In addition, the in vitro antioxidant activities of the pectic fraction and a methanolic extract were investigated. 1,1-Diphenyl-2-picryldydrazyl (DPPH ), thiobarbituric acid, butylated hydroxyanisole (BHA), 3-phenylphenol, ethylenediaminetetraacetic acid (EDTA), DEAE-Trisacryl® Plus, N-cyclohexyl-N′-(2-morpholinoethyl)carbodiimide, metho-p-toluenesulfonate, sodium borodeuteride, ascorbic acid, bovine serum albumin (BSA), deoxyribose,

l-arabinose, d-xylose, d-glucose, d-mannose, d-galactose, l-fucose, l-rhamnose, Transmembrane Transporters modulator d-galacturonic acid and dextran standards were purchased from Sigma–Aldrich Chemical Co. (St. Louis, MO, USA)., Methyl iodide (MeI), phenol, hydrogen peroxide (H2O2) and sulphuric acid were from Merck Co. (Darmstadt, Germany). All other chemicals used were of analytical grade. A commercial sample of guarana (P. cupana) seed powder (batch number 8656A8) was kindly supplied by Herbarium Laboratório Botânico (Paraná, Brazil), which is a herbal medicine pharmaceutical laboratory with a line of products made up of herbal medicine and nutritional supplements. To prepare the guarana AZD6244 cost powder, whole dried seeds of P. cupana L.) Kuntze, collected in Bahia-Brazil, were ground in a hammer mill (60 mesh

sieve-95%). The guarana powder was defatted with toluene:ethanol (2:1, v/v) in a Soxhlet extractor (48 h). Subsequently, the dried material was treated with methanol:water (4:1, v/v) under reflux for 20 min and was immediately cooled to room temperature and centrifuged. This residue (residue 1) was dried and used for polysaccharide extraction as follows. Residue 1 was used Akt inhibitor for polysaccharide extraction according to the scheme depicted in Fig. 1. The extraction procedure was based on the work of Bochicchio, Petkowicz, Alquini, Busato,

and Reicher (2006) with some modifications. Successive extractions were performed in a mechanical blender. After each extraction, the sample was centrifuged, and the residue was subjected to the next extraction step. Each extract was concentrated and treated with ethanol (2:1 v/v) to obtain the precipitated polysaccharides, which were then washed three times with ethanol and dried under a vacuum. The residue 1 was first extracted with DMSO (2×) at 25 °C for 24 h and 120 h to produce fractions GD-I and GD-II, respectively. Residue 2 was subjected to sequential aqueous extractions at 25 °C (2×) and at 90 °C (2×) for 4 h each. Four fractions were obtained: GW-I (25 °C), GW-II (25 °C), GHW-I (90 °C), and GHW-II (90 °C). Then, alkaline extractions with 2 M (2×) then 4 M NaOH (2×) were performed at 25 °C for 120 min in the presence of NaBH4. Each extract was neutralised with aqueous 50% acetic acid, and the precipitated polysaccharides (hemicellulose A) were isolated by centrifugation. The resulting supernatants were dialysed, concentrated to a small volume and then precipitated with ethanol (2:1 v/v) to yield hemicellulose B fractions.

, 2006). Additionally, the isoorientin content in the extracts was determined by HPLC–UV/DAD. P. edulis Sims f. flavicarpa Degener (Passifloraceae)

fruits were picked on São Luiz farm in the municipality of Bauru, São Paulo, Brazil, in January 2008. P. alata Dryander fruits were picked in April 2008 on Morada da Paz farm in the municipality of Arealva, São Paulo, Brazil. The species were identified by Dr. Luís Carlos Bernacci (Herbarium IAC, INCB024360 ic50 Campinas-SP, Brazil) and voucher specimens of P. edulis and P. alata were deposited in the herbarium of the Campinas Agronomic Institute, São Paulo, Brazil (IAC 49929, IAC 50283, respectively). The plants were evaluated individually for incidence of the PWV virus in the fruit, based on typical symptoms, such as wrinkles, deformations and blisters on the leaf and rind surfaces. The fruits pulp and seeds were separated by sieving, after which the pulp was stored in jars and immediately frozen at −20 °C prior to preparation. The rinds (epicarp and mesocarp) were first washed in distilled water, then sliced and dried at 40 °C

until they reached a constant PD98059 supplier weight. The dried rinds were then ground in a food processor and sieved through a 16-mesh sieve to separate the material with a particle size of 1.0 mm. The ground rinds were stored in plastic containers protected from moisture and heat. Analytical-grade ethanol (Merck, VWRI, Leuven, Belgium) and methanol (J.T. Baker, Phillipsburg, NJ) were used in the extraction procedure. Dimethylsulfoxide (DMSO), NaCl, KCl, CaCl2, hydrogen peroxide (30% v/v) and Tween 20 were supplied by Merck. p-Nitrophenyl phosphate, sodium nitrite, bovine serum albumin (BSA), EDTA disodium salt, bis-N-methylacridinium nitrate (lucigenin), and phorbol 12-myristate 13-acetate (PMA) were purchased from

Sigma (Bornem, Belgium). Amplex red was purchased from Molecular Probes (Invitrogen, Merelbeke, Belgium). Isoorientin standard (purity ⩾99%) was purchased from Carl Roth (Karlsruhe, Germany). All the solutions were prepared with water purified in a Milli-Q system (Millipore, Bedford, Amino acid MA). The flavonoids of P. edulis and P. alata pulp were extracted under pre-optimised conditions ( Zeraik & Yariwake, 2010): passion fruit pulp (10.0 mL) was sonicated for 1.5 min with 30.0 mL of 60% ethanol at room temperature. The extracts were centrifuged at 5000g, 25 °C, for 20 min and the supernatant was concentrated to 2.0 mL using a rotary evaporator. The resulting aqueous solution was purified by solid-phase extraction, using Sep-Pak C18 cartridges (400.0 mg, Waters Associates, Milford, MA), which were preconditioned with 5.0 mL of methanol and 5.0 mL of water. The flavonoid fractions were eluted with 60% methanol to a precise volume of 2 mL. The extracts were evaporated to dryness using a rotary evaporator, and solubilised in DMSO to obtain stock solutions of 1.0, 10.0 and 100.0 mg L−1.

The method MEK inhibitor by Vogelsang et al. [43] was used to determine the

limit of detection (LOD), limit of identification (LOI), and limit of quantification (LOQ). The calibration curve was based on calibration standards (in 1 vol% HNO3) of 0, 5, 10, 25, 50, and 100 μg/L. The curve was linear up to 25 μg/L, and non-linear at higher concentrations (100 μg/L deviated −34% from the extrapolated linear curve). The non-linearity of the curve was accounted for by the instrument using a non-linear fitting curve through zero. The LOD, LOI, and LOQ were calculated based on the calibration points 5, 10, and 25 μg/L (in the linear range) by comparing the calibration signals with signals of spiked samples in each fluid. LOD values of 2.1, 0.5, and 0.5 μg/L Fe were determined in citric acid, in 10 mM NaCl, and in NaCl + BSA, respectively. The corresponding LOI numbers were 4.1, 1.0, and 1.0 μg/L Fe, respectively. The LOQ values were determined to be 6.0, 1.4, and 1.5 μg/L Fe in citric acid, in 10 mM NaCl, and in NaCl + BSA, respectively. The recoveries of 5, 10, and 25 μg/L spiked samples, which should not deviate more than 15% from 100%, were all between 94 and 107%.

Since the acidified selleck chemicals HNO3 and NaOH solutions were similar to the calibration standard matrix, their LOD, LOI, and LOQ values were lower compared with the other solutions, <2.1, <4.1, and <6.0 μg/L Fe, respectively. Solution samples of HNO3, NaOH, citric acid, and NaCl + BSA (two samples after 24 h, all samples after 168 h) were diluted 12.5 times to ensure that concentrations were within the calibration range. The blank values

of all samples were positive and subtracted from the significantly higher solution sample values. The blank values were <1% of the sample values in NaCl, <1.7% in citric acid and HNO3, and 24% after 10 min, 16% after 1 h, and <1.7% after 24 or 168 h in NaCl + BSA. Relatively high blank values (between 1.3 and 22 μg/L Fe) and their variation in the BSA contacting fluids were attributed to the iron content of BSA, as previously reported in Lundin et al. [44]. This influence was accounted for in average values and standard deviations using a background correction for Fe in BSA (see supporting information). Surface compositional analysis was performed using X-ray photoelectron Ketotifen spectroscopy, XPS. Spectra were recorded using a Kratos AXIS UltraDLD X-ray photoelectron spectrometer (Kratos Analytical) using a monochromatic Al X-ray source (150 W) on areas of approximate size 700 μm × 300 μm. Wide spectra (survey scans) were run to identify elements present in the outermost surface oxide (information depth of a few nanometers). High resolution spectra (20 eV pass energy) were acquired for the main bulk compositional elements Cr 2p, Fe 2p, and O 1 s of each test coupon including carbon (C 1 s).

Thus it is unlikely that a lack of motivation could be a sufficient explanation for all, as Bickerton puts it, “relatively large-brained species” (Bickerton, 2003, p. 83). On the more technical side, Nowak et al. have some other possible explanations (Nowak & Komarova, 2001). Certain conditions have to be met before natural selection can see the advantages of compounding: 1. The total number of relevant messages has to exceed a critical value, 2. The compound signals must be able to encode the relevant messages in such a way that individual components occur in many different messages. Plausibly, these conditions this website are not met by non-humans. But why? We hypothesize that the degree of differentiation

of conceptual structure in non-humans is insufficient to support these conditions. Specifically, there seems to be something unique about the human capacity for hierarchical conceptualization (but it is difficult to tell what exactly – see Chomsky, 2010, Dessalles, 2008, Fauconnier and Turner, 2008, Hauser et al., 2002, Luuk and Luuk, 2008, Penn and Povinelli, 2007, Penn et al., 2008, Premack and Woodruff, 1978, Suddendorf and Corballis, 2007, Tomasello et al., 2003 and Tulving, 2005, for different hypotheses, some of which appear to be already falsified – Correia et al., 2007 and Osvath, 2009). Curiously, only one possible example of a semantically compositional syntax, the extremely limited communication

system of honeybees,7 is found in non-humans in the wild, and no clear example of semantically compositional communication has been found in non-human FG 4592 vertebrates (Hurford, 2004, Michelsen, 1999 and von Frisch and Lindauer, 1996). There are bird songs, cetacean songs, and primate ‘long calls’ built up out of smaller units, but the units are not meaningful on their own, and/or different combinations are not distinctively meaningful (Jackendoff, 1999 and Ujhelyi, 1998). This argument applies also to the Pyruvate dehydrogenase special case of putty-nose

monkeys (Arnold & Zuberbuhler, 2006). These monkeys produce two calls, ‘pyows’ and ‘hacks’ in response to, mainly, leopards and eagles, respectively. The researches found that the monkeys also produce a third call, ‘pyow–hack’ (P–H), and observed that P–H triggers group movement. In addition, although the putty-nosed monkeys sometimes move through the canopy to escape from an approaching leopard, this strategy is avoided when threatened by large raptors, as it would increase the risk of attack. Leopard growls were played back to 17 different monkey groups. In nine groups, the male produced call series containing at least one P–H. The researchers found that, 20 min later, the groups whose males had produced P–H had traveled significantly farther than other groups. It is important to note that P–H is not a semantic combination, and complies with P and H due to loud call repertoire constraints only (Arnold, p.c.).

, 2004). Peltonen et al. (2002) studied spatial synchrony of forest insect outbreaks found that the Moran effect was likely the dominant mechanism causing spatial synchrony in outbreaks across regional scales and that dispersal

was of lesser importance. This finding was supported by Swetnam and Lynch (1993) who also found that exogenous factors (e.g., climatic variability) played a significant role in regulating regional-scale WSB outbreaks in northern New Mexico. More recently, Flower et al. (2014) found that warm-dry climate preceded outbreaks by up to three years, but during outbreaks conditions

tended to be cooler and wetter. Selumetinib clinical trial The comparison of regionally synchronous WSB outbreaks and climatic proxies from the western portion of the study area suggest that the influence of climate on outbreak dynamics is highly complex (Fig. 5). From the late-1600s to early-1700s and from the 1940s to the end of the record, synchronous outbreaks coincide with positive summer temperature and negative SWE anomalies indicative of warmer and drier climatic conditions (Fig. 5). However, from the Erastin ic50 late-1700s to the around the 1920s synchronous outbreaks coincide with negative temperature and positive SWE anomalies that are indicative of cooler and wetter climatic conditions (Fig. 5). During this same time period (with the exception of the 1920s) extensive wet periods prevailed across the southern Canadian Cordillera (Watson and Luckman, 2004) and there were numerous episodes of glacial expansion in Mt. Waddington range west of the study area (Larocque and Smith, 2003). During

periods when warmer Oxalosuccinic acid and drier conditions were associated with WSB outbreaks (Fig. 5), Starheim et al. (2012) found that the low-frequency signals associated ocean-atmospheric forcing, i.e., Pacific Decadal Oscillation and the Pacific North America Index were prominent in their hydroclimatic reconstructions. Previous research in the western US shows that WSB outbreaks are associated with wetter conditions in the spring and summer, while years leading up to outbreaks are associated with drought conditions (Swetnam and Lynch, 1989, Swetnam and Lynch, 1993, Ryerson et al., 2003 and Flower et al., 2014). In southern BC, outbreaks have been found to be associated with average air temperatures and drier winters (Campbell et al., 2006).

2; SD = 15.8; Sandoz et al., 2013). trans-isomer molecular weight The pretreatment score suggested that her negative body image interfered with her daily activities to a significant degree at pretreatment. At the midpoint of therapy, her body image flexibility score increased to 67, which fell within the average range of a nonclinical sample, and it remained within the average range at posttreatment. Her average

body image flexibility score throughout the course of the ACT intervention was 57.8 and 53 at 3-month follow-up. Participant 1’s scores on disordered eating related measures administered at pretreatment, midpoint, posttreatment, and 3-month follow-up were generally consistent with the findings of the primary outcome and process measures. Participant 2’s daily report revealed that the average weekly number of binge eating was approximately 8 at pretreatment, which was consistent with the diagnostic criteria for BED. During the 10 weeks of the ACT intervention, the average number of binge episodes decreased to approximately 4.6 times per week, which still met the minimum number of binge episodes required for a BED diagnosis (i.e., approximately twice per week). At the 3-month follow-up period, the average number of Nivolumab in vivo binge episodes was approximately 3 times per week. Participant 2’s body image flexibility levels throughout the course of the study revealed a similar

clinical picture. Her body image flexibility score was 28 at pretreatment, which was more than two standard deviations below the mean for a nonclinical sample. Her body image flexibility score improved slightly throughout the course of the ACT intervention, with a weekly average of 35.5, and the improvement was somewhat maintained at follow-up (33). Similarly, Participant 2’s scores on disordered eating related measures suggested that her disordered eating concerns decreased but remained relatively elevated throughout the study. Notably, the participant greatly reduced the amount of time spent overeating with a sense of having lost control over eating throughout the course of study. She endorsed PAK5 engaging in episodes of consuming unusually large amounts of food

at a clinically significant level; however, the number of episodes that were accompanied by a perceived loss of control over eating was 20% at midpoint compared to 100% of the time at pretreatment. This ratio remained at lower levels at posttreatment and follow-up. When asked about the change at posttreatment and follow-up, Participant 2 attributed it to a decrease in the amount of food she consumed during a “binge” episode. While she still considered her food consumption during “binge” episodes to be “unusually large,” the amount she consumed in an episode appeared to have become smaller since the midpoint of therapy. For example, a “binge” for this participant after midpoint might include eating two cheeseburgers and an order of french-fries from a fast food restaurant.

, 2006). WNV-induced respiratory distress mechanisms have been extensively

studied in rodents and are discussed below. Cases of cardiac or renal involvement, although much less frequent, this website have been reported (Table 1). A case study of myocarditis has been reported in a patient having a confirmed case of WNV (Omalu et al., 2003). The patient developed cardiac arrhythmias and global myocardial dysfunction. Cardiac complications including arrhythmia are also described in a report of hospitalized patients with WNV disease (Bode et al., 2006). There are many reports of WNV-induced cardiac involvement in other mammalian (Lichtensteiger et al., 2003) and avian species (Gibbs et al., 2005). Electrocardiograms obtained from radiotelemetry in WNV-infected hamsters revealed some cardiac disturbances, but the implications on WNND have yet to be determined (Wang et al., 2011). In regards to renal function, 22% of patients with WNV-induced paralysis developed bladder dysfunction (Saad et al., 2005). A case study report claimed to be the first report of urological sequelae in a patient with WNV; the patient also had respiratory distress requiring intubation (Shpall et al., 2003). Other more subtle autonomic-like dysfunctions may also

occur in WNV neurological disease. For example, adrenal insufficiency, as detected by a corticotropin test, was identified in 70% patients with severe WNV www.selleckchem.com/products/otx015.html disease (Abroug et al., 2006). A central question is if autonomic dysfunction is due to direct Bacterial neuraminidase damage of motor functions or to damage of neurons generally regulating sympathetic or parasympathetic functions. Rodent studies using heart rate variability as an indicator of autonomic function, electromyography of the intestine and diaphragm, nerve conduction velocity, electrocardiography, plethysmography, and immunofluorescence assays indicated that WNV does cause some autonomic dysfunction, but many of these dysfunctions are caused by direct damage to motor functions (Morrey et al., 2012, Wang et al., 2011, Wang et al., 2013a and Wang et al., 2013b). Parkinsonism has been observed in 69% of WNV patients in one study (Sejvar et al., 2003a) (Table 1). Parkinson’s disease is a neurodegenerative

disease caused by death of dopaminergic neurons in the substantia nigra. Two WNV patients have been described by neuroimaging procedures with heavy involvement of the substantia nigra, which correlated with Parkinsonism features of the patient (Bosanko et al., 2003). It is not known if rodents have Parkinsonism, but hamsters infected with WNV manifest front limb tremors (Morrey et al., 2004b). No studies have been done to correlate these tremors with histopathogensis of infection of the substantia nigra. The other alternative mechanism of tremors that could be addressed with rodent models is hyper-excitability of neurons or synapses. In the mouse model of amyotrophic lateral sclerosis, limb tremors were associated with an elevation of excitatory synapses (Sunico et al., 2011).

, 1992, Hwang et al., 1983 and Saboisky et al., 2007). The XII selleck chemical motoneurons phasically activate the genioglossus muscle during each inspiration (Fig. 1), and some activity is maintained during expiration (Akahoshi et al., 2001, Fogel et al., 2001, Otsuka et al., 2000, Saboisky et al., 2010 and Sauerland and Harper, 1976). Overall, however, respiratory drive increases genioglossus

muscle tone preferentially during inhalation, resulting in a contraction that pulls the tongue forward (Brouillette and Thach, 1979) and enlarges the upper airways (Bailey and Fregosi, 2004, Fuller et al., 1999, Mann et al., 2002, Oliven et al., 2001 and Sokoloff, 2000). This mechanism largely prevents airway collapse

during wakefulness. Indeed during wakefulness, electromyography (EMG) activity of the genioglossus is enhanced in OSA patients when compared to controls (Fogel et al., 2001 and Mezzanotte et al., 1992), an adaptation that seems to compensate for the increased upper airway BMS-387032 supplier resistance and compliance that characterizes OSA patients (Malhotra and White, 2002, Randerath, 2007 and Saboisky et al., 2007). However, during sleep or while anesthetized, the central respiratory drive to the genioglossus muscle weakens, and, as a consequence, anatomical obstructions can occlude the airway during inhalation (Eastwood et al., 2002, Remmers et al., 1978 and Sauerland and Harper, 1976). Because a decreased central drive during sleep is necessary for the occlusion to occur during inhalation, OSA must be considered as a neuronal issue. Indeed, airway obstructions are promoted by multiple central and peripheral nervous systems factors. These factors include sleep state-dependent pathologies and respiratory instabilities that are caused by loop gain changes as has been discussed SB-3CT in great detail (Thomas et al., 2004 and White, 2005). Yet, whether and how an obstruction causes the cessation of breathing, i.e. the actual apnea, are not trivial questions.

It is safe to conclude that the mechanisms and events leading to apneas are not fully understood, and that multiple factors must come together. In the following section we will discuss some of the potential mechanisms that contribute to the apnea. Cessation of airflow with continued respiratory effort is the hallmark of OSA (Praud et al., 1988, Remmers et al., 1978 and Zucconi et al., 1996). Fig. 2 illustrates two example traces from OSA patients (A from, Praud et al., 1988; B from, Remmers et al., 1978). In both examples oro-nasal flow is blocked, while respiratory efforts continue in the abdomen. From a biomechanical perspective, continued respiratory effort in the thorax/abdomen increases thoracic volume and decreases pressure at the level of the pharynx, which would normally enable air to flow into the lungs.

Once again, STOP-IT was employed to measure response inhibition (Verbruggen et al., 2008). The parameters, instructions, and exclusion criteria were the same as those employed in Experiment 1. Six subjects were removed because they performed in a way that did not allow valid estimates of SSRT to be obtained. Specifically, these subjects withheld their response on significantly more or less than the 50% criterion. One additional subject was buy RG7420 removed for having considerable difficulty with the task and exhibiting an SSRT score 15.8 SDs above the mean. Altogether, data from 96 of the 106 subjects were included. Retrieval-practice performance data was lost for 18 of the 96 subjects. The remaining

78 subjects successfully retrieved 82% (SD = 13%) of the exemplars during retrieval practice, a rate very similar to that observed in Experiment 1. Hit rates for Rp+, Rp−, and Rigosertib Nrp items and false alarm rates for lures associated with Rp and Nrp categories are shown in the top row of Table 2. To analyze recognition accuracy, d’ was computed for all three item types by calculating Zhit rate–Zfalse-alarm rate. As expected, a significant effect of retrieval practice was observed such that Rp+ items (M = 2.57, SE = .07)

were better recognized than Nrp items (M = 1.89, SE = .07), t(95) = 8.28, p < .001, d = .85. As shown in the bottom row of Table 2, d′ values were numerically lower for Rp− items (M = 1.80, SE = .08) than they were for Nrp items (M = 1.89, SE = .07). Although a paired-samples t test indicated that this difference was not statistically significant, t(95) = 1.24, p = .22, a repeated-measures ANCOVA with SSRT scores serving as a covariate—thus controlling for additional error variance—found that it was, F(1, 94) = 6.69, MSE = .24, p = .01. This finding replicates the many studies that have observed RIF using item recognition (e.g., Aslan and Bäuml, 2010, Aslan and Bäuml, 2011, Hicks and Starns, 2004, Ortega et al., 2012, Román et al., 2009, Soriano

et al., 2009 and Spitzer and Bäuml, 2007). The fact that including SSRT as a covariate had such a large effect suggests that it accounted for a large proportion of the variance in retrieval-induced forgetting, a possibility we explore more directly below. Before analyzing almost the correlation between retrieval-induced forgetting and SSRT, we computed the amount of retrieval-induced forgetting observed for each participant. As in Experiment 1, we did this by z-normalizing each participant’s retrieval-induced forgetting score relative to the mean and standard deviation of all other participants in their matched counterbalancing condition. An analysis of the resulting RIF-z scores failed to reveal evidence of significant skew (.13, SE = .25) or kurtosis (−.39, SE = .49), and these statistics did not vary significantly from those observed in Experiment 1.

Sediment eroded from these sloping lands is

transported by barrancas toward the Zahuapan, Atenco click here and Atoyac rivers, which are among the few to sustain flow throughout the year. It is eventually deposited in the basin that extends to the south, across the state boundary into Puebla. Once a patchwork of wetlands, it has been drained, and is now intensively cultivated with the aid of irrigation canals ( González Jácome, 2008, Luna Morales, 1993 and Wilken, 1969). Another belt of plains crosses the northern half of Tlaxcala. Their drainage network is more disjointed and the wetlands they once supported were more ephemeral and spatially limited ( Lesure et al., 2006 and Skopyk, 2010, 162–234). They are cultivated more extensively or support pasture that is relatively lush in the wet season. On the basin floors, land degradation takes the form of falling water tables, and the deposition of thick sheets of sterile sand by floods. But it is the sloping lands that are most severely degraded. The silty to sandy soils that develop in tobas are easily tilled and relatively fertile, but at the same time

extremely erodible. Their lower subsoil is rich in silica. Once exposed, it becomes irreversibly indurated, forming what is termed tepetate (“stone mat” in hispanicized Nahuatl). Tepetate is impenetrable to roots, and too hard to be broken up with a tractor-drawn steel plow. The erosion that creates tepetate badlands proceeds by first scarring the slope buy Venetoclax with deep gullies that impede movement between fields. Small fans may accumulate at the mouth of discontinuous gully reaches. With time, the gullies form a more interconnected Bortezomib network and begin to eat into the divides between them, leaving only isolated erosional pedestals ( Fig. 4d). In the end the slope may turn into one continuous expanse of tepetate ( Fig. 4e). Erosion accelerates runoff and sediment delivery from slopes.

Typically a strong pulse of sediment is generated at first, choking stream channels. By the time large swaths of tepetate are exposed, sediment supply diminishes (though never to the level of a vegetated slope) while runoff reaches its peak rates ( Haulon et al., 2007, Heine, 1983 and Wegener, 1979). The streams respond by aggrading sediment on their floodplain, then incising a new channel that will deepen, widen, and cut headward in order to accommodate the increased discharges. All these processes are intricately bound up with the construction, use, maintenance, and decay of agricultural terraces. Practically all sloping land that is still in cultivation in Tlaxcala has had its gradient purposefully modified. Terraces are dry farmed and take two basic forms. The ubiquitous metepantles ( Fig. 2) are bordered by contoured ditches. The spoil from their digging and cleaning is piled up into berms most commonly planted in agaves, hence the name (metl = agave, tetl = stone, pantle = berm).