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At least 973 records · Page 54Linked to original sources
PubMed1994

Cloning and expression in Escherichia coli of the gene coding for phytoene synthase from the cyanobacterium Synechocystis sp. PCC6803.

The gene coding for the carotenoid biosynthesis enzyme phytoene synthase (pys) has been cloned from the unicellular cyanobacterium Synechocystis sp. PCC6803. The gene has been functionally expressed in Escherichia coli, where it directs the biosynthesis of phytoene from geranylgeranyl pyrophosphate (GGPP). Analysis of the sequence of the Synechocystis pys protein deduced from the gene sequence shows that it is highly homologous to the tomato and Synechococcus phytoene synthases and shows conserved domains with other bacterial phytoene synthase enzymes. The pys gene starts 60 nucleotides downstream of the pds gene (which codes for phytoene desaturase). However, it seems to be transcribed mainly from its own promoters, because insertions that disrupt the pds gene do not affect significantly the expression of the pys gene.

Alkyl and Aryl Transferases↗
PubMed1987

Adolescent medicine education in pediatric residency programs following the 1978 Task Force on Pediatric Education report.

In 1982, the Society for Adolescent Medicine initiated a survey of all pediatric residencies in the United States and Canada to determine: if there had been an increase in the amount and quality of adolescent medicine training since the 1978 report by the Task Force on Pediatric Education; if pediatric departments were assuming responsibility for the care of adolescents; and the curriculum objectives for adolescent medicine (AM), the educational methods used, and whether program graduates (PGs) felt competent to care for adolescents. One hundred directors and 72 recent graduates completed an initial questionnaire. A follow-up telephone survey of program directors (PDs) who did not respond resulted in 109 completed interviews. The survey results suggest a favorable trend in AM training. Evidence of this favorable trend includes: a 10% increase (p less than 0.05) in the number of AM wards, and a 33% increase (p less than 0.01) in clinics; a 29% increase (p less than 0.01) in programs having a block of time devoted to AM; increased time spent caring for adolescents at all resident levels; and an increase in adolescent inpatients of 32% and outpatients of 45% (p less than 0.01). An increase in the number of and time for mastery of curriculum objectives and educational methods was reported by PDs.

Adolescent↗
PubMed1989

Separation of different types of afterpotentials following penicillin-induced paroxysmal depolarization shifts of neurons in the motor cortex of the rat.

Afterpotentials of penicillin-induced paroxysmal depolarization shifts (PDS) of neurones in the motor cortex of the rat in vivo were investigated with intracellular recordings. Following the PDS, 4 different types of afterpotentials were observed: fast afterhyperpolarizations with an average duration of 600 ms, fast afterdepolarizations with an average duration of 700 ms, slow afterhyperpolarizations with an average duration of 1.9 s and slow afterdepolarizations with an average duration of 1.8 s. The fast and slow afterpotentials could occur in various combinations with the exception of a fast afterhyperpolarization followed by a slow afterdepolarization. Neurones displaying afterdepolarizations had higher resting membrane potentials than those displaying afterhyperolarizations, i.e. the polarity of the afterpotential depended on membrane potential. Experiments with intracellular Cl- injection indicated that the fast but not the slow afterpotentials are associated with an increase in membrane Cl- conductance. The slow afterhyperpolarizations are suggested to result from a calcium-dependent or a synaptically generated potassium current.

Animals↗
PubMed1993

Growth factor modulation of surface ganglioside expression in cloned neoplastic glia.

Cloned neoplastic astrocytes from a human glioma-derived cell line (IPSB-18) were grown in fetal calf serum (FCS)-supplemented culture medium in the presence of three growth factors. Basic fibroblast growth factor (bFGF), epidermal growth factor (EGF) but not platelet-derived growth factor (PDGF) induced an increase in the number of cells positive for the ganglioside-recognizing monoclonal antibody, A2B5. No such growth factor-mediated induction could be detected in cells maintained in plasma-derived serum (PDS)-supplemented medium. Small molecules, removed from PDS during dialysis, may, therefore, act synergistically with growth factors in the control of ganglioside synthesis.

Astrocytes↗
PubMed1994

Metabotropic glutamate receptor activation decreases epileptiform activity in rat neocortex.

Intracellular and extracellular recordings were obtained from layers II-III of slices of adult rat neocortex maintained in vitro. Excitatory postsynaptic potentials (EPSPs) and epileptiform discharges (paroxysmal depolarizing shifts, PDSs) were evoked in the presence of bicuculline methiodide. Responses were monitored before, during, and after bath application of the putative metabotropic glutamate receptor agonists, 1S, 3R-ACPD and L-AP4. Peak EPSP amplitude and both PDS amplitude and duration were reduced during 1S,3R-ACPD application. Area measurements indicate that PDSs were reduced to 51.7 +/- 19.9% of control. Stimulus threshold for evoking a PDS was increased in the presence of 1S,3R-ACPD or L-AP4. Pretreatment of slices with 1S.3R-ACPD did not prevent the generation of epileptiform events when bicuculline subsequently was applied. These results indicate that mGluR activation by 1S,3R-ACPD has significant suppressive effects on evoked epileptiform activity in the adult rat neocortex in vitro.

Aminobutyrates↗
PubMed1991

Ketamine suppresses synchronized discharges in the disinhibited amygdala slice.

The effect of ketamine on the paroxysmal depolarizing shift (PDS) induced by bicuculline was studied in rat amygdala slices using intracellular recording techniques. Stimulation of the ventral endopyriform nucleus evoked an excitatory postsynaptic potential (EPSP). After exposure to bicuculline (20 microM), the same stimulus intensity evoked burst firing. Superfusion of ketamine reversibly reduced the duration of PDS. Pretreatment of amygdala slices with DL-2-amino-5-phosphonovaleate (DL-APV, 50 microM) occluded the effect of ketamine suggesting that ketamine shortened the burst duration via its blocking action on the NMDA receptors. In all neurons tested, a large depolarizing shift remained in the presence of ketamine. The ketamine-resistant component was blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 8 microM) indicating its mediation by the non-NMDA receptors.

2-Amino-5-phosphonovalerate↗
PubMed1994

Valproic acid suppresses the synaptic response mediated by the NMDA receptors in rat amygdalar slices.

The mechanism of action of the anticonvulsant drug valproic acid (VPA) was studied in rat amygdaloid slices using intracellular recording techniques. In the presence of bicuculline (20 microM), stimulation of the endopyriform nucleus evoked an excitatory postsynaptic potential (EPSP) followed by a paroxysmal depolarizing shift (PDS). Superfusion of VPA (2 mM) reversibly suppressed the PDS. Synaptic response mediated by the N-methyl-D-aspartate (NMDA) receptors (EPSPNMDA) was isolated pharmacologically by application of a solution containing nonNMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and gamma-aminobutyric acid receptor antagonist bicuculline (20 microM). VPA (0.2-10 mM) reversibly reduced the amplitude of the EPSPNMDA in a dose-dependent manner. Higher concentration of VPA (10 mM), in addition, suppressed the normal synaptic transmission. These results suggest that VPA's anticonvulsant effect is due, at least in part, to its blocking action on the EPSPNMDA.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1989

Lysis of erythrocytes by the secreted cysteine proteinase of Porphyromonas gingivalis W83.

The cysteine proteinase produced in the culture supernatant of Porphyromonas gingivalis was extensively purified. Haemagglutination type assays in which the enzyme was titrated against a fixed concentration of erythrocytes, showed that low levels of enzyme directly caused lysis of the red blood cells. However, using the same assay, the presence of stoichiometric amounts of the thiol blocking agent, 2,2'-dipyridyl disulphide (2-PDS) specifically inhibited the action of the enzyme or its haemagglutination with W83 cells or vesicles. In all cases, electron micrographs revealed that in the presence of 2-PDS the erythrocytes remained intact. Thiol activator free enzyme or aerated, inactivated enzyme had no effect on the red blood cells. These results show conclusively that the secreted cysteine proteinase of P. gingivalis causes lysis of erythrocytes and must now be regarded as a potent virulence determinant of P. gingivalis.

Animals↗
PubMedDate not supplied

Epileptic discharges induced by intermittent light stimulation in photosensitive baboons: a current source density study.

The current source density (CSD) method was applied to the study of paroxysmal discharges (PDs) induced by intermittent light stimulation (ILS) in Papio papio baboons made photosensitive by a subconvulsant dose of allylglycine. CSD was studied in the motor and premotor areas (4 and 6). Laminar profiles of sinks and sources are similar in both areas. Nevertheless, the motor area seems to become involved first since it shows the earliest and most prominent sink in layer III. Such a sink, correlated with the PD spike, moves progressively upward to the cortical surface. The localization and other experimental arguments obtained by the same method suggest that this sink could be mainly of dendritic origin. The cortico-cortical afferents to the superficial layers of the motor area might thus determine the generation of this sink. A smaller sink, detected at the same latency between layers V and VI could correspond to synaptic activations due to thalamo-cortical afferents probably arriving on the pyramidal cells which project to the spinal cord. Intense sinks correlated with the PD wave in layer V could be passive, due to active sources lying just above and/or below, because in previous studies an inhibition of the cellular discharges was always observed in correlation with the wave. It is suggested that ILS triggered PDs involve visual cortico-cortical afferents directed mainly to the superficial layers of the motor area provoking an intense synaptic activation of the cellular elements situated at this level.

Allylglycine↗
PubMed1995

Noradrenergic modulation of epileptiform activity in the hippocampus.

Norepinephrine has been proposed to have both pro- and anticonvulsant properties. In the CA3 region of rat hippocampal slices, we studied the effects of norepinephrine and selective adrenergic agonists and antagonists on spontaneously occurring epileptiform discharges produced by either picrotoxin, a convulsant that impairs GABAA-mediated inhibition, or by elevated extracellular potassium ([K+]o). Bath application of 5 microM norepinephrine (NE) increased the rate of discharges produced by 7.5 mM [K+]o but not the rate of picrotoxin-induced discharges. At higher concentrations (> or = 10 microM), NE slowed the rate of spontaneous epileptiform discharges produced by picrotoxin. Spontaneous discharges produced by either picrotoxin or 7.5 mM [K+]o were slowed or stopped by alpha-adrenergic receptor activation, the alpha 1 receptor being most responsible for this slowing effect. The alpha 2 agonist clonidine had minimal effects on the discharge rate; however, the alpha 2 antagonists yohimbine and idazoxan slowed the rate. In contrast, beta receptor or adenylate cyclase activation increased the rate of spontaneous discharges. This acceleration in rate was accompanied by a decrease in the amplitude and duration of the afterhyperpolarization (AHP) that follows the intracellularly recorded paroxysmal depolarizing shift (PDS). These results confirm that beta-adrenergic receptor activation increases the rate of epileptiform discharges and suggest that the acceleration is a result of a decrease in the AHP duration and amplitude. Activation of alpha-adrenergic receptors slowed the rate of epileptiform discharges without an associated change in the AHP. The AHP that follows the PDS helps define the maximal rate of epileptiform discharges in the hippocampal slice and a decrease in the duration of the AHP may contribute to the transition from an interictal to ictal pattern of epileptiform activity.

Adrenergic Agents↗
PubMed1994

Afterpotentials of penicillin-induced epileptiform neuronal discharges in the motor cortex of the rat in vivo.

Interictal spikes and sharp waves in the EEG are followed by intervals in which the excitability of the brain seems to be normal or decreased. Often interictal spikes even appear in rhythmical patterns with intervals in the order of 0.5-2 s. These observations suggest that intrinsic and synaptic inhibitory and excitatory processes are activated which outlast the duration of the interictal discharge. In the present study such afterpotentials were analyzed in penicillin foci of the rat motor cortex in vivo using intracellular recording techniques. Paroxysmal depolarizations (PDS) of neurons within the focus were followed by afterpotentials comprising several components. Fast afterpotentials with a duration of 640 ms were associated with a sevenfold increase in membrane conductance. The fast afterpotentials were depolarizing in the majority of recordings and had an average equilibrium potential of -62 mV. This equilibrium potential was Cl(-)-dependent and was not affected by intracellular EGTA or Cs+. It is suggested that these afterpotentials represent GABAA responses. In 38% of the neurons slow afterhyperpolarizations with a twofold increase in membrane conductance and a duration of 2 s were observed. These afterhyperpolarizations had a reversal potential of -79 mV, were blocked by intracellular Cs+, were reduced in duration and amplitude by intracellular EGTA, and are suggested to present a combination of a GABAB response and a calcium-dependent potassium current. In addition, slow afterdepolarizations with a duration of about 1900 ms were registered in 16% of the recordings. It is concluded that afterpotentials with several intrinsic and synaptic components follow penicillin-induced PDS. Among these are giant Cl(-)-dependent potentials which probably represent GABAA responses, GABAB responses and a slow calcium-dependent potassium current. It is suggested that the depolarizing equilibrium potential of the Cl(-)-dependent component is due to intracellular Cl- accumulation which might favor transition to ictal discharges.

Action Potentials↗
PubMed2006

Impulsivity and negative emotionality associated with substance use problems and Cluster B personality in college students.

The co-occurrence of personality disorders (PDs) and substance use disorders (SUDs) can be partially attributed to shared underlying personality traits. This study examined the role of negative emotionality (NEM) and impulsivity in 617 university students with self-reported substance use problems and Cluster B PD symptoms. Results indicated that NEM was significantly associated with drug and alcohol use problems, antisocial PD, borderline PD, and narcissistic PD. Impulsivity was significantly associated with drug use problems, antisocial PD, and histrionic PD. Only NEM mediated the relationship between alcohol use problems and symptoms of each of the Cluster B PDs while impulsivity mediated only the relationship between drug use problems and histrionic PD. These results suggest that NEM may be more relevant than impulsivity to our understanding of the co-occurrence between substance use problems and Cluster B PD features.

Adolescent↗
PubMedDate not supplied

Large vestibular aqueduct syndrome: audiological, radiological, clinical, and genetic features.

PURPOSE: The aim of this study was to analyze the clinical, audiological, radiological, and genetic features of a group of patients affected with large vestibular aqueduct syndrome. MATERIALS AND METHODS: Seventeen patients affected with large vestibular aqueduct syndrome (LVAS), diagnosed by means of high-resolution magnetic resonance imaging of the inner ear, with 3-dimensional reconstructions of the labyrinth and by high-resolution spiral computed tomography of the temporal bone, performed only on the oldest patients, have been submitted to a complete audiological evaluation, a thyroid functional and ultrasonographic study, and a molecular study of the PDS gene. RESULTS: The clinical presentation of LVAS was very variable in our group of patients. The enlarged vestibular aqueduct was bilateral in 15 cases and unilateral in 2; it was the only malformation of the labyrinth in 12 patients, whereas it was associated with other inner ear anomalies in the other 5. The hearing loss was very variable in degree (from mild to profound), age at onset, and progression. Moreover, among the 17 patients, 10 were clinically affected by Pendred's syndrome (PS), 3 by distal renal tubular acidosis associated with large vestibular aqueduct, whereas in 3 patients the large vestibular aqueduct was not syndromal. Finally, we identified mutations in the PDS gene in 5 of 10 patients with PS. CONCLUSIONS: Our data underscore the frequent role of the large vestibular aqueduct syndrome in the pathogenesis of sensorineural hearing loss and the overall wide variability in its audiological features. It is also highlighted that LVAS is often part of some syndromal diseases, most of which are PS, which is often misdiagnosed because of the varying degree of thyroid symptoms. This study also underscores the possible role of hydro-electrolyte and acid-base endolymphatic fluid disorders in the pathogenesis of enlarged vestibular aqueduct syndrome.

Acoustic Impedance Tests↗
PubMed2005

Hand-assisted laparoscopic pylorus-preserving pancreaticoduodenectomy for pancreas head disease.

Laparoscopic procedures for pancreatic surgery have been significantly improved recently; however, the number of successful laparoscopic or laparoscopy-assisted pancreaticoduodenectomies (PDs) has been limited. The limitations could be attributed to the complexity of the reconstruction procedures under laparoscopic observations and the high incidence of critical morbidity with PDs. To overcome the shortcomings, we developed the first hand-assisted laparoscopic pylorus-preserving PD and, in this report, present the case of a patient with a low-grade malignant tumor on the pancreas head.

Adenocarcinoma, Mucinous↗
PubMed2006

Multidisciplinary management in geriatric day-hospital is beneficial for elderly fallers: a prospective study of 28 cases.

We determined whether management including medical, psychological, and physiotherapeutic approaches, over a period of 6 weeks, has a beneficial effect on motor abilities, psychological status, and independence of elderly fallers with psychomotor disadaptation syndrome (PDS). We included 28 subjects (mean age 81.4 years). They were assessed from a medical, motor, and psychological point of view at both the inclusion and the end of the multidisciplinary intervention. A follow-up was conducted with multidisciplinary assessment at 6 and 9 months after the beginning of the study in order to evaluate duration of benefits of the management. The statistical analysis concerned only subjects who took part in the total multidisciplinary program, i.e., 14 subjects. The multidisciplinary intervention had an overall positive impact on motor abilities as shown by the increase in the mini-motor test scores, the rate of success in rising from the floor and decrease of time for the dual task. This study also showed a reduction in the fear of falling and a decrease in the rate of fallers. This positive effect on motor abilities, fear of falling and rate of fallers was sustained until 9 months after the beginning of the multidisciplinary management. This study shows the importance of a multidisciplinary management of elderly fallers with PDS.

Accidental Falls↗
PubMed2006

Arthroscopic all-inside lateral meniscus suture using posterolateral portal.

A new arthroscopic all-inside suture for lateral meniscus posterior horn tear using a single posterolateral portal is described. A lateral meniscus posterior horn peripheral longitudinal tear is often seen with anterior cruciate ligament injury or discoid lateral meniscus tear. Conventional repair methods, such as arthroscopic inside-out, outside-in, or all-inside sutures, can be cumbersome and technically demanding. Our all-inside suture using the posterolateral portal allows thorough visualization of the posterolateral structures, excellent coaptation of torn meniscus, strong knot tightening, and avoidance of inadvertent cartilage injury. The arthroscope is inserted through the anteromedial portal and reaches the posterolateral compartment by a transcondylar approach. A suture hook is introduced into the posterolateral portal without a cannula, penetrates posterior peripheral rim, crosses the tear, and passes through mobile torn fragment. A large amount of No. 0 PDS is passed, so that it curls up inside the joint. After the suture hook is removed, a suture retriever is inserted through the posterolateral portal to pull out 2 ends of the PDS at the same time. The retrieved suture ends are passed through a knot pusher and a 5.5-mm cannula is introduced over the retrieved suture materials for the SMC knot to be tied. A longitudinal tear of lateral meniscus posterior horn is repaired with 2 to 3 sutures.

Adult↗
PubMed2006

A simple method of meniscus repair using the arthroscopic outside-in technique.

We describe a simple method of arthroscopic outside-in meniscus repair that is easy to perform using readily available materials. The technique uses a 19-gauge venepuncture needle, a 16-gauge epidural needle, a No. 3 Prolene suture as a lasso loop, and No. 2 polydioxanone (PDS) sutures for meniscus repair. The venepuncture needle is used to puncture the meniscus from outside-in to deliver the Prolene lasso loop suture. The epidural needle is used to deliver one end of the PDS repair suture through the lasso loop. This suture end is captured by tightening the lasso loop, and delivered out of the joint by withdrawing the venepuncture needle. The epidural needle is kept in the joint. A second pass is made with the venepuncture needle at an appropriate site on the meniscus, and the lasso loop delivered. The other free end of the repair suture is threaded through the epidural needle and through the lasso loop. This other repair suture end is similarly captured and delivered out of the joint. The repair is completed by pulling on the free ends of the repair suture to apply it across the meniscus tear site, and secured by tying the suture to the capsule through a small incision.

Arthroscopy↗
PubMed2006

Mechanical and handling properties of braided polyblend polyethylene sutures in comparison to braided polyester and monofilament polydioxanone sutures.

PURPOSE: This study was designed to comprehensively compare the mechanical properties of 4 types of braided polyblend sutures with widely used braided polyester and monofilament polydioxanone sutures. METHODS: Polyblend polyethylene sutures (FiberWire [Arthrex, Naples, FL], Herculine [Linvatec, Largo, FL], Orthocord [DePuy Mitek, Raynham, MA], and Ultrabraid [Smith & Nephew Endoscopy, Andover, MA]), a braided polyester suture (Ethibond; Ethicon, Somerville, NJ), and an absorbable monofilament polydioxanone suture (PDS II; Ethicon), all USP No. 2, were mechanically tested. Fraying resistance was tested on eyelets of metallic and absorbable suture anchors. Cartilage abrasion caused by an intra-articularly placed suture knot was simulated by fraying on distal porcine femora. RESULTS: All polyblend sutures were stronger than Ethibond or PDS II sutures by at least a factor of 2, with or without a knot. When knotted, Herculine (261 +/- 44 N) was strongest, followed by Ultrabraid (244 +/- 3 N). FiberWire was most resistant against fraying on metallic anchors. Orthocord was by far least abrasive with absorbable anchors. Resistance to fraying was 100- to 500-fold (absorbable anchors) and 6- to 30-fold (metallic anchor) better for all polyblend sutures than for Ethibond. All braided sutures caused a similar amount of abrasion of joint cartilage, but they caused significantly more abrasion (>20-fold) than the monofilament degradable suture. CONCLUSIONS: The ultimate strength of polyblend suture material was 2- to 2.5-fold greater than that of polyester or polydioxanone sutures, but the resistance to fraying was up to 500-fold greater than that of polyester or polydioxanone sutures. With regard to strength, this makes polyblend sutures particularly advantageous for use with metallic edges of anchors or prostheses or with absorbable anchor eyelets. CLINICAL RELEVANCE: With a high resistance to fraying against metallic edges or a decrease in cutting of absorbable suture eyelets being up to 500-fold greater than with polyester or polydioxanone sutures, the new polyblend sutures appear to fill a void in the armamentarium of the surgeon, provided that at least 2 throws more than with conventional sutures are used for knot tying.

Animals↗