Bone disease in organ transplant patients: pathogenesis and management

Bone disease is common in recipients of kidney, heart, lung, liver, and bone marrow transplants, and causes debilitating complications, such as osteoporosis, osteonecrosis, bone pain, and fractures. The frequency of fractures ranges from 6% to 45% for kidney transplant recipients to 22% to 42% for heart, lung, and liver transplant recipients. Bone disease in transplant patients is the sum of complex mechanisms that involve both preexisting bone disease before transplant and post-transplant bone loss due to the effects of immunosuppressive medications. Evaluation of bone disease should preferably start before the transplant or in the early post-transplant period and include assessment of bone mineral density and other metabolic factors that influence bone health. This requires close coordination between the primary care physician and transplant team. Patients should be stratified based on their fracture risk. Prevention and treatment include risk factor reduction, antiresorptive medications, such as bisphosphonates and calcitonin, calcitriol, and/or gonadal hormone replacement. A steroid-avoidance protocol may be considered.     

Copy number variation leads to considerable diversity for B but not A haplotypes of the human KIR genes encoding NK cell receptors

The KIR complex appears to be evolving rapidly in humans, and more than 50 different haplotypes have been described, ranging from four to 14 KIR loci. Previously it has been suggested that most KIR haplotypes consist of framework genes, present in all individuals, which bracket a variable number of other genes. We used a new technique to type 793 families from the United Kingdom and United States for both the presence/absence of all individual KIR genes as well as copy number and found that KIR haplotypes are even more complex. It is striking that all KIR loci are subject to copy number variation (CNV), including the so-called framework genes, but CNV is much more frequent in KIR B haplotypes than KIR A haplotypes. These two basic KIR haplotype groups, A and B, appear to be following different evolutionary trajectories. Despite the great diversity, there are 11 common haplotypes, derived by reciprocal recombination near KIR2DL4, which collectively account for 94% of KIR haplotypes determined in Caucasian samples. These haplotypes could be derived from combinations of just three centromeic and two telomeric motifs, simplifying disease analysis for these haplotypes. The remaining 6% of haplotypes displayed novel examples of expansion and contraction of numbers of loci. Conventional KIR typing misses much of this additional complexity, with important implications for studying the genetics of disease association with KIR that can now be explored by CNV analysis.The killer immunoglobulin-like receptor (KIR) genes are part of the leukocyte receptor complex (LRC), on chromosome 19q13.4. These genes are highly polymorphic and occupy one of the most rapidly evolving regions of the human genome. A KIR complex is missing in the mouse genome, and even closely related primate species show substantial differences in organization (Parham et al. 2012).KIR molecules modulate the development and activity of natural killer (NK) and some T-cells through interaction with major histocompatibility complex (MHC) class I receptors. Genetic analysis comparing disease with control samples indicates that KIR variation, in conjunction with polymorphic MHC class I molecules, plays a key role both in human reproduction as well as in immune defense (Khakoo and Carrington 2006).Currently, 15 different KIR loci (KIR2DL1, KIR2DL2/KIR2DL3 [2DL2L3], KIR2DL4, KIR2DL5A, KIR2DL5B, KIR2DS1–5, KIR3DL1/KIR3DS1 [3DL1S1], KIR3DL2–3, and two pseudogenes, KIR2DP1 and KIR3DP1; all gene names abbreviated in subsequent text, without “KIR”) have been identified (http://www.ebi.ac.uk/ipd/kir/). Selected combinations of these genes are encoded on haplotypes within a 100- to 200-kb region of the LRC (Martin et al. 2000; Wilson et al. 2000). Most KIR haplotypes contain between seven and 12 genes plus the two pseudogenes. Based on this variation in gene content alone, more than 50 distinct KIR haplotypes have been identified (Hsu et al. 2002; Khakoo and Carrington 2006). Further complexity is introduced by extensive allelic variation, with more than 50 different alleles determined for some loci (Robinson et al. 2010).Previous analyses of these haplotypes suggested that they are subdivided into two distinct groups. Subsequently these two groups were shown to have differential associations with disease and reproductive success (Khakoo and Carrington 2006). Group A haplotypes comprise seven genes and two pseudogenes. Six of the seven KIRs are inhibitory in nature, because they have immunoreceptor tyrosine-based motifs (ITIMs) in their cytoplasmic tails. The seventh gene, KIR2DS4, is potentially activating but is disabled by a 22-bp frameshift deletion on ∼75% of A haplotypes and is only therefore functional in a minority of individuals (Hsu et al. 2002). Activating KIR genes do not contain ITIM motifs and instead are coupled to adaptor proteins, such as DAP12, which contain immunoreceptor tyrosine-based activating motifs (ITAMs).In contrast, Group B haplotypes are composed of variable numbers of KIR genes, and one or more of these are activating. This segregation into distinct and evolutionarily divergent haplotype groups (A and B) is unique to the human species (Parham et al. 2012). Furthermore, both haplotypic groups have been found in all human populations studied to date and are maintained by balancing selection (Gendzekhadze et al. 2009).The recent evolutionary plasticity of the KIRs and human-specific high diversity, in addition to their biomedical relevance, makes it important to study their organization. There is mounting evidence that receptor–ligand specificity between polymorphic KIR and polymorphic MHC class I influences susceptibility to infections, such as HIV and hepatitis C, in addition to cancer, autoimmune diseases, and disorders of pregnancy, as well as outcomes after hematological and solid organ transplantation (Parham 2005).The genomic organization of KIR haplotypes is structured relative to the fixed position of the so-called framework genes, 3DL3, 2DL4, and 3DL2 (Robinson et al. 2010). This gene order has been determined from the mapping and sequencing of several prototypic KIR haplotypes (Pyo et al. 2010). 3DL3 and 3DL2 mark the centromeric and telomeric boundaries of the cluster, respectively. 3DP1 and 2DL4 are placed centrally. Between 3DP1 and 2DL4 is a recombination hotspot. Annotating the haplotype motif structures centromeric (Cen) and telomeric (Tel) of this hotspot based on gene content (Pyo et al. 2010) has simplified and strengthened analysis in disease association studies (Hiby et al. 2010).It has been proposed that the arrangement of KIR genes in close head-to-tail orientation and their high sequence similarity facilitates gene gain and loss or copy number variation (CNV) by unidirectional alignment and sequential non-allelic homologous recombination (NAHR) (Martin et al. 2003). Consistent with this, unusual KIR haplotypes that possess aberrant gene content and fusion genes have been identified (Norman et al. 2002, 2007, 2009; Martin et al. 2008; Traherne et al. 2010).Given this background, we set out to explore variation in KIR haplotypes that may not be detected by conventional typing methods. To do this, we measured copy number as well as KIR presence or absence, using DNA from family-based cohorts in order to ensure the provenance of each haplotype.     

PARK2 gene mutations in early onset Parkinson's disease patients of South India

With the etiology being unclear till date, a combination of age, genetic and environmental factors are known to play a significant role in the pathogenesis of Parkinson's disease. Mutations in PARK2 gene have been implicated to cause autosomal recessive early onset PD. We analyzed the 12 coding exons of PARK2 gene in 16 early onset PD patients of South Indian ethnicity. PARK2 mutations were present in 68% of the early onset cases. We report the presence of four PARK2 sequence variants c.1239G>C, c.171+25T>C, c.202A>G, c.601G>A, and a novel insertion mutation, c.798_799insA in the exon 7 of PARK2 gene. These results suggest that mutations in PARK2 gene may be a common cause of PD among South Indian early onset patients.     

Coordinate linkage of HIV evolution reveals regions of immunological vulnerability

Cellular immune control of HIV is mediated, in part, by induction of single amino acid mutations that reduce viral fitness, but compensatory mutations limit this effect. Here, we sought to determine if higher order constraints on viral evolution exist, because some coordinately linked combinations of mutations may hurt viability. Immune targeting of multiple sites in such a multidimensionally conserved region might render the virus particularly vulnerable, because viable escape pathways would be greatly restricted. We analyzed available HIV sequences using a method from physics to reveal distinct groups of amino acids whose mutations are collectively coordinated ("HIV sectors"). From the standpoint of mutations at individual sites, one such group in Gag is as conserved as other collectively coevolving groups of sites in Gag. However, it exhibits higher order conservation indicating constraints on the viability of viral strains with multiple mutations. Mapping amino acids from this group onto protein structures shows that combined mutations likely destabilize multiprotein structural interactions critical for viral function. Persons who durably control HIV without medications preferentially target the sector in Gag predicted to be most vulnerable. By sequencing circulating viruses from these individuals, we find that individual mutations occur with similar frequency in this sector as in other targeted Gag sectors. However, multiple mutations within this sector are very rare, indicating previously unrecognized multidimensional constraints on HIV evolution. Targeting such regions with higher order evolutionary constraints provides a novel approach to immunogen design for a vaccine against HIV and other rapidly mutating viruses.     

A study on the protective effect of Cynodon dactylon leaves extract in diabetic rats

Objective To investigate the antidiabetic, antioxidant and hypolipidemic efficacy of Cynodon dactylon in diabetic rats. Methods The experimental rats were randomly divided into three groups: Group I: control; Group II: Alloxan diabetic, untreated; and Group III: Alloxan diabetic treated with ethanolic extract of C. dactylon leaves (450 mg/kg bw). Experimental diabetes was induced by alloxan in a single dose of 150 mg/kg bw. Results A Significant diminution of fasting blood sugar level was observed and also ...     

Design and data analysis 1 study design

This article is intended to give the reader guidance in evaluating different study designs used in medical research for better scientific quality, reliability and validity of their research. This article explains three main types of study designs with understanding examples. Care and caution with skills and experience needed to design suitable studies and appropriate design coupled with reliable sampling techniques and appropriate statistical analysis, supported by clear objectives with decent communication of the findings, are essential for good research.