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Biomedical subjects

D Roberts

Publications and source records attributed to D Roberts.

At least 361 records · Page 20Linked to original sources
PubMed1984

Three-dimensional imaging and display of the temporomandibular joint.

Despite recent advances in diagnostic radiology, current techniques for radiographic evaluation of the temporomandibular joint continue to present the clinician with difficult problems in interpretation and diagnosis. The use of three-dimensional images reconstructed from computed tomographic (CT) data improves the diagnostic value of conventional CT at no additional risk to the patient and may provide new insights into this complex anatomic structure. A sequence of 1.5 mm CT sections is made with a slice-to-slice spacing of 1.0 mm. These are used to construct a new sequence of slices by mathematical interpolation in which the new slice spacing equals the size of the pixels. Structures to be imaged separately are then masked in the interpolated sections prior to "windowing" for the appropriate tissue density. A special algorithm detects the boundary surface of the selected structure. The surface pixels are assigned gray levels on the basis of their distance and attitude from the observer. When displayed, this produces a simulated three-dimensional image. The image can be rotated and sectioned. Rotations permit otherwise hidden surfaces to be examined. Images of a human temporomandibular joint in vitro are presented to demonstrate (1) the bony components of the joint and their relationships within the joint; (2) the bony components separated to display hidden surfaces; and (3) the joint meniscus in situ and as a separate component.

Cadaver↗
PubMed1984

Prolonged red cell survival following in vitro treatment with potassium cyanate. A study in patients undergoing open-heart surgery.

Red cel survival was prospectively studied, using Chromium-51 isotope, in 48 patients undergoing cardiopulmonary bypass for single valve replacement (SVR, 24 patients) or coronary bypass graft procedures (CABG, 24 patients). The red cells were labelled on the day before the open heart surgery. Cells from randomly selected patients were treated for 30 min with potassium cyanate (0.5 mg/100 ml) in 5% invertose solution or with 5% invertose alone. The mean red cell survival in the SVR and the CABG group was 21.3 and 23 days, respectively, when the cells had been treated with cyanate, and 12.7 and 12 days when only invertose had been used. In the cyanate groups the loss of isotope during cardiopulmonary bypass and in the first three postoperative days was significantly less than in the control groups indicating improved tolerance to the traumatic effects of cardiopulmonary bypass.

Cardiopulmonary Bypass↗
PubMed1984

Improved red cell survival in patients with chronic subclinical haemolysis due to artificial heart valve. Observations after in vitro treatment of the cells with potassium cyanate.

Red cell survival was studied with use of Chromium-51 isotope and standard haematologic tests of haemolysis. The study comprised 30 patients with normally functioning single artificial heart valves of various types. They were investigated on 2 or 3 occasions. Red cells labelled with Cr-51 were treated for 30 min with potassium cyanate (0.5 mg/100 ml) in 5% invertose or with only 5% invertose. The mean red cell survival without cyanate treatment was 25 (+/- 4.2) days. Following cyanate treatment this figure improved to 31 (+/-4.8) days. Low-grade chronic intravascular haemolysis was associated with all the valve types. Abnormal results were found in 67% and 62% of the tests in patients with ball-type valve (deBakey and Starr-Edwards, respectively). The figures for tilting disc values (Lillehei-Kaster and Björk-Shiley) were 51 and 45.5%, while Carpentier-Edwards bioprosthetic valves gave 15.5% abnormal test results. The findings thus suggested that ball valves are more haemolytic than tilting disc valves, which in turn are more haemolytic than tissue valves.

Anemia, Hemolytic↗
PubMed1984

The effect of urea on red cell deformability during cardiopulmonary bypass.

Red cell deformability was measured from the red cell filtration rate (RFR) in 33 patients undergoing cardiopulmonary bypass (CPB). Urea (1.0 g/kg b.w.) was given to 14 of the patients and 19 were controls in a prospective, blind study. The mean RFR (microliters/s) fell during 120 min of CPB, from 36.8 to 11.2 in the control group and from 37.4 to 25.0 in the urea group. In 17 patients undergoing single valve replacement, the mean RFR at CPB time 120 min had fallen from 38.5 to 17.4 in the controls and from 38.0 to 30.0 in the urea group. The corresponding figures in the 16 patients who underwent coronary bypass graft procedures were 35.0 to 3.5 (controls) and 36.8 to 20.8 (urea). The study confirmed the deleterious effect of CPB on the red cell and showed that this damage can be significantly reduced by administration of urea.

Cardiopulmonary Bypass↗
PubMed1984

Hepatic dysfunction after open-heart surgery.

In a prospective study, 93 patients were observed up to nine months after open-heart surgery using hypothermia, hemodilution and cold cardioplegia. In the first two weeks frequent determinations were made of serum aminotransferase, alkaline phosphatases (ALP), lactic dehydrogenase isoenzymes, gamma glutamyltransferase (GT), total and free bilirubin and bile acids. Plasma hemoglobin was measured at the end of the operation. After the first period, aminotransferases, alkaline phosphatases and bilirubin were determined monthly. On the first postoperative day almost all of the patients showed abnormal aspartate aminotransferase (ASAT) activity and ASAT/ALAT (alanine aminotransferase) greater than 1, and about 25% had hyperbilirubinemia. The findings suggested early postoperative leakage of enzymes not only from the myocardium, but also from the liver. After two weeks the patients presented another pattern of liver dysfunction, with abnormal ALAT in 50%, ASAT/ALAT less than 1, and abnormal ALP and GT in 28 and 45%, respectively. Eight patients were judged to have post-transfusion hepatitis of non-A, non-B type. Six of them had abnormal aminotransferases for more than six months.

Alkaline Phosphatase↗
PubMed1984

Macrophage activation and generation of tumoricidal activity by liposome-associated human C-reactive protein.

The effect of human C-reactive protein incorporated into multilamellar vesicles (CRP-MLV) was studied in assays of macrophage function. Peritoneal exudate macrophages from C57BL/6 mice phagocytosed CRP-MLV in vitro more rapidly than multilamellar vesicles bearing comparable amounts of immunoglobulin G. Exposure of peritoneal exudate macrophages in vitro to CRP-MLV resulted in development of tumoricidal activity against syngeneic T241 fibrosarcoma and B-16 melanoma cells and against allogeneic Sarcoma 1 cells. Peritoneal exudate macrophages obtained from mice given CRP-MLV i.p. demonstrated antitumor activity against the syngeneic T241 fibrosarcoma in a Winn-type assay, and when challenged in vitro with phorbol myristate acetate, they showed elevated superoxide anion production. Administration of CRP-MLV i.p. did not enhance natural killer activity of spleen cells, however. In superoxide anion assays, CRP-MLV were approximately 10 to 100 times more effective than free C-reactive protein. Results indicate that C-reactive protein is capable of activating macrophages, thus supporting the concept of C-reactive protein as an immunomodulator.

Animals↗
PubMed1984

Selection and characterization of L1210 sublines resistant to teniposide (VM-26).

Two spectra of L1210 sublines with gradations of resistance to teniposide (VM-26) were selected by stepwise exposure of cultures to increasing concentrations of the drug. Cultures representing the first spectrum were from 20 times to 1200 times more resistant to VM-26 than were cultures of parental cells. At 24 hr after addition of 22 nM VM-26 to the medium, the growth of cultures of parental cells was inhibited by 50%. Increases in resistance to VM-26 among the sublines coincided with increases in population doubling times. When cells were transferred to drug-free medium, there was a sharp decrease in resistance over the first 10 days; the subsequent decline in resistance, over 2 to 4 months, correlated with a decrease in population doubling times. The second spectrum of resistant sublines arose from the first spectrum after the latter had been maintained for about 1 year on various selective concentrations of VM-26. Resistance to VM-26 by this second group of sublines was from 400 times to over 2000 times greater than that of the parental cell line. Doubling times for these resistant cell populations were similar to the normal rate of the parental cell line. Eight sublines were characterized by two chromosomes with homogeneously staining regions, while the remaining subline had a single chromosome with this anomaly. One of the regions appeared on a submetacentric chromosome in seven of the nine sublines, while the other was on an acrocentric chromosome. These observations indicate that a longer doubling time facilitated selection of increasingly resistant sublines but was not essential for the resistance of sublines in the second spectrum.

Animals↗
PubMed1984

Flux of teniposide (VM-26) across the plasma membrane of teniposide-resistant sublines of L1210 cells.

The flux of teniposide (VM-26) across the cell membrane was compared for L1210 cells, nine VM-26-resistant L1210 sublines, and three partially revertant lines. The nine resistant sublines were maintained in medium with VM-26. A "zero-time," temperature-independent binding of VM-26 to cells, attributable to adsorption on the cell membrane or to solvation in the membrane, varied independently of the sensitivity of cell lines to the drug as measured by the extracellular concentration of drug required to inhibit growth of a subline by 50% at the end of 24 hr (IC50). The IC50 values varied from 22 nM VM-26 for parental cells to 45 microM VM-26 for the most resistant subline. After subtraction of the zero-time values, the initial rates of influx for VM-26 (extracellular concentration, 20.5 microM) and the apparent equilibrium constants for the flux of drug across the cell membrane correlated inversely with the logarithm of the IC50 values. Cellular steady-state levels of VM-26, initial rates of efflux of the drug, and cellular levels of nondiffusible drug varied independently of the IC50 values but in relation to each other. The efflux of VM-26 from the sublines was faster than from the parental cells at both 4 degrees and at 37 degrees. We conclude that resistance of L1210 cells to VM-26 is associated with changes in the flux of the drug across the cell membrane.

Animals↗
PubMed1983

Interaction of Leishmania donovani promastigotes with human phagocytes.

Leishmania donovani is an important intracellular protozoal pathogen of humans, which resides solely within mononuclear phagocytes. Phase-contrast microscopy and cinemicroscopy were used to examine the interaction of L. donovani promastigotes with human phagocytes to characterize and quantitate the sequence of events that results in leishmanial infection.

Animals↗
PubMed1983

The relationship of phenotype changes in Pseudomonas aeruginosa to the clinical condition of patients with cystic fibrosis.

Strains of Pseudomonas aeruginosa, isolated from the sputum of relatively fit patients with cystic fibrosis (CF) who had been recently colonized by the organism, showed typical cultural and serologic characteristics. The majority of strains of P. aeruginosa isolated from CF patients with chronic bronchopulmonary infection had 3 distinctive features, loss of 0 serotype reaction, expression of a new somatic antigen, and sensitivity to normal human serum. Patients with organisms with one or two of these features were more severely affected by the disease. The appearance of these variants may represent a critical stage in the progression of CF.

Adolescent↗
PubMed1983

Changes in plasma zinc and urinary excretion of zinc after operation with extracorporeal circulation.

Sixteen adults undergoing cardiac surgery were studied with respect to postoperative levels of zinc in plasma and urinary excretion of zinc. The preoperative plasma concentrations of zinc were normal. On the first postoperative day the mean for the series had fallen from 15 to 7.2 mumol/l. A gradual rise followed, and on the fifth day all patients had plasma zinc above the lower limit of normal range. The urinary excretion of zinc was significantly increased on the first, second and fifth days after surgery. The mean total of zinc in the urine during five days was 67 mumol. The short-term fall in plasma zinc level had no discernible effect on wound healing. It was therefore apparently harmless and did not indicate a need for zinc supplementation.

Aged↗
PubMed1983

Differential survival of Leishmania donovani amastigotes in human monocytes.

Leishmania donovani is an important intracellular protozoal pathogen of man; it is found solely within macrophages in its amastigote stage in humans, and exists in its extracellular, flagellated promastigote stage in the sandfly, its arthropod vector. To determine if either stage of L. donovani was capable of surviving within monocytes--the oxidatively active precursors of tissue macrophages--interactions of the parasite with human monocytes were studied in vitro. Amastigotes and promastigotes were ingested to a comparable degree by monocytes; whereas 79% of promastigotes were killed within 48 hr, however, amastigotes survived and multiplied threefold over 5 days. Promastigotes, which have been shown to be sensitive to hydrogen peroxide-peroxidase-halide microbicidal mechanisms, elicited a phagocytic oxidative burst that was 49% of the response to serum-opsonized zymosan, as assessed by luminol-enhanced chemiluminescence. NBT was reduced to formazan in 71% of monocytes exposed to promastigotes. The death of promastigotes within monocytes could be attributed at least in part to oxidative microbicidal mechanisms because there was no significant decrease in the number of cell-associated parasites in monocytes from donors with chronic granulomatous disease of childhood. In contrast to promastigotes, amastigotes survived within monocytes, despite eliciting an oxidative response that was 27% of the response produced by serum-opsonized zymosan; this response was not significantly different from that produced by promastigotes. In a phagocyte-free system, amastigotes were found to be sevenfold more resistant than were promastigotes to the lethal effects of hydrogen peroxide. The survival of L. donovani in human monocytes is thus dependent on the parasite stage; promastigotes are ingested, they elicit an oxidative burst, and the majority are killed by oxidative microbicidal mechanisms, whereas amastigotes are ingested and survive to parasitize human monocytes successfully, despite eliciting a phagocytic oxidative burst.

Adult↗
PubMed1982

Neonatal intraspinal 6-hydroxydopamine, 5,7-dihydroxytryptamine or their combination: effects on nociception and morphine analgesia.

Newborn rats received two injections of intraspinal 6-hydroxydopamine (6-OHDA, 10 micrograms) or 5,7-dihydroxytryptamine (5,7-DHT, 8 micrograms preceded by s.c. desmethylimipramine) or a 'cocktail' of both neurotoxins. The two injections were separated by 24 h. When assayed in adulthood, the 6-OHDA rats showed a substantial (about 80%) depletion of spinal norepinephrine (NE) but an elevation of brainstem NE. Conversely, the 5,7-DHT rats showed a modest (about 60%) loss of spinal serotonin (5-HT) but an elevation of brainstem 5-HT. Rats receiving combined 6-OHDA plus 5,7-DHT showed rostro-caudal, decreasing gradients of spinal NE and 5-HT depletions, with the largest loss in the lumbar cord. These depletions were much less than those observed after the respective single neurotoxin treatments. Neither the single nor combined neurotoxin treatments altered the tail-flick analgesia induced by morphine (1.0, 3.0 or 7.5 mg/kg s.c.). Basal nociception, however, was altered by the neurotoxins but in a sexually dimorphic manner. The 6-OHDA lowered baseline tail-flick latencies in females while 5,7-DHT elevated latencies in males. Like the 6-OHDA-only rats, the combined 6-OHDA plus 5,7-DHT lowered latencies in females. We conclude that neither spinal NE nor 5-HT are essential to morphine analgesia but do participate in nociception, seemingly in a sexually dimorphic fashion.

5,7-Dihydroxytryptamine↗
PubMed1982

Transmission of the quantum interaction of erythrocytes.

The previously demonstrated long-range quantum mechanical interaction between human erythrocytes suspended in plasma also occurs with artificial media. Certain macromolecules dissolved in phosphate-buffered saline will transmit the interaction provided their concentration is above a minimum. Extended macromolecules transmit the interaction, whereas a compact macromolecule (albumin) does not.

Cell Communication↗