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Biomedical subjects

M Anderson

Publications and source records attributed to M Anderson.

At least 253 records · Page 14Linked to original sources
PubMed1994

Hemodynamic effects and echocardiographic consequences of tension-free pericardial closure after heart valve surgery.

Pericardial closure early after open heart surgery has been shown to consistently lower cardiac output and stroke volume, while mean arterial blood pressure is maintained by an increase in systemic vascular resistance. In 10 patients (seven females) (mean age 65 +/- 4 years) undergoing an open heart valve procedure, the effects of a tension-free pericardial closure technique were studied using thermodilution studies and transesophageal echocardiography. The following variables were recorded: mean arterial pressure, mean pulmonary artery pressure, right atrial pressure, cardiac output, stroke volume, systemic vascular resistance, and systolic and diastolic left ventricular dimensions, and left ventricular wall thickness. Observations were made after the heart was decannulated, both while the pericardium was open and after it had been closed by a tension-free technique, and then after closure of the chest. Further observations were made while the chest remained closed, both before and after the pericardium had been reopened by removing the pericardial suture through the chest wall. Closing the pericardium with the tension-free technique while the chest remained open was followed by a fall in cardiac output by 8% and a 15% fall in systemic vascular resistance (both n.s.). These changes caused a 13% reduction in the mean arterial pressure (p = 0.03). Ejection fraction did not change, and systolic and diastolic left ventricular dimensions decreased by 6% and 4% respectively (both n.s.). Opening the pericardium (1.5 to 2 hours after the end of the operation) while the chest remained closed was not followed by significant change in any of the hemodynamic or echocardiographic variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

An innovative model of system-linked community care: home-based traction as an alternative to institutional treatment.

Home-based traction is an alternative treatment to conventional hospital-based traction for children with orthopedic conditions such as congenital dislocated hip and Legg-Perthes disease. The application of a proposed theoretical model is used to describe the process of the home-based traction innovation. Creativity and innovation occasions a reconceptualization of stresses. The reconceptualization of stress, plus the operational support of coordinated in-home services, can help families and nurses in the community and in the hospital develop, implement, and evaluate this kind of innovative care. In applying the home-based traction professionals empower and legitimize parents as resourceful co-providers of care. The legitimizing of the alternative in-home service affords parents a more optimistic appraisal of their situation as manageable. Parents are free to develop a coordinated response to their overall circumstance, including the treatment of their one child's illness. The evaluation of this home-based traction example found the alternative to be acceptable, safe, effective in accomplishing treatment goals, and less expensive than conventional hospital-based traction.

Adult↗
PubMed1993

Cellular mechanisms governing synaptic development in Drosophila melanogaster.

The neuromuscular connections of Drosophila are ideally suited for studying synaptic function and development. Hypotheses about cell recognition can be tested in a simple array of pre- and postsynaptic elements. Drosophila muscle fibers are multiply innervated by individually identifiable motoneurons. The neurons express several synaptic cotransmitters, including glutamate, proctolin, and octopamine, and are specialized by their synaptic morphology, neurotransmitters, and connectivity. During larval development the initial motoneuron endings grow extensively over the surface of the muscle fibers, and differentiate synaptic boutons of characteristic morphology. While considerable growth occurs postembryonically, the initial wiring of motoneurons to muscle fibers is accomplished during mid-to-late embryogenesis (stages 15-17). Efferent growth cones sample multiple muscle fibers with rapidly moving filopodia. Upon reaching their target muscle fibers, the growth cones rapidly differentiate into synaptic contacts whose morphology prefigures that of the larval junction. Mismatch experiments show that growth cones recognize specific muscle fibers, and can do so when the surrounding musculature is radically altered. However, when denied their normal targets, motoneurons can establish functional synapses on alternate muscle fibers. Blocking synaptic activity with either injected toxins or ion channel mutants does not derange synaptogenesis, but may influence the number of motor ending processes. The molecular mechanisms governing cellular recognition during synaptogenesis remain to be identified. However, several cell surface glycoproteins known to mediate cellular adhesion events in vitro are expressed by the developing synapses. Furthermore, enhancer detector lines have identified genes with expression restricted to small subsets of muscle fibers and/or motoneurons during the period of synaptogenesis. These observations suggest that in Drosophila a mechanism of target chemoaffinity may be involved in the genesis of stereotypic synaptic wiring.

Animals↗
PubMed1993

Fabrication of surfaces resistant to protein adsorption and application to two-dimensional protein patterning.

Proteins were attached in defined geometric patterns on a surface. A prerequisite to making a pattern of proteins is generation of surfaces resistant to nonspecific protein adsorption. This was accomplished via oxidation of the thiol terminus of an organosilane self-assembled monolayer film by deep ultraviolet (DUV) irradiation. The resultant surface exhibited marked resistance to protein adsorption. Using a mask to protect regions of the silanized surface from irradiation, proteins were selectively adsorbed or attached via covalent linkage at locations protected from the DUV light. Antibodies immobilized in patterns using this procedure retained their antigen-binding capability. Thus chemistry and DUV lithography were combined to create patterns of active biomolecules which could be used in the microfabrication of electronic devices and biosensors.

Adsorption↗
PubMed1993

Large-scale mutational analysis of EMS-induced mutation in the lacI gene of Escherichia coli.

Mutational spectra produced by mutagens in various repair backgrounds can provide important information about the roles of different repair systems in the mutagenic process. Until recently, such studies have been restricted to the characterisation of comparatively small numbers of mutants or reversion analysis at relatively few sites. The colony hybridisation method used in this study in conjunction with DNA sequencing allows the characterisation of large numbers of mutants and therefore allows analysis of resultant mutational distributions to be made with confidence. We have determined the DNA alterations recovered after treatment with EMS in the N-terminal region of the lacI gene of E. coli. A total of 1138 and 1102 independent lacI-d mutants were characterised in Uvr+ and UvrB-, respectively. Consistent with the known ethylating ability of this compound, the predominant mutation was G:C-->A:T transitions, which accounted for 97% and 93% in Uvr+ and UvrB- strains, respectively. An analysis of the DNA context of mutation induction indicates differential reparability by the Uvr repair pathway. Excision repair appears to more efficiently counter EMS-induced G:C-->A:T transitions at sites flanked by A:T base pairs. However, the influence of excision repair on the ultimate distribution of mutation can not be easily defined with respect to neighbouring sequence.

DNA Mutational Analysis↗
PubMed1993

Hydromyelia associated with a posterior fossa cyst.

There are rare reports of children with hydromyelia in association with arachnoid cysts at the foramen of Magendie, and these cases have uniformly been associated with hydrocephalus. We report a case of a 45-year-old woman with a posterior fossa cyst associated with hydromyelia and normal ventricles. This was successfully treated with a cystoperitoneal shunt. We believe this unusual condition is of interest in elucidating potential mechanisms of hydromyelia.

Cerebellar Diseases↗
PubMed1993

Serum albumin: a marker for morbidity in peritoneal dialysis patients.

This study was designed to determine if the serum albumin is a marker for morbidity or mortality in peritoneal dialysis (PD) patients. The impact of a low serum albumin on the risk of hospitalization, peritonitis, or death was examined in 71 patients. Blood urea nitrogen (BUN), cholesterol, age, and the presence or absence of diabetes were also examined. In independent analyses, the serum albumin was lower (32.7 +/- 5.6 v 36.3 +/- 4.3 g/L, P < 0.01), the diagnosis of diabetes was more frequent (41% v 7%, P < 0.01), and the number of episodes of peritonitis were greater (2.0 +/- 1.6 v 0.7 +/- 1.3, P < 0.01) in the group of patients hospitalized compared with those not hospitalized. When diabetics were excluded from analysis, the serum albumin remained significantly lower in hospitalized patients. Stepwise logistic regression analysis, excluding the 10 patients hospitalized only for treatment of peritonitis, confirmed that only a low serum albumin and the diagnosis of diabetes were independent predictors of increased morbidity as evident by the increased frequency of hospitalization. Every 10 g/L decrease in the serum albumin increased the odds ratio for hospitalization by 5.2. The diagnosis of diabetes resulted in a 10-fold increase in the odds ratio. We conclude that a low serum albumin serves as a marker of morbidity in PD patients, primarily as a marker of increased risk for hospitalization. The diagnosis of diabetes also greatly increases the likelihood of hospitalization. Peritonitis is a cause for hospitalization, but not an independent risk factor.

Adult↗
PubMed1993

In vitro isolation and characterization of a Neospora sp. from aborted bovine foetuses.

A Neospora sp. was isolated from the brains of two aborted bovine foetuses and grown continuously in vitro in bovine cell cultures. A comparison of the antigenic reactivity of in vitro cultivated tachyzoites with polyclonal antisera to Neospora caninum, Hammondia hammondi or Toxoplasma gondii revealed that the bovine protozoal isolates were similar to N. caninum and antigenically distinct from T. gondii. Tachyzoites of both bovine isolates had similar ultrastructural features, including an apical polar ring, conoid, electron-dense rhoptries and micronemes. The orientation of the micronemes, presence of micropores and a large number of electron-dense granules in the posterior portion of the bovine isolate tachyzoites differed from previous descriptions of N. caninum in vivo. Tachyzoites of the bovine isolates were ultrastructurally more similar to in vitro cultivated N. caninum tachyzoites than to tachyzoites of T. gondii or H. hammondi. The antigenic and ultrastructural similarities between N. caninum and the protozoal parasites isolated from aborted bovine foetuses in this study support the proposition that these parasites belong to the genus Neospora.

Abortion, Veterinary↗
PubMed1993

Mutational specificities of environmental carcinogens in the lacI gene of Escherichia coli. VI: Analysis of methylene chloride-induced mutational distribution in Uvr+ and UvrB- strains.

To better understand the mechanisms of mutagenesis by the carcinogen, methylene chloride (DCM), we have determined the nature and distribution of forward mutations induced by DCM in the N-terminal region of the lacI gene of Escherichia coli. A total of 116 lacI-d mutations (50 from Uvr+, 66 from UvrB- strain) were characterized by DNA sequencing. Both similarities and differences were observed. Although in both strains base substitutions predominated (74-88%) the distribution among the classes differed. In the case of the Uvr+ strain, DCM substantially increased the frequency of G:C-->C:G transversion and duplication events. Direct repeats were not observed at the endpoints of the duplications, however, all endpoints were in an A:T-rich region. In contrast, in the UvrB- strain, DCM induced A:T-->G:C, A:T-->C:G, G:C-->C:G events as well as deletions. The mutational spectra presented here represent a first step in the elucidation of the mechanism(s) of DCM-induced mutation.

Base Composition↗
PubMed1993

Pathophysiology of supraventricular tachycardia.

Supraventricular tachycardia is due to altered automaticity, triggered activity or most commonly, reentry. Atrial flutter is most frequently due to reentry with counterclockwise activation in the right atrium with the left atrium acting as a bystander. The small wavefronts demonstrated during atrial fibrillation are less random than was previously thought. In the study of atrioventricular (AV) nodal reentrant tachycardia, recent evidence suggests that multiple pathways involving intranodal and perinodal tissue are probably involved. In the Wolff-Parkinson-White (WPW) syndrome, accessory pathways near the AV node have been demonstrated with decremental properties, suggesting conduction through accessory AV nodal tissue. The mechanism for atrial fibrillation in the WPW syndrome is poorly understood, but there is evidence that accessory pathways are branched and may themselves support micro-reentry. In Mahaim nodoventricular pathways, the atrium is not essential for reentry, unlike atriofascicular reentrant circuits. Atriofascicular pathways consist of AV node-like tissue and are usually located in the right atrial free wall.

Animals↗