Artificial intelligence-guided, single-lead EKG may be a game-changer for symptom-to-balloon time reduction in ST-elevated myocardial infarction

Background

Over decades, efforts to shave off life-saving minutes from ST-Elevated Myocardial Infarction (STEMI) care centred on reducing door-to-needle and door-to-balloon times. We firmly believe that symptom-to-balloon time should prove a better focus to this end. Challenges come with this goal as it heavily relies on a patient's perception and initiative to seek care, which we deem intelligent and wearable Artificial Intelligence (AI)-driven Single Lead EKG technologies as an attractive solution in modern-day cardiology.

Purpose

To provide an accurate, accessible, and cost-effective AI-driven Single Lead STEMI detection algorithm that can be embedded into wearable devices and employed in a self-administered fashion.

Methods

Database: EKG records from Mexico, Colombia, Argentina, and Brazil from April 2014 to December 2019. Dataset: A total of 11,567 12-lead EKG records of 10[s] length with a sampling frequency of 500 Hz, including the following balanced classes: angiographically confirmed and unconfirmed STEMI, branch blocks, non-specific ST-T abnormalities, normal and abnormal (200+ CPT codes, excluding those mentioned above). Cardiologists manually checked the label of each record to ensure precision. Pre-processing: We discard the first and last 250 samples as they may contain a standardisation pulse. The study applied a digital low pass filter of order 5 with a frequency cut-off of 35 Hz. The mean was subtracted from each Lead. Classification: The determined classes were “STEMI” (Including STEMI in different locations of the myocardium – anterior, inferior, and lateral); and “Not-STEMI” (Combination of randomly sample, branch blocks, non-specific ST-T changes, and abnormal records – 25% of each). Training and Testing: A 1-D Convolutional Neural Network was trained and tested with a dataset proportion of 90/10, respectively. A different model was trained and tested for each Lead, using the central 4,500 samples of the records. The last dense layer outputs a probability for each report of being STEMI or Not-STEMI. Lead V2 showed the best overall results. The model was further tested through the same methodology using the best Lead with a subset of the previous data, excluding the unconfirmed STEMI EKG records (Total 7,230 12-lead EKG records for Confirmed Only STEMI dataset). Performance metrics were reported for each experiment and compared.

Results

Combined STEMI data: Accuracy: 91.2%; Sensitivity: 89.6%; Specificity: 92.9%. Confirmed STEMI Only dataset: Accuracy: 92.4%; Sensitivity: 93.4%; Specificity: 91.4% (Figure 1).

Conclusion

By assiduously improving the quality of the model's input, we continue to assess our algorithm's performance and reliability for future clinical validation as a potential remote monitoring and early STEMI detection device.

Funding Acknowledgement

Type of funding sources: None.

Pterocarpus marsupium extract extends replicative lifespan in budding yeast

As the molecular mechanisms of biological aging become better understood, there is growing interest in identifying interventions that target those mechanisms to promote extended health and longevity. The budding yeast Saccharomyces cerevisiae has served as a premier model organism for identifying genetic and molecular factors that modulate cellular aging and is a powerful system in which to evaluate candidate longevity interventions. Here we screened a collection of natural products and natural product mixtures for effects on the growth rate, mTOR-mediated growth inhibition, and replicative lifespan. No mTOR inhibitory activity was detected, but several of the treatments affected growth rate and lifespan. The strongest lifespan shortening effects were observed for green tea extract and berberine. The most robust lifespan extension was detected from an extract of Pterocarpus marsupium and another mixture containing Pterocarpus marsupium extract. These findings illustrate the utility of the yeast system for longevity intervention discovery and identify Pterocarpus marsupium extract as a potentially fruitful longevity intervention for testing in higher eukaryotes.

Superoxide-mediated oxidative stress accelerates skeletal muscle atrophy by synchronous activation of proteolytic systems

The maintenance of skeletal muscle mass depends on the overall balance between the rates of protein synthesis and degradation. Thus, age-related muscle atrophy and function, commonly known as sarcopenia, may result from decreased protein synthesis, increased proteolysis, or simultaneous changes in both processes governed by complex multifactorial mechanisms. Growing evidence implicates oxidative stress and reactive oxygen species (ROS) as an essential regulator of proteolysis. Our previous studies have shown that genetic deletion of CuZn superoxide dismutase (CuZnSOD, Sod1) in mice leads to elevated oxidative stress, muscle atrophy and weakness, and an acceleration in age-related phenotypes associated with sarcopenia. The goal of this study is to determine whether oxidative stress directly influences the acceleration of proteolysis in skeletal muscle of Sod1-/- mice as a function of age. Compared to control, Sod1-/- muscle showed a significant elevation in protein carbonyls and 3-nitrotyrosine levels, suggesting high oxidative and nitrosative protein modifications were present. In addition, age-dependent muscle atrophy in Sod1-/- muscle was accompanied by an upregulation of the cysteine proteases, calpain, and caspase-3, which are known to play a key role in the initial breakdown of sarcomeres during atrophic conditions. Furthermore, an increase in oxidative stress-induced muscle atrophy was also strongly coupled with simultaneous activation of two major proteolytic systems, the ubiquitin-proteasome and lysosomal autophagy pathways. Collectively, our data suggest that chronic oxidative stress in Sod1-/- mice accelerates age-dependent muscle atrophy by enhancing coordinated activation of the proteolytic systems, thereby resulting in overall protein degradation.

THE IMPORTANCE OF HSP-25 IN CAENORHABDITIS ELEGANS LONGEVITY

Karl A. Rodriguez’s laboratory at the University of Texas Health Science Center, San Antonio, Texas, is interested in the role of small heat shock proteins in the proteostasis network and aging using the model organism, Caenorhabditis elegans. Molecular chaperones facilitate protein folding and improve the degradation activity of the proteasome and autolysosome hence decreasing disease-associated aggregates. Previous work in rodents have shown an increase in expression levels of the small heat shock protein 25 (HSP-25) correlates with maximum lifespan potential. To further explore the role of HSP-25 in C. elegans, two HSP-25 knock-out strains were exposed to a one-hour heat stress, heat shock, and two non-heat stress conditions.

INCREASE IN HSP25 EXTENDS LIFESPAN AND IMPROVES RESPONSE TO TAU TOXICITY THROUGH A CELL, NON-AUTONOMOUS MECHANISM

The accrual of aggregation-prone cytotoxic proteins underlies neural pathologies seen in aging, Alzheimer’s disease and other dementias. Recent evidence indicates that heat shock protein 25kDa (HSP25) interacts with tau. To demonstrate a causal role for HSP25 in these pathologies, we overexpressed HSP25 protein in worms. This manipulation led to an increase in life span. Moreover, the longevity-effect was associated with increased expression of genes downstream of the SKN-1/Nrf2 stress-response transcription factor. HSP25 over-expression also reduces aggregate pathology and extends lifespan in a C. elegans neuronal-specific, aggregate-prone tau model . We propose that over-expression of HSP25 could provide protection from protein aggregation induced neurodegeneration. However, it is not yet clear whether this HSP25 effect could be efficaciously provided exogenously by other cell types. Thus, we will test whether increased peripheral HSP25 will reduce protein aggregation and stimulate a global Skn-1 stress-response pathway, reduce toxicity in neurons, and improve health outcomes.

INCREASED HSP25 DRIVES THE TRANSITION FROM PROTEASOME TO AUTOPHAGY-MEDIATED DEGRADATION UNDER PROTEOTOXIC STRESS

Accumulation of protein aggregates are a common pathology in many neurodegenerative disorders. This accumulation may be due to a function decline in the protein homeostasis network known to occur during the aging process. Small heat shock proteins are a class of molecular chaperones that assist in protein folding and ameliorates the degradation activity of the proteasome and autolysosome thereby decreasing disease-associated aggregates. Prior work in rodents and C. elegans has shown expression levels of the small heat shock protein 25 (HSP25) correlates with maximum lifespan potential. Increased levels of HSP25 extends lifespan in a transgenic C. elegans model. This lifespan extension is dependent on skn-1 with evidence suggesting an enrichment in several skn-1-related pathways, such as lysosomal genes. Concomitantly, proteasome activity declines while autolysosome activity increases. This observation might suggest a switch from proteasome degradation to autophagy as the main driver of protein degradation in C. elegans in this transgenic model. To investigate if a reduction of proteasome function and elevated lysosomal gene activation during aging and under proteotoxic stress are modulated by HSP25 we have crossed our HSP25-transgenic worm with an aggregating and non-aggregating tau worm model. This work will elucidate a possible mechanism that explains the change in the protein degradation response pathways potentially modulated by HSP25 during increased protein misfolding.

THE ENDOPLASMIC RETICULUM PROTEIN QUALITY CONTROL ADAPTATION IN A LONG-LIVED C. ELEGANS PROTEASOMAL MUTANT

Protein degradation mechanisms are integral to protein homeostasis. Their reduced efficiency during aging leads to accumulation of misfolded and aggregated proteins which potentiate proteotoxic disorders. Paradoxically, our lab reported that the Caenorhabditis elegans rpn-10(ok1865) proteasome mutant possesses enhanced proteostasis and extended lifespan. RPN-10/PSMD4 is a ubiquitin receptor of the 26S proteasome that targets polyubiquitinated substrates to its catalytic core for degradation. Proteasome dysfunction of the rpn-10 mutant is characterized by reduced, not inhibited, ubiquitin fusion degradation. We ascertained that upregulated autophagy and SKN-1/Nrf-mediated responses partially contribute to the robust rpn-10 mutant phenotype. Further investigation of its underlying mechanism revealed that several ERQC genes are transcriptionally upregulated in the rpn-10 mutant. Thus, we hypothesized that the rpn-10 mutant exhibits improved ER proteostasis which mediates its elevated cellular stress resistance. Accordingly, the rpn-10 mutant shows increased ER stress resistance and altered ER homeostasis. Complementarily, attenuated expression of the aggregation-prone α-1 antitrypsin (ATZ) reporter proves that ER proteostasis is ameliorated in the rpn-10 mutant. Via a genetic screen for suppressors of decreased ATZ aggregation in the rpn-10 mutant, we identified novel player H04D03.3, which is a homolog of the proteasome adaptor ECM29. This suggests that assembly of the rpn-10 mutant proteasome itself critically regulates its ER proteostasis. Moreover, we observed that cytosolic proteostasis and longevity depend on ER master chaperone hsp-3/-4(BiP) and ER ATPase cdc-48.2(p97/VCP), further highlighting ERQC significance in the rpn-10 mutant. Altogether, it appears that mild proteasomal dysfunction induces ERQC adaptation that underlies proteostasis and longevity benefits of the rpn-10 mutant.

Oxidative damage to myelin proteins accompanies peripheral nerve motor dysfunction in aging C57BL/6 male mice

Aging is associated with a decline in peripheral nerve function of both motor and sensory nerves. The decline in function of peripheral sensorimotor nerves with aging has been linked to sarcopenia, the age-related decline in muscle mass and function that significantly compromises the quality of life in older humans. In this study, we report a significant increase in oxidized fatty acids and insoluble protein carbonyls in sciatic nerves of aged C57BL/6 male mice (28-30mo) that exhibit a profound decline in motor nerve function and degenerative changes in both axon and myelin structure, compared to young mice (6-8mo). Our data further suggests that this age-related loss of function of peripheral motor nerves is likely precipitated by changes in mechanisms that protect and/or repair oxidative damage. We predict that interventions that target these mechanisms may protect against age-related decline in peripheral sensorimotor nerve function and likely improve the debilitating outcome of sarcopenia in older humans.

Age-related changes in the proteostasis network in the brain of the naked mole-rat: Implications promoting healthy longevity

The naked mole-rat (NMR) is the longest-lived rodent and possesses several exceptional traits: marked cancer resistance, negligible senescence, prolonged genomic integrity, pronounced proteostasis, and a sustained health span. The underlying molecular mechanisms that contribute to these extraordinary attributes are currently under investigation to gain insights that may conceivably promote and extend human health span and lifespan. The ubiquitin-proteasome and autophagy-lysosomal systems play a vital role in eliminating cellular detritus to maintain proteostasis and have been previously shown to be more robust in NMRs when compared with shorter-lived rodents. Using a 2-D PAGE proteomics approach, differential expression and phosphorylation levels of proteins involved in proteostasis networks were evaluated in the brains of NMRs in an age-dependent manner. We identified 9 proteins with significantly altered levels and/or phosphorylation states that have key roles involved in proteostasis networks. To further investigate the possible role that autophagy may play in maintaining cellular proteostasis, we examined aspects of the PI3K/Akt/mammalian target of rapamycin (mTOR) axis as well as levels of Beclin-1, LC3-I, and LC3-II in the brain of the NMR as a function of age. Together, these results show that NMRs maintain high levels of autophagy throughout the majority of their lifespan and may contribute to the extraordinary health span of these rodents. The potential of augmenting human health span via activating the proteostasis network will require further studies.

Epidermal growth factor receptor exon 20 insertions in advanced lung adenocarcinomas: Clinical outcomes and response to erlotinib

BACKGROUND

Epidermal growth factor receptor (EGFR) exon 20 insertions (exon20ins) represent approximately 10% of EGFR-mutant lung adenocarcinomas, and are associated with resistance to EGFR tyrosine kinase inhibitors (TKIs). Clinical outcomes in comparison with patients with sensitizing EGFR mutations are not well established.

METHODS

Patients with stage IV lung adenocarcinomas with EGFR exon20ins were identified through routine molecular testing. Clinicopathologic data were collected. Overall survival (OS) was measured from the diagnosis of stage IV disease, and in patients treated with EGFR TKIs, the time to progression (TTP) on erlotinib was measured.

RESULTS

One thousand eight hundred and eighty-two patients with stage IV lung adenocarcinomas were identified: 46 patients had EGFR exon20ins (2%), and 258 patients had an EGFR exon 19 deletion (exon19del)/L858R point mutation (14%). Among 11 patients with lung adenocarcinomas with EGFR exon20ins who received erlotinib, 3 patients (27%) had a partial response (FQEA, 1; ASV, 1; and unknown variant, 1). TTP for patients with EGFR exon20ins and patients with EGFR exon19del/L858R on erlotinib were 3 and 12 months, respectively (P < .01). Responses to chemotherapy were similar for patients with lung adenocarcinomas with EGFR exon20ins and patients with lung adenocarcinomas with EGFR exon19del/L858R. Median OS from the diagnosis of stage IV disease for patients with EGFR exon20ins and patients with EGFR exon19del/L858R was 26 months (95% confidence interval, 19 months-not reached n = 46) and 31 months (95% confidence interval, 28-33 months; n = 258), respectively (P = .53).

CONCLUSIONS

The majority of patients with advanced lung adenocarcinomas harboring EGFR exon20ins do not respond to EGFR TKI therapy. Standard chemotherapy should be used as first-line therapy. These patients have an OS similar to that of patients with sensitizing EGFR mutations. Individuals with certain variants such as FQEA and ASV may respond to erlotinib.

Metabolic clues to salubrious longevity in the brain of the longest-lived rodent: the naked mole-rat

Naked mole-rats (NMRs) are the oldest-living rodent species. Living underground in a thermally stable ecological niche, NMRs have evolved certain exceptional traits, resulting in sustained health spans, negligible cognitive decline, and a pronounced resistance to age-related disease. Uncovering insights into mechanisms underlying these extraordinary traits involved in successful aging may conceivably provide crucial clues to extend the human life span and health span. One of the most fundamental processes inside the cell is the production of ATP, which is an essential fuel in driving all other energy-requiring cellular activities. Not surprisingly, a prominent hallmark in age-related diseases, such as neurodegeneration and cancer, is the impairment and dysregulation of metabolic pathways. Using a two-dimensional polyacrylamide gel electrophoresis proteomics approach, alterations in expression and phosphorylation levels of metabolic proteins in the brains of NMRs, aged 2-24 years, were evaluated in an age-dependent manner. We identified 13 proteins with altered levels and/or phosphorylation states that play key roles in various metabolic pathways including glycolysis, β-oxidation, the malate-aspartate shuttle, the Tricarboxylic Acid Cycle (TCA) cycle, the electron transport chain, NADPH production, as well as the production of glutamate. New insights into potential pathways involved in metabolic aspects of successful aging have been obtained by the identification of key proteins through which the NMR brain responds and adapts to the aging process and how the NMR brain adapted to resist age-related degeneration. This study examines the changes in the proteome and phosphoproteome in the brain of the naked mole-rat aged 2-24 years. We identified 13 proteins (labeled in red) with altered expression and/or phosphorylation levels that are conceivably associated with sustained metabolic functions in the oldest NMRs that may promote a sustained health span and life span.

Improving preclinic preparation for patients with chronic conditions in quito, ecuador: a randomized controlled trial

Objectives. As in many settings, patients in community health centers in Ecuador do not complete previsit forms or receive assistance to identify questions and concerns they would like to address in brief clinic visits with physicians. We examined the comparative effectiveness of providing (1) a previsit form to complete; (2) a previsit form along with assistance in completing the form; and (3) usual care. Methods. Parallel, three-arm randomized controlled trial in two health centers serving indigent to low-income communities in Quito, Ecuador, among 199 adult patients who took medications for at least one chronic condition. Outcome measures were self-reported satisfaction with the visit, confidence in asking questions, and extent to which patients' objectives were met. Results. Patients who received assistance in completing a previsit form were more than twice as likely as participants in usual care to report achieving everything they wanted during their visit (AOR 2.2, P = 0.039). There were no differences in any outcomes between the groups who received the previsit form with no assistance and usual care. Conclusions. For high-quality patient-centered primary care, it is important to develop and test innovative and scalable interventions for patients and physicians to make the best use of limited clinic time.

Factor VIIa-antithrombin complexes in patients with non-neoplastic portal vein thrombosis with and without cirrhosis

INTRODUCTION

Portal vein thrombosis (PVT) is caused by local and systemic prothrombotic risk factors. In this case-control study, we evaluated the use of the Factor VIIa-antithrombin complex (FVIIa-AT) complex assay as a hypercoagulability marker in patients with PVT.

METHODS

Two different groups of cases were considered: (i) n = 12 noncirrhotic PVT patients, (ii) n = 33 cirrhotic patients with PVT. Controls were sex and age-matched healthy volunteers and cirrhotic subjects without PVT, respectively.

RESULTS

Levels of the FVIIa-AT complex were significantly higher in noncirrhotic PVT subjects (132 ± 32 pM) than in healthy volunteers (108 ± 18 pM, P = 0.04). No significant difference in FVIIa-AT complexes was seen between cirrhotic patients with (64 ± 20 pM) or without (61 ± 24 pM) PVT. A linear correlation was seen between FVIIa-AT and FVIIa in noncirrhotic PVT subjects. In cirrhotic patients, FVIIa-AT complexes depended on both FVIIa and AT.

CONCLUSION

These results confirm the utility of the FVIIa-AT assay in identifying the hypercoagulable state of noncirrhotic patients because of a previous thrombotic event.

Risk factors for portal venous thrombosis after splenectomy in patients with cirrhosis and portal hypertension (Br J Surg 2010; 97: 910-916)

Background

Portal venous thrombosis (PVT) is a potentially fatal complication following splenectomy. Its mechanisms and risk factors are poorly understood, especially in patients with cirrhosis and portal hypertension. This study investigated risk factors for PVT following splenectomy in such patients.

Methods

All consecutive patients with cirrhosis who underwent splenectomy in Kyushu University Hospital between 1998 and 2004 were included in this retrospective study. They were divided into two groups based on the presence or absence of postoperative PVT. Preoperative and operative factors were compared, and the relationships between formation of PVT and its independent variables were analysed. In some cases, portal venous flow was measured before and after splenectomy using duplex Doppler ultrasonography.

Results

PVT developed after surgery in 17 (24 per cent) of 70 patients studied. Multivariable analysis showed that increased splenic vein diameter and low white cell count were significant independent risk factors for PVT. Portal venous flow after splenectomy was greatly reduced in the PVT group, but not in patients without PVT.

Conclusion

Large splenic vein diameter and low white cell count are independent risk factors for PVT after splenectomy in patients with cirrhosis and portal hypertension.

Molecular mechanisms of proteasome plasticity in aging

The ubiquitin-proteasome pathway plays a crucial role in regulation of intracellular protein turnover. Proteasome, the central protease of the pathway, encompasses multi-subunit assemblies sharing a common catalytic core supplemented by regulatory modules and localizing to different subcellular compartments. To better comprehend age-related functions of the proteasome we surveyed content, composition and catalytic properties of the enzyme in cytosolic, microsomal and nuclear fractions obtained from mouse livers subjected to organismal aging. We found that during aging subunit composition and subcellular distribution of proteasomes changed without substantial alterations in the total level of core complexes. We observed that the general decline in proteasomes functions was limited to nuclear and cytosolic compartments. Surprisingly, the observed changes in activity and specificity were linked to the amount of the activator module and distinct composition of the catalytic subunits. In contrast, activity, specificity and composition of the microsomal-associated proteasomes remained mostly unaffected by aging; however their relative contribution to the total activity was substantially elevated. Unexpectedly, the nuclear proteasomes were affected most profoundly by aging possibly triggering significant changes in cellular signaling and transcription. Collectively, the data indicate an age-related refocusing of proteasome from the compartment-specific functions towards general protein maintenance.

The suprachiasmatic nucleus participates in food entrainment: a lesion study

Daily feeding schedules entrain temporal patterns of behavior, metabolism, neuronal activity and clock gene expression in several brain areas and periphery while the suprachiasmatic nucleus (SCN), the biological clock, remains coupled to the light/dark cycle. Because bilateral lesions of the SCN do not abolish food entrained behavioral and hormonal rhythms it is suggested that food entrained and light entrained systems are independent of each other. Special circumstances indicate a possible interaction between the light and the food entrained systems and indicate modulation of SCN activity by restricted feeding. This study explores the influence of the SCN on food entrained rhythms. Food entrained temporal profiles of behavior, core temperature, corticosterone and glucose, as well as Fos and PER1 immunoreactivity in the hypothalamus and corticolimbic structures were explored in rats bearing bilateral SCN lesions (SCNX). In SCNX rats food anticipatory activity and the food entrained temperature and corticosterone increase were expressed with earlier onset and higher values than in intact controls. Glucose levels were lower in SCNX rats in all time points and SCNX rats anticipation to a meal induced higher c-Fos positive neurons in the hypothalamus, while a decreased c-Fos response was observed in corticolimbic structures. SCNX rats also exhibited an upregulation of the PER1 peak in hypothalamic structures, especially in the dorsomedial hypothalamic nucleus (DMH), while in some limbic structures PER1 rhythmicity was dampened. The present results indicate that the SCN participates actively during food entrainment modulating the response of hypothalamic and corticolimbic structures, resulting in an increased anticipatory response.

Highbrow proteasome in high-throughput technology

Proteasome is a major protease of the ubiquitin-proteasome pathway involved in the regulation of practically all intracellular biochemical processes. The enzyme core is created by a heteromultimer of complex architecture built with multiple subunits arranged into a tube-like structure. The multiple active sites of diverse peptidase specificity are hidden inside the tube. Access to the interior is guarded by a gate formed by the N-termini of specialized subunits and by the attachment of additional multisubunit protein complexes controlling the enzymatic capabilities of the core. Proteasome, due to its Byzantine molecular architecture and equally sophisticated enzymatic mechanism, is by itself a fascinating biophysical object. Recently, the position of the protease advanced from an academically remarkable protein processor to a providential anticancer drug target and futuristic nanomachine. Proteomics studies actively shape our current understanding of the protease and direct the future applications of the proteasome in medicine.

Surface activity in vitro: role of surfactant proteins

Pattle, who provided some of the initial direct evidence for the presence of pulmonary surfactant in the lung, was also the first to show surfactant was susceptible to proteases such as trypsin. Pattle concluded surfactant was a lipoprotein. Our group has investigated the roles of the surfactant proteins (SP-) SP-A, SP-B, and SP-C using a captive bubble tensiometer. These studies show that SP-C>SP-B>SP-A in enhancing surfactant lipid adsorption (film formation) to the equilibrium surface tension of approximately 22-25 mN/m from the 70 mN/m of saline at 37 degrees C. In addition to enhancing adsorption, surfactant proteins can stabilize surfactant films so that lateral compression induced through surface area reduction results in the lowering of surface tension (gamma) from approximately 25 mN/m (equilibrium) to values near 0 mN/m. These low tensions, which are required to stabilize alveoli during expiration, are thought to arise through exclusion of fluid phospholipids from the surface monolayer, resulting in an enrichment in the gel phase component dipalmitoylphosphatidylcholine (DPPC). The results are consistent with DPPC enrichment occurring through two mechanisms, selective DPPC adsorption and preferential squeeze-out of fluid components such as unsaturated phosphatidylcholine (PC) and phosphatidylglycerol (PG) from the monolayer. Evidence for selective DPPC adsorption arises from experiments showing that the surface area reductions required to achieve gamma near 0 mN/m with DPPC/PG samples containing SP-B or SP-A plus SP-B films were less than those predicted for a pure squeeze-out mechanism. Surface activity improves during quasi-static or dynamic compression-expansion cycles, indicating the squeeze-out mechanism also occurs. Although SP-C was not as effective as SP-B in promoting selective DPPC adsorption, this protein is more effective in promoting the reinsertion of lipids forced out of the surface monolayer following overcompression at low gamma values. Addition of SP-A to samples containing SP-B but not SP-C limits the increase in gamma(max) during expansion. It is concluded that the surfactant apoproteins possess distinct overlapping functions. SP-B is effective in selective DPPC insertion during monolayer formation and in PG squeeze-out during monolayer compression. SP-A can promote adsorption during film formation, particularly in the presence of SP-B. SP-C appears to have a superior role to SP-B in formation of the surfactant reservoir and in reinsertion of collapse phase lipids.

Clandestine abortion in Latin America: provider perspectives

This paper presents the results of in-depth interviews with ten clandestine abortion providers in urban Latin America. Three related issues are addressed: how abortion providers come to this line of work; their major difficulties; and their sources of job satisfaction. A variety of paths bring health professionals to the practice of abortion; common elements are a sense of calling, a desire to help women, personal experience with abortion, and a commitment to political change. Providers describe difficulties that include a lack of medical support, the need for secrecy, and threats of violence, extortion, and prosecution. In spite of difficulties, all providers report a great deal of fulfillment in their work, based on their satisfaction in saving women's lives, maintaining supportive relationships with colleagues, and empowering women.

Affinity purification and partial characterization of a yeast multiprotein complex for nucleotide excision repair using histidine-tagged Rad14 protein

The nucleotide excision repair (NER) pathway of eukaryotes involves approximately 30 polypeptides. Reconstitution of this pathway with purified components is consistent with the sequential assembly of NER proteins at the DNA lesion. However, recent studies have suggested that NER proteins may be pre-assembled in a high molecular weight complex in the absence of DNA damage. To examine this model further, we have constructed a histidine-tagged version of the yeast DNA damage recognition protein Rad14. Affinity purification of this protein from yeast nuclear extracts resulted in the co-purification of Rad1, Rad7, Rad10, Rad16, Rad23, RPA, RPB1, and TFIIH proteins, whereas none of these proteins bound to the affinity resin in the absence of recombinant Rad14. Furthermore, many of the co-purifying proteins were present in approximately equimolar amounts. Co-elution of these proteins was also observed when the nuclear extract was fractionated by gel filtration, indicating that the NER proteins were associated in a complex with a molecular mass of >1000 kDa prior to affinity chromatography. The affinity purified NER complex catalyzed the incision of UV-irradiated DNA in an ATP-dependent reaction. We conclude that active high molecular weight complexes of NER proteins exist in undamaged yeast cells.

The foundations of literacy: learning the sounds of letters

Learning the sounds of letters is an important part of learning to read and spell. To explore the factors that make some letter-sound correspondences easier for children to learn than others, we first analyzed knowledge of letters' sounds (and names) by 660 children between 3 1/2 and 7 1/2 years old. A second study examined pre-schoolers' (M age 4 years, 11 months) ability to learn various sound-letter mappings. Together, the results show that an important determinant of letter-sound knowledge is whether the sound occurs in the name of the letter and, if so, whether it is at the beginning or the end. The properties of the sound itself (consonant versus vowel, sonorant versus obstruent, stop versus continuant) appear to have little or no influence on children's learning of basic letter-sound correspondences. The findings show that children use their knowledge of letters' names when learning the letters' sounds rather than memorizing letter-sound correspondences as arbitrary pairings.

Children's phonological awareness: confusions between phonemes that differ only in voicing

Given the role of phonemic awareness in learning to read and spell, it is important to examine the linguistic factors that influence children's performance on phonemic awareness tasks. We found that, contrary to some previous claims, children did not perform better with fricative consonants (e.g., /z/) than with stops (e.g., /d/) in a phoneme recognition task. However, preschoolers and kindergartners were more likely to mistakenly judge that a syllable began with a target phoneme when the initial phoneme of the syllable differed from the target only in voicing (e.g., /t/ for the target /d/) than when it differed in place of articulation (e.g., /b/-/d/) or in both place and voicing (e.g., /p/-/d/). These results shed light on the organization of children's phonological systems. They also have implications for the design and interpretation of phonemic awareness tasks.

Agreement between peripheral venous and arterial lactate levels

STUDY OBJECTIVE

To test the hypothesis that measurements of peripheral venous lactate (V-LACT) can be substituted for arterial lactate (A-LACT) in predicting arterial hyperlactacidemia.

METHODS

We conducted a prospective comparison of paired A-LACT and V-LACT measurements obtained from a convenience sample of 74 ED patients who presented to an urban, public teaching hospital, 70% of whom had abnormal A-LACT.

RESULTS

Mean A-LACT and V-LACT were 2.8 mmol/L and 3.0 mmol/L, respectively. A-LACT and V-LACT were strongly correlated (r2 = .89). Simultaneous multivariate adjustment for tourniquet time and for time elapsed between drawing of A-LACT and V-LACT had no effect on this correlation. Although the mean difference between V-LACT and A-LACT was only .22 mmol/L, the range that included 95% of the disagreement between paired measurements in individual patients was-1.3 mmol/L to 1.7 mmol/L. When A-LACT and V-LACT levels were each divided into normal and abnormal (elevated) groups, V-LACT showed 94% sensitivity (95% confidence interval [CI], 83% to 99%), 57% specificity (95% CI, 34% to 78%), a positive likelihood ratio of 2.2, and a negative likelihood ratio of .1. A-LACT values were used as the criterion standard for these calculations.

CONCLUSION

Correlation between A-LACT and V-LACT was high in this cohort of patients, but agreement is imperfect. The odds of arterial hyperlactacidemia appear to be reduced substantially by the finding of a normal V-LACT but are only marginally increased if the V-LACT is increased. Caution should be used in the routine substitution of V-LACT for A-LACT.

Identification of functional domains within the RAD1.RAD10 repair and recombination endonuclease of Saccharomyces cerevisiae

Saccharomyces cerevisiae rad1 and rad10 mutants are unable to carry out nucleotide excision repair and are also defective in a mitotic intrachromosomal recombination pathway. The products of these genes are subunits of an endonuclease which recognizes DNA duplex/single-strand junctions and specifically cleaves the 3' single-strand extension at or near the junction. It has been suggested that such junctions arise as a consequence of DNA lesion processing during nucleotide excision repair and the processing of double-strand breaks during intrachromosomal recombination. In this study we show that the RAD1 RAD10 complex also cleaves a more complex junction structure consisting of a duplex with a protruding 3' single-strand branch that resembles putative recombination intermediates in the RAD1 RAD10-mediated single-strand annealing pathway of mitotic recombination. Using monoclonal antibodies, we have identified two regions of RAD1 that are required for the cleavage of duplex/single-strand junctions. These reagents also inhibit nucleotide excision repair in vitro, confirming the essential role of the RAD1 RAD10 endonuclease in this pathway.

Efficacy of imipenem/cilastatin in endocarditis

Imipenem, a potent new beta-lactam antibiotic, which is bactericidal against most pathogenic bacteria, and cilastatin, a dehydropeptidase inhibitor combined with imipenem to prevent the metabolism of imipenem in the kidney, were evaluated in the treatment of bacterial endocarditis. Seventeen patients, including 14 who used intravenous drugs, were treated with imipenem/cilastatin in a dose of 500 mg each infused over 30 minutes every six hours. The mean duration of treatment was 29 days with a range of 21 to 56 days. Causative bacteria were Staphylococcus aureus in 10 patients, S. aureus plus group B Streptococcus in one, viridans group Streptococcus in two, Neisseria subflava, Eikenella corrodens, and group G Streptococcus in one patient, and Staphylococcus epidermidis, Hemophilus aphrophilus, and Enterobacter aerogenes in one patient each. The minimal bactericidal concentration of imipenem against 16 of 18 isolates tested was 0.04 micrograms/ml, 1 microgram/ml against H. aphrophilus, and 0.4 micrograms/ml against E. aerogenes. The site of infection was the right side of the heart in 11 patients, the left side in five, and both sides in one. The mean number of days to defervescence was 9.7. All patients were cured, and none required cardiac surgery. Adverse effects were few and interrupted treatment occurred in only one patient who had acute dyspnea during an infusion on Day 26 of therapy. Imipenem/cilastatin appears to be a relatively safe and highly effective treatment of staphylococcal endocarditis in intravenous drug users; too few patients with endocarditis caused by other bacteria were treated to allow a firm statement about efficacy in non-staphylococcal endocarditis.

Successful treatment of gram-negative bacillary meningitis with imipenem/cilastatin

A patient with meningitis caused by a strain of Actinetobacter anitratus that was resistant to all commercially available antibiotics was treated with imipenem/cilastatin administered intravenously in a dose of 1 gm of imipenem every six hours. The minimal inhibitory concentration of imipenem against the isolate was less than or equal to 0.04 micrograms/ml. The patient tolerated the drug well and was cured after 12 days of therapy.

University of Washington School of Medicine

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