Greater emotional distress is associated with accelerated CD4+ cell decline in HIV infection

An investigation was conducted to explore the relationship between emotional distress and HIV progression. One hundred twenty-five homosexual, HIV-positive males participated in a 12-month longitudinal investigation. Psychosocial data were collected at 6-month intervals and CD4+ data were collected from diagnosis to the end of the investigation. Principal component analyses were performed initially to identify factors of emotional distress and health status. In addition, CD4+ reliability assessments were performed to ensure the validity of the prognostic assessments made. As a result of these analyses, 47 individuals were eligible for the main analyses. The results from a stepwise regression revealed that disease progression was significantly predicted by CD4+ count at diagnosis (32% of variance) and emotional distress (17% of variance), but was unrelated to subjective perceptions of health. The data suggest that some of the variability in HIV progression can be attributed to emotional distress.

Glycosylphosphatidylinositol anchors represent the major carbohydrate modification in proteins of intraerythrocytic stage Plasmodium falciparum

The nature and extent of carbohydrate modification in intraerythrocytic stage Plasmodium falciparum proteins have been controversial. This study describes the characterization of the carbohydrates in intraerythrocytic P. falciparum proteins and provides an overall picture of the nature of carbohydrate modification in the parasite proteins. P. falciparum strains were metabolically labeled with radioactive sugar precursors and ethanolamine at different developmental stages. The individual parasite proteins separated on SDS-polyacrylamide gels and whole parasite cell lysates were analyzed for the carbohydrate moieties. The results established the following: 1) glycosylphosphatidylinositol (GPI) anchors represent the major carbohydrate modification in the intraerythrocytic stage P. falciparum proteins; 2) in contrast to previous reports, O-linked carbohydrates are either absent or present only at very low levels in the parasite; and 3) P. falciparum contains low levels of N-glycosylation capability. The amount of N-linked carbohydrates in whole parasite proteins is approximately 6% compared with the GPI anchors attached to proteins based on radioactive GlcN incorporated into the proteins. The glycan cores of multiple parasite protein GPI anchors are all similar, consisting of protein-ethanolamine-phosphate-(Manalpha1-2)6Manalpha1-2M analpha1-6Ma nalpha1- 4GlcN. The fourth Man residues distal to GlcN of the GPI anchor glycan cores contain unidentified substituents that are susceptible to conditions of nitrous acid deamination. This unusual structural feature may contribute to the reported pathogenic properties of the P. falciparum GPI anchors.

Upregulation of the tracheobronchial mucin gene involves cyclic AMP response elements

The cAMP response element (CRE)-binding transcription factor CREB can mediate induction of gene transcription in response to cAMP. Since the tracheobronchial mucin gene (TBM) 5'-flanking region contains CREs (located between residues -289 and -376) with an octamer-like motif (TGACGTCC), the cAMP responsiveness of the TBM CREs was investigated in human tracheal epithelial cells HBE1. These cells were isolated from non-cystic fibrosis subjects and immortalized with HPV18 genes E6 and E7 (ref. 1). HBE1 cells express a homolog of canine TBM (as demonstrated by TBM expression at the transcription and translation level). Electrophoretic mobility shift assay (EMSA) indicated that CREs provide a binding site for nuclear proteins. Transient transfection analysis [using the chloramphenicol acetyl transferase (CAT) reporter gene] and nuclear run on analysis indicated cAMP induced transcription of the TBM gene. The transcriptional activity of the HBE1 transfected cells containing CRE was selectively modulated by extracellular 8Br-cAMP in a dose-dependent manner; a 6-fold increase in activity was detected when cells were incubated for 12 hr in the presence of 2 microM vs 1 nM 8BrcAMP. Since mucin gene is over-expressed in diseases such as cystic fibrosis (CF) and asthma, the information presented here will help us understand the mechanisms involved in transcriptional regulation of mucin gene expression in disease states.

Molecular cloning and antigenic mapping of heat-shock protein 70 from the malaria species Plasmodium bergheI

We have isolated a 70-kD heat-shock protein (hsp-70) cDNA from Plasmodium berghei. A cDNA clone encoding the P. berghei hsp-70 was isolated and sequenced, demonstrating that it is highly homologous with other Plasmodium hsp-70s. One of the common features is a series of GGMP amino acid repeats at the carboxy terminus; there is also a long, AT-rich 5' untranslated region, a hallmark of other malarial RNAs. Hydropathy and antigenicity analyses suggest the presence of two hydrophilic domains. Recombinant peptides comprising different fragments of hsp-70 were expressed in Escherichia coli and assessed for antigenicity with antiserum from mice immunized with sonicated extracts of P. berghei. Antigenic sites map to regions that include the two hydrophilic domains.

Interaction between complement proteins C5b-7 and erythrocyte membrane sialic acid

The initial phase of membrane attack by complement is the interaction between C5b6, C7, and the cell membrane that leads to the insertion of C5b-7. Here we investigate the role of sialic acid residues in the assembly of C5b-7 intermediates on erythrocyte cell membranes. We find that C5b6 binds to glycophorin, whereas C5 or C6 does not bind, and desialylation of the glycophorin abolishes C5b6 binding. Complement lysis is inhibited by either masking glycophorin sialic acid with F(ab) fragments of an mAb, or by removal of the sialylated region of glycophorin by mild trypsinization. Gangliosides inhibit C5b-7 deposition when added to the aqueous phase. Asialogangliosides and synthetic gangliosides lacking the carboxylic acid residue have no inhibitory activity. We conclude that C5b6 binds to sialylated molecules on the erythrocyte surface. We propose a new model of membrane attack in which C5b6 initially binds to membranes via ionic forces. C7 then binds to C5b6, disrupting the ionic interaction and leading to the exposure of hydrophobic domains. Sialic acid is known to inhibit complement activation. Thus, these findings reveal a paradoxical role for sialic acid in complement attack; the presence of sialic acid inhibits the generation of C5b6, but once the membrane attack pathway is initiated, sialic acid enhances complement lysis.

Promoter of the canine tracheobronchial mucin gene

The mucin gene is up-regulated in diseases such as cystic fibrosis (CF) and asthma. To understand the mechanisms involved in transcriptional regulation of mucin gene expression we have characterized the region of the mucin gene up-stream of the transcriptional start site and analysed the cis-acting elements required for mucin promoter activity. We isolated clones from a dog genomic library containing the promoter region for the tracheobronchial mucin gene (TBM). The authenticity of the promoter was tested by nucleotide sequencing, primer extension analysis, electrophoretic mobility shift assay (EMSA) and reporter gene expression analysis. The canine TBM promoter is different from housekeeping gene promoters (as it is not rich in GC content and contains TATA- and CAAT-like sequences) and different from that of regulatory genes (because it contains many TATA- and CAAT-like sequences and multiple transcriptional initiation sites). Reporter gene analysis using canine TBM promoter-chloramphenicol acetyltransferase (CAT) fusion plasmids established the regions responsible for promoter activity and verified the positions of the major mucin transcriptional initiation sites. Reporter gene analysis also established that a region of the canine TBM promoter and first exon containing all of the transcriptional initiation sites is more active in mucin expressing cells (e.g. CT1 cells-immortalized canine tracheal epithelial cells, human CFT1 cells-immortalized tracheal epithelial cells from a CF subject, or HBE1 cells-immortalized tracheal epithelial cells from non-CF subject) than in mucin non-expressing cells (COS7, 3T3), suggesting cell specificity. The promoter region contained cAMP response element (CRE) sequences, and the TBM gene transcription was enhanced when cAMP analogs were added to transfected cells. EMSA indicated the presence of at least two DNA binding proteins in CT1 cells. This is the first report describing the characterization of a TBM gene promoter. The information obtained in the present studies will be valuable in understanding mucin gene regulation in normal and pathological conditions.

Core sugar residues of the N-linked oligosaccharides of Russell's viper venom factor X-activator maintain functionally active polypeptide structure

We have previously showed that factor X activator of Russell's viper venom (RVV-X) contains six N-linked oligosaccharide chains: four in the heavy chain and one in each of the two light chains [Gowda, D.C., Jackson, C.M., Hensley, P., & Davidson, E.A. (1994) J. Biol. Chem. 269, 10644-10650]. In the present study, we have investigated the role of the carbohydrate moieties in the structure and functional activity of RVV-X. Sequential removal of sugar residues from the terminal ends by exoglycosidases, up to 50% of total carbohydrates, did not significantly alter the activity of RVV-X, demonstrating that the peripheral carbohydrate moieties are not involved in interactions with factor X. However, removal of whole oligosaccharide chains by N-glycanase caused an almost total loss of the ability of RVV-X to activate factor X to factor Xa. In parallel with these observations, circular dichroism spectroscopy showed that complete deglycosylation, but not the removal of peripheral sugars, caused a significant change in the secondary structure. Together, these data demonstrate that the oligosaccharide chains are necessary for the functional activity, and that the trimannosylchitobiose core residues are sufficient for the maintenance of the native polypeptide structure.

Benzoylecgonine hydrazides: synthesis, coupling to horseradish peroxidase, and characterization of the conjugates

Benzoylecgonine-horseradish peroxidase conjugate (BE-HRP) can be used as a diagnostic reagent for the detection of cocaine in illicit drug samples and in biological fluids. This paper describes the preparation and characterization of BE-HRP. Two hydrazide derivatives of benzoylecgonine, N-2-(tert-butyloxycarbonyl)benzoylecgonine hydrazide and mono(N-2'-benzoylecgoninoyl)adipic dihydrazide, were synthesized by carbodiimide-activated coupling of benzoylecgonine to N-2-(tert-butyloxycarbonyl) hydrazide and adipic dihydrazide, respectively. Removal of the tert-butyloxycarbonyl protecting group in N-2-(tert-butyloxycarbonyl)benzoylecgonine hydrazide with anhydrous HCl yielded benzoylecgonine hydrazide hydrochloride. NMR and high-resolution mass spectral analyses demonstrated that the benzoyl group of benzoylecgonine remained intact under the conditions of both carbodiimide coupling and anhydrous HCl treatment. By aldehyde-hydrazide condensation, the hydrazides were covalently conjugated to the carbohydrate residues of horseradish peroxidase (HRP). Dot blot analysis of the conjugates employing antibodies specific to benzoylecgonine demonstrated the presence of bound benzoylecgonine in HRP. The stoichiometry of benzoylecgonine residues to HRP was determined by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Mono(N-2'-benzoylecgoninoyl)adipic dihydrazide gave a 2.5-3-fold higher coupling compared with benzoylecgonine hydrazide. Conjugates were also prepared by the coupling of the carbodiimide-activated benzoylecgonine to HRP that was derivatized with adipic dihydrazide.

Tracheo-bronchial mucin gene expression as detected by in situ hybridization

To understand regulation of the tracheo-bronchial mucin (TBM) gene expression we developed cDNA probes encoding TBM. We also raised antisera against mucin protein (deglycosylated and glycosylated), and developed immortalized tracheal epithelial cells which express mucin (at the RNA and protein level). TBM cDNA probes can detect TBM mRNA in situ in samples from dog and human primary tracheal epithelial cells and cell lines derived from them. For clinical application, conditions were optimized for detection of the TBM mRNA in human turbinal and nasal polyps and trachea of cystic fibrosis (CF) and non-CF subjects. Fixing and hybridization conditions were found to be critical for the optimum hybridization signal. Riboprobes proved to be better than cDNA or oligonucleotide probes. The application of these newly developed molecular tools in the genetic therapy of CF is discussed herein.

Primary structure of the variable region of monoclonal antibody 2B10, capable of inducing anti-idiotypic antibodies that recognize the C-terminal region of MSA-1 of Plasmodium falciparum

Previously, we reported on the properties of a monoclonal antibody, 2B10, which has the same determinant on the human erythrocyte as MSA-1 of Plasmodium falciparum (FCR3 strain); the binding of both ligands to erythrocyte receptors was totally sialic acid dependent. In this work, rabbit anti-2B10 idiopathic antibodies were generated. The anti-idiotypic antibodies recognized both the erythrocyte binding site of 2B10 and the C-terminal region of MSA-1 (amino acids 1047 to 1640); they were able to inhibit 2B10 and MSA-1 binding to erythrocytes and partially prevent P. falciparum merozoites from invading erythrocytes. The utility of 2B10 in the study of the interaction between MSA-1 and human erythrocytes prompted us to determine the nucleotide and deduced amino acid sequences of its VH and VL regions. The data show that the 2B10 VH region is part of the J558 family and is especially homologous to BALB/c anti-nitrophenyl monoclonal antibody 21.1.43; the VL region belongs to the VK1 subgroup and comes from the same genomic locus as (NZB x W)F1 anti-DNA and C57BL anti-dextran monoclonal antibodies BXW-14 and 42.48.12.2, respectively. Most of the differences among the VH and VL segments are located in CDR1 and -3. The binding site of 2B10 contains both negatively and positively charged amino acid residues. The amino acid sequences of the 2B10 VH region and a region of MSA-1 from the Wellcome strain of P. falciparum (amino acids 1002 to 1115) share 43% similarity, and the amino acid sequences between the 2B10 VL region and another segment of the same MSA-1 (amino acids 1247 to 1394) share 48% similarity. We conclude that the interactions between erythrocyte receptors and their ligands, 2B10 and MSA-1, are related and that the C-terminal region of MSA-1 is the erythrocyte binding domain.

The renin-angiotensin system in the rabbit eye

We analyzed the components of the renin-angiotensin system (RAS) in ocular tissues of normal rabbit eyes and compared the results with those measured in rabbit eyes with proliferative vitreoretinopathy and ocular hypertension. Proliferative vitreoretinopathy was induced by injection of human platelets into the vitreous humor, and ocular hypertension was induced by injection of alpha-chymotrypsin into the posterior chamber. Angiotensinogen, renin, angiotensin converting enzyme (ACE), angiotensin II (Ang II), and Ang II receptors were assessed using conventional biochemical techniques. The vascularized tissues of normal eyes contained high renin and ACE activities concomitant with low concentration of angiotensinogen and Ang II. In general, in the ocular humors, the opposite was found. The Ang II receptor density was highest in the uveal tract [range 35-190 fmol/mg protein]. The AT1 receptor subtype predominated [> 80%]. The RAS was only minimally different in the two pathological models except that, in ocular hypertension, the renin activity in the uveal tract was reduced [-50%]. Also, the ratio of AT1 to AT2 receptors changed as compared to control, although the total receptor density remained unaltered. In conclusion, we present evidence for the presence of a complete local RAS in the rabbit eye, which is only marginally affected by the two pathological models studied.

A technique for accurate use of CD4+ cell counts

Despite uncertainty over their reliability, CD4+ cell counts are used extensively in both clinical and research settings to document progression in HIV infection. We examined, therefore, whether the performance of a simple statistical test would facilitate greater accuracy in the use of this marker. CD4+ cell count data were collected from a cohort of deceased (N = 60) and living HIV-positive gay men (N = 100). Pearson's product moment correlation coefficients were calculated for each individual in order to examine the association between CD4+ counts and time since diagnosis. Correlations of 0.7 or greater were obtained in approximately 50 percent of cases in each cohort. For these individuals, CD4+ cell counts were deemed to be a reliable indicator of rate of progression. The results suggest that the proposed technique ensures greater precision in the use of CD4+ cell counts and that the technique cna be used in individuals with either complete (deceased patients) or partial (living patients) CD4+ data.

Primary structure of the canine U1 snRNA

The nucleotide (nt) sequence of the canine U1 snRNA was determined. It exhibited significant homology (90-98%) with known U1 sequences. The RNA can be folded according to the secondary structure previously proposed for the U1 snRNA. It contained the conserved sequence UUACCUG in loop A (nt 6-12), required for the recognition of the 5' splice site, and the sequence UGCACU in loop B (nt 68-73), required for recognition of the U1-70K protein. The U1 snRNA was localized in the nucleus and its transcription was sensitive to alpha-amanitin, suggesting that it is transcribed by RNA polymerase II. Southern analysis revealed that the canine genome possesses 5-10 copies of U1 snRNA-encoding genes.

Mucin synthesis in immortalized canine tracheal epithelial cells

To study the regulation of mucin synthesis in canine tracheal epithelial cells, it is desirable to establish a cell line which synthesizes mucin continuously. We adopted the approach of immortalizing canine tracheal epithelial cells using a vector encoding the human papillomavirus (type 18) E6 and E7 genes. The E6 and E7 genes are essential and sufficient for the immortalization of human genital keratinocytes, as well as human tracheal epithelium. Primary epithelial cells from dog trachea were transfected with a vector containing HPV18 genes E6 and E7. The resultant cells (CT1) were cloned and maintained in selective medium supplemented with growth factors and hormones. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis indicated the expression of the canine tracheal mucin (CTM) mRNA in these cells. The half-life of the CTM mRNA was found to be 45-60 min. Incorporation of labelled precursor (glucosamine) indicated that high-molecular-weight mucin glycoprotein was synthesized by these immortalized cells, which reacted with the antiserum to the native CTM. Equilibrium gradient centrifugation analysis showed that the buoyant density of the mucin synthesized in CT1 cells (1.486 g/ml) was similar to the reported value for native CTM (1.5 g/ml). Mucin which was isolated from immortalized cells was not a proteoglycan as chondroitinase treatment had no effect. These results suggest that CT1 cells synthesize a mucin glycoprotein which exhibits properties similar to native CTM. When characterized by immunostaining with a pool of monoclonal antibodies, these cells showed common epithelial antigens related to keratin expression. The CT1 cell line represents a unique resource for studying mucin biosynthesis and regulation.

Role of sialic acid on the viscosity of canine tracheal mucin glycoprotein

The role of sialic acid on the viscosity of canine tracheal mucin (CTM) was investigated. The mucin glycoprotein, purified from canine tracheal mucus, was subjected to mild acid hydrolysis with aqueous acetic acid and autohydrolysis in water, in which approximately 50% drop in the relative viscosity (nr) occurred. Carbohydrate compositional analysis before and after mild acid hydrolysis and autohydrolysis showed the complete removal of glycosidically bound sialic acid residues while all other sugar residues (i.e. galactose, N-acetyl galactosamine and N-acetyl glucosamine) remained unaltered, indicating that sialic acid residues are contributing towards the viscosity of CTM to a greater extent.

New approach towards deglycosylation of sialoglycoproteins and mucins

A modified procedure for chemical deglycosylation of glycoproteins containing sialylated and/or O-linked oligosaccharides, using anhydrous trifluoromethane sulfonic acid (TFMSA) is described. Although sialic acid residues are acid labile, it has been known that anhydrous TFMSA does not effectively remove carbohydrate side chains from glycoproteins if they are sialylated. In this procedure, sialic acid residues were removed by mild acid hydrolysis and the desialylated glycoprotein was treated with anhydrous TFMSA reagent under conditions which remove all the carbohydrate residues except the core D-GalNAc linked to serine/threonine. The core D-GalNAc residues were removed by reacting the glycoprotein with periodate followed by a second treatment with anhydrous TFMSA; this procedure gave a completely deglycosylated protein. The protein thus obtained was soluble in aqueous buffers and useful for biochemical and biophysical studies. The method was successfully employed to isolate polypeptides from alpha 1-acid glycoprotein (N-linked), fetuin, canine tracheal mucin and gastric mucin.

Canine U2 snRNA gene: nucleotide sequence, characterization and implications in RNA processing and cancer biology

Abnormal RNA processing (splicing) may lead a cell to become cancerous. Transcription of a gene starts in the nucleus where genomic DNA is converted to precursor RNA by removing introns and joining exons. Splicing, mediated by small nuclear RNA (snRNA) and nuclear proteins, is tightly regulated during growth and development. U2 snRNAs are small, stable RNAs located in the nucleus of eukaryotic cells that recognize the branch point of the intron-exon junction. We describe here the organization of DNA sequences complementary to canine U2 snRNA. From a genomic library we isolated one recombinant containing the U2 gene. Southern analysis revealed that the canine species possesses only 3 to 5 U2 snRNA genes or very closely related sequences. The size of the U2 gene is 125 nt whereas in rat, Drosophila, trypanosome and yeast it is 189, 234, 141, and 192 nt respectively. The nucleotide sequence showed 82, 78, 72 and 95% homology with rat, Drosophila, yeast, and trypanosome U2 snRNA, respectively. The sensitivity of U2 snRNA towards alpha-amanitin suggests that it is transcribed by RNA polymerase II. The conserved nucleotide sequences which have been implicated in heterogeneous nuclear RNA splicing have been identified. The implications of the knowledge gained through above studies in cancer biology are discussed.

Isolation and characterization of novel mucin-like glycoproteins from cobra venom

A high molecular weight, heavily glycosylated protein fraction was isolated from cobra venom. It consists of mucin-like glycoproteins (designated as cobra venom mucin) in noncovalent association with several lower molecular weight proteins and glycoproteins. The mucin was purified by CsBr density gradient centrifugation under dissociative conditions. The purified venom mucin comprised about 85% carbohydrate and 15% protein and was rich in Thr, Ser, Pro, Gly, Glu, Asp, and Ala. The mucin was resolved into two or more distinct classes of mucin-like glycoproteins which differ in their amino acid compositions and/or carbohydrate content. Unlike other mucins, cobra venom mucin does not form highly viscous solutions. It appears to keep several venom proteins and glycoproteins soluble by noncovalent interactions. Cobra venom mucin contains both O- and N-linked oligosaccharides; 1 N-linked chain for every 8-10 O-linked oligosaccharides. The O-linked chains are novel structures with high molar proportions of fucose, galactose, and N-acetylglucosamine relative to N-acetylgalactosamine; they have a very low sialic acid content and lack sulfate esters. The majority of the O-linked oligosaccharides are unusually large and contain 15 to as many as 50 sugar residues. The O-linked oligosaccharides are poly-N-acetyllactosaminyl chains consisting of -3Gal beta 1-4GlcNAc beta 1- and -3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1- repeats and thus they contain inner Le(X) antigenic determinants. These oligosaccharides terminate with novel alpha-galactosylated Le(X) and Le(a) epitopes. Due to the abundance of terminal alpha-galactosyl residues, cobra venom mucin reacts with anti-alpha-Gal antibodies that are normally present in human serum.

Structural features of water-soluble novel polysaccharide components from the leaves of Tridax procumbens Linn

Two water-soluble polysaccharide fractions, WSTP-IA and WSTP-IB were purified from the leaves of Tridax procumbens Linn. with graded ethanol precipitation followed by mild delignification and size-exclusion chromatography. WSTP-IA contained L-Araf and D-Galp in approximately 1:3 molar proportions, and WSTP-IB contained only D-Galp as the major sugar component. The results of methylation linkage analysis, and 1H and 13C NMR studies on the native and modified polysaccharides, indicated that WSTP-IA is an L-arabino-D-galactan with a beta-(1-->6)-D-galactan main chain in which at least one in every two D-Galp residues carries single residues of either L-Araf (alpha-/beta-) or beta-D-Galp end-group as substituents at O-3. WSTP-IB is a linear beta-(1-->6)-D-galactan. This is the first report of polysaccharides containing a beta-(1-->6)-D-galactan main chain isolated from plant sources.

Factor X-activating glycoprotein of Russell's viper venom. Polypeptide composition and characterization of the carbohydrate moieties

There is contradictory information regarding the molecular weight and polypeptide chain composition of RVV-X, a glycoprotein in Russell's viper venom that is capable of activating factor X to Xa. We show that RVV-X is a 92,880-Da glycoprotein. It consists of three disulfide-linked polypeptide chains, one heavy chain (alpha-chain, M(r) 57,600) and two light chains (beta- and gamma-chains, M(r) 19,400 and 16,400, respectively). The two light chains seen on SDS-polyacrylamide gel electrophoresis under reducing conditions are two distinct components of the molecule, rather than a heterogeneous mixture of a single chain as previously reported (Takeya, H., Nishida, S., Miyata, T., Kawada, S., Saisaka, Y., Morita, T., and Iwanaga, S. (1992) J. Biol. Chem. 267, 14109-14117). The following evidence supports this conclusion. (i) The two light chains of RVV-X are present in equal proportion. (ii) The estimated molecular weight of an alpha 1 beta 1 gamma 1-structure closely matches the molecular weight determined by matrix-assisted laser desorption mass spectrometry. (iii) The amino acid compositions and NH2-terminal sequences of the beta- and gamma-chains are different. (iv) Although both the beta- and gamma-chains contain one N-linked oligosaccharide chain each, they are glycosylated differentially. RVV-X contains six N-linked oligosaccharides, four in the alpha-chain and one in each of the beta- and gamma-chains. The carbohydrate structures are different from those known for other snake venom glycoproteins, and they resemble closely those in various mammalian glycoproteins. The majority of the oligosaccharides are complex bi-, tri-, and tetraantennary structures, with a small proportion of multiantennary and high mannose-type structures. Two notable structural features of RVV-X oligosaccharides are as follows. (i) Sialic acid residues are linked to beta-galactosyl residues solely by alpha 2,3-linkages, and (ii) bisecting N-acetylglucosamine residues are present in the majority of the oligosaccharides.

Mucin coding sequences are remarkably conserved

Mucins are complex glycoproteins expressed by glandular epithelia and the carcinoma which develop from these tissues. The core protein is aberrantly glycosylated in cancers, and some antibodies show specificity in their reactions with the cancer-associated mucins, which also contains epitopes recognized by T-cells from pancreatic and breast cancer patients. Based on the PCR amplification of the mucin coding sequences, hybridization analysis and determination of the sequence divergence we present the evidence that mucin coding sequences are conserved in a number of species. A broad series of organisms were examined for analogous sequences. Data show that mucin-type sequences are present in a variety of mammals, but less apparent in chicken and yeast. Divergence increased in the order human, monkey, rabbit/rat/cow, mouse; chicken and yeast exhibited minimal homology. Furthermore, nucleotide sequences not included in the tandem repeats, a common feature of mucin core structure, are more conserved than the flanking sequences which also suggests that the flanking sequences may be functionally significant while repeats are structurally important. The hybridization bands showed different restriction patterns (suggesting for the existence of the restriction fragment length polymorphism). Northern analysis indicates message polydispersity, commonly seen with this class of RNA. The major features of the protein appear broadly conserved in the different mammalian species examined. The evolutionary significance of the above studies has been discussed.