Age differences in speed of processing are partially mediated by differences in axonal integrity.

Advanced age is associated with declines in brain structure and in cognitive performance, but it is unclear which aspects of brain aging mediate cognitive declines. We inquired if individual differences in white matter integrity contribute to age differences in two cognitive domains with established vulnerability to aging: executive functioning and speed of processing. The participants were healthy volunteers aged 50-81, some of whom had elevated blood pressure, a known vascular risk factor. Using latent variable analyses, we examined whether age differences in regional white matter integrity mediated age-related differences in executive functions and speed of processing. Although diffusion-related latent variables showed stronger age differences than white matter volumes and white matter hyperintensity volumes, only one of them was significantly associated with cognitive performance. Smaller linear anisotropy partially mediated age-related reduction in speed of processing. The effect was significant in posterior (temporal-parietal-occipital) but not anterior (frontal) region, and appeared stronger for cognitive rather than reaction time measures of processing speed. The presence of hypertensive participants did not affect the results. We conclude that in healthy adults, deterioration of axonal integrity and ensuing breech of connectivity may underpin age-related slowing of information processing.

Betacellulin: a mitogen from pancreatic beta cell tumors.

Betacellulin, a member of the epidermal growth factor family, has been identified in the conditioned medium of cell lines derived from mouse pancreatic beta cell tumors. Betacellulin is a 32-kilodalton glycoprotein that appears to be processed from a larger transmembrane precursor by proteolytic cleavage. The carboxyl-terminal domain of betacellulin has 50 percent sequence similarity with that of rat transforming growth factor alpha. Betacellulin is a potent mitogen for retinal pigment epithelial cells and vascular smooth muscle cells.

Heparin affinity: purification of a tumor-derived capillary endothelial cell growth factor.

A tumor-derived growth factor that stimulates the proliferation of capillary endothelial cells has a very strong affinity for heparin. This heparin affinity makes it possible to purify the growth factor to a single-band preparation in a rapid two-step procedure. The purified growth factor is a cationic polypeptide, has a molecular weight of about 18,000, and stimulates capillary endothelial cell proliferation at a concentration of about 1 nanogram per milliliter.

Influence of sediment metal spiking procedures on copper bioavailability and toxicity in the estuarine bivalve Indoaustriella lamprelli.

The effect of three methods for spiking sediments with Cu on the reburial behavior, mortality, and tissue Cu accumulation of a lucinid bivalve (Indoaustriella lamprelli) and the influence of the bivalve on the sediment geochemistry were investigated. Methods used to create Cu concentration gradients were direct spiking with and without pH adjustment to pH 7 and also dilution of sediment, previously spiked with Cu and adjusted to pH 7, using a low-Cu sediment (known to produce the lowest pore-water Cu concentrations). The presence of the bivalve within Cu-spiked sediment increased the flux of Cu and Mn to overlying waters at high Cu concentrations (550 microg/g). Bivalve behavioral response, metal accumulation, and mortality varied with the method by which Cu was spiked. In direct Cu-spiked sediment, the bivalves were inactive at concentrations of 550 and 1,100 microg/g, with mortality induced in sediment spiked with 1,100 microg/g (pH 6.5-7.1). Complete bivalve inactivity was observed only at 1,100 microg/g in direct Cu-spiked sediment with pH adjustment, whereas percentage reburial was reduced to 30% at 1,100 microg/g for sediment prepared by the dilution method. Relative reburial rates in the three spiked sediment types (direct << direct pH-7 < dilution) were proportional to dissolved Cu concentrations in the overlying water. Bivalve reburial, in addition to the method of Cu addition, affected tissue Cu accumulation. Inhibition of bivalve reburial decreased the amount of accumulated Cu, confounding relationships between tissue Cu and pore water, overlying water, or extractable metal fractions.

Effect of antiangiogenic therapy on slowly growing, poorly vascularized tumors in mice.

BACKGROUND: Angiogenesis is essential for tumor growth and progression. Therefore, inhibition of angiogenesis is being studied as a new anticancer therapy. Because cytotoxic chemotherapy is more effective on rapidly growing tumors than on slowly growing tumors, it has been assumed that antiangiogenic therapy will also be effective only on rapidly growing, highly vascularized tumors. We compared the effects of two angiogenesis inhibitors, TNP-470 and angiostatin, on slowly growing, poorly vascularized and rapidly growing, highly vascularized human tumors in mice. METHODS: Slowly growing (RT-4) and rapidly growing (MGH-U1) human bladder carcinoma cell lines were grown in severe combined immunodeficiency mice. Established tumors were treated with one of the two angiogenesis inhibitors. Tumor volumes, vascularity, and proliferation indices were determined. The in vitro effects of TNP-470 and of angiostatin on the proliferation of RT-4 and MGH-U1 cells were also investigated. All statistical tests were two-sided. RESULTS: RT-4 and MGH-U1 tumor growth was statistically significantly inhibited by both angiogenesis inhibitors (P<.001). Both inhibitors decreased the blood vessel density in both tumor types but did not alter the in vivo proliferation indices of the tumors. TNP-470, but not angiostatin, marginally decreased the in vitro proliferation of MGH-U1 cells. CONCLUSION: Slowly growing, poorly vascularized tumors in animal models respond as well as rapidly growing, highly vascularized tumors to therapy with the angiogenesis inhibitors TNP-470 and angiostatin.

Partial characterization of a cell motility factor from human urine.

Dialyzed, concentrated urine from 21 patients with a history of bladder cancer or a gross bladder tumor was tested for cell motility activity using BALB/c/3T3 cells. Thirteen urine samples from patients with a gross bladder tumor produced a greater increase in cell migration than 8 urine samples from patients with a history of bladder cancer [167% +/- 14 (S.E.), 64% +/- 19, respectively; p less than 0.001]. Protease treatment of urine from a patient with bladder cancer caused a 95% loss of activity, while heating to 100 degrees for 2 min caused an 86% loss of activity. High-performance liquid chromatography of urine from a patient with bladder cancer revealed that the greatest activity was present in fractions with a molecular weight between 18,000 and 30,000. These results suggest that motility-stimulating factor may be a useful marker for detecting carcinoma of the bladder.

HIF-1alpha-mediated up-regulation of vascular endothelial growth factor, independent of basic fibroblast growth factor, is important in the switch to the angiogenic phenotype during early tumorigenesis.

The switch to the angiogenic phenotype represents a critical checkpoint during tumor progression. The acquisition of new capillary vessels provides newly vascularized tumor nodules with a distinct biological advantage over their avascular counterparts by conferring upon them the ability to expand and develop both locally and metastatically. To identify the molecules and mechanisms underlying this rate-limiting step in successful tumorigenesis, we have developed an in vivo tumor model that reproducibly recapitulates the angiogenic switch. Using this model, we have analyzed vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and hypoxia-inducible factor-1alpha (HIF-1alpha) expression and activity in both avascular and vascular growth phases of the tumor. A significantly higher level of VEGF protein was detected in avascular tumor nodules compared with vascular nodules. As avascular tumors became vascularized, VEGF levels decreased approximately 10-fold. In contrast, bFGF levels were not elevated in avascular nodules but rather were detected at levels approximately 2 times higher in vascular nodules compared with the avascular tumor nodules. Given that VEGF is transcriptionally regulated by HIF-1alpha, immunohistochemical studies of chondrosarcoma nodules were conducted and revealed that the nuclear translocation of HIF-1alpha was detected exclusively in avascular tumor nodules. This study implicates HIF-1alpha-mediated up-regulation of VEGF but not bFGF in the switch to the angiogenic phenotype during tumorigenesis.

Presence of heparin binding growth factor in mouse bladder tumors and urine from mice with bladder cancer.

Heparin affinity chromatography has been used to partially purify angiogenic factors from normal and neoplastic tissue. The same technique was used to partially purify angiogenic-like factors from two mouse bladder tumors and urine from mice with bladder cancer. Both MBT-2 and MB49 tumors contained heparin-binding 3T3 cell growth factor activity that was eluted by 1.2 to 1.4 M salt. The growth factor isolated from MBT-2 tumor was mitogenic for capillary endothelial cells. Analysis of the 1.2 M heparin eluate by high-pressure liquid chromatography showed that it consisted of two 3T3 cell growth factors with molecular weights of 16,000 and 26,000. The growth factor activity isolated from MB49 tumors had an affinity for Bio-rex 70 which was similar to other cationic heparin binding growth factors. Analysis of urine pooled from tumor-bearing mice by heparin-Sepharose chromatography demonstrated 3T3 cell growth factor activity in fractions eluted with 1 to 1.4 and 2.5 M dsalt, whereas no significant growth factor activity was detected in pooled urine from control mice. The growth factor activity found in mouse bladder tumors differed from epidermal growth factor, transforming growth factor-alpha, and platelet-derived growth factor in terms of affinity for heparin-Sepharose and molecular weight. The observation that urine from tumor-bearing mice contains increased concentrations of this growth factor compared to normal urine suggests that a similar relationship may exist for human urine.

The role of growth factors in vascular cell development and differentiation.

The control of vascular growth and differentiation is a complex system of activity and interaction between positive and negative modulators of these processes. A number of important stimulators and inhibitors of both smooth muscle cells and endothelial cells have now been purified and biochemically characterized. Imbalances in the activity of these factors can result in serious pathologies. In this chapter, we briefly discuss the biology of blood vessel development and growth, review the current literature which describes these stimulators and inhibitors, and discuss current therapeutic strategies designed around these growth modulators.

Purification and characterization of a bovine colostrum-derived growth factor.

A growth factor in bovine colostrum was purified to homogeneity by a combination of acid extraction, boiling, cation exchange chromatography, isoelectric focusing, and reverse phase HPLC. The bovine colostrum growth factor (BCGF) had an isoelectric point of about 10, a native mol wt of about 30,000, was resistant to inactivation by boiling and exposure to pH 1, but was inactivated by dithiothreitol. BCGF appeared to be structurally related to human platelet-derived growth factor (PDGF) and competed with human PDGF in a radioreceptor assay. However, while human PDGF appeared to be a heterodimer of 17,000 and 14,000 mol wt subunits, BCGF appeared to be a homodimer of 20,000 mol wt subunits. Purified BCGF had a specific activity in stimulating 3T3 cell proliferation of about 3-6 U/ng and was active at about 1-2 ng/ml.

Human and bovine milk contain different sets of growth factors.

Growth factor activity is present in human milk throughout the lactation period but is in bovine milk only during the colostral phase. Biochemical analysis shows that the growth factors in human and bovine milk are not the same. Human milk contains three species of growth factors. One of these, designated human milk growth factor (HMGF) III, constitutes over 75% of the total growth factor activity of human milk. HMGF III has a mol wt of about 6,000, a pI between 4.4 and 4.7, and is resistant to treatment with dithiothreitol. Comparative biochemical studies strongly suggest that HMGF III is a human epidermal growth factor (EGF). On the other hand, bovine colostrum has no EGF-like growth factor. Instead, the major growth factor component of bovine colostrum has a mol wt between 30,000 and 35,000 and is inactivated by dithiothreitol treatment. The bovine colostrum growth factor (BCGF) is similar biochemically to one of the minor growth factors in human milk, HMGF II, which accounts for about 20% of the growth factor activity of human milk. HMGF III, the EGF-like polypeptide, can be purified to homogeneity by a combination of size exclusion and anion exchange chromatography. Purified HMGF III stimulates DNA synthesis in 3T3 cells at a concentration of about 25 ng/ml.

Purification of polypeptide growth factors from milk.

There appear to be at least three growth factors for mouse BALB/c 3T3 cells in human milk. The purification of the predominant one is described in this chapter. Biochemical and immunological studies indicate that this growth factor is probably a form of human epidermal growth factor (EGF). Like EGF, the major human milk-derived growth factor has a molecular weight of about 6000, a pI of about 4.5, and is resistant to inactivation by dithiothreitol. (See this volume, Harper et al., for purification of human EGF.) In addition, Carpenter has shown that antibodies against human EGF will precipitate most of the growth factor activity for 3T3 cells found in human milk. The EGF-like species of growth factor cannot be detected in bovine milk. Instead, the major growth factor in bovine colostrum appears to be biochemically similar to platelet-derived growth factor (PDGF). Like PDGF, the bovine colostrum-derived growth factor has a molecular weight of about 30,000, a pI of about 10, is totally inactivated by dithiothreitol but is stable to treatments with guanidine-HCl, urea, and heat. Biochemical characterizations of milk-derived growth factors, EGF, and PDGF are summarized in Table III. At present, very little is known about the physiological role of these growth factors in milk. The availability of these growth factors in homogeneous form will facilitate the studies in understanding their possible involvement in the growth process.

Hepatitic graft-versus-host disease after hematopoietic stem cell transplantation: clinicopathologic features and prognostic implication.

BACKGROUND: Graft-versus-host disease (GVHD) of the liver after allogeneic hematopoietic stem cell transplantation classically presents with increased bilirubin and alkaline phosphatase (ALP) levels. A hepatitic variant was recently recognized, with more than a 10-fold increase in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. This study defines the clinicopathologic features and prognostic implications of hepatitic GVHD compared with classic liver GVHD. METHOD: A total of 38 cases of hepatitic GVHD, 68 cases of classic liver GVHD, and 13 cases of hepatitis B virus (HBV)-related hepatitis after hematopoietic stem cell transplantation were analyzed. RESULTS: Hepatitic GVHD cases showed significantly higher ALT, AST, and ALP levels compared with classic liver GVHD cases (at onset, mean ALT: 154 vs. 58 U/L, P <0.001; AST: 167 vs. 77 U/L, P <0.001; at peak, ALT: 435 vs. 112 U/L, P <0.001; AST: 587 vs. 150 U/L, P <0.001; ALP: 416 vs. 238 U/L, P =0.001), persisted longer (74 vs. 32 days, P =0.006), and showed more lobular pathologic changes in biopsy (lobular changes: 16/26 vs. 4/19, P =0.007; hepatocyte necrosis: 16/26 vs. 6/19, P =0.008; acidophil bodies: 15/26 vs. 4/19, P =0.014) but less cholestasis (4/26 vs. 8/19, P =0.045). However, cumulative doses of immunosuppressants prescribed, response, and outcome were similar. Compared with hepatitic GVHD, HBV-related hepatitis occurred later (95 vs. 184 days, P =0.049), but clinical and biochemical profiles were similar, requiring liver biopsies for their distinction. CONCLUSIONS: Hepatitic and classic liver GVHD differed biochemically and pathologically, but these differences showed no obvious impact on outcome. The distinction of hepatitic GVHD from other hepatitis is mandatory.

Control of angiogenesis by heparin and other sulfated polysaccharides.

Heparin and its related polysaccharides are revealed to have important new functions as regulators of blood vessel growth and regression. This regulatory activity may be explained in part by at least five mechanisms in which heparin and heparan sulfate interact with peptide growth factors: (1) Heparin and heparan sulfate have a high affinity for angiogenic growth factors such as the fibroblast growth factors and VEGF, as well as for angiogenic inhibitors such as thrombospondin and platelet factor 4. (2) Heparin and its related polysaccharides stabilize bFGF and other growth factors. (3) FGFs and thrombospondin are stored in the extracellular matrix bound to heparan sulfate; fragments of heparin or heparan sulfate may act as natural chaperones to shuttle bFGF or other growth factors to different cellular compartments. (5) Heparin-like low-affinity receptors on the surface of endothelial cells (and other cells), prepare FGFs for binding to their specific high affinity receptors; and (6) Heparin and its related polysaccharides potentiate angiostatic steroids. It is likely that future investigations will uncover even more fundamental regulatory roles for heparin as well as for other polysaccharides in the normal function of growth factors, especially in the complex process of angiogenesis.

Natural or artificial? Habitat-use by the bull shark, Carcharhinus leucas.

BACKGROUND: Despite accelerated global population declines due to targeted and illegal fishing pressure for many top-level shark species, the impacts of coastal habitat modification have been largely overlooked. We present the first direct comparison of the use of natural versus artificial habitats for the bull shark, Carcharhinus leucas, an IUCN 'Near-threatened' species--one of the few truly euryhaline sharks that utilises natural rivers and estuaries as nursery grounds before migrating offshore as adults. Understanding the value of alternate artificial coastal habitats to the lifecycle of the bull shark is crucial for determining the impact of coastal development on this threatened but potentially dangerous species. METHODOLOGY/FINDINGS: We used longline surveys and long-term passive acoustic tracking of neonate and juvenile bull sharks to determine the ontogenetic value of natural and artificial habitats to bull sharks associated with the Nerang River and adjoining canals on the Gold Coast, Australia. Long-term movements of tagged sharks suggested a preference for the natural river over artificial habitat (canals). Neonates and juveniles spent the majority of their time in the upper tidal reaches of the Nerang River and undertook excursions into adjoining canals. Larger bull sharks ranged further and frequented the canals closer to the river mouth. CONCLUSIONS/SIGNIFICANCE: Our work suggests with increased destruction of natural habitats, artificial coastal habitat may become increasingly important to large juvenile bull sharks with associated risk of attack on humans. In this system, neonate and juvenile bull sharks utilised the natural and artificial habitats, but the latter was not the preferred habitat of neonates. The upper reaches of tidal rivers, often under significant modification pressure, serve as nursery sites for neonates. Analogous studies are needed in similar systems elsewhere to assess the spatial and temporal generality of this research.

Matching mitochondria to metabolic needs at nodes of Ranvier.

Myelinated axons conduct nerve impulses at high speed using a unique mode of excitation, referred to as saltatory conduction, which is enabled structurally by the narrowing of the site of action potentials to a tiny gap in the axon called the node of Ranvier. With this structural specialization comes an interesting metabolic matching problem. How do mitochondria find and supply energy to these tiny nodes of Ranvier distributed sparsely along a myelinated axon? Does the intense Na(+) influx at the node, which is produced by the highest known sodium channel density in all excitable membranes, help guide where mitochondria stop? Evidence suggests that during excitation in the peripheral nervous system, Na(+) influx recruits mitochondria to the node by triggering Ca(2+) elevation and activating Na(+) pumps. Intriguingly, indirect evidence suggests that in the central nervous system, activity recruits mitochondria to the internode (myelin-covered portion of the axon). Metabolic dysfunction thus might produce spatially distinct lesions in PNS and CNS myelinated fibers. Future dissection of regional variation in mitochondrial biology in myelinated axons using live imaging will likely yield surprises about sites of vulnerability in demyelinating diseases and clues for therapeutic intervention strategy.

Using blood samples to estimate persistent organic pollutants and metals in green sea turtles (Chelonia mydas).

Persistent organic pollutants (POPs) and heavy metals have been reported in a number of green turtle (Chelonia mydas) populations worldwide. However, due to ethical considerations, these studies have generally been on tissues from deceased and stranded animals. The purpose of this study was to investigate the use of blood samples to estimate the tissue contamination of live C. mydas populations. This study analysed 125 POP compounds and eight heavy metals in the blood, liver, kidney and muscle of 16 C. mydas from the Sea World Sea Turtle Rehabilitation Program, Gold Coast, Australia. Strong correlations were observed between blood and tissue concentrations for a number of POPs and metals. Furthermore, these correlations were observed over large ranges of turtle size, sex and condition. These results indicate that blood samples are a reliable non-lethal method for predicting chemical contamination in C. mydas.