Epidemiology of physical inactivity in Nigeria: a systematic review and meta-analysis.

BACKGROUND: Physical activity is crucial to preventing noncommunicable diseases. This study aimed to provide up-to-date evidence on the epidemiology of insufficient physical activity across Nigeria to increase awareness and prompt relevant policy and public health response. METHODS: A systematic literature search of community-based studies on physical inactivity was conducted. We constructed a meta-regression epidemiologic model to determine the age-adjusted prevalence and number of physically inactive persons in Nigeria for 1995 and 2020. RESULTS: Fifteen studies covering a population of 13 814 adults met our selection criteria. The pooled crude prevalence of physically inactive persons in Nigeria was 52.0% (95% CI: 33.7-70.4), with prevalence in women higher at 55.8% (95% CI: 29.4-82.3) compared to men at 49.3% (95% CI: 24.7-73.9). Across settings, prevalence of physically inactive persons was significantly higher among urban dwellers (56.8%, 35.3-78.4) compared to rural dwellers (18.9%, 11.9-49.8). Among persons aged 20-79 years, the total number of physically inactive persons increased from 14.4 million to 48.6 million between 1995 and 2020, equivalent to a 240% increase over the 25-year period. CONCLUSIONS: A comprehensive and robust strategy that addresses occupational policies, town planning, awareness and information, and sociocultural and contextual issues is crucial to improving physical activity levels in Nigeria.

Commissioning a multileaf collimator virtual cone for the stereotactic radiosurgery of trigeminal neuralgia.

A multileaf collimator (MLC), virtual-cone treatment technique has been commissioned for trigeminal neuralgia (TGN) at Tri-Cities Cancer Center (TCCC). This novel technique was initially developed at the University of Alabama in Birmingham (UAB); it is designed to produce a spherical dose profile similar to a fixed, 5-mm conical collimator distribution. Treatment is delivered with a 10-MV flattening-filter-free (FFF) beam using a high-definition MLC on a Varian Edge linear accelerator. Absolute dose output and profile measurements were performed in a 20 × 20 × 14 cm3 solid-water phantom using an Exradin W2 scintillation detector and Gafchromic EBT3 film. Dose output constancy for the virtual cone was evaluated over 6 months using an Exradin A11 parallel plate chamber. The photo-neutron dose generated by these treatments was assessed at distances of 50 and 100 cm from isocenter using a Ludlum Model 30-7 Series Neutron Meter. TGN treatments at TCCC have been previously delivered at 6-MV FFF using a 5-mm stereotactic cone. To assess the dosimetric impact of using a virtual cone, eight patients previously treated for TGN with a 5-mm cone were re-planned using a virtual cone. Seven patients have now been treated for TGN using a virtual cone at TCCC. Patient-specific quality assurance was performed for each patient using Gafchromic EBT-XD film inside a Standard Imaging Stereotactic Dose Verification Phantom. The commissioning results demonstrate that the virtual-cone dosimetry, first described at UAB, is reproducible on a second Edge linear accelerator at an independent clinical site. The virtual cone is a credible alternative to a physical, stereotactic cone for the treatment of TGN at TCCC.

Hierarchical clustering optimizes the tradeoff between compositionality and expressivity of task structures for flexible reinforcement learning.

A hallmark of human intelligence, but challenging for reinforcement learning (RL) agents, is the ability to compositionally generalise, that is, to recompose familiar knowledge components in novel ways to solve new problems. For instance, when navigating in a city, one needs to know the location of the destination and how to operate a vehicle to get there, whether it be pedalling a bike or operating a car. In RL, these correspond to the reward function and transition function, respectively. To compositionally generalize, these two components need to be transferable independently of each other: multiple modes of transport can reach the same goal, and any given mode can be used to reach multiple destinations. Yet there are also instances where it can be helpful to learn and transfer entire structures, jointly representing goals and transitions, particularly whenever these recur in natural tasks (e.g., given a suggestion to get ice cream, one might prefer to bike, even in new towns). Prior theoretical work has explored how, in model-based RL, agents can learn and generalize task components (transition and reward functions). But a satisfactory account for how a single agent can simultaneously satisfy the two competing demands is still lacking. Here, we propose a hierarchical RL agent that learns and transfers individual task components as well as entire structures (particular compositions of components) by inferring both through a non-parametric Bayesian model of the task. It maintains a factorised representation of task components through a hierarchical Dirichlet process, but it also represents different possible covariances between these components through a standard Dirichlet process. We validate our approach on a variety of navigation tasks covering a wide range of statistical correlations between task components and show that it can also improve generalisation and transfer in more complex, hierarchical tasks with goal/subgoal structures. Finally, we end with a discussion of our work including how this clustering algorithm could conceivably be implemented by cortico-striatal gating circuits in the brain.

Current prevalence pattern of tobacco smoking in Nigeria: a systematic review and meta-analysis.

BACKGROUND: National smoking cessation strategies in Nigeria are hindered by lack of up-to-date epidemiologic data. We aimed to estimate prevalence of tobacco smoking in Nigeria to guide relevant interventions. METHODS: We conducted systematic search of publicly available evidence from 1990 through 2018. A random-effects meta-analysis and meta-regression epidemiologic model were employed to determine prevalence and number of smokers in Nigeria in 1995 and 2015. RESULTS: Across 64 studies (n = 54,755), the pooled crude prevalence of current smokers in Nigeria was 10.4% (9.0-11.7) and 17.7% (15.2-20.2) for ever smokers. This was higher among men compared to women in both groups. There was considerable variation across geopolitical zones, ranging from 5.4% (North-west) to 32.1% (North-east) for current smokers, and 10.5% (South-east) to 43.6% (North-east) for ever smokers. Urban and rural dwellers had relatively similar rates of current smokers (10.7 and 9.1%), and ever smokers (18.1 and 17.0%). Estimated median age at initiation of smoking was 16.8 years (IQR: 13.5-18.0). From 1995 to 2015, we estimated an increase in number of current smokers from 8 to 11 million (or a decline from 13 to 10.6% of the population). The pooled mean cigarettes consumption per person per day was 10.1 (6.1-14.2), accounting for 110 million cigarettes per day and over 40 billion cigarettes consumed in Nigeria in 2015. CONCLUSIONS: While the prevalence of smokers may be declining in Nigeria, one out of ten Nigerians still smokes daily. There is need for comprehensive measures and strict anti-tobacco laws targeting tobacco production and marketing.

Epidemiology of harmful use of alcohol in Nigeria: a systematic review and meta-analysis.

Background: Nigeria, the most populous country in Africa, has reported relatively high levels of alcohol misuse, yet limited resources to guide effective population-wide response. There is a need to integrate existing empirical information in order to increase the power and precision of estimating epidemiological evidence necessary for informing policies and developing prevention programs. Objectives: We aimed to estimate nationwide and zonal prevalence of harmful use of alcohol in Nigeria to inform public health policy and planning. Methods: Epidemiologic reports on alcohol use in Nigeria from 1990 through 2018 were systematically searched and abstracted. We employed random-effects meta-analysis and meta-regression model to determine the number of harmful alcohol users. Results: 35 studies (n = 37,576 Nigerians) were identified. Pooled crude prevalence of harmful use of alcohol was 34.3% (95% CI: 28.6-40.1); twice as high among men (43.9%, 31.1-56.8) compared to women (23.9%, 16.4-31.4). Harmful alcohol use was higher in rural settings (40.1%, 24.2-56.1) compared to urban settings (31.2%, 22.9-39.6). The number of harmful alcohol users aged ≥15 years increased from 24 to 34 million from 1995 to 2015. However, actual age-adjusted prevalence of harmful use of alcohol in Nigeria decreased from 38.5% to 32.6% over the twenty-year period. Conclusions: While the prevalence of the total population that drinks harmfully appears to be dropping, absolute number of individuals that would be classified as harmful drinkers is increasing. This finding highlights the complexity of identifying and advocating for substance abuse policies in rapidly changing demographic settings common in Africa, Asia, and other developing countries.

Cellular immune correlates analysis of an HIV-1 preexposure prophylaxis trial.

HIV-1-specific T-cell responses in exposed seronegative subjects suggest that a viral breach of the exposure site is more common than current transmission rates would suggest and that host immunity can extinguish subsequent infection foci. The Preexposure Prophylaxis Initiative (iPrEx) chemoprophylaxis trial provided an opportunity to rigorously investigate these responses in a case-control immunology study; 84 preinfection peripheral blood mononuclear cell samples from individuals enrolled in the iPrEx trial who later seroconverted were matched with 480 samples from enrolled subjects who remained seronegative from both the placebo and active treatment arms. T-cell responses to HIV-1 Gag, Protease, Integrase, Reverse Transcriptase, Vif, and Nef antigens were quantified for all subjects in an IFN-γ enzyme-linked immunospot (ELISpot) assay. IFN-γ responses varied in magnitude and frequency across subjects. A positive response was more prevalent in those who remained persistently HIV-1-negative for Gag (P = 0.007), Integrase (P < 0.001), Vif (P < 0.001), and Nef (P < 0.001). When correlated with outcomes in the iPrEx trial, Vif- and Integrase-specific T-cell responses were associated with reduced HIV-1 infection risk [hazard ratio (HR) = 0.36, 95% confidence interval (95% CI) = 0.19-0.66 and HR = 0.52, 95% CI = 0.28-0.96, respectively]. Antigen-specific responses were independent of emtricitabine/tenofovir disoproxil fumarate use. IFN-γ secretion in the ELISpot was confirmed using multiparametric flow cytometry and largely attributed to effector memory CD4+ or CD8+ T cells. Our results show that HIV-1-specific T-cell immunity can be detected in exposed but uninfected individuals and that these T-cell responses can differentiate individuals according to infection outcomes.

Irreversible Electroporation Can Effectively Ablate Hepatocellular Carcinoma to Complete Pathologic Necrosis.

PURPOSE: To describe full explant pathology and radiographic correlation in patients with hepatocellular carcinoma (HCC) treated with irreversible electroporation (IRE) who subsequently underwent liver transplant. MATERIALS AND METHODS: In a retrospective study, 6 patients who had undergone IRE for HCC and subsequent orthotopic liver transplant during the period 2011-2013 were evaluated. Of the 6 patients, 4 had Child-Pugh class A cirrhosis, and 2 had class B cirrhosis. Irreversible electroporation was performed for a single focal HCC with median tumor diameter of 22 mm (range, 6-26 mm). After IRE, follow-up multiphasic cross-sectional imaging was performed at 1 month and every 3 months thereafter until liver transplant. Mean time between IRE and transplant was 10 months (range, 3-17 mo). Assessment of imaging response was based on modified Response Evaluation Criteria In Solid Tumors. Liver explants were evaluated for necrosis and viable carcinoma in IRE-treated tumors. RESULTS: After IRE, all tumors showed a complete response on follow-up imaging. Five tumors showed complete pathologic necrosis without any viable carcinoma, sharply demarcated from the surrounding hepatic parenchyma. Bile ducts within the treatment area were preserved. A single tumor treated with a bipolar IRE probe had < 5% viable carcinoma cells at the periphery. CONCLUSIONS: This study demonstrates the efficacy of IRE for HCC based on pathologic evaluation and correlation to radiologic findings.

The antibacterial and antifungal activity of essential oils extracted from Guatemalan medicinal plants.

CONTEXT: Essential oils are prevalent in many medicinal plants used for oral hygiene and treatment of diseases. OBJECTIVE: Medicinal plant species were extracted to determine the essential oil content. Those producing sufficient oil were screened for activity against Staphylococcus aureus, Escherichia coli, Streptococcus mutans, Lactobacillus acidophilus, and Candida albicans. MATERIALS AND METHODS: Plant samples were collected, frozen, and essential oils were extracted by steam distillation. Minimum inhibitory concentrations (MIC) were determined using a tube dilution assay for those species yielding sufficient oil. RESULTS: Fifty-nine of the 141 plant species produced sufficient oil for collection and 12 species not previously reported to produce essential oils were identified. Essential oil extracts from 32 species exhibited activity against one or more microbes. Oils from eight species were highly inhibitory to S. mutans, four species were highly inhibitory to C. albicans, and 19 species yielded MIC values less than the reference drugs. DISCUSSION: RESULTS suggest that 11 species were highly inhibitory to the microbes tested and merit further investigation. Oils from Cinnamomum zeylanicum Blume (Lauraceae), Citrus aurantiifolia (Christm.) Swingle (Rutaceae), Lippia graveolens Kunth (Verbenaceae), and Origanum vulgare L. (Lamiaceae) yielded highly significant or moderate activity against all microbes and have potential as antimicrobial agents. CONCLUSION: Teas prepared by decoction or infusion are known methods for extracting essential oils. Oils from 11 species were highly active against the microbes tested and merit investigation as to their potential for addressing health-related issues and in oral hygiene.

Pain scores show no monotonic upward or downward trend over time.

BACKGROUND: Self-reported pain scales are commonly used in emergency departments (EDs). The 11-point (0-10) numerical rating scale is a commonly used scale for adults visiting EDs in the United States. Despite their widespread use, little is known about whether distribution of pain scores has remained consistent over time. OBJECTIVES: The objective of this study is to determine if there were upwards or downwards (monotonic) trends in pain scores over time at a single hospital. METHODS: Retrospective chart review for the years 2003-2011. All pain scores for May 1(st) and 2(nd) of those years were collected. Multinomial logistic regression was used to model the probability of a patient rating their pain in each of 11 categories (scores 0 to 10) as a function of the calendar year. Additional analysis was carried out with pain scores grouped into four categories. RESULTS: Data were collected from 2934 patient charts. Pain scores were recorded in 2136 charts, and 1637 of these pain scores were above zero (i.e., 1-10). The pain score distribution differed significantly over time (p = 0.001); however, there was no monotonic (single-direction) trend. CONCLUSION: Although there were significant shifts in pain scores over time, there is not a significant monotonic trend. At this hospital, there was no "inflation" or "deflation" in pain scores over time. Shifts in distribution, even when not in a single direction, may be important for researchers examining pain scores in the ED.

Estimating the prevalence of overweight and obesity in Nigeria in 2020: a systematic review and meta-analysis.

BACKGROUND: Targeted public health response to obesity in Nigeria is relatively low due to limited epidemiologic understanding. We aimed to estimate nationwide and sub-national prevalence of overweight and obesity in the adult Nigerian population. METHODS: MEDLINE, EMBASE, Global Health, and Africa Journals Online were systematically searched for relevant epidemiologic studies in Nigeria published on or after 01 January 1990. We assessed quality of studies and conducted a random-effects meta-analysis on extracted crude prevalence rates. Using a meta-regression model, we estimated the number of overweight and obese persons in Nigeria in the year 2020. RESULTS: From 35 studies (n = 52,816), the pooled crude prevalence rates of overweight and obesity in Nigeria were 25.0% (95% confidence interval, CI: 20.4-29.6) and 14.3% (95% CI: 12.0-15.5), respectively. The prevalence in women was higher compared to men at 25.5% (95% CI: 17.1-34.0) versus 25.2% (95% CI: 18.0-32.4) for overweight, and 19.8% (95% CI: 3.9-25.6) versus 12.9% (95% CI: 9.1-16.7) for obesity, respectively. The pooled mean body mass index (BMI) and waist circumference were 25.6 kg/m2 and 86.5 cm, respectively. We estimated that there were 21 million and 12 million overweight and obese persons in the Nigerian population aged 15 years or more in 2020, accounting for an age-adjusted prevalence of 20.3% and 11.6%, respectively. The prevalence rates of overweight and obesity were consistently higher among urban dwellers (27.2% and 14.4%) compared to rural dwellers (16.4% and 12.1%). CONCLUSIONS: Our findings suggest a high prevalence of overweight and obesity in Nigeria. This is marked in urban Nigeria and among women, which may in part be due to widespread sedentary lifestyles and a surge in processed food outlets, largely reflective of a trend across many African settings.KEY MESSAGESAbout 12 million persons in Nigeria were estimated to be obese in 2020, with prevalence considerably higher among women. Nutritional and epidemiological transitions driven by demographic changes, rising income, urbanization, unhealthy lifestyles, and consumption of highly processed diets appear to be driving an obesity epidemic in the country.

Prevalence, awareness, treatment, and control of hypertension in Nigeria in 1995 and 2020: A systematic analysis of current evidence.

Improved understanding of the current burden of hypertension, including awareness, treatment, and control, is needed to guide relevant preventative measures in Nigeria. A systematic search of studies on the epidemiology of hypertension in Nigeria, published on or after January 1990, was conducted. The authors employed random-effects meta-analysis on extracted crude hypertension prevalence, and awareness, treatment, and control rates. Using a meta-regression model, overall hypertension cases in Nigeria in 1995 and 2020 were estimated. Fifty-three studies (n = 78 949) met our selection criteria. Estimated crude prevalence of pre-hypertension (120-139/80-89 mmHg) in Nigeria was 30.9% (95% confidence interval [CI]: 22.0%-39.7%), and the crude prevalence of hypertension (≥140/90 mmHg) was 30.6% (95% CI: 27.3%-34.0%). When adjusted for age, study period, and sample, absolute cases of hypertension increased by 540% among individuals aged ≥20 years from approximately 4.3 million individuals in 1995 (age-adjusted prevalence 8.6%, 95% CI: 6.5-10.7) to 27.5 million individuals with hypertension in 2020 (age-adjusted prevalence 32.5%, 95% CI: 29.8-35.3). The age-adjusted prevalence was only significantly higher among men in 1995, with the gap between both sexes considerably narrowed in 2020. Only 29.0% of cases (95% CI: 19.7-38.3) were aware of their hypertension, 12.0% (95% CI: 2.7-21.2) were on treatment, and 2.8% (95% CI: 0.1-5.7) had at-goal blood pressure in 2020. Our study suggests that hypertension prevalence has substantially increased in Nigeria over the last two decades. Although more persons are aware of their hypertension status, clinical treatment and control rates, however, remain low. These estimates are relevant for clinical care, population, and policy response in Nigeria and across Africa.

Activity of acetone and methanol extracts from thirty-one medicinal plant species against herpes simplex virus types 1 and 2.

CONTEXT: Thirty-one medicinal plant species from Hawaii, Morocco, and the Sonoran Desert, USA have been shown in past studies to be highly inhibitory to pathogenic bacteria, fungi, and certain cancer cell lines. However, none were tested for antiviral activity. OBJECTIVE: Acetone and methanol extracts from these species were bio-assayed for antiviral activity against herpes simplex virus types 1 and 2, and for cytotoxicity to the Vero C1008 cell line. MATERIALS AND METHODS: Extracts from these species were tested in vitro for antiviral activity using an immunoperoxidase mini-plaque reduction assay to detect viral structural protein synthesis. A 50% inhibitory concentration (IC(50)) was computed. Sulforhodamine B and neutral red assays were used to qualitatively and quantitatively assess the cytotoxicity of extracts to C1008 cells, and to compute a 50% cytotoxic concentration (CC(50)) using a dose response curve. RESULTS: Eight of the 31 plant species assayed showed significant antiviral activity against HSV 1 and HSV 2 viruses. The acetone extract of Kalanchoe pinnata Pers. (Crassulaceae) produced an IC(50) of 0.025 mg/mL and a CC(50) of 1.25 mg/mL yielding a therapeutic index of 50. Additionally, this extract reduced plaque numbers to zero or near zero at a concentration of 0.1 mg/mL when added 30 min before or 30 min after virus infection. DISCUSSION AND CONCLUSION: The mechanism of inhibition against HSV 1 and HSV 2 viruses is now being investigated, along with fractionation of the acetone extract in search of the active compound or compounds.

Estimating morbidity due to stroke in Nigeria: a systematic review and meta-analysis.

BACKGROUND: The response to stroke in Nigeria is impaired by inadequate epidemiologic information. We sought to collate available evidence and estimate the incidence of stroke and prevalence of stroke survivors in Nigeria. METHODS: Using random effects meta-analysis, we pooled nationwide and regional incidence and prevalence of stroke from the estimates reported in each study. RESULTS: Eleven studies met our selection criteria. The pooled crude incidence of stroke in Nigeria was 26.0 (12.8-39.0) /100,000 person-years, with this higher among men at 34.1 (9.7-58.4) /100,000, compared to women at 21.2 (7.4-35.0) /100,000. The pooled crude prevalence of stroke survivors in Nigeria was 6.7 (5.8-7.7) /1000 population, with this also higher among men at 6.4 (5.1-7.6) /1000, compared to women at 4.4 (3.4-5.5) /1000. In the period 2000-2009, the incidence of stroke in Nigeria was 24.3 (95% CI: 11.9-36.8) per 100,000, with this increasing to 27.4 (95% CI: 2.2-52.7) per 100,000 from 2010 upwards. The prevalence of stroke survivors increased minimally from 6.0 (95% CI: 4.6-7.5) per 1000 to 7.5 (95% CI: 5.8-9.1) per 1000 over the same period. The prevalence of stroke survivors was highest in the South-south region at 13.4 (9.1-17.8) /100,000 and among rural dwellers at 10.8 (7.5-14.1) /100,000. CONCLUSION: Although study period does not appear to contribute substantially to variations in stroke morbidity in Nigeria, an increasing number of new cases compared to survivors may be due in part to limited door-door surveys, or possibly reflects an increasing mortality from stroke in the country.

Five-year prospective evaluation of mandibular overdentures retained by two microthreaded, TiOblast nonsplinted implants and retentive ball anchors.

PURPOSE: The aim of this 5-year prospective evaluation was to assess the bone and peri-implant mucosa responses at unsplinted, microthread implants supporting mandibular overdentures and to determine patient responses to therapy. MATERIALS AND METHODS: Two implants were placed by a 1-stage procedure in the parasymphyseal mandibles of 59 subjects. Implant placement was followed by immediate insertion of overdentures without connection to abutments. After 3 months, connection using Dalla Bona attachments was made and peri-implant mucosa, peri-implant bone, and patient perceptions of treatment were evaluated. RESULTS: The implant success rate was 95.9% from 6 to 60 months. The changes in marginal bone levels were positive (bone gain) but did not reach statistical significance at 12, 36, or 60 months (+0.13 +/- 0.59 mm, +0.23 +/- 0.66 mm, and +0.09 +/- 0.79, respectively). Treatment was viewed as effective; patients rating satisfaction with their teeth increased from a preoperative level of 12.1% to 94.6% at overdenture abutment connection and remained high (81.6%) after 5 years. CONCLUSIONS: Expedited mandibular overdenture therapy utilizing unsplinted, microthreaded mandibular parasymphyseal implants was associated with high implant survival, preservation of crestal bone, and high patient satisfaction. Complications were minor and related to prosthodontic features of therapy.

The impact of controlled release capsules of monensin on postcalving haptoglobin concentrations in dairy cattle.

This study was designed to assess the impact of a controlled release capsule (CRC) of monensin, administered prior to calving, on postcalving haptoglobin levels. The role of disease on haptoglobin levels was also studied. The study population consisted of 1010 cows from 25 Holstein dairy herds near Guelph, Ontario. Monensin CRC or placebo capsules were randomly assigned within each herd 3 wk prior to the expected calving date. Serum from week 1 and week 6 postcalving was submitted for quantification of haptoglobin concentrations. Haptoglobin results were analyzed for associations with treatment, health data, and individual cow factors up to 95 d in milk. Haptoglobin concentrations were higher in week 1 than week 6 (P < 0.05). In univariate analysis, several diseases were significantly associated with haptoglobin concentrations. However, occurrence of disease appeared to be a confounding factor in the data interpretation. Thus, the analysis was stratified by the presence or absence of disease. There appeared to be associations between factors other than clinical disease contributing to increased haptoglobin levels in both clinically healthy and unhealthy cattle. Haptoglobin served as a good indicator of inflammatory disease. Monensin CRC treatment was associated with increased haptoglobin concentrations in clinically unhealthy cattle, perhaps reflecting a better ability to respond to disease challenge. The lower haptoglobin concentrations in monensin CRC treated cattle that were clinically normal may be a reflection of reduced subclinical disease.

Host plant predictability and the feeding patterns of monophagous, oligophagous, and polyphagous insect herbivores.

Host plant preferences for 34 insect herbivore species are reported. Most polyphagous herbivores feeding on annuals, herbaceous perennials, and woody perennials show distinct preferences for the least abundant plant species among their various host plants. In addition, some populations of widely distributed polyphagous species are much more specialized in their diet than host plant lists alone would suggest. The high level of polyphagy on annuals and herbaceous perennials is suggested to be strongly influenced by the unpredictability of the host plant that is, in turn, controlled by environmental variability. Oligophagous herbivores preferred the least abundant woody perennials on the study sites. Ten of the 22 monophagous herbivores preferred the rarest of all the plant species on the same sites.

Feeding patterns of monophagous, oligophagous, and polyphagous insect herbivores: The effect of resource abundance and plant chemistry.

Leaf tissue preferences of monophagous, oligophagous, and polyphagous insect herbivores were determined using young and mature leaf tissue abundances and herbivore feeding observations. Larvae of monophagous and oligophagous herbivores preferred young leaf tissues while, overall, larvae of polyphagous species preferred mature leaves of their various host plants. Even though a species is often polyphagous over its geographical range, larvae from local populations may be very specialized in their diet. When this occurs these specialized larvae prefer the more nutritious and perhaps more toxic young leaves of some of their host plants. Resource abundance and plant chemistry are discussed as major factors influencing herbivore feeding patterns.

Douglas-fir (Pseudotsuga menziesii)-spruce budworm (Choristoneura occidentalis) interactions: the effect of nutrition, chemical defenses, tissue phenology, and tree physical parameters on budworm success.

Measurements of foliage quality, physiological, and phenological condition of sample trees were used as independent variables in multiple correlation analyses to determine their effect on female and male spruce budworm larval dry weights. Female budworm from trees high in foliar concentrations of beta-pinene, myrcene and total nitrogen weighed less than those from trees lacking these characteristics. Male budworm from trees high in foliar concentrations of alpha-pinene, myrcene, terpinolene, citronellyl acetate, and bornyl acetate weighted less than those from trees lacking these characteristics. Additionally, relatively vigorous and productive trees tended to be less susceptible (as evidenced by reduced larval weight) to budworm of either sex.