Oculomotor randomness is higher in autistic children and increases with the severity of symptoms

A variety of studies have suggested that at least some children with autism spectrum disorder (ASD) view the world differently. Differences in gaze patterns as measured by eye tracking have been demonstrated during visual exploration of images and natural viewing of movies with social content. Here we analyzed the temporal randomness of saccades and blinks during natural viewing of movies, inspired by a recent measure of "randomness" applied to micro-movements of the hand and head in ASD (Torres et al., 2013; Torres & Denisova, 2016). We analyzed a large eye-tracking dataset of 189 ASD and 41 typically developing (TD) children (1-11 years old) who watched three movie clips with social content, each repeated twice. We found that oculomotor measures of randomness, obtained from gamma parameters of inter-saccade intervals (ISI) and blink duration distributions, were significantly higher in the ASD group compared with the TD group and were correlated with the ADOS comparison score, reflecting increased "randomness" in more severe cases. Moreover, these measures of randomness decreased with age, as well as with higher cognitive scores in both groups and were consistent across repeated viewing of each movie clip. Highly "random" eye movements in ASD children could be associated with high "neural variability" or noise, poor sensory-motor control, or weak engagement with the movies. These findings could contribute to the future development of oculomotor biomarkers as part of an integrative diagnostic tool for ASD.

SNG100, a novel topical treatment for moderate atopic dermatitis, in patients aged 6 years or older: A randomised, double-blind, active-controlled trial

Background

Atopic dermatitis (AD) is one of the most common inflammatory skin diseases. It is associated with significant itch and impaired quality of life. Systemic treatments are efficient but associated with side effects. Novel topical treatments with a favourable safety profile are needed. SNG100 is a novel composition of hydrocortisone 1% in a cream base comprising sulphated polysaccharide (SPS; extracted from in-house cultivated Porphyridium Cruentum unicellular algae), a well-known hydrating, moisturising and a skin barrier repairing agent.

Objectives

To assess the safety, usability and efficacy of SNG100 cream in patients aged ≥6 years with moderate AD.

Methods

In this proof of concept phase I, double-blind, randomised trial, participants received one of three treatments for 14 days: SNG100 twice daily (BID), hydrocortisone 1% BID or mometasone furoate once daily (QD). The primary endpoint was the safety and tolerability of SNG100 cream compared to hydrocortisone 1% and mometasone furoate. The secondary endpoint was the subject's usability of SNG100. Exploratory efficacy endpoints included percent change from baseline in SCOring AD (SCORAD), Eczema Area and Severity Index, Patient-Oriented Eczema Measure, Dermatology Life Quality Index, pruritus Numerical Rating Score (NRS), peak pruritus-NRS and Investigator's Global Assessment. Subjects were also followed up without any treatment for additional 14 days.

Results

Overall, 66 participants were screened, and 60 patients were randomised. SNG100 demonstrated a high safety profile, similar to marketed products hydrocortisone 1% and mometasone furoate 0.1%, with no unanticipated drug safety related events. SNG100 and mometasone furoate 0.1% cream achieved almost similar and statistically significant greater percentage reductions from baseline in SCORAD as compared to hydrocortisone 1% cream. SNG100 demonstrated significant improvement in NRS as compared to hydrocortisone 1% cream. Remarkably, SNG100 led to a lasting effect with only 29.4% of subjects returning to IGA3 during the follow-up period compared to 50% and 38.9% in the hydrocortisone 1% and in mometasone furoate treatment arms, respectively.

Conclusions

Topical SNG100 is an effective, safe, and well-tolerated innovative treatment for moderate AD. Trial registration number: NCT04615962 (Topical Cream SNG100 for Treatment in Moderate AD Subjects).

Genome dilution by cell growth drives starvation-like proteome remodeling in mammalian and yeast cells

Cell size is tightly controlled in healthy tissues and single-celled organisms, but it remains unclear how size influences cell physiology. Increasing cell size was recently shown to remodel the proteomes of cultured human cells, demonstrating that large and small cells of the same type can be biochemically different. Here, we corroborate these results in mouse hepatocytes and extend our analysis using yeast. We find that size-dependent proteome changes are highly conserved and mostly independent of metabolic state. As eukaryotic cells grow larger, the dilution of the genome elicits a starvation-like proteome phenotype, suggesting that growth in large cells is limited by the genome in a manner analogous to a limiting nutrient. We also demonstrate that the proteomes of replicatively-aged yeast are primarily determined by their large size. Overall, our data suggest that genome concentration is a universal determinant of proteome content in growing cells.

Protein aggregation and the evolution of stress resistance in clinical yeast

Protein aggregation, particularly in its prion-like form, has long been thought to be detrimental. However, recent studies have identified multiple instances where protein aggregation is important for normal physiological functions. Combining mass spectrometry and cell biological approaches, we developed a strategy for the identification of protein aggregates in cell lysates. We used this approach to characterize prion-based traits in pathogenic strains of the yeast Saccharomyces cerevisiae isolated from immunocompromised human patients. The proteins that we found, including the metabolic enzyme Cdc19, the translation elongation factor Yef3 and the fibrillarin homologue Nop1, are known to assemble under certain physiological conditions. Yet, such assemblies have not been reported to be stable or heritable. Our data suggest that some proteins which aggregate in response to stress have the capacity to acquire diverse assembled states, certain ones of which can be propagated across generations in a form of protein-based epigenetics. This article is part of the theme issue 'How does epigenetics influence the course of evolution?'

Oculomotor inhibition during smooth pursuit and its dependence on contrast sensitivity

Our eyes are never still, but tend to "freeze" in response to stimulus onset. This effect is termed "oculomotor inhibition" (OMI); its magnitude and time course depend on the stimulus parameters, attention, and expectation. We previously showed that the time course and duration of microsaccade and spontaneous eye-blink inhibition provide an involuntary measure of low-level visual properties such as contrast sensitivity during fixation. We investigated whether this stimulus-dependent inhibition also occurs during smooth pursuit, for both the catch-up saccades and the pursuit itself. Observers followed a target with continuous back-and-forth horizontal motion while a Gabor patch was briefly flashed centrally with varied spatial frequency and contrast. Catch-up saccades of the size of microsaccades had a similar pattern of inhibition as microsaccades during fixation, with stronger inhibition onset and faster inhibition release for more salient stimuli. Moreover, a similar stimulus dependency of inhibition was shown for pursuit latencies and peak velocity. Additionally, microsaccade latencies at inhibition release, peak pursuit velocities, and latencies at minimum pursuit velocity were correlated with contrast sensitivity. We demonstrated the generality of OMI to smooth pursuit for both microsaccades and the pursuit itself and its close relation to the low-level processes that define saliency, such as contrast sensitivity.

A perturbed ubiquitin landscape distinguishes between ubiquitin in trafficking and in proteolysis

Any of seven lysine residues on ubiquitin can serve as the base for chain-extension, resulting in a sizeable spectrum of ubiquitin modifications differing in chain length or linkage type. By optimizing a procedure for rapid lysis, we charted the profile of conjugated cellular ubiquitin directly from whole cell extract. Roughly half of conjugated ubiquitin (even at high molecular weights) was nonextended, consisting of monoubiquitin modifications and chain terminators (endcaps). Of extended ubiquitin, the primary linkages were via Lys48 and Lys63. All other linkages were detected, contributing a relatively small portion that increased at lower molecular weights. In vivo expression of lysineless ubiquitin (K0 Ub) perturbed the ubiquitin landscape leading to elevated levels of conjugated ubiquitin, with a higher mono-to-poly ratio. Affinity purification of these trapped conjugates identified a comprehensive list of close to 900 proteins including novel targets. Many of the proteins enriched by K0 ubiquitination were membrane-associated, or involved in cellular trafficking. Prime among them are components of the ESCRT machinery and adaptors of the Rsp5 E3 ubiquitin ligase. Ubiquitin chains associated with these substrates were enriched for Lys63 linkages over Lys48, indicating that K0 Ub is unevenly distributed throughout the ubiquitinome. Biological assays validated the interference of K0 Ub with protein trafficking and MVB sorting, minimally affecting Lys48-dependent turnover of proteasome substrates. We conclude that despite the shared use of the ubiquitin molecule, the two branches of the ubiquitin machinery—the ubiquitin-proteasome system and the ubiquitin trafficking system—were unevenly perturbed by expression of K0 ubiquitin.

Together, Rpn10 and Dsk2 can serve as a polyubiquitin chain-length sensor

As a signal for substrate targeting, polyubiquitin meets various layers of receptors upstream to the 26S proteasome. We obtained structural information on two receptors, Rpn10 and Dsk2, alone and in complex with (poly)ubiquitin or with each other. A hierarchy of affinities emerges with Dsk2 binding monoubiquitin tighter than Rpn10 does, whereas Rpn10 prefers the ubiquitin-like domain of Dsk2 to monoubiquitin, with increasing affinities for longer polyubiquitin chains. We demonstrated the formation of ternary complexes of both receptors simultaneously with (poly)ubiquitin and found that, depending on the ubiquitin chain length, the orientation of the resulting complex is entirely different, providing for alternate signals. Dynamic rearrangement provides a chain-length sensor, possibly explaining how accessibility of Dsk2 to the proteasome is limited unless it carries a properly tagged cargo. We propose a mechanism for a malleable ubiquitin signal that depends both on chain length and combination of receptors to produce tetraubiquitin as an efficient signal threshold.

Extraproteasomal Rpn10 restricts access of the polyubiquitin-binding protein Dsk2 to proteasome

Polyubiquitin is a diverse signal both in terms of chain length and linkage type. Lysine 48-linked ubiquitin is essential for marking targets for proteasomal degradation, but the significance and relative abundance of different linkages remain ambiguous. Here we dissect the relationship of two proteasome-associated polyubiquitin-binding proteins, Rpn10 and Dsk2, and demonstrate how Rpn10 filters Dsk2 interactions, maintaining proper function of the ubiquitin-proteasome system. Using quantitative mass spectrometry of ubiquitin, we found that in S. cerevisiae under normal growth conditions the majority of conjugated ubiquitin was linked via lysine 48 and lysine 63. In contrast, upon DSK2 induction, conjugates accumulated primarily in the form of lysine 48 linkages correlating with impaired proteolysis and cytotoxicity. By restricting Dsk2 access to the proteasome, extraproteasomal Rpn10 was essential for alleviating the cellular stress associated with Dsk2. This work highlights the importance of polyubiquitin shuttles such as Rpn10 and Dsk2 in controlling the ubiquitin landscape.

The human sef-a isoform utilizes different mechanisms to regulate receptor tyrosine kinase signaling pathways and subsequent cell fate

Negative feedback is among the key mechanisms for regulating receptor tyrosine kinase (RTK) signaling. Human Sef, a recently identified inhibitor of RTK signaling, encodes different isoforms, including a membrane spanning (hSef-a) and a cytosolic (hSef-b) isoform. Previously, we reported that hSef-b inhibited fibroblast proliferation and prevented the activation of mitogen-activated protein kinase (MAPK), without affecting protein kinase B/Akt or p38 MAPK. Conflicting results were reported concerning hSef-a inhibition of MAPK activation, and the effect of hSef-a on other RTK-induced signaling pathways is unknown. Here we show that, in fibroblasts, similar to hSef-b, ectopic expression of hSef-a inhibited fibroblast growth factor-induced cell proliferation. Unlike hSef-b, however, the growth arrest was mediated via a MAPK-independent mechanism, and was accompanied by elevated p38 MAPK phosphorylation and inhibition of protein kinase B/Akt. In addition, hSef-a, but not hSef-b, mediated apoptosis in fibroblast growth factor-stimulated cells. Chemical inhibitor of p38 MAPK abrogated the effect of hSef-a on apoptosis. In epithelial cells, ectopic expression of hSef-a inhibited the activation of MAPK, whereas down-regulation of endogenous hSef-a significantly increased MAPK activation and accelerated growth factor-dependent cell proliferation. These results indicate that hSef-a is a multifunctional negative modulator of RTK signaling and clearly demonstrate that hSef-a can inhibit the activation of MAPK, although in a cell type-specific manner. Moreover, the differences between the activities of hSef-a and hSef-b suggest that hSef isoforms can control signal specificity and subsequent cell fate by utilizing different mechanisms to modulate RTK signaling.

Alternative splicing generates an isoform of the human Sef gene with altered subcellular localization and specificity

Receptor tyrosine kinases (RTKs) control a multitude of biological processes and are therefore subjected to multiple levels of regulation. Negative feedback is one of the mechanisms that provide an effective means to control RTK-mediated signaling. Sef has recently been identified as a specific antagonist of fibroblast growth factor (FGF) signaling in zebrafish and subsequently in mouse and human. Sef encodes a putative type I transmembrane protein that antagonizes the Ras/mitogen-activated protein kinase pathway in all three species. Mouse Sef was also shown to inhibit the phosphatidylinositol 3-kinase pathway. We show here that an alternative splicing mechanism generates an isoform of human Sef, hSef-b, which unlike the previously reported Sef (hSef-a) is a cytosolic protein. Contrary to hSef-a, which is ubiquitously expressed, hSef-b transcripts display a restricted pattern of expression in human tissues. hSef-b inhibits FGF-induced cell proliferation and prevents the activation of mitogen-activated protein kinase without affecting the upstream component MAPK kinase. Furthermore, hSef-b does not antagonize FGF induction of the phosphatidylinositol 3-kinase pathway. In addition to the effects on FGF signaling, hSef-b inhibited cellular response to platelet-derived growth factor but not other RTK ligands. Therefore, alternative splicing of the hSef gene expands the Sef feedback inhibition repertoire of RTK signaling.

Molecular biology of dopamine-induced apoptosis : possible implications for Parkinson's disease

The causes for the highly selective loss of dopaminergic neurons in the substantia nigra pars compacta in Parkinson's disease (PD) are still unknown. However, a major advance has been recently made with the introduction of the concept of apoptosis as the route leading this specific neuronal population to degeneration. Apoptosis, or programmed cell death (PCD), is an active, controlled program inherent in every living cell. Upon receiving certain signals, cells that are destined to die undergo a highly characteristic process of "suicide." This process consists of massive biochemical and morphological alterations, including cell shrinkage, loss of cell-to-cell contacts, blebbing of cell membranes, cytoskeletal rearrangements, and DNA condensation and fragmentation. It culminates in cell conversion to membrane-bound particles (apoptotic bodies) that are ready to be digested by neighboring macrophages (1-3).

The role of glutamatergic transmission in the pathogenesis of levodopa-induced dyskinesias. Potential therapeutic approaches

Dyskinesias are the most frequent adverse effect of chronic levodopa therapy in patients with Parkinson's disease (PD). Current pharmacological treatment for this problem is unsatisfactory. Recently, there is evidence for the role of glutamate in the basal ganglia neuronal circuitry in the generation of dyskinesias. If indeed glutamatergic overactivity beyond the dopaminergic synapses plays a role in the pathogenesis of these involuntary movements, there is hope that its suppression may be beneficial without causing loss of levodopa efficacy and parkinsonian deterioration. Indeed, NMDA receptor antagonists such as amantadine and dextrometorphan can reduce such dyskinesias. We tested the efficacy of riluzole, an inhibitor of glutamatergic transmission in the inhibition of levodopa-induced dyskinesias.

The effect of deprenyl washout in patients with long-standing Parkinson's disease

Deprenyl, an irreversible MAO-B inhibitor, is known to have a symptomatic effect in de novo patients with Parkinson's disease (PD). It has, however, not been studied thoroughly in patients with advanced PD and response fluctuations. This study evaluated the effect of washout of deprenyl in patients with long-standing PD. Eleven PD patients who were on chronic treatment with deprenyl (mean age 57 +/- 8 years, mean disease duration 8.4 +/- 2.9 years), seven with response fluctuations, were enrolled in a double-blind study of a novel MAO-B inhibitor. A deprenyl washout period of one month was required prior to initiation of treatment with the trial drug. Patients were evaluated by Unified Parkinson's Disease Rating scale (UPDRS) before and one month after the washout period. Motor function was quantified by computerized tapping speed and movement time test. Results showed that neither total UPDRS scores (22 +/- 16 vs. 18 +/- 16, respectively) nor tapping speed and movement time changed significantly (4.4 +/- 0.5 vs. 4.2 +/- 0.3 Hz and 159 +/- 45 vs. 161 +/- 40 seconds; p > 0.1, respectively). However, eight patients reported various degrees of subjective deterioration, among them were the seven fluctuating patients. Two patients first began to experience response fluctuations during the washout period. It seems that deprenyl has a symptomatic effect, especially in patients with response fluctuations, and it may postpone the appearance of fluctuations in patients with PD. Attempts to discontinue treatment with deprenyl may aggravate disease symptoms.

The molecular mechanism of dopamine-induced apoptosis: identification and characterization of genes that mediate dopamine toxicity

Parkinson's disease (PD) is a progressive neurological disorder caused by rather selective degeneration of the dopaminergic (DA) neurons in the substantia nigra. Though subject to intensive research, the etiology of this nigral neuronal loss is still enigmatic and treatment is basically symptomatic. The current major hypothesis suggests that nigral neuronal death in PD is due to excessive oxidative stress generated by auto- and enzymatic oxidation of the endogenous neurotransmitter dopamine (DA), the formation of neuromelanin and presence of high concentrations of iron. We have found that DA toxicity is mediated through its oxidative metabolites. Whereas thiol-containing antioxidants provided marked protection against DA toxicity, ascorbic acid accelerated DA-induced death. Using the differential display approach, we sought to isolate and characterize genes whose expression is altered in response to DA toxicity. We found an upregulation of the collapsin response mediator protein (CRM) and TCP-1delta in sympathetic neurons, which undergo dopamine-induced apoptosis. The isolation of these genes led us to examine the expression and activity of CRM and TCP-1delta related genes. Indeed, we found a significant induction of mRNAs of the secreted collapsin-1 and the mitochondrial stress protein HSP60. Antibodies directed against collapsin-1 provided marked and prolonged protection of several neuronal cell types from dopamine-induced apoptosis. In a parallel study, using antisense technology, we found that inhibition of TCP-1delta expression significantly reduced DA-induced neuronal death. These findings suggest a functional role for collapsin-1 and TCP-1delta as positive mediators of DA-induced neuronal apoptosis.

The pharmacokinetic profile of the "first ever" oral dose of levodopa in de novo patients with Parkinson's disease

To understand the delay in the clinical benefit that commonly occurs after initiation of levodopa (L-Dopa) treatment, we examined the pharmacokinetic profile of L-Dopa after the first oral dose ever taken of L-Dopa/carbidopa in untreated patients with Parkinson's disease and followed these parameters after 1 month of treatment. This was performed in correlation with the clinical therapeutic effect. Plasma levels of L-Dopa were measured with use of high-performance liquid chromatography with electrochemical detection after administration of the "first ever" 125 mg L-Dopa/12.5 mg carbidopa tablet in 15 patients with de novo Parkinson's disease (mean age, 69 +/- 11 y, mean disease duration, 1.5 +/- 0.8 years). Blood samples were drawn before administration and thereafter at various intervals for a period of 4 hours. Repeated measurements after the same oral dose were performed after 1 month of continued therapy with L-Dopa/carbidopa 125/12.5 mg three times daily. Patients were clinically evaluated by unified Parkinson's disease rating scale motor scores. There was a modest clinical improvement after 1 month of continuous L-Dopa treatment (motor scores, 13.1 +/- 11.6 vs. 17.6 +/- 11.7; p < 0.01). Peak plasma L-Dopa levels and area under the curve did not differ significantly between the first-ever dose and after 1 month of continuous treatment (0.9 +/- 0.1 vs. 1.0 +/- 0.1 microg/mL and 66.0 +/- 30.9 vs. 86.2 +/- 34.9 microg/mL, respectively; p < 0.1. There was also no change in time to peak levels between measurements. Results indicate that the first-ever dose of oral L-Dopa is well absorbed and that pharmacokinetic mechanisms such as reduced absorption of L-Dopa probably do not play a major role in the initial delay in clinical response to oral L-Dopa/carbidopa in patients with Parkinson's disease. The latter phenomena may be linked to central pharmacodynamic mechanisms.

Involvement of T-complex protein-1delta in dopamine triggered apoptosis in chick embryo sympathetic neurons

The neurotransmitter dopamine (DA) is capable of inducing apoptosis in post-mitotic sympathetic neurons via its oxidative metabolites. The differential display method was applied to cultured sympathetic neurons in an effort to detect genes whose expression is transcriptionally regulated during the early stages of DA-triggered apoptosis. One of the up-regulated genes was identified as the chick homologue to T-complex polypeptide-1delta (TCP-1delta), a member of the molecular chaperone family of proteins. Each chaperone protein is a complex of seven to nine different subunits. A full-length clone of 1.9 kilobases was isolated containing an open reading frame of 536 amino acids with a predicted molecular weight of 57,736. Comparison with the mouse TCP-1delta revealed 78 and 91% homology on the DNA and protein levels, respectively. Northern blot analysis disclosed a steady and significant increase in mRNA levels of TCP-1delta after DA administration, reaching a peak between 4 and 9 h and declining thereafter. Induction of the TCP-1delta protein levels was also observed as a function of DA treatment. Overexpression of TCP-1delta in sympathetic neurons accelerated DA-induced apoptosis; inhibition of TCP-1delta expression in these neurons using antisense technology significantly reduced DA-induced neuronal death. These findings suggest a functional role for TCP-1delta as a positive mediator of DA-induced neuronal apoptosis.

Induction of neuronal apoptosis by Semaphorin3A-derived peptide

Collapsin-1/Semaphorin3A (Sema3A) belongs to the secreted type III semaphorins family of axon guidance molecules with chemorepulsive activity, and is suggested to play a major role in navigating axonal networks throughout development into their correct destinations. We have previously shown that semaphorins are mediators of neuronal apoptosis and can induce neuronal death in the absence of any other apoptotic trigger. We report here that exposure of neuronal cells to a small conserved peptide derived from Sema3A initiates an apoptotic death process. Administration of this peptide to cultured chick sympathetic and mouse cerebellar granule neurons caused a marked shrinkage of their axonal network and cell death, which was characterized as apoptotic, based on nuclear staining. Attenuation of neuronal cell death was obtained by treatment with antioxidants and by vascular endothelial growth factor. Survival of neurons exposed to this peptide increased by co-treatment with caspase inhibitors. Induction of apoptosis was specific to neuronal cells, similarly to that induced by the full-length Sema3A protein. Our findings therefore suggest active participation of this conserved Sema3A-derived peptide in semaphorin-induced neuronal death process.

Weanling ventromedial hypothalamic syndrome. bone geometry and biomechanics

The effect of growth-retarding, obesifying lesions in the ventromedial hypothalamic nucleus (VMN) on bone geometry and biomechanics was investigated in male weanling rats. The animals received bilateral, symmetrical, electrolytic lesions (VMNL rats) shortly after weanling (age 27 days); sham-operated rats served as controls (SCON). The rats were maintained for 42 postoperative days and then terminated. Body weight, nose-tail length, food intake, carcass water, and lean body mass were all significantly (p < 0.001) reduced in the VMNL group compared to SCON rats. Carcass fat, lipogenic efficiency (carcass fat % laid down/mean food intake) (both p < 0.001) and epididymal fat pad weight (p < 0.01) were significantly increased in VMNL versus SCON. Femur length, anteroposterior diameter (both p < 0.001), and mediolateral femur diameter (p < 0.01) were significantly reduced in VMNL versus SCON rats, but torque and angle of torque were comparable among the groups. VMNL rats femora also showed a significant greater maximum shear stress compared to the control animals. The reduced parameters in the VMNL rats are in good agreement with the previously demonstrated reduced plasma and pituitary growth hormone levels found in this hypothalamus preparation.

Effects of titanium prosthesis, offset and size of field of view on bone mineral density measurements using quantitative computed tomography

To estimate the accuracy of quantitative computed tomography (QCT) as a method to measure bone mineral density (BMD) in the vicinity of a titanium prosthesis, we investigated the effects of (1) titanium prosthesis, (2) offset of the longitudinal axis of the bone to be examined from that of the gantry of the CT scanner, (3) size of the field of view (FOV) and (4) the combination of these effects on CT based measurements of mineral density of cortical and cancellous bone specimens. 14 bovine cortical bone parallelepipeds and 14 bovine cancellous bone parallelepipeds were used in this investigation. The bone specimens were scanned with and without a titanium prosthesis, when centered in the gantry of the CT scanner and offset from the axis of the gantry of the CT scanner at a distance of 14 cm. Image data were then reconstructed separately with a FOV of 10 cm and 30 cm. All BMD values taken from CT images obtained under different scanning condition were compared with the BMD values of the corresponding bone parallelepiped obtained under standard condition (centered in the gantry of the CT scanner, 10 cm FOV, without titanium prosthesis). When centered in the gantry of the CT scanner, the mean relative difference of BMD measurements caused by the presence of the titanium prosthesis was less than 1% for both cortical bone and cancellous bone. Size of the FOV had a negligible effect on BMD measurements. Offset at 14 cm, however, caused a significant difference in BMD measurements (p < 0.001). It was concluded that titanium prosthesis did not interfere with BMD measurements of cortical and cancellous bone when both the specimen and prosthesis were centered in the gantry of the CT scanner. However, the effect on BMD measurements of offset at 14 cm combined with the presence of a titanium prosthesis in bone was significant.

Levodopa--an exotoxin or a therapeutic drug?

Auto-oxidation of levodopa generates toxic metabolites, such as free radicals, semiquinones and quinones. In vitro, levodopa is a powerful toxin that is lethal to cultures of neurones. This raises the concern that levodopa may also be toxic in vivo, and that chronic treatment with levodopa could induce further damage to nigrostriatal neurones in patients with Parkinson's disease, accelerating the natural predetermined rate of disease progression. Although a few animal studies have shown that chronic levodopa may be toxic in vivo, most others report that it is not. The few available clinical studies also indicate that the course of Parkinson's disease is not accelerated by chronic systemic treatment with levodopa.

[Apomorphine for treatment of "off-periods" in Parkinson's disease]

After 3-5 years of continuous use of 1-dopa preparations for Parkinson's disease, 25%-50% of patients develop side-effects such as the "on-off" phenomenon and involuntary movements that markedly impair function. One cause of these manifestations is evidently a disturbance in the absorption of 1-dopa. We attempted to avoid this problem by using subcutaneous injections. Apomorphine is a rapid-acting dopamine agonist which causes a return from "off" to "on" within minutes. We present the results of a trial of subcutaneous injections of apomorphine in 22 Parkinsonian patients (12 males, 10 females) with severe motor fluctuations. During 5 days prior to the apomorphine all received Motilium (domperidone, 60 mg/d) to prevent nausea and vomiting. All were hospitalized initially to determine optimal dosage and to teach them the technique of self-injection. 2 to 4 mg of apomorphine were injected 1 to 3 times daily for 2 to 12 months. In 17 patients (80%) "off" periods were reduced without significant side-effects. Apomorphine seems to be effective, tolerable treatment for shortening 1-dopa induced "off" periods.

Double-stranded hamstring tendons for anterior cruciate ligament reconstruction

Bone-patellar tendon-bone autograft is the most commonly used tissue for ACL reconstruction; however, the harvesting of patellar tendon as a free graft can lead to significant morbidity. Alternate grafts may lower morbidity, yet the most commonly used alternate grafts including the double-stranded semi-tendinosus or gracilis have not been studied biomechanically. This study investigated the morphometric and biomechanical properties of double-stranded semi-tendinosus and gracilis tendons separately along with the patellar and quadriceps tendons obtained bilaterally from six fresh, 77-year-old cadaveric specimens. The quadriceps tendon was the thickest and therefore had the largest cross-sectional area, whereas double-stranded semitendinosus had the highest mean peak load to failure (1029+/-158.4 N), 11.5% and 10.3% stronger than patellar tendon and quadriceps tendons, respectively. Midsubstance rupture occurred in the hamstring tendons, whereas the patellar and quadriceps tendons failed at the bone-tendon junctions. Semitendinosus tendons with higher cross-sectional area had higher peak loads to failure. This linear relationship between cross-sectional area and the peak load to rupture also was observed in the other tendon groups (except gracilis). These results indicate that despite a lower cross-sectional area of the double-stranded semitendinosus, this tendon demonstrated a comparable mean peak load to rupture and stress compared with patellar and quadriceps tendons. It also was demonstrated that combined double-stranded semitendinosus and gracilis tendons produce a stronger graft with initial strength twice that of the patellar tendon, but requires further testing.

Semaphorins as mediators of neuronal apoptosis

Shrinkage and collapse of the neuritic network are often observed during the process of neuronal apoptosis. However, the molecular and biochemical basis for the axonal damage associated with neuronal cell death is still unclear. We present evidence for the involvement of axon guidance molecules with repulsive cues in neuronal cell death. Using the differential display approach, an up-regulation of collapsin response mediator protein was detected in sympathetic neurons undergoing dopamine-induced apoptosis. A synchronized induction of mRNA of the secreted collapsin-1 and the intracellular collapsin response mediator protein that preceded commitment of neurons to apoptosis was detected. Antibodies directed against a conserved collapsin-derived peptide provided marked and prolonged protection of several neuronal cell types from dopamine-induced apoptosis. Moreover, neuronal apoptosis was inhibited by antibodies against neuropilin-1, a putative component of the semaphorin III/collapsin-1 receptor. Induction of neuronal apoptosis was also caused by exposure of neurons to semaphorin III-alkaline phosphatase secreted from 293EBNA cells. Anti-collapsin-1 antibodies were effective in blocking the semaphorin III-induced death process. We therefore suggest that, before their death, apoptosis-destined neurons may produce and secrete destructive axon guidance molecules that can affect their neighboring cells and thus transfer a "death signal" across specific and susceptible neuronal populations.

Current management of motor fluctuations in patients with advanced Parkinson's disease treated chronically with levodopa

Motor fluctuations after long-term administration of levodopa may be due to central pharmacodynamic mechanisms such as reduced striatal synthesis and storage of dopamine from exogenous levodopa and subsensitization of postsynaptic dopaminergic receptors. Peripheral pharmacokinetic mechanisms may be equally important, particularly in motor fluctuations of the "delayed on" (increased time latencies from dose intake to start-up of clinical benefit) and "no-on" (complete failure of a levodopa dose to exert an "on" response) types. Levodopa itself has a very poor solubility. In addition, there is delayed gastric emptying in many advanced patients. Therefore, an oral dose of levodopa may remain in the stomach for long periods of time before it passes into the duodenum where there is immediate absorption. Consequently, in order to overcome response fluctuations caused by impaired pharmacokinetic mechanisms and to improve its absorption, we recommend that levodopa be taken in multiple small doses, on an empty stomach, preferably crushed and mixed with a lot of liquid. Protein intake should be minimized. Prokinetic drugs such as prepulsid (Cisaprid) could be used to facilitate gastric motility and levodopa transit time. Administration of crushed levodopa through nasoduodenal or gastrojejunostomy tubes may be helpful in certain circumstances. Bypassing the stomach with subcutaneous injections of apomorphine may provide dramatic rescue from difficult "off" situations. Oral and s.c. administration of novel, extremely soluble prodrugs of levodopa, e.g., levodopa ethylester, may offer a new approach to overcome difficulties in levodopa absorption. Addition of dopamine agonists, MAO-B inhibitors, COMT inhibitors and controlled release levodopa preparations may be helpful in prolonging the duration of efficacy of each single levodopa dose. Levodopa, administered orally, usually combined with peripheral dopa decarboxylase inhibitors, continues to be the most widely-used and most effective pharmacological treatment for Parkinson's disease (Melamed, 1987). Undoubtedly, the outstanding therapeutic success of levodopa represents a dramatic and revolutionary breakthrough in medicine, in general, and in neurology, in particular. Although, since the introduction of levodopa, there have been many additional pharmacological and even surgical anti-parkinsonian strategies, it still stands out as a mandatory axis of treatment in the majority of patients (Steigler and Quinn, 1992). Indeed, levodopa therapy improves, sometimes markedly, the motor signs and symptoms of the illness, the functional capacity and quality of life and perhaps also life expectancy of the afflicted patients. It is therefore unfortunate that after an initial problem-free period of successful, smooth and stable clinical benefit from levodopa that lasts about two to five years, the responsiveness of many patients worsens with the emergence of a variety of complications (Marsden et al., 1982; Hardie et al., 1984). These adverse reactions include dyskinesias and dystonias, psychotic problems and, particularly, the troublesome motor fluctuations (Marsden and Parkes, 1977; Marsden, 1994). The latter phenomenon may be particularly complex, limiting and disabling. It is believed that most patients on long-term levodopa therapy will, sooner or later, develop response fluctuations of varying types and severity (Riley and Lang, 1993). Because of the serious impact of these phenomena on the quality of life and function of the patients, many efforts are now being undertaken to identify the responsible mechanisms and to devise preventive and therapeutic measures.

The involvement of p53 in dopamine-induced apoptosis of cerebellar granule neurons and leukemic cells overexpressing p53

1. The pathogenesis of the selective degeneration of the dopaminergic neurons in Parkinson's disease is still enigmatic. Recently we have shown that dopamine can induce apoptosis in postmitotic neuronal cells, as well as in other cellular systems, thus suggesting a role for this endogenous neurotransmitter and associated oxidative stress in the neuronal death process. 2. Dopamine has been shown to be capable of inducing DNA damage through its oxidative metabolites. p53 is a transcription factor that has a major role in determining cell fate in response to DNA damage. We therefore examined the possible correlation between dopamine-triggered apoptosis, DNA damage and levels of total phosphorylated p53 protein in cultured mouse cerebellar granule neurons. 3. Marked DNA damage and apoptotic nuclear condensation and fragmentation were detected within several hours of exposure to dopamine. An associated marked threefold increase in p53 phosphorylation was observed within this time window. Using a temperature-sensitive p53 activation system in leukemia LTR6 cells, were found that p53 inactivation dramatically attenuated dopamine toxicity. 4. We therefore conclude that DNA damage and p53 activation may have a role in mediating dopamine-induced apoptosis. Modulation of the p53 system may therefore have a protective role against the toxicity of this endogenous neurotransmitter and associated oxidative stress.

Reduced femoral geometry but normal biomechanics in the dorsomedial hypothalamic nucleus-lesioned rat

Bone geometry, structure, and biomechanical properties were investigated in a model of growth retardation, the dorsomedial hypothalamic nucleus-lesioned (DMNL) weanling rat. Male weanling Sprague-Dawley rats received bilateral electrolytic lesions in the dorsomedial hypothalamic nucleus (DMN) at age 27 days. Sham-operated rats served as controls. All rats were maintained postoperatively for 40 days. Upon sacrifice, DMNL rats weighed less (p < 0.01), were shorter (p < 0.01), and ate less (p < 0.01) when compared to controls, but their body composition was normal. The femora in DMNL were shorter (p < 0.01), had a smaller outer anteroposterior (AP) diameter (p < 0.04), polar moment of the area (p < 0.02), and maximal (p < 0.02) and minimal (p < 0.03) principal moment of the area when compared with sham-operated rats. Notably, mean torque at failure, torsional energy, stiffness, and maximal stress did not demonstrate statistically significant differences between the two groups. These data clearly show that despite the reduced size and bone growth, DMNL rats responded normally to the mechanical challenges applied to test bone biomechanical properties. The data, therefore, add to previous evidence and strengthen the hypothesis that DMNL rats are governed by an "organismic" set point.

Early-occurrence of manual motor blocks in Parkinson's disease: a quantitative assessment

OBJECTIVES

Quantitative analysis of internally-cued, repetitive motor performance in patients with Parkinson's disease (PD).

MATERIAL AND METHODS

Computerized quantitative measurements of the frequency, duration and temporal profile of manual motor blocks (MMBs) during performance of a manual tapping task, in 39 patients with PD, as compared to 17 age-matched healthy controls.

RESULTS

Performance of PD patients was markedly abnormal both quantitatively and qualitatively, as reflected by an increase (7.0% vs. 4.6%) in MMBs, and by their occurrence from onset of movement. The phenomenon was already observed in the early stages of the disease, and was also correlated with the occurrence of freezing of gait. A standard levodopa-carbidopa (125-12.5 mg) dose only partially affected this phenomenon.

CONCLUSIONS

Augmented motor blocks in internally-cued performance should be recognized as a frequent, distinct and generalized feature of PD. Whereas the gait disorder is regarded as characteristic of the advanced stage of PD, our findings suggest that the basic defect in internal rhythm formation can be detected by sensitive measurement tools from the early stages of the disease. In addition, the methodology developed in this study to quantitatively measure manual motor blocks may be a useful tool for future development of therapeutic regimens for this debilitating aspect of motor dysfunction in PD.

Cerclage wiring technique after proximal femoral fracture in total hip arthroplasty

Cerclage wires have been used to stabilize proximal femoral cracks after stem insertion in cementless total hip arthroplasty. The objective of this study was to determine the optimal number and orientation of cerclage wires necessary to prevent stem subsidence and crack propagation. The crack was stabilized by 1, 2, or 3 wires placed either normal to the femoral neck axis or normal to the crack. The femora were compressed to 2,670 N while measuring crack opening and stem subsidence. Wires placed normal to the crack allowed less stem subsidence by 3.17 mm and less crack opening by 1.55 mm compared with wires placed normal to the neck. The addition of multiple wires reduced subsidence by 50% and reduced crack opening to <1 mm. Medial and anterior calcar cracks are best stabilized by at least 2 cerclage wires that are placed normal to the crack.

Diagnosis of "non-organic" limb paresis by a novel objective motor assessment: the quantitative Hoover's test

The differentiation of "non-organic" limb weakness from genuine paralysis is sometimes difficult in neurological practice. To address this problem, we developed a computerized quantitative method, based on the Hoover's test principle, that determines the extent of involuntary limb activation when contralateral movement is performed. Measurements of hip or arm extension isometric force are performed during direct maximal voluntary effort and during contralateral hip flexion. Maximal involuntary/voluntary force ratio (IVVR) is calculated. IVVR of the lower limbs in ten healthy subjects was 0.614, 0.044 (mean, SEM). Similar results were obtained from seven patients with genuine weakness and in the non-affected limbs of nine patients with "non-organic" mono- or hemiparesis. In contrast, IVVR in the affected limbs in the "non-organic" group was markedly increased (2.48, 0.61; P < 0.001). The same pattern was elicited in the upper limbs (2.27, 0.46 vs 0.406, 0.06; P < 0,001). We conclude that Hoover's sign in "nonorganic" paralysis is a preservation or increase of a normal synkinetic phenomenon. Quantitative measurement of the IVVR can serve as a useful ancillary test in diagnosing non-organic weakness in either lower or upper limbs.

Enhanced fatigue during motor performance in patients with Parkinson's disease

OBJECTIVE

To measure fatigue quantitatively during continuous motor performance in patients with PD.

BACKGROUND

Enhanced fatigue on performance of motor tasks is a very frequent and disabling complaint of PD patients, and is poorly characterized and understood. Recent evidence suggests a role for mitochondrial dysfunction in the pathogenesis of PD. Reduced exercise capacity is one of the hallmarks of systemic mitochondrial impairment.

METHODS

The authors used an automated system to measure muscle fatigue during a continuous (30-second), maximal, isometric forearm flexion in 17 PD patients and 10 age-matched control subjects. A fatigue index (FI) was then calculated. Peak force (PF) was measured as an internal standard of the examination. Measurements were performed before and 2 hours after an oral dose of levodopa/carbidopa (125 mg/12.5 mg).

RESULTS

In PD patients there was a 50% increase in FI. The increased FI was often asymmetric and more pronounced on the side more affected by the disease. FI was significantly responsive to, and improved after, an oral dose of levodopa. The rate of improvement in FI induced by levodopa correlated with disease severity, as measured by the Unified Parkinson's Disease Rating Scale. No significant alterations in PF were observed.

CONCLUSIONS

Enhanced muscle fatigue should be recognized as an integral part of the spectrum of motor impairment of PD. However, our data argue for its association with a central dopamine deficiency rather than with a muscle mitochondrial abnormality.

Effect of ovariectomy and calcium deficiency on the ultrasound velocity, mineral density and strength in the rat femur

OBJECTIVE: Ultrasound transmission velocity (UTV) and bone mineral density (BMD) were examined as possible predictors of the bending strength of osteoporotic long bones in ovariectomized rats treated with calcium-depleted diet. BACKGROUND: Changes in cancellous bone quality due to osteoporosis have been well documented, but only a few studies described non-invasive assessment of the biomechanical quality of long bones. METHODS: Forty-three rats were divided into three groups: ovariectomized and calcium-depleted diet, ovariectomized and standard diet, and untreated controls. All femora were scanned by quantitative computed tomography (QCT) to measure BMD and cortical dimensions at the mid-diaphysis. Bending strength was determined from the maximum bending moment and the femoral cortical dimensions at the mid-diaphysis. The UTV of cortical bond at the mid-disphysis of the femur was measured in the proximal/distal direction. RESULTS: It was found that bending strength was significantly different among the groups (p<0.0001). Despite the fact that bending strength of the osteoporotic rat femur significantly decreased, the osteoporotic effect did not produce a significant change in cortical thickness. UTV in the ovariectomized and calcium-depleted diet was lower than in the other groups; however, no significant differences were found betwene those on the standard diet and the untreated controls. The BMD in ovariectomized rats was also significantly lower than in the untreated controls (p<0.05); however, the BMD in those fed with the calcium-depleted diet was not significantly different from those with the standard diet. Both cortical UTV and BMD as a single variable may not predict changes in bending strength of the cortical bone at the mid-diaphysis of the rat femur. However, the combined effect of UTV and BMD was significantly better than a single parameter in the assessment of strength. RELEVANCE: Osteoporotic fracture results from the reduced BMD and the microstructural changes involving the entire skeleton. The ovariectomized rats with calcium-depleted diets may simulate a model for the human postmenopausal osteoporosis. Ultrasound measurements of cortical bone may not be better predictors of osteoporotic fracture risk than those of cancellous bone. The strength of osteoporotic long bone may not be properly predicted by either BMD or UTV as a single determinant, measured at the cortical bone of the rat femur.

Levodopa toxicity and apoptosis

Many in vitro studies have shown that levodopa is a potent toxin which is lethal to various cultured neuronal and non-neuronal cells. The in vitro toxicity of levodopa is linked mainly to its auto-oxidation, which generates a variety of harmful free radical species including superoxide, hydrogen peroxide, and hydroxyl radicals, and also semiquinones and quinones produced via the dopa-melanin metabolic route. Such toxic effects of levodopa can be blocked by co-treatment with antioxidants, particularly thiol-containing compounds. Several studies have shown that levodopa kills cells by triggering apoptosis, an active, intrinsic cell suicide program. Exposure of cultured neurons to levodopa induced the characteristic apoptotic cascade, including cell shrinkage, membrane blebbing, and nuclear and DNA fragmentation. Although levodopa is extremely toxic in vitro, there is no evidence that it damages nigrostriatal dopaminergic neurons in vivo in experimental animals and in patients with Parkinson's disease (PD). Likewise, although there is some evidence for the occurrence of apoptosis in the parkinsonian substantia nigra, it is not known whether levodopa administration is capable of inducing or accelerating programmed cell death of residual pigmented nigral neurons in PD.

The effects of dietary-induced obesity on the biomechanical properties of femora in male rats

OBJECTIVE

To assess the effects of diet-induced obesity (DIO), on the biomechanical and biochemical properties of the femur in mature male rats.

DESIGN AND SUBJECTS

Two groups of male rats were studied. The DIO experimental group was fed a high caloric diet and a 31% sucrose solution as drinking fluid for a month, whereas the control group was fed lab chow and tap water.

MEASUREMENT

Body weight; body water; lean body mass; femoral length; average cortical thickness; outer anteroposterior diameter; outer mediolateral diameter; cortex area; moment of inertia; cortical and cancellous bone hydration; tendon and muscle hydration; ash content of cortical and cancellous bone; ultimate load; deflection at ultimate load; ultimate strength; stiffness; elastic modulus and energy absorption capacity.

RESULTS

'Gainers' (final body weight in excess of three standard error of mean of the controls) were 19.1% heavier, with higher body fat, whereas body water, lean body mass, hydration of cancellous bone and ash content of cortical bone were lower, when compared to controls. Rats that failed to gain weight, despite the high caloric diet, were termed 'resisters' (weight gain less than three standard error of mean of the controls). Ultimate load, deflection at ultimate load and femoral energy absorption capacity were significantly higher in the experimental group when compared to the controls. However, no differences were found among the groups with respect to ultimate stress and stiffness.

CONCLUSION

The weight gain produced by DIO may lead to bone adaptation and improved biomechanics.

Enhanced oxidative stress and altered antioxidants in brains of Bcl-2-deficient mice

Bcl-2 is an antiapoptotic protein located in the outer mitochondrial membrane. Cellular perturbations associated with programmed cell death may be the consequence of disrupted mitochondrial function as well as excessive production of reactive oxygen species (ROS). Numerous studies indicate that Bcl-2 is involved in opposing cell death induced by oxidative stimuli, but its mode of action is uncertain. We reexamined the role of Bcl-2 by using a loss-of-function model, Bcl-2 knockout mice. Brains from Bcl-2-deficient mice had a 43% higher content of oxidized proteins and 27% lower number of cells in the cerebellum relative to wild-type mice. Incubation of cerebellar neurons from Bcl-2 +/+ brains with 0.5 mM dopamine caused 25% cell death, whereas in Bcl-2-deficient cells, it resulted in 52% death; glial cells provided protection in both cultures. Splenocytes from Bcl-2-deficient mice were also killed more effectively by dopamine as well as paraquat. Bcl-2-deficient mice did not survive intraperitoneal injection of MPTP, which caused a decrease in dopamine level in the striatum of Bcl-2 +/- brains, which was more significant than in wild-type mice. When compared with Bcl-2 +/+ brains, brains of 8-day-old Bcl-2-deficient mice had higher activities of the antioxidant enzymes GSH reductase (192%) and GSH transferase (142%), whereas at the age of 30 days, GSH peroxidase was significantly lower (66%). Activities of GSH transferase and GSH reductase increased significantly (158 and 262%, respectively) from day 8 to day 30 in Bcl-2 +/+ mice, whereas GSH peroxidase decreased (31%) significantly in Bcl-2 -/- animals. In summary, our results demonstrated enhanced oxidative stress and susceptibility to oxidants as well as altered levels of antioxidant enzymes in brains of Bcl-2-deficient mice. It is concluded that Bcl-2 affects cellular levels of ROS, which may be due to an effect either on their production or on antioxidant pathways.

Expression of cell cycle-related genes during neuronal apoptosis: is there a distinct pattern?

An emerging hypothesis considers the process of neuronal apoptosis as a consequence of unscheduled and unsynchronized induction of cell cycle mediators. Induction of several cell cycle genes precedes neuronal apoptosis and may be involved in determination of cell fate. We have now characterized changes in expression of cell cycle genes during apoptosis induced by oxidative stress in chick post-mitotic sympathetic neurons. Induction of cyclin B occurred prior to the commitment of neurons to both dopamine- and peroxide-triggered apoptosis. Both the neuronal death and the rise in cyclin B were inhibited by antioxidant treatment, suggesting a functional role for cyclin B induction during neuronal apoptosis. Induction of the cyclin dependent kinase CDK5 protein coincided with the time point when neurons were irreversibly committed to die. Expression of other cell cycle mediators such as cyclin D1 and the cyclin dependent kinases CDC2 and CDK2 was undetected and not induced by exposure to oxidative stress. Comparative analysis of the profile of cell cycle mediators induced during neuronal apoptosis of different neuronal cell populations revealed no distinct pattern of events. There are no cell cycle stage-specific mediators that are ultimately stimulated during neuronal apoptosis, suggesting that multiple pathways of re-activating the dormant cell-cycle, converge to determine entry into apoptosis. Nevertheless, the existence of some cell cycle mediators, that were not reported so far to be induced in post mitotic neurons during oxidative stress, substantiate them as part of the strong differentiating forces.