Shape engineering boosts antibacterial activity of chitosan coated mesoporous silica nanoparticle doped with silver: a mechanistic investigation

Mechanism of antibacterial activity of MSPs with high aspect ratio and surface modification.

Tailoring Energy Bandgap of Al Doped ZnO Thin Films Grown by Vacuum Thermal Evaporation Method

The paper presents the results of our experimental investigation pertaining to tailoring of energy bandgap and other associated characteristics of undoped and Al doped ZnO (AZO) thin film by varying the atomic concentration of Al in ZnO. Thin films of ZnO and ZnO doped with Al (1, 3, and 5 atomic percent (at.%)) were deposited on silicon substrate for structural characterization and on glass substrate for optical characterization. The dependence of structural and optical properties of Al doped ZnO on the atomic concentration of Al added to ZnO has been reported. On the basis of the experimental results an empirical formula has been proposed to calculate the energy bandgap of AZO theoretically in the range of 1 to 5 at.% of Al. The study revealed that AZO films are composed of smaller and larger number of grains as compared to pure ZnO counterpart and density of the grains was found to increase as the Al concentration increased (from 1 to 5 at.%). The transmittance in the visible region was greater than 90% and found to increase with increasing Al concentration up to 5 at.%. The optical bandgap was found to increase initially with increase in atomic concentration of Al concentration up to 3 at.% and decrease thereafter with increasing concentration of Al.

Effect of mesa structure formation on the electrical properties of zinc oxide thin film transistors

ZnO based bottom-gate thin film transistor (TFT) with SiO2 as insulating layer has been fabricated with two different structures. The effect of formation of mesa structure on the electrical characteristics of the TFTs has been studied. The formation of mesa structure of ZnO channel region can definitely result in better control over channel region and enhance value of channel mobility of ZnO TFT. As a result, by fabricating a mesa structured TFT, a better value of mobility and on-state current are achieved at low voltages. A typical saturation current of 1.85 x 10(-7) A under a gate bias of 50 V is obtained for non mesa structure TFT while for mesa structured TFT saturation current of 5 x 10(-5) A can be obtained at comparatively very low gate bias of 6.4 V.

Topological organization and functional aspects of the olfactory epithelium of whipfin silver biddy Gerres filamentosus (Cuvier 1829)

The structural organization of different cells lining the olfactory epithelium of Gerres filamentosus (Cuvier 1829) were studied by light and scanning electron microscopy respectively to correlate their role in olfaction. The fan shaped olfactory rosette of G. filamentosus was more or less oval in outline and composed of 13 lamellae of different sizes in both sides. The olfactory epithelium was partitioned into sensory and non-sensory regions. The sensory epithelium was restricted on the flat apical end of the lamellae and embossed with two types of receptor cells bearing either cilia or microvilli. The non-sensory epithelium, covering the middle and basal region of lamellae was comprised of stratified epithelial cells and mucous cells. The orientation of various cells in the surface contour of olfactory epithelium was discussed in light of their functional significance.

Simulation, fabrication and characterization of ZnO based thin film transistors grown by radio frequency magnetron sputtering

We report the performance of the thin film transistors (TFTs) using ZnO as an active channel layer grown by radio frequency (RF) magnetron sputtering technique. The bottom gate type TFT, consists of a conventional thermally grown SiO2 as gate insulator onto p-type Si substrates. The X-ray diffraction patterns reveal that the ZnO films are preferentially orientated in the (002) plane, with the c-axis perpendicular to the substrate. A typical ZnO TFT fabricated by this method exhibits saturation field effect mobility of about 0.6134 cm2/V s, an on to off ratio of 102, an off current of 2.0 x 10(-7) A, and a threshold voltage of 3.1 V at room temperature. Simulation of this TFT is also carried out by using the commercial software modeling tool ATLAS from Silvaco-International. The simulated global characteristics of the device were compared and contrasted with those measured experimentally. The experimental results are in fairly good agreement with those obtained from simulation.

Cytoarchitectural and surface ultrastructural analysis of the olfactory epithelium of Oreochromis nilotica (Linnaeus)

The olfactory organ of Oreochromis nilotica was studied by means of light and scanning electron microscopes. The oval shaped olfactory apparatus consists of 19-20 lamellae radiating from a central raphe. The receptor epithelium occupies the restricted area of the middle swollen region of the lamellae and is framed with receptor cells (both ciliated and microvillous) and rod cells. The larger part of the lateral surface of the olfactory lamella is covered with non-receptor epithelium, which is made up of stratified epithelial cells and mucous cells. The functional significance of various cells lining the olfactory epithelium of this fish are discussed.

Histological and ultrastructural studies of the olfactory epithelium of spotted butter fish Scatophagus argus (Linnaeus)

The olfactory epithelium of Scatophagus argus (Linnaeus) was investigated by light and scanning electron microscopy. The elongated olfactory organ is made up of 20 to 22 primary lamellae arranged on both sides of the narrow median raphe. Sensory and non-sensory regions are located separately on each lamella. The sensory epithelium occupies the upper apical broad half and extreme basal part of the olfactory lamellae whereas the middle slender part is covered with non-sensory epithelium. The sensory epithelium consists of ciliated, microvillus, and crypt cells. The non-sensory epithelium is made up of stratified epithelial cells having different patterns of finger-like micro-ridges and mucous cells. Different cells lining the olfactory epithelium have been correlated with the functional views of the fish concerned.

Cellular organisation and functions of the olfactory epithelium of pearl spot Etroplus suratensis (Bloch): a light and scanning electron microscopic study

The cellular organisation of the olfactory rosettes of Etroplus suratensis was studied by light and scanning electron microscopy. The oval shaped olfactory rosette of the fish consists of 12 lamellae radiating from a central raphe. The olfactory lamellae are comprised of restricted areas of sensory epithelium and broad areas of non-sensory epithelium in the apical, middle, and basal regions. The sensory epithelium contains three types of receptor cells: microvillus, ciliated, and rod cells, as well as labyrinth cells and supporting cells. The non-sensory epithelium consists of stratified epithelial and mucous cells. The transitional region between the sensory and non-sensory epithelium consists of ciliated receptor cells, mucous cells, and stratified epithelial cells. The different cells on the olfactory epithelium were discussed regarding the functional significance of the fish concerned.

Histological and scanning electron microscopical study of the olfactory epithelium of the Indian major carp, Catla catla (Hamilton)

The histological and micro-architecture of different cells lining the olfactory epithelium in Catla catla (Hamilton) have been studied by means of light and scanning electron microscopes. The oval olfactory rosette of the fish consists of a rosette of 30 to 32 primary lamellae. Each lamella is provided with restricted area of sensory epithelium in the middle region while the apical and basal part of the lamella consists of non-sensory epithelium. The non-sensory epithelium is made up of patches of ciliated supporting cells, epidermal or stratified epithelial cells with concentrically arranged microridges and scattered mucous cells. The sensory epithelium contains two types of receptor cell (microvillar and flagellated) and mucous cells. The multilayer olfactory organ in C. catla provides an acute sense of smell, and various aspects of their existence are mediated through olfactory cues.

Application of 16S rDNA based seminested PCR for diagnosis of acute bacterial meningitis

BACKGROUND & OBJECTIVES

The diagnosis of bacterial meningitis remains a challenge to the clinician because of its rapid lethal course lacking the consistency to particular clinical signs and symptoms. Moreover, in many clinical settings use of rampant and short course antibiotic therapy prior to lumbar puncture reduces the chance of isolation of bacteria in CSF culture making the diagnosis difficult. The present study was done to evaluate a multiplex seminested PCR based method for rapid diagnosis of bacterial meningitis even after initiation of antibiotics.

METHODS

A 16S rDNA based PCR technique was evaluated using universal bacterial primers to detect any bacterial pathogen in CSF samples. The simultaneous use of three species-specific primers in a multiplex and seminested PCR format was done to identify Streptococcus pneumoniae, Haemophilus influenzae and Neisseria meningitidis within 4 h.

RESULTS

Analysis of 267 CSF samples obtained from suspected cases of acute bacterial meningitis revealed 94 per cent concordance in results for conventional (Gram stain and culture) and molecular methods. Conventional techniques failed to detect five PCR positive samples where clinical diagnosis, cell count and biochemical findings of CSF supported the evidence of infection. The overall sensitivity, specificity, positive predictive value and negative predictive value of 16S rDNA PCR were 79.24, 97.6, 89.36 and 94.88 per cent respectively when culture was considered as gold standard. The detection limit of 16S rDNA PCR was determined to be 1000 cfu/ml of E. coli and 4000 cfu/ml of S. pneumoniae.

INTERPRETATION & CONCLUSION

The results suggest that 16S rDNA PCR can be used as a valuable supplementary test in routine clinical practice for diagnosis of acute bacterial meningitis in hospital setting.

Ultrastructural organisation and functional aspects of the olfactory epithelium of Wallago attu (Bleeker)

The topological architecture and functions of different cells of the olfactory epithelium in Wallago attu (Bleeker) have been systematically studied using a scanning electron microscope. The elongated olfactory rosette of the fish consists of 62 to 64 primary lamellae in each left and right rosette. Each lamella is provided with apical sensory epithelium and basal non-sensory epithelium. Topological analysis reveals that sensory epithelium contains receptor cells, ciliated supporting cells, labyrinth cells, and goblet cells. The non-sensory epithelium is made up of patches of ciliated supporting cells, epidermal or stratified epithelial cells with concentrically arranged microridges, and scattered goblet cells. Different cells on the olfactory epithelium support the view that the olfactory signalling is important to the survival of this fish in an aquatic environment.

The RD1-encoded antigen Rv3872 of Mycobacterium tuberculosis as a potential candidate for serodiagnosis of tuberculosis

Tuberculosis (TB) infections in India account for one-third of the global burden, making it important to develop speedy, cost-effective diagnostic tools. This study evaluated recombinant RD1-encoded antigens of Mycobacterium tuberculosis as tools for serodiagnosis by determining the immunological reactivity of these proteins against sera from healthy, bacille Calmette-Guérin (BCG)-vaccinated and TB-infected individuals from Kolkata. Rv3872, Rv3875 (ESAT-6) and Rv3878 were able to discriminate healthy BCG-vaccinated controls from TB patients. Rv3872 showed the highest level of antibody response in comparison with other antigens, and also showed statistically significant differences between pulmonary (p <0.0001) or extra-pulmonary (p <0.001) TB patients and healthy BCG-vaccinated individuals. The levels of antibody were measured using 20-mer overlapping peptides spanning the entire Rv3872 sequence. The immunological reactivity against a mixture of two peptides (P8 and P9) encompassing amino-acids 57-84 correlated well with that obtained using full-length Rv3872. This result was explained by the fact that two of the predicted regions of high antigenicity lie within amino-acid residues 57-85 of Rv3872. The high sensitivity and specificity of Rv3872, as well as the mixture of two synthetic overlapping peptides derived from Rv3872, highlight their potential and argue in favour of their use in serodiagnosis of both pulmonary and extra-pulmonary TB.

The fine structural organization of the olfactory epithelium of Cyprinus carpio (Linnaeus): a scanning electron microscopic study

The fine anatomical structures of the olfactory epithelium of Cyprinus carpio (Linnaeus) have been systematically studied with the help of the scanning electron microscope (SEM). The olfactory rosette is an oval structure composed of a number of lamellae arranged on a median raphe. A large part of the lateral surface of the rosette is covered with non-receptor epithelium, whereas the receptor epithelium occupies a much smaller area in the middle part. The nonreceptor epithelium is covered with a tuft of ciliated supporting cells, among which the stratified epithelial cells and mucous cells are located. The receptor epithelium is represented by the flagellated and microvillus receptor and supporting cells. Different cells on the olfactory epithelium correlate with the functional significance of the fish concerned.

e19a2 BCR-ABL fusion transcript in typical chronic myeloid leukaemia: a report of two cases

This report describes two patients with chronic myeloid leukaemia (CML): one of them developed accelerated phase CML and died 8 years after diagnosis and the other is at the chronic phase. Sequence analysis of reverse transcription-polymerase chain reaction products showed the presence of BCR-ABL fusion transcript e19a2. This finding suggests that CML carrying mu-BCR breakpoint may exhibit a clinical course similar to typical CML.

Histological and histochemical studies on the olfactory rosette of Mugil parsia (Hamilton)

The structure and functions of the olfactory organs in Mugil parsia (Ham.) has been described. Histologically each lamella consists of supporting, olfactory receptor, basal, labyrinth and mast cells. The distribution and localization of acid and neutral mucins in the various cells of olfactory epithelium in M. parsia has been studied histochemically. Variations in the localization of glycogen in the different cells of the olfactory epithelium have been correlated with the functional significance of the region concerned in the fish studied.

Conformational properties of alpha-tubulin tail peptide: implications for tail-body interaction

The carboxy-terminal segments of the alpha/beta-tubulins are flexible regions rich in acidic amino acid residues. It is generally believed that these regions play crucial roles in tubulin polymerization and interaction with many ligands, including colchicine. Exactly how these effects are exerted are not known at present. One such interesting aspect is the pH dependence of colchicine-tubulin interaction and the influence of the alpha-tail on the binding interaction. We have investigated the location of the colchicine-binding site on tubulin by docking. It has been located on the alpha/beta interface on the N-terminal side, which is also supported by much of the solution data. This location is too far from the tail regions, suggesting that influence of the tail region is transmitted by a pH-dependent conformational change. Two-dimensional NMR studies indicate that at pH 7 a 13-residue peptide corresponding to alpha-tubulin tail shows little NOE constraints, suggesting extended conformation. On the contrary, at pH 5, a relatively compact structure was deduced from the interproton NOE constraints. Pulsed field gradient measurement of diffusion constant indicates that the peptide at pH 5 is substantially faster diffusing than at pH 7. The Perrin factors calculated from diffusion data indicates that the peptide structure at pH is significantly more compact than at pH 7. Temperature coefficients of several amide protons at pH 5 fall below 5 ppb/(o)K, indicating a degree of protection. A difference is also seen in the CD spectra obtained at different pHs, consistent with the NMR data. We have investigated the probable spatial organization of the tail of the alpha-subunit of tubulin, in the high pH extended form and the low pH compact form. On the basis of correlation of pH dependence of many properties of tubulin and the conformation of the alpha-tail peptide, we propose that the intrinsic conformational preference of the tail-region modulate the tail-body interaction, which in turn has important bearing on colchicine binding properties.

Purification and crystallization of CII: an unstable transcription activator from phage lambda

The CII protein of the temperate bacteriophage lambda is a transcriptional activator involved in the lysis-lysogeny switch of the phage. It is an unstable protein of 97 amino acids and is known to exist as a tetramer in the native state. The cII gene has been cloned and expressed in Escherichia coli using a T7 promoter based over-expression system. The recombinant CII protein has been purified to homogeneity by ammonium sulfate fractionation followed by two steps of ion-exchange chromatography. The purified protein crystallized at pH 8.2 in hanging-drop vapor diffusion method at 293 K. The crystals diffract to a resolution of 2.8 A and belong to the space group C222 with unit-cell parameters a = 64.10, b = 106.95 and c = 120.16 A.

Non-hydrogen bond interactions involving the methionine sulfur atom

Of all the nonbonded interactions, hydrogen bond, because of its geometry involving polar atoms, is the most easily recognizable. Here we characterize two interactions involving the divalent sulfur of methionine (Met) residues that do not need any participation of proton. In one an oxygen atom of the main-chain carbonyl group or a carboxylate side chain is used. In another an aromatic atom interacting along the face of the ring is utilized. In these, the divalent sulfur behaves as an electrophile and the other electron-rich atom, a nucleophile. The stereochemistry of the interaction is such that the nucleophile tends to approach approximately along the extension of one of the covalent bonds to S. The nitrogen atom of histidine side chain is extensively used in these nonbonded contacts. There is no particular geometric pattern in the interaction of S with the edge of an aromatic ring, except when an N-H group in involved, which is found within 40 degrees from the perpendicular to the sulfide plane, thus defining the geometry of hydrogen bond interaction involving the sulfur atom. As most of the Met residues which partake in such stereospecific interactions are buried, these would be important for the stability of the protein core, and their incorporation in the binding site would be useful for molecular recognition and optimization of the site's affinity for partners (especially containing aromatic and heteroaromatic groups). Mutational studies aimed at replacing Met by other residues would benefit from the delineation of these interactions.

The interrelationships of side-chain and main-chain conformations in proteins

The accurate determination of a large number of protein structures by X-ray crystallography makes it possible to conduct a reliable statistical analysis of the distribution of the main-chain and side-chain conformational angles, how these are dependent on residue type, adjacent residue in the sequence, secondary structure, residue-residue interactions and location at the polypeptide chain termini. The interrelationship between the main-chain (phi, psi) and side-chain (chi 1) torsion angles leads to a classification of amino acid residues that simplify the folding alphabet considerably and can be a guide to the design of new proteins or mutational studies. Analyses of residues occurring with disallowed main-chain conformation or with multiple conformations shed some light on why some residues are less favoured in thermophiles.

Simultaneous pancreas-kidney transplantation at the University of Pittsburgh

Analysis of the SPK program at the University of Pittsburgh has led to a number of observations: 1. Under tacrolimus-based immunosuppression, without antibody induction, it has been possible to achieve (a) One- and 3-year actuarial patient survival rates of 98% and 95% (b) One- and 3-year actuarial kidney survival rates of 95% and 87% (c) One- and 3-year actuarial pancreas survival rates of 86% and 80% 2. Steroid withdrawal has been achieved in over half of the successfully transplanted recipients, with excellent outcomes and a low rate (4.7%) of subsequent rejection. 3. Bone marrow augmentation has been associated with (a) less rejection (b) less pancreatic graft loss to rejection (c) an increased ability to withdraw steroids 4. Rejection has been associated with a rising serum lipase. 5. Renal allograft rejection in SPK patients with elevated serum lipase levels has been seen in the setting of normal renal function. 6. Enteric drainage has been associated with a reasonably low complication rate. 7. SPK transplantation is a successful therapeutic option in selected type I diabetics with end-stage renal disease.

Assessing the role of tryptophan residues in the binding site

Instead of looking at the interfacial area as a measure of the extent of a protein--protein recognition site, a new procedure has been developed to identify the importance of a specific residue, namely tryptophan, in the binding process. Trp residues which contribute more towards the free energy of binding have their accessible surface area reduced, on complex formation, for both the main-chain and side-chain atoms, whereas for the less important residues the reduction is restricted only to the aromatic ring of the side chain. The two categories of residues are also distinguished by the presence or absence of hydrogen bonds involving the Trp residue in the complex. A comparison of the observed change in the accessible surface area with the value calculated using an analytical expression provides another way of characterizing the Trp residues critical for binding and this has been used to identify such residues involved in binding non-proteinaceous molecules in protein structures.

Conformational similarity indices between different residues in proteins and alpha-helix propensities

Various amino acid similarity matrices have been derived using data on physicochemical properties and molecular evolution. Conformational similarity indices, CS(XX'), between different residues are computed here using the distribution of the main-chain and side-chain torsion angles and the values have been used to cluster amino acids in proteins. A subset of these parameters, CS(AX') indicates the extent of similarity in the main-chain and side-chain conformations (phi,psi and chi1) of different residues (X) with Ala (A) and is found to have strong correlation with alpha-helix propensities. However, no subset of CS(XX') provides any linear relationship with beta-sheet propensities, suggesting that the conformational feature favouring the location of a residue in an alpha-helix is different from the one favouring the beta-sheet. Conformationally similar residues (close CS(AX) values) have similar steric framework of the side-chain (linear/branched, aliphatic/aromatic), irrespective of the polarity or hydrophobicity. Cooperative nucleation of helix may be facile for a contiguous stretch of residues with high overall CS(AX) values.

Outcome after steroid withdrawal in pediatric renal transplant patients receiving tacrolimus-based immunosuppression

BACKGROUND

Corticosteroids have always been an integral part of immunosuppressive regimens in renal transplantation. The primary goal of this analysis was to assess the safety of steroid withdrawal in our pediatric renal transplant recipients receiving tacrolimus-based immunosuppression.

METHODS

Between December 1989 and December 1996, 82 renal transplantations were performed in pediatric patients receiving tacrolimus-based immunosuppression. Two of these patients lost their grafts within 3 weeks of transplantation (and were still on steroids at the time of graft loss), and were excluded from further analysis. Seventy-four patients (92.5%) were taken off prednisone a median of 5.7 months after transplantation. Of these 74, 56 (70%) remained off prednisone (OFF), and 18 (22.5%) were restarted on prednisone a median of 14.8 months after discontinuing steroids (OFF --> ON). 6(7.5%) were never taken off prednisone (ON). The mean follow-up was 59 +/- 23 months.

RESULTS

The 1-, 3-, and 5-year actuarial patient survival rates in the OFF group were 100%, 98%, and 96%, respectively; in the OFF --> ON group, they were 100%, 100%, and 100%, and in the ON group, they were 100%, 83%, and 83%. The 1-, 3-, and 5- year actuarial graft survival rates in the OFF group were 100%, 95%, and 82%, respectively; in the OFF --> ON group, they were 100%, 89%, and 83%; and in the ON group, they were 100%, 50%, and 33%. Two of the six graft losses in the OFF group, three out of four in the OFF --> ON Group, and two out of five in the ON group, were to chronic rejection. A time-dependent Cox regression analysis showed that the hazard for graft failure for those who came and stayed off prednisone was 0.178 relative to those who were never withdrawn from prednisone (P=0.005). Patients who were 10 years of age or younger were withdrawn from prednisone earlier (median: 5 months) than those older than 10 years (median: 7.3 months, P=0.02). In addition, patients who never had acute rejection were withdrawn from steroids earlier (median: 5 months) than those who had one or more episodes of acute rejection (median: 7.6 months, P=0.001). There was no effect of donor age, race, sex, recipient race, sex, cadaveric versus living donor, 48-hr graft function, panel reactive antibody, and total HLA mismatches or matches on the likelihood of being weaned off steroids. Serum creatinine at most recent follow-up in the OFF group was 1.2 +/- 0.5 mg/dl; in the OFF --> ON group, it was 1.8 +/- 0.9 mg/dl, and in the ON group it was 2.0 mg/dl (P<0.003). The incidence of rejection in the OFF, OFF --> ON, and ON groups was 39%, 77%, and 100%, respectively (P<0.05).

CONCLUSION

These data suggest that steroid withdrawal in pediatric renal transplant patients receiving tacrolimus-based immunosuppression is associated with reasonable short- and medium-term patient and graft survival, and acceptable renal function. Patients who discontinue and then resume steroids had patient and graft survival rates comparable with those in patients who discontinue and stay off steroids, but had a higher serum creatinine and a higher incidence of rejection.

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.

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.

Renal allograft rejection with normal renal function in simultaneous kidney/pancreas recipients: does dissynchronous rejection really exist?

BACKGROUND

Between July 1, 1994 and December 1, 1998, 147 simultaneous kidney/pancreas transplantations were performed at our center. Of 95 patients who experienced at least one acute renal allograft rejection episode after transplantation, 7 (7.4%) developed rejection in the presence of stable and normal or near-normal renal function.

METHODS

The indication for renal allograft biopsy was a rising serum lipase, i.e., suspected pancreatic rejection. All seven patients were treated with steroids and augmentation of the tacrolimus dose, with a fall in the serum lipase and no change in the serum creatinine.

RESULTS

The serum creatinine levels just before, at the time of, 1 week after the biopsy, and at most recent follow-up were 1.4+/-0.4, 1.3+/-0.3, 1.2+/-0.2, and 1.2+/-0.2 mg/dl. The serum lipase levels just before, at the time of, 1 week after the biopsy, and at most recent follow-up were 1022+/-1157 mg/dl, 874+/-996 mg/dl, 243+/-260 mg/dl, and 94+/-75 mg/dl. The tacrolimus dosages and levels at the time of the biopsy and 1 week later were 14.9+/-5.0 mg/day and 15.0+/-4.0 ng/ml, and 16.4+/-6.3 mg/day and 15.1+/-6.8 ng/ml.

CONCLUSIONS

These findings suggest that, in patients undergoing simultaneous kidney/pancreas transplantation, the entity of dissynchronous pancreatic allograft rejection without renal allograft rejection may not really exist. These data also make an additional fundamental point that acute rejection may occur in patients with normal and stable renal function.

Results of pancreas transplantation after steroid withdrawal under tacrolimus immunosuppression

PURPOSE

The results of steroid withdrawal in pancreas transplant recipients under tacrolimus immunosuppression were analyzed.

METHODS

From July 4, 1994 until April 30, 1998, 147 pancreas transplantations were performed in 141 patients, including 126 simultaneous pancreas-kidney transplantations, 13 pancreas after kidney transplantation, and 8 pancreas transplantations alone. Baseline immunosuppression consisted of tacrolimus and steroids without antilymphocyte induction. Twenty-three patients were excluded from analysis because of early graft loss in 17 cases, retransplantation in 5 cases, and simultaneous pancreas-kidney transplantation after heart transplantation in 1 patient.

RESULTS

With a mean follow-up of 2.8+/-1.1 years (range 1.0 to 4.8 years), complete steroid withdrawal was achieved in 58 (47%) patients with a mean time to steroid withdrawal of 15.2+/-8 months (range 4 to 40 months after transplantation). Of the entire cohort of 141 patients, overall 1-, 2-, and 4-year patient survival rates were 98%, 95.5%, and 86%, respectively. Overall 1-, 2-, and 4-year graft survival rates were 83%, 80%, and 71% (pancreas) and 95%, 91%, and 84% (kidney), respectively. Of the 124 patients analyzed for steroid withdrawal, 1-, 2-, and 4-year patient survival rates were 98%, 97%, and 92%, respectively. Overall 1-, 2-, and 4-year graft survival rates were 98%, 91.5%, 83% (pancreas) and 97%, 95%, and 91% (kidney). Patient, pancreas, and kidney survival rates at 1 year were 100%, 100%, and 98% (off steroids) versus 97%, 91%, and 96% (on steroids, all NS) and at 4 years were 100%, 94%, and 95% (off steroids) versus 78%, 68%, and 85% (on steroids, P = 0.01, 0.002, and NS, respectively). The cumulative risk of rejection at the time of follow-up was 76% for patients on steroids versus 74% for patients off steroids (P = NS). Seven patients originally tapered off steroids were treated for subsequent rejection episodes, which were all steroid sensitive, and two of these seven patients are currently off steroids. Thirteen patients received antilymphocyte therapy for steroid-resistant rejection, five of whom are now off steroids. Tacrolimus trough levels were 9.3+/-2.4 ng/ml (off steroids) and 9.7+/-4.3 (on steroids, P = NS). Mean fasting glucose levels were 98+/-34 mg/dl (off steroids) and 110+/-41 mg/dl (on steroids, P = NS). Mean glycosylated hemoglobin levels were 5.2+/-0.9% (off steroids) and 6.2+/-2.1% (on steroids, P = 0.02), and mean serum creatinine levels were 1.4+/-0.8 mg/dl (off steroids) and 1.7+/-1.0 mg/dl (on steroids, P = 0.02).

CONCLUSION

These data show for the first time that steroid withdrawal can be safely accomplished in pancreas transplant recipients maintained on tacrolimus-based immunosuppression. Steroid withdrawal is associated with excellent patient and graft survival with no increase in the cumulative risk of rejection.

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.

Leishmania: naive human T cells sensitized with promastigote antigen and IL-12 develop into potent Th1 and CD8(+) cytotoxic effectors

Russo, D. M., Chakrabarti, P., and Higgins, A. Y. 1999. Leishmania: Naive human T cells sensitized with promastigote antigen and IL-12 develop into potent Th1 and CD8(+) cytotoxic effectors. Experimental Parasitology 93, 161-170. The differentiation of naive human T cells into Leishmania-specific Th1 or cytotoxic effector cells was examined by sensitizing T cells in vitro with dead Leishmania antigen in the presence or absence of IFN-gamma or IL-12. These Leishmania-specific T cell lines proliferated and produced cytokines in response to challenge with autologous Leishmania-infected macrophages. Sensitization in the presence of IL-12 or IFN-gamma induced Leishmania-specific human Th1 responses, with IL-12 inducing more potent Th1 responses. However, IL-12-induced Th1 responses were IFN-gamma dependent. T cell lines exhibited Th2 or Th0 phenotypes when primed in the absence of cytokines. Only T cell lines primed in the presence of IL-12 contained high percentages of CD8(+) cells. These cells lysed autologous Leishmania-infected but not uninfected macrophages in an MHC-dependent manner. Thus, this in vitro sensitization system can be used to delineate the conditions for optimally priming human Leishmania-specific effector cells.