Modified Box-Cox transform for modulating the dynamic range of flow cytometry data

We describe an algorithm, Vout = Integer ([2(12)-1/2(12 lambda)-1] V lambda in-1) + 1; lambda greater than 0 based upon Box-Cox transformations as an alternative to nonlinear electronic amplifiers to expand or compress high- or low-amplitude flow cytometer-derived signals. If the indexing parameter lambda less than 1, input channels in the high-amplitude input range are compressed in the output range as occurs when an electronic logarithmic amplifier is used. However, if lambda greater than 1, input channels in the low-amplitude input range are compressed in the output range as occurs when an electronic power amplifier is used. Our modified Box-Cox transform can be implemented either during data collection or off-line for the transformation of previously collected raw data. The transform is the equivalent of an infinite class of nonlinear amplifiers. As the transform is implemented in software, it does not suffer from many of the disadvantages of nonlinear electronic amplifiers.     

Microwave fixation provides rapid, primary fixation for light and electron microscopy and for immunohistochemistry and immunocytochemistry.

A relatively new approach to specimen preservation for morphologic studies uses microwave energy and chemicals. Microwave fixation can produce fixation results equal in quality to chemical fixation methods and equal in speed to freeze fixation methods. The importance of this microwave fixation technology lies in its potential to provide a standardized fixation approach in histopathology, immunohistochemistry, and immunocytochemistry.     

T cell subsets in allograft rejection. In situ characterization of T cell subsets in human skin allografts by the use of monoclonal antibodies

We have provided evidence that both major T cell subsets, T4-positive (helper/inducer) and T8-positive (cytotoxic/suppressor), infiltrate human skin allografts. Overall, and in the graft dermis and graft bed, T4-positive cells were predominant (1.5 to 3 times more numerous than T8-positive cells). In contrast, T8-positive cells were relatively more numerous in the epidermis and hair follicles. Rejection probably proceeded by two apparently independent pathways: 1) direct contact killing of graft epithelial cells, presumably by immunologically specific T8-positive cytotoxic cells, and 2) injury of microvascular endothelium of both the graft and graft bed with secondary graft infarction. Although important in first set skin allograft rejection, the mechanism of the second type of killing is uncertain. T4-positive cells were probably involved, as evidenced by their greater numbers; furthermore, studies in mice have shown that transfused helper/inducer cells are able to effect first-set skin graft rejection. It remains to be determined whether T4-positive cells act alone or cooperate with other cells to destroy vessels and bring about graft rejection. Langerhans cells were recognized in epithelial and dermal compartments of both allografts and autografts by their reactivity with anti-T6 and anti-Ia antibodies. We could not determine whether such cells in allografts were of host or donor origin.     

Recombination: an underappreciated factor in the evolution of plant genomes

Our knowledge of recombination rates and patterns in plants is far from being comprehensive. However, compelling evidence indicates a central role for recombination, through its influences on mutation and selection, in the evolution of plant genomes. Furthermore, recombination seems to be generally higher and more variable in plants than in animals, which could be one of the primary reasons for differences in genome lability between these two kingdoms. Much additional study of recombination in plants is needed to investigate these ideas further.     

Mycotoxin Production by Fusarium proliferatum isolates from rice with Fusarium sheath rot disease

Twenty samples of unpolished (rough) rice collected in Arkansas and Texas during the 1995 harvesting season from fields exhibiting Fusarium sheath rot disease or panicle blight were previously shown to include 8 samples positive for fumonisin B₁(FB₁) in the range 2.2–5.2 ppm, and moniliformin (MON), but no beauvericin (BEA), deoxynivalenol, its derivatives or zearalenone were detected. Fifteen cultures of F. proliferatum were established from the 20 rough rice samples. Single spore isolates of each culture were grown on rice and tested for the production of fumonisins (FB₁, FB₂, FB₃, etc.), MON and BEA. All 15 isolates produced FB₁, FB₂, MON and BEA in culture on rice. No deoxynivalenol, its derivatives orzearalenone were detected. Seven cultures produced FB₁ at >50ppm (range 80–230 ppm), with therest producing FB₁ in the range 14–43 ppm.FB₂ was produced in the range 5–47 ppm, and those cultures which produced the most FB₁ also produced the most FB₂. Of the 15 cultures producing MON, 11 produced it at >100 ppm in the range 188–6018 ppm, with the rest producing in the range 7–64 ppm. BEA was produced in the range 109–1350 ppm. Other derivatives of fumonisins, including FA₁, FA₂ and partially hydrolyzed FB₁, as well asseveral unknown metabolites including a compound with MW 414, were identified in culture extracts by continuous flow fast atom bombardment with ion spraymass spectrometry (CF/FAB/MS). Further study is needed to identify the factors that control production of FB₁, MON and BEA by F.proliferatu in culture and in field samples. This revised version was published online in June 2006 with corrections to the Cover Date.     

Trypanosoma cruzi: pattern of RNA synthesis following infection of vertebrate cells

The pattern of RNA synthesis of intracellular Trypanosoma cruzi amastigotes, immediately following infection of Lesch-Nyhan human fibroblasts, was studied by autoradiography. Amastigote RNA synthesis, determined by [3H]guanine incorporation, was not detected until 2 h after infection. At 8 h postinfection more than 90% of intracellular amastigotes were labeled. It was verified that extracellular trypomastigotes also synthesized RNA. Therefore it was concluded that, if RNA is required for trypomastigote-to-amastigote transformation, this nucleic acid is already present in the trypomastigotes before infection of the vertebrate cell. It is probable that the RNA synthesized by amastigotes during the prereplicative lag period (the period between initial infection and the onset of DNA synthesis) is required for intracellular growth and reproduction.     

Ultrastructural studies of human basophils and mast cells.

Ultrastructural studies of human mast cells (HMCs) and basophils (HBs) are reviewed. Sources of HMCs include biopsies of tissue sites and in situ study of excised diseased organs; isolated, partially purified samples from excised organs; and growth-factor-stimulated mast cells that develop de novo in cultures of cord blood cells. Sources of HBs for study include partially purified peripheral blood basophils, basophils in tissue biopsies, and specific growth factor-stimulated basophils arising de novo from cord blood cells. The ultrastructural studies reviewed deal with identity, secretion, vesicles, recovery, and synthesis issues related to the biology of these similar cells.