[Hidden care needs in elderly people: a descriptive study of an outpatient geriatric consultation practice in the Netherlands]. / Verborgen zorgbehoeften bij ouderen : Ambulante geriatrische consultatie in de praktijk, een dossieronderzoek.

In general older adults, even the oldest old are community dwelling and vital. However, vulnerability can silently or suddenly exist. Multidisciplinary assessment of health problems and disabilities is necessary to compose a comprehensive intervention program. In the Netherlands, a team specialised in elderly care accomplishes home-based assessments. In 2009 we conducted a case study aiming to describe the characteristics of the patients and the reasons for consultation. A total of 84 records were analysed. 60% of the clients were 85 years or older, 32% were living independently and 61% were residents in homes for elderly people. The majority of clients was female and living alone (widowed). Most clients had multiple issues and were referred for cognitive evaluation. During the process of assessment many underlying behavioural, emotional and social problems became manifest. These findings support that symptoms and complaints of frail elderly are complex. A systematic multidisciplinary approach enhances the dialogue with patients and caregivers to discuss their needs and their attitude towards care. More research, however, is necessary to evaluate the effectiveness of this intervention.

[Psychiatric symptoms in systemic lupus erythematosus]. / Psychiatrische symptomen bij systemische lupus erythematosus.

BACKGROUND: This article focuses on two patients with psychiatric symptoms arising from systemic lupus erythematosus (SLE). Affective and psychotic symptoms frequently occur in SLE, often in combination with cognitive disturbances, and can be a first manifestation of the disorder. The diagnosis and treatment of a possible case of neuropsychiatric SLE should preferably take place in a multidisciplinary setting.

[The winter projects grey from the eyes]. / De winter kaatst grijs uit je ogen.

Selected texts derived from the edited diaries of an eighty year old man shed a light on the troubles of old age, declining health and wellbeing in a year prior to death. The author, Hans Warren (1921-2001) is a well known Dutch poet. Despite his poor physical condition and his mental frailty he confides his daily anguish and his lonely sufferings to his diary, resulting in an upsetting story of unhappiness and frustration. Although quite a few doctors are consulted, their advice seems inadequate or futile. The author's relationship with his supporting partner, who is nearly forty years his junior, suffers under the strain of daily conflicts and humiliating dependency. Despite all this they share moments of love and friendship until the end. The author expresses thankfulness for all things of beauty he can still enjoy.

Effect of cigarette smoke exposure on the modulation of 8-oxo-2'-deoxyguanosine in rat lungs as analyzed by 32P-postlabeling and HPLC-ECD.

Cigarette smoke contains several oxidants and free radicals. In the present study, we examined the formation of 8-oxo-2'-deoxyguanosine (8-oxodG) in the lungs of female Sprague-Dawley rats exposed to side-stream cigarette smoke for 6 h a day, 7 days a week for 1, 2, 4 and 12 weeks in a whole body-exposure system. The samples were analyzed for 8-oxodG by 32P-postlabeling-TLC enrichment and HPLC-ECD techniques to confirm and compare results. Animals were sacrificed 15 h after the cessation of smoke exposure and lung DNA was isolated by phenol/Sevag extractions in the presence of the free radical traps, 8-hydroxyquinoline (6.8 mM) and N-t-butyl-alpha-phenyl nitrone (500 microM) to minimize artifactual formation of 8-oxodG during sample work up. Analysis of lung DNA by 32P-postlabeling-TLC showed 8-oxodG levels (mean +/- SE) of 1.45+/-0.24, 2.68+/-0.65, 2.23+/-0.28 and 2.93+/-0.54 per 106 nucleotides after 1, 2, 4 and 12 weeks of smoke exposure. The respective values in sham-treated rats were 2.76+/-0.19, 3.69+/-0.20, 1.44+/-0.43 and 2.84+/-0.45 per 106 nucleotides, suggesting no significant effect of smoke exposure on tissue levels of 8-oxodG. HPLC-ECD procedure yielded slightly higher values for 8-oxodG in all groups, however, again significant differences between sham and smoke-exposed groups were not detected. It is concluded that the chronic exposure to side-stream cigarette smoke does not enhance the formation of 8-oxodG in rat lungs.

Risk assessment for surgical site infections following total hip and total knee prostheses.

The purpose of the study was to assess the relative importance of risk factors for surgical site infections (SSI) following total hip and total knee prostheses in The Netherlands. In the period 1996-99 63 hospitals in The Netherlands registered SSI after 36,629 orthopedic operations. Total hip and total knee prostheses were analyzed in detail. The results of our study showed that a long preoperative stay was a risk factor for deep SSIs after both procedures. A dirty or contaminated wound and a serious systemic condition were risk factors for deep SSIs after total hip prostheses. If post-discharge surveillance was carried out, more SSIs were found, for total knee prostheses more than twice as many. Independent risk factors for SSIs after total hip prostheses were a contaminated/dirty wound and for total knee prostheses a short operation duration. The authors conclude that surveillance of surgical site infections following total hip and total knee prostheses revealed different risk factors for (deep) SSIs.

Impact of hospital-wide surveillance on hospital-acquired infections in an acute-care hospital in the Netherlands.

The goal of surveillance is to identify hospital-acquired infections (HAI) and risk factors, to apply targeted interventions and to evaluate their effect in an ongoing system. Continuing active surveillance in a 270-bed acute-care hospital is being performed on clinical patients, excluding day-care. The period 1984-1997 is described here. Specific surveillance-based interventions included the introduction of antimicrobial prophylaxis in gynaecology patients with postoperative urinary tract catheters and inpatients scheduled for appendicectomy and hysterectomy. General measures included education, implementation of protocols, feedback of surgeon-specific infection rates. In total, 3545 HAI were found in 13 years of surveillance. The incidence was 4.7/100 admissions and 4. 5/1000 patient days. Age-specific incidences ranged from 1.3 in the age-category 1-14 years, to 10.2 in patients aged 75 years and above. If age-specific incidences had remained at their 1984 level, over 3000 additional infections would have occurred, affecting all age groups except those up to 14 years. The distribution of types of infections differed between services. Following the targeted interventions, the rate of infections in gynaecology decreased from 19.4 per 1000 patient days in 1984 to 2.4 per 1000 patient days in 1996. The rates of wound infection following appendicectomy and hysterectomy decreased by 69% and 82%, respectively, in the period following the institution of antimicrobial prophylaxis. Over 4000 micro-organisms were isolated from the HAI; multi-resistant strains were isolated sporadically. We conclude that hospital-wide surveillance of hospital-acquired infections provides appropriate targets for interventions tailored to the specific needs of the hospital. The impact of such interventions can readily be documented from the surveillance data.

An operating surveillance system of surgical-site infections in The Netherlands: results of the PREZIES national surveillance network. Preventie van Ziekenhuisinfecties door Surveillance.

OBJECTIVES: To describe the results of the first year of the Dutch national surveillance of surgical-site infections (SSIs) and risk factors, which aims to implement a standardized surveillance system in a network of Dutch hospitals, to collect comparable data on SSIs to serve as a reference, and to provide a basic infrastructure for further intervention research. DESIGN: Prospective multicenter cohort study. SETTING: Acute-care hospitals in The Netherlands from June 1996 to May 1997. RESULTS: 38 hospitals participated, with a slight over-representation of larger hospitals. Following a total of 18,063 operations, 562 SSIs occurred, of which 198 were deep. Multivariate analysis of pooled procedures shows that age, preoperative length of stay, wound contamination class, anesthesia score, and duration of surgery were independent risk factors for SSI. When analyzed by procedure, the relative importance of these risk factors changed. Bacteriological documentation was available for 56% of the SSIs; 35% of all isolates were Staphylococcus aureus. Multiple regression analysis computed the mean extra postoperative length of stay associated with SSI to be 8.2 days. CONCLUSION: The first year of national surveillance has shown that it is feasible to collect comparable data on SSI, which are already used for education, policy, and decision making in the network of participating hospitals. This gives room to effectuate the next aim, namely to use the network as an infrastructure for intervention research. Multivariate analysis shows that feedback on a procedure-specific level is important.

Risk assessment for surgical-site infections in orthopedic patients.

OBJECTIVE: To assess the relative importance of risk factors for surgical-site infections (SSIs) in orthopedic patients and thereby determine which risk factors to monitor in the national surveillance of SSI in The Netherlands. DESIGN: Reanalysis of data on SSI and associated risk factors from two surveillance projects on nosocomial infections, carried out in 1992 and 1993 in The Netherlands: Project Surveillance Nosocomial Infections in the region of Utrecht (PSZU) and the first Project Surveillance Surgical Wound Infections (SWIFT-1). Odds ratios (ORs) were calculated for age, gender, preoperative stay, and the number of operations. In addition, in PSZU, other nosocomial infections, and, in SWIFT-1, prophylactic antibiotics, acute surgery, and wound contamination were studied. PARTICIPANTS: The study was confined to hospitalized orthopedic patients (PSZU, 4,872; SWIFT-1, 6,437). RESULTS: In PSZU, the following ORs were significant in a multivariate model: age 0-44 years, 1.0; 45-64 years, 1.6; 65-74 years, 4.7; and 75-99 years, 6.0. For a preoperative stay over 4 days, the OR was 3.3 (95% confidence interval [CI95], 2.5-4.0), and for multiple surgery, 2.5 (CI95, 1.9-3.0). For females, the OR was 0.8 (not significant). The same model applied to SWIFT-1 gave similar ORs. Adjustment for additional nosocomial infections (PSZU) decreased the ORs for ages over 65 years remarkably. The OR for additional nosocomial infections in patients under 65 years of age was 15.6 (CI95, 4.3-57.4). Adjustment for prophylactic antibiotics, acute surgery, and wound-contamination class (SWIFT-1) did not influence the ORs of the original model, but showed that wound-contamination class was an important risk factor. CONCLUSIONS: Age, additional nosocomial infections, wound-contamination class, preoperative stay, and the number of operations were identified as important risk factors for SSI in Dutch orthopedic patients.

Nucleotide excision repair modulates the cytotoxic and mutagenic effects of N-n-butyl-N-nitrosourea in cultured mammalian cells as well as in mouse splenocytes in vivo.

The butylating agent N-n-butyl-N-nitrosourea (BNU) was employed to study the role of nucleotide excision repair (NER) in protecting mammalian cells against the genotoxic effects of monofunctional alkylating agents. The direct acting agent BNU was found to be mutagenic in normal and XPA mouse splenocytes after a single i.p. treatment in vivo. After 25 and 35 mg/kg BNU, but not after 75 mg/ kg, 2- to 3-fold more hprt mutants were detected in splenocytes from XPA mice than from normal mice. Using O6-alkylguanine-DNA alkyltransferase (AGT)-deficient hamster cells, it was found that NER-deficient CHO UV5 cells carrying a mutation in the ERCC-2 gene were 40% more mutable towards lesions induced by BNU when compared with parental NER-proficient CHO AA8 cells. UV5 cells were 1.4-fold more sensitive to the cytotoxic effects of BNU compared with AA8 cells. To investigate whether this increased sensitivity of NER-deficient cells is modulated by AGT activity, cell survival studies were performed in human and mouse primary fibroblasts as well. BNU was 2.7-fold more toxic for mouse XPA fibroblasts compared with normal mouse fibroblasts. Comparable results were found for human fibroblasts. Taken together these data indicate that the role of NER in protecting rodent cells against the mutagenic and cytotoxic effects of the alkylating agent BNU depends on AGT.

8-Hydroxydeoxyguanosine in DNA from leukocytes of healthy adults: relationship with cigarette smoking, environmental tobacco smoke, alcohol and coffee consumption.

8-Hydroxydeoxyguanosine (8-OHdG) has been widely used as a biomarker of oxidative DNA damage in both animal and human studies. However, controversial data exist on the relationship between 8-OHdG formation and age, sex and tobacco smoking in humans, while few or no data are available on other exposures such as environmental tobacco smoke, alcohol, coffee and tea consumption. We investigated the level of 8-OHdG in DNA from peripheral leukocytes among 102 healthy adults living in Brescia province, North Italy, aged 25-45 (mean: 35.2 years), of which 51 were males. 8-OHdG levels expressed as a ratio to total deoxyguanosine (8-OHdG/106 dG) in DNA showed wide interindividual variation, the highest value (63.8) being 6. 2-fold greater than the lowest (10.3). Current smokers showed lower mean 8-OHdG values than subjects who never smoked (29.3 and 34.0, respectively, p<0.05), and an inverse relationship was found between 8-OHdG and lifetime smoking, which was independent of age, sex and body mass index. An inverse relationship was also found with coffee drinking while no association was observed with alcohol and tea consumption, exposure to environmental tobacco smoke and use of vitamins in all subjects, and with use of oral contraceptives in females. The inverse relationship between smoking status and 8-OHdG levels could be explained by the presence of efficient repair processes for the oxidative damage induced by smoking. In this study, the smokers were relatively young (77% were less than 40 years) and only 7% smoked 30 or more cigarettes a day. In conclusion, it would appear that 8-OHdG levels in leukocytes may not provide a sensitive marker of exposure to tobacco smoking.

Elevated frequencies of benzo(a)pyrene-induced Hprt mutations in internal tissue of XPA-deficient mice.

Xeroderma pigmentosum (XP) patients are hypersensitive to sunlight and have a high predisposition to developing cancer. At the cellular level, XP patients are defective in nucleotide excision repair (NER). Recently, mice have been generated via gene targeting that are deficient in the expression of the XPA gene [A. de Vries et al., Nature (Lond.), 377: 169-173, 1995]. We have assessed the consequences of defective NER for mutagenesis in normal and XPA mice exposed to benzo(a)pyrene and 2-acetylaminofluorene. To study mutagenesis, mature T lymphocytes were isolated from the spleen and stimulated to proliferate in vitro to select for mutants at the endogenous Hprt locus. Background mutant frequencies in normal and XPA mice were very similar and not influenced by age. Single doses of benzo(a)pyrene administered i.p. resulted in a dose-dependent increase of the Hprt mutant frequency in normal mice. In addition, after chronic exposure to benzo(a)pyrene, Hprt mutants were readily detectable in XPA mice at an early onset of treatment but only at a later stage in normal mice. In contrast, chronic treatment of either normal or XPA mice with 2-acetylaminofluorene did not increase Hprt mutant frequency above the background frequency. This absence of significant induction of Hprt mutants can be entirely attributed to the low frequency of 2-acetylaminofluorene-induced DNA adducts in lymphoid tissue. These results provide the first direct evidence in mammals that deficient NER leads to enhanced mutagenesis in endogenous genes in internal tissue after exposure to relevant environmental mutagens, such as benzo(a)pyrene.

Lack of transcription-coupled repair of acetylaminofluorene DNA adducts in human fibroblasts contrasts their efficient inhibition of transcription.

The N-(deoxyguanosine-8-yl)-2-acetylaminofluorene (dG-C8-AAF) lesion is among the most helix distorting DNA lesions. In normal fibroblasts dG-C8-AAF is repaired rapidly in transcriptionally active genes, but without strand specificity, indicating that repair of dG-C8-AAF by global genome repair (GGR) overrules transcription-coupled repair (TCR). Yet, dG-C8-AAF is a very potent inhibitor of transcription. The target size of inhibition (45 kilobases) suggests that transcription inhibition by dG-C8-AAF is caused by blockage of initiation rather than elongation. Cockayne's syndrome (CS) cells appear to be extremely sensitive to the cytotoxic effects of dG-C8-AAF and are unable to recover inhibited RNA synthesis. However, CS cells exhibit no detectable defect in repair of dG-C8-AAF in active genes, indicating that impaired TCR is not the cause of the enhanced sensitivity of CS cells. These and data reported previously suggest that the degree of DNA helix distortion determines the rate of GGR as well as the extent of inhibition of transcription initiation. An interchange of the transcription/repair factor TFIIH from promoter sites to sites of damage might underlie inhibition of transcription initiation. This process is likely to occur more rapidly and efficiently in the case of strongly DNA helix distorting lesions, resulting in a very efficient GGR, a poor contribution of TCR to repair of lesions in active genes, and an efficient inhibition of transcription.

[Incidence of postoperative wound infections in The Netherlands]. / Frequentie van postoperatieve wondinfecties in Nederland.

OBJECTIVE: To inventory postoperative infections in Dutch hospitals. DESIGN: Descriptive study. SETTING: National organization for quality assurance in hospitals, Utrecht, the Netherlands. METHOD: In 36 Dutch hospitals data on surgical patients, surgical site infections and risk factors were collected, using standardised methods, as part of a quality system by which hospitals could compare their infection rates with the rates in the database. RESULTS: Surveillance of surgical site infections was introduced in 36/118 (31%) hospitals. Data on 32,869 surgical procedures were collected, 1115 (3.4%) surgical site infections were found. The infection rates by wound contamination class varied from 2.2% (95% confidence interval (CI): 2.0-2.4) in clean wounds to 11% (95% CI: 9.3-12.8) in dirty wounds; the infection rates by duration of operation varied from 3% (95% CI: 2.8-3.2) in operations lasting less than two hours to 10.8% (95% CI: 6.0-18.5) in operations lasting more than 8 hours; the infection rate by ASA classification varied from 2.7% (95% CI: 2.3-3.2) in class I to 15.5% (95% CI: 8.4-26.5) in patients in class IV. Advanced age, emergency, preoperative stay were recognised as risk factors. The infection rates in the most frequently recorded types of operation varied from 0.2% (95% CI: 0.0-1.1) in varicose veins to 9.8% (95% CI: 7.2-13.2) in femoral bypass grafts. The use of antimicrobial prophylaxis varied per type of operation. The micro-organisms most frequently isolated were Staphylococcus aureus. Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli. Of the infections 32% were identified in the first week following surgery. Of the infected patients 88% stayed in hospital during one or more days following the onset of infection.

Electrochemical detection and quantification of the acetylated and deacetylated C8-deoxyguanosine DNA adducts induced by 2-acetylaminofluorene.

The genotoxic agent 2-acetylaminofluorene induces, upon metabolic activation, two main types of DNA adducts in animal tissue, i.e., (deoxyguanine-8-yl)-aminofluorene (dG-C8-AF) and N-(deoxyguanine-8-yl)-acetylaminofluorene (dG-C8-AAF). Quantification of the frequency of these adducts usually relies on the use of radioactively labeled 2-acetylaminofluorene. Here, we report the development of a sensitive, non-radioactive method for the quantification of dG-C8-AF and dG-C8-AAF. Essentially, the modified DNA bases are separated by high-performance liquid chromatography (HPLC) and quantified by electrochemical detection. We established that both modified bases guanine-C8-aminofluorene and guanine-C8-acetylaminofluorene are electrochemically active. Subsequently, a procedure was developed to quantify dG-C8-AF and dG-C8-AAF in genomic DNA. Following DNA hydrolysis the adducted bases were extracted by ethyl acetate, separated by HPLC, and detected electrochemically. This procedure has been applied in the analysis of dG-C8-AAF in N-acetoxy-2-acetylaminofluorene-modified calf thymus DNA and in the detection of dG-C8-AAF and dG-C8-AF in liver DNA of mice injected intraperitoneally with 150-450 mg N-hydroxy-2-acetylaminofluorene/kg. The quantification of relatively low dG-C8-AF and dG-C8-AAF adduct levels (i.e., 0.1-1 adduct/10(6) nucleotides) in mouse liver DNA demonstrates the sensitivity of this electrochemical detection procedure. The detection limit of the method is 1 adduct per 10(6) nucleotides for both adducts using 20 micrograms of DNA and 4 adducts per 10(8) nucleotides using 500 micrograms DNA.

Determination of N7- and O6-methylguanine in rat liver DNA after oral exposure to hydrazine by use of immunochemical and electrochemical detection methods.

Hydrazine belongs to a group of compounds for which there is evidence that the in vivo genotoxic effects become manifest only upon exposure to toxic dose levels. The present study was performed to investigate whether this phenomenon is also reflected in the pattern of DNA methylation. The induction of N7- and O6-methylguanine (MeGua) was studied in liver DNA of rats, 16 hr after treatment with various doses of hydrazine. After DNA isolation, the presence of N7-MeGua in DNA was assessed with an immunochemical method and with a physicochemical technique (HPLC with electrochemical detection). Application of these two methods resulted in almost identical patterns of dose-dependent induction of guanine N7-methylation in rats dosed orally with 0.1 to 10 mg hydrazine per kilogram of body weight, increasing from 1.1-1.3 to 39-45 N7-MeGua per 10(6) nucleotides. At lower dosages a constant adduct level was observed, equivalent to that in untreated rats (background level). The O6-MeGua level was analyzed by a combination of HPLC separation and competitive radioimmunoassay. A background level was observed for untreated rats and no increase was visible up to the 0.2 mg/kg dose group. After hydrazine doses from 0.2 to 10 mg/kg, O6-MeGua increased from 0.29 to 134 per 10(9) nucleotides. These data show that even at dosages below the maximum tolerated dose (0.6 mg/kg/day), for which carcinogenic effects have not been described, DNA adducts are formed. A comparison is made of the data obtained in this study with models that describe the mechanism of hydrazine-induced DNA methylation.

Sentinel system for nosocomial infections in The Netherlands: a pilot study.

OBJECTIVE: To determine the feasibility of standardized surveillance of nosocomial infections (NI) in The Netherlands, using local data on patients with NI collected by infection control practitioners (ICPs) and denominator data on all patients under surveillance obtained from the Dutch National Medical Registry (LMR). DESIGN: A prospective, multicenter study. SETTING: Eight hospitals in the Utrecht region, and the National Institute of Public Health and the Environment. PATIENTS: ICPs traced NI in gynecological and orthopedic patients for 9 to 16 months. Denominator data on all patients under surveillance were obtained from the LMR. RESULTS: Data from 8,922 patients were collected; the ICPs registered 470 patients with 526 NI. Overall, the NI incidence was 5.9 per 100 patients, or 6.3 per 1,000 patient days. Urinary tract infections (UTI) were most frequent (3.3%), followed by surgical-wound infections (SWI; 2.0%) and bloodborne infections (0.12%). The incidence of both SWI and UTI differed markedly between hospitals, only partially on account of differences in patient mix (age, type of operations), antibiotic prophylaxis, and intensity of tracing methods for NI. Delay in the availability of denominator data hampered the timely feedback of incidence figures. CONCLUSIONS: Surveillance of NI in a network of sentinel hospitals offered valuable information on the occurrence of NI and on factors influencing the incidence of NI. It revealed situations in which both NI surveillance and infection control methods in individual hospitals should be improved. Obtaining denominator data on all patients from electronically registered patient discharge data greatly reduces the workload of ICPs and enables surveillance on all types of NI (all body sites and all pathogens). For timely feedback, numerator and denominator data within hospitals must be linked.

Induction of hprt gene mutations in splenic T-lymphocytes from the rat exposed in vivo to DNA methylating agents is correlated with formation of O6-methylguanine in bone marrow and not in the spleen.

The suitability of splenic T-lymphocytes as a substitute tissue for detection of genotoxic effects induced in vivo by chemical agents that are organ-specifically activated was tested in rats exposed to single doses at the potent lung-carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), acetoxymethylmethylnitrosamine (AMMN) or N-methyl-N-nitrosourea (MNU). NNK, AMMN and MNU methylate DNA most likely via the formation of a methanediazohydroxide ion that decomposes to a methyl diazonium ion. For all three agents, an increase in the levels of 06-methylguanine and 7-methylguanine in DNA of rat liver and lung was detected by reverse phase HPLC and electrochemical detection. Treatment with NNK did not result in the formation of O6-methylguanine and 7-methylguanine in DNA of bone marrow and spleen, corresponding with the absence of metabolic activation pathways for this compound in these tissues. For AMMN formation of both 06-methylguanine and 7-methylguanine was detectable in DNA of the spleen, whereas in DNA of bone marrow only very low frequencies of 7-methylguanine were found at a toxic dose. MNU induced O6-methylguanine and 7-methylguanine in both spleen and bone marrow. Using splenic T-lymphocytes from the rat no increase above control levels of the hprt mutant frequencies was found for NNK and AMMN for all exposure levels tested, 32 days after chemical exposure. For MNU a dose-dependent increase in hprt mutant frequency was found at exposure levels of 0.097 mmol/kg up to 0.582 mmol/kg. DNA sequence analysis was performed on PCR products of hprt cDNA from 39 MNU-induced 6-thioguanine-resistant T-lymphocyte clones. Single base pair substitutions were found in 25 of these mutants (64%), GC-->AT transitions being the predominant type of mutation (19 of 25; 76%). These mutations are probably caused by mispairing of 06-methylguanine with thymine during DNA replication. The results indicate that formation of mutagenic lesions in the spleen is not correlated with an enhanced frequency of 6-thioguanine-resistant splenic T-lymphocyte clones from rats, 32 days after exposure in vivo to DNA damaging agents. This suggests that mutation-fixation in T-lymphocytes does not occur in the spleen but at other sites in the body such as bone marrow, after which these mutated cells migrate to the spleen.

Molecular dosimetry of 7-alkyl- and O6-alkylguanine in DNA by electrochemical detection.

A methodology is described for the quantitation of 7-alkyl- and O6-alkylguanine in DNA isolated from experimental animals exposed to alkylating agents. Following purification, the DNA is hydrolysed under acid conditions after which 7-alkyl- and O6-alkylguanine are separated from unmodified bases by HPLC using a strong cation exchange column. The fractions containing the methylated purines are subsequently analyzed by HPLC using a reverse phase column coupled to an electrochemical detector (amperometric). This method allows the detection of 10-20 fmoles 7-alkyl- and O6-alkylguanine, when pure markers are analyzed. In practice, the detection limit is 0.5 adducts per 10(6) nucleotides for the methylated and 1 adduct per 10(6) nucleotides for the ethylated form of 7-alkyl- and O6-alkylguanine using 25 micrograms DNA.