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R T Evans

Publications and source records attributed to R T Evans.

At least 55 records · Page 3Linked to original sources
PubMed1989

Two complementary methods of assessing periodontal bone level in rats.

Several methods have been applied to measure periodontal disease in rats. The purpose of the present study was to test the reproducibility of a morphometric and a radiographic method and to describe the correlation between the two methods. Periodontal bone loss on 25 defleshed rat heads was assessed under microscopic by measuring the distances from the cementoenamel junction to the alveolar bone crest at 36 buccal sites in each animal. On magnified radiographs from 25 rat mandibles periodontal bone support was expressed by the ratio apex-deepest bony defect: apex-cusp tip distally on first molars. All measurements were performed blind and in duplicate on two separate occasions. The bilateral 95% confidence limits for the error of method of measurement were estimated from the t-distribution. In a second experiment 50 rat heads were assessed by both methods, and the correlation between the recordings was estimated by the Spearman rank correlation analysis. Compared to the considerable total variation in the material, the variations due to error of methods of measurement were small, i.e. the reproducibility of both methods was satisfactory. A significant correlation was found between the methods. Since the morphometric method mainly measures horizontal bone loss, whereas the radiographic method detects intrabony interproximal defects, it is concluded that future studies would benefit from applying both methods to assess alveolar bone loss in rats.

Animals↗
PubMed1989

Blood alcohol levels in acute elderly admissions to hospital.

Blood alcohol levels were estimated in 141 patients admitted acutely over a one month period to a geriatric unit. Only four (2.8%) had alcohol detectable in their blood. The levels were low, suggesting that alcohol intoxication is not a major factor in the admission of the elderly to hospital.

Aged↗
PubMed1988

The digestion of perennial ryegrass (Lolium perenne cv. Melle) and white clover (Trifolium repens cv. Blanca) by grazing cattle.

1. Pure swards of perennial ryegrass (Lolium perenne cv. Melle) as a primary growth (May), trimmed primary growth (early June) and regrowth (late June), and white clover (Trifolium repens cv. Blanca) as a mature primary growth (July) and vegetative regrowth (August), were grazed by twelve Friesian steers (mean body-weights throughout experiment 152-231 kg) at daily allocation rates of forage which provided dry matter (DM) intakes ranging from 28 to 36 g/kg body-weight). 2. Total nitrogen contents of the three ryegrasses declined with season (37-20 g/kg DM), but in vitro organic matter (OM) digestibilities were relatively constant (0.76-0.79). The clovers had higher N (average 36.6 g/kg DM) and lower fibre and water-soluble carbohydrate contents than the grasses, and in vitro OM digestibilities of 0.70 and 0.76 respectively. 3. Duodenal digesta samples were obtained, using a portable sampling apparatus from the animals grazing the pasture, and estimates of the flow of nutrients into the small intestine were derived using two indigestible markers which were continuously infused into the rumen using a portable infusion apparatus. Forage intakes were calculated from estimates of faecal output of indigestible OM and the predicted in vivo OM digestibilities of the forages consumed. Coefficients of variation for OM flow to the small intestine and OM intake were 11.8 and 10.9% respectively. 4. The apparent digestion of OM in the rumen ranged from 722 to 741 g/kg digestible OM intake and from 681 to 711 g/kg digestible OM intake for the grass and clover diets respectively. Substantial losses of ingested N before the small intestine were measured on all diets except the regrowth ryegrass. Losses were 0.30 and 0.40 g/g N intake on the primary growth ryegrass and the regrowth clover respectively; N contents were 37 and 39 g/kg DM respectively. 5. Comparison of the values obtained at pasture with that obtained when similar diets were offered to housed cattle (Beever et al. 1985) indicated that combined relations relating duodenal OM and non-ammonia-N (NAN) flows to OM and N intakes respectively could be established for each diet. For two diets (primary-growth grass and regrowth clover) the relations were curvilinear; for the remaining diets, the derived relations were linear.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Nutritional Physiological Phenomena↗
PubMed1988

A longitudinal study of cholinesterase changes in pregnancy.

Serum cholinesterase activity was measured at intervals before, during, and after 44 pregnancies in 43 women. Three patterns of change were seen: (a) A decline in activity after conception, with no return towards pre-conception values before delivery (20 pregnancies). (b) A decline in activity accompanied by a partial or complete return to pre-conception values before delivery (19 pregnancies). (c) Either no discernible decline or increased activity during gestation (five pregnancies). We saw no association between these patterns and either the sex of the child, parity, smoking history, or alcohol intake. However, the continuous decrease in cholinesterase activity occurred in the youngest group of women, a decrease followed by an increase in the intermediate age group, and no decrease at all in the oldest group. Although not all the age-related differences quite reached statistical significance, these findings suggest that the patterns of change may be determined by some aspect of maternal physical maturity.

Adult↗
PubMed1987

Substituted 2-(2-hydroxyphenyl)benzimidazoles as potential agents for the control of periodontal diseases.

A series of 16 substituted 2-(2-hydroxphenyl)benzimidazoles was synthesized and evaluated in vitro for antibacterial activity against bacteria associated with periodontal diseases. Several compounds demonstrated a high level of activity, in tube dilution assay, against Actinomycetes viscosus and Bacteriodes gingivalis. These results indicate that several of these compounds may serve as topical antibacterial agents for the control of acute marginal inflammatory gingivitis and periodontitis.

Actinomycetales↗
PubMed1987

The role of mycoplasmas, ureaplasmas and chlamydiae in the genital tract of women presenting in spontaneous early preterm labour.

The genital carriage of Ureaplasma urealyticum, Mycoplasma hominis and Chlamydia trachomatis was assessed in 72 women admitted to hospital in spontaneous preterm labour and in 26 women requiring preterm delivery for other reasons who formed a control group. Women in preterm labour significantly more often carried ureaplasmas, had large numbers of M. hominis and subsequently developed chorioamnionitis than women in the control group. M. hominis, in particular, occurred more frequently and in large numbers in women who had chorioamnionitis associated with ruptured membranes. Genital carriage of the various micro-organisms appeared not to be associated with fetal growth retardation, although subsequent isolation of ureaplasmas from infants was common. It is suggested that mid-second-trimester vaginal specimens should be cultured on a research basis to establish whether these various micro-organisms identify women at risk of labouring preterm.

Birth Weight↗
PubMed1987

Structural determinants of activity of chlorhexidine and alkyl bisbiguanides against the human oral flora.

We assayed chlorhexidine and a series of its analogues, in which the chlorophenyl terminal substituents were replaced with alkyl chains, for their in vitro antimicrobial activity against the Gram-negative and Gram-positive oral bacteria. Changes in antimicrobial activity were correlated with changes in agent structure for identification of structural criteria which may be important in the optimization of agent activity. Chlorhexidine showed substantial antimicrobial activity against the Gram-negative as well as the Gram-positive oral bacteria. The alkyl agents were comparable with chlorhexidine in their activity against Bacteroides gingivalis and Bacteroides intermedius, black-pigmented Gram-negative obligate anaerobes associated with periodontal disease in adults. Alkyl agents alexidine, heptihexidine (1,6-bis-n-heptylbiguanidohexane), hexoctidine (1,8-bis-n-hexylbiguanidoctane), and hexhexidine (1,6-bis-n-hexylbiguanidohexane), as well as chlorhexidine, were active against Actinobacillus actinomycetemcomitans, a Gram-negative organism associated with localized juvenile periodontitis. Hexidecidine (1,10-bis-n-hexylbiguanidodecane) and heptoctidine (1,8-bis-n-heptylbiguanidooctane) were more active, and hexhexidine was as active as chlorhexidine against Fusobacterium nucleatum, also associated with periodontal disease. Seven of the agents were more active than chlorhexidine against Actinomyces species. All test agents were active against Streptococcus mutans, a Gram-positive coccus associated with dental caries. Hexidecidine had activity equal to that of chlorhexidine when evaluated against the entire battery of organisms. Analysis of structure-activity relationships revealed that alkyl chains could replace chlorophenyl groups with retention or improvement of antimicrobial activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomyces↗
PubMed1987

Improved accuracy of cholinesterase phenotyping after participation in a proficiency survey.

We report results of an investigation into the proficiency of cholinesterase (EC 3.1.1.8) phenotying, assessed in 13 laboratories between 1983 and 1986. Thirty-two specimens of serum were distributed for analysis: two, each in duplicate, from the eight genotypes that can be recognized by differential enzyme inhibitor numbers. The accuracy of genotype ascription was markedly improved over that observed in an earlier study in which 12 of these laboratories took part, although the proportion of clinically significant errors did not change. Consequently, although participation in a proficiency testing program can lead to a considerable enhancement of performance, we still recommend the use of reference centers for detailed cholinesterase studies.

Cholinesterases↗
PubMed1986

5-(Alkylsulfonyl)salicylanilides as potential dental antiplaque agents.

A series of 22 5-(alkylsulfonyl)salicylanilides was synthesized and evaluated for in vitro antibacterial and antiplaque activity against Actinomyces viscosus and Streptococcus mutans, adherent microorganisms implicated in periodontal disease and dental caries. The minimum inhibitory concentrations of 25 salicylanilides (including 5-acyl-, 5-alkyl-, and 5-(alkylsulfonyl)-4'-bromo- and -4'-(trifluoromethyl)salicylanilides) were found to correlate (r = 0.94) with estimated log D values. Several salicylanilides, such as 5-(decylsulfonyl)- and 5-(dodecylsulfonyl)-4'-(trifluoromethyl)salicylanilides (15 and 19) were found to exhibit high levels of in vitro antibacterial and antiplaque activity against A. viscosus and S. mutans.

Actinomyces↗
PubMed1986

Effect of forage species and season on nutrient digestion and supply in grazing cattle.

1. A total of twenty Friesian steers were grazed on pure swards of either perennial ryegrass (Lolium perenne cv. Melle) or white clover (Trifolium repens cv. Blanca) from May to late August to examine the effect of forage species and season on nutrient digestion and supply. Within each forage species, two daily allowances of forage (i.e. 30 and 60 g dry matter (DM)/kg live weight) were given, and nutrient flow into the small intestine was measured on thirteen separate occasions (viz. seven grasses and six clovers). 2. Total nitrogen content of the grasses varied between 28 (early season), 19 (mid-) and 33 (late) g/kg DM, whilst the clovers showed a much narrower range and all values were higher (39-45 g/kg DM). In vitro organic matter (OM) digestibilities of plucked samples ranged from 742 to 809 g/kg OM (grass) and 712 to 790 g/kg OM (clover), the lowest values being noted in late June (grass) and mid-July (clover). 3. OM intakes calculated from estimated faecal OM output (using unlabelled ruthenium) and predicted OM digestibility of the consumed forage indicated mean values of 20.9 (grass) and 26.0 (clover) g/kg live weight (P less than 0.001), whilst the higher forage allowances increased OM intake by approximately 8% on both grass and clover (P less than 0.01) compared with the low allowance. OM intake was significantly (P less than 0.01) lower on the two primary growths of grass examined in May (mean 16.8 g/kg live weight) than the other five grass diets. 4. Rumen molar propionate levels declined with season but were at all times higher on the grass than on the clover diets, whilst acetate levels were unaffected by forage species. Apart from the late-season grass, mean rumen ammonia concentration was less than 100 mg NH3-N/l on all grass diets, whilst values on the clover diets ranged from 200-350 mg/l. 5. Daily duodenal OM flows in relation to animal live weight were approximately 20% higher on the clover than on the grass diets (grass 9.2, clover 11.2 g/kg live weight, P less than 0.001), but estimates of the proportion of digestible OM apparently digested in the rumen were not significantly influenced by forage species (grass 0.69, clover 0.71).(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Nutritional Physiological Phenomena↗
PubMed1986

The effect of forage species and stage of harvest on the processes of digestion occurring in the rumen of cattle.

1. Pure swards of perennial ryegrass (Lolium perenne L. cv. Melle) or white clover (Trifolium repens L. cv. Blanca) were harvested daily as either primary growth (May-June) or mid- (July) and late- (August-September) season 4-week regrowths and offered to Friesian steers at two levels of feed allowance (18 and 24 g dry matter (DM)/kg live weight), to examine the effect of forage species and stage of harvest on nutrient digestion and supply. 2. The early- and mid-season grasses had low nitrogen (23 g/kg DM) and high water-soluble carbohydrate (169 g/kg) contents whilst the late-season grass had a higher N content (28 g/kg). All clover diets had high N (average 45 g/kg) and low water-soluble carbohydrate (89 g/kg) contents, and DM digestibility on all diets ranged from 0.77 to 0.83 (mean of two feeding levels). 3. Mean total rumen volatile fatty acid concentrations were significantly (P less than 0.001) higher on the clover diets, whilst on the grass diets molar proportions of propionate showed a slight but not significant decline with advancing season and tended to be higher than those on the clover diets. Mean rumen ammonia concentrations were significantly (P less than 0.001) lower on the early- and mid-season grasses (59 mg NH3-N/l) than the late-season grass (242 mg/l) and early-season clover (283 mg/l) which were all significantly (P less than 0.01) lower than the mid- and late-season clovers (372 and 590 mg/l) respectively. 4. Rates of organic matter (OM) and N digestion in the rumen were estimated using established nylon-bag techniques and found to be high on all diets, but significant effects due to forage species (clover greater than grass; P less than 0.001) were detected, whilst overall potential degradability in the rumen exceeded 0.89 for both OM and N on all diets. 5. Significantly (P less than 0.001) more OM entered the small intestine of calves fed on white clover (10.2 g/kg live weight) than those fed on ryegrass (8.33 g/kg) and similar effects due to level of feeding (g/kg; low 7.9, high 10.6; P less than 0.05) and stage of harvest (g/kg; early 8.3 v. mid 10.0, late 9.50; P less than 0.05) were also detected.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗
PubMed1986

Effect of short term treatment of non-gonococcal urethritis with minocycline.

Two hundred and forty four men with non-gonococcal urethritis (NGU) took part in a trial of minocycline. Chlamydiae were isolated from 34%, ureaplasmas from 47.1%, and Mycoplasma hominis from 10.2%. These micro-organisms were isolated least often from men suffering their third or more attack of NGU, and men in this group failed most often to respond to minocycline. Irrespective of the micro-organisms isolated originally or the number of previous attacks, the failure rate (10%) for men receiving minocycline for 10 days was significantly less than for those receiving this antibiotic for one or two days. More than half of the men suffering third attacks from whom micro-organisms were not isolated failed to respond to these short regimens. One of the lowest failure rates (4%) after short term treatment, however, was seen in men experiencing first attacks who yielded only ureaplasmas with or without M hominis, which indicates the importance of ureaplasmas in this group of patients. Chlamydiae were not reisolated from any patient after treatment, irrespective of its duration, and the only ureaplasmas that were reisolated were from nine patients who carried tetracycline resistant strains. Reasons for the absence of chlamydiae and ureaplasmas in the presence of disease and the need to look for other microorganisms as a cause of NGU are discussed among other issues raised by these results.

Chlamydia↗
PubMed1986

Cholinesterase phenotyping: clinical aspects and laboratory applications.

The measurement of cholinesterase activity in human serum is an important investigation, especially in patients suspected of poisoning with organophosphate insecticides, or those experiencing prolonged paralysis following treatment with the short acting muscle relaxant succinylcholine. Appropriate clinical management of affected individuals can only be instituted if enzyme activity is measured using a method capable of clear interpretation and phenotypic ascription of cholinesterase, ascertained by use of selected enzyme inhibitors, is reliable. This review considers factors which lead to significant cholinesterase abnormalities and advises on the techniques most appropriate to their investigation. It is concluded that no one method is suitable both for measurement of activity and determination of genotype. The use of propionyl thiocholine is recommended for the first procedure and benzoyl choline for the latter. Those laboratories in which a request for the assessment of cholinesterase status is an unusual event should make greater use of assistance from colleagues whose experience with the problem is greater.

Animals↗
PubMed1986

Plasma cholinesterase phenotyping with use of visible-region spectrophotometry.

A method that overcomes the difficulties of the 240-nm benzoylcholine method for phenotyping plasma cholinesterases has been developed. After a timed reaction, under the same reaction conditions as in the classic procedure, choline is detected at 500 nm by use of choline oxidase coupled with the peroxidase/phenol/aminoantipyrine system. Cholinesterase activity measurements, calibrated by use of choline iodide as standard, are linearly related to results obtained with propionylthiocholine as substrate at 25 degrees C (y = 0.14x + 0.17, n = 30, r = 0.98). Results of differential inhibition with dibucaine and fluoride are virtually identical with those obtained by the ultraviolet method (y = 0.97x + 4.3, r = 0.995, and y = 0.93x - 0.5, r = 0.987, respectively) and give the same classification of homo- and heterozygotes for the usual, atypical, and fluoride-resistant variants. The new method has substantial advantages in that it eliminates the difficulties associated with measuring small changes in high absorbances at a suboptimal wavelength on a steep portion of the absorption curve.

Alcohol Oxidoreductases↗
PubMed1986

Is succinyldicholine the substrate of choice for the measurement of cholinesterase activity?

We have developed a succinyldicholine-based assay for serum cholinesterase (EC 3.1.1.8) to help establish whether patients with suspected sensitivity to drugs of this type have enzyme abnormalities that cannot be detected by conventional laboratory techniques. Although the method discriminates between cholinesterase activities of drug-sensitive and nonsensitive people as well as an assay involving propionylthiocholine does, it has not revealed cholinesterase abnormalities in patients who experienced prolonged apnea after succinyldicholine, in whom no enzyme defect could be demonstrated by other procedures. Of 50 individuals who were apneic for between 20 and 180 min, only one had a cholinesterase activity less than the mean for E1u homozygotes by more than 2.5 SD. We conclude that the number of patients who experience clinical problems due to enzyme abnormalities that at present go unrecognized is small. Consequently, although succinyldicholine might eventually become the substrate of choice for cholinesterase, its advantages over propionylthiocholine are not yet sufficient to encourage its use.

Adult↗