H3K4me2 distinguishes a distinct class of enhancers during the maternal-to-zygotic transition.

After egg fertilization, an initially silent embryonic genome is transcriptionally activated during the maternal-to-zygotic transition. In zebrafish, maternal vertebrate pluripotency factors Nanog, Pou5f3 (OCT4 homolog), and Sox19b (SOX2 homolog) (NPS) play essential roles in orchestrating embryonic genome activation, acting as "pioneers" that open condensed chromatin and mediate acquisition of activating histone modifications. However, some embryonic gene transcription still occurs in the absence of these factors, suggesting the existence of other mechanisms regulating genome activation. To identify chromatin signatures of these unknown pathways, we profiled the histone modification landscape of zebrafish embryos using CUT&RUN. Our regulatory map revealed two subclasses of enhancers distinguished by presence or absence of H3K4me2. Enhancers lacking H3K4me2 tend to require NPS factors for de novo activation, while enhancers bearing H3K4me2 are epigenetically bookmarked by DNA hypomethylation to recapitulate gamete activity in the embryo, independent of NPS pioneering. Thus, parallel enhancer activation pathways combine to induce transcriptional reprogramming to pluripotency in the early embryo.

Executing and facilitating the successful combined multichannel intraluminal impedance and pH monitoring study.

Successful multichannel intraluminal impedance and pH monitoring (MII-pHM) studies rely on constant attendants (CAs) or family members (and sometimes the patients themselves) to assist in the execution and facilitation of the MII-pHM study. While "pushing buttons" [corresponding to specific symptoms, body position (upright versus recumbent), and meal start and stop times] on the MII-pHM system recording box is indeed a big part of MII-pHM study execution and facilitation, there are other concerns and duties that are equally as important. This paper outlines some of the important duties of the study facilitator (or patient) during a MII-pHM study. When provided with the proper training, study facilitators invigilating the MII-pHM study will be better able to contribute to the data collection process and ultimately to produce data that when analyzed will lead to better interpretations, clinical recommendations, and good clinical outcomes. When executed properly, MII-pHM studies have the potential to assess diurnal exposure of the esophageal mucosa to gastric/duodenal contents, provide insight regarding the proximal extent of gastroesophageal reflux (GER), provide a measurement of the mean esophageal pH, and assess mucosal integrity and temporal relationship between GER and the symptoms of interest. While several groups have offered recommendations for proper execution of the MII-pHM study, to our knowledge, there have not been publications wherein recommendations were compiled to form a single source document.

Use of hormone-specific antibody probes for differential labeling of contributor cell populations in trace DNA mixtures.

A significant proportion of casework analyzed by forensic science laboratories is often "touch" or trace forensic DNA evidence, which is deposited through physical contact and is comprised of sloughed epidermal cells. These samples can be challenging to analyze due to low DNA concentrations, frequent degradation, and the presence of cells from multiple individuals in the same sample. To address these challenges, we investigated a new approach for characterizing trace evidence prior to DNA profiling that labels epidermal cells with antibody probes targeting hormone molecules testosterone and dihydrotestosterone (DHT). The goal was to test whether cell populations derived from separate individuals showed different binding efficiencies to hormone probes and, thus, could be used to detect the presence of multiple cell populations. Additionally, we investigated whether antibody probes could be used to isolate contributor cell populations from an epidermal cell mixture and facilitate deconvolution of mixed DNA profiles recovered from touch/trace evidence. Results showed that cell populations from some individuals could differentiated in trace samples based on fluorescence histograms following probe labeling. However, certain pairs of contributors showed largely or completely overlapping histogram profiles and could not be resolved. Preliminary efforts to separate cell populations that could be differentiated with hormone probes with fluorescence-activated cell sorting (FACS) coupled to DNA profiling and probabilistic modeling indicated that it is possible to enrich contributor cell populations from touch/trace samples and produce more probative DNA profiles compared to the original mixture sample. The variability in labeling, differentiation, and physical separation of cell populations may be impacted by similarities in biochemical profiles across some contributors as well as imbalance of contributor DNA quantities in certain mixtures as is typical in casework involving touch/trace evidence. Ultimately, screening and separation of trace DNA samples with this approach may be presumptive and constrained by sample-specific parameters of the original mixture.

Risk Factors of Pneumonia in Primary Antibody Deficiency Patients Receiving Immunoglobulin Therapy: Data from the US Immunodeficiency Network (USIDNET).

BACKGROUND: Despite immunoglobulin replacement (IgRT) therapy, some patients with primary antibody deficiency (PAD) continue to develop respiratory infections. Recurrent and severe respiratory infections, particularly pneumonia, can lead to significant morbidity and mortality. Therefore, we sought to determine the risk factors of developing pneumonia in PAD patients, already receiving IgRT. METHODS: We evaluated clinical and laboratory features of PAD patients enrolled in the US Immune Deficiency Network (USIDNET) registry by April 2017. Patients were included if they met the following criteria: (1) PAD diagnosis (common variable immunodeficiency (CVID), agammaglobulinemia, hypogammaglobinemia, and specific antibody deficiency (SAD) and (2) available data on infections before and after IgRT. Patients were excluded if they were not receiving IgRT, or if no pre/post infections data were available. Descriptive and multivariable logistic regression analyses were used to identify factors associated with pneumonia post-IgRT. RESULTS: A total of 1232 patients met the inclusion criteria. Following IgRT, 218 patients (17.7%) were reported to have at least one pneumonia episode. Using multivariate logistic regression analysis, we found a statistically significant increased risk of pneumonia in patients with asthma (OR: 2.55, 95% CI (1.69-3.85), p < 0.001) bronchiectasis (OR: 3.94, 95% CI (2.29-6.80), p < 0.001), interstitial lung disease (ILD) (OR: 3.28, 95%CI (1.43-7.56), p < 0.005), splenomegaly (OR: 2.02, 95%CI (1.08-3.76), p < 0.027), allergies (OR: 2.44, 95% CI [1.44-4.13], p = 0.001), and patients who were not on immunosuppressives (OR: 1.61; 95%CI [1.06-2.46]; p = 0.027). For every 50 unit increase in IgA, the odds of reporting pneumonia post IgRT decreased (OR: 0.86, 95% CI [0.73-1.02], p = 0.062). Infectious organisms were reported in 35 of 218 patients who reported pneumonia after IgRT. Haemophilus influenzae was the most frequently reported (n = 11, 31.43%), followed by Streptococcus pneumoniae (n = 7, 20.00%). CONCLUSION: Our findings suggest PAD patients with chronic and structural lung disease, splenomegaly, and allergies were associated with persistent pneumonia. However, our study is limited by the cross-sectional nature of the USIDNET database and limited longitudinal data. Further studies are warranted to identify susceptible causes and explore targeted solutions for prevention and associated morbidity and mortality. CLINICAL IMPLICATIONS: Patients with primary antibody deficiency with structural lung disease, allergies, and splenomegaly are associated with persistent pneumonia post-IgRT.

Ostrich eggshell beads reveal 50,000-year-old social network in Africa.

Humans evolved in a patchwork of semi-connected populations across Africa1,2; understanding when and how these groups connected is critical to interpreting our present-day biological and cultural diversity. Genetic analyses reveal that eastern and southern African lineages diverged sometime in the Pleistocene epoch, approximately 350-70 thousand years ago (ka)3,4; however, little is known about the exact timing of these interactions, the cultural context of these exchanges or the mechanisms that drove their separation. Here we compare ostrich eggshell bead variations between eastern and southern Africa to explore population dynamics over the past 50,000 years. We found that ostrich eggshell bead technology probably originated in eastern Africa and spread southward approximately 50-33 ka via a regional network. This connection breaks down approximately 33 ka, with populations remaining isolated until herders entered southern Africa after 2 ka. The timing of this disconnection broadly corresponds with the southward shift of the Intertropical Convergence Zone, which caused periodic flooding of the Zambezi River catchment (an area that connects eastern and southern Africa). This suggests that climate exerted some influence in shaping human social contact. Our study implies a later regional divergence than predicted by genetic analyses, identifies an approximately 3,000-kilometre stylistic connection and offers important new insights into the social dimension of ancient interactions.

COVID-19 Care Clinic in a Medical Center: Lessons Learned.

OBJECTIVE: The purpose of this report is to describe the elements of a Covid-19 Care Clinic (CCC), patient demographics, and outcomes. METHODS: Descriptive statistics were used to describe demographics, clinical characteristics, and outcomes. This report is based on 4934 unique patients seen in the CCC who provided research authorization within a 10-month period of time (April 1, 2020-January 31, 2021). The CCC infection control processes consisted of a rooming process that mitigated SARS-COV-2 transmission, preparing examination rooms, using PPE by staff, in room lab drawing, and escorting services to minimize the time in clinic. RESULTS: Of the 4934 unique patients seen (age range newborn-102 years), 76.8% were tested for COVID-19. Of those tested, 11.8% were positive for SARS-CoV-2. Ninety-two percent of the patients with the reason for the visit documented had COVID-19 type symptoms. Cough, shortness of breath, and chest pain were the most common presenting symptom in those with COVID-19. At the time of the visit in the CCC, 5.8% of the patients were actively contagious. Thirty days after being seen in the CCC, 9.1% of the patients were seen in the emergency department (ED) and 0.2% died. During the 10-month period there were no known occupationally related COVID-19 infections. CONCLUSION: The COVID-19 Care Clinic provided face-to-face access for all ages with COVID-19 type symptoms. A minority of patients had COVID-19 who were seen in the clinic. The clinic provided an additional venue of care outside of the ED. The infectious control measures employed were highly effective in protecting the staff. Lessons learned allow for decentralization of COVID-19 symptom care to the primary care practices employing the infection control measures.

67,000 years of coastal engagement at Panga ya Saidi, eastern Africa.

The antiquity and nature of coastal resource procurement is central to understanding human evolution and adaptations to complex environments. It has become increasingly apparent in global archaeological studies that the timing, characteristics, and trajectories of coastal resource use are highly variable. Within Africa, discussions of these issues have largely been based on the archaeological record from the south and northeast of the continent, with little evidence from eastern coastal areas leaving significant spatial and temporal gaps in our knowledge. Here, we present data from Panga ya Saidi, a limestone cave complex located 15 km from the modern Kenyan coast, which represents the first long-term sequence of coastal engagement from eastern Africa. Rather than attempting to distinguish between coastal resource use and coastal adaptations, we focus on coastal engagement as a means of characterising human relationships with marine environments and resources from this inland location. We use aquatic mollusc data spanning the past 67,000 years to document shifts in the acquisition, transportation, and discard of these materials, to better understand long-term trends in coastal engagement. Our results show pulses of coastal engagement beginning with low-intensity symbolism, and culminating in the consistent low-level transport of marine and freshwater food resources, emphasising a diverse relationship through time. Panga ya Saidi has the oldest stratified evidence of marine engagement in eastern Africa, and is the only site in Africa which documents coastal resources from the Late Pleistocene through the Holocene, highlighting the potential archaeological importance of peri-coastal sites to debates about marine resource relationships.

Integrating National Violent Death Reporting System Data into Maternal Mortality Review Committees.

Background: With the Maternal Mortality Review Information Application (MMRIA) data system, the Centers for Disease Control and Prevention (CDC), alongside Maternal Mortality Review Committees (MMRCs), are developing comprehensive and uniform data collection to eradicate preventable maternal deaths. However, MMRIA is primarily focused on pregnancy-related deaths, and not pregnancy-associated deaths. Currently, the National Violent Death Reporting System Restricted Access Data (NVDRS-RAD) on pregnancy-associated homicides and suicides are not included in MMRIA and by extension the work of most MMRCs. This study examined the NVDRS-RAD data from 2014 to 2017 and argues that the data for pregnancy-associated maternal deaths should be integrated into the work of MMRCs. Methods: A secondary data analysis of the NVDRS-RAD from 2014 to 2017 was conducted. Pregnancy-associated mortality was identified using data available within the NVDRS-RAD and categorized according to period of pregnancy and manner of death. Descriptive statistics and risk ratios were calculated. Chi-square tests were also calculated. Results: The results indicate that pregnancy and the postpartum period show increased risk for homicide and suicide. Pregnant women were found to be five times more likely to die by homicide than their nonpregnant peers who died by violent means. The relationships between periods of pregnancy and manner of death were all found to be significantly associated although the association was weak. Conclusions: Integrating National Violent Death Reporting System data on pregnancy-associated deaths into MMRIA would improve the efficacy of MMRCs and address the intertwined risk factors driving the racial disparities of the United States' maternal mortality rate.

Earliest known human burial in Africa.

The origin and evolution of hominin mortuary practices are topics of intense interest and debate1-3. Human burials dated to the Middle Stone Age (MSA) are exceedingly rare in Africa and unknown in East Africa1-6. Here we describe the partial skeleton of a roughly 2.5- to 3.0-year-old child dating to 78.3 ± 4.1 thousand years ago, which was recovered in the MSA layers of Panga ya Saidi (PYS), a cave site in the tropical upland coast of Kenya7,8. Recent excavations have revealed a pit feature containing a child in a flexed position. Geochemical, granulometric and micromorphological analyses of the burial pit content and encasing archaeological layers indicate that the pit was deliberately excavated. Taphonomical evidence, such as the strict articulation or good anatomical association of the skeletal elements and histological evidence of putrefaction, support the in-place decomposition of the fresh body. The presence of little or no displacement of the unstable joints during decomposition points to an interment in a filled space (grave earth), making the PYS finding the oldest known human burial in Africa. The morphological assessment of the partial skeleton is consistent with its assignment to Homo sapiens, although the preservation of some primitive features in the dentition supports increasing evidence for non-gradual assembly of modern traits during the emergence of our species. The PYS burial sheds light on how MSA populations interacted with the dead.

COVID Care Clinic: A Unique Way for Family Medicine to Care for the Community During the SARS-CoV-2 (COVID-19) Pandemic.

The COVID-19 pandemic has presented new challenges in how Primary Care clinicians care for community patients. Our organization quickly allocated 1 of our community clinic sites into a dedicated COVID Clinic caring for the COVID positive or any patient with COVID like symptoms to minimize contact with the well patients. A prerequisite for all patients to be seen in the COVID Care Clinic was a virtual visit staffed with Advanced Practice Providers that would further determine if the patient needed to seek emergency medical care or be seen in the COVID Clinic. From March 23, 2020 through May 15, 2020, 852 patients with COVID symptoms were seen in this clinic rather than the emergency department. This article describes a collaborative effort to care for a community during the COVID-19 pandemic. This unique setting allowed us to focus an appropriate level of care to a high risk population in a safe and effective manner in the ongoing effort to flatten the epidemiological curve.

Impact of Obesity in Patients with Candida Bloodstream Infections: A Retrospective Cohort Study.

BACKGROUND: Candida species are responsible for 15% of bloodstream infections, leading to prolonged hospitalizations and increased mortality. With the rise in obesity, antifungal dosing is unclear. The purpose of this study was to determine differences in clinical outcomes between obese versus non-obese patients with Candida bloodstream infections. METHODS: This retrospective cohort included adult patient's first episode of Candida bloodstream infection treated with ≥ 48 h of antifungal therapy between 1 June 2013 and 31 August 2019. Patients were excluded for: dual systemic antifungal therapy, polymicrobial infections, or chronic candidiasis. The primary outcome was infection-related length of stay. Secondary outcomes included: time to candidemia resolution, 30-day readmission rates, and in-hospital mortality. RESULTS: Eighty patients were included (28 obese; 52 non-obese). Most were male (55%); median age was 54 years. Median BMI and weight were 36.3 kg/m2 and 103 kg versus 20.4 kg/m2 and 61 kg, respectively (p < 0.01). Baseline characteristics were comparable. C. albicans was isolated in 37.5% of cultures and C. glabrata in 30%. Micafungin was utilized empirically in 72.5% of patients; obese patients received definitive micafungin more frequently (57.1% vs. 21.2%; p < 0.01) and were treated longer (13 versus 10 days; p = 0.04). Infection-related length of stay was 19 days in the obese patients and 13 days in the non-obese patients (p = 0.05). Non-obese patients had a shorter duration of candidemia (5 versus 6 days; p = 0.02). In-hospital mortality was numerically higher in obese patients (21.4% versus 13.5%; p = 0.36). There were no differences in 30-day readmissions between groups. CONCLUSIONS: Worse clinical outcomes were observed for obese versus non-obese patients. Further clinical research is warranted.

The clinical and immune outcomes after food allergen immunotherapy emphasizing the development of tolerance.

PURPOSE OF REVIEW: The present review serves to outline the direction of food allergy immunotherapy research with an emphasis on clinical and immunologic outcomes. It helps to delineate sustained unresponsiveness achieved from food immunotherapy as the clinical outcome most similar to immune tolerance. RECENT FINDINGS: We will discuss the difference between immune tolerance, desensitization, and sustained unresponsiveness in relation to food immunotherapy by discussing the clinical and immunologic changes which have been recently discovered. SUMMARY: Research has recently shown that oral immunotherapy is most efficacious clinically at achieving desensitization to a food and sustained unresponsiveness.

Ostrich eggshell bead diameter in the Holocene: Regional variation with the spread of herding in eastern and southern Africa.

Despite their ubiquity in Holocene African archaeological assemblages, ostrich eggshell (OES) beads are rarely studied in detail. An exception is in southern Africa, where there is a proposed relationship between OES bead diameter and the arrival of herding ~2000 years before present. In 1987, Leon Jacobson first observed that beads from forager sites in Namibia tended to be smaller than those associated with herder sites. Studies examining bead size around the Western Cape have generally confirmed Jacobson's findings, though the driving forces of the diameter change remain unknown. Since this time, diameter has become an informal way of distinguishing forager and herder assemblages in southern Africa, but no large-scale studies of OES bead variation have been undertaken. Here we present an expanded analysis of Holocene OES bead diameters from southern, and for the first time, eastern Africa. Results reveal distinct patterns in OES bead size over time, reflecting different local dynamics associated with the spread of herding. In southern Africa, OES diameters display low variability and smaller absolute size through time. While larger beads begin to appear <2000 years ago, most beads in our study remained smaller. In contrast, eastern African OES bead diameters are consistently larger over the last 10,000 years and show no appreciable size change with the introduction of herding. Notably, larger beads thought to be associated with herders in southern Africa fall within the range of eastern African beads, indicating a potential connection between these regions in the Late Holocene consistent with genetic findings. Regional differences in bead size are subtle, on the order of millimeters, yet offer a potentially important line of evidence for investigating the spread of herding in sub-Saharan Africa. In order to understand the meaning of these changes, we encourage additional studies of OES bead assemblages and urge researchers to report individual bead diameters, rather than averages by level.

Land Snail Shell Beads in the Sub-Saharan Archaeological Record: When, Where, and Why?

Shell beads are well established in the archaeological record of sub-Saharan Africa and appear as early as 75,000 BP; however, most research has focused on ostrich eggshell (OES) and various marine mollusc species. Beads made from various land snails shells (LSS), frequently described as Achatina, also appear to be widespread. Yet tracking their appearance and distribution is difficult because LSS beads are often intentionally or unintentionally lumped with OES beads, there are no directly dated examples, and bead reporting in general is highly variable in the archaeological literature. Nevertheless, Achatina and other potential cases of LSS beads are present at over 80 archaeological sites in at least eight countries, spanning the early Holocene to recent past. Here, we collate published cases and report on several more. We also present a new case from Magubike Rockshelter in southern Tanzania with the first directly dated LSS beads, which we use to illustrate methods for identifying LSS as a raw material. Despite the long history of OES bead production on the continent and the abundance of land snails available throughout the Pleistocene, LSS beads appear only in the late Holocene and are almost exclusively found in Iron Age contexts. We consider possible explanations for the late adoption of land snails as a raw material for beadmaking within the larger context of environmental, economic, and social processes in Holocene Africa. By highlighting the existence of these artifacts, we hope to facilitate more in-depth research on the timing, production, and distribution of LSS beads in African prehistory.

Les perles de coquillages sont bien établies dans les archives archéologiques de l'Afrique subsaharienne et apparaissent dès 75 000 BP, mais la plupart des recherches ont porté sur la coquille d'œuf d'autruche (OES) et diverses espèces de mollusques marins. Les perles fabriquées à partir de diverses coquilles d'escargots terrestres (LSS), souvent décrites comme Achatina, semblent également être répandues. Cependant, le suivi de leur apparence et de leur distribution est. difficile parce que les billes LSS sont souvent volontairement ou involontairement regroupées avec des billes OES, il n'y a pas d'exemples directement datés, et les rapports sur les perles en général sont très variables dans la littérature archéologique. Néanmoins, Achatina et d'autres cas potentiels de perles LSS sont présents sur plus de 80 sites archéologiques dans au moins huit pays, couvrant le début de l'Holocène à un passé récent. Ici, nous rassemblons les cas publiés et rapportons plusieurs autres cas. Nous présentons également un nouveau cas de Magubike Rockshelter dans le sud de la Tanzanie avec les premières perles LSS directement datées, que nous utilisons pour illustrer les méthodes d'identification du LSS comme matière première. Malgré la longue histoire de la production de perles d'OES sur le continent et l'abondance d'escargots terrestres disponibles tout au long du Pléistocène, les perles de LSS n'apparaissent qu'à la fin de l'Holocène et sont presque exclusivement trouvées dans des contextes de l'âge du fer. Nous considérons les explications possibles de l'adoption tardive des escargots terrestres en tant que matière première pour la fabrication de perles dans le contexte plus large des processus environnementaux, économiques et sociaux en Afrique de l'Holocène. En mettant en évidence l'existence de ces artefacts, nous espérons faciliter des recherches plus approfondies sur le calendrier, la production et la distribution des perles LSS dans la préhistoire africaine.

Draft Genome Sequence of Uncultured Upland Soil Cluster Gammaproteobacteria Gives Molecular Insights into High-Affinity Methanotrophy.

Aerated soils form the second largest sink for atmospheric CH4 A near-complete genome of uncultured upland soil cluster Gammaproteobacteria that oxidize CH4 at <2.5 ppmv was obtained from incubated Antarctic mineral cryosols. This first genome of high-affinity methanotrophs can help resolve the mysteries about their phylogenetic affiliation and metabolic potential.

Interleukin-6 levels predict event-free survival in pediatric AML and suggest a mechanism of chemotherapy resistance.

The tumor microenvironment can protect cancer cells from conventional anticancer therapies. Thus, targeting these protective mechanisms could eradicate therapy-resistant cancer cells and improve outcomes. Interleukin-6 (IL-6) provides extrinsic protection for several solid tumors and multiple myeloma. In pediatric acute myeloid leukemia (AML), IL-6-induced STAT3 signaling frequently becomes stronger at relapse, and increases in IL-6-induced STAT3 activity are associated with inferior survival after relapse. These findings suggested that the IL-6-induced STAT3 pathway may promote chemotherapy resistance and disease progression. Thus, we investigated the dysregulation of IL-6 levels in the bone marrow niche in pediatric patients with AML and the association between IL-6 levels and outcome. We measured levels of over 40 cytokines and growth factors in plasma from diagnostic bone marrow aspirates of 45 pediatric AML patients and 7 healthy sibling controls. Of the measured cytokines, only IL-6 levels were associated with event-free survival. Importantly, the effect of elevated IL-6 was most striking among children classified as having a low risk of relapse. In these patients, 5-year event-free survival was 82.5% ± 11% for patients with low IL-6 levels at diagnosis (n = 14) compared with 17.3% ± 11% for patients with elevated IL-6 (n = 13, log-rank P = .0003). In vitro, exogenous IL-6 reduced mitoxantrone-induced apoptosis in cell lines and primary pediatric AML samples. These results suggest that IL-6 levels at diagnosis could be used to help identify children at high risk of relapse, particularly those who are otherwise classified as low risk by current algorithms. Moreover, the IL-6 pathway could represent a target for overcoming environment-mediated chemotherapy resistance.

Quantifying and tracing information cascades in swarms.

We propose a novel, information-theoretic, characterisation of cascades within the spatiotemporal dynamics of swarms, explicitly measuring the extent of collective communications. This is complemented by dynamic tracing of collective memory, as another element of distributed computation, which represents capacity for swarm coherence. The approach deals with both global and local information dynamics, ultimately discovering diverse ways in which an individual's spatial position is related to its information processing role. It also allows us to contrast cascades that propagate conflicting information with waves of coordinated motion. Most importantly, our simulation experiments provide the first direct information-theoretic evidence (verified in a simulation setting) for the long-held conjecture that the information cascades occur in waves rippling through the swarm. Our experiments also exemplify how features of swarm dynamics, such as cascades' wavefronts, can be filtered and predicted. We observed that maximal information transfer tends to follow the stage with maximal collective memory, and principles like this may be generalised in wider biological and social contexts.

A continuum three-zone model for swarms.

We present a progression of three distinct three-zone, continuum models for swarm behavior based on social interactions with neighbors in order to explain simple coherent structures in popular biological models of aggregations. In continuum models, individuals are replaced with density and velocity functions. Individual behavior is modeled with convolutions acting within three interaction zones corresponding to repulsion, orientation, and attraction, respectively. We begin with a variable-speed first-order model in which the velocity depends directly on the interactions. Next, we present a variable-speed second-order model. Finally, we present a constant-speed second-order model that is coordinated with popular individual-based models. For all three models, linear stability analysis shows that the growth or decay of perturbations in an infinite, uniform swarm depends on the strength of attraction relative to repulsion and orientation. We verify that the continuum models predict the behavior of a swarm of individuals by comparing the linear stability results with an individual-based model that uses the same social interaction kernels. In some unstable regimes, we observe that the uniform state will evolve toward a radially symmetric attractor with a variable density. In other unstable regimes, we observe an incoherent swarming state.