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Biomedical subjects

T Miller

Publications and source records attributed to T Miller.

At least 289 records · Page 16Linked to original sources
PubMed1980

Intrinsic control of colonic blood flow and oxygenation.

In a denervated autoperfused dog colon preparation, arterial perfusion pressure, venous outflow pressure, blood flow, and arteriovenous O2 difference were measured during graded arterial pressure alterations, arterial occlusion, venous pressure elevation, venous occlusion, and local intra-arterial infusion of adenosine. As perfusion pressure was reduced from 100 to 30 mmHg, colonic blood flow decreased and arteriovenous O2 difference increased. Although blood flow was not autoregulated O2 delivery was maintained within 10% of control between 70 to 100 mmHg and then decreased with further reduction in perfusion pressure. Arterial occlusion (15, 30, and 60 s) resulted in a postocclusion reactive hyperemia; the magnitude of the hyperemia was directly related to the duration of occlusion. Venous occlusion resulted in a postocclusion reactive hypoemia. Elevation of venous pressure from 0 to 20 mmHg increased vascular resistance, O2 extraction, and the capillary filtration coefficient, but decreased O2 delivery. Infusion of adenosine decreased vascular resistance and O2 extraction, but increased O2 delivery. These data suggest that both metabolic and myogenic mechanisms are involved in the control of colonic blood flow and oxygenation.

Animals↗
PubMed1980

Experimental uremia. Description of a model producing varying degrees of stable uremia.

A model is described for the induction in the rat of varying degrees of stable uremia using controlled resection of renal tissue. Three degrees of uremia have been attained: 'mild--blood urea 40--80 mg/100 ml (6.68--13.36 mmol/1); 'moderate'--blood urea 100--200 mg/100 ml (16.7--33.4 mmol/1), and 'severe'--blood urea greater than 200 mg/100 ml (> 33.4 mmol/1). Mild uremia was produced by unilateral nephrectomy; moderate uremia required the resection of 80 +/- 2% of the total renal mass, and severe uremia was produced by 88 +/- 2% nephrectomy. A sham-operative procedure provided an appropriate control for the model. Evaluation of the model has been carried out using analyses of renal function (GFR, concentrating capacity), blood biochemistry, hematological parameters and histological examination. The ability to induce a standardized, stable uremia at predetermined levels, uncomplicated by the administration of nephrotoxic material, represents an advance on existing methods for producing experimental renal failure.

Animals↗
PubMed1980

Suppressor cell regulation of cell-mediated immune responses in renal infection in vitro modulation of suppressor cell activity.

Infection-induced anergy is a frequent complication of bacterial, viral, and parsitic infection. A marked suppression of the thymus-derived (T) lymphocyte response to concanavalin A has been demonstrated in vitro during renal infection and the mechanisms by which suppression occurs have been investigated. In particular we have considered the possibility that suppression might result from the inhibitory effect of prostaglandins, secreted by activated macrophages with immunoregulatory potential. The experiments have shown that the T-lymphocyte effector status in experimentally-induced renal infection is determined by two suppressor cells, one infection-induced and the other naturally occurring. The inability to respond to mitogenic stimulation was reversible and restoration of immune responsiveness to splenic lymphocytes from infected animals could be achieved in two stepwise manipulations; differential centrifugation removed the infection-induced suppressor cells, and the suppressor activity of the naturally occurring suppressor cells could then be inhibited by indomethacin. Thus the two suppressor cells were distinguishable on the basis of their physical characteristics and their response to indomethacin. The dominant factor determining the immune responsiveness of splenic lymphocytes from the pyelonephritic animals was, however, the infection-induced suppressor cell. This cell has been characterized as a sedimentable cell (30 g) with suppressor activity demonstrable in co-culture experiments. Plastic-adherent cells from the sedimentable fraction of pyelonephritic animals' splenic cells were shown to have suppressor activity that was not inhibited by indomethacin. The infection-induced and naturally occurring suppressor cells can be viewed as prototypes for the equivalent cells in man and may be useful models for studying the role of these cells as determinants in the pathogenesis of infectious disease.

Animals↗
PubMed1979

B lymphocyte colony formation in renal infection.

The effect of renal infection on B lymphocyte colony formation has been investigated in the belief that a study of the effect of infection on subpopulations of lymphoid cells might provide direct evidence of the effect of infection on the immmune system. Renal infection was induced in mice, and the specific immune response of the B lymphocyte compartment was quantitated by determining the serum antibody and plaque-forming cell response to infection. Under the conditions of the experiment, the ability of splenic lymphocytes to form B lymphocyte colonies was significantly depressed during the first 7 days of infection, and the results suggest that a study of the responses of lymphoid cells to infection may provide information of diagnostic and prognostic value.

Animals↗
PubMed1979

Adrenocortical function and a field population of a macropodid marsupial (Setonix brachyurus, Quoy and Gaimard).

Concentrations of corticosteroids and aldosterone have been measured in the plasma and related to the maximum cortisol binding capacity, to the concentration of sodium and potassium of the plasma and to the condition of the animals, in a natural population of the quokka (Setonix brachyurus, Quoy & Gaimard) on Rottnest Island, Western Australia. A marked population in one area has been repetitively sampled at approximately 6 week intervals over a period of 2 years. Animals were found to be in significantly better condition during the hot-dry season. Their plasma concentrations of corticosteroids, 1.09 +/- 0.11 (S.E.M.) and 1.47 +/- 0.14 microgram/100 ml and their plasma sodium concentrations, 147 +/- 0.87 and 142 +/- 1.17 mequiv/1, for the hot-dry and cold-wet seasons respectively, were both significantly different (P less than 0.05). Plasma concentrations of aldosterone were 8.40 +/- 0.57 and 7.06 +/- 0.53 ng/100 ml for the hot-dry and cold-wet seasons. The level of aldosterone fell to levels comparable to those found in salt-replete laboratory animals only during the month of July. In the laboratory, salt deprivation resulted in a significant rise in the concentration of plasma aldosterone, 2.33 +/- 0.57 (S.E.M.) ng/100 ml when salt-replete and 16.95 +/- 2.74 ng/100 ml when salt-deprived (P less than 0.001). Total plasma corticosteroid levels were unaffected by changes in the sodium content of the diet. Injections of ACTH at a rate of 2 i.u./kg caused a significant rise in the levels of plasma corticosteroids which were essentially identical in both high- and low-condition animals. Both temperature fell to a significantly lower level in low-condition animals held in cages after injection of ACTH. These results indicate that the seasonal mortality of th quokka on Rottnest Island does not result from any breakdown in adrenal function, despite a substantial decline in the condition of the animals.

Adrenal Cortex↗
PubMed1979

Permselectivity of cat blood-lymph barrier to endogenous macromolecules.

The restrictive properties of liver blood-lymph barrier to endogenous plasma protein fractions of varying molecular size were studied at different hepatic venous pressures (and lymph flows) using steady-state lymph to plasma protein concentration ratios. At control hepatic venous pressures (0-2 mmHg) the lymph to plasma venous concentration ratios of the various protein fractions indicate significant selectivity by the liver blood-lymph barrier to macromolecules on the basis of molecular size. The sieving observed was consistent with equivalent pore radii of 180-250 A. The transsinusoidal oncotic pressure gradient ranged between 4.0 and 8.0 mmHg at control venous pressures. As venous pressure was increased, liver lymph flow and lymph to plasma protein concentration ratio increased while the blood-lymph oncotic pressure gradient decreased. Liver lymph flow was linearly related to hepatic venous pressure. At lymph flow less than or equal to 10 x control, there is no longer a sieving effect on plasma protein; findings consistent with por radii in excess of 1000 A. The results of this study suggest that maximal sieving by the liver blood-lymph barrier occur at normal capillary filtration rates and support the possibility that the interstitium is the rate limiting barrier for blood to lymph transport of macromolecules in the liver.

Animals↗
PubMed1979

Immunoglobulins and hyposensitization for allergy.

The premise that protracted stimulation of the human immune system might be involved in the induction of malignant immunocytopathies is scrutinized. Studies of the serum immunoglobulins of 313 patients who had been hyposensitized for allergy are compared with those of 138 nonallergic and 189 allergic individuals not subjected to this therapy. Critical historical data in all groups are also evaluated. The investigators concluded that, as far as the parameters studied, there were significant differences in the mean total immunoglobulin G levels in allergic hyposensitized persons compared with the non-allergic control group. It involved a depression of the serum IgG concentration and related to the length of the desensitization program and to whether it was continuous or interrupted. One evolving monoclonal immunocytopathy, etiology of which has not been established, was encountered during the period of study.

Adolescent↗
PubMed1979

Radiology of the acute surgical abdomen in infants and young children.

The most common nontraumatic acute surgical lesions of the infant abdomen are considered. These abdominal lesions are divided into those which do and do not cause bowel obstruction. Lesions causing bowel obstruction are almost always identified as being surgical and are usually appropriately treated. Most common in this group are incarcerated inguinal hernia and malrotation. Among the non-obstructive lesions, appendicitis is the most common and frequently very difficult to diagnose in this age group. The early use of a barium enema is advocated if appendicitis is a diagnostic possibility. Profound ileus can be seen in a variety of medical conditions and several examples are cited.

Abdomen, Acute↗
PubMed1978

Modification by suppressor cells and serum factors of the cell-mediated immune response in experimental pyelonephritis.

A marked suppression of the thymusderived (T)-lymphocyte response to concanavalin A has been demonstrated in vitro during renal infection. Suppression of the T-lymphocyte response in vitro was seen as early as 2 h after the induction of renal infection, but maximum suppression was found 24-72 h later. A population of suppressor cells in the splenic lymphocyte population, generated during the host's response to infection, contributed to the depressed lymphocyte response. Removal of suppressor cells restored the mitogenic responsiveness of the remaining splenic lymphocytes. Conversely, in co-culture experiments, a suppressor cell present in the splenic lymphocyte population of pyelonephritic animals was shown to be capable of suppressing the mitogenic responsiveness of normal splenic lymphocytes. Significantly reduced host vs. graft responses by the pyelonephritic animals confirmed, in vivo, the depression of cell-mediated immune mechanisms. An additional suppressive factor was found in the serum of pyelonephritic animals which depressed in vitro the mitogenic responsiveness of splenic lymphocytes from normal animals. Support for the suppressive role of this serum factor was found when splenic lymphocytes from pyelonephritic animals were tested in vivo in the absence of homolgous serum (graft vs. host). Under these conditions, the lymphocytes showed an enhanced reaction compared with lymphocytes from normal animals. The presence of a suppressor cell population and a serum factor, both capable of depressing cell-mediated mechanisms, may be major factors contributing to the establishment of infection in the kidney.

Animals↗