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Biomedical subjects

J R Jackson

Publications and source records attributed to J R Jackson.

At least 73 records · Page 4Linked to original sources
PubMed1988

Effect of transcutaneous electrical nerve stimulation at auricular points on experimental cutaneous pain threshold.

The purposes of this study were 1) to examine the effect of high intensity, low frequency transcutaneous electrical nerve stimulation at auricular acupuncture points on experimental pain threshold measured at the wrist and 2) to determine the changes in effect over time. Forty-four healthy adult men and women were assigned randomly to one of three treatment groups. Group 1 (n = 15) received TENS to appropriate auricular points for wrist pain, Group 2 (n = 14) received TENS to inappropriate (placebo) auricular points, and Group 3 (n = 15) received no TENS. We measured experimental pain threshold at the wrist after an electrical stimulus during one pretreatment and three posttreatment time periods. Group 1 was the only group that had a statistically significant increase (p less than .05) in pain threshold after testing. This increase remained significant for all posttreatment measurements for Group 1. These results suggest that high intensity, low frequency TENS applied to appropriate auricular acupuncture points can increase pain threshold.

Acupuncture Therapy↗
PubMed1987

Effects of unilateral and bilateral auricular transcutaneous electrical nerve stimulation on cutaneous pain threshold.

This study compared the effects of unilateral and bilateral auricular transcutaneous electrical nerve stimulation on cutaneous pain threshold. Auricular acupuncture points were stimulated with low frequency, high intensity TENS for 45 seconds. Sixty healthy, adult subjects were assigned randomly to one of two treatment groups or to a control group. The two treatment groups received low frequency, high intensity TENS either unilaterally or bilaterally. The control group did not receive auricular stimulation. Experimental pain threshold at the left wrist was determined with a painful stimulus before and after auricular stimulation. Both unilateral and bilateral auricular stimulation groups exhibited a significant increase (p less than .05) in experimental pain threshold, but the control group did not. The mean change values between the unilateral and bilateral stimulation groups were not statistically different. These results suggest that both unilateral and bilateral auricular TENS can increase pain threshold.

Adult↗
PubMed1983

Role of neutrophils in the deposition of platelets during acute inflammation.

Platelets can release a variety of inflammatory mediators. These formed elements have been shown to accumulate early in acute inflammation, often prior to fibrin and thrombus formation. Polymorphonuclear leukocyte (PMNL) infiltration is also an early event and is linked to protein exudation and hyperemia. The relationship between PMNL and platelet accumulation was studied. Inflammation was induced in rabbits by intradermal injection of stimuli, and 51Cr-labeled leukocytes and 111In-labeled platelets were used to quantitate the rates of leukocyte and platelet accumulation in the dermal reactions. A temporal association between the rates of leukocyte infiltration (greater than 95% PMNL) and of platelet deposition at skin sites was observed when killed Escherichia coli, E. coli-derived chemotactic factors, zymosan-activated plasma, f-met-leu-phe, or endotoxin were injected intradermally. A linear correlation (r = 0.96; p less than 0.001) between these parameters was observed. 59Fe-labeled red cells did not accumulate in these lesions. Platelet deposition in response to inflammatory stimuli did not occur in PMNL-depleted (nitrogen mustard treatment) but platelet-sufficient rabbits, in spite of normal platelet deposition in thrombin-injected sites. Platelet responses to inflammatory stimuli were normal when neutropenia, after nitrogen mustard treatment, was prevented. In contrast, in situ PMNL reconstitution of the skin sites in neutropenic rabbits did not cause local platelet accumulation. Intravenous infusion of the synthetic chemotactic factor, f-met-leu-phe, induced transient neutropenia and thrombocytopenia (30% of control) with platelet sequestration primarily in the lung. This is also the known site of PMNL sequestration during f-met-leu-phe infusion. It is concluded that platelets selectively deposit in acutely inflamed tissues primarily during PMNL margination in, and emigration across, the microvasculature. Platelets and PMNLs likely coassociate on the vessel wall, and this interaction may influence the course of inflammation.

Acute Disease↗
PubMed1982

Toxicity of benzyl cyanide in the rat.

Lethal doses of benzyl cyanide in the rat were 0.64 mmol/kg (i.p.), 1.8 and 2.6 mmol/kg (p.o.) for female and male rats, respectively. Sublethal oral doses of benzyl cyanide were nephrotoxic causing increased excretion of protein, amino acids and glucose. Cyanide was slowly liberated from the dosed nitrile and excreted as cyanide and thiocyanate, the proportion of the former increasing with increasing i.p. dose and with the highest oral dose. The oral cyanide antidote was ineffective against benzyl cyanide and the intravenous antidote, Kelocyanor (cobalt edetate), had little beneficial effect.

Acetonitriles↗
PubMed1982

The relationship between prior clerkship experience and student performance in medicine clerkships. Implications for grading.

The purpose of this study was to examine the relationships between prior clerkship experience and student performance in a third-year medicine clerkship. Trend analysis was used to determine if there was a linear relationship between amount of prior clerkship experience and scores on the following performance measures: subjective preceptor ratings; locally developed examinations; and the National Board of Medical Examiners (NBME) Special Examination in Medicine. Results indicated a positive linear relationship between amount of prior experience and the NBME Special Examination in Medicine, but no trends were found for the other performance measures. The effect was found to be a short-term phenomenon, in that no sequencing effect was evident from 1 to 2 years later, as indicated by scores on the Medicine subtest of NBME II. Implications for grading are discussed.

Alabama↗
PubMed1979

Errors in velocity measurement by the Pitot principle in fluids with slowly propagated pressure waves.

An attempt has been made to develop a velocity probe using the Pitot principle for the measurement of fluid velocities in cerebrospinal fluid. Pressures were measured using conventional transducers and amplifiers and the pressure difference signal has the predicted relationship to the square of fluid velocity in the steady state. However, in the clinical situation where slowly propagated pressure waves accompany cerebrospinal fluid movement the pressure difference incorporates an indeterminate term unrelated to velocity, and this imposes severe limitations on the technique. Measurements and discussion are presented.

Amplifiers, Electronic↗
PubMed1979

Amputation: energy cost of ambulation.

A mobile instrument system was used to measure energy consumption by indirect calorimetry at rest and during ambulation in 25 unimpaired subjects, 6 unilateral below-knee (BK) amputee patients, 6 unilateral above-knee (AK) amputee patients and 4 bilateral AK amputee patients. To prevent the introduction of gait difficulties among the impaired subjects, each subject was permitted to walk at his own comfortable speed. Since speed thus varied among subjects, ambulation data were expressed in units of energy per foot traveled. Statistical analyses of the mean oxygen costs indicated several significant differences among the groups. In comparison to unimpaired subjects, the mean oxygen consumption was 9% higher in unilateral BK amputee patients, 49% higher in unilateral AK amputee patients and 280% higher in bilateral AK amputee patients.

Adult↗
PubMed1978

Factors determining the sequence of oxidative decarboxylation of the 2- and 4-propionate substituents of coproporphyrinogen III by coproporphyrinogen oxidase in rat liver.

Coproporphyrinogen oxidase (EC 1.3.3.3) catalyses the oxidative decarboxylation of the 2- and 4-propionate substituents of coproporphyrinogen III to form protoporphyrinogen IX. A 4-propionate-substituted porphyrinogen, harderoporphyrinogen, which is also a substrate for coproporphyrinogen oxidase, is formed during the reaction. Synthetic [(14)C]coproporphyrinogens III, specifically labelled in the carboxyl carbon atoms of either the 2- or 4-propionate substituents, were used to measure the rate of decarboxylation of each substituent by rat liver coproporphyrinogen oxidase. The experimental results, together with the recognition that in all known substrates of coproporphyrinogen oxidase only those propionate groups flanked by a specific arrangement of substituents are decarboxylated, indicate that the 4-propionate group of coproporphyrinogen III cannot be attacked until the 2-propionate group has been decarboxylated. Production of (14)CO(2) from the substrate labelled in the 2-propionate group therefore measures the formation of harderoporphyrinogen, whereas (14)CO(2) from the 4-propionate-labelled substrate measures protoporphyrinogen IX formation. The rate of harderoporphyrinogen formation is about twice that of protoporphyrinogen, and this ratio is unchanged by varying the concentration of coproporphyrinogen III or by competitive inhibition of the enzyme. When coproporphyrinogen III is present in an excess, two fractions of harderoporphyrinogen can be distinguished. One accumulates during the reaction, and the other, which is destined to become protoporphyrinogen IX, does not equilibrate with added harderoporphyrinogen. It is suggested that both decarboxylations take place at the same active centre, which becomes temporarily inaccessible to coproporphyrinogen III and added harderoporphyrinogen, and that the molecule rotates after the first decarboxylation to allow the second to take place.

Animals↗
PubMed1977

A gravimetric plethysmograph and its evaluation in clinical use.

A gravimetric plethysmograph, the technique of its use and its evaluation in vascular surgical practice are described. The instrument measures flow by the increase in leg weight (rather than volume) produced by an increase in blood content resulting from venous occlusion. The instrument was found to be convenient to use and satisfactory records were obtained in 88% of patients. Values for flow at rest and during reactive hyperaemia were clearly related to the presence of indications for surgical treatment and were similar to those reported by other workers. It is suggested that a peak hyperaemic flow of greater than 15 g 100 ml-1 min-1 may indicate that there are no indications for surgical treatment. The changes in hyperaemic flow values after treatment were clearly related to the symptomatic improvement resulting from it. It is concluded that the gravimetric plethysmograph is suitable for use in the assessment of patients with obliterative arterial disease of the legs.

Aged↗