Photobiological properties of positively charged methylene violet analogs

O-Methyl methylene violet (OMeMV), O-methyl bromomethylene violet (OMeBrMV) and O-methyl iodomethylene violet (OMeIMV) have been prepared in order to test their potential utility as anti-viral and anti-tumor phototoxic dyes. Rates of photosensitized toxicity of KB cells with 633 nm irradiation are (x 10(-19) photon-1): 2.4, 2.2, 1.9 and 0.17 for OMeIMV, OMeBrMV, methylene violet (MV) and OMeMV, respectively. Rates of photosensitized inactivation of Sindbis virus in phosphate-buffered saline with 633 nm irradiation are (x 10(-18) photon-1): 3.3, 1.8, 0.99, 0.15 for MV, OMeIMV, OMeBrMV and OMeMV, respectively. Quantum efficiencies for singlet oxygen formation were determined as OMeIMV, 0.64; OMeBrMV, 0.40; OMeMV, 0.054. Titration of the dyes with double-stranded (ds)DNA resulted in bathochromic shifts and hypochromic effects in the visible absorption spectra. Association constants for interaction of the methylated dyes with dsDNA of approximately 1 x 10(5) M-1 were determined by Scatchard analysis of equilibrium dialysis and UV absorption titration data. Photolysis of the halogenated dyes with DNA under argon led to covalent bond formation with the nucleic acid; there was no evidence of covalent binding in the dark.

Photonuclease activity of Taylor's blue

Taylor's blue (1,9-dimethylmethylene blue, DMMB+) associates with DNA, at least in part, through intercalation as is evidenced from the red shift in the absorption maximum, diminution of the fluorescence, and induced circular dichroism in the presence of nucleic acid. Irradiation of DMMB+/covalently closed circular supercoiled phiX174 phage DNA complex at lambda > 520 nm leads to DNA nicking in a dose-dependent manner.

Human X inactivation center induces random X chromosome inactivation in male transgenic mice

X chromosome inactivation is the means to downregulate the transcriptional output of X chromosomes in female mammals. Essential DNA from the murine X inactivation center (Xic) has been identified by introducing it into male embryonic stem (ES) cells. To identify the essential sequences on human X chromosomes, we transfected male mouse ES cells with a YAC transgene containing 480 kb of the putative human X inactivation center (XIC). Despite little DNA sequence conservation, the human transgene is recognized as a second Xic in these XY mouse cells and induces random inactivation in chimeric mice derived from these cells. Inactivation is extensive on the X chromosome, but more localized on chromosome 11 carrying the transgene, demonstrating that initial inactivation and spreading of inactivation signals along the chromosome are independent events. Our results show for the first time that the DNA included in the human XIC transgene is sufficient to initiate random X inactivation, even in cells of another species. Interspecies XIC trangenes should facilitate further investigation of this process in humans and other mammals.

Photoinduced cross-linking of RNA by cis-Rh(phen)2Cl2+ and cis-Rh(phen)(phi)Cl2+: a new family of light activatable nucleic acid cross-linking agents

The metal complexes, cis-Rh(phen)2Cl2+ and its more hydrophobic analog cis-Rh(phen)(phi)Cl2+, have been shown to photocross-link the 120-base phi29-encoded pRNA. Primer extension on the cis-Rh(phen)(phi)Cl2(+)-photocross-linked RNA revealed that guanines are responsible for the interstrand cross-links.

Identification and characterization of a homozygous deletion found in ovarian ascites by representational difference analysis

We have performed representational difference analysis (RDA) on DNA from tumor cells and normal fibroblasts isolated from the ascites of a patient with ovarian cancer. Five of six products of the RDA were homozygously deleted from the tumor DNA. One of these products has been characterized and identifies a homozygous deletion of approximately 6.9 Mb at chromosome 9p21 in the original ovarian tumor material. This deletion encompasses CDKN2A (p16), CDKN2B (p15), and IFN-alpha. PCR analysis of other tumor cell lines using the novel STS based on the RDA product has shown it to lie between IFN-alpha and p16, and to identify the distal extent of a homozygous deletion in another ovarian cancer cell line. These data provide further evidence for a tumor suppressor locus distinct from, but mapping close to, p16 on 9p21. Cytogenetic analysis using comparative genomic hybridization (CGH) performed on the same primary tumor confirmed a loss of material from chromosome 9p. However, the CGH technique had neither the resolution nor the sensitivity to define a subregion of homozygous loss.

Monograph series on aging-related diseases: X. Prostate cancer

Prostate cancer is the most commonly diagnosed cancer among Canadian men, excluding non-melanoma skin cancer. Prostate cancer incidence increases almost exponentially with age; most cases are diagnosed in men aged 65 years or older. With the possible exception of animal fat consumption, no known widespread modifiable risk factors have been identified. Although the prognosis is good if appropriate treatment occurs in the early stages of disease, the ability of existing early detection techniques to decrease mortality has not yet been demonstrated. The considerable economic and societal burden of prostate cancer and its treatment, coupled with the projected large increase in the number of new prostate cancer cases as the population ages, make this disease a very important public health issue.

Survival rates among Canadian children and teenagers with cancer diagnosed between 1985 and 1988

PURPOSE

To describe the survival rates among Canadian children and teenagers with cancer diagnosed between 1985 and 1988 using population-based data, specifically for the more common forms of childhood cancer, and to assess the effect of age at diagnosis and sex as prognostic factors for selected childhood cancers.

DESIGN

Retrospective survival study based on incident cases of cancer identified by the National Cancer Incidence Reporting System and follow-up ascertained by computer record linkage to the Canadian Mortality Database.

SUBJECTS

A total of 4409 patients with cancer first diagnosed at 19 years of age or younger between 1985 and 1988, and followed up to Dec. 31, 1991.

MAIN OUTCOME MEASURES

Survival rates calculated at 1, 3 and 5 years according to the actuarial life table and the proportional hazards models.

RESULTS

The 5-year survival rate for all cancers combined was 71%. Females with acute lymphoblastic leukemia and astrocytoma had markedly higher survival rates than their male counterparts (p < 0.05). Age at diagnosis was a significant predictor of survival among children with acute lymphoblastic leukemia or acute nonlymphoblastic leukemia (p < 0.01), infants having a substantially poorer prognosis than older children. Conversely, the survival rate among infants with neuroblastoma was higher than that among older children, 87% surviving for 5 years after diagnosis.

CONCLUSIONS

The survival rate among Canadian children and teenagers with cancer is favourable in relation to the rate among adults with cancer. Nonetheless, the 5-year survival rates for several childhood cancers remain poor (i.e., less than 65%). The survival rates among Canadian children with cancer are similar to those among children with cancer in other developed countries.

Simultaneous determination of methylene violet, halogenated methylene violet and their photoproducts in the presence of DNA by high-performance liquid chromatography using an internal surface reversed-phase column

A simple and rapid isocratic high-performance liquid chromatographic method for the analysis of methylene violet, a neutral phenothiazine dye, in the presence of DNA has been developed. These chromatographic conditions are also applicable to its N-demethylated, bromo and iodo analogs. The method utilizes an internal surface reversed-phase column and a mobile phase consisting of 20% acetonitrile in 50 mM phosphate buffer (pH 7.0) and detection at 280 nm. Under these conditions all five dyes are well resolved from one another and from the faster migrating DNA. The effects of organic modifiers, ionic strength and pH of the buffer on the capacity factors of the dyes have been investigated. The method has successfully been applied to detect the photoproducts of methylene violet and its bromo analog in the presence of DNA without removing the biopolymer from the reaction mixture.

Photobiological properties of methylene violet

The interaction of methylene violet (MV) and 4-bromomethylene violet (BrMV) with calf thymus and supercoiled phi X174 phage RF I DNA is reported. Measurements employing UV-visible absorption spectroscopy and equilibrium dialysis give evidence for the formation of complexes by each dye with DNA in the dark. They covalently bind to DNA, and MV nicks DNA, when the nucleic acid/dye mixtures are irradiated with visible light in a deoxygenated environment. Quantum efficiencies for singlet oxygen formation are 0.27 and 0.25 for MV and BrMV, respectively. A higher value (0.49) is observed for 4-iodomethylene violet (IMV).

Regulation of tumor antigen presentation by urocanic acid

Urocanic acid (UCA) accumulates in the epidermis after deamination of histidine. UCA isomerizes from the trans to the cis form upon exposure to environmental UV radiation. Cis-UCA is immunosuppressive in several models. Topically applied cis-UCA was reported to enhance the cutaneous tumor yield in chronically UV-irradiated mice, suggesting involvement of cis-UCA in photocarcinogenesis. Since Langerhans cells (LC) are capable of presenting tumor-associated Ags (TAA) for primary and secondary tumor-immune responses, we examined the effects of trans- and cis-UCA on LC tumor Ag presentation in a model of immunity to the S1509a spindle cell tumor (H-2a). In this system, induction of immunity requires exposure of LC to granulocyte-macrophage CSF. Naive CAF1 (H-2(a/d)) mice were immunized against S1509a by injection with granulocyte-macrophage CSF-exposed and TAA-pulsed epidermal cells (EC), as assessed by growth inhibition of inoculated tumor cells. Incubation of EC in cis-, but not trans-UCA completely inhibited Ag presentation in this system. Neither histamine antagonists nor indomethacin reversed these effects of cis-UCA. The ability of trans- and cis-UCA to modulate EC presentation of TAA for secondary immune responses was also examined. EC were pulsed with TAA in vitro and then injected into hind footpads of tumor-immune mice. After 24 h, footpad swelling was assessed as a measure of delayed-type hypersensitivity. Incubation with cis-, but again not trans-UCA before TAA exposure significantly inhibited elicitation of delayed-type hypersensitivity. These data indicate that cis-UCA may be an important regulator of LC Ag-presenting function in tumor-immune responses, and thus may play a role in photocarcinogenesis.

Regulation of tumor antigen presentation by urocanic acid

Urocanic acid (UCA) accumulates in the epidermis after deamination of histidine. UCA isomerizes from the trans to the cis form upon exposure to environmental UV radiation. Cis-UCA is immunosuppressive in several models. Topically applied cis-UCA was reported to enhance the cutaneous tumor yield in chronically UV-irradiated mice, suggesting involvement of cis-UCA in photocarcinogenesis. Since Langerhans cells (LC) are capable of presenting tumor-associated Ags (TAA) for primary and secondary tumor-immune responses, we examined the effects of trans- and cis-UCA on LC tumor Ag presentation in a model of immunity to the S1509a spindle cell tumor (H-2a). In this system, induction of immunity requires exposure of LC to granulocyte-macrophage CSF. Naive CAF1 (H-2(a/d)) mice were immunized against S1509a by injection with granulocyte-macrophage CSF-exposed and TAA-pulsed epidermal cells (EC), as assessed by growth inhibition of inoculated tumor cells. Incubation of EC in cis-, but not trans-UCA completely inhibited Ag presentation in this system. Neither histamine antagonists nor indomethacin reversed these effects of cis-UCA. The ability of trans- and cis-UCA to modulate EC presentation of TAA for secondary immune responses was also examined. EC were pulsed with TAA in vitro and then injected into hind footpads of tumor-immune mice. After 24 h, footpad swelling was assessed as a measure of delayed-type hypersensitivity. Incubation with cis-, but again not trans-UCA before TAA exposure significantly inhibited elicitation of delayed-type hypersensitivity. These data indicate that cis-UCA may be an important regulator of LC Ag-presenting function in tumor-immune responses, and thus may play a role in photocarcinogenesis.

Chest teleradiology in a teaching hospital emergency practice

OBJECTIVE

New standards for hospital accreditation and health care reimbursement may require that faculty subspecialists be more available after regular working hours to supervise residents in academic radiology departments. We designed a receiver operating characteristic study to determine whether a thoracic radiologist who evaluated computed radiography (CR) images of the chest at a home-based teleradiology workstation could add significant value to a junior resident's interpretations of films within the hospital for acutely ill patients.

SUBJECTS AND METHODS

Using a hybrid cassette, we obtained analog chest films and CR images simultaneously for each of 252 acutely ill patients in the emergency department and in an intensive care unit. Interpretations of the analog films by three first-year residents were analyzed for 11 parameters deemed critical for patient management. Likewise, CR images of the same chest studies were viewed on a home teleradiology workstation by a faculty thoracic radiologist who analyzed the images for these 11 interpretive parameters. All interpretations by radiology residents and by the home-based thoracic radiologist were then compared with the interpretations of a consensus panel consisting of another thoracic radiologist and a full-time emergency department radiologist.

RESULTS

Analysis of the pooled results from the three junior residents as a group failed to show significant differences between their interpretations of chest films and the interpretations of CR images by a thoracic radiologist at a home workstation. However, we observed significant differences for several image interpretation parameters between individual residents and the home-based radiology subspecialist.

CONCLUSION

The data confirm that significant value can be added to the interpretations of chest films by individual junior residents when a home-based thoracic radiologist uses teleradiology to provide expert interpretations. Accordingly, it is reasonable to infer that on-line supervision by faculty subspecialists via teleradiology could be used to complement the scheduled visits that are being made now by individual faculty members of our institution to interpret films periodically with a radiology resident during overnight and weekend periods.

Kidney cancer in Canada: the rapidly increasing incidence of adenocarcinoma in adults and seniors

PURPOSE

To examine kidney cancer incidence and mortality patterns since 1969 in Canada.

METHOD

Linear regression of the log rates was used to estimate secular trends by age group and sex, and age-period-cohort models were fitted to examine changes in kidney cancer and renal adenocarcinoma incidence rates.

RESULTS

A substantial increase in incidence rates was observed among those 35 years and older, with average increases of 2.5% or more annually for both sexes. Age-period-cohort modelling suggested that much of this increase resulted from a period effect. Changes in mortality were much more modest, especially among those aged 0-34, for whom mortality rates actually declined by an average of 4.2% and 5.4% annually for males and females respectively.

CONCLUSIONS

Kidney cancer incidence rates have increased significantly, especially renal adenocarcinoma among adults and seniors. Diagnostic improvements and increasing levels of obesity in the Canadian population may have contributed to these trends.

Analysis of loss of inactive X chromosomes in interphase cells

We have developed a method that allows, for the first time, a specific analysis of the inactive X chromosome (Xi) in interphase cells. By combining immunolabeling of acetylated histone H4 with specific antisera and FISH with an X-chromosome centromere-specific DNA probe, micronucleated whole Xis in human female cells may be identified by their lack of histone H4 acetylation. As one example of the potential applications of this methodology in genetic studies in humans, an artifact-free X-chromosome aneuploidy detection in lymphocytes of women of different ages has been performed. Our results indicate that not only the Xi but also the active X chromosome is preferentially lost during aging, indicating that the high frequency of sex-chromosome aneuploidy in human females cannot be explained solely by a lack of negative selection of Xi aneuploid cells. Further applications of the proposed methodology in genetic studies are discussed.

The passing score in the objective structured clinical examination

The objective structured clinical examination (OSCE) now has an established place in the assessment of the medical undergraduate. While much has been written about the reliability of the OSCE, empirical work on the determination of the passing score which represents competence on the OSCE is rarely encountered. If the OSCE is to play its role in the 'high stakes' testing of clinical competence, it is important that this passing score be set reliably and defensibly. This article illustrates how a two-session modified Angoff standard-setting procedure is used to set the passing score on a 14 station Obstetrics and Gynaecology OSCE used to assess final year students at The Queen's University of Belfast. The Angoff methodology harnesses the professional judgement of expert judges to establish defensible standards. Four university teachers, five non-academic consultants and six junior clinical staff took part in a two-session Angoff standard-setting procedure. In the first session, the judges (individually and in silence) used their professional judgement to estimate the score which a minimally competent final year obstetrics and gynaecology student should achieve on each tested element of the OSCE. In the second session they revised their session 1 judgements in the light of the OSCE scores of real students and the opportunity for structured discussion. The passing score for the OSCE is reported together with the statistical measures which assure its reliability.

Epigenetic control of mammalian centromere protein binding: does DNA methylation have a role?

Chromosome 1 of the inbred mouse strain DBA/2 has a polymorphism associated with the minor satellite DNA at its centromere. The more terminal block of satellite DNA sequences on this chromosome acts as the centromere as shown by the binding of CREST ACA serum, anti-CENP-B and anti-CENP-E polyclonal sera. Demethylation of the minor satellite DNA sequences accomplished by growing cells in the presence of the drug 5-aza-2′-deoxycytidine results in a redistribution of the CENP-B protein. This protein now binds to an enlarged area on the more terminal block and in addition it now binds to the more internal block of minor satellite DNA sequences on chromosome 1. The binding of the CENP-E protein does not appear to be affected by demethylation of the minor satellite sequences. We present a model to explain these observations. This model may also indicate the mechanism by which the CENP-B protein recognises specific sites within the arrays of minor satellite DNA on mouse chromosomes.

On the roles of urocanic acid in photoimmunosuppression: attempted photorepair of urocanic acid-DNA cyclobutane adducts with DNA photolyase

It has been reported that UV-induced immunosuppression can be reversed by photoreactivation or exposure to T4 endonuclease V, two treatments that can repair cyclobutane pyrimidine dimers. These observations, together with the known role of urocanic acid (UA) in UV-induced immune suppression, prompted us to study the ability of DNA photolyase to repair UA-DNA cyclobutane photoadducts in single-stranded calf thymus DNA. We did not detect any release of UA, with a sensitivity implying that photolyase is at least 2900 times less active toward UA-DNA adducts than toward cis-syn thymine-thymine dimers. This indicates that any reversal of photoimmunosuppression by photoreactivation cannot significantly involve cleavage of UA-DNA cyclobutane adducts.

The feasibility of dobutamine stress echocardiography in the emergency department with telemedicine interpretation

Dobutamine stress echocardiography (DSE) was performed on 26 patients admitted for chest pain deemed at low risk for myocardial infarction. Pharmacologic stress in the emergency department on a 24-hour basis was administered by nurses and echocardiographic ultrasonographers with electrocardiograms and echocardiograms being interpreted through telemedicine relay by an off-site cardiologist. Target heart rate was achieved in 84% of patients with an average peak dobutamine dose of 48 microg/kg/min. Echocardiographic transmission to the cardiologist over standard telephone lines took 9 minutes per quad-screen cine-loop display. The entire protocol added 2.2 hours to the emergency room evaluation. The one patient out of 26 who had incipient myocardial infarction was diagnosed by resting echocardiography. The remaining 25 patients were found clinically to have no infarction or ischemia. Of these, 22 out of 25 had normal DSE in the emergency department; three had wall motion abnormalities on peak stress images. Another three patients had other cardiac diseases documented by echocardiography. Evaluation of chest pain on a 24-hour basis with DSE with telemedicine interpretation appears to be a rapid and safe means of screening patients at low risk in the emergency department. Further experience with this modality is needed before all patients should be enrolled or early discharge of patients on the basis of DSE can be advised.

Empowering parents of children with special needs

Partnership and empowerment are very much in vogue. In this paper the authors question whether the rhetoric of partnership matches the reality as experienced by families of children with special needs. Research in this area is reviewed and models of good practice are examined.

[The cellular aspects of the development of synovial joints and articular cartilage]

There have been many reports on the histological development of mammalian diarthrodial or synovial joints. While these are useful for comparative purposes, they tell us little of the cellular basis of joint morphogenesis which must underlie a number of morphogenetic defects. The process of joint morphogenesis is complex and can be subdivided into a number of facets and this report will focus on 2 of them. First, the process of joint cavitation in the chick metatarsophalangeal joint, where we propose that the selective secretion of hyaluronan into the presumptive cavity plays a central role. Secondly, the development of articular cartilage where we have used the South American opossum Monodelphis domestica as a model for mammalian development. Like most marsupials, the young are born at a much earlier developmental stage than eutherian mammals. Using antibodies which detect proliferating chondrocytes and those synthesizing insulin-like growth factors 1 and 2 and insulin-like growth factor 1 binding protein, we report that the majority of growth (as assessed by these indicators) appears appositional.

Photoaquation of cis-dichlorobis-(1,10-phenanthroline)chromium(III) and the photochemical and thermal reactions of this complex with native calf-thymus DNA

The photoaquation of the title compound [cis-Cr(phen)2CL+2] has been studied using high performance liquid chromatography. Both monoaquo [cis-Cr(phen)2Cl(OH2)2+2] and diaquo [cis-Cr(phen)2(OH2)3+2] products are formed, and the quantum efficiency for the loss of starting material in Tris buffer (pH 7) under argon and oxygen is 0.010 +/- 0.001 and 0.0026 +/- 0.0002, respectively. The presence of deoxyguanosine (dG) increases the rate of loss, as much as twofold under argon, but only the rate of diaquo product formation is enhanced by the nucleoside. The dG effect is attributed to reductive quenching of the cis-Cr(phen)2Cl+2 excited state by the base. Equilibrium dialysis studies indicate that both cis-Cr(phen)2Cl+2 and cis-Cr(phen)2(OH2)3+2 minimally associate with calf-thymus DNA. However, photolyses of cis-Cr(phen)2Cl+2 with the nucleic acid yield a mixture of unidentified covalent adducts. The diaquo complex also forms covalent adducts with DNA in the absence of light. Photolyses of the cis-Cr(phen)2Cl+2 with polyribonucleotides indicate a clear preference for covalent binding to the purines.