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Biomedical subjects

R A Moss

Publications and source records attributed to R A Moss.

At least 19 recordsLinked to original sources
PubMed2001

The 2-norbornyl cation via the fragmentations of exo- and endo-2-norbornyloxychlorocarbenes: distinction without much difference.

exo- and endo-2-norbornyloxychlorocarbenes (7) were generated photochemically from the corresponding diazirines (6). Both carbenes fragmented to [2-norbornyl cation (carbon monoxide) chloride] ion pairs in MeCN or 1,2-dichloroethane solutions. Products included exo-norbornyl chloride (8), endo-norbornyl chloride (9), norbornene (10), and nortricyclene (11). Fragmentation activation energies were very low (< approximately 4 kcal/mol) and, as a result, the (laser flash photolytic) rate constants for fragmentation were essentially identical for exo-7 and endo-7 ( approximately 5 x 10(5) s(-1) in MeCN). Due to chloride return within the ion pairs, product distributions from exo- and endo-7 differed, with more endo-chloride formed from the endo-carbene: the 8/9 product ratio in MeCN was approximately 41 from exo-7, but only 4.6 from endo-7. Norbornene, formed by proton transfer to Cl(-) within the ion pairs, was a major product in both cases (44% from exo-7 and 62% from endo-7). In MeOH/MeCN, up to 28% of exo-2-norbornyl methyl ether formed at the expense of some of the norbornene, but even in 100% MeOH, the norbornyl chloride products of ion pair return still accounted for 46% and 31% of the exo-7 and endo-7 product mixtures (accompanied by 26-32% of norbornene). Electronic structure calculations on the ground states and fragmentation transition states of exo-7 and endo-7 are presented.

Journal Article↗
PubMed2001

SbF(5)-mediated reactions of oxafluorodiazirines.

[reaction: see text] The reaction of benzyloxyfluorodiazirine (3) with SbF(5) in benzene gives PhCH(2)OCF, which undergoes SbF(5)-mediated fragmentation to PhCH(2)(+), CO, and SbF(6)(-); the benzyl cation alkylates benzene to yield diphenylmethane. Phenoxyfluorodiazirine (4) reacts with SbF(5) in benzene to give PhOCF and (ultimately) triphenylmethane by a pathway that avoids fragmentation.

Antimony↗
PubMed2001

Rearrangement kinetics of spiropentylchlorocarbene, [3]triangulylchlorocarbene, and related species.

[structure: see text] Absolute rate constants were measured for the 1,2-CH(2), 1,2-cyclopropyl, and 1,2-CMe(2) rearrangements of spiropentylchlorocarbene (5), [3]triangulylchlorocarbene (6), and tetramethylcyclopropylchlorocarbene (7). The factors responsible for the observed relative migratory aptitudes (cyclopropyl > CH(2) > CMe(2)) were analyzed with the aid of electronic structure calculations.

Journal Article↗
PubMed1999

Remote substituent effects on phenylchlorocarbene C-H insertion reactions.

[structure: see text] Phenylchlorocarbene inserts into the tertiary CH bonds of 1,3-dimethyladamantane and 1-X-adamantanes (X = H, OMe, COOMe, Cl, CN). There is a good correlation between the relative rate constants for these insertions and the inductive substituent constants, sigma1(X), with rho = -1.5. Absolute rate constants for the insertions range from 2.5 x 10(5) M(-1) s(-1) for Ad-Me2 to 2.5 x 10(4) M(-1) s(-1) for Ad-CN. B3LYP/6-31G* calculations give a good account of reactivity in these systems.

Journal Article↗
PubMed1997

Activation of the receptor for advanced glycation end products triggers a p21(ras)-dependent mitogen-activated protein kinase pathway regulated by oxidant stress.

Advanced glycation end products (AGEs) exert their cellular effects on cells by interacting with specific cellular receptors, the best characterized of which is the receptor for AGE (RAGE). The transductional processes by which RAGE ligation transmits signals to the nuclei of cells is unknown and was investigated. AGE-albumin, a prototypic ligand, activated p21(ras) in rat pulmonary artery smooth muscle cells that express RAGE, whereas nonglycated albumin was without effect. MAP kinase activity was enhanced at concentrations of AGE-albumin, which activated p21(ras) and NF-kappaB. Depletion of intracellular glutathione rendered cells more sensitive to AGE-mediated activation of this signaling pathway. In contrast, signaling was blocked by preventing p21(ras) from associating with the plasma membrane or mutating Cys118 on p21(ras) to Ser. Signaling was receptor-dependent, because it was prevented by blocking access to RAGE with either anti-RAGE IgG or by excess soluble RAGE. These data suggest that RAGE-mediated induction of cellular oxidant stress triggers a cascade of intracellular signals involving p21(ras) and MAP kinase, culminating in transcription factor activation. The molecular mechanism that triggers this pathway likely involves oxidant modification and activation of p21(ras).

Alkyl and Aryl Transferases↗
PubMed1995

Oral habits and TMJ dysfunction in facial pain and non-pain subjects.

Multifactorial theories for facial pain aetiology have been proposed in the past, although little research has been produced to support a multifactorial aetiology. The present study assessed self-rated oral habits over a 7 day period for facial pain and non-pain subjects with and without a clinical symptom of TMJ dysfunction. The results indicate a significant effect for TMJ dysfunction and teeth clenching and an interaction between TMJ dysfunction and facial pain for biting of the lips and mouth. A significant chi-square test showed that most non-pain controls with TMJ dysfunction reported that they never clenched. The results are discussed in terms of support for a multifactorial aetiology in some facial pain patients and the need for future research to delineate subgroups of facial pain and non-pain subjects.

Adult↗
PubMed1990

Effect of pCPA on nicotine-induced analgesia.

This study investigated the effect of para-chlorophenylalanine (pCPA), on nicotine-induced analgesia. pCPA reduces physiological levels of 5-HT, a neurotransmitter that has been linked to pain. The effects of naloxone HCl and mecamylamine HCl on this analgesia were also assessed. Subjects were 24 albino rats. Each group of eight rats was injected subcutaneously (SC) with nicotine sulphate, followed by an intraperitoneal (IP) injection of one of the potential antagonists. Behavioral analgesia was assessed using the tail-flick test. Data analysis revealed that pCPA did not affect nicotine-induced analgesia. Consistent with past research, naloxone also had no effect, and mecamylamine effectively eliminated this analgesia. The results are interpreted in light of current knowledge of this behavioral analgesia and pain perception, in general.

Analgesia↗
PubMed1990

An accurate tip rhinoplasty marking technique.

A marking technique is presented for use in tip rhinoplasty. It enables the intended location of the lower lateral cartilage resection border to be transferred from the external to the vestibular nasal surface.

Anthropometry↗
PubMed1989

Oral habits in common between tension headache and non-headache populations.

Previous research has suggested a relationship between migraine pain and oral habits. The present study was designed as a replication of a prior study that found self-reported higher frequencies of certain oral habits in migraine as opposed to tension headache and non-headache groups. Three groups of subjects (common migraine, tension headache and non-headache) were given a single questionnaire in which five oral habits (i.e. teeth clenching, jaw jutting, cupping the chin in the hand, and resting the right and left side of the face on the hand) were rated on a 0 (not at all) to 10 (almost always) scale. Significant main effects were obtained for groups and oral habits in a 3 (groups) X5 (oral habits) ANOVA. Post hoc Tukey tests revealed the common migraine group reported significantly more frequent oral habits than did the tension headache group. The non-headache control group did not differ significantly from either headache group. Discussion focuses on the need for continued research in this area.

Adult↗
PubMed1987

An atraumatic suture technique for advancing the proximal end of a severed digital flexor tendon through the pulley system.

One may encounter difficulty in attempting to advance the proximal digital flexor tendon into the pulley system. The use of (1) a purse-string suture around the tendon end, and (2) simultaneous prolonged tension on both the purse-string and repair sutures may be helpful. Tension on the purse-string suture converts the shape of the tendon end from an accordion into a bullet, easing its entry into the pulley tunnel.

Humans↗
PubMed1987

The influence of sleep duration on headache pain and frontalis EMG.

Recent evidence has been presented suggesting that 'depression' headaches and classic migraines may be related to extended sleep duration. This analogue study was designed to evaluate the possibility that mild to moderate headaches induced by excessive sleep might be related to increased muscle activity. Eight subjects who experienced headaches as a function of increasing sleep duration by 2 h were evaluated in headache (i.e., extended sleep) and a non-headache (i.e., normal sleep) conditions. Sex- and sleep-duration matched controls were evaluated under the same sleep conditions, although none experienced headaches. Frontalis electromyographic (EMG) data were evaluated in a 2 X 2 analysis of variance. The results indicated no EMG differences between groups or across sleep conditions, even though all experimental subjects experienced headaches on the extended sleep night. Discussion focuses on the implication of these results for future headache research.

Chronic Disease↗
PubMed1987

Masticatory muscle activity as a function of parafunctional, active and passive oral behavioural patterns.

Oral behavioural patterns have received limited empirical support for their causal role in the development of head and facial pain. The present study was designed to assess electromyographic (EMG) variations in six muscle groups (i.e., bilateral masseter, temporalis and orbicularis oris) as a function of various oral behavioural patterns. A second purpose was to determine whether mandibular movement patterns and specific oral behaviours could be predicted by EMG patterns. Eleven non-pain subjects followed each of twenty oral behavioural patterns while EMG was recorded. Electromyographic change scores were computed for each behaviour relative to baseline measures. Initial analyses were performed using factorial repeated measures ANOVAS. Using post hoc analyses as general guides, specific EMG criteria were developed for classifying mandibular movements. For most subjects, EMG patterns accurately classified teeth clenching, protrusive/retrusive movements, right movements, left movements and lip movement patterns. Wide individual variations were found among muscle groups for identical behaviours. The association between particular oral behaviours and EMG patterns may explain 'sinus' headaches and certain types of facial pain.

Adolescent↗