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Biomedical subjects

A Lee

Publications and source records attributed to A Lee.

At least 19 recordsLinked to original sources
PubMed1992

Concentration-dependent modulation of basic fibroblast growth factor action on multiplication and locomotion of human teratocarcinoma cells.

A human teratoma cell line (Tera 2) was grown in serum-free medium, and the population multiplication was stimulated by the addition of 1-10 ng basic fibroblast growth factor (bFGF)/ml. The bFGF-effect was abrogated by the addition of protamine sulphate. When high concentrations of bFGF were added, a preferential effect on cell locomotion was observed. 100 ng bFGF/ml stimulated cell movement but only exerted a marginal effect on cell multiplication. These observed exogenous requirements for multiplication and locomotion were complemented by the expression of bFGF receptors. Scatchard analysis of binding data suggests the existence of a high-affinity and a low-affinity class of receptors.

Cell Division↗
PubMed1992

Use of recombinant fusion proteins for generation and rapid characterization of monoclonal antibodies. Application to the Kunitz domain of human beta amyloid precursor protein.

Production of peptides by recombinant DNA techniques is an efficient alternative to chemical synthesis of peptides. Proteins and peptides produced by recombinant DNA methods in E. coli are routinely used as antigens for the production of antibodies. However, most small peptides are rapidly degraded within the E. coli cell, and therefore, must initially be expressed as components of larger, more stable fusion proteins. The peptide of interest must be cleaved from the fusion protein, and purified prior to immunization to eliminate epitopes contributed by the fusion partner. We have now established methods for the production and characterization of monoclonal antibodies using partially purified, uncleaved fusion proteins. We have also described a method for efficient production and detection of the fusion protein, an EIA for rapid differential screening of hybridoma supernatants, and a strategy for epitope mapping of the antibodies. These methods have been applied to the production and characterization of monoclonal antibodies specific for a 75-amino-acid internal segment of the Alzheimer amyloid precursor protein, and should be applicable to a wide variety of other peptides and proteins.

Amyloid beta-Protein Precursor↗
PubMed1992

Relation of fetal and infant growth to plasma fibrinogen and factor VII concentrations in adult life.

OBJECTIVE: To determine whether reduced fetal and infant growth are associated with higher plasma fibrinogen and factor VII concentrations in adult life. DESIGN: Follow up study of men born during 1920-30 whose weights at birth and at 1 year had been recorded by health visitors, and men born during 1935-43 whose size at birth had been measured in detail. SETTING: Hertfordshire and Preston, England. SUBJECTS: 591 men born in east Hertfordshire who still lived there and 148 men born in Preston who still lived in or close to the city. MAIN OUTCOME MEASURES: Plasma fibrinogen and factor VII concentrations. RESULTS: Among men in Hertfordshire mean plasma fibrinogen and factor VII concentrations fell with increasing weight at 1 year (from 3.21 g/l in men of less than or equal to 18 lb to 2.93 g/l in men greater than or equal to 27 lb and from 122% of standard to 103%; p less than 0.001, p less than 0.005 respectively). The trends were independent of cigarette smoking, alcohol consumption, body mass index, and social class. Neither plasma fibrinogen nor factor VII concentration was related to birth weight. In men in Preston, however, fibrinogen concentration fell progressively as the ratio of placental weight to birth weight decreased (p = 0.01). CONCLUSIONS: Reduced growth in fetal life and infancy is strongly related to high plasma concentrations of the haemostatic factors fibrinogen and factor VII. This may be a persisting response to impaired liver development during a critical early period.

Aged↗
PubMed1992

Intrapartum amniotic fluid index and its relationship to fetal distress.

Amniotic fluid index was measured in 50 consecutive laboring women after membrane rupture. The 10th percentile of the normal range was 6.2 cm. Thirty-three women had a repeat measurement by a second observer. Although there was no systematic bias between the two observers, the limits of agreement were wide: 95% of the measurements by one observer were between 0.59 and 2.07 times those of the second. Closer agreement was observed when amniotic fluid index was low (less than 6.2 cm). The relationship between intrapartum amniotic fluid index and fetal distress was then investigated in a further 60 laboring women. When compared with women with a normal intrapartum amniotic fluid index, women with a low amniotic fluid index had higher incidences of fetal heart rate abnormalities during the first stage of labor (64% vs 20%, p less than 0.01), meconium (grade II or III) at delivery (64% vs 35%, p less than 0.05), and operative delivery for fetal distress (57% vs 17%, p less than 0.01). Umbilical artery pH and Apgar scores were, however, similar for the two groups. Measurement of intrapartum amniotic fluid index may be an appropriate method for selecting women suitable for intrapartum aminoinfusion.

Amniotic Fluid↗
PubMed1992

A cytotonic, cholera toxin-like protein produced by Campylobacter jejuni.

1. Campylobacter jejuni is a major cause of gastroenteric infection. 2. This organism appears to produce both cytotonic and cytotoxic virulence factors. 3. We report here that culture filtrates of some clinical isolates of C. jejuni induce elongation of Chinese hamster ovary (CHO) cells in vitro but do not cause inhibition of fluid absorption in the rat ileum. 4. These culture filtrates contain low levels of a protein which cross-reacts immunologically with the cholera toxin. 5. The cholera toxin-like protein of C. jejuni behaved identically to cholera toxin on non-denaturing polyacrylamide gel electrophoresis. 6. Under denaturing conditions, however, this protein displayed no subunit structure and a molecular weight of approximately 50 kDa with many higher molecular weight aggregates. 7. In conclusion, isolates of C. jejuni produced small amounts of enterotoxin when grown in vitro. 8. The toxin cross-reacted immunologically with cholera toxin and has a similar native structure, but does not appear to possess subunits.

Animals↗
PubMed1992

The role of teacher knowledge in elementary physical education instruction: an exploratory study.

The purpose of this study was to describe how providing teachers with research based knowledge about developmental throwing can influence teachers' observational interpretations and their students' practice patterns. Eight kindergarten classroom teachers with high generic teaching skill competence taught a 6-week overhand throwing unit to the children in their intact classes. Prior to the unit, four of the teachers were randomly assigned to a 4-hour knowledge training program. The other four teachers served as a comparison group (underwent no knowledge training). During the unit, data from stimulated recall interviews were used to describe and compare the thoughts and knowledge concepts expressed by the two groups of teachers. The throwing practice experienced by the children in the knowledge-trained and comparison teachers' classes was videotaped and analyzed for frequency of opposite foot stepping. The knowledge acquired during training was associated with different patterns of skill observation. The knowledge concepts the teachers acquired during training formed the basis of many of their thoughts and were reflected in the instructional procedures implemented. The knowledge-trained teachers' classes demonstrated more than twice as many opposite foot throws during the unit than the comparison teachers' classes.

Achievement↗
PubMed1992

Epidemiology of Helicobacter pylori in southern China: identification of early childhood as the critical period for acquisition.

A large cross-sectional study to investigate the prevalence and possible modes of transmission of Helicobacter pylori was done in southern China. Serum samples (1727) were collected from Guangzhou city and three rural areas of Guangdong Province, and the prevalence of H. pylori infection was determined using an ELISA. Each subject completed a questionnaire. The overall prevalence of H. pylori infection was 44.2%; a significantly higher prevalence was found in Guangzhou (52.4%) than in the rural areas (38.6%). This difference was generally reflected in the group 0-5 years old, but the rate of increase in seroprevalence for H. pylori over 5 years of age was similar (1%/year). This study provides important new data on the acquisition of H. pylori, particularly in the early years of life, and shows that density of living conditions is a prime determinant in the acquisition of H. pylori.

Adolescent↗
PubMed1992

Helicobacter muridarum sp. nov., a microaerophilic helical bacterium with a novel ultrastructure isolated from the intestinal mucosa of rodents.

Helical organisms with novel ultrastructural characteristics were isolated from the intestinal mucosa of rats and mice. These bacteria were characterized by the presence of 9 to 11 periplasmic fibers which appeared as concentric helical ridges on the surface of each cell. The cells were motile with a rapid corkscrewlike motion and had bipolar tufts of 10 to 14 sheathed flagella. The bacteria were microaerophilic, nutritionally fastidious, and physiologically similar to Helicobacter species and Wolinella succinogenes but could be differentiated from these organisms by their unique cellular ultrastructure. Using 16S rRNA sequencing, we found that strain ST1T (T = type strain) was related to previously described Helicobacter species, "Flexispira rappini," and W. succinogenes. The closest relatives of strain ST1T were Helicobacter mustelae and "F. rappini" (average similarity value, 96%). On the basis of phylogenetic data, strain ST1T (= ATCC 49282T) represents a new species of the genus Helicobacter, for which we propose the name Helicobacter muridarum.

Animals↗
PubMed1992

An ultrastructural study of Helicobacter mustelae and evidence of a specific association with gastric mucosa.

The ultrastructure of Helicobacter mustelae, a natural inhabitant of the ferret stomach, has been studied and compared with the human gastroduodenal pathogen H. pylori. H. mustelae is a short, slightly curved rod, 2 microns x 0.5 micron, with four or more sheathed flagella. The most common flagellar configuration is a single flagellum at one terminus, bipolar arrangement at the other end and a lateral flagellum. Dense inclusion bodies were observed below the flagellar insertion sites. It is suggested that this configuration is a specialised adaptation to motility in a viscous environment. On examination of the ferret gastric mucosa, similarities to H. pylori were observed such as adherence to gastric tissue and the formation of adhesion pedestals. However, unlike H. pylori, significant numbers of bacteria were intracellular. Furthermore, a much greater proportion of H. mustelae were attached to the mucosa with few bacteria lying free in the mucus, as is seen with H. pylori. It is concluded that the ferret is an important model for the study of adherence of bacteria to gastric mucosa and their possible role in peptic ulceration.

Animals↗
PubMed1992

Haemagglutination profiles of Helicobacter species that cause gastritis in man and animals.

Thirty-five Helicobacter pylori isolates, 21 H. mustelae isolates and four strains of H. felis were compared for their ability to agglutinate red blood cells (RBCs). Isolates were examined in a slide haemagglutination assay with RBCs from 11 animal species, including rodents, carnivores and primates, as well as man. RBCs were agglutinated by 65-90% of H. mustelae isolates and 16-57% of H. pylori isolates. Treatment of H. mustelae with pronase and heat inhibited haemagglutination (HA) whereas heating only of H. pylori inhibited HA. Treatment of all strains of H. mustelae with trypsin inhibited agglutination of human RBCs; 75% of the treated strains did not agglutinate ferret RBCs. These results suggested that protein(s) may be important haemagglutinins for these bacteria. Variable HA profiles together with varying results after treatment of RBCs with fetuin, D-mannose, and neuraminidase suggested that multiple receptors may be involved in HA reactions with H. pylori and H. mustelae. The observation that H. mustelae and H. pylori agglutinated RBCs of several species and closely adhered to gastric epithelium supported the hypothesis that adherence plays a role in the colonisation and pathogenicity of H. mustelae and H. pylori. H. felis did not adhere to gastric epithelium and did not agglutinate RBCs of any species; nevertheless, H. felis can readily colonise and produce gastritis in several mammals.

Animals↗
PubMed1992

Roles of rpoD, spoIIF, spoIIJ, spoIIN, and sin in regulation of Bacillus subtilis stage II sporulation-specific transcription.

Bacillus subtilis strains containing defects in the sporulation gene spoIIF (kinA), spoIIJ (kinA), or spoIIN (ftsA) cannot transcribe the sigma E-dependent gene spoIID. Results presented here and by other workers demonstrate that the spoIIF, spoIIJ, and spoIIN gene products control spoIID transcription indirectly by coordinating the induction of the spoIIGAB, spoIIE, and spoIIAC operons, which are required for sigma E synthesis and processing. Sporulation competence and spoIIGAB, spoIIE, and spoIIAC transcription were restored in spoIIF, spoIIJ, and spoIIN mutants by introduction of crsA47, a mutation in the major vegetative sigma factor sigma A. crsA mutations are known to restore sporulation in certain spo0 mutants. crsA suppression of kinA and ftsA mutations was achieved through inhibition of the transcription of sin, a gene involved in the selection between several post-exponential-phase cell states. A deletion of sin restored sporulation competence in spoIIF, spoIIJ, or spoIIN mutant strains. A sin deletion was also able to restore sporulation competence in the crsA suppressible stage 0 mutant spo0K141.

Bacillus subtilis↗
PubMed1992

PDGF induces tyrosine phosphorylation in osteoblast-like cells: relevance to mitogenesis.

We have studied the association between protein tyrosine phosphorylation and the mitogenic effect induced by platelet-derived growth factor (PDGF) in the osteoblast-like cell line MC3T3-E1. PDGF caused a dose-dependent increase in [3H]thymidine incorporation in MC3T3-E1 cells, reaching a plateau at 10 ng/ml. Vanadate, a potent phosphatase inhibitor, induced a twofold increase in thymidine incorporation. The combination of vanadate and PDGF resulted in a dose-dependent synergistic effect on thymidine incorporation. Genistein, a tyrosine kinase inhibitor, inhibited in a dose-related manner (2-20 microM) the mitogenic effect induced by either PDGF or the combination of vanadate and PDGF. These observations suggest that tyrosine kinases are involved in mediating the mitogenic effect of PDGF in these cells. PDGF treatment of MC3T3-E1 cells and subsequent immunoblotting with antiphosphotyrosine antibodies resulted in a marked phosphorylation of the PDGF receptor. Vanadate had a lesser effect on PDGF receptor phosphorylation, but given together with PDGF it induced a significant increase in the intensity of receptor phosphorylation. Preincubation with genistein abrogated these effects. Taken together, these findings indicate a direct correlation between thymidine incorporation and tyrosine phosphorylation in MC3T3-E1 cells and suggest that tyrosine phosphorylation plays a role in PDGF-induced mitogenic activity in osteoblast-like cells.

Animals↗
PubMed1992

Cholecystokinin and satiety: effect of hypothalamic obesity and gastric bubble insertion.

Cholecystokinin (CCK) is a gut peptide whose proposed effect on satiety is thought to be related to gastric volume and to be signaled through vagal afferent fibers to the medial hypothalamus. To test these hypotheses we infused CCK C-terminal octapeptide (CCK-8) or saline in a random double-blind fashion in three groups of subjects: 17 obese subjects, 6 of whom subsequently received a gastric bubble, and 5 obese subjects whose obesity was due to hypothalamic injury. The number of sandwich canapes eaten after saline or CCK-8 infusion was recorded during three consecutive 10-min eating periods. Each subject served as his/her own control. The prior infusion of CCK-8 significantly decreased the consumption of sandwich canapes in the first eating period in both the control obese subjects and the subjects with obesity due to hypothalamic injury. Insertion of a gastric bubble did not enhance the satiety effect of CCK-8. These studies support the hypothesis that CCK produces satiety in a time-dependent manner that is not enhanced after the insertion of a gastric bubble but is operative in obese subjects with hypothalamic injury.

Cholecystokinin↗