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Biomedical subjects

R D Lewis

Publications and source records attributed to R D Lewis.

At least 73 records · Page 4Linked to original sources
PubMed1983

Phase-resetting action of light on the circadian activity rhythm of Rattus exulans.

The phase resetting action of light on the circadian rhythm of locomotor activity has been examined in wild-caught Polynesian rats (Rattus exulans). Phase-response curves to 4-, 8-, and 16-h light pulses have been derived. All three curves conform to the generalization that pulses occurring during late subjective day and early subjective night produce delays, whereas advances occur in response to pulses coinciding with the late subjective night and early subjective day. Weak (type 1) phase resetting is observed in response to 4-h pulses and perhaps 8-h pulses, whereas strong (type 0) resetting apparently occurs in response to 16-h pulses. These data evidently constitute the first report of strong phase resetting in mammalian circadian rhythms. The phase relationship between an entrained activity rhythm and the light-dark cycle is dependent on the photoperiod and, in 24-h cycles, on the period difference between the rhythm and the zeitgeber. In longer zeitgeber cycles, activity onset is delayed by a direct masking effect of light. A primarily nonparametric action of light in natural entrainment is consistent with these data and with field observations.

Animals↗
PubMed1982

Cell-mediated immune response to dog pulp tissue altered by Proco-Sol via the root canal.

Pulp tissue from three experimental dogs was tested for its antigenicity before and after incubation with Proco-Sol sealer (PS). Cell-mediated skin test reactions showed an increased response to pulp that had been incubated in Proco-Sol, washed, and then injected, as compared with pulp or PS alone. In vitro analysis of cell-mediated immune response (lymphocyte proliferation) showed a marked increase when pulp tissue was incubated in PS and washed, as compared to saline-treated pulp. Comparison of the saline-incubated pulp to the PS-altered pulp indicated that the increase in radioactivity was statistically significant at p less than 0.0001. Thus, Proco-Sol sealer altered dog pulp tissue and rendered it antigenically active, and a specific cell-mediated lymphocyte response was produced.

Animals↗
PubMed1981

Antibody formation to dog pulp tissue altered by camphor paramonochlorophenol via the root canal.

Pulp tissue from three experimental dogs was tested for its antigenicity before and after incubation with CMCP. Reaction to Arthus skin tests showed an increased response to pulp that had been incubated in CMCP, washed, then injected, as compared with pulp or CMCP alone. Hemagglutinating antibody titers (1:360 to 1:450 dilutions) were obtained from pulp tissue altered by CMCP. Inhibition tests showed the specificity of the antibody to be at a dilution titer of 1:350. Therefore, CMCP altered dog pulp tissue and rendered it antigenically active, and a specific humoral response was produced.

Animals↗
PubMed1980

Systemic distribution of N2 paste containing 14C paraformaldehyde following root canal therapy in dogs.

Using rubber-dam isolation and an aseptic and standardized endodontic technique, root canal therapy was performed on the right and left fourth mandibular premolars in four dogs. Each tooth was obturated with N2 paste containing 6.5 percent 14C paraformaldehyde. In each dog at 1 hour, 1, 7, 14, and 28 days, blood was drawn and biopsy specimens were taken of the adjacent lymph nodes, liver, and kidney. At 28 days, the animals were killed, and the experimental and adjacent tissues were processes for light microscopy. Histologic examination demonstrated that particles of the paste placed in the root canal were present in pulp, periapical, and periodontal tissues remote from the original site in the root canal. In addition, 14C-labeled paraformaldehyde which was contained in the N2 paste was found in blood, regional lymph nodes, kidney, and liver. The amount of radioactivity in all the body organs decreased with time.

Animals↗
PubMed1979

Antibody formation to dog pulp tissue altered by AH-26 sealer via the root canal.

Pulp tissue from three experimental dogs was tested for its antigenicity before and after incubation with AH-26 sealer. identical to Reactions to Arthus skin tests showed an increased response to pulp that had been incubated in AH-26, washed, and then injected, as compared with the material alone. Hemagglutinating antibody titers (1/500 to 1/800) were obtained from pulp tissue altered by AH-26. Inhibition tests showed the apecificity of the antibody to be at a dilution titer of 1:400. Therefore, a mixture of AH-26 sealer altered dog pulp tissue and rendered it antigenically active, and a specific humoral response was produced.

Agglutination Tests↗
PubMed1979

Antibody formation to dog pulp tissue altered by Grossman's Formula Sealer via the root canal.

Pulp tissue from experimental dogs was tested for its antigenicity before and after incubation with Grossman's Formula Sealer (GS). Reactions to Arthus skin tests showed an increased response to pulp that had been incubated in GS, washed, and then injected, as compared with the material alone. Hemagglutinating antibody titers (1:160 to 1:360) were obtained from pulp tissue altered by GS. Inhibition tests showed the specificity of the antibody to be at a dilution titer of 1:200. Therefore, GS altered dog pulp tissue and rendered it antigenically active, and a specific humoral response was produced.

Animals↗
PubMed1979

Cell-mediated immune response to dog pulp tissue altered by Grossman's formula sealer via the root canal.

Pulp tissue from three experimental dogs was tested for its antigenicity before and after incubation with Grossman's formula sealer (GS). Cellmediated skin-test reactions showed an increased response to pulp that had been incubated in Grossman's formula sealer, washed, and then injected as compared with pulp or GS alone. In vitro analysis of cell-mediated immune response (lymphocyte proliferation) showed a marked increase when pulp tissue was incubated in GS and washed as compared to saline-treated pulp. Comparing the saline-incubated pulp to the GS-altered pulp revealed that the increase in radioactivity was statistically significant at p less than 0.0001. Therefore, Grossman's formula sealer altered dog pulp tissue and rendered it antigenically active, and a specific cell-mediated lymphocyte response was produced.

Animals↗
PubMed1979

Effects of vitamin B-12 deprivation on phospholipid fatty acid patterns in liver and brain of rats fed high and low levels of linoleate in low methionine diets.

Experiments were conducted to determine how 20 weeks of deprivation of vitamin B-12 (B-12) would influence polyunsaturated fatty acid (PUFA) patterns in cerebral and liver phospholipids of female rats. All experimental diets included 24% soybean protein and either 3.5 of 0.35% of linoleate (18:2). Deprivation of B-12 and restricted intakes of 18:2 significantly inhibited growth of the rats. Rats depleted of B-12 had 6.7 times more methylmalonic acid in their liver, and significantly more odd-numbered acids (15:0 + 17:0) were present in phosphatidyl choline (PC) of their liver and cerebrum. Deprivation of B-12 promoted 63.3 to 97.3% increases of 18:2 in PC and phosphatidyl ethanolamine (PE) of the liver. Rats deprived of B-12 had significantly less arachidonate (20:4 omega 6) and 22:5 omega 6 in their liver PC, as well as smaller amounts of 20:4 omega 6 and 22:6 omega 3 in their cerebral PC. Some of the observed changes appear to be due to a significant interaction between the effects of B-12 and linoleate. Changes in PUFA patterns of cerebral and hepatic PC suggest that B-12 deprivation may interfere with the conversion of 18:2 omega 6 leads to 20:4 omega 6 leads to 22:5 omega 6. Some of the observed changes may also be related to an inhibited ability to convert PE to PC.

Animals↗
PubMed1979

Complications associated with IUD use in a family practice setting.

This study compares the complication rate of intrauterine contraceptive devices (IUD) with other contraceptive measures in a residency practice. The study population included 220 randomly selected women who had IUDs inserted by residents over a five-year period. One hundred similarly selected women started on birth control pills (BCP) were used as a control group. Of the IUD patients, 8.6 percent developed pelvic inflammatory disease vs 2 percent of the BCP patients. The incidence of gonorrhea was not significantly different between the two groups: 8.2 percent for the IUD groups vs 7 percent for the BCP group. Discontinuation of IUDs for reasons other than desiring pregnancy was significantly higher than discontinuation of BCPs: 41 percent vs 12 percent. Of the total IUD insertions, there were 21 expulsions (10 percent) and one uterine perforation (0.4 percent). Five pregnancies occurred in the IUD group, yielding a pregnancy rate of 1.7 per 100 women-years. There was a four percent rate of gynecologic hospitalizations in the IUD group as contrasted with one percent rate in BCP group. IUD use in the family practice setting under study is associated with comparatively poor long-term acceptance and a relatively high rate of complications.

Adolescent↗
PubMed1978

Antibody formation to dog pulp tissue altered by formocresol uithin the root canal.

After pulpal extirpation of twenty teeth in each of five dogs, these animals were primarily immunized intramuscularly by combining formocresol with the dog's own pulp (three dogs), saline solution with pulp (one dog) and injecting sheep erythrocytes (one dog). A sixth dog was used as a control for the Arthus skin test. Secondary immunizations were accomplished via the root canal every 7 days over a 28-day period. Arthus skin-test reactions demonstrated less of a response to the formocresol alone than when the dogs' pulp was conbined with this material. In vitro analysis of hemagglutinating antibody titer showed a tremendous increase when pulp was incubated with formocresol as compared to the saline-treated pulp. Therefore, dogs' pulp tissue became antigenically altered by the formocresol recognized by the host, and a specific humoral response resulted.

Animals↗
PubMed1978

Cell-mediated immune response to dog pulp tissue altered by N2 paste within the root canal.

After pulpal extirpation of twenty teeth in each of four dogs, these animals were primarily immunized intramuscularly with the dogs' own pulp (three dogs) altered by N2 paste and saline solution with pulp (one dog). A fifth dog was used as a control for skin tests. Secondary immunizations were accomplished via the root canal every 7 days over a 28-day period. Cell-mediated skin tests reactions demonstrated less of a response to the N2 paste alone than when the dogs' pulp was altered with this material. In vitro analysis of cell-mediated immune response (lymphocyte proliferation) showed a marked response to the pulp altered by N2 paste as compared to the saline-treated pulp (P less than 0.002). Therefore, dogs' pulp tissue became antigenically altered by the N2 material, recognized by the host, and a specific cell-mediated lymphocyte proliferation resulted.

Animals↗
PubMed1978

Antibody formation to dog pulp tissue altered by Kerr (Rickert's) sealer via the root canal.

Pulp tissue from three experimental dogs was tested for its antigenicity before and after incubation with Kerr (Rickert's) sealer (KS). Reactions to Arthus skin tests showed an increased response to pulp that had been incubated in KS, washed, and then injected, as compared with the material alone. Hemagglutinating antibody titers (1/360--1/600) were obtained from pulp tissue altered by KS. Inhibition tests showed the specificity of the antibody to be at a dilution of titer of 1:300. Therefore, a mixture of Kerr (Rickert's) sealer altered dog pulp tissue and rendered it antigenically active, and a specific humoral response was produced.

Animals↗
PubMed1978

Cell-mediated immune response to dog pulp tissue altered by eugenol within the root canal.

After pulpal extirpation of twenty teeth in each of four dogs, these animals were primarily immunized intramuscularly with the dog's own pulp (three dogs) and saline solution with pulp (one dog). A fifth dog was used as a control for skin tests. Secondary immunizations were accomplished via the root canal every 7 days over a 28-day period. Cell-mediated skin-test reactions demonstrated less of a response to the eugenol alone than when the dog's pulp was incubated with this material. In vitro analysis of cell-mediated immune response (lymphocyte proliferation) showed a marked response to the pulp altered by eugenol as compared to the saline-treated pulp (p less than 0.004). Therefore, dog's pulp tissue became antigenically altered by eugenol material, recognized by the host, and a specific cell-mediated lymphocyte proliferation resulted.

Animals↗