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Biomedical subjects

B W Morris

Publications and source records attributed to B W Morris.

At least 19 recordsLinked to original sources
PubMed1999

Chromium homeostasis in patients with type II (NIDDM) diabetes.

The purpose of this study was to assess chromium handling in non-insulin dependent diabetic patients (NIDDM) compared to healthy volunteers. Chromium handling was evaluated using fasting blood and second morning void urine samples from 93 NIDDM patients and 33 healthy volunteers. Significant differences in chromium homeostasis were seen between patients and controls. NIDDM patients had mean levels of plasma chromium around 33% lower and urine values almost 100% higher than those found in health. Healthy volunteers showed a significant negative correlation between fasting levels of plasma chromium and insulin. This was not evident in NIDDM patients. In the early years of onset of NIDDM, plasma chromium values were inversely correlated with plasma glucose. This was lost in patients with diabetes of more than 2 years duration. We suggest large losses of chromium over many years may exacerbate an already compromised chromium status in NIDDM patients and might contribute to the developing insulin resistance seen in patients with type 2 diabetes.

Adult↗
PubMed1999

Differentiation of normal human keratinocytes influences hexavalent chromium uptake and distribution and the ability of cells to withstand Cr(VI) cytotoxicity.

The degree of differentiation of normal human keratinocytes determines the biology of the cells to a large extent. We have previously documented that keratinocytes from different donors differ significantly in their ability to withstand hexavalent chromium [Cr(VI)]-induced cytotoxicity. Several factors may contribute to this differing donor sensitivity to Cr(VI). The aims of this study were to investigate to what extent keratinocyte differentiation might influence Cr(VI) uptake and the ability of cells to withstand Cr(VI)-induced cytotoxicity. Keratinocytes from different donors were cultured under identical conditions and exposed to Cr(VI) (as potassium dichromate) at different points during their maturation process. The degree of differentiation of the cells was assessed using a quantitative assay for involucrin and related to the Cr(VI) cytotoxicity experienced by the cells. Chromium content was measured in whole cell, cytosolic and particulate fractions. While proliferative keratinocytes exposed to Cr(VI) showed a high degree of cytotoxicity to dichromate exposure, the more differentiated cells showed significantly less cytotoxicity but a higher uptake of the metal ion into the cells. The relative percentage of cytosolic chromium was high in the proliferative cells and decreased as the cells matured, suggesting that differentiated cultures were binding most of the chromium to the particulate fraction. Total chromium also increased during differentiation. The use of the channel-blocking agent 4, 4'-diisothiocyanate-2-2'-stilbenedisulphonic acid confirmed the spatial differences of chromium accumulation in the phenotypically different cultures, in that it prevented Cr(VI) entry into the proliferative cells and attenuated dichromate cytotoxicity in these cultures, but had no effect on the Cr(VI) uptake in differentiated cells, nor did it reduce its cytotoxicity. These data support the hypothesis that the upper differentiated layers of the epidermis are able to offer considerable physical protection to the lower proliferative layers from chemical pro-oxidants.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1993

Glucose-dependent uptake of chromium in human and rat insulin-sensitive tissues.

1. This study was designed to investigate the influence of insulin and glucose on the distribution of trivalent chromium in human plasma and blood cells and in human and rat insulin-sensitive and -insensitive tissues. 2. Evidence is provided that, in the rat in vitro, a clear difference exists in chromium binding between insulin-sensitive and -insensitive tissues in that chromium binding is significantly enhanced by glucose in insulin-sensitive tissues. 3. Glucose-dependent association of chromium with human adipose tissue was blocked by inhibitors of glucose transport. 4. Addition of insulin slightly increased the response to glucose in muscle and reduced the response to glucose in adipose tissue; such effects were less marked than those seen in response to glucose alone. 5. The results of this study in vitro support the hypothesis that, in vivo, chromium translocates from the blood compartment to insulin-sensitive tissues.

Adipose Tissue↗
PubMed1993

The inter-relationship between insulin and chromium in hyperinsulinaemic euglycaemic clamps in healthy volunteers.

Evidence in the literature suggests that the trace element chromium may have a role in glucose homeostasis through the regulation of insulin action. We have previously reported a significant reduction in plasma chromium levels in healthy individuals, following a 75 g oral glucose load, and after meals and glucose-dependent uptake of chromium in insulin-dependent tissues in vitro. However, in vivo it is unclear whether the changes in plasma chromium relate to changes in plasma glucose or insulin. The present study describes a series of euglycaemic hyperinsulinaemic clamps designed to attempt to define the initiator of changes in plasma chromium levels in ten healthy individuals. The data showed a significant (P < 0.01) reduction in fasting plasma chromium levels following glucose infusion and an initial bolus of insulin. Significant (P < 0.02) increases in post-clamp urinary chromium excretion were insufficient to explain the decrease in plasma levels. During the recovery phase of an extended two-phase clamp protocol we found plasma insulin levels decreased by 70% within 10 min, associated with an increase in plasma chromium levels of 30% and no significant change in plasma glucose level. These data indicate that alterations in plasma glucose are unlikely to be directly related to changes in plasma chromium, whilst supporting the hypothesis that plasma insulin may influence plasma levels of this trace element. In contrast, plasma zinc was unaffected throughout these clamp studies.

Adult↗
PubMed1992

The trace element chromium--a role in glucose homeostasis.

To better define the normal metabolism of the trace element chromium, we studied its diurnal variation and its response to an oral glucose challenge in nine healthy volunteers. Plasma and urine chromium concentrations were measured by electrothermal atomic-absorption spectroscopy and plasma insulin by radioimmunoassay. A significant inverse relationship was found between plasma chromium and plasma insulin concentrations both over a 24-h period (P less than 0.001) and after a 75-g glucose load (P less than 0.01). This interesting observation, suggesting the removal of chromium from the plasma compartment after meals (confirmed by glucose tolerance test), is not explained simply by increased urinary loss but might be explained by transient changes in uptake or binding of chromium by insulin-sensitive tissues.

Adult↗
PubMed1992

Circadian changes in plasma phosphate concentration, urinary phosphate excretion, and cellular phosphate shifts.

The concentration of phosphate (Pi) in plasma, Pi excretion, and the tubular threshold of Pi resorption (TmP/GFR) all increase throughout the day from about 1100 to 0300 h. For plasma [Pi], cosinor analysis yielded the following estimates of the parameters of this pattern (with 95% confidence limits): amplitude = 0.17 (0.07-0.26) mmol/L, phase = peak at 0201 (1127-0342) h, and MESOR = 1.14 (1.11-1.18) mmol/L. The increase in TmP/GFR reflects an underlying change in renal Pi handling, which is not attributable to changes in parathyrin concentrations. The changes in Pi excretion work both for and against the changes in plasma [Pi], at different times. The calculated net nonrenal flux of Pi into the extracellular fluid increases in the morning and remains high until 0300 h, and neither it nor Pi excretion nor plasma [Pi] shows any relation to meals. This illustrates the importance of transient net fluxes of Pi between intracellular and extracellular spaces in the control of hour-to-hour changes of plasma [Pi].

Adult↗
PubMed1989

A longitudinal study of thyroid function in pregnancy.

We undertook a prospective longitudinal study of thyroid function in 36 pregnant women. There were significant increases in thyroxin-binding globulin, thyrotropin, and triiodothyronine. Albumin, free thyroxin (measured by an analog and a nonanalog method), and the free thyroxin index were significantly decreased. Results for the free thyroxin methods were correlated with each other in each trimester. We could find no evidence for artifacts related to albumin or thyroxin-binding globulin with either method for free thyroxin.

Female↗
PubMed1988

Effect of glucose loading on concentrations of chromium in plasma and urine of healthy adults.

We report here a small study designed to identify the effect of a 75-g oral glucose load on concentrations of chromium in plasma and urine of apparently healthy volunteers. We detected a consistent and significant (P less than 0.01) decline in plasma chromium after glucose administration, the nadir of the chromium response coinciding with the zenith of the glucose concentration.

Adult↗
PubMed1984

Retinal damage from the illumination of the operating microscope. An experimental study in pseudophakic monkeys.

An experimental study of retinal damage from the coaxial illumination of the operating microscope was performed in pseudophakic rhesus monkeys. The threshold exposure time for production of an ophthalmoscopically visible lesion was determined, and the lesions were studied with light and electron microscopy. At the "high" illumination setting, the threshold exposure was less than 7 1/2 minutes and consecutive exposures of lesser duration had an additive effect. Histologically, the lesions were identical to those which other authors have described as primarily due to the shorter wavelengths or "blue light mechanism" of damage.

Animals↗