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Biomedical subjects

R Roy

Publications and source records attributed to R Roy.

At least 289 records · Page 16Linked to original sources
PubMed1991

Multivesicular liposomes containing bleomycin for subcutaneous administration.

Optimal cancer treatment with cell-cycle-specific agents requires maintenance of a cytotoxic drug level for a prolonged period. We explored the use of multivesicular liposomes as a slow-release depot of bleomycin for systemic administration via the s.c. route. The average volume-adjusted liposome size was 19.1 microns, the half-life of leakage in human plasma was 32.1 h, and the half-life of s.c. liposomal bleomycin was 31.8 h. When tested against the s.c. B-16 melanoma model in BDF1 mice, the therapeutic index of single-dose bleomycin given s.c. was significantly improved when the drug was encapsulated in multivesicular liposomes. The efficacy was improved as assessed by both inhibition of tumor growth and increased life span, and the toxicity appeared to be decreased.

Animals↗
PubMed1991

Expedient syntheses of neoglycoproteins using phase transfer catalysis and reductive amination as key reactions.

Starting from peracetylated chloro- or bromo-glycosyl donors of N-acetylneuraminic acid, N-acetylglucosamine, glucose and lactose, the corresponding p-formylphenyl glycosides were synthesized stereospecifically under phase transfer catalysed conditions at room temperature in yields of 38-67%. After Zemplén de-O-acetylation, the formyl groups were directly and chemoselectively coupled to the lysine residues of bovine serum albumin by reductive amination using sodium cyanoborohydride. The conjugation reactions were followed as a function of time and under a series of different molar ratios of the reactants to provide glycoconjugates of varying degree of antigenicities. Thus, carbohydrate protein conjugates were made readily available using essentially two key reactions.

Aldehydes↗
PubMed1991

Differential regulation of mouse mammary tumor virus-bacterial chloramphenicol acetyltransferase chimeric gene by human mineralocorticoid hormone-receptor complexes.

The brain tissues of the rat and mouse express two types of corticosteroid binding proteins, the glucocorticoid (GR) and aldosterone (MR) receptors. Unlike the type II (GR) receptor, type I receptor has a high affinity for aldosterone (ALDO) and corticosterone and is structurally similar to the kidney mineralocorticoid receptor (MR). The results reported in this study provide direct evidence for the interaction of dexamethasone (DEX), triamcinolone acetonide (TA), dexamethasone-21-mesylate (DXM) and 11-deoxycorticosterone (DOC) with human MR expressed in cells by transient co-transfection of a hMR expression vector. The interactions of hMR with DEX, TA, DXM, DOC, promegestone (R5020) and methyltrienelone (R1881) were measured by trans-activation of mouse mammary tumor virus long terminal repeat fused to bacterial chloramphenicol acetyltransferase (MMTV-tk-CAT) in gene co-transfection experiments and by cell free hormone binding assay. The incubation of various steroid hormones in the presence of [3H]ALDO in a competition assay with extracts prepared from HeLa cells co-transfected with hMR expression vector, showed that hMR expressed under these conditions has a high relative affinity for DEX which is similar to ALDO, TA and DOC. Incubation with DXM under these conditions showed very little competition, as was observed with R1881 and R5020. Incubation of the co-transfected cells with DEX, ALDO, DOC, R5020, TA, R1881 and DXM demonstrated that the level of trans-activation did not reflect the previously observed order of binding affinity for the hMR. The level of transactivation was always higher with DEX and TA compared to ALDO and DOC. Analysis of the binding of labeled glucocorticoid regulatory element (GRE) and hMR incubated with DEX, ALDO and DXM by gel shift analysis demonstrated that the trans-activation of MMTV-tk-CAT by hMR is a result of the interaction of hMR with GRE in the MMTV-LTR.

Animals↗
PubMed1991

Inhibition of influenza A virus hemagglutinin and induction of interferon by synthetic sialylated glycoconjugates.

Multivalent forms of neoglycoproteins and polyacrylamides containing sialic acid were prepared and shown to be potent inhibitors of influenza A virus (H3N2) hemagglutinin with chick red blood cells. The synthetic sialylated glycoconjugates, although they were neuraminidase substrates, did not suppress viral neuraminidase and did not reduce infectivities in chick embryos. The copolyacrylamide conjugate containing a spacer group of approximately 11 A (1 A = 0.1 nm) between the polymer backbone and the sialic acid residues was the best hemagglutinin inhibitor. Moreover, it exhibited promising interferon-inducing properties.

Animals↗
PubMed1991

Detection of haptoglobin from concentrated urine samples by enzyme immunoassay.

The detection of haptoglobin (Hp) from serum and bloodstains is utilized extensively in forensic science laboratories in order to include or exclude possible donors. There is an increasing need to make the same discriminations utilizing genetic markers from urine samples. This paper describes the use of enzyme immunoassay and Western blotting (electrophoretic) techniques to determine Hp phenotypes from concentrated urine samples. Serum and urine specimens were collected from volunteer donors. The serum sample from each donor was typed for Hp. The urine specimens were concentrated 3000-fold from the starting volume of 15 mL to a final volume of 5 microL and applied to the gradient polyacrylamide gels. This procedure allows the separation of Hp samples into the three common phenotypes as well as the other rare variants found in humans. The Western blotting electrophoretic technique was used to achieve the transfer of Hp bands from the gels to the nitrocellulose membranes. Enzyme immunoassay with goat anti-Hp antiserum and rabbit anti-goat immunoglobulin alkaline phosphatase conjugate were used to identify the Hp bands from the concentrated samples. Specimens stored for six months at -22 degrees C were also concentrated and typed successfully. Recent implementation of drug-screening policies has resulted in an increase in the submission of substituted urine specimens. The above procedure can be used to detect an additional genetic marker from urine samples and thus facilitate the identity of the donor.

Blotting, Western↗
PubMed1991

Haptoglobin phenotyping from older bloodstains by enzyme immunoassay and haptoglobin phenotypes within a Nebraska Caucasian population.

Enzyme immunoassay and Western blotting (electrophoretic) techniques were used to determine haptoglobin (HP) phenotypes from older bloodstains. Serum was collected from liquid blood and the HP phenotypes were determined. Bloodstains were prepared from these specimens and stored at various temperatures for several months. The stains were extracted and applied to gradient polyacrylamide gels. The Western blotting technique was used to achieve the transfer of HP bands from the gels to the nitrocellulose membranes. Enzyme immunoassay with goat anti-HP antiserum and rabbit anti-goat immunoglobulin peroxidase were used to identify the HP bands from the extracted samples. Enzyme immunoassay was found to be clearly more sensitive than o-dianisidine or o-tolidine in detecting HP bands from diluted serum samples. The haptoglobin frequency in a Caucasian population in Nebraska was calculated. The frequencies of Phenotypes 1, 2-1, and 2 were found to be 15.8, 48.4, and 35.8%, respectively.

Blood Preservation↗
PubMed1990

A new antileishmanial compound, phaseolinone.

Inclusion of phaseolinone, a newly described mycotoxin, at 20 micrograms per ml in a solid culture medium (blood agar overlay) and at 50 micrograms per ml in a liquid culture (medium 199) inhibited the growth of L. donovani promastigotes. About 90% of the motile promastigotes lost motility after exposure to 50 micrograms per ml of phaseolinone for 6-7 h and here 3-day-old culture was more sensitive than 7-day-old culture. In an in vitro assay, DNA dependent RNA polymerase activity of 3-day-old promastigotes was considerably inhibited in the presence of this toxin. Therefore, this key enzyme was suggested to be one of the sites of action of phaseolinone.

Animals↗
PubMed1990

Long-term culture and characterization of human limbal microvascular endothelial cells.

Human limbal explants obtained from 44 eyebank donors were cultured in medium 199 supplemented with 20% fetal bovine serum, vascular endothelial cell growth supplement and heparin. Cells grew abundantly out of the explants. They initially formed a 'cobblestone' patterned monolayer but later exhibited an elongated morphology with growth in parallel bundles. These cells could be passaged at least nine times and were identified throughout the consecutive passages as microvascular endothelial cells by the expression of factor VIII-related antigen, laminin and of the H determinant of ABO blood groups. As expected from vascular endothelial cells, flow cytometric analysis demonstrated a strong expression of class I histocompatibility antigens and a weaker expression of class II antigens. Class II antigen expression was enhanced by culturing the cells in the presence of immune interferon. These cells produced immunoreactive interleukin-1, mainly of the alpha type, under endotoxin stimulation. Limbal microvascular cells could be useful to study corneal angiogenesis. Furthermore, long-term culture of limbal cadaveric tissue can potentially be used to characterize donor-specific immunologic responses in corneal graft recipients.

ABO Blood-Group System↗
PubMed1990

Association between corneal allograft reactions and HLA compatibility.

The purpose of this follow-up study is to measure the association between corneal allograft reactions and donor-recipient HLA-A and HLA-B compatibility. Four hundred thirty-eight consecutive adult recipients of corneal grafts with known donor-recipient HLA matching were observed for allograft reactions and failures. Most of the recipients under observation (91%) were well matched for HLA-DR. Of 438 recipients, 158 (36%) completed a 3-year follow-up. Three factors were associated with endothelial allograft reactions: 2 to 4+ corneal vascularization (relative risk, 2.2; P = 0.0006), two mismatched antigens at either the HLA-A or HLA-B locus (relative risk, 2.1; P = 0.0009), and recipient wound size of 8 mm or greater (relative risk, 1.5; P = 0.05). Unexpectedly, a strong association between endothelial allograft reactions and HLA-A or HLA-B incompatibility was found in low-risk recipients defined as unvascularized recipients of a small graft (relative risk, 3.2; P = 0.004). A larger sample size is required to determine if HLA matching offers a solution for recipients with corneal vascularization.

Adolescent↗