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Biomedical subjects

D Parker

Publications and source records attributed to D Parker.

At least 325 records · Page 18Linked to original sources
PubMed1978

Continuous comparison of transcutaneous and arterial oxygen tension in newborn infants with respiratory illnesses.

Transcutaneous oxygen tension (tcPO2) measured by two skin electrodes of different design, and arterial oxygen tension (PaO2) measured by an intravascular oxygen electrode, were continuously compared for periods of 6--27 h in 45 newborn infants with respiratory illnesses. One skin electrode (Dräger) had three microcathodes surrounded by a heated ring-shaped anode and the other (Roche) a large heated cathode. The electrodes were calibrated in vitro; 44 degrees C was found to be a suitable electrode temperature for the estimation of Pao2. tcPo2 recorded by the electrode with the microcathodes estimated Pao2 reasonably accurately for 6 h without the necessity for re-siting. tcPao2 recorded by the electrode with the large cathode gave a similar estimate of Pao2 for 3 h, but then tcPao2 often fell relative to Pao2. This fall was probably caused by skin changes at the electrode site. Poor skin perfusion causing underestimation of Pao2 by tcPo2 could not be identified by a number of methods tried.

Asphyxia Neonatorum↗
PubMed1978

Trancutaneous blood gas measurement by mass spectrometry.

A stainless steel, self heated, flat surface, skin surface probe, covered with a Mylar membrane, admits gases diffusing through the skin surface into a mass spectrometer at rates sufficiently low to provide reasonable measurement of blood PO2 and PCO2. A second thermistor against the Mylar and insulated from the probe monitors skin temperature as an index of blood flow. Advantages of the mass spectrometer method compared to electrodes are that a single sensor detects all gases, including anaesthetics, the sensor is simple in design, the same mass spectrometer can monitor several patients simultaneously, anaesthetics do not interfere (as with halothane and the O2 electrode), comparative checks with blood gas may be done using the same mass spectrometer, and perhaps, by summing all gases it may be possible to determine how fully arterialized the skin is.

Adult↗
PubMed1978

Delay in the development of the allergic response to metals following intratracheal instillation.

Intracheal intubation with the soluble metal salts potassium dichromate (K2Cr2O7) and nickel sulphate (NiSO4) causes a delay of up to 8 weeks in the development of delayed hypersensitivity to the specific agent. It is suggested that absorption of sensitizers by the respiratory route may, under certain circumstances, induce a state of specific immunological unresponsiveness, rather than necessarily lead to the development of a state of allergic sensitivity.

Animals↗
PubMed1978

Plasma parathyroid hormone and calcium are related to sleep stage cycles.

To study dynamic interactions among parathyroid hormone (PTH), plasma calcium, and brain states, seven normal subjects were studied for a total of eight nights in our sleep laboratories. Plasma samples were obtained at 10- to 20-min intervals for PTH and calcium determinations. Electroencephalogram, eye movements, and muscle tone were recorded to determine sleep stages. On each night, several distinct peaks in PTH concentration were seen, which in some cases exceeded the all night mean PTH by as much as 300%. Peaks in plasma PTH were significantly nonrandom and tended to recur about every 100 min. PTH concentration was significantly related to cycles of stages 3 and 4 sleep. Total plasma calcium varied less but was significantly related to cycles of rapid eye movement sleep and to cycles of stage 2 sleep. PTH and calcium were significantly interrelated, especially at high frequencies above 40 cycles/day (1 cycle 36 min). In the 14.4 cycles/day (1 cycle/100 min) frequency range where most PTH and calcium variability was found, however, PTH and calcium were more closely related to sleep stages than to each other. These results suggest that the regulation of PTH and calcium is complex and may involve interactions with neural systems.

Adult↗
PubMed1978

Comparison of transcutaneous oxygen tension with arterial oxygen tension in newborn infants with severe respiratory illnesses.

Transcutaneous oxygen tension (tcPO2), measured by two skin electrodes of different design, and arterial oxygen tension (PaO2), measured by an intravascular oxygen electrode, were continuously recorded for periods of six hours in 15 newborn infants with serious respiratory illnesses. Ten of the infants needed mechanical ventilation and three needed continuous positive airway pressure. One skin electrode had three microcathodes surrounded by a heated ring-shaped anode, and the other had a large heated cathode. The temperature of both electrodes was set at 44 degrees C and they were calibrated in vitro. The tcPO2 recorded by the electrode with the microcathodes was found to estimate PaO2 reasonably accurately for the whole six-hour duration of the study. The tcPO2 recorded by the electrode with the large cathode gave a similar estimate of PaO2 for three hours, but then tcPO2 often fell relative to PaO2. This fall was probably caused by skin changes at the electrode site. For a variety of reasons, our results suggest that measurement of tcPO2 is unlikely to replace continuous intravascular measurement of PaO2 in infants with severe respiratory illnesses.

Arteries↗
PubMed1977

Sensitization with Cr, Ni and Zr salts and allergic type granuloma formation in the guinea pig.

Guinea pigs were sensitized to potassium dichromate, nickel sulfate and sodium zirconium lactate by three methods of immunization in Freund's complete adjuvant: Polak, split adjuvant, and maximization (modified Magnusson and Kligman). These were followed after 2 weeks by weekly intradermal injections of 25 microng of the metal salt. Delayed hypersensitivity-like reactions developed 3 to 12 weeks after initial injection. Reactivity, although strong with an increase in thickness of over 0.7 mm and/or diameter of erythema of over 8 X 8 mm, was frequently transient, the animal losing reactivity on subsequent skin test or after 2 or 3 skin tests. In two-thirds of the experiments using sodium zirconium lactate, delayed hypersensitivity-like reactions at 24 hr developed into nodular lesions which reached peak intensity at 8 days and histologically contained histiocytes with an epithelioid cell appearance and giant cells. In some experiments, sodium zirconium lactate-sensitive animals showed cross reactivity with potassium dichromate, but not with nickel sulfate.

Animals↗
PubMed1977

Modulation of delayed-type hypersensitivity and cellular immunity to microbial vaccines: effects of cyclophosphamide on the immune response to tularemia vaccine.

Treatment of guinea pigs with cyclophosphamide before immunization with killed tularemia vaccine in Freund incomplete adjuvant produced a prolongation and intensification of delayed-type hypersensitivity and in vitro lymphocyte transformation reactions to tularemia antigen. Such reactions resemble those ordinarily associated with the administration of live tularemia vaccine, killed vaccine in Freund complete adjuvant, or recovery from natural infection. The immunopotentiation lasted longer than that seen previously in other antigenic systems with this drug and was dependent on the dose of vaccine used. More intense delayed skin reactivity could be transferred into normal controls by cells from immunized donors pretreated with cyclophosphamide than by cells from immunized donors that were not pretreated.

Animals↗
PubMed1977

The value of an assessment of erythema and increase in thickness of the skin reaction for a full appreciation of the nature of delayed hypersensitivity in the guinea pig.

Delayed type skin reactions in guinea pigs have been assessed by measuring three parameters: increase in skin thickness, diameter of erythema and intensity of erythema. Some groups of animals were immunized with different protein antigens in Freund's complete adjuvant with or without cyclophosphamide (CY) pretreatment; others received a single high dose of antigen intravenously at the time of immunization. The results emphasize the importance of measuring all three parameters for several days after skin testing. The intensity or erythema was found to be an especially useful parameter for assessing CY-induced modification of delayed hypersensitivity (DH) reactions. The increase in skin thickness, which can be measured objectively, was also valuable as both immediate and DH reactions are characterized by induration. The diameter of erythema could only be measured accurately for a short time after skin testing. Furthermore, the effects of intravenous antigen and CY pretreatment were not reflected by that parameter.

Animals↗
PubMed1977

The relation between B-cell stimulation and delayed hypersensitivity. The effect of cyclophosphamide pretreatment on antibody production.

Cyclophosphamide (CY), which can enhance some forms of delayed-type hypersensitivity if given 3 days before immunization, is also a potent suppressor of most antibody mediated 4-h skin reactions to protein antigens. However many haemagglutinating antibodies, which are present in serum at the time of skin testing, are not similarly suppressed. Antibody titres in some sera recovered from CY-pretreated guinea-pigs differ little from titres in control sera. This resistance to CY suggests that long-lived precursors characterize the B-cell lines that produce many haemagglutinating antibodies, whereas the CY-sensitive precursors of skin reactive antibodies, which mediate Arthus-type reactions, are probably rapidly dividing, short-lived cells. Furthermore, the novel appearance of BGG antibodies in sera from CY-pretreated animals immunized with DNP50-BGG indicates that haemagglutinating antibody responses to some antigens are regulated by CY-sensitive mechanisms.

Animals↗
PubMed1977

The relation of immune depression and B-cell stimulation during the development of delayed hypersensitivity to soluble antigens.

A comparison has been made of the effects of cyclophosphamide (CY) pretreatment and i.v. injection of a high dose of antigen on delayed hypersensitivity induced by proteins in Freund's incomplete and complete adjuvants. Five antigens have been studied: obalbumin (OA), bovine serum albumin (BSA) bovine gammaglobulin (BGG), DNP 5-BGG and DNP 50-BGG. A spectrum of reactivity has been detected depending upon the ability of the antigen to stimulate B-cell as well as T-cell activity. Bovine serum albumin and BGG behave as relatively weak antigens in which the T-cell response, measured by delayed hypersensityity, is easily suppressed by i.v. antigen and the B-cell modulating system, revealed by CY sensitivity, is poorly stimulated. These proteins, injected i.v., are weak stimulators of antibody-dependent Arthus reactions. On the other hand, OA, DNP 5-BGG and DNP 50-BGG behave as strong antigens, resisting suppression of the T-cell response by soluble antigen and exhibiting (in Freund's incomplete adjuvant) a strongly developed CY sensitive, B-cell modulating system. Strong Arthus reactivity is readily demonstrated following i.v. administration of these antigens. A dissociation has been demonstrated between B-cell modulation of T-cell function and unresponsiveness induced by i.v. antigen. The failure to reverse the latter type of unresponsiveness by cyclophosphamide pretreatment suggests that separate mechanisms are involved in these systems.

Animals↗