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Biomedical subjects

J Walton

Publications and source records attributed to J Walton.

At least 109 records · Page 6Linked to original sources
PubMed1985

Influence of neural retina on lens fibre differentiation in rats.

Lens epithelial explants grown in retina-conditioned medium (RCM) undergo structural and molecular changes characteristic of fibre differentiation in the intact lens. We suggest that in vivo neural retina releases a fibre differentiation factor (FDF) that interacts with equatorial lens epithelial cells and stimulates them to undergo fibre cell differentiation. According to this model, interaction with neural retina is essential for normal lens formation in embryos and for normal lens growth throughout life. Preliminary work on purification of the factor indicates that FDF activity is associated with a high molecular weight complex of 500 kd. The active component of this complex appears to be an 80 kd molecule.

Animals↗
PubMed1985

Audit of abdominal pain in general practice.

An audit of 150 consecutive cases of abdominal pain presenting to an urban teaching practice between October 1983 and May 1984 was performed. The median duration of pain prior to presentation was two days. Females predominated in all age groups.Eighty-nine per cent of these patients were managed entirely in the practice and of these, 52 per cent were managed with reassurance and advice alone, while 48 per cent also received a prescription. Only 15 per cent of patients were investigated in any way by the practice. Of the 17 patients (11 per cent) referred, nine were referred as emergencies and eight were admitted that day. However, there were only three true surgical emergencies in the entire series (one appendicitis, one intussusception and one fulminating pancreatitis).

Abdomen↗
PubMed1984

Sequential structural response of lens epithelium to retina-conditioned medium.

When lens epithelium is cultured with retina-conditioned medium, many of the cells undergo fibre differentiation within 6-10 days. Here we report the temporal sequence of structural events that characterize this change in an organ culture model system. Within an hour of exposure to conditioned medium, some cells withdrew from the epithelial monolayer and began migrating over stationary cells still attached to the capsule. By 24 hr, migratory activity was largely responsible for causing the explant to become multilayered, increasing its thickness while at the same time reducing its surface area. Control cells attached to each other along their lateral boundaries through interdigitations of microvilli. After BRCM treatment, microvilli flattened out and the membranes had a crinkled appearance. Eventually, as the cultured cells developed into fibres, membranes straightened and developed knob and socket junctions and large numbers of their organelles underwent degradation within autophagic vacuoles. Nucleoli began to enlarge by 16 hr and by the time cells had been exposed for 24 hr, some nucleoli were enlarged to seven-fold their original area, as measured on electron micrographs. This nucleolar change was followed over the next few days by a gradual increase in cytoplasmic protein, and cells became plump or elongated. The ultrastructural changes that we observed in culture are similar to those that can be seen in the intact lens. Such fidelity of change indicates that this cultured lens explant system is an excellent model for experimental intervention and analysis of the processes involved in terminal lens fibre differentiation.

Animals↗
PubMed1984

Effects of reperfusion on complete heart block complicating anterior myocardial infarction.

Two patients with complete heart block complicating extensive anterior myocardial infarction underwent late (greater than 40 hours) coronary reperfusion with angioplasty. One to one atrioventricular conduction was restored within minutes of reperfusion despite a lack of measurable ventricular muscle salvage as demonstrated by ventriculography 1 week later. The evidence favors reversible ischemia rather than extensive necrosis of the proximal conduction system as the mechanism of heart block in this subgroup of patients.

Adult↗
PubMed1984

Count-based left ventricular volume determination utilizing a left posterior oblique view for attenuation correction.

This study aimed to determine the inherent error of the left ventricular volume measurement from the gated equilibrium blood pool scintigram utilizing the count-based technique. The study population consisted of 26 patients who had undergone biplane contrast ventriculography. The patients were imaged with a parallel-hole collimator in the left anterior oblique position showing the septum to best advantage. A reference blood sample was counted and radionuclide volumes calculated without correction for attenuation. Attenuation corrected volumes were derived with the factor 1/e-mud, where d = distance from skin marker to center of the left ventricle in the orthogonal left posterior oblique view and mu = linear attenuation coefficient. A series of mu values from 0.08 to 0.15 cm-1 was evaluated. There was a trend toward improvement in the r value and lowering of the SEE with attenuation correction. The tightest 95% confidence limits achieved for an end-diastolic 150-ml ventricle were +/- 44 ml, and for an end-systolic 75-ml ventricle +/- 32 ml. In view of the magnitude of inherent error, the count-based volume measurement may be more suitable for group analyses and in cases in which an individual patient serves as his own control.

Adult↗
PubMed1982

Radionuclide evaluation of postextrasystolic potentiation of left ventricular function induced by atrial and ventricular stimulation.

Postextrasystolic potentiation of left ventricular function induced by ventricular and atrial stimulation was compared in 10 patients using radionuclide ventriculography. After insertion of pacing wires, a preliminary radionuclide ventriculogram was obtained and then ventricular and atrial trigeminy was induced in random order, each with identical R-R coupling intervals, each for 6 to 10 minutes. During the stimulation studies, radionuclide data were acquired in electrocardiographic gated list mode format. Left ventricular ejection fraction and relative end-diastolic and end-systolic volume changes were measured for each reformatted composite sinus, atrial and ventricular premature beat and potentiated beat. The volume changes were normalized to the count-based values obtained for the sinus beat of the appropriate study. Postextrasystolic potentiation induced by either ventricular or atrial stimulation was characterized by similar significant increases in left ventricular ejection fraction (mean +/- standard deviation 7 +/- 3 percent, p less than 0.01 versus 7 +/- 5 percent, p less than 0.01; difference not significant [NS]) and decreases in relative end-systolic volume (-12 +/- 12 percent, p less than 0.01 versus -12 +/- 8 percent, p less than 0.01; NS) but little change in relative end-diastolic volume (+5 +/- 10 percent, NS versus +4 +/- 7 percent, NS; NS). This was despite a longer compensatory pause (1,120 +/- 220 versus 1,050 +/- 190 ms, p less than 0.01) after the ventricular premature beat. It is concluded that there is no difference in the postextrasystolic potentiation induced by atrial or ventricular premature stimulation.

Adult↗
PubMed1982

The role of limited cell replicative capacity in pathological age change. A review.

Physiological functions are carried out by differentiated cells, with finite lifespans, which age and need to be replaced. In young individuals, tissue functions are sustained at optimal levels because cellular dysfunction and cell loss are balanced by the emergence of newly differentiated cells as stem cells and their partially differentiated descendants replicate. However, with the passage of time the mitotic rates of these cells diminish. Eventually, replications occur too infrequently to offset the loss. It is at this point that the tissue begins to show structural changes and declining function which, as they become pervasive, are identified as "ageing". In this paper the theory is set forth that: (1) Diminishing mitotic activity in older tissues results from limited stem cell replicative capacity. (2) All stem cells, regardless of tissue, exhibit similar replicative patterns over time, progressing from the actively proliferating to the nonproliferating state. However, stem cells in different kinds of tissue have different rates of replicative decline, with the result that some tissues show age earlier than others. (3) The combination of two cellular properties--differentiated cell ageing and limited stem cell replicative capacity--is sufficient to establish the framework in which other pathological changes characteristic of aged people and animals take place.

Aging↗
PubMed1982

Ultrastructure of the rat urothelium in en face section.

We examined en face the fine structure of rat urothelium and describe here some unique subcellular features distinguishable in the various tissue layers by this technique. The most striking finding is that large, compact fibrous bundles lie in the cytoplasm at both sides of the superficial cell tight junction for the entire length around it apical surface. Basal to these bundles, an intricate series of desmosomes alternates with other specialized elaborations of the plasma membrane. These desmosomes anchor the extensive filamentous network that interconnects the nucleus, flattened superficial vesicles, and plaques of the lumenal membrane. En face sections of the urothelium show that large numbers of vesicles form inthe intermediate cell Golgi complexes and are then stored just under the apical membrane. These intermediate vesicles are smaller, more round, and less variable in size than superficial vesicles. After intermediate cells reach the superficial layer, the vesicles mature, undergoing modifications that apparently increase their tendency to fuse.

Animals↗