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Biomedical subjects

M A Moran

Publications and source records attributed to M A Moran.

33 records · Page 2Linked to original sources
PubMed1992

Adaptation of model genetically engineered microorganisms to lake water: growth rate enhancements and plasmid loss.

When a genetically engineered microorganism (GEM) is released into a natural ecosystem, its survival, and hence its potential environmental impact, depends on its genetic stability and potential for growth under highly oligotrophic conditions. In this study, we compared plasmid stability and potential for growth on low concentrations of organic nutrients of strains of Pseudomonas putida serving as model GEMs. Plasmid-free and plasmid-bearing (NAH7) prototrophic isogenic strains and two amino-acid auxotrophs, all containing antibiotic resistance markers, were held physically separate from but in chemical contact with lake water containing the natural bacterium-sized microbial populations. Cells were reisolated at intervals over a 2-month period to determine the percent retaining the plasmid and the specific growth rate on various media. Plasmid stability in lake water was strongly strain specific; the NAH7 plasmid was stably maintained by the prototrophic strain for the duration of the test but was lost within 24 h by both of the auxotrophs. Specific growth rates of reisolates, compared with those of the corresponding non-lake water-exposed strains (i.e., parental strains), were not different when measured in rich medium (Luria-Bertani broth). However, specific growth rates were 42, 55, and 63% higher in reisolates of auxotrophs and the plasmid-free prototroph, respectively, when measured in 10-fold-diluted medium after exposure of 15 days or longer to lake water. Moreover, lake water-exposed strains grew actively when reintroduced into sterile lake water (28- to 33-fold increase in numbers over 7 days), while the corresponding unadapted parental strains exhibited no growth over the same period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Biological↗
PubMed1992

Significantly improved peripheral intravenous catheter performance in neonates: insertion ease, dwell time, complication rate, and costs.

A prospective, randomized, controlled study was performed in neonates in an intensive care nursery to compare the performance of a peripheral intravenous catheter made of Aquavene material (test catheter) with that of a conventional peripheral catheter made of Teflon material (control catheter). Aquavene is a newly developed biomaterial that softens and expands on contact with body fluids. A total of 105 catheters (50 test and 55 control) were inserted in 63 neonates. The median time to a catheter-related complication was 3.60 days for the test catheters and 1.75 days for the control catheters (p = 0.0007). Infiltration rate for the test catheters was 56% as compared with 78% for the control catheters (p = 0.03). The test catheters provided fewer catheter-related complications (p = 0.006), with 34% of the test catheters reaching end of therapy as compared with 9% of the control catheters (p = 0.004). On average, 1.8 test catheters were used per insertion versus 2.3 control catheters (p = 0.08). The test catheters were rated easier to insert (p = 0.05), with a shorter time required for insertion. Because of improved performance, cost savings were realized with the test catheters after the first day of therapy, even though the per unit cost of the test catheter was greater. These data indicate that the test catheter, made of Aquavene material, is superior to the Teflon catheter for peripheral intravenous therapy in neonates.

Biocompatible Materials↗
PubMed1991

The immunosuppressive properties of enisoprost and a 5-lipoxygenase inhibitor (SC-45662).

Metabolic derivatives of arachidonic acid such as prostaglandins and leukotrienes may alter immune responses. Enisoprost (ENO), a synthetic prostaglandin E analog, inhibited the response of human peripheral blood mononuclear cells to phytohemagglutinin in a concentration-dependent fashion: .1, 1.0, and 10 micrograms/ml yielding 4.0, 21.7, and 74.3% inhibition, respectively. ENO also potently inhibited both IL-2 production (measured by ELISA) and IL-2 responsiveness (measured by CTLL-2 response to IL-2) in a concentration-dependent manner, yet did not inhibit acquisition of IL-2 receptors. ENO similarly diminished efferent immune function in a concentration-dependent fashion, as measured by inhibition of cytotoxic T cell and natural killer effector function. A 5-lipoxygenase inhibitor (5-LO), SC-45662, also inhibited mononuclear cell response to PHA in a concentration-dependent manner: 0.1, 1.0, and 10 micrograms/ml yielding 5.0, 9.7, and 79.7% inhibition, respectively. Although 5-LO potently inhibited IL-2 production, it had no effect on IL-2 responsiveness or IL-2 receptor acquisition. Like ENO, 5-LO impaired CTL and NK effector function yet was not as potent in inhibiting CTL effector function. In summary, ENO and 5-LO inhibit afferent and efferent immune function. The inhibitory effects of these drugs are not related to cytotoxicity as cell viability is maintained for 72 hr in the presence of these drugs, and the inhibitory effect is reversible when the drugs are removed. The 5-LO does not inhibit mononuclear cell responses simply by shunting the formation of arachidonic acid precursors to form inhibitory prostaglandins, since it does not impair IL-2 responsiveness in a manner similar to ENO. These two compounds may prove to have clinical utility in organ transplantation if safely achieved serum concentrations of these drugs yield in vivo immunosuppression parallel to our in vitro results.

Acetates↗
PubMed1991

Carbohydrate signatures of aquatic macrophytes and their dissolved degradation products as determined by a sensitive high-performance ion chromatography method.

The sugar contents of emergent macrophytes from a freshwater lake, a freshwater swamp, and a salt marsh in the southeastern United States were examined together with the dissolved free sugars produced during macrophyte degradation and in natural water samples collected adjacent to macrophyte stands. Simultaneous separation of up to 13 neutral and 2 amino sugars together with 3 uronic acids and muramic acid was achieved by anion-exchange high-performance ion chromatography. As little as 10 pmol or a concentration of 20 nM sugar can be detected by pulsed amperometry, a greater sensitivity for sugar quantification than that of previously reported detection techniques used in conjunction with either gas or liquid chromatographic systems. Optimum conditions for hydrolysis of plant material by using trifluoroacetic acid were determined, and internal standards were used to quantify losses due to matrix effects and solid-phase extraction of samples. Our data demonstrate that ratios of certain indicator sugars in undegraded macrophytes differ significantly from ratios of dissolved free sugars formed during macrophyte degradation, reflecting the complex processes (biological and physical) involved in vascular plant degradation in aquatic ecosystems. Natural water samples collected adjacent to macrophyte beds contained dissolved free sugars at concentrations of 620 nM (lake), 890 nM (freshwater swamp), and 2,300 nM (salt marsh). Sugar signatures of these natural water samples were similar to those of macrophyte degradation products.

Journal Article↗
PubMed1990

Relative growth and maturation of axon size and myelin thickness in the tibial nerve of the rat. 1. Normal animals.

Morphometric observations have been made on the medial plantar division of the tibial nerve (MPD) and on the motor branches of the tibial nerve to the calf muscles (MBC) in rats ranging in age from weaning (3 weeks) to 12 months. Axon size, assessed by measurements of circumference and cross-sectional area, increased rapidly until 3 months with further slight increases between 3 and 9 months and a slight fall between 9 and 12 months. Axon size distributions were unimodal throughout in the MPD but bimodal for the MBC except at 3 weeks. Distributions of myelin thickness were bimodal throughout for both nerves. Scatter plots of g ratios (axon diameter:total fibre diameter) confirmed the presence of two fibre populations: a group of small fibres with relatively thin myelin sheaths, and a group of larger fibres within which sheath thickness was relatively less on the larger than on the smaller axons. These two fibres populations were less easily separable in the MBC than in the MPD nerves. These results document morphometrically the normal growth changes in the rat tibial nerve and also provide control data for the analysis of the effects of experimental procedures on the growth and maturation of peripheral nerve fibres.

Aging↗
PubMed1990

Relative growth and maturation of axon size and myelin thickness in the tibial nerve of the rat. 2. Effect of streptozotocin-induced diabetes.

The relative changes in the growth and maturation of axon size and myelin thickness were studied in the medial plantar division of the tibial nerve in the lower leg and in the motor branches of the tibial nerve to the calf muscles in rats in which diabetes mellitus had been induced with streptozotocin at the time of weaning. Observations were made at 6 weeks and 3, 6, 9 and 12 months of diabetes for comparison with age-matched controls. Similar changes were observed in both nerves. Growth in body weight and skeletal growth was severely retarded from the time of induction of diabetes but at the 6-week stage axon size was not reduced, suggesting that neural growth may initially be relatively protected. At later stages axon size was consistently reduced in the diabetic animals as compared with the controls and showed an absolute reduction at 12 months, as compared with 9 months, that was greater than in the controls. Myelin thickness became reduced earlier and was more severely affected than axon size so that the fibers were relatively hypomyelinated. The myelin changes were greater in larger than in smaller fibers. The index of circularity of axons was reduced in the diabetic nerves. These results show that induction of diabetes in prepubertal rats produces effects on peripheral nerve fibers which differ from those resulting from diabetes induced in adult animals. The effects also differ between large and small nerve fibres. These observations may explain some of the disparate findings obtained in previous studies on experimental diabetes in rats.

Animals↗
PubMed1989

Bacterial secondary production on vascular plant detritus: relationships to detritus composition and degradation rate.

Bacterial production at the expense of vascular plant detritus was measured for three emergent plant species (Juncus effusus, Panicum hemitomon, and Typha latifolia) degrading in the littoral zone of a thermally impacted lake. Bacterial secondary production, measured as tritiated thymidine incorporation into DNA, ranged from 0.01 to 0.81 microgram of bacterial C mg of detritus-1 day-1. The three plant species differed with respect to the amount of bacterial productivity they supported per milligram of detritus, in accordance with the predicted biodegradability of the plant material based on initial nitrogen content, lignin content, and C/N ratio. Bacterial production also varied throughout the 22 weeks of in situ decomposition and was positively related to the nitrogen content and lignin content of the remaining detritus, as well as to the temperature of the lake water. Over time, production was negatively related to the C/N ratio and cellulose content of the degrading plant material. Bacterial production on degrading plant material was also calculated on the basis of plant surface area and ranged from 0.17 to 1.98 micrograms of bacterial C cm-2 day-1. Surface area-based calculations did not correlate well with either initial plant composition or changing composition of the remaining detritus during decomposition. The rate of bacterial detritus degradation, calculated from measured production of surface-attached bacteria, was much lower than the actual rate of weight loss of plant material. This discrepancy may be attributable to the importance of nonbacterial organisms in the degradation and loss of plant material from litterbags or to the microbially mediated solubilization of particulate material prior to bacterial utilization, or both.

Bacteria↗
PubMedDate not supplied

Case report of primary squamous carcinoma of the rectum.

PURPOSE: To report a patient with primary squamous carcinoma of the rectum. CASE REPORT: A 40-year-old woman with hematochezia and change in bowel habits was studied. The main laboratory finding was a mild anemia. A barium enema and a proctoscopy revealed a rectal neoplasm at eight cm from the anal verge. A transendoscopic biopsy demonstrated an squamous rectal carcinoma. A transrectal ultrasound and CT scan of the abdomen revealed a big rectal mass with transmural affection and possible involvement of the lymph nodes. The carcinoembriogenic antigen (CEA) was high (32 ng/mL). The patient underwent radiotherapy with 46 Gy, and 5-fluorouracil as radiosensitizer. Three months later, a new CT scan showed significant reduction of the size of the mass, and the patient underwent a very low anterior resection with double-stapled anastomosis. The analysis of the specimen showed a squamous carcinoma of the mid-rectum, invading through the wall without lymph node affection and with proximal, distal, and radial margins free of tumor. The CEA returned to normal after surgery (1.3 ng/mL). The patients is alive and without evidence of disease 18 months after the operation. CONCLUSION: Primary squamous carcinoma of the rectum is a rare disease, and surgery seems to be a good option of treatment, with the possibility of sphincter preservation depending upon the location of the tumor.

Adult↗