An indigenously developed method for sweat collection and estimation of chloride for diagnosis of cystic fibrosis

An indigenously developed method for sweat collection and titration method for estimation of chloride was validated. The mean difference in estimated chloride value from the known strength of saline in 50 samples was -1.04 +/- 4.13 mEq/L (95% CI: -0.07 to 2.28). The mean difference in the estimated chloride values between two observers when the test was performed on known strengths of saline solution was -2.5 +/- 4.24 mEq/L (95% CI: -3.67 to 1.33). The inter observer variability between two observers when the test was performed on sweat samples obtained from 50 individuals was -1.12 +/- 4.34 mEq/L (95% CI: -2.23 to 0.8 ). Sweat weight of more than 100 mg could be collected in first attempt in 602 of 757 (80%) patient with an average sweat weight of 230 mg. This inexpensive method of sweat collection and chloride estimation has acceptable accuracy and repeatability and can be used in resource poor setting for making a diagnosis of cystic fibrosis.

Analysis of equilibrium dissociation and unfolding in denaturants of soybean agglutinin and two of its derivatives

The equilibrium denaturation of tetrameric soybean agglutinin (SBA) in urea and guanidine hydrochloride (GdnHCl) has been examined by steady-state fluorescence and size-exclusion chromatography. The denaturation of SBA reveals two distinct and separable transitions: dissociation (native tetramer<-->tertiary monomer) and unfolding (tertiary monomer<-->unfolded monomer). The urea denaturation curves of N-dimethyl and acetyl derivatives of SBA are also similar to unmodified lectin but the midpoints, [D](1/2), are shifted to lower denaturant concentrations. The free energy of stabilization of tertiary structure (DeltaG(u,aq)) of SBA is estimated to be 4.5-4.6 kcal mol(-1), which shows a decrease by approximately 10-15% for both N-dimethyl SBA and acetyl-SBA. The free energy term (DeltaG(d, aq)) for the relative stability of the quaternary structure of SBA and its derivatives shows that the decrease in stability relative to SBA occurs by <10% for N-dimethyl SBA while for acetyl-SBA, this occurs by approximately 30%. However, the m values depicting the dependence of free energy on denaturant concentration for SBA and its derivatives are similar for dissociation as well as unfolding, which suggest similar denaturation pathways of unmodified and modified SBA.

Boron compounds against human leukemic cells

Two new boron compoumds, dihydroxy(oxybiguanido) boron (iii) hydrochloride monohydrate (HB) and guanidine biboric acid adduct (GB) were used in this study to observe the antitumor effect. Leukemic blast cells isolated from chronic myeloid leukemia (CML) patients showed significant cell growth inhibition within twentyfour hours. IC50 of GB and HB was 2mg/ml. The metabolically active cells were found to be inhibited by drug treatment as assessed by MTT test. Inhibition of 3H Thymidine incorporation also supported the above result. In this study we investigated the molecular mechanisms by which HB and GB induce apoptosis in immature blast cells.

Risk factors for severe acute lower respiratory tract infection in under-five children

BACKGROUND

Acute lower respiratory infection (ALRTI) is the leading cause of death in children below five years of age. Identification of modifiable risk factors of severe ALRTI may help in reducing the burden of disease.

METHODS

A hospital based case control study was undertaken to determine risk factors associated with severe lower respiratory tract infection (LRTI) in under-five children. A case definition of severe ALRTI as given by World Health Organization (WHO) was used for cases. Healthy children attending Pediatrics out patient department for immunization during study period were enrolled as controls. Details of potential risk factors in cases and controls were recorded in pre-designed proforma.

RESULTS

512 children including 201 cases and 311 controls were enrolled in the study. On stepwise logistic regression analysis it was found that lack of breastfeeding (OR: 1.64; 95 percent CI: 1.23-2.17); upper respiratory infection in mother (OR: 6.53; 95 percent CI: 2.73-15.63); upper respiratory infection in siblings (OR: 24; 95 percent CI: 7.8-74.4); severe malnutrition (OR: 1.85; 95 percent CI: 1.14-3.0); cooking fuel other than liquid petroleum gas (OR: 2.5; 95 percent CI: 1.51-4.16); inappropriate immunization for age (OR: 2.85; 95 percent CI 1.59-5.0) and history of LRTI in the family (OR 5.15, 95 percent CI 3.0-8.8) were the significant contributors of ALRTI in children under five years. Sex of the child, age of the parents, education of the parents, number of children at home, anemia, inadequate caloric intake, type of housing were not documented to be significant risk factors of ALRTI.

CONCLUSION

Lack of breast-feeding, upper respiratory infection in mother, upper respiratory infection in siblings, severe malnutrition, cooking fuel other than liquid petroleum gas, inappropriate immunization for age and history of LRTI in the family were the significant risk factors associated with ALRTI

Novel mutations of MYO15A associated with profound deafness in consanguineous families and moderately severe hearing loss in a patient with Smith-Magenis syndrome

Mutations in myosin XVA are responsible for the shaker 2 ( sh2) phenotype in mice and nonsyndromic autosomal recessive profound hearing loss DFNB3 on chromosome 17p11.2. We have ascertained seven families with profound congenital hearing loss from Pakistan and India with evidence of linkage to DFNB3 at 17p11.2. We report three novel homozygous mutations in MYO15A segregating in three of these families. In addition, one hemizygous missense mutation of MYO15A was found in one of eight Smith-Magenis syndrome (del(17)p11.2) patients from North America who had moderately severe sensorineural hearing loss.

Pineal organ-like organization of the retina in megachiroptean bats

Phylogenetically originated from photoreceptive structures, the pineal organ adapts the organism to circadian and circannual light periodicity of the environment, while the retina develops to a light-based locator. Bats have a nocturnal life and an echolocator orientation presumably modifying the task of photoreception. Looking for morphological basis of the special functions, in the present work we compared the fine structure and immunocytochemistry of the retina and pineal organ in micro- and megacrochiroptean bats. We found that there is a high similarity between the retina and pineal organ in megachiropterans when compared to other species investigated so far. Besides of photoreceptor derived pinealocytes, the pineal organ of both micro- and megachiropterans contain intrapineal neurons and/or ganglionic cells as well as glial cells. Like spherules and pedicles of retinal photoreceptors, axon-type processes of pinealocytes form synaptic ribbon containig terminals. Similar to retinal photoreceptors and neurons, pinealocytes and pineal neurons contain immunoreactive glutamate and aspartate. In addition, excitatory amino acids accumulate in the pineal neurohormonal endings and might have a role in the hormonal (serotonin?) release of the organ. Concerning the structure of the retina the highest similarity to the organization of the pineal organ was found in the megachiroptean fruit eating bats Cynopterus sphinx and Rusettus niloticus. The retina of these species forms folds and crypts in its photoreceptor layer. This organization is similar to the folds of the pineal wall successively developed during evolution. Since a folded photoreceptor layer is not viable for a photolocator screen in decoding two-dimensional images, we suppose that this peculiar organization of the megachiropteran retina is connected to a "pineal-like" photometer task of the eye needed by these species active at night.

Biophysical evidence of arm-domain interactions in AraC

We report development of a method for the direct measurement of the interaction between the N-terminal arm and the remainder of the dimerization domain in the Escherichia coli AraC protein, the regulator of the l-arabinose operon. The interaction was measured using surface plasmon resonance to monitor the association between the immobilized peptide arm and the dimerization domain, truncated of its arm, in solution. As expected from genetic and physiological data, the interaction is strongly stimulated by l-arabinose and is insensitive to sugars like d-glucose or d-galactose. Alterations in the sequence of the arm which physiological experiments predict either to strengthen or weaken the arm produce the expected responses.

Characterisation of the gene encoding type II DNA topoisomerase from Leishmania donovani: a key molecular target in antileishmanial therapy

The gene encoding type II DNA topoisomerase from the kinetoplastid hemoflagellated protozoan parasite Leishmania donovani (LdTOP2) was isolated from a genomic DNA library of this parasite. DNA sequence analysis revealed an ORF of 3711 bp encoding a putative protein of 1236 amino acids with no introns. The deduced amino acid sequence of LdTOP2 showed strong homologies to TOP2 sequences from other kinetoplastids, namely Crithidia and Trypanosoma spp. with estimated identities of 86 and 68%, respectively. LdTOP2 shares a much lower identity of 32% with its human homologue. LdTOP2 is located as a single copy on a chromosome in the 0.7 Mb region in the L.donovani genome and is expressed as a 5 kb transcript. 5'-Mapping studies indicate that the LdTOP2 gene transcript is matured post-transcriptionally with the trans-splicing of the mini-exon occurring at -639 from the predicted initiation site. Antiserum raised in rabbit against glutathione S-transferase fusion protein containing the major catalytic portion of the recombinant L.donovani topoisomerase II protein could detect a band on western blots at approximately 132 kDa, the expected size of the entire protein. Use of the same antiserum for immunolocalisation analysis led to the identification of nuclear, as well as kinetoplast, antigens for L.donovani topoisomerase II. The in vitro biochemical properties of the full-length recombinant LdTOP2 when overexpressed in E.coli were similar to the Mg(II) and ATP-dependent activity found in cell extracts of L.donovani.

Gene expression of the key enzymes of melatonin synthesis in extrapineal tissues of the rat

Besides the pineal gland, melatonin is reported to be produced in a number of extrapineal sites, where it could act as an intracellular mediator or paracrine signal in addition to its endocrine effects. In view of the suggested immunoregulatory role of melatonin, we compared lymphoid organs and several other tissues of the rat for their potential to synthesize melatonin. Using the reverse transcription-polymerase chain reaction (RT-PCR) method, we determined the tissue-specific expression of mRNAs encoding two key enzymes of the melatonin biosynthesis: serotonin-N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT). The minimal number of PCR cycles required to obtain a positive signal served as a measure for the abundance of a given mRNA. NAT and HIOMT mRNAs were detected in all tested tissues at high numbers of PCR cycles (40 and 45, respectively). At 35 cycles, only gut, testis, spinal cord, raphe nuclei, stomach fundus and striatum yielded positive signals for both enzymes. In conclusion, the presence of NAT and HIOMT mRNAs in a wide range of tissues corroborates and extends the notion of extrapineal melatonin synthesis. Comparatively low levels of the HIOMT messages in lymphoid organs, however, indicate a limited significance of melatonin synthesis within the immune system.

A 1.8 A resolution structure of pig muscle 3-phosphoglycerate kinase with bound MgADP and 3-phosphoglycerate in open conformation: new insight into the role of the nucleotide in domain closure

3-phosphoglycerate kinase (PGK) is a typical kinase with two structural domains. The domains each bind one of the two substrates, 3-phosphoglycerate (3-PG) and MgATP. For the phospho-transfer reaction to take place the substrates must be brought closer by a hinge-bending domain closure. Open and closed structures of the enzyme with different relative domain positions have been determined from different species, but a comprehensive description of this conformational transition is yet to be attained. Crystals of pig muscle PGK in complex with MgADP and 3-phosphoglycerate were grown under the conditions which have previously resulted in crystals of the closed, catalytically competent conformation of Trypanosoma brucei PGK. The X-ray structure of the pig muscle ternary complex was determined at 1.8 A and the model was refined to R=20.8% and Rfree=24.1%. Contrary to expectation, however, it represents an essentially open conformation compared to that of T. brucei PGK. In addition, the beta-phosphate group of ADP is mobile in the new structure, in contrast to its well-defined position in T. brucei PGK. An extensive comparison of the ternary complexes from these remote species has been carried out in order to establish general differences between the two conformations and is reported here. A second pair of the open and closed structures was also compared. These analyses have made it possible to define several characteristic changes which accompany the structural transition, in addition to those identified previously: (1) the operation of a hinge at beta-strand L in the inter-domain region which greatly affects the relative domain positions; (2) the rearrangement and movement of helix 8, regulated through the interactions with the nucleotide phosphate; and (3) the existence of another hinge between helix 14 and the rest of the C-terminal part of the chain, which allows fine adjustment of the N-domain position. The main hinge at beta-strand L acts in concert with the C-terminal hinge at helix 7 described previously. Simultaneous interactions of the nucleotide phosphate groups with the loop that precedes helix 8, beta-strand J and the N terminus of helix 13 are required for propagation of the nucleotide effect towards the beta-strand L molecular hinge. A detailed description of the role of nucleotide binding in the hinge operation is presented.

Stabilizing C-terminal tails on AraC

We examined the effects of the metabolic stability of random sequences appended to the C-terminus of the dimerization domain of the regulatory protein of the Escherichia coli arabinose operon, AraC. Genetic scoring utilized the trans dominant negative effect of the dimerization domain on the activity of intact AraC, and physical scoring used sodium dodecyl sulfate (SDS) gel electrophoresis. We confirmed previous results obtained with Arc and lambda repressors that C-terminal charged residues tend to be stabilizing and that hydrophobic residues are destabilizing. Additionally, we found that the provision of a single, charged C-terminal residue conferred significant stability that was independent of interior sequence. Hence, it appears that in the engineering of proteins, flexible tails may be freely added, with only the identity of the C-terminal amino acid being restricted. Proteins 2001;42:177-181.

Apoptosis in squamous cell carcinoma of the lung: correlation with survival and clinicopathological features

AIMS

Apoptosis is recognised as a physiological mechanism for controlling cell numbers and its subversion is thought to contribute to carcinogenesis. The aims of this study were to measure the apoptotic index (AI) in a series of squamous cell carcinomas (SCCs) of the lung using standard histological staining and confirm this by immunohistology using an antibody to an apoptosis specific protein (ASP), and to seek to correlate the AI with clinicopathological parameters.

METHODS

Sections of 134 SCCs were stained by haematoxylin and eosin (H&E) for counting apoptotic bodies of determine the AI (number of apoptotic bodies/10,000 tumour cells); 26 of these were also stained with anti-ASP antibody and the proportion of ASP positive cells counted. Clinical data were obtained from hospital notes.

RESULTS

The mean AI obtained by H&E staining of all 134 SCCs was 30.3 (SD, 24.75). Anti-ASP staining allowed easy identification of apoptotic bodies, and generated a somewhat higher index (mean, 51.4; SD 39); this was not a result of the selection of tumours because the AI by H&E in the subset stained with anti-ASP was 31.1. Regression analysis showed that the correlation between the two values of AI was highly significant (Rs = 0.9760; p < 0.001), indicating that the two methods were both reliable measures of apoptosis but that the anti-ASP staining is the more sensitive method. The tumours were grouped into high AI (> 50) and low AI (< 50) and survival analysis was carried out. The mean survival of the high AI group was 109 weeks and of the low AI group 72 weeks (p = 0.036).

CONCLUSIONS

Anti-ASP staining is a reliable, easy, and sensitive method for assessing apoptosis in tumour sections and confirms the validity of the AI obtained by H&E staining. AI is a guide to the behaviour of SCCs of the lung.

Substituting leucine for alanine-86 in the tether region of the iron-sulfur protein of the cytochrome bc1 complex affects the mobility of the [2Fe2S] domain

Mutating three conserved alanine residues in the tether region of the iron-sulfur protein of the yeast cytochrome bc(1) complex resulted in 22-56% decreases in enzymatic activity [Obungu et al. (2000) Biochim. Biophys. Acta 1457, 36-44]. The activity of the cytochrome bc(1) complex isolated from A86L was decreased 60% compared to the wild-type without loss of heme or protein and without changes in the 2Fe2S cluster or proton-pumping ability. The activity of the bc(1) complex from mutant A92R was identical to the wild-type, while loss of both heme and activity was observed in the bc(1) complex isolated from mutant A90I. Computer simulations indicated that neither mutation A86L nor mutation A92R affects the alpha-helical backbone in the tether region; however, the side chain of the leucine substituted for Ala-86 interacts with the side chain of Leu-89. The Arrhenius plot for mutant A86L was apparently biphasic with a transition observed at 17-19 degrees C and an activation energy of 279.9 kJ/mol below 17 degrees C and 125.1 kJ/mol above 17 degrees C. The initial rate of cytochrome c(1) reduction was lowered 33% in mutant A86L; however, the initial rate of cytochrome b reduction was unaffected, suggesting that movement of the tether region of the iron-sulfur protein is necessary for maximum rates of enzymatic activity. Substituting a leucine for Ala-86 impedes the unwinding of the alpha-helix and hence movement of the tether.