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Biomedical subjects

C Prasad

Publications and source records attributed to C Prasad.

At least 91 records · Page 5Linked to original sources
PubMed1992

An antibody to dopamine D2 receptor inhibits dopamine antagonist and agonist binding to dopamine D2 receptor cDNA transfected mouse fibroblast cells.

A polyclonal antibody to dopamine D2 receptor (D2-receptor) has been used to examine the immuno-inhibition in the binding of a D2 antagonist, [3H]YM09151-2 and an agonist, PPHT-fluorescein to dopamine receptor DNA transfected mouse fibroblast cells. The specific activity of the [3H]YM09151-2 binding to transfected (Ltk-RGB) cells is 4-5 fold higher than untransfected (Ltk-) cells. The antibody is able to inhibit the [3H]YM09151-2 binding to the cell membranes from Ltk-RGB cells (Bmax 110.56 +/- 5.26 and 76.20 +/- 5.18 fmoles/mg protein in the presence of preimmune and immune sera, respectively, with no change in the Kd). The flow cytometric analysis of the PPHT-fluorescein labeled Ltk- and Ltk-RGB cells indicated that ligand specific fluorescence is associated only with small Ltk-RGB cells (second peak) and autofluorescence with large cells (first peak). Preincubation of the Ltk-RGB cells with antibody, reduced the fluorescence intensity of the PPHT-fluorescein by 20-25% without changing the auto-fluorescence. These results suggest that peptide antibody recognize D2-receptor in both membranes and in intact cells and interact at or near the ligand binding site of the receptor.

Animals↗
PubMed1992

Resistance to insulin-induced hyperphagia in fat-preferring rats.

Outbred male Sprague-Dawley rats were screened for their macronutrient (fat, carbohydrate and protein) preference profile and divided into two groups, the low- and high fat-preferring groups each deriving 23% and 72% of its total caloric intake from fat respectively. Subcutaneous administration of bovine insulin (6U/kg) resulted in an increase in total caloric intake in the low, but not the high fat-preferring group. Furthermore, the increased caloric intake in the low fat-preferring group was entirely due to increased carbohydrate consumption. These data suggest a defect in the action of insulin in fat-preferring rats.

Animals↗
PubMed1992

Transient decrease in rat striatal D2 dopamine receptor mRNA level after acute haloperidol treatment.

Acute haloperidol administration decreases the number of rat striatal D2 dopamine receptor (D2-receptor). The potential involvement of decreased D2-receptor gene transcription in the above process was examined using Northern blot analysis. There was a dose- and time-dependent transient decrement in the level of striatal D2-receptor mRNA after haloperidol. The decrease in transcription may be mediated via blockade of D2-receptor, since S(-)-sulpiride but not the inactive enantiomer R(+)-sulpiride produced the inhibition.

Animals↗
PubMed1992

Food contains the bioactive peptide, cyclo(His-Pro).

Cyclo(His-Pro) (CHP) is a cyclic dipeptide with numerous biological activities. As small di- and tripeptides may be absorbed intact when ingested orally, we were interested in examining several common foods for the presence of cyclo(His-Pro)-like immunoreactivity (CHP-LI). In all foods tested, CHP-LI was found at levels 5-1500 times those previously found in human plasma. This CHP-LI was identical to authentic CHP by immunoidentity and chromatographic behavior. We conclude that 1) CHP-LI is readily detectable in several common food sources; 2) this CHP-LI is indistinguishable from authentic CHP; and 3) it is likely the CHP-LI in foods is absorbed in quantities sufficient to cause elevations of CHP-LI in plasma to biologically significant levels.

Chromatography↗
PubMed1991

Attenuation of pulsatile changes in the density of striatal [3H]GBR-12935 binding sites during chronic ethanol consumption.

Using [3H]GBR-12935 as a selective ligand, we have examined the properties of rat striatal dopamine transporter complex during chronic ethanol consumption. The results of this study show a significant change in the Bmax (maximal binding capacity), but not Kd (affinity) of [3H]GBR-12935 binding sites. The observed changes were pulsatile and they exhibited an increase (144% of control), decrease (80% of control), tendency to increase (111% of control), increase (141% of control), decrease (84% of control), no change (98% of control), and decrease (80% of control) after 1, 2, 3, 4, 6, 8 and 10 weeks of ethanol consumption, respectively. Since the duration of ethanol exposure appears to be an important variable in regulating the properties of dopamine transporter complex, the behavioral changes observed during chronic ethanol intake may vary with time.

Alcoholism↗
PubMed1991

Motor, but not sensory, cortical potentials are amplified by high-protein diet.

Animals fed a high-protein diet (50% casein) are hyperactive and more responsive to nociceptive stimuli than those fed either a normal- or low-protein diet. The mechanisms mediating dietary protein-induced behavior are unknown and may include both central and peripheral neural effects. Adult, Sprague-Dawley rats were fed 50% casein (treatment group) and 24% casein (control group) ad lib for 36-40 weeks. The animals were anesthetized with alpha-chloralose and urethane (50 mg/kg and 1.5 mg/kg, IP). EEG recordings were averaged while the anesthetized animal was conditioned using an alerting stimulus-imperative stimulus (AS-IS) paradigm. AS consisted of a 1.5 kHz, 90 dB tone cue. This was followed 2 seconds later by IS, an electrical tail stimulation (11 V, 1.4 s duration). Two negative deflections (N1 and N2) were generated by the frontal cortex during the AS-IS interstimulus interval. N1, an alerting response, was not different between the two groups. N2 amplitude and peak latency were significantly increased in the high-protein group (205% and 117% of control, respectively; p less than 0.05). N2 represents the activation of cells in the motor cortex. Brainstem auditory-evoked responses and somatosensory-evoked potentials also were recorded, but no differences were observed between the two diet groups. These data suggest that consumption of a high-protein diet results in an increase in central arousal mechanisms (measured by cortical negativity response), specifically involving increased excitability of the motor cortex, that is not associated with a disorder of information processing in the cerebral cortex (measured by brainstem auditory-evoked responses and somatosensory-evoked potentials).

Animals↗
PubMed1991

Could dietary proteins serve as cyclo(His-Pro) precursors?

Cyclic dipeptides or diketopiperazines are readily generated during in vitro hydrolysis of proteins and polypeptides. This led us to examine whether cyclo(His-Pro) (CHP), a diketopiperazine containing histidine and proline, could be formed in vivo from dietary proteins. The data presented here show that at least in rat, neither urinary nor plasma concentration of CHP is elevated by consumption of a diet rich in proteins. Several dietary supplements derived from casein and/or soy protein hydrolysates, however, contain high levels of CHP-LI. Oral intake of one such supplement led to a sharp increase in the plasma level of CHP-LI.

Animals↗
PubMed1991

Increased cerebrospinal fluid cyclo(His-Pro) content in schizophrenia.

Cyclo(His-Pro) (CHP) is a peptide endogenous to human brain and cerebrospinal fluid (CSF). In animal studies administration of exogenous CHP augments dopaminergic neurotransmission. To explore the role of this peptide in schizophrenia, a disease characterized by a hyperdopaminergic state, we have measured CSF CHP levels in control, never-medicated schizophrenics and medicated schizophrenics. Our data show a 53% increase in CSF levels of CHP in never-medicated schizophrenics (p = 0.015), and a 25% increase in medicated schizophrenics when compared to controls. We speculate that CHP may contribute to the expression of hyperdopaminergic symptoms in schizophrenia.

Adult↗
PubMed1991

Relationship between [3H]mazindol binding to dopamine uptake sites and [3H]dopamine uptake in rat striatum during aging.

Certain drugs exhibit a remarkable correlation between their ability to inhibit synaptosomal uptake of dopamine and the binding of [3H]mazindol to striatal membranes. To investigate the role of mazindol binding sites in the dopamine uptake process and the fate of these sites (labeling dopaminergic neurons) during aging, we have examined the properties of mazindol binding and dopamine uptake in individual young and old rats. There was a 48% decrease (p = 0.0001) in the Bmax of mazindol binding and a 23% decrease (p = 0.0166) in the Vmax of dopamine uptake with no apparent change in their affinities with age. Regression analysis of the relationship between Bmax and Vmax exhibited a significant correlation in old (p = 0.0156) but not young rats (p = 0.1398). These data suggest that the number of mazindol binding sites decreases with age and that the number of sites on the dopamine transporter complex far exceeds the number required to elicit maximal dopamine uptake.

Aging↗
PubMed1991

Antibodies against synthetic peptides predicted from the nucleotide sequence of D2 receptor recognize native dopamine receptor protein in rat striatum.

Two peptides corresponding to amino acid sequences predicted from the nucleotide sequence of the dopamine D2 receptor were synthesized. Peptide I (CGSEG-KADRPHYC) and peptide II (NNTDQNECIIY), corresponding to 24-34 and 176-185 from the NH2 terminus, respectively, were conjugated to keyhold limpet hemocyanin and injected into rabbits. Peptide I showed a greater immunogenic response than did peptide II. Both peptide antibodies exhibited high titer for the homologous antigens, but showed little or no cross-reactivity with heterogeneous peptides. Peptide I antibodies reacted with striatal membrane proteins of apparent molecular masses of 120, 90, 85, and 30 kDa on a western blot. Furthermore, the 90-kDa band was identified as denatured D2 receptor by its high affinity for the D2 selective photoaffinity probe 125I-N'-azidospiperone (125I-NAPS). Photoaffinity labeling of the 90-kDa protein by 125I-NAPS was reduced by 40% in the presence of the peptide I antibody. In addition, evidence is also presented to show the low level of 90-kDa protein in cerebellum which contains little or no D2 ligand binding sites. The antibody to peptide I inhibited the binding of [3H]YM-09151-2, a dopamine D2 receptor selective antagonist, to striatal membranes in a concentration-dependent manner; a 50% inhibition was obtained at a 1:500 dilution of the antisera with 20 pM ligand concentration. The data on the equilibrium inhibition kinetics of [3H]YM-09151-2 binding to striatal membranes were examined in the presence of antibody and showed a 25-30% decrease in Bmax (203.5 +/- 11.0 and 164.6 +/- 3.3 fmol/mg of protein in presence of preimmune and immune sera, respectively) with no change in KD.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Iron deficiency; non-hematological manifestations.

Iron deficiency has far reaching consequences on systemic functions apart from the well known feature of anemia. Because iron deficiency anemia is easy to recognize and treat, the non-hematological manifestations of this trace element deficiency have been overlooked. There is a large body of evidence accumulated from animal and human studies to indicate that iron deficiency states are associated with alterations in cellular function, growth, motor development, behaviour and cognitive function. There are consequences for the host's level of immunocompetence against infection, for physical work and metabolic stress, for altered fetal outcome and premature labour in pregnant women. The gastrointestinal functions and other organ systems are also affected as a result of iron deficiency. The purpose of this review is to emphasize the importance of the non-hematological manifestations of iron deficiency and to highlight areas of interest, both to basic scientists and health care professionals.

Animals↗
PubMed1990

Optimization of conditions for the simultaneous separation of ten tryptophan metabolites using reversed-phase high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method for the separation of tryptophan and ten metabolites of tryptophan pyrrolase pathway has been developed by sequential optimization of mobile phase, by adjusting the pH, the concentration of triethylamine and the gradient elution. The baseline resolution of the compounds, by this optimized procedure, is obtained with an analysis time, including the re-equilibration period, of less than 30 min. We believe this is the first RP-HPLC method that can separate tryptophan and ten of its metabolites in a single chromatographic run.

Chromatography, High Pressure Liquid↗
PubMed1990

The neuropeptide histidyl proline diketopiperazine throughout human pregnancy: an inverse correlation with amniotic fluid prolactin.

Histidyl proline diketopiperazine values have been established in human amniotic fluid (n = 81) and maternal serum (n = 36) throughout gestation (10 to 42 weeks). Newborn cord serum (n = 10) and first-voided fetal urine (n = 10) levels were also documented. These measurements reveal increasing amniotic fluid levels with term gestation values (15,551 pg/ml) nearly thirteen-fold higher than maternal serum concentrations (1150 pg/ml). Corresponding fetal urine and cord serum concentrations were 16,781 and 2160 pg/ml, respectively. The amniotic fluid values are not influenced by fetal sex or maternal labor, nor do they correlate with amniotic fluid alpha-fetoprotein levels. However, there is a significant inverse correlation (r = -0.628; p less than 0.0001) between amniotic fluid prolactin and histidyl proline diketopiperazine after midgestation. The hypothesis that histidyl proline diketopiperazine may be a regulatory peptide for decidual prolactin production was tested by culturing term decidua in the presence of varying concentrations of histidyl proline diketopiperazine, but no inhibitory effect was observed. Decidual cultures did not produce measurable amounts of histidyl proline diketopiperazine. It is suggested that amniotic fluid histidyl proline diketopiperazine is derived from fetal urine.

Adolescent↗
PubMed1990

Acute alterations of cyclo(His-Pro) levels after oral ingestion of glucose.

We analyzed the response of plasma cyclo(His-Pro) (CHP) (N = 14), insulin (N = 8), and glucose (N = 8) to oral ingestion of 75 grams of glucose in normal volunteers. Mean Fasting CHP levels prior to glucose were 614 +/- 112 pg/ml (+/-SE). After glucose ingestion there occurred an acute rise of plasma CHP within 15 minutes (12/14) followed by a fall in plasma concentrations to below baseline values (11 of 14). The mean of highest levels within the first 15 minutes after glucose ingestion was 1035 +/- 300 pg/ml (+/-SE), significantly above baseline (p = 0.002). The mean of lowest values below baseline was 490 +/- 94 pg/ml (+/-SE), p less than 0.001. We conclude that levels of CHP are acutely and reversibly altered by the ingestion of glucose. The possible significance of these perturbations in CHP concentrations is discussed.

Blood Glucose↗