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Biomedical subjects

B E Smith

Publications and source records attributed to B E Smith.

At least 163 records · Page 9Linked to original sources
PubMed1982

Prediction of modeled velopharyngeal orifice areas during steady flow conditions and during aerodynamic simulation of voiceless stop consonants.

Results of a small number of studies (Warren and DuBois, 1964; Lubker, 1969; Smith and Weinberg, 1980; Horii and Lang, 1981) have led to expression of divergent views concerning the accuracy of modeled velopharyngeal orifice area estimates obtained on the basis of hydrokinetic principles. In this work, the hydrokinetic equation (Warren and DuBois, 1964) was subjected to experimentation: (1) in which flow rates through a vocal tract model were not varied and (2) in which flow rates were varied to simulate pressure/flow events found during voiceless, stop consonant production. With consideration given to instrumental and procedural factors, results indicated that accurate estimates of modeled velopharyngeal orifice areas can be obtained during steady flow conditions and during alternating flow conditions when measurements are made at airflow peaks. Results were interpreted to provide strong support for clinical and research use of the hydrokinetic equation to predict velopharyngeal orifice areas during stop consonant production.

Forecasting↗
PubMed1981

A 31P-NMR study of mono- and dimagnesium complexes of adenosine 5'-triphosphate and model systems.

31P-NMR chemical shifts and spin-lattice relaxation times of ATP (adenosine 5'-triphosphate), ribose 5'-triphosphate and tripolyphosphate show closely similar behaviour in aqueous solution at pH 7.5 on titration with Mg2+. The results are interpreted in terms of formation of 1 : 1 and 2 : 1 (dimagnesium) complexes with Mg2+ bound exclusively to the triphosphate chain. Stability constants for these complexes are reported. It is suggested that the predominant form of the 1 : 1 complexes has Mg2+ bound in tridentate manner (via non-bridging oxygen) to the alpha, beta and gamma phosphorus atoms; whilst that of the 2 : 1 complexes has each Mg2+ bound in bidentate manner, one to the alpha and beta, and the other to the beta and gamma, phosphorus positions.

Adenosine Triphosphate↗
PubMed1981

Black lung: the social production of disease.

The black lung movement that erupted in West Virginia in 1968 was not simply a struggle for recognition of an occupational disease; it grew into a bitter controversy over who would control the definition of that disease. This article examines the historical background and medical politics of that controversy, arguing that black lung was socially produced and defined on several different levels. As a medical construct, the changing definitions of this disease can be traced to major shifts in the political economy of the coal industry. As an occupational disease, the history of black lung is internally related to the history of the workplace in which it is produced. As the object of a mass movement, black lung acquired a political definition that grew out of the collective experience of miners and their families. The definition of disease with which black lung activists challenged the medical establishment has historical roots and justification; their experience suggests that other health advocates may need to redefine the diseases they hope to eradicate.

Coal Mining↗
PubMed1980

A Mössbauer spectroscopic investigation of the redox behaviour of the molybdenum-iron protein from Klebsiella pneumoniae nitrogenase. Mechanistic and structural implications.

The redox properties of the nitrogenase Mo-Fe protein from Klebsiella pneumoniae have been monitored by 57Fe Mössbauer spectroscopy between -460 and -160mV (relative to the normal hydrogen electrode). Two redox processes associated with the atoms of the protein were observed. One at -216mV (pH 8.7) was associated with the Fe-Mo cofactor centres in the protein and allowed identification of the Mössbauer parameters of the oxidized form of these centres. The other redox process at -340mV (pH 8.7) was associated with species M5 [Smith & Lang (1974) Biochem. J. 137, 169-180]. This latter redox process may be involved in enzyme turnover. The oxidized form of species M5 interacts magnetically with species M4. The structural implications of the data have been considered in relation to other published data. It is concluded that an unequivocal assignment of the M4 and M5 atoms to Fe-S cluster types is not yet possible.

Chemical Phenomena↗
PubMed1980

Continuous epidural infusion of fentanyl for postoperative analgesia.

A continuous epidural infusion of fentanyl was used for control of postoperative pain in a series of 30 patients who had received an epidural anaesthetic for general surgical procedures. Fentanyl was originally administered at a maximal rate of 50 micrograms/hr but later reduced to 25 micrograms/hour or less. Satisfactory analgesia was provided in 24 patients, who required no other form of analgesia whatsoever. Three patients derived significant analgesia from the infusion, but did require occasional small supplementary doses of opiates. Three patients derived little or no benefit from the procedure. The only noticeable side effect was nausea and vomiting, which was less of a feature with the weaker solution. The method was used on general surgical wards with no extra demands being made on nursing staff. Many nursing procedures and physiotherapy could be carried out more conveniently than usual in the postoperative period.

Adult↗
PubMed1980

Long-time spectral and intensity characteristics of esophageal speech.

Long-time spectral characteristics and distributional properties of speech intensity produced by esophageal speakers were measured and compared with those of normal speakers. Substantial differences were observed in the distributional properties of speech intensity produced by normal and esophageal talkers. On the average, esophageal speech was about 10 dB less intense than normal speech. In addition, the average long-time spectrum for esophageal speech was characterized by a flattened spectral envelope. Other spectral differences between esophageal and normal speech were found and interpreted in terms of the known variations in voice and speech production of these two divergent forms of oral communication.

Aged↗
PubMed1980

Prediction of velopharyngeal orifice area: a re-examination of model experimentation.

Warren has advanced a modification of the hydrokinetic equation for predicting velopharyngeal orifice area (Warren and DuBois, 1964). In the present work, this equation was subjected to extensive controlled model experimentation. The results of this experimentation show that, given the pressure differential across the orifice and the rate of airflow through the orifice, accurate predictions can be made of the area of the velopharyngeal port. These results were interpreted to provide strong support for both clinical and research use of the hydrokinetic equation for predicting velopharyngeal orifice area.

Airway Resistance↗
PubMed1979

Purification and properties of nitrogenase in ethylene glycol at sub-zero temperatures.

Both the protein components Kp1 and Kp2 of nitrogenase from Klebsiella pneumoniae were found to be stable in aq. 50% (v/v) ethylene glycol at +30 degrees C or below. At -20 degrees C in this medium their sensitivities to O2 were diminished somewhat. Though purification could be carried out at -20 degrees C, the product had the same specific activity and was obtained in the same yield as when the purification was carried out by standard procedures. This suggests that such procedures yield enzyme undamaged in the course of the purification by O2, thermal denaturation or proteolytic digestion.

Chemical Phenomena↗
PubMed1979

Characteristics of azurin from Pseudomonas aeruginosa via 270-MHz 1H nuclear magnetic resonance spectroscopy.

Assignments of resonances in the 1H nmr spectra of Cu(I) azurin to proton groups in the protein are discussed in detail. Comparisons are drawn between Cu(I), Cu(II), apo, Hg(II), and Co(II) azurin samples. Redox titration of Cu(I) azurin with K3Fe(CN)6, is used to correlate Cu(I) and Cu(II) 1H nmr spectral features, and observed line broadenings deriving from Cu(II) paramagnetic effects are used to deduce the distances of assigned proton groups from the copper center. Histidine residues are characterized in terms of pK values, rates of acid-base exchange near the the pK, and rates of C2H exchange with solvent deuterium. The possibility of histidine involvement in the azurincytochrome 551 electron exchange mechanism is discussed. A small number of NH protons observed to be distinctively inert to 2H exchange with solvent 2H2O, in the Cu(I) protein, are found to show increased lability on removal of the metal.

Azurin↗
PubMed1979

Circular dichroism and magnetic circular dichroism of nitrogenase proteins.

Circular dichroism (CD) and magnetic circular dichroism (MCD) spectra of nitrogenase components (MoFe protein and Fe protein) from Azotobacter vinelandii (Av) and Klebsiella pneumoniae (Kp) have been obtained in the near infrared-visible-near ultraviolet spectral region. Previously, visible CD was reported to be absent or barely detectable in nitrogenase proteins; MCD spectra have not been reported. The chiroptical spectra can be measured in solution at room temperature, an advantage relative to spectroscopic methods requiring cryogenic sample temperatures. Absorption spectra were also obtained. The CD and MCD are markedly more structured, and thus interpretively more useful, than the corresponding absorption spectra. The dithionite-reduced MoFe proteins (Av1, Kp1) have nearly identical CD and MCD, demonstrating identical numbers and types of metal centers in similar protein environments. The CD and MCD cannot be explained solely in terms of contributions from known 4-Fe or 2-Fe clusters; the near-infrared MCD is inconsistent with the presence of known 4-Fe clusters. CD and MCD spectra of Lauth's violet-oxidized Kp1 are also reported. The reduced Fe proteins (Av2, Kp2) have similar CD and MCD, again indicating significant conservation of chromophore environment. The spectra clearly demonstrate the presence of a reduced bacterial ferredoxin-like (C(3-)) 4-Fe cluster. No obvious evidence of additional chromophores is observed. CD, MCD, and absorption spectra of Av1-oxidized Av2 are reported. The absorption spectrum shows the expected shoulder near 390 nm. The CD and MCD are characteristic of a C(2-) 4-Fe cluster; in particular, the diagnostic near-infrared MCD peak is observed at approximately 8300 cm(-1). The CD of Av2 oxidized in the presence and absence of MgATP are radically different, providing the first direct evidence for MgATP interaction with Fe protein in this oxidation state.

Azotobacter↗
PubMed1978

Histidine residues of zinc ligands in beta-lactamase II.

1. The Zn(II)-requiring beta-lactamase from Bacillus cereus 569/H/9, which has two zinc-binding sites, was examined by 270 MHz 1H n.m.r. spectroscopy. Resonances were assigned to five histidine residues. 2. Resonances attributed to three of the histidine residues in the apoenzyme shift on the addition of one equivalent of Zn(II). 3. Although these three histidine residues are free to titrate in the apoenzyme, none of them titrates over the pH range 6.0--9.0 in the mono-zinc enzyme. 4. The ability of the C-2 protons of these three histidine residues to exchange with solvent (2H2O) is markedly decreased on Zn(II) binding. 5. It is proposed that these three histidine residues act as zinc ligands at the tighter zinc-binding site. 6. Resonances attributed to a fourth histidine residue shift on addition of further zinc to the mono-zinc enzyme. It is proposed that this histidine residue acts as a Zn(II) ligand at the second zinc-binding site.

Apoenzymes↗
PubMed1978

Electron-paramagnetic-resonance studies on the redox properties of the molybdenum-iron protein of nitrogenase between +50 and -450 mV.

The midpoint potentials, Em, for the oxidation of the characteristic e.p.r. signal with g values near 4.3, 3.7 and 2.01, of the nitrogenase Mo-Fe proteins from a number of bacteria were measured. They were 0mV for Clostridium pasteurianum, -42mV for Azotobacter chroococcum and Azotobacter vinelandii, -95mV for Bacillus polymyxa and -180mV for Klebsiella pneumoniae Mo-Fe proteins at pH 7.9. The oxidations were thermodynamically reversible for the proteins from A. chroococcum, A. vinelandii and K. pneumoniae and the Em was independent of protein activity for this last protein. The protein from C. pasteurianum required a lower potential for reduction than for oxidation, and the oxidation of the protein from B. polymyxa was only 70% reversible. The apparent Em of the latter protein was decreased by 40mV in the presence of 60mM-MgCl2. The pH-dependence of the Em of the protein from K. pneumoniae was interpreted in terms of a single ionization, not directly associated with the e.p.r.-active centre, with a pKa of 7.0 in the oxidized form of the protein and a pH-independent region at low pH (Em = 118 +/- 6.3 mV). Approx. 20% increase in activity after oxidation was observed for the proteins from B. polymyxa, A. chroococcum and K. pneumoniae. The significance of the above results and their relationship to other published data are discussed.

Bacteria↗
PubMed1978

Vocal roughness and jitter characteristics of vowels produced by esophageal speakers.

Audiotape recordings of sustained vowels produced by nine esophageal speakers were subjected to acoustic and perceptual analysis. Results indicated that (1) the magnitude of vocal jitter present in the vowels was substantially larger than that observed in normal speakers and speakers with laryngeal/vocal disturbance, (2) listeners could reliably rate the severity of vocal roughness in the vowels, (3) voices of esophageal speakers were characterized by varying degrees of vocal roughness, and (4) mean fundamental frequency, mean jitter, or jitter ratio measures did not serve as useful predictors of the perceived severity of vocal roughness. These findings are interpreted to suggest that the mechanism esophageal speakers employ to regulate fundamental frequency is substantially different from that employed by normal speakers and that the identity of physical variables underlying the perception of roughness severity in naturally produced human speech is not well understood.

Acoustics↗