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A Alam

Publications and source records attributed to A Alam.

At least 73 records · Page 4Linked to original sources
PubMed1992

A model for formulation of protein assay.

The principle of the protein assay using the reaction of an alkaline copper-protein complex with the Folin-Ciocalteu phenol reagent has been investigated. In contrast to the long-established Lowry method, a stable and rapid protein assay is developed without a buffering agent in alkaline copper solution. In the absence of a buffering agent, the reaction pH drops relatively rapidly and moves the reaction toward a more stable pH. When the reaction of alkaline copper-protein complex with Folin-Ciocalteu reagent is started at around pH 11.7, the reaction color absorbance reaches a plateau in approximately 10 min and remains stable to allow a reliable measurement of the absorbance. In the absence of the buffering agent sodium carbonate, the alkaline copper solution is also stable for months. The principle of the protein assay is presented as a model that can be used to formulate protein assays of desired specification.

Colorimetry↗
PubMed1992

Effect of lysine residue modification of ovine luteinizing hormone by heterobifunctional crosslinking reagent SPDP on subunit-subunit association, receptor binding and biological activity.

The increasing use of heterobifunctional crosslinking agent in the design of hormone-carrier conjugates for selective targeting or inducing immune response against the hormone has prompted us to study the effect of epsilon-NH2 group modification of oLH-subunit, their recombination, immunoreactivity, receptor binding and biological activity. The epsilon-NH2 groups of oLH alpha and oLH beta subunits were modified by using SPDP. The SPDP modified oLH alpha derivatives hybridize to native OLH beta as judged by RP-HPLC analysis. The sequential modification of alpha and beta subunits led to progressive reduction in immunoreactivity and receptor binding activities. The steroidogenic potential of oLH beta.SPDP.alpha oLH recombinant was relatively comparable. The modification of six or more epsilon-NH2 groups in oLH alpha although recombine fully with native oLH beta but failed to react to anti-oLH antibody. Moreover, steroidogenic activity was also abolished. Introduction up to four SPDP groups in oLH alpha compromised immunological and biological activities but further addition of two more SPDP groups completely abolished antibody reactivity, receptor binding and steroidogenic activity indicating the importance of later two -NH2 groups in the receptor recognition and steroidogenic potential.

Animals↗
PubMed1991

Evaluation of adjuvanticity of promising new synthetic MDP analogues.

A series of nor-MDP analogues were evaluated for adjuvanticity in rodents using beta hCG-TT conjugate as the antigen. Of these, one compound, N-acetylnor-muramyl-L-N-methylalanyl-D-isoglutamine octylamide (nor-MDP octylamide (N-Me-Ala] was found to be effective. This compound, formulated with beta hCG-TT in water-in-oil emulsion and administered to rodents, significantly enhanced the anti-hCG response. The anti-hCG titers induced were three-fold higher than that of control formulation. Moreover, inclusion of this compound in the first injection only gave adequate levels of antibodies to the hormone which persisted longer in the blood circulation. Effectiveness of antibodies in neutralizing hCG was tested in vitro by the mouse Leydig cell bioassay. Biological vs. immunological binding capacities (B/I ratio) were compared. The results suggest that nor-MDP octylamide (N-Me-Ala) will be useful as an adjuvant for human vaccines.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1990

Serum alkaline phosphatase in apparently healthy Karachi population.

Serum alkaline phosphatase (AP) was estimated in a total of 786 (418 males and 386 females) apparently healthy people aged between 1-75 years selected randomly from a sample of the Karachi population. Reference ranges for AP level were obtained for the males and females stratified into ten successive age groups. The study population was also divided into two main age groups, a paediatric aged between 1-14 years and an adult group aged between 15 to over 50 years to see if the mean AP levels differ significantly between the two groups. Mean AP level for the male paediatric age group was 225 IU/L, significantly higher (P less than 0.005) than those of the male adult mean level of 83 IU/L. Similarly the mean AP levels for the paediatric female age group was 205 IU/L significantly higher (P less than 0.005), compared to the mean AP level of 67 IU/L obtained for the female adult age group.

Adolescent↗
PubMed1989

Semisynthetic anti-LHRH vaccine causing atrophy of the prostate.

A modified luteinizing hormone releasing hormone (LHRH) analog (D-lys)6 was synthesized and linked to epsilon-amino caproic acid at the 6th position. The free amino group thus generated was used for conjugation to diphtheria toxoid. Immunogenicity and bioefficacy studies of this conjugate vaccine were carried out in rodents. All immunized animals produced antibodies reactive with native LHRH. A gradual decline in testosterone levels accompanied the rise in anti-LHRH titers. On necropsy, after 10 weeks, a significant reduction in the relative weights of testes and accessory sex organs was noticed. Of particular significance was the marked atrophy of the prostate, indicating a possible therapeutic application of this vaccine in the treatment of androgen-dependent carcinoma of the prostate.

Animals↗
PubMed1989

Functional morphology of testis and its excurrent ducts in rats immunized with synthetic luteinizing hormone releasing hormone conjugated to tetanus toxoid.

The effects of active immunization against luteinizing hormone releasing hormone (LHRH) on the testis and its excurrent ducts in rats were studied using a synthetic LHRH peptide conjugated to tetanus toxoid (TT), with or without an adjuvant. The study demonstrated that LHRH-TT given alone did not elicit an appreciable immune response and that its immunogenicity could be enhanced by administration with an adjuvant, such as species-specific IgG or SPLPS. The anti-LHRH antibody response showed a corresponding regressive effect on the morphology of the testis and its excurrent ducts. The functional involution of the testis was reflected in the form of a block in spermatogenesis and the lowering of testosterone production; the basic structural organization of the testicular components was, however, maintained. Epididymal ducts displayed rather drastic atrophic changes, indicating that prolonged immunization may result in irreversible damage to the excurrent ducts and could, therefore, adversely affect the restoration of fertility even after the return of testicular function following decline in the immune response against LHRH. This could be an important consideration if LHRH immunization is to be used for male contraception.

Animals↗
PubMed1989

Stability of an antifertility vaccine consisting of gonadotropin subunits linked to tetanus toxoid.

The shelf life and thermal stability of an antifertility vaccine, in which gonadotropin subunits are linked to carriers such as tetanus toxoid and cholera toxin chain B and has successfully completed phase-I clinical trials at five centres in India, was studied. The vaccine adsorbed on alum was stored at three temperatures, 4 degrees C, room temperature (20-30 degrees C) and at 40 degrees C, for a period of up to 1 year. The human chorionic gonadotropin (hCG) binding capacity of antibodies (peak titres) induced in rodents by the vaccine after 6 months of storage at 40 degrees C and at room temperature were 1430 +/- 201 (mean +/- s.e.m.) and 1291 +/- 152 ng ml-1 respectively as compared to 1075 +/- 185 ng ml-1 for the vaccine stored at 4 degrees C. The difference was not statistically significant. After 12 months of storage, the immunogenic properties of the vaccine were nearly the same irrespective of the temperature at which the vaccine was kept. The findings show that the vaccine adsorbed on alum can withstand storage up to at least one year at room temperature and at 40 degrees C. These observations have implications for the current thoughts on storage of tetanus toxoid and diphtheria toxoid at 4-8 degrees C, the two vaccines widely used in immunoprophylaxis, and suggest that similar investigations on these vaccines as cold chain facilities are not universally available in developing countries.

Animals↗
PubMed1989

Human liver GTP cyclohydrolase I: purification and some properties.

Human liver guanosine triphosphate (GTP) cyclohydrolase I has been purified more than 1,700-fold to what appears to be homogeneity. The active enzyme complex has an estimated molecular weight of 453,000 +/- 11,500 by gel filtration chromatography. It consists of a polypeptide of 149,000 +/- 4,000 mol wt by SDS-polyacrylamide gel electrophoresis. The activity of the enzyme is heat stable and is inhibited by di- and trivalent cations. The enzyme has an optimum pH of 7.7 in sodium phosphate buffer. It uses GTP as a sole substrate, with a Km of 116 microM.

Aminohydrolases↗
PubMed1989

Vaccine for control of fertility.

Birth control vaccines constitute a new category of vaccines. Immunization with the objective of selectively blocking a physiological process differs in many respects from immunizing against pathogens. Conceptually, these widen the orbit of therapeutic intervention by immunological methods. Success recorded in making vaccines regulating fertility offers models to regulate any other physiological process in the body. At a practical level, the task of making such vaccines is beset with inherent difficulties and with new challenges. This article, dedicated to Avrion Mitchison, aims to discuss these problems and to record successes wherever achieved.

Family Planning Services↗
PubMed1989

Antibody response and characteristics of antibodies in women immunized with three contraceptive vaccines inducing antibodies against human chorionic gonadotropin.

Data are presented on antibody titers generated in 88 women immunized with three formulations of antihuman chorionic gonadotropin (hCG) vaccine, namely, beta-hCG (formulation B); beta-hCG associated with alpha-subunit of ovine luteinizing hormone (LH) (formulation A) and beta-hCG + beta-ovine LH (formulation M), each linked to tetanus toxoid and cholera toxin chain B as carriers. Each formulation was tested at two dose levels (100 and 500 micrograms). All women without exception developed anti-hCG antibodies having hCG-binding capacity above 20 ng mL-1 (0.5 nM), a level considered to be the threshold for prevention of pregnancy. Formulations A and B gave relatively better immunogenic response in human subjects than M. In each case, the antibody response was reversible. The mean duration of response above 20 ng was 35 to 37 weeks for formulation A, 34 weeks for B, and 17 to 20 weeks for M. Antibodies induced by three formulations of the vaccine had high-affinity (Ka 10(9)-10(10)M-1) for binding with hCG. They were devoid of cross-reaction with human follicle-stimulating hormone and thyroid-stimulating hormone but, as expected, cross-reacted with human LH. Antibodies were competent to block the hCG induced ovarian hyperemia.

Adult↗
PubMed1988

Inhibition of GTP cyclohydrolase I by pterins.

Pterins inhibit rat liver GTP cyclohydrolase I activity noncompetitively. Reduced pterins, such as 7,8-dihydro-D-neopterin, (6R,S)-5,6,7,8-tetrahydro-D-neopterin, 7,8-dihydro-L-biopterin, (6R)-5,6,7,8-tetrahydro-L-biopterin, L-sepiapterin, and DL-6-methyl-5,6,7,8-tetrahydropterin are approximately 12-times more potent as inhibitors than are oxidized pterins, such as D-neopterin, L-biopterin, and isoxanthopterin. They are also 12-times more potent than folates, such as folic acid, dihydrofolic acid, (+/-)-L-tetrahydrofolic acid, and aminopterin. The Ki values for 7,8-dihydro-D-neopterin, 7,8-dihydro-L-biopterin, and (6R)-5,6,7,8-tetrahydro-L-biopterin are 12.7 microM, 14.4 microM, and 15.7 microM, respectively. These results suggest that mammalian GTP cyclohydrolase I may be regulated by its metabolic end products.

Aminohydrolases↗
PubMed1986

Possible basis for membrane changes in nonparasitized erythrocytes of malaria-infected animals.

Previous studies (Gupta et al. (1982) Nature 299, 259-261) have shown that nonparasitized erythrocytes of Plasmodium knowlesi-infected monkeys contain the procoagulant phospholipid phosphatidylserine (PS) in the outer-half of their membrane bilayer. A reinvestigation of this problem has now revealed that in acute P. knowlesi infection, at least 30% of the infected animals do not have this abnormality. However, PS externalization was a consistent feature in the uninfected red cells of chronically infected animals. Also, a similar membrane change was observed in the red cells of uninfected splenectomized monkeys. These results strongly suggest that spleen plays an important role in maintaining the exclusive inner distribution of PS in the normal erythrocyte membrane, and that partial migration of this lipid to the outer monolayer in nonparasitized erythrocytes could be attributed to an abnormal physiology of this organ in malarial infection.

Animals↗
PubMed1985

Orotic acid, a promoter of liver carcinogenesis induces DNA damage in rat liver.

Orotic acid, a precursor of pyrimidine nucleotide biosynthesis and a promoter for liver carcinogenesis, when fed at 1% level in a diet for 5 weeks resulted in liver DNA damage. The damage can be monitored as alkali-labile lesions using alkaline sucrose gradients as well as alkaline elution technique. Furthermore, the induced DNA damage persists for up to three weeks after withdrawal of the orotic acid diet. The fact that several skin-tumour promoters also induce DNA damage raises the question whether DNA damage is a component in tumour promotion.

Animals↗