Search PubMed⌕ Search

Biomedical subjects

T A King

Publications and source records attributed to T A King.

At least 19 recordsLinked to original sources
PubMed1992

Effects of neonatal transection of the infraorbital nerve upon the structural and functional organization of the ventral posteromedial nucleus in the rat.

The present study examined the way in which an indirect partial deafferentation of the medial portion of the ventrobasal complex (VPM/VPL) induced by neonatal transection of the infraorbital nerve (ION) altered the structural and functional properties of its constituent neurons. This manipulation significantly reduced the volume of the contralateral VPM/VPL. In addition, cell counts in Nissl-stained material revealed a significant reduction of the number of VPM/VPL neurons contralateral to neonatal ION transection. We also analyzed the effect of neonatal ION transection on the soma-dendritic morphology of individual neurons in the ventral posteromedial nucleus of the thalamus (VPM) by intracellular injection of horseradish peroxidase (HRP) in vivo and Lucifer yellow in fixed slices. Neonatal transection of the ION resulted in increased dendritic length, area, and volume of VPM neurons in both preparations; however only the changes observed in fixed slices reached statistical significance. Alterations in the functional characteristics of VPM neurons were also observed following neonatal nerve damage. There was a significant decrease in the percentage of vibrissae-sensitive neurons and a corresponding increase in the percentages of neurons responsive to guard hair deflection or that were unresponsive to peripheral stimulation. Neonatal nerve damage also resulted in significantly longer latencies of VPM cells after stimulation of either trigeminal nucleus principalis or subnucleus interpolaris. The present results indicate that the development of normal response properties and soma-dendritic morphology of VPM neurons is dependent upon intact afferent input during development. Indirect partial deafferentation of VPM/VPL by neonatal transection of the ION results in reduced neuron number, which may result in decreased competition among the dendrites of these neurons. This proposal is consistent with observations of increased dendritic dimensions of VPM neurons contralateral to neonatal ION damage.

Animals↗
PubMed1992

Popliteal-to-distal bypass for limb-threatening ischemia.

In a subset of patients requiring lower extremity revascularization, the popliteal artery may be used for inflow, thereby minimizing dissection and the length of vein required for bypass. This retrospective study was done to define the risks and benefits of arterial reconstruction in a population of patients having popliteal-to-distal bypass procedures. Between 1986 and 1990, 32 surgical procedures were performed on 29 patients. The patient's ages ranged from 46 to 86 years, with a mean age of 68 years. Twenty-four of 29 (83%) were men and 19 of the 29 (66%) had diabetes. Most patients had multiple indications for surgical intervention, and these included rest pain (54%), nonhealing ulcers (64%), and gangrene (29%). Arterial bypass with use of the popliteal artery for the proximal anastomosis was performed with in situ saphenous vein (50%), reversed saphenous vein (41%), and orthograde autologous vein (9%). Distal anastomoses were to the posterior tibial artery in 11 bypasses (33%), the peroneal artery in 10 (30%), the anterior tibial artery in two (6%), and the dorsal pedal artery in 10 (30%). Two deaths occurred in the perioperative period for an operative mortality rate of 6.9%. With use of life-table analysis, the cumulative graft patency rate was 97% at 1 year, 97% at 2 years, and 63.5% at 4 years. The overall cumulative limb salvage rate was 90.1% at 1 year, 90.1% at 2 years, and 78.8% at 4 years.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Invasive diagnostic imaging of the lower extremities.

Invasive arterial imaging techniques are crucial to the preoperative evaluation of patients requiring arterial surgery. Venography is important in patients who are candidates for venous reconstruction, and it is also useful in the difficult diagnosis of deep venous thrombosis. The authors discuss the development of angiographic techniques, indications for use, patient preparation, and potential complications. Several examples of these tests are illustrated.

Angiography↗
PubMed1992

Lower extremity arterial occlusive disease.

The clinician must first understand the natural history of chronic lower extremity ischemia before making a decision regarding therapeutic options. Clearly, mild ischemia as evidenced by claudication does not place the patient at significant risk for limb loss. Initial conservative treatment emphasizing abstinence from tobacco products, control of underlying medical maladies, and an exercise program, along with patient reassurance, will adequately treat the majority of claudicators. When ischemia is present, patient education regarding foot care and avoidance of trauma are beneficial. Limb-threatening ischemia often requires revascularization. Adequate preoperative cardiologic evaluation and intraoperative monitoring have greatly reduced the morbidity and mortality of arterial reconstruction. Selection of the appropriate recipient vessel and bypass conduit enables limb salvage, whereas amputation would have been performed just a few years ago. Continued analysis of treatment outcomes will further define appropriate intervention in the future.

Arterial Occlusive Diseases↗
PubMed1991

Discrimination of capillary and arterio-venular blood flow in skin by laser Doppler flowmetry.

The scattering and absorption of light by tissue and blood is wavelength dependent; the tissue penetration of green light (lambda = 543.5 nm) is about 60 per cent of that of red light (lambda = 632.8 nm) but the absorption of green light by blood is about 20 times greater than for red light. The effect of this difference has been studied by observing the responses of skin blood flow to heat and weal, measured by laser Doppler flowmetry at the two wavelengths. By using time autocorrelation function analysis (ACF) of the scattered light measured, low and high frequency components have been associated with capillary and larger vessel flow, respectively. The comparison of ACF from scattered green and red light has shown that measurements cannot be interpreted by only considering light penetration depth through a homogeneous tissue. Light absorption and multiple scattering by blood at the individual microvessel level, blood rheology and vessel morphology are parameters which are considered for greater attention.

Arterioles↗
PubMed1991

Utility of arteriography in penetrating extremity injuries.

The role of contrast arteriography in the management of patients with penetrating injuries of the extremities is a subject of active debate. To examine our experience, the charts of patients with penetrating injuries of the extremities were retrospectively reviewed. Data from 82 consecutive patients with 98 wounds over the 5-year period from January 1984 to December 1988 were reviewed. Sixty-five arteriograms were obtained to investigate 98 wounds: 8 to localize a clinically apparent wound and 57 because of proximity of the wound or the trajectory of the injuring agent to a major neurovascular bundle. Of the 57 arteriograms obtained because of proximity, 11 identified a vascular injury (19%). Six of these wounds required vascular repair; five patients were treated expectantly. Six of the eight arteriograms obtained for clinical indications were positive (75%), while two were negative (25%). There were no amputations in the study, and all vascular reconstructions were considered successful by clinical and vascular laboratory criteria. One patient died of thoracic injuries; otherwise, all patients were discharged in good condition. Long-term follow-up was not available. In summary, 19% of arteriograms done because of proximity criteria alone identified a clinically occult vascular injury. While only 11% of all proximity arteriograms revealed injuries requiring surgical repair, this rate of significant injury warrants aggressive use of proximity arteriography in a patient population that is prone to poor follow-up.

Adolescent↗
PubMed1990

Photodynamic therapy for localised prostatic cancer: light penetration in the human prostate gland.

We are investigating the feasibility of photodynamic therapy in the treatment of localised prostatic cancer. Of major importance in this form of treatment is the extent to which light penetrates the target organ; hence, our interest in the optical properties of the human prostate gland. We obtained three whole prostates from autopsies of patients who died of non-urological causes. Red light was launched interstitially and detector fibres measured light intensity as a function of distance from the delivery fibre end. The optical constants derived from the three prostates were almost identical and indicated that light was predominantly scattered rather than absorbed (mean absorption and scattering coefficients 0.07 +/- 0.02 mm.-1 and 0.86 +/- 0.05 mm.-1 respectively). In a comparison of the tissue penetration by four different wavelengths, 633 nm red light was found to be transmitted best. Light propagation in the heavily absorbing tissue of the human liver was 4.3 times poorer than in the prostate. Such a combination of low absorption and high scattering characteristics in prostatic tissue would enhance the effectiveness of PDT. The optical constants derived will enable "light treatment planning" in patients with prostatic cancer.

Aged↗
PubMed1990

Identification of urinary stone composition by pulsed dye laser.

Stones were recovered from the urinary tract and their composition determined by X-ray diffraction before exposure to a pulsed dye laser beam. The resultant fluorescent emissions were recorded using a scanning reticon and they appeared to be specifically related to the composition of each stone. This technique has a practical application as it may allow identification of the composition of urinary tract stones in vivo, and so indicate the best mode of lithotripsy.

Humans↗
PubMed1988

Carotid endarterectomy in a metropolitan community: the early results after 8535 operations.

Several retrospective community surveys have provoked speculation concerning the safety of carotid endarterectomy (CEA) throughout the United States. To address this serious issue, surgical outcome was calculated for 8535 CEAs entered prospectively into a computer registry by 51 trained vascular surgeons in a large metropolitan area from 1973 to 1985. A total of 7480 procedures (88%) were performed for symptomatic lesions and 1055 (12%) were performed for asymptomatic stenosis or ulceration. There were 178 operative strokes (2.1%) and 135 early deaths (1.6%), for a combined morbidity-mortality rate of 3.2%. Fatal events were attributed to cardiac disease in 0.7%, neurologic complications in 0.6%, and other causes in 0.3%. The stroke rate (n = 148; 2.0%) in symptomatic patients was better than that in asymptomatic patients (n = 30; 2.8%) (chi 2 = 5.2; p less than 0.025), but the combined morbidity-mortality rates (2.9% and 3.7%) were not statistically different. The incidence of stroke reported by surgeons who performed more than 5 CEAs annually (1.7%) was statistically superior to the stroke rate (3.4%) among those with less experience (chi 2 = 37.1; p less than 0.0001). Nevertheless, both groups had acceptable results that were consistent with their training and continued interest in vascular surgery.

Aged↗
PubMed1988

Teaching guided fibreoptic nasotracheal intubation. An assessment of an anaesthetic technique to aid training.

An anaesthetic technique suitable for training in fibreoptic intubation is described. It uses a capped oropharyngeal airway which leaves the nose free for fibreoptic intubation and allows the airway to be maintained and ventilation to be controlled if necessary. An assessment is made of the technique after 50 fibreoptic intubations with the Olympus LF-1 fibrescope. There were no failed intubations and no serious complications.

Adolescent↗
PubMed1986

Delayed skin oxygenation following distal tibial revascularization (DTR). Implications for wound healing in late amputations.

This article summarizes the authors' experience with prospective transcutaneous oxygen mapping (PtcO2 mm Hg) in patients requiring distal tibial revascularization. Simultaneous measurements were performed measuring preoperatively and early (1-3 days) and late (5-8 days) postoperatively in eight patients undergoing DTR (Group 1) at the chest (CT), below-knee (BK), and midfoot (FT) levels. In an additional 12 patients (Group 2), PtcO2 was measured late postoperatively adjacent to forefoot amputations. PtcO2 measurements were made at room air (RA) and after inhalation of oxygen (O2) in order to evaluate restriction of oxygen delivery. Late postoperative PtcO2 at both BK and FT sites increased (P less than .05) compared to either preop or early postop values. Inhaled O2 increased PtcO2 greatest at the FT late postop time (P less than .001). Group 1 amputations and ischemic ulcers all healed within 4 weeks postoperatively, when PtcO2 values were greater than 25 mm Hg. More extensive amputations required in Group 2 also healed when PtcO2 values exceeded 25 mm Hg, but required a hospitalization period almost three times as long as that of Group 1.

Aged↗
PubMed1984

Aspects of laser light scattering from skin tissue with application to laser Doppler blood flow measurement.

Studies of both intensity and Doppler shifted linewidths of light scattered from skin tissue have been made using photon correlation spectroscopy and optical fibre techniques. Measurements as a function of the separation of input and detecting fibre positions show characteristic features. These features are interpreted in terms of the positions of the scattering red blood cells and the tissue structure. Evidence is given for an interpretation of the differences in the scattered light for scattering from superficial vessels including capillary loops and from deeper lying larger vessels and shunts. Measurements using various laser wavelengths are discussed. The results of this study are important in the development of laser light scattering instruments for the measurement of peripheral blood flow and microcirculation.

Blood Flow Velocity↗