Biomedical subjects

J G Luz

Publications and source records attributed to J G Luz.

At least 19 recordsLinked to original sources

PubMed2001

Observation of covalent intermediates in an enzyme mechanism at atomic resolution.

In classical enzymology, intermediates and transition states in a catalytic mechanism are usually inferred from a series of biochemical experiments. Here, we derive an enzyme mechanism from true atomic-resolution x-ray structures of reaction intermediates. Two ultra-high resolution structures of wild-type and mutant d-2-deoxyribose-5-phosphate (DRP) aldolase complexes with DRP at 1.05 and 1.10 angstroms unambiguously identify the postulated covalent carbinolamine and Schiff base intermediates in the aldolase mechanism. In combination with site-directed mutagenesis and (1)H nuclear magnetic resonance, we can now propose how the heretofore elusive C-2 proton abstraction step and the overall stereochemical course are accomplished. A proton relay system appears to activate a conserved active-site water that functions as the critical mediator for proton transfer.

Aldehyde-Lyases↗

PubMed2001

Rotated subcondylar process fracture in the growing animal: an experimental study in rats.

Unilateral, rotated subcondylar fractures were surgically induced in young rats under general anaesthesia. A decrease in body weight was observed in the fractured animals, with recovery at the end of the experimental period. A tendency of deviation of the mandible to the fracture side was noticed on axial radiographs, but without significant difference between experimental and sham-operated animals. Histological data initially demonstrated acute inflammation along the articular capsule and adjacent muscle fibres. Within 2 weeks, exuberant callus formation occurred. Neither devitalized bone ends nor intra-articular granulation tissue were seen. After 1 month, the temporomandibular joint presented characteristics of normality, with the condylar process centralized into the temporal fossa, interposed by the articular disc. These results were preserved after 3 months. We concluded that rotational subcondylar fractures in young rats heal by callus formation, with simultaneous and prompt repositioning of the condyle.

Animals↗

PubMed2000

Crystallization of retinol dehydratase from Spodoptera frugiperda: improvement of crystal quality by modification by ethylmercurythiosalicylate.

Retinol dehydratase is a sulfotransferase which is presumed to catalyze the dehydration of its substrate via a transient retinyl sulfate intermediate. Crystals (space group P2(1), unit-cell parameters a = 82.05, b = 66.61, c = 84.90 A, beta = 111.29 degrees ) are significantly improved by covalent modification of the protein with ethylmercury.

Animals↗

PubMed1999

Effect of freeze-dried bone and a dextran agglutinant on the healing of defects in the rat mandible.

The effects of inorganic, freeze-dried bone, alone or mixed with a dextran agglutinant, on the repair of experimentally created critical-size bone defects were evaluated in the rat mandible. Histological data demonstrated a progressive resorption of the freeze-dried bone particles, without osseous proliferation into the defect, and a posterior foreign-body reaction. These results indicate that the freeze-dried bone did not induce bony healing in the critical-size defect and that the addition of dextran agglutinant did not change the tissue response. Dextran may have other applications as a biocompatible, resorbable agglutinant.

Animals↗

PubMed1998

Substrate specificity and kinetic mechanism of the insect sulfotransferase, retinol dehydratase.

Spodoptera frugiperda retinol dehydratase catalyzes the conversion of retinol to the retro-retinoid anhydroretinol. It shares sequence homology with the family of mammalian cytosolic sulfotransferases and provides the first link between sulfotransferases and retinol metabolism. In this study the enzymatic properties of retinol dehydratase were examined using bacterially expressed protein. We show that retinol dehydratase can catalyze the transfer of the sulfonate moiety to small phenolic compounds and exhibits many functional similarities to the mammalian cytosolic sulfotransferases. The bisubstrate reaction that it catalyzes between retinol and the universal sulfonate donor 3'-phosphoadenosine 5'-phosphosulfate seems to involve ternary complex formation and to proceed via a Random Bi Bi mechanism. In addition to the low nanomolar Km value for free retinol, retinol dehydratase is strongly inhibited by retinol metabolites, suggesting a preference for retinoids. Conversely, a number of tested mammalian cytosolic sulfotransferases do not utilize retinol, indicating that retinol is not a general substrate for sulfotransferases.

Adenosine Diphosphate↗

PubMed1998

Healing of the displaced condylar process fracture: an experimental study.

Healing of the displaced condylar process fracture was analysed by means of an experimental model using adults rats. Displaced fractures of the right condylar process were achieved under general anaesthesia. Histological data initially demonstrated neutrophilic exudation along the articular capsule and adjacent muscle fibres. One week later, devitalized bone areas at the fracture site, as well as proliferation of cartilaginous and osseous tissue were observed. Subsequently, exuberant callus formation and a decrease in the inflammatory process occurred. After 3 months, the condylar process presented characteristics of normality and was centralized into the temporal fossa, with interposition of the articular disc. These results indicate that experimentally induced, displaced condylar process fractures heal by callus formation with simultaneous repositioning of the condyle.

Animals↗

PubMed1997

Effects of unilateral upper incisor extraction on facial growth of young rats.

The effects of unilateral extraction of the upper incisor (one tooth) on facial growth of young rats were studied. The remaining upper incisor showed deviation towards the opposite side, and there was regular dental wear of all the incisors. The effects were evident only in the mid-facial area. Cephalometric measurements showed significant shortening with deviation of the incisor bone on the extraction side. There was no significant disturbance of the growth of the rest of the maxilla and mandible. These results indicate that upper incisor extractions have a localized influence, leading to impairment of incisor bone growth.

Alveolar Process↗

PubMed1997

Characteristics of chief complaints of patients with temporomandibular disorders in a Brazilian population.

A retrospective survey of 894 patients with temporomandibular disorders was conducted in order to analyse the characteristics of chief complaints. The patients presented complaints of pain (82.1%), functional disturbance (12.3%), articular sounds (5.0%) and swelling (0.6%). Unilateral occurrence (66.5%) was more frequent than bilateral. The most frequent location of pain was the temporomandibular joint (TMJ) (82.1%) followed by ear (10.8%), face (2.3%), head (2.3%), mandible (1.0%), neck (0.9%), temporal (0.4%) and frontal (0.1%) areas. Pain in the TMJ occurred in isolation (87.9%) or associated to other locations. The most frequent functional disturbance was limitation of jaw opening (32.1%).

Adolescent↗

PubMed1996

Remodelling of bilateral fractures of the mandibular condyle.

A case of complete remodelling of bilateral fractures of the mandibular condyle in an 11-year-old boy is presented. Initial radiographic examination revealed fractures of the right and left condylar neck with medial and anterior dislocation of the proximal fragment. The fractures were treated conservatively, with a short-time intermaxillary fixation and early jaw function, and thirty-five months later the patient was asymptomatic. Radiographic changes observed following treatment have revealed a gradual return to normal shape and position of the condyles.

Bone Remodeling↗

PubMed1995

Passive mandibular border positions and their relationships with signs and symptoms of craniomandibular disorder. A study of linear and angular measurements.

Linear measurements of passive mandibular border positions and angular measurements of passive opening were recorded in a group of patients with craniomandibular disorders. The relationships between signs and symptoms of craniomandibular disorders and abnormal capacity of movement were studied. There was significant association of some signs and symptoms related to the temporomandibular joint and abnormal vertical and horizontal excursions. On the other hand, there was only one relationship between occlusal factors and abnormal passive mandibular border positions.

Adolescent↗

PubMed1994

Novel Cl(-)-dependent intracellular pH regulation in murine MDR 1 transfectants and potential implications.

Previously [Luz et al. (1994) Biochemistry 33, 7239-7249], we determined that Cl(-)- and -HCO3-dependent pHi homeostasis was perturbed in multidrug resistant (MDR) cells created by transfecting LR73 Chinese hamster ovary fibroblasts with wild-type mu (murine) MDR 1 (Gros et al., 1991). Via single-cell photometry experiments performed under various conditions, we are now able to separate Na(+)-dependent and Na(+)-independent components of Cl-/-HCO3 exchange in the MDR transfectants and the parental LR73 cells. Cl(-)-dependent, Na(+)-independent reacidification of pHi, mediated by the anion exchanger 2 isoform in LR73 cells, is dramatically inhibited by mild overexpression of MDR protein. Analysis of H+ flux at different pHi shows that Cl(-)-dependent reacidification approaches 0.2 mM H+/s for LR73 cells at pHi = 8.0 but is at least 10-fold slower for MDR 1 transfectants that were never exposed to chemotherapeutics (EX4N7 cells). MDR 1 transfectants selected on the chemotherapeutic vinblastine (1-1 cells), which express approximately 10-fold more MDR protein relative to EX4N7 cells, exhibit similar behavior; however, alterations in Cl(-)-dependent pHi regulation are more severe. Hypotonic conditions, which have been shown to increase anomalous Cl- conductance in some cells overexpressing MDR protein (Valverde et al., 1992), are found to amplify the altered pHi homeostasis features in the primary transfectants that express lower levels of MDR protein such that they then mimic the behavior of the drug-selected cells that express substantially more MDR protein. Verapamil reverses the anomalous behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1994

Transfection of mu MDR 1 inhibits Na(+)-independent Cl-/-HCO3 exchange in Chinese hamster ovary cells.

We have used single-cell photometry to measure intracellular pH (pHi) for several MDR cell lines constructed by stably transfecting LR73 chinese hamster ovary fibroblasts with mutant and wild type murine MDR 1 genes. In addition, plasma membrane electrical potential (delta psi) has been measured for the same cells by the K+/valinomycin null point titration method using the ratiometric styryl probe di-4-ANEPPS. Both the untransfected, parental cell line and a cell line expressing substantial mutant MDR 1 protein (K432R/K1074R) that is unable to confer the MDR phenotype are found to have delta psi > or = -40 (+/- 5) mV and pHi < or = 7.16 (+/- 0.03) units. In contrast, MDR cell lines constructed by transfecting wild type mu MDR 1 cDNA are found to exhibit delta psi from 15 to 19 mV lower and pHi from 0.13 to 0.34 units higher. A cell line that overexpresses crippled MDR protein (S941F) that is not resistant to colchicine or doxorubicin, but which is resistant to vinblastine [Gros, P., Dhir, R., Croop, J., & Talbot, F. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 7289-7293], exhibits elevated pHi and slightly elevated delta psi, relative to LR73. Northern and western blot analyses confirm the substantial overexpression of the mu MDR genes and proteins in these lines, as well as the mild overexpression of endogenous hamster p-GP mRNA in some lines. In general agreement with previous studies that examined myeloma cells overexpressing hu MDR 1 protein [Roepe, P.D., Wei, L.-Y., Cruz, J., & Carlson, D. (1993) Biochemistry 32, 11042-11056] we find that overexpression of wild type mu MDR 1 protein inhibits Cl(-)- and -HCO3-dependent pHi homeostasis. Via single-cell photometry studies we now conclude that this is due to inhibition of Na(+)-independent Cl-/-HCO3 exchange (strict anion exchange or AE). As concluded previously for other MDR cells, decreased AE activity is not due to decreased expression of the exchanger; in fact, again similar to previous work [Roepe et al. (1993) Biochemistry 32, 11042-11056], we find increased levels of AE mRNA in some MDR cell lines. Models that may explain these data that are also consistent with the known physiology of cells that endogenously express MDR protein are suggested. These data are consistent with a model for MDR protein function wherein overexpression of the protein decreases delta psi and/or elevates pHi via Cl(-)- and -HCO3-dependent mechanisms.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1994

Active unilateral condylar hyperplasia.

Two cases of active unilateral condylar hyperplasia which were treated with condylectomy alone are presented. The first case was an adult form and the other a juvenile form. Both were classified as active by using 99Tc bone scintigraphy. Clinical and radiographic features of both cases conformed to the hemimandibular hypertrophy type. Satisfactory facial symmetry and dental occlusion were achieved. Histopathological data confirmed the activity of the articular cartilage layers.

Adolescent↗

PubMed1994

Incidence of temporomandibular joint disorders in patients seen at a hospital emergency room.

A retrospective survey of a hospital emergency room population seen at an oral and maxillofacial surgery clinic during a 6-month period found 62 patients (2.7% of the total population) with temporomandibular joint disorders. The diagnoses were myofascial pain-dysfunction/temporomandibular joint dysfunction (MPD/TMJ) syndrome (70.9% of the cases) and dislocation (luxation) (22.5% of the cases). The chief complaint was well defined in relation to the diagnoses: facial pain in the MPD/TMJ syndrome cases, and displacement of the mandible in the dislocation cases.

Adolescent↗

PubMed1994

Incidence of dentoalveolar injuries in hospital emergency room patients.

A retrospective survey over one year of a hospital emergency room population, seen at an oral and maxillofacial surgery clinic, found 271 patients (4.6% of the total population) with dentoalveolar injuries. A very large number of injuries occurred to children between the ages of 0 and 5 years (42.1%), and there was a significant number of injured patients in the adult population (19.1%). The ratio of male to female was 1.9:1. The leading cause of injury was falls (59.8%). The largest number of injuries was seen during summer. The diagnoses were lateral luxation (27.3%), concussion (17.3%), exarticulation (14.3%), tooth fracture (12.5%), intrusive luxation (11.1%), fracture of alveolar process (7.4%), extrusive luxation (3.7%), and cases with more than one diagnosis (6.3%). Most of the involved teeth were maxillary central incisors, in both dentitions.

Adolescent↗

PubMed1993

Passive mandibular border positions in craniomandibular disorder patients and asymptomatic individuals: a comparative study.

Measurements of passive mandibular border positions were recorded in a group of patients with craniomandibular disorders and compared with those of a control group of asymptomatic individuals. The mean values of triplicate measurements did not show significant difference. This finding indicates that a passive measurement is sufficient for surveying mandibular border positions. The mean values of mandibular border positions revealed no significant difference between patients with craniomandibular disorders and asymptomatic individuals. Results indicate that measurement of mandibular border positions is not a specific factor for diagnosis of craniomandibular disorders, but it seems a valuable method to evaluate the treatment of individual cases.

Adolescent↗

PubMed1991

The effect of indirect trauma on the rat temporomandibular joint.

The effect of indirect trauma to the rat temporomandibular joint (TMJ) is analysed by means of an experimental model. The trauma, applied from an angle-glenoid fossa direction, produced injury of the TMJ. The histological data demonstrated that the impact could produce fractures of the glenoid fossa, but no hemarthrosis was observed. Trauma, both with or without fracture, caused proliferative changes in the TMJ. The glenoid fossa, the articular disk and the articular surface of the condyle were injured. Thickening of the articular surfaces had resulted in reduced joint space. Subsequently, remodelling changes in the condyle were found.

Animals↗

PubMed1989

[Statistical considerations of isolated maxillofacial fractures in Sao Paulo].

Statistical analysis of 550 isolated maxillo-facial fractures is presented. Data obtained illustrated the important number of maxillo-facial fractures in Sao Paulo, the automobilistics accidents were responsible for most maxillo-facial trauma, the jaw and the malar were more predominant than the others structures and the conservative treatment was the most used one.

Brazil↗