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Biomedical subjects

C M Brown

Publications and source records attributed to C M Brown.

At least 163 records · Page 9Linked to original sources
PubMed1990

Semiautomated preparation of DNA templates for large-scale sequencing projects.

The rate limiting step in a large-scale sequencing project is the generation of single-stranded DNA templates. We describe a fast, semiautomated procedure, using 96-well microtitre plates, in which 192 templates can be readily prepared in 1 day. The technique can be carried out manually or can be semiautomated using a robot pipetting device. We also provide evidence for the reliability and applicability of this method to a large-scale sequencing project.

Bacteriophages↗
PubMed1990

Use of ketamine-HC1 anesthesia in studies of chylomicron-triglyceride metabolism in the rat.

Ketamine with 10% acepromazine (Km/Ac) was evaluated for use in an investigation of plasma chylomicron-triglyceride clearance in rats. Clearance rate and the half-life of radiolabeled (14C) chylomicron triglycerides plus tissue uptake of 14C-fatty acids were equal in Km/Ac anesthetized and non-anesthetized rats. Km/Ac was found to be a suitable anesthesia in rats for the study of plasma chylomicron-triglyceride clearance.

Acepromazine↗
PubMed1989

Frameshifting in the synthesis of Escherichia coli polypeptide chain release factor two on eukaryotic ribosomes.

A translational frameshift is necessary in the synthesis of Escherichia coli release factor 2 (RF-2) to bypass an in-frame termination codon within the coding sequence. The nucleotide sequence preceding the in-phase stop codon within RF-2 mRNA is complementary to the 3' anti-(Shine-Dalgarno sequence) region found in prokaryotic 16S rRNA and Weiss et al. (1988) have concluded that this pairing triggers the frameshift event. In vitro production of RNA coding for RF-2, suitable for translation on eukaryotic ribosomes, has enabled testing of whether eukaryotic ribosomes can frameshift at this sequence. The 18S rRNA of eukaryotic ribosomes does not contain the 3' anti-(Shine-Dalgarno sequence) region. The prokaryotic RF-2 gene and the gene for the other release factor, RF-1, which does not contain an in-frame stop codon, were subcloned into transcription vectors such that the RNA transcripts produced in vitro would resemble a typical eukaryotic mRNA. These RF-1 and RF-2 RNAs both synthesized a major product of Mr approximately 45,000 when translated in vitro within reticulocyte lysate; the size expected for full length RF-1 and RF-2 molecules. The RF-2 product was immunoprecipitated by RF-2-specific antibodies, including those to regions of the protein encoded in the mRNA downstream from the frameshift site. The putative premature termination product, an oligopeptide of 25 amino acids, was not detected, but a chemically synthesized derivative was shown to be very unstable within the translation system. Although it was not possible therefore to calculate an absolute efficiency of frameshifting, the relative efficiency of the translation of RF-2 RNA was estimated to be 10-20% of that of RF-1 RNA in the reticulocyte system. This was similar to the relative synthesis of the two proteins in a plasmid-DNA-directed prokaryotic transcription/translation system. These results show that in vitro on eukaryotic ribosomes where the Shine-Dalgarno-type interaction is not possible, high efficiency frameshifting around the in-phase stop codon in the RF-2 mRNA can still occur.

Bacterial Proteins↗
PubMed1989

The alpha 2-adrenoceptor antagonist SK&F 104078 has high affinity for 5-HT1A and 5-HT2 receptors.

The affinity of SK&F 104078, a putative selective postjunctional alpha 2-adrenoceptor antagonist, was determined at 5-HT1A and 5-HT2 receptors in rat brain. SK&F 104078 had moderate affinity towards alpha 2-adrenoceptors (pKi 6.7) but displayed higher affinity at 5-HT1A (pKi 8.1) and 5-HT2 (pKi 7.6) receptors. If SK&F 104078 is used in functional studies to define heterogeneity within of alpha 2-adrenoceptors, care must be taken to define the role of 5-HT1A and 5-HT2 receptors in the response being measured.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1989

Oxygen delivery in patients with adult respiratory distress syndrome who undergo surgery. Correlation with multiple-system organ failure.

Identification of the physiologic determinants of survival in patients with adult respiratory distress syndrome (ARDS) has been largely unsuccessful. We evaluated multiple physiologic variables over the first three reversible phases of ARDS. A stepwise multivariant linear regression analysis was used to identify correctable physiologic correlates with survival. Our goal was improved survival. We found that the oxygen delivery and alveolar-arterial oxygen gradient on the third day after the diagnosis of ARDS were the two most important correctable correlates. Both eventually effected the development of multiple-system organ failure and survival. These data provide clinical evidence that optimization of both the oxygen delivery and alveolar-arterial oxygen gradient after the onset of ARDS may allow resolution of ARDS, prevent additional organ dysfunction, and improve survival.

Adult↗
PubMed1989

On the kinetic depth effect.

The problem of the kinetic depth effect is revisited. We study how many points in how many views are necessary and sufficient to recover structure. The constraints in the cases where the velocities of the image points are known, and the positions of the image points are known with the correspondence between them established, are different and they have to be studied separately. In the case of two projections of any number of points there are infinitely many solutions, but if we regularize the problem we get a unique solution under some assumptions. Finally, an algorithm is discussed for learning this particular kind of regularization.

Depth Perception↗
PubMed1989

[3H]-idazoxan binds with high affinity to two sites on hamster adipocytes: an alpha 2-adrenoceptor and a non-adrenoceptor site.

1. [3H]-idazoxan labels a single population of high affinity sites (Kd 2.26 +/- 0.02 nM; Bmax 372 +/- 25 fmol mg-1 protein) in hamster adipocyte membranes. In the presence of 1 microM yohimbine to preclude binding to alpha 2-adrenoceptors, the density of [3H]-idazoxan binding sites was reduced (287 +/- 18 fmol mg-1 protein) without an apparent decrease in the affinity (Kd 2.19 +/- 0.24 nM) of the radioligand. 2. Displacement studies indicate that alpha-adrenoceptor ligands with an imidazoline side chain completely inhibit [3H]-idazoxan binding to hamster adipocyte membranes; in contrast, the alpha 2-adrenoceptor antagonists yohimbine, rauwolscine, BDF 6143 and phentolamine inhibited only 20-30% of the specific binding with affinity values consistent with an interaction at alpha 2-adrenoceptors. 3. The low potency of noradrenaline and adrenaline in displacing [3H]-idazoxan binding to the second site on hamster adipocyte membranes indicates that it is unlikely that this site is a type of adrenoceptor. 4. These results suggest that [3H]-idazoxan binds with high affinity to two sites in hamster adipocytes: an alpha 2-adrenoceptor and a non-adrenoceptor imidazoline site.

Adipose Tissue↗
PubMed1989

Comparison of transtracheal aspirate and bronchoalveolar lavage cytology in 50 horses with chronic lung disease.

Comparisons were made between transtracheal aspirate (TTA) and bronchoalveolar lavage (BAL) cytology obtained from 50 horses with chronic lung disease and from 10 control horses. There was no significant correlation between the TTA cytology and the BAL cytology, suggesting that the cell population in the trachea is not representative of the cell population in the lower airways. In control horses the range of differential cell counts obtained from TTA fluid was remarkably large, whereas the variability in cell populations observed in BAL fluid was smaller. In the principal horses the total and differential cell counts of the TTA and BAL fluids were within the 95 per cent confidence interval in 38 and 24 per cent of cases, respectively; and an increase in percentage neutrophils was most common. It was concluded that BAL may be a useful diagnostic aid when evaluating horses with chronic lung disease, but that the clinical usefulness of cytological evaluations of TTA fluid may be limited in these cases.

Animals↗
PubMed1988

Intramuscular injection techniques and the development of clostridial myositis or cellulitis in horses.

A survey of 584 veterinarians in equine practice was performed to determine their intramuscular injection techniques and the influence of those techniques on the development of clostridial myositis or cellulitis. Usable responses were obtained from 439 veterinarians (75.2%). Of these, 414 used a new needle and syringe for each injection, 241 swabbed the site with a cleansing/disinfectant agent, and 242 swabbed the top of multidose injection bottles with a similar solution. Only 2 clipped the hair at the injection site. Twenty eight of the respondents reported that at least 1 horse developed a clostridial infection at the injection site following 1 of their injections. None of the various injection techniques had a significant influence on the development of clostridial infection at the injection site.

Animals↗
PubMed1988

Progressive myotonia in foals resembling human dystrophia myotonica.

A severe and progressive neuromuscular disorder accompanied by clinical, electrophysiological, and pathological features resembling human dystrophia myotonica was observed in three foals. This disorder was apparent as early as 1 month of age and involved progressive skeletal muscle dysfunction, initially characterized by proximal muscle hypertrophy and hypertonicity with subsequent muscle stiffness, weakness, and atrophy. Multisystem involvement was manifested in one case by testicular hypoplasia, early cataract formation, and borderline glucose intolerance. Prolonged dimpling of these large rear-limb muscles was elicited by percussion. Myotonic discharges were identified by electromyography. Percussion dimpling and the typical myotonic discharges persisted after neuromuscular blockade. Distinctive histologic muscle changes included ring fibers, sarcoplasmic mass formation, variation in fiber diameter size, and internally positioned nuclei.

Animals↗
PubMed1988

Cerebral ischaemia reduces the density of 5-HT2 binding sites in the frontal cortex of the gerbil.

The 5-HT2 antagonist [3H]ketanserin labels a single population of high affinity sites (Kd 0.48 +/- 0.03 nM; Bmax 206 +/- 20 fmol/mg protein) in the frontal cortex of the gerbil. Specific binding of [3H]ketanserin was displaced by a number of 5-HT2A antagonists ritanserin, cyproheptadine and methysergide) but not by the 5-HT1A agonist, 8-hydroxy-2-(di-n- propylamino)tetralin (8-OH-DPAT) or the 5-HT1A/1B agonists 5-carboxyamidotryptamine (5-CT) or RU 24969, indicating that the labelled site probably represents the 5-HT2 receptor. Cerebral ischaemia induced in either a 3 hr unilateral non-recovery model or a 5 min bilateral, 3-day recovery model, resulted in a significant decrease in the density of 5-HT2 binding sites in the ischaemic frontal cortex without an apparent change in their affinity for the ligand. The decrease in density was not simply related to levels of 5-HT because occlusion of the right carotid artery for 3 hr resulted in bilateral depletion of 5-HT but only in an ipsilateral reduction in the density of binding sites. In addition, a significant decrease in the density of 5-HT2 binding sites occurred in the recovery model at a time when the levels of 5-HT in the cortex were unaltered.

Animals↗