Electron microscope studies on developing oocytes of a coelenterate medusa with special reference to vitellogenesis

In a hydrozoan jellyfish, the female gonad is differentiated from a specialized region of the epidermis near the manubrium. Changes in the oocytes during growth and vitellogenesis are described as observed with electron microscopic and cytochemical techniques. Three major types of yolk are formed; these include lipid, glycogen, and membrane-bound granules consisting of both protein and carbohydrate. The latter first appear evident within vesicular and cisternal elements of the numerous Golgi complexes. The orientation and structural variations noted between the endoplasmic reticulum and forming face of the Golgi complexes suggest that the protein component of the yolk granules may be transferred from the cisternae of the endoplasmic reticulum to the Golgi complex where it is joined to carbohydrate perhaps synthesized by the Golgi complexes. Stages in the release of the precursor yolk material sequestered in cisternal elements of the Golgi complexes are illustrated. The presence of coated and uncoated vesicles in the Golgi regions and their possible role in intracellular transport are described and discussed. The presence and possible method of morphogenesis of vesiculate yolk bodies are also described. What appear to represent invaginations of the oolemma extend into the ooplasm and display a special orientation with respect to lamellae of the rough-surfaced endoplasmic reticulum. Intraooplasmic synthesis appears to constitute the major pathway for protein-carbohydrate yolk deposition.     

Cytological studies of ameiotic and normal maize with reference to premeiotic pairing

This study reports cytological observations in maize plants homozygous for the recessive am allele which suppresses meiosis in both male and female meiocytes. The ultimate premeiotic mitosis in anthers from ameiotic plants is normal, but the resulting nuclei do not undergo meiosis. Instead, a synchronized mitosis occurs after which the cells degenerate. No evidence was found for a non-random association of homologous chromosomes in the premeiotic or ameiotic mitoses of homozygous ameiotic plants or in the premeiotic mitosis of normal sibs. These observations are in agreement with the classical view that synapsis of homologous chromosomes does not occur until zygotene.     

Functional complexes of mitochondria with Ca,MgATPases of myofibrils and sarcoplasmic reticulum in muscle cells

Regulation of mitochondrial respiration in situ in the muscle cells was studied by using fully permeabilized muscle fibers and cardiomyocytes. The results show that the kinetics of regulation of mitochondrial respiration in situ by exogenous ADP are very different from the kinetics of its regulation by endogenous ADP. In cardiac and m. soleus fibers apparent K(m) for exogenous ADP in regulation of respiration was equal to 300-400 microM. However, when ADP production was initiated by intracellular ATPase reactions, the ADP concentration in the medium leveled off at about 40 microM when about 70% of maximal rate of respiration was achieved. Respiration rate maintained by intracellular ATPases was suppressed about 20-30% during exogenous trapping of ADP with excess pyruvate kinase (PK, 20 IU/ml) and phosphoenolpyruvate (PEP, 5 mM). ADP flux via the external PK+PEP system was decreased by half by activation of mitochondrial oxidative phosphorylation. Creatine (20 mM) further activated the respiration in the presence of PK+PEP. It is concluded that in oxidative muscle cells mitochondria behave as if they were incorporated into functional complexes with adjacent ADP producing systems - with the MgATPases in myofibrils and Ca,MgATPases of sarcoplasmic reticulum.     

Historical view of DNA replication studies, with special reference to Japan

Almost forty years after the key contributions to the field by Okazaki and coworkers that gave rise to the concept of leading and the lagging strand, we are still at the state of uncertainty about the proteins that replicate each strand. Perhaps, one main conclusion that should be drawn from the data currently available is that the protein architecture at the fork is more plastic than originally thought.     

Compositional studies of myofibrils from rabbit striated muscle

The localization of high-molecular-weight (80,000-200,000-daltons) proteins in the sarcomere of striated muscle has been studied by coordinated electron-microscopic and sodium dodecyl sulfate (SDS) gel electrophoretic analysis of native myofilaments and extracted and digested myofibrils. Methods were developed for the isolation of thick and thin filaments and of uncontracted myofibrils which are devoid of endoproteases and membrane fragments. Treatment of crude myofibrils with 0.5% Triton X-100 results in the release of a 110,000-dalton component without affecting the myofibrillar structure. Extraction of uncontracted myofibrils with a relaxing solution of high ionic strength results in the complete disappearance of the A band and M line. In this extract, five other protein bands in addition to myosin are resolved on SDS gels: bands M 1 (190,000 daltons) and M 2 (170,000 daltons), which are suggested to be components of the M line; M 3 (150,000 daltons), a degradation product; and a doublet M 4, M 5 (140,000 daltons), thick-filament protein having the same mobility as C protein. Extraction of myofibrils with 0.15% deoxycholate, previously shown to remove Z-line density, releases a doublet Z 1, Z 2 (90,000 daltons) with the same mobility as alpha-actinin, as well as proteins of 60,000 daltons and less, and small amounts of M 1, M 2, M 4, and M 5; these proteins were not extracted with 0.5% Triton X-100. The C, M-line, and Z-line proteins and/or their binding to myofibrils are very sensitive to tryptic digestion, whereas the M 3 (150,000 daltons) component and an additional band at 110,000 daltons are products of proteolysis. Gentle treatment of myofibrils with an ATP relaxing solution results in the release of thick and thin myofilaments which can be pelleted by 100,000-g centrifugation. These myofilaments lack M-and Z-line structure when examined with the electron microscope, and their electrophoretograms are devoid of the M 1, M 2, Z 1, and Z 2 bands. The M 4, M 5 (C-protein doublet), and M 3 bands, however, remain associated with the filaments.     

Immunocytochemical identification of cytoskeletal linkages to smooth muscle cell nuclei and mitochondria

In avian smooth muscle cells, desmin-containing intermediate filaments (IFs) are a prominent component of the cytoskeleton and are readily seen in several domains, including the axial intermediate filament bundle (IFB). Both the nucleus and some of the mitochondria are partly surrounded by elements of the IFB. By using anti-desmin and protein-A-colloidal gold labeling, we have identified intermediate filaments that form linkages with the nuclear envelope and with mitochondria. These linkage regions seem to occupy a proportionately greater part of the mitochondrial surface than of the nuclear envelope. The existence of these linkages in smooth muscle cells is consistent with results that support similar linkages to mitochondria and other cellular structures in various cells that contain either vimentin or keratin IFs. These linkages could functionally restrain or assist in homeostatically restoring organelles to their normal position after the rearrangement that accompanies the substantial shortening of smooth muscle cells.     

Analytical study of Xenopus hindlimb regenerate with special reference to muscle regeneration

Amputated hindlimbs of Xenopus laevis, develop various types of regenerates in relation with amputation level as well as stage development. The present experiments is an attempt to study the histological characteristics of Xenopus regenerations, i.e., rational changes of tissue components along the length of the regenerated part with special emphasis on the degree of muscle regeneration. Four types of regenerates were studied viz; a 4th toe obtained from a completely restored regenerated limb at 126 days after amputation of limb at base level in stage 51. An amputated limb with no external sign of regeneration of limb at thigh level in stage 60. A spike-shaped regenerate at 96 days after amputation of limb at shank level in stage 63. A spike-shaped regenerate at about 2 years after amputation of limb at shank level in stage 60. Cross sectional areas of muscle, skin gland, epidermis and cartilage in each of the four types of regenerates were measured with Image Analyzing Apparatus (VIP 121 CH, Olympus Co.). The relative area of each tissue was expressed as a percentage of the cross sectional area of the limb. The obtained values were plotted along the length of the regenerate. Digitiform regenerates were found to be more or less similar to the control limbs, i.e., provided joints and muscle, while the heteromorphic spike or rod shaped regenerates were simply provided with cartilaginous axial core without joint formation. Muscle area were reduced rapidly near the amputation area of these heteromorphic regenerates with no more continuation in the regenerated tissue. It is interesting to mention that percentage cartilage area of about 2 years old spike regenerate was higher than that of similar 96 days regenerate. In addition muscle regeneration was completely absent even in such an aged regenerate. The area showed fairly similar ratio irrespective of the external appearance of the regenerate. In 32 regenerates of which limbs were amputated at various developmental stages ranging between stage 51 and adult stage, the histological condition of muscle at the amputation site, were well observed. In all digitated types of regenerates even in those with reduced number of toes, muscles were found grown well in the regenerates. In heteromorphic regenerates without toe formation muscle did not usually regenerate. In few cases, however, a small mass of myoblastic like cells or small aggregation of differentiated muscle cells without any structural continuation with the stump muscles, were seen to develop in the midst of the regenerate.(ABSTRACT TRUNCATED AT 400 WORDS)     

Small scale preparation of skeletal muscle mitochondria, criteria of integrity, and assays with reference to tissue function

Mitochondria prepared in small scale from skeletal muscle were studied with respiration measurements and low temperature spectroscopy. The method of preparation was developed for 25–100 mg tissue with pigeon breast muscle as model organ. The yield was 40%. Data collected during the developmental work were used to evaluate criteria of mitochondrial quality. The cytochrome c conservation, i.e. cytochrome c per mitochondrial quantity in the preparation relative to that in the tissue, is a most useful test parameter. It is bounded between 0–100%. Proportionality between the state 3 rate and the cytochrome c conservation was not rejected by statistical tests. The respiratory control ratio (RCR) was also highly correlated to the cytochrome c conservation. These correlations might be extrapolated to 100% conservation to give hypothetical tissue values. The cause for the correlations is discussed. The P/O ratio showed only weak dependence on the cytochrome c conservation and the state 4 rate s howed no dependence. Other, rather insensitive test parameters are also discussed. The pigeon breast muscle mitochondria isolated by the final method showed cytochrome c conservation of 73 ± 9% (n = 16). They are compared with pig biceps femoris mitochondria prepared by the same method. The two types of mitochondria show many similarities. Some differences may be explained by a different amount of inner mitochondrial membrane relative to mitochondrial protein. The pig tissue contains ten times less mitochondrial protein than the pigeon tissue does. (Mol Cell Biochem 174: 55–60, 1997)     

Some studies on Nigerian palm wine with special reference to yeasts

The identification and enumeration of yeasts and the effect of chemical preservatives on the yeast load in Nigerian palm wine have been studied. Yeast found largely belong to the genus Saccharomyces. Other genera found were Candida, Endomycopsis, Hansenula, Kloeckera, Pichia, Saccharomycoides and Schizosaccharomyces. The viable yeast count ranged from 0.5 × 10⁷ cfu/ml to 4.2 × 10⁹ in both fresh Elaeis and Raphia spp. of palms. Yeasts in palm wine were least sensitive to sodium nitrate and most sensitive to sodium benzoate. The addition of these two chemical preservatives amongst others reduced the yeast count to 3.2 × 10⁸ (in Raphia sp.), and 4.1 × 10⁹ (in Elaeis sp.) with 0.025% sodium nitrate and 1.2 × 10⁶ (in Raphia sp.) and 1.9 × 10⁷ (in Elaeis sp.) with 0.1% sodium benzoate. The values of the yeast count in bottled and fresh palm wine were between 1.3 × 10³ cfu/ml to 9.8 × 10⁶ and 0.5 × 10⁷ to 4.2 × 10⁹, respectively. Maximum values of actual dry and theoretical yeast weights were 1.09 and 42 mg/ml, respectively.