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Biomedical subjects

J W Cox

Publications and source records attributed to J W Cox.

At least 19 recordsLinked to original sources
PubMed1992

Biochemistry and pharmacology of lipid antioxidants in acute brain and spinal cord injury.

Oxygen radical-mediated lipid peroxidation (LP) has been suggested increasingly to be an important factor in posttraumatic neuronal degeneration. Thus, numerous studies have evaluated the neuroprotective efficacy of pharmacological agents with lipid antioxidant activity in models of spinal cord and brain injury. Intensive pretreatment of animals with the endogenous lipid peroxyl radical scavenger vitamin E (i.e., alpha-tocopherol) has been shown to decrease posttraumatic spinal cord ischemia and to enhance chronic neurological recovery. However, the slow CNS tissue uptake of vitamin E requires chronic dosing, making it an impractical agent for treatment of acute neural injury. The glucocorticoid steroid, methyl-prednisolone (MP), has been shown to possess significant antioxidant efficacy and, when administered to animals or humans in antioxidant doses, improves chronic neurological recovery after spinal cord injury. This activity of MP is independent of the steroid's glucocorticoid receptor-mediated actions, as evidenced by the efficacy of the novel antioxidant 21-aminosteroids, which are devoid of glucocorticoid activity but have greater antioxidant efficacy than MP. One of these, tirilazad mesylate (U-74006F), has been shown to be effective in animal models of brain and spinal cord injury and is currently the subject of phase II clinical trials. Recently, compounds that combine the amino functionality of the 21-amino-steroids with the peroxyl radical scavenging chromanol portion of vitamin E (i.e., 2-methylaminochromans) also have shown promise as neuroprotective agents. The consistent benefit afforded by antioxidant compounds further supports the concept that LP is an important therapeutic target for acute pharmacological neuroprotection.

Animals↗
PubMed1979

Infant mortality in 12 Aboriginal settlements: Queensland, 1972--1976.

The infant mortality rate amongst Aborigines from 12 Queensland Aboriginal settlements and missions over the years 1972 to 1976 was 72 per 1000 live births. This rate is comparable with that for Queensland of 60 years ago. The Aboriginal infants had twice the present-day Queensland risk of neonatal death and eight times the risk of postneonatal death. Prematurity was the major cause of neonatal deaths; gastroenteritis and pneumonia were the major causes of infant deaths. These rates emphasise the need for community and preventive health care for the Aboriginal children, particularly during the postneonatal period.

Australia↗
PubMed1979

Synthesis of choline and ethanolamine phospholipids with thiophosphoester bonds as substrates for phospholipase C.

Spectrophotometric assays of esterases are sensitive, rapid, and quite specific when thioester substrates are used. Glycerophospholipids with thiophosphoester bonds may be useful as substrates for phospholipase C (EC 3.1.4.3). These have been made from mercaptoglycerol and mercaptoethanol. The thiols were oxidized to disulfides, acylated, and reduced with dithiothreitol. Phosphocholine derivatives were made by the classical methods for oxyphosphoesters. The phosphatidyl choline analogue was converted to the phosphatidyl ethanolamine analogue by transphosphatidylation with cabbage phospholipase D and ethanolamine. Structures were proved with enzymic hydrolysis, infrared spectra, TLC behavior, and elemental analyses. The synthesized compounds were rac-1-S-phosphocholine-2,3-O-didecanoyl-1-mercapto-2,3-propanediol, 1-S-phosphoethanolamine-2,3-O-didecanoyl-1-mercapto-2,3-propanediol, and 1-S-phosphocholine-2-O-hexadecanoyl-1-mercapto-2-ethanol.

Bacillus cereus↗
PubMed1979

A system oriented electrocardiographic amplifier.

A low noise, programmable gain amplifier has been developed for acquiring ECG data from a variety of recording environments. Features include: low noise (4muV peak-to-peak) differential inputs; digitally programmable gains (range 100 to 16000) and output DC offsets (range -3.5 to +4 V) controlled via a serial interface; externally selectable low frequency response (0.04 or 0.08 Hz); and an on-board output monitor multiplexer controlled via a second serial interface.

Amplifiers, Electronic↗
PubMed1979

Factors influencing the time of introduction of steroidal contraception in the breast-feeding mother.

To ensure infertility whilst breast feeding many mothers ingest steroidal contraceptives. Animal experiments have shown how sexual differentiation of the brain occurs during perinatal life and can be affected by exogenous steroids. The amount of sex steroid secreted in the milk of lactating mothers is very small and dependent on the type of steroid chosen. "On demand" breast feeding is associated with a longer period of lactational amenorrhoea, obviating the necessity for early usage of contraceptives. In view of the possibility that sexual differentiation may be disturbed, it is suggested that, where steroidal contraception is required, the progesterone with the minimal amount of oestrogenic metabolite be used.

Animals↗
PubMed1978

The MEDLINE hardware and software.

The National Library of Medicine's computer system has developed from a second generation computer to the large IBM multiprocessor system that is now used to maintain the MEDLINE file, provide retrieval services, and produce the computer photocomposed products of the NLM. On-line maintenance facilities have been developed for the final steps in the input and file maintenance processes. The retrieval program, ELHILL, and its supporting programs now provide more bibliographic searches than any other system in the world. The photocomposed products, including Index Medicus, are produced through the use of flexible publication programmes which have allowed NIH to use several different photocomposers.

Computers↗
PubMed1977

The electrocardiographic image surface revisited.

An image torso may be viewed as a one-to-one transform of a physical volume conductor to a geometric form which defines both the axis and sensitivity of any electrocardiographic connection. In this report, the image surfaces of laminar, spherical, rectangular and humanoid physical torsos are explored theoretically and experimentally. All proved to be rounded or spherical in form despite the marked differences in the configuration of the physical conductor. Moderate degrees of dipole eccentricity induced only small departures from this basic circular pattern. Introduction of phase inhomogeneity, however, resulted in more striking deviations from roundness.

Animals↗
PubMed1977

Left precordial isopotential mapping during supine exercise.

Junctional depression is often observed during physical exercise in overtly normal subjects. To explore its pathogenesis, 15 normal volunteers were studied during supine, bicycle ergometer, submaximal stress tests. Electrocardiograms were simultaneously recorded from 42 electrodes on the left anterior precordium at two minute intervals at rest and during exercise. Data were used to construct isopotential maps throughout the P-QRS-T intervals. At rest, maps throughout the ST segment were dominated by a single maximum along the upper left sternal border. During exercise, all subjects developed junctional depression that was maximal along the lower left sternal border. Exercise maps during the early to mid-ST segment showed an intense minimum along the lower left sternal border that was continuous with terminal QRS forces in both intensity and location. Later in ST, this minimum decreased in strength and was replaced by a maximum located in the same area as that observed at rest. These observations suggest that junctional depression is the result of competition between two effects, one being normal repolarization which is obscured in the early ST segment by the second, possibly representing delayed terminal depolarization forces.

Action Potentials↗
PubMed1977

Relative dipolar behavior of the equivalent T wave generator: quantitative comparison with ventricular excitation in the rabbit heart.

We studied the relative dipolar and nondipolar content of signal energy throughout ventricular excitation and recovery in 34 isolated, perfused rabbit hearts, suspended in an electrolyte-filled spherical chamber. Computer-processed signals were derived from 20 evenly spaced tank-surface electrodes, and a single, moving, equivalent cardiac dipole generator was optimally fitted to the recorded potentials for each 1-msec sampling interval. Superimposed, time-based plots of signal energy for the 34 preparations showed ventricular excitation to be strikingly more nondipolar than was recovery. In terms of the summed square ratio of nondipolar residual energies, overall nondipolarity of QRS exceed that of ST-T by 41%. Furthermore, the maximum instantaneous ratio during QRS was considerably greater than during the ST-T. Evaluation of paired differences, comparing nondipolar behavior throughout QRS with all of ST-T, proved highly significant (P less than .005). We also found that in contrast to the considerable mobility exhibited by the equivalent QRS dipole, the ST-T dipole locus remained nearly stationary during most of ventricular recovery. Presumably because repolarization is temporally and spatially a relatively diffuse process, it may generate electrical fields which are notably more dipolar than those caused by depolarization.

Animals↗
PubMed1977

Detection and localization of multiple epicardial electrical generators by a two-dipole ranging technique.

The ability of a numerical procedure to detect and to localize two experimentally induced, epicardial dipolar generators was tested in 24 isolated, perfused rabbit heart preparations, suspended in an electrolyte-filled spherical tank. Electrocardiograms were recorded from 32 electrodes on the surface of the test chamber before and after placement of each of two epicardial burns. The second lesion was located either 180 degrees, 90 degrees, or 45 degrees from the first. Signals were processed by iterative routines that computed the location of one or two independent dipoles that best reconstruced the observed surface potentials. The computed single dipole acounting for 99.68% of root mean sequare (RMS) surface potential recorded after the first burn was located 0.26 +/- 0.10 cm from the centroid of the lesion. Potentials recorded after the second lesions were fit with two dipoles that accounted for 99.36 +/- 1.51% of RMS surface potentials and that were located 0.42 +/- 0.26 cm and 0.57 +/- 0.49 cm from the centers of the corresponding burn. Seventy-one percent of computed dipoles were located within the visible perimeter of the burn. Thus, two simultaneously active dipolar sources can be detected and accurately localized by rigorous study of the generated electrical field.

Animals↗