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Biomedical subjects

D Donaldson

Publications and source records attributed to D Donaldson.

At least 109 records · Page 6Linked to original sources
PubMed1991

The cost of rural health services in Papua New Guinea.

In 1988 a countrywide study was conducted on the costs of rural health services in Papua New Guinea. 16% of all health centres and subcentres were surveyed. Information was collected on physical facilities, recurrent costs, staff time allocation, service outputs and quality of services. Wide variation was found in the costs of rural health facilities overall, and significant differences were found between the costs and outputs of health centres and subcentres. Average levels of service output were found to be similar at church and government facilities but average levels of utilization by the population were higher at church facilities. Despite government policy on extension of preventive health care, a strong emphasis was found on curative care. Many facilities were found to have significant excess bed capacity. Recurrent financing for transportation and maintenance was found to be inadequate.

Cost Allocation↗
PubMed1990

Identification and characterization of an inhibitor of haemopoietic stem cell proliferation.

The haemopoietic system has three main compartments: multi-potential stem cells, intermediate stage progenitor cells and mature cells. The availability of simple reproducible culture systems has made possible the characterization and purification of regulators of the progenitor cells, including colony-stimulating factors and interleukins. In contrast, our knowledge of the regulators involved in the control of stem cell proliferation is limited. The steady-state quiescent status of the haemopoietic stem cell compartment is thought to be controlled by locally acting regulatory elements present in the stromal microenvironment, but their purification has been hampered by the lack of suitable culture systems. We have recently developed a novel in vitro colony assay that detects a primitive cell (CFU-A) which has similar proliferative characteristics, in normal and regenerating bone marrow, to the CFU-S (haemopoietic stem cells, as defined by the spleen colony assay) and which responds to CFU-S-specific proliferation regulators. We have now used this assay to purify to homogeneity a macrophage-derived reversible inhibitor of haemopoietic stem cell proliferation (stem cell inhibitor, SCI). Antibody inhibition and sequence data indicate that SCI is identical to a previously described cytokine, macrophage inflammatory protein-1 alpha (MIP-1 alpha), and that SCI/MIP-1 alpha is functionally and antigenically identical to the CFU-S inhibitory activity obtained from primary cultures of normal bone marrow cells. The biological activities of SCI/MIP-1 alpha suggest that it is a primary negative regulator of stem cell proliferation and that it has important therapeutic applications in protecting haemopoietic stem cells from damage during cytotoxic therapies for cancer.

Amino Acid Sequence↗
PubMed1990

Focal cerebral infarction in cats in the presence of hyperglycemia and increased insulin.

Although it has been well established that hyperglycemia increases cerebral damage following transient cerebral ischemia, its effect on permanent focal ischemia is controversial. We hypothesized that other factors associated with hyperglycemia, such as plasma insulin, may alter the brain's response to hyperglycemia. The objective of this study was to determine if hyperglycemia changes infarction size following 8 hr of middle cerebral artery occlusion in the anesthetized cat and to examine if changes in plasma insulin levels alter hyperglycemia's effects. Infarct size in hyperglycemic cats with increased plasma insulin (38.3 +/- 8.4, mean +/- SE) or in hyperglycemic cats without increased plasma insulin (30.5 +/- 7.6%) was not significantly different from that of ischemic controls (33.8 +/- 2.8%). However, the variability in infarct size tended to be greater (P = 0.0647) among all hyperglycemic cats compared to control animals. The source of the variability is unknown, but this observation is dependent on the exact nature of the focal ischemic insult (i.e., degree of collateral blood supply) and that this effect may vary greatly from individual to individual within a population.

Analysis of Variance↗
PubMed1990

Albumin Redhill (-1 Arg, 320 Ala----Thr): a glycoprotein variant of human serum albumin whose precursor has an aberrant signal peptidase cleavage site.

Albumin Redhill is an electrophoretically slow genetic variant of human serum albumin that does not bind 63Ni2+ and has a molecular mass 2.5 kDa higher than normal albumin. Its inability to bind Ni2+ was explained by the finding of an additional residue of Arg at position -1. This did not explain the molecular basis of the genetic variation (since proalbumin contains adjacent Arg residues at -1 and -2) or the increase in apparent molecular mass. Fractionation of tryptic digests on concanavalin A-Sepharose followed by peptide mapping of the bound and unbound fractions and sequence analysis of the glycopeptides identified a mutation of 320 Ala----Thr. This introduces an Asn-Tyr-Thr oligosaccharide attachment sequence centered on Asn-318 and explains the increase in molecular mass. This, however, did not satisfactorily explain the presence of the additional Arg residue at position -1. DNA sequencing of polymerase chain reaction-amplified genomic DNA encoding the prepro sequence of albumin indicated an additional mutation of -2 Arg----Cys. This introduces a prepro sequence, Met-Lys-Trp-Val-Thr-Phe-Ile-Ser-Leu-Leu-Phe-Leu-Phe-Ser-Ser-Ala-Tyr- Ser-Arg-Gly-Val-Phe-Cys-Arg (cf.-Tyr-Ser-Arg-Gly-Val-Phe-Arg-Arg- in normal human pre-proalbumin). We propose that the new Phe-Cys-Arg sequence in the propeptide is an aberrant signal peptidase cleavage site and that the signal peptidase cleaves the propeptide of albumin Redhill in the lumen of the endoplasmic reticulum before it reaches the Golgi vesicles, the site of the diarginyl-specific proalbumin convertase.

Alanine↗
PubMed1990

Relationship between plasma glucose, brain lactate, and intracellular pH during cerebral ischemia in gerbils.

The dose-response relation between plasma glucose and brain lactate and the relation of these parameters to intracellular pH during severe cerebral ischemia have not been well characterized over a wide range of plasma glucose levels. Experiments to delineate these relations in the gerbil model of global ischemia were performed by using phosphorus-31 nuclear magnetic resonance spectroscopy to measure intracellular pH and a new method to measure brain lactate. Ischemia increased final brain lactate linearly 4 mumol/g for every 100 mg/dl increase in plasma glucose up to 650 mg/dl (p = 0.0001, r2 = 0.9); beyond 650 mg/dl, saturation of the glucose transport-glycolysis system occurred. Plasma glucose correlated better with ischemic intracellular pH than did brain lactate. However, when brain lactate levels are compared with intracellular pH during ischemia, the relation may be threshold rather than linear. A narrow transition zone, during which ischemic intracellular pH decreased precipitously with increasing brain lactate, was observed between 17 and 22 mumol/g; below 17 mumol/g, intracellular pH remained stable at 6.8-6.9, whereas above 22 mumol/g, intracellular pH decreased maximally to about 6.2. The marked decrease in intracellular pH that occurs when brain lactate surpasses 17 mumol/g suggests that this sudden drop in intracellular pH may account for the "lactate threshold" for increased cerebral ischemic damage.

Analysis of Variance↗
PubMed1989

The combined effect of nitrous oxide and oxygen and electrical stimulation during restorative dental treatment.

A total of 124 adult patients were treated with nitrous oxide (N2O) and oxygen (O2), an electrical analgesic, or a combination of N2O/O2 and an electrical analgesic during restorative dental procedures. The use of electrical analgesic or N2O/O2 without local anesthetics resulted in a high failure rate and poor patient acceptance. However, combining N2O/O2 sedation with electrically induced analgesia resulted in a statistically significant improvement over either technique used alone, and provided an overall 81% success rate when used during restorative dentistry.

Adult↗
PubMed1989

The mechanisms of nitrous oxide scavenging devices.

A recent publication discussing the concern with nitrous oxide pollution in dental offices and the methods available to reduce this risk aroused interest in scavenging systems. This is the first in a series of three articles and will explain the mechanisms of the nitrous oxide systems available. The second describes the testing of these systems under ideal conditions and the third will assess their efficiency in various dental offices and the factors which were found to detract from that efficiency.

Air Pollution↗
PubMed1989

A comparison of the effectiveness of nitrous oxide scavenging devices.

Four nitrous oxide scavenging systems were tested for their efficiency under ideal standardized conditions. The volunteers received 35% nitrous oxide for 20 minutes and the levels of nitrous oxide recorded and averaged every five minutes. No density was carried out. All four systems achieved levels below 30 parts per million. With the recommended limit for nitrous oxide levels in dental operatory being 50 parts per million (ppm) rather than the several thousand ppm reached without scavenging, it is necessary to ensure that the scavenging devices available are capable of achieving this level. To do so under normal dental operating conditions provides many variables, such as the type of procedure carried out, movement by the patient, ventilation efficiency of the operatory, type of mouth pack utilized etc. This investigation was therefore designed to eliminate all operator and procedure variabilities. Each system was evaluated under ideal identical conditions and with no actual treatment being carried out.

Air Pollutants, Occupational↗
PubMed1989

The efficiency of nitrous oxide scavenging devices in dental offices.

Five scavenging systems were installed in 10 dental office and the levels of nitrous oxide were closely monitored for each. While the readings were higher than the previous non-clinical study, all appeared to be reasonably efficient. The various factors which caused increases in background levels were also recorded in the investigation.

Air Pollutants, Occupational↗
PubMed1988

Do antidepressants cause folic acid depletion? A pilot study.

Chronic administration of tricyclic antidepressants is common; folic acid depletion is a potential consequence adversely affecting the mental state. In a pilot study prior to research in the community, serum and red cell folate and serum vitamin B (12) levels were measured in the following elderly psychiatric inpatients: 14 controls (patients not receiving any drugs with known antifolate activity), 11 receiving tricyclic antidepressants, 13 receiving antipsychotics (phenothiazines) and four receiving an anticonvulsant (carbamazepine). Patients on prolonged treatment with carbamazepine or phenothiazine drugs had lower concentrations of folate in serum and erythrocytes compared with controls; the decrease was statistically significant for the effect of phenothiazines on serum folate levels. Tricyclic antidepressants, which are in widespread use in the community, did not cause folate depletion during the first two years of treatment.

Aged↗
PubMed1984

Albumin Redhill, a human albumin variant.

Albumin Redhill, a variant human albumin with the same C-terminal amino acid as albumin A but with arginine at the N-terminus has been isolated by chromatofocusing from the sera of an English family. Albumin Redhill appears to contain two sites of mutation in its protein chain and is probably a proalbumin. The ability of albumin Redhill to bind Ni(II) or Cu(II) ions is considerably less than that of albumin A.

Aged↗