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Biomedical subjects

G Young

Publications and source records attributed to G Young.

At least 199 records · Page 11Linked to original sources
PubMed1989

Ocular surface temperature.

A wide-field color-coded infra-red imaging device was applied to the measurement of i) the temperature profile across the ocular surface and ii) the temporal stability of central corneal temperature, on 21 subjects. The thermographs showed a pattern of ellipsoidal isotherms (major axis horizontal) approximately concentric about a temperature apex (coldest point) which was slightly inferior to the geometric center of the cornea (GCC). The GCC had a mean temperature (+/- SD) of 34.3 +/- 0.7 degrees C (range 32.8 to 35.4 degrees C). Temperature increased towards the periphery of the cornea with the limbus being 0.45 degrees C warmer than the GCC (p less than 0.0001). Following a blink, the GCC cooled at a mean (+/- SD) rate of 0.033 +/- 0.024 degrees C/s (p less than 0.0001) over the first 15s. Subjects whose corneas cooled more slowly following a blink demonstrated a greater capacity to avoid blinking for a prolonged period (p less than 0.05). This improved method of measuring ocular surface temperature has important applications in modeling corneal physiology and pathology.

Adult↗
PubMed1988

Response of the interrenal to adrenocorticotropic hormone after short-term thyroxine treatment of coho salmon (Oncorhynchus kisutch).

The effects of experimentally elevated plasma thyroxine levels on the subsequent response of interrenals of coho salmon (Oncorhynchus kisutch) to adrenocorticotropic hormone (ACTH) in vitro were examined. Animals were treated with thyroxine by immersion (200 micrograms/L) for 3 days, which resulted in physiological elevations in circulating thyroxine. In animals treated before the parr-smolt transformation was completed (early smolts), thyroxine had no effect on plasma cortisol levels but significantly enhanced the sensitivity of the interrenal to ACTH in vitro. In animals treated after the period of smoltification (postsmolts), plasma cortisol levels were significantly higher than those of controls; both experimental and control animals had plasma cortisol levels higher than normally observed at this stage of development. The response of the interrenals of thyroxine-treated postsmolts to ACTH in vitro was significantly lower than that of controls. Results from the experiments using early smolts are in agreement with studies in other vertebrates showing that thyroid hormones are involved in maintaining the normal functioning of corticosteroidogenic tissue and suggest that thyroid hormones may be involved in the activation of the interrenal that occurs during smoltification. The results obtained using postsmolts are more difficult to interpret because of the possibility that these animals were physiologically stressed by the treatment. Increased ACTH release in vivo resulting from stress may have led to a depression of interrenal sensitivity to ACTH in vitro and may have masked a refractoriness of the pituitary-interrenal axis to thyroxine.

Adrenal Glands↗
PubMed1988

Enhanced response of the interrenal of coho salmon (Oncorhynchus kisutch) to ACTH after growth hormone treatment in vivo and in vitro.

The effects of ovine growth hormone (GH) on the response of the interrenal of yearling coho salmon (Oncorhynchus kisutch) to ACTH were examined in two series of experiments. In the first series, GH was administered intraperitoneally (2 micrograms/g body wt, three daily injections) to coho salmon which had not undergone the parr-smolt transformation. Animals were sacrificed 30 hr after the final injection and head kidney tissue was prepared for in vitro incubation. GH had no effect on plasma cortisol levels but tissue taken from treated fish had an enhanced sensitivity to ACTH in vitro and its steroidogenic capacity was increased. In the second series of experiments, interrenal tissue was preincubated with GH in the dose range of 10-1000 ng/ml and was then challenged with ACTH or was incubated with 1-10 microM pregnenolone. GH-pretreated tissue displayed an enhanced response to ACTH. Cortisol production by tissue pretreated with 500 ng/ml GH was significantly enhanced after incubation with pregnenolone. No significant effect of GH was found after simultaneous exposure of interrenal tissue to combinations of ACTH and GH for 3 hr. Pretreatment of interrenal tissue with salmon prolactin had no significant effect on the subsequent response of tissue to ACTH. These results indicate that GH regulates interrenal activity in coho salmon and that one probable site of action is on the biosynthetic pathway between pregnenolone and cortisol.

Adrenal Glands↗
PubMed1988

Cardiovascular actions of the primate-selective renin inhibitor, A-62198.

A-62198 [dimethylacetyl-Phe-His-NHCH(cyclohexylmethyl)CH-(OH)C H(OH)CH2N3] is a potent, selective inhibitor of primate renin. This compound induced a dose-dependent fall in mean arterial blood pressure (MAP) when administered as an i.v. bolus to anesthetized, salt-depleted monkeys. Both the magnitude and the duration of the hypotensive effect were dose related. Its actions were also studied during acute infusions in anesthetized anephric, normal and salt-depleted monkeys. MAP, heart rate and plasma renin activity (PRA) were determined during baseline and 30-min infusions of vehicle alone, followed by A-62198 as boluses of 0.01, 0.1 and 1.0 mg/kg, each maintained by infusing one-tenth of the bolus dose per minute. Vehicle did not alter base-line values. In the normal monkeys, A-62198 induced a dose-related fall in MAP which achieved statistical significance only at the highest dose, while maximally suppressing PRA at all doses (P less than .05, compared to vehicle). The salt-depleted monkeys responded with a dose-related fall in MAP and inhibition of PRA at all doses (P less than .05, compared to vehicle). A-62198 was relatively ineffective in the anephric monkeys which, as expected, had exceedingly low levels of PRA. Heart rate was unaltered regardless of dose or treatment group. Finally, infusion of 1.0 mg/kg bolus + 0.1 mg/kg/min of A-62198 had no effect on MAP or PRA in 2 kidney-1 clip rats, although MAP was reduced subsequent to a superimposed bolus of 0.1 mg/kg of captopril. We conclude that the renin inhibitor, A-62198, is an effective, primate selective hypotensive agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

DRG reimbursement for trauma: the demise of the trauma center (the use of ISS grouping as an early predictor of total hospital cost).

All institutional reimbursement for inpatient care in the State of New Jersey is administered by the DRG methodology (Prospective Payment System). This system is essentially identical to federal Medicare. In 1983 our hospital was designated the Level I trauma center for southern New Jersey (population, 2.6 million). Prehospital triage guidelines based on anatomic injury were implemented, and, as a result, an annual 30% increase in severe trauma cases (ISS greater than 16) was realized. In late 1984 serious financial shortfalls were noticed, especially in the higher ISS cases. A 1-year study (1985) of all patients admitted through the Trauma Center to an intensive care unit was completed (523 patients; mean ISS, 15.16; ISS greater than 16, 37.8%). All patients were stratified to one of five ISS groups (A: ISS 1-8; B: ISS 9-15; C: ISS 16-24; D: ISS 25-40; E: ISS greater than 40). Average cost, reimbursement, ISS, LOS, and mortality were reviewed for the entire aggregate and each severity group. The system of ISS grouping was an accurate method of cost analysis, and prospectively, ISS grouping allowed prediction of length of stay and total hospital cost. In addition, these data allowed early fiscal management decisions and resource allocation. As a reimbursement system, DRG falls short of the cost of care for all ISS levels and groups. As severity of injury rose, costs increased in a linear manner, but reimbursement did not, resulting in a substantial financial loss. The net loss to the hospital in 1 year was $1.86 million.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis-Related Groups↗
PubMed1988

Dehydration of hydrogen contact lenses in vitro and in vivo.

An attempt was made to derive a model for predicting the extent of hydrogel lens dehydration in vivo (delta Wv) by using a contact lens refractometer to (1) measure the water content (W) of eight lenses ranging from 36.5 to 85.8% water before and after 90 min lens wear by six subjects; and (2) measure the rate of dehydration of the same lenses in vitro (delta Wt), in a controlled, randomized, double-masked experiment. A significant correlation was demonstrated between W and the rate of change of delta Wt (the dehydration rate, D), whereby lenses of higher water content dehydrate at a slower rate. No correlation was found between W and delta Wv or between D and delta Wv, thus precluding the development of a predictive model. Possible reasons for this failure, and directions for further research, are discussed.

Adult↗
PubMed1987

Aortic and mitral valve calcification in patients with end-stage renal disease.

The frequency and aetiology of aortic valve and mitral annular calcification was studied by echocardiography in 87 patients aged 35-70 on maintenance haemodialysis for a mean of 7.5 years (range 0.5-19). Aortic valve calcification (AVC) was found in 24 patients (28%) and mitral annular calcification (MAC) was found in 31 (36%). AVC was severe and produced aortic stenosis in 5 patients with a tricuspid aortic valve (mean age 51.6 years), which confirms that calcific aortic stenosis is a complication of chronic uraemia. MAC was associated with functional mitral stenosis in 1 patient. Premature AVC and MAC were associated with an increased calcium X phosphate product and long-term haemodialysis. There were no significant differences between those patients with aortic stenosis and those with AVC but no stenosis. Patients with AVC had an increased incidence of MAC and vascular calcification. Premature AVC and MAC is frequent in dialysis patients and appears to be related to abnormal calcium and phosphate metabolism and to increased mechanical stress on the valve cusps. In a small but important group of patients on long-term dialysis, premature valve calcification is severe and produces aortic stenosis, or less frequently, mitral stenosis.

Adult↗
PubMed1987

Are isolated maternity units run by general practitioners dangerous?

A retrospective survey was carried out of women admitted in labour to an isolated maternity unit run by general practitioners in Penrith. In the five years 1980-4, 1267 women began labour in Penrith, of whom 1153 (91%) never required help from a consultant unit. Ninety required transfer during labour. Ten mothers and four neonates required transfer during the early puerperium, all to one receiving unit in Carlisle. There were six perinatal deaths during the five years; five occurred in babies delivered after transfer. The perinatal mortality was 4.7/1000. The low mortality, the low level of intervention, and the preference of women all support the retention of isolated units.

England↗
PubMed1987

Age-related rise in parathyroid hormone in man: the use of intact and midmolecule antisera to distinguish hormone secretion from retention.

Circulating levels of parathyroid hormone (PTH) rise with age in normal men and women. To resolve the basis for this observation we measured iPTH in 137 normal men and women, age 23 to 85 years, using two antisera which responded to different portions of the PTH molecule. A midmolecule assay (Mid-PTH) employed antiserum NG-5, which recognizes mid- and carboxy-terminal portions of hPTH, whereas antiserum CK-67, which recognizes determinants in the 1-34 hPTH sequence, was used to measure intact PTH (NH2-PTH). Two-hour fasting urine was collected for measurement of creatinine clearance and excretion indices of phosphorus and cyclic AMP. Serum was analyzed for 25-hydroxyvitamin D (25-OHD) in addition to iPTH. Mid-PTH rose significantly with age in the 72 women (r = 0.38, p less than 0.001) and in the 65 men (r = 0.40, p less than 0.001). NH2-PTH rose with age in women (r = 0.23, p less than 0.05), but a change in men was not significant (r = 0.19, n.s.). Cyclic AMP excretion rose significantly with age in both women (r = 0.42) and men (r = 0.41), whereas phosphorus excretion rose significantly in women only (r = 0.32, p less than 0.01). 25-OHD levels were 27.5 +/- 1.3 ng/ml for women and 26.1 +/- 1.2 ng/ml for men. No change in 25-OHD was observed with age in women, and a significant decrease in men was due entirely to extremely high values in three young subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Effects of cortisol and growth hormone replacement on osmoregulation in hypophysectomized coho salmon (Oncorhynchus kisutch).

Both cortisol and GH were able to reverse partially the effects of hypophysectomy on coho salmon (Oncorhynchus kisutch) as judged by improved seawater (SW) tolerance after long-term treatment; however, neither hormone significantly restored gill Na+, Na+,K+-ATPase activity. In the first experiment, gill Na+,K+-ATPase activity remained low in hypophysectomized (Hx) coho treated with cortisol (15 micrograms/g body wt, suspended in cocoa butter) for 96 hr (48 hr in fresh water followed by 48 hr in seawater). In addition, plasma sodium levels were higher in the cortisol-treated Hx animals compared with those in untreated controls. In the second experiment, treatment with cortisol-filled Silastic capsules and implants of bovine GH (mixed with cholesterol in a ratio calculated to yield a dose of 1.5 microgram/g body wt/week) for 12 days also failed to alter gill Na+,K+-ATPase activity, but did reduce plasma sodium levels in animals transferred to SW for 48 hr. These results suggest that these hormones may be involved in the development of hypoosmoregulatory ability in coho salmon. However, the failure of either hormone to restore gill Na+,K+-ATPase activity suggests that a combination of these hormones and/or an additional hormone(s) acting in a synchronized fashion may be required for full effectiveness.

Animals↗
PubMed1987

Dimensions of religiosity in old age: accounting for variation in types of participation.

Research on religiosity and aging has focused more on church attendance than on the religious role and the strength of beliefs and the extent of private devotions. This study of 123 older West Texans examines the degree to which nine variables account for variation in both organized religious activities and private religious behavior. These include three social activity and interaction variables, three religion variables, and three personal variables (health, age, and income). Strength of religious conviction proved to be the strongest predictor of both types of religious participation. Multiple-regression analysis did not support the hypothesis that private religious activity is compensatory; that is, it does not make up for increased social or personal deprivation. Poor health, low income, reduced activity, and living alone did not predict higher levels of nonorganized religious behavior. However, strong kin/friend networks did predict high levels of private devotion. This research suggests that frequent interaction in a social network contributes to the spiritual well-being of elderly persons; that is, it affirms the wholeness of their lives.

Age Factors↗
PubMed1986

Plasma lactoferrin in patients with neutropenia.

This study examines the role of plasma lactoferrin in the assessment of neutropenia. In particular, we have studied lactoferrin as an inhibitor of granulopoiesis and as an indicator of the size of the total blood granulocyte pool (TBGP). Plasma lactoferrin concentration was determined in a heterogeneous group of 30 patients with neutropenia. Serial plasma lactoferrin levels in a patient with cyclic neutropenia correlated with the cycles of the neutrophil count. Patients with splenomegaly had a grossly elevated lactoferrin:neutrophil ratio. Most chronic idiopathic neutropenia patients had no real clinical problems and a normal plasma lactoferrin level. The results provide further evidence to support the concept that plasma lactoferrin indicates the size of the TBGP and the lactoferrin: neutrophil ratio indicates the degree of granulocyte margination. There was no evidence to suggest that lactoferrin acting as a feedback inhibitor of granulopoiesis caused neutropenia in these patients.

Agranulocytosis↗