Specificity of chimpanzee antibodies binding a strain-specific HIV-1 neutralization epitope of the external envelope

Sera from three chimpanzees infected with a primary lymphadenopathy-associated virus (LAV-1) or human T-lymphotropic virus type III (HTLV-IIIB) passage, from two chimpanzees infected with blood from the primary infected chimpanzees, and from one chimpanzee infected with blood from a secondary passage animal all bound the peptides 3B and 3B/RF, sharing the sequence IQRGPGR, with equally high titers. Pepscan analysis confirmed the amino acids Q, R, G, P, and G as irreplaceable in order to retain antigenicity.     

The asymptotic transectional/circumferential homogeneity of the solutions of reaction-diffusion systems in/on cylinder-like domains

It is often reported that an animal with spotty coat markings on its body has a tail with stripe-shaped pattern. In other various biological and chemical phenomena in/on cylinder-like domains, longitudinally periodic band patterns are observed much more often than the other non-uniform patterns. This paper mathematically explains these observations by proving that, in/on a long and narrow cylinder-like domain, any solution of reaction-diffusion system asymptotically loses its spatial dependence in the transectional/circumferential direction.     

Immunological studies of ferredoxin-nitrite reductases and ferredoxin-glutamate synthases from photosynthetic organisms

Polyclonal antiserum specific for ferredoxin-nitrite reductase (EC 1.7.7.1) from the green alga Chlamydomonas reinhardii recognized the nitrite reductase from other green algae, but did not cross-react with the corresponding enzyme from different cyanobacteria or higher plant leaves. An analogous situation was also found for ferredoxin-glutamate synthase (EC 1.4.7.1), using its specific antiserum. Besides, the antibodies raised against C. reinhardii ferredoxin-glutamate synthase were able to inactivate the ferredoxin-dependent activity of nitrite reductase from green algae.These results suggest that there exist similar domains in ferredoxin-nitrite reductases and ferredoxin-glutamate synthases from green algae. In addition, both types of enzymes share common antigenic determinants, probably located at the ferredoxin-binding domain. In spite of their physicochemical resemblances, no apparent antigenic correlation exists between the corresponding enzymes from green algae and those from higher plant leaves or cyanobacteria.Abbreviations Fd ferredoxin - GOGAT glutamate synthase - MV⁺ reduced methyl viologen (radical cation) - NiR nitrite reductase - PMSF phenylmethylsulphonyl fluoride - SDS sodium dodecyl sulfate     

Adenylyl cyclase in yeast: antibodies and mutations identify a regulatory domain

The adenylyl cyclase system of the yeast Saccharomyces cerevisiae contains the CYR1 polypeptide, responsible for catalyzing formation of cAMP from ATP, and two RAS polypeptides, responsible for stimulation of cAMP synthesis by guanine nucleotides. We have obtained rabbit antibodies that recognize the CYR1 protein. Antibodies were raised against synthetic oligopeptides and against a recombinant beta-galactosidase/CYR1 fusion protein. These antibodies have allowed the identification of the CYR1 gene product as a 205 kDa protein. Treatment with trypsin (2 micrograms/ml) reduced the size of the CYR1 protein from 205 to 155 kDa and produced an activated enzyme which no longer responded to guanine nucleotides. This result is consistent with a model in which adenylyl cyclase activity is regulated by an inhibitory domain near the amino-terminus of the CYR1 protein. This model is further supported by the finding that adenylyl cyclase activity is also markedly elevated and unresponsive to guanine nucleotides in mutant yeast strains that express only the carboxy-terminal half of the CYR1 protein. Treatment with high trypsin concentrations (greater than 10 micrograms/ml) caused release of adenylyl cyclase activity from the membrane. Comparison of immunoreactive CYR1 fragments released by trypsin and membrane bound genetically altered proteins suggests that the CYR1 protein is attached to the membrane via a separate trypsin sensitive anchoring protein rather than via a membrane anchoring domain.     

Diagnosis of a peripheral neuroectodermal tumour by fine needle aspiration

One case of malignant peripheral neuroectodermal tumour successfully diagnosed by cytology is presented. Although a Papanicolaou stained smear could not lead to a diagnosis more specific than a malignant small cell tumour, ancillary analytic methods performed on the cytologic material including immunocytochemistry and electron microscopy yielded the correct diagnosis of peripheral neuroectodermal tumour. This case demonstrates that a precise categorization of small round cell tumours may be achieved by cytology as long as some material is kept for immunocytochemical and ultrastructural studies.     

33-kDa C-terminal heparin binding fragment of fibronectin promotes attachment and spreading of hepatocytes

The possibility of interaction of hepatocytes with the heparin binding domain of Fibronectin was examined. Rat hepatocytes adhered to coverslips coated with the 33-kDa heparin binding fragment of the C-terminal region of plasma fibronectin. When different concentrations of the heparin binding fragment were used to coat coverslips and used as substratum, cell attachment showed saturation kinetics. Half the maximum attachment was observed at 30–40 min after seeding of cells. The cells became flat after 2–3 h indicating that they spread on the heparin binding domain as they do on intact fibronectin. Among the different glycosaminoglycans tested, maximum inhibition of attachment was observed for heparin. However it was not possible to completely inhibit attachment even at high concentrations. These results indicate that hepatocytes interact with fibronectin not only through the Arg-Gly-Asp-containing cell binding fragment, but also through the heparin binding domain of fibronectin and, further, that there exist heparin-dependent and heparin-independent mechanisms of interaction of cells with the 33-kDa heparin binding fragment of fibronectin     

Application of three-dimensional molecular hydrophobicity potential to the analysis of spatial organization of membrane domains in proteins: I. Hydrophobic properties of transmembrane segments of Na+, K+-ATPase

A new computer-aided molecular modeling approach based on the concept of three-dimensional (3D) molecular hydrophobicity potential has been developed to calculate the spatial organization of intramembrane domains in proteins. The method has been tested by calculating the arrangement of membrane-spanning segments in the photoreaction center ofRhodopseudomonas viridis and comparing the results obtained with those derived from the X-ray data. We have applied this computational procedure to the analysis of interhelical packing in membrane moiety of Na⁺, K⁺-ATPase. The work consists of three parts. In Part I, 3D distributions of electrostatic and molecular hydrophobicity potentials on the surfaces of transmembrane helical peptides were computed and visualized. The hydrophobic and electrostatic properties of helices are discussed from the point of view of their possible arrangement within the protein molecule. Interlocation of helical segments connected with short extramembrane loops found by means of optimization of their hydrophobic/hydrophilic contacts is considered in Part II. The most probable 3D model of packing of helical peptides in the membrane domain of Na⁺, K⁺-ATPase is discussed in the final part of the work.     

A plastome mutation affects processing of both chloroplast and nuclear DNA-encoded plastid proteins

Summary A bovine tRNA gene cluster has been characterized and the sequences of four tDNAs determined. Two of the tDNAs could encode tRNA^Ser _IGA, one tDNA^Ser _UGA, and the fourth tRNA^Gln _CUG. The three serine tDNAs representing the UCN codon isoacceptor family are almost identical. However, the sequence of the tDNA^Ser _TGA differs from a previously sequenced bovine tDNA^Ser _TGA at 12 positions (ca. 14%). This finding suggests that in the bovine genome, two subfamilies of genes might encode tRNA^Ser _UGA. It also raises the possibility that new genes for a specific UCN isoacceptor might arise from the genes of a different isoacceptor, and could explain previously observed differences between species in the anticodons of coevolving pairs of tRNAs^Ser _UCN. The gene cluster also contains complete and partial copies, and fragments, of the BCS (bovine consensus sequence) SINE (short interspersed nuclear element) family, six examples of which were sequenced. Some of these elements occur in close proximity to two of the serine tDNAs.     

Naloxone and TRH affect regional blood flows in the anesthetized rabbit

The cardiovascular effects of IV naloxone and a subsequent administration of TRH IV were studied in the rabbit. Naloxone caused a vasodilation in the myocardium and adrenal glands. Naloxone elicited an increment in cerebral blood flow in several regions which attenuated the cerebrovasodilating effect of TRH in a few regions. The blockade of endogenous opioids with naloxone did not modify the peripheral vasoconstricting effect of TRH or affect the vascular effects of TRH mediated by the peripheral sympathetic nerves. The results indicate that naloxone has a vasodilating effect in the myocardium and CNS in anesthetized rabbits. The major part of the cardiovascular effect of TRH is not dependent on mechanisms sensitive to naloxone.