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Biomedical subjects

J M Diamond

Publications and source records attributed to J M Diamond.

At least 19 recordsLinked to original sources
PubMed2001

Identifying sources of stress to native aquatic fauna using a watershed ecological risk assessment framework.

The free-flowing Clinch and Powell River Basin, located in southwestern Virginia, United States, historically had one of the richest assemblages of native fish and freshwater mussels in the world. Nearly half of the species once residing here are now extinct, threatened, or endangered. The United States Environmental Protection Agency's framework for conducting an ecological risk assessment was used to structure a watershed-scale analysis of human land use, in-stream habitat quality, and their relationship to native fish and mussel populations in order to develop future management strategies and prioritize areas in need of enhanced protection. Our analyses indicate that agricultural and urban land uses as well as proximity to mining activities and transportation corridors are inversely related to fish index of biotic integrity (IBI) and mussel species diversity. Forward stepwise multiple regression analyses indicated that coal mining had the most impact on fish IBI followed by percent cropland and urban area in the riparian corridor (R2 = 0.55, p = 0.02); however, these analyses suggest that other site-specific factors are important. Habitat quality measures accounted for as much as approximately half of the variability in fish IBI values if the analysis was limited to sites within a relatively narrow elevation range. These results, in addition to other data collected in this watershed, suggest that nonhabitat-related stressors (e.g., accidental chemical spills) also have significant effects on biota in this basin. The number of co-occurring human land uses was inversely related to fish IBI (r = -0.49, p < 0.01). Sites with > or = 2 co-occurring land uses had >90% probability of having <2 mussel species present. Our findings predict that many mussel concentration sites are vulnerable to future extirpation. In addition, our results suggest that protection and enhancement of naturally vegetated riparian corridors, better controls of mine effluents and urban runoff, and increased safeguards against accidental chemical spills, as well as reintroduction or augmentation of threatened and endangered species, may help sustain native fish and mussel populations in this watershed.

Agriculture↗
PubMed2001

Thermodynamics of three-way multibranch loops in RNA.

RNA multibranch loops (junctions) are loops from which three or more helices exit. They are nearly ubiquitous in RNA secondary structures determined by comparative sequence analysis. In this study, systems in which two strands combine to form three-way junctions were used to measure the stabilities of RNA multibranch loops by UV optical melting and isothermal titration calorimetry (ITC). These data were used to calculate the free energy increment for initiation of a three-way junction on the basis of a nearest neighbor model for secondary structure stability. Imino proton NMR spectra were also measured for two systems and are consistent with the hypothesized helical structures. Incorporation of the experimental data into the mfold and RNA structure computer programs has contributed to an improvement in prediction of RNA secondary structure from sequence.

Bacteriophage T7↗
PubMed2001

Delayed disaccharidase development in a rabbit model of intrauterine growth retardation.

Intrauterine growth retardation (IUGR) affects almost 10% of infants born in the United States. It may be responsible for delayed gastrointestinal function and is an important cause of perinatal morbidity and mortality. The New Zealand White rabbit provides an optimal model for the study of naturally occurring IUGR. At term, birth weight is determined by fetal position within the bicornuate uterus. The small intestinal disaccharidase enzymes are indicators of bowel maturity and function. To examine potential differences in disaccharidase development between normal and IUGR fetuses, this rabbit model was investigated. Jejunum was harvested at multiple stages in rabbit development including the third trimester fetus, neonate, and adult. Lactase, maltase, and sucrase enzyme activity, as well as total protein content, was determined. Results were analyzed by the 2-tailed t test and ANOVA. Lactase activity appeared in the mid-third trimester, peaked in the early neonatal period, then declined to adult levels. Maltase activity appeared in the early third trimester and gradually rose to adult levels. Sucrase remained at trace levels until the mid-neonatal period, reaching adult levels by weaning. Both lactase and maltase activity were depressed in IUGR fetuses compared with their normal littermates. This pattern of disaccharidase depression continued into the neonatal period until catch-up growth occurred at 2 wk when levels equalized. This report describes differential small intestinal disaccharidase development between normal and growth-retarded rabbit fetuses in a naturally occurring model of IUGR.

Animals↗
PubMed1997

A new self-report scale for assessment of adolescent psychopathology: factor structure, reliability, validity, and diagnostic sensitivity.

This paper describes four studies on self-reported problems in 2,243 adolescent males and females, 12 to 17 years of age. In Study 1, principal-axis factoring of 102 items covering 11 problem domains revealed six factors comprising 49.5% of the variance. Study 2 used confirmatory factor analysis of a 64-item reduced set on a new sample of 408 adolescents. Goodness-of-fit indicators suggested that the six-factor model had excellent fit to the data. Study 3 used data from the 2,157 adolescents used in the first two studies. Coefficient alphas ranged from .83 to .92. Median test-retest reliability for the six factors was .86. There was a consistent structure of the correlation matrix across age and gender. Study 4 was a study of criterion validity, using an additional sample of 86 children with attention-deficit hyperactivity disorder (ADHD). Sensitivity and specificity were high, with an overall diagnostic efficiency of 83%. This new self-report scale, the Conners/Wells Adolescent Self-Report of Symptoms (CASS), may provide a useful component of a multimodal assessment of adolescent psychopathology.

Adolescent↗
PubMed1997

ADHD and EEG.

Explore the source record for details and available documents.

Arousal↗
PubMed1994

Impairment of nutrient uptake in a rabbit model of gastroschisis.

Infants with gastroschisis (GS) commonly require total parenteral nutrition and prolonged hospitalization because of intestinal dysfunction resulting from dysmotility and/or malabsorption. To investigate prepartum small intestinal (SI) nutrient absorption in GS, a fetal rabbit model was surgically created on gestational day 24 (term, 31 to 33 days) in 11 time-mated New Zealand White does in each left ovarian-end fetus. Each right ovarian-end fetus served as a control (C) and was manipulated only. All does, 10 of 11 GS fetuses (91%), and 8 of 11 C fetuses (73%) survived to gestational day 30. GS fetuses had significantly reduced total body weights, SI weights, and SI lengths compared with C fetuses. Using the everted mucosal sleeve technique, the uptakes of an amino acid (proline) and a sugar (glucose) were determined. The uptakes of proline per milligram SI, proline per centimeter SI, and glucose per milligram SI were significantly impaired in GS fetuses compared with C fetuses (P < .04 by Student's paired t test). The uptake of glucose per centimeter SI was also reduced in GS fetuses, but not significantly. Uptake capacities (a measure of the entire SI's ability to absorb a given nutrient) were significantly reduced in GS fetuses compared with C fetuses (proline, 2,670 +/- 612 nmol/min/entire SI v 6,842 +/- 399 nmol/min/entire SI, P < .008 by Student's paired t test; glucose, 402 +/- 69 nmol/min/entire SI v 950 +/- 103, P < .008 by Student's paired t test).

Abdominal Muscles↗
PubMed1993

Crypt/villus site of substrate-dependent regulation of mouse intestinal glucose transporters.

The intestinal epithelium is in a constant state of turnover, with cells differentiating at the crypts and then migrating toward the tips of the villi. Does substrate-dependent regulation of intestinal Na+/D-glucose cotransporters occur only in crypt cells, or can transport activity be subsequently reprogrammed in mature enterocytes? We used in situ, glucose-protectable specific phlorizin binding to determine site density of brush border glucose transporters in enterocytes fractionated along the crypt/villus axis of mice that were killed shortly after drastic changes in carbohydrate levels of their diets. Dietary carbohydrate-induced changes in site density of specific phlorizin binding initially appeared only in crypt cells before spreading, over the course of several days, to the villus tips. Thus, only crypt cells perceive the signal for glucose transporter regulation, and the observed time lag of diet-induced changes in intestinal glucose uptake is due mainly to cell migration times.

Alkaline Phosphatase↗
PubMed1993

Effect of esophageal ligation on the development of fetal rabbit intestinal lactase.

To investigate the effect of normal fetal swallowing and amniotic fluid ingestion on small intestinal disaccharidase development, 13 pregnant New Zealand White rabbits underwent operation on day 24 of a normal 31-day gestation. The right ovarian fetus in the bicornuate uterus underwent esophageal ligation (EL), while the contralateral left fetus underwent cervical exploration only, and served as the control (C). Rabbits were sacrificed on gestational day 31, fetal somatic measurements obtained, and the midjejunum removed for determination of disaccharidase activity and protein content. There was one maternal death, and 9 of 12 fetal pairs survived the entire study period (75%). Results are reported as mean +/- SEM, analyzed by two-tailed Student's t testing with P < .05 being considered significant. Fetal weight was decreased in EL (48.6 +/- 2.7 g) versus C (51.4 +/- 3.2 g) (P = .06). Small intestinal length decreased in EL (49.2 +/- 2.0 cm) versus C (54.9 +/- 1.1 cm) (P = .01). Midjejunal protein content (mg/mL homogenate) was also significantly decreased in EL (38.4 +/- 3.4) versus C (46.2 +/- 3.7) (P = .05). Sucrase activity was not detectable in either group. Lactase activity in jejunal mucosa was not effected when expressed as units of enzyme per milliliter of homogenate (EL = 0.357 +/- 0.03 v C = 0.373 +/- 0.04; P = .70) and units enzyme per gram of protein (EL = 38.8 +/- 4.2 v C = 34.2 +/- 4.6; P = .44). We have confirmed previous studies demonstrating decreases in somatic growth, small intestinal length, and mucosal nutrient transport in rabbit fetuses following esophageal ligation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniotic Fluid↗
PubMed1993

Effect of transamniotic administration of epidermal growth factor on fetal rabbit small intestinal nutrient transport and disaccharidase development.

As fetal swallowing is documented in utero, supplementation of the ingested amniotic fluid with nutrients or hormones has been postulated as a potential prenatal treatment for intrauterine growth retardation (IUGR). To study the effect of epidermal growth factor (EGF) on the developing fetal small intestine, 12 pregnant rabbits underwent operation on day 24 of a normal 31-day gestation. Bilateral ovarian end fetuses underwent catheterization of their respective amniotic cavities with attachment to a miniosmotic pump. Study fetuses received recombinant human EGF at approximately 300 micrograms/kg/d for 1 week; controls received carrier solution only at an equivalent rate. On gestational day 31, fetuses were delivered by cesarean section and somatic measurements were recorded. The small intestine was harvested and proximal, middle, and distal regions were analyzed for lactase and maltase enzyme activity. Additionally, the uptake of radiolabeled glucose and proline was measured by a standard everted mucosal sleeve technique for each segment. Results were analyzed by Student's paired t test and reported as mean +/- SEM. Nine fetal pairs survived (75%). Small intestinal (SI) length was increased in EGF fetuses (54.8 +/- 1.9 cm) versus control (50.4 +/- 2.7 cm) (P = .02). Lactase activity, reported as UE/g protein, was significantly increased in the proximal segments in the EGF-infused fetuses; maltase was significantly increased in both the proximal and middle segments (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Amnion↗