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Biomedical subjects

D Johnson

Publications and source records attributed to D Johnson.

At least 541 records · Page 30Linked to original sources
PubMed1988

Detection of surface differences between closely related cell populations by partitioning. Cultured K-562 cell sublines.

The K-562 cell line is a culture of human leukemia stem cells originally derived from a patient with chronic myelogenous leukemia in blast crisis. We have applied a sensitive method capable of detecting subtle differences in charge-associated and noncharge-related cell surface properties between closely related cell populations to K-562 cells from different sources and having different histories. The method consists of isotopically labeling aliquots of each of two cell populations to be compared with 51Cr-chromate and mixing the labeled cells with an excess of unlabeled cells with which they are to be compared. The mixtures are subjected to countercurrent distribution in either a charge-sensitive or a noncharge-sensitive dextran-poly(ethylene glycol) aqueous two-phase system. The distribution curves are analyzed for total cells (in terms of electronic counts) and labeled cells (in terms of cpm). Alterations in relative specific activities through the distribution curves are indicative of differences in surface properties between such cell populations. Using this method we have found surface differences, both charge-associated and noncharge-related, between any two K-562 cell sublines examined. Interestingly, whereas we observed differences among K-562 sublines, we never witnessed a change in surface properties of the respective sublines. The differences among the sublines examined remained unaltered for more than 40 passages in our hands. It thus appears likely that the event(s) leading to an altered K-562 cell surface, detectable by partitioning, does not occur gradually.

Cell Line↗
PubMed1988

High spatial resolution spectroscopy in the elemental microanalysis and imaging of biological systems.

The application of analytical electron microscopy to the high spatial resolution study of biological systems is reviewed. Specimen preparation, quantitative analysis, capabilities and limitations are all discussed, principally in the context of energy-dispersive X-ray analysis. Results are presented using both current techniques and the developing quantitative image analysis. Finally the role of new instrumental approaches, including electron energy loss spectrometry, is discussed.

Animals↗
PubMed1988

Rhizomelic chondrodysplasia punctata: clinical, pathologic, and biochemical findings in two patients.

The clinical, pathologic, and biochemical features of rhizomelic chondrodysplasia punctata are described in two patients. Although both patients had clinical and radiologic similarities, one patient survived for only 13 days and the other is still alive at 8 years. The most prominent pathologic feature was the marked degenerative change in the chondrocytes from resting cartilage. Fibroblast alkyldihydroxyacetone phosphate synthase activity was markedly reduced in both patients (approximately 10% of control mean); in contrast, dihydroxyacetone phosphate acyltransferase activity was only moderately reduced (50% of control mean). Alkyl and alk-l-enyl ether (plasmalogens) levels were very low in brain and liver. The accumulation of phytanic acid observed in plasma or liver was paralleled by a reduced ability of the patients' fibroblasts to oxidize phytanic acid. Our data indicate that the genetic defect in rhizomelic chondrodysplasia punctata results in abnormalities in two apparently unrelated pathways (i.e., phytanic acid oxidation and ether lipid biosynthesis.

Brain↗
PubMed1988

Infarction of the upper limbs associated with oligohydramnios and intrauterine compression.

We describe a case of neonatal infarction involving both upper extremities. Oligohydramnios, resulting in compression of both arms within the uterus, is proposed as the cause of this congenital gangrene. Despite attempted conservative management, both arms became flaccid and moist. By the third day of life, the infant's worsening cardiovascular status necessitated amputation. This rare disorder has varying degrees of presentation. Limbs have been salvaged with conservative management of the extremity, coupled with appropriate surgical intervention, and neonatal intensive care.

Adult↗
PubMed1988

Cholinergic amacrine cells of the rabbit retina contain glutamate decarboxylase and gamma-aminobutyrate immunoreactivity.

The transmitters acetylcholine and gamma-aminobutyrate (GABA) play critical roles in the formation of receptive-field properties of retinal ganglion cells. In rabbit retina, cholinergic amacrine and displaced amacrine cells were identified by immunohistochemical staining for the enzyme choline acetyltransferase and by their avid accumulation of the fluorescent dye 4',6-diamidino-2-phenylindole. Several GABA-immunoreactive and glutamate decarboxylase-immunoreactive cell types, including a prominent population of small, round amacrine and displaced amacrine cells, were also identified. Double-label experiments demonstrated that all amacrine and displaced amacrine cells that prominently accumulate 4',6-diamidino-2-phenylindole contain GABA and glutamate decarboxylase immunoreactivity. However, not all GABA-immunoreactive cells accumulate this dye. Quantitative analysis of the ganglion cell layer of whole mount preparations of the retina showed that choline acetyltransferase-immunoreactive cells and the majority of GABA-immunoreactive cells have a small, round shape and similar cell density profiles that parallel that of displaced amacrine cells. These studies establish that cholinergic cells are a major subpopulation of GABA-immunoreactive amacrine and displaced amacrine cells. The role these cells have in the formation of ganglion cell receptive-field properties may be parsimoniously explained by an excitatory postsynaptic action mediated by acetylcholine and an inhibitory presynaptic action mediated by GABA.

Acetylcholine↗
PubMed1988

Homograft replacement of single aortic valve cusps: 22 years follow-up.

Single aortic valve cusp replacement with fresh aortic homografts were performed in four patients from November 1966 to April 1970. All had preoperative aortic insufficiency due to destruction of a single cusp, with the remaining two cusps structurally and functionally intact. Replacement was performed using the noncoronary cusp from fresh aortic valve homografts. Patient one had homograft cusp replacement of the left coronary cusp at age 13 due to bacterial endocarditis. She recently underwent mitral valve replacement; study and inspection of the aortic valve showed it to be structurally and functionally intact 22 years following homograft cusp replacement. Patient two sustained a gunshot wound perforating his right coronary cusp. He underwent single cusp replacement in January 1967. Currently, he is asymptomatic and has been without evidence of significant aortic valve dysfunction for the past 21 years. Patient three had destruction of the noncoronary cusp due to endocarditis and had homograft cusp replacement in October 1967. Four and a half years later he developed recurrent endocarditis, presented with severe congestive heart failure due to aortic insufficiency, and died. Patient four had bacterial endocarditis affecting the right coronary cusp and had replacement in April 1970. In February 1980, he underwent aortic valve replacement for aortic stenosis. Inspection revealed calcification of the other two cusps with the homograft cusp structurally normal. In summary, follow-up of homograft replacement of single aortic valve cusps from 4 1/2 to 22 years, shows it to be a durable and feasible alternative to prosthetic valve replacement.

Adolescent↗
PubMed1988

Degradation of explanted polyurethane cardiac pacing leads and of polyurethane.

Polyurethane cardiac pacing leads explanted at autopsy and from reoperated patients were examined for degradation in the insulation. Scanning electron microscopy (SEM) analysis showed cracks on the polyurethane surface which were both parallel and perpendicular to the longitudinal axis of the lead. Surface analyses of leads were performed using Fourier-Transform Infra-red (FT-IR) spectrophotometry in the attenuated total reflectance mode. The FT-IR spectra of visibly deteriorated polyurethane from explanted lead sheaths were compared with that of unused polyurethane tubing used for such sheaths. Changes were most evident in the regions of 3000-2800, 1730 and 1368 cm-1. The observed alterations in the FT-IR spectra were consistent with a degradation mechanism involving oxidative chain cleavage in the polyurethane amorphous regions. New polyurethane tubing (Pellethane-Type 80A) was exposed to sodium hypochlorite to simulate a possible in-vivo process and generate reference material. Degradation with associated decreases in tensile strength and molecular weight was recorded. This study showed that polyurethane insulation used in pacing leads is susceptible to oxidative degradation.

Biocompatible Materials↗
PubMed1988

Absence of gliosis in the brains of epileptic fowl.

Chickens homozygous for the epi gene (epileptics) suffer from spontaneous seizures throughout their life, whereas heterozygous (carriers) are phenotypically normal. Seizures can also be evoked in epileptics by photic stimulation. In addition, epileptic chickens' brains are 25% heavier than those of carriers. We have investigated whether hyperplasia or hypertrophy of astrocytes or increased numbers of astrocytic processes are involved in the development of seizures and the megalencephaly in this model by quantitative comparison of sections immunocytochemically stained for glial fibrillary acidic protein (GFAP). No statistically significant differences between epileptics and controls were found in any of seven areas selected for comparison. In this model gliosis is not involved in the development of epilepsy, nor does it result from repeated seizures.

Animals↗
PubMed1987

Structure and lipid distribution of polyenoic very-long-chain fatty acids in the brain of peroxisome-deficient patients (Zellweger syndrome).

The polyenoic fatty acids with carbon chain lengths from 26 to 38 (very-long-chain fatty acids, VLCFA) previously detected in abnormal amounts in Zellweger syndrome brain have been shown to be n-6 derivatives and therefore probably derived by chain elongation of shorter-chain n-6 fatty acids such as linoleic acid and arachidonic acid. Polyenoic VLCFA are also present in Zellweger syndrome liver, but this tissue differs significantly from brain in that the saturated and mono-unsaturated derivatives are the major VLCFA. Zellweger syndrome brain polyenoic VLCFA are present in the neutral lipids predominantly in cholesterol esters, with smaller amounts in the non-esterified fatty acid and triacylglycerol fractions. These fatty acids are barely detectable in any of the major phospholipids, but are present in significant amounts in an unidentified minor phospholipid. The polyenoic VLCFA composition of this lipid differs markedly from that observed for all other lipids, as it contains high proportions of pentaenoic and hexaenoic fatty acids with 34, 36 and 38 carbon atoms. A polar lipid with the chromatographic properties in normal brain contains similar fatty acids. It is postulated that the polyenoic VLCFA may play an important role in normal brain and accumulate in Zellweger syndrome brain because of a deficiency in the peroxisomal beta-oxidation pathway, although a possible peroxisomal role in the control of carbon-chain elongation cannot be discounted.

Brain Chemistry↗
PubMed1987

Adipsin: a circulating serine protease homolog secreted by adipose tissue and sciatic nerve.

Adipsin is a serine protease homolog whose primary structure was predicted from the nucleotide sequence of a differentiation-dependent adipocyte messenger RNA. Immunoblots probed with antisera to synthetic peptides identify two forms of adipsin that are synthesized and secreted by 3T3 adipocytes. These proteins of 44 and 37 kilodaltons are converted to 25.5 kilodaltons by enzymatic deglycosylation. Although adipsin is principally synthesized in adipose tissue, it is also produced by sciatic nerve and is found in the bloodstream. Because of the apparent restriction of adipsin synthesis to tissues highly active in lipid metabolism, its presence in serum, and its modulation in altered metabolic states, this molecule may play a previously unrecognized role in systemic lipid metabolism or energy balance.

Adipose Tissue↗
PubMed1987

Type 1 human poliovirus binds to human synaptosomes.

Poliovirus is a neurotropic virus that selectively infects human motoneurons in vivo. The basis for the specificity of this infection is not fully understood. It has been suggested that this tropism occurs because motoneurons are the only neurons to express poliovirus receptors. We have examined this hypothesis by measuring the binding of 125I-labeled poliovirus type 1 to neural tissues. With this assay we have detected highly specific binding sites in human but not rodent neural tissue. Regional assays of binding in human central nervous system homogenates demonstrate that binding sites are not confined to motoneurons. Rather, they are widely distributed throughout the human neuraxis. Particularly in the forebrain, binding is more abundant in gray than white matter. For this reason, we performed tissue fractionation studies which indicate that poliovirus binding sites are enriched in synaptosomes, the subfraction of central nervous system gray matter tissue rich in synaptic endings. The preferential expression of poliovirus binding sites in synaptic endings may be an important factor in the motor tropism of this virus, inasmuch as the major category of neurons with synaptic endings outside the central nervous system are motoneurons; thus, particles of virus may preferentially bind to this cell type during poliovirus viremia.

Animals↗
PubMed1987

Femoral nerve block with bupivacaine 0.25 per cent for postoperative analgesia after open knee surgery.

An assessment was made, in a randomised double-blind fashion, of the pain relief afforded by femoral nerve block (FNB) performed at the end of ligament reconstruction of the knee, using 0.25 per cent bupivacaine in ten patients, and normal saline in ten patients. All patients commenced "continuous passive motion" (CPM) of the operated knee after arrival in the Recovery Room. The postoperative analgesic requirement, both for intravenous fentanyl in the Recovery Room, and intramuscular and oral analgesia on the ward, was then studied. The time interval between FNB and first dose of analgesia was significantly longer in the bupivacaine group than in the control group. The bupivacaine group also required significantly less intravenous fentanyl in the Recovery Room. On the ward, there was no difference between the two groups in the total dose of intramuscular meperidine given in the first 12 hours postoperatively. We conclude that femoral nerve block is a useful adjunct in pain management after ligament reconstruction of the knee, especially in the early postoperative period, but does not decrease the total intramuscular dose of analgesia in the first 12 postoperative hours.

Bupivacaine↗