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Biomedical subjects

K Hummeler

Publications and source records attributed to K Hummeler.

At least 37 records · Page 2Linked to original sources
PubMed1971

Studies on antibody-producing cells. II. Appearance of 3 H-thymidine-labeled rosette-forming cells.

A study of the kinetics of antibody-producing cells has been carried out by the use of rosette formation for detection of individual antibody-producing cells, and labeling with tritiated thymidine, in cells obtained from mouse spleens at intervals after injection of SRBC. Following a primary injection of the antigen, the number of RFC per million cells was found to increase to a peak at 5 days, then, after a decrease, to a second peak at about the 10th day. The curve of tritium labeling of RFC was also biphasic, with peaks on the 3rd and 7th day. The second increase in rosette-forming cells could be shown to involve, especially between the 7th and 9th day, a second increase in lymphoid cell RFC and, among these, 7S antibody-producing cells. When the population examined was restricted to large lymphocytes, two peaks of RFC per million cells and two peaks of labeling were again found. In this case, however, the peaks of RFC and of labeling were reached on the same day in each instance, rather than with the 2 day difference found in the entire spleen cell suspension or the entire lymphoid cell population. Electron microscopic examination of labeled rosette-forming cells showed these to be largely lymphocytes, but to include rather well differentiated plasmablasts as well. No macrophages were found among labeled RFC in the primary response. A substantial number of labeled lymphocytes were found in close contiguity with rosette-forming macrophages. The percentage of labeling in such lymphocytes was as high, on the respective days, as the percentage of labeled cells among the RFC of the entire suspension.

Animals↗
PubMed1970

Studies on antibody-producing cells. I. Ultrastructure of 19S and 7S antibody-producing cells.

Antibody-bearing cells of spleen and lymph node of the mouse and rabbit detected by rosette formation with the antigenic red blood cells were collected by micropipet and studied by electron microscopy. More than 300 such cells were examined. In the lymph nodes, rosette-forming cells were all in the lymphocytic and plasmacytic categories. In cells of the mouse spleen, macrophages were also found among the RFC, especially in the later days after immunization. The great majority of the RFC, 70-100%, were of the lymphocytic category. These included small, medium, and large lymphocytes with fine gradations of differentiation, and blast forms with little heterochromatin. The endoplasmic reticulum of these cells occurred in short, very narrow pieces, usually in contact with a mitochondrion. The cells of the plasmacytic category also showed fine gradations from plasmablasts to typical mature plasma cells. Plaque-forming cells of mouse and rabbit were also collected by micropipet. Of 162 such cells, fine gradations were also found throughout the lymphocytic and plasmacytic categories, but in this case the great majority were in the plasmacytic group, and more plasma cells showed amorphous nuclear chromatin. Among antibody-forming cells detected by both reactions, some of the more highly differentiated large lymphocytes contained ER which differed from that in the other large lymphocytes in that the channels were slightly and variably distended, with deposition of some precipitate, and with some tendency to a more nearly parallel orientation of the few channels seen. These were considered transitional cells. Of 10 RFC found in mitosis, all were in the lymphocytic category, in various stages of differentiation, the most advanced of which (in 2 of the 10 cells) was that of the transitional lymphocyte described here. Cells producing plaques facilitated by antisera vs. IgG of the mouse or rabbit (7S) showed the same distribution between cell categories and the same fine gradations as the direct (19S) PFC. Cells producing rosettes which were resistant to lysis in the presence of complement, and were thus presumably producing 7S antibody, showed a distribution similar to that found generally with rosette-forming cells, approximately 80-90% in the lymphocytic category.

Animals↗
PubMed1970

Morphological aspects of the uptake of simian virus 40 by permissive cells.

After exposure of permissive cells to simian virus 40 (SV40), single particles were engulfed by the cell membrane and transported to the nucleus. The cell membrane closed tightly around the particles, increasing their diameter from 40 to 55 nm. The cell membrane was lost during interaction with the nuclear membranes, and particles of the original size were found in the nucleus 1 hr after infection. Uncoating of these nuclear particles occurred rapidly, and none could be found 4 hr after infection. Viral progeny appeared 24 hr after infection.

Animals↗
PubMed1970

Morphogenesis of the nucleoprotein of vesicular stomatitis virus.

Accumulation of the nucleoprotein of vesicular stomatitis virus (VSV) in the cytoplasm of BHK-21 cells and in two of four human cell lines was demonstrated. Appearance and progression of the nucleoprotein inclusions paralleled development of virus-specific immunofluorescence and production of virus progeny. The inclusions appeared early as discrete foci of filamentous material which eventually increased in size to form large masses which replaced normal cytoplasmic constituents. The filamentous strands were found in close proximity to budding virions. The inclusion material was extracted from infected cells and purified in cesium chloride gradients. The isolated filaments resembled the ribonucleoprotein isolated from purified virions. They incorporated (3)H-uridine, exhibited virus-specific complement-fixing activity, had a buoyant density of 1.32 g/cm(3), and appeared as single wavy strands the width of which varied from 2.5 to 8.5 nm, depending on the angle of viewing.

Amnion↗
PubMed1969

Early events in herpes simplex virus infection: a radioautographic study.

The early events in herpes simplex virus infection were studied by means of radio-autography. The virus was rapidly taken up by the host cells and uncoated. Viral deoxyribonucleic acid (DNA) reached the nuclear sites of replication in 15 to 30 min after infection. The viral DNA occasionally associated with chromosomes or condensed chromatin but was more frequently found to be randomly distributed. Viral progeny appeared 3 hr after infection. These particles did not show any particular spatial relationship to the parental DNA. The morphological latent period lasted 2.5 hr.

Animals↗
PubMed1968

Morphology of the nucleoprotein component of rabies virus.

The intracytoplasmic ground substance, or matrix, associated with the development of rabies virus and the nucleocapsid of the virus were investigated. The filaments of the matrix were identified as virus-specific by means of ferritin-labeled antibodies. In thin sections, the diameter was 15 nm and the strands seemed to be incorporated into virions during morphogenesis of the virus. The nucleocapsid was isolated from purified virus preparations and was studied in negative contrast. The rabies nucleocapsid appeared as a single-stranded helix with a diameter of 16 nm and a periodicity of 7.5 nm; its length was in excess of 1 mum.

Chemical Phenomena↗
PubMed1968

Purification of rabies virus grown in tissue culture.

Extracellular rabies virus, grown in monolayer cultures of BHK21 cells in the presence of medium supplemented with bovine serum albumin, was purified by the following procedure. Virus was precipitated from infectious tissue culture fluid by zinc acetate and was resuspended in a solution of ethylenediaminetetraacetate. The suspension was filtered through a Sephadex column and was treated with ribonuclease and deoxyribonuclease. The virions were then pelleted by centrifugation at high speed and were resuspended in buffer solution. Banding of the virus by centrifugation in a sucrose density gradient was the final step in the purification procedure. Purified preparations contained bullet-shaped virus particles of variable length and little (up to 5%) contaminating host-cell material. Most of the virions were "complete", i.e., 180 nm long, but some virus particles were shorter. The length distribution of the virions was nonrandom. Shorter virions seemed to be noninfectious and showed markedly decreased hemagglutinating activity. The complement-fixing activity and the ribonucleic acid to protein ratio of the virions were not related to the length of the virus particles. Although the properties of extracellular and intracellular viruses were similar, the procedure was not suitable for purification of intracellular rabies virus.

Centrifugation, Density Gradient↗
PubMed1967

Structure and development of rabies virus in tissue culture.

Structure and development of two fixed rabies virus strains in baby hamster kidney cells (BHK/21) were investigated by electron microscopy. The morphological development was correlated with fluorescent-antibody staining and infectivity titration. The uptake of virus was enhanced by addition of diethylaminoethyl dextran, and structural changes became apparent in the cytoplasm 8 to 9 hr after infection, when fluorescent-antibody staining was first discernible. These changes consisted of matrices containing fibers replacing normal cytoplasmic structures. Virus particles appeared at the edges of these matrices and inside them at 24 to 48 hr. This corresponded to significant rises in intracellular infectious virus. Formation of virus particles by budding from cell membranes was seen at 72 hr. Further incubation of the infected cells resulted in synthesis of bizarre structural elements. The complete virus particle was bullet-shaped with an average size of 180 by 75 mmu. It consisted of an inner core of filamentous material surrounded by two membranes of different densities. The surface showed a honeycomb arrangement with surface protrusions 60 to 70 A long having a knoblike structure at their distal end. These surface protrusions were absent at the flat end of the virus particle.

Animals↗
PubMed1967

Comparative study of cultured Burkitt tumor cells by immunofluorescence, autoradiography, and electron microscopy.

Cultured Burkitt cells were examined by immunofluorescence, autoradiography, and electron microscopy in an effort to identify the stainable cells with those harboring herpes-type virus particles. Immediately after a 2-hr pulse of (3)H-thymidine, from 30 to 60% of the cells revealed heavy nuclear labeling. In most cases the grains were evenly dispersed, but in about 3 to 5% the grains showed a focal distribution and occasionally they extended into the cytoplasm. Such nuclear foci were rarely seen at 8 hr after the pulse. When the analysis was restricted to preselected immunofluorescent cells, up to 80% showed label at 8 hr and cytoplasmic grains were prominent. To reduce cellular deoxyribonucleic acid (DNA) synthesis, cells were X-irradiated with 3,000 to 6,000 R, and the isotope pulse was applied 1, 4, or 7 days later. Whereas the total number of labeled cells decreased in roughly twofold steps at the respective intervals (from 40 to 10%), the incorporation of (3)H-thymidine into fluorescent cells was not affected by X irradiation. In each series, about 70% of the fluorescent cells contained label when they were examined at 24 and 48 hr after the pulse, whereas at 8 and 72 hr fewer were positive. At the earlier intervals, unlabeled fluorescent cells most likely represented cells which had completed viral DNA synthesis prior to the pulse; at the later intervals, unlabeled fluorescent cells were probably cells which commenced viral replication after the pulse. These data support the conclusion that the immunofluorescent cells are the ones which harbor virus, and also confirm the expectation that the virus is a DNA virus from a member of the herpes group. This conclusion was firmly established by sectioning and electron microscopic examination of individual fluorescent cells, all of which contained numerous virus particles, whereas the nonstained cells prepared in a similar manner were free of them.

Autoradiography↗