Revisiting Sustained Phonation Time of /s/, /z/, and /a/

PURPOSE

Research studies of maximum phonation time, have questioned its validity and value as a tool to assess laryngeal competence. This study proposes a fresh look at phonation time, from a different perspective. The interrelationships of the durations between semiocclusion vs. open vocal tract (/s/-/z/ vs. /a/) and voiced vs voiceless (/z/-/a/ vs. /s/) sound are examined to determine whether this approach might provide additional clinical insight into the respiratory phonatory efficiency of patients.

METHODS

Comfortable sustained phonation time of /s/, /z/ and /a/ was collected as part of the voice evaluation of patients referred by laryngologists for voice therapy. Inclusionary criteria: male and female subjects 19 years of age or older. Exclusionary criteria: autoimmune disorders, malignancies, major pulmonary/respiratory disorders.

RESULTS

A total of 218 patients (150 females and 68 males) mean age of 53.6 met all the criteria. Means, standard deviations and t test were conducted to determine whether significant differences existed. t test results indicate significance between s/z P = 0.002 and z/a P = 0.004 for females but only slight significance in s/a P = 0.03 for males. Close analysis of individual results observed four (4) different conditions or effects of fricative/semiocclusion and voicing: the close durations of the /s/ and /z/ relative to the /a/; the /z/ and /a/ are close in duration relative to the /s/; the spread of more than 5 seconds between /s/, /z/ and /a/ relative to the others; and similar duration of /s/, /z/, and /a/.

CONCLUSION

Significant differences exist in the durations of comfortable phonation time of sustained /s/ and /z/ and /a/ thought to be related to effects of semiocclusion, fricative consonants, and voicing. Phonation time should be seen not only in terms of duration, but the interplay of the phonemic qualities of the sounds as they relate of laryngeal efficiency.

Aerodynamic Patterns in Patients With Voice Disorders: A Retrospective Study

OBJECTIVE

A recently published retrospective chart review of aerodynamic profiles of women with primary muscle tension dysphonia by Gillespie et al (2013) identified various relationships between mean airflow rate (MFR) and estimated subglottal pressure (est-Psub). The current retrospective study expanded the diagnostic categories to include all voice disorders referred for voice therapy. Three research questions were proposed: (1) Are there differences in the MFR and the est-Psub compared with the normal control group? (2) Within the disordered population, are there different variations in the pairing of MFR and est-Psub? (3) If these variations exist, are they diagnosis specific?

METHODS

A retrospective chart review of patients seen for acoustic and aerodynamic voice assessment at the Emory Voice Center between January 1, 2013 and December 31, 2014, were examined for aerodynamic measures of est-Psub and MFR; of these, 192 met the inclusion criteria. Simple t test, two-step cluster analysis, and analysis of variance, as well as Tukey multiple comparisons, were performed using R and SPSS.

RESULTS

Mean est-Psub was significantly greater in the group with voice disorder than in the control group (P value < 0.001). However, no statistical significance was found when comparing the MFR with the control group (P value <0.59). Nine possible pairings of MFR and est-Psub were found. Sufficient evidence was not found to detect significant differences in these pairings across diagnostic groups.

CONCLUSION

With regard to the rate and interrelationships of MFR and est-Psub, the findings of this study are similar to those of Gillespie et al, that is, MFR and est-Psub are not determinate of diagnosis.

The Effect of Head Position and/or Stance on the Self-perception of Phonatory Effort

BACKGROUND

Vocal fatigue is a common but poorly defined complaint of patients presenting with voice disorders. Definitions of vocal fatigue generally include increased self-perceived phonatory effort resulting from references to vocal loading or prolonged voice use resulting in deterioration of function. The present study looks at the role of posture, specifically head position and stance, in self-perceived phonatory effort.

METHODS

Forty-six healthy adults, 13 males and 33 females (mean age was 27.5), with no history of vocal problems/disorders within the past year were recruited. Subjects were asked to sustain the vowel /a/ at a comfortable pitch and loudness for 5-10 seconds in each of six positions: sitting and standing in the manner habitual for each subject, two exaggerated positions of the head (head back and head forward), and two exaggerated positions in standing (standing with knees locked and with knees soft). Each position was repeated three times in randomized order, resulting in 18 trials for each subject. After each repetition of the sustained /a/, subjects were asked to rate their experience of vocal effort using a 100-mm visual analog scale (0-40 least effort, 40-60 habitual effort, and 60-100 increased effort).

RESULTS

Repeated measures analysis of variance revealed significant difference in the self-perceived phonatory effort levels across positions (P value < 0.001). The exaggerated forward and back head positions in both sitting and standing positions showed the greatest significance on the Tukey post hoc tests (P < 0.000).

CONCLUSIONS

Based on the findings, posture may play a more important role in vocal fatigue than previously thought.

Analysis of voice change during cellular phone use: a blinded controlled study

It is a growing belief that cellular phone use may be hazardous to the voice. This study aims to assess voice production in different conversational scenarios to identify any changes in vocal production that may be specific to cellular phone use. Twenty healthy participants were randomized to seven conversational scenarios: quiet conditions face to face; quiet conditions over a landline; quiet conditions using a cellular phone (QCP); quiet conditions using cellular phone with earpiece (QCPE); noisy conditions face to face (NFF); noisy conditions using cellular phone (NCP); and noisy conditions using cellular phone with earpiece (NCPE). In each condition, participants performed spontaneous speech, a standardized reading passage, and sustained voicing. Sound pressure levels (dB SPL) and fundamental frequencies (F(0)[Hz]) were measured. Subjects completed a 100-mm visual analog scale measuring vocal effort after each speaking scenario. Statistical analysis was performed using analysis of variance (ANOVA). There was a significant difference in dB SPL and F(0) between all quiet conditions relative to all noisy conditions (P<0.001). There was no difference in cellular phone use relative to any other conversational condition in mean dB SPL, respective of ambient noise. Vocal effort was rated greater for noisy conditions compared with quiet conditions. Cellular phone use does not lead to a significant change in voice production relative to other speaking conditions. Voice problems associated with cellular phone use may simply be a function of the increased amount of voice use and increased vocal loudness (Lombard effect) associated with speaking in noisy situations rather than a variable inherent to the phone.

Preparation of RNA from tissues and cells

Most procedures for isolating RNA from eukaryotic cells involve lysing and denaturing cells to liberate total nucleic acids. Additional steps are then required to remove DNA. The first basic protocol describes hot phenol extraction of RNA; the method eliminates or minimizes DNA contamination by the shearing of DNA. The second basic protocol allows rapid preparation of total cytoplasmic RNA by using a nonionic detergent to lyse the plasma membrane, leaving the nuclei intact. The nuclei and hence the bulk of the cellular DNA are then removed with a simple brief centrifugation. A guanidinium thiocyanate protocol describes the separation of RNA from other cellular macromolecules in a guanidinium lysate using a CsCl step gradient. A protocol is also provided for isolation of poly(A(+)) mRNAs from total RNA.

Preparation of RNA from tissues and cells

Most procedures for isolating RNA from eukaryotic cells involve lysing and denaturing cells to liberate total nucleic acids. Additional steps are then required to remove DNA. The first basic protocol describes hot phenol extraction of RNA; the method eliminates or minimizes DNA contamination by the shearing of DNA. The second basic protocol allows rapid preparation of total cytoplasmic RNA by using a nonionic detergent to lyse the plasma membrane, leaving the nuclei intact. The nuclei and hence the bulk of the cellular DNA are then removed with a simple brief centrifugation. A guanidinium thiocyanate protocol describes the separation of RNA from other cellular macromolecules in a guanidinium lysate using a CsCl step gradient. A protocol is also provided for isolation of poly(A(+)) mRNAs from total RNA.

Preparation of bacterial RNA

Procedures for isolating RNA from bacteria involve disruption of the cells, followed by steps to separate the RNA from contaminating DNA and protein. Lysis strategies differ in the protocols presented in this unit, including chemical degradation of gram-negative cell walls using sucrose/detergent or lysozyme, and sonication to break open gram-positive cell walls. Combinations of enzymatic degradation, organic extraction, and alcohol or salt precipitation are employed in the procedures to isolate the RNA from other cellular components, and various inhibitors of ribonuclease activity (diethylpyrocarbonate, vanadyl-ribonucleoside complex, and aurintricarboxylic acid) are described. If extremely high-quality RNA is required (e.g., for gene expression studies), instructions are provided for CsCl step-gradient centrifugation to remove all traces of contaminating DNA.

Ribonuclease protection assay

Sequence-specific hybridization probes of high specific activity are prepared by cloning the probe sequence downstream of a bacteriophage promoter. The plasmid is cleaved with a restriction enzyme, and the plasmid DNA is transcribed with bacteriophage RNA polymerase, which efficiently transcribes the cloned sequence into a discrete RNA species of known specific activity and high abundance. The RNA is purified by removal of the DNA template, protein, and the unincorporated label. Alternatively, the probe is purified by gel electrophoresis, as described in a support protocol. The probe RNA is hybridized to sample RNAs and the hybridization reactions are treated with ribonuclease to remove free probe, leaving intact fragments of probe annealed to homologous sequences in the sample RNA. These fragments are analyzed by electrophoresis on a sequencing gel and the presence of the target mRNA is revealed by the appearance of an appropriately sized fragment of the probe.

Electrotherapy and the Human Voice: A Literature Review of the Historical Origins and Contemporary Applications

SUMMARY

The present article surveys the literature on the electrotherapy treatment for voice disorders from the mid-18th century to World War I (1914--1918) and the post 1970s reappearance of such therapies. The reappearance of electrotherapy as treatment for voice disorders in the past 20 years has been heralded as a major breakthrough. In light of our reading of the scientific literature of the 19th century, it can be shown to repeat many of the presuppositions of electrotherapists of that time. The current resurgence of interest and research in electrical stimulation of the larynx is buoyed by technological innovations analogous to those in the 19th century. Although the current state of research has enhanced our understanding of vocal fold physiology, it does not necessarily provide a new therapeutic approach as a survey of the most recent literature shows.

Early-onset type 2 diabetes in obese white subjects is characterised by a marked defect in beta cell insulin secretion, severe insulin resistance and a lack of response to aerobic exercise training

AIMS/HYPOTHESIS

Early-onset type 2 diabetes is associated with marked visceral obesity and extreme insulin resistance, but its pathogenesis and response to treatment are not completely understood. We studied physical fitness, whole-body and hepatic glucose turnover, and insulin secretion in young obese Irish subjects before and after 3 months of aerobic exercise training. We hypothesised that exercise alone, with stable diet, should improve insulin sensitivity.

MATERIALS AND METHODS

Anthropometric parameters and maximum volume of oxygen utilisation (VO(2max)) were measured in 13 subjects with type 2 diabetes and 18 non-diabetic control subjects, matched for age and BMI. Insulin sensitivity and hepatic glucose turnover were measured using the hyperinsulinaemic-euglycaemic clamp. Insulin secretion was assessed from an OGTT and a modified intravenous glucose tolerance test. Some subjects (seven type 2 diabetic, 14 non-diabetic control subjects) then completed a 12-week supervised aerobic exercise programme. All measurements were repeated on completion of the exercise programme.

RESULTS

Type 2 diabetic subjects had higher WHR, systolic blood pressure and triacylglycerols than non-diabetic control subjects. They were significantly more insulin-resistant as measured both by the clamp and oral glucose insulin sensitivity. They also displayed marked defects in insulin secretion in response to oral and intravenous glucose challenges. Exercise intervention had no significant effect on whole-body or hepatic insulin sensitivity or insulin secretion. VO(2max) increased significantly in the non-diabetic control subjects, but not in the type 2 diabetic subjects after exercise training.

CONCLUSIONS/INTERPRETATION

Young obese subjects with type 2 diabetes are severely insulin-resistant with marked loss of beta cell function compared with control subjects matched for age and obesity. Neither group responded metabolically to aerobic exercise intervention.

Performance-related pay in health care

OBJECTIVE

Performance-related pay (PRP) has been widely extended within the British public sector in the last 15-20 years, mostly because of pressure from central government. Its penetration in the National Health Service (NHS) has not so far been very deep but it has been sufficient to permit preliminary judgements on its likely impact.

METHODS

Review of published accounts of the extent of use of PRP in the NHS and its impact, plus two case studies.

RESULTS

There have been few rigorous studies reported. PRP has been introduced for a variety of reasons: an incentive to motivate staff; to enhance staff recruitment and retention; to signal a change in organizational culture; to control staff costs; to reduce the power of trades unions; to reinforce staff development policies. Very few NHS provider organizations have implemented PRP. Despite this, senior managers see real merit in it in improving staff performance and delivering a clear message about the importance of organizational performance. Employees are much more skeptical, seeing PRP as having no effect or being detrimental.

CONCLUSIONS

PRP has had, at most, only a very modest beneficial impact in the British NHS. In the absence of better evidence, it would be sensible for government to continue to encourage local initiatives rather than propose a mandatory national scheme. It would also be prudent to subject local schemes to rigorous evaluation.

Expression and isolation of antimicrobial small molecules from soil DNA libraries

Natural products have been a critically important source of clinically relevant small molecule therapeutics. However, the discovery rate of novel structural classes of antimicrobial molecules has declined. Recently, increasing evidence has shown that the number of species cultivated from soil represents less than 1% of the total population, opening up the exciting possibility that these uncultured species may provide a large untapped pool from which novel natural products can be discovered. We have constructed and expressed in E. coli a BAC (bacterial artificial chromosome) library containing genomic fragments of DNA (5-120kb) isolated directly from soil organisms (S-DNA). Screening of the library resulted in the identification of several antimicrobial activities expressed by different recombinant clones. One clone (mg1.1) has been partially characterized and found to express several small molecules related to and including indirubin. These results show that genes involved in natural product synthesis can be cloned directly from S-DNA and expressed in a heterologous host, supporting the idea that this technology has the potential to provide novel natural products from the wealth of environmental microbial diversity and is a potentially important new tool for drug discovery.

A Fas-based suicide switch in human T cells for the treatment of graft-versus-host disease

Graft-versus-host disease (GVHD) is a major complication of allogeneic bone marrow transplantation. One strategy to treat GVHD is to equip donor T cells with a conditional suicide mechanism that can be triggered when GVHD occurs. The herpes simplex virus thymidine kinase (HSV-tk)/ganciclovir system used clinically has several limitations, including immunogenicity and cell cycle dependence. An alternative switch based on chemically inducible apoptosis was designed and evaluated. A chimeric human protein was expressed comprising an extracellular marker (DeltaLNGFR), the Fas intracellular domain, and 2 copies of an FK506-binding protein (FKBP). Primary human T lymphocytes retrovirally transduced with this construct could be purified to homogeneity using immunomagnetic beads. Genetic integrity of the construct was ensured by redesigning repetitive sequences. Transduced T cells behaved indistinguishably from untransduced cells, retaining the ability to mount a specific antiallogeneic immune response. However, they rapidly underwent apoptosis with the addition of subnanomolar concentrations of AP1903, a bivalent "dimerizer" drug that binds FKBP and induces Fas cross-linking. A single 2-hour treatment eliminated approximately 80% of T cells, and multiple exposures induced further apoptosis. T cells were eliminated regardless of their proliferation state, suggesting that the AP1903/Fas system, which contains only human components, is a promising alternative to HSV-tk for treating GVHD.

A ligand-reversible dimerization system for controlling protein-protein interactions

Chemically induced dimerization provides a general way to gain control over intracellular processes. Typically, FK506-binding protein (FKBP) domains are fused to a signaling domain of interest, allowing crosslinking to be initiated by addition of a bivalent FKBP ligand. In the course of protein engineering studies on human FKBP, we discovered that a single point mutation in the ligand-binding site (Phe-36 --> Met) converts the normally monomeric protein into a ligand-reversible dimer. Two-hybrid, gel filtration, analytical ultracentrifugation, and x-ray crystallographic studies show that the mutant (F(M)) forms discrete homodimers with micromolar affinity that can be completely dissociated within minutes by addition of monomeric synthetic ligands. These unexpected properties form the basis for a "reverse dimerization" regulatory system involving F(M) fusion proteins, in which association is the ground state and addition of ligand abolishes interactions. We have used this strategy to rapidly and reversibly aggregate fusion proteins in different cellular compartments, and to provide an off switch for transcription. Reiterated F(M) domains should be generally useful as conditional aggregation domains (CADs) to control intracellular events where rapid, reversible dissolution of interactions is required. Our results also suggest that dimerization is a latent property of the FKBP fold: the crystal structure reveals a remarkably complementary interaction between the monomer binding sites, with only subtle changes in side-chain disposition accounting for the dramatic change in quaternary structure.

Cloning the soil metagenome: a strategy for accessing the genetic and functional diversity of uncultured microorganisms

Recent progress in molecular microbial ecology has revealed that traditional culturing methods fail to represent the scope of microbial diversity in nature, since only a small proportion of viable microorganisms in a sample are recovered by culturing techniques. To develop methods to investigate the full extent of microbial diversity, we used a bacterial artificial chromosome (BAC) vector to construct libraries of genomic DNA isolated directly from soil (termed metagenomic libraries). To date, we have constructed two such libraries, which contain more than 1 Gbp of DNA. Phylogenetic analysis of 16S rRNA gene sequences recovered from one of the libraries indicates that the BAC libraries contain DNA from a wide diversity of microbial phyla, including sequences from diverse taxa such as the low-G+C, gram-positive Acidobacterium, Cytophagales, and Proteobacteria. Initial screening of the libraries in Escherichia coli identified several clones that express heterologous genes from the inserts, confirming that the BAC vector can be used to maintain, express, and analyze environmental DNA. The phenotypes expressed by these clones include antibacterial, lipase, amylase, nuclease, and hemolytic activities. Metagenomic libraries are a powerful tool for exploring soil microbial diversity, providing access to the genetic information of uncultured soil microorganisms. Such libraries will be the basis of new initiatives to conduct genomic studies that link phylogenetic and functional information about the microbiota of environments dominated by microorganisms that are refractory to cultivation.

Regulation of protein secretion through controlled aggregation in the endoplasmic reticulum

A system for direct pharmacologic control of protein secretion was developed to allow rapid and pulsatile delivery of therapeutic proteins. A protein was engineered so that it accumulated as aggregates in the endoplasmic reticulum. Secretion was then stimulated by a synthetic small-molecule drug that induces protein disaggregation. Rapid and transient secretion of growth hormone and insulin was achieved in vitro and in vivo. A regulated pulse of insulin secretion resulted in a transient correction of serum glucose concentrations in a mouse model of hyperglycemia. This approach may make gene therapy a viable method for delivery of polypeptides that require rapid and regulated delivery.

A general strategy to enhance the potency of chimeric transcriptional activators

Efforts to increase the potency of transcriptional activators are generally unsuccessful because poor expression of activators in mammalian cells limits their delivery to target promoters. Here we report that the effectiveness of chimeric activators can be dramatically improved by expressing them as noncovalent tetrameric bundles. Bundled activation domains are much more effective at activating a reporter gene than simple monomeric activators, presumably because, at similar expression levels, up to 4 times as many the activation domains are delivered to the target promoter. These bundled activation domains are also more effective than proteins in which activation domains are tandemly reiterated in the same polypeptide chain, because such proteins are very poorly expressed and therefore not delivered effectively. These observations suggest that there is a threshold number of activation domains that must be bound to a promoter for activation, above which promoter activity is simply a function of the number of activators bound. We show that bundling can be exploited practically to enhance the sensitivity of mammalian two-hybrid assays, enabling detection of weak interactions or those between poorly expressed proteins. Bundling also dramatically improves the performance of a small-molecule-regulated gene expression system when the expression level of regulatory protein is limiting, a situation that may be encountered in gene therapy applications.

Proteasome-mediated degradation of transcriptional activators correlates with activation domain potency in vivo

We show that the intracellular concentration of transcriptional activator proteins is regulated by the proteasome-mediated protein degradation pathway. The rate of degradation of activators by proteasomes correlates with activation domain potency in vivo. Mutations either in the activation domain residues involved in target protein interaction or in the DNA-binding domain residues essential for DNA binding abolish the transcriptional activation function in vivo and render the activator resistant to degradation by proteasomes. Finally, using a rapamycin-regulated gene expression system, we show that recruiting activation domains to DNA-bound receptor proteins greatly enhanced the rate of degradation of reconstituted activators. These observations suggest that in mammalian cells efficient recruitment of activator-target protein complexes to the promoter means that they are subjected to rapid degradation by proteasomes. We propose that proteasome-mediated control of the intracellular levels of transcriptional activators could play an important role in the regulation of gene expression.

Cell surface tagging and a suicide mechanism in a single chimeric human protein

Many therapeutic uses of gene-modified cells could benefit from inclusion of a surface marker for immunoselecting transduced cells. Another desired feature is a failsafe mechanism to ablate engineered cells if required. We describe here a system that combines a cell surface tag and an inducible apoptosis mechanism in a single protein. Spencer et al. (Curr. Biol. 1996;6:839-847) described an inducible cell suicide gene containing a myristoylation sequence, the human protein FKBP12, and the intracellular domain of Fas. Cells expressing this protein apoptose on treatment with a cell-permeable chemical dimerizing agent that binds two FKBP domains and cross-links the chimeric Fas proteins. We modified this system by anchoring a Fas-FKBP construct to the membrane with the extracellular and transmembrane domains of the low-affinity nerve growth factor receptor (LNGFR), thereby uniting cell surface tagging with the inducible apoptosis mechanism. Cells retrovirally transduced with this construct apoptosed on exposure to a chemical dimerizer, AP1903 (Clackson et al., Proc. Natl. Acad. Sci. U.S.A. 1998;95:10437-10442). The LNGFR-tagged construct showed an unpredicted clear advantage over the myristoylation-anchored construct in its efficiency of signaling in HT1080 cells. This linked marker and failsafe mechanism may have particularly attractive safety properties for gene therapy. The use of gene-modified cells in basic research and clinical studies is enhanced by the use of a selectable surface marker for immunoselection of transduced cells. Another desired feature for gene and cell therapies is an inducible suicide system to eliminate transduced cells when necessary. Spencer et al. (Curr. Biol. 1996;6:839-847) described a potential failsafe mechanism whereby exposure of cells to a chemical dimerizing agent activates the Fas-mediated apoptotic pathway. In this system, the intracellular signaling domain of Fas is linked to one or more copies of the human protein FKBP12. Treatment of engineered cells with a cell-permeable chemical dimerizing agent that simultaneously binds to two FKBP domains cross-links the chimeric Fas protein and induces apoptosis. Here, we modify the system by anchoring a Fas-FKBP construct to the membrane with the extracellular domain of the low-affinity nerve growth factor receptor (LNGFR), to unite cell surface tagging of transduced cells with the inducible apoptosis mechanism. Cells retrovirally transduced with this construct undergo apoptosis on exposure to a chemical dimerizer, AP1903. A linked marker and failsafe mechanism may have particularly attractive safety properties for gene therapy.

Controlled dimerization of ErbB receptors provides evidence for differential signaling by homo- and heterodimers

The four members of the ErbB family of receptor tyrosine kinases are involved in a complex array of combinatorial interactions involving homo- and heterodimers. Since most cell types express more than one member of the ErbB family, it is difficult to distinguish the biological activities of different homo- and heterodimers. Here we describe a method for inducing homo- or heterodimerization of ErbB receptors by using synthetic ligands without interference from the endogenous receptors. ErbB receptor chimeras containing synthetic ligand binding domains (FK506-binding protein [FKBP] or FKBP-rapamycin-binding domain [FRB]) were homodimerized with the bivalent FKBP ligand AP1510 and heterodimerized with the bifunctional FKBP-FRB ligand rapamycin. AP1510 treatment induced tyrosine phosphorylation of ErbB1 and ErbB2 homodimers and recruitment of Src homology 2 domain-containing proteins (Shc and Grb2). In addition, ErbB1 and ErbB2 homodimers activated downstream signaling pathways leading to Erk2 and Akt phosphorylation. However, only ErbB1 homodimers were internalized upon AP1510 stimulation, and only ErbB1 homodimers were able to associate with and induce phosphorylation of c-Cbl. Cells expressing AP1510-induced ErbB1 homodimers were able to associate with and induce phosphorylation of c-Cbl. Cells expressing AP1510-induced ErbB1 homodimers were able to form foci; however, cells expressing ErbB2 homodimers displayed a five- to sevenfold higher focus-forming ability. Using rapamycin-inducible heterodimerization we show that c-Cbl is unable to associate with ErbB1 in a ErbB1-ErbB2 heterodimer most likely because ErbB2 is unable to phosphorylate the c-Cbl binding site on ErbB1. Thus, we demonstrate that ErbB1 and ErbB2 homodimers differ in their abilities to transform fibroblasts and provide evidence for differential signaling by ErbB homodimers and heterodimers. These observations also validate the use of synthetic ligands to study the signaling and biological specificity of selected ErbB dimers in any cell type.

Long-term regulated expression of growth hormone in mice after intramuscular gene transfer

Effective delivery of secreted proteins by gene therapy will require a vector that directs stable delivery of a transgene and a regulatory system that permits pharmacologic control over the level and kinetics of therapeutic protein expression. We previously described a regulatory system that enables transcription of a target gene to be controlled by rapamycin, an orally bioavailable drug. Here we demonstrate in vivo regulation of gene expression after intramuscular injection of two separate adenovirus or adeno-associated virus (AAV) vectors, one encoding an inducible human growth hormone (hGH) target gene, and the other a bipartite rapamycin-regulated transcription factor. Upon delivery of either vector system into immunodeficient mice, basal plasma hGH expression was undetectable and was induced to high levels after administration of rapamycin. The precise level and duration of hGH expression could be controlled by the rapamycin dosing regimen. Equivalent profiles of induction were observed after repeated administration of single doses of rapamycin over many months. AAV conferred stable expression of regulated hGH in both immunocompetent and immunodeficient mice, whereas adenovirus-directed hGH expression quickly extinguished in immunocompetent animals. These studies demonstrate that the rapamycin-based regulatory system, delivered intramuscularly by AAV, fulfills many of the conditions necessary for the safe and effective delivery of therapeutic proteins by gene therapy.

Distinct mechanisms of activation of Stat1 and Stat3 by platelet-derived growth factor receptor in a cell-free system

Ligand-dependent activation of the platelet-derived growth factor receptor (PDGFR) in fibroblasts in culture leads to the activation of the JAK family of protein-tyrosine kinases and of the transcription factors Stat1 and Stat3. To determine the biochemical mechanism of STAT activation by PDGFR, we devised a cell-free system composed of a membrane fraction from cells overexpressing PDGFR. When supplemented with crude cytosol, the membrane fraction supported PDGF- and ATP-dependent activation of both Stat1 and Stat3. However, the extent of Stat3 activation differed depending on the source of the cytosolic fraction. Using purified recombinant STAT proteins produced in Escherichia coli, we found that Stat1 could be activated by immunopurified PDGFR and showed no additional requirement for membrane- or cytosol-derived proteins. In contrast, activation of Stat3 exhibited a strong requirement for the cytosolic fraction. The activity present in the cytosolic fraction could be depleted with antibodies to JAK proteins. We conclude that the mechanisms of activation of Stat1 and Stat3 by PDGFR are distinct. Stat1 activation appears to result from a direct interaction with the receptor, whereas Stat3 activation additionally requires JAK proteins.

Regulated delivery of therapeutic proteins after in vivo somatic cell gene transfer

Stable delivery of a therapeutic protein under pharmacologic control was achieved through in vivo somatic gene transfer. This system was based on the expression of two chimeric, human-derived proteins that were reconstituted by rapamycin into a transcription factor complex. A mixture of two adeno-associated virus vectors, one expressing the transcription factor chimeras and one containing erythropoietin (Epo) under the control of a promoter responsive to the transcription factor, was injected into skeletal muscle of immune-competent mice. Administration of rapamycin resulted in 200-fold induction of plasma Epo. Stable engraftment of this humanized system in immune-competent mice was achieved for 6 months with similar results for at least 3 months in a rhesus monkey.

Drosophila unpaired encodes a secreted protein that activates the JAK signaling pathway

In vertebrates, many cytokines and growth factors have been identified as activators of the JAK/STAT signaling pathway. In Drosophila, JAK and STAT molecules have been isolated, but no ligands or receptors capable of activating the pathway have been described. We have characterized the unpaired (upd) gene, which displays the same distinctive embryonic mutant defects as mutations in the Drosophila JAK (hopscotch) and STAT (stat92E) genes. Upd is a secreted protein, associated with the extracellular matrix, that activates the JAK pathway. We propose that Upd is a ligand that relies on JAK signaling to stimulate transcription of pair-rule genes in a segmentally restricted manner in the early Drosophila embryo.

Redesigning an FKBP-ligand interface to generate chemical dimerizers with novel specificity

FKBP ligand homodimers can be used to activate signaling events inside cells and animals that have been engineered to express fusions between appropriate signaling domains and FKBP. However, use of these dimerizers in vivo is potentially limited by ligand binding to endogenous FKBP. We have designed ligands that bind specifically to a mutated FKBP over the wild-type protein by remodeling an FKBP-ligand interface to introduce a specificity binding pocket. A compound bearing an ethyl substituent in place of a carbonyl group exhibited sub-nanomolar affinity and 1,000-fold selectivity for a mutant FKBP with a compensating truncation of a phenylalanine residue. Structural and functional analysis of the new pocket showed that recognition is surprisingly relaxed, with the modified ligand only partially filling the engineered cavity. We incorporated the specificity pocket into a fusion protein containing FKBP and the intracellular domain of the Fas receptor. Cells expressing this modified chimeric protein potently underwent apoptosis in response to AP1903, a homodimer of the modified ligand, both in culture and when implanted into mice. Remodeled dimerizers such as AP1903 are ideal reagents for controlling the activities of cells that have been modified by gene therapy procedures, without interference from endogenous FKBP.

Synthesis and activity of bivalent FKBP12 ligands for the regulated dimerization of proteins

The total synthesis and in vitro activities of a series of chemical inducers of dimerization (CIDs) is described. The use of small-molecule CIDs to control the dimerization of engineered FKBP12-containing fusion proteins has been demonstrated to have broad utility in biological research as well as potential medical applications in gene and cell therapies. The facility and flexibility of preparation make this new class of wholly synthetic compounds exceptionally versatile tools for the study of intracellular signaling events mediated by protein-protein interactions or protein localization. While some congeners possess potency comparable to or better than the first generation natural product-derived CID, FK1012, structure-activity relationships are complex and underscore the need for application-specific compound optimizations.

Pharmacologic control of a humanized gene therapy system implanted into nude mice

Systemic delivery of specific therapeutic proteins by a parenteral route of administration is a recognized practice in the management of several gene defects and acquired diseases. As an alternative to repetitive parenteral administration, gene therapy may provide a novel means for systemic delivery of therapeutic proteins while improving patient compliance and therapeutic efficacy. However, for gene therapy to be an efficacious and safe approach to the clinical management of such diseases, gene expression must be tightly regulated. These investigations demonstrate precise in vivo control of protein expression from cells that are engineered to secrete human growth hormone (hGH) in response to stimulation by rapamycin. The cells were implanted intramuscularly into nu/nu mice and stimulated by intravenous or oral administration of rapamycin. In vivo experiments demonstrate that the activity and pharmacokinetics of rapamycin determine the level of serum hGH that result from the engineered cells. In addition, responsiveness of the cells to rapamycin, number of cells implanted, hGH expression kinetics, and the pharmacokinetics of hGH itself, also influence the circulating levels of hGH after rapamycin stimulation. Controlled manipulation of several of these parameters, either independently or in combination, allows for precise regulation of circulating hGH concentration in vivo.

Protein and DNA contact surfaces that mediate the selective action of the Phox1 homeodomain at the c-fos serum response element

The human homeodomain protein Phox1 can impart serum-responsive transcriptional activity to the c-fos serum response element (SRE) by interacting with serum response factor (SRF). This activity is shared with other Paired class homeodomains but not with more distantly related homeodomains. To understand the mechanism of action of Phox1 at the SRE and the basis for the selective activity of Paired class homeodomains in this context, we performed a detailed mutagenesis of the Phox1 homeodomain. We found that amino acid residues that contact the major groove of the DNA are required for SRE activation in vivo, suggesting an in vivo requirement for major-groove DNA contact by the homeodomain. In contrast, substitution of a lysine residue in the N-terminal arm of the Phox1 homeodomain appeared to abolish DNA binding without affecting activity in vivo. Certain substitutions on the exposed surfaces of helices 1 and 2, not required for DNA binding, abolished activity in vivo, suggesting that these surfaces contact an accessory protein(s) required for this activity. We also found that transfer of a single amino acid residue from the surface of Phox1 helix 1 to the corresponding position in the distantly related Deformed (Dfd) homeodomain imparts to Dfd the ability to activate the SRE in vivo. We propose that Phox1 interacts with one or more factors at the SRE, in addition to SRF, and that the specificity of this interaction is determined by residues on the surfaces of helices 1 and 2.

A multifunctional DNA-binding protein that promotes the formation of serum response factor/homeodomain complexes: identity to TFII-I

The human homeodomain protein Phox1 interacts functionally with serum response factor (SRF) to impart serum responsive transcriptional activity to SRF-binding sites in a HeLa cell cotransfection assay. However, stable ternary complexes composed of SRF, Phox1, and DNA, which presumably mediate the transcriptional effects of Phox1 in vivo, have not been observed in vitro. Here, we report the identification, purification, and molecular cloning of a human protein that promotes the formation of stable higher-order complexes of SRF and Phox1. We show that this protein, termed SPIN, interacts with SRF and Phox1 in vitro and in vivo. Furthermore, SPIN binds specifically to multiple sequences in the c-fos promoter and interacts cooperatively with Phox1 to promote serum-inducible transcription of a reporter gene driven by the c-fos serum response element (SRE). SPIN is identical to the initiator-binding protein TFII-I. Consistent with this hypothesis, SPIN exhibits modest affinity for a characterized initiator sequence in vitro. We propose that this multifunctional protein coordinates the formation of an active promoter complex at the c-fos gene, including the linkage of specific signal responsive activator complexes to the general transcription machinery.

A versatile synthetic dimerizer for the regulation of protein-protein interactions

The use of low molecular weight organic compounds to induce dimerization or oligomerization of engineered proteins has wide-ranging utility in biological research as well as in gene and cell therapies. Chemically induced dimerization can be used to activate intracellular signal transduction pathways or to control the activity of a bipartite transcription factor. Dimerizer systems based on the natural products cyclosporin, FK506, rapamycin, and coumermycin have been described. However, owing to the complexity of these compounds, adjusting their binding or pharmacological properties by chemical modification is difficult. We have investigated several families of readily prepared, totally synthetic, cell-permeable dimerizers composed of ligands for human FKBP12. These molecules have significantly reduced complexity and greater adaptability than natural product dimers. We report here the efficacies of several of these new synthetic compounds in regulating two types of protein dimerization events inside engineered cells--induction of apoptosis through dimerization of engineered Fas proteins and regulation of transcription through dimerization of transcription factor fusion proteins. One dimerizer in particular, AP1510, proved to be exceptionally potent and versatile in all experimental contexts tested.

A humanized system for pharmacologic control of gene expression

Gene therapy was originally conceived as a medical intervention to replace or correct defective genes in patients with inherited disorders. However, it may have much broader potential as an alternative delivery platform for protein therapeutics, such as cytokines, hormones, antibodies and novel engineered proteins. One key technical barrier to the widespread implementation of this form of therapy is the need for precise control over the level of protein production. A suitable system for pharmacologic control of therapeutic gene expression would permit precise titration of gene product dosage, intermittent or pulsatile treatment, and ready termination of therapy by withdrawal of the activating drug. We set out to design such a system with the following properties: (1) low baseline expression and high induction ratio; (2) positive control by an orally bioavailable small-molecule drug; (3) reduced potential for immune recognition through the exclusive use of human proteins; and (4) modularity to allow the independent optimization of each component using the tools of protein engineering. We report here the properties of this system and demonstrate its use to control circulating levels of human growth hormone in mice implanted with engineered human cells.

Platelet-derived growth factor induces phosphorylation of multiple JAK family kinases and STAT proteins

Receptors for interferons and other cytokines signal through the action of associated protein tyrosine kinases of the JAK family and latent cytoplasmic transcription factors of the STAT family. Genetic and biochemical analysis of interferon signaling indicates that activation of STATs by interferons requires two distinct JAK family kinases. Loss of either of the required JAKs prevents activation of the other JAK and extinguishes STAT activation. These observations suggest that JAKs provide interferon receptors with a critical catalytic signaling function and that at least two JAKs must be incorporated into an active receptor complex. JAK and STAT proteins are also activated by ligands such as platelet-derived growth factor (PDGF), which act through receptors that possess intrinsic protein tyrosine kinase activity, raising questions about the role of JAKs in signal transduction by this class of receptors. Here, we show that all three of the ubiquitously expressed JAKs--JAK1, JAK2, and Tyk2--become phosphorylated on tyrosine in both mouse BALB/c 3T3 cells and human fibroblasts engineered to express the PDGF-beta receptor. All three proteins are also associated with the activated receptor. Through the use of cell lines each lacking an individual JAK, we find that in contrast to interferon signaling, PDGF-induced JAK phosphorylation and activation of STAT1 and STAT3 is independent of the presence of any other single JAK but does require receptor tyrosine kinase activity. These results suggests that the mechanism of JAK activation and JAK function in signaling differs between receptor tyrosine kinases and interferon receptors.

YY1 facilitates the association of serum response factor with the c-fos serum response element

YY1 is a multifunctional transcription factor that acts as an activator or repressor in different contexts. YY1 binds to multiple sites in the mouse c-fos promoter, inducing at each site a sharp DNA bend. Binding of YY1 to a site situated between the cyclic AMP response element (CRE) and the TATA box bends the DNA in a way that interferes with the interaction of proteins bound at the CRE and TATA elements, resulting in repression of transcription. Here, we show that binding of YY1 to a different site in the c-fos promoter has a different result. Binding of YY1 to the c-fos serum response element (SRE) enhances the binding of serum response factor (SRF). This enhancement requires the binding of YY1 to SRE DNA. YY1 and SRF can cooccupy the SRE at least transiently. In the region of overlapping contact, YY1 contacts DNA in the major groove, while SRF contacts DNA in the minor groove. YY1 also enhances the association of SRF with the SRE in transfected insect cells. Thus, although YY1 induces similar structural changes in DNA at different binding sites, it can have distinct local effects on protein-DNA and protein-protein interactions. These data support a general role for YY1 in the building of highly organized promoter complexes.

Activation of a Drosophila Janus kinase (JAK) causes hematopoietic neoplasia and developmental defects

In mammals, many cytokines and growth factors stimulate members of the Janus kinase (JAK) family to transduce signals for the proliferation and differentiation of various cell types, particularly in hematopoietic lineages. Mutations in the Drosophila hopscotch (hop) gene, which encodes a JAK, also cause proliferative defects. Loss-of-function alleles result in lethality and underproliferation of diploid tissues of the larva. A dominant gain-of-function allele, Tumorous-lethal (hopTum-l), leads to formation of melanotic tumors and hypertrophy of the larval lymph glands, the hematopoietic organs. We show that a single amino acid change in Hop is associated with the hopTum-l mutation. Overexpression of either wild-type hop or hopTum-l in the larval lymph glands causes melanotic tumors and lymph gland hypertrophy indistinguishable from the original hopTum-l mutation. In addition, overexpression of Hop in other tissues of the larva leads to pattern defects in the adult or to lethality. Finally, overexpression of either hop or hopTum-l in Drosophila cell culture results in tyrosine phosphorylation of Hop protein. However, overexpression of hopTum-l results in greater phosphorylation than overexpression of the wild-type. We conclude that hopTum-l encodes a hyperactive Hop kinase and that overactivity of Hop in lymph glands causes malignant neoplasia of Drosophila blood cells.

Sequence-specific targeting of nuclear signal transduction pathways by homeodomain proteins

Cells translate extracellular signals into specific programs of gene expression that reflect their developmental history or identity. We present evidence that one way this interpretation may be performed is by cooperative interactions between serum response factor (SRF) and certain homeodomain proteins. We show that human and Drosophila homeodomain proteins of the paired class have the ability to recruit SRF to DNA sequences not efficiently recognized by SRF on its own, thereby imparting to a linked reporter gene the potential to respond to polypeptide growth factors. This activity requires both the DNA-binding activity of the homeodomain and putative protein-protein contact residues on the exposed surfaces of homeodomain helices 1 and 2. The ability of the homeodomain to impart signal responsiveness is DNA sequence specific, and this specificity differs from the simple DNA-binding specificity of the homeodomain in vitro. The homeodomain imparts response to a spectrum of signals characteristic of the natural SRF-binding site in the c-fos gene. Response to some of these signals is dependent on the secondary recruitment of SRF-dependent ternary complex factors, and we show directly that a homeodomain can promote the recruitment of one such factor, Elk1. We infer that SRF and homeodomains interact cooperatively on DNA and that formation of SRF-homeodomain complexes permits the recruitment of signal-responsive SRF accessory proteins. The ability to route extracellular signals to specific target genes is a novel activity of the homeodomain, which may contribute to the identity function displayed by many homeodomain genes.

Dual modes of control of c-fos mRNA induction by intracellular calcium in T cells

Cytoplasmic calcium is a nearly universal second messenger in eukaryotes. In many cell types, elevated intracellular calcium interacts synergistically with inducers of protein kinase C to elicit activation of complete biological programs normally induced by extracellular signals. In T cells, elevated cytoplasmic calcium is a critical mediator of activation in response to stimulation of the antigen receptor, and in some T-cell lines, treatment with a combination of calcium ionophore and protein kinase C activator mimics authentic antigen treatment. The synergistic interaction of calcium and protein kinase C in T cells is also observed at the level of gene expression. Here we examine the molecular mechanisms through which these agents exert synergistic control over the expression of the c-fos proto-oncogene in a T-cell hybridoma. We find that the principal effect of calcium is on the elongation of c-fos transcripts. This step constitutes the major control of c-fos mRNA accumulation in these cells. In addition, calcium regulates the initiation of c-fos transcription. This effect requires the serum response element of the c-fos gene and an additional sequence immediately 3' to this element. Thus, calcium regulates c-fos expression through at least two distinct molecular pathways.

Distinct protein targets for signals acting at the c-fos serum response element

The c-fos serum response element (SRE) is a primary nuclear target for intracellular signal transduction pathways triggered by growth factors. It is the target for both protein kinase C (PKC)-dependent and -independent signals. Function of the SRE requires binding of a cellular protein, termed serum response factor (SRF). A second protein, p62TCF, recognizes the SRE-SRF complex to form a ternary complex. A mutated SRE that bound SRF but failed to form the ternary complex selectively lost response to PKC activators, but retained response to PKC-independent signals. Thus, two different signaling pathways act through discrete nuclear targets at the SRE. At least one of these pathways functions by recruitment of a pathway-specific accessory factor (p62TCF). These results offer a molecular mechanism to account for the biological specificity of signals that appear to act through common DNA sequence elements.

Amniocentesis for gram stain and culture in preterm premature rupture of the membranes

A retrospective study was conducted to assess the predictive value and clinical usefulness of amniotic fluid Gram stain and culture in the management of preterm premature rupture of the membranes (PROM). Amniocentesis was attempted in 79 patients and was successful in 53 patients for a success rate of 67%. The complication rate was 1.8%. Fifty-three patients from whom amniotic fluid was obtained after preterm PROM were studied. Patients were managed expectantly unless clinical chorioamnioitis developed, a positive Gram stain or culture was found, or a mature lung profile after 34 weeks' gestation was established. A low incidence of chorioamnionitis (5.5%), postpartum endometritis (11%), and neonatal sepsis (3.5%) was found with expectant management. A statistically significant association between Gram stain and antepartum infection, postpartum infection, and neonatal infection was noted. Gram stain had a 100% sensitivity and 82% specificity as predictor of chorioamnionitis. Amniotic fluid culture had a 100% sensitivity and 76% specificity as predictor of chorioamnionitis. As predictor of a positive culture result, Gram stain had a sensitivity of 60% and specificity of 92%. No patient with a negative Gram stain or culture developed infectious sequelae regardless of the timing of amniocentesis. All positive Gram stains and cultures were found within 48 hours of rupture of membranes. Amniocentesis for Gram stain and culture has clinical usefulness in preterm PROM and, despite false-positive tests, the authors' data support intervention on the basis of a positive Gram stain.

Analysis of the human fetal skeleton and organs with xeroradiography

We have used xeroradiography to study normal and abnormal fetuses including some with anencephaly, hydrocephalus, spina bifida, osteogenesis imperfecta (type IV), Jeune syndrome, radial aplasia, thanatophoric dysplasia, and Pena-Shokeir syndrome. Xeroradiography images the lines of ossification and epiphyses in great detail, shows ossification, and reveals abnormalities that alter bone modeling as seen in Jeune syndrome, osteogenesis imperfecta (type IV), and thanatophoric dysplasia. This technique can be used successfully to examine soft tissues and organs. It can also be used in combination with contrast materials to identify the lateral ventricles, the cardiovascular, gastrointestinal, urinary, and respiratory systems, and the cavities (pleural and peritoneal) of the fetal body.

Assessing the activity of sarcoidosis: quantitative 67Ga-citrate imaging

Three different methods of quantitating 67Ga-citrate lung images--a visual index, a computer-assisted index, and the total-lung-to-background ratio--were compared in 71 studies of patients with biopsy-proven sarcoidosis. Fifty consecutive cases were analyzed independently by two different observers using all three methods. In 45 patients, both gallium lung scans and bronchoalveolar lavage were performed within 2 weeks. In these studies, each index was correlated with the cell differential in the bronchoalveolar lavage fluid. The total-lung-to-background ratio proved to be the simplest to perform; correlated best with the original visual index (r = 0.81, p less than 0.00001) and the percentage of lymphocytes obtained in bronchoalveolar lavage fluid (r = 0.39, p less than 0.004); and showed the lowest interobserver variation. Sensitivity for detecting active disease was 84% compared with 64% and 58% for the visual and computer-assisted indices, respectively, with no sacrifice in specificity.

Metastatic pulmonary calcification in the renal transplant recipient

An asymptomatic immunosuppressed renal transplant patient presented with diffuse alveolar infiltrates on a routine chest roentgenogram. An open lung biopsy revealed changes compatible with metastatic pulmonary calcification. The etiology, pathogenesis, and diagnostic approach to this rare disorder are discussed.

Unilateral cryptophthalmia

Two patients had the variable clinical features of unilateral cryptophthalmia. A 5-month-old boy had isolated unilateral cryptophthalmia: a small boney orbit, deformed optic canal, and a small amorphous mass with no normal intraocular tissue representing the globe. No extraocular muscles or optic nerve were identified by B-scan ultrasound or by computed axial tomography x-ray techniques. The second patient, a 13-year-old girl, had unilateral cryptophthalmia, and numerous systemic abnormalities including a head circumference less than the third percentile, severe mental retardation, hypoplasia of the left side of the head, and a left facial cleft deformity. She also had contractures of hips, knees and ankles, and bilateral spasticity and jerky movements. The left boney orbit was contracted and deformed and contained a small amorphous tissue with no ocular detail, as revealed by B-scan and computed tomography scan.