Real-time chest-wall-motion tracking by a single optical fibre grating: a prospective method for ventilator triggering.

OBJECTIVE: The ventilators involved in non-invasive mechanical ventilation commonly provide ventilator support via a facemask. The interface of the mask with a patient promotes air leaks that cause errors in the feedback information provided by a pneumatic sensor and hence patient-ventilator asynchrony with multiple negative consequences. Our objective is to test the possibility of using chest-wall motion measured by an optical fibre-grating sensor as a more accurate non-invasive ventilator triggering mechanism. APPROACH: The basic premise of our approach is that the measurement accuracy can be improved by using a triggering signal that precedes pneumatic triggering in the neuro-ventilatory coupling sequence. We propose a technique that uses the measurement of chest-wall curvature by a long-period fibre-grating sensor. The sensor was applied externally to the rib-cage and interrogated in the lateral (edge) filtering scheme. The study was performed on 34 healthy volunteers. Statistical data analysis of the time lag between the fibre-grating sensor and the reference pneumotachograph was preceded by the removal of the unwanted heartbeat signal by wavelet transform processing. MAIN RESULTS: The results show a consistent fibre-grating signal advance with respect to the standard pneumatic signal by (230 ± 100) ms in both the inspiratory and expiratory phases. We further show that heart activity removal yields a tremendous improvement in sensor accuracy by reducing it from 60 ml to 0.3 ml. SIGNIFICANCE: The results indicate that the proposed measurement technique may lead to a more reliable triggering decision. Its imperviousness to air leaks, non-invasiveness, low-cost and ease of implementation offer good prospects for applications in both clinical and homecare ventilation.

Rib-cage-movement measurements as a potential new trigger signal in non-invasive mechanical ventilation.

Non-invasive ventilation performed through an oronasal mask is a standard in clinical and homecare mechanical ventilation. Besides all its advantages, inevitable leaks through the mask cause errors in the feedback information provided by the airflow sensor and, hence, patient-ventilator asynchrony with multiple negative consequences. Here we investigate a new way to provide a trigger to the ventilator. The method is based on the measurement of rib cage movement at the onset of inspiration and during breathing by fibre-optic sensors. In a series of simultaneous measurements by a long-period fibre grating sensor and pneumotachograph we provide the statistical evidence of the 200 ms lag of the pneumo with respect the fibre-optic signal. The lag is registered consistently across three independent delay metrics. Further, we discuss exceptions from this trend and identify the needed improvements to the proposed fibre-sensing scheme.

Alternative lengthening of telomeres in cancer stem cells in vivo.

Chromosome ends are protected by telomeres that prevent DNA damage response and degradation. Telomerase expression extends telomeres and inhibits DNA damage response. Telomeres are also maintained by the recombination-based alternative lengthening pathway. Telomerase is believed to be the sole mechanism for telomere maintenance in the epidermis. We show that basal cells in the epidermis maintain telomeres both by telomerase and alternative lengthening of telomere (ALT) mechanisms in vivo. ALT was detected in epidermal stem cells in Terc(-/-) mice, and normal human epidermal keratinocytes are also ALT-positive. The ALT pathway is suppressed in primary, but not metastatic, epidermal squamous cell carcinomas (SCC) in Terc(+/+) mice. The ALT pathway is expressed in stem cells and basal cells in epidermal SCC in Terc(-/-) mice, and in some telomerase-positive human SCC lines. Telomeres shorten markedly in stem cells and basal cells in epidermal SCC in vivo. Telomere shortening is associated with telomeric DNA damage response and apoptosis in stem cells and basal cells. Stem cells were transformed in both primary and metastatic epidermal SCC. Genetic ablation of this small cell population resulted in significant tumor regression in vivo. We concluded that alternative lengthening of telomeres is important in epidermal homeostasis and tumorigenesis in vivo.

Non-invasive respiratory monitoring using long-period fiber grating sensors.

In non-invasive ventilation, continuous monitoring of respiratory volumes is essential. Here, we present a method for the measurement of respiratory volumes by a single fiber-grating sensor of bending and provide the proof-of-principle by applying a calibration-test measurement procedure on a set of 18 healthy volunteers. Results establish a linear correlation between a change in lung volume and the corresponding change in a local thorax curvature. They also show good sensor accuracy in measurements of tidal and minute respiratory volumes for different types of breathing. The proposed technique does not rely on the air flow through an oronasal mask or the observation of chest movement by a clinician, which distinguishes it from the current clinical practice.

Algorithm for total face and multiorgan procurement from a brain-dead donor.

Procurement of a facial vascularized composite allograft (VCA) should allow concurrent procurement of all solid organs and ensure their integrity. Because full facial procurement is time-intensive, "simultaneous-start" procurement could entail VCA ischemia over 12 h. We procured a total face osteomyocutaneous VCA from a brain-dead donor. Bedside tracheostomy and facial mask impression were performed preoperative day 1. Solid organ recovery included heart, lungs, liver, kidneys, and pancreas. Facial dissection time was 12 h over 15 h to diminish ischemia while awaiting recipient preparation. Solid organ recovery began at 13.5 h, during midfacial osteotomies, and concluded immediately after facial explantation. Facial thoracic and abdominal teams worked concurrently. Estimated blood loss was 1300 mL, requiring five units of pRBC and two units FFP. Urine output, MAP, pH and PaO2 remained normal. All organs had good postoperative function. We propose an algorithm that allows "face first, concurrent completion" recovery of a complex facial VCA by planning multiple pathways to expedient recovery of vital organs in the event of clinical instability. Beginning the recipient operation earlier may reduce waiting time due to extensive recipient scarring causing difficult dissection.

Stem cell expansion during carcinogenesis in stem cell-depleted conditional telomeric repeat factor 2 null mutant mice.

To examine the role of telomeric repeat-binding factor 2 (TRF2) in epithelial tumorigenesis, we characterized conditional loss of TRF2 expression in the basal layer of mouse epidermis. These mice exhibit some characteristics of dyskeratosis congenita, a human stem cell depletion syndrome caused by telomere dysfunction. The epidermis in conditional TRF2 null mice exhibited DNA damage response and apoptosis, which correlated with stem cell depletion. The stem cell population in conditional TRF2 null epidermis exhibited shorter telomeres than those in control mice. Squamous cell carcinomas induced in conditional TRF2 null mice developed with increased latency and slower growth due to reduced numbers of proliferating cells as the result of increased apoptosis. TRF2 null epidermal stem cells were found in both primary and metastatic tumors. Despite the low-grade phenotype of the conditional TRF2 null primary tumors, the number of metastatic lesions was similar to control cancers. Basal cells from TRF2 null tumors demonstrated extreme telomere shortening and dramatically increased numbers of telomeric signals by fluorescence in situ hybridization due to increased genomic instability and aneuploidy in these cancers. DNA damage response signals were detected at telomeres in TRF2 null tumor cells from these mice. The increased genomic instability in these tumors correlated with eightfold expansion of the transformed stem cell population compared with that in control cancers. We concluded that genomic instability resulting from loss of TRF2 expression provides biological advantages to the cancer stem cell population.

The transactivation function of the Pea3 subfamily Ets transcription factors is regulated by sumoylation.

Pea3, an Ets transcriptional factor, comprises multiple regulatory domains that affect its DNA binding and transcriptional activation. The aim of this work is to uncover the mechanism of action of negative regulatory regions flanking the transactivation domain. Mutagenesis of amino acid residues in the C-terminal negative regulatory region for transactivation revealed critical residues, including a lysine residue, K96, required for its function. Corresponding mutations in the closely related Pea3 subfamily members, Erm and Er81, also dramatically increased the transactivation capacity of their activation domains. Interestingly, all three proteins are sumoylated at this conserved lysine residue. Pea3 contains four other lysines, K222, K256, K318, and K437, embedded in a perfect SUMO consensus motif. The contribution of these lysine residues to the regulation of Pea3 activity and their sumoylation pattern was explored using a GAL4-PEA3 chimera devoid of the ETS DNA-binding domain and by analyzing the native protein. All four candidate SUMO sites included in the GAL4-PEA3 chimera were modified by sumoylation, and their simultaneous mutation dramatically increased the transactivation potential of Pea3. Similar analysis of full-length Pea3 confirmed K96, K222, and K256 as major SUMO modification sites. Collectively, these observations suggest that the activity of Pea3 and its paralogs, Erm and Er81, is negatively regulated by sumoylation.

The constitutive activation of the CEF-4/9E3 chemokine gene depends on C/EBPbeta in v-src transformed chicken embryo fibroblasts.

The CEF-4/9E3 chemokine gene is expressed constitutively in chicken embryo fibroblasts (CEF) transformed by the Rous sarcoma virus (RSV). This aberrant induction is controlled at the transcriptional and post-transcriptional levels. Transcriptional activation depends on multiple elements of the CEF-4 promoter composing a Src-responsive-Unit or SRU. The SRU includes a TPA responsive element, a PRDII/kappaB domain and a CAAT box. In this report, we identify C/EBPbeta as a component of the trans-acting factor interacting with the CAAT box of the CEF-4 promoter. In addition, we show that C/EBPbeta binds to a second element located in proximity of the TRE. A mutation of this distal CAAT box impaired the activation of the CEF-4 promoter by pp60(v-src) indicating that this element is also part of the SRU. Using the RCASBP retroviral vector, we expressed a dominant negative mutant of C/EBPbeta (designated Delta184-C/EBPbeta) in RSV-transformed CEF. Delta184-C/EBPbeta decreased the accumulation of the CEF-4 mRNA and activation of the CEF-4 promoter by pp60(v-src). The induction of the Cox-2 gene (CEF-147) was also reduced by Delta184-C/EBPbeta. The effect of the dominant negative mutant was observed within 1 h of the activation of a thermolabile pp60(v-src) suggesting that C/EBPbeta is an early target of v-src transformation. The dominant negative mutant did not inhibit the transformation of CEF by RSV and in fact accentuated the transformed cell phenotype. Therefore, the activation of C/EBPbeta is important for the expression of v-src regulated genes but is not required for the in vitro transformation of CEF by pp60(v-src).

The PEA3 Ets transcription factor comprises multiple domains that regulate transactivation and DNA binding.

PEA3, a member of the Ets family of transcription factors, is a nuclear phosphoprotein capable of activating transcription. Mouse PEA3 comprises 480 amino acids and bears an approximately 85-amino acid ETS domain near its carboxyl terminus. Whereas analyses of bacterially expressed PEA3 revealed that the ETS domain is required for sequence-specific DNA binding, little is known of the functional domains in the protein required for its activity in mammalian cells. To this end, we defined the location of the PEA3 functional domains in COS cells. PEA3 bears a strong activation domain near its amino terminus, which is flanked by two regions that independently negatively regulate its activity. PEA3 expressed in COS cells was incapable of binding to DNA in vitro. However, DNA binding activity could be unmasked by incubation with a PEA3-specific antibody. Analyses of the DNA binding activity of PEA3 deletion mutants revealed that two regions flanking the ETS domain independently inhibited DNA binding; deletion of both regions was required to detect DNA binding in the absence of a PEA3-specific antibody. Under these conditions, the ETS domain was sufficient for sequence-specific DNA binding. These findings suggest that the activity of PEA3 is exquisitely controlled at multiple functional levels.

Cloning and molecular analysis of promoter-like sequences isolated from the chromosomal DNA of Lactobacillus acidophilus ATCC 4356.

Promoter-like sequences from the chromosomal DNA of thermophilic strain Lactobacillus acidophilus ATCC 4356 were cloned. Analysis of the three DNA fragments showing promoter activity, designated P3, P6, and P15, were performed in Lactobacillus reuteri, Lactococcus lactis, and E. coli. The reporter cat-86 gene was expressed in all three bacterial species under control of the fragments P3 and P6. Fragment P15 showed promoter activity only in Lactobacillus reuteri and E. coli but not in Lactococcus lactis. The three host-specific transcriptional start points (TSPs) were used when transcription of the cat-86 gene was controlled by fragment P3 in Lactobacillus reuteri, E. coli, and Lactococcus lactis. Similarly, fragment P15 initiated transcription of the cat-86 gene at two distinctive sites in Lactobacillus reuteri and E. coli. Only within fragment P6, a common TSP was used in Lactobacillus reuteri and E. coli, but different from that used in Lactococcus lactis. Each TSP was preceded by the putative -35 and -10 hexamers. Computer analysis of the fragment P3 sequence revealed the existence of divergent promoter-like sequence (P3rev) located on the complementary DNA strand. Fragments P6 and P15 were also functional in Lactobacillus acidophilus ATCC 4356 from which chromosomal DNA they were originally cloned.

Multiple signaling pathways control the activation of the CEF-4/9E3 cytokine gene by pp60v-src.

The CEF-4/9E3 cytokine gene is expressed aberrantly in chicken embryo fibroblasts (CEF) transformed by the Rous sarcoma virus. The expression of CEF-4 is dependent on both transcriptional and post-transcriptional mechanisms of regulation. The characterization of the promoter region indicated that three distinct regulatory elements corresponding to an AP-1 binding site (or TRE), a PRDII/kappaB domain, and a CAAT box are involved in the activation by pp60(v-)src. In this report we investigate the signaling pathways controlling the expression of the TRE and PRDII domain. The expression of a dominant negative mutant of p21(ras) reduced the activity of both elements. In contrast a similar mutant of c-Raf-1 affected modestly the activation dependent on the TRE but not PRDII. The stress-activated protein kinase (SAPK)/Jun N-terminal kinase (JNK) pathway was important for the activity of PRDII and the TRE but was not markedly stimulated by pp60(v-)src. The addition of calphostin C and the inhibition of protein kinase C (PKC) diminished the accumulation of the CEF-4 mRNA and reduced the activity of a TRE-controlled promoter. Likewise, the depletion of PKC by chronic treatment with phorbol esters inhibited the activation of the TRE. Rous sarcoma virus-transformed CEF treated with calphostin C were also flatter, did not display a high degree of criss-crossing, and appeared morphologically normal. Hence PKC was important for the activation of AP-1 and the morphological transformation of CEF. The constitutive expression of CEF-4 was correlated with transformation only when dependent on the TRE. This was not true for PRDII, which was the only element required for the constitutive activation to the CEF-4 promoter in nontransformed cells treated chronically with phorbol esters.

Cloning of promoter-like sequences from Lactobacillus paracasei subsp. paracasei CG11 and their expression in Escherichia coli, Lactococcus lactis, and Lactobacillus reuteri.

Fragments of chromosomal DNA from Lactobacillus paracasei subsp. paracasei CG11 (formerly Lactobacillus casei CG11) capable of functioning as promoters were isolated using the broad host range, promoter-probe vector pGKV210. Five such fragments designated P61, P79, P80, P116, and P144 were completely sequenced and analyzed. Fragment P61 had the highest transcriptional efficiency in Escherichia coli and Lactobacillus reuteri whereas P80 was the most active in Lactococcus lactis. In general, the orders of the transcriptional strengths were almost identical in E. coli and Lactobacillus reuteri but different from that in Lactococcus lactis. Mapping of the 5' end of cat mRNA showed that different regions of fragments P79 and P144 were used as promoters in Lactococcus lactis than in E. coli and Lactobacillus reuteri. Analysis of these DNA sequences revealed that the putative -35 and -10 hexanucleotides resembled those of E. coli, Bacillus subtilis, and lactococci. The spacing between these two hexanucleotides and between the putative -10 hexanucleotide and the transcriptional start point (A residues predominated) ranged from 17 to 18 base pairs and from 5 to 7 base pairs, respectively. Each of the cloned Lactobacillus paracasei CG11 promoter-like fragments contained an AT-rich sequence upstream of the putative -35 region (from 60 to 73%).

Mutational analysis of cat-86 gene expression controlled by lactococcal promoters in Lactococcus lactis subsp. lactis and Escherichia coli.

Promoters were cloned from the chromosomal DNA of Lactococcus lactis subsp. lactis NP4510 by using promoter-probe vector pGKV210. N-Methyl-N'-nitro-N-nitrosoguanidine-induced mutagenesis of L. lactis-(pBV413), with low-level expression of the cat-86 gene, resulted in enhanced expression. Subcloning and sequencing of the mutated plasmid designated pBV415 revealed that the mutation is located within the PstI-HindIII fragment containing the coding sequence of the cat-86 gene (the 10th CTG codon was replaced by a TTG; both code for leucine). A set of otherwise identical plasmids with four combinations of CTG and TTG codons at the 10th and 46th positions in the cat-86 gene were constructed by site-directed mutagenesis. These plasmids containing cat-86 derivatives displayed a significant variation in cat expression in L. lactis and E. coli. The data suggest that cat expression is dependent on the secondary structure of the cat mRNA. New cat-86 derivatives described here can be used in lactococci, in which they provide additional flexibility for promoter cloning.

Improved vector for promoter screening in lactococci.

Fragments of Lactococcus lactis subsp. lactis NP45 chromosomal DNA provided promoter activity in Escherichia coli when cloned into the promoter probe vector pGKV210. Only 13% of these recombinant plasmids promoted detectable cat-86 activity when transferred to L. lactis, i.e., expressed chloramphenicol resistance. In these promoter-containing versions of pGKV210, the cat-86 gene specifies chloramphenicol-inducible chloramphenicol acetyltransferase expression. This could be a limiting factor for cloning of promoters with lower activity in L. lactis. Therefore, we have constructed a new promoter probe vector, pBV5030, with the mutated version of the cat-86 gene, which is constitutively expressed when transcriptionally activated by the insertion of a promoter. We found that in L. lactis IL1403 the constitutively expressed cat-86 gene (on a pBV5030 derivative) has four times higher activity than the inducible version of the same gene (on a pGKV210 derivative) when both have the same promoter inserted upstream of the cat-86 gene. These results suggest that plasmid pBV5030 could be a more efficient vector for the cloning of promoters from lactococci.