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C Pavlides

Publications and source records attributed to C Pavlides.

At least 37 records · Page 2Linked to original sources
PubMed1990

Long-term potentiation in the cat somatosensory cortex.

Intracellular, in-vivo recordings were used to identify neurons in the cat somatosensory cortex in which long-term potentiation (LTP) was induced. Amplitudes of EPSPs produced by microstimulation in the motor cortex (area 4 gamma) were recorded before and after tetanic stimulation (200 Hz, 20 s). In 8/13 cells (62%), EPSP amplitudes increased significantly following the tetanic stimulation. LTP was induced exclusively in cells which produced monosynaptic EPSPs. Six of these cells were labeled by intracellular injections of biocytin. All the cells in which LTP was induced were pyramidal neurons, and were located exclusively in layers II or III of the somatosensory cortex; cells in deeper cortical layers were not potentiated. These data substantiate our previous findings demonstrating LTP in corticocortical pathways and suggest that these pathways play an important role in cortical synaptic plasticity.

Animals↗
PubMed1990

Long-lasting facilitation of pyramidal tract input to spinal interneurons.

The purpose of this study was to determine whether long-term changes in synaptic efficacy can be induced in the pyramidal tract (PT). Tetanic stimulation of the PT induced long-term facilitation of PT input to spinal cord neurons. In contrast, tetanic stimulation of the pyramidal tract did not alter the efficacy of synaptic inputs of PT cells' intracortical axon collaterals to other cortical neurons. These findings suggest that the PT participates in motor learning by modulating the excitability of spinal cord neurons. The results also indicate that induction of LTP in the PT is dependent on postsynaptic mechanisms.

Animals↗
PubMed1989

Long-term potentiation in the motor cortex.

Long-term potentiation (LTP) is a model for learning and memory processes. Tetanic stimulation of the sensory cortex produces LTP in motor cortical neurons, whereas tetanization of the ventrolateral nucleus of the thalamus, which also projects to the motor cortex, does not. However, after simultaneous high-frequency stimulation of both the sensory cortex and the ventrolateral nucleus of the thalamus, LTP of thalamic input to motor cortical neurons is induced. This associative LTP occurs only in neurons in the superficial layers of the motor cortex that receive monosynaptic input from both the sensory cortex and the ventrolateral nucleus of the thalamus. Associative LTP in the motor cortex may constitute a basis for the retention of motor skills.

Animals↗
PubMed1989

Influences of hippocampal place cell firing in the awake state on the activity of these cells during subsequent sleep episodes.

Rat hippocampal (CA1) complex spike "place cells" of freely behaving rats were recorded in pairs continuously during a series of waking (exploration and still-alert), drowsy (quiet-awake), and sleeping (slow-wave, pre-rapid-eye-movement and rapid-eye-movement sleep) behaviors. Pairs of units were selected that had nonoverlapping place fields. The rats were restricted from entering the place field of either cell overnight, and on the day of recording cells were exposed to their individual place fields independently and in a counterbalanced manner. Following exposure, recordings were made in the subsequent sleep episodes and the firing characteristics of both cells were analyzed. Following exposure, significant increases in the spiking activity of the exposed cell were observed in the subsequent sleeping states that were not evident in the unexposed cell. The increased activity was observed in the rate of firing (spikes/sec), the rate of occurrence of bursts with multiple spikes, as well as the number of bursts displaying short (2-4 msec) interspike intervals. The findings suggest that neuronal activity of hippocampal place cells in the awake states may influence the firing characteristics of these cells in subsequent sleep episodes. The increased firing rates along with the greater number of multiple spike bursts and the shorter interspike intervals within the burst, following exposure to a cell's place field, may represent possible information processing during sleep.

Action Potentials↗
PubMed1988

Comparative extracellular current flow at dendrites and soma of dentate granule cells during long-term potentiation.

In the study of long-term potentiation (LTP) in the dentate gyrus, the magnitude of the initial slope of the evoked synaptic potential (ESP) in the region of the granule cell layer, is commonly used as a measure of synaptic efficacy at the site of the perforant path (PP) input. To investigate the viability of this assumption, in rats anesthetized with either chloropent or urethane, LTP was induced by tetanic stimulation of the PP and ESPs were measured simultaneously at both the soma and dendritic site of the PP input. Following LTP, the two responses were decoupled, the somal response being greater than the dendritic in rats anesthetized with chloropent, the opposite being true in urethanized animals. We conclude that in investigating changes in synaptic efficacy following LTP, measurements should be taken at the site of the PP input.

Action Potentials↗
PubMed1988

Long-term potentiation in the dentate gyrus is induced preferentially on the positive phase of theta-rhythm.

Long-term potentiation (LTP), a long lasting enhancement of synaptic efficacy is considered a model for learning and memory. In anesthetized rats, theta-rhythm was induced in the dentate gyrus by midbrain stimulation. Short trains of pulses were applied to the perforant pathway either at the peak of theta-rhythm or its trough. Trains applied at the peak of theta-rhythm induced LTP while trains applied at the trough produced a decrease of synaptic efficacy or had no effect. Thus, theta-rhythm may play a modulating role in the induction of LTP, suggesting a possible mnemonic function for the rhythm during the behaviors in which it occurs.

Animals↗
PubMed1988

Long-term potentiation in the dentate gyrus is preferentially induced at theta rhythm periodicity.

In urethane-anesthetized rats, high frequency stimulation was applied to the medial perforant pathway at various time intervals (50, 100, 200, 350 and 500 ms) following stimulation of the same pathway by a single pulse of equal intensity. Recordings of dentate gyrus granule cell evoked responses were made to investigate the range of stimuli that are effective in inducing long-term potentiation (LTP). LTP was induced almost exclusively at the 200 ms interval, corresponding to the periodicity of the theta rhythm. Taken in conjunction with similar findings reported in the CA1 field of the hippocampal slice, these results suggest that the correlation between theta rhythm periodicity and LTP is a general phenomenon within the hippocampal formation and lends further support to the hypothesis that the naturally occurring theta rhythm may play a modulatory role in the induction of LTP.

Action Potentials↗
PubMed1987

Differential glucose utilization in the parafascicular region during slow-wave sleep, the still-alert state and locomotion.

Regional cerebral glucose utilization (CGU), detectable by the uptake of 2-deoxy-[14C]glucose [( 14C]2DG), was examined during 3 behavioral states--slow-wave sleep (SWS), the still-alert state (SAL) and locomotion (LOC). Examination of the autoradiograms, generated by exposing the [14C]2DG incorporated brain sections to Kodak Royal X Pan film revealed a high level of uptake bilaterally and discretely in the parafascicular (PF) region during these behaviors. This pattern of [14C]2DG uptake does not correspond to any of the anatomical structures previously identified by histo- and cytochemical methods, including the [14C]2DG method. Further, optical density measurements of this region indicated that the [14C]2DG uptake was significantly lower during SWS than during SAL or LOC. The present finding is compatible with the interpretations of previous physiological and behavioral studies that there is an inhibition by cells at the PF relay to the dentate gyrus that is lowered during the SWS compared to the SAL state, thus allowing preferential brain-stem activation of the dentate gyrus.

Animals↗
PubMed1981

Absorbable suture materials for vascular anastomoses. Tensile strength and axial pressure studies using polyglycolic acid sutures.

This study attempted to evaluate how vascular healing itself is sufficient enough to provide adequate strength to autogenous vein grafts in small arteries without the use of nonabsorbable sutures. The absorbable suture, Dexon, was used in small canine femoral vein graft anastomoses over a two-month trial period with nonabsorbable Prolene as a control. Tensile strength and resistance to axial leak were measured. Results show that Dexon had 93 per cent of the tensile strength of Prolene immediately; 76 per cent at 14 days, 111 per cent at 21 days, and 110 per cent at 30 days, and 124 per cent at 60 days as an average for all suture lines. The per cent mean resistance to leakage that Dexon had compared to Prolene for all suture lines was 102 per cent at seven days, 97 per cent at 14 days, 107 per cent at 21 days, and 97 per cent at 30 days. There is no evidence of aneurysms, suture line disruptions, dilations, or infections of any anastomoses. Our ultimate conclusion is that the integrity of small autogenous vein graft is dependent on healing rather than on the permanent strength of the suture material and that Dexon maintains vascular integrity long enough to permit this healing to occur.

Absorption↗
PubMed1981

Early splenectomy in chronic myelogenous leukemia: surgical aspects.

A retrospective study was conducted to analyze the surgical aspects of the splenectomy in chronic myelogenous leukemia. Twenty patients, Philadelphia chromosome-positive, were initially treated with busulfan until remission was reached. Elective splenectomy was then performed and chromosomal studies repeated at four- and six-month intervals yielding the indication for cyclic intensive chemotherapy. There ws no mortality, one episode of gram-negative sepsis with shock, and five instances of minimal complications. The spleen weights averaged 265 g, ranging from 60 to 800 g. All patients had normal coagulation profiles at the time of surgery, but four of them developed a postoperative thrombocytosis without related complications. A specific correlation was noted between postoperative thrombocytosis and splenomegaly (average weight 570 g). Eleven patients showed a high postoperative leukemoid reaction (average 40,500 cells/cu mm). The interval between diagnosis and splenectomy was shorter (average 7.5 months) in this group than for the patients who had a lower granulocytosis (average 19.5 months).

Adult↗
PubMed1980

Central peripheral temperature gradient. Its value and limitations in the management of critically iii surgical patients.

Monitoring the central peripheral temperature gradient in critically ill surgical patients is a simple, sensitive, noninvasive and inexpensive method that can accurately reflect the state of peripheral circulation. It serves as an early warning sign, and its return to normal is a good measure of the efficacy o f therapy. Recognition of the cause of an abnormal gradient is essential to successful management since it can result from pain as well as hypovolemia. Warm-up patterns vary, and every patient should be treated individually. Forcing vasodilatation is usually unnecessary and amy be dangerous in hypothermic patients and in patients with hypovolemia if blood volume is not corrected simultaneously. Peripheral vascular disease, central hypothermia and the use of vasoactive drugs limit the usefulness of this method.

Adolescent↗
PubMed1980

Catheter culture as a guide in the management of infection in the critically ill surgical patient.

Results of a bacteriologic study of 194 intravascular catheters inserted in 56 critically ill surgical patients showed that with strict adherence to aseptic insertion techniques and proper care, catheter contamination could be reduced to a minimum, and catheter-induced septicemia could be avoided. Our findings in septic patients showed that in the critically ill surgical patients, routine bacteriologic studies of intravascular catheters helped in anticipation and diagnosis of sepsis as well as selection of appropriate antiobiotic therapy.

Catheters, Indwelling↗
PubMed1976

Staging laparotomy for Hodgkin's disease.

We reviewed 39 patients with untreated Hodgkin's disease who underwent staging laparotomy and such cases in the English literature over the past two-and-a-half years. In the group of institutions in our compilation, the accuracies of clinically positive and negative judgments of liver involvement were 28 per cent and 95.4 per cent respectively, while in our institution the accuracies were 100 per cent and 95 percent respectively. The accuracies of the clinically positive and negative determinations of splenic involvement were 61.2 per cent and 67.3 per cent respectively after histological examination, whereas we had accuracies of 100 per cent and 74 per cent respectively. The accuracies of the clinically positive and negative determination of lymph nodes were 72.1 per cent and 86.7 per cent respectively, whereas the results were 70.6 per cent and 100 per cent respectively in our 39 cases. The percentage of complications was 10 per cent and the mortality rate was 0.9 per cent among 719 staging laparotomies. The common complications were atelectasis, pneumonia, wound infection and dehiscence, abscess, intestinal obstruction and thrombocytosis. We think more aggressive staging laparotomy should be performed for Hodgkin's disease under one surgeon or one surgical team.

Adolescent↗
PubMedDate not supplied

Brain gene expression during REM sleep depends on prior waking experience.

In most mammalian species studied, two distinct and successive phases of sleep, slow wave (SW), and rapid eye movement (REM), can be recognized on the basis of their EEG profiles and associated behaviors. Both phases have been implicated in the offline sensorimotor processing of daytime events, but the molecular mechanisms remain elusive. We studied brain expression of the plasticity-associated immediate-early gene (IEG) zif-268 during SW and REM sleep in rats exposed to rich sensorimotor experience in the preceding waking period. Whereas nonexposed controls show generalized zif-268 down-regulation during SW and REM sleep, zif-268 is upregulated during REM sleep in the cerebral cortex and the hippocampus of exposed animals. We suggest that this phenomenon represents a window of increased neuronal plasticity during REM sleep that follows enriched waking experience.

Analysis of Variance↗