Sustained activation of the mitogen-activated protein (MAP) kinase cascade may be required for differentiation of PC12 cells. Comparison of the effects of nerve growth factor and epidermal growth factor

Stimulation of PC12 cells with nerve growth factor (NGF) increased mitogen-activated protein kinase kinase (MAPKK) activity > 20-fold after 5 min to a level that was largely sustained for at least 90 min. MAPKK activity was stimulated to a similar level by epidermal growth factor (EGF), but peaked at 2 min, declining thereafter and returning to basal levels after 60-90 min. Activation of MAPKK by either growth factor occurred prior to the activation of MAP kinase, consistent with MAPKK being the physiological activator of MAP kinase. The results demonstrate that the transient activation of MAPKK by EGF and its sustained activation by NGF underlies the transient and sustained activation of MAP kinase induced by EGF and NGF respectively. NGF or EGF induced the same two forms of MAPKK that were resolved on a Mono Q column. The Peak-1 MAPKK was activated initially and partially converted into the more acidic peak-2 MAPKK after prolonged growth-factor stimulation. The Peak-2 MAPKK was 20-fold more sensitive to inactivation by the catalytic subunit of protein phosphatase 2A. Stimulation with NGF caused a striking translocation of MAP kinase from the cytosol to the nucleus after 30 min, but not nuclear translocation of MAP kinase occurred after stimulation with EGF. The results suggest that sustained activation of the MAP kinase cascade may be required for MAP kinase to enter the nucleus, where it may initiate the gene transcription events required for neuronal differentiation of PC12 cells.

MAPKAP kinase-2; a novel protein kinase activated by mitogen-activated protein kinase

A novel protein kinase, which was only active when phosphorylated by the mitogen-activated protein kinase (MAP kinase), has been purified 85,000-fold to homogeneity from rabbit skeletal muscle. This MAP kinase activated protein kinase, termed MAPKAP kinase-2, was distinguished from S6 kinase-II (MAPKAP kinase-1) by its response to inhibitors, lack of phosphorylation of S6 peptides and amino acid sequence. MAPKAP kinase-2 phosphorylated glycogen synthase at Ser7 and the equivalent serine (*) in the peptide KKPLNRTLS*VASLPGLamide whose sequence is similar to the N terminus of glycogen synthase. MAPKAP kinase-2 was resolved into two monomeric species of apparent molecular mass 60 and 53 kDa that had similar specific activities and substrate specificities. Peptide sequences of the 60 and 53 kDa species were identical, indicating that they are either closely related isoforms or derived from the same gene. MAP kinase activated the 60 and 53 kDa forms of MAPKAP kinase-2 by phosphorylating the first threonine residue in the sequence VPQTPLHTSR. Furthermore, Mono Q chromatography of extracts from rat phaeochromocytoma and skeletal muscle demonstrated that two MAP kinase isoforms (p42mapk and p44mapk) were the only enzymes in these cells that were capable of reactivating MAPKAP kinase-2. These results indicate that MAP kinase activates at least two distinct protein kinases, suggesting that it represents a point at which the growth factor-stimulated protein kinase cascade bifurcates.

Hippocampal volume and everyday memory in children of very low birth weight

Children born preterm and of very low birth weight have an increased incidence of learning difficulties, but little is known about the specific nature of their cognitive deficits and the underlying neuropathology. We hypothesized that their vulnerability to hypoxic, metabolic, and nutritional insults would lead to reduced hippocampal volumes and to deficits in memory because of the role of the hippocampus in this domain of cognition. Neuropsychological and magnetic resonance imaging methods were used to investigate this hypothesis in adolescents born preterm (< or = 30 wk gestation, n = 11) or full-term (n = 8). The preterm group had significantly smaller hippocampal volumes bilaterally, despite equivalent head size, and showed specific deficits in certain aspects of everyday memory, both on objective testing and as indicated by parental questionnaires. The preterm group also had a specific deficit in numeracy. The reduced hippocampal volumes and deficits in everyday memory have previously been unrecognized, but their prevalence in a group of neurologically normal children is striking.

Pulmonary artery NADPH-oxidase is activated in hypoxic pulmonary vasoconstriction

An NADPH-oxidase complex containing at least two protein components (gp91-phox and p22-phox) and a unique low redox potential (-245 mV) cytochrome b-245 is the source of superoxide generated for bacterial killing in neutrophils and has been suggested as the oxygen sensor in the carotid body. In pure cultures of smooth muscle cells from calf small pulmonary arteries (300 microns diameter) the presence of the 91 kD protein specific to this cytochrome was demonstrated by Western blot analysis with monoclonal antibody 48. Low-temperature-difference spectrophotometry of homogenates of these cells demonstrated the characteristic cytochrome b-245 spectrum when titrated between redox potentials of -152 and -345 mV, consistent with the low redox potential form. When these same cells were exposed to hypoxia (approximately 40 mmHg), superoxide production increased significantly from 1.4 +/- 0.2 to 73 +/- 12 nmoles.min-1 mg-1 protein. Hypoxic generation of superoxide was inhibited by the NADPH-oxidase inhibitor diphenyleneiodonium (DPI: 10 microM) but not by the mitochondrial inhibitor myxathiazole (10 microM). The hypoxic superoxide increase was significantly greater than that observed from smooth muscle cells from large pulmonary arteries or from large or small systemic arteries. Fluorescence immunocytochemistry revealed the presence of the NADPH-oxidase protein in the walls of pulmonary arteries in rat lung slices, and confocal microscopy showed the complex to be widely distributed in the vicinity of the arterial smooth muscle walls. In hypoxia or norepinephrine (NP)-induced vasoconstriction of pulmonary artery rings from cats, the sensitivity to inhibition by DPI was observed to be significantly greater for hypoxia (ED50 = 0.8 microM) than for NP-induced (ED50 = 13.4 microM) constriction. Together these observations demonstrate that the unique cytochrome b-245 containing NADPH-oxidase is present in pulmonary artery smooth muscle and that an NADPH-oxidase or NADH-oxidoreductase complex is activated to release superoxide by hypoxic conditions. It is concluded that a trans-membrane NADPH-oxidase is the most likely and that activation of this system may be involved in the initiation of hypoxic pulmonary vasoconstriction.

Cutaneous Scarring: Basic Science, Current Treatments, and Future Directions

Significance: Scarring of the skin from burns, surgery, and injury constitutes a major burden on the healthcare system. Patients affected by major scars, particularly children, suffer from long-term functional and psychological problems. Recent Advances: Scarring in humans is the end result of the wound healing process, which has evolved to rapidly repair injuries. Wound healing and scar formation are well described on the cellular and molecular levels, but truly effective molecular or cell-based antiscarring treatments still do not exist. Recent discoveries have clarified the role of skin stem cells and fibroblasts in the regeneration of injuries and formation of scar. Critical Issues: It will be important to show that new advances in the stem cell and fibroblast biology of scarring can be translated into therapies that prevent and reduce scarring in humans without major side effects. Future Directions: Novel therapies involving the use of purified human cells as well as agents that target specific cells and modulate the immune response to injury are currently undergoing testing. In the basic science realm, researchers continue to refine our understanding of the role that particular cell types play in the development of scar.

Single- versus multiple-dose antimicrobial prophylaxis for major surgery: a systematic review

BACKGROUND

Single-dose antimicrobial prophylaxis for major surgery is a widely accepted principle; recommendations have been based on laboratory studies and numerous clinical trials published in the last 25 years. In practice, single-dose prophylaxis has not been universally accepted and multiple-dose regimens are still used in some centres. Moreover, the principle has recently been challenged by the results of an Australian study of vascular surgery. The aim of this current systematic review is to determine the overall efficacy of single versus multiple-dose antimicrobial prophylaxis for major surgery and across surgical disciplines.

METHODS

Relevant studies were identified in the medical literature using the MEDLINE database and other search strategies. Trials included in the review were prospective and randomized, had the same antimicrobial in each treatment arm and were published in English. Rates of postoperative surgical site infections (SSI) were extracted, 2 x 2 tables prepared and odds ratios (OR) [with 95% confidence intervals (95% CI)] calculated. Data were then combined using fixed and random effects models to provide an overall figure. In this context, a high value for the combined OR, with 95% CI > 1.0, indicates superiority of multiple-dose regimens and a low OR, with 95% CI < 1.0, suggests the opposite. A combined OR close to 1.0, with narrow 95% CI straddling 1.0, indicates no clear advantage of one regimen over another. Further subgroup analyses were also performed.

RESULTS

Combined OR by both fixed (1.06, 95% CI, 0.89-1.25) and random effects (1.04, 95% CI, 0.86-1.25) models indicated no clear advantage of either single or multiple-dose regimens in preventing SSI. Likewise, subgroup analysis showed no statistically significant differences associated with type of antimicrobial used (beta-lactam vs other), blinded wound assessment, length of the multiple-dose arm (> 24 h vs 24 h or less) or type of surgery (obstetric and gynaecological vs other).

CONCLUSIONS

Continued use of single-dose antimicrobial prophylaxis for major surgery is recommended. Further studies are required, especially in previously neglected surgical disciplines.

Evolution of the primate lentiviruses: evidence from vpx and vpr

The genomes of the four primate lentiviral groups are complex and contain several regulatory or accessory genes. Two of these genes, vpr and vpx, are found in various combinations within the four groups and encode proteins whose functions have yet to be elucidated. Comparison of the encoded protein sequences suggests that the vpx gene within the HIV-2 group arose by the duplication of an ancestral vpr gene within this group. Evolutionary distance analysis showed that both genes were well conserved when compared with viral regulatory genes, and indicated that the duplication occurred at approximately the same time as the HIV-2 group and the other primate lentivirus groups diverged from a common ancestor. Furthermore, although the SIVagm vpx proteins are homologous to the HIV-2 group vpx proteins, there are insufficient grounds from sequence analysis for classifying them as vpx proteins. Because of their similarity to the vpr proteins of other groups, we suggest reclassifying the SIVagm vpx gene as a vpr gene. This creates a simpler and more uniform picture of the genomic organization of the primate lentiviruses and allows the genomic organization of their common precursor to be defined; it probably contained five accessory genes: tat, rev, vif, nef and vpr.

National Ignition Facility laser performance status

The National Ignition Facility (NIF) is the world's largest laser system. It contains a 192 beam neodymium glass laser that is designed to deliver 1.8 MJ at 500 TW at 351 nm in order to achieve energy gain (ignition) in a deuterium-tritium nuclear fusion target. To meet this goal, laser design criteria include the ability to generate pulses of up to 1.8 MJ total energy, with peak power of 500 TW and temporal pulse shapes spanning 2 orders of magnitude at the third harmonic (351 nm or 3omega) of the laser wavelength. The focal-spot fluence distribution of these pulses is carefully controlled, through a combination of special optics in the 1omega (1053 nm) portion of the laser (continuous phase plates), smoothing by spectral dispersion, and the overlapping of multiple beams with orthogonal polarization (polarization smoothing). We report performance qualification tests of the first eight beams of the NIF laser. Measurements are reported at both 1omega and 3omega, both with and without focal-spot conditioning. When scaled to full 192 beam operation, these results demonstrate, to the best of our knowledge for the first time, that the NIF will meet its laser performance design criteria, and that the NIF can simultaneously meet the temporal pulse shaping, focal-spot conditioning, and peak power requirements for two candidate indirect drive ignition designs.

Mechanical Forces in Cutaneous Wound Healing: Emerging Therapies to Minimize Scar Formation

Significance: Excessive scarring is major clinical and financial burden in the United States. Improved therapies are necessary to reduce scarring, especially in patients affected by hypertrophic and keloid scars. Recent Advances: Advances in our understanding of mechanical forces in the wound environment enable us to target mechanical forces to minimize scar formation. Fetal wounds experience much lower resting stress when compared with adult wounds, and they heal without scars. Therapies that modulate mechanical forces in the wound environment are able to reduce scar size. Critical Issues: Increased mechanical stresses in the wound environment induce hypertrophic scarring via activation of mechanotransduction pathways. Mechanical stimulation modulates integrin, Wingless-type, protein kinase B, and focal adhesion kinase, resulting in cell proliferation and, ultimately, fibrosis. Therefore, the development of therapies that reduce mechanical forces in the wound environment would decrease the risk of developing excessive scars. Future Directions: The development of novel mechanotherapies is necessary to minimize scar formation and advance adult wound healing toward the scarless ideal. Mechanotransduction pathways are potential targets to reduce excessive scar formation, and thus, continued studies on therapies that utilize mechanical offloading and mechanomodulation are needed.

How do small GTPase signal transduction pathways regulate cell cycle entry?

A variety of studies have shown that activation of the cell cycle machinery requires the participation of multiple signalling pathways. These pathways include Ras-dependent effectors such as the extracellular-signal related kinases, otherwise known as mitogen-activated protein kinases (ERKs, MAPKs), phosphatidylinositol 3 (PI3)-kinase and p21Ral pathways, as well as other signalling pathways regulated by the small GTPases p21Rho, p21Rac and p21Cdc42.

Mechanoresponsive stem cells acquire neural crest fate in jaw regeneration

During both embryonic development and adult tissue regeneration, changes in chromatin structure driven by master transcription factors lead to stimulus-responsive transcriptional programs. A thorough understanding of how stem cells in the skeleton interpret mechanical stimuli and enact regeneration would shed light on how forces are transduced to the nucleus in regenerative processes. Here we develop a genetically dissectible mouse model of mandibular distraction osteogenesis-which is a process that is used in humans to correct an undersized lower jaw that involves surgically separating the jaw bone, which elicits new bone growth in the gap. We use this model to show that regions of newly formed bone are clonally derived from stem cells that reside in the skeleton. Using chromatin and transcriptional profiling, we show that these stem-cell populations gain activity within the focal adhesion kinase (FAK) signalling pathway, and that inhibiting FAK abolishes new bone formation. Mechanotransduction via FAK in skeletal stem cells during distraction activates a gene-regulatory program and retrotransposons that are normally active in primitive neural crest cells, from which skeletal stem cells arise during development. This reversion to a developmental state underlies the robust tissue growth that facilitates stem-cell-based regeneration of adult skeletal tissue.

Regulation of mitogen-activated protein kinases in cardiac myocytes through the small G protein Rac1

Small guanine nucleotide-binding proteins of the Ras and Rho (Rac, Cdc42, and Rho) families have been implicated in cardiac myocyte hypertrophy, and this may involve the extracellular signal-related kinase (ERK), c-Jun N-terminal kinase (JNK), and/or p38 mitogen-activated protein kinase (MAPK) cascades. In other systems, Rac and Cdc42 have been particularly implicated in the activation of JNKs and p38-MAPKs. We examined the activation of Rho family small G proteins and the regulation of MAPKs through Rac1 in cardiac myocytes. Endothelin 1 and phenylephrine (both hypertrophic agonists) induced rapid activation of endogenous Rac1, and endothelin 1 also promoted significant activation of RhoA. Toxin B (which inactivates Rho family proteins) attenuated the activation of JNKs by hyperosmotic shock or endothelin 1 but had no effect on p38-MAPK activation. Toxin B also inhibited the activation of the ERK cascade by these stimuli. In transfection experiments, dominant-negative N17Rac1 inhibited activation of ERK by endothelin 1, whereas activated V12Rac1 cooperated with c-Raf to activate ERK. Rac1 may stimulate the ERK cascade either by promoting the phosphorylation of c-Raf or by increasing MEK1 and/or -2 association with c-Raf to facilitate MEK1 and/or -2 activation. In cardiac myocytes, toxin B attenuated c-Raf(Ser-338) phosphorylation (50 to 70% inhibition), but this had no effect on c-Raf activity. However, toxin B decreased both the association of MEK1 and/or -2 with c-Raf and c-Raf-associated ERK-activating activity. V12Rac1 cooperated with c-Raf to increase expression of atrial natriuretic factor (ANF), whereas N17Rac1 inhibited endothelin 1-stimulated ANF expression, indicating that the synergy between Rac1 and c-Raf is potentially physiologically important. We conclude that activation of Rac1 by hypertrophic stimuli contributes to the hypertrophic response by modulating the ERK and/or possibly the JNK (but not the p38-MAPK) cascades.

Scarless wound healing: finding the right cells and signals

From the moment we are born, every injury to the skin has the potential to form a scar, many of which can impair form and/or function. As such, scar management constitutes a billion-dollar industry. However, effectively promoting scarless wound healing remains an elusive goal. The complex interactions of wound healing contribute to our inability to recapitulate scarless wound repair as it occurs in nature, such as in fetal skin and the oral mucosa. However, many new advances have occurred in recent years, some of which have translated scientific findings from bench to bedside. In vivo lineage tracing has helped establish a variety of novel cellular culprits that may act as key drivers of the fibrotic response. These newly characterized cell populations present further targets for therapeutic intervention, some of which have previously demonstrated promising results in animal models. Here, we discuss several recent studies that identify exciting approaches for diminishing scar formation. Particular attention will also be paid to the canonical Wnt/β-catenin signaling pathway, which plays an important role in both embryogenesis and tissue repair. New insights into the differential effects of Wnt signaling on heterogeneous fibroblast and keratinocyte populations within the skin further demonstrate methods by which wound healing can be re-directed to a more fetal scarless phenotype. Graphical abstract Recent approaches to reducing scar formation. Representation showing novel scientific approaches for decreasing scar formation, including the targeting of pro-fibrotic cell populations based on surface molecule expression (e.g. DPP4(+) fibroblasts, ADAM12(+) pericytes). Modulation of cellular mechanotransduction pathways are another means to reduce scar formation, both at the molecular level or, macroscopically with dressings designed to offload tension, at cutaneous wound sites (ADAM12 a disintegrin and metalloprotease 12, DPP4 dipeptidyl peptidase-4, FAK focal adhesion kinase).

Role of hypoxic pulmonary vasoconstriction in pulmonary gas exchange and blood flow distribution. 2. Pathophysiology

In this review, the second of a two part series, the analytic techniques introduced in the first part are applied to a broad range of pulmonary pathophysiologic conditions. The contributions of hypoxic pulmonary vasoconstriction to both homeostasis and pathophysiology are quantitated for atelectasis, pneumonia, sepsis, pulmonary embolism, chronic obstructive pulmonary disease and adult respiratory distress syndrome. For each disease state the influence of principle variables, including inspired oxygen concentration, cardiac output and severity of pathology are explored and the actions of selected drugs including inhaled nitric oxide and infused vasodilators are illustrated. It is concluded that hypoxic pulmonary vasoconstriction is often a critical determinant of hypoxemia and/or pulmonary hypertension. Furthermore this analysis demonstrates the value of computer simulation to reveal which of the many variables are most responsible for pathophysiologic results.

Site and sensitivity for stimulation of hypoxic pulmonary vasoconstriction

Rat lungs were perfused in an in vitro circuit with separate control of alveolar and pulmonary arterial O2 tension. With perfusion flow constant, the hypoxic pulmonary vasoconstrictor (HPV) response was measured as changes of perfusion pressure. HPV was a function of both alveolar O2 tension (PvO2) and was described by a double sigmoid response surface. Where RA-v is this pressure response expressed as a percent of the maximum, the linearized form of the response surface is given by log [RA-v/(100-RA-v)] = 3.93 - 1.029 (log PvO2) - 1.623 (log PAO2). From this relationship it was concluded that 1) HPV is determined by PAO2 and PvO2; 2) the fundamental stimulus-response relationship is a sigmoid with a 50% response when both PAO2 and PvO2 are 30.3 Torr; 3) PAO2 has a greater effect than PvO2 due in part to the geometry of the vascular wall but principally due to O2 exchange between alveolar gas and blood in small pulmonary arteries; 4) there is not a localized sensor for HPV (the response is accounted for by each smooth muscle cell in the pulmonary arterial wall responding to the O2 tension in its vicinity); and 5) the characteristics of the response suggest that the cell sensor resembles a cytochrome.

Integrated spatial multiomics reveals fibroblast fate during tissue repair

In the skin, tissue injury results in fibrosis in the form of scars composed of dense extracellular matrix deposited by fibroblasts. The therapeutic goal of regenerative wound healing has remained elusive, in part because principles of fibroblast programming and adaptive response to injury remain incompletely understood. Here, we present a multimodal -omics platform for the comprehensive study of cell populations in complex tissue, which has allowed us to characterize the cells involved in wound healing across both time and space. We employ a stented wound model that recapitulates human tissue repair kinetics and multiple Rainbow transgenic lines to precisely track fibroblast fate during the physiologic response to skin injury. Through integrated analysis of single cell chromatin landscapes and gene expression states, coupled with spatial transcriptomic profiling, we are able to impute fibroblast epigenomes with temporospatial resolution. This has allowed us to reveal potential mechanisms controlling fibroblast fate during migration, proliferation, and differentiation following skin injury, and thereby reexamine the canonical phases of wound healing. These findings have broad implications for the study of tissue repair in complex organ systems.

Jaw muscles and the skull in mammals: the biomechanics of mastication

Among non-mammalian vertebrates, rigid skulls with tight sutural junctions are associated with high levels of cranial loading. The rigid skulls of mammals presumably act to resist the stresses of mastication. The pig, Sus scrofa, is a generalized ungulate with a diet rich in resistant foods. This report synthesizes previous work using strain gages bonded to the bones and sutures of the braincase, zygomatic arch, jaw joint, and mandible with new studies on the maxilla. Strains were recorded during unrestrained mastication and/or in anesthetized pigs during muscle stimulation. Bone strains were 100-1000 micro epsilon, except in the braincase, but sutural strains were higher, regardless of region. Strain regimes were specific to different regions, indicating that theoretical treatment of the skull as a unitary structure is probably incorrect. Muscle contraction, especially the masseter, caused strain patterns by four mechanisms: (1) direct loading of muscle attachment areas; (2) a compressive reaction force at the jaw joint; (3) bite force loading on the snout and mandible; and (4) movement causing new points of contact between mandible and cranium. Some expected patterns of loading were not seen. Most notably, strains did not differ for right and left chewing, perhaps because pigs have bilateral occlusion and masseter activity.

Hypoxic pulmonary vasoconstriction in dogs: effects of lung segment size and oxygen tension

Six pentobarbital-anesthetized dogs were prepared with endobronchial tubes and electromagnetic flow probes. The effects of changing inspired oxygen concentrations (FIO2 = 1, 0.21, 0.15, 0.1, 0.075, 0.05, and 0) were tested on test segments of different size corresponding to left lower lobe, left upper lobe-lingula, left lung, right lung, right lung plus left lower lobe, right lung plus left upper lobe-lingula, and whole lung. In each test the rest of the lung received oxygen. Hypoxic pulmonary vasoconstriction is demonstrated by both diversion of blood flow away from hypoxic test segments and by increased perfusion pressure. Flow diversion (FD%) decreases with the size of the hypoxic test segment (%QSN) from a maximum of 75% for very small segments to zero when the whole lung is hypoxic. FD% increases linearly as alveolar oxygen tension (PAO2) of the test segment is decreased in the range of 130--28 Torr. When mixed venous oxygen tension (PVO2) is less than 45 Torr FD% is reduced. These relationships are described by FD% = [74.99 - 0.0778 (%QSN) - 0.00661 (%QSN)2] [1.268 - 0.0096 (PAO2)] [0.47 + 0.012 (PVO2)], with r = 0.92 and standard error for prediction of 8.4%. Pulmonary perfusion pressure changes (PPH/PPN) increase with the size of the hypoxic test segments from 0 with very small segments to approximately 2.2 for the hypoxic whole lung. For all test segments PPH/PPN increases linearly with PAO2. These relationships are described by PPH/PPN = 1 + [0.0043 (%QSN) + 0.000072 (%QSN)2] [1.234 - 0.0096 (PAO2)], with r = 0.91 and standard error for prediction of 0.3 units. Responses to hypoxic pulmonary vasoconstriction in dogs are therefore shown to be predictable and continuous, and the physiological basis for action of each of the variables is discussed.

Scarless wound healing: Transitioning from fetal research to regenerative healing

Since the discovery of scarless fetal skin wound healing, research in the field has expanded significantly with the hopes of advancing the finding to adult human patients. There are several differences between fetal and adult skin that have been exploited to facilitate scarless healing in adults including growth factors, cytokines, and extracellular matrix substitutes. However, no one therapy, pathway, or cell subtype is sufficient to support scarless wound healing in adult skin. More recently, products that contain or mimic fetal and adult uninjured dermis were introduced to the wound healing market with promising clinical outcomes. Through our review of the major experimental targets of fetal wound healing, we hope to encourage research in areas that may have a significant clinical impact. Additionally, we will investigate therapies currently in clinical use and evaluate whether they represent a legitimate advance in regenerative medicine or a vulnerary agent. WIREs Dev Biol 2018, 7:e309. doi: 10.1002/wdev.309 This article is categorized under: Adult Stem Cells, Tissue Renewal, and Regeneration > Regeneration Plant Development > Cell Growth and Differentiation Adult Stem Cells, Tissue Renewal, and Regeneration > Environmental Control of Stem Cells.

Effects of halothane, enflurane, and isoflurane on hypoxic pulmonary vasoconstriction in rat lungs in vitro

Rat lungs were ventilated and perfused at a constant rate in vitro. The maximal hypoxic pulmonary vasoconstrictor (HPV) response was recorded by measuring the pulmonary artery pressure change when the inspired oxygen concentration was changed from 21% to 3% (with 5.5% carbon dioxide) in the absence of anesthetic vapor. In different experimental groups, the effects of halothane, enflurane, and isoflurane on HPV were examined. In random order the anesthetics were added to the inspired gas in concentrations of 0.25, 0.5, 1, 1.5, and 2 or 2.5 MAC units. The HPV pressor response to 3% oxygen in the presence of anesthetic agent was expressed as a per cent of the pressure response observed in the absence of anesthetic (R%MAX). All three agents depressed HPV in a dose-related manner. The concentrations in MAC units at which 50% depression of HPV (ED50) occurred was 0.47, 0.60, and 0.56 for halothane, isoflurane, and enflurane, respectively, and neither the ED50 values nor the slopes of these dose response curves were significantly different. It was concluded that these halogenated general anesthetics inhibit HPV with essentially the same potency.

Influence of isoflurane on hypoxic pulmonary vasoconstriction in dogs

The authors studied the influence of locally administered isoflurane anesthesia on the pulmonary vascular response to regional alveolar hypoxia (hypoxic pulmonary vasoconstriction [HPV]) over a range of cardiac outputs (COs) in seven mechanically ventilated, closed-chest dogs. The right lung was ventilated with 100% O2 throughout the study. The left lung was ventilated with either 100% O2 (normoxia) or an hypoxic gas mixture (hypoxia). Different alveolar concentrations of isoflurane (0, 1, and 2.5 MAC) were administered to the left lung in a randomized sequence. The CO was altered by opening and closing surgically produced arteriovenous fistulae, at all isoflurane concentrations, and by hemorrhage at 0 MAC isoflurane. The magnitude of the HPV response was measured by differential CO2 elimination in the absence of isoflurane and by venous admixtures in all phases. During normoxia, the left lung effective flow (QL%) measured from differential CO2 excretion was 39.9 +/- 1.2% of the total blood flow and decreased to 18.8 +/- 2.6% when ventilated with the hypoxic gas mixture. Venous admixture (QVA/QT%) was significantly correlated with QL% during hypoxic ventilation in the absence of isoflurane. QVA/QT% was 22.3 +/- 2.7% during hypoxia with normal CO, and it increased significantly to 27.7 +/- 1.1% when the CO was increased 43%. It was not significantly altered (23.6 +/- 3.6%) when the CO was decreased by 54%. Isoflurane 2.5 MAC significantly increased QVA/QT% during hypoxic ventilation of the left lung to 33.9 +/- 2.6% with low CO and 35.4 +/- 1.7% with normal CO. Isoflurane 1 MAC increased QVA/QT% to 27.2 +/- 2.7% with normal CO and 28.1 +/- 2.6% with high CO.(ABSTRACT TRUNCATED AT 250 WORDS)

Activated N-ras controls the transformed phenotype of HT1080 human fibrosarcoma cells

To investigate whether the activated N-ras oncogene of HT1080 human fibrosarcoma cells contributes to the expression of the transformed phenotype, we have isolated flat revertants. In two independent revertant lines, an increase in chromosomal ploidy occurred without a concomitant increase in the number of copies of the N-ras transforming allele. Immunoprecipitation confirms that the level of the mutant N-ras p21 gene product in the revertants is correspondingly lower than in HT1080. Analysis of sporadic tumors derived from the revertant cells reveals an increased dosage of the transforming allele. The revertants also retransform after transfection of cloned activated ras oncogenes. These results imply direct participation of an N-ras oncogene in maintaining the transformed phenotype of a human tumor cell line.

Clinical outcome and quality of life following enterocystoplasty for idiopathic detrusor instability and neurogenic bladder dysfunction

OBJECTIVE

To study the long-term outcome of patients undergoing enterocystoplasty.

PATIENTS AND METHODS

The study comprised 48 patients (17 men and 31 women; mean age 46 years) who underwent enterocystoplasty for idiopathic detrusor instability (DI, 35 patients) or neurogenic bladder dysfunction (13 patients). Symptoms were scored from 0 to 14 and the overall outcome and generic quality of life were assessed using a Visick grading system (groups A to E) and the Nottingham Health Profile (NHP). These assessments were carried out before, 3 months after operation and at the final follow-up (38 +/- 18 months, range 13-78). Urodynamic studies were performed before and after operation.

RESULTS

No patient died after operation and there was minimal early morbidity. Late complications (> 30 days) included incisional hernia (3), anastomotic perforation (1), calculus formation (1) and urethral stricture (1). Clean intermittent self-catheterization (CISC) was performed by 36 (75%) patients. Early symptomatic outcome was good in 40 (83%) patients, moderate in seven (15%) and unsatisfactory in one (2%) patient. The mean symptom scores before and 3 months after surgery were 10 (range 2-14) and 3 (range 2-14), respectively (P < 0.001). There was a significant increase in total bladder capacity (307 +/- 140 to 588 +/- 217 mL; P < 0.001) and bladder compliance (37 +/- 50 to 169 +/- 162 mL/cm H2O; P < 0.001). DI persisted in 15 (31%) patients. NHP scores revealed significant improvements in all domains. Final assessment showed a less satisfactory situation, with recurrent urinary tract infection (UTI) in 17 (37%) patients, a need for long-term antibiotic therapy in seven (15%) and a change in bowel habit in 15 (33%) (13 DI, two with neurogenic bladder dysfunction). CISC was performed by 39 (85%) patients. The long-term outcome was good or moderate in 12 patients (92%) with neurogenic bladder dysfunction and good or moderate in only 19 patients (58%) with DI.

CONCLUSION

Clam enterocystoplasty remains an effective management option in some patients with DI, but most patients with neurogenic bladder dysfunction do well. The procedure is, however, associated with long-term complications such as disturbance of bowel habit and recurrent UTIs, which impair the outcome in the long-term in patients with DI despite general improvements in irritative bladder symptoms.