Utility of Ultrasound and Magnetic Resonance Imaging in Patients with Disorders of Sex Development Who Undergo Prophylactic Gonadectomy.

STUDY OBJECTIVE: To evaluate ultrasonography and magnetic resonance imaging (MRI) in identifying gonads in patients with disorders of sex development (DSD) who undergo prophylactic gonadectomy, and to assess the capacity of preoperative imaging to detect premalignant and malignant transformation. DESIGN, SETTING, AND PARTICIPANTS: Retrospective cohort at a tertiary referral center of 39 patients with DSD who underwent MRI and/or ultrasonography before prophylactic gonadectomy. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Identification of gonads on preoperative imaging. RESULTS: Thirty-three patients underwent ultrasonography, which identified 54% (35/65) of gonads and 14 patients had MRI, which identified 41% (11/27) of gonads. There was no significant difference between imaging modalities in the proportion of gonads identified (P = .25). The proportion of pathology-confirmed dysgenetic gonads identified was higher on ultrasound compared with MRI (51% vs 8%; P = .02). There was no difference in the proportion of pathology-confirmed testes identified on ultrasound and MRI (54% vs 71%; P = .33). Eleven out of 39 patients (28%) were diagnosed with a premalignant lesion, and there were no distinguishing characteristics documented on imaging reports to suggest transformation. The only diagnosed malignancy in this series had imaging describing a "normal-sized ovary." CONCLUSION: Ultrasonography and MRI identified 40%-50% of gonads in patients with DSD who underwent prophylactic gonadectomy, with no significant difference between the 2 modalities. Clinicians should, therefore, consider ultrasonography as a first-line imaging modality. Premalignant lesions were not detected on either imaging modality. The only malignancy was described as a "normal-sized ovary" which should raise concern in a patient with complete gonadal dysgenesis expected to have streak gonads.

The natural history of the multicystic dysplastic kidney--is limited follow-up warranted?

OBJECTIVE: Imaging of patients with multicystic dysplastic kidney (MCDK) has increased over the past three decades. This increased use of imaging has provided additional insights into the natural history of MCDK. The present study looked at this data for predictors of involution and associated anomalies. METHODS AND MATERIALS: Institutional review board approval was obtained for this retrospective study. The University of Michigan Departments of Urology and Radiology records were searched to identify unilateral MCDK patients during 1980-2012. Available clinical, radiological and surgical records were reviewed, and pertinent data were recorded. The log-rank test and a Cox proportional regression analysis were performed to identify predictors of MCDK involution. Probability of involution over time was assessed using Kaplan-Meier methodology. RESULTS: 301 unilateral MCDKs were identified; 195 (64.8%) were detected antenatally. Of the MCDKs found, 136 (45.2%) were in girls; 160 (53.2%) were right-sided. Mean size at baseline was 5.0 ± 0.2 cm (Mean ± SE). Associated abnormalities included: contralateral ureteropelvic junction obstruction (n = 10; 3.3%); contralateral ureterovesical junction obstruction/primary megaureter (n = 6; 2.0%); ipsilateral VUR (n = 21; 7.0%); contralateral VUR (n = 63; 20.1%); and renal fusion anomaly (n = 4; 1.3%). The cumulative probability of involution was: 9.8% at one year, 38.5% at five years, and 53.5% at ten years of age. Baseline MCDK size was the only significant predictor of involution at bivariate (p < 0.0001) and multivariate (p < 0.0001; HR 0.58 [95% CI: 0.49, 0.69]) analyses. No MCDK developed malignancy during the follow-up period. CONCLUSION: As many MCDKs eventually involute and the risk of associated malignancy appears to be very low, there is no absolute indication for nephrectomy. Based on the data and other recent studies, it is believed that pediatric MCDK patients with no other urologic abnormalities can safely tolerate more limited urological and radiological follow-up.

In vivo corrosion, tumor outcome, and microarray gene expression for two types of muscle-implanted tungsten alloys.

Tungsten alloys are composed of tungsten microparticles embedded in a solid matrix of transition metals such as nickel, cobalt, or iron. To understand the toxicology of these alloys, male F344 rats were intramuscularly implanted with pellets of tungsten/nickel/cobalt, tungsten/nickel/iron, or pure tungsten, with tantalum pellets as a negative control. Between 6 and 12 months, aggressive rhabdomyosarcomas formed around tungsten/nickel/cobalt pellets, while those of tungsten/nickel/iron or pure tungsten did not cause cancers. Electron microscopy showed a progressive corrosion of the matrix phase of tungsten/nickel/cobalt pellets over 6 months, accompanied by high urinary concentrations of nickel and cobalt. In contrast, non-carcinogenic tungsten/nickel/iron pellets were minimally corroded and urinary metals were low; these pellets having developed a surface oxide layer in vivo that may have restricted the mobilization of carcinogenic nickel. Microarray analysis of tumors revealed large changes in gene expression compared with normal muscle, with biological processes involving the cell cycle significantly up-regulated and those involved with muscle development and differentiation significantly down-regulated. Top KEGG pathways disrupted were adherens junction, p53 signaling, and the cell cycle. Chromosomal enrichment analysis of genes showed a highly significant impact at cytoband 7q22 (chromosome 7) which included mouse double minute (MDM2) and cyclin-dependant kinase (CDK4) as well as other genes associated with human sarcomas. In conclusion, the tumorigenic potential of implanted tungsten alloys is related to mobilization of carcinogenic metals nickel and cobalt from corroding pellets, while gene expression changes in the consequent tumors are similar to radiation induced animal sarcomas as well as sporadic human sarcomas.

Vaginal masses: magnetic resonance imaging features with pathologic correlation.

The detection of vaginal lesions has increased with the expanding use of cross-sectional imaging. Magnetic resonance imaging (MRI) - with its high-contrast resolution and multiplanar capabilities - is often useful for characterizing vaginal masses. Vaginal masses can be classified as congenital, inflammatory, cystic (benign), and neoplastic (benign or malignant) in etiology. Recognition of the typical MR imaging features of such lesions is important because it often determines the treatment approach and may obviate surgery. Finally, vaginal MR imaging can be used to evaluate post-treatment changes related to previous surgery and radiation therapy. In this article, we will review pertinent vaginal anatomy, vaginal and pelvic MRI technique, and the MRI features of a variety of vaginal lesions with pathological correlation.

Growth factor regulation of cytoplasmic dynein intermediate chain subunit expression preceding neurite extension.

Cytoplasmic dynein is a motor protein responsible for intracellular movements toward the minus ends of microtubules. The intermediate chains are one of the subunits important for binding dynein to cargo. The intermediate chains are encoded by two genes and are translated into at least five different polypeptide isoforms in rat brain. In rat optic nerve, dynein with only one of the intermediate chain polypeptides is found associated with membrane bounded organelles in fast anterograde transport. Dynein containing the other intermediate chain polypeptides associates with a different set of proteins, in the slow transport component. To determine if the intermediate chain expression levels are regulated during neurite differentiation, we analyzed the protein levels by two-dimensional SDS-PAGE and intermediate chain mRNA by RT-PCR in cultured rat pheochromocytoma (PC12) cells. In the absence of nerve growth factor, the major intermediate chain isoform is the IC74-2C polypeptide. IC74-2C is ubiquitous and is utilized for constitutive dynein function and association with membrane bounded organelles. Within 24 hr of the addition of nerve growth factor to the cultures, there is an increased expression of the developmentally regulated isoforms that are associated with the actin cytoskeleton. This change in intermediate chain isoform expression preceded neurite growth. Nerve growth factor induced differentiation also results in increased light intermediate chain phosphorylation. The growth factor induced changes in the expression of dynein intermediate chains suggests that specific intermediate chain isoforms are utilized during axon growth.

Nuclear antisense effects of neutral, anionic and cationic oligonucleotide analogs.

The antisense activity of oligomers with 2'-O-methyl (2'-O-Me) phosphorothioate, 2'-O-methoxyethyl (2'-O-MOE) phosphorothioate, morpholino and peptide nucleic acid (PNA) backbones was investigated using a splicing assay in which the modified oligonucleotides blocked aberrant and restored correct splicing of modified enhanced green fluorescent protein (EGFP) precursor to mRNA (pre-mRNA), generating properly translated EGFP. In this approach, antisense activity of each oligomer was directly proportional to up-regulation of the EGFP reporter. This provided a positive, quantitative readout for sequence-specific antisense effects of the oligomers in the nuclei of individual cells. Nuclear localization of fluorescent labeled oligomers confirmed validity of the functional assay. The results showed that the free uptake and the antisense efficacy of neutral morpholino derivatives and cationic PNA were much higher than that of negatively charged 2'-O-Me and 2'-O-MOE congeners. The effects of the PNA oligomers were observed to be dependent on the number of L-lysine (Lys) residues at the C-terminus. The experiments suggest that the PNA containing Lys was taken up by a mechanism similar to that of cell-penetrating homeodomain proteins and that the Lys tail enhanced intracellular accumulation of PNA oligomer without affecting its ability to reach and hybridize to the target sequence.

School-based health centers as a locus for community health improvement.

School-based health centers are critical resources for providing and coordinating health and medical services for children and adolescents. As such, they are an increasingly important component in a strategy to meet the comprehensive health, social, and educational needs of students and families. We show how educators and health professionals, using the language, methods and principles of continuous improvement, can collaborate effectively in addressing the specific concerns of school attendance and teen smoking.

Neuroimmunophilins: novel neuroprotective and neuroregenerative targets.

Cyclosporin A (CsA) and FK506 (tacrolimus) are immunosuppresants that are widely used in organ transplantation. CsA is an 11-member cyclic peptide, whereas FK506 is a macrolide antibiotic. Recently, these powerful and useful compounds have become of great interest to neuroscientists for their unique neuroprotective and neuroregenerative effects. These drugs and nonimmunosuppressive analogs protect neurons from the effects of glutamate excitotoxicity, focal ischemia, and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic cell death. They also stimulate functional recovery of neurons in a variety of neurologic injury paradigms. These drugs exert their effects via immunophilins, the protein receptors for these agents. The immunophilin ligands show particular promise as a novel class of neuroprotective and neuroregenerative agents that have the potential to treat a variety of neurologic disorders.

Leader protein of encephalomyocarditis virus binds zinc, is phosphorylated during viral infection, and affects the efficiency of genome translation.

Encephalomyocarditis virus (EMCV) is the prototype member of the cardiovirus genus of picornaviruses. For cardioviruses and the related aphthoviruses, the first protein segment translated from the plus-strand RNA genome is the Leader protein. The aphthovirus Leader (173-201 amino acids) is an autocatalytic papain-like protease that cleaves translation factor eIF-4G to shut off cap-dependent host protein synthesis during infection. The less characterized cardioviral Leader is a shorter protein (67-76 amino acids) and does not contain recognizable proteolytic motifs. Instead, these Leaders have sequences consistent with N-terminal zinc-binding motifs, centrally located tyrosine kinase phosphorylation sites, and C-terminal, acid-rich domains. Deletion mutations, removing the zinc motif, the acid domain, or both domains, were engineered into EMCV cDNAs. In all cases, the mutations gave rise to viable viruses, but the plaque phenotypes in HeLa cells were significantly smaller than for wild-type virus. RNA transcripts containing the Leader deletions had reduced capacity to direct protein synthesis in cell-free extracts and the products with deletions in the acid-rich domains were less effective substrates at the L/P1 site, for viral proteinase 3Cpro. Recombinant EMCV Leader (rL) was expressed in bacteria and purified to homogeneity. This protein bound zinc stoichiometrically, whereas protein with a deletion in the zinc motif was inactive. Polyclonal mouse sera, raised against rL, immunoprecipitated Leader-containing precursors from infected HeLa cell extracts, but did not detect significant pools of the mature Leader. However, additional reactions with antiphosphotyrosine antibodies show that the mature Leader, but not its precursors, is phosphorylated during viral infection. The data suggest the natural Leader may play a role in regulation of viral genome translation, perhaps through a triggering phosphorylation event.

Overview of the pathway and functions of nitric oxide.

Nitric oxide has been recognized for years as a toxic, reactive, free radical gas, but in recent years it has been identified as having functions in a variety of metabolic and signaling pathways. NO is synthesized, by nitric oxide synthase, on demand and diffuses to the site of action where it forms noncovalent and covalent linkages with target molecules. This overview presents the pathway of NO formation and also discusses the functions of NO in the nervous, immune and vascular systems.

Requirement for nitric oxide activation of p21(ras)/extracellular regulated kinase in neuronal ischemic preconditioning.

The mechanisms underlying neuronal ischemic preconditioning, a phenomenon in which brief episodes of ischemia protect against the lethal effects of subsequent periods of prolonged ischemia, are poorly understood. Ischemia can be modeled in vitro by oxygen-glucose deprivation (OGD). We report here that OGD preconditioning induces p21(ras) (Ras) activation in an N-methyl-D-aspartate receptor- and NO-dependent, but cGMP-independent, manner. We demonstrate that Ras activity is necessary and sufficient for OGD tolerance in neurons. Pharmacological inhibition of Ras, as well as a dominant negative mutant Ras, block OGD preconditioning whereas a constitutively active form of Ras promotes neuroprotection against lethal OGD insults. In contrast, the activity of phosphatidyl inositol 3-kinase is not required for OGD preconditioning because inhibition of phosphatidyl inositol 3-kinase with a chemical inhibitor or with a dominant negative mutant does not have any effect on the development of OGD tolerance. Furthermore, using recombinant adenoviruses and pharmacological inhibitors, we show that downstream of Ras the extracellular regulated kinase cascade is required for OGD preconditioning. Our observations indicate that activation of the Ras/extracellular regulated kinase cascade by NO is a critical mechanism for the development of OGD tolerance in cortical neurons, which may also play an important role in ischemic preconditioning in vivo.

Identification and molecular characterization of the p24 dynactin light chain.

Intracellular transport along microtubules uses the motor proteins cytoplasmic dynein and kinesin. Cytoplasmic dynein is responsible for movement to the minus ends of microtubules and the evidence indicates that dynein interacts with another protein complex, dynactin. In order to better understand how these proteins function, we have sought to identify and clone the subunit polypeptides of these two complexes, in particular their light chains. Dynactin is made up of eight subunits of approximately 24,000 to 160,000 Da. In order to clone the p24 subunit, the components of purified dynactin were resolved by SDS polyacrylamide gel electrophoresis. The amino acid sequence of a tryptic peptide from the 24,000-Mr region of the gel was obtained and a candidate polypeptide identified by a screen of the databases. This polypeptide has a predicted molecular weight of 20,822 Da. Using an antibody to a different region of this protein, we demonstrate that it copurifies with microtubules and elutes from the microtubule pellet with characteristics similar to those of the dynactin complex and distinct from those of cytoplasmic dynein. This polypeptide co-sediments with dynactin on sucrose density gradients and it also co-immunoprecipitates with dynactin, but not with kinesin or cytoplasmic dynein. Together these results demonstrate that this polypeptide is the p24 subunit of dynactin. Analysis of the predicted amino acid sequence of p24 shows that it is a unique protein that has no significant similarity to known enzymes or other proteins. Structural analysis indicates that most of this protein will form an alpha-helix and that portions of the molecule may participate in the formation of coiled-coils. Since stoichiometric analysis of dynactin indicates that there is one molecule of p24 per dynactin complex, these characteristics suggest that this polypeptide may be involved in protein-protein interactions, perhaps in the assembly of the dynactin complex.

Cytoplasmic dynein contains a family of differentially expressed light chains.

Cytoplasmic dynein contains a series of accessory proteins associated with the motor containing heavy chains.1 These include three distinct classes of light chains (Mr < approximately 22 000). Here we demonstrate that a previously cloned protein termed rp3 is a bona fide Mr 14 000 light chain component of this microtubule motor complex. The rp3 polypeptide is approximately 55% identical to the Tctex1 dynein light chain, and together, these two proteins define one branch of a diverse family of Mr 14 000 light chains associated with both cytoplasmic and flagellar dyneins. The Tctex1 and rp3 light chains are differentially expressed in various tissues: rp3 is most prevalent in liver and brain cytoplasmic dynein, whereas those tissues contain the least amounts of Tctex1. Immunofluorescence analysis was consistent with the tissue-specific distribution of these proteins and revealed that both rp3 and Tctex1 are present in multiple perinuclear punctate particles. Furthermore, in two cell lines, rp3 was found associated with an elongated structure located in the layer of cytoplasm above the nucleus. Electrophoretic/immunological analysis indicates that there are only single isoforms for these proteins in brain and PC-12 cells, suggesting that alterations in the Mr 14 000 light chains of dynein are achieved at the level of the individual proteins and not by posttranslational modification. Dissection of the cytoplasmic dynein complex revealed that Tctex1, an Mr 8000 LC dimer, and IC74 associate to define a basal-located intermediate chain/light chain complex analogous to that found in flagellar outer arm dynein.

The mouse t-complex-encoded protein Tctex-1 is a light chain of brain cytoplasmic dynein.

Mammalian brain cytoplasmic dynein contains three light chains of Mr = 8,000, 14,000, and 22,000 (King, S. M., Barbarese, E., Dillman, J. F., III, Patel-King, R. S., Carson, J. H., and Pfister, K. K. (1996) J. Biol. Chem. 271, 19358-19366). Peptide sequence data (16/16 residues correct) implicate the Mr = 14,000 polypeptide as Tctex-1, a protein encoded within the mouse t-complex. Tctex-1 cosediments with microtubules and is eluted with ATP or salt but not with GTP as expected for a dynein subunit. The ATP-eluted protein precisely cosediments with known cytoplasmic dynein proteins in sucrose density gradients. Tctex-1 also is immunoprecipitated from brain and other tissue homogenates by a monoclonal antibody raised against the 74-kDa cytoplasmic dynein intermediate chain. Quantitative densitometry indicates that Tctex-1 is a stoichiometric component of the dynein complex. As Tctex-1 is a candidate for involvement in the transmission ratio distortion (meiotic drive) of mouse t-haplotypes, these results suggest that cytoplasmic dynein dysfunction may play an important role in non-mendelian chromosome segregation.

Functional analysis of dynactin and cytoplasmic dynein in slow axonal transport.

The neuron moves protein and membrane from the cell body to the synapse and back via fast and slow axonal transport. Little is known about the mechanism of microtubule movement in slow axonal transport, although cytoplasmic dynein, the motor for retrograde fast axonal transport of membranous organelles, has been proposed to also slide microtubules down the axon. We previously showed that most of the cytoplasmic dynein moving in the anterograde direction in the axon is associated with the microfilaments and other proteins of the slow component b (SCb) transport complex. The dynactin complex binds dynein, and it has been suggested that dynactin also associates with microfilaments. We therefore examined the role of dynein and dynactin in slow axonal transport. We find that most of the dynactin is also transported in SCb, including dynactin, which contains the neuron-specific splice variant p135(Glued), which binds dynein but not microtubules. Furthermore, SCb dynein binds dynactin in vitro. SCb dynein, like dynein from brain, binds microtubules in an ATP-sensitive manner, whereas brain dynactin binds microtubules in a salt-dependent manner. Dynactin from SCb does not bind microtubules, indicating that the binding of dynactin to microtubules is regulated and suggesting that the role of SCb dynactin is to bind dynein, not microtubules. These data support a model in which dynactin links the cytoplasmic dynein to the SCb transport complex. Dynein then may interact transiently with microtubules to slide them down the axon at the slower rate of SCa.

Brain cytoplasmic and flagellar outer arm dyneins share a highly conserved Mr 8,000 light chain.

Sequence comparisons with the Mr 8,000 light chain from Chlamydomonas outer arm dynein revealed the presence of highly conserved homologues (up to 90% identity) in the expressed sequence tag data base (King, S. M. & Patel-King, R. S. (1995a) J. Biol. Chem. 270, 11445-11452). Several of these homologous sequences were derived from organisms and/or tissues that lack motile cilia/flagella, suggesting that these proteins may function in the cytoplasm. In Drosophila, lack of the homologous protein results in embryonic lethality (Dick, T., Ray, K., Salz, H. K. & Chia, W.(1996) Mol. Cell. Biol., 16, 1966-1977). Fractionation of mammalian brain homogenates reveals three distinct cytosolic pools of the homologous protein, one of which specifically copurifies with cytoplasmic dynein following both ATP-sensitive microtubule affinity/sucrose density gradient centrifugation and immunoprecipitation with a monoclonal antibody specific for the 74-kDa intermediate chain (IC74). Quantitative densitometry indicates that there is one copy of the Mr 8,000 polypeptide per IC74. Dual channel confocal immunofluorescent microscopy revealed that the Mr 8,000 protein is significantly colocalized with cytoplasmic dynein but not with kinesin in punctate structures (many of which are associated with microtubules) within mammalian oligodendrocytes. Thus, it appears that flagellar outer arm and brain cytoplasmic dyneins share a highly conserved light chain polypeptide that, at least in Drosophila, is essential for viability.

Identification and developmental regulation of a neuron-specific subunit of cytoplasmic dynein.

Cytoplasmic dynein is the microtubule minus-end-directed motor for the retrograde axonal transport of membranous organelles. Because of its similarity to the intermediate chains of flagellar dynein, the 74-kDa intermediate chain (IC74) subunit of dynein is thought to be involved in binding dynein to its membranous organelle cargo. Previously, we identified six isoforms of the IC74 cytoplasmic dynein subunit in the brain. We further demonstrated that cultured glia and neurons expressed different dynein IC74 isoforms and phospho-isoforms. Two isoforms were observed when dynein from glia was analyzed. When dynein from cultured neurons was analyzed, six IC74 isoforms were observed, although the relative amounts of the dynein isoforms from cultured neurons differed from those found in dynein from brain. To better understand the role of the neuronal IC74 isoforms and identify neuron-specific IC74 dynein subunits, the expression of the IC74 protein isoforms and mRNAs of various tissues were compared. As a result of this comparison, the identity of each of the isoform spots observed on two-dimensional gels was correlated with the products of each of the IC74 mRNAs. We also found that between the fifteenth day of gestation (E15) and the fifth day after birth (P5), the relative expression of the IC74 protein isoforms changes, demonstrating that the expression of IC74 isoforms is developmentally regulated in brain. During this time period, there is relatively little change in the abundance of the various IC74 mRNAs. The E15 to P5 time period is one of rapid process extension and initial pattern formation in the rat brain. This result indicates that the changes in neuronal IC74 isoforms coincide with neuronal differentiation, in particular the extension of processes. This suggests a role for the neuronal IC74 isoforms in the establishment or regulation of retrograde axonal transport.

Cytoplasmic dynein is associated with slow axonal transport.

Neuronal function is dependent on the transport of materials from the cell body to the synapse via anterograde axonal transport. Anterograde axonal transport consists of several components that differ in both rate and protein composition. In fast transport, membranous organelles are moved along microtubules by the motor protein kinesin. The cytoskeleton and the cytomatrix proteins move in the two components of slow transport. While the mechanisms underlying slow transport are unknown, it has been hypothesized that the movement of microtubules in slow transport is generated by sliding. To determine whether dynein, a motor protein that causes microtubule sliding in flagella, may play a role in slow axonal transport, we identified the transport rate components with which cytoplasmic dynein is associated in rat optic nerve. Nearly 80% of the anterogradely moving dynein was associated with slow transport, whereas only approximately 15% of the dynein was associated with the membranous organelles of anterograde fast axonal transport. A segmental analysis of the transport of dynein through contiguous regions of the optic nerve and tract showed that dynein is associated with the microfilaments and other proteins of slow component b. Dynein from this transport component has the capacity to bind microtubules in vitro. These results are consistent with the hypothesis that cytoplasmic dynein generates the movement of microtubules in slow axonal transport. A model is presented to illustrate how dynein attached to the slow component b complex of proteins is appropriately positioned to generate force of the correct polarity to slide microtubules down the axon.

Differential expression and phosphorylation of the 74-kDa intermediate chains of cytoplasmic dynein in cultured neurons and glia.

The 74-kDa intermediate chains (IC74) of the cytoplasmic dynein complex are believed to be involved in the association of dynein with membranous organelles. While each dynein molecule is thought to have two or three IC74 subunits, at least six different IC74 protein isoforms were found in dynein from brain. Therefore we investigated the relationships of the brain cytoplasmic dynein IC74 isoforms and their association in the dynein complex at the cellular level. We found that cultured cortical neurons and glia express distinct IC74 isoforms. The IC74 isoform pattern observed in dynein from cortical neurons was generally similar to that found in dynein from adult brain, indicating that there are different populations of cytoplasmic dynein in neurons. Two IC74 isoforms were observed on two-dimensional gels of dynein from glia, while a single glial IC74 mRNA was detected. Metabolic labeling of glial dynein with 32P followed by treatment of the isolated dynein with phosphatase in vitro demonstrated that one of the glial IC74 isoforms is the product of the single glial IC74 mRNA and that the other is its phosphoisoform. A single mRNA product and its phosphoisoform are therefore sufficient for constitutive dynein function and regulation in glial cells.

Proteoglycan biosynthesis is required in BC3H1 myogenic cells for modulation of vascular smooth muscle alpha-actin gene expression in response to microenvironmental signals.

Induction of vascular smooth muscle (VSM) alpha-actin mRNA expression during cytodifferentiation of mouse BC3H1 myogenic cells coincides with the accumulation of cell surface- and extracellular matrix-associated sulfated proteoglycans. Inhibition of proteoglycan biosynthesis in myogenic cells using an artificial beta-D-xyloside glycosaminoglycan acceptor was accompanied by a reduction in cell surface/extracellular matrix proteoglycans and VSM alpha-actin mRNA expression while enhancing the secretion of free chondroitin sulfate/dermatan sulfate and heparan sulfate glycosaminoglycans into the culture medium. Maximum inhibition of VSM alpha-actin mRNA expression required that proteoglycan biosynthesis be blocked during the early phase of cytodifferentiation when myoblasts were fully confluent and quiescent. The inhibitory effect of beta-D-xyloside on alpha-actin mRNA expression resulted from attenuation at both the transcriptional and post-transcriptional control points. Sustained proteoglycan biosynthesis was required for induction of VSM alpha-actin mRNA in quiescent myoblasts in response to cytodifferentiation-permissive, substrate-associated macromolecules (SAM) or upon exposure to soluble serum factors capable of transiently stimulating VSM alpha-actin gene transcription. The results suggested that efficient myoblast cytodifferentiation and modulation of VSM alpha-actin mRNA levels depended on intact cell surface proteoglycans to convey signals generated as a consequence of cellular interaction with substrate components and serum factors.