The effect of reduced activity on the enzymatic development of phasic and tonic muscles in the chicken

The effects of reduced activity (immobilisation) on the development of the contractile enzyme, Mg2+-activated myofibrillar ATPase was studied in a tonic muscle, the anterior latissimus dorsi and in a phasic muscle, the posterior latissimus dorsi of the chicken. Mg2+-activated myofibrillar ATPase activity showed a decreased and delayed activity peak in both the immobilised muscles. Large differences between the two muscles were observed using this marker enzyme. These data indicate that the activity of Mg2+-activated myofibrillar ATPase and the associated differential gene expression involved in fibre type differentiation are influenced by the early activity pattern of the muscles.     

The effects of starvation upon protein turnover in red and white myotomal muscle of rainbow trout, Salmo gairdneri Richardson

Protein synthesis rates of both red and white muscle were measured using a constant infusion technique in fed and starved rainbow trout over a period of 2 months. In both tissues, rates of protein synthesis fell during starvation although the fall was more rapid in white than in red muscle. The reduced rates of protein synthesis were correlated to a reduced level of RNA in the tissues and a lower rate of translation of the RNA present. Estimated rates for protein degradation in white muscle showed a marked initial increase but with more prolonged starvation the degradation rate become only slightly greater than that in the fed fish.     

Chromatographic resolution of nucleic acids extracted from Penicillium chrysogenum

Summary High molecular weight DNA extracted from Penicillium chrysogenum has been fractionated using RPC-5 Analog, into three distinct types designated 1, 2 and 3. Types 1 and 2 have the same buoyant density of 1.710 g/cm³ and together appear to comprise the nuclear DNA. Type 1 is enriched for repeated sequences which are normally observed in restriction digests of P. chrysogenum total DNA. Conversely, type 2 appears to be composed entirely of non-repetitive sequences. Type 3 has been identified as mitochondrial DNA, having a buoyant density of 1.695 g/cm³ and an estimated molecular weight of 31.6×10⁶ Daltons.     

Culture of intramural cardiac ganglia of the newborn guinea-pig

Summary The present study describes the ultrastructure of non-neuronal cells and their interrelationships with intracardiac neurones present in cultures dissociated atria and interatrial septum from newborn guinea-pig. When compared with the in situ preparation, most of these features in culture were similar to those observed in situ, but some differences were also apparent. Both mature and immature Schwann cells were observed in culture, and as in situ, the latter were closely associated with intracardiac neurones, whilst the former were more widely separated. The ultrastructure of satellite cells was more variable in culture than in situ: three general types were distinguished on the basis of their 10-nm filament content. This variation could be due to conditions of culture. Interstitial cells were present in culture and closely resembled those described in situ, although there was less space between cultured interstitial cells and their associated cells. Many fibroblasts, some myoblasts and a few mast cells were also found in the culture preparations.     

The effect of chronic and acute dietary restriction on the growth and protein turnover of fast and slow types of rat skeletal muscle

Changes in the growth and protein turnover of the anterior tibialis and soleus muscles were studied in response to acute and chronic dietary restriction (50% of ad libitum intake) between 3 and 149 weeks post partum. The effect of long-term dietary restriction from weaning to senescence was to retard the growth and normal developmental of the two types of skeletal muscle. This was evident from measurements of various parameters of growth, i.e. total protein, RNA and DNA and protein/DNA-P, which were reduced by approximately 50% when compared with age-matched controls. These decreases, however, were not accompanied by a decline in the fractional rate of synthesis (%/day) or ribosomal activity (mg protein/day per mg RNAP). The slowing down of the age-related decline in muscle growth has been attributed to a reduction in RNA capacity (RNA/protein), with similar responses in the fast- and slow-twitch skeletal muscles. The initial effects of piecemeal feeding of this restricted diet on the two types of muscle were also monitored. Short term starvation effects, i.e. 24 hr after feeding a reduced ration, were measured on the protein content and RNA/protein of both the anterior tibialis and soleus muscles; both parameters were unchanged within 24 hr. In contrast, a rapid and significant decline in the ribosomal synthetic activity (mg/d per mg RNAP), and a corresponding fall in the fractional rate of synthesis, occurred within 24 hr of feeding.     

Transformation ofBacillus spp.: An examination of the transformation ofBacillus protoplasts by plasmids pUB110 and pHV33

The protoplasting and transformation techniques described by Chang and Cohen [5] have been modified by the inclusion of mutanolysin and these techniques have been used to prepare protoplasts of a number ofBacillus spp. Cells of some, however, remained resistant to cell wall hydrolysis by both mutanolysin and lysozyme. Protoplasts were prepared from sixBacillus species, including a strain ofB. subtilis, and transformed with the plasmid pUB110. Transformation with the shuttle vector pHV33 was, however, less successful and antibiotic-resistant protoplasts, although detected, either failed to regenerate their osmotic stability or rapidly lost their antibiotic resistance.     

Kinetic studies on the chymotrypsin Aα-catalyzed hydrolysis of a series of N-acetyl-l-phenylalanyl peptides

A series of N-acetyl-l-phenylalanyl peptides of general formula Ac-Phe-(Gly)_n-NH₂ (n = 0–2) has been synthesized to study the effect of leaving group chain length on the efficiency of chymotrypsin A_α amidase and peptidase activities. The effect upon catalysis of hydrophobic side chains on the leaving group was investigated using similar substrates with one of the glycine residues selectively substituted by an alanine residue as in AcPheAlaNH₂, AcPheAlaGlyNH₂, and AcPheGlyAlaNH₂. Values of k_cat and K_m have been obtained from kinetic measurements at pH 8.00 and 25 °C. The results are shown to be consistent with binding schemes postulated from published model building studies. The catalytic reactions were studied over a range of temperature (15–35 °C) and in each case the Arrhenius law was obeyed. It was thus possible to obtain meaningful values for the thermodynamic functions of activation for the acylation step of the catalytic reaction. The results are shown to confirm the findings of postulated binding schemes but indicate that conclusions drawn from kinetic measurements at a single temperature may sometimes be misleading.     

Kinetic evidence for involvement of two cytochrome b-563 hemes in photosynthetic electron transport

The effect of 2-(n-heptyl)-4-hydroxyquinoline N-oxide (HQNO) on the kinetics of cytochrome b-563 and cytochrome c² turnovers following single-turnover flashes was measured in isolated heterocysts. Low concentrations of HQNO (below 3 μM) blocked reoxidation of cytochrome b-563, whereas higher concentrations (above 5 μM) resulted in additional inhibition of cytochrome b-563 oxidation and also inhibited reduction of cytochrome b-563 and cytochrome c. Similar effects on cytochrome b-563 reduction and reoxidation were obtained with a combination of 5 μM HQNO and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (1–7 μM). In HQNO-inhibited heterocysts, cytochrome c reduction following a flash occurred in three phases with half-times of 0.5, 2.8 and 45 ms. The second phase nearly equalled the cytochrome b-563 reduction in half-time and magnitude. In the presence of HQNO, the reoxidation of cytochrome b-563 following two closely spaced actinic flashes displayed biphasic kinetics. The two phases correspond to reoxidation of cytochrome b-563 in which one or both of the cytochrome b-563 hemes in the cytochrome b–f complex are reduced. These results are interpreted in terms of a Q-loop in which HQNO, at low concentrations, blocks the site of rapid cytochrome b-563 reoxidation and at higher concentrations, also inhibits the site of electron donation by plastoquinol to the cytochrome b-f complex.     

Altered gene products are associated with activation of cellular rasK genes in human lung and colon carcinomas

Two lung and two colon carcinoma cell lines of human origin, which contained the same activated ras^K transforming gene, expressed abnormal species of p21 that were distinct from the p21 proteins expressed in normal human cells and other human carcinomas. The abnormal species of p21 expressed by three of these cell lines were indistinguishable from each other, but differed from the abnormal p21 expressed by one lung carcinoma cell line. NIH cells transformed by DNAs of these carcinomas expressed the same abnormal p21 species, indicating that these abnormal proteins were encoded by the activated ras^K genes detected by transfection. These results indicate that transforming activity of ras^K genes in human lung and colon carcinoma cell lines is activated by mutations which alter the structure of their gene products, and that activation of ras^K genes can result from different molecular alterations in different individual neoplasms.