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Biomedical subjects

M Singer

Publications and source records attributed to M Singer.

At least 181 records · Page 10Linked to original sources
PubMed1990

Expression of two molecular forms of the complement decay-accelerating factor in the eye and lacrimal gland.

Complement is present in ocular fluids, but the molecular mechanism(s) restricting its activation to exogenous targets and not to autologous ocular cells are currently unknown. To clarify how this control is achieved, monoclonal antibody (mAb)-based techniques were used to examine the eye, the lacrimal gland, and ocular fluids for the decay-accelerating factor (DAF), a membrane regulatory protein which protects blood cells from autologous complement activation on their surfaces. Immunohistochemical staining of tissue sections revealed DAF antigen on corneal and conjunctival epithelia, corneal endothelium, trabecular meshwork, and retina, as well as on lacrimal gland acinar cells and in adjacent lumens. By flow cytometry, cultures of conjunctival epithelium exhibited the highest DAF levels and levels on corneal epithelium greater than corneal endothelium greater than conjunctival fibroblasts. Biosynthetic labeling of corneal endothelium yielded de novo DAF protein with an apparent molecular weight (Mr) of 75 kD, approximating that of blood cell DAF protein, and digestions of conjunctival epithelium with phosphatidylinositol-specific phospholipase C (PI-PLC), an enzyme which cleaves glycoinositolphospholipid membrane anchors, released approximately 70% of the ocular surface DAF protein similar to leukocyte surface DAF protein. Quantitations of DAF by radioimmunometric assay employing mAbs against two DAF epitopes revealed 325 ng/ml (n = 12), 4.8 ng/ml (n = 10), and 22.0 ng/ml (n = 8) of soluble DAF antigen in tears, aqueous humor, and vitreous humor, respectively. Western blot analyses of the tear DAF antigen revealed two DAF forms, one with an apparent Mr of 72 kD resembling membrane DAF forms in other sites, and a second with an apparent Mr of 100 kD, which is previously undescribed. Since DAF activity is essential physiologically in protecting blood cells from autologous complement attack, the identification of DAF on the ocular surface, intraocularly, in the lacrimal gland, and in tears suggests that DAF-mediated control of complement activation is also required in these locations.

Antibodies, Monoclonal↗
PubMed1989

Tumour necrosis factor in bronchopulmonary secretions of patients with adult respiratory distress syndrome.

Tumour necrosis factor (TNF) concentrations were measured in the bronchopulmonary secretions of 5 patients with the adult respiratory distress syndrome. Each patient underwent fibreoptic bronchoscopy and bronchopulmonary aspiration, and control samples were obtained in an identical manner from 24 patients who underwent bronchoscopy for other reasons (8 had tuberculosis, 6 had sarcoidosis, and 10 had haemoptysis but no abnormal findings). Aspirated fluid was assayed for the presence of TNF by use of an enzyme-linked immunosorbent assay. In the 5 patients with adult respiratory distress syndrome, TNF concentrations exceeded 500 U/ml (12.5 ng/ml), whereas in the control samples no TNF was detected.

Bronchoalveolar Lavage Fluid↗
PubMed1989

Optimisation of positive and expiratory pressure for maximal delivery of oxygen to tissues using oesophageal Doppler ultrasonography.

OBJECTIVE: To assess oesophageal Doppler ultrasonography as a convenient means of optimising positive end expiratory pressure for maximal delivery of oxygen to tissues. DESIGN: Measurements of blood flow, arterial oxygen saturation, and cardiac output by thermodilution (when available) at baseline and at 20-30 minutes after each incremental increase (2.5-5.0 cm H2O) in positive and expiratory pressure to a maximum of 20.0 cm H2O. If the cardiac output fell by more than 15% measurements were repeated after stepwise decreases in positive end expiratory pressure. No other manoeuvre such as endotracheal suction or changing ventilator settings, drug or fluid dosage, or the patient's position was performed for at least one hour before the start of the study or during it. SETTING: Intensive care unit. PARTICIPANTS: 10 Patients being mechanically ventilated for acute respiratory failure who had stable haemodynamic and blood gas values and required a fractional inspired oxygen concentration of greater than or equal to 0.45. They were assessed on a total of 11 occasions. INTERVENTIONS: Incremental increases in positive end expiratory pressure followed when indicated by stepwise decreases. END POINT: The positive end expiratory pressure providing maximal delivery of oxygen to tissues. MEASUREMENTS AND MAIN RESULTS: Arterial oxygen saturation increased with positive end expiratory pressure in all patients by an average of 6.1%. In nine of the 11 studies, however, cardiac output fell by 15% to 30% after the second increment. On the two other occasions cardiac output and oxygen delivery rose by up to 54%. Positive end expiratory pressure was decreased on seven occasions; there was considerable individual variation in the time taken for cardiac output to rise and arterial oxygen saturation to fall. In six patients good agreement was seen between the results from Doppler ultrasonography and thermodilution, the mean of the differences being -0.3% with narrow limits of agreement (-14.4% to 13.9%). CONCLUSIONS: Oesophageal Doppler ultrasonography is a rapid, safe, and reliable technique for optimising positive end expiratory pressure to obtain maximal delivery of oxygen to tissues. The results show the need to consider haemodynamic consequences when altering positive end expiratory pressure.

Acute Disease↗
PubMed1989

Multiple carpo-metacarpal dislocations.

Ten patients with closed multiple carpo-metacarpal dislocations have been reviewed. Closed manipulation was found to be successful if performed within two days of the injury. Plaster cast immobilisation supplemented by percutaneous Kirschner wire fixation is recommended to maintain the reduction, due to the unstable nature of the dislocation. Early appropriate treatment of these injuries carries a good prognosis.

Bone Wires↗
PubMed1989

The coming of age of critical medical anthropology.

This paper reviews the development over the last 15 years of a broadening critical trend in the field of medical anthropology by: (1) examining shortcomings of conventional medical anthropology that led to interest in critical alternatives; (2) examining historical and occupational factors that tend to conservatize the subdiscipline; (3) reviewing the body of literature produced thus far by its adherents; and (4) suggesting directions for future work.

Anthropology↗
PubMed1989

Effects of atrial natriuretic peptide on systemic haemodynamics and cardiac function in normal man.

Atrial natriuretic peptides (ANP) reduce blood pressure. Animal experiments suggest that this depressor action results from a reduction in cardiac output rather than peripheral vascular resistance but it is unresolved whether this is wholly due to their effect of reducing left ventricular filling or whether they have a negatively inotropic effect. We have therefore investigated the effects of ANP in normal man using Doppler measurements of ascending aortic blood flow. Six normal volunteers underwent infusions of placebo and incremental doses of ANP in the range 0.25 to 12 micrograms.min-1. Each infusion was given for 15 min and measurements made both in the supine and erect positions (passive tilt). In both positions ANP had dose dependent effects of increasing heart rate (HR) and maximal acceleration whilst lowering an index of systemic vascular resistance (ISVR). In the erect position ANP also lowered systolic blood pressure. In the 30 min after completion of the infusions there were significant decreases in peak velocity and cardiac output with increases in ISVR in both positions, but HR fell and diastolic pressure increased only when supine. During the course of the experiment mean haematocrit (SEM) increased from 43.9 (1.2) to 46.7 (1.0), indicating a mean reduction in plasma volume of 10.5%. This occurred despite a negative fluid balance of only 31(7) ml over the 2 h. These data suggest that ANP is not negatively inotropic and that, at pharmacological doses, it is an arteriolar dilator of rapid offset and reduces cardiac filling pressures by a mechanism of slower offset.

Adult↗
PubMed1989

Continuous hemodynamic monitoring by esophageal Doppler.

A new 5.1-mHz continuous wave esophageal Doppler system is described for continuous hemodynamic monitoring in ventilated patients. Information is obtained from the size, shape, and changes in shape of the velocity waveforms of descending aortic blood flow. Minute distance, the product of waveform area (stroke distance) and heart rate, provides a measure of cardiac output. Good agreement between this technique and thermodilution was shown for cardiac output changes with 238 paired measurements made in 38 patients. The coefficient of variation was lower for Doppler (3.8%) than for simultaneous thermodilution measurements (6.2%). Seventy-eight changes in left ventricular filling, systemic vascular resistance, or inotropic state produced consistent alterations in waveform shape with a narrow-based waveform being indicative of hypovolemia. This development marks a significant advance in the technique and provides a useful alternative to invasive hemodynamic monitoring, both in the ICU and perioperatively.

Adult↗
PubMed1989

A collection of strains containing genetically linked alternating antibiotic resistance elements for genetic mapping of Escherichia coli.

We present a collection of 182 isogenic strains containing genetically linked antibiotic resistance elements located at approximately 1-min intervals around the Escherichia coli chromosome. At most positions both Tn10 (Tetr) and TN10kan (Kanr) elements are available, so that the collection contains a linked set of alternating antibiotic resistance markers. The map position of each insertion has been aligned to the E. coli genetic map as well as to the Kohara ordered clone bank. These strains are designed to be used in a rapid two-step mapping system in E. coli. In the first step, the mutation is localized to a 5- to 15-min region of the chromosome by Hfr mapping with a set of Hfr strains containing either Tn10 or Tn10kan elements located 20 min from their respective origins of transfer. In the second step, the mutation is localized to a 1-min region by P1 transduction, with a collection of isogenic insertion strains as donors. We discuss the uses of this collection of strains to map and eventually to clone a variety of mutations in E. coli.

Chromosome Mapping↗
PubMed1989

Freeze fracturing properties of native and heat-adapted Chinese hamster ovary (CHO) cells.

Chinese hamster ovary cells were either maintained at 37 degrees C (native cells) or heat adapted by exposure to a temperature of 40 degrees C for 2 h. Thereafter, native and heat-adapted cells were incubated at different temperatures for various times, harvested, fixed with glutaraldehyde and glycerol, and studied by freeze fracture microscopy. We observed that the fracture plane either passed through the cell, exposing cytoplasm, or stayed within the plasma membrane, and that the location of the fracture plane was strongly determined by the previous thermal history of the cell. We believe that these differences reflect changes in membrane lipid packing arrangements.

Animals↗
PubMed1989

Invasive hemodynamic monitoring in the United Kingdom. Enough or too little?

In response to a questionnaire regarding use of invasive hemodynamic monitoring techniques in the United Kingdom, 211 replies were received from 276 hospitals (76.4 percent). Over one fifth of Intensive Care or combined Intensive/Coronary Care Units did not use pulmonary artery catheters (PAC); of those that did, two thirds used no more than two/month, and only two units used more than ten/month. Nearly a quarter did not possess a cardiac output computer. Only 18 complications occurring in the preceding year were reported, which suggests underrecognition. Clinical indications and lack of expertise were the main reasons proferred for limited use; however, cost (which was generally underestimated) and clinical value also were mentioned. The majority of CCUs did not use PACs, and only 10 percent used more than two/month. Only 10 percent of hospitals have used them perioperatively and most cardiothoracic units used no more than two PACs/month. In view of the large difference in numbers used between the United Kingdom and the United States, a large-scale study is warranted to determine the actual value of PACs in reducing mortality and morbidity.

Catheterization, Peripheral↗
PubMed1989

Focused search of semantic cases: the effects of question form and case status.

The present study was designed to identify and examine some of the variables that influence the focused search of semantic cases in question answering. Singer, Parbery, and Jakobson (1988) have previously reported that people can focus on the case interrogated by a question and can largely disregard irrelevant cases. In the present study, people learned facts, such as the pilot painted the garage with the roller, the spraygun, and the brush. One day later, they answered questions that focused on a particular case. For example, the question did the pilot paint with a spraygun? focuses on the instrument case. Experiment 1 revealed that people can focus on a particular case in response both to complete questions and to comparable word probes, such as "pilot spraygun." Therefore, the given-new structure of questions is not essential to focused search. Experiment 2 revealed that people have a difficult time ignoring the agent case, even when it is irrelevant to the question. This corroborates proposals that agent and action information are closely interrelated in the representation of a fact. These results help to delineate the phenomenon of the focused search of semantic cases.

Cues↗