Identification of a neural stem cell in the adult mammalian central nervous system

New neurons are continuously added in specific regions of the adult mammalian central nervous system. These neurons are derived from multipotent stem cells whose identity has been enigmatic. In this work, we present evidence that ependymal cells are neural stem cells. Ependymal cells give rise to a rapidly proliferating cell type that generates neurons that migrate to the olfactory bulb. In response to spinal cord injury, ependymal cell proliferation increases dramatically to generate migratory cells that differentiate to astrocytes and participate in scar formation. These data demonstrate that ependymal cells are neural stem cells and identify a novel process in the response to central nervous system injury.

Osteoinduction, osteoconduction and osseointegration

Osteoinduction is the process by which osteogenesis is induced. It is a phenomenon regularly seen in any type of bone healing process. Osteoinduction implies the recruitment of immature cells and the stimulation of these cells to develop into preosteoblasts. In a bone healing situation such as a fracture, the majority of bone healing is dependent on osteoinduction. Osteoconduction means that bone grows on a surface. This phenomenon is regularly seen in the case of bone implants. Implant materials of low biocompatibility such as copper, silver and bone cement shows little or no osteoconduction. Osseointegration is the stable anchorage of an implant achieved by direct bone-to-implant contact. In craniofacial implantology, this mode of anchorage is the only one for which high success rates have been reported. Osseointegration is possible in other parts of the body, but its importance for the anchorage of major arthroplasties is under debate. Ingrowth of bone in a porous-coated prosthesis may or may not represent osseointegration.

Generalized potential of adult neural stem cells

The differentiation potential of stem cells in tissues of the adult has been thought to be limited to cell lineages present in the organ from which they were derived, but there is evidence that some stem cells may have a broader differentiation repertoire. We show here that neural stem cells from the adult mouse brain can contribute to the formation of chimeric chick and mouse embryos and give rise to cells of all germ layers. This demonstrates that an adult neural stem cell has a very broad developmental capacity and may potentially be used to generate a variety of cell types for transplantation in different diseases.

The neuropeptide Y/agouti gene-related protein (AGRP) brain circuitry in normal, anorectic, and monosodium glutamate-treated mice

Neuropeptide Y (NPY) and the endogenous melanocortin receptor antagonist, agouti gene-related protein (AGRP), coexist in the arcuate nucleus, and both exert orexigenic effects. The present study aimed primarily at determining the brain distribution of AGRP. AGRP mRNA-expressing cells were limited to the arcuate nucleus, representing a major subpopulation (95%) of the NPY neurons, which also was confirmed with immunohistochemistry. AGRP-immunoreactive (-ir) terminals all contained NPY and were observed in many brain regions extending from the rostral telencephalon to the pons, including the parabrachial nucleus. NPY-positive, AGRP-negative terminals were observed in many areas. AGRP-ir terminals were reduced dramatically in all brain regions of mice treated neonatally with monosodium glutamate as well as of mice homozygous for the anorexia mutation. Terminals immunoreactive for the melanocortin peptide alpha-melanocyte-stimulating hormone formed a population separate from, but parallel to, the AGRP-ir terminals. Our results show that arcuate NPY neurons, identified by the presence of AGRP, project more extensively in the brain than previously known and indicate that the feeding regulatory actions of NPY may extend beyond the hypothalamus.

Rapid, widespread, and longlasting induction of nestin contributes to the generation of glial scar tissue after CNS injury

Neuronal regeneration does generally not occur in the central nervous system (CNS) after injury, which has been attributed to the generation of glial scar tissue. In this report we show that the composition of the glial scar after traumatic CNS injury in rat and mouse is more complex than previously assumed: expression of the intermediate filament nestin is induced in reactive astrocytes. Nestin induction occurs within 48 hours in the spinal cord both at the site of lesion and in degenerating tracts and lasts for at least 13 months. Nestin expression is induced with similar kinetics in the crushed optic nerve. In addition to the expression in reactive astrocytes, we also observed nestin induction within 48 hours after injury in cells close to the central canal in the spinal cord, while nestin expressing cells at later timepoints were found progressively further out from the central canal. This dynamic pattern of nestin induction after injury was mimicked by lacZ expressing cells in nestin promoter/lacZ transgenic mice, suggesting that defined nestin regulatory regions mediate the injury response. We discuss the possibility that the spatiotemporal pattern of nestin expression reflects a population of nestin positive cells, which proliferates and migrates from a region close to the central canal to the site of lesion in response to injury.

Aseptic loosening, not only a question of wear: a review of different theories

Today, aseptic loosening is the most common cause of revision of major arthroplasties. Aseptic loosening accounts for more than two-thirds of hip revisions and almost one-half of knee revisions in Sweden. Several theories on the cause of aseptic loosening have been proposed. Most of these theories, however, are based on empiric observations, experimental animal models or anecdotal cases. In this review, we discuss the most common theories concerning aseptic loosening. It emerges from this review that aseptic loosening has a multifactorial etiology and cannot be explained by a single theory.

Abnormal heart rate and body temperature in mice lacking thyroid hormone receptor alpha 1

Thyroid hormone, acting through several nuclear hormone receptors, plays important roles in thermogenesis, lipogenesis and maturation of the neonatal brain. The receptor specificity for mediating these effects is largely unknown, and to determine this we developed mice lacking the thyroid hormone receptor TR alpha 1. The mice have an average heart rate 20% lower than that of control animals, both under normal conditions and after thyroid hormone stimulation. Electrocardiograms show that the mice also have prolonged QRS- and QTend-durations. The mice have a body temperature 0.5 degrees C lower than normal and exhibit a mild hypothyroidism, whereas their overall behavior and reproduction are normal. The results identify specific and important roles for TR alpha 1 in regulation of tightly controlled physiological functions, such as cardiac pacemaking, ventricular repolarisation and control of body temperature.

Abnormal reaction to central nervous system injury in mice lacking glial fibrillary acidic protein and vimentin

In response to injury of the central nervous system, astrocytes become reactive and express high levels of the intermediate filament (IF) proteins glial fibrillary acidic protein (GFAP), vimentin, and nestin. We have shown that astrocytes in mice deficient for both GFAP and vimentin (GFAP-/-vim-/-) cannot form IFs even when nestin is expressed and are thus devoid of IFs in their reactive state. Here, we have studied the reaction to injury in the central nervous system in GFAP-/-, vimentin-/-, or GFAP-/-vim-/- mice. Glial scar formation appeared normal after spinal cord or brain lesions in GFAP-/- or vimentin-/- mice, but was impaired in GFAP-/-vim-/- mice that developed less dense scars frequently accompanied by bleeding. These results show that GFAP and vimentin are required for proper glial scar formation in the injured central nervous system and that some degree of functional overlap exists between these IF proteins.

Neural stem cells in the adult human brain

New neurons are continuously generated in certain regions of the adult brain. Studies in rodents have shown that new neurons are generated from self-renewing multipotent neural stem cells. Here we demonstrate that both the lateral ventricle wall and the hippocampus of the adult human brain harbor self-renewing cells capable of generating neurons, astrocytes, and oligodendrocytes in vitro, i.e., bona fide neural stem cells.

Cloning and expression of a novel human glutaredoxin (Grx2) with mitochondrial and nuclear isoforms

Glutaredoxin (Grx) is a glutathione-dependent hydrogen donor for ribonucleotide reductase. Today glutaredoxins are known as a multifunctional family of GSH-disulfide-oxidoreductases belonging to the thioredoxin fold superfamily. In contrast to Escherichia coli and yeast, a single human glutaredoxin is known. We have identified and cloned a novel 18-kDa human dithiol glutaredoxin, named glutaredoxin-2 (Grx2), which is 34% identical to the previously known cytosolic 12-kDa human Grx1. The human Grx2 sequence contains three characteristic regions of the glutaredoxin family: the dithiol/disulfide active site, CSYC, the GSH binding site, and a hydrophobic surface area. The human Grx2 gene, located at chromosome 1q31.2--31.3, consisted of five exons that were transcribed to a 0.9-kilobase human Grx2 mRNA ubiquitously expressed in several tissues. Two alternatively spliced Grx2 mRNA isoforms that differed in their 5' region were identified. These corresponded to alternative proteins with a common 125-residue C-terminal Grx domain but with different N-terminal extensions of 39 and 40 residues, respectively. The 125-residue Grx domain and the two full-length variants were expressed in E. coli and exhibited GSH-dependent hydroxyethyl disulfide and dehydroascorbate reducing activities. Western blot analysis of subcellular fractions from Jurkat cells with a specific anti-Grx2 antibody showed that human Grx2 was predominantly located in the nucleus but also present in the mitochondria. We further showed that one of the mRNA isoforms corresponding to Grx2a encoded a functional N-terminal mitochondrial translocation signal.

Experimental study of turned and grit-blasted screw-shaped implants with special emphasis on effects of blasting material and surface topography

In the rabbit tibia, commercially pure titanium implants blasted with 25-microns Al2O3 and TiO2 particles respectively were inserted and studied with respect to removal torque and histomorphometry. In the rabbit femur, as-machined implants and implants blasted with 75-microns Al2O3 particles were histomorphometrically compared. Before implant insertion, the differently produced surface topographies were characterized numerically and visually. The tibial implants blasted with different materials and the same sized (25 microns) blasting particles demonstrated similar results. Comparing implants blasted with 75-microns Al2O3 particles to as-machined implants, the blasted specimens exhibited a statistically significant higher bone-to-metal contact after 12 weeks in the rabbit bone.

The 5'-AMP-activated protein kinase gamma3 isoform has a key role in carbohydrate and lipid metabolism in glycolytic skeletal muscle

5'-AMP-activated protein kinase (AMPK) is a metabolic stress sensor present in all eukaryotes. A dominant missense mutation (R225Q) in pig PRKAG3, encoding the muscle-specific gamma3 isoform, causes a marked increase in glycogen content. To determine the functional role of the AMPK gamma3 isoform, we generated transgenic mice with skeletal muscle-specific expression of wild type or mutant (225Q) mouse gamma3 as well as Prkag3 knockout mice. Glycogen resynthesis after exercise was impaired in AMPK gamma3 knock-out mice and markedly enhanced in transgenic mutant mice. An AMPK activator failed to increase skeletal muscle glucose uptake in AMPK gamma3 knock-out mice, whereas contraction effects were preserved. When placed on a high fat diet, transgenic mutant mice but not knock-out mice were protected against excessive triglyceride accumulation and insulin resistance in skeletal muscle. Transfection experiments reveal the R225Q mutation is associated with higher basal AMPK activity and diminished AMP dependence. Our results validate the muscle-specific AMPK gamma3 isoform as a therapeutic target for prevention and treatment of insulin resistance.

Characteristics of the surface oxides on turned and electrochemically oxidized pure titanium implants up to dielectric breakdown: the oxide thickness, micropore configurations, surface roughness, crystal structure and chemical composition

Titanium implants have been used widely and successfully for various types of bone-anchored reconstructions. It is believed that properties of oxide films covering titanium implant surfaces are of crucial importance for a successful osseointegration, in particular at compromized bone sites. The aim of the present study is to investigate the surface properties of anodic oxides formed on commercially pure (c.p.) titanium screw implants as well as to study 'native' oxides on turned c.p. titanium implants. Anodic oxides were prepared by galvanostatic mode in CH3COOH up to the high forming voltage of dielectric breakdown and spark formation. The oxide thicknesses, measured with Auger electron spectroscopy (AES), were in the range of about 200-1000 nm. Barrier and porous structures dominated the surface morphology of the anodic film. Quantitative morphometric analyses of the micropore structures were performed using an image analysis system on scanning electron microscopy (SEM) negatives. The pore sizes were < or = 8 microm in diameter and had 1.27-2.1 microm2 opening area. The porosity was in the range of 12.7-24.4%. The surface roughness was in the range of 0.96-1.03 microm (Sa), measured with TopScan 3D. The crystal structures of the titanium oxide were amorphous, anatase, and a mixtures of anatase and rutile type, as analyzed with thin-film X-ray diffractometry (TF-XRD) and Raman spectroscopy. The chemical compositions consisted mainly of TiO2, characterized with X-ray photoelectron spectroscopy (XPS). The native (thermal) oxide on turned implants was 17.4 nm (+/- 6.2) thick and amorphous. Its chemical composition was TiO2. The surface roughness had an average height deviation of 0.83 microm (Sa). The present results are needed to elucidate the influence of the oxide properties on the biological reaction. The results of animal studies using the presently characterized surface oxides on titanium implants will be published separately.

Increased plasma protein binding of propranolol and chlorpromazine mediated by disease-induced elevations of plasma alpha1 acid glycoprotein

To assess the importance of disease-induced increases in plasma concentrations of alpha1 acid glycoprotein (an acute-phase plasma protein that binds cationic drugs), we determined binding of propranolol in plasma from 53 patients and 25 healthy volunteers. Binding was increased in 10 patients with Crohn's disease (P less than 0.002), nine with inflammatory arthritis (P less than 0.002) and eight with chronic renal failure with superimposed inflammatory disease (P less than 0.01) as compared with healthy controls. The plasma binding of control subjects did not differ from that of 12 patients with chronic hepatic disease (P greater than 0.45) or 14 with uncomplicated renal failure (P greater than 0.80). Chlorpromazine binding, determined in 60 subjects, yielded similar results. Percentage of free drug and alpha1 acid glycoprotein concentration were inversely correlated (r = -0.77 with propranolol, P less than 0.001, and r = -0.69 with chlorpromazine, P less than 0.001). Increases in plasma protein binding in patients with inflammatory disease appear mediated by increases in alpha1 acid glycoprotein concentration, which may influence drug kinetics.

Anchorage of TiO2-blasted, HA-coated, and machined implants: an experimental study with rabbits

The purpose of this study was to evaluate the histometrical and biomechanical anchorage of TiO2-blasted implants and TiO2-blasted implants coated with hydroxyapatite. The control implants were machined. Twenty-six rabbits had a total of 156 implants placed in the proximal part of the tibia. Each rabbit had a machined, a TiO2-blasted, and a TiO2-blasted, HA-coated implant placed in each tibia. After a healing period of 3 and 12 weeks, respectively, the implants placed in the right tibia were used for removal torque test, and the implants placed in the left tibia were used for histomorphometrical measurements. Preoperatively, implants from the same batches were examined topographically with a TopScan 3D system. The TiO2-blasted implants demonstrated significantly higher removal torque values than the machined implants, and they also had a significantly more irregular surface. Furthermore, significantly higher bone-to-implant contact length fractions were measured adjacent to the TiO2-blasted implants in contrast to the machined implants. The advantages of a TiO2-blasted surface were more pronounced after 3 weeks than after 12 weeks. The results demonstrated that it was possible to influence the anchorage of implants by altering the surface structure morphology. The new method with TiO2 blasting on the titanium surface improves the anchorage of implants but is not yet practicable for HA coating.

Defecography. Results of investigations in 2,816 patients

PURPOSE

This study was designed to analyze the frequency of different findings at defecography in patients with defecation disorders and see in what way the evaluation could be improved.

METHODS

The reports of investigations in 2,816 patients were analyzed.

RESULTS

Twenty-three percent of the investigations were considered normal. Thirty-one percent of the patients had rectal intussusception, 13 percent had rectal prolapse, 27 percent had rectocele, and 19 percent had enterocele. Twenty-one percent of the patients had a combination of two or three of these diagnoses. The combination of rectocele and enterocele was rare. The majority of patients with enterocele had other concomitant findings. Patients with or without abnormal perineal descent had similar frequencies of rectal prolapse, rectal intussusception, and enterocele. Rectocele was more common in patients with abnormal perineal descent.

CONCLUSIONS

Defecography is valuable when investigating patients with defecation disorders. Pathologic findings were found in 77 percent of the patients. A standardized protocol should ensure a complete evaluation of defecography.

Results of rectocele repair. A prospective study

PURPOSE

This study was designed to evaluate the results of rectocele repair and parameters that might be useful in selecting patients for this operation.

METHODS

Twenty-five patients with symptom-giving rectoceles were prospectively evaluated with a standardized questionnaire, physical examination, defecography, colon transit studies, anorectal manometry, and electrophysiology. Patients underwent posterior colporrhaphy and perineorrhaphy. They were followed postoperatively (mean, 1.0 year) with the same questionnaire, physical examination, defecography, anorectal manometry, and electrophysiology.

RESULTS

Constipation had improved postoperatively in 21 of 24 constipated patients (88 percent). At postoperative follow-up 13 patients (52 percent) had no constipation symptoms, 8 (32 percent) had occasional symptoms, and 4 (16 percent) had symptoms more than once per week. Four patients with rectocele at preoperative defecography, but not at physical examination, had favorable outcomes following surgery. The majority of patients not using vaginal digitalization preoperatively had improved with respect to constipation. All patients with pathologic transit studies had various degrees of constipation postoperatively. Constipation was not improved in two of five patients with preoperative paradoxic sphincter reaction.

CONCLUSIONS

Rectocele is one cause of constipation that can be treated with good results. Preoperative use of vaginal digitalization is not mandatory for a good postoperative result. Defecography is an important complement to physical examination. Patients with pathologic transit study might have a less favorable outcome of rectocele repair with respect to constipation. More studies about the significance of paradoxic sphincter reaction in these patients are indicated.

A histomorphometric evaluation of screw-shaped implants each prepared with two surface roughnesses

Four different surface modifications were designed. Forty screw-shaped implants were divided into 4 groups, 10 screws in each. Every screw was prepared with 2 different surface topographies. The surface topography was measured with a confocal laser scanning profilometer and the surface roughness was characterized using 1 height, 1 spatial and 1 hybrid descriptive parameter. After 12 weeks in rabbit bone all screws were histomorphometrically evaluated. Blasted surfaces demonstrated more bone in contact to implant surface compared with turned surfaces. Most bone in close contact to implant surface was found for a surface blasted with 75 microns sized particles, numerically characterized with an average height deviation (Sa) of 1.4 microns, an average wavelength (Scx) of 11.6 microns and a developed surface area ratio (Sdr) of 1.5.

The electrochemical oxide growth behaviour on titanium in acid and alkaline electrolytes

Titanium implants have a thin oxide surface layer. The properties of this oxide layer may explain the good biocompatibility of titanium implants. Anodic oxidation results in a thickening of the oxide film, with possible improved biocompatability of anodized implants. The aim of the present study was twofold: (1) firstly, to characterize the growth behaviour of galvanostatically prepared anodic oxide films on commercially pure (c.p.) titanium and (2) secondly, to establish a better understanding of the electroche0mical growth behaviour of anodic oxide on commercially pure titanium (ASTM grade 1) after changes of the electrochemical parameters in acetic acid, phosphoric acid, calcium hydroxide, and sodium hydroxide under galvanostatic anodizing mode. The oxide thickness was measured by Ar sputter etching in Auger Electron spectroscopy (AES) and the colours were estimated by an L*a*b* system (lightness, hue and saturation) using a spectrophotometer. In the first part of our study, it was demonstrated that the interference colours were useful to identify the thickness of titanium oxide. It was also found that the anodic forming voltages with slope (dV/dt) in acid electrolytes were higher than in alkaline electrolytes. Each of the used electrolytes demonstrates an intrinsically specific growth constant (nm/V) in the range of 1.4--2.78 nm/V. In the second part of our study we found, as a general trend, that an increase of electrolyte concentration and electrolyte temperature respectively decreases the anodic forming voltage, the anodic forming rate (nm/s) and the current efficiency (nm.cm(2)/C), while an increase of the current density and the surface area ratio of the anode to cathode increase the anodic forming voltage, the anodic forming rate and the current efficiency. The effects of electrolyte concentration, electrolyte temperature, and agitation speed were explained on the basis of the model of the electrical double layer.

CD44 is necessary for optimal contact allergic responses but is not required for normal leukocyte extravasation

The in vivo administration of certain monoclonal antibodies (mAbs) against the adhesion receptor, CD44, into normal mice induces both a modulation of CD44 from the surface of peripheral lymphocytes, and a concomitant increase in the amount of soluble CD44 in the serum. CD44-negative lymphocytes isolated from anti-CD44-treated mice exhibit normal homing patterns upon adoptive transfer, and are capable of reexpressing CD44 upon activation. The treatment of haptensensitized mice with anti-CD44 mAb inhibits their ability to mount a cutaneous delayed-type hypersensitivity (DTH) response within the first 24 h after hapten challenge. This inhibition reflects a block in both the edema and leukocyte infiltration of the cutaneous site of DTH, whereas the extravasation and accumulation of leukocytes in the draining lymph nodes progress normally. After 72 h, the leukocytes that extravasate into the site of antigen challenge express CD44. These results indicate that CD44 is not necessary for normal leukocyte circulation but is required for leukocyte extravasation into an inflammatory site involving nonlymphoid tissue.

Thiol redox control via thioredoxin and glutaredoxin systems

The Trx (thioredoxin) and Grx (glutaredoxin) systems control cellular redox potential, keeping a reducing thiol-rich intracellular state, which on generation of reactive oxygen species signals through thiol redox control mechanisms. Here, we give a brief overview of the human Trx and Grx systems. The main part focuses on our current knowledge about mitochondrial Grx2, which facilitates mitochondrial redox homoeostasis during oxidative stress-induced apoptosis.

Differential induction of cytochrome P-450-dependent monooxygenase, epoxide hydrolase, glutathione transferase and UDP glucuronosyl transferase activities in the liver of the rainbow trout by beta-naphthoflavone or Clophen A50

After administration of beta-naphthoflavone and Clophen A50 to juvenile rainbow trout, activities of hepatic cytochrome P-450-dependent deethylation of 7-ethoxyresorufin was increased 172- and 49-fold, respectively. Glutathione transferase activity towards 1-chloro 2,4 dinitrobenzene and UDP glucuronosyltransferase activities towards p-nitrophenol, 1-naphthol and testosterone were increased 1.4 to 3.0-fold by beta-naphthoflavone or Clophen A50. However, significant increases of the rate of glucuronidation of 1-naphthol by Clophen A50 and of testosterone by both Clophen A50 and beta-naphthoflavone were only determined when the activities were measured in digitonin activated microsomes. Epoxide hydrolase activity was not affected by beta-naphthoflavone or Clophen A50. The time course of induction of the various xenobiotic metabolizing enzymes exhibited different patterns. 7-Ethoxyresorufin-O-deethylase activity reached peak values 3 and 7 days after the administration of beta-naphthoflavone and Clophen A50, respectively. The rate of induction of glutathione transferase activity and UDP glucuronosyltransferase activities towards p-nitrophenol and 1-naphthol were relatively slow and did not reach distinct peak levels. These activities were still on maximum levels 4-6 weeks after the treatment. Glucuronidation of testosterone reached peak values 1 week after treatment with both beta-naphthoflavone and Clophen A50. The dissimilar patterns of induction of the cytochrome P-450-dependent activities and the various conjugation activities may indicate that these xenobiotic metabolizing enzymes are differently regulated in the rainbow trout liver.