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Biomedical subjects

A Whittaker

Publications and source records attributed to A Whittaker.

At least 19 recordsLinked to original sources

Refining in vitro digestibility assays: fractionation of digestible and indigestible peptides.

Typically, in vitro methods used for estimating the amount of ileal digestible AA do not exhaustively digest samples, and arbitrary methods for separating digestible from indigestible protein are used. This may lead to over- or underestimation of digestibility coefficients. A method that exhaustively digests proteins using pepsin and pancreatin was developed, and the first objective of this research was to confirm that exhaustive digestion was indeed appropriate and to determine the fractionation method for separating digestible from indigestible proteins. For this, three homoarginine-labeled animal proteins were prepared. Samples were subsequently digested in vivo and in vitro to determine which fraction should be considered indigestible, and in vitro followed by in vivo to determine whether the extent of digestion in vivo was improved by predigestion. In vivo, soluble but unabsorbed peptides were smaller than 1 kDa, suggesting that the size of soluble peptides is not what prevents their absorption. Thus, all in vitro-soluble proteins should be considered digestible. In vitro, 88 +/- 3% of the soluble peptides were smaller than 1 kDa, with the remainder between 1 and 5 kDa, suggesting that in vitro digestion is less complete. Predigested samples were digested in vivo to the same size distribution as the nonpredigested samples. The second objective was to test whether in vitro digestibility assays based on these principles equaled in vivo digestibility. For this, digestibility data for 25 animal proteins were compared. Results showed a lack of correlation between lysine digestibility coefficients; however, across samples, the extent of digestion did not differ for lysine (P = 0.71), threonine (P = 0.26), methionine (P = 0.18), or valine (P = 0.66), whereas in vitro digestibility coefficients were lower for (the less water-soluble) histidine (P = 0.05), isoleucine (P < 0.01), leucine (P < 0.01), and phenylalanine (P = 0.05). In conclusion, in vitro digestibility assays should exhaustively digest proteins to mimic in vivo digestibility. All in vitro-soluble peptides could be considered digestible, because in vivo, no large soluble peptides were observed whose size prevented them from being absorbed. However, an in vitro assay based on these principles lacked precision for highly water-soluble AA, and underestimated digestibility for other AA. Better solubilization of the digesta and more replicates may improve the in vitro assay further.

Amino Acids↗

Social network and social support characteristics amongst individuals recently discharged from acute psychiatric units.

This study compares the social support network of a diagnostically heterogeneous group of community mental health service users recently discharged from acute inpatient units, with that of a mental health service user comparison group with no history of hospital admission. Social data were elicited by a structured interview schedule (the Social Network Schedule). It was observed that the study group was characterized by smaller overall social networks, particularly within the primary network, but conversely the group had a greater proportion of service user peer contact. Few differences in perceived social support between groups were observed, although the study group reported fewer confidants. The implications of the study for nursing staff are discussed.

Acute Disease↗

A physical map of the human genome.

The human genome is by far the largest genome to be sequenced, and its size and complexity present many challenges for sequence assembly. The International Human Genome Sequencing Consortium constructed a map of the whole genome to enable the selection of clones for sequencing and for the accurate assembly of the genome sequence. Here we report the construction of the whole-genome bacterial artificial chromosome (BAC) map and its integration with previous landmark maps and information from mapping efforts focused on specific chromosomal regions. We also describe the integration of sequence data with the map.

Chromosomes, Artificial, Bacterial↗

The physical maps for sequencing human chromosomes 1, 6, 9, 10, 13, 20 and X.

We constructed maps for eight chromosomes (1, 6, 9, 10, 13, 20, X and (previously) 22), representing one-third of the genome, by building landmark maps, isolating bacterial clones and assembling contigs. By this approach, we could establish the long-range organization of the maps early in the project, and all contig extension, gap closure and problem-solving was simplified by containment within local regions. The maps currently represent more than 94% of the euchromatic (gene-containing) regions of these chromosomes in 176 contigs, and contain 96% of the chromosome-specific markers in the human gene map. By measuring the remaining gaps, we can assess chromosome length and coverage in sequenced clones.

Chromosomes, Human, Pair 1↗

Consulting about consulting: challenges to effective consulting about public health research.

OBJECTIVE: To understand barriers to obtaining input from consumers in developing public health research. METHODS: Documentation of a failed attempt at consumer consultation supplies information on barriers to effective involvement and conditions that must prevail to improve consultation. RESULTS: People are keen to be heard in the formulation of health research. However, competing demands and limited resources make it difficult for community groups to allocate scarce resources to consultation. Sometimes research issues may seem 'academic' and thus remote from the urgent priorities of the people with whom researchers wish to consult. Consultation may require more time than researchers on limited budgets can afford. CONCLUSIONS: Despite a general public health commitment to involving consumers in research development, obstacles to consultation make it difficult to incorporate it into the research agenda. IMPLICATIONS: Researchers and funding bodies will need to allocate resources to consumer consultation if it is to become the rule rather than the exception in public health research.

Australia↗

A comparison of the anthropometric, strength, endurance and flexibility characteristics of female elite and recreational climbers and non-climbers.

There is limited information on the anthropometry, strength, endurance and flexibility of female rock climbers. The aim of this study was to compare these characteristics in three groups of females: Group 1 comprised 10 elite climbers aged 31.3 +/- 5.0 years (mean +/- s) who had led to a standard of 'hard very severe'; Group 2 consisted of 10 recreational climbers aged 24.1 +/- 4.0 years who had led to a standard of 'severe'; and Group 3 comprised 10 physically active individuals aged 28.5 +/- 5.0 years who had not previously rock-climbed. The tests included finger strength (grip strength, finger strength measured on climbing-specific apparatus), flexibility, bent arm hang and pull-ups. Regression procedures (analysis of covariance) were used to examine the influence of body mass, leg length, height and age. For finger strength, the elite climbers recorded significantly higher values (P < 0.05) than the recreational climbers and non-climbers (four fingers, right hand: elite 321 +/- 18 N, recreational 251 +/- 14 N, non-climbers 256 +/- 15 N; four fingers, left hand: elite 307 +/- 14 N, recreational 248 +/- 12 N, non-climbers 243 +/- 11 N). For grip strength of the right hand, the elite climbers recorded significantly higher values than the recreational climbers only (elite 338 +/- 12 N, recreational 289 +/- 10 N, non-climbers 307 +/- 11 N). The results suggest that elite climbers have greater finger strength than recreational climbers and non-climbers.

Abdominal Muscles↗

Are grammatical representations useful for learning from biological sequence data?--a case study.

This paper investigates whether Chomsky-like grammar representations are useful for learning cost-effective, comprehensible predictors of members of biological sequence families. The Inductive Logic Programming (ILP) Bayesian approach to learning from positive examples is used to generate a grammar for recognising a class of proteins known as human neuropeptide precursors (NPPs). Collectively, five of the co-authors of this paper, have extensive expertise on NPPs and general bioinformatics methods. Their motivation for generating a NPP grammar was that none of the existing bioinformatics methods could provide sufficient cost-savings during the search for new NPPs. Prior to this project experienced specialists at SmithKline Beecham had tried for many months to hand-code such a grammar but without success. Our best predictor makes the search for novel NPPs more than 100 times more efficient than randomly selecting proteins for synthesis and testing them for biological activity. As far as these authors are aware, this is both the first biological grammar learnt using ILP and the first real-world scientific application of the ILP Bayesian approach to learning from positive examples. A group of features is derived from this grammar. Other groups of features of NPPs are derived using other learning strategies. Amalgams of these groups are formed. A recognition model is generated for each amalgam using C4.5 and C4.5rules and its performance is measured using both predictive accuracy and a new cost function, Relative Advantage (RA). The highest RA was achieved by a model which includes grammar-derived features. This RA is significantly higher than the best RA achieved without the use of the grammar-derived features. Predictive accuracy is not a good measure of performance for this domain because it does not discriminate well between NPP recognition models: despite covering varying numbers of (the rare) positives, all the models are awarded a similar (high) score by predictive accuracy because they all exclude most of the abundant negatives.

Bayes Theorem↗

Changes in leaf hexokinase activity and metabolite levels in response to drying in the desiccation-tolerant species Sporobolus stapfianus and Xerophyta viscosa.

The phosphorylation of glucose and fructose is an important step in regulating the supply of hexose sugars for biosynthesis and metabolism. Changes in leaf hexokinase (EC 2.7.1.1) activity and in vivo metabolite levels were examined during drying in desiccation-tolerant Sporobolus stapfianus and Xerophyta viscosa. Leaf hexokinase activity was significantly induced from 85% to 29% relative water content (RWC) in S. stapfianus and from 89% to 55% RWC in X. viscosa. The increase in hexokinase corresponded to the region of sucrose accumulation in both species, with the highest activity levels coinciding with region of net glucose and fructose removal. The decline of hexose sugars and accumulation of sucrose in both plant species was not associated with a decline in acid and neutral invertase. The increase in hexokinase activity may be important to ensure that the phosphorylation and incorporation of glucose and fructose into metabolism exceeded production from potential hydrolytic activity. Total cellular glucose-6-phosphate (Glc-6-P) and fructose-6-phosphate (Fru-6-P) levels were held constant throughout dehydration. In contrast to hexokinase, fructokinase activity was unchanged during dehydration. Hexokinase activity was not fully induced in leaves of S. stapfianus dried detached from the plant, suggesting that the increase in hexokinase may be associated with the acquisition of desiccation-tolerance.

Carbohydrate Metabolism↗

An aldose reductase homolog from the resurrection plant Xerophyta viscosa Baker.

An aldose reductase homologue (ALDRXV4) was cloned from the resurrection plant Xerophyta viscosa Baker using complementation by functional sufficiency in Escherichia coli. A cDNA library constructed from X. viscosa leaves dehydrated to 85%, 37% and 5% relative water contents (RWC) was converted into an infective phagemid library. Escherichia coli (sr1::Tn10) cells transformed with ds-pBluescript phagemids were selected on minimal medium plates supplemented with 1 mM isopropyl beta-D-thiogalactopyranoside and 1.25 M sorbitol. Nine cDNA clones that conferred tolerance to the osmotically stressed E. coli cells were selected. The phagemid from one clone contained the ALDRXV4 insert. The E. coli cells expressing ALDRXV4 were capable of tolerating the osmotic stress, whereas control cultures were not. The ALDRXV4 insert contained an open reading frame that can code for 319 amino acids, and the predicted protein had a calculated Mr of 35,667. Amino acid sequence comparisons revealed significant similarity to several aldose reductases, with the highest similarity to aldose reductase proteins from Hordeum vulgare, Bromus inermis and Avena fatua, in the order of 66%, 65% and 65% respectively. Northern blot analysis revealed that ALDRXV4 was expressed only under dehydration conditions in X. viscosa leaves. Western blot analysis detected a protein of 36 kDa under dehydration conditions only. Aldose reductase activity levels in X. viscosa leaves increased as the leaf RWC decreased, whereas there was no significant change in aldose reductase activity in Sporobolus stafianus as the leaf RWC decreased.

Aldehyde Reductase↗

A new member of the IL-1 receptor family highly expressed in hippocampus and involved in X-linked mental retardation.

We demonstrate here the importance of interleukin signalling pathways in cognitive function and the normal physiology of the CNS. Thorough investigation of an MRX critical region in Xp22.1-21.3 enabled us to identify a new gene expressed in brain that is responsible for a non-specific form of X-linked mental retardation. This gene encodes a 696 amino acid protein that has homology to IL-1 receptor accessory proteins. Non-overlapping deletions and a nonsense mutation in this gene were identified in patients with cognitive impairment only. Its high level of expression in post-natal brain structures involved in the hippocampal memory system suggests a specialized role for this new gene in the physiological processes underlying memory and learning abilities.

Amino Acid Sequence↗

Talk about cancer: environment and health in Oceanpoint.

Based on an ethnographic study, this paper explores one Australian community's 'popular epidemiology' of the role of the environment on health. Residents express concern about cancer risks due to contamination from a land-fill dump site and from radioactivity from previous mining activities. These concerns carry a range of meanings, not only regarding the threats to the physical place of Oceanpoint, but the social space the community occupies and the values they espouse. The perceptions of health risks in this location involve a contest over the cultural politics of place, the political economy of development and the sense of a former authentic 'community' that is being lost and disempowered from controlling its future.

Australia↗

Engendering stress in Australia: the embodiment of social relationships.

This study draws on data from an ethnographic study of health and illness in a suburb of a regional city of southeastern Australia. "Stress" was a significant emergent theme in one-third of 111 semistructured interviews, as well as focus groups and informal conversation. The researchers were able to construct a "lay epidemiology" in which stress was important in residents' understandings of the causes and symptoms of a range of health problems. The paper explores the different ways in which discourses of stress articulated the experience of structured gender relations among residents of Oceanpoint within the wider framework of a cultural critique of modernity in relation to the embodied self.

Australia↗

High-resolution physical map of the X-linked retinoschisis interval in Xp22.

X-linked retinoschisis (RS) is the leading cause of macular degeneration in young males and has been mapped to Xp22 between DXS418 and DXS999. To facilitate identification of the RS gene, we have constructed a yeast artificial chromosome (YAC) contig across this region comprising 28 YACs and 32 sequence-tagged sites including seven novel end clone markers. To establish the definitive marker order, a PAC contig containing 50 clones was also constructed, and all clones were fingerprinted. The marker order is: Xpter-DXS1317-(AFM205yd12-DXS7175-DXS7992) -60N8-T7-DXS1195-DXS7993-DXS7174 -60N8-SP6-DXS418-DXS7994-DXS7995-DXS7996-+ ++HYAT2-25HA10R-HYAT1-DXS7997-DXS7998- DXS257-434E8R-3542R-DXS6762-DXS7999-DXS 6763-434E8L-DXS8000-DXS6760-DXS7176- DXS8001-DXS999-3176R-PHKA2-Xcen. A long-range restriction map was constructed, and the RS region is estimated to be 1300 kb, containing three putative CpG islands. An unstable region was identified between DXS6763 and 434E8L. These data will facilitate positional cloning of RS and other disease genes in Xp22.

Chromosome Mapping↗

Anthropometric, strength, endurance and flexibility characteristics of elite and recreational climbers.

There has been remarkable development in the scope and quality of rock climbing in recent years. However, there are scant data on the anthropometry, strength, endurance and flexibility of rock climbers. The aim of this study was to compare these characteristics in three groups of subjects-elite rock climbers, recreational climbers and non-climbers. The 30 male subjects were aged 28.8 +/- 8.1 (mean +/- S.D.) years. Group 1 (n = 10) comprised elite rock climbers who had led a climb of a minimum standard of 'E1' (E1-E9 are the highest climbing grades) within the previous 12 months; Group 2 (n = 10) comprised rock climbers who had achieved a standard no better than leading a climb considered 'severe' (a low climbing grade category); and Group 3 (n = 10) comprised physically active individuals who had not previously done any rock climbing. The test battery included tests of finger strength [grip strength, pincer (i.e. thumb and forefinger) strength, finger strength measured on climbing-specific apparatus], body dimensions, body composition, flexibility, arm strength and endurance, and abdominal endurance. The tests which resulted in significant differences (P < 0.05) between the three groups included the bent arm hang (elite 53.1 +/- 1.32 s; recreational 31.4 +/- 9.0 s; non-climbers 32.6 +/- 15.0 s) and pull-ups (elite 16.2 +/- 7.2 repetitions; recreational 3.0 +/- 4.0 reps; non-climbers 3.0 +/- 3.9 reps); for both tests, the elite climbers performed significantly better than the recreational climbers and non-climbers. Regression procedures (i.e. analysis of covariance) were used to examine the influence of body mass and length. Using adjusted means (i.e. for body mass and leg length), significant differences were obtained for the following: (1) finger strength, grip 1, four fingers (right hand) (elite 447 +/- 30 N; recreational 359 +/- 29 N; non-climbers 309 +/- 30 N), (2) grip strength (left hand) (elite 526 +/- 21 N; recreational 445 +/- 21 N; non-climbers 440 +/- 21 N), (3) pincer strength (right hand) (elite 95 +/- 5 N; recreational 69 +/- 5 N; non-climbers 70 +/- 5 N) and (4) leg span (elite 139 +/- 4 cm; recreational 122 +/- 4 cm; non-climbers 124 +/- 4 cm). For tests 3 and 4, the elite climbers performed significantly better than the recreational climbers and non-climbers for any variable. These results demonstrate that elite climbers have greater shoulder girdle endurance, finger strength and hip flexibility than recreational climbers and non-climbers. Those who aspire to lead 'E1' standard climbs or above should consider training programmes to enhance their finger strength, shoulder girdle strength and endurance, and hip flexibility.

Abdominal Muscles↗

Qualitative methods in general practice research: experience from the Oceanpoint Study.

BACKGROUND: The Oceanpoint Study is a collaborative study between general practice and medical anthropology. METHODS: The study involved a qualitative ethnographic approach including long-term participant observation, in-depth interviews, health diaries and focus group discussions. Qualitative methods are suited to describing the phenomenological perspectives of people through the generation of rich detailed accounts which leave participants' perspectives intact. RESULTS: The use of these methods in this study has enabled the researchers to explore a range of community beliefs and practices concerning health and illness. The underlying concerns and approach of general practice medicine are similar to those of the qualitative research tradition. CONCLUSIONS: The experience of being a general practitioner parallels the experience of an ethnographer conducting qualitative research and the paper explores the similarities and differences between them and discusses the usefulness of such collaborative research.

Adult↗

Structure and orientation of the pore-forming peptide, melittin, in lipid bilayers.

Ten analogues of the 26-residue, bee venom peptide, melittin (H3N(+)-GIGAVLKVLTTGLPALISWIKRKRQQ-CONH2), were synthesized, each with 13C enrichment of a single peptide carbonyl carbon. These peptides were incorporated into bilayers of the diether lipid, ditetradecylphosphatidylcholine, aligned between stacked glass plates. Solid-state 13C nuclear magnetic resonance spectra were obtained as a function of the angle between the bilayer planes and the magnetic field of the spectrometers, and at temperatures above and below the lipid gel-to-liquid crystalline transition temperature, Tc. For bilayers aligned with the normal along the applied magnetic field there was no shift in the carbonyl resonances of residues Ile2, Ala4, Leu9, Leu13, or Ala15, with minor changes for residues Val8 and Ile20, and small changes at Val5, Leu6 and Ile17 on immobilization of the peptide below Tc. In contrast, the spectra for bilayers aligned at right angles to the field showed greatly increased anisotropy below Tc for all analogues. From these experiments it was evident that the peptide was well-aligned in the bilayers and reoriented about the bilayer normal. The observed reduced chemical shift anisotropies and the chemical shifts were consistent with melittin adopting a helical conformation with a transbilayer orientation in the lipid membranes. With the exception of Ile17, there was no apparent difference between the behaviour of residues in the two segments that form separate helices in the water-soluble form of the peptide, suggesting that in membranes the angle between the helices is greater than the 120 degrees observed in the crystal form.

Amino Acid Sequence↗