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Biomedical subjects

D Smith

Publications and source records attributed to D Smith.

At least 595 records · Page 33Linked to original sources
PubMed1995

Inflammatory leukocytic recruitment and diffuse neuronal degeneration are separate pathological processes resulting from traumatic brain injury.

The present study characterized whether inflammatory leukocytic infiltration is temporally and regionally correlated with neuronal degeneration and/or blood brain barrier (BBB) breakdown resulting from traumatic brain injury. Adult rats were sacrificed at 5 min, 2, 4, 12, 24, and 72 hr after lateral fluid percussion brain injury. BBB breakdown, neuronal degeneration and leukocyte infiltration were assessed using immunocytochemistry, silver impregnation and toluidine blue and eosin staining. BBB breakdown and neuronal degeneration occurred concomitantly in injured cortex, hippocampus, and along the dorsolateral quadrant of the diencephalon. However, neuronal degeneration within deep diencephalic structures transpired in the absence of IgG extravasation. Neutrophils were observed only in regions exhibiting BBB damage and were first apparent in injured cortex and hippocampus between 2-12 hr posttrauma lining the vasculature and filling subarachnoid/subdural spaces. Neutrophils then migrated from damaged vasculature into traumatized cortical and hippocampal parenchyma by 24 hr after lateral fluid percussion injury. Macrophages were also observed within cortical parenchyma at 24 hr and completely filled the cortical lesion site by 72 hr after injury. Macrophages were not as abundant throughout hippocampal parenchyma and were found only in hippocampal regions exhibiting focal hemorrhage at 72 hr. Finally, neutrophils did not migrate to deep diencephalic structures that showed no BBB damage despite extensive neuronal degeneration. Indeed, lateral fluid percussion elicits inflammatory leukocytic recruitment only in regions experiencing concomitant BBB damage and neuronal degeneration. In summary, inflammatory leukocytic recruitment and diffuse neuronal degeneration are separate pathological processes resulting from traumatic brain injury.

Animals↗
PubMed1995

The composition and ultrastructure of resin tags in etched dentin.

PURPOSE: To examine in vitro the composition of resin tags in etched dentin by SEM and vital staining using Alcian Blue dye. MATERIALS AND METHODS: Bovine and human teeth were used. The dentin surface was exposed using water-irrigated #600 grit SiC paper and etched with varying dilutions of aquaeous solutions of phosphoric and maleic acid. Groups of 10 teeth per acid concentration were embedded in PMMA and Scotchbond Multi-Purpose (SMP) and cylinders of Z100 resin composite were bonded to their surfaces. These teeth were shear tested to failure and the failed surfaces subjected to SEM. Groups of three teeth per acid concentration had SMP and cylinders of Z100 bonded to their surfaces. These teeth were decalcified in concentrated HCL acid. The resultant cylinders and their attached resin tags were either subjected to SEM or stained with Alcian Blue dye. The latter specimens were embedded and prepared for light-microscopic examination. A further three human and three bovine teeth per acid concentration were etched and then prepared for SEM examination. All teeth for SEM were critical point dried. RESULTS: Resin tags were shown to consist of both resin and the glycosaminoglycans (GAG) sheath lining of the dentin tubule. As a result of the SEM observations, three mechanisms are suggested for the formation of resin tags, two of which will probably be found in vivo.

Acid Etching, Dental↗
PubMed1994

Hemoglobin stimulates mononuclear leukocytes to release interleukin-8 and tumor necrosis factor alpha.

Incubation of human mononuclear leukocytes (MNL) with human stroma-free hemolysate (SFH), purified adult hemoglobin Ao (HbAo), and oxidized HbAo (METHb) caused MNL to release compounds into the supernate that mediated neutrophil (polymorphonuclear leukocytes, PMN) chemotaxis and PMN adherence to human umbilical vein endothelial cells (HUVEC). Chemotaxis and PMN adherence to HUVEC were reduced significantly when supernates were preincubated with neutralizing antibodies to interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-alpha), respectively, suggesting that IL-8 and TNF-alpha played significant roles in mediating these activities. Greatest chemotactic activity was observed in supernates of MNL treated with HbAo; while greatest PMN/endothelial cell (EC) adherence activity was observed in supernates of MNL treated with METHb. Furthermore, PMN/EC adherence activity was a function of METHb content in each hemoglobin solution. PMN chemotaxis, PMN adherence to HUVEC, and cytokine release increased as a function of increasing incubation time. Chemotactic activity was detected in HbAo-treated and METHb-treated MNL supernates after incubation for 6 hours and was maximal by 10 hours. IL-8 was detected in both HbAo and METHb-MNL supernates by 4 hours. PMN/EC adherence activity was detected in HbAo-MNL supernates at 10 hours and in METHb-MNL supernates at 4 hours. TNF-alpha was detected in METHb and HbAo-MNL supernates at 4 and 12 hours, respectively. These results suggest that hemoglobin solutions stimulate MNL to release IL-8 and TNF-alpha in quantities sufficient to induce PMN chemotaxis and PMN adherence to HUVEC. This is a US government work. There are no restrictions on its use.

Cell Adhesion↗
PubMed1994

Interactions of peroxynitrite with human plasma and its constituents: oxidative damage and antioxidant depletion.

Endothelial cells and activated phagocytes produce both nitric oxide (.NO) and superoxide (O2.-), which react to form peroxynitrite. Peroxynitrite has been suggested to be directly cytotoxic and also to decompose into other toxic species. In order to understand the consequences of peroxynitrite generation in vivo, we examined its reaction with human blood plasma. Peroxynitrite decreased the total peroxyl-trapping capacity of plasma. In terms of specific antioxidants, addition of peroxynitrite to plasma leads to rapid oxidation of ascorbic acid, uric acid and plasma SH groups. The oxidation of plasma SH groups was enhanced in dialysed plasma and returned to control levels by the addition of physiological levels of bicarbonate. Evidence was found for formation of nitro-adducts to aromatic side chains in plasma proteins by peroxynitrite. Peroxynitrite also leads to depletion of ubiquinol and formation of traces of lipid hydroperoxides in plasma, although alpha-tocopherol levels were only slightly decreased. Peroxynitrite formation in human body fluids is likely to cause antioxidant depletion and oxidative damage.

Antioxidants↗
PubMed1994

Single-channel activity induced in mitoplasts by alkaline pH.

Exposure of patch-clamped mitoplasts to alkaline pH induces a reversible conductance increase (Antonenko, Yu. N., Kinnally, K.W. and Tedeschi, H. (1991) J. Membr. Biol. 124, 151-158) which is due to an increase in open probability of a channel activity of 15 pS and larger transitions. The present study defines in more detail some of the characteristics of the channel activity involved in this conductance increase. The results suggest the presence of two channels one slightly cation-selective of approx. 15 pS (referred to here as alkaline-induced cation-selective activity, ACA) and another slightly anion selective of approx. 45 pS (referred to as alkaline-induced anion-selective activity, AAA). The possible implication of these results in relation to other channels and the permeability transitions reported by others using mitochondrial suspensions is discussed.

4-Aminopyridine↗
PubMed1994

Detection of breast cancer micrometastases in axillary lymph nodes by using polymerase chain reaction.

Breast cancer micrometastases in axillary lymph nodes have been detected by serial sectioning and immunohistochemistry, and shown to have prognostic significance. We have used polymerase chain reaction (PCR) to see whether we could further improve the detection rate of micrometastases. Fifty-seven axillary lymph nodes from patients with breast cancer were examined histologically to assess the proportion of tumor involvement. Immunohistochemical staining with the use of an anti-keratin 19 antibody confirmed the histological findings. Reverse transcription PCR was then performed on extracted RNA by using K19 primers, and all 18 histologically involved nodes yielded the expected 460-base pair product. Of 39 histologically negative nodes, 4 (10%) gave K19 bands detectable with ethidium staining and a further 10 (28%) gave K19 bands after Southern hybridization. To further increase the detection sensitivity a two stage amplification was performed by using nested primers, and K19 product was found in lymph nodes from patients without cancer, as well as in all the nodes from cancer patients. This was shown to be genuine low level expression from endogenous mRNA template, and not derived from amplification of a K19 pseudogene. Reducing the number of PCR cycles in the two amplification steps did not allow sufficient discrimination between normal nodes and those involved nodes in which K19 expression was only detectable after Southern hybridization. The optimal "cut-off" point to distinguish involved nodes from normal nodes remained at the level of 40 cycles of PCR and Southern hybridization. PCR, using K19 as a tumor marker, has been demonstrated in this study to improve the detection of micrometastases in axillary lymph nodes in patients with breast cancer: sensitivity is limited by the specificity of the tumor marker.

Adult↗
PubMed1994

A panel of radiation hybrids for human chromosome 8.

We have developed a panel of radiation hybrids containing fragments of chromosome 8 as the only human material. The human chromosome content of each cell line was determined relative to an ordered map of sequence tagged sites (STSs) specific to chromosome 8. Between one and four fragments of chromosome 8 were identified in each cell line, with an average of 25% of the STSs retained in each line. Subclones of one radiation hybrid were examined to determine whether all cells within a line are homogeneous with respect to chromosome 8 sequence content. There was considerable variability between subclones, with retention rates for individual STSs ranging from 5 to 100% in different clones. Furthermore, a gradient of retention of sequences along the length of one large chromosome fragment was found, suggesting that sequence loss involved deletions from one end of the fragment at early stages in the establishment of the cell line. We have also made use of the radiation hybrids to develop novel sequence tagged sites for the pericentromeric region of chromosome 8.

Adenine Phosphoribosyltransferase↗
PubMed1994

Folate-deficiency-induced homocysteinaemia in rats: disruption of S-adenosylmethionine's co-ordinate regulation of homocysteine metabolism.

In a recent hypothesis [Selhub and Miller (1992) Am. J. Clin. Nutr. 55, 131-138], we proposed that homocysteinaemia arises from an interruption in S-adenosylmethionine's (AdoMet) coordinate regulation of homocysteine metabolism. The present study was undertaken to test a prediction of this hypothesis, that homocysteinaemia due to folate deficiency results from impaired homocysteine remethylation due to the deficiency and impaired synthesis of AdoMet, with the consequent inability of this metabolite to function as an activator of homocysteine catabolism through cystathionine synthesis. Rats were made folate-deficient by feeding them with a folate-free amino-acid-defined diet supplemented with succinylsulphathiazole. After 4 weeks, the deficient rats exhibited a 9.8-fold higher mean plasma homocysteine concentration and a 3.2-fold lower mean hepatic AdoMet concentration compared with folate-replete controls. Subsequent supplementation for 3 weeks of the folate-deficient rats with increasing levels of folate in the diet resulted in graded decreases in plasma homocysteine levels, accompanied by graded increases in hepatic AdoMet levels. Thus plasma homocysteine and hepatic AdoMet concentrations were inversely correlated as folate status was modified. In a second experiment, the elevation of plasma homocysteine in the deficient rats was found to be reversible within 3 days by intraperitoneal injections of ethionine. This effect of ethionine is thought to be exerted through S-adenosylethionine, which is formed in the liver of these rats. Like AdoMet, S-adenosylethionine is an activator of cystathionine beta-synthase and will effectively promote the catabolism of homocysteine through cystathionine synthesis. In crude liver homogenates of the rats treated with ethionine, cystathionine beta-synthase activity was 3-fold higher than that measured in homogenates from vehicle-treated controls.

Animals↗
PubMed1994

Evaluation of three new hydrocolloid dressings: retention of dressing integrity and biodegradability of absorbent components attenuate inflammation.

Residues from hydrocolloid dressings (HCDs) that originate from matrix disintegration and nonbiodegradability of the absorbent components, may cause deep-seated, unresolved inflammation in tissue that appears otherwise healed. The purpose of this study was to evaluate three new HCDs that were formulated with the goal of attenuating the inflammatory responses that may arise from HCD therapy. Two of the HCDs (A-106 and A-107) consisted of conventional absorbents dispersed in a new maceration-resistant adhesive matrix. The same matrix, mixed with potentially biodegradable dextran microspheres, formed the third dressing (Dextran Bead Dressing [DBD]). In this pilot scale study these novel dressings were evaluated on full-thickness dermal wounds on swine. Restore (Hollister) and DuoDERM CGF (Convatec) dressings were used as controls. Wound healing was evaluated histomorphometrically. Pertinent histologic parameters were ranked from wound tissue that was harvested 18 days after wounding. Grossly visible dressing disintegration ranged from minimal (DBD) to severe (Restore). Disintegration of other dressings was moderate. The percentage of tissue sections exhibiting giant cells reflected, in parallel, the observed extent of dressing disintegration. Thirty-eight percent of wounds dressed with DBD contained giant cells; 74 and 100% of wounds treated with DuoDERM CGF and Restore, respectively, contained giant cells. DBD-dressed wounds had relatively fewer chronic inflammatory cells than other dressings. These wounds were also characterized by a well-organized collagen matrix and complete reepithelialization. The extent of wound closures was similar for all dressing types except Restore. Closure of Restore-dressed wounds was delayed compared with closure with DBD and DuoDERM CGF on all days of evaluation except one. A-106 and A-107 were comparable to DuoDERM CGF in retention of dressing integrity and the elicited inflammatory tissue response. The DBD dressing appears to possess equivalent properties of typical HCDs while causing minimal tissue reactions.

Absorption↗
PubMed1994

Merkel cell carcinoma: an aggressive skin neoplasm.

Merkel cell carcinoma (MCC) is an aggressive skin neoplasm of neuroendocrine origin. To clarify those factors important in improving survival, we retrospectively reviewed the charts of all patients with Merkel cell carcinoma treated at two tertiary referral centers. Eighty percent of the patients with stage I disease were initially treated with local therapy alone, while all of the patients with stage II disease were treated with local and regional therapy. The overall survival rate for all patients was 64%. Regardless of stage, patients treated with local excision alone had a 52% 5-year survival rate, while patients treated with local excision and lymph node dissection had an 87% survival rate. We conclude that the aggressive nature of this tumor warrants radical therapy.

Adult↗
PubMed1994

Value of maternal serum unconjugated oestriol measurement in prenatal screening for Down's syndrome.

We compared the medical and financial cost-effectiveness of prenatal serum screening for Down's syndrome using maternal age, serum alpha-fetoprotein and human chorionic gonadotrophin with and without the use of unconjugated oestriol. The use of unconjugated oestriol is medically more cost-effective than screening without it at all levels of detection. The actual performance depends on whether gestational age is estimated using 'dates' or an ultrasound scan. At a detection rate of 60 per cent, the proportion of unaffected fetal losses per case diagnosed at amniocentesis is about 22 per cent less if gestational age is estimated using dates (time since the first day of the last menstrual period) and about 47 per cent less if it is based on an ultrasound scan examination. At this detection rate, the inclusion of unconjugated oestriol increases costs by about 2k pounds per case diagnosed (36k pounds instead of 34k pounds) if gestational age is estimated using dates, but it is no more expensive if gestational age is measured from an ultrasound scan examination (indeed, it is more cost-effective at detection rates above 60 per cent). Since there is little change in the financial cost with the inclusion of unconjugated oestriol, for the improved medical performance of screening, it is worthwhile including it in the screening test.

Amniocentesis↗
PubMed1994

Four-marker serum screening for Down's syndrome.

The value of measuring the separate sub-units of human chorionic gonadotrophin (free alpha-hCG and free beta-hCG) instead of total hCG together with alpha-fetoprotein (AFP) and unconjugated oestriol (uE3) was examined to determine the effect on the performance of serum screening for Down's syndrome between 15 and 22 weeks of pregnancy. The study was based on stored serum samples relating to 75 singleton pregnancies with fetal Down's syndrome and 367 unaffected singleton pregnancies, matched for maternal age, gestational age, and duration of storage of the serum sample, supplemented by data from 970 white women with unaffected pregnancies. Using the four serum markers AFP, uE3, free beta-hCG, and free alpha-hCG, in addition to maternal age, 65 per cent of Down's syndrome pregnancies were detected for a 5 per cent false-positive rate compared with 59 per cent with the conventional triple test (AFP, uE3, total hCG with maternal age). If gestation was based on an ultrasound scan examination, the detection rate was 72 per cent using the four serum markers compared with 67 per cent with the triple test. As an alternative illustration, if the detection rate was kept at 60 per cent and gestation was estimated by an ultrasound scan examination the four-marker test reduced the false-positive rate by one-third from 3 per cent using the triple test to 2 per cent with the four-marker test. Screening performance was hardly affected by adjusting marker levels for maternal weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers↗
PubMed1994

Role of neutrophils in breakdown of the blood-retinal barrier following intravitreal injection of platelet-activating factor.

Breakdown of the blood-retinal barrier occurs in inflammatory conditions and in ischemic retinal diseases such as diabetic retinopathy. Platelet-activating factor (PAF) is a potent inflammatory mediator which increases vascular permeability. The purpose of this study was to determine if intravitreally-injected PAF would cause breakdown of the blood-retinal barrier and, if so, by what mechanism. Fluorescein angiography was performed before and at 0.5, 1, 2, 3 and 4 hr after PAF injection into the vitreous cavity of rabbit eyes and the eyes were enucleated immediately for light and electron microscopy. Slow flowing thrombi were observed in all PAF-injected eyes. Complete vascular occlusion was observed in 10 of 16 eyes after 3 and 4 hr. There was no fluorescein leakage in any of eyes before or at 0.5 or 1 hr after PAF injection. Fourteen of 20 eyes had fluorescein leakage at 2, 3 and 4 hr after PAF injection. The extent of fluorescein leakage correlated with the degree of polymorphonuclear leukocyte (PMN) margination, disruption of the endothelial cell layer, infiltration into vascular walls and migration into the vitreous cavity. PMNs appeared to migrate by both intercellular and transcellular routes across the endothelium. Pretreatment of rabbits with a PAF inhibitor, BN52021, prevented most of the abnormal findings.

Animals↗