Level of contact hypersensitivity response to diphencyprone and keratinocyte cancer.

BACKGROUND: Keratinocyte cancers (KC) are common and pose a significant financial burden globally. Ultraviolet radiation is a significant factor in their development, through mutagenesis promotion but also through local and systemic immunosuppression. Although systemic immunosuppression is well understood, cutaneous immunity has been more difficult to evaluate. OBJECTIVES: This study used a contact sensitizer, diphencyprone (DPCP), which elicits a contact hypersensitivity reaction in skin, to compare the degree of reactivity to DPCP in patients with a high KC burden versus those with a low KC burden. METHODS: A prospective study was performed in immunocompetent patients aged 70 ± 5 years of age, comparing patients with a high KC burden (>10 previous KC) with those with a low KC burden (<2 previous KC). All patients were sensitized with 2% DPCP and then patch tested two weeks later with eight different concentrations of DPCP with the threshold concentration and total degree of reaction recorded. RESULTS: Nine patients were recruited, 5 in the 'high cancer' group and 4 in the 'low cancer' group. All patients were Fitzpatrick skin type 1 or 2. All patients developed a reaction to DPCP. Patients in the low cancer group developed a reaction at a significantly lower threshold DPCP concentration than the high cancer group (P = 0.039). The cumulative intensity of reaction was higher in the low cancer group (P = 0.087). CONCLUSION: Patients with a high KC burden required a higher threshold concentration of DPCP to elicit a hypersensitivity reaction, supporting the concept of a lower skin immunity in these patients. DPCP reactivity threshold could be a useful tool in the evaluation of skin immunity and propensity to develop keratinocyte cancers.

Survival outcomes in patients with multiple primary melanomas.

BACKGROUND: A substantial number of melanoma patients will develop multiple primary melanomas (MPM). Currently, little is known about the impact of MPM on survival. OBJECTIVE: We aimed to determine whether melanoma survival is worse for patients with MPM compared to those with a single invasive primary melanoma (SPM). MATERIALS AND METHODS: A cohort study was conducted. Patients were sourced from an Australian population, with follow-up information collected retrospectively from registry data. Melanoma-specific survival analysis was performed to find associated variables after adjustment for known prognostic factors, using four different models, each selecting a different index melanoma lesion. RESULTS: 1068 stage I and II melanoma patients were followed up for a median of 24.4 years. MPM was found in 17.8% of the cohort (190 patients), more likely among males and older age groups. Other clinicopathological parameters were similar between the MPM and SPM (878 patients) cohorts. After adjustment for age, sex and Breslow thickness, MPM was a hazard for death from melanoma, across all models, reaching significance when considering the last invasive lesion as the index melanoma (HR = 2.76, P = 0.017). CONCLUSION: Patients with multiple invasive lesions seem more at risk of death from melanoma, independent of known prognostic factors.

Engineering a polyketide with a longer chain by insertion of an extra module into the erythromycin-producing polyketide synthase.

BACKGROUND: Modular polyketide synthases catalyse the biosynthesis of medically useful natural products by stepwise chain assembly, with each module of enzyme activities catalysing a separate cycle of polyketide chain extension. Domain swapping between polyketide synthases leads to hybrid multienzymes that yield novel polyketides in a more or less predictable way. No experiments have so far been reported which attempt to enlarge a polyketide synthase by interpolating additional modules. RESULTS: We describe here the construction of tetraketide synthases in which an entire extension module from the rapamycin-producing polyketide synthase is covalently spliced between the first two extension modules of the erythromycin-producing polyketide synthase (DEBS). The extended polyketide synthases thus formed are found to catalyse the synthesis of specific tetraketide products containing an appropriate extra ketide unit. Co-expression in Saccharopolyspora erythraea of the extended DEBS multienzyme with multienzymes DEBS 2 and DEBS 3 leads to the formation, as expected, of novel octaketide macrolactones. In each case the predicted products are accompanied by significant amounts of unextended products, corresponding to those of the unaltered DEBS PKS. We refer to this newly observed phenomenon as 'skipping'. CONCLUSIONS: The strategy exemplified here shows far-reaching possibilities for combinatorial engineering of polyketide natural products, as well as revealing the ability of modular polyketide synthases to 'skip' extension modules. The results also provide additional insight into the three-dimensional arrangement of modules within these giant synthases.

Novel octaketide macrolides related to 6-deoxyerythronolide B provide evidence for iterative operation of the erythromycin polyketide synthase.

BACKGROUND: The macrolide antibiotic erythromycin A, like other complex aliphatic polyketides, is synthesised by a bacterial modular polyketide synthase (PKS). Such PKSs, in contrast to other fatty acid and polyketide synthases which work iteratively, contain a separate set or module of enzyme activities for each successive cycle of polyketide chain extension, and the number and type of modules together determine the structure of the polyketide product. Thus, the six extension modules of the erythromycin PKS (DEBS) together catalyse the production of the specific heptaketide 6-deoxyerythronolide B. RESULTS: A mutant strain of the erythromycin producer Saccharopolyspora erythraea, which accumulates the aglycone intermediate erythronolide B, was found unexpectedly to produce two novel octaketides, both 16-membered macrolides. These compounds were detectable in fermentation broths of wild-type S. erythraea, but not in a strain from which the DEBS genes had been specifically deleted. From their structures, both of these octaketides appear to be aberrant products of DEBS in which module 4 has 'stuttered', that is, has catalysed two successive cycles of chain extension. CONCLUSIONS: The isolation of novel DEBS-derived octaketides provides the first evidence that an extension module in a modular PKS has the potential to catalyse iterative rounds of chain elongation like other type I FAS and PKS systems. The factors governing the extent of such 'stuttering' remain to be determined.

Construction of new vectors for high-level expression in actinomycetes.

A new integrative vector (pCJR24) was constructed for use in the erythromycin producer Saccharopolyspora erythraea and in other actinomycetes. It includes the pathway-specific activator gene actII-ORF4 from the actinorhodin biosynthetic gene cluster of Streptomyces coelicolor. The actI promoter and the associated ribosome binding site are located upstream of an NdeI site (5'-CATATG-3') which encompasses the actI start codon allowing protein(s) to be produced at high levels in response to nutritional signals if these signals are faithfully mediated by the ActII-ORF4 activator. Several polyketide synthase genes were cloned in pCJR24 and overexpressed in S. erythraea after integration of the vector into the chromosome by homologous recombination, indicating the possibility that the S. coelicolor promoter/activator functions appropriately in S. erythraea. pCJR24-mediated recombination was also used to place the entire gene set for the erythromycin-producing polyketide synthase under the control of the actI promoter. The resulting strain produced copious quantities of erythromycins and precursor macrolides when compared with wild-type S. erythraea. The use of this system provides the means for rational strain improvement of antibiotic-producing actinomycetes.

Analysis of the conversion of delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-alpha-aminobutyrate by active-site mutants of Aspergillus nidulans isopenicillin N synthase.

BACKGROUND: Penicillins and cephalosporins constitute a major class of clinically useful antibiotics. A key step in their biosynthesis involves the oxidative cyclisation of delta-(Lalpha-aminoadipoyl)-L-cysteinyl-D-valine to isopenicillin N by isopenicillin N synthase (IPNS). This chemically remarkable transformation has been extensively studied using substrate analogues. The conversion of an analogue in which the valine is replaced by alpha-aminobutyrate results in three products, two epimeric penams and a cepham. The ratio of these products in reactions catalysed by four different IPNS isozymes has been used previously to probe the thermicity of the chemical mechanism. But how IPNS restricts the products from the natural substrate to a single penam (isopenicillin N) has remained unknown. RESULTS: A key active-site residue, Leu223, identified according to a model of enzyme-substrate binding, has been altered to sterically less demanding residues. As the steric constraints on the upper part of the active site are reduced, the ratio of the beta-methyl penam to the cepham increases when the alpha-aminobutyrate-containing substrate analogue is used. These results suggest a mechanism for processing of the natural substrate in which IPNS uses steric control to restrict the conformational freedom of an intermediate such that the only product is the penam. CONCLUSIONS: Using steric pressure to control conformation, and hence to disfavour reactions leading to alternate products, is probably the result of evolutionary selection for a biologically active product at the expense of biologically inactive byproducts. It is likely that this sort of enzymatic catalysis is used in situations where substrate conversion is highly exothermic and a variety of products are possible.

HIV, substance use and related behaviour of gay and bisexual men: an examination of the talking sex project cohort.

This paper reports on the substance use of 612 gay and bisexual men who participated in an HIV risk reduction project. Use/non-use, level of substance use, and reported frequency of use prior to sexual activity were examined in relation to number of sexual partners, sexual activities, HIV antibody test seeking behaviour and known HIV status. The use of substances among the study cohort appear to be higher than in a comparable heterosexual male group. An association was found between substance use, and both number of sexual partners and sexual activities. However, no significant difference was found in substance use between men participating in protected versus unprotected anal sex. Similarly, no significant difference was found in the reported frequency of substance use prior to sex by those participating in protected and unprotected anal intercourse. Greater drug use was reported among those who were known to be HIV antibody positive. These findings raise issues for further research. The high use of alcohol and drugs by gay and bisexual men may pose significant health risks for this group of men.

The Talking Sex Project: descriptions of the study population and correlates of sexual practices at baseline.

The Talking Sex Project is an HIV risk reduction education project for gay and bisexual men. It was developed to evaluate two types of small discussion groups using a randomized control study design. This paper reports on the baseline measures of knowledge, attitudes and sexual practices. The 612 subjects had a mean age of 32 years, were all English speaking and were relatively highly educated. Bivariate analyses found that younger men, those in a relationship, those reporting bisexual activity and those with higher levels of substance use were significantly more likely to have unprotected anal intercourse. While overall knowledge was not associated with sexual behaviour, a significant relationship was found with knowledge of risk of anal sex. Attitudes, in particular, the belief in the efficacy of condoms and the enjoyment of safer sex were found to have the strongest associations with protected anal intercourse. The paper provides an understanding of some of the factors which may be important to behaviour change and clues for the targeting of programs.

PIP: Baseline data on a cohort of 612 homosexual and bisexual men were analyzed in order to examine the interrelationships between sociodemographic, knowledge, and attitude factors and sex behavior. Men were recruited for a randomized control study of small group AIDS risk reduction education in Toronto, Canada: The Talking Sex Project. Questionnaire validity and reliability checks were conducted. The development of knowledge and attitude scores is provided and includes reliability checks. Chi square and analysis of variance (ANOVA), Turkey's Studentized range Test, Pearson product moment correlations, and stepwise logistic regression analyses were performed. Population characteristics included a mean age of 32 years; 1.8% were teenagers, 2.8 had AIDS, and 6.2% had HIV-related diseases. Sociodemographic, health and life style, and sexual behavior characteristics were also reported. The univariate description of scaled knowledge and attitude variables is given. Knowledge is fairly high including knowledge or risk. Both scales had skewing toward the higher ends of the scale. 16.3% reported no sexual activity, but 52.6% reported 1 or more sexual activities in the last 3 months, excluding kissing or masturbation, which was the most common activity. 88.4% reported insertive oral-genital intercourse. 61.5% reported receptive of insertive anal sex. 42.2% had oral-anal sex. 4.1% participated in hand-anal sexual practices. Those with high school or less education had significantly lower scores on knowledge. Higher scores on knowledge of risk were found among men who had safer or protected sex than those who had unprotected anal intercourse. The relationship of background variables to sexual behavior showed that bisexuality was found to be associated with men under 24 years of age. 50% of bisexual men under 24 years reported unprotected anal intercourse vs. 24.4% of homosexual men. Alcohol or drug use was associated with sexual behavior, and men with reported safer sex consumed slightly less. Men practicing safer sex were more likely to report impulse control difficulties, had a stronger belief in the efficacy of condoms, and rated sexual practices safer. The logistic model correctly classified 94.5% of safer sex cases and 54.9% of unprotected sex. Efficacy of condoms was the best predictor of safer sex, as well as lower drug use, not being in a relationship, greater enjoyment of safer sex, being older, having fewer sexual partners, and lower, more cautious self-rating of knowledge of risk. Bisexuality needs further exploration.

Pitfalls and pratfalls in consultation-liaison psychiatry in a general hospital.

As Consultation-Liaison Services continue to develop and expand in general hospitals, psychiatrists must be aware of pitfalls and pratfalls inherent in dealing with medical colleagues and other allied health professionals, as well as with the patients. Practical considerations in answering consultation requests are discussed with respect to "hidden agendas" of the consultee, role and expectations of the psychiatrist, and problem referrals. It is only through mutual respect and collaboration that Consultation-Liaison Services can truly be effective.

Narrow-linewidth fiber laser operating at 1.55 microm.

We report the fabrication and operation of an Er(3+)-doped silica single-mode fiber laser operating at 1.55 microm and using a distributed fiber grating to provide feedback. The output bandwidth was measured as 0.04 nm, significantly narrower than the conventional cavity design. The laser had a threshold of 13 mW and a slope efficiency of 5%.

Is it normal for terminally ill patients to desire death?

Among 44 terminally ill patients, the majority (N = 34) had never wished death to come early. Of the remainder, three were or had been suicidal and seven more had desired early death. All 10 patients who had desired death were found to be suffering from clinical depressive illness. The methodologic difficulties encountered by the authors were the lack of a brief, efficient interview schedule suitable for debilitated patients and criteria for depressive disorder that do not depend on suicidal thoughts or on symptoms that can also be caused by physical disease.

Premenstrual syndrome: diagnosis and management.

Premenstrual syndrome is a recurrent set of disabling symptoms that occur in a definite relation to the menstrual cycle. Patients chart the severity of symptoms over time during consecutive menstrual cycles while the physician should rule out other possible gynecological and psychiatric disorders. Management is through education, environmental manipulation and symptomatic relief of stressors, using a variety of medications. Often a multidisciplinary approach of family physician, psychiatrist and gynecologist is needed.