Association of current substance use treatment with future reduced methamphetamine use in an observational cohort of men who have sex with men in Los Angeles

INTRODUCTION

Methamphetamine use is highly prevalent among men who have sex with men (MSM), but knowledge of the long-term dynamics, and how they are affected by substance use treatment, is limited. This study aimed to describe trajectories of methamphetamine use among MSM, and to evaluate the impact of treatment for any kind of substance use on frequency of methamphetamine use.

METHODS

This analysis used data from a cohort of MSM in Los Angeles, CA, who participated in semi-annual study visits from 2014 to 2022. The study characterized trajectories of methamphetamine use using a continuous time multistate Markov model with three states. States were defined using self-reported frequency of methamphetamine use in the past six months: frequent (daily), occasional (weekly or less), and never. The model estimated the association between receiving treatment for any kind of substance use and changes in state of frequency of methamphetamine use.

RESULTS

This analysis included 2348 study visits among 285 individuals who were followed-up for an average of 4.4 years. Among participants who were in the frequent use state, 65 % (n = 26) of those who were receiving any kind of substance use treatment at a study visit had reduced their methamphetamine use at their next visit, compared to 33 % (n = 95) of those who were not receiving treatment. Controlling for age, race/ethnicity, and HIV-status, those who reported receiving current treatment for substance use were more likely to transition from occasional to no use (HR: 1.63, 95 % CI: 1.10-2.42) and frequent to occasional use (HR: 4.25, 95 % CI: 2.11-8.59) in comparison to those who did not report receiving current treatment for substance use.

CONCLUSIONS

Findings from this dynamic modeling study provide a new method for assessing longitudinal methamphetamine use outcomes and add important evidence outside of clinical trials that substance use treatment may reduce methamphetamine use.

Emergency Department Access to Buprenorphine for Opioid Use Disorder

Importance

Although substantial evidence supports buprenorphine for treatment of opioid use disorder (OUD) in controlled trials, prospective study of patient outcomes in clinical implementation of emergency department (ED) buprenorphine treatment is lacking.

Objective

To examine the association between buprenorphine treatment in the ED and follow-up engagement in OUD treatment 1 month later.

Design, Setting, and Participants

This multisite cohort study was conducted in 7 California EDs participating in a statewide implementation project to improve access to buprenorphine treatment. The study population included ED patients aged at least 18 years identified with OUD between April 1, 2021, and June 30, 2022. Data analysis was performed in October 2023.

Exposure

All participants were offered buprenorphine treatment for OUD (either in ED administration, prescription, or both), the uptake of which was examined as the exposure of interest.

Main Outcomes and Measures

The primary outcome was engagement in OUD treatment 30 days after the ED visit, determined by patient report or clinical documentation. The association of ED buprenorphine treatment with subsequent OUD treatment engagement was estimated using hierarchical generalized linear models.

Results

This analysis included 464 ED patients with OUD. Their median age was 36.0 (IQR, 29.0-38.7) years, and most were men (343 [73.9%]). With regard to race and ethnicity, 64 patients (13.8%) self-identified as non-Hispanic Black, 183 (39.4%) as Hispanic, and 185 as non-Hispanic White (39.9%). Most patients (396 [85.3%]) had Medicaid insurance, and more than half (262 [57.8%]) had unstable housing. Self-reported fentanyl use (242 [52.2%]) and a comorbid mental health condition (328 [71.5%]) were common. Interest in buprenorphine treatment was high: 398 patients (85.8%) received buprenorphine treatment; 269 (58.0%) were administered buprenorphine in the ED and 339 (73.1%) were prescribed buprenorphine. With regard to OUD treatment engagement at 30 days after the ED visit, 198 participants (49.7%) who received ED buprenorphine treatment remained engaged compared with 15 participants (22.7%) who did not receive ED buprenorphine treatment. An association of ED buprenorphine treatment with subsequent OUD treatment engagement at 30 days was observed (adjusted risk ratio, 1.97 [95% CI, 1.27-3.07]).

Conclusions and Relevance

The findings of this cohort study suggest that among patients with OUD presenting to EDs implementing low-threshold access to medications for OUD, buprenorphine treatment was associated with a substantially higher likelihood of follow-up treatment engagement 1 month later. Future research should investigate techniques to optimize both the uptake and effectiveness of buprenorphine initiation in low-threshold settings such as the ED.

A COVID-19 Vaccination Program to Promote Uptake and Equity for People Experiencing Homelessness in Los Angeles County

People experiencing homelessness (PEH) have been disproportionately affected by COVID-19, yet their vaccination coverage is lower than is that of the general population. We implemented a COVID-19 vaccination program that used evidence-based and culturally tailored approaches to promote vaccine uptake and equity for PEH in Los Angeles County, California. From February 2021 through February 2022, 33 977 doses of vaccine were administered at 2658 clinics, and 9275 PEH were fully vaccinated. This program may serve as a model for future service delivery in vulnerable populations. (Am J Public Health. 2023;113(2):170-174. https://doi.org/10.2105/AJPH.2022.307147).

Financial incentives for COVID-19 vaccines among people experiencing homelessness

Introduction

Novel strategies are needed to address barriers to COVID-19 vaccination among people experiencing homelessness (PEH), a population that faces increased COVID-19 risk. While growing evidence suggests that financial incentives for vaccination are acceptable to PEH, their impact on uptake is unknown. This study aimed to assess whether offering $50 gift cards was associated with uptake of first doses of COVID-19 vaccine among PEH in Los Angeles County.

Methods

Vaccination clinics began on March 15, 2021; the financial incentive program was implemented from September 26, 2021 until April 30, 2022. Interrupted time series analysis with quasi-Poisson regression was used to evaluate level and slope change in the number of weekly first doses administered. Time-varying confounders included the weekly number of clinics and the weekly number of new cases. Demographic characteristics were compared for PEH vaccinated before and after implementation of the incentive program using chi-squared tests.

Results

Offering financial incentives was associated with administration of 2.5 times (95% CI: 1.8, 3.1) more first doses than would have been expected without the program. Level (-0.184, 95% CI: -1.166, -0.467) and slope change (0.042, 95% CI: 0.031, 0.053) were observed. Individuals who were unsheltered, under age 55 years, and identified as Black or African American accounted for a higher percentage of those vaccinated during the post-intervention period than during the pre-intervention period.

Conclusions

Financial incentives may be an effective tool for increasing vaccine uptake among PEH, but important ethical considerations must be made to avoid coercion of vulnerable populations.

Community Health Worker Perspectives on Engaging Unhoused Peer Ambassadors for COVID-19 Vaccine Outreach in Homeless Encampments and Shelters

BACKGROUND

COVID-19 vaccination is a priority for people experiencing homelessness. However, there are barriers to vaccine access driven in part by mistrust towards clinicians and healthcare. Community health workers (CHWs) and Peer Ambassadors (PAs) may be able to overcome mistrust in COVID-19 vaccine outreach. An unhoused PA program for COVID-19 vaccine outreach by CHWs was implemented in Los Angeles using a participatory academic-community partnership.

OBJECTIVE

The purpose of this study was to evaluate CHW perspectives on an unhoused PA COVID-19 vaccine outreach program in Los Angeles.

DESIGN

This study used a participatory community conference and qualitative focus groups to understand CHW perspectives on the PA program. The one-day conference was held in November 2021.

PARTICIPANTS

Of the 42 conference participants, 19 CHWs participated in focus groups for two-way knowledge exchange between CHWs and researchers.

APPROACH

Four focus groups were held during the conference, with 4-6 CHWs per group. Each group had a facilitator and two notetakers. Focus group notes were then analyzed using content analysis to derive categories of findings. CHWs reviewed the qualitative analysis to ensure that findings represented their experiences with the PA program.

KEY RESULTS

The five categories of findings from focus groups were as follows: (1) PAs were effective liaisons to their peers to promote COVID-19 vaccines; (2) CHWs recognized the importance of establishing genuine trust and equitable working relationships within CHW/PA teams; (3) there were tradeoffs of integrating unhoused PAs into the existing CHW workflow; (4) CHWs had initial misgivings about the research process; and (5) there were lingering questions about the ethics of "exploiting" the invaluable trust unhoused PAs have with unhoused communities.

CONCLUSIONS

CHWs were in a unique position to empower unhoused PAs to take a leadership role in reaching their peers with COVID-19 vaccines and advocate for long-term employment and housing needs.

COVID-19 Vaccine Acceptability and Financial Incentives among Unhoused People in Los Angeles County: a Three-Stage Field Survey

Unhoused people have higher COVID-19 mortality and lower vaccine uptake than housed community members. Understanding vaccine hesitancy among unhoused people is key for developing programs that address their unique needs. A three-round, rapid, field-based survey was conducted to describe attitudes toward COVID-19 vaccination. Round 1 assessed vaccine brand preference, round 2 assessed intention to accept a financial incentive for vaccination, and round 3 measured vaccine uptake and assessed reasons for vaccine readiness during implementation of a financial incentive program. A total of 5177 individuals were approached at COVID-19 vaccination events for unhoused people in Los Angeles County from May through November 2021. Analyses included 4949 individuals: 3636 (73.5%) unsheltered and 1313 (26.5%) sheltered. Per self-report, 2008 (40.6%) were already vaccinated, 1732 (35%) wanted to get vaccinated, 359 (7.3%) were not yet ready, and 850 (17.2%) did not want to get vaccinated. Brand preference was evenly split among participants (Moderna 31.0%, J&J 35.5%, either 33.5%, p = 0.74). Interest in a financial incentive differed between those who were not yet ready and those who did not want to get vaccinated (43.2% vs. 16.2%, p < 0.01). After implementing a financial incentive program, 97.4% of participants who indicated interest in vaccination were vaccinated that day; the financial incentive was the most cited reason for vaccine readiness (n = 731, 56%). This study demonstrated the utility of an iterative, field-based assessment for program implementation during the rapidly evolving pandemic. Personal engagement, a variety of brand choices, and financial incentives could be important for improving vaccine uptake among unhoused people.

Blood and Breath Alcohol Concentration from Transdermal Alcohol Biosensor Data: Estimation and Uncertainty Quantification via Forward and Inverse Filtering for a Covariate-Dependent, Physics-Informed, Hidden Markov Model

Transdermal alcohol biosensors that do not require active participation of the subject and yield near continuous measurements have the potential to significantly enhance the data collection abilities of alcohol researchers and clinicians who currently rely exclusively on breathalyzers and drinking diaries. Making these devices accessible and practical requires that transdermal alcohol concentration (TAC) be accurately and consistently transformable into the well-accepted measures of intoxication, blood/breath alcohol concentration (BAC/BrAC). A novel approach to estimating BrAC from TAC based on covariate-dependent physics-informed hidden Markov models with two emissions is developed. The hidden Markov chain serves as a forward full-body alcohol model with BrAC and TAC, the two emissions, assumed to be described by a bivariate normal which depends on the hidden Markovian states and person-level and session-level covariates via built-in regression models. An innovative extension of hidden Markov modeling is developed wherein the hidden Markov model framework is regularized by a first-principles PDE model to yield a hybrid that combines prior knowledge of the physics of transdermal ethanol transport with data-based learning. Training, or inverse filtering, is effected via the Baum-Welch algorithm and 256 sets of BrAC and TAC signals and covariate measurements collected in the laboratory. Forward filtering of TAC to obtain estimated BrAC is achieved via a new physics-informed regularized Viterbi algorithm which determines the most likely path through the hidden Markov chain using TAC alone. The Markovian states are decoded and used to yield estimates of BrAC and to quantify the uncertainty in the estimates. Numerical studies are presented and discussed. Overall good agreement between BrAC data and estimates was observed with a median relative peak error of 22% and a median relative area under the curve error of 25% on the test set. We also demonstrate that the physics-informed Viterbi algorithm eliminates non-physical artifacts in the BrAC estimates.

DNA methylation age is accelerated in alcohol dependence

Alcohol dependence (ALC) is a chronic, relapsing disorder that increases the burden of chronic disease and significantly contributes to numerous premature deaths each year. Previous research suggests that chronic, heavy alcohol consumption is associated with differential DNA methylation patterns. In addition, DNA methylation levels at certain CpG sites have been correlated with age. We used an epigenetic clock to investigate the potential role of excessive alcohol consumption in epigenetic aging. We explored this question in five independent cohorts, including DNA methylation data derived from datasets from blood (n = 129, n = 329), liver (n = 92, n = 49), and postmortem prefrontal cortex (n = 46). One blood dataset and one liver tissue dataset of individuals with ALC exhibited positive age acceleration (p < 0.0001 and p = 0.0069, respectively), whereas the other blood and liver tissue datasets both exhibited trends of positive age acceleration that were not significant (p = 0.83 and p = 0.57, respectively). Prefrontal cortex tissue exhibited a trend of negative age acceleration (p = 0.19). These results suggest that excessive alcohol consumption may be associated with epigenetic aging in a tissue-specific manner and warrants further investigation using multiple tissue samples from the same individuals.

Methylomic profiling and replication implicates deregulation of PCSK9 in alcohol use disorder

Alcohol use disorder (AUD) is a common and chronic disorder with substantial effects on personal and public health. The underlying pathophysiology is poorly understood but strong evidence suggests significant roles of both genetic and epigenetic components. Given that alcohol affects many organ systems, we performed a cross-tissue and cross-phenotypic analysis of genome-wide methylomic variation in AUD using samples from 3 discovery, 4 replication, and 2 translational cohorts. We identified a differentially methylated region in the promoter of the proprotein convertase subtilisin/kexin 9 (PCSK9) gene that was associated with disease phenotypes. Biological validation showed that PCSK9 promoter methylation is conserved across tissues and positively correlated with expression. Replication in AUD datasets confirmed PCSK9 hypomethylation and a translational mouse model of AUD showed that alcohol exposure leads to PCSK9 downregulation. PCSK9 is primarily expressed in the liver and regulates low-density lipoprotein cholesterol (LDL-C). Our finding of alcohol-induced epigenetic regulation of PCSK9 represents one of the underlying mechanisms between the well-known effects of alcohol on lipid metabolism and cardiovascular risk, with light alcohol use generally being protective while chronic heavy use has detrimental health outcomes.

Genetic Association and Expression Analyses of the Phosphatidylinositol-4-Phosphate 5-Kinase (PIP5K1C) Gene in Alcohol Use Disorder-Relevance for Pain Signaling and Alcohol Use

BACKGROUND

The gene encoding phosphatidylinositol-4-phosphate 5-kinase (PIP5K1C) has been recently implicated in pain regulation. Interestingly, a recent cross-tissue and cross-phenotypic epigenetic analysis identified the same gene in alcohol use disorder (AUD). Given the high comorbidity between AUD and chronic pain, we hypothesized that genetic variation in PIP5K1C might contribute to susceptibility to AUD.

METHODS

We conducted a case-control association study of genetic variants in PIP5K1C. Association analyses of 16 common PIP5K1C single nucleotide polymorphisms (SNPs) were conducted in cases and controls of African (427 cases and 137 controls) and European ancestry (488 cases and 324 controls) using standard methods. In addition, given the prominent role of the opioid system in pain signaling, we investigated the effects of acute alcohol exposure on PIP5K1C expression in humanized transgenic mice for the μ-opioid receptor that included the OPRM1 A118G polymorphism, a widely used mouse model to study analgesic response to opioids in pain. PIP5K1C expression was measured in the thalamus and basolateral amygdala (BLA) in mice after short-term administration (single 2 g/kg dose) of alcohol or saline using immunohistochemistry and analyzed by 2-way analysis of variance.

RESULTS

In the case-control association study using an NIAAA discovery sample, 8 SNPs in PIP5K1C were significantly associated with AUD in the African ancestry (AA) group (p < 0.05 after correction; rs4807493, rs10405681, rs2074957, rs10432303, rs8109485, rs1476592, rs10419980, and rs4432372). However, a replication analysis using an independent sample (N = 3,801) found no significant associations after correction for multiple testing. In the humanized transgenic mouse model with the OPRM1 polymorphism, PIP5K1C expression was significantly different between alcohol and saline-treated mice, regardless of genotype, in both the thalamus (p < 0.05) and BLA (p < 0.01).

CONCLUSIONS

Our discovery sample shows that genetic variants in PIP5K1C are associated with AUD in the AA group, and acute alcohol exposure leads to up-regulation of PIP5K1C, potentially explaining a mechanism underlying the increased risk for chronic pain conditions in individuals with AUD.

Genome-wide association study of treatment response to venlafaxine XR in generalized anxiety disorder

We conducted the first genome-wide association study (GWAS) in Generalized Anxiety Disorder (GAD) to identify potential predictors of venlafaxine XR treatment outcome. Ninety-eight European American patients participated in a venlafaxine XR clinical trial for GAD, with Hamilton Anxiety Scale (HAM-A) response/remission at 24 weeks as the primary outcome measure. All participants were genotyped with the Illumina PsychChip, and 266,820 common single nucleotide polymorphisms (SNPs) were analyzed. Although no SNPs reached genome-wide significance, 8 SNPs were marginally associated with treatment response/remission and HAM-A reduction at week 12 and 24 (p<0.00001). Several identified genes may indicate markers crossing neuropsychiatric diagnostic categories.

Nonlinear temperature modulation of sodium channel kinetics in GH(3) cells

The effect of temperature on sodium channel function was examined in GH(3) cells, using the whole cell patch-clamp methodology. Specific parameters examined were current-voltage relationships, activation time, and inactivation time. For the temperature range studied, 23-37 degrees C, there was no change in the current-voltage relationship. A linear response to temperature was seen in the inactivation time constant, tau(h). The activation time constant, tau(m), was clearly nonlinear, with a sharp discontinuity at 28 degrees C. This nonlinearity was especially evident at lower membrane voltages. These findings are consistent with the hypothesis that membrane structural changes, which occur during the thermotropic phase transition, are capable of influencing the function of the intramembranous portion of the channel. Caution should, therefore, be exercised in extrapolating data on channel function obtained at room temperature to physiological temperatures.

Relationship of extent of revascularization with angina at one year in the Bypass Angioplasty Revascularization Investigation (BARI)

OBJECTIVES

To determine the relative degree of revascularization obtained with bypass surgery versus angioplasty in a randomized trial of patients with multivessel disease requiring revascularization (Bypass Angioplasty Revascularization Investigation [BARI]), one-year catheterization was performed in 15% of patients.

BACKGROUND

Complete revascularization has been correlated with improved outcome after coronary artery bypass grafting (CABG) but not with percutaneous transluminal coronary angioplasty (PTCA). Relative degrees of revascularization after PTCA and surgery have not been previously compared and correlated with symptoms.

METHODS

Consecutive patients at four BARI centers consented to recatheterization one year after revascularization. Myocardial jeopardy index (MJI), the percentage of myocardium jeopardized by > or =50% stenoses, was compared and correlated with angina status.

RESULTS

Angiography was completed in 270 of 362 consecutive patients (75%) after initial CABG (n = 135) or PTCA (n = 135). Coronary artery bypass grafting patients had 3+/-0.9 distal anastomoses and PTCA patients had 2.4+/-1.1 lesions attempted at initial revascularization. At one year, 20.5% of CABG patients had > or =1 totally occluded graft and 86.9% of vein graft, and 91.6% of internal mammary artery distal anastomotic sites had <50% stenosis. One year jeopardy index in surgery patients was 14.1+/-11%, 46.6+/-20.3% improved from baseline. Initial PTCA was successful in 86.9% of lesions and repeat revascularization was performed in 48.4% of PTCA patients by one year. Myocardial jeopardy index one year after PTCA was 25.5+/-22.8%, an improvement of 33.8+/-26.1% (p<0.01 for greater improvement with CABG than PTCA). At one year, 29.6% of PTCA patients had angina versus 11.9% of surgery patients, p = 0.004. One-year myocardial jeopardy was predictive of angina (odds ratio 1.28 for the presence of angina per every 10% increment in myocardial jeopardy, p = 0.002). Randomization to PTCA rather than CABG also predicted angina (odds ratio 2.19, p = 0.03).

CONCLUSIONS

In this one-year angiographic substudy of BARI, CABG provided more complete revascularization than PTCA, and CABG likewise improved angina to a greater extent than PTCA.

Is a strategy of intended incomplete percutaneous transluminal coronary angioplasty revascularization acceptable in nondiabetic patients who are candidates for coronary artery bypass graft surgery? The Bypass Angioplasty Revascularization Investigation (BARI)

OBJECTIVES

Our objective was to determine whether a strategy of intended incomplete percutaneous transluminal coronary angioplasty revascularization (IR) compromises long-term patient outcome.

BACKGROUND

Complete angioplasty revascularization (CR) is often not planned nor attempted in patients with multivessel coronary disease, and the extent to which this influences outcome is unclear.

METHODS

Before randomization, in the Bypass Angioplasty Revascularization Investigation, all angiograms were assessed for intended CR or IR via angioplasty. Outcomes were compared among patients with IR intended if assigned to angioplasty, randomized to coronary artery bypass graft surgery (CABG) versus angioplasty; and within angioplasty patients only, among patients with IR versus CR intended.

RESULTS

At 5 years, there was a trend for higher overall (88.6% vs. 84.0%) and cardiac survival (94.5% vs. 92.1%) in CABG versus angioplasty patients with IR intended. The excess mortality in angioplasty patients occurred solely in diabetic subjects; overall and cardiac survival were similar among nondiabetic CABG and angioplasty patients. Freedom from myocardial infarction (MI) at 5 years was higher in nondiabetic CABG versus angioplasty patients (92.4% vs. 85.2%, p = 0.02), vet was similar to the rate observed (85%) in nondiabetic CABG and angioplasty patients with CR intended. Five-year rates of death, cardiac death, repeat revascularization and angina were similar in all angioplasty patients with IR versus CR intended. However, a trend for greater freedom from subsequent CABG was seen in CR patients (70.3% vs. 64.0%, p = 0.08).

CONCLUSIONS

Intended incomplete angioplasty revascularization in nondiabetic patients with multivessel disease who are candidates for both angioplasty and CABG does not compromise long-term survival; however, subsequent need for CABG may be increased with this strategy. Whether the risk of long-term MI is also increased remains uncertain.

Study of condom integrity after brief exposure to over-the-counter vaginal preparations

BACKGROUND

Latex condoms are used as contraceptives and as preventives against sexually transmitted diseases. Latex rapidly and significantly deteriorates when exposed to pure mineral oil and vegetable oil. We wanted to determine if short exposures to readily available over-the-counter (OTC) intravaginal preparations could affect latex condom integrity.

METHODS

We compared the mean burst time of test latex condoms, which had 5-minute exposure to various OTC vaginal products, with the mean burst time of control (unexposed) condoms during pressurized air inflation.

RESULTS

Baby oil reduced the mean burst time from nearly a minute to just over 11 seconds. One intravaginal moisturizer and two intravaginal antifungal preparations also adversely affected latex condom integrity. Products that weakened latex condoms contained either mineral oil or vegetable oil.

CONCLUSIONS

Women who rely on latex condoms should exercise caution if using OTC vaginal products containing either mineral oil or vegetable oil. Such products apparently can decrease condom strength and potentially jeopardize efficacy.

Coronary revascularization in diabetic patients: a comparison of the randomized and observational components of the Aypass Angioplasty Revascularization Investigation (BARI)

BACKGROUND

Patients with treated diabetes in the randomized-trial segment of the Bypass Angioplasty Revascularization Investigation (BARI) who were randomized to initial revascularization with PTCA had significantly worse 5-year survival than patients assigned to CABG. This treatment difference was not seen among diabetic patients eligible for BARI who opted to select their mode of revascularization. We hypothesized that differences in patient characteristics, assessed and unmeasured, together with the treatment selection in the registry, at least partially account for this discrepancy.

METHODS AND RESULTS

Among diabetics taking insulin or oral hypoglycemic drugs at entry, angiographic and clinical presentations were comparable between randomized and registry patients. However, more registry patients were white, and registry diabetics tended to be more educated and more physically active and to report better quality of life. Procedural characteristics and in-hospital complications were comparable. The 5-year all-cause mortality rate was 34.5% in randomized diabetic patients assigned to PTCA versus 19.4% in CABG patients (P=0.0024; relative risk [RR]=1.87); corresponding cardiac mortality rates were 23.4% and 8.2%, respectively (P=0.0002; RR=3.10). The CABG benefit was more apparent among patients requiring insulin. In the registry, all-cause mortality was 14.4% for PTCA versus 14.9% for CABG (P=0.86, RR=1.10), with corresponding cardiac mortality rates of 7.5% and 6. 0%, respectively (P=0.73; RR=1.07). These RRs in the registry increased to 1.29 and 1.41, respectively, after adjustment for all known differences between treatment groups.

CONCLUSIONS

BARI registry results are not inconsistent with the finding in the randomized trial that initial CABG is associated with better long-term survival than PTCA in treated diabetic patients with multivessel coronary disease suitable for either surgical or catheter-based revascularization.

Cognitive function 5 years after randomization to coronary angioplasty or coronary artery bypass graft surgery

BACKGROUND

Coronary bypass surgery often leads to short-term cognitive dysfunction, whereas coronary angioplasty does not. Perioperative cognitive dysfunction usually resolves, although a subgroup of surgical patients may continue to exhibit long-term cognitive dysfunction. The purpose of this study was to compare cognitive function 5 years after randomization to a strategy of either initial coronary surgery or initial angioplasty.

METHODS AND RESULTS

Five centers in the Bypass Angioplasty Revascularization Investigation participated in this ancillary study. Patients with multivessel coronary disease randomized to angioplasty or surgery were eligible at the time of their 5-year clinic visit. A battery of five measures previously shown to be sensitive to perioperative changes in cognitive function was administered, including the Logical and Figural Memory Scales from the Wechsler Memory Scale, the Digit Symbol and Digit Span subtests from the Wechsler Adult Intelligence Scale, and Part B of the Reitan Trail Making Test. The 125 study patients were generally similar to the 133 patients who were eligible but did not participate, although study participants were significantly younger (P=.003). The 64 patients randomly assigned to angioplasty had baseline characteristics similar to those of 61 patients randomly assigned to surgery. Cognitive function scores were not significantly different between angioplasty or surgery patients in an intention-to-treat analysis (P=.57). There also was no difference in cognitive function scores when the data were analyzed according to whether the patient had ever undergone bypass surgery (P=.59).

CONCLUSIONS

Long-term cognitive function is similar after coronary bypass surgery and coronary angioplasty in the majority of patients.

Myocardial infarction and cardiac mortality in the Bypass Angioplasty Revascularization Investigation (BARI) randomized trial

BACKGROUND

Cardiac mortality and myocardial infarction (MI) rates are used to evaluate the efficacy of coronary artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA). We compared 5-year cardiac mortality and MI rates in 1829 patients with multivessel disease randomized to CABG or PTCA.

METHODS AND RESULTS

The 5-year cardiac mortality rate was 8.0% in patients assigned to PTCA compared with 4.9% in those assigned to CABG (relative risk [RR] of 1.55 with a 95% confidence interval [CI] of 1.07 to 2.23; P=.022). In a subgroup of 1476 nondiabetic patients, there were no significant differences between treatment groups in cardiac mortality either overall (4.6% versus 4.2%; RR= 1.04, 95% CI, 0.65 to 1.66; P=.908) or in subgroups based on symptoms, left ventricular function, number of diseased vessels, or stenotic proximal left anterior descending artery. The two treatment groups had similar event rates for the combined end point of cardiac death or MI. The RR for cardiac mortality in 264 patients who sustained an MI compared with those who did not was 5.9 (P<.001). MIs were more common after CABG during index hospitalization (P=.004), but in the PTCA group, they were more common after discharge (P<.001).

CONCLUSIONS

The Bypass Angioplasty Revascularization Investigation (BARI) trial indicates 5-year cardiac mortality in patients with multivessel disease was significantly greater after initial treatment with PTCA than with CABG. The difference was manifest in diabetic patients on drug therapy. There were no significant differences overall for the composite end point of cardiac mortality or MI between treatment groups or for cardiac mortality in nondiabetic patients regardless of symptoms, left ventricular function, number of diseased vessels, or stenotic proximal left anterior descending artery.

Cause of death analysis in the NHLBI PTCA Registry: results and considerations for evaluating long-term survival after coronary interventions

OBJECTIVES

We examined cause of death in relation to age, length of follow-up and other baseline characteristics in patients in the 1985-1986 National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty (NHLBI PTCA) Registry.

BACKGROUND

The manner in which cardiac versus noncardiac mortality of patients with coronary revascularization varies in relation to patient and study characteristics has not been well documented.

METHODS

Cause of death determined from a review of 5 years of annual follow-up forms and death certificates was analyzed in 2,127 patients who had coronary angioplasty (mean age 57.6 years) without acute myocardial infarction.

RESULTS

Within 5 years of the initial procedure, there were 205 deaths (9.6%), with 52.7% attributed to cardiac causes. Patients with a low baseline ejection fraction, history of hypertension, previous bypass surgery, previous myocardial infarction, inoperable or high surgical risk or multivessel disease had significantly higher 5-year cardiac mortality. Patients with a history of diabetes, congestive heart failure or severe concomitant noncardiac disease had higher rates of both cardiac and noncardiac mortality. As length of follow-up increased, older patients died of noncardiac causes more often than cardiac causes. Age > or = 65 years was a strong independent predictor of 5-year noncardiac mortality (p < 0.001), but not cardiac mortality (p = 0.08).

CONCLUSIONS

All-cause mortality rates may be high in elderly revascularized patients, yet cardiac mortality may be less than that expected because of a high risk of noncardiac death. Although all-cause mortality is a more reliable end point than cause-specific mortality, both cardiac and all-cause mortality should be considered in coronary intervention studies involving older patients and long-term follow-up.

Contemporary practice of coronary revascularization in U.S. hospitals and hospitals participating in the bypass angioplasty revascularization investigation (BARI)

OBJECTIVES

To assess generalizability of the Bypass Angioplasty Revascularization Investigation (BARI), we conducted a separate study comparing revascularization in U.S. and BARI hospitals.

BACKGROUND

The BARI trial is a multicenter investigation comparing initial revascularization with percutaneous transluminal coronary angioplasty and coronary bypass graft surgery in patients with symptomatic multivessel coronary disease.

METHODS

All revascularization procedures during 5 consecutive workdays were surveyed at 75 U.S. hospitals offering coronary angioplasty and bypass surgery and at all BARI hospitals. Data collected were demographics, extent of disease and type of current and previous revascularization.

RESULTS

At both U.S. and BARI hospitals, 57% of all revascularization procedures were coronary angioplasty and 43% were bypass surgery. The U.S. hospitals had more patients with single-vessel disease, acute myocardial infarction and primary procedures. Other characteristics were similar. The majority of revascularization procedures were angioplasty for single-vessel disease (U.S. 32% vs. BARI 25%) and bypass surgery for triple-vessel disease (U.S. 31% vs. BARI 31%). Overall, the choice between bypass surgery and angioplasty was similar in BARI and U.S. hospitals (adjusted odds ratio [OR] 1.0, p = 0.914). However, older patients were more likely and younger patients less likely to undergo bypass surgery in BARI versus U.S. hospitals (older patients: adjusted OR 1.6, p = 0.031; younger patients: adjusted OR 0.6, p = 0.028). The BARI protocol would have excluded 65% of all candidates for revascularization, for whom indications already exist for angioplasty or bypass surgery, and another 23%, for whom angioplasty would be contraindicated for individual lesions.

CONCLUSIONS

Patients undergoing coronary revascularization in BARI and U.S. hospitals were generally similar, as was the choice between types of revascularization. Results from the BARI trial apply to approximately 300 (12%) candidates for coronary revascularization/workday.

Temperature modulation of calcium channel function in GH3 cells

The effect of temperature on calcium channel function was studied in GH3 cells, using the whole cell patch-clamp methodology. Specific parameters examined were peak current amplitude, activation time, and inactivation time. Over the temperature range studied (22-37 degree C), the peak current amplitude was found to be a non-linear function of temperature, with low-threshold currents more temperature dependent than high-threshold currents. Both activation time and inactivation time were faster at higher temperatures, but, whereas inactivation was a continuous function of temperature, activation was not, with a distinct discontinuity between 27 and 32 degrees C. These findings suggest that caution must be exercised in extrapolating data on channel function obtained at room temperature to physiological temperatures.

Inhibition of calcium channel activation in GH3 cells by static magnetic fields

Voltage-activated calcium channel function was examined in cultured GH3 cells using the whole-cell patch clamp technique. Exposure to a 120 mT static magnetic field resulted in a slight reduction in the peak calcium current amplitude and shift in the current-voltage relationship. The most significant change was a slowing of the channel activation rate without any change in the inactivation rate. All changes in channel function were reversible, with return to pre-exposure values within 3 min after the field was turned off. These alterations in channel function were temperature-dependent. The present findings are consistent with a functional disruption of the intramembranous portion of the calcium channel by a magnetically induced membrane deformation.

Angiographic correlates of lesion relevance and suitability for percutaneous transluminal coronary angioplasty and coronary artery bypass grafting in the Bypass Angioplasty Revascularization Investigation study (BARI)

The Bypass Angioplasty Revascularization Investigation (BARI) randomized 1,829 patients to percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG). Clinical site angiographers categorized lesions of > or = 50% diameter stenosis (n = 4,977) as clinically significant (86.4%) or nonsignificant (13.6%), and as favorable or nonfavorable for PTCA or CABG. More lesions were considered favorable for revascularization by CABG than by PTCA (91.5% vs 78.4%; p <0.001), particularly in the subgroup of 99% to 100% lesions (77.6% for CABG vs 21.9% for PTCA, p <0.001). Lesion features, characterized by the BARI core laboratory, were correlated with clinical site angiographers' assessment of clinical importance and suitability for PTCA or CABG. By multivariate analysis, positive predictors of clinical importance for 50% to 95% stenoses were greater stenosis severity, more jeopardized myocardium, larger reference diameter, and proximal vessel location. For 99% to 100% occlusions, predictors were shorter duration of occlusion and more jeopardized myocardium. PTCA suitability for 50% to 95% stenoses was inversely related to lesion length, ostial location, location on a bend, difficult access, and age, and was directly associated with greater Thrombolysis in Myocardial Infarction (TIMI) trial flow rate and more jeopardized myocardium. Predictors of PTCA suitability for 99% to 100% lesions were a lower American College of Cardiology/American Heart Association class and higher TIMI grade. Predictors for 50% to 95% stenoses were more jeopardized myocardium, larger reference diameter, and more proximal vessel location, and for 99% to 100% occlusions, more jeopardized myocardium and shorter duration of occlusion. Suitability for PTCA depended on lesion potency (<99%) and multiple morphologic characteristics that contrasted with the few angiographic features that adversely affect CABG suitability.

Clinical and operative characteristics of patients randomized to coronary artery bypass surgery in the Bypass Angioplasty Revascularization Investigation (BARI)

The surgical cohort of the Bypass Angioplasty Revascularization Investigation (BARI) is the largest group of patients with multivessel coronary artery disease randomly assigned to surgical treatment. This report presents baseline and operative characteristics of the cohort and describes some aspects of the variability in surgical practice among the 14 primary clinical centers and 4 co-investigational sites participating in BARI. Preoperative clinical and angiographic data and intraoperative variables were reviewed in 892 patients who were randomly assigned to coronary artery bypass grafting (CABG) and underwent operation. Associations between patient/lesion variables and operative characteristics are described. Of patients assigned to CABG, 87% underwent an operation within 2 weeks of randomization, as recommended in the protocol. Mean age of the 892 patients was 61 years, and mean age of the 235 women was greater than that of men (64 years vs 60 years); 64% of the surgical patients were classified as having unstable angina during the 6 weeks prior to randomization. Coronary angiography demonstrated 3-vessel disease (50% diameter narrowing by caliper measurement) in 41% of patients, and disease of the left anterior descending coronary artery was present in 87% of patients. A mean of 3.1 coronary arteries per patient were bypassed, and 82% of patients received 1 (70%) or 2 (12%) internal thoracic artery grafts. Prevalence of internal thoracic grafts was lower in elderly patients (74% of patients > or = 70 years), in women (72% vs 85% in men; p < 0.01), and in black participants (65%).(ABSTRACT TRUNCATED AT 250 WORDS)

Bypass Angioplasty Revascularization Investigation (BARI): baseline clinical and angiographic data

This report presents baseline clinical and angiographic data from the Bypass Angioplasty Revascularization Investigation (BARI), a multicenter international trial assessing the relative efficacy of percutaneous transluminal coronary angioplasty (PTCA) versus coronary artery bypass graft surgery (CABG) in selected patients with multivessel coronary artery disease. PTCA is commonly performed in patients with multivessel coronary artery disease, yet its long-term efficacy in comparison to CABG is unknown. From August 1988 through August 1991, 1,829 qualifying patients with multivessel disease suitable for either procedure were randomized to PTCA or CABG; sample size estimates were based on anticipated 5-year mortality. Two registry populations were also defined for follow-up: (1) 2,013 patients eligible for randomization but not randomized; and (2) 422 patients considered by angiography as unsuitable for randomization. Patients randomized in BARI were at relatively high risk for subsequent cardiac events: 39% were > or = 65 years old, 55% had prior myocardial infarction, 69% presented with unstable angina or non-Q wave myocardial infarction, and 43% had 3-vessel coronary artery disease. Patients randomized to PTCA and CABG were equally matched in all the important baseline variables. The randomized and the eligible but not randomized groups were similar in most respects. However, the nonrandomized group had a higher proportion with college education; fewer with a history of myocardial infarction, heart failure, diabetes, and smoking; and a somewhat better average ejection fraction. At the 3-month follow-up, PTCA had been performed more commonly in the nonrandomized eligible patients, especially those with 2-vessel disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Threshold and limits of magnetic field action at the presynaptic membrane

The relationship of field intensity and exposure duration to the inhibitory effect of static magnetic fields on presynaptic membrane function was examined in order to further define the mechanism of action of these fields. Miniature endplate potentials (MEPPs) were recorded from the isolated murine neuromuscular junction, maintained at a temperature of 35.5 degrees C, during exposure to static magnetic fields of varying duration and intensity. Inhibition of MEPP generation correlated well with the product of the square of the flux density and exposure time. At lower product values the relationship was linear with an absolute flux density threshold of 37.9 mT. Higher product values were associated with deviation from linearity indicative of a limit on the extent of inhibition. These findings are consistent with the hypothesis that static magnetic fields induce a reorientation of diamagnetic molecular domains within the membrane but with a restriction on the degree of reorientation imposed by the membrane's cytoskeleton.

A proposed mechanism for the action of strong static magnetic fields on biomembranes

Experimental studies have demonstrated a temperature dependent effect by strong static magnetic fields on synaptic function. It is proposed that these findings may be explained by the diamagnetic properties of membrane phospholipids. The change in diamagnetic anisotropy coincidental with membrane thermotropic phase transition is responsible for the temperature dependence of this phenomenon and provides insight into the mechanism of action of these fields. At the prephase transition temperature highly diamagnetic anisotropic gel phase domains exist within a more fluid liquid-crystal phase. The partial magnetic reorientation of these domains results in membrane distortion and, thereby, functional impairment of contiguous ion specific channels. This mechanism adequately explains observations of the effects of static magnetic fields both on the central nervous system and at the neuromuscular junction. It is suggested that the same mechanism may be operative in other biosystems.

Membrane response to static magnetic fields: effect of exposure duration

The time-course for the reversible alteration in presynaptic membrane function associated with exposure to a 123 mT static magnetic field was examined in an attempt to help define the mechanism whereby these fields influence biomembranes. Miniature endplate potentials (MEPPs) were recorded in the isolated murine neuromuscular junction preparation, maintained at a temperature of 35.5 degrees C. A minimum field duration of 50 s was found to be necessary for MEPP inhibition, with the efficacy of the field in inducing further inhibition being a function of its duration, but only for periods up to 150 s. Longer durations were not associated with additional inhibition. The time required for MEPP frequency to return to baseline, following deactivation of the field, was found to be linear for field durations up to 150 s. At and above this limit, recovery time remained constant at 135 s. These findings are consistent with the slow reorientation of diamagnetic molecular domains within the membrane and suggest tight coupling to the mechanism responsible for neurotransmitter release. The limits on this effect are compatible with the mechanical constraints imposed by the membrane's cytoskeleton.

Magnetic field influence on acetylcholine release at the neuromuscular junction

The effects of a static magnetic field on the frequency of miniature end-plate potentials (MEPPs), recorded from the murine phrenic nerve-diaphragm preparation, were studied. In the presence of a 1,200-G field, statistically significant changes in MEPP frequency were observed. There was a modest increase in frequency at temperatures at and below 34 degrees C and a prominent decrease in frequency at temperatures above 35 degrees C. This temperature-dependent phenomenon was not seen in the absence of calcium in the perfusate. These results suggest that, at its phase transition temperature, the diamagnetic anisotropy of the presynaptic membrane is sufficient to influence neurotransmitter release by altering the function of the transmembrane calcium transfer mechanism.

Modification of spontaneous unit discharge in the lateral geniculate body by a magnetic field

The effects of a 1230-G static magnetic field on spontaneous discharge frequency and discharge pattern of principle cells in the cat's lateral geniculate body (LGB) were examined. In 45% of cells studied, a decrease in frequency was seen after the field was turned on. This progressed, even after the field was turned off, with return to baseline after an average duration of 250 s. Onset typically was 75 s after the field was activated, with maximum effect occurring 135 sec thereafter. In 67% of those cells which exhibited a decrease in frequency and in 50% of those which did not, a change in discharge pattern, as reflected by the interspike interval histogram, was seen. When present, this was manifested as a decrease in short interspike intervals. The change in the interspike interval histogram usually persisted longer than the change in frequency. The gradual onset and prolonged time course of changes in LGB cell activity suggest either an alteration in the synaptic ionic environment or in neurotransmitter availability. It is hypothesized that strong magnetic fields produce a partial realignment of diamagnetically anisotropic molecules within the cell membrane, thereby distorting ion-specific channels sufficiently to alter their function.

Magnetic field influence on paramecium motility

The influence of a moderately intense static magnetic field on movement patterns of free swimming Paramecium was studied. When exposed to fields of 0.126 T, these ciliated protozoa exhibited significant reduction in velocity as well as a disorganization of movement pattern. It is suggested that these findings may be explained on the basis of alteration in function of ion specific channels within the cell membrane.

Magnetic field influence on central nervous system function

The effects of strong static magnetic fields on the excitability of striate cortex in adult cats was studied. The visual evoked response was used as a measure of cortical excitability. In all animals a 1200-G field was associated with a significant decrease in both amplitude and variability of the evoked response. This effect began more than 50 s after the field was turned on and persisted, even after the field was turned off, for several minutes. This phenomenon appears to be due to action of the magnetic field at the synapse rather than on axonal conduction.

Regional variations in cortical cholinergic innervation: chemoarchitectonics of acetylcholinesterase-containing fibers in the macaque brain

There are marked regional variations in the laminar distribution and intensity of acetylcholinesterase containing fibers in cortex. These fibers were particularly prominent in the 5 major paralimbic (mesocortical) regions of the brain: the insula, the caudal orbito-frontal cortex, the temporal pole, the cingulate gyrus and the parahippocampal region. Within these 5 areas, the part of cortex which is adjacent to allocortex has the most acetylcholinesterase and there is a gradual decline towards granular isocortex. The primary sensory-motor areas have distinctive laminar patterns of enzyme distribution. For example, primary visual, auditory and somesthetic konio-cortices are characterized by a salient band in layer IV. On the other hand, motor and premotor areas are characterized by a concentration of radially arranged fibers within the deeper layers of cortex. High order sensory association areas throughout the cortical mantle consistently contain the least amount of acetylcholinesterase-positive fibers. It is conceivable that these patterns reflect regional variations in the distribution of cortical cholinergic innervation. The cortical topography of cholinergic markers may be relevant to the biological organization of mood and memory and also to the pathophysiology of Alzheimer's disease and of partial epilepsy.

Visual evoked potentials altered by serum IgG of patients with multiple sclerosis

Immunoglobulin G, isolated from serum of patients with multiple sclerosis was repeatedly injected into guinea pigs and serial visual evoked potentials were recorded. Latency changes indicated a reversible delay in conduction velocity in the central visual pathways. This finding suggests that some component of immunoglobulin plays a role in the pathogenesis of multiple sclerosis.

A cognitive-motor network demonstrated by positron emission tomography

The rate of local cerebral glucose metabolism was measured in subjects receiving a verbal (n = 4) and a spatial (n = 4) task. The verbal task produced greater metabolism in Wernicke's area relative to the right hemispheric homotopic region, whereas the spatial task produced greater metabolic activity in the right hemispheric homotopic region. Broca's area and its right hemisphere counterpart showed symmetrical activity during the verbal task, but there was a significant asymmetry to the right during the spatial task. Lateralized task effects were also obtained in the frontal eye fields, supporting a hypothesized neural network linking cognitive activity with motor orientation.

Positron emission tomography in two cases of childhood epileptic encephalopathy (Lennox-Gastaut syndrome)

Two patients with childhood epileptic encephalopathy were studied by positron emission tomography before and after corpus callosotomy. Preoperatively, both patients showed in the temporal lobe unilateral hypometabolism that is characteristic of interictal epileptic foci. Postoperatively, the first patient had no seizures by the time of scanning, and his temporal lobe metabolism was bilaterally symmetric. Seizure control in the second patient did not improve by the time of scanning, and unilateral temporal hypometabolism persisted. This finding suggests a temporal lobe focus in two patients with Lennox-Gastaut syndrome.

Sex and handedness differences in cerebral blood flow during rest and cognitive activity

Cognitive activity resulted in increased flow of blood to the cerebral hemispheres. The increase was greater to the left hemisphere for a verbal task and greater to the right hemisphere for a spatial task. The direction and degree of hemispheric flow asymmetry were influenced by sex and handedness, females having a higher rate of blood flow per unit weight of brain, and females and left-handers having a greater percentage of fast-clearing tissue, presumably gray matter.

Antidromic influence on lateral geniculate excitability

Eighty-four percent of principal cells in the dorsal nucleus of the lateral geniculate body exhibited a transient depression of spontaneous activity following optic tract stimulation. Antidromic corticofugal activity, generated by the evoked cortical field potential, was seen in 21% of the cells studied. In those cells, depression of spontaneous activity lasted an average of 20 msec longer than in those cells where no antidromic activity was present. Longer duration post-stimulus depression of spontaneous activity was often followed by a period of rebound excitation. These findings support the hypothesis that antidromic activity, generated during the evoked response in striate cortex, has a significant influence on excitability pattern of principal cells in the dorsal nucleus of the lateral geniculate body.

Cortical modification of an epileptogenic focus

The influence of cerebral cortex on penicillin-induced spikes in striate cortex was studied with the technique of hypothermic block. Direct cooling of the involved or contralateral striate cortex markedly reduced seizure activity. Significant reduction in seizure activity was also seen with cooling of ipsilateral and contralateral visual association cortex. None of the other cortical areas tested had a reproducible effect on the frequency of seizures. These findings are discussed in term of local and remote factors influencing the epileptogenic focus.

Pre- and postsynaptic effects of pancuronium at the neuromuscular junction of the mouse

The dose-effectiveness of pancuronium as it relates to membrane potentials, action potentials, electrical membrane constants, miniature endplate potentials, endplate potentials, and quantal release was studied in murine phrenic nerve-diaphragm preparations in vitro. Emphasis was placed on comparison of presynaptic with postsynaptic effects of pancuronium under similar experimental conditions. At low concentrations of pancuronium (5 X 10(-8) g/ml or less), no presynaptic effect was found. At high concentration (5 X 10(-7) g/ml), pancuronium depressed quantal release to 26 per cent of control in cut-fiber preparations and 40 per cent of control in high-magnesium preparations. Postsynaptic effects as measured by the amplitude of miniature endplate potentials and relative depolarization induced by 20 microns carbachol, revealed depression to 16 and 22 per cent of control, respectively, at a pancuronium concentration of 5 X 10(-7) g/ml. Pancuronium had no effect on directly elicited action potentials and electrical membrane constants. The authors conclude that presynaptic as well as postsynaptic effects of pancuronium in paralytic doses are essential in contributing to the total efficacy of neuromuscular depression.

Amyotrophic lateral sclerosis. Clinical features and prognosis

The clinical diagnosis of amyotrophic lateral sclerosis was identified in 668 patients who were followed up for periods up to three years. This disease was found to be more common in women than previously believed. The five-year survival for all patients was found to be 39.4%, but younger patients had a substantially better prognosis than those in whom the disease was diagnosed when over the age of 50 years. When the mode of onset was considered, the spinal form was associated with a threefold better five-year survival than the bulbar form.

Antidromic activity in visual radiation during evoked cortical responses

1. Antidromic stimulation of the visual radiation of cats has been used to investigate the possibility that some of the activity in principal geniculate cells following an optic tract stimulus is antidromic. Single spikes were selected from two classes of poststimulus activity to condition the antidromic test spike--the undoubted orthodromic postsynaptic spike and the later spikes, occurring up to 100 ms after the optic tract stimulus. 2. In 15 of 39 cells the minimum antidromic activation times and the minimum spike-spike intervals were found to be shorter and latencies for antidromic stimulation were longer when the conditioning spikes belonged the class of late poststimulus activity. The differences are in accord with the assumption that some of the conditioning spikes were antidromic. 3. Test spikes were frequently found to have long and variable latency when the conditioning spike occurred more than 45 ms after the optic tract stimulus. Possible reasons are briefly discussed. 4. It is suggested that antidromic activity may occur in conditions of the cortex that are more physiological than those associated with a penicillin-induced seizure focus. Some possible mechanisms and functional significance are briefly discussed.

Influence of association cortex on penicillin discharges in the primary visual cortex

The influence of visual association cortex on the pattern of neuronal activity in the lateral geniculate body, during penicillin-induced discharges in visula cortex, was studied. In a majority of those geniculate cells which exhibited a pre-penicillin discharge increment in activity, that increment was abolished or significantly reduced during focal hypothermia of the visual association cortex. The frequency of penicillin discharges in visual cortex was, in most cases, reduced during cooling of association cortex. These findings are briefly discussed in terms of corticothalamic interactions.