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Biomedical subjects

D K Agrawal

Publications and source records attributed to D K Agrawal.

At least 73 records · Page 4Linked to original sources
PubMed1992

Characteristics of alpha-adrenoceptors in two human colorectal cancer cell lines.

The DiFi and HT-29 human colorectal cancer cell lines were characterized and compared with respect to binding properties of alpha adrenoceptors present on the cell surface. Both cell lines possessed alpha-1 and alpha-2 adrenoceptors of high affinity; however, DiFi cells were rich in alpha-1 adrenoceptors, whereas HT-29 cells were rich in alpha-2 adrenoceptors. In each cell line, specificity of radioligand binding to alpha-1 or alpha-2 adrenoceptors was proved via competition studies using non-tritiated drugs. We believe this to be the first characterization of alpha-1 adrenoceptors in cell line HT-29 and of alpha-1 and alpha-2 adrenoceptors in DiFi cells. Differences between these cell lines in alpha adrenoceptor expression are discussed in relation to colon carcinogenesis. The high level of alpha-1 adrenoceptors seen in DiFi cells should make this cell line useful in studies of the function and regulation of this adrenoceptor subtype.

Binding, Competitive↗
PubMed1992

Sequence and analysis of the capsid protein of Nudaurelia capensis omega virus, an insect virus with T = 4 icosahedral symmetry.

We have determined the nucleotide sequence of the RNA2 segment of the Nudaurelia capensis omega virus genome. It was found to consist of 2448 nucleotides and contained one long open reading frame (ORF) encoding the 644 residue capsid protein. The deduced amino acid sequence of this protein reveals a positively charged amino terminus, a characteristic exhibited by several other viral capsid proteins, that is thought to be important for interactions between the capsid and the genomic RNA. There are 366 and 150 bases of untranslated sequence on the 5' and 3' ends, respectively. The ORF encoding the capsid protein initiates at the second AUG from the 5' end. The 5' proximal AUG specifies a short ORF (30 codons) which terminates 1 base before the initiation codon for the coat protein. Our analysis also revealed the presence of a second, previously unidentified polypeptide associated with Nudaurelia capensis omega virus particles. The amino terminal sequence of this protein corresponds to a portion of the long ORF beginning at codon 571. The lack of an initiation codon near this sequence indicates that the small polypeptide is most likely produced as a carboxy terminal cleavage product from a 70-kDa capsid protein precursor, yielding the previously identified 62-kDa protein and the 8-kDa protein that we have observed. The putative cleavage site would be at an Asn/Phe pair, somewhat resembling known cleavage sites (Asn/Ala) in the T = 3 Nodaviridae. In addition, we have found that there is also a second polypeptide similar in size to that from Nudaurelia capensis omega virus associated with particles of Nudaurelia capensis beta virus, the type member of Tetraviridae.

Amino Acid Sequence↗
PubMed1992

Liver microsomes contain multiple forms of inositol 1,4,5-trisphosphate binding proteins: identification by nitrocellulose blot overlay.

A group of proteins binding to inositol 1,4,5-trisphosphate (IP3) has been identified in rat liver microsomes by a nitrocellulose blot-overlay technique. Proteins were resolved by SDS-PAGE, blotted on nitrocellulose and incubated with [32P]IP3 followed by autoradiography. Approximately eight IP3-binding polypeptides ranging M(r) 23-50 kDA were present exclusively in microsomes; these were absent from plasma membrane and mitochondrial fractions. Binding of [32P]IP3 to these proteins was displaceable to a great extent by 5 microM unlabeled IP3 but not by 10 microM IP1, IP2, IP4, ATP, or GTP gamma S. These results suggest that liver microsomes contain multiple forms of IP3-binding proteins that can be detected by this new method.

Animals↗
PubMed1992

Abnormal magnesium metabolism in two rat models of genetic hypertension.

Magnesium concentrations in erythrocyte ghosts and arterial tissue of male, spontaneously hypertensive rats (SHR) were significantly less than in these tissues of male normotensive controls (Wistar-Kyoto; WKY) of the same age, which were also fed rat chow and tap water. The magnesium concentration in SHR erythrocyte ghosts was increased to the control value by incubating SHR erythrocytes with WKY blood plasma; SHR plasma did not affect the magnesium concentration in WKY erythrocyte ghosts. The magnesium concentrations in erythrocyte ghosts, aortas, and mesenteric arteries from female salt-sensitive (SS/JR) and salt-resistant (SR/JR) Dahl-derived rats, both maintained ad libitum on laboratory rat chow and either tap water or 0.9% NaCl, were not different but were significantly less than those of Sprague-Dawley rats considered as controls. While the ingestion of 0.9% NaCl had no effect on the magnesium concentrations measured in these animals, it caused the salt-sensitive rats to become severely hypertensive. It is evident from these observations that the decreased binding of magnesium to the plasma membrane of cells may be an inheritable metabolic defect that may be associated with the development of hypertension. However, in those instances of hypertension in which this defect occurs, it appears to be a contributing cause of the hypertension; by itself the defect is not a cause of hypertension.

Animals↗
PubMed1991

Terfenadine effect on the bronchoconstriction, dermal response, and leukopenia induced by platelet-activating factor.

We have investigated the protective effect of oral terfenadine, a H1 antagonist, on the dermal and pulmonary response, and changes of circulating WBCs to injected and inhaled platelet activating factor. Nine men with mild asthma participated in a double-blind, crossover study using terfenadine, 120 mg, or placebo. Three hours after administration of study drug, pulmonary function was measured, and a PAF challenge was performed. Skin test to histamine and PAF was performed prior to study drug, and 2.5 hours after drug. Circulating WBC count was determined prior to PAF inhalation and during the PAF challenge. There was a significant improvement in pulmonary function on terfenadine. Terfenadine significantly inhibited the wheal and flare response to histamine and the flare response to injected PAF. Terfenadine did not have an effect on the change in circulating WBC count or the change in pulmonary function to inhaled PAF. These results suggest a limited role for endogenous histamine for the effects of PAF.

Asthma↗
PubMed1991

Platelet alpha-2 adrenoreceptor activity pre-treatment and post-treatment in major depressive disorder with melancholia.

Changes in alpha-2 adrenoreceptor density and affinity during antidepressant treatment were studied using 3H-yohimbine binding to human platelet membranes. Baseline measurements were conducted in 21 patients diagnosed as having major depressive disorder with melancholia, and an equal number of age and sex matched normal controls. No differences were observed in receptor density or binding between pre-treatment subject groups and normal matched controls. Subjects participated for 6 weeks in a trial of placebo, adinazolam, or amitriptyline. Alpha-2 adrenoreceptor binding was not significantly changed from baseline following antidepressant treatment.

Adult↗
PubMed1991

Platelet-activating factor induces nonspecific desensitization to bronchodilators in guinea pigs.

Platelet-activating factor (PAF) is a potent mediator of inflammation and is a mediator which is known to cause airway hyperresponsiveness in human and experimental animals. However, the mechanism of action of PAF is not clear. In this study we examined the effect of methacholine upon specific airway resistance (SRaw) in guinea pigs and the ability of either isoproterenol or prostaglandin E2 to reverse this effect both before and after PAF administration at sub-bronchoactive doses in conscious guinea pigs as well as in isolated airway tissues. SRaw in conscious guinea pigs was monitored using a whole-body plethysmograph. In nonsensitized guinea pigs, a concentration of PAF (0.1 micrograms/ml), which by itself did not affect SRaw, potentiated the methacholine-induced increase in SRaw. In ovalbumin-sensitized animals, the response to methacholine was significantly greater as compared to the nonsensitized group. Prior administration of PAF did not potentiate the response to methacholine in ovalbumin-sensitized animals. In isolated tracheal rings and lung parenchymal strips of nonsensitized guinea pigs, preincubation of the tissue with 0.1 microM PAF decreased the sensitivity of isoproterenol to induce relaxation. However, in the ovalbumin-sensitized group of guinea pig tracheas or lung parenchymas, PAF did not reduce further the effect of isoproterenol to elicit relaxation. Furthermore, PAF did not alter the affinity or the density of beta adrenoceptors in guinea pig lung membranes. These data suggest that PAF may potentiate the responses to bronchoconstrictors and desensitize the responses to bronchodilators in a nonspecific manner. This may be a mechanism underlying PAF-induced airway hyperresponsiveness in asthma.

Airway Resistance↗
PubMed1991

Variations in chemotaxis and chemokinesis of neutrophils of different densities from patients with allergic rhinitis.

We investigated chemotaxis and chemokinesis of neutrophils of different densities from normals and subjects with allergic rhinitis (AR). The chemotaxis of neutrophils with lower density was significantly increased compared with neutrophils with higher density in AR using fMLP (P less than .01) or PAF (P less than .05). In normal subjects, however, there was no significant difference in neutrophil chemotaxis of the two fractions. No significant difference was found in neutrophil chemokinesis of the two fractions from AR or normals. These results indicate that neutrophils with lower density from AR possess greater affinity to fMLP or PAF as compared with neutrophils with higher density and this may be relevant to the pathophysiology of AR.

Cell Movement↗
PubMed1990

A phoA structural gene mutation that conditionally affects formation of the enzyme bacterial alkaline phosphatase.

The phoA503 mutant was identified as a mutant that shows a novel phoA regulatory phenotype. The phoA503 allele dramatically reduces the synthesis of bacterial alkaline phosphatase activity during Pi starvation in an otherwise wild-type host and during the logarithmic growth phase in a phoR or phoU background. Near-normal amounts of enzyme activity are found in phoR phoA503 or phoU phoA503 mutants when starved for carbon, nitrogen, or sulfur or during the stationary phase, however. Marker rescue and DNA sequence analysis located the phoA503 mutation to the phoA coding region. It is a C-to-T transition that would cause a substitution of Val for Ala-22 in the mature protein. Transcriptional and translational lacZ fusions to both wild-type and mutant alleles demonstrated that phoA gene expression is unaltered. Also, the mutant protein was secreted and processed as efficiently as the wild type. Furthermore, the subunits appeared to dimerize and to be stable in the periplasm. But, greater than 98% of the dimers were inactive and found exclusively as isozyme 1. An activation of preformed phoA503 dimers occurred during the stationary phase with the concomitant conversion into isozymes 2 and 3. We propose that the phoA503 mutation affects a late stage in the formation of active enzyme. An unknown change when Pi is present during stationary-phase growth leads to formation of active dimers, which is responsible for this new conditional phenotype.

Alkaline Phosphatase↗
PubMed1990

Fibronectin levels in plasma after platelet-activating factor inhalation.

We evaluated fibronectin levels in plasma and blood leukocyte counts after platelet-activating factor-acether (PAF) inhalation to examine whether PAF may cause pulmonary vascular injury. PAF inhalation challenges were performed on 5 normal subjects and 5 atopic asthmatics. Fibronectin levels in plasma were significantly increased at 5 min (342.5 +/- 36.9 micrograms/ml) after PAF challenge as compared with the baseline values of 277.1 +/- 33.0 micrograms/ml (p less than 0.024). Total white blood cell and neutrophil counts were significantly decreased 5 min after PAF inhalation (WBC from 5,360 +/- 460 to 4,260 +/- 380/mm3, p less than 0.028; neutrophils from 3,113 +/- 441 to 2,214 +/- 344/mm3, p less than 0.043). Our study shows that plasma fibronectin levels transiently increase and that peripheral total WBC counts decrease after PAF inhalation. Elevated fibronectin levels may provide evidence of pulmonary vascular injury due to neutrophils which might be primed and recruited to pulmonary circulation by PAF.

Administration, Inhalation↗
PubMed1990

Elevation of neutrophil chemotactic activity in the human serum and the decreased number of neutrophils after platelet-activating factor inhalation.

We previously reported a significant decrease in neutrophils at 5 min and an increased number of neutrophils at 15 min after PAF-acether inhalation. To investigate the mechanism, we measured the neutrophil chemotactic activity of the sera. Neutrophil chemotactic activity (NCA) of the serum at 5 min was greater than at baseline (p less than 0.01) or at 15 min (p less than 0.05). Furthermore, we investigated the correlation between the change in NCA and decreased number of neutrophils. A significant correlation was found between these two at 5 min (r = 0.751, p less than 0.05). These data suggest that an elevation of NCA may play an important role in the decrease of circulating neutrophils after PAF-acether inhalation.

Administration, Inhalation↗
PubMed1990

Density distribution and density conversion of neutrophils in allergic subjects.

We investigated the density distribution of neutrophils in peripheral blood of allergic subjects. We divided neutrophils into four groups: fraction 1 (density greater than 1.085), fraction 2 (1.081 less than density less than or equal to 1.085), fraction 3 (1.077 less than density less than or equal to 1.081) and fraction 4 (density less than or equal to 1.077). The percentage of neutrophils in fraction 2 in allergic rhinitis (AR) subjects or asthmatics was lower than that in normals (p less than 0.01). The percentage of neutrophils in fraction 3 and fraction 4 from AR or asthmatics was greater than that in normals (fraction 3, p less than 0.01; fraction 4, p less than 0.05). In neutrophils from AR subjects (fraction 3), chemotaxis to N-formyl-methionyl-leucyl-phenylalanine or platelet-activating factor (PAF) was enhanced compared to fraction 2. PAF (10(-7) M) changed the density of neutrophils (p less than 0.01), which were inhibited by WEB 2086 (p less than 0.05). Furthermore, granulocyte-macrophage colony-stimulating factor changed the density of neutrophils (p less than 0.01). These findings suggest that biological agents may activate neutrophils and convert their density resulting in neutrophils with lower density in allergic subjects.

Asthma↗
PubMed1990

Effect of PAF-acether inhalation on nonspecific bronchial reactivity and adrenergic response in normal and asthmatic subjects.

Bronchial hyperreactivity, although recognized as a hallmark of asthma, is not totally understood. Mast cell-derived mediators, including histamine, have been shown to cause immediate bronchoconstriction, but until recently, no single mediator has been shown to induce prolonged changes in airway reactivity. Recent reports indicate PAF-acether (PAF) can induce increased nonspecific bronchial reactivity in normal subjects but not in asthmatics. We sought to elucidate the role of PAF in airway hyperreactivity by comparing the effect of inhaled PAF on methacholine and isoproterenol airway responsiveness in six nonasthmatic and six asthmatic subjects. Neither nonspecific airway reactivity nor isoproterenol responsiveness was changed following PAF inhalation in the nonasthmatic subjects in the six days following PAF. Asthmatics had increased airway responsiveness to methacholine at two hours post-PAF, which did not persist. Responsiveness to isoproterenol did not change in the asthmatic subjects. Additional evaluation of the role of PAF in causing changes in airway reactivity is warranted.

Adult↗
PubMed1989

Characterization of autoantibodies to vasoactive intestinal peptide in asthma.

Vasoactive intestinal peptide (VIP) is a potent relaxant of the airway smooth muscle. In this study, VIP-binding autoantibodies were observed in the plasma of 18% asthma patients and 16% healthy subjects. Immunoprecipitation studies and chromatography on DEAE-cellulose and immobilized protein G indicated that the plasma VIP-binding activity was largely due to IgG antibodies. Saturation analysis of VIP binding by the plasmas suggested the presence of one or two classes of autoantibodies, distinguished by their apparent equilibrium affinity constants (Ka). The autoantibodies from asthma patients exhibited a larger VIP-binding affinity compared to those from healthy subjects (Ka 7.8 x 10(9) M-1 and 0.13 x 10(9) M-1, respectively; P less than 0.005). The antibodies were specific for VIP, judged by their poor reaction with peptides bearing partial sequence homology with VIP (peptide histidine isoleucine, growth hormone releasing factor and secretin). IgG prepared from the plasma of an antibody-positive asthma patient inhibited the saturable binding of 125I-VIP by receptors in guinea pig lung membranes (by 39-59%; P less than 0.001). These observations are consistent with a role for the VIP autoantibodies in the airway hyperresponsiveness of asthma.

Adult↗