In vitro DNA labeling of bone marrow and leukemic blood leukocytes with tritiated thymidine. I. Physical and chemical factors which affect autoradiographic cell labeling.
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Animals↗
Biomedical subjects
S Keller
Publications and source records attributed to S Keller.
Mapping piezoelectric-field distribution in gallium nitride with scanning second-harmonic generation microscopy.
Taking advantage of the electric field-enhanced second-harmonic generation effect in bulk gallium nitride (GaN) and indium gallium nitride (InGaN) quantum wells, we demonstrated the piezoelectric field distribution mapping in bulk GaN and InGaN multiple-quantum-well (MQW) samples using scanning second-harmonic generation (SHG) microscopy. Scanning SHG microscopy and the accompanying third-harmonic generation (THG) microscopy of the bulk GaN sample were demonstrated using a femtosecond Cr:forsterite laser at a wavelength of 1230 nm. Taking advantage of the off-resonant electric field-enhanced SHG effect and the bandtail state-resonance THG effect, the second- and third-harmonic generation microscopic images obtained revealed the piezoelectric field and bandtail state distributions in a GaN sample. Combined with 720 nm wavelength excited two-photon fluorescence microscopy in the same sample, the increased defect density around the defect area was found to suppress bandedge photoluminescence, to increase yellow luminescence, to increase bandtail state density, and to decrease residue piezoelectric field intensity. Scanning SHG microscopy of the InGaN MQW sample was resonant excited with 800 nm femtosecond pulses from a Ti:sapphire laser in order to suppress SHG contribution from the bulk GaN substrate. Taking advantage of the strong piezoelectric field inside the InGaN quantum well, the wavelength resonant effect, and the electric field-enhanced SHG effect of InGaN quantum wells, resonant scanning SHG microscopy revealed the piezoelectric field distribution inside the wells. Combined with accompanying three-photon fluorescence microscopy from the bulk GaN substrate underneath the quantum wells, the direct correspondence between the piezoelectric field strength inside the quantum well and the substrate quality can be obtained. According to our study, the GaN substrate area with bright bandedge luminescence corresponds to the area with strong SHG signals indicating a higher stained-induced piezoelectric field. These scanning harmonic generation microscopies exhibit superior images of the piezoelectric field and defect state distributions in GaN and InGaN MQWs not available before. Combining with scanning multiphoton fluorescence microscopy, these techniques open new ways for the physical property study of this important material system and can provide interesting details that are not readily available by other microscopic techniques.
Journal Article↗
Relationship between peripheral intravenous catheter Dwell time and the development of phlebitis and infiltration.
The purpose of this study was to evaluate whether lengthening the dwell time of peripheral i.v. catheters from 72 hours to 144 hours resulted in increased rates of phlebitis and/or infiltration. The study was conducted in medical/surgical units at a 110-bed teaching hospital with an i.v. team. Kaplan-Meier estimates of the success and failure and conditional failure probabilities were calculated for phlebitis and infiltration scores. Log rank tests were used to test for an association between the covariates and the time until failure. Drug irritation was the most significant predictor of phlebitis and infiltration rates in this study. The total difference in the estimated failure rates for the catheter lasting 6 days versus a new catheter inserted for another 3 days is 1.3%. Because the conditional failure probability estimates for days 4, 5, and 6 are slightly higher than for days 1, 2, and 3, consideration may be given to extending the dwell time of a peripheral i.v. catheter beyond 72 hours under certain circumstances.
Adult↗
Pulmonary air-space enlargement induced by intratracheal instillment of hyaluronidase and concomitant exposure to 60% oxygen.
Although emphysema is generally characterized by damage to pulmonary elastic fibers, the causes of such injury appear to be complex and are not entirely explained by a singular imbalance between elastases and their inhibitors. Other factors could compromise elastic fiber integrity. To test the validity of this argument, hamsters were instilled intratracheally with a nonelastolytic enzyme, hyaluronidase (which reduces lung hexuronic acid content by 21% after 24 h), then exposed to an otherwise nontoxic concentration of oxygen (60%) for 4 days. Additional groups were given (1) hyaluronidase and room air, (2) saline and 60% oxygen, and (3) saline and room air. Treatment with both hyaluronidase and 60% oxygen resulted in a significant increase in air-space enlargement at 4 days (67.1 vs. 57.9 microns for saline/room air controls; p < .05), which was accompanied by only minimal inflammatory changes, as determined by both light microscopy and lavage cytology. Animals receiving either hyaluronidase or 60% oxygen alone showed no significant increases in air-space size compared to those given saline and exposed to room air. While the mechanisms responsible for these results are unclear, the marked increase in radiolabeling of lung elastin cross-links (desmosine and isodesmosine) in animals receiving both hyaluronidase and 60% oxygen (429 vs. 168 cpm/g dry lung for saline/room air controls; p < .05), as well as a significant decrease in total lung desmosine and isodesmosine (32.5 vs. 37.7 micrograms/lung for saline/room air controls; p < .05), suggests that elastic fiber damage is a potential factor. Moreover, only those animals receiving both hyaluronidase and 60% oxygen showed a significant rise in cell-free elastase activity in lavage fluids compared to saline/room air controls (83.3 vs. 48.3 ng; p < .05). On the basis of these findings, it is concluded that while elastic fiber damage may be a common pathway in emphysema, the factors that initiate the disease may be more varied than previously suspected and not always related to the balance between elastases and their inhibitors.
Animals↗
Modulation of airspace enlargement in elastase-induced emphysema by intratracheal instillment of hyaluronidase and hyaluronic acid.
The study examined how lung hyaluronic acid content influences airspace enlargement in elastase-induced emphysema. To determine the effect of a decrease in hyaluronic acid, hamsters received a single intratracheal instillment of hyaluronidase 24 h prior to administration of pancreatic elastase by the same route. One week later, these animals showed significantly greater airspace enlargement than controls sequentially instilled with saline and elastase (128 vs. 100 microns; p < .05). Conversely, intratracheal administration of hyaluronic acid immediately after elastase instillment resulted in a marked decrease in airspace enlargement at 1 week compared to controls receiving elastase followed by saline (82 vs. 122 microns; p = .005). Since hyaluronic acid has no elastase inhibitory capacity, its effect may involve extracellular matrix interactions not directly related to elastic fiber breakdown. This concept is supported by the finding that animals treated with hyaluronidase and elastase showed no greater loss of lung elastin than that observed in the saline/elastase control group, despite demonstrating a marked increase in airspace enlargement. Further work is needed to determine how hyaluronic acid influences airspace enlargement and to evaluate the potential use of this substance as a treatment for emphysema.
Animals↗
Personal pollen exposure compared to stationary measurements.
The aim of this study was to examine to what extent stationary outdoor pollen measurements are representative for estimating personal exposure to pollen. Ten subjects were studied during a total of 36 days in spring and summer Pollen was sampled using personal SKC total dust samplers and stationary Burkard pollen traps. The personal activity pattern was recorded quarter-hourly as well as the time spent outdoors. As a reference, SKC and Burkard samplers were run stationary and in parallel. Stationary comparison of the samplers showed good correlation (r = 0.981, p <0.001). However, the SKC sampler collected systematically about four times less pollen than the Burkard sampler. Taking into account the systematic difference between the sampling devices, the personal exposure data were about 30% of the stationary pollen concentrations with significant correlation (log-transformed data, r = 0.719, p <0.0001). Considering the average time the subjects spent outdoors (14% of sampling time), the indoor-outdoor ratio for pollen was 0.2. In conclusion, pollen reports are reliable for estimating personal exposure over a limited time period although personal pollen exposure is much lower.
Air Pollution↗
Neuropsychiatric manifestations of cardiovascular drug therapy.
Commonly used cardiovascular medications have neuropsychiatric effects, which can be either harmful or of therapeutic benefit to patients. For example, sedation and mental depression have been described with centrally acting antihypertensive drugs and beta-adrenergic drugs, and are related to their antiadrenergic actions. At the same time, because of these antiadrenergic actions, agents like clonidine have been used for treatment of opiate, alcohol, and nicotine withdrawal, and beta blockers have been used to treat performance anxiety and psychocardiac disorders. Antiarrhythmic drugs have been associated with delirium, and digitalis toxicity can be associated with hallucinations, mania, euphoria, and depression. Antiarrhythmic agents such as verapamil are used as adjunctive treatment for managing patients with bipolar disorders. Because neuropsychiatric disorders can be seen in patients with cardiovascular disease, it is important for the clinician to be aware of the possible relationships between these disorders and concurrent cardiovascular drug therapy. The neuropsychiatric actions of antihypertensive, antiarrhythmic, and hypolipidemic agents are discussed in this article.
Anti-Arrhythmia Agents↗