Effect of reduced dose schedules and intramuscular injection of anthrax vaccine adsorbed on immunological response and safety profile: a randomized trial

OBJECTIVE

We evaluated an alternative administration route, reduced schedule priming series, and increased intervals between booster doses for anthrax vaccine adsorbed (AVA). AVA's originally licensed schedule was 6 subcutaneous (SQ) priming injections administered at months (m) 0, 0.5, 1, 6, 12 and 18 with annual boosters; a simpler schedule is desired.

METHODS

Through a multicenter randomized, double blind, non-inferiority Phase IV human clinical trial, the originally licensed schedule was compared to four alternative and two placebo schedules. 8-SQ group participants received 6 SQ injections with m30 and m42 "annual" boosters; participants in the 8-IM group received intramuscular (IM) injections according to the same schedule. Reduced schedule groups (7-IM, 5-IM, 4-IM) received IM injections at m0, m1, m6; at least one of the m0.5, m12, m18, m30 vaccine doses were replaced with saline. All reduced schedule groups received a m42 booster. Post-injection blood draws were taken two to four weeks following injection. Non-inferiority of the alternative schedules was compared to the 8-SQ group at m2, m7, and m43. Reactogenicity outcomes were proportions of injection site and systemic adverse events (AEs).

RESULTS

The 8-IM group's m2 response was non-inferior to the 8-SQ group for the three primary endpoints of anti-protective antigen IgG geometric mean concentration (GMC), geometric mean titer, and proportion of responders with a 4-fold rise in titer. At m7 anti-PA IgG GMCs for the three reduced dosage groups were non-inferior to the 8-SQ group GMCs. At m43, 8-IM, 5-IM, and 4-IM group GMCs were superior to the 8-SQ group. Solicited injection site AEs occurred at lower proportions in the IM group compared to SQ. Route of administration did not influence the occurrence of systemic AEs. A 3 dose IM priming schedule with doses administered at m0, m1, and m6 elicited long term immunological responses and robust immunological memory that was efficiently stimulated by a single booster vaccination at 42 months.

CONCLUSIONS

A priming series of 3 intramuscular doses administered at m0, m1, and m6 with a triennial booster was non-inferior to more complex schedules for achieving antibody response.

Safety and comparative immunogenicity of an HIV-1 DNA vaccine in combination with plasmid interleukin 12 and impact of intramuscular electroporation for delivery

BACKGROUND

DNA vaccines have been very poorly immunogenic in humans but have been an effective priming modality in prime-boost regimens. Methods to increase the immunogenicity of DNA vaccines are needed.

METHODS

HIV Vaccine Trials Network (HVTN) studies 070 and 080 were multicenter, randomized, clinical trials. The human immunodeficiency virus type 1 (HIV-1) PENNVAX®-B DNA vaccine (PV) is a mixture of 3 expression plasmids encoding HIV-1 Clade B Env, Gag, and Pol. The interleukin 12 (IL-12) DNA plasmid expresses human IL-12 proteins p35 and p40. Study subjects were healthy HIV-1-uninfected adults 18-50 years old. Four intramuscular vaccinations were given in HVTN 070, and 3 intramuscular vaccinations were followed by electroporation in HVTN 080. Cellular immune responses were measured by intracellular cytokine staining after stimulation with HIV-1 peptide pools.

RESULTS

Vaccination was safe and well tolerated. Administration of PV plus IL-12 with electroporation had a significant dose-sparing effect and provided immunogenicity superior to that observed in the trial without electroporation, despite fewer vaccinations. A total of 71.4% of individuals vaccinated with PV plus IL-12 plasmid with electroporation developed either a CD4(+) or CD8(+) T-cell response after the second vaccination, and 88.9% developed a CD4(+) or CD8(+) T-cell response after the third vaccination.

CONCLUSIONS

Use of electroporation after PV administration provided superior immunogenicity than delivery without electroporation. This study illustrates the power of combined DNA approaches to generate impressive immune responses in humans.

Health-related quality of life in the CDC Anthrax Vaccine Adsorbed Human Clinical Trial

BACKGROUND

After the Department of Defense implemented a mandatory anthrax vaccination program in 1998 concerns were raised about potential long-term safety effects of the current anthrax vaccine. The CDC multicenter, randomized, double-blind, placebo-controlled Anthrax Vaccine Adsorbed (AVA) Human Clinical Trial to evaluate route change and dose reduction collected data on participants' quality of life. Our objective is to assess the association between receipt of AVA and changes in health-related quality of life, as measured by the SF-36 health survey (Medical Outcomes Trust, Boston, MA), over 42 months after vaccination.

METHODS

1562 trial participants completed SF-36v2 health surveys at 0, 12, 18, 30 and 42 months. Physical and mental summary scores were obtained from the survey results. We used Generalized Estimating Equations (GEE) analyses to assess the association between physical and mental score difference from baseline and seven study groups receiving either AVA at each dose, saline placebo at each dose, or a reduced AVA schedule substituting saline placebo for some doses.

RESULTS

Overall, mean physical and mental scores tended to decrease after baseline. However, we found no evidence that the score difference from baseline changed significantly differently between the seven study groups.

CONCLUSIONS

These results do not favor an association between receipt of AVA and an altered health-related quality of life over a 42-month period.

A genome-wide association study of host genetic determinants of the antibody response to Anthrax Vaccine Adsorbed

Several lines of evidence have supported a host genetic contribution to vaccine response, but genome-wide assessments for specific determinants have been sparse. Here we describe a genome-wide association study (GWAS) of protective antigen-specific antibody (AbPA) responses among 726 European-Americans who received Anthrax Vaccine Adsorbed (AVA) as part of a clinical trial. After quality control, 736,996 SNPs were tested for association with the AbPA response to 3 or 4 AVA vaccinations given over a 6-month period. No SNP achieved the threshold of genome-wide significance (p=5 × 10(-8)), but suggestive associations (p<1 × 10(-5)) were observed for SNPs in or near the class II region of the major histocompatibility complex (MHC), in the promoter region of SPSB1, and adjacent to MEX3C. Multivariable regression modeling suggested that much of the association signal within the MHC corresponded to previously identified HLA DR-DQ haplotypes involving component HLA-DRB1 alleles of *15:01, *01:01, or *01:02. We estimated the proportion of additive genetic variance explained by common SNP variation for the AbPA response after the 6 month vaccination. This analysis indicated a significant, albeit imprecisely estimated, contribution of variation tagged by common polymorphisms (p=0.032). Future studies will be required to replicate these findings in European Americans and to further elucidate the host genetic factors underlying variable immune response to AVA.

The role of HLA-DR-DQ haplotypes in variable antibody responses to anthrax vaccine adsorbed

Host genetic variation, particularly within the human leukocyte antigen (HLA) loci, reportedly mediates heterogeneity in immune response to certain vaccines; however, no large study of genetic determinants of anthrax vaccine response has been described. We searched for associations between the immunoglobulin G antibody to protective antigen (AbPA) response to Anthrax Vaccine Adsorbed (AVA) in humans, and polymorphisms at HLA class I (HLA-A, -B, and -C) and class II (HLA-DRB1, -DQA1, -DQB1, -DPB1) loci. The study included 794 European-Americans and 200 African-Americans participating in a 43-month, double-blind and placebo-controlled clinical trial of AVA (clinicaltrials.gov identifier NCT00119067). Among European-Americans, genes from tightly linked HLA-DRB1, -DQA1, -DQB1 haplotypes displayed significant overall associations with longitudinal variation in AbPA levels at 4, 8, 26 and 30 weeks from baseline in response to vaccination with three or four doses of AVA (global P=6.53 × 10(-4)). In particular, carriage of the DRB1-DQA1-DQB1 haplotypes (*)1501-(*)0102-(*)0602 (P=1.17 × 10(-5)), (*)0101-(*)0101-(*)0501 (P=0.009) and (*)0102-(*)0101-(*)0501 (P=0.006) was associated with significantly lower AbPA levels. In carriers of two copies of these haplotypes, lower AbPA levels persisted following subsequent vaccinations. No significant associations were observed amongst African-Americans or for any HLA class I allele/haplotype. Further studies will be required to replicate these findings and to explore the role of host genetic variation outside of the HLA region.

Safety and immunogenicity of a CTL multiepitope peptide vaccine for HIV with or without GM-CSF in a phase I trial

There is an urgent need for a vaccine capable of preventing HIV infection or the development of HIV-related disease. A number of approaches designed to stimulate HIV-specific CD8+ cytotoxic T cell responses together with helper responses are presently under evaluation. In this phase 1, multi-center, placebo-controlled trial, we tested the ability of a novel multiepitope peptide vaccine to elicit HIV-specific immunity. To enhance the immunogenicity of the peptide vaccine, half of the vaccine recipients received recombinant granulocyte-macrophage colony stimulating factor (GM-CSF) protein as a coadjuvant. The vaccine was safe; tolerability was moderate, with a number of adverse events related to local injection site reactogenicity. Anti-GM-CSF antibody responses developed in the majority of GM-CSF recipients but were not associated with adverse hematologic events. The vaccine was only minimally immunogenic. Six of 80 volunteers who received vaccine developed HIV-specific responses as measured by interferon-gamma ELISPOT assay, and measurable responses were transient. This study failed to demonstrate that GM-CSF can substantially improve the overall weak immunogenicity of a multiepitope peptide-based HIV vaccine.

Effects of a reduced dose schedule and intramuscular administration of anthrax vaccine adsorbed on immunogenicity and safety at 7 months: a randomized trial

CONTEXT

In 1999, the US Congress directed the Centers for Disease Control and Prevention to conduct a pivotal safety and efficacy study of anthrax vaccine adsorbed (AVA).

OBJECTIVE

To determine the effects on serological responses and injection site adverse events (AEs) resulting from changing the route of administration of AVA from subcutaneous (s.q.) to intramuscular (i.m.) and omitting the week 2 dose from the licensed schedule.

DESIGN, SETTING, AND PARTICIPANTS

Assessment of the first 1005 enrollees in a multisite, randomized, double-blind, noninferiority, phase 4 human clinical trial (ongoing from May 2002).

INTERVENTION

Healthy adults received AVA by the s.q. (reference group) or i.m. route at 0, 2, and 4 weeks and 6 months (4-SQ or 4-IM; n = 165-170 per group) or at a reduced 3-dose schedule (3-IM; n = 501). A control group (n = 169) received saline injections at the same time intervals.

MAIN OUTCOME MEASURES

Noninferiority at week 8 and month 7 of anti-protective antigen IgG geometric mean concentration (GMC), geometric mean titer (GMT), and proportion of responders with a 4-fold rise in titer (%4 x R). Reactogenicity outcomes were proportions of injection site and systemic AEs.

RESULTS

At week 8, the 4-IM group (GMC, 90.8 microg/mL; GMT, 1114.8; %4 x R, 97.7) was noninferior to the 4-SQ group (GMC, 105.1 microg/mL; GMT, 1315.4; %4 x R, 98.8) for all 3 primary end points. The 3-IM group was noninferior for only the %4 x R (GMC, 52.2 microg/mL; GMT, 650.6; %4 x R, 94.4). At month 7, all groups were noninferior to the licensed regimen for all end points. Solicited injection site AEs assessed during examinations occurred at lower proportions in the 4-IM group compared with 4-SQ. The odds ratio for ordinal end point pain reported immediately after injection was reduced by 50% for the 4-IM vs 4-SQ groups (P < .001). Route of administration did not significantly influence the occurrence of systemic AEs.

CONCLUSIONS

The 4-IM and 3-IM regimens of AVA provided noninferior immunological priming by month 7 when compared with the 4-SQ licensed regimen. Intramuscular administration significantly reduced the occurrence of injection site AEs. Trial Registration clinicaltrials.gov Identifier: NCT00119067.

HIV-1(89.6) Gag expressed from a replication competent HSV-1 vector elicits persistent cellular immune responses in mice

We have constructed a replication competent, gamma(1)34.5-deleted herpes simplex virus type-1 (HSV-1) vector (J200) that expresses the gag gene from human immunodeficiency virus type-1, primary isolate 89.6 (HIV-1(89.6)), as a candidate vaccine for HIV-1. J200 replicates in vitro, resulting in abundant Gag protein production and accumulation in the extracellular media. Immunization of Balb/c mice with a single intraperitoneal injection of J200 elicited strong Gag-specific CD8 responses, as measured by intracellular IFN-gamma staining and flow cytometry analysis. Responses were highest between 6 weeks and 4 months, but persisted at 9 months post-immunization, the last time-point evaluated. These data highlight the potential utility of neuroattenuated, replication competent HSV-1 vectors for delivery of HIV-1 immunogens.

Activation of the Mason-Pfizer monkey virus protease within immature capsids in vitro

For all retroviruses, the completion of the viral budding process correlates with the activation of the viral protease by an unknown mechanism, and, as the structural (Gag) polyproteins are cleaved by the viral protease, maturation of the immature virus-like particle into an infectious virion. Unlike most retroviruses, the Mason-Pfizer monkey virus Gag polyproteins assemble into immature capsids within the cytoplasm of the cell before the viral budding event. The results reported here describe a unique experimental system in which Mason-Pfizer monkey virus immature capsids are removed from the cell, and the protease is activated in vitro by the addition of a reducing agent. The cleavage of the protease from the precursor form is a primary event, which proceeds with a half time of 14 min, and is followed by authentic processing of the Gag polyproteins. Activity of the viral protease in vitro depends on pH, with an increase in catalytic rates at acidic and neutral pH. The initiation of protease activity within immature capsids in vitro demonstrates that viral protease activity is sensitive to oxidation-reduction conditions, and that the viral protease can be activated in the absence of viral budding.

Analysis of Mason-Pfizer monkey virus Gag particles by scanning transmission electron microscopy

Mason-Pfizer monkey virus immature capsids selected from the cytoplasm of baculovirus-infected cells were imaged by scanning transmission electron microscopy. The masses of individual selected Gag particles were measured, and the average mass corresponded to 1,900 to 2,100 Gag polyproteins per particle. A large variation in Gag particle mass was observed within each population measured.

Effectiveness of remifentanil versus traditional fentanyl-based anesthetic in high-risk outpatient surgery

STUDY OBJECTIVE

To determine if remifentanil would offer a superior hemodynamic and recovery profile compared to the current standard of care, which implements a fentanyl-based technique.

DESIGN

Randomized, single-blind study.

SETTING

Outpatient center associated with tertiary care center.

PATIENTS

75 outpatients undergoing microsuspension laryngoscopy.

INTERVENTIONS

Patients were randomized to either a remifentanil induction (0.5 microg/kg/min) and maintenance (0.25 microg/kg/min) versus fentanyl (maximum of 250 microg) as the only opioid. All patients received propofol as part of the induction and maintenance with or without the use of nitrous oxide.

MEASUREMENTS

Assessment of hemodynamics [heart rate (HR) and blood pressure(BP)], presence of perioperative myocardial ischemia on ambulatory electrocardiographic monitoring, and time to discharge.

MAIN RESULTS

Significantly fewer patients in the remifentanil group demonstrated episodes of tachycardia (HR > 100 beats per min) compared to the fentanyl group (14% vs. 40%, p<0.05), with significantly fewer episodes of tachycardia and hypertension per patient. Recovery profiles between the two groups did not show clinically significant differences.

CONCLUSIONS

Remifentanil, a new short-acting opioid, offers excellent hemodynamic control for brief, intense outpatient procedures performed in high-risk patients; however, its use was not associated with any improvement in recovery profiles.

Characterisation of a Rrhodobacter sphaeroides gene that encodes a product resembling Eescherichia coli cytochrome b(561) and R. sphaeroides cytochrome b(562)

Analysis of the photoactive yellow protein (pyp) gene region of Rhodobacter sphaeroides has revealed the presence of an additional open reading frame, orfD, that had not previously been identified. Here we report the location of this new gene and the predicted amino acid sequence of the encoded protein. The translation product resembles a group of small cytochrome b-like proteins, including Escherichia coli cytochrome b(561), R. sphaeroides cytochrome b(562), and two new cytochrome b(561)-like proteins identified using the E. coli genome sequence, for which functions have not yet been established. To determine OrfD function in R. sphaeroides, an orfD mutant was constructed. The OrfD mutant exhibited growth rates and yields very similar to those of the wild-type strain when grown under a variety of growth conditions. Respiration rates, reduced-minus-oxidised spectra and levels of photosynthetic complexes were also very similar in the two strains. Although the role of OrfD was therefore not determined here, we demonstrate that the orfD gene is expressed in R. sphaeroides under aerobic, semi-aerobic and photosynthetic growth conditions.

A cell-line-specific defect in the intracellular transport and release of assembled retroviral capsids

Retrovirus assembly involves a complex series of events in which a large number of proteins must be targeted to a point on the plasma membrane where immature viruses bud from the cell. Gag polyproteins of most retroviruses assemble an immature capsid on the cytoplasmic side of the plasma membrane during the budding process (C-type assembly), but a few assemble immature capsids deep in the cytoplasm and are then transported to the plasma membrane (B- or D-type assembly), where they are enveloped. With both assembly phenotypes, Gag polyproteins must be transported to the site of viral budding in either a relatively unassembled form (C type) or a completely assembled form (B and D types). The molecular nature of this transport process and the host cell factors that are involved have remained obscure. During the development of a recombinant baculovirus/insect cell system for the expression of both C-type and D-type Gag polyproteins, we discovered an insect cell line (High Five) with two distinct defects that resulted in the reduced release of virus-like particles. The first of these was a pronounced defect in the transport of D-type but not C-type Gag polyproteins to the plasma membrane. High Five cells expressing wild-type Mason-Pfizer monkey virus (M-PMV) Gag precursors accumulate assembled immature capsids in large cytoplasmic aggregates similar to a transport-defective mutant (MA-A18V). In contrast, a larger fraction of the Gag molecules encoded by the M-PMV C-type morphogenesis mutant (MA-R55W) and those of human immunodeficiency virus were transported to the plasma membrane for assembly and budding of virions. When pulse-labeled Gag precursors from High Five cells were fractionated on velocity gradients, they sedimented more rapidly, indicating that they are sequestered in a higher-molecular-mass complex. Compared to Sf9 insect cells, the High Five cells also demonstrate a defect in the release of C-type virus particles. These findings support the hypothesis that host cell factors are important in the process of Gag transport and in the release of enveloped viral particles.

Disseminating information using an anesthesiology consultant report: impact on patient perceptions of quality of care

STUDY OBJECTIVE

To determine if providing an Anesthesiology Consultant Report (ACR) to patients would result in enhanced patients' perceptions of their knowledge about their care and improve their perception of the quality of their care.

DESIGN

Randomized, unblinded study.

SETTING

Outpatient center associated with tertiary care center.

PATIENTS

371 outpatients without adverse anesthetic events.

INTERVENTIONS

Patients were randomized to receive either routine discharge instructions or routine instructions and an anesthesia discharge summary (ACR).

MEASUREMENTS AND MAIN RESULTS

Short questionnaire with discharge packet regarding knowledge of anesthetic and questions regarding satisfaction and perceptions of quality of care was distributed. The patients in the group that received an ACR were more satisfied with the management of their pain and other symptoms (p < 0.05, by Wilcoxon rank sums) and were more satisfied overall with the quality of the anesthesia care (p < 0.01, by Wilcoxon rank sums). Taken another way, significantly more patients deemed the quality of their anesthetic care as excellent in the ACR group compared to control (83% vs. 67%, p < 0.01).

CONCLUSIONS

Providing patients, with uneventful anesthetic courses, with information regarding their anesthetic care, in the form of the ACR, results in improved perceptions of the quality of care.

Is outpatient laparoscopic cholecystectomy safe and cost-effective? A model to study transition of care

BACKGROUND

There is increasing pressure to perform traditional inpatient surgical procedures in an outpatient setting. The aim of the current trial was to determine the safety and cost savings of performing laparoscopic cholecystectomy in an outpatient setting using a "mock" outpatient setting.

METHODS

Patients who were scheduled for laparoscopic cholecystectomy by four attending surgeons and for whom operating time was available in the outpatient center were studied. All patients received a standardized anesthetic, including ondansetron, and were discharged from the outpatient postanesthesia care unit if appropriate. At discharge, all patients were admitted to a clinical research center where they were observed in a "mock home" setting and monitored for complications that would have necessitated readmission. A decision analysis was created assuming all patients underwent outpatient surgery with either direct admission or discharge to home and readmission if complications developed.

RESULTS

Of 99 patients who were enrolled in this study, 96 patients would have met the discharge criteria for home. No major complications were observed in these 96 patients. Eleven patients experienced postoperative nausea and vomiting, 3 of whom required an additional 24 h of hospital observation. In the decision model, the optimal strategy would be to perform the procedure on an outpatient basis and readmit patients only for complications, with an average baseline cost savings of $742/patient.

CONCLUSIONS

The results show that outpatient laparoscopic cholecystectomy is safe and cost-effective in selected patients, and that the mock home setting provides a means of studying the safety of transition of care.

Laparoscopic cholecystectomy as a "true" outpatient procedure: initial experience in 130 consecutive patients

Laparoscopic cholecystectomy has received nearly universal acceptance and is currently considered the "gold standard" for the treatment of cholelithiasis. Many centers have employed "short-stay" units or "23-hour admissions" for postoperative observation following laparoscopic cholecystectomy. The practice of early discharge as "true" outpatients following this procedure has not been well defined. A retrospective analysis of 130 consecutive patients undergoing laparoscopic cholecystectomy in an outpatient surgery unit was performed. A follow-up telephone survey was carried out of patients who successfully completed the procedure as outpatients. One hundred thirty patients underwent outpatient laparoscopic cholecystectomy. The patient population consisted of 78% women, with an age range of 17 to 76 years (mean age 47.1 years). Symptomatic gallstone disease was the indication for laparoscopic cholecystectomy in 92% of the patients. All patients underwent successful completion of laparoscopic cholecystectomy with no conversions to an open procedure. The mean length of operation was 75 +/- 23 minutes (range 25 to 147 minutes). The mean length of stay in the postanesthesia care unit (PACU) ranged from 95 to 460 minutes with a mean length of stay of 200 +/- 79 minutes. A total of eight patients (6.2%) were admitted to the hospital directly from the PACU in the immediate postoperative period. Six of these eight patients were discharged on the first postoperative day. Following discharge from the PACU, an additional six patients (4.6%) required hospital admission. Three of these six patients were discharged after a single day of hospitalization. Ninety-eight of 116 eligible patients were available for follow-up telephone evaluation. The outpatient experience was rated as good by 75.5% of the patients, fair by 22.5%, and poor by 2%. In retrospect, 20.4% of the patients stated that they would have preferred an inpatient to an outpatient procedure. Laparoscopic cholecystectomy can be performed as a true outpatient procedure with patients discharged to home within hours of completion of the procedure. Less than 10% of patients will fail this protocol and another 5% of the patients may require hospitalization after returning to their homes.

Safety of direct laryngoscopy as an outpatient procedure

The safety of outpatient direct laryngoscopy has recently been challenged in the literature. We reviewed the first 589 direct laryngoscopies performed at a new outpatient surgery center. There were nine unplanned admissions to the hospital, including five airway emergencies that developed within the first 30 min after extubation. Three patients required reintubation before leaving the operating room. On postoperative telephone follow-up, 9% complained of mild to moderate sore throat. There were no major complications after discharge. We conclude that the risk of airway emergencies after direct laryngoscopy is less than 1% in carefully selected patients. The procedure can be safely performed as an outpatient procedure as long as transportation to a hospital is readily available for the few patients in whom complications arise.

Changes in cerebrospinal fluid pressure and lactate concentrations during thoracoabdominal aortic aneurysm surgery

BACKGROUND

Although ischemic injury to the spinal cord is a well-known complication of aortic surgery, no metabolic markers have been identified as predictors of an adverse outcome. This study evaluated the effect of cerebrospinal fluid (CSF) drainage, with and without distal femoral perfusion or moderate hypothermia on blood and CSF lactate concentrations and CSF pressure during thoracoabdominal aortic aneurysm surgery.

METHODS

Three nonconcurrent groups of patients were studied prospectively: patients with normal body temperature (35 degrees C) but without distal femoral bypass (n = 6), patients with normal body temperature with bypass (n = 7), and patients with hypothermia (30 degrees C) and bypass (n = 8). In all patients, CSF pressure was recorded before, during, and after aortic cross-clamping. During the surgical repair, CSF drainage was performed using a 4-Fr intrathecal silicone catheter. Blood and CSF lactate concentrations were measured throughout the operation.

RESULTS

Significant increases in blood (490%) and CSF (173%) lactate concentrations were observed during and after thoracic aortic occlusion in patients with normothermia and no bypass (P < 0.02 and 0.05, respectively). Distal perfusion attenuated the increase in both blood and CSF lactate (P < 0.01), and a further reduction was achieved with hypothermia of 30 degrees C (P < 0.001). Patients who became paraplegic showed a greater increase in CSF lactate concentrations after aortic clamp release compared with those who suffered no neurological damage (275% vs. 123% of baseline; P < 0.05). Increased CSF pressure of 42-60% (P < 0.005) was noted soon after thoracic aortic occlusion, both with and without distal femoral bypass.

CONCLUSIONS

Incremental reductions in CSF lactate concentrations were achieved using distal femoral bypass and hypothermia. The reduction in CSF lactate correlated with the methods used to protect the spinal cord during thoracoabdominal aortic aneurysm surgery and was associated with better outcome. Decompression by distal bypass of the hemodynamic overload caused by aortic occlusion was insufficient to eliminate the acute increase in CSF pressure. Cerebrospinal fluid lactate measurements during high aortic surgery may accurately represent the spinal cord metabolic balance.

Microleakage of amalgam restorations using dentin bonding system primers

PURPOSE

To evaluate and compare in vitro microleakage of etched and non-etched Class I amalgam restorations lined with various dentin bonding system primers to amalgam restorations with or without a Copalite liner.

MATERIALS AND METHODS

Class I amalgam preparations were made in 140 extracted molars and divided into 14 groups of 10 teeth each. Permite C dispersed phase alloy restorations were placed after the following treatments: Group 1: No liner; Group 2: Lined with two coats of Copalite; Group 3(A): Lined with Amalgambond AA and 3(B): Etched with 35% Ultra-etch and lined with Amalgambond AA; Group 4(A): Lined with Scotchbond Multi-Purpose Primer and 4(B): Etched and lined with the primer; Group 5(A): Lined with ProBond and 5(B): Etched and lined with the primer; Group 6(A): Lined with All-Bond 2 Primer A & B and 6(B): Etched and lined with the primer; Group 7(A): Lined with OptiBond and 7(B): Etched and lined with the primer; Group 8(A): Lined with Permagen Primer and 8(B): Etched and lined with the primer. All primers were applied per manufacturers' specifications. After storage in water for 24 hours, all restorations were polished and then aged in water at 37 degrees C for 90 days. The specimens were then thermocycled for 300 cycles at 5 degrees C and 55 degrees C in basic fuchsin dye with a 30-second dwell time, mounted in epoxy rings, sectioned longitudinally, mesiodistally and buccolingually into four sections, then evaluated at x100 and the extent of dye penetration at the tooth/amalgam interface scored (two scores for each section, eight for each specimen).

RESULTS

The unlined and Copalite-lined groups and all non-etched groups showed considerable marginal leakage. All the etched restorations were significantly more effective in reducing microleakage than the non-etched, no liner and Copalite-lined groups. Etching prior to application of the primers is significantly more effective than nonetching, however the effectiveness of the primer alone to seal the dentin needs to be evaluated. Overall, Amalgam-bond AA had the least microleakage of all the groups.

Synthesis and assembly of retrovirus Gag precursors into immature capsids in vitro

The assembly of retroviral particles is mediated by the product of the gag gene; no other retroviral gene products are necessary for this process. While most retroviruses assemble their capsids at the plasma membrane, viruses of the type D class preassemble immature capsids within the cytoplasm of infected cells. This has allowed us to determine whether immature capsids of the prototypical type D retrovirus, Mason-Pfizer monkey virus (M-PMV), can assemble in a cell-free protein synthesis system. We report here that assembly of M-PMV Gag precursor proteins can occur in this in vitro system. Synthesized particles sediment in isopycnic gradients to the appropriate density and in thin-section electron micrographs have a size and appearance consistent with those of immature retrovirus capsids. The in vitro system described in this report appears to faithfully mimic the process of assembly which occurs in the host cell cytoplasm, since M-PMV gag mutants defective in in vivo assembly also fail to assemble in vitro. Likewise, the Gag precursor proteins of retroviruses that undergo type C morphogenesis, Rous sarcoma virus and human immunodeficiency virus, which do not preassemble capsids in vivo, fail to assemble particles in this system. Additionally, we demonstrate, with the use of anti-Gag antibodies, that this cell-free system can be utilized for analysis in vitro of potential inhibitors of retrovirus assembly.

Catecholamine and cortisol responses to lower extremity revascularization: correlation with outcome variables. Perioperative Ischemia Randomized Anesthesia Trial Study Group

OBJECTIVE

To determine whether catecholamine and cortisol secretory responses to surgery contribute to postoperative complications.

DESIGN

Prospective, randomized, case series.

SETTING

A university hospital operating suite and surgical intensive care unit.

PATIENTS

Sixty patients undergoing lower extremity vascular surgery.

INTERVENTIONS

Patients were randomized to receive either epidural anesthesia/epidural opiate analgesia (regional anesthesia) or general anesthesia/intravenous patient-controlled analgesia (general anesthesia).

MEASUREMENTS AND MAIN RESULTS

Anesthesia was managed according to a prospectively designed protocol. Hemodynamic parameters and plasma catecholamine concentrations were determined at specific intraoperative and postoperative time points. Intraoperative and postoperative urine samples were collected and analyzed for free cortisol concentrations. Outcomes evaluated were cardiac (nonfatal myocardial infarction and cardiac death) and surgical (graft occlusion). Mean arterial pressure during emergence from anesthesia and in the early postoperative period correlated positively with plasma norepinephrine concentration (p < .01). In addition, plasma catecholamine concentrations were higher in patients with postoperative hypertension. Plasma norepinephrine concentrations at the time of emergence from anesthesia and postoperatively were also higher in patients requiring repeat surgery for graft revision, thrombectomy, or amputation (p < .05). Multivariate analysis indicated that the norepinephrine concentration at the time of emergence, but not type of anesthesia, correlated with reoperation for graft occlusion, suggesting that the previously reported beneficial effect of regional anesthesia may be due to modulation of the stress response. Myocardial infarction or cardiac death occurred in three patients. These patients had markedly increased catecholamine concentrations.

CONCLUSIONS

The catecholamine response to lower extremity vascular surgery contributes to the development of postoperative hypertension and may also be important in the development of thrombotic complications.

Moderate hypothermia, with partial bypass and segmental sequential repair for thoracoabdominal aortic aneurysm

PURPOSE

Ischemic injury to the spinal cord, kidneys, and viscera occurs in a significant number of patients undergoing surgical repair of thoracoabdominal aortic aneurysms. Partial bypass has been used to perfuse the arterial system distal to the cross-clamp, but the primary determinant of ischemic morbidity remains the duration of aortic cross-clamping. Hypothermia may favorably affect outcome during these procedures, but moderate or deep hypothermia has traditionally required full cardiopulmonary bypass with cardiac arrest.

METHODS

In a series of patients undergoing thoracoabdominal (n = 14) or thoracic (n = 4) aneurysm repair, we used moderate hypothermia (30 degrees C) and partial bypass (aortofemoral or atriofemoral) while maintaining an intrinsic cardiac rhythm. Body temperature was controlled with a heat exchanger in the bypass circuit, which allowed for rapid cooling and rewarming. In addition to hypothermia and bypass, a segmental sequential surgical repair was used to minimize the duration of ischemia to any given vascular bed.

RESULTS

All patients survived the surgical procedure, and 16 patients survived until discharge from the hospital. None of the 18 patients had paraplegia or significant renal dysfunction. The only complication related to hypothermia was atrial fibrillation, which occurred in three patients and was amenable to therapeutic measures.

CONCLUSIONS

We conclude that moderate hypothermia, partial bypass, and segmental sequential repair may reduce ischemic injury. This combination of adjuncts was not associated with significant complications in this series of patients.

Determinants of catecholamine and cortisol responses to lower extremity revascularization. The PIRAT Study Group

BACKGROUND

Surgical trauma elicits diffuse changes in hormonal secretion and autonomic nervous system activity. Despite studies demonstrating modulation of the stress response by different anesthetic/analgesic regimens, little is known regarding the determinants of catecholamine and cortisol responses to surgery.

METHODS

Plasma catecholamines and cortisol secretion data were obtained from 60 patients undergoing lower extremity revascularization. Patients were randomized to receive either general anesthesia combined with patient-controlled intravenous morphine (GA) or epidural anesthesia combined with epidural fentanyl analgesia (RA). All aspects of intra- and postoperative clinical care were defined by written protocol. Plasma catecholamines were measured before induction, intraoperatively, and for the first 18 h postoperatively (by HPLC). Urine cortisol was measured intra- and postoperatively using RIA. Data were evaluated using univariate and multivariate analyses to evaluate demographic and perioperative variables as determinants of stress hormone secretion.

RESULTS

Plasma catecholamines increased during skin closure in the GA group, and remained higher relative to the RA group in the postoperative period. Multivariate analysis indicated that age and anesthetic regimen predicted increases in catecholamines during skin closure (P < 0.005), although duration of surgery, blood loss, and body temperature were not correlated. Early postoperative norepinephrine concentrations were correlated with pain score and duration of surgery (P < 0.004), but not with anesthetic management, blood loss, or body temperature. All postoperative norepinephrine levels were highly correlated (r = 0.7) with norepinephrine levels during skin closure. Cortisol excretion was higher postoperatively than intraoperatively. No patient or perioperative variable predicted cortisol excretion, and cortisol excretion was not correlated with catecholamine levels at any time.

CONCLUSIONS

These data indicate that patient factors, such as age and inherent sympathetic responsivity, are important determinants of the catecholamine response to surgery. Modulation of the norepinephrine response by regional anesthesia/analgesia appears to be related, in part, to superior analgesia. The lack of correlation between catecholamine and cortisol secretion indicates that the stress response may consist of discrete systems responding to different stimuli.

Perioperative morbidity in patients randomized to epidural or general anesthesia for lower extremity vascular surgery. Perioperative Ischemia Randomized Anesthesia Trial Study Group

BACKGROUND

Perioperative morbidity may be modifiable in high risk patients by the anesthesiologist's choice of either regional or general anesthesia. This clinical trial compared outcomes between epidural (EA) and general (GA) anesthesia/analgesia regimens in a group of patients at high risk for cardiac and other morbidity who were undergoing similarly stressful surgical procedures.

METHODS

One hundred patients scheduled for elective vascular reconstruction of the lower extremities were randomized to receive either EA for surgery followed by epidural analgesia, or GA for surgery followed by intravenous patient-controlled analgesia. Hemodynamic monitoring, blood pressure, and heart rate limits were determined prior to randomization. Management of anesthesia in the immediate postoperative period was standardized. The data collected included continuous electrocardiographic monitoring from the day before surgery through the third postoperative day, serial electrocardiograms, and cardiac enzymes. Cardiac ischemia, myocardial infarction, unstable angina, and cardiac death were identified by a cardiologist blinded to the type of anesthesia received. Other major morbidity was determined at the time of hospital discharge and at 1 and 6 months after surgery.

RESULTS

Eleven patients who received GA required regrafting or an embolectomy during their hospital stay, compared with two patients who received EA. This association of GA with reoperation remained significant after adjustment for baseline differences. Cardiac outcomes were similar in the two groups with respect to perioperative death (1 EA and 1 GA), death within 6 months (4 EA and 3 GA), nonfatal myocardial infarction within 7 days (2 EA and 2 GA), unstable angina (0 EA and 2 GA), and myocardial ischemia following randomization (17 EA and 23 GA). Rates of major infections in the two groups (1 EA and 2 GA), renal failure (3 EA and 3 GA), and pulmonary complications (3 EA and 7 GA) also were similar.

CONCLUSIONS

Carefully conducted epidural and general anesthesia appear to be associated with comparable rates of cardiac and most other morbidity in patients undergoing lower extremity vascular surgery. However, compared with general anesthesia, epidural anesthesia is associated with a lower incidence of reoperation for inadequate tissue perfusion and, therefore, may be advantageous for this surgical population.

The effects of different anesthetic regimens on fibrinolysis and the development of postoperative arterial thrombosis. Perioperative Ischemia Randomized Anesthesia Trial Study Group

BACKGROUND

The purpose of this clinical trial was to compare the effects of different anesthetic and analgesic regimens on hemostatic function and postoperative arterial thrombotic complications.

METHODS

Ninety-five patients scheduled for elective lower extremity vascular reconstruction were randomized to receive either epidural anesthesia followed by epidural fentanyl (RA) or general anesthesia followed by intravenous morphine (GA). Intraoperative and postoperative care were controlled by protocol using predetermined limits for heart rate, blood pressure, and other monitoring criteria. Data collection included serial physical examinations, electrocardiograms, and cardiac isoenzymes to detect arterial thrombosis (defined as unstable angina, myocardial infarction, or vascular graft occlusion requiring reoperation). Fibrinogen, plasminogen activator inhibitor-1 (PAI-1), and D-dimer levels were measured preoperatively and at 24 and 72 h postoperatively.

RESULTS

Preoperative fibrinogen levels were similar in both groups, remained unchanged after 24 h, and increased equally (45%) in the first 72 h postoperatively. PAI-1 levels in the GA group increased from 13.6 +/- 2.1 activity units (AU)/ml to 20.2 +/- 2.6 AU/ml at 24 h and returned to baseline at 72 h. In contrast, PAI-1 levels in the RA group remained unchanged over time. Twenty-two of 95 patients (23%) had postoperative arterial thrombosis, 17 of whom had received GA and 5 of whom, RA. Preoperative PAI-1 levels were higher in patients who developed postoperative arterial thrombosis (20.5 +/- 3.6 AU/ml vs. 11.2 +/- 1.4 AU/ml). Multiple logistic regression analysis indicated that GA and preoperative PAI-1 levels were predictive of postoperative arterial thrombotic complications.

CONCLUSIONS

Impaired fibrinolysis may be related causally to postoperative arterial thrombosis. Because RA combined with epidural fentanyl analgesia appears to prevent postoperative inhibition of fibrinolysis, this form of perioperative management may decrease the risk of arterial thrombotic complications in patients undergoing lower extremity revascularization.

Spinal cord stimulation evoked potentials during thoracoabdominal aortic aneurysm surgery

Although monitoring of somatosensory evoked potentials elicited from stimulation of lower extremity peripheral nerves has been suggested as a method for assessing neural function during thoracoabdominal aortic aneurysm surgery, this technique has been reported to yield a large number of false positives. It was believed that direct stimulation of the spinal cord would eliminate some of the problems associated with peripheral evoked potentials. The present study compared in 18 patients the use of scalp recorded evoked potential following stimulation of either the posterior tibial nerve via percutaneous needles or the spinal cord via an epidural electrode previously placed fluoroscopically. In 10 patients in whom distal bypass or shunt was not used, peripheral evoked potentials totally disappeared within 5-30 min of aortic clamping. Spinal cord stimulation evoked potentials disappeared permanently in 2 patients shortly after aortic cross-clamping; 1 died shortly after the procedure, and the other awoke densely paraplegic and died the next day. When distal perfusion was maintained by shunt or bypass, the disappearance of both peripheral and spinal evoked potentials accurately predicted the neurologic outcome of 1 paralyzed patient. Loss of spinal cord stimulation evoked potentials was found to be correlated with adverse neurologic outcome. Over the period of aortic clamping a gradual decrease in mean amplitude (50% at 45 min [P less than 0.05]) and a 20% increase in mean latency time were observed. Maintenance of adequate distal perfusion may permit the use of peripheral evoked potentials in the assessment of spinal cord ischemia during aortic cross-clamping.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effect of glucocorticoids on pulmonary responses and eosinophils

The persistent airway hyperresponsiveness of Basenji-Greyhound (BG) dogs to 10% citric acid (CA) is abolished by chronic administration of methylprednisolone (MP) and is accompanied by the disappearance of eosinophils from the bronchoalveolar lavage (BAL) fluid. To determine whether the disappearance of eosinophils from BAL fluid was temporally related to the loss of airway responsiveness to CA, we investigated the time course of the reduction in airway responsiveness to CA and correlated it with changes in cell profiles in BAL fluid in a group of BG dogs treated with MP for 1 to 7 days. Six dogs in separate studies were pretreated with MP (2 mg/kg/day) subcutaneously for either 1, 3 or 7 days. Each dog served as its own control for each set of studies. Under thiopental anesthesia, lung resistance (RL) was calculated from transpulmonary pressure and flow measurements prior to and 5 minutes following the completion of a 10% CA aerosol. BAL was performed on a separate occasion with the animals pretreated with MP for either 1, 7, 10 or 14 days. Baseline RL was not significantly different in each control and treatment group. The pulmonary response to CA challenge was diminished following 1, 3 and 7 days of MP pretreatment. Although eosinophils disappeared from the peripheral blood following 1 day of MP treatment, eosinophils in BAL did not begin decreasing until 10 days of MP pretreatment. This temporal dissociation between CA hyperresponsiveness and eosinophils in the BAL fluid suggests that epithelial damage by toxic products of eosinophils in the airway lumen does not play a direct role in citric acid induced airway hyperresponsiveness in BG dogs.

Angiographic localization of spinal cord blood supply and its relationship to postoperative paraplegia

Forty-seven patients underwent selective catheterization of middle and lower thoracic intercostal and upper lumbar arteries to define the origin of the artery of Adamkiewicz. One patient had significant atheroembolism, and a second had transient lower extremity paresthesias. No other complications occurred. The origin was found in 26 (55%), and 21 patients underwent thoracoabdominal aneurysm repair with this knowledge. When the critical lumbar or intercostal artery could be included as part of a long proximal or distal anastomosis, all 12 patients could be included as part of a long proximal or distal anastomosis, all 12 patients survived, and one was paralyzed. However, if the aneurysm repair mandated a midgraft anastomosis to intercostal arteries critical to spinal cord perfusion, seven of nine patients either died or were paralyzed (p less than 0.05). In the group of 19 patients operated on in whom spinal cord blood supply was not identified three patients had a technically unsuccessful operation; two died, and one was paralyzed. Twelve of 16 patients who had an adequate, but unsuccessful attempt at localization were treated by intercostal "neglect" and survived. Late paresis developed in two patients, but they are walking now. One of the patients who died had multiple systems failure and awakened paraplegic. She had a patent, enlarged, thoracic radicular artery at T-5 which probably supplied to spinal cord and which was missed angiographically. Paralysis was associated with aneurysm extent (group 2 and III B, dissections vs group 1 & 3, p less than 0.05). Selective intercostal angiography requires further refinement, but it is safe and offers the promise of understanding the mechanisms and risks of spinal cord complications after repair of extensive thoracoabdominal aneurysms.

Halothane alters the oxygen consumption-oxygen delivery relationship compared with conscious state

The authors' objectives were as follows: 1) to characterize for the first time the relationship between whole body O2 delivery (DO2) and O2 consumption (VO2) in adult conscious dogs; and 2) to asses the effects of the inhalational anesthetic, halothane, on that relationship. DO2 was varied over a wide range in chronically instrumented dogs by gradual inflation and deflation of a hydraulic occluder implanted around the thoracic inferior vena cava to alter venous return and cardiac output. VO2 was measured at different values of DO2 in dogs in the fully conscious state and again during halothane anesthesia. A "binning" technique indicated that halothane decreased VO2 (P less than 0.01) at any given value of DO2 over a broad range of VO2. A two-line piecewise linear regression analysis technique indicated that halothane decreased (P less than 0.01) the critical O2 delivery (COD) from 20 +/- 3 to 10 +/- 1 ml.kg-1.min-1 and increased (P less than 0.01) O2 extraction at COD from 31 +/- 3 to 40 +/- 2%. However, the DO2-VO2 plots measured in both conscious and halothane-anesthetized dogs did not exhibit a discrete discontinuity but rather were closely fit (correlation coefficient = 0.98) by an exponential equation of the following form: O2 extraction = B1.(1 - exp (-DO2/B2))/DO2, where B1 is the delivery-independent estimate of VO2 and B2 is the "delivery constant," i.e., the DO2 associated with a VO2 equal to 63% of B1. Halothane decreased B1 (P less than 0.01) from 5.3 +/- 0.1 to 3.9 +/- 0.1 ml.kg-1.min-1 and decreased B2 (P less than 0.01) from 5.6 +/- 0.3 to 3.6 +/- 0.3 ml.kg-1.min-1 compared with that measured in conscious dogs. Thus, compared with the conscious state, halothane anesthesia alters the fundamental relationship between DO2 and VO2 and may have a beneficial effect on tissue oxygenation at low values of DO2.

Risk factors for late relapse in male and female ex-smokers

Three hundred twenty-nine ex-smokers (149 males and 180 females) who had maintained abstinence for at least 3 months prior to intake were followed for a period of 1 year to ascertain individual characteristics from cognitive, behavioral, environmental, and health domains that were predictive of later relapse. Multiple logistic regression analysis revealed significant associations between relapse, family history, and stress variables in males and between relapse, family history, stress, pre- and postcessation smoking characteristics, work-related variables, and physical activity in females. Within the predictor sets, both risk and protective factors were identified. The male and female models are discussed separately, compared, and related to previous research. Implications for further model development are specified; most notably, the utility of conceptualizing relapse independent of gender is questioned. Future research efforts could focus on the role played by family smoking history in adult relapse behavior. Smoking cessation interventions may need to tailor their efforts specifically to men and to women. Along with techniques to manage stress both during and after cessation, women may benefit especially from interventions that provide nicotine replacement and counseling for work-related difficulties.

Effect of vasopressors on organ blood flow during endotoxin shock in pigs

A volume-resuscitated porcine endotoxin shock model was used to evaluate the effect on organ blood flow of increasing systemic arterial blood pressure with vasopressors. Administration of 0.05-0.2 mg/kg of Escherichia coli endotoxin (E) reduced mean arterial blood pressure (MAP) to 50 mmHg, decreased systemic vascular resistance to 50% of control, and did not change cardiac output or heart rate. Blood flow to brain, kidney, spleen, and skeletal muscle was reduced during endotoxin shock, but blood flow to left ventricle, small and large intestine, and stomach remained at pre-endotoxin levels throughout the study period. Four groups of animals were used to evaluate the effect of vasopressor therapy. A control group received E and no vasopressor, whereas the other three groups received either norepinephrine, dopamine, or phenylephrine. Vasopressors were administered starting 60 min after E exposure, and the dose of each was titrated to increase MAP to 75 mmHg. Despite the increase in MAP, brain blood flow did not increase in any group. Norepinephrine alone increased blood flow to the left ventricle. Kidney, splanchnic, and skeletal muscle blood flow did not change with vasopressor administration. The dose of norepinephrine required to increase MAP by 20-25 mmHg during E shock was 30 times the dose required for a similar increase in MAP in animals not receiving E. We conclude that hypotension in the fluid resuscitated porcine E shock model is primarily the result of peripheral vasodilatation, that the vascular response to vasoconstrictors in this model is markedly attenuated following E administration, that blood pressure elevation with norepinephrine, dopamine, and phenylephrine neither decreases blood flow to any organ nor increases blood flow to organs with reduced flow, and that norepinephrine, dopamine, and phenylephrine affect regional blood flow similarly in this model.

Cardiovascular responses in type A and type B men to a series of stressors

Fifty-six healthy adult males were administered the Type A Structured Interview and assessed as exhibiting either Type A (N = 42) or Type B (N = 14) behavior pattern. They were monitored for systolic (SBP) and diastolic blood pressure (DBP) and heart rate (HR) responses during a series of six challenging tasks: Mental Arithmetic, Hypothesis Testing, Reaction Time, Video Game, Handgrip, and Cold Pressor. The results indicated that Type A subjects exhibited greater cardiovascular responses than did Type B subjects during some (Hypothesis Testing, Reaction Time, Video Game and Mental Arithmetic) but not all (Handgrip and Cold Pressor) of the tasks. These results are discussed in terms of previously reported findings on conditions that do and do not produce differences in Type A/B cardiovascular stress responses.

Reducing the confounding effects of environment and diet on saliva thiocyanate values in ex-smokers

This study focuses on the use of saliva thiocyanate to corroborate self-report in 391 adult ex-smokers who claimed abstinence from cigarettes for a minimum of 3 months. Results indicated significant thiocyanate confounders, such as using and inhaling nontobacco organic substances, working in a "smoky" environment (i.e., tobacco smoke), and consuming varieties of Brassica oleracea (e.g., cabbage), that could be identified and adjusted for in order to clarify classification of smoking status. Before adjustment for confounders, 18% of subjects reporting abstinence had saliva thiocyanate values greater than the standard cut-off point of 100 micrograms/ml, which would classify them as current smokers. After adjustment, only 12% of subjects still had values greater than 100 micrograms/ml.

Epinephrine and norepinephrine responses in continuously collected human plasma to a series of stressors

The present study employed continuous blood withdrawal to examine epinephrine and norepinephrine responses to a cognitive stressor (mental arithmetic), active physical stressors (handgrip and knee bends), passive painful stressors (venipuncture and cold pressor), and a medical procedure that was considered nonstressful (blood pressure measurements). The data were analyzed by analysis of variance (ANOVA) and by time series analysis. The ANOVA indicated that epinephrine and norepinephrine increased significantly in response to the stressors. Epinephrine showed a greater increase to the cognitive stressor than to the others. Time series analysis, however, showed a more varied pattern. It indicated that the height and duration of response differed considerably across subjects and across interventions. The results from both analytic procedures are compared and discussed in terms of current hypotheses of catecholamine response.

Striatal dopaminergic modulation of lateral hypothalamic self-stimulation

The bilateral application of crystalline 6-hydroxydopamine to the ventral anterior head of the corpus striatum of rats severely suppressed responding for electrical stimulation of the lateral hypothalamus. This suppression lasted for days or weeks, after other behavioral deficits in food and water intake and activity had recovered. Application of crystalline dopamine through the same cannulas temporarily reversed the impairment. Applications of crystalline dopamine to the same striatal region of untreated rats were more effective in enhancing self-stimulation than similar applications of norepinephrine.