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Biomedical subjects

J C Hamilton

Publications and source records attributed to J C Hamilton.

35 records · Page 2Linked to original sources
PubMed1992

Generalized rank annihilation method using similarity transformations.

Recently several papers have described the generalized rank annihilation method; however, in some cases complex eigenvalues and eigenvectors may appear when the generalized eigenproblem is solved. When complex eigenvalues and eigenvectors are encountered, the results cannot be used to estimate pure component profiles (e.g. spectra or chromatograms). In this paper, a similarity transformation is used to transform complex eigenvalues and eigenvectors into real eigenvalues and eigenvectors, thereby permitting spectra and profiles of pure constituents to be estimated. The modified GRAM method is illustrated with simulated and real data.

Algorithms↗
PubMed1980

The effects of season and stage of pregnancy on plasma 25-hydroxy-vitamin D concentrations in pregnant women.

Plasma 25-OHD levels were measured in the same 26 Caucasian women before pregnancy and during the first, second and third trimesters of their pregnancy. This was done to assess whether pregnancy alters vitamin D status in healthy women. During most times of the year there was no association between the 25-OHD levels and the stage of pregnancy, but between January and March there was a progressive fall in 25-OHD levels with each trimester. When 25-OHD levels were related to hours of possible sunlight exposure a negative association between 25-OHD levels and stage of pregnancy was noted only in subjects with the lowest possible exposure to sunlight. These observations suggest that pregnancy has an effect on vitamin D metabolism, but that in healthy Caucasian women these effects only become manifest where there is a low level of exposure to sunlight.

England↗
PubMed1979

Plasma binding capacity for 25-hydroxy-vitamin D in the elderly.

Plasma 25-hydroxy-vitamin D (25-OHD) concentrations and 25-OHD binding capacities were measured in 14 elderly patients and in 14 young controls. Both 25-OHD concentrations and 25-OHD binding capacities were reduced in the elderly. In neither group, however, was there a significant correlation between 25-OHD binding capacities and 25-OHD concentrations. Thus, although 25-OHD binding capacities are reduced in sick old people this does not account for the low 25-OHD concentrations often found in this group.

Adult↗
PubMed1978

Ultra-violet irradiation and 25-hydroxy-vitamin D levels in sick old people.

Twelve elderly patients in a rehabilitation ward were given a four-week course of ultra-violet irradiation from a Vitalux lamp. They were compared with 12 controls selected from the same ward. Treatment produced a significant elevation in plasma 25-hydroxy-vitamin D (25OHD) by the end of the second week and concentrations continued to rise over the four-week period. Subject showing the greatest response were those starting with the lowest levels of plasma 25OHD. The findings suggest that ultra-violet irradiation is an effective means of treating vitamin D deficiency in old age and that patients with the greatest degree of deficiency show the greatest response.

Aged↗
PubMed1978

25-hydroxy-vitamin D, diet and sunlight exposure in patients admitted to a geriatric unit.

Dietary intake, sunlight exposure and 25-hydroxy-vitamin D levels were estimated in 62 patients admitted to a geriatric assessment unit. There was a significant correlation between vitamin D intake and 25-hydroxy-vitamin D levels but none between sunlight exposure and these. This suggests that in old age dietary deficiency may be a more important cause of metabolic bone disease than limited sunlight exposure.

Adolescent↗
PubMed1978

Adrenal function and ascorbic acid concentrations in elderly women.

Tetracosactrin (Synacthen) tests were performed on 19 elderly women who had leucocyte ascorbic acid (LAA) levels of less than 15 microgram/108 WBC. 9 were then given a daily dose of 200 mg ascorbic acid orally for 2 weeks while the other 10 were left untreated. Following this, tetracosactrin tests were repeated in both groups. All initial plasm cortisol responses to tetracosactrin were within normal limits. Treatment with ascorbic acid produced no changes in these. This suggests that the low LAA levels often found in old people do not result in adrenal insufficiency.

Adrenal Glands↗
PubMed1977

Vitamin D supplements and 25-hydroxy vitamin D concentrations in the elderly.

Serial 25-hydroxy vitamin D (25-OHD) concentrations were measured in long-stay geriatric patients treated with vitamin D. Comparison between a treatment and a control group showed that a daily dose of 500 IU vitamin D produced a significant increase in 25-OHD levels by two months. The supplement had a striking effect when the initial 25-OHD level was low and very little effect when it was high. 25-OHD levels in subjects on 2000 IU vitamin D daily were only marginally higher than those in subjects on 500 IU. A dose of 500 IU vitamin D daily should therefore produce adequate blood 25-OHD concentrations in most old people, and probably prevent most cases of osteomalacia in the elderly--though a large-scale study is needed to confirm this.

Aged↗
PubMed1977

The effect of acute illness on leucocyte and plasma ascorbic acid levels.

1. Serial estimations of plasma (PAA) and leucocyte (LAA) ascorbic acid concentrations were made in geriatric patients in a stable phase of their illness, and compared with a similar ('unstable') group suffering from acute illness. 2. In the 'unstable' group, though PAA levels were unchanged, LAA levels were reduced. 3. The 'follow-up' period of 7-8 d there was much greater variation in both PAA and LAA levels in the 'unstable' group. 4. Acute illness was often accompanied by an increase and then a decrease in LAA levels. Recovery was associated with an increase in LAA levels.

Acute Disease↗
PubMed1976

Ascorbic acid levels in stored blood and in patients undergoing surgery after blood transfusion.

Blood was obtained from 11 healthy voluteers, mixed with two standard types of anticoagulant used in blood transfusion centres and stored for 21-28 days at 4 degrees C. Leucocyte ascorbic acid (LAA) fell to deficient levels after 7 days in all cases. There were no corresponding changes in plasma ascorbic acid (PAA) levels. LAA and PAA were measured before, during and after surgery in 5 control patients who underwent definitive operations for benign peptic ulceration and in 4 patients under-going surgery for bleeding peptic ulceration. The average amount of blood administered to the latter group was 10 units. There was a fall in LAA and PAA in both groups of patients after operation. This fall had returned to normal by 7 days in the controls, but the LAA remained at a deficient level at 7 days in the patients who had bled. Deficient ascorbic acid in stored blood may contribute to low leucocyte ascorbic acid levels in patients after blood transfusion and may contribute to the increased complication rate when surgery is undertaken in these patients.

Adult↗
PubMed1976

The effect of leucocytosis on leucocyte ascorbic acid levels.

White-blood counts, polymorph counts, leucocyte ascorbic-acid and plasma ascorbic-acid levels were measured in 91 samples of blood obtained from patients admitted to a geriatric assessment unit. There was a correlation between both white-blood counts and polymorph counts and leucocyte ascorbic-acid levels. There was no correlation between white-blood counts and polymorph counts and plasma ascorbic-acid concentrations. It is suggested that this phenomenon represents migration of ascorbate-rich polymorphs to areas of infection and infarction.

Aged↗
PubMedDate not supplied

Quality assurance: an approach.

An approach to quality assurance in the physiotherapy department of the University Hospital in London, Ontario, is presented. The importance of assessing the quality of care is stressed. To reach a level at which quality can be assessed, a system of recording must be developed, complete with guidelines; this recording system can then be audited. A method of recording--the Problem Oriented Method of Recording, or the Problem Oriented Medical Record (POMR)--and a method of auditing are presented and discussed. Prospects for future audits are also discussed. The importance of sharing knowledge with other physiotherapists, by establishing criteria with which critical evaluation of physiotherapeutic treatments can be performed, is pointed out.

Hospital Departments↗
PubMedDate not supplied

Evaluation of custom occlusal matrix technique for posterior light-cured composites.

Posterior composite restorations are difficult to contour and polish due to their occlusal anatomy and opposing occlusion. Recently a new technique utilizing a clear custom occlusal matrix showed promise in reducing the chair time necessary to place posterior composite restorations. Sixty specially molded plastic mandibular right second molar teeth with a mesio-occlusal composite preparation were restored with a light-cured composite in a typodont, using either the custom occlusal matrix (experimental) or the standard technique (control) as taught at the University of Michigan School of Dentistry. The times necessary to complete the procedures were recorded. The teeth were evaluated in a blind manner by two evaluators using a modified Ryge criteria. The times to place and finish the control and experimental restorations were subjected to a t-test. The evaluations of surface smoothness, margin adaptation, occlusal anatomy, and axial form were compared using a Fisher exact test. The custom occlusal matrix significantly reduced placement and finishing time and improved surface smoothness of mesio-occlusal posterior composite restorations placed in vitro. Due to the time needed to construct the custom occlusal matrix, there was no significant difference in total mean time of the two procedures.

Composite Resins↗