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Biomedical subjects

A Tucker

Publications and source records attributed to A Tucker.

At least 19 recordsLinked to original sources
PubMed1992

Uptake of Al3+ into the N-lobe of human serum transferrin.

We have studied the binding of Al3+ to human serum apotransferrin (80 kDa) and recombinant N-lobe human apotransferrin (40 kDa) in 0.1 M-sodium bicarbonate solution at a pH meter reading in 2H2O (pH*) of 8.8 using 1H n.m.r. spectroscopy. The results show that for the intact protein, preferential binding of Al3+ to the N-lobe occurs. Molecular modelling combined with an analysis of ring-current-induced shifts suggest that n.m.r. spectroscopy can be used to probe hinge bending processes which accompany metal uptake in solution.

Aluminum↗
PubMed1992

Proton NMR studies of bovine serum albumin. Assignment of spin systems.

A variety of one- and two-dimensional 1H-NMR methods have been applied to the study of defatted 66.5-kDa bovine serum albumin in solution. 1. The majority of the protons gave rise to broad unresolved resonances and spectral enhancement methods for one-dimensional spectra were investigated in detail. A combination of exponential and sine-bell functions was particularly effective. 2. The presence of contaminating glycoproteins in some commercial samples of bovine serum albumin was readily detectable from their N-acetyl resonances at about 2.1 ppm. 3. The release of bound Cys (from mixed disulphide at Cys34) was observed after addition of dithiothreitol. 4. Through the use of two-dimensional shift-correlated spectroscopy, assignments of some 80 spin systems to amino acid type were made. 5. The pKa of the N-terminal Asp was measured as 7.8 (0.1 M phosphate buffer, 310 K). 6. 1H NMR spectra of bovine, human, porcine and rat serum albumins have been compared. Using sequence comparisons, specific assignments have been made for the N-terminal residues of bovine (Asp-Thr-His), human (Asp-Ala-His), porcine (Asp-Thr-Tyr) and rat (Glu-Ala-His) albumins, and for Thr189, Tyr155 and His59/377 of bovine albumin. 7. These NMR data suggest that certain local regions of bovine serum albumin are highly mobile yet structured in solution, and demonstrate that the application of both one- and and two-dimensional NMR methods will allow more detailed investigations of structural transitions in serum albumins induced by, for example, pH, drug and metal binding.

Amino Acid Sequence↗
PubMed1992

Is transcutaneous electrical nerve stimulation of any value during cervical laser treatment?

OBJECTIVE: To assess the value of transcutaneous electrical nerve stimulation (TENS) during cervical laser therapy. DESIGN: Randomized three arm controlled clinical trial comparing (i) TENS, (ii) local anaesthetic and (iii) TENS plus local anaesthetic (direct infiltration of 2% lignocaine and 0.03 iu/ml octopressin). SETTING: Colposcopy Unit adapted to run randomized trials. SUBJECTS: 100 women with CIN and no previous experience of cervical surgery. MAIN OUTCOME MEASURE: Visual linear analogue pain scores. RESULTS: The median pain score associated with TENS was greater than the score associated with local anaesthesia (23% compared with 17%; P = 0.1). Combining TENS with local anaesthesia did not further reduce pain scores. CONCLUSION: Although there was considerable consumer satisfaction with TENS it provided no additional pain relieving effect in addition to direct infiltration of lignocaine and it is inferior to lignocaine alone. We are unable to advocate the use of TENS for laser treatment of the cervix.

Adult↗
PubMed1992

Acute and long-term TNF-alpha administration increases pulmonary vascular reactivity in isolated rat lungs.

Tumor necrosis factor-alpha (TNF-alpha) causes pulmonary hypertension and arterial hypoxemia, but the mechanisms are unknown. We conducted two experiments to test the hypothesis that TNF-alpha alters pulmonary vascular reactivity, which in turn could cause either pulmonary hypertension or arterial hypoxemia. In experiment 1, rats were given acute or long-term injections of TNF-alpha (recombinant human) in vivo. Rats treated acutely received either saline or TNF-alpha (40 micrograms/kg iv in saline) 3 min (TNF-3 min; n = 8), 20 min (TNF-20 min; n = 8), or 24 h (TNF-24 h; n = 5) before the lungs were isolated. Rats treated chronically received injections of either saline or TNF-alpha (250 micrograms/kg ip in saline) two times per day for 7 days (TNF-7 days; n = 9). Lungs were isolated and perfused with Earle's salt solution (+2 g/l NaHCO3 + 4 g/100 ml Ficoll), and vascular reactivity was tested with acute hypoxia (3 min; 3% O2) and angiotensin II (ANG II; 0.025-0.40 micrograms). Pulmonary pressor responses to hypoxia were greater (P less than 0.05) in TNF-20 min and TNF-7 day groups. ANG II responses were increased (P less than 0.05) in TNF-7 day rats. In experiment 2, lungs were isolated and perfused and received direct pulmonary arterial injections of TNF-alpha (0.2, 2.0, and 20 micrograms) or saline, after stable responses to hypoxia and ANG II (0.10 microgram) were attained. Reactivity was not different between control and TNF-alpha rats before the injections, but TNF-alpha increased (P less than 0.05) responses to hypoxia and ANG II.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1992

Heart and lung alterations in neonatal rats exposed to CO or high altitude.

We wished to determine whether cardiac changes produced by CO are related to the development of pulmonary hypertension and whether they are specific for CO or also occur with high-altitude exposure. Newborn male Sprague-Dawley rats were exposed to 500 ppm CO for 32 days (CO) at Detroit, MI or to 11,500-ft simulated altitude at Fort Collins, CO (barometric pressure 495 Torr; 11K); ambient air controls were maintained at Detroit (657 ft, 200 m; AIR) and at Fort Collins (5,000 ft, 1,524 m; 5K). Rats were maintained at Fort Collins after 34 days of age. Hematocrit was elevated to a greater extent in the CO than in the 11K group 2 days postexposure; however, no differences existed 40, 76, or 112 days postexposure. Right ventricle (RV) and left ventricle plus septum (LV + S) mass in CO rats were increased 38.0 and 37.4%, respectively, relative to the AIR group 2 days after CO exposure; RV and LV + S in the 11K group were increased 55.7 and 9.3%, respectively, relative to the 5K group. Cardiac hypertrophy declined in the CO and 11K groups postexposure but remained significant for the RV, reaching 20.7% above the AIR group (CO) and 29.7% above the 5K group (11K) at 145 days of age. By use of an in vitro preparation, pulmonary vascular resistance (PVR) and pulmonary arterial pressure were significantly increased immediately after altitude but not after CO exposure and remained elevated in adulthood after altitude exposure. PVR was correlated with hematocrit in altitude- but not in CO-exposed rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1992

Factors influencing the idiopathic development of pulmonary hypertension in the fawn hooded rat.

Fawn hooded rats (FHR), a strain of rat with a hereditary bleeding tendency due to a genetic defect in platelet aggregation, have recently been found to develop pulmonary hypertension. However, whether the pulmonary hypertension in FHR has a genetic basis or simply reflects the influence of extrinsic factors known to increase pulmonary artery pressure in other rat strains has not been fully evaluated. To further examine the structural and hemodynamic changes of pulmonary hypertension in FHR, and to investigate the extent to which alveolar hypoxia may have promoted these abnormalities, hemodynamic and morphometric measurements were made in FHR (4 to 24 wk) and compared with age-matched Sprague-Dawley (SDR) control rats. Increases in mean pulmonary artery pressure, total pulmonary resistance, and right ventricular enlargement were present in both male and female FHR and were evident at an early age (4 wk). Morphometric analysis of barium gelatin-infused lungs revealed marked pulmonary vascular remodelling in FHR characterized as extension of muscle into more peripheral pulmonary vessels, medial hypertrophy of proximal vessels, and reduced number of barium-filled arteries. The increases in pulmonary artery pressure in FHR were not due to the influence of more severe hypoxia, hypoventilation, or polycythemia, as blood gas tension and hematocrit were similar in FHR and SDR. Moreover, we found that pulmonary hypertension could be transmitted to backcross and second filial generation offspring arising from selective matings between FHR and control Wistar Kyoto rats, confirming the heritable basis for pulmonary hypertension in the FHR.

Animals↗
PubMed1991

Vascular cell responses to a hybrid transforming growth factor-beta molecule.

Functional biological assays were performed using a hybrid molecule of Transforming Growth Factor-Beta (TGF-5 beta) where nine amino acids near the cleavage site of TGF-beta 1 were substituted with nine amino acids located in the identical position of TGF-beta 2. Bovine aortic endothelial and smooth muscle cells as well as rat epididymal fat pad microvascular endothelia were studied in three distinct bioassays examining proliferation, migration and angiogenesis. The data suggested TGF-5 beta elicited results that do not differ significantly from the TGF-beta 1 isoform, while TGF-beta 2 expressed unique characteristics. We have also shown that these amino acid substitutions to TGF-beta 1 do not, in fact, alter the biological functions of the growth factor.

Animals↗
PubMed1991

DNA sequence analysis of X-ray induced Adh null mutations in Drosophila melanogaster.

The mutational spectrum for 28 X-ray induced mutations and 2 spontaneous mutations, previously determined by genetic and cytogenetic methods, consisted of 20 multilocus deficiencies (19 induced and 1 spontaneous) and 10 intragenic mutations (9 induced and 1 spontaneous). One of the X-ray induced intragenic mutations was lost, and another was determined to be a recombinant with the allele used in the recovery scheme. The DNA sequence of two X-ray induced intragenic mutations has been published. This paper reports the results of DNA sequence analysis of the remaining intragenic mutations and a summary of the X-ray induced mutational spectrum. Only one of the X-ray induced mutations is a single base change, a C to G transversion (AdhnLA80). Therefore, the mutational spectrum of X-ray induced mutations consists predominantly of deletions that are observed to range in size from two base pairs to deletions of a large number of loci as determined by genetic complementation analysis. The combination of DNA sequence analysis with genetic complementation analysis shows a continuous distribution in size of deletions rather than two different types of mutations consisting of deletions and "point mutations." Sequencing is shown to be essential for detecting intragenic deletions. Of particular importance for future studies is the observation that all of the intragenic deletions consist of a direct repeat adjacent to the break-point with one of the repeats deleted.

Alcohol Dehydrogenase↗
PubMed1991

Iron supplementation and running performance in female cross-country runners.

The purpose of this study was to determine the effects of two weeks of high dosage iron supplementation on various blood iron indices and metabolic parameters in non-anemic, iron-depleted competitive female cross-country runners. The subjects were highly trained members of the Colorado State University cross-country team and were completing 40 to 50 miles of training weekly. A pretest, post-test single-blind crossover design was employed. Upon collection of baseline exercise blood and metabolic data, five subjects were randomly assigned to iron supplementation (650 mg ferrous sulfate; 130 mg elemental iron) and five subjects to placebo treatment. At two weeks the treatments were reversed. Exercise blood and metabolic data were collected at two-week intervals. Dietary iron intake was assessed using a three-day dietary survey. Dietary analysis revealed deficiencies in vitamin B-6, iron, magnesium, and zinc according to USRDA standards. Baseline blood samples revealed no deficiencies in iron storage or transport proteins. Two weeks of iron supplementation resulted in no significant increases in blood iron indices. Metabolic parameters related to running performance were also unchanged after iron supplementation. High dosage, short-term iron supplementation appears to have no effect on blood or metabolic parameters in iron-depleted but non-anemic female cross-country runners.

Adult↗
PubMed1991

Vascular cell responses to TGF-beta 3 mimic those of TGF-beta 1 in vitro.

The vascular cell responses to the type 3 isoform of transforming growth factor-beta (TGF-beta 3) were studied using bovine aortic endothelial (BAECs) and smooth muscle cells (BASMCs) as well as rat epididymal fat pad microvascular endothelia (RFCs). Four distinct bioassays indicated that TGF-beta 3 elicits results that do not differ significantly from those of the TGF-beta 1 isoform in all three cell populations. Inhibition of proliferation by TGF-beta 3 at a 5-day time point ranged from 85% on BAECs, to 55% and 53% on RFCs and BASMCs, respectively. The effects of TGF-beta 3 and TGF-beta 1 on cell migration were also found to be similar; migration of large vessel endothelial cells was inhibited 35%, while migration of smooth muscle cells was enhanced 30%. TGF-beta 1 and TGF-beta 3 also had equivalent effects on neovascularization while a 10-fold higher concentration of TGF-beta 2 was required to elicit a similar response. Experimentation to decipher cell surface binding by the different isoforms revealed that iodinated TGF-beta 1 bound to the surface of all three vascular cell types can be competed off in similar fashion by either TGF-beta 1 or TGF-beta 3; however, competition with TGF-beta 2 produced unique binding profiles dependent upon the cell type examined. In summary, both the TGF-beta 1 and TGF-beta 3 isoforms of the transforming growth factor-beta family evoke comparable responses in proliferation, migration, angiogenic and cell surface binding assays using three distinct vascular cell types, while the biofunctions of TGF-beta 2 on these cells are distinct.

Animals↗
PubMed1991

Pulmonary particle deposition and airway mucociliary clearance in cold-exposed calves.

Effect of cold-induced changes in respiratory pattern on pulmonary particle deposition was investigated in 10 male Holstein calves between the ages of 1 and 3 months. Deposition of intranasally instilled fluorescence-enhanced Pasteurella haemolytica was significantly higher (P less than 0.05) for cold-exposed calves and appears to be caused by the cold-induced respiratory pattern change. Deposition was greater in apical and mediastinal lung lobes, but the reason for this preferential deposition is uncertain. Nasal mucus velocity was measured in 4 nonanesthetized calves at ambient temperature of 2 to 4 C and 16 to 18 C, using tantalum-paraffin oil droplets and serial radiography. Nasal mucus velocity was 24% lower during cold exposure. In addition, the effect of mucosal temperature on tracheal mucus velocity was determined in excised tracheas from 7 calves. A direct relationship existed between mucosal temperature and tracheal mucus velocity within the mucosal temperature range studied (35.0 to 39.5 C). Tracheal air temperature measurements in calves at ambient temperatures of -10.4 C (n = 4) and 18.5 C (n = 5) indicated that conditioning of inspired air is not complete at the tracheal level during extreme cold exposure. Therefore, cold air may directly influence tracheal mucociliary clearance. It is speculated that cold exposure increases pulmonary deposition of pathogens, while simultaneously decreasing mucociliary clearance of the upper airways, thus predisposing cold-exposed calves to respiratory tract infection.

Animals↗
PubMed1991

Vascular cells respond differentially to transforming growth factors beta 1 and beta 2 in vitro.

Transforming growth factor beta 1 (TGF-beta 1) and beta 2 (TGF-beta 2) are equipotent in many cell systems studies thus far. Recent data, however, show different effects elicited by these two growth factors in specific biologic systems. This investigation compares the effects of TGF-beta 1 and TGF-beta 2 bovine aortic endothelial cells (BAECs), rat epididymal fat pad microvascular endothelium (RFCs), and bovine aortic smooth muscle cells (BASCs). In two-dimensional cultures, proliferation of BAECs, BASMCs, and RFCs were all inhibited by TGF-beta 1, while in response to TGF-beta 2, BASMCs were fully inhibited, RFCs were modestly inhibited, and BAECs were unaffected. Bovine aortic endothelial cell migration was significantly inhibited by TGF-beta 1, but only slightly inhibited by TGF-beta 2. In contrast, BASMC migration was enhanced by TGF-beta 1 and was not affected by TGF-beta 2. In three-dimensional cultures, RFCs were stimulated to undergo in vitro angiogenesis in response to TGF-beta 1 and TGF-beta 2 at 10-fold higher concentrations. Three distinct receptor assays demonstrated the presence of type I and type II TGF-beta 1 cell-surface-binding proteins on BAECs, BASMCs, and RFCs. Labeled TGF-beta 1 was competed off completely with 100-fold molar excess unlabeled TGF-beta 1, but only partially with equivalent excess unlabeled TGF-beta 2. Furthermore the ratios of type I to type II TGF-beta receptors in these three vascular cell types vary from 1:1 in BAECs to 1.5:1 in RFCs to 3:1 in BASMCs and can be correlated with the differences noted in cellular responses to TGF-beta 1 and TGF-beta 2 in proliferation, migration, and in vitro angiogenic assays. These findings support the hypothesis that there are different responses to the TGF-beta s, depending on the cell type and experimental conditions as well as the TGF-beta concentration and isoform used.

Animals↗
PubMed1990

Colicins: prokaryotic killer-pores.

Colicins are plasmid-encoded protein antibiotics which kill bacteria closely related to the producing strain (generally Escherichia coli). The study of the function of colicins has revealed many features which reflect common targeting and translocation mechanisms with bacteriophages and toxins. Like many toxins, colicins are composed of structural domains specialized in one of the different steps of the activity, targeting, translocation and killing. The major group comprises those colicins which permeabilize the cytoplasmic membrane, thereby destroying the cell's membrane potential. These colicins form well-defined voltage-gated ion channels in artificial membranes. The scope of this review is to describe some of the more recent findings concerning the structure and mode of action of pore-forming colicins with a special attention to models of membrane insertion and pore structure based on the recently determined three-dimensional structure of the pore-forming domain of colicin A.

Amino Acid Sequence↗
PubMed1990

Metabolic consequences of reduced frequency breathing during submaximal exercise at moderate altitude.

The intention of this study was to determine the metabolic consequences of reduced frequency breathing (RFB) at total lung capacity (TLC) in competitive cyclists during submaximal exercise at moderate altitude (1520 m; barometric pressure, PB = 84.6 kPa; 635 mm Hg). Nine trained males performed an RFB exercise test (10 breaths.min-1) and a normal breathing exercise test at 75-85% of the ventilatory threshold intensity for 6 min on separate days. RFB exercise induced significant (P less than 0.05) decreases in ventilation (VE), carbon dioxide production (VCO2), respiratory exchange ratio (RER), ventilatory equivalent for O2 consumption (VE/VO2), arterial O2 saturation and increases in heart rate and venous lactate concentration, while maintaining a similar O2 consumption (VO2). During recovery from RFB exercise (spontaneous breathing) a significant (P less than 0.05) decreases in blood pH was detected along with increases in VE, VO2, VCO2, RER, and venous partial pressure of carbon dioxide. The results indicate that voluntary hypoventilation at TLC, during submaximal cycling exercise at moderate altitude, elicits systemic hypercapnia, arterial hypoxemia, tissue hypoxia and acidosis. These data suggest that RFB exercise at moderate altitude causes an increase in energy production from glycolytic pathways above that which occurs with normal breathing.

Adult↗
PubMed1990

Lung volumes and maximal respiratory pressures in collegiate swimmers and runners.

To determine whether respiratory muscle strength is related to pulmonary volume differences in athletes and nonathletes, 11 intercollegiate female swimmers, 11 female cross-country runners, and two nonathletic control groups, matched to the athletes in height and age, were evaluated for pulmonary parameters including maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax). Swimmers exhibited larger (p less than .05) vital capacities (VC), residual lung volumes (RV), inspiratory capacities (IC), and functional residual capacities (FRC) than both the runners or the controls but no difference (p greater than .05) in either PImax or inspiratory flow (FIV 25%-75%). Timed expiratory volumes (FEV 0.5 and FEV 1.0) were significantly (p less than .05) lower in the swimmers than in the controls. These data suggest that an adaptational growth may be responsible, in part, for the augmented static lung volumes demonstrated in swimmers.

Adolescent↗
PubMed1990

Hepatobiliary cystadenoma with mesenchymal stroma.

In a detailed review of cystic hepatobiliary neoplasms, we identified a subset of 50 cases in which tumors were characterized by the presence of a mesenchymal cell layer interposed between an inner epithelial lining and an outer connective tissue layer. We have recently seen three such patients, making a total of 53 patients reported in the English literature. All of the patients were female, 44 of whom, with an average age of 41 years, had benign tumors. The average age of the remaining nine patients was 57 years and these patients had malignant tumors. In seven patients, the malignancy arose from the epithelial layer, but in two patients sarcomatous changes were identified in the mesenchymal tissues. The older age of the patients with malignant tumors with adequate serial biopsies in two cases supported the thesis that malignant transformation may occur in the benign tumors. Moreover the location of the tumor in one of our patients in whom the resected tumor was associated with anomalous right hepatic ducts and portal veins supported the theory that these tumors develop embryologically from nests of primitive hepatobiliary endodermal and mesodermal cells. Although surgical treatment was performed in all patients, 25% of the patients with benign hepatobiliary cystadenoma with mesenchymal stroma (CMS), and 33% of the patients with malignant CMS had tumor recurrence after primary resection. Ninety per cent of these patients had an incomplete resection at the time of their initial operations. Forty-four per cent of the patients with malignant CMS died after a mean follow-up of 17 months. We conclude that CMS (Edmonson's tumor) occurs uniquely in young female patients, develops from nests of primitive embryonal cells, has the potential for malignant transformation, and should be completely resected at primary operation to avoid recurrence.

Adult↗