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Biomedical subjects

R Brown

Publications and source records attributed to R Brown.

At least 649 records · Page 36Linked to original sources
PubMed1986

Changes in lung volume and rib cage configuration with abdominal binding in quadriplegia.

Previous studies suggest that abdominal binding may affect the interaction of the rib cage and the diaphragm over the tidal range of breathing in quadriplegia. To determine whether abdominal binding influences rib cage motion over the entire range of inspiratory capacity, we used spirometry and the helium-dilution technique to measure functional residual capacity (FRC), inspiratory capacity, and total lung capacity (TLC) in eight quadriplegic and five normal subjects in supine, tilted (37 degrees), and seated positions. Combined data in all three positions indicated that, with abdominal binding, FRC and TLC decreased in normal subjects [delta FRC = -0.33 + 0.151 (SD) P less than 0.01); delta TLC = -0.16 + 0.121, P less than 0.05]. In quadriplegia there was also a reduction in FRC with binding (delta FRC = -0.32 + 0.101, P less than 0.001). However, TLC increased in quadriplegia (delta TLC = 0.07 + 0.061, P less than 0.025). In an additional six quadriplegic and five normal subjects, we used magnetometers to define the influences of abdominal binding on rib cage dimensions and TLC. In quadriplegia, rib cage dimensions were increased at TLC with abdominal binding, whereas there was no change in normals. Our data suggest that this inspiratory effect of abdominal binding on augmenting rib cage volume in quadriplegia is greater than the effect of impeding diaphragm descent, and thus abdominal binding produces a net increase in TLC in quadriplegia.

Abdomen↗
PubMed1986

Effect of flow rate on blood gases during constant flow ventilation in dogs.

We studied the effect of flow rate (V) on arterial blood gases during constant flow ventilation (CFV) in 9 anesthetized, paralyzed dogs weighing 9.5 to 26.5 kg. The constant flow was administered through catheters placed in each mainstem bronchus. Alveolar ventilation increased linearly with increasing V over the range of 0.18 to 1.0 L/s but was relatively constant at flows above 1.0 L/s. We found that CFV produced normocapnia at a mean V of 0.48 +/- 0.21 L/s (mean +/- SD). However, we did not find any significant relationship between body weight and the V required for normocapnia. At all flow rates we found a relatively large alveolar to arterial oxygen difference (48.9 +/- 8.8 mmHg, mean +/- SD), suggesting significant inhomogeneities in ventilation-perfusion. Our data are consistent with a 2-zone model of gas exchange where gas exchange is dominated by bidirectional convective streaming in the airways closest to the jets, cardiogenic induced flows in the most peripheral airways, and jet-induced turbulence in those airways between these 2 regions.

Animals↗
PubMed1986

Boundary artifact due to truncation errors in MR imaging.

A boundary artifact in MR images due to truncation of the infinite Fourier series necessary to encode tissue discontinuities was investigated by using doped water phantoms and normal volunteers. All images were obtained on 0.3-T permanent and 0.6-T superconducting MR imagers with varying phase and frequency sampling rates. The artifact appeared in both the phase and frequency encoding direction as parallel lines or ringing adjacent to borders or tissue discontinuities. This was unlike motion artifacts, which occur predominantly in the phase direction, and chemical shift misregistration errors, which are most pronounced in the frequency direction. Increasing the sampling frequency from 128 to 512 resulted in higher frequency ringing and more rapid drop-off in amplitude. Low-pass digital filtering also decreased the ringing at the expense of fine detail. The truncation of the infinite Fourier series necessary to encode edges to the 128-512 terms used for most MR imaging produces the artifact. It is important to recognize this common artifact and not mistake it for patient motion or disease.

Diagnostic Errors↗
PubMed1986

Celiprolol, atenolol and propranolol: a comparison of pulmonary effects in asthmatic patients.

Celiprolol, a new beta-adrenoceptor antagonist, blocks serotonin- and methacholine-mediated bronchoconstriction in animals, even in the presence of propranolol. In two, randomized, placebo-controlled, 5-way crossover trials, the pulmonary effects of celiprolol 200 and 400 mg, propranolol 40 mg and atenolol 100 mg were compared in 34 asthmatic patients. Pulmonary function was measured after single doses of each agent, and again following subsequent, graded doses of albuterol or isoproterenol aerosol. Changes in one-second forced expiratory volume (FEV1) and maximal midexpiratory flow rate (FEF25-75) prior to albuterol or isoproterenol were positive after placebo and both doses of celiprolol. Propranolol, and to a lesser extent, atenolol, caused significant reductions in both measures of pulmonary function. Overall changes in FEV1 following each drug plus isoproterenol or albuterol were positive, in the rank order, celiprolol approximately placebo greater than atenolol greater than propranolol. Propranolol pretreatment caused a significant reduction in the effect of bronchodilator. Unlike atenolol and propranolol, celiprolol was highly bronchosparing and did not antagonize sympathomimetic bronchodilators.

Adrenergic beta-Antagonists↗
PubMed1986

Patterns of melatonin rhythms in depression.

The nocturnal rise of melatonin in serum of humans is the result of endogenously released norepinephrine (NE) acting upon beta-adrenergic receptors of the pineal gland. As there is much interest in the possibility of there being changes in the function of beta-receptors in depressed patients, the nocturnal rise of melatonin was measured in depressives and healthy control subjects. In one study, multiple serum samples were taken between 4.30 p.m. to 7.30 a.m. in seven male depressed patients with melancholia and five healthy male control subjects. The melancholic patients had a significantly reduced nocturnal elevation of melatonin. In a separate study, serum samples were taken at 8 a.m. and 11 p.m. in melancholic depressives, non-melancholic depressives and healthy control subjects. The melancholic patients had a significantly lower concentration of melatonin at 11 p.m., but not at 9 a.m., than that measured in either the control subjects or the non-melancholic depressed patients. These results are similar to those found recently by several other groups of investigators. Further research is indicated to elucidate mechanism(s) responsible for this phenomenon.

Adult↗
PubMed1985

Human N-ras: cDNA cloning and gene structure.

The structure and organisation of the human N-ras gene has been determined by analysing cDNA clones derived from the two main mRNA transcripts. One clone in particular is 4.1 Kb long and originates from the larger (4.3 Kb) message. Sequence analysis of this clone has revealed that the N-ras gene consists of seven exons. A second clone deriving from the smaller (2 Kb) message shows that the difference between the two transcripts is a simple extension through the termination site of the 2 Kb transcript. Using S1 analysis, two transcriptional starts have been mapped, 10 bp apart. There is no obvious TATA box in the expected promoter region of the gene, though there are 4 GGGCGG sequences surrounding the start sites. The 5' untranslated sequence contains 2 ATGs upstream of the initiation codon.

Amino Acid Sequence↗
PubMed1985

Intraductal signet ring carcinoma. A hitherto undescribed form of intraductal carcinoma of the breast.

Attention is directed to a unique but apparently heretofore undescribed and overlooked form of intraductal carcinoma of female breast characterized by varying numbers of intraductal neoplastic cells with eccentric nuclei and either ground-glass or optically clear, mucin-containing cytoplasm. Eight examples have been observed in breast tissue submitted consultatively for the distinction of hyperplasia and intraductal carcinoma. This lesion, designated as intraductal signet ring carcinoma, may be found in some of the ducts of otherwise benign fibrocystic disease and radial scars, as well as breasts with other forms of intraductal carcinoma or invasive carcinoma. Four hundred consecutive examples of the latter examined prospectively revealed this intraductal lesion in 12 or 3%. Only 3 of the 12 examples were associated with either pure or combination forms of lobular invasive carcinoma.

Adenocarcinoma, Mucinous↗
PubMed1985

Genetic studies in multiple myeloma. II. Immunoglobulin allotype associations.

A weakly positive but statistically significant association between HLA-Cw5 and myeloma has been reported in black patients. The authors attempted to determine whether immunoglobulin allotypes of the Gm series demonstrate any such association. They were identified in the sera of 29 black patients and 160 healthy black control subjects by a standard hemagglutination-inhibition technique. The results indicate that the G3m(g5) allotype is significantly associated with myeloma. Furthermore, addition of that immunoglobulin allotype to a Gm phenotype that is negatively associated with myeloma gives a phenotype that is positively associated with the disease, both associations being statistically significant. It was concluded that G3m(g5) is a marker of inherited susceptibility to myeloma in black Americans. Furthermore, as G3m(g5) is present in almost 50% of normal control subjects, it was proposed that its expression in a much greater proportion of patients may be related to an underlying genetic rearrangement that is also associated with neoplastic transformation.

Adult↗
PubMed1985

Influence of rectal washout on bacterial counts in the rectal stump.

Forty-three patients undergoing a restorative colorectal resection were randomized to have their rectal stump washed out with either 0.9 per cent saline, 2.5 per cent povidone-iodine or 0.3 per cent sodium hypochlorite. The bacterial counts before and after washout for Escherichia coli and Bacteroides fragilis were compared using the Mann-Whitney U test. There was no significant difference in the counts for E. coli before and after washout with saline (log 9.7-log 9.7 organisms/ml) and saline had no influence on the counts of B. fragilis (log 7.9-log 6.5 organisms/ml). Hypochlorite was associated with a significant reduction in E. coli counts (log 6.1-log 1.1 organisms/ml, P less than 0.005) and the counts of B. fragilis (log 8.1-log 0.0 organisms/ml, P less than 0.005). The counts of B. fragilis were significantly reduced by povidone-iodine (log 8.1-log 1.1 organisms/ml, P less than 0.005) but there was no significant reduction in counts of E. coli (log 5.6-log 5.3 organisms/ml). The data suggest that sodium hypochlorite is better than povidone-iodine or saline as a rectal washout for colorectal anastomosis.

Bacteroides fragilis↗
PubMed1985

Use of gene transfer and a novel cosmid rescue strategy to isolate transforming sequences.

Mouse Lewis Lung tumor DNA was ligated to a cosmid containing a geneticin (G418)/kanamycin resistance gene and transferred into NIH3T3 cells. Recipient cells were first selected for geneticin resistance and subsequently for their ability to grow as a tumour when injected into nude mice. By repeating this transfection procedure with DNA from resultant tumours, geneticin-resistant NIH3T3 cells were obtained which were tumorigenic and contained approximately 1-5 copies of the transferred cosmid. The functional oncogene was cloned by preparing cosmid libraries of third round tumour DNAs, using a cosmid which does not contain a kanamycin resistance gene. Due to the original linkage of the oncogene with the cosmid containing the kanamycin resistance gene, a series of kanamycin-resistant cosmids were isolated, five of which contained an active oncogene. Subsequent analysis showed that the oncogene present was highly related to the human N-ras gene. Using a DNA probe from the MLL N-ras gene, a non-transforming counterpart was isolated from mouse liver DNA. A comparison between the two N-ras genes showed that a mutation at the amino acid position corresponding to 61 in the human gene is responsible for transforming activity of the rescued gene.

Animals↗
PubMed1985

Use of amiodarone in the treatment of persistent and paroxysmal atrial fibrillation resistant to quinidine therapy.

The efficacy of amiodarone was assessed in 38 patients with atrial fibrillation resistant to quinidine and an effort made to identify factors correlated with amiodarone response. The study group included 29 patients with and 9 without organic heart disease and either persistent (n = 11) or paroxysmal (n = 27) atrial fibrillation. All patients were treated with amiodarone and followed up in a research clinic. Efficacy was classified as excellent (no recurrent symptomatic atrial fibrillation) in 15 (55%) of 27 patients with paroxysmal and 5 (45%) of 11 patients with persistent atrial fibrillation. Efficacy was poor (no effect on atrial fibrillation) in 5 (19%) of 27 patients with paroxysmal and 6 (55%) of 11 patients with persistent atrial fibrillation. Efficacy was good (amelioration but not total suppression) in 7 (26%) of 27 patients with paroxysmal atrial fibrillation. Efficacy was related to echocardiographic left atrial dimension, left ventricular ejection fraction and, in patients with persistent atrial fibrillation, the duration of the arrhythmia. During the follow-up period of 15 months (range 1 to 36), overall efficacy (considering response and toxicity) was 67% in the 27 patients with paroxysmal and 45% in the 11 patients with persistent atrial fibrillation. It is concluded that amiodarone offers an additional therapeutic alternative in quinidine-resistant atrial fibrillation and that certain clinical factors are correlated with amiodarone response.

Adult↗
PubMed1985

Tracheal insufflation of O2 (TRIO) at low flow rates sustains life for several hours.

The emergency management of respiratory arrest can be a difficult problem. The authors hypothesized that tracheal insufflation of O2 (TRIO) at low flows could provide adequate oxygenation and sufficient CO2 elimination to sustain life until more definitive (but more difficult to implement) measures could be applied. Therefore, 10 anesthetized, paralyzed dogs (15.9-48.2 kg), initially ventilated with conventional mechanical ventilation (CMV) using room air, were studied. CMV was stopped and a 1- or 5-mm id catheter with a constant flow (V) of O2 ranging from 0.2 to 3.0 l/min was inserted to within 1 cm of the carina. With all flow rates, PaO2 and PaCO2 initially increased with time; the rate of increase of PaO2 was greater and that of PaCO2 was less, with increasing V. In three dogs studied at flow rates of 2.0 or 3.0 l/min, arterial blood gases reached a plateau after about 2 h: pH = 6.87; PCO2 = 164 mmHg; and PO2 = 363 mmHg (mean values). These studies were stopped at between 4 and 5 h, with no dogs showing any signs of cardiovascular or other decompensation. Results in which catheter position was studied indicated that as long as the catheter tip was at or past the carina, gas transport was similar to that observed when the catheter tip was 1 cm proximal to the carina. The authors conclude that TRIO at low flow rates can produce sufficient gas exchange to support life for prolonged periods in apneic dogs.

Animals↗
PubMed1985

Evaluation of flatbed reciprocal motion agitators for resuspension of stored platelet concentrates.

We studied the storage characteristics of platelet concentrates prepared in polyolefin (PL-732) and thin-film polyvinyl chloride (CLX) plastic bags and stored on a newly designed flatbed reciprocal motion agitator with a 1.5 inch (3.8 cm) lateral movement and an oscillation frequency of 70 cycles/min. We also studied the ability of this device to resuspend the platelet button formed after preparative centrifugation. Results showed that platelet concentrates stored on the 1.5-inch shaker had storage characteristics equivalent to those reported for the conventional 70 cycles/min, 1-inch (2.5-cm) lateral movement flatbed shaker. Due to a more rapid acceleration and deceleration rate, however, the 1.5-inch shaker resuspended the platelet button formed after preparative centrifugation much more efficiently than did the less dynamic 1-inch shaker. Furthermore, with either agitator, platelet aggregates in the CLX bag were more readily resuspended than were aggregates in the PL-732 bag due in part to differences in plastic bag wall elasticity.

Blood Platelets↗