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Biomedical subjects

A Berry

Publications and source records attributed to A Berry.

At least 235 records · Page 13Linked to original sources
PubMedDate not supplied

Clues from Xanthomonas campestris about the evolution of aromatic biosynthesis and its regulation.

The recent placement of major Gram-negative prokaryotes (Superfamily B) on a phylogenetic tree (including, e.g., lineages leading to Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter calcoaceticus) has allowed initial insights into the evolution of the biochemical pathway for aromatic amino acid biosynthesis and its regulation to be obtained. Within this prokaryote grouping, Xanthomonas campestris ATCC 12612 (a representative of the Group V pseudomonads) has played a key role in facilitating deductions about the major evolutionary events that shaped the character of aromatic biosynthesis within this grouping. X. campestris is like P. aeruginosa (and unlike E. coli) in its possession of dual flow routes to both L-phenylalanine and L-tyrosine from prephenate. Like all other members of Superfamily B, X. campestris possesses a bifunctional P-protein bearing the activities of both chorismate mutase and prephenate dehydratase. We have found an unregulated arogenate dehydratase similar to that of P. aeruginosa in X. campestris. We separated the two tyrosine-branch dehydrogenase activities (prephenate dehydrogenase and arogenate dehydrogenase); this marks the first time this has been accomplished in an organism in which these two activities coexist. Superfamily B organisms possess 3-deoxy-D-arabino-heptulosonate 7-P (DAHP) synthase as three isozymes (e.g., in E. coli), as two isozymes (e.g., in P. aeruginosa), or as one enzyme (in X. campestris). The two-isozyme system has been deduced to correspond to the ancestral state of Superfamily B. Thus, E. coli has gained an isozyme, whereas X. campestris has lost one. We conclude that the single, chorismate-sensitive DAHP synthase enzyme of X. campestris is evolutionarily related to the tryptophan-sensitive DAHP synthase present throughout the rest of Superfamily B. In X. campestris, arogenate dehydrogenase, prephenate dehydrogenase, the P-protein, chorismate mutase-F, anthranilate synthase, and DAHP synthase are all allosteric proteins; we compared their regulatory properties with those of enzymes of other Superfamily B members with respect to the evolution of regulatory properties. The network of sequentially operating circuits of allosteric control that exists for feedback regulation of overall carbon flow through the aromatic pathway in X. campestris is thus far unique in nature.

3-Deoxy-7-Phosphoheptulonate Synthase↗
PubMedDate not supplied

Neonatal echoencephalography.

The recent development of high-resolution real-time ultrasound scanners has coincided with the awareness of the high incidence of intracranial haemorrage in low birthweight babies, resulting in a considerable expansion in the use of echoencephalography in newborns in recent years. The uses are now further expanded and an overview of the subject is presented.

Brain Neoplasms↗
PubMedDate not supplied

A challenge for clinical nurses: a new nursing role.

As a result of difficulties in attracting resident medical officers (RMOs) to the outer western suburbs of Sydney, the intensive care unit at Nepean Hospital created a new nursing position in 1992 called the clinical assistant (CA). This position was trialed and, after a successful period in the intensive care unit, it was expanded to the surgical, pediatric, and mental health divisions. The generic job description of the CA is comprehensive and includes advanced clinical, educational, research, and managerial components. There are a number of variations within the areas of practice. For example, within the clinical component, the intensive care CA is expected to be able to insert central venous and arterial catheters, whereas the mental health CA adopts a full caseload and is responsible for patient assessment and management. A working party was established in 1995 and comprised previous and current CAs, an education manager, a senior nursing administrator, and representatives from personnel and the New South Wales Nursing Association (nursing union). The working party conducted an extensive evaluation of this new nursing role, and the recommendations that followed received a positive response from the hospital management.

Clinical Competence↗
PubMedDate not supplied

Early disruption of the mother-infant relationship: effects on brain plasticity and implications for psychopathology.

Early environmental manipulations can impact on the developing nervous system, contributing to shape individual differences in physiological and behavioral responses to environmental challenges. In particular, it has been shown that disruptions in the mother-infant relationship result in neuroendocrine, neurochemical and behavioural changes in the adult organism, although the basic mechanisms underlying such changes have not been completely elucidated. Recent data suggest that neurotrophins might be among the mediators capable of transducing the effects of external manipulations on brain development. Nerve growth factor and brain-derived neurotrophic factor are known to play a major role during brain development, while in the adult animal they are mainly responsible for the maintenance of neuronal function and structural integrity. Changes in the levels of neurotrophic factors during critical developmental stages might result in long-term changes in neuronal plasticity and lead to increased vulnerability to aging and to psychopathology.

Aging↗
PubMedDate not supplied

Effects of the fourth chromosome on the sterility of hybrids between Drosophila simulans and its relatives.

Genetic analysis of the fourth chromosome of Drosophila simulans shows that it has no effect on either male or female fertility in hybrids with two sibling species, D. mauritiana and D. sechellia. The lack of effect holds even when the D. simulans chromosome is homozygous in a foreign genetic background. The absence of major fourth chromosome "sterility genes" in these hybridizations contrasts with the presence of a fourth-chromosome gene causing complete male sterility in hybrids of the more distantly related species D. melanogaster and D. simulans.

Animals↗
PubMedDate not supplied

Healing of transected equine superficial digital flexor tendons with and without tenorrhaphy.

Healing of transected superficial digital flexor tendons was evaluated mechanically and histologically in eight horses. Tendons sutured with polyglyconate had higher loads at failure than nonsutured tendons at weeks 5 and 9. The tendon stress at failure (force per unit area) was higher in the sutured tendons at week 5 but not at week 9, reflecting the increased size of the scar at week 9. Histologically, scars after tenorrhaphy were consistently more mature than nonsutured tenotomy scars. The mean maturity score for sutured tendons was higher than for nonsutured tendons at weeks 5 and 9. Overall, these data support tenorrhaphy with absorbable suture.

Animals↗