Expression of the HNK-1/NC-1 epitope in early vertebrate neurogenesis

Summary A family of glycoconjugates has recently been shown to share a common carbohydrate epitope recognized by the mouse monoclonal antibody HNK-1. The specificity of HNK-1 was found to be similar to that of another monoclonal antibody, NC-1. These two IgM monoclonal antibodies were raised after immunization of mice with a human T-cell line and avian neural crest-derived ganglia, respectively. The antigens recognized by these antibodies include the myelin-associated glycoprotein, MAG, a glycolipid of defined structure, and a set of molecules involved in cell adhesion. The timing and pattern of appearance of these antigens are distinct. Moreover, the epitope may be absent on an antigen at a given stage or in a given tissue. Therefore, although the molecules able to carry the NC-1/ HNK-1 epitope are numerous and expressed in various tissues, the use of the monoclonal antibodies on tissue sections has proven adequate for following the migration of avian neural crest cells, the major cell lineage recognized by NC-1 and HNK-1 during early embryogenesis. Analogies in several other species have been found on the basis of HNK-1 reactivity. In this study we show that NC-1 and HNK-1 can be used successfully to label migrating neural crest cells in dog, pig and human. On the other hand, the NC-l/HNK-1 epitope was not present on migrating crest cells in amphibians or mice and was found only transiently on the neural crest of rats.     

Trace elements in human parotid saliva

Although various proteins and some electrolytes have been measured in human saliva, little systematic data about the major and minor elemental components of this body fluid have been obtained. In order to obtain such data, concentrations of C, Na, P, Cl, K, Ca, Sc, Cr, Fe, Co, Zn, Se, Br, Rb, Sb, I, and Cs in human parotid saliva were measured by instrumental nuclear methods. The data obtained confirmed the relative lack of Zn in saliva of patients with hypogeusia (decreased taste acuity) and suggested that concentrations of Na, Cl, Br, and Ca followed the order: normals > hypogeusia > hyposmia (decreased smell acuity). To compare concentrations of elements in saliva with those in blood and urine, absolute concentrations were normalized to that of Na through the use of a concept called an enrichment factor. On this basis, parotid saliva is relatively depleted in Se, Zn, and Fe and enriched for most other elements relative to blood plasma indicating that the fluid is not simply a transudate of blood plasma. Using this same technique, saliva composition was found more similar to urine than blood plasma, being relatively depleted in Se, Cs, and Co, being enriched in I, Br, and Cr and having about the same relative concentrations of P, Cl, Zn, Fe, Ca, K, and Rb. As the total body concentrations of many of the enriched elements in saliva are extremely small, their enrichment in saliva suggests special roles for these elements in the oral cavity. Because of its accessibility, ease of collection, and interaction with some body constituents, saliva represents a useful, albeit neglected, tool in the diagnosis of some physiological and pathological changes in body function and in understanding important aspects of trace metal metabolism.     

Genetic information could be integrated extrinsically for simplest life forms

Polynucleotides and proteins coupled in mutual synthesis are widely believed to have been needed for the origin of life, but this theory encounters grave problems. Simple catalysts reproducing by positive feedback, sometimes advocated as an alternative, lack a built-in mechanism for generating and accumulating genetic information. Modern organisms, however, integrate genetic information by extrinsic in addition to intrinsic mechanisms, and extrinsic mechanisms were available even at the beginning of chemical evolution for any self-reproducing entities that might have appeared. Novel molecules were generated by reactions among prevailing molecules, and a catalyst multiplying by positive feedback would have transmitted structural information not only to progeny molecules of its kind, but to derivatives and by-products. New molecules derived immediately or remotely from successfully reproducing catalysts would be favored to have catalytic properties. New catalysts with effective positive feedback would increase autocatalytically and be integrated with others into a metabolizing system by natural selection.     

Missense mutation in the lacI gene of Escherichia coli. Inferences on the structure of the repressor protein

The lac repressor has been studied extensively but a precise three-dimensional structure remains unknown. Studies using mutational data can complement other information and provide insight into protein structure. We have been using the lacI gene-repressor protein system to study the mutational specificity of spontaneous and induced mutation. The sequencing of over 6000 lacI- mutations has revealed 193 missense mutations generating 189 amino acid replacements at 102 different sites within the lac repressor. Replacement sites are not distributed evenly throughout the protein, but are clustered in defined regions. Almost 40% of all sites and over one-half of all substitutions found occur within the amino-terminal 59 amino acid residues, which constitute the DNA-binding domain. The core domain (residues 60 to 360) is less sensitive to amino acid replacement. Here, substitution is found in regions involved in subunit aggregation and at sites surrounding residues that are implicated in sugar-binding. The distribution and nature of missense mutational sites directs attention to particular amino acid residues and residue stretches.     

Derived amino acid sequence and identification of active site residues of Escherichia coli beta-hydroxydecanoyl thioester dehydrase

The nucleotide sequence of the fabA gene encoding beta-hydroxydecanoyl thioester dehydrase, a key enzyme of the unsaturated fatty acid synthesis pathway of Escherichia coli, has been determined by the dideoxynucleotide sequencing technique. Most of the sequence was obtained by sequencing intragenic insertions of the transposon, Tn1000, isolated in vivo. A synthetic primer complementary to a portion of the inverted repeat sequences at the ends of the transposon was used to prime DNA synthesis into the flanking fabA sequences. The gene is composed of 516 nucleotides (171 amino acid residues) encoding a protein with a molecular weight of 18,800. Approximately half of the derived amino acid sequence was confirmed by automated Edman sequencing of peptides obtained by cyanogen bromide cleavage. The active site histidine residue (His-70) has been identified by analysis of the peptides labeled by reaction with 14C-labeled 3-decynoyl-N-acetylcysteamine, a specific mechanism-activated inhibitor. A cysteine residue (Cys-69) adjacent to the active site histidine may play the role in catalysis previously assigned to a tyrosine residue. We also report a simplified purification process for the dehydrase beginning with extracts of a brain which greatly overproduces the enzyme.     

A murine IgM monoclonal antibody binds an antigenic determinant in outer surface protein A, an immunodominant basic protein of the Lyme disease spirochete

A hybridoma cell line formed by the fusion of the P3x63-Ag8.653 myeloma cell line with splenocytes from BALB/c mice immunized with Borrelia burgdorferi produced an IgM monoclonal antibody (mAb-11G1) with kappa-light chains which detected an antigenic determinant in a major spirochetal protein of m.w. approximately 31,000, also known as outer surface protein A (OSP-A). Apparent saturation was reached in approximately 35 min with 34 ng of mAb-11G1 binding to 5 X 10(7) spirochetes giving an estimated 4.8 X 10(2) IgM molecules per spirochete and thus a minimum of 480 binding sites per organism. Enzymatic digestion studies suggest that the antigenic determinant to mAb-11G1 is contained within the peptide chain of OSP-A as binding could be eliminated by treatment of the spirochetes with proteinase K, Pronase and pepsin (100 to 200 micrograms/ml of enzyme) but not by trypsin or bromelain treatment. Periodate oxidation as well as mixed and endoglycosidase treatment of the spirochetes did not alter the binding of mAb-11G1. Two-dimensional gel electrophoresis of whole spirochetal cell lysates disclosed that OSP-A is a heterogeneously charged basic protein with an apparent isoelectric point range from 8.5 to 9.0. Amino acid analysis of OSP-A showed a 10% lysine component which could provide the basic nature to the protein. OSP-A with the intact antigenic determinant for mAb-11G1 can be found in the urine of hamsters experimentally infected with B. burgdorferi.     

Ketomethylureas. A new class of angiotensin converting enzyme inhibitors

The design rationale for a new series of tripeptide derived angiotensin converting enzyme (ACE) inhibitors, which we term "ketomethylureas", is described. Analogs of tripeptide substrates (i.e. N-benzoyl-Phe-Ala-Pro) in which the nitrogen atom of the scissile amide bond and the adjacent asymmetric carbon atom of the penultimate amino acid residue are formally transposed give rise to this novel class of inhibitors. The most potent ketomethylureas inhibit ACE with I50 values in the nM range.     

Patents and patent office resources in biotechnology

Patents play an increasingly important role in the dissemination of information in many fast moving fields such as biotechnology and semiconductors. Quite a few new developments are introduced as patents, and only later, if at all, do they find their way into the scientific literature. In spite of this, patents lack wide acceptance as a source of information among scientists in academia and, to a lesser degree, industry. Patents share many similarities with scientific papers. They both are organized in a similar way and are carefully reviewed by experts in the field. Both can be effective and timely sources of information. Patents can be accessed through data bases, library collections, the "Official Gazette of the Patent and Trademark Office," or directly in the Patent and Trademark Office. This article is designed to serve as a guide to the type of information which can be found in patents, and alternatives for obtaining this information.     

Human progesterone receptor transformation and nuclear down-regulation are independent of phosphorylation

We have studied the phosphorylation of progesterone receptors (PR) in T47Dco human breast cancer cells using a monoclonal antibody directed against human PR called AB-52. This antibody recognizes both the A- (Mr approximately 94,000) and B- (Mr approximately 120,000) hormone binding proteins of PR, and was used to immunoprecipitate phosphorylated receptors isolated from cells incubated in vivo with [32P]orthophosphate. The specific activity, or phosphorylation levels, relative to protein levels was quantified by combined immunoblotting and autoradiography followed by densitometry. We find that immunopurified untransformed hormone-free receptors, which have a characteristic triplet B, singlet A structure, are phosphoproteins with similar levels of phosphate incorporation in all protein bands. If PR are first transformed to the nuclear binding form by treatment of cells with progesterone, and then labeled with [32P]orthophosphate, the receptor proteins are additionally phosphorylated. These chromatin-bound hormone occupied receptors incorporate five to 10 times more labeled phosphate per total receptor protein than do PR from untreated cells during the same [32P]incubation time. The second round of phosphorylation may also account for mobility shifts of transformed A- and B-receptors observed in sodium dodecyl sulfate-polyacrylamide gels. Both untransformed and transformed species of A- and B-receptors are phosphorylated only on serine residues, and neither the extent of phosphorylation, nor the phosphoamino acids, are affected by treatment of the cells with epidermal growth factor or insulin. We previously reported that after hormone binding and transformation of receptors to the tight chromatin binding state, PR undergo processing, or nuclear down-regulation. AB-52 was used to compare PR protein and phosphorylation levels when cells were treated for 0.5-48 h with progesterone or the synthetic progestin R5020. Both agonists lead to hyperphosphorylation of nuclear PR before phosphorylation levels decrease, in parallel with the drop in protein levels as receptors down-regulate. Treatment of cells with RU 486, an antiprogestin, leads to PR transformation as determined by immunoblotting, but subsequent down-regulation does not occur. After transformation, chromatin-bound RU 486-occupied receptors become intensely phosphorylated however, with specific activities 15 times greater than those of untransformed PR. Since these receptors are phosphorylated but not processed, the hormone-induced nuclear phosphorylation of PR is unlikely to be a signal for receptor processing.(ABSTRACT TRUNCATED AT 400 WORDS)     

Altered amount and activity of superoxide dismutase in sickle cell anemia

The amount and activity of superoxide dismutase (SOD) (EC 1.15.1.1) were measured in red cells collected from 50 white controls, 101 black controls, 50 patients with sickle hemoglobin (SS Hb), 12 with sickle trait, and 11 with other sickling hemoglobinopathies. Red cells from normal black subjects had more SOD amount and activity than normal whites (1.77 U/mg Hb and 2.96 micrograms/mg Hb vs. 1.47 U/mg Hb and 2.64 micrograms/mg Hb, respectively) or blacks with SS Hb or other sickling hemoglobinopathies. Patients with more severe manifestations of SS Hb had lower levels of SOD activity than those with milder symptoms but had the same amount of enzyme protein. Individuals with sickle trait had amounts and activities of SOD comparable to black controls. An alteration in defense to free radical oxygen may play a role in the severity of symptoms experienced by patients with homozygous sickle cell disease.