Radiation enhances the efficacy of EGFR-targeted CAR-T cells against triple-negative breast cancer by activating NF-κB/Icam1 signaling

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype, with limited treatment options. Epidermal growth factor receptor (EGFR) is reported to be expressed in 50%-75% of TNBC patients, making it a promising target for cancer treatment. Here we show that EGFR-targeted chimeric antigen receptor (CAR) T cell therapy combined with radiotherapy provides enhanced antitumor efficacy in immunocompetent and immunodeficient orthotopic TNBC mice. Intriguingly, this combination therapy resulted in a substantial increase in the number of tumor-infiltrating CAR-T cells. The efficacy of this combination was independent of tumor radiosensitivity and lymphodepleting preconditioning. Cytokine profiling showed that this combination did not increase the risk of cytokine release syndrome (CRS). RNA sequencing (RNA-seq) analysis revealed that EGFR-targeting CAR-T therapy combined with radiotherapy increased the infiltration of CD8+ T and natural killer (NK) cells into tumors. Mechanistically, radiation significantly increased Icam1 expression on TNBC cells via activating nuclear factor κB (NF-κB) signaling, thereby promoting CAR-T cell infiltration and killing. These results suggest that CAR-T therapy combined with radiotherapy may be a promising strategy for TNBC treatment.

Olaparib Suppresses MDSC Recruitment via SDF1α/CXCR4 Axis to Improve the Anti-tumor Efficacy of CAR-T Cells on Breast Cancer in Mice

A hostile tumor microenvironment is one of the major obstacles for the efficacy of chimeric antigen receptor modified T (CAR-T) cells, and combination treatment might be a potential way to overcome this obstacle. Poly(ADP-ribose) polymerase inhibitor (PARPi) has demonstrated tremendous potential in breast cancer. In this study, we explored the possible combination of the PAPRi olaparib with EGFRvIII-targeted CAR (806-28Z CAR) T cells in immunocompetent mouse models of breast cancer. The results indicated that the administration of olaparib could significantly enhance the efficacy of 806-28Z CAR-T cells in vivo. Interestingly, we observed that olaparib could suppress myeloid-derived suppressor cell (MDSC) migration and promote the survival of CD8⁺ T cells in tumor tissue. Mechanistically, olaparib was shown to reduce the expression of SDF1α released from cancer-associated fibroblasts (CAFs) and thereby decreased MDSC migration through CXCR4. Taken together, this study demonstrated that olaparib could increase the antitumor activities of CAR-T cell therapy at least partially through inhibiting MDSC migration via the SDF1α/CXCR4 axis. These findings uncover a novel mechanism of PARPi function and provide additional mechanistic rationale for combining PARPi with CAR-T cells for the treatment of breast cancer.

Armored Inducible Expression of IL-12 Enhances Antitumor Activity of Glypican-3-Targeted Chimeric Antigen Receptor-Engineered T Cells in Hepatocellular Carcinoma

Adoptive immunotherapy based on chimeric antigen receptor-modified T (CAR-T) cells has been demonstrated as one of the most promising therapeutic strategies in the treatment of malignancies. However, CAR-T cell therapy has shown limited efficacy for the treatment of solid tumors. This is, in part, because of tumor heterogeneity and a hostile tumor microenvironment, which could suppress adoptively transferred T cell activity. In this study, we, respectively, engineered human- or murine-derived-armored glypican-3 (GPC3)-specific CAR-T cells capable of inducibly expressing IL-12 (GPC3-28Z-NFAT-IL-12) T cells. The results showed that GPC3-28Z-NFAT-IL-12 T cells could lyse GPC3⁺ tumor cells specifically and increase cytokine secretion compared with GPC3-28Z T cells in vitro. In vivo, GPC3-28Z-NFAT-IL-12 T cells augmented the antitumor effect when encountering GPC3⁺ large tumor burdens, which could be attributed to IL-12 increasing IFN-γ production, favoring T cells infiltration and persistence. Furthermore, in immunocompetent hosts, low doses of GPC3-m28Z-mNFAT-mIL-12 T cells exerted superior antitumor efficacy without prior conditioning in comparison with GPC3-m28Z T cells. Also, mIL-12 secretion decreased regulatory T cell infiltration in established tumors. In conclusion, these findings demonstrated that the inducible expression of IL-12 could boost CAR-T function with less potential side effects, both in immunodeficient and immunocompetent hosts. The inducibly expressed IL-12-armored GPC3-CAR-T cells could broaden the application of CAR-T-based immunotherapy to patients intolerant of lymphodepletion chemotherapy and might provide an alternative therapeutic strategy for patients with GPC3⁺ cancers.

Combined Antitumor Effects of Sorafenib and GPC3-CAR T Cells in Mouse Models of Hepatocellular Carcinoma

Our previous study indicated that GPC3-targeted chimeric antigen receptor (CAR) T cell therapy has a high safety profile in patients with hepatocellular carcinoma (HCC). However, the response rate requires further improvement. Here, we analyzed the combined effect of GPC3-CAR T cells and sorafenib in both immunocompetent and immunodeficient mouse models of hepatocellular carcinoma. In immunocompetent mouse model, mouse CAR (mCAR) T cells induced regression of small tumors (approximately 130 mm³ tumor volume) but had no effect on large, established tumors (approximately 400 mm³ tumor volume). Sorafenib, at a subpharmacologic but not a pharmacologic dose, augmented the antitumor effects of mCAR T cells, in part by promoting IL12 secretion in tumor-associated macrophages (TAMs) and cancer cell apoptosis. In an immunodeficient mouse model, both subpharmacologic and pharmacologic doses of sorafenib had limited impacts on the function of human CAR (huCAR) T cells in vitro and showed synergistic effects with huCAR T cells in vivo, which can at least partially be ascribed to the upregulated tumor cell apoptosis induced by the combined treatment. Thus, this study applied two of the most commonly used mouse models for CAR T cell research and demonstrated the clinical potential of combining sorafenib with GPC3-targeted CAR T cells against HCC.

Combined Adjuvant of Poly I:C Improves Antitumor Effects of CAR-T Cells

Chimeric antigen receptor modified T cells (CAR-T) therapy is an emerging immunotherapy against malignancies. However, only limited success was obtained in solid tumors. Polyinosinic-polycytidylic acid (poly I:C), ligand of TLR3, mediates innate immune and adaptive immune and shows broad antitumor effect on many types of cancer. In the present study, we combined EGFRvIII-targeted CAR-T cells with poly I:C treatment and evaluated the synergic antitumor effect in vitro and in immunocompetent mice bearing subcutaneous colon or orthotopic breast cancer xenografts. Poly I:C significantly promoted more IL-2 and IFN γ production as well as higher lytic activity of CAR-T cells. Upon systemic administration in vivo, CAR-T cells obviously suppressed tumor growth, and poly I:C significantly enhanced the suppression. Further study showed that poly I:C exerted antitumor effect dependent on type I IFNs. In addition, poly I:C decreased myeloid-derived suppressor cells (MDSC) number in peripheral blood and spleen, and attenuated the immunosuppressive activity of MDSC on proliferation and cytolytic function of CAR-T. Depletion of MDSC with anti-Gr1 Ab further increased the antitumor effect of CAR-T cells plus poly I:C treatment. In conclusion, CAR-T treatment combined with intratumoral delivery of poly I:C resulted in synergistic antitumor activity. We thus provide a rationale to translate this immunotherapeutic strategy to solid tumors.

Antitumor efficacy of chimeric antigen receptor T cells against EGFRvIII-expressing glioblastoma in C57BL/6 mice

Chimeric antigen receptor (CAR) T cell therapy has shown remarkable success in hematological tumors. However, many challenges remain in improving the efficacy of CAR T cells in solid tumors. The epidermal growth factor receptor variant III (EGFRvIII) is only expressed in tumors but barely found in normal tissues, making it a good target for CAR T therapy. It is reported that 31-64% of glioblastoma (GBM) patients are EGFRvIII positive. Here we report the robust antitumor activities of CAR T cells targeting EGFRvIII-expressing mouse GBM cells. In vitro and in vivo, 806-28Z CAR T cells were able to lyse GL261/EGFRvIII cellsin a dose-dependent manner. A low dose of 806-28Z CAR T cells suppressed GL261/EGFRvIII tumor growth, whereas a high dose of 806-28Z CAR T cells completely eradicated xenograft tumors. Higher concentrations of granzyme B in mice plasma were correlated with increased CAR T cells infusion. Enhanced CD8⁺ T cells infiltration within the tumors were detected by immunohistochemistry in sections from the mice treated by CAR T cells. The 806-28Z CAR T cells can also inhibit the growth of antigenic heterogeneous GBM tumors. More importantly, additional rechallenge experiments indicated that GL261/EGFRvIII cells or parental GL261 cells could not grow in the cured mice. Therefore, the cell dose is a crucial determinant for CAR T efficacy against EGFRvIII-expressing GBM and granzyme B release is a predictive marker for the antitumor efficacy of CAR T cells.

Increased antitumor activities of glypican-3-specific chimeric antigen receptor-modified T cells by coexpression of a soluble PD1-CH3 fusion protein

Our recent clinical study demonstrated that glypican-3 (GPC3)-specific chimeric antigen receptor-modified T (CAR-T) cells are a promising treatment for hepatocellular carcinoma (HCC). However, the interaction of programmed cell death 1 (PD-1) and PD-L1-mediated T-cell inhibition is involved in immune evasion in a wide range of solid tumors, including HCC. To overcome this problem, we introduced a fusion protein composed of a PD-1 extracellular domain and CH3 from IgG4 into GPC3-specific CAR-T cells (GPC3-28Z) to block the PD-1/PD-L1 pathway. GPC3-specific CAR-T cells carrying the PD-1-CH3 fusion protein (sPD1) specifically recognized and lysed GPC3-positive HCC cells. The proliferation capacity of GPC3-28Z-sPD1 T cells after weekly stimulation with target cells was much higher than that of control GPC3-28Z T cells. Additionally, the coexpression of sPD1 could protect CAR-T cells from exhaustion when incubated with target cells, as phosphorylated AKT and Bcl-xL expression levels were higher in GPC3-28Z-sPD1 T cells than in GPC3-28Z cells. Importantly, in two HCC tumor xenograft models, GPC3-28Z-sPD1 T cells displayed a significantly higher tumor suppression capacity than GPC3-28Z T cells. In addition, an increased number of CD3+ T cells in the circulation and tumors and increased granzyme B levels and decreased Ki67 expression levels in the tumors were observed in the mice treated with GPC3-28Z-sPD1 T cells. Together, these data indicated that GPC3-specific CAR-T cells carrying sPD1 show promise as a treatment for patients with HCC.

Development of GPC3-Specific Chimeric Antigen Receptor-Engineered Natural Killer Cells for the Treatment of Hepatocellular Carcinoma

Chimeric antigen receptor (CAR)-modified natural killer (NK) cells represent a promising immunotherapeutic modality for cancer treatment. However, their potential utilities have not been explored in hepatocellular carcinoma (HCC). Glypian-3 (GPC3) is a rational immunotherapeutic target for HCC. In this study, we developed GPC3-specific NK cells and explored their potential in the treatment of HCC. The NK-92/9.28.z cell line was established by engineering NK-92, a highly cytotoxic NK cell line with second-generation GPC3-specific CAR. Exposure of GPC3+ HCC cells to this engineered cell line resulted in significant in vitro cytotoxicity and cytokine production. In addition, soluble GPC3 and TGF-β did not significantly inhibit the cytotoxicity of NK-92/9.28.z cells in vitro, and no significant difference in anti-tumor activities was observed in hypoxic (1%) conditions. Potent anti-tumor activities of NK-92/9.28.z cells were observed in multiple HCC xenografts with both high and low GPC3 expression, but not in those without GPC3 expression. Obvious infiltration of NK-92/9.28.z cells, decreased tumor proliferation, and increased tumor apoptosis were observed in the GPC3+ HCC xenografts. Similarly, efficient retargeting on primary NK cells was achieved. These results justified clinical translation of this GPC3-specific, NK cell-based therapeutic as a novel treatment option for patients with GPC3+ HCC.

A Fusion Receptor as a Safety Switch, Detection, and Purification Biomarker for Adoptive Transferred T Cells

The incorporation of an endogenous safety switch represents a rational strategy for the control of toxicities following the administration of adoptive T cell therapies. An ideal safety switch should be capable of depleting the transferred T cells with minimal injury to normal tissues. We generated a fusion receptor by engineering a cryptic 806 epitope of human epidermal growth factor receptor (EGFR) into the N terminus of the full-length human folate receptor 1 (FOLR1), designated as FR806. The expression of FR806 allows transduced T cells to be targeted with CH12, a monoclonal antibody recognizing the 806 epitope, but not wild-type EGFR in healthy tissues. FR806, therefore, constitutes a specific cell-surface marker for the elimination of transduced T cells. We demonstrate that the antibody-drug conjugate (ADC) CH12-MMAF is efficiently internalized by FR806-expressing T cells and has the potential to eliminate them. Transfected T cells could, furthermore, be efficiently detected and purified using CH12 antibodies. In immuno-compromised mice, CH12-MMAF eliminated the majority of transferred T cells expressing FR806 and anti-CD19 chimeric antigen receptor (CAR). The selectivity for the 806 epitope and internalization capacity of FOLR1 makes FR806 an efficient safety switch, which may additionally be used as a detection and purification biomarker for human T cell immunotherapies.

The emerging role of Toll-like receptor 4 in myocardial inflammation

Toll-like receptors (TLRs) are a family of pattern recognition receptors involved in cardiovascular diseases. Notably, numerous studies have demonstrated that TLR4 activates the expression of several of pro-inflammatory cytokine genes that play pivotal roles in myocardial inflammation, particularly myocarditis, myocardial infarction, ischemia-reperfusion injury, and heart failure. In addition, TLR4 is an emerging target for anti-inflammatory therapies. Given the significance of TLR4, it would be useful to summarize the current literature on the molecular mechanisms and roles of TLR4 in myocardial inflammation. Thus, in this review, we first introduce the basic knowledge of the TLR4 gene and describe the activation and signaling pathways of TLR4 in myocardial inflammation. Moreover, we highlight the recent progress of research on the involvement of TLR4 in myocardial inflammation. The information reviewed here may be useful to further experimental research and to increase the potential of TLR4 as a therapeutic target.

Treatment of solid tumors with chimeric antigen receptor-engineered T cells: current status and future prospects

Chimeric antigen receptors (CARs) are artificial recombinant receptors that generally combine the antigen-recognition domain of a monoclonal antibody with T cell activation domains. Recent years have seen great success in clinical trials employing CD19-specific CAR-T cell therapy for B cell leukemia. Nevertheless, solid tumors remain a major challenge for CAR-T cell therapy. This review summarizes the preclinical and clinical studies on the treatment of solid tumors with CAR-T cells. The major hurdles for the success of CAR-T and the novel strategies to address these hurdles have also been described and discussed.

Large gradient high magnetic field affects FLG29.1 cells differentiation to form osteoclast-like cells

PURPOSE

We aimed to investigate the effects of different apparent gravities (μ g, 1 g and 2 g) produced by large gradient high magnetic field (LGHMF) on human preosteoclast FLG29.1 cells.

MATERIALS AND METHODS

FLG29.1 cells were cultured in Roswell Park Memorial Institute (RPMI)-1640 medium. Cells were exposed to LGHMF for 72 h. On culture day 1, 2, 3, cell proliferation was detected by 3-(4,5)-dimethylthiahi-azo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) method. On day 3, cell apoptosis and necrosis were assayed by Hoechst and propidium iodide (PI) staining. After cells were exposed to LGHMF for 72 h with the induction of 12-o-tetradecanoylphorbol 13-acetate (TPA), Tartrate-Resistant Acid Phosphatase (TRAP) positive cells and nitric oxide (NO) release were detected by TRAP staining and Griess method, respectively. Intracellular TRAP activity was measured using nitrophenylphosphate (pNPP) as the substrate.

RESULTS

MTT detection revealed that compared to control, FLG 29.1 cell proliferation in the μ g and 2 g groups were promoted. However, there is no obvious difference between the 1 g and control groups. Hoechst-PI staining showed that LGHMF promoted cell apoptosis and necrosis, especially in the 2 g group. Exposure to LGHMF inhibited the NO concentration of supernatant. Both the TRAP activity and the number of TRAP positive cells were higher in cells of μ g group than those in 2 g group. In the 1 g group, they were decreased significantly compared to control.

CONCLUSIONS

These findings indicate that LGHMF could directly affect human preosteoclast FLG29.1 cells survival and differentiation. High magnetic flux inhibited osteoclasts formation and differentiation while reduced apparent gravity enhanced osteoclastogenesis.

Selection of suitable reference genes from bone cells in large gradient high magnetic field based on GeNorm algorithm

Studies of animals and humans subjected to spaceflight demonstrate that weightlessness negatively affects the mass and mechanical properties of bone tissue. Bone cells could sense and respond to the gravity unloading, and genes sensitive to gravity change were considered to play a critical role in the mechanotransduction of bone cells. To evaluate the fold-change of gene expression, appropriate reference genes should be identified because there is no housekeeping gene having stable expression in all experimental conditions. Consequently, expression stability of ten candidate housekeeping genes were examined in osteoblast-like MC3T3-E1, osteocyte-like MLO-Y4, and preosteoclast-like FLG29.1 cells under different apparent gravities (μg, 1 g, and 2 g) in the high-intensity gradient magnetic field produced by a superconducting magnet. The results showed that the relative expression of these ten candidate housekeeping genes was different in different bone cells; Moreover, the most suitable reference genes of the same cells in altered gravity conditions were also different from that in strong magnetic field. It demonstrated the importance of selecting suitable reference genes in experimental set-ups. Furthermore, it provides an alternative choice to the traditionally accepted housekeeping genes used so far about studies of gravitational biology and magneto biology.

cDNA microarray reveals the alterations of cytoskeleton-related genes in osteoblast under high magneto-gravitational environment

The diamagnetic levitation as a novel ground-based model for simulating a reduced gravity environment has been widely applied in many fields. In this study, a special designed superconducting magnet, which can produce three apparent gravity levels (0, 1, and 2 g), namely high magneto-gravitational environment (HMGE), was used to simulate space gravity environment. The effects of HMGE on osteoblast gene expression profile were investigated by microarray. Genes sensitive to diamagnetic levitation environment (0 g), gravity changes, and high magnetic field changes were sorted on the basis of typical cell functions. Cytoskeleton, as an intracellular load-bearing structure, plays an important role in gravity perception. Therefore, 13 cytoskeleton-related genes were chosen according to the results of microarray analysis, and the expressions of these genes were found to be altered under HMGE by real-time PCR. Based on the PCR results, the expressions of WASF2 (WAS protein family, member 2), WIPF1 (WAS/WASL interacting protein family, member 1), paxillin, and talin 1 were further identified by western blot assay. Results indicated that WASF2 and WIPF1 were more sensitive to altered gravity levels, and talin 1 and paxillin were sensitive to both magnetic field and gravity changes. Our findings demonstrated that HMGE can affect osteoblast gene expression profile and cytoskeleton-related genes expression. The identification of mechanosensitive genes may enhance our understandings to the mechanism of bone loss induced by microgravity and may provide some potential targets for preventing and treating bone loss or osteoporosis.

[Cloning of silkworm 3-hydroxyisobutyrate dehydrogenase gene and its expression patterns analysis in simulated weightless environment]

The full length cDNA of silkworm hibadh gene was cloned by RT-PCR and RACE (Rapid amplification of cDNA ends) technique. The hibadh gene and its deduced amino acid sequences were analyzed. The tissue distribution of hibadh gene in 5th instar silkworm larvae was tested by RT-PCR. The expression patterns of hibadh gene in simulated weightless environment were analyzed by real time RT-PCR. The results showed that the full length hibadh cDNA sequence was 1074 bp in lenth, including an open read frame of 969 bp encoding the entire coding region of Hibadh (GenBank accession No. EU719652). The deduced amino acid sequence similarities of hibadh between silkworm and Burkholderia ambifaria, Drosophila melanogaster, Apis mellifera, Xenopus tropicalis, Mus musculus, Homo sapiens were 46%, 43%, 48%, 44%, 45%, 45%, respectively. Signal peptide analysis showed that Hibadh was a secretory protein. There wasn't glycosyl-phosphatidyl inositol anchor site in Hibadh amino acid sequence. Molecular weight and isoelectric point of Hibadh were 34.1 kD and 9.14 respectively. The RT-PCR tests indicated that the hibadh gene expressed in head, silk gland, midgut, cuticle, blood, fat body, tuba malpighii of the 5th instar silkworm larvae. There were different expression patterns of hibadh gene during different silkworm embryo period in simulated weightless environment. Simulated weightlessness resulted in the expression of silkworm hibadh gene up regulated 2.3-fold (P < 0.05), up regulated 4.6-fold (P<0.01), down regulated 7.6-fold (P < 0.01), down regulated 2.6-fold (P < 0.05) during apophysis formation period, inverse period, trachea formation period, and whole embryo period, respectively. There was no significant change of hibadh gene expression during other period of silkworm embryo between simulated weightless and control groups. There were different response patterns to simulated weightless environment between hibadh gene and whole body of silkworm. Gene showed much higher sensitivity compared to whole body in response to environment. This study is useful for the further research on the gravity biological mechanism of hibadh gene.

Presynaptic noradrenergic regulation of glutamate inputs to hypothalamic magnocellular neurones

Glutamate and norepinephrine transmitter systems play critical roles in the synaptic control of hypothalamic magnocellular neurones. We recently reported on a norepinephrine-sensitive glutamate circuit within the paraventricular nucleus (PVN) that projects to magnocellular neurones. Here, we present evidence for norepinephrine regulation of glutamate release in the PVN and supraoptic nucleus (SON) via actions on presynaptic terminals. Whole-cell synaptic currents were recorded in magnocellular neurones of the SON and PVN in an acute slice preparation. Bath application of norepinephrine (100 microm) caused a robust, reversible increase in the frequency of spontaneous glutamatergic excitatory postsynaptic currents in 100% of SON neurones (246%) and in 88% of PVN magnocellular neurones (259%). The norepinephrine-induced increase in glutamate release was mediated by activation of both presynaptic alpha1 receptors and alpha2 receptors, but the alpha1-receptor component was the predominant component of the response. The presynaptic actions of norepinephrine were predominantly, although not completely, resistant to blockade of Na-dependent spikes, implicating a presynaptic terminal locus of action. Interestingly, the spike-dependent component of the response was greater in PVN than in SON magnocellular neurones. This robust presynaptic facilitation of glutamate release by norepinephrine, combined with the known excitatory postsynaptic actions of norepinephrine, activational effects on local glutamate circuits, and inhibitory effects on gamma-aminobutyric acid release, indicate a strong excitatory role of norepinephrine in the regulation of oxytocin and vasopressin release during physiological stimulation.

Influence of sextant prostate needle biopsy or surgery on the detection and harvest of intact circulating prostate cancer cells

PURPOSE

The feasibility of harvesting intact, circulating prostate cancer cells from the blood of men with advanced prostate cancer has previously been demonstrated. We studied the influence of sextant prostate needle biopsy and radical prostatectomy on harvesting intact circulating prostate cancer cells.

MATERIALS AND METHODS

Via standard venipuncture 20 c.c. blood were obtained preoperatively, and 30 minutes and 3 days postoperatively from 23 men with clinically localized prostate cancer undergoing surgery. Similarly, blood was obtained before and after routine prostate biopsy from 13 men for an elevated prostate specific antigen level and/or abnormal digital rectal examination. The blood cells were removed via density centrifugation and magnetic cell sorting. The remaining prostate epithelial cells were characterized by indirect fluorescent immunocytochemical staining and fluorescent in situ hybridization using deoxyribonucleic acid probes.

RESULTS

Sextant biopsy of the prostate induced circulating cells in 3 of 13 men (23%), only 1 of whom demonstrated cells with aneuploidy (Gleason score 3+4 = 7). Circulating cells were detected preoperatively, 30 minutes or 3 days postoperatively in 35% of radical prostatectomy cases. Of the patients 13% had detectable circulating cells 30 minutes postoperatively only and 9% had cells harvested on postoperative day 3. Persistence of circulating prostate cancer cells was noted in 13% of men on postoperative day 3. Serum prostate specific antigen level and pathological stage did not appear to be related to harvested cell number.

CONCLUSIONS

Prostate cancer cells can be harvested from men with clinically localized disease undergoing sextant needle biopsy or radical prostatectomy. Routine prostate biopsy and surgery may influence the number of measurable circulating cells in the short term but the clinical significance and long-term prevalence of detectable circulating cells are unknown. Further studies are needed to evaluate the clinical usefulness of this assay for detecting, staging and monitoring prostate cancer.

A novel herpesvirus amplicon system for in vivo gene delivery

For gene therapy approaches to succeed, improved vector systems are needed that combine a large carrying capacity with high transduction efficiency in vivo. Towards this goal, we have developed a novel herpes simplex virus (HSV) amplicon vector, pHE, which contains an HSV-1 replication origin (ori S) and packaging sequence that permit vector replication and packaging into HSV-1 capsids. The vector also contains the Epstein-Barr virus (EBV) unique latent replication origin (ori P) sequence and a modified EBNA-1 gene to allow the vector to be maintained as an episome in transfected E5 helper cells. This system allows for efficient packaging of high-titer vector since the E5 cells are first selected for the presence of the pHE vector before helper virus infection. The infectious pHE vector has efficient transgene expression in a variety of human cell lines in vitro. Stereotactic injection of pHE vector supernatant into the rat brain resulted in high, localized reporter gene expression. Finally, the pHE vector could carry a stable 21 kb DNA payload into HSV virions. This pHE vector system should have a broad range of gene transfer applications.

Relaxin-induced expression of Fos in the forebrain of the late pregnant rat

Relaxin, administered parenterally, has been shown to increase the release of oxytocin (OT) into the circulation and increase the firing rate of OTergic neurons. The objective of the present study was to determine if relaxin administration can result in the expression of a transcription factor, suggesting that it alters transcriptional activity within OTergic neurons at the level of the hypothalamus. Primigravid rats were ovariectomized and a jugular cannula was inserted on day 11 of gestation (g11). Pregnancy was maintained by implanting 17 beta-estradiol and progesterone caplets subcutaneously at the time of ovariectomy. At gl9, rats were challenged with intravenous relaxin or isotonic saline and the brains were removed for study. Immunohistochemistry was performed on coronal brain sections, utilizing Fos as a marker of cellular activation. In the group receiving relaxin, Fos-like immunoreactivity (Fos-IR) was abundant only in the supraoptic (SON) and paraventricular nuclei (PVN) of the hypothalamus as well as in the subfornical organ (SFO). In contrast, Fos-IR in the group given isotonic saline was lacking in these three brain regions. A double label study using antibodies against Fos and OT demonstrated that a majority of the Fos-labeled cells in the hypothalamus were OTergic. Because Fos can act as a transcription factor, we interpret these data to indicate that transcription within OTergic cells is altered following relaxin administration, with abundant Fos-IR being limited to the SON and PVN of the hypothalamus and the SFO during late pregnancy in the rat.

The spatiotemporal organization of auditory, visual, and auditory-visual evoked potentials in rat cortex

Four placements of an 8 x 8 channel microelectrode array were used to map auditory, visual, and combined auditory-visual evoked potentials (AEP, VEP, AVEP) from a total of 256 electrode sites over a 7 x 7 mm2 area including most of somatosensory, auditory, and visual cortex in the right hemisphere of the rat. The unimodal AEP and VEP consisted of an archetypal response sequence representing a systematic spatial and temporal activation of primary and secondary sensory cortex. Spatiotemporal analysis of these waveforms indicated that they could be decomposed into a small number of spatial and temporal components; components that are related to patterns of specific and non-specific thalamocortical projections connecting the auditory and visual nuclei of the thalamus with primary and secondary auditory and visual cortex. These data suggest that the AEP and VEP complex are the cortical reflection of asynchronous activation of parallel thalamocortical projection systems. The areal distribution of the AEP and VEP also overlapped, primarily in secondary auditory and visual cortex, indicating that these regions contain populations of cells responding to either modality. Polymodal auditory-visual stimulation resulted in unique activation of two isolated populations of neurons positioned in secondary auditory and secondary visual cortex which were revealed by difference waveforms, computed by subtracting the sum of the AEP and VEP from the AVEP complex. Retrograde labeling of the polymodal zones indicated that they receive parallel thalamocortical projections primarily from non-specific auditory and visual thalamic nuclei including the medial and dorsal divisions of the medial geniculate nucleus (MGm and MGd), the suprageniculate nucleus (SGN), and the lateral posterior nucleus (LP). The polymodal zone in visual cortex also receives specific projections from the dorsal division of the lateral geniculate nucleus (LGd). These data conform to a general model of thalamocortical organization in which specific thalamic nuclei with a high degree of modality specificity make restricted projections to primary sensory cortex and parts of secondary sensory cortex, and association thalamic nuclei with a high degree of sensory convergence make more divergent cortical projections. Primary and secondary sensory cortex, as well as distinct zones of polysensory cortex appear to be activated in tandem via parallel thalamocortical projections. Thus, the cerebral cortex must have simultaneous access to both unimodal and polymodal sensory information.

The anatomic organization of evoked potentials in rat parietal cortex: electrically evoked commissural responses

1. Two 8 x 8 channel microelectrode arrays were positioned over 3.5 x 3.5 mm2 areas in homologous regions of right and left parietal cortex of four rats. Potentials were evoked by delivering epicortical electrical stimulation to each electrode on one hemisphere while mapping the commissural response from the contralateral array. Spatial distributions of the electrically evoked potential (EECP) complex were compared directly with cytochrome oxidase-stained sections of the recorded region. 2. Electrode sites most capable of eliciting a commissural EECP were arranged along a diagonal band extending medially from the rostral to caudal region of each electrode array, approximating the pattern of dysgranular cortex separating primary auditory (Te1) from primary somatosensory (Par1) cortex. Electrode sites in the rostromedial and caudolateral region were ineffectual in eliciting an EECP in either hemisphere. Stimulation sites within secondary visual cortex (Oc2L) also produced strong responses. Only weak responses were elicited from stimulation of Te1 and no EECP could be evoked when stimulating within Par1. 3. When an EECP in the maximally sensitive diagonal region was elicited, its spatial distribution was typically asymmetrical throughout the recording array; the response was largest along a diagonal region also extending medially from the rostral to caudal area of each electrode array. Thus the pattern of EECP in each hemisphere closely matched the pattern of electrically excitable regions in the contralateral hemisphere. 4. The EECP was usually heterogeneous. EECP distributions within the strongly responding diagonal area often formed two regions of maximum amplitude separated by a less active zone. Although responses in Te1 were significantly weaker than those in the adjacent dysgranular cortex, they also revealed a heterogeneous spatial distribution with multiple closely spaced maxima. Only responses in Oc2L appeared consistently homogeneous, with a single maximum representing the EECP. 5. These results provide functional evidence supporting a model of parietal cortex in which there are two basic types of recipient regions, densely granular regions, which are the termination sites of specific thalamocortical fibers, and dysgranular or agranular regions, which receive both ipsilateral and contralateral projections. The functional parceling of rodent parietal cortex on the basis of the spatial and temporal distribution of the epicortical evoked potential complex may be superimposed onto the anatomic parceling into granular and dysgranular zones. Implications for stages of sensory information processing are discussed.

A horseradish peroxidase study of parallel thalamocortical projections responsible for the generation of mid-latency auditory-evoked potentials

Mid-latency auditory-evoked potentials (MAEP) were recorded from the parietotemporal region of the rat using a high spatial resolution epicortical multielectrode array. Horseradish peroxidase was injected into regions of primary and secondary auditory cortex which generate spatially and temporally distinct components of the MAEP complex to retrogradely label their thalamocortical projections. These data provide anatomical evidence for three parallel thalamocortical projection systems, originating in the ventral, dorsal and medial subdivisions of the medial geniculate nucleus, which may be responsible for the asynchronous activation of three distinct subpopulations of cortical neurons giving rise to components of the MAEP complex. Specific and non-specific characteristics of the thalamocortical projections are discussed.

Polysensory evoked potentials in rat parietotemporal cortex: combined auditory and somatosensory responses

A 64 channel microelectrode array was used to map auditory evoked potentials (AEP), somatosensory evoked potentials (SEP) as well as combined auditory and somatosensory evoked potentials (ASEP) from a 7 x 7 mm2 area in rat parietotemporal neocortex. Cytochrome oxidase (CO) stained sections of layer IV were obtained in the same animals to provide anatomical information underlying epicortical field potentials. Epicortical responses evoked by click or vibrissa stimuli replicated earlier findings from our laboratory, and appeared as a family of waveforms centered on primary auditory (AI) or somatosensory (SI) cortical areas as determined from CO histology. Selective microinjections of HRP to AI and SI further confirmed their specific sensory relay nuclei in the thalamus. A small polysensory area between AI and SI, responded uniquely with an enhanced negative sharp wave to combined auditory and somatosensory stimuli. HRP retrograde labeling revealed that the thalamocortical projections to this area were from the posterior nuclear group (Po) and medial division of the medial geniculate (MGm). These data establish close relationships between epicortical AEP, SEP, and especially ASEP and corresponding cortical structures and thalamocortical projections. The neurogenesis of unimodal and polysensory evoked potentials is discussed in terms of specific and non-specific systems.

Binaural vs. monaural auditory evoked potentials in rat neocortex

High spatial resolution epicortical recording techniques and numerical modeling were used to investigate laterality effects on the middle latency auditory evoked potential (MAEP) complex. Our data confirm previous reports that auditory stimulus laterality has a consistent effect on the amplitude, timing, and spatial distribution of the MAEP complex. The earliest temporal components (P1a, P1b and N1) show the greatest sensitivity, and are absent during ipsilateral stimulation. The later positive slow wave (P2) is present at the same amplitude during all stimulation conditions. Generation of the P2 appears to be independent of prior activation of areas 36 and 41 reflected in the early components, suggesting its generation by a more diffuse thalamocortical pathway, possibly from the medial division of the medial geniculate. Serial vs. parallel activation of rodent auditory cortex is discussed in the context of laterality-sensitive MAEP components.

Anatomic organization of evoked potentials in rat parietotemporal cortex: somatosensory and auditory responses

1. Two 8 x 8-channel microelectrode arrays were used to map epicortical field potentials from a 3.5 x 3.5-mm2 area in homologous regions of right and left parietotemporal cortex of four rats. Potentials were evoked with bilaterally presented click stimuli and with bilateral tactile stimulation of the 25 major vibrissae. The spatial distribution of temporal components of the somatosensory evoked potential (SEP) and auditory evoked potential (AEP) complex were compared directly with cytochrome oxidase-stained sections of the recorded region. 2. Epicortical responses in both hemispheres to bilateral vibrissal stimuli consisted of a biphasic sharp wave (P1a-N1) constrained to the vibrissa/barrel granular region of primary somatosensory cortex (SmI). A slightly later sharp positive wave (P1b) was localized to secondary somatosensory cortex (SmII) and to perigranular cortex medial to the vibrissa/barrel field. The SEP complex ended with a biphasic slow wave (P2-N2). The P2 was centered on SmI and spread to dysgranular lateral cortex, caudal to but excluding SmII. The N2 was centered on SmII and spread to dysgranular cortex caudal to but excluding SmI. 3. The anatomic organization of the AEP in many ways approximated that of the SEP in the same animals. The timing and morphology of the AEP were nearly identical to the SEP. The AEP consisted of a P1a-N1 sharp wave constrained to the estimated region of primary auditory cortex (AI) in the lateral parietotemporal region, a later P1b localized to secondary auditory cortex (AII), and subsequent slow waves (P2 and N2) that were centered on AI and AII, respectively, and spread to dysgranular regions overlapping the distributions of the P2 and N2 of the SEP complex. 4. These data suggest that the basic neural generators for the SEP and AEP in parietotemporal cortex are quite similar, and provide evidence for the functional anatomy of each temporal component of the sensory evoked potential complex. It is concluded that the early fast waves of the SEP and AEP are modality specific and may represent the parallel activation of primary and secondary sensory cortex through established parallel afferent projections from lateral and medial thalamic nuclei. The later slow waves of the SEP and AEP appear to selectively involve primary and secondary sensory cortex but are more widely distributed, possibly reflecting a less modality-specific level of information processing in dysgranular cortex.

Topographical analysis of epileptiform potentials in rat somatosensory cortex: the interictal to ictal transition

Large quantities of penicillin were applied to the face and forelimb region of rat somatosensory cortex, producing an epileptic focus with both electrographic and behavioral signs of seizures that regularly repeated over a period of several minutes. Epicortical potentials were recorded simultaneously from a 64 channel micro-electrode array (8 x 8 platinum electrodes) with inter-electrode distances of 0.5 mm, covering a 3.5 x 3.5 mm2 area centered on the penicillin injection site. Cluster analysis was used to classify successive epileptiform discharges into interictal, transitional, and ictal groups. Principal components analysis (PCA) was used to extract fundamental waveforms producing the spike complex in each group, and to estimate the locations and spatial extent of neuronal populations participating in epileptiform discharge. During all states of epileptic excitability, it was possible to account for over 90% of the variance in the epicortical potential waveforms using a model with only two spatially overlapping populations of cells. The location and spatial extent of the populations remained unchanged by the transition to seizures; the interictal and ictal states were distinguished only by changes in the timing and amplitude of potentials in the two putative neuronal populations. The present model, using only two stationary neuronal populations to reproduce all spatiotemporal patterns in the neocortical epileptogenic focus, is compared to models proposed by others in which epileptic discharge is thought to propagate sequentially through adjacent cortex. It is concluded that the initiation, maintenance, and termination of seizures in neocortex relies on mechanisms that are not necessarily reflected in changes in spatiotemporal interactions among epicortically recorded cell groups within the focus. These mechanisms may be distinguished from those responsible for the spread of seizures within neocortex.

The functional anatomy of middle-latency auditory evoked potentials: thalamocortical connections

1. An 8 x 8-channel microelectrode array was used to map epicortical field potentials from a 4.375 x 4.375-mm2 area in the right parietotemporal neocortex of four rats. Potentials were evoked with bilaterally presented click stimuli and with electrical stimulation of the ventral and dorsal divisions of the medial geniculate body. 2. Epicortical responses to click stimuli replicated earlier findings. The responses consisted of a positive-negative biphasic waveform (P1a and N1) in the region of primary auditory cortex (area 41) and a positive monophasic waveform (P1b) in the region of secondary auditory cortex (area 36). Two potential patterns, one at the latency of the N1 and the other at the latency of the P1b, were used to represent activation of cells within areas 41 and 36. A linear combination of these patterns was sufficient to explain from 90 to 94% of the variance of the evoked potential complex at all latencies. 3. In the same animals, epicortical responses to electrical stimulation of the ventral and dorsal divisions of the medial geniculate body were also localized to areas 41 and 36, respectively. A linear combination of potential patterns from these separate stimulation conditions was sufficient to explain from 80 to 93% of the variance of the original click-evoked potential complex at all latencies. 4. These data provide functional evidence for anatomically defined topographical thalamocortical projections to primary and secondary auditory cortex. They suggest that short-latency cortical evoked potentials (10-60 ms poststimulus) are dominated by parallel thalamocortical activation of areas 41 and 36.

The functional anatomy of middle latency auditory evoked potentials

The neural origins of middle latency auditory evoked potentials (MAEP) were studied in rat cortex. MAEP were mapped from the cortical surface with a high spatial resolution electrode array. Spatiotemporal analysis, based on multivariate statistical methods, was then used to relate putative neural generators of the MAEP complex to established cytoarchitectural anatomy. These data indicate that the MAEP waveform reflects systematic asynchronous activation of both primary and secondary auditory cortex during the processing of simple click stimuli.

The electrophysiological basis of epileptiform magnetic fields in neocortex: spontaneous ictal phenomena

In a previous report (Barth, D.S. and Di, S., Brain Research, 530 (1990) 35-39), electrical measurements of epileptiform cellular currents produced by physiologically evoked interictal penicillin spikes in rat somatosensory cortex were directly compared to the extracranial magnetic fields these currents generate. The present study uses the same methodology to extend these observations to spontaneous interictal and ictal phenomena in rat auditory cortex, and provides a more realistic empirical foundation for physical models with which to interpret non-invasive neuromagnetic recordings of human focal seizures. These data indicate that seizure foci under 1 x 1 cm2 in cortical surface area are capable of producing magnetic fields that may be recorded at extracranial distances similar to those used in humans. Furthermore, physical models based on the dipole approximation appear to be appropriate for the interpretation of ictal magnetic field phenomena in neocortex.

Spatiotemporal modeling of cerebral evoked magnetic fields to median nerve stimulation

We measured somatosensory evoked magnetic fields during median nerve stimulation in 6 normal subjects. We applied multiple dipole models to study the spatiotemporal structure of early somatosensory evoked magnetic fields (SEFs), as well as the number, 3-dimensional location and time activity of their underlying neuronal sources. Two dipole sources were necessary to model the first 40 msec of SEFs explaining 85% of the data variance. Source 1 was located deeper than source 2, showed primarily a tangential orientation, and accounted for a larger part of the variance; source 2 showed no consistent orientation across subjects. Both sources showed biphasic time activities corresponding to the previously described N20-P30 and P25-N35 components. Spatiotemporal modeling could identify sources which could not be modeled consistently above noise by single moving dipoles (P25 component), revealed small latency differences of the two sources in some subjects suggesting parallel activation of these sources, and allowed separation of sources overlapping considerably both in space and time. We conclude that spatiotemporal modeling of SEFs may be useful to study functional anatomy of human sensorimotor cortex non-invasively.

Topographic analysis of field potentials in rat vibrissa/barrel cortex

An 8 x 8 multichannel microelectrode array was used to simultaneously record epicortical field potentials, evoked by displacement of contralateral vibrissae, from a 4 x 4 mm2 area of vibrissa/barrel cortex in 4 rats. The epicortical responses began with early positive (P1) and negative (N1) sharp waves, followed by slower positive (P2) and negative (N2) waves. The potential complex systematically shifted location with vibrissa stimulated, in accordance with the known somatotopic anatomy of vibrissa/barrel cortex. Topographical distributions of potentials at the P1, N1, P2 and N2 peaks were approximately concentric, but had distinct spatial extents, suggesting that they were generated by different but overlapping neuronal subpopulations. We propose that the SEP in the vibrissa/barrel cortex is produced by both sequential and parallel processing of somatosensory information, and that all components of the epicortical SEP are generated only in primary somatosensory cortex of the rat. Applications and weaknesses of topographic analysis methods are discussed.

Laminar excitability cycles in neocortex

1. Laminar field potentials produced by paired electrocortical stimuli were recorded with a linear microelectrode array inserted perpendicular to the surface of rat somatosensory cortex. Current source-density (CSD) distributions of the direct cortical response (DCR) were computed from the potential profiles. Principal component analysis (PCA) was used to estimate the time course of evoked transmembrane currents of putative pyramidal cell populations in the supragranular and infragranular layers. 2. Both supra- and infragranular cells displayed an initial period after the conditioning stimulus in which test stimuli produced subnormal evoked response amplitudes. This was followed in both layers by a long period of supernormal then subnormal responses and a second period of supernormal responses. 3. The main laminar difference encountered was a general shortening of all phases of the excitability cycle in the supragranular cells. 4. Excitability cycles in the supra- and infragranular layers closely followed the morphology of average evoked responses to the conditioning stimulus alone. These results and physiological support to the validity of lamina-specific evoked response waveforms derived from combined CSD and PCA analysis of extracellular potential measurements. 5. The relationship between evoked potential amplitude changes and cortical excitability is discussed.

Three-dimensional analysis of auditory-evoked potentials in rat neocortex

1. A 8 X 8-channel microelectrode array was used to map epicortical field potentials evoked by bilaterally presented click stimuli from a 8 X 8-mm2 area in the right parietotemporal neocortex of four rats. In two rats, a 16-channel microelectrode array was also inserted into primary auditory cortex to record the laminar profile of auditory evoked potentials (AEP). 2. The epicortical responses began with a positive-negative fast wave followed by a positive-negative slow wave, similar to the previously reported P1, N1, P2, N2 complex. Topographical distributions of the potentials at the peak of each of these waves were distinct, suggesting that they were produced by separate but overlapping populations of cells. 3. Laminar recording revealed the asynchronous participation of supragranular and infragranular pyramidal cells in the generation of the evoked-response complex. The surface-recorded P1 was primarily produced by supragranular cells and the N1, by infragranular cells. The P2 and N2 were produced by temporally overlapping contributions from both cell groups. 4. We conclude that middle-latency components of the AEP complex are produced by both sequential and parallel activation of subpopulations of pyramidal cells in primary auditory cortex.

The electrophysiological basis of epileptiform magnetic fields in neocortex

Electrical measurements of epileptiform cellular currents in a penicillin model of focal epilepsy were directly compared to the extracranial magnetic fields these currents produce. Our data support the hypothesis that epileptiform magnetic fields result from intradendritic currents oriented perpendicular to the cortical surface. Furthermore, magnetic fields could be detected from epileptic foci smaller than 3 mm2. This work provides an empirical foundation for physical models with which to interpret noninvasive neuromagnetic recordings of epileptic discharge in human focal seizure disorders.

Laminar analysis of extracellular field potentials in rat vibrissa/barrel cortex

1. A 16-channel electrode array was used to record simultaneously extracellular laminar field potentials evoked by displacement of contralateral vibrissa from vibrissa/barrel cortex in five rats. Current source-density (CSD) analysis combined with principal component analysis (PCA) was used to determine the time course of laminar-specific transmembrane currents during the evoked response. 2. The potential complex consisted of biphasic fast components followed by long-lasting slow waves. It began with activity in supragranular cells consisting of a source in layers I-II and a sink in layers IV-V; this was followed by activation of the infragranular cells with a paired sink and source in layers I-IV and V-VI, respectively. The slow-wave sequences also began in the supragranular cells followed by infragranular neurons. 3. We propose that the fast components reflect sequential intralaminar depolarization processes, and the slow waves, hyper- or repolarization processes. These results suggest that a basic neuronal circuit, consisting of sequential activation of the supragranular and then the infragranular pyramidal cells, gives rise to the field potentials evoked by physiological stimulation. This is consistent with our previous studies of direct cortical responses (DCR) and pathological discharges of the penicillin focus.

Laminar interactions in rat motor cortex during cyclical excitability changes of the penicillin focus

Laminar interactions between neurons in rat motor cortex during cyclical seizure episodes in the penicillin focus were studied using a combination of current source-density (CSD) and principal component analysis (PCA), combined with computer-based physical modeling. These data suggest that all phases of cyclical seizure phenomena are produced by interactions between two distinct populations of neurons, the same neuronal circuits previously reported to give rise to the direct cortical response (DCR) and electrically evoked interictal penicillin spikes (EIIS). The first population consists of small pyramidal cells in the supragranular layer, and the second population consists of larger pyramidal cells in the infragranular layers with apical dendrites extending to the cortical surface. The supragranular cells serve as a trigger zone for initiating both spontaneous interictal spikes (IIS) and polyspike bursts (PSB) during seizures. Fast activity in the supragranular cells is typically followed by a hyperpolarizing slow wave that may be the result of Ca2+-activated K+ currents. This slow wave increases during seizures, possibly reflecting changes in extracellular Ca2+ associated with seizure onset and termination. The monophasic response of infragranular cells is similar for both IIS and PSB and consists of a large depolarizing shift followed by a rapid but partial repolarization period and a subsequent gradual repolarization period lasting several hundred milliseconds. The infragranular response is similar in polarity and morphology to the intracellularly recorded paroxysmal depolarization shift (PDS) and may indicate that these deeper neurons are mainly responsible for this phenomena in neocortex. Finally, there is a marked postictal slow oscillation between the supra- and infragranular layers. This oscillation appears first and largest in the supragranular cells and may reflect a disturbance in excitatory feedback in these cells produced by the disinhibitory effect of penicillin, a disturbance capable of pathologically synchronizing the epileptic neuronal aggregate sufficiently for activation of the spike-generating mechanism and subsequent seizures.

Investigation of multiple simultaneously active brain sources in the electroencephalogram

We present a method of investigating multiple simultaneously active brain sources that overlap both in space and time in the scalp electroencephalogram (EEG). In order to identify the contributions of the individual brain sources to measured potentials, we applied principal component analysis and various methods of rotating the principal components including a newly developed rotation procedure using frequency criteria. We related the results of these multivariate statistical techniques to a new physical model using multiple current dipoles with fixed anatomical locations and time-varying activities. We thus are able to study 3-dimensional location, time activity and interaction of multiple simultaneously active brain sources in the scalp EEG.

Laminar cortical interactions during epileptic spikes studied with principal component analysis and physiological modeling

The direct cortical responses (DCR) to electrical stimulation and electrically evoked interictal penicillin spikes (EIIS) were studied in the same rats using current source-density (CSD) analysis to directly compare regions of neuronal depolarization and hyperpolarization in neocortex. Principal component analysis (PCA) was further used to evaluate patterns of covariance in the CSD that were characteristic of interactions between pyramidal cell populations with spatially and temporally distinct transmembrane currents. A physical model was applied to the physiological interpretation of PCA results and the optimal model parameters used to estimate neuronal generators of recorded laminar field potentials. The data suggested that the DCR and EIIS were produced by the same neuronal circuit which could be represented by two anatomically distinct populations of pyramidal cells. The first of these populations was situated in the upper and middle layers (supragranular pyramidal neurons) and formed a dipolar CSD pattern that reversed polarity in layers II and III. The second deeper population (infragranular pyramidal neurons) extended throughout most of the cortical thickness and formed a dipolar CSD pattern that reversed polarity in layer V. We propose that excitatory intracortical connections of supragranular pyramidal cells may pathologically synchronize depolarization within the epileptic focus. In this way, supragranular pyramidal cells may provide a trigger mechanism for interictal spikes in neocortex.

Long-term evaluation of human teeth after Le Fort I osteotomy: a histologic and developmental study

Transient pulpal vascular ischemia and direct injury to the apices of the teeth have been implicated as the causes of degenerative and atrophic pulpal changes in experimental animals after Le Fort I osteotomy despite the presence of collateral circulation. The long-term clinical effect of these pathologic changes in human teeth has not been studied. Seventeen maxillary third molar teeth from 10 patients whose postsurgical follow-up ranged from 6 months to 78 months (mean, 40 months) were extracted. The long-term biologic effects of Le Fort I osteotomy on the pulp and on the development of teeth were retrospectively evaluated with clinical and standard histologic techniques. Normal teeth from patients who were not operated on were used as controls. Histologic examination revealed an intact pulpal circulation and minimal pathologic changes in the pulpal tissue. Clinical and radiographic studies showed that the growing teeth developed normally after surgery. The Le Fort I downfracture procedure had little discernible long-term effect on the pulp and on the development of human third molar teeth.

Early color deprivation and subsequent color vision in a dichromatic monkey

A squirrel monkey (Saimiri sciureus) was reared for the first 4 months of life in a dim, colorless environment. Following an additional 10 months of normal visual experience, tests of color vision and spectral sensitivity were run on this animal and a control subject. The results suggest that the adult expression of dichromatic color vision does not depend on color experience during the first 4 months of life.