Allelic loss on chromosome 11p is a less frequent event in bilateral than in unilateral Wilms' tumours

Analyses to detect loss of heterozygosity (LOH) were performed at 11 polymorphic loci on chromosome 11 and, using a polymorphic CA repeat sequence in the WT1 gene, on a series of 39 tumours from 28 unilateral and 10 tumours from 6 bilateral Wilms' tumour (WT) patients. LOH was seen in 13 out of 35 patients including 12 out of 29 unilateral tumours, but only one of 10 bilateral tumours. This suggests that bilateral WT represents a subgroup of WT in which tumour initiating events less frequently involve LOH on chromosome 11 and that either epigenetic events, point mutations or another non-chromosome 11p locus are important in bilateral tumours. The observation of LOH in one WT but not another WT in a bilateral WT patient provides evidence that these tumours arising in the same patient are not monoclonal proliferations and most likely arise via different molecular pathways.

Regulation of gene expression by insulin and tumor necrosis factor alpha in 3T3-L1 cells. Modulation of the transcription of genes encoding acyl-CoA synthetase and stearoyl-CoA desaturase-1

Insulin and tumor necrosis factor alpha (TNF alpha) produce potent and opposing physiological signals in adipocytes. However, genes that are co-regulated by the hormone and cytokine during and after adipocyte differentiation have not been characterized. Using 3T3-L1 cells, we have studied the regulation of the expression of genes encoding acyl-CoA synthetase (ACS), and stearoyl CoA desaturase-1 (SCD-1), two enzymes that play key roles in the metabolism of long chain fatty acids. Insulin is required for triggering the transcriptional activation of the ACS and SCD-1 genes at an early stage in adipocyte differentiation. In mature adipocytes insulin elicits a 4-fold increase in the rates of transcription of the two genes. However, when 3T3-L1 adipocytes are treated with TNF alpha the cytokine causes a 75-90% decrease in the levels of ACS and SCD-1 mRNAs. The decline in mRNA content is associated with similar decrements in the rates of transcription of the ACS and SCD-1 genes. Thus, the ACS and SCD-1 genes are subject to stimulation and counter-regulation (at the transcriptional level) by insulin and TNF alpha, respectively. The opposing effects of insulin and TNF alpha are observed in developing and terminally differentiated adipocytes. Unlike the ACS and SCD-1 genes, the genes that encode the lipogenic enzymes lipoprotein lipase and malic enzyme are not subject to counter-regulation by insulin and TNF alpha at the transcriptional level in 3T3-L1 adipocytes. These observations on the control of ACS and SCD-1 expression suggest possible mechanisms by which adipocytes can markedly adjust their capacity for long chain fatty acid metabolism in response to external stimuli.

Comparison of in vitro activity of epipodophyllotoxins with other chemotherapeutic agents in human medulloblastomas

Surgical specimens from 15 medulloblastoma patients were used to establish early passage cultures. In vitro sensitivity to a battery of cytotoxic agents, including some in current medulloblastoma treatment protocols, was measured. Drug sensitivity was assessed at clinically relevant drug concentrations using the 3H-thymidine uptake method. Tumours were predicted to be sensitive if greater than 37% were killed by exposure to drugs at clinically achievable levels. A poor response to vincristine (Vcr), cis-platin (CDDP), hydroxyurea (HU) or diaziquone (AZQ) (no responders), and cytosine arabinoside (AraC) (1/12), was seen. Nine of ten tumours tested were sensitive to mafosfamide (Mfs); seven out of 12 were sensitive to carmustine (BCNU), 12 of 13 to teniposide (VM-26) and seven of 13 to etoposide (VP16-213). VM-26 was the best of the agents tested with most tumours responding to very low concentrations of drug, suggesting that the role of epipodophyllotoxins in treatment of brain tumours be further investigated. Despite the marked sensitivity of the medulloblastomas to the epipodophyllotoxins, three early passage cultures were much more resistant to these drugs than the average for the group. The basis of this resistance was investigated. Deficient cellular uptake of drug was excluded as a cause of resistance. One resistant early passage culture displayed low cellular activity of topoisomerase II and decreased levels of drug induced enzyme-DNA strand break activity. This was not the case for the other resistant early passage cultures: the basis of resistance in these cells does not appear to be due to any previously reported mechanism.

Deoxyguanosine enhances the cytotoxicity of the topoisomerase I inhibitor camptothecin by reducing the repair of double-strand breaks induced in replicating DNA

Deoxyguanosine (dG) enhances the S phase cytotoxicity of camptothecin (CPT), a topoisomerase I (topo I) inhibitor, but by contrast does not affect the toxicity of VM26, a topoisomerase II inhibitor. The 80% survival of S phase human fibroblasts after a 60 min exposure to 0.2 microM CPT is reduced by half in the presence of 25 microM dG. G1 cells are resistant to CPT toxicity, though the levels of the single-strand DNA breaks induced by the drug are similar in G1 and S phase cells. Higher concentrations of dG retard the recovery of RNA and DNA synthesis and inhibit recovery from the S-G2 cycle block after CPT removal. At 100 microM dG the number of CPT-induced protein-linked single-strand DNA breaks is almost doubled, suggestive of a direct effect of dG on the cellular activity of topo I. In the presence or absence of dG, single-strand breaks disappear within minutes of the removal of CPT. We found that the inhibition of topo I by CPT induces the formation of double as well as single-strand breaks in the chromosomal DNA. Previously we have shown, using a pulse-field gel electrophoresis technique, that the double-strand breaks (DSBs) are generated predominantly at sites of replication and not in the bulk DNA. A number of these DSBs are long-lived. The present study shows that dG affects the repair of these DSBs in a dose-dependent manner, and that a higher proportion of the initial lesions induced in nascent DNA remain 24 h after removal of CPT. We suggest that the long-lived double-strand breaks, formed in replicating DNA at the time of CPT exposure, are the lethal drug-induced lesions, which explains both the selective cytotoxicity of CPT towards S phase cells and the enhancement of CPT cytotoxicity by dG.

Pentraxin binding to isolated rat liver nuclei

The interaction of human C-reactive protein (CRP) and serum amyloid P-component (SAP) with isolated rat liver nuclei was studied to identify nuclear ligands for each pentraxin using the iodinatable heterobifunctional thiol-cleavable cross-linking reagent sulphosuccinimidyl-2-(p-azidosalicylamido)-1,3'-dithiopropio nate (SASD). Nuclei (100 micrograms of DNA) bound 21 pmol of 125I-labelled CRP Ca(2+)-dependently at saturation with half-saturation occurring at 200 pmol of 125I-CRP. By contrast, only 2.7 pmol of 125I-labelled SAP was bound at saturation, with half-saturation at 50 pmol. The binding of pentraxins to nuclei is, in addition to putative chromatin binding, due to nuclear-envelope binding, where 3.2 pmol 125I-labelled CRP binds Ca2+ dependently to nuclear envelopes (25 micrograms) at saturation, but only 0.62 pmol SAP is required to saturate. Specific photocross-linking of 125I-2-(p-azidosalicylamido)-1,3'-dithiopropionate (125I-ASD)-CRP and 125I-ASD-SAP to nuclei revealed transfer of 125I-photoreactive azides to nuclear-envelope proteins of 43, 46, 52 and 70 kDa. In addition, SAP binding to histones H2A, H2B, H3 and H4 was detected, whereas CRP bound only to H4. Neither pentraxin cross-linked to histone H1.

HLA antigens influence resistance to lung carcinoma

The concept of genetic factors playing a role in the pathogenesis of lung cancer has gained increased attention. The present study was undertaken to reexamine the question of HLA antigen association with carcinoma of the lung. In a study of 90 patients, a significant association occurred between HLA-DR7 and resistance to lung cancer, after accounting for smoking status and sex. HLA class I antigens were also implicated. These results suggest that major histocompatibility complex loci affect carcinoma of the lung.

The role of NAD(P)H: quinone reductase (EC 1.6.99.2, DT-diaphorase) in the reductive bioactivation of the novel indoloquinone antitumor agent EO9

EO9 [3-hydroxymethyl-5-aziridinyl-1-methyl-2-(H-indole-4, 7-indione)-propenol] is a novel indoloquinone structurally related to mitomycin C, a quinone anticancer drug that requires reductive bioactivation. NAD(P)H: (quinone-acceptor) oxidoreductase (quinone reductase, DT-diaphorase, EC 1.6.99.2) is an obligate 2-electron donating enzyme that can reduce a variety of quinones resulting either in bioactivation or bioprotection. Using quinone reductase (QR) preparations from rat Walker 256 mammary tumor cells and human HT29 colon carcinoma cells, we have characterized the role of this enzyme in EO9 reductive metabolism. QR activity was assayed under optimal conditions by following cytochrome c reduction at 550 nm in the presence of enzyme, quinone substrate, NADH, and bovine albumin, and confirmed by loss of EO9 absorbance at 550 nm. Both the rat and human tumor cell enzymes catalyzed reduction of the benchmark quinone menadione with a similar Km of 1.4-3.1 microM, although the Vmax was 7 to 8-fold lower for the human preparation. EO9 was readily reduced by the rat Walker QR. The mean Km was about 5-fold higher than for menadione at around 15 microM and the Vmax was 6-fold lower at around 2.5 mumol of cytochrome c reduced mg-1 of protein. EO9 was also metabolized by QR from HT29 human colon carcinoma cells but rather less efficiently than by the rat tumor enzyme. For example, the rate was 6-fold lower than that for the Walker tumor enzyme at 100 microM substrate concentration after correcting for the 7- to 8-fold difference in specific activity for the two preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

Cutting out the eyewash

I was most interested in the article Conjunctival Swabs: assessment of value (Nursing Standard May 29).

Technical evaluation of a CAD system for orthopaedic shoe-upper design

Computer aided design is now employed routinely in the volume shoe trade. New styles are developed on a three-dimensional image of the last followed by automated pattern generation and engineering. It is suggested that such systems could be useful in the orthopaedic footwear industry although the different requirements for these bespoke products need careful consideration. A clinical trial has been conducted on the Shoemaster (Clarks Shoes) upper design system both to assess its technical capabilities and to consider its role in improvement of service and cosmetic appearance. This particular system works throughout on a three-dimensional representation of the shoe last, which offers particular advantages for integration with shape capture and reproduction. The report concentrates on the technical evaluation to assess (a) its ability to work with unusual last shapes dictated by medical requirements and (b) its potential for integration into a complete computer system for design of both shoe lasts and shoe uppers. The trial indicates that this particular system is promising in both respects.

An empirical evaluation of the performance of antibody identification tasks

Four empirical studies were conducted for better understanding of the nature of problem-solving activities by medical technologists and medical technology students when performing antibody identification tasks. The results indicated the importance of strategies that ensure the collection of converging evidence, as these strategies protect against the fallibility of commonly used heuristics and against errors due to simple slips. The results also indicate that not only do students make significant numbers of errors, but so do practicing technologists. In one of the studies covering a 1-year period, for instance, a group of 16 technologists made a total of 41 errors in 1057 cases. On the basis of these findings, several alternatives are proposed to reduce errors.

Functional myocardial impairment in children treated with anthracyclines for cancer

A non-invasive exercise method was used to look for myocardial damage in apparently normal children who had received moderate doses of anthracyclines for treatment of cancer. 19 children (mean [SD] age 10.6 [4.3] years) who had received anthracyclines (mean total dose 230 [119] mg/m2) and 10 who had received other cytotoxic drugs (mean age 13.3 [4.9] years) were selected from 263 children attending routine follow-up examinations. They underwent measurement of heart rate, blood pressure, and left ventricular dimensions by echocardiography before and after exercise on a bicycle for a maximum of 10 min. All 29 were in remission. All the subjects showed normal fractional shortening (FS = left ventricular end-diastolic minus end-systolic diameter as a percentage of the end-diastolic diameter) at rest, but the increase in FS on exercise was significantly lower in the children who had received anthracyclines than in those who had not (3 [16]% vs 23 [17]%; p less than 0.05). This difference remained significant after adjustment for age and drug exposure. However, there were no significant differences between the groups in the adjusted mean percentage changes on exercise in heart rate or systolic or diastolic blood pressure. Disease type had no effect on the cardiological indices. Thus, many children who have received anthracyclines may have suffered subclinical myocardial damage. Post-exercise echocardiography seems a useful non-invasive method for detecting such damage. Long-term cardiological follow-up of these patients is needed.

Long-term growth in vitro of isolated, fully differentiated neurones from the central nervous system of an adult insect

A method is described for the isolation and growth in vitro of fully differentiated neurones from the thoracic ganglia of adult cockroaches. The presence of insect blood in the culture system is shown to promote growth. The morphology of the growing neurones and the plasticity of the branching processes are described and growth rates are measured. Using a fluorescent Ca2+ indicator dye, changes of intracellular calcium levels in the growing neurones in response to K+ depolarization have been measured. The results, indicating the presence of voltage-dependent Ca2+ channels on neuronal processes in vitro, show that neurones can be maintained in a functional state for several weeks by this technique. Such preparations could prove useful for studying a variety of physiological and pharmacological properties of neurones, including the mechanisms controlling growth, synapse formation and neuronal interactions with other cell types.

Neural repair and glial proliferation: parallels with gliogenesis in insects

There is a growing recognition, stemming from work with both vertebrates and invertebrates, that the capacity for neuronal regeneration is critically dependent on the local microenvironment. That environment is largely created by the non-neuronal elements of the nervous system, the neuroglia. Therefore an understanding of how glial cells respond to injury is crucial to understanding neuronal regeneration. Here we examine the process of repair in a relatively simple nervous system, that of the insect, in which it is possible to define precisely the cellular events of the repair process. This repair is rapid and well organised; it involves the recruitment of blood cells, the division of endogenous glial elements and, possibly, migration from pre-existing glial pools in adjacent ganglia. There are clear parallels between the events of repair and those of normal glial development. It seems likely that the ability of the insect central nervous system to repair resides in the retention of developmental capacities throughout its life and that damage results in the activation of this potential.

The use of streptokinase in replant salvage

This is the first report of the clinical use of direct intra-arterial streptokinase infusion to promote the salvage of a failing thumb replant. Anastomotic revision was performed on two occasions following thrombosis in the vein grafts used to replant an avulsed thumb. Recurrent thrombosis was treated successfully with conservative thrombolytic therapy consisting of a direct infusion of streptokinase, 20,000 I.U. per hour into the radial artery for 32 hours, followed by intravenous heparin, 40,000 I.U. for 24 hours. The thumb survived, with no tissue loss. Thrombolytic therapy is the only non-surgical means of dissolving intraluminal thrombus, and should be considered when thrombosis occurs in a replanted extremity.

Detection of multidrug resistance and quantification of responses of human tumour cells to cytotoxic agents using flow cytometric spectral shift analysis of Hoechst 33,342-DNA fluorescence

We describe the application of a flow cytometric technique for assessing the radiation or drug sensitivity characteristics of human tumour cells. The technique makes use of the phenomenon that a red shift occurs in the fluorescence emission spectrum of a DNA-specific dye (Hoechst 33,342) as an increasing number of dye molecules bind to nuclear DNA. Intact, viable cells undergo a time-dependent spectral shift that can be distinguished from the rapid shift observed in cells with damaged membranes by the use of multiparametric flow cytometry. The responses of various human cell lines were compared, namely, those of normal and ataxia-telangiectasia (A-T) lymphoblastoid lines, a small-cell lung carcinoma line and its (in vitro) derived multidrug-resistant variants. A close correlation was found between dye toxicity and the degree of DNA binding of Hoechst 33,342 independent of cellular DNA content, with lymphoblastoid and multidrug-resistant small-cell lung cancer cells showing enhanced and restricted dye-binding rates, respectively. VP16- and radiation-induced cell kill was found to result in a quantifiable increase in the fraction of cells undergoing a rapid spectral shift and was capable of detecting the increased radiation sensitivity of A-T-derived cells. Spectral shift analysis provides a rapid method for assessing the responses of tumour cells to cytotoxic agents and for determining the general ability of cells to protect cellular DNA from a model DNA-binding agent (Hoechst 33,342) that participates in the multidrug resistance phenotype.

Carcinogenesis: molecular defences against carcinogens

It has long been recognized that exposure to specific chemical and physical agents can result in the appearance of tumours in both man and animals. There is substantial evidence that DNA is the ultimate cellular target of carcinogens and that DNA repair is an important cellular defence against the effects of carcinogen exposure. Some insight into the molecular processes involved in cellular responses to carcinogens is provided by the occurrence of rare human disorders that display complex abnormalities in processing DNA damage or maintaining genomic integrity. These disorders include xeroderma pigmentosum, Cockayne syndrome, ataxia telangiectasia, dysplastic nevus syndrome and Bloom syndrome. Such disorders have provided clues to some of the basic mechanisms involved in carcinogenesis.

Bayesian methods for prevalence estimation from incomplete administrative lists

Many studies aimed at estimating prevalence use several administrative lists from different sources in an attempt to enumerate all persons affected with the health condition of interest. Each list is 'incomplete' in the sense that none of them enumerates all persons affected with the health condition. Further, because the lists are drawn from different administrative sources the probability of enumeration varies from list to list. The goal is to use information from the lists to estimate the total number of affected persons in the population, but with some accounting for the different but unknown probabilities of enumeration on each list. This paper presents a Bayesian method to estimate prevalence when the probability of enumeration varies from list to list. Data from a survey of children with spina bifida illustrate the methodology.

Procedural errors in antibody identification

In experimental studies of students and line technologists performing antibody identification procedures, both groups made errors. These errors included, at times, either failing to identify an antibody or misidentifying the specficity(ies)A. prospective study was undertaken to identify errors made in a laboratory setting. Errors were classified as 1) failing to follow protocol (procedural error) or 2) arriving at the wrong answer (misidentification error). Over a 1-year period, 1,057 workups were reviewed. There were 41 (3.88%) procedural errors and no misidentification errors. In 25 workups (61% of errors), the selection of cells m rule out underlying alloantibody(ies) was in error. The remaining 16 involved various "slips" (minor mistakes or memory lapses) and clerical errors. Based on an analysis of the probable causes of these errors, potential solutions include 1) developing computer aids to detect "rule-out" errors or missing tests results; 2) providing timely, careful review of workups before transfusion; and 3) designing better panel layout and cell selection.

Reduced nuclear binding of a DNA minor groove ligand (Hoechst 33342) and its impact on cytotoxicity in drug resistant murine cell lines

The reduced cellular uptake, and subsequent reduced nuclear availability, of cytotoxic agents is a factor in the resistance of mammalian cells to anti-cancer drugs that act by interaction with DNA. The whole cell uptake, nuclear binding and cytotoxicity of a DNA-specific ligand, Hoechst dye number 33342 (Ho342), has been studied in cytotoxic drug resistant variants of a murine tumour cell line. Cell lines showing various degrees of cross-resistance to adriamycin as a part of the phenotype of classical multi-drug resistance (MDR) demonstrated a reduction in intranuclear Ho342 content, up to a maximum of 35% of the level found in the parent as assessed by flow cytometry, despite similar levels of whole cell uptake determined using radiolabelled ligand. Ability to limit nuclear accessibility of Ho342 correlated closely with cellular resistance to Ho342 and to adriamycin. All drug resistant cell lines showed a significant increase in nuclear accessibility to Ho342 after verapamil treatment, including a methotrexate resistant cell line. The methotrexate resistant variant, not demonstrating MDR, showed reduced nuclear binding of Ho342 but increased cell kill associated with a propensity to develop a population of cells showing extra DNA replication in response to Ho342 exposure. Differences between cell lines in the relationship between Ho342-induced cell cycle perturbation and cell kill supported the conclusion that modulation of several pathways of response to cytotoxic agents had occurred in the development of drug resistance.