Interpretation of quantitative structure-property and -activity relationships

The potential utility of data reduction methods (e.g. principal component analysis) for the analysis of matrices assembled from the related properties of large sets of compounds is discussed by reference to results obtained from solvent polarity scales, ongoing work on solubilities and sweetness properties, and proposed general treatments of toxicities and gas chromatographic retention indices.

Effect of cholesterol on interaction of dibucaine with phospholipid vesicles: a fluorescence study

Interaction of the local anesthetic dibucaine with small unilamellar vesicles of dimyristoylphosphatidylcholine (DMPC) and dioleoyl phosphatidylcholine (DOPC) containing different mol percents of cholesterol has been studied by fluorescence spectroscopy. Fluorescence measurements on dibucaine in presence of phospholipid vesicles containing various amounts of cholesterol yielded a pattern of variation of wavelength at emission maximum and steady-state anisotropy which indicated that the microenvironment of dibucaine is more polar and flexible in membranes that contain cholesterol than in membranes without cholesterol. Experiments on quenching of fluorescence from membrane-associated dibucaine by potassium iodide showed a marked increase in quenching efficiency as the cholesterol content of the vesicles was increased, demonstrating increased accessibility of the iodide quenchers to dibucaine in the presence of cholesterol, when compared to that in its absence. Total emission intensity decay profiles of dibucaine yielded two lifetime components of approximately 1 ns and approximately 2.8--3.1 ns with mean relative contributions of approximately 25 and approximately 75%, respectively. The mean lifetime in vesicles was 20--30% smaller than in the aqueous medium and showed a moderate variation with cholesterol content. Fluorescence measurements at two different temperatures in DMPC SUVs, one at 33 degrees C, above the phase transition temperature and another at 25 degrees C, around the main phase transition, indicated two different mode of dibucaine localization. At 25 degrees C dibucaine partitioned differentially in presence and absence of cholesterol. However, at 33 degrees C the apparent partition coefficients remained unaltered indicating differences in the microenvironment of dibucaine in presence and absence of cholesterol in the phospholipid membranes.

Structural perturbation of proteins in low denaturant concentrations

The presence of very low concentrations of the widely used chemical denaturants, guanidinium chloride and urea, induce changes in the tertiary structure of proteins. We have presented results on such changes in four structurally unrelated proteins to show that such structural perturbations are common irrespective of their origin. Data representative of such structural changes are shown for the monomeric globular proteins such as horseradish peroxidase (HRP) from a plant, human serum albumin (HSA) and prothrombin from ovine blood serum, and for the membrane-associated, worm-like elongated protein, spectrin, from ovine erythrocytes. Structural alterations in these proteins were reflected in quenching studies of tryptophan fluorescence using the widely used quencher acrylamide. Stern-Volmer quenching constants measured in presence of the denaturants, even at concentrations below 100 mM, were higher than those measured in absence of the denaturants. Both steady-state and time-resolved fluorescence emission properties of tryptophan and of the extrinsic probe PRODAN were used for monitoring conformational changes in the proteins in presence of different low concentrations of the denaturants. These results are consistent with earlier studies from our laboratory indicating structural perturbations in proteins at the tertiary level, keeping their native-like secondary structure and their biological activity more or less intact.

Inhibition of Mycobacterium smegmatis topoisomerase I by specific oligonucleotides

DNA topoisomerase I from Mycobacterium smegmatis unlike many other type I topoisomerases is a site specific DNA binding protein. We have investigated the sequence specific DNA binding characteristics of the enzyme using specific oligonucleotides of varied length. DNA binding, oligonucleotide competition and covalent complex assays show that the substrate length requirement for interaction is much longer ( approximately 20 nucleotides) in contrast to short length substrates (eight nucleotides) reported for Escherichia coli topoisomerase I and III. P1 nuclease and KMnO(4) footprinting experiments indicate a large protected region spanning about 20 nucleotides upstream and 2-3 nucleotides downstream of the cleavage site. Binding characteristics indicate that the enzyme interacts efficiently with both single-stranded and double-stranded substrates containing strong topoisomerase I sites (STS), a unique property not shared by any other type I topoisomerase. The oligonucleotides containing STS effectively inhibit the M. smegmatis topoisomerase I DNA relaxation activity.

N-terminal region of P protein of Chandipura virus is responsible for phosphorylation-mediated homodimerization

The phosphoprotein P of Chandipura (CHP) virus, an Indian isolate of rhabdovirus, was found to support transcription upon phosphorylation by casein kinase II (CKII). A phosphorylation-induced change in the protein conformation was found to occur at the N-terminal region of the protein. Biochemical studies for further characterization of this phosphorylation-based conformational alteration demonstrated that phosphorylation leads to the transition from an 'open' to 'closed' structure of the protein. The phosphate group introduced by CKII was found to be resistant to phosphatases. This phosphorylation-based structural alteration changes the accessible hydrophobic surface area of the protein and also the available digestion sites of different proteases. The phosphorylated form of P protein was found to be a dimer by His-tag dilution assay. Using the same approach it was found that the N-terminal 46 amino acids are responsible for P-P dimerization, only after phosphorylation.

Colorectal cancer vaccines: antiidiotypic antibody, recombinant protein, and viral vector

The colorectal cancer antigen GA733 (also termed CO17-1A, KSI-4, Ep-CAM, KSA) has proved to be a useful target in passive immunotherapy with monoclonal antibody and in active immunotherapy with antiidiotypic antibodies in cancer patients. The GA733 antigen was molecularly cloned and expressed in baculovirus (BV), adenovirus (AV), and vaccinia virus (VV). Recombinant BV-, VV-, and AV-GA733 induced antigen-specific cytotoxic antibodies and proliferative and delayed-type hypersensitive lymphocytes. However, only the AV recombinant induced antigen-specific cytolytic T lymphocytes and regression of established tumors. Cured mice were protected against challenge with antigen-negative tumors, indicating antigen spreading of immune responses. In a model of active immunotherapy against the murine homologue of the human GA733 antigen, murine epithelial glycoprotein (mEGP), BV-derived mEGP protein in various adjuvants did not protect mice against a challenge with mEGP-positive tumors. AV mEGP, only when combined with interleukin-2, significantly inhibited growth of established mEGP-positive tumors. This is in contrast to the same vaccine expressing the human antigen that was effective without interleukin-2. AV GA733, in combination with interleukin-2, is a candidate vaccine for colorectal cancer patients.

Structural changes of horseradish peroxidase in presence of low concentrations of urea

The presence of very low concentrations of the widely used denaturant urea induces structural changes in the monomeric heme-containing enzyme, horseradish peroxidase (HRP). Structural alterations in the protein were reflected in quenching studies of tryptophan fluorescence using the widely used quencher acrylamide. Stern-Volmer quenching constants measured in presence of urea, even in concentrations below 100 mm, were higher than those measured in absence of the denaturant. The fluorescence emission maximum of 1, 8-ANS, used as a probe for monitoring conformational changes in the enzyme, was blue-shifted from 530 nm in aqueous buffer to 518 nm when incorporated in native HRP. This blue shift increased further by 3 nm in presence of HRP preincubated with 100 mm urea, whereupon it steadily decreased with increasing urea concentration to become zero at 8 m urea. The mean fluorescence lifetime of 1,8-ANS incorporated in HRP was much higher than that of ANS in aqueous buffer, and showed continuous variation with the concentration of urea in which the enzyme was incubated. Systematic changes in the microenvironment of the heme moiety in HRP were also reflected in the visible CD spectra of the enzyme incubated with low concentrations of urea. These results are consistent with those of our earlier studies performed with the denaturant guanidinium chloride and indicate structural relaxation of HRP, with retention of enzymatic activity and native-like secondary structure, in presence of millimolar concentrations of urea.

Sensorineural hearing loss associated with otitis media with effusion in children

Sensorineural hearing loss (SNHL) is known to occur in various types of otitis media. Although the mechanism by which SNHL develops in association with otitis media with effusion (OME) is unknown, several hypotheses have been advocated up to now. We reviewed the clinical records of children with otitis media with effusion (OME) to reveal the association with sensorineural hearing loss. The material consisted of 71 children (119 ears) who were diagnosed as having OME and gave reliable audiograms in our clinic during an 11 month period from February 1997 through January 1998. From these cases those which showed bone conduction loss of 25 dB or higher at any one of the frequencies of 250 through 4 kHz were selected and considered to be cases of SNHL. Eight cases (9%) which had temporary threshold shift (TTS) or permanent threshold shift (PTS) were considered to be etiologically related to OME. The clinical course in each of these cases with SNHL was reviewed and evaluated in detail. We noted that all children with TTS improved completely. The result of this study indicates that we have to be aware of a possible development of SNHL during the course of OME.

Transcriptional activator C protein-mediated unwinding of DNA as a possible mechanism for mom gene activation

The bacteriophage Mu mom gene encodes the unique DNA-modification function of the phage. Regulation of the mom gene at the transcriptional level is brought about by the transactivator protein C of the phage. The mom promoter is an activator-dependent weak promoter having poor -10 and -35 elements separated by a 19 bp suboptimal spacer region. These features could constrain RNA polymerase occupancy at the promoter. Here, we have probed into the mechanism by which C protein acts as a transcriptional activator at Pmom. In vivo dimethyl sulfate footprinting studies demonstrate C protein-mediated asymmetric distortion of its specific site at the mom regulatory region. Using a coupled topoisomerase assay, we demonstrate that C protein induces the unwinding of DNA. This C-mediated unwinding seems to be localised to the 3' flanking region of the C binding site located adjacent to and overlapping the -35 element of Pmom. These results suggest that C protein-mediated torsional changes could be reorienting the -10 and -35 elements to a favorable conformation for RNA polymerase occupancy at the mom promoter.

Conformation induction in melanotropic peptides by trifluoroethanol: fluorescence and circular dichroism study

Conformation induction in the two related peptides, alpha-melanocyte stimulating hormone (alpha-MSH) and delta-melanocyte stimulating hormone (delta-MSH), have been studied in solvent media containing varying percentages of the membrane-mimetic solvent 2,2,2-trifluoroethanol (TFE) using fluorescence and circular dichroism (CD) spectroscopy. Singular value decomposition (SVD) analysis of the CD spectra at different TFE concentrations showed that these spectra can be described as linear combinations of only two distinct basis spectra, corresponding to the peptides in the random-coil and 'folded' conformations. For alpha-MSH the spectrum of the folded state is very similar to the standard spectrum of the alpha-helix, while that for delta-MSH has partial resemblance to the helical spectrum. Fitting the data on ellipticity (at 222 nm) as a function of TFE volume fraction to an equation based on a two-state model describing TFE-induced conformation induction in the peptides gave values of (1.1 +/- 0.4) and (4.2 +/- 0.5) kcal mol-1 for alpha-MSH and delta-MSH, respectively, for the free energy of equilibrium between the helix and coil forms in water. Measurement of fluorescence emission parameters (emission maximum, quantum yield, steady-state anisotropy and mean excited-state lifetime) indicated that the microenvironment around the single tryptophan residues of both peptides changes in like manner with increasing concentration of TFE in the solvent. The similarity of fluorescence behaviour of the peptides suggests that their Trp fluorophores do not participate in secondary structure formation in TFE.

Benign fibrous histiocytoma of the nasal septum

Among the non-epithelial tumours of the nasal cavity, paranasal sinuses and nasopharynx, fibrous histiocytoma is rarely encountered. A 45 year-old male patient complaining about nasal obstruction and nasal swelling was seen in the hospital ENT department. On examination, there was a mass located on the right anterior part of the nasal septum, about 2 x 1 x 1 cm in size. The pathologic diagnosis was benign fibrous histiocytoma. In this article we discuss the clinical, radiological, histopathological characteristics of fibrous histiocytoma and its differential diagnosis.

Health profile of two social groups living in a squatter settlement in Calcutta

Health and well-being of individuals largely depend on socioeconomic and environmental conditions. The low socioeconomic groups face the highest health burdens. In the present study an attempt has been made to compare and contrast the health related traits prevalent in two social groups (Hindu and Muslim), living in a squatter settlement in Calcutta, India. The study has been conducted on women between 20 to 40 years of age. The results show that the Muslims are more frequently affected with respect to most of the traits than the Hindus, but the difference is significant with respect to only a few traits. Thus, micro-cultural traits associated with religion do not seem to have much effect on the health related traits considered in this study.

Colorectal carcinoma invasion inhibition by CO17-1A/GA733 antigen and its murine homologue

BACKGROUND

The gastrointestinal carcinoma antigen GA733 is a potential target for passive and active immunotherapy for patients with colorectal carcinoma. This antigen has been characterized previously as a homophilic adhesion (i.e., adhesion to self) protein, but the functional consequences of homophilic adhesion for tumor growth and invasion are unknown. The availability of a murine homologue of GA733, i.e., murine epithelial glycoprotein (mEGP), allows for functional analysis of cell adhesion as it relates to tumor growth and invasion, both in vitro and in vivo.

METHODS

CT-26 murine colorectal carcinoma cells were transfected with complementary DNAs encoding either the human or the murine antigen. GA733- or mEGP-producing cells were evaluated for homophilic adhesion, growth on plastic surfaces, colony formation in soft agar, and invasion through a reconstructed basement membrane (Matrigel). mEGP-producing cells were also examined for their capacity to metastasize in mice. Reported P values are two-sided.

RESULTS

Compared with control cells, mEGP-producing cells showed significantly lower growth rates, colony formation, and invasion through Matrigel in vitro (all P values <.05). Compared with vector-only transfected cells and parental cells, mEGP-producing cells showed a reduction in metastatic potential in syngeneic immunodeficient and immunocompetent mice (all P values <.05). In contrast to mEGP-transfected cells, GA733-transfected cells did not exhibit significantly reduced growth or colony formation in vitro (all P values >.05). However, GA733-transfected cells did show reduced invasion through Matrigel compared with vector-only transfected cells or parental cells (all P values <.05).

CONCLUSION

The adhesion proteins GA733 and mEGP inhibit invasion of tumor cells.

Construction and characterization of encapsidated poliovirus replicons that express biologically active murine interleukin-2

Poliovirus genomes have been constructed in which the capsid genes have been substituted with the murine gene encoding interleukin-2 (IL-2) (referred to as replicons). One replicon contained the gene for IL-2 in place of the poliovirus capsid VP2 and VP3 genes, and a second replicon was constructed that contained the murine IL-2 substituted for the poliovirus VP3 and VP1 genes. The IL-2 genes were cloned into the replicon so as to maintain the translational reading frame with the remaining poliovirus proteins. Transfection of either replicon into cells resulted in the expression of replicon-encoded proteins and replication of replicon RNA. Using a procedure developed in this laboratory, we have encapsidated these replicons into authentic polio virions by passaging the replicons in the presence of a recombinant vaccinia virus, VVP1, which expresses the capsid precursor, P1, protein. Using a quantitative immunoassay, we determined that the majority of the IL-2 produced remained intracellular, with approximately 1%-2% released from the infected cells, and that the IL-2 was biologically active. The results of these studies demonstrate the utility of poliovirus replicons for expression of small bioactive molecules and are discussed with respect to future applications as immune adjuvants as well as potential new tumor therapies.

Immunodiagnosis of human hydatid disease

A study was undertaken to evaluate the efficacy of Enzyme Linked Immunosorbent Assay using locally prepared antigens for immunodiagnosis of human hydatid disease. A total of 90 cases clinically suspected to be suffering from hydatid disease and 100 controls matched for age and sex were included in the study. Two types of ELISA were performed on detected specific antihydatid antibodies belonging to IgG/IgM/IgA classes and other type detected IgE class of antibodies. Antigen prepared from the human hydatid fluid was found to be unsuitable for diagnosis as it contained host proteins i.e. IgG. Sheep hydatid fluid obtained from the fertile hydatid cyst was used to prepare and standardize the antigen. ELISA test to detect anti hydatid antibodies belonging to either IgG, IgM and or IgA was found to be highly specific (98 per cent) in surgically confirmed hydatid disease and was negative in all the controls. The results of the study indicate that ELISA along with casoni test may provide the best results in diagnosis of hydatid disease.

Overoxidized poly(pyrrole-co-[3-(pyrrol-1-yl)-propanesulfonate])-coated platinum electrodes for selective detection of catecholamine neurotransmitters

The cation-exchange and anion-exclusion properties of the poly¿pyrrole-co-[3-(pyrrol-1-yl)propanesulfonate]¿-(PPy-PS) copolymer are exploited for imparting higher selectivity to measurements of primary neurotransmitters in the presence of ascorbic acid. Such incorporation of ionizable sulfonated groups in the pyrrole ring prior to its electropolymerization leads to effective rejection of the anionic ascorbate species and preferential collection of the cationic dopamine and norepinephrine. Overoxidized PPy-PS films thus offer better discrimination against ascorbic acid than Nafion or overoxidized polypyrrole coatings. Experimental variables influencing the permselective behavior of the PPy-PS layer, including the electropolymerization time and solution pH, were explored. The selectivity and sensitivity improvements associated with the increased electrostatic character of overoxidized polypyrrole films hold promise for neurochemical electrochemical studies.

Human colorectal cancer (CRC) antigen CO17-1A/GA733 encoded by adenovirus inhibits growth of established CRC cells in mice

The human colorectal carcinoma (CRC)-associated Ag CO17-1A/GA733, originally defined by mAbs CO17-1A and GA733, has been a useful target in passive immunotherapy of CRC patients with mAb and in active immunotherapy with anti-idiotypic Abs mimicking the CO17-1A or GA733 epitope. Both approaches have targeted single epitopes. We investigated the capacity of full-length CO17-1A/GA733 Ag expressing multiple potentially immunogenic epitopes and encoded by recombinant adenovirus 5 (Ad5 GA733-2) to induce humoral, cellular, and/or protective immunity in mice. Ad5 GA733-2 induced Ag-specific Abs that reacted predominantly to CO17-1A- and GA733-unrelated epitopes on the Ag and lysed Ag-positive CRC targets in conjunction with effector cells. Ad5 GA733-2-immune mice developed Ag-specific, proliferative lymphocytes of Th1 type and cytolytic lymphocytes. The use of Ad5 GA733-2 to immunize mice bearing established syngeneic CRC cells transfected with the human Ag induced significant and specific tumor regression. Cured mice resisted rechallenge with human CO17-1A/GA733 Ag-negative parental CRC cells, suggesting that targeting the human Ag on the murine transfectants induced protective immunity to other Ag expressed by the parental tumor. These results may explain the high potency of the recombinant vaccine. Thus, rAd5 GA733-2 may have potential as a vaccine for CRC patients.

Human colorectal cancer (CRC) antigen CO17-1A/GA733 encoded by adenovirus inhibits growth of established CRC cells in mice

The human colorectal carcinoma (CRC)-associated Ag CO17-1A/GA733, originally defined by mAbs CO17-1A and GA733, has been a useful target in passive immunotherapy of CRC patients with mAb and in active immunotherapy with anti-idiotypic Abs mimicking the CO17-1A or GA733 epitope. Both approaches have targeted single epitopes. We investigated the capacity of full-length CO17-1A/GA733 Ag expressing multiple potentially immunogenic epitopes and encoded by recombinant adenovirus 5 (Ad5 GA733-2) to induce humoral, cellular, and/or protective immunity in mice. Ad5 GA733-2 induced Ag-specific Abs that reacted predominantly to CO17-1A- and GA733-unrelated epitopes on the Ag and lysed Ag-positive CRC targets in conjunction with effector cells. Ad5 GA733-2-immune mice developed Ag-specific, proliferative lymphocytes of Th1 type and cytolytic lymphocytes. The use of Ad5 GA733-2 to immunize mice bearing established syngeneic CRC cells transfected with the human Ag induced significant and specific tumor regression. Cured mice resisted rechallenge with human CO17-1A/GA733 Ag-negative parental CRC cells, suggesting that targeting the human Ag on the murine transfectants induced protective immunity to other Ag expressed by the parental tumor. These results may explain the high potency of the recombinant vaccine. Thus, rAd5 GA733-2 may have potential as a vaccine for CRC patients.

Cytotoxic T-cell clone against rectal carcinoma induced by stimulation of a patient's peripheral blood mononuclear cells with autologous cultured tumor cells

In an effort to establish cytolytic T lymphocytes (CTLs) against colorectal carcinoma (CRC) by stimulating patients' lymphocytes with autologous tumor cells, we used peripheral blood mononuclear cells (PBMC) from a patient with minimal residual rectal carcinoma following removal of the primary lesion and involved regional lymph nodes as a source to generate CTLs in culture. A CTL line and clone were established from the patient's PBMC following stimulation of PBMC with autologous, cultured tumor cells and interleukin-2. The CTL line and the clone consisted predominantly of CD4+ lymphocytes. The CTL clone expressed two T-cell receptor variable alpha chains (V alpha11 and V alpha22) and one beta chain (Vbeta14). The cytokine secretion pattern of the CTL line was of the Th1-type. Both the CTL line and the clone lysed the autologous rectal carcinoma cells, but not the allogeneic, partially human lymphocyte antigen (HLA)-matched or nonmatched CRC cells, autologous Epstein-Barr virus-transformed B cells, K562 (natural killer target) cells or Daudi (lymphokine-activated killer target) cells. Lysis of autologous tumor cells most likely was HLA class I-restricted. Our unique success in generating CTLs against this tumor type may rest in the inclusion of a patient with minimal residual, rather than advanced, disease.

Expression of an antigen homologous to the human CO17-1A/GA733 colon cancer antigen in animal tissues

The CO17-1A/GA733 antigen is associated with human carcinomas and some normal epithelial tissues. This antigen has shown promise as a target in approaches to passive and active immunotherapy of colorectal cancer. The relevance of animal models for studies of immunotherapy targeting this antigen in patients is dependent on the expression of the antigen on normal animal tissues. Immunohistoperoxidase staining with polyclonal rabbit antibodies to the human antigen revealed the human homologue on normal small intestine, colon and liver of mice, rats and non-human primates, whereas mouse monoclonal antibodies to the CO17-1A or GA733 epitopes on the human antigen did not detect the antigen. Polyclonal rabbit antibodies, elicited by the murine antigen homologue derived from recombinant baculovirus-infected insect cells, immunoprecipitated the antigen from mouse small intestine, colon, stomach, kidney and lung. The isolated recombinant murine protein bound polyclonal, but not monoclonal, antibodies to the human CO17-1A/GA733 antigen, and recombinant human antigen bound polyclonal antibodies elicited by the murine antigen homologue. Thus, the antigen homologue expressed by animal tissues is similar, but not identical, to the human antigen. These results have important implications for experimental active and passive immunotherapy targeting the CO17-1A/GA733 antigen.

Epidemiology of group-A streptococcal infection amongst children of different ethnic groups in Darjeeling

The carrier rate of Group A Streptococcus (GAS) was studied amongst 932 children from 1+ upto 12 years of age in three major racial groups in the foothills of the Darjeeling district of West Bengal. It was altogether 13 per cent and was found to be evenly distributed in the three ethnic groups as Gurkhas: 11 per cent, Rajbanshis: 15 per cent and Cosmopolitans: 13 per cent, but the incidence of Rheumatic fever and/or Rheumatic heart diseases were unnoticed among the Gurkha children who also had significant low ASO titres.

Structural alterations of horseradish peroxidase in the presence of low concentrations of guanidinium chloride

The presence of very low concentrations of guanidinium chloride (GdmCl) alters the tertiary structure of the monomeric heme-containing enzyme, horseradish peroxidase (HRP). The change in tertiary structure of the protein was reflected in the mean fluorescence lifetime of its single tryptophan residue, which increased from 2.3 +/- 0.1 ns in the native enzyme to 2.7 +/- 0.2 ns in the presence of 100 mM GdmCl. More convincing evidence in support of such alterations came from quenching study of tryptophan fluorescence using the most widely used quencher, acrylamide. It revealed significant differences between the Stern-Volmer quenching constants observed in the absence and in the presence of GdmCl concentrations below 100 mM. The fluorescence emission maximum of 6-propionyl-2-(dimethylamino)naphthalene (PRODAN), used as an extrinsic fluorophore to probe any changes in the tertiary structure of the enzyme, was blue-shifted from 522 nm in aqueous buffer to 509 nm in the presence of 27 microM native HRP. However, this emission maximum appeared at 519 nm when the PRODAN was incorporated in HRP previously incubated with 100 mM GdmCl. The fluorescence lifetime of PRODAN incorporated in HRP was also different from that of PRODAN in buffer, but much more so in absence of GdmCl than in its presence. Taken together, these results indicate partial unfolding of HRP leading to a conformation with native-like secondary structure and unaltered enzymatic activity, in presence of millimolar concentrations of GdmCl.