Inelastic-scattering effects on single-barrier tunneling.
Explore the source record for details and available documents.
Journal Article↗
Biomedical subjects
S Datta
Publications and source records attributed to S Datta.
Potentiation of growth suppression and modulation of the antigenic phenotype in human melanoma cells by the combination of recombinant human fibroblast and immune interferons.
Administration of interferon as a single therapeutic regimen in cancer patients with various neoplasias has had only limited efficacy in ameliorating the negative clinical course of their disease. In the present study, we have evaluated the effect of recombinant human fibroblast (IFN beta) and immune (IFN gamma) interferon, alone and in combination, on growth, differentiation and the expression of class I and II histocompatibility locus antigens (HLA) and melanoma-associated antigens on the human melanoma cell line H0-1. The effect of combinations of interferons on the antigenic profile of human melanoma cells displaying different organ colonization and spontaneous metastatic potential in athymic nude mice was also determined. H0-1 cells were more sensitive to the antiproliferative activity of IFN beta than to IFN gamma and the combination of interferons resulted in a potentiation of growth suppression. The antiproliferative effect of both interferons was greater in later-passage than in earlier-passage H0-1 cells, possibly reflecting alterations in the evolving tumor cell population as a result of long-term in vitro propagation and/or the selective outgrowth of cells with an increased growth rate. The enhanced growth suppression observed in H0-1 cells treated with the combination of IFN beta plus IFN gamma was not associated with a significant increase in the level of melanin, a marker of melanoma differentiation, above that observed with either interferon used alone. IFN beta and IFN gamma differentially modulated the expression of class I and II HLA and melanoma-associated antigens in H0-1 cells and a series of melanoma cells with different organ colonization and metastatic potential, including MeWo, MeM 50-10, MeM 50-17, 3S5 and 70W. No consistent potentiation or antagonism in the expression of any specific antigen was observed in any of the melanoma cell lines exposed to the combination of interferons. The present study demonstrates that the combination of IFN beta plus IFN gamma can potentiate growth suppression in H0-1 human melanoma cells and that this effect is not associated with an increase in differentiation or a potentiation in antigenic modulation. In addition, no direct correlation between the expression of any specific antigen or its modulation by IFN beta or IFN gamma, alone or in combination, and organ colonization and metastatic potential in nude mice was observed in the different melanoma cell lines.
Animals↗
Expression of virulence and antibiotic resistance in an Escherichia coli transconjugant carrying a large plasmid pCAT120 of Shigella dysenteriae type I and its spontaneous fragmentations.
The role of a 120-kb plasmid in relation to virulence and drug resistance factor in Shigella dysenteriae was studied. For characterization of plasmids, the mating system is a useful and efficient means of transferring both large and small plasmids to a new host. The conjugative transfer of a 120-kb (pCAT120) ampicillin-resistant plasmid of S. dysenteriae to E. coli K-12 was not successful. Introduction of an E. coli fertility factor plasmid F, did not help to mobilize the plasmid. Low transfer frequencies of antibiotic markers to E. coli were achieved by treatment of the donor S. dysenteriae with N-methyl-N'-nitro-N-nitrosoguanidine. The transconjugants showed resistance to ampicillin, chloramphenicol, tetracycline and cadmium. A transconjugant carrying the 120-kb plasmid of S. dysenteriae produced keratoconjunctivitis in guinea pigs. Repeated subculture of Clmr transconjugant (pCAT120) on tryptic soya agar plates became Clms and showed four distinct DNA bands ranging from 3 to 10 kb in size on agarose gel electrophoresis. Utilization of organic acids, metal resistance (Cd), dye-binding properties (Crb+, Ebr+) and drug resistance (Amp, Tet) were identified on 10, 7, 4 and 3-kb plasmid DNA fragment of pCAT120 respectively. Crb+ 4-kb DNA fragment of pCAT120 was isolated, purified and transferred to an avirulent E. coli K12 by transformation. However, transformant (pET4) showed poor growth on solid media and its growth in liquid culture was only possible after supplementation of the unknown low-molar-mass thermolabile factor(s) secreted by the recipient strain.(ABSTRACT TRUNCATED AT 250 WORDS)
Bacterial Outer Membrane Proteins↗
Epidural nalbuphine for analgesia following caesarean delivery: dose-response and effect of local anaesthetic choice.
The analgesic profile of epidural nalbuphine for postoperative pain relief and the impact of local anaesthetic choice upon this profile was investigated in 58 patients undergoing elective Caesarean delivery under epidural anaesthesia. Patients were randomized to receive either lidocaine 2% with 1:200,000 epinephrine or 2-chloroprocaine 3% for perioperative anaesthesia, followed by either 10, 20, or 30 mg of epidural nalbuphine administered at the first complaint of postoperative discomfort. Postoperative analgesia was quantitated on a visual analogue (VAS) scale, and by the time from the epidural opioid injection until the first request for supplemental pain medication. The duration of analgesia after lidocaine anaesthesia followed by 10, 20 or 30 mg nalbuphine was 77 (53-127) min, 205 (110-269) min, and 185 (116-241), respectively (median, 95% confidence interval, P less than 0.01, 20 and 30 mg vs 10 mg). Following 2-chloroprocaine anaesthesia, VAS remained consistently elevated: the median duration of analgesia was only 30-40 min and did not differ among the three doses of nalbuphine. Side-effects consisted only of somnolence, and were noted only following lidocaine anaesthesia. Somnolence was observed in 0, 20% and 50% of those receiving 10 mg, 20 mg and 30 mg of nalbuphine respectively (NS). No evidence of respiratory depression was noted in any patient. It is concluded that 20 or 30 mg of epidural nalbuphine provides analgesia for only two to four hours following Caesarean delivery with lidocaine anaesthesia, but anaesthesia with 2-chloroprocaine resulted in minimal or no analgesia from this opioid. Nalbuphine appears to be a disappointing agent for epidural use after Caesarean delivery.
Adult↗
Red cell use during cesarean delivery.
The transfusion of red cells (RBCs) was analyzed over a 4-year period (1984-1987), during which 9596 cesarean deliveries were performed. A total of 336 patients were identified as receiving RBC transfusions during or after cesarean delivery; 747 units of RBCs were administered. The overall incidence of transfusion in this patient population declined from 6.2 to 3.2 percent during the study period (p less than 0.001). Slightly more than one-half (54.4%) of all transfusions were given in the operating room or recovery room. The majority of patients (68.4%) received 2 units of RBCs, 11.6 percent received a 1-unit transfusion, and 8.3 percent received 5 units or more. The most common obstetric diagnoses associated with RBC transfusion were disorders of placental implantation, preeclampsia, premature labor with tocolytic therapy, fetal distress, and augmentation of dysfunctional labor. In patients without risk factors for bleeding, there was no trend indicating increased transfusion requirements when general anesthesia was employed. In conclusion, this study documents a decline in the transfusion rate during cesarean delivery.
Anesthesia, Epidural↗
Maternal temperature regulation during extradural analgesia for labour.
We have studied the effect of analgesia on maternal temperature (oral and tympanic membrane) progression in 53 women during normal spontaneous labour. Three groups were studied: two received extradural analgesia with a continuous infusion of 0.25% bupivacaine with or without the addition of fentanyl; the third group received only parenteral opioid analgesia. All patients were afebrile and without clinical evidence of infection at the beginning of the study. Both groups of patients receiving extradural analgesia had a consistent and significant increase in temperature after approximately 5 h of analgesia; no such trend was observed in the parenteral opioid group. Alterations in mechanisms of heat dissipation may explain these findings.
Adolescent↗
A preferential inhibition of impulses in C-fibers of the rabbit vagus nerve by veratridine, an activator of sodium channels.
In seeking a means to reverse local anesthetic block of peripheral nerve, we examined the actions of veratridine (VTD), an agent known to antagonize competitively the binding of local anesthetics to Na channels. The actions of VTD, a steroidal alkaloid "activator" of voltage-gated Na channels, were studied in the rabbit vagus nerve by two methods. In one, the effects of VTD on compound action potentials (APc) propagating through a "veratrinized" segment (11-mm) of nerve were measured by extracellular recording. Single volleys of impulses were unaffected by VTD, but trains of impulses, triggered by repetitive stimulation, were selectively diminished. This "use-dependent" reduction was greatest for the C-fiber component of the APc, less for B-fibers, and inconsequential for A-fibers. Use-dependent inhibition was enhanced by higher stimulation frequency and by increased VTD concentration, and reversed rapidly when stimulation ceased. If the nerve sheath remained intact, the rate of VTD action was far less than in desheathed nerves, but the effects were the same. In the other experimental system, membrane potentials were measured in the veratrinized region of the nerve by a sucrose-gap method. Repetitive stimulation, particularly of C-fibers, produced a cumulative VTD-induced depolarization (VID) that was sustained over several seconds and during which the C-fiber APc was selectively reduced. We propose that this local, use-dependent VID provides the means to inhibit impulses propagating through the veratrinized region. The preferential effect of VTD on C-fibers suggests its possibilities as a relatively selective agent for block of impulse trains in nociceptive afferents.
Action Potentials↗
Long-term enhancement of REM sleep following cholinergic stimulation.
A six day long increase in rapid eye movement (REM) sleep followed the unilateral microinjection of a single dose of the cholinergic agonist drug carbachol into the brain stem of cats. Effective drug injection sites were localized to the pontine peribrachial region containing cholinergic choline acetyltransferase (ChAT) labeled neurons. At the peak of the effect, which occurred 24-28 h post-injection, the relative amount of time devoted to REM sleep tripled, resulting in an absolute time increase from 3.12 to 11.28 h REM sleep per day. This pronounced and prolonged REM sleep increase was associated with marked enhancement of ponto-geniculo-occipital (PGO) waves and with PGO burst cell activity unilateral to the site of injection.
Analysis of Variance↗
Maternal and fetal plasma atrial natriuretic peptide concentrations during elective caesarean section.
Atrial natriuretic peptide (ANP) is stored in the atrial cardiocyte and is capable of exerting potent, selective, and transient effects on fluid and electrolyte balance and on blood pressure. Because fluid shifts and hemodynamic adjustments occur during parturition, ANP might play a homeostatic role in the parturient and fetoplacental unit. We measured maternal and fetal plasma ANP concentrations in 19 parturients during elective caesarean section. Plasma ANP levels were also measured in seven nonpregnant women of the same age group. The baseline ANP concentration in parturients was significantly higher (29.77 +/- 6.06 pg/ml vs 7.37 +/- 2.1 pg/ml; mean +/- s.e.mean) than in their nonpregnant counterparts. The umbilical artery (UA) ANP concentration was significantly higher than the umbilical vein concentration (91.91 +/- 14.91 pg/ml vs. 40.04 +/- 9.71 pg/ml). Factors under the anaesthesiologist's control may influence maternal and fetal plasma ANP levels. There was a significant correlation between the volume of maternal Ringer's lactate infusion received and maternal ANP concentration. A significant correlation was seen between the total dose of ephedrine administered acutely prior to delivery and the UA ANP concentration. These data suggest that: 1) increased blood volume during pregnancy is associated with increased maternal plasma ANP levels, and 2) the fetus can produce its own ANP, and is thereby capable of responding to ANP stimulating factors.
Anesthesia, Obstetrical↗
A purified adenovirus 289-amino-acid E1A protein activates RNA polymerase III transcription in vitro and alters transcription factor TFIIIC.
We have previously demonstrated that a purified bacterially synthesized E1A 289-amino-acid protein is capable of stimulating transcription from the promoters of genes transcribed by RNA polymerase II in vitro (R. Spangler, M. Bruner, B. Dalie, and M. L. Harter, Science 237:1044-1046, 1987). In this study, we show that this protein is also capable of transactivating in vitro the adenovirus virus-associated (VA1) RNA gene transcribed by RNA polymerase III. Pertinent to the transcription of this gene is the rate-limiting component, TFIIIC, which appears to be of two distinct forms in uninfected HeLa cells. The addition of an oligonucleotide containing a TFIIIC binding site to HeLa whole-cell extracts inhibits VA1 transcription by sequestering TFIIIC. However, the addition of purified E1A to extracts previously challenged with the TFIIIC oligonucleotide restores the level of VA1 transcription. When included in the same reaction, an E1A-specific monoclonal antibody reverses the restoration. Incubation of purified E1A with either HeLa cell nuclear or whole-cell extracts alters the DNA-binding properties of TFIIIC as detected by gel shift assays. This alteration does not occur if E1A-specific antibody and E1A protein are added simultaneously to the extract. In contrast, the addition of this antibody to extracts at a later time does not reverse the alteration observed in the TFIIIC binding activities. Never at any time did we note the formation of novel TFIIIC-promoter complexes after the addition of E1A to nuclear extracts. These results clearly establish that E1A mediates its effect on VA1 transcription through TFIIIC in a very rapid yet indirect manner.(ABSTRACT TRUNCATED AT 250 WORDS)
Adenovirus Early Proteins↗
Thyroid hormone resistance syndrome. Inhibition of normal receptor function by mutant thyroid hormone receptors.
Thyroid hormone (T3) resistance is inherited in most cases in an autosomal dominant manner. The disorder is characterized by elevated free thyroid hormone levels and partial resistance to thyroid hormone at the cellular level. Distinct single amino acid substitutions in the ligand binding domain of the beta form of the thyroid hormone receptor have been described in two kindreds with this disorder. We used transient expression assays to characterize the functional properties of these receptor mutants, one containing a Gly to Arg change at amino acid 340 (G340R) and the other a Pro to His change at amino acid 448 (P448H). A nine amino acid carboxy terminal deletion (delta 448-456), analogous to an alteration that occurs in v-erbA, was also studied for comparison with the mutations that occur in the T3 resistance syndrome. None of the receptor mutants were able to mediate thyroid hormone dependent activation (TreTKCAT) or repression (TSH alpha CAT) of reporter genes when compared with the wild type receptor. In addition, the mutants inhibited the activity of normal alpha and beta receptor isoforms when examined in coexpression assays. This activity, referred to as dominant negative inhibition, was manifest with respect to both the positively and negatively regulated reporter genes. Although mutant receptor binding to DNA was unaffected, ligand binding studies showed that the G340R and delta 448-456 mutants failed to bind T3, whereas the P448H mutant bound hormone with reduced affinity (approximately 10% of normal) compared to the wild type receptor. Consistent with this finding, the P448H mutant receptor was partially active at higher T3 concentrations. Furthermore, the dominant negative inhibition elicited by the P448H receptor mutant at higher T3 concentrations was reversed in the presence of high doses of T3. These findings indicate that mutant beta receptors in patients with thyroid hormone resistance have reduced affinity for T3 and are functionally deficient, but impair the activity of normal receptors, thereby providing a mechanism for the dominant mode of inheritance in this disorder.
Base Sequence↗
Patient-controlled epidural analgesia: demand dosing.
A double-blind, placebo-controlled study was designed to compare the efficacy of demand-dose patient-controlled epidural analgesia (PCEA) with continuous epidural infusion (CEI) for treatment of pain during labor and delivery. Forty patients were randomized to receive 0.125% bupivacaine with fentanyl (2 micrograms/mL) through CEI at 12 mL/h or through demand-dose PCEA. Patients using PCEA could demand 3 mL every 10 min without restriction. Analgesia in both groups was comparable. However, there was a significant reduction in total bupivacaine consumption (in milligrams) associated with the use of PCEA (mean +/- SEM: CEI = 76.1 +/- 8.5 mg; PCEA = 42.2 +/- 5.9 mg; 45% reduction). The hourly bupivacaine consumption during the first (CEI = 15.8 +/- 0.6 mg/h; PCEA = 8.8 +/- 1.1 mg/h) and second (CEI = 17.2 +/- 1.2 mg/h; PCEA = 6.8 +/- 1.2 mg/h) stages of labor was also reduced. Overall, this represented a 47% "sparing" of bupivacaine use per hour with PCEA. Similar reductions occurred in the use of fentanyl. The reductions in analgesic requirement, however, were not associated with a reduction in the degree of motor blockade or in the cephalad extent of sensory blockade. A significant dose-sparing effect was associated with the use of demand-dose PCEA as compared with standard CEI for analgesia during labor and delivery.
Adult↗
Obstructing cancers of the right and left colon: critical analysis of perioperative risk factors, morbidity, and mortality.
Significant hospital mortality has been observed in right-sided obstructing colonic cancer patients but remains unexplained. The medical records of 52 patients with obstructing colonic cancer seen between 1980-88 were reviewed to identify prognostic factors influencing mortality when carcinoma involved either the right or the left segments of the colon. The mean age, sex, incidence, and distribution of perioperative risk factors and rate of postoperative complications were comparable between the two groups. Right colonic cancer patients had a higher incidence of advanced disease (16 of 19 had Dukes C and D tumors). Their mortality was higher than that of their counterparts (21% vs 9%), correlating primarily with advanced cancer stage rather than with preoperative risk factors or technical (operative) complications. Though the difference in mortality rates is not statistically significant, patients with obstructing cancers of the right colon, compared to their left counterparts, are hospitalized in more advanced stages of disease and have a worse prognosis.
Aged↗
Zero-field spin splitting in a two-dimensional electron gas.
Explore the source record for details and available documents.
Journal Article↗
T cell receptor V beta genes expressed by IgG anti-DNA autoantibody-inducing T cells in lupus nephritis: forbidden receptors and double-negative T cells.
In the (SWR x NZB)F1 (SNF1) model of lupus nephritis, pathogenic variety of IgG anti-DNA autoantibodies are induced by certain T helper (Th) cells that are either CD4+ or CD4-CD8- (double negative; DN) in phenotype. From the spleens of eight SNF1 mice with lupus nephritis, 149 T cell lines were derived and out of these only 25 lines (approximately 17%) were capable of augmenting the production of pathogenic anti-DNA autoantibodies. Herein, we analyzed the T cell receptor (TcR) V beta genes used by 16 such pathogenic autoantibody-inducing Th cell lines. Twelve of the Th lines were CD4+ and among these five lines expressed V beta 8 (8.2 or 8.3). The V beta 8 gene family is contributed by the NZB parent to the SNF1 mice, since it is absent in the SWR parental strain. Three other CD4+ Th lines expressed V beta 4, another was V beta 2+ and one line with poor autoantibody-inducing capability expressed V beta 1. Four autoantibody-inducing Th lines from the SNF1 mice had a DN phenotype and these lines were also autoreactive, proliferating in response to syngeneic spleen cells. Among these DN Th lines, two expressed V beta 6 and one expressed V beta 8.1 TcR. Both of these are forbidden TcR directed against Mls-1a (Mlsa) autoantigens expressed by the SNF1 mice and such autoreactive T cells should have been deleted during thymic ontogeny. Thus, the DN Th cells of non-lpr SNF1 mice are different from the DN cells or MRL-lpr which lack helper activity and do not express forbidden TcR. The spleens of 6 out of 19 nephritic SNF1 animals tested also showed an expansion of forbidden autoreactive TcR+ cells that were mainly DN. Two of these animals expressed high levels of V beta 6 (anti-Mlsa) and V beta 11 (anti-I-E) TcR+ cells, three others had high levels of V beta 11+ cells alone and one animal had an expanded population of V beta 17a+ (anti-I-E) cells. The I-E-reactive TcR again should have been eliminated in the SNF1 thymus, since they express I-E molecules contributed by the NZB parent. The SWR parents of SNF1, are I-E-; moreover, they lack the V beta 11 gene but they express V beta 17a in peripheral T cells. Whereas the NZB parents are I-E+, they lack a functional V beta 17a gene and they delete mature V beta 11+ T cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Spontaneous and evoked activities of anterior thalamic neurons during waking and sleep states.
In contrast with most dorsal thalamic nuclei, the anterior thalamic (AT) complex is devoid of input from the reticular (RE) thalamic nucleus. Instead, it is interposed in a limbic circuit linking the mammillary bodies (MB) to various allo- and periallocortical fields. To investigate the electrophysiological consequences of this peculiar pattern of connectivity, a sample of 92 AT cells, physiologically identified by their short-latency response to MB stimulation, was recorded in chronically-implanted animals and compared to a group of rostral intralaminar centralis-paracentralis (CL-PC) thalamic neurons receiving a dense innervation from the RE nucleus. Numerous similarities were found between the state-related fluctuations in spontaneous and evoked activities of AT and CL-PC neurons. For instance, both types of cells displayed stereotyped, high-frequency (250-300 Hz) bursts of 2-4 spikes in S and a more tonic discharge pattern in W and D. However, the high-frequency bursts of the S state occurred randomly in AT cells, whereas in CL-PC neurons they appeared rhythmically in clusters closely related to spindle waves. In addition, we found that a period of decreased responsiveness consistently followed the ortho- or antidromic activation of AT an CL-PC cells. This inhibitory period lasted less than 80 ms in AT cells and contrasted with the much longer (less than or equal to 120 ms) period of decreased excitability observed in CL-PC neurons during S. We suggest that these differences reflect the lack of RE input to the AT group.(ABSTRACT TRUNCATED AT 250 WORDS)
Action Potentials↗
Brainstem genesis of reserpine-induced ponto-geniculo-occipital waves: an electrophysiological and morphological investigation.
Several experimental results indicate that the peribrachial (PB) cholinergic area of the pedunculopontine nucleus is the final relay for the transfer of brainstem-generated pontogeniculo-occipital (PGO) waves to the thalamus. However, the mechanisms underlying the PGO-related activity of PB neurons remain unknown. In order to study these mechanisms, single unit recordings in the PB area were performed in reserpinized cats. Because PGO waves are closely related to rapid eye movements, our microelectrode explorations were also aimed to some structures of the preoculomotor network, namely, the superior colliculus (SC) and parts of the central tegmental field (FTC). We have found several classes of PGO-on cells in the PB area, most of them descharging 80 ms or less before the peak of PGO waves. These cell-classes comprised high-frequency bursting cells, slow-frequency bursting cells, and neurons discharging single spikes or doublets. Intracellular recordings showed that PGO-on single spikes arise from conventional excitatory postsynaptic potentials. Among PGO-related cells in structures outside the PB limits, it was found that most SC cells discharge during or after the PGO, whereas FTC cells increase their discharge rate several hundreds of ms before PGO waves, thus indicating that PGO waves are elaborated long before the activation of PB neurons. Massive retrograde labeling was found in FTC following horseradish peroxidase injections into the PB area. We suggest that long-lead FTC neurons provide an excitatory input to PGO-on PB neurons.
Animals↗
Influence of local anesthetic solution on postdural puncture headache.
A total of 2,511 patients who received spinal anesthesia for cesarean delivery were observed for the development of postdural puncture headache (PDPH); 804 patients received a mixture of tetracaine and procaine, 942 received bupivacaine-glucose, and 765 received lidocaine-glucose. They were observed for the development of PDPH for a minimum of 72 h. PDPH occurred in 9.54% of patients who received lidocaine-glucose during the first 36 h compared with 7.64% of patients who received bupivacaine-glucose and 5.85% of patients who received tetracaine-procaine. The differences between all groups was statistically significant. No differences were found in the percentage of patients who ultimately required epidural blood patch for relief of symptoms after 36 h.
Adult↗