A critical period of neuronal activity results in aberrant neurogenesis rewiring hippocampal circuitry in a mouse model of epilepsy

In the mammalian hippocampus, adult-born granule cells (abGCs) contribute to the function of the dentate gyrus (DG). Disruption of the DG circuitry causes spontaneous recurrent seizures (SRS), which can lead to epilepsy. Although abGCs contribute to local inhibitory feedback circuitry, whether they are involved in epileptogenesis remains elusive. Here, we identify a critical window of activity associated with the aberrant maturation of abGCs characterized by abnormal dendrite morphology, ectopic migration, and SRS. Importantly, in a mouse model of temporal lobe epilepsy, silencing aberrant abGCs during this critical period reduces abnormal dendrite morphology, cell migration, and SRS. Using mono-synaptic tracers, we show silencing aberrant abGCs decreases recurrent CA3 back-projections and restores proper cortical connections to the hippocampus. Furthermore, we show that GABA-mediated amplification of intracellular calcium regulates the early critical period of activity. Our results demonstrate that aberrant neurogenesis rewires hippocampal circuitry aggravating epilepsy in mice.

Nonradioactive in situ hybridization. A rapid approach for the identification of marker chromosomes: study of a case of acute leukemia with a Yq specific DNA probe

Nonradioactive in situ hybridization provides a rapid method for detecting specific nucleic acid sequences. In this study of a patient with acute leukemia, we applied in situ hybridization for identification of a marker chromosome and determination of the number of copies of this marker in interphase nuclei using a biotinylated Yq-specific DNA probe (pY3.4). We show that nonradioactive interphase in situ hybridization can be a useful method for karyotypic analysis in addition to routine cytogenetic techniques in neoplastic disorders.

Lymphocyte subpopulation profiles and mitogen kinetics in immunological deficiency testing

The correlation between lymphocyte proliferative responses to mitogens and T4/T8 ratios was analyzed in a cross section of patients who either were in a high-risk group for HTLV-III infection or fulfilled clinical criteria for acquired immune deficiency syndrome (AIDS). The patient results showed that, correlated with decreased T4/T8 ratios, there was a decrease in mitogen responsiveness first to pokeweed mitogen (PWM), followed by concanavalin A (Con A) and then phytohemagglutinin (PHA). Parallel to this decrease there was a shift toward higher concentrations of mitogens needed for optimal proliferation. In comparison, depletion of T4+ lymphocytes from normal healthy controls also decreased lymphocyte proliferative responses to all three mitogens but shifted the amount of mitogen needed for optimal proliferation toward lower concentrations. The differences in mitogen-induced proliferation between patients and healthy controls suggest a model whereby there is a functional defect(s) in mitogen responsiveness of the remaining T4- lymphocyte population that can be overcome when higher concentrations of mitogen are used.

An acquired Robertsonian translocation in prolymphocytic leukemia: a case presentation and review

Robertsonian translocations between the acrocentric autosomes are the most common type of constitutional chromosome rearrangement in humans. However, Robertsonian translocations are very rarely acquired in cancer cells. We report a patient with prolymphocytic leukemia and an acquired Robertsonian translocation in the leukemic cells. The translocation was between chromosomes #13 and #15; t(13;15)(q11;p12). Two other cases of malignancy with an acquired Robertsonian translocation have been found, one being of the t(13;15) type, which accounts for only 1% of constitutional Robertsonian translocations. We propose, therefore, that although Robertsonian translocations are occasionally observed in cancer cells, they are very rarely acquired.

Telomeric fusion in pre-T-cell acute lymphoblastic leukemia

Telomeric fusion, a rare phenomenon, was observed in malignant cells from the peripheral blood of an 18-year-old male with rapidly progressive pre-T-cell acute lymphoblastic leukemia (ALL). Only two comparable cases, both with B-cell ALL, have been reported with telomeric fusion in neoplasia. All of the leukemic cells examined from our patient had two chromosome abnormalities consisting of partial triplication (trp) of chromosome 2 and a derivative chromosome 3. Approximately a third of the leukemic cells showed in addition telomere-telomere fusions. These involved the telomeric regions of 1p, 2p, 4q, 5q, 7q, 10q, 11q, 12p, 15p, 21p, and Xq and 3p of the derivative (3). The findings in this case suggest that telomeric fusion may function as a mechanism for the development of chromosome rearrangements that may play a role, albeit rarely, in human neoplasia.

Position effect in translocation (2;8) in acute lymphocytic leukemia with kappa light chain immunoglobulin expression

We report a correlation between t(2;8) translocation in acute lymphocytic leukemia and kappa light chain immunoglobulin production. Since the kappa chain genes are on chromosome #2, this, as well as data on Burkitt lymphoma, points to the possibility of position effect on the level of gene action. Chromosome #2 in the translocation together with chromosome #8 is concerned with malignancy, while the normal homologous chromosome #2 transcribes kappa chains. This model applies to B cell leukemias and lymphomas with changes in chromosome #2 which will predictably express kappa chains. The model also applies to B-cell malignancies with changes in chromosome #22 which will predictably express lambda chains.