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Biomedical subjects

W A Anderson

Publications and source records attributed to W A Anderson.

At least 19 recordsLinked to original sources
PubMed1992

Factors affecting mitral valve reoperation in 317 survivors after mitral valve reconstruction.

From a very heterogeneous group of 340 patients undergoing mitral valve reconstruction from 1969 through 1988, 313 hospital survivors were analyzed for factors affecting the occurrence of reoperative mitral valve procedures related to native mitral valve dysfunction. Follow-up was 100% and extended from 1 year to 20 years (mean follow-up, 7.2 years). Sixty-three patients (18.5% of the 340) required mitral valve reoperation at a mean postoperative interval of 6 years (range, 1 to 15 years). Incremental risk factors analyzed for the event late mitral valve failure included age, sex, preoperative New York Heart Association class, cause of valvular disease, pathophysiology of the mitral valve, previous mitral valve operation, mitral valve pathology, and estimation of mitral valve function at operation after repair. Mitral valve pathophysiology affected the actuarial freedom from mitral valve replacement (p = 0.023 [log-rank]). Actuarial freedom from mitral valve reoperation was 90% at 5 years and 80% at 8 years in patients who had either pure mitral regurgitation or isolated mitral stenosis compared with 80% and 72% at 5 and 10 years, respectively, in patients who had mixed mitral stenosis and regurgitation (p = 0.023). Patients undergoing late reoperation were younger (51.7 +/- 1.56 years [+/- the standard error of the mean]) than those not having reoperation (p less than 0.0003). Durability of the repair was less in patients with rheumatic heart disease (p less than 0.025) and greater in patients with ischemic heart disease (p less than 0.004). Seventy-three percent of patients undergoing reoperation had concomitant operations compared with 68% of those not having reoperation (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Cryopreserved allograft veins as alternative coronary artery bypass conduits: early phase results.

Traditional autologous conduits are sometimes unavailable or unsuitable to permit total revascularization during coronary artery bypass grafting. In these patients the results of using nonautologous alternative conduits has been disappointing. Encouraged by the excellent long-term results seen with cryopreserved allograft valves, a clinical protocol was developed to evaluate the use of a commercially cryopreserved allograft saphenous vein (CPV). Our protocol consisted of using CPV when left internal mammary arteries and autologous saphenous vein grafts were unavailable or unsuitable for complete revascularization. Blood group (ABO) typed CPVs were thawed and implanted as required using standard surgical techniques. From December 1989 through June 1991, 19 of 1,602 patients who underwent coronary revascularization had CPVs implanted (1.2%). There were no operative deaths. An attempt was made to evaluate the patency of all grafts with coronary arteriography or ultrafast computed tomographic scans. Fourteen patients were available for patency evaluation. Patency rate in the 14 patients studied at a mean of 7 +/- 2 months (range, 2 to 16 months) were: internal mammary artery, 93% (14/15); saphenous vein graft, 80% (4/5); and CPV, 41% (7/17). The patency of the CPV was significantly less than the patency rate for the saphenous vein and internal mammary artery (p = 0.004). We conclude that the short-term patency rate of CPVs is inferior to that of autologous vessels. Due to its poor patency, we recommend that CPV should only be used when no other autologous conduit is available.

Aged↗
PubMed1992

Amelioration of nephrotoxicity associated with synthetic oxygen transport media.

Use of synthetic oxygen transport media offers the potential advantages of reducing requirements for coadministration of blood products and oxygen at the scene of mass casualty situations. Previous studies have shown perfusions of isolated kidneys with stroma-free hemoglobin (SFH) to be physiological while those with Fluosol-DA (20% FDA) have been associated with low glomerular filtration rate, urinary flow rate, and fractional reabsorption of sodium and potassium (FrNa+ and FrK+). In the present studies, perfusions with SFH/FDA mixtures showed normal glomerular filtration rate, a 50% lower urinary flow rate, and FrNa+ values 3% to 5% higher than SFH controls. Compared with 20% FDA perfusions, nephrotoxic effects of SFH/FDA combinations were moderate. Compared with SFH/FDA mixtures, perfusion with 20% FDA showed lower urinary flow and glomerular filtration rates. Ultrastructural assessment of glomerular filter revealed that FDA emulsion particles were adherent to epithelial podocytes. We conclude that resuscitation with a mixture of SFH and FDA may ameliorate the previously reported nephrotoxicity associated with the use of FDA alone.

Animals↗
PubMed1992

NCAA institutionally based drug testing: do our athletes know the rules of this game?

One aspect of the current drug-testing controversy that has gone relatively unexamined concerns the extent to which student-athletes are fully informed of the testing procedures employed by their institution. College athletes (N = 2,282) participating at 11 NCAA-affiliated institutions nationwide were surveyed as to their awareness of their school's drug-testing program. Results indicate athletes have numerous misconceptions regarding the drug testing to which they may be subjected. Over one-third of the athletes attending "testing" institutions were oblivious to the fact their school was engaged in drug-testing, and more than 70% were unable to correctly identify their school's drug-testing protocol. Implications of such ignorance are discussed.

Adult↗
PubMed1991

Modulation of sympathetic activity by brain neuropeptide Y in cardiac hypertrophy.

Several observations now support the view that the sympathetic system actively participates in the development of cardiac hypertrophy. Since norepinephrine (NE)-containing neurons involved in cardiovascular regulation in the brain are known to coexist with neuropeptide Y (NPY), it is possible that a functional interaction between NPY and NE exists centrally. In an effort to clarify whether or not central catecholamine systems are modulated by NPY soon after imposing an increased pressure overload on the heart, male Sprague-Dawley rats underwent aortic constriction and were examined 14 days later. Rats were anesthetized and subjected to microdialysis sampling by stereotaxically implanting a probe into the caudal ventrolateral medulla (A1). Perfusate was collected after a 1-hour stabilization period, purified, and analyzed for interstitial concentrations of NE and other catecholamines using high-performance liquid chromatography with an electrochemical detector. Extracellular NE concentrations in the A1 area were found to be decreased. These results were associated with increased rate of change in the specific activity of NE (NE turnover) in heart, indicating increased sympathetic activity and an increased left ventricular weight. Also, infusion of NPY (10(-9) mol/L) by microdialysis in the A1 area resulted in the reduction of NE concentration; epinephrine and dopamine levels were also decreased. In contrast, methionine-enkephalin, another neuropeptide, had no effect on the extracellular catecholamine concentrations in the A1 area. Since neurons of the A1 group project almost exclusively to forebrain structures inhibiting sympathetic activity, it is concluded that decreases of NE and other catecholamines in afferent pathways regulating the caudal ventrolateral medulla may lead to an enhanced sympathetic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Thermal inactivation of Listeria monocytogenes studied by differential scanning calorimetry.

The effect of NaCl on the thermal inactivation of Listeria monocytogenes has been investigated by conventional microbiological techniques and by using differential scanning calorimetry (DSC). Addition of 1.5 M-NaCl to cells grown at lower NaCl concentrations significantly increases the tolerance of cells to mild heat stress (56-62 degrees C). DSC thermograms show five main peaks which are shifted to higher temperatures in the presence of 1.5 M-NaCl. Measurement of loss of viability in the calorimeter gave good correlation between cell death and the first major thermogram peak at two NaCl concentrations. The time course of the loss of this first peak when cells were heated and held at 60 degrees C in the calorimeter matched the loss of viability, whereas the peak attributable to DNA showed little change during this process. The use of DSC to investigate the mechanisms involved in thermal inactivation is discussed.

Calorimetry, Differential Scanning↗
PubMed1991

Correlates of fatigue resistance in canine skeletal muscle stimulated electrically for up to one year.

In response to patterns of chronic electrical stimulation that increase its overall level of use, mammalian skeletal muscle becomes highly resistant to fatigue. The metabolic basis for this adaptation is well documented in the rabbit, but up to now it has not been possible to identify analogous changes in the dog. In this study, canine latissimus dorsi muscles were stimulated in situ for 2, 6 and 12 mo. Marked increases in fatigue resistance were consistently demonstrated. Citrate synthase and succinic dehydrogenase, conventionally used as markers of oxidative metabolism, did not increase in activity, but enzymes involved in major pathways supplying substrates to the tricarboxylic acid cycle increased up to threefold. Stimulation elevated the volume fraction of mitochondria 1.5-fold and that of lipid droplets 4.5-fold. After 6 mo of stimulation, mean fiber diameter had decreased by 30% and the area occupied by nonmuscle tissue had increased by 11%; these changes showed no further progression at 12 mo. Thus stimulated muscle becomes stably adapted to an increase in use, but the metabolic strategies for achieving increased fatigue resistance vary between species.

Adaptation, Physiological↗
PubMed1990

Adsorption of Streptococcus faecalis on diatomite carriers for use in biotransformations.

Adsorption of cells on particulate carriers is potentially one of the most cost-effective immobilization techniques available. Diatomite carriers, such as Celite, have desirable physical properties, are inexpensive, and are suitable for both mycelial and bacterial systems. This work investigated the use of diatomite carriers as a biocatalyst support in a packed-bed reactor where L-tyrosine was enzymatically decarboxylated using adsorbed, non-growing cells of Streptococcus faecalis. Composition of microbial adsorption on different Celite types, with mean pore sizes ranging from 0.55 to 22 microns, showed there was no significant difference in biomass loading capacity under the conditions used. Using Celite 560, biomass loadings in a packed-bed reactor varied from 10 to 30 g dm-3 of reactor volume, which compares favourably with other adsorption methods. When used to decarboxylate L-tyrosine, the reactor was found to have a half-life of 15-20 h. A combination of enzyme activity loss and slow leakage of biomass from the packed-bed reactor was responsible for the decline in conversion. Treatment of the S. faecalis cells with glutaraldehyde significantly reduced the enzyme activity loss and extended the reactor half-life to 65 h, but had little effect on the rate of cell leakage from the reactor. Further work on reduction of cell leakage rate seems necessary for evaluation of the system's practicality.

Adsorption↗
PubMed1990

Afferent connections of the rat's supraoptic nucleus.

Neurons projecting to the supraoptic nucleus (SON) have been identified following stereotaxic injections of either horseradish peroxidase or fast blue into the SON region of adult rats. The subfornical organ, median preoptic nucleus, organum vasculosum of the lamina terminalis and medial septal nucleus were the source of the largest numbers of supraoptic-projecting neurons. Several smaller projections also originate from the ipsilateral locus coeruleus, preoptic area, lateral parolfactorial area, dorsomedial nucleus of the hypothalamus, lateral parabrachial nucleus and ventrolateral medulla. Several other areas appeared to project only to the region immediately dorsal to the SON: lateral septal nucleus, diagonal band of Broca, ventral tegmental nucleus, and the supramamillary nucleus. These areas may influence SON neurosecretory function by way of interneurons found immediately dorsal to SON. Additional areas were identified with retrograde fluorescent label only, and these projected to the area immediately dorsal to SON and/or to SON itself.

Amidines↗
PubMed1990

Specific localization of lectins in boar and bull spermatozoa.

The roles that complex carbohydrates play in gamete recognition and fertilization are well-documented. This study was designed to identify and map sites of N-linked oligosaccharides in boar and bull sperm. Plant lectins, conjugated with FITC, RITC and gold particles, were used as probes for specific sugar moieties in sperm membranes. Results showed strong labeling of sperm heads by most lectins. However, lectins with specificities for mannosyl, glucosyl, and sialic acid were predominantly distributed over the sperm acrosomal region. Lectins specific for fucosyl residues predominantly stained the postacrosomal regions of both boar and bull sperm. Lectin gold studies revealed that mannosyl and galactosyl-linked residues occupied the acrosomal membrane and plasma membrane in the postacrosomal region, but not the nucleus or nuclear membrane. The cytoplasmic droplet, middle piece and flagellum of boar and bull sperm were moderately stained by lectins. The microquantitative analysis confirmed the fluorescence data. The presence of fucosyl residues predominantly in the postacrosomal regions lends credence to the suggestion that glycoproteins rich in fucosyl-like residues may be a universal carbohydrate moiety involved in recognition processes in mammalian fertilization.

Animals↗
PubMed1989

Skeletal muscle ventricles: improved performance at physiologic preloads.

We attempted to construct skeletal muscle ventricles (SMVs) so that they would develop optimal stroke work at physiologic preloads of 5 to 15 mm Hg. Thirty-one SMVs were constructed in mongrel dogs. The effects of electrical preconditioning with 2 Hz continuous and 25 Hz burst patterns were evaluated, as well as the application of passive stretch to the muscle fibers during preconditioning. We evaluated the stroke work developed by these SMVs at afterloads of 30 mm Hg and 80 mm Hg in vivo, using a mock circulation device. During mock circulation studies, the SMVs were stimulated via the thoracodorsal nerve with either a 25 Hz or 85 Hz burst pattern. SMVs with 2 Hz preconditioning developed significantly higher stroke work than SMVs with 25 Hz preconditioning under all conditions of afterload, preload, and stimulation frequency (p less than or equal to 0.001). Under these conditions, for the 2 Hz preconditioned SMVs, passive stretch during preconditioning resulted in a further significant increase in developed stroke work (p less than 0.05). For these SMVs, with an 85 Hz stimulation frequency, stroke work averaged 410% of canine RV stroke work, and 59% of canine LV stroke work at physiologic preloads and afterloads.

Animals↗
PubMed1989

Functional right-heart replacement with skeletal muscle ventricles.

Skeletal muscle ventricles were constructed from the latissimus dorsi in seven dogs. All skeletal muscle ventricles underwent a vascular delay period followed by 4-7 weeks of electrical preconditioning. In group 1 (n = 5), the skeletal muscle ventricle was used to replace native right-heart function. Venous return from the superior and inferior venae cavae was directed to the skeletal muscle ventricle with outflow directed to the pulmonary artery. In group 2 (n = 2), the skeletal muscle ventricle was used for partial bypass of the right heart. In both groups, right-heart bypass was continued for as long as 8 hours. In group 1 after 4 hours of continuous complete right-heart bypass, stroke work was 163 +/- 63% of canine right ventricular stroke work. Skeletal muscle ventricle output was 1.14 +/- 0.02 l/min, central venous pressure was 13 +/- 1.5 mm Hg, and systemic systolic blood pressure was 95 +/- 9 mm Hg. Skeletal muscle ventricles are capable of performing the work of the right heart with near-physiological filling pressures.

Animals↗
PubMed1988

Estimated prevalence of anabolic steroid use among male high school seniors.

The use of anabolic-androgenic steroids (AS) is perceived by the media, by segments of the sports medicine and athletic communities, and by the public to have grown to epidemic proportions. Unfortunately, the incidence and prevalence of AS use among elite, amateur, and recreational athletes is poorly documented. This study was designed to help identify AS use patterns among the male portion of the general adolescent population. The overall participation rate on a schoolwide basis was 68.7% and on an individual basis reached 50.3%. Participants in this investigation were 12th-grade male students (N = 3403) in 46 private and public high schools across the nation who completed a questionnaire that established current or previous use of AS as well as user and nonuser characteristics. Results indicate that 6.6% of 12th grade male students use or have used AS and that over two thirds of the user group initiated use when they were 16 years of age or younger. Approximately 21% of users reported that a health professional was their primary source. The evidence indicates that educational intervention strategies should begin as early as junior high school; the intervention should not be directed only toward those individuals who participate in school-based athletics.

Adolescent↗