Bone strain index reproducibility and soft tissue thickness influence: a dual x-ray photon absorptiometry phantom study

Background

Bone strain index (BSI) is a tool measuring bone strain, derived from dual x-ray photon absorptiometry. It is able to characterise an aspect of bone quality that, joined to the quantity and quality parameters of bone mineral density (BMD) and trabecular bone score (TBS), permits an accurate definition of fracture risk. As no data are available about BSI precision, our aim was to assess its in vitro reproducibility.

Methods

A Hologic spine phantom was used to perform BSI scans with three different scan modes: fast array (FA), array (A), and high definition (HD). Different soft tissue thicknesses (1, 3, 6 cm) of fresh pork rind layers as a surrogate of abdominal fat were interposed. For each scan mode, the phantom was consecutively scanned 25 times without repositioning.

Results

In all scan modes (FA, A, HD) and at every fat thickness, BSI reproducibility was lower than that of BMD. The highest reproducibility was found using HD-mode with 1 cm of pork rind and the lowest one using HD-mode with 6 cm of pork rind. Increasing fat thickness, BSI reproducibility tended to decrease. BSI least significant change appeared to be about three times that of BMD in all modalities and fat thicknesses. Without pork rind superimposition and with 1-cm fat layer, BSI reproducibility was highest with HD-mode; with 3 or 6 cm fat thickness, it was higher with A-mode.

Conclusions

BSI reproducibility was worse than that of BMD, but it is less sensitive to fat thickness increase, similarly to TBS.

Shape-matching soft mechanical metamaterials

Architectured materials with rationally designed geometries could be used to create mechanical metamaterials with unprecedented or rare properties and functionalities. Here, we introduce "shape-matching" metamaterials where the geometry of cellular structures comprising auxetic and conventional unit cells is designed so as to achieve a pre-defined shape upon deformation. We used computational models to forward-map the space of planar shapes to the space of geometrical designs. The validity of the underlying computational models was first demonstrated by comparing their predictions with experimental observations on specimens fabricated with indirect additive manufacturing. The forward-maps were then used to devise the geometry of cellular structures that approximate the arbitrary shapes described by random Fourier's series. Finally, we show that the presented metamaterials could match the contours of three real objects including a scapula model, a pumpkin, and a Delft Blue pottery piece. Shape-matching materials have potential applications in soft robotics and wearable (medical) devices.

Crumpling-based soft metamaterials: the effects of sheet pore size and porosity

Crumpled-based materials are relatively easy to fabricate and show robust mechanical properties for practical applications, including meta-biomaterials design aimed for improved tissue regeneration. For such requests, however, the structure needs to be porous. We introduce a crumpled holey thin sheet as a robust bio-metamaterial and measure the mechanical response of a crumpled holey thin Mylar sheet as a function of the hole size and hole area fraction. We also study the formation of patterns of crease lines and ridges. The area fraction largely dominated the crumpling mechanism. We also show, the crumpling exponents slightly increases with increasing the hole area fraction and the total perimeter of the holes. Finally, hole edges were found to limit and guide the propagation of crease lines and ridges.

Thyromimetic actions of tetrabromobisphenol A (TBBPA) in steatotic FaO rat hepatoma cells

Tetrabromobisphenol A (2,2-bis(3,5-dibromo-4-hydroxyphenyl propane-TBBPA) is the most produced brominated flame retardant, detected in the environment and in biological samples. TBBPA shares structural similarities with thyroid hormones (THs), and it has been shown to interfere with different aspects of TH physiology, this raising concern on its possible effects as an endocrine disruptor in humans and wildlife. THs play a major role in lipid metabolism, with the liver representing one of their main target tissues. At the cellular level, THs act through interactions with TH receptors (TRs), as well as through TR-independent mechanisms. Rat hepatoma FaO cells (a liver cell line defective for functional TRs) overloaded with lipids have been utilized as a model to investigate the anti-steatotic effects of THs in the hepatocyte. In this work, the possible effects of TBBPA in steatotic FaO cells were investigated. Exposure to TBBPA for 24 h reduced triglyceride (TAG) content and the size of lipid droplets (LDs); similar effects were obtained with equimolar doses (10(-6) M) of T3 (3,3',5-L-triiodothyronine). TBBPA and T3 showed common effects on transcription of genes involved in lipid homeostasis. In particular, TBBPA mainly up-regulated mRNA levels for LD-associated oxidative tissue-enriched PAT protein (OXPAT), peroxisome proliferator-activated receptor (PPAR) isoform β/δ, and the mitochondrial uncoupling protein 2 (UCP2). The results demonstrate that TBBPA can decrease lipid accumulation in steatotic cells through stimulation of oxidative pathways. These data identify novel thyromimetic actions of TBBPA at the cellular level.

The CTG repeat expansion size correlates with the splicing defects observed in muscles from myotonic dystrophy type 1 patients

BACKGROUND

Myotonic dystrophy type 1 is caused by an unstable (CTG)n repetition located in the 3'UTR of the DM protein kinase gene (DMPK). Untranslated expanded DMPK transcripts are retained in ribonuclear foci which sequester CUG-binding proteins essential for the maturation of pre-mRNAs.

AIM

To investigate the effects of CTG expansion length on three molecular parameters associated with the DM1 muscle pathology: (1) the expression level of the DMPK gene; (2) the degree of splicing misregulation; and (3) the number of ribonuclear foci.

METHODS

Splicing analysis of the IR, MBNL1, c-TNT and CLCN1 genes, RNA-FISH experiments and determination of the DMPK expression on muscle samples from DM1 patients with an expansion below 500 repetitions (n = 6), DM1 patients carrying a mutation above 1000 CTGs (n = 6), and from controls (n = 6).

RESULTS

The level of aberrant splicing of the IR, MBNL1, c-TNT and CLCN1 genes is different between the two groups of DM1 muscle samples and correlates with the CTG repeat length. RNA-FISH analysis revealed that the number of ribonuclear foci in DM1 muscle sections increases in patients with a higher (CTG)n number. No relationships were found between the expression level of the DMPK gene transcript and average expansion sizes.

CONCLUSION

The CTG repeat length plays a key role in the extent of splicing misregulation and foci formation, thus providing a useful link between the genotype and the molecular cellular phenotype in DM1.

Activities of mitochondrial complexes correlate with nNOS amount in muscle from ALS patients

The pathogenesis of amyotrophic lateral sclerosis (ALS) is poorly understood. Increased levels of free radicals derived from nitric oxide (NO), the product of nitric oxide synthase (NOS), may damage mitochondrial function leading to motor neurone death. Previous studies demonstrated a specific impairment of mitochondrial function in skeletal muscle of ALS patients. In order to verify a pathogenetic relationship between neuronal NOS (nNOS) and mitochondrial function, we studied nNOS expression by Western blot and mitochondrial enzyme activity by spectrophotometric assays in muscle biopsies of 16 sporadic ALS patients and 16 controls subjects. We observed a reduced activity of respiratory chain complexes with mitochondrial encoded subunits and a lower nNOS amount in ALS muscles. There was a direct correlation between levels of nNOS and values of mitochondrial enzymes function. In ALS muscles we found normal levels of manganese superoxide dismutase (SOD2) that is assumed as related to mitochondrial DNA abnormalities. Our data suggest a beneficial role for NO to mitochondrial function and lead to the hypothesis of a common oxidative damage in motor neurones and skeletal muscle in sporadic ALS patients.

Familial neuromuscular disease with tubular aggregates

We have studied four members of a family in which five individuals of both sexes in three generations have mild weakness and muscle aching. Serum creatine kinase (CK) and/or aldolase were mildly to moderately elevated. Tubular aggregates were present in all patients in all fiber types. Type 1 fiber predominance and type 2 hypotrophy or atrophy was noted in three biopsies. Fiber splitting was prominent in two cases. Electron microscopic studies confirm that the tubular aggregates originate from muscle sarcoplasmic reticulum (SR). The presence of T tubules making contacts with some tubules inside the collection of tubular aggregates is suggestive of their derivation from terminal cisternae.

Chemoprevention of Tumors: The Role of RAR-Beta

Chemoprevention can be defined as the use of specific natural or synthetic chemical agents to reverse, suppress, or prevent carcinogenic progression to invasive cancer. The knowledge of carcinogenic mechanisms provides the scientific rationale for chemoprevention. Epithelial carcinogenesis proceeds through multiple discernible stages of molecular and cellular alterations. Understanding of the multistep nature of carcinogenesis has evolved through highly controlled animal carcinogenesis studies, and these studies have identified three distinct phases: initiation, promotion and progression. Animal model studies have provided evidence that the development of cancer involves many different factors, including alterations in the structures and functions of different genes. Transitions between successive stages can be enhanced or inhibited in the laboratory by different types of agents, such activities providing the fundamental basis for chemoprevention.

Relationship between chromatin compactness and dye uptake for in situ chromatin stained with DAPI

BACKGROUND

This study investigated the relationship between chromatin compactness, which is directly related to chromatin condensation, and DAPI uptake. Materials and Methods For the structural characterization of in situ chromatin, we used fluorescence microscopy and differential scanning calorimetry on calf thymocytes. The compactness of nuclear chromatin was altered by permeabilizing native cells with NP40 detergent. A time-dependent analysis of detergent effects was performed by acquiring nuclear images at different time intervals after permeabilization. In order to compare nuclei of different sizes, we implemented a geometrical correction in the calculation of the integrated fluorescence intensity. For a quantitative evaluation of chromatin condensation we introduced two new parameters, "average chromatin packing ratio" and "average dye spatial density."

RESULTS

This approach allowed us to estimate the effects of NP40 detergent at the level of in situ chromatin. Detergent effects could be modulated by changing the ionic composition of buffer. Moreover, changes of chromatin condensation induced by detergent were inversely related to modifications of nuclear volume.

CONCLUSIONS

The combination of complementary information obtained by fluorescence microscopy, supported by a proper geometrical correction, and differential calorimetry allowed us to interpret the patterns of fluorescence intensities inside the nucleus in terms of chromatin structure.

Changes of nuclear structure induced by increasing temperatures

Despite the recent improvement in understanding the higher-order structure of chromatin fibers, the organization of interphase chromosomes in specific nuclear domains emerged only recently and it is still controversial. This study took advantage of an integrated approach using complementary techniques in order to investigate the structure and organization of chromatin in interphase nucleus. Native CHO-K1 cells were progressively heated from 310 K to 410 K and the effects of increasing temperatures on nuclear chromatin were analyzed in situ by means of cytometric and calorimetric techniques. Distribution and organization of chromatin domains were analyzed by Fluorescence microscopy, while the mean condensation of nuclear chromatin was measured by Differential scanning calorimetry. The results show as changes of nuclear structures (envelope and matrix, namely) affect significantly organization and condensation of in situ chromatin. Moreover when volume is modified by an external force (the temperature gradient in our case) we observe significant alterations of chromatin structure. These data are in accordance with the hypothesis of an inverse relationship between nuclear volume and chromatin condensation.

Rhabdomyosarcoma rho(0) cells: isolation and characterization of a mitochondrial DNA depleted cell line with 'muscle-like' properties

Mutations of mitochondrial DNA are a significant cause of neuromuscular disease. Pathological mutant mitochondrial DNA has been studied in control nuclear backgrounds. These experiments entailed transfer of patient-derived mitochondria to rho(0) cells that lack mtDNA. A limitation of these studies has been the fact that the control nuclear backgrounds were unrelated to the affected tissues of patients. Therefore a rhabdomyosarcoma cell line that has 'muscle-like' properties was tested to determine whether it could be depleted of mtDNA. A human rhabdomyosarcoma cell line was treated with the DNA intercalating dye ethidium bromide (3, 8-diamino-5-ethyl-6-phenylphenanthridinium bromide) for 45 days. The treatment induced complete and permanent loss of mitochondrial DNA (rho(0)) in the rhabdomyosarcoma cells, as mtDNA remained undetectable after 8 months of growth in medium without drug. Crucially, the rhabdomyosarcoma rho(0) cells retained the ability to differentiate into myotubes with expression of muscle specific isoenzymes. The rhabdomyosarcoma rho(0) cell line provides a model system for studying pathological mutant mtDNA in cells that more closely resemble human muscle than the hitherto available human rho(0) cell lines.

Changes of chromatin condensation in one patient with ataxia telangiectasia disorder: a structural study

Differential scanning calorimetry and quantitative fluorescence microscopy have been employed to characterize the structure and organization of in situ chromatin in lymphoblastoid cells obtained from one ataxia telangiectasia (A-T) patient and one healthy family member. The proven capability of these biophysical techniques to measure changes of chromatin condensation directly inside the cells makes them very powerful in studying the eventual structural changes associated with the appearance of a pleiotropic genetic disorder such as ataxia telangiectasia. A-T syndrome is genetically heterogeneous and can be induced by different mutations of a single gene. The aim of this work is to determine whether the genetic mutation exhibited by the A-T patient of this study may be associated with modifications of chromatin structure and organization. Both the calorimetric and the fluorescence microscopy results acquired on cells from the A-T patient show that the structure and distribution of nuclear chromatin in situ change considerably with respect to the control. A significant decondensation of the nuclear chromatin is in fact associated with the appearance of the A-T disorder in the A-T patient under analysis, together with a rearrangement of the chromatin domains inside the nucleus.

Riboflavin therapy. Biochemical heterogeneity in two adult lipid storage myopathies

Two unrelated adult males, aged 36 (patient 1) and 25 (patient 2) years, presented with subacute carnitine-deficient lipid storage myopathy that was totally and partly responsive to riboflavin supplementation in the two patients, respectively. Plasma acyl-carnitine and urinary organic acid profiles indicated multiple acyl coenzyme A dehydrogenase deficiency, which was mild in patient 1 and severe in patient 2. The activities of short-chain and medium-chain acyl coenzyme A dehydrogenases in mitochondrial fractions were decreased, especially in patient 2. This was in agreement with Western blotting results. Flavin-dependent complexes I and II were studied by immunoblotting and densitometric quantification of two-dimensional electrophoresis with comparable results. Complex I was present in normal amounts in both patients, whereas complex II was decreased only in the pretherapy muscle of patient 2. Flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) concentrations in muscle and isolated mitochondria, and the activity of mitochondrial FAD pyrophosphatase, showed that patient 1 had low levels of FAD (46%) and FMN (49%) in mitochondria, with a significant increase (P < 0.01) in mitochondrial FAD pyrophosphatase (273%) compared with controls. Patient 2 had similar low levels of FAD and FMN in both total muscle (FAD and FMN 22% of controls) and mitochondria (FAD 26%; FMN 16%) and normal activity of mitochondrial FAD pyrophosphatase. All of these biochemical parameters were either totally or partly corrected after riboflavin therapy.

Introduction of heteroplasmic mitochondrial DNA (mtDNA) from a patient with NARP into two human rho degrees cell lines is associated either with selection and maintenance of NARP mutant mtDNA or failure to maintain mtDNA

Mitochondria from a patient heteroplasmic at nucleo-tide position 8993 of mitochondrial DNA (mtDNA) were introduced into two human tumour cell lines lacking mtDNA. The donor mitochondria contained between 85 and 95% 8993G:C mtDNA. All detectable mtDNA in the mitochondrially transformed cells contained the pathological 8993G:C mutation 3 months after transformation. These results suggest that 8993G:C mtDNA had a selective advantage over 8993T:A mtDNA in both lung carcinoma and osteo-sarcoma cell backgrounds. In contrast, two other presumed pathological mtDNA variants were lost in favour of 'wild-type' mtDNA molecules in the same lung carcinoma cell background. Taken together, these findings suggest that the transmission bias of mtDNA variants is dependent upon a combination of nuclear background and mtDNA genotype. A second phenomenon observed was a marked decrease in the growth rate of many putative transformed cell lines after 6 weeks of culturing in selective medium, and in these cell lines mtDNA was not readily detectable by Southern blotting. Restriction endonuclease analysis and sequencing of amplified mtDNA demonstrated that the slow growing cells contained little or no mtDNA. It is concluded that these cells represented transient mitochondrial transformants.

Glycosaminoglycans boost insulin-like growth factor-I-promoted neuroprotection: blockade of motor neuron death in the wobbler mouse

Wobbler mice display forelimb weakness, altered paw positioning, reduced running speed, muscle atrophy and motor neuron loss; co-treatment with glycosaminoglycans and insulin-like growth factor-I counteracts the progression of the disease. Reportedly, treatment with glycosaminoglycans or insulin-like growth factor-I slows the early stages of progressive forelimb dysfunction in wobbler mice. Our aim was to study whether the combination of these two drugs would result in greater neuroprotective effects. In a group of wobbler mice, combined treatment with daily s.c. administration of 20 microg/kg insulin-like growth factor-I and 1 mg/kg glycosaminoglycans was begun upon diagnosis at three weeks of age and continued for the next six weeks. This treatment halted motor neuron loss and markedly reduced the decay of forelimb muscle morphometry and function. Moreover, the mouse phenotype itself was strikingly improved. The effect of the combination treatment was significantly higher than that of the single drugs, even at a dosage as high as 1 mg/kg insulin-like growth factor-I. The ability of the insulin-like growth factor-I/glycosaminoglycans pharmacological cocktail to arrest the progression of motor neuron disease in wobbler mice and the safety of the low dose of insulin-like growth factor-I used hold promise that this combination might represent a novel approach for the treatment of motor neuron disease and peripheral neuropathies.

Infantile lipid storage myopathy with nocturnal hypoventilation shows abnormal low-affinity muscle carnitine uptake in vitro

An infant with respiratory insufficiency, cardiomyopathy, lipid storage myopathy and low muscle carnitine was diagnosed as having 'Ondine's curse' because of recurrent nocturnal hypoventilation. Carnitine uptake was studied in 20-day-old cultured muscle, where two distinct saturable transport components are recognized: the high- and low-affinity-uptake. Experimental evidence suggests that low-affinity-uptake is muscle-specific, operating at physiological carnitine concentration. In the patient's cultured myotubes, the low-affinity-uptake K(m) was 260% of controls (P < 0.01), whereas kinetic parameters of high-affinity uptake were normal. The high K(m) indicates an immature or altered carnitine muscle carrier, which may decrease the physiologic carnitine uptake.

Glycosaminoglycans treatment increases IGF-I muscle levels and counteracts motor neuron death: A novel nonanticoagulant action

The present study shows that sciatic nerve crush in 2-day-old rats causes extensor digitorum longus (EDL) muscle atrophy and motor neuron loss and that treatment with glycosaminoglycans (GAGs) promotes muscle reinnervation, motor neuron survival, and markedly increases insulin-like growth factor-I (IGF-I) content in the denervated muscles. EDL muscle denervation-induced atrophy in saline-treated rats is progressive and reaches the greatest extent at 42 days after birth, which correlates with reduced EDL weight growth. There is also a partial reinnervation as shown by the number of reinnervated EDL muscle fibers (65.4% of control) and by the poor restoration of the indirect isometric twitch tension (62% of control) that is further reduced under tetanic stimulation (34% of control). The number of surviving motor neurons that innervate EDL muscle drops from 55 +/- 3 to 29 +/- 8. In GAGs-treated 42-day-old rats, the effects of neonatal nerve lesioning on EDL muscle atrophy and denervation are successfully reversed, and the isometric twitch tension and the capacity to hold tetanic stimulation are restored to almost control levels. The number of surviving EDL motor neurons is also increased to 43 +/- 4. Treatment with GAGs selectively affects IGF-I content in denervated hindlimb muscles, which is augmented from 7.02 +/- 0.71 ng/mg tissue to 25.72 +/- 0.7 in the EDL and from 3.2 +/- 0.18 to a robust 211 +/- 9.6 in the soleus.

Systemic administration of insulin-like growth factor decreases motor neuron cell death and promotes muscle reinnervation

Neonatal sciatic nerve axotomy causes motoneuron death and muscle denervation atrophy. The aim of the present study was to determine whether insulin-like growth factor-I (IGF-I) administration promotes muscle reinnervation and counteracts motor neuron loss after such an injury. Six weeks after sciatic nerve axotomy performed in 2-day-old pups, the number of motor neurons, as assessed by retrograde transport of horseradish peroxidase injected into the extensor digitorum longus (EDL) muscle, was reduced from 52 +/- 3 to 26 +/- 3. Subsequent administration of IGF-I at the doses of 0.02 mg/kg or 1 mg/kg increased the number of motor neurons to 35 +/- 2 and 37 +/- 5, respectively. The effect on motoneuron survival was accompanied by improved muscle fibre morphometry and restoration of indirect EDL muscle isometric twitch tension, which was about 80 % of control values for both doses of IGF-I compared with 60% observed with saline treatment. Reinnervated EDL muscle from saline-treated rats cannot hold tetanic tension, which is, however, achieved after IGF-I treatment at either dose. Thus, both high and low doses of IGF-I counteracted motoneuron death and improved muscle reinnervation following neonatal sciatic nerve axotomy. IGF-I at 5 microg/kg failed to increase muscle reinnervation.

Effects of polyamines on higher-order folding of in situ chromatin

Modifications of the higher-order chromatin structure induced by polyamines have been quantitatively investigated in situ through a non-invasive biophysical approach using Differential Scanning Calorimetry and Quantitative Fluorescence Microscopy. Calorimetric and intensitometric profiles have been acquired for samples of native thymocytes, alternatively suspended in buffers, with or without natural polyamines (spermine and spermidine). The results here reported show that the structure and distribution of nuclear chromatin in situ considerably change upon the ionic composition of the environment. A quantitative analysis of this data and a comparison with previous results obtained from isolated chromatin fibers was carried out. Finally, an inverse relationship between chromatin condensation and nuclear volume was observed.

Muscle reinnervation following neonatal nerve crush. Interactive effects of glycosaminoglycans and insulin-like growth factor-I

This study shows that glycosaminoglycans promote muscle reinnervation following neonatal sciatic nerve injury. Such an effect appears to be mediated by insulin-like growth factor-1. The glycosaminoglycan moiety of proteoglycans is a constituent of the basal lamina active on nerve regeneration by means of the interaction with laminin and with several growth factors. We have previously shown that supplementation of glycosaminoglycans affects neuronal degeneration and regeneration. In this study we report that following neonatal lesion of the rat sciatic nerve glycosaminoglycan treatment promoted extensor digitorum longus muscle reinnervation with consequent improvement of muscle morphology. In saline-treated rats, reinnervation was only partial and there was a marked muscle fibre atrophy. In addition glycosaminoglycan treatment of lesioned rats increased insulin-like growth factor-I messenger RNA and protein in the reinnervated muscle, and insulin-like growth factor-I and insulin-like growth factor binding protein-3 plasma levels. Similarly, treatment of nerve lesioned rats with insulin-like growth factor-I promoted muscle reinnervation and prevention of muscle fibre atrophy, higher levels of insulin-like growth factor-I in the reinnervated muscle and of insulin-like growth factor-I and insulin-like growth factor binding proteins in plasma. These data suggest that glycosaminoglycans are potent stimulants of muscle reinnervation and that their effects may be mediated by increased levels of insulin-like growth factor-I.

Neuroprotection, neuroregeneration, and interaction with insulin-like growth factor-I: novel non-anticoagulant action of glycosaminoglycans

We present recent developments in the area of glycosaminoglycans (GAGs) and their possible interaction with insulin-like growth factor-I (IGF-I). GAGs are constituents of proteoglycans, and the combination of a core protein and a specific GAG makes a unique proteoglycan with a precise developmental pattern and with the ability to bind growth factors. This process is apparently regulated by the moiety of the peripheral GAGs. The supplementation of GAGs promotes neuritogenesis in vitro and stimulates nerve regrowth and muscle reinnervation, an effect correlated with an increase in trophic factor mRNA expression. In the case of neonatal nerve lesion, there is in addition an enhanced motor neuron survival, accompanied by higher levels of IGF-I in plasma and denervated muscle. The neurotrophic and neuroregenerative effects of exogenous GAGs were also observed in motor neuron disease in the wobbler mouse.

X-ray small angle scattering study of chromatin as a function of fiber length

This work investigates the structure of native calf thymus chromatin as a function of fiber length and isolation procedures by using X-ray small angle scattering technique. Two methods of chromatin isolation have been compared in order to better understand the differences reported by various authors in terms of chromatin high order structure. In addition to these experimental results the effects of shearing have also been studied. In order to explain the differences among these chromatin preparations we built several models of chromatin fibers (represented as a chain of spherical subunits) assuming increasing level of condensation at increasing salt concentrations. For all these fiber models the corresponding theoretical X-ray scattering curves have been calculated and these results have been used to explain the influence of fiber length on the scattering profiles of chromatin. The comparison between experimental and theoretical curves confirms that the high molecular weight chromatin-DNA prepared by hypotonic swelling of nuclei (without enzymatic digestion) displays a partially folded structure even at low ionic strength, whereas the low molecular weight chromatin-DNA prepared by a brief nuclease digestion appears very weakly folded at the same ionic conditions.

Quantification of muscle mitochondrial oxidative phosphorylation enzymes via histochemical staining of blue native polyacrylamide gels

Blue native-polyacrylamide gel electrophoresis is a powerful technique that enables the separation of intact multi-subunit complexes. However, positive identification of particular enzymes generally requires further separation in a second dimension on a denaturing polyacrylamide gel. Histochemical staining is widely used to demonstrate enzyme activities in tissues, including oxidative phosphorylation enzymes. In this report, we demonstrate that the two techniques can be combined to quantify in situ mitochondrial enzymes, separated on nondenaturing polyacrylamide gels. The method gives quantitative results with human skeletal muscle as well as heart that contains higher mitochondrial numbers. Comparison of muscle from patients with oxidative phosphorylation enzyme deficiencies, such as those of two riboflavin-responsive patients, before and after vitamin treatment, gives results in agreement with those obtained by analyzing the activity of the mitochondrial enzymes in muscle homogenates.

Glycosaminoglycan supplementation promotes nerve regeneration and muscle reinnervation

This study shows that treatment of rats with exogenous glycosaminoglycans stimulates peripheral nerve regeneration, increases the abundance of mRNAs for myelin proteins and promotes muscle reinnervation. After the sciatic nerve had been crushed the number of regenerating axons in the distal stump was markedly and highly significantly increased by glycosaminoglycan treatment throughout the experimental period. The increased number of axons was correlated with increased axon and fibre (axon+myelin) diameter. The abundance of mRNAs for P0 protein and myelin basic protein of regenerating nerves was also affected by treatment with glycosaminoglycans. The increase in mRNA was also observed in the contralateral unlesioned nerve. Such a phenomenon did not occur in saline-treated rats. Glycosaminoglycan treatment markedly increased the number of muscle fibres reinnervated and accelerated the restoration of muscle twitch tension elicited by nerve stimulation. The effect was particularly evident during the early stages (16 and 21 days after nerve crush) of muscle reinnervation.

Effects of low doses of glycosaminoglycans and insulin-like growth factor-I on motor neuron disease in wobbler mouse

In this study we examined the effects of insulin-like growth factor-I (IGF-I) and of glycosaminoglycans (GAGs) on the progressive motor neuron disease in wobbler mice. After clinical diagnosis at age 3 weeks, mice received daily subcutaneous injections of IGF-I, or GAGs, or saline for 3 weeks. The histometric analysis revealed that biceps muscle fiber diameter was reduced in wobbler mice and that treatments with GAGs and IGF-I prevented such a drop. The number of atrophic small fibers was markedly reduced and that of the larger ones augmented. No effects on body growth and biceps muscle weight were observed. The combined AChE-silver staining revealed that both treatments promoted intramuscular axonal sprouting. The typical decline of grip strength in wobbler mice was also prevented. This study suggests that GAGs and IGF-I administrations can retard the onset of motor deficit, and reduce muscle atrophy in wobbler mice.

Effects of histone acetylation on chromatin structure

The effect of histone acetylation was monitored on CHO chromatin structure, following the addition of 7 mM Na-butyrate to the cell culture medium. The properties of both control and hyperacetylated chromatins and nuclei were investigated by circular dichroism, ethidium bromide intercalation, differential scanning calorimetry, and affinity chromatography. Our results are compatible with modest but significant alterations in the various levels of chromatin organization, as a result of the charge neutralization of some lysine residues within the N-terminal region of the histonic octamer. Namely, large statistically significant differences do exist in the heat capacity thermograms of native nuclei, where unfolding into single nucleofilament of the highly packed native chromatin superfiber appears associated with acetylation; at the same time CD, EB, and affinity chromatography point to modest but consistent differences in the compactness of isolated nucleosomes and polynucleosomes.

Glycosaminoglycans in nerve injury: II. Effects on transganglionic degeneration and on the expression of neurotrophic factors

Injury to the sciatic nerve leads to the transganglionic degeneration of sensory axons and to the induction of neurotrophins and p75 nerve growth factor receptor synthesis by the denervated Schwann cells. Sciatic nerve axotomy caused a marked loss of substance P and of met-enkephalin in the lumbar cord. Substance P immunostaining and pre-proenkephalin mRNA expression were reduced in the dorsal horn layers I and II ipsilaterally to the lesion. Treating rats with low doses (0.25 mg/kg) of heparin or COS 8, a natural glycosaminoglycan mixture with low anticoagulant activity, the peptide loss was prevented and the content increased of about 50% above control values. The effects of COS 8 treatment were also evident on Schwann cells. COS 8 augmented the increase of nerve growth factor, brain-derived neurotrophic factor, and NT-3 mRNA expression in the distal stump of the axotomized sciatic nerve. Therefore, it can be concluded that glycosaminoglycans neuroprotective effects on lesioned sensory axons might have been mediated by the dramatic promotion of neurotrophin synthesis. Although the in vitro studies (Lesma et al.: J Neurosci Res, 1996) suggested also a likely direct effect as extracellular matrix components that is not mediated by trophic factors.

Exposure to perinatal morphine promotes developmental changes in rat striatum

This study shows that perinatal exposure to morphine promotes developmental changes (up to 8 months of life) in the striatum by up-regulating concentrations of substance P and met-enkephalin with changes of prometenkephalin A mRNA expression at the day of birth only. Dopamine metabolism (up to 60 days) is also increased as suggested by the reduced concentrations of dopamine and increased content of 3,4-dihydroxyphenylacetic acid. Tyrosine hydroxylase mRNA expression is selectively reduced only in the substantia nigra by perinatal morphine. Serotonin content is reduced only during the early postnatal days and is unaffected thereafter. Supplementation of naltrexone to morphine-exposed rats prevents monoaminergic and neuropeptidergic changes in the striatum, which directly implicates opioid receptors in the developmental changes caused by morphine. The data suggest that perinatal morphine may inhibit met-enkephalin release, causing accumulation of the peptide without corresponding changes in specific mRNA. Dopamine release may also be increased as indicated by a higher metabolism and consequent reduction of tyrosine hydroxylase mRNA expression in the substantia nigra.

Perinatal exposure to morphine: reactive changes in the brain after 6-hydroxydopamine

The effects of neonatal 6-hydroxydopamine treatment on the brain of control rats and of rats perinatally exposed to morphine were examined. Noradrenaline levels were increased in the pons-medulla, mesencephalon and caudate of 8-week-old control rats lesioned with neonatal 6-hydroxydopamine; perinatal morphine treatment prevented such an increase. In the caudate, there was a loss of dopamine and an increase of serotonin following the neurotoxic lesion; exposure to perinatal morphine prevented the serotonin increase. Brain expression of synapsin I mRNA was particularly abundant in cerebral cortex, hippocampus, dentate gyrus and olfactory bulb. In perinatal morphine-treated rats, the expression of synapsin I mRNA was significantly reduced; interestingly, the neonatal treatment with 6-hydroxydopamine normalized its expression. Therefore, brain-reactive neurochemical changes triggered by 6-hydroxydopamine were suppressed by perinatal morphine exposure whereas the association of morphine exposure and 6-hydroxydopamine lesion promoted the normal mRNA expression of the synaptic marker synapsin I.

Molecular characterization of myophosphorylase deficiency in a group of patients from northern Italy

We studied a group of 14 patients from Northern Italy with myophosphorylase deficiency. The disease presented considerable clinical and biochemical heterogeneity, which was reflected at the molecular level. The clinical presentation was typical in 3 patients, mild in 7 (exercise intolerance), and severe in 4 (fixed weakness). Enzyme activity was undetectable in 10 patients, below 3% of control in 3, and 13% of control in one. Enzymatic protein was detectable immunologically only in 1 patient. Myophosphorylase mRNA was present in 8 patients, but in 7 of them it was reduced in amount. Two patients were homozygous for the common nonsense R49X mutation, 5 were heterozygous. Two missense mutations not previously observed were identified in this group of patients. The frequency of alleles with the R49X mutation was significantly lower in this group of patients than in previously reported series. Myophosphorylase deficiency is genetically heterogeneous even among patients living in a small region and with a common ethnic background.

Residual muscle cytochrome c oxidase activity accounts for submaximal exercise lactate threshold in chronic progressive external ophthalmoplegia

The data from histological, biochemical, and mitochondrial DNA (mtDNA ) studies of muscle biopsies from 10 patients affected with chronic progressive external ophthalmoplegia (CPEO) were related to dynamic and metabolic parameters of incremental submaximal exercise. Maximum power output was reduced in all patients as compared to controls. Analysis of the venous lactate curve during exercise revealed a lactate threshold at exercise levels ranging from 40 to 50% of the predicted maximal power output. An earlier significant increase in lactate could be detected by calculating the mean delta lactate. Lactate values were inversely correlated with the cytochrome c oxidase (COX) activity of isolated muscle mitochondria. No relationship was found between lactate values and the number of ragged red fibers, or cytochrome c oxidase-negative fibers of the proportion of deleted mtDNA measured in muscle biopsy specimens. The discussion underscores the value of lactate kinetics in assessing skeletal muscle function, as well as the use of muscle COX levels to predict the effectiveness of wild-type complementation of deleted skeletal muscle mtDNA in in vivo contractile performance of CPEO subjects.

Effect of fixatives on calf thymocytes chromatin as analyzed by 3D high-resolution fluorescence microscopy

Two common fixatives--glutaraldehyde and ethanol/acetic acid mixture--were studied to understand their effects on DNA distribution inside the cell nucleus. Native calf thymocytes were analyzed by using a DNA selective fluorescent dye (DAPI) and computational optical sectioning microscopy on isolated cells before and after fixation. In order to estimate quantitatively the intranuclear DNA distribution, the stained calf thymocytes images were processed by removing the out-of-focus contributions present in each optical section. Although preliminary, the results show that within individual nuclei the frequency distribution of the fluorescence intensity appears significantly and differentially altered by the two fixatives. Namely with respect to the native unfixed preparation, the ethanol/acetic acid causes the complete disappearance of the higher intensity pixels, whereas glutaraldehyde fixation can be associated with the appearance of new ones of an even higher intensity. The quantitative analysis of the processed images allowed us to reconstruct the topological distribution of DNA inside the nucleus and to correlate the data with the results obtained by differential scanning calorimetry on similar samples.

Perinatal morphine. I: Effects on synapsin and neurotransmitter systems in the brain

We have previously shown that rat perinatal exposure to morphine causes dopaminergic and met-enkephalin (ME) and substance P (SP) changes in the striatum during the early postnatal period (Tenconi et al.: Int J Dev Neurosci 10: 517 - 526, 1992); in addition it increases the susceptibility to neurotoxic lesions and impairs regenerative capacity of the serotoninergic system (Gorio et al.: J Neurosci Res 34: 462 - 471, 1993). Our study shows that ME and SP levels increase postnatally in several areas of the rat brain, reaching the highest values between 30 and 60 days, after which the peptide content subsides to lower levels. Perinatal exposure to morphine increases such ME and SP levels during the early stages of postnatal life. No effect of morphine on 5-HT and NE is observed, while the dopaminergic system is mainly affected in the mesencephalon. The pre- and postnatal brain expression of synapsin I mRNA is gradually and progressively localized in discrete areas of the brain. In the brain of rats perinatally exposed to morphine, the abundance of synapsin I mRNA expression is markedly reduced. Therefore, perinatal exposure to morphine affects early postnatal synaptic development in the brain as shown by the altered peptidergic and monoaminergic content and by the reduced synapsin I mRNA expression.

MtDNA mutations associated with Leber's hereditary optic neuropathy: studies on cytoplasmic hybrid (cybrid) cells

Leber's hereditary optic neuropathy (LHON) has been associated with "primary" and "secondary" mtDNA missense point mutations, and a synergistic role has been proposed for secondary mutations. No previous study has investigated the effects of LHON primary or primary plus secondary mutations on the respiratory competence of cell lines. We constructed and compared cybrid cell lines obtained from two unrelated LHON patients both carrying the common 11778/ND4 primary mutation. One of the patients also carried the 13708/ND5 and 4216/ND1 secondary mutations. The cybrid clones were evaluated for growth efficiency, oxygen consumption, complexes I, III and IV enzymatic activity and mitochondrial protein synthesis. Complex activity and mitochondrial protein synthesis were not significantly changed in cybrid clones from the patients. Oxygen consumption was significantly decreased in all clones carrying the 11778/ND4 primary mutation demonstrating its pathogenic role in impairing cell respiration. Clones also carrying the secondary mutations showed an even lower oxygen consumption and a significantly higher doubling time, suggesting that the co-presence of the secondary mutations could be relevant in further reducing the cell fitness.

Ethidium bromide intercalation and chromatin structure: a spectropolarimetric analysis

Native chromatin has been characterized at different ionic strengths, according to different methods of preparation, by means of circular dichroism and ethidium bromide intercalation. For a more precise interpretation of these results, a series of analogous experiments on phagic DNA, as a function of its circularization, and on mononucleosomes have been performed. Results are discussed here in terms of high order chromatin structure, DNA supercoiling, and topological constraints.

Expression of muscle-type phosphorylase in innervated and aneural cultured muscle of patients with myophosphorylase deficiency

Patients with McArdle's myopathy lack muscle glycogen phosphorylase (M-GP) activity. Regenerating and cultured muscle of patients with McArdle's myopathy presents a glycogen phosphorylase (GP) activity, but it is not firmly established whether M-GP or non-M-GP isoforms are expressed. We have cultured myoblasts from biopsy specimen of five patients with McArdle's myopathy. Skeletal muscle was cultured aneurally or was innervated by coculture with fetal rat spinal cord explants. In the patients' muscle biopsies and in their cultured innervated and aneural muscle we studied total GP activity, isoenzymatic pattern, reactivity with anti-M-GP antiserum, and presence of M-GP mRNA. There was no detectable enzymatic activity, no immunoreactivity with anti-M-GP antiserum, and no M-GP mRNA in the muscle biopsy of all patients. GP activity, M-GP isozyme, and anti-M-GP antiserum reactivity were present in patients' aneural cultures, increased after innervation, and were undistinguishable from control. M-GP mRNA was demonstrated in both aneural and innervated cultures of patients and control by primer extension and PCR amplification of total RNA. Our studies indicate that the M-GP gene is normally transcribed and translated in cultured muscle of patients with myophosphorylase deficiency.

Hypertrophic cardiomyopathy with mitochondrial myopathy. A new phenotype of complex II defect

Two brothers, 25 and 19 years old, were affected by asymmetrical hypertrophic cardiomyopathy. The older brother had waddling gait and weakness of the proximal girdle muscles, while the younger had a broad-based gait and weakness of selected limb girdle muscles. EMG exam was myopathic. Serum enzyme, CPK and aldolase were elevated. Histochemical reactions in muscle revealed "core-like" areas, subsarcolemmal rims of mitochondria and lipid accumulation. Succinate-dehydrogenase stain showed a lack of activity in both biopsies, with the exception of intrafusal fibers. Microphotometric quantitative measurements confirmed the defect in both biopsies. Biochemical measurements of several mitochondrial enzymes in muscle showed a reduced activity of succinate-dehydrogenase (33%) and succinate-cytochrome C reductase (36-47%) which are both components of complex II. On myocardial biopsy lipid and mitochondrial abnormalities were found. This mitochondriopathy represents a new phenotype of partial complex II defect.

Fluorescence cytometry of microtubules and nuclear DNA during cell-cycle and reverse-transformation

Synchronized CHO-K1 cells and their dibutyryl c-AMP treated counterparts have been characterized by means of static and flow fluorescence cytometry at the level of nuclear DNA and cytoplasmic microtubules. In order to confirm earlier findings on synchronized population, Carnoy fixed and hydrolyzed, several new findings are here reported at the level of single intact cell. The fluorescence intensity of DAPI-stained glutaraldehyde fixed 2C cells correlates well with the average absorbance of the corresponding Feulgen-stained cells, thereby appearing also to be a measure of chromatin condensation during the G1 phase. In the early part of G1, the drastic alteration in anti-beta tubulin immunostaining is shown to parallel microtubule depolymerization induced by calcium or colcemide. The known 1-2 h lengthening of the G1 period after reverse-transformation appears to correlate with a similar delay in the abrupt chromatin decondensation. The above results are discussed in terms of the role of microtubules and nuclear morphometry (and their coupling) in the control of cell cycle progression of transformed vs. fibroblast-like cells.

Clinical and biochemical aspects of carnitine deficiency and insufficiency: transport defects and inborn errors of beta-oxidation

Carnitine is required for entry of long chain fatty acids into mitochondria where beta-oxidation occurs. Primary carnitine deficiency, due to a generic defect in cellular carnitine transport, exists in myopathic and systemic forms. Secondary carnitine deficiency may be due to multiplicity of inherited abnormalities, including deficiencies in carnitine palmitoyl-transferase acyl-CoA dehydrogenases, electron transfer flavoprotein, and 3-ketoacyl-CoA-thiolase. The clinical features, diagnosis, and treatment of these conditions are described.

L-carnitine uptake in differentiating human cultured muscle

We studied carnitine uptake in human skeletal muscle growing in culture for up to 30 days, and correlated it to the degree of muscle differentiation revealed by myotube formation and muscle-specific creatine-kinase isozyme accumulation. In our study carnitine uptake was a saturable specific process with two distinct components: a high affinity uptake at carnitine concentration between 0.5 and 10 microM and a low affinity uptake at carnitine concentration between 25 and 200 microM. High affinity uptake (Km 4.17-5.50 microM, Vmax 11.78-19.6 pmol/h per mg protein) did not change during muscle maturation in culture. Low affinity uptake showed significant changes in Km and Vmax in the various stages of muscle differentiation. Our studies suggest the existence of a muscle-specific system, operating at physiological carnitine concentration, which gradually develops during muscle maturation in culture. We hypothesize that a defect of the low affinity muscle-specific uptake might be the cause of the primary muscle carnitine deficiency syndrome.

Polarized light scattering of nucleosomes and polynucleosomes--in situ and in vitro studies

Nucleosomes, chromatin and nuclei, extracted from rat hepatocytes, are studied by a new "in house" experimental configuration which measures circular intensity differential scattering (CIDS) and other elements of the polarized light scattering matrix. The Mueller matrix elements, S14 and S34, that are related to the geometric parameters of the superhelical arrangement of polynucleosomes point to the existence of a quaternary structure at low ionic strength for chromatin prepared by the cold-water method, which is lost by shearing, and is not found in the soluble chromatin prepared through the nuclease method. Only salt addition to a final concentration of 5 mM MgCl2, 150 mM NaCl and 10 mM Tris HCl (pH 7) yields a sizeable (S14 + S34) signal in the latter chromatin, which is however still different from the corresponding signal of native nuclei and of "cold-water" chromatin. Comfortingly, the (S14 + S34) signal from isolated nucleosomes is consistently very low (nearly zero) as predicted by multiple dipole simulation within the framework of classical electrodynamics. Results are discussed in terms of the topological constraints present in the native long chromatin fiber, which are lost after limited nuclease digestion and after shearing.