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Biomedical subjects

J M Johnson

Publications and source records attributed to J M Johnson.

At least 217 records · Page 12Linked to original sources
PubMed1977

Altered control of skin blood flow during exercise at high internal temperatures.

We have investigated further the behavior of skin blood flow (SkBF) as internal temperature (measured as esophageal temperature (Tes)) rises in a heated exercising man. A previous study showed that when skin temperature (Tsk) is driven up in exercising men, the increase in SkBF is less than that found for the same Tes and Tsk in a resting man. In this study, we extended our observations into the range of higher Tes to see if SkBF (measured plethysmographically as changes in forearm blood flow) could be driven to higher levels despite competition with skeletal muscle for cardiac output. After Tsk was elevated to 38 degrees C by means of water-perfused suits, subjects exercised at 525-900 kp.m/min (86-147 W) for 17-30 min while Tsk was held at 38 degrees C. We found that SkBF increase per unit increase in Tes is attenuated at higher Tes. In seven men, the average slope obtained from linear regression of FBF on Tes below 38 degrees C was 7.6 flow units/degrees C. Above 38 degrees C, the average was 2.12 flow units/degrees C. In some subjects, the FBF response appeared virtually saturated at a plateau despite a steady rate of increase in Tes with time. Clearly, SkBF does not increase in direct proportion to Tes without bound. Other stimuli (presumably related to blood pressure regulation) interact either to reduce the rate of SkBF increase or to prevent any further increase after Tes exceeds 38 degrees C.

Adult↗
PubMed1977

The histochemical localization of prostaglandin synthetase activity in reproductive tract of the male rat.

PG synthetase activity was assessed histochemically in the reproductive tract of male rats. Moderate activity was observed in tails of spermatozoa within the corpus and cauda epididymidis but there was no activity in the caput epididymidis or the seminiferous tubules. The sperm tail activity was maximal for cells within the vas deferens. PG synthetase activity was also observed in individual adipose cells adhering to the testicular capsule, epididymis and vas deferens, and in isolated interstitial cells of the testis and the caput, corpus and cauda epididymidis. Specific cells in the capsules of the testes, epididymis and vas deferens also produced PGs. The activity observed in the interstitial cells of the testis and the caput epididymidis was less than that for the other tissues in terms of the proportion of possible cells. The demonstration of PG synthetase activity paralleled to known loss of arachidonic acid from the phospholipids of the spermatozoa as they pass through the male tract. Endogenous substrate was not limiting in the assay system, even in the testis and caput epididymidis where PG synthesis was not normally observed, indicating that a PG synthesis inhibitor may be present in these two tissues. PG synthetase activity within teased seminiferous tubules was markedly increased by physical trauma. Indomethacin diminished but did not eliminate synthesis.

Animals↗
PubMed1976

The relationship between thermographic findings and size and depth of tumour in carcinoma of the breast.

Fifty thermograms of histologically proved breast carcinomas have been analysed without knowledge of the clinical or mammographic findings. Thermographic asymmetry between the breasts was found in 76 percent of the patients, but in only 64 per cent of the patients was the correct side indicated. Poor correlations has also been found between the thermographic findings and the size of a tumour and its distance from the skin.

Body Temperature↗
PubMed1976

Expanded polytetrafluoroethylene as a small artery replacement. A preliminary report.

Recent laboratory and clinical investigations have demonstrated a specific configuration of polytetrafluoroethylene (PTFE) to be a superior biocompatible material for small artery replacement. Twenty such vascular grafts have been implanted in eighteen patients. Grafts were placed in the femoropopliteal or femoral posterior tibial or anterior tibial positions in fifteen patients and in the aortorenal position in three patients. The early results have been satisfying as judged by follow-up angiography and/or clinical examination. There has been no aneurysmal formation in this series of Impragrafts. No infections have been noted. We believe that Impragraft may offer a logical substitute for the inadequate or surgically absent saphenous vein autograft.

Adult↗
PubMed1976

The modified bovine heterograft in vascular access for chronic hemodialysis.

The results of 100 modified bovine heterografts constructed in 93 patients for subcutaneous arteriovenous fistulas for chronic hemodialysis have been reviewed. Fifty-seven patients had the bovine heterograft inserted as the primary method of vascular access. Twenty-eight patients had complications consisting of graft thrombosis and stenosis, graft infection, and hemorrhage that required additional surgical procedures. Three patients with diabetes mellitus developed ischemia of the hand. Fourteen patients have died but none of the deaths could be attributable to the use of the bovine heterograft. In our experience the modified bovine heterograft has enjoyed a higher patient acceptance as compared to other methods of vascular access for hemodialysis. The chief advantage of the bovine graft has been the ability to use the graft in any patient as a means of immediate dialysis.

Adolescent↗
PubMed1976

Interactions between local and reflex influences on human forearm skin blood flow.

A three-part experiment was designed to examine interactions between local and reflex influences on forearm skin blood flow (SkBF). In part I locally increasing arm skin temperature (Tsk) to 42.5 degrees C was not associated with increases in underlying forearm muscle blood flow, esophageal temperature (Tes), or forearm blood flow in the contralateral cool arm. In part II whole-body Tsk was held at 38 or 40 degrees C and the surface temperature of one arm held at 38 or 42 degrees C for prolonged periods. SkBF in the heated arm rose rapidly with the elevation in body Tsk and arm Tsk continued to rise as Tes rose. SkBF in the arm kept at 32 degrees C paralleled rising Tes. In six studies, SkBF in the cool arm ultimately converged with SkBF in the heated arm. In eight other studies, heated arm SkBF maintained an offset above cool arm SkBF throughout the period of whole-body heating. In part III, local arm Tsk of 42.5 degrees C did not abolish skin vasoconstrictor response to lower body negative pressure. We conclude that local and reflex influences to skin interact so as to modify the degree but not the pattern of skin vasomotor response.

Adult↗
PubMed1976

The morphologic features of the bronchi, bronchioles, and alveoli in chronic airway obstruction: a clinicopathologic study.

A 6-year semiquantitative clinicopathologic study revealed that among 196 men and 46 women 40 or more years of age at death, the severity of destructive emphysema was overwhelmingly the most important morphologic correlate of the clinical state of chronic airway obstruction. The pathogenic mechanisms whereby emphysema may lead to airway obstruction are probably multifactorial, but our data are consistent with a growing consensus that loss of small airway support by surrounding lung tissue in emphysema may cause kinking, tortuosity, and collapse of the airways, with subsequent increased airflow resistance and clinical obstruction. Pathologic changes (inflammation, fibrosis, increased goblet cells, and mucous gland enlargement) in large or small airways in the absence of much emphysema were very seldom associated with significant chronic airway obstruction, and correlated rather poorly with chronic airway obstruction, regardless of severity of emphysema. A subjective method of evaluating mucous gland enlargement in the large airways was consistently better than the Reid Index in correlations with clinical and anatomic abnormalities, presumably because it took all glands into consideration. The clinical features of subjects with severe centrilobular versus severe panlobular emphysema were essentially the same. "Blue bloater" and "pink puffer" clinical types of chronic airway obstruction continued to reveal differences in airway pathologic features, but no longer revealed a major difference in the severity of emphysema at the time of death. Presumably this was due, at least partially, to improved treatment, longer survival, and fusion into a similar end-stage. The total exposure to cigarette smoke was quantitatively related to clinical chronic airway obstruction and to both alveolar and airway pathologic features.

Aged↗
PubMed1976

Organochlorine pesticides in the Hawaii Kai Marina, 1970-74.

Sediments, water, and oysters from the receiving waters of the Hahaione Valley, a suburban development in south-easter Oahu, Hawaii, were analyzed for organochlorine pesticidal compounds. The insecticides dieldrin, alpha- and gamma- chlordane, and p,p'-DDT were found in the study site environment. Levels were in the low parts per billion range for oysters and sediments and in the low parts per trillion range for water. During the past several years dieldrin residues in the marina study site have increased, even though the only activity known to influence pesticide levels in the valley is the chronic treatment for subterranean and dry wood termites. If present trends continue, dieldrin may pose a threat to biota of the aquatic environment. Findings have shown that residue levels of dieldrin and p,p'-DDT in the sediments are within the LD50 (median lethal dose) range for estuarine fish and thus may have a deleterious effect on bottom-feeding organisms. According to present standards of the Food and Agriculture Organization/World Health Organization, pesticide residue levels within the study site do not appear to constitute a health hazard to humans.

Animals↗
PubMed1976

Expanded polytetrafluoroethylene (PTFE) subcutaneous arteriovenous conduit: an improved vascular access for chronic hemodialysis.

The early results with 84 PTFE grafts used as subcutaneous A-V conduits for vascular access in 72 patients requiring chronic hemodialysis have been quite promising. Initial follow-up has revealed that these grafts functioned at least as well as the bovine heterograft, and the complications seen within the 2 groups being somewhat similar. Should the complications and rate of complications with PTFE be no greater than those seen with the bovine heterograft, then its availability, ease of handling and significant decrease in cost would make the PTFE graft a significant improvement as a means of creating vascular access for chronic hemodialysis.

Adult↗
PubMed1975

Altered control of skin blood flow at high skin and core temperatures.

Five subjects were studied during periods of controlled increases and decreases in skin temperature (Ts) over the Ts range of 34-40 degrees C. One protocol was designed to observe changes in forearm blood flow (FBF) and heart rate (HR) with changes in core temperature (Tc; right atrial blood temperature and esophageal temperature were measured) with Ts held constant at two levels. FBF and HR changed linearly with Tc in the Tc range of 37-38 degrees C with Ts constant at 38 degrees C. A second protocol imposed Ts changes at two levels of Ts and Tc; this protocol also included a prolonged cooling period. The influence of Ts on FBF and HR was reduced when Ts changes occurred at an elevated Ts and Tc, and FBF showed considerable hysteresis during cooling. We conclude that a linear model for the control of FBF or HR is inadequate as a tool for predicting the control of these variables.

Adult↗
PubMed1975

Forearm skin and muscle vascular responses to prolonged leg exercise in man.

To determine the cutaneous and resting skeletal muscle vascular responses to prolonged exercise, total forearm blood flow (FBF-plethysmography) (5 men) and forearm muscle blood flow (MBF-[125I]antipyrine clearance) (4 men) were measured throughout 55-60 min of bicycle exercise (600-750 kpm/min). Heart rate (HR) and esophageal temperature (Tes) were also measured throughout exercise. FBF showed only small changes during the first 10 min followed by progressive increments during the 10-40 min interval and smaller rises thereafter. For the full 60 min of exercise, there was an average increase in FBF of 8.26 ml/100 ml-min. MBF showed an initial fall with the onset of exercise (on the average from 3.84 to 2.13 ml/100 ml-min) which was sustained or fell further as exercise continued, indicating that increments in FBF were confined to skin. Much of the increase in FBF occurred despite essentially constant Tes. Results suggest that the progressive decrements in central venous pressure, stroke volume, and arterial pressure previously seen during prolonged exercise are due in part to progressive increments in cutaneous blood flow and volume.

Adult↗