Distinct mechanisms of nonhomologous end joining in the repair of site-directed chromosomal breaks with noncomplementary and complementary ends.

DNA double-strand breaks (DSBs) are considered the most important type of DNA damage inflicted by ionizing radiation. The molecular mechanisms of DSB repair by nonhomologous end joining (NHEJ) have not been well studied in live mammalian cells, due in part to the lack of suitable chromosomal repair assays. We previously introduced a novel plasmid-based assay to monitor NHEJ of site-directed chromosomal I-SceI breaks. In the current study, we expanded the analysis of chromosomal NHEJ products in murine fibroblasts to focus on the error-prone rejoining of DSBs with noncomplementary ends, which may serve as a model for radiation damage repair. We found that noncomplementary ends were efficiently repaired using microhomologies of 1-2 nucleotides (nt) present in the single-stranded overhangs, thereby keeping repair-associated end degradation to a minimum (2-3 nt). Microhomology-mediated end joining was disrupted by Wortmannin, a known inhibitor of DNA-PKcs. However, Wortmannin did not significantly impair the proficiency of end joining. In contrast to noncomplementary ends, the rejoining of cohesive ends showed only a minor dependence on microhomologies but produced fivefold larger deletions than the repair of noncomplementary ends. Together, these data suggest the presence of several distinct NHEJ mechanisms in live cells, which are characterized by the degree of sequence deletion and microhomology use. Our NHEJ assay should prove a useful system to further elucidate the genetic determinants and molecular mechanisms of site-directed DSBs in living cells.

[Markedly increasing incidence of apoplexy among men. A clinical, epidemiologic study of apoplexy incidence between 1972 and 1990 in the municipality of Frederiksberg]. / Markant stigning i apopleksiincidensen blandt maend. En klinisk, epidemiologisk undersøgelse af apopleksisygdommens incidens mellem 1972 og 1990 i Frederiksberg Kommune.

The purpose of this study was to determine possible temporal changes of stroke incidence in a European community. All cases of first-ever stroke (n = 927) were prospectively recorded in the municipality of Frederiksberg, Denmark, in the two periods 1972-1974 and 1989-1990. Complete case ascertainment was ensured by registration of both hospitalized and nonhospitalized patients. Death certificates were also scrutinized. The annual stroke incidence rate per 1000 increased by 18% from 2.6 in 1972-1974, to 3.1 in 1989-1990 (p < 0.01). This increase was due solely to a 42% increase in men, for whom stroke incidence rose from 2.1 to 3.0 (p < 0.0005). Incidence was unchanged in women, 3.0 and 3.1 respectively. In the second study period 85% had CT or necropsy; 91% had cerebral infarction; 8% had intracerebral haemorrhage and 1% had subarachnoid haemorrhage. In a period when decline in stroke incidence has stopped in USA and has continued in Japan, a marked increase in stroke incidence in European men was observed.

[Apoplexy units--reduced mortality, need for nursing homes, length of stay and cost savings]. / Apopleksiafsnit--reducerer dødelighed, plejehjemsbehov, liggetid og sparer penge.

Treatment of stroke patients on specialised stroke units has become more frequent, yet the effect of this treatment has not been determined. In this prospective, community-based study of 1241 unselected acute stroke patients we compared outcome between patients geographically randomised to treatment on a stroke unit or a general neurological/medical ward, from the time of acute admission to the end of rehabilitation. Baseline characteristics were comparable between the two treatment groups regarding age, sex, marital status, prestroke residence, and stroke severity. The patients treated on the stroke unit had higher comorbidity with regard to hypertension and diabetes. Multivariate linear and logistic regression analyses were applied to estimate the independent influence of stroke unit treatment on outcome. Stroke unit treatment significantly reduced in-hospital mortality (OR 0.50), case-fatality rate (OR 0.45), 6-month mortality (OR 0.57), 1-year mortality (0.59, and discharge rate to a nursing home (OR 0.61). The relative chance of being discharged to own home was almost doubled (OR 1.9), and the length of hospital stay reduced by 30% in patients treated on the stroke unit, P < 0.001. Treatment of unselected stroke patients on a stroke unit saves lives, nursing homes, and cost.

[Treatment and rehabilitation in an apoplexy unit increases the 5-year survival]. / Behandling og rehabilitering på apopleksiafsnit øger 5-års-overlevelsen.

Treatment of stroke patients in specialised stroke units has become more frequent, but the longterm effect of this treatment has not been determined. In this prospective, community-based study of 1241 unselected acute stroke patients we compared outcome between patients geographically randomised to treatment in a stroke unit or in a general neurological/medical ward, from the time of acute admission to the end of rehabilitation. Baseline characteristics were comparable between the two treatment groups regarding age, sex, marital status, pre-stroke residence, and stroke severity. Patients treated in the stroke unit had higher comorbidity with regard to hypertension and diabetes. Multivariate linear and logistic regression analyses were applied to estimate the independent influence of stroke unit treatment on outcome. Stroke unit treatment significantly reduced not only initial mortality, but also mortality within five years from stroke onset. The relative risk of dying within the first five years from stroke was reduced by 40%, p < 0.01. Treatment and rehabilitation of unselected stroke patients in a stroke unit reduces initial mortality, discharge rate to nursing home, reduces cost of treatment, and improves longterm survival up to five years after stroke.

Marked increase of stroke incidence in men between 1972 and 1990 in Frederiksberg, Denmark.

BACKGROUND AND PURPOSE: Stroke incidence declined until the end of the 1970s in the United States, and the decline continued into the 1980s in Japan. The purpose of this study was to determine possible temporal changes of stroke incidence in a European community. METHODS: A prospective stroke registry was established in the community of Frederiksberg (population, approximately 90,000), Denmark, in the two periods 1972-1974 and 1989-1990. All patients suspected of stroke were clinically evaluated by a neurologist. Only patients with first-ever stroke were included. Complete case ascertainment was ensured by registration of both hospitalized and nonhospitalized patients. Death certificates were also scrutinized. RESULTS: A total of 927 patients with first-ever stroke was recorded. The annual stroke incidence rate per 1,000 increased by 18% from 2.6 in 1972-1974 to 3.1 in 1989-1990 (p < 0.01). This increase was due solely to a 42% increase in men, in whom stroke incidence rose from 2.1 to 3.0 (p < 0.0005). Incidence was unchanged in women at 3.0 and 3.1, respectively. The incidence rates from 1972-1974 were age and sex adjusted to the 1990 population. After adjustment to the Danish population, stroke incidence in Denmark was 2.0 for all, 2.3 for men, and 1.9 for women. In the second study period computed tomography or necropsy was performed in 85% of cases; 2.4/1,000 had cerebral infarction; 0.20/1,000 had intracerebral hemorrhage; and 0.02/1,000 had subarachnoid hemorrhage. CONCLUSIONS: In a period when decline in stroke incidence has stopped in the United States and has continued in Japan, a marked increase of stroke incidence in Danish men was observed.

Homologous recombination in extrachromosomal plasmid substrates is not suppressed by p53.

We and others reported previously that the tumor suppressor p53 down-regulates spontaneous homologous recombination in chromosomally integrating plasmid substrates, but how p53 affects homology-dependent repair of DNA double-strand breaks has not been established. Furthermore, it has been hypothesized that p53 may suppress homologous recombination by direct interaction with recombination intermediates, but it is not known whether p53 directly acts on extrachromosomal plasmid substrates. In the present study, we asked whether p53 can suppress extrachromosomal spontaneous and double-strand break-induced homologous recombination. A plasmid shuttle assay was employed utilizing episomally replicating substrates, which carried mutated tandem repeats of a CAT reporter gene. Spontaneous homologous recombination and homology-dependent repair of double-strand breaks induced by the I-SceI nuclease led to reconstitution of the reporter. Extrachromosomal homologous recombination was found to proceed independently of the p53 status of isogenic mouse fibroblast lines, contrasting the p53-mediated suppression of chromosomal recombination. The lack of p53 effect applied not only to the dominating single-strand annealing pathway, which is Rad51-independent, but also to Rad51-dependent gene conversion events. Comparison of homologous and non-homologous recombination frequencies revealed similar contributions to the repair of I-SceI-induced breaks irrespective of p53 status. Our results are consistent with a model in which the regulation of homologous recombination by p53 is restricted to the highly ordered chromosomal chromatin structure. These data may serve as a cautionary note for future investigations using solely extrachromosomal model systems to address DNA repair in intact cells.

Clonidine in the prophylaxis of migraine.

The prophylactic effect of clonidine in a dosage of 0.05 mg twice daily was investigated in 49 patients using a double-blind, crossover trial carried out in four Departments of Neurology. Seventy-one patients were originally included but 22 patients withdrew, two of them due to side effects,the remainder because of inability to keep the requisite diary, lack of drug compliance or refusal to attend the checkups. Approximately equal numbers withdrew during the clonidine and placebo periods. There was no statistically significant difference between the number of migraine attacks or between the number of severe attacks (8 hours' duration or more) during the placebo and clonidine periods. This also applied to the patients with foodstuff-provoked migraine attacks. Sixty-three patients carried through a double-blind, crossover trial with capsules containing either 125 mg tyramine or placebo. There was no significant difference between the number of patients who developed attacks after the ingestion of placebo and the number who did so after the ingestion of tyramine. The same is true of the group with foodstuff-provoked migraine. As a rule side effects were few and mild. This study has not confirmed that clonidine has any pharmacological effect in prophylaxis of migraine.

The effect of a stroke unit: reductions in mortality, discharge rate to nursing home, length of hospital stay, and cost. A community-based study.

BACKGROUND AND PURPOSE: Treatment of stroke patients in specialized stroke units has become more frequent, yet the effect of this treatment has not been determined. METHODS: In a community-based, prospective, and consecutive study of 1241 unselected acute stroke patients, we compared outcome of stroke treatment between two neighboring communities within Greater Copenhagen: the Bispebjerg community, where all acute stroke patients are treated and rehabilitated on a stroke unit, and Frederiksberg community, where all acute stroke patients are treated and rehabilitated on general neurological and medical wards. Except for the different organization of stroke treatment, the two communities and the two patient groups were comparable. Specifically, age, sex, marital status, prestroke residence, and stroke severity were not statistically different between patients treated on the stroke unit and those treated on the general neurological and medical wards. Multivariate regression analyses were used to estimate the independent influence of stroke unit treatment on outcome. RESULTS: Stroke unit treatment significantly reduced in-hospital mortality (odds ratio [OR], 0.50; 95% confidence interval [CI], 0.34 to 0.74; P < .001), case-fatality rate (OR, 0.45; CI, 0.28 to 0.71; P < .001), 6-month mortality (OR, 0.57; CI, 0.39 to 0.82; P = .002), 1-year mortality (OR, 0.59; CI, 0.42 to 0.84; P = .003), and discharge rate to a nursing home (OR, 0.61; CI, 0.38 to 0.98; P = .04). Discharge rate to the patient's own home was significantly increased (OR, 1.90; CI, 1.30 to 2.70; P < .001). The length of hospital stay (including rehabilitation) was reduced significantly by 30% in patients treated on the stroke unit despite their lower mortality (P < .001). The savings due to stroke unit treatment were estimated at 1313 bed-days and three places at a nursing home per 100 stroke patients. CONCLUSIONS: Treatment of unselected acute stroke patients on a stroke care unit saved lives, reduced the length of hospital stay, reduced the frequency of discharge to a nursing home, and potentially reduced cost.

Treatment and rehabilitation on a stroke unit improves 5-year survival. A community-based study.

BACKGROUND AND PURPOSE: We have previously reported a marked reduction in mortality up to 1 year after treatment and rehabilitation on a stroke unit versus on general neurological and medical wards in unselected stroke patients. In the present study we wanted to test the hypothesis that this mortality-reducing effect is not temporary but is long lasting. METHODS: We performed a community-based comparison of outcome in 1241 stroke patients from 2 adjacent communities in Copenhagen: in one (Frederiksberg), treatment and rehabilitation were provided on general neurological and medical wards, and in the other (Bispebjerg), treatment and rehabilitation were provided on a single large stroke unit. RESULTS: The 2 stroke populations were comparable regarding age, sex, initial stroke severity, lesion diameter on CT, and stroke subtype (hemorrhage/infarct), but patients treated on the stroke unit had a higher frequency of comorbidity and lower incomes. One-year mortality was 39% (general wards) versus 32% (stroke unit) (P=0.01). This difference was still present 5 years after stroke (71% versus 64%; P=0.02). In a multiple logistic regression model of 5-year mortality, treatment on a stroke unit reduced the relative risk of death by 40% (odds ratio, 0.60; 95% CI, 0.42 to 0.85; P<0.01), independent of age, sex, stroke severity, and comorbidity. CONCLUSIONS: The mortality-reducing effect of treatment and rehabilitation on a dedicated stroke unit is long lasting rather than temporary. Stroke unit treatment reduced the relative risk of death within 5 years after stroke by 40% in an unselected, community-based stroke population. These results emphasize the need for organization of treatment and rehabilitation of unselected stroke patients on dedicated stroke units.

Who benefits from treatment and rehabilitation in a stroke Unit? A community-based study.

BACKGROUND AND PURPOSE: The beneficial effects of treatment and rehabilitation of patients with acute stroke in a dedicated stroke unit (SU) are well established. We wanted to examine if these effects are limited to certain groups of patients or if they apply to all patients independent of age, sex, comorbidity, and initial stroke severity. METHODS: This was a community-based study of outcome in 1241 consecutive stroke patients from 2 communities in Copenhagen: In one (Frederiksberg), treatment and rehabilitation were given in general neurological and medical wards (GW), and in the other (Bispebjerg) in one single large SU. Outcome measures were initial, 1-year, and 5-year mortality rates, a poor outcome (initial death or discharge to a nursing home), and length of hospital stay (LOHS). Multivariate regression analyses were used to examine the independent effect of SU treatment on the various subgroups. RESULTS: The relative risks of initial death, poor outcome, and 1-year and 5-year mortality rates were reduced by 40% on average in patients treated in the SU compared with the GW. A beneficial effect of SU treatment was observed regardless of the patient's age, sex, comorbidity, and initial stroke severity. Those who benefited most appeared to be the patients with the most severe strokes (poor outcome: OR 0.17; 95% CI 0.05 to 0.58). Those who benefited least were patients with mild or moderate strokes (poor outcome: OR 0.66; 95% CI 0.41 to 0.98) and patients <75 years of age (poor outcome: OR 0.66; 95% CI 0.36 to 1.19). LOHS was reduced by 2 to 3 weeks in all who had their treatment in the SU except in patients with the most severe strokes. LOHS in these patients was similar to LOHS in the GW. CONCLUSIONS: A beneficial effect of treatment in a SU is achieved in completely unselected patients independent of their age, sex, comorbidity, and stroke severity. Those who had the most severe strokes appeared to benefit most. All patients with acute stroke should therefore have access to treatment and rehabilitation in a dedicated SU.