Unsuspected Pneumocystis carinii pneumonia and vertically acquired HIV infection in infants requiring intensive care.

When an infant develops acute respiratory failure of sufficient severity to necessitate supportive mechanical ventilation a cause should always be sought. A chest radiograph showing predominantly interstitial lung disease and an infant''s failure to respond to standard antibiotic treatment are indications for non-bronchoscopic bronchoalveolar lavage. If P carinii pneumonia is diagnosed a congenital immunodeficiency should be sought and the parents counselled about HIV infection. Earlier investigation may be indicated by features of immunodeficiency when taking a history, performing a general examination, or analysing the results of basic haematological testing.     

Did lemurs have sweepstake tickets? An exploration of Simpson's model for the colonization of Madagascar by mammals

Aim  To investigate the validity of Simpson's model of sweepstakes dispersal, particularly as it applies to the colonization of Madagascar by African mammals. We chose lemurs as a classic case.
Location  The East African coast, the Mozambique Channel and Madagascar.
Methods  First, we investigated the assumptions underlying Simpson's statistical model as it relates to dispersal events. Second, we modelled the fate of a natural raft carrying one or several migrating mammals under a range of environmental conditions: in the absence of winds or currents, in the presence of winds and currents, and with and without a sail. Finally, we investigated the possibility of an animal being transported across the Mozambique Channel by an extreme climatic event like a tornado or a cyclone .
Results  Our investigations show that Simpson's assumptions are consistently violated when applied to scenarios of over-water dispersal by mammals. We suggest that a simple binomial probability model is an inappropriate basis for extrapolating the likelihood of dispersal events. One possible alternative is to use a geometric probability model. Our estimates of current and wind trajectories show that the most likely fate for a raft emerging from an estuary on the east coast of Africa is to follow the Mozambique current and become beached back on the African coast. Given prevailing winds and currents, transport from Madagascar to Africa is very much more likely than the reverse process. Freak transport by means of a hurricane or tornado is even less likely than rafting for mammals.
Main conclusions  Our models suggest that the scenario of sweepstakes dispersal that currently enjoys wide support is not valid at either the theoretical or the applied level when applied to the hypothetical invasion of Madagascar by African mammals. Alternative explanations should be sought.     

A test of the humped-back theory of species richness in New Zealand native forest

The Humped-back theory of plant species richness, a theory related to Grime's C-S-R 'triangular' model, has been widely discussed, and some evidence has been claimed in support of it. The theory suggests that species richness is maximal at intermediate levels of productivity, i.e., at intermediate positions on a stress/favourability gradient. We sought evidence for the theory from 90 stands of native podocarp/broadleaved and beech forest in the Coastal Otago region, with an adjustment made for the effect of stand area on species richness. There was no relation between adjusted species richness and an index of site stress/favourability, i.e., no support for the Humped-back theory. The theory may be inapplicable to woody vegetation, or it may be applicable only when the 'favourable' end of the spectrum comprises agricultural communities, or support for the theory might be inflated in the literature by a wish to find ecological generalisations.     

An ontological dilemma: epistemology and methodology of historical biogeography

The task of historical biogeography is to reveal and explain the history of biotas and their historical connections. Historical «relationship>> between biotas is defined as the sharing of descendants of the same ancestor. Several generalized patterns of relationship, rather than a single universal one, should be expected for any set of biotas or areas. Such generalized patterns must be sought by comparison of individual patterns, based on individual monophyletic groups. Generalized patterns of biota relationships are formally statements about numerical universals, while a pattern derived from an individual group is a statement about a particular. Such statements are not subject to testing in the Popperian sense; they may be falsified as well as verified. As in other historical sciences, explanation in historical biogeography is genetic in form and probabilistic in nature. An explanation is falsified when an explanatory premise is, and corroborated when an explanatory premise is verified. Two major methodologies exist to derive «area cladograms>> from substituted (taxon) cladograms, Component Analysis and Parsimony Analysis. It is argued that Parsimony Analysis is the theoretically more satisfactory of these because it treats all sources of «error>> in the same way, making no process-related assumptions about the sources of conflicts. The rooting of area dendrograms is problematic. The rooting by an «allzero>> outarea is theoretically unsound and the dendrogram should be rooted a posteriori adjacent to the ancestral area(s), or not at all.     

Ascorbate 6-palmitate protects human erythrocytes from oxidative damage

Lipid-soluble antioxidants, such as α-tocopherol, protect cell membranes from oxidant damage. In this work we sought to determine whether the amphipathic derivative of ascorbate, ascorbate 6-palmitate, is retained in the cell membrane of intact erythrocytes, and whether it helps to protect the cells against peroxidative damage. We found that ascorbate 6-palmitate binding to erythrocytes was dose-dependent, and that the derivative was retained during the multiple wash steps required for preparation of ghost membranes. Ascorbate 6-palmitate remained on the extracellular surface of the cells, because it was susceptible to oxidation or removal by several cell-impermeant agents. When bound to the surface of erythrocytes, ascorbate 6-palmitate reduced ferricyanide, an effect that was associated with generation of an ascorbyl free radical signal on EPR spectroscopy. Erythrocyte-bound ascorbate 6-palmitate protected membrane α-tocopherol from oxidation by both ferricyanide and a water-soluble free radical initiator, suggesting that the derivative either reacted directly with the exogenously added oxidant, or that it was able to recycle the α-tocopheroxyl radical to α-tocopherol in the cell membrane. Ascorbate 6-palmitate also partially protected cis-parinaric acid from oxidation when this fluorescent fatty acid was intercalated into the membrane of intact cells. These results show that an amphipathic ascorbate derivative is retained on the exterior cell surface of human erythrocytes, where it helps to protect the membrane from oxidant damage originating outside the cells.     

Machine vision automated species identification scaled towards production levels

Computer‐automated identification of insect species has long been sought to support activities such as environmental monitoring, forensics, pest diagnostics, border security and vector epidemiology, to name just a few. In order to succeed, an automated identification programme capable of addressing the needs of the end user should be able to classify hundreds of taxa, if not thousands, and is expected to distinguish closely related and hence morphologically similar species. However, it remains unknown how automated identification methods might handle an increase in data quantity, be it in reference imagery or taxonomic diversity. We sought to test the scalability of an automated identification method in terms of the number of reference specimens used to train the classifier and the number of taxa into which the classifier should assign unknown specimens. Is there an optimal number of reference images, where the cost of acquiring more images becomes greater than the marginal increase in identification success? Does increasing taxonomic diversity affect identification success, whether negatively or positively? In order to test the scalability of the automated insect identification enterprise, we used a sparse processing technique and support vector machine to test the largest dataset to date: 72 species of fruit flies (Diptera: Tephritidae) and 76 species of mosquitoes (Diptera: Culicidae). We found that: (i) machine vision methods are capable of correctly classifying large numbers of closely related species; (ii) when the misclassification of a specimen occurs at the species level, it is often classified in the correct genus; (iii) classification success increases asymptotically as new training images are added to the dataset; (iv) broad taxon sampling outside a focal group can increase classification success within it.     

A Comment on Maximum Likelihood Estimation for Finite Mixtures of Distributions

Iterative numerical methods are necessary to find the maximum likelihood estimates for finite mixture distributions. This paper shows that it will often be possible to analytically reduce the number of equations that must ultimately be solved numerically. Such a reduction in dimensionality has not generally been used, or sought after, for mixture distributions. Yet such results are easily derived when each mixture component is assumed to be from the same parametric model within the exponential family.     

Centrally Administered Ghrelin Acutely Influences Food Choice in Rodents

We sought to determine whether the orexigenic hormone, ghrelin, is involved in the intrinsic regulation of food choice in rats. Ghrelin would seem suited to serve such a role given that it signals hunger information from the stomach to brain areas important for feeding control, including the hypothalamus and reward system (e.g. ventral tegmental area, VTA). Thus, in rats offered a choice of palatable foods (sucrose pellets and lard) superimposed on regular chow for 2 weeks, we explored whether acute central delivery of ghrelin (intracerebroventricular (ICV) or intra-VTA) is able to redirect their dietary choice. The major unexpected finding is that, in rats with high baseline lard intake, acute ICV ghrelin injection increased their chow intake over 3-fold, relative to vehicle-injected controls, measured at both 3 hr and 6 hr after injection. Similar effects were observed when ghrelin was delivered to the VTA, thereby identifying the VTA as a likely contributing neurobiological substrate for these effects. We also explored food choice after an overnight fast, when endogenous ghrelin levels are elevated, and found similar effects of dietary choice to those described for ghrelin. These effects of fasting on food choice were suppressed in models of suppressed ghrelin signaling (i.e. peripheral injection of a ghrelin receptor antagonist to rats and ghrelin receptor (GHSR) knock-out mice), implicating a role for endogenous ghrelin in the changes in food choice that occur after an overnight fast. Thus, in line with its role as a gut-brain hunger hormone, ghrelin appears to be able to acutely alter food choice, with notable effects to promote “healthy” chow intake, and identify the VTA as a likely contributing neurobiological substrate for these effects.     

Imagining One's Own and Someone Else's Body Actions: Dissociation in Anorexia Nervosa

Background

Patients with anorexia nervosa (AN) usually report feeling larger than they really are. This body overestimation appears to be related not only to the patient’s body image but also to an abnormal representation of the body in action. In previous work on a body-scaled anticipation task, anorexic patients judged that they could not pass through a door-like aperture even when it was easily wide enough - suggesting the involvement of the body schema. In the present study, we sought to establish whether this erroneous judgment about action is specifically observed when it concerns one’s own body or whether it is symptomatic of a general impairment in perceptual discrimination.

Methods

Twenty-five anorexic participants and 25 control participants were presented with a door-like aperture. They had to judge whether or not the aperture was wide enough for them to pass through (i.e. first-person perspective, 1PP) and for another person present in the testing room to pass through (i.e. third-person perspective, 3PP).

Results

We observed a higher passability ratio (i.e. the critical aperture size to shoulder width ratio) in AN patients for 1PP but not for 3PP. Moreover, the magnitude of the passability ratio was positively correlated not only with the extent of the patient’s body and eating concerns but also with the body weight prior to disease onset. Our results suggest that body overestimation can affect judgments about the capacity for action but only when they concern the patient’s own body. This could be related to impairments of the overall network involved in the emergence of the body schema and in one’s own perspective judgments.

Conclusion

Overestimation of the body schema might occur because the central nervous system has not updated the new, emaciated body, with maintenance of an incorrect representation based on the patient’s pre-AN body dimensions.     

An investigation of the role of transmembrane domains in Golgi protein retention.

The single transmembrane domains (TMDs) of the resident glycosylation enzymes of the Golgi apparatus are involved in preventing these proteins moving beyond the Golgi. It has been proposed that either the TMDs associate, resulting in the formation of large oligomers of Golgi enzymes, or that they mediate the lateral segregation of the enzymes between lipid microdomains. Evidence for either type of interaction has been sought by examining the retention of sialyltransferase (ST), an enzyme of the mammalian trans Golgi. No evidence could be obtained for specific interactions or 'kin recognition' between ST and other proteins of the trans Golgi. Moreover, it is shown that the previously described kin recognition between enzymes of the medial Golgi involves the lumenal portions of these proteins rather than their TMDs. To investigate further the role of the ST TMD, the effects on Golgi retention of various alterations in the TMD were examined. The addition or removal of residues showed that the efficiency of retention of ST is related to TMD length. Moreover, when a type I plasma membrane protein was expressed with a synthetic TMD of 23 leucines it appeared on the cell surface, but when the TMD was shortened to 17 leucines accumulation in the Golgi was observed. These observations are more consistent with lipid-based sorting of ST TMD, but they also allow for reconciliation with the kin recognition model which appears to act on sequences outside of the TMD.     

Heterogeneous cholinergic reactions of ringed seal coronary arteries

Coronary blood flow of some seal species is unusual in that it is highly variable in both non-diving and diving conditions and shows intermittent fluctuations, especially during dives when it frequently ceases for brief periods. We sought regulatory mechanisms governing these reactions by studying isometric tension recordings of isolated left circumflex (LC) and left anterior descending (LAD) coronary arteries of ringed seals, Phoca hispida, during reactions to a variety of agents for stimulating or blocking autonomic responses of the vascular smooth muscle. Micromolar acetylcholine (ACh) produced constriction of the small diameter segments of the LAD, but relaxation of the LC and larger segments of LAD. Both constrictions and dilations were prevented by atropine. Small vessel constriction by ACh was prevented by micromolar indomethacin and by a thromboxane receptor antagonist. Large vessel ACh dilations were prevented or reduced by rubbing off the endothelium and by the -arginine analog, -NG-nitro-arginine, an inhibitor of nitric oxide synthesis. We conclude that cholinergic, muscarinic, dilation of ringed seal large coronary arteries is mediated by endothelial-derived relaxing factor (EDRF), whereas ACh constriction of small arteries is mediated by a prostaglandin.     

The solution structure of a superpotent B-chain-shortened single-replacement insulin analogue

This paper reports on an insulin analogue with 12.5-fold receptor affinity, the highest increase observed for a single replacement, and on its solution structure, determined by NMR spectroscopy. The analogue is [D-AlaB26]des-(B27-B30)-tetrapeptide-insulin-B26-amide. C-terminal truncation of the B-chain by four (or five) residues is known not to affect the functional properties of insulin, provided the new carboxylate charge is neutralized. As opposed to the dramatic increase in receptor affinity caused by the substitution of D-Ala for the wild-type residue TyrB26 in the truncated molecule, this very substitution reduces it to only 18% of that of the wild-type hormone when the B-chain is present in full length. The insulin molecule in solution is visualized as an ensemble of conformers interrelated by a dynamic equilibrium. The question is whether the "active" conformation of the hormone, sought after in innumerable structure/function studies, is or is not included in the accessible conformational space, so that it could be adopted also in the absence of the receptor. If there were any chance for the active conformation, or at least a predisposed state to be populated to a detectable extent, this chance should be best in the case of a superpotent analogue. This was the motivation for the determination of the three-dimensional structure of [D-AlaB26]des-(B27-B30)-tetrapeptide-insulin-B26-amide. However, neither the NMR data nor CD spectroscopic comparison of a number of related analogues provided a clue concerning structural features predisposing insulin to high receptor affinity. After the present study it seems more likely than before that insulin will adopt its active conformation only when exposed to the force field of the receptor surface.     

Cadaver nephrectomy: an operation on the donor's family.

Thirty-two relatives of cadaver kidney donors were interviewed six months or longer after the donor''s death. Most had positive attitudes to kidney transplantation that had been strengthened by experience, especially when they knew that they were fulfilling the donor''s wishes. Twenty-three of the relatives had gained some solace from knowing that others might benefit from their misfortune, but three claimed adverse effects. In identifying the factors that influenced them to grant permission or hesitate, relatives revealed defects in the way their permission had been sought. Twelve did not clearly understand the donor''s hopeless prognosis until then, and seven reacted adversely to the interviewers, finding them blunt and callous. Nevertheless, most were pleased that they had been asked. Doctors who care for unconscious, dying patients should try to give relatives explicit information on the patient''s condition, whether or not the patient is a potential kidney donor, and permission for organ recovery should not be sought until they understand that death is inevitable.     

Barriers and Enablers of Kangaroo Mother Care Practice: A Systematic Review

Kangaroo mother care (KMC) is an evidence-based approach to reducing mortality and morbidity in preterm infants. Although KMC is a key intervention package in newborn health initiatives, there is limited systematic information available on the barriers to KMC practice that mothers and other stakeholders face while practicing KMC. This systematic review sought to identify the most frequently reported barriers to KMC practice for mothers, fathers, and health practitioners, as well as the most frequently reported enablers to practice for mothers. We searched nine electronic databases and relevant reference lists for publications reporting barriers or enablers to KMC practice. We identified 1,264 unique publications, of which 103 were included based on pre-specified criteria. Publications were scanned for all barriers / enablers. Each publication was also categorized based on its approach to identification of barriers / enablers, and more weight was assigned to publications which had systematically sought to understand factors influencing KMC practice. Four of the top five ranked barriers to KMC practice for mothers were resource-related: “Issues with the facility environment / resources,” “negative impressions of staff attitudes or interactions with staff,” “lack of help with KMC practice or other obligations,” and “low awareness of KMC / infant health.” Considering only publications from low- and middle-income countries, “pain / fatigue” was ranked higher than when considering all publications. Top enablers to practice were included “mother-infant attachment” and “support from family, friends, and other mentors.” Our findings suggest that mother can understand and enjoy KMC, and it has benefits for mothers, infants, and families. However, continuous KMC may be physically and emotionally difficult, and often requires support from family members, health practitioners, or other mothers. These findings can serve as a starting point for researchers and program implementers looking to improve KMC programs.     

Statistical measures for defining an individual's degree of independence within state-dependent dynamic games

Background  

For organisms living or interacting in groups, the decision-making processes of an individual may be based upon aspects of both its own state and the states of other organisms around it. Much research has sought to determine how group decisions are made, and whether some individuals are more likely to influence these decisions than others. State-dependent modelling techniques are a powerful tool for exploring group decision-making processes, but analyses conducted so far have lacked methods for identifying how dependent an individual's actions are on the rest of the group.     

Feeder use predicts both acquisition and transmission of a contagious pathogen in a North American songbird

Individual heterogeneity can influence the dynamics of infectious diseases in wildlife and humans alike. Thus, recent work has sought to identify behavioural characteristics that contribute disproportionately to individual variation in pathogen acquisition (super-receiving) or transmission (super-spreading). However, it remains unknown whether the same behaviours enhance both acquisition and transmission, a scenario likely to result in explosive epidemics. Here, we examined this possibility in an ecologically relevant host–pathogen system: house finches and their bacterial pathogen, Mycoplasma gallisepticum, which causes severe conjunctivitis. We examined behaviours likely to influence disease acquisition (feeder use, aggression, social network affiliations) in an observational field study, finding that the time an individual spends on bird feeders best predicted the risk of conjunctivitis. To test whether this behaviour also influences the likelihood of transmitting M. gallisepticum, we experimentally inoculated individuals based on feeding behaviour and tracked epidemics within captive flocks. As predicted, transmission was fastest when birds that spent the most time on feeders initiated the epidemic. Our results suggest that the same behaviour underlies both pathogen acquisition and transmission in this system and potentially others. Identifying individuals that exhibit such behaviours is critical for disease management.     

The question of derepression ofH-2 specificities in virus-infected cells: Failure to detect specific alloreactive T cells after systemic virus infection or alloantigens detectable by alloreactive T cells on virus-infected target cells

Cultured cells of variousH-2 haplotypes were infected acutely with vaccinia, lymphocytic choriomeningitis, or vesicular stomatitis virus and tested for the appearance of newly expressed, unexpected alloantigens or the absence of expected antigens of variousH-2 haplotypes. No repression or derepression of unexpected alloantigens could be detected when such specificities were sought by using alloreactive cytotoxic T cells. Similarly, immune virus-specific cytotoxic T cells from various strains of mice with differentH-2 haplotypes did not lyse uninfectedH-2-incompatible target cells differentially in an alloantigen-specific fashion. Therefore, it seems unlikely that the H-2-restricted specificity of cytotoxic T cells generated in these acute virus infections can be explained by their being sensitized to derepressed H-2 antigens.Abbreviations used in this paper are H major transplantation antigen - LCMV lymphocytic choriomeningitis - VSV vesicular stomatitis virus - MLC mixed lymphocyte culture     

Termination of a visual search with large display size effects

The ability to locate an object in the visual field is a collaboration of at least three intermingled processes: scanning multiple locations, recognizing the object sought (the target), and ending the search in cases when the target is not found. In this paper, we focus on the termination rule. Using distribution analyses, it is possible to assess the probability of termination conditional on the number of locations examined. The results show that on some trials without target, the participants carried out more comparisons than there are objects in the display; in other conditions, they carried out fewer comparisons than objects. Because there were very few errors, the premature stops were not pure guesses. We present models to account for these findings. The distributions of terminations help determine the slopes of the functions relating response time to set size.     

Down‐regulation of Pyruvate Dehydrogenase Phosphatase in Obese Subjects is a Defect that Signals Insulin Resistance

Objective: The objective of this study was to determine whether down‐regulation of pyruvate dehydrogenase phosphatase (PDP) is responsible for poorly active pyruvate dehydrogenase (PDH) in circulating lymphocytes (CLs) of obese subjects (ObS), and if so, whether it improves when their plasma insulin rises. Research Methods and Procedures: PDH activity was compared in lysed CLs of 10 euglycemic ObS and 10 sex‐ and age‐matched controls before and during plasma insulin enhancement in an oral glucose tolerance test. It was evaluated without (PDHa) or with Mg/Ca or Mg at various concentrations to assess PDP1 or PDP2 activities or with Mg/Ca and exogenous PDP to determine total PDH activity (PDHt), which is an indirect measure of the amount of PDH. The insulin sensitivity index was calculated, and PDP1 and PDP2 mRNA was sought in the CLs. Results: At T₀ in ObS, PDHt was normal, whereas PDHa and PDP1 activity was below normal at all Mg/Ca concentrations. PDP2 activity was undetectable in both groups. PDP1 and PDP2 mRNA was identified, and insulin sensitivity index and PDHa were directly correlated. During the oral glucose tolerance test, plasma insulin rose considerably more in ObS than in controls; PDHa and PDP1 activity also increased but remained significantly below normal, and PDHt was unvaried in both groups. Discussion: PDP1 is down‐regulated in CLs of ObS because it is poorly sensitive to Mg/Ca; this defect is attenuated when plasma insulin is greatly enhanced.     

Why do juvenile fish utilise mangrove habitats?

Three hypotheses to discern the strong positive association between juvenile fish and mangrove habitat were tested with field and laboratory experiments. Artificial mangrove structure in the field attracted slightly more juvenile fish than areas without structure. Artificial structure left to accumulate fouling algae attracted four-times the total number of juvenile fish than areas without structure or areas with clean structure. Community composition of fish attracted to structure with fouling algae was different when compared with areas with no structure or clean structure; five species were attracted by structure with fouling algae whilst two species were associated with structure regardless of fouling algae. Algae were linked to increased food availability and it is suggested that this is an important selection criteria for some species. Other species were apparently attracted to structure for different reasons, and provision of shelter appears to be important. Predation pressure influenced habitat choice in small juvenile fish in laboratory experiments. In the absence of predators, small juveniles of four out of five species avoided shelter but when predators were introduced all species actively sought shelter. Large fish were apparently less vulnerable to predators and did not seek shelter when predators were added to their tank. Feeding rate was increased in the mangrove habitat for small and medium-sized fish compared with seagrass beds and mudflats indicating increased food availability or foraging efficiency within this habitat. Larger fish fed more effectively on the mudflats with an increased feeding rate in this habitat compared with adjacent habitats. The most important aspect of the mangrove habitat for small juvenile fish is the complex structure that provides maximum food availability and minimises the incidence of predation. As fish grow a shift in habitat from mangroves to mudflat is a response to changes in diet, foraging efficiency and vulnerability to predators.