Biomedical subjects

J Cullen

Publications and source records attributed to J Cullen.

96 records · Page 6Linked to original sources

PubMed1967

An extracellular lipopolysaccharide-phospholipid-protein complex produced by Escherichia coli grown under lysine-limiting conditions.

Lysine limitation during growth of the lysine-requiring mutant of Escherichia coli 12408 resulted in the excretion of a complex containing 60% of lipopolysaccharide, 26% of extractable phospholipid and 11% of protein. The complex was obtained from the culture filtrate in yields of about 0.5g./l. by precipitation with chloroform or gel filtration; some purification steps are described. The greater part of the phospholipid consisted of phosphatidylethanolamine, which contained four main fatty acids; two monoenoic acids and a cyclopropane acid were esterified mainly in the beta-position, and a saturated acid was located mainly in the gamma-position. The protein component was relatively insoluble and contained an excess of acidic over basic amino acids and little cystine. The lipopolysaccharide resembled in composition the intracellular lipopolysaccharides from rough strains of E. coli. Both protein and lipopolysaccharide constituents of the complex were serologically active; the complex was less toxic than the purified lipopolysaccharide. In the electron microscope the complex showed a mixture of particles of various sizes and shapes. Rods and hollow spheroids (diameter 12-200mmu) were most common and resembled the particles previously found surrounding cells actively excreting the complex. The chloroform-precipitated material showed a tubular lamellar structure. Soluble lipopolysaccharide prepared from the complex also consisted of hollow spheres and rods.

Bacterial Proteins↗

PubMed1967

Fatty acid synthesis in Escherichia coli.

1. Fatty acid formation by cells of a strain of Escherichia coli has been studied in the exponential, post-exponential and stationary phases of growth. 2. During the exponential phase of growth, the metabolic quotient (mmumoles of fatty acid synthesized/mg. dry wt. of cells/hr.) for each fatty acid in the extractable lipid was constant. 3. The newly synthesized fatty acid mixtures produced during this phase contained hexadecanoic acid (41%), hexadecenoic acid (31%), octadecenoic acid (21%) and the C(17)-cyclopropane acid, methylenehexadecanoic acid (4%). 4. As the proportion of newly synthesized material increased, changes in the fatty acid composition of the cells during this period were towards this constant composition. 5. Abrupt changes in fatty acid synthesis occurred when exponential growth ceased. 6. In media in which glycerol, or SO(4) (2-) or Mg(2+), was growth-limiting there was a small accumulation of C(17)-cyclopropane acid in cells growing in the post-exponential phase of growth. 7. Where either NH(4) (+) or PO(4) (3-) was growth-limiting and there were adequate supplies of glycerol, Mg(2+) and SO(4) (2-), there was a marked accumulation of C(17)-cyclopropane acid and C(19)-cyclopropane acid appeared. 8. Under appropriate conditions the metabolic quotient for C(17)-cyclopropane acid increased up to sevenfold at the end of exponential growth. Simultaneously the metabolic quotients of the other acids fell. 9. A mixture of glycerol, Mg(2+) and SO(4) (2-) stimulated cyclopropane acid formation in resting cells.

Bacteriological Techniques↗

PubMed1965

Some factors affecting cyclopropane acid formation in Escherichia coli.

1. The fatty acid composition of the extractable lipids of Escherichia coli varied with growth conditions. 2. The principal fatty acids were palmitic acid, hexadecenoic acid, octadecenoic acid and the cyclopropane acids, methylenehexadecanoic acid and methyleneoctadecanoic acid. 3. Cyclopropane acid formation from monoenoic acids was increased by acid media, poor oxygen supply, or high growth temperature. 4. Cyclopropane acid formation was decreased by alkaline media, well oxygenated conditions, the presence of citrate, or lack of Mg(2+).

Chromatography, Gas↗

PubMedDate not supplied

Utility of serial EEGs in neonates during extracorporeal membrane oxygenation.

We found electroencephalographic (EEG) studies to be useful for monitoring cerebral function, for confirming seizure activity, and for limited prediction of short-term outcome in 145 neonates who required extra-corporeal membrane oxygenation (ECMO) of reversible respiratory failure. The EEG tracings were classified as normal or as mildly, moderately, or markedly abnormal; abnormal recordings were further classified as focal, diffuse, or predominantly lateralized. A significant decrease in frequency and degree of EEG abnormalities was observed in recordings obtained after ECMO compared to those obtained prior to (P = .001) or during ECMO (P = .001). There was no significant increase in marked EEG abnormalities when recordings obtained before and during ECMO were compared (P = 0.41). Of 11 infants with electrographic seizures during ECMO, 7 (64%) either died during their nursery courses or were developmentally handicapped at age 1 year which is a significantly greater adverse outcome than that observed in infants without EEG seizure activity (P less than .003). No consistently lateralized EEG abnormalities were observed during or after ECMO when compared to tracings obtained before cannulation of the right common carotid artery. There was no acute change in EEG rhythm or amplitude over the right cerebral hemisphere during right common carotid artery cannulation. Our observations support the value of serial EEG in the assessment of cerebral function in critically ill infants undergoing ECMO. They further suggest that, in this patient population, cannulation of the right common carotid artery is a safe procedure that does not result in lateralized abnormalities of cerebral electrical activity.

Brain Damage, Chronic↗

PubMedDate not supplied

Experimental prosthetic vein valve.

Medical and surgical management of venous insufficiency syndrome (VIS) has produced disappointing results despite the recent introduction of new surgical techniques. This has prompted the investigation of a sutureless prosthetic vein valve. Ten prosthetic sutureless vein valves have been tested to date. The valves are of two types, one constructed of platinum, the other of titanium. Fourteen to eighteen months post-insertion into the femoral vein or vena cava of mongrel dogs, five valves remain patent as shown be venography. The sutureless prosthetic vein valve is a promising development in the treatment of venous insufficiency.

Animals↗

PubMedDate not supplied

Measurement of single-breath carbon monoxide transfer factor (diffusing capacity) during progressive exercise.

The transfer factor (diffusing capacity) for carbon monoxide (TLCO) is known to rise with increasing levels of work, but uncertainty remains as to the exact relationship of TLCO and the transfer coefficient (KCO) to oxygen uptake (VO2). We have studied the effects of increasing levels of work on TLCO and KCO in 22 normal male subjects using the single-breath technique and a standardized protocol. Additionally, we have investigated whether young people were different from a middle-age group, the need for carboxyhaemoglobin corrections in current smokers and non-smokers, and the variations of cardiac frequency during breath-holding. Our results show that TLCO and KCO increase in a curvilinear manner up to maximal VO2, a quadratic equation describing the relationship. There was no effect of age up to 50 years. There was no significant increase in the carboxyhaemoglobin levels, and therefore this correction is unnecessary. Cardiac frequency showed no significant variation during the breath-holding manoeuvre, except at rest and at low levels of exercise.

Adult↗