Growth, CO2 consumption and H2 production of Anabaena variabilis ATCC 29413-U under different irradiances and CO2 concentrations.

AIMS: The objective of this study is to develop kinetic models based on batch experiments describing the growth, CO(2) consumption, and H(2) production of Anabaena variabilis ATCC 29413-U(TM) as functions of irradiance and CO(2) concentration. METHODS AND RESULTS: A parametric experimental study is performed for irradiances from 1120 to 16100 lux and for initial CO(2) mole fractions from 0.03 to 0.20 in argon at pH 7.0 +/- 0.4 with nitrate in the medium. Kinetic models are successfully developed based on the Monod model and on a novel scaling analysis employing the CO(2) consumption half-time as the time scale. CONCLUSIONS: Monod models predict the growth, CO(2) consumption and O(2) production within 30%. Moreover, the CO(2) consumption half-time is an appropriate time scale for analysing all experimental data. In addition, the optimum initial CO(2) mole fraction is 0.05 for maximum growth and CO(2) consumption rates. Finally, the saturation irradiance is determined to be 5170 lux for CO(2) consumption and growth whereas, the maximum H(2) production rate occurs around 10,000 lux. SIGNIFICANCE AND IMPACT OF THE STUDY: The study presents kinetic models predicting the growth, CO(2) consumption and H(2) production of A. variabilis. The experimental and scaling analysis methods can be generalized to other micro-organisms.

Persistent MR contrast enhancement of calcified neurocysticercosis lesions.

PURPOSE: We sought to determine whether cysticercosis lesions in the brain continue to enhance after nodular involution and complete calcification, and to investigate the clinical significance of this finding with respect to seizure recurrence after cysticidal treatment. METHODS: Serial contrast-enhanced MR images were obtained in all patients with neurocysticercosis seen at our hospital over a 6-year period (1991-1997). From this group, all patients with nodular calcified lesions were selected for study. RESULTS: Sixteen of 29 patients with neurocysticercosis had nodular calcified lesions. Six of these 16 had rim enhancement of nodular calcified lesions for at least 1 year after imaging evidence of complete calcification. Three of these six patients with enhancing, calcified lesions continued to experience seizures. Three of the 10 patients without enhancement also continued to have seizures. CONCLUSION: Contrary to the literature, which states that enhancement and disease activity cease with calcification, six (38%) of 16 patients had lesions that continued to enhance after complete calcification. This abnormality may be a risk factor for posttreatment seizures or may suggest eventual resorption of the calcified lesion.

Transformation of NIH 3T3 cells by herpes simplex type 2 BglII n fragment and sub-fragments is independent from induction of mutation at the HPRT locus.

The effect of transfection of the herpes simplex virus type 2 transforming fragment BglII n and of its three Xhol subfragments on mutagenesis and morphological transformation was assayed in NIH 3T3 cells. While BglII n and the right hand portion of this fragment increased the number of transformed foci, no significant effects on the mutation frequency at the hprt locus were observed. Our results indicate that transformation by BglII n is independent from the induction of somatic mutations and suggest that other mechanisms must be considered to explain transformation by this sequence.

Herpes simplex virus type 2 mutagenesis: characterization of mutants induced at the hprt locus of nonpermissive XC cells.

In a previous report, herpes simplex virus type 2 (HSV-2) was shown to increase the frequency of mutation at the hypoxanthine phosphoribosyltransferase (hprt) locus of nonpermissive rat XC cells (L. Pilon, A. Royal, and Y. Langelier, J. Gen. Virol. 66:259-265, 1985). A series of 17 independent mutants were isolated after viral infection together with 12 spontaneous noninfected mutants to characterize the nature of the mutations induced by the virus at the molecular level. The DNA of the mutants isolated after viral infection was probed with cloned HSV-2 fragments representing the entire genome. In these mutants, no authentic HSV-2 hybridization could be detected. This was indicative of a mechanism of mutagenesis which did not require the permanent integration of viral sequences in the host genome. The structure of the hprt gene was determined by the method of Southern (J. Mol. Biol. 98:503-517, 1975), and the level of hprt mRNA was analyzed by Northern blots. Except for the identification of one deletion mutant in each of the two groups, the HPRT- clones showed no evidence of alteration in their hprt gene. A total of 7 of 12 spontaneous mutants and 11 of 15 mutants isolated from the infected population transcribed an hprt mRNA of the same size and abundance as did the wild-type cells. Thus, the majority of the mutants seemed to have a point mutation in their hprt structural gene. Interestingly, the proportion of the different types of mutations was similar in the two groups of mutants. This analysis revealed that HSV-2 infection did not increase the frequency of rearrangements but rather that it probably induced a general increase of the level of mutations in the cells. This type of response is thought to be compatible with the biology of the virus, and the possible mechanisms by which HSV-2 induces somatic mutations in mammalian cells are discussed.

Increased mutation frequency after herpes simplex virus type 2 infection in non-permissive XC cells.

The effect of herpes simplex virus type 2 (HSV-2) infection on the frequency of mutations at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus was studied in the non-permissive XC cell line. When the cells were infected with 20 to 800 p.f.u./cell, there was initially a lag in cell growth and cell death, but after 4 days there was no difference in growth rate between infected and control cultures. However, the mutation frequency, as determined by the number of 6-thioguanine-resistant colonies, was increased in infected cultures by factors ranging from 2.5 to 10.3. This effect was found to be dependent on the multiplicity of infection. The maximum effect was obtained between 20 and 100 p.f.u./cell while further increase in the amount of virus resulted in a drop in the yield of mutants. The optimum multiplicity of infection was a reproducible characteristic but was variable between viral stocks. When a number of mutant clones were examined they were found to have HGPRT activities ranging from undetectable to 6.9% of wild-type, indicating that the mutations were in the HGPRT gene. These results show that, in a non-productive infection, HSV-2 particles can increase the mutation frequency. The possible mechanisms by which this effect is brought about in the host genome are discussed.

Fungal treatment of mechanical pulps-its effect on paper properties.

Refiner mechanical pulp was biologically treated with several higher fungi in order to test their potential for increasing the strength of paper. It was among the white-rot fungi that the best results were obtained. Polyporus versicolor gave the best overall improvement in handsheet properties with no reduction in tear. The strength improvement is due to attack on lignin and to an increase in fiber flexibility as measured by water retention values and by acidic group content of the treated pulps. The brown-rot fungi had a detrimental effect on paper properties.

[Chronic osteomyelitis: open excision and grafting after saucerization (author's transl)]. / Ostéomyélite chronique: excision et greffe de spongieux à l'air libre après mises à plat extensives.

From January 1960 to January 1974, 180 cases of chronic osteomyelitis were treated by the same surgeon in the infection unit of Notre-Dame Hospital in Montreal. Of these cases, 71.4% were treated by saucerization, followed by secondary closure or by skin grafting. In ten cases (5.4%) the limb was amputated. However, in 39 cases two similar techniques of open excision and grafting were used. The infection was mostly traumatic in origin and a staphylococcus was cultured in 75% of cases. The organism was sensitive to cloxacillin and dicloxacillin in the majority of cases. Since 50% of these 39 cases were referred for amputation, the results were much betts. Two late recurrences were recently seen and treated, one 17 years and one 4 years after the initial treatment.