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Biomedical subjects

J M Lacroix

Publications and source records attributed to J M Lacroix.

At least 37 records · Page 2Linked to original sources
PubMed1989

Molecular cloning and expression of a locus (mdoA) implicated in the biosynthesis of membrane-derived oligosaccharides in Escherichia coli.

Mutants of Escherichia coli defective in the mdoA locus are blocked at an early stage in the biosynthesis of membrane-derived oligosaccharides. The mdoA locus has now been cloned into multicopy plasmids. A 5 kb DNA fragment is necessary to complement mdoA mutations. Cells harbouring the mdoA+ plasmid produced three to four times more MDO than wild-type cells. MDO overproduction did not affect the degree of MDO substitution with sn-1-phosphoglycerol residues. The biosynthesis of MDO remained under osmotic control in overproducing strains.

Chromosome Mapping↗
PubMed1989

The effect of subminimal inhibitory concentrations of antimicrobial agents on three bacterial mixtures.

A test tube technique was developed to screen bacterial mixtures to detect interbacterial interactions that play a role in determining sensitivity to antimicrobial agents. We found 3 mixtures where these bacterial interactions change the sensitivity to antimicrobials or change the proportions of each bacterial species in the mixture. The mixtures were: Fusobacterium nucleatum 102.3 and Bacteroides endodontalis ATCC 35406; F. nucleatum 102.3 and B. endodontalis BN11 a-f; and Capnocytophaga ochracea 1956c and Eubacterium saburreum 162.4. The antimicrobials used were metronidazole for the first 2 mixtures and tetracycline for the last. F. nucleatum seems to protect B. endodontalis from the action of metronidazole. Conversely, the growth inhibition of C. ochracea by E. saburreum was lifted when tetracycline was present. We also found that the growth of C. ochracea can then permit the subsequent growth of E. saburreum. The test tube method permits the evaluation both of interbacterial interactions and the detection of any protective mechanism against antimicrobial agents in a bacterial mixture. We found that F. nucleatum 102.3 can decrease the metronidazole level in the culture medium, and by the use of 14C-metronidazole we demonstrated that acetamide is produced from metronidazole.

Bacteria↗
PubMed1988

Predictors of outcome in back surgery candidates.

This study employed a prospective design to examine the value of three demographic, three orthopaedic, and four psychometric variables as predictors of orthopaedic and rehabilitation outcome in 116 Workers' Compensation patients seriously considered for first lumbar surgery, separately for the 74 who eventually did undergo surgery, and the 42 who did not. The two groups differed only with respect to the number of Nonorganic Physical Signs, but a complex pattern of predictive relationships emerged, in which orthopaedic outcome was generally easier to predict than rehabilitation outcome. Among the demographic factors, level of English proficiency was the best predictor and correlated positively with orthopaedic outcome in both surgery and non-surgery cases and with rehabilitation outcome in non-surgery patients. The Nonorganic Physical Signs test emerged as the predictor of choice and correlated with orthopaedic outcome in both groups and with rehabilitation outcome in the non-surgery group. Scale 1 of the MMPI correlated with orthopaedic outcome in both groups and Scale 3 with both orthopaedic and rehabilitation outcome, but only in the non-surgery patients.

Achievement↗
PubMed1988

Type A behavior pattern and symptom reports: a prospective investigation.

This study examined the relationship between the Type A Behavior Pattern and reporting of a constellation of physical symptoms related to respiratory infections using a prospective design. The results indicate that Types A and B students did not differ significantly in their reports of the frequency or severity of the constellation of symptoms or of individual symptoms over an 87-day period. Furthermore, there were no type differences in the frequency or severity of the symptom constellation reported during a competitive and highly challenging period of time. In view of the contradiction in previously published reports (i.e., reports of both positive and negative relationships between Type A and symptom reporting) and the robust methodological design utilized in the present study, the wholly negative nature of these findings point strongly to the absence of Type A/B differences in symptom reporting.

Adult↗
PubMed1988

Type A and genital herpes.

This study investigated a possible relationship between the Type A Behavior Pattern (TABP) and genital herpes, and sought to confirm earlier observations of a relationship between TABP, allergies, and upper respiratory infections. The research participants were 105 members of a herpes self-help group. The subjects conformed to epidemiological evidence of a greater prevalence of genital herpes in young adult women; they were also highly educated and tended to be single and to live in rental accommodations. TABP was measured by Form C of the Jenkins Activity Survey. The Type A subjects were not more prevalent in our sample, and there were no A-B differences in the frequency of recurrences. However, Type A subjects experienced significantly greater symptom severity during recurrences and were more likely to seek symptomatic treatment. The overall pattern of results suggested that these A-B differences in severity likely reflected physiological or immunological differences rather than simply differences in response bias between Type A and B subjects. Finally, the study failed to replicate earlier observations of associations between TABP and allergies, and TABP and respiratory infections.

Adult↗
PubMed1987

Microcomputer package for statistical analysis of microbial populations.

We have developed a Pascal system to compare microbial populations from different ecological sites using microcomputers. The values calculated are: the coverage value and its standard error, the minimum similarity and the geometric similarity between two biological samples, and the Lambda test consisting of calculating the ratio of the mean similarity between two subsets by the mean similarity within subsets. This system is written for Apple II, IBM or compatible computers, but it can work for any computer which can use CP/M, if the programs are recompiled for such a system.

Algorithms↗
PubMed1986

Inactivation of cefoxitin and moxalactam by Bacteroides bivius beta-lactamase.

Moxalactam and cefoxitin are known for their high stability against Bacteroides beta-lactamases. We investigated the beta-lactamase activity of crude extracts obtained from three strains of Bacteroides bivius and two strains of Bacteroides fragilis against cefoxitin and moxalactam. In a spectrophotometric antibiotic assay with a 24-h incubation period, B. bivius extracts decreased the initial concentration (10 micrograms/ml) of moxalactam and cefoxitin by 60%, whereas B. fragilis extracts had no effect. In a microbiological assay, when B. bivius or B. fragilis extracts were added to cephalothin (10 micrograms/ml) or cefamandole (4 micrograms/ml), we observed complete disappearance of the inhibitory zones against the indicator strain (Clostridium perfringens ATCC 13124). Only the B. bivius extracts were able to decrease the inhibitory activity (from 10 to 100%) of cefoxitin and moxalactam (each at 10 micrograms/ml). Prior addition of clavulanic acid to crude extracts prevented the losses of antibacterial activity. Furthermore, the inhibition of the beta-lactamase hydrolysis of nitrocefin by cefoxitin or moxalactam was prevented by a 12-h preincubation of the beta-lactam with the B. bivius extracts but not with the B. fragilis extracts. Finally, with the B. bivius strain producing the most beta-lactamase, we showed an effect of inoculum size on the MICs of cefoperazone, cefoxitin, and moxalactam with a broth dilution technique. Increasing the inoculum size with the B. fragilis strains had no effect on the MISs of cefoxitin and moxalactam. These results indicate a slow and clavulanate-sensitive beta-lactamase activity of B. bivius extracts against cefoxitin and moxalactam.

Bacteroides↗
PubMed1986

Physiological changes after biofeedback and relaxation training for multiple-pain tension-headache patients.

This paper is concerned with the psychophysiology of "muscle-contraction" headaches in a group of Compensation patients suffering from multiple pain problems in addition to headaches. A total of 55 of these patients were divided into 4 groups which received frontalis EMG biofeedback, relaxation training, combined biofeedback-relaxation training, or no treatment. Differences were observed among the 3 experimental treatments and the control group with respect to headache changes, but there were no differences among groups with respect to the changes observed in four underlying physiological responses as a function of time or practice. While the subjects who showed the largest changes in headache characteristics were those who exhibited the largest decreases in frontalis EMG, these were also the subjects whose initial frontalis EMG levels were the highest. It is concluded that, in keeping with a growing literature, the link between frontalis EMG and "muscle-contraction" headaches is a tenuous one and that the changes brought about in headache symptomatology through biofeedback or relaxation training are most likely attributable to a generalization of feelings of mastery over the environment or of self-efficacy brought about in the subjects through apparent success at the task.

Adult↗
PubMed1986

Muscle-contraction headaches in multiple-pain patients: treatment under worsening baseline conditions.

A total of 55 muscle-contraction headache patients were divided into four groups which received frontalis EMG biofeedback, relaxation training, combined biofeedback-relaxation training, or no-treatment control. All patients were compensation patients undergoing assessment and brought to a high level of activity for the first time since going into chronicity. In all cases, onset or aggravation of the headaches coincided with the compensation-related injury. All treatment modalities led to significant but similar levels of improvement in headaches, while the control group worsened.

Adult↗
PubMed1984

Effect of clavulanic acid on the activities of ten beta-lactam agents against members of the Bacteroides fragilis group.

Clavulanic acid reduced the MICs of amoxicillin, carbencillin , cefamandole, cefotaxime, ceftazidime, ceftizoxime, cephalothin, and penicillin G, but not of cefoxitin or moxalactam, against 77 isolates of the Bacteroides fragilis group, all rapidly beta-lactamase positive by the nitrocefin slide test. It had no effect on the susceptibilities of eight Bacteroides distasonis strains that were slowly beta-lactamase positive (18 h of incubation).

Anti-Bacterial Agents↗
PubMed1984

Role of Bacteroides bivius beta-lactamase in beta-lactam susceptibility.

The susceptibility of 46 clinical isolates of Bacteroides bivius to amoxicillin, cefotaxime, cefoxitin, ceftizoxime, cephaloridine, cephalothin, moxalactam, penicillin G, amoxicillin plus clavulanic acid in a ratio of 2:1, carbenicillin, cefamandole, and ceftazidime was determined by an agar dilution technique. For the first eight agents susceptibility testing was also done with the addition of clavulanic acid (0.75 microgram/ml). For all agents, beta-lactamase-positive strains (35, using a nitrocefin slide test) were inhibited at higher concentrations than beta-lactamase-negative strains. Clavulanic acid reduced the susceptibility of the beta-lactamase-positive strains to the level of the beta-lactamase-negative strains to all agents. We prepared crude extracts of beta-lactamase from six strains. Activity against nitrocefin was directly related to their susceptibilities. The beta-lactamase had a mixed-substrate profile, hydrolyzing both penicillins and cephalosporins. Our results suggest a slow inactivation of cefoxitin, ceftizoxime, and moxalactam by the beta-lactamase. Clavulanic acid and cefoxitin inhibited the enzyme, whereas p-hydroxymercuribenzoate and cloxacillin did not. Thus, there was a clear relationship between beta-lactamase activity and susceptibility to beta-lactams, including cefoxitin and third-generation cephalosporins. The substrate and inhibition profiles of the B. bivius beta-lactamase were different from those of enzymes found in the "B. fragilis group."

Anti-Bacterial Agents↗
PubMed1984

Properties of oral asaccharolytic black-pigmented Bacteroides.

Bacteroides endodontalis, a newly described asaccharolytic black-pigmented Bacteroides, along with the other two recognized species of this group (B. gingivalis and B. asaccharolyticus) were studied for their susceptibility to various dyes and inhibitory agents and for some of their enzymatic activities to facilitate differentiating between them. Bacteroides endodontalis resembles B. asaccharolyticus physiologically except for the fact that the former cannot grow on media containing methylene blue, neutral red, or 3% sodium chloride, whereas B. asaccharolyticus can. On the other hand, B. endodontalis and B. gingivalis can grow on a medium containing Congo red while B. asaccharolyticus cannot.

Bacteroides↗
PubMed1983

Biofeedback and relaxation in the treatment of migraine headaches: comparative effectiveness and physiological correlates.

Twenty-seven migraine headache patients were divided into three equal groups which received thermal biofeedback, frontalis EMG biofeedback, or relaxation training. Training was given under "massed" practice conditions (nine sessions per week) and consisted of 18 training sessions and six test-generalisation sessions. While improvements in headaches were observed in all groups, the best improvements took place in the thermal biofeedback group, which had almost complete elimination of migraine attacks by the end of training, and maintained that performance as long as six months after training. Examination of the patterns of skin temperature and EMG changes in the three groups over the course of training also points to a relationship between skin temperature control and reduction in migraine headache symptomatology, and suggests that this relationship is worthy of further investigation.

Adult↗
PubMed1978

A comparison of the mechanisms and some properties of instructed sudomotor and cardiac control.

Instructed control defined as differential compliance with verbal instructions to increase and decrease a response was assessed when a change in sudomotor activation or heart rate was specified as the behavioral goal. Instructed control of heart rate was evident prior to explicit feedback training for this response, but instructed control of sudomotor activation defined as finger sweating and measured as skin conductance was not. Feedback training subsequently established instructed control of sudomotor responding, but such training did not lead to a significant improvement in control of heart rate. Explicit strategy suggestions emphasizing emotional responding and intended or actual movement appeared to interfere with the performance of instructed control under both target conditions. Instructed changes in heart rate were attended by correlated changes in somatomotor and respiratory function. Somatomotor and respiratory responses were also observed when subjects were instructed to change sudomotor activation, but these correlated activities were of small magnitude and were not augmented by feedback training as was target responding. Several accounts of the basis for differences that were evident between the target conditions with respect to feedback effects and response patterns are discussed.

Adult↗