Concentration and purification of plant pathogenic viruses by field step electrophoresis

Concentration and purification of plant pathogenic viruses by field step electrophoresis comprises a new and rapid preparative method with high throughput and short separation time. With this technique and combinations of field step and zone electrophoresis it is possible to purify plant pathogenic viruses from several contaminants in one separation step. Another application of field step electrophoresis allows the separation of viruses from each other.

Frequency of herpes simplex virus-specific murine cytotoxic T lymphocyte precursors in mitogen- and antigen-driven primary in vitro T cell responses

The aim of this study was to assess and to compare the frequencies and specificities of herpes simplex virus (HSV)-specific cytotoxic T lymphocyte precursors (CTL-p) in mitogen (concanavalin A)-activated splenic T cells, as well as in antigen-activated splenic T cells of normal nonimmunized mice. In the mitogen-driven system one of 130 T cell blasts developed clonal progenies able to lyse specifically HSV-infected syngeneic targets. In the antigen-driven system HSV-specific CTL-p could be detected in normal lymphocytes provided the stimulator cells used were enriched for dendritic cells and pulsed with high concentrations of heat-inactivated HSV. Depending on the mouse strain used, the frequencies of HSV-specific CTL-p ranged from 1/500 to 1/10,000 in normal mice. Upon antigen priming within local lymph node cells, an increase of frequencies from 1/500 to 1/170 was observed in CBA/Ca mice.

Frequency of herpes simplex virus-specific murine cytotoxic T lymphocyte precursors in mitogen- and antigen-driven primary in vitro T cell responses

The aim of this study was to assess and to compare the frequencies and specificities of herpes simplex virus (HSV)-specific cytotoxic T lymphocyte precursors (CTL-p) in mitogen (concanavalin A)-activated splenic T cells, as well as in antigen-activated splenic T cells of normal nonimmunized mice. In the mitogen-driven system one of 130 T cell blasts developed clonal progenies able to lyse specifically HSV-infected syngeneic targets. In the antigen-driven system HSV-specific CTL-p could be detected in normal lymphocytes provided the stimulator cells used were enriched for dendritic cells and pulsed with high concentrations of heat-inactivated HSV. Depending on the mouse strain used, the frequencies of HSV-specific CTL-p ranged from 1/500 to 1/10,000 in normal mice. Upon antigen priming within local lymph node cells, an increase of frequencies from 1/500 to 1/170 was observed in CBA/Ca mice.

Treatment toxicity reduction: breast cancer

Since curative treatment of advanced breast cancer is still beyond our reach, the importance of reducing overall toxicity of systemic treatment must be stressed. This seems to be possible by adapting the form and intensity of therapy to the prognosis and stage of disease and by using drugs exhibiting high antitumoral efficacy combined with low systemic toxicity. In 475 patients with metastatic breast cancer, we initiated a prognosis-oriented therapeutic strategy. We developed a prognostic score so as to classify patients into 'high' and 'low' risk groups. In this way we were able to separate patients into two groups with statistically different survival times. In addition, we found that the impact of the first polychemotherapy on survival is different when comparing patient with favourable and unfavourable prognostic scores. Patients with favourable prognostic factors had exactly the same survival time independent of tumour progression, stable disease or even partial remission. Only patients achieving a complete remission survived longer. In contrast, patients with unfavourable prognostic factors apparently benefited from chemotherapy. Patients achieving stable disease or objective tumour remission had a significantly longer survival time than those patients with immediate tumour progression. Additionally, for most of the patients in this group, chemotherapy induced a transient stabilization or improvement of tumour induced symptoms. Therefore, we conclude that chemotherapy of advanced breast cancer is necessary. However, to reduce overall toxicity, it must be planned and administered according to the prognostic picture of the individual patient.

Clonal specificity analysis of mitogen-activated murine T lymphoblasts

We have determined the frequencies and specificities of MHC-reactive and MHC-restricted cytotoxic T lymphocyte precursors (CTL-p) in mitogen (ConA)-activated splenocytes of normal unprimed mice. The limiting dilution (LD) system supported the growth of one out of three Lyt2+ T cell blasts. The generated CTL-populations lysed blast cell targets specifically as determined by split well analyses. MHC-gene product expression was necessary for lysis to occur, since MHC-negative F9 teratocarcinoma cells were not lysed. The frequency determinations and split well analyses revealed: 1) equally high numbers (approximately 1/100) of CTL-p that generated specific allo-MHC or self-MHC reactive CTL populations, 2) high frequencies of CTL-p which recognized hapten (TNP) or minor H (MH)-antigens in the context of self MHC or allo-MHC determinants. The results are discussed with respect to antigen, restriction and receptor specificities of mitogen-activated unprimed T cell blasts.

Representation of interaural time difference in the central nucleus of the barn owl's inferior colliculus

This paper investigates the role of the central nucleus of the barn owl's inferior colliculus in determination of the sound-source azimuth. The central nucleus contains many neurons that are sensitive to interaural time difference (ITD), the cue for azimuth in the barn owl. The response of these neurons varies in a cyclic manner with the ITD of a tone or noise burst. Response maxima recur at integer multiples of the period of the stimulating tone, or, if the stimulus is noise, at integer multiples of the period corresponding to the neuron's best frequency. Such neurons can signal, by means of their relative spike rate, the phase difference between the sounds reaching the left and right ears. Since an interaural phase difference corresponds to more than one ITD, these neurons represent ITD ambiguously. We call this phenomenon phase ambiguity. The central nucleus is tonotopically organized and its neurons are narrowly tuned to frequency. Neurons in an array perpendicular to isofrequency laminae form a physiological and anatomical unit; only one ITD, the array-specific ITD, activates all neurons in an array at the same relative level. We, therefore, may say that, in the central nucleus, an ITD is conserved in an array of neurons. Array-specific ITDs are mapped and encompass the entire auditory space of the barn owl. Individual space-specific neurons of the external nucleus, which receive inputs from a wide range of frequency channels (Knudsen and Konishi, 1978), are selective for a unique ITD. Space-specific neurons do not show phase ambiguity when stimulated with noise (Takahashi and Konishi, 1986). Space-specific neurons receive inputs from arrays that are selective for the same ITD. The collective response of the neurons in an array may be the basis for the absence of phase ambiguity in space-specific neurons.

Methylation of the enhancer region of avian sarcoma virus long terminal repeat suppresses transcription

The effect of methylation of an enhancer on transcription was studied. A 245 bp enhancer-containing a fragment of the LTR of the avian sarcoma virus was methylated in vitro and ligated back into a vector which lacked the upstream enhancer sequence. The transient expression in QT6 cells indicated that methylation of the enhancer-containing sequence severely reduced the extent of transcription.

[Revision prosthesis for the hip joint in severe bone loss]

When total hip prostheses loosen after initial implantation and subsequent prosthesis replacement, increasing bone resorption occurs in the bed of the prosthesis. Finally, a very thin cortex remains in the bed of the prosthesis, which no longer provides sufficient mechanical stability. The replacement prosthesis described, which is anchored in the distal medullary canal without cement, provides a bridge over the damaged prosthesis bed and results in a condition of relative mechanical stability. After implantation of the replacement prosthesis, lively proliferation of the bone tissue occurs in the old prosthesis bed, which again replaces the bone loss that had taken place previously. The late results that would permit a final assessment of the procedure are not yet available.

Frequency analysis of class I MHC-reactive Lyt-2+ and class II MHC-reactive L3T4+ IL 2-secreting T lymphocytes

The reactivity of Lyt-2+ or L3T4+ T cells stimulated with either mutant class I or class II MHC alloantigens was studied. Whereas stimulation with class I MHC antigens induced only Lyt-2+ T cells to proliferate and to secrete IL 2, stimulation with class II MHC alloantigens induced L3T4+ but not Lyt-2+ T cells. When the frequencies of precursors of IL 2-secreting T lymphocytes (IL 2TL-p) were determined by limiting dilution analyses, class I MHC-reactive Lyt-2+ T cells displayed frequencies (f = 1/200) as high in magnitude as those within class II MHC-reactive L3T4+ (f = 1/100). Clonally developing IL 2TL of either T cell subset were antigen-specific, as shown in split-culture experiments. Whereas L3T4+ helper TL could be induced to specific IL 2 secretion over a long time period (days 3 to 9), Lyt-2+ TL showed a marked time optimal on day 4; thereafter, the number of TL colonies inducible to secrete IL 2 decreased steadily. IL 2 production and IL 2TL-p frequencies of unseparated T responder cells were not the numerical superposition of the two individual T cell subsets (Lyt-2+ + L3T4+); the latter finding is likely to reflect regulatory influences of Lyt-2+ T cells on IL 2-secreting L3T4+ T cells.

Frequency analysis of class I MHC-reactive Lyt-2+ and class II MHC-reactive L3T4+ IL 2-secreting T lymphocytes

The reactivity of Lyt-2+ or L3T4+ T cells stimulated with either mutant class I or class II MHC alloantigens was studied. Whereas stimulation with class I MHC antigens induced only Lyt-2+ T cells to proliferate and to secrete IL 2, stimulation with class II MHC alloantigens induced L3T4+ but not Lyt-2+ T cells. When the frequencies of precursors of IL 2-secreting T lymphocytes (IL 2TL-p) were determined by limiting dilution analyses, class I MHC-reactive Lyt-2+ T cells displayed frequencies (f = 1/200) as high in magnitude as those within class II MHC-reactive L3T4+ (f = 1/100). Clonally developing IL 2TL of either T cell subset were antigen-specific, as shown in split-culture experiments. Whereas L3T4+ helper TL could be induced to specific IL 2 secretion over a long time period (days 3 to 9), Lyt-2+ TL showed a marked time optimal on day 4; thereafter, the number of TL colonies inducible to secrete IL 2 decreased steadily. IL 2 production and IL 2TL-p frequencies of unseparated T responder cells were not the numerical superposition of the two individual T cell subsets (Lyt-2+ + L3T4+); the latter finding is likely to reflect regulatory influences of Lyt-2+ T cells on IL 2-secreting L3T4+ T cells.

The Berlin cochlear implant--surgical concept

The extent of channel interactions using monopolar extrascalar stimulation probably limits the number of independently acting electrodes of a cochlear implant to three. Comparison of psychoacoustic and histopathological findings led to the conclusion that stimulation of the neurons in the upper basal and the second coil is of greatest benefit to the patient. By using a middle fossa approach, access to the upper basal coil and the second coil is possible without destruction of middle ear structures. The danger of infection is probably reduced. Using an additional external round-window electrode, a device providing three different stimulating electrodes can be applied.

Human cytotoxic T lymphocytes. II. Frequency analysis of cyclosporin A-sensitive alloreactive cytotoxic T-lymphocyte precursors

A limiting dilution (LD) culture system was used to investigate the effect of cyclosporin A (CsA) on the activation and differentiation of human alloreactive cytotoxic T-lymphocyte precursors (CTL-p). CsA reduced in a dose-dependent fashion the frequency of alloantigen-inducible CTL-p. With most normal individuals tested there was a 20- to 50-fold reduction of alloreactive CTL-p frequencies in the presence of 500-1000 ng/ml CsA. Both unseparated T cells and CD8+ T cells were CsA-sensitive under LD culture conditions. Importantly, however, alloreactive CTL-p from two out of 21 normal individuals were found to be largely CsA-resistant. CsA did not affect the growth of MLR-primed CTL in secondary LD culture. Furthermore, CsA slightly inhibited the cytolytic activity of some alloantigen-specific CTL clones. These results are discussed with respect to the clinical use of CsA in transplantation medicine.

Selective reduction of donor-specific cytotoxic T lymphocyte precursors in patients with a well-functioning kidney allograft

We have recently developed a sensitive limiting dilution (LD) culture system to measure human alloreactive cytotoxic T lymphocyte precursors (CTL-p) in a given lymphoid cell population. We have now used this system to determine frequencies of donor HLA antigen-inducible CTL-p in the peripheral blood of human allograft recipients at various stages after transplantation. All patients (1 pancreas recipient and 9 kidney recipients) were on continuous cyclosporine treatment throughout the study. We report that, in patients with a well-functioning kidney graft (6/9), the number of donor-reactive CTL-p among peripheral blood lymphocytes decreased within 3-8 months after transplantation--in some cases (2/6) more than 10-fold. In contrast, frequencies of CTL-p with specificity for third-part HLA antigens remained largely unaltered in these patients. Furthermore, no decrease of donor-reactive CTL-p frequencies was seen in 3 of 4 patients showing clinical symptoms of graft rejection. These results indicate that functional clonal deletion of antigraft-reactive CTL-p may contribute to the state of graft tolerance in certain patients with a well-functioning kidney allograft.

Identification of interleukin 2-producing T helper cells within murine Lyt-2+ T lymphocytes: frequency, specificity and clonal segregation from Lyt-2+ precursors of cytotoxic T lymphocytes

The prime aim of this study was to assess whether the autonomous primary mixed lymphocyte culture response of Lyt-2+ T cells towards class I major histocompatibility complex (MHC) antigens reflects in terms of interleukin 2 (IL2) production and cytotoxicity the activation of multifunctional Lyt-2+ T cells, or the activation of functionally distinct T cell subsets. The results demonstrate that highly purified Lyt-2+ T cells proliferate in response to class I MHC antigens, as opposed to L3T4+ T cells which react towards class II MHC antigens. In both responder cell types proliferative responses are associated with IL2 secretion, while only Lyt-2+ T cells develop measurable cytotoxic effector cells. The precursor frequency of IL2-producing helper cells in MHC class I-reactive Lyt-2+ T cells equals that in MHC class II-reactive L3T4+ T cells (f = 1/500-1/1000). In clonal segregation analysis greater than 90% of Lyt-2+ colonies secreting IL2 do not develop cytotoxic activity, while greater than 90% of Lyt-2+ cytotoxic T cells fail to produce detectable IL2. A minority of less than 10% of Lyt-2+ T cells appears to be bifunctional. As such the results point out the existence of functionally committed T cells within class I MHC-reactive Lyt-2+ T cells able to produce either IL2 or to develop into cytotoxic effector cells.

Human mumps virus-specific cytotoxic T lymphocytes: quantitative analysis of HLA restriction

To obtain quantitative information about the use of HLA antigens as restriction element by antiviral cytotoxic T lymphocytes (CTL), we have analyzed precursors of human mumps virus-specific CTL by limiting dilution. CTL generated by restimulation of peripheral blood T lymphocytes with autologous mumps virus (MV)-infected stimulator cells were restricted by autologous HLA class I antigens, and derived from the T4-8+ population. They were specific for MV and did not lyse autologous target cells infected with other viruses. Frequencies of MV-specific CTL precursors ranged from 1/500 to 1/8000. HLA restriction was analyzed by split-well analysis of individual CTL colonies. CTL recognizing HLA-A or B antigens were unequally distributed: HLA-B7, -B13, and -B27 were found to function as predominant, in some cases as exclusive, restriction elements, whereas other antigens such as HLA-A24 were never or rarely used. In several combinations, there was no evidence for antigenic variants of HLA molecules as reason for the failure to be recognized. The proportion of CTL precursors recognizing HLA-A2 and -B8 seemed to be dependent on the presence or absence of "dominant" restriction elements. We conclude that CTL precursors recognizing certain virus-HLA combinations are preferentially expanded during an infection, but that low responsiveness to a given combination is not necessarily absolute.