Visual adaptation to convexity in macaque area V4

Aftereffects are perceptual illusions caused by visual adaptation to one or more stimulus attribute, such as orientation, motion, or shape. Neurophysiological studies seeking to understand the basis of visual adaptation have observed firing rate reduction and changes in tuning of stimulus-selective neurons following periods of prolonged visual stimulation. In the domain of shape, recent psychophysical work has shown that adaptation to a convex pattern induces a subsequently seen rectangle to appear slightly concave. In the present study, we investigate the possible contribution of V4 neurons of rhesus monkeys, which are thought to be involved in the coding of convexity, to shape-specific adaptation. Visually responsive neurons were monitored during the brief presentation of simple shapes varying in their convexity level. Each test presentation was preceded by either a blank period or several seconds of adaptation to a convex or concave stimulus, presented in two different sizes. Adaptation consistently shifted the tuning of neurons away from the convex or concave adapter, including shifting response to the neutral rectangle in the direction of the opposite convexity. This repulsive shift resembled the known perceptual distortion associated with adaptation to such stimuli. In addition, adaptation caused a nonspecific response decrease, as well as a specific decrease for repeated stimuli. The latter effects were observed whether or not the adapting and test stimuli matched closely in their size. Taken together, these results provide evidence for shape-specific adaptation of neurons in area V4, which may contribute to the perception of the convexity aftereffect.

Reorganization of the cerebro-cerebellar network of language production in patients with congenital left-hemispheric brain lesions

Patients with congenital lesions of the left cerebral hemisphere may reorganize language functions into the right hemisphere. In these patients, language production is represented homotopically to the left-hemispheric language areas. We studied cerebellar activation in five patients with congenital lesions of the left cerebral hemisphere to assess if the language network is reorganized completely in these patients, i.e. including also cerebellar language functions. As compared to a group of controls matched for age, sex, and verbal IQ, the patients recruited an area not in the right but in the left cerebellar hemisphere. The extent of laterality of the cerebellar activation correlated significantly with the laterality of the frontal activation. We suggest that the developing brain reacts to early focal lesions in the left hemisphere with a mirror-image organization of the entire cerebro-cerebellar network engaged in speech production.

[Comparative in vitro analysis of vacuum plasma-sprayed titanium implants--evaluation of OPG, Osteokalzin and AP expression]

INTRODUCTION

The purpose of this study was to evaluate the influence of different surface topographies on the expression of bone cell-associated proteins, such as osteoprotegerin (OPG), osteocalcin and alkaline phosphatase (AP), and the production of the extracellular matrix (ECM) in vitro. Another aspect was the question as to whether a hydroxyapatite (HA) coating offers additional advantages. Vacuum plasma-sprayed (VPS) pure titanium was used to generate different surface topographies.

MATERIALS AND METHODS

The in vitro response of human bone marrow cells to VPS implants (porosity ranging from 25 to 50%, pore size ranging from 50 to 200 microm and roughness ranging from 0.191 to 0.547 mm) and cancellous structured titanium (cs-Ti) as a reference material (55% porosity, pore size of 500 microm, roughness 0.836 mm) were compared. The expression of bone cell-associated proteins, such as OPG, osteocalcin and alkaline phosphatase (AP), was evaluated. Scanning electron microscopy (SEM) was used to judge the production of ECM.

RESULTS

All implant materials induced the release of OPG, osteocalcin and AP. Significant differences were evident between the cs-Ti and the different VPS-Ti surface structures. There was no difference in the response between the VPS-Ti surfaces. SEM showed a dense and increased production of ECM on the VPS-Ti surfaces. An additional HA coating caused a faster production of ECM and higher levels of OPG.

CONCLUSIONS

The in vitro data presented here demonstrate the superiority of VPS-Ti surfaces over cs-Ti, which is already in clinical use. Differences between the VPS-Ti surfaces were not evident. Presumably, VPS-Ti surfaces offer good prerequisites for a successful integration of the implant in the surrounding tissue. An additional HA coating could influence these events positively.

Diffusion-weighted magnetic resonance imaging of treatment-associated changes in recurrent and residual medulloblastoma: preliminary observations in three children

PURPOSE

To emphasize a possible role of magnetic resonance (MR) diffusion-weighted imaging (DWI) for lesion conspicuity and detection of treatment effects in children with medulloblastoma.

MATERIAL AND METHODS

Three children with medulloblastoma (two residual and one recurrent) were examined repetitively by MR diffusion-weighted imaging. Regional assessment of the apparent diffusion coefficient (ADC) was done for tumorous lesions and periventricular white matter appearing normal on standard MR images.

RESULTS

All lesions were clearly visible on DWI. In the case of recurrent tumor, on one scan, DWI showed lesions that were not seen on contrast-enhanced MRI. Increase (41%) of ADC was seen in one lesion, which subsequently responded completely to treatment over 27 months' follow-up. Intermediate increases (23-26%) of ADC were found with partial therapy response in three lesions. In contrast, a decrease (-11%) of ADC in two lesions was seen with tumor progression.

CONCLUSION

These observations may suggest a role for DWI in early detection of metastatic disease and treatment monitoring of medulloblastoma, warranting a formal study.

The diallelic locus encoding the minor histocompatibility antigen HA-1 is evolutionarily conserved

The polymorphic minor histocompatibility antigen HA-1 induces powerful T-cell alloreactivities with important consequences for graft-vs-tumor activity and development of graft-vs-host disease in patients after human leukocyte antigen-matched stem-cell transplantation (SCT). In view of possible translational animal studies, we analyzed the evolutionary conservation of the diallelic HA-1 locus in four mammalian species. Our results show that rodents do not encode the HA-1(H) allele, neither show polymorphism in this position on the HA-1 gene. Contrariwise, the HA-1(H) allele is present in non-human primate species and dogs. Interestingly, both the HA-1(H) T-cell epitope and its non-immunogenic counterpart HA-1(R) are present in the latter species. Thus, the HA-1 allelic polymorphism is conserved in evolution in primates and dogs.

[Maillard reaction products in food as pro-inflammatory and pro-arteriosclerotic factors of degenerative diseases]

Heating of food induces the formation of Maillard reaction products (MRPs) caused by the reaction of reducing sugars with proteins or amino acids. Analogous reactions occur in the human body, eventually forming "Advanced Glycation Endproducts" (AGEs). AGEs accumulate in aging tissues accelerating degenerative-inflammatory and proliferative processes. MRPs present in food can also directly cause inflammatory processes in the intestines and, once absorbed, would support and reinforce any inflammatory and degenerative process occurring in the body. The contribution of AGEs (and additional MRPs) in the development of diabetic complications as well as nephropathy, neuropathy, micro- and macroangiopathies is now well established. Which of the MRPs or AGEs in particular induce these cellular processes is currently unknown. Thus the exact knowledge of the chemical structures of the MRPs could help to minimize the formation of "harmful MRPs" that occur due to heating in food processing. Because MRPs play a decisive role in the successful marketing of edibles due to their characteristics as flavor components, it is important to increase the amount of innocuous and palatable MRPs, and minimize signal active pro-inflammatory MRPs by the use of defined preparation methods. It is practicable to use low-priced immunological methods for the quantitative determination of specific MRPs or AGEs. In the medical area, the knowledge of the signal active MRP/AGE structures provides the opportunity to measure their concentrations in body fluids and tissues and thus determine their influence on inflammatory and age-related degenerative processes (e. g., late diabetic complications, arteriosclerosis, degeneration of neurons). From a clinical perspective, the application of RAGE antagonists after an appropriate chemical diagnosis could be effective in supporting the treatment of affected patient groups, especially older diabetic and dialysis patients.

[Ocular changes in tropical malaria with cerebral involvement--results from the Blantyre Malaria Project]

INTRODUCTION

Malaria is a tropical disease causing an estimated 300 million infections and one million deaths per year. In sub-Saharan Africa, most infections are due to Plasmodium falciparum. The hallmark of the clinical syndrome of cerebral malaria is coma, and the associated mortality rate, even in appropriately treated patients, is 15 - 50 %. Funduscopy plays a major role for the ophthalmologist in the differential diagnosis because of the characteristic changes.

METHODS

To date more than 1000 children who satisfied the standard clinical case definition of cerebral malaria were admitted to the Blantyre Malaria Project (Malawi, Africa) for inpatient treatment and examined using indirect ophthalmoscopy through fully dilated pupils. The gender distribution was homogeneous and the children were between 2 and 14 years old. The optic nerve head, central and peripheral retina and central and peripheral vessels were described and photographed using a hand-held fundus camera (KOWA).

RESULTS

The spectrum and severity of findings of the ocular fundus in children with CM include the following distinct entities: haemorrhages (with and without a white centre), cotton wool spots, papilloedema, retinal whitening and retinal vessel abnormalities that may appear to be orange or white. Most of the retinal haemorrhages (in 40 %) have white centres and resemble Roth spots. Cotton wool spots were seen in only 5 %. Papilloedema was also not commonly seen (8 %) but is a poor prognostic sign. Retinal whitening (in 50 %) is seen more commonly at the posterior pole than in the periphery. 20 % of patients show retinal vessel abnormalities that may be orange or white in colour.

CONCLUSION

Ocular fundus changes in CM can be detected by the ophthalmologist using simple means and are decisive for the prognosis and timely therapy for this potentially lethal disease.

1H-MRS alterations in the cerebellum of patients with familial hemiplegic migraine type 1

BACKGROUND

About 20% of patients with familial hemiplegic migraine (FHM) develop progressive cerebellar signs. Genetic studies have established an association with mutations in the CACNA1A gene. However, the mechanisms underlying cerebellar involvement are largely unknown.

OBJECTIVE

To use proton MR spectroscopy (1H-MRS) to investigate metabolic alterations in the cerebellum as well as cortical regions known to be involved in the propagation of migraine aura.

METHODS

Fifteen CACNA1A mutation carriers from three FHM families and 17 healthy control subjects were studied. Eleven patients had clinical signs of cerebellar involvement. LCModel fits were used to estimate absolute concentrations of N-acetyl aspartate (NAA), myo-inositol (mI), glutamate (Glu), choline-containing compounds, total creatine, and lactate in the superior cerebellar vermis (SCV), parietal cortex, and occipital cortex. To control for atrophy effects, automated image segmentation was performed using SPM99. The brain parenchyma fraction (BPF) was determined for all three regions.

RESULTS

Compared with controls, the brain parenchyma fraction (BPF), NAA, and Glu were significantly reduced and mI was significantly elevated in the SCV of patients with FHM. In contrast, no metabolite alterations were found in supratentorial regions. BPF and NAA in the SCV significantly correlated with cerebellar scores, in particular, gait ataxia.

CONCLUSIONS

The findings suggest that there is a regionally distinct neuronal impairment in the superior cerebellar vermis that exceeds macroscopic tissue loss. Correlations with clinical scores emphasize the functional relevance of localized atrophy (brain parenchyma fraction) and N-acetyl aspartate levels. These measures may be useful to monitor disease progression. The observed reduction in glutamate may in part reflect impaired glutamatergic neurotransmission.

Histomorphometrische Evaluation poröser Titanprobenkörper anhand eines computergestützten Bildanalysesystems / Histomorphometric evaluation of bone ingrowth of porous titanium by a computer-assisted analyzing system

The objective of this study was to evaluate the bone ingrowth of a new vacuum plasma sprayed titanium surface (vps-ti) in comparison to cs-titanium implants in a göttinger minipig model. Fifteen göttinger minipigs each received the two implants, vacuum plasma sprayed titanium with a porosity of 50% and a pore size of 200 microm (vps-ti) and an implant with a similar porosity but a different pore size 500 microm (cs-ti), at the proximal femur metaphysis by press-fit technique. The pigs were euthanized at three different postsurgical periods: 4, 8 and 12 weeks. Each femur was harvested and qualitative (macroscopic and microscopic) and quantitative (histomorphometric) histological analysis was done on histological slides. The results indicated that there was a difference in bone ingrowth between the two implants, whereas the bone ingrowth of vps-ti was superior to cs-ti after 4 and 8 weeks healing time. 12 weeks post implantationem no statistiscal difference was evident. The pore size of 200 microm seemed superior to a pore size of 500 microm. Whether or not these effects lead to a better mechanical stability remains unanswered.

Escherichia coli-nitroreductase suicide gene control of human telomerase reverse transcriptase-transduced minor histocompatibility antigen-specific cytotoxic T cells

Adoptive immunotherapy with ex vivo generated cytotoxic T lymphocytes (CTLs) is applied for the treatment of leukemia relapses or viral infections after allogeneic stem cell transplantation. A common problem of adoptive immunotherapy strategies is the ex vivo expansion of the generated T cells to sufficient numbers. CTLs can be efficiently expanded by ectopic expression of the human telomerase gene (hTert). However, hTert transduction may also increase the chance for malignant transformation. Therefore, we explored the feasibility of suicide gene control of ex vivo generated CTLs expanded through the ectopic expression of hTert. To this end, we compared the efficacy of the new Escherichia coli-nitroreductase (E. coli-Ntr) suicide gene with the well-known herpes simplex virus-thymidine kinase (HSV-Tk). Introduction of hTert provided the transduced CTLs with a distinct growth advantage over the nontransduced CTLs. The hTert-E. coli-Ntr double-transduced CTLs retained their antigen-specific functions. Treatment of hTert-E. coli-Ntr double-transduced CTLs with metronidazole significantly inhibited the proliferation to a similar extent to the treatment of hTert-HSV-Tk double-transduced CTLs with ganciclovir. This is the first application of the E. coli-nitroreductase gene for the elimination of human T cells with metronidazole.

The prevention of intrapartum HIV/AIDS transmission from mother to child

The transmission of HIV/AIDS from mother to child is the main cause of HIV/AIDS in children and child mortality. Two-thirds of children with HIV/AIDS are infected in the intrapartum period (Farley, 2000:1-2). Midwives, through effective practices, can lower the transmission of HIV/AIDS from mother to child in the intrapartum period. The aim of the study was to determine which preventive practices registered midwives in provincial labour wards in Bloemfontein, implement to lower the risk of mother to child transmission of HIV/AIDS and in doing so to lower child mortality. A descriptive research design was used. Fifty-one midwives completed questionnaires to determine what preventive practices are used. The study showed that most of the midwives did not implement the interventions that could lower the chances of HIV/Aids transmission from mother to child during the intrapartum period. Midwives therefore may not have a positive impact on child mortality. The researchers concluded that midwives do not implement the interventions mentioned in the study because of a lack of knowledge and skills. Of the midwives who completed questionnaires, 67% completed their training between 1990 and 2000. This lack of knowledge may be due to a lack in the curriculum of training institutions and of an up-to-date policy concerning the transmission of HIV/Aids in provincial institutions in Bloemfontein. It is recommended that all affordable interventions should be incorporated in the policy.

DRG-based cost analysis of inpatient conservative treatment of PAD stage III/IV

Hintergrund: In einer von der Deutschen Gesellschaft für Angiologie (DGA) und dem DRG Competence Center, München, durchgeführten prospektiven Studie wurde geprüft, ob die Kosten für eine konservative Behandlung von Patienten mit PAVK Stadium III/IV (DRG F65) im derzeitigen G-DRG-System adäquat abgebildet sind. Methode und Patienten: Im Zeitraum vom 1. September. bis 16. Dezember 2002 wurden an acht angiologischen Zentren in Deutschland insgesamt 704 Patienten mit der DRG F65 (periphere Gefäßerkrankungen) ausgewertet. Neben der Verweildauer im Krankenhaus wurden die Gesamtkosten (Kostenäquivalente) nach einer von der DRG Research Group der Universität Münster entwickelten Methodik berechnet. Darüber hinaus erfolgte ein Vergleich des Studienkollektivs mit einer von InEK veröffentlichten bundesdeutschen Kalkulationsstichprobe für die DRGs F65A/B. Ergebnisse: Es zeigte sich, dass konservativ behandelte Patienten mit einer PAVK Stadium III/IV (DRGs F65A/B) signifikant mehr Kosten verursachen (p < 0,001) und signifikant längere Verweildauern (p < 0,001) aufweisen als Patienten, die wegen anderer Gefäßerkrankungen ebenfalls in die DRG F65 eingruppiert wurden. Gleichzeitig wurde deutlich, dass angiologische Zentren doppelt so viele Patienten mit kritischer Extremitätenischämie behandeln, wie dies im bundesdeutschen Mittel der Fall ist. Die von InEK bislang veranschlagte Vergütung deckt nicht einmal die Hälfte der tatsächlich entstandenen Kosten für die konservative Therapie der PAVK Stadium III/IV. Schlussfolgerung: Um eine leistungsgerechte Vergütung zu gewährleisten, muss – wie von der DGA beantragt – eine neue Basis-DRG für Patienten mit PAVK Stadium III/IV gebildet werden. Andernfalls wird in Zukunft eine adäquate – den Leitlinien entsprechende – konservative Therapie dieser Patienten, die weder operativ noch interventionell behandelt werden können, nicht mehr möglich sein.

Normative pediatric brain data for spatial normalization and segmentation differs from standard adult data

Spatial normalization and morphological studies of pediatric brain imaging data based on adult reference data may not be appropriate due to the developmental differences between the two populations. In this study, we set out to create pediatric templates and a priori brain tissue data from a large collection of normal, healthy children to compare it to standard adult data available within a widely used imaging software solution (SPM99, WDOCN, London, UK). Employing four different processing strategies, we found considerable differences between our pediatric data and the adult data. We conclude that caution should be used when analyzing pediatric brain data using adult a priori information. To assess the effects of using pediatric a priori brain information, the data obtained in this study is available to the scientific community from our website (www.irc.cchmc.org).