Biomedical subjects

N Hunter

Publications and source records attributed to N Hunter.

At least 181 records · Page 10Linked to original sources

PubMed1989

Perivascular hyaline deposits in inflamed gingival tissues.

A perivascular hyaline material (PHyM) was found in gingival biopsies from patients with periodontitis, gingivitis and minimally inflamed gingiva. PHyM was found only in association with the sulcular or pocket epithelium. The extent and frequency of the deposits was quantitatively associated with inflammation of the gingival tissues, as well as with the apical region of periodontal pockets. Evidence for angiogenesis was found in association with the deposition of PHyM. The ultrastructure of the PHyM indicated that the material, which was of an amorphous hyaline appearance at the light microscope level, was composed of multiple basal lamina impregnated with irregular collagen fibrils, fine fibrils and cellular debris. The basal lamina material was degraded at many sites. Immunohistochemistry confirmed the abundance of type IV collagen, supporting the basal lamina origin for PHyM. It is proposed that the deposition of the hyaline matrix is related to the effect of angiogenic and injurious agents on the vascular endothelium. PHyM could contribute to the development of periodontitis by impairing the emigration of polymorphonuclear leukocytes into the gingival sulcus.

Basement Membrane↗

PubMed1989

Histochemical identification of the vascular endothelial isoenzyme of alkaline phosphatase.

Alkaline phosphatase (AP) is a widely studied membrane bound ecto-enzyme with an extensive distribution in nature. Three major human isoenzymes have been defined and can be distinguished on the basis of their differential sensitivity to specific inhibitors. Despite the voluminous literature describing AP, the physiological role of this enzyme is unclear. Microvascular endothelium is strongly AP positive and may provide a convenient model for study of the role of AP in vitro. This report describes the use of freeze-substitution and high-resolution plastic embedding techniques to identify the isoenzyme of endothelial AP by quantitative analysis of the relative inhibition by specific inhibitors of AP, using human gingival tissues and a number of rat tissues. Endothelial AP is found to be the liver/bone/kidney isoenzyme, indicating kidney as a credible source of enzyme for further experimental work investigating the role of AP.

Alkaline Phosphatase↗

PubMed1989

Protection by WR-3689 against gamma-ray-induced intestinal damage: comparative effect on clonogenic cell survival, mouse survival, and DNA damage.

The aminophosphorothioate WR-3689 was characterized for its ability to protect mouse jejunal cells in vivo from single doses of X or gamma radiation. First, the effect of the drug on the survival of jejunal stem cells was examined using a clonogenic end point, the crypt microcolony assay. When WR-3689 was administered 30 min prior to whole-body irradiation, the number of surviving crypt cells was markedly increased at all doses of the drug, although protection began to level out at doses larger than 600 mg/kg. Protection was maximal when the drug was given 30 min before whole-body irradiation and declined rapidly with both shorter and longer intervals. Protection factors (PFs) were obtained by measuring survival curves for clonogenic crypt cells as a function of radiation dose; WR-3689 given 30 min before whole-body irradiation protected jejunum in the microcolony assay with a PF of 1.26 +/- 0.02, 1.50 +/- 0.10, and 1.65 +/- 0.10 at doses of 200, 400, and 800 mg/kg, respectively. Next, the effect of WR-3689 on the survival of jejunal stem cells was determined by assaying the survival of mice given X-ray doses to the whole abdomen in the range leading to death from the gastrointestinal syndrome. The PFs based on the LD50 values for 11-day survival were 1.31 +/- 0.05 (200 mg/kg) and 1.48 +/- 0.05 (400 mg/kg). Crypt-cell survival and animal survival were thus modified to a similar extent by this agent. Finally, the effect of WR-3689 on the induction of DNA single-strand breaks (SSBs) in jejunal cells was measured using an adaptation of the alkaline elution methodology. In mice treated with WR-3689 (400 or 800 mg/kg) 30 min prior to whole-body irradiation with 10 Gy there was no significant reduction in the number of DNA SSBs induced either in samples of the jejunum or in the cycling crypt cells, providing further evidence that there is no simple relationship between the modification of DNA SSBs and the survival of jejunal stem cells.

Amifostine↗

PubMed1989

Bovine spongiform encephalopathy: a scrapie-like disease of British cattle.

Scrapie is a CNS degenerative infection of sheep and goats, which is invariably fatal after incubation periods of several months to years. Related disorders are found naturally in man and other species. There is a impairment of protein catabolism in scrapie and related diseases which leads to the accumulation of sparingly-soluble protein deposits in brain. These protein aggregates may share with the amyloid of Alzheimer's disease (AD) some common stage in the biochemical pathways of their formation, although different proteins are affected in scrapie (the PrP protein) and AD (the A4-precursor protein). Recently, cattle with the clinical signs and brain pathology of a neurodegenerative disease have been reported, and this cattle disorder has been called bovine spongiform encephalopathy (BSE). BSE-affected brains contain abnormal forms of the bovine homologue of PrP. This provides biochemical evidence that BSE is cattle scrapie rather than cattle AD.

Animals↗

PubMed1988

Fibrils from brains of cows with new cattle disease contain scrapie-associated protein.

During the past two years, more than 1,000 cases of a neurological disorder of cattle, bovine spongiform encephalopathy (BSE), have been confirmed from farms throughout Great Britain. The neurological signs and brain pathology of BSE resemble those produced in other species by the pathogens of scrapie and related disorders. The discovery of fibrils similar to scrapie-associated fibrils in detergent extracts o BSE-affected brain supported the clinical and pathological diagnosis of the disease, but has been controversial. Scrapie-associated fibrils are found in brain extracts of all species affected by scrapie and diseases caused by related pathogens. They are pathological aggregates of a neuronal membrane protein termed PrP and a protease-resistant form of PrP is a molecular marker of scrapie-associated fibrils. In this report, we show the major protein of BSE fibrils is the bovine homologue of PrP as judged by its size, protease resistance, immunoreactivity, lectin binding and partial N-terminal protein sequence. This confirms that BSE is a scrapie-like disease.

Amino Acid Sequence↗

PubMed1988

Increase in radioresponse of murine tumors by treatment with indomethacin.

Indomethacin, an inhibitor of prostaglandin (PG) synthesis, was investigated for its ability to increase radioresponse of two fibrosarcomas, FSA and NFSA, in C3Hf/Kam mice. In addition, the effect of indomethacin on radioresponse of hematopoietic tissue, jejunum, hair follicles, and tissues involved in the development of radiation-induced leg contractures was determined. Indomethacin greatly increased radioresponse of 8-mm tumors, as assessed by both tumor growth delay and TCD50 assays. Enhancement factors for tumor growth delay and tumor radiocurability (TCD50) were 1.55 and 1.39, respectively, for FSA, and 1.4 and 1.26, respectively, for NFSA tumors. Of four normal tissues assessed, two (hair follicles and tissues responsible for development of leg contractures) showed no change in radioresponse after treatment with indomethacin, one (hematopoietic tissue) exhibited radioprotection, and one (jejunum) exhibited slight radiosensitization (enhancement factor, 1.12). Therefore, indomethacin significantly augmented tumor radiocurability but had minimal effect on radioresponse of some normal tissues.

Animals↗

PubMed1988

Effect of radiation-induced injury of tumor bed stroma on metastatic spread of murine sarcomas and carcinomas.

The study was performed to determine whether irradiation of the tumor bed alters the propensity of tumors to metastasize, and if so, whether the effect is dependent on the property of tumors to exhibit the tumor bed effect (TBE). Ten tumors, of which 5 were sarcomas and 5 were carcinomas syngeneic to C3Hf/Kam mice, were used. Tumors were grown s.c. in the right thighs of mice that had or had not been irradiated with 20-Gy gamma-rays 1 day before tumor cell transplantation. All 5 carcinomas and 2 of 5 sarcomas exhibited TBE, as assessed by a significant retardation of growth rate. To test whether irradiation of the tumor bed influenced metastatic spread independently of TBE, tumors of various sizes were surgically removed, and at appropriate times thereafter the lungs were examined for the presence of metastases. All tumors that exhibited TBE, and only 1 of 3 tumors that did not exhibit TBE, metastasized more than tumors of the same size growing in an unirradiated tumor bed. TBE-induced enhancement of metastasis was not seen in tumors less than approximately 7 mm in diameter. All tumors, whether they exhibited TBE or not, were more necrotic if they grew in a preirradiated tumor bed. These observations show that size for size, most tumors growing in irradiated tissues have an increased propensity to metastasize, which is linked to their manifestation of TBE. The evidence presented suggests that TBE-induced retardation of tumor growth is the major factor responsible for the observed enhancement of metastasis. The clinical implication of these findings is that tumors recurrent after radiotherapy should be diagnosed and treated promptly to reduce the risk of metastatic spread.

Animals↗

PubMed1988

Scrapie-associated fibrils, PrP protein and the Sinc gene.

Scrapie-associated fibrils (SAF) are disease-specific structures found in extracts of the brains of animals affected with scrapie. These structures are pathological aggregates of a normal host protein called PrP. In collaboration with Konrad Beyreuther (Heidelberg), we have characterized the multiple forms of PrP found in SAF fractions from mouse brain affected by the ME7 strain of scrapie. There is no in vivo N-terminal cleavage of the most abundant forms of PrP. However, N-terminal cleavage of some minor forms of PrP does occur in vivo within a domain of repetitive sequences at sites similar to but distinct from those cut by proteinase K in vitro. We suggest that such covalently modified forms of PrP may be the result of enzymic degradation occurring as a consequence rather than as a cause of disease. We also found a novel, as yet unidentified, amino acid derivative of the arginine residue at position 3 in both hamster and mouse PrP 33-35, which may predispose PrP to form SAF. Carlson and colleagues have discovered a linkage between the PrP gene and the murine gene provisionally called Prn-i which, from the work of Carp and coworkers, appears identical to the Sinc gene. The Sinc gene is the major gene determining the incubation period of all strains of scrapie in mice. We have evidence for a linkage of the PrP gene and Sinc using inbred mice of known Sinc genotype, including VM(Sincp7) and VM(Sincs7) congenic mice. PrP may even be the protein product of the Sinc gene.

Amino Acid Sequence↗

PubMed1988

A monokine which binds to class II histocompatibility proteins.

There is a marked decrease in the viability, in vitro, of dense, immature rat thymocytes over a 4 h incubation period. The addition of a monokine of relative molecular weight 36,000 derived from cultured rat peritoneal macrophages which had been previously stimulated with lipopolysaccharide prevented these cells from dying. The early release of this factor, together with preliminary results of its physical and functional properties suggest that it is distinct from the well characterized monokines. The macrophage factor was found to bind in competition with a monoclonal antibody directed against a common determinant on the Ia antigen complex, but also to bind non-competitively with a monoclonal antibody to a strain-specific epitope on Ia. Based on the results of experiments using a fractionated thymic cell model, it would appear that this monokine binds to the Ia protein complex on the cell surface of thymic epithelial cells, causing them in turn to release an activity which is responsible for the survival of thymocytes.

Animals↗

PubMed1988

Augmentation of mitogen-induced thymocyte proliferation by bacterial products is mediated by an Mr 36,000 monokine.

The addition of picogram quantities of bacterial products to rat thymic cells in culture produced a doubling of the proliferative response to suboptimal levels of Concanavalin-A (Con-A). This effect was prevented by the depletion of adherent cells which comprised less than 0.1% of the total population. The response was restored by the addition of supernatants from peritoneal macrophages which had been stimulated 2 h previously with lipopolysaccharide. Treatment of these supernatants with phenylglyoxal, an inhibitor of interleukin-1 (IL-1), did not prevent the stimulatory effect. Augmentation of the thymocyte proliferative response could also be achieved by the addition of a partially purified monokine of relative molecular weight (Mr) 36,000 which is biochemically and functionally distinct from IL-1 and by a monoclonal antibody which binds to a common determinant on the Ia molecule. Fractionation of the thymic cells on a density gradient yielded a buoyant population which accounted for the majority of the proliferative activity and a dense fraction which was poorly responsive to the mitogen. The addition of the monokine to this latter fraction produced a significant increase in proliferation in response to Con-A. It is proposed that in the thymus, bacterial products stimulate thymic macrophages to release the Mr 36,000 monokine which in turn stimulates the thymic epithelial cells to release products which promote the survival and maturation of immature thymocytes. This work has implications for the regulation of thymocyte maturation.

Animals↗

PubMed1987

Macrophage content of murine sarcomas and carcinomas: associations with tumor growth parameters and tumor radiocurability.

Experiments were designed to investigate whether the tumor-associated macrophage (TAM) content of murine solid tumors correlates with the clonogenic ability of tumor cells to establish s.c. tumors, tumor growth rate, extent of tumor necrosis, tumor metastatic propensity, and tumor radioresponse. Of 13 tumors studied, 6 were sarcomas and 7 were carcinomas; all tumors were of spontaneous origin in C3Hf/Kam mice, with the exception of one sarcoma that was induced by 3-methylcholanthrene. Tumors were growing in the hind thighs of syngeneic mice, and their TAM content was determined when they were 8 mm in diameter. The TAM content varied greatly among tumors, ranging from 9 to 83%. Tumor bearing mice experienced a reduction of 50% or more in the number of peritoneal macrophages, but the degree of reduction was independent of TAM content. A significant negative correlation was noted between TAM content and TD50 values (i.e., the number of tumor cells needed to produce tumors in 50% of injected sites) and between TAM content and the amount of tumor necrosis. Also, an obvious trend toward positive correlation between TAM content and reduced local tumor radiocurability was apparent. No correlation was found between TAM content and tumor growth rate or metastatic spread. TAM from the NFSA sarcoma (a tumor with a low TD50 value, almost without necrosis, and poorly responsive to radiation) stimulated the in vitro growth of NFSA tumor cells. These observations suggest that high TAM content could be conductive to tumor cell proliferation and could be a factor in poor tumor radioresponse.

Animals↗

PubMed1987

Enhancement of lung colony formation by admixing irradiated with viable tumor cells: dependence on host status.

The study was designed to determine whether whole-body irradiation or stimulation of the reticuloendothelial system of mice influences the ability of heavily irradiated tumor cells to enhance formation of artificial metastases when given simultaneously with viable tumor cells. Experiments were performed with a nonimmunogenic sarcoma syngeneic to C3Hf/Kam mice. Whole-body irradiation augmented and stimulation of the reticuloendothelial system abolished the metastasis-enhancing effect of tumor cells. Another observation was that heavily irradiated tumor cells can enhance formation of metastases if given i.v. within several hours before or after i.v. injection of tumor cells.

Animals↗

PubMed1987

Inhibition of human neutrophil phagocytosis and intracellular killing of yeast cells by fluoride.

These processes depend upon the catabolism of glucose, which can be inhibited by fluoride (F-). We studied them with a radiolabelling technique using [3H]-uridine, which is incorporated into viable yeast cells, but hardly at all into neutrophils and dead or phagocytosed yeast cells. Lysis of neutrophils and treatment of the lysate with [3H]-uridine allowed estimation of intracellular killing of yeast cells. F- inhibited neutrophil phagocytosis and intracellular killing in a dose-related manner. Intracellular killing was significantly more sensitive to environmental F- than was phagocytosis. This effect on phagocytosis was not because of inhibition of opsonization of yeast, nor was it related to an effect on medium Ca2+.

Candida↗

PubMed1987

The tumor bed effect: dependence of tumor take, growth rate, and metastasis on the time interval between irradiation and tumor cell transplantation.

Experiments were designed to investigate the influence of time interval between leg irradiation and tumor cell transplantation on 3 different aspects of the tumor bed effect (TBE): tumor take, growth rate, and metastasis formation. MCA-4 tumor cells were injected subcutaneously into the legs of syngeneic C3Hf/Kam mice that had been locally irradiated with 30 Gy gamma rays 1, 50, 100, or 200 days previously. Interim TD50 values were higher in the day 1, 50, and 100 preirradiated mice than in controls for about 100 days after tumor cell transplantation. However, the final TD50 values determined 220 days after cell transplantation were marginally lower than controls in the day 1, and 50 preirradiated groups. TD50 values in the day 200 preirradiated group were similar to those of controls at all times after tumor cell injection. Retardation of tumor growth rate was observed in all preirradiated groups, but with a progressive decrease in effect as the time between irradiation and tumor cell injection was increased. In the day 200 preirradiated group it was noted that the degree of tumor growth rate retardation decreased as the number of injected tumor cells was increased. The incidence of lung metastases when the "primary" tumor reached a size of 20 mm was higher than in controls in mice irradiated 1, 50, and 100 days before tumor cell injection, but not in the 200-day preirradiated group. Thus, in this tumor system TBE influences tumor take, growth rate, and lung metastasis formation differently; but for all parameters, the effect decayed with increasing time between irradiation and tumor cell transplantation.

Animals↗

PubMed1987

Leg contracture in mice after single and multifractionated 137Cs exposure.

This is a report of studies of time-dose relationships for post-irradiation leg contractures in mice. The isoeffect doses for various degrees of contracture, measured 250 days after irradiation, increased with the number of fractions, but not with the overall treatment times, throughout 30 days. The isoeffect curves relating the total doses for given levels of responses to the doses per fraction were steeper for leg contractures than for acute skin reactions. The alpha/beta ratios ranged from 1.4 to 5.0 Gy, depending on the degrees of contracture. They were less than the 7.5 to 50 Gy for acute skin reactions as determined in previous experiments using the same animals and irradiation systems. Thus, the data resembled those from other slowly-responding normal tissues such as the spinal cord, kidney and lung. The leg contracture consisted of dermatogenic, myogenic, and arthrogenic components; after the mice were sacrificed there was residual contracture following removal of the skin and muscle. Inhibition of bone growth accounted for only a small proportion of the contracture. The overall response reflected responses of several tissue types.

Animals↗

PubMed1987

Modification of tumor and normal tissue radioresponse in mice by N-methylformamide.

The effects of the differentiation-inducing agent N-methylformamide (NMF) on the in vivo response of the murine tumor FSA and its pulmonary metastases to ionizing radiation were investigated. In addition, the radioresponse of acutely responding normal tissues was determined in mice receiving systemic NMF. A dosage of 300 mg/kg administered for 8 days had little effect on the FSA tumor growth, yet enhanced the growth inhibitory actions of ionizing radiation with dose enhancement factors ranging from 1.5 to 1.7. Administration of NMF also enhanced the radiation response of FSA micrometastases. The response to irradiation of hematopoietic tissue, jejunum, and testes in mice receiving NMF was also investigated. NMF administered before or before and after radiation enhanced the formation of endogenous spleen colonies, yet did not influence the LD50/30 for radiation. Jejunal crypt cell survival after radiation was slightly increased in mice receiving NMF, but the survival of spermatogonia after radiation was not affected. These data indicate that NMF administration results in an increase in the radiosensitivity of the FSA tumor and its metastases with no concomitant increase in the radiation response of the normal tissue tested. Thus, at least in this model system, a therapeutic gain is achieved through the combination of NMF and ionizing radiation.

Animals↗

PubMed1987

Linkage of the scrapie-associated fibril protein (PrP) gene and Sinc using congenic mice and restriction fragment length polymorphism analysis.

Sinc, with two alleles p7 and s7, is the major gene determining the incubation period of all strains of scrapie in mice. The major protein (PrP) of scrapie-associated fibrils is encoded by a cellular gene and we have used a cDNA copy of the hamster PrP mRNA to carry out restriction fragment length polymorphism (RFLP) analysis of different inbred mouse strains including VM(Sincp7) and VM(Sincs7) congenic mice. In VM(Sincp7) mice, a 5.5 kb XbaI fragment hybridized to the PrP cDNA sequence whereas VM(Sincs7) congenic mice had a 3.8 kb XbaI fragment. The VM X VM(Sincs7) congenic F1 mice had both the 5.5 kb and the 3.8 kb fragments. The Sincs7 donor mouse strain, C57BL, had the 3.8 kb fragment suggesting that the Sinc gene and the gene coding for PrP are linked, and could even be the same gene. Other Sincp7 inbred mice (IM and MB) had the 5.5 kb fragment but so too did some Sincs7 strains (RIII and VL), implying that the XbaI site polymorphism is not functionally involved in the difference between the two Sinc alleles. We have mapped the polymorphic XbaI site to the 3' flanking region of the PrP gene. TaqI and HhaI were also found to show polymorphisms in the inbred mouse strains studied. The apparent RFLP with HhaI may be a result of differences in methylation rather than in sequence.

Animals↗

PubMed1987

The expression of HLA-DR on keratinocytes in oral lichen planus.

HLA-DR is a Class II histocompatibility antigen which has recently been reported to occur in increased amounts in dermal and oral lichen planus. Its expression in epithelium was previously thought to be limited to Langerhans cells. In this study, formalin-fixed sections of oral lichen planus and a variety of other oral mucosal lesions were stained with a monoclonal antibody to HLA-DR using an indirect immunofluorescence test. The expression of HLA-DR by keratinocytes did not appear to be a specific marker for lichen planus as demonstrated by the reactivity of the epithelium in a variety of lesions of the oral mucosa. If HLA-DR expression is considered to be an inducible function, perhaps in response to gamma interferon secreted by activated lymphocytes, then keratinocyte reactivity would not be expected to occur only in lichen planus.

Fluorescent Antibody Technique↗