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Biomedical subjects

E W Small

Publications and source records attributed to E W Small.

At least 37 records · Page 2Linked to original sources
PubMed1985

The intrinsic tyrosine fluorescence of histone H1. Steady state and fluorescence decay studies reveal heterogeneous emission.

In wavelength-resolved steady state spectra we observe three different kinds of emission from histone H1, a class A protein with only a single tyrosine residue. Unfolded H1 emissions that peak at approximately 300 and 340 nm can both be excited maximally at approximately 280 nm. Another, peaking much further to the red at approximately 400 nm, can be excited maximally at approximately 320 nm. The 300-nm fluorescence can be resolved by lifetime measurements into three components with decay times of approximately 1, 2, and 4 ns. On sodium-chloride-induced refolding of H1, simplification of the emission properties occurs. The 340 and 400-nm components disappear while the two shorter lifetime components of the 300-nm band diminish in amplitude and are replaced by the 4-ns decay. We believe that the 340-nm emission is tyrosinate fluorescence resulting from excited-state proton transfer. The origin of the 400-nm emission remains uncertain. We assign the 1 and 2-ns components of the 300-nm emission to two states of tyrosine in denatured H1 and the 4-ns decay to fluorescence of the single tyrosine residue in the globular region of refolded H1. Our results support the contention that salt induced folding of H1 is a cooperative two state process, and permit us to better understand the previously reported increases in fluorescence intensity and anisotropy on salt-induced folding.

Animals↗
PubMed1984

Effects of pH on the stability of chromatin core particles.

Chromatin core particles near physiological ionic strength undergo a reversible transition induced by changes in pH near neutrality. While sedimentation studies indicate no significant effect on size or shape, changes in tyrosine fluorescence anisotropy and in circular dichroism suggest a somewhat looser structure at high pH. Further support of this suggestion is given by high salt dissociation experiments; at pH 8 core particles begin to show changes at lower salt concentration than at pH 6. The pH transition appears unaffected by the presence of Mg2+ but can be blocked by crosslinking of the histones. A possible relationship is suggested between this transition and increases in intracellular pH which correlate with enhancement in several aspects of cellular activity including DNA replication.

Animals↗
PubMed1984

F/F deconvolution of fluorescence decay data.

An approach for the deconvolution of multiexponential fluorescence decay data in which a single exponential decay is used in place of the usual excitation profile is described. For analysis by the method of moments, the resulting decay lifetimes are identical to those in the multiexponential decay, while the pre-exponential factors are a simple function of the true values and the parameters of the single exponential decay. This approach, which we call the F/F deconvolution method, is capable of eliminating the errors in decay analyses which arise from the wavelength dependence of the instrument response function.

Computers↗
PubMed1982

Effects of pH on low-salt transition of chromatin core particles.

The low-salt transition of chicken erythrocyte core particles containing uniform 145 base pair DNA was studied as a function of pH and of salt concentration. Intrinsic tyrosine fluorescence was used to follow the changes. Potassium salts of the anions C1-, H2PO4-, and SO4(2-) were indistinguishable in their ability to affect the transition. Divalent cations (Mg2+, Mn2+, Ca2+) were effective at 36-fold lower total concentration than monovalent cations (Li+, Na+, K+, Tris+), but no significant differences were observed within the two classes of cations. These results indicate that cation binding to the core particle is involved in the transition. At pH 9 the transition was broadened and shifted to higher monovalent cation concentration as compared to that at pH 6. At both pHs the fluorescence changes could be resolved into two steps by numerical least-squares analysis. On the basis of what is known about histone--histone interactions, a two-step mechanism is suggested, involving changes in the interactions between dimers of histones 2a and 2b with a tetramer of histones 3 and 4. The pH-induced changes appear to be correlated with a structural transition, which was detected as a function of pH at near physiological ionic strength (0.1 M). This structural change was accompanied by a small decrease in the tyrosine fluorescence anisotropy. An apparent pKa value near 7 is indicated, suggesting that the structural changes involved may be of physiological significance.

Animals↗
PubMed1980

Analysis of nonexponential fluorescence decay data by a method of moments.

A method of moments is presented for the analysis of convoluted fluorescence decay data when the impulse response function is given by f(t) = alpha exp (-At - Bt1/2). Examples of this method are given using both simulated and measured fluorescence decays. It is also shown that this method, used with moment index displacements, will correct for light-scatter leakage, zero-point time shifts, and slow lamp drift.

Benz(a)Anthracenes↗
PubMed1979

Aggressive ossifying fibroma of the maxilla: review of the literature and report of case.

A case of a large aggressive ossifying fibroma of the maxilla has been presented. Review of the literature shows the literature shows the difficulty in establishing a definitive diagnosis through any single diagnostic modality. Much of this is due to the confusion surrounding classification of the tumor. Adjunctive radiographic and nuclear medicine diagnostic aids were utilized, as were clinical, laboratory, and histopathologic studies, in resolving the diagnostic questions posed by this large and aggressive tumor. Surgical intervention through conservative enucleation produced few operative or postoperative difficulties and minimal residual deformity. Differentiation of ossifying fibroma from other benigh and malignant neoplasms as well as fibrous dysplasia is important in the correct management of this lesion.

Adolescent↗
PubMed1977

Arteriovenous malformation of the mandible: report of case.

A case of a potentially lethal arteriovenous malformation of the right side of the mandible has been presented. Procedures that may be helpful in diagnosing the lesion have been discussed, and a protocol for treatment of these lesions in the mandible has been proposed. Research of the cause and management of these lesions is greatly needed.

Adult↗
PubMed1976

Emotional response to intravenous delta9tetrahydrocannabinol during oral surgery.

The administration of delta9THC intravenously as a premedicant to oral surgery resulted in acute pronounced elevations in anxiety states, a predominance of dysphoria over euphoria, and varying degrees of psychotic-like paranoiac thought. Neural effects that appeared to promote these effects included distortions of perception with sensory delusions, and heightened sensory receptiveness including antalgesic impressions of surgery; autonomic and visceral arousal greater than control or placebo levels; lack of overt behavioral signals of distress due to depersonalization; and time disintegration leading to fear-inducing misinformation about real surgical events. Introverted subjects who generally were inclined to rely on drug solutions to their problems tended to respond poorly to surgical pain and anxiety with delta9THC. These results, obtained from subjects considered to have levels of presurgical apprehension that were average or below average, suggest that the environment in which high doses of cannabinols are experienced is a potent factor in determining the quality of the emotional response. A surgical environment containing even the mild stress of outpatient oral surgery appears to have the potential to precipitate undesirable emotional responses among cannabinol-intoxicated patients. There is continued high-level social use of cannabinols inour society, with an estimate of 40% to 55% among the college-age group seen frequently by oral surgeons. Results of this study suggest that clinicians should be prepared to detect the subtle signs of marijuana intoxication to protect their patients from further psychophysiologic complications during surgery.

Adolescent↗
PubMed1975

An appliance that permits early mobilization after correction of mandibular prognathism.

With certain orthognathic surgery patients, such as epileptics, severe asthmatics, or those with other medical problems that increase risk during intermaxillary fixation, there occasionally may be an indication for a reduced fixation time. By using Vitallium mesh for stability, immobilization for 2 to 2 1/2 weeks has proved to be sufficient in a limited number of cases. Mobilization before two weeks has not been attempted. The procedure, however, is not recommended as a routine method of fixation.

Humans↗