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Biomedical subjects

D L Brown

Publications and source records attributed to D L Brown.

At least 217 records · Page 12Linked to original sources
PubMed1990

Comparison of 0.5% ropivacaine and 0.5% bupivacaine for epidural anesthesia in patients undergoing lower-extremity surgery.

Ropivacaine is an amide local anesthetic structurally related to, but appearing less cardiotoxic, than bupivacaine. The authors' investigation was designed in a randomized, double-blind fashion to compare the clinical effectiveness of ropivacaine and bupivacaine in patients undergoing lower-extremity surgery. Forty-five patients were randomized to receive 20 ml of 0.5% ropivacaine or bupivacaine. Intermittent sensory (pinprick) and motor (Bromage score) measurements were made while the block was in effect, and changes in heart rate, blood pressure and amounts of additional analgesics, sedatives and other medications were also recorded. Presence of tourniquet pain and the quality of anesthesia were also assessed. One patient was excluded from analysis; thus, 22 patients each received ropivacaine or bupivacaine. No differences were found in patient or perioperative characteristics between the groups. The quality and extent of sensory and motor blockade between groups were comparable, although bupivacaine was slightly longer acting. Cardiovascular changes, incidence of tourniquet pain, and the amounts of supplemental medications necessary were also similar between groups. The authors found 0.5% ropivacaine and bupivacaine to be clinically similar in both sensory- and motor-blocking characteristics, with the exception that bupivacaine produced a blockade of slightly longer duration. Because ropivacaine is reported to be less cardiotoxic than bupivacaine in animal studies, the similarity of clinical epidural anesthesia may make ropivacaine the preferred agent.

Adolescent↗
PubMed1990

Diagnosis of early embryonic demise by endovaginal sonography.

To determine the embryonic size at which cardiac activity is always seen in a normal early pregnancy, 398 endovaginal sonograms were evaluated in which the gestational sac contained a yolk sac and/or embryo of less than or equal to 12 mm in crown-rump length (CRL). In the 99 sonograms in which there was a yolk sac but no identifiable embryo, cardiac activity was absent in 75; 58 of these pregnancies progressed normally. Of the 299 sonograms where there was an identifiable embryo with CRL less than or equal to 12 mm, cardiac activity was absent in 31; 29 of these were proven to be failed pregnancies. In two cases the pregnancy progressed normally; the CRL was 2 mm in one case and 4 mm in the other. We conclude that once an embryo is seen by endovaginal sonography, the absence of cardiac activity usually indicates embryonic demise. However, when cardiac activity is absent, one should refrain from definitively diagnosing embryonic demise, based on a single sonogram, if the CRL is less than 5 mm.

Embryo, Mammalian↗
PubMed1990

Anomalous systemic and pulmonary venous pathways diagnosed in utero by ultrasound.

Anomalies of systemic and pulmonary venous return are found as either isolated lesions or as part of a complex cardiac malformation. Specifically, these venous pathway malformations are associated frequently with the cardiac defects in asplenia or polysplenia. This report describes the prenatal ultrasound diagnosis of both anomalous pulmonary and systemic venous drainage in three late gestation fetuses with a splenic syndrome and complex congenital heart disease. In addition, the utility of color-flow Doppler as an aid in making the diagnosis is emphasized.

Adult↗
PubMed1990

Anti-neutrophil cytoplasm antibodies in patients with monoclonal gammopathies.

Anti-neutrophil cytoplasm antibodies (ANCA) are specific markers for systemic vasculitis. In view of the autoreactivity to other autoantigens reported in patients with monoclonal immunoglobulins (MIg), the reactivity of 150 sera from 125 patients with MIg was tested for ANCA by radioimmunoassay (RIA) with inhibition stage and indirect immunofluorescence (IIF). Seven were positive for IgG ANCA, all with IgG MIg and 5 were positive for IgM ANCA, 4 with IgM MIg and 1 with IgG MIg. No IgA ANCA were found. The patterns seen on IIF were identical to those seen with sera from patients with systemic vasculitis and were cytoplasmic in 6 and peri-nuclear in 6. The restriction of the ANCA activity to the MIg was studied in six sera by light chain specific RIA, and anion exchange fractionation of the sera. The ANCA activity appeared to be polyclonal in at least three sera and could be found in the monoclonal fraction in only three patients. Associated autoimmune diseases were found in some of these ANCA positive patients including Sjögren's syndrome, MacDuffie hypocomplementemic vasculitis and rheumatoid polyarthritis but the classical vasculitic features normally associated with ANCA were not observed. We conclude that ANCA is a further autoreactivity present in some sera with MIg and discuss the relation between monoclonal gammopathies and autoimmunity.

Aged↗
PubMed1990

Residential preferences and population redistribution: 1972-1988.

In seeking to explain recent trends in population distribution, there has been increased interest in residential preferences. This study is a comparison of preferences based on 1972 and 1988 national surveys, years that bracket a period of considerable change in distribution patterns. Over time there has been a small shift in preference toward cities less than 500,000 in size, primarily by those already living there. Rural settings, especially near cities, continue to be very attractive. At both times studied, more than half of those preferring a smaller or more remote place would retain this preference even if it meant 10% less income. Nevertheless, the proportion preferring to live more than 30 miles from a large city was unchanged and approximately equal to the proportion already living there at both times, indicating that a discrepancy between where people live and where they want to live is not an important basis for the upturn in nonmetropolitan growth away from large cities in the 1970s or the downturn in the 1980s.

Choice Behavior↗
PubMed1990

Serum antibodies to oxidized low-density lipoprotein and ceroid in chronic periaortitis.

The incidence of serum antibodies to human low-density lipoprotein, to oxidized low-density lipoprotein, and to ceroid extracted from human atheroma was assessed in 100 subjects using an adaptation of the enzyme-linked immunosorbent assay technique. Patients with chronic periaortitis, subclinical chronic periaortitis, and ischemic heart disease, and "elderly control" individuals were compared with young, healthy adults. Provided that precautions were taken to prevent oxidation of the low-density lipoprotein during the assay, antibodies were not found to native human low-density lipoprotein. Antibodies to oxidized low-density lipoprotein or ceroid, usually both, were detected in all 20 patients with clinical chronic periaortitis, in 17 of 20 patients with subclinical chronic periaortitis, in 12 of 20 patients with ischemic heart disease, and in 10 of 20 elderly control subjects. Binding inhibition studies showed cross-reactions between oxidized low-density lipoprotein and ceroid. Western blotting after sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that in some patients with clinical chronic periaortitis, these antibodies were directed against breakdown products of apolipoprotein B that resulted from oxidation of low-density lipoprotein. Antibodies to oxidized low-density lipoprotein or ceroid were not detected in healthy young adults. These findings show that chronic periaortitis is accompanied by autoallergy to ceroid, which is probably at least partly composed of low-density lipoprotein oxidized within the human atherosclerotic plaque, and that a number of middle-aged and elderly people without chronic periaortitis also have such antibodies.

Aged↗
PubMed1989

Establishment of a stable, acetylated microtubule bundle during neuronal commitment.

Two posttranslational modifications of alpha-tubulin, acetylation and detyrosination, are associated with stable microtubule (MT) populations, including those of neuronal processes. We have used a pluripotent embryonal carcinoma cell line, P19, to investigate changes in MT isotype and stability found in MT arrays during neurogenesis. This cell line has an advantage in that both commitment- and differentiation-related events can be observed. Uncommitted P19 cells have minimal arrays of acetylated and detyrosinated MTs. Following neuronal induction with retinoic acid (RA), indirect immunofluorescence microscopy shows that the first MT modifications occur during commitment and before any morphological change is observed. RA-induced cells initially polymerize a temporarily enlarged population of MTs. Included in this population is a new array of acetylated MTs arranged in a bundle of parallel MTs. This bundle is colchicine-stable, although no MT-associated proteins (MAPs) are detectable using a battery of anti-MAP antibodies. Observation of MT arrays with patterns that are intermediate between the early bundles and short neurites suggests that the acetylated MT bundle subsequently extends to form a neurite. MAP 2 is first detected at about the time of neurite extension. However, at this early stage of differentiation, MAP 2 is not yet limited to dendritic processes. This report provides the first evidence that the stable MTs of mature neurons may be initiated during neuronal commitment.

Acetylation↗
PubMed1989

A comparison of two pulmonary artery mixed venous oxygen saturation catheters during the changing conditions of cardiac surgery.

Continuous mixed venous oxygen saturation (SvO2), using modified pulmonary artery (PA) catheters, can assist in the management of cardiac surgery patients. Two FDA-approved catheters are available for SvO2 monitoring. One system uses two wavelengths of light and the other is a three-wavelength system. The present study was designed to determine the accuracy of the two catheters during cardiac surgery. Sixty-five consecutive patients were assigned to one of the two catheter groups. Data were collected pre- and post-induction, after sternotomy, and after extracorporeal circulation. An updated hematocrit was entered in the two-wavelength system preceding the last two measurements. Patient demographics, severity of preoperative cardiac disease, and intraoperative hemodynamics were comparable between groups. Two-wavelength determinations varied inconsistently from cooximeter values, while three-wavelength measurements did not differ significantly. Changes in hematocrit were responsible in part for the variability in two-wavelength measurements. In summary, three-wavelength measurements by the Shaw system were more accurate than two-wavelength measurements by the Edwards system.

Aged↗
PubMed1989

Influence of sometribove, USAN (recombinant methionyl bovine somatotropin) on the body composition of lactating cattle.

Ten cattle were injected with 40 mg/d sometribove (United States adopted name for recombinant methionyl bovine somatotropin) in bicarbonate buffer, and nine with the bicarbonate buffer only. These treatments continued from the first day of wk 11 of lactation through the end of wk 18 of lactation. Deuterium oxide (D2O) dilution was used to estimate D2O space at wk 10 and 18. All cattle were fed a dry, complete diet containing 2.9% nitrogen, and an estimated 1.7 Mcal/kg net energy for lactation (NE1). After 18 wk of lactation, carcass composition was determined from carcass density and the composition of the rest of the body was determined by direct chemical analyses. Regression equations were constructed relating chemical composition at 18 wk to D2O space and live body mass. These equations were used to estimate body composition at wk 10. The estimated wk 10 composition was used to adjust wk 18 body composition for pretreatment inter-animal variation. Treatment with sometribove resulted in increased milk production (34.3 kg/d vs. 30.2 kg/d), foregut tissue (25.2 kg vs. 23.2 kg), foregut contents (72.0 vs. 62.1 kg), and reduced total body fat (28.3 vs. 45.7 kg), body energy (760 vs. 916 Mcal) and visceral fat mass.

Animals↗
PubMed1989

Effect of midazolam and diazepam premedication on central nervous system and cardiovascular toxicity of bupivacaine in pigs.

To determine the effect of benzodiazepine premedication on central nervous system and cardiovascular effects of bupivacaine, the authors administered toxic doses of bupivacaine to awake spontaneously breathing pigs after intravenous premedication with midazolam (0.06 mg/kg), diazepam (0.15 mg/kg), or saline. Five minutes after administration of one of these solutions, they began an infusion of bupivacaine at 2 mg.kg-1.min-1. The bupivacaine infusion was continued until cardiovascular collapse. They then attempted to resuscitate the animals via open chest cardiac massage and a standard resuscitation protocol. Premedication with midazolam or diazepam significantly delayed the onset of ventricular dysrhythmias (P less than 0.05), decreased the incidence of seizures (P less than 0.05), and prevented the increase in blood pressure and heart rate following bupivacaine infusion (P less than 0.05). Benzodiazepine premedication did not affect the dose of bupivacaine or the blood concentration required to produce cardiovascular collapse. The ability to resuscitate animals premedicated with midazolam did not differ from control; however, significantly fewer animals premedicated with diazepam were resuscitated (P less than 0.05). A clinically relevant observation was that almost all animals premedicated with a benzodiazepine progressed directly to cardiovascular collapse without first manifesting seizures.

Animals↗
PubMed1989

Effect of epinephrine on central nervous system and cardiovascular system toxicity of bupivacaine in pigs.

To determine what effect the addition of epinephrine has on bupivacaine toxicity, toxic doses of bupivacaine were administered to awake spontaneously breathing pigs. Twenty animals were randomized to one of two groups. One group received an infusion of bupivacaine with epinephrine (5 micrograms/ml) at a rate of 2 mg.kg-1.min-1; the other received an infusion of plain bupivacaine at the same rate. Bupivacaine infusion was continued until cardiovascular collapse. Following cardiovascular collapse we attempted to resuscitate the animals via open chest cardiac massage and a standardized resuscitation protocol. The addition of epinephrine to bupivacaine significantly increased blood pressure and systemic vascular resistance but not heart rate or cardiac output early in the bupivacaine infusion. Epinephrine had no effect on the dose of bupivacaine that caused cardiovascular collapse (P = 0.1), on the plasma concentration of bupivacaine at collapse (P = 0.9), or on the ability to resuscitate animals following cardiovascular collapse. The addition of epinephrine decreased the dose of bupivacaine required to initiate cardiac dysrhythmias (P = 0.003). The first dysrhythmia experienced by the epinephrine group was second degree heart block, which contrasts with the premature ventricular and atrial dysrhythmias experienced by the plain group. The dose of bupivacaine that produced seizures was also reduced by the addition of epinephrine (P = 0.006). The addition of epinephrine to bupivacaine did not alter the dose of bupivacaine that caused cardiovascular collapse in awake spontaneously breathing pigs but did decrease the dose of bupivacaine that caused seizures and dysrhythmias.

Animals↗
PubMed1989

Association of acetylated microtubules, vimentin intermediate filaments, and MAP 2 during early neural differentiation in EC cell culture.

Pluripotent P19 embryonal carcinoma cell cultures can be induced to differentiate into neurons and glial cells by the addition of 10(-6) M retinoic acid. During early neural differentiation, a bundle of colchicine-stable, acetylated microtubules is formed. This acetylated microtubule array apparently extends to form neurites during neurogenesis. In this paper, we analyze changes in vimentin and MAP 2 distributions during neural differentiation with respect to the changes in the acetylated microtubule array. During a brief period early in differentiation, indirect immunofluorescence staining shows the colocalization of colchicine-stable acetylated microtubules, vimentin, and MAP 2. Using acrylamide to disrupt the organization of vimentin intermediate filaments and estramustine to disrupt the binding of MAP 2 to microtubules, we show that acetylated microtubules, MAP 2, and vimentin intermediate filaments are arranged in an interdependent cytoskeletal array. We suggest this array may serve to stabilize processes in neural stem cells, before the final decision to differentiate into neurons or glia is made.

Acetylation↗
PubMed1989

Ultrastructural localization of nuclear antigens during interphase in mouse 3T3 fibroblasts.

Thin sections of mouse 3T3 fibroblast nuclei labelled by immunoperoxidase with anti-nuclear antibodies I1, PI1, PI2, anti-peripherin, -lamin, and -centromere have been examined in the electron microscope. Staining was compared with the corresponding immunofluorescence labelling patterns, and was correlated with nuclear ultrastructure in conventionally fixed and uranyl-lead stained samples and in unlabelled immunoperoxidase controls. Peripherin was detected at the nuclear rim in a band broader and more irregular than the lamins/lamina. The peripheral components of PI1 and PI2 appear to be localized at nuclear pores and the nuclear envelope, respectively. The internal component of PI1 staining consisted of irregular patches and strands in the nucleoplasm, closely resembling snRNP staining as reported by others. Internal P12 labelling consisted of spots distributed apparently at random in interchromatinic regions. The spots resembled labelling by antibody I1, but were fewer and more irregular in size. Neither the PI2 nor the I1 spots were centromere associated, nor could they be correlated with specific interchromatinic structures in conventional preparations and in unlabelled controls. The results support the hypothesis that the nucleus is segregated into function-specific domains, distinguished by morphology and (or) composition from surrounding regions of the nucleus.

Animals↗
PubMed1989

Twin-twin transfusion syndrome: sonographic findings.

Twin-twin transfusion syndrome (intrauterine parabiotic syndrome) is a potentially serious complication of monochorionic twinning. The frequency of fetal and neonatal death and perinatal morbidity is significantly higher than that in twin pregnancies uncomplicated by the syndrome. The authors present sonographic findings in ten cases of twin-twin transfusion syndrome proved by means of pathologic examination of the placenta and/or laboratory findings. The cases all involved diamniotic twins and covered a broad range of severity. Discordant fetal size and differing amniotic fluid volume in the two sacs were the most common findings. In more severe cases, hydrops of the recipient fetus and/or a "stuck" donor fetus was seen. Intrauterine death of one or both twins was observed in four cases. Familiarity with the sonographic patterns of the twin-twin transfusion syndrome can allow one to suggest the diagnosis in utero so that appropriate management can be undertaken.

Female↗
PubMed1989

Synthesis and expression of the fibroblast fibronectin receptor in human monocytes.

Human monocytes adhere to fibronectin, but the receptor (or receptors) mediating this interaction has not been clearly identified. To examine the nature of this receptor, human monocytes were obtained by counter-current elutriation and were found to adhere to immobilized fibronectin but not to vitronectin or von Willebrand factor. Antibodies and peptides were used to determine whether monocyte adherence to immobilized fibronectin was mediated by a receptor similar to that which mediates the adherence of fibroblasts to fibronectin. Antibodies against both the alpha and beta subunits of the fibroblast fibronectin receptor (VLA-5) inhibited monocyte adherence to fibronectin. These antibodies immunoprecipitated two surface proteins from monocytes that migrated at 140 and 120 kD under nonreducing conditions. Surface proteins with identical apparent molecular weights were immunoprecipitated from surface-labeled MG-63 cells, a fibroblast-like cell line. A synthetic peptide containing the Arg-Gly-Asp-Ser (RGDS) sequence also inhibited monocyte adherence to fibronectin. cDNA hybridization experiments revealed the presence of mRNA for both the alpha and beta subunits of the fibroblast fibronectin receptor in human monocytes. We conclude that circulating monocytes express a fibronectin receptor that is structurally and functionally very similar, if not identical, to the fibronectin receptor in adherent fibroblasts, and that this receptor mediates monocyte adherence to immobilized fibronectin.

Antibodies, Monoclonal↗