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Biomedical subjects

S Agrawal

Publications and source records attributed to S Agrawal.

At least 73 records · Page 4Linked to original sources
PubMed2001

Antisense and/or immunostimulatory oligonucleotide therapeutics.

Antisense technology, which is based on a simple and rational principle of Watson-Crick complementary base pairing of a short oligonucleotide with the targeted mRNA to downregulate the disease-causing gene product, has progressed tremendously in the last two decades. Antisense oligonucleotides targeted to a number of cancer-causing genes are being evaluated in human clinical trials. While the first-generation phosphorothioate antisense oligonucleotides are in clinical trials, a number of factors, including sequence motifs that could lead to unwanted mechanisms of action and side effects, have been identified. The severity of the side effects of first-generation antisense oligonucleotides is mostly dependent on the presence of certain sequence motifs, such as CpG dinucleotides. A number of second-generation chemical modifications have been proposed to overcome the limitations of the first-generation antisense oligonucleotides. The safety and efficacy of several second-generation mixed-backbone antisense oligonucleotides are being evaluated in clinical trials. The immune stimulation affects observed with CpG-containing antisense oligonucleotides are being exploited as a novel therapeutic modality, with several CpG oligonucleotides being evaluated in clinical trials. A number of medicinal chemistry studies performed to date suggest that the immunomodulatory activity of CpG oligonucleotides can be fine-tuned by site-specific incorporation of chemical modifications in order to design disease-specific oligonucleotide therapeutics.

Adjuvants, Immunologic↗
PubMed2001

Predictability of hypocalcemia using early postoperative serum calcium levels.

OBJECTIVE: In operations involving the thyroid or parathyroid glands, postoperative serum calcium levels are one contributing factor to patients' length of hospital stay. In this study, we wanted to determine whether early postoperative serum calcium levels could be used to predict hypocalcemia following operations of the thyroid or parathyroid glands. METHODS: A retrospective chart review was performed on 203 patients who had undergone operations involving risk to the parathyroid glands. This included patients who had bilateral thyroid operations or those who had one or more parathyroid glands removed for various disease processes. Postoperative calcium levels were plotted as a function of time, and the slope between the first two levels was examined. Both serum calcium levels were drawn within 12 hours after the operation. RESULTS: A positive slope predicted normocalcemia in 100% of patients undergoing thyroid or parathyroid procedures. A negative slope was predictive in magnitude. Patients who developed hypocalcemia had an average slope two to three times more negative than those remaining normocalcemic. CONCLUSIONS: It appears that early serum calcium levels may be predictive for postoperative hypocalcemia in operations that put the parathyroid glands at risk.

Biomarkers↗
PubMed2001

Potentiation of antitumor activity of irinotecan by chemically modified oligonucleotides.

Co-administration of synthetic chemically modified oligonucleotides with irinotecan, a selective topoisomerase I inhibitor, provided a significant enhancement in the antitumor activity of irinotecan. The enhancement of antitumor activity of irinotecan with co-administration of chemically modified oligonucleotides was observed in several tumor models--pancreatic cancer (Panc-1), colon cancer (HCT-116) and melanoma (A375). Inhibition of tumor growth in all three models required the co-administration of irinotecan and chemically modified oligonucleotides, but was independent of the nucleotide sequence of the oligonucleotides. The potentiation of antitumor activity was dependent on the dose of irinotecan and chemically modified oligonucleotides administered. The enhancement of antitumor activity of irinotecan was also observed by co-administration of a phosphorothioate oligonucleotide, however, to a lesser extent than did chemically modified oligonucleotides, suggesting that metabolic stability of the oligonucleotide contributes to the enhancement of antitumor activity seen with irinotecan. The co-administration of dextran sulfate sodium with irinotecan showed insignificant potentiation of antitumor activity of irinotecan, suggesting that the enhancement of antitumor activity of irinotecan observed was not a result of polyanionic characteristic of oligonucleotides. Co-administration of irinotecan and chemically modified oligonucleotides did not result in increased toxicity in the tumor models studied. Potentiation of antitumor activity of irinotecan observed with co-administration of oligonucleotides suggests that the oligonucleotides affect the pharmacokinetics and/or metabolism of irinotecan. The use of chemically modified oligonucleotides together with irinotecan may increase the therapeutic index of irinotecan in cancer patients and continued development of such agents should be considered.

Animals↗
PubMed2001

The Cockayne syndrome group B DNA repair protein as an anti-cancer target.

Cells from individuals with Cockayne syndrome (CS) have a defect in transcription-coupled DNA repair (TCR), which rapidly corrects certain DNA lesions located on the transcribed strand of active genes. Despite this DNA repair defect, individuals with CS (of which there are two complementation groups, CSA and CSB) do not demonstrate an elevated incidence of cancer. Recently, we demonstrated that disruption of the CSB gene reduces the spontaneous tumor rate in cancer predisposed Ink4a/ARF-/- mice as well as causing their embryo fibroblasts to proliferate more slowly and be more sensitive to UV-induced apoptosis. In the present study we characterized phosphorothioate backbone antisense oligodeoxynucleotides (AOs) that reduced the levels of CSB mRNA in A2780/CP70 ovarian carcinoma cells. The AOs caused the cells to proliferate more slowly and made them more sensitive to either cisplatin or oxaliplatin. The AOs also enhanced the cytotoxicity of hydrogen peroxide and gamma-radiation, both of which can induce oxidative DNA lesions, which are subject to TCR. The AOs did not potentiate the cytotoxicity of topotecan, which induces DNA strand breaks. Chemically modified ( ) AOs (MBOs) targeting CSB were able to potentiate the anti-tumor effect of cisplatin against A2780/CP70 tumor xenografts formed in nude mice. The MBOs enabled a non-toxic (3 mg/kg) dose of cisplatin to have the same degree of anti-tumor efficacy as a more toxic (5 mg/kg) cisplatin dose. Collectively, these results suggest that the CSB gene product may be viewed as an anti-cancer target.

Animals↗
PubMed2001

Bioequivalence of isoniazid in a two drug fixed dose combination and in a single drug dosage form.

To increase the patient compliance and reduce the risk of drug resistant strains, WHO and IUATLD recommend the use of Fixed Dose Combination (FDC) tablets as a routine therapeutic regimen in Directly Observed Treatment Shortcourse (DOTS). But the main issue in the use of FDC is the quality of the formulation. At present WHO and IUATLD suggest the bioequivalence assessment of only rifampicin from FDC compared to separate formulations. For the therapeutic effectiveness all the components of the FDCs should be bioavailable at tissue site. Also, the primary and acquired resistance rate of isoniazid is much higher compared to other anti-tubercular drugs. Hence, a comparative bioavailability study of isoniazid from a two drugs FDC compared to a separate formulation was carried out on a group of 12 healthy volunteers. When evaluated by normal or log transformed confidence interval, Two Way ANOVA and Hauschke analysis, the bioequivalence limits for AUC0-8 and AUC0-24 were within 0.8-1.25. For Cmax and Tmax, these limits were within 0.7-1.43. Hence, isoniazid from a FDC formulation was found to be bioequivalent to a separate formulation at same dose levels.

Adolescent↗
PubMed2001

Antisense anti-MDM2 oligonucleotides as a novel therapeutic approach to human breast cancer: in vitro and in vivo activities and mechanisms.

The mouse double minute 2 (MDM2) oncogene has been suggested as a target for cancer therapy. It is amplified or overexpressed in many human cancers, including breast cancer, and MDM2 levels are associated with poor prognosis of several human cancers, including breast cancer, ovarian cancer, osteosarcoma, and lymphoma. In the present study, we investigated the functions of MDM2 oncogene in the growth of breast cancer and the potential value of MDM2 as a drug target for cancer therapy by inhibiting MDM2 expression with a specific antisense antihuman-MDM2 oligonucleotide (oligo). The selected antisense mixed-backbone oligo was evaluated for its in vitro and in vivo antitumor activity in human breast cancer models: MCF-7 cell line containing wild-type p53 and MDA-MB-468 cell line containing mutant p53. In MCF-7 cells, p53 and p21 levels were elevated, resulting from specific inhibition of MDM2 expression by the antisense oligo (AS). In MDA-MB-468 cells, after inhibition of MDM2 expression, p21 levels were elevated, although p53 levels remained unchanged. After i.p. administration of the antisense anti-MDM2 oligo, in vivo antitumor activity occurred in a dose-dependent manner in nude mice bearing MCF-7 or MDA-MB-468 xenografts. In both models, in vivo synergistically or additive therapeutic effects of MDM2 inhibition and the clinically used cancer chemotherapeutic agents irinotecan, 5-fluorouracil, and paclitaxel (Taxol) were observed. These results suggest that MDM2 have a role in tumor growth through both p53-dependent and p53-independent mechanisms. We speculate that MDM2 inhibitors, such as ASs, have a broad spectrum of antitumor activities in human breast cancers, regardless of p53 status. This study should provide a basis for future development of anti-MDM2 ASs as cancer therapeutic agents used alone or in combination with conventional chemotherapeutics.

Animals↗
PubMed2001

DNA short tandem repeat profiling of three North Indian populations.

POPULATION: Fifty healthy unrelated individuals were randomly chosen from each of the three populations viz., Bhargavas, Chaturvedies, and Brahmins. Three generation pedigree charts were prepared to ensure sirname endogamy in Bhargavas Chaturvedies and group endogamy in Brahmins subjects were chosen from several parts of Uttar Pradesh, a northern state of the Indian republic.

Alleles↗
PubMed2001

Unilateral frosted branch angiitis with vitreous haemorrhage.

Idiopathic retinal frosted branch angiitis is a rare bilateral condition and presents with an acute reduction of vision. Unilateral affection is rare. We report an unusual case of unilateral frosted branch angiitis where the patient developed total vitreous haemorrhage.

Fluorescein Angiography↗
PubMed2000

Accessible 5'-end of CpG-containing phosphorothioate oligodeoxynucleotides is essential for immunostimulatory activity.

In our ongoing efforts to decipher the sequence and structural requirements in the flanking region of the CpG motif in phosphorothioate oligodeoxynucleotides (PS-oligos), we have examined the requirement of free 5'- and 3'-ends of PS-oligos on immune stimulation. Our model studies using 3'-3'-linked (containing two free 5'-ends) and 5'-5'-linked (containing two free 3'-ends) CpG-containing PS-oligos demonstrate that immunostimulatory activity is significantly reduced when the 5'-end of the PS-oligo is not accessible, rather than the 3'-end, suggesting that the 5'-end plays a critical role in immunostimulatory activity.

Adjuvants, Immunologic↗
PubMed2000

A novel MDM2 anti-sense oligonucleotide has anti-tumor activity and potentiates cytotoxic drugs acting by different mechanisms in human colon cancer.

MDM2 is over-expressed in several human tumors. Its product is a negative-feedback regulator of p53, which interferes with the control of cell proliferation and apoptosis, interacting not only with p53 but also with retinoblastoma (Rb) and E2F. Moreover, mutations in the ARF-Ink4a locus may also allow MDM2 to override p53 functions. In this study, we have used a novel oligonucleotide anti-sense MDM2, with mixed-backbone structure and demonstrate that it causes inhibition of MDM2 expression, induction of both p53 and p21/WAF1 expression and a dose-dependent, growth-inhibitory effect in human GEO colon-cancer cells. We also show that anti-sense MDM2 has a co-operative growth-inhibitory effect with different classes of cytotoxic drugs acting by different mechanisms. Moreover, anti-sense MDM2 induces apoptosis and markedly enhances the apoptotic activity of different cytotoxic drugs. Finally, we show that anti-sense MDM2 has anti-tumor activity in vivo in nude mice bearing GEO xenografts and potentiates the anti-tumor effect of cytotoxic drugs. Indeed, despite the short treatment period, the combination of anti-sense MDM2 and cytotoxic drugs causes a marked delay in tumor growth and prolongation of mice survival, lasting several months after treatment cessation. The anti-tumor effect is associated with inhibition of MDM2 expression in tumor specimens of animals treated with anti-sense MDM2, alone or in combination with a cytotoxic drug. Our results provide the rationale for development of a novel mixed-backbone anti-sense MDM2 into a clinical setting in therapeutic combination strategies with conventional cytotoxic drugs.

Animals↗
PubMed2000

Gallstones, from gallbladder to gut. Management options for diverse complications.

Gallstones may be incidental and asymptomatic or painful and accompanied by life-threatening obstruction or infection. A thorough knowledge of potential complications is therefore critical, especially because some asymptomatic stones require prompt treatment. In this article, Drs Agrawal and Jonnalagadda provide valuable instructions for recognizing and treating the various manifestations of gallstone disease.

Acute Disease↗
PubMed2000

Biotinylation of substituted cysteines in the nicotinic acetylcholine receptor reveals distinct binding modes for alpha-bungarotoxin and erabutoxin a.

Although previous results indicate that alpha-subunit residues Trp(187), Val(188), Phe(189), Tyr(190), and Pro(194) of the mouse nicotinic acetylcholine receptor are solvent-accessible and are in a position to contribute to the alpha-bungarotoxin (alpha-Bgtx) binding site (Spura, A., Russin, T. S., Freedman, N. D., Grant, M., McLaughlin, J. T., and Hawrot, E. (1999) Biochemistry 38, 4912-4921), little is known about the accessibility of other residues within this region. By determining second-order rate constants for the reaction of cysteine mutants at alpha184-alpha197 with the thiol-specific biotin derivative (+)-biotinyl-3-maleimidopropionamidyl-3,6-dioxaoctanediamine , we now show that only very subtle differences in reactivity (approximately 10-fold) are detectable, arguing that the entire region is solvent-exposed. Importantly, biotinylation in the presence of saturating concentrations of the long neurotoxin alpha-Bgtx is significantly retarded for positions alphaW187C, alphaF189C, and reduced wild-type receptors (alphaCys(192) and alphaCys(193)), further emphasizing their major contribution to the alpha-Bgtx binding site. Interestingly, although biotinylation of position alphaV188C is not affected by the presence of alpha-Bgtx, erabutoxin a, which is a member of the short neurotoxin family, inhibits biotinylation at position alphaV188C, but not at alphaW187C or alphaF189C. Taken together, these results indicate that short and long neurotoxins establish interactions with distinct amino acids on the nicotinic acetylcholine receptor.

Amino Acid Substitution↗
PubMed2000

Immunostimulatory activity of CpG containing phosphorothioate oligodeoxynucleotide is modulated by modification of a single deoxynucleoside.

Phosphorothioate oligodeoxynucleotides (PS-oligos) containing the CpG motif have immunostimulatory properties. Our earlier study had shown that the immunostimulatory activity of PS-oligos containing the CpG motif can be modulated by incorporation of 2'-O-methylribonucleosides (Zhao, Q.; Yu, D.; Agrawal, S. Bioorg. Med. Chem. Lett. 1999, 9, 3453). Here we show that the immunostimulatory activity of a PS-oligo containing a CpG motif can be modulated by substitution of a single deoxynucleoside at specific sites with either 2'-O-methylribonucleoside or 3'-O-methylribonucleoside in the flanking region to CpG motif. Furthermore, substitution of deoxynucleosides with 2'-O-methoxyethoxyribonucleosides also results in modulating immunostimulatory activity of PS-oligos.

Animals↗
PubMed2000

Percutaneous treatment of catheter-induced dissection of the left main coronary artery and adjacent aortic wall: a case report.

Left main coronary artery dissection complicating selective coronary angiography is uncommon. Moreover, aortic root dissection associated with coronary intervention is underreported and may require urgent surgical intervention. During percutaneous coronary angioplasty of a catheter-induced left main coronary artery dissection, retrograde dissection of the adjacent aortic root occurred. Both were successfully treated by stenting of the left main coronary artery. Cathet. Cardiovasc. Intervent. 49:86-89, 2000.

Aged↗
PubMed2000

A comparison of a brief and long version of the Situational Confidence Questionnaire.

Assessing confidence to resist drinking in high risk situations is an important part of behavioral treatments for alcohol problems. The present study assessed the reliability and validity of the original 100-item Situational Confidence Questionnaire (SCQ) and of an 8-item brief version (BSCQ). Using a visual analog scale, the BSCQ asked respondents to report their confidence to resist urges to drink heavily using the original eight SCQ subscales (e.g., pleasant times with others, social pressure). Data were collected from 120 adult problem drinkers who voluntarily entered an outpatient alcohol treatment program. The comparability of the BSCQ and the SCQ-100 was evaluated through intraclass correlations between the eight subscales and comparison of both instruments' underlying factor structures. Correlation coefficients for the subscales ranged from 0.56 to 0.80. Both instruments showed similar, but not identical factor structures. The present results indicate that the BSCQ provides comparable information to the SCQ-100. Limitations, as well as the clinical advantages, of using the BSCQ over longer versions are discussed.

Adult↗
PubMed2000

Non-specific antiviral activity of antisense molecules targeted to the E1 region of human papillomavirus.

Antisense phosphorothioate oligonucleotides (ODN1 0x5 OMe) directed against the E1 start region of human papillomavirus 11 (HPV11) can inhibit papillomavirus induced growth of implanted human foreskin in a mouse xenograft model. Administration of a mismatch control oligonucleotide (ODN9 0x5 OMe), in which guanine was replaced with adenine in the same model, had no effect on papilloma induced growth. However, the apparent antiviral activity of ODN1 0x5 OMe was also shown in a lethal mouse cytomegalovirus (CMV) model, in which the oligonucleotides are not expected to have antisense activity. To understand the mechanisms of action of these oligonucleotides, a mismatch oligonucleotide (ODN61 0x5 OMe) was prepared which retained the CpG motifs of ODN1 0x5 OMe. This was tested in the mouse xenograft model and shown to have moderate inhibitory activity. As a definitive experiment, a comparison was made between the efficacy of the active oligonucleotide ODN1 0x5 OMe against two papilloma viruses HPV11 and HPV40. Both these viruses cause benign genital warts, but differ by four bases in their E1 sequence that was the target for ODN1 0x5 OMe. Papillomavirus induced growth in the mouse xenograft model was inhibited by ODN1 0x5 OMe in both cases, suggesting that oligonucleotide molecules have a non-specific antiviral activity that is not directly related to their antisense sequence.

Animals↗
PubMed2000

Complete capsular bag distension syndrome.

After conventional extracapsular cataract extraction and in-the-bag intr aocular lens (IOL) implantation 3 years previously, the partially cut su perior one-third of the anterior capsulotomy flap resealed in the eye of a 55-year-old woman. With the integrity of the capsular bag restored, it distended fully; the IOL was in the center and milky fluid accumulated inside. A neodymium:YAG laser was used to drain the milky fluid and di srupt the opacified anterior and posterior capsules, restoring vision.

Capsulorhexis↗