Verapamil enhances doxorubicin activity in cultured human renal carcinoma cells

Cells from 22 renal cell carcinomas (RCC) were established in culture. Sensitivity of the tumour cells to doxorubicin alone and in combination with racemic verapamil, which reverses multidrug resistance, was tested using a [75Se]selenomethionine uptake assay to measure protein synthesis. The effect of verapamil was expressed as a potentiation index: LD50doxorubicin/LD50doxorubicin + verapamil. The potentiation index in 15 of these carcinomas was determined for cells within the first 14 days of culture. At 3.3 mumol/l concentration of verapamil, of the tumours sensitive to doxorubicin alone (LD50 < 0.75 microgram/ml) five of seven showed a potentiation index of > 2. For the less sensitive tumours the analogous proportion was seven of eight. Tumour cell expression of glycoprotein P-170, associated with multidrug resistance, was estimated using the monoclonal antibody C-219. Initial expression levels were unrelated to the action of verapamil. In five tumours the proportion of cells expressing P-170 declined as the period of culture increased. This was not associated with any consistent change in the LD50 for doxorubicin or in potentiation of doxorubicin sensitivity by verapamil. Cell cloning associated with prolonged cell growth in vitro could mimic tumour cell cloning which accompanies the formation of metastases. Thus reduced expression of P-170 on prolonged cell growth in vitro may be a pointer to the efficacy of combination therapy in the treatment of patients with metastatic renal cell carcinoma.

Bitis arietans nerve growth factor is a disulphide-linked homodimer

1. Nerve growth factor from Bitis arietans venom was isolated in high yield and purified to homogeneity using a rapid two-step procedure involving gel exclusion chromatography and reversed-phase HPLC. 2. On polyacrylamide gel electrophoresis in SDS, the NGF migrates as a 25 kDa homodimer and is thus atypical of other Viperid NGFs. 3. Evidence suggests that, unlike mammalian beta NGFs, the subunits of the Bitis arietans homodimer are covalently linked by a disulphide bond(s). 4. Partial sequence analysis shows that only 6 out of the first 21 amino acids are identical with those of cobra NGF including cys-14 and val-21 which are known to be important for NGF activity.

Metabolic acidosis and fatal myocardial failure after propofol infusion in children: five case reports

OBJECTIVE

To examine the possible contribution of sedation with propofol in the deaths of children who were intubated and required intensive care.

DESIGN

Case note review.

SETTING

Three intensive care units.

SUBJECTS

Five children with upper respiratory tract infections aged between 4 weeks and 6 years.

RESULTS

Four patients had laryngotracheo-bronchitis and one had bronchiolitis. All were sedated with propofol. The clinical course in all five cases was remarkably similar: an increasing metabolic acidosis was associated with brady-arrhythmia and progressive myocardial failure, which did not respond to resuscitative measures. All children developed lipaemic serum after starting propofol. These features are not usually associated with respiratory tract infections. No evidence was found of viral myocarditis, which was considered as a possible cause of death.

CONCLUSION

Although the exact cause of death in these children could not be defined, propofol may have been a contributing factor.

Sensitivity and specificity for correlated observations

A general estimating equation approach is used to obtain estimates of sensitivity and specificity when the data consist of correlated binary outcomes. First order approximations to the variances of estimated sensitivity and specificity for prospective and retrospective studies are given. Data from a dental study are used to motivate and illustrate the methods.

DNA damaging and cell cycle effects of the topoisomerase I poison camptothecin in irradiated human cells

This study addressed the potential radiosensitizing and DNA-damaging actions of the DNA topoisomerase I poison camptothecin (CPT) on SV40 transformed normal (MRC5CVI) and ataxia-telangiectasia (AT5BIVA) fibroblast cell lines. In both cell lines CPT induced a dose-dependent delay of cells in S phase, followed by a dose-dependent trapping in G2/M phase. Acute X-irradiation produced patterns of G2/M arrest and S-phase delay similar to those observed for CPT in the MRC5CVI cell line, but no S phase delay was observed in the AT5BIVA cell line consistent with the ataxiatelangiectasia phenotype of this cell line. X-irradiation of CPT-treated cells resulted in additive prolongation of S phase delay in MRC5CVI cultures and additive effects for cell killing in both cell lines. The potential for topoisomerase I-DNA cross-linking by CPT was not altered by 24h pretreatment with CPT, or by acute X-irradiation. Hypersensitivity of AT5BIVA to CPT was not attributable to elevated levels of complex trapping. These findings suggest that in a rapidly proliferating human tumour there is unlikely to be synergistic therapeutic gain when the two agents are used concurrently, and that previously reported radiosensitization by CPT is restricted to G0 phase cells.

Subcellular distribution of the anticancer drug mitoxantrone in human and drug-resistant murine cells analyzed by flow cytometry and confocal microscopy and its relationship to the induction of DNA damage

Flow cytometry and laser scanning confocal imaging have been used to analyze the uptake of the anticancer topoisomerase II poison mitoxantrone by intact mammalian cells and the results correlated with the induction of DNA damage. Unlike Adriamycin, mitoxantrone displays only minimal levels of red fluorescence when excited at 514 wavelength. However, using these excitation and emission conditions, flow cytometry could detect low levels of fluorescence in human transformed fibroblasts exposed to high concentrations (5-20 microM) of mitoxantrone for 1 h. Over this dose range whole cell fluorescence was a function of cell size and increased with drug concentration while drug-induced DNA-protein cross-linking showed saturation. Confocal microscopy revealed the time- and dose-dependent appearance of fluorescence, interpreted here as reflecting the disposition of drug molecules, preferentially within the cytoplasm, nuclear membrane, and nucleoli. This pattern contrasted with the intense intranuclear fluorescence observed in Adriamycin-treated human cells. Loss of the nuclear membrane during mitosis resulted in an apparent increase in chromatin-associated fluorescence. Photon counting procedures revealed a predominantly cytoplasmic, possibly lysosomal, location for fluorescence from human cells exposed for 1 h to a low but cytotoxic concentration (0.1 microM, yielding approximately 90% cell kill) of mitoxantrone. At this low concentration, human cells displayed minimal levels of DNA strand cleavage or DNA-protein cross-linking. Murine cells, displaying mitoxantrone resistance as part of the P-glycoprotein-mediated multidrug resistance phenotype, showed specific extinction of mitoxantrone-associated fluorescence from inside nuclei but not from within extranuclear compartments. The study demonstrates the feasibility of high resolution studies on the intracellular distribution of mitoxantrone in intact living cells. We suggest a mechanism by which cytoplasmic sequestration of mitoxantrone may be important in determining the response of normal and multidrug-resistant cells as they attempt to progress through mitosis.

Verrucous carcinoma: epithelioma cuniculatum plantare

Verrucous carcinoma is a well-differentiated form of squamous cell carcinoma. This tumor has been shown to mimic a variety of other skin lesions with its insidious onset and apparently benign course. Early detection and a thorough histologic examination of this growth aid in proper diagnosis, treatment, and reduction in morbidity. An interesting case history and literature survey are presented to facilitate diagnosis and treatment of this rare pedal neoplasm.

The faces of group practice. The transformation and progression of physician organizations

The future will bring an increase in the economic forces which drive the succession of organizational forms. Migrating to integrated models of medical practice will become a survival technique for more and more physicians. This is a frightening prospect for individuals trained to be independent and self reliant. Fortunately, there are a variety of organizational models through which physicians can progress to ease the transition from solo to larger integrated practice forms. Regardless of the evolutionary course, successful physician organizations of the future will be primary care-based, geographically distributed, meaningfully partnered with hospital entities, equipped to accept risk, and lead by strong, business-savvy physician leaders and administrators. This organization will have the ability to flourish within a radically changing climate and will result in the delivery of measurably superior health care to its community.

Overexpression of the c-erbB-2 oncoprotein: why does this occur more frequently in ductal carcinoma in situ than in invasive mammary carcinoma and is this of prognostic significance?

Overexpression of c-erbB-2 occurs in 60% of in situ and 25% of infiltrating ductal carcinomas. We have previously found very strong associations between immunohistochemical staining for c-erbB-2 and histological pattern and nuclear size in ductal carcinoma in situ (DCIS) and less strong correlation with proliferative activity. In a further study of infiltrating ductal carcinomas we have found that, in addition to tumours arising from c-erbB-2 positive, large celled, rapidly proliferating, comedo carcinomas and c-erbB-2 negative small celled cribriform/micropapillary carcinomas with a low proliferative rate, there is a third group of c-erbB-2 negative tumours with large nuclei and variable proliferative activity. These latter tumours are not seen in pure DCIS suggesting that they have a very transient in situ stage. Therefore, although in pure DCIS c-erbB-2 positively appears to be associated with tumours with a greater invasive potential, and c-erbB-2 negativity with tumours having a more favourable prognosis, the latter is not necessarily true in infiltrating disease.

Zinc finger point mutations within the WT1 gene in Wilms tumor patients

A proposed Wilms tumor gene, WT1, which encodes a zinc finger protein, has previously been isolated from human chromosome 11p13. Chemical mismatch cleavage analysis was used to identify point mutations in the zinc finger region of this gene in a series of 32 Wilms tumors. Two exonic single base changes were detected. In zinc finger 3 of a bilateral Wilms tumor patient, a constitutional de novo C----T base change was found changing an arginine to a stop codon. One tumor from this patient showed allele loss leading to 11p hemizygosity of the abnormal allele. In zinc finger 2 of a sporadic Wilms tumor patient, a C----T base change resulted in an arginine to cysteine amino acid change. To our knowledge, a WT1 gene missense mutation has not been detected previously in a Wilms tumor. By comparison with a recent NMR and x-ray crystallographic analysis of an analogous zinc finger gene, early growth response gene 1 (EGR1), this amino acid change in WT1 occurs at a residue predicted to be critical for DNA binding capacity and site specificity. The detection of one nonsense point mutation and one missense WT1 gene point mutation adds to the accumulating evidence implicating this gene in a proportion of Wilms tumor patients.

Early diagnosis and management of 5 alpha-reductase deficiency

Two siblings of Pakistani origin, karyotype 46 XY, were born with predominantly female external genitalia with minute phallus, bifid scrotum, urogenital sinus, and palpable gonads. The older sibling at the age of 8 days showed an adequate testosterone response to human chorionic gonadotrophin (hCG) stimulation. The diagnosis of 5 alpha-reductase deficiency was made at age 6 years when no 5 alpha-reduced glucocorticoid metabolites were detectable in urine even after tetracosactrin (Synacthen) stimulation. In the younger sibling the diagnosis of 5 alpha-reductase deficiency was provisionally made at the early age of 3 days on the basis of high urinary tetrahydrocortisol (THF)/allotetrahydrocortisol (5 alpha-THF) ratio and this ratio increased with age confirming the diagnosis. Plasma testosterone: dihydrotestosterone (DHT) ratio before and after hCG stimulation was within normal limits at age 3 days but was raised at age 9 months. Topical DHT cream application to the external genitalia promoted significant phallic growth in both siblings and in the older sibling corrective surgery was facilitated. In prepubertal male pseudohermaphrodites with normal or raised testosterone concentrations, phallic growth in response to DHT cream treatment could be an indirect confirmation of 5 alpha-reductase deficiency.

A third Wilms' tumor locus on chromosome 16q

Loss of heterozygosity studies have been used to identify chromosomal regions which are frequently deleted and thus indicate areas which may harbor tumor suppressor genes. As a result, both the WT1 gene located in chromosome 11p13 and an unidentified gene(s) within chromosome 11p15 have been implicated in Wilms' tumorigenesis. Cytogenetic and linkage studies suggest that additional non-chromosome 11 sites are involved in Wilms' tumor. Because these sites may also involve loss of heterozygosity, loci on 33 autosomal arms were screened for allele loss in a series of Wilms' tumors. We found that in addition to loss on chromosome 11p (11 of 25 informative tumors) there was significant loss on chromosome 16q (9 of 45 informative tumors), while the total frequency of allele loss excluding these loci was low (9 of 426 total informative loci). These data indicate that losses of both chromosome 11p and 16q alleles are nonrandom events and suggest that 16q is the location of a third tumor suppressor gene underlying Wilms' tumorigenesis. The parental origin of the lost chromosome 16q allele was determined in eight sporadic tumors. Alleles of paternal and of maternal origin were each lost in four sporadic tumors indicating that, unlike chromosome 11p, alleles of either parental origin are lost on 16q.

Do histocompatibility antigens antigence influence the risk of head and neck carcinoma?

Associations were sought between specific histocompatibility antigens (HLA) of the human major histocompatibility complex and the incidence of head and neck squamous cell carcinoma (SqCC). Seventy sequential patients with SqCC and 217 control subjects from the same geographic region were typed for HLA-A, HLA-B, and HLA-DR loci. These results were compared. Multivariate statistical analysis using stepwise logistic regression revealed significant associations between the incidence of SqCC and HLA-B14, HLA-DR3, and HLA-DR4 as well as smoking and the sex-smoking interaction. The authors concluded that certain host factors, including genetic constitution, and behavioral characteristics (i.e., smoking) as well as tumor biology, can influence the development of SqCC. The mechanism(s) of these associations may involve as yet undefined relationships between HLA region genes and the immune response.

Equivalent expression of paternally and maternally inherited WT1 alleles in normal fetal tissue and Wilms' tumours

Observations of non-random maternal 11p allele loss in Wilms' tumour (WT) have implied the possible involvement of an imprinted 11p locus in WT aetiology. A proposed 11p13 Wilms' tumour gene, WT1, has recently been isolated and encodes a zinc finger DNA-binding protein, the 3' untranslated region of which contains a polymorphic dinucleotide repeat (CA repeat) motif. We have exploited this transcribed CA repeat to examine the allelic expression pattern of WT1 and thereby determine whether transcriptional imprinting of this gene occurs. DNA and reverse-transcribed RNA from tumours and normal tissue were subjected to the polymerase chain reaction (PCR) using radiolabelled primers flanking the CA repeat. The gene was seen to be expressed from both of the constitutive alleles in 9-week human fetal kidney, all informative Wilm's tumours and neonatal kidney tissue adjacent to the tumours. In one tumour, known to be heterozygous for a point mutation in zinc finger 2, direct sequencing confirmed that both mutant and wild-type transcripts were being expressed. These results demonstrate that this gene is not subject to transcriptional imprinting in tumours or normal fetal kidney.

The M1 subunit of ribonucleotide reductase refines mapping of genetic rearrangements at chromosome 11p15

We report the first use of the ribonucleotide reductase M1 subunit (RRM1) locus as a marker to assist in defining genetic rearrangements at 11p15. Our sample consisted of 21 Wilms' tumors from 18 patients, and one adrenal adenoma from a patient with Beckwith-Wiedemann syndrome, preexisting chromosome 11 maps being refined by the use of the RRM1 locus in all cases. Significantly, one Wilms' tumor showed loss of heterozygosity at the RRM1 locus only, whereas the adrenal adenoma showed a maintenance of heterozygosity at the RRM1 locus, loss having been previously demonstrated at the c-Ha-ras locus. The relevance of this finding to the location of one or more disease-associated loci at 11p15 is discussed.

Cell specific DNA-labelling in the repairing blood-brain barrier of the insect Periplaneta americana

This study uses a recently developed technique for preserving the ultrastructure of cells in the insect CNS during immunohistochemical processing for 5-bromo-2-deoxyuridine incorporation into newly synthesised DNA. The results allow us to identify the proliferating cell classes in the regenerating blood-brain barrier. High resistance barrier cells do not label with the antibody but sheath cells clearly do. Intermediate cell types appearing during repair are identified. It is hypothesised that these cells generate matrix molecules for neural lamella repair and may represent transitional forms as invasive blood cells transdifferentiate into functional sheath cells.

Erratum

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

The key words for this article should read: camptothecin, DSBs in replicating DNA, deoxyguanosine, toxicity.

The catalytic consequences of experimental evolution. Studies on the subunit structure of the second (ebg) beta-galactosidase of Escherichia coli, and on catalysis by ebgab, an experimental evolvant containing two amino acid substitutions

1. The ratio of ebgA-gene product of ebgC-gene product in the functional aggregate of ebg beta-galactosidases was determined to be 1:1 by isolation of the enzyme from bacteria grown on uniformly radiolabelled amino acids and separation of the subunits by gel-permeation chromatography under denaturing conditions. 2. This datum, taken together with a recalculation of the previous ultracentrifuge data [Hall (1976) J. Mol. Biol. 107, 71-84], analytical gel-permeation chromatography and electron microscopy, strongly suggests an alpha 4 beta 4 quaternary structure for the enzyme. 3. The second chemical step in the enzyme turnover sequence, hydrolysis of the galactosyl-enzyme intermediate, is markedly slower for ebgab, having both Asp-97----Asn and Trp-977----Cys changes in the large subunit, than for ebga (having only the first change) and ebgb (having only the second), and is so slow as to be rate-determining even for an S-glycoside, beta-D-galactopyranosyl thiopicrate, as is shown by nucleophilic competition with methanol. 4. The selectivity of galactosyl-ebgab between water and methanol on a molar basis is 57, similar to the value for galactosyl-ebgb. 5. The equilibrium constant for the hydrolysis of lactose at 37 degrees C is 152 +/- 19 M, that for hydrolysis of allolactose is approx. 44 M and that for hydrolysis of lactulose is approx. 40 M. 6. A comparison of the free-energy profiles for the hydrolyses of lactose catalysed by the double mutant with those for the wild-type and the single mutants reveals that free-energy changes from the two mutations are not in general independently additive, but that the changes generally are in the direction predicted by the theory of Burbaum, Raines, Albery & Knowles [(1989) Biochemistry 28, 9283-9305] for an enzyme catalysing a thermodynamically irreversible reaction. 7. Michaelis-Menten parameters for the hydrolysis of six beta-D-galactopyranosylpyridinium ions and ten aryl beta-galactosides by ebgab were measured. 8. The derived beta 1g values are the same as those for ebgb (which has only the Trp-977----Cys change) and significantly different from those for ebgo (the wild-type enzyme) and ebga. 9. The alpha- and beta-deuterium secondary isotope effects on the hydrolysis of the galactosyl-enzyme of 1.08 and 1.00 are difficult to reconcile with the pyranose ring in this intermediate being in the 4C1 conformation.

The recovery of sensation and function after cross-finger flaps for fingertip injury

Over a five-year period, 54 patients had cross-finger flaps at Mount Vernon Hospital for single fingertip injuries. A retrospective study was carried out to evaluate the recovery of sensation and function. 92% of the patients were satisfied with the result although 53% suffered cold sensitivity. All the cross-finger flaps tested had diminished sweating and a raised threshold for electrical stimulation. Despite the presence of protective sensation, dynamic sensory discrimination and the return of advanced A beta fibre innervation, none of the cross-finger flaps was found to have recovered tactile gnosis.

Intravesical BCG treatment for superficial bladder cancer: long-term results using two different strains of BCG

A total of 21 patients received intravesical BCG for the prevention of recurrence of superficial transitional cell carcinoma of the bladder. Twelve patients received the Glaxo strain and 9 the Pasteur strain of the bacillus. Although thought to have different anti-tumour activities owing to a difference in antigenicity, these 2 strains produced similar tumour-free rates at 5 years' mean follow-up with an overall tumour-free rate of 43%.