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Biomedical subjects

G A Qureshi

Publications and source records attributed to G A Qureshi.

At least 19 recordsLinked to original sources
PubMed2001

Polyamines as cancer markers: applicable separation methods.

Spermine, spermidine, putrescine and cadaverine are aliphatic amines widely spread in the human body. Their concentrations together with their acetyl conjugates increase significantly in the biological fluids and the affected tissues of cancer patients. Their concentrations decrease with the improvement in the patient's condition on multiple therapy. Various chromatographic techniques are frequently used in monitoring concentrations of di- and polyamines in cancer. Among these techniques, thin-layer chromatography and liquid chromatography using pre- or postcolumn derivatization, separating on a reversed-phase or an ion-exchange column are the most commonly used. Besides, high-resolution capillary column gas chromatography (GC) is increasingly used over packed column GC, and in recent years, capillary zone electrophoresis has also gained some importance in polyamine determinations. The review examines the prospects and the limitations of polyamines as cancer markers using chromatographic and electrophoretic techniques.

Biogenic Polyamines↗
PubMed1998

The neurochemical markers in cerebrospinal fluid to differentiate between aseptic and tuberculous meningitis.

In this study, the use of neurochemical markers in patients with aseptic and tuberculous meningitis has been investigated. The cerebrospinal fluid levels of amino acids, nitrite (a metabolite of nitric oxide), vitamin B12 and homocysteine were quantitated in both groups of patients. Among the amino acids, aspartic acid and glutamic acid both excitatory amino acid, GABA, glycine and tryptophan were all significantly increased in both patient groups whereas decreased level of taurine and increased level of phenylalanine were only found in patients with tuberculous meningitis. The levels of nitrite and its precursor arginine were significantly higher in patients with tuberculous meningitis whereas unchanged levels were found in patients with aseptic meningitis. A significantly increased homocysteine level and a decreased level of vitamin B12 were found only in patients with tuberculous meningitis whereas unchanged levels were found in patients with aseptic meningitis. This indicates that patients with tuberculous meningitis are particularly prone to vitamin B12 deficiency resulting into increased level of HC, and involvement of free radical showing the importance of these biological markers for promoting the possibility for the design of therapeutic approach.

Adult↗
PubMed1997

Cholecystokinin peptides in cerebrospinal fluid: a study in healthy male subjects.

The clinical reliability of measuring cholecystokinin (CCK) peptides in the cerebrospinal fluid (CSF) has not been fully elucidated. Therefore, we have assayed CCK-8S and CCK-4 in CSF obtained from 14 healthy male subjects, lumbar-punctured at the L4-5 level following a strictly standardised procedure. CSF concentrations of free CCK-8S and free CCK-4 were used as dependent variables while age, height, body weight, atmospheric pressure and some other factors served as independent variables. It was shown that the CCK-8S ratio between the second (7-12 ml) and first (0-6 ml) CSF fractions, correlated significantly with the atmosphere pressure at the time of puncture. Neither CCK-8S nor CCK-4 displayed concentration gradients in CSF. The CCK-4 levels, expressed as pmol l-1 in the total amount of CSF were found to be positively correlated with the neuraxis distance in the lying position and negatively with the neuraxis distance in the sitting position. Furthermore, CCK-4, expressed as pmol l-1 per min of tapping-time (pmol l-1 min-1), showed a negative correlation with storage time, presumably mirroring a proteolytic process. CCK-8S and CCK-4 intercorrelated positively independently of whether expressed as pmol l-1 or pmol l-1 min-1. In conclusion, the results of this exploratory study indicate that the neuraxis distance (in the sitting and lying positions) and storage-time have to be accounted for when interpreting data on CSF levels of CCK-4. Attention has to be paid to the potential influence of atmospheric pressure on the concentration ratio of CCK-8S.

Adult↗
PubMed1995

Increased cerebrospinal fluid concentration of nitrite in Parkinson's disease.

The concentration of nitrite, a metabolite of nitric oxide (NO), was increased in the cerebrospinal fluid (CSF) of untreated patients with Parkinson's disease and in patients treated with L-DOPA in comparison with a group of patients without dopaminergic dysfunction. There was no difference in the concentration of L-arginine (ARG), a precursor of NO, between the groups. There was a highly significant, linear relationship between the concentration of nitrite and ARG in the CSF suggesting that the production of NO is dependent on the availability of ARG. The results support the possibility that production of NO is increased in the brain in Parkinson's disease.

Aged↗
PubMed1995

Inhibition of serotonin synthesis attenuates inhibition of ingestive behavior by CCK-8.

Ingestive behavior was activated in male rats by intraoral infusion of a 1-M solution of sucrose. Injection of cholecystokinin octapeptide (CCK-8; 1.6 or 5.0 micrograms) inhibited ingestion of the sucrose solution and increased the concentration of 5-hydroxytryptamine (5-HT) in the paraventricular hypothalamic nuclei. The inhibitory effect of the low, but not the high, dose of CCK-8 was attenuated by depleting 5-HT in the brain with p-chlorophenylalanine (PCPA; 100 mg/kg for 3 days). Treatment with 5-hydroxytryptophan (20 mg/kg) increased the concentration of 5-HT in the brain of rats pretreated with either NaCl or PCPA and enhanced the inhibitory effect of CCK-8 on ingestive behavior in the PCPA-, but not NaCl-, treated rats. 5-HT may play a role in the mechanism of action of CCK-8 but additional factors must be involved.

5-Hydroxytryptophan↗
PubMed1995

Nitric oxide synthase pathway may mediate human natural killer cell cytotoxicity.

The present study provides evidence that the human natural killer (NK) cell effector mechanism causing target cytolysis has a requirement for L-arginine. In a deficient medium (DM) containing only salts, buffer system and glucose, NK cell-mediated cytotoxicity was found to decrease by 70% as compared to that obtained in a complete medium (CM). However, adding L-arginine to such DM could restore the activity of NK cells to the normal level. Many other components of CM, such as serum, glutamine and vitamins did not improve NK cell-mediated killing in DM. When all amino acids except L-arginine were added to DM only a partial recovery of NK cell functional cytolysis was seen. L-arginine enhanced the NK cell activity in a dose-dependent manner. Additionally, the inhibitor of both inducible and constitutive nitric oxide synthase, N-monomethyl-L-arginine (L-NMMA) inhibited NK cytolytic activity in DM supplemented with L-arginine indicating participation of nitric oxide (NO). The results also show that the stimulatory effect of L-arginine on human NK cell-mediated cytotoxicity was accompanied by an increase in NO formation as determined by accumulation of nitrite and citrulline. L-NMMA gave a dose-dependent reduction in NO generation as well. The nitrite and citrulline production dose-dependently correlated with not only the concentration of L-arginine in the cultivation medium, but also the enhanced NK cell-mediated cytolysis. Taken together, these findings could define a L-arginine/NO-linked effector mechanism in human NK cells. Nitrite and citrulline were not formed when NK cell-mediated target cell killing took place in a L-arginine-free DM supplemented with additives. Thus, it appears as if human NK cells may cause target cell killing via both NO-dependent and -independent processes.

Arginine↗
PubMed1995

Diet-independent suppression of ingestive behavior by cholecystokinin octapeptide and amino acids.

Male rats consumed much more of an intraorally administered mixed protein, fat and carbohydrate solution than of a carbohydrate solution. Injection of cholecystokinin octapeptide (CCK-8, 0.6-5.0 microgram) suppressed intake of both solutions, but the CCK-A receptor antagonist L-364, 718 (20-40 micrograms) facilitated only carbohydrate intake. Blood levels of CCK-8 were higher after intake of the carbohydrate than the mixed solution. Blood levels of isoleucine, leucine, lysine, threonine, valine, and tryptophan increased only after intake of the mixed solution. Injection of these amino acids suppressed intake of both solutions. Blood levels of amino acids were also less after the seventh than after the first session ingesting the mixed solution. Treatment with CCK-8 or amino acids inhibits intake of any diet, but when secreted endogenously, these signals may terminate the meal in a diet-dependent manner.

Amino Acids↗
PubMed1995

Dopamine D1 or D2 antagonists enhance inhibition of consummatory ingestive behavior by CCK-8.

A dopamine D1 (SKF-38393, 1 mg)- or D2 (LY-171555, 0.1 mg)-receptor agonist inhibited intake of an intraorally infused solution of sucrose by male rats, a test of consummatory ingestive behavior. Treatment with a D1 (SCH-39166, 0.1 mg) or D2 (raclopride, 0.6 mg) antagonist reversed inhibition by the respective agonist but enhanced the inhibitory effect of cholecystokinin octapeptide (CCK-8; 1.8 micrograms). It was not possible to demonstrate specific effects of D1 and D2 agonists on intake of pellets, a test that does not discriminate consummatory ingestive behavior from appetitive ingestive behavior, i.e., behavior used to obtain food. The results demonstrate specific involvement of dopamine D1 and D2 receptors in inhibition of consummatory ingestive behavior.

Animal Feed↗
PubMed1994

Glutamate inhibits ingestive behaviour.

Male rats treated with reserpine were motionless and ingested only a few of ten consecutive intraoral injections of a 1 M solution of sucrose. While injection of apomorphine, a dopamine agonist, stimulated locomotion and stereotyped sniffing in reserpinized rats, it did not reactivate ingestive responses. The non-competitive N-methyl-D-aspartate receptor antagonist MK801, however, stimulated locomotion as well as ingestion suggesting involvement of glutamate in the suppressive effect of resperpine on ingestive responses. A series of experiments was therefore undertaken to investigate the possible physiological role of glutamate in feeding. For this purpose, we used Grill's intraoral intake test, in which the rat is infused intraorally with a sucrose solution and the amount ingested measured. In untreated rats, MK801 dose-dependently facilitated ingestion of the sucrose solution and antagonized inhibition of ingestion by cholecystokinin octapeptide. Administration of cholecystokinin octapeptide or ingestion of sucrose increased the concentration of glutamate in the nucleus of the solitary tract, a brain stem relay transmitting sensory information from the gastrointestinal tract to the forebrain. MK801 was found to bind specifically to this brain area and block the elevation of glutamate and dopamine levels which occurred after treatment with cholecystokinin octapeptide in this neural site. Together these data suggest that dopamine and glutamate may interact within the nucleus of the solitary tract in controlling ingestive behaviour.

Animals↗
PubMed1993

Brain cholecystokinin tetrapeptide levels are increased in a rat model of anxiety.

Rats exposed to the smell of a predator adopted the freezing posture indicative of anxiety. Correlatively, the concentration of cholecystokinin tetrapeptide (CCK-4) was increased in the olfactory bulb, frontal and central cortex, dorsal and ventral striatum, central amygdala and the nucleus of the solitary tract. The concentration of CCK-8 was increased only in the ventral striatum. Glutamate was increased in the cortex and the striatum and dopamine was increased in the cortex. Intraperitoneal injection of CCK-4 increased brain levels of CCK-4 and replicated, in part, the behavioural effect of the smell of the predator. Injection of a CCK-B-receptor antagonist had the opposite behavioural effect. The results support a role for CCK-4 in anxiety.

Animals↗
PubMed1993

The role of tryptophan, 5-hydroxy indole-3-acetic acid and their protein binding in uremic patients.

An on-line high performance liquid chromatography (HPLC) method of analysis with electrochemical detection was developed to quantitate catecholamines, tryptophan (Trp) and 5-hydroxy indoleacetic acid (5-HIAA) in muscle and plasma samples from healthy subjects and uraemic patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Equilibrium dialysis was performed on the plasma samples from 14 healthy and 14 uraemic subjects for the separation of free Trp and its metabolites from bound Trp. The results demonstrate abnormal Trp-albumin binding probably with accumulation of indolic metabolites and abnormally high muscle Trp concentration in uraemic patients.

Adult↗
PubMed1993

Application of high performance liquid chromatography in study of sulphur amino acid metabolism in uremic patients.

High-performance liquid chromatography (HPLC) was used for the quantitation of the free amino acids in plasma and muscle samples from 34 patients with chronic renal failure; of these patients, 18 were treated by hemodialysis (HD) and 16 by continuous ambulatory peritoneal dialysis (CAPD). Depletion of taurine was observed in plasma and muscle of uremic patients, whereas methionine was normal. Cysteine sulphinic acid was present in plasma of all uremic patients. The results suggest that taurine depletion is due to decreased endogenous synthesis in uremic patients.

Aged↗
PubMed1992

Influence of a meat-free diet on the urinary excretion of 3-methylhistidine and creatinine in chronic renal failure.

Urinary excretion of 3-methylhistidine has been proposed as an index of internal protein breakdown provided that the intake of exogenous 3-methylhistidine (meat) is excluded. To evaluate the potential use of 3-methylhistidine in the metabolic assessment of patients with advanced renal failure, we studied a group of 11 patients with markedly reduced renal function who were put on a meat-free diet (the protein intake was kept constant). Steady-state plasma concentration and urinary excretion of 3-methylhistidine were not achieved until 14 d after exclusion of meat from the diet. At that time the plasma concentration and urinary excretion of 3-methylhistidine had decreased by 43% and 60%, respectively. We conclude that the delay in reaching steady state makes the clinical use of urinary excretion of 3-methylhistidine in patients with advanced renal failure unpracticable as an index of protein breakdown. The exclusion of meat also resulted in a continuous decrease in the plasma level and urinary excretion of creatinine, with the result that plasma creatinine or its reciprocal become misleading for evaluation of changes in renal function until a new steady state has been reached.

Adult↗
PubMed1991

High performance liquid chromatography as a tool in the definition of abnormalities in monoamine and tryptophan metabolites in cerebrospinal fluid from patients with neurological disorders.

In this study we report the levels of 3-methoxy-4-hydroxyphenylglycol, 3,4-dihydroxyphenylacetic acid, homovallinic acid, tryptophan, 5-hydroxyindole-3-acetic acid and serotonin in lumbar cerebrospinal fluid (CSF) from patients with multiple sclerosis, cerebrovascular disease and muscular tension headache the later, as healthy controls. The separation of these substances was performed on a reversed phase column by ion pair high performance liquid chromatography and detection was made by a glassy carbon electrode set at +900 mV vs Ag+/AgCl. The whole separation was achieved within 25 min. Concentrations of all substances (10-1000 pmole/L) were linearly proportional to areas obtained. The system is sensitive, stable and reproducible. The significance of CSF levels of these metabolites from patients groups compared with healthy controls are discussed.

Biogenic Amines↗
PubMed1991

Use of high performance liquid chromatography in defining the abnormalities in the free amino acid patterns in the cerebrospinal fluid of patients with aseptic meningitis.

Free amino acids were quantitatively determined in cerebrospinal fluid (CSF) and plasma samples from patients with aseptic meningitis by a newly developed high performance liquid chromatographic (HPLC) method. The method of analysis was based on precolumn derivatization of orthophthaladehyde in the presence of 2-mercaptoethanol and detection was made at Eex = 340 nm and Eem = 450 nm. The method was sensitive and the limit for detection was less than 1 pmol for most of the amino acids. It took 45 min to separate 26 amino acids with highly reproducible results, giving a coefficient of variance for retention times and integrated areas less than 0.4% and 2%, respectively, after five replicate runs. The results accumulated in 10 patients were compared statistically with 11 age-matched healthy controls. Among the amino acids almost all the neurotransmitter candidates, such as aspartic acid, glutamic acid, glutamine, glycine, tyrosine, phenylalanine and gamma-aminobutyric acid (GABA), were significantly increased in the patients' CSF, whereas arginine and threonine were low. No change was observed in plasma amino acids in patients as compared to healthy controls. The higher levels of most of the neurotransmitters, especially GABA, aspartic acid and glutamic acid, could be used diagnostically in assessing the progression and remission in aseptic meningitis.

Adult↗
PubMed1989

Determination of free amino acids in biological samples: problems of quantitation.

An automatic on-line high-performance liquid chromatographic method was developed to study the effects of various precipitating agents and delayed deproteinization procedures on the estimation of plasma levels of amino acids. The optimized method for analysis is based on pre-column derivatization with o-phthalaldehyde in the presence of 2-mercaptoethanol. The separation of 25 amino acids is accomplished within 45 min on a 5-microns C18 column, using a multi-step gradient with two solvents. The method is sensitive and reproducible, and the relationship between the fluorescence intensity and concentration is linear for each amino acid over a wide concentration range.

Adult↗
PubMed1989

Tryptophan, 5-HTP, 5-HT and 5-HIAA in the cerebrospinal fluid and sexual behavior in male rats.

No changes were found in the concentration of tryptophan (Trp), 5-hydroxytryptophan (5-HTP), 5-hydroxytryptamine (5-HT) or 5-hydroxyindole acetic acid (5-HIAA) in the cerebrospinal fluid (CSF) of male rats either before sexual activity, immediately after ejaculation of after the postejaculatory refractory period (PEI). Injection of the Trp hydroxylase inhibitor p-chlorophenylalanine (PCPA, 25 or 100 mg/kg i.p. for 3 days) in combination with an injection of the monoamine oxidase inhibitor pargyline (100 mg/kg i.p.) increased the concentration of Trp while decreasing the concentration of 5-HTP, 5-HT and 5-HIAA in the CSF. Furthermore 100 (but not 25) mg/kg PCPA in combination with pargyline caused a significant reduction in the latency to ejaculation. Injection of probenecid (200 mg/kg i.p.), an inhibitor of the transport of 5-HIAA from the CSF, increased the concentration of 5-HIAA in the CSF and slightly prolonged the latency to ejaculation. Sexual activity caused no further increase in CSF 5-HIAA levels in the probenecid-treated rats. Since drug-induced changes in sexual behavior are associated with marked alterations in 5-HT metabolism in the CSF, whereas the changes in the behavior which occur normally are not, these results question the physiological significance of the proposed inhibitory role of 5-HT in male rat sexual behavior.

5-Hydroxytryptophan↗