Energy metabolism in human erythrocytes. I. Effects of sodium fluoride.

Exposure of red cells to fluoride produces a variety of metabolic alterations, most of which are based upon the secondary effects of enolase inhibition, which reduces pyruvate synthesis and interferes with the regeneration of diphosphopyridine nucleotide (NAD). Adenosine triphosphate (ATP) is consumed in the hexokinase and phosphofructokinase reactions but is not regenerated since the deficiency of NAD limits glyceraldehyde phosphate dehydrogenase. ATP depletion in the presence of fluoride and calcium induces a massive loss of cations and water. Of the other known sites of ATP utilization, membrane-bound ATPase is inhibited by fluoride, but the incorporation of fatty acids into membrane phospholipids is unaffected until ATP is depleted. The addition of methylene blue to fluoride-treated red cells regenerates NAD, permitting triose oxidation and the generation of 3-phosphoglycerate and 2,3-diphosphoglycerate. Enolase inhibition is then partially overcome by mass action, and sufficient glycolysis proceeds to maintain the concentration of ATP. This in turn prevents the massive cation and water loss, and permits membrane phospholipid renewal to proceed. Membrane ATPase activity is not restored by the oxidant so that normal cation leakage remains unopposed by cation pumping in red cells exposed to the combination of fluoride and methylene blue.

Energy metabolism in human erythrocytes. II. Effects of glucose depletion.

Normal red cells were incubated in the absence of glucose to develop a system in which total adenosine triphosphate (ATP) turnover could be assessed. After 1 hr, the triose pool had been completely consumed. Thereafter, the metabolism of 2,3-diphosphoglycerate (DPG) to pyruvate and lactate was the sole significant source of ATP synthesis.10(-3)M CuCl(2), which did not enter the cells, diminished ATP utilization by more than 50%. This could be only partially attributed to the inhibition by copper of residual acylation and cation pumping, which were already reduced by glucose depletion. Other membrane enzymes, which presumably function in the maintenance of membrane integrity, must, therefore, use a significant portion of erythrocyte ATP. The behavior of glucose-depleted red cells with respect to cation transport was complex. The addition of ouabain did not decrease ATP utilization in these red cells. Ouabain inhibitable potassium influx was nearly normal after triose depletion, but total potassium influx was decreased. In contrast, the ouabain inhibitable sodium efflux was markedly reduced after triose depletion, although the concentration of ATP was 70% of normal. The dissociation of monovalent cation pumping suggests that the energy for active sodium transport is derived from a specific source (such as the ATP produced by the phosphoglycerate kinase reaction) distinct from that for potassium transport.

Paying attention to the thalamic reticular nucleus.

The thalamic reticular nucleus can be divided into a number of sectors, each concerned with a different function (sight, touch, hearing, movement or 'limbic' functions). Each sector is connected to more than one thalamic nucleus and to more than one cortical area, and each sector has topographically mapped connections with the thalamus and the cortex. We consider the known details of these connections and show: (1) that they are not the same for each sector; (2) that the reticular nucleus serves as a nexus, where several functionally related cortical areas and thalamic nuclei can interact, modifying thalamocortical transmission through the inhibitory connections that go from the reticular cells to thalamic relay cells; and (3) that we need much more detailed information about these highly organized connections before we can understand exactly how the thalamic reticular nucleus might be influencing thalamocortical pathways in attentional mechanisms or in other, as yet undefined, roles.

Postremission therapy for children with acute myeloid leukemia: the children's cancer group experience in the transplant era.

We reviewed consolidation therapy results and analyzed postremission outcomes for 1464 children less than 21 years old at diagnosis in five consecutive Children's Cancer Group acute myeloid leukemia trials between 1979 and 1996. Children in remission were allocated to allogeneic bone marrow transplantation (BMT) (N=373) in first remission, if a matched family donor was available. Remaining children were assigned consolidation chemotherapy (N=688) or autologous purged BMT (N=217), or withdrew from study before assignment, or with unknown data (N=186). Overall and disease-free survival were superior for children assigned allogeneic transplants. High (>50,000/microl) diagnostic white blood cell (WBC) count was prognostic for inferior outcome, but French-American-British (FAB) subtypes were not. Inv(16) is a favorable karyotypic feature for children in first remission and t(8;21) is not. Allogeneic transplantation benefit was evident in most children, including those with high or low diagnostic WBC count, each FAB subtype, and t(8;21), but was not seen in children with inv(16). Therefore, these data suggest reserving matched related donor allogeneic transplantation for children with inv(16) for second remission, but not those with t(8;21).

Feasibility, toxicity, and biologic response of interleukin-2 after consolidation chemotherapy for acute myelogenous leukemia: a report from the Children's Cancer Group.

PURPOSE: Although remission can be achieved in 80% of children with acute myelogenous leukemia (AML), many patients experience relapse. Because interleukin-2 (IL-2) can induce remission in patients with overt evidence of AML, we hypothesized that IL-2 given to patients in first remission after intensive consolidation chemotherapy might prevent relapse. This study sought to determine whether such an approach was feasible. PATIENTS AND METHODS: Twenty-one patients in complete remission received IL-2 after completion of treatment on Children's Cancer Group (CCG) protocol 2941. Recombinant IL-2 9 x 10(6) IU/m2 daily by continuous intravenous infusion (c.i.v.) was given for 4 days. After 4 days rest, IL-2 1.6 x 10(6) IU/m2 daily c.i.v. was resumed for 10 days. We monitored patients for toxicity and measured absolute lymphocyte count, the absolute count of cells that express CD56 and CD3 antigen, and soluble IL-2 receptor alpha-chain (sIL-2R alpha) levels before the start of IL-2 and after completion of each of the two courses of IL-2. RESULTS: Observed toxicities included fever (57%), vascular leak (48%), hypotension (38%), tachycardia (14%), rash (29%), septicemia (5%), thrombocytopenia (29%), elevated transaminase (14%), electrolyte disturbance (29%), and hyperglycemia (10%). No patient required cardiac pressors or transfer to an intensive care unit. All patients studied developed an increase in lymphocyte count, CD56 count, CD3 count, and sIL-2R alpha levels after treatment with IL-2. CONCLUSION: This schedule of IL-2 was reasonably well tolerated by children with AML in first remission. After treatment, increased levels of sIL-2R alpha were observed. CCG is conducting a randomized prospective trial to assess the efficacy of IL-2 to prevent the relapse of AML (CCG-2961).

Double-alkylator non-total-body irradiation regimen with autologous hematopoietic stem-cell transplantation in pediatric solid tumors.

PURPOSE: To determine the maximum-tolerated dose (MTD) of cyclophosphamide (CTX) when administered with fixed doses of carboplatin, etoposide, and melphalan (CEM) followed by autologous hematopoietic stem-cell transplantation (HSCT) in children with recurrent or high-risk solid tumors as a consolidation chemotherapy, and to make preliminary observations on efficacy. PATIENTS AND METHODS: Twenty-seven patients with solid tumors between the ages of 2 and 21 years were enrolled. Twenty of 27 had recurrent disease, whereas seven were treated in first remission. Nine were treated with melphalan 50 mg/m2/d for 4 days, carboplatin 300 mg/m2/d for 4 days as a continuous infusion (CI), and etoposide 200 mg/m2/d for 4 days as a CI (level I). CTX 750 mg/m2/d for 4 days was added to this regimen for the next 18 patients (level II). Seven of nine patients at level I and four of 18 at level II received bone marrow (BM) only, while two of nine at level I and 14 of 18 at level II received BM plus peripheral-blood stem cells (PBSC). RESULTS: The median time to reach an absolute neutrophil count (ANC) greater than 500/microl was 12.5 and 10 days for patients who received BM only and BM plus PBSC, respectively. Three cases of grade 3 mucositis, one Candida sepsis, and two transient hypoxemias were the main nonfatal toxicities. No toxic mortality was observed among level I patients. Three of 18 (16%) level II patients, all in second CR, died of transplant-related complications. Median follow-up is 29 months. Nine died of progressive disease (one second malignancy), six relapsed and are alive with disease, and nine are in continuous CR. Among the 15 PNET/Ewing's sarcoma patients, seven are in continuous CR (three of nine in second CR/VGPR, four of six in first CR/VGPR). CONCLUSION: The addition of CTX 3 g/m2 to CEM followed by autologous HSCT as a consolidation therapy resulted in 16% toxic mortality in children with recurrent or high-risk solid tumors. Further CTX dose escalation was aborted. No common nonhematologic toxicity was identified. The event-free survival (EFS) of 66% +/- 19% at 3 years for patients with metastatic PNET/Ewing's sarcoma in first remission is encouraging. However, this is based on only six patients. Both level I and II need further exploration in high-risk pediatric solid tumors in first remission.

Treatment of newly diagnosed children and adolescents with acute myeloid leukemia: a Childrens Cancer Group study.

PURPOSE: The objectives of this study were to determine if the addition of etoposide, thioguanine, and dexamethasone to daunorubicin and cytarabine (five-drug regimen) during induction would improve remission induction rates and survival of children with acute myeloid leukemia (AML) when compared with the standard regimen of cytarabine and daunorubicin (7 + 3) and whether allogeneic bone marrow transplantation (BMT) or intensive chemotherapy consolidation with or without maintenance would give a superior outcome. PATIENTS AND METHODS: A total of 591 assessable children with AML entered Childrens Cancer Group (CCG) trial 213 between January 1986 and February 1989. The status of patients as of September 1, 1992 forms the basis of this report. The results were compared with previous AML studies. RESULTS: The projected survival rate of all patients at 5 years is 39% (event-free survival [EFS] rate, 31%), which is superior to that of the prior CCG study (P = .01). The induction rate was 79% for 7 + 3 and 76% for the five-drug regimen (not significant). Comparisons of BMT to chemotherapy favored BMT, but these differences do not always reach statistical significance (eg, 5-year disease-free survival [DFS] rate, 46% v 38% [P = .06] with donor available and 54% v 37% [P = .002] if treated according to protocol intent). No benefit for maintenance therapy was found and, in some comparisons, it was inferior to discontinuation of therapy (5-year survival rate, 46% v 68%, P < .01). CONCLUSION: The 5-year EFS rate of patients with AML is 31% and has improved. The five-drug induction regimen is no better than standard induction, BMT appears superior to chemotherapy, and maintenance therapy was not beneficial.

Correlation of chromosome abnormalities with patient characteristics, histologic subtype, and induction success in children with acute nonlymphocytic leukemia.

Cytogenetic analyses of bone marrow cells were performed in 195 children with acute nonlymphocytic leukemia (ANLL) at diagnosis, as part of Childrens Cancer Study Group Study No. 251. Ninety-six patients (49%) exhibited clonal abnormalities, including trisomy 8 in 18 patients, t(8;21) in 11, t(15;17) in seven, loss of a sex chromosome in seven, monosomy 7 in seven, and the Philadelphia chromosome in four. Clonal abnormalities were found significantly more often in younger patients. Furthermore, recurring cytogenetic abnormalities tended to correlate with specific ages. For example, t(8;21) was associated significantly with children over four years of age, while -7 associated with overall loss of genetic material from the long arm of chromosome 7 (7q) and 11q- were associated significantly with younger children. Recurring chromosome abnormalities also correlated with specific ANLL histologic subtypes, such as t(8;21) with acute myelogenous leukemia and t(15;17) with acute promyelocytic leukemia. Presence or absence of cytogenetic abnormalities was compared with the ability of patients to achieve remission. Individuals exhibiting clonal abnormalities in bone marrow cells had an equally likely chance of achieving remission (74%) as those individuals with normal karyotypes (75%). Nonrandom chromosome abnormalities associated with a high induction success rate included +8 with a 94% induction success rate (P = .13) and t(8;21) with a 91% success rate (P = .46). Patients exhibiting the -7 abnormality associated with overall loss of 7q had a significantly less successful induction outcome, with only 28% achieving remission (P = .02); three of seven patients with t(15;17) died during induction therapy.

Chemotherapy for induction of remission of childhood acute myeloid leukemia followed by marrow transplantation or multiagent chemotherapy: a report from the Childrens Cancer Group.

PURPOSE: In an effort to evaluate the usefulness of bone marrow transplantation, the Childrens Cancer Group (CCG) initiated a multiinstitutional study comparing bone marrow transplantation versus chemotherapy after successful induction of remission for previously untreated children and young adults with acute myeloid leukemia. PATIENTS AND METHODS: From 1979 to 1983, 508 patients were entered onto this study and 490 were treated. After induction, patients with an HLA mixed leukocyte culture (MLC)-compatible sibling underwent bone marrow transplantation. Patients not eligible for bone marrow transplantation were eligible for randomization to two chemotherapy maintenance regimens. All patients undergoing bone marrow transplantation were conditioned with cyclophosphamide and total-body irradiation (TBI). Methotrexate was used to prevent or modify graft-versus-host disease (GVHD). RESULTS: Three hundred eighty-one patients achieved bone marrow remission (78%). Eighty-nine patients had an HLA/MLC-compatible sibling donor and were eligible for bone marrow transplantation, and 252 had no match. Comparison of survival estimates for patients eligible for transplantation versus not eligible at 3 years (52% v 41%), 5 years (50% v 36%), and 8 years (47% v 34%) showed a significant difference in favor of bone marrow transplantation (P < .05). Disease-free survival (DFS) demonstrated similar results. Application of a cure model to the results showed a better outcome for those eligible for transplantation (P = .04). Patients randomized between the two chemotherapy regimens did not show any significant difference between those treated with a continuous maintenance versus a cyclic regimen (P = .16). CONCLUSION: Children and young adults who successfully achieved a remission with multiple-agent chemotherapy who had an HLA/MLC-compatible donor and were thus eligible for an allogeneic bone marrow transplant had better survival than those not eligible for transplantation.

The differential distribution of the growth-associated protein-43 in first and higher order thalamic nuclei of the adult rat.

Corticothalamic axons from layer 5 of primary and secondary auditory and visual areas have large terminals that make multiple synaptic contacts on proximal dendrites of relay cells in higher order thalamic nuclei and have been termed "driver" inputs. The corticothalamic cells express mRNA for the presynaptic growth-associated protein-43, in the adult rat [Feig SL (2004) Corticothalamic cells in layers 5 and 6 of primary and secondary sensory cortex express GAP-43 mRNA in the adult rat. J Comp Neurol 468:96-111]. In contrast, ascending driver afferents to first order nuclei (e.g. retinal, inferior collicular, and lemniscal) lose growth-associated protein-43 as mature synaptic terminals are established. Levels of immunoreactivity for growth-associated protein-43 are compared for first and higher order visual (lateral geniculate and lateral posterior), auditory (ventral and dorsal divisions of the medial geniculate), and somatosensory (ventral posterior and posterior) thalamic nuclei. At one week postnatal, staining for growth-associated protein-43 is uniform throughout first and higher order thalamic nuclei. By three weeks and thereafter, staining is denser in the higher order than first order thalamic nuclei. Electron microscopy shows growth-associated protein-43 in profiles with characteristics of afferents from layer 5 in LP and medial geniculate nucleus and no such label in retinal afferents in lateral geniculate nucleus. In these nuclei, approximately 25% of the profiles with characteristics of cortical afferents from layer 6 have label for growth-associated protein-43. The superficial layers of the superior colliculus also show growth-associated protein-43 positive profiles with characteristics of terminals from cortical layer 5. Some growth-associated protein-43 positive terminals were also positive for GABA in the thalamic nuclei studied and in the superior colliculus. The data suggest that sensory afferents to first order thalamocortical relays become stabilized once mature synaptic patterns are established, but the higher stages of information processing involving higher order thalamic relays, via cells in cortical layer 5, retain plasticity related to growth-associated protein-43 in the adult.

Prognostic variables in newly diagnosed children and adolescents with acute myeloid leukemia: Children's Cancer Group Study 213.

The objective of this study was to identify biologic parameters that were associated with either exceptionally good or poor outcome in childhood acute myeloid leukemia (AML). Among the children with AML who entered Children's Cancer Group trial 213, 498 patients without Down syndrome or acute promyelocytic leukemia (APL) comprise the basis for this report. Univariate comparisons of the proportion of patients attaining complete remission after induction (CR) indicate that, at diagnosis, male gender, low platelet count (< or =20 000/microl), hepatomegaly, myelodysplastic syndrome (MDS), French-American- British (FAB) category M5, high (>15%) bone marrow (BM) blasts on day 14 of the first course of induction, and +8 are associated with lower CR rates, while abnormal 16 is associated with a higher CR rate. Multivariate analysis suggests high platelet count at diagnosis (>20 000/microl), absence of hepatomegaly, < or =15% day 14 BM blast percentage, and abnormal 16 are independent prognostic factors associated with better CR. Univariate analysis demonstrated a significant favorable relationship between platelet count at diagnosis (>20 000/microl), absence of hepatomegaly, low percentage of BM blasts (< or =15%), and abnormal 16 with overall survival. Absence of hepatomegaly, < or =15% day 14 BM blast percentage, and abnormal 16 were determined to be independent prognostic factors associated with better survival.

Pneumococcal vaccination of recipients of bone marrow transplants.

A 14-valent pneumococcal vaccine was administered to 39 recipients of allogeneic bone marrow transplants, and their type-specific antibody responses were compared with normal control subjects. Preimmunization antibody levels in patients were twofold to 12-fold lower than those levels in control subjects for all serotypes. Mean postimmunization antibody levels for each serotype were also considerably lower in patients (range, 56 to 859 ng of antibody nitrogen per milliliter) than in control subjects (range, 727 to 5,626 ng/mL). Poor antibody responses were primarily associated with early vaccination after transplantation, corticosteroid therapy for graft-v-host disease and other illnesses, and the male sex. Antibody responses of patients not given corticosteroids and vaccinated more than seven months after transplantation improved with time after transplantation. Postvaccination infection occurred in five patients who were vaccinated early after transplantation. Pneumococcal vaccination has limited potential for providing protection in marrow transplant recipients except in the cases of those patients who are not receiving corticosteroids and are vaccinated more than seven months after transplantation.

Case problems in bone marrow transplantation. I. Graft failure in aplastic anemia: its biology and treatment.

An unusual case of graft failure following bone marrow transplantation for aplastic anemia is reported in which the patient had delayed and incomplete recovery of hematopoiesis despite documentation of sustained engraftment. The pathophysiology of graft failure following bone marrow transplantation is discussed and recent advances in pretransplant immunosuppressive therapy to prevent graft rejection are reviewed.

Autotransplantation after in vitro immunotherapy of lymphoblastic leukemia.

We have used in vitro immunotherapy before autologous bone marrow transplantation for three patients with acute lymphoblastic leukemia (ALL). Bone marrow was removed during remission, and mononuclear cells were separated by density-step centrifugation on Ficoll-Hypaque. The cells from each patient were treated with a heteroantiserum and complement to eliminate leukemic cells and were cryopreserved. Following chemotherapy and total body irradiation, the treated marrows were thawed and infused. All the patients showed positive evidence of returning marrow function before death. One patient who survived 4 months showed no evidence of leukemia at post mortem, and marrow sections demonstrated active hematopoiesis of all cell lines.

Autologous bone marrow transplantation in patients with cancer.

Ten patients with non-leukemic neoplasms received intensive, marrow-lethal doses of drugs and radiation followed by rescue with autologous cryopreserved bone marrow (nine) or marrow from an identical twin as part of a phase 1-2 study. Nine patients had extensive disease that was unresponsive to conventional therapy. Marrow engraftment was documented in all evaluable cases and most patients had a substantial anti-tumor response. Three patients are alive from 4 to 10 months following transplantation without evidence of disease.

Radiation risk from screening mammography of women aged 40-49 years.

Although direct evidence of carcinogenic risk from mammography is lacking, there is a hypothetical risk from screening because excess breast cancers have been demonstrated in women receiving doses of 0.25-20 Gy. These high-level exposures to the breast occurred from the 1930s to the 1950s due to atomic bomb radiation, multiple chest fluoroscopies, and radiation therapy treatments for benign disease. Using a risk estimate provided by the Biological Effects of Ionizing Radiation (BEIR) V Report of the National Academy of Sciences and a mean breast glandular dose of 4 mGy from a two-view per breast bilateral mammogram, one can estimate that annual mammography of 100,000 women for 10 consecutive years beginning at age 40 will result in at most eight breast cancer deaths during their lifetime. On the other hand, researchers have shown a 24% mortality reduction from biennial screening of women in this age group; this will result in a benefit-to-risk ratio of 48.5 lives saved per life lost and 121.3 years of life saved per year of life lost. An assumed mortality reduction of 36% from annual screening would result in 36.5 lives saved per life lost and 91.3 years of life saved per year of life lost. Thus, the theoretical radiation risk from screening mammography is extremely small compared with the established benefit from this life-saving procedure and should not unduly distract women under age 50 who are considering screening.

Ultrastructural studies of the primate lateral geniculate nucleus: morphology and spatial relationships of axon terminals arising from the retina, visual cortex (area 17), superior colliculus, parabigeminal nucleus, and pretectum of Galago crassicaudatus.

The electron microscopic autoradiographic tracing method has been used to examine the morphology and postsynaptic relationships of five projections (retina, cortical area 17, superior colliculus (tectal), parabigeminal nucleus, and pretectum) to the dorsal lateral geniculate nucleus of the greater bush baby Galago crassicaudatus. Retinal terminals have been examined in the contralaterally innervated layer of each of the three matched pairs [parvi- (X-cell), magno- (Y-cell), and koniocellular (small, W-cell)] of geniculate layers. These terminals are large and contain pale mitochondria and round vesicles (RLPs). RLPs are presynaptic to juxtasomatic regions of parvi- and magnocellular neurons. In contrast, RLPs innervate more distal regions of koniocellular neurons. Labeled cortical, tectal, and parabigeminal terminals are relatively small and contain round vesicles and dark mitochondria. Cortical terminals in each of the three representative layers are presynaptic to small diameter dendrites. No convergence of cortical and retinal terminals has been seen in any layer. Labeled tectal and parabigeminal terminals are found primarily in the koniocellular layers, but the latter are also seen in all other layers. Tectal and parabigeminal terminals have been observed converging with retinal terminals on dendrites of some koniocellular neurons. Labeled pretectogeniculate terminals contain densely packed pleomorphic vesicles, dark mitochondria, and a dark cytoplasmic matrix. These terminals, which are present in each of the representative layers, are presynaptic to conventional dendrites and profiles containing loosely dispersed pleomorphic vesicles and a pale cytoplasmic matrix.

Corticocortical communication via the thalamus: ultrastructural studies of corticothalamic projections from area 17 to the lateral posterior nucleus of the cat and inferior pulvinar nucleus of the owl monkey.

Electron microscopic anterograde autoradiography has been used to analyze the morphology and postsynaptic relationships of area 17 cortical terminals in the lateral division of the lateral posterior nucleus (LPl) of the cat and medial division of the inferior pulvinar nucleus (IPm) of the owl monkey. Such terminals are thought to arise exclusively from layer 5 in the cat and primate (Lund et al. [1975] J. Comp. Neurol. 164:287-304; Abramson and Chalupa [1985] Neuroscience 15:81-95). All labeled terminals in both nuclei exhibited the morphology of ascending "lemniscal" afferents. That is, they contained round vesicles, were large, made asymmetrical synaptic and filamentous nonsynaptic contacts, and were classified as RLs. These cortical RLs also exhibited the postsynaptic relationships of lemniscal afferents. Thus, they were presynaptic to large dendrites within glial encapsulated glomeruli, where a majority was involved in complex synaptic arrangements called triads. They also were found adjacent to terminal profiles with pleomorphic vesicles but never adjacent to small terminals containing round vesicles. Our results suggest that the layer 5 projection from area 17 provides a functional "drive" for some LPl and IPm neurons. Information carried over this "re-entrant" pathway (Guillery [1995] J. Anat. 187:583-592) could be modified within the LPl and IPm by both cortical and subcortical pathways and subsequently conveyed to higher visual cortical areas, where it could be integrated with messages carried through the well-documented corticocortical pathways (Casagrande and Kaas [1994] Cerebral cortex New York: Plenum Press).

Distribution and ultrastructure of neurons in opossum piriform cortex displaying immunoreactivity to GABA and GAD and high-affinity tritiated GABA uptake.

GABAergic neurons have been identified in the piriform cortex of the opossum at light and electron microscopic levels by immunocytochemical localization of GABA and the GABA-synthesizing enzyme glutamic acid decarboxylase and by autoradiographic visualization of high-affinity 3H-GABA uptake. Four major neuron populations have been distinguished on the basis of soma size, shape, and segregation at specific depths and locations: large horizontal cells in layer Ia of the anterior piriform cortex, small globular cells with thin dendrites concentrated in layers Ib and II of the posterior piriform cortex, and multipolar and fusiform cells concentrated in the deep part of layer III in anterior and posterior parts of the piriform cortex and the subjacent endopiriform nucleus. All four populations were well visualized with both antisera, but the large layer Ia horizontal cells displayed only very light 3H-GABA uptake, thus suggesting a lack of local axon collaterals or lack of high-affinity GABA uptake sites. The large, ultrastructurally distinctive somata of layer Ia horizontal cells receive a very small number of symmetrical synapses; the thin, axonlike dendrites of small globular cells are exclusively postsynaptic and receive large numbers of both symmetrical and asymmetrical synapses, in contrast to somata which receive a small number of both types; and the deep multipolar and fusiform cells receive a highly variable number of symmetrical and asymmetrical synapses on somata and proximal dendrites. Labeled puncta of axon terminal dimensions were found in large numbers in the neuropil surrounding pyramidal cell somata in layer II and in the endopiriform nucleus. Moderately large numbers of labeled puncta were found in layer I at the depth of pyramidal cell apical dendrites with greater numbers in layer Ia at the depth of distal apical segments than in layer Ib. High-affinity GABA uptake was demonstrated in the termination zone of the projection from the anterior olfactory nucleus to the anterior piriform cortex. Cell bodies of origin of this projection displayed heavy retrograde labeling with 3H-GABA. Matching neuropil and cellular labeling was demonstrated with the GABA-BSA antiserum but not with the GAD antiserum, thus suggesting that GABA is normally present in these cells but is taken up from the neuropil rather than synthesized. No comparable high-affinity GABA uptake was demonstrated in the association fiber systems that originate in the piriform cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Connections of higher order visual relays in the thalamus: a study of corticothalamic pathways in cats.

Axonal markers injected into layers 5 and 6 of cortical areas 17, 18, or 19 labeled axons going to the lateral geniculate nucleus (LGN), the lateral part of the lateralis posterior nucleus (LPl), and pulvinar (P). Area 19 sends fine axons (type 1, Guillery [1966] J Comp Neurol 128:21-50) to LGN, LPl, and P, and thicker, type 2 axons to LPl and P. Areas 17 and 18 send type 1 axons to LGN, and a few type 1, but mainly type 2 axons to LPl and P. Type 1 and 2 axons from a single small cortical locus distribute to distinct, generally nonoverlapping parts of LP and P; type 1 axons have a broader distribution than type 2 axons. Type 2 axons, putative drivers of thalamic relay cells (Sherman and Guillery [1998] Proc Natl Acad Sci USA 95:7121-7126; Sherman and Guillery [2001] Exploring the thalamus. San Diego: Academic Press), supply small terminal arbors (100- to 200-microm diameter) in LPl and P, and then continue into the midbrain. Each thalamic type 2 arbor contains two terminal types. One, at the center of the arbor, is complex and multilobulated; the other, with a more peripheral distribution, is simpler and may contribute to adjacent arbors. Type 2 arbors from a single injection are scattered around and along "isocortical columns" in LPl, (i.e., columns that represent cells having connections to a common cortical locus). Evidence is presented that the connections and consequently the functional properties of cells in LP change along these isocortical columns. Type 2 driver afferents from a single cortical locus can, thus, be seen as representing functionally distinct, parallel pathways from cortex to thalamus.