Trunk muscle activation characteristics in patients with severe haemophilia.

INTRODUCTION: Recurrent bleeding episodes in patients with haemophilia (PWH) lead to joint alterations and therewith disturbed muscle coordination patterns. Major weight-bearing joints are affected most. However, possible effects on trunk muscle activity have not been examined so far. The objective of this work was to study consequences of haemarthropathy on characteristics of trunk muscles in PWH while standing on surfaces with different mechanical properties. METHODS: Surface EMG of internal oblique (IO) and multifidus (MF) muscles were bilaterally recorded during a natural bilateral stance in 20 PWH with severe haemophilia A [age: 42 years (SD: 10)] and 25 non-haemophilic controls [NHC, 43 (12)]. Amplitude ratios, a symmetry index between sides and the co-activation ratio of IO over MF served as outcome measures and compared standing on three different surfaces (stable, soft, unsteady). RESULTS: PWH revealed markedly restricted lower extremity joints (P < 0.001), but without any hint of back pain. Neither result revealed significant main or interaction effects of 'group' (P > 0.24). Group-independent analyses showed amplitude ratios (MF: P < 0.05) as well as symmetry indices (MF: P < 0.02) significantly altered by 'surface' in NHC only. Effects of utilizing soft vs. unsteady surfaces were not detectable (P > 0.77). CONCLUSION: Utilizing unstable surfaces does not lead to altered trunk muscle activity in PWH. Differently than expected, a quite similar behaviour of lower trunk muscles in terms of applied indices can be found in PWH and NHC. Ascending alterations of muscle coordination in PWH could not be verified.

[Interdisciplinary Assessment Criteria for Rehabilitation after Injuries of the Lower Extremity: A Function-Based Return to Activity Algorithm]. / Interdisziplinäre Beurteilungskriterien für die Rehabilitation nach Verletzungen an der unteren Extremität: Ein funktionsbasierter Return to Activity Algorithmus.

BACKGROUND: In the treatment of patients with lower extremity injuries, a paradigm shift is taking place: Time-dependent concepts are increasingly being replaced by function-based concepts. METHODS: A function-based Return to Activity Algorithm is presented which contains a level classification (I-IV). Qualitative and subsequent quantitative tests are assigned to every level. Within each level, first the respective qualitative test has to be passed before patients are allowed to perform the corresponding quantitative test. Criteria for success are qualitative and quantitative comparisons with the unaffected side. Before entering the next level, both tests have to be successfully passed. The levels are ordered according to increasing demands on the loco-motor system. These demands are adequate stability without impact interaction in sagittal plane for level I, followed by dynamic stability demands for level II. Impacts in frontal plane are added for level III and finally multidirectional impacts have to be compensated at level IV. The time expenditure per level is no more than five minutes. The case of a professional soccer player will serve to exemplify the Return to Activity Algorithm. Following a knee injury, he underwent arthroscopy with ACL reconstruction (patellar tendon) and a partial meniscectomy (lateral and medial). RESULTS: The athlete was able to successfully pass each level and finished his rehabilitation 203 days post injury. He returned to the team training 221 days post injury. 247 days post injury, the athlete completed his first game. CONCLUSION: The Return to Activity Algorithm is able to support the evaluation of the functional status of the loco-motor system after injury or surgery and is furthermore capable of uncovering deficits or asymmetries, which are a proven risk for re-injury. This function-oriented individual approach is able to adequately dose the therapeutic efforts on an individual basis. With this approach, the right timing for a safe return to sports activities can be detected with high certainty.

Fabrication and characterization of an electrically contacted vapor cell.

We demonstrate the use of electrically contacted vapor cells to switch the transmission of a probe laser. The excitation scheme makes use of electromagnetically induced transparency involving a Rydberg state. The cell fabrication technique involves thin-film-based electric feedthroughs, which are well suited for scaling this concept to many addressable pixels like in flat panel displays.

Ankle muscle activation in people with haemophilia.

Since normative surface EMG (SEMG) values for muscles acting at the knee joint are available for people with haemophilia, increasing interest is noticeable for other joints affected by haemophilic arthropathy. Adequate activity of shank muscles is an important key for appropriate postural control. The aim of this study was to determine differences in muscle activation patterns of lower leg muscles between people with and without haemophilia during upright standing. SEMG of tibialis anterior (TA), fibularis longus (FL), lateral (LG) and medial (MG) heads of gastrocnemius, and soleus (SO) muscles of both sides were recorded in 25 haemophilic patients (H) and 25 non-haemophilic control subjects (C) while standing on even ground. The Gilbert-Score was used to assign sides to major (H-MA) and minor (H-MI) affected ankle joints in H. To normalize the SEMG amplitudes, amplitude ratios (percentage of cumulated activity) were calculated. Compared to controls, TA ratios showed higher and MG reduced levels in both H groups (P < 0.01). In the H-MA subgroup of H, FL also joined the TA behaviour whereas SO had similar activation direction as MG. Although possible descending influences from the knee joints cannot be excluded, this can be interpreted as a compensational mechanism due to the severity of the orthopaedic status of the ankle, which with increasing heaviness is accompanied by reduced plantar flexion capability. However, ankle joint integrity appears to be reduced in H, with TA and MG seeming to play key roles for neuromuscular control of upright posture.

SEMG activation patterns of thigh muscles during upright standing in haemophilic patients.

Although electromyography (EMG) is a common method to evaluate muscle activity, studies utilizing EMG in haemophilic patients are rare. The haemophilic arthropathy, resulting in altered afferent information is expected to cause disturbed activation and inter-muscular coordination patterns in haemophilic subjects. The aim of this study was to determine differences of selected knee muscles between haemophilic patients and non-haemophilic subjects during upright standing. Surface EMG (SEMG) amplitudes of rectus femoris, vastus medialis (VM), vastus lateralis (VL) and biceps femoris (BF) muscles of both sides were measured in 27 haemophilic patients (H) and 26 control subjects (C) while standing on an even surface. Data from both sides were pooled in C, but data of H were subdivided further according to major (H-MA) and minor (H-MI) affected joints. To normalize the data, amplitude ratios (percentage of cumulated activity) were calculated as well. Regardless of whether H-MA or H-MI was compared with C, amplitudes of all extensor muscles reached significantly higher levels in H (P < 0.05). SEMG amplitude ratios also differed between H and C. Independent of subgroup, BF showed significantly reduced activation ratios (P < 0.01). Only the ratios of VM and VL of H-MA could replicate the observed amplitude differences to C (P < 0.05). These findings show that while standing, haemophiliacs maintain the necessary stability demands through increased extensor activities and modulated coordination patterns. Although all thigh muscles of haemophiliacs are characterized by distinct atrophy, increased amplitude levels could be proved for the knee extensor muscles only. Therefore, general atrophy-related effects cannot explain these results.

Catalytic inhibition of human DNA topoisomerase IIalpha by hypericin, a naphthodianthrone from St. John's wort (Hypericum perforatum).

St. John's wort (Hypericum perforatum) is the most widely used herbal medicine for the treatment of depression. However, concerns have arisen about the potential of its interaction with other drugs due to the induction of cytochrome P450 isozymes 1A2 and 3A4 by the components hypericin and hyperforin, respectively. Structurally similar natural products are often employed as antitumor agents due to their action as inhibitors of DNA topoisomerases, nuclear enzymes that modify DNA during cellular proliferation. Preliminary findings that hypericin inhibited the DNA relaxation activity of topoisomerase IIalpha (topo II; EC 5.99.1.3) led us to investigate the mechanism of enzyme inhibition. Rather than stabilizing the enzyme in covalent complexes with DNA (cleavage complexes), hypericin inhibited the enzyme prior to DNA cleavage. In vitro assays indicate that hypericin is a potent antagonist of cleavage complex stabilization by the chemotherapeutics etoposide and amsacrine. This antagonism appears to be due to the ability of hypericin to intercalate or distort DNA structure, thereby precluding topo II binding and/or DNA cleavage. Supporting its non-DNA damaging, catalytic inhibition of topo II, hypericin was shown to be equitoxic to both wild-type and amsacrine-resistant HL-60 leukemia cell lines. Moreover, hypericin was incapable of stimulating DNA damage-responsive gene promoters that are activated by etoposide. As with the in vitro topo II assay, antagonism of DNA damage stimulated by 30 microM etoposide was evident in leukemia cells pretreated with 5 microM hypericin. Since many cancer patients experience clinical depression and concomitantly self-medicate with herbal remedies, extracts of St. John's wort should be investigated further for their potential to antagonize topo II-directed chemotherapy regimens.

Identification of DNA-protein interactions in the 5' flanking and 5' untranslated regions of the human multidrug resistance protein (MRP1) gene: evaluation of a putative antioxidant response element/AP-1 binding site.

Overexpression of the multidrug resistance protein, MRP1, confers resistance to multiple natural product-type chemotherapeutics. MRP1 amplification is observed in some multidrug-resistant cell lines, while in others, increased transcription occurs in the absence of gene amplification. To investigate mechanisms influencing MRP1 transcription, three small cell lung cancer cell lines were examined: drug sensitive H69 cells with two apparently normal MRP1 alleles, highly resistant H69AR cells in which MRP1 is amplified and low level resistant H69PR cells that contain only one MRP1 allele. Deoxyribonuclease I footprinting and gel mobility shift assays were undertaken using nuclear extracts from the three cell lines and a 1 kb region encompassing the 5' flanking region of MRP1. Thirteen protein binding sites were identified of which six were sequence specific. Differences in levels of protein binding occurred with a putative antioxidant response element (ARE)/AP-1 binding site at -511 to -477. Levels of protein binding to this site were 2.5- to 3.0-fold higher in H69AR nuclear extracts versus extracts from H69 or H69PR cells. The AP-1 sequence is required for binding and c-Jun and JunD were identified as components of the protein complex. The ARE/AP-1 element functioned as a transcriptional enhancer but did not mediate induction of a luciferase reporter gene upon beta-naphthoflavone treatment.

Benzene metabolites antagonize etoposide-stabilized cleavable complexes of DNA topoisomerase IIalpha.

Chronic exposure to benzene is associated with hematotoxicity and acute myelogenous leukemia. Inhibition of topoisomerase IIalpha (topo II) has been implicated in the development of benzene-induced cytogenetic aberrations. The purpose of this study was to determine the mechanism of topo II inhibition by benzene metabolites. In a DNA cleavage/relaxation assay, topo II was inhibited by p-benzoquinone and hydroquinone at 10 microM and 10 mM, respectively. On peroxidase activation, inhibition was seen with 4,4'-biphenol, hydroquinone, and catechol at 10 microM, 10 microM, and 30 microM, respectively. But, in no case was cleavable complex stabilization observed and the metabolites appeared to act at an earlier step of the enzyme cycle. In support of this conclusion, several metabolites antagonized etoposide-stabilized cleavable complex formation and inhibited topo II-DNA binding. It is therefore unlikely that benzene-induced acute myelogenous leukemia stems from events invoked for leukemogenic topo II cleavable complex-stabilizing antitumor agents. (Blood. 2001;98:830-833)

The histone deacetylase inhibitor sodium butyrate induces DNA topoisomerase II alpha expression and confers hypersensitivity to etoposide in human leukemic cell lines.

The differentiating agent and histone deacetylase inhibitor, sodium butyrate (NaB), was shown previously to cause a transient, 3-17-fold induction of human DNA topoisomerase II alpha (topo II alpha) gene promoter activity and a 2-fold increase in topo II alpha protein early in monocytic differentiation of HL-60 cells. This observation has now been extended to other short chain fatty acids and aromatic butyrate analogues, and evidence is presented that human topo II alpha promoter induction correlates closely with histone H4 acetylation status. Because increased topo II alpha expression is associated with enhanced efficacy of topo II-poisoning antitumor drugs such as etoposide, the hypothesis tested in this report was whether NaB pretreatment could sensitize HL-60 myeloid leukemia and K562 erythroleukemia cells to etoposide-triggered DNA damage and cell death. A 24-72 h NaB treatment (0.4-0.5 mM) induced topo II alpha 2-2.5-fold in both HL-60 and K562 cells and caused a dose-dependent enhancement of etoposidestimulated, protein-linked DNA complexes in both cell lines. At concentrations with minimal effects on cell cycle kinetics (0.4 mM in HL-60; 0.5 mM in K562), NaB pretreatment also modestly enhanced etoposidetriggered apoptosis in HL-60 cells, as determined morphologically after acridine orange/ethidium bromide staining, and substantially increased K562 growth inhibition and poly(ADP-ribose)polymerase cleavage after etoposide exposure. Therefore, a temporal window may exist whereby a differentiating agent may sensitize experimental leukemias to a cytotoxic antitumor agent. These results indicate that histone deacetylase inhibitors should be investigated for etoposide sensitization of other butyrate-responsive hematopoietic and nonhematopoietic tumor lines in vitro and in vivo.

Modulation of human DNA topoisomerase IIalpha function by interaction with 14-3-3epsilon.

Human DNA topoisomerase IIalpha (topo II), a ubiquitous nuclear enzyme, is essential for normal and neoplastic cellular proliferation and survival. Several common anticancer drugs exert their cytotoxic effects through interaction with topo II. In experimental systems, altered topo II expression has been associated with the appearance of drug resistance. This mechanism, however, does not adequately account for clinical cases of resistance to topo II-directed drugs. Modulation by protein-protein interactions represents one mechanism of topo II regulation that has not been extensively defined. Our laboratory has identified 14-3-3epsilon as a topo II-interacting protein. In this study, glutathione S-transferase co-precipitation, affinity column chromatography, and immunoprecipitations confirm the authenticity of these interactions. Three assays evaluate the impact of 14-3-3epsilon on distinct topo II functional properties. Using both a modified alkaline comet assay and a DNA cleavage assay, we demonstrate that 14-3-3epsilon negatively affects the ability of the chemotherapeutic, etoposide, to trap topo II in cleavable complexes with DNA, thereby preventing DNA strand breaks. By electrophoretic mobility shift assay, this appears to be due to reduced DNA binding activity. The association of topo II with 14-3-3 proteins does not extend to all 14-3-3 isoforms. No protein interaction or disruption of topo II function was observed with 14-3-3final sigma.

FK506 prevents stroke-induced generation of ceramide and apoptosis signaling.

Ceramide is a key mediator of apoptosis during the cellular stress response which is also involved in stroke-induced death. Transient occlusion of the middle cerebral artery (MCA) in rats led to a strong generation of ceramide as measured in thalamus and entorhinal cortex of the ischemic brain tissue. Enhanced levels of ceramide may be involved in apoptosis signaling following stroke since exogenously added synthetic C2-ceramide increased expression of c-jun and the death-inducing ligands (DILs) CD95-L, TRAIL and TNF-alpha in neuroblastoma cells. DILs in turn mediated death via binding to their respective receptors as concluded from diminished apoptosis upon blocking of the common pathway by dominant negative FADD. C2-ceramide induced both necrosis and apoptosis in a concentration-dependent manner corresponding to the situation present in the ischemic brain. The immunosuppressant FK506 inhibited the release of ceramide, expression of CD95-L and apoptosis in an in vitro and in vivo model for ischemia/reperfusion. These data suggest that ceramide is a crucial initiator of death, e.g., by induction of DILs following stroke.

CD95 (APO-1/Fas) mutations in childhood T-lineage acute lymphoblastic leukemia.

CD95 (APO-1/Fas)-mediated apoptosis is pivotal in normal lymphocyte homeostasis and mutations of CD95 cause a benign autoimmune lymphoproliferation syndrome (ALPS) in humans and mice. However, tumors only rarely develop in these patients, and no CD95 mutations have yet been directly implicated in tumorigenesis. We therefore examined 81 de novo childhood T-lineage acute lymphoblastic leukemias (T-ALL) including 54 steroid-poor responders, 10 relapsed T-ALL, and 10 leukemic T-cell lines, for the presence of CD95 mutations using single-strand confirmation polymorphism and sequence analysis. In leukemic blasts and normal T cells of one patient, a heterozygous mutation in exon 3 of CD95 causing a 68Pro --> 68Leu change associated with decreased CD95-mediated apoptosis was found. In leukemic blasts and normal T cells of a second patient, a homozygous mutation in the promoter of CD95 causing disruption of a consensus sequence for AP-2 binding without decreasing constitutive CD95 expression was detected. No large intragenic alterations of CD95 were found, no homozygous loss was detected in the cell lines, and no CD95 mutations were detected in the relapses. The data presented here show that CD95 mutations occur in some T-ALL and may be of biological importance.

Spinalin, a new glycine- and histidine-rich protein in spines of Hydra nematocysts.

Here we present the cloning, expression and immunocytochemical localization of a novel 24 kDa protein, designated spinalin, which is present in the spines and operculum of Hydra nematocysts. Spinalin cDNA clones were identified by in situ hybridization to differentiating nematocytes. Sequencing of a full-length clone revealed the presence of an N-terminal signal peptide, suggesting that the mature protein is sorted via the endoplasmic reticulum to the post-Golgi vacuole in which the nematocyst is formed. The N-terminal region of spinalin (154 residues) is very rich in glycines (48 residues) and histidines (33 residues). A central region of 35 residues contains 19 glycines, occurring mainly as pairs. For both regions a polyglycine-like structure is likely and this may be stabilized by hydrogen bond-mediated chain association. Similar sequences found in loricrins, cytokeratins and avian keratins are postulated to participate in formation of supramolecular structures. Spinalin is terminated by a basic region (6 lysines out of 15 residues) and an acidic region (9 glutamates and 9 aspartates out of 32 residues). Western blot analysis with a polyclonal antibody generated against a recombinant 19 kDa fragment of spinalin showed that spinalin is localized in nematocysts. Following dissociation of the nematocyst's capsule wall with DTT, spinalin was found in the insoluble fraction containing spines and the operculum. Immunocytochemical analysis of developing nematocysts revealed that spinalin first appears in the matrix but then is transferred through the capsule wall at the end of morphogenesis to form spines on the external surface of the inverted tubule and the operculum.

Analysis of the intron-exon organization of the human multidrug-resistance protein gene (MRP) and alternative splicing of its mRNA.

Overexpression of multidrug-resistance protein (MRP) and P-glycoprotein confers similar but not identical multidrug-resistance phenotypes. However, unlike P-glycoprotein, which comprises two membrane-spanning domains (MSDs) and two nucleotide-binding domains, MRP contains a third NH2-proximal MSD, a feature now identified in several other ATP-binding cassette transmembrane transporters. MRP is located on chromosome 16 at band 13.1 close to the short-arm breakpoint of the pericentric inversion associated with the M4Eo subclass of acute myeloid leukemia. We have defined the intron-exon structure of MRP and characterized a number of splicing variants of MRP mRNA. The gene spans at least 200 kb. It contains 31 exons and a high proportion of class 0 introns, alternative splicing of which results in significant levels of variant transcripts that maintain the original open reading frame of MRP mRNA. Analyses of the conservation of intron-exon organization and protein primary structure suggest that the MRP-related transporters evolved from a common ancestor shared with the cystic fibrosis transmembrane conductance regulator, by fusion with one or more genes encoding polytopic membrane proteins.

Response of Cultured Maize Cells to (+)-Abscisic Acid, (-)-Abscisic Acid, and Their Metabolites.

The metabolism and effects of (+)-S- and (-)-R-abscisic acid (ABA) and some metabolites were studied in maize (Zea mays L. cv Black Mexican Sweet) suspension-cultured cells. Time-course studies of metabolite formation were performed in both cells and medium via analytical high-performance liquid chromatography. Metabolites were isolated and identified using physical and chemical methods. At 10 [mu]M concentration and 28[deg] C, (+)-ABA was metabolized within 24 h, yielding natural (-)-phaseic acid [(-)-PA] as the major product. The unnatural enantiomer (-)-ABA was less than 50% metabolized within 24 h and gave primarily (-)-7[prime]-hydroxyABA [(-)-7[prime]-HOABA], together with (+)-PA and ABA glucose ester. The distribution of metabolites in cells and medium was different, reflecting different sites of metabolism and membrane permeabilities of conjugated and nonconjugated metabolites. The results imply that (+)-ABA was oxidized to (-)-PA inside the cell, whereas (-)-ABA was converted to (-)-7[prime]-HOABA at the cell surface. Growth of maize cells was inhibited by both (+)- and (-)-ABA, with only weak contributions from their metabolites. The concentration of (+)-ABA that caused a 50% inhibition of growth of maize cells was approximately 1 [mu]M, whereas that for its metabolite (-)-PA was approximately 50 [mu]M. (-)-ABA was less active than (+)-ABA, with 50% growth inhibition observed at about 10 [mu]M. (-)-7[prime]-HOABA was only weakly active, with 50% inhibition caused by approximately 500 [mu]M. Time-course studies of medium pH indicated that (+)-ABA caused a transient pH increase (+0.3 units) at 6 h after addition that was not observed in controls or in samples treated with (-)-PA. The effect of (-)-ABA on medium Ph was marginal. No racemization at C-1[prime] of (+)-ABA, (-)-ABA, or metabolites was observed during the studies.

An unexpected pathway for the metabolic degradation of 1,3-dialkyl-3-acyltriazenes.

In the presence of NADPH, rat liver microsomes catalyzed the degradation of a series of 1,3-dialkyl-3-acyltriazenes, and the extent of the reaction was correlated with compound lipophilicity. In the case of two methylcarbamoyltriazenes, 1-(2-chloroethyl)-3-benzyl-3- (methylcarbamoyl)triazene (CBzM) and 1-(2-chloroethyl)-3-methyl-3-(methylcarbamoyl)triazene (CMM), microsomal metabolites were isolated. Identification of the CBzM metabolites as 1-(2-chloroethyl)-3-benzyl-3-(hydroxymethylcarbamoyl)triazene and 1-(2-chloroethyl-3-benzyl-3-carbamoyltriazine, and the CMM metabolite as 1-(2-chloroethyl)-3-methyl-3-(hydroxymethylcarbamoyl)triazene indicated that the first metabolic step involves hydroxylation of the methylcarbamoyl substituent. Detailed studies of the metabolism of CBzM indicated that the Km for the reaction was 84 microM, and that metabolism was more efficient if microsomes were prepared from male than from female rats. During prolonged incubation, the metabolites of CBzM were also degraded. The degradation of CBzM and its metabolites was inhibited by SKF-525A and metyrapone, suggesting the involvement of a cytochrome P450 isozyme, and supporting the hypothesis that the process is oxidative rather than hydrolytic in both cases. Metabolic oxidation represents an alternative pathway to chemical or enzymatic hydrolysis for the in vivo decomposition of (methylcarbamoyl)triazenes. This mechanism may ultimately explain the antitumor efficacy and low acute toxicity of selected compounds.

Localization of a novel multidrug resistance-associated gene in the HT1080/DR4 and H69AR human tumor cell lines.

Two doxorubicin-selected human tumor cell lines, H69AR and HT1080/DR4, display a multidrug resistance phenotype but do not overexpress P-glycoprotein. Recently, a 6.5-kilobase mRNA encoding a novel member of the ATP-binding cassette superfamily of transport proteins, designated multidrug resistance-associated protein (MRP), has been identified in the H69AR cell line. In the present study, the levels of MRP mRNA were found to be 14-fold higher in HT1080/DR4 cells relative to sensitive HT1080 cells. Southern blotting indicates that gene amplification contributes to the overexpression of MRP in HT1080/DR4 cells. Using a 4-kilobase MRP complementary DNA probe, MRP genes were localized to 2-5 chromosomes bearing homogeneously staining regions and to multiple double minute chromosomes in H69AR cells. Resistant H69AR cells also contained a new der(16) with a structural aberration affecting 16p13.1, the normal cellular locus of the MRP gene. The MRP probe hybridized to two small homogeneously staining regions (hsr) in HT1080/DR4 cells including hsr(7)(p12p15). MRP localization was restricted to the normal cellular locus, 16p13.1, in the parental H69 and HT1080 cells and the drug-sensitive H69PR revertant cells. Our data provide combined evidence that amplification of the MRP gene is associated with the expression of drug resistance in selected solid tumor cell lines.

Changes in dendritic morphology of rat spinal motoneurons during development and after unilateral target deletion.

During normal development, motoneuron dendrites in the spinal nucleus of the bulbocavernosus (SNB) grow exuberantly to almost twice their adult length and then retract. In this study, we retrogradely labeled SNB motoneurons with cholera toxin B-conjugated horseradish peroxidase (BHRP) to examine the maturation of SNB dendritic arbors in more detail, particularly with regard to its spatial distribution and reorganization. The number and orientation of SNB motoneuron primary processes did not change over the first ten weeks of life. In contrast, total dendritic length, radial extent and arbor area increased significantly through the first four postnatal weeks and declined thereafter. The declines in length and extent were restricted to particular portions of the arbor, specifically the dorsal, ipsi- and contralateral projections. Estimates of the degree of overlap between the dendritic arbors from both sides of the SNB reflected these changes, with overlap initially increasing and then decreasing as the SNB established its adult dendritic morphology. To determine if dendritic interactions facilitated by this arbor overlap might be involved in regulating the normal retraction of SNB dendrites, we reduced SNB motoneuron numbers unilaterally by target muscle removal on the day of birth. Somal size, number and orientation of primary processes developed normally in unilateral muscle-extirpated animals. The dendritic morphology of surviving SNB motoneurons in unilateral muscle extirpated males was altered, with significant increases in dendritic length, extent and arbor area relative to those of normal males. These results indicate that substantial changes in dendritic organization of SNB motoneurons occur in normal development and may be influenced by interactions between dendrites from the two halves of the SNB.

Mechanisms of cartilage degradation in inflammatory arthritis: interaction between chondrocytes and immunoglobulin G.

A possible role for immune complexes in the degradation of cartilage (rheumatoid arthritis and antigen induced arthritis) has been modelled in vitro by studying interactions between cultured bovine chondrocytes and monomeric (M) or heat aggregated (HA) IgG. Concentrations of IgG used were within the range of values reported in the synovial fluids of rheumatoid joints. ELISA and rosetting assays revealed Fc receptor mediated binding of MIgG and HAIgG to chondrocytes that had been cultured, but not to freshly isolated cells. Both forms of IgG stimulated the production of metalloprotease, but only HAIgG boosted generation of superoxide anion and reduced proteoglycan synthesis. HAIgG also stimulated cells to produce immunoreactive interleukin 1 although no biological activity was apparent. It is concluded that the equivalent behavior of chondrocytes in vivo, triggered by immune complexes, could contribute or lead directly to matrix degradation.