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Biomedical subjects

D Johnson

Publications and source records attributed to D Johnson.

At least 649 records · Page 36Linked to original sources
PubMed1982

Myelin formation in rotation-mediated aggregating cell cultures: immunocytochemical, electron microscopic, and biochemical observations.

Myelination was studied in aggregating cell cultures derived from mechanically 15- to 16-day fetal rat brains. Myelin basic protein (MBP) and myelin-associated glycoprotein (MAG) were localized immunocytochemically in 20-micrometers-thick Vibratome and 1-micrometer-thick Epon sections at 15, 20, 25, and 30 days in vitro. The occurrence of these proteins was correlated with the ultrastructural appearance of oligodendrocytes and myelin sheaths and with biochemical levels of MBP, MAG, and the myelin-related enzyme, 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP). MBP appeared in ultrastructurally immature oligodendrocyte cytoplasm at 15 days in vitro. As oligodendrocytes developed a more differentiated fine structure, MBP and MAG antisera stained oligodendrocyte processes and myelin sheaths. Immunostaining in Vibratome sections demonstrated that MBP was detectable in oligodendrocytes and myelin prior to MAG. At 25 days in vitro, all Vibratome sections contained MBP- and MAG-stained oligodendrocytes and myelin sheaths. Radioimmunoassays for MBP and MAG and enzyme assays for CNP in whole homogenates of the aggregates revealed that each of these components increased with the progression of myelination. However, MBP only reached 8% of the level in adult rat brain, while MAG and CNP increased to more than half of the adult level. The protein composition of myelin purified from 30-day aggregates resembled that of myelin purified from immature rat brain.

Animals↗
PubMed1981

Resistance of Plasmodium falciparum malaria to sulfadoxine-pyrimethamine ('Fansidar') in a refugee camp in Thailand.

Since it was first introduced 'Fansidar' (pyrimethamine 25 mg, sulfadoxine 500 mg) has been the preferred treatment for uncomplicated chloroquine-resistant Plasmodium falciparum malaria in Thailand. Because many patients at a refugee camp in Thailand did not seem to be responding to therapy 9 patients who received fansidar for P. falciparum infection were followed up with serial parasite counts. In all of them the infection was resistant to fansidar. The results of this study suggest that fansidar resistance is prevalent at this camp and should prompt more exhaustive studies of the epidemiology of fansidar resistance in the area.

Adolescent↗
PubMed1981

Immunization with purified myelin-associated glycoprotein does not evoke myelination-inhibiting or demyelinating antibodies.

Antisera produced in rabbits against purified myelin-associated glycoprotein did not inhibit myelin formation in cerebellar tissue cultures or demyelinate centrally or peripherally myelinated fibers in spinal cord-dorsal root ganglia cultures. These results suggest that antibodies directed against other myelin components are responsible for the myelination-inhibition and demyelination produced by anti-central nervous system (CNS) and anti-myelin antisera in vitro.

Animals↗
PubMed1981

Furosemide use in premature infants and appearance of patent ductus arteriosus.

Furosemide is a known stimulant of the renal release of prostaglandin E2, a potent dilator of the ductus arteriosus. A possible relationship between furosemide use in infants with respiratory distress syndrome (RDS) and the incidence of patent ductus arteriosus (PDA) was investigated using two different retrospective analyses. The amount of furosemide administered prior to the day a murmur was heard in the infants with PDA was higher than the amount given to patients without PDA during the same period. In a historical analysis of patients treated for RDS in the years 1970 through 1979, furosemide use and fluid intake appeared to be independent factors contributing to the incidence of PDA. The proposed relationship between furosemide use and the occurrence of PDA in patients with RDS warrants further study.

Ductus Arteriosus↗
PubMed1981

Subglottic stenosis in newborn intensive care unit graduates.

Five infants with postintubation subglottic stenosis were identified among 64 intubated patients in a follow-up clinic. The presence of laryngeal lesions was not suspected until three weeks to three months after discharge from their initial hospitalization. The onset of stridor, often precipitated by respiratory illness, led to the diagnosis, which in one case was delayed for as long as three months. No correlation was found between the presence of the severity of laryngeal pathology and the gestational age of the infants or the duration of intubation in this study. In spite of the precautions taken for the intubation of neonates requiring assisted ventilation, subglottic stenosis may develop in these infants and should always be considered in newborn intensive care unit graduates when they manifest refractory or recurrent respiratory obstruction in the first year of life. Routine follow-up of all intubated neonates to detect subglottic stenosis is recommended.

Critical Care↗
PubMed1981

pED100, a conjugative F plasmid derivative without insertion sequences.

The largest HindIII fragment of F includes the entire replication and transfer regions, and its circularisation with ligase gave the conjugative plasmid pED100. This plasmid, which contains none of the F insertion sequences, was essentially unable to mobilise the E. coli chromosome or to give integrative suppression of a dnaA strain.

Chromosome Mapping↗
PubMed1981

Preparation and characterization of antisera to the myelin-associated glycoprotein.

Rabbits were immunized with the myelin-associated glycoprotein (MAG) that had been purified from isolated rat brain myelin by selective extraction with lithium diiodosalicylate (LIS) and phenol followed by preparative SDS gel electrophoresis. Antibodies to MAG were detected qualitatively by immunodiffusion and quantitatively by a double antibody assay utilizing [3H]fucose-labeled MAG as antigen. The antisera were capable of precipitating between 300 and 500 micrograms of MAG/ml of serum under the conditions of the assay. Preincubation of the anti-MAG serum with other glycoproteins or glycolipids did not inhibit the precipitation of labeled MAG. Similarly, preincubation of the antiserum with LIS-phenol extracts of non-neural tissues did not inhibit the immune precipitation of MAG. The specificity of the antiserum was also indicated by the selective double antibody precipitation of MAG from solubilized whole myelin that contained a heterogeneous mixture of [3H]fucose-labeled glycoproteins. The antibodies to MAG were not effectively absorbed by whole brain homogenate or purified myelin, indicating that the antigenic site(s) is not accessible in the intact membranes, but can be exposed by treatment with detergent or partial purification. Low levels of antibodies reacting with MAG were detected in three rabbits with experimental allergic encephalomyelitis induced by injection of purified myelin in complete Freund's adjuvant.

Animals↗
PubMed1981

Immune thrombocytopenia in severe neonatal infections.

Thrombocytopenia occurs frequently in newborn infants with sepsis, but the exact mechanism remains obscure in those infants who do not have evidence of disseminated intravascular coagulation. Since recent work has suggested a possible immune mechanism for thrombocytopenia observed in adults with sepsis, we have investigated the role of platelet-associated immunoglobulin in severe neonatal infections. To detect PAIgG we use a method employing protein A and peroxidase-antiperoxidase as a labeled antibody. PAIgG was quantitated by phase contrast microscopy and expressed as a reactive index. Our control group included 16 normal newborn infants whose mean RI was 0.65 +/- 0.01 SE. In addition to the control group, five infants with nonimmune thrombocytopenia were included; their mean RI was 0.66 +/- 0.01 SE. Seventeen newborn infants with severe infections were assayed for PAIgG. Eight of nine infants with bacterial infections had increased RI, with a mean of 1.16 +/- 0.03 SE (P less than 0.01). Six of the eight infants with viral infections had elevated RI, with a mean of 1.23 +/- 0.03 SE (P less than 0.01). These findings suggest that an immune mechanism may be involved in the thrombocytopenia of severe neonatal infection.

Bacterial Infections↗
PubMed1981

Biochemical demonstration of the myelin-associated glycoprotein in the peripheral nervous system.

Recent immunocytochemical studies indicated that the myelin-associated glycoprotein (MAG) is localized in the periaxonal region of central nervous system (CNS) and peripheral nervous system (PNS) myelin sheaths but previous biochemical studies had not demonstrated the presence of MAG in peripheral nerve. The glycoproteins in rat sciatic nerves were heavily labeled by injection of [3H]fucose in order to re-examine whether MAG could be detected chemically in peripheral nerve. Myelin and a myelin-related fraction, W1, were isolated from the nerves. Labeled glycoproteins in the PNS fractions were extracted by the lithium diiodosalicylate (LIS)-phenol procedure, and the extracts were treated with antiserum prepared to CNS MAG in a double antibody precipitation. This resulted in the immune precipitation of a single [3H]fucose-labeled glycoprotein with electrophoretic mobility very similar to that of [14C]fucose-labeled MAG from rat brain. A sensitive peptide mapping procedure involving iodination with Bolton-Hunter reagent and autoradiography was used to compare the peptide maps generated by limited proteolysis from this PNS component and CNS MAG. The peptide maps produced by three distinct proteases were virtually identical for the two glycoproteins, showing that the PNS glycoprotein is MAG. The MAG in the PNS myelin and W1 fractions was also demonstrated by Coomassie blue and periodic acid-Schiff staining of gels on which the whole LIS-phenol extracts were electrophoresed, and densitometric scanning of the gels indicated that both fractions contained substantially less MAG than purified rat brain myelin. The presence of MAG in the periaxonal region of both peripheral and central myelin sheaths is consistent with a similar involvement of this glycoprotein in axon-sheath cell interactions in the PNS and CNS.

Animals↗
PubMed1981

Effects of zinc deficiency on rat parotid gland.

Hitherto, the effect of zinc deficiency on the rat parotid gland was not known. Male rats were fed either a low zinc diet (0.4-0.8 ppm Zn) or a zinc adequate diet (approximately 40 ppm Zn) for 35-42 days. The experimental animals exhibited retarded body growth, anorexia, loss of hair and decreases in plasma and hair zinc levels. In comparison to the ad libitum controls, the parotid glands of the pair-fed group showed a decrease in cell number, but an increase in cell mass, protein and amylase content. In the parotid glands of the experimental group, cell number was comparable to the pair-fed group, but there was a decrease in cell mass and protein content as compared to the pair-fed group. These findings suggest that zinc deficiency and its associated reduced food intake impair growth of the parotid gland and, further, that zinc deficiency per se appears to lead to a diminution in gland protein synthesis. It is proposed that a compromise in parotid gland function could be a contributory factor underlying the increased susceptibility to dental cares known to occur in zinc deficiency.

Animals↗
PubMed1981

Embolization of renal carcinoma.

Preoperative transcatheter embolization of a renal neoplasm is helpful to the urologist, especially with large, hypervascular tumors. When combined with nephrectomy and hormonal therapy, it offers promise in the management of patients with renal carcinoma. Delay between embolization and nephrectomy seems to be important, but the optimal time for stimulating a therapeutic response has not been established. Among 49 patients in this series with known metastases, occlusion of the renal artery followed 4 to 7 days later by nephrectomy and hormonal therapy changed the course of the disease, producing a 36% response rate.

Adult↗
PubMed1981

Absorption resistance of cerebrospinal fluid after subarachnoid hemorrhage in the monkey; effects of heparin.

The morbidity and mortality of subarachnoid hemorrhage (SAH) is directly related to blood in the subarachnoid space. Blood was injected intracisternally in 10 monkeys, and the absorption resistance of cerebrospinal fluid (CSF) was studied. The monkeys given injections of nonheparinized blood maintained high absorptive resistances, whereas the resistances of the group that received heparinized blood returned to the original levels. If heparinization of the CSF can be achieved rapidly after SAH and the deposition of fibrin clots along the pathways of CSF drainage can be prevented, the resorption of blood through the arachnoid granulations might be facilitated.

Absorption↗
PubMed1981

Vitamin A does not alter immunosuppressive properties of simultaneously administered steroids.

The use of immunosuppressive steroids in transplant patients is associated with complications of wound healing and increased peptic ulceration. Vitamin A is known to reverse ill effects of steroids on wound healing and peptic ulcerogenesis; however, its effects on the immunologic properties of steroids are less well defined. The effect of vitamin A on steroid-induced immunosuppression was assessed through first and second set skin graft rejection, mixed lymphocyte culture reaction, and humoral antibody response to sheep erythrocytes. Results show tha vitamin A does not affect in vivo immunosuppression, although in vitro studies yield a conflicting result.

Adrenal Cortex Hormones↗
PubMed1981

Postpericardiotomy syndrome in adults: incidence, autoimmunity and virology.

While continuing a study of immunologic and virologic aspects of the postpericardiotomy syndrome (PPS) in infants and children, we undertook a companion study in adults. Whereas the incidence in 119 children was 27.8%, as is usual for our hospital, the incidence in 142 adults was 17.6%. Most of the operations (95 of 142) were performed on patients who were 50-69 years old. Incidence decreased as age increased: 28.5% for ages less than 40 years, 19.7% for ages 40--59 years, 14.2% for ages 60--69 years, and 10% for ages 70 years and older. Heart-reactive antibody in high titer was found in all patients with PPS; a rise in antiviral antibody to one or more of a battery of eight common viruses (adenovirus, cytomegalovirus, and coxsackie-virus B 1 to 6) was identified in 68% of these with PPS but in only 5% of those without clinical manifestations. We conclude that in adults, as in children, PPS may be an autoimmune phenomenon triggered by viral illness.

Adult↗
PubMed1981

A precision pump for simulated cardiographic studies.

A system simulating physiologic and pathologic changes in left-ventricular volume is presented. Its purpose is to provide a model to establish the accuracy of current equipment for assessing a heart's performance where the actual volume and size are measurable. The versatility of the model allows a wide range of variability of various parameters for simulation of many clinical situations.

Cardiac Output↗