Cardiovascular benefits of phlebotomy: relationship to changes in hemorheological variables.

Renewed interest in the age-old concept of "bloodletting", a therapeutic approach practiced until as recently as the 19th century, has been stimulated by the knowledge that blood loss, such as following regular donation, is associated with significant reductions in key hemorheological variables, including whole blood viscosity (WBV), plasma viscosity, hematocrit and fibrinogen. An elevated WBV appears to be both a strong predictor of cardiovascular disease and an important factor in the development of atherosclerosis. Elevated WBV through wall shear stress is the most direct physiological parameter that influences the rupture and erosion of vulnerable plaques. In addition to WBV reduction, phlebotomy may reduce an individual's cardiovascular risk through reductions in excessive iron, oxidative stress and inflammation. Reflecting these findings, blood donation in males has shown significant drops in the incidence of cardiovascular events, as well as in procedures such as percutaneous transluminal coronary angioplasty and coronary artery bypass grafting. Collectively, the available data on the benefits of therapeutic phlebotomy point to the importance of monitoring WBV as part of a cardiovascular risk factor, along with other risk-modifying measures, whenever an increased cardiovascular risk is detected. The development of a scanning capillary tube viscometer allows the measurement of WBV in a clinical setting, which can prove to be valuable in providing an early warning sign of an increased risk of cardiovascular disease.

Bacterial infection promotes DNA hypermethylation.

Maternal oral infection, caused by bacteria such as C. rectus or P. gingivalis, has been implicated as a potential source of placental and fetal infection and inflammatory challenge, which increases the relative risk for pre-term delivery and growth restriction. Intra-uterine growth restriction has also been reported in various animal models infected with oral organisms. Analyzing placental tissues of infected growth-restricted mice, we found down-regulation of the imprinted Igf2 gene. Epigenetic modification of imprinted genes via changes in DNA methylation plays a critical role in fetal growth and development programming. Here, we assessed whether C. rectus infection mediates changes in the murine placenta Igf2 methylation patterns. We found that infection induced hypermethylation in the promoter region-P0 of the Igf2 gene. This novel finding, correlating infection with epigenetic alterations, provides a mechanism linking environmental signals to placental phenotype, with consequences for development.

The genome of Salinibacter ruber: convergence and gene exchange among hyperhalophilic bacteria and archaea.

Saturated thalassic brines are among the most physically demanding habitats on Earth: few microbes survive in them. Salinibacter ruber is among these organisms and has been found repeatedly in significant numbers in climax saltern crystallizer communities. The phenotype of this bacterium is remarkably similar to that of the hyperhalophilic Archaea (Haloarchaea). The genome sequence suggests that this resemblance has arisen through convergence at the physiological level (different genes producing similar overall phenotype) and the molecular level (independent mutations yielding similar sequences or structures). Several genes and gene clusters also derive by lateral transfer from (or may have been laterally transferred to) haloarchaea. S. ruber encodes four rhodopsins. One resembles bacterial proteorhodopsins and three are of the haloarchaeal type, previously uncharacterized in a bacterial genome. The impact of these modular adaptive elements on the cell biology and ecology of S. ruber is substantial, affecting salt adaptation, bioenergetics, and photobiology.

Genome of Geobacter sulfurreducens: metal reduction in subsurface environments.

The complete genome sequence of Geobacter sulfurreducens, a delta-proteobacterium, reveals unsuspected capabilities, including evidence of aerobic metabolism, one-carbon and complex carbon metabolism, motility, and chemotactic behavior. These characteristics, coupled with the possession of many two-component sensors and many c-type cytochromes, reveal an ability to create alternative, redundant, electron transport networks and offer insights into the process of metal ion reduction in subsurface environments. As well as playing roles in the global cycling of metals and carbon, this organism clearly has the potential for use in bioremediation of radioactive metals and in the generation of electricity.

Whole-genome comparison of Mycobacterium tuberculosis clinical and laboratory strains.

Virulence and immunity are poorly understood in Mycobacterium tuberculosis. We sequenced the complete genome of the M. tuberculosis clinical strain CDC1551 and performed a whole-genome comparison with the laboratory strain H37Rv in order to identify polymorphic sequences with potential relevance to disease pathogenesis, immunity, and evolution. We found large-sequence and single-nucleotide polymorphisms in numerous genes. Polymorphic loci included a phospholipase C, a membrane lipoprotein, members of an adenylate cyclase gene family, and members of the PE/PPE gene family, some of which have been implicated in virulence or the host immune response. Several gene families, including the PE/PPE gene family, also had significantly higher synonymous and nonsynonymous substitution frequencies compared to the genome as a whole. We tested a large sample of M. tuberculosis clinical isolates for a subset of the large-sequence and single-nucleotide polymorphisms and found widespread genetic variability at many of these loci. We performed phylogenetic and epidemiological analysis to investigate the evolutionary relationships among isolates and the origins of specific polymorphic loci. A number of these polymorphisms appear to have occurred multiple times as independent events, suggesting that these changes may be under selective pressure. Together, these results demonstrate that polymorphisms among M. tuberculosis strains are more extensive than initially anticipated, and genetic variation may have an important role in disease pathogenesis and immunity.

Evaluation of a skeletal muscle energy convertor in a chronic animal model.

A device is under development for powering cardiac assist devices with skeletal muscle contracting in a linear configuration by converting muscle work to hydraulic energy. Prototype devices are being implanted in goats to study device performance and associated muscle mechanics. Percutaneous hydraulic lines provide the means to control muscle load and evaluate muscle performance during an electrical conditioning protocol. Chronic implant durations ranged from 36 to 87 days in 7 goats. The latissimus dorsi muscle (LDM) insertion was reconnected to the device with a tendon loop. A sternal plate attached with bone screws, and a rib clamp secured the device. A new modular sternal mount design was implemented to eliminate plate loosening that complicated early implants. Extensive bone remodeling around the rib clamp was observed. The tendon attachment demonstrated sufficient initial strength; however, in five implants, efforts to repair the tendon were required. Device encapsulation was observed, but the device continued to cycle freely and no tethering adhesions to the device were found. Interactions between the capsule wall and LDM seemed to limit LDM movement in some cases. Development of a long-term animal model for energy convertor evaluations is an important step toward skeletal muscle powered cardiac assist.

Development of an intracorporeal Thoratec ventricular assist device for univentricular or biventricular support.

There is a need for a small, simple, and versatile intracorporeal ventricular assist device (IVAD) as an alternative to the large implantable electromechanical LVAD systems in current use. Because the basic design of the Thoratec paracorporeal VAD has been demonstrated in over 1,000 patients, weighing from 17 to 144 kg, and for durations up to 515 days including patient discharge (by using the portable driver), we are developing a new intracorporeal version of our VAD. This IVAD has a smooth contoured, polished titanium housing, and maintains the same blood flow path and Thoralon polyurethane blood pumping sac as the paracorporeal VAD. The IVAD is controlled with the Thoratec TLC-II Portable VAD Driver, which is a small briefcase sized, battery powered, pneumatic control unit. Intracorporeal LVADs and/or RVADs are implanted in a preperitoneal position, with a single small (9 mm OD) percutaneous pneumatic driveline for each VAD. The major advantages of the new IVAD design are size and simplicity. The IVAD weight (339 g) and implanted volume (252 ml) are substantially smaller than current implantable electromechanical LVAD systems. Only the small blood pump is implanted, leaving the more complex control unit external, where it can be serviced and replaced. The versatile design is intended for left and/or right heart support in large or small patients. The IVAD in combination with the TLC-II portable driver will be a viable and attractive alternative to large, implanted electromechanical systems.

Genome sequences of Chlamydia trachomatis MoPn and Chlamydia pneumoniae AR39.

The genome sequences of Chlamydia trachomatis mouse pneumonitis (MoPn) strain Nigg (1 069 412 nt) and Chlamydia pneumoniae strain AR39 (1 229 853 nt) were determined using a random shotgun strategy. The MoPn genome exhibited a general conservation of gene order and content with the previously sequenced C.trachomatis serovar D. Differences between C.trachomatis strains were focused on an approximately 50 kb 'plasticity zone' near the termination origins. In this region MoPn contained three copies of a novel gene encoding a >3000 amino acid toxin homologous to a predicted toxin from Escherichia coli O157:H7 but had apparently lost the tryptophan biosyntheis genes found in serovar D in this region. The C. pneumoniae AR39 chromosome was >99.9% identical to the previously sequenced C.pneumoniae CWL029 genome, however, comparative analysis identified an invertible DNA segment upstream of the uridine kinase gene which was in different orientations in the two genomes. AR39 also contained a novel 4524 nt circular single-stranded (ss)DNA bacteriophage, the first time a virus has been reported infecting C. pneumoniae. Although the chlamydial genomes were highly conserved, there were intriguing differences in key nucleotide salvage pathways: C.pneumoniae has a uridine kinase gene for dUTP production, MoPn has a uracil phosphororibosyl transferase, while C.trachomatis serovar D contains neither gene. Chromosomal comparison revealed that there had been multiple large inversion events since the species divergence of C.trachomatis and C.pneumoniae, apparently oriented around the axis of the origin of replication and the termination region. The striking synteny of the Chlamydia genomes and prevalence of tandemly duplicated genes are evidence of minimal chromosome rearrangement and foreign gene uptake, presumably owing to the ecological isolation of the obligate intracellular parasites. In the absence of genetic analysis, comparative genomics will continue to provide insight into the virulence mechanisms of these important human pathogens.

Sequence and analysis of the 60 kb conjugative, bacteriocin-producing plasmid pMRC01 from Lactococcus lactis DPC3147.

The complete sequence of pMRC01, a large conjugative plasmid from Lactococcus lactis ssp. lactis DPC3147, has been determined. Using a shotgun sequencing approach, the 60,232 bp plasmid sequence was obtained by the assembly of 1056 underlying sequences (sevenfold average redundancy). Sixty-four open reading frames (ORFs) were identified. Analysis of the gene organization of pMRC01 suggests that the plasmid can be divided into three functional domains, with each approximately 20 kb region separated by insertion sequence (IS) elements. The three regions are (i) the conjugative transfer region, including a 16-gene Tra (transfer) operon; (ii) the bacteriocin production region, including an operon responsible for the synthesis of the novel bacteriocin lacticin 3147; and (iii) the phage resistance and plasmid replication region of the plasmid. The complete sequence of pMRC01 provides important information about these industrially relevant phenotypes and gives insight into the structure, function and evolution of large gram-positive conjugative plasmids in general. The completely sequenced pMRC01 plasmid should also provide a useful framework for the design of novel plasmids to be incorporated into starter strain improvement programmes for the dairy industry.

Complete genome sequence of Treponema pallidum, the syphilis spirochete.

The complete genome sequence of Treponema pallidum was determined and shown to be 1,138,006 base pairs containing 1041 predicted coding sequences (open reading frames). Systems for DNA replication, transcription, translation, and repair are intact, but catabolic and biosynthetic activities are minimized. The number of identifiable transporters is small, and no phosphoenolpyruvate:phosphotransferase carbohydrate transporters were found. Potential virulence factors include a family of 12 potential membrane proteins and several putative hemolysins. Comparison of the T. pallidum genome sequence with that of another pathogenic spirochete, Borrelia burgdorferi, the agent of Lyme disease, identified unique and common genes and substantiates the considerable diversity observed among pathogenic spirochetes.

Hydrothorax secondary to a perinephric pseudocyst in a cat.

Hydrothorax was identified in a 14-year-old Siamese cat with a pre-existent perinephric pseudocyst. The pleural fluid was classified as a low-protein transudate. Intrapseudocystic scintigraphy confirmed a direct communication between the pseudocyst and the pleural space. The hydrothorax resolved following pseudocystectomy and unilateral nephrectomy, demonstrating that the pseudocyst caused the hydrothorax.

Genomic sequence of a Lyme disease spirochaete, Borrelia burgdorferi.

The genome of the bacterium Borrelia burgdorferi B31, the aetiologic agent of Lyme disease, contains a linear chromosome of 910,725 base pairs and at least 17 linear and circular plasmids with a combined size of more than 533,000 base pairs. The chromosome contains 853 genes encoding a basic set of proteins for DNA replication, transcription, translation, solute transport and energy metabolism, but, like Mycoplasma genitalium, it contains no genes for cellular biosynthetic reactions. Because B. burgdorferi and M. genitalium are distantly related eubacteria, we suggest that their limited metabolic capacities reflect convergent evolution by gene loss from more metabolically competent progenitors. Of 430 genes on 11 plasmids, most have no known biological function; 39% of plasmid genes are paralogues that form 47 gene families. The biological significance of the multiple plasmid-encoded genes is not clear, although they may be involved in antigenic variation or immune evasion.

The complete genome sequence of the hyperthermophilic, sulphate-reducing archaeon Archaeoglobus fulgidus.

Archaeoglobus fulgidus is the first sulphur-metabolizing organism to have its genome sequence determined. Its genome of 2,178,400 base pairs contains 2,436 open reading frames (ORFs). The information processing systems and the biosynthetic pathways for essential components (nucleotides, amino acids and cofactors) have extensive correlation with their counterparts in the archaeon Methanococcus jannaschii. The genomes of these two Archaea indicate dramatic differences in the way these organisms sense their environment, perform regulatory and transport functions, and gain energy. In contrast to M. jannaschii, A. fulgidus has fewer restriction-modification systems, and none of its genes appears to contain inteins. A quarter (651 ORFs) of the A. fulgidus genome encodes functionally uncharacterized yet conserved proteins, two-thirds of which are shared with M. jannaschii (428 ORFs). Another quarter of the genome encodes new proteins indicating substantial archaeal gene diversity.

The complete genome sequence of the gastric pathogen Helicobacter pylori.

Helicobacter pylori, strain 26695, has a circular genome of 1,667,867 base pairs and 1,590 predicted coding sequences. Sequence analysis indicates that H. pylori has well-developed systems for motility, for scavenging iron, and for DNA restriction and modification. Many putative adhesins, lipoproteins and other outer membrane proteins were identified, underscoring the potential complexity of host-pathogen interaction. Based on the large number of sequence-related genes encoding outer membrane proteins and the presence of homopolymeric tracts and dinucleotide repeats in coding sequences, H. pylori, like several other mucosal pathogens, probably uses recombination and slipped-strand mispairing within repeats as mechanisms for antigenic variation and adaptive evolution. Consistent with its restricted niche, H. pylori has a few regulatory networks, and a limited metabolic repertoire and biosynthetic capacity. Its survival in acid conditions depends, in part, on its ability to establish a positive inside-membrane potential in low pH.

The minimal gene complement of Mycoplasma genitalium.

The complete nucleotide sequence (580,070 base pairs) of the Mycoplasma genitalium genome, the smallest known genome of any free-living organism, has been determined by whole-genome random sequencing and assembly. A total of only 470 predicted coding regions were identified that include genes required for DNA replication, transcription and translation, DNA repair, cellular transport, and energy metabolism. Comparison of this genome to that of Haemophilus influenzae suggests that differences in genome content are reflected as profound differences in physiology and metabolic capacity between these two organisms.

Orthopedic nursing practice guidelines. The NAON Standards Task Force.

The NAON Standards Task Force has revised Orthopaedic Nursing: Process and Outcome Criteria for Selected Nursing Diagnoses published jointly by the American Nurses' Association (ANA) and NAON in 1986. The new document is entitled Orthopaedic Nursing Practice Guidelines. It contains guidelines for the care of orthopaedic patients with 11 selected nursing diagnoses and is an important decision-making tool for orthopaedic nurses. This article contains excerpts from the new guidelines with suggestions for its use.

Sickle cell chronic lung disease: prior morbidity and the risk of pulmonary failure.

Sickle cell chronic lung disease (SCLD) is a prime contributor to mortality in young adult patients with sickle cell disease, especially those with sickle cell anemia (SS). Both perfusion and diffusion defects have been demonstrated, with generalized pulmonary fibrosis and disabling restrictive lung failure. We report 28 cases (25 SS, 1 S beta(0) thalassemia, 1 S beta(+) thalassemia and 1 SO-Arab) which began during the second decade of life and which ended in death by the fourth decade, after an ordered progression to pulmonary failure and cor pulmonale. Myocardial hypoxia with multifocal fibrosis and segmental infarction occurred in more than one-third of the cases and sudden death was a frequent final event. We define 4 stages of SCLD, based on pulmonary function tests, chest roentgenograms, blood gases, and noninvasive cardiac studies; each stage is 2 or 3 years in length, until death ensues in Stage 4. Case-control analysis showed that the significant risk factors associated with SCLD are 1) the total number of acute chest syndrome events in an individual before the onset of SCLD, (p = 0.0001), 2) sickle cell crisis marked by chest pain (p = 0.03) and 3) aseptic necrosis (p = 0.005). Temporal clustering of acute chest syndrome episodes frequently heralds the onset of SCLD. The pulmonary arterial bed, which has low oxygen tension and low pressure in a slow-flow system, is ideally suited to facilitate the polymerization of sickle hemoglobin, causing endothelial damage and culminating in an obstructive arteriolar vasculopathy. Identification of the significant risk factors predictive of SCLD can lead to early diagnosis of the disease; this is the only hope for effective intervention therapy.