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Biomedical subjects

T Miller

Publications and source records attributed to T Miller.

At least 235 records · Page 13Linked to original sources
PubMed1988

Accuracy of fiberoptic central venous saturation catheter below 50%.

The fiberoptic central venous flotation catheter has gained widespread clinical acceptance for continuous monitoring of mixed venous oxyhemoglobin saturation. There are obvious research applications to this device, especially in monitoring very low central venous saturations in response to hypoxic challenge and cardiopulmonary exercise testing. However, the accuracy of this device has not been established in such low saturation ranges in humans. This study examines the tracking characteristics of the Opticath (Oximetrix, Mountain View, CA) pulmonary arterial catheter in comparison to simultaneously drawn blood specimens in which oxyhemoglobin saturation was determined by direct spectrophotometric oximetry. The results show that the catheter follows saturation established by bench oximetry quite closely between 50 and 80%, the range most commonly encountered in the clinical setting. However, at saturations below this range, the catheter consistently underestimates direct spectrophotometry. Since accuracy is extremely important for research purposes, two equations that can be used to correct catheter readings for mixed venous saturations less than 50% are presented.

Catheterization, Central Venous↗
PubMed1988

Significance of cyclosporin-A-associated renal surface irregularities.

The purpose of this study was to investigate unusual irregularities observed on the surface of kidneys from rats which had been treated with seven 'clinically effective doses' (25 or 50 mg/kg) of cyclosporin A (CsA). Surface corrugations were obvious on gross examination and were a universal finding in our study which involved greater than 50 rats. Examination by scanning electron microscopy (SEM) showed that the surface irregularities resulted from swollen peritubular capillaries adjacent to vacuolized and partially collapsed tubules at the cortical surface. The enlarged capillaries were associated with vascular congestion, and although peritubular capillary congestion has been recognized in CsA-treated patients, it has been difficult to determine whether this reaction is associated with drug toxicity or graft rejection. Our findings, indicating that peritubular capillary congestion in addition to vacuolization and collapse of subcapsular tubules is a drug-associated phenomenon, may help give a more accurate assessment of biopsy and autopsy material from CsA-treated patients and laboratory animals.

Animals↗
PubMed1987

Expression of functional cell-cell channels from cloned rat liver gap junction complementary DNA.

An oocyte expression system was used to test the relation between a complementary DNA (cDNA) clone encoding the liver gap junction protein and cell-cell channels. Total liver polyadenylated messenger RNA injected into oocytes induced cell-cell channels between paired oocytes. This induction was blocked by simultaneous injection of antisense RNA transcribed from the gap junction cDNA. Messenger RNA selected by hybridization to the cDNA clone and translated in oocyte pairs yielded a higher junctional conductance than unselected liver messenger RNA. Cell-cell channels between oocytes were also formed when the cloned cDNA was expressed under the control of a heat-shock promoter. A concentration-dependent induction of channels was observed in response to injection with in vitro transcribed gap junction messenger RNA. Thus, the liver gap junction cDNA encodes a protein that is essential for the formation of functional cell-cell channels.

Animals↗
PubMed1987

Diagnosis of Kaposi's sarcoma by fine-needle aspiration biopsy.

Fifteen cases of Kaposi's sarcoma diagnosed by fine-needle aspiration biopsy were reviewed. The diagnosis was confirmed by tissue biopsy in eight of the cases. All of the patients were homosexual males, and 13 had a previous diagnosis of AIDS. The aspirates were obtained from enlarged lymph nodes (five cases), soft-tissue masses (two cases), oral cavity lesions (seven cases), and an abdominal mass. The most characteristic cytologic features were intact tissue fragments composed of overlapping spindle cells with nuclear distortion and ill-defined cytoplasmic borders. Smaller groups of loosely cohesive spindle-shaped cells and individual spindle cells with cytoplasm were also helpful features. In the appropriate clinical setting, these cytologic features on FNAB are felt to be diagnostic of Kaposi's sarcoma.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Maturational changes in the pharmacological characteristics and actomyosin content of canine arterial and venous tissue.

The purpose of this study was to compare the pharmacological characteristics and actomyosin content of arterial and venous tissue at different times during development. Rings of arteries (femoral, renal, carotid, pulmonary) and veins (saphenous, pulmonary, jugular) were obtained from 1 wk, 1 month, and adult dogs, mounted at their optimal length for force development and the contractile response to potassium chloride and phenylephrine determined. The strain at optimal length was less at all ages in pulmonary artery and pulmonary and jugular veins than in other vessels. All vessels exhibited an increase in maximum contractile response with development but the increase was greater for phenylephrine. In general, the magnitude of the maximum response of the jugular and pulmonary veins and pulmonary artery was less than other vessels at all ages. The sensitivity (half maximum response) either increased or was unchanged in arteries with development, while in the veins it either decreased or was unchanged. The relaxant effects of verapamil and isoproterenol were determined on potassium chloride contracted vessels. Arterial tissue was minimally responsive to isoproterenol at all ages while venous tissue either increased its responsiveness (saphenous, pulmonary) with development or remained highly responsive (jugular). Verapamil, unlike isoproterenol, was an effective relaxant of all vessels. The actomyosin content (mg/mm) of femoral and renal arteries and saphenous and jugular veins increased with development but this increase was accompanied by a parallel increase in total protein so that the ratio (actomyosin/total protein) was unchanged. In jugular veins from adult dogs this ratio was smaller than in arterial tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Actomyosin↗
PubMed1987

Nocturnal oxyhemoglobin desaturation in COPD patients with arterial oxygen tensions above 60 mm Hg.

We studied 152 COPD patients with a daytime PaO2 greater than or equal to 60 mm Hg using formal polysomnography (EEG, airflow, respiratory muscle movement, ear oximeter) to detect the presence of nocturnal, nonapneic, oxyhemoglobin desaturation. Nine subjects were disqualified by the unexpected discovery of sleep apnea, as were another eight because they could not sleep in the laboratory setting. Of the remaining 135 subjects, 37 (27 percent) desaturated below a baseline sleep saturation of 90 percent for five minutes or more, reaching a nadir saturation of at least 85 percent. Anthropomorphic, pulmonary function, and historic factors comparing desaturators and nondesaturators failed to separate the groups. Awake PaO2 at rest in the desaturators was significantly lower than in the nondesaturators. The PaCO2 was higher in the desaturators. Reversibility of the desaturation phenomenon was demonstrated in three patients during subsequent polysomnographic studies following periods of clinical improvement. Continuous oxyhemoglobin monitoring during sleep remains the only reliable tool for detecting nocturnal desaturation.

Aged↗
PubMed1987

Mucus stabilization in the urinary bladder.

Mucus in the urinary bladder may act as an important intrinsic defence mechanism by shielding the epithelial layer from pathogens. Visualization of any such layer of mucus using electron microscopy has not been possible, as preparative procedures in current use result in the loss or distortion of mucus. We evaluated methods reported to stabilize polysaccharide layers and demonstrated that pretreatment of rat bladder tissue with anti-mucus antiserum, minimized the collapse of the mucus that normally occurred during dehydration of the tissue for electron microscopic examination. Under these conditions, mucus was stabilized as a layer closely adherent to the epithelium.

Animals↗
PubMed1986

Dietary fat and cholesterol modification of rat abdominal aorta prostacyclin and leukotriene production (in vitro).

Groups of weanling male Sprague-Dawley rats fed formulated diets containing 15% by weight of corn oil (CO), linseed oil (LNO), or corn oil plus 1% cholesterol and 0.25% cholic acid (CH-CH) were sacrificed after 8 weeks and the aortas removed. Three mm length cross-sectional rings were cut from the distal abdominal aorta segment and incubated in either Tris buffer (pH 7.4, 37 degrees, 10 min.) for measurements of prostacyclin as 6-Keto-prostaglandin in F1 alpha (6-Keto-PGF1 alpha) or Tris buffer plus 10 microM ionophore A23187 for measurement of leukotriene C4 (LTC4) production using radioimmunoassay (RIA) procedures. 6-Keto-PGF1 alpha production was greater (p less than 0.01) in the CO than in the LNO and CH-CH fed rats by 54% and 40% respectively. LNO diets significantly lowered LTC4 production when compared to tissues from CO-fed rats (p less than 0.05). LTC4 production by tissues from the CH-CH-fed animals was lower than tissues from CO-fed animals, however, the difference failed to reach levels of significance because of data spread and the number of tissues. Tissues from the CH-CH-fed and LNO-fed rats were significantly different than those of the CO since LTC4 formation was high relative to 6-Keto-PGF1 alpha production (LTC4/6-Keto-PGF1 alpha). These results suggest distinctive effects of dietary fat and cholesterol on the syntheses of vasoactive eicosanoids that may be relevant to arterial tissue physiology and pathology.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Adaptation of the duodenum and ileum of the rat to mid-gut resection: enzyme activity and trace metal status.

Activities of the enzymes lactase, sucrase, maltase, alkaline phosphatase, and superoxide dismutase (SOD) were measured in mucosa of duodenum and ileum of the rat after 70% resection of mid-small intestine or sham operation (transection). We also measured the concentrations of zinc, copper, and manganese in several tissues to assess trace metal homeostasis postresection. Resection resulted in decreased specific activities of disaccharidases and alkaline phosphatase in duodenum, while specific activities remained unchanged in ileum. Specific activity of total SOD (the sum of Cu-Zn and Mn SOD) and Mn SOD was the same in duodenum after resection but was markedly increased in ileum. Tissue trace metal concentrations changed minimally. Because of postresection mucosal growth, total segmental activity of disaccharidases and alkaline phosphatase was the same in duodenum and increased in ileum of resected compared to transected rats. Segmental activity of total SOD and Mn SOD doubled in duodenum and trebled in ileum of resected as compared to transected rats. Thus, total segmental enzyme activity is maintained or increased postresection by increased enterocyte proliferation rate and mucosal growth.

Alkaline Phosphatase↗