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Biomedical subjects

B Burgess

Publications and source records attributed to B Burgess.

At least 19 recordsLinked to original sources
PubMed2004

Early phase process scale-up challenges for fungal and filamentous bacterial cultures.

Culture pelleting and morphology has a strong influence on process productivity and success for fungal and filamentous bacterial cultures. This impact is particularly evident with early phase secondary metabolite processes with limited process definition. A compilation of factors affecting filamentous or pelleting morphology described in the literature indicates potential leads for developing process-specific control methodologies. An evaluation of the factors mediating citric acid production is one example of an industrially important application of these techniques. For five model fungal and filamentous bacterial processes in an industrial fermentation pilot plant, process development strategies were developed and effectively implemented with the goal of achieving reasonable fermentation titers early in the process development cycle. Examples of approaches included the use of additives to minimize pelleting in inoculum shake flasks, the use of large-volume frozen bagged inoculum obtained from agitated seed fermentors, and variations in production medium composition and fermentor operating conditions. Results were evaluated with respect to productivity of desired secondary metabolites as well as process scalability. On-line measurements were utilized to indirectly evaluate the cultivation impact of changes in medium and process development. Key laboratory to pilot plant scale-up issues also were identified and often addressed in subsequent cultivations.

Bacteria↗
PubMed2001

Carbon and complex nitrogen source selection for secondary metabolite cultivation at the pilot scale.

The fermentation of desmethyl-asterriquinone B-1, a diabetes target, by a Pseudomonasarias species was conducted at the 600-l scale using a revised complex medium containing yeast extract and soy hydrolysate. Oat flour and tomato paste were removed from this medium due to difficulties in sterilization. An initial cerelose charge of 40 g/l improved titer and reduced product degradation in the broth at cultivation conditions. An initial mannitol concentration of 65 g/l effectively avoided mid-cycle mannitol additions necessary for the 40 g/l mannitol concentration without the reduction in productivity seen at 90 g/l mannitol. These additions diluted the broth because of the low aqueous solubility of mannitol. Titers reached 3.0 g/l after 158 h with an optimized process, increasing two-fold from the original medium and operating conditions. Reproducible foaming occurred at the point of glucose exhaustion when the culture switched to mannitol consumption. Use of alternative carbon sources (glycerol, soybean oil, sorbitol in conjunction with cerelose) was not effective in attaining similar productivity and did not reduce the extent of foaming. In the case of fructose, the extent of foaming was markedly reduced but product formation was negligible.

Journal Article↗
PubMed2000

Reproductive decisions after neonatal screening identifies cystic fibrosis.

AIMS: To document the reproductive choices made by women in New South Wales, Australia, after neonatal screening has identified cystic fibrosis (CF). METHODS: A sample of women attending cystic fibrosis clinics in New South Wales who had a child (or children) diagnosed by neonatal screening between 1981 and 1996 were interviewed. RESULTS: Two thirds of the women chose to avoid having another child with CF. The uptake of prenatal diagnosis was 66% in women who had a subsequent pregnancy; of these 69% terminated or would have terminated an affected fetus. Fifty nine per cent of the women who decided against a further pregnancy made this decision in order to avoid having another child with CF. CONCLUSIONS: These data show that having a child with CF influenced subsequent reproductive choices. In addition to the medical advantages of an early diagnosis offered by neonatal screening, this also allows informed future reproductive decisions.

Cystic Fibrosis↗
PubMed1999

Production of a family of kinase-inhibiting lactones from fungal fermentations.

During the course of our screening for natural products from fungi, extracts of several cultures were found to make a family of related resorcylic acid lactone compounds, which are potent inhibitors of MEK kinase. Comparative and empirical studies of fermentation conditions improved the titers of the compounds of interest. Striking changes in the ratios and amounts of the major and minor compounds in some cases were achieved by manipulations of media composition.

Culture Media↗
PubMed1999

Clinics go electronic: two stories from the field.

We hear a lot about computerized record system implementations in hospitals, but other settings are making the transition as well. How does the move to an electronic record system affect day-to-day operations in clinics? Our writers tell how a student health center and a family clinic did it--and how they're working now.

Ambulatory Care Information Systems↗
PubMed1997

Perforated duodenal ulcer presenting with shock in a child.

Presentation of peptic ulcer disease in children covers a broad spectrum ranging from subtle, and thus overlooked and underdiagnosed, to catastrophic, as in this case. It is important for the emergency physician to realize the potential morbidity and mortality of this disease and be aware of the spectrum of presentation for primary and secondary pediatric ulcer disease.

Abdomen, Acute↗
PubMed1995

A case of pneumatosis coli managed by restorative proctectomy and ileal pouch-anal anastomosis.

Pneumatosis coli is a rare condition in which gas filled cysts occur in the wall of the intestines. Most symptomatic patients can be managed conservatively but those who fail medical management or who develop bowel obstruction will require surgery. Surgery usually involves a limited colectomy with a potential for recurrence. We describe a case of pneumatosis coli managed successfully by restorative proctocolectomy and ileal pouch-anal anastomosis.

Anastomosis, Surgical↗
PubMed1994

Overexpression of ferredoxin I in Azotobacter vinelandii.

Azotobacter vinelandii has recently been used for a variety of genetic experiments which take advantage of its facile transformation system and its high-frequency homologous recombination. One gene that has been cloned and sequenced is the fdxA gene that encodes a small Fe-S protein called A. vinelandii ferredoxin I (AvFdI). Because this protein has been extensively characterized by X-ray crystallography and spectroscopic methods, we are using it as a model to address some general questions in Fe-S biochemistry. AvFdI is not a very abundant protein in wild-type cells, so to facilitate our biochemical studies we have developed the overexpression system described herein. The results show that AvFdI can be easily overproduced ca. 50-fold in its native background, by introducing multiple copies of the fdxA gene into A. vinelandii, on the broad-host-range multicopy plasmid, pKT230. The protein can be expressed from its own constitutive promoter or from the controlled nifH promoter. The overproduced protein has no deleterious effects on the organism and is identical to the protein produced by wild-type cells. This A. vinelandii-based system should be generally useful for the overproduction of other A vinelandii proteins or for the expression of genes from thermophilic or other organisms with similarly high G-C contents, or for the expression of O2-sensitive metalloproteins that are unstable in other systems.

Azotobacter vinelandii↗
PubMed1991

Characterization of cultured alveolar epithelial cell xanthine dehydrogenase/oxidase.

Conversion of xanthine dehydrogenase (XDH) to xanthine oxidase (XO) and the toxic reactions of subsequent XO-derived superoxide, hydrogen peroxide and hydroxyl radical, have been suggested to be critical factors in several mechanisms of tissue pathophysiology. In the lung, intracellular XO-derived products may modulate type II pneumocyte surfactant turnover and barrier function, jeopardizing the pulmonary air-blood barrier. We characterized total cellular XDH/XO enzymatic activity in freshly isolated and cultured rat pulmonary type II epithelial cells. Type II cells were isolated and cultured on fibronectin-pretreated dishes, with a plating efficiency after 36 h in culture of 40% or 14% when quantified via cellular protein or DNA, respectively. Over the subsequent 96 h in culture, monolayer DNA was unchanged, whereas protein per cell increased continuously. Alterations in different cellular enzymatic activities were also detected in these cultured cells. In culture, total cellular XDH/XO and catalase activities decreased in a logarithmical fashion with respect to time, whether normalized for cellular protein or DNA. The rate of loss of these enzymes was greatest when normalized for cell protein, but was also significant when the activities were normalized for DNA. When compared to freshly isolated type II cells, catalase and total XDH/XO activities normalized for protein decreased 78% and 72%, respectively, during the first 36 h of culture. After 132 h in culture, XDH/XO and catalase activities normalized for protein decreased 93% and 84%, respectively, when compared to freshly isolated cell values. Total cellular XDH/XO activity in the oxidase form (% XO) was initially 31% in freshly isolated type II cells and increased to 67% during the 132 h culture period. In contrast to the loss of total cellular XDH/XO and catalase, no significant change in lactate dehydrogenase (LDH) activity occurred during culture of the type II cells. In type II cells the conversion of XDH to XO, the cytotoxic potential of XO, and the activity of the hydrogen peroxide scavenger, catalase, is expected to be strongly influenced by in vitro culture. Thus, strong consideration should be made before transposing information obtained from cultured type II cells to in vivo situations.

Analysis of Variance↗
PubMed1985

A study of postmortem autolysis in the human organ of Corti.

Forty-six human temporal bones from 24 individuals were removed at autopsy and prepared for electron microscopy. The adequacy of histologic preservation was evaluated by light and electron microscopy. Characteristic autolytic changes included vacuolization of afferent neurons and neural poles of inner and outer hair cells, lysis of limiting membranes of hair and supporting cells, swelling of endoplasmic reticulum, and dissolution of mitochondrial cristae. The rate of autolysis varied significantly within cellular components of the inner ear. The neural poles of hair cells demonstrated more rapid autolysis than apical poles and nerve terminals showed more autolysis than myelinated nerve fibers. Postmortem time and the cause of death affected the adequacy of histologic preservation. Fixation in patients dying of pneumonia, hypoxia, head injury, or malignancy tended to be poor, whereas the fixation achieved in patients dying of cardiac disease with postmortem time of under 140 minutes was generally good.

Autolysis↗
PubMed1982

Cochleosaccular degeneration of the inner ear and progressive cataracts inherited as an autosomal dominant trait.

A new syndrome of cataracts and progressive sensorineural hearing loss, inherited as an autosomal dominant trait, is described. The histopathology of the inner ears in the proband demonstrated severe degeneration limited to the cochlea and saccule. This case represents the second reported example of genetically determined cochleosaccular degeneration in man. The cochleosaccular pattern of histopathology is found in both man and animals and may be the end result of prenatal dysplasia or postnatal degeneration. It also appears that cochleosaccular dysplasia and degeneration may be the result of genetically determined or acquired defects. Previously reported examples of cochleosaccular dysplasia and degeneration are reviewed including human cases in which the histopathology is similar to, but not characteristic of, the cochleosaccular pattern.

Adolescent↗
PubMed1975

Depressed cell-mediated immunity in megaloblastic anemia due to folic acid deficiency.

Cell-mediated immunity has been studied in patients with 1) megaloblastic anemia of folic acid deficiency, 2)megaloblastic anemia of pregnancy, or 3) iron-deficiency anemia. Using dinitrochlorobenzene skin tests, phytohemagglutinin-stimulated lymphocyte transformation, and rosette inhibition by antilymphocyte globulin, we have shown that cell-mediated immunity is depressed in megaloblastic anemia due to folate deficiency; this depression was reversed by folate treatment. Cell-mediated immunity was not impaired by iron-deficiency anemia. Suggested interactions between iron deficiency and folate metabolism were not clarified by these studies.

Adolescent↗