Feasibility of UV-inactivated vaccinia virus in the modification of tumor cells for augmentation of their immunogenicity

We compared the immunity induced by tumor cells modified with UV-inactivated purified vaccinia virus (UV-VV) and with live purified vaccinia virus (L-VV). C3H/HeN mice were inoculated i.p. with UV-VV or L-VV after whole-body irradiation with 150 rads of X-rays (priming). After 3 weeks the mice were immunized i.p. 3 times at weekly intervals with syngeneic X5563 or MH134 cells that had been absorbed in vitro with UV-VV or infected with L-VV and subsequently irradiated with 10(4) rads of X-rays. Then 1 week after the last immunization, the mice were challenged s.c. with X5563 viable tumor cells or challenged i.p. with MH134 viable tumor cells. The 50% lethal dose (TLD50) of X5563 in mice primed and immunized with UV-VV (UV-VV group) on s.c. challenge (10(6.06)) was the same as for mice treated with L-VV (L-VV group), whereas the TLD50 of unprimed or nonimmunized mice (control group) was 10(2.61). The TLD50 of MH134 in the UV-VV treated group on i.p. challenge (10(6.48)) was similar to that of the L-VV treated group (10(6.54)), while the TLD50 of the control group was 10(1.00). The difference between the TLD50 values of X5563 on s.c. challenge of mice primed and immunized with UV-VV or L-VV and control mice was 10(3.4). The difference between the TLD50 values of MH134 on i.p. challenge of primed and immunized mice and control mice was 10(5.5). These results indicate that the in vivo helper function of UV-VV is similar to that of L-VV and that the augmenting effect of this protocol depends on the kind of tumor.

Exchangeability of alpha-actinin in living cardiac fibroblasts and muscle cells

We have investigated the exchangeability of alpha-actinin in various structures of cultured chick cardiac fibroblasts and muscle cells using fluorescent analogue cytochemistry in combination with fluorescence recovery after photobleaching. Living cells were microinjected with tetramethylrhodamine-labeled alpha-actinin, which became localized in cellular structures. Small areas of labeled structures were then photobleached with a laser pulse, and the subsequent recovery of fluorescence was monitored with an image intensifier coupled to an image-processing system. In fibroblasts, fluorescence recovery was studied in stress fibers and in adhesion plaques. Bleached spots in adhesion plaques generally attained complete recovery within 20 min; whereas complete recovery in stress fibers occurred within 30 to 60 min. In muscle cells, alpha-actinin became localized in the Z-lines of sarcomeres, in punctate structures, and in apparently continuous bundle-like structures. Fluorescence recovery in Z-lines, punctate structures, and some bundle-like structures was extremely slow. Complete recovery did not occur within the 6- to 7-h observation period. However, some bundle-like structures recovered completely within 60 min, a rate similar to that of stress fibers in fibroblasts. These results indicate that fluorescently labeled alpha-actinin is more stably associated with structures in muscle cells than in fibroblasts. In addition, different structures within the same cell can display different alpha-actinin exchangeabilities which, in muscle cells, could be developmentally related.

Exchange of actin subunits at the leading edge of living fibroblasts: possible role of treadmilling

Previous observations indicated that the lamellipodium ("leading edge") of fibroblasts contains a dense meshwork, as well as numerous bundles (microspikes) of actin filaments. Most, if not all, of the filaments have a uniform polarity, with the "barbed" end associated with the membrane. I investigated whether and how actin subunits exchange in this region by microinjecting living gerbil fibroma cells (IMR-33) with actin that had been labeled with iodoacetamidotetramethylrhodamine. After incorporation of the labeled actin into the lamellipodium, I used a laser microbeam to photobleach a 3-4-micron region at and surrounding a microspike, without disrupting the integrity of the structure. I then recorded the pattern of fluorescence recovery and analyzed it using a combination of TV image intensification and digital image processing techniques. Fluorescence recovery was first detected near the edge of the cell and then moved toward the cell's center at a constant rate of 0.79 +/- 0.31 micron/min. When only part of the lamellipodium near the edge of the cell was photobleached, the bleached spot also moved toward the cell's center and through an area unbleached by the laser beam. These results indicated that steady state incorporation of actin subunits occurred predominantly at the membrane-associated end of actin filaments, and that actin subunits in the lamellipodium underwent a constant movement toward the center of the cell. I suggest that treadmilling, possibly in combination with other molecular interactions, may provide an effective mechanism for the movement of actin subunits and the protrusion of cytoplasm in the lamellipodium of fibroblasts.

Identical distribution of fluorescently labeled brain and muscle actins in living cardiac fibroblasts and myocytes

We have investigated whether living muscle and nonmuscle cells can discriminate between microinjected muscle and nonmuscle actins. Muscle actin purified from rabbit back and leg muscles and labeled with fluorescein isothiocyanate, and nonmuscle actin purified from lamb brain and labeled with lissamine rhodamine B sulfonyl chloride, were co-injected into chick embryonic cardiac myocytes and fibroblasts. When fluorescence images of the two actins were compared using filter sets selective for either fluorescein isothiocyanate or lissamine rhodamine B sulfonyl chloride, essentially identical patterns of distribution were detected in both muscle and nonmuscle cells. In particular, we found no structure that, at this level of resolution, shows preferential binding of muscle or nonmuscle actin. In fibroblasts, both actins are associated primarily with stress fibers and ruffles. In myocytes, both actins are localized in sarcomeres. In addition, the distribution of structures containing microinjected actins is similar to that of structure containing endogenous F-actin, as revealed by staining with fluorescent phalloidin or phallacidin. Our results suggest that, at least under these experimental conditions, actin-binding sites in muscle and nonmuscle cells do not discriminate among different forms of actins.

Industrial lead poisoning in China over the past 33 years

This paper is a review of the 48 articles in scientific journals and special reports of investigations emanating from the author's department involving 2504 subjects. During the past 33 years, as a result of the establishment of health and antiepidemic stations throughout the country, the enactment of hygienic standards, and the setting up of the reporting system for industrial poisoning and occupational diseases, the air lead level has been reduced from 10 mg/m3 in the years soon after liberation (1949) to below 0.03 mg/m3 at present. Severe plumbism has disappeared. Some mild cases, however, could still be found among workers in lead smelters and electric battery plants. Great advances have been made in techniques for early diagnosis of lead poisoning. Blood lead, urine lead, aminolevulinic dehydrase, free erythrocyte protoporphyrin, and zinc protoporphyrin (ZnPP) have been used as criteria for lead exposure. For the purpose of preventive monitoring, ZnPP as a screening index is the first choice. Behavioral function and sensory and motor nerve conduction velocity measurements of median nerve might also be used for the investigation of lead exposure. The maximum allowable concentration of 0.03 mg/m3 for air lead level in the workshop, in agreement with the results of a nationwide lead industry investigation, has been proven safe. There is also the need to monitor the air lead level and blood lead level in the general population and children living adjacent to a lead industry.

Reorganization of actin filament bundles in living fibroblasts

We investigated how actin bundles assemble, disassemble, and reorganize during cell movement. Living chick embryonic fibroblasts were microinjected with actin molecules that had been fluorescently labeled with tetramethylrhodamine. We found that the fluorescent analogue of actin can be used successfully by both existing and newly formed cellular structures. Using time-lapse photography coupled to image-intensified fluorescence microscopy, we were able to detect various patterns of reorganization in motile cells. Assembly of stress fibers occurred near both the leading and the trailing ends of the cell. The initial structure appeared as discrete spots that subsequently extended into stress fibers. The extension occurred unidirectionally. The site of initiation near the leading edge remained stationary relative to the substrate during subsequent cell advancement. However, the orientation of the fiber could change according to the direction of cell movement. In addition, existing stress fibers could merge or fragment. The shortening of stress fibers can occur from either end of the fiber. Shortening from the proximal end (centrifugal shortening) was accompanied by a decrease in fluorescence intensity, as if the bundle were disassembling, and usually led to the total disappearance of the bundle. Shortening from the distal end (centripetal shortening), on the other hand, is usually accompanied by an increase in fluorescence intensity at the distal end of the bundle, as if this end had pulled loose from its attachment and retracted toward the center of the cell. Besides stress fibers, arc-like actin bundles have also been detected in spreading cells. These observations can explain how the organization of actin bundles coordinates with cell movement, and how stress fibers reach a highly regular pattern in static cells.