High-mannose glycopeptides from embryonal carcinoma cells

Endo-beta-N-acetylglucosaminidase H released four major oligosaccharides from high-mannose glycopeptides prepared from embryonal carcinoma cells. The oligosacchaides were indistinguishable from (Man)9GlcNAc, (Man)8GlcNAc, (Man)7GlcNAc, and (Man)6GlcNAc isolated from fibroblasts. This result suggests that the biosynthetic pathway of asparagine-linked oligosaccharides in early embryonic cells is controlled as in adult cells, at least to the initial stage of processing of the nascent oligosaccharide transferred from lipid-linked intermediate.     

Fractionation of constituents of ribonucleoproteins containing heterogeneous nuclear ribonucleic acid.

A method of fractionation of hnRNP constituents adaptable to large-scale preparation is presented. It is based on differential resistance to salt dissociation of the two classes of units of hnRNP, the 30--50S monoparticles and the heterogeneous complexes. The monoparticle proteins were released from hnRNP by 0.4 M NaCl. They were separated from the salt-resistant RNP corresponding to the heterogeneous complexes in three steps: chromatography on DEAE-cellulose, high-speed centrifugation, and Bio-Gel chromatography. The latter chromatography permitted a first fractionation of monoparticle proteins according to molecular weight. Such fractions may serve for purification of individual proteins of molecular weight below 80 000. After the two first steps, two fractions of salt-resistant RNP were obtained. In addition to heterogeneous RNA up to 30 S, small nuclear RNAs were detected which represented 6% of total RNA. The protein pattern was complex, and no clear-cut segregation of groups of proteins could be observed between the two fractions. They were both highly enriched in phosphoproteins as compared to nomoparticle proteins. In another fraction corresponding to the void volume of Bio-Gel chromatography, one-third of the RNA was small nuclear RNA. It is suggested that this fraction contains snRNP in addition to free proteins of molecular weight above 80 000 and to salt-resistant RNP similar to those described above but of small size.     

Liver as a source of transformed cell growth factor

Isolated rat hepatocytes release an acidic glycoprotein(s) that can selectively promote the growth of transformed cells. This factor has a molecular weight of 60 000–70 000 D. Liver microsomal and cytosol fractions contain two species of stimulatory activity—44 000 and 3 500 D. Mitochondrial and nuclear fractions contain only the lower molecular weight factor.     

Distinctive properties of fucosyl glycopeptides on human teratoma cells

Fucose-labeled glycopeptides from four human teratoma cell lines of independent origin show similar elution profiles on Sephadex G-50 column chromatography. The fucosyl glycopeptides elute in two major regions: one near the void volume, the other in fractions corresponding to a molecular weight of 2500-3000. These elution profiles are very different from those obtained with the other human cell lines examined which included 3 lymphomas, 2 colon carcinomas, and HeLa. The elution profiles of the human teratomas, however, show remarkable similarities to those obtained with murine embryonal carcinoma cell culture and early mouse embryos. These results suggest that the excluded G-50 fraction may well contain glycopeptides playing a role in mammalian embryogenesis.     

Studies on a strain of Fusarium solani (Mart.) Sacc. Isolated from a case of mycotic keratitis

A strain of Fusarium solani (Mart.) Sacc. (IMI-216517), isolated from a patient of mycotic keratitis, produced experimental keratomycosis in albino rabbit cornea and survived in internal tissues of albino mice for varying periods. Alantolactone, isolated from the plant — Inula racemosa Hook. f. exhibited marked in vitro fungistatic activity against this strain of F. solani at 100–200 g/ml concentrations. The strain was less sensitive to amphotericin B and showed more acid than alkaline proteinase and phosphatase activities.Communication No. 2526.     

Behavioural displays to gustatory stimuli in newborn rabbit pups

Motor displays in the face and head regions of 33 neonate rabbits(less than 24 hrs post partum) in response to taste stimulationwere examined. A droplet of taste solution was placed mediallyon the pup's lips and the ensuing behavioral repertoire wastallied over a 60 sec period in a double blind situation. Tastantsincluded 2 concentrations each of sucrose, saccharin, citricacid and quinine. Distilled water was used as a stimulant andfor intertrial rinses. Response characteristics to the varioustaste stimuli were differentiable, specific and reproduciblewithin and across animals. Certain response features were moreoften associated with one stimulus than with another. Quinineoften produced mouth opening (gaping) and head movements, whereassucrose was associated with a quiet animal licking and makingcharacteristic mouth movements. Sour reactions often resembledthose to sweet, but other features helped distinguish thoseresponses. Reactions proved to be concentration-dependent anddifferent from those to water. Quality and hedonic value wereusually accurately judged and corresponded to adult preferencebehaviors. It was inferred that rabbits at this early age arealready equipped with a functioning taste system up to the brainstemlevel. Cross-species comparisons of stereotyped reactions werediscussed.     

Relaxation of solvent protons by cobalt bovine carbonic anhydrase.

In a recent report, Bertini et al. (Biochem. Biophys. Res. Comm.78, 158–160 (1977)) argued that the low-pH form of Co²⁺-substituted bovine carbonic anhydrase contains a rapidly exchanging water molecule at the cobalt site. The basis for this was the observation of a pH-independent contribution to the solvent water proton relaxation rate; it was suggested that the result was unobserved by previous workers because of the presence of sulfate in the sample buffer. We have repeated the experiments of Bertini et al. and find that the results can be attributed to an ionic strength-induced shift of the pK of the group responsible for the relaxation enhancement. The amount of high-pH form of the enzyme present (determined spectrophotometrically) at every pH correlates with the relaxation rate, whereas the fraction of high-pH form present at a given pH depends on ionic strength. These results are in agreement with earlier data indicating that the low-pH form of the enzyme does not contribute to solvent water proton relaxation.     

Magnetic cross-relaxation among protons in protein solutions.

The magnetic spin-lattice relaxation rates of solvent water nuclei are known to increase upon addition of diamagnetic solute protein. This enhancement of the relaxation rate is a function of magnetic field, and the orientational relaxation time of the protein molecules can be deduced from analysis of the field-dependent relaxation rates. Although the nature of the interactions that convey information about the dynamics of protein motion to the solvent molecules is not established, it is known that there is a contribution to the relaxation rates of solvent protons that plays no role in the relaxation of solvent deuterons and 17O nuclei. We show here that the additional interaction arises from a cross-relaxation process between solvent and solute protons. We introduce a heuristic three-parameter model in which protein protons and solvent protons are considered as two separate thermodynamic systems that interact across the protein-solvent interface. The three parameters are the intrinsic relaxation rates of each system and a cross-relaxation term. The sign of the latter term must always be positive, for all values of magnetic field, in order for magnetization energy to flow from the hotter to the cooler system. We find that the magnetic field-dependence of the cross-relaxation contribution is much like that of the remaining solvent proton relaxation, i.e., about the same as the deuteron relaxation field dependence. This finding is not compatible with the predictions of expressions for the cross-relaxation that have been used by other authors, but not applied to data over a wide range of magnetic field strength. The model predicts that the relaxation behavior of both the protein protons and the solvent protons is the sum of two exponentials, the relative contributions of which would vary with protein concentration and solvent isotopic composition in a fashion suggestive of the presence of two classes of protein protons, when there is in reality only one. This finding has immediate implications for the interpretation of published proton relaxation rates in complex systems such as tissues; these data should be reexamined with cross-relaxation taken into account.