Complications associated with pectoral cardioverter-defibrillator implantation: comparison of subcutaneous and submuscular approaches. Worldwide Jewel Investigators

OBJECTIVES

The aim of this study was to compare complications in a large cohort of patients undergoing pectoral cardioverter-defibrillator implantation with a subcutaneous or submuscular approach.

BACKGROUND

Pectoral placement of implantable cardioverter-defibrillator (ICD) pulse generators is now routine because of downsizing of these devices. subcutaneous implantation has been advocated by some because it is a simple surgical procedure comparable to pacemaker insertion. Others have favored submuscular insertion to avoid wound complications. These surgical approaches have not been compared previously.

METHODS

The subjects for this study were 1,000 consecutive patients receiving a Medtronic Jewel ICD at 93 centers worldwide. Cumulative follow-up for all patients was 633.7 patient-years, with 64.9% of patients followed up for > or = 6 months. The complications evaluated were erosion, pocket hematoma, seroma, wound infection, dehiscence, device migration, lead fracture and dislodgment.

RESULTS

Subcutaneous implantation was performed in 604 patients and submuscular implantation in the remaining 396. The median procedural times were shorter for subcutaneous implantation (p = 0.014). In addition, the cumulative percentage of patients free from erosion was greater for subcutaneous implantations (p = 0.03, 100% vs. 99.1% at 6 months). However, lead dislodgment was more common with subcutaneous implantations (p = 0.019, 2.3% vs. 0.5% at 6 months) and occurred primarily during the first month postoperatively. Overall, there were no significant differences in cumulative freedom from complications between groups (4.1% vs. 2.5%, p = 0.1836).

CONCLUSIONS

Subcutaneous pectoral implantation of this ICD can be performed safely and has a low complication rate. This approach requires a simple surgical procedure and, compared with the submuscular approach, is associated with shorter procedure times and comparable overall complication rates. However, early follow-up is important in view of the increased lead dislodgment rate.

Voltage-dependent interaction of open-channel blocking molecules with gating of NMDA receptors in rat cortical neurons

1. The mechanisms by which four adamantane derivatives (IEM-1857, -1592, -1460 and -1754) block the open NMDA-activated channel were studied at membrane voltages (Vm) from -170 to +30 mV. The rate constants of channel block (k+) and of channel unblock (k-) were measured from the fully resolvable flicker of single-channel currents induced by each compound. 2. The k+ of each compound exhibited a similar exponential dependence on voltage over the Vm range studied. 3. The k- of IEM-1857 and IEM-1592 over the Vm range studied, and of IEM-1754 and IEM-1460 from -30 to -90 mV, exhibited similar exponential dependencies on voltage. However, the k- of IEM-1754 and IEM-1460 at Vm values more hyperpolarized than -90 mV were much more steeply voltage dependent, suggesting that at these Vm values the two drugs can occupy a deeper binding site. 4. Each of the drugs induced a concentration-dependent prolongation of the mean burst length at -90 mV, suggesting that while blocking they can interfere with channel closure. 5. The prolongation of mean burst length induced by the largest drug (IEM-1857) increased with hyperpolarization. The increase was consistent at each Vm with the predictions of the sequential scheme of block, suggesting that channel closure is prevented when IEM-1857 is bound. The prolongation of burst length induced by the smallest drug (IEM-1754) was less than predicted by the sequential scheme and the deviation increased with hyperpolarization. 6. The IEM-1857 concentration-dependence of number of blockages per unit open time had a slope equal to k+ at -150 mV. The IEM-1754 concentration-dependence of number of blockages per unit open time revealed a slope about two times less than k+ for this compound at -150 mV. 7. The mean patch current was not significantly altered by 3 microM IEM-1857 at Vm values from -90 to -150 mV, as expected of a drug that prevents channel closure when blocking. Mean patch current significantly decreased with hyperpolarization beyond -90 mV in the presence of 1 microM IEM-1754. 8. The data suggest that there are two blocking sites at different depths within the NMDA-activated channel. Channel closure is prevented when any of the IEM drugs occupy the shallow blocking site. Channel closure is permitted during occupation of a deeper blocking site that can be reached only by the smaller IEM drugs at hyperpolarized voltages.

Mechanisms of glutamate-stimulated Mg2+ influx and subsequent Mg2+ efflux in rat forebrain neurones in culture

1. Mag-fura-2 fluorescence microscopy and whole-cell patch-clamp recordings were used to measure glutamate-induced changes in the intracellular free Mg2+ concentration ([Mg2+]i) and Mg2+ currents, respectively, in cultured forebrain neurones from fetal rats in the absence of extracellular Na+ (Nao+) and Ca2+ (Cao2+). 2. Increasing the extracellular Mg2+ concentration ([Mg2+]o) from 9 to 70 mM significantly enhanced the maximum [Mg2+]i induced by a 5 min 100 microM glutamate plus 1 microM glycine stimulation ([Mg2+]i,5 min) from 2.04 +/- 0.07 to 2.98 +/- 0.20 mM. Increasing [Mg2+]o from 9 to 70 mM also significantly enhanced the initial rate of rise in [Mg2+]i upon glutamate stimulation from 0.41 +/- 0.02 to 0.81 +/- 0.08 mM min-1. 3. The glutamate-stimulated increase in [Mg2+]i was not altered by prior depletion of intracellular free Na+ (Nai+). For paired stimulations in single neurones, the mean [Mg2+]i,5 min was 1.95 +/- 0.17 mM under Na(+)-depleted conditions and 1.94 +/- 0.16 mM under control conditions. 4. The glutamate-stimulated increase in [Mg2+]i was significantly reduced when NMDA channel-permeant Cs+ or K+ ions were used as the Na+ substitute instead of the presumably NMDA channel-impermeant ions N-methyl-D-glucamine (NMDG), Tris or sucrose. The mean [Mg2+]i,5 min was 0.56 +/- 0.06 and 0.74 +/- 0.08 mM in the presence of Cs+ or K+, respectively, compared with 2.13 +/- 0.10, 1.93 +/- 0.11 and 2.07 +/- 0.22 mM in the presence of NMDG, Tris or sucrose, respectively. 5. In whole-cell recordings performed with Cs+ as the primary intracellular cation, application of 100 microM NMDA plus 10 microM glycine induced inward currents that reversed around -55 mV in an extracellular solution containing 70 mM Mg2+ and 31 mM NMDG as the only cations. The currents were reversibly inhibited by DL-2-amino-5-phosphonovaleric acid (APV). In an extracellular solution containing 2 mM Mg2+ and 140 mM NMDG, NMDA plus glycine activated outward currents at potentials more depolarized than -90 mV. 6. In whole-cell recordings made with NMDG as the principal cation in the patch pipette, application of NMDA plus glycine in the 70 mM Mg2+ extracellular solution induced inward currents at voltages more negative than +15 mV. The ratio of the current measured under these conditions to the current measured in an extracellular solution containing Na+ as the principal cation (0.073:1) was nearly constant from cell to cell. 7. Following a 5 min glutamate stimulation in the presence of 9 mM Mg2+, [Mg2+]i returned to basal levels at a mean rate of 58.1 +/- 2.1 microM min-1. Complete removal of Nao+ significantly inhibited the rate of recovery to 31% of control. Raising [Mg2+]o to 30 mM in combination with removal of Nao+ did not inhibit recovery significantly more than either manipulation alone (28% of control). 8. These results suggest that glutamate-stimulated increases in [Mg2+]i that occur in the absence of Nao+ and Cao2+ result from Mg2+ entry through NMDA-activated ion channels. Furthermore, recovery from a glutamate-induced Mg2+ load appears to be primarily due to Mg2+ efflux via a mechanism whose characteristics are consistent with Na(+)-Mg2+ exchange.

Effects of intracellular Mg2+ on channel gating and steady-state responses of the NMDA receptor in cultured rat neurons

1. The effects of intracellular Mg2+ (Mgi2+) on the single N-methyl-D-aspartate (NMDA)-activated channel burst duration and frequency and on the mean NMDA-activated patch current were studied in outside-out patches from cultured rat cortical neurons. The inhibition by Mgi2+ of mean patch and whole-cell currents were compared, and some possible explanations for the observed differences were investigated. 2. The burst duration at +60 mV did not depend on Mgi2+ concentration, suggesting that the channel can close when blocked by Mgi2+. The number of bursts per second increased significantly in the presence of Mgi2+, suggesting that the rate of channel opening is higher when Mg2+ from the intracellular solution occupies its binding site. 3. Mgi2+ caused a voltage- and concentration-dependent inhibition of mean patch current. The inhibition is in quantitative agreement with the effects of Mgi2+ on the single-channel current and on burst parameters. 4. Based on the effects of Mgi2+ on burst parameters and on single-channel current, a four-state model in which the NMDA-activated channel can close while blocked by Mgi2+ is proposed. By fitting the model to the mean patch current data, we estimate that the rate of channel opening is increased by a factor of 1.4 when Mgi2+ occupies the channel. This estimation provides evidence that occupancy of the NMDA-activated channel by Mgi2+ destabilizes the closed state. 5. Mgi2+ reduced NMDA-activated whole-cell currents in a voltage- and concentration-dependent manner. However, normalized whole-cell and mean patch currents at positive voltages differed in two significant respects. First, when currents were recorded in a 0 Mg2+ pipette solution, whole-cell currents at positive voltages were smaller. Second, Mgi2+ appeared to inhibit whole-cell current less effectively than it inhibited mean patch current. 6. Inclusion of the Mg2+ chelators EDTA and ATP in 0 Mg2+ pipette solutions did not increase the whole-cell current measured at +60 mV. This observation suggests that the difference between normalized whole-cell and mean patch currents with 0 Mg2+ pipette solution was not due to block of whole-cell currents by residual Mgi2+. 7. When a pipette solution containing EGTA and Mg2+ was used to buffer Mgi2+, inhibition by Mgi2+ of the whole-cell current was enhanced, suggesting that the free Mg2+ concentration inside a neuron can remain below the pipette Mg2+ concentration. However, we cannot exclude other explanations for the differences between the inhibition by Mg2+ of mean patch and whole-cell currents.

Kinetics of the block by intracellular Mg2+ of the NMDA-activated channel in cultured rat neurons

1. Single-channel currents activated by the glutamate agonist N-methyl-D-aspartate (NMDA) were recorded from outside-out patches of cultured rat cortical neurons in the presence of intracellular Mg2+ (Mgi2+). The rate constants of the block by Mgi2+ were measured using amplitude distribution analysis. 2. At a membrane potential of 0 mV, the blocking rate constant (k+) of Mgi2+ was estimated to be 2.1 x 10(7) M-1 S-1 and the unblocking rate constant (k-) 1.7 x 15(5)s-1. The very fast rate constants of the block by Mgi2+ explain why channel flicker was not fully resolvable during block of the NMDA-activated single-channel current by Mgi2+. 3. The blocking rate constant of Mgi2+ increased with increasing concentrations of Mgi2+. The unblocking rate constant was Mgi2+ concentration independent. 4. The blocking rate constant increased e-fold per 64 mV depolarization, whereas the unblocking rate constant decreased e-fold per 133 mV depolarization. The dissociation constant (KD) calculated from the blocking rates (k-/k+) decreased e-fold per 43 mV depolarization, and had a value at 0 mV of 7.8 mM. These values are consistent with previous estimates obtained from the voltage-dependent inhibition of the single-channel current amplitude. Both results predict, based on the Woodhull model, that Mgi2+ traverses about one-third of the membrane field to reach its blocking site. 5. The unblocking rate constant of Mgi2+ is one to two orders of magnitude faster than the previously reported unblocking rate constant of extracellular Mg2+ (Mgo2+) in the physiological voltage range, and their voltage dependencies are of opposite signs. These findings are consistent with the hypothesis that there are separate binding sites in the channel for Mgi2+ and Mgo2+. 6. Based on the blocking kinetics of Mgi2+ and Mgo2+, an energy profile of three barriers and two binding sites for Mg2+ is proposed.

A critique of the new recommendations for weight gain in pregnancy

Recent Institute of Medicine recommendations for weight gain in pregnancy advocate a marked increase over prior guidelines, and for reasons that must be questioned. The objectives of these new guidelines are to reduce perinatal mortality, prematurity, and fetal growth retardation. Evidence of a causal relationship between less maternal weight gain and these adverse outcomes is lacking. In addition, the consequences of increased pregnancy weight gain have been incompletely assessed. The risk-to-benefit ratio may be prohibitive. The new recommendations, which will be considered by many to be clinical guidelines, fall short of the formulation criteria recommended by the United States Preventive Services Task Force.

Synthesis and evaluation of [123I]-iodo-PK11195 for mapping peripheral-type benzodiazepine receptors (omega 3) in heart

An iodinated analog of PK11195, 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)isoquinoline-3-carboxamide , a specific antagonist of the peripheral-type benzodiazepine receptor (omega 3), has been synthesized in three steps with an overall chemical yield of 40%. Both [123I]- and [125I]-Iodo-PK11195 have been synthesized by solid-state isotopic exchange in > 60% isolated radiochemical yield and specific activity of 233-348 mCi/mmol. Tissue distribution studies in rats indicate a high uptake of radioactivity in adrenal glands, heart, lung and kidneys, which was blocked 63-87% by preadministration of cold PK11195. Single photon emission computer tomography (SPECT) imaging of the canine heart has been accomplished with [123I]PK11195. These results suggest that [123I]PK11195 has potential as a SPECT radiotracer for studying the omega 3 receptor in humans.

Regulation of endometrial prostaglandin synthesis during early pregnancy in cattle: effects of phospholipases and calcium in vitro

In experiment 1, endometrial explants from 3 cyclic (Day 17) cows were incubated with arachidonic acid (AA), phospholipase A-2 (PLA-2) and calcium ionophore A23187 (CaI) or control. AA (0.2 mg), PLA-2 (1 U/ml) and CaI (4 micrograms/ml) increased PGF and PGE secretion. In experiment 2, endometrial explants from cyclic (n = 4) and pregnant (n = 3) cows were incubated +/- Ca++ and with either: control, AA, PLA-2, CaI, PLA-2 + CaI, or AA + CaI. PG secretion was higher in cultures with Ca++. In presence of Ca++, PGF secretion was lower for pregnant than cyclic endometrium. AA with Ca++ stimulated PGF and PGE secretion, indicating that AA availability may limit PG secretion. The stimulatory effect of PLA-2 on PGF and PGE secretion was greater in pregnant than cyclic endometrium. However, CaI inhibited the PLA-2 response of pregnant, but not cyclic endometrium. In experiment 3, endometrium (4 cyclic cows) failed to convert 3H-PGF2 alpha to PGE2 or 3H-PGE2 to PGF2 alpha. Responsiveness of PG secretion to PLA-2, and CaI is altered by reproductive status suggesting that these factors may be involved in the differential regulation of PG production during early pregnancy in cattle.

Effect of aspirin use on death and recurrent myocardial infarction in current and former cigarette smokers. Program on the Surgical Control of the Hyperlipidemias Group

The purpose of this study was to examine the effects of aspirin use on mortality and morbidity rates in a subset of the control group of the Program on the Surgical Control of the Hyperlipidemias (POSCH) that was stratified by cigarette smoking status at the time of randomization. The clinical impact of aspirin intake in cigarette smokers and former cigarette smokers has not been well studied. POSCH was a randomized, controlled, clinical trial designed to ascertain the effects of lipid modification by the partial ileal bypass operation on clinical end-points and arteriographic changes in postmyocardial infarction subjects with hypercholesterolemia. Cohorts of cigarette smokers in the diet-control group were evaluated for overall and atherosclerotic coronary heart disease (ACHD) mortality rates and recurrent confirmed nonfatal myocardial infarction rates. In current cigarette smokers at baseline (n = 90) with a mean follow-up of 8.3 years, the overall mortality rate was 45.2% in patients with no aspirin use and 10.4% in patients who reported even infrequent aspirin use (relative risk = 4.3, 95% confidence interval (CI) = 2.4 to 10.6, p < 0.001). For ACHD mortality in this cohort, the relative risk was 17.1 (35.7% vs 2.1%, 95% CI = 1.4 to 125.0, p < 0.001); for the combined end-point of ACHD mortality and nonfatal myocardial infarction, the relative risk was 2.4 (40.5% vs 16.7%, 95% CI = 1.2 to 5.1, p = 0.018).(ABSTRACT TRUNCATED AT 250 WORDS)

Posttetanic potentiation and presynaptically induced long-term potentiation at the mossy fiber synapse in rat hippocampus

A form of long-term potentiation (LTP) is induced at the mossy fiber (MF) synapse in the hippocampus by high-frequency presynaptic stimulation (HFS). It is generally accepted that induction of this form of LTP (MF LTP) does not depend on postsynaptic Ca2+ current gated by N-methyl-D-aspartate receptors, but it has remained controversial whether induction depends on postsynaptic depolarization and voltage-gated entry of Ca2+. There are also contradictory data on the time course of both LTP and post-tetanic potentiation (PTP), a shorter duration form of potentiation observed at MF synapses immediately following HFS. It has been proposed that some of these differences in results may have arisen because of difficulties in isolating monosynaptic responses to MF input. In the present study, whole cell recording was used to observe excitatory postsynaptic currents (EPSCs) elicited in CA3 pyramidal cells by input from MFs. Postsynaptic cells were dialyzed with 1,2-bis(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA) and F- to inhibit postsynaptic mechanisms that required Ca2+, cells were under voltage clamp during HFS, and conditions were selected to minimize the likelihood of polysynaptic contamination. Under these conditions, HFS nevertheless induced robust LTP (mean magnitude, 62%). The possibility that EPSCs were contaminated by polysynaptic components was investigated by exposing the slices to a suppressing medium (one that partially blocked neurotransmission). EPSC waveforms did not change shape during suppression, indicating that contamination was absent. The LTP observed always was accompanied by prominent PTP that lasted through the first 5 to 15 min following HFS (mean decay time constant, 3.2 min). Induction of this LTP was not cooperative; there was no relationship between the size of responses and the magnitude of the LTP induced. LTP magnitude also was unrelated to the extent to which postsynaptic cells depolarized during HFS. These results show that high rates of presynaptic MF activity elicit robust LTP whether or not there is accompanying postsynaptic depolarization or increase in the concentration of postsynaptic Ca2+. High-frequency MF activity also results in a PTP that is unusually large and long.

Novel adamantane derivatives act as blockers of open ligand-gated channels and as anticonvulsants

We examined the influence of the molecular structure of four novel adamantane derivatives on their ability to block the channels of nicotinic acetylcholine (ACh) and N-methyl-D-aspartate (NMDA) receptors. The structure of the drugs is Ad-CH2-N+H2-(CH2)5-R, where Ad is adamantane and R was varied from ammonium (IEM-1754) to tert-butyldimethylammonium (IEM-1857) radical. The compounds induced double-exponential decays of postsynaptic currents in frog muscles and flickering of NMDA-activated channels, suggesting that each drug acts as a fast open-channel blocker at both types of receptors. The equilibrium dissociation constants (Kd) of the drugs for ACh-activated channels at -80 mV were similar, whereas the Kd values for NMDA-activated channels at -80 mV were 2-10 times lower. Several observations suggested that occupation of either type of channel by these compounds inhibited channel closure; the time constant (tau) of the slow component of the decay of postsynaptic currents in the presence of each compound was greater than the control tau, the IC50 of IEM-1754 for inhibition of NMDA-activated whole-cell currents was > 20 times larger than its Kd for the open channel, and a transient increase in NMDA-activated whole-cell currents was observed after washout of IEM-1754. Thus, these drugs appear to act on nicotinic ACh and NMDA receptors via similar mechanisms, although the voltage dependence of block suggested that the drugs bind at a more superficial site in the ACh-activated channel. All compounds also potently prevented NMDA-induced convulsions in mice. The ED50 of IEM-1754 was 4 times lower than the ED50 of MK-801.

[The blockade of glutaminergic and cholinergic ion channels by adamantane derivatives]

It has been shown that a homologous series of adamantane derivatives of general structure Ad-CH2-N+H2-(CH2)5-N+R3, where Ad, adamantane, R varied from H (hydrogen) to t-Bu (tertiary butyl), blocks the open state of postsynaptic activated channels. In the presence of the drugs studied the decay of evoked cholinergic postsynaptic currents in frog neuromuscular junction could be fitted by two exponentials. However, the rate constants of interaction of blocker with channel did not depend on the R structure and membrane potential. The rate of blockade of glutamatergic postsynaptic currents in insect neuromuscular junction increased as the radicals at nitrogen atom became heavier, but was independent on membrane potential. The drugs studied affected in voltage dependent manner the kinetic properties of single channels (recorded in outside-out patches excised from cultured neurones of embryonic rat brain cortex) induced by NMDA application. Each of these compounds evoked fast flickering of single channels between an open and blocked state. Drugs effectively prevented the convulsions evoked by intraventricular injection of NMDA into mouse brain. The compound IEM-1754 that was the most potent blocker in the experiments on NMDA-activated single channels possessed six times higher anticonvulsant activity than dizocilpine (MK-801).

Gender dimorphism of a visual anomaly: a deductive prediction based on an ethological model

Using an ethological model, we deduced a prediction concerning gender dimorphism in a visual anomaly from a re-construction of the phylogeny of man. The prediction, which is based on four premises, is that deficits in distance vision (myopia) would be more prevalent in contemporaneous women than in men. Data collected in a de facto double-blind method support the prediction, and thereby support the unique efficacy in using an ethological model to understand facets of the contemporary human condition.

Response of male eye-spotted bud moth,Spilonota ocellana (Lepidoptera: Tortricidae), to different pheromone blends in north America and The Netherlands

Response of male eye-spotted bud moth,Spilonota ocellana (Denis and Schiffermüller), to different ratios of synthetic sex pheromone components, (Z)-8-tetradecenyl acetate (Z8-14:OAc) and (Z)-8-tetradecenyl alcohol (Z8-14:OH), were compared in four North American locations and in one location in The Netherlands. In British Columbia, Nova Scotia, Michigan, and The Netherlands, a 99:1 blend ofZ8-14:OAc andZ8-14:OH captured significantly more maleS. ocellana thanZ8-14:OAc alone or binary blends containing 10-50%Z8-14:OH. In Ontario, where population sizes were low compared to the other four locations, trends in trap catches were similar, and there was no indication that maleS. ocellana responded differently to the tested pheromone blends. A 99:1 blend ofZ8-14:OAc andZ8-14:OH should be most effective in pheromone-based control programs ofS. ocellana in North America and in The Netherlands. Our results confirm earlier studies that a 99:1 blend ofZ8-14:OAc andZ8-14:OH captures significantly more maleS. ocellana thanZ8-14:OAc alone. However, our finding that a 99:1 blend ofZ8-14:OAc andZ8-14:OH is significantly more attractive than binary blends containing 10-50%Z8-14:OH differs from previous findings in Germany and Switzerland.

Asynchrony of mossy fibre inputs and excitatory postsynaptic currents in rat hippocampus

1. Excitatory postsynaptic currents (EPSCs) were studied by whole-cell voltage-clamp recording (WCR) from pyramidal cells in the CA3 field of rat hippocampal slices. Input from mossy fibres was evoked by stimuli applied to stratum granulosum ('dentate gyrus stimulation'). This often resulted in complex, multi-component EPSCs with rise times as long as 5.0 ms (mean = 2.5 ms). In contrast, individual EPSC components typically had rise times between 0.3 and 1.0 ms. 2. To isolate monosynaptic, mossy fibre-driven EPSC components, slices were exposed to 'suppressing' media that reduced response amplitudes by 64-88%. In five out of six cases, long EPSC rising phases (> 3 ms) retained the same shape during suppression. This implied that EPSCs were driven by asynchronously active mossy fibre inputs. 3. From latencies of antidromically driven granule cell population spikes (GCPSs) a mean conduction velocity of 0.67 m/s was inferred. Conduction distance had practically no correlation with GCPS duration, implying that velocity dispersion was small and did not desynchronize mossy fibre impulses. EPSC components exhibited 'surplus' latency; they occurred 0.9-4.8 ms after latencies expected on the basis of direct conduction distances. 4. Mossy fibre volleys (MFVs) were evoked by dentate gyrus stimulation and studied with neurotransmission disabled. MFV negative phases lasted from 2.5 to 4.5 ms and had multiple components. By comparison, negative phases of Schaffer collateral fibre volleys (SCFVs) were always simple in shape and lasted 1.5 ms or less. MFV components had surplus latencies similar to those of EPSC components. Late MFV components did not require high stimulus intensities. 5. Widespread activation of granule cells occurred when stimuli were applied to single loci in the stratum granulosum. This implies that such stimuli elicit antidromic impulses in hilar collaterals of mossy fibres, which could result in activation of orthodromic impulses in mossy fibre trunks that had not been stimulated directly. After anti-, then orthodromic conduction, impulses would arrive in the CA3 subfield with 'surplus' latency. 6. When cuts were made in the hilus to prevent anti-/orthodromic conduction, MFV durations were reduced, but only to a small extent. This implies that surplus latency and asynchrony arise in part by anti-/orthodromic conduction, and partly by a mechanism that is intrinsic to mossy fibres or their 'giant' boutons. 7. Because of desynchronization of mossy fibre inputs, there probably are significant differences between kinetic properties of averaged, compound mossy fibre EPSCs and those of unitary mossy fibre EPSCs (i.e. currents driven by input from single presynaptic axons).(ABSTRACT TRUNCATED AT 400 WORDS)

Perception of quality of life before and after disclosure of trial results: a report from the Program on the Surgical Control of the Hyperlipidemias (POSCH)

The Program on the Surgical Control of the Hyperlipidemias (POSCH) was a randomized controlled clinical trial designed to ascertain whether cholesterol lowering induced by the partial ileal bypass operation would favorably affect overall mortality and the mortality and morbidity due to coronary heart disease. The trial results provided strong clinical and coronary arteriographic support for the beneficial effects of lipid modification for the reduction of atherosclerosis progression. At the same time, the surgery-assigned group experienced diarrhea and an increased incidence of kidney stones and gallstones compared to the control-assigned group. Identical quality of life determinations were performed in the POSCH study population shortly before disclosure of the trial results to the patients and shortly thereafter. The purpose of this dual assessment was to evaluate the effect of knowledge of outcomes on the patients' subjective evaluation of quality of life. The primary instrument utilized for analysis of the perception of quality of life in POSCH was the McMasters Health Index Questionnaire (MHIQ). In addition, four study-specific questions were asked of the trial patients. The results for the MHIQ before disclosure of trial results showed a difference (p = 0.07) favoring the control-assigned group (diet-treated), for the social function index of the MHIQ. After disclosure of the trial results, the difference was larger (p < 0.05). For the four study-specific questions, all differences favored the control-assigned group (p < 0.01) before and after disclosure of the trial results, with the exception of satisfaction with randomization allocation in the surgery-assigned group (p = 0.08). The intragroup MHIQ indices before and after disclosure of the trial results showed no suggestive significant differences, except in the surgery-assigned group, in which there was an improvement in the emotional function index after disclosure of the trial results (p = 0.03). The intragroup responses to the study-specific questions before and after disclosure of the trial results again showed no significant differences, except in the surgery-assigned group, in which there was an improvement in patient satisfaction with randomization allocation after disclosure of the trial results (p = 0.04).(ABSTRACT TRUNCATED AT 400 WORDS)

Serum creatinine as an independent predictor of coronary heart disease mortality in normotensive survivors of myocardial infarction. POSCH Group

BACKGROUND

Serum creatinine has been reported in previous studies to be a prognostic indicator for overall mortality, in particular in a hypertensive population.

METHODS

The Program on the Surgical Control of the Hyperlipidemias (POSCH) was a randomized, controlled clinical trial. All patients had survived a single myocardial infarction, were normotensive, were not obese, were not having heart failure, and were free of diabetes mellitus and renal disease at entry into the study. POSCH had followed its control group patients (N = 417) for a minimum of 7.0 years. In this group, a prospective post hoc analysis of the relationship of baseline serum creatinine with subsequent overall and atherosclerotic coronary heart disease mortality was performed.

RESULTS

The baseline serum creatinine values in the control group patients ranged from 0.7 to 1.9 mg/dL (60 to 170 mumol/L), and were found to be independent predictors (P < .01) of both overall mortality and atherosclerotic coronary heart disease mortality. Each 0.1 mg/dL (9 mumol/L) increment in the baseline serum creatinine increased the relative risk for subsequent overall mortality by 36% and the relative risk for subsequent atherosclerotic coronary heart disease mortality by 47%.

CONCLUSIONS

These results demonstrate that a serum creatinine value, obtained in normotensive, nonobese, normoglycemic survivors of a myocardial infarction without preexistent renal disease or heart failure, provides independent prognostic information regarding subsequent overall and atherosclerotic coronary heart disease mortality.

Plasma lipid concentrations and subsequent coronary occlusion after a first myocardial infarction. The POSCH Group

This study correlated plasma lipid values with angiographic evidence of progression to complete coronary occlusion. Baseline triglycerides (TGs), total cholesterol (Chol), high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, very low density lipoprotein (VLDL) cholesterol, and HDL/LDL and HDL/Chol ratios were compared with coronary angiograms taken at baseline, 3 and 5 years in a prospective angiographic study. Results were from part of the multicenter trial of plasma lipid reduction in patients after a single myocardial infarction (POSCH). Comparison of patient's baseline lipids in the absence or presence of a new total coronary occlusion at 3 years showed a significant difference (p = 0.01) in TGs of 197 +/- 147 versus 250 +/- 162 mg/dl (p = 0.02) and VLDL of 30 +/- 23 (n = 284) versus 40 +/- 30 (n = 49) mg/dl. Stratification by the mean HDL/Chol ratio (16%) demonstrated that baseline TG levels were significantly increased in patients with a new coronary occlusion by 3 years despite a higher HDL/Chol ratio. When measured at the 3-year visit, plasma TG (176 +/- 91 versus 212 +/- 146 mg/dl; p = 0.02) and VLDL (28 +/- 18 versus 35 +/- 29 mg/dl; p = 0.04) were significantly elevated in the presence of a new 3-year coronary occlusion. Stratification by the mean HDL/Chol ratio (16%) demonstrated that 3-year TG levels increased significantly in patients with a new 3-year coronary occlusion despite a higher HDL/Chol ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Collecting and analyzing cord blood gases

The analysis of cord blood respiratory gases and acid-base values is an important adjunct for determining the extent and cause of fetal acidosis at delivery. Although the quality and reliability of the blood gas instruments have improved dramatically, constant vigilance still is required and mandated to ensure accurate and precise results. Failure to control the many sampling and analysis variables that affect cord blood gas results will limit their usefulness. Most preanalytic problems become a minor concern when the blood gas analyses are done within a few minutes after obtaining the sample. Comparison of data among centers requires, not only that reference ranges be stated, but also that various corrections or factors that were used to adjust the results be described. Perhaps, a consensus could be reached to establish the optimal method of collection and the best methods for analyzing and reporting the results from cord blood gas and acid-base studies.

Vaporized hydrogen peroxide sterilization of freeze dryers

The feasibility of using vapor hydrogen peroxide (VHP) as an alternative to steam sterilization has been examined using a pilot plant freeze dryer equipped with a prototype vapor generator. Specific objectives of the study discussed in this presentation were to: 1. Identify critical process variables affecting the lethality of VHP to Bacillus stearothermophilus spores, particularly within dead legs in the system. 2. Measure the efficacy of system degassing after sterilization. 3. Determine the effect of repeated sterilization cycles on the integrity of elastomeric components of the freeze dryer. Penetration of adequate concentrations of hydrogen peroxide vapor into small diameter piping, such as tubing connected to pressure gauges, is the most challenging aspect of VHP sterilization of freeze dryers. Prior to equipment modifications, spore strips placed within such dead legs remained positive irrespective of the number of gas/degas pulses and system pressure. Equipment modifications necessary to effect complete kill of biological indicators placed in system dead legs is discussed. Results of this study support the conclusion that vaporized hydrogen peroxide shows promise as an alternative sterilization method for freeze dryers.

Equilibrium and kinetic study of glycine action on the N-methyl-D-aspartate receptor in cultured mouse brain neurons

1. The characteristics of the activation of the N-methyl-D-aspartate (NMDA) response by glycine were studied using whole-cell and outside-out patch clamp recording techniques. 2. Glycine concentration-response (C-R) curves were measured in the presence of 10 microM-NMDA and fitted with the Hill equation modified to account for the response to NMDA observed in the absence of added glycine. The mean value of the apparent dissociation constant (KD) was 150 nM, and the mean value of the Hill coefficient (nH) was 1.1. When the KD was corrected for the concentration of contaminating glycine in nominally glycine-free solutions, estimated assuming that there is no response in the absence of glycine, the value was 130 nM. 3. The question of how many glycine binding sites there are on each NMDA receptor-channel complex was addressed by examining the curvature at the foot of the glycine C-R curve. An equation that allowed estimation of both the concentration of contaminating glycine and of the value of nH was fitted to glycine C-R data up to 50 nM. The mean value of nH was found to be 1.0, consistent with the idea that there is one glycine binding site. 4. The kinetics of the interaction of glycine with the NMDA receptor were measured by fitting single exponential curves to the current relaxation following a jump in glycine concentration in the presence of 10 microM-NMDA. The plot of the inverse of the relaxation time constant as a function of glycine concentration after the concentration jump was linear. The association rate constant was estimated from these data as 1.2 x 10(7) M-1 s-1 and the dissociation rate as 1.0 s-1. 5. Experiments were devised to allow the evaluation of the KD and dissociation rates of glycine in the absence of NMDA. They led to a value for KD of 80 nM, slightly but significantly lower than the value of 150 nM estimated in the presence of 10 microM-NMDA. The glycine dissociation rate in the absence of NMDA was found to be 0.7 s-1, not significantly different from that measured in the presence of 10 microM-NMDA. 6. The results are consistent with a model of the NMDA receptor with a single glycine binding site. The characteristics of glycine binding are similar in the absence and the presence of 10 microM-NMDA, although NMDA binding may cause a small increase in the glycine KD.(ABSTRACT TRUNCATED AT 250 WORDS)

Excessive maternal weight and pregnancy outcome

OBJECTIVES

This study was undertaken to determine the influences of increased maternal prepregnancy weight and increased gestational weight gain on pregnancy outcome.

STUDY DESIGN

This was a longitudinal retrospective study of 7407 term pregnancies delivered from 1987 through 1989. After excluding cases with multiple fetuses, stillbirths, fetal anomalies, no prenatal care, selected medical and surgical complications, and those with incomplete medical records, 3191 cases remained for analyses by determination of odds ratios for obstetric outcomes, by chi 2 tests for significant differences and by adjustment for risk factors with stepwise logistic regression.

RESULTS

Both increased maternal prepregnancy weight (body mass index) and increased maternal gestational weight gain were associated with increased risks of fetal macrosomia (p less than 0.0001), labor abnormalities (p less than 0.0001), postdatism (p = 0.002), meconium staining (p less than 0.001), and unscheduled cesarean sections (p less than 0.0001). They were also associated with decreased frequencies of low birth weight (p less than 0.001). The magnitude of the last was less than that of the other outcomes.

CONCLUSIONS

Increased maternal weight gain in pregnancy results in higher frequencies of fetal macrosomia, which in turn lead to increased rates of cesarean section and other major maternal and fetal complications. Because these costs of increased maternal weight gain appear to outweigh benefits, weight gain recommendations for pregnancy warrant careful review.