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Biomedical subjects

I J Dunn

Publications and source records attributed to I J Dunn.

18 recordsLinked to original sources
PubMed1999

Modeling of enzymatic reactions in vesicles: the case of alpha-chymotrypsin.

The kinetic behavior of the alpha-chymotrypsin-catalyzed hydrolysis of the two p-nitroanilide substrates succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide (Suc-Ala-Ala-Pro-Phe-pNA) and benzoyl-L-Tyr-p-nitroanilide (Bz-Tyr-pNA) was modeled and simulated for two different systems, namely for an aqueous solution and for a vesicle system, which was composed of phospholipid vesicles containing entrapped alpha-chymotrypsin. In the case of the vesicles, the substrate was added to the bulk, exovesicular aqueous phase. The experimentally determined time-dependence of product (p-nitroaniline) formation was modeled by considering the kinetic behavior of the enzyme and-in the case of vesicles-the substrate permeability across the bilayer membrane. In aqueous solution-without vesicles-the kinetic constants kcat and KS (respectively KM) were determined from fitting the model to experimental data of batch product concentration-time curves. The results were in good agreement with the corresponding values obtained from initial velocity measurements. For the vesicle system, using the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), simulation showed that the substrate permeation across the bilayer was rate limiting. Using experimental data, we could obtain the substrate permeability coefficient for Bz-Tyr-pNA by parametric fitting as 2. 45 x 10(-7) cm/s.

Animals↗
PubMed1998

Filarial diseases.

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Diagnosis, Differential↗
PubMed1998

Malaria.

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Diagnosis, Differential↗
PubMed1998

Toxoplasmosis.

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AIDS-Related Opportunistic Infections↗
PubMed1998

Sparganosis.

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Brain Diseases↗
PubMed1998

Babesiosis.

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Animals↗
PubMed1994

The value of open lung biopsy in immunocompetent patients with community-acquired pneumonia requiring hospitalization.

OBJECTIVE: To determine the role of open lung biopsy in immunocompetent patients with community-acquired pneumonia who require hospitalization. DESIGN: A group of 1,118 patients with severe community-acquired pneumonia that required hospitalization were enrolled in the study. Of the patients, 26 underwent open lung biopsy. Another 18 of these patients were immunocompromised and were excluded from this segment of the study. SETTING: Tertiary care 800-bed hospital from November 1981 to May 1989. RESULTS: Progressive diffuse pulmonary infiltrates and negative conventional cultures were the indications for biopsy in most of these patients. Eighteen (69 percent) were immunocompromised. The eight immunocompetent patients underwent a retrospective review of their course in hospital. Three patients died. The diagnostic yield from open lung biopsy was 25 percent. A specific histologic diagnosis was made in one patient--lipoid pneumonia. The pulmonary histologic finding were nonspecific in the remaining patients, but in four, in combination with the clinical data, gave useful information and resulted in therapy change. Culture of a pulmonary tissue yielded cytomegalovirus in one other patient. Serologic testing had a low yield in this group with three patients having a positive result. CONCLUSIONS: Open lung biopsy is rarely necessary in immunocompetent patients with community-acquired pneumonia. In a small group of patients where it is necessary, however, both positive and negative results are important in directing therapy.

Adult↗
PubMed1993

The complementary role of hepatobiliary scintigraphy and abdominal sonography in a patient with a hepatic cyst and suspected acute cholecystitis.

A 51-year-old woman was admitted with suspected acute cholecystitis. A large hepatic cyst was found incidentally by abdominal sonography, which displaced an "abnormal" gallbladder. Hepatobiliary scintigraphy visualized the gallbladder and excluded acute cholecystitis, but required the anatomic information from sonography to verify the abnormal location of the gallbladder. Additionally, scintigraphy showed the cyst not to communicate with the biliary tract. Pathologic findings revealed mild chronic cholecystitis and a simple mesothelial hepatic cyst. This case illustrates the complementary role of hepatobiliary scintigraphy and abdominal sonography in patients with distorted hepatobiliary anatomy and suspected acute cholecystitis.

Acute Disease↗
PubMed1988

Mast cell protease release and mucosal ultrastructure during intestinal anaphylaxis in the rat.

Intestinal anaphylaxis is associated with disturbances in gut function that are antigen-specific and dependent on mast cell degranulation. Using an animal model of intestinal anaphylaxis, we have correlated alterations in water and electrolyte transport, associated with intraluminal challenge, with specific intestinal mucosal mast cell degranulation by following systemic as well as local release of rat mast cell protease II. This protease is specific for intestinal mucosal mast cells and is known to selectively attack type IV collagen, which is found in basement membranes. Intraluminal antigen challenge in sensitized animals dramatically increased serum and intraluminal levels of rat mast cell protease II. Serum levels continued to rise throughout the duration of antigen challenge. Although light microscopy of challenged intestine demonstrated little distortion of mucosal architecture, ultrastructural examination revealed significant disruption to the basement membrane and underlying collagenous matrix of the intestinal mucosa. Our findings indicate that during mucosal immunoglobulin E-mediated reactions, rat mast cell protease II is released and is associated with ultrastructural changes in the intestinal mucosa. The systemic appearance of this specific protease provides a serum marker of intestinal anaphylaxis.

Anaphylaxis↗
PubMed1987

The response of the intestinal epithelium in B10.A mice to infection with Trichinella spiralis.

Previous studies on intestinal trichinosis have dealt mainly with areas other than the intestinal epithelium. Since the epithelium is now known to be the parasite's habitat, its response to infection is important. Infection with Trichinella spiralis in immunologically slow-responding B10.A mice was associated with crypt hyperplasia and villus atrophy. With similar infection levels in both primary and challenge infections, there was no difference in the maximal degree of atrophy or hyperplasia between the 2 groups. However, challenged mice underwent these mucosal changes in about half the time. Expulsion of worms always occurred during regeneration of the intestinal epithelium suggesting that the host's defense mechanism of altering the kinetics of the epithelium was not the prime factor causing expulsion. Pulse labelling of enterocytes with [3H] thymidine showed that there was no significant increase in the relative size of the proliferation zone. This indicates that the crypt cell output was not altered by this parasite. Atrophy of the villus was analysed with respect to its 3-dimensional shape. There was a decrease in both height and width of the villus but not thickness. Thus, there is a real decrease in the size of the enterocyte population per villus. Histochemical staining of the enterocyte brush border by an alkaline phosphatase method showed that (1) hyperplastic crypts have an enlarged maturation zone and (2) the villus epithelium is composed entirely of mature cells. The distribution of the nematode population was compared to these changes in the intestine. Trichinella spiralis showed a marked anteriad (distal to proximal) migration prior to expulsion. Thus, utilizing a novel approach to study intestinal trichinosis, the response of the mucosal epithelium has been characterized.

Alkaline Phosphatase↗
PubMed1985

Cell injury caused by Trichinella spiralis in the mucosal epithelium of B10A mice.

Most of the mucosal epithelium in the anterior small intestine of B10A mice infected with Trichinella spiralis showed no cytopathology. However, isolated foci of damaged cells or dense masses of multinucleate cytoplasm were seen in the crypt-villus junction, or the base of the villi. Cells occupied by the nematode ranged from a nearly normal appearance, showing only compressed nuclei and organelles, to progressive inflation and vesiculation of endoplasmic reticulum, loss of terminal web and hence disoriented and reduced microvilli, and pycnosis of nuclei. Damaged cells and multinucleate cytoplasmic masses may be derived from the cells previously occupied by the nematode that were linked together by fusion of their lateral cell membranes. Damaged cells and multinucleate masses are apparently sloughed from the epithelium at the villus base without migrating up the villi. Eosinophils were seen in the lamina propria, in the mucosal epithelium (usually associated with damaged cells) and in the intestinal lumen (also with damaged cells). As no eosinophils were seen in contact with the nematode, their activities may be related more to the cells killed by the worm than to the worm itself.

Animals↗
PubMed1977

The tubular loop fermentor: oxygen transfer, growth kinetics, and design.

Oxygen transfer measurements using a dynamic method and evaluated with an appropriate mathematical model have been made on a tubular loop bioreactor, Correlations of the type used in tank systmes are used to describe the influence of power and aeration rate on the mass transfer coefficient. Yeast cultures grown on hydrocarbon and glucose substrates show growth characteristics similar to conventional tank results. Model considerations for large-scale tubular fermentors allow for the prediction of the steady-state oxygen profiles and maximum reactor length. Combination with two-phases flow and oxygen transfer correlations yields a design procedure for commercial scale tubular loop fermentors.

Absorption↗