Biomedical subjects

A Alfonso

Publications and source records attributed to A Alfonso.

At least 55 records · Page 3Linked to original sources

PubMed1994

Functional characterization of the Na(+)-H+ exchanger in rat mast cells: crosstalks between different kinase pathways.

In our effort to understand the mechanisms by which rat mast cells regulate intracellular pH (pHi), we studied the effect of drugs acting on different transducting signals on the Na(+)-H+ antiport. We studied the activity of the antiporter in recovering pHi after an acid load with sodium propionate. The drugs used were okadaic acid, which inhibits the phosphatases 1 and 2A, pertussis toxin, which ADP-rybosylates the Gi-protein, cholera toxin, which ADP-rybosylates the Gs-protein, NaF which non-specifically activates G-proteins, and the phorbol esther 12-O-tetradecanoylphorbol 13-acetate (TPA) which specifically activates protein kinase C. The effect of TPA is a two-fold stimulation of the activity of the antiporter. A similar activation was observed with the combination okadaic acid plus cholera toxin. All the drugs alone did not modify the activity of the antiporter, and they all blocked the stimulatory activity of TPA. In a Ca(2+)-free medium, okadaic acid inhibits the activity of the antiporter. All the mechanisms affected by these drugs have some regulatory role on the Na(+)-H+ antiport. Our results indicate the great complexity of the crosstalks between the different signal transducing pathways.

Animals↗

PubMed1994

Effect of lyophilization on the stability of gonyautoxins obtained from contaminated mussels.

This study describes the stability of gonyautoxins (GTX) and C toxins obtained from contaminated mussels and stored at different temperatures in lyophilized samples. Analyses of extracts from mussels contaminated with paralytic shellfish poison (PSP) indicated the presence of gonyautoxins as the major component in red tides of the North-West coast of Spain. These GTX and C toxins were extracted from contaminated mussels (Mytilus galloprovincialis Lmk) and partially purified by chromatography on Bio-Gel P-2 and Bio-Rex 70. The stability of these toxins was analysed by high performance liquid chromatography. GTX 4 and GTX 6 are the most stable toxins among GTX. We conclude that the lyophilization procedure is not the safest way to process most of the gonyautoxins. However, the lyophilization procedure made the C toxins unstable, so clearly this procedure must be rejected.

Animals↗

PubMed1994

Comparative study of the stability of saxitoxin and neosaxitoxin in acidic solutions and lyophilized samples.

Paralytic shellfish poison (PSP) has historically been a problem for the shellfish industry. In order to prevent the marketing of contaminated seafood products, governments have implemented monitoring programs where standards of toxins are necessary. The stability of these standard toxins is very important. In this paper we analysed the stability of saxitoxin (STX) and neosaxitoxin in acidic solution and lyophilized samples. Individual toxins were determined in each sample using a high-performance liquid chromatographic procedure employing post-column oxidation of the toxins to form fluorescent derivatives. Our results demonstrate that STX is very stable in solution samples and could be adopted as a reference standard. This toxin can be kept in dilute acidic solutions for 18 months without loss of potency. However, neosaxitoxin is unstable, possibly due to transformation to other toxins.

Animals↗

PubMed1994

Cloning and characterization of the choline acetyltransferase structural gene (cha-1) from C. elegans.

We have cloned the cha-1 gene from Caenorhabditis elegans using the method of transposon tagging, cha-1 is the structural gene for ChAT, the enzyme that synthesizes ACh. Sequence analysis of cDNAs predicts a protein of 71.5 kDa; comparison of the deduced amino acid sequence with ChAT sequences from other species confirms that cha-1 encodes ChAT. Comparison of cDNA and genomic sequences reveals that transcription is from right to left on the genetic map, and that some of the transcripts may result from trans-splicing of the 22-base spliced leader SL 1. The cha-1 gene is organized into 11 exons. The first exon contains only untranslated sequences, and is followed by an extremely long intron. The coding sequence of the cha-1 transcript is disrupted by mutations in the cha-1 gene. We have determined the sites of four transposon insertions and the end-points of two deletions that lead to the cha-1 mutant phenotype; one of the deletions appears to eliminate gene function completely. Comparison of the Drosophila, rat, and C. elegans genes reveals conserved motifs and conserved intron sites.

Amino Acid Sequence↗

PubMed1993

The Caenorhabditis elegans unc-17 gene: a putative vesicular acetylcholine transporter.

Mutations in the unc-17 gene of the nematode Caenorhabditis elegans produce deficits in neuromuscular function. This gene was cloned and complementary DNAs were sequenced. On the basis of sequence similarity to mammalian vesicular transporters of biogenic amines and of localization to synaptic vesicles of cholinergic neurons in C. elegans, unc-17 likely encodes the vesicular transporter of acetylcholine. Mutations that eliminated all unc-17 gene function were lethal, suggesting that the acetylcholine transporter is essential. Molecular analysis of unc-17 mutations will allow the correlation of specific parts of the gene (and the protein) with observed functional defects. The mutants will also be useful for the isolation of extragenic suppressors, which could identify genes encoding proteins that interact with UNC-17.

Acetylcholine↗

PubMed1993

Solid-phase radioreceptor assay for paralytic shellfish toxins.

Sodium channels obtained from rat brain membrane preparations were coated onto microtiter plates and used to develop a direct solid-phase binding assay. The tritiated sodium channel blocker saxitoxin ([3H]-saxitoxin; STX) was used to detect toxins in paralytic shellfish poisoning (PSP) by measuring the competitive displacement of other toxins. With this assay the amount of STX and tetrodotoxin needed to displace 50% of bound [3H]STX was 1.7 and 1.76 ng/ml for buffer samples, respectively. In the direct solid-phase binding assays, the PSP toxins were effectively bound to the rat brain membranes. The IC50 of this assay for different PSP toxin solutions obtained from mussels contaminated in red tides ranged from 0.03 to 0.30 ng/ml. Therefore, this assay represents a potentially useful method for the detection of toxin-contaminated mussels.

Animals↗

PubMed1992

Effect of purification, theophylline and sodium fluoride on histamine release produced by antineoplastic drugs on rat mast cells. A distinctive mechanism of action for carboplatin.

The antineoplastic drugs, cytarabine, ifosfamide, vinorelbine, doxorubicin, asparaginase and carboplatin, elicit histamine release from rat pleural and peritoneal mast cells. Both cell populations do not show heterogeneity in their response to stimulation by any of these drugs, with the exception of cytarabine, which activates pleural mast cells at lower concentrations. When these cells are purified with Percoll, L-asparaginase, vinorelbine and cytarabine completely lose their capability of inducing histamine release in both cell populations, while the other drugs still show the same pattern of response as with unpurified cells. These results indicate that some membrane component crucial for the action of vinorelbine, L-asparaginase and cytarabine is lost during the purification procedure. Pretreatment of the cells with theophylline completely inhibits the response to cytarabine, ifosfamide, vinorelbine and asparaginase, and inhibits the response to doxorubicin by up to 75% only. Theophylline does not change the response to carboplatin. Sodium fluoride does not change the response to any of the drugs tested, with the exception of carboplatin, in which case a complete inhibition is observed. In conclusion, carboplatin activates rat mast cells through a completely different mechanism of action with respect to the other drugs studied.

Animals↗

PubMed1992

Non-immunological release of histamine from rat mast cells elicited by antineoplastic agents.

We studied the histamine-releasing activity of several antineoplastic drugs on rat pleural and peritoneal mast cells. The drugs tested included the nitrogen mustards cyclophosphamide and ifosfamide, the nitrosourea carmustine, the triazene dacarbazine, the folic acid analogue methotrexate, the pyrimidine analogue cytarabine and fluorouracil, the vinca alkaloids vinblastine, vincristine and Vinorelbine, the epipodophyllotoxins etoposide and teniposide, and the enzyme L-asparaginase. Methotrexate, carmustine, fluorouracil, vinblastine and vincristine failed to elicit histamine release on rat mast cells. All of the other drugs evoked histamine release in both the presence and the absence of extracellular calcium, but ifosfamide, cytarabine and asparaginase induced a much lower release in the absence of this cation. The response elicited by cytarabine and etoposide was much higher in pleural than in peritoneal mast cells. These results indicate that some antineoplastic drugs may directly activate the release of histamine, which could contribute to some of their secondary effects.

Animals↗

PubMed1992

Nonimmunological release of histamine from rat mast cells elicited by antineoplastic agents: effect of drug combinations.

We studied the release of histamine elicited by some antineoplastic drugs in rat pleural and peritoneal mast cells. The drugs tested included the antibiotic mitomycin; the anthracyclines daunorubicin, doxorubicin, and epirubicin; the glycopeptide bleomycin; the chromopeptide dactinomycin; the platinum coordination complexes carboplatin and cisplatin; and the anthracenedione mitoxantrone. Mitomycin and bleomycin failed to elicit any release of histamine, whereas all of the other drugs induced histamine release from either pleural or peritoneal mast cells, the release being independent of extracellular calcium. The results indicate that antineoplastic drugs activate histamine release in a manner similar to that shown by compound 48/80, which may contribute to some of their secondary effects.

Animals↗

PubMed1992

Influence of protein kinase C, cAMP and phosphatase activity on histamine release produced by compound 48/80 and sodium fluoride on rat mast cells.

We have studied the effect of protein kinase C and protein kinase A activation, and phosphatase inhibition on two different stimuli with distinct mechanisms of action. The first stimulus is compound 48/80, and its action is mediated probably by a Gi-protein, while the other is sodium fluoride, which unspecifically activates G-proteins. We established a comparative study because the action of compound 48/80 is calcium-independent, while fluoride is strictly calcium-dependent. The activation of protein kinase C was attained with the phorbol esther 12-O-tetradecanoylphorbol-13-acetate, protein kinase A was activated by increasing cAMP levels with forskolin or rolipram, and the phosphatase activity was inhibited with okadaic acid (OA), which inhibits phosphatases type 1 and 2A. Our results show that OA enhances the response to fluoride and compound 48/80 in the absence of calcium, and we conclude that calcium has a negative feedback role on the cell response. Protein kinase A activation strongly inhibits the response to fluoride, and the results show a positive regulation of protein kinase C and a negative regulation of protein kinase A over fluoride response. As previously reported by other authors for the ionophore A23187, TPA notably potentiates the response to fluoride, which supports its possible modulatory role on extracellular calcium-dependent stimuli.

Animals↗

PubMed1991

Lack of specific saxitoxin binding to rat mast cells.

We studied whether or not mast cells are endowed with specific sodium channels, by using tritiated saxitoxin which binds to site 1 of sodium channels on excitable tissues. Our results suggest that rat pleural and peritoneal mast cells lack specific sodium channels.

Animals↗

PubMed1991

Changes in rat mast cell responses in sodium-free media. Lack of demonstrable sodium channel activity.

Exposure of rat mast cells to isotonic sucrose (employed as a sodium free medium) increased several-fold the sensitivity to calcium, which itself became a stimulus for exocytosis. Concentrations of the cation as low as 25 microM permitted maximal histamine release. Preincubation of cells in sucrose to allow sodium efflux before adding the ionophore A23187 led to a slower release of histamine. We postulate that sodium efflux can generate a membrane potential that causes the increased sensitivity to calcium and the delay in response after preincubation. The response to A23187 is somewhat unspecific since the ionophore can release histamine from internal calcium reservoirs. Saxitoxin or veratridine did not affect cell responses, so that sodium activity is not mediated through defined sodium channels.

Animals↗

PubMed1989

Goiters and airway problems.

Even though thyroid enlargement occurs commonly, the incidence of goiter has decreased in the United States due to the routine use of iodized salt. We continue to see a large number of patients with neglected goiters that cause airway compression. The progressive nature of this disease occasionally results in severe tracheal compression and acute airway distress. We treated 120 patients with airway compression secondary to goiters during a 7-year period. Thirty patients presented initially with acute airway distress requiring either intubation or semiemergent surgery. The decision to operate was based primarily on clinical evaluation and airway films. Ninety patients had substernal goiters. Only one patient required sternal splitting. If one lobe was enlarged causing tracheal deviation, lobectomy was performed; if both lobes were enlarged, subtotal thyroidectomy was performed. Two patients required tracheostomy. There were no operative deaths, and morbidity was limited to minor wound problems. It is important to consider early surgical decompression whenever tracheal compression is caused by goiters, especially if the patients are symptomatic or there is mediastinal extension.

Adult↗

PubMed1987

Acute airway distress due to thyroid pathology.

Patients with multinodular goiter or related thyroid disorders rarely have acute airway distress due to tracheal deviation or compression. However, our institution cares for a large number of patients with untreated multinodular goiters, and in the progression of this disorder, tracheal deviation and airway problems are relatively common. During the past 4 years, we have cared for 24 patients who were admitted with acute, life-threatening airway distress that required emergency intervention. Nine patients had emergency intubation, the remaining 15 had stridor on admission and underwent emergency operations. The series consists of 19 females and five males whose ages ranged from 37 to 89 years. Only four patients had malignant thyroid lesions (two papillary-follicular, two anaplastic), and two of these had multiple pulmonary metastases. Fifteen of the patients with multinodular goiters had a mediastinal extension that led to marked tracheal deviation. Three patients had recurrent multinodular goiters decades after previous surgery. Twenty-one patients underwent surgery at our institution, and all did well. Only one patient required sternotomy for thyroidectomy. Two patients required tracheostomy procedures, one because of tracheomalacia and the other because of poor pulmonary reserve. Interestingly, two patients had acute symptoms when in their third trimester of pregnancy. We have routinely used the laryngoscope (fiberoptic rigid or flexible) for preoperative and postoperative evaluation of the vocal cords and for determination of the condition of the larynx. On the basis of our experience with acute airway distress, we strongly advocate elective surgery for patients with multinodular goiter at the first sign of tracheal compression, especially if they have mediastinal extension.

Acute Disease↗

PubMed1981

Tracheal or esophageal compression due to benign thyroid disease.

Tracheal or esophageal compression was present in 91 (33 percent) of 273 consecutive patients with benign goiter during a 7 year experience. The underlying disease was nodular colloid goiter in 66 percent, adenoma in 21 percent, thyroiditis in 9 percent and Graves' disease in 4 percent. The incidence of tracheoesophageal compression was higher in patients with thyroiditis (67 percent) than in those with colloid goiter (46 percent). Thirty of 91 patients were completely asymptomatic but had marked tracheal deviation on roentgenography. Two thirds presented with significant dyspnea, or dysphagia or both. A long history of goiter preceding the onset of symptoms and progressive worsening of compression symptoms after its onset were common in the latter group. Previous radiographs demonstrating significant tracheal deviation during a previous presymptomatic period were available in 11 of 36 dyspneic patients. Sudden tracheal occlusion developed in 3 percent and required emergency treatment. Tracheal compression occurred more often and when present was a more ominous symptom. Compression manifestations were more frequent in patients with multinodular goiter, were more likely to appear when the underlying disorder was thyroiditis affected the tracheal more often than the esophagus and were generally gradually progressive with time. A clinical spectrum ranging from a presymptomatic tracheal compression stage to one wherein progressive worsening of symptoms occurs is suggested. After symptoms of tracheal compression become clinically manifest, the occurrence of complete airway occlusion may be sudden and unpredictable. Early operation whenever roentgenographic evidence of tracheal deviation becomes manifest is recommended.

Adolescent↗

PubMed1981

The influence of age upon the survival of adult patients with carcinoma of the colon.

Five hundred adult patients with carcinoma of colon were studied to determine the relationship between age and prognosis. Regardless of the stage of disease or curative or palliative operation, younger patients had a better prognosis. Deaths after three years postresection were usually due to associated disease, which probably accounts for the poorer prognosis in the older patient. The poor prognosis frequently reported in young patients with carcinoma of the colon usually applies to those less than 25 years of age who may have a different form of the disease.

Adult↗

PubMed1979

Relationship of race to functional status among breast cancer patients after curative surgery.

Analysis of functional status of 197 breast cancer patients three years after curative radical mastectomy indicated a cumulative probability of disability of 25%, whereas the probability of death regardless of prior disability was 40.5%. Analysis of functional status by patient characteristics indicated that nonwhites were three times more likely than whites to experience disability (P less than 0.01) as defined in terms of their ability to carry on normal activities without assistance. Although whites and nonwhites were diagnosed at similar stages of disease, nonwhites were, on average, eight years younger than whites. They younger age may reflect a larger proportion of premenopausal breast cancer cases among nonwhites, which if associated with more rapidly progressing disease could account for their poorer prognosis. Alternatively there may exist factors in the nonwhites' social or economic environment that limited the ability of the family to care for the patient at home. These data reaffirm the need to monitor closely breast cancer patients to diagnose acute complications, and they indicate that most patients can resume normal activities shortly after curative surgery.

Activities of Daily Living↗

PubMed1979

Local duodenal metastasis from colonic carcinoma.

The clinical and radiologic appearance of an isolated metastasis to the duodenum may mimic a primary pancreatic or duodenal cancer. As lymphatics from the right colon drain to periduodenal lymph nodes, lymphatic spread from right colon cancer can cause enlargement of the duodenal loop, with ulceration or distortion of the mucosa on the medial aspect of the duodenum. We present three patients with ulcerating metastases in the duodenum from colon cancer whose cases exemplify the problems of diagnosis and management.

Adenocarcinoma↗