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Biomedical subjects

A Rastegar

Publications and source records attributed to A Rastegar.

34 records · Page 2Linked to original sources
PubMed1991

Long-lasting effects of audiogenic seizures on neurotransmitter amino acids in Rb mice.

The existence of long-lasting (15-18 h) alterations of neurotransmitter amino acid levels following a single or repeated acoustic stimulations in audiogenic seizure-prone Rb1 and Rb2 mice and seizure-resistant Rb3 mice were investigated. The levels of glutamate, aspartate, glycine, taurine, and of some of their precursors: glutamine and serine were determined. Fourteen brain areas were examined. Alterations were found only in 6 brain areas (pons, olfactory bulbs, superior colliculus, inferior colliculus, olfactory tubercles and raphe). Most frequent occurring changes were observed in pons and olfactory tubercles. These changes concerned mainly the excitatory amino acids, glutamate, and aspartate. Alterations of taurine, glycine and serine were also recorded.

Acoustic Stimulation↗
PubMed1990

Sensitive analysis of phospholipid molecular species by high-performance liquid chromatography using fluorescent naproxen derivatives of diacylglycerols.

A sensitive high-performance liquid chromatographic (HPLC) method for the separation and determination of diacylglycerophospholipid and diacylglycerol (DAG) molecular species has been developed. Phospholipids are hydrolysed with phospholipase C and the resulting DAGs are reacted with naproxen chloride in the presence of 4-dimethylaminopyridine. The naproxen-DAGs were purified by thin-layer chromatography on silica gel G plates. Molecular species were separated using reversed-phase HPLC with isocratic elution and determined by measuring the absorbance at 230 nm or fluorescence at 352 nm (excitation at 332 nm). The method was applied to the determination of diacylglycerophosphoethanolamine in rat cerebrum and cerebellum. The molar absorption coefficient of the naproxen derivatives was 53,000 lmol-1 cm-1 at 230 nm, permitting the generation of linear concentration-dependent determinations down to less than 10 pmol. A ten-fold increase in sensitivity was obtained with a fluorescence detection system owing to the fluorescent properties of the proposed adduct.

Animals↗
PubMed1990

[Effect of ceftriaxone on aerobic fecal flora in children].

Counts of aerobic faecal flora were done using serial dilutions of stools cultured on selective media in order to estimate the ecological effects of ceftriaxone. Twenty children were studied (24 courses of treatment), 17 of them with post-chemotherapy agranulocytosis. Enterobacteriaceae disappeared in all cases. After treatment, they rose again, unless another antibiotic was administered. No Pseudomonas could be found, due to the protective isolation. Streptococci D disappeared in 6 children. Staphylococcus aureus was present transiently at a low level in one case. Candida persisted in two cases at the same level in spite of antifungal therapy.

Adolescent↗
PubMed1987

[Effect of aztreonam on the fecal aerobic flora in children].

Aztreonam, a new monobactam, has a spectrum limited to Gram negative aerobic bacilli. To evaluate its effect after parenteral administration on aerobic stool flora (Gram negative bacilli, Streptococci D, Staphylococci, Candida), quantitative cultures used serial dilution of stools twice a week on selective media. For Gram negative bacilli, agar dishes containing aztreonam or not were used. Colonies of different morphologies were counted. Representatives of each morphological type were then picked for identification and susceptibility tests. Among the 16 patients treated, 12 were decontaminated for aerobic gram negative bacilli by the 3rd day. Sensitive bacteria persisted in 4 cases, although at a low level. Resistant bacteria (Enterobacter cloacae and Acinetobacter) appeared at a "normal" level in 2 patients initially decontaminated. No dramatic change could be detected for Streptococci D, Staphylococci and Candida. In twelve additional infants neither hospitalized nor treated, no aztreonam resistant Gram negative bacilli could be found.

Adolescent↗
PubMed1986

The effect of imipenem/cilastatin on the aerobic faecal flora of children.

In 18 children treated with imipenem iv, quantitative cultures for aerobic faecal flora were performed on selective media (before, when possible, during and after treatment). In ten children who had not received previous antibiotic therapy, susceptible enterobacteria could be detected at a normal level throughout treatment. Eight children had received other antibiotics beforehand; during the first week of imipenem therapy, enterobacteria were undetectable in two and at low levels in three patients. In one patient previously treated with aztreonam, a strain of Pseudomonas aeruginosa became resistant to imipenem and increased in numbers. No dramatic change could be detected in group D streptococci, staphylococci or candida. The surprisingly small effect of imipenem on faecal Enterobacteriaceae could be explained by its inconstant presence in stools at the dose administered.

Adolescent↗
PubMed1985

[Effect of an amoxicillin-clavulanic acid combination on the aerobic fecal flora in children].

Counts of aerobic fecal pathogens were done using serial dilutions of stools cultured on selective media with or without amoxicillin + clavulanic acid in 15 hospitalized pediatric patients under oral treatment with the association and in 12 non-hospitalized, non-treated controls. Susceptibility was confirmed by disk antibiotic sensitivity testing. The following microorganisms were studied: Enterobacteriaceae, Pseudomonas, Streptococci D, Staphylococci and Candida. In 8 of the 15 treated patients, Enterobacteriaceae were lacking in one sample or more, but subsequent emergence of resistant Enterobacteriaceae during treatment occurred in 4 of these cases. The 7 other treated patients were immediately colonized by resistant Enterobacteriaceae. No resistant Pseudomonas strains emerged. Streptococci D decreased in some cases. No detectable effect on Staphylococci or Candida was found. Enterobacteriaceae resistant to amoxicillin + clavulanic acid were found in 5 of the 12 controls and in 2 cases accounted for the majority of Enterobacteriaceae.

Adolescent↗
PubMed1980

Changes in membrane surfaces of collecting duct cells in potassium adaptation.

Chronic potassium loading results in an increased capacity of the distal nephron to secrete potassium. The cellular mechanism for this adaptation has been correlated to an increase in the activity of sodium-potassium-ATPase. Because adaptation may be dependent on the greater availability of potassium pumps in the basolateral membrane, a stereologic analysis of the membrane surface area was performed to determine whether the apparent increase in pump sites was due to an increase in cell membrane surface. With potssium adaptation, the number of microplicated cells in the outer medulla was reduced from 31 to 18%. There was a marked increase in the basolateral infolding of principal cells, and membrane surface increased by 32%. In papillary collecting duct cells, the basolateral membrane surface was unchanged but the surface density of the luminal membrane increased by 50%. These observations suggest that amplification of the basolateral cell membrane to increase the number of potassium pump sites per cell plays an important role in the mechanism of potassium adaptation in the outer medulla. A different mechanism involving the luminal membrane operates in the papillary collecting duct. Structural alterations in cell membrane surfaces are thus related to the regulation of the epithelial transport of electrolytes.

Adaptation, Physiological↗
PubMed1975

Long-term therapy of viramin D-resistant richets with 25-hydroxycholecalciferol.

The long-term effects of the vitamin D metabolite, 25-hydroxycholecalciferol (25-HCC), were evaluated in 2 children with hypophosphatemic vitamin D-resistant rickets. Serial total balance studies demonstrated an apparent lack of correlation between the effects of the vitamin on intestinal absorption of calcium and phosphorus and both the onset of healing in 1 of the 2 patients treated with 5,000 to 7,500 u of the metabolite and the absence of demonstrable radiologic improvement in another patient in whom the final dosage was 20,000 u. per day. At first, the metabolite induced a positive calcium balance in both patients resulting largely from a reduction in intestinal calcium excretion. Despite a continued positive calcium balance, 1 of the 2 patients did not demonstrate further healing, while in the other patient healing was noted even when total calcium balance was negative. Serum phosphate levels did not return to normal in either patient, nor was phosphate excretion altered by 25-HCC. Serum alkaline phosphatase remained elevated in both. Serum immunoassayable parathyroid hormone levels were consistently normal to high-normal in the 2 patients throughout more than 24 months of observation. No instances of hypercalcemia and only occasional hypercalciuric episodes were noted.

Alkaline Phosphatase↗
PubMedDate not supplied

Lactic acidosis in the setting of antiretroviral therapy for the acquired immunodeficiency syndrome. A case report and review of the literature.

Type B lactic acidosis, a rare but often fatal disorder, has been reported in 21 AIDS patients on antiretroviral therapy (ART). We present an AIDS patient with severe and prolonged lactic acidosis on stavudine and lamivudine. The lactic acidosis occurred in the absence of mitochondrial myopathy, hepatomegaly, or liver failure. This is the second report of lactic acidosis in a patient on stavudine and lamivudine. This patient recovered after aggressive supportive therapy including intravenous alkali and fluid administration as well as continuous venovenous hemodiafiltration. A single dose of dichloroacetate (DCA) was associated with a decrease in the serum lactate level by 20%, which persisted for more than 24 h. Seventeen months after recovery, the patient was rechallenged with ART without recurrence of lactic acidosis. We review and summarize all reported cases of patients with ART-associated lactic acidosis reported in the English literature.

Acidosis, Lactic↗
PubMedDate not supplied

Effects of calcium channel blockers on potassium homeostasis.

The known effects of calcium channel blockers on various aspects of potassium homeostasis are reviewed. Regulation of potassium homeostasis requires both renal and external handling mechanisms. Signaling by calcium appears to mediate both of these. Calcium channels have been identified in adrenal glomerulosa cells, and cellular calcium entry has been demonstrated in vitro to be necessary for the synthesis and secretion of aldosterone. Calcium channel antagonists such as verapamil and nifedipine, at pharmacologic doses, can block aldosterone production. In vivo, however, only chronic administration of verapamil appears to attenuate aldosterone responsiveness to angiotensin II. Chronic administration of nifedipine does not have a dramatic effect on aldosterone production following potassium loading. Other studies have demonstrated improved extrarenal potassium disposal following treatment with calcium channel blocking agents. Clinically, there are no reports of either hyperkalemia or hypokalemia with the routine therapeutic use of these agents given alone. This review was prompted by the development of hyperkalemia in a patient with chronic renal failure following the initiation of therapy with the calcium channel blocker diltiazem: however, numerous other etiologies may also have contributed to the development of hyperkalemia in this case. Review of the data indicates that current evidence implicating this class of drugs in the pathogenesis of disordered potassium regulation remains equivocal.

Adrenal Cortex↗