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Biomedical subjects

L J Bell

Publications and source records attributed to L J Bell.

13 recordsLinked to original sources
PubMed1994

Bond strengths between elastomeric impression materials and disinfected preliminary impressions.

Bond strengths between disinfected putty impressions and subsequent wash applications were determined in specimens made to simulate clinically an interrupted two-step impression technique. The effect of a disinfectant on the bond strength between a disinfected wash impression and a subsequent wash application was also evaluated to simulate perfecting a disinfected final impression clinically. Vinyl polysiloxane (putty or wash) and polyether (wash only) impression materials were placed in perforated metal cylinders, allowed to set, and dipped in an iodine or glutaraldehyde disinfectant. Wash material was then applied to the disinfected material by use of another metal cylinder and allowed to set before the specimen was tested in tensile mode. Significant decreases in bond strengths were found in both clinical simulations but were limited to specific impression material and disinfectant combinations.

Dental Bonding↗
PubMed1992

Murine susceptibility to mercury. I. Autoantibody profiles and systemic immune deposits in inbred, congenic, and intra-H-2 recombinant strains.

Inbred, congenic, and intra-H-2-recombinant mouse strains were given subcutaneous injections of either 1.6 mg HgCl2/kg body wt or 0.1 ml NaCl thrice weekly for 5-6 weeks. Mercury-treated mice from strains carrying the H-2s haplotype developed antinucleolar antibodies (ANoA), which targeted the 34-kDa nucleolar protein fibrillarin, and in some instances also nucleolar proteins of 60-70 and 10-15 kDa, the latter corresponding to histones. Strains with H-2b and H-2d haplotypes were resistant to induction of ANoA. The susceptibility to development of AnoA/antifibrillarin antibodies (AFA) was mapped to the H-2A-region using intra-H-2-recombinant strains. We were not able to confirm earlier reports that expression of H-2E genes dampens the development of ANoA. Mercury treatment caused a substantial increase in the titer of antichromatin (ACA) and/or antihistone (AHA) antibodies in a fraction of SJL/J, A.SW, A.TH, B10.S, and B10.HTT mice (H-2s), and in A/J (H-2k) mice, whereas mice from the C57BL/6J and C57BL/10J (H-2b), and the DBA and BALB/c (H-2d) strains were low or nonresponders. The development of AHA and ACA could not be linked to the H-2 complex. A significant, substantial increase of granular mesangial and systemic vessel wall IgG deposits occurred in mice with serum ANoA/AFA. However, the B10.S(9R) and B10.HTT strains, which express the H-2E genes, developed only an intermediately increased titer of mesangial IgG deposits. Systemic vessel wall IgG deposits occurred in only 60-80% of the B10.S(9R) mice and in none of the B10.HTT mice. This contrasted with the high titer of mesangial IgG deposits and uniform development of systemic vessel wall IgG deposits observed in B10.S mice not expressing H-2E. Mice with mesangial IgG deposits showed a mild glomerulonephritis. There was no systemic vasculitis. The susceptibility to development of ANoA, AHA, ACA, and systemic, granular IgG deposits in the B10.S strain was influenced by the sex, since males showed less uniform development of these immunopathologic features than females.

Animals↗
PubMed1985

The maintenance and survival of Theileria annulata in colonies of Hyalomma anatolicum anatolicum.

Procedures are described for the colonization of Hyalomma anatolicum anatolicum ticks using gerbils, rabbits and cattle as hosts. On rabbits H. a. anatolicum undergoes a two-host cycle but methods are described for obtaining either unfed or engorged nymphs. Data are given on the life cycle timings and the numbers and timings of tick feeding regimes. The infection of H. a. anatolicum with two strains of Theileria annulata is described and methods given for monitoring the development and survival of T. annulata in H. a. anatolicum. Data are presented indicating the optimum maintenance conditions for T. annulata in H. a. anatolicum. Piroplasm parasitaemias in cattle greater than 2% gave high infection rates in adult ticks if engorged nymphs were moulted at 28 degrees C for 28 days. The Theileria will survive for ten months in such adults stored at 12 degrees C after moult, and when fed the ticks will produce maximum numbers of sporozoites on the third day of feeding, whatever their age. The moult of engorged nymphs is retarded at 18 degrees C but the Theileria in such ticks will develop normally when the ticks are moulted at 28 degrees C after four months storage at 18 degrees C.

Animals↗
PubMed1984

The development of Theileria annulata in the salivary glands of the vector tick Hyalomma anatolicum anatolicum.

The development at 28 degrees C of Theileria annulata (Hissar) in the salivary glands of its tick vector, Hyalomma anatolicum anatolicum, was studied using Giemsa-stained smears, methyl green-pyronin-stained preparations of whole glands, and electron microscopy. Nymphs which had engorged on T. annulata-infected calves showed kinetes in the haemolymph from Day 7 to Day 14 post engorgement, when all ticks had completed moult. Intracellular sporonts were observed within salivary gland acini from Day 7 onwards and these developed by rapid nuclear division and cytoplasmic proliferation to form primary sporoblasts. Further development was stimulated by feeding on a rabbit or by incubation at 36 degrees C. The primary sporoblasts appeared to become organized into membrane-bound subunits. Within 48 hours of attachment to the host, or 72 hours of 36 degrees C incubation, these units dissociated to form secondary sporoblasts. The final phase of development resulted in the progressive formation of discrete, uninuclear sporozoites within these secondary sporoblasts. No morphological differences were observed in parasite maturation between the fed and incubated groups although development was retarded by at least 24 hours in the latter. In the incubated group there was also a marked decrease in the degree of synchrony of development which resulted in fewer sporozoites being present at any one time.

Animals↗
PubMed1980

Organ culture of Rhipicephalus appendiculatus with maturation of Theileria parva in tick salivary glands in vitro.

A technique is described for the organ culture of Rhipicephalus appendiculatus ticks. Whole, unfed adult ticks with the dorsal integument removed, known as backless tick explants, were cultured in enriched Leibovitz' L-15 medium in which they remained active for at least 32 days at 28 degrees C and 9 days at 36 degrees C. Development of Theileria parva, as demonstrated by methyl green-pyronin staining, occurred in the salivary glands of infected backless tick explants held for 8 days at 28 degrees C or 3 days at 36 degrees C. Maturation in vitro of T. parva in backless tick explants was compared with that in cultured excised salivary glands. After 3-7 days at 36 degrees C glands from backless tick explants and excised salivary glands showed similar numbers of infected acini per infected tick. However, after 12 days at 28 degrees C backless tick explants showed 20-30 times as many infected acini per infected tick as excised salivary glands, in two experiments. No assessment was made of degree of parasite maturity or infectivity. It was concluded that both organ culture techniques supported development in vitro of the salivary gland stages of T. parva, but the backless tick explant technique was simpler and gave generally better results than culture of excised salivary glands.

Animals↗
PubMed1979

Rapid quantitative assessment of Theileria infection in ticks.

A simplified method for methyl green pyronin staining is described for Theileria parva and T. annulata in whole salivary glands of Rhipicephalus appendiculatus and Hyalomma anatolicum subspecies respectively. The stain gives results comparable with Feulgen staining and can be used after the ticks have been in cold storage for 3 days. There is considerable variability in the rate and intensity of infection of these ticks with theilerial parasites and it is concluded that the method permits large samples (60 ticks per person per day) to be examined to overcome this variability when assessing infection quantitatively.

Animals↗
PubMed1978

Arsenic and cancer: effects of joint administration of arsenite and selenite on the genesis of mammary adenocarcinoma in inbred female C3H/St mice.

The joint administration of 2 ppm of arsenic as arsenite and of 2 ppm of selenium as selenite in the drinking water of inbred female C3H/St mice increases the incidence of spontaneous mammary adenocarcinoma significantly over the simultaneous controls and animals receiving 2 ppm As as arsenite or 2 ppm Se as selenite alone, indicating that arsenic abolishes the anticarcinogenic effect of selenium. Arsenite caused a significant increase of the tumor growth rates and raised the incidence of multiple tumors. The tumor growth rates in the As-Se group were also increased, but the incidence of multiple tumors was lower than in the 2 ppm As group.

Adenocarcinoma↗
PubMed1977

A study of the acceptability of lateral records by the Whip-Mix articulator.

1. Of 50 lateral condylar settings made, 10 were not accepted by the Whip-Mix articulator. 2. An improved method of obtaining lateral interocclusal records was described. 3. The Whip-Mix articulator is considered useful in diagnosis and treatment in prosthodontic procedures if one is aware of its limitations.

Dental Articulators↗
PubMed1970

Time course of the effects of 6-hydroxydopamine on catecholamine-containing neurones in rat hypothalamus and striatum.

1. The effects of intraventricular injection of 6-hydroxydopamine (6-OHDA) on tyrosine hydroxylase activity, uptake of (3)H-noradrenaline and endogenous catecholamine concentration in rat hypothalamus and striatum were investigated at various times after the injection of 6-OHDA.2. In the hypothalamus after the injection of 250 mug of 6-OHDA there was a rapid decrease in tyrosine hydroxylase activity, (3)H-noradrenaline uptake and noradrenaline content, which was essentially complete within 2 hours.3. In the striatum after this dose of 6-OHDA there was a much slower reduction in tyrosine hydroxylase activity and (3)H-noradrenaline uptake during the first 48 h after drug injection. For the first 24 h the dopamine concentration in this brain area was increased significantly above control values, but had fallen below control values by 48 hours.4. After the injection of a smaller dose of 6-OHDA (25 mug) the only detectable change in the striatum was a rapid increase in the dopamine concentration. In the hypothalamus this dose induced a rapid depletion of noradrenaline, not accompanied initially by any significant reduction in tyrosine hydroxylase activity.5. These results are consistent with the hypothesis that 6-OHDA causes a rapid degeneration of catecholamine-containing nerve terminals in the central nervous system (CNS). These degenerative changes, indicated by the loss of tyrosine hydroxylase and noradrenaline uptake sites, did not appear to be preceded by an initial displacement of endogenous catecholamines by 6-OHDA, except possibly at early times after the administration of small doses of the drug.

Animals↗
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Education, Nursing, Continuing↗