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Biomedical subjects

G P Talwar

Publications and source records attributed to G P Talwar.

At least 37 records · Page 2Linked to original sources
PubMed1998

Immunocontraceptive activity guided fractionation and characterization of active constituents of neem (Azadirachta indica) seed extracts.

A novel approach for immunocontraception by intervention of local cell mediated immunity in the reproductive system by using single intrauterine application of neem oil has been described earlier. The reversible block in fertility was reported to last for 107-180 days in female Wistar rats (Upadhyay et al., 1990. Antifertility effects of neem oil by single intrauterine administration: A novel method of contraception. Proceedings Of The Royal Society Of London B 242, 175-180) and 7-11 months in monkeys (Upadhyay et al., 1994. Long term contraceptive effects of intrauterine neem treatment (IUNT) in bonnet monkeys: An alternative to intrauterine contraceptive devices. Contraception 49, 161-167). The present study, describes the identification and characterization of the biologically active fraction from neem seeds (Azadirachta indica A. Juss. Family Meliaceae), responsible for the above activity in adult female Wistar rats. Initial studies with the mechanically extracted oil and solvent extracts of neem seeds have revealed that the antifertility activity was present in constituents of low to intermediate polarity. A hexane extract of neem seeds was reported to be biologically active (Garg et al., 1994. Comparison of extraction procedures on the immunocontraceptive activity of neem seed extracts. Journal of Ethnopharmacology 22, 87-92). Subsequently, hexane extract was sequentially fractionated through the last active fraction using various separation techniques and tested for antifertility activity at each step. Preparative HPLC was used for isolating individual components of the active fraction in quantities, sufficient for characterization. An analytical HPLC method was developed for standardization of the fraction. The active fraction was identified to be a mixture of six components, which comprises of saturated, mono and di-unsaturated free fatty acids and their methyl esters. Dose response study was performed with the last active fractions. The antifertility activity with the active fraction was reversible in nature and it was completely active until 5% concentration. There was no systemic toxic effect following the administration of the active fraction. This study, for the first time, proposes an active fraction from neem seeds, responsible for long term and reversible blocking of fertility after a single intrauterine administration with high efficacy.

Animals↗
PubMed1998

Inhibition of the growth and development of asexual and sexual stages of drug-sensitive and resistant strains of the human malaria parasite Plasmodium falciparum by Neem (Azadirachta indica) fractions.

Neem (Azadirachta indica) has been shown to possess anti-malarial activity. In this study we systematically evaluated extracts of neem seeds and purified fractions further enriched in polar or non-polar constituents for their effect on in vitro growth and development of asexual and sexual stages of the human malaria parasite Plasmodium falciparum. Use of synchronized stages of parasites suggested trophozoites/schizonts as the susceptible target stages to various neem extracts. In addition, all the maturation stages of gametocytes were also killed by various neem fractions tested. The anti-plasmodial effect of neem components was also observed on parasites previously shown to be resistant to other anti-malarial drugs, i.e. chloroquine and pyrimethamine suggesting a different mode of action. Neem seed fractions are thus active not only against the parasite stages that cause the clinical infection but also against the stages responsible for continued malaria transmission.

Animals↗
PubMed1998

Identification of novel transmembrane gene sequence and its use for cell-surface targeting of beta subunit of human chorionic gonadotropin.

We identified a 685-nucleotide gene fragment that codes for the transmembrane and cytoplasmic domains of glycoprotein of the LEP strain rabies virus and carried out experiments designed to express a novel fusion protein on the cell surface. The cDNA encoding the membrane anchor sequence was fused in the correct reading frame to the 3' end of the cDNA encoding the beta subunit of human chorionic gonadotropin (beta(h)CG), a secretory glycoprotein that is used as an antigen for a contraceptive vaccine being developed in our laboratory. The fusion gene cassette was placed under the control of a vaccinia virus early promoter and cloned in a host-restricted fowlpox viral vector. The recombinants, when used to infect mammalian cells that do not allow the replication of fowlpox virus, expressed the N-terminal 135 amino acid residues of beta(h)CG anchored in the cell membrane by the 75-amino acid C-terminal sequence derived from rabies virus glycoprotein. This hybrid protein is correctly processed post-translationally and transported efficiently to the plasma membrane of non-permissive cells such that the anchored beta(h)CG molecule retains the correctly folded native antigenic epitope(s).

Amino Acid Sequence↗
PubMed1998

Regain of fertility and normality of progeny born during below protective threshold antibody titers in women immunized with the HSD-hCG vaccine.

PROBLEM: Phase II clinical trials with the heterospecies dimer of beta hCG and alpha-subunit of ovine luteinizing hormone (HSD)-human chorionic gonadotrophin (hCG) vaccine showed that pregnancy was prevented at and above 50 ng/ml titers, whereas conceptions occurred below 35 ng/ml of hCG bioneutralization capacity. The effect of below-protective threshold anti-hCG antibodies on the progression of pregnancy and the normality of progeny was studied. METHOD OF STUDY: Four women enrolled by informed consent in the Phase II trials. The women studied were immunized with the HCG vaccine and did not receive booster injections in consideration of their desire to have another child. They were examined clinically at least once every month until delivery. The babies were followed up from 2 to 3.5 years, and their anthropometric indices were compared with elder siblings. RESULTS: The pregnancies progressed to 35 to 38 weeks with the usual obstetric problems, and the children developed normally. CONCLUSIONS: The anti-fertility effect of the HSD-hCG vaccine is reversible and low titers of antibodies below the protective threshold have no apparent side effects on the progression of pregnancy and on the early development of the progeny.

Adult↗
PubMed1997

Ability of an anti-luteinizing hormone-releasing hormone vaccine to inhibit gonadotropins in postmenopausal women.

OBJECTIVE: To determine the effects of immunization with an anti-LH-releasing hormone (LH-RH) vaccine in postmenopausal women. DESIGN: Pilot clinical study. SETTING: Normal human volunteers in a medical research-training environment. PATIENT(S): Three postmenopausal women with a mean age of 60 years, 5 years of amenorrhea, and severe hypoestrogenism with elevated serum LH and FSH. INTERVENTION(S): Intramuscular immunization with 300 micrograms LH-RH equivalent of the vaccine in two occasions 1 month apart. MAIN OUTCOME MEASURE(S): Patients were followed for clinical assessment and serum LH, FSH, and anti-LH-RH titers at regular monthly intervals for 7 months. RESULTS(S): The injection of the anti-LH-RH vaccine followed by a booster injection 1 month later resulted in a sharp decrease, 60 days after the first injection, of both serum gonadotropins, accompanied by an increase in anti-LH-RH antibody titers, which were reversible after 180 days in the absence of further booster immunization. CONCLUSION(S): Active immunization offer a safe option to induce antibody response, which in the present regime employed was of about 6-months duration. This procedure opens new possibilities for its use as an affordable therapeutic agent in some hormone-dependent clinical conditions.

Antibodies↗
PubMed1997

Long-term high immune response to diphtheria toxoid in rodents with diphtheria toxoid conjugated to dextran as a single contact point delivery system.

Cross-linked dextran beads were used as a carrier for development of a 'single-contact' vaccine delivery system. Diphtheria toxoid (DT) was covalently coupled to dextran beads (DEX-DT conjugate). The conjugate was immunoreactive with antibodies raised against native DT. Immunization of rats with DEX-DT conjugate generated on average 24 times higher antibody titres against diphtheria toxoid than immunization with the conventional DT absorbed on alum. The immune response was sustained for 9 months, with gradual decline of antibody titres thereafter. Significant antibody titres were measurable in rats after 1 year of immunization. DEX-DT had neither acute nor long-term adverse effects on the health of animals, as evidenced by local reactions, general behaviour, food intake, body weight gain and survival compared with controls.

Animals↗
PubMed1997

Biphasic testosterone delivery profile observed with two different transdermal formulations.

PURPOSE: Our long-term goal is to develop formulations for pulsatile testosterone (T) delivery. T has been reported earlier to show biphasic pharmacokinetics in humans by Mazer et al, as well as biphasic permeation across excised rat skin by our group. We examined two kinds of formulations to evaluate their delivery profiles and to assess whether differences in the formulation approach affect pharmacokinetics in animal models. METHODS: One formulation consisted of T and a polymer blend dissolved in isopropanol; administered by dispensing the solution on the skin to cast a film in situ. The other was an adhesive-dispersion patch. In vitro release from the patch was evaluated using a flow-through cell interfaced with an HPLC pump and UV detector. Single dose pharmacokinetics were evaluated in castrated Wistar rats and bonnet monkeys immunized against gonadotropin-releasing hormone to deplete endogenous T. RESULTS: Two maximas were observed in the T release profile from the patch and in serum concentration versus time profiles in both animal models on application of either formulation. The relative magnitudes of the two maximas and the time interval separating them were different in the case of each formulation. CONCLUSIONS: Both formulations result in biphasic pharmacokinetics of T in the animal models studied. Discrete maximas presumably correlate with "burst" and "sustained" phases of drug release.

Animals↗
PubMed1997

Vaccines for control of fertility and hormone-dependent cancers.

This article traces and reviews the development of vaccines against two reproductive hormones, luteinizing hormone release hormone (LHRH) and human chorionic gonadotrophin (hCG). The heterospecies dimer (HSD)-dehydrogenase hCG vaccine is the first to have completed phase II clinical trials providing evidence for the prevention of pregnancy in humans by immunization with this vaccine. The vaccine acts without blocking ovulation or disturbance of menstrual bleeding. Its effect is fully reversible and fertility is regained with decline of the antibodies. The antibody response in humans is directed against immunodominant epitopes located in the core part of beta hCG, distinct from the C-terminal region. However, problems arising from carrier-conjugated vaccines against 'self' hormones such as carrier-induced immuno-suppression on repeated immunization are evoked and solutions discussed. The LHRH vaccine, a model semi-synthetic vaccine, can be used in both sexes and has applications in regulation of fertility of animals. It has therapeutic applications as a cost-effective approach in clinical conditions where LHRH agonists and antagonists have therapeutic action. The vaccine has undergone phase I and II clinical trials in advanced-stage carcinoma of prostate patients with encouraging results.

Cancer Vaccines↗
PubMed1997

Plant immunomodulators for termination of unwanted pregnancy and for contraception and reproductive health.

Neem (Azadirachta indica) seed and leaf extracts have spermicidal, anti-microbial, anti-fungal and anti-viral properties. They are also immunomodulators that induce primarily a TH1 type response. These properties are being exploited to develop two different useful methods of fertility control. Neem extracts given orally at early post-implantation stage terminate pregnancy in rodents and primates. Treatment has no residual permanent effect and fertility is regained in subsequent cycles. The mechanism by which the action occurs is not fully clear. A transient increase in CD4 and more significantly in CD8 cells is noticed in mesenteric lymph nodes and spleen. A rise in immunoreactive and bioactive TNF-alpha and IFN-gamma in draining lymph nodes, serum and foetal-placental tissue is observed. A polyherbal cream and pessary have been developed containing three active ingredients of plant origin. These have synergistic spermicidal properties on human sperm as determined by the Sander Cramer test. Their use before mating has high contraceptive efficacy in rabbits and baboons. Another interesting property is their inhibitory action on a wide spectrum of micro-organisms, including Candida albicans, C. tropicalis, Neisseria gonorrhoeae, the multidrug-resistant Staphylococcus aureus and urinary tract Escherichia coli, Herpes simplex-2 and HIV-1. Phase I clinical trials have been completed in India, Egypt and the Dominican Republic, and indicate the safety of the formulation, its acceptability and beneficial action invaginosis due to infections.

Abortion, Induced↗
PubMed1997

The HSD-hCG vaccine prevents pregnancy in women: feasibility study of a reversible safe contraceptive vaccine.

PROBLEM: To develop a vaccine for reversible control of fertility in women. MATERIALS AND PROTOCOLS: Purified beta subunit of hCG annealed to purified alpha subunit of ovine LH linked chemically to tetanus toxoid (TT) and diphtheria (DT); vaccine employed at 300 micrograms gonadotropin equivalent per injection adsorbed on alhydrogel with 1 mg SPLPS added in the first injection; Phase I safety trials in 47 women with elective tubal ligation; Phase II efficacy studies in 148 proven fertile women (2 children), sexually active, desirous of family planning using IUD; IUD removed when anti-hCG titres exceed 50 ng/ml hCG bioneutralization capacity; boosters given to maintain above threshold antibody levels; post coital tests conducted in 8 volunteers; sera of protected women analysed for immuno-determinants recognized by competitive enzyme immunoassays employing a panel of monoclonal antibodies and by direct binding to synthetic peptides; recombinant vaccines expressing beta hCG as a secreted product or as a fused protein anchored on membrane. RESULTS: Immunization was well tolerated with no significant changes in endocrine, metabolic and hematological indices. Normal ovulatory cycles were maintained as indicated by menstrual regulation. The vaccine was highly effective in preventing pregnancy (1 pregnancy in 1224 cycles ) at and above antibody titres of 50 ng/ml. Antibodies declined in course of time in absence of boosters, with conceptions occurring below 35 ng/ml titres indicating regain of fertility. Ability of antibodies to prevent pregnancy was confirmed by post coital tests. High avidity (10(10) M-1) and other characteristics of antibodies generated by the vaccine are described and compared with those induced by two other hCG vaccines having undergone Phase I trials. The antibody response of the HSD vaccine in humans is characterized predominantly to an epitope recognized by the monoclonals 206 and P3W80. The antibodies had low or no reactivity with the carboxy terminal peptide and 38-57 region peptide. Live recombinant vaccines expressing beta hCG as a membrane anchored peptide generated antibody response to hCG in all animals following a single injection. CONCLUSIONS: Reversible fertility control is feasible with the HSD-hCG vaccine without impairment of ovulation or disturbance of menstrual regularity. Suggestions have been made for further optimization of the vaccine, which include replacement of TT and DT by a panel of T non B determinants communicating with the entire MHC spectrum and development of recombinant vaccine expressing beta hCG along with membrane anchored carrier.

Animals↗
PubMed1997

Induced termination of pregnancy by purified extracts of Azadirachta Indica (Neem): mechanisms involved.

PROBLEM: To develop a self-administered, orally delivered method for abrogation of early pregnancy. METHOD: Use of purified Neem extracts containing immunomodulators stimulating Th1 cells and macrophages; test animals, rats, baboons, and monkeys, onset of pregnancy confirmed by surgery and counting of implants on day 7 in rats and by chorionic gonadotropin (CG) and progesterone assays in primates; termination defined by complete resorption on day 15 in rats and by bleeding and decline of CG and progesterone in baboons. RESULTS: Pregnancy was terminated successfully in both rodents and primates with no significant side effects. Fertility was regained in both species after one or two irregular cycles. Progeny born had normal developmental landmarks and mothered normal litters in the course of time. The active principle in Neem has been partially fractionated by activity-guided purification. A cascade of events are involved in abrogation of pregnancy. In primates, a decrease in progesterone is an early event. A transient increase in CD4 and CD8 cells is noted in spleen at 96 hr and in mostly CD8 cells in mesenteric lymph nodes. Treatment causes an elevation of both immunoreactive and bioactive TNF-alpha and gamma-interferon in serum, mesenteric lymph nodes, and foetoplacental tissue. CONCLUSION: Immunomodulators of plant origin are potentially usable for termination of unwanted pregnancy

Abortifacient Agents, Nonsteroidal↗
PubMed1996

Purified neem (Azadirachta indica) seed extracts (Praneem) abrogate pregnancy in primates.

The use of neem (Azadirachta indica) seed extracts (Praneem) given orally for abrogation of pregnancy in subhuman primates is described. Oral administration of Praneem was initiated after confirmation of pregnancy using Leydig cell bioassay estimating rising levels of chorionic gonadotropin (CG) in the blood from day 25 onwards of the cycle and continued for six days. Termination of pregnancy was observed with the appearance of blood in the vaginal smears and decline in CG and progesterone. Pregnancy continued in the control animals treated with peanut oil at the same dose. The effect was observed in both baboons and bonnet monkeys. The treatment was well tolerated; blood chemistry and liver function tests had normal values. The animals regained their normal cyclicity in the cycles subsequent to Praneem treatment.

Abortifacient Agents, Nonsteroidal↗
PubMed1996

Effect of volatiles from neem and other natural products on gonotrophic cycle and oviposition of Anopheles stephensi and An. culicifacies (Diptera: Culicidae).

The gonotrophic cycle of female Anopheles was impaired by exposure to volatiles of neem, (Azadirachta indica), reetha, (Sapindus mukorossi), and garlic, (Allium sativum), but not to castor seeds and cotton seed oil. A brief exposure to contact or volatile extracts from neem suppressed rather than inhibited oviposition. Complete inhibition of oviposition was observed by exposure of mosquitoes to neem oil and 1 fraction containing volatile components. Vitellogenesis was impaired irreversably by long-term exposure to neem odor and some extracts. The effect of volatiles on oviposition seems to be regulated by absorption through the cuticle, although passage through the spiracles could not be excluded.

Animals↗
PubMed1996

Termination of pregnancy in rodents by oral administration of praneem, a purified neem seed extract.

PROBLEM: Development of an orally administered abortifacient. METHODS: Subjects were female Wistar rats, weighing 150 to 200 g at the time of experiments. Praneem (a purified extract of neem Azadirachta indica) at a dose of 0.6 ml was given orally from day 8 to 10 after confirming presence and number of implants surgically on day 7 of pregnancy. The animals were examined again under anesthesia on day 15 of pregnancy to check the number of developing embryos. Controls received an equivalent regime of peanut oil. The number and size of implants were counted five days after treatment. RESULTS: Complete resorption of embryos was observed on day 15 of pregnancy in every animal treated with Praneem in contrast to normally developing embryos in rats given peanut oil. In repeat batch experiments, it was established that the effect of the treatment was reversible and animals regained fertility in cycles subsequent to treatment with Praneem. Cytokines of Th1 type, i.e., gamma interferon and TNF, were raised on administration of Praneem, which may be the probable cause of pregnancy termination. CONCLUSIONS: Praneem on oral administration can cause termination of pregnancy in rodents, and the action is probably mediated by TH1 cytokines.

Abortifacient Agents, Nonsteroidal↗
PubMed1995

Carrier-induced epitope-specific regulation and its bypass in a protein-protein conjugate.

In the course of clinical trials on a birth control vaccine, it was found that some of the immunized women responded poorly to booster immunizations. This vaccine consists of a dimer of the beta chain of human chorionic gonadotropin (beta hCG) and the alpha chain of ovine luteinizing hormone (alpha oLH), linked to tetanus toxoid (TT) as a carrier. Changing this carrier to diphtheria toxoid resulted in reversion to high anti-hCG antibody titers, indicating the extent to which the carrier influences anti-ligand responses in this system. The suppression of anti-hCG responses after booster immunizations was reminiscent of the phenomenon of carrier-induced, epitope-specific regulation. In a mouse model designed to test the effects of preimmunization with TT on anti-hCG responses, we found that a single preimmunization with TT causes reduced anti-hCG antibody responses in two out of four mouse strains, while anti-alpha oLH antibody responses were not affected by the preimmunization with TT. This is particularly interesting considering that beta hCG and alpha oLH were not presented when linked separately to TT. In an effort to devise a strategy to circumvent this carrier-induced, ligand-specific hyporesponsiveness, we investigated the effectiveness of a synthetic T helper epitope from TT as carrier. We show that preimmunization with TT causes a less profound reduction in anti-hCG titers if the preimmunized mice are subsequently injected with alpha oLH-beta hCG conjugated to a synthetic tetanus toxin peptide recognized by TT-induced and peptide-induced T cells.

Amino Acid Sequence↗
PubMed1995

Species-specific 18S rRNA gene amplification for the detection of P. falciparum and P. vivax malaria parasites.

Based on the sequence diversity of the Plasmodium 18S ribosomal RNA (rRNA), we designed oligonucleotide primers for polymerase chain reaction (PCR) to yield different size fragments for P. falciparum and P. vivax. The primers for the PCR procedure were chosen such that the 5' primer was Plasmodium-conserved while the 3' primers were species-specific. Using primer cocktails and cloned plasmid DNAs containing the 18S rRNA genes or parasite genomic DNA as targets, we show that the PCR procedure yields 1.4-kb and 0.5-kb DNA fragments for P. falciparum and P. vivax, respectively. Limited field testing of this procedure demonstrated the utility of a ribosomal gene based species-specific malaria diagnosis.

Animals↗
PubMed1995

Biodegradable delivery system for a birth control vaccine: immunogenicity studies in rats and monkeys.

PURPOSE: The purpose of this study was to develop a single administration delivery system for a model birth control vaccine, in order to reduce the need for multiple injections and enhance immunogenicity. METHODS: The immunogen-loaded microspheres were prepared by solvent evaporation method and characterized for loading levels, size distribution and in vitro release kinetics. The microspheres were immunized intramuscularly in wistar rats and bonnet monkeys, and the antibody response was compared to that obtained with the same total dose of the immunogen on alum given at a monthly interval. RESULTS: Results indicated that a single injection of the immunogen entrapped in the microspheres generated a response comparable to that obtained by the same immunogen on alum injected at a monthly interval. The antibodies generated by the microspheres in the monkeys also had a good bioneutralization capacity indicating immunogen integrity during the microencapsulation process. CONCLUSIONS: Biodegradable microspheres served as an effective delivery system for a model immunogen used in this study to reduce the need for frequent immunizations and enhance immunogenicity.

Animals↗