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Biomedical subjects

R Zeman

Publications and source records attributed to R Zeman.

17 recordsLinked to original sources
PubMed1996

Promoter elements and second messenger pathways involved in transcriptional activation of tyrosine hydroxylase by ionomycin.

Membrane depolarization, or agents which increase intracellular calcium, elicit transcriptional activation of tyrosine hydroxylase (TH). In this study we analyze the factors involved in the regulation of the TH promoter by a calcium ionophore. PC12 cells were transiently transfected with plasmids containing wild type or mutated 5' flanking sequences of the rat TH gene, fused to bacterial chloramphenicol acetyl transferase (CAT). Point mutations introduced into the consensus cAMP-regulatory element (CRE) abolished the induction of CAT by ionomycin indicating that it is essential for mediating the calcium response. An intact and functional AP1 site did not confer calcium inducibility when the CRE/CaRE sequence was mutated. The extent and kinetics of the increase in intracellular calcium as well as the induction of CAT activity under the control of TH promoter by ionomycin were similar in PC12 cells and in the A123.7, protein kinase A (PKA) deficient cell line. In both cell lines addition of ionomycin rapidly increased the phosphorylation of transcription factor CREB at Ser-133. These results suggest that the activation of TH transcription by ionomycin does not require PKA. However, KN62 an inhibitor of Ca2+/calmodulin dependent (CaM) kinases prevented the induction indicating possible involvement of CAM kinases in the calcium response.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1996

Involvement of intracellular or extracellular calcium in activation of tyrosine hydroxylase gene expression in PC12 cells.

The relationship between elevations in intracellular free Ca2+ concentration ([Ca2+]i) by different mechanisms and tyrosine hydroxylase (TH) gene expression was examined. Depolarization by an elevated K+ concentration triggered rapid and sustained increases in [Ca2+]i from a basal level of approximately 50 to 110-150 nM and three- to fourfold elevations in TH mRNA levels, requiring extracellular calcium but not inositol 1,4,5-trisphosphate (IP3). On the other hand, bradykinin or thapsigargin, both of which induce release of intracellular calcium stores via IP3 or inhibition of Ca(2+)-ATPase, rapidly elevated [Ca2+]i to > 200 nM and increased TH gene expression (three-to fivefold). Confocal imaging showed that the elevations in [Ca2+]i in each case occurred throughout the cyto-and nucleoplasm. The initial rise in [Ca2+]i due to either bradykinin or thapsigargin, which did not require extracellular calcium, was sufficient to initiate the events leading to increased TH expression. Consistent with this, the effects of bradykinin on TH expression were inhibited by 1, 2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid or 3,4,5-trimethoxybenzoic acid 8-(diethylamino)-octyl ester which chelates or inhibits the release of intracellular calcium, respectively. Bradykinin required a rise in [Ca2+]i for < 10 min, as opposed to 10-30 min for depolarization to increase TH mRNA levels. These results demonstrate that although each of these treatments increased TH gene expression by raising [Ca2+]i, there are important differences among them in terms of the magnitude of elevated [Ca2+]i, requirements for extracellular calcium or release of intracellular calcium stores, and duration of elevated [Ca2+]i, indicating the involvement of different calcium signalling pathways leading to regulation of TH gene expression.

Animals↗
PubMed1996

[The dipeptide L-alanyl-L-glutamine--its preparation and therapeutic use].

L-glutamine, representing one of the principal sources of nitrogen for the organism, can be used in infusion solutions employed in clinical nutrition in the form of the dipeptide L-alanyl-L-glutamine. It can be prepared with the use of biotechnological methods, viz. the enzymic synthesis of the peptide, and fermentation preparation of L-glutamine and the proteases catalyzing the formation of the peptidic bond. Suitable producers of amino acids and enzymes are microorganisms (both bacteria and fungi). The procedures used in the preparation of the components as well as the dipeptide itself are a combination of biotransformations and fermentations.

Bacteria↗
PubMed1995

Safety and effectiveness of Lithostar shock tube C in the treatment of urinary calculi.

Over 14 years of clinical use of extracorporeal shockwave lithotripsy (SWL), great technical modifications resulted in the development of many second-generation lipthotripters. The Siemens Lithostar machine, with its standard shockwave tube, was introduced in 1986. The objective of this study was to assess the safety and effectiveness of the newly proposed Lithostar shock tube C in the treatment of urinary calculi. Between July 1992 and August 1993, 319 patients (214 males and 105 females, average 49.7 years) with 433 renal or ureteral stones or both were treated at five centers in Canada and the United States. Most of the stones (72%) were located in the kidneys, while 28% were located in the ureters. Most (81%) of the treated sides (side = kidney and ureter) presented with single stones, 11% presented with two stones, and 8% presented with three or more stones. The average stone burden was 13.6 mm. The average duration of treatment for the whole population of patients was 39.3 minutes using an average number of shockwaves of 3633 in a minimum and maximum energy setting of 0.11 and 3.82, respectively. The majority of treatments (92%) were performed without anesthesia. Fragmentation was achieved in 93.5% of treatments, with a 3-month stone-free rate of 62.5% and a success rate (stone free or fragment < 5 mm) of 72%. Auxiliary procedures were necessary in conjunction with 108 treatments, and most of them were in form of catheter/stent placement. Treatment applied on a separate occasion to different stones but in the same collecting system (either a kidney or a ureter) were considered retreatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

The use of single photon emission computerized tomography in neuropsychiatric SLE: a pilot study.

OBJECTIVE: To test the sensitivity of single photon emission computerized tomography (SPECT) in detecting brain abnormalities in cases of definite active neuropsychiatric systemic lupus erythematosus (NPSLE) in a blinded, prospective pilot study. METHODS: Fourteen patients fulfilling at least 4 of the American College of Rheumatology criteria for the classification of SLE plus positive serology manifested by either elevated DNA binding or decreased serum complement and a recent neuropsychiatric event were evaluated with cerebral SPECT using hexa-methyl-propylene-amine-oxime labeled 99Tc. Secondary causes such as infection, uremia, hypertension, drugs, and metabolic abnormalities were excluded. Patients underwent brain scan and electroencephalogram (EEG) for comparison. When clinically indicated, CT scan, magnetic resonance imaging, angiography, and lumbar puncture were performed. RESULTS: SPECT scan abnormalities were noted in 12/14 patients and brain scan was abnormal in 12/14 patients. SPECT and brain scan were in accordance in 12/14 patients (11 patients both positive and 1 both negative) and the combination of SPECT and brain scan yielded 13/14 positive results. In the 3 patients with headache, SPECT scan was negative in 2/3, despite positive EEG and one with a positive brain scan. The positive SPECT in the patient with headache showed an old cerebrovascular accident (CVA), which was confirmed by CT scan. The most consistent CT finding was cortical atrophy; however, SPECT identified a lesion in the occipital cortex in a patient with seizure, and a lesion in the basal ganglia in a patient with ataxia. CONCLUSION: In clinically and serologically active NPSLE, SPECT is a sensitive diagnostic tool. When further stratifying NPSLE into focal (seizure, ataxia, CVA) and diffuse (headache, organic brain syndrome, psychosis), SPECT appeared to be sensitive for focal disease and for most diffuse manifestations, with the exception of headache. The high sensitivity of SPECT in patients with true, positive NPSLE merits further controlled studies in unselected patients with SLE.

Adult↗
PubMed1993

Nicotine increases expression of tyrosine hydroxylase gene. Involvement of protein kinase A-mediated pathway.

Nicotine, a major component of tobacco smoke, stimulates catecholamine secretion and activates catecholamine biosynthetic enzymes such as tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) in adrenal medullary cells. We investigated the effect of long term treatment with nicotine on TH and DBH gene expression in rat PC12 pheochromocytoma cells. Nicotine treatment for 1-2 days increased both the TH and DBH mRNA levels. The effect of nicotine on TH mRNA seems to be transcriptionally mediated. Deletion analysis of the 5' promoter region of the TH gene showed that the region containing a cyclic AMP/calcium regulatory element is sufficient for the nicotinic induction of TH. Nicotine did not induce TH mRNA or chloramphenicol acetyltransferase reporter activity in mutant PC12 cells deficient in protein kinase A activity. However, the deficiency in protein kinase A activity did not affect the elevation in intracellular calcium concentration caused by nicotine, indicating normal receptor function. These results suggest that a cAMP-mediated pathway plays a crucial role in the long term nicotine-induced activation of the TH gene.

Animals↗
PubMed1991

Cell aggregates of Escherichia coli with benzylpenicillin amidase activity.

Intact cells Escherichia coli CCM 2843, exhibiting substantial benzylpenicillin amidase activity, were bound mutually with supporting waste microbial cells, native or treated, to obtain an inexpensive biocatalyst for the production of 6-aminopenicillanic acid (6-APA). The bond was effected by glutaraldehyde (GA) and Sedipur CL-930 (PEI), without any carrier. The optimal concentration of GA was 2%, that of PEI 1%. The optimal biocatalyst was obtained by immobilization of productive cells with their fragments at a mass ratio of 4:1. The cell aggregates were used for hydrolysis of potassium benzyl-penicillin at a concentration of 5% to 6-APA. After 25 repeated batch conversions the degree of conversion did not decrease; its average value was 96.4%.

Bacterial Adhesion↗
PubMed1990

Enzyme synthesis of L-tryptophan.

Enzyme synthesis of tryptophan from indole, pyruvate and ammonium salts was studied using Escherichia coli cells exhibiting a significant tryptophanase activity. In addition to the effect of cultivation medium composition and cultivation conditions, factors affecting the course of the conversion were investigated. Production of 32.4 g/L of L-tryptophan was reached after 48 h under optimal conditions.

Acetates↗
PubMed1987

Radiotherapy in the management of pancreatic islet cell tumors.

Malignant islet cell tumors are commonly treated with surgical resection. Chemotherapy is reserved for residual, unresectable, or metastatic disease. The role for radiotherapy has not been clearly defined. This article describes three cases of advanced islet cell tumors treated effectively with radiotherapy. This experience, in addition to that from other published reports, suggests that radiotherapy is a useful mode for treating advanced islet cell carcinoma.

Adenoma, Islet Cell↗
PubMed1980

Ultrasound demonstration of anicteric dilatation of the biliary tree.

This report presents eight patients with dilatation of the biliary tree, six of whom had no clinical or laboratory evidence of biliary tract disease except for elevated levels of serum alkaline phosphatase. In two patients, dilatation was caused by obstruction of only one hepatic duct; in three, it was caused by a pancreatic tumor; and in three, it was associated with gallstones which exercised a ball-valve effect, producing intermittent obstruction. The elevation of the alkaline phosphatase level in six of these patients suggests that it is a more sensitive indicator of biliary tract obstruction than the serum bilirubin level is. The recognition of biliary dilatation in one or both lobes of the liver should lead to a careful examination, with ultrasound or another modality, of the porta hepatis, common bile duct, and pancreas.

Aged↗