Biomedical subjects

W F Taylor

Publications and source records attributed to W F Taylor.

At least 19 recordsLinked to original sources

PubMed1998

Physiologic and perceptual responses to hypercarbia during warm- and cold-water immersion.

Thermoregulatory, respiratory, and perceptual responses to acute CO2 exposure during light exercise (75 W) were assessed in 12 U.S. Navy divers clad only in swim trunks while immersed to the neck in water at 18 degrees and 34 degrees C. The CO2 exposures consisted of a linear 10-min ramp increase in the inspired fraction of CO2 (FICO2) from 0 to 6% followed by 5 min of breathing 6% CO2. The ability to detect and rate the severity of hypercarbia, as well as subjective changes in thermal comfort, were assessed by comparing subjective ratings given during the CO2 exposures with those given during immersion trials where the FICO2 was maintained at 0%. Hypercarbia was recognized earlier and, at a given PETCO2, was perceived to be greater during cold- than during warm-water immersions (P < 0.01). The CO2 exposures did not affect the thermal balance of divers as assessed by changes in heat flux and rectal temperature. However, increased feelings of warmth were reported during both the cold and warm immersions when breathing raised concentrations of CO2 (P < 0.01). During the cold immersions, acute exposure to 6% CO2 significantly decreased forearm blood flow (P < 0.05), but did not affect finger blood flow. It is concluded that PETCO2 levels can reach unacceptably high concentrations (> 60 mmHg) before hypercarbia can be reliably detected by working divers. Furthermore, the ability to detect hypercarbia is poorer when immersed in warm water than when in cold water.

Adult↗

PubMed1998

Enhanced aggregability of human red blood cells by diving.

In vitro studies have shown that mild pressure increases red blood cell (RBC) aggregation. Enhanced RBC aggregation in pathologic states can drive the circulation into stasis. This investigation examined the effects of pressure on RBC aggregation in human volunteers. The hypothesis tested is that RBC aggregation is increased during hyperbaric exposure. Eleven subjects participated in dives to 300 feet of seawater (fsw) in a man-rated chamber complex. Blood samples were taken at the surface, at 66 fsw, and at 300 fsw. Data were analyzed with a repeated measures one-way analysis of variance for a complete randomized design. Statistical significance was achieved at P < 0.05. Data are expressed as mean +/- SEM. The median aggregate size (number of RBC/aggregate) of RBCs was significantly increased at depth. At a shear stress of 0.1 dyne/cm2, median aggregate size was 12.0 +/- 2.1, 33.0 +/- 7.3, and 48.8 +/- 10.8 at the surface, at 66 fsw, and at 300 fsw, respectively. These results show that mild pressure increases RBC aggregation in the human circulation.

Adult↗

PubMed1997

Arterial baroreflex modulation of heat-induced vasodilation in the rabbit ear.

The purpose of this study was to determine whether nonthermal baroreflexes arising from cardiopulmonary and/or arterial baroreceptors modulate rabbit ear blood flow (EBF) during hyperthermia. Intact and sinoaortic-denervated (SAD) rabbits were chronically instrumented with a Doppler ultrasonic flow probe for measurement of EBF velocity (kHz). During whole body heating in conscious rabbits, EBF and ear vascular conductance (EVC) increased as core temperature increased until maximal plateau levels of EBF and EVC were reached. The maximal plateau level of EVC attained during heat stress was lower in SAD than in intact rabbits. Subsequent intrapericardial administration of procaine at maximal EBF blocked cardiac afferents but did not alter EVC in either animal group. In a second experiment, ramp decreases in mean arterial pressure were produced by vena caval occlusion at maximal EBF. In intact rabbits, EBF and EVC decreased linearly as mean arterial pressure fell, but EBF and EVC did not decrease during vena caval occlusion in SAD rabbits. Thus neither pharmacological nor mechanical unloading of cardiac baroreceptors results in reflex vasoconstriction in the heat-stressed rabbit ear. However, baroreflexes arising from arterial baroreceptors may modulate EBF in heat-stressed rabbits.

Animals↗

PubMed1995

The relationship between the U.S. Navy fleet diver physical screening test and job task performance.

The development of job-related selection and training methods will improve safety and lead to substantial cost savings to the U.S. Navy through enhanced screening and productivity. The present investigation determined the extent to which the current U.S. Navy fleet diver physical screening test predicted performance of five representative physically demanding job tasks. Subjects were 146 male diver candidates (age 25.1 +/- 4.3 years, X +/- SD, range 18-37 years) undergoing training at the Naval Diving and Salvage Training Center, Panama City, FL. Results indicate the current U.S. Navy fleet diver physical screening test provides a poor estimate of representative job task performance for the population of diver candidates tested. A finding of particular operational significance was that a substantial number of diver candidates who passed current physical screening test standards were unable to complete (i.e., failed) the tool-bag swim (18.5%) and fin-kick (25.7%) tasks. Results suggest the current screening test has limited utility for physical selection purposes and underscore the need for developing a requirements-based selection battery to ensure that diver physical capabilities are aligned to the job.

Adolescent↗

PubMed1994

Silastic dural substitute: experience of its use in spinal and foramen magnum surgery.

In an attempt to prevent tethering following intradural procedures in the spine or at the foramen magnum silastic film has been inserted as a dural substitute. Magnetic resonance imaging has enabled us to judge the effectiveness of this material in preventing tethering at the operative site. Our experience of Silastic dura substitute in 43 paediatric and adult cases is discussed, and illustrated together with a description of the technique of insertion and an analysis of the complications associated with its use.

Adolescent↗

PubMed1993

Prognostic significance of spontaneous tumour necrosis in osteosarcoma.

Preoperative chemotherapy is an integral part of the management of osteosarcoma, and the extent of tumour necrosis found at operation is an important prognostic variable. Knowledge about spontaneous, pretherapy necrosis is difficult to obtain but provides important quantitative information about the necrotic effect of chemotherapy. Using three different methods, we studied spontaneous tumour necrosis in 20 localized intramedullary osteosarcomas of the distal femur diagnosed between 1963 and 1972. All patients received surgical treatment only. All six patients with spontaneous necrosis involving more than 20% of tumour died. Five of 14 patients with necrosis amounting to less than 20% were long-term, disease-free survivors. The extent of necrosis was independent of tumour size. Two semiquantitative methods of evaluation were easily applied and reproducible. Spontaneous necrosis in untreated osteosarcomas occurs frequently; extensive necrosis may indicate a rapid clinical course. Tumour necrosis can be quantified reliably in clinical work.

Adolescent↗

PubMed1993

A role for nitric oxide in active thermoregulatory vasodilation.

We have shown previously that an increase in ear blood flow velocity (EBF) in the conscious, chronically instrumented rabbit during whole body heating (WBH) involves active neurogenic vasodilation that is abolished by local nerve block. This study was designed to test the potential role of nitric oxide (NO) in rabbit ear neurogenic vasodilation during hyperthermia. Rabbits were instrumented for the measurement of arterial pressure, heart rate, and EBF (Doppler ultrasound). A catheter was also placed in the left lingual artery for administration of drugs to the left ear. WBH was achieved by circulating warm water through a rubber pad placed around the rabbit. Internal temperature was measured with a rectal thermocouple. During WBH, bolus injections of N omega-nitro-L-arginine (L-NNA), a false substrate for the formation of NO, were given via the lingual artery (10(-5) M, 4-5 ml total) to determine whether NO was involved in the increase in EBF. During WBH, left ear vascular conductance (EVC) increased from 0.07 +/- 0.03 to 5.87 +/- 0.73 kHz/100 mmHg and right EVC from 0.20 +/- 0.13 to 4.49 +/- 1.73 kHz/100 mmHg. When EVC was maximum, L-NNA was administered into the left lingual artery. EVC began to decrease after a latency of 23 min. At 56 +/- 8 min, left and right EVC had decreased to 0.18 +/- 0.10 and 0.23 +/- 0.11 kHz/100 mmHg, respectively (P < 0.05). Subsequent infusions of L-arginine, the true substrate for NO formation, restored EVC. These results suggest that NO is involved in active vasodilation during heating in the rabbit ear.

Acetylcholine↗

PubMed1992

Neurogenic vasodilator control of rabbit ear blood flow.

Ear blood flow subserves thermoregulation in the rabbit. The purpose of this study was to determine if the increase in rabbit ear blood flow, in response to increases in internal temperature (Ti) of approximately 2 degrees C (38.0-40.0 degrees C), is due to an active vasodilation or a withdrawal of adrenergic vasoconstrictor activity. New Zealand White rabbits were chronically instrumented with a pulse Doppler flow probe on the central ear artery of the left and right ear for the measurement of ear blood flow velocity (EBF, kHz). Catheters were also positioned in one occipital artery for selective administration of an alpha 1-adrenergic antagonist to one ear, while the contralateral ear served as a control. During hyperthermia (H) (increase in rectal temperature) alpha 1-adrenergic blockade had no effect on the maximum EBF (5.95 +/- 0.87 before vs. 6.11 +/- 1.04 kHz after). However, alpha 1-adrenergic blockade increased resting EBF during normothermia from 0.18 +/- 0.04 to 1.23 +/- 0.27 kHz (P less than 0.05), suggesting that a decrease in alpha 1-adrenergic tone may account for approximately 20% of the increase in EBF during heating. The second protocol was designed to determine if blockade of the auricular nerve would alter EBF response to H. During maximum EBF during H, saline or procainamide was injected in the tissue surrounding the auricular nerve. Injection of procainamide decreased EBF from 5.99 +/- 0.87 to 0.48 +/- 0.19 kHz, while injection of saline had no effect on EBF of the contralateral ear (4.33 +/- 1.16 before vs. 3.97 +/- 1.04 kHz after).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗

PubMed1991

Screening for lung cancer. A critique of the Mayo Lung Project.

The National Cancer Institute of the United States recently sponsored three large-scale, randomized controlled trials of screening for early lung cancer. The trials were conducted at the Johns Hopkins Medical Institutions, the Memorial Sloan-Kettering Cancer Center, and the Mayo Clinic. Participants were middle-aged and older men who were chronic heavy cigarette smokers and thus at high risk of developing lung cancer. Screening procedures were chest radiography and sputum cytology, the only screening tests of established value for detecting early stage, asymptomatic lung cancer. In the Hopkins and Memorial trials the study population was offered yearly chest radiography plus sputum cytology every 4 months. The control population was offered yearly chest radiography only. In these trials the addition of sputum cytology appeared to confer no lung cancer mortality rate advantage. The Mayo Clinic trial compared offering chest radiography and sputum cytology every 4 months to offering advice that the two tests be obtained once a year. This trial demonstrated significantly increased lung cancer detection, resectability, and survivorship in the group offered screening every 4 months compared with the control group. However, there was no significant difference in lung cancer mortality rate between the two groups. The statistical power of these trials was somewhat limited. Nevertheless, results do not justify recommending large-scale radiologic or cytologic screening for early lung cancer at this time.

Clinical Trials as Topic↗

PubMed1991

Manual ventilation during magnetic resonance imaging.

Mechanical ventilation during magnetic resonance imaging (MRI) requires a specially constructed ventilator that contains no ferromagnetic components; however, the expense of acquiring such a ventilator may not be warranted if projected use is infrequent. We adapted a Laerdal manual resuscitator to allow its use during MRI, and report the simulation and monitoring procedure that we developed and the successful ventilation of three pediatric patients with the device.

Child, Preschool↗

PubMed1990

Epstein-Barr virus-related antibody. Changes in titers after therapy for nasopharyngeal carcinoma.

Using long-term follow-up data from a prospective, collaborative study of 182 North American patients, we evaluated the significance of various serologic tests for antibody to Epstein-Barr virus in predicting outcome after treatment in patients with nasopharyngeal carcinoma. We restudied these patients by examining repeated measurements of each titer at various times after diagnosis and treatment. We looked for associations between trends of titers, measured as the slope of log(titer) against time, and titer level, measured as the mean of log(titer), with the outcome: alive and no evidence of disease; alive with recurrence; or dead of nasopharyngeal carcinoma. We found that posttreatment sequential measurements do not predict outcome.

Antibodies, Viral↗

PubMed1990

Roles of absolute and relative load in skin vasoconstrictor responses to exercise.

Systemic hemodynamic responses to exercise (e.g., heart rate, blood pressure) depend on the relative intensity, the active muscle mass, and the mode of exercise. It is not known whether regional vasomotor responses follow the same pattern. To answer this question, in five men we examined cutaneous vascular responses to dynamic and isometric exercise of two legs, one leg, one arm, and one hand, each at high and low work loads. Skin blood flow was monitored by laser-Doppler flowmetry (LDF) at the forearm. Mean arterial pressure (MAP) was measured each minute. Cutaneous vascular conductance (CVC) was indexed as LDF/MAP. Reductions in CVC during the 1st min of dynamic exercise were statistically significant for two-leg exercise at either level and for one-leg exercise at the higher level. Dynamic exercise of smaller muscle groups at either intensity was not associated with significant changes in CVC. The reduction in CVC correlated with external work load (r = 0.75). Work load relative to the capacity of a given muscle group had no identifiable role in the response of CVC to dynamic exercise but did have a role in the increase in MAP at the beginning of exercise. Isometric exercise did not have a measurable effect on CVC regardless of the muscle group or the intensity of the exercise. We conclude that the level of external work determines the redistribution of blood flow from skin to active muscle. Furthermore, absolute rather than relative work and dynamic rather than isometric modes of exercise are the dominant factors.

Adult↗

PubMed1989

Forearm and finger hemodynamics, blood pressure control, and lipid changes in diabetic hypertensive patients treated with atenolol and prazosin. A brief report.

Hypertension and diabetes mellitus frequently coexist and are independent risk factors for reduced peripheral perfusion. Antihypertensive medications that reduce blood pressure and improve peripheral perfusion would have advantages in diabetic hypertensive patients. In a randomized, two-placebo-period, single-blind, two-way, crossover study, finger and forearm blood flow, lipid levels, and blood pressure control were determined in 19 diabetic hypertensive patients given prazosin and atenolol, with each drug and placebo period lasting four weeks. Both drugs reduced blood pressure (sitting, 157/95 to 142/84 mm Hg for atenolol and 155/95 to 138/82 mm Hg for prazosin; standing, 154/94 to 144/84 mm Hg for atenolol and 154/94 to 133/81 mm Hg for prazosin). Lipid levels did not change, except that low-density lipoprotein levels decreased from 148 to 127 mg/dl with prazosin. Atenolol did not change forearm or finger blood flow or vascular resistance. Prazosin increased blood flow and reduced vascular resistance in both finger and forearm. In conclusion, prazosin demonstrated a potentially more appropriate hemodynamic profile than atenolol in diabetic hypertensive patients in this study.

Adult↗

PubMed1989

Prognostic variables in osteosarcoma: a multi-institutional study.

This is a report of a multi-institutional study of all patients with osteosarcoma who were seen at 13 comprehensive cancer centers from July 1, 1977, to December 31, 1982. Follow-up extended to 9 years; a minimum of 3 years was obtained for greater than 90% of the patients. All patients with osteosarcoma were considered, but only those with tissue confirmation who had had at least part of their first course of treatment at one of the 13 institutions were included. There were 543 patients. In a search for prognostic indicators, 38 patient characteristics, three treatment categories, and an institutional variable were studied. A combination of nine of these constituted the best indicator of survival. They were morphology (two parts), site of primary cancer (two parts), spread of tumor, grade and size of tumor, duration of symptoms, weight loss of greater than 4.5 kg (10 lb), swelling at primary site, and lytic appearance. Unexpectedly, treatment was not one of the indicators of survival. A prognostic score was developed in which the coefficients were obtained from the Cox regression (step-down) method. Each patient had a score (S) and an observed survival time that together provided the expected risk of death for that patient. Although this was not a randomized study, treatments were compared before and after adjusting for characteristics identified as prognostic. Three treatments differed little: surgery alone, surgery plus chemotherapy and/or radiotherapy, and chemotherapy and/or radiotherapy followed in 1-4 months by surgery. Patients with amputations and those with resections had similar death rates, but the observed progression rates differed widely. However, when the rates were adjusted for prognostic characteristics, the difference disappeared. Complete surgery (if osteosarcoma existed within surgical margins) was no better than incomplete surgery (if osteosarcoma existed beyond surgical margins) with respect to death but, as would be expected, complete surgery was much better with respect to disease progression.

Follow-Up Studies↗

PubMed1989

New staging system for nasopharyngeal carcinoma. Long-term outcome.

We report prognostic determinants and survival found after a long follow-up of 182 patients in North America in a prospective collaborative study. All patients were under observation since enrollment, and all were treated with modern equipment and techniques at major medical centers. Use of Cox regression methods identified five disease-related characteristics significantly associated with survival. These form the basis of the new staging system. A second system including antibody-dependent cellular cytotoxicity was developed because a high antibody-dependent cellular cytotoxicity titer correlated with good prognosis. The two new systems are better predictors of outcome than are the traditional staging systems. The unique World Health Organization 2 and 3 morphologic forms of nasopharyngeal carcinoma appear to be chronic diseases, because the risk of death does not level off with time, as it does for most other cancers.

Adult↗

PubMed1989

Cutaneous vascular responses to isometric handgrip exercise.

Cutaneous vascular responses to dynamic exercise have been well characterized, but it is not known whether that response pattern applies to isometric handgrip exercise. We examined cutaneous vascular responses to isometric handgrip and dynamic leg exercise in five supine men. Skin blood flow was measured by laser-Doppler velocimetry and expressed as laser-Doppler flow (LDF). Arterial blood pressure was measured noninvasively once each minute. Cutaneous vascular conductance (CVC) was calculated as LDF/mean arterial pressure. LDF and CVC responses were measured at the forearm and chest during two 3-min periods of isometric handgrip at 30% of maximum voluntary contraction and expressed as percent changes from the preexercise levels. The skin was normothermic (32 degrees C) for the first period of handgrip and was locally warmed to 39 degrees C for the second handgrip. Finally, responses were observed during 5 min of dynamic two-leg bicycle exercise (150-175 W) at a local skin temperature of 39 degrees C. Arm LDF increased 24.5 +/- 18.9% during isometric handgrip in normothermia and 64.8 +/- 14.1% during isometric handgrip at 39 degrees C (P less than 0.05). Arm CVC did not significantly change at 32 degrees C but significantly increased 18.1 +/- 6.5% during isometric handgrip at 39 degrees C (P less than 0.05). Arm LDF decreased 12.2 +/- 7.9% during dynamic exercise at 39 degrees C, whereas arm CVC fell by 35.3 +/- 4.6% (in each case P less than 0.05). Chest LDF and CVC showed similar responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Measurement of degraded fecal hemoglobin-heme to estimate gastrointestinal site of occult bleeding. Appraisal of its clinical utility.

Hemoglobin-heme is variably converted to porphyrin during enterocolic transit. This intestinal converted fraction, as measured by HemoQuant, was elevated as a predictor of the occult bleeding site in 152 patients with discrete lesions. The intestinal converted fraction, expressed as the percentage of total fecal hemoglobin, was similar with upper gastrointestinal and proximal colon lesions. Within the colon, values trended downward with more distal location: means +/- standard deviations were 18 +/- 14 proximal colon, 16 +/- 15 sigmoid, and 10 +/- 10 rectum. The amount of fecal blood also affected the intestinal converted fraction; correcting for hemoglobin concentration improved separation by site. Corrected intestinal converted fraction values were significantly lower with rectal (P less than 0.0005) and sigmoid (P less than 0.02) lesions than with proximal colon lesions. Unfortunately, large within-site variation caused considerable overlap between sites. We conclude that the intestinal converted fraction is influenced by the site and amount of bleeding. However, its clinical utility is compromised by substantial individual differences in luminal hemoglobin metabolism.

Aged↗

PubMed1988

Metastatic renal cell cancer and radical nephrectomy: identification of prognostic factors and patient survival.

Between January 1, 1970 and December 31, 1980 (followup 2 years or more) 158 patients with histologically proved metastatic renal cell cancer and no prior therapy were seen. Statistical analyses identified variables that significantly influenced survival, including grade of the primary lesion (p equals 0.002), weight loss of more than 10 per cent (p less than 0.0001) and multiple versus single metastases (p equals 0.0001). Cell type, soft tissue versus bone metastasis, age, sex, site and size of primary lesion, and delay in the diagnosis did not influence survival significantly. Adjuvant nephrectomy markedly influenced survival only in patients with solitary metastasis, low grade primary tumor and weight loss of less than 10 per cent (p equals 0.06). Based on this analysis a score system was constructed to help predict survival and the impact of new forms of therapy in the future.

Adult↗