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J B Howell

Publications and source records attributed to J B Howell.

At least 55 records · Page 3Linked to original sources
PubMed1983

A Signal Detection Theory analysis of the effect of chest cage restriction upon the detection of inspiratory resistive loads.

1. By the use of Signal Detection Theory techniques, resistive load detection sensitivity was estimated in six normal subjects, and compared with detection when the chest cage was strapped in the position of full expiration. 2. With chest cage restriction there was both a decrease in detection sensitivity and an increase in the willingness to report the presence of an added load to breathing. 3. This suggests that the similarity of detection in chest clamping and control previously reported was due partly to increased detection bias with chest clamping. 4. These results have implications concerning the dependence of detection on afferent information from the chest wall.

Adult↗
PubMed1982

The contribution of the accelerating phase of inspiratory flow to resistive load detection in man.

1. By the use of Signal Detection Theory techniques resistive load detection sensitivity was estimated in ten normal subjects during loading of the whole of inspiration and compared with loading restricted to the initial, accelerating phase of inspiratory air flow. 2. Detection sensitivity during the accelerating-flow phase of inspiration was not significantly different from that in the control conditions. 3. These results suggest that the information for detection is generated in the accelerating phase of inspiratory air flow. 4. We propose that the stimulus for resistive load detection is the ratio of the rate of change of pressure to the rate of change of flow.

Adult↗
PubMed1981

Prevention.

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Adolescent↗
PubMed1981

Detection and interaction of elastic and flow-resistive respiratory loads in man.

1. The detection of added inspiratory airflow resistances was studied in normal individuals under two circumstances: first, while breathing unhindered, and secondly, while breathing against continuously applied ('basal') inspiratory elastic loads. The addition of basal elastic loads resulted in impaired detection of flow-resistive loads whether expressed as added flow resistance or as a proportion of the basal flow resistance. 2. When loads were plotted on a logarithmic scale, load-detection relationships were linear, permitting both threshold and slope of the detection response ('sensitivity') to be assessed. Impaired detection associated with basal elastic loads was shown to be due to a raised threshold without change in 'sensitivity'. 3. When the flow resistances submitted for detection were expressed as a proportion of the sum of the basal flow resistance and added elastance, the probability of detection was independent of the magnitude of the added elastance. 4. The interaction between basal elastic and added flow-resistive loads suggests that at the time of detection the basal elastance acts in a manner similar to that of an added flow resistance. 5. Added basal flow resistances had no significant effect on the detection of threshold elastic loads.

Adult↗
PubMed1980

Structure and significance of the pits with their tumors in the nevoid basal cell carcinoma syndrome.

Parallel histopathologic, histochemical, scanning, and transmission electron microscopic (EM) observations were made on palmar pits of one patient and on palmar pits, with an unprecedented number of basal cell carcinomas. of another patient. The first scanning view of tumor growing into the lumen of a pit from the genetically defective epidermis below is presented. The anatomy of the pit is demonstrated for the first time by scanning view of a transected pit. Our observations confirmed those of Hashimoto et al on the mechanisms involved in premature desquamation of the stratum corneum and on the true nature of the epithelium at the base of the pit. This epithelium resembled closely basal cell epithelioma and represented carcinoma in situ. The striking demarcation afforded by the axure B stain of normal and abnormal portions of the palmar epidermis with pit and the poor stainability of the pit with tumor was likewise confirmed. The tumors exhibit aggressive behavior infrequently.

Adolescent↗
PubMed1980

Effect of timing, flow, lung volume, and threshold pressures on resistive load detection.

The acuity of resistive load detection (RLD) has been tested by comparing threshold detection (delta R50) under control conditions with that obtained when loads were applied at different times in inspiration, with different inspiratory flows, at different lung volumes, and with different background loads. For loads applied suddenly during established inspiratory flow, the mean delta R50 was 0.94 +/- 0.04 (+/- SEE) cmH2O . 1(-1) . s compared with 0.42 +/- 0.13 cmH2O . 1(-1) . s (P < 0.01) for loads applied before inspiration, suggesting that information generated early in the breath is important and the RLD is not subserved by a simple peripheral proprioceptive mechanism. Rapid voluntary inspiration through nonlinear resistances did not improve RLD (mean delta R50 0.86 cmH2O . 1(-1) . s compared with a control of 0.56 cmH2O . 1(-1) . s; P < 0.05) despite the much greater pressures and resistances at high flow rates, further suggesting that detection of a resistive load occurs early in inspiration. Alteration of the background load by breathing at increased lung volume (1 liter above FRC) or by breathing against a standing pressure of 1 or 3 cmH2O (i.e., pressure independent of volume or flow) did not significantly reduce RLD. This suggests that the change in pressure due to the added load, expressed as a fraction of the total driving pressure, cannot subserve RLD. Our results suggest that external resistive load detection is subserved by the relation between pressure and flow over the early part of inspiration.

Adult↗
PubMed1979

The effect of increased ventilation on resistive load discrimination.

The ability of normal subjects to detect the addition of external resistive loads was determined both at rest and when ventilation was increased to more than 30 L/min by CO2 administration or exercise. Tidal volume, flow, and mouth and transpulmonary pressures were recorded during resistive load discrimination using standard psychophysical techniques. The mean resistance detection threshold was 0.40 +/- 0.06 cm H2O/L/s at rest, 0.36 cm H2O/L/s during administration of CO2, and 0.44 cm H2O/L/s with exercise. The Weber fraction was 0.28 +/- 0.04 at rest, 0.29 +/- 0.08 with CO2, and 0.34 +/- 0.04 with exercise. The lack of change in the ability to detect resistive loads when ventilation was increased was surprising because changes in both pressure and flow were tripled. The findings were supportive of the hypothesis that resistance or something like it is perceived, rather than change in flow or pressure.

Adult↗
PubMed1978

Reticular pigmented anomaly of the flexures.

Reticular pigmented anomaly of the flexures (Dowling-Degos' anomaly) is a rare, benign, new genodermatosis that has recently evolved from independent observations and studies by several dermatologists. Because of its favorable prognosis, differentiation of this benign disorder from acanthosis nigricans, a cutaneous marker of possible or existing internal malignant disease, is highly important. Careful clinical appraisal of the eruption in correlation with the characteristic microscopic features makes the diagnosis simple and straightforward.

Humans↗
PubMed1976

Assessment of responsiveness to carbon dioxide in patients with chronic airways obstruction by rate of isometric inspiratory pressure development.

1. Responsiveness to CO2 was measured in forty patients with chronic airways obstruction in terms of ventilation and rate of isometric inspiratory pressure change [(dP/dt)max]. 2. The ventilatory response was below the normal range in eighteen out of twenty-two patients with normal arterial CO2 tensions and in all of eighteen patients with CO2 retention. 2. The (dP/dt)max. response was distributed throughout the normal range in all but one of the patients with normal arterial CO2 tension. In all the patients with CO2 retention the (dP/dt)max. response was either at or below the lower limit of the normal range. 4. Although the ventilatory responses correlated significantly with FEV1 there was no such correlation for the (dP/dt)max. responses. 5. The (dP/dt)max. response showed a significant negative correlation with Pa,CO2. 6. It is believed that the (dP/dt)max. response to CO2 can be used to assess central CO2 responsiveness in subjects with airways obstruction independently of mechanical factors limiting their ventilation.

Aged↗
PubMed1976

Epithelioma adenoides cysticum: genetic update.

Epithelioma adenoides cysticum (EAC) is a well-known genodermatosis which follows an autosomal dominant mode of inheritance. Questions still remain, however, concerning an apparent excess of females with EAC. An analysis of nineteen previously published pedigrees and one newly ascertained pedigree, which in the aggregate included over 175 cases of EAC, induced no excess of affected females, but rather, a marked deficit males. This deficiency was not the consequence of sex linkage or decreased viability, and was most evident in large pedigrees and sibships, sibships not including the probands, and late birth orders. In these situations, the penetrance of EAC in male gene carriers was only 50%, but was close to 100% in female gene carries. Under maximum detection conditions, i.e. small pedigrees, small sibships, sibships containing the proband, and early birth orders, the penetrance in males increased to 85% and was again close to 100% in females. These findings suggested that the deficit of affected males was best explained by a comination of lessened expressivity and penetrance, effects which were magnified under situations of poor detection. A review of familial cases of EAC indicated no consistent associated anomalies such as those that characterize the naevoid basal cell carcinoma syndrome.

Adolescent↗
PubMed1976

Transformation of epithelioma adenoides cysticum into multiple rodent ulcers: fact or fallacy. A historical vignette.

This historical study has examined the persistent controversy about the propensity of epithelioma adenoides cysticum (EAC) to transform into multiple rodent ulcers, by reviewing cases reported through the years that seemed to support the idea. After focusing on the biological behaviour and natural history of the tumours and comparing them with our present knowledge of the behaviour of EAC, we believe that these cases were incorrectly diagnosed. Rather than EAC, they were probably examples of the naevoid basal cell carcinoma syndrome. The latter syndrome was actually established by the recognition that patients who have multiple rodent ulcers that appear early in life and behave aggressively usually have a constellation of associated developmental defects and that the tumours sould be classified as genetically determined basal cell carcinomas and not as EAC.

Adolescent↗