Metal wear particle characterization from metal on metal total hip replacements: transmission electron microscopy study of periprosthetic tissues and isolated particles

The less intense tissue reaction around metal on metal total hip replacements (THRs) compared to metal on polyethylene (PE) THRs may be explained by the differences in the characteristics of metal wear particles. In this study, transmission electron microscopy was used to study metal wear particles that were either in situ in cells or had been extracted from the cells by a new technique based on enzymatic tissue digestion. The tissues were obtained from 13 patients undergoing revision of metal on metal THRs with cobalt-chromium-molybdenum (CoCrMo) bearing couples. Most of the CoCrMo wear particles were smaller than 50 nm (range 6-834 nm) and round to oval in shape with irregular boundaries. This size range is considerably smaller than that reported for PE particles. While even a small volume of metal wear will produce high numbers of particles, the apparently less severe local tissue reaction to metal particles may be due to the possibility that corrosion, dissolution, and dissemination of metal particles may result in fewer local biological effects than the long-term retention of PE particles in the periprosthetic tissues.

The central role of mitochondria in axonal degeneration in multiple sclerosis

Neurodegeneration in multiple sclerosis (MS) is related to inflammation and demyelination. In acute MS lesions and experimental autoimmune encephalomyelitis focal immune attacks damage axons by injuring axonal mitochondria. In progressive MS, however, axonal damage occurs in chronically demyelinated regions, myelinated regions and also at the active edge of slowly expanding chronic lesions. How axonal energy failure occurs in progressive MS is incompletely understood. Recent studies show that oligodendrocytes supply lactate to myelinated axons as a metabolic substrate for mitochondria to generate ATP, a process which will be altered upon demyelination. In addition, a number of studies have identified mitochondrial abnormalities within neuronal cell bodies in progressive MS, leading to a deficiency of mitochondrial respiratory chain complexes or enzymes. Here, we summarise the mitochondrial abnormalities evident within neurons and discuss how these grey matter mitochondrial abnormalities may increase the vulnerability of axons to degeneration in progressive MS. Although neuronal mitochondrial abnormalities will culminate in axonal degeneration, understanding the different contributions of mitochondria to the degeneration of myelinated and demyelinated axons is an important step towards identifying potential therapeutic targets for progressive MS.

Human chromosome-specific aneuploidy is influenced by DNA-dependent centromeric features

Intrinsic genomic features of individual chromosomes can contribute to chromosome-specific aneuploidy. Centromeres are key elements for the maintenance of chromosome segregation fidelity via a specialized chromatin marked by CENP-A wrapped by repetitive DNA. These long stretches of repetitive DNA vary in length among human chromosomes. Using CENP-A genetic inactivation in human cells, we directly interrogate if differences in the centromere length reflect the heterogeneity of centromeric DNA-dependent features and whether this, in turn, affects the genesis of chromosome-specific aneuploidy. Using three distinct approaches, we show that mis-segregation rates vary among different chromosomes under conditions that compromise centromere function. Whole-genome sequencing and centromere mapping combined with cytogenetic analysis, small molecule inhibitors, and genetic manipulation revealed that inter-chromosomal heterogeneity of centromeric features, but not centromere length, influences chromosome segregation fidelity. We conclude that faithful chromosome segregation for most of human chromosomes is biased in favor of centromeres with high abundance of DNA-dependent centromeric components. These inter-chromosomal differences in centromere features can translate into non-random aneuploidy, a hallmark of cancer and genetic diseases.

Knockout of the PKN Family of Rho Effector Kinases Reveals a Non-redundant Role for PKN2 in Developmental Mesoderm Expansion

In animals, the protein kinase C (PKC) family has expanded into diversely regulated subgroups, including the Rho family-responsive PKN kinases. Here, we describe knockouts of all three mouse PKN isoforms and reveal that PKN2 loss results in lethality at embryonic day 10 (E10), with associated cardiovascular and morphogenetic defects. The cardiovascular phenotype was not recapitulated by conditional deletion of PKN2 in endothelial cells or the developing heart. In contrast, inducible systemic deletion of PKN2 after E7 provoked collapse of the embryonic mesoderm. Furthermore, mouse embryonic fibroblasts, which arise from the embryonic mesoderm, depend on PKN2 for proliferation and motility. These cellular defects are reflected in vivo as dependence on PKN2 for mesoderm proliferation and neural crest migration. We conclude that failure of the mesoderm to expand in the absence of PKN2 compromises cardiovascular integrity and development, resulting in lethality.

Effect of diabetes and peritonitis on the peritoneal equilibration test

Peritoneal equilibration tests (PET) were performed on 47 patients (15 diabetics) who had been on CAPD for 1 to 112 months. Among new patients on CAPD (1 to 3 months) with no history of peritonitis, diabetics had higher D/PCr than non-diabetics (P < 0.02). However, after > or = 7 months of CAPD, in patients with < or = 2 episodes of peritonitis, glucose and creatinine transport rates were lower (P < 0.05) in diabetic than non-diabetic patients. Among patients on CAPD for > or = 7 months, creatinine (P < 0.05) and glucose transport (P < 0.01) were higher in patients with a history of > or = 3 episodes of peritonitis than in those with < or = 2 episodes. Drain volumes did not differ between any of the subgroups (all P > 0.05). The observations in patients newly established on CAPD were substantiated in a larger study of 55 non-diabetic and 35 non-insulin dependent diabetic patients. D/D0 glucose correlated with plasma glucose (r = 0.40, P < 0.02) in the diabetic group. Net ultrafiltration was reduced in hyperglycemic (P = 0.022) but not normoglycemic diabetics (non-diabetics 231 +/- 167 ml, hyperglycemic diabetics 127 +/- 177 ml, normoglycemic diabetics 238 +/- 159 ml). Creatinine clearance was higher in normoglycemic (P = 0.02) but not hyperglycemic diabetics (non-diabetics 6.8 +/- 0.9 ml/min, hyperglycemic diabetics 6.9 +/- 0.8 ml/min, normoglycemic diabetics 7.4 +/- 0.7 ml/min). These data show that diabetes and peritonitis incidence should be borne in mind when interpreting results of the PET.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of radioimmunoassay with homogeneous enzyme immunoassay for the determination of theophylline concentration in serum

The homogeneous enzyme immunoassay (EMIT) and radioimmunoassay (RIA) procedures for the quantitation of theophylline concentrations in serum were evaluated and compared. Both methods exhibited curves linear over the therapeutic range (range of concentration, 2.0-33.0 microgram/ml). Precision was acceptable for both methods with the coefficient of variation being less than 8.3%. The RIA procedure was found to be slightly more precise. The correlations between the EMIT and RIA procedures was found to be sufficient to allow the procedures to be used interchangeably. This would facilitate the test availability on a 24 hr, 7 day basis.

Engineering potent long-acting variants of the Wnt inhibitor DKK2

Wnt signaling pathways are required for a wide variety of biological processes ranging from embryonic development to tissue repair and regeneration. Dickkopf-2 (DKK2) is classically defined as a canonical Wnt inhibitor, though it may play a role in activating non-canonical Wnt pathways in the context of endothelial network formation after acute injury. Here we report the discovery of a fusion partner for a DKK2 polypeptide that significantly improves the expression, biochemical properties and pharmacokinetics (PK) of the DKK2 polypeptide. Specifically, human serum albumin (HSA) was identified as a highly effective fusion partner. Substitution of selected amino acid residues in DKK2 designed to decrease heparan sulfate binding by HSA-DKK2 variants, further improved the PK properties of the molecule in rodents. The HSA-DKK2 variants were monomeric, as thermally stable as wild type, and active as measured by their ability to bind to and prevent phosphorylation of the Wnt coreceptor LRP6. Our engineering efforts resulted in potent long-lived variants of the canonical Wnt inhibitor DKK2, applicable for Wnt pathway manipulation either by systematic delivery or focused administration at sites of tissue injury.

Evaluation of a discrete-sample computer-directed clinical analyzer

The operational characteristics of the Gilford System 3500 were evaluated for six months as to accuracy, precision, carry-over, reliability, and ease of operation. Accuracy was evaluated by comparison to manual methods of established accuracy. The tests evaluated and their respective correlation coefficients are as follows: glucose (0.99), blood urea nitrogen (0.99), calcium (0.97), total bilirubin (0.99), aspartate aminotransferase (0.97), alkaline phosphatase (0.98), albumin (0.96), and total protein (0.96). Within-run precision (CV) for three commercial calibration sera of differing analyte concentrations (low, intermediate, and high) were respectively: 0.69, 1.02, 1.18; 5.4, 1.2, 1.09; 0.83, 0.77, 0.86; 5.9, 1.0, 0.86; 6.4, 5.2, 2.1; 3.7, 1.5, 1.3; 0.0, 1.4, 0.97; and 1.2, 1.3, 0.75. Day-to-day precision, similarly evaluated during 101-164 days, met accepted criteria for clinically acceptable precision. Carry-over for each of the eight tests was less than 1%. Instrument reliability has been excellent, and training time is short. In summary, we have found the Gilford System 3500 to be sufficiently precise and fast, easy to operate, highly accurate, and flexible.

Evaluation of a discrete-sample computer-directed clinical analyzer

The operational characteristics of the Gilford System 3500 were evaluated for six months as to accuracy, precision, carry-over, reliability, and ease of operation. Accuracy was evaluated by comparison to manual methods of established accuracy. The tests evaluated and their respective correlation coefficients are as follows: glucose (0.99), blood urea nitrogen (0.99), calcium (0.97), total bilirubin (0.99), aspartate aminotransferase (0.97), alkaline phosphatase (0.98), albumin (0.96), and total protein (0.96). Within-run precision (CV) for three commercial calibration sera of differing analyte concentrations (low, intermediate, and high) were respectively: 0.69, 1.02, 1.18; 5.4, 1.2, 1.09; 0.83, 0.77, 0.86; 5.9, 1.0, 0.86; 6.4, 5.2, 2.1; 3.7, 1.5, 1.3; 0.0, 1.4, 0.97; and 1.2, 1.3, 0.75. Day-to-day precision, similarly evaluated during 101-164 days, met accepted criteria for clinically acceptable precision. Carry-over for each of the eight tests was less than 1%. Instrument reliability has been excellent, and training time is short. In summary, we have found the Gilford System 3500 to be sufficiently precise and fast, easy to operate, highly accurate, and flexible.

Kinship care of the abused child: the New Zealand experience

The concept of continuity--keeping children within their own kinship, community, and cultural networks--has found international favor in contemporary child welfare practice. This principle is reflected in the 1989 New Zealand Children, Young Persons, and Their Families Act. The Act represents a significant shift--from the state to the family--in responsibility for children in need of care. The increasing use of the Family Group Conference process allows families to make decisions about the future of kin children and reflects the belief that, although most abuse is intrafamilial, the family will also be the most committed to keeping the child safe. Other countries have adapted this model to suit their own cultural child welfare needs. The international trend toward formal use of kinship care for children who have suffered abuse or neglect is likely to continue as foster care resources shrink. Drawing on qualitative research, this article describes the experiences of caregivers and their kin children who have been the subject of a care and protection order.

An effect of gravity on bud-burst in balsam fir

Bud-burst on first order lateral branches of Abies bafsamea L. (balsam fir) was delayed when the branches were rotated 180 degrees about their long axis. This was not a consequence of injury caused by the treatment because buds rotated 180 degrees on inverted plants flushed at the same time as the controls, whereas flushing of all other buds was delayed. Buds thus appear to be more vigorous when maintained in the same orientation to gravity in which they are formed and the site of gravitational stimulus perception appears to be the bud itself. Except on the leading shoot, leaves from inverted buds turned so that their adaxial surface faced upward, unless there was intense illumination from below. However, both anisophylly and positioning of leaves on lateral shoots were apparently predetermined because the shorter, more forward pointing leaves appeared below the longer distichous leaves on shoots from inverted buds. Shoots with normally oriented leaves appeared the next season.