Kelp detritus: Unutilized productivity or an unacknowledged trophic resource?

Kelp beds are one of the most productive marine systems and, while little of this production is directly consumed, there is growing evidence that kelp detritus is an essential food source for many detrital and suspension feeders, and forms an important component of offshore sedimentary carbon pools. However, the extent of the contribution of kelp detritus to the nutrition of coastal fauna is not well resolved. In this study, we compare the contribution of phytoplankton, kelp detritus, and waste from fish cages to the diet of a sentinel suspension feeder, the blue mussel (Mytilus edulis) using stable isotopes. We found a significant depletion in both 13C and 15N in kelp tissue with age (distance from stipe to the deteriorating distal end of the kelp frond) which may have biased dietary estimates in previous studies which have applied isotopic source values derived from fresh kelp. Our mixing models indicate that macroalgal detritus formed 59% of the diet of the mussels in Berehaven, Bantry Bay, Ireland. We support the isotopic mixing model results by modelling the relative production of phytoplankton, kelp, and salmon farm waste, and found the supply of C and N from kelp and phytoplankton far exceeded the requirements of the mussels with much less coming from the nearby fish cages. Monthly chlorophyll measurements indicated there was only sufficient phytoplankton density to support mussel growth during the spring and autumn, explaining our observation of patterns in the relative importance of utilization of kelp detritus. Where there is pressure to harvest kelp beds, this study highlights the supporting ecosystem service they provide as an important dietary source in coastal food webs and emphasises the need for appropriate management measures for this resource.

Impact of peer support on inpatient and outpatient payments among people with Type 2 diabetes: a prospective cohort study

AIM

To investigate the impact of a low-cost diabetes peer-support intervention, aimed at reducing inpatient and outpatient care utilization and healthcare payments, by conducting a cohort study that followed up a randomized controlled trial.

METHODS

A total of 1121 adults with Type 2 diabetes were recruited through general practices in Cambridgeshire and Hertfordshire, UK, and were followed up for 3.25 financial years after 8-12 months of one-to-one, group or combined diabetes peer support and usual care. Use of, and payments for inpatient and outpatient services were fully recorded in the follow-up. Adjusted mean inpatient and outpatient payments per person were estimated using a two-part model after adjusting for baseline characteristics.

RESULTS

The mean age of the recruited adults was 65.6±11.4 years, 60.4% were male, and 16.8% were insulin-treated. Compared with the control group, less healthcare utilization (especially non-elective inpatient care and outpatient consultations) was observed in each of the intervention groups, particularly the combined intervention group. Over the course of 3.25 financial years, significant reductions of 41% (£909.20 per head) were observed for overall inpatient payments (P<0.0001), 51% (£514.67 per head) for non-elective inpatient payments (P=0.005) in the combined intervention group, and 34% (£413.30 per head) and 32% (£388.99 per head) for elective inpatient payments in the one-to-one (P=0.029) and combined intervention (P=0.048) groups, respectively.

CONCLUSIONS

Type 2 diabetes peer support, whether delivered using a one-to-one, group or combined approach was associated with reduced inpatient care utilization (particularly non-elective admissions) and payments over 3.25 years.

Mitigation assessment of vegetated drainage ditches for collecting irrigation runoff in California

Widespread contamination of California water bodies by the organophosphate insecticides diazinon and chlorpyrifos is well documented. While their usage has decreased over the last few years, a concomitant increase in pyrethroid usage (e.g., permethrin) (replacement insecticides) has occurred. Vegetated agricultural drainage ditches (VADD) have been proposed as a potential economical and environmentally efficient management practice to mitigate the effects of pesticides in irrigation and storm runoff. Three ditches were constructed in Yolo County, California for a field trial. A U-shaped vegetated ditch, a V-shaped vegetated ditch, and a V-shaped unvegetated ditch were each amended for 8 h with a mixture of diazinon, permethrin, and suspended sediment simulating an irrigation runoff event. Water, sediment, and plant samples were collected spatially and temporally and analyzed for diazinon and permethrin concentrations. Pesticide half-lives were similar between ditches and pesticides, ranging from 2.4 to 6.4 h. Differences in half-distances (distance required to reduce initial pesticide concentration by 50%) among pesticides and ditches were present, indicating importance of vegetation in mitigation. Cis-permethrin half-distances in V ditches ranged from 22 m (V-vegetated) to 50 m (V-unvegetated). Half-distances for trans-permethrin were similar, ranging from 21 m (V-vegetated) to 55 m (V-unvegetated). Diazinon half-distances demonstrated the greatest differences (55 m for V-vegetated and 158 m for V-unvegetated). Such economical and environmentally successful management practices will offer farmers, ranchers, and landowners a viable alternative to more conventional (and sometimes expensive) practices.

Oxygen free radical damage to DNA. Translesion synthesis by human DNA polymerase eta and resistance to exonuclease action at cyclopurine deoxynucleoside residues

Cyclopurine deoxynucleosides are common DNA lesions generated by exposure to reactive oxygen species under hypoxic conditions. The S and R diastereoisomers of cyclodeoxyadenosine on DNA were investigated separately for their ability to block 3' to 5' exonucleases. The mammalian DNA-editing enzyme DNase III (TREX1) was blocked by both diastereoisomers, whereas only the S diastereoisomer was highly efficient in preventing digestion by the exonuclease function of T4 DNA polymerase. Digestion in both cases was frequently blocked one residue before the modified base. Oligodeoxyribonucleotides containing a cyclodeoxyadenosine residue were further employed as templates for synthesis by human DNA polymerase eta (pol eta). pol eta could catalyze translesion synthesis on the R diastereoisomer of cyclodeoxyadenosine. On the S diastereoisomer, pol eta could catalyze the incorporation of one nucleotide opposite the lesion but could not continue elongation. Although pol eta preferentially incorporated dAMP opposite the R diastereoisomer, elongation continued only when dTMP was incorporated, suggesting bypass of this lesion by pol eta with reasonable fidelity. With the S diastereoisomer, pol eta mainly incorporated dAMP or dTMP opposite the lesion but could not elongate even after incorporating a correct nucleotide. These data suggest that the S diastereoisomer may be a more cytotoxic DNA lesion than the R diastereoisomer.

Uracil-DNA glycosylase (UNG)-deficient mice reveal a primary role of the enzyme during DNA replication

Gene-targeted knockout mice have been generated lacking the major uracil-DNA glycosylase, UNG. In contrast to ung- mutants of bacteria and yeast, such mice do not exhibit a greatly increased spontaneous mutation frequency. However, there is only slow removal of uracil from misincorporated dUMP in isolated ung-/- nuclei and an elevated steady-state level of uracil in DNA in dividing ung-/- cells. A backup uracil-excising activity in tissue extracts from ung null mice, with properties indistinguishable from the mammalian SMUG1 DNA glycosylase, may account for the repair of premutagenic U:G mispairs resulting from cytosine deamination in vivo. The nuclear UNG protein has apparently evolved a specialized role in mammalian cells counteracting U:A base pairs formed by use of dUTP during DNA synthesis.

Molecular characterization of a human DNA kinase

Human polydeoxyribonucleotide kinase is an enzyme that has the capacity to phosphorylate DNA at 5'-hydroxyl termini and dephosphorylate 3'-phosphate termini and, therefore, can be considered a putative DNA repair enzyme. The enzyme was purified from HeLa cells. Amino acid sequence was obtained for several tryptic fragments by mass spectrometry. The sequences were matched through the dbEST data base with an incomplete human cDNA clone, which was used as a probe to retrieve the 5'-end of the cDNA sequence from a separate cDNA library. The complete cDNA, which codes for a 521-amino acid protein (57.1 kDa), was expressed in Escherichia coli, and the recombinant protein was shown to possess the kinase and phosphatase activities. Comparison with other sequenced proteins identified a P-loop motif, indicative of an ATP-binding domain, and a second motif associated with several different phosphatases. There is reasonable sequence similarity to putative open reading frames in the genomes of Caenorhabditis elegans and Schizosaccharomyces pombe, but similarity to bacteriophage T4 polynucleotide kinase is limited to the kinase and phosphatase domains noted above. Northern hybridization revealed a major transcript of approximately 2.3 kilobases and a minor transcript of approximately 7 kilobases. Pancreas, heart, and kidney appear to have higher levels of mRNA than brain, lung, or liver. Confocal microscopy of human A549 cells indicated that the kinase resides predominantly in the nucleus. The gene encoding the enzyme was mapped to chromosome band 19q13.4.

Microcystic adnexal carcinoma: collaborative series review and update

BACKGROUND

Microcystic adnexal carcinoma (MAC) is a malignant appendageal tumor first described in 1982. It can be clinically and histologically confused with other malignant and benign cutaneous neoplasms, leading to inadequate initial treatment. This neoplasm is locally aggressive and deeply infiltrating, characterized by high morbidity and frequent recurrence. Mohs micrographic surgery has been used to conserve tissue and improve the likelihood for cure.

OBJECTIVE

We report our experience using Mohs micrographic surgery for the treatment of MAC and compare with earlier reports in the literature. In addition, we review the epidemiology, clinical and histologic characteristics, and optimal treatment of this rare neoplasm. We also describe a 15-year-old white male patient with MAC on the scalp occurring only 7 years after radiation exposure.

METHODS

The medical records of 11 patients with MAC who were treated by Mohs micrographic surgery were reviewed at both departments, and follow-up data were obtained.

RESULTS

In all patients treated with Mohs micrographic surgery, there were no recurrences after a mean follow-up of 5 years.

CONCLUSION

Mohs technique enables the detection of clinically unrecognizable tumor spread and perineural invasion often encountered with MAC. Aggressive initial treatment by microscopically controlled excision appears to offer the greatest likelihood of cure for this neoplasm, while providing conservation of normal tissue. In addition, we describe the second youngest patient with MAC and readdress the issue of previous radiotherapy as an important predisposing factor.

A human DNA editing enzyme homologous to the Escherichia coli DnaQ/MutD protein

Mammalian DNA polymerases alpha and beta lack 3' exonuclease activity and are unable to edit errors after DNA synthesis. However, editing exonucleases can be functions of separate polypeptides. We isolated a widely distributed DNA-specific 3' exonuclease from rabbit liver nuclei, sequenced tryptic peptides by mass spectrometry, and identified the corresponding human open reading frame. The protein expressed from the cloned human sequence exhibits 3' exonuclease activity. The human clone shares sequence homology with the editing function of the Escherichia coli DNA polymerase III holoenzyme, i.e., the DnaQ/MutD protein, and weakly with the editing 3' exonuclease domain of eukaryotic DNA polymerase epsilon. The gene maps to human chromosome 3p21.2-21.3. In a reconstituted human DNA repair system containing DNA polymerase beta and DNA ligase III-XRCC1, accurate rejoining of a 3' mismatched base residue at a single-strand break is dependent on addition of the exonuclease.

Thoracic chordoma mimicking a neurogenic tumour

A case of chordoma arising in the thoracic spine of a 20-year-old man is presented. Plain film and magnetic resonance imaging findings are included. The case is unusual in that the neoplasm presented as dumb-bell-shaped extradural mass, traversing and expanding a thoracic neural foramen and thereby mimicking a neurogenic tumour.

Protein farnesyltransferase and adenosine receptors

Many exciting advances in the treatment of cancer were presented at the symposium entitled 'Protein prenylation' which was chaired by Professor Richard A Gibbs (Wayne State University, Detroit, MI, USA). Prenylation, or the covalent attachment of isoprenoid lipids, is now recognized as an important component in the post-translational localization and functionalization of many cellular proteins. The majority of prenylated proteins are modified by one of two specific enzymes: protein farnesyl-transferase (FTase) and geranylgerany-ltransferase type I (GGTase-I). The finding that farnesylation of oncogenic forms of Ras proteins is required for expression of their transforming activity has led to FTase becoming an important target for anticancer drug design.

Anticoagulation strategies

A number of individual presentations at this meeting dealt with the burgeoning field of anticoagulation strategies, and the fourth day (Wednesday) provided one of the most interesting symposia of the meeting, entitled 'Anticoagulation Strategies: Thrombin and Factor Xa Inhibition'. Chair RR Wexler (DuPont Merck, PA, USA) pointed out that classical anticoagulants, such as warfarin, suffer from poor oral bioavailability, lack of selectivity and short plasma half-life. In addition, there are safety issues, for instance, an increased risk of bleeding, and a large peak-to-trough ratio. Hirudin is a recently-approved thrombin inhibitor, but is suitable for parenteral administration only. New therapies are needed and many advances in this field were presented in the ensuing sessions.

Infrastructure for reaching disadvantaged consumers: telecommunications in rural and remote nursing in Australia

Both consumers and health service providers need access to up-to-date information, including patient and practice guidelines, that allows them to make decisions in partnership about individual and public health in line with the primary health care model of health service delivery. Only then is it possible for patient preferences to be considered while the health of the general population is improved. The Commonwealth Government of Australia has allocated $250 million over five years, starting July 1, 1997, to support activities and projects designed to meet a range of telecommunication needs in regional, rural, and remote Australia. This paper defines rural and remote communities, then reviews rural and remote health services, information, and telecommunication technology infrastructures and their use in Australia to establish the current state of access to information tools by rural and remote communities and rural health workers in Australia today. It is argued that a suitable telecommunication infrastructure is needed to reach disadvantaged persons in extremely remote areas and that intersectoral support is essential to build this infrastructure. In addition, education will make its utilization possible.

Activation of the transcription factor Gli1 and the Sonic hedgehog signalling pathway in skin tumours

Sporadic basal cell carcinoma (BCC) is the most common type of malignant cancer in fair-skinned adults. Familial BCCs and a fraction of sporadic BCCs have lost the function of Patched (Ptc), a Sonic hedgehog (Shh) receptor that acts negatively on this signalling pathway. Overexpression of Shh can induce BCCs in mice. Here we show that ectopic expression of the zinc-finger transcription factor Gli1 in the embryonic frog epidermis results in the development of tumours that express endogenous Gli1. We also show that Shh and the Gli genes are normally expressed in hair follicles, and that human sporadic BCCs consistently express Gli1 but not Shh or Gli3. Because Gli1, but not Gli3, acts as a target and mediator of Shh signalling, our results suggest that expression of Gli1 in basal cells induces BCC formation. Moreover, loss of Ptc or overexpression of Shh cannot be the sole causes of Gli1 induction and sporadic BCC formation, as they do not occur consistently. Thus any mutations leading to the expression of Gli1 in basal cells are predicted to induce BCC formation.

P53 oncoprotein expression and gene mutations in some keratoacanthomas

OBJECTIVE

To analyze the relationship of p53 oncoprotein overexpression in most keratoacanthomas (KAs) with gene mutations.

DESIGN

Expression of p53 oncoprotein in immunohistochemical staining and its correlation to gene mutations in DNA extracted from KAs and tested in single-strand conformational polymorphism (SSCP) analysis and direct sequencing.

SETTING

A micrographic surgery unit and a dermatopathology unit at a university medical center.

PATIENTS

Sixteen formalin-fixed, paraffin-embedded skin biopsy specimens were retrieved from dermatopathology archives. Biopsies were performed to establish the diagnosis of KA before surgical treatment.

MAIN OUTCOME MEASURES

Intensity of staining in immunohistochemical testing for p53 oncoprotein expression and sequencing of gene mutations.

RESULTS

Immunohistochemical staining of 16 KA specimens detected p53 oncoprotein in 15 (94%), distributed as strong in 4 (25%), moderate in 2 (12%) mild in 9 (56%), and negative in 1 (6%), compared with control specimens. Specimens were screened by SSCP for mutations in the p53 gene, and 1 specimen showed a potential mutation in exon 7. Direct sequencing of the samples revealed 2 point mutations. One specimen showed a change of G:A for A:G in codon 146 of exon 5, predicting an amino acid substitution of tryptophan for a stop codon. Another specimen revealed a change of T:A for A:T in codon 234 of exon 7, predicting an amino acid substitution of tyrosine for asparagine.

CONCLUSIONS

Ninety-four percent of KA specimens evaluated had detectable p53 oncoprotein. This protein was associated with a point mutation in the p53 gene in 2 of 16 KAs evaluated. In a small fraction of KAs, overexpression of p53 oncoprotein may be associated with point mutations in the p53 gene.

Regulation of DNA metabolic enzymes upon induction of preB cell development and V(D)J recombination: up-regulation of DNA polymerase delta

Withdrawal of interleukin-7 from cultured murine preB lymphocytes induces cell differentiation including V(D)J immunoglobulin gene rearrangements and cell cycle arrest. Advanced steps of the V(D)J recombination reaction involve processing of coding ends by several largely unidentified DNA metabolic enzymes. We have analyzed expression and activity of DNA polymerases alpha, beta, delta and epsilon, proliferating cell nuclear antigen (PCNA), topoisomerases I and II, terminal deoxynucleotidyl transferase (TdT) and DNA ligases I, III and IV upon induction of preB cell differentiation. Despite the immediate arrest of cell proliferation, DNA polymerase delta protein levels remained unchanged for approximately 2 days and its activity was up-regulated several-fold, while PCNA was continuously present. Activity of DNA polymerases alpha,beta and epsilon decreased. Expression and activity of DNA ligase I were drastically reduced, while those of DNA ligases III and IV remained virtually constant. No changes in DNA topoisomerases I or II expression and activity occurred and TdT expression was moderately increased early after induction. Our results render DNA polymerase delta a likely candidate acting in DNA synthesis related to V(D)J recombination in lymphocytes.

DNA ligase IV from HeLa cell nuclei

A human cDNA encoding a previously unrecognized DNA ligase IV has been identified (Wei, Y.-F., Robins, P., Carter, K., Caldecott, K., Pappin, D. J. C., Yu, G.-L., Wang, R.-P., Shell, B. K., Nash, R. A., Schär, P., Barnes, D. E., Haseltine, W. A., and Lindahl, T. (1995) Mol. Cell. Biol. 15, 3206-3216). Antibodies have been raised against predicted peptide sequences of DNA ligase IV and used to identify the enzyme during purification from HeLa cell nuclei. The 96-kDa DNA ligase IV and the 103-kDa DNA ligase III co-migrate during SDS-polyacrylamide gel electrophoresis and have similar column fractionation properties, which complicates the distinction between the two enzymes, but they have been separated by Mono S liquid chromatography. During initial size fractionation by gel chromatography in 1 M NaCl, DNA ligase IV elutes in the same position as the DNA ligase III-XRCC1 protein complex, indicating that DNA ligase IV is also bound to another protein or occurs as a dimer. DNA ligase IV has been purified free from other DNA ligases, and its enzymatic properties have been examined. The purified protein effectively joins single-strand breaks in a double-stranded polydeoxynucleotide in an ATP-dependent reaction. The substrate specificity of DNA ligase IV differs from those of the other two cloned human DNA ligases, I and III, with regard to their ability to join the hybrid substrates oligo(dT).poly(rA) and oligo(rA).poly(dT). DNA ligase IV occurs in part as an enzyme-adenylate complex in HeLa cell nuclear extracts.

Violence and remote area nursing

The Federal government and others have accepted that violence is a problem in rural and remote communities across Australia. The issue of personal safety for Remote Area Nurses (RANs) living in remote areas has been mentioned in a number of State and Regional reports. However, to the knowledge of this research group, no systematic attempt to gather data on the incidence of violence experienced by RANs and other remote health workers has occurred. This study aims to redress the lack of data on the experience and description of violence against remote area nurses. Results indicate that remote area nurses are living with frequent threats to their personal safety while on duty, on call and off duty, and that violent incidents are often handled badly by employers, the community and remote area nurses themselves. Twenty-four-hour call is an employment requirement for 82% of respondents. Those required to be on call 24 hours experience episodes of violence more frequently. Despite nearly all of the respondents experiencing episodes of violence within the 12 months prior to the study, there was a tendency for remote area nurses, except in the case of physical violence, to perceive both the frequency and the severity of their experiences with violence as low and not personally directed.

Molecular cloning and expression of human cDNAs encoding a novel DNA ligase IV and DNA ligase III, an enzyme active in DNA repair and recombination

Three distinct DNA ligases, I to III, have been found previously in mammalian cells, but a cloned cDNA has been identified only for DNA ligase I, an essential enzyme active in DNA replication. A short peptide sequence conserved close to the C terminus of all known eukaryotic DNA ligases was used to search for additional homologous sequences in human cDNA libraries. Two different incomplete cDNA clones that showed partial homology to the conserved peptide were identified. Full-length cDNAs were obtained and expressed by in vitro transcription and translation. The 103-kDa product of one cDNA clone formed a characteristic complex with the XRCC1 DNA repair protein and was identical with the previously described DNA ligase III. DNA ligase III appears closely related to the smaller DNA ligase II. The 96-kDa in vitro translation product of the second cDNA clone was also shown to be an ATP-dependent DNA ligase. A fourth DNA ligase (DNA ligase IV) has been purified from human cells and shown to be identical to the 96-kDa DNA ligase by unique agreement between mass spectrometry data on tryptic peptides from the purified enzyme and the predicted open reading frame of the cloned cDNA. The amino acid sequences of DNA ligases III and IV share a related active-site motif and several short regions of homology with DNA ligase I, other DNA ligases, and RNA capping enzymes. DNA ligases III and IV are encoded by distinct genes located on human chromosomes 17q11.2-12 and 13q33-34, respectively.

Structural and functional homology between mammalian DNase IV and the 5'-nuclease domain of Escherichia coli DNA polymerase I

A nuclear 42-kDa 5'-->3'-exonuclease, DNase IV, was found previously in animal tissues. The enzyme has been purified from HeLa cells and shown to possess two catalytic properties characteristic of the 5'-nuclease function of Escherichia coli DNA polymerase I,-DNase IV removes single-stranded 5' regions from splayed-arm DNA structures by endonucleolytic incision at the bifurcation point and possesses RNase H activity. Determination of the molecular masses of tryptic and V8 peptides of DNase IV by mass spectrometry identified the enzyme as the human homolog of the Schizosaccharomyces pombe Rad2 protein. The protein sequence retains conserved residues and shows significant homology to the sequences of the 5'-nuclease domain of E. coli DNA polymerase I and related microbial enzymes.

Different active sites of mammalian DNA ligases I and II

Bovine DNA ligases I and II were adenylylated in the presence of [alpha-32P]ATP and digested with limiting amounts of trypsin or V8 protease. The generation of radioactive peptides of decreasing size was monitored by polyacrylamide gel electrophoresis and autoradiography. Active site peptides obtained by complete proteolytic digestions with trypsin, V8, or Lys-C protease were also compared. The partial digestion products of DNA ligases I and II were entirely different, with no indication of extensive sequence homology. Furthermore, the sequence of the active site region of DNA ligase I is clearly different from that of DNA ligase II. Similar analysis of a third chromatographically distinct mammalian DNA ligase indicated that it is different from DNA ligase I but related to DNA ligase II.

Complementation of DNA repair in xeroderma pigmentosum group A cell extracts by a protein with affinity for damaged DNA

Complementation group A of xeroderma pigmentosum (XP) represents one of the most prevalent and serious forms of this cancer-prone disorder. Because of a marked defect in DNA excision repair, cells from individuals with XP-A are hypersensitive to the toxic and mutagenic effects of ultraviolet light and many chemical agents. We report here the isolation of the XP-A DNA repair protein by complementation of cell extracts from a repair-defective human XP-A cell line. XP-A protein purified from calf thymus migrates on denaturing gel electrophoresis as a doublet of 40 and 42 kilodaltons. The XP-A protein binds preferentially to ultraviolet light-irradiated DNA, with a preference for damaged over nondamaged nucleotides of approximately 10(3). This strongly suggests that the XP-A protein plays a direct role in the recognition of and incision at lesions in DNA. We further show that this protein corresponds to the product encoded by a recently isolated gene that can restore excision repair to XP-A cells. Thus, excision repair of plasmid DNA by cell extracts sufficiently resembles genomic repair in cells to reveal accurately the repair defect in an inherited disease. The general approach described here can be extended to the identification and isolation of other human DNA repair proteins.

[Moh's micrographic surgery: first experience in Israel]

Moh's micrographic surgery is a method by which cancer of the skin may be excised under complete microscopic control. It consistently offers the highest cure rate in the treatment of malignancy of the skin, while the least amount of uninvolved tissue is sacrificed. This, the first center for Moh's micrographic surgery in Israel, started functioning in 1989. The first 50 patients included 33 women (average age 50.7 years) and 17 men (average age 60.6 years) suffering from basal cell carcinoma of the face. 56% of the patients were referred for Moh's surgery after failure of other primary treatments, and the rest were referred due to the problematic location of the lesion or its size. 13 patients (28%) were referred after previous treatment with solcoderm (Mardi's method). In these patients the lesions were especially deep and aggressive.

Prolongation of anesthesia in Mohs micrographic surgery with 2% lidocaine jelly

The authors performed a prospective, randomized trial of topical 2% lidocaine jelly in patients with basal cell or squamous cell carcinomas to test the effectiveness of the jelly in prolonging the time of anesthesia between the multiple stages of Mohs micrographic surgery. There was a 48% increase in the duration of anesthesia achieved by the use of 2% lidocaine jelly in patients given 1% lidocaine with epinephrine. In patients given 1% lidocaine without epinephrine, there was approximately a 2.5 times greater duration of anesthesia achieved by using topical 2% lidocaine jelly.

Effect of exogenous DNA fragments on human cell extract-mediated DNA repair synthesis

Extracts from HeLa cells were used to study the susceptibility of repair synthesis in UV-irradiated plasmid DNA to inhibition by exogenously added nucleic acid. Purified DNA restriction fragments have little inhibitory effect on repair synthesis. However, activated calf thymus DNA fragments, genomic DNA fragments in cell extracts, and sonicated plasmid DNA all inhibited repair synthesis. Degraded DNA fragments arising from E. coli during bacterial plasmid purification were found to be particularly inhibitory. tRNA is not a potent inhibitor of in vitro repair synthesis. In order to observe efficient DNA repair synthesis mediated by human cell extracts, it is essential to prepare highly purified closed circular plasmid DNA, and we describe a reliable method for doing so.

Use of in vivo and in vitro assays for the characterization of mammalian excision repair and isolation of repair proteins

Elucidation of the molecular mechanism of mammalian nucleotide excision repair requires the availability of purified proteins, DNA substrates with defined lesions and suitable repair assays. Repair assays introduced in recent years vary from testing individual steps and successions of steps in vitro to systems that closely reflect the entire process in vivo. In the first part of this review, an in vivo microinjection system is discussed. The second part of the article reviews an in vitro system for study of repair synthesis promoted by cell extracts. Both systems can be utilized as assays during the purification of protein factors that complement repair-defective xeroderma pigmentosum cells. The effect of purified repair proteins from other organisms on mammalian repair is also considered.

DNA repair replication by soluble extracts from human lymphoid cell lines

A system is described in which extracts from human cells can perform repair replication on DNA damaged by ultraviolet light or chemical carcinogens. Whole cell extracts from lymphoid cell lines are incubated with damaged plasmid DNA circles at 30 degrees C in the presence of ATP and the four deoxynucleoside triphosphates. Repair synthesis is monitored by the incorporation of alpha-32P-dATP into closed circular plasmid molecules. Analysis of the time course of the reaction suggests that the slowest step in repair is incision, rather than polymerization or ligation. The size of repair patches inserted into ultraviolet-irradiated DNA during a reaction was estimated by substitution of thymidine triphosphate with 5-bromodeoxyuridine triphosphate and sedimentation in alkaline cesium chloride gradients. Patches with heterogeneous sizes of less than 120 bases were observed.

Complementation of the xeroderma pigmentosum DNA repair defect in cell-free extracts

Soluble extracts from human lymphoid cell lines that perform repair synthesis on covalently closed circular DNA containing pyrimidine dimers or psoralen adducts are described. Short patches of nucleotides are introduced by excision repair of damaged DNA in an ATP-dependent reaction. Extracts from xeroderma pigmentosum cell lines fail to act on damaged circular DNA, but are proficient in repair synthesis of ultraviolet-irradiated DNA containing incisions generated by Micrococcus luteus pyrimidine dimer-DNA glycosylase. Repair is defective in extracts from all xeroderma pigmentosum cell lines investigated, representing the genetic complementation groups A, B, C, D, H, and V. Mixing of cell extracts of group A and C origin leads to reconstitution of the DNA repair activity.

Activity of a new nitrosourea (TCNU) in human lung cancer xenografts

The activity of a new nitrosourea (TCNU) based on the endogenous amino acid taurine was assessed in three human lung cancer xenografts growing in immunodeficient mice. Moderate activity (specific growth delays of 0.63 and 1.13 compared with controls) was seen in two non-small cell tumours after a single oral administration of 20 mg-1kg. This dose was curative in a small cell xenograft. By using high performance liquid chromatography it was possible to detect parent drug in the tumours as well as the plasma and tissues after oral administration of TCNU. Drug sensitivity was correlated inversely with the amount of the DNA repair enzyme 0(6)-methylguanine-DNA methyltransferase assayed from extracts of the tumour cells but not with the levels of parent drug within the tumour. This compound appears to have unique pharmacokinetic properties compared with other chloroethylnitrosoureas.

Functional domains and methyl acceptor sites of the Escherichia coli ada protein

The ada gene of Escherichia coli encodes a 39-kDa protein which serves both as a transcriptional activator of the adaptive response to alkylating agents and as a DNA repair enzyme demethylating O6-methyl-guanine and phosphotriester residues. Here, the isolated Ada protein was found to be readily cleaved into two fragments of similar size by treatment with trypsin, chymotrypsin, subtilisin, or V8 protease. The fragments retained their respective methyltransferase activities. The Ada protein is, therefore, comprised of two stable active domains united by a central hinge region of about 10 amino acids. Post-translational modification of the Ada protein by methylation of a specific cysteine residue in the NH2-terminal domain is known to convert it to an efficient transcriptional activator. This residue has now been identified as Cys-69.