The influence of race and gender on depressive and substance abuse symptoms in high-risk adolescents

Concerns about the cultural competence of child mental health services has led to the examination of racial/ethnic and gender differences in the prevalence of psychiatric symptoms. This study examines racial and gender differences in depressive and substance abuse symptomatology in a high-risk population of adolescents living in five residential group homes in South Carolina. We surveyed 299 youth ages 12 to 17, including 101 African American and 198 Whites. They completed the Centers for Epidemiological Studies-Depression scale (CES-D) and questions on substance abuse, demographics, and psychosocial functioning. No significant differences were found in the percentages of Whites and African Americans scoring above 16+ and 23+ cutoff scores on the CES-D, but significant gender differences were identified. Neither race nor race by age group interactions were found to be significantly correlated in regression analyses with CES-D score nor multiple substance use, whereas gender (p < .001) and school performance were significantly correlated with CES-D score, and poverty was correlated with multiple substance use. Our results indicate that levels of depressive symptomatology as measured by the CES-D are much more sensitive to gender than to race in high-risk populations. Different gender cutoffs are indicated when using systematic instruments in the measurement of depressive symptoms.

Can diagnostic laparoscopy be avoided in routine investigation for infertility?

OBJECTIVE

To determine whether routine testing for serum Chlamydia trachomatis antibodies, considered in combination with a woman's clinical features, may avoid the need for diagnostic laparoscopy in routine investigation for infertility.

DESIGN

Retrospective case notes analysis.

SETTING

Secondary level care infertility clinic.

POPULATION

Eighty women who had undergone both laparoscopy and serum Chlamydia trachomatis antibody testing.

METHODS

Ascertainment of any history of suspected pelvic inflammatory disease, pelvic pain, cervical intraepithelial neoplasia, pelvic surgery or appendicectomy; any abnormality on clinical pelvic examination; the findings at laparoscopy; the result of serum Chlamydia trachomatis antibody testing by enzyme-linked immunosorbent assay (ELISA) screening with microimmunofluorescence (MIF) confirmatory diagnostic testing. The usefulness of clinical features, the serum Chlamydia trachomatis antibody test and these two variables combined in the detection of tubal disease and pelvic pathology of relevance to infertility were measured statistically.

MAIN OUTCOME MEASURES

Specificity, sensitivity, positive predictive value, negative predictive value and likelihood ratio for each of the tests.

RESULTS

The combination of any positive clinical feature with a positive test for serum Chlamydia trachomatis antibodies detects tubal disease with sensitivity 92%, specificity 70%, positive predictive value 72%, negative predictive value 91% and likelihood ratio 3 x 1; it detects bilateral tubal obstruction with sensitivity 84%, specificity 51%, positive predictive value 35%, negative predictive value 91% and likelihood ratio 1 x 7; it detects pelvic pathology relevant to infertility with sensitivity 76%, specificity 71%, positive predictive value 80%, negative predictive value 65% and likelihood ratio 2 x 6. The negative predictive value for pelvic pathology from the use of clinical features in addition to the chlamydia antibody test is not significantly higher than that from the chlamydia antibody test alone (53%).

CONCLUSIONS

A policy of selective laparoscopy in routine investigation for infertility, based on the result of the test for serum Chlamydia trachomatis antibodies and a woman's clinical features, is not supported.

Surgical interruption of pelvic nerve pathways for primary and secondary dysmenorrhoea

BACKGROUND

Dysmenorrhoea is the occurrence of painful menstrual cramps of uterine origin and is a very common gynaecological complaint. Medical therapy for dysmenorrhoea includes oral contraceptive pills (OCP) and nonsteroidal anti-inflammatory drugs (NSAIDS) which both act by suppressing prostaglandin levels. While these treatments are very successful there is still a 20-25% failure rate and surgery has been an option for cases of dysmenorrhoea that fail to respond to medical therapy. Uterine nerve ablation (UNA) and presacral neurectomy (PSN) are two surgical treatments that have become increasingly utilised in recent years. These procedures both interrupt the majority of the cervical sensory nerve fibres, thus diminishing uterine pain. Uncontrolled studies have supported the use of these procedures for primary dysmenorrhoea however both operations only partially interrupt some of the cervical sensory nerve fibres in the pelvic area; therefore dysmenorrhoea associated with additional pelvic pathology may not always benefit from this type of surgery.

OBJECTIVES

To assess the effectiveness of surgical interruption of pelvic nerve pathways as treatment for primary and secondary dysmenorrhoea, and to determine the most effective surgical treatment.

SEARCH STRATEGY

Electronic searches of the Cochrane Menstrual Disorders and Subfertility Group Register of controlled trials, MEDLINE, and EMBASE were performed to identify relevant randomised controlled trials (RCTs). Attempts were also made to identify trials from citation lists of review articles and handsearching. In most cases, the first or corresponding author of each included trial was contacted for additional information.

SELECTION CRITERIA

The inclusion criteria were randomised comparisons of surgical techniques of interruption of the pelvic nerve pathways (both open and laparoscopic procedures) for the treatment of primary and secondary dysmenorrhoea. The main outcome measures were pain relief and adverse effects.

DATA COLLECTION AND ANALYSIS

Seven RCTs were identified that fulfilled the inclusion criteria for this review. One trial (Sutton 1994) was excluded because another treatment was given in combination with destruction of pelvic nerve pathways and the effects of these two treatments could not be separated. Of the remaining six trials, three were included in the meta-analysis (Chen 1996, Candiani 1992, Lichten 1987). The results of the other three trials (Dover 1999, Tjaden 1990, Vercellini 1997) were included in the text of the review for discussion because the data were not available in a form that allowed them to be combined in a meta-analysis.

MAIN RESULTS

For the treatment of primary dysmenorrhoea there is some evidence of the effectiveness of uterine nerve ablation (UNA) when compared to a control of no treatment. The comparison between UNA with presacral neurectomy (PSN) for primary dysmenorrhoea showed no significant difference in pain relief in the short term, however long term PSN was shown to be significantly more effective. For the treatment of secondary dysmenorrhoea the identified RCTs addressed only endometriosis. The treatment of UNA combined with surgical treatment of endometrial implants versus surgical treatment of endometriosis alone showed that the addition of UNA did not aid pain relief. For PSN combined with endometriosis treatment versus endometriosis treatment alone there was also no overall difference in pain relief, although the data suggests a significant difference in relief of midline abdominal pain. Adverse events were significantly more common for presacral neurectomy, however the majority were complications such as constipation, which may spontaneously improve.

REVIEWER'S CONCLUSIONS

There is insufficient evidence to recommend the use of nerve interruption in the management of dysmenorrhoea, regardless of cause. Future RCTs should be undertaken.

Postoperative procedures for improving fertility following pelvic reproductive surgery

BACKGROUND

Hydrotubation with oil-soluble contrast media for unexplained infertility and adhesiolysis for infertility due to peritubal adhesions are primary procedures of recognised benefit. It is less clear whether postoperative procedures such as hydrotubation or second-look laparoscopy with adhesiolysis are beneficial following pelvic reproductive surgery.

OBJECTIVES

To assess the value of postoperative hydrotubation and second-look laparoscopy with adhesiolysis following female pelvic reproductive surgery.

SEARCH STRATEGY

The search strategy of the Menstrual Disorders and Subfertility Group was used for the identification of all relevant randomised controlled trials.

SELECTION CRITERIA

All trials where a postoperative procedure following pelvic reproductive surgery was compared with a control group generated by randomisation were considered for inclusion in the review.

DATA COLLECTION AND ANALYSIS

Five randomised controlled trials were identified and included in this review, after an attempt to obtain further information from authors of all five trials. All trials were assessed for quality criteria. The studied outcomes were pregnancy, live birth, ectopic pregnancy and miscarriage rates and the rates of tubal patency and procedure-related complications. Reviewers extracted the data independently and odds ratios for these dichotomous outcomes were estimated from the data.

MAIN RESULTS

The odds of pregnancy, live birth, ectopic pregnancy and miscarriage were not significantly different with postoperative hydrotubation versus no hydrotubation nor with second-look laparoscopy and adhesiolysis versus no second-look laparoscopy. Whether hydrotubation was early or late and whether hydrotubation fluid contained steroid or not had no significant impact on the odds of pregnancy, live birth, ectopic pregnancy or miscarriage. The odds of pregnancy and live birth were significantly increased and infective complications significantly decreased by hydrotubation with fluid containing antibiotic versus hydrotubation with fluid containing no antibiotic, in late hydrotubation following tubal stent removal six weeks after tubal surgery. The odds of at least one patent fallopian tube were significantly increased with late hydrotubation following tubal stent removal versus early hydrotubation in women who had no tubal stenting, but this intervention had no significant impact on the odds of pregnancy, live birth, ectopic pregnancy or miscarriage.

REVIEWER'S CONCLUSIONS

There is insufficient evidence to support the routine practice of hydrotubation or second-look laparoscopy following female pelvic reproductive surgery. The studies on which this conclusion is based were either poor quality or underpowered. These interventions should be performed in the context of a good quality, adequately powered randomised controlled trial. Postoperative hydrotubation with fluid containing antibiotic following tubal surgery may offer benefit over hydrotubation fluid without antibiotic. A randomised controlled trial of postoperative hydrotubation with antibiotic-containing fluid versus no hydrotubation for improving fertility following tubal surgery is justified.

Emotional disturbance and substance abuse in youth placed in residential group homes

Residential group homes are increasingly important components of the system of mental health care for children and adolescents. However, they often do not have sufficient resources to provide active therapeutic programs as a result of their usual missions in serving abandoned or runaway youth. The authors studied 299 youth, ages 12 to 17 years, in five large residential group home programs in South Carolina. The instruments administered were (1) the Center for Epidemiological Survey-Depression Scale (CES-D), (2) a brief substance abuse questionnaire, and (3) questions about socioeconomic status, previous placements, and family relationship variables. A significant percentage scored above conservative clinical cut-off scores for the CES-D (51.7% scored 16 or above and 33.6% scored 23 or above). The youth also had significant levels of substance abuse problems. However, these variables were not predictive of previous multiple out-of-home placements (runaway behavior was predictive). These findings support the importance of addressing the clinical needs of youth in these programs.

Do men undergoing sterilizing cancer treatments have a fertile future?

This study was designed to assess the effect of cancer treatments on the natural and assisted reproductive potential of men. A cohort of men with cancer, in whom radiotherapy and/or chemotherapy was planned, were invited to participate. Twenty-two pre- and post-treatment semen samples were analysed. The reproductive potential of participants was assessed with respect to the current range of fertility treatment options available. Abnormal sperm concentrations were found in 27% of patients pre-treatment compared to 68% post-treatment following a mean latency of 20 months from treatment. Fifty-nine percent of patients experienced a clinically significant decrease in sperm, concentration following radiotherapy and/or chemotherapy; 23% developed azoospermia following treatment. Eighty-two percent of patients with testicular malignancy had oligo- or azoospermia post-treatment. Only one patient had a clinically significant reduction in the percentage of motile spermatozoa post-treatment. Cryopreservation of semen prior to treatment improved the fertility prospects of 55% of patients. Intracytoplasmic sperm injection (ICSI) enhanced the fertility prospects of a further 14%. In the absence of, or after depletion of, cryopreserved semen, ICSI could enhance the fertility prospects of 45% of patients. Fertilization has been achieved by ICSI using spermatozoa retrieved by testicular biopsy from an azoospermic testicular cancer survivor 8 years after chemotherapy. It was concluded that chemotherapy and/or radiotherapy may depress semen concentration to the extent of rendering a man infertile. The severity of the reduction in sperm concentration following treatment is unpredictable but likely to be most severe in those with testicular malignancy and those treated with radiotherapy or alkylating chemotherapy agents. Not all men are keen to undergo an appraisal of their post-treatment fertility potential, for reasons which are unclear. Improving awareness and education of patients concerning the effects of both cancer and cancer treatments on reproductive potential is essential. With the advent of ICSI, it is possible to offer a very reasonable chance of conception in all men with cancer who present for cryopreservation of semen prior to treatment in whom spermatozoa (even in very low concentrations) are present in the ejaculate.

Investigation of the secondary DNA-binding site of the bacterial recombinase RecA

The L2 loop is a DNA-binding site of RecA protein, a recombinase from Eschericha coli. Two DNA-binding sites have been functionally defined in this protein. To determine whether the L2 loop of RecA protein is part of the primary or secondary binding site, we have constructed proteins with site-specific mutations in the loop and investigated their biological, biochemical, and DNA binding properties. The mutation E207Q inhibits DNA repair and homologous recombination in vivo and prevents DNA strand exchange in vitro (Larminat, F., Cazaux, C., Germanier, M., and Defais, M. (1992) J. Bacteriol. 174, 6264-6269; Cazaux, C., Larminat, F., Villani, G., Johnson, N. P., Schnarr, M., and Defais, M. (1994) J. Biol. Chem. 269, 8246-8254). We have found that mutant protein RecAE207Q lacked one of the two single stranded DNA-binding sites of wild type RecA. The remaining site was functional, and biochemical activities of the mutant protein were the same as wild type RecA with ssDNA in the primary binding site. The second mutation, E207K, reduced but did not eliminate DNA repair, SOS induction, and homologous recombination in vivo. In the presence of ATP, mutant protein RecAE207K catalyzed DNA strand exchange in vitro at a slower rate than wild type protein, and ssDNA binding at site I was competitively inhibited. These results show that the L2 loop is or is part of the functional secondary DNA-binding site of RecA protein.

Strandedness discrimination in peptide-polynucleotide complexes

Preferential binding to single- or double-stranded nucleic acids is important for the activity of many proteins that process RNA and DNA. We have investigated the mechanism of strandedness discrimination with peptides derived from the putative DNA-binding domain of the RecA protein, a bacterial recombinase that modulates its affinity for single-stranded DNA by means of ATP binding and hydrolysis. Contributions of electrostatic and non-electrostatic interactions to binding of these peptides with polynucleotides were evaluated by fluorescence spectroscopy as a function of salt concentration and peptide charge. Binding of these peptides to single- and double-stranded nucleic acids was dominated by non-electrostatic interactions. Small electrostatic contributions selectively enhanced peptide complexation with single-stranded nucleic acids. Similar results were observed in control experiments carried out with tripeptides containing charged and aromatic amino acid residues. It was possible to modify the strandedness preference of peptide-polynucleotide complexes by changing electrostatic contributions to the binding free energy. These observations suggest a mechanism whereby some proteins that interact with DNA or RNA might determine and regulate their relative affinity for single- and double-stranded nucleic acids.

Drinking Problems of Nursing Students

A sample of 315 nursing students in yearly cohorts (1988-1992) completed the Michigan Alcoholism Screening Test (MAST). A simple and quick instrument with established reliability and validity, the MAST had a reliability coefficient of .78 with this sample. The MAST scores of the nursing students indicated that 21.5% had probable alcoholism or were alcoholic. Drinking problems among these nursing students were similar to those of other nursing students and college students in general. Implications for nurse educators include recognition that nursing students need continuing self-assessment and monitoring to avoid drinking problems as a student and future practitioner. Alcoholism self-screening is an excellent introduction to client assessment for drinking problems. Implications for future research include identifying correlates and determinants of problem drinking behaviors and ultimately developing and testing educational interventions to eliminate the problem.

Does ethnicity influence obstetric intervention?

AIMS

To examine whether the high proportion of Polynesian women giving birth at Middlemore Hospital contributes to its low interventional delivery rate.

METHODS

A study of a one-year cohort of women delivering at Middlemore Hospital. Delivery suite records were scrutinised to determine ethnicity and mode of delivery. Statistical comparisons were made.

RESULTS

In Maori, Pacific Island and European women the caesarean section rates were 6.5%, 9.5% and 11.5% respectively. Maori women have a significantly lower rate of caesarean section than Pacific Island women and both groups have a significantly lower rate than European women. The spontaneous vaginal delivery rates in Maori, Pacific Island and European women were 89.0%, 87.4% and 74.8% respectively.

CONCLUSION

The high proportion New Zealand Maori and Pacific Island women contributes to, but does not fully explain, the low interventional delivery rate at Middlemore Hospital.

Assessment of the laparoscopic treatment of ectopic pregnancy

AIMS

To assess the first 2 years experience of the laparoscopic surgical treatment of ectopic pregnancy in a regional referral centre.

METHODS

All cases of ectopic pregnancy in a 2 year period from August 1991 were evaluated to assess the impact on the routine management of this condition.

RESULTS

In the first year 14 cases were managed by laparoscopic means and took an average operating time of mean 73.8 (SD 17.2) minutes compared to mean 69.1 (17.9) minutes in the 26 cases managed this way in the second year. The 40 patients were hospitalised for an average of 1.4 days and 24 stayed one night only. There was no difference in operating time between registrars and consultants. The only major complication was a patient who required an emergency laparotomy because of continued bleeding. When all cases of ectopic surgery were evaluated in the second year, six of the 32 cases required laparotomy to complete the operation.

CONCLUSION

The benefits of laparoscopic surgical treatment of ectopic pregnancy dictate that this should be employed as first line treatment for all cases of tubal ectopic gestation. Our experience suggests that achieving such a service, whilst not without pitfalls, should be possible in all gynaecology units provided that staff are motivated and that laparoscopic equipment is available.

Double-stranded DNA templates can induce alpha-helical conformation in peptides containing lysine and alanine: functional implications for leucine zipper and helix-loop-helix transcription factors

Transcription factors of the basic-leucine zipper and basic-helix-loop-helix families specifically recognize DNA by means of intrinsically flexible peptide domains that assume an alpha-helical conformation upon binding to target DNA sequences. We have investigated the nonspecific interactions that underlie specific DNA recognition. Circular dichroism measurements showed that 20-bp double-stranded DNA oligonucleotides can act as templates to promote random coil-->alpha-helix transitions in short peptides containing alanine and lysine. This conformational change takes place without altering the structure of the DNA, and neither specific peptide-DNA contacts nor cooperative interactions between peptides are necessary. The conformational change does require (i) double-stranded (but not single-stranded) oligodeoxynucleotides in either the B or the B' conformation and (ii) peptides that can form positively charged amphipathic alpha-helices. In 10 mM Na2HPO4 (pH 7.5; 10 degrees C), the excess free-energy contribution of the DNA template to the stability of the alpha-helical form of the oligopeptides tested was delta Gex = -0.15 (+/- 0.07) kcal/mol per lysine residue. The implications of these results for the thermodynamics and kinetics of DNA target site selection by basic-leucine zipper and basic-helix-loop-helix regulatory proteins are discussed.

Purification and biochemical characterization of Escherichia coli RecA proteins mutated in the putative DNA binding site

Escherichia coli RecA protein plays a central role both in DNA repair and in recombination. We report biochemical properties of three new RecA proteins mutated at positions 199 (RecA694), 207 (RecA659), and 211 (RecA611) in the putative DNA binding site. RecA694 had a wild-type phenotype, whereas RecA611 and RecA659 were deficient in promoting both the self-cleavage of LexA repressor and the DNA-strand exchange reaction. In order to determine the origin of this inhibition, we examined the capacity of wild-type and mutant proteins to bind to single-stranded DNA (with and without single-stranded binding protein, SSB), double-stranded DNA, and ATP. DNA strand exchange defects were correlated with the inability of mutant proteins to displace SSB from DNA. For the recA659 mutation this inhibition was reversed by equimolar wild-type protein. In contrast, mixtures of either wild-type/RecA659 or wild-type/RecA611 proteins remained deficient in LexA cleavage, suggesting that the dominant negative phenotype of the mutant proteins may be a consequence of the formation heterologous RecA complexes. Various mutations in the putative DNA binding site of RecA protein altered ATP binding, ATPase activity, displacement of SSB from single-stranded DNA, and protein-protein interactions. These results are consistent with the hypothesis that DNA binding to this site of RecA relays allosteric effects to several functional domains throughout the protein.

Effect of the amine non-leaving group on the structure and stability of DNA complexes with cis-[Pt(R-NH2)2(NO3)2]

The antitumor compound cis-[Pt(NH3)2Cl2] (cisplatin), conserves two ammine ligands during the reaction with its cellular target DNA. Modifications of these non-leaving groups change the antineoplastic properties of this compound and its genotoxic effects. It is therefore of interest to determine the influence of non-leaving groups on the structure and stability of DNA in vitro. We have investigated platinum-DNA adducts formed by cis-[Pt(R-NH2)2(NO3)2] (where R-NH2 = NH3, methylamine, cyclobutylamine, cyclopentylamine and cyclohexylamine) as a function of DNA binding. All compounds quantitatively reacted with DNA in less than 1 h at 37 degrees C. They formed bifunctional adducts with adjacent nucleotides judging from the displacement of the intercalating molecule ethidium bromide, ultraviolet absorption spectroscopy and circular dichroism. Substitution of a H on the NH3 ligand by alkyl groups dramatically destabilized the platinum-DNA complex. Thermal stability decreased progressively with an increasing number of carbon atoms, delta tm = -4.4 degrees C for 3 cyclohexylamine-platinum-DNA adducts/1000 nucleotides, conditions where cisplatin had no effect. DNA adducts with cyclobutylamine and cyclohexylamine ligands inhibited the hydrolysis of platinum-DNA complexes by S1 nuclease. Km for the digestion of DNA containing these lesions was 2.3 times greater than for cisplatin, indicating steric inhibition of enzyme-substrate complex formation. These results show that the non-leaving groups of substituted cis-Pt(II) compounds may destabilize DNA and interfere with protein-DNA interactions. These perturbations may have consequences for the genotoxic and antitumor activities of platinum compounds.

Awareness of substance abuse in orthopedic patients: a survey of orthopedic surgeons

We surveyed 178 orthopedic physicians in the Washington, DC, area to ascertain the effect on patient care of previous education in the area of drug and alcohol issues. The return rate was 75%. Of the respondents, 99% were male, average age was 46.7 years (+/- 9.3), and average number of years in practice was 15.2 (+/- 9.6). A majority of respondents indicated that they did not have training in the abuse potential of analgesics (92 [69%]), characteristics of benzodiazepine abuse (77 [58%]), or when to seek the assistance of an addiction medicine specialist for patients with chronic pain (106 [80%]). Only 41 (31%) of the orthopedists indicated that they inquire about alcohol and drug use before prescribing opiates for more than a week. We offer suggestions for self-education for interested physicians.

Teniposide and cisplatin given by intraperitoneal administration: preclinical and phase I/pharmacokinetic studies

Cisplatin and teniposide given by intraperitoneal (IP) route exert a synergistic therapeutic effect against ascitic P388 leukemia in mice. As single agents, they display different dose-limiting toxicities and favourable pharmacokinetic characteristics in IP phase I trials. We administered cisplatin (fixed dose: 200 mg/m2) and teniposide (escalating doses) by IP route without dwell-time to investigate the toxicity, pharmacokinetics and clinical activity of this 2-drug combination. Nine patients received a total of 14 courses. Myelosuppression, nausea and vomiting were the most frequent toxicities. Leukopenia was the dose-limiting toxicity. The maximum tolerated dose of teniposide was 100 mg/m2 when administered with a fixed dose of 200 mg/m2 cisplatin. Pharmacokinetic analysis showed that the main parameters of both cisplatin and teniposide in the peritoneum and in the plasma were not modified when the drugs were combined. It appears that a pharmacodynamic interaction exists between cisplatin and teniposide which results in increased hematologic toxicity. Although an objective response has been observed in one patient with refractory ovarian cancer, such association should not be applicable for further clinical development due to marked toxicity and the low dose of teniposide recommended.

The importance of street drug terms as diagnostic clues

"Words are both better and worse than thoughts; they express them and add to them" [Tyrone Edwards]. Choice of street terms is a clinical expression of the mental state and the drug history of the individual which evolves from repetition and frequent use. Broadened experiences usually accompany continued use, including experimentation with esoteric and powerful drug combinations. Drug terms employed by the user may have diagnostic utility for the experienced clinician in determining severity of symptoms. Recommendations for relapse prevention become more credible through a familiar lexicon. Practitioner understanding of drug terms as a tool to elicit information may lead to a deeper understanding of the breadth and depth of patient use of drugs. The authors recognize that they have contributed to the homogeneity, understanding, and distribution of terms by this article.

Biophysical studies of the modification of DNA by antitumour platinum coordination complexes

Cisplatin (cis-diamminedichloroplatinum(II] is widely used in the treatment of various human tumours. A large body of experimental evidence indicates that the reaction of cisplatin with DNA is responsible for the cytostatic action of this drug. Several platinum-DNA adducts have been identified and their effect on the conformation of DNA has been investigated. Structural studies of platinum-DNA adducts now permit a reasonably good explanation of the biophysical properties of platinated DNA. Antitumouractive platinum compounds induce in DNA, at low levels of binding, local conformational alterations which have the character of non-denaturing distortions. It is likely that these changes occur in DNA due to the formation of intrastrand cross-links between two adjacent purine residues. On the other hand, the modification of DNA by antitumour-inactive complexes results in the formation of more severe local denaturation changes. Conformational alterations induced in DNA by antitumour-active platinum compounds may be reparable with greater difficulty than those induced by the inactive complexes. Alternatively, non-denaturation change induced in DNA by antitumour platinum drugs could represent more significant steric hindrance against DNA replication as compared with inactive complexes.