Effects of castration and home cage residency on aggressive behavior in rats

The effects of castration of both resident and intruder rats on territorial aggressive behavior were studied. The results suggest that residence in a home cage is more important than gonadal status in determining the outcome of an aggressive encounter. Resident rats were more likely to be dominant especially if they were intact. Intact residents directed less aggressive behavior toward castrated intruders than toward intact intruders. Intruder rats generally showed low levels of aggressive behavior and were only dominant when the resident had been castrated. Thus, the aggressive behavior of a male rat depends upon both his gonadal status and that of his opponent.     

Effect of DNA base composition on the intercalation of proflavine. A kinetic study.

The effect of DNA base composition on the kinetics of the association between DNA and proflavine has been investigated using the temperature jump relaxation method. It is found that, regardless of the G + C base composition the results fit a two step mechanism, the second of which exhibits characteristics of intercalation of proflavine into DNA. However, they two equilibrium constants corresponding to these steps, KI and KII, depend on the nature of the DNAs. The constant KI is found to be an order of magnitude greater for M. lysodeikticus DNA (72% G + C) than for calf thymus DNA (48% G + C). Increasing G-C content thus appears to favor the intermediate non-intercalated complex of proflavine with DNA. Methylation of M. lysodeikticus DNA with dimethyl sulfate, preferentially yielding N7 methyl guanine as the modified base, again leads to an apparent two step mechanism, with the value of KI unchanged with respect to untreated DNA, while the affinity of proflavine for the intercalated complex measured by the value of KII increases for methylated DNA.     

Frequency of influenza-responsive cytolytic T-lymphocyte precursors in the thymus and spleen of unprimed mice

Limiting dilution culture conditions were established which allowed the differentiation and quantitation of influenza-specific cytotoxic T-cell precursors (CTL.Ps) from naive mouse spleen and thymus. One in 49,000 nucleated spleen cells and 1 in 40,000 thymocytes responded to stimulation with influenza-infected, anti-Thy 1.2 and complement-treated spleen cells, in the presence of ConA-stimulated cell supernatant, with the production of cytotoxic effector cells. These frequencies are 4- to 15-fold higher than those for influenza-responsive B cells in the relevant lymphoid compartments, and it is argued that major quantitative discrepancies may exist in the sizes of the B- and CTL-receptor repertoires.     

The digital pads of the tree frog, Hyla cinerea. I. The epidermis

As the digital pad cells grow from the germinal epithelium, the desmosomes on the distal surface oF tile cells become aligned and form pegs filled with tonofilaments on the surface of the outer row of cells. The outer pad cells are separated from each other distally, thus the cell and the pegs form two sizes of protrusions in series on the pad surface which can fit into substratum/irregularities. A dense material, apparently derived from transforming bodies in the cells, coats the plasma membrane of the surface cells, presumably to strengthen them.     

The digital pads of the tree frog, Hyla cinerea. II. The mucous glands

The mucous glands consist of a single row of cells surrounded by smooth muscle. The cells are attached at their apical and basal regions and only cytoplasmic projections loosely link the lateral aspects of adjacent cells. Material accumulates in the cisternae of the rough endoplasmic reticulum, appears to form into dense granules in the Golgi apparatus, and then before being secreted, undergoes chemical and morphological alterations. Since some glands secrete onto the dorsal epidermis of the digits, the mucous is believed to function as a wetting agent for the skin as well as an aid to climbing.     

Cellular cooperation in hapten-carrier responses in the newt, Triturus viridescens

Heterologous erythrocyte responses in the three hematopoietic organs, spleen, liver and kidney, were studied in the American Common Newt, Triturus (Diemictylus) viridescens. These responses were measured by immunocytoadherence. Horse (HRBC) and sheep (SRBC) red cells were used as immunogens. Background and response values to HRBC were consistent in all three organs. Activity levels and their kinetics were greater in spleen than in liver or kidney. Anti-SRBC activity levels proved to be too variable and as a consequence HRBC's were used in subsequent studies. Secondary responses in the newt showed modest increases in the spleen, a decrease in liver activity levels and a proportionately large (5×) increase within kidney. While splenectomy prior to immunization did not effect primary response activity in liver and kidney, it caused a three-fold enhancement of the usual loss of activity in secondary responses within liver. Kidney secondary response levels were unaffected by prior splenectomy. Spleen-liver lymphoid traffic may be involved in anamnestic responses in the newt.The main question had to do with whether one could demonstrate cellular cooperation in immune responses in so primitive a vertebrate. Chicken (CRBC) and toad (TRBC) red cells were used as carriers for the hapten trinitrophenol (TNP). Pre-immunization with the carrier immunogen led to the development of rosette forming cells (RFC) specific for the hapten in spleen, liver, and kidney after challenge with the TNP on the same carrier. Injection of the TNP carrier alone or pre-immunization with a different carrier caused no TNP-specific RFC's to be generated. The anti-TNP responses were assayed with HRBC and TNP-HRBC. Prior treatment with TNP-HSA (human serum albumin), before TNP-HRBC assay, blocked the RFC with TNP-HRBC and helped to establish the specificity of the hapten-specific RFC's. These kinds of immune responses in the newt require at least two cooperating cellular populations. Cellular cooperation may have been an early phylogenetic feature of immune responses.     

Binding of active and inactive hemolytic factor of sea anemone nematocyst venom to red blood cells

Sea anemone nematocyst venom, in the presence of Ca²⁺, induced the lysis of red blood cells after an induction period. In the absence of Ca²⁺, however, no lysis occurred, but the hemolytic factor was shown to bind to the cells. This binding was shown to be requisite for the Ca²⁺ dependent lysis to ensue. After freeze thawing, the venom proteins responsible for lysis lost their hemolytic activity, yet still bound to the cells. The freezethawed inactivated venom competitively blocked hemolysis by active venom.     

The flexibility during the juxtaposition of reacting groups and the upper limits of enzyme reactions

The combinations between enzymes and substrates occur only after their reacting groups are in juxtaposition with each other. This will greatly reduce the probability of their effective encounters. However, the results calculated with the finite element method show that the reaction limits will not decrease substantially if van der Waal's forces and a reasonable flexibility during such a juxtaposition are taken into account.     

The influence of rotor speed on the sedimentation behavior in sucrose gradients of high molecular weight DNA's

Anomalous sedimentation behavior has been observed for high molecular weight duplex DNA's in sucrose gradients. The sedimentation rate of DNA's having molecular weights of 10⁸ or higher is influenced by high centrifugal fields. The change in the sucrose sedimentation coefficient due to this effect, S^RPM_suc-S⁰_suc, is equal to 1 × 10^?48M^3.65( The anomalous behavior is not influenced by DNA concentration at sufficiently low concentrations. Because of the smallness of the coefficient this effect has not been previously detected for DNA's the size of T2 or smaller at rotor speeds below 40000 RPM. For example, the relative sedimentation coefficient of T2 DNA at 65 000 RPM is only 9% less than at 10000 RPM. However, the sedimentation profile of heterogeneous high molecular weight [(100 – 350) × 10⁶] E. coli DNA is severely altered even at moderate rotor speeds (37000 RPM). Therefore, it seems advisable to use low rotor speeds when sedimenting high molecular weight DNA's.     

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.     

The role of tissue interactions in the skeletogenic differentiation of avian neural crest cells

In the avian embryo, cranial neural crest (NC) cells migrate extensively throughout the head region and give rise to most of the cranial skeleton (Le Lievre, C. S. (1978). J. Embryol. Exp. Morphol.47, 17–37). To investigate the skeletogenic differentiation of these cells, NC explants from the mesencephalic level of st. 9+ embryos were grown in standard organ culture on Millipore filter substrates either in isolation or in combination with those tissues with which the cells normally associate during their in vivo migration and at their final tissue sites. The results demonstrate that interaction between premigratory NC and cranial ectoderm leads to chondrogenic differentiation of NC cells. Combination of premigratory NC with presumptive site tissues led to a pattern of NC cell differentiation normally expressed after in vivo migration: Combinations of NC with retinal pigmented epithelia gave cartilage, whereas NC with maxillary ectoderm formed cartilage and membrane bone. Both resulting skeletal tissues possessed their characteristic collagen types (II in cartilage and I in bone) as shown by indirect immunofluorescence using antibodies raised against specific types of collagen. It is concluded that avian cephalic NC cells require tissue interactions if chondrogenic and osteogenic differentiation is to ensue, but that migration per se is not an absolute prerequisite for these types of differentiation. The degree of specificity underlying such interactions is discussed.     

Age-associated changes in plasma testosterone levels in male mice and their relation to social dominance or subordinance

Plasma testosterone (T) levels were determined in male mice of the CD-1 (ICR) strain from 30 to 680 days of age. The mean plasma T was 5.2 ± 1.0 ng/ml for adult male mice (70–400 days old, 102 mice) and 1.8 ± 0.9 ng/ml for old males (450–680 days old, 11 mice). Through 140 determinations, the highest T value obtained was 52.3 ng/ml in an 80-day-old individual while the lowest was 0.08 ng/ml in a 680-day-old animal. It was found that plasma T was significantly decreased in the old age, although individual variation in T levels was considerable. On the other hand, social dominance or subordinance was examined among male mice in each cage and its relation to plasma T was investigated. Dominance or subordinance was verified by frequency of chases or attacks delivered or received, or number of fights won or lost. It was observed that dominant-subordinate relationships were present in 6 out of 10 cages and that the dominant individual had a significantly higher T level than the subordinate male; the mean T level was 10.5 ± 2.5 ng/ml for the dominant individuals vs 2.2 ± 0.8 ng/ml for the subordinate ones. Marked individual variation in plasma T titers in male mice seems to be related to the dominance/subordinance rank within a group.     

Human procollagen : I. An anionic tropocollagen precursor from skin fibroblasts in culture

Tropocollagen is derived from an extracellular precursor, procollagen. Conversion to tropocollagen is accomplished by one or more tissue pioteases dependent in vitro on the presence of serum in the culture medium. Twenty-four hour cultures in which serum has been excluded yield an apparently undegraded precursor, procollagen I. The latter is approximately twice the size of tropocollagen, possesses an acidic pl in contrast to the alkaline pl of tropocollagen, and shares secondary structural characteristics common to tropocollagen. Procollagen I exhibits a sharp thermal transition point at 39° with a ΔT of 2° indicating that the collagenous portion of the molecule is in the triple helical configuration prior to proteolytic excision from the parent molecule. The amino acid composition is remarkable when compared to tropocollagen in the large quantity of acidic residues, decreased glycine and imino acids, and the presence of cystcine. Three models of procollagen I structure are presented and discussed relative to the available experimental evidence.     

Tissue-specific synthesis of yolk proteins in Caenorhabditis elegans

The primary site of yolk protein synthesis in the nematode, Caenorhabditis elegans, has been determined. In animals containing no gonadal cells (obtained by laser ablation of the gonadal precursor cells early in development), yolk proteins are present in abundance. This demonstrates that yolk proteins are made outside the gonad. An examination of proteins present in tissues isolated by dissection, and a comparison of proteins synthesized by isolated tissues incubated in vitro have identified the intestine as the major site of yolk protein synthesis. We propose that yolk proteins are synthesized in the intestine, secreted from the intestine into the body cavity, and taken up from the body cavity by the gonad to reach oocytes. The site of yolk protein synthesis has also been examined in four mutants that have largely male somatic tissues, but a hermaphrodite germ line. Here again, yolk proteins are produced by intestines in a hermaphrodite-specific manner. This suggests that sex determination is coordinately regulated in intestinal and germ line tissues.     

Structural change of myofibrils during mitosis of newt embryonic myocardial cells in culture

Newt embryonic myocardial cells can undergo mitosis in culture. The successive changes in the striation pattern of sarcomeres of myofibrils during mitosis were studied by polarization microscopy without fixing or killing the cells. Birefringence of well-organized striation patterns, i.e., bright A-bands and dark I-bands, was clearly visible in interphase cells and did not show any detectable changes during incubation for 3 h or more. Electron microscopy showed the presence of well-organized myofibrils with Z-bands in these interphase cells. When myocardial cells entered the mitotic stage, the birefringence of striation pattern of their myofibrils gradually changed with the pattern in small parts of the myofibrils gradually becoming indistinct (called 'indistinct striation' in this paper). These indistinct regions increased in size during the mitotic stage. In addition, in some regions of the indistinct striation, the birefringence of sarcomeres gradually decreased and finally disappeared (called 'disappearance of sarcomeres' in this paper). No myocardial cells underwent mitosis without these disruptive changes of the myofibril striation patterns. In the post-mitotic stage, the well-organized striation of the myofibrils reappeared. Electron microscopy showed disorganized sarcomeres without Z-bands in the regions of indistinct striation, and no well-organized myofibrils in the regions where the sarcomeres had disappeared. Thus the well-organized myofibrils with Z-bands became transiently disorganized at least in some parts, during mitosis. They were then reorganized into daughter myocardial cells.     

Efficient extraction and quantitative determination of nanogram amounts of cellular RNA

An assay for quantitating nanogram amounts of cellular RNA is described. RNA is efficiently extracted from cells, using RNA-free DNA as carrier, by conventional chloroform: phenol procedures and the nucleic acids are precipitated with ethanol. Isolated RNA is hydrolyzed by RNase T2 to ribonucleoside 3′-monophosphates which in turn are converted to 5′-³²P-labeled ribonucleoside 3′,5′-diphosphates in the presence of T4 polynucleotide kinase and [γ-³²P]ATP. Radiolabeled products are separated from remaining [γ-³²P]ATP by chromatography on polyethyleneimine-cellulose, located by autoradiography, excised from the chromatogram, and subjected to liquid scintillation counting to quantitate the amount of RNA. Using mouse liver ribosomal RNA as a standard, the assay is linear over a range of 0 to 64 ng of RNA. The assay has been used to determine the amount of RNA in fully grown mouse oocytes arrested at the dietyate stage of first meiotic prophase. Each oocyte contains 0.61 ± 0.05 ng of RNA and only 25 oocytes have been used for such assays.     

The arrangement of nucleosomes in nucleoprotein complexes from polyoma virus and SV40.

Androgen-dependent and androgen-independent (autonomous), cloned, cultured cell lines of the androgen-dependent mouse mammary adenocarcinoma, Shionogi carcinoma 115, have been established. Growth of the dependent cells requires the presence of androgen, provided they are grown in suspension culture in medium containing dextran-charcoal-treated fetal calf serum. The growth rate of autonomous cells in the presence or absence of DHT is similar to that of dependent cells grown in its presence. An agar culture method has been developed that enables the proportion of dependent and autonomous cells in mixed populations to be determined. Autonomous cells appear in dependent clones, and their frequency increases with increasing time of subculture. Dependent cells from tumors preferentially in male animals, and dependent cell cytosols contain significant amounts (approximately 300 femtomoles per mg protein) of a specific androgen-binding macromolecule. Autonomous cells formed tumors equally well in both male and female mice, and autonomous cell cytosols contain very low levels (≤ 7 femtomoles per mg protein) of the specific androgen-binding macromolecule(s). These studies delineate a system which can be used to investigate the mechanism of steroid hormone-dependent and autonomous tumor growth, and the transitions between the hormone-dependent and autonomous states.     

The cytoskeletal framework of sea urchin eggs and embryos: developmental changes in the association of messenger RNA

Extraction of sea urchin eggs and embryos with Triton X-100 generated a cytoskeletal framework (CSK) composed of a cortical filamentous network and an internal system of filaments associated with ribosomes. The CSK contained only 10-20% of the cellular protein, RNA, and lipid. A specific subset of proteins was enriched in the CSK. Several lines of evidence suggest that mRNA is a component of the CSK of both eggs and embryos. First, the CSK contained poly(A) sequences which hybridized with [3H]poly(U). Second, the CSK contained polyribosomes. Finally, RNA extracted from the CSK showed translational activity in an in vitro system. The nonhistone messages present in the CSK were qualitatively similar to those solubilized by detergent, as determined by separation on polyacrylamide gels of the products of in vitro translation. In the unfertilized egg, most mRNA was present as nonpolyribosomal messenger ribonucleoprotein complexes which, along with monoribosomes, were efficiently extracted by Triton X-100. The converse was found in blastulae, as most of the mRNA was present as polyribosomes associated with the CSK, although monoribosomes were still efficiently extracted by detergent. These results indicate a correlation between the activation of protein synthesis in eggs and the association of polyribosomes with the CSK.