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Biomedical subjects

J Field

Publications and source records attributed to J Field.

At least 163 records · Page 9Linked to original sources
PubMed1983

Lytic effect of heparin on liposomes: possible mechanism of lysis of red blood cells by heparin.

Heparin causes lysis of the multilamellar liposomes of all three charges, positive, neutral, and negative, and thus releases the entrapped [3H]glucose or chromate. The lytic effect of heparin is also observed in liposomes prepared from the lipids extracted from human red blood cells. Heparin is found to interact with the phospholipid bilayers, which suggests that the reported lytic effect of heparin on the red blood cells may be mediated through the membrane phospholipid components of these cells.

Blood Glucose↗
PubMed1983

Aspirin kinetics and platelet aggregation in man.

Our aims were (1) to determine the effect of six commercially available aspirin (ASA) preparations on in vitro platelet aggregation, and (2) to relate changes in platelet function to ASA kinetics. Each of six subjects took a single dose of one of the following preparations--600 mg Asproclear, 600 mg Bufferin, 600 mg Bi-prin, 600 mg compressed ASA, 650 mg Ecotrin, or 650 mg S.R.A.--in random order every 3 wk. Venous blood was drawn before and at 2, 4, 6, and 24 hr after ASA dosage to measure platelet aggregation in response to collagen and adenosine diphosphate and, at more frequent intervals, to characterize ASA kinetics. Asproclear, Bufferin, Bi-prin, and compressed ASA yielded peak plasma ASA levels of 28 to 56 mumol/l (5 to 10 mg/l) within 15 to 60 min and peak salicylic acid (SA) levels of 72 to 290 mumol/l (10 to 40 mg/l) within 2 hr. Ecotrin and S.R.A. yielded plasma SA levels of 14 to 87 mumol/l (2-12 mg/l) within 4 to 24 hr and no measurable ASA at any time after dosing. Platelet aggregation was inhibited to an equal extent by all preparations. The time course for this inhibition was the same for all preparations but Ecotrin (which led to a more delayed effect). There was significant recovery of collagen-induced platelet aggregation at 24 hr with all preparations but Ecotrin. With Ecotrin and S.R.A. there was inhibition of platelet aggregation in the absence of measurable circulating ASA. We postulate that this was due to acetylation of cyclooxygenase in the portal circulation and that inhibition of peripheral cyclooxygenase may be spared.

Adult↗
PubMed1982

Separation of the adenovirus terminal protein precursor from its associated DNA polymerase: role of both proteins in the initiation of adenovirus DNA replication.

A complex containing the 80,000-dalton precursor to the adenovirus (Ad)-encoded terminal protein (pTP) and a 140,000-dalton protein is required for Ad DNA replication in vitro. This complex has been separated into subunits by glycerol gradient centrifugation in the presence of urea. The isolated 140,000-dalton subunit contains a DNA polymerase activity which can be differentiated from all host DNA polymerases. No enzyme activity was detected with the isolated pTP. The requirements for reactions involved in the initiation of Ad DNA replication were determined by using the isolated subunits. The covalent addition of dCMP, the first nucleotide in the DNA chain, to the pTP, which serves as the primer for replication, required the DNA polymerase subunit as well as the pTP. Synthesis of viral DNA in vitro also required both subunits. The properties of the DNA polymerase suggest that it may be a viral gene product.

Adenoviruses, Human↗
PubMed1982

Combined immunosuppressive therapy with cyclosporin A and azathioprine. A synergistic effect in three of four experimental models.

Cyclosporin A (Cy A) by itself is limited in its clinical application by its dose-related liver and kidney toxicity. Combining Cy A with prednisone allows lower doses of Cy A to be used, but the side effects of steroids are cumulative. Thus, we tested the effect of Cy A and various drug-dose combinations with azathioprine (AZA) in four different models. The one that gave the best results with the least toxicity was 1.25 mg of Cy A plus 15 mg of AZA for islet allotransplantation in rats across a minor histocompatibility barrier and for heterotopic heart allotransplantation in rats across a major histocompatibility barrier. In the latter, using the same strain of rats, no significant effect can be shown in rat pancreas allotransplantation. In canine renal allografts, only one dose combination (5 mg of Cy A plus 2.5 mg of AZA) was tested, but it was synergistic. Cy A may potentiate the myelosuppressive effect of AZA, and the dose may have to be adjusted to avoid this problem.

Animals↗
PubMed1980

The mechanism of adaptive hyperlipogenesis: insulin receptor binding and glucokinase activity in rat liver during fasting and refeeding.

In the present study, rats were fasted for 3 days and subsequently refed for 1, 3, or 5 days. Measurements of insulin binding to its receptors on liver plasma membranes were carried out in conjunction with measurements of the activity of an insulin-regulated enzyme from liver cytosol, glucokinase. In response to the 3-day fast (chronic hypoinsulinemia), the insulin receptor number almost tripled, whereas the glucokinase activity was halved. The insulin receptor number slowly fell to control values during the 5 days of refeeding. In contrast, glucokinase activity rose to levels 2.5 times higher than control (5 times higher than the fasting values) after 1 day of refeeding. Altough the activity fell off somewhat during refeeding it was still dobule control values after 5 days refeeding. It was concluded that in the fasted rat there was a dissociation between insulin receptor concentration and the activity of the insulin-regulated enzyme glucokinase. However, the fasting-induced increase in receptor concentration appeared to play a permissive role in the rapid overshoot of glucokinase activity observed in the early stages of refeeding. Such a scheme would explain the metabolic changes occurring in the fasted-refed rat.

Animals↗
PubMed1980

Beneficial effect of dexamethasone on the "no reflow" phenomenon in canine myocardium.

The purpose of the present study was to determine if pretreatment with dexamethasone 6 mg.kg-1 would preserve coronary artery blood flow during reperfusion, thus preventing the no reflow phenomenon. Blood flow to small segments of the left ventricle was measured by the use of 15 micrometer tracer microspheres in intact dog hearts. During 2 hours of occlusion of the anterior descending coronary artery by balloon catheter, dexamethasone produced a small increase of the blood flow to perfused myocardium, when compared with untreated animals; this effect was not seen in underperfused segments of the myocardium. In nontreated animals, reperfusion of the underperfused portion of the left ventricle did not lead to a restoration of flow to normal when measured 1 hour later. In fact, the "no reflow" phenomenon resulted in a post reperfusion left ventricular segment which was similar to that measured during coronary arterial occlusion. However in the dexamethasone treated animals there was a decrease in the extent of left ventricular underperfusion from 19 to 6%. It is concluded that dexamethasone protects the border zone of canine myocardium during occlusion, and prevents the no reflow phenomenon in underperfused regions during reperfusion

Animals↗
PubMed1980

Infants' orientation to lateral sounds from birth to three months.

Head turning to off-centered sound was videotaped monthly in a group of infants during their first 3 months of life. Infants turned reliably toward the sound at birth and at 1 and 3 months of age. They failed to respond reliably at 2 months due to an increase in no-turn responses. Potential explanations for the temporary decline in orientation responses to sound are discussed.

Auditory Perception↗
PubMed1980

Problems of urgent consultations within an appointment system.

Patients for whom there is no appointment who ask to be seen on the same day can be a source of irritation. During March 1978, 214 of these patients were compared with 749 who made appointments. No evidence was found that such patients were abusing the system, and almost half were found to be children. It was concluded that these consultations were inevitable, but the attitude of the doctors to them may have been affecting their management. The system used produces some loss of personal care, the effects of which need to be studied further.

Adolescent↗
PubMed1979

Newborn infants orient to sounds.

In 2 experiments, the majority of 21 newborn infants who were maintained in an alert state consistently turned their heads toward a continuous sound source presented 90 degrees from midline. For most infants this orientation response was rather slow, taking median latencies of 2.5 sec to begin and 5.5 sec to end. The most important factors in producing this impressive response seem to be the method of holding the infants during testing and the nature of the auditory stimulus.

Acoustic Stimulation↗
PubMed1978

Type-specific radioimmunoassays for the gp70s of mink cell focus-inducing murine leukemia viruses: expression of a cross-reacting antigen in cells infected with the Friend strain of the spleen focus-forming virus.

We have isolated the gp70 of a helper-independent strain of a Friend mink cell focus-inducing (MCF) virus, Fr-MCF-1. This recombinant virus, like the previously described AKR-MCF viruses, has been shown by both biological and biochemical means to be an envelope gene recombinant between Friend murine leukemia virus (F-MuLV) and a mouse xenotropic virus. Utilizing (125)I- labeled Fr-MCF-1 gp70 and antiserum prepared against an MCF strain of Moloney type-C virus (Mol-MCF(83)), we have developed a radioimmunoassay which detects immunological determinant (s)contained in the gp70s of MCF viruses derived from F-MuLV, Mol-MuLV, and AKR-MuLV. This MCF determinant(s) is not detected in the ecotropic parents of each of these MCF viruses, nor in helper-independent murine xenotropic viruses derived from Swiss or BALB/c mice. A protein partially cross-reactive with the MCF gp70 determinant(s) is detected in a replicating xenotropic virus derived from NZB mice. Utilizing this MCF gp70 specific immunoassay, we can detect a cross-reacting gene product coded for by the Friend strain of the spleen focus-forming virus (SFFV) in rat fibroblasts nonproductively infected with SFFV. The results support earlier molecular hybridization studies which indicated that the genome of SFFV contains genetic information derived from both F-MuLV and xenotropic virus, and that the xenotropic-related sequences in SFFV are highly related to those found in MCF murine type-C viruses.

Antigens, Viral↗
PubMed1978

The ageing gut: a study of intestinal absorption in relation to nutrition in the elderly.

This study was designed to assess the functional efficiency of the ageing small intestine and the possible role of malabsorption in old people with nutritional deficiencies. Fifty subjects aged 65 to 92 years were studied, of whom 33 presented with anaemia, chronic diarrhoea or bone pains, and 17 were apparently healthy 'controls' with no relevant symptoms. Tests of intestinal function included blood xylose and iron absorption curves, a double isotope Schilling test, faecal fat, urinary indican and small bowel radiology, with duodenal aspiration and jejunal biopsy in some cases. On the basis either of steatorrhoea or at least two other abnormal parameters of absorption, there were 15 cases of malabsorption. Thirteen of these had symptoms but two were 'controls'. Four of these had duodenal diverticulosis, two had the post-gastrectomy syndrome, and one had calcific pancreatitis. Malabsorption in the remaining eight cases was not fully explained. The age range of this last group was 72--86 years; one of them had a contaminated small bowel and two showed some evidence of pancreatic insufficiency. Malabsorption emerged as a significant cause of low levels of serum iron, haemoglobin and calcium. The blood xylose test is a useful screening procedure for intestinal malabsorption in old age, but full evaluation calls for investigation of pancreatic function.

Aged↗