +/- 0.02 to 7.3 +/- 0.05, as measured by the fluorescence of 2',7'-bis(carboxyethyl)-5-(6)-carboxy-fluorescein. The effect of 1,25-dihydroxyvitamin D3 on pHi is dose dependent in a parallel manner to its effect on the proliferation and differentiation processes. The elevation of pHi by 1,25-dihydroxyvitamin D3 is gradual but precedes the differentiation process. A significant increase in pHi was obtained after 16 h of incubation with the hormone and reached its maximum level after 48 h. pHi then dropped back to its initial level, which is also similar to that of peripheral normal blood monocytes. A rise in pHi was not observed during incubation of HL-60 cells with 24,25-dihydroxyvitamin D3, a metabolite which does not promote their differentiation. In contrast, other agents such as phorbol 12-myristate 13-acetate known to induce differentiation in this cell line do cause an increase in pHi. Moreover, alkalinization of HL-60 cells by NH4Cl causes induction of differentiation to monocytes. The results suggest that a rise in pHi plays a role in regulating the molecular mechanism of the inhibition of proliferation and the induction of differentiation in HL-60 cells.

Ammonium Chloride↗
PubMed1989

Very late recurrence of childhood acute lymphoblastic leukemia treated with chemoimmunotherapy: a report of three cases occurring 19, 11, and 9 years after discontinuation of chemotherapy.

Current therapeutic modalities for childhood acute lymphoblastic leukemia (ALL) are associated with a high cure rate, and recurrences more than 4 years after therapy cessation are very unusual. We report three cases of exceptionally late recurrences of childhood ALL after cessation of chemotherapy (CT) given for respective periods of 8, 7, and 24 months. CT was followed by maintenance immunotherapy (IMT) with Bacillus Calmette-Guérin (BCG) and allogeneic leukemic lymphoblasts pretreated with formaldehyde or irradiated in vitro. Leukemic recurrences were observed 19, 11, and 9 years after cessation of CT and appeared morphologically similar to the original blasts. A second complete remission was easily achieved in all three patients, but two went on to repeated relapse (one has died following the fourth recurrence). We speculate that some residual leukemic cells, remaining after the inadequate, short-term CT, were responsible for these unusual evolutions, and we question a possible delaying role of IMT in prolonging remission. Other possible etiologies are discussed.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1989

Chondroitin sulfate proteoglycan synthesis and reutilization of beta-D-xyloside-initiated chondroitin/dermatan sulfate glycosaminoglycans in fetal kidney branching morphogenesis.

Branching morphogenesis and chondroitin sulfate proteoglycan synthesis by explanted fetal mouse kidneys were previously shown to be inhibited by p-nitrophenyl beta-D-xylopyranoside (beta-D-xyloside) while glomerular development and heparan sulfate proteoglycan synthesis were unaffected. The metabolic fate of fetal kidney explant proteoglycans was investigated to determine whether or not recovery of proteoglycan synthesis and morphogenesis occur after exposure to beta-D-xyloside. Chondroitin sulfate proteoglycan synthesis resumed within 4 hr of removal of beta-D-xyloside and was enhanced once beta-D-xyloside-initiated chondroitin/dermatan-35SO4 glycosaminoglycans (GAGs) were released from the tissue. Radioactivity incorporated into beta-D-xyloside-initiated chondroitin/dermatan-35SO4 GAGs during labeling in the presence of beta-D-xyloside was reutilized in the synthesis of chondroitin-35SO4 proteoglycan during a 24-hr chase in nonradioactive medium without beta-D-xyloside. Further, highly purified beta-D-xyloside-initiated chondroitin/dermatan-35SO4 GAGs were taken up by kidneys more avidly than was free [35S]sulfate. These 35S-GAGs were degraded and reutilized in the synthesis of chondroitin-35SO4 proteoglycan. Ureteric bud branching resumed 48 hr after beta-D-xyloside was removed from the incubation medium. These findings support the idea that both chondroitin sulfate proteoglycan synthesis and proteoglycan processing may be involved in branching morphogenesis.

Animals↗
PubMed1988

The role of HCO3- and Na+/H+ exchange in the response of rat parotid acinar cells to muscarinic stimulation.

The intracellular pH (pHi) of a rat parotid acinar preparation was monitored using the pH-sensitive fluorescent dye, 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Under resting (unstimulated) conditions both Na+/H+ exchange and CO2/HCO3- buffering contribute to the regulation of pHi. Muscarinic stimulation (carbachol) of the acini produced a gradual rise in pHi (approximately 0.1 unit by 10 min) possibly due to activation of the Na+/H+ exchanger. When the exchanger was blocked by amiloride or sodium removal, carbachol induced a dramatic (atropine inhibitable) decrease in pHi (approximately 0.4 pH unit with t1/2 approximately 0.5 min at 1 mM carbachol). The rate of this acidification was reduced by removal of exogenous HCO3- and by the carbonic anhydrase inhibitor methazolamide. Also, acini stimulated with carbachol in Cl- -free solutions showed a more pronounced acidification than in the corresponding Cl- -replete media. Taken together, these data indicate that the carbachol-induced acidification of rat parotid acinar cells unmasked by inhibition of the Na+/H+ exchanger is due to a rapid loss of intracellular HCO3-. Carbachol induced acidification was inhibited by the Cl- channel blocker diphenylamine 2-carboxylate but not by 4-acetomido-4'-isothiocyanostilbene-2,2'-disulfonic acid, an inhibitor of Cl-/HCO3- exchange. In addition, this acidification could not be sustained in Ca2+-free media and was totally blocked by chelation of intracellular Ca2+. Interpreted in terms of HCO3- loss, these results closely parallel the pattern of carbachol-induced Cl- release from this same preparation and indicate that HCO3- is secreted in response to muscarinic stimulation via the same or a very similar exit pathway, presumably an apical anion channel. Under normal physiological conditions the intracellular acidification resulting from HCO3- secretion is buffered by the Na+/H+ exchanger.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1988

Conductive sodium pathway with low affinity to amiloride in LLC-PK1 cells and other epithelia.

Electrical potential driven 22Na+ fluxes were measured in membrane vesicles prepared from a number of cultured and naturally occurring epithelia. In all preparations a rheogenic pathway blocked by 200 microM (but not by 1.5 microM) amiloride was noted. This transporter was characterized in membranes prepared from cultured LLC-PK1 cells. In this preparation more than 50% of the rheogenic 22Na+ uptake was blocked by amiloride (IC50 approximately 30 microM), phenamil (IC50 approximately 66 microM), or ethylisopropylamiloride (IC50 approximately 5 microM). This amiloride-sensitive flux was not seen if the vesicles were partially depolarized by external Na+ or K+. It could not be driven by a pH gradient, did not require the presence of Ca2+, sugars, or amino acids, and showed little dependence on temperature (25 versus 0 degrees C). The data suggest the existence of an epithelial amiloride-blockable Na+ transporter different from the previously characterized Na+ channel, Na+/H+ and Na+/Ca2+ exchangers, and the Na+-hexose co-transporter. In rat kidney cortex membranes prepared by Mn2+ precipitation, this transporter is primarily located in the brush-border fraction.

Amiloride↗
PubMed1988

Salvage chemotherapy in refractory germ cell tumors with etoposide (VP-16) plus ifosfamide plus high-dose cisplatin. A VIhP regimen.

Twenty-one patients with refractory germ cell tumors were treated with a chemotherapy regimen containing etoposide (VP-16) (V) 75 mg/m2/day (days 1 to 5), ifosfamide (I) 3 g/m2/day (days 1 and 2) with a 3.6 g/m2 continuous infusion of mesna (days 1 and 2), and high-dose cisplatin (hP) 40 mg/m2/day (days 1 to 5). The regimen is referred to as VIhP. Nineteen patients were evaluable for response. Five patients (26%) achieved a complete remission (CR) with chemotherapy alone, and three patients (16%) were in CR after resection of a residual nonactive tumoral mass (e.g., necrosis and/or fibrosis and/or mature teratoma). Thus, a CR rate of 42% was achieved with the entire treatment. One additional patient achieved a CR after resection of active, bulky disease. Among the responders, five patients (26%) are still alive and disease-free at 6, 7, 9, 10, and 18 months after the initiation of the chemotherapy. However, toxicity was heavy in this protocol. Severe myelosuppression was observed with 10 patients developing aplasia and six patients documented sepsis. Reversible Grade 1-2 renal toxicity occurred in 14 patients, and Grade 2-3 peripheral neurotoxicity occurred in six patients. No hemorrhagic cystitis was encountered. We conclude that a VIhP regimen seems to play an active role in refractory germ cell tumors although the presence of high-dose cisplatin in this regimen does not appear to improve the response rate compared to that of a conventional dose. Toxicity, which seems to be enhanced, is currently under detailed study. However, the contribution of VIhP as a first-line treatment in poor prognosis, advanced germ cell tumors warrants further study.

Adolescent↗