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Biomedical subjects

S Datta

Publications and source records attributed to S Datta.

At least 253 records · Page 14Linked to original sources
PubMed1990

Chloroprocaine antagonism of epidural opioid analgesia: a receptor-specific phenomenon?

Sixty healthy patients scheduled for elective cesarean delivery under epidural anesthesia were randomized to receive either lidocaine or 2-chloroprocaine as the primary local anesthetic agent. When patients first complained of postoperative pain in the recovery room, they were given either fentanyl 50 micrograms or butorphanol 2 mg, epidurally, in a randomized, blinded fashion. Postoperative analgesia, quantitated on a visual analogue scale, as well as time elapsed until first request for supplemental opioid, did not differ for patients receiving butorphanol after either 2-chloroprocaine or lidocaine anesthesia. In contrast, epidural fentanyl produced a shorter and lesser degree of sensory analgesia after 2-chloroprocaine use, whereas epidural fentanyl after lidocaine anesthesia provided pain relief similar to that seen in the butorphanol groups. Side effects were limited to somnolence with butorphanol and pruritus with fentanyl. No evidence of respiratory depression was seen in any patient. We conclude that 2 mg of butorphanol epidurally provides approximately 2 to 3 h of effective analgesia after cesarean delivery with either lidocaine or 2-chloroprocaine anesthesia. Epidural fentanyl seems to be antagonized when 2-chloroprocaine, but not lidocaine, is used as the primary local anesthetic agent. We suggest a possible mu-receptor-specific etiology for this effect.

Adult↗
PubMed1990

Negative and positive transcriptional regulation by thyroid hormone receptor isoforms.

Multiple forms of human thyroid hormone (T3) receptor have been identified, including true receptors that bind T3 (alpha 1 and beta) and a splicing variant (alpha 2) that does not bind T3. The alpha 1- and beta-receptors activate transcription through interactions with positive thyroid response elements (TREs). The alpha 2 variant is unable to activate transcription and has been reported to inhibit alpha 1 or beta stimulation of positive TREs, a property referred to as dominant negative activity. In this report we have performed studies to assess the functional properties of different members of the thyroid receptor family with regard to both positive and negative transcriptional regulation. The alpha 1-, alpha 2-, and beta-receptors were each coexpressed in JEG-3 cells with either TreTKCAT (CAT = chloramphenicol acetyltransferase), a reporter gene that contains a positive TRE, or TSH alpha CAT, a negatively regulated reporter gene. The alpha 1 and beta isoforms stimulated transcription of TreTKCAT and inhibited TSH alpha CAT transcription in a T3-dependent manner, whereas the alpha 2 variant was inactive. When coexpressed with alpha 1- or beta-receptors, alpha 2 inhibited regulation of positive TREs, but the effects of alpha 2 were modest and only occurred when relatively high doses of receptor were transfected. The alpha 2-receptor variant did not affect negative regulation by alpha 1- or beta-receptors. Thus, in both positive and negative regulation, thyroid hormone receptor isoforms that bind T3 (alpha 1, beta) are functional, whereas the alpha 2 isoform, which does not bind T3, is not functional.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1990

Acute progesterone treatment has no effect on bupivacaine-induced conduction blockade in the isolated rabbit vagus nerve.

Pregnancy decreases anesthetic requirements during regional anesthesia. Using an in vitro animal model, this study attempts to elucidate the mechanism of hormonal effects on nerve conduction in desheathed rabbit vagus nerve. The acute effects of progesterone administration on neural blockade induced by bupivacaine were investigated in terms of changes in compound action potentials of A, B, and C fibers. No change in baseline compound action potential was found after 30 min of perfusion of the nerve with progesterone. Exposure of the nerve to progesterone before exposure to bupivacaine did not significantly increase the degree of conduction blockade produced by bupivacaine, and a radioactive assay demonstrated that progesterone was taken up acutely by neural tissue over a 45-min measurement period. These results indicate that although progesterone was taken up in significant amounts by neural tissue, an acute exposure does not increase the sensitivity of the nerves to bupivacaine. Hence, the increased sensitivity of nerves to local anesthetics seen with pregnancy or with chronic progesterone treatment requires some period of time to occur. The mechanism is therefore unlikely to be a direct effect of progesterone on the cell membrane but may involve hormonal effects on protein synthesis.

Animals↗
PubMed1990

Maternal and fetal catecholamines and uterine incision-to-delivery interval during elective cesarean.

The fetal sympathoadrenal system is activated during periods of intrauterine stress such as inadequate uterine perfusion. During cesarean, the period of interruption of utero-placental blood flow is extended as the time interval from uterine incision to delivery increases. An increasing uterine incision-to-delivery interval with spinal or general anesthesia has been associated with a poorer neonatal outcome. This association has not been demonstrated previously in patients undergoing cesarean delivery under epidural anesthesia. We investigated the correlation between prolonged uterine incision-to-delivery intervals, fetal catecholamine concentrations, and fetal blood gas values at delivery in 25 parturients undergoing cesarean under epidural anesthesia and in 28 under spinal anesthesia. Infants delivered after prolonged uterine incision-to-delivery intervals had significantly lower pH values in both the epidural and spinal groups. With longer uterine incision-to-delivery intervals, umbilical arterial norepinephrine concentrations were increased significantly. Umbilical arterial pH values were significantly lower in infants with higher umbilical arterial catecholamine concentrations. The importance of minimizing the uterine incision-to-delivery interval, regardless of the type of anesthetic selected, is demonstrated.

Anesthesia, Epidural↗
PubMed1990

Different cellular types in mesopontine cholinergic nuclei related to ponto-geniculo-occipital waves.

The only mesopontine neurons previously described as involved in the transfer of ponto-geniculo-occipital (PGO) waves from the brain stem to the thalamus were termed PGO-on bursting cells. We have studied, in chronically implanted cats, neuronal activities in brain-stem peribrachial (PB) and laterodorsal tegmental (LDT) cholinergic nuclei in relation to PGO waves recorded from the lateral geniculate (LG) thalamic nucleus during rapid-eye-movement (REM) sleep. We constructed peri-PGO histograms of PB/LDT cells' discharges and analyzed the interspike interval distribution during the period of increased neuronal activity related to PGO waves. Six categories of PGO-related PB/LDT neurons with identified thalamic projections were found: 4 classes of PGO-on cells: PGO-off but REM-on cells: and post-PGO cells. The physiological characteristics of a given cell class were stable even during prolonged recordings. One of these cell classes (1) represents the previously described PGO-on bursting neurons, while the other five (2-6) are newly discovered neuronal types. (1) Some neurons (16% of PGO-related cells) discharged stereotyped low-frequency (120-180 Hz) spike bursts preceding the negative peak of the LG-PGO waves by 20-40 msec. These neurons had low firing rates (0.5-3.5 Hz) during all states. (2) A distinct cell class (22% of PGO-related neurons) fired high-frequency spike bursts (greater than 500 Hz) about 20-40 msec prior to the thalamic PGO wave. These bursts were preceded by a period (150-200 msec) of discharge acceleration on a background of tonically increased activity during REM sleep. (3) PGO-on tonic neurons (20% of PGO-related neurons) discharged trains of repetitive single spikes preceding the thalamic PGO waves by 100-150 msec, but never fired high-frequency spike bursts. (4) Other PGO-on neurons (10% of PGO-related neurons) discharged single spikes preceding thalamic PGO waves by 15-30 msec. On the basis of parallel intracellular recordings in acutely prepared, reserpine-treated animals, we concluded that the PGO-on single spikes arise from conventional excitatory postsynaptic potentials and do not reflect tiny postinhibitory rebounds. (5) A peculiar cellular class, termed PGO-off elements (8% of PGO-related neurons), consisted of neurons with tonic, high discharge rates (greater than 30 Hz) during REM sleep. These neurons stopped firing 100-200 msec before and during the thalamic PGO waves. (6) Finally, other neurons discharged spike bursts or tonic spike trains 100-300 msec after the initially negative peak of the thalamic PGO field potential (post-PGO elements, 23% of PGO-related neurons).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Significance of CA3 region of hippocampus in memory function.

In mobile unanaesthetised adult rabbits, spontaneous single unit activities of CA3 neurons of Hippocampus showed a specific change in firing pattern in response to conditioned stimuli (CS+). This pattern could be correlated with changes in the general behaviour of these animals. Major deafferntation of the CA3 region did not alter the conditioned response, though neuronal firing pattern and behavioural response changed to that of the pre-conditioned state after antidromic stimulation of CA3 region through fimbria. The importance of CA3 region in memory retention process has been indicated in these experiments.

Animals↗
PubMed1990

How to insert a peripheral venous cannula.

Peripheral venous cannulation is the commonest vascular surgical procedure. It is usually performed by a junior doctor who has learnt the skill from a colleague only marginally more skilled. Correct technique will improve the chances of success and patient comfort and safety.

Antisepsis↗
PubMed1990

Neuronal activities in brain-stem cholinergic nuclei related to tonic activation processes in thalamocortical systems.

This study was performed to examine the hypothesis that thalamic-projecting neurons of mesopontine cholinergic nuclei display activity patterns that are compatible with their role in inducing and maintaining activation processes in thalamocortical systems during the states of waking (W) and rapid-eye-movement (REM) sleep associated with desynchronization of the electroencephalogram (EEG). A sample of 780 neurons located in the peribrachial (PB) area of the pedunculopontine tegmental nucleus and in the laterodorsal tegmental (LDT) nucleus were recorded extracellularly in unanesthetized, chronically implanted cats. Of those neurons, 82 were antidromically invaded from medial, intralaminar, and lateral thalamic nuclei: 570 were orthodromically driven at short latencies from various thalamic sites: and 45 of the latter elements are also part of the 82 cell group, as they were activated both antidromically and synaptically from the thalamus. There were no statistically significant differences between firing rates in the PB and LDT neuronal samples. Rate analyses in 2 distinct groups of PB/LDT neurons, with fast (greater than 10 Hz) and slow (less than 2 Hz) discharge rates in W, indicated that (1) the fast-discharging cell group had higher firing rates in W and REM sleep compared to EEG-synchronized sleep (S), the differences between all states being significant (p less than 0.0005); (2) the slow-discharging cell group increased firing rates from W to S and further to REM sleep, with significant difference between W and S (p less than 0.01), as well as between W or S and REM sleep (p less than 0.0005). Interspike interval histograms of PB and LDT neurons showed that 75% of them have tonic firing patterns, with virtually no high-frequency spike bursts in any state of the wake-sleep cycle. We found 22 PB cells that discharged rhythmic spike trains with recurring periods of 0.8-1 sec. Autocorrelograms revealed that this oscillatory behavior disappeared when their firing rate increased during REM sleep. Dynamic analyses of sequential firing rates throughout the waking-sleep cycle showed that none of the full-blown states of vigilance is associated with a uniform level of spontaneous firing rate. Signs of decreased discharge frequencies of mesopontine neurons appeared toward the end of quiet W, preceding by about 10-20 sec the most precocious signs of EEG synchronization heralding the sleep onset. During transition from S to W, rates of spontaneous discharges increased 20 sec before the onset of EEG desynchronization.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

The role of reticular activating system in altering medial preoptic neuronal activity in anesthetized rats.

The influence of the ascending reticular activating system (ARAS) on the medial preoptic unit activity was studied in urethane anesthetized rats. Alterations in the unit activity were also correlated with cortical EEG changes. A fourth of the medial preoptic units showed alterations in their discharges with cortical EEG changes. These units were also influenced by high frequency stimulation of ARAS, which simultaneously produced EEG desynchronization. On the other hand they were generally not influenced by 1 Hz stimulation of ARAS. These results indicate that the anatomically demonstrated projections from midbrain (forming ARAS), involving very few synapses, may not be involved in the regulation of sleep-wakeful function of the medial preoptic area. Interaction of some of the inputs at the medial preoptic area is discussed.

Action Potentials↗
PubMed1989

Delivery temperature of heated intravenous solutions during rapid infusion.

Warming of intravenous fluids may help to prevent shivering and hypothermia in the surgical patient. Increasing the fluid temperatures to as high as 60 degrees C has been suggested. An in vitro study was performed in which temperature changes following the rapid infusion of heated lactated Ringer's solution within a vein were measured. When 1 L of solution was warmed to 55 degrees C and then was infused over 4 min, local model vein temperatures rose from 37 degrees C to 44 degrees C. This effect of possible regional tissue heating may well occur in vivo. It is known that the rate of human blood cell hemolysis and membrane enzymatic function is affected by temperature. Further efforts need to be directed toward appreciating the effects of warmed intravenous fluids upon intact physiologic preparations and red blood cells.

Hot Temperature↗
PubMed1989

Fetal surgery and general anesthesia: a case report and review.

Fetal surgery, in utero, is now a viable option for some congenital conditions due to recent advances in ultrasound and microsurgical technology. Previous reports of anesthesia for such procedures have focused on spinal or epidural conduction techniques. General endotracheal anesthesia may have several advantages in this setting. In addition to maternal anesthesia, general anesthesia can provide fetal neuromuscular block (without direct fetal injection of blocking agents) and uterine relaxation. It may also blunt fetal response to surgical stimulation.

Adult↗
PubMed1989

Perioperative analgesia with subarachnoid fentanyl-bupivacaine for cesarean delivery.

Addition of fentanyl to bupivacaine administered for spinal anesthesia for cesarean delivery was evaluated in 56 ASA physical status 1 term parturients. Preservative-free saline was added to 0, 2.5, 5, 6.25, 12.5, 25, 37.5, or 50 micrograms fentanyl to make a 1 ml total volume, which was injected intrathecally prior to bupivacaine in a double-blind, randomized fashion. Vital signs, sensory level, motor block, pain score, and side effects were recorded every 2 min for the first 12 min and then at 15, 30, 45, and 60 min and at 30-min intervals until the patient complained of pain. At delivery maternal vein, umbilical artery, and umbilical vein blood gases were obtained. Apgar scores at 1 and 5 min were recorded. Early Neonatal Neurobehavioral Scales (ENNS) were performed on days 1 and 2. Side effects and opioid requirements were recorded for the first 24 h. All of the patients in the control group reported a pain score greater than 0 during surgery and 67% required intraoperative opioids. None of the patients who received greater than or equal to 6.25 micrograms fentanyl required intraoperative opioids. Complete analgesia (time from injection to first report of pain) lasted 33.7 +/- 30.8 min (mean +/- SD) in the control group and increased to 130 +/- 30 min (P less than 0.05) with addition of 6.25 micrograms fentanyl. Duration of effective analgesia (time from injection to first parenteral opioid) was 71.8 +/- 43.2 min in the control group and increased (P less than 0.05) to 192 +/- 74.9 min with addition of 6.25 micrograms fentanyl.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Comparison of bupivacaine- and ropivacaine-induced conduction blockade in the isolated rabbit vagus nerve.

Ropivacaine (LEA-103) is a new amino-amide local anesthetic agent the chemical structure and anesthetic properties of which are similar to bupivacaine. Preliminary studies in animals indicate that the CNS toxicities of ropivacaine and bupivacaine are similar, but that ropivacaine may have less arrhythmogenic effects than bupivacaine. The current study arrhythmogenic effects than bupivacaine. The current study was designed to compare the in vitro potency, onset and recovery from block of ropivacaine and bupivacaine using an isolated rabbit vagus nerve model. The effect of varying concentrations of ropivacaine and bupivacaine on the compound action potential of A and C nerve fibers was assessed to determine whether motor and sensory fibers have different sensitivities to the two agents. The results showed that the depressant effect of bupivacaine was 16% greater than that of ropivacaine on motor fibers, but only 3% greater on sensory fibers. An analysis of variance indicated that this was a statistically significant difference (P = 0.028). Thus, at the concentrations tested, ropivacaine appears to produce relatively less blockade of motor fibers than does bupivacaine but with similar sensory blockade. The onset of this difference became significant as early as five minutes after the drug exposure was begun. No significant differences in recovery times were observed.

Action Potentials↗