Gene flow on the ice: genetic differentiation among Adélie penguin colonies around Antarctica.

Each summer Adélie penguins breed in large disjunct colonies on ice-free areas around the Antarctic continent. Comprising > 10 million birds, this species represents a dominant feature of the Antarctic ecosystem. The patchy distribution within a large geographical range, natal philopatry and a probable history of refugia, suggest that this species is likely to exhibit significant genetic differentiation within and among colonies. We present data from seven microsatellite DNA loci for 442 individuals from 13 locations around the Antarctic continent. With the exception of one locus, there was no significant genic or genotypic heterogeneity across populations. Pairwise FST values were low with no value > 0.02. When all colonies were compared in a single analysis, the overall FST value was 0.0007. Moreover, assignment tests were relatively ineffective at correctly placing individuals into their respective collection sites. These data reveal a lack of genetic differentiation between Adélie penguin colonies around the Antarctic continent, despite substantial levels of genetic variation. We consider this homogeneity in terms of the dispersal of individuals among colonies and the size of breeding groups and discuss our results in terms of the glacial history of Antarctica.

Genetic distinctness of isolated populations of an endangered marsupial, the mountain pygmy-possum, Burramys parvus.

The mountain pygmy-possum, Burramys parvus, exists in isolated and fragmented populations in the Australian alps. To examine the degree of interpopulation divergence, mitochondrial cytochrome b and NADH dehydrogenase subunit 2 (NADH2) sequences were obtained from samples representing all populations of B. parvus. Three divergent mitochondrial DNA (mtDNA) lineages were identified which exhibited strong phylogeographical structure. This indicates the presence of three maternal clades corresponding to populations in the northern, central and southern Australian alps. Molecular clock estimates suggest that the mtDNA lineages diverged from one another 420-680 thousand years ago. On this basis it is argued that B. parvus populations have probably been isolated since the mid-Pleistocene, and that management should focus on maintaining viable B. parvus populations in each of the three regional localities.

Intolerance to protein hydrolysate infant formulas: an underrecognized cause of gastrointestinal symptoms in infants.

The purpose of this study was to determine the effectiveness of an amino acid-based infant formula in infants with continued symptoms suggestive of formula protein intolerance while they were receiving casein hydrolysate formula (CHF). Twenty-eight infants, 22 to 173 days of age, were enrolled; each had received CHF for an average of 40 days (10 to 173 days) and continued to have bloody stools, vomiting, diarrhea, irritability, or failure to gain weight, or a combination of these symptoms. Sigmoidoscopy with rectal biopsy was performed in all infants. The infants then received an amino acid-based infant formula, Neocate, for 2 weeks. After 2 weeks of treatment, 25 of the infants demonstrated resolution of their symptoms and underwent challenge with CHF. Of the 25 who were challenged, eight tolerated the CHF and the remainder had recurrence of their symptoms. The histologic features in these infants varied from eosinophilic infiltration to normal. We conclude that not all infants with apparent formula protein-induced colitis respond to CHF and that these infants may have resolution of their symptoms when fed an amino acid-based infant formula.

Influence of bacterial overgrowth and intestinal inflammation on duration of parenteral nutrition in children with short bowel syndrome.

OBJECTIVES: Massive intestinal resection results in short bowel syndrome and necessitates prolonged parenteral feeding. The purpose of this work was to assess the impact of late complications of short bowel syndrome, including intestinal bacterial overgrowth and enterocolitis, on the duration of parenteral nutrition (PN) in comparison with factors evident in the neonatal period. METHODS: Retrospective chart review. RESULTS: Of 49 children, 42 were weaned from parenteral nutrition after a treatment course of 17 +/- 14 months. In these 42, postresection small intestinal length equaled 81 +/- 65 cm; 45% had an ileocecal valve. Small intestinal length in the seven children who were PN dependent was 31 +/- 30 cm (p < 0.05); none had an ileocecal valve (p < 0.05). Bacterial overgrowth occurred in all seven PN-dependent children and in 23 of 42 children eventually weaned from PN (p < 0.05). When bacterial overgrowth was identified before weaning (n = 12), the duration pf PN was 28 +/- 17 months, but when bacterial overgrowth was first identified only after weaning (n = 11), the duration of PN was 16 +/- 13 months (p < 0.05). Small intestinal inflammation correlated with bacterial overgrowth (r = 0.69). Those children with severe enteritis identified before weaning remained on the PN regimen for 36 +/- 15 months, in comparison with 21 +/- 14 months in those with mild enteritis and 13 +/- 11 months in those without inflammation (p < 0.02). CONCLUSIONS: Although the length of small intestine remaining after resection is the best immediate predictor of final success in terminating PN in children with short bowel syndrome, PN is prolonged by bacterial overgrowth and associated enteritis in those who will ultimately be weaned.

Use of soy fiber in acute diarrhea in infants and toddlers.

Soy fiber has been shown to reduce the duration of watery stools during acute diarrhea caused by bacterial and viral pathogens in underdeveloped countries. A randomized blinded clinical trial was conducted with middle-class American children to assess the efficacy of soy fiber-supplemented infant formula. Stool characteristics, intake, and weight were recorded. Infants > 6 months of age (n = 44) fed soy fiber-supplemented formula (Isomil DF) had a significantly shorter estimated median duration of diarrhea (9.7 hours vs. 23.1 hours) than those fed soy formula (Isomil). The use of fiber-supplemented soy formula may reduce the duration of diarrheal symptoms in U.S. infants more than 6 months of age with acute diarrhea.

Conservation genetics of the koala (Phascolarctos cinereus): low mitochondrial DNA variation amongst southern Australian populations.

Koala (Phascolarctos cinereus) populations in southern Australia have a history of bottlenecks-earlier this century the species became extinct in South Australia, and almost so in Victoria. Subsequently large numbers of animals from island populations (founded from very few animals) have been translocated back to mainland sites and to other islands in the region. As part of a larger study of the genetic structure of koala populations in southern Australia, we have undertaken a survey of mitochondrial DNA restriction fragment length polymorphism (mtDNA-RFLP) variability. Genomic DNA from 91 koalas from five populations was examined using 23 restriction enzymes, and mtDNA fragments were detected using a domestic cat full-length mtDNA clone. Only one of the enzymes, TaqI, revealed polymorphism-a relatively low amount of variation compared with other mammals, although low mtDNA-RFLP variation has also been reported in Queensland koalas. French Island and populations established predominantly from French Island immigrant koalas, either directly or via other island populations, were indistinguishable by haplotype frequencies. The mtDNA data are thus consistent with the interpretation that the koala translocation programme has homogenized gene frequencies amongst those populations involved. South Gippsland is not recorded as having received translocated koalas directly, and has significantly different mtDNA-RFLP haplotype frequencies from all other populations examined. The fact that this distinction was not previously observed in nuclear gene frequencies may reflect predominantly male-mediated dispersal in koalas.

Microsatellite differentiation between Phillip Island and mainland Australian populations of the red fox Vulpes vulpes.

Predation by the red fox Vulpes vulpes is believed to be threatening the little penguin Eudyptula minor on Phillip Island in Victoria. Polymorphism at seven microsatellite loci was examined to estimate the extent of differentiation between Phillip Island and mainland populations of V. vulpes. Loss of alleles has occurred on Phillip Island where foxes first appeared approximately 88 years ago compared with mainland populations. Genetic differentiation between the Phillip Island and mainland populations was high. The relatively high differentiation found between the two populations could be due to either low migration rates, the effect of the composition of founder animals or both effects. Further ecological and historical information about the populations is needed to explore the likely significance of these effects.

Conservation genetics of the koala (Phascolarctos cinereus). II. Limited variability in minisatellite DNA sequences.

We have examined variability in TaqI and EcoRI restriction fragment sizes of DNA from the koala (Phascolarctos cinereus) using six HVR (hypervariable region) probes which reveal complex, individual-specific restriction patterns in humans and other species. Frequency of band-sharing among unrelated koalas was extremely high. This result is likely to be a consequence of the history of near-extinction and artificial recolonization of the populations we have studied, rather than a general marsupial or koala-wide phenomenon.

Semen characteristics in free-living koalas (Phascolarctos cinereus).

Spermic electroejaculates (range in motile sperm/ejaculate, 0.50-122.9 x 10(6); mean +/- s.e.m., 38.6 +/- 4.9) were recovered from 47 of 48 adult koalas captured from 3 wild populations in Australia. Semen was characterized by (i) a high density of globular bodies, which prevented the estimation of sperm motility without dilution; (ii) a brownish colour; and (iii) an acidic pH. Spermatozoa were categorized on the basis of 10 head forms, most cells being a curved or hooked shape. The koala populations differed in sperm concentration and motility ratings, but not in testes size, testosterone production or proportions of spermatozoa with various head shapes. These data confirm that free-living koalas normally produce spermatozoa with a high incidence of structural heterogeneity almost solely confined to the head region; and demonstrate the utility and safety of conventional gamete and endocrine studies, approaches which will be useful for determining the impact of genetic isolation and venereal disease on species fertility.

Nutritional support for the infant with extrahepatic biliary atresia.

Some infants with biliary atresia obtain dramatic improvement for prolonged periods after the performance of hepatic portoenterostomy. Such infants may have life styles not substantially different from those of normal children. In others, the benefit from this operation, if any, is short lived. These infants are very vulnerable to the debilitating effects of severe, prolonged malabsorption and ultimately require orthotopic liver transplantation to sustain life. The physician caring for infants awaiting liver transplantation can do much, not only to prolong survival but to maintain satisfactory growth and development. The key consideration is to provide adequate nitrogen and nonnitrogen calories, liberally utilizing modern methods of enteral alimentation when necessary. In addition, attention must be directed toward several vitamin and mineral deficiencies, particularly those of the fat-soluble vitamins, that inevitably accompany severe malabsorption in children. Management of extrahepatic biliary atresia in infants is difficult and requires meticulous attention to details. Nevertheless, the long-term cure of this disorder provided by liver transplantation makes their care a rewarding experience.

Continuous enteral feedings. An important adjunct to the management of complex congenital heart disease.

Eleven infants with complex congenital heart lesions were given continuous enteral infusions after failure to gain weight adequately despite use of hypercaloric formulas and nutritional supplementation. Formulas used before institution of enteral feedings were continued. Dietary and caloric intake and weight measurements were obtained at weekly or monthly intervals. Both mean daily caloric intake and mean daily weight gain were greater after initiation of continuous enteral feedings. Rate of weight gain improved in all 11 children after institution of enteral feedings. Continuous enteral feeding increases weight gain in babies with complex congenital heart disease, allowing earlier and safer surgical intervention.