Neutralizing antibody vaccine for pandemic and pre-emergent coronaviruses.

Betacoronaviruses caused the outbreaks of severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome, as well as the current pandemic of SARS coronavirus 2 (SARS-CoV-2)1-4. Vaccines that elicit protective immunity against SARS-CoV-2 and betacoronaviruses that circulate in animals have the potential to prevent future pandemics. Here we show that the immunization of macaques with nanoparticles conjugated with the receptor-binding domain of SARS-CoV-2, and adjuvanted with 3M-052 and alum, elicits cross-neutralizing antibody responses against bat coronaviruses, SARS-CoV and SARS-CoV-2 (including the B.1.1.7, P.1 and B.1.351 variants). Vaccination of macaques with these nanoparticles resulted in a 50% inhibitory reciprocal serum dilution (ID50) neutralization titre of 47,216 (geometric mean) for SARS-CoV-2, as well as in protection against SARS-CoV-2 in the upper and lower respiratory tracts. Nucleoside-modified mRNAs that encode a stabilized transmembrane spike or monomeric receptor-binding domain also induced cross-neutralizing antibody responses against SARS-CoV and bat coronaviruses, albeit at lower titres than achieved with the nanoparticles. These results demonstrate that current mRNA-based vaccines may provide some protection from future outbreaks of zoonotic betacoronaviruses, and provide a multimeric protein platform for the further development of vaccines against multiple (or all) betacoronaviruses.

Preliminary examination of sounds produced by Pacific salmon (Oncorhynchus spp.) during their fall spawning migrationa).

A preliminary description of sounds produced by three species of Pacific salmon was conducted to address the lack of quantified call characteristics in previous studies. Wild Chinook salmon (Oncorhynchus tshawytscha), pink salmon (O. gorbuscha), and coho salmon (O. kisutch) were diverted from a natural spawning migration in the Big Qualicum River located on Vancouver Island, British Columbia, Canada and held in the adjacent hatchery during the 2017 fall migration. Underwater sounds were opportunistically recorded continuously over four week in holding raceways containing Chinook only, coho only, or mixed pink and Chinook salmon, and examined for sounds. All groups produced sounds in three categories based on mechanism: hydrodynamic (surface splash), air movement (miscellaneous and 7 named types), and unknown mechanism (pulse). Pulse, gill-bubble fast repetitive tick air movement sounds, and miscellaneous air movement sounds occurred in all groups and differences in some characteristics of sounds were found between the species groups. Additionally, even though pink salmon were not recorded separately, data suggest they produce a very fast repetitive tick air movement sound more often compared to Chinook salmon. Our results represent the first detailed description of the types and characteristics of sounds produced by wild Pacific salmon.

A placebo-controlled trial of a proprietary lipid-lowering nutraceutical supplement in the management of dyslipidemia.

There is an ever growing emergence in the popularity of patient-driven care. As this health and wellness model grows, inquiries into diet, lifestyle, and supplemental approaches will continue to become a focal point for the healthcare consumer. Because of this, the aim of this study is to determine the tolerability, and overall effectiveness of a proprietary multi-ingredient lipid-lowering supplement in subjects with dyslipidemia. Forty participants were recruited for a single-center, double-blind randomized, placebocontrolled trial. Study participants were recruited between December 2014 and March 2015. Initial screening included a physical examination, renal and hepatic function, serum lipid, serum electrolytes, complete blood counts, and urine analysis. The 40 participants were randomly assigned to receive either the proprietary multi-ingredient lipid-lowering supplement (PMILLS) n= 20 or placebo n= 20. The trial consisted of a screening visit, a two-week run-in, and a four-month treatment period. Samples were taken at baseline, one month and four months of treatment. Results from the trial showed that the PMILLS significantly reduced total cholesterol (TC), low density lipoprotein (LDL-C), very low density lipoprotein (VLDL-C), oxidized LDL (oxLDL), Apo-lipoprotein B, triglycerides (TG), LDL particle number (LDL-P), heart rate, and diastolic blood pressure compared to placebo at one month and four months. The PMILLS significantly increased high density lipoprotein (HDL) particle number (HDL-P), and low density lipoprotein (LDL) particle size from dense type III and IV to larger type I and II LDL particle, compared to placebo at one month and four months. In addition, the PMILLS significantly reduced high sensitivity C-reactive protein (hs-CRP), tumor necrosis alpha (TNF-α), and interleukin 6 (IL-6) within the treatment group from baseline. There were no adverse effects noted in the treatment group after four months of supplementation. The present study demonstrates this PMILLS improves all relevant lipid parameters, such as particle numbers and particles sizes, as well as showing a significant reduction in inflammatory markers linked to cardiovascular health. With such combined changes in lipids, lipid sub-fractions, and inflammation, which are considered among the most effective means of reducing coronary heart disease (CHD), this PMILLS represents a new addition to safe and effective lipid-modifying strategies.

Does the Arctic charr Salvelinus alpinus produce sounds in a captive setting?

Arctic charr Salvelinus alpinus did not appear to invest in acoustic communication during courtship and agonistic interactions in captivity. Salvelinus alpinus did, however, produce four different types of sounds which were found to be associated with three different types of air exchange behaviours which probably have a swimbladder regulation function. Since air passage sounds appear to be common among Salmonidae, it is suggested that the potential of passive acoustics techniques for behavioural and ecological monitoring should be further investigated in future field and laboratory investigations.

Relationship between body size and habitat complexity preference in age-0 and -1 year winter flounder Pseudopleuronectes americanus.

The interaction between body size, habitat complexity and interstice width on habitat preference of age-0 and -1 year Pseudopleuronectes americanus was examined using continuous remote video observation. The habitat choices of juvenile P. americanus were recorded over a 6 h period in tanks with four treatments: bare sand, sand with low complexity cobble, sand with intermediate complexity cobble and sand with high complexity cobble. Both age-0 and -1 year fish preferred cobble to bare sand. Within cobble treatments, age-0 year fish preferred intermediate complexity cobble, with a 1.59 ratio of interstitial space to body width. The largest age-1 year fish (123-130 mm standard length, L(S) ) preferred low complexity cobble. While a significant preference was not detected, medium age-1 year fish (83-88 mm L(S) ) tended to select low complexity cobble, whereas small age-1 year fish (73-82 mm L(S) ) tended to select low and intermediate cobble, with an interstitial space to body width ratio of 1.05. For medium and large age-1 year fish, there was an increased selection of low complexity cobble, corresponding to larger interstitial space to body size ratios. This study indicates that juvenile P. americanus prefer complex habitat to unstructured habitat and that this preference is mediated by a relationship between fish body size and the size of structure interstices. These results contribute to the growing body of knowledge of complex habitat selection and drivers of habitat choice in flatfishes.

Stabilized HIV-1 envelope immunization induces neutralizing antibodies to the CD4bs and protects macaques against mucosal infection.

A successful HIV-1 vaccine will require induction of a polyclonal neutralizing antibody (nAb) response, yet vaccine-mediated induction of such a response in primates remains a challenge. We found that a stabilized HIV-1 CH505 envelope (Env) trimer formulated with a Toll-like receptor 7/8 agonist induced potent HIV-1 polyclonal nAbs that correlated with protection from homologous simian-human immunodeficiency virus (SHIV) infection. The serum dilution that neutralized 50% of virus replication (ID50 titer) required to protect 90% of macaques was 1:364 against the challenge virus grown in primary rhesus CD4+ T cells. Structural analyses of vaccine-induced nAbs demonstrated targeting of the Env CD4 binding site or the N156 glycan and the third variable loop base. Autologous nAb specificities similar to those elicited in macaques by vaccination were isolated from the human living with HIV from which the CH505 Env immunogen was derived. CH505 viral isolates were isolated that mutated the V1 to escape both the infection-induced and vaccine-induced antibodies. These results define the specificities of a vaccine-induced nAb response and the protective titers of HIV-1 vaccine-induced nAbs required to protect nonhuman primates from low-dose mucosal challenge by SHIVs bearing a primary transmitted/founder Env.

Lipid nanoparticle encapsulated nucleoside-modified mRNA vaccines elicit polyfunctional HIV-1 antibodies comparable to proteins in nonhuman primates.

The development of an effective AIDS vaccine remains a challenge. Nucleoside-modified mRNAs formulated in lipid nanoparticles (mRNA-LNP) have proved to be a potent mode of immunization against infectious diseases in preclinical studies, and are being tested for SARS-CoV-2 in humans. A critical question is how mRNA-LNP vaccine immunogenicity compares to that of traditional adjuvanted protein vaccines in primates. Here, we show that mRNA-LNP immunization compared to protein immunization elicits either the same or superior magnitude and breadth of HIV-1 Env-specific polyfunctional antibodies. Immunization with mRNA-LNP encoding Zika premembrane and envelope or HIV-1 Env gp160 induces durable neutralizing antibodies for at least 41 weeks. Doses of mRNA-LNP as low as 5 µg are immunogenic in macaques. Thus, mRNA-LNP can be used to rapidly generate single or multi-component vaccines, such as sequential vaccines needed to protect against HIV-1 infection. Such vaccines would be as or more immunogenic than adjuvanted recombinant protein vaccines in primates.

SARS-CoV-2 vaccination induces neutralizing antibodies against pandemic and pre-emergent SARS-related coronaviruses in monkeys.

Betacoronaviruses (betaCoVs) caused the severe acute respiratory syndrome (SARS) and Middle East Respiratory Syndrome (MERS) outbreaks, and now the SARS-CoV-2 pandemic. Vaccines that elicit protective immune responses against SARS-CoV-2 and betaCoVs circulating in animals have the potential to prevent future betaCoV pandemics. Here, we show that immunization of macaques with a multimeric SARS-CoV-2 receptor binding domain (RBD) nanoparticle adjuvanted with 3M-052-Alum elicited cross-neutralizing antibody responses against SARS-CoV-1, SARS-CoV-2, batCoVs and the UK B.1.1.7 SARS-CoV-2 mutant virus. Nanoparticle vaccination resulted in a SARS-CoV-2 reciprocal geometric mean neutralization titer of 47,216, and robust protection against SARS-CoV-2 in macaque upper and lower respiratory tracts. Importantly, nucleoside-modified mRNA encoding a stabilized transmembrane spike or monomeric RBD protein also induced SARS-CoV-1 and batCoV cross-neutralizing antibodies, albeit at lower titers. These results demonstrate current mRNA vaccines may provide some protection from future zoonotic betaCoV outbreaks, and provide a platform for further development of pan-betaCoV nanoparticle vaccines.

The Functional Medicine Approach to COVID-19: Virus-Specific Nutraceutical and Botanical Agents.

As the novel infection with SARS-CoV-2 emerges, objective assessment of the scientific plausibility of nutraceutical and botanical interventions for prevention and treatment is important. We evaluate twelve such interventions with mechanisms of action that modulate the immune system, impair viral replication, and/or have been demonstrated to reduce severity of illness. These are examples of interventions that, mechanistically, can help protect patients in the presence of the prevalent and infectious SARS-CoV-2 virus. While there are limited studies to validate these agents to specifically prevent COVID-19, they have been chosen based upon their level of evidence for effectiveness and safety profiles, in the context of other viral infections. These agents are to be used in a patient-specific manner in concert with lifestyle interventions known to strengthen immune response (see related article in this issue of IMCJ).

Lipid nanoparticle encapsulated nucleoside-modified mRNA vaccines elicit polyfunctional HIV-1 antibodies comparable to proteins in nonhuman primates.

Development of an effective AIDS vaccine remains a challenge. Nucleoside-modified mRNAs formulated in lipid nanoparticles (mRNA-LNP) have proved to be a potent mode of immunization against infectious diseases in preclinical studies, and are being tested for SARS-CoV-2 in humans. A critical question is how mRNA-LNP vaccine immunogenicity compares to that of traditional adjuvanted protein vaccines in primates. Here, we found that mRNA-LNP immunization compared to protein immunization elicited either the same or superior magnitude and breadth of HIV-1 Env-specific polyfunctional antibodies. Immunization with mRNA-LNP encoding Zika premembrane and envelope (prM-E) or HIV-1 Env gp160 induced durable neutralizing antibodies for at least 41 weeks. Doses of mRNA-LNP as low as 5 µg were immunogenic in macaques. Thus, mRNA-LNP can be used to rapidly generate single or multi-component vaccines, such as sequential vaccines needed to protect against HIV-1 infection. Such vaccines would be as or more immunogenic than adjuvanted recombinant protein vaccines in primates.

Effect of L-carnitine pretreatment on 3-nitropropionic acid-induced inhibition of rat brain succinate dehydrogenase activity.

L-Carnitine (LC) plays an important regulatory role in the mitochondrial transport of long chain free fatty acids (FFA). 3-Nitropropionic acid (3-NPA) is known to induce cellular energy deficit and oxidative stress-related neurotoxicity via an irreversible inhibition of mitochondrial succinate dehydrogenase (SDH). In the present study, activity of SDH was measured in order to evaluate neuroprotective effects of LC against the 3-NPA-induced neurotoxicity. Male, CD Sprague-Dawley rats, three months old, were injected with either 50 or 100 mg/kg of LC, i.p., 30 min prior to 3-NPA (30 mg/kg, s.c.) or with 3-NPA alone. The activity of brain SDH was quantified spectrophotometrically in caudate nucleus (CN), frontal cortex (FC), and hippocampus (HIP) 60 min after the 3-NPA injection. The SDH activity in the animals treated with 3-NPA alone was 38% (CN), 50% (FC), and 36% (HIP) that of saline controls. Pretreatment with LC prior to 3-NPA injection attenuated decreases of SDH activity by approximately 15 and 29% (LC low and high dose, respectively). Despite the attenuation of SDH inhibition, the activity of SDH in these regions remained significantly lower in treated than in control rats (p < 0.05). It appears that the protective effect of LC against 3-NPA-induced oxidative stress cannot be explained by the direct action of LC to interfere with the SDH inhibition but are rather achieved by LC actions downstream of the SDH inhibition.

Biomarkers of 3-nitropropionic acid (3-NPA)-induced mitochondrial dysfunction as indicators of neuroprotection.

In humans or animals, symptoms of mitochondrial energy dysfunction may be produced by mutations or inborn errors of the necessary enzymes, as well as by enzyme inhibitors or uncouplers of the oxidative phosphorylation process. 3-Nitropropionic acid (3-NPA) is a toxin that is sometimes produced on moldy crops (sugarcane, peanuts, etc.) in amounts sufficient to cause severe neuromuscular disorders when consumed by humans. In vitro, 3-NPA irreversibly inactivates SDH, a Complex II respiratory enzyme important for mitochondrial energy production. We have been studying biomarkers of 3-NPA exposure in the expectation that such markers may be useful in the screening process to identify neuroprotective agents against neurotoxicity produced by mitochondrial energy dysfunction. Animals were sacrificed at various times after 3-NPA exposure for histochemical visualization of SDH activity and measurement of immediate postmortem rectal temperature. 3-NPA-treated rats experienced progressive hypothermia that reached a loss of 3 degrees C or more in core body temperature by three hours after dosing. The optical density of the SDH stain in brain was reduced, following a similar time course, most prominently in the cerebellum and least sharply in the thalamus. Some rats were given injections of L-carnitine (an enhancer of fatty acid transport) either alone, or as a pretreatment prior to a dose of 3-NPA. Although L-carnitine deficiency by itself can produce mitochondrial dysfunction, pretreatment with L-carnitine was of limited efficacy at overcoming the effects of 3-NPA on either body temperature or quantitative SDH histochemistry. Body temperature and SDH histochemistry may be useful biomarkers for evaluating the efficacy of neuroprotective agents against lower doses of 3-NPA, against other pharmacological models of mitochondrial dysfunction, or even against genetic mitochondrial diseases.

Contraceptive effectiveness of a polyurethane condom and a latex condom: a randomized controlled trial.

OBJECTIVE: To compare the contraceptive effectivenesses of a polyurethane condom and a standard latex condom. Secondary outcomes of interest were safety, functionality, discontinuation, and acceptability. METHODS: We randomized 901 couples to use either the polyurethane condom or a standard latex condom as their only form of contraception. We tested for pregnancy at enrollment and at every scheduled follow-up visit (weeks 4, 10, 16, 22, and 30). RESULTS: The 6-month typical-use pregnancy probabilities were 9.0% (95% confidence interval [CI] 5.9, 12.2) for the polyurethane group and 5.4% (95% CI 2.9, 7.8) for the latex group; the hazard ratio was 1.7 (95% CI 1.1, 2.7), and we failed to reject the null hypothesis of our test of noninferiority. Females in the polyurethane group reported fewer genital irritations (hazard ratio 0.6; 95% CI 0.5, 0.8; P <.01), whereas males in both groups reported the same number of genital irritations (hazard ratio 1.0; 95% CI 0.7, 1.5; P =.94). Total clinical failures (breakage and slippage) were 8.4% for the polyurethane condom and 3.2% for the latex condom (difference 5.3%, 90% CI 2.8, 7.7). The risk of discontinuation did not differ between groups. Participants judged both condoms favorably in terms of the four primary acceptability outcomes (willingness to purchase, willingness to recommend, confidence in method, and general comfort). CONCLUSION: The polyurethane condom was not shown to be as effective as the latex comparator condom for pregnancy prevention. However, the risk of pregnancy in the polyurethane group falls in the range of other barrier methods. For people with latex sensitivity or who find latex condoms unacceptable, this polyurethane condom represents one of several synthetic male condom alternatives currently available on the US market.

Meclizine for prevention of nausea associated with use of emergency contraceptive pills: a randomized trial.

OBJECTIVE: We conducted a randomized trial to determine whether pretreatment with meclizine reduces the incidence of nausea and vomiting associated with the Yuzpe regimen of emergency contraception. METHODS: We randomly assigned 343 women aged 18-45 years who were not at risk for pregnancy to pretreatment with 50 mg of meclizine, placebo, or no drug 1 hour before the first of two doses of emergency contraceptive pills. We asked participants to complete three questionnaires over the following 48 hours. RESULTS: The incidence of nausea was 47% in the group pretreated with meclizine and 64% in the other two groups (relative risk adjusted for center 0.7, 95% confidence intervals 0.6, 0.9 for comparisons of meclizine with both placebo and no drug). The severity of nausea and the incidence of vomiting were also significantly lower in the meclizine pretreatment group than in the other two groups. Drowsiness was reported by about twice as many women in the meclizine pretreatment group (31%) than in the other two groups (13% in the placebo group, 16% in the no-pretreatment group; P < .01 for both comparisons). CONCLUSION: Meclizine is effective for preventing nausea and vomiting associated with the Yuzpe regimen of emergency contraceptive pills. Women using this drug should be cautioned to anticipate drowsiness.

A dose-response study of ibogaine-induced neuropathology in the rat cerebellum.

Ibogaine (IBO) is an indole alkaloid from the West African shrub, Tabernanthe iboga. It is structurally related to harmaline, and both these compounds are rigid analogs of melatonin. IBO has both psychoactive and stimulant properties. In single-blind trials with humans, it ameliorated withdrawal symptoms and interrupted the addiction process. However, IBO also produced neurodegeneration of Purkinje cells and gliosis of Bergmann astrocytes in the cerebella of rats given even a single dose (100 mg/kg, ip). Here, we treated rats (n = 6 per group) with either a single ip injection of saline or with 25 mg/kg, 50 mg/kg, 75 mg/kg, or 100 mg/kg of IBO. As biomarkers of cerebellar neurotoxicity, we specifically labeled degenerating neurons and axons with silver, astrocytes with antisera to glial fibrillary acidic protein (GFAP), and Purkinje neurons with antisera to calbindin. All rats of the 100-mg/kg group showed the same pattern of cerebellar damage previously described: multiple bands of degenerating Purkinje neurons. All rats of the 75-mg/ kg group had neurodegeneration similar to the 100-mg/kg group, but the bands appeared to be narrower. Only 2 of 6 rats that received 50 mg/kg were affected; despite few degenerating neuronal perikarya, cerebella from these rats did contain patches of astrocytosis similar to those observed with 75 or 100 mg/kg IBO. These observations affirm the usefulness of GFAP immunohistochemistry as a sensitive biomarker of neurotoxicity. None of the sections from the 25-mg/kg rats, however stained, were distinguishable from saline controls, indicating that this dose level may be considered as a no-observable-adverse-effect level (NOAEL).

Quantitating silver-stained neurodegeneration: the neurotoxicity of trimethlytin (TMT) in aged rats.

This report describes the development of a histoanalytical procedure to measure the degree of neurodegeneration produced by the organometal toxicant trimethyltin (TMT). Based on a previous, non-quantitated experiment we hypothesized that the same dose of TMT would produce greater damage in animals of increasing age. Male rats aged 6, 12, 18, or 24 months at the time of dosing were given either 4.5 mg/kg TMT or saline (i.p.). One month after dosing, rats were perfused and their brains removed and processed to selectively silver-impregnate degenerating cell bodies as well as axon terminals and dendrites. Neurodegeneration was most prominent in the hippocampi (especially CA1 stratum radiatum) of TMT-treated rats, but not in the controls. Computer-assisted counting of the silver grains marking damage indicated greater neurotoxicity from the same dose of TMT when given to the older animals. Thus the grain density in the 6-month-old TMT-treated rats was not significantly elevated from the 6-month-old controls (P>0.10). The 12-month-old TMT-treated rats had significantly increased grain densities compared to their controls (P<0.05), but still larger increases of grain counts were observed in the 18- and 24-month-old rats (both P-values<0.01). Our findings with TMT are similar to previous, but nonquantitative, reports that the neurotoxic effects of kainic acid and methionine sulfoximine were also greater in older rats. An increased sensitivity to neurotoxicants might help explain the apparently spontaneous degeneration of cortical neurons in aging and in the neurological diseases of old age. The method we report here for quantitation of silver grains marking neurodegeneration should be adaptable to a wide range of histologically-based neurotoxicology investigations.

Neuronal degeneration in rat forebrain resulting from D-amphetamine-induced convulsions is dependent on seizure severity and age.

Neuronal damage and degeneration in the rat forebrain was characterized by B4 isolectin and Fluoro-Jade labeling techniques after 4 doses of 15 mg/kg amphetamine i.p. in 70- and 180-day-old Sprague-Dawley rats. In amphetamine-dosed rats some seizure activity occurred in all rats exhibiting pronounced hyperthermia but the degree of seizure activity varied greatly between individual rats. Over 90% of the rats in both age groups that showed behavioral signs of limbic seizures had somatic degeneration in the taenia tecta within 3 days of amphetamine exposure. Degenerating small star-shaped cells were seen in the septum and hippocampus in 70-day-old rats having extensive seizure activity. Although somatic degeneration only sporadically occurred in the piriform cortex of the younger rats, extensive B4 isolectin binding to activated microglia was observed in this area. In older rats prominent somatic degeneration was seen in the piriform cortex and orbital and insular areas of the frontal cortex of rats having seizures. Damage to the basal ganglia and related areas, including the thalamus, parietal cortex and dorsal medial striatum, occurred in rats with pronounced hyperthermia but only correlated with seizures in older rats. In the more severe cases of thalamic damage the highest density of neurodegeneration was localized perivascularly. Thus, amphetamine can produce notable damage to the limbic system when seizures occur and to the basal ganglia and related areas when hyperthermia occurs but the neurotoxicity profiles in these areas are age-dependent and not produced solely by hyperthermia. Further studies to determine whether neuronal damage is the result of or the cause of amphetamine-induced seizures are necessary.

Evaluation of neurodegeneration in scrapie-infected animals by selective methods that detect cellular degeneration.

Scrapie is a fatal neurodegenerative disease of sheep and goats. The precise details of neuronal and neurite degeneration in scrapie-infected animals remain unknown. Using specific silver staining methods, we compared the neurodegeneration caused by treatment of rats with kainic acid (KA) or ibogaine (IBO) to the neuropathology observed in mice infected with the C602 strain of scrapie. As reported previously, KA resulted in extensive silver labeling of neurons, especially in the cortex, putamen and hippocampus. IBO silver labeling was observed only in small clusters of Purkinje neurons in the paravermal region of the cerebellum. However, in scrapie-infected mice, a few silver stained neurons (differing from the dark degenerating neurons observed following neurotoxic exposure) were found in layer II of cortex, cingulate cortex, zona incerta, thalamus and hypothalamus. Some silver grains were observed in glial-like cells, especially those in the paraventricular region. Degenerating axons were positive for silver staining and were found in the cortex, cingulate cortex, corpus callosum, habenulae, septum, fornix, thalamus, caudate putamen and a few in fasciculus retroflexus and substantia nigra. Our results suggest that the limbic system is one of the important loci for the neurodegenerative effect of at least some scrapie strains.

Domoic acid-treated cynomolgus monkeys (M. fascicularis): effects of dose on hippocampal neuronal and terminal degeneration.

Domoic acid is a tricarboxylic amino acid (structurally related to kainic acid and glutamic acid) that is found in the environment as a contaminant of some seafood. To determine the nature of any neurological damage caused by domoate, as well as the minimum neurotoxic dose, juvenile and adult monkeys were dosed intravenously with domoate at one of a range of doses from 0.25 to 4 mg/kg. When animals were perfused one week later, histochemical staining using a silver method to reveal degenerating axons and cell bodies showed two distinct types of hippocampal lesions. One lesion, termed 'Type A', was a small focal area of silver grains restricted to CA2 stratum lucidum, the site of greatest kainic acid receptor concentration in the brain. Type A lesions occurred over a dose range of 0.5 to 2.0 mg/kg in juvenile animals and 0.5 to 1.0 mg/kg in adult animals. No mortality occurred in any of the juvenile monkeys, but one juvenile animal that received 4.0 mg/kg sustained a second type of lesion, termed 'Type B', characterized by widespread damage to pyramidal neurons and axon terminals of CA4, CA3, CA2, CA1, and subiculum subfields of the hippocampus. Doses of more than 1.0 mg/kg in the adult monkeys either proved lethal or resulted in Type B lesions. Induction of c-fos protein had occurred in the hippocampal dentate gyrus and CA1 regions of moribund animals perfused within hours of their initial dose.(ABSTRACT TRUNCATED AT 250 WORDS)