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K Benton

Publications and source records attributed to K Benton.

6 recordsLinked to original sources
PubMed1999

Identification of a Clostridium perfringens enterotoxin region required for large complex formation and cytotoxicity by random mutagenesis.

Clostridium perfringens enterotoxin (CPE), a single polypeptide of 319 amino acids, has a unique multistep mechanism of action. In the first step, CPE binds to claudin proteins and/or a 50-kDa eukaryotic membrane protein receptor, forming a small ( approximately 90-kDa) complex. This small complex apparently then associates with a 70-kDa eukaryotic membrane protein, resulting in formation of a large complex that induces the onset of membrane permeability alterations. To better define the boundaries of CPE functional regions and to identify specific amino acid residues involved in various steps of CPE action, in this study we subjected the cloned cpe gene to random mutagenesis in XL-1 Red strains of Escherichia coli. Seven CPE random mutants with reduced cytotoxicity for Vero cells were phenotypically characterized for the ability to complete each step in CPE action. Five of these seven recombinant CPE (rCPE) random mutants (G49D, S59L, R116S, R137G, and S167P) exhibited binding characteristics similar to those of rCPE or native CPE, while the Y310C and W226Stop mutants showed reduced binding and no binding, respectively, to brush border membranes. Interestingly, two completely nontoxic mutants (G49D and S59L) were able to bind and form small complex but they did not mediate any detectable large complex formation. Another strongly attenuated mutant, R116S, formed reduced amounts of an anomalously migrating large complex. Collectively, these results provide further support for large complex formation being an essential step in CPE action and also identify the CPE region ranging from residues approximately 45 to 116 as important for large complex formation. Finally, we also report that limited removal of extreme N-terminal CPE sequences, which may occur in vivo during disease, stimulates cytotoxic activity by enhancing large complex formation.

Animals↗
PubMed1999

Factors affecting men's liking of condoms they have used.

The objective of this study was to assess the impact on men's liking for the condoms they use of a range of factors including demographic variables and variables that describe men's experience of using particular condoms. One hundred and ninety-four men used 3765 condoms for which they provided a liking rating. The condoms were manufactured to one of 2 published standards and the study employed a double-blind crossover design. Sixty-one per cent of condoms were rated favourably, 31% were rated neutrally and the remainder (8%) unfavourably. Men rated condoms less favourably if they were experienced as too loose, too tight, too short, if difficulty was experienced applying the condom, if the condom slipped partially or completely down the penis or if the condom broke. Men rated more highly condoms which were experienced as well lubricated throughout use. Men with larger penises rated condoms less favourably and, of all the variables considered, ejaculating in the condom was the variable which had the largest positive impact. Men's liking for the condoms they use is influenced by a range of factors. However, given that most of the factors associated with men liking condoms less are those that can be addressed through better condom design and manufacture, the opportunity exists to enhance men's experience of condom use and hence help reduce resistance to the adoption of consistent condom use.

Adult↗
PubMed1998

Does additional lubrication affect condom slippage and breakage?

The risk of condom slippage (1.94%) and breakage (0.89%) among 3607 condoms was analysed with respect to the use of additional lubricant. Whether or not lubricant was used, the site at which it was applied and the type of lubricant used were all found to vary significantly with the type of sexual act(s) for which the condoms were used. Little evidence was found for differing effects of type of additional lubricant (water-based, saliva or other) or site of lubricant use (on penis/inside condom, on condom, in vagina/anus). The use of lubricant more than doubles the risk of slippage for vaginal sex. While anal sex is associated with much higher risks of slippage the use of lubricant for this practice actually reduces the risk of slippage to that similar for vaginal sex where lubricant is used. No significant effect of additional lubricant on condom breakage was observed. It is recommended that education messages concerning the use of additional lubricant may need to change to take into account the varied nature of lubricant use practices and the differential effects of lubricant with respect to sexual practices. Specifically, if the use of additional lubricant has little or no impact on condom breakage but increases condom slippage then encouraging its use may be counterproductive if condom users consider slippage to be a reason not to use condoms.

Adult↗
PubMed1998

Does penis size influence condom slippage and breakage?

This study examined the effect of penis dimensions on the probability of complete condom slippage and condom breakage in actual use. Men were recruited through advertising, used the condoms supplied and completed a diary sheet for each condom used. A total of 3658 condoms were used by 184 men of which 1.34% broke and 2.05% slipped off. No significant effect was demonstrated for penile dimensions on the probability of complete condom slippage. However, condom breakage was strongly associated with penile circumference. These findings suggest that condom manufacturers may need to increase the range of condom sizes available, or some aspects of their performance, in order to ensure that condoms meet the needs of all men without unduly exposing them to risk.

Condoms↗