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Biomedical subjects

K M Hanson

Publications and source records attributed to K M Hanson.

9 recordsLinked to original sources
PubMed1992

Solvent and temperature effects on the excited singlet state absorption of diphenylbutadiene.

Nanosecond excited state absorption spectra of all-trans-1,4-diphenyl-1,3-butadiene (DPB) and a rigid s-cis DPB analog, 1,4-diphenyl-1,3-cyclopentadiene, were obtained in several hydrocarbon solvents at room temperature and low temperatures. Analysis of the excited state absorption spectra of these two molecules suggests the presence of excited state s-cis rotamers in DPB at room temperature.

Butadienes↗
PubMed1991

Optimization of the constrained Algebraic Reconstruction Technique for the performance of a variety of visual tasks.

This work demonstrates the application of a method to optimize image reconstruction algorithms on the basis of the performance of specific visual tasks that are to be accomplished using the reconstructed images. The evaluation of task performance is numerically realized by a Monte Carlo simulation of the complete imaging chain, including the final inference based on the reconstructions. Fundamental to this evaluation is that it yields an average response by consideration of many initial scenes. It is shown that the use of the nonnegativity constraint in the Algebraic Reconstruction Technique can significantly improve performance in situations where there is a severe lack of measurements when the relaxation factor is optimized. There is no indication in any of the cases studied hitherto that the nonnegativity constraint can improve performance in situations where the data are complete, but noisy. It is also shown that neither the rms error nor the L1 error in constrained reconstructions are good predictors of task performance.

Algorithms↗
PubMed1977

Treatment of severe drug overdosage with charcoal hemoperfusion.

Mortality from severe poisoning remains excessively high in patients managed conservatively. In this report, charcoal hemoperfusion was used as a therapeutic aid to active drug removal in 10 patients (9 of whom were in Grade IV coma) intoxicated with a variety of drugs and a further 3 patients poisoned with the highly lethal herbicide, paraquat. All 10 patients who ingested drugs recovered. One of the 3 patients ingesting paraquat survived. The hemoperfusion treatments were associated with demonstrated drug removal. Complications associated with hemoperfusion were minor. Decreases in platelet levels were observed but were not accompanied by clinically important bleeding. The technique of hemoperfusion is simple and provides a therapeutic aid in the care of the severely poisoned patient.

Adolescent↗
PubMed1977

Species specificity and other aspects of chymotrypsin inhibition by plasma.

The inhibition of chymotrypsin activity by pig, dog, human and rat blood plasma was studied. N-Benzoyl-L-tyrosyl-p-amino-benzoate (PABA-peptide) was used as the substrate. Crystalline bovine chymotrypsin as well as activated lyophilized human, pig, rat and chicken pancreatic secretions were used as enzyme sources. Certain species differences were noted. Swine plasma had no effect on bovine or human chymotrypsin while it inhibited that of the chicken by 67%. Dog plasma was a potent inhibitor of chymotrypsin activity from all sources tested. An acute pancreatitis model using the rat was also developed in which pancreatic juice flow was blocked without interference with biliary flow. After 24 h, these animals had increased plasma amylase activity, decreased plasma protease inhibitor and decreased hematocrit. By 72 h, amylase, trypsin inhibitor and hematocrit had nearly recovered while chymotrypsin inhibitor had actually increased above control levels. In rats subjected to hepatectomy or to hepatectomy plus pancreatic blockage, plasma protease inhibitor was even more severely depressed and remained so.

Acute Disease↗
PubMed1976

A new substrate for the rapid evaluation of enteric microbial overgrowth.

The possibility of a new approach to diagnosis of intestinal bacterial overgrowth has been evaluated in laboratory animals. The diagnostic test involves oral administration of an enzyme-labile substrate consisting of para-aminobenzoic acid (PABA) conjugated to a bile acid. In the presence of enteric bacteria, PABA is split from the bile acid and is rapidly absorbed and excreted in the urine. The amount of PABA recovered during the 6 hr following the administered dose of the conjugate may be used as an index of bacterial overgrowth in the upper-gastrointestinal tract. The procedure has been shown to be a reliable index of this condition in laboratory animal models.

Aminobenzoates↗
PubMed1976

Splanchnic vascular responses to the infusion of prostaglandins A1, A2 and B1.

The effects of PGA1, PGA2 and PGB1 on the vasculature of the liver and small intestine were studied in 73 dogs. Infusions were made into a branch of the superior mesenteric artery, the hepatic artery, portal vein or femoral vein. They decreased systemic arterial pressure and dilated the hepatic arterial and prehepatic splanchnic (small intestinal) vascular beds, PGA being most active. Dilator response was not decreased by beta-adrenergic blockade. Compounds appear to be inactivated by liver and decreased systemic pressure less when infused directly into liver circulation. Dilator response was transient, particulary in small intestine, and abated or even converted to constriction when infusion was continued for a period of time. Intrahepatic portal venous vasculature appeared to be constricted by PGA.

Animals↗
PubMed1975

Hepatic, vascular and biliary responses to infusion of gastrointestinal hormones and bile salts.

The effects of secretin, cholecystokinin, synthetic pentagastrin, sodium dehydrocholate and sodium taurocholate on hemodynamics of the canine liver were studied in a total of 57 dogs. Bile flow was also measured. Dehydrocholate and cholecystokinin significantly decreased systemic arterial pressure while the other substances did not. Hepatic arterial vessels were dilated by pentagastrin and the bile salts; however, flow was not increased in the latter case. Intraheptic portal venous resistance was decreased by pentagastrin and increased by the bile salts. Portal flow was decreased by the bile salts and increased by pentagastrin. Apart from this, mean changes in portal venous flow and portal pressure were not statistically significant. All were potent choleretic agents except pentagastrin which produced only a relatively small transient increase in bile flow.

Animals↗
PubMedDate not supplied

Detectability in computed tomographic images.

The detection limitations inherent in statistically limited computed tomographic (CT) images are described through the application of signal detection theory. The detectability of large-area, low-contrast objects is shown to be chiefly dependent upon the low-frequency content of the noise power spectral density. For projection data containg uncorrelated noise, the resulting ramplike, low-frequency behavior of the noise power spectrum of CT reconstructions may be conveniently characterized by the number of noise-equivalent x-ray quanta (NEQ) detected in the projection measurements. The NEQ for a given image may be determined either from a measurement of the noise power spectrum or from the noise granularity computed with an appropriate weighting function. A measure of the efficiency of scanner dose utilization is proposed which compares the average dose to that required by an ideal scanner to obtain the same NEQ.

Humans↗