Transport of cosalane-a highly lipophilic novel anti-HIV agent-across caco-2 cell monolayers

Cosalane is a potent inhibitor of HIV replication with activity against a broad range of viral targets. However, the oral bioavailability of this highly lipophilic compound is extremely poor (<1%). Also, cosalane accumulates in high concentration in the liver after intravenous administration, with clear resistance to hepatic metabolism. In the present study, the transcellular permeability of cosalane was examined using Transwell(R) filter as well as plastic-grown confluent Caco-2 cell monolayers. A cell-culture-based biophysical model was adopted to understand the interactions of protein binding, membrane partitioning, and aqueous solubility of cosalane in limiting transcellular flux of cosalane across Caco-2 cell monolayers. The transcellular permeability (P(app)) of cosalane was extremely low (4.494 x 10(-8) cm/s) and the effect of p-glycoprotein on the efflux of cosalane was negligible. A characteristic disparity exists between the kinetics of cosalane uptake from apical (AP) donor solution and efflux into basolateral (BL) receiver side. The AP uptake of cosalane was rapid, exhibiting exponential kinetics, and reached equilibrium within 60 min, whereas the concomitant appearance of the compound into the BL receiver side was slow but linear over time. Furthermore, the uptake of cosalane was significantly reduced in the presence of bovine serum albumin (BSA). In unidirectional efflux studies, AP efflux of cosalane was limited in the absence of BSA. Also, no detectable metabolites were found in Caco-2 cell incubations. In conclusion, the present study demonstrates that diffusion of cosalane across Caco-2 cell monolayers is extremely limited and kinetically regulated essentially by the equilibrium between protein-bound and free drug partitioning into cell membrane.

Noninvasive, transthoracic, low-frequency ultrasound augments thrombolysis in a canine model of acute myocardial infarction

BACKGROUND

Limitations of coronary thrombolysis include the time to reperfusion, patency rate, and bleeding. We evaluated the use of noninvasive transcutaneous ultrasound to augment coronary thrombolysis.

METHODS AND RESULTS

In 24 dogs, a thrombotic occlusion of the left anterior descending coronary artery was induced and documented by 12-lead ECG and coronary angiography. After >/=60 minutes of occlusion, tissue-type plasminogen activator (t-PA; 1.42 mg/kg) was given intravenously over 90 minutes. A total of 12 of the 24 dogs had concomitant transcutaneous application of low-frequency ultrasound (27 kHz) over the chest. At 90 minutes, the mean TIMI grade flow in the t-PA alone group was 0.92+/-1.4 compared with 2. 42+/-1.9 in the t-PA plus ultrasound group (P=0.006). TIMI 2 to 3 flow was present in 4 of 12 cases receiving t-PA alone compared with 10 of 12 cases receiving t-PA plus ultrasound (P=0.003). At 180 minutes, mean TIMI grade flow was 0.75+/-1.4 in the t-PA alone group versus 2.58+/-0.9 in the t-PA plus ultrasound group (P=0.001). Pathological examination confirmed the angiographic patency rate and did not reveal injury secondary to ultrasound in the skin, soft tissues, heart, or lungs.

CONCLUSIONS

In vivo, the noninvasive transthoracic application of low-frequency ultrasound (1) greatly augments the efficacy of t-PA-mediated thrombolysis, (2) seems safe, and (3) has substantial potential as a noninvasive adjunct to improve coronary patency without increasing the risk of bleeding.

beta-sheet propensity and its correlation with parameters based on conformation

The dispersion of the main-chain and side-chain conformations in the phi, psi, chi(1) space for all residues have been estimated in terms of three parameters corresponding to the entropy (S) of the distribution, the volume (D(V)) and the area (D(A)) the points are enclosed in. These parameters are inversely correlated with Chou and Fasman beta-sheet propensities, P(beta) (Gly and Pro excluded), suggesting that residues with greater dispersion in the conformational space are weak beta-sheet formers. It was also found that different residues have different relative populations in the bridging region (intervening between the helical and beta-sheet regions) which may lie on the pathway for interconversion between alpha and beta conformations. The energy barrier for this transformation, as obtained from the population of residues in the bridging region relative to the beta region, is directly correlated to P(beta). Residues with high P(beta) have branched side chains, which have greater steric interactions with the main-chain atoms resulting in a shrinking of the available conformational space (first correlation) and a steeper energy gradient beyond the allowed space (second correlation) compared with linear residues. It is proposed that if residues exist in an extended conformation when the polypeptide chain is synthesized, a stretch of residues with high P(beta), because of the high energy barrier for their conversion into the alpha conformation, will continue to remain in the extended conformation and will ultimately constitute a beta-strand in the folded structure.

Terminal residues in protein chains: residue preference, conformation, and interaction

The known protein structures have been analyzed to find out if there is any pattern in the type of residues used and their conformation at the two terminal positions of the polypeptide chains. While the N-terminal position is overwhelmingly occupied by Met (followed by Ala and Ser), the preference for the C-terminal is not as distinct, the residues with highest propensities being Lys, Arg, Gln, and Asn. Only one main-chain torsion angle, psi, can be defined for the N-terminal residue, which is found to be in the extended conformation due to a favorable electrostatic interaction between the charged amino group and the carbonyl oxygen atom. The distribution of the angle phi for the C-terminal residue, on the other hand, is not much different from that of the nonterminal residues. There are some differences in the distribution of the side-chain torsion angle chi1 of both the terminal residues from the general distribution. The terminal segments are generally flexible and there is a tendency for the more ordered residues to have lesser solvent exposure. About 40% of the terminal groups form a hydrogen bond with protein atoms--a slight preference is observed for the side-chain atoms (more than half of which belong to charged residues) over the main-chain ones. Although the terminal residues are not included in any regular secondary structure, the adjacent ones have a high preference to occur in the beta conformation. There is a higher chance of a beta-strand rather than an alpha-helix to start within the first 6 positions from the N-terminal end. It is suggested that the extended conformation observed for the N-terminal residue propagates along the chain leading to the formation of beta-strand. In the C-terminal end, on the other hand, as one moves upstream the alpha and beta structures are encountered in proportion similar to the average value for these structures in the database. The cleavage site of the zymogen structures has a conformation that can be retained by the N-terminal residue of the active enzyme.

Involvement of estrogen receptors alpha and beta in the regulation of cervical permeability

Estrogen increases the permeability of cultured human cervical epithelia (Gorodeski, GI. Am J Physiol Cell Physiol 275: C888-C899, 1998), and the effect is blocked by the estrogen receptor modulators ICI-182780 and tamoxifen. The objective of the study was to determine involvement of estrogen receptor(s) in mediating the effects on permeability. In cultured human cervical epithelial cells estradiol binds to high-affinity, low-capacity sites, in a specific and saturable manner. Scatchard analysis revealed a single class of binding sites with a dissociation constant of 1.3 nM and binding activity of approximately 0.5 pmol/mg DNA. Estradiol increased the density of estrogen-binding sites in a time- and dose-related manner (half time approximately 4 h, and EC(50) approximately 1 nM). RT-PCR assays revealed the expression of mRNA for the estrogen receptor alpha (alphaER) and estrogen receptor beta (betaER). Removal of estrogen from the culture medium decreased and treatment with estrogen increased the expression of alphaER and betaER mRNA. In cells not treated with estrogen, ICI-182780 and tamoxifen increased betaER mRNA. In cells treated with estrogen, neither ICI-182780 nor tamoxifen had modulated significantly the increase in alphaER or betaER mRNA. The transcription inhibitor actinomycin D blocked the estrogen-induced increase in permeability, and it abrogated the estradiol-induced increase in estrogen binding sites. These results suggest that the estrogen-dependent increase in cervical permeability is mediated by an alphaER-dependent increase in transcription.

Recent trends in leprosy in a large district of West Bengal, India, revealed by a modified leprosy elimination campaign (MLEC), 1998

A Modified Leprosy Elimination Campaign (MLEC) in September 1998 in the District of Midnapore, West Bengal, covered a population of 8.1 million people and detected 8181 new cases. Available data from 7328 cases were studied to observe the trend for leprosy in this area. Data are presented on sex and age distribution, classification and the proportions of multibacillary (MB), paucibacillary (PB) and single skin lesion (SSL) cases discovered in a period of only 8 days. The large numbers of people examined in this district and the high total of new cases revealed are in keeping with experience in other parts of the State and in other parts of India. However, many cases were found in endemic areas and these will receive special attention in a second MLEC, planned for January 2000.

Synthesis of 11beta-(4-dimethylaminophenyl)-17beta-hydroxy-17alpha- (3-methyl-1-butynyl)-4, 9-estradien-3-one and 11beta-(4-acetophenyl)- 17beta-hydroxy-17alpha-(3-methyl-1-butynyl)-4, 9-estradien-3-one: two new analogs of mifepristone (RU-486)

From the structure activity relationship, two new analogs, 2 and 3, of the potent progesterone antagonist mifepristone 1 have been designed. The syntheses of these two analogs have been achieved in eleven steps through modified synthetic sequences and improved procedures starting from (+)-estrone. In comparison with mifepristone 1, the relative binding affinities of compound 2 for the progesterone receptor was found to be more, whereas that of compound 3 was less.

Environment of tryptophan side chains in proteins

Although relatively rare, the tryptophan residue (Trp), with its large hydrophobic surface, has a unique role in the folded structure and the binding site of many proteins, and its fluorescence properties make it very useful in studying the structures and dynamics of protein molecules in solution. An analysis has been made of its environment and the geometry of its interaction with neighbors using 719 Trp residues in 180 different protein structures. The distribution of the number of partners interacting with the Trp aromatic ring shows a peak at 6 (considering protein residues only) and 8 (including water and substrate molecules also). The means of the solvent-accessible surface areas of the ring show an exponential decrease with the increase in the number of partners; this relationship can be used to assess the efficiency of packing of residues around Trp. Various residues exhibit different propensities of binding the Trp side chain. The aromatic residues, Met and Pro have high values, whereas the smaller and polar-chain residues have weaker propensities. Most of the interactions are with residues far away in sequence, indicating the importance of Trp in stabilizing the tertiary structure. Of all the ring atoms NE1 shows the highest number of interactions, both along the edge (hydrogen bonding) as well as along the face. Various weak but specific interactions, engendering stability to the protein structure, have been identified.

Cis peptide bonds in proteins: residues involved, their conformations, interactions and locations

An analysis of a non-redundant set of protein structures from the Brookhaven Protein Data Bank has been carried out to find out the residue preference, local conformation, hydrogen bonding and other stabilizing interactions involving cis peptide bonds. This has led to a reclassification of turns mediated by cis peptides, and their average geometrical parameters have been evaluated. The interdependence of the side and main-chain torsion angles of proline rings provided an explanation why such rings in cis peptides are found to have the DOWN puckering. A comparison of cis peptides containing proline and non-proline residues show differences in conformation, location in the secondary structure and in relation to the centre of the molecule, and relative accessibilities of residues. Relevance of the results in mutation studies and the cis-trans isomerization during protein folding is discussed.

Estimates of the loss of main-chain conformational entropy of different residues on protein folding

The average contribution of conformational entropy for individual amino acid residues towards the free energy of protein folding is not well understood. We have developed empirical scales for the loss of the main-chain (torsion angles, phi and psi) conformational entropy by taking its side-chain into account. The analysis shows that the main-chain component of the total conformational entropy loss for a residue is significant and reflects intrinsic characteristics associated with individual residues. The values have direct correlation with the hydrophobicity values and this has important bearing on the folding process. Proteins 1999;36:332-339.

Packing of aromatic rings against tryptophan residues in proteins

The geometry of the interaction of the aromatic side chains of phenylalanine (Phe), tyrosine (Tyr), tryptophan (Trp) and histidine (His) with the indole ring of Trp has been analyzed using the structures in the Protein Data Bank in order to understand the dependence of the packing behaviour on the size and chemical nature of the aromatic rings. The Phe ring prefers to interact either perpendicularly, with its edge pointing towards the Trp face, or in an offset-stacked arrangement. The edge-to-face motif is typical of a Trp-Trp pair. While parallel stacking is the dominant feature of Trp-His interaction, Tyr packs in a more uniform manner around Trp with a higher than expected occurrence at the edge and a few cases of possible OH-pi interaction.

Graphical representation of the salient conformational features of protein residues

A composite plot for depicting in two dimensions the conformation and the secondary structural features of protein residues has been developed. Instead of presenting the exact values of the main- and side-chain torsion angles (&phi;, psi and chi(1)), it indicates the region in the three-dimensional conformational space to which a residue belongs. Other structural aspects, like the presence of a cis peptide bond and disulfide linkages, are also displayed. The plot may be used to recognize patterns in the backbone and side-chain conformation along a polypeptide chain and to compare protein structures derived from X-ray crystallography, NMR spectroscopy or molecular modelling studies and also to highlight the effect of mutation on structure.

Evaluation of hematological and hepatorenal functions of methanolic extract of Moringa oleifera Lam. root treated mice

Methanolic extract of M. oleifera root was found to contain some alkaloids (total alkaloid 0.2%). Effects of multiple weekly (35, 46, 70 mg/kg) and daily therapeutic (3.5, 4.6, 7.0 mg/kg) i.p. doses of the crude extract (CE) on liver and kidney functions and hematological parameters in mice were studied. No alteration in hematological and biochemical parameters at low and moderate dose level of daily and low dose level of weekly treatment of the extract was observed. However, the extract at moderate dose level in weekly treatment changed serum aminotransferase and plasma cholesterol levels significantly. High dose in addition to the above parameters changed total bilirubin, non protein nitrogen, blood urea and plasma protein. High dose of daily treatment and moderate and high dose of weekly treatment of CE increased WBC count and decreased clotting time significantly. The results indicate that the weekly moderate and high dose (> 46 mg/kg body wt.) and daily/therapeutic high dose (7 mg/kg) of CE affects liver and kidney functions and hematological parameters whereas the weekly dose (3.5 mg/kg) and low and moderate daily/therapeutic dose (3.5 and 4.6 mg/kg) did not produce adverse effects on liver and kidney functions.

A community based study on health impact of flood in a vulnerable district of West Bengal

In order to ascertain the disaster vulnerability and health risks of flood in Hooghly district of West Bengal, this community based study was conducted through record analysis, interview of concerned authorities and household survey of morbidities before and after flood. Two blocks, with most of its population, were found to be the worst affected among all the disaster vulnerable blocks of the district. Incidence of diarrhoea, other enteric diseases and respiratory infections were significantly higher (P < 0.05) among the population in flood affected blocks, compared to the unaffected. The attack rate of diarrhoea in the flood affected population had increased significantly following flood (P < 0.05).

Estrogen modulates paracellular permeability of human endothelial cells by eNOS- and iNOS-related mechanisms

Estradiol had a biphasic effect on permeability across cultures of human umbilical vein endothelial cells (HUVEC): at nanomolar concentrations it decreased the HUVEC culture permeability, but at micromolar concentrations it increased the permeability. The objective of the present study was to test the hypothesis that the changes in permeability were mediated by nitric oxide (NO)-related mechanisms. The results revealed dual modulation of endothelial paracellular permeability by estrogen. 1) An endothelial NO synthase (eNOS)-, NO-, and cGMP-related, Ca2+-dependent decrease in permeability was activated by nanomolar concentrations of estradiol, resulting in enhanced Cl- influx, increased cell size, and increases in the resistance of the lateral intercellular space (RLIS) and in the resistance of the tight junctions (RTJ); these effects appeared to be limited by the ability of cells to generate cGMP in response to NO. 2) An inducible NO synthase (iNOS)- and NO-related, Ca2+-independent increase in permeability was activated by micromolar concentrations of estradiol, resulting in enhanced Cl- efflux, decreased cell size, and decreased RLIS and RTJ. We conclude that the net effect on transendothelial permeability across HUVEC depends on the relative contributions of each of these two systems to the total paracellular resistance.

Protein folding in Escherichia coli: role of 23S ribosomal RNA

Post-translational control of Escherichia coli ribosome on newly synthesised polypeptide leading to its active conformation (protein folding) has been shown in the case of the enzyme beta-galactosidase. As expected, antibiotics chloramphenicol and lincomycin, which bind to 23S rRNA/50S subunit and kasugamycin and streptomycin which interact with the 30S subunit instantaneously inhibited protein synthesis when they were added to the growing cells. The increase in beta-galactosidase activity, though stopped immediately after the addition of chloramphenicol and lincomycin, went on considerably in the presence of streptomycin and kasugamycin even after the stoppage of protein synthesis.

Sterility testing of disposable syringes and needles marketed in Calcutta

Presterilized (disposable) syringes and needles were subjected to sterility testing for aerobic cultures. It was found that 56.3% of the samples were contaminated indicating failure of the sterilisation process. The implications of this could be far reaching and is discussed alongwith.

Effects of estrogen on tight junctional resistance in cultured human umbilical vein endothelial cells

OBJECTIVE

To study the effects of estrogen on transendothelial paracellular permeability in women.

METHODS

Human umbilical vein endothelial cells (HUVEC) obtained from women were grown on filters. The paracellular permeability characteristics were determined in terms of changes in the permeability to the polar acid pyranine (Ppyr) and as changes in the transendothelial electrical resistance (RTE). Tight junctional resistance characteristics were assayed by lowering luminal NaCl and measuring the dilution potential, and were expressed as the ratio of monoion mobility uCl/uNa (cation selectivity).

RESULTS

Low extracellular calcium and hyperosmolarity increased Ppyr and decreased RTE. The former but not the latter condition abolished the endothelium-specific cation selectivity. Treatment with 10 nM of estradiol-17 beta had no effect on RTE, but it increased the cation selectivity. The effect of estradiol required 1-6 hours' incubation with the hormone; it was dose dependent and saturable, with a median effective concentration of estradiol of 1 nM. Diethylstilbestrol, but not estriol, could mimic the effect of estradiol, and the estrogen receptor antagonist ICI-182, 780 blocked it.

CONCLUSION

Cultured HUVEC cells form patent tight junctions. Estrogens increase the cation selectivity across HUVEC cultures. The effect of estrogen may be mediated by an estrogen receptor. These effects may be important for vasculoprotection in cases of sudden changes in ions levels across the capillary wall, such as ischemia or reperfusion.

Regulation by retinoids of P2Y2 nucleotide receptor mRNA in human uterine cervical cells

Extracellular ATP stimulates acute changes in paracellular permeability across cultures of human uterine cervical epithelial cells [G. I. Gorodeski, D. E. Peterson, B. J. De Santis, and U. Hopfer. Am. J. Physiol. 270 (Cell Physiol. 39): C1715-C1725, 1996]. In this paper, we characterize mRNA for a P2Y2 nucleotide receptor in human cervical cells. Using oligonucleotide primers based on the sequence of human airway epithelium P2Y2 receptor, a single 632-bp cDNA band was identified in RT-PCR experiments in extracts of human endocervical and ectocervical tissues and in lysates of human cervical CaSki cells, but not in 3T3 fibroblasts. The nucleotide sequence was homologous to the corresponding human airway epithelium P2Y2 receptor. Northern blot analyses revealed hybridization of the P2Y2 receptor probe to a 2.0-kb mRNA fragment, as well as to 2.2-, 3. 0-, and 4.6-kb species, indicating that human cervical cells express P2Y2 receptor mRNA. Incubation of CaSki cells in retinoid-free medium abolished the ATP-induced changes in permeability and decreased the expression of the P2Y2 receptor mRNA; treatment with retinoids restored the responses to ATP and upregulated the P2Y2 receptor mRNA, suggesting that the receptor mediates ATP-related changes in permeability. Treatment with actinomycin D decreased the expression of the P2Y2 receptor RNA, but the ratio density of the receptor RNA relative to glyceraldehyde-3-phosphate dehydrogenase RNA remained unchanged, suggesting that retinoids upregulate transcription of the receptor mRNA. We conclude that retinoid-dependent modulation of the P2Y2 receptor expression, and hence of the responses to ATP, may be an important mechanism for the regulation of secretion of cervical mucus in vivo.

Main-chain conformational features at different conformations of the side-chains in proteins

An analysis of the known protein structures has shown that the main-chain torsion angles, phi and psi of a residue can be affected by the side-chain torsion angle, chi1. The (chi1, psi) plot of all residues (except Gly, Ala and Pro) show six distinct regions where points are concentrated-although some of these regions are nearly absent in specific cases. The mean of these clusters can show a shift along the psi axis by as much as 30 degrees as chi1 is changed from around 180 to -60 to 60 degrees. Because of the lesser steric constraint points are more diffused along the psi axis when chi1 is approximately -60 degrees. Although points are more spread out along the phi axis in the (chi1, phi) plot, the dependence of phi on chi1 shows up in a shortened phi range (by about 30 degrees) when chi1 is around -60 degrees, and a distinct tendency of clustering of points into two regions when chi1 is approximately equal to 60 degrees, especially for the aromatic residues. Based on the dependence of the backbone conformation on its side-chain the 17 amino acids can be grouped into five classes: (i) aliphatic residues branched at the Cbeta position (although Thr is atypical), (ii) Leu (branched at the Cgamma position), (iii) aromatic residues (Trp can show some deviations), (iv) short polar residues (Asp and Asn), and (v) the remaining linear-chain residues, mainly polar. Ser and Thr have the highest inclination to occur with two different orientations of the side-chain that can be located through crystallography. Such residues exhibiting two chi1 angles have their phi and psi angles in a region that is common to the Ramachandran plots at the two different chi1 angles. The dependence of phi and psi angles on chi1 can be used to understand the helical propensities of some residues. Moreover, the average phi, psi values in the alpha-helices vary with the side-chain conformation.

Different types of interactions involving cysteine sulfhydryl group in proteins

Various types of interactions involving the sulfhydryl group of free cysteine residues have been analyzed using known protein structures. In a hydrogen bond the -SH group is more amenable to donating its proton to a carbonyl group, rather than acting as a proton acceptor. It rarely interacts with a carboxylate group, and is a poor ligand to bind an anionic substrate. It is quite prone to make contacts that are definitely non-hydrogen bond type. In the S...C=O interaction the S atom is placed on the face of an amide group (mostly from the main-chain, but there are cases from the side-chain also) close to the C atom. Cases of S...N interaction, where the S atom is on top of the N atom of another residue (both main-, as well as side-chains, including the guanidinium group) are also observed. A considerable number of Cys residues have aromatic residues as neighbors, and here too, the preferred mode of interaction is along the face. The intra-residue S...C=O interaction constrains the main-chain and side-chain torsion angles (psi and chi1), whereas the inter-residue interactions are non-local and stabilize the tertiary structure. The S...C=O interaction may have a role in lowering the pKa values of the Cys residues in enzyme active sites.

Retinoids modulate P2U purinergic receptor-mediated changes in transcervical paracellular permeability

In human cervical cells, extracellular ATP induces an acute decrease in the resistance of the lateral intercellular space, the phase I response, followed by a delayed increase in tight junctional resistance, the phase II response. These responses depend on vitamin A because incubation of cells in retinoid-free medium (RFM) abolished both responses. Treatment with retinoic acid restored the phase I response in full, but the amplitude of the phase II response was restored only partly. Shorter incubations and lower concentrations of retinoic acid [half-maximal effective concentrations (K 1/2) = 0.1 microM] were required for restoring the phase I response than were required for reversing the phase II response (K 1/2 = 1 microM). The phase I response could be restored by ligands that bind to either retinoic acid receptors (RARs) or retinoid X receptors, but only RAR agonists had an effect on phase II response. RFM had no effect on decreases in resistance induced by ionomycin, but it attenuated phase II-like increases in resistance induced by KCl or by 1,2-dioctanoyl-sn-diglycerol (diC8). Actinomycin D blocked phase II response but not phase I response or the responses to ionomycin, KCl, or diC8. These results suggest that retinoids act on cervical cells via distinct retinoid receptor mechanisms and modulate phase I and phase II changes in resistance by regulating distinct signal mechanisms.

Reactivation of denatured proteins by domain V of bacterial 23S rRNA

In vitro transcripts containing domain V of the 23S rRNA of Escherichia coli and Bacillus subtilis can reactivate denatured proteins almost as efficiently as the total 23S rRNA. Here we show that almost the full length of domain V is required for reactivation of denatured pig muscle lactate dehydrogenase and pig heart cytoplasmic malate dehydrogenase: the central loop of this domain alone is not enough for this purpose. The antibiotic chloramphenicol, which binds to domain V of 23S rRNA, can inhibit reactivation of these proteins completely. Activity is eliminated by EDTA at a concentration of <1 mM, even in the presence of 4 mM MgCl2, suggesting that the three-dimensional conformation of the RNA should be maintained for this activity.

Retinoids regulate tight junctional resistance of cultured human cervical cells

The objective of the study was to determine the effect of retinoids on paracellular resistance across the cervical epithelium and the mechanisms involved. The experimental model was cultures of human CaSki cells on filters, which retain phenotypic characteristics of the endocervical epithelium. End points for paracellular resistance were measurements of transepithelial electrical resistance and fluxes of pyranine (a trisulfonic acid that traverses the epithelium via the intercellular space). Paracellular resistance was significantly increased in cells grown in retinoid-free medium; the effect could be blocked and reversed with all-trans-retinoic acid (tRA) and with agonists of RAR and RXR receptors but only partially with retinol. The effect of tRA was dose dependent and saturable, with a 50% effective concentration of 0.8 nM. The increases in paracellular resistance induced by vitamin A deficiency required longer incubation in retinoid-free medium than decreases in resistance induced by retinoic acid. tRA had only a minimal effect on paracellular resistance in cells maintained in regular medium. Retinoid-free medium increased and tRA decreased the relative cation mobility across CaSki cultures. Also the effects of tRA were nonadditive to those of cytochalasin D (which decreases tight junctional resistance) and additive to those of ionomycin (which decreases the resistance of the lateral intercellular space), suggesting that tRA modulates tight junctional resistance. It is concluded that vitamin A determines the degree of paracellular resistance across cervical cells by a mechanism that involves modulation of tight junctional resistance.

Inhibition of homotypic adhesion of T-cells: secondary structure of an ICAM-1-derived cyclic peptide

The objective of this study was to elucidate the solution conformation of cyclo-(1,12) Pen1-Pro2-Ser3-Lys4-Val5-Ile6-Leu7-Pro8-Ar g9-Gly10-Gly11-Cys12 (1) derived from the intercellular adhesion molecule-1 (ICAM-1). Cyclic peptide 1 inhibits homotypic adhesion of T-cells (Molt-3) mediated by ICAM-1 and the leukocyte function-associated antigen-1 (LFA-1) on the surface of T-cells. Cyclic peptide 1 is more potent than is the linear peptide Pen1-Pro2-Ser3-Lys4-Val5-Ile6-Leu7-Pro8-Ar g9-Gly10-Gly11-Cys12 (2) in inhibiting homotypic adhesion. The difference in biological activity of peptides 1 and 2 may be due to the more stable conformation of cyclic peptide 1 compared to linear peptide 2 or because cyclization prevents the peptide from adopting non-productive conformation. Therefore, conformational studies of cyclic peptide 1 will give a better understanding of its biological active conformation. The conformational studies of cyclic peptide 1 were done by NMR, CD and molecular dynamics simulations. NMR studies indicated that the major conformation of cyclic peptide 1 contained trans-configuration at both X-Pro peptide bonds. Type I beta-turns at Lys4-Val5-Ile6-Leu7 and Leu7-Pro8-Arg9-Gly10 were found in cyclic peptide 1. The C- and N-terminal regions of this peptide were stabilized by antiparallel beta-sheet-like structure with the presence of intramolecular hydrogen bonds. The overall structure of this peptide exposed the hydrophobic side chains on one face of the molecule and the hydrophilic side chains on the other.

An electrophile-nucleophile interaction in metalloprotein structures

A new attractive interaction in metalloprotein structures, between the thiolate anion of a metal-bound cysteine (acting as a nucleophile) and a carbonyl carbon of a peptide group (an electrophile), has been identified. From 82 cases extracted from 23 metalloprotein structures, the interacting S and C atoms are found to be at a distance of 3.2 (+/-2) A, such that the angle S ... C-O is 109 degrees (+/-15 degrees). Usually, the interacting atoms are from the same Cys residue, and to allow the S to interact with the carbonyl group the side-chain and the main-chain torsion angles deviate from those found in cysteines not bound by metals. There is a good correlation between the S...C distance and the angular deviation of the S...C vector from the normal to the peptide plane. Various data points may be envisaged to represent "snapshots" along the reaction coordinate for the intra-residue attack of Cys S on the CO group.

Modulation of cellular adhesion in bovine brain microvessel endothelial cells by a decapeptide

The importance of cell adhesion molecules in maintaining the cellular integrity of the endothelial layer is well recognized, yet their exact participation in regulating the blood-brain barrier (BBB) is poorly understood. Both Ca(2+)-dependent and Ca(2+)-independent cell adhesion molecules are found in endothelial cells. In this study, we used immunofluorescence, ELISA, Western blot and cell adhesion assay to identify a Ca(2+)-dependent cell adhesion molecule, E-cadherin, in bovine brain microvessel endothelial cells (BBMECs). Monoclonal anti-E-cadherin antibody specifically interacted with cultured BBMECs and decorated the cellular junctions with a series of punctate fluorescence spots as seen by indirect immunofluorescence using a confocal microscope. The intensity of these fluorescence spots increased after brief treatment with hIFN-gamma or CPT-cAMP. In the cellular extract of BBMECs, a 120 kDa protein was immunoprecipitated with anti-E-cadherin antibody. BBMECs did not react with anti-N-cadherin antibody, but recognized the FITC-labeled LRAHAVDVNG-NH2, a decapeptide generated from the EC-1 domain of N-cadherin, which decorated the lateral margins of the cells with fluorescence spots. A concentration-dependent binding of this decapeptide was also observed in the flow cytometry assay. BBMECs dissociated with trypsin plus Ca2+ were able to reaggregate only in the presence of Ca2+. However, such cell-cell aggregations of BBMECs were prevented by the presence of either anti-E-cadherin antibody or the decapeptide in the assay medium. These results confirm that BBMECs possess a distinct Ca(2+)-dependent cell adhesion mechanism that can be modulated by the decapeptide. This modulation of cell-cell adhesion in BBMECs by the decapeptide is thought-provoking for creating channels for paracellular drug delivery across the BBB.

Derivatives of melphalan designed to enhance drug accumulation in cancer cells

The objective of this study was to develop chemical strategies to improve the uptake and accumulation of melphalan (L-Mel and D-Mel), a cytotoxic agent, into cancer cells. Dipeptides synthesized from L- (or D-) Mel and L-glutamic acid (L-Glu) or L-valine (L-Val) and their methyl or ethyl esters (all compounds were trifluoroacetic acid salts) were evaluated for cytotoxicity and cellular uptake using Caco-2 cells, a human colon carcinoma cell line, and RT-2 cells, a rat brain glioma cell line. Treatment of Caco-2 cells with L-Mel or D-Mel (0.5 mg/ml equivalent of melphalan) for 48 h resulted in approximately 50% cell survival. Treatment of the Caco-2 cells with dipeptide derivatives of L-Mel (or D-Mel) (11c-d, 12c-d and 13) caused similar cytotoxicity effects (approximately 50-70% of cell survival). When the cytotoxicities of the esters of L-Mel, D-Mel and their dipeptide derivatives (11a-b, 12a-b and 14) in Caco-2 cells were determined, less than 10% cell survival was observed. Similar results were observed in RT-2 cells. When the cellular uptake properties of these compounds were determined in Caco-2 cell monolayers, L-Glu-L-Mel (12c), L-Glu-D-Mel (12d), and L-Mel-L-Glu (11c) generated slightly lower intracellular levels of L-Mel or D-Mel than when the cell monolayer was treated with the amino acids (L-Mel or D-Mel). In Caco-2 cells treated with 11c, 12c or 12d, low levels of the dipeptides were also detected. Caco-2 cell monolayers treated with D-Mel-L-Glu (11d) or D-Mel-L-Val (13) showed very low levels of the amino acids (L-Mel or D-Mel), but generally higher levels of the dipeptides. In contrast to the amino acids (L-Mel, D-Mel) or the dipeptide derivatives (11c-d, 12c-d and 13), the ester derivatives of the amino acids [L-Mel(OEt), D-Mel(OEt)] or the dipeptides (11a-b, 12a-b and 14) produced 5-20 times higher intracellular concentrations of potentially cytotoxic metabolites (e.g., L-Mel, D-Mel, Mel-containing dipeptides or Mel-containing dipeptide monoesters). L-Mel(OEt), D-Mel(OEt), L-Glu(OEt)-L-Mel(OEt) (12a), L-Glu(OEt)-D-Mel(OEt) (12b), and L-Mel-L-Glu(OEt)2 (11a) accumulated mainly as either L-Mel or D-Mel, and the percentages of L-Mel or D-Mel were 99%, 99%, 90%, 75% and 98% of the total intracellular concentration of potentially cytotoxic agents, respectively. D-Mel-L-Glu(OEt)2 (11b) accumulated as its monoester (> 95%) and D-Mel-L-Val(OMe) (14) accumulated as its dipeptide metabolite (> 98%). Inclusion of Gly-Pro, carnosine, L-Phe or L-Glu did not inhibit uptake of the dipeptide derivatives of L-Mel (or D-Mel) or their esters. These results suggest that the cellular uptake of the dipeptide derivatives of melphalan and their esters is probably via passive diffusion rather than being facilitated by an amino acid transporter or a di/tripeptide transporter. The higher intracellular levels of cytotoxic agents generated from the ester derivatives of the amino acids and the dipeptides are probably due to their higher lipophilicity and the overall neutral charge of the esters and subsequent intracellular formation of the more polar amino acids (L- or D-Mel) and/or Mel-containing dipeptides. Finally, these studies suggest that dipeptides of D-Mel [11b, 11d, 13] have inherent cytotoxicity properties.

A study of nosocomial diarrhea in Calcutta

BACKGROUND

Nosocomial infection is a major problem in hospitalized patients, particularly those who are debilitated. These infections may manifest as diarrhea. The spectrum of infections agents causing nosocomial diarrhea in our country is not known.

METHODS

Thirty-two patients, admitted to the hospital with various complaints, who developed diarrhea during their hospital stay, were studied to identify the causative agents of diarrhea. Hospital food samples were also processed for pathogens.

RESULTS

The bacteria isolated from patients included established enteropathogens like Salmonella, enteropathogenic Escherichia coli, Campylobacter species and organisms with low pathogenicity like Serratia marsescens, Pseudomonas aeruginosa and Morganella morganii. The bacterial pathogens isolated were resistant to most antibiotics, suggesting their nosocomial character. Hospital food samples contained Salmonella typhimurium, Campylobacter jejuni (biotype 1) and enteropathogenic Escherichia coli, suggesting that food might have been the vehicle for these infections.

CONCLUSION

Nosocomial infection was found to be an important cause of diarrhea (34%), EPEC and Salmonell being the predominant pathogens. Water, egg and milk were the source of infection in these cases. Special measures to obtain uneffected items will prevent occurrence of nosocomial diarrhea in our hospitals.

GnRH receptor site increase on the surface of cultured gonadotropes of senescent C57BL/6NNia mice

Anterior pituitary cells were cultured for 2 days from 6-, 14-, and 23-25-month-old C57BL/6NNia mice. The cells were then stimulated with one of three biotinylated GnRHs [biotinyl-Lys6]-[D-Lys6]GnRH, [biotinyl-Ser4]-[D-Lys6]GnRH, [biotinyl-Ser4]-[D-Trp6, des-Gly10]GnRH) at 4 degrees C for 1 h. Some of these cells were processed unfixed, attaching avidin-fluorescein and examined with fluorescent microscopy. Other cells were fixed and the biotinylated GnRH coupled to avidin-gold (20 nm particles), which was subsequently silver-enhanced (70 nm particles) and examined with light and scanning electron microscopy (SEM). To enhance the location of receptor sites for quantitation, a back-scattering electron detector was employed with the SEM. Gonadotropes from all three age groups ranged in size from 3 to 13 microns in diameter. The largest gonadotropes in each age group displayed the highest number of GnRH receptors, but the concentration/surface area (microns2) was less than for smaller cells. Smaller gonadotropes (3-6 microns diameter) from 14- and 23-25-month-old mice contained more GnRH receptor sites/microns2 (p < .001) than those from 6-month-old mice; the percentage of these gonadotropes was markedly higher for 14-(65%) and 25-(52%) versus 6-month-old (5%) mice. The number of receptor sites in larger gonadotropes (6.1-13 microns diameter) did not decline with the increasing age of the mouse. Decreased secretory activity in gonadotropes of 25-month-old mice may result from age-related changes in pituitary peptide processing or release, but it is not due to a lack of GnRH receptors or the inability of GnRH to bind to its receptor site.

Isolation of Capnocytophaga species from non-vital anterior teeth

Root-canal infection is very common in India. Both aerobic and anaerobic organisms have been claimed for its aetiology. However, isolation of Capnocytophaga species from non-vital anterior teeth is sparse. In this study a solitary case of Capnocytophagal root canal infection is reported.

Topographical mapping of GnRH receptors on dispersed mouse pituitary cells by backscattered electron imaging

Mouse anterior pituitary cells cultured for 2 days were stimulated with one of three biotinylated-GnRH probes ([biotinyl-Lys6]-[D-Lys6]GnRH, [biotinyl-Ser4]-[D-Lys6]GnRH, [biotinyl-Ser4]-[D-Trp6, des-Gly10]GnRH) in the cold (4 degrees C) for 1 hr. These cells were subsequently fixed and an avidin-gold complex was conjugated to the bound GnRH. After a second fixation, the gold label was silver-enhanced for viewing with a scanning electron microscope. Gonadotropes were identified as a result of the labeling procedure, measured for size, and the number of GnRH receptor sites counted. Gonadotropes ranged from 3 to 13 microns in diameter and contained from 23.2 +/- 3.3 to 338.4 +/- 25.2 sites per cell depending upon the size of the cell and the ligand employed. The methods described should be applicable for studying the topographical distribution of a variety of cellular receptors.

Incidence of Campylobacter species in animal handlers

From the stool samples collected from diarrhoeic and healthy handlers of domestic animals different Campylobacter species were isolated in 16.6 and 21.1 per cent respectively. Both biotypes 1 and 2 were identified. All the 10 strains of C. jejuni were found to be enterotoxigenic or potentially enterotoxigenic in the ligated ileal loop of albino rats.

Levels of alpha-inhibin in aging female mice

alpha-inhibin was immunocytochemically localized in granulosa cells of different stages of developing follicles, freshly formed corpora lutea, and scattered interstitial cells (pigmented or ceroid cells) in ovaries of 6-, 14-, and 23-25-mo-old C57BL/6NNia mice. Developing follicles exhibited the greatest amount of staining. Quantitation of the stain using an image analysis system indicated the staining intensity within ovarian follicles of 14-mo-old mice was greater than that in 23-25-mo-old mice. The levels of plasma alpha-inhibin and estradiol (E2) decreased with age. The number of follicles present in ovaries of middle-aged mice was comparable to those of 6-mo-old mice, yet plasma levels of FSH were significantly higher than those of 6-mo-old mice. This may be due to an age-related loss in the sensitivity of the hypothalamus and/or pituitary of middle-aged mice to ovarian hormones. In contrast, ovaries of 23-25-mo-old mice contained few antral follicles and consequently produced little alpha-inhibin. There appeared to be little negative feedback regulation of FSH secretion in 23-25-mo-old mice as a result of age-related ovarian impairments. This study supports an earlier hypothesis from our laboratory [Biol Reprod 1985; 32:989-997] that the primary defect(s) limiting age-related reproductive performance in mice appears to reside within the hypothalamo-hypophyseal axis, whereas secondary defects arise from the ovary.

Prevalence of the type of hepatitis virus in hospitalized jaundiced individuals

The prevalence of different types of hepatitis virus was estimated in 185 hospitalized jaundiced patients. It was found that 41.08% were positive for HBs Ag by ELISA method. The jaundiced group was also tested for IgM antibody and for total antibodies (IgG and IgM) to HAV infection by ELISA method and 5.40% were found to be positive. All patients in the jaundiced group had serum bilirubin above normal values. It was, therefore, assumed that the rest 52.92% were suffering from Non A Non B virus infection.

Comparison of a phenolic and a 0.2% chlorhexidine mouthwash on the development of plaque and gingivitis

Chlorhexidine and phenolic mouthrinses have attracted considerable interest as adjuncts to oral hygiene. The aim of this study was to compare two well known proprietary mouthrinse products for their effects on plaque regrowth, the development of gingivitis and the formation of toothstaining. The study was a single-blind, randomized, placebo-controlled, triple cross-over experimental, gingivitis design. A group of 15 volunteers with a very high standard of oral hygiene and gingival health used each rinse for 19 days in the absence of normal toothcleaning. Each period was separated by a 21 day washout. Plaque scores were significantly different between the rinses, being lowest with chlorhexidine and highest with saline. The plaque area increased 3-fold with the phenolic rinse and 6-fold with the saline rinse compared to the chlorhexidine rinse. Similarly, gingivitis increments were lowest with chlorhexidine and highest with saline but differences between rinses did not reach significance. Staining was significantly different between rinses, primarily due to minimal staining associated with the saline rinse. Staining occurred with both the chlorhexidine and phenolic mouthrinses. It is concluded that the 0.2% chlorhexidine rinse offers greater oral hygiene benefits than the phenolic rinse. The question of indications and durations of use of mouthwash products should be addressed.

Enterotoxigenicity of human and animal isolates of Campylobacter jejuni in ligated rat ileal loops

Human and animal isolates of Campylobacter jejuni were tested for enterotoxigenicity in ligated loop of Charles-Foster rats. Of 21 isolates, 13 were proved to be toxin-positive in the initial experiments. However, the remaining 8 required one to three passages through the rat ileal loop before showing the capacity to produce enterotoxin. All isolates caused fluid accumulation comparable with the amount produced by the standard toxigenic strain of Vibrio cholerae 01 1naba 569B. The isolates of C. jejuni from human and animal sources did not show any quantitative difference in their capacity to produce enterotoxin.

Effect of stress on the catecholamine content of the adrenal gland of intact and bursectomized chicks

1. Bursa-intact and bursectomized chicks were exposed to cold-wet immobilization (CWI) stress for 1.5 min. The catecholamines (CA) from the adrenal gland were measured spectrofluorometrically 5, 15, 30 and 60 min after stress. 2. In bursa-intact chicks, the CWI stress caused decrease of both norepinephrine and epinephrine from the adrenal glands 5 min after stress. Resynthesis of epinephrine exceeded the control value 30 and 60 min after stress. 3. In bursectomized chicks, the CWI stress brought about a decrease of norepinephrine 15 and 30 min and of epinephrine 30 and 60 min after stress. 4. The findings suggest that bursa facilitates early (5 min) release of CA and also helps in quick resynthesis of epinephrine during stress.

Is leprosy bacillus a chemo-autotrophic nocardioform organism?

Numerous attempts at in vitro cultivation of the leprosy bacillus have all proved to be unsuccessful. Recently, we have repeatedly isolated chemo-autotrophic nocardioform (CAN) organisms in pure culture from multibacillary cases of leprosy. We find that these resemble the leprosy bacillus in many respects and suggest that the leprosy bacillus may be closer to the genus Nocardia than to Mycobacterium, and that it may be a chemo-autotroph, requiring only simple sources of carbon and nitrogen for its growth. This is in contrast to most other human pathogens, which are heterotrophs requiring complex sources of carbon and nitrogen for their growth. This could offer a possible explanation for the repeated failure at in vitro cultivation of the leprosy bacillus.