Linking breeding and wintering ranges of a migratory songbird using stable isotopes.

We used the natural abundance of stable isotopes (carbon and hydrogen) in the feathers of a neotropical migrant songbird to determine where birds from particular breeding areas spend the winter and the extent to which breeding populations mix in winter quarters. We show that most birds wintering on western Caribbean islands come from the northern portion of the species' North American breeding range, whereas those on more easterly islands are primarily from southern breeding areas. Although segregated by breeding latitude, birds within local wintering areas derive from a wide range of breeding longitudes, indicating considerable population mixing with respect to breeding longitude. These results are useful for assessing the effects of wintering habitat loss on breeding population abundances and for predicting whether the demographic consequences will be concentrated or diffuse.

Multiscale assessment of patterns of avian species richness.

The search for a common cause of species richness gradients has spawned more than 100 explanatory hypotheses in just the past two decades. Despite recent conceptual advances, further refinement of the most plausible models has been stifled by the difficulty of compiling high-resolution databases at continental scales. We used a database of the geographic ranges of 2,869 species of birds breeding in South America (nearly a third of the world's living avian species) to explore the influence of climate, quadrat area, ecosystem diversity, and topography on species richness gradients at 10 spatial scales (quadrat area, approximately 12,300 to approximately 1,225,000 km(2)). Topography, precipitation, topography x latitude, ecosystem diversity, and cloud cover emerged as the most important predictors of regional variability of species richness in regression models incorporating 16 independent variables, although ranking of variables depended on spatial scale. Direct measures of ambient energy such as mean and maximum temperature were of ancillary importance. Species richness values for 1 degrees x 1 degrees latitude-longitude quadrats in the Andes (peaking at 845 species) were approximately 30-250% greater than those recorded at equivalent latitudes in the central Amazon basin. These findings reflect the extraordinary abundance of species associated with humid montane regions at equatorial latitudes and the importance of orography in avian speciation. In a broader context, our data reinforce the hypothesis that terrestrial species richness from the equator to the poles is ultimately governed by a synergism between climate and coarse-scale topographic heterogeneity.

Detection of macro-ecological patterns in South American hummingbirds is affected by spatial scale.

Scale is widely recognized as a fundamental conceptual problem in biology, but the question of whether species-richness patterns vary with scale is often ignored in macro-ecological analyses, despite the increasing application of such data in international conservation programmes. We tested for scaling effects in species-richness gradients with spatially scaled data for 241 species of South American hummingbirds (Trochilidae). Analyses revealed that scale matters above and beyond the effect of quadrat area. Species richness was positively correlated with latitude and topographical relief at ten different spatial scales spanning two orders of magnitude (ca. 12,300 to ca. 1,225,000 km2). Surprisingly, when the influence of topography was removed, the conditional variation in species richness explained by latitude fell precipitously to insignificance at coarser spatial scales. The perception of macro-ecological pattern thus depends directly upon the scale of analysis. Although our results suggest there is no single correct scale for macro-ecological analyses, the averaging effect of quadrat sampling at coarser geographical scales obscures the fine structure of species-richness gradients and localized richness peaks, decreasing the power of statistical tests to discriminate the causal agents of regional richness gradients. Ideally, the scale of analysis should be varied systematically to provide the optimal resolution of macro-ecological pattern.

Role of postnatal penicillin prophylaxis in prevention of neonatal group B streptococcus infection.

This prospective study was designed to identify the role of postnatal penicillin prophylaxis in the prevention of neonatal group B streptococcus (GBS) infection. We studied 10 998 infants. Of these, 5389 were in the penicillin prophylaxis group (PP) and 5609 infants did not receive penicillin prophylaxis (NPP). Infants were allocated to treatment by month of birth, alternating 3-mo blocks or 2-mo blocks to the two groups after the first block was randomly assigned. The use of PP reduced the incidence of clinical sepsis (1.7% PP versus 2.5% NPP, p < 0.01), GBS infection (0.4% PP versus 0.9% NPP, p < 0.001) and deaths from sepsis (0.1% PP versus 0.3% NPP, p < 0.05). We conclude that the routine use of postnatal penicillin prophylaxis appears to be effective in reducing the incidence of clinical sepsis and death from sepsis in neonates.

Long-term outcome of infants at the margin of viability.

The outcome of babies at extremely short gestational age (22 to 26 weeks) effects our clinical decisions regarding their care. We looked at survival and presence of disability at 25 +/- 11 months of age in 246 of these infants born at our hospital between 1992 and 1996 who were average weight for gestational age. Babies were evaluated in our follow up clinic by a pediatrician, and a physical therapist for cerebral palsy, blindness and deafness, and by a psychologist with the Bayley II. Chances for survival without disability exceeded 50% of live born infants at 25 weeks gestation or a birth weight of 700 to 800 grams. Chances for survival exceeded 50% of live born infants at 24 weeks gestation or a birth weight of 600 to 700 grams. Chances for intact survival reached 50% of survivors at 23 weeks gestation or a birth weight of 400 to 500 grams.

Immunogenicity of hepatitis B vaccine in healthy very low birth weight infants.

We studied the immunogenic response to hepatitis B vaccine of infants weighing < or = 1500 gm at birth. Infants were divided into two groups: those weighing < or = 1000 gm (n = 22) and those weighing 1001 to 1501 gm (n = 28). When immunized early (3 days of age, n = 25), these infants had a response rate (defined as antibody to hepatitis B surface antigen titer > 10 mIU/ml) of 68%, whereas when the first vaccine was given at 1 month of age (n = 25), a 96% response rate was noted, irrespective of birth weight and weight at the time of immunization (p < 0.02).

Effect of birth order on incidence of periventricular-intraventricular hemorrhage in very low birth weight twins.

The purpose of the study was to determine whether the incidence of periventricular-intraventricular hemorrhage (PV-IVH) is significantly different between the firstborn and secondborn of very low birth weight twins. The firstborn and secondborn of 102 sets of twins were compared by incidence of PV-IVH, mode of delivery, birth weight, 5-minute Apgar score, pH, duration of oxygen therapy, duration of ventilator support, and occurrence of patent ductus arteriosus, air leak, bronchopulmonary dysplasia, or hyaline membrane disease. PV-IVH was graded by the Papile classification. Statistical data were analyzed by either the paired t test or McNemar's test. Major PV-IVH (grades III and IV) occurred in 11 firstborn and 14 secondborn infants. Minor PV-IVH (grades I and II) occurred in 11 firstborn and 8 secondborn twins. Neither these findings nor those from other measured variables showed a statistically significant difference.

The use of isotope tracers for identifying populations of migratory birds.

To determine whether stable isotopes can be used for identifying the geographic origins of migratory bird populations, we examined the isotopic composition of hydrogen (deuterium, δD), carbon (δ13C), and strontium (δ87Sr) in tissues of a migratory passerine, the black-throated blue warbler (Dendroica caerulescens), throughout its breeding range in eastern North America. δD and δ13C values in feathers, which are grown in the breeding area, varied systematically along a latitudinal gradient, being highest in samples from the southern end of the species' breeding range in Georgia and lowest in southern Canada. In addition, δD decreased from east to west across the northern part of the breeding range, from New Brunswick to Michigan. δ87Sr ratios were highest in the Appalachian Mountains, and decreased towards the west. These patterns are consistent with geographical variation in the isotopic composition of the natural environment, i.e., with that of precipitation, plants, and soils for δD, δ13C, and δ87Sr, respectively. Preliminary analyses of the δD and δ13C composition of feathers collected from warblers in their Caribbean winter grounds indicate that these individuals were mostly from northern breeding populations. Furthermore, variances in isotope ratios in samples from local areas in winter tended to be larger than those in summer, suggesting that individuals from different breeding localities may mix in winter habitats. These isotope markers, therefore, have the potential for locating the breeding origins of migratory species on their winter areas, for quantifying the degree of mixing of breeding populations on migratory and wintering sites, and for documenting other aspects of the population structure migratory animals - information needed for studies of year-round ecology of these species as well as for their conservation. Combining information from several stable isotopes will help to increase the resolution for determining the geographic origins of individuals in such highly vagile populations.

Postnatal penicillin prophylaxis and the incidence of group B streptococcal sepsis in neonates.

We conducted a retrospective chart review of infants, born over a 3-year period, who had positive urine latex agglutination and/or positive blood culture for group B streptococci (GBS). Infants routinely received intramuscular aqueous penicillin for the first half of the study period, and no penicillin was given for the subsequent 18 months. Overall, infants who received penicillin prophylaxis had a decreased incidence of clinical sepsis and positive blood culture for GBS (4.8/1,000 versus 8/1,000 and 1.3/1,000 versus 5.4/1,000, respectively). The incidence of GBS sepsis during the time of penicillin prophylaxis was not different from that in previously reported studies. When analyzed by weight groups, no difference in clinical sepsis or positive blood cultures for GBS was seen in the subset of infants weighing < or = 2,500 g at birth. There were fewer positive blood cultures in the infants who received penicillin and met the criteria for clinical sepsis. Mortality from GBS sepsis was unchanged during these two study periods in all weight groups.

Relationship of cranial midline shift to outcome of very-low-birth-weight infants with periventricular hemorrhagic infarction.

The purpose of this study was to determine the relationship of a cranial midline shift accompanying periventricular hemorrhagic infarction to subsequent handicap in very-low-birth-weight infants. A study group of 44 infants with intraventricular hemorrhage and an associated periventricular hemorrhagic infarction was retrospectively selected from 1,080 very-low-birth-weight infants evaluated by cranial sonography. A cranial midline shift is defined sonographically as displacement of the septum pellucidum (or cavum septi pellucidi) more than 3 mm from the spatial midline. The midline is measured as half the distance between the right and left inner tables on an anterior coronal view. Other sonographic data recorded were the size of the lateral ventricle, the intracranial hemisphere, and the periventricular hemorrhagic infarction. Also noted was the appearance of the area of infarction at the time of initial detection of a midline shift. After discharge, the infants were periodically evaluated for major handicap in vision, hearing, cognition, and motor activity. A midline shift was identified in 29 (66%) of 44 infants with periventricular hemorrhagic infarction. Seven (24%) of the 29 infants with midline shift and 3 (20%) of the 15 infants without a midline shift died. In all of the 22 surviving infants with a midline shift and in 3 (25%) of 12 survivors without a midline shift, a handicap developed (p < 0.01). As a predictor of handicap, midline shift showed a sensitivity of 88% and a specificity of 100%. Predictability was not improved by combining midline shift with the size of the parenchymal infarct.(ABSTRACT TRUNCATED AT 250 WORDS)

Neonatal salvage by week's gestation in pregnancies complicated by HELLP syndrome.

OBJECTIVE: For clinical management and counseling purposes, we determined the neonatal salvage by weeks' gestation and birth weight of pregnancies complicated by HELLP syndrome (hemolysis, elevated liver enzymes, and low platelets). METHODS: All patients who delivered with a diagnosis of HELLP syndrome between January 1, 1980 and December 31, 1991 at a single tertiary care medical center were evaluated for neonatal outcome and survival. The syndrome was diagnosed in the presence of severe preeclampsia/eclampsia accompanied by laboratory evidence of hemolysis, hepatic dysfunction, and thrombocytopenia. RESULTS: During the study interval, 58,670 live-born deliveries occurred, of which 527 (0.11%) had HELLP syndrome. In this population, 143 patients delivered fetuses at less than 30 weeks' gestational age. Based upon gestational age intervals, neonatal salvage was 0% at 23 weeks in 13 deliveries, 17% (intact salvage 8.5%) at 24 weeks, 31% (intact salvage 15%) at 25 weeks, 75% (intact salvage 65%) at 26 weeks, 80% (intact salvage 70%) at 27 weeks, and 83% at 28 and 29 weeks (intact salvage 70 and 76%). Based on birth weight intervals, neonatal salvage was 0% at less than 600 g, 34% at 600-700 g (intact salvage 17%), 69% at 700-800 g (intact salvage 53%), and 84% or more at greater than 800 g. These pregnancy outcomes are similar to those in this institution in patients without HELLP syndrome. Disease severity was distributed evenly among the 143 patients at less than 30 weeks' gestation. Apart from gestational age, there was no significant relation between the severity of the HELLP disease process and ultimate neonatal salvage. CONCLUSIONS: Intact neonatal salvage in pregnancies complicated by HELLP syndrome is poor at weights less than 700 g and gestation of 25 weeks or less, but is more optimistic in pregnancies of greater than 700 g and 26 weeks' gestation or later. Aggressive efforts to enhance perinatal outcome, by operative delivery if indicated for fetal compromise, appear especially appropriate in gestations of greater than 700 g and 26 weeks' gestation or later, provided that adequate intensive care nursery facilities and neonatal expertise are available.

Neonatal fungemia and amphotericin B.

Disseminated candidemia is a common nosocomial infection in the neonatal intensive care unit, though only a few studies have reported the outcome of amphotericin B therapy in neonatal candidiasis. Our treatment regimen consisted of an initial daily amphotericin B dose of 0.5 mg/kg. (For infants weighing > 1 kg, the second dose was increased to 1 mg/kg.) At 3 to 5 days, if the blood culture was negative, amphotericin B therapy was changed to every other day and continued for a total of 10 doses. Records of 36 patients given this regimen were reviewed for signs of toxicity or treatment failure. The mean birth weight was 988 +/- 510 g, and the gestational age was 28 +/- 3.9 weeks. The patients were ventilated for 13 +/- 15 days and had central lines for 6.7 +/- 9.3 days before development of candidemia. The mean age at onset of candidemia was 29.1 +/- 19.8 days. The interval from culture to treatment was 2.9 days. Six of 36 patients died, 2 of candidal meningitis and 4 of complications unrelated to candidal infection. Thirteen (36%) of the patients had candidal pustules during the course of their disease; 1 had osteomyelitis. There was no evidence of toxicity from this drug regimen and no apparent treatment failures. There were no changes in BUN and creatinine before or during therapy and no change in total urinary output. Blood cultures became sterile except in one patient who died on the first day of therapy. Most of the patients in this study had candidemia in the absence of a central indwelling catheter. Further prospective pharmacokinetic and therapeutic studies are warranted for this regimen of amphotericin B, which carries a low risk for toxicity.

The effect of nalmefene on pulsatile secretion of luteinizing hormone and prolactin in men.

Luteinizing hormone (LH) and prolactin are released in pulses which are relatively synchronous in the luteal phase of the menstrual cycle in women. The concordance of LH and prolactin pulses in normal men has not been reported. The objectives of this study were firstly to determine whether LH and prolactin pulses are synchronous in men, and secondly to examine the effects of naloxone and a new orally active opiate antagonist, nalmefene, on LH and prolactin release in men. Three groups of normal male subjects received saline infusion (control n = 5), naloxone infusion (2 mg/h; n = 5) or nalmefene (10 mg p.o.; n = 6). Blood samples were collected every 15 min for 2 h before and 6 h after study medication for determination of LH, prolactin and testosterone by radioimmunoassay. Both naloxone and nalmefene resulted in a significant increase in LH pulse frequency and in mean serum LH and testosterone concentrations with no change in LH pulse amplitude, prolactin pulse frequency or amplitude. In controls, 61% of LH pulses were synchronous with prolactin pulses. There was a decrease in concomitance of LH and prolactin pulses with naloxone (48%) and nalmefene (24%; P < 0.025) administration. In contrast, 52% of prolactin pulses were concomitant with LH pulses in controls, while naloxone (100%) but not nalmefene (67%) resulted in a significant (P < 0.01) increase in pulse synchrony. The difference observed between naloxone and nalmefene on prolactin--LH pulse synchrony is probably due to differential opioid receptor activity at the pituitary and hypothalamic level.(ABSTRACT TRUNCATED AT 250 WORDS)

Torulopsis glabrata in the neonate: an emerging fungal pathogen.

Fungi are becoming increasingly common nosocomial pathogens in the neonatal intensive care patient. The fungus Torulopsis glabrata, a common skin inhabitant, is a potential pathogen in the high-risk neonate. In this report we have reviewed the cases of two infants in which systemic T glabrata infection was diagnosed. One patient survived without apparent sequelae; the other died before diagnosis and initiation of therapy. Five other cases of systemic infection by T glabrata in neonates have been reported previously, with only one survivor. Early recognition and treatment of this nearly uniformly fatal infection is imperative.

Corticosteroids for enhanced fetal lung maturation in patients with HELLP syndrome: impact on neonates.

This study was undertaken to determine retrospectively, in women with the HELLP syndrome, the perinatal effects of corticosteroid administration for promotion of fetal lung maturity. Twenty-seven of 427 women with the HELLP syndrome treated between 1980 and 1991 received a full course of steroids prior to preterm delivery. They were compared to 27 control patients with the HELLP syndrome matched for maternal age, severity of disease, gestational age, race, and sex of the fetus. Respiratory distress requiring mechanical ventilation occurred in 13 of 27 neonates who received steroid administration and in 23 of 27 who did not receive steroids (p < 0.001). The average stay in the neonatal intensive care unit was 29.8 +/- 50.6 days for the steroid-treated group and 45.2 +/- 35.3 days for the group without steroid use (p = NS). The incidence of neonatal deaths, intraventricular haemorrhage type III and IV, necrotizing enterocolitis, and retrolental fibroplasia was greater in the control group but the difference was not statistically significant.

Assembly of avian mixed-species flocks in Amazonia.

Diamond's "assembly rules" model posits that competitive interactions among species govern the composition of avifaunas. Although originally applied to islands in archipelagoes, this controversial set of hypotheses is difficult to test because islands differ in habitat and resource availability, colonization history, and stochastic effects. Permanent mixed-species flocks of Amazonian birds are a model system for testing the assembly rules hypothesis because flocks occur in relatively homogeneous tracts of rain forest and because resident species are potentially interactive from minute to minute. To analyze cooccurrence patterns of species in flocks, we used null models that incorporate realistic autecological colonization parameters. Potentially competing pairs of congeneric species with similar ecologies cooccur in flocks less often than expected by chance, resulting in perfect checkerboard distributions. Interactions among more distantly related species, however, appear to have little effect on the assembly of mixed-species flocks. Checkerboard distributions enhance local species diversity within habitats by generating different combinations of species in different flocks. This process may have contributed to the immense species richness of the Amazonian avifauna.

Bergmann's rule near the equator: latitudinal clines in body size of an Andean passerine bird.

Critical correlative support for Bergmann's ecogeographic rule is provided by symmetrical patterns of size variation in Diglossa carbonaria, a tropical passerine bird whose geographic range in the Andes Mountains of South America straddles the equator. Body size is positively correlated with latitude both north and south of the equator. Moreover, parapatric taxa that exhibit either partial (north-western Bolivia) or complete (northern Peru) reproductive isolation converge in body size. Relative uniformity in the length of the highly modified flower-piercing bill among populations of D. carbonaria that differ significantly in body size suggests that character displacement or interspecific competition is not responsible for these patterns. These findings support the hypothesis that climate, particularly temperature seasonality, is an important environmental determinant of geographic size variation in homeotherms. In addition they demonstrate that clinal variation correlated with subtle climatic gradients can occur in tropical environments.

Improving access to pediatric health care in Mississippi.

Working under the Mississippi Postneonatal Death Impact Project, the Mississippi Chapter of the American Academy of Pediatrics, in conjunction with the State Department of Health, helped improve access to pediatric health care in Mississippi. This was accomplished by developing a statewide telephone information and referral service (telephone case management), enlisting primary care physicians to treat a limited number of children without specific compensation and staging a public awareness campaign. System barriers encountered were identified and interagency coordination and cooperation suggested. This effort could be easily replicated and expanded.