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R Reyes

Publications and source records attributed to R Reyes.

At least 109 records · Page 6Linked to original sources
PubMed1979

Acidic ribosomal proteins from eukaryotic cells. Effect on ribosomal functions.

Precipitation of Saccharomyces cerevisiae ribosomes by ethanol under experimental conditions that do not release the ribosomal proteins can affect the activity of the particles. In the presence of 0.4 M NH4Cl and 50% ethanol only the most acidic proteins from yeast and rat liver ribosomes are released. At 1 M NH4Cl two more non-acidic proteins are lost from the ribosomes. The release of the acidic proteins causes a small inactivation of the polymerizing activity of the particles, additional to that caused by the precipitation itself. The elongation-factor-2-dependent GTP hydrolysis of the ribosomes is, however, more affected by the loss of acidic proteins. These proteins can stimulate the GTPase but not the polymerising activity when added back to the treated particles. Eukaryotic proteins cannot be substituted for bacterial acidic proteins L7 and L12. We have not detected immunological cross-reaction between acidic proteins from Escherichia coli and those from yeast, Artemia salina and rat liver or between acidic proteins from these eukaryotic ribosomes among themselves.

GTP Phosphohydrolase-Linked Elongation Factors↗
PubMed1978

Structure of the yeast ribosomes. Proteins associated with the rRNA.

Polyamines have been shown to bind to doubled stranded regions of rRNA [3]. Therefore, ribosomal proteins that can be cross linked to these molecules in the ribosomes structure must be bound to or located in the vicinity of the RNA. This technique is the first to yield results on the proteins associated with the rRNA in the eukaryotic ribosome where the lack of purified ribosomal proteins does not allow the use of direct binding studies as in bacterial systems. Proteins S7, S10, S13, S21, S22 and S27 in the small subunit and L2/3, L5, L10/12, L19/20, L22, L23, L36/37, L42 and L43' in the large subunit are labelled when cross linked to [14C]spermidine using 1,5-difluoro 2,4-dinitrobenzene and are good candidates to be RNA-binding proteins in ribosomes from Saccharomyces cerevisiae.

Molecular Weight↗
PubMed1977

Peptidyl transferase center of rat-liver ribosome cores.

Protein-deficient particles have been obtained by treating rat liver 80-S ribosomes or their 60-S subunits with 1 M NH4Cl in the presence of 50% ethanol at 0 degrees C (Po-cores) and 37 degrees C (P37-cores). The Po-cores from 80-S ribosomes are totally inactive in polyphenylalanine synthesis but fully active in the 'fragment assay' to test peptidyl transferase activity. The polymerizing activity of the cores is restored up to 40--50% of control activity by incubation in the presence of the split proteins. Three proteins are totally lost in the treatment, namely proteins L12, L40/41 ans S25. A series of up to nine different spots in the region of the L40/41 proteins are detected when the split fraction is analyzed by two-dimensional electrophoresis. This series of spots is, however, reduced to only two proteins when the second dimension is carried out in the presence of sodium dodecylsulphate. 80-S ribosome-derived P37-cores are about 80% active in the 'fragment reaction' while 60-S-subunit-derived particles are inactive in this assay. The inhibitory effect of a number of antibiotics is differentially affected by the treatment suggesting different localization of their binding sites. A comparative study of the proteins released by treatment in the two types of particles suggests the involvement in the peptidyl transferase center of the ribosome of one or more of the floolwing proteins: L21, L24, L27, L28 and L36.

Acyltransferases↗
PubMed1976

Structure and function of rat-liver ribosomes. Modification by 2-methoxy-5-nitrotropone treatment.

Rat liver ribosomes and 60-S ribosome subunits were treated with the primary-amino-group-specific reagent 2-methoxy-5-nitrotropone. Important differences in the sensitivity of several ribosomal activities to inactivation by the reagent were observed. While elongation-factor-dependent activities are totally abolished in the treated particles, peptidyl transferase activity is either unaffected in 60-S ribosomal subunits or even strongly stimulated in 80-S ribosomes. Analysis of the ribosomal proteins modified by nitrotropone made it possible to draw some conclusions on their accessibility in the ribosomal structure and to relate some proteins with their involvement in the ribosome active centers. Thus, proteins L3, L13, L15 and L23 seem to be in a rather well protected position while proteins L10, L35, L37, X1 and X2 are totally exposed to the reagent. The protein accessibility also depends on the ribosome conformation, proteins L14 and L17, for instance, being sensitive in 80-S ribosomes and protected in 60-S subunits. In relation to the implication of proteins in functional centers, the data presented here together with other data obtained from protein-deficient core particles seem to indicate a possible role of proteins L21 and/or L26 in the peptidyl transferase center.

Animals↗
PubMed1976

Activities of nucleoprotein particles derived from rat liver ribosome.

80-S ribosomes and 60-S subunits from rat liver were treated at increasing KC1 concentrations giving protein-deficient ribosomal particles whose components were analyzed and their activity tested. Most of the activities assayed stand treatment up to KC1 concentrations of around 0.6 M; peptidyl transferase, measured by the fragment reaction, however was 50% inhibited by 0.5 M KC1 in 60-S subunits but not in 80-S ribosomes. Three proteins, L21, L26 and L31, might be implicated in this loss of activity. 60-S subunits forming part of the 80 S ribosome are more resistant to the salt treatment and the pattern of proteins released by the treatment differs from the one obtained from free 60-S subunits, implying perhaps a change of conformation of this subunit upon association to form 80-S couples. According to their resistance to release by KC1 the proteins of the large sub-unit can be divided into three groups: (1) easily removed, including proteins: L1, L11, L17 and L25 in 80-s subunits and in addition, L5, L8, L9, L13, L20, L22, L26, L29, L31 and L32/33 in 60-S subunits; (2) proteins resistant to release by high salt concentrations in 80-S ribosomes as well as in 60-S subunits, namely proteins L3, L14, L27, L36, L40, L41, X1 and X2; (3) the rest of the proteins which are released in a more or less continuous way throughout the treatment. 5 S RNA is not released by KC1 treatment at the concentrations used. The binding sites for the antibiotics trichodermin and anisomycin are affected in a different way by the salt treatment, indicating that they are structurally different.

Animals↗
PubMed1976

Binding of aminoacyl-tRNA to rat liver ribosomal proteins.

Rat liver ribosome treatment with ethanol and 1 M NH4Cl releases some 31-33 ribosomal proteins. This split protein fraction binds Phe-tRNA, Ac-Phe-tRNA, Met-tRNAM and f-Met-tRNAF in the absence of K+ and Mg++ ions. When the split protein fraction is passed through Sephadex G-100 only six proteins are retained in the column: S10, S14, S15, S19, L35, and L36. The aminoacyl-tRNA binding activity of this protein fraction retained in the Sephadex G-100 column is similar to that of the total split protein fraction, suggesting that the above six proteins, or only some of them, are involved in the binding reaction.

Animals↗
PubMed1975

Long-term deficits after somatosensory cortical lesions in rats.

Rats having either sham operations or one-stage bilateral lesions of the two somatosensory areas of the cortex were tested for acquisition of five tactile discriminations after postoperative recovery intervals of 14, 35, 180, 365 or 730 days. The group with lesions performed worse than its time-matched control group in every instance, and there was no evidence for recovery of function with the longer postoperative recovery periods. These results suggest that time per se is not a significant determinant of restitution after somatosensory cortical ablations.

Animals↗
PubMedDate not supplied

Transjugular liver biopsy: a review of 77 biopsies using a spring-propelled cutting needle (biopsy gun).

Seventy-seven transjugular liver biopsies were performed with a coaxial, spring-loaded, 18-gauge cutting needle, the Biopty gun (Bard Biopsy System, Covington, GA, USA) on consecutive patients between July 1993 and February 1995. Fifty men and 27 women were included in the study; the mean age was 45 years (range 15-69 years). The average number of punctures per patient was 5.2, with a range of 2-9, yielding an average of 4.8 samples per patient (range 1-7). The length of the samples varied from 10 to 22 mm with a constant diameter of 1 mm. The mean time required to complete the procedure was 48 min (43-52 min). Histological diagnoses were obtained in 74 of 77 patients (96%), with non-diagnostic specimens attributed to excessive fragmentation (3 cases). Complications occurred in 10 patients (puncture site hematoma, carotid artery puncture, abdominal pain, vasovagal reaction, hepatic capsule perforation, and hemobilia). The latter two complications were self-limited. In our experience this transjugular hepatic biopsy method is promising for performing biopsies in patients with chronic liver disease, due to its high success rate and low morbidity rate.

Adolescent↗
PubMedDate not supplied

Retrieval of migrated colonic stents from the rectum.

Palliative stenting of malignant colonic obstruction may be complicated by stent migration. Stents that migrate into the rectum cannot be passed with bowel movements and frequently cause obstruction. We present two simple means to retrieve stents from the rectum using fluoroscopic guidance. These techniques were used successfully without complication in four stent migrations.

Colonic Neoplasms↗
PubMedDate not supplied

Treatment of complete and partial obstruction of the nasolacrimal system with polyurethane stents: initial experience.

PURPOSE: To present our experience in the treatment of nasolacrimal occlusion by means of polyurethane stents. METHODS: Forty polyurethane stents were placed under fluoroscopic guidance in 35 consecutive patients with epiphora due to total or partial obstruction of the nasolacrimal system. The set designed by Song was used in all patients. The procedure was performed by introducing a guidewire through the superior punctum into the canaliculus and advancing it across the obstruction into the inferior meatus of the nasal cavity. After pulling out the guidewire, the stent was advanced in retrograde fashion and released into the sac and the nasolacrimal duct. RESULTS: The technical success rate was 100%. The average time for the procedure was 25 min (range 10-60 min). Immediate complications were: mild pain (n = 5), severe pain (n = 1), minimal epistaxis (n = 7), and moderate epistaxis (n = 1). No major complications occurred. The last clinical control revealed complete resolution of epiphora in 35 eyes and partial resolution in four; one patient did not improve. CONCLUSION: This technique for treatment of obstruction of the nasolacrimal system is simple and safe, and may obviate the use of more invasive procedures.

Adult↗
PubMedDate not supplied

Microtia: a clinical and genetic study at the National Institute of Pediatrics in Mexico City.

BACKGROUND: Microtia is a malformation of the ear with extreme variability of expression. It is generally seen as an isolated malformation. However, some authors consider it to be a minimal manifestation of the oculo-auriculo-vertebral spectrum (OAVS), where, in addition, there are facial, vertebral, and renal abnormalities, among others. METHODS: A total of 145 pediatric patients with unilateral or bilateral microtia not considered as part of a syndrome were studied. All patients were subjected to an intentional clinical examination, a familial history, and radiographic imaging studies for ruling out associated malformations. Patients were classified into two groups: group 1 (60%), with isolated microtia; and group 2 (40%), considered as OAVS, with microtia associated with hemifacial skeletal microsomia, vertebral and/or renal malformations. RESULTS: No significant differences were found between the groups when the following variables were compared: gender; presence of unilateral or bilateral microtia; atretic external auditory canal; presence of preauricular tags; hearing loss of any type, and affection of the seventh cranial nerve, as well as associated malformations of other organs or systems. There were significant differences in relation to the presence of soft-tissue hemifacial microsomia, more frequently seen in patients with OAVS, because the majority of these patients had bone microsomia. Over 66% of the cases were sporadic and the rest were familiar. In 28.3% of the cases, the history suggested an autosomal-dominant inheritance pattern, and in 5.5%, an autosomal-recessive inheritance pattern, although in some familial cases, multifactorial inheritance could not be ignored. Some members in several families had isolated microtia, and others had mild characteristic manifestations of OAVS. CONCLUSIONS: Our results support the hypothesis that isolated microtia is a minimal expression of OAVS. Therefore, it is recommended that patients with microtia be subjected to intentional studies that search for malformations and physical examinations of first-degree relatives for adequate genetic counseling and management.

Adolescent↗