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Biomedical subjects

B Sawyer

Publications and source records attributed to B Sawyer.

At least 19 recordsLinked to original sources
PubMed2005

Endothelial progenitor cells are recruited into resolving venous thrombi.

BACKGROUND: The purpose of this study was to determine whether endothelial cells of bone marrow origin are involved in thrombus recanalization. METHODS AND RESULTS: Irradiated mice were reconstituted with bone marrow from transgenic donors expressing green fluorescent protein (GFP) linked to the Tie2 promoter. Thrombi were formed in 2 groups of 6 mice. GFP-expressing cells were located and quantified in sections of the thrombi taken after 7 and 14 days. The cell markers Mac-3, F4/80, CD68 (macrophage), and vascular endothelial growth factor receptor 2 (VEGFR2; endothelial cells) were used to determine colocalization with GFP expression in tissue sections and peritoneal macrophages. The markers CD34 and VEGFR2 were used to quantify changes in circulating endothelial cells by flow cytometry of blood from 3 cohorts of wild-type animals that had either a thrombus induced (n=18), a sham operation (n=18), or no operation (n=10). The number of GFP-expressing cells was found to increase by approximately 3-fold in thrombi formed in transplanted animals between 7 and 14 days after induction (P=0.0022). No GFP-expressing cells were found lining the new vascular channels that formed at either time interval, but many of the GFP-expressing cells also expressed Mac-3, CD68, and VEGFR2. Approximately twice as many circulating CD34+/VEGFR2+ cells were found by day 3 in animals with thrombus compared with sham controls (CD45-, P=0.046 and CD45(+), P=0.016). CONCLUSIONS: Bone marrow-derived, Tie2-expressing cells were recruited into the thrombus during resolution but did not line the new vessels. Many of these cells expressed a macrophage phenotype and may represent a population of plastic stem cells that orchestrate thrombus recanalization.

Animals↗
PubMed2001

Ribozyme genes protecting transgenic melon plants against potyviruses.

Potyviruses are the most important viral pathogens of crops worldwide. Under a contract with Gene Shears Pty Limited, we are using ribozyme genes to protect melon plants against two potyviruses: WMV2 and ZYMV. Different polyribozyme genes were designed, built and introduced into melons plants. Transgenic melon plants containing a resistance gene were obtained and their progeny was challenged by the appropriate virus. Most of the genes tested conferred some degree of resistance to the viruses in glasshouse trials. Melon plants from one family containing one gene directed against WMV2 were also field-trialed on small plots under natural infection pressure and were found immune to WMV2. Field trial is in progress for plants containing genes against ZYMV. Some of the ribozyme genes used in the plants were also assayed in a transient expression system in tobacco cells. This enabled us to study the sequence discrimination capacity of the ribozyme in the case of one ribozyme target site. We found that a mutated target GUG (non cleavable) was less susceptible to inhibition by the ribozyme gene than the corresponding wild type target GUA (cleavable). Work is now in progress to incorporate multiple resistance genes in melon plants, in constructs designed in compliance with the evolving European regulations concerning transgenic plants. The use of ribozyme genes to protect plants against viruses provides an alternative to the technologies currently used for protecting crops against viruses, based on the concept of Pathogen Derived Resistance (see for example 14). In the light of concerns expressed by some plant virologists (13) about the use of viral genes in transgenic plants, it may be that ribozyme genes will find many uses in this area of agricultural biotechnology.

Agriculture↗
PubMed1994

Primary thrombocythaemia: a composite approach to diagnosis.

Traditional diagnostic criteria for primary thrombocythaemia (PT) remain essentially negative, aiming to exclude other myeloproliferative disorders and causes of reactive thrombocytosis (RT). It would be useful to have positive markers. We have examined several parameters to see how well they discriminate between PT and RT. Three groups of patients were studied: new, untreated PT (17), treated PT (12) and RT (17). Data consisted of: ESR, plasma fibrinogen, factor VIIIC, von Willebrand factor antigen (vWF:Ag), PDW, platelet nucleotide ratio (ATP:ADP) serum erythropoietin (Epo), ristocetin cofactor (vWF:RiCoF), multimeric structure of vWF, interleukin-6, evidence of clinical ischaemia and erythroid colony formation. Erythroid colonies were assayed in a serum-free system with the addition of Epo, IL3 or alpha-IFN to produce a discriminant function (DF) successfully used in the diagnosis of primary polycythaemia in an earlier study. Acute phase reactants (ESR, fibrinogen, VIIIC, vWF:Ag) and IL6 were the best discriminants, while PDW and serum Epo were less so. ATP:ADP and clinical ischaemia were nondiscriminatory in this study. Reduction in vWF:RiCof and in high molecular weight multimers were clearly associated with PT. Endogenous erythroid colonies were nondiscriminatory, but half the PT group and only one patient in the RT group obtained a DF suggestive of myeloproliferative disorder. Judicious use of a battery of tests may provide support for diagnosis of PT in difficult cases.

Adolescent↗
PubMed1994

Idiopathic erythrocytosis--additional new study techniques suggest a heterogenous group.

25 patients with idiopathic erythrocytosis (absolute increase in red cell mass without conventional criteria of primary polycythaemia or known underlying cause) have been further studied for evidence of primary or secondary polycythaemia. Additional non-conventional criteria used were: platelet distribution width, platelet nucleotide ratio, serum erythropoietin, clinical evidence of ischaemic vascular disease and erythroid culture variables in serum-free system. All had been used in an earlier study in score form to assist in the diagnosis of primary polycythaemia. These patients were also newly assessed for the presence of hypoxia (supine oximeter values, history suggestive of sleep apnoea), for renal lesions and for splenic enlargement (impalpable) by ultrasound or computerized tomography. 7 patients had erythroid culture scores suggesting primary polycythaemia but the addition of non-culture criteria did not result in any scores more strongly predictive of primary polycythaemia. Supine oximeter values < 92% suggested hypoxaemia as the mechanism of polycythaemia in 3 patients in whom it had not previously been suspected. Some splenic enlargement (impalpable) was demonstrated in 6 patients, only 1 of whom had erythroid culture scores suggesting primary polycythaemia. 12 patients had confirmed, raised erythropoietin levels. We conclude that idiopathic erythrocytosis refers to a heterogenous group of patients. Features of primary or secondary polycythaemia may be demonstrated in some of them by additional new study techniques. The raised erythropoietin values found in half the patients were unexpected.

Adolescent↗
PubMed1993

Primary polycythaemia: diagnosis by non-conventional positive criteria.

Patients with polycythaemia and normal controls have been studied to establish and subsequently test non-conventional criteria for the diagnosis of primary polycythaemia (primary proliferative polycythaemia, polycythaemia vera) as compared with conventional Polycythaemia Vera Study Group (PVSG) assessment. One criterion was erythroid colony formation from peripheral blood in a serum-free system, assayed alone and with the addition of recombinant human erythropoietin (Epo), interleukin 3 (IL3), or alpha interferon (alpha-IFN) (Dudley et al. 1990). The remaining criteria were non-culture associated and comprised platelet distribution width (PDW), platelet nucleotide ratio (ATP:ADP), serum erythropoietin and clinical evidence of ischaemic vascular disease. The combination of culture associated and non-culture associated variables, by use of a simple additive scoring system, gave no false positive and only 6% false negative results in distinguishing primary polycythaemia from other polycythaemias and normal controls in those (34 patients Group A) used in its derivation. Testing the scoring system in a newly presenting group (25 patients Group B) was highly satisfactory with no false positives and only a few false negative results (14%). Use of these non-conventional criteria should allow more confident diagnosis of primary polycythaemia, where conventional clinical and laboratory assessment is inconclusive.

Adenosine Diphosphate↗
PubMed1993

Bacterial aerosol emission rates from municipal wastewater aeration tanks.

In this report we describe the results of a study conducted to determine the rates of bacterial aerosol emission from the surfaces of the aeration tanks of the Metropolitan Water Reclamation District of Greater Chicago John E. Egan Water Reclamation Plant. This study was accomplished by conducting test runs in which Andersen six-stage viable samplers were used to collect bacterial aerosol samples inside a walled tower positioned above an aeration tank liquid surface at the John E. Egan Water Reclamation Plant. The samples were analyzed for standard plate counts (SPC), total coliforms (TC), fecal coliforms, and fecal streptococci. Two methods of calculation were used to estimate the bacterial emission rate. The first method was a conventional stack emission rate calculation method in which the measured air concentration of bacteria was multiplied by the air flow rate emanating from the aeration tanks. The second method was a more empirical method in which an attempt was made to measure all of the bacteria emanating from an isolated area (0.37 m2) of the aeration tank surface over time. The data from six test runs were used to determine bacterial emission rates by both calculation methods. As determined by the conventional calculation method, the average SPC emission rate was 1.61 SPC/m2/s (range, 0.66 to 2.65 SPC/m2/s). As determined by the empirical calculation method, the average SPC emission rate was 2.18 SPC/m2/s (range, 1.25 to 2.66 SPC/m2/s). For TC, the average emission rate was 0.20 TC/m2/s (range, 0.02 to 0.40 TC/m2/s) when the conventional calculation method was used and 0.27 TC/m2/s (range, 0.04 to 0.53 TC/m2/s) when the empirical calculation method was used.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗
PubMed1992

Novel functional M1 selective muscarinic agonists. 2. Synthesis and structure-activity relationships of 3-pyrazinyl-1,2,5,6-tetrahydro-1-methylpyridines. Construction of a molecular model for the M1 pharmacophore.

A series of 3-(3-substituted-pyrazinyl)-1,2,5,6-tetrahydro-1-methylpyridines were synthesized and found to have high affinity for central muscarinic receptors. The ability of some of these compounds to inhibit the electrically stimulated twitch of the guinea pig vas deferens indicated that the compounds were M1 agonists. M1 agonist activity was related to the length of the side chain attached to the pyrazine ring, with maximal activity being obtained with the hexyloxy side chain. The (hexyloxy)pyrazine 3f lacked M2 agonist activity as it failed to affect the guinea pig atria and was also relatively devoid of M3 agonist activity as determined by its lack of tremorogenic and sialogogic effects in mice. A comparison of the M1 agonist efficacy of these pyrazines and related 1,2,5-thiadiazoles and 1,2,5-oxadiazoles suggested that M1 efficacy was related to the magnitude of electrostatic potential located over the nitrogens of the respective heterocycles. The heteroatom directly attached to the 3 position of the pyrazine or 1,2,5-thiadiazole heterocycle markedly influenced the M1 efficacy of the compounds by determining the energetically favorably conformers for rotation about the bond connecting the tetrahydropyridyl ring and the heterocycle. A three-dimensional model for the M1-activating pharmacophore was proposed based on computational studies and the model of the muscarinic pharmacophore proposed by Schulman.

Animals↗
PubMed1991

Erythropoietin gene expression in haemopoietic cell lines.

Erythropoietin (Epo) gene expression was studied in a number of different haemopoietic cell lines by in situ hybridization and Northern Blot analysis using a radioisotope-labelled monkey Epo DNA probe. A positive message was expressed by a human cell line, CM-S, derived from a patient with congenital hypoplastic anemia, and by a murine erythro-leukaemic cell line, clone 707, derived from the spleen of Friend virus-infected mice. No message was detected in two megakaryoblastic cell lines, and in a monocytic cell line, derived from a patient with acute monocytic leukaemia. These data may fit with the hypothesis of expression of Epo and other growth factors by haemopoietic cells through a mechanism of so-called autocrine secretion.

Animals↗
PubMed1991

Night-to-night variability of disturbed breathing during sleep in an elderly community sample.

Night-to-night variability of breathing and oxygenation during sleep was examined with portable monitoring equipment in 30 residents of a retirement village. Subjects had a variety of health problems as might be expected in the elderly, but all were living independently in self-contained units. None had clinical features to suggest obstructive sleep apnea. Two pairs of consecutive nights were studied, separated by 4-6 months. Satisfactory recordings on all four nights were obtained in 15 subjects, and in these subjects variability of measurements was examined across nights 1-4 using the kappa (K) statistic. There was low but significant agreement in estimated total sleep time (K = 0.23, p less than 0.01) and estimated wakefulness after sleep onset (K = 0.18, p less than 0.05) as assessed with a wrist actigraph. Good agreement was found among measures of disturbed breathing during sleep whether expressed in terms of numbers of events [respiratory disturbance index (RDI), K = 0.62, p less than 0.0001], their duration (event minutes, K = 0.53, p less than 0.0001), or associated disturbance of oxygenation (% cumulative time less than 90% SaO2, K = 0.50, p less than 0.001, n = 9). Twenty-eight subjects had at least two nights' satisfactory recordings. Although some of these individuals showed considerable variation in RDI, this had little overall effect on classification of them into normal (RDI less than or equal to 15) and abnormal groups. The accuracy of the first night's recording in predicting classification derived from recording on three or four nights was 83%.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

In vitro colony culture and chromosomal studies in hepatic and portal vein thrombosis--possible evidence of an occult myeloproliferative state.

We have studied the prevalence of an underlying myeloproliferative state in 20 patients with either hepatic or portal vein thrombosis. Using conventional clinical and laboratory criteria, an underlying myeloproliferative state was identified as the cause of the thrombosis in five patients (25%). A further 10 of the remaining 15 cases were found to have characteristic in vitro bone marrow culture studies and cytogenetic abnormalities suggestive of an underlying myeloproliferative disorder. Although none of these 10 cases have developed overt clinical and laboratory features of such a myeloproliferative disorder after a median observation period of two years, the presence of clonal karyotypic abnormalities in three cases, increased megakaryocyte colony growth in three cases and endogenous erythropoietin independent colony growth of the marrow erythroid progenitors in seven cases, argues strongly in favour of a primary haematological disorder. This has important therapeutic implications, particularly in cases being considered for orthotopic liver transplantation.

Adolescent↗
PubMed1989

Interrater reliability of computer-assisted scoring of breathing during sleep.

Twenty-six records of sleep and breathing obtained with a portable monitoring system from elderly subjects were scored by three raters with computer assistance to examine interrater reliability of scoring. Raters were a medical student, a nurse practitioner, and a family physician, all of whom had at least one month's experience with the equipment. Agreement among raters was measured with the unweighted kappa statistic. Significant agreement was observed for all variables, although agreement was better for variables describing breathing (range of kappa 0.71-0.87) than for those describing sleep (range of kappa 0.34-0.57). Complete agreement among the three raters on diagnostic classification occurred in 17 cases. In the remaining 9 cases, 2 raters agreed, whereas the third differed by not more than one category for type of disturbance (e.g., normal versus hypopnea, hypopnea versus apnea) or severity (e.g., mild versus moderate). There was only one disagreement among raters for the 9 subjects with severe respiratory disturbance. We conclude that interrater reliability of identifying and characterizing breathing disturbance during sleep as recorded by portable monitoring is high among trained raters using computer assistance.

Aged↗
PubMed1989

Primary thrombocythaemia: diagnostic criteria and a simple scoring system for positive diagnosis.

Forty new patients with elevated platelet counts (greater than 600 x 10(9)/l) and without palpable splenomegaly were assigned to diagnostic groups defined by essentially conventional criteria after 3 months follow up: Proliferative (17), reactive (17) or unclassified (six). Mean platelet volume (MPV), platelet distribution width (PDW), platelet nucleotide ratio (ATP:ADP), unstimulated BFU-E derived colony formation from peripheral blood, spleen scan and clinical ischaemia were assessed at the outset, with a view to defining diagnostic criteria for distinguishing primary thrombocythaemia from reactive thrombocytosis. All except the first variable were significantly associated with diagnostic group (P less than 0.05). A simple scoring system was devised: enlarged spleen on scan, or presence of BFU-E, each scored 2; elevated PDW (greater than 2 SD from mean), elevated ATP:ADP (greater than 4 SD from mean) or presence of clinical ischaemia, each scored 1. Score totals greater than or equal to 3 predicted primary thrombocythaemia, and totals less than 3 suggested reactive thrombocytosis (predictive value 89%). The system correctly predicted diagnosis in four out of four (probably six out of six) patients whose diagnosis was not apparent initially, and thus whose results were not used in constructing the scoring system. Exclusion of BFU-E from the system resulted in only one incorrect prediction in this group.

Blood Platelets↗
PubMed1987

Evaluation of a microprocessor-based portable home monitoring system to measure breathing during sleep.

Study of the epidemiology of disturbances of breathing during sleep was hampered until recently by the need to conduct studies in the laboratory, with attendant inconvenience and limited sample sizes. We assessed the accuracy of a microprocessor-based portable monitoring system (Vitalog PMS-8, Vitalog Corp., CA) to detect and classify episodes of disturbed breathing during sleep in 14 patients with sleep apnea by simultaneously recording oxygenation and thoracoabdominal motion on the portable system and a polygraph. Each patient slept in the laboratory for 1 night. In two subjects, the portable system failed to record thoracoabdominal signals. In the remaining subjects, the portable system detected 78% of 2,340 episodes of disturbed breathing, but the recorded information was not sufficient to allow confident classification into central or obstructive events. The positive predictive value of disturbed breathing detected by the portable system was 64%, Respiratory disturbance indices (RDI) computed from the polygraph and portable records were correlated (r = 0.70; p less than 0.01), and all patients with sleep apnea were correctly diagnosed by the portable system. The portable system overestimated arterial oxygen saturation (SaO2) recorded by an ear oximeter (Biox IIA, Ohmeda, CO) but the error was less than 10% of the true value at SaO2 greater than 60%. Seven normal subjects were studied while awake to examine the accuracy of volume measurements made by the portable system and the system's ability to detect paradoxical thoracoabdominal motion of various degrees. Absolute measurement of tidal volume was inaccurate, but detection rate of paradoxical thoracoabdominal motion was excellent (97%). We conclude that the portable system is sufficiently sensitive to allow detection of patients with breathing disorders during sleep, but further developments are necessary before the system can be relied on for accurate classification of apneas and hypoventilation.

Adult↗
PubMed1987

Patterns of in vitro BFU-E proliferation in different forms of polycythaemia and in thrombocythaemia.

To investigate erythroid colony formation in polycythaemia of different types and in thrombocythaemia, a study was performed in 121 subjects, including 13 normal volunteers (N), 30 patients with Primary Proliferative Polycythaemia (PPP), 35 with Idiopathic Erythrocytosis (IE), 19 with Secondary Polycythaemia (SP), 10 with Primary Thrombocythaemia (PT) and 14 with Secondary Thrombocytosis (ST); BFU-E colony formation from peripheral blood samples was studied in the presence of medium only, medium plus a source of burst-promoting activity (BPA) and medium BPA, plus erythropoietin (Ep). In the presence of medium only, practically no colonies were seen in cultures from N and SP, while a variable number was observed in cultures from PPP, IE and PT. Significant differences between groups were as follows: N v PPP; IE v PPP; SP v PPP; N v PT; ST v PT. Such differences persisted in the presence of BPA, but disappeared when Ep was added to the cultures. Further experiments, plating non-adherent mononuclear cells in a chemically defined serum-free medium, confirmed the growth of tiny erythropoietic colonies from circulating stem cells of patients with PPP and PT, in the absence of BPA and EP. These results provide a useful criterion to differentiate PPP, as a group, from other types of polycythaemia; individual cases of IE may need further characterization.

Blood Proteins↗
PubMed1986

Pure red cell aplasia and thymoma: demonstration of persisting inhibition of erythropoiesis after thymectomy and resolution after immune suppressive treatment.

A 61 year-old woman presented with general malaise, hair loss, pure red cell aplasia (PRCA) and thymoma: no growth of erythropoietic colonies in vitro (BFU-E) was observed in the presence of her own serum. The thymoma was removed: after the operation no improvement of her anaemic condition was observed and colony growth was very poor, although T-depleted narrow preparations showed a modest BFU-E formation in autologous serum. Following treatment with azathioprine, a complete recovery was seen, associated with normal BFU-E formation in vitro. This observation suggests that a complex inhibition of erythropoiesis may operate in PRCA involving both humoral and cellular factors; thymectomy alone may not be sufficient to restore haemopoiesis, but has to be followed by immune suppressive treatment.

Antibody Formation↗
PubMed1984

Erythroid colony formation in primary thrombocythaemia: evidence of hypersensitivity to erythropoietin.

In a group of 14 patients with primary thrombocythaemia (PT) the study of erythropoietic colony formation in vitro showed the development of so-called 'endogenous' colonies, namely colonies with no added erythropoietin (Ep), in all but one case. In the presence of added Ep the colony formation increased slightly in the PT group, but the rise in the control group was so pronounced that any statistical difference between the two groups disappeared. No 'endogenous' colonies were observed in cases of secondary thrombocytosis. This finding reinforces the view that PT is a myeloproliferative disorder and establishes that some erythroid progenitors show the same high sensitivity to Ep as that found in polycythaemia vera; it is of interest that, in the patients studied, there was no apparent involvement of erythropoiesis.

Adult↗