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D Hess

Publications and source records attributed to D Hess.

At least 91 records · Page 5Linked to original sources
PubMed1998

Esthetic single-tooth replacement with implants: a team approach.

The range of indications for implant-borne prostheses in partially edentulous patients has expanded in recent years as a consequence of advances in regenerative techniques for bone and soft tissues. The esthetic demands of both patients and dentists have risen in parallel with these advances. Esthetic compromises in prostheses have become increasingly less tolerable, particularly in the anterior region of the maxilla. If the presenting situation is less than optimal, extensive preprosthetic measures may be required to prepare local tissues for acceptance of esthetically and functionally adequate prostheses. Particularly in difficult situations, collaboration by a team is recommended. The exchange of ideas and experience among specialists should begin as early as the treatment planning stage and extend over the entire course of therapy. The objective should be defined and the various steps of treatment should be coordinated with participation from all team members.

Adolescent↗
PubMed1997

The methylated DNA binding protein-2-H1 (MDBP-2-H1) consists of histone H1 subtypes which are truncated at the C-terminus.

The methylated DNA binding protein-2-H1 (MDBP-2-H1), present in rooster liver, is a member of the histone H1 family which inhibits transcription by binding selectively to methylated promoters. Here we have determined the primary structure of MDBP-2-H1. A comparison between histone H1 and MDBP-2-H1 was achieved by analyzing reversed phase HPLC-purified and V8-digested proteins by mass spectrometry and/or microsequencing. In rooster liver the most abundant histone H1 subtypes are H1 01 and H1 11L. Similarly, MDBP-2-H1 contains the same subtypes of histone H1. The histone H1 subtype H1 01 in MDBP-2-H1 has 150 amino acids, whereas the full-size histone H1 01 is 218 amino acids. The difference in mass between the two proteins is explained by C-terminal truncation of histone H1 01.

Amino Acid Sequence↗
PubMed1997

Examining F-actin interaction with intact talin and talin head and tail fragment using static and dynamic light scattering.

We examined the binding kinetics of intact talin and talin head and tail fragment with F-actin at pH 7.0 and at low ionic strength. We observed by a transient kinetic method a fast followed by a slower binding process for intact talin and talin tail fragment with filamentous actin. The latter can be attributed to F-actin cross-linking and/or bundling, which was observed in cosedimentation assays as well as by low shear viscometry and electron microscopy [Zhang, J., Robson, R. M., Schmidt, J. M. & Stromer, M. H. (1996) Biochem. Biophys. Res. Commun. 218, 530-537]. This finding is supported by dynamic light scattering measurements, indicating changes in internal actin filament dynamics due to cross-linking/bundling events with intact talin and talin tail fragment. No binding of the talin head fragment with F-actin was detected by either method.

Actins↗
PubMed1997

C-Mannosylation of human RNase 2 is an intracellular process performed by a variety of cultured cells.

C2-alpha-Mannosyltryptophan was discovered in RNase 2 from human urine, representing a novel way of attaching carbohydrate to a protein. Here, we have addressed two questions related to the biosynthesis of this modification: (i) is C-mannosylation part of the normal intracellular biosynthetic route, and (ii) how general is it, i.e. which organisms perform this kind of glycosylation? To answer the first question, RNase 2, which is identical to the eosinophil-derived neurotoxin, was isolated from intracellular stores of cultured human HL-60 cells. The enzyme was C-mannosylated at Trp-7, showing that the modification occurs intracellularly, before secretion of the protein. The second question was investigated by immunological and chemical analysis of RNase 2 purified from the supernatant of transiently transformed cells from different organisms. This revealed that C-mannosylation occurs in cells from man, green monkey, pig, mouse, and hamster. The observation that pig kidney cells contain the machinery for C-mannosylation of Trp-7 of human RNase 2 but that the homologous RNase from porcine kidney is not a substrate, since it does not contain a tryptophan at position 7, strongly suggests that C-mannosylated proteins other than RNase 2 exist. Recombinant RNase 2 isolated from insect cells, plant protoplasts, and Escherichia coli was not C-mannosylated. These results not only form the basis for further studies on the biochemical aspects of C-mannosylation but also have implications for the choice of cells for production of recombinant glycoproteins.

Animals↗
PubMed1997

Demethylation of DNA by purified chick embryo 5-methylcytosine-DNA glycosylase requires both protein and RNA.

We have previously purified and characterized a 5-methylcytosine (5-MeC)-DNA glycosylase from 12 day old chick embryos [Jost,J.P. et al. (1995) J. Biol. Chem. 270, 9734-9739]. The activity of the purified enzyme is abolished upon treatment with proteinase K and ribonuclease A. RNA copurifies with 5-MeC-DNA glycosylase activity throughout all chromatographic steps and preparative gel electrophoresis. RNA with a length of approximately 300-500 nucleotides was isolated from the gel purified enzyme. Upon extensive treatment with proteinase K, the gel eluted and labeled RNA did not show any significant change in molecular mass. The purified RNA incubated alone or in the presence of Mg2+and deoxyribonucleotide phosphates had no 5-MeC-DNA glycosylase or demethylating activities. However, activity of 5-MeC-DNA glycosylase could be restored when the purified RNA was incubated with the inactive protein, free of RNA.

Animals↗
PubMed1997

Nitric oxide (NO) measurement accuracy.

BACKGROUND: Evaluation of the clinical utility of NO requires accurate assessment of inspired [NO]. Currently, chemiluminescence analyzers are the clinical standard for analysis; however, their performance in the clinical setting has not been systemically evaluated. METHODS: We evaluated the performance of four chemiluminescence analyzers (270B NOA, Sievers Instruments, Inc.; CLA 510S, Horiba Co., Ltd.; CLD 700 AL, Eco Physics Corp.; Model 42, Thermo Environmental Instruments Inc.) in simulated clinical settings. Transport delay and dynamic 95% response time were measured by the balloon in a glass chamber puncture technique. Fluctuating [NO] in a continuous flow of gas and [NO] during mechanical ventilation, where NO was premixed prior to entering the ventilator, were evaluated. RESULTS: Transport delay ranged from 1.02 +/- 0.02 to 24.36 +/- 2.47 s (p < 0.05) and the 95% response time ranged from 0.22 +/- 0.04 to 70.03 +/- 0.03 s (p < 0.05). Accurate analysis of [NO] in a continuous flow system was only possible with the most rapid response analyzer (270B NOA). All other analyzers under reported the maximum [NO] (p < 0.05) and over reported the minimum [NO] (p < 0.05). All analyzers accurately determined [NO] in the inspiratory limb of the ventilator circuit, but none accurately determined [NO] at the airway opening. CONCLUSIONS: Measurements of inhaled [NO] can vary greatly, dependent upon the performance characteristics of the analyzer and the location of NO analysis. All studies evaluating the clinical use of NO should fully describe the technical gas delivery methodology and the response time and transport delay of the chemiluminescence analyzer used.

Administration, Inhalation↗
PubMed1997

Evaluation of electrochemical nitric oxide and nitrogen dioxide analyzers suitable for use during mechanical ventilation.

OBJECTIVE: Inhaled nitric oxide (NO) is increasingly being used in the treatment of diseases characterized by hypoxemia and pulmonary hypertension. To avoid complications, accurate quantitative analysis of NO and NO2 is necessary during this therapy. We evaluated the accuracy of electrochemical NO and nitrogen dioxide (NO2) analyzers suitable for use during mechanical ventilation. METHODS: We evaluated six electrochemical NO analyzer brands (Bedfont, B & W, Dräger, EIT, Pulmonox, Saan). All were calibrated and used per manufacturer's specifications. An adult mechanical ventilator was used to produce serial dilutions of NO with O2 for [NO] of 0-80 ppm. F1O2 settings of 0.90, 0.70, 0.50, 0.30, and 0.21 were used. Settings of low, moderate, and high ventilation pressures were evaluated. Gas was sampled from the inspiratory limb of the ventilator circuit using either a sidestream or mainstream technique. [NO] was also measured using a calibrated chemiluminescence analyzer. For the analyzers that measured NO2, serial dilutions of 8.5 ppm NO2 with O2 were analyzed using chemiluminescence and the electrochemical analyzers. RESULTS: Bias +/- precision for [NO] by individual devices ranged from 1.8 +/- 1.9 ppm to -1.0 +/- 0.7 ppm. There were significant differences in the bias between analyzers (P < 0.001), pressure settings (P < 0.001), and NO level (P < 0.017). The difference in bias between levels of F1O2 was not significant (P = 0.062). Bias +/- precision for NO2 ranged from 0.18 +/- 0.12 ppm to -0.14 +/- 0.13 ppm, with a significant difference between analyzers (P < 0.001). CONCLUSIONS: The bias and precision of these analyzers was acceptable for clinical use. The devices tended to be most accurate at [NO] < or = 20 ppm-the clinical conditions at which NO is most commonly used.

Administration, Inhalation↗
PubMed1997

Assessment of errors when expiratory condensate PCO2 is used as a proxy for mixed expired PCO2 during mechanical ventilation.

OBJECTIVES: We designed a series of experiments to determine whether expiratory water condensate (PconCO2) can be used as a proxy for mixed expired gas collection. METHODS: In 18 adult mechanically ventilated patients with ARDS (40 samples), simultaneous collections of arterial blood, expiratory water trap condensate, mixed expired gas, and minute ventilation were used to calculate VCO2 and VD/VT. To assess the effect of temperature, a constant gas flow (PCO2 10-30 mm Hg) was bubbled through water at temperatures of 19.5-37 degrees C. Gas and water samples were collected, immediately analyzed for PCO2, and a temperature correction factor was calculated. A lung model was constructed using a 5 L anesthesia bag connected to a mechanical ventilator with a heated humidifier. Temperature at the Y-piece was set to approximately 37 degrees C and CO2 was injected into the bag to establish an end-tidal PCO2 of 20-70 mm Hg. After equilibration, condensate was collected, PCO2 was measured, and the temperature-corrected PCO2 was compared to PECO2. The capnogram at points along the expiratory limb circuit was used to evaluate gas mixing. RESULTS: There was an over-estimation of PECO2 by PconCO2 (p < 0.001) for the patient data, resulting in an underestimation of VD/VT (p < 0.001) and an overestimation of VCO2 (p < 0.001). The temperature correction factor for PCO2 in water was -0.010 (about half of the factor used for whole blood). The bias between temperature-corrected PconCO2 and PECO2 was 0.3 +/- 3.2 mm Hg in the lung model. Mixing in the expiratory limb was poor, as evaluated by the capnogram. CONCLUSIONS: Even with temperature correction, we failed to precisely predict PECO2 from PconCO2. For measurement of VD/VT and VCO2, we do not recommend methods that use PconCO2.

Adult↗
PubMed1997

Inaccuracies of nitric oxide delivery systems during adult mechanical ventilation.

BACKGROUND: Various systems to administer inhaled nitric oxide (NO) have been used in patients and experimental animals. We used a lung model to evaluate five NO delivery systems during mechanical ventilation with various ventilatory patterns. METHODS: An adult mechanical ventilator was attached to a test lung configured to separate inspired and expired gases. Four injection systems were evaluated with NO injected either into the inspiratory circuit 90 cm proximal to the Y piece or directly at the Y piece and delivered either continuously or only during the inspiratory phase. Alternatively, NO was mixed with air using a blender and delivered to the high-pressure air inlet of the ventilator. Nitric oxide concentration was measured from the inspiratory limb of the ventilator circuit and the tracheal level using rapid- and slow-response chemiluminescence analyzers. The ventilator was set for constant-flow volume control ventilation, pressure control ventilation, pressure support ventilation, or synchronized intermittent mandatory ventilation. Tidal volumes of 0.5 l and 1 l were evaluated with inspiratory times of 1 s and 2 s. RESULTS: The system that premixed NO proximal to the ventilator was the only one that maintained constant NO delivery regardless of ventilatory pattern. The other systems delivered variable NO concentration during pressure control ventilation and spontaneous breathing modes. Systems that injected a continuous flow of NO delivered peak NO concentrations greater than the calculated dose. These variations were not apparent when a slow-response chemiluminescence analyzer was used. CONCLUSIONS: NO delivery systems that inject NO at a constant rate, either continuously or during inspiration only, into the inspiratory limb of the ventilator circuit produce highly variable and unpredictable NO delivery when inspiratory flow is not constant. Such systems may deliver a very high NO concentration to the lungs, which is not accurately reflected by measurements performed with slow-response analyzers.

Adult↗
PubMed1997

Physiologic determinants of the response to inhaled nitric oxide in patients with acute respiratory distress syndrome.

BACKGROUND: The response to inhaled nitric oxide (NO) in patients with acute respiratory distress syndrome (ARDS) varies. It is unclear which patients will respond favorably and whether the initial response persists over time. The authors defined a clinically useful response to inhaled NO as an increase of more than 20% of the ratio of the partial pressure of oxygen (Pa(O2)) to the inspiratory fraction of oxygen (FIO2), a decrease of more than 20% of pulmonary vascular resistance, or both. The authors hypothesized that patients who initially respond favorably are likely to show persistent improvements of gas exchange and hemodynamics after 48 h of NO inhalation. METHODS: The medical records and collected research data of 88 patients with ARDS who received 92 trials of NO inhalation between March 1991 and February 1996 were reviewed. RESULTS: Fifty-three of the 92 trials (58%) produced a clinically significant response to NO. In the responding patients who continued to receive NO therapy (n = 43), the Pa(O2)/FiO2 ratio remained higher (120 +/- 46 vs. 89 +/- 32 mmHg before NO; P < 0.01) and the mean pulmonary artery pressure remained lower (35 +/- 8 vs. 40 +/- 12 mmHg before NO; P < 0.01) at 48 h. Only 33% of the patients with septic shock responded to inhaled NO compared with 64% of those without septic shock (P < 0.02). CONCLUSIONS: Most patients with ARDS had clinically useful responses to NO inhalation. Patients with an initial favorable response maintained the improvement at 48 h. Patients with septic shock were less likely to respond favorably.

Administration, Inhalation↗
PubMed1997

Unloadiing of the work of breathing by proportional assist ventilation in a lung model.

OBJECTIVES: Proportional assist ventilation is devised to increase airway pressure in proportion to inspiratory effort. A systematic study of the performance of this new mode of ventilation has not been presented. We tested in the laboratory the capability of proportional assist ventilation to unload the work of breathing in proportion to ventilatory drive, under a variety of mechanical loads. DESIGN: During variations of "ventilatory drive" (i.e., tidal volume), unloading of the work of breathing by proportional assist ventilation was contrasted with unloading by pressure-support ventilation. SETTING: The respiratory laboratory of a university-affiliated teaching hospital. SUBJECT: A bellows-in-a-box lung model, powered by a sine wave air flow generator. INTERVENTIONS: Proportional assist and pressure-support ventilation were preset to provide comparable support at a baseline "ventilatory drive" of 0.7-L tidal volume. The set levels of proportional assist and pressure-support ventilation were subsequently applied to five tidal volumes, from 0.2 to 1.2 L. Three levels of inspiratory support and three settings of mechanical load were evaluated. MEASUREMENTS AND MAIN RESULTS: Proportional assist ventilation significantly (p < .05) reduced the work of breathing of the lung model at all but the lowest tidal volume (0.2 L). The preset proportion of ventilatory support (30%, 50%, and 70%) unloaded the work of breathing uniformly as ventilatory drive was varied at tidal volumes of > or = 0.5 L, but not always at tidal volumes of < or = 0.4 L. In contrast, pressure-support ventilation overassisted low tidal volumes and underassisted high tidal volumes (p < .05). CONCLUSIONS: In a lung model, a prototype system delivering proportional assist ventilation provided uniform unloading of the work of breathing as the ventilatory drive was varied within a tidal volume range of 0.5 to 1.2 L. These findings confirm the theoretical modeling of proportional assist ventilation. This system, however, failed to properly unload low tidal volumes of 0.2 to 0.4 L.

Humans↗
PubMed1997

Disruption of each of the secreted aspartyl proteinase genes SAP1, SAP2, and SAP3 of Candida albicans attenuates virulence.

Secreted aspartyl proteinases (Saps), encoded by a gene family with at least nine members (SAP1 to SAP9), are one of the most discussed virulence factors produced by the human pathogen Candida albicans. In order to study the role of each Sap isoenzyme in pathogenicity, we have constructed strains which harbor mutations at selected SAP genes. SAP1, SAP2, and SAP3, which are regulated differentially in vitro, were mutated by targeted gene disruption. The growth rates of all homozygous null mutants were similar to those of the isogenic wild-type parental strain (SC5314) in complex and defined media. In medium with protein as the sole source of nitrogen, sap1 and sap3 mutants grew with reduced growth rates but reached optical densities similar to those measured for SC5314. In contrast, sap2 null mutants tended to clump, grew poorly in this medium, and produced the lowest proteolytic activity. Addition of ammonium ions reversed such growth defects. These results support the view that Sap2 is the dominant isoenzyme. When sap1, sap2, and sap3 mutants were injected intravenously in guinea pigs and mice, the animals had increased survival rates compared to those of control animals infected with SC5314. However, reduction of proteolytic activity in vitro did not correlate directly with the extent of attenuation of virulence observed for all Sap-deficient mutants. These data suggest that SAP1, SAP2, and SAP3 all contribute to the overall virulence of C. albicans and presumably all play important roles during disseminated infections.

Animals↗
PubMed1997

Recovery of diaphragmatic function in awake sheep after two approaches to thoracic surgery.

Video-assisted thoracoscopic surgery (VATS) is replacing thoracotomy, but no study has addressed the extent or duration of VATS-induced diaphragmatic alteration. We hypothesized that VATS would impair diaphragmatic function less and return diaphragmatic function faster than thoracotomy. In eight sheep, sonomicrometers were randomly implanted on the right costal diaphragm via VATS or thoracotomy. Diaphragmatic resting length, shortening fraction, and respiratory function were measured weekly during quiet breathing (QB) and CO2 rebreathing for 4 wk. For VATS, shortening fraction was smallest on postoperative days 1 (POD 1) (6.4 +/- 3.4 and 12.9 +/- 8.7% during QB and 10% CO2 rebreathing, respectively) and 7 (6.3 +/- 3.4 and 16.9 +/- 4.0% during QB and 10% CO2 rebreathing, respectively) and recovered by 3 wk (13.2 +/- 1.8 and 28.9 +/- 8.0% during QB and 10% CO2 rebreathing, respectively). For thoracotomy, shortening fraction at 10% CO2 rebreathing was smaller on PODs 1, 7, 14 (15.9 +/- 7.1, 13.6 +/- 5.4, and 19.0 +/- 6.9%) than on POD 28 (29.9 +/- 8.2%), but not during QB on POD 1 or 7 (7.5 +/- 3.8 and 3.4 +/- 2.6%) compared with POD 28 (10.7 +/- 8.7%). Shortening fraction did not differ between surgeries. There was no group difference in minute ventilation, respiratory rate, transdiaphragmatic pressure, or esophageal and gastric pressures. In conclusion, although shortening fraction recovered faster for VATS, this translated into insignificant functional differences.

Animals↗
PubMed1997

Performance characteristics of bilevel pressure ventilators: a lung model study.

Bilevel pressure ventilators are being used increasingly to provide noninvasive ventilatory support in the management of obstructive sleep apnea, chronic ventilatory failure, and acute respiratory failure. However, the ability of these ventilators to respond to inspiratory demand without imposing expiratory loads has not been evaluated extensively. We evaluated the performance of nine bilevel pressure ventilators in a lung model, as compared with the Nellcor Puritan-Bennett 7200ae adult critical care ventilator. All ventilators were set to provide pressure support ventilation (PSV) and positive end-expiratory pressure (PEEP) at a rate of 10 breaths/min with an inspiratory time of 1.0 s. Simulated pleural pressure, airway pressure, and flow at airway opening were continuously monitored. We studied the effects of three PSV levels (5, 10, and 15 cm H2O) with 5 cm H2O PEEP at two lung compliances (50 and 80 mL/cm H2O) and four peak inspiratory flow demands (20, 40, 60, and 80 L/min) on seven dependent variables: inspiratory delay time (D-I), inspiratory trigger pressure (P-I), inspiratory area percent (Area I%), expiratory delay time (D-E), supraplateau expiratory pressure change (P-E), expiratory area (Area E), and ventilator peak flow (VPF). Most ventilators performed as well as or significantly (p<0.05) better than the 7200ae in all studied variables. Compliance did not significantly affect ventilator performance. Increasing inspiratory flow demand significantly (p<0.05) increased D-I, P-I, P-E, and VPF and decreased Area I% with most ventilators. As ventilatory demand increased, D-E and Area E significantly (p<0.05) changed. With some units, D-E and Area E increased, while with others they decreased. Most bilevel pressure ventilators evaluated were able to respond to high ventilatory demands and outperformed the Nellcor Puritan-Bennett 7200ae ventilator.

Calibration↗
PubMed1997

Pressure vs flow triggering during pressure support ventilation.

BACKGROUND: Adult mechanical ventilators have traditionally been pressure- or time-triggered. More recently, flow triggering has become available and some adult ventilators allow the choice between pressure or flow triggering. Prior studies have supported the superiority of flow triggering during continuous positive airway pressure, but few have compared pressure and flow triggering during pressure support ventilation (PSV). The purpose of this study was to compare pressure and flow triggering during PSV in adult mechanically ventilated patients. METHODS: The study population consisted of 10 adult patients ventilated with a mechanical ventilator (Nellcor-Puritan-Bennett 7200ae) in the PSV mode. In random order, we compared pressure triggering of -0.5 H2O, pressure triggering -1 cm H2O, flow triggering of 5/2 L/min, and flow triggering 10/3 L/min. Pressure was measured for 5 min at the proximal endotracheal tube using a data acquisition rate of 100 Hz. From the airway pressure signal, trigger pressure (deltaP) was defined as the difference between positive end-expiratory pressure (PEEP) and the maximum negative deflection prior to onset of the triggered breath. Pressure-time product (PTP) was defined as the area produced by the pressure waveform below PEEP during onset of the triggered breath. Trigger time (deltaT) was defined as the time interval below PEEP during onset of the triggered breath. RESULTS: A pressure trigger of -0.5 cm H2O was significantly more sensitive than the other trigger methods for deltaP, PTP, and deltaT (p<0.001). There was also a significant difference between patients for deltaP, deltaT, and PTP for each trigger method (p<0.001). CONCLUSIONS: For this group of patients, flow triggering was not superior to pressure triggering at -0.5 cm H2O during PSV.

Acute Disease↗
PubMed1997

Employee perceived stress. Relationship to the development of repetitive strain injury symptoms.

Repetitive strain injuries (RSIs), specifically carpal tunnel syndrome, are the fastest growing type of occupational injury. Research about precipitating factors and prevention has been controversial and inconclusive. Preventive measures typically have addressed ergonomic changes. The purpose of this research article is to describe the effects of several variables on the perceived development of RSI symptoms, particularly those of carpal tunnel syndrome. Emphasis was placed on the role of perceived stress. The study design was a descriptive survey using a nonprobability sampling method. The study focused on four variables related to perceptions of symptoms: 1) perceptions of level of knowledge related to the prevention of RSIs; 2) taking a specific action to make one's workstation more ergonomically correct; 3) perceptions of having ergonomically correct workstations; and 4) perceptions of being stressed. Study results indicated that perceived stress was significantly associated with perceived RSI symptoms. Workers who use a computer 4 or more hours per day reported significantly more symptoms than those who did not. At risk computer users who perceive an ergonomically correct workstation reported fewer symptoms. To prevent RSIs, occupational health nurses must address ergonomics, stress levels, and knowledge levels.

Adult↗
PubMed1997

Delivery systems for inhaled nitric oxide.

From a practical standpoint, technical issues related to NO delivery are as important as therapeutic issues. The benefits can be appreciated only if a reliable delivery system is used. Further, hazards and toxicity may be more problematic with an unreliable delivery system. It is incumbent on clinicians using inhaled NO to ensure that the delivery system is safe and reliable.

Administration, Inhalation↗