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Biomedical subjects

B Rubinstein

Publications and source records attributed to B Rubinstein.

At least 19 recordsLinked to original sources
PubMed2005

The physics of filopodial protrusion.

Filopodium, a spike-like actin protrusion at the leading edge of migrating cells, functions as a sensor of the local environment and has a mechanical role in protrusion. We use modeling to examine mechanics and spatial-temporal dynamics of filopodia. We find that >10 actin filaments have to be bundled to overcome the membrane resistance and that the filopodial length is limited by buckling for 10-30 filaments and by G-actin diffusion for >30 filaments. There is an optimal number of bundled filaments, approximately 30, at which the filopodial length can reach a few microns. The model explains characteristic interfilopodial distance of a few microns as a balance of initiation, lateral drift, and merging of the filopodia. The theory suggests that F-actin barbed ends have to be focused and protected from capping (the capping rate has to decrease one order of magnitude) once every hundred seconds per micron of the leading edge to initiate the observed number of filopodia. The model generates testable predictions about how filopodial length, rate of growth, and interfilopodial distance should depend on the number of bundled filaments, membrane resistance, lamellipodial protrusion rate, and G-actin diffusion coefficient.

Actins↗
PubMed2001

Pathologic analysis of routine tonsillectomy and adenoidectomy specimens.

OBJECTIVES: Recent literature has suggested that histopathologic analysis of routine tonsillectomy and adenoidectomy (T&A) specimens may be unnecessary. This study investigates T&A specimen handling practices in the United States between 1989 and 1999. METHODS: Surveys were sent to 4715 members of the American Academy of Otolaryngology. Surveys assessed practice type, pathologic processing practices (full, gross, no pathology), and reasons for change. The authors also performed a retrospective analysis of 1583 pediatric T&A specimens for evidence of occult malignancy. RESULTS: Practice types were 80% private, 12% academic, 6% salaried, and 2% military. Chi squared analysis revealed a significant increase (P < 0.001) in respondents ordering "gross only" and "no pathology." The retrospective analysis found no occult malignancies. CONCLUSIONS: There is a statistically significant increase in the number of otolaryngologists sending routine T&A specimens for "gross only" and "no pathology." There was no correlation between the type of practice and changes in pathologic analysis performed.

Adenoidectomy↗
PubMed2000

Management of nasal fractures.

The nasal bones are the most commonly fractured bones in the body. Accurate diagnosis and appropriate surgical intervention are key in the management of nasal fractures. While these injuries are not life-threatening, mismanagement of nasal fractures can lead to both aesthetic and functional deformities. A thorough history and careful physical examination are adequate for the diagnosis of nasal fractures. Literature in the field does not support the use of x-ray films to aid in the diagnosis. The majority of injuries are seen after significant edema becomes present and cannot be accurately reduced at that time. Therefore, with the exception of grossly displaced fractures, open fractures, and septal hematomas, most nasal fractures should be definitively treated after 3 to 10 days once swelling has resolved. This article will review pertinent nasal anatomic structure, pathophysiological characteristics of nasal fractures, diagnostic techniques, treatment modalities, and common controversies associated with nasal fractures.

Fracture Fixation↗
PubMed2000

Regulation of cell death in flower petals.

The often rapid and synchronous programmed death of petal cells provides a model system to study molecular aspects of organ senescence. The death of petal cells is preceded by a loss of membrane permeability, due in part to increases in reactive oxygen species that are in turn related to up-regulation of oxidative enzymes and to a decrease in activity of certain protective enzymes. The senescence process also consists of a loss of proteins caused by activation of various proteinases, a loss of nucleic acids as nucleases are activated, and enzyme-mediated alterations of carbohydrate polymers. Many of the genes for these senescence-associated enzymes have been cloned. In some flowers, the degradative changes of petal cells are initiated by ethylene; in others, abscisic acid may play a role. External factors such as pollination, drought and temperature stress also affect senescence, perhaps by interacting with hormones normally produced by the flowers. Signal transduction may involve G-proteins, calcium activity changes and the regulation of protein phosphorylation and dephosphorylation. The efficacy of the floral system as well as the research tools now available make it likely that important information will soon be added to our knowledge of the molecular mechanisms involved in petal cell death.

Apoptosis↗
PubMed1999

Identification of senescence-associated genes from daylily petals.

The petals of daylily (Hemerocallis hybrid) have a genetically based program that leads to senescence and cell death ca. 24 h after the flower opens. In order to determine the components of this program, six cDNAs, whose levels increase during petal senescence, were isolated and sequenced and designated DSA3, 4, 5, 6, 12 and 15. All six DSAs are members of gene families and all but DSA5 and DSA6 have one to three other very similar genes. GenBank database homology searches indicate that DSA3 is most similar at the amino acid level to an in-chain fatty acid hydroxylase which is bound to cytochrome P450, DSA4 may be an aspartic proteinase, DSA5 is as yet unidentified, DSA6 is a putative S1-type nuclease, DSA12 is very similar to a cytochrome P450-containing allene oxide synthase, and DSA15 may be a fatty acid elongase. Except for DSA12, the genes are expressed at low levels in daylily roots. Levels of the DSA mRNAs in leaves are less than 4% of the maximum detected in petals, and there are no clear differences between younger and older leaves. With the exception of DSA4, accumulation of the DSA mRNAs is increased 3.2 to 43 times by a concentration of abscisic acid that causes premature senescence of the petals. The relationship of the putative DSA gene products to senescence and cell death of daylily petals is discussed.

Abscisic Acid↗
PubMed1996

On the mechanism of hyperacidification in lemon. Comparison of the vacuolar H(+)-ATPase activities of fruits and epicotyls.

Lemon fruit vacuoles acidify their lumens to pH 2.5, 3 pH units lower than typical plant vacuoles. To study the mechanism of hyperacidification, the kinetics of ATP-driven proton pumping by tonoplast vesicles from lemon fruits and epicotyls were compared. Fruit vacuolar membranes. H+ pumping by epicotyl membranes was chloride-dependent, stimulated by sulfate, and inhibited by the classical vacuolar ATPase (V-ATPase) inhibitors nitrate, bafilomycin, N-ethylmaleimide, and N,N'-dicyclohexylcarbodiimide. In addition, the epicotyl H+ pumping activity was inactivated by oxidation was reversed by dithiothreitol. Cold inactivation of the epicotyl V-ATPase by nitrate ( > or = 100 mM) was correlated with the release of V1 complexes from the membrane. In contrast, H+ pumping by the fruit tonoplast-enriched membranes was chloride-independent, largely insensitive to the V-ATPase inhibitors, and resistant to oxidation. Unlike the epicotyl inhibitors, and resistant to oxidation. Unlike the epicotyl H(+)-ATPase, the fruit H(+)-ATPase activity was partially inhibited by 200 microM vanadate. Cold inactivation treatment failed to inhibit H+ pumping activity of the fruit membranes, even though immunoblasts showed that V1 complexes were released from the membrane. However, cold inactivation doubled the percent inhibition by 200 microM vanadate from 30% to 60%. These results suggest the presence of two H(+)-ATPases in the fruit preparation: a V-ATPase and an unidentified vanadate-sensitive H(+)-ATPase. Attempts to separate the two activities in their native membranes on linear sucrose density density gradients were unsuccessful. However, following detergent-solubilization and centrifugation on a glycerol density gradient, the two ATPase activities were resolved: a nitrate-sensitive V-type ATPase that is also partially inhibited by 200 microM vanadate, and an apparently novel vanadate-sensitive ATPase that is also partially inhibited by nitrate.

Adenosine Diphosphate↗
PubMed1996

Association between radiographic findings in the mandibular condyle and temporomandibular dysfunction in an elderly population.

Our aims were to study the prevalence of abnormal radiographic findings in mandibular condyles and the possible association between such findings and clinical signs and symptoms of temporomandibular dysfunction (TMD) and dental state. Two cohorts of 70-year-old people, 384 men and 484 women, living in Göteborg, Sweden, participated in the study. The first cohort was examined in 1972 and the other one in 1992. Besides a functional and clinical examination, a questionnaire on TMD and panoramic radiography were included. A deviation from the normal appearance of one or both condyles was found in 26% of the subjects (17% of the condyles). There was no significant difference in this respect between the two cohorts. There were in general only minor and no statistically significant differences between those with normal and deviating condylar findings with regard to various TMD signs and symptoms. The subjects in Eichner group A (with dental support in all zones) showed a slightly lower frequency of abnormal radiographic condylar findings (22%) than those in groups B (reduced dental support) and C (edentulous in one or both jaws; both B and C, 28%). It is concluded that abnormal radiographic condylar findings in these elderly people were not at all or only weakly correlated with signs and symptoms of TMD and dental status.

Aged↗
PubMed1994

Functional analysis of conserved cysteine residues in the catalytic subunit of the yeast vacuolar H(+)-ATPase.

The A subunit of the yeast vacuolar ATPase contains three highly conserved cysteines: Cys-261, Cys-284, and Cys-538. Cys-261 is located within the nucleotide-binding P-loop. Each of the conserved cysteines, and one nonconserved cysteine, Cys-254, were altered to serine by site-directed mutagenesis, and the effects on growth at pH 7.5 were determined. The Cys-254-->Ser, Cys-261-->Ser and the double mutants all grew at pH 7.5 and contained nitrate- and bafilomycin-sensitive ATPase activity. However, the ATPase activities of the Cys-261-->Ser and the double mutants were insensitive to the sulfhydryl group inhibitor, N-ethylmaleimide, demonstrating that Cys-261 is the site of inhibition by N-ethylmaleimide. Changing either Cys-284 or Cys-538 to serine prevented growth at pH 7.5. Cys-284 and Cys-538 thus appear to be essential cysteine residues which are required either for assembly or catalysis.

Base Sequence↗
PubMed1994

The action of ascorbate in vesicular systems.

Many effects of ascorbate center on its interactions with membranes from plant and animal cells. These actions can be studied using vesicles produced from phospholipid components (liposomes), by isolating naturally occurring vesicles, or by purifying particular membranes that form vesicles during the extraction process. Liposomes have provided information concerning the anti- and prooxidant properties of ascorbate and about how the water-soluble vitamin can have effects within the phospholipid bilayer. The involvement of ascorbate in transmembrane electron transport has been characterized in vesicles normally found in certain cells, such as, chromaffin granules, synaptosomes, glyoxisomes, peroxisomes, and clathrin-coated vesicles. Redox activity using reducing power associated with ascorbate/ascorbate free radical (AFR) has been characterized in some of these vesicles and it appears to be mediated by a b-type cytochrome. Ascorbate also participates in the reduction of iron within clathrin-coated vesicles. Vesicles appearing during purification of plasma membranes have transmembrane electron transport, oxidoreductase activity with ascorbate/AFR as redox agents, and an ascorbate-reducible b-type cytochrome. It is also possible that ascorbate-related redox activity exists at the tonoplast of plant cells.

Animals↗
PubMed1993

Tinnitus and craniomandibular disorders--is there a link?

Associations between tinnitus and craniomandibular disorders (CMD) were investigated in an epidemiological sample, in tinnitus patients, and in patients attending a 'CMD-clinic'. Natural course of tinnitus was explored in a longitudinal epidemiological study of an elderly population. Several findings indicating a relatively strong relationship between CMD, tinnitus and subjective hearing loss were noted. This relationship seemed to be independent of objectively assessed degree of hearing loss, occupational noise exposure, general morbidity, medication or socioeconomic status. The prevalence of frequent headaches and fatigue or tenderness in jaw muscles was higher in tinnitus patients than would be expected if these conditions were unrelated. About one third of the individuals affected by tinnitus reported influence on tinnitus by jaw movements or pressure on the temporomandibular joint (TMJ). Diurnal bruxism and jaw fatigue appeared to be related to fluctuating tinnitus, vertigo, and hyperacusis. Stomatognathic and biofeedback treatment seemed to be able to reduce or eliminate tinnitus in some patients. Relatively low severity of tinnitus, normal hearing, fluctuating tinnitus, and some signs and symptoms of CMD are believed to constitute predictors of successful treatment outcome. Substantial longitudinal fluctuations with a high occurrence of spontaneous remissions of tinnitus were found in elderly people.

Adolescent↗
PubMed1992

Relationship between Electron Transport across the Plasmalemma and a pH Decrease in the Bulk Medium.

The hypothesis is tested that acidification of the bulk medium during transplasmalemma electron transport to ferricyanide is due solely to a requirement for charge balance. According to this hypothesis, reduction of the trivalent anion, ferricyanide, to the tetravalent anion, ferrocyanide, results in a charge difference that is balanced by protons. A coulometric device is used that rapidly and efficiently reoxidizes ferrocyanide to ferricyanide, thus maintaining a constant charge in the bulk medium. Oat (Avena sativa L. cv Garry) mesophyll protoplasts are chosen as experimental material to facilitate ferricyanide reduction and the concomitant ferrocyanide reoxidation by the coulometric device. The kinetics of ferricyanide reduction and proton excretion by protoplasts are similar to those of other cell types and tissues. Rates of net proton excretion are identical regardless of whether the ferrocyanide is simultaneously reoxidized. We conclude that acidification may occur during transplasmalemma electron transport when there is no change in negative charge of the bulk medium.

Journal Article↗
PubMed1991

The role of plasma membrane redox activity in light effects in plants.

Stimulations by light of electron transport at the plasma membrane make it possible that redox activity is involved in light-induced signal transduction chains. This is especially true in cases where component(s) of the chain are also located at the plasma membrane. Photosynthetic reactions stimulate transplasma membrane redox activity of mesophyll cells. Activity is measured as a reduction of the nonpermeating redox probe, ferricyanide. The stimulation is due to production of a cytosolic electron donor from a substance(s) transported from the chloroplast. It is unknown whether the stimulation of redox activity is a requirement for other photosynthetically stimulated processes at the plasma membrane, but a reduced intermediate may regulate proton excretion by guard cells. Blue light induces an absorbance change (LIAC) at the plasma membrane whose difference spectrum resembles certain b-type cytochromes. This transport of electrons may be due to absorption of light by a flavoprotein. The LIAC has been implicated as an early step in certain blue light-mediated morphogenic events. Unrelated to photosynthesis, blue light also stimulates electron transport at the plasma membrane to ferricyanide. The relationship between LIAC and transmembrane electron flow has not yet been determined, but blue light-regulated proton excretion and/or growth may depend on this electron flow. No conclusions can be drawn regarding any role for phytochrome because of a paucity of information concerning the effects of red light on redox activity at the plasma membrane.

Cell Membrane↗
PubMed1991

Psychological dimensions in patients with disabling tinnitus and craniomandibular disorders.

Forty-two patients with severe tinnitus and craniomandibular disorders (CMD) are presented from an audiological and psychological point of view. During a 2-week period, the patients rated their mood and their tinnitus. Based upon mood ratings, patients were grouped into three clusters (high, medium and low mood). The three groups differed in a number of respects, audiological as well as psychological. Patients in the low mood group experienced significantly more intense and severe tinnitus and more daily stress than patients in the high mood group. Ratings of irritation and concentration difficulties seemed to be mood related, and discriminated between patients in the low mood group and patients in the moderate and the high mood groups. Difference in hearing level between the left and the right ear was more pronounced in patients with low mood. There were, however, no significant differences between the groups in the stomatognathic variables. It is concluded that the above mentioned audiological and psychological observations should be considered as potentially important for satisfactory management of individual tinnitus patients. Further studies of the effects of optimally compensated hearing on depressed mood in patients with noise-induced hearing loss (NIHL) and tinnitus are required.

Affect↗
PubMed1991

A stomatognathic analysis of patients with disabling tinnitus and craniomandibular disorders (CMD).

Forty-two patients with disabling tinnitus and reported symptoms of craniomandibular disorders (CMD) were investigated by means of questionnaire, semistructured interview, stomatognathic examination and 2-week diary with thrice-daily ratings of tinnitus and mood. The findings have been analysed in order to identify symptoms of CMD related to tinnitus, and it was concluded that awareness of diurnal bruxism and feeling of jaw tenderness/fatigue may be related to fluctuating tinnitus, vertigo and hyperacusis.

Adult↗