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Biomedical subjects

R Black

Publications and source records attributed to R Black.

At least 19 recordsLinked to original sources
PubMed1992

Frequency of late potentials on signal-averaged electrocardiograms during thallium stress testing in coronary artery disease.

Late potentials detected by signal-averaged electrocardiography (SAECG) are an important noninvasive indicator identifying patients with previous myocardial infarction at risk for developing ventricular tachycardia. The role of myocardial ischemia in the development of late potentials is undefined. This study attempts to determine if late potentials on SAECG can be produced during scintigraphically proven ischemia. A signal-averaged electrocardiogram was obtained before and immediately after single-photon emission computed tomography thallium exercise testing in 51 patients. Reversible ischemia was documented in 25 cases with no significant changes in the parameters of SAECG; patients with previous myocardial infarction (n = 10) also had no significant changes from baseline. Multivariate analysis with respect to reversible ischemia and previous myocardial infarction was unrevealing. Patients with late potentials at baseline (n = 10) who developed reversible ischemia (n = 5) had a shorter QRS duration than those with late potentials at baseline and no reversible ischemia. The data indicate that exercise-induced scintigraphically proven ischemia does not alter SAECG even in the presence of previous myocardial infarction. Patients with late potentials at baseline may actually have a shortened QRS duration during reversible ischemia as opposed to the expected lengthening of the QRS.

Coronary Disease↗
PubMed1992

Theory-driven behavioral intervention research for the control of diarrheal diseases.

Essentially all methods to reduce diarrheal morbidity and mortality require behavioral change. Research is required to design, implement and evaluate behavior-modifying interventions. Accumulated experience in the many involved disciplines should serve as a basis for this research. However, each of these disciplines is associated with different research perspectives and analytic assumptions; thus integration of these varied but potentially complementary experiences has been elusive. In the present paper, arguing that such perspectives and assumptions are embodied in discipline-based theory, we have developed a generic framework for the conduct of theory-based behavioral intervention research. We illustrate the application of this framework through two vignettes applying two of the theories and models to the development of hypothetical handwashing interventions.

Behavior Therapy↗
PubMed1992

Panniculus morbidus.

Eight patients with large panniculi are described where severe problems with hygiene, immobility, and chronic infection were caused by the lymphedematous, chronically infected pannus. Protracted nonsurgical management of the infected panniculus had failed in all 8 patients. Wedge resection without fat undermining removed diseased tissue. Infection and sepsis were eliminated and ambulation was restored in all patients. Formerly immobile patients were returned to normal activity. Significant self-induced weight loss was not observed in a 2-year follow-up period; weight gain, however, was not experienced. The primary anesthetic method was thoracic epidural reducing the requirements for general endotracheal anesthesia. The chronically infected pannus is a surgical problem deserving earlier recognition and resection.

Abdomen↗
PubMed1992

A probe for specimen magnetic resonance microscopy.

One of the primary limits to spatial resolution in magnetic resonance (MR) microscopy is the limited signal. The purpose of this study is to build a radiofrequency (rf) probe for MR microscopy of fixed specimens at 300 MHz. The design criteria for the probe were (1) high sensitivity; (2) good rf homogeneity; (3) minimization of BO variations. All probes were Helmholtz pairs operating at 300 MHz. Coils were constructed from copper/Teflon/copper microwave substrate which eliminated susceptibility problems from solder and discrete capacitors. Signal-to-noise ratio (SNR) was compared with a conventional solenoid. Phantoms of agar gels and saline-filled tubes were used to characterize the SNR and homogeneity. SNR measurements of the coil pairs showed a marked improvement (up to 60%) over that of the reference solenoid. The region of homogeneity was defined as a 10% variation in signal intensity. This correlated with the coil's inner diameter. Graphs of SNR versus diameter, separation, and copper foil width allowed for optimization of the structure. Using this coil, MR microscopy is now possible on small, fixed specimens with pixels as small as 20 x 20 x 30 microns. Work is currently under way exploiting the SNR and homogeneity provided by this probe to determine the degree to which MR microscopy might add to the pathologists' diagnostic tools.

Copper↗
PubMed1992

Graphic summaries of expert knowledge for the medical curriculum: an experiment in second-year nephrology.

This study was conducted to test the effects of Concept Graphics on learning in clinical nephrology. Second-year medical students were exposed to summaries of the major renal pathologies presented as text with, or without Concept Graphics for 30 minutes, followed by a quiz. Concept Graphics summarize diagnoses using icons that are metaphors of objects or processes. Of nine quiz questions, five were classified as correlation questions and four as memorization questions. The experimental group (n = 39) performed better than the controls (n = 33) in answering the correlation questions (p = 0.018). The experimental group mentioned more frequently than the controls two pathogonomic criteria of the nephritic syndrome (p = 0.02). Results of an opinion poll of the students, comparing sources used in their studies of nephrology were treated by correspondence analysis; the Concept Graphics ranked closest to the classification "very useful".

Computer Graphics↗
PubMed1991

Effects of indomethacin on prostaglandin E2 and thromboxane B2 contents of tracheal lavage fluids in premature infants.

A prospective longitudinal study was conducted in 14 premature infants intubated and receiving ventilatory support from birth, in order to evaluate the levels of prostaglandins E2 (PGE2) and thromboxane B2 (TxB2) in the tracheal lavage fluids (TLF) after treatment with indomethacin. Eight were treated with indomethacin, a cyclooxygenase inhibitor, for patient ductus arteriosus and the others served as controls. Infants who received indomethacin during the first postnatal week had significantly lower levels of eicosanoids in TLF during the first week. Our results suggest that levels of eicosanoids in TLF of premature infants are related to an inflammatory reaction and may serve as an index of the infant's overall clinical condition.

Body Fluids↗
PubMed1991

Peri-operative colonoscopy detects synchronous tumours in patients with colorectal cancers.

The aim of this study was to assess the value of colonoscopy as a peri-operative investigation in patients treated for colorectal cancer by surgical excision. Patients (134 male, 83 female) undergoing curative resection for colorectal carcinoma between August 1984 and January 1989 had colonoscopy within 3 months of surgery. Eleven patients (5%) had a synchronous cancer, which was diagnosed by colonoscopy in eight. In six of these eight, the diagnosis was made after surgery and 3 patients needed a second colectomy. However, in 3 patients the synchronous cancer was removed endoscopically without the need for further surgical resection. Most synchronous cancers had an earlier pathological stage than the index tumour. The rate of synchronous cancers was higher in patients with synchronous benign polyps (16%) than in those without polyps (3%). Colonoscopy is clearly justified as a peri-operative investigation in all patients undergoing potentially curative resection of colorectal cancer. If possible, the examination should be carried out prior to surgery, to guide the extent of resection.

Adult↗
PubMed1991

Human keratinocytes produce but do not process pro-interleukin-1 (IL-1) beta. Different strategies of IL-1 production and processing in monocytes and keratinocytes.

Keratinocytes comprise the majority of cells in the epidermis, the interleukin-1 rich layer of tissue contiguous with the outside world. Keratinocytes produce IL-1 alpha and beta mRNA in vitro, but only IL-1 alpha biological activity has been identified in keratinocyte cultures. In contrast, monocytes secrete biological activities attributable to both species of IL-1. Using several monoclonal antibodies to IL-1 beta, significant amounts of IL-1 beta protein could be found in keratinocyte cultures; all of this immunoreactive IL-1 beta was in the 31-kD form. This latent cytokine has been shown to bind inefficiently to the IL-1 receptor and to be (in relative terms) biologically inactive. Chymotrypsin cleaves 31-kD IL-1 beta at Tyr 113-Val 114, generating an 18-kD IL-1 species with activity equivalent to the authentic mature IL-1 beta (NH2-terminal Ala 117). Treatment of 31-kD keratinocyte IL-1 beta with chymotrypsin also generated an 18-kD molecule and significant IL-1 activity. Monocytes contain an IL-1 convertase enzyme that cleaves the IL-1 beta promolecule at Ala 117. We demonstrate here that keratinocytes do not contain such an IL-1 convertase activity, nor do they contain any activity capable of productively processing 31-kD IL-1 beta into a biologically active form. These data suggest that keratinocytes (and other non-bone marrow-derived cells) produce IL-1 beta in an inactive form that can be processed only after leaving the cell.

Blotting, Western↗
PubMed1991

The proteolytic activation of interleukin-1 beta.

Interleukin-1 beta (IL-1 beta) is released from an inactive precursor by a proteolytic cleavage. A monocytic protease has been identified that appears to be involved in the physiological activation of this cytokine. Two situations have been found in which precursor IL-1 beta exists without the monocytic processing enzyme, and in these cases other proteases, such as neutrophil elastase, cathepsin G and cathepsin L, may be involved in generating the active cytokine.

Cell Line↗
PubMed1990

Somatic growth in infants receiving prolonged caffeine therapy.

We have evaluated the longitudinal growth of 28 premature infants who had been treated by prolonged caffeine therapy (mean: 23.8 weeks). Routine follow-up included at least 5 physical examinations with measurement of length, weight and head circumference at the beginning of caffeine therapy, at mid therapy, at the end of the therapy and at 3 and 6 months after therapy. The distribution of the infants on the growth curves according to weight, length and head circumference showed a regular increase in growth parameters. Analysis of variance was highly significant at p less than 0.0001. We conclude that long term caffeine treatment does not adversely influence growth parameters, at least during early infancy.

Anthropometry↗
PubMed1990

Breast-feeding and diarrheal morbidity.

This study used a unique longitudinal survey of more than 3000 mother-infant pairs observed from pregnancy through infancy. The sample is representative of infants from the Cebu region of the Philippines. The sequencing of breast-feeding and diarrheal morbidity events was carefully examined in a longitudinal analysis which allowed for the examination of age-specific effects of feeding patterns. Because the work controlled for a wide range of environmental causes of diarrhea, the results can be generalized to other populations with some confidence. The addition to the breast-milk diet of even water, teas, and other nonnutritive liquids doubled or tripled the likelihood of diarrhea. Supplementation of breast-feeding with additional nutritive foods or liquids further increased significantly the risk of diarrhea; most benefits of breast-feeding alone or in combination with nutritive foods/liquids became small during the second half of infancy. Benefits of breast-feeding were slightly greater in urban environments.

Breast Feeding↗
PubMed1989

Idiopathic constipation by colonic dysfunction. Relationship with personality and anxiety.

The personality of two groups of constipated women (by delayed colonic transit or by colonic inertia) was compared to that of two control groups of arthritic patients (rheumatoid or degenerative disease) with the Minnesota Multiphasic Personality Inventory (MMPI). All subjects suffered from chronic pain. Constipated women were found to have significantly higher scores on the hypochondria, hysteria, control, and low back pain scales and a lower score on the masculinity-femininity scale. Discriminant analysis permitted us to sort out constipated from arthritic patients in 83% of the cases, on the basis of only the personality data. In women with constipation by delayed colonic transit, multiple regression analysis demonstrated a close link (r = 0.90; P less than 0.001) between transit time in the ascending colon and levels of anxiety. It is concluded that women with constipation of colonic origin have a different pattern of personality than arthritic women and that severe constipation may play the role of a defense mechanism, where psychophysiologic responses to life stresses replace normal emotional reactions.

Adolescent↗
PubMed1988

Lectin histochemistry of the liver in biliary disease, following transplantation and in cholangiocarcinoma.

Evidence is accumulating that there are changes in the expression of antigens on biliary epithelium in early primary biliary cirrhosis and graft rejection. If any of the biliary diseases including rejection are associated with specific alterations in biliary glycoprotein structure, lectin histochemistry could be useful for detecting these abnormalities. Lectin histochemistry, using a panel of five lectins with differing carbohydrate specificities, was therefore performed on liver biopsies from patients with primary biliary cirrhosis, sclerosing cholangitis, cholangiocarcinoma, liver transplantation, extrahepatic biliary obstruction and normal liver. Reproducible high-quality lectin histochemistry was obtained on formalin-fixed paraffin-embedded tissue. In normal liver wheat germ agglutinin selectively bound to Kupffer cells, Griffonia simplicifolia II bound to hepatocytes, peanut agglutinin (PNA) bound to portal tract macrophages and liver capsule, and Ulex europaeus I (UEA I) bound to endothelium. Bile ducts were variably bound by all these lectins and soy bean agglutinin. In all the cholestatic biopsies PNA identified 'activated' Kupffer cells but there was no alteration in lectin binding specific to any of the benign conditions studied. Cholangiocarcinoma cells bound PNA and UEA I, so UEA I binding should not be regarded as specific for tumours of endothelial origin.

Adenoma, Bile Duct↗
PubMed1988

Use of lectin histochemistry in pancreatic cancer.

Lectin peroxidase histochemical analysis was carried out on pancreatic tissue from patients with pancreatic carcinoma and chronic pancreatitis and from subjects with normal pancreas to find a tumour specific pattern of lectin binding that would aid histological and cytological diagnosis. There were striking differences between the lectin binding characteristics of the different cell types in the normal pancreas. Acinar cells were uniformly positive for binding with wheat germ agglutinin and soy bean agglutinin while islet cells were usually negative for these lectins. Ulex europaeus I lectin however, was found not to be specific for endothelium, showing positivity also for acinar and ductal tissue. Griffonia simplicifolia II lectin was found to be highly specific for ductal epithelium, and because of this was tested in a hamster pancreatic cancer model where it was not specific for ductal epithelium, reflecting differing carbohydrate expression in the hamster pancreas. Pancreatic carcinomas and chronic pancreatitis bound all five lectins without any qualitative distinction from each other or from normal pancreatic tissue, but there was increased intensity of peanut agglutinin binding to secreted mucins in pancreatic carcinoma, which may be of potential use in radiolabelled lectin scanning.

Animals↗