Quantitative Aspects of the M Protein Capillary Precipitin Test

A capillary procedure for quantitatively determining M protein is described. Capillaries were filled with measured amounts of serum and streptococcal extract. The capillaries were incubated, and then centrifuged to pack the precipitates. The relative sizes of the precipates were compared by a determination of the weights of their paper images (obtained by reflection from a microscope). Meaningful dilution curves were determined by this method. Variations of pH from 6 to 8 had little effect on the M protein precipitin test, and the test was not seriously affected by variations of the NaCl concentration from 0.85 to 4.67%. The addition of divalent ions (Ca(++) and Mg(++)) did not influence the results. This test can be used to make quantitative comparisons of M protein preparations and to titrate type-specific antisera.     

饲喂黄曲霉毒素B_1大鼠肝中AFB_1-DNA加合物的免疫组织化学研究

应用免疫组织化学ＳＰ法对４例饲喂黄曲霉毒素Ｂ１的Ｗｉｓｔａｒ大鼠肝组织中ＡＦＢ１－ＤＮＡ加合物的染色及常规ＨＥ染色发现,４例肝细胞核均出现异型性,但未见肝细胞坏死、增生灶及肝细胞癌;免疫组化揭示部分肝细胞核出现棕黄色、不均质状的ＡＦＢ１－ＤＮＡ加合物,阳性细胞数占１０～８５％。结果提示免疫组织化学方法可作为一种ＡＦＢ１的定位方法,ＡＦＢ１在动物致癌过程中ＡＦＢ１－ＤＮＡ加合物可能具有启动作用     

Preparation and description of high-molecular-weight soluble surface antigens from a group A Streptococcus

High-molecular-weight proteins having M protein reactivity were isolated without acid or alkaline digestion. Treatment of a heat-killed group A Streptococcus with sonic vibration released antigens which reacted strongly and specifically with absorbed type-specific antiserum. This antigen preparation was released without diminishing the total yield of acid-extractable M protein of the original heat-killed cells. Fractionation of the sonic preparation on a sucrose gradient yielded four peaks of M reactivity. When these fractions were placed on Sephadex G-200 columns, the M reactive material of three fractions appeared in the void volumes, suggesting that the active material in each had a molecular weight greater than 300,000. The reactivity of the fourth fraction followed closely the void volume of Sephadex G-100. Chemical analysis revealed heterogeneity of the fractions. Spectral analysis showed virtual absence of nucleic acid in three of the fractions and a moderate amount in the fourth. Bactericidal inhibition tests showed activity of three of the four fractions. Analysis of the fractions by Ouchterlony double-diffusion technique revealed that each of the four fractions had several antigenic constituents. All four contained M antigen. T antigen and a third unnamed antigen were present in some of the fractions. Group reactivity was present in all fractions, but did not reside on the M molecule. The enhanced potential of sonically released antigens to induce high-titer specific precipitating antibodies to M protein is discussed.     

Hemoglobin synthesis in isolated erythroid colonies from the chick embryo.

Primary cultures derived from mechanically dissociated definitive streak chick blastoderms were grown in a warm air stream on the stage of inverted phase microscope, through which in vitro erythroid development could be observed. Proerythroid cells divide three or four times in 48 hr to give rise to erythroid colonies ranging from 10 to 1000 cells, depending on the size of the blastoderm fragments from which they were derived.Erythroid cell development follows a similar course in cultures grown in a carbon dioxide incubator. Colonies consisting of about 50 cells, derived from blastoderm fragments containing 5 to 10 cells, were isolated and labeled with [³H]leucine, and their labeled hemoglobins were analyzed by isoelectric focusing. Both early hemoglobins (E,M,P,P′, and P″) and late hemoglobins (A and D) are made in colonies derived from single blastoderm fragments. The ratio of late to early hemoglobins is about 1.7 in all colonies analyzed. The implications of this finding for the clonal model of erythroid development are discussed.     

Preemption versus Entrenchment: Towards a Construction-General Solution to the Problem of the Retreat from Verb Argument Structure Overgeneralization

Participants aged 5;2-6;8, 9;2-10;6 and 18;1-22;2 (72 at each age) rated verb argument structure overgeneralization errors (e.g., *Daddy giggled the baby) using a five-point scale. The study was designed to investigate the feasibility of two proposed construction-general solutions to the question of how children retreat from, or avoid, such errors. No support was found for the prediction of the preemption hypothesis that the greater the frequency of the verb in the single most nearly synonymous construction (for this example, the periphrastic causative; e.g., Daddy made the baby giggle), the lower the acceptability of the error. Support was found, however, for the prediction of the entrenchment hypothesis that the greater the overall frequency of the verb, regardless of construction, the lower the acceptability of the error, at least for the two older groups. Thus while entrenchment appears to be a robust solution to the problem of the retreat from error, and one that generalizes across different error types, we did not find evidence that this is the case for preemption. The implication is that the solution to the retreat from error lies not with specialized mechanisms, but rather in a probabilistic process of construction competition.     

Hormonal regulation of DNA synthesis in primary cultures of adult rat hepatocytes : Action of glucagon

Primary cultures of adult rat hepatocytes, grown in modified minimal essential medium (Eagle's) containing 10% calf serum, could be induced into DNA replication by combinations of epidermal growth factor (EGF), insulin and glucagon. The three hormones acted synergistically, and cells began entering DNA synthesis 48 h after hormone addition. The ability of the hormones to stimulate DNA synthesis was enhanced by plating cells at high cell concentrations or by conditioned medium, and was diminished by daily medium change. The contribution of glucagon to DNA synthesis was replaced by cAMP plus 1-methyl, 3-isobutyl xanthine or by adrenergic agents. Evidence is presented which suggests that all three hormones are required on the first day of culture, and that EGF and insulin are also required after the first day. This appears to be a useful system for studies on the hormonal initiation of growth in quiescent cells.     

Taxonomic Comparison of the Amino Termini of Microbial Cell Proteins

A comparison was made of the distribution of amino terminal end groups in the cellular proteins of a number of microbes. Among the procaryotes, methionine is a highly variable but virtually ubiquitous major protein end group. This is consistent with its possible role as a general amino acid initiator of protein biosynthesis in the procaryotes. Generally, however, alanine is the most abundant of the major end groups, followed in decreasing order by serine, threonine, the acidic amino acids, and occasionally lysine. No other new major end-groups were found. Among 15 representatives of the Enterobacteriaceae, retention of the initiating methionine terminus of the cellular protein varies considerably at a tribal level and is randomized at a familial level. The profiles of the five remaining end groups, however, are strikingly uniform, and are, for example, close to but significantly different from those of the Erwineae. Among the taxonomically more heterogeneous Bacillaceae, end-group profiles vary more and are sometimes unrelated. End-group analysis is thus particularly useful as a molecular criterion of taxonomy in assessing familial homogeneity. Free NH(2) termini in eucaryote cell proteins are fewer, and they have increased acidic amino acid components and no methionine; they are otherwise similar to those of the procaryotes.