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Biomedical subjects

M D Jones

Publications and source records attributed to M D Jones.

At least 163 records · Page 9Linked to original sources
PubMed1980

Atelectasis associated with mechanical ventilation for hyaline membrane disease.

The occurrence of atelectasis among infants, who were intubated and mechanically ventilated for hyaline membrane disease and who survived the neonatal period, was examined after omitting atelectasis associated with obvious malposition of the endotracheal tube. Atelectasis occurred both while intubated and after extubation. There was a pronounced effect of birth weight. The incidence among 131 surviving infants increased from 9% while intubated and 15% after extubation in infants with birth weights > 2000 g to 50% while intubated and 56% after extubation in those with birth weights < 1000 g. Although in general, the incidence fell as the duration of intubation diminished, postextubation atelectasis was a problem even in larger infants with comparatively short intubations. The pattern of atelectasis showed a disproportionate involvement of all lobes of the right lung, both while intubated and after extubation. This suggests that the incidence of atelectasis might be lowered by minimizing traumatic damage to the mucosa of the right sided bronchi.

Birth Weight↗
PubMed1980

The complete amino-acid sequence of elongation factor Tu from Escherichia coli.

The complete primary structure of elongation factor Tu from Escherichia coli has been elucidated. The protein, which is a mixture of two gene products, consists of a single polypeptide chain of 393 residues. After tryptic digestion of S-carboxymethylated protein, 50 tryptic peptides were isolated covering the complete protein chain. Their alignment was established with overlapping peptides obtained by chemical cleavage with cyanogen bromide and subsequent enzymic subdigestion with Staphylococcus aureus protease, chymotrypsin, elastase and thermolysin. Peptides were sequenced by manual dansyl-Edman and direct Edman degradation procedures. The N-terminal amino acid of EF-Tu is serine and is N-acetylated. The lysine residue at positon 56, in the polypeptide chain is partly methylated. The C-terminal residue is a mixture of serine and glycine, and this was the only heterogeneity found in the EF-Tu preparation used in this study.

Amino Acid Sequence↗
PubMed1980

Jefferson fracture: presentation of a new diagnostic sign.

A case of a Jefferson fracture is presented. A new diagnostic sign, which is viewed on a lateral radiograph and consists of interposition of the basion between the anterior arch of C-1 and the odontoid process, is described. This sign may aid in the rapid identification of Jefferson fractures.

Adult↗
PubMed1980

Retinal and choroidal blood flow in unstressed fetal and neonatal lambs.

The relationship between retinal blood flow (RBF) and choroidal blood flow (ChBF) and the oxygen content of arterial blood was investigated in 12 fetal lambs. The postnatal changes in these flows were studied in twelve newborn lambs. RBF and ChBF were determined by means of radioactive microspheres 3 to 10 days after implantation of the injection and sampling catheters. Fetal blood flows were measured at different levels of oxygenation. The postnatal flows were measured while the lamb breathed room air. The fetal data suggest an inverse relationship between RBF and arterial oxygen content. Concomitant changes in fetal ChBF were unrelated to arterial oxygen content. Because of the inverse relationship between RBF and arterial oxygen content, the product of RBF and arterial oxygen content was independent of the state of fetal oxygenation. RBF did not change with birth, whereas ChBF increased. There was no change in RBF with postnatal age whereas ChBF decreased significantly with increasing age.

Animals↗
PubMed1979

Redistribution of cardiac output and oxygen delivery in the hypoxemic fetal lamb.

In hypoxia, fetal cardiac output and the product arterial O2 content x blood flow to the fetal heart and central nervous system (CNS) tend to remain constant. As a consequence the percentage of cardiac output directed to the heart and CNS increases hyperbolically in inverse relation to the oxygen content of the fetal ascending aorta, [O2]as. The fetal lamb maintains [O2]as approximately 0.45 mM (0.45 +/- 0.02 SEM) higher than the O2 content in the abdominal aorta, [O2]ab, over a wide range of oxygenation. When [O2]as decreases below the 2 mM level, the [O2]as--[O2]ab difference (delta O2) decreases also. A mathematical model of the fetal circulation shows that delta O2 is a function of the ratio oxygen consumption of fetal upper body/abdominal aorta blood flow (VU/FA). The behavior of delta O2 in hypoxia can be explained by assuming that the VU/FA ratio is maintained in moderate hypoxia and decreases in sever hypoxia.

Animals↗
PubMed1979

Blood flow to fetal organs as a function of arterial oxygen content.

In a sheep preparation the blood flow to fetal organs was studied 3 to 10 days after surgery by means of the microsphere technique over a range of fetal arterial O2 content from 6 to 1 mM. Blood flows to neural tissues (cerebrum, cerebellum, brain stem), heart, and the adrenals increased in inverse relation to arterial O2 content. As a result the arterial supply of O2 to these organs tended to remain constant over the O2 range studied. Blood flow to the fetal lungs decreased progressively with hypoxia. The blood flow to kidneys, digestive tract, pancreas, and carcass had a tendency to remain constant or increase gradually in the transition from high to moderately low levels of arterial O2 content and then to decrease abruptly in more severe hypoxia. Umbilical blood flow did not change systematically in relation to arterial O2 content.

Acid-Base Equilibrium↗
PubMed1978

Lap-sash three point seat belt fractures of the cervical spine.

Cervical spine injuries associated with three-point fixation lap-sash seat belts result from impact against the sash. While such injuries are infrequent and often without serious neurologic sequelae, they may produce serious deficits with grave injuries. Flexion-extension fractures of the lower cervical vertebrae, fractures of the transverse and spinous processes of the lower cervical and uppermost thoracic vertebrae, discal disruptions, and brachial plexus avulsions may occur. Of the 3 patients reported here, 2 escaped serious damage.

Accidents, Traffic↗
PubMed1978

Regulation of cerebral blood flow in the ovine fetus.

The effects on fetal cerebral blood flow (Qc) of changes in the carotid arterial and sagittal sinus venous PO2, PCO2, and oxygen content were studied in the chronically catheterized ovine fetus in utero at 130-140 days of gestation. Forty-seven measurements of Qc were made in 20 fetuses with radioactive microspheres. In 11 of these animals, 84 measurements of cerebral arteriovenous differences of oxygen content were performed, permitting an indirect measurement of cerebral blood flow (Qc*), assuming a constant cerebral metabolic rate. Arterial and, in 11 animals, sagittal sinus blood was withdrawn for analysis of PO2, PCO2, oxygen content, and pH at the time of the flow measurements. Preliminary analysis showed the best predictor of Qc and Qc* to be the reciprocal of the arterial oxygen content (1/CaO2). Multiple linear regression analysis combining the effects of 1/CaO2 with arterial PCO2 (PaCO2) gave the following equations: Qc = 458.8 (1/CaO2) + 2.68 PaCO2 - 107.93 (R2 = 0.68); Qc* = 435.54 (1CaO2) + 2.20 PaCO2 - 75.03 (R2 = 0.86). As a result of the hyperbolic relationship between Qc (and Qc*) and CaO2, changes in CaO2 at the low levels found during intrauterine life exert an important influence on the fetal cerebral circulation.

Animals↗
PubMed1978

Insulin effect on fetal glucose utilization.

Insulin infused into a sheep fetus over a 3-hr period at the rate of approximately 0.24 U.kg-1.h-1 increased fetal glucose uptake (utilization) from 4.4 +/- 0.7 mg.min-1.kg-1 to 6.9 +/- 0.9 mg.min-1.kg-1 as compared to a noninsulin control period. Insulin administration did not alter fetal oxygen consumption (8.6 +/- 0.7 ml.min-1.kg-1 vs. 7.7 +/- 0.7 ml.min-1.kg-1), umbilical blood flow (220 +/- 1 ml.min-1.kg-1 vs. 209 +/- 16 ml.min-1.kg-1), or the placental clearances of antipyrine (114 +/- 7 ml.min-1.kg-1 vs. 109 +/- 8ml.min-1.kg-1) and urea (24.5 +/- 2.2 ml.min-1.kg-1 vs. 25.0 +/- 2.1 ml.min-1.kg-1). Fetal plasma glucose concentration fell significantly (0.22 +/- 0.01 mg.ml-1 to 0.16 +/- 0.01 mg.ml-1) during insulin infusion. The insulin effect on fetal glucose uptake occurred over a range of maternal glucose concentrations (0.32 leads to 0.78 mg.ml-1), which were not altered by the infusion of insulin in the fetal compartment. Insulin has a specific effect on increasing fetal glucose uptake and utilization.

Animals↗