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The coronavirus disease 2019 (COVID-19) has serious physiological and psychological consequences. The long-term (>12 weeks post-infection) impact of COVID-19 on mental health, specifically in older adults, is unclear. We longitudinally assessed the association of COVID-19 with depression symptomatology in community-dwelling older adults with metabolic syndrome within the framework of the PREDIMED-Plus cohort.
Methods
Participants (n = 5486) aged 55–75 years were included in this longitudinal cohort. COVID-19 status (positive/negative) determined by tests (e.g. polymerase chain reaction severe acute respiratory syndrome coronavirus 2, IgG) was confirmed via event adjudication (410 cases). Pre- and post-COVID-19 depressive symptomatology was ascertained from annual assessments conducted using a validated 21-item Spanish Beck Depression Inventory-II (BDI-II). Multivariable linear and logistic regression models assessed the association between COVID-19 and depression symptomatology.
Results
COVID-19 in older adults was associated with higher post-COVID-19 BDI-II scores measured at a median (interquartile range) of 29 (15–40) weeks post-infection [fully adjusted β = 0.65 points, 95% confidence interval (CI) 0.15–1.15; p = 0.011]. This association was particularly prominent in women (β = 1.38 points, 95% CI 0.44–2.33, p = 0.004). COVID-19 was associated with 62% increased odds of elevated depression risk (BDI-II ≥ 14) post-COVID-19 when adjusted for confounders (odds ratio; 95% CI 1.13–2.30, p = 0.008).
Conclusions
COVID-19 was associated with long-term depression risk in older adults with overweight/obesity and metabolic syndrome, particularly in women. Thus, long-term evaluations of the impact of COVID-19 on mental health and preventive public health initiatives are warranted in older adults.
OBJECTIVES/GOALS: Diagnostic odyssey is the time it can take to a patient for receiving a diagnosis. Diagnostic process in rare diseases can be complex due to the heterogeneity of symptoms and lack of access to care. We aim to evaluate the association between diagnostic odyssey, perceived stress, and access to care, in parents of Puerto Rican patients with a rare disease. METHODS/STUDY POPULATION: We propose a cross-sectional study in parents of 100 children who received an uninformative whole exome sequencing (WES) report during a scheduled appointment with their geneticist. Discussion of WES results during clinical session, followed by a Perceived Stress Scale (PSS-10) and semi-structured interview to explore the experience of access to care during the diagnostic process will be arranged. Observation and interviews will be recorded. Data analysis and descriptive statistics will be calculated using STATA. Statistical associations (OR) will be estimated using generalized linear models at a 5% significance level. RESULTS/ANTICIPATED RESULTS: We expect to find high perceived stress in parents of Puerto Rican pediatric individuals having rare diseases, especially among single mothers. We will be able to identify limited access to care in Puerto Rico, especially in the testing pre-authorization process and long waits for geneticist appointments. Demand for advanced diagnostics is above the number of medical geneticists available in Puerto Rico, which triggers delayed diagnosis, management, and counseling. Therefore, these could affect the health disparities in our population with rare diseases. DISCUSSION/SIGNIFICANCE: This descriptive study will evaluate perceived stress in parents of pediatric patients living a diagnostic odyssey in Puerto Rico. No study has described perceived stress and access to care in this Hispanic population with undiagnosed conditions. Findings will contribute to a deep understanding of diagnostic process and limited access to care.
Given $a,\,b\in \mathbb {R}$ and $\Phi \in C^{1}(\mathbb {S}^{2})$, we study immersed oriented surfaces $\Sigma$ in the Euclidean 3-space $\mathbb {R}^{3}$ whose mean curvature $H$ and Gauss curvature $K$ satisfy $2aH+bK=\Phi (N)$, where $N:\Sigma \rightarrow \mathbb {S}^{2}$ is the Gauss map. This theory widely generalizes some of paramount importance such as the ones constant mean and Gauss curvature surfaces, linear Weingarten surfaces and self-translating solitons of the mean curvature flow. Under mild assumptions on the prescribed function $\Phi$, we exhibit a classification result for rotational surfaces in the case that the underlying fully nonlinear PDE that governs these surfaces is elliptic or hyperbolic.
The early clinical predictors of respiratory failure in Latin Americans with Guillain–Barré syndrome (GBS) have scarcely been studied. This is of particular importance since Latin America has a high frequency of axonal GBS variants that may imply a worse prognosis.
Methods:
We studied 86 Mexican patients with GBS admitted to the Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, a referral center of Mexico City, to describe predictors of invasive mechanical ventilation (IMV).
Results:
The median age was 40 years (interquartile range: 26–53.5), with 60.5% men (male-to-female ratio: 1.53). Most patients (65%) had an infectious antecedent (40.6% gastrointestinal). At admission, 38% of patients had a Medical Research Council (MRC) sum score <30. Axonal subtypes predominated (60.5%), with acute motor axonal neuropathy being the most prevalent (34.9%), followed by acute inflammatory demyelinating polyneuropathy (32.6%), acute motor sensory axonal neuropathy (AMSAN) (25.6%), and Fisher syndrome (7%). Notably, 15.1% had onset in upper limbs, 75.6% dysautonomia, and 73.3% pain. In all, 86% received either IVIg (9.3%) or plasma exchange (74.4%). IMV was required in 39.5% patients (72.7% in AMSAN). A multivariate model without including published prognostic scores yielded the time since onset to admission <15 days, axonal variants, MRC sum score <30, and bulbar weakness as independent predictors of IMV. The model including grading scales yielded lower limbs onset, Erasmus GBS respiratory insufficiency score (EGRIS) >4, and dysautonomia as predictors.
Conclusion:
These results suggest that EGRIS is a good prognosticator of IMV in GBS patients with a predominance of axonal electrophysiological subtypes, but other early clinical data should also be considered.
Although bovine embryo in vitro production (IVP) is a common assisted reproductive technology, critical points warrant further study, including sperm traits and oxidative status of sperm for in vitro fertilization (IVF). Our aim was to evaluate whether the lipid peroxidation index of commercial bull semen is influenced by sperm traits and oxidative status of sperm populations selected using Percoll® gradient. Semen straws from 48 batches from 14 Nelore bulls were thawed individually, analyzed for motility and subjected to Percoll selection. After Percoll, the lipid peroxidation index of the extender was evaluated, whereas selected sperm were analyzed for motility, acrosome and membrane integrity, mitochondrial membrane potential, chromatin resistance and oxidative potential under IVF conditions. Batches were divided retrospectively in four groups according to lipid peroxidation index. Sperm from Group 4 with the lowest index of lipid peroxidation had, after Percoll selection, greater plasma membrane integrity (81.3%; P = 0.004), higher mitochondrial potential (81.1%; P = 0.009) and lower oxidative potential (135.3 ng thiobarbituric acid reactive substances (TBARS)/ml; P = 0.026) compared with Group 1 with highest lipid peroxidation index (74.3%, 73% and 213.1 ng TBARS/ml, respectively). Furthermore, we observed negative correlations for the lipid peroxidation index with motility, membrane integrity and mitochondrial potential, and positive correlations with oxidative potential. In conclusion, oxidative stress in semen straws, as determined using lipid peroxidation in the extender, is associated with sperm traits and their oxidative potential under IVF conditions. These results provided further insights regarding the importance of preventing oxidative stress during semen handling and cryopreservation, as this could affect sperm selected for IVF. Finally, Percoll selection did not completely remove sperm with oxidative markers.
The Mexico City Basin has had exceptional plant and animal diversity since ancient times due to its varied orography and benign climate. This environment attracted diverse human groups, from hunter-gatherers to one of the most influential pre-Hispanic cultures of Mesoamerica: the Mexica, also known as the Aztec. The subsoil of Mexico City hides a rich and varied cultural heritage. The Archaeological Rescue Department works to preserve cultural heritage, review archaeological studies, and expand archaeological information with new findings. We report on archaeological rescue works carried out at two sites in the Mexico City Basin prior to the beginning of new construction projects. The first one is the Reforma Hidalgo Complex Office in Teocaltitlán, one of the neighborhoods of ancient Mexica City, Mexico-Tenochtitlan. Some wooden post samples were selected for accelerator mass spectrometry radiocarbon (AMS 14C) dating, believed to have been used as chinampa supports. We seek to determine their temporality and possible reuse by Hispanic builders. The second one, the La Otra Banda Site, is part of the human settlements that were founded around Cuicuilco, one of the main ancient urban centers of the highlands of Central Mexico. Some human bones and coal samples were selected to be dated, aiming to establish the site’s occupation time.
2020 was to be a landmark year for setting targets to stop biodiversity loss and prevent dangerous climate change. However, COVID-19 has caused delays to the 15th Conference of the Parties (COP) of the UN Convention on Biological Diversity and the 26th COP of the UN Framework Convention on Climate Change. Negotiations on the Global Biodiversity Framework and the second submission of Nationally Determined Contributions under the Paris Agreement were due to take place at these COPs. There is uncertainty as to how the COVID-19 disruption will affect the negotiations, whether parties will pursue more ambitious actions or take a weaker stance on issues. Our policy analysis shows there are broad opportunities for climate and biodiversity frameworks to better respond to COVID-19, by viewing future pandemics, biodiversity loss, and climate change as interconnected problems. Importantly, there needs to be greater focus on agriculture and food systems in discussions, establishing safeguards for carbon markets, and implementing nature-based solutions in meeting the Paris Agreement goals. We can no longer delay action to address the biodiversity and climate emergencies, and accelerating sustainable recovery plans through virtual spaces may help keep discussions and momentum before the resumption of in-person negotiations.
Non-technical summary:
High ambition needed at UN biodiversity and climate conferences to address pandemics, biodiversity, climate change, and health.
Standard external beam radiotherapy is a treatment option for patients with localised prostate cancer and is used in patients with low-, intermediate- and high-risk disease with androgen deprivation according to the risk of the disease. In the last few years, hypofractionated radiotherapy has been demonstrated to be as safe as standard radiotherapy if given over a shorter time than standard radiotherapy with larger doses per fraction. External radiotherapy for localised prostate cancer typically delivers 37–42 fractions of 1·8–2·0 Gy per fraction given 5 days per week over 7·5–8·5 weeks. Hypofractionated radiotherapy delivers 20–28 fractions of 2·5–2·6 Gy per fraction given 5 days per week over 4–5·6 weeks.
Methods:
A retrospective analysis of assessment of 30 patients was undertaken from 2016 to 2018. The aim of this study was to evaluate the 2-year outcomes of 30 patients with prostate cancer treated with hypofractionated radiotherapy 70 Gy in 28 fractions.
Results:
Biochemical failure with hypofractionated radiotherapy was found in a total of 20% of patients. In the classification by risk groups, there were no biochemical failures in low-risk patients; in the low intermediate course, 3·3% of patients; in the high intermediate group, 3·3% patients; and in the high-risk group, the largest documented biochemical failure was in 13·3% of patients. For acute urinary toxicity, grade I was 56·6%; grade II, 6·6%. For acute rectal toxicity, grade I was 46·6%; grade II, 3·3%.
Conclusion:
This is one of the first studies of hypofractionated radiotherapy in prostate cancer in Latin America, and the results of this study demonstrated that the outcomes were similar to the standard regimen in all risk groups.
Tuberous sclerosis complex is a rare genetic disorder leading to the growth of hamartomas in multiple organs, including cardiac rhabdomyomas. Children with symptomatic cardiac rhabdomyoma require frequent admissions to intensive care units, have major complications, namely, arrhythmias, cardiac outflow tract obstruction and heart failure, affecting the quality of life and taking on high healthcare cost. Currently, there is no standard pharmacological treatment for this condition, and the management includes a conservative approach and supportive care. Everolimus has shown positive effects on subependymal giant cell astrocytomas, renal angiomyolipoma and refractory seizures associated with tuberous sclerosis complex. However, evidence supporting efficacy in symptomatic cardiac rhabdomyoma is limited to case reports. The ORACLE trial is the first randomised clinical trial assessing the efficacy of everolimus as a specific therapy for symptomatic cardiac rhabdomyoma.
Methods:
ORACLE is a phase II, prospective, randomised, placebo-controlled, double-blind, multicentre protocol trial. A total of 40 children with symptomatic cardiac rhabdomyoma secondary to tuberous sclerosis complex will be randomised to receive oral everolimus or placebo for 3 months. The primary outcome is 50% or more reduction in the tumour size related to baseline. As secondary outcomes we include the presence of arrhythmias, pericardial effusion, intracardiac obstruction, adverse events, progression of tumour reduction and effect on heart failure.
Conclusions:
ORACLE protocol addresses a relevant unmet need in children with tuberous sclerosis complex and cardiac rhabdomyoma. The results of the trial will potentially support the first evidence-based therapy for this condition.
Sensitive and selective detection for cancer biomarkers is critical in cancer clinical diagnostics. In this work, we report an electrochemical detection platform for the carbohydrate antigen tumor marker 15-3 (CA15-3). It is based on a composite material of poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene] (MEH-PPV) and multi-walled carbon nanotubes (MWCNT), which deposited as active layer of an organic thin-film transistor. This layer was surface functionalized with the Anti-CA15-3 monoclonal antibody. The devices have a favorable electrical output response for VSD source-drain potentials between 0 to 5 volts, and VG as 8 volts. Once the antigen (CA15-3) is recognized by the antibody, the electrical response is diminished. The test has a linear response in the concentration range of 0–30 U mL - 1 of CA 15–3, with a lower detection limit of ~1 U mL - 1 and a stability of 90% with respect to the initial values after storing the device for two weeks. The method was successfully applied to the determination of CA15-3 in serum samples. Possibly, this used composite material has a greater scope and can be applied to another type of detection scheme.
To determine if specific dietary patterns are associated with risk of hypertension, type 2 diabetes mellitus (T2DM) and high BMI in four sites in Peru.
Design:
We analysed dietary patterns from a cohort of Peruvian adults in four geographical settings using latent class analysis. Associations with prevalence and incidence of hypertension, T2DM and high BMI were assessed using Poisson regression and generalised linear models, adjusted for potential confounders.
Setting:
Four sites in Peru varying in degree of urbanisation.
Participants:
Adults aged ≥35 years (n 3280).
Results:
We identified four distinct dietary patterns corresponding to different stages of the Peruvian nutrition transition, reflected by the foods frequently consumed in each pattern. Participants consuming the ‘stage 3’ diet, characterised by high proportional consumption of processed foods, animal products and low consumption of vegetables, mostly consumed in the semi-urban setting, showed the highest prevalence of all health outcomes (hypertension 32·1 %; T2DM 10·7 %; high BMI 75·1 %). Those with a more traditional ‘stage 1’ diet characterised by potato and vegetables, mostly consumed in the rural setting, had lower prevalence of hypertension (prevalence ratio; 95 CI: 0·57; 0·43, 0·75), T2DM (0·36; 0·16, 0·86) and high BMI (0·55; 0·48, 0·63) compared with the ‘stage 3’ diet. Incidence of hypertension was highest among individuals consuming the ‘stage 3’ diet (63·75 per 1000 person-years; 95 % CI 52·40, 77·55).
Conclusions:
The study found more traditional diets were associated with a lower prevalence of three common chronic diseases, while prevalence of these diseases was higher with a diet high in processed foods and low in vegetables.
Long-term heat stress (HS) induced by testicular insulation generates oxidative stress (OS) on the testicular environment; consequently activating antioxidant enzymes such as superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GPx). The aim of this work was to immunolocalize antioxidant enzymes present in different cells within the seminiferous tubule when rams were submitted to HS. Rams were divided into control (n = 6) and treated group (n = 6), comprising rams subjected to testicular insulation for 240 h. After the testicular insulation period, rams were subjected to orchiectomy. Testicular fragments were submitted to immunohistochemistry for staining against SOD, GR and GPx enzymes. We observed immunolocalization of GPx in more cell types of the testis after HS and when compared with other enzymes. In conclusion, GPx is the main antioxidant enzyme identified in testicular cells in an attempt to maintain oxidative balance when HS occurs.
To determine the association between excess body fat, assessed by skinfold thickness, and the incidence of type 2 diabetes mellitus (T2DM) and hypertension (HT).
Design:
Data from the ongoing PERU MIGRANT Study were analysed. The outcomes were T2DM and HT, and the exposure was skinfold thickness measured in bicipital, tricipital, subscapular and suprailiac areas. The Durnin–Womersley formula and SIRI equation were used for body fat percentage estimation. Risk ratios and population attributable fractions (PAF) were calculated using Poisson regression.
Setting:
Rural (Ayacucho) and urban shantytown district (San Juan de Miraflores, Lima) in Peru.
Participants:
Adults (n 988) aged ≥30 years (rural, rural-to-urban migrants, urban) completed the baseline study. A total of 785 and 690 were included in T2DM and HT incidence analysis, respectively.
Results:
At baseline, age mean was 48·0 (sd 12·0) years and 47 % were males. For T2DM, in 7·6 (sd 1·3) years, sixty-one new cases were identified, overall incidence of 1·0 (95 % CI 0·8, 1·3) per 100 person-years. Bicipital and subscapular skinfolds were associated with 2·8-fold and 6·4-fold risk of developing T2DM. On the other hand, in 6·5 (sd 2·5) years, overall incidence of HT was 2·6 (95 % CI 2·2, 3·1) per 100 person-years. Subscapular and overall fat obesity were associated with 2·4- and 2·9-fold risk for developing HT. The PAF for subscapular skinfold was 73·6 and 39·2 % for T2DM and HT, respectively.
Conclusions:
We found a strong association between subscapular skinfold thickness and developing T2DM and HT. Skinfold assessment can be a laboratory-free strategy to identify high-risk HT and T2DM cases.
The predominantly carbonate nature of the mountains near the coast of Málaga and Marbella (Costa del Sol, southern Spain) and the presence of springs have favored the formation of travertine buildups during the Quaternary. The geomorphic characteristics of the slopes and the location of the springs have determined the development of three types of travertine growths: (1) spring travertines, located preferentially on the south mountainside, where the slope is steepest; (2) pool-dam-cascade travertines, which form along the north and east edges, far from the carbonate relief and with a gentler slope; and (3) river-valley travertines, formed in the courses of the springs of any sector. Field observations combined with new amino acid racemization (AAR) dating of Helicidae gastropods show that most of the travertine formations are polyphasic and that their development was interrupted by stages of erosion and incision. Five stages of travertine development are evident, most of which are related to warm, moist episodes corresponding to marine oxygen isotope stages (MIS) 7, 5, 3, and 1, although local travertine growth also occurred during MIS 6 and during the transition from MIS 3 to 2.
Hernia is defined as the protrusion of one or several internal organs through an opening in the cavity that contains them due to a tissue defect, abdominal wall surgery by means of synthetic meshes is the most common method used for hernia repair, however, postsurgical effects can range from some discomfort, to chronic pain and even the reappearance of the hernia due to a poor mechanical adaptability between the synthetic tissue and the host tissue. The knowledge of the mechanical properties of the materials involved in hernia repair is fundamental in the understanding and subsequent solution of this type of problems. In this work, experimental data were obtained by means of uniaxial tensile tests in two perpendicular directions of commercial meshes used in hernia repair. The tests were carried out on the UniVert® machine of the CellScale® brand. Anisotropic mechanical behavior is observed due to the structure of the mesh and the interaction between each of the yarns that make it up. The data found vary with respect to the direction of traction and also has non-linear hyperelastic behavior, so the adjustment of curves was made through a hyperelastic model in the COMSOL Multiphysics® software through the Levenberg-Marquardt Algorithm for the characterization of these materials.
To determine the association between consumption of snacks and sweetened beverages and risk of overweight among children.
Design
Secondary analysis of the Young Lives cohort study in Peru.
Setting
Twenty sentinel sites from a total of 1818 districts available in Peru.
Subjects
Children in the younger cohort of the Young Lives study in Peru, specifically those included in the third (2009) and the fourth (2013) rounds.
Results
A total of 1813 children were evaluated at baseline; 49·2 % girls and mean age 8·0 (sd 0·3) years. At baseline, 3·3 (95 % CI 2·5, 4·2) % reported daily sweetened beverage consumption, while this proportion was 3·9 (95 % CI 3·1, 4·9) % for snacks. Baseline prevalence of overweight was 22·0 (95 % CI 20·1, 23·9) %. Only 1414 children were followed for 4·0 (sd 0·1) years, with an overweight incidence of 3·6 (95 % CI 3·1, 4·1) per 100 person-years. In multivariable analysis, children who consumed sweetened beverages and snacks daily had an average weight increase of 2·29 (95 % CI 0·62, 3·96) and 2·04 (95 % CI 0·48, 3·60) kg more, respectively, than those who never consumed these products, in approximately 4 years of follow-up. Moreover, there was evidence of an association between daily consumption of sweetened beverages and risk of overweight (relative risk=2·12; 95 % CI 1·05, 4·28).
Conclusions
Daily consumption of sweetened beverages and snacks was associated with increased weight gain v. never consuming these products; and in the case of sweetened beverages, with higher risk of developing overweight.
The Short Obsessive–Compulsive Disorder Screener (SOCS) is recommended by the National Institute for Health and Care Excellence as a suitable and validated screening tool for 11- to 15-year olds. Despite its excellent sensitivity and specificity in detecting obsessive–compulsive disorder (OCD), it has limitations.
Aims
To empirically examine whether the SOCS is suitable for assessing OCD symptoms across a wide age range of children and adolescents and to provide new data about its psychometric properties.
Method
Participants were 94 patients (9–19 years) with OCD, and 880 healthy controls.
Results
The results supported the SOCS' unidimensional factor structure and metric invariance across samples. It showed good reliability in terms of internal consistency and temporal stability. Furthermore, it had significantly high correlations with other OCD measures and an acceptable sensitivity and specificity for detecting OCD.
Conclusions
The SOCS is a brief screening tool suitable for detecting OCD in children and adolescents.
Country-specific data on resource use and costs associated with Alzheimer's disease (AD) help inform governments about the increasing need for medical and financial support as the disease increases in prevalence.
Methods:
GERAS II, a prospective observational study, assessed resource use, costs, and health-related quality of life (HRQoL) among patients with AD and their caregivers in Spain. Community-dwelling patients aged ≥55 years with probable AD, and their primary caregivers, were recruited by study investigators during routine clinical practice and assessed as having mild, moderate, or moderately severe/severe (MS/S) AD dementia based on patient Mini-Mental State Examination scores. Costs of AD were calculated by applying costs to resource-use data obtained in caregiver interviews using the Resource Utilization in Dementia instrument. Total societal costs included patients’ health and social care costs and caregiver informal care costs. Baseline results are presented.
Results:
Total mean monthly societal costs/patient (2013 values) were €1514 for mild (n = 116), €2082 for moderate (n = 118), and €2818 for MS/S AD dementia (n = 146) (p value <0.001 between groups). Caregiver informal care costs comprised most of the total societal costs and differed significantly between groups (€1050, €1239, €1580, respectively; p value = 0.013), whereas patient healthcare costs did not. Across AD dementia severity groups, patient HRQoL (measured by proxy) decreased significantly (p value <0.001), caregiver subjective burden significantly increased (p value <0.001) and caregiver HRQoL was similar.
Conclusions:
Societal costs associated with AD in Spain were largely attributable to caregiver informal care costs and increased with increasing AD dementia severity.
The hypothesis of limiting similarity, which postulates that morphologically and/or ecologically similar species will differ enough in shape, size, or other variables to minimize competition, has been controversial among ecologists and paleoecologists. Many studies have reported the occurrence of limiting similarity in modern environments or in time-averaged fossil deposits; however, empirical high-resolution time series demonstrating limiting similarity over longer time scales are lacking. We have integrated radiocarbon-calibrated amino acid dating techniques, stable isotope estimates, and morphometric data to test the hypothesis of limiting similarity in late Quaternary land snails from the Canary Islands over a period of 42,500 years. We tested for both ecological character displacement (two closely related species will differ in size in order to minimize competition in sympatry and these differences will be minimized in allopatry) and communitywide character displacement (overdispersion of body size among competitors in a guild). Multiple proxies of body size consistently show that two endemic congeneric pulmonate gastropod species (Theba geminata and T. arinagae) maintained a difference in size from ~42,500 B.P. through the last occurrence of T. arinagae 14,900 B.P., with a concomitant trend of a decreasing body size. Theba geminata body size did not converge on that of T. arinagae and variation in T. geminata body size did not increase significantly following the extinction of T. arinagae; therefore, ecological character displacement and release did not occur. Community-wide character displacement was found in only one time bin over the last 42,500 years. These results suggest that limiting similarity is a transient ecological phenomenon rather than a long-term evolutionary process. This study not only demonstrates the problems inherent in biological “snapshot” studies and geological studies of time-averaged deposits to test limiting similarity adequately, but it also presents a more adequate research protocol to test the importance of interspecific competition in the history of life.