Age-related hair cell loss and strial atrophy were investigated in an accelerated senescence-prone strain, SAMP1 mice, and an accelerated senescence-resistant strain, SAMR1 mice. The loss of inner and outer hair cells in SAMP1 progressed more rapidly than that in SAMR1 with age. In both strains, areas of the loss of inner and outer hair cells were located mainly in the apex and base. Atrophy of the stria vascularis was observed in both strains, but in SAMP1 it appeared to increase earlier than in SAMR1. These results reveal that age-related hair cell loss and atrophy of the stria vascularis comparable to that in the human cochlea occur earlier and progress more rapidly in SAMP1 than in SAMR1. Hearing impairment in SAM may be due to a combination of sensory and strial presbycusis as well as to neural presbycusis, as reported previously. The morphological changes in the cochlea observed in SAMP1 and SAMR1 make these strains suitable for the study of the mechanisms of presbycusis.

Aging↗

PubMedDate not supplied

Teratogenicity of Aino virus in the chick embryo.

Aino virus (JaNAr 28 strain), a possible agent of a congenital anomaly of calves, was inoculated into the yolk sac of chick embryos at a dose of 10(2), 10(3), 10(4) or 10(5) TCID50 0.2 ml-1 at four, six or eight days of incubation. At 21 days of incubation all the unhatched embryos or hatched chickens in the experimental and control groups were sacrificed for pathological examination. The incidence of hydranencephaly, cerebellar hypoplasia or agenesis and arthrogryposis or scoliosis was highest (85 per cent in the chicks inoculated with 10(3) TCID50 0.2 ml-1 at eight days of incubation. The lesions were very similar to those found in congenital abnormalities in calves suspected of a natural infection with Aino virus.

Animals↗

PubMedDate not supplied

A special theory of hemagglutination.

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ABO Blood-Group System↗

PubMedDate not supplied

A study of the Su alleles in northeastern Brazil.

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Black or African American↗

PubMedDate not supplied

Hybrid layer as a dentin-bonding mechanism.

A number of mechanisms (both mechanical and chemical) have been proposed as the cause of dentin adhesion. Extensive research in Japan during the past 10 years has shown that strong, long-lived bonds between resin and living dentin will form when a monomer such as 4-META, which contains both hydrophilic and hydrophobic chemical groups, penetrates the tissue and polymerizes in situ. This resin-impregnation creates a transitional "hybrid" layer, that is neither resin nor tooth, but a hybrid of the two. The thin layer of resin-reinforced dentin locks the two dissimilar substances together on a molecular level, sealing the surface against leakage and imparting a high degree of acid resistance.

Acrylic Resins↗

PubMedDate not supplied

Unpolymerized layer on autopolymerizing, hard reline materials.

PURPOSE: The purpose of this study was to clarify certain properties of the resulting unpolymerized surface layer on 6 hard, autopolymerizing reline resins. MATERIALS AND METHODS: Two of the resins examined were the conventional type with a base monomer composition of mainly methyl methacrylate, and the other four were cross-linked reline materials containing difunctional monomers. For curing, the materials were polymerized in air at 24 and 37 degrees C, and in distilled water at 37 degrees C. The powder-to-liquid ratio was changed by +/- 20 wt% of the manufacturer's specified ratio. The inhibition depth processed under these conditions was measured with an optical microscope. Each sample was then immersed in methylene blue dye bath for 3 weeks before its surface was observed. RESULTS: Especially on cross-linked reline materials, the unpolymerized layer was significantly reduced with higher temperature, lower oxygen presence, and lower powder-to-liquid ratio (P < 0.01). The unpolymerized layer was stained in all materials. There were tiny, stained voids in the polymerized region on the conventional type of reline resins, whereas no staining was found in the polymerized region on the cross-linking reline resins. CONCLUSION: The inhibition depth was strongly affected by the temperature, the presence of air, and viscosity. The unpolymerized layer was easily contaminated in all materials. However, the highly polymerized, cross-linked reline materials might be harder to contaminate than the conventional type of reline resins.

Analysis of Variance↗

PubMedDate not supplied

Growth rate of experimental colon cancer in the absence of fecal stream and antitumor effect of UFT in rats.

Growth rate of a chemically-induced colon tumor in the absence of fecal stream was investigated and the tumors to a chemotherapeutic agent tested. Eighty Sprague-Dawley rats received dimethylhydrazine (40 mg/kg) s.c. once weekly for 10 wk to induce colon cancer. Then a colostomy was performed to produce a defunctioning colon without fecal stream. 22 wk after beginning the carcinogen treatment, a barium enema was performed to visualize tumors in the defunctionalized colon. 29 rats died postoperatively and 16 had no tumor radiographically. The remaining 35 rats were divided into a control group and UFT treatment group. After 5 wk of treatment, the barium enema was repeated. The mean doubling time of 19 tumors in the control group was 9.8 days +/- 4.0 (SD). Response to UFT was judged as effective when the doubling time exceeded 17.8 days, calculated from the mean +/- 2SDs in the control group. The response rate of UFT was 48%. The growth rate of colon tumors without fecal stream was faster and more stable than those with fecal stream; as a result, the sensitivity to UFT became higher than that in tumors with fecal stream (36%), which was reported in our previous study. The present experimental system may be more accurate for assessing the response to chemotherapeutic agents.

Animals↗

PubMedDate not supplied

A model for sensitivity determination of anticancer agents against chemically-induced colon cancer in rats.

Chemically-induced colon cancer was used to test the sensitivity of tumors to chemotherapeutic agents. Seventy-one Sprague-Dawley rats received dimethylhydrazine (20mg/kg) s.c. once weekly for 20 weeks to induce colon cancer. Then a barium enema was performed to see the size of colon tumors. The animals were divided into three groups that were subjected to the following treatments: 5-fluorouracil (5 FU); 1-(2-tetrahydrofuryl)-5 FU(FT); and a mixture of FT and uracil (UFT). After 5 weeks of treatment, the barium enema was repeated. "Response" was assessed on the basis of tumor doubling time. Response rates in the 5-FU, FT, and UFT groups were 25%, 33% and 36%, respectively and this reflects the clinical data of these drugs. The present system may be a predictive model for screening anticancer drugs for human colorectal cancer.

1,2-Dimethylhydrazine↗

PubMedDate not supplied

Participation of vasoactive intestinal polypeptide (VIP) as a humoral mediator in the erectile response of canine corpus cavernosum penis.

The ability of anti-vasoactive intestinal peptide (anti-VIP) serum to suppress the electrically induced relaxation of the corpus cavernosum was evaluated in vitro to define the role of VIP in penile erection. Strips of canine corpora cavernosa were placed in 5-ml organ chambers containing oxygenated Krebs-Ringer solution. They were stretched and fixed in place at both ends and pretreated with 2 x 10(-7)M noradrenaline (NA). NA was given to produce an optimal state of isometric smooth muscle contraction so that subsequent electrical field stimulation (EFS) could induce a good range of measurable relaxation response. This response was deemed to be an in vitro representation of penile erection. After NA treatment the cavernous tension rose markedly by 2-2.5 g; it then declined by up to 1-1.2 g upon EFS. Anti-VIP serum (1:16) or atropine sulfate (10(-6)M) was added at various time points between NA administration and EFS. When anti-VIP serum was administered, subsequent EFS-induced relaxation was attenuated by 20%-55% compared to the control EFS treatments. The degree of attenuation depended upon the frequency of EFS applied, being 20.6% +/- 4.0% at 20 Hz and 54.7% +/- 6.3% at 2 Hz. Atropine administered additionally following anti-VIP serum produced no further attenuation. However, atropine alone was capable of producing up to 23.7% +/- 3.5% attenuation. When anti-VIP serum was administered following atropine, the degree of attenuation that ensured was the sum of the attenuations produced by each of the two substances independently.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMedDate not supplied

Involvement of vasoactive intestinal peptide (VIP) as a humoral mediator of penile erectile function in the dog.

The effects of intracorporeal infusion of anti-vasoactive intestinal peptide (anti-VIP) antisera on electrically induced penile erection were studied in 18 male mongrel dogs. Electrical pulse stimulation (4 V, 4 milliseconds, 40 Hz) of the pelvic splanchnic nerve consistently produced penile erection ("electroerection"). Using this erection model, effects of anti-VIP serum were evaluated with regard to the peak intracorporeal pressure during electroerection. Pretreatment of the animals with repetitive intracorporeal infusion of anti-VIP rabbit serum completely abolished the electroerection in nine dogs, partially suppressed it (P < 0.01) in five, and was without effects in four. In contrast, control treatment of the same 18 dogs with normal rabbit serum was totally ineffective. In six dogs in which anti-VIP serum failed to produce a complete suppression of electroerection, 0.5 mg atropine sulfate was additionally given i.v. All six dogs exhibited significant (P < 0.01) suppression of the peak intracorporeal pressure after atropine. However atropine alone did not affect the intracorporeal pressure to any significant degree. To five of these six dogs with positive response to the combination treatment with anti-VIP serum and atropine, prazosin HCl was added i.v. It was found that prazosin HCl reversed the attenuation of electroerection produced by combined anti-VIP serum and atropine. Prazosin did not affect the intracorporeal pressure when administered following anti-VIP serum. These results suggest that VIP plays a role as a humoral mediator involved in penile erection and that there is a synergistic interaction between VIP and acetylcholine. Also it appears that the effect of acetylcholine but not that of VIP is mediated by the alpha-1 adrenergic mechanism.

Animals↗

PubMedDate not supplied

Effect of sodium benzylideneascorbate on chemically-induced tumors in rats.

Intravenous administration of sodium benzylideneascorbate (SBA) dose-dependently induced degeneration (vacuolar and eosinophilic degeneration and cell shrinkage and nuclear condensation, which are characteristic of apoptotic cell death) of 3'-methyl-4-dimethylaminoazobenzene-induced rat hepatocellular carcinoma. SBA did not significantly induce lymphocyte infiltration and fibrosis in the liver, nor damage the gross morphology of kidney and spleen cells. SBA failed to stimulate the production of tumor necrosis factor and interleukin-1 beta in both in vitro and in vivo systems. These results may suggest a direct antitumor action of SBA via induction of apoptosis in the tumor. However, SBA did not significantly affect the doubling time, or the extent of invasion and differentiation of dimethylhydrazine-induced colon carcinoma in rats. These data suggest that the conditions of SBA administration should be re-established for each tumor sample to produce maximum antitumor activity.

Animals↗

PubMedDate not supplied

Suppressive effects of chronic hyperprolactinemia on penile erection and yawning following administration of apomorphine to pituitary-transplanted rats.

Recent studies showed in vivo and in vitro that acutely introduced prolactin (PRL) excess was capable of diminishing penile erectile function independently of the LH-testosterone (T) dynamics. In the present investigation, we examined if such independent suppressive effects can be demonstrated in the pituitary-transplant rat model with chronically elevated serum PRL. We also compared the effects of pituitary transplantation and castration on the level of erectile activity. Rats were made hyperprolactinemic by homologous transplantation of three anterior pituitaries underneath the kidney capsules, with the eutopic pituitaries left in situ. Before and 3, 5, and 8 weeks after transplant or sham surgeries, 80 micrograms/kg s.c. injection of apomorphine was given as an inducer of erection. This was followed by 30-minute observation periods during which the numbers of erections and yawning were recorded. Similar experiments were also performed with castrated rats without transplanted pituitaries. In the transplanted rats plasma PRL was markedly elevated (51.4 +/- 3.7 ng/ml) and was significantly (P < 0.001) higher than the values in the sham group (6.0 +/- 2.7 ng/ml). In contrast, plasma T was not different (P > 0.05) between the two groups. The castrated rats showed very low plasma T (0.17 +/- 0.01 ng/ml, P < 0.05 compared to the sham group) and normal PRL (P > 0.05). The numbers of both erection and yawning were significantly (P < 0.05-0.01) less in the transplant than in the sham group 8 weeks after surgeries. Castrated rats showed a significant reduction (P < 0.05) only in the numbers of erection. These results indicated that the pituitary transplantation with chronic excess of PRL and castration with T deficiency caused roughly comparable degrees of suppression of penile erectile activity through mechanisms presumably independent from one another in the rat.

Animals↗