PubMed Health⌕ Search

Biomedical subjects

L D Nelson

Publications and source records attributed to L D Nelson.

At least 19 recordsLinked to original sources
PubMed2001

Handling and culture of bovine embryos: survey of media used by 26 embryo transfer companies in the USA.

Embryo transfer has evolved from a few highly centralized clinics to a widespread number of clinics offering both clinic and on-the-farm services. Practitioners in the field have made very few changes in the handling and culture of embryos. A short review of general handling techniques, plus a survey of media used by 26 companies in the USA, is presented here. Currently, phosphate-bufferend saline (PBS) plus two other commercially available media (EMCARE and ViGro) are used by these companies. Fourteen different combinations of these products were reported and only 11 of the 26 consistently used the same medium for flushing, culture and freezing.

Animals↗
PubMed2001

Neurological changes and emotional functioning in adults with Down Syndrome.

This study was designed to examine emotional changes in adults with Down Syndrome (DS) over time and whether changes in these psychological variables were associated with brain atrophy on MRI scan and the presence of pathological reflexes on the neurological examination. Participants were 26 adults with DS and their caregivers. Caregivers completed a measure of emotional functioning about individuals with DS at two different time points (1 year apart). Levels of cognitive functioning were measured and neurological and MRI examinations were performed on all subjects at initial testing. Significant group effect separated those with and without pathological findings on MRI and neurological exam across three different scales: depression, indifference, and pragmatic language functioning. Problems of poor pragmatic language functioning appeared later in the course of suspected Alzheimer's disease (AD), as demonstrated by a significant group effect at time 2, but not at initial testing. In these subjects, the primary emotional change was a decline in social discourse (e.g. conversational style, literal understanding, verbal expression in social contexts). These emotional levels were stable over time, regardless of degree of cognitive decline. Specific emotional changes occur during the course of AD which were associated with abnormal findings from MRI and from neurological examination. These results, along with abnormalities in brain imaging and the presence of pathological reflexes, suggested that frontal lobe dysfunction is likely to be an early manifestation of Alzheimer's Disease in Down Syndrome.

Adult↗
PubMed2001

Mathematical coupling does not explain the relationship between right ventricular end-diastolic volume and cardiac output.

OBJECTIVE: To evaluate the clinical significance of mathematical coupling on the correlation between cardiac output and right ventricular end-diastolic volume (RVEDV) through measurement of cardiac output by two independent techniques. DESIGN: Prospective, observational study. SETTING: Surgical intensive care unit in a level 1 trauma center. PATIENTS: Twenty-eight critically ill surgical patients who received mechanical ventilation and hemodynamic monitoring with a pulmonary artery catheter. INTERVENTIONS: A pulmonary artery catheter designed to measure right ventricular ejection fraction (RVEF) and cardiac output by the intermittent bolus thermodilution (TDCO) method and continuous cardiac output by the pulsed thermal energy technique was placed. A computerized data logger was used to collect data simultaneously from the RVEF/TDCO system and the continuous cardiac output system. MEASUREMENTS AND MAIN RESULTS: Two hundred forty-nine data sets from 28 patients were compared. There is statistical correlation between TDCO and continuous cardiac output measurements (r = 0.95, p < 0.0001) with an acceptable bias (-0.11 L/min) and precision (+/-0.74 L/min). The correlation was maintained over a wide range of cardiac outputs (2.3-17.8 L/min). There is a high degree of correlation between RVEDV and both TDCO (r = 0.72, p < 0.0001) and independently measured continuous cardiac output (r = 0.68, p < 0.0001). These correlation coefficients are not statistically different (p = 0.15). CONCLUSIONS: The continuous cardiac output technique accurately approximates cardiac output measured by the TDCO method. RVEDV calculated from TDCO correlates well with both TDCO and independently measured continuous cardiac output. Because random measurement errors of the two techniques differ, mathematical coupling alone does not explain the correlation between RVEDV estimates of preload and cardiac output.

Adult↗
PubMed2001

Percutaneous dilational tracheostomy: a comparison of single- versus multiple-dilator techniques.

OBJECTIVE: To compare the safety and efficacy of single- vs. multiple-dilator techniques in the performance of percutaneous dilational tracheostomy. DESIGN: Prospective randomized trial. SETTING: Intensive care units at a level 1 trauma center. PATIENTS: Fifty consecutive patients requiring tracheostomy for airway control or prolonged mechanical ventilatory support. INTERVENTIONS: Patients were randomized to receive a percutaneous dilational tracheostomy by either the single- or multiple-dilator technique described by Ciaglia. MEASUREMENTS AND MAIN RESULTS: Percutaneous dilational tracheostomy was performed using the single-dilator technique in 6:01 +/- 3:03 mins and by the multiple-dilator technique in 10:01 +/- 4:26 mins (p <.0006). There were no statistically significant differences in complication rates between the two techniques. No major complications occurred with either technique. CONCLUSION: The single-dilator percutaneous tracheostomy technique is a safe, cost-effective, and more rapidly performed method for bedside tracheostomy in the intensive care unit.

Adult↗
PubMed2000

The yeast STM1 gene encodes a purine motif triple helical DNA-binding protein.

The formation of triple helical DNA has been evoked in several cellular processes including transcription, replication, and recombination. Using conventional and affinity chromatography, we purified from Saccharomyces cerevisiae whole-cell extract a 35-kDa protein that avidly and specifically bound a purine motif triplex (with a K(d) of 61 pM) but not a pyrimidine motif triplex or duplex DNA. Peptide microsequencing identified this protein as the product of the STM1 gene. Confirmation that Stm1p is a purine motif triplex-binding protein was obtained by electrophoretic mobility shift assays using either bacterially expressed, recombinant Stm1p or whole-cell extracts from stm1Delta yeast. Stm1p has previously been identified as G4p2, a G-quartet nucleic acid-binding protein. This suggests that some proteins actually recognize features shared by G4 DNA and purine motif triplexes, e.g. Hoogsteen hydrogen-bonded guanines. Genetically, the STM1 gene has been identified as a multicopy suppressor of mutations in several genes involved in mitosis (e.g. TOM1, MPT5, and POP2). A possible role for multiplex DNA and its binding proteins in mitosis is discussed.

Arginine↗
PubMed2000

Clinical and research implications of revising psychological tests.

This article integrates those of other contributors to this special section, "Methods and Implications of Revising Assessment Instruments," to underscore important conceptual factors to consider when undertaking test revisions. These considerations include determination of when test measures have become sufficiently understood to be incorporated in a test revision, cohort effects, revision of administration formats and test instructions, and comparisons of performance levels across test versions. The discussion of these factors also takes into consideration clinical practice and educational implications of making a transition to revised test versions.

Humans↗
PubMed1999

Preload assessment in patients with an open abdomen.

BACKGROUND: Intra-abdominal hypertension and abdominal compartment syndrome cause significant morbidity and mortality in surgical and trauma patients. Maintenance of intravascular preload and use of open abdomen techniques are essential. The accuracy of pulmonary artery occlusion pressure (PAOP) and central venous pressure (CVP) in patients with intra-abdominal hypertension has been questioned. METHODS: Twenty surgical and trauma patients with intra-abdominal hypertension requiring open abdominal decompression were monitored using volumetric thermodilution pulmonary artery catheters. Hemodynamic, oxygenation, inspiratory, and intravesicular pressure measurements were collected prospectively. PAOP, CVP, and right ventricular end-diastolic volume index (RVEDVI) were compared as estimates of preload status. RESULTS: Multiple regression analysis demonstrated that cardiac index correlated significantly better with RVEDVI (r = 0.69) than with PAOP (r = -0.27) or CVP (r = -0.28) during resuscitation after open abdominal decompression (p < 0.0001). CONCLUSION: RVEDVI is superior to PAOP and CVP as an estimate of preload status in patients with an open abdomen.

Adolescent↗
PubMed1999

Renal arteriolar Na+/Ca2+ exchange in salt-sensitive hypertension.

The present studies were performed to assess Na+/Ca2+ exchange activity in afferent and efferent arterioles from Dahl/Rapp salt-resistant (R) and salt-sensitive (S) rats. Renal arterioles were obtained by microdissection from S and R rats on either a low-salt (0.3% NaCl) or high-salt (8.0% NaCl) diet. On the high-salt diet, S rats become markedly hypertensive. Cytosolic calcium concentration ([Ca2+]i) was measured in fura 2-loaded arterioles bathed in a Ringer solution in which extracellular Na (Nae) was varied from 150 to 2 mM (Na was replaced with N-methyl-D-glucamine). Baseline [Ca2+]i was similar in afferent arterioles of R and S rats fed low- and high-salt diet. The change in [Ca2+]i (Delta[Ca2+]i) during reduction in Nae from 150 to 2 mM was 80 +/- 10 and 61 +/- 3 nM (not significant) in afferent arterioles from R rats fed the low- and high-salt diet, respectively. In afferent arterioles from S rats on a high-salt diet, Delta[Ca2+]i during reductions in Nae from 150 to 2 mM was attenuated (39 +/- 4 nM) relative to the Delta[Ca2+]i of 79 +/- 13 nM (P < 0.05) obtained in afferent arterioles from S rats on a low-salt diet. In efferent arterioles, baseline [Ca2+]i was similar in R and S rats fed low- and high-salt diets, and Delta[Ca2+]i in response to reduction in Nae was also not different in efferent arterioles from R and S rats fed low- or high-salt diets. Differences in regulation of the exchanger in afferent arterioles of S and R rats were assessed by determining the effects of protein kinase C (PKC) activation by phorbol 12-myristate 13-acetate (PMA, 100 nM) on Delta[Ca2+]i in response to reductions in Nae from 150 to 2 mM. PMA increased Delta[Ca2+]i in afferent arterioles from R rats but not from S rats. These results suggest that Na+/Ca2+ exchange activity is suppressed in afferent arterioles of S rats that are on a high-salt diet. In addition, there appears to be a defect in the PKC-Na+/Ca2+ exchange pathway that might contribute to altered [Ca2+]i regulation in this important renal vascular segment in salt-sensitive hypertension.

Animals↗
PubMed1999

Right heart volumetric monitoring: measuring preload in the critically injured patient.

Accurate assessment of preload status is a major concern in the resuscitation of the critically injured patient. Of the three physiologic determinants of stroke volume, preload is the variable that is most frequently influenced by an insult or intervention or both in the trauma patient. In the critically injured patient, clinicians focus on the preload status to restore and maintain intravascular volume in attempts to optimize cardiac output and oxygen delivery. Until recently, efforts to measure and optimize ventricular preload have focused on intracardiac filling pressures (central venous pressure and pulmonary artery occlusion pressure). The purpose of this review is to discuss the application of volumetric measurements that provide a more accurate means of determining recruitable ventricular preload in the critically injured patient.

Acute Disease↗
PubMed1999

Ingested endotracheal tube in an adult following intubation attempt for head injury.

General surgeons are often consulted for assistance in the management of ingested foreign bodies. Deglutition of an endotracheal tube is an unusual complication of airway management. In these cases, the artificial airway is "lost" when it becomes lodged deep into the esophagus. Endoscopic extraction has been described as therapeutic. We report a case in which prehospital endotracheal intubation attempt for the management of closed head injury resulted in a swallowed endotracheal tube. The tube remained undetected until radiographs were performed for a second unrelated traumatic event 2 years later. Endoscopic extraction was unsuccessful, due to rigidity of the tube. Surgical extraction via gastrotomy was uneventful. Surgeons involved in trauma and other emergency settings should be aware of this complication and options in management.

Adult↗
PubMed1998

Characterization of purine-motif triplex DNA-binding proteins in HeLa extracts.

One piece of evidence indicating that triple-helical DNAs exist in vivo would be the demonstration of cellular proteins that recognize such structures. Using oligonucleotide probes containing a GT-rich purine-motif triplex, proteins from either HeLa nuclear or cytoplasmic extracts and electrophoretic mobility shift assays, we identified four specific human protein-triplex complexes. Proteins in these complexes did not recognize an analogous homopurine/homopyrimidine duplex DNA or a pyrimidine-motif triplex but did recognize purine-motif triplexes regardless of whether they possessed a phosphodiester or phosphorothioate backbone in the third strand or involved A*AT instead of T*AT base triplets. For each of these proteins, binding affinity increased with increasing triplex length. For some triplex-binding proteins, a weak affinity was noted for individual G-rich oligonucleotides, though this may actually reflect an affinity for quadruplex structures, which these oligonucleotides are prone to adopt. Ion exchange chromatographic fractionation of HeLa nuclear extracts indicated that at least three different proteins were responsible for the observed electrophoretic mobility shifts. Southwestern blotting methods identified three major polypeptides, with apparent molecular masses of 100, 60, and 15 kDa, that preferentially recognized purine-motif triplexes. These data demonstrate the existence of eukaryotic proteins that specifically recognize one triplex motif and support the idea of a biological role for triple helical DNA.

Binding, Competitive↗
PubMed1998

Fibrinolytic agents inhibit platelet adhesion onto collagen type I-coated surfaces at high blood flow conditions.

The effect of fibrinolytic agents on platelet adhesion onto insolubilized collagen type I was evaluated. Normal human whole blood samples were incubated with agents and perfused over collagen-coated surfaces in a parallel-plate flow chamber. Platelet adhesion and aggregation were analyzed by video microscopy and image processing. When blood was perfused at 1500/s, both streptokinase and urokinase, each at 500 U/ml, caused a significantly less normalized platelet deposition, compared with controls. At 480/s, platelet deposition was not different between controls and test samples. Inhibition of platelet deposition at high flow rates was partly due to inhibition of platelet adhesion. Both ristocetin- and ADP-induced platelet aggregation were inhibited in test samples. The agents caused proteolytic degradation of plasma fibrinogen, but no degradation of platelet glycoproteins Ib and IIb-IIIa (GPIb and GPIIb-IIIa) and of plasma von Willebrand factor in test samples prior to perfusion. Post-perfusion von Willebrand factor degradation was not found. Plasmin may cause functional changes to plasma proteins and/or platelet receptors, altering their adhesive properties under flow. At high shear, fibrinogen degradation products may interfere with GPIIb-IIIa binding to insolubilized von Willebrand factor, leading to decreased platelet adhesion. Inhibition of platelet adhesion by thrombolytic agents could help maintain vessel patency after recanalization in stenosed arteries. Publishers.

Adenosine Diphosphate↗
PubMed1998

Right ventricular end-diastolic volume index as a predictor of preload status in patients on positive end-expiratory pressure.

OBJECTIVE: To evaluate the clinical utility of right ventricular end-diastolic volume index (RVEDVI) and pulmonary artery occlusion pressure (PAOP) as measures of preload status in patients with acute respiratory failure receiving treatment with positive end-expiratory pressure. DESIGN: Prospective, cohort study. SETTING: Surgical intensive care unit in a Level I trauma center/university hospital. PATIENTS: Sixty-four critically ill surgical patients with acute respiratory failure. INTERVENTIONS: All patients were treated for acute respiratory failure with titrated levels of positive end-expiratory pressure (PEEP) with the goal of increasing arterial oxygen saturation to > or =0.92, reducing FIO2 to <0.5, and reducing intrapulmonary shunt to < or =0.2. Serial determinations of RVEDVI, PAOP, and cardiac index (CI) were recorded. MEASUREMENTS AND MAIN RESULTS: Two hundred-fifty sets of hemodynamic variables were measured in 64 patients. The level of PEEP ranged from 5 to 50 cm H2O (mean 12+/-9 [SD] cm H2O). At all levels of PEEP, CI correlated significantly better with RVEDVI than with PAOP. At levels of PEEP > or =15 cm H2O, CI was inversely correlated with PAOP, but remained positively correlated with RVEDVI. CONCLUSIONS: CI correlates significantly better with RVEDVI than PAOP at all levels of PEEP up to 50 cm H2O. RVEDVI is a more reliable predictor of volume depletion and preload recruitable increases in CI, especially in patients receiving higher levels of PEEP where PAOP is difficult to interpret.

Acute Disease↗
PubMed1998

Personality change in head trauma: a validity study of the Neuropsychology Behavior and Affect Profile.

This study represents the first attempt to cross validate and report on the Neuropsychology Behavior and Affect Profile (NBAP) using closed head injury (CHI) participants. The NBAP is designed to measure emotional functioning before and following a brain event. Two CHI samples, differing primarily by method of ascertainment, were compared to a group of normal controls. Results provided support for concurrent and predictive validity of the NBAP across both CHI samples. Significantly higher levels of postinjury emotional functioning in clinic-referred CHI patients compared to CHI individuals not seeking treatment (strictly research participants) was demonstrated. A surprising finding was that pre-injury emotional levels of clinic-referred subjects were rated as less severe than that of controls. Based on this finding, the possibility of a gradient effect was discussed in which raters appeared to place selectively greater weight on current condition, while simultaneously making premorbid levels less severe than they really were. Results were discussed in the context of study limitations and directions for further research.

Journal Article↗