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Biomedical subjects

J Botts

Publications and source records attributed to J Botts.

At least 19 recordsLinked to original sources
PubMed2001

Giant hamartoma of the breast.

Hamartoma of the breast is a rare clinico-pathologic entity. Its clinical diagnosis can be extremely difficult; however, diagnosis is not difficult when it is made on the basis of a combination of radiologic and pathologic features. Its differential diagnosis includes a circumscribed fibrocystic mass, fibroadenoma, lipoma, cystosarcoma phylloides, and various carcinomas. A high index of suspicion is mandatory. In this study, we report a case of giant hamartoma of the breast in a young postlactational female patient, including treatment of the tumor by excisional biopsy and correction of the resulting breast deformity by mastopexy. Clinical, radiologic, and pathologic features are discussed.

Adolescent↗
PubMed2001

Changes in speech following unilateral mandibular distraction osteogenesis in patients with hemifacial microsomia.

OBJECTIVE: The purpose of this study was to describe changes in articulation, resonance, and velopharyngeal function following mandibular distraction osteogenesis. DESIGN: This is a descriptive, post hoc study comparing the performance of patients on measures of articulation, resonance, and velopharyngeal function before and after mandibular distraction. SETTING: The data were collected at a tertiary health care center located in Chicago. PATIENTS: The clinical data from preoperative and postoperative evaluations of seven mandibular distraction patients were used. OUTCOME MEASURES: The outcome measures were number of articulation errors, severity of hypernasality and audible nasal emission, and velopharyngeal orifice size as estimated using the pressure-flow technique. RESULTS: Immediately after distraction, 28% (2/7) experienced a temporary deterioration in articulation and 42% (3/7) experienced a deterioration in nasal resonance. But by the long-term follow-up evaluation, all had returned to their preoperative levels. Pressure-flow test results generally support the perceptual findings. CONCLUSIONS: Patients being considered for mandibular distraction surgery should receive preoperative and postoperative speech evaluations and be counseled about risks for changes in their speech following surgery.

Adolescent↗
PubMed1989

On the origin and transmission of force in actomyosin subfragment 1.

A proximity map showing the three-dimensional arrangement of 12 chemically defined points in actomyosin subfragment 1 is developed and roughly correlated with published electron microscope reconstruction of others. Several additional points and topological relationships in the primary polypeptide chain folding are assimilated into this model. Certain crosslinkings and distance change observations are interpreted as indicators of transmission of force/displacement between the nucleotide-binding and an actin-binding site--i.e., as indications of how energy is transduced in this system.

Microscopy, Electron↗
PubMed1984

On the mechanism of energy transduction in myosin subfragment 1.

It is proposed that the myosin subfragment 1 moiety of the muscle contractile apparatus is a self-contained "engine" whose operational plan is based on the interactive nature of ATP (or degradation intermediate) binding and actin binding, made possible by an intersite communication system. It is suggested that the spatial information required for examining this engine can, at least provisionally, be derived from fluorescence resonance energy transfer measurements interpreted by the Förster equation and that the existence of an intersite communication system can be deduced from piece-wise detection of interacting pairs of points.

Actins↗
PubMed1982

Effects of tryptic digestion on myosin subfragment 1 and its actin-activated adenosinetriphosphatase.

Myosin subfragment 1 (S-1) was fluorescently labeled at its rapidly reacting thiol ("SH1"). Short exposure to trypsin cuts the S-1 heavy chain into three still-associated fragments (20K, 50K, and 27K) [Balint, M., Wolf, L., Tarcsafalvi, A., Gergely, J., & Sreter, F.A. (1978) Arch. Biochem. Biophys. 190, 793-799] which bind F-actin to the same extent as does the uncut labeled S-1, as indicated by time-resolved fluorescence anisotropy decay (at 4 degrees C, pH 7, in 0.15 M KC1 and 5 mM MgC12, +/- 1 mM ADP). These results are thus in agreement with turbidity measurements on similar systems as reported by Mornet et al. [Mornet, D., Pantel, P., Audemard, E., & Kassab, R. (1979) Biochem. Biophys. Res. Commun. 89, 925-932]. The excited-state lifetime of the fluorescent label on cut S-1 is indistinguishable from that on normal S-1 (+/- ADP, +/- F-actin). F-Actin activation of MgATPase of cut S-1 is lower than that for normal S-1 at moderate concentrations of F-actin, as reported by Mornet et al. (1979). But as the F-actin concentration is increased, the MgATPase activities for cut S-1 approach those for uncut S-1. In terms of an eight-species steady-state kinetics scheme involving actin binding to free S-1, S-1 . ATP, S-1. ADP X P, and S-1 . ADP, actin affinity for the species S-1 . ADP X P was found to be 13.4 times greater for uncut S-1 than for cut S-1 [at 24 degrees C, pH 7.0, in 3 mM KC1, 1 mM ATP, 1 mM MgCl2, and 20 mM N-[tris(hydroxymethyl)methyl]-2-aminoethanesulfonic acid].

Actins↗
PubMed1982

Spatial relationship between a fast-reacting thiol and a reactive lysine residue of myosin subfragment 1.

Fluorescence energy transfer was used to examine the spatial proximity between two key side chains in myosin subfragment 1 (S-1), viz., the reactive thiol (SH1) located on the C-terminal 20K tryptic fragment and the reactive lysyl (RLR) on the N-terminal 27K tryptic fragment of S-1 heavy chain. S-1 was specifically labeled at SH1 with an energy donor, N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl)ethylenediamine (AEDANS), and at RLR with an energy acceptor, 2,4,6,-trinitrobenzenesulfonate (TNBS). Prior blocking of SH1 with AEDANS increased the pK of RLR from 9.04 to 9.42. Trinitrophenylation of SH1-blocked S-1 was about 50% slower and sharply reduced the Ca2+ ATPase activity. Reciprocally, blocking of RLR with TNBS slowed the rate of reaction of SH1 and AEDANS by 40-60%. Addition of the second label does not grossly alter the conformation resulting from the first label. S-1 labeled at RLR with TNBS and at SH1 with optically inert iodoacetamide shows the same TNP difference spectrum +/- MgADP (lambda min 365 nm) as S-1 with S 1 free. Also, S-1 labeled at SH1 with AEDANS and at RLR with an optically inert methyl group shows the same AEDANS emission spectrum (lambda em max 475 nm), excited-state lifetime (tau = 20.3 ns) and rotational correlation time (phi = 106 ns) as S-1 with RLR free. When the decrease of either the quantum yield or the excited-state lifetime of the donor in the absence and presence of the acceptor was measured, the energy transfer efficiency was found to be 70%. The apparent interchromophore distance was calculated to be 2.6 nm through the use of the Förster equation with an uncertainty of less than 12%.

Calcium-Transporting ATPases↗
PubMed1981

EPR and fluorescence depolarization studies on bovine cardiac myosin.

To test for possible differences in local conformation and S1 flexibility, bovine cardiac and rabbit skeletal myosins were labeled with a fluorophore (1,5-IAEDANS) and a spin label having iodoacetamide reactivity. The marked activation of the Ca2+-ATPase (6- to 8-fold) and inhibition of the K+ (EDTA)-ATPase (80-90%) by both labels indicated specific labeling of the fast-reacting thiols (SH1) of both myosins. Fluorescence depolarization studies of 1,5-IAEDANS-labeled cardiac myosin indicated that, like skeletal myosin, the SI moieties of cardiac myosin exhibit considerable segmental flexibility with respect to the rod portion of the molecule. This indicates that segmental flexibility may be a property of all myosins. Cardiac and skeletal myosins immobilized spin labels to approximately the same extent, indicating a similarity in steric restraints around the SH1 thiol of the two myosins. The magnitude of the changes in spin label mobility accompanying binding of MgADP and hydrolysis of MgATP was reduced in cardiac myosin relative to skeletal myosin. This suggests that the lower catalytic center activity of cardiac myosin is associated with more restricted conformational changes accompanying formation of M.ADP and M.ADP.Pi. From measurements of spin label mobility, the affinity of cardiac and skeletal myosin for ADP were similar: Kd (ADP) = 7 microM, n = 1.6. The EPR spectrum of spin labels attached to cardiac and skeletal myosin showed similar saturation effects upon actin binding indicating immobilization of myosin heads occurs with both proteins.

Actins↗
PubMed1979

On the molecular basis for chemomechanical energy transduction in muscle.

Herein it is developed that energy transduction in muscle is an activity of myosin S-1 and its ligands, actin (A) and nucleotide (N). S-1 shares with other molecular particles (e.g., hemoglobin) the property that binding events at one of its sites, the N-site, influences binding events at a remote site, the A site (specifically, influences both the actin affinity and actin attachment angle at the A site). However, there is a crucial difference between S-1 and the better-known systems. Because the N site is enzymatic, it has a temporal sequence of occupants; this imposes a temporal sequence of actin attitudes--i.e., a sequence of mechanical events.

Actins↗
PubMed1975

Electron paramagnetic resonance and nanosecond fluorescence depolarization studies on creatine-phosphokinase interaction with myosin and its fragments.

Recent reports in the literature have indicated a physical association of creatine-phosphokinase (CPK) with the tail portion of the myosin molecule. The present paper describes further studies on the interaction of CPK with myosin and myosin fragments, using the techniques of electron paramagnetic resonance (EPR) and nanosecond fluorescence depolarization. From EPR work, spin-labeled CPK appears to interact with myosin, tail-less myosin (heavy meromyosin [HMM]), and myosin heads (subfragment-1 [S1]), the extent of interaction being proportional to the S1 content of myosin or its fragments. Spin-labeled CPK did not evidence interaction with the headless myosin "rods," with myosin tails (light meromyosin [LMM]), with S2 necks (which connect S1 to the rest of the myosin molecule), or with actin. When a fluorescent dye is directed to the essential epsilon-amino group of CPK, nanosecond fluorescence depolarization studies indicate a substantial interaction with myosin, HMM, and S1, but very little with F-actin. When the "fast-reacting" thiol of the S1 moiety or the "essential thiol" of CPK was labeled with either a fluorescent dye or a spin label, no interaction between CPK and myosin (or S1) was detected.

Actins↗
PubMed1974

Use of fluorescence polarization to observe changes in attitude of S-1 moieties in muscle fibers.

The fluorophore, N(iodoacetylamino)-1-naphthylamine-5-sulfonic acid (1,5-IAEDANS), incubated with glycerinated psoas fibers primarily labels the S-1 moieties of such fibers, but it does not impair fiber contractility even when the degree of labeling is as high as 0.8 moles fluorophore per mole myosin. The polarization of the on-axis fluorescence from either the IAEDANS fluorophore, or the intrinsic tryptophane fluorophore, depends on whether the fiber is relaxed, in rigor, or developing isometric tension; furthermore, the changes in polarization on going from one state to another are much the same with either tryptophane or IAEDANS fluorophores. The foregoing is true whether the plane of the exciting light is parallel or perpendicular to the fiber axis. Also, if a fiber is first freed of its myosin by extraction, and is then incubated with IAEDANS-labeled S-1 the resulting polarization approaches that observed with a labeled, unextracted fiber in rigor. By contrast, incubation with the fluorophore, 7-nitro-4-chlorobenz-2-oxa-1,3-diazole (NBD-Cl) confers fluorescence only on actin, without impairing contractility, but the polarization of such fluorescence changes in a different direction and magnitude from myosin-originating fluorescence. It is concluded from these various observations that whether the fluorophore is IAEDANS or tryptophane the polarization change with change in physiological state originates in the S-1 moieties of fibers, and relates to the space attitude of these moieties.

Acetamides↗
PubMed1974

The site of force generation in muscle contraction as deduced from fluorescence polarization studies.

The fluorescent dye, N(-iodoacetylamino)-l-naphthylanine-5-sulfonic acid, labeled exclusively the myosin cross-bridges in rabbit glycerinated psoas muscle fibers, without impairing their function. Fluorescence polarization was used to study cross-bridge orientation in rigor, relaxation, and contraction, as a function of sarcomere length. At a length where no overlap between thick and thin filaments occurs, rigor-inducing, relaxation-inducing, and contraction-inducing solutions all induced the relaxation attitude. At lengths where overlap does exist, the slowly-hydrolyzing ATP analog, "alpha,beta-methylene ATP," induced the relaxation attitude. The data were consistent with the A. F. Huxley-Simmons model of force generation. Combined with our earlier results, the data indicated that torque was generated at the actin-myosin interface.

Animals↗