Developmentally regulated sphingolipid degradation in Leishmania major

Leishmania parasites alternate between extracellular promastigotes in sandflies and intracellular amastigotes in mammals. These protozoans acquire sphingolipids (SLs) through de novo synthesis (to produce inositol phosphorylceramide) and salvage (to obtain sphingomyelin from the host). A single ISCL (Inositol phosphoSphingolipid phospholipase C-Like) enzyme is responsible for the degradation of both inositol phosphorylceramide (the IPC hydrolase or IPCase activity) and sphingomyelin (the SMase activity). Recent studies of a L. major ISCL-null mutant (iscl(-)) indicate that SL degradation is required for promastigote survival in stationary phase, especially under acidic pH. ISCL is also essential for L. major proliferation in mammals. To further understand the role of ISCL in Leishmania growth and virulence, we introduced a sole IPCase or a sole SMase into the iscl(-) mutant. Results showed that restoration of IPCase only complemented the acid resistance defect in iscl(-) promastigotes and improved their survival in macrophages, but failed to recover virulence in mice. In contrast, a sole SMase fully restored parasite infectivity in mice but was unable to reverse the promastigote defects in iscl(-). These findings suggest that SL degradation in Leishmania possesses separate roles in different stages: while the IPCase activity is important for promastigote survival and acid tolerance, the SMase activity is required for amastigote proliferation in mammals. Consistent with these findings, ISCL was preferentially expressed in stationary phase promastigotes and amastigotes. Together, our results indicate that SL degradation by Leishmania is critical for parasites to establish and sustain infection in the mammalian host.     

Synthesis and thermochemical study of ligand substitution reactions of aminobis(phosphines), Ph2P(R)NPPh2, with [Me2Pt(COD)]

The reactions of aminobis(phosphines), Ph₂PN(R)PPh₂ (R = H, Me, Et, ⁿPr, ⁿBu, Ph), with Me₂Pt(COD) led to the formation of four-membered metallacycles in good yield. The enthalpies of the ligand substitution reactions are measured by the anaerobic solution calorimetry in THF at 30 °C.     

Identification of critical residues of subunit H in its interaction with subunit E of the A-ATP synthase from Methanocaldococcus jannaschii

The boomerang-like H subunit of A(1)A(0) ATP synthase forms one of the peripheral stalks connecting the A(1) and A(0) sections. Structural analyses of the N-terminal part (H1-47) of subunit H of the A(1)A(0) ATP synthase from Methanocaldococcus jannaschii have been performed by NMR spectroscopy. Our initial NMR structural calculations for H1-47 indicate that amino acid residues 7-44 fold into a single alpha-helical structure. Using the purified N- (E1-100) and C-terminal domains (E101-206) of subunit E, NMR titration experiments revealed that the N-terminal residues Met1-6, Lys10, Glu11, Ala15, Val20 and Glu24 of H1-47 interact specifically with the N-terminal domain E1-100 of subunit E. A more detailed picture regarding the residues of E1-100 involved in this association was obtained by titration studies using the N-terminal peptides E1-20, E21-40 and E41-60. These data indicate that the N-terminal tail E41-60 interacts with the N-terminal amino acids of H1-47, and this has been confirmed by fluorescence correlation spectroscopy results. Analysis of (1)H-(15)N heteronuclear single quantum coherence (HSQC) spectra of the central stalk subunit F in the presence and absence of E101-206 show no obvious interaction between the C-terminal domain of E and subunit F. The data presented provide, for the first time, structural insights into the interaction of subunits E and H, and their arrangement within A(1)A(0) ATP synthase.     

Molecular dynamic simulations study of the effect of salt valency on structure and thermodynamic solvation behaviour of anionic polyacrylate PAA in aqueous solutions

The effect of salt concentration and valency on intermolecular structure and solvation thermodynamic properties of aqueous solution containing polyacrylicacid (PAA) chains and multi-valent salts calcium chloride (CaCl₂) and aluminium chloride (AlCl₃) as a function of charge density was investigated using atomistic molecular dynamic simulations with explicit solvent. Salt-free solution favours the self-association of uncharged (acidic form) PAA chains facilitated by inter-chain hydrogen bonds. The ionised (charged) PAA chains are not associated in salt-free aqueous solutions and undergo self-association in the salt solutions due to bridging effect induced by condensed salt ions in agreement with scattering investigations available in literature. The collapse behaviour of PAA in presence of CaCl₂ and re-expansion behaviour of PAA chains in case of AlCl₃ salt solutions are observed. The rigidity of PAA chains decrease with increase in salt concentration, in agreement with experimental results available in literature. The trivalent salt favours relatively the greater extent of shrinking of PAA chains as well as inter-chain interactions as compared to divalent salts as evident from radius-of-gyration, H-bond and pair-wise solvation enthalpy data. The conformation and hydration behaviour of the acid form of PAA chains are not significantly altered by added salt ions. The hydration behaviour of ionised PAA chains is significantly reduced by added salts due to screening effect of the condensed salt ions. The pair correlation functions of solutions species such as Ca²⁺, Al³⁺, Na⁺ and Cl^? with respect to PAA oxygen show the greater affinity of PAA units with the higher valency Al³⁺ ions over Ca²⁺ and Na⁺ in solution. With increase in concentration of AlCl₃ and CaCl₂ salts, a decrease in effective charge density of ionised PAA chains is observed from the existence of unfavourable PAA–water, PAA–Ca²⁺ and PAA–Al³⁺ interactions.     

Current status of fertility control methods in India

Approximately 48.2% of couples of 15 to 49 years of age practice family planning methods in India. Female sterilization accounts for 34.2%, with male sterilization declining from 3·4% in 1992–93 to 1·9% in 1998–99. Use of the condom increased to 3·1% from 2·4%. There is an urgent need for research to develop new contraceptive modalities especially for men and also for women and to make existing methods more safe, affordable and acceptable. Current efforts in India to develop a male contraceptive are mainly directed towards (i) development of antispermatogenic agents to suppress sperm production, (ii) prevention of sperm maturation, (iii) prevention of sperm transport through vas deferens or rendering these sperm infertile and (iv) prevention of sperm deposition. Research work in the field of prevention of sperm transport through vas deferens has made significant advances. Styrene maleic anhydride (SMA) disturbed the electrical charge of spermatozoa leading to acrosome rupture and consequent loss in fertilizing ability of sperm. A multicentre phase-III clinical trial using SMA is continuing and it is hoped that the SMA approach would be available in the near future as an indigenously developed injectable intra-vasal male contraceptive. The safety and efficacy of available oral contraceptives were evaluated. An indigenously developed oral contraceptive ‘Centchorman’, which is a nonsteroidal, weakly estrogenic but potently antiestrogenic, was found to be safe and effective and is now being marketed in India since 1991 as a ‘once a week’ pill. Cyclofem and Mesigyna have been recommended as injectable contraceptives with proper counselling and service delivery by Indian studies. It has been recommended that these injectable contraceptives be added to the existing range of contraceptive methods available in the National Family Planning Programme. Based on the Indian studies CuT 200 was also recommended. Studies have indicated the advantage of intrauterine devices (IUD); they are long acting, relatively easily removed and fertility returns rapidly after their removal. Recent studies have recommended CuT 200 for use up to 5 years. The combination of some plant products i.e.Embelia ribes, Borax andPiper longum has been found to be safe and effective as a female contraceptive and the results of phase-I clinical trials are encouraging. Research work is going on in the country in various areas with special reference to hormonal contraceptive — a three monthly injectable contraceptive, immuno-contraceptives, antiprogestins, etc.     

Requirement offlex (femalelethal onX) in the development of the female germ line ofDrosophila melanogaster

Drosophila melanogaster females homozygous forflex, an X-linked recessive mutation, do not survive. Hemizygous males are unaffected. Homozygous embryos appear to lack SXL, the product of theSex-lethal (Sxl) gene, apparently as a result of disruption ofSxl splicing. It is known that bothSxl and its somatic splicing regulators [snf andfl(2)d] also function in the development of the female germ line. For this reason, we investigated the role offlex in the germ line by generatingflex/flex clones inflex/+ females. Females carrying such clones in their germ lines do not lay eggs whereas females carryingflex+ eggs lay viable eggs. Additionally, DAPI staining of ovarioles showed that diploid germ cells that are homozygous mutant forflex do not complete oogenesis. These results indicate that theflex+ gene product may be required for the development of the female germ line.     

Neutralizing the free radicals could alleviate the disease severity following an infection by positive strand RNA viruses

Free radical release due to oxidative stress is gaining importance in the field of viral pathogenesis. Recent studies suggest the involvement of oxidative stress and ROS levels in regulating disease virulence during RNA virus infection. Most of the RNA virus infections lead to vascular dysfunction and disease severity. However, the biology of free radicals in maintaining vascular endothelium integrity is not completely understood. In the present review, we discuss some of the common features in positive-strand RNA virus infections such as dengue and SARS-CoV-2 and suggest that anti-oxidant therapy could pave the way to develop therapeutic strategies in combating emerging and re-emerging RNA viruses.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12192-022-01269-x.     

Effect of iron deficiency anaemia over glycated hemoglobin in non-diabetic women

Background: Glycated hemoglobin (HbA1c) is a form of hemoglobin bound to glucose and used as an index of glycaemic control reflecting glucose levels of the previous three months. Iron deficiency anemia (IDA) is the commonest form of anemia that affects HbA1c. Reports on the effects of IDA on HbA1c levels are inconsistent in India. Therefore, the study correlated the HbA1c and IDA in non-diabetic female patients. Methods: A correlative study between HbA1c and IDA was carried out at the Department of Biochemistry, A. J. Institute of Medical Sciences, Mangaluru, India. A total of 50 non-diabetic female patients, aged between 20-50 years, with decreased levels of Hb, MCV and MCHC were selected. Their ferritin levels were determined by ELISA method to confirm IDA. Forty confirmed iron-deficient samples whose serum ferritin levels were <90 pg/dL, were tested for HbA1c levels by nephelometry method. Results: HbA1c correlated positively with serum ferritin, Hb, MCV, MCH and MCHC (P<0.05). There was a significant decrease in mean value of HbA1c in those with severe anemia (4.50±0.34) compared to those with moderate anemia (5.18±0.35) (P<0.001). Conclusion: Results showed positive correlation of HbA1c with ferritin and hemoglobin. Therefore, iron status should be considered during the interpretation of the HbA1c concentrations in diabetes mellitus.     

Micropropagation ofUraria picta, a medicinal plant, through axillary bud culture and callus regeneration

Summary Micropropagation ofUraria picta, a leguminous herb, was achieved through axillary bud culture and nodal callus culture. Bud break was best when nodes were cultured on Murashige and Skoog (1962) (MS) medium supplemented with 2.6 μM α-naphthalene acetic acid and 4.4 μM N⁶-benzyladenine. Optimum shoot multiplication was observed in adenine sulphate at 2.47 μM concentration. Competent callus was initiated around the nodal ring of the explant on the basal medium supplemented with cytokinins and auxin (α-naphthalene acetic acid and N⁶-benzyladenine), which regenerated into new profusely growing shoots on transferring to 0.13 μM N⁶-benzyladenine. Shoots elongated to 5 node length with 1.11 μM N⁶-benzyladenine were rooted on half-strength MS basal medium. The rooted plants were successfully established with 80% survival. About 400 such plants were transferred to the field.     

Comparative study of the expression of Rb and p53 genes in human colorectal cancers,colon carcinoma cell lines and synchronized human fibroblasts

We have compared the expression of the retinoblastoma (Rb) and p53 genes in normal human fibroblasts, colon carcinoma cell lines, matched pairs of colorectal tumor tissues and adjacent normal mucosa and in synchronized human diploid fibroblast cell line W138. The increased expression of Rb and p53 RNA was observed in a majority of colorectal cancers in comparison to adjacent normal mucosa and is accompanied by proportional increase in the expression of histone H3 gene. The Rb and p53 RNA levels varied significantly between the various colon carcinoma cell lines. However, we found that the expression of Rb and p53 RNA is regulated differently in cell cycle synchronized normal human fibroblasts. The Rb mRNA level did not change with the position in the cell cycle and did not differ significantly whether the cells were serum deprived or in 10% serum. But p53 mRNA expression follows the same pattern as histone H3 mRNA.