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Biomedical subjects

D Duncan

Publications and source records attributed to D Duncan.

At least 55 records · Page 3Linked to original sources
PubMed1993

A prospective study of dietary intake and acquired immune deficiency syndrome in HIV-seropositive homosexual men.

We prospectively studied the relationship between dietary intake at baseline and the development of AIDS over 6 years in a population-based sample of 296 human immunodeficiency virus (HIV)-seropositive men. Nutrient intake was assessed before HIV serostatus was known. Subjects diagnosed with AIDS at baseline or during the 1st year were excluded. After adjustment for baseline CD4 T-lymphocyte count, HIV symptoms, and other risk factors, no nutrients were significantly associated with AIDS. However, when the continuous CD4 count and HIV symptom variables were replaced with a single binary health status variable, the hazard of AIDS decreased as consumption increased for all 11 micronutrients; this relationship was statistically significant for iron, vitamin E, and riboflavin and approached significance for vitamins C, thiamine, and niacin. Higher intake of all 11 micronutrients was associated with higher CD4 counts at baseline, and was significantly so for six of them. Daily multivitamin use was associated with a reduced hazard of AIDS [hazard ratio (HR) = 0.7; 95% confidence interval (CI) = 0.5, 1.0] and a significantly reduced risk for low CD4 counts at baseline (HR = 0.6, 95% CI = 0.4, 0.9). Additional studies are needed to determine whether dietary intake modifies the rate of developing AIDS in those who are HIV seropositive.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Association between alcoholic and caffeinated beverages and premenstrual syndrome.

We examined the association between alcohol and caffeine consumption and premenstrual syndrome (PMS). One hundred two women with PMS matched by age and race to an equal number of women without PMS were compared for differences in intake of alcoholic and caffeinated beverages, with differences determined using Student's t-tests and conditional logistic regression for matched pairs. Information on alcohol and caffeinated beverage consumption was obtained from three 24-hour dietary recall interviews conducted during the postmenstrual period and from three conducted during the premenstrual period. Results showed that no significant difference was observed in total caffeine intake or in the individual caffeinated beverages consumed during either the post-menstrual or the premenstrual period. For alcohol consumption, however, women with PMS drank 1.41 (95% confidence interval; range, 0.34-2.47) more servings per week during the postmenstrual period. Based on post-menstrual consumption, women in the heaviest drinking category (> or = 10 drinks per week) were significantly more likely to have moderate to severe PMS (P < .005) than nondrinkers. This same significant relation, but to a lesser degree, was observed based on premenstrual consumption. We conclude that because PMS is more strongly associated with alcohol consumed in the symptom-free, postmenstrual period, drinking is unlikely to be simply a response to PMS symptoms as others have previously suggested.

Alcohol Drinking↗
PubMed1993

Theory in vivo.

Due to a formerly held assumption that psychoanalytic theories operate exclusively in the positivistic manner associated with the natural sciences, current thinking on how they operate specifically or in their own terms is addressing a long-neglected task. In this paper it is suggested that inherent and acquired modes of theorizing interplay when an analyst is working; and that a dialogue involving these two modes which began in Freud's inner life has evolved into our communal conceptual discourse. A series of situationally connected interchanges with a female analysand, over a two-week period, is presented. An attempt is made to demonstrate some theorizing, not 'in vitro'--'in the test-tube' of abstraction, but where most use and discovery of theory happens, 'in vivo'--within the living experience of therapeutic analysis.

Adult↗
PubMed1992

Unfolding and refolding of hen egg-white riboflavin binding protein.

The unfolding and refolding of riboflavin-binding protein (RfBP) from hen egg-white induced by addition of guanidinium chloride (GdnHCl), and its subsequent removal by dialysis have been studied by c.d. and fluorescence for both the native and reduced protein. The reduction of its nine disulphide bonds causes a reduction in the secondary structure (alpha-helix plus beta-sheet) from 63% to 33% of the amino acid residues. Unfolding of the native protein occurred in two phases; the first involving a substantial loss of tertiary structure, followed by a second phase involving loss of secondary structure at higher GdnHCl concentrations. By contrast this biphasic behaviour was not discernible in the reduced protein. The loss of ability to bind riboflavin occurred after the first phase of unfolding. Comparison of unfolding of the holoprotein and apoprotein suggested that riboflavin has only a small stabilizing effect on the unfolding process. After removal of GdnHCl, the holoprotein, apoprotein and reduced protein assumed their original conformation. The significance of the results in relation to various models for protein folding is discussed.

Animals↗
PubMed1991

A comparative study of the structure of egg-white riboflavin binding protein from the domestic fowl and Japanese quail.

1. The riboflavin binding proteins from domestic fowl and Japanese quail have been isolated and their structures compared by circular dichroism, fluorescence and peptide mapping. 2. The two proteins have similar secondary structures, but differ in their tertiary structures as reflected in the environments of aromatic amino acid side chains. 3. Differences in amino acid sequence between the proteins are indicated by the digestion patterns obtained with thermolysin, chymotrypsin and V8 proteinase from Staphylococcus aureus. Both proteins are resistant to digestion by trypsin.

Animals↗
PubMed1991

Percutaneous endoscopic gastrostomy in elderly patients.

Percutaneous endoscopic gastrostomy (PEG) was performed on 28 elderly patients (mean age 82 years) who were dysphagic and intolerant of naso-gastric feeding. Twenty-six patients were recovering from a stroke; the interval between the onset of stroke and PEG averaged 63 days. The procedure was successful and well tolerated by all patients. Nineteen (68%) still had a functioning PEG a median of 14 weeks after placement. One patient whose swallowing recovered had the tube removed 6 months after its insertion. Seven patients (25%) subsequently died from their underlying disease, a mean of 92 days following PEG. There was one procedure-related death from peritonitis. PEG is a useful alternative to surgical gastrostomy in selected elderly patients with dysphagia who are intolerant of naso-gastric feeding.

Aged↗
PubMed1991

Percutaneous endoscopic gastrostomy.

Percutaneous endoscopic gastrostomy is a useful alternative to long-term nasogastric feeding or surgical gastrostomy for dysphagic patients. It is simple to perform and is relatively safe.

Deglutition Disorders↗
PubMed1990

Suspected actinobacillosis manifested by facial enlargement in a heifer.

Actinobacillosis was the suspected cause of severe, bilateral facial enlargement of 8 months' duration in a 2.5-year-old Holstein heifer. Serum protein electrophoresis revealed a polyclonal gammopathy. Necropsy findings indicated that facial swelling was caused by fibrosis between the skin and underlying bone. Lesions were characterized microscopically by scattered pyogranulomas containing eosinophilic, club-like colonies surrounding gram-negative bacterial rods. The lesion was compatible with diagnosis of actinobacillosis. It is unusual for severe bilateral facial enlargement to be associated with actinobacillosis.

Actinobacillosis↗
PubMed1990

Alcohol treatment of defective lambda lysogens is deletionogenic.

We ascertained that transient exposure to ethanol, above 18%, was deletionogenic to an Escherichia coli strain with a fragment (12.5 kb) of bacteriophage lambda integrated within the chromosome. The lambda attL B.P' through P fragment provided a forward selection for mutants, and a target for mutagenesis. The cells were killed by thermal derepression of transcription and replication of the lambda fragment when transferred from 30 degrees to 42 degrees C. Survivor mutants, capable of forming colonies at 42 degrees C, were selected from untreated starting cells. About half no longer supported marker rescue of the lambda fragment imm lambda (immunity) region, comprising the cI repressor, and the PL and PR promoters. Ethanol treatment of starting cells increased the occurrence of imm lambda-defective clones to near 100%. The mutations responsible for the imm lambda defect were found to be large deletions (12 kb or more of DNA). Ethanol treatment of the starting cells also produced a 5- to 18-fold increase in the occurrence of E. coli pgl mutations, which likely arose by the deletion mechanism generating the imm lambda defects, since pgl was closely linked to the integrated lambda fragment. A unifying hypothesis for these observations was that ethanol was deletionogenic. The inclusion or substitution of the int-kil segment of the lambda fragment produced no real change in the spontaneous occurrence of large imm lambda deletions from the untreated cells. Substitution of this segment suppressed the deletionogenic effect of ethanol, implying a prerequisite for sequence homology or gene function from this interval.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriophage lambda↗
PubMed1990

Feasibility of reversible pulmonary artery banding: early results and intermediate-term follow-up.

Development of a reversible pulmonary artery band might obviate the need for a second cardiac surgical procedure in children with some forms of congenital heart disease. We evaluated a segmented Silastic-coated Dacron mesh band 2 to 4 mm wide sewn together with absorbable 2-0 polydioxanone suture for use as a reversible pulmonary artery band. Nine puppies 6 to 8 weeks old (mean weight, 5.8 kg) underwent placement of this pulmonary artery band. All survived the operation with a mean initial systolic gradient of 6.5 +/- 1.6 mm Hg and underwent cardiac catheterization at monthly intervals for 3 months. Two puppies died of right ventricular failure. The remaining puppies underwent balloon angioplasty with balloons 20 to 25 mm in diameter. No complications resulted from balloon angioplasty, but 1 puppy died 24 hours later of unidentified causes. Balloon angioplasty decreased the mean gradient from 46.7 +/- 6.8 mm Hg to 6.7 +/- 2.6 mm Hg. Angiography showed an increase in mean diameter of the site of the pulmonary artery band from 5.2 +/- 1.0 to 10.8 +/- 1.7 mm Hg. There was no evidence of vessel injury on angiograms. Fourteen months after balloon angioplasty, the mean gradient was 22.3 +/- 17.0 mm Hg. Our data demonstrate that a functionally reversible pulmonary artery band constructed of segmented Silastic-coated Dacron mesh and 2-0 polydioxanone suture is feasible.

Angioplasty, Balloon↗
PubMed1990

Stimulation of mutations suppressing the loss of replication control by small alcohols.

Transient exposure of lysogenic Escherichia coli cells to small alcohols stimulated the frequency of mutations suppressing the lethal loss of replication control from a prophage fragment of bacteriophage lambda. The stimulation in mutation frequency paralleled the effect of mutagenic agents, and in this sense the alcohols behaved as mutagens. 10-min treatments above distinct threshold concentrations at 23%, 18%, 10% and 4% (v/v) were required in order for methanol, ethanol, isopropanol and propanol to evoke mutagenic effects. The selected mutant cells were, in general, equally or more sensitive to ethanol than the starting cells. The mutagenicity of methanol and ethanol was detected only with E. coli strains with lambda fragments that included the site-specific and general recombination genes found within the phage int-kil gene interval; whereas, stimulation of the frequency of phenotypically identical mutations by nitrosoguanidine or ionizing radiation did not require that the lambda fragment encode these genes. Treatments of lysogenic cells with mutagenic concentrations of ethanol did not trigger prophage induction and were concluded not to induce a cellular SOS response nor to denature the prophage repressor, or to disrupt repressor-operator binding. The toxicity of ethanol was pH-dependent. Cellular sensitivity to ethanol toxicity was unaffected by the integrated lambda fragment(s) or by an intact lambda prophage; but, it was increased by deletions of the E. coli chromosome extending rightward from bio into uvrB, and rightward from chlA.

1-Propanol↗
PubMed1989

Purification and characterisation of NAD-glutamate dehydrogenase from Aspergillus nidulans.

NAD-Glutamate dehydrogenase has been purified from mycelia of A. nidulans. The enzyme comprises subunits of 110 kDa. It is located in the cytosol. It is completely denatured by 1.0 M guanidine hydrochloride, and is not renatured by subsequent dilution. Isophthalate is a strong competitive inhibitor and the enzyme is also inhibited by thiol reagents. The properties of the enzyme were compared to those from other fungi in terms of size, sensitivity to inhibitors, intracellular distribution and mode of regulation, and were found to resemble most closely those of Neurospora crassa.

Aspergillus nidulans↗
PubMed1989

The flow of interpretation. The collateral interpretation, force and flow.

This paper was presented to a Conference on the theme 'The Formulation of Interpretations in Clinical Practice'. It suggests that, impressionistically in line with the identification of psychoanalysis with natural science, an unconscious metaphor which sees interpretation as something like a force inserted on a physical particle has been more influential conceptually than the unconscious metaphor naturally complementary to it, that of interpretation as something like a liquid in flow. The concept of 'the collateral interpretation' is introduced. Loosely speaking, this is what an analyst thinks he would interpret at any given moment. It is tentative, unformed, and changes kaleidoscopically. It accommodates psychoanalytic concepts. It is suggested that examination of the mode of operation of 'the collateral interpretation' is important in understanding the formulation of interpretations. A single session is used for clinical illustration.

Consciousness↗
PubMed1988

Absorption characteristics of human fetal hemoglobin at wavelengths used in pulse oximetry.

The absorption characteristics of fetal and adult human hemoglobin samples were determined for the range of 600 to 1,050 nm. Over this range, fetal hemoglobin absorption is nearly identical to that of adult hemoglobin. Since currently available two-wavelength pulse oximeters base their calculations of arterial oxyhemoglobin saturation on absorption at the wavelengths of 660 and 920 nm, we conclude that the accuracy of two-wavelength pulse oximetry previously demonstrated in adults can be extrapolated to infants with high concentrations of fetal hemoglobin.

Fetal Hemoglobin↗
PubMed1987

Hypertonic saline as a resuscitation solution in hemorrhagic shock: effects on extravascular lung water and cardiopulmonary function.

To determine the effect of resuscitation with hypertonic saline on extravascular lung water, seven adult sheep were endotracheally intubated; mean arterial pressure (MAP), pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP), and central venous pressure (CVP) were monitored. A 5-French, thermistor-tipped catheter was used to measure extravascular lung water (EVLW). Colloid oncotic pressure (COP), serum electrolytes and osmolality, and arterial and mixed venous blood gas tensions were measured. The COP-PCWP gradient and the shunt fraction (Qsp/Qt) were calculated. After baseline measurements, the animals were bled to an MAP of 50 mm Hg (blood volume removed, 16.2 +/- 3.6 ml/kg), which was maintained for 30 min, measurements then being repeated. Three percent sodium chloride solution was infused at 500 ml/15 min until two of three parameters--cardiac output (CO), PCWP, or MAP--were restored to baseline values. Data were recorded again and then 60 min later. No shed blood was reinfused. The total volume of hypertonic saline infused was 39 +/- 19 ml/kg. Pulmonary artery pressure did not vary throughout the study. PCWP, MAP, and CO were significantly lower than baseline (P less than 0.05) 30 min after bleeding but all except MAP returned to baseline with resuscitation. Throughout the study, EVLW did not vary despite a COP-PCWP gradient less than 4 mm Hg. Serum sodium levels and serum osmolality were significantly above baseline values after resuscitation. In this animal model of hemorrhagic shock, infusion of hypertonic saline effected resuscitation without compromising cardiopulmonary function or increasing EVLW.

Animals↗
PubMed1986

Production and characterization of rabbit anti-idiotypic antibodies specific to mouse monoclonal anti-human IgE and reacting with IgE-binding factors and lymphocyte receptors for IgE.

A mouse monoclonal antibody specific to human IgE (mAb 75) was employed to immunize a rabbit to obtain anti-idiotypes (aId) bearing the internal image of human IgE determinants and reacting with IgE-binding factors (IgE-BF) and/or lymphocyte receptors for IgE (Fc epsilon R). mAb 75 was selected on the basis of inhibition assays where the binding of mAb 75 to radiolabeled IgE was blocked by IgE-BF. The latter were produced by a lymphoblastoid cell line (RPMI 8866) expressing Fc epsilon R. Sequential samples of rabbit serum, collected during the immunization period, were extensively absorbed on mouse and human Ig-Sepharose 4B. The IgG fractions of the rabbit serum displayed the following activities: (a) they reacted with 125I-labeled mAb 75 but not with other labeled mouse Ig including mAb-aIgE, (b) this binding was inhibited in a dose-dependent fashion by human IgE but not by other human Ig classes nor by heat-inactivated IgE, (c) they reacted with a polyclonal rabbit anti-human IgE and (d) they blocked the binding of 125I-labeled IgE to mAb 75. It was concluded that the rabbit IgG contained aId (RaId) bearing the internal image of heat labile determinants of human IgE. The rosetting of IgE-coated bovine erythrocytes with Fc epsilon R-bearing cells was inhibited by preincubating the receptor-bearing cells with IgG RaId or its F(ab')2 but not with normal rabbit IgG. The ability of RaId to react with IgE-BF as well as with Fc epsilon R was also shown in inhibition experiments where IgE-BF and solubilized Fc epsilon R blocked the binding of mAb 75 to RaId. Finally, Western blot analysis of human colostrum, known to contain IgE-BF, indicated that radioiodinated RaId and IgE identified the same 12-16-kDa molecules corresponding to IgE-BF. It is concluded that RaId expresses the internal image of a heat-labile determinant of IgE which is involved in the binding of IgE to IgE-BF and Fc epsilon R. An alternative interpretation is that RaId reacts with an idiotypic determinant of mAb 75 which is shared by IgE-BF and Fc epsilon R.

Animals↗
PubMed1986

Presence of IgE suppressor factors in human colostrum.

In spite of intensive investigations, the ability of breast feeding to delay and to attenuate atopic diseases in children remains debatable. This study documents a mechanism whereby breast feeding might interfere with the synthesis of IgE by breast-fed infants. Indeed, we show that colostrum contains IgE-binding factors (IgE-BF) capable of suppressing the in vitro synthesis of human IgE. Colostrum obtained from 15 donors was successively depleted of lipids and casein, filtered through Amicon XM50 membrane (mol. mass cut-off 50 kDa) and lyophilized. IgE-BF was demonstrated in such preparations by two different approaches, i.e. a classical rosette inhibition assay and Western blot analysis. In the first instance, lyophilized preparations of colostrum inhibited the binding of IgE-coated bovine erythrocytes to IgE recovered on the surface of RPMI 8866 lymphoblastoid cells. The rosette-inhibiting activity could be absorbed on IgE- but not on IgG-Sepharose 4B and it could be recovered in the eluate of IgE-Sepharose 4B. The molecular mass of IgE-BF was comprised between 10 to 20 kDa as estimated by gel filtration through a calibrated Sephadex G-75 column. After fractionation on 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transfer to nitrocellulose membrane, colostrum displayed one band of 14 kDa and reacted with radiolabeled IgE but not with IgG nor IgM. This 14-kDa band could be removed by absorbing colostrum with IgE- but not with IgG-Sepharose 4B. Most importantly, the colostrum IgE-BF suppressed the spontaneous in vitro synthesis of IgE by B lymphocytes derived from allergic donors without altering the production of IgM.

Colostrum↗