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Biomedical subjects

A P Gupta

Publications and source records attributed to A P Gupta.

At least 19 recordsLinked to original sources
PubMed1998

Presence of Dirofilaria repens and an insect immunocyte (plasmatocyte) in a human subcutaneous nodule, induced by a mosquito bite.

It is well known that the nematode Dirofilaria repens is transmitted to humans by vector mosquito bite. Examination of a fine needle aspiration biopsy drawn from a month-old nodule on the chest of a woman, residing in Garlasco, province of Pavia, Northern Italy, revealed the presence of not only one immature female of D. repens, but also some scattered cells that we believe to be mosquito's blood cells, plasmatocytes (immunocytes). We presume that plasmatocytes were carried into the bite wound with the mosquito's hemolymph that had oozed from a rupture in its mouthparts during feeding. Because Aedes albopictus recently colonized certain areas in the above region, we suspect that the nodule resulted from the bite of this mosquito.

Animals↗
PubMed1996

Cytoskeletal F-actin polymerization from cytosolic G-actin occurs in the phagocytosing immunocytes of arthropods (Limulus polyphemus and Gromphadorhina portentosa): does [cAMP]i play any role?

Phagocytosis is a major defense reaction in arthropods and is accomplished by two blood cells (hemocytes), the granulocyte (GRs) and plasmatocytes (PLs), collectively called immunocytes. Immunocytes (principally the GRs) from two arthropods, Limulus polyphemus (horseshoe crab) and Gromphadorhina portentosa (Madagascar hissing cockroach) effectively phagocytose fluorescein isothiocyanate (FITC)-conjugated fluoresbrite microspheres (FITC-FM) and chicken (Gallus domesticus) erythrocytes within 1 hr of incubation. Although actin polymerization and changes in intracellular cAMP ([cAMP]i) levels occur during the early stages of phagocytosis in vertebrates, these two phenomena have not been studied in arthropod immunocytes. Using the DNase I inhibition assay, we found a decrease in cytosolic G-actin and an increase in the cytoskeletal F-actin in the phagocytosing immunocytes; the total actin in both resting and phagocytosing immunocytes remained constant. These results showed an 86% increase in F-actin in G. portentosa immunocytes and a 29% increase in those of L. polyphemus after 1 hr of initial incubation with FITC-FM. As in some vertebrates, the role of [cAMP]i in the early stages of phagocytosis in these two animals- and perhaps in arthropods in general-is variable; although we detected some negligible amounts of [cAMP]i (0.10-0.80 pmol/cell at different time intervals) in L. polyphemus immunocytes, it was inconclusive whether those in G. portentosa also contained [cAMP]i. Even in L. polyphemus, the difference in the amounts of [cAMP]i in resting and phagocytosing cells was insignificant (P > 0.05). It was also inconclusive whether [Ca2+]i and/or [Mg2+]i play any roles in the early stages of phagocytosis in the two arthropods in this study. These results suggest that the two phenomena (F-actin polymerization and levels of [cAMP]i in arthropods) are basically similar to those in vertebrate neutrophils and macrophages, which suggests that certain immunological mechanisms are conserved in nature.

Actins↗
PubMed1991

Lectin-binding receptors, Na+,K(+)-ATPase, and acetylcholinesterase on immunocyte plasma membrane of Limulus polyphemus.

Plasma membrane receptors are crucial for nonself tissue recognition. Using concanavalin A (Con A), wheat germ agglutinin, peanut agglutinin, soybean agglutinin (SBA), and winged pea agglutinin, five lectin-binding receptor molecules have been recognized on the plasma membrane of the granulocyte (immunocyte) of the horseshoe crab, Limulus polyphemus. Only Con A and SBA caused capping of surface receptors. On the basis of the known functions of these lectin-binding receptor molecules in other invertebrates and vertebrates, their roles in phagocytosis, encapsulation, signaling, and possibly in complement pathway activation are postulated. In addition to lectin-binding receptors, Na+,K(+)-ATPase and acetylcholinesterase were detected on the plasma membrane. Because Limulus dates back to some 200 million years, the antiquity of these molecules is suggested. Furthermore, some of the lectin-binding surface receptors have the potential to be used as markers to separate different kinds of hemocytes in higher arthropods and to distinguish between normal and neoplastic cells in humans.

Acetylcholinesterase↗
PubMed1988

Arthropod immune system. V. Activated immunocytes (granulocytes) of the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae) show increased number of microtubules and nuclear pores during immune reaction to foreign tissue.

The German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae) has two major immunocytes (blood cells) (granulocytes (GRs) and plasmatocytes). The GRs participate both in encapsulation and phagocytosis of nonself tissue. Structurally, the GRs are flattened and discoid, and contain, among other organelles, microtubules that are arranged in the form of a bundle in their peripheral region in the plane of flattening. If one implants a foreign tissue in the cockroach's abdomen, the GRs become activated and begin to encapsulate the implant by flattening and wrapping around it. The activated GRs show considerable increase in the number of both the microtubules and the nuclear pores of the nuclear envelope. Such structural changes in an activated arthropod immunocyte and their functional significance in its immune reaction against a foreign tissue have not been previously reported. We believe that the large number of microtubules is necessary not only to maintain the flattened nature of the GRs, but also to ensure the formation of an effective capsule against the deforming and shearing forces of the foreign tissue. And to keep up with the rapid assembly of new microtubules during encapsulation, the nucleus apparently triggers the synthesis of tubulin via ribosomes, its nuclear pores serving as channels for molecular transport to and from the nucleus. A structural and functional analogy between GRs and human platelet has also been suggested.

Animals↗
PubMed1985

Metoclopramide as a lactogogue.

Thirty-two mothers with no or inadequate breast milk were treated with metoclopramide. Improved lactation occurred in 66.67 percent of mothers with no breast milk and 100 percent of those with inadequate milk output. Improvement persisted after discontinuing the treatment. No untoward effects were noticed in any of the mothers or their infants.

Adult↗
PubMed1984

Stereochemical course of the 3'----5'-exonuclease activity of DNA polymerase I.

(Sp)-2'-Deoxyadenosine 5'-O-[1-17O,1-18O,1,2-18O]triphosphate has been synthesized by desulfurization of (Sp)-2'-deoxyadenosine 5'-O-(1-thio[1,1-18O2]diphosphate) with N-bromosuccinimide in [17O]water, followed by phosphorylation with phosphoenolpyruvate-pyruvate kinase. A careful characterization of the product using high-resolution 31P NMR revealed that the desulfurization reaction proceeded with approximately 88% direct in-line attack at the alpha-phosphorus and 12% participation by the beta-phosphate to form a cyclic alpha,beta-diphosphate. The latter intermediate underwent hydrolysis by a predominant nucleophilic attack on the beta-phosphate. This complexity of the desulfurization reaction, however, does not affect the stereochemical integrity of the product but rather causes a minor dilution with nonchiral species. The usefulness of the (Sp)-2'-deoxyadenosine 5'-O-[1-17O,1-18O,1,2-18O]triphosphate in determining the stereochemical course of deoxyribonucleotidyl-transfer enzymes is demonstrated by using it to delineate the stereochemical course of the 3'----5'-exonuclease activity of DNA polymerase I. Upon incubation of this oxygen-chiral substrate with Klenow fragment of DNA polymerase I in the presence of poly[d(A-T)] and Mg2+, a quantitative conversion into 2'-deoxyadenosine 5'-O-[16O,17O,18O]monophosphate was observed. The stereochemistry of this product was determined to be Rp. Since the overall template-primer-dependent conversion of a deoxynucleoside triphosphate into the deoxynucleoside monophosphate involves incorporation into the polymer followed by excision by the 3'----5'-exonuclease activity and since the stereochemical course of the incorporation reaction is known to be inversion, it can be concluded that the stereochemical course of the 3'----5'-exonuclease is also inversion.

Chemical Phenomena↗
PubMed1984

The effect of the 3',5' thiophosphoryl linkage on the exonuclease activities of T4 polymerase and the Klenow fragment.

The 3'----5' exonuclease activities of T4 DNA polymerase and the Klenow fragment of Polymerase I towards the phosphoryl and thiophosphoryl 3',5' linkage were examined under comparable conditions of idling-turnover, duplex hydrolysis and turnover during polymerization. With the T4 enzyme there is a negligible effect of thiosubstitution on these activities; with the Klenow fragment there is a greater than one hundred-fold reduction in rate with the thiolinkage for the exonuclease but not polymerization activities. This inability to hydrolyze rapidly the thiophosphoryl linkage extends to the hydrolytic activity of Exonuclease III. The quantitation of the exonuclease activities of these three proteins under various conditions should aid in the successful employment of thiophosphoryl nucleoside triphosphates for their incorporation into DNA.

DNA Polymerase I↗