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Curriculum↗
Biomedical subjects
D E Byrne
Publications and source records attributed to D E Byrne.
The effect of exposure to increased hydrostatic pressure up to 46 ATA on respiratory sinus arrhythmia in humans.
Respiratory sinus arrhythmia (RSA) has been used as a non-invasive estimate of vagal tone to determine whether the reduction in resting heart rate commonly seen when humans are exposed to increases in the ambient pressure is associated with changes in vagal autonomic control. Two sets of divers (n = 4) were examined during two simulated saturation dives, one to 46 atmospheres absolute (ATA) and another to 37 ATA. A significant reduction in resting heart rate was seen in both dives upon exposure to high pressure compared with controls at 1 ATA. The reduction in heart rate seen at increased pressure was consistent regardless of respiratory rate, indicating that moderate changes in respiratory rate do not affect heart rate under these conditions. No changes in the overall magnitude of RSA were observed over a range of respiratory rates during either dive compared with control values at 1 ATA. During both dives, RSA was significantly larger (P < 0.05) at low respiratory rates compared with higher rates for both 1 ATA controls and at high pressure. The presence of a hyperbaric bradycardia strongly suggests that vagal tone is altered during hyperbaric exposure; however, the lack of change in the magnitude of RSA at high pressure brings into question the viability of using RSA as an accurate indicator of vagal tone and this lack of correspondence deserves further investigation.
Adult↗
The effect of raised hydrostatic pressure on heart rate variability during breath holding in man.
Changes in cardiac interval (difference between two consecutive R waves of the ECG) during an expiratory breath hold (16 s) were examined in four divers during a saturation dive to 450 msw (metres of seawater). At 450 msw, breath hold caused a progressive shortening of cardiac interval that was significantly different from the changes seen at surface. The cause and significance of this shortening is unknown, but it might serve to maintain normal cardiovascular dynamics under hyperbaric conditions.
Adult↗
Urinary tract glycoprotein: distribution and antigenic specificity.
It has previously been demonstrated that the urinary tract contains a unique glycoprotein (GP1) that appears to serve a function in the clearance of pathogenic bacteria. We prepared a panel of monoclonal antibodies (mAbs) to human GP1 and examined its antigenic specificity and distribution in the human urinary tract. This was also observed in relation to another glycoprotein associated with infection, Tamm-Horsfall protein (THP), as well as to URO-5, a protein used in identifying the lower urinary tract. In enzyme-linked immunoadsorbent assays (ELISA), all of the GP1 mAbs reacted with GP1 prepared from both human urine and rabbit bladder mucosa. No immunoreactivity was observed with either THP mAbs or URO-5 mAbs. Western-blot analyses using GP1 mAbs with human urine GP1 preparations detected a single band of approximately 50-52 kDa. Human urinary tract tissues were also examined by immunohistochemical techniques using the GP1 mAbs, commercial THP, and URO-5 mAbs. In paraffin-embedded bladder sections, only GP1 mAbs reacted with the urothelium. Selective staining of distal collecting tubules, renal pelvis, and ureters was demonstrated for GP1 mAbs. Proximal convoluted tubules, loops of Henle, and Bowman's capsule failed to stain for GP1. In the same tissues, THP mAbs reacted with the thick and thin segments of medullary loops of nephrons (Henle's loops). URO-5 mAbs stained fresh frozen sections of bladder urothelium, distal collecting tubules, and portions of Henle's loops; however, they failed to stain paraffin-embedded tissue sections. These GP1 mAbs provide a new tool for biochemical and histochemical investigations of the mucin layer in both healthy and diseased urinary tract tissue.
Animals↗
Traumatic vena caval injuries.
Vena caval injuries are relatively rare and are associated with a high mortality before the patient arrives at a medical facility and even after initial resuscitation and operative intervention. Survival is directly related to (1) the location of the injury, (2) the amount of active bleeding, and (3) the type and number of associated injuries. To achieve maximum survival in patients with serve injury, rapid transportation to an emergency room is necessary. Resuscitation must then be aggressive, with rapid transferral to the operating room, and the surgeon must know the various techniques available for repair.
Adult↗