Age-related changes of the somatotrophs of the domestic fowl Gallus gallus

Summary The ultrastructure of the somatotrophs of the caudal pituitary of the domestic fowl was studied quantitatively. Two age groups of male chickens were compared: 4–6 weeks and 24–30 weeks post-hatching. With age, somatotrophs decreased from about 40% to about 30% of the pituitary cell population. Their volume density decreased similarly. Mean volume of a somatotroph was the same in young and adult animals. Because the granule volume density of the somatotrophs was unchanged, but the somatotroph volume density of the gland declined, the granule volume density of the caudal pituitary gland dropped in parallel with that of the somatotrophs. Thus the volume of the gland comprised of somatotroph granules fell about 32%: from 6.57% to 4.45%. This lowered pool of stored hormone may be linked to the lowered circulating levels of growth hormone found in older animals by other investigators.The granule volume density of the somatotrophs was unchanged but the numerical density approximately doubled; thus the mean granule size decreased by 47% with age. The relationship of the size reduction of the granules to the lowered plasma growth hormone levels is not understood at present.Supported in part by Hatch and State funds from the New Jersey State Agricultural Experimental Station and NSF grants PCM 8,0227,27 and PCM 8,302197.     

Carbon-cycling changes during regeneration of a decinduous broadleaf forest after clear-cutting II. Aboveground net production

Growth and death rates of aboveground plant parts were measured in a mature forest and four different-aged deciduous broadleaf forests regeneratede after clear-cutting, with special reference to rates for woody parts (stems and branches) of different diameters (ø) in rerms of the pipe model theory (Shinozaki et al., 1964). The total biomass increment of woody parts of trees higher than 1.3 m varied within a range of 2.1-4.6 ton ha^?1 yr^?1, the increase beingdue largely to the growth of canopy trees exposed to direct sunlight. Biomass increments of small (ø<1 cm) and medium (1≤ø<5 cm) woody parts were negligibly small except in the youngest forest, and changes in aboveground woody biomass with forest age after clear-cutting mainly resulted from accumulation of large (5 cm<ø) woody parts of canopy trees. Biomass loss of trees due to death and grazing increased with forest age from 4.0 to 8.3 ton ha^?1 yr^?1. Recovery of leaf and small wood falls was observed at the early stage of regeneration, while large wood falls increased during regeneration. Flower and fruit fall was markedly higher in the mature forest than in the other four forest types. Mortality of woody parts became higher with forest age and was 20, 5.0 and 0.46% yr^?1 for small, medium and large parts, respectively, at the mature stage. Aboveground net production of the forest was in therange 7.6-13.3 ton ha^?1 yr^?1 with the undergrowth vegetation lower than 1.3 m being 0.4-1.4 ton ha^?1 yr^?1. Production recovered rapidly at an early stage of regeneration and was highest in mature forest.     

Effect of genetic background on growth of mice hemizygous for wild-type or dwarf mutated bovine growth hormone transgenes

The effects of a high-growth genetic background on the growth of mice hemizygous for one of two growth hormone transgenes were examined. Male mice hemizygous for wild-type (W) and dwarf mutant (M) bovine growth hormone (bGH) transgenes were crossed with females of a high-growth selected (S) and control (C) line as follows: W x S, W x C, M x S and M x C. Body weights of progeny were recorded weekly from 2 to 10 weeks of age. F₁ progeny were classified as carriers (P) or non-carriers (N) of the transgene by assaying tail DNA for bGH using the polymerase chain reaction and agarose gel electrophoresis. A deficiency in the number of f₁ progeny carrying the W (P<0.05) and M (P<0.01) bGH transgene was most likely due to differential prenatal and early postnatal mortality. Bodyweight means of wild-type transgenic mice were larger (P < 0.05) than those of non-transgenic littermates by 3 weeks of age in a C background in contrast to 5 weeks in S. The wild-type bGH transgene increased adult body weights more in the C (155%) than in the S (136%) background, indicating transgene expression by selection background interaction (P < 0.05). However, the growth response to the wild-type transgene in the S background was still large. The dwarf mutant transgene had a greater effect on growth reduction in the S (70%) than in the C (84%) background, thus causing transgene expression by selection background interaction (P < 0.05). Gender by wild-type transgene effect interactions (P < 0.001) for adult body weight were caused by the transgene reducing the gender difference for body weight in C and eliminating it in S. The dwarf mutant caused a larger negative effect on growth in males than in females, resulting in a gender by dwarf mutant transgene interaction (P < 0.001) for adult body weights. Results indicate that the effect of a GH transgene on growth can be affected both by a high-growth genetic background and the gender of progeny.     

Cell wall synthesis during growth and maturation of Nitella internodal cells

An improved ¹³C-density-labeling method was used to study cell wall synthesis in rapidly expanding, slowly expanding and recently mature internodes of Nitella translucens var axillaris (A.Br.) R.D.W. As cells matured, the rate of wall synthesis slowed and the deposition of cellulose microfibrils changed from a predominantly transverse direction in the primary wall of rapidly expanding internodes to a helicoidal array in the secondary wall of mature internodes. The secondary wall was characterized by relatively higher rates of cellulose synthesis and lower rates of pectin synthesis than the primary wall. The synthesis of xyloglucan also decreased markedly at the transition to secondary wall synthesis, while the synthesis of mannose-rich hemicellulose increased. Even though structural differences were striking between the primary and secondary walls of Nitella, compositional differences between the two types of wall were quantitative rather than qualitative. The authors appreciate the assistance of Martin Yousef with the electron microscopy.     

Rapid changes in amplification and methylation pattern of genomic DNA in cultured carrot root explants (Daucus carota L.)

Summary Rapid genomic DNA variation due to methylation and copy number alteration was observed in carrot root explants 6 h after inoculation and during a 36-h period of exponential callus growth. De novo methylation and amplification of restricted BspNI fragments of low molecular weight occurred before cell cycle activation and should, therefore, be independent of progression through the S-phase of the cell cycle. Growth regulators seemed to influence the amplification pattern indirectly by regulating cell division activity. In exponentially growing callus tissue the copy number of most of the repetitive fragments was dramatically reduced. It is presumed that this reduction in the copy number of repetitive fragments is characteristic of rejuvenilization. 3-Indole-acetic-acid (IAA) and inositol in the medium increased the degree of unspecific genomic DNA methylation in growing rhizogenic carrot callus tissue in the absence of kinetin, which inhibits root induction at that stage. A possible relation to the induction of rhizogenesis is considered. The observed reduction in number of repetitive restriction fragments and the increase in DNA methylation are gross changes covering the total genome. The results are discussed in relation to the controversy concerning the general biological significance of the methylation and amplification of DNA sequences.     

Sodium and potassium relations of Spergularia marina following N and P deprivation: results of short-term growth studies

In this, we consider the coordination of plant growth and ion acquisition, reporting the short-term adjustments of growth and K⁺ and Na⁺ relations which follow when plants are subject to a sudden deprivation of N and P. The plant used for the experiments, Spergularia marina (L.) Grieseb., is a small coastal halophyte, and the growth medium was 0.2 × modified seawater. By considering nutrients whose availability has not been changed, we report on an aspect of organismal integration which has received little attention either experimentally or in mathematical models. The studies are limited to the first 60 h after N and P deprivation in order to consider changes that, if they are not primary responses, are not temporally remote, passive adjustments. For growth analyses, plants were used approximately 30 days after germination and 16 days after transfer to solution culture. Random harvests were made at hourly invervals, and after 12 h, one-half of the plants were transferred to cultures without N or P. Tissue analyses were used to calculate relative growth rates, relative accumulation rates and net uptake rates. For comparison, isotope uptake studies using ⁴²K⁺ and ²²Na⁺ were conducted at 12, 36 and 60 h after deprivation. The effects on growth and biomass allocation were very rapid, detectable within 13 h. K⁺ transport also responded quickly, and from the beginning of the study, there was essentially no net translocation of K⁺ to the shoot. Isotope studies confirmed the responsiveness, with translocation reduced 33 and 90% after 12 and 36 h, respectively. Though Na⁺ adjustments were slower, they were coordinated with growth such that tissue concentrations in the N and P-deprived plants were comparable to those in the controls. We conclude that N and C are insufficient elements on which to build mathematical models useful to environmental physiologists. At a minimum, the incorporation of K⁺ relations in growth models would both allow the development of the osmotic potential needed to drive cell expansion, and provide a means to probe –experimentally as well as mathematically – the coordinating mechanisms of plant growth and resource management.     

Genetics of size and growth rate through sexual maturity in freshwater-reared coho salmon (Oncorhynchus kisutch)

Genetic parameters of size through sexual maturity have been relatively unexplored for Pacific salmon. In this study, individually tagged coho salmon were raised in freshwater, and the heritabilities of size and growth rate were estimated at several intervals between 13 and 24 months of age (spawning). Heritability estimates for size were moderate to high from 13 to 19 months of age, ranging from 0.36 to 0.50, and lower from 21 months to spawning at 24 months, ranging from 0.17 to 0.32. Heritabilities of specific growth rates estimated over 3-month intervals were moderate from 16 to 21 months of age, ranging from 0.21 to 0.34. Genetic and phenotypic correlations between sizes measured at different ages were moderate to high, ranging from about 0.7 to 1.0. Correlations between growth rate and size indicated that the larger fish were the fastest growing between 16 and 19 months of age and were slower growing between 19 and 21 months of age.     

Growth responses of some soil fungi to spatially heterogeneous nutrients

Abstract The natural nutritional environments of most fungi are spatially non-uniform, yet the majority of studies of fungal growth take no account of this fact. An experimental system is described which permits the growth responses of eucarpic fungi to heterogeneously distributed nutrient resources to be studied. The system comprises tesselations of agar tiles of contrasting nutrient status separated by air gaps. Growth responses in such systems of Alternaria alternata, Mucor sp., Phoma foveata , Rhizoctonia solani and Trichoderma viride are described. Generally, the growth of the fungi reflected the nutrient status of the underlying substrate. There was evidence for growth in low-nutrient tiles being greater when high-nutrient tiles were included in the tessellation. Reproductive structures tended to be formed only in low nutrient tiles with Trichoderma and Rhizoctonia and only high nutrient tiles with Alternaria . Growth responses of Rhizoctonia were strongly asymmetric in nutritionally symmetric, but heterogeneous, tesselations. The consequences of the observations for fungal growth in heterogeneous environments such as soil is discussed.     

Interaction of force transmission and sarcomere assembly at the muscle-tendon junctions of carp (Cyprinus carpio): ultrastructure and distribution of titin (connectin) and α-actinin

At muscle-tendon junctions of red and of white axial muscle fibres of carp, new sarcomeres are found adjacent to existing sarcomeres along the bundles of actin filaments that connect the myofibrils with the junctional sarcolemma. As the filament bundles that transmit force to the junction originate proximal to new sarcomeres, they probably relieve these new sarcomeres from premature loading. In red fibres, these filament bundles are long (up to 20 m) and dense, permitting light-microscopical immunohistochemistry (double reactions: anti-titin or anti--actinin and phalloidin). New sarcomeres have clear I bands; their A band lengths are similar to those of older sarcomeres and the thick filaments lie in register. T tubules are found at the distal side of new sarcomeres but terminal Z lines are absent. The late addition of -actinin suggests that -actinin mainly has a stabilizing role in sarcomere formation. The presence of titin in the terminal fibre protrusions is in agreement with its supposed role in sarcomere formation, viz. the integration of thin and thick filaments. The absence of a terminal Z line from sarcomeres with well-registered A bands suggests that this structure is not essential for the anchorage of connective (titin) filaments.