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Biomedical subjects

R H Johnson

Publications and source records attributed to R H Johnson.

At least 19 recordsLinked to original sources
PubMed1992

Autonomic responses to carbohydrate ingestion and head-up tilt in elderly subjects with orthostatic hypotension.

To investigate the role of glucose and insulin in the development of hypotension following glucose ingestion in elderly subjects with orthostatic hypotension, the autonomic responses to glucose and xylose ingestion were studied in five elderly subjects with age related orthostatic hypotension (without autonomic failure), five elderly control subjects and three elderly subjects with evidence of autonomic failure. Heart rate, blood pressure, plasma noradrenaline and plasma arginine vasopressin responses to glucose ingestion and to xylose ingestion were investigated. All subjects were supine for 90 min following ingestion of each carbohydrate and were then tilted 45 degrees head-up for 10 min. Blood pressure was maintained in elderly control subjects following ingestion of both carbohydrates and during tilting. The elderly group with orthostatic hypotension, while supine had a fall in systolic blood pressure 60-90 min following both glucose and xylose ingestion. Diastolic blood pressure was lowered 60-90 min after glucose but not xylose. During tilting, blood pressure fell by similar levels following both carbohydrate ingestions; plasma noradrenaline levels after 2 min and plasma arginine vasopressin levels after 10 min tilting were significantly less following glucose ingestion compared to xylose ingestion. The autonomic failure group while supine had a fall in systolic blood pressure 60-90 min following both glucose and xylose ingestion. Diastolic blood pressure was lowered 60-90 min after glucose but not xylose. During tilting, blood pressure fell by similar levels following both carbohydrate ingestion. Plasma noradrenaline and arginine vasopressin levels were unchanged after ingestion of either carbohydrate, and during tilting.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Autonomic involvement in systemic diseases.

It is now well recognized that autonomic dysfunction may occur in disorders affecting the various body systems. Over the past year important observations have been reported in congestive cardiac failure, reflex sympathetic dystrophy (RSD), acquired immune deficiency syndrome (AIDS) and diabetes mellitus.

Autonomic Nervous System↗
PubMed1991

A new set of calibration standards for estimating the fat and mineral content of vertebrae via dual energy QCT.

A new set of calibration standards has been developed for implementing a dual-energy (DE) quantitative CT technique for estimating the fat and bone content of vertebrae. The QCT technique is based upon a three-component model of bone and utilizes calibration materials that mimic those components in their X-ray attenuation properties. The three components we chose to simulate are bone (mineral plus collagen), fat and a fat-free red marrow. This choice was predicated upon our desire to employ materials that would facilitate later experimental verification of the method. The calibration standards and a set of test samples were manufactured of tissue-simulating epoxy resins. They were employed in studies of the accuracy (consistency) and precision of the technique and in a study of 21 normal postmenopausal women. Estimates of the bone and fat content of the test samples were consistent with the manufacturer's specifications to within 13 mg/ml and 7 vol%, respectively. Long-term reproducibility (coefficient of variation) for both quantities was about 3%. The average bone content of the T12-L3 vertebrae of the human subjects was 262 +/- 32 mg/ml (152 +/- 18 mg/ml calcium hydroxyapatite or mineral) and the average fat content was 63 +/- 8%. Conventional single energy (SE) QCT measurements of these vertebrae were about 23% less than the DE mineral measurements, which is consistent with the differences between SEQCT and ash content that others have determined via chemical analysis. The DE fat content is, in absolute terms, about 15% greater than values reported in the literature and may be due to an error in the assumed composition of red marrow. The true accuracy of the bone and fat estimates is to be determined in a planned human vertebral specimen study.

Bone Density↗
PubMed1991

The identification of female sandflies of the subgenus Larroussius by the morphology of the spermathecal ducts.

The complete spermathecae of 13 species of Larroussius were dissected and examined. The base of the duct of 4 species (aculeatus, guggisbergi, tobbi, wui) is bell-shaped: they are easily distinguished by differences in shape. Five other species (perniciosus, pedifer, longicuspis, perfiliewi, galilaeus) have lateral structures at the base of the duct: slight differences between perniciosus, pedifer and longicuspis distinguish these species: the structures of perfiliewi and galilaeus are the same. Species of a third group (neglectus, syriacus) have a common duct with no lateral structures: they are distinguishable by minor differences. Two species (ariasi, orientalis) from a fourth group with expanded distal parts of the duct; the size and shape of the expanded parts easily separates the species. The study shows a great variation in the morphology of the base of the spermathecal ducts of Larroussius and confirms the value of this feature in identifying otherwise indistinguishable females of the subgenus.

Animals↗
PubMed1990

Theoretical and experimental comparison of three types of electromagnetic hyperthermia applicator.

There is evidence that heating of malignant tissue in the treatment of cancer may be beneficial and so the performance of different applicator designs needs to be established. A theoretical model of the dielectric loaded waveguide applicator is compared with models of two other applicators which depend on energy radiated from conductors carrying high frequency current. The latter are exemplified by the compact resonant patch applicator and the lightweight inductive current sheet applicator. It is shown that heating profiles and field penetration of each applicator are similar for equal radiating areas, and these results have been substantiated experimentally. Impedance match as a function of frequency and load is also compared for the three types of applicator.

Electromagnetic Phenomena↗
PubMed1990

Is orthostatic hypotension in the elderly due to autonomic failure?

In order to investigate whether orthostatic hypotension in elderly people is due to autonomic nervous system dysfunction or blood vessel abnormalities, we have measured platelet and lymphocyte adrenoceptor numbers and agonist binding in addition to venous plasma catecholamine concentrations. Eight elderly subjects with orthostatic hypotension and six control elderly subjects were studied. None of the subjects had other symptoms of autonomic failure. There was no significant difference between the heart rate or plasma catecholamine responses to standing of the two groups. The orthostatic hypotension subjects had a significant rise of their plasma vasopressin levels whereas the control group had no significant change. The number of alpha 2-adrenoceptor sites in platelets was lower in the orthostatic hypotensive group compared to the controls and the binding affinity was greater than in the controls. There were no significant differences in beta-adrenoceptor binding sites or affinities in isolated lymphocytes between the two groups. The similar changes in heart rate and catecholamines together with the vasopressin changes suggest that, in these elderly patients with an abnormal drop of blood pressure on standing, there is no dysfunction of autonomic pathways concerned with cardiovascular function. The lower numbers of alpha 2-adrenoceptor sites on isolated platelets in subjects with orthostatic hypotension could indicate reduced alpha 2-adrenoceptor numbers on their blood vessels which could contribute to their inability to maintain blood pressure while standing.

Aged↗
PubMed1990

Do thermoregulatory reflexes pass through the hypothalamus? Studies of chronic hypothermia due to hypothalamic lesion.

A 38-year-old man presented with chronic hypothermia. He also had evidence of hypothalamo-pituitary dysfunction and CT scans showed a discrete hypothalamic lesion. Thermoregulatory impairment was found although there was normal circulatory control of blood pressure. Reflex vasodilatation could be initiated when hypothermia was present and also in response to raised body temperature. Shivering was initiated reflexly but did not otherwise occur. These observations imply that thermoregulatory reflexes are independent of central thermoregulatory mechanisms and do not pass through the hypothalamus.

Adult↗
PubMed1990

Assessment of the efficacy of a nonsteroidal anti-inflammatory drug, Naprosyn, in the treatment of gingivitis.

A double-blind, placebo-controlled trial was conducted to determine the effects of the nonsteroidal anti-inflammatory drug Naprosyn (naproxen) on gingival inflammation. The enrollment of 114 patients provided 102 patients valid for efficacy evaluation, each having a mean gingival index (GI) score of 1.5 or greater at test-teeth sites. Patients were given oral Naprosyn 500 mg b.i.d. or placebo for 30 days. At 28 d, full-mouth prophylaxis was performed. Gingival index, modified sulcular bleeding index (SBI), and plaque index (PII) scores were taken at baseline, at 28 d, and at 30 d. When the 28-d index measurements were compared to baseline, the drug had no significant effect on plaque index scores or gingival inflammation. Statistically, Naprosyn enhanced the resolution of gingival inflammation following removal of microbial plaque. Thus, although this drug does not suppress the inflammation-inducing properties of plaque, Naprosyn may enhance recovery following plaque removal.

Adult↗
PubMed1990

Lengthening clinical crowns.

Finding a solution to the short clinical crown is based on an appreciation of the biological width of attachment plus the dimensional requirements of sound restorative procedures. The collective talents of restorative dentist, orthodontist, and periodontist often are needed to cope with the problem.

Dental Restoration, Permanent↗
PubMed1989

Increased peritoneal fluid lactic acid values and progressive bowel strangulation in dogs.

In the present study, we determined values for peritoneal fluid and blood ammonia, amylase, and lactic acid content in 11 dogs after experimental bowel strangulation. In the nine survivors of this group, we demonstrated a near linear increase in peritoneal fluid lactic acid over a 24-hour period, during which the plasma lactic acid remained relatively constant. A significant increase in peritoneal fluid ammonia was also demonstrated, but this did not occur until more than 16 hours after strangulation. In a second group of two dogs in which simple obstruction was produced, no significant increase in peritoneal fluid lactic acid or ammonia occurred. We did not find significant changes in peritoneal fluid amylase in this study. These data suggest that the determination of peritoneal fluid lactic acid content, especially when compared with concomitant plasma lactic acid, may be useful in the accurate preoperative diagnosis of bowel strangulation.

Ammonia↗
PubMed1989

Is clonidine useful in the treatment of alcohol withdrawal?

The comparative efficacy of clonidine and chlormethiazole has been examined in the management of acute alcohol withdrawal. A double blind randomized study was conducted in consecutive patients admitted to a hospital detoxification unit. Patients were assessed regularly by a standard alcohol withdrawal rating-scale. Thirty-two patients received either clonidine or chlormethiazole in reducing dosages over 96 hr. All the patients receiving chlormethiazole had uneventful withdrawals. However, eight patients treated with clonidine were withdrawn from the trial due to hallucinations (two), seizures (two), symptomatic orthostatic hypotension (three) or drowsiness (one), indicating that clonidine is less effective than chlormethiazole in the prevention of the major manifestations of alcohol withdrawal.

Adult↗
PubMed1989

Traumatic hemisomato-tmesis: a case report and review of the literature.

A case of traumatic hemisomato-tmesis is presented. The line of complete transection passed obliquely from the suprapubic skin to the lumbosacral junction. There were associated visceral injuries. We describe our experience of such a case and review the surgical options in the light of the current literature.

Adult↗
PubMed1989

The effect of a new electric toothbrush on supragingival plaque and gingivitis.

This study tested the effectiveness of a rechargeable electric toothbrush, Interplak, in removing supragingival plaque and resolving gingivitis. Forty adults with gingivitis were randomly assigned to either a "manual" or "electric" group. Detailed oral hygiene instructions were given and a blind examiner assessed plaque scores before and after brushing, toothbrush abrasion, and gingival inflammation at baseline, 1, 2, and 4 weeks. Subjects using the electric brush had significantly lower (P less than 0.05) mean plaque and gingival inflammation scores. The electric group's plaque scores fell from 77% at baseline to 28% (before brushing) and 14% (after brushing) at 4 weeks; the manual group's dropped from 75% to 50% and 30% (before and after brushing, respectively). The mean G.I. for the electric group fell from 1.65 at baseline to 1.28 at 4 weeks, while the manual group's scores decreased from 1.65 to 1.43. The results suggest that the electric brush removed supragingival plaque and resolved gingivitis better than the manual brush over a 28-day period. However, a telephone survey conducted 6 months later indicated that most subjects were not using the device twice a day as they had during the study.

Adolescent↗
PubMed1989

Radiation litigation in retrospect.

Most of the radiation litigation filed against the United States pursuant to the Federal Tort Claims Act has been defended by asserting federal sovereign immunity or by proving that the plaintiff's injury is unrelated to his radiation exposure. This paper reports that the second defense is best advanced by comprehensive pretrial investigation of the plaintiff's claim, which frequently results in voluntary dismissal of the legal action.

Humans↗
PubMed1988

Epidemiological studies of bovine spumavirus.

Bovine spumavirus (BSV) infection is shown to be endemic in some herds in north Queensland. The virus was readily isolated from leucocytes of the majority of mature cattle which were BSV antibody positive (BSV reactors) in the agar gel precipitin test (AGPT). Calves born to dams which were BSV reactors showed no BSV antibody or circulatory leucocyte-associated BSV (CLAB) at birth, but became BSV reactors following ingestion of colostrum, and maintained such evidence of passive immunity until 3-5 months of age. Experimental infection of dams with BSV at 5-7 months of gestation did not cause foetal infection. In groups of young animals at pasture, segregated by age and sex, no evidence of BSV infection occurred, following loss of passive immunity, until 18-24 months of age. At this time, occasional members of some groups (both male and female) became BSV reactors and showed CLAB. At approximately 24 months old, following mixing in groups with older cows, and single-sire mating, 34% of heifers became BSV reactors within 10 weeks. A herd survey indicated 85% of 2-3-year-old cows to be BSV reactors; thereafter, the percentage of reactors declined gradually with increasing age. Using BSV grown in cell culture, transmission of infection by throat spray was the most successful route, 7 of 7 (100%) of susceptible cattle becoming BSV reactors within 8 weeks of spraying. Using the intravenous route, only 2 of 5 (40%) susceptible cattle became BSV reactors, and swabbing of cell culture virus into the prepuce or vagina did not result in infection of 4 BSV-susceptible animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Detection of immunological tolerance to bovine spumavirus (BSV) with evidence for salivary excretion and spread of BSV from the tolerant animal.

A group of 17 Friesian-Holstein steers held in individual pens was examined for evidence of infection with bovine spumavirus (BSV). Serum was examined for specific antibody by 2 serological procedures, and circulatory leucocytes and throat swabs were examined for the presence of circulatory leucocyte-associated BSV (CLAB) and saliva-associated BSV (SAB). Initial tests showed that 7 of the 17 steers had specific antibody to BSV by both serological procedures, and a further steer developed such antibody during the first 3 months of holding the animals in single contiguous pens. All 8 of these specific antibody-positive steers were CLAB positive and SAB negative. Nine steers showed no specific antibody to BSV by either of the 2 serological procedures; 8 of these 9 steers showed no evidence of CLAB or SAB. The exception was one steer which was CLAB- and SAB-positive at each of 30 samplings taken over a period of 9 months observation, whilst remaining specific-antibody free. This steer was classed as immunologically tolerant of BSV, and epidemiological data suggested that lateral spread of infection had originated from this animal through the agency of saliva.

Animals↗
PubMed1988

Why does vasodilatation occur during syncope?

1. Syncopal or near syncopal episodes have been observed in five subjects who stood or were tilted and in whom blood samples were being taken. 2. In all subjects bradycardia and hypotension developed before the onset of symptoms. Increases in plasma adrenaline concentrations occurred in all subjects, beginning before the faint. Changes in plasma noradrenaline concentrations were variable: in three subjects there was a marked fall and in the other two subjects an increase. Plasma vasopressin increased in all subjects. 3. Increase in plasma adrenaline may be contributing to the vasodilatation and arterial hypotension which occur during syncope.

Adult↗