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Biomedical subjects

A Ibarra

Publications and source records attributed to A Ibarra.

At least 37 records · Page 2Linked to original sources
PubMed1996

Alteration of cyclosporin-A pharmacokinetics after experimental spinal cord injury.

The pharmacokinetics of the immunosuppressive agent cyclosporin-A (CsA) were studied in rats submitted to spinal cord (SC) injury. A single CsA 10 mg/kg dose was given either intraperitoneally (i.p.) or orally to rats submitted to experimental SC injury at the T8 level. Twenty four hours after lesion (acute stage of SC injury) i.p. CsA bioavailability was increased, while t1/2 was prolonged. However, oral bioavailability was reduced. Seven weeks after lesion (chronic stage of SC injury) CsA bioavailability, by either route, was not significantly different from control values. Results indicate that parenteral CsA bioavailability is increased during the acute stage of SC lesion, probably due to an impaired elimination. Oral bioavailability, however, is decreased, since there is also an important reduction in gastrointestinal CsA absorption that overrides the effect of impaired elimination. Alterations in CsA pharmacokinetics appear to revert during the chronic stage of SC injury. Changes in CsA bioavailability, depending on the route of administration and on time, must be considered to design an adequate immunosuppressive treatment in SC injury.

Administration, Oral↗
PubMed1996

Use of cyclosporin-A in experimental spinal cord injury: design of a dosing strategy to maintain therapeutic levels.

Cyclosporin-A (CsA) is frequently used as an immunosuppressive agent in experimental transplantations. CsA has been used in nervous tissue transplants in spinal cord injury (SCI). However, optimal results have not been obtained. This is likely due to the fact that SCI alters CsA pharmacokinetics and hence fixed dose regimens are not adequate. In this study, several CsA dosing regimens were evaluated in Long-Evans female rats subjected to a severe low thoracic (T8) SCI by the contusion method. Serum CsA concentrations were measured to determine which dosing regimen allowed CsA levels to be maintained within the therapeutic window. It was found that administration of 2.5 mg/kg/12 h intraperitoneally during the first 2 days after SCI (acute phase) followed by 5 mg/kg/12 h orally thereafter (subacute and chronic phases) yields CsA circulating levels within the therapeutic window, i.e., 0.120-0.275 microgram/mL. This dosing regimen represents a suitable alternative to fixed dosing to achieve an optimal CsA-induced immunosuppression in experimental models of SCI.

Animals↗
PubMed1996

Comparison between Sprague-Dawley and Wistar rats as an experimental model of pharmacokinetic alterations induced by spinal cord injury.

Two strains of rats, Sprague-Dawley and Wistar, were assayed in order to determine which strain is the more suitable experimental model for the study of pharmacokinetic alterations induced by spinal cord injury. Animals were submitted to spinal cord contusion at the T8-T9 level by the weight drop method. A single acetaminophen oral dose (100 mg/ kg) was administered 24 h after injury and blood samples were drawn for a period of 4 h. Acetaminophen concentration in whole blood was determined by high performance liquid chromatography and pharmacokinetic parameters were estimated. For both strains, Cmax and AUC were significantly lower, whereas tmax remained unchanged, in injured animals compared to sham-injured controls. Circulating acetaminophen concentrations were higher; therefore, pharmacokinetic alterations were more easily discerned, in Sprague-Dawley than in Wistar rats. It is concluded that the Sprague-Dawley strain is a more suitable model for the study of pharmacokinetic alterations induced by spinal cord injury.

Acetaminophen↗
PubMed1995

Survival of cultured plant cells grafted into the subcutaneous tissue of rats (preliminary report).

To evaluate the survival of plant tissue in an animal environment, cultured calli from a Mexican medicinal plant (Mimosa tenuiflora Poir.) were transplanted under sterile conditions into the subcutaneous tissue of rats. Microscopic studies of grafted areas were carried out at the 30th, 60th and 120th days after transplantation. Histological evidence of plant graft survival was found in specimens of all groups. during the first month of subcutaneous grafting a moderate inflammatory reaction around the callus was observed characterized by the presence of polymorphonuclear cells and some macrophages and the formation of a fibrous capsule. Nevertheless, the plant grafts remained viable and a decrease of the inflammatory reaction around the callus was observed in the specimens during the following months. In the fourth month specimens the formation of blood vessels inside the grafted plant tissue was observed. Once removed from rats, plant tissues showed high viability according to the fluorescein test. These calli were then transferred to the original in vitro medium showing growth capacity during the following weeks. These results demonstrate, for the first time, that cultivated cells of higher plants survive in an animal environment, suggesting the possibility to utilize pharmacologically active plant transplants in animals, a technique proposed here as inter-regni transplants. Further studies are required to explore this new field of research that opens numerous questions about plant-animal cellular interaction.

Animals↗
PubMed1995

[Thyroid nodule in Basedow-Graves disease and thyroid cancer: experience in 6 patients].

Traditionally, Basedow-Graves disease was considered a protection against thyroid cancer. However, recent reports suggest that cancer occurs with a higher frequency than expected and is more aggressive in this disease. We report six patients with hyperthyroidism due to a Basedow Graves disease that presented a palpable thyroid nodule, which was cold in the scintiscan and solid in the ultrasound examination. Fine needle cytology disclosed cancer in five cases (two with cytological features of greater aggressiveness) and a nodular hyperplasia in one. The diagnosis was confirmed in the surgical piece in all patients. We conclude that Basedow-Graves disease and thyroid cancer, which can have an increased aggressiveness, may coexist.

Adolescent↗
PubMed1994

Development of post-traumatic cysts in the spinal cord of rats-subjected to severe spinal cord contusion.

To study the development of post-traumatic spinal cord (SC) cysts, and their fine anatomic characteristics, rats were subjected to severe SC contusion. Specimens were analyzed from day 1 to 1 year post-injury. Using conventional light, and transmission and scanning electron microscopy, three stages were typified, namely: necrosis, repair, and stability. The final cell composition and thickness of the cyst walls were not uniform. Astrocytes, fibroblasts, ependymal cells, and collagen fibers were the main constituents. Chronic inflammatory cells were also observed. The neuropathologic characterization of posttraumatic SC cysts could be useful in planning strategies for SC reconstruction at different times post-injury.

Animals↗
PubMed1992

[Percutaneous puncture thyroid cytology: cyto-histologic correlations in 136 nodular goiter surgical patients].

Percutaneous puncture for cytologic study was performed in 136 patients with nodular goiter. All patients were operated on and correlation of cytologic and histologic findings was obtained. Echographic study revealed a solid aspect in 72%, cystic aspect in 10% and mixed in 18%. The cytologic findings were classified as: benign--hyperplasia--, chronic thyroiditis, follicular neoplasm (adenoma and carcinoma), oxyphilic neoplasm (adenoma and carcinoma), papillary cancer, medullary cancer, anaplastic cancer and insufficient material. Surgery revealed cancer in 36 patients (26.5%). There were 3 false positives for cancer in the cytologic study. Percutaneous cytology was able to detect 88% of patients with cancer and 83% of patients with neoplasms. False negatives for cancer (n = 5) were due to insufficient sample (2), topographic error (2) and cytology error (1). No follicular cells were obtained in 13 patients with cystic follicular adenoma and the diagnosis was missed. Surgery confirmed that 24 of 25 patients with cystic aspect on echography had a basic underlying lesion. Thus, percutaneous cytology of the thyroid is useful in the evaluation of patients with cold nodules. Main limitations of the technique are found in patients with cystic lesions and follicular neoplasms.

Adolescent↗
PubMed1990

[A giant diverticulum of the colon].

A male patient complaining of abdominal pain developed rectal bleeding and a painful mass located in the left side of the abdomen. Barium enema revealed a giant diverticulum of the colon. Surgical resection was performed successfully. A brief review of the literature follows.

Colectomy↗
PubMed1985

Adrenal rest tumor of the liver causing Cushing's syndrome: treatment with ketoconazole preceding an apparent surgical cure.

Ketoconazole, an imidazole derivative known to inhibit cytochrome P450-dependent adrenal enzymes was given to a patient with a functioning adrenal rest tumor of the liver in preparation for surgery. The drug was administered in a stepwise manner for 42 days starting with 400 mg and reaching 1 g the last 4 weeks of the trial. Clear clinical improvement was evident early in the trial and was associated with evidence of amelioration of her hypercortisolism and striking changes in serum and urinary levels of steroid hormones and metabolites. Sex steroids in serum and urine fell dramatically from the first day to the end of the trial. Urinary 17-ketosteroid excretion fell from a basal average of 139 mg/24 h to near normal levels within a week of therapy; serum testosterone fell from a basal level of 2.4 to 0.18 ng/ml; serum 17 beta-estradiol fell likewise from 1096 to 150 pg/ml. In contrast, cortisol levels in serum and urine increased in the first 2 weeks of the trial and subsequently fell to values below the basal levels. Similarly, serum 17 alpha-OH-progesterone levels increased 63% above the basal levels by day 6 of the trial and declined afterwards. Nine months after successful tumor resection the patient is apparently cured as judged by steroid hormone levels and physical appearance. We conclude that ketoconazole was effective in blocking tumoral steroidogenesis which resulted in clinical benefit.

11-Hydroxycorticosteroids↗
PubMed1984

Occult carcinoma of the thyroid gland.

Ten occult carcinomas of the thyroid gland were found in 274 unselected autopsies at the Pathology Service, Hospital José Joaquín Aguirre, between December 1980 and March 1983. This is the lowest incidence among the most recent published series. The present results suggest that environmental factors play an important role in the etiology of this type of carcinoma.

Adult↗