Search PubMed⌕ Search

Biomedical subjects

V Srivastava

Publications and source records attributed to V Srivastava.

At least 37 records · Page 2Linked to original sources
PubMed1996

Insulin-like growth factor I of peripheral origin acts centrally to accelerate the initiation of female puberty.

In several species, including humans, circulating insulin-like growth factor I (IGF-I) levels increase during the onset of puberty, suggesting that this peptide contributes to attaining sexual maturity. Because IGF-I elicits LHRH release from the median eminence (ME) of immature female rats in vitro, we hypothesized that it may represent one of the peripheral signals suspected to link somatic development to the LHRH-releasing system at puberty. We now present evidence in support of this concept. Quantitation of IGF-I messenger RNA (mRNA) levels by ribonuclease protection assay revealed that expression of the IGF-I gene did not change in the medial basal hypothalamus or preoptic area of female rats during peripubertal development. In contrast, the contents of both IGF-Ia and IGF-Ib mRNA, the two alternatively spliced forms of the IGF-I gene, increased significantly in the liver during the early proestrous phase of puberty. This change was followed by an elevation in serum IGF-I levels during the late proestrous phase of puberty along with a concomitant increase is serum gonadotropin levels. The proestrous change in serum IGF-I levels was accompanied by a selective increase in IGF-I receptor (IGF-IR) mRNA in the ME. Small doses of IGF-I (2-200 ng), administered intraventricularly, effectively induced LH release in both juvenile and peripubertal female rats, an increase prevented by prior immunoneutralization of LHRH actions. Importantly, intraventricular injections of IGF-I (20 ng), administered twice daily in the afternoon to immature animals, significantly advanced puberty. Thus, these results suggest that IGF-I of peripheral origin contributes to the initiation of female puberty by stimulating LHRH release from the hypothalamus, an effect that appears to be amplified by the increased synthesis of IGF-I receptors in the ME during first proestrus.

Animals↗
PubMed1995

Effect of ethanol on the synthesis of insulin-like growth factor 1 (IGF-1) and the IGF-1 receptor in late prepubertal female rats: a correlation with serum IGF-1.

For several years, it has been well accepted that insulin-like growth factor 1 (IGF-1) plays a critical role in peripubertal growth. Recently, we have provided evidence to suggest that this peptide may also be involved in the sexual maturation process, via an action to stimulate hypothalamic luteinizing hormone releasing hormone release. Because ethanol (ETOH) delays puberty, an event that is associated with depressed growth rates and decreased growth hormone and luteinizing hormone (LH) secretion via actions at the hypothalamic level, we investigated whether this drug is capable of altering the expression of genes encoding IGF-1 in liver and brain, as well as the expression of the type 1 IGF receptor (IGF-1R) within the median eminence (ME). Also, we wanted to determine if any regional changes in the expression of these genes were associated with concomitant alterations in the serum levels of IGF-1 and LH. Rats were implanted with gastric cannulae on day 24 and began receiving specific control or ETOH diets on day 29. Rats were killed on day 34, determined to be in the late juvenile stage of development, and their tissues and blood were collected. Results indicate that the ETOH-fed rats showed a decrease (p < 0.01) in the expression of hepatic IGF-1 mRNA when compared with the controls, and this paralleled depressions in both serum IGF-1 (p < 0.01) and LH (p < 0.01). In contrast, no changes were detected in IGF-1 mRNA expression in the preoptic area and hypothalamus, as well as in IGF-1R mRNA expression within the ME. These results suggest that the well-known detrimental effects of ETOH on growth rates and the progression of the female pubertal process in the rat may be associated with the drug's ability to depress the hepatic synthesis of IGF-1 and the subsequent prepubertal circulating levels of the protein.

Alcoholism↗
PubMed1995

N-methyl-D-aspartic acid receptor messenger ribonucleic acid levels and luteinizing hormone release in immature female rats: effects of stage of pubertal development and exposure to ethanol.

This research was designed to determine 1) whether changes occur in the levels of N-methyl-D-aspartic acid (NMDA) receptor (NMDA-R) messenger RNA (mRNA) in the reproductive hypothalamus of female rats as they approach puberty, 2) whether NMDA-R stimulation would promote differential LH responses during the specific stages of peripubertal development, and 3) whether ethanol (ETOH), which is known to affect the NMDA-R in other brain systems, can alter NMDA-R-activated LH secretion at puberty. In the first experiment, female rats were killed at 15, 20, 25, and 34-36 days of age to determine the levels of mRNA that code for the NMDA-R, specifically NMDA-R1, in the arcuate nucleus-median eminence (AN-ME) and preoptic area (POA) during pre- and peripubertal development by a ribonuclease protection assay. Results indicate that in juvenile animals, NMDA-R mRNA levels in the AN-ME increased at 25 days (P < 0.01). In the POA, the levels increased at 20 days (P < 0.05), but were unchanged at 25 days. During the peripubertal period, NMDA-R gene expression in the AN-ME did not change; however, gene expression in the POA increased (P < 0.05) during first proestrus, then declined during first estrus. In the second experiment, NMDA-R stimulation with N-methyl-D,L-aspartic acid (NMA; 2.5 mg/kg) produced differential stimulatory effects on LH release depending upon the stage of pubertal development. In this regard, significant post-NMA percent increases in LH released over pre-NMA (basal) levels occurred during anestrus (46%; P < 0.01) and first proestrus (95%; P < 0.01), with nonsignificant increases of 18% and 28% during first estrus and diestrus, respectively. Finally, a 3 g/kg dose of ETOH given intragastrically 90 min before the NMA challenge blocked (P < 0.05) NMA-induced LH release during first proestrus. In conclusion, these findings demonstrate regional differences in the timing of NMDA-R gene expression in the reproductive hypothalamus during pubertal development, show differential responses of LH to NMDA-R activation during the peripubertal period, and continue to demonstrate the vulnerability of the hypothalamic-pituitary axis to the detrimental effects of ETOH at this critical time of development.

Animals↗
PubMed1994

Immunostimulant activity of Nyctanthes arbor-tristis L.

Nyctanthes arbor-tristis L. (Oleaceae), a plant widely used in the traditional medicinal systems of India, has recently been reported to possess hepatoprotective, antileishmanial, antiviral and antifungal activities. In the present study strong stimulation of antigen specific and non-specific immunity, as evidenced by increases in humoral and delayed type hypersensitivity (DTH) response to sheep red blood cells (SRBC) and in the macrophage migration index (MMI), has been demonstrated in mice fed with 50% ethanolic extract of seeds, flowers and leaves of this plant. Maximum activity was found in the seeds in which the active principle(s) appear to be mainly associated with lipids. In flowers and leaves, however, the major activity was found in the aqueous fraction of the 50% ethanol extract. The immunostimulant substance(s) found in N. arbor-tristis L. are likely to play a role in its antiamoebic, antileishmanial, antiviral and certain other activities.

Adjuvants, Immunologic↗
PubMed1994

Activity of alpha-anilinobenzyl cyanides and 2-methoxycarbonylamino-1-phenylimidazoles, a new class of antifilarial agents.

The activity of alpha-anilinobenzyl cyanides (2a-f), 5-aryl-4,5-dihydro-2-methoxycarbonylamino-1-phenylimidazoles (5a-d) and 2-methoxycarbonylamino-1-phenyl-1,3-diazaspiro[4:5]dec-2-ene (5f) have been tested for their micro- and macrofilaricidal activity against Litomosoides carinii and Acanthocheilonema viteae in rodents. In this test alpha-anilinobenzyl cyanides (2a-b), 5-(4-methoxyphenyl)-4,5-dihydro-2-methoxy-carbonylamino-1-phenylim idazole (5b) and 2-methoxycarbonylamino-1-phenyl-1,3-diazaspiro[4:5]dec-2-ene (5f) were found to possess marked filaricidal activity at doses ranging from 3-100 mg/kg given parenterally or orally for 5 days.

Animals↗
PubMed1993

Structural analysis of sialic acid-containing carbohydrates by the reductive-cleavage method.

The applicability of the reductive-cleavage method to the structural analysis of sialic acid-containing carbohydrates was investigated using fully methylated methyl alpha- and beta-N-acetylneuraminic acid (1 and 2, respectively). Both compounds were fully stable to reductive cleavage in the presence of borane dimethylsulfide and boron trifluoride etherate but were slowly degraded in the presence of triethylsilane and promoters such as trimethylsilyl trifluoromethanesulfonate, boron trifluoride etherate, or a mixture of trimethylsilyl methanesulfonate and boron trifluoride etherate. However, after selective reduction of the ester groups of 1 and 2 with sodium borohydride, the products (3 and 4, respectively) underwent rapid reductive cleavage to yield the expected anhydroalditols, which were characterized as their acetates (8 and 11) by GLC-MS. The major product was also characterized as its benzoate (9) by 1H NMR spectroscopy. The usefulness of this analytical method was demonstrated using 3'-sialyllactose, i.e., alpha-Neu5Ac-(2-->3)-beta-D-Galp-(1-->4)-D-Glc. The methylated and ester-reduced trisaccharide (13) was reductively cleaved with Me2S.BH3-BF3.ET2O and the products were acetylated. Analysis by GLC-MS revealed the products expected from terminal (nonreducing) Neu5Ac (8 and 11), 3-linked Galp (16), and 4-linked Glcp (15) residues in relative molar ratios of 1.2:1.0:1.0, respectively. However, direct reductive cleavage of the fully methylated trisaccharide (12) yielded the fully methylated disaccharide-anhydroalditol derivative alpha-Neu5Ac-(2-->3)-1,5An-D-Gal (14) and the product (15) derived from 4-linked Glcp residues. These experiments therefore established both the composition and the sequence of the trisaccharide.

Borohydrides↗
PubMed1993

Immunofluorescent evaluation of DNA repair synthesis using interactive laser cytometry.

An improved differential fluorescence analysis technique which employs scanning laser cytometry for the detection of two DNA binding fluorochromes was used to quantitate both total DNA and cellular incorporation of the base analogue, bromodeoxyuridine (BrdUrd), into UV- or methyl methane sulphonate (MMS)-treated DNA. In this procedure DNA containing BrdUrd was partially denatured and immunolabeled by binding anti-BrdUrd monoclonal IgG to incorporated BrdUrd. Anti-BrdUrd was detected with a secondary fluorochrome-labeled polyclonal anti-IgG. Cells were counterstained with propidium iodide to allow the determination of total DNA. Fluorescence was determined using the Meridian ACAS 570 Scanning Laser Cytometer. The computer-analyzed images were generated from monodisperse populations of UV- or MMS-treated cells, allowing the evaluation of DNA synthesis associated with excision repair and of total DNA content in single cells. These data were compared with 3H-thymidine incorporation occurring as a function of excision repair. The analysis of DNA synthesis with this technique is consistent, relatively simple, and rapid with excellent sensitivity and provides a viable method for determining cycling vs. non-cycling cells, total cellular DNA, and excision repair-associated DNA synthesis of individual cells within heterogeneous cell populations.

Bromodeoxyuridine↗
PubMed1993

Immunostimulant agents from Andrographis paniculata.

EtOH extract and purified diterpene andrographolides of Andrographis paniculata (Acanthaceae) induced significant stimulation of antibody and delayed type hypersensitivity (DTH) response to sheep red blood cells (SRBC) in mice. The plant preparations also stimulated nonspecific immune response of the animals measured in terms of macrophage migration index (MMI) phagocytosis of 14C-leucine labelled Escherichia coli and proliferation of splenic lymphocytes. The stimulation of both antigen specific and nonspecific immune response was, however, of lower order with andrographolide than with the EtOH extract, suggesting thereby that substance(s) other than andrographolide present in the extract may also be contributing towards immunostimulation.

Adjuvants, Immunologic↗
PubMed1992

Enhanced unscheduled DNA synthesis by secondary cultures of lung cells established from calorically restricted aged rats.

Unscheduled DNA synthesis (UDS) induced by two exposure levels of ultraviolet light (UV) or two concentrations of methyl methane sulfonate (MMS) was evaluated in secondary cultures of lung fibroblasts established from weanling, 11-month-old and 31-month-old female Fischer 344 rats fed ad libitum (AL) or calorically restricted (CR) diets. [3H]Thymidine incorporation as a function of UDS was highest for weanling-derived cells treated with either UV or MMS, declining consistently with increased age between cells from weanling, 11-month-old and 31-month-old animals. [3H]Thymidine incorporation as a function of UDS in cells from 11-month-old AL vs. CR rats differed only at the highest UV exposure level. In contrast, cells derived from 31-month-old CR rats exhibited UDS levels which were at least twice as high at each UV treatment level as UDS levels of cells derived from the same age AL rats. Cells from both old AL and old CR rats were shown to initiate DNA excision repair at about the same rate. Cells from CR rats, however, repaired DNA damage at an accelerated rate and completed excision repair while repair in cells from AL animals was slower and apparently did not proceed to completion. Data from this study indicate that cells from young and old AL and CR animals initiate excision repair, but demonstrate an age-related loss of UV- or MMS-stimulated [3H]thymidine incorporation in cells derived from AL animals. Cells derived from CR animals did not exhibit that age-related loss of UDS activity; rather, they showed an enhanced UDS response to DNA damage and appeared to complete ligation as the final step in excision repair. The data suggest that caloric restriction of a cell donor animal not only delays the age-associated decrease in in vitro DNA excision repair capacity in cells from that animal, but may actually enhance repair capacity.

Aging↗
PubMed1991

A hepatic reticuloendothelial cell receptor specific for SO4-4GalNAc beta 1,4GlcNAc beta 1,2Man alpha that mediates rapid clearance of lutropin.

We have identified a receptor in hepatic endothelial and Kupffer cells that binds oligosaccharides terminating with the sequence SO4-4GalNAc beta 1,4GlcNAc beta 1,2-Man alpha (S4GGnM). This receptor can account for the rapid removal of the glycoprotein hormone lutropin, which bears unique Asn-linked oligosaccharides terminating in S4GGnM, from the circulation. Hepatic endothelial cells express 579,000 S4GGnM receptors at their surface and bind lutropin with an apparent Kd of 1.63 x 10(-7) M. Bound ligand is rapidly internalized. Binding does not require divalent cations, is reversed by incubation at pH 5.0 or below, and is inhibited by fucoidin but not by hyaluronate, heparin, chondroitin sulfate, or dextran sulfate. We propose that the S4GGnM-specific receptor represents a major mechanism for clearance of certain sulfated glycoproteins from the blood, including members of the glycoprotein hormone family.

Amino Acid Sequence↗
PubMed1991

Characterization of a sulfotransferase responsible for the 4-O-sulfation of terminal beta-N-acetyl-D-galactosamine on asparagine-linked oligosaccharides of glycoprotein hormones.

The Asn-linked oligosaccharides on the glycoprotein hormones lutropin (LH) and thyrotropin terminate with the sequence SO4-4GalNAc beta 1-4GlcNAc beta 1-2 Man alpha-. Using a chemically synthesized trisaccharide GalNAc beta 1-4GlcNAc beta 1-2Man alpha 1-O(CH2)8COOCH3 (GGnM-MCO), we have developed a sensitive assay for the sulfotransferase responsible for the 4-O-sulfation of the terminal beta-D-GalNAc. GGnM-MCO is incubated with a bovine pituitary membrane extract and [35S]3'-phosphoadenosine 5'-phosphosulfate ([35S]PAPS). The sulfated product [35S]SGGnM-MCO is separated from [35S]PAPS, PAPS degradation products and endogenous sulfated products by a two-step procedure utilizing an Ecteola cellulose column and a Sep-Pak (C18) cartridge. Characterization of the [35S]SGGnM-MCO produced in the assay indicates that sulfate is incorporated exclusively on the 4-position of GalNAc. Linear incorporation of sulfate into GGnM-MCO can be maintained for greater than 10 h. GGnM-4-sulfotransferase has a pH optimum of 7.2, requires the presence of a reducing agent, and is stimulated by, but does not require, divalent cations. Initial velocity studies indicate an apparent Km (Henri-Michaelis-Menten equilibrium constant) for PAPS of 4 microM and for GGnM-MCO of 9 microM. Incorporation of sulfate into the trisaccharide is stimulated 3-fold by the presence of basic proteins including deglycosylated LH. The stimulation by deglycosylated LH suggests that the protein component of glycoproteins that bear oligosaccharides terminating with GalNAc-GlcNAc-Man- may modulate GGnM-4-sulfotransferase.

Acetylgalactosamine↗
PubMed1991

Incorporation of [1-14C]-Isopentenyl Pyrophosphate into Monoterpenes by a Cell-Free Homogenate Prepared from Callus Cultures of Chrysanthemum cinerariaefolium.

Callus culture of CHRYSANTHEMUM CINERARIAEFOLIUM (Trev.) Bocc. (Asteraceae), initiated with axillary buds from the plant, have been shown to produce chrysanthemyl alcohol and chrysanthemic acid. Incubation of a cell-free homogenate from the callus with [1- (14)C]-isopentenyl pyrophosphate demonstrated incorporation of radioactivity into chrysanthemyl alcohol and chrysanthemic acid as well as products from isopentenyl pyrophosphate isomerase (EC 5.3.3.2; isopentenyl diphosphate Delta (3)-Delta (2)-isomerase) and prenyltransferase activities (EC 2.5.1.11; allylic-terpene-diphosphate:isopentenyl diphosphate terpenoid-allyltransferase).

Journal Article↗
PubMed1990

Mitogen-activation of spleen cells in aged animals is potentiated by dietary restriction: a preliminary report.

Dietary restriction has been reported to be associated with increased life span and increased DNA repair capacity in both male and female rats and mice. We examined dietary restriction effects on immune system function and prolongation of life span in specific pathogen free rats and mice. In this preliminary report the authors show that dietary restriction is correlated with a dramatic increase in the lifespan of both male and female rats and mice in a pathogen free environment, and in the capacity of cultured splenocytes from those animals to initiate blastogenesis in response to antigenic stimulation.

Aging↗