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Biomedical subjects

R Marks

Publications and source records attributed to R Marks.

At least 181 records · Page 10Linked to original sources
PubMed1995

The effect of regular sunscreen use on vitamin D levels in an Australian population. Results of a randomized controlled trial.

BACKGROUND AND DESIGN: Studies published have suggested a possibility that regular use of sunscreen to prevent skin cancer may put the population, particularly elderly people, at risk of vitamin D deficiency. We aimed to determine whether regular use of sunscreens in the normal adult population, as recommended by public health authorities for the prevention of skin cancer, may put individuals at risk of vitamin D deficiency. A randomized double-blind control trial of the daily use of a broad-spectrum sunscreen (sun protection factor [SPF] 17) vs placebo cream over a summer period in Australia was conducted in 113 people aged 40 years and over, with sampling stratified by age. All participants had at least one solar keratosis. Serum samples taken at the beginning and at the end of the study were analyzed for 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3. RESULTS: Mean levels of 25-hydroxyvitamin D3 rose significantly by the same amount in both groups over the period of the study (placebo, +12.8 mmol/L; sunscreen, +11.8 mmol/L). Mean levels of 1,25-dihydroxyvitamin D3 increased significantly in the placebo group only (placebo, +10.8 pmol/L; sunscreen, +1.3 pmol/L), but for no subject in either group was the level of 1,25-dihydroxyvitamin D3 outside the reference range either at the start or at the end of the study. There were no significant differences by age, sex, and skin type in the change in 25-hydroxyvitamin D3 or 1,25-dihydroxyvitamin D3 over the study period. CONCLUSIONS: No person, including those aged 70 years and over, developed any vitamin D levels outside the normal reference range during the period of the study. The data suggest that over an Australian summer sufficient sunlight is received, probably through both the sunscreen itself and the lack of total skin cover at all times, to allow adequate vitamin D production in people who are recommended to use sunscreens regularly. More work is required to elucidate the relationship between 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3, particularly during the different seasons of the year.

Adult↗
PubMed1994

Quadriceps femoris activation changes in genu varum: a possible biomechanical factor in the pathogenesis of osteoarthrosis.

This study was designed to determine whether the presence of an alignment deformity of the lower leg, known as genu varum, causes abnormalities in individual- or group-activation of the surrounding knee extensors, a situation which might accelerate knee deterioration. Nine healthy women with normal tibial alignment were compared with nine age-matched healthy women with genu varum. The outcome measure of maximal quadriceps femoris activity was recorded during successive maximal concentric isometric and isokinetic contractions of the knee extensors performed on a dynamometer using surface electromyography. The results showed that, taken as a whole, the percentage utilization of quadriceps motor units was higher for those subjects with genu varum (p < 0.01). These findings demonstrate that the extensors surrounding a varus knee might function less efficiently than those surrounding a normally aligned knee. As such they suggest that pathological force generation across a varus knee might be caused, in part, by associated alterations in quadriceps tension generating capacity.

Adult↗
PubMed1994

Early detection of skin cancer. Knowledge, perceptions and practices of general practitioners in Victoria.

OBJECTIVE: To determine the current knowledge, perceptions and practices of general practitioners (GPs) in Victoria in the diagnosis and management of skin cancer. METHOD: A stratified random sample of 666 Victorian GPs was surveyed by postal questionnaire (a colour photographic quiz on 12 examples of benign and malignant skin tumours). RESULTS: GPs were better at recognising the 12 skin tumours as suspicious or benign than they were at providing the correct diagnosis. They were better at providing the correct diagnosis for benign lesions (75%) than for skin cancers (61%) or dysplastic lesions (61%). They had more difficulty in recognising early melanoma than late melanoma and were more likely to manage benign lesions (85%) and dysplastic lesions (34%) than skin cancers (4%). Knowledge of appropriate management was high for GPs who correctly identified tumours. Most perceived skin cancer as an important public and individual health concern. CONCLUSIONS: Overall, GPs had a good knowledge of diagnosis and management of skin cancer and related benign tumours. Several gaps in knowledge and practice were apparent and need specific targeting for educational programs.

Adolescent↗
PubMed1994

Reliability and validity of self-paced walking time measures for knee osteoarthritis.

This study assessed the reliability and validity of self-paced walking time as an outcome measure for osteoarthritis (OA) of the knee. The 13-m timed walking tests were carried out twice on two separate occasions for 15 patients using photocells. Validity was examined by comparing the walking time data with results of other methodologies for evaluating osteoarthritic gait. As indicated by intra- and inter-day intraclass correlation coefficients of 0.97 and 0.88 the gait measurements were reliable. The measurements also compared favorably with a validated subjective functional index for knee OA (P < 0.01). The findings suggest that measurements of self-paced walking time can provide both reliable and valid data for evaluating functional performance in this patient population.

Adult↗
PubMed1994

Expression of c-fos proto-oncogene mRNA in non-melanoma skin cancer.

c-fos is a member of the proto-oncogene family and is implicated in the modulation of cell proliferation and differentiation. Previous studies have shown that the c-fos gene expression is regulated in a tissue specific manner. In order to clarify the role of the c-fos gene in human epidermis, we have investigated c-fos mRNA expression in both normal skin and non-melanoma skin cancer. In normal skin the intensity of the c-fos mRNA expression in spinous cells was found to be stronger than that observed in basal cells. In lesions of solar keratosis and Bowen's disease the spinous cells also showed stronger c-fos mRNA expression than in basal cells. In two of four cases of Bowen's disease some upper spinous cells showed very strong mRNA expression of the c-fos gene. In squamous cell carcinomas studied there was considerable variation in the intensity of c-fos mRNA expression. Our findings indicate that the degree of c-fos mRNA expression is related to the degree of dysplasia present. In all cases of basal cell carcinoma examined the c-fos mRNA expression was markedly decreased. These results suggest that c-fos expression may be involved in the differentiation of human keratinocytes in vivo rather than in the neoplastic process itself.

3T3 Cells↗
PubMed1994

An investigation of the influence of age, clinical status, pain and position sense on stair walking in women with osteoarthrosis.

The objective of this study was to determine the extent to which stair walking in persons with osteoarthrosis of the knee is influenced by age, weight, height, pain, clinical status, and position sense. The subjects were six women with severe knee joint disease who attended a single test session at which clinical status, disease severity, pain, position sense and stair-walking time was assessed. The results of correlation analyses revealed significant correlations of r = 0.84 and r = 0.95 (p < 0.05) between the measurements of stair-walking time and pain and between the measurements of stair-walking time and position sense, respectively. There was no relationship between stair-walking time and age, height, weight, clinical status or disease severity. It is concluded that knee pain and positional sense are strong determinants of the stair-walking ability of individual osteoarthrotic patients. In treating stair-walking problems in this group, it is recommended that effort be directed to improving proprioception as well as to reducing pain.

Aged↗
PubMed1994

Melanoma prevention: is it possible to change a population's behavior in the sun?

With the highest incidence and mortality rates of melanoma in the world, Australia has been running carefully designed primary prevention programs for more than 10 years. These have included public education programs aimed at all ages but concentrating particularly on young people. The programs have also included structural changes such as provision of shade in open space, rescheduling work and sport activities, removal of sales tax from approved sunscreens, and provision of cheap sunscreens. There have been substantial changes in knowledge, attitudes, and beliefs about melanoma, sunlight, and suntans. There have been significant increases in sun protective behavior reflected in the reduced proportions of people sunburnt at the weekend in summer in recent years. The incidence rate of melanoma continues to rise, as expected. Although there has been considerable success so far, we still have a long way to go.

Australia↗
PubMed1994

Plasma and cutaneous drug levels after topical application of piroxicam gel: a study in healthy volunteers.

Two studies in healthy male and female volunteers (aged 18-65 years) were undertaken to determine plasma and cutaneous levels of drug following topical application of piroxicam gel. Twelve subjects applied piroxicam gel to the knee (1 g of 0.5% Feldene gel) at baseline and then after 6, 12 and 24 h. Plasma was collected after 1, 2, 4, 6, 14, 24, 28 and 48 h and piroxicam content determined by high-pressure liquid chromatography (HPLC). For the majority of samples collected, piroxicam levels were below the limit of detection (LOD) of the assay and the maximum recorded plasma level in any subject at any time point was 75.4 ng/ml. A single application of gel was administered to the forearms of four groups each of 6 subjects, and biopsy samples of the stratum corneum (skin surface biopsy, SBB) and epidermis/dermis were taken after 0.5, 1, 2 and 4 h. The levels of piroxicam were again measured in each sample by HPLC. The highest levels of piroxicam were found in the superficial skin surface biopsy with the lowest levels recorded in the skin surface biopsies nearest the viable epidermis. The mean tissue concentrations ranged from 160 to 640 ng per sample (calculated to be 80-320 micrograms/g of tissue). The mean levels of piroxicam in a 4-mm punch biopsy showed an increase with time after application, rising from 60.3 to 94.6 ng per biopsy (calculated to be 2.4 to 3.8 micrograms/g of tissue). It may be concluded that piroxicam rapidly permeates through the stratum corneum into the epidermis/dermis after application of the gel. Low and often undetectable plasma levels of drug were observed after topical application of piroxicam gel in a manner comparable to clinical usage.

Administration, Topical↗
PubMed1994

Medical maintenance: an interim report.

In a pilot study, 130 methadone maintained subjects with a six-month history of good treatment performance were assigned randomly, for a one-year study period, to an experimental condition (once per month non-random urine screen, counseling session and doctor visit, two times per month methadone pick up, a quarterly true random urine screen, and participation in a diversion control program), or they were assigned to a control condition of staying under standard conditions for six months and then being transferred to the experimental condition for six months. Three out of four subjects (73%) completed the year in good standing with no differences between control and experimental conditions. Subject satisfaction was such that the Institutional Review Board judged that return to standard conditions would be a hardship. A Study of Medical Maintenance (SMM) continues and extends the pilot study with two protocols: (1) for new subjects and (2) for subjects entered from the pilot study. SMM requires a once per month random urine screen and extends the experimental condition to two years but is otherwise identical to the pilot study; 71 of 107 S's (66%) entered protocol 1 and are in good standing. Pilot subjects (N = 75) are holding their good performance, some for over four years. The reduced levels of services in these studies free up resources which can be applied to entering IDU's into treatment thereby contributing to a slowing of the HIV epidemic.

Adult↗
PubMed1994

Cutaneous vasculitis in psoriasis.

Cutaneous vasculitis has been reported as a complication of pustular psoriasis but not of plaque type psoriasis. In the past 5 years we have observed 3 patients who in the course of their psoriasis developed cutaneous vasculitis. Two of these patients also had severe psoriatic arthropathy and were on etretinate during the onset of vasculitis. However, there was no deterioration or recurrence of vasculitis whilst the patients were maintained on the drug. The third patient with vasculitis had not received retinoids. No obvious causes of vasculitis were found in the 3 patients and the rash resolved spontaneously without any systemic complications though surgical amputation was necessary in one case. None of the cases required immunosuppressive therapy and the skin lesions mostly resolved spontaneously. The mechanisms that triggered off vasculitis in our patients are unknown but are likely to be immune-mediated.

Aged↗
PubMed1994

The effects of 16 months of angle-specific isometric strengthening exercises in midrange on torque of the knee extensor muscles in osteoarthritis of the knee: a case study.

Although often advocated for arthritis rehabilitation, several studies conducted on healthy subjects have demonstrated conflicting results as to whether isometric strengthening exercises performed at one joint angle can result in strength gains at other angles. The objective of this study was to determine whether midrange strength training of the quadriceps surrounding an osteoarthritic knee would increase strength in this part of the range of motion as well at other knee angles. The midrange position was chosen because the subject, a 57-year-old female with a 2-year history of moderately severe osteoarthritis of the left knee, had greatest weakness in this position. The training occurred three times per week for 16 months using a resistance training program of three sets of two maximal isometric contractions at a knee angle of 60 degrees. The dependent variable of maximal isometric knee extensor torque was recorded on an isokinetic dynamometer at knee angles of 90, 60, and 30 degrees at 6 weeks, 1 year, and 16 months. These data demonstrated a progressive torque increase at all angles over the 16-month period, with a steeper slope at the training angle. Contrary to the specificity of training concept, angle-specific strengthening in midrange may be sufficient to strengthen the extensors surrounding an osteoarthritic knee through a wide range of motion. Mid-range isometric strengthening exercises might thus prove useful in the rehabilitation of patients with knee osteoarthritis who are unable to exercise their weakened quadriceps at other angles due to pain or swelling.

Exercise Therapy↗
PubMed1994

[Correlations between measurements of the sense of knee position and the severity of joint lesions in knee osteoarthritis].

The primary purpose of this study was to analyse the relationship between 4 different methods of measuring the knee position sense of persons diagnosed as having osteoarthritis of the knee and position sense deficit with their disease severity. To this end, the active position sense of 8 patients was assessed in sitting using a potentiometer known to measure knee angles precisely. Also administered was a validated subjective questionnaire, the Lequesne algofunctional index. The measurements of position sense included: total reproduction error; mean absolute reproduction error; variability in algebraic error or variable error; and the average constant error of 5 angle reproduction tests. The total error, mean absolute error and constant error measurements were significantly correlated with the handicap scores on the questionnaire (p < 0.01). These results plus the further finding of a bias towards target underestimation in this group strongly suggests that impaired proprioception might be an important pathogenetic factor in determining the severity of this disabling disease.

Aged↗
PubMed1993

Reduction of solar keratoses by regular sunscreen use.

BACKGROUND: The incidence of and mortality from skin cancer are increasing in many countries. In view of the added concern about ozone depletion, many organizations are promoting the regular use of sunscreens to prevent skin cancer, despite the absence of evidence that these products have this effect. Solar (actinic) keratosis is a precursor of squamous-cell carcinoma of the skin. METHODS: We conducted a randomized, controlled trial of the effect on solar keratoses of daily use of a broad-spectrum sunscreen cream with a sun-protection factor of 17 in 588 people 40 years of age or older in Australia during one summer (September 1991 to March 1992). The subjects applied either a sunscreen cream or the base cream minus the active ingredients of the sunscreen to the head, neck, forearms, and hands. RESULTS: The mean number of solar keratoses increased by 1.0 per subject in the base-cream group and decreased by 0.6 in the sunscreen group (difference, 1.53; 95 percent confidence interval, 0.81 to 2.25). The sunscreen group had fewer new lesions (rate ratio, 0.62; 95 percent confidence interval, 0.54 to 0.71) and more remissions (odds ratio, 1.53; 95 percent confidence interval, 1.29 to 1.80) than the base-cream group. There was a dose-response relation: the amount of sunscreen cream used was related to both the development of new lesions and the remission of existing ones. CONCLUSIONS: Regular use of sunscreens prevents the development of solar keratoses and, by implication, possibly reduces the risk of skin cancer in the long-term.

Adult↗