Spatial overlap between populations of synapses determines the extent of their associative interaction during the induction of long-term potentiation and depression

1. This study evaluates the associative interactions between inputs that lead to long-term potentiation (LTP) and long-term depression (LTD) in the dentate gyrus (DG). Previous studies have revealed that when two inputs are coconditioned, the extent of LTP is greater than when each input is conditioned alone. Moreover, for a weak input that does not show LTP when conditioned alone, LTP can be induced in that weak input if it is coconditioned with a strong input. LTD results when one input is silent when another is conditioned. In the present study, we evaluate whether these associative interactions depend on the extent of overlap of the terminal fields of the different inputs. 2. The experiment took advantage of the topographical organization of the temporodentate pathway from the entorhinal cortex (EC) to the DG. Four stimulating electrodes were placed so as to activate ipsilateral and crossed components of the projections from medial and lateral portions of the EC. Recording electrodes were positioned unilaterally in the DG so as to record field potentials. The localization of the synaptic field that was activated by each electrode was determined by current source density (CSD) analysis. The extent of overlap between the terminal fields of ipsi- and contralateral pathways was assessed, and the pathways were divided into groups where the overlap between current sinks was 0-50 or 51-100%. 3. Conditioning stimulation (400-Hz trains of 8 pulses delivered 8 times) was delivered to pathways alone or in combination with other pathways. The extent of LTP was evaluated after coactivation of pathways that overlapped substantially (51-100%) or minimally (0-50%). The extent of LTD was evaluated in pathways that were silent during conditioning of other overlapping or nonoverlapping pathways. 4. The extent of associative LTP or LTD depended on the extent of overlap between the terminal fields of pathways. Coactivation of two pathways that overlapped by 51-100% led to LTP; coactivation of pathways that overlapped by 0-50% did not. Moreover, LTD was induced in a crossed pathway when an ipsilateral pathway that overlapped by 51-100% was activated, but not when a nonoverlapping (0-50% overlap) ipsilateral pathway was activated. The degree of associative LTP or LTD that was induced in crossed pathways was correlated with the percent overlap with the terminal field of the active ipsilateral pathway. 5. Evaluation of whether LTD was induced when one division (medial or lateral) of the ipsilateral pathway was silent when the other division was conditioned revealed similar relationships.(ABSTRACT TRUNCATED AT 400 WORDS)     

Subcellular Localization of Salmonella enteritidis Endotoxin in Liver and Spleen of Mice and Rats

Salmonella enteritidis¹⁴C-endotoxin was recovered predominantly from the nuclear and mitochondrial subcellular fractions of livers and spleens of mice and rats, 3.5 hr and 3 days after intravenous administration. Of the recovered radioactivity, 10 to 20% was present in the liver mitochondrial fraction as high-molecular-weight, biologically active material, suggesting the presence of intact endotoxin. Autoradiographic studies demonstrated nuclear and cytoplasmic labeling in the liver and at least nuclear label in spleen cells. The resistance of rats, as compared to mice, to the induction of amyloidosis does not appear to be based on a difference in subcellular localization of endotoxin within the reticuloendothelial system.     

Modified polyriboinosinic-polyribocytidylic acid, an immunological adjuvant.

Stabilization of polyriboinosinic-polyribocytidylic acid against enzymatic hydrolysis by addition of poly-1-lysine and carboxymethylcellulose (PICLC) resulted in a compound with marked adjuvanticity. The primary antibody response of rhesus monkeys to formalin-inactivated Venezuelan equine encephalomyelitis virus vaccine was significantly potentiated if the vaccine was combined with PICLC prior to vaccination. The antibody response was maintained at a significantly higher level than controls for 2.5 months postvaccination and paralleled immunological responses reported for live, attenuated (TC-83) vaccine.     

Podocytic cytoskeletal disaggregation and basement-membrane detachment in puromycin aminonucleoside nephrosis.

Puromycin aminonucleoside--(PAN) treated rats develop acute nephrotic syndrome, mimicking human minimal lesion disease. In PAN nephrosis, podocyte detachment from the glomerular basement membrane (GBM) is the most likely cause of massive proteinuria in this model. To elucidate further the mechanisms of PAN-induced cellular dysfunction, new methods were employed to visualize podocyte cytoskeletal aggregation and to measure fibrillar attachment to the GBM. Adult Sprague-Dawley rats (n = 4/group) received a single tail-vein injection of PAN (75 mg/kg). On days 1, 2, 3, and 5 following injection, 24-hour urine collections were obtained for creatinine clearance, albuminuria, and total proteinuria. Then kidneys from each group were fixed by perfusion. Podocytic cytoskeleton was visualized by scanning electron microscopy. Subepithelial GBM staining and attachment fiber number, observed on digitized images of transmission electron micrographs, were quantitated with computer-based density analysis. A significant reduction in attachment fiber number in the GBM lamina rara externa occurred by day 5. On scanning electron micrographs, the secondary and tertiary podocytic processes were observed to be formed by highly aggregated cytoskeleton, which became partially disaggregated by day 3, was totally absent by day 5, and normalized by day 20. Immunogold staining revealed that actin and vinculin localized to the tertiary podocytic processes in the normal state were dispersed into the cell body following PAN. Podocyte cytoskeletal disaggregation precedes, and detachment from the GBM occurs simultaneously with, the onset of massive proteinuria in the PAN model.     

A controlled trial of acyclovir for chickenpox in normal children

BACKGROUND. Chickenpox, the primary infection caused by the varicella-zoster virus, affects more than 3 million children a year in the United States. Although usually self-limited, chickenpox can cause prolonged discomfort and is associated with infrequent but serious complications. METHODS. To evaluate the effectiveness of acyclovir for the treatment of chickenpox, we conducted a multicenter, double-blind, placebo-controlled study involving 815 healthy children 2 to 12 years old who contracted chickenpox. Treatment with acyclovir was begun within the first 24 hours of rash and was administered by the oral route in a dose of 20 mg per kilogram of body weight four times daily for five days. RESULTS. The children treated with acyclovir had fewer varicella lesions than those given placebo (mean number, 294 vs 347; P less than 0.001), and a smaller proportion of them had more than 500 lesions (21 percent, as compared with 38 percent with placebo; P less than 0.001). In over 95 percent of the recipients of acyclovir no new lesions formed after day 3, whereas new lesions were forming in 20 percent of the placebo recipients on day 6 or later. The recipients of acyclovir also had accelerated progression to the crusted and healed stages, less itching, and fewer residual lesions after 28 days. In the children treated with acyclovir the duration of fever and constitutional symptoms was limited to three to four days, whereas in 20 percent of the children given placebo illness lasted more than four days. There was no significant difference between groups in the distribution of 11 disease complications (10 bacterial skin infections and 1 case of transient cerebellar ataxia). Acyclovir was well tolerated, and there was no significant difference between groups in the titers of antibodies against varicella-zoster virus. CONCLUSIONS. Acyclovir is a safe treatment that reduces the duration and severity of chickenpox in normal children when therapy is initiated during the first 24 hours of rash. Whether treatment with acyclovir can reduce the rare, serious complications of chickenpox remains uncertain.     

2-Mercaptoethanol and n-acetylcysteine enhance T cell colony formation in AIDS and ARC.

One contributing factor to the loss of T cells in AIDS may be the impaired ability of T cell precursors to expand, as reflected in a decreased ability of patient cells to form T cell colonies in agar. We and others have noted such a defect in people with AIDS and ARC, and have found that suppressor cells and suppressive plasma contribute to decreased T-CFC formation. We report here that the reducing agents 2-mercaptoethanol (2-ME) and n-acetyl cysteine (NAC) can enhance colony formation in vitro. In part, 2-ME can reverse the defect in T cell colony-forming cells (T-CFC) formation by overcoming the effect of suppressor cells. In a group of 46 AIDS patients, T-CFC formation was initially 42 +/- 8% (mean +/- s.e.) that of control levels. 2-ME caused an increase of 401 +/- 76% in T-CFC formation which was significantly greater than the increase in control T-CFC formation; it also significantly enhanced T-CFC formation by cells from ARC patients. Suppressor cell activity from ten AIDS patients decreased from 58 +/- 21% to 12 +/- 10% when 2-ME was added. Similar data were obtained from 14 ARC patients. NAC, a related antioxidant with low toxicity, also enhanced T-CFC in cells of AIDS and ARC patients. Vitamin C generally did not increase T-CFC formation. The data suggest that certain antioxidants such as 2-ME and NAC may be useful in treatment protocols to enhance T cell numbers in patients with AIDS or ARC.     

Susceptibility of thymectomized and irradiated mice to challenge with several organisms and the effect of dapsone on infection with Mycobacterium leprae.

B6C3F1 mice that had been thymectomized at 8 to 12 weeks of age, subjected to 950 R of whole-body X irradiation, and transfused with syngeneic bone marrow were challenged in a footpad with Mycobacterium leprae or M. marinum, or intravenously or intraperitioneally with Listeria monocytogenes. Also, mice inoculated with M. leprae in a hind footpad were administered dapsone in the mouse chow. The thymectomized-irradiated (T + R) mice did not survive as well as non-thymectomized mice when housed in the vivarium with no special precautions, but survived sufficiently well to permit the completion of some long-term experiments. M. leprae multiplied to a higher "ceiling" and survived longer in the T + R mice than in the non-thymectomized controls. But a ceiling to multiplication of M. leprae was imposed, and finally the organisms were killed. The histopathological appearance of the footpad tissues, studied by electron microscopy, was consistent with the measurements of bacterial numbers and viability. Swelling of the footpad after local inoculation with M. marinum was greater in T + R mice than in non-thymectomized controls. Similarly, the number of L. monocytogenes following intravenous challenge was greater in the spleens of T + R than of non-thymectomized mice, and the survival of the T + R mice was impaired after intraperitoneal challenge with L.monocytogenes, compared to the survival of non-thymectomized mice. None of these differences was striking, suggesting that these T + R mice had retained or regained some immune competence. The effects of dapsone treatment of T + R mice inoculated with M. leprae were much the same as those of treatment of non-thymectomized mice. Because these T + R mice were not greatly immunosuppressed, they would not have provided a model of human lepromatous leprosy suitable for chemotherapeutic studies.     

Association of defensin beta-1 gene polymorphisms with asthma

BACKGROUND: Defensins are antimicrobial peptides that may take part in airway inflammation and hyperresponsiveness. OBJECTIVE: We characterized the genetic diversity in the defensin beta-1 (DEFB1) locus and tested for an association between common genetic variants and asthma diagnosis. METHODS: To identify single nucleotide polymorphisms (SNPs), we resequenced this gene in 23 self-defined European Americans and 24 African Americans. To test whether DEFB1 genetic variants are associated with asthma, we genotyped 4 haplotype-tag SNPs in 517 asthmatic and 519 control samples from the Nurses' Health Study (NHS) and performed a case-control association analysis. To replicate these findings, we evaluated the DEFB1 polymorphisms in a second cohort from the Childhood Asthma Management Program. RESULTS: Within the NHS, single SNP testing suggested an association between asthma diagnosis and a 5' genomic SNP (g.-1816 T>C; P = .025) and intronic SNP (IVS+692 G>A; P = .054). A significant association between haplotype (Adenine, Cytosine, Thymine, Adenine [ACTA]) and asthma ( P = .024) was also identified. Associations between asthma diagnosis and both DEFB1 polymorphisms were observed in Childhood Asthma Management Program, a second cohort: g.-1816 T>C and IVS+692 G>A demonstrated significant transmission distortion ( P = .05 and .007, respectively). Transmission distortion was not observed in male subjects. The rare alleles (-1816C and +692A) were undertransmitted to offspring with asthma, suggesting a protective effect, contrary to the findings in the NHS cohort. Similar effects were evident at the haplotype level: ACTA was undertransmitted ( P = .04) and was more prominent in female subjects ( P = .007). CONCLUSION: Variation in DEFB1 contributes to asthma diagnosis, with apparent gender-specific effects.     

Further investigation of the HEXA gene intron 9 donor splice site mutation frequently found in non-Jewish Tay-Sachs disease patients from the British Isles.

In a previous study we found that a Tay-Sachs disease (TSD) causing mutation in the intron 9 donor splice site of the HEXA gene occurs at high frequency in non-Jewish patients and carriers from the British Isles. It was found more frequently in subjects of Irish, Scottish, and Welsh origin compared with English origin (63% and 31% respectively). We have now tested, in a blind study, 26 American TSD carriers and 28 non-carriers who have British ancestry for the intron 9 splice site mutation. Six of the carriers and none of the controls were positive for the mutation. All six had Irish ancestry, compared with nine of the 20 other (intron 9 mutation negative) TSD carriers (p < 0.05). These results confirm the previously found high frequency of the intron 9 mutation in non-Jewish TSD families of British Isles, particularly Irish, origin, and reinforce the need to screen such families for this mutation.     

Induction of immune responses in patients with B-cell lymphoma against the surface-immunoglobulin idiotype expressed by their tumors.

BACKGROUND. The idiotypic determinants of the surface immunoglobulin of a B-cell lymphoma can serve as a clonal tumor-specific marker, which may have implications for immunotherapy. We sought to determine whether idiotype-specific immune responses against this autologous antigen could be induced in patients with B-cell lymphoma. METHODS. Nine patients were selected who had minimal residual disease or a complete remission after chemotherapy. Each received a series of subcutaneous injections of the immunoglobulin derived from his or her tumor cells (immunoglobulin-idiotype protein), which had been conjugated to a protein carrier and mixed with an immunologic adjuvant. RESULTS. In seven of the nine patients the injections induced sustained idiotype-specific immunologic responses of the humoral type (two patients), the cell-mediated type (four patients), or both (one patient). The use of an adjuvant was essential for these immune responses. The induced antibodies bound specifically to autologous immunoglobulin idiotype, inhibited the binding of murine monoclonal antiidiotype antibodies, and bound autologous tumor cells. Cell-mediated responses were demonstrated by the specific proliferation of immune peripheral-blood mononuclear cells to the soluble immunoglobulin-idiotype protein in vitro. The tumors of both of the patients with measurable disease regressed completely. Toxicity associated with the vaccine was minimal and consisted only of mild reactions at the site of intramuscular injection. CONCLUSIONS. These results demonstrate that autologous immunoglobulin idiotype can be formulated into an immunogenic, tumor-specific antigen in humans with B-cell lymphoma, and they provide the background for large-scale trials of active specific immunotherapy of this disease.