Mammalian mitochondria possess homologous DNA recombination activity

Mitochondrial protein extracts from normal and immortalized mammalian somatic cells catalyze homologous recombination of plasmid DNA substrates. Mitochondrial homologous recombination activity required exogenous adenosine triphosphate, although substantial activity remained when non-hydrolyzable analogs were used instead. There was no requirement for added nucleoside triphosphates, and the reaction was not inhibited by dideoxyadenosine triphosphate or aphidicolin. The majority of recombinant plasmid molecules result from a conservative process, indicating that nuclease-mediated strand-annealing is not responsible for the mitochondrial homologous recombination activity. Affinity-purified anti-recA antibodies inhibited the reaction, suggesting that activity is dependent on a mammalian mitochondrial homolog of the bacterial strand-transferase protein. The presence of homologous recombination activity within mammalian mitochondrial extracts suggests that this process is involved in mitochondrial DNA repair.

A phase III, multicenter, open-label, randomized, comparative study evaluating the effect of sevoflurane versus isoflurane on the maintenance of anesthesia in adult ASA class I, II, and III inpatients

STUDY OBJECTIVE

To compare the clinical efficacy and safety of sevoflurane and isoflurane when used for the maintenance of anesthesia in adult ASA I, II, and III inpatients undergoing surgical procedures of at least 1 hour's duration.

DESIGN

Phase III, randomized, open-label clinical trial.

SETTING

12 international surgical units.

PATIENTS

555 consenting inpatients undergoing surgeries of intermediate duration.

INTERVENTIONS

Subjects received either sevoflurane (n = 272) or isoflurane (n = 283) as their primary anesthetic drug, each administered in nitrous oxide (N2O) (up to 70%) and oxygen (O2) after an intravenous induction using thiopental and low-dose fentanyl. The concentration of volatile drug was kept relatively constant but some titration in response to clinical variable was permitted. Comparison of efficacy was based on observations made of the rapidly and ease of recovery from anesthesia and the frequency of untoward effects for the duration of anesthesia in the return of orientation. Safety was evaluated by monitoring adverse experiences, hematologic and non-laboratory testing, and physical assessments. In 25% of patients (all patients 171 both treatment groups at selected investigational sites), plasma inorganic fluoride concentrations were determined preoperatively, every 2 hours during maintenance, at the end of anesthesia, and at 1, 2, 4, 8, 12, 24, 48, and 72 hours postoperatively.

MEASUREMENTS AND MAIN RESULTS

Emergence, response to commands, orientation, and the first request for postoperative analgesia were all more rapid following discontinuation of sevoflurane than following discontinuation of isoflurane (sevoflurane, 11.0 +/- 0.6, 12.8 +/- 0.7, 17.2 +/- 0.9, 46.1 +/- 3.0 minutes, respectively, versus isoflurane, 16.4 +/- 0.6, 18.4 +/- 0.7, 24.7 +/- 0.9, 55.4 +/- 3.2 minutes). The incidence of adverse experiences was similar for sevoflurane and isoflurane patients. Forty-eight percent of patients on the sevoflurane group had no untoward effect versus 39% in the isoflurane group. Three patients who received sevoflurane had serum inorganic fluoride levels 50 microM/I. or greater though standard tests indicated no evidence of associated renal dysfunction.

CONCLUSION

Sevoflurane anesthesia, as compared with isoflurane, may be advantageous in providing a smoother clinical course with a more rapid recover.

Characterization of homologous DNA recombination activity in normal and immortal mammalian cells

Homologous DNA recombination levels were measured in normal and spontaneously immortalized murine and human fibroblasts, and in a number of primate and murine established fibroblast cell lines. Immortal cell lines and tumor-derived clones homologously recombined extrachromosomal plasmid substrates at frequencies approximately 100-fold higher than did normal cells. To further explore the mechanism responsible for this phenotype, homologous recombination frequency was measured using nuclear extracts derived from normal and immortalized murine and human fibroblasts. Extracts prepared from immortal cells catalyzed high levels of homologous recombination, whereas very little recombination activity was detected in extracts prepared from normal fibroblasts. Similarly, only extracts derived from immortal cells contained strand-transferase activity as measured by the recently described pairing-on-membrane assay. Mixing experiments indicated that a recombination enhancing factor or factors present in immortal cells, rather than a recombination inhibitor in normal cells, was responsible for the enhanced homologous recombination activity observed using extracts derived from the former.

Breastfeeding and health in the Western world

Considerable evidence suggests that infant feeding practices are associated with variations in health. This paper reviews research relating to the health of infants who receive breast milk, and of women who breastfeed, in the developed world. Obstacles to breastfeeding are examined, and current initiatives to increase breastfeeding levels are discussed.

Prevalence and impact of exposure to interpersonal violence among suburban and urban middle school students

OBJECTIVE

The purpose of this study was to determine the prevalence of exposure to violence in preadolescent children in communities that vary by family income and to determine patterns of physical symptomatology and communication after exposure to a traumatic event.

METHODS

Two hundred twenty-eight sixth-grade students from a suburban middle school (school A) and 209 sixth-grade students from an urban middle school (school B) in the Philadelphia metropolitan area were surveyed by a group-administered anonymous questionnaire.

RESULTS

Two hundred two students (89%) from school A and 200 students (96%) from school B reported knowing someone who had been robbed, beaten, stabbed, shot, or murdered. One hundred twenty-nine students (57%) and 183 students (88%), respectively, witnessed a robbing, beating, stabbing, shooting, or murder. Ninety-one students (40%) and 141 students (67%) had been personally robbed, beaten up, stabbed, shot, or caught in gun cross fire. One hundred thirty-four (59%) and 152 (73%) reported hearing gunfire in their neighborhood. One hundred eighty-eight (82%) and 202 (97%) had at least one positive response in all three categories: knowing a victim, witnessing an event, and being a victim of violence. The proportion of positive responses from school B was significantly greater than the proportion from school A for all of these results. Many students reported symptoms associated with somatization syndromes, depression, and posttraumatic stress disorder; the school B group had significantly more symptoms than the school A group. Both student groups had discussed episodes of witnessing an event or victimization with others, mostly family members and friends, and expressed feelings of fear, anger, sadness, and frustration about these episodes. A very low percentage of the students (from 1% to 8% in the different analyses) consulted a medical or mental health professional.

CONCLUSIONS

These data support a substantial prevalence or exposure to violence for suburban and, even more dramatically, for urban middle school-aged children. The higher-prevalence group reported a higher incidence of symptoms sometimes seen after traumatic stress. Many students in both groups expressed multiple feelings about their exposure to violence, and most talked to someone about their exposure; rarely was this person a health professional.

Use of sodium hetastarch (Hespan) solution for reduction of postoperative adhesion formation in rabbits

A study was conducted to determine the effect of sodium hydroxy ethyl starch (Hespan) on primary adhesion formation in a rabbit model. Hespan is a readily available volume expander. This was a randomized, double-blinded animal model in which New Zealand white rabbits were subjected to midline celiotomy. Adhesions were created by abrasion in both uterine horns, adjacent bowel, and peritoneum. Necropsies were performed at the 2-week interval and adhesions were graded. Significant decreases in type II and type III adhesions (p = .032 and p = .020, respectively) were demonstrated in Hespan-treated animals. Sodium hetastarch appears to decrease significant adhesion formation in treated animals and may have a role as an adjunct for postsurgical prevention.

Assessment of clinical decision-making ability of critical care nurses

What are nurse administrators to do when their institution is in need of competent nurses to staff the ICU and the majority of applicants are either inexperienced or new graduates? Nurses from one institution grappled with this question. They decided that it was their job to teach novice nurses to make sound clinical judgments in life-threatening situations. As part of this process, they developed a Clinical Decision-Making Assessment (CDMA) tool. This article describes the CDMA and provides suggestions for classroom and clinical teaching.

Anabolic-androgenic steroid use among 133 prisoners

We performed a forensic evaluation of a 16-year-old boy convicted of murdering his 14-year-old girlfriend while he was taking anabolic steroids. Prior to steroid use, he had displayed no features of antisocial personality disorder and no criminal record. Prompted by this index case, we interviewed 133 consecutive male convicts at the same facility where this boy was incarcerated to assess whether steroid use frequently contributed to criminal acts. Two other cases of apparent steroid-induced crimes were found in this cohort, suggesting that steroid use is an uncommon, though occasionally significant, factor in criminal behavior.

Elevated levels of recombinational DNA repair in human somatic cells expressing the Saccharomyces cerevisiae RAD52 gene

The Saccharomyces cerevisiae RAD52 gene was introduced into the human fibrosarcoma-derived cell line HT1080. Transfected cell lines that expressed the yeast transgene catalyzed inter-plasmid homologous DNA recombination at frequencies approx. 12-fold higher than did control cells. Additional experiments revealed that yeast RAD52 gene expression increased the level of resistance to the DNA damaging agents diepoxybutane, and methyl methanesulfonate, but did not alter sensitivity to ultraviolet radiation. These results indicate that the S. cerevisiae Rad52 protein can function in a human somatic cell background and provide support for the idea that a homologous recombination-based DNA repair process functions in mammalian somatic cells.

Financial performance of safety-net hospitals in a changing health care environment

Safety-net hospitals serving the poor and indigent in inner-cities have received inadequate research attention regarding the determinants of their financial performance in the changing health care environment. We analyze how the 1990-92 financial performance of 275 such hospitals is related to exogenous and endogenous factors such as payer mix, service mix, staffing and ownership. Models of hospital financial performance are developed using operating margin, cost per discharge and revenue per discharge as measures of performance. Stepwise regression is used to test the model with data from the American Hospital Association (AHA) and Health Care Investment Analysts (HCIA). Results suggest that: 1) The profitability of inner-city hospitals appears positively related with technical complexity of care; 2) High interest and low operating surplus may constrain the addition of technically sophisticated services to enhance profitability; 3) There is some evidence that new governmental programs, e.g. Medicaid managed care and Medicaid Diagnosis Related Groups (DRGs), may not have improved operating margins, though Medicaid DRGs appear to have contained costs. Follow-up research is needed on this issue; 4) Given external fiscal realities, internal management strategies for inner-city hospitals require research, e.g. developing appropriate managed care systems and timely expansion of sub-acute services and; 5) Services such as AIDS treatment and community health education represent opportunities to respond to community needs, especially since unit cost of such services will decline with high volume.

[Initial experience with the PCDiary: software for physicians for documenting and evaluating individual learning]

A computer diary was developed for physicians to create a portfolio of their self-directed learning. Each item of learning is recorded in the form of a question along with the stimulus, the learning resources used and the outcome planned for the learning. The records of 123 physicians which volunteered to use the diary were analyzed. Their response to the software, elicited by survey, is described. Items of learning were most often stimulated by scanning the literature and while seeking information to manage a patient. The physicians recorded their intent to change their practice as the outcome to learning most often when the learning was stimulated while managing a patient. One-half of the physicians reported that keeping the diary made them think about their patient care.

Effects of a child abuse prevention unit in health classes in four schools

The purpose of this study was to assess changes in parenting attitudes among high school students as an effect of a child abuse prevention unit taught in a required health class. Attitudes were measured using the Adult-Adolescent Parenting Inventory (AAPI), which was administered as a pretest-posttest. This was a primary prevention approach targeting students before they become parents. The unit consisted of an overview of child abuse, normal developmental expectations of children, anger management, and positive parenting techniques. Students from 4 schools participated in the study, and most students in the sample (N = 585) demonstrated healthy parenting attitudes. Low scores on multiple scales at pretest were recorded for 3.6% of the sample. Effect of intervention was measured using paired t tests, and a positive and statistically significant effect of intervention was noted, especially in 2 of 4 schools. Low-scoring students increased scores significantly although not up to mean pretest levels for the whole sample. Recommendations for further community health nursing research and educational initiatives are supported by these findings.

Cloning and characterization of HuR, a ubiquitously expressed Elav-like protein

The neuronal-specific Elav-like proteins (HuD, Hel-N, and HuC) contain three RNP-type concensus motifs and bind to AU-rich elements. We have identified and cloned a fourth member of this family (HuR) that is expressed in a wide variety of cell types. The purified recombinant protein binds avidly to the AU-rich element in c-fos and interleukin-3 mRNAs. In the case of the c-fos AU-rich element, HuR binds to a core element of 27 nucleotides that contain AUUUA, AUUUUA, and AUUUUUA motifs. Mutational analysis has shown that all three AU motifs are required for maximal binding.

Phase I/II trial of biweekly paclitaxel and cisplatin in the treatment of metastatic breast cancer

PURPOSE

To determine the maximum-tolerated dose of escalating doses of paclitaxel (Taxol; Bristol-Myers Squibb, Princeton, NJ) administered biweekly with a fixed dose of cisplatin, to assess the toxicity, and to evaluate the activity of this combination in a phase I/II trial in metastatic breast cancer.

PATIENTS AND METHODS

Twenty-nine women with metastatic breast cancer were enrolled; 27 were assessable for response and 29 for toxicity. All but two of the women had received prior adjuvant chemotherapy, with 23 receiving anthracyclines and six previous cisplatin.

RESULTS

The initial starting dose of paclitxel 90 mg/m2 and cisplatin 60 mg/m2 became the phase II dose due to dose-limiting neutropenia. Responses were seen in 85% of assessable patients, with three patients (11%) achieving a complete response (CR) and 20 patients (14%) a partial response (PR), for an overall response rate of 85% (95% confidence interval [CI], 66% to 96%). The time to disease progression for patients who achieved a CR was 110 to 200 days, and for those with a PR, it was 96 to 377+ days, with a median time to progression of 7.1 months and a median response duration of 7.9 months. Sites of CR were skin, soft tissue, and lung, and all occurred in women with previous exposure to anthracyclines. Septic events were rare, with two grade 3 infections (7%), only one of which required hospital admission. There were no grade 4 nonhematologic toxicity and minimal grade 3 toxicity. A total of 251 chemotherapy cycles were given -- 16 with paclitaxel alone in five patients. Forty-five percent of patients required dose reductions, while 52% had delays due to neutropenia.

CONCLUSION

Biweekly paclitaxel and cisplatin is an active combination in the treatment of metastatic breast cancer, including for patients with previous exposure to anthracyclines.

Identification of a human RAD52 pseudogene located on chromosome 2

A human testis cDNA library was screened with a hybridization probe encoding the mouse RAD52 gene. Two classes of clones were identified, one derived from the human RAD52 homolog (hRAD52), the other derived from a pseudogene. In addition to many point mutations, several of which encode stop codons, the pseudogene contains a number of frame shifts and a 103-bp deletion. We further determined that the pseudogene is processed and is located on human chromosome 2, in contrast to hRAD52 which is found on chromosome 12. Reverse transcription-PCR analysis of cultured human diploid fibroblasts, as well as fibrosarcoma cells, revealed that while hRAD52 is expressed at low, but detectable levels in these cells, the pseudogene is not.

A death in the family: household structure and mortality in rural Liaoning: life-event and time-series analysis, 1792-1867

"Through a discrete-time life-event analysis of triennial household register data from a northeast Chinese village, Daoyi, between 1774 and 1873, we find that an individual's probability of dying, which we treat as an indicator of access to resources and the nature of household roles, was affected by the composition of their coresident kin.... Widows and widowers had higher mortality than the currently married. Orphans had higher mortality than children with at least one parent present. Reflecting the dependence of a wife's status on whether she had produced an heir for her husband, married women in young adulthood and middle age who had at least one son had substantially lower mortality than those without. Reflecting the strength of the claim that elderly males could make on household resources, children with coresident grandfathers had higher mortality than those without. Even though sons were supposed to be a form of old-age security, however, the death rate of the elderly was not reduced by the presence of sons and grandsons."

Elevated levels of homologous DNA recombination activity in the regenerating rat liver

We have characterized homologous DNA recombination activity in nuclear protein extracts prepared from quiescent and regenerating rat livers. Activity measured in regenerating liver extracts was elevated approximately 35-fold above control, and its appearance closely mirrored the first wave of DNA synthesis, peaking 24 hours after a regenerative stimulus, and returning fairly rapidly to basal levels. We also identified a strand-transferase protein of approximately 100 kDa whose presence in these extracts correlates with homologous recombination activity. Recent evidence suggests that mammalian somatic cells possess a recombinational DNA repair mechanism analogous to that described in the yeast Saccharomyces cerevisiae. Our results indicate that this recombinational repair process may be regulated in vivo by, or play a role in, progression through the cell division cycle.

Marital fertility control among the Qing nobility: implications for two types of preventive check

Demographers, as early as Malthus, have assumed that the preventive checks, delayed marriage and celibacy, were absent in traditional China. In this paper on the Qing (1644-1911) imperial lineage, we demonstrate that, instead, there may have been a different, more 'modern' preventive check: fertility control within marriage. Marital fertility of lineage couples during the eighteenth and nineteenth centuries was low to moderate. Such low fertility was the product of three behavioural mechanisms: late starting, early stopping and, most significantly, long spacing. Couples apparently regulated their fertility according to their economic resources and the sex of their surviving children. Moreover, they did so, we suggest, by regulating their coital frequency. Deliberate fertility control, in other words, was already within the 'calculus of conscious choice' for some Chinese well before this century. the speed of contemporary sinitic fertility transitions may accordingly be attributed to the fact that they did not require a change in attitudes, only the diffusion of new incentives and effective technologies.

The target switch algorithm: a constructive learning procedure for feed-forward neural networks

We propose an efficient procedure for constructing and training a feed-forward neural network. The network can perform binary classification for binary or analogue input data. We show that the procedure can also be used to construct feedforward neural networks with binary-valued weights. Neural networks with binary-valued weights are potentially straightforward to implement using microelectronic or optical devices and they can also exhibit good generalization.

Clinical comparison of sevoflurane and isoflurane when administered with nitrous oxide for surgical procedures of intermediate duration

The purpose of this study was to compare the haemodynamic effects and emergence times of anaesthesia with sevoflurane with those of isoflurane when the agents were administered with nitrous oxide to adult patients (ASA I and II) undergoing surgery of at least an hour in duration. Fifty patients were randomly assigned to receive either 0.65 minimum alveolar concentration (MAC) (1.3%) sevoflurane or 0.65 MAC (0.8%) isoflurane together with 60% nitrous oxide following induction with thiopentone, fentanyl, and succinylcholine. Systemic blood pressure and heart rate trends were similar for both groups for the duration of anaesthesia. However, differences in systolic blood pressure measurements were noted at one minute after incision (99 +/- 3 mmHg, mean +/- SE, in the sevoflurane group compared with 109 +/- 4 mmHg for isoflurane), and at emergence (125 +/- 3 mmHg for sevoflurane, 134 +/- 3 mmHg for isoflurane), and in diastolic blood pressure measurements at five minutes after intubation (64 +/- 2 mmHg for sevoflurane, 73 +/- 3 mmHg for isoflurane). Recovery of response to command was more rapid after discontinuation of sevoflurane-nitrous oxide (9.9 +/- 1.1 min) than after isoflurane-nitrous oxide (13.9 +/- 1.3 min). Despite earlier emergence, patients who had received sevoflurane did not request postoperative analgesia sooner. We conclude that the purported advantages of sevoflurane, namely haemodynamic stability and rapid emergence, can be expected even when the agent is administered at 0.65 MAC (1.3%) in nitrous oxide to a typical adult surgical population undergoing procedures of intermediate duration (2.3 +/- 0.2 hr).

Unequal homologous recombination of human DNA on a yeast artificial chromosome

We examined unequal homologous DNA recombination between human repetitive DNA elements located on a yeast artificial chromosome (YAC) and transforming plasmid molecules. A plasmid vector containing an Alu element, as well as a sequence identical to a unique site on a YAC, was introduced into yeast and double recombinant clones analyzed. Recombination occurs between vector and YAC Alu elements sharing as little as 74% identity. The physical proximity of an Alu element to the unique DNA segment appears to play a significant role in determining the frequency with which that element serves as a recombination substrate. In addition, cross-over points of the recombination reaction are largely confined to the ends of the repetitive element. Since a similar distribution of crossover sites occurs during unequal homologous recombination in human germ and somatic tissue, we propose that similar enzymatic processes may be responsible for the events observed in our system and in human cells. This suggests that further examination of the enzymology of unequal homologous recombination of human DNA within yeast may yield a greater understanding of the molecular events which control this process in higher eukaryotes.