The efficacy of app‐supported smartphone interventions for mental health problems: a meta‐analysis of randomized controlled trials

Although impressive progress has been made toward developing empirically‐supported psychological treatments, the reality remains that a significant proportion of people with mental health problems do not receive these treatments. Finding ways to reduce this treatment gap is crucial. Since app‐supported smartphone interventions are touted as a possible solution, access to up‐to‐date guidance around the evidence base and clinical utility of these interventions is needed. We conducted a meta‐analysis of 66 randomized controlled trials of app‐supported smartphone interventions for mental health problems. Smartphone interventions significantly outperformed control conditions in improving depressive (g=0.28, n=54) and generalized anxiety (g=0.30, n=39) symptoms, stress levels (g=0.35, n=27), quality of life (g=0.35, n=43), general psychiatric distress (g=0.40, n=12), social anxiety symptoms (g=0.58, n=6), and positive affect (g=0.44, n=6), with most effects being robust even after adjusting for various possible biasing factors (type of control condition, risk of bias rating). Smartphone interventions conferred no significant benefit over control conditions on panic symptoms (g=–0.05, n=3), post‐traumatic stress symptoms (g=0.18, n=4), and negative affect (g=–0.08, n=5). Studies that delivered a cognitive behavior therapy (CBT)‐based app and offered professional guidance and reminders to engage produced larger effects on multiple outcomes. Smartphone interventions did not differ significantly from active interventions (face‐to‐face, computerized treatment), although the number of studies was low (n≤13). The efficacy of app‐supported smartphone interventions for common mental health problems was thus confirmed. Although mental health apps are not intended to replace professional clinical services, the present findings highlight the potential of apps to serve as a cost‐effective, easily accessible, and low intensity intervention for those who cannot receive standard psychological treatment.     

Correlation between mental health co-morbidity screening scores and clinical response in collaborative care treatment for depression

The hypothesis for this paper is that adult patients who have higher screening scores for mental health co-morbidities and depression have a greater likelihood of not responding to treatment with collaborative care management (CCM) for their depression within six months.For the 334 patients in this study, the primary endpoints were if the patient was in remission at six months (PHQ-9 score <5) or if they were non-responsive (NR) (PHQ-9 >50% of baseline score). Initial evaluation included screening for alcoholism (AUDIT), anxiety (GAD-7) and bipolar disorders (MDQ).The differences in marital status, percentage of minority patients, gender, initial PHQ-9 and AUDIT scores were not statistically significant. Mood Disorders Questionnaire (MDQ) screening was more likely to be negative for the group in remission (96.2% vs 90.0%, P=0.049) and positive for the NR group (8.0% vs 2.1%, P=0.026). GAD-7 screening was significantly lower in the remission group (9.85) than in the NR group (11.53, P=0.009).Results of multiple logistic regression analysis demonstrated that age, gender, race, marital status, PHQ-9 score and AUDIT score were not related to the odds of being NR. A one-point higher GAD-7 score was associated with approximately 6% higher adjusted odds of being NR. Patients with a positive MDQ were associated with elevated odds of non-response (adjusted OR=3.4714, P=0.044) when controlling for all other variables.A higher initial screening score for anxiety or bipolar disorder is associated with a statistically significant increase in the relative risk of patients in CCM not responding to current treatments for depression within six months.     

Post-partum depression: a comprehensive approach to evaluation and treatment

Post-partum depression (PPD) presents a significant disruption to the mother-infant relationship. Such disruptions are associated with risks to the neurological, socio-emotional and cognitive functioning of the developing infant. A review of this literature supports the early detection of PPD and the application of comprehensive, psychotherapeutic interventions that target the functioning of the infant, the mother and the mother-infant relationship. Ecological factors important to evaluation and avenues of intervention are emphasised. The need for further research to determine evidence-based methods of intervention is described.     

Inbreeding depression and mixed mating in Leptosiphon jepsonii: a comparison of three populations

BACKGROUND AND AIMS: Inbreeding depression is thought to play a central role in the evolution and maintenance of cross-fertilization. Theory indicates that inbreeding depression can be purged with self-fertilization, resulting in positive feedback for the selection of selfing. Variation among populations of Leptosiphon jepsonii in the timing and rate of self-fertilization provides an opportunity to study the evolution of inbreeding depression and mating systems. In addition, the hypothesis that differences in inbreeding depression for male and female fitness can stabilize mixed mating in L. jepsonii is tested. METHODS: In a growth room experiment, inbreeding depression was measured in three populations with mean outcrossing rates ranging from 0.06 to 0.69. The performance of selfed and outcrossed progeny is compared at five life history stages. To distinguish between self-incompatibility and early inbreeding depression, aborted seeds and unfertilized ovules were counted in selfed and outcrossed fruits. In one population, pollen and ovule production was quantified to estimate inbreeding depression for male and female fitness. KEY RESULTS: Both prezygotic barriers and inbreeding depression limited self seed set in the most outcrossing population. Cumulative inbreeding depression ranged from 0.297 to 0.501, with the lowest value found in the most selfing population. Significant inbreeding depression for early life stages was found only in the more outcrossing populations. Inbreeding depression was not significant for pollen or ovule production. CONCLUSIONS: The results provide modest support for the hypothesized relationship between inbreeding depression and mating systems. The absence of early inbreeding depression in the more selfing populations is consistent with theory on purging. Differences in male and female expression of inbreeding depression do not appear to stabilize mixed mating in L. jepsonii. The current estimates of inbreeding depression for L. jepsonii differ from those of previous studies, underscoring the effects of environmental variation on its expression.     

Inbreeding depression and outbreeding depression in Digitalis purpurea: optimal outcrossing distance in a tetraploid

An optimal crossing distance exists within plant populations if inbreeding and outbreeding depression operate simultaneously. In a population of tetraploid Digitalis purpurea, maternal plants were pollinated with donors at four distances: 0 (self-pollination), 1, 6 and 30 m. Lifetime fitness of F1 progeny was investigated in greenhouse experiments, and significant inbreeding and outbreeding depression were detected at five vs. three life history traits. Inbreeding depression increased at later life stages, whereas outbreeding depression was relatively constant. The existence of within-population outbreeding depression suggests substantial genetic structuring at moderate distances in D. purpurea, and corroborates recent findings of significant outbreeding depression in F1 progeny in polyploids. The moderate inbreeding depression found in this predominately outcrossing population supports the notion that effects of inbreeding are less severe in polyploids than in diploids.     

Changing disease patterns in patients with AIDS in a referral centre in the United Kingdom: the changing face of AIDS.

OBJECTIVE--To study the changes in morbidity, mortality, and survival patterns in a population of patients with AIDS in the United Kingdom from 1982 to 1989. DESIGN--A retrospective analysis of inpatient and outpatient records of patients with AIDS. SUBJECTS--347 Patients with AIDS, predominantly homosexual or bisexual men. SETTING--Departments of immunology and genitourinary medicine, St Mary''s Hospital, London. MAIN OUTCOME MEASURES--Presenting diagnosis of AIDS, occurrence of other opportunist diseases, cause of death, and survival since AIDS was diagnosed, in particular for those patients with Pneumocystis carinii pneumonia or Kaposi''s sarcoma. RESULTS--The overall proportion of patients who developed P carinii pneumonia dropped from 56% (20/36) in 1984 to 24% (46/194) in 1989, although it has remained the index diagnosis in about half of new patients. Kaposi''s sarcoma has decreased as index diagnosis from 30% (20/67) to 20% (15/74) over the same period, though the prevalence has remained constant at around 35%. P carinii pneumonia accounted for 46% (16/35) of known causes of death in 1986 but only 3% (1/31) in 1989. Conversely, deaths due to Kaposi''s sarcoma rose from 14% (1/7) to 32% (10/31) between 1984 and 1989. Lymphoma accounted for an increased proportion of deaths among these patients with 16% (5/31) of deaths in 1989. Their median survival increased from 10 months in 1984-6 to 20 months in 1987. CONCLUSIONS--The changing patterns of disease in patients with AIDS have important implications both for health care provision and future medical research. Medical and nursing provision must be made for the increased morbidity of these diseases and the increased survival of these patients. Research should now be directed towards developing effective treatments for the opportunist infections which are currently more difficult to treat, the secondary malignancies of AIDS, as well as more effective immunorestorative treatments. Future changes in disease patterns must be recognised at an early stage so that resources can be adequately planned and allocated.     

All in for mental health: a pilot study of group therapy for people experiencing anxiety and/or depression and a significant other of their choice

Background A need to provide treatment for people with anxiety and/or depression, and to provide preventive strategies for individuals who love them has been identified. In response, an innovative group therapy programme for people with anxiety and/or depression and a significant other of their choice was developed and implemented.Methods Mixed methods were employed. Five 'significant other' groups were held between May 2005 and June 2006. All group participants were requested to complete the Depression Anxiety Stress Scale (DASS), World Health Organization Quality of Life Assessment (WHOQol) and Connor-Davidson Resilience Scale (CD-RISC), pre- and post-therapy, and three months after their last therapy session. In addition, participants who attended groups between July and September 2005 were invited to provide feedback about the group therapy in an individual semi-structured interview.Results Pilot results indicate positive responses from clients, related to facilitation of knowledge and understanding and skills development. For people referred to the group significant improvements were found in the DASS scores, resilience, psychological health and living environment.Limitations Due to the small sample size, and lack of follow-up data and control group, the findings need to be considered with caution and indicate the necessity to collect further data to provide conclusive findings.Conclusions Overall, the outcome of the 'significant other' pilot programme was useful, in that it facilitated a number of positive outcomes for participants. Areas for further research have been identified including strategies to improve social relationships, the de-identification with the sick/supporter role, and testing this model with diverse populations and clinical groups.     

Regional alterations in the endocannabinoid system in an animal model of depression: effects of concurrent antidepressant treatment

It has been suggested that disturbances in endocannabinoid signaling contribute to the development of depressive illness; however, at present there is insufficient evidence to allow for a full understanding of this role. To further this understanding, we performed an analysis of the endocannabinoid system in an animal model of depression. Male rats exposed to chronic, unpredictable stress (CUS) for 21 days exhibited a reduction in sexual motivation, consistent with the hypothesis that CUS in rats induces depression-like symptoms. We determined the effects of CUS, with or without concurrent treatment with the antidepressant imipramine (10 mg/kg), on CP55940 binding to the cannabinoid CB(1) receptor; whole tissue endocannabinoid content; and fatty acid amide hydrolase (FAAH) activity in the prefrontal cortex, hippocampus, hypothalamus, amygdala, midbrain and ventral striatum. Exposure to CUS resulted in a significant increase in CB(1) receptor binding site density in the prefrontal cortex and a decrease in CB(1) receptor binding site density in the hippocampus, hypothalamus and ventral striatum. Except in the hippocampus, these CUS-induced alterations in CB(1) receptor binding site density were attenuated by concurrent antidepressant treatment. CUS alone produced a significant reduction in N-arachidonylethanolamine (anandamide) content in every brain region examined, which was not reversed by antidepressant treatment. These data suggest that the endocannabinoid system in cortical and subcortical structures is differentially altered in an animal model of depression and that the effects of CUS on CB(1) receptor binding site density are attenuated by antidepressant treatment while those on endocannabinoid content are not.     

Evolution of the prevalence and incidence of consumption of antidepressants in a Spanish region (2002-2007)

Background The treatment of depressive disorders involves the administration of drugs of proven efficacy at the correct doses and for specific periods of time, in conjunction with psychotherapeutic support.Aim To assess the evolution of the consumption of antidepressants in the Health Region of Lleida (Spain).Method A retrospective cohort study of the antidepressant medication prescribed via the Spanish National Health System in the Health Region of Lleida between 2002 and 2007. The variables recorded in the study were age, sex, number of patients in antidepressant treatment in the Health Region of Lleida, length of treatment and type of drug. The prevalence of the population of the health region who were receiving antidepressant drugs and the incidence for each particular year was calculated.Results The mean prevalence of patients in treatment with antidepressant drugs was 8.5% (5% in men and 12.1% in women). The highest prevalence was observed in the higher age groups. By therapeutic groups, selective serotonin reuptake inhibitors (SSRIs) were the most frequently prescribed, five times more than the next group, tricyclics/heterocyclics. The follow-up assessment of the medication prescribed showed that one out of every four patients did not continue treatment after the first month, and 38.4% did not continue after three months. Very few were treated for more than six months.Conclusion This study stresses the high rate of antidepressant treatment in the older women's group. One of every four treatments initiated did not last more than one month. Over the six-year period, 16 506 patients dropped out of treatment.     

Movement patterns of an Australian chrysomelid beetle in a stand of two Eucalyptus host species

Summary We examined the movements of Chrysophtharta hectica, a eucalypt-feeding chrysomelid beetle in New South Wales, Australia, in relation to the beetle's sex, age and life-history, and to attributes of its Eucalyptus host plants. Beetle movements within the site were not influenced by beetle age or sex, but may be related to generation. Beetle distributions on the two host plant species, Eucalyptus stellulata and E. pauciflora, were generally clumped. Some of this clumping resulted from preference for E. stellulata over E. pauciflora. Clumping of beetles also occurred within host plant species; some plant individuals were consistently heavily used by beetles over the course of three years. We examined nutritional, spatial and biomass attributes of plants and found plant height and foliage production to be the best predictors of beetle numbers.     

Ant- and termite-eating in Australian mammals and lizards: a comparison

Abstract Relative abundance is one factor that influences selection of prey by insectivorous mammals and lizards. Ants and termites are extremely abundant over most of inland Australia. Their patterns of abundance are also broadly similar across climatic gradients, being most and least abundant in seasonally arid (tropic and sub-tropic) and temperate mesic regions, respectively. All else being equal (e. g. mechanisms of prey defence, palat-ability, availability), animals that eat many termites should also eat many (adult) ants. The present study asks three questions: (i) What is the diversity of specialized ant-eaters (>50% volume)?; (ii) Does specialization vary with climate?; and (iii) Are ants and termites eaten in broadly similar proportions (using an earlier study on termites). Of the mammals, only the echidna (Tachyglossus aculeatus) in mesic regions, and probably the marsupial mole (Notoryctes typhlops) in the arid zone and the striped possum (Dactylopsila trivirgata) in mesic regions are ant-specialized. Ant-specialization in mammals shows no pattern with regard to climate. Of the lizards, only four agamid lizards are ant-specialized: Moloch horridus (arid, semi-arid), Ctenophorus fordi (arid, semi-arid), Ctenophorus isolepis (arid) and Ctenophorus maculatus (arid). Specialization on ants by lizards is greatest in the arid zone (4 spp.); no lizard species were found to be ant-specialists in mesic regions. In the arid and semi-arid zone, two mammals each specialize on termites and one on ants; in mesic regions, two mammals specialize on ants and one on termites. Specialized insectivorous mammals thus demonstrate no marked preference for either termites or ants. Lizards, in contrast, are markedly termite-specialized (4 ant-specialist spp., 16 termite-specialist spp.), and specialization is greatest in the arid zone (16 spp.). Greater specialization on termites than on (adult) ants in lizards is explained with reference to differences in prey defence and palatability between ants and termites. Consumption of ant brood (eggs, larvae, pupae) appears to be associated with a fossorial foraging mode (the marsupial mole N. typhlops; spp. of Aprasia lizards; spp. of blindsnakes Ramphotyphlops).     

Retention time as a primary determinant of colour and light attenuation in two tropical Australian reservoirs

1. The light climates of Darwin River Reservoir (DRR) and Manton River Reservoir (MRR), in northern Australia, are compared for an 8-year period. The reservoirs are subject to the same wet/dry tropical climate and have similar catchment characteristics, but differ in their basin morphology, retention time and trophic status.
2. Median euphotic depths in DRR and MRR were 9.7 and 4.4 m, respectively. Seasonal variation in each reservoir's euphotic depth was best explained by colour, based on a stepwise linear regression. Turbidity was excluded from the two regressions, while chlorophyll a concentration was significant only for the MRR regression.
3. Both reservoirs showed the same seasonal pattern for colour. Wet season inflow increased reservoir colour, and was followed by a reduction in colour due to photodegradation and microbial decomposition of humic material, reaching a minimum before the next wet seasons inflow.
4. Although the colour of catchment run-off into both reservoirs was similar, MRR colour was two to three times greater than that measured in DRR. The higher colour and greater light attenuation of MRR is attributed primarily to its shorter retention time, and therefore shorter time for colour removal. Annual retention time accounted for 97% of the variability of average annual colour (measured as absorption at 440 nm), based on a linear regression of log₁₀ transformed data for both reservoirs.
5. Long retention times favour reduced colour, increasing water transparency, particularly in water bodies of low trophic state and inorganic turbidity.     

Retention time as a primary determinant of colour and light attenuation in two tropical Australian reservoirs

1. The light climates of Darwin River Reservoir (DRR) and Manton River Reservoir (MRR), in northern Australia, are compared for an 8-year period. The reservoirs are subject to the same wet/dry tropical climate and have similar catchment characteristics, but differ in their basin morphology, retention time and trophic status.
2. Median euphotic depths in DRR and MRR were 9.7 and 4.4 m, respectively. Seasonal variation in each reservoir's euphotic depth was best explained by colour, based on a stepwise linear regression. Turbidity was excluded from the two regressions, while chlorophyll a concentration was significant only for the MRR regression.
3. Both reservoirs showed the same seasonal pattern for colour. Wet season inflow increased reservoir colour, and was followed by a reduction in colour due to photodegradation and microbial decomposition of humic material, reaching a minimum before the next wet seasons inflow.
4. Although the colour of catchment run-off into both reservoirs was similar, MRR colour was two to three times greater than that measured in DRR. The higher colour and greater light attenuation of MRR is attributed primarily to its shorter retention time, and therefore shorter time for colour removal. Annual retention time accounted for 97% of the variability of average annual colour (measured as absorption at 440 nm), based on a linear regression of log₁₀ transformed data for both reservoirs.
5. Long retention times favour reduced colour, increasing water transparency, particularly in water bodies of low trophic state and inorganic turbidity.     

Patients' experiences of receiving collaborative care for the treatment of depression in the UK: a qualitative investigation

Objective We explored the experiences of patients who received treatment for depression during a 'phase II' platform trial of collaborative care in the UK.Method Semi-structured interviews were used to obtain information from 13 patients receiving collaborative care. Patients from a range of general practitioner (GP) practices within the trial were purposively sampled. The constant comparative approach within a framework analysis was used to identify emerging concepts and key themes.Results Three distinct themes in people's experience of collaborative care were identified: (1) the process of collaborative care; (2) the content of collaborative care; and (3) staying well. These themes were set against a backdrop in which patients described how they had been struggling with lowmood. Our central therapeutic ingredients of information giving, behavioural activation and medication management were supported by patients. Patients expressed reservations about the rigid inflexibility of telephone-based treatment.Conclusions While most of the protocol elements were supported by patients, we have been able to amend our protocol to allow for greater delivery flexibility and more attention to the therapeutic alliance and relapse prevention. We are now testing this in a multicentre randomised controlled trial.     

Income inequality and depression: a systematic review and meta‐analysis of the association and a scoping review of mechanisms

Most countries have witnessed a dramatic increase of income inequality in the past three decades. This paper addresses the question of whether income inequality is associated with the population prevalence of depression and, if so, the potential mechanisms and pathways which may explain this association. Our systematic review included 26 studies, mostly from high‐income countries. Nearly two‐thirds of all studies and five out of six longitudinal studies reported a statistically significant positive relationship between income inequality and risk of depression; only one study reported a statistically significant negative relationship. Twelve studies were included in a meta‐analysis with dichotomized inequality groupings. The pooled risk ratio was 1.19 (95% CI: 1.07‐1.31), demonstrating greater risk of depression in populations with higher income inequality relative to populations with lower inequality. Multiple studies reported subgroup effects, including greater impacts of income inequality among women and low‐income populations. We propose an ecological framework, with mechanisms operating at the national level (the neo‐material hypothesis), neighbourhood level (the social capital and the social comparison hypotheses) and individual level (psychological stress and social defeat hypotheses) to explain this association. We conclude that policy makers should actively promote actions to reduce income inequality, such as progressive taxation policies and a basic universal income. Mental health professionals should champion such policies, as well as promote the delivery of interventions which target the pathways and proximal determinants, such as building life skills in adolescents and provision of psychological therapies and packages of care with demonstrated effectiveness for settings of poverty and high income inequality.     

A feasibility study of a telephone-supported self-care intervention for depression among adults with a comorbid chronic physical illness in primary care

Objective We assessed the feasibility and acceptability to patients of a telephone-supported self-care intervention for depression among adults aged 40 years or over with one of six targeted chronic physical illnesses and comorbid depressive symptoms in family practice settings.Methods An open, uncontrolled trial (feasibility study) was conducted among patients treated in Montreal family practices. Eligible patients were aged 40 years or over, had one or more of the targeted chronic physical illnesses for at least 6 months (arthritis, hypertension, diabetes, heart disease, asthma and chronic obstructive pulmonary disease) and were evaluated as having at least mild depressive symptoms (a score of ≥ 5 on the 9-item Patient Health Questionnaire, PHQ-9). Participants received a package of six self-care tools (information booklet, video, Internet programme, action plan, workbook and mood-monitoring tool) with telephone support by a lay coach for up to 6 months.Results In total, 63 eligible patients provided written consent and completed the baseline interview; 57 (90%) and 55 (87%) patients completed 2-month and 6-month follow-up interviews, respectively. The mean number of telephone calls made by coaches to participants was 10.5 (SD 4.0), and the average length of these calls was 10.6 minutes. At the 6-month follow-up, 83.6% of the participants reported that one or more of the tools were helpful. Clinically significant improvements were seen in depressive symptoms (as assessed by the PHQ-9) at 6 months, with an effect size of 0.88 (95% CI, 0.55, 1.14).Conclusion A telephone-supported self-care intervention for depression was feasible, was acceptable to patients, and was associated with a significant 6-month improvement in depressive symptoms. A randomised trial of this intervention is justified.     

A therapeutic application of the experience sampling method in the treatment of depression: a randomized controlled trial

In depression, the ability to experience daily life positive affect predicts recovery and reduces relapse rates. Interventions based on the experience sampling method (ESM-I) are ideally suited to provide insight in personal, contextualized patterns of positive affect. The aim of this study was to examine whether add-on ESM-derived feedback on personalized patterns of positive affect is feasible and useful to patients, and results in a reduction of depressive symptomatology. Depressed outpatients (n=102) receiving pharmacological treatment participated in a randomized controlled trial with three arms: an experimental group receiving add-on ESM-derived feedback, a pseudo-experimental group participating in ESM but receiving no feedback, and a control group. The experimental group participated in an ESM procedure (three days per week over a 6-week period) using a palmtop. This group received weekly standardized feedback on personalized patterns of positive affect. Hamilton Depression Rating Scale – 17 (HDRS) and Inventory of Depressive Symptoms (IDS) scores were obtained before and after the intervention. During a 6-month follow-up period, five HDRS and IDS assessments were completed. Add-on ESM-derived feedback resulted in a significant and clinically relevant stronger decrease in HDRS score relative to the control group (p<0.01; −5.5 point reduction in HDRS at 6 months). Compared to the pseudo-experimental group, a clinically relevant decrease in HDRS score was apparent at 6 months (B=−3.6, p=0.053). Self-reported depressive complaints (IDS) yielded the same pattern over time. The use of ESM-I was deemed acceptable and the provided feedback easy to understand. Patients attempted to apply suggestions from ESM-derived feedback to daily life. These data suggest that the efficacy of traditional passive pharmacological approach to treatment of major depression can be enhanced by using person-tailored daily life information regarding positive affect.     

Conservation genetics in a globally changing environment: present problems,paradoxes and future challenges

Despite recent advances in conservation genetics and related disciplines and the growing impact that conservation genetics is having in conservation biology, our knowledge on several key issues in the field is still insufficient. Here we identify some of these issues together with addressing several paradoxes which have to be solved before conservation genetics can face new challenges that are appearing in the transitory phase from the population genetics into the population genomics era. Most of these issues, paradoxes and challenges, like the central dogma of conservation genetics, the computational, theoretical and laboratory experiment achievements and limitations in the conservation genetics field have been discussed. Further knowledge on the consequences of inbreeding and outbreeding depression in wild populations as well as the capacity of small populations to adapt to local environmental conditions is also urgently needed. The integration of experimental, theoretical and applied conservation genetics will contribute to improve our understanding of methodological and applied aspects of conservation genetics.     

Ovine lymphocyte antigens: a comparison of Australian and European antisera

Lymphocyte alloantigens were determined in 183 Australian merino sheep, using antisera from Australian and European laboratories. The study had two aims: (1) to compare reagents characterized in the different laboratories and to correlate antigen definition; and (2) to define lymphocyte antigens for use as genetic markers in two flocks of sheep which had been selectively bred for resistance or susceptibility to the intestinal parasite Trichostrongylus colubriformis, in order to extend a previous study which had indicated linkage between resistance to the parasite and the sheep major histocompatibility system. Good or excellent correspondence was found between four Australian and four European specificities and it was concluded that continued international collaboration would allow definition of markers for future genetic or disease susceptibility studies.     

Polyploidy and cellular mechanisms changing leaf size: comparison of diploid and autotetraploid populations in two species of Lolium

BACKGROUND AND AIMS: Growth and development of plant organs, including leaves, depend on cell division and expansion. Leaf size is increased by greater cell ploidy, but the mechanism of this effect is poorly understood. Therefore, in this study, the role of cell division and expansion in the increase of leaf size caused by polyploidy was examined by comparing various cell parameters of the mesophyll layer of developing leaves of diploid and autotetraploid cultivars of two grass species, Lolium perenne and L. multiflorum. METHODS: Three cultivars of each ploidy level of both species were grown under pot conditions in a controlled growth chamber, and leaf elongation rate and the cell length profile at the leaf base were measured on six plants in each cultivar. Cell parameters related to division and elongation activities were calculated by a kinematic method. KEY RESULTS: Tetraploid cultivars had faster leaf elongation rates than did diploid cultivars in both species, resulting in longer leaves, mainly due to their longer mature cells. Epidermal and mesophyll cells differed 20-fold in length, but were both greater in the tetraploid cultivars of both species. The increase in cell length of the tetraploid cultivars was caused by a faster cell elongation rate, not by a longer period of cell elongation. There were no significant differences between cell division parameters, such as cell production rate and cell cycle time, in the diploid and tetraploid cultivars. CONCLUSION: The results demonstrated clearly that polyploidy increases leaf size mainly by increasing the cell elongation rate, but not the duration of the period of elongation, and thus increases final cell size.