We carried out a full-coverage survey of the Yautepec Valley in the 1990s to reconstruct demography and settlements and their changes through time. We investigated the extent to which well-documented ...developments in the adjacent Basin of Mexico were paralleled in Yautepec, as well as the impact of regional empires and economies on local society. Our analyses focused on Teotihuacan relations in the Classic period and relations with the Aztec empire and the Mesoamerican world system in the Middle and Late Postclassic periods. In addition to locating, mapping, and describing sites and taking grab-bag artifact collections, we also made a series of systematic intensive surface collections (5 × 5 m) and test excavations at samples of Classic and Postclassic sites. In this paper, we describe the survey and changing settlement patterns in the Yautepec Valley. We also present several analyses of changing patterns of urbanization through the Prehispanic era. We conclude with a synthesis of changing social and cultural dynamics in this region.
•This article uses methods and theory from urban economics and economic geography to examine urban structure at Teotihuacan.•We find evidence of spatial equilibrium at Teotihuacan.•Competition for ...desirable land near urban amenities acted as a gravitational force for residential location and land use preferences.•We find evidence of a strong spatial gradient of class composition indicating that higher wealth groups outcompeted lower wealth groups for more valuable land.
This study employs canonical methods and theory from urban economics and economic geography to analyze the urban structure of the ancient city of Teotihuacan. We present evidence that Teotihuacan’s overall configuration, which includes spatial patterning in land use, demography, and social class, reveals density gradients that are consistent with the assumptions of urban spatial equilibrium. In general, spatial equilibrium posits that locational advantages conferred by proximity to desirable land (i.e., urban amenities) are offset by the associated land and transportation costs. These results provide insights into the process of urbanization at the ancient metropolis as well as its structural underpinnings such as social inequality and spatial competition. Based on these results, we argue that the framework employed here is broadly applicable to archaeological case studies and can lead to new inferences about the comparative dynamics of ancient urbanization.
The systematic application of living-related and cadaveric, in situ split-liver transplantation has helped to alleviate the critical shortage of suitable-sized, pediatric donors. Undoubtedly, both ...techniques are beneficial and advantageous; however, the superiority of either graft source has not been demonstrated directly. Because of the potential living-donor risks, we reserve the living donor as the last graft option for pediatric recipients awaiting liver transplantation. Inasmuch as no direct comparison between these two graft types has been performed, we sought to perform a comparative analysis of the functional outcomes of left lateral segmental grafts procured from these donor sources to determine whether differences do exist.
A retrospective analysis of all liver transplants performed at a single institution between February 1984 and January 1999 was undertaken. Only pediatric (<18 years) recipients of left lateral segmental grafts procured from either living-related (LRD) or cadaveric, in situ split-liver (SLD) donors were included. A detailed analysis of preoperative, intraoperative, and postoperative variables was undertaken. Survival was estimated using the Kaplan-Meier method, and comparison of variables between groups was undertaken using the t test of Wilcoxon rank sum test.
There were no significant differences in the preoperative variables between the 39 recipients of SLD grafts and 34 recipients of LRD grafts. The donors did differ significantly in mean age, ABO blood group matching, and preoperative liver function testing. Postoperative liver function testing revealed significant early differences in aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, prothrombin time, and alkaline phosphatase, with grafts from LRD performing better than those from SLD. SLD grafts also had significantly longer ischemia times and a higher incidence of graft loss owing to primary nonfunction and technical complications (9 vs. 2, P<0.05). However, six of these graft losses in the SLD group were because of technical or immunologic causes, which, theoretically, should not differ between the two groups. Furthermore, these graft losses did not negatively impact early patient survival as most patients were successfully rescued with retransplantation (30-day actuarial survival, 97.1% SLD vs. 94.1% LRD, P=0.745). In the surviving grafts, the early differences in liver function variables normalized.
Inherent differences in both donor sources exist and account for differences seen in preoperative and intraoperative variables. Segmental grafts from LRD clearly performed better in the first week after transplantation as demonstrated by lower liver function variables and less graft loss to primary nonfunction. However, the intermediate function (7-30 days) of both grafts did not differ, and the early graft losses did not translate into patient death. Although minimal living-donor morbidity was seen in this series, the use of this donor type still carries a finite risk. We therefore will continue to use SLD as the primary graft source for pediatric patients awaiting liver transplantation.
: The purpose of this study was to determine whether calcineurin inhibitor (CNI)‐induced chronic nephrotoxicity in liver transplant patients is reversible by replacement of the CNI with rapamycin as ...the primary immunosuppressive agent. CNIs, while providing potent immunosuppression for liver transplant patients, exhibit nephrotoxicity as a major side‐effect. Whereas acute CNI‐induced nephrotoxicity is reversible by withdrawal of the CNI, chronic nephrotoxicity due to CNIs is a progressive process thought to be irreversible. Eight liver transplant patients with CNI‐induced chronic nephrotoxicity were converted to rapamycin as the primary immunosuppressive agent. The CNI was either discontinued (four patients) or the dosage lowered to maintain a subtherapeutic level (four patients). Renal function as assessed by serum creatinine was measured before and after conversion to rapamycin. Two patients progressed to dialysis dependence following conversion to rapamycin. These two patients had been on CNIs for a mean of 112 months (range 93–131 months) prior to conversion to rapamycin. Five patients experienced improvement in renal function. These patients had been on calcineurin inhibitors for a mean of 60 months (range 42–75 months) prior to conversion. One patient with chronic nephrolithiasis as a contributing factor to his renal dysfunction has progressed to dialysis dependence despite conversion to rapamycin following exposure to a CNI for 24 months. In the five patients with improved renal function, serum creatinine levels decreased significantly (2.4 ± 0.3 mg/dL to 1.5 ± 0.1 mg/dL, p < 0.05) by a mean of 7.2 months (range 5–10 months) after conversion from CNI to rapamycin‐based immunosuppression. Liver function remained stable after conversion to rapamycin. CNI‐induced chronic nephrotoxicity can be reversed upon withdrawal of the CNI. Rapamycin is an effective replacement agent as primary immunosuppressive therapy following withdrawal of CNIs in liver transplant patients with CNI‐induced chronic nephrotoxicity.
Renal transplant recipients with positive flow cytometric crossmatches (FCXM) face greater risk of early rejection and graft failure. It is clear that the pharmacologic needs of this high risk group ...have not been identified. We retrospectively compared the impact of two drug regimens upon early rejection and 5 yr actuarial survival among 324 primary cadaveric transplant recipients with positive and negative FCXM. Patients received either Regimen I (OKT3 induction, cyclosporine and steroids) or Regimen II (mycophenolate mofetil with cyclosporine or Prograf). Recipient gender, age, disease etiology, ethnic distribution and cytotoxic panel reactive antibody (PRA) were equivalent between regimens (p=ns). With Regimen I, the incidence of rejection was greater for FCXM positive vs. FCXM negative patients (51 vs. 21%, p=0.001). In contrast, with Regimen II the incidence of rejection for FCXM positive and FCXM negative patients was equivalent (18 vs. 12%, p=ns) and lower than patients treated with Regimen I (p < 0.01). Ethnic variation was only observed with Regimen I in which African Americans with positive FCXM had more rejections than Caucasians (60 vs. 45%, p < 0.05). Five‐year actuarial survival was lower for FCXM positive vs. FCXM negative patients treated with Regimen I (40 vs. 75%, p=0.0006) or Regimen 2 (60 vs. 90%, p=0.001). Allograft survival was equivalent (p=ns) among FCXM positive individuals receiving Regimen I or II. However, allograft survival among FCXM negative individuals improved with Regimen II (p < 0.05). Ethnic variation in survival was not observed with either regimen (p=ns).
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