miR-23a suppression accelerates functional decline in the rNLS8 mouse model of TDP-43 proteinopathy

Skeletal muscle dysfunction may contribute to the progression and severity of amyotrophic lateral sclerosis (ALS). In the present study, we characterized the skeletal muscle pathophysiology in an inducible transgenic mouse model (rNLS8) that develops a TAR-DNA binding protein (TDP-43) proteinopathy and ALS-like neuropathology and disease progression; representative of >90% of all familial and sporadic ALS cases. As we previously observed elevated levels of miR-23a in skeletal muscle of patients with familial and sporadic ALS, we also investigated the effect of miR-23a suppression on skeletal muscle pathophysiology and disease severity in rNLS8 mice. Five weeks after disease onset TDP-43 protein accumulation was observed in tibialis anterior (TA), quadriceps (QUAD) and diaphragm muscle lysates and associated with skeletal muscle atrophy. In the TA muscle TDP-43 was detected in muscle fibres that appeared atrophied and angular in appearance and that also contained β-amyloid aggregates. These fibres were also positive for neural cell adhesion molecule (NCAM), but not embryonic myosin heavy chain (eMHC), indicating TDP-43/ β-amyloid localization in denervated muscle fibres. There was an upregulation of genes associated with myogenesis and NMJ degeneration and a decrease in the MURF1 atrophy-related protein in skeletal muscle. Suppression of miR-23a impaired rotarod performance and grip strength and accelerated body weight loss during early stages of disease progression. This was associated with increased AchRα mRNA expression and decreased protein levels of PGC-1α. The TDP-43 proteinopathy-induced impairment of whole body and skeletal muscle functional performance is associated with muscle wasting and elevated myogenic and NMJ stress markers. Suppressing miR-23a in the rNLS8 mouse model of ALS contributes to an early acceleration of disease progression as measured by decline in motor function.

Striated muscle activator of Rho signalling (STARS) overexpression in the mdx mouse enhances muscle functional capacity and regulates the actin cytoskeleton and oxidative phosphorylation pathways

NEW FINDINGS

What is the central question of this study? Striated muscle activator of rho signalling (STARS) is an actin-binding protein that regulates transcriptional pathways controlling muscle function, growth and myogenesis, processes that are impaired in dystrophic muscle: what is the regulation of the STARS pathway in Duchenne muscular dystrophy (DMD)? What is the main finding and its importance? Members of the STARS signalling pathway are reduced in the quadriceps of patients with DMD and in mouse models of muscular dystrophy. Overexpression of STARS in the dystrophic deficient mdx mouse model increased maximal isometric specific force and upregulated members of the actin cytoskeleton and oxidative phosphorylation pathways. Regulating STARS may be a therapeutic approach to enhance muscle health.

ABSTRACT

Duchenne muscular dystrophy (DMD) is characterised by impaired cytoskeleton organisation, cytosolic calcium handling, oxidative stress and mitochondrial dysfunction. This results in progressive muscle damage, wasting and weakness and premature death. The striated muscle activator of rho signalling (STARS) is an actin-binding protein that activates the myocardin-related transcription factor-A (MRTFA)/serum response factor (SRF) transcriptional pathway, a pathway regulating cytoskeletal structure and muscle function, growth and repair. We investigated the regulation of the STARS pathway in the quadriceps muscle from patients with DMD and in the tibialis anterior (TA) muscle from the dystrophin-deficient mdx and dko (utrophin and dystrophin null) mice. Protein levels of STARS, SRF and RHOA were reduced in patients with DMD. STARS, SRF and MRTFA mRNA levels were also decreased in DMD muscle, while Stars mRNA levels were decreased in the mdx mice and Srf and Mrtfa mRNAs decreased in the dko mice. Overexpressing human STARS (hSTARS) in the TA muscles of mdx mice increased maximal isometric specific force by 13% (P < 0.05). This was not associated with changes in muscle mass, fibre cross-sectional area, fibre type, centralised nuclei or collagen deposition. Proteomics screening followed by pathway enrichment analysis identified that hSTARS overexpression resulted in 31 upregulated and 22 downregulated proteins belonging to the actin cytoskeleton and oxidative phosphorylation pathways. These pathways are impaired in dystrophic muscle and regulate processes that are vital for muscle function. Increasing the STARS protein in dystrophic muscle improves muscle force production, potentially via synergistic regulation of cytoskeletal structure and energy production.

The ketogenic diet preserves skeletal muscle with aging in mice

The causes of the decline in skeletal muscle mass and function with age, known as sarcopenia, are poorly understood. Nutrition (calorie restriction) interventions impact many cellular processes and increase lifespan and preserve muscle mass and function with age. As we previously observed an increase in life span and muscle function in aging mice on a ketogenic diet (KD), we aimed to investigate the effect of a KD on the maintenance of skeletal muscle mass with age and the potential molecular mechanisms of this action. Twelve‐month‐old mice were assigned to an isocaloric control or KD until 16 or 26 months of age, at which time skeletal muscle was collected for evaluating mass, morphology, and biochemical properties. Skeletal muscle mass was significantly greater at 26 months in the gastrocnemius of mice on the KD. This result in KD mice was associated with a shift in fiber type from type IIb to IIa fibers and a range of molecular parameters including increased markers of NMJ remodeling, mitochondrial biogenesis, oxidative metabolism, and antioxidant capacity, while decreasing endoplasmic reticulum (ER) stress, protein synthesis, and proteasome activity. Overall, this study shows the effectiveness of a long‐term KD in mitigating sarcopenia. The diet preferentially preserved oxidative muscle fibers and improved mitochondrial and antioxidant capacity. These adaptations may result in a healthier cellular environment, decreasing oxidative and ER stress resulting in less protein turnover. These shifts allow mice to better maintain muscle mass and function with age.

blaIMP-27 on transferable plasmids in Proteus mirabilis and Providencia rettgeri

OBJECTIVES

A carbapenem-resistant Providencia rettgeri (PR1) isolate was recovered from a wound infection in Missouri, USA. This isolate possessed an EDTA-inhibitable carbapenemase that was unidentified using the Xpert CARBA-R assay. Our objective was to elucidate the molecular determinant of carbapenem resistance in this isolate. We then sought to test the transmissibility of bla_IMP-27 loci in clinical P. rettgeri and Proteus mirabilis isolates.

METHODS

In October 2016 the novel ambler Class B carbapenemase bla_IMP-27, was reported in two different Proteus mirabilis (PM185 and PM187) isolates. Broth mating assays for transfer of carbapenemase activity were performed for the three clinical isolates with recipient sodium azide-resistant Escherichia coli J53. Antibiotic susceptibility testing and phenotypic carbapenemase activity testing were performed on the clinical isolates, J53 and transconjugants using the Kirby-Bauer disc diffusion method according to CLSI guidelines. Plasmid DNA from PM187, PR1 and their transconjugants were used as input for Nextera Illumina sequencing libraries and sequenced on a NextSeq platform.

RESULTS

PR1 was resistant to both imipenem and meropenem. PM187 and PR1 could transfer resistance to E. coli through plasmid conjugation (pPM187 and pPR1). pPM187 had a virB/virD4 type IV secretion system whereas pPR1 had a traB/traD type IV secretion system.

CONCLUSION

Two of three bla_IMP-27-bearing clinical isolates tested could conjugate resistance into E. coli. The resulting transconjugants became positive for phenotypic carbapenemase production but did not pass clinical resistance breakpoints. bla_IMP-27 can be transmitted on different plasmid replicon types that rely on distinct classes of type IV secretion system for horizontal transfer.

Age-related Differences in Dystrophin: Impact on Force Transfer Proteins, Membrane Integrity, and Neuromuscular Junction Stability

The loss of muscle strength with age has been studied from the perspective of a decline in muscle mass and neuromuscular junction (NMJ) stability. A third potential factor is force transmission. The purpose of this study was to determine the changes in the force transfer apparatus within aging muscle and the impact on membrane integrity and NMJ stability. We measured an age-related loss of dystrophin protein that was greatest in the flexor muscles. The loss of dystrophin protein occurred despite a twofold increase in dystrophin mRNA. Importantly, this disparity could be explained by the four- to fivefold upregulation of the dystromir miR-31. To compensate for the loss of dystrophin protein, aged muscle contained increased α-sarcoglycan, syntrophin, sarcospan, laminin, β1-integrin, desmuslin, and the Z-line proteins α-actinin and desmin. In spite of the adaptive increase in other force transfer proteins, over the 48 hours following lengthening contractions, the old muscles showed more signs of impaired membrane integrity (fourfold increase in immunoglobulin G-positive fibers and 70% greater dysferlin mRNA) and NMJ instability (14- to 96-fold increases in Runx1, AchRδ, and myogenin mRNA). Overall, these data suggest that age-dependent alterations in dystrophin leave the muscle membrane and NMJ more susceptible to contraction-induced damage even before changes in muscle mass are obvious.

Emergence of community-associated methicillin-resistant Staphylococcus aureus strains in the neonatal intensive care unit: an infection prevention and patient safety challenge

Methicillin-resistant Staphylococcus aureus (MRSA) infections cause significant morbidity and mortality in neonatal intensive care units (NICUs). We characterized the clinical and molecular epidemiology of MRSA strains colonizing NICU patients. Nasal MRSA isolates (n = 250, from 96 NICU patients) recovered through active surveillance from 2009 to 2014 were characterized with staphylococcal cassette chromosome mec (SCCmec) typing and detection of mupA (marker of high-level mupirocin resistance) and qacA/B (marker associated with chlorhexidine resistance). Factors associated with community-associated (CA-) or healthcare-associated (HA-) MRSA were evaluated. The overall prevalence of MRSA nasal colonization was 3.9%. Of 96 neonates in our retrospective cohort, 60 (63%) were colonized with CA-MRSA strains and 35 (36%) were colonized with HA-MRSA strains. Patients colonized with HA-MRSA were more likely to develop MRSA infections than patients colonized with CA-MRSA (13/35, 37% versus 8/60, 13%; p 0.007), although the interval from colonization to infection was shorter in CA-MRSA-colonized infants (median 0 days, range -1 to 4 versus HA-MRSA-colonized infants, 7 days, -1 to 43; p 0.005). Maternal peripartum antibiotics were associated with CA-MRSA colonization (adjusted odds ratio (aOR) 8.7; 95% CI 1.7-45.0); intubation and surgical procedures were associated with HA-MRSA colonization (aOR 7.8; 95% CI 1.3-47.6 and aOR 6.0; 95% CI 1.4-24.4, respectively). Mupirocin- and chlorhexidine-resistant MRSA was isolated from four and eight patients, respectively; carriage of a mupirocin-resistant strain precluded decolonization. CA-MRSA strains are prominent in the NICU and associated with distinct risk factors. Given community reservoirs for MRSA acquisition and transmission, novel infection prevention strategies are needed.

Overexpression of Striated Muscle Activator of Rho Signaling (STARS) Increases C2C12 Skeletal Muscle Cell Differentiation

Background: Skeletal muscle growth and regeneration depend on the activation of satellite cells, which leads to myocyte proliferation, differentiation and fusion with existing muscle fibers. Skeletal muscle cell proliferation and differentiation are tightly coordinated by a continuum of molecular signaling pathways. The striated muscle activator of Rho signaling (STARS) is an actin binding protein that regulates the transcription of genes involved in muscle cell growth, structure and function via the stimulation of actin polymerization and activation of serum-response factor (SRF) signaling. STARS mediates cell proliferation in smooth and cardiac muscle models; however, whether STARS overexpression enhances cell proliferation and differentiation has not been investigated in skeletal muscle cells.

Results: We demonstrate for the first time that STARS overexpression enhances differentiation but not proliferation in C2C12 mouse skeletal muscle cells. Increased differentiation was associated with an increase in the gene levels of the myogenic differentiation markers Ckm, Ckmt2 and Myh4, the differentiation factor Igf2 and the myogenic regulatory factors (MRFs) Myf5 and Myf6. Exposing C2C12 cells to CCG-1423, a pharmacological inhibitor of SRF preventing the nuclear translocation of its co-factor MRTF-A, had no effect on myotube differentiation rate, suggesting that STARS regulates differentiation via a MRTF-A independent mechanism.

Conclusion: These findings position STARS as an important regulator of skeletal muscle growth and regeneration.

Effects of aging, exercise, and disease on force transfer in skeletal muscle

The loss of muscle strength and increased injury rate in aging skeletal muscle has previously been attributed to loss of muscle protein (cross-sectional area) and/or decreased neural activation. However, it is becoming clear that force transfer within and between fibers plays a significant role in this process as well. Force transfer involves a secondary matrix of proteins that align and transmit the force produced by the thick and thin filaments along muscle fibers and out to the extracellular matrix. These specialized networks of cytoskeletal proteins aid in passing force through the muscle and also serve to protect individual fibers from injury. This review discusses the cytoskeleton proteins that have been identified as playing a role in muscle force transmission, both longitudinally and laterally, and where possible highlights how disease, aging, and exercise influence the expression and function of these proteins.

PGC-1α and PGC-1β increase CrT expression and creatine uptake in myotubes via ERRα

Intramuscular creatine plays a crucial role in maintaining skeletal muscle energy homeostasis, and its entry into the cell is dependent upon the sodium chloride dependent Creatine Transporter (CrT; Slc6a8). CrT activity is regulated by a number of factors including extra- and intracellular creatine concentrations, hormones, changes in sodium concentration, and kinase activity, however very little is known about the regulation of CrT gene expression. The present study aimed to investigate how Creatine Transporter (CrT) gene expression is regulated in skeletal muscle. Within the first intron of the CrT gene, we identified a conserved sequence that includes the motif recognized by the Estrogen-related receptor α (ERRα), also known as an Estrogen-related receptor response element (ERRE). Additional ERREs confirming to the known consensus sequence were also identified in the region upstream of the promoter. When partnered with peroxisome proliferator-activated receptor-gamma co-activator-1alpha (PGC-1α) or beta (PGC-1β), ERRα induces the expression of many genes important for cellular bioenergetics. We therefore hypothesized that PGC-1 and ERRα could also regulate CrT gene expression and creatine uptake in skeletal muscle. Here we show that adenoviral overexpression of PGC-1α or PGC-1β in L6 myotubes increased CrT mRNA (2.1 and 1.7-fold, P<0.0125) and creatine uptake (1.8 and 1.6-fold, P<0.0125), and this effect was inhibited with co-expression of shRNA for ERRα. Overexpression of a constitutively active ERRα (VP16-ERRα) increased CrT mRNA approximately 8-fold (P<0.05), resulting in a 2.2-fold (P<0.05) increase in creatine uptake. Lastly, chromatin immunoprecipitation assays revealed that PGC-1α and ERRα directly interact with the CrT gene and increase CrT gene expression.

Comparison and optimization of two MALDI-TOF MS platforms for the identification of medically relevant yeast species

The rapid identification of yeast is essential for the optimization of antifungal therapy. The objective of our study was to evaluate two matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) platforms, the bioMérieux VITEK MS (IVD Knowledgebase v.2.0) and Bruker Biotyper (software version 3.1), for the rapid identification of medically relevant yeast. One hundred and seventeen isolates, representing six genera and 18 species, were analyzed using multiple direct smear methods to optimize identification. Sequence analysis was the gold standard for comparison. Isolates were analyzed with VITEK MS using the direct smear method +/- a 25 % formic acid on-plate extraction. For Biotyper, isolates were analyzed using direct smear without formic acid, and with 25 % and 100 % formic acid on-plate extractions. When all methods were included, VITEK MS correctly identified 113 (96.6 %) isolates after 24 h with one misidentification, and Biotyper correctly identified 77 (65.8 %) isolates using a threshold of ≥2.0 with no misidentifications. Using a revised threshold of ≥1.7, Biotyper correctly identified 103 (88.0 %) isolates, with 3 (2.6 %) misidentifications. For both platforms, the number of identifications was significantly increased using a formic acid overlay (VITEK MS, p < 0.01; Biotyper, p < 0.001), and reducing the Biotyper threshold from ≥2.0 to ≥1.7 significantly increased the rate of identification (p < 0.001). The data in this study demonstrate that the direct smear method with on-plate formic acid extraction can be used for yeast identification on both MS platforms, and more isolates are identified using the VITEK MS system (p < 0.01).

Influence of divergent exercise contraction mode and whey protein supplementation on atrogin-1, MuRF1, and FOXO1/3A in human skeletal muscle

Knowledge from human exercise studies on regulators of muscle atrophy is lacking, but it is important to understand the underlying mechanisms influencing skeletal muscle protein turnover and net protein gain. This study examined the regulation of muscle atrophy-related factors, including atrogin-1 and MuRF1, their upstream transcription factors FOXO1 and FOXO3A and the atrogin-1 substrate eIF3-f, in response to unilateral isolated eccentric (ECC) vs. concentric (CONC) exercise and training. Exercise was performed with whey protein hydrolysate (WPH) or isocaloric carbohydrate (CHO) supplementation. Twenty-four subjects were divided into WPH and CHO groups and completed both single-bout exercise and 12 wk of training. Single-bout ECC exercise decreased atrogin-1 and FOXO3A mRNA compared with basal and CONC exercise, while MuRF1 mRNA was upregulated compared with basal. ECC exercise downregulated FOXO1 and phospho-FOXO1 protein compared with basal, and phospho-FOXO3A was downregulated compared with CONC. CONC single-bout exercise mediated a greater increase in MuRF1 mRNA and increased FOXO1 mRNA compared with basal and ECC. CONC exercise downregulated FOXO1, FOXO3A, and eIF3-f protein compared with basal. Following training, an increase in basal phospho-FOXO1 was observed. While WPH supplementation with ECC and CONC training further increased muscle hypertrophy, it did not have an additional effect on mRNA or protein levels of the targets measured. In conclusion, atrogin-1, MuRF1, FOXO1/3A, and eIF3-f mRNA, and protein levels, are differentially regulated by exercise contraction mode but not WPH supplementation combined with hypertrophy-inducing training. This highlights the complexity in understanding the differing roles these factors play in healthy muscle adaptation to exercise.

Striated muscle activator of Rho signaling is required for myotube survival but does not influence basal protein synthesis or degradation

Skeletal muscle mass is regulated by sensing and transmitting extracellular mechanical stress signals to intracellular signaling pathways controlling protein synthesis and degradation. Striated muscle activator of Rho signaling (STARS) is a muscle-specific actin-binding protein that is sensitive to extracellular stress signals. STARS stimulates actin polymerization and influences serum response factor (SRF) and peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α transcription of genes involved in muscle growth, structure, and contraction. The role of STARS in skeletal muscle cells is not well understood. This study investigated whether STARS influenced C2C12 myotube growth by regulating protein synthesis and degradation. The influence of STARS on Pgc-1α, Srf, and Errα mRNA levels, as well as several of their downstream targets involved in muscle cell growth, contraction, and metabolism, was also investigated. STARS overexpression increased actin polymerization, with no effect on protein synthesis, protein degradation, or Akt phosphorylation. STARS overexpression increased Pgc-1α, Srf, Ckmt2, Cpt-1β, and Mhc1 mRNA. STARS knockdown reduced actin polymerization and increased cell death and dead cell protease activity. It also increased markers of inflammation (Casp1, Il-1β, and Mcp-1), regeneration (Socs3 and Myh8), and fast myosin isoforms (Mhc2a and Mhc2x). We show for the first time in muscle cells that STARS overexpression increases actin polymerization and shifts the muscle cell to a more oxidative phenotype. The suppression of STARS causes cell death and increases markers of necrosis, inflammation, and regeneration. As STARS levels are suppressed in clinical models associated with increased necrosis and inflammation, such as aging and limb immobilization, rescuing STARS maybe a future therapeutic strategy to maintain skeletal muscle function and attenuate contraction-induced muscle damage.

Effect of resistance exercise contraction mode and protein supplementation on members of the STARS signalling pathway

The striated muscle activator of Rho signalling (STARS) pathway is suggested to provide a link between external stress responses and transcriptional regulation in muscle. However, the sensitivity of STARS signalling to different mechanical stresses has not been investigated. In a comparative study, we examined the regulation of the STARS signalling pathway in response to unilateral resistance exercise performed as either eccentric (ECC) or concentric (CONC) contractions as well as prolonged training; with and without whey protein supplementation. Skeletal muscle STARS, myocardian-related transcription factor-A (MRTF-A) and serum response factor (SRF) mRNA and protein, as well as muscle cross-sectional area and maximal voluntary contraction, were measured. A single-bout of exercise produced increases in STARS and SRF mRNA and decreases in MRTF-A mRNA with both ECC and CONC exercise, but with an enhanced response occurring following ECC exercise. A 31% increase in STARS protein was observed exclusively after CONC exercise (P < 0.001), while pSRF protein levels increased similarly by 48% with both CONC and ECC exercise (P < 0.001). Prolonged ECC and CONC training equally stimulated muscle hypertrophy and produced increases in MRTF-A protein of 125% and 99%, respectively (P < 0.001). No changes occurred for total SRF protein. There was no effect of whey protein supplementation. These results show that resistance exercise provides an acute stimulation of the STARS pathway that is contraction mode dependent. The responses to acute exercise were more pronounced than responses to accumulated training, suggesting that STARS signalling is primarily involved in the initial phase of exercise-induced muscle adaptations.

The regulation and function of the striated muscle activator of rho signaling (STARS) protein

Healthy living throughout the lifespan requires continual growth and repair of cardiac, smooth, and skeletal muscle. To effectively maintain these processes muscle cells detect extracellular stress signals and efficiently transmit them to activate appropriate intracellular transcriptional programs. The striated muscle activator of Rho signaling (STARS) protein, also known as Myocyte Stress-1 (MS1) protein and Actin-binding Rho-activating protein (ABRA) is highly enriched in cardiac, skeletal, and smooth muscle. STARS binds actin, co-localizes to the sarcomere and is able to stabilize the actin cytoskeleton. By regulating actin polymerization, STARS also controls an intracellular signaling cascade that stimulates the serum response factor (SRF) transcriptional pathway; a pathway controlling genes involved in muscle cell proliferation, differentiation, and growth. Understanding the activation, transcriptional control and biological roles of STARS in cardiac, smooth, and skeletal muscle, will improve our understanding of physiological and pathophysiological muscle development and function.

Striated muscle activator of Rho signalling (STARS) is a PGC-1α/oestrogen-related receptor-α target gene and is upregulated in human skeletal muscle after endurance exercise

The striated muscle activator of Rho signalling (STARS) is an actin-binding protein specifically expressed in cardiac, skeletal and smooth muscle. STARS has been suggested to provide an important link between the transduction of external stress signals to intracellular signalling pathways controlling genes involved in the maintenance of muscle function. The aims of this study were firstly, to establish if STARS, as well as members of its downstream signalling pathway, are upregulated following acute endurance cycling exercise; and secondly, to determine if STARS is a transcriptional target of peroxisome proliferator-activated receptor gamma co-activator 1-α (PGC-1α) and oestrogen-related receptor-α (ERRα). When measured 3 h post-exercise, STARS mRNA and protein levels as well as MRTF-A and serum response factor (SRF) nuclear protein content, were significantly increased by 140, 40, 40 and 40%, respectively. Known SRF target genes, carnitine palmitoyltransferase-1β (CPT-1β) and jun B proto-oncogene (JUNB), as well as the exercise-responsive genes PGC-1α mRNA and ERRα were increased by 2.3-, 1.8-, 4.5- and 2.7-fold, 3 h post-exercise. Infection of C2C12 myotubes with an adenovirus-expressing human PGC-1α resulted in a 3-fold increase in Stars mRNA, a response that was abolished following the suppression of endogenous ERRα. Over-expression of PGC-1α also increased Cpt-1β, Cox4 and Vegf mRNA by 6.2-, 2.0- and 2.0-fold, respectively. Suppression of endogenous STARS reduced basal Cpt-1β levels by 8.2-fold and inhibited the PGC-1α-induced increase in Cpt-1β mRNA. Our results show for the first time that the STARS signalling pathway is upregulated in response to acute endurance exercise. Additionally, we show in C2C12 myotubes that the STARS gene is a PGC-1α/ERRα transcriptional target. Furthermore, our results suggest a novel role of STARS in the co-ordination of PGC-1α-induced upregulation of the fat oxidative gene, CPT-1β.

Regulation of STARS and its downstream targets suggest a novel pathway involved in human skeletal muscle hypertrophy and atrophy

Skeletal muscle atrophy is a severe consequence of ageing, neurological disorders and chronic disease. Identifying the intracellular signalling pathways controlling changes in skeletal muscle size and function is vital for the future development of potential therapeutic interventions. Striated activator of Rho signalling (STARS), an actin-binding protein, has been implicated in rodent cardiac hypertrophy; however its role in human skeletal muscle has not been determined. This study aimed to establish if STARS, as well as its downstream signalling targets, RhoA, myocardin-related transcription factors A and B (MRTF-A/B) and serum response factor (SRF), were increased and decreased respectively, in human quadriceps muscle biopsies taken after 8 weeks of both hypertrophy-stimulating resistance training and atrophy-stimulating de-training. The mRNA levels of the SRF target genes involved in muscle structure, function and growth, such as alpha-actin, myosin heavy chain IIa (MHCIIa) and insulin-like growth factor-1 (IGF-1), were also measured. Following resistance training, STARS, MRTF-A, MRTF-B, SRF, alpha-actin, MHCIIa and IGF-1 mRNA, as well as RhoA and nuclear SRF protein levels were all significantly increased by between 1.25- and 3.6-fold. Following the de-training period all measured targets, except for RhoA, which remained elevated, returned to base-line. Our results show that the STARS signalling pathway is responsive to changes in skeletal muscle loading and appears to play a role in both human skeletal muscle hypertrophy and atrophy.

A hatching enzyme substrate in the Xenopus laevis egg envelope is a high molecular weight ZPA homolog

The Xenopus laevis egg envelope is composed of six or more glycoproteins, three of which have been cloned and identified as the mammalian homologs ZPA (ZP2), ZPB (ZP1) and ZPC (ZP3). The remaining glycoproteins are a triplet of high molecular weight components that are selectively hydrolyzed by the hatching enzyme. We have isolated one of these proteins and cloned its cDNA. The mRNA for the protein was found to be expressed only in early stage oocytes, as are other envelope components. From the deduced amino acid sequence, it was indicated to be a secreted glycoprotein with a characteristic ZP domain in the C-terminal half of the molecule. The N-terminal half was unrelated to any known glycoprotein. Comparative sequence analysis of the ZP domain indicated that it was derived from an ancestor of ZPA and ZPB, with the greatest identity to ZPA. This envelope component has been designated ZPAX.

Metabolites of caspofungin acetate, a potent antifungal agent, in human plasma and urine

Caspofungin acetate (MK-0991) is a semisynthetic pneumocandin derivative being developed as a parenteral antifungal agent with broad-spectrum activity against systemic infections such as those caused by Candida and Aspergillus species. Following a 1-h i.v. infusion of 70 mg of [(3)H]MK-0991 to healthy subjects, excretion of drug-related material was very slow, such that 41 and 35% of the dosed radioactivity was recovered in urine and feces, respectively, over 27 days. Plasma and urine samples collected around 24 h postdose contained predominantly unchanged MK-0991, together with trace amounts of a peptide hydrolysis product, M0, a linear peptide. However, at later sampling times, M0 proved to be the major circulating component, whereas corresponding urine specimens contained mainly the hydrolytic metabolites M1 and M2, together with M0 and unchanged MK-0991, whose cumulative urinary excretion over the first 16 days postdose represented 13, 71, 1, and 9%, respectively, of the urinary radioactivity. The major metabolite, M2, was highly polar and extremely unstable under acidic conditions when it was converted to a less polar product identified as N-acetyl-4(S)-hydroxy-4-(4-hydroxyphenyl)-L-threonine gamma-lactone. Derivatization of M2 in aqueous media led to its identification as the corresponding gamma-hydroxy acid, N-acetyl-4(S)-hydroxy-4-(4-hydroxyphenyl)-L-threonine. Metabolite M1, which was extremely polar, eluting from HPLC column just after the void volume, was identified by chemical derivatization as des-acetyl-M2. Thus, the major urinary and plasma metabolites of MK-0991 resulted from peptide hydrolysis and/or N-acetylation.

Renal transplantation

Medical and scientific advances have improved the diagnosis and treatment of kidney disorders. Organ transplantation has evolved from an experimental surgery to a medically accepted form of treatment for organ failure. The kidney was the first organ to be successfully replaced by a donor organ, and it is presently the most commonly transplanted organ. Kidney transplantation restores reasonably normal health to patients whose kidneys no longer function, and it frees them from the limitations imposed by dialysis. Improved graft survival rates have further enhanced the desirability of transplantation.

Anatomy and physiology of the kidney

The kidneys are complex organs, and they are vital in maintaining normal body functions. A human being's survival depends, to a large degree, on the crucial functions and processes performed by the kidneys. The renal system affects all parts of the body by keeping body fluids in balance and other organ systems functioning normally. Renal and urologic disorders may strike anyone at any age and at any time. An estimated 20 million Americans are affected with renal disorders each year.

Pharmacokinetics and disposition of the oxytocin receptor antagonist L-368,899 in rats and dogs

L-368,899 is a potent, orally-active oxytocin antagonist that completed phase I clinical trials for the prevention of preterm labor. The pharmacokinetics and disposition of L-368,899 were studied in rats (female and male) and dogs (female), the two species used in the toxicology studies. L-368,899 exhibited similar pharmacokinetics in rats and dogs. After iv dosing at 1, 2.5, and 10 mg/kg, the compound had a t1/2 of approximately 2 hr and plasma clearance between 23 and 36 ml/min/kg at all doses and in both species. The exception was female rats at the 10 mg/kg dose where plasma clearance decreased to 18 ml/min/kg. The Vdss was between 2.0 and 2.6 liters/kg for rats and 3.4 to 4.9 liters/kg for dogs. After oral doing, L-368,899 was rapidly absorbed. Mean Cmax values were achieved at <1 hr at the low doses (25 mg/kg in rats and 5 mg/kg in dogs) and between 1 and 4 hr at the higher doses (100 mg/kg in rats and 33 mg/kg in dogs). In bile duct-cannulated female rats, approximately 70% of a radioactive 28 mg/kg dose was recovered in bile and urine within 72 hr post dose. Plasma drug concentrations were higher in female than in male rats especially at the 25 mg/kg dose, where mean AUC values were 4.5-fold higher in the females. In both rats and dogs, plasma drug levels increased more than proportionally with increasing oral dose. In female rats, the mean AUC increased by approximately 8-fold between 25 and 100 mg/kg, while in female dogs, the mean AUC at the 33 mg/kg dose was 12-fold higher than that at 5 mg/kg. Oral bioavailability was estimated at 14% and 18% for the 5 mg/kg dose in female and male rats, respectively, 41% for the 25 mg/kg dose in male rats and 17% and 41%, respectively, for the 5 and 33 mg/kg doses in dogs. Owing to nonlinear kinetics, bioavailability could not be calculated for the other oral doses. L-368,899 was metabolized extensively in both species after iv and oral dosing, with <10% of the dose excreted unchanged. The main route of elimination was via the feces, which contained >70% of the radioactive dose by 48 hr, primarily as metabolites. The gender and dose dependence of the pharmacokinetics of L-389,899 in rats were attributed to gender differences in metabolizing capacity and saturation of hepatic metabolism, respectively. This conclusion was based primarily on results from experiments comparing the rate of in vitro metabolism of L-368,899 in liver microsomes, which showed that the Vmax and KM values for L-368,899 were 4-fold lower in female than in male rat liver microsomes.

Multicentric lymphosarcoma with ovarian involvement in a Nubian goat

Multiple lymph node enlargement and an intra-abdominal mass were diagnosed in a 6-year-old doe. Necropsy revealed lymphosarcoma involving multiple organs, including the ovaries. Lymphosarcoma is rare in goats; ovarian involvement has not previously been reported.

Lithium toxicosis in a cow

A case of lithium toxicosis is described in a cow that had consumed grease. Clinical signs included increased salivation, ataxia, reduced consciousness, seizures and diarrhea. No treatment was instituted. The grease did not contain high concentrations of other heavy metals or minerals.

Effects of Alzheimer's disease-related beta amyloid protein fragments on enzymes metabolizing phosphoinositides in brain

Phosphatidylinositol 4-kinase (PI 4-kinase) and phosphatidylinositol 4-phosphate kinase (PIP kinase) were assayed in membranes prepared from samples of human frontal cortex initially frozen at autopsy. PI 4-kinase activity was significantly lower in Alzheimer's disease patients relative to age-matched controls or patients with Parkinson's disease. PIP kinase was not different in Alzheimer's versus age-matched controls. The beta amyloid protein fragment 1-40 inhibited PI 4-kinase activity in assays of control human or rat cortical membranes. Fragments 1-28 and 25-35 could not mimic the effects of fragment 1-40 while a reverse peptide 40-1 was equipotent. The inhibition of PI 4-kinase by fragment 1-40 was competitive with substrate. The beta amyloid protein fragments had diverse effects on phosphoinositide-specific phospholipase C (PI-PLC) as assayed in rat cortical membranes. Low concentrations of fragment 1-40 stimulated, while high concentrations of 1-40 or 40-1 inhibited PI-PLC activity. Fragment 25-35 stimulated PI-PLC nearly 3-fold, while fragment 1-28 had only minor effects on the enzyme. The results suggest alterations in phosphoinositide metabolism in Alzheimer's disease which could affect signal transduction and/or cytoskeletal organization.

Modulation of the phospholipase C activity in rat brain cortical membranes by simultaneous activation of distinct monoaminergic and cholinergic muscarinic receptors

The activation of phospholipase C (PLC) was examined in membranes of rat cerebral cortex simultaneously exposed to monoaminergic receptor and muscarinic receptor agonists after the treatment of membranes with two alkylating agents, N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (100 microM EEDQ) and propylbenzilylcholine (10 nM PrBCM). Treatment of membranes with PrBCM results in a selective inactivation of M3 muscarinic receptors, while treatment with EEDQ results in a relative sparing of M1 muscarinic receptors. Stimulation of PLC by GTP gamma S alone in rat cortical membranes had an apparent EC50 of about 0.4 microM, but in the presence of carbachol (1 mM) was 0.09 microM. Treatment of rat cortical membranes with EEDQ or PrBCM did not modify the concentration-response curves for GTP gamma S alone, but the ability of carbachol (1 mM) to shift the EC50 of GTP gamma S was lost in PrBCM-treated membranes. We have previously shown that dopamine, working through D1-like dopamine receptors, alters the PLC response to carbachol by preventing this shift in the apparent EC50 for GTP gamma S16. When we reproduced these experiments in EEDQ- and PrBCM-treated membranes, only in EEDQ-treated membranes was dopamine able to inhibit the PLC response to carbachol. The results indicate that the post-receptor mechanisms of PLC activation are distinct for the putative M1 as opposed to M3 muscarinic receptors in rat cortical membranes. Further, there appears to be a specific interaction between D1 and M3 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of alkylating agents on the multiple muscarinic receptor subtypes linked to activation of phospholipase C by carbachol in rat brain cortical membranes

Muscarinic cholinergic receptor function in rat brain cortex was characterized by performing binding assays with [3H](-)quinuclidinyl benzilate ([3H]QNB) in parallel with assays of phospholipase C (PLC) activation by carbachol using membrane preparations and exogenous [3H]-phosphatidylinositol 4,5-bisphosphate ([3H]PIP2). Competitive binding studies revealed high- and low-affinity binding sites for the receptor antagonists, pirenzepine, methoctramine and the p-fluoro analog of hexahydro-sila-difenidol (p-F-HHSiD). Carbachol-stimulated [3H]-phosphatidylinositol 4,5-biphosphate breakdown was specifically inhibited by pirenzepine and p-F-HHiSD. The inhibition curves for these antagonists were best described by interactions at two sites. There was quantitative agreement between the antagonist affinity constants and the proportion of high- and low-affinity sites derived in functional and binding studies. The characteristics of the putative subtypes of muscarinic receptors and their stimulation of phospholipase C was examined after treatment with two alkylating agents, N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline and propylbenzilylcholine mustard. Loss of receptors was closely correlated with loss of PLC activation by carbachol, without alteration of the EC50 value (21 microM) of this agonist, clearly demonstrating a lack of receptor reserve. When both alkylating treatments were adjusted to induce a decrease of 60% in the maximal number of [3H]QNB binding sites, a similar (60%) reduction in the maximal effect of carbachol on PLC activation was found. However, the characteristics of the remaining receptors after the treatment with the two alkylating agents differ markedly as determined by competition of pirenzepine, p-F-HHSiD and methoctramine for [3H]QNB binding, and for inhibition of carbachol-stimulated phospholipase C by pirenzepine and p-F-HHSiD.(ABSTRACT TRUNCATED AT 250 WORDS)

Transmembrane signaling through phospholipase C in human cortical membranes

Stimulation of phosphoinositide-specific phospholipase C (PLC) by carbachol, dopamine and serotonin was measured by supplying exogenous [3H]phosphatidylinositol 4,5-bisphosphate to membranes prepared from human cortex dissected and frozen at autopsy. Subjects with Alzheimer's disease, Parkinson's disease or schizophrenia were compared to age-matched controls with no known neurological disorders. Stimulation of PLC by the neurotransmitters was dependent on the presence of GTP gamma S. Carbachol elicited the greatest stimulations of PLC followed by serotonin and then dopamine. The maximal stimulations of PLC evoked by a neurotransmitter were similar for the various categories of subjects except in Parkinson's patients, where dopamine failed to stimulate PLC beyond the activity attained with carbachol. In the presence of carbachol, the sensitivity of PLC to GTP gamma S was significantly increased in Alzheimer's membranes, but not in age-matched controls or Parkinson's. Overall, the experiments demonstrate the feasibility for using the exogenous substrate assay to study the functionality of the phosphoinositide transmembrane signaling system in human brain.

Semantically-bounded anomia: implications for the neural implementation of naming

We describe a patient whose anomia is disproportionately severe for fruits and vegetables when familiarity and name frequency are taken into account. His fruit and vegetable naming impairment was evident in a variety of different tasks. In contrast, he retained good general knowledge of fruits and vegetables, and he could access their names when given a phonemic cue. We discuss the phenomenon of semantically-bounded anomia in relation to the issues of local vs distributed representation, the existence of semantic "maps" in the brain, and the implementation of arbitrary associations in neural networks.

Concerted CMP-dependent [3H]inositol labeling of phosphoinositides and agonist activation of phospholipase C in rat brain cortical membranes

[3H]Inositol ([3H]Ins) labeling of phosphoinositides was studied in rat brain cortical membranes. [3H]Ins was incorporated into a common lipid pool through both CMP-dependent and independent mechanisms. These are as follows: (1) a reverse reaction catalyzed by phosphatidyl-inositol (PtdIns) synthase, and (2) the reaction performed by the PtdIns headgroup exchange enzyme, respectively. Membrane phosphoinositides prelabeled in either CMP-dependent or independent fashions were hydrolyzed by guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S)- and carbachol-stimulated phospholipase C. Unlike CMP-dependent labeling, however, CMP-independent incorporation of [3H]Ins into lipids was inhibited by 1 mM (0.04%) sodium deoxycholate. Thus, when PtdIns labeling and phospholipase C stimulation were studied in a concerted fashion, [3H]Ins was incorporated into lipids primarily through the PtdIns synthase-catalyzed reaction because of the presence of deoxycholate required to observe carbachol-stimulation of phospholipase C. Little direct breakdown of [3H]PtdIns was detected because production of myo-[3H]inositol 1-monophosphate was minimal and myo-[3H]inositol 1,4-bisphosphate was the predominant product. Although PtdIns labeling and 3H-polyphosphoinositide formation were unaffected by GTP gamma S and carbachol and had no or little lag period, GTP gamma S- and carbachol-stimulated appearance of 3H-Ins phosphates exhibited an appreciable lag (10 min). Also, flux of label from [3H]Ins to 3H-Ins phosphates was restricted to a narrow range of free calcium concentrations (10-300 nM). These results show the concerted activities of PtdIns synthase, PtdIns 4-kinase, and phospholipase C, and constitute a simple assay for guanine nucleotide-dependent agonist stimulation of phospholipase C in a brain membrane system using [3H]Ins as labeled precursor.

Altered phosphoinositide-specific phospholipase C and adenylyl cyclase in brain cortical membranes of cats with GM1 and GM2 gangliosidosis

Phosphoinositide-specific phospholipase C and adenylyl cyclase were studied in brain cortical membranes from cats with GM1 and GM2 gangliosidosis. In contrast to brain cortical membranes from unaffected control cats, phospholipase C acting against exogenously supplied phosphoinositide substrates did not respond to stimulation by GTP gamma S, carbachol or fluoroaluminate in cortical membranes of cats with gangliosidosis. However, the enzyme was activated by calcium in membranes from affected cats to the same extent as in membranes from control cats. Basal adenylyl cyclase activity was increased 3-fold in cortical membranes of cats with GM1 and GM2 gangliosidosis, compared with unaffected sibling controls. Fluoroaluminate was equally effective in stimulating adenylyl cyclase in controls and in membranes of affected and normal cats. In addition, GppNHp was able to inhibit the forskolin-activated enzyme both in membranes from cats with gangliosidosis and sibling controls. These data suggest that the activation of phosphoinositide-specific phospholipase C in brain membranes by guanine nucleotide binding proteins is markedly impaired in GM1 and GM2 gangliosidoses.

Unconscious perception of "extinguished" visual stimuli: reassessing the evidence

When parietal-damaged patients fail to report a contralesional stimulus because of extinction, is this because the stimulus is not perceived, or because it is perceived but cannot reach conscious awareness? VOLPE et al. [10] reported an intriguing study that seemed to locate the problem at least partly in the transfer of information to conscious awareness. They showed patients with extinction pairs of stimuli, one in each hemifield. Although patients were predictably poor at reporting the identity of the contralesional stimulus, they were able to make accurate same/different judgements comparing the two stimuli. This was interpreted as evidence that both stimuli were perceived. In the present paper, we point out that the dissociation between identification and same/different matching could also be due to the possibility that less visual information about the contralesional stimulus is necessary to make a same/different judgement than to identify the stimulus, and that chance performance is considerably higher in the first than in the second type of task. In Experiment 1, we verified this by degrading one side of a stimulus display and "replicating" the dissociation with normal subjects. We also equated the amount of visual information needed for the two tasks by yoking the stimulus pairs on "different" trials of the same/different matching task with the choice pairs on a forced choice identification task. Under these conditions, the dissociation vanished. In Experiment 2, we administered these tasks to three parietal-damaged patients with extinction. When the original method was used, same/different matching was better than identification of the contralesional stimulus. With the forced choice identification method, the dissociation again vanished.

Comparison of serotoninergic to muscarinic cholinergic stimulation of phosphoinositide-specific phospholipase C in rat brain cortical membranes

Stimulation of phosphoinositide-specific phospholipase C (PLC) by muscarinic cholinergic and serotoninergic agonists was measured in rat brain cortical membranes by using exogenously supplied substrates. Serotonin, tryptamine, 5-fluorotryptamine and 5-methyltryptamine stimulated PLC with EC50 values of 1.7, 11.2, 15.0, and 29.4 microM, respectively. Maximal PLC stimulation by serotoninergic agonists, which were all equally efficacious, was about 30% of that attained by carbachol. Ketanserin blocked serotoninergic but not cholinergic activation of PLC, whereas, conversely, atropine blocked the latter but not the former response. The rank order of potency for muscarinic agonists was oxotremorine-M greater than pilocarpine = arecoline greater than carbachol = bethanecol. Unlike the case with tissue slices, all of these muscarinic agonists exhibited full efficacy in this assay of PLC stimulation. Activation of PLC by the neurotransmitters or their analogs was dependent on the addition of guanosine 3'-O-thiotriphosphate (GTP gamma S). Stimulation of PLC by GTP gamma S alone or in combination with 5-methyltryptamine had an apparent EC50 of about 0.4 microM. However, when carbachol or other muscarinic agonists were used, the EC50 for GTP gamma S was significantly lower. We have previously shown that dopamine working through D1 receptors inhibits the PLC response to carbachol by preventing this shift in the apparent EC50 for GTP gamma S. Dopamine did not have a similar effect on 5-methyltryptamine stimulation of PLC. The results indicate that the postreceptor mechanisms of PLC activation are distinct for muscarinic as opposed to serotoninergic agonists in brain cortex.

Purification and characterization of PLC-beta m, a muscarinic cholinergic regulated phospholipase C from rabbit brain membrane

Two isozymes of phosphoinositide-specific phospholipase C were isolated and purified from salt-washed rabbit brain membranes. The membranes were extensively washed with isotonic, hypertonic and hypotonic buffers prior to solubilization with sodium cholate. Two isozymes (PLC-IV and PLC-beta m) were purified by a combination of DEAE-Sephacel, AH-Sepharose, heparin-Sepharose, AcA-34 gel filtration and mono-Q FPLC chromatographies. The major activity (PLC-beta m) was purified to homogeneity and had an estimated molecular weight of 155,000 on sodium-dodecyl sulfate-polyacrylamide gels (SDS-PAGE). This isozyme was immunologically identified as PLC-beta, an isozyme previously characterized in bovine brain cytosol and 2 M KCl membrane extracts. A second isozyme, PLC-IV, was immunologically distinct from PLC-beta and PLC-gamma and was purified to a stage where three protein bands (Mr 66,000, 61,000 and 54,000) on SDS-PAGE correlated with enzyme activity. The catalytic properties of the isozymes were studied and found to be very similar. The specific activities for PIP2 were greater than those obtained when PI was used. Both PLC-IV and PLC-beta m were Ca2(+)-dependent; near maximal stimulation for PI and PIP2 hydrolysis was observed at 0.5 microM free Ca2+. Sodium pyrophosphate and sodium fluoride stimulated phospholipase C activity of both isozymes. Polyclonal antibodies raised against PLC-beta m were able to inhibit carbachol and GTP gamma S stimulated phospholipase C activity in 2 M KCl washed rabbit cortical membranes. This suggests that in rabbit brain muscarinic cholinergic stimulation regulates PLC-beta m.

Activation of phospholipase C in rabbit brain membranes by carbachol in the presence of GTP gamma S; effects of biological detergents

Rabbit brain cortical membranes incubated with carbachol in the presence of GTP gamma S show a marked increase in the degradation of exogenous phosphatidylinositol 4,5-bisphosphate. This activation of phospholipase C is dependent on the presence of deoxycholate and maximal at 0.8-1 mM deoxycholate. There is negligible activation by carbachol alone but in the presence of GTP gamma S a carbachol effect can be readily demonstrated. Optimal activation of phospholipase C by carbachol was seen at 10 to 100 nM free Ca2+. Washing cortical membranes with hypertonic buffer extracted 60% of the membrane protein yet the carbachol and GTP gamma S coupling remained intact. Incubation of the membranes with lysophosphatidylcholine, Nonidet P-40, sodium deoxycholate or digitonin at concentrations considerably less than those frequently used to solubilize membrane proteins abolished the carbachol response. Octyl glucoside and sodium cholate also uncoupled receptor regulation of phospholipase C but only at concentrations where solubilization of membrane proteins occurred. Prior exposure of membranes to carbachol did not prevent the uncoupling observed as a result of detergent treatment. Incubation of the membranes with carbachol and GTP gamma S did not appear to be accompanied by specific release of either active phospholipase C or inhibitors of phospholipase C activity.

Dual effect of fluoride on phosphoinositide metabolism in rat brain cortex. Stimulation of phospholipase C and inhibition of polyphosphoinositide synthesis

We have studied the effects of fluoride, guanosine 5'-[gamma-thio]triphosphate (GTP[S]) and carbachol on phospholipase C and polyphosphoinositide synthesis. The experimental system consisted of membranes from rat brain cortex, with exogenous [3H]phosphatidylinositol ([3H]PtdIns) as substrate. In such systems, we have not found evidence to support carbachol and/or GTP[S] stimulation of PtdIns phosphorylation. Fluoride inhibited synthesis of PtdIns4P and PtdIns(4,5)P2 from PtdIns. Consequently, under conditions where breakdown of polyphosphoinositides by phospholipase C was dependent on PtdIns kinase activity, fluoride inhibited activation by GTP[S] plus carbachol of phospholipase C. When conditions allowed direct breakdown of PtdIns and precluded PtdIns kinase activity, the stimulatory effects of fluoride and GTP[S] plus carbachol on phospholipase C activity were additive.

A novel role for dopamine: inhibition of muscarinic cholinergic-stimulated phosphoinositide hydrolysis in rat brain cortical membranes

Dopamine inhibited phosphoinositide breakdown as stimulated by carbachol in rat brain cortical membranes. The IC50 value was 14 +/- 2 microM for dopamine's inhibition of phosphatidylinositol hydrolysis as stimulated by 1 mM carbachol. The inhibition was found at low (0.1 microM), but not high (greater than 0.3 microM), concentrations of the non-hydrolyzable guanine nucleotide analog, GTP gamma S. Pharmacological characterization of the response indicated that the dopamine effects were mediated by D1 receptors. The assay conditions precluded any involvement of cyclic-AMP as a mediator of the dopamine response, and thus, a novel role is proposed for dopamine in cortex working through D1 receptors to inhibit phosphoinositide degradation.

Frames of reference for allocating attention to space: evidence from the neglect syndrome

With respect to what frames of reference, or spatial coordinate systems, is attention allocated to locations in space? We posed this question about the spatial attention system that has been damaged in neglect patients, distinguishing among three possible types of spatial reference frame: viewer-centered, according to which locations are coded with respect to the viewer, environment-centered, according to which locations or coded with respect to the environment, and object-centered, according to which locations are coded with respect to an object. The three candidate frames of reference were decoupled from one another by rotating either the viewer or the stimulus object. Visual search performance suggested that the neglected hemifield was defined with respect to both viewer-centered and environment-centered frames of reference, but not with respect to an object-centered frame of reference. The role of objects in the allocation of attention to space, and the relation between our findings and the "two cortical visual systems" hypothesis, are discussed.

Effects of the wasp venom peptide, mastoparan, on a phosphoinositide-specific phospholipase C purified from rabbit brain membranes

The wasp venom peptide, mastoparan (Ile-Asn-Leu-Lys-Ala-Leu-Ala-Ala-Leu-Ala-Lys-Lys-Ile-LeuNH2), activated phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis as catalyzed by a phosphoinositide-specific phospholipase C (PLC-Im) purified from rabbit brain membranes. This activation was found when the molar ratio of mastoparan to PIP2 was less than 1 and when the concentration of PIP2 exceeded 10 microM. PIP2 breakdown was inhibited at both high and low substrate concentrations if the molar ratio of mastoparan to PIP2 was greater than 1. The stimulatory effect of mastoparan correlated with its ability to restrict aggregation of PIP2 into higher order structures (liposomes or mixed deoxycholate/phospholipid micelles) as the concentration of PIP2 was increased to 10 microM or greater. Mastoparan stimulation of PIP2 breakdown required the presence of a higher calcium concentration than was necessary for detection of enzyme activity. Both the stimulatory and inhibitory effects of mastoparan on PIP2 hydrolysis were lost if 2.5 mM deoxycholate was present in the assays. Hydrolysis of phosphatidylinositol (PI) by PLC-Im was inhibited at all concentrations of mastoparan tested. These results show that both PIP2 and PI are suitable substrates for PLC-Im, depending on the physical characteristics of their aggregates in aqueous suspension. An amphiphilic alpha-helix-forming peptide such as mastoparan may modulate phospholipase C activity due to the peptide's interaction with phospholipid substrates.

Carbachol in the presence of guanosine 5'-O-(3-thiotriphosphate) stimulates the breakdown of exogenous phosphatidylinositol 4,5-bisphosphate, phosphatidylinositol 4-phosphate, and phosphatidylinositol by rat brain membranes

The breakdown of exogenously added [3H]inositol-labeled phosphoinositides by rat brain cortical membranes was stimulated by the muscarinic cholinergic agonist carbachol. The stimulation required the presence of guanine nucleotide. Optimal conditions were similar to those described for guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) + carbachol stimulation of phosphoinositide breakdown in [3H]inositol-prelabeled brain membranes (Claro, E., Garcia, A., and Picatoste, F. (1989) Biochem J. 261, 29-35). Carbachol stimulated [3H]phosphatidylinositol 4,5-bisphosphate (PIP2) breakdown was inhibited by atropine and guanosine 5'-O-(2-thiobisphosphate). The magnitude of the stimulation of exogenous PIP2 breakdown by carbachol and GTP gamma S (2- to 3-fold) was little affected over a PIP2 concentration range of 0.03-100 microM. Phosphatidylinositol 4-phosphate (PIP) was as good a substrate at all concentrations as PIP2 for carbachol stimulation of phospholipase C activity. There was appreciable phosphomonoesterase degradation of PIP to phosphatidylinositol (PI) over 10 min. There was also some conversion of added PIP to PIP2 in the presence of added ATP. The effect of calcium on PIP breakdown was similar to that on PIP2 breakdown, with an apparent EC50 for Ca2+ stimulation of 0.74 and 0.72 microM, respectively, under basal conditions. The stimulation of PIP2 and PIP breakdown by carbachol in the presence of GTP gamma S was greatest on a percentage basis at the lowest free Ca2+ concentrations. Above 1 microM free Ca2+, the stimulatory effect was lost, whereas 10 microM free Ca2+ gave a maximal stimulation of basal phospholipase C activity. Degradation of added PI was also stimulated by carbachol in the absence of ATP. PI breakdown had an EC50 for Ca2+ stimulation of 1.07 microM. The best stimulation of PI breakdown due to carbachol plus GTP gamma S was seen with 0.3 microM free Ca2+ and 100 microM PI. Maximal activation of PI breakdown was seen at 1 mM deoxycholate as was true for PIP2 and PIP breakdown. There was little effect, even of 30 microM GTP gamma S alone or of carbachol alone, on PI breakdown. Half-maximal activation of the carbachol response required only 0.2 microM GTP gamma S. These results indicate that the phospholipase C enzyme(s) activated by carbachol in the presence of GTP gamma S in rat brain cortical membranes can degrade PIP2, PIP, and PI to inositol phosphates and diacylglycerol.

Evidence for involvement of guanine nucleotide-binding regulatory proteins in the activation of phospholipases by hormones

Guanine nucleotide-binding regulatory proteins similar to Gs and Gi may be involved in the activation of phospholipases C and A2 by hormones and other ligands. The binding of hormones to receptors that activate phospholipase C is decreased by guanine nucleotides and these hormones also stimulate a high-affinity GTPase activity in cell membranes. Effects of hormones on phospholipase C activity in cell-free preparations are dependent on the presence of guanine nucleotides. In addition, fluoride and nonhydrolyzable GTP analogs activate phospholipases in a manner that can be blocked by GDP beta S. The putative guanine nucleotide-binding regulatory protein that appears to be involved in activation of phospholipase C is sensitive to pertussis toxin in some cells but not in others.

Worldwide experience in newborn screening for classical congenital adrenal hyperplasia due to 21-hydroxylase deficiency

The need for a reliable screening test for classical congenital adrenal hyperplasia prompted development of newborn screening programs. Worldwide incidence of classical congenital adrenal hyperplasia in this report was taken from newborn screening programs in France, Italy, Japan, New Zealand, Scotland, and the United States. Two populations in which the occurrence of congenital adrenal hyperplasia among live births has been reported with greater than usual frequency are the Yupik Eskimos of southwestern Alaska (1:282) and the people of La Reunion, France (1:2,141). Aside from these populations, 1,093,310 newborns were screened between 1980 and 1988, of whom 77 had congenital adrenal hyperplasia. Thus, worldwide incidence of this disorder was estimated at 1:14,199 live births for homozygous patients, 1:60 for heterozygous subjects, with a gene frequency of 0.0083. Incidence of congenital adrenal hyperplasia among whites was estimated to be 1:11,909 (41:488,279) for homozygous patients, 1:55 for heterozygous subjects with a gene frequency of 0.0091. Incidence for the salt-wasting form of congenital adrenal hyperplasia was 1:18,850 (58:1,093,310) compared with 1:57,543 (19:1,093,310) for congenital adrenal hyperplasia in the simple virilizing form. Thus, salt-wasting congenital adrenal hyperplasia was three times more common than simple virilizing congenital adrenal hyperplasia. Estimated incidence of congenital adrenal hyperplasia in white populations in Italy and France (1:10,866) was higher than in Scotland (1:17,098), New Zealand (1:14,500). The incidence in an Asian population (Japan) (1:15,800) did not differ significantly from that of the white population. In four of five populations, overall incidence was higher than previously reported, as was the frequency of the salt-wasting form (75% v 50% to 66%), suggesting improved case detection by newborn screening.(ABSTRACT TRUNCATED AT 250 WORDS)

Guanine nucleotide and pyrophosphate activate exogenous phosphatidylinositol 4,5-bisphosphate hydrolysis in rat liver plasma membranes

5'-guanylylimidodiphosphate (GppNHp) in the presence of deoxycholate, stimulated the phospholipase C-mediated hydrolysis of exogenous [3H]phosphatidylinositol 4,5-bisphosphate ([3H]PIP2) to myo-[3H]inositol 1,4,5-trisphosphate in rat liver plasma membranes. Activation was not specific for guanine nucleotides as 5'-adenylylimidodiphosphate, imidodiphosphate and pyrophosphate stimulated the enzyme with similar efficacies and potencies. Enzyme activation by GppNHp was most pronounced when [3H]PIP2 was used as substrate. No added Ca++ was required for [3H]PIP2 breakdown but hydrolysis was inhibited by divalent ion chelators. GppNHp stimulation was apparent in the presence of Ca++ or Mg++ as well as chelator concentrations that partially inhibited the enzyme, indicating that this effect was not attributed to changes in affinity of these divalent cations for the enzyme or substrate. These results suggest that guanine nucleotides can stimulate the hydrolysis of exogenous [3H]PIP2 in rat liver membranes by a non-specific effect probably due to the interaction of the diphosphate moiety with the enzyme or substrate.

Analysis of the effects of inhaled diesel exhaust on the alveolar intravascular and interstitial cellular components of rodent lungs

Transmission electron microscopy (TEM) was used to determine the effect of diesel engine exhaust (DEE) on the intravascular and interstitial cellular population of the lungs of exposed rats and guinea pigs. Animals with matched controls were subjected to environments of either 250, 750, 1500 or 6000 micrograms/m3 for either 2 weeks, 6 weeks, 10 weeks or 18 months. These animals were sacrificed immediately following the exposure periods and their lungs perfused with fixative. Following dissection, random stratified biopsies from the lungs of these animals were made. Ultrathin sections from the alveolar lung were prepared and conventionally processed for TEM and randomly photographed to compose a micrograph database. These micrographs were analyzed by point counting using a Zeiss MOP 3 Digital Image Analyzer. The results indicated no significant intravascular cellular response but a significant increase in the mononuclear population in the interstitium.

Conditioned media from cultured cystic fibrosis fibroblasts inhibits Na/K ATPase activity

Conditioned culture media taken from fibroblast cell lines derived from skin biopsies of control or of patients with Cystic Fibrosis (CF) were incubated with membranes of rat submandibular glands. The Na/K - ATPase activity of these membranes was inhibited when treated with CF-media, including both ouabain sensitive and insensitive activities. However, the membrane associated Mg-ATPase, Ca-ATPase, and both basal and hormone-stimulated adenylate cyclase activities were relatively unaffected. Thus, a factor or factors produced by CF-fibroblasts was shown to be active in a cell-free system derived from an exocrine gland.