Stepped-wedge randomized controlled trial of laparoscopic ventral mesh rectopexy in adults with chronic constipation.

BACKGROUND: The effectiveness of laparoscopic ventral mesh rectopexy (LVMR) in patients with defecatory disorders secondary to internal rectal prolapse is poorly evidenced. A UK-based multicenter randomized controlled trial was designed to determine the clinical efficacy of LVMR compared to controls at medium-term follow-up. METHODS: The randomized controlled trial was conducted from March 1, 2015 TO January 31, 2019. A stepped-wedge RCT design permitted observer-masked data comparisons between patients awaiting LVMR (controls) with those who had undergone surgery. Adult participants with radiologically confirmed IRP refractory to conservative treatment were randomized to three arms with different delays before surgery. Efficacy outcome data were collected at equally stepped time points (12, 24, 36, 48, 60, and 72 weeks). Clinical efficacy of LVMR compared to controls was defined as ≥ 1.0-point reduction in Patient Assessment of Constipation-Quality of Life and/or Symptoms (PAC-QOL and/or PAC-SYM) scores at 24 weeks. Secondary outcome measures included 14-day diary data, the Generalized Anxiety Disorder scale (GAD-7), the Patient Health Questionnaire-9 (PHQ-9), St Marks incontinence score, the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire (PISQ-12), the chronic constipation Behavioral Response to Illness Questionnaire (CC-BRQ), and the Brief Illness Perception Questionnaire (BIPQ). RESULTS: Of a calculated sample size of 114, only 28 patients (100% female) were randomized from 6 institutions (due mainly to national pause on mesh-related surgery). Nine were assigned to the T0 arm, 10 to T12, and 9 to T24. There were no substantial differences in baseline characteristics between the three arms. Compared to baseline, significant reduction (improvement) in PAC-QOL and PAC-SYM scores were observed at 24 weeks post-surgery (- 1.09 [95% CI - 1.76, - 0.41], p = 0.0019, and - 0.92 [- 1.52, - 0.32], p = 0.0029, respectively) in the 19 patients available for analysis (9 were excluded for dropout [n = 2] or missing primary outcome [n = 7]). There was a clinically significant long-term reduction in PAC-QOL scores (- 1.38 [- 2.94, 0.19], p = 0.0840 at 72 weeks). Statistically significant improvements in PAC-SYM scores persisted to 72 weeks (- 1.51 [- 2.87, - 0.16], p = 0.0289). Compared to baseline, no differences were found in secondary outcomes, except for significant improvements at 24 and 48 weeks on CC-BRQ avoidance behavior (- 14.3 [95% CI - 23.3, - 5.4], and - 0.92 [- 1.52, - 0.32], respectively), CC-BRQ safety behavior (- 13.7 [95% CI - 20.5, - 7.0], and - 13.0 [- 19.8, - 6.1], respectively), and BIPQ negative perceptions (- 16.3 [95% CI - 23.5, - 9.0], and - 10.5 [- 17.9, - 3.2], respectively). CONCLUSIONS: With the caveat of under-powering due to poor recruitment, the study presents the first randomized trial evidence of short-term benefit of LVMR for internal rectal prolapse. TRIAL REGISTRATION: ISRCTN Registry (ISRCTN11747152).

Mechanistic Models of Conflict between Ant Colonies and Their Consequences for Territory Scaling.

Territory size in social insects depends on the rules by which border conflicts are resolved. We present three mechanistic mathematical models of conflict, inspired by the behavior of the pavement ant Tetramorium immigrans, to predict the advantage of larger colonies in pairwise contests and the resulting scaling of territory size with worker force. The models track the number of ants in the nest traveling to and from the boundary or engaged at the boundary. Ants at the boundary base their recruitment response on the relative numbers of ants from the two colonies. With two colonies, our central result is that the larger colony gains a territory disproportionately larger than the ratio of worker forces would indicate. This disproportionate territory control determines the scaling relation of territory size with worker force in a population. In two dimensions, if territory size were proportional to worker force, the slope of the scaling relation between log territory size and log worker force would be 1.0. With disproportionate territories, this slope is larger and can be explicitly approximated in terms of model parameters, and it is steepest when colonies are packed close to each other, when ants run quickly, or when colonies are small. A steeper slope exaggerates the advantage of larger colonies, creating a positive feedback that could amplify the inequality of the worker force distribution.

Effectiveness of group body psychotherapy for negative symptoms of schizophrenia: multicentre randomised controlled trial.

BACKGROUND: Negative symptoms of schizophrenia have a severe impact on functional outcomes and treatment options are limited. Arts therapies are currently recommended but more evidence is required. AIMS: To assess body psychotherapy as a treatment for negative symptoms compared with an active control (trial registration: ISRCTN84216587). METHOD: Schizophrenia out-patients were randomised into a 20-session body psychotherapy or Pilates group. The primary outcome was negative symptoms at end of treatment. Secondary outcomes included psychopathology, functional, social and treatment satisfaction outcomes at treatment end and 6-months later. RESULTS: In total, 275 participants were randomised. The adjusted difference in negative symptoms was 0.03 (95% CI -1.11 to 1.17), indicating no benefit from body psychotherapy. Small improvements in expressive deficits and movement disorder symptoms were detected in favour of body psychotherapy. No other outcomes were significantly different. CONCLUSIONS: Body psychotherapy does not have a clinically relevant beneficial effect in the treatment of patients with negative symptoms of schizophrenia.

Trial Forge Guidance 4: a guideline for reporting the results of randomised Studies Within A Trial (SWATs).

BACKGROUND: Evidence to support decisions on trial processes is minimal. One way to generate this evidence is to use a Study Within A Trial (SWAT) to test trial processes or explore methodological uncertainties. SWAT evidence relies on replication to ensure sufficient power and broad applicability of findings. Prompt reporting is therefore essential; however, SWAT publications are often the first to be abandoned in the face of other time pressures. Reporting guidance for embedded methodology trials does exist but is not widely used. We sought therefore to build on these guidelines to develop a straightforward, concise reporting standard, which remains adherent to the CONSORT guideline. METHODS: An iterative process was used to develop the guideline. This included initial meetings with key stakeholders, development of an initial guideline, pilot testing of draft guidelines, further iteration and pilot testing, and finalisation of the guideline. RESULTS: We developed a reporting guideline applicable to randomised SWATs, including replications of previous evaluations. The guideline follows the Consolidated Standards for Reporting Trials (CONSORT) statement and provides example text to ensure ease and clarity of reporting across all domains. CONCLUSIONS: The SWAT reporting guideline will aid authors, reviewers, and journal editors to produce and review clear, structured reports of randomised SWATs, whilst also adhering to the CONSORT guideline. TRIAL REGISTRATION: EQUATOR Network - Guidelines Under Development ( https://www.equator-network.org/library/reporting-guidelines-under-development/reporting-guidelines-under-development-for-clinical-trials/#SWAT ). Registered on 25 March 2021.

Influence of a single oral dose of vitamin D(2) on serum 25-hydroxyvitamin D concentrations in tuberculosis patients.

SETTING: Newham Chest Clinic, London, UK. OBJECTIVE: To determine the safety and efficacy of the administration of bolus-dose vitamin D(2) in elevating serum 25-hydroxyvitamin D (25[OH]D) concentrations in tuberculosis (TB) patients. DESIGN: A multi-ethnic cohort of TB patients was randomised to receive a single oral dose of 2.5 mg vitamin D(2) (n = 11) or placebo (n = 14). Serum 25(OH)D and corrected calcium concentrations were determined at baseline and 1 week and 8 weeks post-dose, and compared to those of a multi-ethnic cohort of 56 healthy adults receiving an identical dose of vitamin D(2). RESULTS: Hypovitaminosis D (serum 25[OH]D < 75 nmol/l) was present in all patients at baseline. A single oral dose of 2.5 mg vitamin D2 corrected hypovitaminosis D in all patients in the intervention arm of the study at 1 week post-dose, and induced a 109.5 nmol/l mean increase in their serum 25(OH)D concentration. Hypovitaminosis D recurred in 10/11 patients at 8 weeks post-dose. No patient receiving vitamin D(2) experienced hypercalcaemia. Patients receiving 2.5 mg vitamin D(2) experienced a greater mean increase in serum 25(OH)D at 1 week post-dose than healthy adults receiving 2.5 mg vitamin D(2). CONCLUSION: A single oral dose of 2.5 mg vitamin D(2) corrects hypovitaminosis D at 1 week but not at 8 weeks post-dose in TB patients.

Self-organizing conflicts: Group assessment and the spatio-temporal dynamics of ant territory battles.

Territorial battles among ants exhibit temporal and spatial patterns that self-organize, arising spontaneously from distributed decisions by large numbers of individuals. We describe agent-based models of inter-group fights in ants and show that two behavioral mechanisms that are rarely quantified have large effects on the dynamics of intraspecific battles; specifically, the pattern of search by unengaged ants, and assessment of relative numbers. In the absence of assessment, recruitment by both colonies rises to steady averages. Alternatively, if ants tend to lay trails only when they detect that their nestmates outnumber opponents, fights can be rapidly resolved as one colony ceases recruiting. If ants tend to lay trails when their nestmates are locally outnumbered, the position of the battle may oscillate. We show that the collective ability of fighting ants to accurately compare group sizes may be high even if each ant has limited perception and memory. However, amplification of small initial numerical advantages can lead to priority effects favoring the first colony to recruit even if it is the smaller colony.

Genetic Analysis of Invasive Conehead Termites (Blattodea: Termitidae) Reveals a Single Origin for Two Populations in Florida.

In 2001, Nasutitermes corniger (Motschulsky), common name conehead termite, were discovered near a marina in Dania Beach, FL, where the invasive species was probably transported from its native range in Central and South America or the Caribbean. In January 2016, an infestation was found in Pompano Beach, Florida, approximately 21 km north of the Dania Beach population. This study compares variants in seven microsatellite loci across specimens from 11 nests in Dania Beach and 8 nests in Pompano Beach. Results are consistent with all N. corniger in both locations being descendants of a single introduced colony, spreading within Broward County, FL through human transport of infested materials. No more than four alleles were found at any of the seven microsatellite loci analyzed, inferring that a single Queen and King, or multiple sibling reproductives descended from a monogamous pair, headed the colony that arrived in Florida. The potential economic and environmental impacts of this invasive termite are enormous due to its broad diet, including agricultural crops and orchards, native and ornamental plants, natural landscapes, and structures. Conspicuous tunnels and aboveground nests are the key aspects of N. corniger biology that render colonies vulnerable to discovery and control. The now proven ability of N. corniger to establish breeding populations in the United States, to cause extensive property and landscape destruction, and to spread by human transport underscores the need for continued aggressive efforts toward eradication of known infestations as well as quick operational actions the next time invasive N. corniger are discovered.

Effects of the Diabetes Manual 1:1 structured education in primary care.

AIMS: To determine the effects of the Diabetes Manual on glycaemic control, diabetes-related distress and confidence to self-care of patients with Type 2 diabetes. METHODS: A cluster randomized, controlled trial of an intervention group vs. a 6-month delayed-intervention control group with a nested qualitative study. Participants were 48 urban general practices in the West Midlands, UK, with high population deprivation levels and 245 adults with Type 2 diabetes with a mean age of 62 years recruited pre-randomization. The Diabetes Manual is 1:1 structured education designed for delivery by practice nurses. Measured outcomes were HbA(1c), cardiovascular risk factors, diabetes-related distress measured by the Problem Areas in Diabetes Scale and confidence to self-care measured by the Diabetes Management Self-Efficacy Scale. Outcomes were assessed at baseline and 26 weeks. RESULTS: There was no significant difference in HbA(1c) between the intervention group and the control group [difference -0.08%, 95% confidence interval (CI) -0.28, 0.11]. Diabetes-related distress scores were lower in the intervention group compared with the control group (difference -4.5, 95% CI -8.1, -1.0). Confidence to self-care Scores were 11.2 points higher (95% CI 4.4, 18.0) in the intervention group compared with the control group. The patient response rate was 18.5%. CONCLUSIONS: In this population, the Diabetes Manual achieved a small improvement in patient diabetes-related distress and confidence to self-care over 26 weeks, without a change in glycaemic control. Further study is needed to optimize the intervention and characterize those for whom it is more clinically and psychologically effective to support its use in primary care.

A cluster-randomised controlled trial of a brief training session to facilitate general practitioner referral to smoking cessation treatment.

OBJECTIVES: General practitioners (GPs) are the main source of referrals to specialist smoking cessation services (SSCS), but the referral rates are low. We evaluated effects of a brief GP training session on the number of referrals received by their local SSCS. METHODS: A cluster-randomised controlled trial was undertaken across three East London primary care trusts. A total of 91 GPs were randomly allocated to a training session or usual care. Participants in the intervention arm were offered a 40-min training session addressing the rationale and skills for referral of smokers for treatment. Participants in the usual care arm received referral guidance by post. The main outcome measure was the number of referrals recorded by the SSCS over 3 months after the intervention. RESULTS: Over the 3-month baseline period the average number of referrals per GP was 1.0 and 0.6 in the intervention and usual care arms, respectively. During the post-intervention period the mean number of referrals was 6.4 and 1.8 per GP. When adjusting for baseline variables the incidence rate ratio for the referrals from the intervention arm compared to usual care was 4.9 (p<0.001; 95% CI 1.7 to 14.7). CONCLUSION: A brief training session can significantly increase GP referral to smoking cessation services. TRIAL REGISTRATION: National Research Register, Department of Health, UK N0261148824 (available online at: http://www.nrr.nhs.uk/ViewDocument.asp?ID = N0261148824).

A randomised controlled trial is not a pilot trial simply because it uses a surrogate endpoint.

BACKGROUND: It has been argued that true endpoints (or 'hard' endpoints) for clinical trials, which are meaningful to clinicians, researchers and patients alike, are limited to those that measure health status, survival and cost. Other endpoints are termed 'surrogate' endpoints and are intended to substitute and predict the true endpoint.  A number of trials that describe using surrogate endpoints use the term 'pilot' in the title of the paper but the reason for this, as related by the authors, is the use of these surrogate endpoints in the trial. The conduct and reporting of such a trial may follow the traditional pattern for a conventional randomised controlled trial (RCT) as defined by the original CONSORT statement, with power-based sample size calculations, and significance tests of the results. However, this is contrary to the guidelines of the CONSORT extension for the reporting of pilot trials. MAIN BODY: We review the definition of a surrogate endpoint and the use of surrogate endpoints in clinical trials. We consider to what extent a trial could be considered a pilot trial if it uses a surrogate endpoint and discuss two examples that illustrate current practice. CONCLUSION: Trials which use surrogate endpoints should only be described as 'pilot' when a definitive trial is a distinct possibility and the authors consider conditions which would indicate whether the definitive main trial was worthwhile and feasible. Simply because a trial uses a surrogate endpoint is not justification for calling it a pilot trial.

The Distribution and Habitat Affinities of the Invasive Ant Myrmica rubra (Hymenoptera: Formicidae) in Southern New England.

The Eurasian ant Myrmica rubra (L.) (Hymenoptera: Formicidae) was first discovered in North America in the early 1900s in Massachusetts. Populations have since appeared in at least seven states within the United States and in seven Canadian provinces. We conducted a systematic search for the ant across southern New England-the states of Connecticut, Massachusetts, and Rhode Island-where M. rubra is spreading from multiple loci. The species occurs in two large regions in Massachusetts, each spanning approximately 75 km, and in several smaller populations in Massachusetts and Rhode Island. No populations were discovered anywhere in Connecticut or across large expanses of central Massachusetts and northern Rhode Island, despite the presence of apparently favorable habitat. This pattern of distribution suggests a combination of long-distance dispersal by human transport coupled with slow local spread. Resurveys of sites previously known to support M. rubra showed that populations persist for decades. Within invaded areas, M. rubra was strongly associated with particular habitats. Colonies were most prevalent in freshwater wetlands and in moist forests near wetlands and water; they were uncommon in drier forests and were rare in open habitats outside of wetlands. The slow rate of spread over the last 110 yr suggests that the ants do not easily disperse between patches of suitable habitat.

Self-management education programmes by lay leaders for people with chronic conditions.

BACKGROUND: Lay-led self-management programmes are becoming widespread in the attempt to promote self-care for people with chronic conditions. OBJECTIVES: To assess systematically the effectiveness of lay-led self-management programmes for people with chronic conditions. SEARCH STRATEGY: We searched: the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library 2005, Issue 1), MEDLINE (January 1986 to May 2006), EMBASE (January 1986 to June 2006), AMED (January 1986 to June 2006), CINAHL (January 1986 to June 2006), DARE (1994 to July 2006, National Research Register (2000 to July 2006), NHS Economic Evaluations Database (1994 to July 2006), PsycINFO (January 1986 to June 2006), Science Citation Index (January 1986 to July 2006), reference lists and forward citation tracking of included studies. We contacted principal investigators and experts in the field. There were no language restrictions. SELECTION CRITERIA: Randomised controlled trials (RCTs) comparing structured lay-led self-management education programmes for chronic conditions against no intervention or clinician-led programmes. DATA COLLECTION AND ANALYSIS: Two authors independently assessed trial quality and extracted data. We contacted study authors for additional information. Results of RCTs were pooled using a random-effects model with standardised mean differences (SMDs) or weighted mean differences (WMDs) for continuous outcomes. MAIN RESULTS: We included seventeen trials involving 7442 participants. The interventions shared similar structures and components but studies showed heterogeneity in conditions studied, outcomes collected and effects. There were no studies of children and adolescents, only one study provided data on outcomes beyond six months, and only two studies reported clinical outcomes. PRIMARY OUTCOMES: Health status: There was a small, statistically-significant reduction in: pain (11 studies, SMD -0.10 (95% confidence interval (CI) -0.17 to -0.04)); disability (8 studies, SMD -0.15 (95% CI -0.25 to -0.05); and fatigue (7 studies, SMD -0.16 (95% CI -0.23 to -0.09); and small, statistically-significant improvement in depression (6 studies, SMD -0.16 95% CI -0.24 to -0.07). There was a small (but not statistically- or clinically-significant) improvement in psychological well-being (5 studies; SMD -0.12 (95% CI -0.33 to 0.09)); but no difference between groups for health-related quality of life (3 studies; WMD -0.03 (95% CI -0.09 to 0.02). Six studies showed a statistically-significant improvement in self-rated general health (WMD -0.20 (95% CI -0.31 to -0.10). Health behaviours: 7 studies showed a small, statistically-significant increase in self-reported aerobic exercise (SMD -0.20 (95% CI -0.27 to -0.12)) and a moderate increase in cognitive symptom management (4 studies, WMD -0.55 ( 95% CI -0.85 to -0.26)). Healthcare use: There were no statistically-significant differences between groups in physician or general practitioner attendance (9 studies; SMD -0.03 (95% CI -0.09 to 0.04)). There were also no statistically-significant differences between groups for days/nights spent in hospital (6 studies; WMD -0.32 (95% CI -0.71 to 0.07)). Self-efficacy: (confidence to manage condition) showed a small statistically-significant improvement (10 studies): SMD -0.30, 95% CI -0.41 to -0.19. No adverse events were reported in any of the studies. AUTHORS' CONCLUSIONS: Lay-led self-management education programmes may lead to small, short-term improvements in participants' self-efficacy, self-rated health, cognitive symptom management, and frequency of aerobic exercise. There is currently no evidence to suggest that such programmes improve psychological health, symptoms or health-related quality of life, or that they significantly alter healthcare use. Future research on such interventions should explore longer term outcomes, their effect on clinical measures of disease and their potential role in children and adolescents.

Genotoxicity of environmental agents in human mammary epithelial cells.

Despite an increasing incidence of human breast cancer, its etiology remains unknown. Since some environmental chemicals are stored in human breast fat and are rodent mammary carcinogens, determining the genotoxic potential of environmental agents in this key target tissue is important. An assay was developed for detecting genotoxic activity, as unscheduled DNA synthesis (UDS), induced by chemicals and UV radiation in early passage cultures of normal human mammary epithelial cells (HMEC) derived from 5 different women. In order to measure UDS in culture, reduction in the percentage of cells in S-phase was accomplished either by depriving the cells of epidermal growth factor and bovine pituitary extract or by contact inhibition of growth. Cultures were incubated with test chemicals for 24 h in the presence of [3H]-thymidine. UDS was quantitated autoradiographically as net grains per nucleus (nuclear grains minus cytoplasmic background, population average) with > or = 6 net nuclear grains considered in repair for any individual cell. A positive response was observed with UV radiation, benzo(a)-pyrene, aflatoxin B1, ethylmethanesulfonate, 1,6-dinitropyrene, 2-acetylaminofluorene, and tobacco smoke condensate but not 7,12-dimethylbenz(a)anthracene or 2,3,7,8-tetrachlorodibenzo-p-dioxin. These results demonstrate that HMEC from all 5 women examined have the ability to metabolize a variety of environmental chemicals to DNA-reactive forms. Furthermore, some chemicals known either to cause mammary cancer in rodents or to be contaminants in human breast tissue are genotoxic in HMEC. A positive response in passage 9 cultures was observed only with direct acting agents, suggesting that HMEC may lose their metabolic capabilities in longer-term cultures. The HMEC UDS assay may be used to address the role of environmental agents in human breast cancer by determining whether chemicals are DNA reactive or metabolized to DNA reactive species in this critical target tissue.

Quantitation of benzo(a)pyrene and 7,12-dimethylbenz(a)anthracene binding to nuclear macromolecules in human and rat mammary epithelial cells.

Our laboratory has developed virtually identical techniques for the isolation and culture of mammary epithelial cells (MEC) from rats and humans. In a cell-mediated mutagenesis assay, rat MEC activated 7,12-dimethylbenz(a)anthracene (DMBA) but not benzo(a)pyrene [B(a)P] to mutagenic forms, and the opposite pattern was found with human MEC. These species-specific patterns were not readily explained by either qualitative or quantitative differences in Phase I metabolism of these compounds. In contrast, relative levels of covalent binding of these compounds to DNA in the human and rat cells under identical assay conditions generally parallel the pattern of the mutagenesis results, while not reflecting the absolute levels of metabolism in each system. The ability of the rat MEC to bind relatively higher levels of DMBA than B(a)P to nuclear DNA, and the reversed pattern in human MEC, was found at all incubation times tested between 6 and 48 h. Culture density was found to exert a greater effect on the levels of PAH-DNA binding in rat than in human cells, but in neither case did it affect the ratio of DMBA to B(a)P binding within a species. C2SO4 gradient separation of nuclear macromolecules from PAH-treated MEC revealed that the relative DNA binding levels of DMBA and B(a)P did not correlate with relative levels of nuclear protein binding. For both species, nuclear (DNA + protein) binding levels of B(a)P were approximately 2-fold higher than DMBA. However, these binding levels were 4 to 5-fold higher for both carcinogens in the human than in the rat MEC. The species-specific patterns of PAH activation shown by these cells suggest that caution should be used in extrapolating rodent carcinogenesis data to humans, for either quantitative or qualitative purposes.

Association of decreased intercellular communication with the immortal but not the tumorigenic phenotype in human mammary epithelial cells.

Intercellular communication was compared in early passage cultures of human mammary epithelial cells (HMEC) from normal and malignant breast tissues and immortalized nontumorigenic human breast cell lines (184A1 and 184B5). A clonogenic assay for the cell-mediated transfer of toxic metabolites of 6-thioguanine (TG) between cells was used as a measure of intercellular communication. We examined the effects of wild-type TG-sensitive (TGs) HMEC density on the survival of mutant TG-resistant (TGr) immortalized HMEC in TG-containing medium. Survival rates of TGr HMEC cocultured with TGs normal HMEC, malignant HMEC, or immortalized nontumorigenic HMEC were dependent on the density of TGs cells. For example, the percentage of recovery of TGr cells cocultured with 10(5) TGs immortalized, normal, or carcinoma HMEC was 88 +/- 4, 41 +/- 10, or 2.0 +/- 1.7, respectively. Gap junction-mediated intercellular communication between homologous HMEC types was also studied, as quantitated on the basis of Lucifer yellow dye transfer between cells in culture. Results from the dye transfer studies supported those from the metabolic cooperation studies. These results using nonimmortalized tumor cells differ from previous reports in which immortal tumor cells have been found to communicate less than their normal counterparts. Previous reports suggesting that tumor cell lines communicate less than normal cells may have resulted from the confounding influence of the immortal phenotype on the tumor phenotype.

An empirical test of Lanchester's square law: mortality during battles of the fire ant Solenopsis invicta.

Lanchester's models of attrition describe casualty rates during battles between groups as functions of the numbers of individuals and their fighting abilities. Originally developed to describe human warfare, Lanchester's square law has been hypothesized to apply broadly to social animals as well, with important consequences for their aggressive behaviour and social structure. According to the square law, the fighting ability of a group is proportional to the square of the number of individuals, but rises only linearly with fighting ability of individuals within the group. By analyzing mortality rates of fire ants (Solenopsis invicta) fighting in different numerical ratios, we provide the first quantitative test of Lanchester's model for a non-human animal. Casualty rates of fire ants were not consistent with the square law; instead, group fighting ability was an approximately linear function of group size. This implies that the relative numbers of casualties incurred by two fighting groups are not strongly affected by relative group sizes and that battles do not disproportionately favour group size over individual prowess.

Aging human RPE: morphometric analysis of macular, equatorial, and peripheral cells.

Retinal pigment epithelium (RPE) of 50 human eyes, five from each 10 decades of life, were analyzed using ultrastructural morphometric techniques. Content of three types of pigments, lipofuscin, melanin, and complex granules, (melanolipofuscin, melanolysosomes) were recorded for cells from macular, equatorial, and peripheral retinal specimens. Areas occupied by pigments, nucleus, and cytoplasmic space were calculated. Data were analyzed by a computer for age-related changes and effects of fixation delay time. The largest increase in lipofuscin granules occurred between the first and second decade of life, and further increases occurred with age. The content of "pure" melanin declined with age, whereas the number of complex melanin granules increased. Macular RPE contained more complex granules than nonmacular RPE, particularly in young eyes. The volume of RPE cytoplasm not occupied by pigments ("free space") decreased with age. No significant effects of fixation delays between 2 and 9 hours postmortem were found on the parameters studied here. These findings may serve as a baseline for estimating normalcy of human RPE specimens.

Retrospective evaluation of alpha 2u-globulin accumulation in male rat kidneys following high doses of diisononyl phthalate.

Diisononyl phthalate (DINP), a widely used plasticizer, has been evaluated in two chronic studies in rats and one in mice. In the early 1980s, Exxon found no carcinogenic potential at the estimated maximum tolerated dose (MTD) of 0.6% (307 mg/kg/ day for male rats) administered in the diet of rats for 2 years. A recent study conducted at dietary levels up to 1.2% DINP (733 mg/kg/d for male rats) reported kidney tumors in male rats at the high treatment level, but not in female rats nor mice of either sex. Because these tumors occurred only in male rats, and only at high doses, the male rat-specific alpha 2u-globulin (alpha2UG) mechanism of action was investigated. Technological advances in immunohistochemical staining and computerized image analysis techniques permitted measuring the accumulation of alpha2UG in archived kidneys from the earlier Exxon study. Using archived tissue obtained at the 12-month interim sacrifice, we identified a dose-dependent accumulation of alpha2UG in specific regions of male rat kidneys only. An increase in cell proliferation was confirmed by immunohistochemical detection of proliferating-cell nuclear antigen (PCNA) and was confined to the areas of alpha2UG accumulation. H and E-stained sections revealed tubular epithelial hypertrophy and regeneration, consistent with the immunohistopathology findings. These findings are consistent with the alpha2UG mechanism of tumorigenesis, which is not regarded as relevant for humans. Thus, exposure to DINP produced a dose-dependent alpha2UG accumulation in male rat kidneys, significant at a dietary level of 0.6% and a likely mechanism for the kidney tumors seen only in male rats administered higher dietary levels of DINP.

Characterization of hepatocellular resistance and susceptibility to styrene toxicity in B6C3F1 mice.

Short-term inhalation exposure of B6C3F1 mice to styrene causes necrosis of centrilobular (CL) hepatocytes. However, in spite of continued exposure, the necrotic parenchyma is rapidly regenerated, indicating resistance by regenerated cells to styrene toxicity. These studies were conducted to test the hypothesis that resistance to repeated styrene exposure is due to sustained cell proliferation, with production of hepatocytes that have reduced metabolic capacity. Male mice were exposed to air or 500 ppm styrene (6 h/day); hepatotoxicity was evaluated by microscopic examination, serum liver enzyme levels, and bromodeoxyuridine (BrdU)-labeling index (LI). Metabolism was assessed by measurement of blood styrene and styrene oxide. Both single and repeated exposures to styrene resulted in mortality by Day 2; in mice that survived, there was CL necrosis with elevated BrdU LI at Day 6, and complete restoration of the necrotic parenchyma by Day 15. The BrdU LI in mice given a single exposure had returned to control levels by Day 15. Re-exposure of these mice on Day 15 resulted in additional mortality and hepatocellular necrosis, indicating that regenerated CL cells were again susceptible to the cytolethal effect of styrene following a 14-day recovery. However, in mice repeatedly exposed to styrene for 14 days, the BrdU LI remained significantly increased on Day 15, with preferential labeling of CL hepatocytes with enlarged nuclei (karyomegaly). If repeated exposures were followed by a 10-day recovery period, CL karyomegaly persisted, but the BrdU LI returned to control level and CL hepatocytes became susceptible again to styrene toxicity as demonstrated by additional mortality and acute necrosis after a challenge exposure. These findings indicated a requirement for continued styrene exposure and DNA synthesis in order to maintain this resistant phenotype. Analyses of proliferating-cell nuclear-antigen (PCNA) labeling were conducted to further characterize the cell cycle kinetics of these hepatocytes. The proportion of cells in S-phase was increased by repeated exposure. However, PCNA analysis also revealed an even larger increase in the G1 cell compartment with repeated exposures, without a concurrent increase in G2 phase or in mitotic cell numbers. These data indicate that resistance to styrene-induced necrosis under conditions of repeated exposure is not due to sustained cell turnover and production of new, metabolically inactive cells, but rather is due to some other, as yet unknown, protective phenotype of the regenerated cells.

Tissue-specific genotoxic effects of acrylamide and acrylonitrile.

Acrylamide (AA) has been reported to induce dominant lethal mutations in male rat germ cells and tumors in a variety of organs, including the scrotum, thyroid and mammary glands, but not the liver of rats. The structurally similar vinyl monomer acrylonitrile (ACN) does not induce dominant lethal mutations but does induce tumors of the brain, Zymbal gland, forestomach and mammary gland, but not the liver of rats. Several in vitro and/or in vivo unscheduled DNA synthesis (UDS) assays were employed to examine the potential tissue-specific genotoxic activity of these compounds. Neither AA nor ACN induced DNA repair in either the in vitro or in vivo hepatocyte DNA repair assays. Glycidamide (GA), a mutagenic metabolite of AA, induced DNA repair in the in vitro hepatocyte DNA repair assay. Cyanoethylene oxide (CEO), a mutagenic metabolite of ACN, did not yield a DNA repair response in the in vitro hepatocyte DNA repair assay, but was highly toxic and could not be tested at doses equivalent to GA. AA, but not ACN, produced a DNA repair response in the in vivo spermatocyte DNA repair assay. AA produced a slight response in the in vitro human mammary epithelial cell (HMEC) DNA repair assay in normal cells derived from discarded surgical samples from five different women. GA produced a strong UDS response in all cases in the same assay. CEO, but not its parent compound ACN, produced a response in the HMEC DNA repair assay. These results show a highly tissue-specific pattern of genotoxic activity for AA and ACN that correlates, to the extent that it has been examined, with the tissue-specific pattern of carcinogenic and dominant lethal activity. The induction of DNA repair by GA and CEO confirms the genotoxic potential of these metabolites. While the observation of genotoxic activity of AA in the HMEC DNA repair assay suggests that mammary cells might be a target for carcinogenic activity of this compound in humans, other factors such as pharmacokinetics and epidemiology must be evaluated to establish that effect.