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Biomedical subjects

T A King

Publications and source records attributed to T A King.

At least 19 recordsLinked to original sources
PubMed1995

Impact of shock on pain reactivity: I. Whether hypo- or hyperalgesia is observed depends on how pain reactivity is tested.

Prior research has shown that exposure to shock can induce a decrease in pain reactivity (hypoalgesia). The present experiments show that, at the same time points that subjects are less responsive to radiant heat applied to the tail (the tail-flick test), tailshock elicits enhanced motor reactivity and vocalization. This enhanced responsiveness, or hyperalgesia, is observed with both magnitude (Experiment 1) and threshold (Experiment 2) measures and decays within 32 min (Experiment 2). Experiment 3 shows that the hyperalgesia decays irrespective of whether or not subjects remain in the shock context, which suggests that the loss of hyperalgesia does not reflect extinction of the context-shock association. Neither removing subjects from the shock context (Experiment 4) nor the presentation of a postshock distractor (Experiment 5) affected the hyperalgesia.

Animals↗
PubMed1995

Neurologic manifestations of in utero cocaine exposure in near-term and term infants.

OBJECTIVE: To determine whether the incidence of neurosonographic and neurologic abnormalities is higher in cocaine-exposed infants at birth. METHODS: In utero exposure to cocaine was investigated in 39 term and near-term infants with positive urine screens for cocaine only and 39 matched control infants without drug exposure admitted to the regular term newborn nursery. Serial evaluations were performed on each infant on postnatal days 1 and 2 and included a cranial sonogram, a neurologic and behavioral assessment for drug withdrawal, and Doppler interrogation of the anterior and middle cerebral arteries. RESULTS: There were no differences between groups in neurosonographic abnormalities. Grade I or II intraventricular hemorrhage occurred in 11% of cocaine-exposed and 11% of control infants. There were no cases of grade III intraventricular hemorrhage, cystic periventricular leukomalacia, or neonatal stroke. Head size was smaller in cocaine-exposed infants, ie, 32.7 +/- 0.1 cm versus 33.8 +/- 0.1 cm. The neurologic examination was similar between groups with regard to tone, reflexes, and cranial nerves. Behavioral scores were higher on both days, in cocaine-exposed versus control infants, ie, 4.4 +/- 0.5 versus 2.7 +/- 0.03 on day 1 and 5.0 +/- 0.5 versus 1.71 +/- 0.31 on day 2. Cerebral blood flow velocity measurements in the anterior cerebral artery were similar between groups on both days of examination. However, cocaine-exposed infants demonstrated a significant increase in flow velocity from day 1 to day 2, ie, 0.48 +/- 0.03 to 0.57 +/- 0.04. There was a concomitant decrease in the pulsatility index from day 1 to day 2 in the cocaine-exposed, ie, 0.74 +/- 0.02 to 0.69 +/- 0.02, but not in the control infants. No differences were noted in the flow velocities in the middle cerebral arteries between groups. CONCLUSIONS: Term and near-term infants admitted to a regular nursery who are exposed to cocaine in utero: (1) do not exhibit an increased incidence of neurosonographic abnormalities; (2) do exhibit altered behavior consistent with drug withdrawal; and (3) do demonstrate changes in flow velocity in the anterior cerebral artery consistent with the vasoconstrictive effects of the drug. However, these changes were not accompanied by changes in the neurologic examination or altered care. The long-term neurodevelopmental implications of these subtle abnormalities in the neonatal period remain to be determined.

Blood Flow Velocity↗
PubMed1993

Nonvisual laser lithotripsy aided by plasma spectral analysis: viability study and clinical application.

Nonvisual laser lithotripsy implies laser fragmentation without the aid of endoscopic or direct vision. Using the laser delivery fiber for retrograde transmission of plasma spectrum and its analysis on an optical multichannel analyzer, we designed a project with the objective of identification and fragmentation of calculi by continuous analysis of the plasma feedback spectrum. We were successful in achieving the objectives in the in vitro and ex vivo studies. In the in vivo studies we successfully recorded the plasma spectrum of the stones from inside the ureter and monitored the process of fragmentation with the laser. We have been able to identify the problems for its clinical application. We conclude that by monitoring the feedback spectrum of plasma emission, nonvisual laser lithotripsy is reliable and safe, and can be used successfully in patients with some modifications. Its development is not to replace established endoscopic lithotripsy procedures but rather as an additional armament for the urologist in special situations. Also, the technique can be further exploited for a variety of clinical uses.

Humans↗
PubMed1993

Arteriovenous reversal for limb salvage in unreconstructible upper extremity arterial occlusive disease.

PURPOSE: Peripheral vascular disease of the upper extremity as a result of atherosclerotic disease or systemic vascular disorders presents a difficult management problem to the vascular surgeon. When extensive distal disease is present bypass procedures with standard arterial reconstruction techniques may not be possible. The use of retrograde perfusion to deliver oxygenated blood to the capillary bed by means of a normal venous system is not new. Flow reversal has been attempted in the myocardial, cerebral, and distal extremity circulations. Arteriovenous reversal (AVR) has been described for limb salvage in patients with upper extremity ischemia, with variable results. METHODS: We performed six AVR procedures on five patients with diffuse distal arterial disease and limb-threatening upper extremity ischemia. Two patients had insulin-dependent diabetes, one had systemic lupus erythematosus (two extremities), one had rheumatoid arthritis with vasculitis, and the remaining patient had CRST (calcinosis, Raynaud's disease, sclerodactyly, telangiectasia) syndrome. The two patients with diabetes had systemic manifestations of atherosclerotic vascular disease and lower extremity ischemia; the remaining three patients had no evidence of atherosclerosis. In all patients the AVR was performed at the most distal site of nondiseased artery. RESULTS: Limb salvage was obtained in all cases; one patient had a healed minor digital amputation, and another patient had a healed major amputation. Clinical improvement with resolution of pain was achieved in five of six cases. The remaining patient had a significant diabetic neuropathy that was believed to contribute to her persistent pain. CONCLUSIONS: In patients with severe upper extremity ischemia not amenable to standard revascularization techniques, AVR should be considered to provide limb salvage and maximize hand function.

Adult↗
PubMed1993

Risk assessment in patients undergoing carotid endarterectomy.

Factors that contribute to the outcome of carotid endarterectomy include appropriate patient selection, preoperative medical optimization, meticulous operative technique and postoperative management. This study was designed to evaluate associated medical and operative risk factors with surgical outcomes for 9795 consecutive carotid endarterectomies performed by members of a voluntary regional vascular society. All data were reviewed and subject to a variety of statistical analyses in a blinded retrospective fashion. Factors including sex, increased age (> 70 years), cigarette smoking, chronic pulmonary disease and diabetes did not contribute independently to either increased operative neurologic morbidity or mortality rates. Cardiac disease (P < 0.0001) and chronic renal failure (P < 0.001) correlated independently with increased operative mortality, while hypertension (P < 0.05), cardiac disease (P < 0.01), renal failure (P < 0.0001), emergency surgery (P < 0.0001) and advanced neurologic symptoms at the time of operation (P < 0.0001) were associated with an increased operative stroke rate. In a group of 9021 patients who underwent 9795 carotid endarterectomies with a combined 3.1% incidence of operative neurologic morbidity or mortality (neurologic morbidity, 2.0%; mortality, 1.5%), specific preoperative medical risk factors could be identified. Only cardiac disease and chronic renal failure were associated with both significantly increased operative neurologic morbidity and operative mortality rates.

Adult↗
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↗