Hsp27 protects mitochondria of thermotolerant cells against apoptotic stimuli

Enhanced cell survival and resistance to apoptosis during thermotolerance correlates with an increased expression of heat shock proteins (Hsps). Here we present additional evidence in support of the hypothesis that the induction of Hsp27 and Hsp72 during acquired thermotolerance in Jurkat T-lymphocytes prevents apoptosis. In thermotolerant cells, Hsp27 was shown to associate with the mitochondrial fraction, and inhibition of Hsp27 induction during thermotolerance in cells transfected with hsp27 antisense potentiated mitochondrial cytochrome c release after exposure to various apoptotic stimuli, despite the presence of elevated levels of Hsp72. Caspase activation and apoptosis were inhibited under these conditions. In vitro studies revealed that recombinant Hsp72 more efficiently blocked cytochrome c-mediated caspase activation than did recombinant Hsp27. A model is presented for the inhibition of apoptosis during thermotolerance in which Hsp27 preferentially blocks mitochondrial cytochrome c release, whereas Hsp72 interferes with apoptosomal caspase activation.

Accelerated telomere shortening following allogeneic transplantation is independent of the cell source and occurs within the first year post transplant

Telomere shortening has been documented in the blood cells of recipients of allogeneic bone marrow transplants compared with their donors. Allogeneic peripheral blood progenitor cells (PBPCs) have been increasingly used as an alternative to bone marrow. Their advantages include earlier engraftment and immune reconstitution following transplantation. We have measured telomere length of neutrophils and T cells in fully engrafted recipients of allogeneic bone marrow (n = 19) and allogeneic PBPC (n = 17) and also measured sequential telomere length in four patients after transplantation. Overall, significant telomere shortening occurred in recipients in neutrophils (0.3 kb, P < 0.001) and T cells (0.2 kb, P = 0.045). The data demonstrate that first, the degree of shortening was the same for BM and PBPC transplants and was not related to the time taken to engraft neutrophils and platelets and second, telomere shortening occurs in the first year post transplant without further shortening during the period of observation. These data suggest that the superiority of engraftment seen in PBPC transplants is independent of telomere shortening and other mechanisms such as homing or seeding may be more important.

Cytochrome c release occurs via Ca2+-dependent and Ca2+-independent mechanisms that are regulated by Bax

Release of cytochrome c from mitochondria is a key initiative step in the apoptotic process, although the mechanisms regulating this event remain elusive. In the present study, using isolated liver mitochondria, we demonstrate that cytochrome c release occurs via distinct mechanisms that are either Ca(2+)-dependent or Ca(2+)-independent. An increase in mitochondrial matrix Ca(2+) promotes the opening of the permeability transition (PT) pore and the release of cytochrome c, an effect that is significantly enhanced when these organelles are incubated in a reaction buffer that is based on a physiologically relevant concentration of K(+) (150 mm KCl) versus a buffer composed of mannitol/sucrose/Hepes. Moreover, low concentrations of Ca(2+) are sufficient to induce mitochondrial cytochrome c release without measurable manifestations of PT, though inhibitors of PT effectively prevent this release, indicating that the critical threshold for PT varies among mitochondria within a single population of these organelles. In contrast, Ca(2+)-independent cytochrome c release is induced by oligomeric Bax protein and occurs without mitochondrial swelling or the release of matrix proteins, although our data also indicate that Bax enhances permeability transition-induced cytochrome c release. Taken together, our results suggest that the intramitochondrial Ca(2+) concentration, as well as the reaction buffer composition, are key factors in determining the mode and amount of cytochrome c release. Finally, oligomeric Bax appears to be capable of stimulating cytochrome c release via both Ca(2+)-dependent and Ca(2+)-independent mechanisms.

Hsp27 protects mitochondria of thermotolerant cells against apoptotic stimuli

Enhanced cell survival and resistance to apoptosis during thermotolerance correlates with an increased expression of heat shock proteins (Hsps). Here we present additional evidence in support of the hypothesis that the induction of Hsp27 and Hsp72 during acquired thermotolerance in Jurkat T-lymphocytes prevents apoptosis. In thermotolerant cells, Hsp27 was shown to associate with the mitochondrial fraction, and inhibition of Hsp27 induction during thermotolerance in cells transfected with hsp27 antisense potentiated mitochondrial cytochrome c release after exposure to various apoptotic stimuli, despite the presence of elevated levels of Hsp72. Caspase activation and apoptosis were inhibited under these conditions. In vitro studies revealed that recombinant Hsp72 more efficiently blocked cytochrome c-mediated caspase activation than did recombinant Hsp27. A model is presented for the inhibition of apoptosis during thermotolerance in which Hsp27 preferentially blocks mitochondrial cytochrome c release, whereas Hsp72 interferes with apoptosomal caspase activation.

Distinct pathways for stimulation of cytochrome c release by etoposide

Induction of apoptosis by DNA-damaging agents, such as etoposide, is known to involve the release of mitochondrial cytochrome c, although the mechanism responsible for this event is unclear. In the present study, using Jurkat T-lymphocytes, a reconstituted cell-free system, or isolated liver mitochondria, we demonstrate the ability of etoposide to induce cytochrome c release via two distinct pathways. Caspase inhibition by either benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (z-VAD-fmk) or benzyloxycarbonyl-Val-Asp-Val-Ala-Asp-fluoromethyl ketone (z-VDVAD-fmk) attenuates cytochrome c release triggered by a low dose of etoposide via an apparent inhibition of nuclear events involving the release of protein factor(s) that is (are) able to interact with mitochondria. In contrast, caspase inhibition has no effect on cytochrome c release induced by a higher dose of etoposide. Moreover, the higher dose of etoposide heightens the sensitivity of Ca(2+)-loaded isolated mitochondria to mitochondrial permeability transition, an effect that is completely abolished by cyclosporin A. Interestingly, cyclosporin A is ineffective at preventing similar mitochondrial damage in Jurkat cells treated with etoposide. We propose that lower doses of etoposide predominantly target the nucleus and stimulate the release of caspase-sensitive protein factor(s) that interact with mitochondria to trigger cytochrome c release, whereas higher doses of the drug impart a more direct effect on mitochondria and thus are not mitigated by caspase inhibition.

Molecular mechanisms of apoptosis induced by cytotoxic chemicals

The purpose of this review article is to discuss established molecular mechanisms of apoptosis and their relevance to cell death induced by environmental toxicants. Apoptosis is a highly regulated form of cell death distinguished by the activation of a family of cysteine-aspartate proteases (caspases) that cleave various proteins resulting in morphological and biochemical changes characteristic of this form of cell death. Abundant evidence supports a role for mitochondria in regulating apoptosis. Specifically, it seems that a number of death stimuli target these organelles and stimulate, by an unknown mechanism, the release of several proteins, including cytochrome c. Once released into the cytosol, cytochrome c binds to its adaptor molecule, Apaf-1, which oligomerizes and then activates pro-caspase-9. Caspase-9 can signal downstream and activate pro-caspase-3 and -7. The release of cytochrome c can be influenced by different Bcl-2 family member proteins, including, but not limited to, Bax, Bid, Bcl-2, and Bcl-X(L). Bax and Bid potentiate cytochrome c release, whereas Bcl-2 and Bcl-X(L) antagonize this event. Although toxicologists have traditionally associated cell death with necrosis, emerging evidence suggests that different types of environmental contaminants exert their toxicity, at least in part, by triggering apoptosis. The mechanism responsible for eliciting the pro-apoptotic effect of a given chemical is often unknown, although in many instances mitochondria appear to be key participants. This review describes our current understanding of the role of apoptosis in environmental toxicant-induced cell death, using dioxin, metals (cadmium and methylmercury), organotin compounds, dithiocarbamates, and benzene as specific examples. Finally, we conclude with a critical discussion of the current knowledge in this area and provide recommendations for future directions.

Speciation of elements in NIST particulate matter SRMs 1648 and 1650

X-ray absorption fine structure (XAFS) spectra for S, Cl, V, Cr, Mn, Cu, Zn, As, Br, Cd and Pb and Mossbauer spectra for Fe have been obtained for two National Institute of Standards and Technology (NIST) particulate matter (PM) standard reference materials (SRMs): urban PM (SRM 1648) and diesel PM (SRM 1650). The spectral data, complemented by information on elemental concentrations from proton-induced X-ray-emission (PIXE) spectroscopy, were used to interpret the speciation of these elements in these complex materials. It appears that all the metallic elements investigated occur in oxidized forms, principally as sulfates in the diesel PM SRM and as sulfates, oxides, and possibly other forms (e.g. clays?) in the urban PM. A minor fraction of the sulfur and major fractions of the halogens, Cl and Br, occur as organosulfide (thiophene) and organohalide occurrences, respectively, that must be associated with the abundant carbonaceous matter that constitutes the major component of the two PM SRMs. Most of the sulfur, however, occurs as sulfate in the urban PM and as bisulfate in the diesel PM. In addition, elemental oxidation states have been determined directly by the spectroscopic techniques. Such information is often the key parameter in determining the toxicity and solubility of specific elements in PM, both of which are important in understanding the threat that such elements may pose to human health. For the two HAP elements, Cr and As, for which the toxicity depends greatly on oxidation state, the XAFS data showed that both elements are present in both SRMs predominantly in the less toxic oxidation states, Cr(III) and As(V). The potential of the XAFS spectra for use as source apportionment signatures is illustrated by reference to chromium, which exists in these two PM SRMs in very different forms.

Dynamics of telomere shortening in neutrophils and T lymphocytes during ageing and the relationship to skewed X chromosome inactivation patterns

Human haemopoiesis undergoes profound changes throughout life, resulting in compromised regenerative capacity of haemopoietic stem cells. It has been suggested that telomere shortening results in senescence of haemopoietic stem cell subsets and may influence the balance between stem cell renewal and proliferation. Telomere length and telomerase activity was measured in whole blood leucocytes, neutrophils and T cells from cord blood and individuals aged from 1 year to 96 years. Rapid telomere shortening [700 base pairs (bp)] was demonstrated in the first year of life, followed by a gradual decline of 31 bp/year. T cells were shown to have longer telomeres than neutrophils (mean difference 372 bp, P = < 0.001) but demonstrated similar rates of shortening (20 +/- 0.3 bp/year vs. 22 +/- 0.3 bp/year). Telomerase was detectable in T cells but not in neutrophils, suggesting that telomerase is not the rate-limiting step for regulation of telomere length in haemopoietic cells. Stem cell utilization as measured by X chromosome inactivation patterns was found to be independent of telomere length. This supports the concept that age-dependent skewed haemopoiesis is the result of random stem cell loss or X-allelic exclusion rather than telomeric senescence. These studies provide insight into the ageing process and a reference point for evaluating replicative stress in individuals of different age groups.

Immunogenicity of vaccination against influenza, Streptococcus pneumoniae and Haemophilus influenzae type B in patients with multiple myeloma

Vaccination against influenza and Streptococcus pneumoniae is recommended for elderly and immunocompromised individuals. However, there is little information concerning the efficacy of vaccination in specific groups of patients. In this study, 52 patients underwent vaccination against influenza, S. pneumoniae and Haemophilus influenzae type b (Hib) as they attended hospital outpatient clinics. Serum was analysed prior to vaccination and 4-6 weeks afterwards. Antibody titres against S. pneumoniae and Hib were compared with reference values corresponding to the geometric mean titres of a healthy UK population. For influenza vaccination, haemagglutination inhibition (HI) titres were measured against three inactivated strains; a titre of > or = 1/40 was considered protective. No patient had protective titres to all three antigens prior to vaccination and 41 patients (85%) had titres < 1/40 to all 3 strains. Post vaccination only 9/48 patients (19%) achieved protective antibody titres. Resistance to S. pneumoniae and response to Pneumovax II was also poor: prevaccination, 45 patients (93%) had suboptimal antibody titres and in 26/43 patients (61%) titres remained low post vaccination. Resistance to Hib and response to vaccination was comparable with the healthy adult UK population. These results question the practice of routine influenza and pneumococcal vaccination in myeloma patients.

Review: nuclear events in apoptosis

Initial apoptosis research characterized this form of cell death based on distinct nuclear morphology that was subsequently shown to be associated with the appearance of oligonucleosomal DNA fragments. More recent evidence has indicated that apoptosis depends upon a tightly regulated cellular program for its successful initiation and execution. Molecular participants in this program are present in different subcellular compartments, including the plasma membrane, cytosol, mitochondria, and nucleus. The interplay among these compartments and the exchange of specific signaling molecules are critical for the systematic progression of apoptosis. While numerous reports have described a key role for caspase activity in the signaling and executive steps of apoptotic cell death, there are some instances where well-established nuclear changes, characteristic of this form of cell death, can occur independently of caspase activity. Moreover, evidence indicates that certain nuclear events, including chromatin condensation and DNA fragmentation, are controlled separately and depend upon a persistent supply of energy in vivo. In this review, we discuss our current understanding of the role and regulation of nuclear events in the apoptotic process with an emphasis on protease and endonuclease activities as well as the ability of certain Bcl-2 family proteins to influence this process.

Serum zinc levels and Alzheimer's disease

Concentrations of zinc in postmortem serum and four brain regions were measured by flame atomic absorption spectrometry and instrumental neutron activation analysis, respectively, in nine Alzheimer's disease (AD) and eight control subjects. A statistically significant elevation of zinc serum was observed in AD subjects (136.4+/-66.8 microg/dL) compared with age-matched control subjects (71.1+/-35.0 microg/dL). No significant differences were observed between AD and control zinc concentrations in the amygdala, hippocampus, cerebellum, and superior and middle temporal gryi.

Glutathione oxidation and mitochondrial depolarization as mechanisms of nordihydroguaiaretic acid-induced apoptosis in lipoxygenase-deficient FL5.12 cells

Nordihydroguaiaretic acid (NDGA) induces apoptosis in a variety of cell lines. The mechanism(s) of this effect is not known, although the focus has been on the ability of NDGA to inhibit lipoxygenase (LOX) activities. In the present study, NDGA-induced apoptosis was studied in a murine hematopoietic cell line, FL5.12. Although this cell line lacks detectable LOX protein or activities, NDGA (10 microM) was able to induce apoptosis. There was a massive loss of mitochondrial membrane potential by 4 h after the addition of NDGA, suggesting that this organelle might be targeted by NDGA. A pro-oxidant NDGA effect has been suggested as playing a role in apoptosis. This was supported by the findings that glutathione disulfide levels were increased by 4 h following treatment with 10 microM NDGA, that pretreatment with N-acetylcysteine completely blocked the NDGA-induced loss of membrane potential and apoptosis, and that lipid peroxidation was enhanced in cells treated with NDGA. However, no evidence of increased levels of reactive oxygen could be seen in NDGA-treated cells loaded with dichlorofluorescin diacetate or dihydrorhodamine and analyzed by flow cytometry. Bcl-X(L) protein levels were unaffected by NDGA treatment. Caspase-3 was rapidly activated with a peak at 8 h after FL5.12 cells were treated with NDGA. Ac-DEVD-CHO (25 microM) and boc-asp-FMK (20 microM) both inhibited caspase-3 enzyme activity by 97% 8 h after NDGA treatment. Boc-asp-FMK, a more general caspase inhibitor, delayed NDGA-induced apoptosis while Ac-DEVD-CHO, a more specific inhibitor of caspase-3, had no effect. These results suggest that NDGA-induced apoptosis happens through reactions that depolarize mitochondria, oxidize glutathione and lipids, but do not generate significant amounts of free reactive oxygen species.

Heat-shock protein 70 antisense oligomers enhance proteasome inhibitor-induced apoptosis

Recent evidence supports a role for heat-shock protein 70 (hsp70) and the 26 S proteasome in regulating apoptosis, although the precise nature of their involvement is not known. In the present study, control and Bcl-x(L)-overexpressing, interleukin-3-dependent FL5.12 cell lines were treated with the proteasome inhibitor N-benzoyloxycarbonyl (Z)-Leu-Leu-leucinal (MG132). Basal proteasome activity appeared to be approximately 30% lower in bcl-x(L) cells compared with control cells using a substrate for the chymotrypsin-like activity. However, no difference in proteasome activity was detected using substrates for the trypsin-like or peptidylglutamyl peptide-hydrolysing activities. In addition, protein levels of the 20 S proteasome beta-subunit, as determined by Western blot analyses, were similar in control and bcl-x(L) cells, leading to the conclusion that proteasome activities were the same in these two cell lines. At 24 h after treatment with 500 nM MG132, apoptosis in bcl-x(L) cells (22%) was less than that observed in control cells (34%). Concomitantly, caspase activity in control cells, as assessed by N-acetyl-l-aspartyl-l-glutamyl-l-valyl-l-aspartyl-7-amino-4-methylcou marin (Ac-DEVD-AMC), was twice that observed in bcl-x(L) cells. By 48 h after MG132 treatment, apoptosis and caspase activity in bcl-x(L) cells were similar to those observed in control cells at 24 h. Proteasome inhibition stimulated increases in hsp70 protein levels in control and bcl-x(L) cells by 12 h, although the maximal increases found in bcl-x(L) cells were less. Blocking this induction with hsp70 antisense oligonucleotides potentiated apoptosis after treatment with MG132. Inhibiting caspase activity with a broad-spectrum caspase inhibitor, t-butoxycarbonyl-Asp(OMe)-fluoromethyl ketone, prevented MG132-induced apoptosis. The more specific caspase-3 inhibitor, Ac-DEVD-aldehyde, afforded less protection, although both inhibitors completely inhibited Ac-DEVD-AMC cleavage. These data indicate that both hsp70 and Bcl-x(L) provide some protection against proteasome inhibitor-induced apoptosis.

Copper, iron and zinc in Alzheimer's disease senile plaques

Concentrations of copper (Cu), iron (Fe) and zinc (Zn) were measured in the rims and cores of senile plaques (SP) and in the neuropil of the amygdala of nine Alzheimer's disease (AD) patients and in the neuropil of the amygdala of five neurologically normal control subjects using micro particle-induced X-ray emission (micro-PIXE). Comparison of SP rim and core values revealed no significant differences between levels of Cu, Fe or Zn. Zinc and Fe in SP rims and cores were significantly elevated in AD compared with AD neuropil (P<0.05). Copper was significantly elevated (P<0.05) in the rim of SP compared with AD neuropil. Comparison of AD and control neuropil revealed a significant (P<0.05) elevation of Zn in AD subjects. The elevation of these elements in SP in AD is of interest in light of the observation that Cu, Fe and particularly Zn, can accelerate aggregation of amyloid beta peptide.

Cosubstrates involved in the reduction of cytosolic glutathione disulfide in rat heart

The functionality of glutathione (GSH), which is present in separate mitochondrial and cytosolic pools, hinges on a steady supply of reducing equivalents, provided by NADPH, to convert glutathione disulfide (GSSG) to GSH. It is believed traditionally that glucose 6-phosphate (G6-P) via the pentose phosphate pathway is the main cellular source of NADPH. The current study examined the ability of NADH- and NADPH-linked cosubstrates to support cardiac cytosolic GSSG reduction. Exogenous NADP+ was added to the incubation mixtures because of the loss of this nucleotide during homogenization. Exogenous GSSG was added to all samples to levels that were approximately 60% of total glutathione. In both the 500 x g (with mitochondria) and 10,000 x g (without mitochondria) rat heart supernatants, isocitrate supported reduction of approximately 90% of available GSSG within 10 min. Malate, pyruvate and palmitoyl carnitine did not support GSSG reduction in either supernatant. G6-P yielded GSH levels within 10 min equal to 77% of total glutathione in the 1,0000 x g supernatant and 47% in the 500 x g supernatant. The current data indicate: (1) The pentose phosphate pathway, alone, is less efficient than isocitrate at supplying reducing equivalents for cytosolic GSSG reduction; and (2) some confounding factor(s) occur in the 500 x g and reconstituted 500 x g supernatants whereby G6-P-supported GSSG reduction is attenuated.

Bcl-xL overexpression restricts heat-induced apoptosis and influences hsp70, bcl-2, and Bax protein levels in FL5.12 cells

Although several proteins have been identified that can inhibit stress-induced apoptosis, the cytoprotective potential of bcl-xL against heat shock and its ability to alter hsp70 induction is not known. The current study, using control and bcl-xL-overexpressing IL-3-dependent FL5.12 cells, compared the effects of 1 h of acute heat stress (42 degrees C) followed by 1, 4, and 8 h recovery (37 degrees C) on hsp70, bax, bcl-2, and bcl-xL protein levels and apoptosis. Less than 0.5% of untreated cells were apoptotic. There was significantly more apoptosis in control ( approximately 16%) as compared to bcl-xL cells ( approximately 3%) 8 h after heat stress. Immunoblotting revealed a time-dependent increase in hsp70 protein levels following 1 h of heat stress in control, but not bcl-xL-overexpressing cells. bcl-2 protein levels were lower in bcl-xL-overexpressing cells than in controls, but decreased in both cell lines after heat stress. bax protein levels in bcl-xL-overexpressing cells were decreased approximately 80% below baseline levels 1 h post heat shock. This decrease was maintained to 8 h. No change in bax protein was observed in control cells up to 8 h post heat shock. These data indicate that bcl-xL overexpression mitigates the effects of acute heat stress so that hsp70 induction is eliminated and apoptosis is prevented. The rapid loss of bax protein following heat stress in bcl-xL-overexpressing, but not control, cells may contribute to their resistance to apoptosis. Conversely, the loss of bcl-2 protein following heat stress in control cells may contribute to their susceptibility to apoptosis.

Selenium status of a group of Scottish adults

OBJECTIVE

To examine dietary selenium intake and indices of selenium status (plasma and red blood cell selenium and glutathione peroxidase activities) in apparently healthy Scottish individuals.

DESIGN AND SUBJECTS

One hundred subjects, aged between 40 and 60 y, completed a seven day weighed food intake and provided blood samples for selenium status analysis.

SETTING

Inverurie, Aberdeenshire, Scotland.

RESULTS

Average reported selenium intake was low (43 micrograms/d). A significant number of subjects had reported intakes below the RNI. Low levels of plasma selenium were also found but no subject had values below 40 micrograms/1. Red blood cell selenium was within the reference range established for a healthy UK population. Smoking status had no consistent effect on selenium status.

CONCLUSIONS

The results of the present study suggest that selenium status of certain Scottish individuals may be compromised and that further studies are warranted.

SPONSORSHIP

BASF, Germany; The Tobacco Products Research Trust, UK; Scottish Office Agriculture Environment and Fisheries Department.

Nitric oxide is necessary for visual learning in Octopus vulgaris

We recently reported that inhibition of nitric oxide synthase (NOS) in Octopus vulgaris by intramuscular injections of an analog of L-arginine, N-omega-nitro-L-arginine methyl ester (L-NAME), blocked touch learning in Octopus vulgaris. The inactive enantiomorph (D-NAME), which had no effect on learning, was used for control. We now report that essentially the same procedures block visual learning in this animal. We used a visual paradigm in which the octopus was trained to respond positively to a smooth black plastic ball 2.5 cm diameter and negatively to a similar white ball, or vice versa. One set of eight animals was trained to the black ball positive, and another set of six to the white ball positive. Each set was trained at different times by two different trainers. We found that a 1 h pretreatment with the nitric oxide synthase inhibitor L-NAME blocks visual learning in Octopus vulgaris in both sets of animals.

Cytochalasin D blocks touch learning in Octopus vulgaris

Supraoesophageal lobes in 11 specimens of Octopus vulgaris were split sagitally into two symmetrical halves and isolated by a thin inert mica barrier. Each half-brain is known to control the four arms on its side of the animal and to be able to learn opposite touch paradigms mediated by its four arms. Powdered cytochalasin D was applied directly in each animal to the subfrontal lobe of one half-brain, and both half-brains were then trained to opposite touch paradigms. The cytochalasin treated half-brains could not learn either touch paradigm whereas the control half-brains learned readily. In another set of four animals, cytochalasin D was similarly applied but to the vertical lobe of one half-brain. In this case all the half-brains learned the touch paradigm.

Nitric oxide is required for tactile learning in Octopus vulgaris

Nitric oxide, produced by nitric oxide synthase in brain tissue, is essential for several different kinds of learning in vertebrates. We present the first evidence that it is also essential for learning in an invertebrate. Intramuscular injections of an inhibitor of the enzyme completely block touch learning in Octopus vulgaris. Eight control animals learned a touch paradigm, but none of eight synthase-inhibited ones learned it.

Carbocyanine dye labeling reveals a new motor nucleus in octopus brain

This work aims at a better understanding of the organization of the brain of Octopus vulgaris, emphasizing the touch and visual learning centers. We injected the carbocyanine dye, DiI, into the cerebrobrachial connectives and, separately, into the brachial nerves of living octopuses. In both experiments, retrogradely transported granules of DiI appeared in motor neurons in the superior buccal, posterior buccal and subvertical lobes and in a hitherto unsuspected motor nucleus of several hundred neurons in the posterior dorsal basal and median basal lobes. In addition we labeled afferent fibers by injecting DiI into the caudal (sensory) division of the cerebrobrachial connective on one side; the label spread throughout the superior buccal, posterior buccal and the lateral and median inferior frontal lobes mainly on the injected side. It extended through the cerebral tract into the subvertical lobe, into the superior frontal lobe through the interfrontal tract, through the posterior buccal commissure into the opposite posterior buccal lobe and into the median inferior frontal lobe. The work suggests a new function for the posterior dorsal and median basal lobes, which are shown for the first time to project through the inferior frontal lobe system into the brachial nerves. In addition it represents the first full report of the successful use of the carbocyanine dyes DiI and DiO for labeling nerve tissue in a live invertebrate animal.