ACL anatomy: Is there still something to learn? / [Artículo traducido] Anatomía del LAC: ¿queda algo por aprender?

BACKGROUND: The different bony and soft tissue reference points and the micro and macroscopic structures of the knee continue to be the object of focused study and analysis. Upon reviewing the most recent literature, we saw the wide spectrum of studies that seek to define the different anatomical aspects of the anterior cruciate ligament (ACL). PURPOSE: The purpose of this paper is to review the most recent publications on the ACL and its morphology in which its microscopic composition and macroscopic anatomy are addressed. RESULTS: The ACL consists of typeI (90%) and typeIII (10%) collagen matrix. Its length ranges from 27 to 38mm and its width from 10 to 12mm. The ACL cross-section area measures an average of 44mm2, and its shape resembles that of an hourglass or a bow tie. ACL bundles have been defined as anteromedial, intermediate, and posterolateral. Femoral and tibial footprints were seen to present a high degree of variability in shape and size. Furthermore, the blood supply is given by the medial genicular artery and innervation by the tibial nerve branches. Additionally, the ACL functionally prevents anterior translation of the tibia and stabilizes against the internal rotation of the tibia and valgus angulation of the knee. CONCLUSIONS: There is great variability in the anatomy of the ACL as well as its attachment sites. At the same time, the shape and size of its footprint has become a factor in determining individualized ACL reconstruction. The persistence of morphological variability in the aging of the ACL and important aspects of surgical planning and decision making with respect to anatomical risk factors suggest that further studies are called for.

ACL anatomy: Is there still something to learn?

BACKGROUND: The different bony and soft tissue reference points and the micro and macroscopic structures of the knee continue to be the object of focused study and analysis. Upon reviewing the most recent literature, we saw the wide spectrum of studies that seek to define the different anatomical aspects of the anterior cruciate ligament (ACL). PURPOSE: The purpose of this paper is to review the most recent publications on the ACL and its morphology in which its microscopic composition and macroscopic anatomy are addressed. RESULTS: The ACL consists of type I (90%) and type III (10%) collagen matrix. Its length ranges from 27 to 38mm and its width from 10 to 12mm. The ACL cross-section area measures an average of 44mm2, and its shape resembles that of an hourglass or a bow tie. ACL bundles have been defined as anteromedial, intermediate, and posterolateral. Femoral and tibial footprints were seen to present a high degree of variability in shape and size. Furthermore, the blood supply is given by the medial genicular artery and innervation by the tibial nerve branches. Additionally, the ACL functionally prevents anterior translation of the tibia and stabilizes against the internal rotation of the tibia and valgus angulation of the knee. CONCLUSIONS: There is great variability in the anatomy of the ACL as well as its attachment sites. At the same time, the shape and size of its footprint has become a factor in determining individualized ACL reconstruction. The persistence of morphological variability in the aging of the ACL and important aspects of surgical planning and decision making with respect to anatomical risk factors suggest that further studies are called for.

Effect of three feeding levels on the pathogenesis and establishment of Haemonchus contortus in parasite-naïve Pelibuey hair sheep lambs during their first infection.

This study evaluated the effect of three feeding levels on the pathogenesis and establishment of H. contortus upon the first infection of parasite-naïve Pelibuey hair sheep lambs. Forty-two 6-month-old hair sheep lambs (24 ± 4 kg) raised parasite free from birth were used. The lambs were assigned to 3 groups (n = 14), and each was fed a diet designed for different daily weight gain (DWG): 75 g/d (Diet 1), 125 g/d (Diet 2) and 200 g/d (Diet 3). After four weeks of diet adaptation, 10 lambs/group were infected with 450 L3H. contortus/kg BW (infected), and 4 lambs/group were kept parasite-free (NInf). DWG, hematocrit (Ht), hemoglobin (Hb), peripheral eosinophils (EOS), IgG concentration against H. contortus, and eggs per gram (EPG) of feces were measured in each lamb from day 14 before infection until day 29 postinfection (PI). On day 29 PI, the lambs were slaughtered to determine the total number of adult parasites (TAW), the length of the female worms, and the number of eggs in utero (EIU). Each group reached the expected DWG (P = 0.001), and there was no effect of infection or the diet × infection interaction. Ht was lower in infected lambs than in NInf lambs, and this difference was significant for animals on Diets 1 and 2 (P = 0.044). From day 14 PI onward, Hb was lower in the infected lambs than in the NInf lambs (P = 0.001). Furthermore, compared with NInf lambs, the infected lambs had higher EOS from day 7 PI and higher IgG from day 14 PI. Neither EOS nor IgG were affected by diet. Lambs on Diet 3 had lower EPG during patency than those fed Diets 1 or 2 (days 25 and 28 PI; P = 0.002). Furthermore, lambs fed Diet 3 had lower TAW (Diet 1 vs 3 P = 0.037; Diet 2 vs 3 P = 0.049) and EIU (P = 0.004) than lambs fed Diet 1 or 2. Lambs were resilient to infection regardless of diet. Although EOS and IgG were higher in all infected animals than in Ninf animals, EPG, TAW and EIU decreased only in lambs fed Diet 3. Thus, a diet targeting a DWG of 200 g/d can significantly limit the establishment of H. contortus in Pelibuey lambs infected for the first time.

[Tropical pyomyositis of the iliacus, obturator internus, piriformis and psoas major muscles in an immunocompetent patient with claudication]. / Piomiositis tropical del músculo ilíaco, obturador interno, piriforme y psoas mayor en un paciente inmunocompetente con claudicación.

INTRODUCTION: Pyomyositis is a term that denotes pyogenic infection usually primary skeletal muscle, associated with hematogenous dispersion due to transient bacteremia, or penetrating trauma, usually forming abscesses. Classically described frequently in tropical areas and predominantly affecting the lower limb musculature, however, in recent decades it has increasingly been associated with areas of temperate climates and relatively more frequently in immunosuppressed patients, being the patients under 30 years the most affected. CLINICAL CASE: Male of 15 years without relevant medical history. The patient had no history of trauma, falls, surgical interventions, infections or any other systemic condition. He came because of a clinical picture of 7 days of evolution characterized by pain referred to the groin and left iliac crest area associated with claudication and hyperthermia not quantified, which yielded partially to NSAIDs and paracetamol, but without achieving improvement so it is taken emergency by relatives. CONCLUSIONS: It is necessary to bear in mind this pathology when performing the differential diagnostic approach of a patient presenting with pain and functional limitation of some joint associated with data suggestive of an infectious or inflammatory process.

INTRODUCCIÓN: La piomiositis es un término que denota infección piógena por lo general primaria de músculo esquelético. Clásicamente descrita de manera frecuente en zonas tropicales y en pacientes inmunocomprometidos; sin embargo, en las últimas décadas se observa cada vez más en zonas de climas templados y con relativa mayor frecuencia en pacientes inmunocompetentes, siendo el grupo etario más afectado el de menores de 30 años. CASO CLÍNICO: Masculino de 15 años sin antecedentes médicos de relevancia. Acude por presentar cuadro clínico de siete días de evolución caracterizado por dolor referido en ingle y zona de la cresta ilíaca izquierda asociado a claudicación e hipertermia no cuantificada, que cedían parcialmente a AINES y paracetamol, pero sin lograr mejoría, por lo que es llevado a urgencias por familiares. CONCLUSIONES: Es necesario tener en mente esta patología al momento de realizar el abordaje diagnóstico diferencial de un paciente que se presenta con dolor y limitación funcional de alguna articulación asociada a datos sugestivos de un proceso infeccioso o inflamatorio.

[External fixation with reconstruction rail system as a treatment for pseudoarthrosis of the distal femur]. / Fijación externa con sistema de riel de reconstrucción como tratamiento para seudoartrosis del fémur distal.

Distal femur pseudoarthrosis also called «distal femur non-union¼ (DFNU) represents a rare complication associated with a fracture caused by high-energy trauma; its treatment is controversial, as there is a wide variety of surgical techniques that can be implemented, from open reduction plus internal fixation with plates, to the use of fixed angle plates combined with bone autograft. We expose the case of a 24-year-old man who shows up for consultation with the history of having presented a left femoral supracondylar fracture with a year of evolution, treated by osteosynthesis of the distal femur with dynamic condylar screws (DCS plate); developed a torpid evolution with severe pain in the distal third of the left thigh and functional limitation, developed a progressive varus deformity of the left thigh that caused a shortening of 3.8 cm of the limb. A focus of pseudoarthrosis was identified, which was surgically removed, the intramedullary canal was recanalized, and a lateral closed wedge osteotomy was performed to correct the angulation and allow reduction. 5.5 mm (three proximal and three distal) hydroxyapatite screws and an external fixator were placed. In addition, a review of the literature focused on the use of external fixation was carried out as a treatment for the pseudoarthrosis of the distal femur.

La seudoartrosis del fémur distal, también llamada «no unión del fémur distal¼ (NUFD), representa una complicación poco frecuente asociada a una fractura causada por un traumatismo de alta energía; su tratamiento es controversial, ya que existe una gran variedad técnicas quirúrgicas que pueden ser implementadas desde la reducción abierta más la fijación interna con placas hasta el uso de placas de ángulo fijo combinadas con autoinjerto óseo. Exponemos el caso de un hombre de 24 años de edad, el cual se presenta a la consulta con el antecedente de haber sufrido una fractura supracondílea femoral izquierda con un año de evolución, tratada mediante una osteosíntesis del fémur distal con tornillos condilares dinámicos (placa DCS); mostró una evolución tórpida con dolor severo en el tercio distal del muslo izquierdo y limitación funcional, desarrolló una deformidad en varo progresiva del muslo izquierdo que causó un acortamiento de 3.8 cm de la extremidad. Se identificó un foco de seudoartrosis, el cual se retiró quirúrgicamente, se recanalizó el canal intramedular y se realizó una osteotomía de cuña cerrada lateral para corregir la angulación y permitir la reducción. Se colocaron tornillos de hidroxiapatita de 5.5 mm (tres proximales y tres distales) y un fijador externo. Además se hizo una revisión de la literatura enfocada en el uso de la fijación externa como tratamiento de la seudoartrosis del fémur distal.

Alginate molecular mass produced by Azotobacter vinelandii in response to changes of the O2 transfer rate in chemostat cultures.

Alginate production by Azotobacter vinelandii growing in chemostat cultures was evaluated under different O(2) transfer rates (OTR). As a result of modifying the culture's agitation rate from 300 to 500 rpm, the OTR increased from 9 to 15.1 mmol l(-1) h(-1) and a slight variation in the alginate production (1.7-2.2 g l(-1)) was observed. At a constant growth rate (0.1 h(-1)), the mean molecular mass of the alginate was strongly influenced by changes in the OTR, varying from 860 to 1,690 kDa. These results support a possible relationship between alginate polymerization-depolymerization process and the O(2) uptake rate.

A modified chemical protocol of decellularization of rat sciatic nerve and its recellularization with mesenchymal differentiated schwann-like cells: morphological and functional assessments.

The functional reconstruction of large neural defects usually requires the use of peripheral nerve autografts, though these have certain limitations. As a result, interest in new alternatives for autograft development has risen. The acellular peripheral nerve graft is an alternative for peripheral nerve injury repair, but to date there is not a standardized chemical decellularization method widely accepted. The objective of this study was to propose a modified chemical protocol of decellularization of rat sciatic nerve and its recellularization in vitro with mesenchimal differentiated Schwann-like cells. After the transplantation, an evaluation of its regeneration was performed using morphological and functional tests. The study consisted of two phases; in phase 1, different concentrations and times of exposure of rat sciatic nerves to detergents were tested, to establish a modified chemical protocol for nerve decellularization. The chemical treatment with 3% triton X-100 and 4% sodium deoxycholate for 15 days allowed a complete decellularization whilst conserving the extracellular matrix of the harvested nerve. In phase 2, the decellularized and recellularized alografts were compared against autografts. The morphological analysis showed a higher positivity to specific myelin antibodies in the recellularized group compared to the autograft. There were no differences in this parameter between the control limb and the experimental limb (recellularized group). The functional analysis showed no statistical differences at week 15 in the Sciatic Function Index in the autograft group vs the other groups. This study sets the morphological and functional bases for posterior studies about nerve defects regeneration in humans.

Prevalence, topographic and morphometric features of femoral cam-type deformity: changes in relation to age and gender.

Femoroacetabular impingement (FAI) syndrome is a frequent cause of pain and in recent years considered to be a precursor of premature hip osteoarthritis. The structural abnormalities which characterize FAI syndrome, such as the cam-type deformity, are associated with morphological alterations that may lead to hip osteoarthritis. The aim of this study was to determine the prevalence and topographic and morphometric features of the cam deformity in a series of 326 femur specimens obtained from a Mexican population, as well as changes in prevalence in relation to age and gender. The specimens were subdivided into groups according to gender and age. A standardized photograph of the proximal femur of each specimen was taken, and the photograph was used to determine the alpha angle using a computer program; the location of the lesion was determined by quadrant and the morphometric characteristics were determined by direct observation. The overall prevalence of cam deformities in the femur specimens was 29.8 % (97/326), with a prevalence by gender of 35.2 % (64/182) in men and 22.9 % (33/144) in women. The mean alpha angle was 54.6° ± 8.5° in all of the osteological specimens and 65.6° ± 7.5° in those specimens exhibiting a cam deformity. Cam deformities were found topographically in the anterior-superior quadrant of the femoral head-neck junction in 86.6 % (84/97) of the femurs. Deformities were found in 28.2 % of the right femurs and 31.3 % of the left femurs. The prevalence of cam deformity was higher in the femur specimens of young men and in those of middle-aged and older women. There were no significant differences in this deformity in relation to the alpha angle according to age and gender.

Hyperstable stacked-disk structure of tobacco mosaic virus protein: electron cryomicroscopy image reconstruction related to atomic models.

The stacked disk aggregate of tobacco mosaic virus protein is an intriguing object due to its high degree of stability, in spite of indications that the aggregate is held together to a great extent by water-mediated interactions between adjacent protein rings. Here, we present a set of models that were constructed using the atomic coordinates of the four-layer aggregate, and compare these with a three-dimensional reconstruction of the stacked disk obtained by means of cryoelectron microscopy and helical image processing. The comparison of the four possible models of the stacked disk with the data shows that there is a better correlation of the data with the left-handed model built from the A-A ring pair coordinates than with the two models involving the A-B ring pair, or with the right-handed model of the A-A ring pair. This establishes that the packing of the protein subunits in the stacked disk is different from that previously believed. We also note some differences between the observed structure and A-A ring pair model in the region of the flexible loop at small radius that might be an indication of conformational differences that give rise to the stability of the aggregate.

A new look at the microtubule binding patterns of dimeric kinesins.

The interactions of monomeric and dimeric kinesin and ncd constructs with microtubules have been investigated using cryo-electron microscopy (cryo-EM) and several biochemical methods. There is a good consensus on the structure of dimeric ncd when bound to a tubulin dimer showing one head attached directly to tubulin, and the second head tethered to the first. However, the 3D maps of dimeric kinesin motor domains are still quite controversial and leave room for different interpretations. Here we reinvestigated the microtubule binding patterns of dimeric kinesins by cryo-EM and digital 3D reconstruction under different nucleotide conditions and different motor:tubulin ratios, and determined the molecular mass of motor-tubulin complexes by STEM. Both methods revealed complementary results. We found that the ratio of bound kinesin motor-heads to alphabeta-tubulin dimers was never reaching above 1.5 irrespective of the initial mixing ratios. It appears that each kinesin dimer occupies two microtubule-binding sites, provided that there is a free one nearby. Thus the appearances of different image reconstructions can be explained by non-specific excess binding of motor heads. Consequently, the use of different apparent density distributions for docking the X-ray structures onto the microtubule surface leads to different and mutually exclusive models. We propose that in conditions of stoichiometric binding the two heads of a kinesin dimer separate and bind to different tubulin subunits. This is in contrast to ncd where the two heads remain tightly attached on the microtubule surface. Using dimeric kinesin molecules crosslinked in their neck domain we also found that they stabilize protofilaments axially, but not laterally, which is a strong indication that the two heads of the dimers bind along one protofilament, rather than laterally bridging two protofilaments. A molecular walking model based on these results summarizes our conclusions and illustrates the implications of symmetry for such models.

Electron diffraction of helical particles.

The development of low-dose electron cryo-microscopy has provided the means to see structural details to better than 10 A resolution in helical structures. The application of techniques of image analysis to micrographs can yield accurate phases, but not amplitudes with which to generate three-dimensional maps of the structure. Electron diffraction can provide reliable amplitudes, which can be combined with the phases from the images. In order to collect amplitude data, two problems have to be overcome: the pattern should be obtained from a large well ordered sample of particles, and the inelastic background should be properly subtracted. In this paper, we present three simple methods to produce rafts of helical particles. Using these methods we have obtained electron diffraction patterns from TMV (with data out to 0.28 nm), TMV protein stacked disks (with data out to 0.3 nm) and bacterial flagellar filaments (with data out to 0.5 nm). In addition, we describe the algorithms used to extract the amplitudes from the diffraction patterns.

[Vertebral fixation with a transpedicular approach. Relevance of anatomical and imaging studies]. / Fijación vertebral por vía transpedicular. Importancia de los estudios anatómicos y de imagen.

The number of patients with spine conditions has grown exponentially in recent years leading to an increase in the number of cases requiring surgical treatment. Currently vertebral fusion surgery with a transpedicular approach represents the most commonly used technique to treat any type of vertebral disorder. The morphometric characteristics of vertebrae, particularly the pedicle, determine the size of pedicular implants, including width and length, as well as the shape and direction of the screw and its ideal angulation at the time of introduction. Knowing these characteristics is important to prevent injuring important adjacent structures and to decrease the postoperative complication rate. In recent decades numerous studies on the morphometric characteristics of the vertebral pedicle have been conducted in different populations to determine its real dimensions by means of direct measurement and imaging methods. These studies have concluded that there are significant differences in these measurements among the different ethnic groups, races, genders, ages and the vertebral regions studied. This paper analyzes the different morphometric studies of the pedicle and all the other vertebral elements studied in Mexico and the rest of the world and explain the importance of their knowledge and surgical application for the correct development of vertebral fusion surgery with a transpedicular approach.

Association of influenza virus NP and M1 proteins with cellular cytoskeletal elements in influenza virus-infected cells.

We have investigated the association of the influenza virus matrix (M1) and nucleoprotein (NP) with the host cell cytoskeletal elements in influenza virus-infected MDCK and MDBK cells. At 6.5 h postinfection, the newly synthesized M1 was Triton X-100 (TX-100) extractable but became resistant to TX-100 extraction during the chase with a t1/2 of 20 min. NP, on the other hand, acquired TX-100 resistance immediately after synthesis. Significant fractions of both M1 and NP remained resistant to differential detergent (Triton X-114, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate [CHAPS], octylglucoside) extraction, suggesting that M1 and NP were interacting with the cytoskeletal elements. However, the high-molecular-weight form of the viral transmembrane protein hemagglutinin (HA), which had undergone complex glycosylation, also became resistant to TX-100 extraction but was sensitive to octylglucoside detergent extraction, indicating that HA, unlike M1 or NP, was interacting with TX-100-insoluble lipids and not with cytoskeletal elements. Morphological analysis with cytoskeletal disrupting agents demonstrated that M1 and NP were associated with microfilaments in virus-infected cells. However, M1, expressed alone in MDCK or HeLa cells from cloned cDNA or coexpressed with NP, did not become resistant to TX-100 extraction even after a long chase. NP, on the other hand, became TX-100 insoluble as in the virus-infected cells. M1 also did not acquire TX-100 insolubility in ts 56 (a temperature-sensitive mutant with a defect in NP protein)-infected cells at the nonpermissive temperature. Furthermore, early in the infectious cycle in WSN-infected cells, M1 acquired TX-100 resistance very slowly after a long chase and did not acquire TX-100 resistance at all when chased in the presence of cycloheximide. On the other hand, late in the infectious cycle, M1 acquired TX-100 resistance when chased in either the presence or absence of cycloheximide. Taken together, these results demonstrate that M1 and NP interact with host microfilaments in virus-infected cells and that M1 requires other viral proteins or subviral components (possibly viral ribonucleoprotein) for interaction with host cytoskeletal components. The implication of these results for viral morphogenesis is discussed.

cAMP-dependent phosphorylation of neurofilament proteins NF-L and NF-M inhibits their coassembly into filaments in vitro.

The effects of cAMP-dependent phosphorylation of neurofilament proteins NF-L and NF-M on the coassembly of the two proteins into filaments in vitro was examined. Sedimentation velocity experiments revealed that phosphorylated NF-M sedimented more slowly and resisted salt-induced aggregation. Filaments reconstituted from various mixtures of proteins were pelleted were pelleted and examined by gel electrophoresis and electron microscopy. Phosphorylation of either protein inhibited the formation of heteropolymer filaments containing NF-L and NF-M. However, phosphorylated proteins were fully competent in forming heterooligomeric assembly intermediates; therefore, phosphorylation blocks a later stage of filament assembly.

Structure of the stacked disk aggregate of tobacco mosaic virus protein.

The coat protein of tobacco mosaic virus is known to form three different classes of aggregate, depending on environmental conditions, namely helical, disk, and A-protein. Among the disk aggregates, there are four-layer, six-layer, and long stacks, which can be obtained by varying the ionic strength and temperature conditions during the association process. The four-layer aggregate has been crystallized, and its structure solved to atomic resolution. The stacked disk aggregate had been presumed to be built of a polar two-layer disk related to the crystalline A and B rings. A study using monoclonal antibodies specific to the bottom surface of TMV protein demonstrated that the stacked disk aggregate is bipolar, and suggested that the repeating two-layer unit might be similar to the dihedrally symmetrical A-ring pair in the disk crystal. In this paper we present a three-dimensional reconstruction of the stacked disk aggregate obtained by electron microscopy of ice-embedded samples. After modeling of the structure, we found the ring pairs to have the same quaternary structure as the A-ring pair of the four-layer aggregate. The resolution achieved in the image processing of the electron micrographs is on the order of 9 A in the meridional direction and 12 A in the equatorial. The identification of the structure of the stacked disk with the A-ring pair of the disk crystal provides an explanation of the observation that the axial periodicity of the disk pair, which is approximately 53 A when fully hydrated, can shrink to approximately 43 A in the dry state.

Influenza virus assembly: effect of influenza virus glycoproteins on the membrane association of M1 protein.

Influenza virus matrix protein (M1), a critical protein required for virus assembly and budding, is presumed to interact with viral glycoproteins on the outer side and viral ribonucleoprotein on the inner side. However, because of the inherent membrane-binding ability of M1 protein, it has been difficult to demonstrate the specific interaction of M1 protein with hemagglutinin (HA) or neuraminidase (NA), the influenza virus envelope glycoproteins. Using Triton X-100 (TX-100) detergent treatment of membrane fractions and floatation in sucrose gradients, we observed that the membrane-bound M1 protein expressed alone or coexpressed with heterologous Sendai virus F was totally TX-100 soluble but the membrane-bound M1 protein expressed in the presence of HA and NA was predominantly detergent resistant and floated to the top of the density gradient. Furthermore, both the cytoplasmic tail and the transmembrane domain of HA facilitated binding of M1 to detergent-resistant membranes. Analysis of the membrane association of M1 in the early and late phases of the influenza virus infectious cycle revealed that the interaction of M1 with mature glycoproteins which associated with the detergent-resistant lipid rafts was responsible for the detergent resistance of membrane-bound M1. Immunofluorescence analysis by confocal microscopy also demonstrated that, in influenza virus-infected cells, a fraction of M1 protein colocalized with HA and associated with the HA in transit to the plasma membrane via the exocytic pathway. Similar results for colocalization were obtained when M1 and HA were coexpressed and HA transport was blocked by monensin treatment. These studies indicate that both HA and NA interact with influenza virus M1 and that HA associates with M1 via its cytoplasmic tail and transmembrane domain.

Transmembrane domain of influenza virus neuraminidase, a type II protein, possesses an apical sorting signal in polarized MDCK cells.

The influenza virus neuraminidase (NA), a type II transmembrane protein, is directly transported to the apical plasma membrane in polarized MDCK cells. By using deletion mutants and chimeric constructs of influenza virus NA with the human transferrin receptor, a type II basolateral transmembrane protein, we investigated the location of the apical sorting signal of influenza virus NA. When these mutant and chimeric proteins were expressed in stably transfected polarized MDCK cells, the transmembrane domain of NA, and not the cytoplasmic tail, provided a determinant for apical targeting in polarized MDCK cells and this transmembrane signal was sufficient for sorting and transport of the ectodomain of a reporter protein (transferrin receptor) directly to the apical plasma membrane of polarized MDCK cells. In addition, by using differential detergent extraction, we demonstrated that influenza virus NA and the chimeras which were transported to the apical plasma membrane also became insoluble in Triton X-100 but soluble in octylglucoside after extraction from MDCK cells during exocytic transport. These data indicate that the transmembrane domain of NA provides the determinant(s) both for apical transport and for association with Triton X-100-insoluble lipids.

Interaction of Sendai viral F, HN, and M proteins with host cytoskeletal and lipid components in Sendai virus-infected BHK cells.

We have studied the interaction of Sendai viral fusion (F), hemagglutinin/neuraminidase (H/N), and matrix (M) proteins with host cytoskeletal and lipid components in Sendai virus-infected BHK cells using two nonionic detergents Triton X-100 (TX-100) and octyl glucoside (OG). Our results show that while M protein acquired resistance to both TX-100 and OG extraction, F and HN exhibited insolubility only to TX-100 but not to OG. Furthermore, in the presence of high salt (1 M NaCl), M, but not F or HN, became TX-100 soluble. Both type I (F) and type II (HN) viral glycoproteins acquired TX-100 insolubility at a late stage during exocytic transport as they acquired endo H resistance. In addition, TX-100 insoluble F and HN exhibited a lighter density compared to TX-100 resistant M by flotation analysis. Using recombinant vaccinia viruses that express Sendai virus HN, F, or M protein individually, we observed that each viral protein (F, HN, or M) was independently capable of acquiring TX-100 insolubility in the absence of other viral components. These results would indicate that while Sendai viral F and HN became bound to TX-100 insoluble lipids, M protein bound ionically to TX-100 insoluble cytoskeletal components and not to TX-100 insoluble lipids.