PubMed Health⌕ Search

Biomedical subjects

D J Simmons

Publications and source records attributed to D J Simmons.

At least 91 records · Page 5Linked to original sources
PubMed1982

Formation of bone by isolated, cultured osteoblasts in millipore diffusion chambers.

Osteoblast-like and osteoclast-like cells freed from neonatal calvaria by sequential enzymatic digestion after 6-7 days in culture were placed in diffusion chambers and implanted in the peritoneal cavities of CD-1 mice. About half of the chambers also contained a dead calvarium to test for the need of an "inducer." After 20 days, 11 of 18 chambers containing to osteoblast-like cells formed large foci of mineralized bone that corresponded to alkaline phosphatase activity throughout the chambers. Moreover, only type I (i.e., bone) collagen was formed. Occasional deposits of bone were found in only 3 of 22 chambers containing the osteoclast-like cells. The presence of dead bone did not affect any of the results. These data confirm the osteoblast-like nature of the isolated cell populations and demonstrate that these cells retain their differentiated function in culture.

Animals↗
PubMed1981

Altered metabolic rhythm of rabbit osteoblasts by tetracycline.

To establish whether there are single or multiple pools of osteoblasts in rabbit bone, animals were injected with tetracycline on various schedules for 1-3 days. Metabolic restraints predicted that a multiple pool model would be feasible only if the percent labeled surfaces of trabecular bone (tibia) doubled when animals were injected on days 1 and 2, 1 and 3, or on days 1, 2, and 3. A single population would be indicated if the extent of labeled surfaces failed to double. Herein, 41.9 +2- 8.1% of bone surfaces labeled after a single injection, and only 60-68% of surfaces labeled after injections on the other schedules. The data inferred tht serial pulse tetracycline injections at 24h intervals caused a shift in the activities of a single population of osteoblasts and their progenitor cells.

Animals↗
PubMed1980

Salmonella montevideo salmonellosis in laboratory mice: successful treatment of the disease by oral oxytetracycline.

In an epidemic outbreak of salmonellosis associated with Salmonella montevideo in 6 mouse colonies, most deaths occurred in BALB/c and ASI mice, although the carrier rate was similar in other mouse strains. The salmonella was eradicated from ASI mice of 4-6 weeks old, and the carrier rate considerably reduced at 12-26 weeks of age, by use of oral oxytetracycline in conjunction with strict hygiene measures. Housing mice on wire grids instead of wood shavings did not affect the efficacy of the treatment.

Animals↗
PubMed1980

Two Actinobacillus species isolated from laboratory rodents.

A study was made of the cultural and biochemical characteristics of 17 strains of Actinobacillus isolated from laboratory rats and hamsters. 2 types were recognized which differed in their urease reaction and colony colour on blood agar. The results obtained suggest that one was Actinobacillus equuli but the other could not be identified as belonging to a described species. The characteristics of both organisms are such that they could be confused with Pasteurella pneumotropica. One of the types was isolated from tapwater.

Actinobacillus↗
PubMed1980

Observations on the host specificity of Hymenolepis straminea (Goeze).

The experimental infection of rodents as potential, definitive hosts with Hymenolepis straminea indicated that hamsters and field mice were susceptible to infection. By comparison, laboratory mice exhibited a significantly lowered susceptibility. Artificially induced depression of the immune response enabled the parasite to be cultured in several strains of laboratory mice, and suggested that the thymus played a major role in rejection of the parasite.

Animals↗
PubMed1980

Postfracture linear bone growth in rats: a diurnal rhythm.

The effect of fracture of the tibia on the subsequent overgrowth of the femur in the injured limb has been studied in ad lib, -fed rats. The thrust of these studies was to determine if the time in the body rhythm (diurnal) when injury was sustained could influence the rate of postfracture linear bone growth. Accordingly, different groups of young rats were subjected to tibial fracture at one of 4 times in a 24 hour day (6 hours apart), and a ratio of femur lengths (injured left side/intact right side) in each group was calculated 30 days thereafter. The data indicated that midday was the only time when tibial fracture elicited significant femoral overgrowth. At this time, the femur length differential in the fractured rats was small (0.52 mm), but it was significantly greater than that observed in intact control rats. The diurnal response was not present in fractured hypophysectomized rats, nor could it be detected in normal rats by measuring the thicknesses of the growth cartilages from the intact and fractured tibias. However, in 2 separate studies, the patterns of radiostrontium retention in the tibias and in the femurs confirmed that midday was the time in the rat body rhythm when processes of ossification in the epiphyses and in the remodeling fracture callus proceeded most actively. The 24-hour retention of 85Sr in the fractured tibias was greater than that in the intact tibias (5 days postfracture), but the 5-day retention of isotope in the femurs on the side of tibial fracture (30 day postfracture) was significantly less than that of the bone in the uninjured limb. The skeletal responses to fracture are not limited to the injured element; the magnitude of the responses both in injured and intact bones of a limb have a diurnal component.

Animals↗