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Biomedical subjects

L M Smith

Publications and source records attributed to L M Smith.

At least 163 records · Page 9Linked to original sources
PubMed1990

High-speed separations of DNA sequencing reactions by capillary electrophoresis.

Fluorescently labeled DNA fragments generated in enzymatic sequencing reactions are rapidly separated by capillary gel electrophoresis and detected at attomole levels within the gel-filled capillary. The application of this technology to automated DNA sequence analysis may permit the development of a second generation automated sequencer capable of efficient and cost-effective sequence analysis on the genomic scale.

Base Sequence↗
PubMed1990

Conjunctival allergen challenge. A clinical approach to studying allergic conjunctivitis.

To evaluate antiallergic agents, we conducted five allergen challenge studies of increasing refinement. The final study design that evolved included two baseline visits, when skin test-positive subjects were administered a bilateral ocular allergen challenge. At the first visit, the threshold dose of reactivity was determined by increasing allergen doses at 10-minute intervals. At the second baseline visit, 3 days later, the responsive subjects were challenged with the final, highest dose used on visit 1 to assure that the allergic reaction was reproducible and not a cumulative effect of multiple allergen doses. The responsive subjects then returned 3 days later for the drug efficacy evaluation. After a slit-lamp examination, subjects were pretreated with the test drug in one eye and the placebo in the fellow eye in a randomized, double-masked fashion. After 10 minutes, subjects were challenged bilaterally with the allergen dose identified on the previous visits. Postchallenge evaluations of hyperemia, itching, chemosis, eyelid swelling, and tearing were performed at 3, 10, and 20 minutes. Subjects were rechallenged 4 hours after drug administration to assess duration of action. Slit-lamp examinations were again performed at the same intervals as after the initial challenge. A total of 396 subjects were given a baseline allergen challenge; 83.6% responded with a moderate (2+) ocular allergic reaction. Of the 266 given a second baseline challenge, 87.2% responded positively again, suggesting that ocular challenge was highly correlated with skin reactivity and reproducible with a second challenge. No statistically significant difference in redness and itching was found when both eyes were challenged with the same dose of allergen.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Effects of Vasocon-A in the allergen challenge model of acute allergic conjunctivitis.

The ophthalmic combination product of 0.05% naphazoline hydrochloride and 0.5% antazoline phosphate (Vasocon-A) was evaluated as an antiallergic agent in 100 subjects with a known allergic history to cat dander, ragweed, or bluegrass pollen. Three independent study sites were used. The allergen challenge model of acute allergic conjunctivitis was selected to assess the agent as it provided a standardized and precise way to measure drug effectiveness for this indication. In a double-masked randomized fashion, the subjects were assigned to one of three groups that received one drop of Vasocon-A in one eye and one drop of either 0.05% naphazoline (group 1), 0.5% antazoline (group 2), or placebo (group 3) in the contralateral eye. After 10 minutes, the dose of allergen shown to elicit a 2+ redness and itching reaction was instilled bilaterally. Signs and symptoms of allergic conjunctivitis were evaluated after 3, 5, and 10 minutes. Subjects were then rechallenged 2 hours after drug administration to assess the duration of action of the agents. Vasocon-A was found to significantly inhibit all five major signs and symptoms of allergic conjunctivitis: itching, redness, chemosis, lid swelling, and tearing, for more than 85% of the comparisons when compared over time with placebo, naphazoline alone, or antazoline alone. The results of this study indicate that the combination of naphazoline and antazoline was more effective in inhibiting redness than naphazoline and more effective in inhibiting itching than antazoline. These findings support the use of such a combination for the treatment of allergic conjunctivitis.

Allergens↗
PubMed1990

Developmental regulation of expression of the malate synthase gene in transgenic plants.

The cucumber malate synthase (MS) gene, including 1856 bp of 5' non-transcribed sequence, has been transferred into Petunia (Mitchell) and Nicotiana plumbaginifolia plants using an Agrobacterium binary vector. The transferred gene is found in variable copy number in different transformants, and is stably transmitted in each case as a single Mendelian character. Transgene mRNA accumulates in the seedling during the first three days of germination, then declines in amount as the cotyledons emerge from the seed. The decline is more pronounced in light-grown seedlings than in dark-grown seedlings. Expression of the MS transgene is also detected at a low level in petals of transformed Petunia plants. In these respects the pattern of MS gene expression is similar in cucumber and in transformed plants, showing that the transferred DNA fragment contains a functional MS gene. A 1076 bp fragment of 5' sequence was linked to the beta-glucuronidase reporter gene and transferred into Nicotiana, where it was shown to direct temporal and spatial patterns of expression similar to that of the complete MS gene. However, histochemical localisation of beta-glucuronidase activity demonstrated that the chimaeric gene is expressed not only in cotyledons of transgenic plants, but also in endosperm and some hypocotyl cells during early germination. The relevance of these findings to the control of malate synthase gene expression is discussed.

Base Sequence↗
PubMed1990

Magnesium transport in ferret red cells.

1. Mg2+ efflux from ferret red cells into a nominally Mg2(+)-free medium is 41 +/- 2 mumol (l cell)-1 h-1. The properties of Mg2+ transport can be measured in these cells without the need for Mg2+ loading. 2. Amiloride, quinidine, imipramine and external divalent cations partially inhibit Mg2+ efflux. Maximal inhibition by these agents is about 60-70% suggesting that at least two Mg2+ transport pathways exist. 3. As external Na+ is replaced by choline or N-methyl-D-glucamine Mg2+ efflux is first stimulated, reaching a peak when external [Na+] ([Na+]o) is about 10 mM, and then inhibited. Mg2+ transport reverses direction so net Mg2+ uptake occurs when [Na+]o is reduced below 1 mM. 4. Mg2+ efflux is stimulated when 0.1 mM-EDTA is added to the medium only when [Na+]o is low. 5. Reduction of cell ATP content to about 20 mumol (l cell)-1 by treating cells with 2-deoxyglucose stimulates Mg2+ efflux measured over the 2 h period following depletion. 6. Substantial Mg2+ influx can be observed in ferret red cells when they are incubated in media containing 10 mM-Mg2+. Influx is stimulated by reducing [Na+]o to 10 mM. Further reduction of [Na+]o to below 1 mM reduces Mg2+ uptake. A component of uptake is inhibited by external Co2+. 7. Na(+)-Mg2+ antiport may account for a substantial component of Mg2+ transport in ferret red cells. The direction of transport can be reversed by sufficiently lowering [Na+]o or by increasing external [Mg2+]. Analysis of the conditions at which transport reverses direction suggests transport with a stoichiometry of 1 Na+:1 Mg2+. Antiport with this stoichiometry would also explain maintenance of the physiological level of intracellular ionized Mg2+ in these cells.

Amiloride↗
PubMed1990

Acoustic cues for consonant identification by patients who use the Ineraid cochlear implant.

Ten patients who use the Ineraid cochlear implant were tested on a consonant identification task. The stimuli were 16 consonants in the "aCa" environment. The patients who scored greater than 60 percent correct were found to have high feature information scores for amplitude envelope features and for features requiring the detection of high-frequency energy. The patients who scored less than 60 percent correct exhibited lower scores for all features of the signal. The difference in performance between the two groups of patients may be due, at least in part, to differences in the detection or resolution of high-frequency components in the speech signal.

Adult↗
PubMed1990

An automated instrument for the performance of enzymatic DNA sequencing reactions.

An instrument has been developed for the automation of enzymatic DNA sequencing reactions. Up to 96 DNA templates contained in a microtiter plate can be processed for either radioactive or fluorescence-based sequence analysis in a three-hour period. The quality of the resultant data is comparable to that obtained manually. The system is simple, flexible and is readily adapted to the use of new polymerases or modified experimental protocols.

Automation↗
PubMed1989

Unfractionated heparin inhibits thrombin-catalysed amplification reactions of coagulation more efficiently than those catalysed by factor Xa.

We have proposed previously that the steps in coagulation most sensitive to inhibition by heparin are the thrombin-dependent amplification reactions, and that prothrombinase is formed in heparinized plasma only after Factor Xa activates Factor VIII and Factor V. These propositions were based on the demonstration that both heparin and Phe-Pro-Arg-CH2Cl completely inhibited 125I-prothrombin activation for up to 60 s when contact-activated plasma (CAP) was replenished with Ca2+. Furthermore, the addition of thrombin to CAP before heparin or Phe-Pro-Arg-CH2Cl completely reversed their inhibitory effects. Additional support for the above hypotheses is provided in this study by demonstrating that, when the activity of thrombin is suppressed by heparin (indirectly) or by Phe-Pro-Arg-CH2Cl (directly), exogenous Factor Xa reverses the ability of these two agents to inhibit prothrombin activation. Prothrombin activation was initiated by adding Factor Xa (1 nM) or thrombin (1 or 10 nM) simultaneously with CaCl2 to CAP. In the absence of heparin or Phe-Pro-Arg-CH2Cl, prothrombin activation was seen 15 s later in either case. Heparin failed to delay, and Phe-Pro-Arg-CH2Cl delayed for 15 s, prothrombin activation in CAP supplemented with Factor Xa. In contrast, heparin and Phe-Pro-Arg-CH2Cl completely inhibited prothrombin activation for at least 45 s in CAP supplemented with 1 nM-thrombin. Heparin failed to delay prothrombin activation in CAP supplemented with 10 nM-thrombin, whereas Phe-Pro-Arg-CH2Cl completely inhibited prothrombin activation in this plasma for 45 s. These results suggest that in CAP: (1) Factor Xa can effectively activate Factor VIII and Factor V when the proteolytic activity of thrombin is suppressed; (2) heparin-antithrombin III is less able to inhibit Factor Xa than thrombin; (3) suppression of the thrombin-dependent amplification reactions is the primary anticoagulant effect of heparin.

Antithrombin III↗
PubMed1989

The malate synthase gene of cucumber.

The complete sequences of a full-length cDNA clone and a genomic clone encoding the Cucumis sativus glyoxysomal enzyme malate synthase, have been determined. The sequences have enabled us to identify putative control regions at the 5' end of the gene, three introns, and possible alternative polyadenylation sites at the 3' end. The deduced amino acid sequence predicts a polypeptide of 64,961 molecular weight, which has 48% identity with that of Escherichia coli. Comparison of the sequence of malate synthase from cucumber with that from E. coli and with other glyoxysomal and peroxisomal enzymes, shows that a conserved C-terminal tripeptide is a common feature of those enzymes imported into microbodies.

Amino Acid Sequence↗
PubMed1989

Microcontaminants and reproductive impairment of the Forster's tern on Green Bay, Lake Michigan--1983.

For the 1983 nesting season, Forster's tern (Sterna forsteri) reproductive success was significantly impaired on organochlorine contaminated Green Bay, Lake Michigan compared to a relatively uncontaminated inland location at Lake Poygan, Wisconsin. Compared with tern eggs from Lake Poygan, eggs from Green Bay had significantly higher median concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), other polychlorinated dibenzo-p-dioxins (PCDDs), total polychlorinated biphenyls (PCBs), total (three congeners) non-ortho, ortho' PCBs, five individual PCB congeners known to induce aryl hydrocarbon hydroxylase (AHH) and several other organochlorine contaminants. Conversions of analytical concentrations of TCDD and PCB congeners based on relative AHH induction potencies allowed for estimation of total 2,3,7,8-TCDD equivalents. Two PCB congeners, 2,3,3',4,4'- and 3,3',4,4',5-pentachlorobiphenyl (PeCB) accounted for more than 90% of the median estimated TCDD equivalents at both Green Bay and Lake Poygan. The median estimated TCDD equivalents were almost 11-fold higher in tern eggs from Green Bay than in eggs from Lake Poygan (2175 and 201 pg/g). The hatching success of Green Bay sibling eggs from nests where eggs were collected for contaminant analyses was 75% lower at Green Bay than at Lake Poygan. Hatchability of eggs taken from other nests and artificially incubated was about 50% lower for Green Bay than for Lake Poygan. Among hatchlings from laboratory incubation, those from Green Bay weighed approximately 20% less and had a mean liver weight to body weight ratio 26% greater than those from Lake Poygan. In both field and laboratory, mean minimum incubation periods were significantly longer for eggs from Green Bay compared to Lake Poygan (8.25 and 4.58 days, respectively). Mean minimum incubation time for Green Bay eggs in the field was 4.37 days longer than in the laboratory. Hatchability was greatly improved when Green Bay eggs were incubated by Lake Poygan adults in an egg-exchange experiment, but was sharply decreased in Lake Poygan eggs incubated in Green Bay nests. Nest abandonment and egg disappearance were substantial at Green Bay but nil at Lake Poygan. Thus, not only factors intrinsic to the egg, but also extrinsic factors (parental attentiveness), impaired reproductive outcome at Green Bay. The epidemiological evidence from this study strongly suggested that contaminants were a causal factor. AHH-active PCB congeners (intrinsic effects) and PCBs in general (extrinsic effects) appeared to be the only contaminants at the concentrations measured in eggs, capable of producing the effects that were observed at Green Bay.

Animals↗
PubMed1989

Results of a prospective study evaluating the effects of mantle irradiation on pulmonary function.

Thirty patients with Stages I-III Hodgkin's disease receiving mantle irradiation were prospectively evaluated prior to therapy with spirometry, lung volumes, and tests of diffusing capacity (DLCO). Follow-up examinations were performed at 3, 6, and 12 months and then yearly. Sixteen patients had Hodgkin's disease involving the mediastinum at presentation, 10 were smokers, and 16 received either preirradiation or postirradiation chemotherapy. Mantle doses ranged between 2300 cGy and 4000 cGy (mode of 3750 cGy) given at 150 cGy to 170 cGy tumor dose per day with split-course technique. Pulmonary function test results were translated to percent change from predicted values obtained from normal standards for each age, sex, race, and height. These percent changes were then analyzed as a linear function of time. Twenty patients have been tested greater than or equal to 4 years after treatment with a median time from treatment to last pulmonary function test of 8 years. Changes over time in spirometry included an early, mild decrease in both forced vital capacity (FVC) and forced expiratory volume at 1 second (FEV1), which returned to baseline by 2 years and then gradually decreased to a 10-15% deficit as compared with predicted values at 6-10 years. Additionally, there was a very slight decrease in FEV1/FVC beginning at 1 year and gradually increasing to an 8% deficit at 6-10 years. Changes over time in lung volumes included a mild nadir of total lung capacity (TLC) and functional residual capacity (FRC) at 6 months to a year, which returned to baseline at 2-4 years and then gradually dropped to a 5-10% deficit at 6-10 years. Mean DLCO for the study group was 20% below predicted values prior to treatment and dropped to a low of 30% below predicted at 6 months following treatment, then gradually returned to baseline by 4 years and showed continued improvement to an overall deficit of approximately 10% at 6-10 years. With the exception of FEV1/FVC, the changes noted in spirometry and lung volumes were of insufficient degree to be classified as abnormal. The decrease in FEV1/FVC is indicative of a significant and progressive obstructive ventilatory defect. The effects on pulmonary function tests of smoking, the presence of mediastinal involvement by Hodgkin's disease, and exposure to chemotherapy were assessed by statistical analysis. No subsets of patients demonstrated consistent evidence of a restrictive ventilatory defect expected after irradiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1989

Aggressive management of second primary tumors in survivors of hereditary retinoblastoma.

Survivors of hereditary retinoblastoma are at increased risk for the development of second primary tumors, most commonly osteosarcoma. Recent molecular genetic data demonstrate that a pleiotrophic effect of the retinoblastoma gene may be responsible for the development of these sarcomas. This report describes the incidence of second nonocular malignancies among 53 infants seen at Stanford University Medical Center who have been followed a median of 11.7 years. Of these, 42 initially had bilateral disease and eleven had unilateral disease. Of 53 infants, 50 received irradiation either as part of the initial therapy or as treatment for recurrent disease. The actuarial survival for the entire group is 67% at 30 year follow-up with a median survival of 79% at 11.7 years. Eight patients developed eleven second primary tumors. All occurred in the group having hereditary retinoblastoma. Eight were within the previously irradiated field and three were at distant sites. The second tumors included seven osteosarcomas, one angiosarcoma, one rhabdomyosarcoma, one malignant fibrous histiocytoma, and one unclassifiable round blue cell tumor. The actuarial incidence of the development of a second primary malignancy was 6% at 10 years, 19% at 20 years, and 38% at 30 years. The latent period from treatment of retinoblastoma to the diagnosis of malignancy ranged from 5.2 years to 36.2 years (median 16 years). An aggressive approach with combined modality therapy including radical resection, re-irradiation and/or chemotherapy was used to treat these second primary tumors in five of eight patients. In four of the five, there was no evidence of disease at 22-72 months following treatment. In the three patients who did not receive aggressive combined treatment, there were no survivors. These data confirm the previously reported risk of developing a second primary tumor among survivors with hereditary retinoblastoma. Careful long-term follow-up for this genetically susceptible group is essential for early detection and implementation of curative therapy.

Bone Neoplasms↗
PubMed1989

Adaptability of endothelial orientation to blood flow dynamics--a morphologic analysis.

Vascular endothelium has a certain specificity in its anatomical orientation. The long axis of the endothelial cell and the shingle effect of cell process overlapping is always oriented parallel to the direction of blood flow. To determine whether this specific anatomical orientation would be maintained when the direction of blood flow was altered, twenty ilio-femoral vein segments and twenty vascular patches of carotid artery and jugular vein were studied. Valvulotomised ilio-femoral vein segments (n = 20) were interposed into adjacent arteries in a non-reversed fashion (the direction blood flow is reversed to the cell process overlapping). One centimeter-square carotid artery and jugular vein patches (n = 20) were rotated 90 degrees (endothelial cell orientation is perpendicular to the direction of blood flow). Reversal of endothelial cell overlapping to complement the complete reversal of the direction of blood flow exists in the vein graft through re-endothelialisation and endothelial reorientation. The process of endothelial reversal occurred in stages (endothelial cell process retraction, interdigitation, complete reversal) and was completed within 8-16 days. In the vascular patch, endothelial re-orientation occurred in 8 days through cell re-orientation and replacement. Mitosis was not encountered in either study. This report highlights certain functions and the adaptive capability of endothelial cells to complement the direction of blood flow.

Adaptation, Physiological↗
PubMed1989

Prospective, randomized trial of oral piroxicam in the prophylaxis of postoperative cystoid macular edema.

One hundred and seventy-eight patients undergoing uncomplicated cataract extraction with posterior chamber intraocular lens insertion completed a prospective, randomized, controlled trial of oral piroxicam in the prophylaxis of postoperative cystoid macular edema (CME), with a 1-year follow up. The incidence of "visually significant" CME, the mean interval to onset following surgery, clinical severity, recurrence rate, and the time to achieve best corrected visual result were unaffected by a 17-day piroxicam course. Oral steroid CME treatment produced a rapid response, but could not be shown to change the ultimate visual results. High-performance liquid chromatography analysis of aqueous humor obtained at cataract surgery suggested that piroxicam's pharmacokinetics might be a factor in this lack of response; the large number of potential inflammatory mediators uninfluenced by cyclo-oxygenase inhibition also may implicate piroxicam pharmacodynamics.

Administration, Oral↗
PubMed1989

The effect of dietary fatty acid composition on liver retinyl ester (vitamin A ester) composition in the rat.

The dependence of liver retinyl ester (vitamin A ester) composition on dietary fatty acid composition was studied in rats. Weanling male Sprague-Dawley rats were fed purified test diets containing 8% of one of 10 test triglycerides (either tributyrin, tricaproin, tricaprylin, tricaprin, trilaurin, trimyristin, tripalmitin, tristearin, triolein, trilinolein) or corn oil (a mixed triglyceride) for 23 d after an initial 1-wk stabilization period. Essential fatty acids were provided by safflower oil (8 g/kg diet). Total liver fatty acid composition showed the expected responses to dietary fatty acid intake; short-chain and medium-chain fatty acids were readily elongated to palmitate and stearate, and palmitate and stearate were readily desaturated. Consumption of oleate or linoleate (as their triglycerides) markedly enriched their concentrations in liver lipids. The proportions of palmitate were generally greater in liver retinyl esters than in total liver fatty acids, and the proportions of oleate were less. However, retinyl ester composition was significantly affected by dietary triglyceride, particularly by diets providing long-chain fatty acids. Total liver vitamin A levels were depressed in the group fed trilinolein.

Animals↗
PubMed1989

Plasma anticoagulant mechanisms of heparin, heparan sulfate, and dermatan sulfate.

The relationship between two anticoagulant actions of glycosaminoglycans (GAGs), namely the catalysis of thrombin inhibition (assessed by thrombin-antithrombin-III and thrombin-heparin-cofactor-II formation) and the inhibition of prothrombin activation, was explored by comparing the effects of heparin, heparan sulfate, and dermatan sulfate on the two reactions in plasma. Heparan sulfate and dermatan sulfate were also resulfated in vitro to yield products with sulfate/carboxylate ratios similar to those of heparin. Their effects on thrombin inhibition and the activation of prothrombin were also determined. The catalytic efficiency of the five GAGs on thrombin inhibition and their inhibitory effects on prothrombin activation decreased in the following order: heparin; resulfated dermatan sulfate; resulfated heparan sulfate; heparan sulfate = dermatan sulfate. These results suggest that the catalytic efficiency of a glycosaminoglycan on thrombin inhibition translates to its inhibitory effect on prothrombin activation, since catalysis of thrombin inhibition results in the inhibition of the thrombin-dependent positive feedback reactions of coagulation which facilitate prothrombinase formation.

Antithrombin III↗
PubMed1989

Automated DNA sequencing and the analysis of the human genome.

The Human Genome Initiative is a complex, multifaceted, international effort to establish a massive data base of map and sequence information for humans and other organisms. The success of this initiative is dependent upon the development of new technologies for the analysis of genomes. In this paper, an overview of the Human Genome Initiative is presented, and the current status of efforts to automate large-scale DNA sequence analysis is reviewed.

Automation↗