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Biomedical subjects

S Collins

Publications and source records attributed to S Collins.

At least 181 records · Page 10Linked to original sources
PubMed1993

Is there only one type of male handicap?

The handicap principle has been one of the most important developments in sexual selection theory. Numerous theoretical papers have considered whether extreme male ornaments could have arisen through female choice by being handicaps to the male. These models have been defined as belonging to one of three categories: (i) Zahavi's (J. theor. Biol. 53, 205 (1975)); (ii) the revealing; or (iii) the condition-dependent handicap. Here I discuss whether the division is still helpful for empirical purposes, or whether handicaps are not best considered as being condition dependent. I argue that in fact the revealing and condition-dependent handicaps are indistinguishable empirically, and that the 'Zahavi' handicap models arose due to a misunderstanding of what Zahavi originally proposed, which was in fact a condition-dependent handicap.

Animals↗
PubMed1993

Cloning and sequence analysis of the human beta 1-adrenergic receptor 5'-flanking promoter region.

We present 3.1 kb of the nucleotide sequence from the 5'-flanking region of the human beta 1-adrenergic receptor gene. The first 1.0 kb upstream from the translational start site is composed of 72% G + C residues. The sequence was analyzed for the presence of transcriptional regulatory elements and contains putative thyroid hormone, glucocorticoid hormone and cAMP response elements. These putative hormone response elements support physiological evidence that thyroid and glucocorticoid hormones regulate beta 1AR function by affecting receptor expression in tissues such as heart and adipose, where beta 1-adrenergic receptors are important regulators of heart rate and lipolysis, respectively.

Base Sequence↗
PubMed1993

Recent perspectives on the molecular structure and regulation of the beta 2-adrenoceptor.

The recent cloning of the beta 2-AR and other members of the adrenergic receptor family and related molecules has generated a flood of new information about the structure of this ubiquitous class of receptor molecules, and the ways in which their unique structures determine their function. Agonists interact with the receptor-binding pocket and somehow trigger conformational changes in the cytoplasmic portions of the receptor. These intracellular changes are then transmitted to the G-protein alpha-subunit. Phosphorylation of the receptor by several protein kinases and subsequent binding of additional cytosolic factors appear to be a major step in the control of receptor function. Changes in receptor gene expression which regulate receptor number and responsiveness provide another means to regulate transmembrance signalling. The realization that G-protein-coupled receptors are transcriptionally regulated by their own second messengers indicates that the parallels among the various members of this receptor family extend beyond their structural homologies, of 7 transmembrane segments and G-protein coupling, to include the genetic aspects of their regulation.

Animals↗
PubMed1993

Decreasing the risk of implantation of cancer cells intraoperatively.

Maneuvers are suggested to decrease the likelihood of disseminating and implanting cancer cells in wounds during head and neck oncologic surgery, and thereby the risk of local-regional recurrence. These include occlusive covering of fresh tracheotomy sites and areas of skin ulceration, excising the primary tumor before performing neck dissection(s) to avoid contamination of uninvolved tissue planes, irrigation of the field with hypotonic solution after removal of the primary tumor, and using clean instruments and apparel when moving between anatomical sites (e.g., donor flaps/grafts, skull base extensions, percutaneous or standard gastrostomies, etc.).

Head and Neck Neoplasms↗
PubMed1992

Somatic sympathetic vasomotor changes documented by medical thermographic imaging during acupuncture analgesia.

Acupuncture is widely used for pain relief in many musculoskeletal disorders, and evidence suggests that modulation of the sympathetic nervous system responses which play an integral part in somatic pain, is an important mechanism of acupuncture action. This prospective study of 20 patients with neck and arm pain measured finger temperature, controlled by somatic sympathetic vasomotor activity before and after needle acupuncture. Responses were correlated with visual analogue scale (VAS) of pain severity. An association was found between pain relief and reduced sympathetic vasomotor activity. In 10 patients with significant reduction in visual analogue scale (VAS) pain (p less than .05), the mean change in temperature (delta t degrees C) was 0.55 (SD +/- 0.86) with significant difference in pre to post treatment temperatures (p less than .01). In 10 patients without significant pain relief on VAS scoring (p greater than .05), the mean t degrees C was 0.20 (SD +0.72) without significant difference in pre to post treatment temperatures (p greater than .05). The relevance of somatic sympathetic influences on musculoskeletal pain and modulation of sympathetic activity by acupuncture will be discussed.

Acupuncture Analgesia↗
PubMed1992

A cytotonic, cholera toxin-like protein produced by Campylobacter jejuni.

1. Campylobacter jejuni is a major cause of gastroenteric infection. 2. This organism appears to produce both cytotonic and cytotoxic virulence factors. 3. We report here that culture filtrates of some clinical isolates of C. jejuni induce elongation of Chinese hamster ovary (CHO) cells in vitro but do not cause inhibition of fluid absorption in the rat ileum. 4. These culture filtrates contain low levels of a protein which cross-reacts immunologically with the cholera toxin. 5. The cholera toxin-like protein of C. jejuni behaved identically to cholera toxin on non-denaturing polyacrylamide gel electrophoresis. 6. Under denaturing conditions, however, this protein displayed no subunit structure and a molecular weight of approximately 50 kDa with many higher molecular weight aggregates. 7. In conclusion, isolates of C. jejuni produced small amounts of enterotoxin when grown in vitro. 8. The toxin cross-reacted immunologically with cholera toxin and has a similar native structure, but does not appear to possess subunits.

Animals↗
PubMed1992

From ligand binding to gene expression: new insights into the regulation of G-protein-coupled receptors.

Transmembrane signaling systems relay information from the exterior to the interior of a cell, through a series of complex protein-protein interactions and second messenger cascades. One such system consists of the G-protein-coupled receptors, which interact with G proteins upon ligand binding, and in turn activate an effector molecule. The receptor is the first component in this signaling cascade and is subject to considerable regulation. Recent studies have shown that these regulatory events can occur at the levels of receptor protein modification and receptor gene expression. Interestingly, some of these processes appear to be mediated by the same second messenger systems that these receptors activate, which leads to various forms of positive and negative feedback regulation.

Amino Acid Sequence↗
PubMed1992

Acyloin formation by benzoylformate decarboxylase from Pseudomonas putida.

Whole cells and cell extracts of Pseudomonas putida grown in a medium containing ammonium mandelate have the capacity to produce the acyloin compound 2-hydroxypropiophenone when incubated with benzoylformate and acetaldehyde. Benzaldehyde and benzyl alcohol were formed as reaction by-products. The enantiomeric excess of the 2-hydroxypropiophenone product was found to be 91 to 92%. The absolute configuration of the enzymatically prepared product at the carbinol carbon was found to be S. The thiamine PPi-linked enzyme benzoylformate decarboxylase, purified to give a single protein band on polyacrylamide gel electrophoresis, was shown to be responsible for the catalysis of this novel condensation reaction.

Benzaldehydes↗