Developmental changes in pre-adult behavior in confined colonies of golden hamsters.

Eight litters of hamsters living in a large enclosure were observed from birth to 120 days. For the first 65 days each litter was confined to a separate compartment. Basic motor coordination was reached by the 3rd week. Marking was seen during the 6th week when males began to mount their mothers sexually, but lordosis was not seen in female pups before the 7th week. Fighting appeared at this time with the females being the more aggressive. At 65 days the litters were combined into 2 groups of 4.A gradual shift followed in the relative aggressiveness of the sexes. Females, which had previously initiated over 90% of attacks, became less aggressive, whereas attacks by males increased to the former female level. This unusual behavior for hamsters, where females are normally dominant, may have been due to crowding. Also, severe disruption of maternal behavior occurred with marked infanticidal tendencies.     

Crosslinked polyimide foams derived from poly(imidepropylene oxide) copolymers

A new route for the synthesis of high glass transition temperature, thermally stable polymer foams has been developed, using compositionally asymmetric microphase-separated block copolymers where the minor component (poly(propylene oxide)) is thermally labile and the major component (polyimide) is thermally stable. The minor component decomposes to low molecular weight species upon heating, and the decomposition products diffuse out of the film, leaving behind pores embedded in a matrix of the thermally stable component. In this study, the polyimide block was crosslinked with ethynyl functionalities to obtain a stable porous structure. The decomposition of the propylene oxide in the block copolymer was studied by thermogravimetric, dynamic mechanical and thermomechanical analyses. Mild conditions were required to avoid rapid depolymerization of the propylene oxide and plasticization of the polyimide matrix. The foams showed pore sizes with diameters up to a micrometer in size as well as the expected reduction in the mass density.     

Antigen-binding peripheral blood lymphocytes in guinea-pigs immunized with human thyroglobulin in BCG

Guinea-pigs were immunized with an emulsion of human thyroglobulin (Tg) and BCG vaccine in Freund's incomplete adjuvant. Peripheral blood lymphocytes binding Tg and purified protein derivative of mammalian tuberculin (PPD) labelled with ¹²⁵I were demonstrated with an autoradiographic technique. The percentage of these cells was compared with the size of the delayed hypersensitivity (DH) skin reactions to Tg and PPD, and Tg antibody titres at intervals up to 35 days after immunization. The individual responses to Tg showed the time course of primary immune reactions although they did not parallel each other closely. By contrast, a depression of cutaneous DH to PPD was observed in spite of the presence of substantial numbers of ¹²⁵I-PPD-binding peripheral blood lymphocytes. In non-immune guinea-pigs, approximately 2·8% of peripheral blood lymphocytes bound ¹²⁵I-PPD whereas <0·1% bound ¹²⁵I-Tg.

The significance of antigen-binding lymphocytes in the immune response is discussed, and it is suggested that the presence of a substantial pool of antigen-binding lymphocytes in unprimed may be of importance in the induction of DH.

     

PC-based system for collection and analysis of physiological data

A personal computer based system for data acquisition and analysis appropriate to physiological experiments is described in detail. The system is independent of the details of the analog signal generation. The software, written in C, is modular and easily portable to other PC systems. The system is capable of: (a) sampling many analog signals at an appropriate rate (100 Hz), (b) storing large quantities of digitized data, (c) analysing digitized waveforms to obtain signal parameters, and (d) storing signal parameters in a format suitable for statistical analysis. Computer processed cardiopulmonary data are compared with data derived from standard ICU equipment.     

Genetic diversity and relationships among Streptococcus pyogenes strains expressing serotype M1 protein: recent intercontinental spread of a subclone causing episodes of invasive disease.

Chromosomal diversity and relationships among 126 Streptococcus pyogenes strains expressing M1 protein from 13 countries on five continents were analyzed by multilocus enzyme electrophoresis and restriction fragment profiling by pulsed-field gel electrophoresis. All isolates were studied for the presence of the gene encoding streptococcal pyrogenic exotoxin A by PCR. Strain subsets were also examined by automated DNA sequencing for allelic polymorphism in genes encoding M protein (emm), streptococcal pyrogenic exotoxin A (speA), streptokinase (ska), pyrogenic exotoxin B (interleukin-1 beta convertase) (speB), and C5a peptidase (scp). Seven distinct emm1 alleles that encode M proteins differing at one or more amino acids in the N-terminal variable region were identified. Although substantial levels of genetic diversity exist among M1-expressing organisms, most invasive disease episodes are caused by two subclones marked by distinctive multilocus enzyme electrophoretic profiles and pulsed-field gel electrophoresis restriction fragment length polymorphism (RFLP) types. One of these subclones (ET 1/RFLP pattern 1a) has the speA gene and was recovered worldwide. Identity of speA, emm1, speB, and ska alleles in virtually all isolates of ET 1/RFLP type 1a means that these organisms share a common ancestor and that global dispersion of this M1-expressing subclone has occurred very recently. The occurrence of the same emm and ska alleles in strains that are well differentiated in overall chromosomal character demonstrates that horizontal transfer and recombination play a fundamental role in diversifying natural populations of S. pyogenes.