The neural basis of orienting behavior: a computational approach to the escape turn of the cockroach

Using computer simulation, we demonstrate that the information encoded by the ventral giant interneurons is particularly suited to orienting the escape turn of the adult cockroach with a degree of variation seen experimentally. The type of model we present for sensorimotor integration incorporates a simple comparator of sensory evoked GI activity and is extremely robust with respect to underlying assumptions.     

Bone morphometrics and tetracycline marking patterns in young growing American alligators (Alligator mississippiensis)

Nine young American alligators (Alligator mississippiensis) were injected at monthly intervals with tetracycline to determine the bone apposition rate and the resorption patterns over a 3-mo period. The periosteal apposition rate increased progressively over the 3-mo period from 2.99 microns/day to 5.94 microns/day. Endosteal apposition rate was much slower with incomplete tetracycline lines being observed on the endosteum. This suggests that most modeling-resorptive activities occur on the endosteal envelope.     

Enhanced recognition of a modified peptide antigen by cytotoxic T cells specific for influenza nucleoprotein

A previously identified Kd restricted epitope of influenza A virus nucleoprotein (147-161) was modified, resulting in recognition by Kd restricted cytotoxic T cells at significantly lower concentrations than the natural peptide sequence. This was achieved by first refining the epitope to the minimum determinant 147-158. Deletion of arginine 156 resulted in a peptide that was shown to be greatly superior in both dose response titrations and in its rate of association with cells to form targets. Analog peptides were tested to determine the important amino acid changes. These data suggest that T cell epitopes can be modified to result in improved immunological recognition.     

R plasmids in environmental Vibrio cholerae non-O1 strains

The occurrence of drug resistance and its plasmid-mediated transferability was investigated in 140 environmental strains of Vibrio cholerae non-O1 and 6 strains of Vibrio cholerae, both O1 and non-O1, of clinical origin. Of the 146 strains tested, 93% were resistant to at least one drug and 74% were resistant to two or more antibiotics. The O1 strains were susceptible to all antibiotics used. A total of 26 of 28 selected resistant wild strains carried R plasmids that were transferable by intraspecific and intergeneric matings. The most common transmissible R factor determined resistance to ampicillin, amoxicillin, and sulfanilamide (30%), followed by resistance to ampicillin and amoxicillin (13%) and resistance to ampicillin, amoxicillin, phosphomycin, and sulfanilamide (9%). Comparison of the three methods of plasmid analysis showed that the method of Birnboim and Doly (Nucleic Acids Res. 7:1513-1523, 1979) without EDTA and lysozyme was optimal for isolation of both large and small plasmids in environmental V. cholerae strains. Most strains harbored more than one plasmid, and the molecular sizes ranged from 1.1 to 74.8 megadaltons. The plasmids of high molecular size (around 74 megadaltons) were responsible for the resistance pattern transferred and were maintained with high stability in the hosts.     

Immunological relevance of malonic dialdehyde (MDA): II. Precipitation reactions of human sera with MDA-crosslinked proteins

Using precipitation reactions in agarose gels (Bidimensional double diffusion: Ouchterlony. Counterimmunoelectrophoresis: CEP), we showed that: a) sera from normal human subjects contain components able to bind and precipitate with MDA-crosslinked lysozyme (ML) and not with native lysozyme, which indicates that the chemical structures involved in such bindings arise from reaction of MDA with lysozyme and probably include 1-amino-3-iminopropene (AIP) bridges. b) some if not all of these seric components are immunoglobulins. c) the F(ab')2 regions of these immunoglobulins are involved in their binding and precipitating properties. These results lead us to assume that sera from normal human subjects contain immunoglobulins with antibody-like specificity for MDA-crosslinked proteins. Nevertheless, this assumption remains to be assessed by further studies, especially about the "epitopes" involved in such reactions.     

Branched chain amino acid transaminases in brain in methionine sulphoximine (MSI) toxicity

The effect of intraperitoneal administration of L-methionine-DL-sulphoximine (MSI) was studied on branched-chain amino acid transaminases (BCAA-T) in different regions of rat brain and in liver. Administration of an acute dose of MSI (300 mg/kg body weight) resulted in a significant decrease in leucine aminotransferase activity in cerebral cortex, cerebellum, and brain-stem, while the activity of isoleucine aminotransferase was enhanced in hippocampus, corpus striatum, brain stem, and midbrain. Activities of both these enzymes changed marginally or remained unaltered in other regions of the brain. Valine aminotransferase showed a significant decrease in all the regions of the brain except in cerebellum. Following the administration of a sub-acute dose of MSI (150 mg/kg body wt.), the activities of the three BCAA aminotransferases were found to be enhanced in all regions of the brain. The results are discussed in relation to the utilization of BCAA for the production of glutamate and glutamine in hyperammonemia.     

Iron kinetics effects of 88 millirads. Partial-versus-total body X-irradiation

Rats were irradiated with one tibia shielded (95% marrow exposure), total body exposed (TBI, 100%), and only one tibia exposed (5%), or they were sham irradiated (SI, 0%). Plasma Fe-59 clearance time (T1/2) and Fe-59 content ratio in the right and left tibia (RT/LT) were assayed to determine the erythroid activity of the overall marrow of the animals and the relative marrow activity in the exposed and shielded tibias, respectively. When a major fraction of the overall marrow was shielded or irradiated, the overall erythroid activity levels were identical to those of the SI and TBI animals, respectively. Interestingly, enhanced normoblastosis was observed in the marrow of the exposed tibia of individual animals exhibiting normal erythroid activity in 95% of the marrow. Conversely, localized marrow with normal erythroid activity was found in a shielded tibia of individual rats, demonstrating an enhanced erythroid activity in a major fraction of the total body. It was concluded that 88 mrad can alter marrow functions in a small isolated skeletal region as effectively as in the whole body, and tandem assays of the Fe-59 T1/2 and Fe-59 RT/LT can facilitate ultra-low-dose X-ray studies involved with partial body exposures.     

Parallel bioassay of 27 bombesin-like peptides on 9 smooth muscle preparations. Structure-activity relationships and bombesin receptor subtypes

Thirteen natural bombesin-like peptides and 14 synthetic analogues were submitted to parallel bioassay on 9 smooth muscle preparations in order to determine their relative potency, in comparison to bombesin and litorin. The natural peptides of the bombesin subfamily showed a uniformly high or moderate potency on all preparations. However, synthetic bombesins of shorter chain length (hepta- and octapeptides) manifested a good potency only on the rat uterus preparation. Among the peptides of the litorin and phyllolitorin subfamilies, only litorin and ranatensin presented a full spectrum of potency, equalling or even surpassing that of bombesin. All other natural and synthetic members of the two subfamilies showed a sharply dissociated spectrum of potency on the different smooth muscle preparations. The only exception was the rat urinary bladder and, in part, the chicken intestine, on which the peptides displayed a uniformly high potency, comparable to, or even greater than that of bombesin. The present results help to explain structure/activity relationships and suggest the probable existence, in the periphery, of multiple bombesin receptor subtypes.     

The effect of serum on lipid synthesis and on the expression of oligodendrocyte marker-enzymes in oligodendrocyte-enriched glial cells in culture

Glial cells were isolated from the cerebra of 7-day old rats and the effect of serum on the development of these cells in culture was studied. The activities of the oligodendrocyte marker-enzymes, 2′3′-cyclic nucleotide 3′-phosphodiesterase and glycerol 3-phosphate dehydrogenase and the synthesis of the myelin-associated sulpholipid, sulphatide, were used to monitor the differentiation of these cells in vitro. The results indicate that serum: (i) represses lipogenesis, cholesterogenesis and sulphatide synthesis, (ii) lowers the expression of 2′3′-cyclic nucleotide 3′ phosphodiesterase and glycerol 3-phosphate dehydrogenase but not of lactate dehydrogenase and (iii) thus impairs the differentiation of oligodendrocytes.