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Biomedical subjects

J M Knox

Publications and source records attributed to J M Knox.

At least 37 records · Page 2Linked to original sources
PubMed1979

Group B streptococcal infection: a review and update.

The problems posed by the sudden increase in serious group B streptococcal disease among infants since the early 1970s are described and discussed. Virtually all offspring of colonised mothers harbour the organism and infection develops in about 1% of these infants. The mortality rate, even with immediate antibiotic treatment of early onset disease, is 30%; delay in treatment leads to much higher mortality. Late onset disease starting around the seventh to ninth day of life, but sometimes as late as the second month, is less frequently fatal. Preventive measures include active and passive immunisation or intravenous ampicillin during labour. Experimental evidence indicates that each of these methods gives protection.

Antibodies, Bacterial↗
PubMed1978

Systemic protection by antioxidants against UVL-induced erythema.

An antioxidant supplemented diet provided marked systemic protection against ultraviolet light mediated erythema in hairless mice. Among the individual constituents of the diet, butylated hydroxytoluene was most effective whereas glutathione and vitamins C and E afforded negligible protection. The mixture of antioxidants, and butylated hydroxytoluene individually, demonstrated diminished, but significant, protection when applied topically. The safety of this systemic photoprotectant and its clinical relevance at present is unknown.

Administration, Oral↗
PubMed1978

Method for studying the role of indigenous cervical flora in colonisation by Neisseria gonorrhoeae.

A method for quantitating cervical flora has been evaluated statistically and used to study the bacterial flora of the cervix in 14 women sexually exposed to men with gonococcal urethritis. A comparison was made between those women who subsequently became colonised with Neisseria gonorrhoeae and those who did not to determine whether either total microbial populations or the different species present could be related to colonisation by N. gonorrhoeae. Two control groups of healthy women, one of patients from a public clinic and the other of patients from a private practice, were studied in the same way. Normal flora isolates were tested in vitro for antagonism or synergism toward N. gonorrhoeae or both. Cervical flora was characterised in all patient groups by wide variations between individuals, both in type and numbers of organisms. No significant differences were found in total bacterial populations or in the number of species isolated from the cervix between patient groups. Populations of N. gonorrhoeae ranged from less than 10 bacteria to log104.36. Only one normal flora isolate, a strain of Streptococcus viridans isolated from a woman exposed to but not infected by N. gonorrhoeae, demonstrated inhibition of growth towards N. gonorrhoeae.

Bacteriological Techniques↗
PubMed1978

Influence of heat, wind, and humidity on ultraviolet radiation injury.

We investigated the influence of heat, wind, and humidity on UVR-induced acute and chronic skin damage of experimental animals housed in environmental chambers and irradiated under controlled conditions. Hairless mice (strain HRS/J) irradiated after an increase of 10 degrees F in skin temperature had more skin damage than irradiated controls. Significantly more Swiss albino mice irradiated for 400 days while maintained at 90 degrees F developed tumors than did those receiving the same amount of UVR but maintained at room temperature. Mice exposed to UVR daily for 4 weeks while kept in wind of 7 mph had greater damage and slower recovery than animals irradiated but protected from wind. Wind also accelerated tumorigenesis in mice than received chronic UVR. Mice kept at 80% relative humidity and given a single dose of UVR had greater skin injury than animals irradiated while at 5% relative humidity. High midity also appears to accelerate skin cancer formation in animals that were exposed to chronic UVR.

Air Movements↗
PubMed1977

Influence of wind on chronic ultraviolet light-induced carcinogenesis.

Wind enhances the carcinogenic effect of chronic Iltraviolet radiation (UVL). This was demonstrated in hairless mice that were irradiated for 42 weeks with mercury are lamps. One group of animals was exposed to continuous wind flow of 2.7 m/s except for the daily I-2 min time interval when they were removed from the wind tunnel and irradiated. Another group of animals received identical irradiation but were protected from wind. The first tumour appeared in the UVL and wind group after 105 days of irradiation, and at 164 days of irradiation all surviving mice in the group had developed tumours. The group of mice receiving identical irradiation but protected from wind had their first tumour appear at 154 days of irradiation, and by 164 days of irradiation only 40% of the mice had developed tumours.

Air Movements↗
PubMed1977

Cutaneous microflora of patients with repeated skin infections.

The microflora of normal skin in 16 patients with repeated staphylococcal and streptococcal skin infections was examined to determine whether abnormalities existed which would indicate a protective role for the indigenous flora against colonization by pathogens. Five sites-hands, feet, axilla, groin and back-were examined quantitatively and qualitatively and compared with a control group. Total populations of indigenous flora were significantly higher from patients with repeated skin infections of the back, axillae and feet. The frequency of isolation of different species from normal skin was comparable between the control and experimental groups, with the exception of the incidence of Staphylococcus aureus and Proteus species which were isolated only from patients with repeated skin infections. Gram-negative bacteria were isolated with comparable frequency between the two groups, but patients with repeated skin infections tended to carry gram-negative bacteria on multiple sites. It was concluded from the high population of indigenous flora and the types of microogranisms present that the microflora of normal skin did not appear to protect patients with repeated skin infections against colonization by pathogens. The presence of high populations of Staphylococcus aureus on the normal skin of patients with repeated skin infections would appear to be the most important contributing factor.

Bacteria↗
PubMed1977

The environment and the microbial ecology of human skin.

Microbial flora of the skin of three human population groups representing different natural environments was examined quantitatively and qualitatively to determine whether environmental differences in temperature and humidity can influence the microbial flora of normal skin. Five anatomical skin sites - hands, back, axillae, groin, and feet - were sampled from 10 subjects working in a high-humidity, high-temperature environment, 10 subjects from a low-temperature, high-humidity environment, and 10 subjects working in a moderate-temperature and low-humidity environment. Bacterial populations were significantly larger from the back, axillae, and feet in individuals from the high-temperature and high-humidity environment as compared to the moderate-temperature, low-humidity environment. High humidity and low temperature had no significant effect on total populations, but this group showed a higher frequency of isolation of fungi, and gram-negative bacteria from the back and feet. Although there was an indication that increase in the environmental humidity could result in an increased frequency of isolation of gram-negative bacteria, there was no evidence that an increase in either temperature or humidity altered the relative proportions of gram-negative bacteria in the predominantly gram-positive microbial flora found on normal skin. It was concluded that, although climatic changes may cause fluctation in microbial populations from certain sites, they are not a major influence on the ecology of the microbial flora of normal skin in the natural environment. The variables introduced by studying individuals in their natural environment and the influence of these on the results are discussed.

Journal Article↗
PubMed1977

Effect of sensitization with Propionibacterium acnes on the growth of Listeria monocytogenes and Treponema pallidum in rabbits.

Sensitization of rabbits with Propionibacterium acnes, a nonspecific stimulant of the reticuloendothelial system, was investigated as a means of enhancing resistance to Treponema pallidum. A single i.v. dose of P. acnes given 3 or 7 days before challenge with Listeria monocytogenes was capable of suppressing the growth of the heterologous organism, whereas a single i.v. dose 24 hr or 14 days before challenge was not. Reactivation via i.v. elicitation with P. acnes 14 days after sensitization (1 day before challenge) caused significant suppression of listerial growth in the major organs 30 hr after i.v. challenge. A series of similar experiments was designed with T. pallidum as the challenge organism. Sensitization and repetitive elicitation with P. acnes did not change the time of appearance or progression of syphilitic chancres after i.v or i.d. challenge. Injection of P. acnes into sites of intradermal T. pallidum challenge in previously sensitized rabbits also failed to alter the evolution of syphilitic lesions. These results suggest that macrophage activation does not alter the host's ability to suppress the growth of T. pallidum.

Animals↗
PubMed1976

Attachment of gonococci to sperm. Influence of physical and chemical factors.

Neisseria gonorrhoeae of pilated T1 and nonpilated T4 colony types attached themselves to human sperm in greatest numbers and most reproducibly when suspensions of the cells were incubated at 35 degrees C in Ringer's solution, pH 6-8. After incubation for 15 or 30 min. in a water bath shaker, 50 per cent. of human sperm had T1 gonococci attached and 25 per cent. T4. Sperm and both types of gonococci were pre-incubated separately with various chemical agents, selected because the agent is found in genital fluids, or has a known effect on bacterial cell walls or sperm membrane. After treatment, sperm were washed or were not washed, and were then tested for attachment by mixture with untreated gonococci. Treated gonococci were handled in the same manner. Change in the percentage of attachment was defined as deviation from the range expected on the basis of a standard curve. Treatment of sperm with the nucleotides, ATP or cAMP, curtailed attachment by T1 gonococci but had no effect on attachment by T4.

Adenosine Triphosphate↗