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Biomedical subjects

G Piperno

Publications and source records attributed to G Piperno.

At least 37 records · Page 2Linked to original sources
PubMed1994

Mutations in the "dynein regulatory complex" alter the ATP-insensitive binding sites for inner arm dyneins in Chlamydomonas axonemes.

To understand mechanisms of regulation of dynein activity along and around the axoneme we further characterized the "dynein regulatory complex" (drc). The lack of some axonemal proteins, which together are referred to as drc, causes the suppression of flagellar paralysis of radial spoke and central pair mutants. The drc is also an adapter involved in the ATP-insensitive binding of I2 and I3 inner dynein arms to doublet microtubules. Evidence supporting these conclusions was obtained through analyses of five drc mutants: pf2, pf3, suppf3, suppf4, and suppf5. Axonemes from drc mutants lack part of I2 and I3 inner dynein arms as well as subsets of seven drc components (apparent molecular weight from 29,000 to 192,000). In the absence of ATP-Mg, dynein-depleted axonemes from the same mutants bind I2 and I3 inner arms at both ATP-sensitive and -insensitive sites. At ATP-insensitive sites, they bind I2 and I3 inner arms to an extent that depends on the drc defect. This evidence suggested to us that the drc forms one binding site for the I2 and I3 inner arms on the A part of doublet microtubules.

Adenosine Triphosphate↗
PubMed1993

[Mammary duct ectasia: nosologic assessment. Features and echographic incidence].

This work was aimed at framing duct ectasia as a nosologic entity and at studying its features and US incidence. Duct ectasia is a generally asymptomatic disorder of the mammary gland, which is usually included in the generic terms of mammary dysplasia, mastopathy, and so on. Nine hundred patients underwent US with a high-definition probe. They were divided into five groups according to age--i.e., 20-30, 30-40, 40-50, 50-60 years old, and over 60. Three hundred and two patients had undergone mammography in the previous six months: mammograms were selected according to Wolfe patterns. Radial US scans were performed around the nipple to detect the presence of major duct ectasia, which spreads centrifugally following a segmental pattern through the breast. US features included linear rosary-like dilatations and pseudocystic ectasia. On transverse scans, the ducts sometimes exhibited cyst-like appearance. Nearly 50% of patients was asymptomatic. US incidence rates did not differ from histologic rates; duct disorder prevails between 50 and 60 years of age and is absent in women under 30. US is an extremely simple method to study this disorder of the mammary gland.

Adult↗
PubMed1992

The inner dynein arms I2 interact with a "dynein regulatory complex" in Chlamydomonas flagella.

We provide indirect evidence that six axonemal proteins here referred to as "dynein regulatory complex" (drc) are located in close proximity with the inner dynein arms I2 and I3. Subsets of drc subunits are missing from five second-site suppressors, pf2, pf3, suppf3, suppf4, and suppf5, that restore flagellar motility but not radial spoke structure of radial spoke mutants. The absence of drc components is correlated with a deficiency of all four heavy chains of inner arms I2 and I3 from axonemes of suppressors pf2, pf3, suppf3, and suppf5. Similarly, inner arm subunits actin, p28, and caltractin/centrin, or subsets of them, are deficient in pf2, pf3, and suppf5. Recombinant strains carrying one of the mutations pf2, pf3, or suppf5 and the inner arm mutation ida4 are more defective for I2 inner arm heavy chains than the parent strains. This evidence indicates that at least one subunit of the drc affects the assembly of and interacts with the inner arms I2.

Actins↗
PubMed1992

[Teleradiography for diagnosis in emergency care. A clinical experience].

This work was aimed at evaluating the role of teleradiology in a diagnostic emergency room. Over a 6-month period (September 1991-February 1992), 2,000 films made in the emergency room were transmitted to a resident radiologist 1 kilometer away: each examination included patient's data (sex, age, site of trauma, etc.) which were sent by the admitting physician. A teleradiology system (Lumiscan 100 AT&T and Philips) was used. Films were digitized on a 1024 x 1024 x 8-bit image matrix and then transmitted over a dedicated standard phone line to the Department of Radiology. The autograph report was sent by fax to the emergency room. Four radiologists, of varying experience, independently reviewed a sample of 179 digitized radiographs and, 30 days later, the original films on a conventional light-box. The results appear to be encouraging because no significant differences were observed in the performance of any of the radiologists. Good video/films agreement was obtained, together with high sensitivity and specificity. A good result was the relatively small number (0.4% of all examined cases) of false negatives diagnosed on faxed films relative to the actual clinical diagnosis.

Computer Peripherals↗
PubMed1992

[Mammary ductal system. Echographic features].

Real-time breast US is useful in the evaluation of localized lesions. Our study was aimed at examining the US features of the ductolobular system in physiological condition. To this purpose, all breasts were imaged on the radial plane by rotating the probe around the nipple, thus depicting the ductal system from nipple to gland periphery. The patients were made to lie supine or to sit down. In order to depict small lobular excrescences, TV magnification was employed on the target areas. Five hundred and twenty asymptomatic women were evaluated with US; preliminary mammograms had been obtained in 440 of them. Any subject with prominent duct shadows on mammography or mammographic and/or US demonstration of focal lesions was excluded from the study. Different US patterns were observed in the ductolobular system, depending on patients' age, mammographic patterns, physiological hyperplasia during pregnancy and/or involution after pregnancy and lactation. The ductal branches were demonstrated by US only in mammographically dense areas. Thus, US has been observed to allow the evaluation of the physiological changes in the ductolobular system.

Adult↗
PubMed1991

The proximal portion of Chlamydomonas flagella contains a distinct set of inner dynein arms.

A specific type of inner dynein arm is located primarily or exclusively in the proximal portion of Chlamydomonas flagella. This dynein is absent from flagella less than 6 microns long, is assembled during the second half of flagellar regeneration time and is resistant to extraction under conditions causing complete solubilization of two inner arm heavy chains and partial solubilization of three other heavy chains. This and other evidence described in this report suggest that the inner arm row is composed of five distinct types of dynein arms. Therefore, the units of three inner arms that repeat every 96 nm along the axoneme are composed of different dyneins in the proximal and distal portions of flagella.

Cell Movement↗
PubMed1991

[Calcaneal fractures: CT aspects].

Calcaneal fractures account for 33.3% of foot fractures and 1.5% of all fractures. They were divided by Warrick and Brenner into two main groups according to whether they modify the astragalocalcaneal joint or not. Given the anatomical complexity of the foot, conventional X-rays are not always able to correctly visualize the articular facets and therefore provide insufficient information as to the characteristics of the fracture line, the position of bone fragments, and the involvement of capsulo-ligamentous structures. The authors report their personal experience with CT in the study of 12 patients with monolateral calcaneal fractures previously diagnosed on conventional X-rays. High-resolution CT (HRCT) was employed with 3-mm contiguous sections on the axial and the coronal planes. CT was used to study the normal anatomy of the foot and to evaluate 3 patients with calcaneal fracture without impaction of the posterior facet; 9 patients with impaction into the calcaneal body were also examined with CT. In the first 3 cases, an oblique fracture line was observed crossing from craniolateral to mediocaudal and thus dividing the calcaneus into 2 large fragments: sustentaculum tali and posterior facet of the talar joint. In the extant 9 cases the impaction of the posterior facet was indicated by an interruption in lateral and/or medial calcaneal walls. In 2/9 cases bone fragments were seen in the tarsal sinus, in 4/9 the sustentacular fragment was displaced, in 2 the cuboid bone was impacted into the anterior process of the calcaneus and, finally, in 7/9 cases a lateral/medial dislocation of the calcaneal tuberosity was observed. On the basis of these results, CT proved to be of greater value than conventional X-rays in the imaging of calcaneal fractures and to have a fundamental role every time an accurate evaluation of the region is needed to plan treatment.

Adult↗
PubMed1990

Three distinct inner dynein arms in Chlamydomonas flagella: molecular composition and location in the axoneme.

The molecular composition and organization of the row of axonemal inner dynein arms were investigated by biochemical and electron microscopic analyses of Chlamydomonas wild-type and mutant axonemes. Three inner arm structures could be distinguished on the basis of their molecular composition and position in the axoneme as determined by analysis of pf30 and pf23 mutants. The three inner arm structures repeat every 96 nm and are referred to here as inner arms I1, I2, and I3. I1 is proximal to the radial spoke S1, whereas I2 and I3 are distal to spokes S1 and S2, respectively. The mutant pf30 lacks I1 whereas the mutant pf23 lacks both I1 and I2 but has a normal inner arm I3. Each of the six heavy chains that was identified as an inner dynein arm subunit has a site for ATP binding and hydrolysis. Two of the heavy chains together with a polypeptide of 140,000 molecular weight form the inner arm I1 and were extracted from the axoneme as a complex that had a sedimentation coefficient close to 21S at high ionic strength. Different subsets of two of the remaining four heavy chains form the inner arms I2 and I3. These arms at high ionic strength are dissociated as 11S particles that include one heavy chain, one intermediate chain, two light chains, and actin. These and other lines of evidence indicate that the inner arm I1 is different in structure and function from the inner arms I2 and I3.

Adenosine Triphosphatases↗
PubMed1990

Breast cancer screening by impedance measurements.

More efficient screening for breast cancer can lead to a reduction in the need for radical surgery and improved survival rates. Modern technology, particularly electronics and computerized instrumentation, makes such improvement feasible. We have developed an instrument for screening for breast cancer based on measuring the dielectric properties of tissues. An image of the electric properties of the breast is presented on a monitoring screen, using 512 'pixels', from which it is possible to distinguish pathological tissue. The image can be recalled on the monitor at will. The test can be performed by paramedical personnel. In the present study 6000 patients were tested with this instrument; 745 of these have undergone biopsy and these had been tested with all available instrumentation. A number of cases were found in which only this instrument detected a pathology which proved malignant. Instruments of such a type could become an additional part of breast cancer clinics.

Breast Neoplasms↗
PubMed1988

Distribution of acetylated alpha-tubulin in retina and in vitro-assembled microtubules.

We have used the mouse monoclonal antibody 6-11 B-1, specific for acetylated alpha-tubulin, to determine the distribution of acetylated alpha-tubulin in in vitro-assembled microtubules and retinal tissue. Analysis by immunoblots revealed that microtubules assembled from bovine brain extracts contain both acetylated and nonacetylated alpha-tubulin. Immunofluorescence, using 6-11 B-1 and antitubulin B-5-1-2, a monoclonal antibody specific for alpha-tubulin, demonstrated the colocalization of both alpha-tubulin species in neurons of the retina and that acetylated microtubules are relatively abundant in neurons. However, analysis at higher resolution revealed that rod photoreceptors contain spatially distinct microtubule arrays which differ in content of acetylated alpha-tubulin and differ in stability. Acetylated microtubules which composed those of the rod outer segment and connecting cilium were resistant to depolymerization in nocodazole or colchicine. In contrast, the nonacetylated microtubules which composed those of the rod-inner segment were depolymerized in nocodazole or colchicine. Therefore, these acetylated microtubules are more resistant to depolymerization than non-acetylated microtubules.

Acetylation↗
PubMed1988

Isolation of a sixth dynein subunit adenosine triphosphatase of Chlamydomonas axonemes.

This study of the axoneme led to the identification of a previously unknown adenosine triphosphatase (ATPase), which is likely a major component of inner dynein arms. The ATPase was isolated from a soluble fraction of axonemes obtained from pf 28, a Chlamydomonas mutant lacking the outer dynein arms. The activity hydrolyzed up to 2.3 mumol of ATP.min-1.mg-1 of protein (at pH 7.2, in the presence of both Ca++ and Mg++), had a sedimentation coefficient of 11S in sucrose gradient, and cosedimented with four polypeptides of apparent molecular weight 325,000, 315,000 140,000, and 42,000. Several arguments indicate that the new ATPase is a component of the inner dynein arms. Three or four polypeptides cosedimenting with the activity belong to a group of axonemal components that are deficient in the axonemes of pf 23 and pf 30, two mutants that display different levels of inner dynein arm deficiency. The 42,000 component is axonemal actin, a subunit of two other inner dynein ATPases. The two polypeptides of molecular weight greater than 300,000 have electrophoretic mobility similar to that of high molecular weight components of outer and inner dynein arms. In spite of some similarities each ATPase isolated from inner or outer arms is composed of a different set of polypeptides. Different ATPases may be required for the modulation of localized sliding of adjacent outer double microtubules in the axoneme.

Actins↗
PubMed1988

Posttranslational modifications of alpha tubulin: detyrosination and acetylation differentiate populations of interphase microtubules in cultured cells.

Subsets of microtubules enriched in posttranslationally detyrosinated (Gundersen, G. G., M. H. Kalnoski, and J. C. Bulinski. 1984. Cell. 38:779) or acetylated (Piperno, G., M. Le Dizet, and X. Chang. 1987. J. Cell Biol. 104:298), alpha tubulin have previously been described in interphase cultured cells. In this study an immunofluorescence comparison of these minor populations of microtubules revealed that, in African green monkey kidney epithelial cells (TC-7 line), the population of microtubules enriched in detyrosinated tubulin was virtually coincident with the population enriched in acetylated alpha tubulin. In some cell types, however, such as human HeLa or marsupial PtK-2 cells, only one posttranslationally modified form of tubulin, i.e., acetylated or detyrosinated, respectively, was detectable in microtubules. In TC-7 cells, although both modifications were present, dissimilar patterns and kinetics of reappearance of microtubules enriched in detyrosinated and acetylated tubulin were observed after recovery of cells from microtubule-depolymerizing treatments or from mitosis. Thus, a minor population of microtubules exists in cultured cells that contains an elevated level of tubulin modified in either one or two ways. While these two modifications occur primarily on the same subset of microtubules, they differ in their patterns of formation in vivo.

Acetylation↗
PubMed1987

Identification of an acetylation site of Chlamydomonas alpha-tubulin.

An acetylation site of Chlamydomonas axonemal alpha-tubulins was identified near, or within, the binding site of 6-11B-1, a monoclonal antibody specific for posttranslationally acetylated alpha-tubulins. In a first approach, axonemal proteins were hydrolyzed by formic acid, cyanogen bromide, or chymotrypsin and analyzed with immunoblots. The smallest alpha-tubulin peptide retained on nitrocellulose and containing antibody-binding site(s) was found to span amino acids 37-138 (alpha 37-138). A smaller antibody-binding peptide, identified as alpha 25-50, was obtained by complete digestion of alpha-tubulin with chymotrypsin. This fragment was purified by reversed-phase HPLC and assayed by its ability to bind 6-11B-1 in solution. Determination of the amino acid sequences of alpha 37-138 and alpha 25-50 showed that residue 40 in axonemal alpha-tubulin is epsilon N-acetyllysine. A sequence very similar to Chlamydomonas alpha 25-50 is found in the majority of alpha-tubulins analyzed so far. However, the corresponding region is markedly divergent in some alpha-tubulin isoforms from chicken, Drosophila, and yeast.

Acetylation↗
PubMed1987

Microtubules containing acetylated alpha-tubulin in mammalian cells in culture.

The subcellular distribution of microtubules containing acetylated alpha-tubulin in mammalian cells in culture was analyzed with 6-11B-1, a monoclonal antibody specific for acetylated alpha-tubulin. Cultures of 3T3, HeLa, and PtK2 cells were grown on coverslips and observed by immunofluorescence microscopy after double-staining by 6-11B-1 and B-5-1-2, a monoclonal antibody specific for all alpha-tubulins. The antibody 6-11B-1 binds to primary cilia, centrioles, mitotic spindles, midbodies, and to subsets of cytoplasmic microtubules in 3T3 and HeLa cells, but not in PtK2 cells. These observations confirm that the acetylation of alpha-tubulin is a modification occurring in different microtubule structures and in a variety of eukaryotic cells. Some features of the acetylation of cytoplasmic microtubules of mammalian cells are also described here. First, acetylated alpha-tubulin is present in microtubules that, under depolymerizing conditions, are more stable than the majority of cytoplasmic microtubules. In addition to the specific microtubule frameworks already mentioned, cytoplasmic microtubules resistant to nocodazole or colchicine, but not cold-resistant microtubules, contain more acetylated alpha-tubulin than the rest of cellular microtubules. Second, the alpha-tubulin in all cytoplasmic microtubules of 3T3 and HeLa cells becomes acetylated in the presence of taxol, a drug that stabilizes microtubules. Third, acetylation and deacetylation of cytoplasmic microtubules are reversible in cells released from exposure to 0 degrees C or antimitotic drugs. Fourth, the epitope recognized by the antibody 6-11B-1 is not absolutely necessary for cell growth and division. This epitope is absent in PtK2 cells. The acetylation of alpha-tubulin could regulate the presence of microtubules in specific intracellular spaces by selective stabilization.

Acetylation↗