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Biomedical subjects

M L Brown

Publications and source records attributed to M L Brown.

At least 163 records · Page 9Linked to original sources
PubMed1990

Utility of gallium imaging of the kidneys in diagnosing primary amyloid nephrotic syndrome.

We undertook a study to determine the value of gallium imaging of the kidneys in patients who had primary amyloidosis that was manifest clinically by nephrotic syndrome. We studied 28 patients with gallium-67 (67Ga) citrate scans performed 48 hr after injection. Intense (3+ to 4+) uptake was noted in both kidneys in 25 of 28 patients. Renal amyloidosis should be considered in the differential diagnosis when diffuse bilateral renal uptake of [67Ga]citrate is seen in the setting of nephrotic syndrome. Gallium uptake did not differentiate amyloid nephrotic syndrome from other causes of nephrotic syndrome. Renal gallium uptake showed a weak correlation with 24-hr urine protein excretion (p = 0.06).

Amyloidosis↗
PubMed1990

Fitting and interpreting loglinear interactions in cross-classifications from health policy and medicine.

A nontechnical exposition is presented of current statistical techniques for the analysis of multidimensional tables of counted data. Performing an original analysis of a data set of interest to researchers in health policy and medicine, the paper considers what kinds of questions an analysis by loglinear modeling can address, and what kinds of answers it can obtain and how they may be sought. Unlike most previous expository accounts seeking to provide introductions to this field, this paper does not require a background from the reader in either regression or the analysis of variance. By a thoroughgoing use of odds ratios and higher-order odds ratios, it nevertheless provides a technically accurate account of the key concepts of higher-order interactions among variables, and of models being hierarchical. Statistically more advanced readers are provided with a means of effectively expositing their loglinear modeling methods and conclusions to nonstatisticians; a number of footnotes are directed toward such readers.

California↗
PubMed1989

Molecular basis of lipid transfer protein deficiency in a family with increased high-density lipoproteins.

Plasma high density lipoproteins (HDL) are a negative risk factor for atherosclerosis. Increased HDL is sometimes clustered in families, but a genetic basis has never been clearly documented. The plasma cholesteryl ester transfer protein (CETP) catalyses the transfer of cholesteryl ester from HDL to other lipoproteins and therefore might influence HDL levels. Using monoclonal antibodies, we show that CETP is absent in two Japanese siblings who have markedly increased and enlarged HDL. Furthermore, they are homozygous for a point mutation in the 5'-splice donor site of intron 14 of the gene for CETP, a change that is incompatible with normal splicing of pre-messenger RNA. The results indicate that the family has an inherited deficiency of CETP due to a gene splicing defect, and illustrate the key role that CETP has in human HDL metabolism.

Adult↗
PubMed1989

Mechanism of cholesteryl ester transfer protein inhibition by a neutralizing monoclonal antibody and mapping of the monoclonal antibody epitope.

The plasma cholesteryl ester transfer protein (CETP, Mr 74,000) has a binding site for neutral lipid which can readily equilibrate with lipoprotein cholesteryl esters or triglycerides. Recently, a monoclonal antibody (TP2) was obtained which neutralizes the cholesteryl ester (CE) and triglyceride (TG) transfer activities of the CETP. In this report, the epitope of the inhibitory monoclonal antibody has been localized to a hydrophobic 26-amino acid sequence at the COOH terminus of CETP. The Fab fragments of TP2 caused partial (50%) inhibition of CE transfer and complete inhibition of TG transfer by the CETP. Similarly, the Fab fragments inhibited (37%) the binding of CE to the CETP and abolished the binding of TG to the CETP. Surprisingly, the TP2 Fab was also found to enhance the binding of CETP to plasma lipoproteins and to phospholipid vesicles. In conclusion, the TP2 monoclonal antibody inhibits lipid transfer by blocking the uptake of lipid by CETP. The COOH-terminal epitope may be in or near the neutral lipid binding site. Occupancy of this site by TP2 Fab fragments or by neutral lipid may result in a conformational change of CETP causing enhanced binding to lipoproteins or vesicles.

Amino Acid Sequence↗
PubMed1989

Structure-function analysis of plasma cholesteryl ester transfer protein by protease digestion and expression of cDNA fragments in Escherichia coli.

In an attempt to define an active domain of the protein, fragments of cholesteryl ester transfer protein (CETP) were obtained by limited digestion of the native, plasma-derived protein with trypsin, chymotrypsin, or Staphylococcus aureus V8 protease or by expression of CETP cDNA restriction fragments in Escherichia coli. Although digestion of native CETP with these proteases resulted in extensive fragmentation of the protein and loss of the intact 74-kDa molecule as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, CE transfer activity was unaffected (trypsin or chymotrypsin treatment) or only partially lost (V8 protease treatment). Analysis by molecular sieve chromatography showed that the CE transfer-active product of this proteolysis consisted of polypeptide fragments which remained associated, retaining the native molecular weight of CETP. These proteolyzed complexes were resistant to dissociation by dithiothreitol, 8 M urea, or delipidating agents. As shown by CE transfer activity, native CETP was found to possess a stable conformation which remained unchanged in buffers containing up to 4.5 M urea, or following exposure to even higher (8 M) urea concentrations. CETP polypeptides from bacterially expressed cDNA fragments were found to be catalytically inactive although they contained the epitope for an inhibitory anti-CETP monoclonal antibody and had emulsion binding properties similar to native CETP. Selected synthetic CETP peptides (including the peptide containing the inhibitory monoclonal antibody epitope) were also devoid of CE transfer activity. Thus, no evidence was found for an independently active subunit of the CETP. Together, the results indicate that the CETP possesses a distinct and highly stable tertiary structure which is required for CE transfer catalytic activity.

Antibodies, Monoclonal↗
PubMed1989

Gender-related differences in cardiac response to supine exercise assessed by radionuclide angiography.

This study examines the recently reported gender differences in cardiac responses to exercise. The study group consisted of 192 men and 67 women with a low probability of coronary artery disease who underwent supine exercise radionuclide angiography. Men had a lower rest ejection fraction than that of women (0.63 versus 0.66, p = 0.02) and greater increases in ejection fraction with exercise (0.08 versus 0.02, p = 0.0001). The slope relating ejection fraction to metabolic equivalents of exercise (METs) was greater (p = 0.004) for men, even after adjustment for differences in rest ejection fraction and end-diastolic volume index. Compared with men, women had a smaller rest end-diastolic volume index (87 versus 97 ml/m2, p = 0.003) and a greater increase in end-diastolic volume index with exercise (6 versus -2 ml/m2, p = 0.002). The slope relating end-diastolic volume to METs was greater for women, even after adjustment for differences in rest end-diastolic volume index and peak work load. There are clear gender differences in the supine exercise response of ejection fraction and end-diastolic volume that are not explained by differences in exercise capacity.

Adult↗
PubMed1989

Stimulation of ileal emptying by short-chain fatty acids.

We have shown previously that short-chain fatty acids (mixtures of acetic, propionic, and butyric acids; SCFAs) in the proportions found usually in stool water stimulate fasting ileal motility. Based on indirect evidence, we proposed that these motor patterns (bursts of phasic pressure waves that were propagated) would be propulsive, but the capacity of these stimulated patterns of motility to propel contents has not been established directly. Healthy, surviving dogs were provided with motility sensors and a cannula through which SCFAs could be instilled into the ileum. Boluses of SCFAs were much more likely to stimulate phasic bursts of motility than was saline. Scintigraphic studies using a gamma camera showed that the motility stimulated by SCFAs was propulsive and that the ileum was thereby emptied. We also tested whether SCFAs were equally effective stimuli during fasting and after food. SCFAs were equally effective during fasting and soon after food, but in the late postprandial period, when the meal reached the ileum, SCFAs were much less likely to stimulate motility. These observations shed further light on the capacity of the ileum to sense and react to the nature of the contents.

Animals↗
PubMed1989

Effect of ileal perfusion of carbohydrates and amylase inhibitor on gastrointestinal hormones and emptying.

To determine if carbohydrates perfused into the ileum affect gastric emptying and circulating levels of gastrointestinal hormones, 18 healthy subjects were intubated with an oroileal tube. A 400-cal (60% carbohydrate, 20% protein, 20% fat) homogenized meal labeled with 111In-DTPA was then infused into the stomach over 10 min. Simultaneously, a test solution of normal saline (n = 6) or 12.5 (n = 4), 25 (n = 4), 50 (n = 2), or 100 (n = 2) mg/min of carbohydrates (75% rice starch, 25% glucose) containing a nonabsorbable marker, polyethylene glycol, was continuously perfused into the terminal ileum at 3 ml/min for 7 h. In one-half of the subjects the perfusate contained an amylase inhibitor (3.3 mg/ml) that reduced starch digestion and carbohydrate absorption. Gastric emptying was measured by a dual-headed gamma-camera. Plasma concentrations of hormones and the amount of carbohydrates passing the ileum were measured every 10 min. The amylase inhibitor significantly reduced the absorption of complex carbohydrates from the terminal ileum (p less than 0.05). Gastric emptying was significantly slowed by ileal perfusion of carbohydrates (p less than 0.01). This effect was enhanced by the amylase inhibitor (p = 0.06). Plasma concentrations of C-peptide, glucagon, motilin, gastrin, and human pancreatic polypeptide were not related to gastric emptying or ileal perfusates, but decreased concentrations of gastric inhibitory polypeptide and neurotensin and increased concentrations of peptide YY were significantly associated (p less than 0.05) with slowing of gastric emptying. Perfusing carbohydrates into the ileum was associated with nausea, abdominal pain, and vomiting, but we could detect no direct relationship between the onset of these symptoms and gastric emptying. Slowing of gastric emptying of a homogenized mixed meal by the entry of complex carbohydrates into the ileum may be partly mediated by peptide YY or nonvagally mediated neural mechanisms.

Abdomen↗
PubMed1989

Gastrointestinal transit after proctocolectomy with ileal pouch-anal anastomosis or ileostomy.

Proctocolectomy with ileal pouch-anal anastomosis increases the frequency of stooling, perhaps due in part to the loss of an ileocecal or colonic braking effect on gastrointestinal transit. To assess whether colectomy with ileal pouch-anal anastomosis (IPAA) or with ileostomy accelerates gastrointestinal transit, we studied 16 IPAA patients (mean +/- SEM stool frequency, 8 +/- 1 stools/day), 5 patients after colectomy and Brooke ileostomy, and 8 healthy, unoperated controls (1 +/- 1 stools/day). Gastric emptying of liquids and small bowel transit of chyme were measured concurrently with a dual isotope technique. Gastric emptying was similar among all groups. In contrast, postprandial small bowel transit of the head of a duodenal marker was slowed, not accelerated, in IPAA patients (178 +/- 26 min) compared to Brooke subjects (80 +/- 32 min, P less than 0.05) and controls (75 +/- 15 min, P less than 0.01). Maximal filling of both the ileal pouch (341 +/- 19 min) and the ileostomy bag (348 +/- 12 min) occurred later than filling of the colon in controls (243 +/- 32 min, P less than 0.01). Overall stool frequency did not correlate with small bowel transit in the ileoanal patients, but the two ileoanal subjects with greatest stool frequency (11 and 18 stools/day) had the earliest arrival of marker at the pouch. In conclusion, removal of the colon markedly slowed small bowel transit in most patients, although it did not alter gastric emptying of liquids. Creation of an ileal pouch and ileoanal anastomosis further slowed transit of the head of the meal.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

The release of neutrophil chemoattractant activity by bronchoalveolar macrophages from adult and senescent mice.

To assess the effects of advanced age on the release of neutrophil chemoattractant activity by resident bronchoalveolar macrophages (BAM), cells from three strains of pathogen- and disease-free mice were secured by lung lavage and stimulated in vitro with unopsonized zymosan or the calcium ionophore, A23187. Chemoattractant release by BAM from adult (5-8 mos) and senescent (19-26 mos) C57BL/6 and DBA/2 mice in response to both stimulants was comparable; however, the generation of chemoattractant activity by BAM from senescent (18-20 mos) BALB/c mice was greater than that observed with cells from younger (4-6 mos) animals with both zymosan and A23187. In the presence of 50 microM piriprost potassium, a 5-lipoxygenase inhibitor, the release of chemoattractant activity and leukotriene B4 (LTB4) in response to zymosan and A23187 by BAM from both groups of C57BL/6 mice was significantly impaired. With BAM from BALB/c mice, 100 microM piriprost potassium was required to produce changes in A23187-stimulated chemoattractant and LTB4 release; of note, the generation of LTB4 in response to A23187 by BAM from aged BALB/c mice was significantly greater than that observed with cells from the younger animals under all conditions studied. Finally, with BAM from DBA/2 mice, 50 microM piriprost potassium significantly reduced chemoattractant activity in both groups of animals, but the lipoxygenase inhibitor had no effect on LTB4 production. Thus, although these studies revealed substantial age and strain-related differences in the release of neutrophil chemoattractant activity by murine BAM, they did not demonstrate deficiencies that might enhance the susceptibility of the senescent host to infection of the lower respiratory tract.

Aging↗
PubMed1989

Lymphoscintigraphy as a guide to treatment in malignant melanoma.

Regional node dissection is practiced as a measure of prophylaxis in patients with stage I and II malignant melanoma. Although the drainage pattern of the extremities is obvious, in the head and neck and trunk it may be ambiguous. We have used lymphoscintigraphy to assist in delineating the lymphatic drainage in 22 patients with primary malignant melanoma. Fourteen patients had melanoma in the head and neck region, and eight had melanoma in the trunk region. Based on Clark's classification there were ten level III melanomas, eight level IV melanomas, and two level V melanomas; the levels of the remaining two melanomas were unspecified. Seven melanomas were between 0.76 and 1.5-mm thick, eleven were between 1.51 and 4.0-mm thick, and two were over 4.0-mm thick (the remaining two were unspecified). Regional nodes were clinically negative in 18 patients. The scan distribution was unexpected in 13 patients (59%), and it influenced the surgical procedure in 11 patients (50%). No patient incurred an adverse effect from the scan. We conclude that lymphoscintigraphy may be of value in guiding prophylactic lymph node dissection in melanoma patients.

Adult↗
PubMed1989

Electron microscopy reveals that transcription factor TFIIIA bends 5S DNA.

We have used a high-resolution analytical electron microscopic technique, electron spectroscopic imaging, to study the in vitro interaction between the transcription factor IIIA (TFIIIA) and 5S ribosomal gene DNA. The images and analytical measurements support our proposal that the helix axis is bent by the protein into a hairpin-shaped configuration.

Animals↗
PubMed1989

Human gastric emptying and colonic filling of solids characterized by a new method.

Our first aim was to compare 111In-labeled Amberlite IR-12OP resin pellets and 131I-labeled fiber in the assessment of gastric and small bowel transit and colonic filling in healthy humans. Both radiolabels were highly stable for 3 h in an in vitro stomach model and remained predominantly bound to solid phase of stools collected over 5 days [90.5 +/- 2.1 (SE)% for 131I and 87.4 +/- 1.4% for 111In). The lag phase of gastric emptying was shorter for 111In-pellets (30 +/- 11 min compared with 58 +/- 12 min for 131I-fiber, P less than 0.05). However, the slope of the postlag phase of gastric emptying and the half time of small bowel transit were not significantly different for 111In-pellets and 131I-fiber. Filling of the colon was characterized by bolus movements of the radiolabel (10-80% range, 26% mean) followed by plateaus (periods of no movement of isotope into colon lasting 15-120 min, range; 51 min, mean). Half of the bolus movements occurred within 1 h of the intake of a second meal. Thus 111In-labeled Amberlite pellets provide an excellent marker for the study of gastric and small bowel transit and colonic filling in humans. The ileum acts as a reservoir and transfers boluses of variable sizes into the colon, often soon after the intake of a subsequent meal.

Adult↗
PubMed1989

Effect of six weeks of treatment with cisapride in gastroparesis and intestinal pseudoobstruction.

We have investigated the effect of oral cisapride (10 mg t.i.d.) in a double-blind, placebo-controlled trial in 26 patients with upper gut dysmotility: 11 with gastroparesis (8 diabetic, 3 idiopathic) and 15 with chronic idiopathic intestinal pseudoobstruction. Patients were evaluated at entry and at the end of the 6-wk study by upper gastrointestinal manometry, scintigraphic evaluation of gastric emptying of solids and liquids, measurement of body weight, and scoring of the following symptoms: abdominal pain, nausea, vomiting, early satiety, bloating, and distention. Cisapride and placebo groups were strictly comparable for all parameters assessed. Cisapride resulted in a significant increase in the gastric emptying of solids (p less than 0.05) compared with placebo; cisapride also tended to increase the postcibal antral motility and normalize the abnormal manometric features in the patients with intestinal dysmotility, particularly the characteristics of fasting interdigestive motor complexes and the fed motor pattern. Both cisapride and placebo groups showed an improvement in total symptom scores and there was no significant difference in overall symptom response between the two groups. However, the change in abdominal pain was greater with cisapride (p = 0.07). Cisapride facilitates gastric emptying in patients with upper gut dysmotility. The overall symptomatic benefit during a 6-wk trial of cisapride, 10 mg t.i.d., was not greater than that of placebo, and dose-response as well as longer term trials are necessary to determine the clinical efficacy of this medication.

Adult↗