Stereo Light Microscope Research Articles

Activity of tea tree oil and nerolidol alone or in combination against Pediculus capitis (head lice) and its eggs.

Head lice infestation is an emerging social problem in undeveloped and developed countries. Because of louse resistance increasing, several long-used insecticidal compounds have lost their efficacy, and alternatives, such as essential oils, have been proposed to treat this parasitic infestation. The present study investigated the efficacy of two natural substances: tea tree (Melaleuca alternifolia) oil and nerolidol (3,7,11-trimethyl-1,6,10-dodecatrien-3-ol) against lice and its eggs. Products were used alone and in combination (ratio 1:1 and 1:2) from 8 % dilution. The in vitro effect of natural substances at different concentrations were evaluated against 69 head lice (adults and nymphs) and 187 louse eggs collected from school children in Chieti–Pescara (Central Italy) over a 6-month period. The lice mortality was evaluated for 24 h by a stereo light microscope. The ovicidal activity was monitored by microscopic inspections for 15 days. Tea tree oil was more effective than nerolidol against head lice with 100 % mortality at 30 min and 1 % concentration. On the contrary, nerolidol expressed a more pronounced ovicidal activity inducing the failure of 50 % of the eggs to hatch at 1 % concentration after 4 days; the same effect was achieved by using a twice concentration of tea tree oil. The association of the two substances both in ratios 1:1 and 1:2 combined efficaciously their insecticidal and ovicidal effect; in particular, the ratio 1:2 (tea tree oil 0.5 % plus nerolidol 1 %) acted producing both the death of all head lice at 30 min and the abortive effect of louse eggs after 5 days. These results offer new potential application of natural compounds and display a promising scenario in the treatment of pediculosis resistant cases. The development of novel pediculicides containing essential oils could be, in fact, an important tool to control the parasitic infestation.Electronic supplementary materialThe online version of this article (doi:10.1007/s00436-012-3045-0) contains supplementary material, which is available to authorized users.

Mathematical Model Incorporated Fractal Geometry and Permeability of Compressed Peanut and Sesame for Oil Extraction

Considering the fractal characteristic of oilseed cake, the relationship between the permeability and the pore fractal dimension of peanut and sesame cake has been investigated. The microstructures of peanut and sesame cake under five applied pressures are measured by using stereo light microscope and Image-pro image analyzer. Using the box-counting method, the fractal dimensions of pore size distributions are measured. A mathematical model incorporated fractal dimension and permeability has been developed to predicate the permeability of compressed peanut and sesame under cold condition based upon combining Hagen-Poiseulle equation with Darcy’s law for flow of fluid through porous media. There is a prediction of permeability of peanut and sesame cake. Thus, a measurement is carried out for validation. The values of mean relative errors are 19.4% and 11.4 respectively. A fairly good agreement is obtained in the case of high applied pressure. And there exists a tendency that the value of the difference between the theoretical calculation and the permeability measurement decrease significantly with the increase of applied pressure.

Evaluation of Chemical Treatment on Zirconia Surface with Two Primer Agents and an Alkaline Solution on Bond Strength

This study evaluated the effect of an alkaline solution and two 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer agents on bond strength to zirconia (yttria-stabilized tetragonal zirconium polycrystal [Y-TZP]) through the shear bond strength (SBS) test. Sixty square-shaped Y-TZP samples were embedded in an acrylic resin mold, polished, and randomly assigned to one of six groups (n=10) according to treatment surface: group CR, no treatment (control); group NaOH, 0.5 M NaOH; group AP, Alloy Primer; group ZP, Z-Primer Plus; group NaOH-AP, 0.5 M NaOH + Alloy Primer; and group NaOH-ZP, 0.5 M NaOH + Z-Primer Plus. The resin cement (Rely X U100) was applied inside a matrix directly onto the Y-TZP surface, and it was light-cured for 40 seconds. The samples were stored in distilled water at 37°C for 24 hours prior to the test, which was performed in a universal machine at a crosshead-speed of 0.5 mm/min. The data were analyzed by one-way analysis of variance and Tukey tests (p<0.05). Light stereomicroscopy and scanning electron microscopy were used to assess the surface topography and failure mode. The SBS was significantly affected by the chemical treatment (p<0.0001). The AP group displayed the best results, and the use of NaOH did not improve SBS results relative to either AP or ZP. The samples treated with Alloy Primer displayed mainly mixed failures, whereas those conditioned with Z-Primer Plus or with 0.5 M NaOH presented a balanced distribution of adhesive and mixed failure modes. The use of a NaOH solution may have modified the reactivity of the Y-TZP surface, whereas the employment of a MDP/6-4-vinylbenzyl-n-propyl amino-1,3,5-triazine-2,4-dithione-based primer enhanced the Y-TZP bond strength.

Calibration error for dual-camera digital image correlation at microscale

Digital image correlation (DIC) has been widely conducted in many engineering applications. This paper describes a dual-camera system which is mounted on a stereo light microscope to achieve 3D displacement measurement at microscale. A glass plate etched with precision grids was used as the calibration plate and a translation calibration procedure was introduced to obtain the intrinsic and extrinsic parameters of the cameras as well as the aberration of the imaging system. Two main error sources, including grid positioning and stage translation, were discussed. It was found that the subpixel positioning errors had limited influences on displacement measurement, while the incorrect grid positioning can be avoided by analyzing the standard deviation between the grid spacing. The systematic translation error of the stage must be eliminated to achieve accurate displacement measurement. Based on the above analysis, a precisely controlled motorized calibration stage was developed to fulfill fully automatic calibration for the microscopic dual-camera system. An application for measuring the surface texture of the human incisor has been presented. It is concluded that the microscopic dual-camera system is an economic, precise system for 3D profilometry and deformation measurement.

Effect of different palatal vault shapes on the dimensional stability of glass fiber-reinforced heat-polymerized acrylic resin denture base material

The aim of this study was to determine the effect of different palatal vault shapes on the dimensional stability of a glass fiber reinforced heat polymerized acrylic resin denture base material. Three edentulous maxilla with shallow, deep and medium shaped palatal vaults were selected and elastomeric impressions were obtained. A maxillary cast with four reference points (A, B, C, and D) was prepared to serve as control. Point (A) was marked in the anterior midline of the edentulous ridge in the incisive papillary region, points (B) and (C) were marked in the right and left posterior midlines of the edentulous ridge in the second molar regions, and point (D) was marked in the posterior palatal midline near the fovea palatina media (Figure 2). To determine linear dimensional changes, distances between four reference points (A-B, A-C, A-D and B-C) were initially measured with a metal gauge accurate within 0.1 mm under a binocular stereo light microscope and data (mm) were recorded. No significant difference of interfacial distance was found in sagittal and frontal sections measured 24 h after polymerization and after 30 days of water storage in any of experimental groups (P>.05). Significant difference of linear dimension were found in all experimental groups (P<.01) between measurements made 24 h after polymerization of specimens and 30 days after water storage. Palatal vault shape and fiber impregnation into the acrylic resin bases did not affect the magnitude of interfacial gaps between the bases and the stone cast surfaces.

Comparative studies on the invasion of cattle ticks ( Rhipicephalus ( Boophilus) microplus) and sheep blowflies ( Lucilia cuprina) by Metarhizium anisopliae (Sorokin)

Microscopic investigations over time were carried out to study and compare the pathogenesis of invasion of ticks and blowflies by Metarhizium anisopliae. The scanning electron microscope and stereo light microscope were used to observe and record processes on the arthropods’ surfaces and the compound light microscope was used to observe and record processes within the body cavities. Two distinctly different patterns of invasion were found in ticks and blowflies. Fungal conidia germinated on the surface of ticks then hyphae simultaneously penetrated into the tick body and grew across the tick surface. There was extensive fungal degradation of the tick cuticle, particularly the outer endocuticle. Although large numbers of conidia adhered to the surface of blowflies, no conidia were seen to germinate on external surfaces. A single germinating conidium was seen in the entrance to the buccal cavity. Investigations of the fly interior revealed a higher density of hyphal bodies in the haemolymph surrounding the buccal cavity than in haemolymph from regions of the upper thorax. This pattern suggests that fungal invasion of the blowfly is primarily through the buccal cavity. Plentiful extracellular mucilage was seen around the hyphae on tick cuticles, and crystals of calcium oxalate were seen amongst the hyphae on the surface of ticks and in the haemolymph of blowflies killed by M. anisopliae isolate ARIM16.

External morphology of the egg and the first and fifth instars of Cyrtocoris egeris Packauskas &amp;amp; Schaefer (Hemiptera: Heteroptera: Pentatomidae: Cyrto-corinae)

Cyrtocorinae is an uncommon, small, and exclusively Neotropical group in Pentatomidae, whose immatures are poorly understood. In this paper, the egg and first and fifth instars of Cyrtocoris egeris Packauskas &amp; Schaefer are studied with the scanning electron microscopy (SEM). Specimens were collected in Maquiné, Rio Grande do Sul, Brazil. Immatures were analyzed with light stereomicroscope and SEM. The egg’s chorion surface is predominantly smooth alternated with granulated areas, and an average of 54 clubbed aero-micropylar processes are arranged in three irregular rows. In the first and fifth instars, organization of the external dorso-abdominal scent efferent system suggests an analogy to the metathoracic external scent efferent system of the adult, because of structures similar to the evaporatorium, evaporatory channel, and auricle peritreme; the last structure is absent in the first instar. Abdominal sterna III–VII have 1+1 (first instar) and 2+2 trichobothria (fifth instar). Ultrastructural observations allowed recognition of unique characters at the egg stage and conserved features at the nymphal stage in C. egeris.

Sealing ability of the formed apical calcified bridge in open apex roots

One of the most difficult endodontic problems is the management of necrotic immature tooth because of the difficulty in achieving a completely sealed apex. The aim of this study is to evaluate the sealing ability of the apical bridge formed by calcium hydroxide, white mineral trioxide aggregate (MTA) or gray MTA during apexification procedure. Thirty roots were prepared to simulate an open apex. These roots were divided into 3 groups: Group A: 10 roots filled with Ca(OH)2paste, Group B: 10 roots filled with white mineral trioxide aggregate (WMTA), and Group C: 10 roots filled with gray mineral trioxide aggregate (GMTA). Each root was placed in synthetic tissue fluid (STF) for 3 months. Then each root was immersed in methylene blue dye. The leakage was examined by light stereomicroscope at (40 ×) magnification. Results showed that Ca(OH)2 paste group had the highest mean value of apical dye penetration followed by WMTA, while GMTA group showed the lowest mean value of apical dye penetration. There was a highly significant difference in the apical dye penetration (p<0.01) among these groups, concluded that the apical bridge formed by GMTA had the best sealing ability followed by that formed by WMTA. While the apical calcified bridge formed by Ca(OH)2 paste had the lowest sealing ability. Key words: Sealing ability, apexification, Ca(OH)2 paste, white mineral trioxide aggregate, with gray mineral trioxide aggregate.

Cavity Preparation with Er:YAG Laser or Rotary Instruments: Investigation of the Composite Resin Restorations Interface

ABSTRACT This study evaluated the sealing of composite resin restorations after cavity preparation with high speed diamonds burs or Er:YAG laser. Two different adhesive systems were used; conventional and self-etching. Seventy bovine incisors were divided into groups according to the cavity treatment (N = 10): G1 (bur + acid + Excite); G2 (bur + One Up); G3 (bur + laser + Excite); G3 (bur + laser + One Up); G4 (laser + acid + Excite); G5 (laser + One Up) and G6 (laser + Excite). Restorations were performed with Filtek Z250 3M/ESPE. The specimes were then thermocycled and placed in a vacuum machine, at a negative atmosphere of 20 inch Hg for 5 minutes, for removal of entrapped air. This procedure was followed by immersion in a 50% silver nitrate solution. The teeth were sectioned and the evaluation of the marginal leakage was performed in a light stereomicroscope. The results were submitted to the ANOVA and Tukey statistical tests. It was concluded that preparations performed with high-speed turbines and Er:YAG laser presented the same performance; preparations with Er:YAG laser submitted to acid-etching and conventional adhesive system presented high values of marginal leakage, with statistical significance; conventional and self-etching adhesive systems presented the same performance as to marginal microleakage.

Processing and characterization of chitosan microspheres to be used as templates for layer-by-layer assembly

Chitosan (Ch) microspheres have been developed by precipitation method, cross-linked with glutaraldehyde and used as a template for layer-by-layer (LBL) deposition of two natural polyelectrolytes. Using a LBL methodology, Ch microspheres were alternately coated with hyaluronic acid (HA) and Ch under mild conditions. The roughness of the Ch-based crosslinked microspheres was characterized by atomic force microscopy (AFM). Morphological characterization was performed by environmental scanning electron microscopy (ESEM), scanning electron microscopy (SEM) and stereolight microscopy. The swelling behaviour of the microspheres demonstrated that the ones with more bilayers presented the highest water uptake and the uncoated cross-linked Ch microspheres showed the lowest uptake capability. Microspheres presented spherical shape with sizes ranging from 510 to 840 mum. ESEM demonstrated that a rougher surface with voids is formed in multilayered microspheres caused by the irregular stacking of the layers. A short term mechanical stability assay was also performed, showing that the LBL procedure with more than five bilayers of HA/Ch over Ch cross-linked microspheres provide higher mechanical stability.

The variable refractive index correction algorithm based on a stereo light microscope

Refraction occurs at least twice on both the top and the bottom surfaces of the plastic plate covering the micro channel in a microfluidic chip. The refraction and the nonlinear model of a stereo light microscope (SLM) may severely affect measurement accuracy. In this paper, we study the correlation between optical paths of the SLM and present an algorithm to adjust the refractive index based on the SLM. Our algorithm quantizes the influence of cover plate and double optical paths on the measurement accuracy, and realizes non-destructive, non-contact and precise 3D measurement of a hyaloid and closed container.

Dietary interpretation and paleoecology of herbivores from Pikermi and Samos (late Miocene of Greece)

A large sample of the Pikermi and Samos ungulates was examined by microwear analysis using a light stereomicroscope (561 extinct and 809 extant comparative specimens). The results were used to infer the dietary adaptations of individual species and to evaluate the Pikermian Biome ungulate fauna. Many of the bovids have wear consistent with mixed feeding, although a few mesodont taxa apparently enjoyed an exclusive browsing and or grazing diet. The giraffids spanned the entire dietary spectrum of browsing, mixed feeding, and grazing, but most of the three-toed horses (Hippotherium) were hypsodont grazers. The colobine monkeyMesopithecus pentelicidisplays microwear consistent with a mixed fruit and leaf diet most likely including some hard objects. Similar results were obtained from prior scanning electron microscopy microwear studies at 500 times magnification and from the light microscope method at 35 times magnification for the same species. Results show that diet can differ between species that have very similar gross tooth morphology. Our results also suggest that the Pikermian Biome was most likely a woodland mosaic that provided a diversity of opportunities for species that depended on browsing as well as species that ate grass. The grasses were most likely C3grasses that would grow in shaded areas of the woodland, glades, and margins of water. The ungulate component of the Pikermi and Samos fauna was more species-rich and more diverse in diet than the ungulates observed in modern African forests, woodlands, or savannas, yet dietarily most similar to the ungulates found in woodland elements of India and to some extent of Africa. It is unlikely that the Pikermi and Samos ungulates inhabited dense forests because we find no evidence for heavy fruit browsing. Conversely, a pure savanna is unlikely because many mixed feeders are present as well as browsers. Extant woodland African species are morphologically and trophically very similar to the African savanna species. Therefore the evolution of grazing and of hypsodont morphology for Africa may have evolved within the Plio-Pleistocene woodlands of Africa. Our results show that major dietary and morphologic ungulate evolution may take place within woodlands rather than as a consequence of species moving into savannas both during the late Miocene of Pikermi and Samos and during the Pleistocene–Recent of Central Africa.

Fine-hybrid and nanohybrid restorative materials show similar durability in Class II cavities

This was a randomised trial. Individuals who required a minimum of two replacement fillings were recruited. Restorations were placed using either Grandio bonded with Solobond M (Voco, Cuxhaven, Germany) or Tetric Ceram bonded with Syntac (Ivoclar Vivadent, Schaan, Liechtenstein). At the initial recall (baseline, ie, within 2 weeks), and after 6 months, 1 and 2 years, all restorations were assessed according to the modified United States Public Health Service (US PHS) criteria by two independent investigators using mirrors, probes, bitewing radiographs, impressions and intra-oral photographs. Recall assessments were not performed by the clinician who initially placed the restorations. Both recall rate and survival rate were 100% after 4 years of clinical service. No significant difference was found between the restorative materials. Hypersensitivities were significantly reduced over time (P < 0.05; Friedman test). A significant deterioration over time was found for the criteria of marginal integrity (66% sufficient after 4 years),tooth integrity (15% sufficient), filling integrity (73% sufficient) and proximal contact. Stereo light microscopy and scanning electron microscopy (SEM) analysis of restoration margins revealed differences in the amount of perfect margins in favour of Tetric Ceram (P <0.05). Both materials performed satisfactorily over the 4-year observation period. Because of the extension of the restorations, wear was clearly visible after 4 years of clinical service with 50% sufficient ratings.

Nanohybrid vs. fine hybrid composite in Class II cavities: Clinical results and margin analysis after four years

Objectives This controlled prospective split-mouth study evaluated the clinical behavior of two different resin composites in extended Class II cavities over a period of four years. Methods Thirty patients received 68 direct resin composite restorations (Grandio bonded with Solobond M: n = 36, Tetric Ceram bonded with Syntac: n = 32) by one dentist in a private practice. All restorations were replacement fillings, 24 cavities (35%) revealed no enamel at the bottom of the proximal box, in 33 cavities (48%) the proximal enamel width was less than 0.5 mm. The restorations were examined according to modified USPHS criteria at baseline, and after six months, one, two, and four years. At each recall, impressions were taken for replica preparation. Replicas of 44 select subjects were assessed for marginal quality under a stereo light microscope (SLM) at 130× and 22 replicas were assessed under a scanning electron microscope (SEM) at 200×. Results Both recall rate and survival rate were 100% after four years of clinical service. No significant difference was found between the restorative materials ( p > 0.05; Mann–Whitney U-test). Hypersensitivities were significantly reduced over time ( p < 0.05; Friedman test). A significant deterioration over time was found for the criteria marginal integrity (66% bravo after four years), tooth integrity (15% bravo), filling integrity (73% bravo) and proximal contact ( p < 0.05; Friedman test). SLM and SEM analysis of restoration margins revealed differences in the amount of perfect margins, in favor of Tetric Ceram ( p < 0.05). Significances Both materials performed satisfactorily over the four-year observation period. Due to the extension of the restorations, wear was clearly visible after four years of clinical service with 50% bravo ratings.

Effects of cryogenic treatment and refrigerated air on tool wear when machining medium density fiberboard

Cooling of cutting tools with liquid coolants and lubricants is impractical when machining dry wood or wood composites. This study examines the combined effect of cryogenic tool treatment and using refrigerated air for cooling tools on reducing tool wear. A total of four, double-flute, solid, tungsten carbide router bits were used to machine medium density fiberboard with a CNC router. Three of the four tools were cryogenically treated to below −149 °C. During cutting, refrigerated air was applied to two tools, while the other two cut at ambient temperature. All tools were examined under the stereo light microscope to capture images in order to measure tool wear. Elemental analysis was performed using scanning electron microscopy to determine the percentage of specific elements present on clearance faces of tools after cutting was completed. Results show that less tool wear occurs when using refrigerated air and cryogenic treatment, thereby increasing tool life when cutting medium density fiberboard.

Clinical Performance of Viscous Glass Ionomer Cement in Posterior Cavities over Two Years

In this controlled prospective clinical study the highly viscous glass ionomer cement Ketac Molar was clinically assessed in Class I and Class II cavities. Forty-nine subjects (mean age 32.3 years) received 108 restorations placed by six operators in conventional Black I and II type cavities with undercuts after excavating primary lesions or after removing insufficient restorations. At baseline, and after 6, 12, and 24 months, restorations were assessed by two independent investigators according to modified USPHS codes and criteria. Impressions of the restorations were taken and epoxy replicas were made. Between the baseline and the 24-month recall, 51 representative samples were analyzed at 130 × magnification by use of a stereo light microscope (SLM). Recall rates were 83% after 6 months, 50% after 12 months, and 24% after 24 months. Failure rates after 24 months were 8% for Class I and 40% for Class II fillings, mainly due to bulk fracture at occlusally loaded areas (Kaplan Meier survival analysis). Significant changes over time were found for the criteria “surface roughness”, “marginal integrity”, “restoration integrity”, and “overall judgement” (P < .05; Friedman test). SLM analysis revealed statistically significant differences for the following criteria over time (baseline/6 months/12 months (in % of entire evaluable margin length); P < .05; Friedman 2-way ANOVA): perfect margin 37/19/11, negative step formation 26/49/57, gap formation 2/7/9, and overhang 24/11/8. Replicas exhibited mainly negative step formation as main finding due to apparently inferior wear resistance (P < .05). Gap formations were more frequently observed in Class II restorations than in Class I (12% versus 3% after 12 months; P < .05, Mann-Whitney-U test). The evaluated margin lengths were not statistically different (P > .05, Friedman 2-way ANOVA).

Recovering obliterated laser engraved serial numbers in firearms

An easy procedure for recovering obliterated firearms serial numbers, which are laser engraved is presented in this case report. For these serial numbers, the traditional recovering method using acid etching generally fails, once marking the serial number does not necessarily imply a deep permanent deformation of the crystalline array. The standard required mirror-like finish of the surface commonly can destroy any evidence of the original serial number, i.e., can destroy the heat affected zone (HAZ) of only few micra, if it is still present. It is shown in this report that relief polishing and reflected light stereomicroscopy can, in certain cases, successfully reveal obliterated serial numbers, originally marked by laser. The use of this procedure for recovering this type of obliterated serial number is illustrated and discussed with an example we have dealt with.

Evidence for a risk of tick-borne infection in the city parks of Vilnius, Lithuania

Th irty-six adult ticks collected in the parks of the Lithuanian capital Vilnius in the spring of 2005 were identifi ed as Ixodes ricinus (L.) and studied for the presence of live pathogens by darkfi eld microscopy, of exoskeleton anomalies by light stereomicroscopy, and of several tickborne pathogens by PCR. One of the ticks was positive for three pathogens simultaneously: Ehrlichia muris (monocitic ehrlichiosis agent), Borrelia afzelii, and Borrelia garinii; one was dually infected by both species of Borrelia. In addition, ticks positive for several species of Borrelia were detected: B. afzelii (n = 5), B. garinii (n = 2), some other species of B. burgdorferi sensu lato (n = 2), Ehrlichia muris (n = 1). Th e total proportion of infected ticks was 27.8% (10 of 36), of which 20% (2 of 10) were multiply infected; 47.2% of ticks had exoskeleton anomalies, and such specimens had more multiple infections (35.3% versus 21%). One triply infected tick was found only among the anomalous specimens. Live spirochaetes prevailed among the anomalous specimens: 35.3% (6/17) vs. 5.3% (1/19). Th e diff erence was statistically signifi cant: chi square was equal 5.166, P < 0.05. In conclusion, even this small sample size reveals several important tick-borne pathogens in the newly detected focus in the centre of Vilnius, transmitted by I. ricinus. It suggests that people visiting these parks are exposed to the risk of tick-borne infection, especially when resting on the grass.

Correlation analysis of couple optical paths for micro stereovision with stereo light microscope

A micro stereovision system with a stereo light microscope (SLM) has been applied in micromanipulation systems. There is a coupling connection between two optical paths of a stereo light microscope. The coupling intension corresponds with two factors: the structure of an SLM and the position of an object point in the view of an SLM. In this paper, a correlation function is proposed to describe the coupling intension between the couple optical paths of an SLM. The quantified results are applied to the error analysis of the imaging model. Experiments show that the correlation of the optical paths of a common main objective of stereo light microscope (CMO-SLM) is little more than that of a G-SLM, and the error must be considered when a pinhole imaging model is used to analyze its correlation.

Was grass more prevalent in the pronghorn past? An assessment of the dietary adaptations of Miocene to Recent Antilocapridae (Mammalia: Artiodactyla)

Molar teeth of both Tertiary and Quaternary representatives of the family Antilocapridae were examined using mesowear and light stereomicroscopy microwear. Taxa from the Central and Southern Great Plains and the Northern and Southern Great Basin were included in the analyses and results compared to those obtained on the modern pronghorn ( Antilocapra americana). Species included spanned from the early Miocene (late Hemingfordian) to the late Pleistocene (Rancholabrean). Results are concordant with well-known trends toward increasing aridity and shifts in vegetational structure in the late Miocene–early Pliocene of North America. Both mesowear and microwear results indicate a shift toward more abrasive diets beginning in the Hemphillian (late Miocene–Pliocene) and then a return to a less abrasive dietary regime for the duration of the Pleistocene and into the Recent. The more derived antilocaprines (more hypsodont, relatively longer limbs) apparently depended more on grass than the less advanced merycodontines, but even the earliest of the latter seem to have relied more on grass as a dietary staple than the modern pronghorn. Seasonal grit encroachment on food items encountered by fossil antilocaprids coupled with a heavier reliance on grasses may provide a possible explanation for the extreme hypsodonty present in the modern pronghorn despite its mainly browsing dietary behavior.