Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SPECIALISM”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,675 records · Page 93Linked to original sources
PubMed2003

Multiple, recurring origins of aposematism and diet specialization in poison frogs.

Aposematism is the association, in a prey organism, of the presence of a warning signal with unprofitability to predators. The origin of aposematism is puzzling, because of its predicted low probability of establishment in a population due to the prey's increased conspicuousness. Aposematism is a widespread trait in invertebrate taxa, but, in vertebrates, it is mostly evident in amphibians, reptiles, and fishes. Poison frogs (Dendrobatidae) are one of the most well known examples of the co-occurrence of warning coloration and toxicity. This monophyletic group of mostly diurnal leaf-litter Neotropical anurans has both toxic/colorful and palatable/cryptic species. Previous studies suggested a single origin of toxicity and warning coloration, dividing the family in two discrete groups of primitively cryptic and more derived aposematic frogs. Recent molecular phylogenetic analyses using mostly aposematic taxa supported this conclusion and proposed a single tandem origin of toxicity and conspicuous warning coloration. By using expanded taxon and character sampling, we reexamined the phylogenetic correlation between the origins of toxicity and warning coloration. At least four or five independent origins of aposematism have occurred within poison frogs; by using simulations, we rejected hypotheses of one, two, or three origins of aposematism (P < 0.002). We also found that diet specialization is linked with the evolution of aposematism. Specialization on prey, such as ants and termites, may have evolved independently at least two times.

Animals↗
PubMed1976

Suppression of the neoplastic state with the acquisition of specialized functions in cells, tissues, and organs of crown gall teratomas of tobacco.

The neoplastic state in cells of tissues and organs that develop from cloned lines of crown gall teratomas of tobacco may be completely but reversibly suppressed. Stems and leaves found on teratoma shoots may appear morphologically normal and such organs contain all of the specialized cell types and are histologically and functionally indistinguishable from those found in normal tobacco shoots of comparable age. When however, specialized cells of several different kinds that are present in stems and leaves of the teratomas are excised from the plant and grown on a basic culture medium they again assume their neoplastic properties. The results of this study indicate that the morphogenetic factors and mechanisms that govern so precisely growth, cellular differentiation, and organogenesis during the normal course of development can completely suppress the tumorous state, leading to the formation of cells, tissues, and organs that appear normal in every respect but are, in fact, inherently neoplastic. Whether the normal or tumor phenotype is expressed appears to depend on the activation or repression of select biosynthetic systems, one of which, the auxin sytems, has been identified here.

Cell Differentiation↗
PubMed1976

New proposal for structure of special-pair chlorophyll.

A new model is proposed for the structure of the special pair of chlorophyll a molecules believed to correspond to the P700 species in green plants and algae. The proposed model, although admittedly speculative, is based upon exciton-theoretical considerations and on in vitro infrared and visible absorption spectra of a 700 nm absorbing ethanol adduct of chlorophyll a. In the new model, two chlorophyll a molecules are held together by (a) two strong ring V keto C[unk]O[unk]H[unk]O (or keto C[unk]O[unk]H[unk]N, or keto C[unk]O[unk]H[unk]S) hydrogen bonds and by (b) pi-pi van der Waals stacking interactions between the two chlorophyll a macrocycles. Macrocycle stacking provides the intermolecular pi-pi overlap necessary to promote the (experimentally observed) delocalization of the unpaired electron of the in vivo radical over two chlorophyll pi systems. The new model provides an explicit role for the participation of protein in the formation of the chlorophyll special pair. The in vitro system yields an electron spin resonance signal indistinguishable from that of oxidized P700 in Chlorella vulgaris.

Journal Article↗
PubMed1985

Specialized nucleoprotein structures at the origin of replication of bacteriophage lambda: complexes with lambda O protein and with lambda O, lambda P, and Escherichia coli DnaB proteins.

The O protein of bacteriophage lambda is required for initiation of DNA replication at the lambda replicative origin designated ori lambda. The binding sites for O protein are four direct repeats, each of which is an inverted repeat. By means of electron microscopy, we have found that phage lambda O protein utilizes these multiple binding sites to form a specific nucleoprotein structure in which the origin DNA is inferred to be folded or wound. The phage lambda O and P proteins and host DnaB protein interact at ori lambda to generate a larger structure than that formed by O protein alone; P and DnaB proteins fail to form any observable complex when O protein is excluded from the reaction mixture. We conclude that the specialized nucleoprotein structure formed by phage lambda O protein and ori lambda provides for localized initiation of DNA replication by serving as the foundation for the assembly of the initial priming structure. Specialized nucleoprotein structures may be a general means to confer exceptional accuracy on DNA transactions requiring extraordinary precision.

Bacterial Proteins↗
PubMed1989

Hippocampal specialization of food-storing birds.

In a study of 52 individuals belonging to 35 species or subspecies of passerine birds it was shown that the volume of the hippocampal complex relative to brain and body size is significantly larger in species that store food than in species that do not. Retrieval of stored food relies on an accurate and long-lasting spatial memory, and hippocampal damage disrupts memory for storage sites. The results suggest, therefore, that food-storing species of passerines have an enlarged hippocampal complex as a specialization associated with the use of a specialized memory capacity. Other life-history variables were examined and found not to be correlated with hippocampal volume.

Animals↗
PubMed1990

Streamlined approach to creating yeast artificial chromosome libraries from specialized cell sources.

The study of tumor-specific chromosomal abnormalities has been severely impeded by an inability to link cytogenetic to molecular data. Restriction fragment length polymorphism mapping of any particular chromosomal rearrangement to the resolution limit of genetic methodology generates sets of probes that frequently are still too widely spaced to render the rearrangement breakpoints accessible to molecular isolation. The stable propagation of genomic fragments of up to one million base pairs in size as yeast artificial chromosomes (YACs) represents an important development in this regard. However, existing YAC libraries have been made from karyotypically normal sources making the localization and cloning of specific rearrangement breakpoints much more difficult. As a solution to this problem, we present an improved method for creating YAC libraries that can utilize specialized tumor-derived materials and that can be executed effectively in a small laboratory setting. Procedures that enabled more consistent DNA insert size selection and enhanced yeast transformation frequency were employed to generate a human YAC library from a neuroepithelioma cell line containing a characteristic t(11;22) chromosomal translocation. Approximately 40,000 colonies with an average insert size of 330 kilobase pairs were created. This library was screened with two single-copy probes that bracket the translocation breakpoint. YAC clones ranging from 370 to 550 kilobase pairs that were specific for each single-copy probe were identified. Specialized YAC libraries will make many more tumor-specific chromosomal abnormalities accessible to molecular isolation.

Cell Line↗
PubMed1992

[D-Ala2]deltorphin I binding and pharmacological evidence for a special subtype of delta opioid receptor on human and invertebrate immune cells.

The effects of the opioid neuropeptide [D-Ala2]deltorphin I, isolated from amphibian skin, on immunoregulatory activities were studied in representatives of vertebrates and invertebrates. The high potency of this compound parallels that of [Met]enkephalin, which was previously demonstrated in vertebrate plasma and invertebrate hemolymph. The addition of [D-Ala2]deltorphin I at 10(-11) M to human granulocytes or immunocytes of the mollusc Mytilus edulis resulted in cellular adherence and conformational changes indicative of cellular activation. This value is in line with the concentrations obtained with [Met]enkephalin, tested in the presence of the specific neutral endopeptidase 24.11 inhibitor phosphoramidon, and this opioid's synthetic analog [D-Ala2, Met5]enkephalin which, like [D-Ala2]deltorphin I, is resistant to proteolytic degradation. Both ligands appear to be acting on the same population of immunocytes. The same relationship was estimated to exist in the insect Leucophaea maderae, in which the high viscosity of the hemolymph makes the quantification of reactive cells more difficult than in Mytilus. In addition, [D-Ala2]deltorphin I is as potent as beta-endorphin in affecting the proliferation of lymphocytes in response to mitogen. Saturation experiments with unlabeled ligands and the radioligands [3H][D-Ala2]deltorphin I and [3H][D-Ala2,Met5]enkephalinamide revealed the presence of two high-affinity binding sites on human granulocytes, one sensitive to the nonequilibrium delta opioid antagonist [D-Ala2,Leu5,Cys6]enkephalinamide and the other relatively insensitive. The results obtained with [D-Ala2]deltorphin I support the view that the special role played by endogenous [Met]enkephalin in immunobiological activities of vertebrates and invertebrates is mediated by a special subtype of delta opioid receptor.

Animals↗
PubMed1999

Replicated evolution of trophic specializations in an endemic cichlid fish lineage from Lake Tanganyika.

The current phylogenetic hypothesis for the endemic Lake Tanganyika cichlid fishes of the tribe Eretmodini is based solely on morphology and suggests that more complex trophic morphologies derived only once from a less specialized ancestral condition. A molecular phylogeny of eretmodine cichlids based on partial mitochondrial DNA cytochrome b and control-region sequences was used to reconstruct the evolutionary sequence of trophic adaptations and to test alternative models of morphological divergence. The six mitochondrial lineages found disagree with the current taxonomy and the morphology-based phylogeny. Mitochondrial lineages with similar trophic morphologies are not grouped monophyletically but are typically more closely related to lineages with different trophic phenotypes currently assigned to other genera. Our results indicate multiple independent origins of similar trophic specializations in these cichlids. A pattern of repeated divergent morphological evolution becomes apparent when the phylogeography of the mitochondrial haplotypes is analyzed in the context of the geological and paleoclimatological history of Lake Tanganyika. In more than one instance within Lake Tanganyika, similar morphological divergence of dentitional traits occurred in sympatric species pairs. Possibly, resource-based divergent selective regimes led to resource partitioning and brought about similar trophic morphologies independently and repeatedly.

Animals↗
PubMed1999

Neandertal nasal structures and upper respiratory tract "specialization".

Schwartz and Tattersall [Schwartz, J. H. & Tattersall, I. (1996) Proc. Natl. Acad. Sci. USA 93, 10852-10854] have argued for a previously unrecognized suite of autapomorphies in the internal nasal region of Neandertals that make them unique, not only among hominids, but possibly among all other terrestrial mammals. These purported autapomorphies include (i) the development of an internal nasal margin bearing a well developed and vertically oriented medial projection; (ii) a pronounced medial swelling of the lateral nasal wall into the posterior nasal cavity; and (iii) the lack of an ossified roof over the lacrimal groove. In addition, Laitman et al. [Laitman, J. T., Reidenberg, J. S., Marquez, S. & Gannon, P. J. (1996) Proc. Natl. Acad. Sci. USA 93, 10543-10545] pointed to these features as evidence for upper respiratory tract specializations among the Neandertals, indicating potential differences in behavior compared with modern humans. Critically reviewing the anatomical basis for Schwartz and Tattersall's contentions reveals several serious problems with their analysis, including (i) reliance on specimens with damaged, incomplete, or, in some cases, entirely absent relevant anatomy; (ii) failure to consider primary vs. secondary spatial consequences in nasal trait conceptualization; and (iii) failure to consider actual ranges of variation in these traits in both fossil and recent humans. Accordingly, the unique phylogenetic and adaptive "specializations" attributed to Neandertal internal nasal structures are unwarranted.

Animals↗
PubMed1999

The mutagenesis protein UmuC is a DNA polymerase activated by UmuD', RecA, and SSB and is specialized for translesion replication.

Replication of DNA lesions leads to the formation of mutations. In Escherichia coli this process is regulated by the SOS stress response, and requires the mutagenesis proteins UmuC and UmuD'. Analysis of translesion replication using a recently reconstituted in vitro system (Reuven, N. B., Tomer, G., and Livneh, Z. (1998) Mol. Cell 2, 191-199) revealed that lesion bypass occurred with a UmuC fusion protein, UmuD', RecA, and SSB in the absence of added DNA polymerase. Further analysis revealed that UmuC was a DNA polymerase (E. coli DNA polymerase V), with a weak polymerizing activity. Upon addition of UmuD', RecA, and SSB, the UmuC DNA polymerase was greatly activated, and replicated a synthetic abasic site with great efficiency (45% bypass in 6 min), 10-100-fold higher than E. coli DNA polymerases I, II, or III holoenzyme. Analysis of bypass products revealed insertion of primarily dAMP (69%), and to a lesser degree dGMP (31%) opposite the abasic site. The UmuC104 mutant protein was defective both in lesion bypass and in DNA synthesis. These results indicate that UmuC is a UmuD'-, RecA-, and SSB-activated DNA polymerase, which is specialized for lesion bypass. UmuC is a member of a new family of DNA polymerases which are specialized for lesion bypass, and include the yeast RAD30 and the human XP-V genes, encoding DNA polymerase eta.

Bacterial Proteins↗
PubMed2002

Structure-function analysis of HscC, the Escherichia coli member of a novel subfamily of specialized Hsp70 chaperones.

Hsp70 chaperones assist protein folding processes through nucleotide-controlled cycles of substrate binding and release. In our effort to understand the structure-function relationship within the Hsp70 family of proteins, we characterized the Escherichia coli member of a novel Hsp70 subfamily, HscC, and identified considerable differences to the well studied E. coli homologue, DnaK, which together suggest that HscC is a specialized chaperone. The basal ATPase cycle of HscC had k(cat) and K(m) values that were 8- and 10,000-fold higher than for DnaK. The HscC ATPase was not affected by the nucleotide exchange factor of DnaK GrpE and stimulated 8-fold by DjlC, a DnaJ protein with a putative transmembrane domain, but not by other DnaJ proteins tested. Substrate binding dynamics and substrate specificity differed significantly between HscC and DnaK. These differences are explicable by distinct structural variations. HscC does not have general chaperone activity because it did not assist refolding of a denatured model substrate. In vivo, HscC failed to complement temperature sensitivity of DeltadnaK cells. Deletion of hscC caused a slow growth phenotype that was suppressed after several generations. Triple knock-outs of all E. coli genes encoding Hsp70 proteins (DeltadnaK DeltahscA DeltahscC) were viable, indicating that Hsp70 proteins are not strictly essential for viability. An extensive search for DeltahscC phenotypes revealed a hypersensitivity to Cd(2+) ions and UV irradiation, suggesting roles of HscC in the cellular response to these stress treatments. Together our data show that the Hsp70 structure exhibits an astonishing degree of adaptive variations to accommodate requirements of a specialized function.

Adenosine Triphosphatases↗
PubMed2005

The role of the hinge loop in domain swapping. The special case of bovine seminal ribonuclease.

Bovine seminal ribonuclease (BS-RNase) is a covalent homodimeric enzyme homologous to pancreatic ribonuclease (RNase A), endowed with a number of special biological functions. It is isolated as an equilibrium mixture of swapped (MxM) and unswapped (M=M) dimers. The interchanged N termini are hinged on the main bodies through the peptide 16-22, which changes conformation in the two isomers. At variance with other proteins, domain swapping in BS-RNase involves two dimers having a similar and highly constrained quaternary association, mainly dictated by two interchain disulfide bonds. This provides the opportunity to study the intrinsic ability to swap as a function of the hinge sequence, without additional effects arising from dissociation or quaternary structure modifications. Two variants, having Pro19 or the whole sequence of the hinge replaced by the corresponding residues of RNase A, show equilibrium and kinetic parameters of the swapping similar to those of the parent protein. In comparison, the x-ray structures of MxM indicate, within a substantial constancy of the quaternary association, a greater mobility of the hinge residues. The relative insensitivity of the swapping tendency to the substitutions in the hinge region, and in particular to the replacement of Pro19 by Ala, contrasts with the results obtained for other swapped proteins and can be rationalized in terms of the unique features of the seminal enzyme. Moreover, the results indirectly lend credit to the hypothesis that the major role of Pro19 resides in directing the assembly of the non-covalent dimer, the species produced by selective reduction of the interchain disulfides and considered responsible for the special biological functions of BS-RNase.

Animals↗
PubMed2003

Causal inference in lead research: introduction to the special section on the neurobehavioral effects of environmental lead.

This Special Section on the Neurobehavioral Effects of Environmental Lead includes empirical reports from three major longitudinal prospective studies and a review of animal research modeling effects of lead on human cognition. This Introductory article addresses a fundamental controversy in lead and other epidemiologic research. It is argued that, contrary to conventional wisdom, valid causal inferences can be made from correlational research. Justification for this is to be found in contemporary frameworks drawn from the field of the philosophy of science; an essential, but often neglected perspective for such metatheoretical issues as causal inference. It is concluded that the nonexperimental methods described in the articles comprising this Special Section can, indeed, contribute to causal formulations of lead effects on human development, and that such inferences are not exclusive to experimental evidence.

Causality↗
PubMed2005

Host selection by the generalist aphid Myzus persicae (Hemiptera: Aphididae) and its subspecies specialized on tobacco, after being reared on the same host.

Decision-making during host selection by phytophagous insects has proved to be related to host range, with specialists taking faster decisions than generalists; however, this pattern fails to materialize in some host selection studies performed with aphids. Differences found in testing designs point to rearing effects on aphid host selection. To test whether specialization patterns derive from the nature of the aphid or as a consequence of rearing environment, host selection behaviours were compared between the generalist Myzus persicae (Sulzer) s.s. and its subspecies specialized on tobacco when reared on a common host and offered the choice of an alternative host and a non-host plant. Pre-alighting (host finding and attraction towards host volatiles) and post-alighting (leaf surface exploration and probing) behaviours did not differ between the generalist and the tobacco-specialist, except in the allocation of time to probing behaviour; furthermore, all specialists chose the host on which they performed best. Thus, although the specialist was not faster than the generalist, it showed a higher level of commitment to its preferred host plant.

Adaptation, Physiological↗
PubMed1998

Institutional Review Board issues related to special populations.

The present article begins with an introduction to the role of Institutional Review Boards (IRBs) in research activities in general and proceeds to issues IRBs face with relation to special populations, including children and terminally ill individuals, as well as developmentally disabled and cognitively impaired persons. A historical overview of research with these special populations is included, and the report concludes with a real-world example of how IRB-related issues with developmentally disabled and cognitively impaired individuals are discussed and resolved.

Child↗
PubMed1984

Respiratory distress in a special care baby unit in Nigeria.

Although respiratory distress is common among African newborn infants in special care, respiratory distress syndrome, which is the commonest cause of respiratory distress in other races, has been reported as uncommon among African infants. A prospective study of 312 consecutive newborn Nigerian infants admitted to a special care unit revealed 103 (33%) with respiratory distress. In 100 cases studied there was transient tachypnoea of the newborn ( TTN ) in 40% while specific diseases such as pneumonia and septicaemia, severe aspiration syndromes and respiratory distress syndrome (RDS) accounted for 25%, 19% and 12%, respectively. TTN and RDS occurred mostly among preterm infants with moderate perinatal asphyxia while severe aspiration syndrome was found among term infants with severe birth asphyxia. The study suggests that prevention and/or improved management of perinatal asphyxia and infections should reduce the incidence and mortality associated with neonatal respiratory distress.

Birth Weight↗
PubMed1992

Morbidity and mortality in the Special Care Baby Unit of New Mulago Hospital, Kampala.

The morbidity and mortality of admissions to the Special Care Baby Unit at New Mulago Hospital, Kampala are described for 1598 infants seen during the 12-month period of 1989. The overall neonatal mortality rate on the Unit was 18.0%, which has shown only slight improvement during the period 1984-1989. The major causes of death were, in descending order of frequency: birth asphyxia, respiratory distress syndrome, aspiration syndromes, very low birthweight, infection, anaemia and congenital malformations. Birth asphyxia was the most common cause of death in infants weighing over 2500 g while respiratory distress syndrome predominated among deaths below 2500 g. Birth injuries and transient tachypnoea of the newborn were also common reasons for admission. Difficulties of caring for infants requiring special care in a developing country are emphasized. These include inadequate equipment and supplies, poor investigative facilities and scarcity of well trained personnel. The situation is further aggravated by low morale among health workers due to poor working conditions.

Cause of Death↗
PubMedDate not supplied

Gender differences in the assessment of specialized treatments for substance abuse among people with severe mental illness.

A recent study examined the relative cost-effectiveness of three specialized interventions for treating people with both severe mental illness and substance abuse disorders: behavioral skills training, intensive case management, and 12-Step recovery. This article reports the changes in client psychosocial outcomes, psychiatric and substance abuse symptomatology, and service utilization and costs for the 31 women involved in the study, and compares these results to similar data on the men in the study sample and to the existing literature. Also presented are the most salient clinical impressions of the treating staff of issues affecting the course of treatment and outcomes for these women. Similarities were found in treated prevalence, service utilization, and related clinical issues in women with dual disorders compared to those reported in the existing psychiatric or substance abuse literature. Compared to men in the same sample, the women had higher functioning scores, more psychiatric symptomatology, and greater reductions in 24-hour acute or subacute treatment services used during the first six months of the specialized intervention programs. These results provide some insight into ways of serving dually diagnosed women more effectively in community-based treatment programs and of investigating these services more fruitfully.

Adult↗