Effect of whole-plant corn silage treated with lignocellulose-degrading bacteria on growth performance, rumen fermentation, and rumen microflora in sheep.

Lignification of cellulose limits the effective utilisation of fibre in plant cell wall. Lignocellulose-degrading bacteria secrete enzymes that decompose lignin and have the potential to improve fibre digestibility. Therefore, this study aimed to investigate the effect of whole-plant corn silage inoculated with lignocellulose-degrading bacteria on the growth performance, rumen fermentation, and rumen microbiome in sheep. Twelve 2-month-old male hybrid sheep (Dorper ♂ × small-tailed Han ♀) were randomly assigned into two dietary groups (n = 6): (1) untreated whole-plant corn silage (WPCS) and (2) WPCS inoculated with bacterial inoculant (WPCSB). Whole-plant corn silage inoculated with bacterial inoculant had higher in situ NDF digestibility than WPCS. Sheep in the WPCSB group had significantly higher average daily gain, DM intake, and feed conversion rate than those in the WPCS group (P < 0.05). Furthermore, higher volatile fatty acid concentrations were detected in WPCSB rumen samples, leading to lower ruminal pH (P < 0.05). The WPCSB group showed higher abundance of Bacteroidetes and lower abundance of Firmicutes in the rumen microbiome than the WPCS group (P < 0.05). Multiple differential genera were identified, with Prevotella being the most dominant genus and more abundant in WPCSB samples. Moreover, the enriched functional attributes, including those associated with glycolysis/gluconeogenesis and citrate cycle, were more actively expressed in the WPCSB samples than in the WPCS samples. Additionally, certain glucoside hydrolases that hydrolyse the side chains of hemicelluloses and pectins were also actively expressed in the WPCSB microbiome. These findings suggested that WPCSB increased NDF digestibility in three ways: (1) by increasing the relative abundance of the most abundant genera, (2) by recruiting more functional features involved in glycolysis/gluconeogenesis and citrate cycle pathways, and (3) by increasing the relative abundance and/or expression activity of the glucoside hydrolases involved in hemicellulose and pectin metabolism. Our findings provide novel insights into the microbial mechanisms underlying improvement in the growth performance of sheep/ruminants. However, the biological mechanisms cannot be fully elucidated using only metagenomics tools; therefore, a combined multi-omics approach will be used in subsequent studies.

Novel screening strategy reveals a potent Bacillus antagonist capable of mitigating wheat take-all disease caused by Gaeumannomyces graminis var. tritici.

Take-all is a severe root disease of wheat worldwide that is caused by the soilborne fungal pathogen Gaeumannomyces graminis var. tritici (Ggt). In this study, 272 Bacillus isolates were screened for their antifungal activity in vitro to Ggt. Of the 128 strains that demonstrated an antagonistic action, 24 of these exhibited at least three of the four plant growth promotion parameters (i.e. indole acetic acid and siderophore production, inorganic phosphorus solubilization and organic phosphorus solubilization) that were tested in wheat plants. The most effective strain found was Bacillus subtilis Pnf-12; its disease reduction effect reached 69%. Pnf-12 also caused a significant improvement (P < 0·05) in the root and shoot weights of wheat plants, though their root length and shoot height were similar to the noninoculated treatment (P > 0·05). The mechanism for this disease control may be linked to the production of the antifungal lipopeptides surfactin, iturin and fengycin production, all of which were detected in the cell-free supernatant of Pnf-12. SIGNIFICANCE AND IMPACT OF THE STUDY: Take-all, which is caused by the soilborne fungal pathogen Gaeumannomyces graminis var. tritici (Ggt), is one of the most widespread and devastating root diseases of wheat plants. This study focuses on a novel screening strategy of Bacillus isolates to evaluate their potential biological control capacity for suppressing wheat take-all. The joint assessment of antifungal activities, growth promotion factors and variety of antibiotic synthesis genes, in addition to greenhouse experiments, allowed for the identification and demonstration of the Bacillus isolate Pnf-12 as an effective disease control agent.

Quantitative study of the quadratic magneto-optical Kerr effects in Fe films.

We present a rotating field method to separate the linear and quadratic magneto-optical Kerr effects (LMOKE and QMOKE) in Fe/GaAs(001) films. The LMOKE is isotropic in crystal orientation, while the QMOKE has both isotropic and anisotropic contributions. The experimental observation is well explained by Yeh's 4×4 matrix formalism. We also report the incident angle and the thickness dependences of the LMOKE and QMOKE, and extract the material's index of refraction n and the magneto-optical coupling constant K and G. The study gives a full description of the Kerr effect in Fe films, and the proposed method can be applied to other magneto-optical coupling systems.

Evaluation of vetiver oil and seven insect-active essential oils against the Formosan subterranean termite.

Repellency and toxicity of 8 essential oils (vetiver grass, cassia leaf, clove bud, cedarwood, Eucalyptus globules, Eucalyptus citrodora, lemongrass and geranium) were evaluated against the Formosan subterranean termite, Coptotermes formosanus Shiraki. Vetiver oil proved the most effective repellent because of its long-lasting activity. Clove bud was the most toxic, killing 100% of termites in 2 days at 50 micrograms/cm2. The tunneling response of termites to vetiver oil also was examined. Vetiver oil decreased termite tunneling activity at concentrations as low as 5 micrograms/g sand. Tunneling and paper consumption were not observed when vetiver oil concentrations were higher than 25 micrograms/g sand. Bioactivity of the 8 oils against termites and chemical volatility were inversely associated. Listed in decreasing order of volatility, the major constituents of the 8 oils were: eucalyptol, citronellal, citral, citronellol, cinnamaldehyde, eugenol, thujopsene, and both alpha- and beta-vetivone. Vetivor oil is a promising novel termiticide with reduced environmental impact for use against subterranean termites.

Nootkatone is a repellent for Formosan subterranean termite (Coptotermes formosanus).

We examined the behavior of Formosan subterranean termites toward one of the components of vetiver grass oil, the roots of which manufacture insect repellents. We found nootkatone, a sesquiterpene ketone, isolated from vetiver oil is a strong repellent and toxicant to Formosan subterranean termites. The lowest effective concentration tested was 10 micrograms/g substrate. This is the first report of nootkatone being a repellent to insects.

[Studies on the Robertsonian translocation of Microtus mandarinus].

The type of chromosome No. 1 and chromosome number from 53 individuals of Microtus mandarinus have been studied and compared in three sex types: XY, XX, XO. We found that the first pair of autosomes are very unstable, and there are three types: (1) M, M (With a double metacentric chromosome), (2) M, T, T, (With single metacentric chromosome). (3) T, T, T, T (Without metacentric chromosome). The chromosome number of the same sex individuals changes regularly with the type change of chromosome No. 1, that is, the increase of one chromosome in 2n number is always accompanied by the increase of two T and the decrease of one M, and vice versa. The synaptonemal complexes (SCs) of spermatocyte in pachytene nuclei from the males (2n = 51) were analysed by the electron microscopy. The SCs studies demonstrate that there are 23 fully paired autosomal bivalents, XY-bivalent and an autosomal trivalent. This trivalent is formed by one metacentric and two telocentric elements and characterized by the presence of two short side-arms. Meanwhile, all trivalents are in a cis configuration. The study of G-banding also demonstrates that the No. 1 autosome polymorphism is caused by Robertsonian translocation. Robertsonian fission is the main reason of the polymorphism of chromosome No. 1 and of variation of chromosome number in M. mandarinus.

Neural control of the compensatory increase of testosterone in hemicastrated adult male rats.

It is unclear why the concentration of testosterone increases in the testicular vein after hemicastration without corresponding alteration in gonadotropins. The present work was undertaken to examine whether the testosterone levels could be modified by denervation of the testis in adult rats. Both systemic and testicular blood samples were collected either immediately before or 6 and 24 hours after hemicastration from the rats two weeks after denervation of either inferior spermatic nerves (ISN) or ISN plus superior spermatic nerves (ISN-SSN). Increase of testicular testosterone induced by hemicastration was significantly (P<0.05) inhibited in these rats, as compared with the sham animals (at 6 and 24 hours, ISN vs sham: 16.00+/-3.35 vs 42.72+/-13.85 and 26.93+/-8.68 vs 71.16+/-13.30 whilst ISN-SSN vs sham: 31.63+/-7.92 vs 60.61+/-18.11 and 27.70+/-8.93 vs 93.92+/-19.73 ng/ml, respectively), whereas no significant change in LH was observed in all the experimental groups. FSH underwent no alteration in all the ISN denervation groups, but a significant elevation was observed in the ISN-SSN denervation groups (P<0.05) before hemicastration. Therefore, it appears that the change in FSH is not the cause of the inhibition of testosterone increase in the hemicastrated rats after testicular denervation and that ISN plays an active role in regulation of testosterone increase induced by hemicastration.

Differential effects of superior and inferior spermatic nerves on testosterone secretion and spermatic blood flow in cats.

It has been postulated that testosterone secretion is partially regulated by signals from the spermatic nerves. To further examine this hypothesis in vivo, the superior (SSN) or the inferior (ISN) spermatic nerves were stimulated electrically (varying intensity, 25 Hz, 0.2 msec, 10 min) in anesthetized cats, determining the testosterone concentration and the blood flow in the spermatic vein. In some additional experiments arterial blood was sampled, and norepinephrine (NE) output was calculated. Stimulation of the SSN (25-35 V) increased the testosterone concentration in spermatic vein blood (P < 0.01 compared with prestimulation levels). The response varied among animals, reaching a 50-100% increase in some animals, whereas in others it ranged from almost undetectable to more than 10 ng/100 g x min. Under the same experimental conditions, the NE output increased from 135.4 +/- 99 to 1614.2 +/- 347 pg/ml (P < 0.01), and spermatic blood flow decreased from 24.1 +/- 1.42 to 20.2 +/- 1.65 ml/min x 100 g (P < 0.05) during nerve stimulation. By contrast, stimulation of the ISN (25-35 V) modified neither the testosterone concentration, the NE output, nor the blood flow in the spermatic vein. High intensity stimulation (36-70 V) of each spermatic nerve evoked different vascular and hormonal effects. SSN activation induced a marked decrease in spermatic blood flow during stimulation and an increase in the testosterone response, whereas ISN activation resulted only in an enhanced spermatic blood flow. Our results suggest that testosterone secretion, although mainly dependent on gonadotropin secretion, could be further regulated by neural inputs from the SSN acting directly or alternatively through changes in blood flow. It would appear that the SSN mainly supplies the vasoconstrictor fibers to the testis, whereas the ISN provides vasodilator fibers.

[Vasoactive intestinal polypeptide induced prolactin release is model dependent in free-moving rats].

Our previous experiments in vitro showed that the stimulating effects of vasoactive intestinal polypeptide (VIP) on pituitary (PRL) depended on the endocrinal status of the animals. The present investigation was to determine whether the effect of VIP varied in vivo with changes of different physiological conditions. For infusion of VIP (5 micrograms/100 g body weight) and collection of blood sample, all the animals were cannulated with silicon tube into jugular vein 2-3 d before the experiments. The results showed that VIP concentration in blood was increased rapidly after the infusion (maximum: 21.32 +/- 2.33 ng/ml at 10 min and lasting more than 30 min). The concentration of PRL in blood of all the animals tested was increased significantly (P < 0.05) after VIP infusion. The increase rate of PRL induced by VIP was higher in male rats (158.04 +/- 37.06), but lower in the female (Diestrus: 50.42 +/- 16.44, Proestrus: 62.67 +/- 21.34) and in Suckling-depended lactating ones (Suckled 90.00 +/- 36.00 vs. Separated 31.05 +/- 4.42). The above observations suggest that the VIP action in vivo depends on the endocrinal and/or neural status of the animals.

Sertoli cell nuclear pore number changes in some stages of the spermatogenic cycle of the rat seminiferous epithelium.

In an earlier study we described changes in the number and distribution of nuclear pores during maturation of germ cells at given stages of the spermatogenic cycle; these changes were related to the activity of nucleus-cytoplasm transport. Similarly, the present work was performed by combining freeze-fracture techniques with Sertoli nuclei identification criteria, using fragments of tubules isolated by transillumination under stereomicroscopy. We studied the density of nuclear pores in freeze-fracture replicas of the Sertoli nuclear envelope at stages XIII-XIV-I compared with stages IX-XII. Pore counts were carried out on photographs of the platinum replicas using a digitalized morphometric board. The results were statistically analyzed using Student's t test. The difference in density (pore number/micron2 +/- SEM) was significant between stages IX-XII (8.25 +/- 0.63) and XIII-XIV-I (10.80 +/- 0.60). We postulate that this density appears to be increased at the time of increased metabolic requirements of the Sertoli cell.

Dolichyl-phosphomannose synthase from the archae Thermoplasma acidophilum.

Archae (formerly Archaebacteria) comprise an entire kingdom of organisms placed halfway between prokaryotes and eucaryotes in evolution. This class of organisms lacks murein cell wall and is devoid of organelles, yet Archae synthesize and export N-linked and O-linked glycoproteins utilizing only the plasma membrane. Study of glycosylation systems in Archae is extremely interesting because the plasma membrane must perform many functions normally carried out by the endoplasmic reticulum and Golgi in eucaryotes. This report represents the first glycosyl transferase system enzyme demonstrated from archae showing a functional relationship with homologous eucaryotic enzymes. Archae dolichyl-phosphoryl-mannose synthase was purified 1070-fold from Thermoplasma acidophilum by column chromatography on Sephacryl S-200, Cibacron blue 3GA-agarose, Octyl-Sepharose, and hydroxylapatite in the presence of 0.2% polioxyethylene 9 lauryl ether. The enzyme activity was stimulated by MgCl2 (20 mM optimum) and exhibited a pH optimum at 6.0. Although the native polyisoprenoid has not been isolated or characterized, the enzyme prefers dolichyl phosphate (dol-P) to C55-polyisoprenol as an acceptor, and the Km value for dol-P was calculated to be 2.6 microM. Amphomycin, an inhibitor of dol-P-Man synthase, blocked mannosyl transfer to the endogenous lipids, proteins, and to dol-P; 100 micrograms/ml amphomycin inhibited 97% of mannosyl transfer to dol-P, and 50% to endogenous acceptors, indicating direct transfer from GDP-mannose to some intermediates or final structures. The size range of [3H]Man-oligosaccharides from acid-labile manno-lipid product was from dp 1 to 4. dol-P-Man synthase activity could be correlated directly with a 42 kDa band on SDS/polyacrylamide gel electrophoresis.

Inhibition of glycosylation by amphomycin and sugar nucleotide analogs PP36 and PP55 indicates that Haloferax volcanii beta-glucosylates both glycoproteins and glycolipids through lipid-linked sugar intermediates: evidence for three novel glycoproteins and a novel sulfated dihexosyl-archaeol glycolipid.

Arachaebacteria have been recently placed in evolution as a separate kingdom of organisms between procaryotes and eucaryotes. Although these organisms contain both glycolipids and glycoproteins, they possess no Golgi. No biosynthetic work has been published on the complex carbohydrates of these newly reassigned organisms. This report describes preliminary results from one member of this kingdom, Haloferax volcanii, which suggest that all glycosylation proceeds through lipid intermediates. Evidence for novel glycolipid structure was also found during this study. H. volcanii plasma membranes contain all of the enzyme activities for synthesis of N-linked glycoproteins and archaeol-based glycolipids. For glucose transfer, all reactions apparently proceed through glucose-phosphopolyisoprenol using UDP-glucose as primary donor. Incorporation of D-[3H]glucose from UDP-D-[3H]glucose into glycoproteins and glycolipids of H. volcanii was stimulated by addition of C55-polyisoprenol phosphate, but not by C85-105 dolichol phosphate, and was inhibited by amphomycin and two recently described sugar nucleotide analogs, PP36 (5'-[N-(2-decanoylamino-3-hydroxy-3-phenylpropyloxy carbonyl)glycyl]amino]-5'-deoxyuridine) and PP55 (5'-O-[[(2-decanoylamino-3-phenylpropyloxycarbonyl) amino]sulfonyl]uridine). All three inhibitors are reported to block transfer of sugar from UDP-sugars to phosphopolyisoprenols in eucaryotes. However, in H. volcanii these inhibitors apparently block transfer of glucose from polyprenyl intermediates to final glycoproteins and glycolipid products. The sulfodihexosyl archaeol glycolipid fraction was partially characterized by mass spectrometry and was found to contain a previously unreported structure with sulfate on the reducing-end sugar. Four major glycoproteins 190, 105, 56, and 52 kDa and an archaeol-based glycolipid fraction were labeled by amphomycin-sensitive pathways. Photoaffinity labeling of H. volcanii homogenate with 5-azido-[32P]UDP-Glc tagged only one 45-kDa polypeptide which is a probable glucosyl-phosphorylpolyisoprenol synthase. The fact that only one polypeptide band was photoaffinity-labeled indicated that no other transferase utilized UDP-glucose directly in H. volcanii. The salt requirement of the UDP-glucose-dependent pathways suggests that cytoplasmic enzymes function in a high salt environment in H. volcanii. The archaebacterial plasma membrane thus expresses many functions for glycosylation of both glycoproteins and glycolipids, normally found in the endoplasmic reticulum and Golgi of eucaryotes.

Monoaminergic and peptidergic contributions of the superior and the inferior spermatic nerves to the innervation of the testis in the rat.

Sections of the rat testis and whole-mounts of the testicular capsule were studied microscopically using the glyoxylic acid-induced fluorescence method, to detect monoamines, and immunohistochemical procedures for the detection of immunoreactivities to protein gene-product 9.5 (PGP 9.5), the C-terminal accompanying peptide of neuropeptide Y (CPON), and vasoactive intestinal polypeptide (VIP). Monoaminergic nerves were only observed around the intracapsular blood vessels: the initial segment of the testicular artery and the superior venous plexus, and in the anterior aspect of the upper and lower testicular poles. These capsular nerve networks were associated with the superior and inferior ligaments of the testis. Nerves displaying PGP 9.5 and CPON immunoreactivity appeared in the same sites and followed the same distribution as monoaminergic nerves. By contrast, VIP-immunoreactive fibers were only found in the nerve network of the lower pole. Observations done after different surgical denervation procedures demonstrated that the superior spermatic nerve was the source of fibers for testicular vessels and for the nerve network of the upper pole. On the other hand, fibers from the inferior spermatic nerve were restricted to the nerve network of the lower pole.

Chitovibrin: a chitin-binding lectin from Vibrio parahemolyticus.

A novel 134 kDa, calcium-independent chitin-binding lectin, 'chitovibrin', is secreted by the marine bacterium Vibrio parahemolyticus, inducible with chitin or chitin-oligomers. Chitovibrin shows no apparent enzymatic activity but exhibits a strong affinity for chitin and chito-oligomers > dp9. The protein has an isoelectric pH of 3.6, shows thermal tolerance, binds chitin with an optimum at pH 6 and is active in 0-4 M NaCl. Chitovibrin appears to be completely different from other reported Vibrio lectins and may function to bind V. parahemolyticus to chitin substrates, or to capture or sequester chito-oligomers. It may be a member of a large group of recently described proteins in Vibrios related to a complex chitinoclastic (chitinivorous) system.

Thermostable, salt tolerant, wide pH range novel chitobiase from Vibrio parahemolyticus: isolation, characterization, molecular cloning, and expression.

A chitobiase gene from Vibrio parahemolyticus was cloned into plasmid pUC18 in Escherichia coli strain DH5 alpha. The plasmid construct, pC120, contained a 6.4 kb Vibrio DNA insert. The recombinant gene expressed chitobiase [EC 3.2.1.30] activity similar to that found in the native Vibrio. The enzyme was purified by ion exchange, hydroxylapatite and gel permeation chromatographies, and exhibited an apparent molecular weight of 80 kDa on SDS-polyacrylamide gel electrophoresis. Chitobiose and 6 more substrates, including beta-N-acetyl galactosamine glycosides, were hydrolyzed by the recombinant chitobiase, indicating its putative classification as an hexosaminidase [EC 3.2.1.52]. The enzyme was resistant to denaturation by 2 M NaCl, thermostable at 45 degrees C and active over a very unusual (for glycosyl hydrolases) pH range, from 4 to 10. The purified cloned chitobiase gave 4 closely focussed bands on an isoelectric focusing gel, at pH 4 to 6.5. The N-terminal 43 amino acid sequence shows no homology with other proteins in commercial databanks or in the literature, and from its N-terminal sequence, appears to be a novel protein, unrelated in sequence to chitobiases from other Vibrios reported and unrelated to hexosaminidases from other organisms.

Intrinsic tryptophan fluorescence measurements suggest that polylactosaminyl glycosylation affects the protein conformation of the gelatin-binding domain from human placental fibronectin.

Glycosylation can affect the physical and biochemical properties of the polypeptide chain in glycoproteins. Asparagine-N-linked polylactosaminyl glycosylation of the chymotryptic 44-kDa gelatin-binding domain from human placental fibronectin confers protease resistance [Zhu, B. C. R., Fisher, S. F., Panda, H., Calaycay, J., Shively, J. E. & Laine, R. A. (1984) J. Biol. Chem. 259, 3962-3970] and weaken the binding to gelatin [Zhu, B. C. R. & Laine, R. A. (1985) J. Biol. Chem. 260, 4041-4045]. Intrinsic tryptophan fluorescence of the gelatin-binding domain was used to probe glycosylation-dependent protein conformation changes. In gelatin-binding fragments containing incrementally smaller polylactosamine oligosaccharides, the fluorescence intensity progressively decreased and the emission spectrum shifted about 7 nm to the blue. Removal of the polylactosamine chains from a highly glycosylated fragment with endo-beta-galactosidase from Escherichia freundii also quenched the protein fluorescence. The fluorescence lifetimes did not appear to be affected by the extent of glycosylation, suggesting static quenching of the tryptophan emission in the low glycosylated fragments. Acrylamide quenching studies showed that the accessibility of the tryptophans to small solutes was not altered by glycosylation. The steady-state emission anisotropy increased with decreasing polylactosamine chain length. The results indicate that the polylactosamine chains alter the tryptophan environments in the gelatin-binding domain, probably by changing the polypeptide conformation. These putative protein conformation changes may be partially responsible for the altered gelatin binding, protease resistance, and cell adhesion functions of fetal tissue fibronectin.

Novel hyperglycosylated weak gelatin-binding fibronectin from human fetal placenta. Fractionation of a high poly(N-acetyllactosamine) fragment by tomato lectin affinity chromatography.

A novel hyperglycosylated fraction of human term fetal placental fibronectin was detected by long-term affinity binding to gelatin-Sepharose. An 18-h batch-wise gelatin-binding step was necessary to obtain a very low-affinity binding fraction, characterized by especially high N-acetylglucosamine and galactose content, and diffuse, poorly stained Coomassie bands on SDS/polyacrylamide electrophoretograms. The presence of a high proportion of long 7-10-kDa poly(N-acetyllactosamine)-containing N-linked carbohydrate chains was confirmed by their gel permeation behavior, susceptibility to endo-beta-galactosidase and by methylation analysis. Our previous results suggest that 4.5-7-kDa poly(N-acetyllactosamine) structures reduce the binding of fibronectin and its chymotryptic Ala260-Trp599 subdomain GB44 to gelatin [Zhu, B. C. R. & Laine, R. A. (1985) J. Biol. Chem. 260, 4041-4045]. Based on a gradient of urea used to dissociate gelatin-bound GB44, in the present study, fractions containing the novel 7-10-kDa carbohydrates showed significantly weaker binding to gelatin. Weak gelatin-binding characteristics of this novel hyperglycosylated fraction suggest that extended poly(N-acetyllactosamine) N-linked chains can significantly weaken heterotropic binding functions of fetal glycoproteins. The combined properties of weak Coomassie staining and weak gelatin binding have caused the novel hyperglycosylated fibronectin to be overlooked in previous investigations.

Purification of acetyllactosamine-specific tomato lectin by erythroglycan-sepharose affinity chromatography.

Tomato lectin is specific for oligomers of poly-N-acetyllactosamine containing 3 repeating Gal(beta 1-4)GlcNAc (beta 1-3)-disaccharides. As such it is highly useful for purifying oligosaccharides or glycopeptides with poly-N-acetyllactosamine character. We have found the lectin very useful as an affinity reagent for isolating glycoproteins or glycoprotein domains having poly-N-acetyllactosamine glycosylation. Conventional preparation of tomato lectin by ovomucoid-Sepharose affinity chromatography was found to be unsatisfactory due to instability of column and bleeding of ovomucoid into eluents requiring the necessity for additional purification steps following affinity chromatography. We prepared a column of human erythrocyte band 3 carbohydrate glycopeptide (erythroglycan) attached to Sepharose as an affinity matrix. The purification of tomato lectin to homogeneity in one step on this column matrix is described in this report.

Developmental study of human fetal placental fibronectin: alterations in carbohydrates of tissue fibronectin during gestation.

Human term placental tissue fibronectin contains about twice the carbohydrate content of human adult plasma fibronectin or fetal plasma fibronectin. The chief difference is the presence of substantial amounts of large N-linked polylactosamine chains on the placental fibronectin. The large carbohydrate on placental tissue fibronectin weakens the binding of fibronectin to denatured collagen. To examine whether a developmental change takes place in the placental fibronectin during gestation, fibronectin was isolated from placentas of different developmental stages beginning with the first trimester and ending with term. Polylactosamine carbohydrate, as well as total quantity of carbohydrate, increased steadily during gestation, reaching a maximum at term of more than 9% carbohydrate. Weakened binding of fibronectin to collagen occurred near the end of gestation concomitant with an increase in the quantity of larger polylactosamine glycopeptides. Relationships among these developmental changes, the impending birth, and the end of the function of the placenta remain to be investigated.