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Biomedical subjects

L Bell

Publications and source records attributed to L Bell.

At least 91 records · Page 5Linked to original sources

Current practices and improved recommendations for treating hereditary fructose intolerance.

A study of treatment practices of pediatric centers managing hereditary fructose intolerance and a review of recent literature on this subject were undertaken in an attempt to establish the degree of dietary liberalization allowable with age and the acceptability of foods containing trace amounts of fructose. The information was needed to plan optimal therapy and thus avoid the consequences of the disorder, namely intestinal dysfunction, metabolic imbalance, and hepatic and renal damage. Fifty responses to 113 letters to centers in Canada and the United States, as well as data from The Hospital for Sick Children, Toronto, Ontario, identified only 29 affected children and provided information on their care, including food lists and literature references. Major principles of treatment were similar, but the approach to allowing and quantifying dietary fructose differed. In response to the apparent need for standardization of treatment, the authors formulated improved recommendations for the control of dietary fructose (less than 1.5 gm/day). Only a few foods of vegetable origin are allowed, including a limited selection of vegetables and cereal products from grain endosperm. Repeated dietary counseling is advocated with regard to allowed foods, sweeteners, and medications to ensure long-term dietary compliance.

Carbohydrate Metabolism, Inborn Errors↗

The role of the splanchnic circulation in the regulation of total intravascular volume during alpha adrenergic receptor stimulation.

Previous studies have not defined the contribution of the splanchnic circulation to the total intravascular volume change associated with selective alpha adrenergic receptor stimulation. Since the splanchnic circulation is responsible for the total volume changes associated with other types of selective autonomic receptor stimulation, the present study was undertaken to examine the influence of alpha adrenergic receptor stimulation on splanchnic intravascular volume, the hemodynamic mechanism responsible for the splanchnic volume change, and the contribution of the splanchnic volume change to the change in total volume. In 35 anesthetized dogs, blood from the vena cavae was drained into an extracorporeal reservoir and returned to the right atrium at a constant rate so that changes in total intravascular volume could be measured as reciprocal changes in reservoir volume. Phenylephrine infusion (100 micrograms/min) for 20 min in 28 dogs was associated with a decrease in total volume of 64 +/- 17 (SEM) ml (P less than 0.0001). The response was abolished by either alpha adrenergic blockade or evisceration but was not attenuated by beta adrenergic blockade, sinoaortic baroreceptor denervation, ganglionic blockade, or splenectomy. In 5 animals with separate splanchnic perfusion and drainage, total and splanchnic volumes decreased 59 +/- 8 ml (P less than 0.0001) and 317 +/- 20 ml (P less than 0.0001), respectively, while transhepatic vascular resistance increased 17 +/- 4 cm H2O X min/l (P less than 0.0001). These responses were abolished after alpha adrenergic blockade. Thus, splanchnic volume decreases with alpha adrenergic receptor stimulation, despite an increase in hepatic resistance to splanchnic venous outflow. The splanchnic volume decrement is entirely responsible for the total volume decrement.

Adrenergic alpha-Antagonists↗

An ultrastructural study of meconium corpuscles in human foetal colon.

In human foetal colon meconium corpuscles were observed in the colonic epithelium during the stage of secondary lumina development and enlargement. Transmission electron microscopy of these specimens revealed inclusion bodies in the superficial and deeper layers of the epithelium. Many of the membrane-bounded inclusion bodies contained well-preserved organelles and some inclusions contained nuclear fragments. There was evidence of nuclear fragmentation with condensed chromatin arranged in crescentic caps. The ultrastructural observations are typical of apoptosis, a mode of cell death first described in 1972 by Kerr and colleagues. Thus, meconium corpuscles are apoptotic bodies found as a result of the deletion of healthy normal cells during the reshaping and development of organs.

Colon↗

Model for determination of 13C substrate oxidation rates in humans in the fed state.

The effect of a test diet of conventional North American foods on breath 13CO2 abundance was determined in 4 healthy males. Subjects consumed a diet containing 41.9% energy as fat and a polyunsaturated:saturated fatty acid ratio of 0.217 for 5 days at a level equal to estimated requirements for total energy. One subject underwent four 5-day feeding periods. Over the feeding period mean change in subjects' body weight was -0.165 +/- 0.64% (means +/- SEM) of initial body weight. On day 5 breath samples were collected hourly from 0745 to 1645 h and analyzed for 13CO2 enrichment relative to the pre-breakfast fasted state (level at 0745 h). Breakfast and lunch were consumed at 0820 and 1300 h respectively. Mean enrichment peaked at 1445 h at 0.00311 atom % excess above fasting level for all subjects and 0.00243 atom % excess for the four repeated trials on one subject. Between subject variation (SEM) in 13CO2 enrichment (0.000618 atom %) was significantly greater than within subject variation (0.000308 atom %). These results indicate that ingestion of normal meals during the breath test period increases breath 13CO2 abundance due to a shift in substrate oxidation. The small within subject variation in repeated 13CO2 enrichment profiles indicates the reliability of 13C breath tests using controlled diets. It is concluded that for tests conducted under identical conditions, an initial background 13CO2 abundance profile determined once for each subject, can be subtracted from the subsequent enrichment profile generated by a labeled test substrate.

Adult↗

Influence of naloxone on the total capacitance vasculature of the dog.

The opiate antagonist, naloxone, which is associated with prolonged survival in animal models of shock, has been demonstrated to increase arterial pressure and cardiac output. It is possible that the increase in cardiac output is due to a decrease in volume in the total capacitance vasculature and a subsequent increase in venous return. Because the influence of naloxone on the capacitance vasculature is unknown, the present study was undertaken to determine the influence of naloxone on intravascular volume in the total capacitance circulation. In 31 anesthetized dogs, blood from the vena cavae was drained into an extracorporeal reservoir and returned to the right atrium at a constant rate so that changes in total intravascular volume could be measured as reciprocal changes in reservoir volume. In five animals, naloxone infusion (2 mg/ml X min for 20 min) was associated with a decrease in total capacitance volume of 121 +/- 30 ml (P less than 0.05). To determine regional volume effects, naloxone was infused in 11 animals in which the splanchnic and extrasplanchnic vasculatures were separately perfused and drained: total and splanchnic volume decreased 64 +/- 13 ml (P less than 0.05) and 126 +/- 17 ml (P less than 0.0001), respectively, and extrasplanchnic volume increased 62 +/- 13 ml (P less than 0.001). After ganglionic blockade with mecamylamine (n = 3), total volume decreased 89 +/- 16 ml (P less than 0.05), splanchnic volume did not change, and extrasplanchnic volume decreased 91 +/- 32 ml (P less than 0.05). In another five animals, naloxone was infused during diversion of the splanchnic venous outflow to a nonrecirculating extracorporeal reservoir: total volume decreased 122 +/- 33 ml (P less than 0.05), splanchnic volume did not change, and extrasplanchnic volume decreased 101 +/- 16 ml (P less than 0.01). When the splanchnic venous effluent was reinfused without naloxone administration (n = 4), total volume decreased 43 +/- 5 ml (P less than 0.05), splanchnic volume decreased 113 +/- 14 ml (P less than 0.05), and extrasplanchnic volume increased 68 +/- 10 ml (P less than 0.05). Thus, naloxone is associated with a decrease in total capacitance volume, which is due entirely to a decrease in splanchnic volume. The splanchnic volume decrement would appear to be mediated through neurogenic and hormonal influences. In an animal not on bypass, it would be expected that naloxone would be associated with a decrease in total capacitance volume and subsequent increases in venous return and cardiac output.

Animals↗

Use of information technology by clinical dietitians in Canada.

Information technology in health care in Canada is beginning to show an impact in clinical dietetics. Good response (64%) to a survey of 307 hospitals indicated that 15 hospitals now use computers for the assessment of nutrients in patients' food intakes, in menus, and in recipes. Another 76 plan to initiate computer use. The majority of nutrition and food service departments categorize computers as potentially 'very useful' in clinical dietetics. The 15 respondents who use computers serve as models for future users. Hand calculation of nutrients is performed to some degree by 170 hospitals. Information from these respondents indicated that they share many common needs, thus encouraging a cooperation of effort in future computer applications.

Canada↗

Protein-sparing diet for severely obese adolescents: design and use of an equivalency system for menu planning.

When severe, obesity in adolescence demands effective treatment, thus justifying use of a protein-sparing, low-energy diet for periods of 3 to 4 months. When properly planned and supervised, this diet is safe and effective, even if only to maintain a functional body weight. The regimen used at the Hospital for Sick Children, Toronto, provides 2.0 to 2.5 gm protein per kilogram ideal body weight, plus adequate fluid and nutrient supplements. The amounts of meat, poultry, and fish that supply this allocation of protein are determined using a protein equivalency system developed for the diet. The system allows both dietitians and patients to plan meals that minimize energy intake while maintaining protein adequacy and dietary variety. With prolonged use of the diet, limited carbohydrate may be added in the form of selected vegetables measured using a similar carbohydrate equivalency system. Recent use of the diet for 21 patients, 8 to 20 1/2 years old and averaging 211% ideal body weight, resulted in acceptable weight control.

Adolescent↗

General practice audit of asthma in childhood.

It has been suggested that asthma is underdiagnosed in children. We studied the records of 52 children with asthma in our group practice. Although asthma had been positively diagnosed in roughly 10% of the children aged 18 months to 11 years, to make the diagnosis required an average of 16 to 20 consultations for respiratory problems. According to the symptoms recorded before the diagnosis was made, only three quarters of the children had presented with wheeze and roughly a third had had difficulty in sleeping. We think that the doctor's time would be better spent teaching patients about their asthma than by repeatedly treating non-existent respiratory infection.

Asthma↗

An ultrastructural study on the "meconium corpuscles" in rat foetal intestinal epithelium with particular reference to apoptosis.

During the embryonic development of the intestine, programmed deletion of epithelial cells plays a vital role in the formation of secondary lumina and of villi. Electron microscopy shows that this deletion is effected by apoptosis, a distinctive mode of cellular death recently recognised as being implicated in normal tissue involution in the adult, as well as during intrauterine development. The process involves cellular condensation and budding to form membrane-bounded apoptotic bodies containing well-preserved organelles. These are then either engulfed by neighbouring principal cells or sloughed off into the intestinal lumen. Engulfed apoptotic bodies that show various degrees of lysosomal degradation have previously been referred to as "meconium corpuscles".

Animals↗

Expression in Bacillus subtilis of the gene for human urogastrone using synthetic ribosome binding sites.

A chemically synthesised gene coding for human urogastrone which was earlier cloned in E. coli (Smith et al. 1982) has now been cloned into expression vectors for Bacillus subtilis. Two types of constructs have been made, one giving production of methionyl-urogastrone and the other giving rise to a methionyl-urogastrone-beta galactosidase fusion polypeptide facilitating quantification of expression levels. The ribosome binding sites used in the expression plasmids are synthetically made oligonucleotides residing on short restriction fragments to allow easy replacement by other ribosome binding sites. Using "shuttle" vectors and constitutive promoters from Bacillus phages phi 105 and SPP1, we were able to detect levels of expression amounting to a few thousand molecules per cell during logarithmic growth in both E. coli and B. subtilis.

Amino Acid Sequence↗

Cloning and expression of a porcine prorelaxin gene in E. coli.

A porcine prorelaxin gene has been constructed partly by synthetic means and partly from its natural messenger RNA. A gene coding for the 32 N-terminal amino acids including a chain initiator methionine codon (B gene) was synthesised and inserted in a plasmid at a site downstream from a tryptophan promoter in such a way that its expression is under the control of the trp promoter. DNA corresponding to the rest of the prorelaxin was prepared using reverse transcriptase extension of a primer complementary to relaxin mRNA and joined at a suitable restriction site to the B gene. Transformation of E. coli with this plasmid followed by suitable induction resulted in the synthesis of a new protein identified as prorelaxin by its size and its antigenic similarity to relaxin.

Amino Acid Sequence↗

Separation of branched from linear DNA by two-dimensional gel electrophoresis.

A general method for separating branched DNA molecules, such as replication forks and recombination intermediates, from linear forms has been developed. Using as a model a stable X-shaped molecule constructed in vitro, it was found that this branched form migrated more slowly during agarose gel electrophoresis than did a linear form of the same mass. Higher agarose concentrations and higher electrophoretic voltages enhanced the extent of retardation. These properties provided the basis for an electrophoretic method of separating branched from linear molecules by variation of agarose concentration and voltage over two dimensions. In the first dimension, concentration and voltage were low; in the second, both parameters were increased, thereby forcing X-shaped molecules to migrate to positions distinct from a diagonal arc of linear molecules. In addition, two-dimensional electrophoresis was capable of separating X-shaped forms of different mass from each other, as well as from linear molecules.

Chemical Phenomena↗

Early gastric cancer in a United States hospital.

Early gastric cancer (EGC) confined to mucosa and submucosa, described by Japanese physicians over 20 years ago, yields about 90% 5-year postoperative survival. EGC has been increasingly reported from centers outside Japan, but rarely from the United States. Between 1976-1981, EGC was found in six patients or about 8.5% of all gastric carcinomas diagnosed in our hospital. Diagnoses were established by following suspicious upper gastrointestinal series or negative x-rays in patients with dyspepsia by means of gastroscopy and gastroscopically obtained biopsies, brush, and/or wash cytology. All six patients underwent subtotal gastrectomy with histological findings of EGC not invading the muscularis and with no metastases. So far no tumor recurrences have been found in these six patients. The results suggest that EGC as defined by Japanese investigators occurs in our hospital and presumably across the United States more often than heretofore appreciated. Previous fatalistic attitudes toward diagnosing gastric cancer should be replaced by efforts at early diagnosis. Patients with symptoms suggestive of gastric carcinoma, including unexplained dyspepsia, should undergo early upper gastrointestinal x-ray and endoscopic examinations with biopsies and cytological tests of any suspicious raised, flat, or depressed area.

Aged↗

The molecular cloning and characterisation of cDNA coding for the alpha subunit of the acetylcholine receptor.

A rare cDNA coding for most of the alpha subunit of the Torpedo nicotinic acetylcholine receptor has been cloned into bacteria. The use of a mismatched oligonucleotide primer of reverse transcriptase facilitated the design of an efficient, specific probe for recombinant bacteria. DNA sequence analysis has enabled the elucidation of a large part of the polypeptide primary sequence which is discussed in relation to its acetylcholine binding activity and the location of receptor within the plasma membrane. When used as a radioactive probe, the cloned cDNA binds specifically to a single Torpedo mRNA species of about 2350 nucleotides in length but fails to show significant cross-hybridisation with alpha subunit mRNA extracted from cat muscle.

Amino Acid Sequence↗

A scanning and transmission electron microscopical study of the morphogenesis of human colonic villi.

The morphogenetic events that occur in the development of villi in human foetal colon have been observed by light microscopy and scanning and transmission electron microscopy. At nine weeks, the colon is a simple tube composed of pseudostratified columnar epithelium and mesenchyme. By ten weeks, up to eight longitudinal ridges have formed by an elongation of individual epithelial cells. Even as the ridges are forming, the bases of some of the ridges become indented with mesenchyme thus forming longitudinal mucosal folds. By eleven and a half weeks, these have folded in a concertina fashion forming a longitudinal zig-zag pattern. From ten and a half weeks, small lumina develop within the epithelium near to its base. At this stage, they are not in continuity with the main lumen. Extension of these lumina to the main luminal surface and exfoliation of redundant cells result in division of the zig-zag folds into broad primary villi. Division of the primary villi occurs when cyst-like structures which develop within the pseudostratified columnar epithelium of the primary villi enlarge and extend to the lumen. Together with upgrowth of mesenchyme this results in small secondary villi with simple columnar epithelium.

Colon↗