Chromosome aberration induction is dependent on the spatial distribution of energy deposition through a cell nucleus

The importance of the spatial distribution of energy deposition through the nucleus in determining the resultant chromosome rearrangements was investigated using fluorescent in situ hybridisation technique following either uniform or partial irradiation of HF19 human fibroblast cells with low-LET 1.5 keV ultrasoft X-rays. Irradiations were performed with and without a copper irradiation mask with a Poisson distribution of micron-sized holes immediately below the irradiation dish and the results are compared with previous results obtained following exposure to a Poisson distribution of alpha particles. For the same radiation quality, the spatial distribution of energy deposition within the nucleus was found to be important in determining the ultimate biological response, with an increased ratio of complex-to-simple aberrations observed for partial compared to uniform irradiation. Comparisons between low-LET ultrasoft X-rays and high-LET alpha particles indicate that the sub-micron clustering of damage along the alpha particle track is more important than just the total number of double-strand breaks produced.

Direct Comparison between Protons and Alpha-particles of the Same LET: I. Irradiation Methods and Inactivation of Asynchronous V79, HeLa and C3H 10T½ Cells

A direct comparison was carried out of the biological effectiveness of protons and alpha-particles of the same linear energy transfer (LET) under identical conditions with a variety of in vitro biological systems. Monolayers of mammalian cells were irradiated with accelerated beams of protons (1.2 and 1.4 MeV) and alpha-particles (30 and 35 MeV) corresponding to LETs of 23 and 20 keV microns-1 for each particle type. For V79-4 cells it was observed that the linear term of the dose-response for cell inactivation by protons was significantly greater than that for alpha-particles of the same LET. For HeLa and HeLa S3 cells, also, the linear term appeared to be greater for protons, but this was not observed with more limited data for C3H 10T1/2 cells. The result for V79 cells is in agreement with the report of Belli et al. (1989) who observed that the biological effectiveness of protons rose sharply between 17 and 30 keV microns-1 in strong contrast to alpha-particles which reached a peak effectiveness at greater than 100 keV microns-1. These results place new constraints on the biologically relevant features of the microscopic structure of radiation tracks, and have implications for the mechanistic and practical comparison between radiations.

Innate immune recognition of, and response to, Clostridium sordellii

Clostridium sordellii, an anaerobic pathogen, has recently been associated with rapidly fatal infections following medically induced abortions and injecting drug use. Patients with C. sordellii infection display few signs of inflammation such as fever, or redness and pain at the site of infection. We hypothesized that this could be due to reduced recognition of the organism by Toll-like receptors (TLRs) of the innate immune system. An ELAM-NF-kappaB luciferase reporter system in TLR-transfected HEK cells was used to measure TLR-dependent recognition of washed, heat-killed C. sordellii and other pathogenic clostridial species. Results demonstrated that all clostridia were well recognized by TLR2 alone and that responses were greatest when TLR2 was co-expressed with TLR6. Further, isolated human monocytes produced the pro-inflammatory cytokine TNFalpha and the immunoregulator IL-10 in response to C. sordellii. In addition, C. sordellii-stimulated monocytes produced 30% less TNFalpha following treatment with an anti-TLR2 blocking antibody. These data demonstrate that innate immune recognition of, and response to, cell-associated components of C. sordellii and other clostridial pathogens are mediated by TLR2 in combination with TLR6. We conclude that the characteristic absence of inflammatory signs and symptoms in C. sordellii infection is not related to inadequate immune detection of the organism, but rather is attributable to a species-specific immune system dysfunction that remains to be elucidated.

Hereditary multi-infarct dementia of the Swedish type is a novel disorder different from NOTCH3 causing CADASIL

Several hereditary small vessel diseases (SVDs) of the brain have been reported in recent years. In 1977, Sourander and Wålinder described hereditary multi-infarct dementia (MID) in a Swedish family. In the same year, Stevens and colleagues reported chronic familial vascular encephalopathy in an English family bearing a similar phenotype. These disorders have invariably been suggested to be cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) but their genetic identities remain unknown. We used molecular, radiological and neuropathological methods to characterize these disorders. Direct DNA sequencing unexpectedly confirmed that affected members of the English family carried the R141C mutation in the NOTCH3 gene diagnostic of CADASIL. However, we did not detect any pathogenic mutations in the entire 8091 bp reading frame of NOTCH3 or find clear evidence for NOTCH3 gene linkage in the Swedish DNA. This was consistent with the lack of hyperintense signals in the anterior temporal pole and external capsule in Swedish subjects upon magnetic resonance imaging. We further found no evidence for granular osmiophilic material in skin biopsy or post-mortem brain samples of affected members in the Swedish family. In addition, there was distinct lack of NOTCH3 N-terminal fragments in the cerebral microvasculature of the Swedish hereditary MID subjects compared to the intense accumulation in the English family afflicted with CADASIL. Several differences in arteriosclerotic changes in both the grey and white matter were also noted between the disorders. The sclerotic index values, density of collagen IV immunoreactivity in the microvasculature and number of perivascular macrophages were greater in the English CADASIL samples compared to those from the Swedish brains. Multiple approaches suggest that the Swedish family with hereditary MID suspected to be CADASIL has a different novel disorder with dissimilar pathological features and belongs to the growing number of genetically uncharacterized familial SVDs.

Clostridium sordellii infection: epidemiology, clinical findings, and current perspectives on diagnosis and treatment

Clostridium sordellii infections pose difficult clinical challenges and are usually fatal. Most commonly, these infections occur after trauma, childbirth, and routine gynecological procedures, but they have recently been associated with medically induced abortions and injection drug use. We report 2 fatal cases, one of which was associated with minor trauma, and the other of which was associated with normal childbirth, and we summarize the clinical features of 43 additional cases of reported C. sordellii infection. Of these 45 cases, 8 (18%) were associated with normal childbirth, 5 (11%) were associated with medically induced abortion, and 2 (0.4%) were associated with spontaneous abortion. The case-fatality rate was 100% in these groups. Ten (22%) of the C. sordellii infections occurred in injection drug users, and 50% of these patients died. Other cases of C. sordellii infection (in 19 patients [43%]) occurred after trauma or surgery, mostly in healthy persons, and 53% these patients died. Overall, the mortality rate was 69% (31 of 45 patients). Eighty-five percent of all patients with fatal cases died within 2-6 days of initial infection, and nearly 80% of fatal cases developed leukemoid reactions. Rapid diagnostic tests and improved treatments are needed to reduced the morbidity and mortality associated with this devastating infection.

Clostridium perfringens phospholipase C-induced platelet/leukocyte interactions impede neutrophil diapedesis

Clostridium perfringens gas gangrene is a fulminant necrotizing infection in which inflammatory cells are notably absent from infected tissues but are often massed within adjacent vessels. It has been shown that C. perfringens phospholipase C (PLC) stimulates formation of large intravascular platelet/leukocyte complexes and that PLC-induced activation of platelet gpIIbIIIa plays a major role. In vivo, such aggregates contribute to microvascular thrombosis and ischaemic necrosis of tissue. However, the effects of adherent platelets on neutrophil diapedesis have not been established. The present work investigated (1) the contribution of platelet P-selectin (CD62P) to PLC-induced cellular complex formation and (2) the effects of platelet adhesion on neutrophil diapedesis. The effects of anti-gpIIbIIIa and anti-CD62P strategies on PLC-induced complex formation were measured by flow cytometry and followed by light microscopy. Both platelet gpIIbIIIa and CD62P contributed to the formation of platelet/leukocyte complexes. Specifically, gpIIbIIIa mediated the formation of large platelet/platelet aggregates that were tethered to the leukocyte principally via CD62P. Neutrophil diapedesis, quantified by a transendothelial cell migration assay and visualized by electron microscopy, was significantly reduced (>60%) by the adherence of large platelet aggregates. It was concluded that the absence of a tissue inflammatory response in C. perfringens gas gangrene is due, in part, to impaired neutrophil mobility caused by large aggregates of adherent platelets induced by PLC. Further, an adjunctive immunotherapeutic strategy targeting both gpIIbIIIa and CD62P may improve the tissue inflammatory response, prevent vascular occlusion, maintain tissue viability, and reduce the need for radical amputation in patients with clostridial gas gangrene.

Keeping up with the neighbours--measuring the bystander response

Ionising radiation can induce responses within non-exposed neighbouring (bystander) cells, which potentially have important implications on the estimates of risk at environmentally relevant doses. Using human skin fibroblasts (AG1522), a range of methods were used to investigate the nature of the signal(s) arising from the exposed cells. The signal(s) can be transmitted by direct cell-cell communication (investigated by using partial dish irradiations) or by medium-borne factors (a co-culture system where two monolayers share the same medium but only one monolayer is exposed to ionising radiation). CDKN1A was found to be up-regulated in both directly exposed and non-exposed cells. The data suggest that direct cell-cell communication dominates for these confluent cells, with medium-borne factors also contributing.

Experimental techniques for studying bystander effects in vitro by high and low-LET ionising radiation

Ionising radiation can induce responses within non-exposed neighbouring (bystander) cells which potentially have important implications on the estimates of risk from low dose or low dose rate exposures of ionising radiations. A range of strategies have been developed for investigating bystander effects in vitro for both high-LET alpha particles or low-LET ultrasoft X rays using either partial shielding (grids, half-shields and slits) or by using a co-culture system where two physically separated populations of cells can be cultured together, allowing one population of cells to be irradiated while the second population remains unirradiated. The techniques described provide a useful tool to study bystander effects and complement microbeam studies. Studies using these systems show significant increases in the unirradiated bystander cells for various end points including the induction of chromosomal instability in haemopoetic stem cells and transformation in CGL1 cells.

Increased complexity of radiation-induced chromosome aberrations consistent with a mechanism of sequential formation

Complex chromosome aberrations (any exchange involving three or more breaks in two or more chromosomes) are effectively induced in peripheral blood lymphocytes (PBL) after exposure to low doses (mostly single particles) of densely ionising high-linear energy transfer (LET) alpha-particle radiation. The complexity, when observed by multiplex fluorescence in situ hybridisation (m-FISH), shows that commonly four but up to eight different chromosomes can be involved in each rearrangement. Given the territorial organisation of chromosomes in interphase and that only a very small fraction of the nucleus is irradiated by each alpha-particle traversal, the aim of this study is to address how aberrations of such complexity can be formed. To do this, we applied theoretical "cycle" analyses using m-FISH paint detail of PBL in their first cell division after exposure to high-LET alpha-particles. In brief, "cycle" analysis deconstructs the aberration "observed" by m-FISH to make predictions as to how it could have been formed in interphase. We propose from this that individual high-LET alpha-particle-induced complex aberrations may be formed by the misrepair of damaged chromatin in single physical "sites" within the nucleus, where each "site" is consistent with an "area" corresponding to the interface of two to three different chromosome territories. Limited migration of damaged chromatin is "allowed" within this "area". Complex aberrations of increased size, reflecting the path of alpha-particle nuclear intersection, are formed through the sequential linking of these individual sites by the involvement of common chromosomes.

Diabetic ketoacidosis associated with aripiprazole

BACKGROUND

Atypical antipsychotics have become the mainstay of management of schizophrenia and other psychotic disorders due to low risk of extrapyramidal symptoms. However, postmarketing data has reported atypical antipsychotic agents being associated with hyperglycaemia and diabetic ketoacidosis (DKA). We believe this to be the first published report of hyperglycaemia and DKA with the newest atypical antipsychotic agent, aripiprazole.

CASE REPORT

A 34-year-old African-American female with schizophrenia presented to the emergency department with nausea, vomiting, and malaise for 3-4 days shortly after initiation of aripiprazole therapy. Initial laboratory results revealed significant hyperglycaemia with metabolic acidosis. The patient received treatment for DKA with an intravenous insulin infusion and fluid replacement. Isophane insulin suspension (NPH insulin) was begun immediately following the insulin drip and continued upon discharge from the hospital. Outpatient follow-up information was not available.

CONCLUSION

To our knowledge, this is the first case report of aripiprazole associated with hyperglycaemia and DKA. This case is striking in that DKA occurred 4 days following initiation of aripiprazole and the patient had rapid resolution of symptoms and normalization of laboratory values upon discontinuation of aripiprazole. It is important that health-care providers monitor for hyperglycaemia when prescribing atypical antipsychotics including aripiprazole.

Bound PCNA in nuclei of primary rat tracheal epithelial cells after exposure to very low doses of plutonium-238 alpha particles

Bystander effects from ionizing radiation have been detailed for a number of cell systems and a number of end points. We wished to use a cell culture/ex vivo rat model of respiratory tissue to determine whether a bystander effect detected in culture could also be shown in a tissue. Examination by immunofluorescence techniques of tracheal cell cultures after exposure to very low doses of alpha particles revealed a large proportion of cells with proliferating cell nuclear antigen (PCNA) bound in their nuclei. PCNA was selected as an end point because it is involved in both DNA repair and the changes in cell cycle that are typical of many reported bystander effects. Maximum response can be detected in up to 28% of the cells in sub-confluent cultures with a dose of only 2 mGy. At this dose less than 2% of the cell nuclei have experienced a particle traversal and less than 6% of the cells have experienced an alpha-particle traversal through either their nucleus or some part of their cytoplasm. The hypothesis that this bystander response in nontargeted cells is mediated through secreted factor(s) is presented, and supporting evidence was found using partial irradiation and co-culture experiments. Examination of the effect with excised pieces of trachea demonstrated a response similar to that seen in culture.

M type 1 and 3 group A streptococci stimulate tissue factor-mediated procoagulant activity in human monocytes and endothelial cells

Streptococcal toxic shock syndrome (StrepTSS) is an invasive infection characterized by marked coagulopathy, multiple organ failure, and rapid tissue destruction and is strongly associated with M type 1 and 3 group A streptococci (GAS). Initiation of the coagulation cascade with formation of microvascular thrombi contributes to multiple organ failure in human cases of gram-negative bacteremia; however, little is known regarding the mechanism of coagulopathy in StrepTSS. Thus, we investigated the abilities of several strains of M type 1 and 3 GAS isolated from human cases of StrepTSS to stimulate production of tissue factor (TF), the principal initiator of coagulation in vivo. Washed, killed M type 1 and 3 GAS, but not M type 6 GAS, elicited high-level TF-mediated procoagulant activity from both isolated human monocytes and cultured human umbilical vein endothelial cells. M type 1 GAS consistently elicited higher levels of TF from monocytes than did M type 3 GAS. GAS-induced TF synthesis in monocytes did not correlate with production of tumor necrosis factor alpha or interleukin-8. Conversely, M type 3 GAS were consistently more potent than M type 1 GAS in stimulating endothelial cell TF synthesis. These results demonstrate that (i) M type 1 and 3 strains of GAS are potent inducers of TF synthesis, (ii) GAS-induced TF synthesis is not simply an epiphenomenon of cytokine generation, and (iii) induction of TF in endothelial cells and monocytes may be M type specific. In total, these findings suggest that a novel interaction between GAS and host cells contributes to the observed coagulopathy in StrepTSS.

Biological effectiveness of isolated short electron tracks: V79-4 cell inactivation following low dose-rate irradiation with Al(K) ultrasoft X-rays

PURPOSE

To investigate the biological effect of single, isolated, short electron tracks (<70 nm) relevant to practical human exposures to low-linear energy transfer radiation.

MATERIALS AND METHODS

An irradiation rig was constructed that allowed environmentally controlled, protracted irradiations with an individually prescribed dose to up to 20 samples over a period of days. Inactivation of V79-4 mammalian cells by Al(K) ultrasoft X-rays was studied at high and low dose-rates with a maximum exposure time of 42 h.

RESULTS

A significant increase in clonogenic survival was observed at the higher doses when the exposure time was increased from <6 min to 21 h, with no further increase observed for 42-h exposures. Despite the short range of the low-energy electrons produced (<70 nm), significant cell inactivation was observed for these low dose-rate exposures.

CONCLUSIONS

The results are consistent with the hypothesis that even individual tracks can be biologically effective.

Is the increased relative biological effectiveness of high LET particles due to spatial or temporal effects? Characterization and OER in V79-4 cells

The efficiency of producing biological damage varies with radiation quality. Conventional explanations rely on spatial differences in the radiation track structure; generally however there are also very large temporal differences in delivery of the radiation at the cellular level. High-LET radiation normally deposits substantial amounts of energy by individual heavily ionizing tracks on a timescale of the order of picoseconds. By contrast each low-LET radiation track deposits a small amount of energy. Many of these tracks, distributed over the whole cell, are required to deliver an equivalent dose to a high-LET track and they are usually delivered over much longer timescales (typically seconds) during which chemical, biochemical and biological processes are occurring. In this paper the design, characterization and initial application of a high-brightness, laser-plasma ultrasoft x-ray source is described. This has been used to investigate the importance of the temporal differences by irradiating mammalian cells with an energy deposition with spatial properties of low-LET radiation and temporal properties similar to high-LET radiation. The present system delivers a typical dose, to the incident surface of the cells, of 0.12 Gy per pulse delivered in <10 ps. The capabilities of the x-ray source were tested by determining the survival of V79-4 hamster cells irradiated with picosecond pulses of ultrasoft x-rays under aerobic and anaerobic conditions, which were found to be consistent with previously published non pulsed data with x-rays of similar energy. These results support the expectation that the disappearance of an oxygen effect for high-LET radiation particles is due to their spatial properties rather than the very short timescale of each particle traversal. For other effects, particularly non-targeted phenomena such as induced genomic instability, expectations may be less clear cut.

Streptococcal toxic shock syndrome

Perhaps more noteworthy than the emergence of Streptococcal toxic shock syndrome (StrepTSS) is its persistence for a period of more than 15 years in most geographical areas and an actual increase in incidence in some regions. Early diagnosis remains a problem, and aggressive surgery often cannot be avoided. The continuing rates of mortality and morbidity indicate the need for novel approaches to diagnosis and treatment.

Cell inactivation and double-strand breaks: the role of core ionizations, as probed by ultrasoft X rays

The large RBE (approximately 7) measured for the killing of Chinese hamster V79 cells by 340 eV ultrasoft X rays, which preferentially ionize the K shell of carbon atoms (Hervé du Penhoat et al., Radiat. Res. 151, 649-658, 1999), was used to investigate the location of sensitive sites for cell inactivation and the physical modes of action of radiation. The enhancement of the RBE above the carbon K-shell edge either may indicate a high intrinsic efficiency of carbon K-shell ionizations (due, for example, to a specific physical or chemical effect) or may be related to the preferential localization of these ionizations on the DNA. The second interpretation would indicate a strong local (within 3 nm) action of K-shell ionizations and consequently the importance of a direct mechanism for radiation lethality (without excluding an action in conjunction with an indirect component). To distinguish between these two hypotheses, the efficiencies of core ionizations in DNA atoms (phosphorus L-shell, carbon K-shell, and oxygen K-shell ionizations) to induce damages were investigated by measuring their capacities to produce DNA double-strand breaks (DSBs). The effect of photoionizations in isolated DNA was studied using pBS plasmids in a partially hydrated state. No enhancement of the efficiency of DSB induction by carbon K-shell ionizations compared to oxygen K-shell ionizations was found, supporting the hypothesis that it is the localization of these carbon K-shell events on DNA which gives to the 340 eV photons their high killing efficiency. In agreement with this interpretation, cell inactivation and DSB induction, which do not appear to be correlated when expressed in terms of yields per unit dose in the sample, exhibit a rather good correlation when expressed in terms of efficiencies per core event in the DNA. These results suggest that core ionizations in DNA, through core-hole relaxation in conjunction with localized effects of spatially correlated secondary and Auger electrons, may be the major critical events for cell inactivation, and that the resulting DSBs (or a constant fraction of these DSBs) may be a major class of unrepairable lesions.

Opsonization of T1M1 group A Streptococcus: dynamics of antibody production and strain specificity

A chemiluminescence method was used to study opsonization of group A Streptococcus (GAS) of serotype T1M1 in serum samples ("sera") obtained from Swedish patients with invasive and noninvasive GAS infection and from healthy blood donors. Acute-phase serum samples ("acute sera") generally demonstrated low ability to opsonize the patient's own GAS isolate, regardless of clinical manifestation. Only approximately 15% of serum samples obtained from healthy blood donors demonstrated high opsonic activity against a standard T1M1 strain. Opsonization of 62 T1M1 isolates (obtained during 1980-1998) by a single immune serum sample showed considerable variation; this indicates that high opsonic immunity may develop only against the infecting isolate or identical clones. T1M1 GAS isolated from 1987 through 1990 were better opsonized by the immune serum sample than were isolates obtained before 1987 or after 1990, a finding that suggests a temporal change of the surface properties that affect opsonization.

Randomized comparison of linezolid (PNU-100766) versus oxacillin-dicloxacillin for treatment of complicated skin and soft tissue infections

This randomized, double-blind, multicenter trial compared the efficacy and safety of linezolid, an oxazolidinone, with those of oxacillin-dicloxacillin in patients with complicated skin and soft tissue infections. A total of 826 hospitalized adult patients were randomized to receive linezolid (600 mg intravenously [i.v.]) every 12 h or oxacillin (2 g i.v.) every 6 h; following sufficient clinical improvement, patients were switched to the respective oral agents (linezolid [600 mg orally] every 12 h or dicloxacillin [500 mg orally] every 6 hours). Primary efficacy variables were clinical cure rates in both the intent-to-treat (ITT) population and clinically evaluable (CE) patients and microbiological success rate in microbiologically evaluable (ME) patients. Safety and tolerability were evaluated in the ITT population. Demographics and baseline characteristics were similar across treatment groups in the 819 ITT patients. In the ITT population, the clinical cure rates were 69.8 and 64.9% in the linezolid and oxacillin-dicloxacillin groups, respectively (P = 0.141; 95% confidence interval -1.58 to 11. 25). In 298 CE linezolid-treated patients, the clinical cure rate was 88.6%, compared with a cure rate of 85.8% in 302 CE patients who received oxacillin-dicloxacillin. In 143 ME linezolid-treated patients, the microbiological success rate was 88.1%, compared with a success rate of 86.1% in 151 ME patients who received oxacillin-dicloxacillin. Both agents were well tolerated; most adverse events were of mild-to-moderate intensity. No serious drug-related adverse events were reported in the linezolid group. These data support the use of linezolid for the treatment of adults with complicated skin and soft tissue infections.

Molecular epidemiology of nga and NAD glycohydrolase/ADP-ribosyltransferase activity among Streptococcus pyogenes causing streptococcal toxic shock syndrome

Severe invasive group A streptococcal (GAS) infections emerged in the late 1980s, yet no single virulence factor has been common to all isolates from infected patients. A strong association was recently found between isolates of such cases (regardless of M type) and the production of NAD glycohydrolase (NADase). Of interest, all M-1 strains isolated after 1988 were positive for NADase, whereas virtually all M-1 GAS were previously negative for NADase. Genetic analysis demonstrated that GAS isolates were >96% identical in nga and >99% identical in their upstream regulatory sequences. Furthermore, because NADase-negative strains did not produce immunoreactive NADase, we concluded that additional regulatory element(s) control NADase production. NADase purified from GAS altered neutrophil-directed migration and chemiluminescence responses and had potent ADP-ribosyltransferase activity. In summary, the temporal relationship of NADase expression, alone or with other streptococcal virulence factors, may contribute to the pathogenesis of invasive GAS infections.

The pathogenesis of clostridial myonecrosis

These pieces of evidence can be assimilated into a molecular and cellular model of pathogenesis which is initiated by direct toxin effects upon venous capillary endothelial cell function, leading to expression of pro-inflammatory mediators and adhesion molecules, and initiation of platelet aggregation. Toxin-induced hyperadhesion of leukocytes (see above section) with enhanced respiratory burst activity (due to toxins directly or to toxin-induced IL-8 or PAF synthesis by host cells) and toxin-induced chemotaxis deficits could result in neutrophil-mediated vascular injury. Direct toxin-induced cytopathic effects on EC may also contribute to vascular abnormalities associated with gas gangrene. Over prolonged incubation periods, PLC at sublytic concentrations causes EC to undergo profound shape changes similar to those described following prolonged TNF or interferon gamma exposure. In vivo, conversion of EC to this fibroblastoid morphology could contribute to the localized vascular leakage and massive swelling observed clinically with this infection. Similarly, the direct cytotoxicity of PFO could disrupt endothelial integrity and contribute to progressive edema both locally and systemically. Thus, via the mechanisms outlined above, both PLC and PFO may cause local, regional and systemic vascular dysfunction. For instance, local absorption of exotoxins within the capillary beds could affect the physiological function of the endothelium lining the postcapillary venules, resulting in impairment of phagocyte delivery at the site of infection. Toxin-induced endothelial dysfunction and microvascular injury could also cause loss of albumin, electrolytes, and water into the interstitial space resulting in marked localized edema. These events, combined with intravascular platelet aggregation and leukostasis, would increase venous pressures and favor further loss of fluid and protein in the distal capillary bed. Ultimately, a reduced arteriolar flow would impair oxygen delivery thereby attenuating phagocyte oxidative killing and facilitating anaerobic glycolysis of muscle tissue. The resultant drop in tissue pH, together with reduced oxygen tension, might further decrease the redox potential of viable tissues to a point suitable for growth of this anaerobic bacillus. As infection progresses and additional toxin is absorbed, larger venous channels would become affected, causing regional vascular compromise, increased compartment pressures and rapid anoxic necrosis of large muscle groups. When toxins reach arterial circulation, systemic shock and multiorgan failure rapidly ensue, and death is common.

Clostridial gas gangrene. I. Cellular and molecular mechanisms of microvascular dysfunction induced by exotoxins of Clostridium perfringens

Mechanisms responsible for the rapid tissue destruction in gas gangrene are not well understood. To examine the early effects of Clostridium perfringens exotoxins on tissue perfusion, a rat model of muscle blood flow was developed. Intramuscular injection of a clostridial toxin preparation containing both phospholipase C (PLC) and theta-toxin caused a rapid (1-2 min) and irreversible decrease in blood flow that paralleled formation of activated platelet aggregates in venules and arterioles. Later (20-40 min), aggregates contained fibrin and leukocytes, and neutrophils accumulated along vascular walls. Flow cytometry confirmed that these clostridial toxins or recombinant PLC induced formation of P-selectin-positive platelet aggregates. Neutralization of PLC activity in the clostridial toxin preparation completely abrogated human platelet responses and reduced perfusion deficits. It is concluded that tissue destruction in gas gangrene is related to profound attenuation of blood flow initiated by activation of platelet responses by PLC.

Clostridial gas gangrene. II. Phospholipase C-induced activation of platelet gpIIbIIIa mediates vascular occlusion and myonecrosis in Clostridium perfringens gas gangrene

Clostridium perfringens gas gangrene is a fulminant infection, and radical amputation remains the single best treatment. It has been hypothesized that rapid tissue destruction is related to tissue hypoxia secondary to toxin-induced vascular obstruction, and previous studies demonstrated that phospholipase C (PLC) caused a rapid and irreversible decrease in skeletal muscle blood flow that paralleled the formation of intravascular aggregates of activated platelets, fibrin, and leukocytes. In this study, flow cytometry demonstrated that PLC stimulated platelet/neutrophil aggregation in a gpIIbIIIa-dependent fashion. Pretreatment of animals with heparin or depletion of leukocytes reduced blood-flow deficits, and aggregate formation caused by PLC. It is concluded that fulminant tissue destruction in gas gangrene results from profound attenuation of blood flow caused by PLC-induced, gpIIbIIIa-mediated formation of heterotypic platelet/polymorphonuclear leukocyte aggregates. Therapeutic strategies that target gpIIbIIIa may prevent vascular occlusion, maintain tissue viability, and provide an alternative to radical amputation for patients with this infection.

Streptococcal toxic shock syndrome associated with necrotizing fasciitis

Streptococcal toxic shock syndrome (strep TSS) with associated necrotizing fasciitis is a rapidly progressive process that kills 30-60% of patients in 72-96 h. Violaceous bullae, hypotension, fever, and evidence of organ failure are late clinical manifestations. Thus, the challenge to clinicians is to make an early diagnosis and to intervene with aggressive fluid replacement, emergent surgical debridement, and general supportive measures. Superantigens such as pyrogenic exotoxin A interact with monocytes and T lymphocytes in unique ways, resulting in T-cell proliferation and watershed production of monokines (e.g. tumor necrosis factor alpha, interleukin 1, interleukin 6), and lymphokines (e.g. tumor necrosis factor beta, interleukin 2, and gamma-interferon). Penicillin, though efficacious in mild Streptococcus pyogenes infection, is less effective in severe infections because of its short postantibiotic effect, inoculum effect, and reduced activity against stationary-phase organisms. Emerging treatments for strep TSS include clindamycin and intravenous gamma-globulin.

Construction and virulence testing of a collagenase mutant of Clostridium perfringens

Clostridium perfringens produces several extracellular toxins and enzymes, including an extracellular collagenase or kappa toxin that is encoded by the colA gene. To determine if the ability to produce collagenase was a significant virulence factor in cases of gas gangrene or clostridial myonecrosis that are caused by C. perfringens, a chromosomal colA mutant was constructed by homologous recombination and subsequently virulence tested in the mouse myonecrosis model. The results clearly indicate that loss of the ability to produce collagenase does not alter the ability of the mutant to establish a virulent infection. By contrast, infection with a mutant unable to produce alpha-toxin led to a marked decrease in virulence. These results indicate that collagenase is not a major determinant of virulence in C. perfringens -mediated clostridial myonecrosis.

Variable susceptibility to opsonophagocytosis of group A streptococcus M-1 strains by human immune sera

Immunity to group A streptococci (GAS) is thought to be related to the acquisition of type-specific antibody directed against the M protein. However, recent work suggests that immunity may only be strain and not M-type specific. Therefore, susceptibility of 70 different GAS M-1 strains to opsonization and killing by convalescent sera was compared by using a highly sensitive chemiluminescence assay and by standard bactericidal assay. Sequencing of the emm1 gene in 10 strains with variable susceptibility to opsonization revealed 100% homology in 9 strains. Several substitutions in the N-terminal and 2 in the A3 repeat regions of strain CS-190 were associated with profound resistance to opsonization. Thus amino acid substitutions within different regions of the M-1 protein molecule may adversely affect opsonization by immune sera. In addition, non-M protein factors from identical M types influence susceptibility to phagocytosis. These findings may in part explain the persistently high prevalence of M-1 strains worldwide over the last 15 years.

Staging of the baboon response to group A streptococci administered intramuscularly: a descriptive study of the clinical symptoms and clinical chemical response patterns

Group A streptococcal infections, ranging from necrotizing fasciitis and myositis to toxic shock syndrome, have increased over the last 10 years. We developed the first primate model of necrotizing fasciitis and myositis. Thirteen baboons were inoculated intramuscularly with group A streptococci (GAS). Eleven animals survived for > or = 11 days before sacrifice, and two animals died within 2 days. The site of inoculation of the survivors exhibited an intense neutrophilic influx (stage I), followed by a lymphoplasmacytic influx (stages II and III). This was accompanied by the appearance of markers of an acute and then a chronic systemic inflammatory response. In contrast, the site of inoculation of the two nonsurvivors exhibited intravascular aggregates of neutrophils at its margin with no influx of neutrophils and with extensive bacterial colonization. We conclude that GAS inoculation induces a local and systemic acute neutrophilia followed by a chronic lymphoplasmacytic response; failure, initially, of neutrophilic influx into the site of inoculation predisposes to systemic GAS sepsis and death; and this three-stage primate model approximates the human disease.

Lethal effect of carbon K-shell photoionizations in Chinese hamster V79 cell nuclei: experimental method and theoretical analysis

To test a possible specific effect of carbon K-shell ionizations in DNA, survival curves for Chinese hamster V79 cells were measured for X irradiations at energies below and above the carbon K-shell ionization threshold. Specific values of the X-ray energies (250 and 340 eV) were chosen to ensure isoattenuation of the two kinds of radiation within the cell. An enhancement of lethality by a factor of about 2 was found for X rays at 340 eV compared to below the threshold at 250 eV. This may be attributed to the production of highly efficient carbon K-shell ionizations located on DNA. A model of X-ray lethality (Goodhead et al., Radiat. Prot. Dosim. 52, 217-223, 1994) was extended to allow for a possible lethal effect from clusters of reactive species induced by K-shell photoionizations (K-shell clusters). Within this model, the increase in lethality above the carbon K-shell threshold may be explained by a value of 2% for the lethal efficiency of K-shell clusters overlapping the DNA. An extrapolation to the lethal effect of more complex ion-induced K-shell ionizations indicates that K-shell ionization may be a major process in the biological effectiveness of heavy ions.

Mycobacterium fortuitum meningitis associated with an epidural catheter: case report and a review of the literature

Mycobacterium fortuitum is a rapidly growing organism that has rarely been associated with meningitis. A patient developed M. fortuitum meningitis as the result of a permanent indwelling, contaminated, epidural catheter. Diagnosis and treatment of the disease are difficult in that clinical features may be indolent, and many antimicrobials with activity against M. fortuitum have minimal cerebrospinal fluid penetration. This patient was cured with an antibiotic regimen that consisted of doxycycline, ciprofloxacin, imipenem, and clarithromycin, and removal of the epidural catheter.

Type-specific opsonophagocytosis of group A Streptococcus by use of a rapid chemiluminescence assay

A whole-blood chemiluminescence (CL) assay was developed to determine the presence of type-specific opsonic antibodies against group A streptococcus (GAS). Convalescent sera with high bactericidal activities against an M-1 serotype were used to opsonize different M-types of GAS. CL responses were monitored for 20 min, and results were expressed as integral counts/minute per phagocyte. CL responses of phagocytes incubated with M-1 GAS opsonized with homologous (M-1) serum were significantly higher than responses of phagocytes incubated with heterologous (M-3) GAS. Adsorption of convalescent serum against the homologous, but not the heterologous, strain markedly reduced the CL response, demonstrating type specificity. The CL assay showed a high correlation with the indirect bactericidal test (r=0.90). In conclusion, this CL assay is a rapid, highly sensitive, specific, and reproducible method for quantifying type-specific opsonic antibodies against GAS and will be a useful tool for future clinical, basic science, and epidemiological studies.

Reduction of the gamma-ray component from 252Cf fission neutron source--optimization for biological irradiations and comparison with MCNP code

Gamma-rays contribute 33% of the absorbed dose from an unfiltered 252Cf fission neutron source. To reduce this gamma-ray component and to enable radiobiological experiments at as high a dose rate as possible, Monte Carlo calculations for several filter materials (Al, Fe, Pb and concrete) have been made using MCNP neutron and photon transport code version 4a. A lead filter of thickness 4 cm was found to reduce the gamma-ray component to 6.7% of the total dose whilst reducing the neutron dose by only about 10%. Such a filter was installed at the MRC 252Cf neutron irradiation facility and dosimetric measurements were made using a TE-TE chamber and a 7LiF(Mg, Cu, P) TLD. Monte Carlo simulations agree with experimental measurements of neutron and gamma-ray doses within 6%. V79-4 Chinese hamster cells were irradiated with lead-filtered and unfiltered neutrons and also with 60Co gamma-rays at two dose rates. The survival fraction obtained for each radiation was consistent with the reduced gamma-ray dose. The relative biological effectiveness for neutrons alone, corrected for gamma-ray effects, was found to be 9.2 +/- 3.4 from the initial slopes and 3.1 +/- 0.5 at 10% survival, both relative to the acute gamma-rays.

Comparison of adherence to and penetration of a human laryngeal epithelial cell line by group A streptococci of various M protein types

Clinically isolated group A streptococci (GAS) of different M protein types were studied using aminoglycoside exclusion and [2,8-3H]adenine radiolabeled GAS assays to compare the abilities of different strains to adhere to and internalize within human laryngeal epithelial (HEp-2) cells. GAS isolated from patients with pharyngitis and GAS isolated from patients with more severe disease, such as necrotizing fasciitis, adhered to and penetrated HEp-2 cells equally well. M3, M4, M6, and M12 strains adhered to and were internalized within HEp-2 cells more than M1 strains. M18 GAS producing hyaluronic acid capsules were less adherent and less invasive than the M3, M4, M6, and M12 strains. An M3-producing GAS strain and its M protein-deficient isogenic strain adhered similarly to HEp-2 cells, but the M protein-deficient strain exhibited greater penetration. Preincubation of HEp-2 cells with an N-terminal synthetic M3 peptide did not alter the adherence or penetration by an M3 strain. In summary, this study demonstrates that GAS from invasive and non-invasive disease adhere to and penetrate HEp-2 cells equally well and that multiple strains of GAS with various M protein types have the ability to adhere to and penetrate HEp-2 cells.

The flesh-eating bacterium: what's next?

Since the 1980s, there has been a marked increase in the recognition and reporting of highly invasive group A streptococcal (GAS) infections associated with shock and organ failure, with or without necrotizing fasciitis. Such dramatic cases have been defined as streptococcal toxic shock syndrome (StrepTSS). Strains of GAS isolated from patients with invasive disease have been predominantly M types 1 and 3, which produce either pyrogenic exotoxin A or B or both. The clinical and demographic features of streptococcal bacteremia, myositis, and necrotizing fasciitis are presented and compared with those of StrepTSS. Current concepts in the pathogenesis of invasive streptococcal infection will be presented, with emphasis on the interaction between GAS virulence factors and host defense mechanisms. Finally, new concepts in the treatment of StrepTSS will be discussed.

Teicoplanin for skin and soft tissue infections: An open study and a randomized, comparative trial versus cefazolin

An open trial and a multicenter, three-group, randomized trial versus cefazolin were performed to study the use of teicoplanin in the treatment of serious skin and soft tissue infections caused by Gram-positive bacteria. A total of 418 patients were entered into the randomized trial, 293 of whom were available for efficacy analysis, and 262 patients were entered in the open trial. The randomized trial had three arms: intramuscular (125 patients) vs intravenous (148 patients) teicoplanin vs cefazolin (145 patients). In both trials teicoplanin was administered once daily, originally as 3 mg/kg per day, with the option of higher doses in the open trial. Cefazolin was given at a dose of 1.5-4 g/day, in three divided doses. In the randomized trial, teicoplanin and cefazolin showed similar overall efficacy. The higher dose of teicoplanin (6 mg/kg) was significantly more effective than the lower dose (3 mg/kg), particularly in patients with diabetes. In the open trial, teicoplanin had a clinical success rate of 93%. There was no significant difference in the incidence of adverse events between the cefazolin and teicoplanin groups. Outpatient ambulatory therapy was shown to be a practical method of administering teicoplanin. Once-daily dosing with teicoplanin may allow physicians to treat skin and soft tissue infections on a totally outpatient basis.

Induction of DNA-protein crosslinks in Chinese hamster V79-4 cells exposed to high- and low-linear energy transfer radiation

The induction of DNA-protein crosslinks (DPCs) in Chinese hamster V79-4 cells after irradiation under hypoxic and aerobic conditions at 277 K with 60Co gamma rays, 238Pu alpha particles and aluminum K (Al(K)) ultrasoft X rays has been determined using a nitrocellulose filter binding assay. The dose dependences for the induction of DPCs, which involves covalent linkage, are linear over the absorbed dose range used (0-400 Gy with alpha-particle and gamma radiation, 0-600 Gy with Al(K) X rays). The yield of DPCs induced under hypoxic conditions is 55, 51 and 25 DPCs per gray per cell for 60Co gamma rays, alpha particles and Al(K) X rays, respectively. The yield of DPCs is significantly reduced in the presence of oxygen by 20, 50 and 79% for 60Co gamma rays, alpha particles and Al(K) X rays, respectively. Since the mean size of the DNA attached to the protein is uniform for 60Co gamma rays and alpha particles, variations in the DNA size do not influence the yields of DPCs. Although a DPC may be considered as a complex lesion combining two macromolecules, the dependence of the yield of DPCs on LET does not reflect the ionizing density of the radiations used. Further, this dependence on LET and the effect of oxygen do not reflect the corresponding dependences determined for a variety of biological responses. From these findings and knowledge of the radiation tracks, it is proposed that DPCs induced particularly under aerobic conditions with 60Co gamma rays are formed mainly in the sparsely ionizing segments of the radiation track.

Novel therapies in streptococcal toxic shock syndrome

The systemic manifestations of severe invasive group A streptococcal infections, such as streptococcal toxic shock syndrome, are mediated by an overwhelming inflammatory response induced by streptococcal superantigens and other virulence factors. The high mortality rates associated with streptococcal toxic shock syndrome demonstrate a need for better therapy in these diseases. Novel strategies to attenuate or prevent streptococcal toxic shock syndrome at different stages of illness have been proposed. The most promising therapies include agents that by various mechanisms attenuate the inflammatory response or the action of streptococcal toxins/superantigens, or both.

Chromosomal instability in the descendants of unirradiated surviving cells after alpha-particle irradiation

We have demonstrated chromosomal instability in the clonal descendants of hemopoietic stem cells after irradiating murine bone marrow with alpha-particles. However, because cells that are irradiated by alpha-particles are defined by a Poisson distribution of individual particle traversals, there is an inevitable proportion of unirradiated cells in the surviving population. The calculated expected proportions of irradiated and nonirradiated cells indicate that the number of clonogenic cells transmitting chromosomal instability is greater than the number expected to be hit and survive. To investigate further this discrepancy, we studied the effects of interposing a grid between the cells and the alpha-particle source so that the surviving population consists predominantly of untraversed stem cells. Comparison with the same irradiation conditions without the grid reveals that the same level of instability is induced. The data confirm that alpha-particles induce chromosomal instability but instability is demonstrated in the progeny of nonirradiated stem cells and must be due to unexpected interactions between irradiated and nonirradiated cells. This untargeted effect has important implications for mechanistic studies of radiation action and for assessment of radiation risk.