Species specificity of iron delivery in hybridomas

Summary Studies with Human x Human (HxH), Human x Mouse (HxM), and Mouse x Mouse (MxM) hybridomas have enabled us to define specific factors that affect hybridoma growth in a species-specific manner. Three transferrins and three lipophilic iron chelates have been tested for their ability to support hybridoma proliferation and antibody production. The results of these studies demonstrate that HxH hybridomas do not respond to bovine transferrin a⁺ concentrations up to 100 μg/ml and are approximately 100-fold less responsive to mouse transferrin than to human transferrin. HxM and MxM hybridomas respond equally to human or mouse transferrin but are 100-fold less sensitive to bovine transferrin. An antibody to the human transferrin receptor inhibited the growth-promoting activity of human or mouse transferrin on HxH hybridomas but was ineffective on HxM hybridomas. This semonstrated the functionality of the human transferrin receptor in HxH hybridomas and that human, mouse, and bovine transferrin were interacting through the mouse transferrin receptor in HxM hybridomas. HxH and HxM hybridomas respond similarly to three different iron chelates exhibiting 80 to 110% of the growth response to human transferrin. MxM hybridomas fail to respond to the iron chelates at similar concentrations, suggesting that the human genome present in the other hybridoma species confers a unique ability for utilizing iron when delivered in this form.     

Bioengineering in development of the hybrid artificial pancreas

The hybrid artificial pancreas for treatment of diabetes consists of insulin-secreting pancreatic tissue which is surrounded by a membrane that protects the tissue from rejection by the immune system following implantation. In this paper, we review the alternative therapeutic approaches for diabetes under study and then discuss the technical requirements that must be met by a hybrid device useful to humans. Previous work on intravascular and extravascular immunoisolation devices is reviewed from the standpoint of these requirements, and three critical unresolved issues are discussed: biocompatibility, oxygen supply limitations, and prevention of immune rejection.     

Effect of pressure on [3H]GABA release by synaptosomes isolated from cerebral cortex

High hydrostatic pressure has been shown to produce neurological changes in humans which manifest, in part, as tremor, myoclonic jerks, electroencephalographic changes, and convulsions. This clinical pattern has been termed high-pressure nervous syndrome (HPNS). These symptoms may represent an alteration in synaptic transmission in the central nervous system with the inhibitory neural pathways being affected in particular. Since gamma-aminobutyric acid (GABA) transmission has been implicated in other seizure disorders, it was of interest to study GABAergic function at high pressure. Isolated synaptosomes were used to follow GABA release at 67.7 ATA of pressure. The major observation was a 33% depression in total [3H]GABA efflux from depolarized cerebrocortical synaptosomes at 67.7 ATA. The Ca2+-dependent component of release was found to be completely blocked during the 1st min of [3H]GABA efflux with a slow rise over the subsequent 3 min. These findings lead us to conclude that high pressure interferes with the intraterminal cascade for Ca2+-dependent release of GABA.     

Developmental modulation of deoxyribonucleic acid-binding proteins of Bacillus subtilis during sporulation stages

The isolation of deoxyribonucleic acid (DNA)-binding proteins from various stages of growth and sporulation of Bacillus subtilis is described. After adsorption and elution from phosphocellulose, the proteins were fractionated according to their ability to adsorb to denatured calf thymus DNA-cellulose or native B. subtilis DNA-cellulose. The proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and purification was monitored by a nitrocellulose filter binding assay. Approximately 1% of the proteins in the crude extract adsorbed to denatured calf thymus DNA-cellulose and 0.1% adsorbed to native B. subtilis DNA-cellulose. Each class of proteins varied qualitatively and quantitatively as sporulation proceeded. Several proteins from the exponential phase of growth that bound to denatured DNA were lost by T(0), whereas at T(5) new polypeptides appeared. Fewer changes in the profile of proteins with affinity for native DNA were observed between exponential phase and T(0); however, the dominant species in these eluates were clearly different.     

The action of hydrogen peroxide on paired pulse and long-term potentiation in the hippocampus

The action of a reactive oxygen intermediate, that is, hydrogen peroxide (H2O2) on modulation of synaptic transmission was examined in the hippocampal brain slice preparation. Microinjection of H2O2 into the apical dendritic region of the CA1 pyramidal cells produced no change in either the pattern or amplitude of paired pulse facilitation compared to saline injection (control). Long term potentiation (LTP), induced by high frequency stimulation of homosynaptic inputs, however, was blocked by microinjection of H2O2 into the dendritic tree. LTP was seen in only 2 out of 10 slices investigated when treated with H2O2 while LTP was seen in 4 out of 5 slices when saline injected. The results suggest that a reactive oxygen intermediate can selectively modify synaptic mechanisms in the hippocampus.     

Hydrolysis, synthesis, and release of acetylcholine in the isolated heart

The occurrence of unhydrolyzed acetylcholine (ACh) in the cardiac perfusate during vagal stimulation in the absence of cholinesterase inhibition has been demonstrated by several methods. Because some ACh was found unhydrolyzed in the extracellular space for several seconds after vagal stimulation (half-time of decay 2.5 s), it appears that the prolonged time course of the cardiac responses to bursts of vagal activity is determined by a slow rate of transmitter inactivation (diffusion plus hydrolysis) in addition to slowly operating postsynaptic mechanisms mediated by activation of the muscarinic receptor. The neuronal uptake of choline in isolated heart preparations was found to be Na+ dependent, sensitive to hemicholinium 3, and activated by vagal stimulation. Activation occurred after a delay of 1 or 2 min and slowly faded within 5 min after stimulation. Resting release of ACh was insensitive to extracellular Ca2+ and to muscarinic feedback inhibition, in contrast to the evoked transmitter release. Inasmuch as atropine increased ACh release by vagal and field stimulation to the same extent, muscarinic feedback inhibition is likely to occur at postganglionic parasympathetic neurons. Adrenergic agonists and propranolol did not significantly change the release of ACh.     

Inversion polymorphism in Drosophila obscura

The inversion polymorphism of Drosophila obscura Fallen, a European species of the obscura group of the subgenus Sophophora, is described. A total of 21 inversions have been recorded; they are located in the five large chromosomes of the species (a dot chromosome is also present) and form 25 gene arrangements present in the species' natural populations. Strains from five different countries were studied. Two of these inversions were found to be pericentric, and the remaining were paracentric. The presence of "hot" points (multibreaks) was noticed. The distribution of the relative lengths of inversions conformed to the Van Valen-Levins distribution, contrary to what happens in D. subobscura. Observations also showed that there is no crossover inhibition between nonoverlapping inversions. The phylogeny of chromosome C was reconstructed; the existence of several arrangements not found was postulated; and the primitive gene arrangement, linking D. obscura to its closely related species was identified, as well as the primitive gene arrangements of the other chromosomes. Photographic maps of the chromosomes of D. obscura are provided here.