The conditions under which Brevibacterium linens CNRZ 918, a strain isolated from the surface smear flora of Gruyère de Comté cheese, produced methanethiol from methionine were studied. Demethiolation was estimated from the methanethiol production capacity of resting cells. Methionine was demethiolated mainly during the exponential growth phase of the organism during which time the cells were rod-shaped and had a generation time of 5 h, and the medium became alkaline. At the end of growth (pH 9) the cells were coccoid, and produced only very little methanethiol. The production of methanethiol required the presence of methionine in the culture medium, this reflecting the probable induction of the enzyme systems involved. Glucose favoured growth and inhibited production of methanethiol. Lactate favoured both growth and methanethiol production. Resting rod cells also produced methanethiol from structural analogues of methionine and from methionine-containing peptides. The apparent kinetic constants of the production of methanethiol for rod and coccoid cells were respectively Km = 14 mM and 46 mM, Vmax = 208 nkat g-1 and 25 nkat g-1. The optimum temperature and pH for production were 30 degrees C and pH 8. Azide or malonate favoured the production of methanethiol by resting cells, whereas chloramphenicol had no effect.

A non-inducing medium (NID) was defined for studying the induction of methanethiol production by Brevibacterium linens CNRZ 9 18. The lowest L-methionine concentration capable of inducing maximal methanethiol production by the cells was 7 mM. The peptides L-Ala-L-Met and L-Met-L-Ala induced greater methanethiol production than free L-methionine. DMethionine, L-cysteine, S-methyl-L-cysteine and L-ethionine were poor inducers. Culture temperature affected the duration of induction. An Na+ concentration of 1 M in the culture medium led to maximal methanethiol production capacity of both cells and cell extracts. LMethionine and L-ethionine were the best substrates for the crude soluble cells extract (with release of methanethiol and ethanethiol respectively). Neither the derivatives of L-methionine that acted as inducers, nor D-methionine, were substrates for demethiolation. Demethiolation activity of the crude extract was thermolabile, not stimulated by Na+ and strongly inhibited by Zn2+, Mn2+ and Cu2+. The shortest generation time obtained for B. linens CNRZ 918 in NID medium + L-methionine was 4 h at 26 "C. Only coccoid forms were present when the culture temperature was 30 "C. The presence of L-methionine in the medium favoured their appearance.The strain grew best in the presence of 1 % NaCl but tolerated concentrations up to 15%. The induction of methfiethiol production was due to the inductionbf L-methionine-y-demethiolase. The level of induction was probably related to the intracellular concentration of L-methionine. The transport system of L-methionine by B. linens CNRZ918 was constitutive and Na+ dependent.

Purpose The long incubation period and asymptomatic spread of COVID-19 present considerable challenges for health care institutions when patients return to elective surgery. Methods A retrospective review of the first adult elective cases performed between May 18, 2020 and June 14, 2020, after the end of lockdown was analysed in Belgium to answer the following questions: (1) for the 236 cancelled patients during the outbreak, how easy was rescheduling? (2) How useful was universal RT-PCR testing and chest CT scan for the 211 orthopaedic and trauma admissions? (3) How were surgical difficulty category, number of operations and complications different when compared to the pre-COVID period? (4) How would patients balance the benefit of surgery against the unknown risk of developing COVID-19? Results Before surgery, blood tests for anaesthesiology and imaging related to the surgical procedure were scheduled prior to universal testing (COVID-19 PCR and chest CT) performed 72-120 hours before surgery. Among the 211 asymptomatic patients who were tested before surgery, six had positive PCR, while no abnormality was found on the chest CT scan of all the patients. With this timing for tests, the 104 patients included in the current study for elective surgery were free of disease before undergoing surgery and remained without COVID-19 after surgery. Among the 366 cancelled patients during the outbreak, only 12% of the patients accepted to proceed with rescheduling immediately. Therefore, this resulted in a 70% reduction for elective surgery and in a 50% reduction for arthroplasties as compared to pre-COVID period. The rate of complications was not increased during the post-COVID period. A portion of patients have confused idea of screening and have difficulty to perceive the new rules of health organization. Conclusions Resumption of elective surgical procedures appears more difficult for patients than for surgeons with a low percentage of cancelled patients accepting to reschedule surgery. Universal testing allowed securing patients; however, surgeons must explore better patient perceptions regarding COVID-19 to facilitate a fully informed decision in the current period.

Abstract. Research to assess the effect of single genes on reproductive traits in bovine species is imperative to elucidate genes' functions and acquire a better perspective of quantitative traits. The present study was undertaken to characterize genetic diversity in the bovine growth hormone (GH) gene in a population of 410 Holstein dairy cows in Tunisia. The analyses were based on single nucleotide polymorphisms, and GH-AluI and GH-MspI detections and genotyping were carried out using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Data were analyzed using a mixed linear model with the MIXED procedure to reveal the possible effect of GH genotypes on reproductive traits. The frequency data of AluI(L//V) and MspI(+//−) alleles were 87.04//12.96 and 70.06//29.94, respectively. The distribution of the frequency of GH genotypes for LL/LV/VV and (−/−)//(+/−)//(+/+) were 77.75//18.59//3.66 and 15.37//29.13//55.50, respectively. The results of the statistical analyses proved that GH-AluI showed a substantial favorable effect on exanimate traits except for the age at first calving; however, only a suggestive effect of GH-MspI on the calving interval (CI) and the days open (DI) was found. The homozygous LL genotype seemed to be advantageous with respect to the CI and the DI compared with LV and VV genotypes. Heterozygous MspI(+/−) cows tended to have a longer CI and DI than MspI(+/+) and MspI(−/−) cows, but the difference was not statistically significant. A significant effect of different GH-AluI–MspI combined genotypes was found on the number of inseminations per conception, the CI and the DI, and the LL/– combined genotype seemed to be associated with better reproductive performance. Based on these results, the LL genotype of the GH locus can be considered to be a favorable genotype for reproductive traits in Holstein dairy cattle, although these findings need to be confirmed by further research before polymorphisms can be used in a marker-assisted selection program.

Abstract. Multi-trait Bayesian procedure was used to estimate genetic parameters for reproductive traits in Tunisian Holstein cows. A total of 31 348 lactations of the calving years 2005 to 2012 were analyzed. Fertility traits were the calving interval (CI), days open (DO), days to first insemination (DFI), days from first insemination to conception (FIC), and number of inseminations per conception (NI). Posterior means of heritabilities of CI, DO, DFI, FIC, and NI were 0.047, 0.03, 0.025, 0.024, and 0.069, respectively. Posterior means of repeatabilities of the same respective traits were 0.106, 0.094, 0.051, 0.036, and 0.17. Genetic correlations among female fertility traits were also computed. Calving interval and DO had the highest genetic correlation estimate (0.85) because they have overlapping genetic meanings. The lowest genetic correlation estimate ( − 0.25) was found between DFI and NI. Genetic parameter estimates are low and are even lower than those reported in most literature, implying that more focus should be put upon improving the management of reproduction in dairy cattle herds in Tunisia.