A head impact model of early axonal injury in the sheep

Axonal injury (AI), one of the principal determinants of clinical outcome after head injury, may evolve over several hours after injury, raising the future possibility of therapeutic intervention during this period. A new head impact model of AI in sheep was developed to examine pathological and physiological changes in the brain resulting from a graded traumatic insult. In this preliminary study 10 anesthetized and ventilated Merino ewes were used. Head injury was produced by impact from a humane stunner to the temporal region of an unrestrained head. Eight sheep were studied for 1, 2, 4, or 6 h after impact. Two sham animals (no impact, 6 h survival) were also examined. Arterial blood pressure, intracranial pressure, and cerebral blood flow were monitored continuously. A physiological index of injury severity was calculated by weighting the percentage shift from preinjury values for each monitored parameter over the first hour after injury. Immunostaining with amyloid precursor protein (APP) was used as a marker of axonal damage and the distribution of APP positive axons was recorded according to a sector scoring method (APPS). Widespread AI was identified in 7 of the 8 impacted animals, around cerebral contusions and in hemispheric white matter, central gray matter, brain stem, and cerebellum, and was detected as early as 1 h after injury. The degree of axonal injury (APPS) correlated well with an index of physiological response to injury (r = 0.83, p = 0.005).

Research needs for the risk assessment of health and environmental effects of endocrine disruptors: a report of the U.S. EPA-sponsored workshop

The hypothesis has been put forward that humans and wildlife species adverse suffered adverse health effects after exposure to endocrine-disrupting chemicals. Reported adverse effects include declines in populations, increases in cancers, and reduced reproductive function. The U.S. Environmental Protection Agency sponsored a workshop in April 1995 to bring together interested parties in an effort to identify research gaps related to this hypothesis and to establish priorities for future research activities. Approximately 90 invited participants were organized into work groups developed around the principal reported health effects-carcinogenesis, reproductive toxicity, neurotoxicity, and immunotoxicity-as well as along the risk assessment paradigm-hazard identification, dose-response assessment, exposure assessment, and risk characterization. Attention focused on both ecological and human health effects. In general, group felt that the hypothesis warranted a concerted research effort to evaluate its validity and that research should focus primarily on effects on development of reproductive capability, on improved exposure assessment, and on the effects of mixtures. This report summarizes the discussions of the work groups and details the recommendations for additional research.

Stem cell factor regulates the melanocyte cytoskeleton

Stem cell factor is a growth factor for normal human melanocytes, that acts through the tyrosine kinase receptor c-kit. We have previously demonstrated that stem cell factor increases melanocyte adhesion and migration on fibronectin, and regulates integrin protein expression. In this report, we have characterized the effect of stem cell factor on the organization of the actin cytoskeleton in human melanocytes attached to fibronectin, and have examined the effect of stem cell factor on the phosphorylation of the focal contact protein paxillin and on the expression of the focal contact proteins talin, paxillin, vinculin, and alpha-actinin. Paxillin is a vinculin-binding protein that is a substrate of focal adhesion kinase, a nonreceptor tyrosine kinase, and in its phosphorylated form is believed to stabilize focal contacts. We show that stem cell factor induces a rapid increase in actin stress fiber formation in melanocytes, which can be abrogated by genistein, a tyrosine kinase inhibitor, and that stem cell factor induces phosphorylation of paxillin on tyrosine residues. In contrast, stem cell factor did not regulate expression of any of the four focal contact proteins tested. These findings have implications for the models describing the mechanisms of action of stem cell factor on melanocyte adhesion and migration, and suggest that reorganization of the cytoskeleton is a primary effect of stem cell factor on human melanocytes.

Bone formation and bone resorption in failed total joint arthroplasties: histomorphometric analysis with histochemical and immunohistochemical technique

To elucidate the reactions of bone around aseptically loosened total joint arthroplasties, 24 interface tissues with adjacent bone were obtained in 17 revision operations (11 hips and six knees). The morphology of the bone surface next to the interface membrane was investigated with histochemical and immunohistochemical techniques and then histomorphometrically analysed. One-third of the total bone surface. 32.69 +/- 5.16% (mean +/- SE) (n = 24), showed positive alkaline phosphatase activity. The bone surface in contact with the cells positive for CD11b (a macrophage marker) amounted to 19.33 +/- 5.16% (n = 24). The proportion of the osteoclastic bone resorption estimated by vitronectin receptor expression was 7.67 +/- 1.82% (n = 21). Tissues retrieved from the sites where radiographic evidence of osteolysis was present (n = 12) had a significantly larger extent of the bone surface in contact with CD11b-positive cells than did the tissues from areas without osteolysis (n = 12, p = 0.0067, Mann-Whitney U test), whereas no significant difference was observed in the extent of osteoclastic bone resorption. These data demonstrate that active bone formation, regarded as a repair process, is the most common feature even in revised cases. They also highlight the role played by macrophages, not as cells producing inflammatory mediators that could activate osteoclasts, but as cells primarily responsible for the bone loss in osteolytic lesions.

Dimerization of tear lysozyme on hydrophilic contact lens polymers

PURPOSE

Following the solubilization of protein from patient worn soft contact lenses and subsequent analysis via SDS-PAGE, an unidentified 30 kDa protein deposit was commonly observed. The mysterious deposit was found to accumulate on a variety of soft contact lens material.

METHODS

Acuvue, Cibasoft, Excelens and Newvue soft contact lenses were worn by three asymptomatic patients using both daily-wear and extended wear regimens. To characterize the unknown deposit, human tear samples and lens eluted protein were subjected to SDS-PAGE, immunoblotting, enzymatic assays and protein sequencing.

RESULTS

Results show that the 30 kDa protein deposit is the homologous dimer of tear lysozyme. Polymerized lysozyme was found on each of the three lens materials within one h of wear. However, the dimer was not present in the normal tear film.

CONCLUSIONS

Therefore, this dimerization phenomenon is the result of an aggregation and interaction of lysozyme with various soft contact lens polymers.

A model for keratinocyte gene therapy: preclinical and therapeutic considerations

Gene transfer to the skin is essential for correcting genetic disorders and studying skin biology. Previous attempts at in vivo gene transfer have employed replication-deficient adenovirus injected subcutaneously and plasmid DNA propelled by a gene gun. In this report, we used mouse skin as a model and evaluated the efficiency of these two methods. Using the luciferase reporter gene, we found that adenovirus injected subcutaneously transduced primarily cells in the dermis. However, particle bombardment of skin by gene gun delivered the reporter gene mainly into the epidermis. When mouse skin was bombarded with a DNA construct expressing human TGF-alpha, the epidermis of the treated mice showed localized epidermal acanthosis and hypergranulosis, which resembled the histological phenotype of previously described transgenic mice overexpressing TGF-alpha in the epidermis. These results suggest that the gene gun may be an effective tool for epidermal gene transfer and could be potentially useful in determining in vivo effects of growth factors and cytokines on the epidermis.

Hydroxyapatite coating of an acetabular prosthesis. Effect on stability

We report the radiological and clinical outcome of a press-fit (SLF) acetabular component at two to three years in two groups of patients having primary total hip replacement. In 69 the implant was coated with hydroxyapatite (HA) and in 40 it was uncoated. The stability of the cup was assessed by measurement of proximal migration and change in the angle of inclination. The clinical results in the two groups did not differ significantly, and the mean proximal linear wear was similar in both. Fewer radiolucent lines (RLLs) were seen on the radiographs of cups coated with HA. The mean proximal migration was studied by calculating regression lines for each patient using migration measurements: for the SLF+HA group the mean slope was 0.06 mm/year and for the SLF-HA group 0.20 mm/year (p = 0.22). The change in the angle of inclination during follow-up was also consistently smaller in HA-coated cups. Using regression methods the SLF+HA group had a mean slope of 0.08 degrees/year and the SLF-HA group 0.44 degrees/year and the SLF-HA group 0.44 degrees/year (p = 0.023). Partial HA coating appeared to have no effect on the clinical outcome or on the rate of wear of polyethylene, but there was a trend towards a reduced rate of proximal migration, and a significant reduction in rotational migration and the number of radiolucent lines. This suggests that HA coating enhances the stability of this acetabular component.

Activation of hamster suprachiasmatic neurons in vitro via metabotropic glutamate receptors

The neurophysiological effects of ionophoretic application of the metabotropic glutamate receptor agonist (1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid on the firing rate of single suprachiasmatic nucleus cells was studied in a hypothalamic slice preparation. In addition, the effects of the phenylglycine derivative (RS)-alpha-methyl-4-carboxyphenylglycine, a selective metabotropic glutamate receptor antagonist, on responses evoked by (1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid and N-methyl-D-aspartate were assessed. (1S,3R)-1-Amino-1,3-cyclopentanedicarboxylic acid elicited current-dependent increases in neuronal activity in 65% of all suprachiasmatic nucleus cells studied, while N-methyl-D-aspartate activated 93% of the same cells. Cells in the ventrolateral suprachiasmatic nucleus were more sensitive to (1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid application (82% of cells activated) than those in the dorsomedial suprachiasmatic nucleus (28% of cells activated). In addition, responses evoked by (1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid in the ventrolateral suprachiasmatic nucleus had a rapid onset and a prolonged recovery from agonist application, whereas responses elicited in the dorsomedial suprachiasmatic nucleus were slower in onset and recovered more quickly from agonist application. Co-application of (RS)-alpha-methyl-4-carboxyphenylglycine selectivity attenuated (1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid-evoked responses but had no effect on N-methyl-D-aspartate-evoked activity in the same cells. These results indicate that (1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid application activates single cells in the hamster suprachiasmatic nucleus and these responses are selectively attenuated by (RS)-alpha-methyl-4-carboxyphenylglycine. Cells in the ventrolateral suprachiasmatic nucleus are more sensitive to (1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid application than those in the dorsomedial suprachiasmatic nucleus. These results are the first demonstration that metabotropic glutamate receptors can modulate spontaneous neuronal activity within the suprachiasmatic nucleus, the predominant mammalian circadian pacemaker.

HYDROXYAPATITE COATING OF AN ACETABULAR PROSTHESIS

We report the radiological and clinical outcome of a press-fit (SLF) acetabular component at two to three years in two groups of patients having primary total hip replacement. In 69 the implant was coated with hydroxyapatite (HA) and in 40 it was uncoated. The stability of the cup was assessed by measurement of proximal migration and change in the angle of inclination.

The clinical results in the two groups did not differ significantly, and the mean proximal linear wear was similar in both. Fewer radiolucent lines (RLLs) were seen on the radiographs of cups coated with HA.

The mean proximal migration was studied by calculating regression lines for each patient using migration measurements: for the SLF+HA group the mean slope was 0.06 mm/year and for the SLF–HA group 0.20 mm/year (p = 0.22). The change in the angle of inclination during follow-up was also consistently smaller in HA–coated cups. Using regression methods the SLF+HA group had a mean slope of 0.08°/year and the SLF-HA group 0.44°/year (p = 0.023).

Partial HA coating appeared to have no effect on the clinical outcome or on the rate of wear of polyethylene, but there was a trend towards a reduced rate of proximal migration, and a significant reduction in rotational migration and the number of radiolucent lines. This suggests that HA coating enhances the stability of this acetabular component.

Reactive angioendotheliomatosis. Case report and review of the literature

Angioendotheliomatosis is an uncommon disease characterized histologically by proliferation of cells within vascular lumina with secondary intravascular thrombi resulting in obliteration of the involved vessels. While angioendotheliomatosis was initially thought to be a single disease entity, recent studies show that the disease may be divided into benign (reactive) and malignant variants, with the malignant variant representing intravascular malignant lymphoma. The reactive variant is rare, with only 16 cases reported in the literature, and is characterized histologically by proliferating endothelial cells within vessel lumina. In this report we present a case of reactive angioendotheliomatosis and review the literature on this rare entity.

Metabolism of the bisphosphonate ester U-91502 in rats

The major metabolites of the bisphosphonate ester U-91502 were isolated from the bile and urine of male Sprague-Dawley rats and identified by NMR and MS. Bile duct-exteriorized and taurocholate-supplemented rats received single oral doses of 10-140 mg/kg of labeled U-91502. Analysis of radioactivity in bile, urine, and feces showed that U-91502-related radioactivity was rapidly excreted, predominantly in bile, achieving peak concentrations in bile of 1250 +/- 622 micrograms-eq/g during first 3 hr after a 10 mg/kg dose. The three major drug-related materials in bile and urine were separated by HPLC and designated in order of reversed-phase elution as metabolites A, B, and C. The least polar metabolite (C) was shown by HPLC/particle beam/MS and HPLC/electrospray/MS to be the triester, U-94532. Metabolite C cochromatographed with a synthesized standard of U-94532A. Metabolite B was the glucuronide conjugate of the 5-hydroxy pyrimidinone, U-97294. Metabolite A was a product of glutathione addition to a putative pyrimidinone 4,5-epoxide. Mechanisms for the formation of metabolites A, B, and C based on metabolite structure and stability were proposed.

A biomarker that identifies senescent human cells in culture and in aging skin in vivo

Normal somatic cells invariably enter a state of irreversibly arrested growth and altered function after a finite number of divisions. This process, termed replicative senescence, is thought to be a tumor-suppressive mechanism and an underlying cause of aging. There is ample evidence that escape from senescence, or immortality, is important for malignant transformation. By contrast, the role of replicative senescence in organismic aging is controversial. Studies on cells cultured from donors of different ages, genetic backgrounds, or species suggest that senescence occurs in vivo and that organismic lifespan and cell replicative lifespan are under common genetic control. However, senescent cells cannot be distinguished from quiescent or terminally differentiated cells in tissues. Thus, evidence that senescent cells exist and accumulate with age in vivo is lacking. We show that several human cells express a beta-galactosidase, histochemically detectable at pH 6, upon senescence in culture. This marker was expressed by senescent, but not presenescent, fibroblasts and keratinocytes but was absent from quiescent fibroblasts and terminally differentiated keratinocytes. It was also absent from immortal cells but was induced by genetic manipulations that reversed immortality. In skin samples from human donors of different age, there was an age-dependent increase in this marker in dermal fibroblasts and epidermal keratinocytes. This marker provides in situ evidence that senescent cells may exist and accumulate with age in vivo.

Topography of axonal injury as defined by amyloid precursor protein and the sector scoring method in mild and severe closed head injury

Axonal injury (AI), as defined by amyloid precursor protein (APP) positive axonal swellings, was recorded on a series of line diagrams of standard brain sections divided into 116 sectors to provide an Axonal Injury Sector Score (AISS) ranging from 0 to 116. This sector scoring method of recording axonal damage and providing a topographic overview of AI was applied to a series of 6 mild head injury cases [Glasgow Coma Scale (GCS) 13-15] and six severe head injury cases (GCS 3-8). The AISS ranged from 4 to 107 overall and varied from 4 to 88 in the mildly injured group and 76 to 107 in the severe head injury group, supporting the concept that there is a spectrum of AI in traumatic head injury and that the AISS is a measure of the extent of AI. APP immunostaining demonstrated positive axonal swellings 1.75 h after head injury and analysis of the pattern of AI in the mild and severe head injury groups showed that axons were more vulnerable than blood vessels and that the axons in the corpus callosum and fornices were the most vulnerable of all.

pp125FAK in human melanocytes and melanoma: expression and phosphorylation

Focal adhesion kinase (pp125FAK) is a nonreceptor tyrosine kinase which colocalizes with integrins to focal contacts, sites where multiple proteins interact to regulate the assembly of the actin cytoskeleton. Autophosphorylation and activation of pp125FAK occur after integrin clustering or cell adhesion to ligands through cognate integrin receptors and are postulated to mediate integrin signaling events. In this report we examined pp125FAK expression and phosphorylation in normal human melanocytes, an adherent human metastatic melanoma cell line (SKMEL28), and a nonadherent human metastatic melanoma cell line (SKMEL1). We show that SKMEL28 cells express constitutively phosphorylated pp125FAK and that pp125FAK phosphorylation in melanocytes is induced by phorbol esters and growth factors present in melanocyte growth medium. Focal adhesion kinase phosphorylation could be enhanced by b1 integrin-activating antibodies in human melanocytes, but not in SKMEL28 cells. In contrast with SKMEL28 cells, constitutive phosphorylation of pp125FAK was not observed in SKMEL1 cells, and incubation with activating b1 integrin antibodies had no effect on pp125FAK phosphorylation. Absence of pp125FAK phosphorylation in SKMEL1 cells was not due to lack of expression of pp125FAK, as shown by immunoprecipitation of the pp125FAK protein from cell lysates. However, b1 integrin expression was significantly less in SKMEL1 cells than in human melanocytes and SKMEL28 cells. This study further supports the importance of integrins in pp125FAK-mediated signaling and indicates that transformation-related changes in pp125FAK phosphorylation exist in human melanocytes and melanoma cells.