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Biomedical subjects

A Becker

Publications and source records attributed to A Becker.

At least 289 records · Page 16Linked to original sources
PubMed1996

Host defense within the urinary tract. I. Bacterial adhesion initiates an uroepithelial defense mechanism.

Uroepithelial defense has ben suggested to contribute to the local host resistance against ascending urinary tract infection. The cellular mechanism, however, is not known. In this study, bacterial growth was measured under the direct and indirect influence of uroepithelial cells. To study if a specific ligand-receptor interaction is required for uroepithelial cell (UEC) activation, isogenic Escherichia coli mutants expressing either mannose-sensitive, mannose-resistant (p), or mannose resistant (s) pili were tested for their capacity to induce the UEC defense mechanism. The antibacterial effect of UEC was abolished either by performing coculture in chambers with a fluid-permeable membrane which separates UEC from bacteria or by inhibiting membrane contact using the antiadherence factor pentosane polysulfate. No difference between the various types of pili could be shown. All E. coli strains adhered comparably to the UEC and were subsequently suppressed in their growth. Even a "naked" mutant without expression of common pili showed a similar behavior. In conclusion, bacterial growth suppression depends on direct contact between the UEC and bacteria, but is independent of common pili expressed on E. coli.

Adolescent↗
PubMed1996

Illumination has no effect on rats' behavior in the elevated plus-maze.

Male Wistar rats Shoe:Wist(Shoe) were tested in the elevated plus-maze under three different illumination levels (30, 300, and 900 lx). It was found that illumination did not change percentage of time spent in closed arms, number of closed arm entries, or time spent on open arms, or total arm entry. This confirms earlier findings that rat's behavior in the elevated plus-maze is independent of light levels.

Albinism↗
PubMed1996

The pathophysiology of alveolar osteonecrosis of the jaw: anticardiolipin antibodies, thrombophilia, and hypofibrinolysis.

We studied 55 patients (50 women, 5 men) with severe facial pain and biopsy-proven neuralgia-inducing cavitational osteonecrosis (NICO) of the alveolar bone of the jaws. Our aim was to assess the pathophysiologic contributions to NICO of anticardiolipin antibodies (aCLA), thrombophilia (increased tendency to intravascular thrombi), and hypofibrinolysis (reduced ability to lyse thrombi). Of the 55 patients, 43 (78%) had one or more tests positive for thrombophilia or hypofibrinolysis (or both), and only 12 (22%) were normal. Eighteen of 55 (33%) patients had high aCLA (> 2 SD above mean value for control subjects); immunoglobulin G (IgG) (p = 0.01) and immunoglobulin A (IgA)(p = 0.001) levels were higher in patients than in controls. The distribution of elevated aCLA immunoglobulin classes among patients was as follows: IgG alone, 5 (9%); IgA alone, 7 (13%); and IgM alone, 3 (5%). Three patients (5%) had high levels of both IgG and IgA aCLA. Other defects of the thrombotic or fibrinolytic systems in the 55 patients included high lipoprotein(a) in 36% (vs 20% in control subjects (p = 0.03)), low stimulated tissue plasminogen activator activity (tPA-Fx) in 22% (vs 7% in control subjects (p = 0.08)), high plasminogen activator inhibitor activity (PAI-Fx) in 18% (vs 8% in control subjects (p = 0.03)), resistance to activated protein C in 16% (vs 0% in control subjects (p = 0.007)), low antigenic protein C in 4+ (vs 0% in control subjects (p > 0.2)), and low antigenic protein S in 4% (vs 0% in control subjects (p > 0.2)). Anticardiolipin antibodies and other defects of the thrombotic and fibrinolytic systems appear to be common, potentially reversible pathogenetic risk factors associated with osteonecrosis of the jaw.

Adolescent↗
PubMed1996

Potentiation effects in the dentate gyrus of pentylenetetrazol-kindled rats.

The study examines changes in the function of perforant pathway dentate granule cell synapses after pentylenetetrazol (PTZ) kindling. Field potentials evoked in the dentate area by test stimuli to the perforant pathway were recorded in freely moving rats at different times after injection of PTZ. In fully kindled animals, but not in sham-kindled controls, subconvulsive test doses of PTZ induced long-lasting potentiation of the population spike. Also, potentiation was not induced in naive controls injected with equieffective doses of the convulsant. The slope function of the field EPSP was depressed 90-120 min after PTZ administration, in both kindled and control animals, indicating that this was an effect of acute-injected PTZ. Later on, only in kindled animals that showed seizure stages 4 or 5 did it increase in parallel with the population spike potentiation. Finally, when compared to controls the kindled animals showed a greater pop spike potentiation induced by moderate tetanization of the perforant pathway. The model offers the possibility of differentiating between acute effects of the convulsant drug and kindling-related changes in neuronal plasticity.

Animals↗
PubMed1996

The resolution of palatally impacted canines using palatal-occlusal force from a buccal auxiliary.

Palatally impacted canines can usually be mechanically drawn directly to the labial arch wire after they have been surgically exposed. Occasionally, the direct line between the impacted tooth and the arch wire is obstructed by the presence of the root of the lateral incisor, or the tooth is very superiorly displaced, which makes direct traction ill-advised and impractical. In this situation, it is recommended that the tooth be erupted vertically downward, through the palatal tissue on the palatal side of the dental arch, as a first stage and, only then moved buccally into its place in the arch. This article describes a method whereby an auxiliary spring is placed on the buccal side of the arch to produce the vertical and palatal traction needed. There are no palatal accessories, and the auxiliary is tied in, "piggy-back" fashion, over the main base arch, by using the multibracketed appliance already present.

Cuspid↗
PubMed1996

Effect of application of benzyl benzoate on house dust mite allergen levels.

BACKGROUND: Several acaricides have become available for reducing house dust mite allergen levels. OBJECTIVE: The purpose of this study was to assess whether the use of benzyl benzoate (Acarosan) provides additional benefit to the usual mite control measures including encasement of mattress and pillows with vinyl covers. METHODS: A randomized controlled trial was carried out in 26 homes (14 control versus 12 treatment) of asthmatic patients in two cities (Vancouver and Winnipeg). The control group had the usual house dust mite control measures including the use of vinyl covers for mattresses and pillows while the treatment group had application of benzyl benzoate to mattresses and carpets in the bedroom and the most commonly used room, in addition to the above control measures. Mite allergen levels were measured 3 months and immediately before, 1 week, and 1 and 3 months after the application of house dust mite control measures. Patients kept diary cards on asthma symptoms and peak expiratory flow rates morning and evening one month before and three months after the onset of mite allergen control measures. RESULTS: A reduction of mite allergen level was found in mattress samples in both groups, statistically significant at all times in the treatment group and at one and three months in the control group. Mite allergen levels on floor carpets also showed progressive reduction in both groups, but were significantly different in the treatment group (compared with controls) at 1 week, and were lower compared with baseline in the treatment group up to 3 months. No significant changes in asthma symptoms, peak expiratory flow rates, spirometric measurements, or bronchial hyperresponsiveness were observed among treatment or control group subjects. CONCLUSION: The addition of benzyl benzoate to conventional house dust mite control measures resulted in a significant reduction in floor carpet dust mite levels that persisted for 3 months. The results of this study should be confirmed in a larger and longer study.

Adult↗
PubMed1996

Orthodontics for the handicapped child.

The broad spectrum of difficulties that exist in providing orthodontic treatment for handicapped children is well known and few practitioners offer such a service. The present article offers an analysis of the problems involved and provides some practical answers designed to overcome them. It describes some of the newer modalities that have become available to the dental profession over the last few years and shows how advantage may be gained by their exploitation, in orthodontic treatment. Additionally, some of the older and largely-forgotten methods, appropriately modified and updated, are represented in this context, where they find particular relevance. Guidelines are given to enable the orthodontic profession to gain therapeutic access to a section of the population that urgently requires treatment.

Behavior Therapy↗
PubMed1996

Attachment bonding to impacted teeth at the time of surgical exposure.

This study examines the relative success of bonding an attachment to an impacted tooth at the time of surgical exposure, compared with placing it on a subsequent occasion. In addition, the relative merits of various attachments, the choice of bonding site and whether or not pumice prophylaxis is necessary, were tested. The results showed that bonding at the time of exposure is superior to its performance at a later date, that the use of an eyelet attachment has a lower failure rate than the use of a conventional bracket, that the palatal aspect offers the poorest bonding surface and that pumicing the exposed tooth offers no advantage over immediate etching of the exposed enamel. The results of this study refute the view that the circumstances prevalent at the time of surgical exposure are not conducive to the reliable bonding of an attachment to an impacted tooth.

Acid Etching, Dental↗
PubMed1996

Expression, purification and characterisation of recombinant pallidipin, a novel platelet aggregation inhibitor from the haematophageous triatomine bug Triatoma pallidipennis.

Pallidipin is a platelet aggregation inhibitor protein originating from the saliva of the haematophageous triatomine bug Triatoma pallidipennis. Its inhibitory effects are specific for collagen-induced platelet aggregation. The recombinant form of the protein was expressed in the periplasmic space of transformed Escherichia coli using a vector based on the alkaline phosphatase gene promoter and leader peptide. Recombinant pallidipin was purified in three chromatographic steps including cation exchange, anion exchange and size exclusion gel chromatography. SDS/PAGE and N-terminal amino acid sequencing showed that recombinant pallidipin had a molecular weight similar to that of the salivary protein (approximately 19 kDa) and had been correctly processed. The yield was 864 micrograms of pure protein from one litre of bacterial culture. The biological activity of recombinant pallidipin was assessed in a platelet aggregation assay using collagen at a concentration of 2 micrograms/ml as inducer, and the IC50 found to be 33 nM, similar to that determined for the native protein. When the collagen concentration used for induction was increased, higher pallidipin concentrations were also needed to achieve a comparable inhibition of platelet aggregation.

Animals↗
PubMed1996

Promoter analysis of the Xanthomonas campestris pv. campestris gum operon directing biosynthesis of the xanthan polysaccharide.

The Xanthomonas campestris gum gene cluster is composed of 12 genes designated gumB, -C, -D, -E, -F, -G, -H, -I, -J, -K, -L, and -M. The transcriptional organization of this gene cluster was analyzed by the construction of gum-lacZ transcriptional fusions in association with plasmid integration mutagenesis. This analysis, coupled with primer extension assays, indicated that the gum region was mainly expressed as an operon from a promoter located upstream of the first gene, gumB.

Base Sequence↗
PubMed1996

Changes in peak flow, symptom score, and the use of medications during acute exacerbations of asthma.

Changes in symptom score and peak expiratory flow (PEF) and the use of medications during the first acute exacerbation of asthma were studied in 41 patients and matched controls who took part in a panel study. An acute exacerbation was defined as the presence of at least one of the following: any unscheduled physician visit, visit to an emergency room, or hospitalization for treatment of asthma; a decrease in PEF by 30% from the patient's best reading; an increase in asthma symptoms during the day and night for over 48 h and not responding to usual medications; and the commencement or doubling of the dose of oral or inhaled steroids for any of the foregoing reasons. Data from -9 to -7 d before the onset of an acute exacerbation were taken as the baseline data, with which the values of the subsequent 14 d were compared. Significant increases in symptoms occurred before a significant reduction in PEF. None of the patients had a decrease of more than 30% in PEF before the onset of symptoms. Daily variation in PEF was not significantly increased from the baseline. Our results suggest that PEF monitoring is not as sensitive as a symptom diary for revealing acute exacerbations of asthma, and that a 30% decrease in PEF is too stringent a criterion for defining an acute exacerbation.

Acute Disease↗
PubMed1996

Serum sex hormone-binding globulin and osteocalcin in systemic nonthyroidal illness associated with low thyroid hormone concentrations.

To test the hypothesis that patients with systemic nonthyroidal illness (NTI) and impaired thyroid hormone metabolism most commonly present with the low T3 or low T4 syndrome are in an euthyroid status at the tissue level, we determined serum sex hormone-binding globulin (SHBG) and osteocalcin (OC) as parameters for thyroid hormone availability to liver and bone. Serum SHBG and OC concentrations were measured in 61 severely ill patients with decreased serum levels of either T3 alone (n = 47) or both T3 and free T4 (n = 14). None of the patients had primary thyroid disorder indicated by regular thyroid sonomorphology and normal basal TSH concentrations. Data were compared with values obtained from age- and sex-matched controls without impairment of thyroid hormone physiology. The respective results from the study groups and from control subjects were as follows: low T3 SHBG, 49 +/- 30 nmol/L; low T4 SHBG, 35 +/- 14 nmol/L; control SHBG, 45 +/- 28 nmol/L; low T3 OC, 0.87 +/- 0.75 nmol/L; low T4 OC, 0.75 +/- 0.71 nmol/L; control OC, 0.98 +/- 0.87 nmol/L. SHBG and OC do not differ significantly between NTI patients with low T3 or low T4 syndrome and controls, and no significant relationship was found between thyroid hormone parameters and SHBG or OC, respectively. We conclude that the term euthyroid sick syndrome applied for the condition of systemic NTI associated with reduced circulating thyroid hormone concentrations appears to be appropriate at the level of hepatocytes and osteoblasts. Data are in partial contradiction to the results of previous studies using alternative serum parameters for assessment of peripheral thyroid hormone action (e.g. angiotensin-converting enzyme). Due to the tissue specificity of the biochemical serum markers, conflicting results may be explained by organ-specific differences in local thyroid hormone exposure. In case of doubt, SHBG and OC determinations may help specify peripheral thyrometabolic status in NTI.

Adult↗
PubMed1996

Neonatal characteristics as risk factors for preschool asthma.

Childhood asthma usually begins early in life. Neonatal characteristics are reportedly predictive of symptom onset. This investigation utilized data from a provincial health organization to evaluate the effect of several birth characteristics on asthma incidence and hospitalization for asthma during age 0-4. Using logistic regression, the odds ratios (OR) for the following variables indicate a significant (p < 0.05) association with physician-diagnosed preschool asthma: male gender (OR = 1.72), birthweight < 1500 g (OR = 2.11), prematurity (OR = 1.34), respiratory distress syndrome (RDS) in the presence (OR = 2.95) or absence (OR = 1.61) of bronchopulmonary dysplasia (BPD), and transient tachypnea of the newborn (TTN; OR = 1.36). Male gender (OR = 1.91), birthweight < 1500 g (OR = 2.56), RDS with and without BPD (OR = 3.35 and 2.50, respectively), TTN (OR = 2.08), and severe birth asphyxia (OR = 1.94) showed an important association with hospitalization due to asthma. Neonatal characteristics are important determinants for the risk of preschool asthma, even after mutual adjustment.

Asthma↗
PubMed1996

Critical role of the sinuses of Valsalva in the durability of valved conduits.

BACKGROUND AND AIMS OF THE STUDY: Most work in search of an ideal extracardiac valved conduit has assumed that the type of tissue used for construction is the determining factor for its behavior and durability. The excellent results of our study with a valved conduit incorporating sinuses of Valsalva and made of autologous pericardium showed that the design plays a crucial role in addition to the type of material. MATERIALS AND METHODS: We report the experimental results of three different pericardial sinus bearing valved conduits made of 0.5% glutaraldehyde treated autologous pericardium (Group 1), dye mediated photooxidized bovine pericardium (Group 2), and glutaraldehyde treated bovine pericardium (Group 3) implanted in the right ventricular outflow tract of sheep. Groups 1, 2 and 3 had 11, 11 and four animals available for assessment out of 12, 18 and six implantations respectively. The valved conduits were explanted at varying intervals between one and 11 months. The conduit function was assessed with hemodynamic, echocardiographic and Doppler studies both at the time of implantation and sacrifice. The explanted conduit was studied macroscopically and subjected to histopathologic examination. RESULTS: The hemodynamic and echocardiographic studies at implantation showed very satisfactory results in all three groups. At the time of sacrifice, Group 1 showed consistently good results. In a significant number of animals in Groups 2 and 3, one, two or even three cusps had become adherent to the conduit wall, resulting in severe regurgitation. The sinuses were well preserved in Group 1, while they were less prominent in Group 2 and least in Group 3. Histopathologically, the three groups basically showed the same feature, a process of fibrocellular proliferation resulting in thickening. In this study the adhesion of the cusps to the sinus wall was related to the degree of prominence of the sinuses of Valsalva, which in turn depended on the ability to shape the pericardium at the time of construction of the valved conduit. CONCLUSIONS: This study stresses the importance of the sinuses in the behavior of the semilunar valve leaflets.

Animals↗
PubMed1996

Analysis of the complementary determining region III of the immunoglobulin heavy chain locus in acute lymphoblastic leukemia in Chilean children.

We have analyzed the sequence of 40 VDJ rearrangements of the immunoglobulin heavy chain gene locus on 32 unselected children from Chile with precursor B cell ALL at diagnosis. Rearrangements were derived by PCR with VH gene family-specific primers and sequenced directly. The number of VDJ rearrangements, and the pattern of VH, DH and JH gene usage was identical to the one reported by groups from developed countries. CDR3 regions represented an unbiased repertoire; VH to JH joinings were in frame in 36% of cases. Absent N nucleotides in the DJ border, suggestive of fetal origin of ALL, were seen in 9/40 rearrangements but they did not correlate with younger age. More than one rearrangement was sequenced in six patients, representing independent events with no signs of clonal evolution. One patient was analyzed at first bone marrow relapse showing persistence of one rearrangement and evolution of a second one which conserved the DJ border. The subset of B cell precursors which suffer malignant transformation to ALL appear to be common in different parts of the world.

Adolescent↗