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PubMed1978

An economic analysis of migration in Mexico.

This paper analyzes internal migration in Mexico over the 1960-70 period. A model of the determinants of migration is specified and estimated for aggregated interstate migration flows. Results show that distance serves as a significant deterrent to migration, that higher destination earning levels are attractive to migrants, and that regions with high unemployment rates experience lower rates of inmigration. An unanticipated finding is that regions with higher earning levels have greater rates of outmigration. The data are disaggregated to examine separate migration relationships for each state. The results are that distance is a lesser deterrent for those migrants with more accessible alternatives, that higher earning levels reduce the deterring effects of distance, and that regions with higher earning levels have lower associated elasticities of migration. It is concluded that economic factors have played a crucial role in internal migration and thus in the changing occupational and geographic structure of the Mexican labor force.

Americas↗
PubMed1990

A comparative clinical trial of Norinyl 1 + 35 versus Norinyl 1 + 50 in Merida, Yucatan, Mexico.

A comparative clinical trial of two combined oral contraceptives differing only in estrogen type and dosage was conducted at the Centro de Investigaciones Hideyo Noguchi in Merida, Yucatan, Mexico. The trial was designed to determine the differences between Norinyl 1 + 50 (Syntex) and Norinyl 1 + 35 (Syntex) in rates of discontinuation and frequency of selected side-effects which might contribute to method discontinuation. Three hundred women were randomly assigned to either the Norinyl 1 + 35 group or to the Norinyl 1 + 50 group and follow-up visits were scheduled at 1, 4, 8 and 12 months after admission. In the Norinyl 1 + 35 group, more women experienced an increase in intermenstrual bleeding (primarily staining and spotting) (p less than 0.05), breast discomfort (p less than 0.05) and nausea than in the Norinyl 1 + 50 group. There was a significantly higher discontinuation rate for personal reasons, such as desired change of method and method not needed, among the women taking Norinyl 1 + 35 (p less than 0.05). The largest number of discontinuations comprised women discontinuing for menstrual problems in both groups. The life-table total discontinuation rate at 12 months was 52.0 for the Norinyl 1 + 35 group and 50.7 for the Norinyl 1 + 50 group. The lost-to-follow-up rates at 12 months were 17.8 for the Norinyl 1 + 35 group and 22.8 for the Norinyl 1 + 50 group.

Adolescent↗
PubMed1993

Environmental and genetic effects on preweaning growth performance of hair sheep in Mexico.

Data on 4,754 lambs born from Pelibuey (PB) and Barbados Blackbelly (BB) ewes collected over 9 years at the Mococha Experimental Centre in Yucatan, Mexico, were used to determine environmental, dam-breed and sire-breed effects on birth weight (BW), weaning weight (WW) and average daily gain (ADG). Effects of year and season of birth, sex of the lamb, type of birth, breed of dam, breed of sire, their interaction and ewe body weight were included. Heritabilities were estimated for each breed. Season of lambing was a significant source of variation on WW and ADG. Male lambs weighed more than female lambs at birth and weaning. Single born lambs were heavier than twins and triplets. Lambs born from PB dams were heavier and grew faster than those born from BB dams. Heritabilities of BW, WW and ADG for the PB breed were 0.16 +/- 0.04, 0.12 +/- 0.03 and 0.11 +/- 0.03, respectively and 0.04 +/- 0.07, 0.17 +/- 0.09 and 0.15 +/- 0.08 for the BB breed. Heterosis values were close to zero.

Animals↗
PubMed1980

Bovine babesiosis in northern Mexico.

The occurrence of Boophilus microplus infections accompanied by bovine babesiosis was confirmed for 2 locations in northern Mexico. The confirmation at one location was made by transferring whole blood to a splenectomised calf which subsequently developed an acute Babesia bovis infection. Examination of thin blood smears from a suspect animal at the second location revealed B. bovis-infected erthrocytes. A serological survey of other herd members at both locations showed antibody activity against both Babesia and Anaplasma spp.

Anaplasmosis↗
PubMed1994

Drug prevention in Zuni, New Mexico: creation of a teen center as an alternative to alcohol and drug use.

In 1991, the Center for Substance Abuse Prevention of the Department of Health and Human Services funded a project to develop alcohol prevention-oriented messages targeting teenagers of the Zuni Tribe in New Mexico. A lengthy needs assessment determined that alcohol was the most serious drug problem on the pueblo, and that Zuni teenagers often resorted to alcohol and other drug use because they had little else to do during their free time. Communication products were developed which publicized and promoted the creation of a Zuni Teen Center as a fun and safe alternative to drug use. These products, then, are serving as a catalyst for mobilizing the Zuni community around the cause of preventing alcohol use and abuse among their teens via the conversion of an old warehouse to a Zuni Teen Center. The following article describes the needs assessment, product development and distribution, and evaluation of the project's success.

Adolescent↗
PubMed1993

Is microalbuminuria part of the prediabetic state? The Mexico City Diabetes Study.

Microalbuminuria is associated with increased cardiovascular mortality in both diabetic and non-diabetic subjects. A number of studies have indicated that insulin resistance, increased blood pressure and dyslipidaemia precede the onset of clinical diabetes. We examined various correlates of microalbuminuria in 1,298 non-diabetic subjects who participated in the Mexico City Diabetes Study, a population-based study of diabetes and cardiovascular risk factors. Both parental history of diabetes and impaired glucose tolerance were significantly associated with microalbuminuria. These results were not explained by differences in age or blood pressure between subjects with or without a parental history of diabetes or impaired glucose tolerance. In addition, subjects with microalbuminuria had increased 2-h insulin and triglyceride concentrations, a higher prevalence of hypertension, and decreased high density lipoprotein cholesterol concentrations relative to subjects without microalbuminuria. These results that microalbuminuria may be a feature of the prediabetic state.

Albuminuria↗
PubMed1997

Developmental patterns of jicama (Pachyrhizus erosus (L.) Urban) plant and the chemical constituents of roots grown in Sonora, Mexico.

The developmental pattern of jicama (Pachyrhizus erosus (L.) Urban) was studied by sampling plants aged 20 to 36 weeks at weekly intervals. There was an increase in all characteristics of foliage: fresh and dry weight, number of leaves per plant, main stem length, number of leaves, nodes and internodes of the main stem; and in all root characteristics: fresh and dry weight, diameter and length. The chemical analysis was determined for roots at different plant ages. The range values for dry matter were 16.19-22.28%, protein 1.11-1.62%, fat 0.553-0.867%, crude fiber 0.3048-0.3943%, and ash 0.669-1.089%. The chemical constituents fluctuated with age but without specific trends. These values are considered the first record of roots produced by plants grown in Mexico.

Dietary Fats↗
PubMed2002

Survey of the black howler monkey, alouatta pigra, population at the Mayan site of Palenque, Chiapas, Mexico.

A survey of the population of the black howler monkey (Alouatta pigra) present at the Mayan site of Palenque was conducted during 2000. A total of 911 man/hours, spread over 112 days were spent surveying the 600 ha area of pristine forest at the site for howler troops. We detected the presence of 136 individuals of which 131 were members of 20 troops, the rest were 3 solitary adult males and 2 adult males travelling as a pair. Ecological density was estimated at 23 individuals/km(2). Mean troop size was 7.0 individuals and it ranged from 2 - 12 individuals; 60% of the troops were multimale. All sighting of howler monkeys were in evergreen rain forest and 75% were in trees > or = 20 m in height. The reported densities and mean troop size are higher than those reported for the species in Guatemala and in central Quintana Roo, Mexico. The vegetation of the forest contains tree species reported to be used by species of Alouatta in the Moraceae, Sapotaceae, Leguminosae, and Lauraceae plant families. Protection of a large perimeter area (ca 1700 ha) around the archeological site by the Mexican government ensures the conservation of the forest and of the black howler monkey population present at the site.

Alouatta↗
PubMed1997

Factors affecting mortality of crossbred and exotic chickens kept under backyard systems in Yucatan, Mexico.

Chicken mortality was studied in 24 randomly selected smallholder flocks in one village in Yucatan, Mexico between July and December 1993. Each family received a package of 10 to 12 chicks of 3 weeks of age. Approximately half of the chicks were purebred and the remainder were crosses produced by mating exotic with local breeds. All smallholders were visited twice a week. Feeding and management (except vaccination and medication) were left to smallholders. Data were processed by Chi-square, Mantel-Haenzel test and survival analysis. Before reaching 140 days of age 43.2% of the birds died. The highest mortality was observed during the 113 to 140 days of age period and the lowest was in the period between 22 and 56 days of age. Of all birds, 10.5% died from coccidiosis and 7.6% from Marek's disease. Of the risk factors investigated only medication and genotype showed significant effects on mortality. The effect of genotype was significant up to 112 days of age (P < 0.05). Crossbred birds lived longer than purebred; independently, medicated birds lived longer than non-medicated birds.

Animal Husbandry↗
PubMed1997

Heritability and factors affecting growth traits and age at first calving of zebu beef heifers in south-eastern Mexico.

Information for this study was obtained from a commercial beef enterprise located in the subhumid tropics of Yucatan, Mexico. Data from 664 females of different zebu breeds born from 1972 to 1983 were considered for analyses. Weaning and 18-month weights were adjusted to 240 (W240) and to 550 (W550) days of age, respectively. The statistical model included the fixed effects of years of birth, season of birth, age of dam at calving, breed of heifer and the random effect of sire within breed. Arithmetic mean +/- standard deviations were 32.1 +/- 3.6 kg, 208.3 +/- 29.1 kg, 678.1 +/- 94.6 g, 308.7 +/- 29.7 kg, 342.3 +/- 89.8 g and 1,060.2 +/- 118.7 days for birth weight (BW), W240, average preweaning daily gain (ADG), W550 postweaning daily gain (PDG) and age at first calving (AFC), respectively. Year and season of birth had significant (P < 0.05) effects on W240, ADG, W550, PDG and AFC. Parity number was significant (P < 0.05) for BW, W240, ADG and AFC. Breed differences were significant (P < 0.01) for all traits, except BW. Guzerat heifers were heavier at weaning and W550 than heifers from the other breeds. Guzerat heifers first calved at an average age of 995 days; Brahman and commercial zebu heifers calved about 50 to 60 days later and the Indubrazil and Gyr heifers about 2 months later still. The heritability estimates were 0.24 +/- 0.13 for BW, 0.26 +/- 0.14 for W240, 0.29 +/- 0.14 for ADG, 0.43 +/- 0.17 for W550, 0.56 +/- 0.20 for PDG and 0.46 +/- 0.15 for AFC.

Aging↗
PubMed2002

Carbonyls in the metropolitan area of Mexico City: calculation of the total photolytic rate constants Kp(s(-1)) and photolytic lifetime (tau) of ambient formaldehyde and acetaldehyde.

A great number of studies on the ambient levels of formaldehyde and other carbonyls in the urban rural and maritime atmospheres have been published because of their chemical and toxicological characteristics, and adverse health effects. Due to their toxicological effects, it was considered necessary to measure these compounds at different sites in the metropolitan area of Mexico City, and to calculate the total rate of photolytic constants and the photolytic lifetime of formaldehyde and acetaldehyde. Four sites were chosen. Sampling was carried out at different seasons and atmospheric conditions. The results indicated that formaldehyde was the most abundant carbonyl, followed by acetone and acetaldehyde. Data sets obtained from the 4 sites were chosen to calculate the total rate of photolysis and the photolytic lifetime for formaldehyde and acetaldehyde. Maximum photolytic rate values were obtained at the maximum actinic fluxes, as was to be expected.

Acetaldehyde↗
PubMed1999

Mercury distribution in blood, tissues, and feathers of double-crested cormorant nestlings from arid-lands reservoirs in south central New Mexico.

Eggs, blood, liver, muscle, and feathers were analyzed for concentrations of total mercury in double-crested cormorant (Phalacrocorax auritus) nestlings from two reservoirs in south central New Mexico. Total mercury concentrations among eggs, tissues, and feathers were not significantly correlated. Concentrations of total mercury averaged 0.40 microg/g in liver and 0.18 microg/g in muscle tissues in both populations of nestlings. There were no significant changes in concentrations of total mercury in whole blood of nestlings collected 7-10 days and 17-22 days posthatch in Caballo Reservoir (0.36 microg/g and 0.39 microg/g, respectively) and in Elephant Butte Reservoir (0.36 microg/g and 0.34 microg/g, respectively). Total mercury concentrations were similar for blood, muscle, and liver in nestlings for both reservoirs. Total mercury concentrations were higher in eggs and tail, primary, and secondary feathers from nestlings at Caballo Reservoir compared to Elephant Butte Reservoir. Although there were no differences in concentrations of total mercury in fishes between the two reservoirs, bioaccumulation and biomagnification was evident in planktivorous and piscivorous fishes. The data demonstrate that feather analysis may not be a good predictor of tissue burden in nestlings from regions of low contamination.

Animals↗
PubMed2006

Primary colonization and breakdown of igneous rocks by endemic, succulent elephant trees (Pachycormus discolor) of the deserts in Baja California, Mexico.

Trees growing in rocks without soil are uncommon. In two arid regions in Baja California, Mexico, field surveys found large numbers of rock-colonizing elephant trees (Pachycormus discolor (Benth.) Coville ex Standl. (Mexican name: copalquin) growing in igneous rocks (granite and basalt) as primary colonizers without the benefit of soil or with a very small amount of soil generated by their own growth. Many adult trees broke large granite boulders and were capable of wedging, growing in, and colonizing rocks and cliffs made of ancient lava flows. This is the first record of a tree species, apart from the previously recorded cacti, capable of primary colonization of rocks and rock rubble in hot deserts.

Acclimatization↗
PubMed2004

Pollination between maize and teosinte: an important determinant of gene flow in Mexico.

Gene flow between maize [Zea mays (L.)] and its wild relatives does occur, but at very low frequencies. Experiments were undertaken in Tapachula, Nayarit, Mexico to investigate gene flow between a hybrid maize, landraces of maize and teosinte (Z. mays ssp. mexicana, races Chalco and Central Plateau). Hybridization, flowering synchrony, pollen size and longevity, silk elongation rates, silk and trichome lengths and tassel diameter and morphology were measured. Hybrid and open-pollinated maize ears produced a mean of 8 and 11 seeds per ear, respectively, when hand-pollinated with teosinte pollen, which is approximately 1-2% of the ovules normally produced on a hybrid maize ear. Teosinte ears produced a mean of 0.2-0.3 seeds per ear when pollinated with maize pollen, which is more than one-fold fewer seeds than produced on a maize ear pollinated with teosinte pollen. The pollination rate on a per plant basis was similar in the context of a maize plant with 400-500 seeds and a teosinte plant with 30-40 inflorescences and 9-12 fruitcases per inflorescence. A number of other factors also influenced gene-flow direction: (1) between 90% and 95% of the fruitcases produced on teosinte that was fertilized by maize pollen were sterile; (2) teosinte collections were made in an area where incompatibility systems that limit fertilization are present; (3) silk longevity was much shorter for teosinte than for maize (approx. 4 days vs. approx. 11 days); (4) teosinte produced more pollen on a per plant basis than the landraces and commercial hybrid maize; (5) teosinte frequently produced lateral branches with silks close to a terminal tassel producing pollen. Collectively these factors tend to favor crossing in the direction of teosinte to maize. Our results support the hypothesis that gene flow and the subsequent introgression of maize genes into teosinte populations most probably results from crosses where teosinte first pollinates maize. The resultant hybrids then backcross with teosinte to introgress the maize genes into the teosinte genome. This approach would slow introgression and may help explain why teosinte continues to co-exist as a separate entity even though it normally grows in the vicinity of much larger populations of maize.

Breeding↗
PubMed1997

Total immunoreactive proinsulin, immunoreactive insulin and specific insulin in relation to conversion to NIDDM: the Mexico City Diabetes Study.

Although insulin resistance and decreased insulin secretion are characteristic of established non-insulin-dependent diabetes mellitus (NIDDM), which of these metabolic abnormalities is the primary determinant of NIDDM is still controversial. A disproportionate increase in the proinsulin to insulin ratio has been proposed as a marker of compromised insulin secretion. We examined the association of fasting immunoreactive insulin (which cross-reacts with proinsulin), specific insulin (which does not cross-react with proinsulin), total immunoreactive proinsulin (or insulin precursors), and the fasting proinsulin/specific insulin ratio to the risk of developing NIDDM in the 3.25-year follow-up of the Mexico City Diabetes Study. These measurements were made in 85 subjects who subsequently converted to NIDDM (prediabetic subjects) and in 85 age and gender matched subjects who remained non-diabetic at follow-up (control subjects). Immunoreactive insulin, proinsulin and the proinsulin/specific insulin ratio were significantly higher in prediabetic than in control subjects. However, the relation between specific insulin and the development of NIDDM was weaker than for proinsulin or immunoreactive insulin. After further adjustment for obesity, body fat distribution and glucose tolerance status, proinsulin and the proinsulin/specific insulin ratio, but not specific or immunoreactive insulin, predicted conversion to NIDDM. A high proinsulin/specific insulin ratio predicted conversion to NIDDM both in subjects with normal and those with impaired glucose tolerance at baseline. We conclude that in prediabetic subjects increased proinsulin, a marker of islet cell distress or compromised insulin secretion, is associated with rapid conversion (within 3.25 years) to NIDDM even in obese populations.

Adult↗
PubMed2006

Diverse endophytic bacteria isolated from a leguminous tree Conzattia multiflora grown in Mexico.

Conzattia multiflora is a leguminous tree present only in Mexico and Guatemala. There is no record about its symbiotic or pathogenic microbes. In this study, we found that numerous bacteria with 10(4)-10(6) individuals per gram of fresh epidermis were distributed in the tissue of this plant. All the bacteria isolated from the Conzattia epidermis were Gram-negative, facultative anaerobic rods and formed yellow or colorless colonies. They were identified as endophytes by inoculation tests. Some of the bacteria could significantly promote the growth of Conzattia seedlings. Nine different groups were defined by PCR-based RFLP, which were classified as Pantoea, Erwinia, Salmonella, Enterobacter, Citrobacter and Klebsiella by the phylogenetic analysis of 16S rRNA genes. The existence of plant-borne lineages of Salmonella indicates that the unexplored plants may harbor some unknown microbes.

Acetylene↗
PubMed1999

Altered activity of heme biosynthesis pathway enzymes in individuals chronically exposed to arsenic in Mexico.

Our objective was to evaluate the activities of some enzymes of the heme biosynthesis pathway and their relationship with the profile of urinary porphyrin excretion in individuals exposed chronically to arsenic (As) via drinking water in Region Lagunera, Mexico. We selected 17 individuals from each village studied: Benito Juarez, which has current exposure to 0.3 mg As/l; Santa Ana, where individuals have been exposed for more than 35 years to 0.4 mg As/l, but due to changes in the water supply (in 1992) exposure was reduced to its current level (0.1 mg As/l), and Nazareno, with 0.014 mg As/l. Average arsenic concentrations in urine were 2058, 398, and 88 microg As/g creatinine, respectively. The more evident alterations in heme metabolism observed in the highly exposed individuals were: (1) small but significant increases in porphobilinogen deaminase (PBG-D) and uroporphyrinogen decarboxylase (URO-D) activities in peripheral blood erythrocytes; (2) increases in the urinary excretion of total porphyrins, mainly due to coproporphyrin III (COPROIII) and uroporphyrin III (UROIII); and (3) increases in the COPRO/URO and COPROIII/COPROI ratios. No significant changes were observed in uroporphyrinogen III synthetase (UROIII-S) activity. The direct relationships between enzyme activities and urinary porphyrins, suggest that the increased porphyrin excretion was related to PBG-D, whereas the increased URO-D activity would enhance coproporphyrin synthesis and excretion at the expense of uroporphyrin. None of the human studies available have reported the marked porphyric response and enzyme inhibition observed in rodents. In conclusion, chronic As exposure alters human heme metabolism; however the severity of the effects appears to depend on characteristics of exposure not yet fully characterized.

Arsenic↗