Intersegmental Space Research Articles

Larval internal morphology of the introduced blowfly Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae)

The blowfly Chrysomya megacephala (Diptera: Calliphoridae) colonizes different environments and is found in many global regions. Its importance includes its involvement in the decomposition of organic matter, forensic entomology, maggot therapy, bioprospecting, source of biodiesel, industry, stabilization of heavy metals in soil, pollination, and as a vector of diseases and causing secondary myiasis. Internal morphological studies contribute to understanding insect's function and provide basic data for applied areas with interest in this specie. The objective of this study was to describe the internal morphology of C. megacephala larvae. Post-embryonic development occurred over 240 h, equally divided into larval and pupal stages. After hatching, the larvae averaged <1 mm in length and 0.02 mg in weight, growing to 13.83 mm and 50.4 mg in the third instar. We utilized whole, third-instar larvae to perform histology. Sensory organs were observed in the cephalic region, antennae, maxillary palps, and ventral organ. The alimentary canal comprises a foregut, midgut, and hindgut, including tracheal insertions and accessory organs, such as salivary glands. The midgut is the largest organ of the alimentary canal and fat body are present in body cavity and intersegmental space. Thus, our data about the internal morphology of C. megacephala larvae describe the structure and position of the alimentary canal, salivary gland, sensory organs, and fat body.

In-house virtual surgical planning and guided mandibular reconstruction is less precise, but more economical and time-efficient than commercial procedures.

To compare an in-house and a commercially available surgical planning solution for mandibular reconstruction in terms of postoperative reconstruction accuracy and economic benefit. Twenty-nine consecutive patients with advanced oral squamous cell carcinoma (OSCC) requiring segmental mandibular reconstruction were enrolled. Fifteen patients underwent in-house surgical planning and 14 patients underwent a commercially available planning solution. A morphometric comparison of preoperative and postoperative computed tomography (CT) data sets and a cost-benefit comparison were performed. Volumes of planned and reconstructed bone segments differed significantly for both in-house planning (p = 0.0431) and commercial planning (p < 0.0001). Significant differences in osteotomy angles were demonstrated for in-house planning (p = 0.0391). Commercial planning was superior to in-house planning for total mandibular deviation (p = 0.0217), intersegmental space volumes (p = 0.0035), and lengths (p = 0.0007). No significant difference was found between the two planning solutions in terms of intersegmental ossification and the incidence of wound healing disorders. In-house planning took less time than commercial planning (p < 0.0001). Component manufacturing costs (p < 0.0001) and total cumulative costs (p < 0.0001) were significantly lower for in-house planning. In-house surgical planning is less accurate but has a cost advantage and could be performed in less time.

Regioisomeric Spirobifluorene CANAL Ladder Polymers and Their Gas Separation Performance.

We synthesized and characterized two isomeric microporous hydrocarbon ladder polymers from catalytic arene norbornene annulation (CANAL) of regioisomeric bis-norbornene fused spirobifluorenes, where the ladder chains are connected either through the same fluorene unit or across two different fluorene units in spirobifluorene. This pair of isomeric polymers was used to investigate the effect of ladder macromolecular structures on the microporosity and transport properties. Both polymers form mechanically intact films with thermal stability up to 480 °C and relatively high BET surface areas. The polymer formed from 2,7-dibromospirobifluorene showed higher BET surface area and higher gas permeability than the polymer from 2,2'-dibromospirobifluorene despite similar intersegmental spacing as indicated by X-ray scattering. The aging behavior for both polymers followed the same trend as the previously reported CANAL-fluorene polymers, with dramatically increased permselectivities over time, resulting in gas separation performance above the 2008 upper bounds for H2/CH4 and O2/N2.

Correlation between direction of pedicle screw and restoration of lumbar degenerative scoliosis in degenerative lumbar spondylolisthesis: a retrospective study.

Inferior clinical outcomes have been reported in patients with degenerative lumbar spondylolisthesis (DLS) accompanied by lumbar degenerative scoliosis, but little attention has been paid to its radiologic assessment or preoperative planning. The aim of this study was to analyze the effect of transforaminal lumbar interbody fusion on patients with DLS and lumbar degenerative scoliosis and explore the surgical aspects benefiting the restoration of lumbar degenerative scoliosis. All patients with DLS and lumbar degenerative scoliosis undergoing single-level unilateral transforaminal lumbar interbody fusion surgery between July 1, 2015, and April 30, 2021, were screened in this retrospective cohort study. Clinical outcomes including visual analog scale (VAS), Oswestry disability index (ODI), and radiographic parameters of sagittal and coronal alignment, cage spatial locations, and angle of pedicle screw (parallel, cranial, and caudad angle) were assessed. Coronal asymmetry was demonstrated by the intervertebral height difference between the medial and lateral margins of indexed intersegmental space. The correlations between Δintervertebral height difference (postoperative intervertebral height difference-preoperative intervertebral height difference) and radiographic parameters and clinical outcomes were analyzed by univariable, multivariable, mediation, and correlation analyses. Significance was set at a bilateral P<0.05. A total of 57 included patients were followed up for a minimum of 1 year. Reduction of VAS, ODI, and improvement of radiographic parameters were found after surgery. The cranial angle of the lower pedicle screw positively correlated with Δintervertebral height difference restoration (b=0.54; standard error=0.11; P<0.001). Transforaminal lumbar interbody fusion surgery appears to be an effective approach to improving the radiographic and clinical outcomes of patients with DLS and lumbar degenerative scoliosis. The cranial direction of the lower pedicle screws in single-level unilateral transforaminal lumbar interbody fusion surgery may be associated with a better postoperative restoration of lumbar degenerative scoliosis.

Facile Synthesis and Study of Microporous Catalytic Arene-Norbornene Annulation-Tröger's Base Ladder Polymers for Membrane Air Separation.

We report the facile synthesis and study of two soluble microporous ladder polymers, CANAL-TBs, by combining catalytic arene-norbornene annulation (CANAL) and Tröger's base (TB) formation. The polymers were synthesized in two steps from commercially available chemicals in high yields. CANAL-TBs easily formed mechanically robust films, were thermally stable up to 440 °C, and exhibited very high Brunauer-Teller-Emmett surface areas of 900-1000 m2 g-1. The gas separation performance of the CANAL-TBs for the O2/N2 pair is located between the 2008 and 2015 permeability/selectivity upper bounds. After 300 days of aging, CANAL-TBs still exhibited O2 permeability of 200-500 barrer with O2/N2 selectivity of about 5. The polymer with more methyl substituents exhibited higher permeability and slightly larger intersegmental spacing as revealed by WAXS, presumably due to more frustrated chain packing. The facile synthesis, excellent mechanical properties, and promising air separation performance of the CANAL-TB polymers make them attractive membrane materials for various air separation applications, such as aircraft on-board nitrogen generation and oxygen enrichment for combustion.

Tetraphenylsilane‐Cored Star‐Shaped Amphiphilic Block Copolymers for pH‐Responsive Anticancer Drug Delivery

AbstractFour‐arm star‐shaped poly[2‐(diethylamino)ethyl methacrylate]‐b‐poly[2‐hydroxyethyl methacrylate]s block copolymers using tetraphenylsilane (TPS) as a core with adjustable arm lengths are synthesized through two‐step atom transfer radical polymerizations. For comparison, a linear block copolymer with similar molecular weight is also prepared. The assembled star‐shaped copolymer micelles exhibit sizes of 102–139 nm and critical micelle concentrations of 1.49–3.93 mg L−1. Moreover, the bulky and rigid TPS core is advantageous for propping up the four star‐shaped arms to generate large intersegmental space. As a result, the drug‐loading capacity in the micelles is up to 33.97 wt%, much surpassing the linear counterpart (8.92 wt%) and the previously reported star‐shaped copolymers prepared using pentaerythritol as the core. Furthermore, the micelles show sensitive pH‐responsive drug release when the pH changes from 7.4 to 5.0. The in vitro cytotoxicity to Hela cells indicates that the doxorubicin (DOX)‐loaded micelles have similar anticancer activity to the pristine DOX. The combination of excellent micelle stability, high drug‐loading, sensitive pH response, and good anticancer activity endows the copolymers with promising application in drug control delivery for anticancer therapy.

66 - Effect of Posterior Cervical Cages Supplemental to Anterior Cervical Integrated Cage Fusion on Lordotic Alignment, Foraminal Height, and Intersegmental Space

66 - Effect of Posterior Cervical Cages Supplemental to Anterior Cervical Integrated Cage Fusion on Lordotic Alignment, Foraminal Height, and Intersegmental Space

Subnanoscopic inhomogeneities in model end-linked PDMS networks probed by positron annihilation lifetime spectroscopy and their effects on thermomechanical properties

The subnanoscopic free volume hole properties of model poly(dimethylsiloxane) (PDMS) networks with unimodal and bimodal distribution of chain lengths between the cross-links were determined using positron annihilation life time spectroscopy (PALS). Wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS) studies were carried out to further understand the structural inhomogeneities of the networks at different length scales. The networks were prepared by end-linking combinations of sufficiently longer (Mn = 18,952) and shorter (Mn = 4323) precursor PDMS chains relative to entanglement spacing (Me). The macroscopic properties of the networks were studied by tensile testing, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), as well as equilibrium swelling measurements. Through PALS studies it was possible to delineate the subtle variations in the elementary mesh sizes, a measure of the segmental spacing, of the unimodal short and long chain networks influenced by cross-links or entanglements. The intersegmental spacing of the unimodal PDMS networks at a length scale of few angstroms obtained from WAXD measurements were found to be almost in quantitative agreement with the free volume hole sizes obtained from PALS. SAXS measurements on solvent swollen PDMS networks from short and long chain precursors were used to obtain correlation length of the networks at a higher length scale of a few nanometers. Further, the studies revealed that the enhanced mechanical properties seen in certain bimodal elastomer networks are connected with topological features of the networks. A noteworthy finding from PALS studies was that the bimodal composition with 20 wt% short chain, which showed the best combination of mechanical properties with a feature of stress-upturn in tensile testing, exhibited the least free volume size and relatively lower dispersion in its size distribution among the networks. These fundamental studies are expected to provide new insights into the network structure of model elastomers at a molecular scale and its possible connection with macroscopic properties.

MECANISMOS DA AÇÃO LARVICIDA DO DIFLUBENZURON SOBRE Aedes aegypti EVIDENCIADOS PELAS ALTERAÇÕES ULTRAESTRUTURAIS

Dengue is a viral disease transmitted by Aedes aegypti in over 100 countries in the intertropical band in the world and the main forms of control are antivectorial actions. In this paper, ultrastructural changes caused by diflubenzuron (DFB) are presented. The experiments were performed with 3rd instar larvae of Ae. aegypti with DFB at concentrations of 0.1 and 1 ?g/mL. After 24h of exposure, larvae were collected, fixed, dehydrated, embedded, cut, contrasted with uranyl acetate and 3% lead citrate and examined under the electron microscope. Ultrastructural alterations caused by the diflubenzuron inhibitory activity were observed in the cuticle and in the midgut of Ae. aegypti larvae treated with 0.1 and 1 ?g/mL, for 24 hours. The alterations observed by scanning microscopy included higher number of bristles, which were thinner and longer than the controls and exhibited a coiling pattern in the intersegmental grooves. Transmission electron microscopy analysis revealed that the epicuticle almost came entirely off the new epicuticle and had no points of reinforcements commonly found in the control. The midgut cells of the larvae treated with diflubenzuron presented a spongy skeleton and in the ultrathin sections, the cells showed intense vacuolation and damage, however with secretion vesicles present and mitochondria preserved. These studies indicate that the diflubenzuron can also act in the midgut cells, being a promising product for use in Ae. aegypti control. This study showed that the DFB interferes with the process of ecdysis, prevents the release of the old cuticle that accumulates in the intersegmental spaces and strangle the segmental portions in a successive and cumulative process, blocked the changes, causing the death of the larva. It also acts destroying the midgut cells.

Echinoid regulates tracheal morphology and fusion cell fate in Drosophila

Morphogenesis of the Drosophila embryonic trachea involves a stereotyped pattern of epithelial tube branching and fusion. Here, we report unexpected phenotypes resulting from maternal and zygotic (M/Z) loss of the homophilic cell adhesion molecule Echinoid (Ed), as well as the subcellular localization of Ed in the trachea. ed(M/Z) embryos have convoluted trachea reminiscent of septate junction (SJ) and luminal matrix mutants. However, Ed does not localize to SJs, and ed(M/Z) embryos have intact SJs and show normal luminal accumulation of the matrix-modifying protein Vermiform. Surprisingly, tracheal length is not increased in ed(M/Z) mutants, but a previously undescribed combination of reduced intersegmental spacing and deep epidermal grooves produces a convoluted tracheal phenotype. In addition, ed(M/Z) mutants have unique fusion defects involving supernumerary fusion cells, ectopic fusion events and atypical branch breaks. Tracheal-specific expression of Ed rescues these fusion defects, indicating that Ed acts in trachea to control fusion cell fate.

Postoperative Condylar Position by Sagittal Split Ramus Osteotomy With and Without Bone Graft

The purpose of the present study was to determine how the condylar position is affected by the bone graft in the intersegmental space created by sagittal split ramus osteotomy. We compared the position of the condyle after sagittal split ramus osteotomy, without the bone graft (control group, n = 30) and with the bone graft (study group, n = 30) using computed tomography with a 2-mm thickness. Using 3-dimensional images and a 3-dimensional computer program, the pre- and postoperative displacement and rotation of the condyle in the axial (rotation and mediolateral movement of the condyle) and sagittal plane (anteroposterior and superoinferior movement of the condyle and rotation of the proximal segment) were measured. In addition, the relationship of the amount of rotation and backward movement of the mandible and the change in the condylar position was analyzed. For the statistical analysis, the t test (P = .05) and Wilcoxon rank sum test were used. No statistically significant differences were found in any of the measurements of the 2 groups. Nevertheless, the mediolateral movement (P = .051) showed a relatively greater apparent difference, although the difference was not statistically significant. The condylar displacement had no relationship to the rotation of the mandible. However, the condylar displacement in relation to the amount of backward movement of the mandible was significant, especially when it was greater than 10 mm of setback. Using a bone graft in the intersegmental gap of a sagittal split ramus osteotomy is considered an effective clinical method to secure the desirable intersegmental position because it helps to maintain the space with ease. Especially in cases with greater than 10-mm setback of the mandible, it prevents excessive condylar displacement.

Dehydration of acetic acid by pervaporation using SPEK-C/PVA blend membranes

Sulfonated cardo polyetherketone (SPEK-C) and poly(vinyl alcohol) (PVA) blend membranes were prepared by solution casting method and used in pervaporation (PV) dehydration of acetic acid. The membranes were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and contact angle meter. The results show that thermal crosslinking occurred to the membrane under high temperature annealing. The effective d-spacing (inter-segmental spacing) decreased with PVA content decreasing. The hydrophilicity of the blend membrane increased with SPEK-C content increasing. Swelling and sorption experiments show that the swelling degree of the blend membrane increased, however both the sorption and diffusion selectivities decreased with increasing PVA content. The diffusion selectivity is higher than the sorption selectivity. This suggests that PV dehydration of acetic acid is dominated by the diffusion process. The pervaporation separation index (PSI) of the membrane increases with increasing PVA content and arrives at a maximum when the SPEK-C/PVA ratio is 3/2, then decreases with further addition of PVA. The membrane has an encouraging separation performance with a flux of 492 g m −2 h −1 and separation factor of 59.3 at 50 °C at the feed water content 10 wt%.

A lock-on system in precopulae of Dikerogammarus villosus (Sowinsky, 1894), also present in Gammarus pulex pulex (Linnaeus, 1758) (Amphipoda). Amphipod Pilot Species Project (AMPIS) Report 2

In Dikerogammarus villosus and Gammarus p. pulex, a lock-on mechanism for amplexus was found. Large pores on the first and fifth female pereionites are involved, as well as the first pair of male gnathopods. On the anterior edge of pereionite 1 and the posterior edge of pereionite 5, specialized areas were found that allow penetration of the male's dactyli in the inter-segmental spaces of the female. Also, a guidance system for male attachment to the female was found using palmar spines of the first pair of gnathopods. The mechanism is described and discussed. Morphometric analysis of this lock-on system explains the strong size-relationship between partners.

Correlative radiological, self-assessment and clinical analysis of evolution in instrumented dorsal and lateral fusion for degenerative lumbar spine disease. Autograft versus coralline hydroxyapatite.

This prospective longitudinal randomized clinical and radiological study compared the evolution of instrumented posterolateral lumbar and lumbosacral fusion using either coralline hydroxyapatite (CH), or iliac bone graft (IBG) or both in three comparable groups, A, B and C, which included 19, 18 and 20 patients, respectively, who suffered from symptomatic degenerative lumbar spinal stenosis and underwent decompression and fusion. The patients were divided randomly according to the graft used and the side that it was applied. The spines of group A received autologous IBG bilaterally; group B, IBG on the left side and hydroxyapatite mixed with local bone and bone marrow on the right side; group C, hydroxyapatite mixed with local bone and bone marrow bilaterally. The age of the patients in the groups A, B and C was 61+/-11 years, 64+/-8 years and 58+/-8 years, respectively. The SF-36, Oswestry Disability Index (ODI), and Roland-Morris (R-M) surveys were used for subjective evaluation of the result of the surgery and the Visual Analogue Scale (VAS) for pain severity. Plain roentgenograms including anteroposterior, lateral and oblique views, and lateral plus frontal bending views of the instrumented spine and CT scan were used to evaluate the evolution of the posterolateral fusion in all groups and sides. Two independent senior orthopaedic radiologists were asked to evaluate first the evolution of the dorsolateral bony fusion 3-48 months postoperatively with the Christiansen's radiologic method, and secondly the hydroxyapatite resorption course in the spines of groups B and C. The diagnosis of solid spinal fusion was definitively confirmed with the addition of the bending views, CT scans and self-assessment scores. The intraobserver and interobserver agreement (r) for radiological fusion was 0.71 and 0.69, respectively, and 0.83 and 0.76 for evaluation of CH resorption. T(12)-S(1) lordosis and segmental angulation did not change postoperatively. There was no radiological evidence for non-union on the plain roentgenograms and CT scans. Radiological fusion was achieved 1 year postoperatively and was observed in all groups and vertebral segments. Six months postoperatively there was an obvious resorption of hydroxyapatite granules at the intertransverse intersegmental spaces in the right side of the spines of group B and both sides of group C. The resorption of hydroxyapatite was completed 1 year postoperatively. Bone bridging started in the third month postoperatively in all instrumented spines and all levels posteriorly as well as between the transverse processes in the spines of the group A and on the left side of the spines of group B where IBG was applied. SF-36, ODI, and R-M score improved postoperatively in a similar way in all groups. There was one pedicle screw breakage at the lowermost instrumented level in group A and two in group C without radiologically visible pseudarthrosis, which were considered as having non-union. Operative time and blood loss were less in the patients of group C, while donor site complaints were observed in the patients of the groups A and B only. This study showed that autologous IBG remains the "gold standard" for achieving solid posterior instrumented lumbar fusion, to which each new graft should be compared. The incorporation of coralline hydroxyapatite mixed with local bone and bone marrow needs adequate bleeding bone surface. Subsequently, hydroxyapatite was proven in this series to not be appropriate for intertransverse posterolateral fusion, because the host bone in this area is little. However, the use of hydroxyapatite over the decorticated laminae that represents a wide host area was followed by solid dorsal fusion within the expected time.

Scanning electron microscopy studies of sensilla and other structures of adult Dermatobia hominis (L. Jr., 1781) (Diptera: Cuterebridae).

The surfaces of the body segments and appendages of male and female Dermatobia hominis (L. Jr., 1781) were studied by scanning electron microscopy with the objective of contributing to the current knowledge of the morphology of this insect. The image analyses were done with consideration of the scientific literature on morphology, ultrastructure, and insect sensory structures. A new criterion for distinguishing the sexes of this fly was observed as well as a new setiform empodium type associated with other smaller setae. Different types of trichoid sensilla were observed, as well as spinules, a type of cuticular setiform projection and a scale-like structure. The possible function of the sensilla was discussed, and sensilla with mechanosensory and chemosensory functions were found. Pilose regions that could be involved in the production and/or liberation of pheromones were encountered in the intersegmental spaces of the female abdomen. The current study of the ultrastructure of the body surface of D. hominis contributes to current knowledge of morphology, taxonomy, and sensory structures of this species.

Unique rodent model of distraction osteogenesis of the mandible.

Despite the increasing use of distraction osteogenesis (DO) of the mandible, the molecular mechanisms regulating new bone formation during DO remain poorly understood. The purposes of this study were (1) to establish a unique rodent model of DO capable of outlining parameters for new bone formation at the distraction site and (2) to determine a critical-size defect to differentiate osteogenesis resulting from distraction from conventional fracture healing at the osteotomy site. Adult Sprague-Dawley rats were fitted successfully with this newly developed distraction device. Analyses demonstrated that the device could distract the rat mandible reliably to 5.1 mm with complete union. Acute intersegmental gaps of 2 mm resulted in complete bony union in a manner consistent with fracture healing, whereas 3-mm acute gaps resulted in varying degrees of bony union. Acute intersegmental gaps of 5.1 mm invariably resulted in fibrous nonunion. In summary, the authors have developed a rodent model of DO of the mandible. Their distraction protocols resulted successfully in advancement to 5.1 mm with bony consolidation. Notable fracture healing occurred at immediate intersegmental spaces as large as 3 mm. A gap of 5.1 mm was sufficient to act as a critical-size defect, resulting consistently in fibrous nonunion. These findings validate the effectiveness of this distraction device and establish the critical-size defect of a rat mandible at more than 3 mm. This novel model of DO provides an effective method of examining fundamental mechanisms responsible for new bone formation in the craniofacial skeleton.

Production of wax by virgin queens of the stingless bee Melipona bicolor (Apidae, Meliponinae)

Young virgin queens of the stingless bee Melipona bicolor have been shown to produce wax like workers. The small, white to transparent flakes of wax of the queens protrude from the intersegmental space and cover the anterior part of the tergite cuticle, in a way similar to that in workers. This points to the presence of wax glands in the queens. However, workers produce wax from glands located at the fourth to seventh tergites whereas queens secrete wax from the epidermal gland at the third tergite only. Analysis of the queen-produced wax showed that it contains the same substances as the worker-produced wax with minor differences in composition. The wax consists chiefly of the long-chain esters triacontanyl acetate and octacosanyl acetate, smaller amounts of linear C21 to C31 alkanes and alkenes, and still smaller quantities of linear aldehydes and isobutyrate esters. Analysis of wax from wax deposits and wax constructs showed the same composition. Wax from M. bicolor is similar to that of other stingless bees in containing the range of linear long-chain alkenes and alkanes and different from that of Apis bees which contains a more complex mixture, less hydrocarbons and more long chain esters.

Correlational analysis of fictive swimming in the lamprey reveals strong functional intersegmental coupling

1. Cycle-to-cycle fluctuations in cycle periods and intersegmental burst delays of ventral root activity were studied during stable fictive swimming in the adult lamprey spinal cord. High spatial resolution was obtained by recording from 16 ventral roots, 1/2 on each side of the spinal cord. For ipsilateral ventral roots, correlations between cycle periods on the same cycle were high (0.50 +/- 0.16, mean +/- SD), and autocorrelations of intersegmental delays with a shift of one cycle were low (0.03 +/- 0.06). Correlations between cycle periods tended to decrease with intersegmental spacing but remained positive over the range of spacings tested (1-47 segments). 2. Sinusoidal movement imposed on the caudal end of the spinal cord/notochord was used to entrain the fictive swimming rhythm. When the phase between the movement and the rhythm was perturbed, several cycles were required for the phase to return to its preferred value, indicating that in these experiments the effect of the movement was weak. In the absence of external perturbations, autocorrelations of delays between the movement and ventral root bursts with a shift of one cycle were high. 3. Numerical simulations with a simple stochastic phase model of the lamprey central pattern generator (CPG) were conducted. High correlations of periods and low autocorrelations of delays, the pattern observed experimentally, emerged as intersegmental connection strengths were increased. Coupling including both long and short connections produced this pattern of correlations with an average connection strength less than that required by short connections alone. 4. It is concluded that functional intersegmental coupling in the lamprey CPG during stable fictive swimming is strong. Specifically, the low autocorrelations of intersegmental delays indicate that intersegmental coupling is sufficiently strong to ensure that perturbations are almost completely corrected within one cycle.

Gas permeabilities of bisphenol bridge-disubstituted polyarylates

This study reports the physical properties and gas permeation characteristics of polyarylates prepared by disubstitution of the bisphenolA bridge carbon. The results are compared with data from previously reported unsubstituted and mono-substituted polyarylates. Disubstitution is an effective method of changing the packing density, as measured by the d-spacing, and also increases the chain stiffness. The intersegmental spacing can be either decreased (by phenyl disubstitution) or significantly increased (by -CF3 disubstitution). Increased d-spacing in the case of -CF3 disubstitution increases permeabilities and reduces selectivities compared to the unmodified bisphenolA based polymer. The increased permeability and selectivity of the phenyl disubstituted polyarylates, in spite of the reduced d-spacing, supports an earlier finding that decreased bisphenol phenyl ring mobility tends to increase permeability.

Tunicamycin does not inhibit transport of phosphatidylinositol toXenopus rod outer segments

Tunicamycin inhibits the dolichol pathway for N-linked glycosylation of proteins, including photoreceptor opsin, and causes a buildup of tubulo-vesicular profiles in the intersegmental space between photoreceptor rod inner and outer segments associated with disruption of new disc assembly. We tested the hypothesis that a tunicamycin lesion in photoreceptors would block lipid transport into the outer segment. Adult Xenopus retinas were preincubated in dim red light with 20 micrograms ml-1 of tunicamycin for one hour followed by incubation in the light for 2-6 h with tunicamycin plus either [3H]mannose, [3H]leucine, [2-(3)H]glycerol or [3H]myo-inositol. Tunicamycin caused accumulation of tubulo-vesicular membranes in the intersegmental space and significantly reduced both [3H]leucine and [3H]mannose incorporation into the basal region of rod outer segments. However, tunicamycin had no effect on [3H]glycerol incorporation into the rod outer segment phospholipids. After 5 h incubation with [3H]glycerol, radiolabel in outer segment fractions was associated primarily with phosphatidylinositol in both control and tunicamycin treated retinas. Quantitative light microscope autoradiography of both [3H]glycerol and [3H]inositol labelled retinas showed diffuse labelling over the entire rod outer segment in both control and tunicamycin treated retinas with no accumulation of radioactivity in the basal discs of control retinas or in the tubulo-vesicular structures in the intersegmental space of tunicamycin treated retinas. Our results indicate that despite the morphological disruption and inhibition of glycoprotein transport to outer segments after tunicamycin treatment, transport of labelled phosphatidylinositol occurs normally. These data add to a growing body of evidence separating the lipid and protein transport pathways to the outer segment.