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Biomedical subjects

H Spencer

Publications and source records attributed to H Spencer.

At least 19 recordsLinked to original sources
PubMed1995

Hearing loss and motorcyclists.

Motorcyclists are known to be exposed to excessive wind noise levels when riding. The potential adverse effects of this exposure on their hearing was investigated. Temporary threshold shift (TTS) was assessed by asking 18 riders to undertake a standard test run of one hour at a steady 80 mph, and performing audiometry before and immediately afterwards. Permanent threshold shift (PTS) was assessed by performing pure-tone audiograms on a highly screened group of 246 motorcyclists and comparing their hearing thresholds with those of an appropriate control group obtained from the MRC National Study of Hearing. Significant TTS was found at 0.25, 0.5, 1 and 2 kHz. The greatest TTS occurred at 1 kHz, with a mean hearing loss of 10.3 dB. The hearing thresholds of the motorcyclists were significantly worse than the controls at 0.25, 0.5, 1 and 2 kHz, and was most marked at 0.5 and 1 kHz where their hearing loss (PTS) was, respectively, 3.7 and 3.6 dB greater than expected. These findings demonstrate evidence of both temporary and permanent hearing loss from motorcycling and present a strong argument for the need for some form of remedial action.

Adolescent↗
PubMed1994

Inhibitory effects of zinc on magnesium balance and magnesium absorption in man.

OBJECTIVE: Both zinc (Zn) and magnesium (Mg) are widely used as nutritional supplements and the possibility was considered that Zn may interfere with the absorption of Mg, similar to previously reported results [1,2] obtained with the same dose of supplemental Zn on the absorption of calcium (Ca). METHODS: Mg absorption studies and metabolic balances of Mg and of Zn were carried out in three groups of adult males in a metabolic research unit during the intake of supplemental doses of 142 mg Zn as Zn sulfate (ZnSO4) during Ca intakes of 230, 500 and 800 mg/day. RESULTS: The Zn intake of 142 mg/day decreased the Mg balance and Mg absorption only during the 500 mg Ca intake compared to control values. However, the overall effect of the high Zn intake of the three groups combined, regardless of the Ca intake, was a highly significant decrease of Mg absorption and of the Mg balance. CONCLUSION: Zn supplements of 142 mg/day decreased Mg absorption and the Mg balance significantly during all Ca intakes for the three groups combined.

Calcium↗
PubMed1994

Effect of magnesium on the intestinal absorption of calcium in man.

OBJECTIVE: In view of the widespread use of magnesium (Mg) as a nutritional supplement, we investigated whether Mg would affect the absorption of calcium (Ca) as the intestinal absorption sites for Mg and Ca differ. METHODS: The intestinal absorption of Ca, using 47CaCl2 as the tracer, and metabolic balances of Ca, phosphorus (P) and Mg were determined in five adult males under strictly controlled dietary conditions in control studies and during Mg supplementation. Mg was given as magnesium oxide (MgO) in 10 studies during two Ca intakes: five studies during a low Ca intake of 241 mg/day and five studies during a normal Ca intake of 812 mg/day. Dietary Mg intake ranged from 241 to 264 mg/day in control studies. During Mg supplementation, the total Mg intake ranged from 789 to 826 mg/day. RESULTS: There was no change of the intestinal Ca absorption during Mg supplementation during the two Ca intakes. The only change was the higher 1-hour 47Ca plasma level in the 47Ca absorption studies during the high Mg intake. Urinary Ca increased during Mg supplementation only during the low Ca intake, the Ca balance became more negative but this difference was not significant. There was also no change in Ca excretion or Ca balance during the high Mg intake at the normal Ca intake of 800 mg/day. P balance studies showed a slight decrease in urinary P and an increase in fecal P, but the P balances did not change. Mg balances were negative in control studies during the two Ca intakes. Supplemental Mg increased both urinary and fecal Mg excretion and the Mg balance became positive, but these differences were not significant. CONCLUSION: The increased Mg intake of 826 mg did not affect intestinal Ca absorption determined with tracer doses of 47Ca during Ca intakes of 241 and 812 mg/day.

Adult↗
PubMed1992

Further studies of the effect of zinc on intestinal absorption of calcium in man.

In a previous study dietary supplementation with 140 mg zinc (Zn) as Zn sulfate (ZnSO4) per day significantly decreased absorption of calcium (Ca) during a low Ca intake (230 mg/day) but not during a normal Ca intake (800 mg/day). The purpose of the present study was to determine whether smaller doses of Zn would also inhibit Ca absorption during the 230 mg Ca intake, and whether the 140 mg dose of Zn would inhibit Ca absorption during a Ca intake less than 800 mg/day. To investigate the first aspect, 100 mg Zn as ZnSO4, was given daily during a low Ca intake (230 mg/day) in six studies, and in the second phase, 140 mg Zn as ZnSO4 was given during a Ca intake of of 500 mg/day in five studies. Intestinal absorption of Ca was determined with tracer doses of 47CaCl2 in control studies and in the two Zn supplementation studies. Results showed that 100 mg Zn/day during a low Ca intake (230 mg/day) did not inhibit Ca absorption and that 140 mg Zn given during the 500 mg Ca intake also did not affect the absorption of Ca.

Aged↗
PubMed1992

The paediatric otological caseload resulting from improved screening in the first year of life.

Improved test technique by health visitors has been shown to lead to higher accuracy in the screen of hearing aimed traditionally at prelingual sensorineural deafness. However, it gives greatly increased referrals of children having otitis media with effusion (OME) around the end of the first year of life. Two samples of children (n = 29 and 61) were tested in a children's hearing assessment clinic with properly documented testing techniques and trained personnel. The samples were each formed on a fixed population base, one before and one after screen improvements. This enabled characterization of two outcome groups within each sample (severe/persistent enough to refer to ENT vs discharged, despite slight hearing impairment). The average audiometric criterion for onward referral to ENT rose only very little, despite the increased assessment caseload resulting from more detections by the screen. This usefully permitted the conclusion that the number of true cases found due to the screen and assessed as lying beyond a specifiable degree of severity (average cut-off approximately 47 dB(A) or 35 dBHTL) had increased not through lower criteria for referral to ENT, but through the improvements to the screen. The increase was from approximately 0.4% to 1.3% of the base population screened. Thus a change materially enhancing the sensitivity and positive predictive value of a screen considerably enlarges the eventual otological caseload of children with middle-ear disease thought to justify concern at around the end of their first year. If done properly, screening is hence in practical terms about OME, not about prelingual sensorineural hearing impairment. This conclusion presses the urgency of evaluation and consensus on the otological management of the young child with OME.

Analysis of Variance↗
PubMed1992

Thymectomy in myasthenia gravis. The Jamaican experience.

Forty-five patients with myasthenia gravis (MG) were subjected to thymectomy by the median sternotomy technique and were followed up for 4,380 patient months. No operative deaths occurred and 93.3% of the patients benefited from surgery with 28.8% achieving remission. Forty patients (88.5%) showed improvement within one month, and 73% of those who achieved remission did so in the first 2 years. Outcome was not affected by thymic pathology except in one patient who had a thymoma removed. These results confirm the value of thymectomy in the management of MG patients with generalised disease and the efficacy of the simple median sternotomy procedure.

Adolescent↗
PubMed1991

Effect of oat bran muffins on calcium absorption and calcium, phosphorus, magnesium and zinc balance in men.

Metabolic balance studies were conducted in adult human males to investigate the effect of oat bran on the nitrogen, calcium, phosphorus, magnesium and zinc balance, on the intestinal absorption of calcium and on the endogenous fecal calcium, using 47CaCl2 as the tracer. A 40-d control period preceded a 32-d experimental period in which subjects consumed four oat bran muffins daily as part of a constant metabolic diet. No significant changes in the calcium, magnesium or zinc balances were observed, but the nitrogen and phosphorus balances increased. The net or apparent absorption of nitrogen, magnesium and phosphorus expressed per milligram of intake increased significantly in the oat bran period due to the added content of these nutrients in the oat bran muffins. The intake of the oat bran muffins led to a significant increase in urinary phosphorus and significant decreases in urinary calcium and 47Ca excretions. The intestinal absorption of calcium, determined with 47Ca, did not change, whereas the endogenous fecal calcium increased slightly but significantly.

Adult↗
PubMed1991

Myasthenia gravis in Jamaica. Clinical, immunological and genetic studies.

Clinical, immunological and genetic parameters were studied in 73 Jamaican patients with myasthenia gravis (MG). The reported bimodal clinical distribution of females with early onset of disease and males with late onset was not observed. The female to male ratio was 2:1. The most frequent manifestations of disease were ptosis (84.9%), general muscle weakness (68.5%), bulbar symptoms (41.1%) and diplopia (32.9%). Unusual presenting features such as unilateral ptosis, recurrent chest infection and stumbling while walking resulted in diagnosis being missed in 5.8% of cases. The sensitivity of radioimmunoassay in detecting acetylcholine receptor antibody (AchR-Ab) in sera from a subgroup of 35 MG patients was 71.4% whilst that of the ELISA was only 14.2%. There was no correlation between concentration of AchR-Ab and severity of disease. Similarly, there was no association between HLA-type, thymic pathology and course of disease. HLTV-I could not be implicated in the pathogenesis of this disease. There was a paucity of other associated autoimmune conditions among MG patients. Thymectomy was an important therapeutic modality in that improvement was observed in 22 cases and remission in 11.

Adolescent↗
PubMed1990

Caustic strictures of the oesophagus.

Ingestion of caustic material is a major management problem which occurs most commonly in children. Twenty-five patients with caustic ingestion seen over a ten-year period are reported. Twelve patients had severe burns, resulting in oesophageal strictures. Of these, ten were children below six years of age (median age, 3 years). Dysphagia and vomiting were the main presenting features. Oropharyngeal burn was present in 83% of patients with oesophageal burns. The strictures involved the entire oesophagus in two patients, the upper third in four, the mid oesophagus in two and the lower third in four. Periodic dilatations were successful in restoring an adequate lumen in 7 patients with short strictures. Five patients required surgery. There was one death. Caustic damage to the oesophagus is preventable. Education of the public and simple measures by manufacturers of caustics are urgently needed.

Accidents, Home↗
PubMed1990

Survey of general practitioners' opinions on the role of radiology in patients with low back pain.

Ninety general practitioners responded to a questionnaire about the role of radiology in patients with low back pain. Their clinical indications for requesting radiographs were mostly in agreement with the opinions of radiologists, but nearly 80% requested investigations for their own or patients' reassurance. Understanding of the terms used by radiologists was good, although 25% thought that acute disc prolapse could be demonstrated on plain films. Previous training in radiology did not seem to influence knowledge. When general practitioners understood radiological terms they had clear therapeutic and specialist referral preferences. Poorly understood terms and those with which they were familiar but unclear about the implications for management were also identified.

Attitude of Health Personnel↗
PubMed1990

Measured intake and excretion patterns of naturally occurring 234U, 238U, and calcium in humans.

The normal dietary and fluid intake and urinary and fecal excretion of 234U and 238U were determined in humans under strictly controlled conditions in the Metabolic Research Ward at Hines Hospital. These values formed the basis of the metabolic balances of these uranium isotopes. The major pathway of 234U and of 238U excretion was via the intestine while the urinary 234U and 238U were very low, averaging 2% of the total excretion. The uranium balances were roughly in equilibrium. These data were used in combination with measurements of tissue concentrations of uranium from nonoccupationally exposed humans to calculate steady-state uptake factors for environmental exposure to uranium isotopes during baseline conditions of a normal dietary intake.

Animals↗
PubMed1988

Effects of chronic administration of benfluorex to rats on the metabolism of corticosterone, glucose, triacylglycerols, glycerol and fatty acid.

(1) Rats were fed on diets enriched with sucrose, beef tallow or corn oil and treated for 11-16 days with 50 mg of benfluorex per kg of body weight. By these times the growth rate and food intake were not significantly different from those of control rats. (2) Benfluorex approximately halved the concentration of circulating triacylglycerol in rats fed the beef tallow or sucrose diets. (3) It did not significantly alter the total lipoprotein lipase activity in diaphragm, heart and adipose tissue. (4) The clearance of triacylglycerols from chylomicrons exhibited two t 1/2 values of about 0.6 and 6.9 min in rats fed the beef tallow diet. Benfluorex did not significantly alter these values. (5) Benfluorex did not significantly alter the rate of appearance of triacylglycerol in the blood of rats injected with Triton WR 1339 to block triacylglycerol uptake. It did, however, decrease the rise in circulating glucose which presumably resulted from the stress of the procedure. (6) Benfluorex decreased the extent and duration of the rise in serum corticosterone when rats maintained on the corn oil diet were fed acutely with fructose. It also decreased the circulating concentrations of glycerol, triacylglycerol and glucose after fructose feeding. (7) Rats fed on the corn oil diet and then treated with benfluorex had lower concentrations of circulating glucose, triacylglycerol, glycerol and fatty acids after being injected with 2-deoxyglucose. (8) It is proposed that some of the long-term hypoglycaemic and hypotriglyceridaemic effects of benfluorex could be mediated indirectly through changes in endocrine balance, perhaps via the serotonergic system and in particular, by decreasing the effects of stress hormones relative to insulin. The implications of these findings are discussed in relation to controlling metabolism in stress conditions and for the management of obesity, diabetes and atherosclerosis.

Animals↗
PubMed1988

Do protein and phosphorus cause calcium loss?

The widespread opinion that both protein and phosphorus cause calcium loss is examined. Controlled human studies show that commonly used complex dietary proteins, which have a high phosphorus content, do not cause calcium loss in adult humans. Similarly, a phosphorus intake of up to 2000 mg/d does not have adverse effects on calcium metabolism; however, the type of phosphate contained in carbonated beverages may not behave in the same manner. In contrast, a diet low in protein and phosphorus may have adverse effects on calcium balance in the elderly. Studies with adults suggest that high protein foods do not cause calcium loss.

Animals↗
PubMed1988

Alveolar enlargement in obesity-induced hyperplastic lung growth.

Structural changes underlying obesity-induced pulmonary cellular hyperplasia were evaluated by lung morphometry and stereology in 8-wk-old male Long-Evans rats made obese by nursing in small litters with subsequent feeding of a high-fat diet. Control animals were raised in normal-sized litters and then fed standard rat chow. Compared with controls, obese rats had significant elevations in body weight (31%), fat pad weight (158%), fat pad weight-to-body weight ratio (97%), snout-to-anus length (8%), snout-to-tail length (7%), serum insulin concentration (64%), fixed lung volume (56%), and the ratios of lung volume to body weight (18%) and lung volume to body length3 (24%). Lungs of obese rats had enlarged alveoli, with significant increases in mean (182%) and total (71%) alveolar volume, mean chord length (28%), and mean (89%) and total (25%) alveolar surface area. Surface density (24%), surface-to-volume2/3 ratio (24%), and numerical density (43-53%) of alveoli in obese rats were significantly diminished compared with lungs of control rats. Unchanged were total alveolar number and alveolar volume density. Measurements of perihilar and subpleural alveoli within the obese and control groups were indistinguishable. These results indicate the presence of alveolar enlargement with relatively diminished respiratory surface area in lungs of young rats made obese by diet. This relative decrease in gas-exchanging area may contribute to physiological and functional alterations present in obesity.

Animals↗