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Biomedical subjects

R F Collins

Publications and source records attributed to R F Collins.

At least 19 recordsLinked to original sources
PubMed1998

Self-cleaving circular RNA associated with rice yellow mottle virus is the smallest viroid-like RNA.

We report the sequence, structural features, and self-cleaving activity of the small circular RNA (sc-RNA) associated with rice yellow mottle sobemovirus (RYMV). At 220 nucleotides, the RYMV sc-RNA represents the smallest naturally occurring viroid-like RNA currently documented in the literature. It is similar to other circular satellite RNAs (sat-RNAs) and viroids in being G-C-rich with a high level of self-complementarity. The predicted native structure is essentially a rod with one branched terminus. A region of the RYMV sc-RNA, constituting 24% of the sequence, exhibits 89% identity to the sat-RNA associated with the Australasian isolates of lucerne transient streak sobemovirus. This region is also structurally similar in all three RNAs in that it forms the left terminus of each rod. Dimeric runoff transcripts of cloned RYMV sc-RNA undergo efficient autocatalytic in vitro cleavage in the (+) but not the (-) polarity. Analysis of the (+) sequence indicates the presence of a hammerhead ribozyme resembling that of carnation small retroviroid-like RNA and the genomic satellite transcript of newt. Inefficient cleavage of (+) monomeric transcripts, and a short stem III in the hammerhead, are features consistent with a double-hammerhead mode of self-cleavage. The presence of sat-RNA and retroviroid-like structures within a single RNA suggests a possible role for the RYMV sc-RNA as an evolutionary intermediate between these subviral RNAs.

Base Sequence↗
PubMed1996

Structural changes in photosystem II after treatment with the zero-length bifunctional cross-linker 1-ethyl-3-(3-dimethylaminopropyl)carbodi-imide: an electron microscopic study.

Two-dimensional (2D) crystals of photosystem II (PS II) treated with various concentrations of the zero-length crosslinker 1-ethyl-3-(3-dimethylaminopropyl))carbodi-imide (EDC) were analysed by electron microscopy in conjunction with crystallographic image processing. The preparations were characterized by SDS/PAGE and oxygen-evolution measurements, and the effectiveness of cross-linking was monitored by measuring the level of protection afforded against high concentrations of NaCl and CaCl2, which normally remove extrinsic proteins from PS II. We found that low concentrations of EDC (0.25%) increase the order of 2D crystals of PS II. Treatments with EDC concentrations higher than 0.5% did not improve the order of 2D crystals but induced gross structural changes, which were correlated with a decrease in oxygen evolution activity. Structural changes due to cross-linking did not affect packing or symmetry of the 2D crystals, further supporting the conclusion that PS II has a monomeric nature in vivo.

Cross-Linking Reagents↗
PubMed1994

Electroconvulsive therapy.

Electroconvulsive therapy (ECT) has evolved into a useful treatment alternative for a select psychiatric patient population. With thorough knowledge of ECT and judicious candidate selection, positive therapeutic responses can be achieved with minimal risk of complications. ECT, in its state-of-the-art application, offers certain severely-ill psychiatric patients a treatment option that can provide immediate results.

Electroconvulsive Therapy↗
PubMed1993

Cloning and nucleotide sequence of the capsid protein and the nuclear inclusion protein (NIb) of potato virus A.

The sequence of the 3'-terminal 2597 nucleotides of potato virus A (PVA) genome has been determined from cDNA clones. An open reading frame was identified and potentially encodes a large polyprotein containing 789 amino acid residues. This large open reading frame was found to have a high similarity to the nuclear inclusion protein (NIb) and the capsid protein (CP) genes of several potyviruses. The data suggest that the PVA NIb and CP are products arising from the maturation of the large polyprotein as observed for other potyviruses. Putative cleavage sites corresponded to consensus sequences NIa/NIb and NIb/CP, respectively, of other potyviruses. The NIb (putative RNA polymerase) and CP are expected to be 516 and 269 amino acid residues (M(r) of 58,939 and 30,094), respectively. The non-coding region is 227 nucleotides long, rich in A and U and unlike other viruses. Furthermore, there are two AUG codons in frame in front of the capsid protein gene suggesting an alternative mode for the capsid protein expression.

Amino Acid Sequence↗
PubMed1981

Prevalence of intestinal helminths and protozoans in a rural population segment of the Dominican Republic.

There are few reports of parasitic disease prevalence in the Dominican Republic. The most recent study was that by Mackie et al. (1951). Examination of purged specimens from individuals employed by two sugar plantations demonstrated generally high prevalences of a number of helminths and protozoans. We report here the findings of a prevalence study using a population sample of 453 individuals. Ascaris lumbricoides, Trichuris trichiura, hookworm, Enterobius vermicularis, Giardia lamblia and Entamoeba coli were found.

Adolescent↗
PubMed1980

A simple radioimmunoassay of acebutolol in plasma.

Antisera against acebutolol were produced in rabbits immunized by means of this drug conjugated with bovine serum albumin. These antisera were used to develop a method of radioimmunoassay for acebutolol. The plasma radioimmunoassay, described here, requires no extraction and is very easy to perform besides being quick, specific and sensitive. As little as 2.97 X 10(-9) mol/l of acebutolol can be detected. This radioimmunoassay is suitable for assaying the large number of samples usually measured in pharmacological studies.

Acebutolol↗
PubMed1980

Treatment of twelve burn wound infections and eight other serious infections with cefazolin and tobramycin: in vitro and in vivo evaluation.

20 patients with serious infections were treated with cefazolin and tobramycin for 9--64 days. Minimal inhibitory concentration (MIC) values and minimal bactericidal concentration (MBC) values were determined for each of the 112 clinical bacterial isolates. The median cefazolin MIC/MBC was 1.56/12.5 micrograms/ml, and the median tobramycin MIC/MBC was 6.25/25.0 micrograms/ml for all organisms studied. Median cefazolin doses of 49.0 mg/kg/day gave median peak/trough serum levels of 43.0/11.0 micrograms/ml. Median tobramycin doses of 4.3 mg/kg/day gave median peak/trough serum levels of 5.0/1.4 micrograms/ml. Checkerboard studies revealed synergy with 65% of strains. Bacteriologic and clinical success was obtained in 17 of 20 patients.

Acute Kidney Injury↗
PubMed1979

Cefazolin treatment of bacterial infections. In vitro and in vivo evaluation.

Cefazolin sodium was used to treat 20 serious bacterial infections in 19 patients, 11 of whom were infected by coagulase-positive Staphylococci. Clinical and bacteriologic success were initially obtained in 15 patients with 16 infections. 2 additional patients were cured after surgery for removal of foreign bodies and a second course of the antibiotic. 1 asplenic patient had bacteremia and died 5 days after initiating therapy with negative blood cultures and multiple abscesses. 1 patient with endocarditis relapsed 19 months after treatment with 6 weeks of cefazolin and prolonged oral antibiotics. Calculated median, trough, free drug levels were 1.5--15.3 times the minimum inhibitory concentration for 27 of 29 pathogens.

Adult↗
PubMed1977

Plasma levels and electrophysiological effects of acebutolol (M & B 17.803) in the dog heart in situ.

The effect of acebutolol a beta-adrenergic receptor blocking agent was tested on the dog heart in situ. The drug decreased heart rate, and caused a reduction in the conduction velocity and a significant increase in the functional refractory period of the atrioventricular node. The functional and the effective refractory period of the right atrium was increased by acebutolol. During sinus rhythm, the drug did not affect conduction velocity in the rest of the conduction pathway. During atrial pacing, however, the intra-atrial and His-Purkinje conduction times were slightly increased. The plasma concentrations of acebutolol were in the range between 0.09 and 0.5 mug/ml, which is far below those values expected to cause a membrane-stabilizing or quinidine-like effect. The clinical applications of the results are discussed.

Acebutolol↗
PubMed1976

Comparative effects of acebutolol and practolol on the lipolytic response to isoprenaline.

1 The effects of beta-adrenoceptor blockade on the metabolic responses to isoprenaline have been studied in an in vitro system of isolated fat cells and in six normal subjects. 2 The inhibitory effects of varying concentrations of acebutolol, practolol and propranolol on free fatty acid (FFA) release produced by isoprenaline (10(-7) M) were compared in isolated fat cells prepared from rat epididymal adipose tissue. Acebutolol and practolol, at equimolar concentrations, showed a similar inhibitory effect whilst propranolol was approximately 100 times more potent then either drug. At 10(-5)M concentration of propranolol, lipolysis was virtually abolished whilst at the same molar concentration, acebutolol and practolol halved the response. 3 Six healthy volunteers received three successive 15 min intravenous isoprenaline challenges (0.03 mug kg-1 min-1) per individual experiment. The first acted as a control whilst the following two were given either after single oral doses of placebo, acebutolol or practolol. The mean (+/- s.e. mean) basal FFA level was 0.77 +/- 0.06 mE1/1 and subsequent resting values after the administration of placebo or beta-adrenoceptor blocker were not significantly different. 4 Acebutolol inhibited the respective mean rises in FFA, produced by both post-control isoprenaline challenges, by (mean +/- s.e. mean) 70 +/- 4% and 84% +/- 5%. The comparable figures for practolol were 33 +/- 15% and 24 +/- 20%. The higher serum concentration of acebutolol produced greater inhibition but correlation of log serum concentration of the drug with percentage inhibition of FFA rise did not achieve significance. 5 Administration of isoprenaline, acebutolol or practolol did not significantly alter serum glucose, triglyceride or cholesterol levels. 6 Acebutolol and practolol effectively blocked the isoprenaline-induced tachycardia. The degree of blockade produced by practolol was greater than its inhibitory effect on FFA release. The diatolic fall in blood pressure in response to isoprenaline was abolished by acebutolol suggesting that its beta-adrenoceptor blocking action encompasses peripheral vascular sites. The comparable effect with practolol was a partial inhibition of the diastolic fall.

Acebutolol↗
PubMed1975

[Pharmacokinetics of acebutolol].

Pharmacodynamic data correlating beta-adrenoceptor blockade with plasma level of drug were obtained in healthy male volunteers (3). Direct comparison of the inhibition of isoprenaline induced tachycardia was achieved in each volunteer after the administration of single doses of either acebutolol (300 mg), practolol (400 mg) or propranolol (40 mg). These drugs were approximately equipotent at these doses, at the times of maximum beta-adrenoceptor blockade. Pharmacokinetic data were obtained in hypertensive male patients (4) after treatment with 14C-radioactively labelled acebutolol hydrochloride. Both 'total-14C' levels and specific '14C-acebutol' levels were determined in plasma, urine and faeces. It was shown, by calculation from the renal clearance, that the late biological half-life for the decline of 14C-acebutolol in plasma was 9.4 h and 13.2 h, respectively, in two of these patients treated with a single oral dose (200 mg) of 14C-acebutolol hydrochloride. In one of the patients treated by intravenous infusion (20 mg/10 mn), the late biological half-life plasma was calculated to be 7.5 h. Renal clearance of acebutolol was shown to be close to a mean of 83 ml plasma/mn for each of three patients (two oral and one intravenous) in spite of the fact that one of the orally treated patients had an elevated level of urea in his plasma (47 mg/100 ml) indicative of some impairment of kidney function. The recovery of 14C-radioactivity in the urine (29 p. cent) and faeces (64 p. cent) was 93 p.cent of the dose of labelled acebutolol in one of the orally treated patients. The overall proportion of the dose excreted as unchanged 14C-acebutolol was 62 p.cent. The major metabolite was the product formed by shortening of the butyramido-group of acebutolol to form an acetamido-group. This metabolite was also readily excreted in both urine and faeces and was also detected in an extract of the 4 h plasma from an orally treated patient. It was identified by co-chromatography as the acetyl analogue (M & B 16 942) of acebutolol. It would be detected by the colorimetric assay of acebutolol in plasma because the same aromatic amino-compound (M & B 17 127) would be formed during the acid hydrolysis procedure. A small quantity of an other unidentified metabolite was detected in an extract of freeze-dried urine after autoradiography of a two dimensional thin layer silica-gel chromatogram.

Acebutolol↗
PubMed1975

Plasma levels and beta-adrenoceptor blockade with acebutolol, practolol and propranolol in man.

1 The degree of beta-adrenoceptor blockade of isoprenaline-induced tachycardia has been determined in three healthy volunteers after the administration of single oral doses of acebutolol, practolol or propranolol. 2 Plasma levels of these drugs were determined either colorimetrically (acebutolol and practolol) or fluorimetrically (propranolol). The colorimetric assay of acebutolol in plasma is fully described but the other drugs were assayed by published methods. 3 The degree of beta-adrenoceptor blockade and the plasma level for acebutolol and practolol were well correlated, whereas in the case of propranolol correlation was poor, due in part to the presence in plasma of active metabolites not detected by the fluorimetric assay. The plasma levels of practolol and propranolol are in agreement with those previously reported. 4 The maximum cardiac beta-adrenoceptor blockade achieved in this study with the respective single oral doses of acebutolol (300 mg), practolol (400 mg) or propranolol (40 mg) were similar in each of the three subjects. Therefore the beta-adrenoceptor blocking potencies of these drugs against isoprenaline-induced tachycardia are inversely related to these doses; indicating that propranolol is 7-8 times more potent than acebutolol and the latter slightly more potent than practolol.

Acebutolol↗
PubMed1975

Specificity and sensitivity of skin test reactions to extracts of Toxocara canis and Ascaris suum. I. Skin tests done on infected guinea pigs.

The specificity and sensitivity of adult and larval somatic antigens, and perienteric fluid of Toxocara canis and Ascaris suum were investigated by using intradermal skin tests in guinea pigs. These animals were infected with low doses (0.01, 0.1 or 1.0 egg/g) of these helminths. Toxocara larval antigen (TL) induced larger reactions in Toxocara-infected animals than did the other antigens, suggesting a superior sensitivity for this antigen. In addition, Ascaris perienteric fluid (AP) provoked skin responses in these animals of a magnitude similar to those induced by TL. The reciprocal relationship, i.e., comparable reactivity of AP and TL in Ascaris-infected animals, was not apparent. In general, Ascaris larval antigen and AP elicited larger intradermal reactions than other antigens in Ascaris-infected animals. The results of this study indicated no superiority of adult antigens in differentiating Ascaris and Toxocara infections.

Animals↗