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E Aranda

Publications and source records attributed to E Aranda.

At least 55 records · Page 3Linked to original sources
PubMed1997

Detection of Clostridium botulinum types A, B, E and F in foods by PCR and DNA probe.

A PCR procedure was developed for the detection of Clostridium botulinum in foods. PCR products were detected in agarose gels and by Southern hybridization. The sensitivity of PCR was tested in broth cultures and in canned asparagus, dry cured ham and honey. The sensitivity of the method in broth was high (2.1-8.1 cfu ml-1) for types A and B, but rather low (10(4) cfu ml-1) for types E and F. However, after enrichment at 37 degrees C for 18 h, it was possible to detect Cl. botulinum types A, B, E and F in food samples at initial levels of about 1 cfu 10 g-1 of food. This PCR detection protocol provides a sensitive and relatively rapid technique for the routine detection of Cl. botulinum in foods.

Animals↗
PubMed1997

Cellular redox status influences both cytotoxic and NF-kappa B activation in natural killer cells.

The role of cellular redox status in both cytotoxic activity and NF-kappa B activation in natural killer (NK) cells was investigated. The results indicate that stimulation of NK cells, either freshly isolated from peripheral blood lymphocytes (PBL) or long-term cultured NK clones, with specific cell targets results in an increased binding activity of NF-kappa B and AP-1 transcription factors measured by gel retardation. Pretreatment of NK cells with the antioxidant pyrrolidine dithiocarbarmate (PDTC) leads to the inhibition of NF-kappa B activation but the AP-1 binding to DNA was superinduced. The inhibition of NF-kappa B by PDTC paralleled with an inhibition of spontaneous cytotoxicity mediated by NK cells. Moreover, the inhibitors of serine proteases, N-alpha-tosyl-L-lysine chloromethyl ketone and N-alpha-tosyl-L-phenylalanine chloromethyl ketone, also blocked the cytolytic activity of NK cells against the sensitive target K562. In contrast, NK activity was not affected by pretreatment of the effector cells with the proteasome inhibitor N-acetyl-leu-leu-norleucinal which selectively inhibits NF-kappa B activation. Altogether, these results support the hypothesis that the activation of NK cells involved transcriptional and post-transcriptional events, and that reactive intermediates may play an important role in the molecular processes related with the generation of a cytotoxic response by NK cells.

Antioxidants↗
PubMed1997

A preliminary report of a phase II trial. UFT plus oral folinic acid as therapy for metastatic colorectal cancer in older patients. Spanish Group for the Treatment of Gastrointestinal Tumors (TTd Group).

The oral fluoropyrimidines have proved to be active in colorectal cancer in Japan and, recently, in the United States and Europe. Continuous oral administration simulates protracted fluorouracil (5-FU) continuous intravenous infusion. The purpose of this trial was to evaluate the tolerability and potential advantages of oral treatment for colorectal cancer in the elderly. The main inclusion criterion was age over 72 years. Patients were treated with UFT (tegafur plus uracil) 400 mg/24 hours (fixed doses) continuously plus folinic acid 45 mg/24 hours until toxicity. If grade 3 or 4 toxicity appeared, treatment was stopped until recovery. From September 1994 to November 1996, 126 patients were included. For the analysis in November 1996, 77 patients were evaluable for response, toxicity, and survival. The patients, including 34 women and 43 men, had a median age of 74 years (range, 72 to 82 years of age). The Karnofsky performance status was 60% to 80% for 41 patients and 90% to 100% for 36 patients. Liver metastasis was present in 48% of the cases, and 42% were locoregional and peritoneal. Toxicity was mild, with only one patient having grade 3 thrombocytopenia, 11 (14%) grade 3 or 4 nausea/vomiting, seven (9%) grade 3 or 4 diarrhea, and one grade 3 mucositis. Four patients (5%) had complete responses and nine (11.6%) partial responses, for an objective response rate of 16.9% (95% confidence interval, 9% to 27%). Twenty-two patients (28.6%) showed no change. The number of patients in whom disease did not progress (ie, patients with complete plus partial responses plus those with stable disease) was 35 (45.4%) (95% confidence interval, 34% to 57%). With a maximum follow-up of 24 months, the median actuarial survival is 14.4 months. The number without disease progression and the median survival in this preliminary analysis suggests that this schedule is a moderately effective, comfortable, treatment with only mild toxicity, that can be recommended for use in the elderly, and it warrants further study.

Aged↗
PubMed1997

[Skin and mucous membrane hemorrhages: clinical assessment, study sequence and relative frequency of hereditary diseases of the hemostasis in a Chilean population].

BACKGROUND: Skin and mucous membrane hemorrhages are distinctive manifestations of hereditary diseases of primary hemostasis and, among them, the different types of von Willebrand disease and of platelet function disorders are the most prevalent. AIM: To know the relative frequency of these disorders and to know the clinical features of patients with mucocutaneous hemorrhages. PATIENTS AND METHODS: Five hundred eighty nine patients whose main symptom was the presence of mucocutaneous hemorrhages were studied. Bleeding time, platelet count, coagulant activity of factor VIII (FVIII:C), FvW: Ag and FvW: CoRis and ABO blood group were measured in all patients in a first stage. According to the results of these tests, further studies were decided. RESULTS: In patients younger than 13 years old, male predominated and, in older patients, females consulted with higher frequency. There was a higher proportion of individuals with O blood type than in the normal population. Bleeding time was abnormal in 330 patients (56%). One hundred ten patients (19%) had won Willebrand disease and, among them, one third had a normal bleeding time. Isolated reduction of factor WII activity was found in 66 patients (11%, 51 males) and 32 of these had normal bleeding time. Eighty one patients (14%) were considered to have an hereditary platelet function defect. A precise diagnosis was not achieved in 332 patients (56%). CONCLUSIONS: Among patients consulting for mucocutaneous hemorrhages, 19% had von Willebrand disease, 11 had an isolated reduction of factor VIII activity, 14% had platelet function defects and in 56%, a precise diagnosis was not reached.

ABO Blood-Group System↗
PubMed1996

Interactions of Bacillus thuringiensis crystal proteins with the midgut epithelial cells of Spodoptera frugiperda (Lepidoptera: Noctuidae).

Binding of different Bacillus thuringiensis insecticidal crystal proteins (ICPs) to the midgut epithelium of Spodoptera frugiperda larvae was characterized by binding experiments with midgut tissue sections and isolated brush border membrane vesicles. Our results show that ICPs interact with the microvilli of epithelial cells of S. frugiperda in two different ways. The first is typical of highly toxic proteins (like CryIC and CryID); this interaction is saturable and specific. In contrast, some nontoxic proteins (like CryIAb) interact nonspecifically with the microvilli, since the binding of this toxin is not affected by the presence of high concentrations of homologous competitor. The CryIC toxin binds to two brush border proteins of 40 and 44 kDa and the CryIAb toxin binds to a single protein of 150 kDa. Immunological detection of ingested B. thuringiensis ICPs on gut sections of S. frugiperda larvae revealed that CryIC and CryID toxins bound along the epithelial brush border microvilli membrane. Binding of the nontoxic protein CryIAb was also observed in the epithelial brush border membrane of fed larvae, but it was extremely weak, implying that this type of interaction occurs also in vivo although it is not related to toxicity.

Animals↗
PubMed1996

Bioactive polyacetylenes from Bidens pilosa.

From the methanolic extract of the whole plants of Bidens pilosa the new beta-D-glucopyranosyloxy-3-hydroxy-6(E)-tetradecen-8, 10,12-triyne besides a known polyine has been isolated and identified mainly by IR and NMR methods. The new compound showed overgrowing action against normal and transformed human cell lines in culture.

Alkynes↗
PubMed1996

Outpatient weekly high-dose continuous-infusion 5-fluorouracil plus oral leucovorin in advanced colorectal cancer. A phase II trial. Spanish Cooperative Group for Gastrointestinal Tumor Therapy (TTD).

BACKGROUND: In a previous phase I-II trial we showed that the maximum tolerable dose (MTD) of 5-fluorouracil (5-FU) in a weekly 48-hour continuous infusion (CI) was 3.5 g/m2. In a subsequent confirmative phase II trial with 85 evaluable patients, a 38.5% response rate was obtained, and a median survival of 12 months. These data were comparable to those achieved by biochemical modulation of 5-FU with leucovorin. On this basis we attempted to modulate high-dose 5-FU (3 g/m2) with oral leucovorin (LV) but the regimen was too toxic and the dose had to be reduced. A new phase II trial with 2 g/m2/week plus oral leucovorin was planned. PATIENTS AND METHODS: From July 1992 to June 1994, 110 previously untreated patients with advanced, measurable colorectal cancer were included in a multicenter study. The patients received, on an outpatient basis, 5-FU 2 g/m2 by continuous infusion for 48 hours once a week until progression or the appearance of toxic effects. Oral leucovorin (60 mg every six hours) was also given during the 5-FU infusion. RESULTS: Patients received a median dose intensity of 5-FU of 1.6 g/m2/week (range 0.9-2). Three complete responses and 36 partial responses were observed. The overall response rate was 37.5% (95% CI, 28% to 46.8%), the median time to progression 7.4 months and median survival 14.5 months. W.H.O. grade 3 diarrhea occurred in 27 patients (24.5%); grade 3 mucositis was observed in 9 (8.1%) patients and grade 4 in one. Grade 3 nausea and vomiting was reported in 13 (11.7%) patients, while grade 3 hand-foot syndrome was detected in only 5 (4.5%). Grade 4 leukopenia occurred in one patient and grade 3-4 thrombocytopenia in two. CONCLUSIONS: Oral leucovorin modulation of weekly 48-hour continuous infusion of 5-FU at 2 g/m2 is an active regimen, with diarrhea and mucositis as the main limiting toxic effects. Its antitumor activity does not seem superior to that obtained with a weekly 48-hour continuous infusion of 5-FU alone at a dose of 3.5 g/m2.

Administration, Oral↗
PubMed1996

Hemostatic disorder of uremia: the platelet defect, main determinant of the prolonged bleeding time, is correlated with indices of activation of coagulation and fibrinolysis.

Several parameters of primary hemostasis and markers of activation of coagulation and fibrinolysis were measured in 48 patients with severe (creatinine clearance < 20 ml/min) chronic renal failure (CRF) without dialysis and disease or drugs affecting hemostasis. Bleeding time (BT) was prolonged in 25/48 patients, and was correlated with age of patients, severity of renal failure, hematocrit, impairment in platelet aggregation-secretion and decrease in platelet ATP content. Defects in von Willebrand factor played no role in the prolongation of the BT. Multivariate analysis showed that only platelet dysfunction and severity of renal disease were independent predictors of the BT in uremia. The platelet functional disorder was significantly correlated with a reduction in platelet ATP and ADP. High levels of plasma thrombin-antithrombin complexes (TAT), prothrombin fragment F1 + 2, fibrinogen and factor VIIc were observed in patients with CRF, as described in prethrombotic states. Plasmin-antiplasmin complexes (PAP), fibrinogen and fibrin degradation products (FgDP, FnDP) were significantly increased, and the activity of plasminogen activator inhibitor (PAI-1) was slightly reduced, denoting an activation of fibrinolysis. A negative correlation was found between platelet levels of ATP and ADP with plasma TAT, F1 + 2 and PAP. Furthermore, plasma PAI-1 activity was negatively correlated with the BT and was lower in patients with prolonged BT as compared with controls and patients with normal BT. These links between primary hemostasis and activation of coagulation and fibrinolysis suggest that increased intravascular generation of thrombin and/or plasmin is an important mediator of the defects in primary hemostasis, prolongation of the BT and, probably, bleeding in CRF.

Adolescent↗
PubMed1996

Comparison of the biochemical properties, regulation and function of ATP-diphosphohydrolase from human placenta and rat kidney.

ATP-diphosphohydrolase (apyrase. EC 3.6.1.5) has both ATPase and ADPase activity that are stimulated by bivalent metals, with Ca2+ being the most effective. The possible physiological function of this enzyme, associated with placental and renal microvilli, is related to the extracellular metabolism of nucleotides. A comparison of the biochemical properties of human placenta and rat kidney apyrase is presented, showing similarities in Mr. bivalent metal stimulation, nucleotide nonspecificity, insensitivity towards specific ATPase inhibitors, and lack of essential sulfhydryl and aliphatic hydroxyl groups. We describe the treatment of membrane preparations from both tissues with different detergents and the isoelectric focusing of the solubilized proteins to partially purify apyrase. An ectoenzyme localization is assigned both in microvillus membranes and in the vasculature on the basis of organ perfusion experiments with nucleotides in the presence of antibodies. Placental and kidney microvillus membranes inhibited ADP-induced platelet aggregation, in agreement with an extracellular role. Initial studies on enzyme regulation suggested the existence of at least two types of modulatory proteins: an activating protein in the cytosol of both tissues, and an inhibitory protein associated with placental microsomes. Possible hormonal regulation was investigated in kidneys using in vivo estradiol treatment, but only slight changes in total apyrase activity were observed.

Animals↗
PubMed1996

A double-blind, randomised comparison of the anti-emetic efficacy of two intravenous doses of dolasetron mesilate and granisetron in patients receiving high dose cisplatin chemotherapy.

This multicentre, double-blind, double-dummy, randomised trial was designed to compare the efficacy and safety of single intravenous doses of dolasetron mesilate and granisetron in the prevention of acute emesis and nausea due to high-dose (> or = 80 mg/m2) cisplatin. Single intravenous doses of 1.8 or 2.4 mg/kg of dolasetron mesilate or 3 mg of granisetron hydrochloride were administered in a volume of 50 ml over a 5-min period, beginning 30 min prior to cisplatin (> or = 80 mg/m2) administration. The number and timing of emetic episodes, time to administration of escape anti-emetic medication, severity of nausea by visual analogue scale (VAS), and safety were monitored for 24 h after the start of cisplatin-containing chemotherapy. Investigators' evaluations of overall efficacy and patients' satisfaction with therapy were recorded at the end of the 24-h study period. Of the 474 patients evaluable for efficacy, complete responses were achieved by 54, 47 and 48% of patients given dolasetron mesilate 1.8 mg/kg, dolasetron mesilate 2.4 mg/kg and granisetron, respectively. Statistically, treatment groups had comparable complete and complete plus major responses, times to first emesis, and use of escape medication; patient maximum nausea severity and treatment satisfaction ratings; and physician nausea severity and overall efficacy assessments. For the majority of efficacy endpoints, 1.8 mg/kg dolasetron mesilate produced numerically superior responses compared with the 2.4 mg/kg dose. Gender and prior chemotherapy were significant predictors of complete response; males and chemotherapy-naive patients had higher responses. The overall incidences of adverse events were comparable among the treatment groups; headache and diarrhoea were most common. In conclusion, 1.8 and 2.4 mg/kg of dolasetron mesilate and granisetron (3 mg) were equally effective in preventing nausea and vomiting induced by highly emetogenic cisplatin-containing chemotherapy. In addition, because no additional benefit was observed with 2.4 mg/kg of dolasetron mesilate and numerically greater responses were observed with the 1.8 mg/kg dose, the lower dose of 1.8 mg/kg is optimal for further clinical development.

Adult↗
PubMed1996

The Spanish experience with high-dose infusional 5-fluorouracil (5-FU) in colorectal cancer. The Spanish Cooperative Group For Gastrointestinal Tumor Therapy (TTD).

Background In a previous phase I to II trial, we have shown that the maximum tolerable dose (MTD) of 5-Fluorouracil (5-FU) in 48-hour continuous infusion (CI) weekly was 3.5 gr/m2. In a subsequent confirmative phase II trial with 85 evaluable patients, a 38.5% response rate was obtained and the median survival reached was 12 months. These data were comparable to those achieved by biochemical modulation of 5-FU with Leucovorin. On this basis we tried to modulate high-dose 5-FU (3 gr/m2) with oral leucovorin (LV) but the regimen was too toxic and the dose had to be reduced. A new phase II trial with 2 g/m2/week plus oral leucovorin was planned. Patients received a median dose intensity of 5-FU of 1.6 g/m2/week (range 0.9-2). Three complete responses and 36 partial responses were observed. Overall response rate was 37.5% (95% CI, 28% to 46.8%). Median time to progression has been 7.4 months, and median survival 14.4 months. WHO grade 3 diarrhea was seen in 27 patients (24.5%). Grade 3 mucositis was also seen in 9 (8.1%) patients, and grade 4 was observed in one. Grade 3 nausea and vomiting was reported in 13 (11.7%) patients. Grade 3 hand-foot syndrome was detected in only 5 (4.5%) patients. Grade 4 leukopenia was observed in 1 case and grade 3 to 4 thrombocytopenia was observed in two cases, respectively. Oral leucovorin modulation of weekly 48-hour continuous infusion of 5-FU at 2 g/m2 is an active regimen, with diarrhea and mucositis as main limiting toxicities. Its antitumor activity does not seem superior to that obtained with a weekly 48 hour continuous infusion of 5-FU alone at a dose of 3.5 g/m2.

Administration, Oral↗
PubMed1995

A phase II trial of weekly high dose continuous infusion 5-fluorouracil plus oral leucovorin in patients with advanced colorectal cancer. The Spanish Cooperative Group for Gastrointestinal Tumor Therapy (TTD).

BACKGROUND: In a previous Phase II trial, the authors showed that a weekly continuous infusion of 5-fluorouracil (5-FU) at a dose of 3.5 g/m2 for 48 hours is an active treatment for advanced colorectal cancer. The overall response rate was 38.5%, and the median survival was 12 months. These data were comparable to those achieved by biochemical modulation of 5-FU with leucovorin. To study the modulation of this weekly, high dose, continuous infusion 5-FU with oral leucovorin, a new Phase II trial was planned. METHODS: From December 1991 to July 1992, 43 previously untreated patients with measurable advanced colorectal cancer were included in a multicenter study. They received on an outpatient basis 5-FU at a weekly dose of 3 g/m2 by continuous infusion for 48 hours until progression or toxicity. Oral leucovorin (60 mg every 6 hours) also was given during the infusion of 5-FU. RESULTS: Patients received a median dose intensity of 5-FU of 2.2 g/m2/week (range, 0.76-3 g/m2/week). One complete response and 11 partial responses were observed. The overall response rate was 29% (95% confidence interval [CI], 16-45%). Median time to progression was 7 months, and the median survival was 15 months. World Health Organization Grades 3 and 4 diarrhea were observed in 19 (45%) and 6 (14%) patients, respectively. Grade 3 mucositis also was observed in 10 (24%) patients, and Grade 4 mucositis was observed in 1. Grade 3 nausea and vomiting were reported in seven (17%) patients. Grade 3 hand-foot syndrome was detected in only two (2.5%) patients. No leukopenia or thrombocytopenia was observed. CONCLUSIONS: Oral leucovorin modulation of a weekly 48-hour infusion of 5-FU at a dose of 3 g/m2 of leucovorin is a toxic regimen, always requiring dose reduction, with diarrhea and mucositis as the main limiting toxicities. Its antitumor activity does not seem superior to that observed with a weekly 48-hour infusion of 5-FU alone at a dose of 3.5 g/m2.

Administration, Oral↗
PubMed1995

Decreased platelet counts and decreased platelet serotonin in poststreptococcal nephritis.

Mean platelet survival time in patients with acute poststreptococcal glomerulonephritis (APSGN) is reduced to 50-60% of the control values, and glomerular deposits of platelet factor 4 are found in these patients. In order to investigate further systemic platelet changes of pathogenic, clinical or prognostic significance, we measured the platelet serotonin (5-HT) content and the blood platelet counts during the 1st week of the disease in 27 patients with APSGN. Platelet 5-HT was significantly reduced in patients with APSGN as compared with patients with impetigo without glomerular involvement (785 +/- 54 vs. 1,329 +/- 94 ng 5-HT/10(9) platelets; p < 0.001). Similarly, the mean blood platelet count was reduced to 247 +/- 16 x 10(3) as compared with 303 +/- 14 x 10(3) in the controls (p < 0.05). Thirteen (48%) of these patients had individual values of platelet 5-HT lower than the 95% confidence interval calculated in the control group. No significant correlation was observed between the concentration of 5-HT and either the severity of the disease judged by the amount of urinary protein excretion and the serum creatinine value or the presence of circulating immune complexes. Significant correction of the platelet 5-HT content (to 1,180 +/- 111 ng/10(9) platelets; p < 0.01) and of the platelet counts (to 309 +/- 21 x 10(3); p < 0.01) were observed in the longitudinal study at least 2 weeks later. Platelet activation, with secretion of granular content and increased consumption, may explain these findings. Additionally, the reduced mean age of the circulating platelets could contribute to their decreased 5-HT levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1994

Phase II study with iododoxorubicin in measurable advanced colorectal adenocarcinoma. Effective rescue using weekly high-dose 5-fluorouracil (WFU). Spanish Cooperative Group for Gastrointestinal Tumor Therapy (TTD), Work Group of SEOM (Spanish Medical Oncology Society).

AIMS AND BACKGROUND: To evaluate a new anthracycline 4'-iodo-4'-deoxydoxorubicin (I-DOX) in patients with measurable advanced colorectal adenocarcinoma in a phase II study. METHODS: We investigated therapeutic activity and toxicities associated with repeated courses of I-DOX 80 mg/m2 administered every 3 weeks. Eighteen patients entered the trial, all of them evaluable for response and toxicity. RESULTS: A total of 47 courses were administered. The median cumulative I-DOX dose was 238 mg/m2 (80-320). Myelosuppression, particularly leukopenia, was the most frequent and serious side effect associated with I-DOX treatment; World Health Organization (WHO) grade 3-4 leukopenia occurred in 4 patients (22%). No thrombocytopenia was observed except in 1 patient who presented WHO grade 4. Only 1 patient developed febrile neutropenia but recovered uneventfully. Overall, the I-DOX treatment was well tolerated. Grade 3-4 nausea/vomiting was observed in 2% of the cycles and no other severe toxicities were recorded. Echocardiography or multiple gated scan was performed before treatment and during follow-up in 14 patients to measure left ventricular ejection fraction (LVEF), and a decrease > 15% was detected in 3, including 1 whose LVEF fell below normal values (48%) (normal range > 49%). There were no cases of congestive heart failure or treatment-related deaths. No complete or partial response (PR) was observed. Twelve patients received weekly high-dose 5-fluorouracil (WFU) as rescue. Four patients had PR, 5 no change and 3 progressive disease (PD). The median time to PD of the whole group from study entry to failure after WFU was 30 weeks and the overall median survival was 11 months. CONCLUSIONS: As reported for other anthracyclines, I-DOX showed no activity in colorectal adenocarcinoma; however, the use of an investigational agent as front-line chemotherapy for colorectal adenocarcinoma does not compromise further response to 5-FU.

Adenocarcinoma↗
PubMed1994

Human placental ATP-diphosphohydrolase: biochemical characterization, regulation and function.

1. Kinetic and physico-chemical studies on human placental microsomal fraction confirmed that the ATPase and ADPase activities detected in this fraction correspond to the enzyme ATP-diphosphohydrolase or apyrase (EC 3.6.1.5). These include substrate specificity, and coincident M(r) and pI values of both ATPase-ADPase activities. 2. This enzyme hydrolyses both the free unprotonated and cation-nucleotide complex, the catalytic efficiency for the latter being considerably higher. 3. Microsomal apyrase is insensitive to ouabain and Ap5A. The highly purified enzyme was only inhibited by o-vanadate, DES and slightly by DCCD. 4. Apyrase seems to be a glycoprotein from its interaction with Concanavalin-A. 5. Preliminary studies on the essential amino acid residues suggest the participation of Arg, Lys and His residues, and discard the requirement of -SH, COO-, -OH, and probably also Tyr and Trp. 6. Two kinetic modulatory proteins of apyrase were detected in placental tissue. An activating protein was found in the soluble fraction and an inhibitory protein was loosely bound to the membranes. 7. The proposed in vivo function for apyrase is related to the inhibition of platelet aggregation due to its ADPase activity, which is supported by the direct effect on washed platelets and by its plasma membrane localization.

Adenosine Diphosphate↗
PubMed1994

PCR analysis of the cryI insecticidal crystal family genes from Bacillus thuringiensis.

A method allowing rapid and accurate identification of different subgroups within the insecticidal crystal CryI protein-producing family of Bacillus thuringiensis strains was established by using PCR technology. Thirteen highly homologous primers specific to regions within genes encoding seven different subgroups of B. thuringiensis CryI proteins were described. Differentiation among these strains was determined on the basis of the electrophoretic patterns of PCR products. B. thuringiensis strains, isolated from soil samples, were analyzed by PCR technology. Small amounts of bacterial lysates were assayed in two reaction mixtures containing six to eight primers. This method can be applied to rapidly detect the subgroups of CryI proteins that correspond with toxicity to various lepidopteran insects.

Bacillus thuringiensis↗
PubMed1994

Accumulation of 5-hydroxytryptamine by aging platelets: studies in a model of suppressed thrombopoiesis in dogs.

Thrombocytopenia was induced in healthy, male mongrel dogs by intramuscular injection of a single dose of estradiol valerate (1 mg/kg). A steady, almost linear decay of the blood platelet count starting about day 6 post-estradiol and attaining a mean value of 14 x 10(3) platelets/microliters one week later was observed. Thrombocytopenia is explained mainly by suppression of thrombocytopoiesis, as established by two independent ways: 1. Megakaryocytes in the bone marrow were markedly reduced. 2. Kinetic studies with 111In labeled autologous platelets revealed a nearly linear decay of the radioactivity and mean survival times within the expected range. The progressive reduction in the platelet count is associated with an increase in the mean age of the platelets still circulating. Following estradiol injection, platelet 5-hydroxytryptamine (5-HT) increased from a basal value of 130 +/- 30 ng/10(8) platelets (platelet count of 351 +/- 53 x 10(3) platelets/microliters) to 343 +/- 100 ng/10(8) platelets eleven days latter, when the platelet count dropped to 32 +/- 18 x 10(3) platelets/microliters. No significant changes in the number or affinity of the 5-HT uptake receptors could be demonstrated in platelets exposed in vitro and in vivo to estradiol. Our results indicate that aging platelets accumulate 5-HT, probably by a sustained exposure to the monoamine in plasma, confirming previous observations based on models in which thrombopenia was induced by immune and mechanical means.

Animals↗