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PubMed1981

Contractile activities of structural analogs of leukotrienes C and D: role of the polar substituents.

Twenty-three structural analogs of the leukotriene components of slow reacting substance of anaphylaxis (SRS-A), in which the polar regions of the leukotriene were systematically modified, were tested for their contractile activities on guinea pig pulmonary parenchymal strips and guinea pig ileum. The structural modifications allowed evaluation of the separate contributions of the four polar units in the C-1 to C-6 region of the SRS-A leukotrienes to smooth muscle spasmogenic activity. The free NH2-terminal amino group of the S-linked peptide was necessary for full activity, and its deletion or substitution reduced activity by more than one but less than two orders of magnitude. A similar level of importance was apparent for the free glycine carboxyl group. In contrast, a free eicosanoid carboxyl at C-1 is not required for full activity on the airway and for substantial activity on the ileum. A role for the C-5 hydroxyl is indicated by the inactivity of the one available 5-desoxy analog. Nucleophilic, divalent sulfur is not critical to leukotriene D (LTD) activity, in that one sulfoxide had substantial function. The conformational relationship between the eicosanoid and peptide moieties of LTD is of considerable importance in that epimers at the C-5 or C-6 position were less active than LTD by more than two orders of magnitude. Several lines of evidence suggest that the relative geometrical arrangement of the C20 chain and the peptide unit is important to activity, consistent with the existence of a true receptor for LTD.

Animals↗

PubMed1986

A comparative study of muscle spindles in slow and fast neonatal muscles of normal and dystrophic mice.

Muscle spindles from the slow-twitch soleus and the fast-twitch extensor digitorum longus (EDL) muscles of genetically dystrophic mice of the dy2J/dy2J strain were compared with age-matched normal animals at neonatal ages of 1-3 weeks according to histochemical, quantitative, and ultrastructural parameters. Intrafusal fibers in both the soleus and EDL exhibited similar regional differences in myosin ATPase activity, and conformed to those noted previously in various adult species. In distal polar regions, all nuclear bag fibers resembled extrafusal fibers of the type 1 variety, whereas in capsular zones they could be divided into two subtypes. Nuclear chain fibers possessed a staining pattern similar to type 2 extrafusal fibers, and in contrast to the bag fibers they exhibited no regional variations. These features were consistently observed in both the normal and dystrophic muscles at all ages. Spindles varied only slightly in their number and distribution in the two types of muscle, and their location followed the neurovascular branching pattern in each. Irrespective of age or genotype, spindles in the soleus were more homogeneously dispersed, but those in the EDL were concentrated along the dorsal aspect of the muscle. No significant differences were noted in the total number of spindles between normal and dystrophic muscles. In addition, no dramatic differences were observed in the muscle spindle index for soleus and EDL. The first obvious disease-related changes were noted in extrafusal fibers of the soleus of 3-week-old mice, and spindles were often located close to these areas of fiber degeneration. Despite alterations in the surrounding tissue, however, spindles appeared morphologically unaltered in dystrophy. These observations indicate that intrafusal fibers of spindles in neonatal mice appear enzymatically and histologically unaffected in incipient stages of progressive muscular dystrophy.

Adenosine Triphosphatases↗

PubMed2004

Autoradiographic distribution of serotonin transporters and receptor subtypes in human brain.

Several neurochemical in vitro and in vivo imaging studies have been aimed at characterizing the localization of serotonin receptors and transporters in the human brain. In this study, a detailed comparison of the distribution of a number of 5-HT receptor subtypes and the 5-HT transporter was carried out in vitro using human postmortem brain tissue. Anatomically adjacent whole hemisphere sections were incubated with specific radioligands for the 5-HT(1A), 5-HT(1B), 5-HT(2A), 5-HT(4) receptors and the 5-HT transporter. The autoradiograms revealed different laminar and regional distribution patterns in the isocortex, where 5-HT(1A) and 5-HT(4) receptor binding showed highest densities in superficial layers and 5-HT(2A) receptor binding was most abundant in middle layers. In cortical regions, 5-HT transporters were concentrated to several limbic lobe structures (posterior uncus, entorhinal, cingulate, insular and temporal polar regions). 5-HT(1A) receptor densities were also high in limbic cortical regions (hippocampus, posterior entorhinal cortex, and subcallosal area) compared to the isocortex. Subregionally different distribution patterns were observed in the basal ganglia with a trend toward higher levels in ventral striatal (5-HT(1B) receptors) and pallidal (5-HT transporters and 5-HT(1B) receptors) regions. The localization in regions belonging to limbic cortico-striato-pallido-thalamic circuits is in line with the documented role of 5-HT in modulation of mood and emotion, and the suggested involvement of this system in pathophysiology of various psychiatric disorders. The qualitative and quantitative information reported in this study might provide important complements to in vivo neuroimaging studies of the 5-HT system.

Autoradiography↗

PubMed1982

Sarcolemmal desmosterol accumulation and membrane physical properties in 20,25-diazacholesterol myotonia.

In rats treated biweekly with 20,25-diazacholesterol (200 mg/kg orally), the desmosterol level in skeletal muscle sarcolemma increased progressively to about 80% of membrane sterol while total sterol levels remained constant. Following a single oral dose of 20,25-D, the kinetics of desmosterol accumulation and subsequent loss in sarcolemma were more rapid than in whole muscle homogenates. The anisotropy of diphenylhexatriene fluorescence and the calculated microviscosity of the probe's microenvironment decreased significantly with increasing desmosterol levels in a temperature-dependent manner, although fluorescent lifetimes were not altered. Fluorescent probes which localize in more superficial regions of the membrane detected no change. Studies with erythrocyte ghost membranes yielded results comparable to sarcolemma. Replacement of membrane yielded results comparable to sarcolemma. Replacement of membrane cholesterol with desmosterol reduced the local microviscosity of membrane cholesterol with desmosterol reduced the local microviscosity of the membrane hydrophobic region associated with phospholipid acyl chains and sterol side chains, but had little apparent effect on more superficial, polar regions. These observations can be correlated with the membrane location of the unsaturated side chain in desmosterol.

Animals↗

PubMed1989

Effect of pH on the interaction of botulinum neurotoxins A, B and E with liposomes.

The interaction of botulinum neurotoxin serotypes A, B and E with membranes of different lipid compositions was examined by photolabelling with two photoreactive phosphatidylcholine analogues that monitor the polar region and the hydrophobic core of the lipid bilayer. At neutral pH the neurotoxins interacted both with the polar head groups and with fatty acid chains of phospholipids. At acidic pHs the neurotoxins underwent structural changes characterized by a more extensive interaction with lipids. Both the heavy and light chain subunits of the neurotoxins were involved in the process. The change in the nature and extent of toxin-lipid interaction occurred in the pH range 4-6 and was not influenced by the presence of polysialogangliosides. The present data are in agreement with the idea that botulinum neurotoxins enter into nerve cells from a low pH intracellular compartment.

Animals↗

PubMed2004

Vibrational spectroscopic study on the origin of stress oscillation during step-wise stretching in poly(ethylene terephthalate).

The origin of the phenomenon of stress oscillation during step-wise stretching at room temperature for amorphous poly(ethylene terephthalate) (PET) was investigated using vibrational spectroscopy. For the first time, transmission Fourier transform infrared (FT-IR), attenuated total reflection (ATR) FT-IR, and micro-Raman spectroscopies were used in order to investigate the correlation of the orientation of the molecular chains, their conformational transformations, and the appearance of stress-induced crystallization to the phenomenon of stress oscillation during the step-wise stretching procedure. The phenomenon of stress oscillation occurs when amorphous PET is exposed to mechanical stress during which the extension rate is increased in a step-wise manner. This phenomenon leads to the formation of a pattern of opaque and transparent stripes (''striated'' or oscillating region), clearly distinguished from the unstretched (''bulk'') and the ''necking'' regions. Both infrared and Raman spectroscopic investigations revealed that the main conformational transformations and a significant increase of the crystallinity occur simultaneously in the ''striated'' region. Polarized infrared experiments showed the presence of increased molecular orientation, which is more profound for the ''intense striated'' region. Finally, micro-Raman spectroscopy allowed the study of opaque and transparent stripes individually and showed that the opaque stripes are more crystalline. Thus, our findings provide conclusive experimental support for the theory, which directly correlates the appearance of the stress-oscillation phenomenon with the induction of crystallinity and heat release and is based on Barenblatt's model. Our study also provides new conformational assignments for the infrared bands in PET for the high-frequency region from 3200 to 3800 cm(-1). Specifically, the bands at 3336 cm(-1) and at 3298 cm(-1) have been attributed to the trans and gauche conformations, respectively.

Journal Article↗

PubMed2004

Mouse limb deformity mutations disrupt a global control region within the large regulatory landscape required for Gremlin expression.

The mouse limb deformity (ld) mutations cause limb malformations by disrupting epithelial-mesenchymal signaling between the polarizing region and the apical ectodermal ridge. Formin was proposed as the relevant gene because three of the five ld alleles disrupt its C-terminal domain. In contrast, our studies establish that the two other ld alleles directly disrupt the neighboring Gremlin gene, corroborating the requirement of this BMP antagonist for limb morphogenesis. Further doubts concerning an involvement of Formin in the ld limb phenotype are cast, as a targeted mutation removing the C-terminal Formin domain by frame shift does not affect embryogenesis. In contrast, the deletion of the corresponding genomic region reproduces the ld limb phenotype and is allelic to mutations in Gremlin. We resolve these conflicting results by identifying a cis-regulatory region within the deletion that is required for Gremlin activation in the limb bud mesenchyme. This distant cis-regulatory region within Formin is also altered by three of the ld mutations. Therefore, the ld limb bud patterning defects are not caused by disruption of Formin, but by alteration of a global control region (GCR) required for Gremlin transcription. Our studies reveal the large genomic landscape harboring this GCR, which is required for tissue-specific coexpression of two structurally and functionally unrelated genes.

Amino Acid Sequence↗

PubMed1991

Protein kinase C beta-subtype-immunoreactive motor and sensory nerves in rat muscle spindle.

The localization of protein kinase C beta-subtype-like immunoreactivity (PKC-beta-LI) was studied in the muscle spindles of rat neck muscles. In the equatorial regions of muscle spindles PKC-beta-LI was detected in spiral sensory nerve endings surrounding intrafusal muscle fibers. In polar regions single PKC-beta-immunoreactive (IR) nerve fibers were found between intrafusal muscle fibers and some PKC-beta-IR motor nerve endings were seen on the surface of intrafusal fibers. These results suggest that PKC-beta may be involved in regulation of muscle contraction and tonus by modulating the sensitivity of afferent and efferent innervation of muscle spindles.

Animals↗

PubMed2001

Scanning electron microscopic study of muscle spindles in the tenuissimus muscle of the Chinese hamster: with reference to the outer capsule, inner capsule and fusimotor endings.

The outer capsule, inner capsule and fusimotor endings of muscle spindles in the tenuissimus muscle of mature Chinese hamsters were examined by scanning electron microscopy (SEM). The thin and long tenuissimus muscle was transversely cut into several segments, and the segments were longitudinally or obliquely cut with a razor blade to mechanically remove the spindle sheath (outer capsule). These specimens were treated with 8 N HCl at 60 degrees C to isolate the muscle spindles and clearly expose the internal structures such as the inner capsule and fusimotor endings innervating intrafusal muscle fibers. The spindle sheath was about 1 mm long and at the equator about 50 microm in diameter. Within the outer capsule, cells of the inner capsule in the equatorial region were polygonal in shape, and continuously surrounded the axial bundle like a sleeve. This continuous sheath became sieve-like in the juxta-equatorial region, depending on the twining of thin and flattened cytoplasmic extensions and/or processes of the cells. Owing to the continuous inner capsular sheath in the equatorial region, the arrangement of sensory endings were not visualized under SEM. Fusimotor endings observed in the juxta-equatorial and polar regions consisted of poorly-developed subneural apparatuses with predominantly pit-like and short slit-like junctional folds.

Animals↗

PubMed1988

Purified thick filaments from the nematode Caenorhabditis elegans: evidence for multiple proteins associated with core structures.

The thick filaments of the nematode, Caenorhabditis elegans, arising predominantly from the body-wall muscles, contain two myosin isoforms and paramyosin as their major proteins. The two myosins are located in distinct regions of the surfaces, while paramyosin is located within the backbones of the filaments. Tubular structures constitute the cores of the polar regions, and electron-dense material is present in the cores of the central regions (Epstein, H.F., D.M. Miller, I. Ortiz, and G.C. Berliner. 1985. J. Cell Biol. 100:904-915). Biochemical, genetic, and immunological experiments indicate that the two myosins and paramyosin are not necessary core components (Epstein, H.F., I. Ortiz, and L.A. Traeger Mackinnon. 1986. J. Cell Biol. 103:985-993). The existence of the core structures suggests, therefore, that additional proteins may be associated with thick filaments in C. elegans. To biochemically detect minor associated proteins, a new procedure for the isolation of thick filaments of high purity and structural preservation has been developed. The final step, glycerol gradient centrifugation, yielded fractions that are contaminated by, at most, 1-2% with actin, tropomyosin, or ribosome-associated proteins on the basis of Coomassie Blue staining and electron microscopy. Silver staining and radioautography of gel electrophoretograms of unlabeled and 35S-labeled proteins, respectively, revealed at least 10 additional bands that cosedimented with thick filaments in glycerol gradients. Core structures prepared from wild-type thick filaments contained at least six of these thick filament-associated protein bands. The six proteins also cosedimented with thick filaments purified by gradient centrifugation from CB190 mutants lacking myosin heavy chain B and from CB1214 mutants lacking paramyosin. For these reasons, we propose that the six associated proteins are potential candidates for putative components of core structures in the thick filaments of body-wall muscles of C. elegans.

Animals↗

PubMed1995

NuMA is required for the organization of microtubules into aster-like mitotic arrays.

NuMA (Nuclear protein that associates with the Mitotic Apparatus) is a 235-kD intranuclear protein that accumulates at the pericentrosomal region of the mitotic spindle in vertebrate cells. To determine if NuMA plays an active role in organizing the microtubules at the polar region of the mitotic spindle, we have developed a cell free system for the assembly of mitotic asters derived from synchronized cultured cells. Mitotic asters assembled in this extract are composed of microtubules arranged in a radial array that contain NuMA concentrated at the central core. The organization of microtubules into asters in this cell free system is dependent on NuMA because immunodepletion of NuMA from the extract results in randomly dispersed microtubules instead of organized mitotic asters, and addition of the purified recombinant NuMA protein to the NuMA-depleted extract fully reconstitutes the organization of the microtubules into mitotic asters. Furthermore, we show that NuMA is phosphorylated upon mitotic aster assembly and that NuMA is only required in the late stages of aster assembly in this cell free system consistent with the temporal accumulation of NuMA at the polar ends of the mitotic spindle in vivo. These results, in combination with the phenotype observed in vivo after the prevention of NuMA from targeting onto the mitotic spindle by antibody microinjection, suggest that NuMA plays a functional role in the organization of the microtubules of the mitotic spindle.

Animals↗

PubMed1983

[Fine structure of intrafusal and extrafusal nerve segments of the rat muscle spindle after sciatic nerve transsection].

Intrafusal and extrafusal nerve segments in muscle spindles from lumbricalis muscles of the hindpaw of the rat were studied by electron microscopy from 10 h to 5 days after severance of the sciatic nerve. In several spindles examined, nerve fascicles piercing the spindle capsule in the equatorial region contained a large myelinated, a smaller myelinated, and an unmyelinated fiber. Unmyelinated fibers were not present in small fascicles leading to the polar region. The changes in the extrafusal nerve segments followed the pattern of Wallerian degeneration. Intra-axonal glycogen deposits were prominent in sensory fibers. The unmyelinated fibers were the earliest to degenerate, the large myelinated ones the latest. Differences between motor and sensory fiber degeneration emerged in their preterminal intrafusal segments and were analogous to those of the nerve endings. Terminal nerve fibers in the spindle equator succumbed to attack of mesenchymal cells, leaving extensive basement membrane reduplications around myelin debris-laden Schwann cells, while polar fibers were engulfed by Schwann cell processes, leaving regular bands of Büngner.

Animals↗

PubMedDate not supplied

Genetic analysis of myosin assembly in Caenorhabditis elegans.

The established observations and unresolved questions in the assembly of myosin are outlined in this article. Much of the background information has been obtained in classical experiments using the myosin and thick filaments from vertebrate skeletal muscle. Current research is concerned with problems of myosin assembly and structure in smooth muscle, a broad spectrum of invertebrate muscles, and eukaryotic cells in general. Many of the general questions concerning myosin assembly have been addressed by a combination of genetic, molecular, and structural approaches in the nematode Caenorhabditis elegans. Detailed analysis of multiple myosin isoforms has been a prominent aspect of the nematode work. The molecular cloning and determination of the complete sequences of the genes encoding the four isoforms of myosin heavy chain and of the myosin-associated protein paramyosin have been a major landmark. The sequences have permitted a theoretical analysis of myosin rod structure and the interactions of myosin in thick filaments. The development of specific monoclonal antibodies to the individual myosins has led to the delineation of the different locations of the myosins and to their special roles in thick filament structure and assembly. In nematode body-wall muscles, two isoforms, myosins A and B, are located in different regions of each thick filament. Myosin A is located in the central biopolar zones, whereas myosin B is restricted to the flanking polar regions. This specific localization directly implies differential behavior of the two myosins during assembly. Genetic and structural experiments demonstrate that paramyosin and the levels of expression of the two forms are required for the differential assembly. Additional genetic experiments indicate that several other gene products are involved in the assembly of myosin. Structural studies of mutants have uncovered two new structures. A core structure separate from myosin and paramyosin appears to be an integral part of thick filaments. Multifilament assemblages exhibit multiple nascent thick filament-like structures extending from central paramyosin regions. Dominant mutants of myosin that disrupt thick filament assembly are located in the ATP and actin binding sites of the heavy chain. A model for a cycle of reactions in the assembly of myosin into thick filaments is presented. Specific reactions of the two myosin isoforms, paramyosin, and core proteins with multifilament assemblages as possible intermediates in assembly are proposed.

Animals↗

PubMed1999

The effect of daunorubicin and glutaraldehyde treatment on the structure of erythrocyte membrane.

The effect of daunorubicin (DNR) and glutaraldehyde on erythrocyte membrane structure was examined by Electron Spin Resonance spectroscopy. Human erythrocytes were incubated with daunorubicin and then with glutaraldehyde to prevent drug efflux. We have demonstrated that DNR alone caused changes in membrane fluidity mainly in the hydrophobic regions of the lipid bilayer. When DNR-preincubated erythrocytes were treated with glutaraldehyde, the alterations in fluidity were observed in the polar regions as well as in the deeper regions of the cell membrane. The incorporation of drug and glutaraldehyde into human erythrocytes also caused conformational alterations in membrane cytoskeletal proteins and changes in the internal viscosity of the cells. The results suggest that glutaraldehyde in the drug-pretreated erythrocytes may lead to significant perturbations in the organization of the plasma membrane lipids and proteins.

Daunorubicin↗

PubMed2002

The chemical toxic benzo[a]pyrene perturbs the physical organization of phosphatidylcholine membranes.

The interaction of the chemical carcinogen benzo[a]pyrene (BaP) with phosphatidylcholine membranes has been investigated by using various physical techniques. Differential scanning calorimetry showed that BaP, at concentrations as low as 2 mol% in mixtures with dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine, and distearoylphosphatidylcholine, abolished the pretransition and broadened and shifted to lower temperatures the main gel-to-liquid crystalline phase transition. The effect was stronger as the lipid acyl chain length decreased. Infrared spectroscopy indicated that inclusion of BaP had a strong influence on the carbonyl (C=O) stretching band. Fitting of this band resulted in the presence of three components in the case of samples containing BaP, centered at 1,742, 1,727, and 1,704 cm(-1) (only two components, at 1,742 and 1,727 cm(-1), were observed for pure DMPC). The component at 1,704 cm(-1) corresponded to a disolvate and strongly supported the notion that inclusion of BaP increases hydration of the bilayer C=O. Small-angle x-ray diffraction showed that incorporation of 10 mol% BaP into DMPC increased bilayer thickness from 66.7 to 71 A in the gel state and from 58.9 to 60.9 A in the fluid phase. It is proposed that, when BaP is incorporated into a phospholipid bilayer, it locates in the most apolar region of the phospholipid palisade, resulting in expansion and swelling of the membrane. These two effects will facilitate water penetration into the polar region of the membrane, as observed by the increased hydration of the C=O groups, and thus perturb both membrane integrity and functionality.

Benzo(a)pyrene↗

PubMed2000

North-south geological differences between the residual polar caps on Mars.

Polar processes can be sensitive indicators of global climate, and the geological features associated with polar ice caps can therefore indicate evolution of climate with time. The polar regions on Mars have distinctive morphologic and climatologic features: thick layered deposits, seasonal CO2 frost caps extending to mid latitudes, and near-polar residual frost deposits that survive the summer. The relationship of the seasonal and residual frost caps to the layered deposits has been poorly constrained, mainly by the limited spatial resolution of the available data. In particular, it has not been known if the residual caps represent simple thin frost cover or substantial geologic features. Here we show that the residual cap on the south pole is a distinct geologic unit with striking collapse and erosional topography; this is very different from the residual cap on the north pole, which grades into the underlying layered materials. These findings indicate that the differences between the caps are substantial (rather than reflecting short-lived differences in frost cover), and so support the idea of long-term asymmetry in the polar climates of Mars.

Carbon Dioxide↗

PubMed1997

Localization of enzymically enhanced heavy metal accumulation by Citrobacter sp. and metal accumulation in vitro by liposomes containing entrapped enzyme.

A heavy-metal-accumulating Citrobacter sp. has been used for the treatment of metal-laden industrial wastes. Metal uptake is mediated via a cell-bound phosphatase that liberates inorganic phosphate which precipitates with heavy metals as cell-bound metal phosphate. A phosphatase-efficient mutant accumulated little UO(2)2+, while a phosphatase-overproducing mutant accumulated correspondingly more metal, with a uranium loading equivalent to the bacterial dry weight achieved after 6 h exposure of resting cells to uranyl ion in the presence of phosphatase substrate (glycerol 2-phosphate). The phosphatase, visualized by immunogold labelling in the parent and overproducing strains, but not seen in the deficient mutant, was held within the periplasmic space with, in some cells, a higher concentration at the polar regions. Enzyme was also associated with the outer membrane and found extracellularly. Accumulated uranyl phosphate was visible as cell-surface- and polar-localized deposits, identified by energy-dispersive X-ray analysis (EDAX), proton-induced X-ray emission analysis (PIXE) and X-ray diffraction analysis (XRD) as polycrystalline HUO2PO4.4H2O. Nucleation sites for initiation of biocrystallization were identified at the cytoplasmic and outer membranes, prompting consideration of an in vitro biocatalytic system for metal waste remediation. Phosphatidylcholine-based liposomes with entrapped phosphatase released phosphate comparably to whole cells, as shown by 31P NMR spectroscopy in the presence of 'NMR-silent' 112Cd2+. Application of liposome-immobilized enzyme to the decontamination of uranyl solutions was, however, limited by rapid fouling of the biocatalyst by deposited uranyl phosphate. It is suggested that the architecture of the bacterial cell surface provides a means of access of uranyl ion to the inner and outer membranes and enzymically liberated phosphate in a way that minimizes fouling in whole cells.

Bacterial Proteins↗

PubMed1987

The internal signal sequence of Escherichia coli leader peptidase is necessary, but not sufficient, for its rapid membrane assembly.

Leader peptidase of Escherichia coli, a protein of 323 residues, has three hydrophobic domains. The first, residues 1-22, is the most apolar and is followed by a polar region (23-61) which faces the cytoplasm. The second hydrophobic domain (residues 62-76) spans the membrane. The third hydrophobic domain, which has a minimal apolar character, and the polar, carboxyl-terminal two-thirds of the protein are exposed to the periplasm. Deletion of either the amino terminus (residues 4-50) or the third hydrophobic region (residues 83-98) has almost no effect on the rate of leader peptidase membrane assembly, while the second hydrophobic domain is essential for insertion (Dalbey, R., and Wickner, W. (1987) Science 235, 783-787). To further define the roles of these domains, we have replaced the normal, cleaved leader sequence of pro-OmpA and M13 procoat with regions containing either the first or second apolar domain of leader peptidase. The second apolar domain supports the translocation of OmpA or coat protein across the plasma membrane, establishing its identity as an internal, uncleaved signal sequence. In addition to this sequence, we now find that leader peptidase needs either the amino-terminal domain or the third hydrophobic domain to permit its rapid membrane assembly. These results show that, although a signal sequence is necessary for rapid membrane assembly of leader peptidase, it is not sufficient.

Base Sequence↗