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Biomedical subjects

D J Murphy

Publications and source records attributed to D J Murphy.

At least 181 records · Page 10Linked to original sources
PubMed1986

Color Doppler detection of multiple ventricular septal defects.

Combined two-dimensional and Doppler echocardiography has a high sensitivity and specificity for detection of isolated perimembranous ventricular septal defects. However, muscular or multiple ventricular septal defects may be difficult to diagnose with noninvasive methods, particularly in older children, necessitating angiography for accurate diagnosis. Detection of single and multiple ventricular septal defects with two-dimensional color flow mapping was compared with detection by standard two-dimensional imaging and Doppler. Both techniques were compared with four-chamber left ventricular angiography. Fifty-one patients (age 3 months to 25 years, mean 5.6 years) were studied. Eighteen had solitary ventricular septal defects, 18 had multiple ventricular septal defects, and 15 patients with intact ventricular septum served as a control group. At least one ventricular septal defect was detected by color Doppler and two-dimensional/Doppler methods in all patients with ventricular septal defect proved by angiography with no false positives. In the detection of multiple ventricular septal defects, the sensitivity of color Doppler was 72% and that of two-dimensional/Doppler was 38% (100% specificity in both). Color Doppler failed to identify multiple ventricular septal defects in five patients (two weighing less than 4 kg and three with reduced pulmonary blood flow). However, no large additional muscular defects were missed by imaging and color Doppler. Color Doppler is useful for the detection of ventricular septal defects and has higher sensitivity than two-dimensional/Doppler for multiple ventricular septal defects. The contribution of color Doppler appears to be in the detection of additional small muscular ventricular septal defects.

Adolescent↗
PubMed1986

Force transmission through the distal radioulnar carpal joint: effect of ulnar lengthening and shortening.

Although numerous surgical procedures are performed on the wrist joint, little has been written regarding the effect of these procedures on the biomechanics of the wrist. This study has been undertaken to examine the in vitro consequences of ulnar lengthening and shortening. We have measured the axial forces transmitted through the distal radius and ulna and the pressure distribution on the articulating surface of the radius and triangular fibrocartilage complex for the intact wrist, with ulnar lengthening and with ulnar shortening. Lengthening of the ulna by 2.5 mm in the intact wrist increased the force borne by the ulna from 18.4% to 41.9% of the total axial load. Shortening of the ulna by 2.5 mm decreased axial load borne by the ulna to 4.3%. Removal of the articular disc portion of the triangular fibrocartilage complex decreased the load on the intact ulna from 18.4% to 6.2%. The peak pressure at the ulnolunate articulation increased from 1.4 N/mm2 for the unaltered wrist to 3.3 N/mm2 when the ulna was lengthened by 2.5 mm. These results suggest that the biomechanics of the wrist joint can be dramatically altered with relatively small (2.5 mm) changes in ulnar length and by removal of the articular disc portion of the triangular fibrocartilage complex.

Biomechanical Phenomena↗
PubMed1985

Interaction of Triton X-100 with the pigment-protein complexes of photosynthetic membranes.

The interaction of the non-ionic detergent Triton X-100 with photosynthetic membrane components of Pisum sativum (pea) is described. The detergent affected both the wavelength and the intensity of the 77K fluorescence-emission peaks of both Photosystem I and Photosystem II preparations, in addition to the effects on whole thylakoids recently described by Murphy & Woodrow [(1984) Biochem. J. 224, 989-993]. Below its critical micellar concentration, Triton X-100 had no effect on 77K fluorescence emissions even after prolonged incubations of up to 30 min. Above the critical micellar concentration of about 0.16 mg X ml-1, Triton X-100 caused a dramatic increase in the intensity of the 680 nm emission. The intensity of the 680 nm fluorescence emission continued to increase as more Triton X-100 was added, until limiting concentrations of detergent were reached. These limiting concentrations were proportional to the amount of membrane present and generally occurred at Triton X-100/chlorophyll (w/w) ratios of 100-200:1. In all cases the detergent effect was seen within 10 min, and is often considerably faster, with longer detergent treatments causing no further effects. The data are discussed in terms of a three-stage mechanism for detergent solubilization of membrane components.

Cell Membrane↗
PubMed1985

Substrate specificities of the enzymes of the oleate desaturase system from photosynthetic tissue.

In the microsomal fraction from young pea (Pisum sativum L.) leaves, the oleoyl moieties from oleoyl-CoA are principally transferred to the sn-2 position of phosphatidylcholine by oleoyl-CoA:1-acyl-lysophosphatidylcholine acyltransferase. The major product of this acyl transfer is 1-palmitoyl(stearoyl)-2-oleoyl phosphatidylcholine. The 1-palmitoyl(stearoyl)-2-oleoyl phosphatidylcholine is subsequently converted into 1-palmitoyl(stearoyl)-2-linoleoyl phosphatidylcholine by the oleate desaturase complex without equilibrating with the bulk membrane phosphatidylcholine pool. Hence, both the acyl transfer to phosphatidylcholine and the subsequent desaturation of oleoyl moieties occur on the sn-2 position of phosphatidylcholine, and there is also a functional coupling of the acyltransferase and oleate desaturase.

Fabaceae↗
PubMed1985

Noninvasive evaluation of newborns with suspected congenital heart disease.

In the distressed newborn, the presence or absence of congenital heart disease (CHD) may be difficult to determine on clinical grounds alone. We prospectively studied 104 infants who were younger than 7 days of age and in whom CHD was suspected. The presence of CHD was detected noninvasively in 64 infants. The other 40 infants were considered not to have CHD. None of these 40 infants underwent cardiac catheterization for the purpose of excluding CHD, although three (7.5%) were subsequently found to have incidental cardiac lesions. In nine (14%) of the patients with CHD, the noninvasive diagnosis was incomplete. In four patients, ventricular septal defects were not detected; in another patient, a suspected ventricular septal defect was not confirmed at catheterization. In addition, three abnormalities of the great vessels were misdiagnosed noninvasively. We conclude that cardiac catheterization is not necessary to exclude significant CHD in the distressed newborn resulting from noncardiac causes, but significant diagnostic errors regarding anomalies of the aortic arch and ventricular septal defects may occur, based on the noninvasive evaluation alone.

Cardiac Catheterization↗
PubMed1985

Tractor stability indicator.

Tractor overturns are a major cause of death in farm operations. The overturns are the result of interactions between the tractor operator, the tractor and the environment. Numerous variables involved in tractor overturn have been identified. Previous stability analyses have resulted in attempts to design devices to warn or prevent tractor rollover but to date nothing has proved successful. A newer approach to the rollover problem is to develop instrumentation that will give the operator instantaneous cues concerning the tractor's stability as it is operated. The device is perceived as a learning instrument which will increase both cognitive and motor skills.

Journal Article↗
PubMed1985

Concomitant psychological and cardiac improvement during successful treatment of anorexia nervosa.

A patient with anorexia nervosa in whom concurrent nutritional, psychological, and cardiovascular assessments were obtained sequentially during successful treatment is presented. At the time of diagnosis, severe multisystem dysfunction was present including depression, low self-esteem, hypotension, bradycardia, exercise intolerance, and abnormalities of systolic and diastolic cardiac function. Treatment resulted in weight gain and increased skinfold thickness and arm circumference. There were concomitant improvements in the psychometric indices of depression and self-esteem as well as decreased anorectic tendencies. During her recovery, working capacity increased and diastolic function improved. However, echocardiographic evidence of impaired systolic function persisted. Despite the apparent treatment success in this patient, this report suggests a potential need for further studies to determine the extent, if any, of long-term cardiac sequelae.

Adolescent↗
PubMed1985

Intracardiac undifferentiated sarcoma in infancy.

A rare case of an intracardiac undifferentiated sarcoma in a 3 month old infant is described together with the clinical, angiographic, echocardiographic, surgical and histopathologic findings. The tumor was successfully removed surgically, and monthly echocardiographic follow-up is being performed.

Echocardiography↗
PubMed1985

Effects of neonatal polycythemia and partial exchange transfusion on cardiac function: an echocardiographic study.

Although infants with neonatal polycythemia and hyperviscosity often present with cardiorespiratory distress, little information is available regarding the cardiac function of such babies before or after partial exchange transfusion. To assess cardiac function, we performed M-mode echocardiograms in 19 asymptomatic newborn infants (4 to 12 hours of age) who had venous hematocrits greater than 65%. The echocardiograms were performed immediately prior to and following partial exchange transfusion and were repeated at 48 hours of age. Eighteen matched newborn controls also underwent echocardiography within the first 12 hours of life and again at 48 hours. Polycythemic newborns had elevated right ventricular preejection period to right ventricular ejection time ratios compared with controls (0.46 +/- 0.11 v 0.37 +/- 0.04, P = .002), suggestive of increased pulmonary vascular resistance. These indexes normalized following partial exchange transfusion. In addition, the polycythemic newborns were relatively bradycardic prior to exchange (116 +/- 13 beats per minute v 125 +/- 16 beats per minute, P less than .05), but heart rates normalized following the procedure. At 48 hours, the polycythemic and control groups were different only in that the mean shortening fraction of the polycythemic group was lower than that of the controls (32% +/- 4% v 36% +/- 6%, P = .02). The findings are consistent with elevated pulmonary vascular resistance associated with polycythemia and hyperviscosity. Cardiac output may be lower in polycythemic infants. The finding of reduced fractional shortening in polycythemic infants at 48 hours following partial exchange transfusion is unexplained.

Blood Viscosity↗
PubMed1984

The effects of Triton X-100 and n-octyl beta-D-glucopyranoside on energy transfer in photosynthetic membranes.

The effects of the non-ionic detergents Triton X-100 and n-octyl beta-D-glucopyranoside on energy transfer between pigment-protein complexes of Pisum sativum thylakoids were investigated. This was done by monitoring the 77K fluorescence-emission characteristics of stacked and unstacked thylakoids exposed to a range of detergent concentrations. At sub-critical micellar concentrations, the detergents had little effect, whereas above these concentrations they caused increases of up to 20-fold in short-wavelength fluorescence intensity and a shift in its maximum wavelength from 685 to 680 nm. Fluorescence-emission intensities at 695 and 735 nm were relatively unaffected by detergent treatments, although Triton X-100 caused a wavelength shift in the emission peak from 735 to 728 nm. The results are discussed in terms of reversible dissociation of pigment-protein complexes induced by mild detergent solubilization and the consequent cessation of inter-complex energy transfer.

Cell Membrane↗
PubMed1984

Solubilization, purification and kinetic properties of three membrane-bound long-chain acyl-coenzyme-A thioesterases from microsomes of photosynthetic tissue.

Microsomal membranes of developing pea (Pisum sativum) leaves contained almost one third of the total long-chain acyl-CoA thioesterase activity found in the leaf cell. Three distinct forms of long-chain acyl-CoA thioesterase were purified by a combination of cholate-solubilization, dialysis, ion-exchange, and gel-filtration chromatography. Purification factors of 4600, 100 and 280 were achieved for the thioesterase forms I, II and III, respectively. Apparent molecular masses were: form I, 28 kDa; form II, 140 kDa; form III, 139 kDa. All the three thioesterases showed overlapping specificities towards palmitoyl-CoA, stearoyl-CoA, and oleoyl-CoA but were inactive towards short-chain acyl-CoAs, such as acetyl-CoA and malonyl-CoA. Each thioesterase exhibited complex kinetic behavior, which was consistent with differential affinities of the enzymes for monomeric and micellar forms of their substrates. The significance of the kinetic behavior and possible regulatory role of these enzymes are discussed.

Chromatography, DEAE-Cellulose↗
PubMed1984

Regulation of stromal sedoheptulose 1,7-bisphosphatase activity by pH and Mg2+ concentration.

A scheme is proposed for the regulation of stromal sedoheptulose 1,7-bisphosphatase activity which enlarges upon a previously elaborated mechanism (Woodrow, I.E., and Walker, D.A. (1983) Biochim. Biophys. Acta 722, 508-516). The latter involves oxidized (inactive) and reduced (active) enzyme forms. Both the free enzymes and the enzyme-substrate complexes undergo slow oxidation/reduction. This study examines the behavior of the system under pH and Mg2+ concentration regimes that are likely to occur in the chloroplast stroma. The control of enzyme activity by pH can be described in terms of each free enzyme and enzyme-substrate complex existing in protonated and nonprotonated forms. The molecular dissociation constants for each protonation reaction were calculated from kinetic data. Mg2+ concentration changes modulate these constants. Under conditions that are likely to obtain in the stroma in the dark, the model predicts that approximately 99.1% of the enzyme will be in the inactive forms. Such inactivation is important since it would prevent the reductive pentose phosphate pathway from operating in darkness.

Enzyme Activation↗
PubMed1984

Functional association of a monoacylglycerophosphocholine acyltransferase and the oleoylglycerophosphocholine desaturase in microsomes from developing leaves.

The biosynthesis of linoleic acid has been investigated, using oleoyl-CoA as a substrate, in microsomal preparations from young leaves of Pisum sativum. Oleoyl moieties from oleoyl-CoA were preferentially acylated to lysophosphatidylcholine by an acyltransferase to produce an oleoylglycerophosphocholine. Kinetic data are presented which argue for a direct desaturation of the oleoyl moieties of this oleoyl glycerophosphocholine to linoleoyl moieties. There was no evidence of a subsequent acyltransfer of linoleoyl moieties either to form thioesters or oxygen esters in other complex lipids. The kinetics were also consistent with a functional coupling of the lysophosphatidylcholine acyltransferase with the oleate desaturase. There was little exchange of the oleoyl glycerophosphocholine from the bulk membrane lipid with that newly synthesised by the lysophosphatidylcholine acyltransferase. Rather, the newly synthesised oleoylglycerophosphocholine seemed to be directly channelled to the vicinity of the desaturase. The results are discussed in the context of 'metabolite channelling'. The consequences for desaturase activity and its regulation are also examined.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1983

Lipid metabolism in microsomal fraction from photosynthetic tissue. Effects of catalase and hydrogen peroxide on oleate desaturation.

On incubation of microsomal fraction from pea (Pisum sativum L.) leaves with ammonium [1-14C]oleate or [1-14C]oleoyl-CoA in the presence of ATP, CoA, Mg2+ and NADH, the major reactions observed were those catalysed by oleoyl-CoA synthetase, oleoyl-CoA thioesterase, oleoyl-CoA:phosphatidylcholine acyltransferase and oleoyl phosphatidylcholine desaturase. The reaction catalysed by oleoyl phosphatidylcholine desaturase was specifically inhibited by H2O2, and this inhibitory effect was overcome by catalase (EC 1.11.1.6).

Acyl Coenzyme A↗
PubMed1983

Regulation of photosynthetic carbon metabolism. The effect of inorganic phosphate on stromal sedoheptulose-1,7-bisphosphatase.

The activation and steady-state kinetics of wheat chloroplast sedoheptulose-1,7-bisphosphatase at several concentrations of inorganic phosphate are examined. Inorganic phosphate competitively inhibits substrate binding to both the active and inactive forms of the enzyme and reduces the rate of enzyme activation. Modulation of the apparent Km of sedoheptulose-1,7-bisphosphatase and fructose-1,6-bisphosphatase for their substrates by inorganic phosphate is discussed in terms of the control of intermediate pool sizes in the reductive pentose phosphate pathway and of the flux of fixed carbon towards starch synthesis or export from the chloroplast.

Carbon↗
PubMed1983

Freezing resistance in intertidal invertebrates.

Intertidal invertebrates survive exposures to temperatures as low as -20 degrees C by tolerating the presence of tissue ice. This resistance to freezing is influenced by such factors as the time and temperature of exposure, the rate of cooling during tissue ice formation, the temperature and salinity of the seawater to which the animals have adapted, and the oxygen content of tissues. Freezing injury appears to result primarily from extracellular ice formation, although for certain smaller invertebrates that cool at rates exceeding 0.4 degrees C min-1 during tissue ice formation, intracellular ice formation may be the cause of freezing injury. Extracellular ice formation is a dehydration stress, and injury resulting from extracellular ice appears to involve membrane damage resulting from the loss of a critical amount of cellular water. Physiological mechanisms that lower the temperatures at which extracellular ice causes injury are dependent on factors that either (a) "bind" a certain fraction of intracellular water and thus reduce the amount of water lost during freezing, or (b) increase the resistance of cells to greater quantities of tissue ice. Certain structural components and glycoproteins have been isolated from an intertidal mollusk that can impede or prevent the formation of ice. However, a quantitative relationship between these components and freezing resistance has not been established. The resistance to greater quantities of tissue ice appears to be associated with low levels of tissue oxygen and with anaerobic metabolism. A rise in blood calcium concentration following a shift from aerobic to anaerobic metabolism can account for part of the increased resistance of an intertidal mollusk to greater quantities of tissue ice, while membrane changes and factors that reduce the toxic effects of oxygen may also be involved. The possibility that oxygen is associated with injury resulting from extracellular ice formation in intertidal invertebrates deserves further investigation.

Adaptation, Physiological↗
PubMed1983

Group A streptococcal meningitis.

A retrospective record study of six cases of meningitis caused by group A beta-hemolytic Streptococcus is presented. Associated findings included otitis media, pharyngitis, and erysipelas. All patients survived their infections despite major complications including seizures, shock, coma, renal failure, and hepatitis. Two patients had neurologic sequelae. Group A Streptococcus causes a severe form of bacterial meningitis in apparently healthy children.

Child↗