Tactile acuity of fingertips and hand representation size in human Area 3b and Area 1 of the primary somatosensory cortex.

Intracortical mapping in monkeys revealed a full body map in all four cytoarchitectonic subdivisions of the contralateral primary somatosensory cortex (S1), as well as positive associations between spatio-tactile acuity performance of the fingers and their representation field size especially within cytoarchitectonic Area 3b and Area 1. Previous non-invasive investigations on these associations in humans assumed a monotonous decrease of representation field size from index finger to little finger although the field sizes are known to change in response to training or in disease. Recent developments improved noninvasive functional mapping of S1 by a) adding a cognitive task during repetitive stimulation to decrease habituation to the stimuli, b) smaller voxel size of fMRI-sequences, c) surface-based analysis accounting for cortical curvature, and d) increase of spatial specificity for fMRI data analysis by avoidance of smoothing, partial volume effects, and pial vein signals. We here applied repetitive pneumatic stimulation of digit 1 (D1; thumb) and digit 5 (D5; little finger) on both hands to investigate finger/hand representation maps in the complete S1, but also in cytoarchitectonic Areas 1, 2, 3a, and 3b separately, in 21 healthy volunteers using 3T fMRI. The distances between activation maxima of D1 and D5 were evaluated by two independent raters, blinded for performance parameters. The fingertip representations showed a somatotopy and were localized in the transition region between the crown and the anterior wall of the post central gyrus agreeing with Area 1 and 3b. Participants were comprehensively tested for tactile performance using von Freyhair filaments to determine cutaneous sensory thresholds (CST) as well as grating orientation thresholds (GOT) and two-point resolution (TPD) for spatio-tactile acuity testing. Motor performance was evaluated with pinch grip performance (Roeder test). We found bilateral associations of D1-D5 distance for GOT thresholds and partially also for TPD in Area 3b and in Area 1, but not if using the complete S1 mask. In conclusion, we here demonstrate that 3T fMRI is capable to map associations between spatio-tactile acuity and the fingertip representation in Area 3b and Area 1 in healthy participants.

Point mutation in an AMPA receptor gene rescues lethality in mice deficient in the RNA-editing enzyme ADAR2.

RNA editing by site-selective deamination of adenosine to inosine alters codons and splicing in nuclear transcripts, and therefore protein function. ADAR2 (refs 7, 8) is a candidate mammalian editing enzyme that is widely expressed in brain and other tissues, but its RNA substrates are unknown. Here we have studied ADAR2-mediated RNA editing by generating mice that are homozygous for a targeted functional null allele. Editing in ADAR2-/- mice was substantially reduced at most of 25 positions in diverse transcripts; the mutant mice became prone to seizures and died young. The impaired phenotype appeared to result entirely from a single underedited position, as it reverted to normal when both alleles for the underedited transcript were substituted with alleles encoding the edited version exonically. The critical position specifies an ion channel determinant, the Q/R site, in AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate) receptor GluR-B pre-messenger RNA. We conclude that this transcript is the physiologically most important substrate of ADAR2.

The effects of prenatal care utilization and maternal risk factors on pregnancy outcome between Mexican Americans and non-Hispanic whites.

This study evaluates the effects of prenatal care classification and levels of maternal risk status on pregnancy outcomes in Mexican Americans and non-Hispanic whites in Arizona. All live birth certificates from 1986 and 1987 were reviewed yielding a total population of 101,206 (26,827 Mexican Americans). The adequacy of prenatal care was evaluated based on an index that includes six prenatal care groups. Two levels of maternal risk status (low and high) were defined based on a series of maternal risk factors. Overall, Mexican Americans had a greater proportion of maternal risk factors and a greater proportion of mothers with inadequate or no prenatal care compared with non-Hispanic whites. Prematurity and macrosomia were more prevalent than low birthweight in Mexican Americans. Low-risk status and adequate prenatal care regardless of ethnicity were found to be associated with a lower prevalence of low birthweight and preterm delivery. Whites, however, had a greater variation in the prevalence of low birthweight associated with changes in prenatal care utilization and maternal risk status compared with Mexican Americans. Finally, logistic regression analysis showed an independent effect of prenatal care, maternal risk status, maternal age, and maternal birthplace in predicting the overall low birthweight rate in Mexican Americans. The implications of these results are discussed relative to the usefulness of prenatal care as a health-care intervention in Mexican Americans.

Mexican-Americans' use of prenatal care and its relationship to maternal risk factors and pregnancy outcome.

We evaluate the adequacy of prenatal care use and the association of use to a series of maternal risk factors and pregnancy outcomes, such as low birthweight, preterm delivery, and macrosomia in both Mexican-Americans and non-Hispanic whites in Arizona. The data came from all live-birth certificates from 1986 and 1987 for a total of 101,202 (26,826 Mexican-Americans). We evaluated the adequacy of prenatal care using a redesigned index that accounts for three factors: the month when prenatal care began, the number of prenatal care visits, and the duration of pregnancy. From this index we identified six prenatal care groups: intensive, adequate, intermediate, inadequate, no-care, and missing/unknown. Overall, we observed ethnic differences in patterns of prenatal care use, social profiles, and medical risk factors. Non-Hispanic whites, compared to Mexican-Americans, showed a greater risk for low birthweight and preterm delivery in those groups receiving poor prenatal care versus those who received adequate care. Within Mexican-Americans the risk of low birthweight was not the same for all subgroups. A higher overall prevalence of preterm delivery and macrosomia in comparison to low birthweight occurred in Mexican-Americans. We discuss the implications of the results for the identification, interpretation, evaluation, and public health significance of perinatal health problems of Mexican-Americans.

Breast-feeding policies and routines among Arizona hospitals and nursery staff: results and implications of a descriptive study.

In 1988, Arizona's 61 hospitals providing obstetrical services were canvased with regard to hospital routines that favor either breast-feeding or bottle-feeding. Forty-five hospitals provided responses that were used in the survey. Practices favoring breast-feeding, which were reported by a majority of the hospitals (more than 50%), were demand feeding, staff assessment for "latch-on" (the action of nipple presentation and sucking initiation) and positioning, "rooming-in" (the practice of minimal mother-infant separation), and information about follow-up support services. Hospital practices suggested to promote bottle-feeding were the provision of pacifiers and supplemental water or glucose, issuance of formula packs at discharge, and a first feed of sterile water. A positive significant relationship was identified for policies advocating breast-feeding and the prevalence of breast-feeding encouragement from professional staff. Of 44 respondents, 41 indicated that their hospital's policies endorse breast-feeding as the ideal method of feeding healthy newborns. Hospital staff perceived that they encourage mothers to breast-feed and offer support to those who initiate breast-feeding. On the basis of this information, we conclude that dietetics practitioners should evaluate current breast-feeding practices and integrate policies supportive of breast-feeding into the health care system.

Lower-extremity amputations in NIDDM. 12-yr follow-up study in Pima Indians.

The incidence of lower-extremity amputations was estimated in the Pima Indians of the Gila River Indian Community in Arizona, a population with a high prevalence of non-insulin-dependent diabetes mellitus (NIDDM). Between 1972 and 1984, from a study population of 4399 subjects, lower-extremity amputations were performed on 84 patients, 80 (95%) of whom had NIDDM. Among diabetic subjects, the incidence rate of first lower-extremity amputations was higher in men than in women. Rates increased significantly with increasing duration of diabetes. Presence of medial arterial calcification, retinopathy, or nephropathy; absence of patellar tendon reflexes; impaired great toe vibration-perception threshold; and degree of fasting and 2-h postload hyperglycemia were significant risk factors for amputations. Serum cholesterol concentration, blood pressure, age, and absence of Achilles tendon reflexes were not predictive of amputations. The death rate was greater in diabetic amputees than in diabetic nonamputees of similar age, sex, and duration of diabetes, and a significant increase in cardiovascular deaths was observed in diabetic subjects with amputations. The incidence rate of lower-extremity amputations in diabetic Pima Indians is higher than that reported in other diabetic populations. This may reflect differences in risk or a more complete case ascertainment than was possible in previous studies. If the latter is true, the rate of amputations in diabetic individuals may be higher than has been previously appreciated.

Stability of carmustine in the presence of sodium bicarbonate.

The stability of carmustine in 5% dextrose injection and 0.9% sodium chloride injection, with and without added sodium bicarbonate, was studied at room temperature. Solutions of carmustine (0.1 mg/ml) in dextrose or saline with and without added sodium bicarbonate (1 meq/ml) were prepared. After 0, 15, 30, 60, and 90 minutes, aliquots of each test solution were analyzed for carmustine using the Bratton-Marshall test with absorbance at 540 nm. There was no significant decomposition of carmustine in dextrose or saline alone. However, the addition of sodium bicarbonate increased carmustine degradation; after 90 minutes, approximately 73% of the active drug remained. It is recommended that carmustine be neither admixed with nor administered piggyback with parenteral infusion solutions containing sodium bicarbonate.