Susceptibility of raccoons (Procyon lotor) to infection with Mycobacterium bovis

Tuberculosis due to Mycobacterium bovis infection is endemic in white-tailed deer (Odocoileus virginianus) in the northeastern portion of the lower Michigan peninsula (USA). Various wild carnivores and omnivores, including raccoons (Procyon lotor), are infected with M. bovis within the endemic area. To investigate the pathogenesis of tuberculosis in raccoons and the likelihood of M. bovis transmission from infected raccoons to other susceptible hosts, we experimentally inoculated raccoons with single oral doses of M. bovis (ranging from 30 to 1.7 x 10(5) colony forming units [CFU]), five daily oral doses of M. bovis (ranging from 10 to 1 x 10(5) CFU), or a single intravenous (i.v.) dose of 1 x 10(5) CFU of M. bovis, from November 1998 through December 2000. Granulomatous lesions consistent with tuberculosis, or tissue colonization with M. bovis, were seen in one of five raccoons in the single low oral dose group, one of five raccoons in the multiple low oral dose group, two of five raccoons in the multiple medium oral dose group, five of five raccoons in the multiple high oral dose group, and five of five raccoons in the i.v. inoculated group. In oral inoculated raccoons, lesions were most common in the tracheobronchial and mesenteric lymph nodes and lung. Excretion of M. bovis in saliva or nasal secretions was noted in all i.v. inoculated raccoons and two of five multiple low oral dose raccoons. Mycobacterium bovis was not isolated from urine or feces from any experimentally inoculated raccoons. The need for multiple large oral doses to establish infection, and the low number of orally inoculated raccoons that excreted M. bovis in nasal secretions or saliva, suggest that wide-spread tuberculosis among raccoons is unlikely.     

KINETIC PROPERTIES OF HAEMOPOIETIC STEM CELLS

A comparison of the exocolonizing and autorepopulating tests for haemopoietic stem-cell assay indicate that the ‘overshoot’in splenic colony formation, observed 12–14 days after 150 rad total-body radiation (TBR), only occurs with the auto-repopulation assay. The explanation is that the priming dose of 150 rad increases the absolute seeding rate of stem cells from the marrow. A seeding rate significantly greater than normal can ‘take’only if the spleen is available—it can expand and accommodate stem cells while the bone marrow cannot. If, however, the absolute number of colony-forming cells are decreased in the femur, a relative increase in seeding rate can take place even in the splenectomized animal. Evidence is presented concerning the different turnover states of exo- and autorepopulating stem cells (CFU) and those responsible for erythropoietic response (ERC), and the precursors of agar colony-formers.     

Dose responses of two pea lines to ultraviolet‐B radiation (280–315 nm)

UV‐B dose responses of two lines of pea were quantified at 2.3, 4.6, 6.9 and 9.2 kJ m⁻² day⁻¹ UV‐B (weighted according to Caldwell's generalised plant action spectrum) in controlled environments providing near‐field doses of photosynthetic radiation. Increasing UV‐B significantly increased UV‐B absorbing compounds in both lines. In the UV‐B sensitive line, JI1389, increasing UV‐B significantly inhibited most aspects of plant morphology and biomass. In the more UV‐B‐tolerant line, Scout, increasing UV‐B significantly reduced foliage area but had no effect on above‐ground biomass, although root biomass was significantly increased. Reduced plant height in JI1389 was caused by shorter internodes, in turn due to reduced cell number but not cell length. UV‐B had no significant effects on photosynthesis in either line. Significant dose responses were linear for the growth of the main stem in JI1389 but remaining significant dose responses were better fitted by quadratics with maximum UV‐B effects occurring in the range 5–7 kJ m⁻² day⁻¹ PAS300, due to stimulation of branch growth at the highest dose. However, growth stimulation by UV‐B was confined to PAS300 doses which at temperate latitudes would result only from rather extreme ozone depletions. We conclude that investigations using relatively low UV‐B doses, rather than those well above the current maximum, may be the best approach to both understanding of the fundamental mechanisms of plant responses to UV‐B and quantifying the magnitude of responses to stratospheric ozone depletion.     

Kinetics of haemopoietic recovery in endotoxin-treated mice.

Kinetics of mouse spleen colony forming units were studied after intra-peritoneal injection of 1 mug/blody weight bacterial endotoxin S. typhosa. When these mice were used as unirradiated and sublethally irradiated donors, it was possible to study the effect of the endotoxin injection upon the cells.Use of the treated mice as irradiated recipients of normal cells gave information about the host effect. In treated unirradiated mice, the total nucleated cell and the CFU counts were disturbed, and 2 days later a large fraction of the CFU were found in the DNA synthesis (S) phase. This meant that injection of endotoxin generated factors affecting the kinetics of the CFU and triggering the resting CFU into the proliferative cycle. If then the mice were given supralethal irradiation and used as recipients of normal bone marrow cells, more CFU seeded to the spleen as compared to normal recipients; but the dip and the growth rate of the CFU were not changed. Hence the endotoxin-generated factors had been eliminated in 2 days. A total body sublethal irradiation by 400 rad X-ray 2 days after endotoxin injection reduced the post-irradiation dip in the recovery curve of the CFU, indicating that though the factors affecting the cell kinetics had been eliminated, the cycling CFU behaved like a growing population. During the first week, the growth rate of the CFU remained the same as in control irradiated mice. The growth rate of the spleen CFU of the endotoxin-treated mice slowed down during the second week, and their self-replicating ability was low. Fluctuations in the DNA synthesizing fraction of the spleen CFU suggested a variability in the ratio of the length of the S phase and the cell generation time.     

MOBILIZATION OF HAEMOPOIETIC STEM CELLS (CFU) INTO THE PERIPHERAL BLOOD OF THE MOUSE; EFFECTS OF ENDOTOXIN AND OTHER COMPOUNDS

Factors affecting the circulation of haemopoietic stem cells (CFU) in the peripheral blood of mice were investigated. I.v. injection of sublethal doses of endotoxin, trypsin and proteinase appeared to raise the number of CFU per ml blood from about 30–40 to about 300–400 or more within 10 min. The effect was smaller when smaller doses of the substances were injected. After this initial rise the number of circulating cells returned to normal in a few hours. Following endotoxin there was a second rise which started 2–3 days after injection and attained a peak on the 6th–7th day. The first rise is explained as a mobilization of stem cells from their normal microenvironments into the blood stream; the second rise is considered to reflect proliferation of CFUs in the haemopoietic tissues. The spleen seems to be acting as an organ capturing CFUs from the blood and not as a source adding stem cells to the blood.
The early mobilization of CFU after endotoxin injection did not coincide with a mobilization of neutrophils. The number of circulating band cells was increased during the first hours.
The importance of 'open sites'in the haemopoietic tissue for capturing CFUs was studied by emptying these sites through a lethal X-irradiation and injecting normal bone marrow cells. When a greater number of syngeneic bone marrow cells was injected intravenously, the level of circulating CFU in irradiated mice was slightly lower than the level in unirradiated mice during the first hours.     

Effects of exposure to low-dose-rate (60)co gamma rays on human tumor cells in vitro

Cells of three asynchronously growing human tumor cell lines, PC3 (human prostate carcinoma), T98G and A7 (human glioblastomas), which have been shown previously to demonstrate low-dose hyper-radiosensitivity to low acute single doses, were irradiated with (60)Co gamma rays at low dose rates (2 cGy-1 Gy h(-1)). Instead of a dose-rate sparing response, these cell lines demonstrated an inverse dose-rate effect on cell survival at dose rates below 1 Gy h(-1), whereby a decrease in dose rate resulted in an increase in cell killing per unit dose. A hyper-radiosensitivity-negative cell line, U373MG, did not demonstrate an inverse dose-rate effect. Analysis of the cell cycle indicated that this inverse dose-rate effect was not due to accumulation of cells in G(2)/M phase or to other cell cycle perturbations. T98G cells in reversible G(1)-phase arrest also showed an inverse dose-rate effect at dose rates below 30 cGy h(-1) but a sparing effect as the dose rate was reduced from 60 to 30 cGy h(-1). We conclude that this inverse dose-rate effect in continuous exposures reflects the hyper-radiosensitivity seen in the same cell lines in response to very small acute single doses.     

EFFECT OF BLEOMYCIN ON MOUSE HAEMOPOIETIC COLONY FORMING CELLS IN CULTURE (CFUc)

The kinetics of CFUc studied by hydroxyurea and endotoxin treatments indicate that this cell population is proliferating actively (some 50% in S-phase). This fact implies a peculiar response to (BLM) treatment with Bleomycin, a drug which appears to be proliferation—dependent. The dose—response has a steep initial slope resulting in a low extrapolation number (n= 0·66; D37 = 960 ± 70 mg BLM/kg body weight). The steep initial slope is confirmed by split-dose experiments resulting in a potentiation effect by fractionation. Further evidence for the dependence of the action of this drug upon the proliferative state of the cell population is derived from time—response studies after single doses of BLM.     

The effect of endotoxin on murine stem cells

Previous studies showed that after 5 μg of Salmonella typhosa endotoxin there was an increase in colony stimulating factor temporally related to a fall in murine marrow in vitro colony forming cells (CFC). This was followed by differentiation along the marrow granulocytic pathway. The present studies showed that after 5 μg of endotoxin the peripheral blood CFC fell by approximately 50% at one hour, rose to a level ten fold that of control at six hours and then returned to control values by 48 hours. There was a progressive increase in the number of splenic CFC to ten fold that of control from 24 to 72 hours after endotoxin. These data imply a migration of CFC from the marrow to the spleen along with an in-situ increase in splenic CFC. Thus, either migration or differentiation may explain the fall in marrow CFC after endotoxin. Spleen colony forming units (CFU) in the marrow were measured by a transplantation technique and the transplantation fraction (f Fx) determined. A decrease in marrow CFU at 24 hours after endotoxin was secondary to a change in the f Fx. from 11.1% to 7.6%. There was however, an increased percentage of CFU in DNA synthesis in the interval of 6–48 hours after endotoxin, as judged by the hydroxyurea technique. As the marrow CFC fell within 20 minutes of endotoxin administration, the data suggest the CFC may be affected initially and that changes in the generative cycle of the CFU may be of a secondary nature.     

Dual biological function of a T-cell-derived murine immunoenhancing factor.

Murine enhancing factor (MEF), derived from the culture fluid of mixtures of histoincompatible spleen cells, was found to have two apparently different, but perhaps closely related, biological activities. First, MEF can functionally replace T cells in nonspecifically augmenting the anti-sheep erythrocyte plaque-forming cell response of T-cell-depleted, mouse splenic B-cell cultures. Second, the mediator acts similarly to colony stimulating factor from human urine in promoting the formation of colony-forming units (CFU) in soft agar bone marrow cell cultures. This latter function of MEF was manifest in the absence of detectable increases in the level of incorporation of [³H]thymidine by cultured bone marrow cells. Morphologically, the cells comprising the CFU were macrophage-like in appearance. The data suggest that MEF may function as a differentiation signal for the maturation of antigen-activated B lymphocytes into immunoglobulin-secreting cells, as well as for the modulation of hematopoietic or granulopoietic macrophage stem cells into mature, functional macrophages.     

Human placenta-conditioned medium for stimulation of human granulopoietic precursor cell (CFU-C) colony growth in vitro.

Human placenta-conditioned medium (HPCM) has been reported to stimulate colony formation by human granulopoietic stem cells (CFU-C) in vitro. The present work was performed to further characterize this colony formation. The majority of HPCM batches tested stimulated colony growth equivalent to recombined human leukocyte feeder layers with optimal cellular composition. A broad plateau of the dose-response curve of HPCM was found. A linear correlation exists between the number of marrow cells plated and the number of colonies grown. Optimal duration of culture is between 9 and 11 days. Colonies are large and tend to be compact. Admixture of mature granulocytes does not affect the colony growth pattern under optimal culture conditions. These data document that HPCM is a suitable source of colony-stimulating activity for the routine assay of human CFU-C. Due to the constant colony stimulation, HPCM appears particularly valuable for longitudinal studies of human CFU-C.     

Effect of Myleran On Murine Hemopoiesis

Time- and dose-dependent patterns of depletion and regeneration of hemopoietic progenitor cells in mouse femora and spleens following treatment with the antileukemic agent Myleran (Busulphan, MY) were studied using the murine spleen colony system and the agar gel in vitro colony system. MY was found to depress granulopoiesis selectively, as manifested by the development of marked prolonged neutropenia, hypoplasia of the bone marrow and (to a lesser degree) of the spleen, reduction of the incidence of multipotential hemopoietic progenitor cells (CFU-S) and of granulocytic progenitor cells (CFU-C) in both femora and spleens, and impairment of the capacity of CFU-S from either tissue to generate granulocytic colonies in the spleens of irradiated hosts. the severity and duration was greatest at high dose levels of MY (800 μ). the action of MY on CFU-S was more pronounced than that on CFU-C, suggesting that MY is a cycle-independent agent. Repopulation of the CFU-C pool preceded that of the CFU-S pool. Development of neutropenia and maximal marrow hypoplasia followed the onset of depression of CFU-S and CFU-C incidence, while recovery of normal nucleated cellularity in the blood, femur and spleen preceded repopulation of the CFU-S and CFU-C pools. MY treatment resulted in transitory stimulation of colony stimulating factor (CSF) generation by the femur but had no effect on serum CSF levels. the peak of femoral CSF generation coincided with the nadir of CFU-C depression. These findings indicated that the prolonged neutropenia following MY treatment was secondary to depletion of the progenitor cell pools, that during recovery granulopoietic repopulation took precedence over self-maintenance of the hemopoietic progenitor cell pools, and that increased generation of CSF may play a role in the early phase of granulopoietic recovery.     

The dose response of granulocyte-macrophage colony stimulating activity (GM-CSA) for sera of "Swiss" mice after endotoxin "lipopolysaccharide B" Escherichia coli (0127: B8) intraperitoneal administration

The effect of different doses of endotoxin (Lipopolysaccharide B) on Granulocyte-Macrophage Colony Stimulating Activity (GM-CSA) in the sera of "Swiss" male mice was measured by granulocyte-macrophage "in vitro" colony formation. The highest GM-CSA was found to be present 3-4 hours after 200 micrograms of endotoxin intraperitoneal injection.     

KINETICS OF HAEMOPOIETIC RECOVERY IN ENDOTOXIN-TREATED MICE

Kinetics of mouse spleen colony forming units were studied after intra-peritoneal injection of 1 μ/g body weight bacterial endotoxin S. typhosa. When these mice were used as unirradiated and sublethally irradiated donors, it was possible to study the effect of the endotoxin injection upon the cells. Use of the treated mice as irradiated recipients of normal cells gave information about the host effect. In treated unirradiated mice, the total nucleated cell and the CFU counts were disturbed, and 2 days later a large fraction of the CFU were found in the DNA synthesis (S) phase. This meant that injection of endotoxin generated factors affecting the kinetics of the CFU and triggering the resting CFU into the proliferative cycle. If then the mice were given supralethal irradiation and used as recipients of normal bone marrow cells, more CFU seeded to the spleen as compared to normal recipients; but the dip and the growth rate of the CFU were not changed. Hence the endotoxin-generated factors had been eliminated in 2 days. A total body sublethal irradiation by 400 rad X-ray 2 days after endotoxin injection reduced the post-irradiation dip in the recovery curve of the CFU, indicating that though the factors affecting the cell kinetics had been eliminated, the cycling CFU behaved like a growing population. During the first week, the growth rate of the CFU remained the same as in control irradiated mice. The growth rate of the spleen CFU of the endotoxin-treated mice slowed down during the second week, and their self-replicating ability was low. Fluctuations in the DNA synthesizing fraction of the spleen CFU suggested a variability in the ratio of the length of the S phase and the cell generation time.     

Inhibition of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse skin ornithine decarboxylase and protein kinase C by polyphenolics from grapes

Ornithine decarboxylase is the rate-limiting enzyme in the biosynthesis of polyamines, which are believed to play an essential role in diverse biological processes including cell proliferation and differentiation. We have previously reported [J. Bomser, K. Singletary, M. Wallig, M. Smith, Inhibition of TPA-induced tumor promotion in CD-1 mouse epidermis by a polyphenolic fraction from grape seeds, Cancer Letters 135 (1999) 151-157] that pre-application of a grape polyphenolic fraction (GPF) to mouse skin epidermis inhibits 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ornithine decarboxylase (ODC) activity, as well as 7, 12-dimethylbenz[a]anthracene (DMBA)-initiated, TPA-promoted mouse skin tumorigenesis. The present studies were designed to further characterize the effect of time and dose of application of GPF on TPA-induced ODC activity and protein expression, and on protein kinase C activity in mouse skin epidermis. In addition, the effect of GPF on ODC kinetics in vitro was examined. Application of 5, 10, and 20 mg of GPF 20 min prior to treatment with TPA resulted in a significant decrease in epidermal ODC activity of 54, 53, 90%, respectively, compared with controls. Yet, ODC protein levels (Western blot) in the 10 and 20 mg GPF groups were significantly increased by 1.8 and 1.9-fold, respectively, compared with controls. A similar response was observed with the ODC inhibitor 2-difluoromethylornithine (DFMO), which served as a positive control. Application of grape polyphenolics (20 mg) at 60 and 30 min prior to treatment with TPA inhibited ODC activity by 62 and 68%, respectively, compared with controls (P<0.05). In contrast, application of grape polyphenolics (20 mg) at 60, 120 and 240 min after treatment with TPA resulted in no significant changes in ODC activity. A similar increase in epidermal ODC protein was observed in these GPF-treated animals, similar to that observed when GPF application preceded TPA. When applied to mouse skin prior to TPA, GPF was associated with a decrease in subsequent PKC activity compared with controls at 10 and 30 min following TPA treatment. The GPF-associated decrease in PKC activity preceded the decrease in ODC activity. In a separate in vitro study, kinetic analyses indicated that GPF is a competitive inhibitor of ODC activity. Collectively these data suggest that the grape polyphenolic fraction is effective as an inhibitor of ODC activity when applied before TPA, and that the magnitude of inhibition is independent of epidermal ODC protein content. In addition, GPF is a competitive inhibitor of ODC activity in vitro. The decrease in TPA-induced ODC activity due to GPF treatment is preceded by an inhibition of TPA-induced PKC activity. Thus, the polyphenolic fraction from grapes warrants further examination as a skin cancer chemopreventive agent that interferes with cellular events associated with TPA promotion.     

GRAFT SIZE CONSIDERATIONS IN THE KINETICS OF SPLEEN COLONY DEVELOPMENT

The kinetics of spleen colony development has been studied after the injection of 10⁶, 10⁵ and 3 × 10⁴ bone marrow cells. The results indicate that:

• 1 The CFU population growth rate is independent of cell dose until the logarithmic growth phase is passed. Slowing of growth was seen by day 12 after the highest dose, by day 15 after the median dose, but was not observed during the period of observation after the low dose.
• 2 The growth rate of CFU per colony is independent of cell dose, but the curves are not identical. The differences between the curves leads to the conclusion that there is a dose-dependent delay in the commencement of CFU proliferation. The delay is roughly equal to one cell cycle time between the medium and high inoculum groups and also between the medium and low inoculum groups.
• 3 The number of cells per colony is graft size dependent, the doubling times, where these can be roughly assessed, being inversely related to the graft size. From the average number of cells per colony on day 6 it is calculated that the mean doubling time in the early stages of colony development is less than 7 hr.
• 4 The proportion CFU:colony cells is dose dependent with the highest inoculum having the highest proportion and the low inoculum group having the lowest proportion.

     

Properties of a murine monocytic tumor cell line J-774 in vitro. II. Enzyme activities.

Lysosomal enzyme activities, collagen degrading activity and sensitivity to bacterial infection were tested in a murine monocytic cell line, J-774, during cultivation with or without fetal calf serum (FCS) or endotoxin, and compared with the same parameters in normal murine peritoneal macrophages. The basic intracellular level of two out of three lysosomal enzyme activities tested (acid phosphatase and β-glucuronidase) and their extracellular release were higher in the J-774 cells than in normal macrophages, indicating that the tumor cells were more “activated”. This was further supported by the moderate increase in intracellular enzyme activities after FCS and endotoxin stimulation of the J-774 cells. Normal macrophages showed a much more impressive rise in these parameters after stimulation. Collagen-degrading activity was found at the same magnitude, or lower, in tumor cell cultures, compared to normal macrophage cultures. However, the activity in the tumor cultures was enhanced by endotoxin stimulation. The J-774 cells showed a higher sensitivity to bacterial contamination, tested after E. coli addition to the cultures, than normal macrophages. This high sensitivity could be prevented by pretreatment of the tumor cells with endotoxin.     

Serum factors in chronic myeloid leukemia

Mononuclear cells from the peripheral blood of healthy test persons were cultivated in a methylcellulose medium with serum samples taken from 13 patients with chronic myeloid leukemia (CML) and with osteomyelosclerosis (OMS) as well as with serum samples of 6 healthy test persons. From evaluating the proliferation of granulopoietic cells quantitatively, conclusions were made concerning the concentrations of granulopoietic stimulating substances in these sera. In all cultures with the serum of patients the number of granulopoietic cell colonies was greater than that in cultures with the serum of normal persons. The stronger proliferation of granulopoietic precursor cells in cultures with serum of patients is seen to be due to an enhanced production of the granulocyte-macrophage colony stimulating factor (GM-CSF) by leukemic cells. The differential hemograms and curves indicating the course of leukocytes in patients are compared with the corresponding results of cultures. In patients with CML an increased output of GM-CSF will apparently influence the increase in size of the granulopoietic stem cell pool, which is evident in the steep increase of those curves indicating the course of leukocytes. In patients with OMS, however, there is a discrepancy between granulopoietic serum activity and proliferation in vivo. From these investigations the hypothesis is derived that an increased synthesis of GM-CSF in patients with CML may be one of the causes underlying hyperplastic granulopoiesis. A direct advantage of leukemic cells in proliferation cannot be derived from it.(ABSTRACT TRUNCATED AT 250 WORDS)     

Therapeutic implications of serum factors inhibiting proliferation and inducing differentiation of myeloid leukemic cells

Murine post-endotoxin sera contain high levels of myeloid colony-stimulating factor(s) (GM-CSF) and factors capable of inducing terminal granulocyte and macrophage differentiation of the murine myelomonocytic leukemic cell line WEHI-3. The combination of C. parvum and endotoxin induced a serum activity capable of inducing tumor necrosis and inhibiting leukemic colony formation in vitro. This factor (TNF) could be separated from the differentiation-inducing factor (GM-DF) and from CSF. In conjunction with a Phase I trial of highly purified endotoxin in patients with advanced malignancy, we monitored human post-endotoxin sera for CSF and GM-DF. Induction of GM-DF occurred maximally at 2-6 h and was associated with increased serum levels of CSF active against the patient's own bone marrow. Following repeated injections of escalating doses of endotoxin, persistent levels of GM-DF were detected both pre-endotoxin and 24 h post-endotoxin treatment. The ability to induce repeatedly a serum protein with potent capacity to promote terminal differentiation of myelomonocytic leukemic cells suggests a possible therapeutic role in human myeloid leukemias.     

Effect of myleran on murine hemopoiesis. I. Granulocytic cell line specificity of action on progenitor cells.

Time- and dose-dependent patterns of depletion and regeneration of hemopoietic progenitor cells in mouse femora and spleens following treatment with the antileukemic agent Myleran (Busulphan, MY) were studied using the murine spleen colony system and the agar gel in vitro colony system. MY was found to depress granulopoiesis selectively, as manifested by the development of marked prolonged neutropenia, hypoplasia of the bone marrow and (to a lesser degree) of the spleen, reduction of the incidence of multipotential hemopoietic progenitor cells (CFU-S) and of granulocytic progenitor cells (CFU-C) in both femora and spleens, and impairment of the capacity of CFU-S from either tissue to generate granulocytic colonies in the spleens of irradiated hosts. The severity and duration was greatest at high dose levels of MY (800 microgram). The action of MY on CFU-S was more pronounced than that on CFU-C, suggesting that MY is a cycle-independent agent. Repopulation of the CFU-C pool preceded that of the CFU-S pool. Development of neutropenia and maximal marrow hypoplasia followed the onset of depression of CFU-S and CFU-C incidence, while recovery of normal nucleated cellularity in the blood, femur and spleen preceded repopulation of the CFU-S and CFU-C pools. MY treatment resulted in transitory stimulation of colony stimulating factor (CSF) generation by the femur but had no effect on serum CSF levels. The peak of femoral CSF generation coincided with the nadir of CFU-C depression. These findings indicated that the prolonged neutropenia following MY treatment was secondary to depletion of the progenitor cell pools, that during recovery granulopoietic repopulation took precedence over self-maintenance of the hemopoietic progenitor cell pools, and that increased generation of CSF may play a role in the early phase of granulopoietic recovery.     

γ射线对副溶血性弧菌辐射效应的PCR检测

目的:研究γ射线对副溶血性弧菌(Vibrio parahaemolyticus)的辐射效应。方法:采用0kGy~7.0kGy内不同剂量的60Co-γ对浓度为2.0×108CFU/mL的副溶血性弧菌进行辐射,通过菌落计数计算该菌的致死率与存活率,并采用菌液PCR和常规PCR间接检测DNA浓度研究其致死效应。结果:菌落计数表明,在0kGy~3.0kGy内,该菌致死率随辐射剂量增加而呈线性增长;3.0kGy以上可全部杀灭试验浓度的副溶血性弧菌。常规PCR和菌液PCR结果表明,PCR扩增条带亮度都随着辐射剂量的增大而增强。常规PCR中,辐射剂量3.0kGy以上,电泳条带的亮度明显增加。结论:γ射线辐射剂量与存活副溶血性弧菌数、DNA的释放量都有明显的剂量-反应关系,辐射致死的主要原因是由射线对菌体细胞膜造成损伤、DNA外流造成的。