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Biomedical subjects

R Pace

Publications and source records attributed to R Pace.

At least 19 recordsLinked to original sources
PubMed1992

[A scanning electron microscope assessment of the changes induced by wear on subsonic endodontic instruments].

The aim of the present work was to study the wear of a special kind of subsonic instruments with usage. We have examined with scanning electron microscope new and used instruments: the first to estimate the features and degree of final touches; the second to examine how they wear after 1, 3 and 5 minutes. We tested for each period 3 instruments per size. In all we controlled 72 instruments. The results of the study show that after 5 minutes the instruments are very worn.

Materials Testing↗
PubMed1992

[Preliminary research on the prognosis of late reimplants with prior conditioning with a fluoridated solution].

The principal factors that affect the prognosis of a posttraumatic reimplantation are the length of the extra-alveolar persistence and the manner in which the extracted tooth is preserved. Both are fundamental for the maintenance of the fiber vitality of the periodontal ligament. The necrosis of these fibers cause ankylosis. It is observed that the conditioning of the radicular surface with fluoride solutions before the reimplantation is likely to slow down the evolution of radicular resorption. To evaluate the effectiveness of such methodology six cases of traumatic extractions, characterized by a length of extra-alveolar persistency (not longer than 24 hours), and unfavorable conditions of the preserved tooth have been treated by conditioning the radicular surface with the Na-fluoride solution before the reimplantation. Another group of reimplantation cases with the same characteristics have been examined without proceeding first to the radicular conditioning. The results of the study, although preliminary, verified the positive influence of the Na fluoride upon the radicular resorption.

Follow-Up Studies↗
PubMed1991

Methods for analysis of multiple cystic fibrosis mutations.

A large number of mutations causing cystic fibrosis (CF) have been reported. In an attempt to improve methods for genetic diagnosis and for heterozygote screening, we evaluated methods for efficient analysis of the delta F508, G542X, G551D, R553X, and N1303K mutations. We found that multiple mutations can be analyzed simultaneously using hybridization with allele-specific oligonucleotides. Alternatively all of these mutations can be detected by amplification of DNA followed by restriction enzyme digestion and analysis on polyacrylamide gels. A previously reported method for use of modified primers for DNA amplification to allow detection of virtually any single-base change by restriction enzyme analysis proved particularly useful. The common delta F508 mutation and three mutations in exon 11 were analyzed using a multiplex amplification reaction followed by double digestion with restriction enzymes and electrophoresis in a single lane on a polyacrylamide gel. In a sample of 439 CF chromosomes from North American Caucasians, the frequencies of various mutations were as follows: delta F508 = 75.8%, G542X = 2.7%, G551D = 3.2%, R553X = 1.4%, and N1303K = 1.4% for a total of 84.5% detection of CF chromosomes by analysis for these five mutations.

Base Sequence↗
PubMed1990

Visual and neural function in Leber's optic neuropathy.

This report details the chronology of vision loss for an 18-year-old Caucasian male with Leber's optic neuropathy. Findings of an oculo-visual assessment with auxiliary in-office tests of visual neural function, results of neurophysiological testing, and rehabilitative therapy with low vision aids are presented. The clinical characteristics of this devastating disorder are reviewed.

Adolescent↗
PubMed1990

HLA-DR RFLP distributions in two groups of aboriginal Australians.

HLA-DR and -DQ typing by restriction fragment length polymorphism (RFLP) in Aboriginal Australians from the Kimberleys and from Coen shows a restricted number of HLA-DR types in these populations. The polymorphism is essentially limited to DR2, DR4, DRw14 and DRw8. The most common DR.DQ RFLP haplotype in Aborigines shows a novel arrangement of DR and DQ alleles that has important implications for histocompatibility matching if the RFLP patterns reflect functional variation in HLA class II molecules.

Australia↗
PubMed1990

Plexiform neurofibroma: report of an unusual presentation.

We describe a plexiform neurofibroma discovered incidentally in a patient who was involved in a motor vehicle accident. The lesion simulated a subcapsular liver hematoma or diaphragmatic rupture on sonography, computed tomography and angiography.

Adult↗
PubMed1989

Immune restoration with interleukin-2 in patients with squamous cell carcinoma of the head and neck.

Patients with head and neck squamous cell carcinoma commonly have depressed cell-mediated immunity which is known to correlate with ultimate prognosis. Selective immune studies were conducted in 27 head and neck cancer patients to determine the potential of interleukin-2 as an immune restorative agent. Patients showed the expected depression of lymphocyte proliferation to phytohemagglutinin and had borderline depressed natural killer cell activity and relatively normal interleukin-2 production. Addition of interleukin-2 at 100 units/ml markedly enhanced natural killer cell activity to normal levels. Serum from head and neck patients was also immune-suppressive. Heat-inactivated serum depressed lymphocyte proliferation and natural killer cell activity of control leukocytes. Lymphocyte incubation with interleukin-2 significantly counteracted immune suppressive serum effects and restored depressed lymphocyte function to normal levels. The effective in vitro interleukin-2 dose is potentially achievable by infusion at approximate doses of 3 X 10(6) units/M2.

Adult↗
PubMed1989

Bile duct carcinoma and biliary tract dysplasia in chronic ulcerative colitis.

A case of chronic ulcerative colitis with a moderately differentiated adenocarcinoma of the common hepatic duct is described. Throughout the entire biliary tree, there was extensive epithelial dysplasia associated with changes of primary sclerosing cholangitis. The development of primary sclerosing cholangitis in the biliary tract of patients with ulcerative colitis appears to precede dysplasia and may be a marker of patients at risk for developing biliary tract carcinomas.

Adenocarcinoma↗
PubMed1989

The influence of the surgical wound on local tumor recurrence.

Failure of a primary surgical treatment for cancer is often caused by recurrence of the tumor at the surgical site. The KHT mouse tumor system recapitulates this experience and provides a useful model to test strategies for reducing the incidence of local recurrence after surgical excision. There was an 82% local recurrence of the KHT tumor after surgery. A cell dilution assay indicated that it would require only 39 tumor cells injected into the wound site to result in the same (82%) incidence of tumors. This figure is in contrast to 340 cells required when the cells were injected into an unwounded flank. With the B16 melanoma in C57B1 mice and the Meth A sarcoma in BALB/c mice, the number of cells necessary to induce a tumor (TD/50) was also significantly reduced when the cells were injected into a surgical wound rather than into nonwounded tissue. The difference in cell number was interpreted as the result of the presence of growth factors derived from the traumatized tissue and the inflammatory cells at the wound site. Neither a 5 nor a 15 Gy dose of x-radiation delivered to the wound site immediately after surgical excision of the KHT tumor resulted in a significant reduction in the incidence of local recurrences. When the same doses of x-radiation were given immediately after injecting 36 KHT cells into a wound, no tumors developed. This difference was believed to have resulted from the hypoxic condition in the wound site and the presence of residual clonogenic tumor cells in a nonproliferating (radioresistant) state.

Animals↗
PubMed1986

Production of and response to interleukin-2 in peripheral blood lymphocytes of cancer patients.

Interleukin-2 (IL2) is essential for the expansion of antigen-triggered lymphocytes and cytotoxic T-cells, processes necessary for tumor control that are frequently depressed in malignancy. The authors measured certain aspects of IL2 function in cancer patients and controls and correlated the findings with the general immune response as indicated by the proliferative response to phytohemagglutinin (PHA) in peripheral blood lymphocytes (PBL). The major questions focused on the capacity of PBL to produce IL2, the correlation of this with the proliferative response to PHA, and whether exogenous IL2 could restore T-cell responses and natural killer cell activity in immunodepressed cancer patients. IL2 production was measured by the 3H-thymidine-labeled CT6 assay on the supernatants of the PBL of cancer patients and normal controls after 24 hours of stimulation with PHA. There were 115 cancer patients (70 head and neck, 13 melanoma, 12 breast, 10 colorectal, and 6 other) and 52 controls. IL2 production was essentially normal in the head and neck cancer patients as a group, although their PHA response was depressed. The mean IL2 generated per 3 X 10(6) PBL over 24 hours were 129 mu/ml in the head and neck patients and 132 mu/ml in the breast patients, similar to the 129 mu/ml generated in the controls. There was modest but not significant depression in the melanoma (78 mu/ml) and colorectal cancer patients (81 mu/ml). Although subsets of patients showed depressed IL2 production, there was no significant correlation of IL2 production with the PHA response. Depressed IL2 production showed only limited correlation with depressed lymphocyte responses (r = -0.25), which suggested a dissociation of these functions. Of interest was the finding that indomethacin did augment IL2 production in both cancer patients and controls, suggesting that prostaglandin-mediated regulation is involved. Addition of exogenous IL2 of recombinant origin (Biogen) produced significant augmentation in more than three fourths of the cancer patients and controls. Adding indomethacin further increased this response. Addition of IL2 also significantly increased natural killer activity in both groups. It was concluded that PBL in cancer patients generally have a normal capacity to generate IL2, and this capacity is not related to the proliferative response, which is frequently depressed in these patients. Exogenous IL2 can significantly augment lymphoproliferative and natural killer responses in cancer patients, suggesting that there is merit in exploring the potential therapeutic role of IL2 in these patients.

Adult↗
PubMed1986

Major operative trauma increases peripheral amino acid release during the steady-state infusion of total parenteral nutrition in man.

The effect of major operative trauma on skeletal muscle metabolism was examined in nine patients receiving a constant infusion of calories (1460 kcal/m2/day) and protein (75 gm of amino acids/m2/day) for 5 days before and 4 days after an operation. Compared with the preoperative state, 72 hours after the operation there was a significant rise in arterial levels of glucagon, cortisol, norepinephrine, and inactive triiodothyronine and a drop in concentrations of insulin, active triiodothyronine, and amino acids. Forearm blood flow increased, as well as the efflux from forearm muscle of lactate, taurine, serine, glycine, valine, methionine, isoleucine, leucine, phenylalanine, lysine, arginine, and total amino acid nitrogen (440%). This loss of muscle protein after trauma is associated with increased muscle proteolysis, as measured by increased urinary 3-methylhistidine excretion (83%), and accounts for increased nitrogen loss (54%) from the body. Increased activity of the sympathetic nervous system is manifested by increased levels of epinephrine and norepinephrine, a relative lack of insulin, and increased levels of glucagon. This hormonal milieu plays an important role in the production of hypoaminoacidemia, increased efflux of amino acids and lactate from muscle, and negative nitrogen balance observed in these traumatized patients.

Aged↗
PubMed1986

Insulin decreases muscle protein loss after operative trauma in man.

Seventy-two hours after major operative trauma, nine patients receiving a constant infusion of calories (1460 kcal/m2/day) and protein (75 gm of amino acid/m2/day) showed a negative nitrogen balance, increased muscle catabolism, as measured by 3-methylhistidine excretion, increased amino acid efflux from muscle, and decreased circulating levels of insulin. When 5 U of insulin/hr were added to the infusate, arterial insulin levels rose significantly from 39.7 +/- 4.1 microU/ml to approximately the pretrauma levels (74.6 +/- 7.7 microU/ml). Despite this normalization of insulin levels, excretion of nitrogen and 3-methylhistidine and the efflux of amino acids from forearm muscle fell but did not return to pretraumatic levels, suggesting some insulin resistance. Visceral gluconeogenesis from amino acids appeared to decrease, since insulin infusion decreased the efflux of alanine from skeletal muscle with no change in its arterial level. Insulin also significantly reduced the efflux of isoleucine, tyrosine, phenylalanine, glutamine, and total amino acid nitrogen from forearm muscle. These findings, along with the partial reduction in the excretion of 3-methylhistidine and nitrogen, suggest that insulin, in combination with infused calories and protein, decreases the loss of muscle protein after trauma.

Aged↗
PubMed1985

Interleukin-2 production in head and neck cancer patients.

Interleukin-2, a lymphocyte-produced hormone or lymphokine, is required to support proliferation of antigen-triggered T lymphocytes and cytotoxic T cells that are considered essential elements for host tumor control. We have addressed the question of whether interleukin-2 production is altered in head and neck cancer patients, a group that is frequently immunosuppressed. Interleukin-2 production was measured by the tritium-labeled thymidine CT6 assay on the supernatants of peripheral blood lymphocytes of head and neck cancer patients and controls after 24 hour stimulation with phytohemagglutinin. The mean levels of interleukin-2 produced were 127 units (range 3 to 336 units) in the head and neck cancer patients versus 125 units (range 26 to 307 units) in the control group (not statistically significant). There were no significant differences in mean interleukin-2 values between cancer patients with stages I and II or III and IV disease compared with the control subjects. Twenty-seven percent of the cancer patients had interleukin-2 levels below the 10th percentile cutoff point (p = 0.015). The lymphocyte proliferative response to phytohemagglutinin was significantly depressed in the head and neck cancer patients compared with the control subjects. This did not correlate with interleukin-2 production abnormalities, except in patients with advanced disease, in whom there was a borderline correlation between phytohemagglutinin response and interleukin-2 production (correlation coefficient 0.23, p = 0.05). We conclude that the commonly observed depressed T-cell proliferative response to phytohemagglutinin in head and neck cancer patients is not explained by impaired interleukin-2 production.

Adult↗