Surface-dimpled commercially pure titanium implant and bone ingrowth

The purpose of this investigation was to examine the effect of the surface macrostructure of a dimpled commercially pure titanium (cp Ti) implant on bone ingrowth in vivo by means of histological examination and a push-out test. Cylindrical implants were inserted in one femur of each experimental rabbit and the animals were killed at 1.5, 3 and 13 months after implantation. The femur with the implant of each animal was then examined in a push-out test. The fracture surfaces of the bone-implant interface after the push-out test were examined under light and electron microscopy. It seems that the dimpled cp Ti surface results in the increased retention of the cp Ti implant in bone due to interlocking between vital bone and the dimples.     

Mechanobiological adaptation of subchondral bone as a function of joint incongruity and loading

Computed tomography (CT) has been employed to determine non-invasively the distribution of subchondral bone density in joints and to evaluate their dominant loading pattern. The objective of this study was to investigate the relationship between subchondral bone adaptation, joint incongruity and loading, in order to determine to what extent the loading conditions and/or geometric configuration can be inferred from the distribution of subchondral density. Finite element models of joints with various degrees of incongruity were designed and a current remodeling theory implemented using the node-based approach. Appropriate combinations of joint incongruity and loading yielded subchondral bone density patterns consistent with experimental findings, specifically a bicentric distribution in the humero-ulnar joint and a monocentric distribution in the humero-radial joint. However, other combinations of incongruity and loading produced similar subchondral density patterns. Both the geometric joint configuration and the loading conditions influence the distribution of subchondral density in such a way that one of these factors must be known a priori to estimate the other. Since subchondral density can be assessed by CT and joint geometry by magnetic resonance imaging, the dominant loading pattern of joints may be potentially derived in the living using these non-invasive imaging methods.     

Comparison of primate and canine models for bone ingrowth experimentation, with reference to the effect of ovarian function on bone ingrowth potential

Bone growth into porous composite (mesh-bead) titanium plugs was compared in elderly (postmenopausal) female monkeys and female dogs as a means of validating the cross-species interpretations so often made between data from research on dogs and human applications. The effect of oophorectomy on bone ingrowth in the canine model was defined by the comparison of data on fractional ingrowth in animals that had had oophorectomy and in control animals that had had a sham operation. No significant difference in bone growth into the experimental plugs was identified between the two animal models, which lends credence to cross-species interpretation of existing data from dogs. The presence or absence of active ovaries did not affect the ingrowth fraction in the canine model; this suggests that existing data are not confounded by the lack of control of ovarian function. Estrogen depletion does not appear to influence bone ingrowth adversely.     

Whole body stiffness as a function of developmental level in children's hopping.

This article proposed that a continuous variable, whole body stiffness, may cause the discontinuous or qualitative change that occurs between two specific developmental levels within the developmental sequence for hopping. Ss were 7 children who hopped at Level 2 on one leg and Level 3 on the other. Force and cinematographic data were collected; from these data, measures of both estimated average and instantaneous whole body stiffness were calculated and compared across developmental levels. Both instantaneous and estimated average whole body stiffness showed dramatic reductions between developmental Levels 2 and 3. It was proposed that stiffness may be a key parameter controlled by the central nervous system as children hop. Children at early developmental levels set this parameter too high. At some critical value of stiffness, in order to continue locomotion, the movement must reorganize, which in turn, lowers the stiffness setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intensity and duration of suicidal crisis vary as a function of previous suicide attempts and negative life events.

Borrowing from past conceptual work on the unique characteristics of multiple suicide attempters, as well on the effect of previous suicidal and depressive experience on later functioning, the authors hypothesized that negative events would be related to intensity of suicidal crises among never– and first–attempters, but not among multiple attempters and that negative events would be related to duration of suicidal crises among multiple attempters but not among never– and first–attempters. Data on past suicide history, negative life events, and clinician– and self–rated suicidal symptoms were collected on 326 suicidal patients, 249 of whom were available at 1–month follow–up. Findings conformed to prediction Previous suicidal experience alters the parameters of current suicidal crises. Implications of these findings for suicide risk and clinical assessment and management are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serotonin transporter gene associations with psychopathic traits in youth vary as a function of socioeconomic resources.

Although prior research has examined the genetic correlates of antisocial behavior, molecular genetics influences on psychopathic traits remain largely unknown. Consequently, we investigated the influence of polymorphic variation at the serotonin transporter protein gene (SLC6A4) and socioeconomic resources (SES) on psychopathic traits in youth across two distinct samples in two separate studies. In Study 1, a main effect of serotonin transporter (5-HTTLPR) genotype was associated with the impulsivity dimension of psychopathy. That is, individuals homozygous for the short allele evidenced more impulsivity than did those homozygous for the long allele. In contrast, a gene–environment interaction was associated with the callous-unemotional and narcissistic features of psychopathy. Callous-unemotional and narcissistic traits increased as SES decreased only among youths with the homozygous-long (l/l) genotype, a novel finding replicated and extended in Study 2. These studies provide preliminary results that the l/l genotype confers risk for the emotional deficits and predatory interpersonal traits associated with psychopathy among youths raised in disadvantaged environments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distortion of drivers' estimates of automobile speed as a function of speed adaptation.

10 male undergraduate drivers made 4 estimates of 40 mph speed after varying amounts of exposure to an adapting speed of 70 mph. The influence of these amounts of exposure to the adapting speed on speed judgments was studied, and a significant (p     

Wear analysis of a retrieved hip implant with titanium nitride coating

There is increasing interest in using surface modification technology to improve the wear properties of titanium alloy and limit articular surface wear of metal and polyethylene components. This report details the in vivo wear performance of titanium nitride coating on a retrieved hip implant obtained postmortem from a low demand patient 1 year after total hip arthroplasty. Analysis of the well-functioning implant revealed that wear debris can originate from a titanium nitride coated femoral head, as delaminated surface asperities, and manifest as adhesive wear on the articular surface. The wear observed on this implant indicates that rigorous testing and evaluation of titanium nitride coating technology should be conducted prior to widespread use on total joint implants.     

Backward pattern masking can vary as a nonmonotonic function of target duration: on the influence of intratraget metacontrast

The magnitude of backward masking is usually found to vary inversely with the amount of information about a target that is made available to the visual system. Contrary to these findings, we report a nonmonotonic relation between the magnitude of backward pattern masking and target duration. Specifically, masking decreased as target duration was increased to about 8 msec and, then, became more severe as target duration was further increased to a value of at least 40 msec. The occurrence of the nonmonotonic function depended on (a) the degree of definition of the target's edges, (b) the luminance levels within the target stimulus, and (c) the state of adaptation of the eye. It is hypothesized that the source of the nonmonotonic function was metacontrast interference that originated from within the target stimulus configuration. This hypothesis was supported by data that indicated that in the absence of any mask presentations, the apparent contrast between the target and its immediate background varied as a nonmonotonic function of target duration.     

Skeletal cell stresses and bone adaptation

BACKGROUND: We have previously shown that growth hormone (GH) consistently stimulates proliferation of human osteoblasts in vitro. In rat osteoblasts, GH augments the effects of insulin-like growth factor (IGF) I on cell proliferation and differentiation. We therefore investigated the effects of IGF-I and -II alone and in combination with GH on human osteoblasts in vitro. METHODS: Human osteoblast-like cells (HOB) were established from trabecular explants (n = 18) and human marrow stromal cells (HMS) from marrow aspiration (n = 21). The cell cultures were stimulated with IGF-I or IGF-II (1, 10 or 100 ng mL-1) alone, in combination with hGH (100 ng mL-1) or after prestimulation with hGH. RESULTS: IGF-I alone, in combination with hGH and after pretreatment with hGH, increased proliferation of HOB and HMS by 49-190% (P < 0.05-0.01). IGF-II alone, in combination with hGH and after pretreatment with hGH increased proliferation of HOB by 57-158% (P < 0.01). In HMS only IGF-II in combination with hGH and after prestimulation with hGH increased proliferation. IGF-I alone and in combination with hGH decreased alkaline phosphatase (AP) in both cell types. IGF-II did not affect AP in HOB, but increased AP in HMS, this effect was abolished by hGH. In HOB, collagen production (PICP) was increased by IGF-II but unaffected by IGF-I. In HMS, PICP was decreased by IGF-I and -II but increased by hGH. Co-stimulation further increased PICP. CONCLUSION: IGF-I and -II exerted proliferative effects on both HOB and HMS. Co-stimulation with GH exhibited synergism in enhancing the proliferative response. In HMS prestimulation improved the proliferative response significantly. The effects of the IGFs on differentiation are more complex and dependent on cell maturation and of the IGF used.     

Myocardial tactile stiffness: a variable of regional myocardial function

OBJECTIVES: We developed a new sensor system for in situ measurement of myocardial tactile stiffness-stiffness in a direction perpendicular to the wall-and validated its use for providing a reasonable estimation of regional myocardial function. BACKGROUND: Numerous attempts have been made to directly assess regional myocardial function. The complexity and highly invasive nature of the measuring devices have hampered their in situ application. METHODS: In open chest mongrel dogs, myocardial tactile stiffness, ventricular pressure and ventricular volume were monitored. Under the preload reduction, these variables were measured to determine the relation between the end-systolic pressure-volume relation (ESPVR) and the end-systolic tactile stiffness-volume relation (ESSVR). The changes in myocardial tactile stiffness were monitored in the regional ischemic myocardial model and infarcted model to evaluate their usefulness as indexes of regional myocardial function. RESULTS: Myocardial tactile stiffness changed cyclically and followed a time course similar to left ventricular pressure. When preload was altered, the ESSVR was as linear as the ESPVR. The slope of the ESSVR and that of the ESPVR showed a strong correlation over a wide range of contractility. These results suggest that myocardial tactile stiffness can be a good index of regional wall stress or fiber stress. End-systolic myocardial tactile stiffness of ischemic and infarcted regions decreased significantly, with a concomitant increase in end-diastolic stiffness compared with that of intact myocardium. CONCLUSIONS: Using our tactile sensor system, regional myocardial tactile stiffness of a beating heart was measured with reasonable temporal resolution. We consider myocardial tactile stiffness to be a useful index of regional myocardial function.     

Transforming growth factor-beta 1 and 2 in the synovial-like interface membrane between implant and bone in loosening of total hip arthroplasty

OBJECTIVE: Development of a synovial-like membrane in the implant-bone or cement-bone interface has been linked to aseptic loosening of total hip arthroplasties (THA). This tissue consists of a fibrous stroma containing blood vessels and macrophages, but with relatively few lymphocytes, compared to "autoimmune" rheumatoid synovitis. Our aim was to examine transforming growth factor-beta (TGF-beta) in the synovial-like membrane of the interface and pseudocapsular tissue of loose THA and compare it to control knee synovial membrane. METHODS: Twenty samples obtained from 10 patients with loose THA at revisions performed for aseptic loosening and 10 samples of knee synovial membrane as controls were analyzed for TGF-beta expression using rabbit antihuman TGF-beta 1 and TGF-beta 2 IgG in immunohistochemical staining. Results were quantitated by a semi-automatic VIDAS image analysis system. RESULTS: Immunoperoxidase staining disclosed TGF-beta in macrophages and fibroblasts and also in some vascular endothelial cells and in occasional lymphocytes. Image analysis showed an increased number of positive cells/mm2 of both TGF-beta 1 (2327 +/- 212 vs 946 +/- 136; p < 0.01) and TGF-beta 2 (2292 +/- 594 vs 311 +/- 113; p < 0.01) compared to the control tissue. Increased expression of both TGF-beta 1 and TGF-beta 2 was also shown in the pseudocapsule (3210 +/- 585 and 1796 +/- 214). Use of cement or type of alloy did not seem to have any great effect on local expression of TGF-beta. CONCLUSION: Profibrotic and immunosuppressive TGF-beta are increased in the synovial-like membrane in periprosthetic tissues around loose hip prostheses. They may play a role in the formation, maintenance, and growth of the interface tissue, and thus in the aseptic loosening of THA.     

Follicular fluid insulin-like growth factor-I and insulin-like growth factor-binding protein-1 and -3 vary as a function of ovarian reserve and ovarian stimulation

PURPOSE: Follicular fluid concentrations of insulin-like growth factor (IGF)-I, IGF-II, IGF-binding protein (BP)-1, and IGFBP-3 in 57 women undergoing in vitro fertilization and embryo transfer were examined to determine whether levels reflected differences in patients' exposure to gonadotropin stimulation and a diminished ovarian reserve. METHODS: Preovulatory follicular fluid was obtained from both gonadotropin-stimulated and unstimulated cycles. Subjects were grouped according to normal or decreased ovarian reserve and whether or not they received gonadotropin stimulation. RESULTS: The mean follicular fluid concentrations of IGF-I and IGFBP-1 were significantly lower in the "decreased" ovarian reserve group compared with the "normal" ovarian reserve group, with no change in estradiol or IGF-II levels. This resulted in a decreased molar IGF-I: BP ratio and an increased molar IGF-II:IGFBP-1 ratio. In unstimulated cycles, mean follicular fluid concentrations of IGFs did not differ significantly compared with those in stimulated cycles, whereas concentrations of IGFBP-1 and IGFBP-3 were significantly lower, leading to higher molar ratios of the IGFs to the binding proteins. CONCLUSIONS: Follicular fluid IGF and binding proteins vary as a function of ovarian reserve and gonadotropin stimulation. This may reflect either differences in oocyte quality or a suboptimal follicular fluid environment.     

Impulse response of a dental implant in bone by numerical analysis

The osseointegration process of titanium dental implants in bone has been simulated previously using natural frequency and impulse excitation. However, the impulse strength was arbitrarily chosen and may not have yielded the correct frequencies and displacements to be compared with those measured in a clinical situation. In this work the range of impulse excitation strengths applied to a dental implant osseointegrated in bone and the corresponding response have been examined using the finite element method. Both conditions of a dental pin only and a dental pin with attached cantilever integrated in the mandible have been examined. The dynamic analysis indicated that the frequency and displacement responses are indeed sensitive to impulse duration and direction but independent of impulse load. The analysis summarizes the proper impulse excitation values for a correct interpretation of clinically measured frequency response data.     

The central adaptation syndrome: psychosocial stress as a trigger for adaptive modifications of brain structure and brain function

This review makes an attempt to combine data from biological and psychosocial stress literature and to suggest an alternative interpretation of the relationship between stress and disease. It rearranges the presently available knowledge on the short- and long-term effects of stress on many different aspects of brain structure and brain function in the form of a new conceptualization of the biological role of the stress response. The higher associative brain structures are not only the sites in which environmental and psychosocial demands are recognized and from which a less or more systemic, i.e. controllable or uncontrollable, stress response is initiated. They are also the sites which are primarily affected in the course of the stress response: the stress response acts as a trigger for the adaptive modification of the structure and the function of the brain of higher vertebrates and serves thus to adjust, in a self-optimizing manner, the behavior of an individual to the ever-changing requirements of its external world. This novel concept summarizes a large amount of information into a framework that lends itself to testable strategies for future research.     

Molecular adaptation of Drosophila melanogaster lysozymes to a digestive function

A lysozyme (pI 5.5) was purified to homogeneity from heated acid extracts of Drosophila melanogaster larvae, using gel filtration in a Superose column and ion-exchange chromatography in a Mono Q column. The final yield was 67%. The purified lysozyme with Mr 13,700 (determined by SDS-polyacrylamide gel electrophoresis) decreases in activity and has its pH optimum displaced towards acidic values and Km increases as the ionic strength of the medium becomes higher. The lysozyme is resistant to a cathepsin D-like proteinase present in cyclorrhaphous Diptera and displays a chitinase activity which is 11-fold higher than that of chicken lysozyme. Microsequencing of an internal peptide of the purified lysozyme showed that this enzyme is the product of the previously sequenced Lys D gene. The results suggest that the product of the Lys P gene has pI 7.2, a pH optimum around 5 and is not a true digestive enzyme. The most remarkable sequence convergence of D. melanogaster lysozyme D and lysozymes from vertebrate foregut fermenters are serine 104 and a decrease in the number of basic amino acids, suggesting that these features are necessary for digestive function in an acid environment. Adaptive residues putatively conferring stability in an acid proteolytic environment differ between insects and vertebrates, probably because they depend on the overall three-dimensional structure of the lysozymes. A maximum likelihood phylogeny and inferences from insect lysozyme sequences showed that the recruitment of lysozymes as digestive enzymes is an ancestral condition of the flies (Diptera: Cyclorrhapha).     

Guided bone regeneration in dental implant treatment using a bioabsorbable membrane

1. Australia has some of the most venomous fauna in the world. Although humans are not usually perceived as being predators against these animals they are often envenomated, accidentally or otherwise. This has led to the development of antivenoms against some of the potentially lethal venoms. However, further understanding of the mechanism(s) of action of these and other venoms is important, not only for developing new treatment strategies but also in the search for novel research tools. 2. The present review discusses the pharmacology of some of the components found in venoms and outlines the research undertaken on some of Australia's venomous animals, with the exception of snakes. 3. Biogenic amines, peptides and enzymes are common venom components and produce a wide range of effects in envenomated humans. For example, respiratory failure observed after envenomation by the box jellyfish (Chirnex fleckeri) and Sydney funnel-web spider (Atrax robustus) is most likely due to potent neurotoxins in the venoms. Stonefish (Synanceja trachynis) and platypus (Ornithorhynchus anatinus) venoms, although not considered lethal, cause severe pain. However, the components responsible for these effects have not been isolated. Venom components, as yet unidentified, may be responsible for the cutaneous necrotic lesions that have been reported after some spider bites (e.g. Lampona cylindrata). Other venoms, such as those of the jumper ant (Myrmecia pilosula) and bull ant (M. pyriformis), may produce only mild skin irritation to the majority of humans but a severe anaphylactic response in sensitized victims. 4. While there has been a renewed interest in toxinology, further research is required to fully elucidate the pharmacological action of many of these venoms.