The fine structure of spermatozoa of Hydrolagus colliei (Chondrichthyes, Holocephali)

The ultrastructure of spermatozoa in Hydrolagus colliei is described. Basic similarities of structure to the sperm of the related elasmobranch fish are noted. The most significant features of sperm structure in Hydrolagus that differ from those of elasmobranch fish occur in the tail. The axoneme is eccentrically located and forms a double helix with a single longitudinal column. A second longitudinal column is reduced to a short remnant at the base of the tail. Microtubules within the axoneme are also helically disposed, a feature that is consistent with the rotating motion of the sperm. Abundant glycogen reserves are stored along the length of the tail.     

Cerebral Blood Flow and Oxidative Metabolism in Conscious Fischer-344 Rats of Different Ages

Abstract: The cerebral metabolic rates for O₂ and for glucose were measured in conscious, fasted male Fischer-344 rats at the ages of 3, 12, and 24 months, and cerebral blood flow was determined with ¹⁴C-iodoantipyrine. The metabolic rates for oxygen and glucose were obtained by multiplying blood flow by the O₂ and glucose concentration differences, respectively, between blood in the femoral artery and in the superior sagittal sinus. Mean cerebral blood flow and the metabolic rates for oxygen and glucose did not differ significantly (p > 0.05) between 3 and 12 or between 12 and 24 months. Nor did the arteriovenous differences for O₂ and for glucose change significantly with age. Because the superior sagittal sinus drains blood mainly from the cerebral cortex, the results indicate that average cerebral cortical oxidative metabolism, and the coupling ratios between the cerebral metabolic rate for oxygen and cerebral blood flow and between the cerebral metabolic rate for glucose and cerebral blood flow, do not change significantly with age in the Fischer-344 rat.     

A calcium antagonist drug binding site in skeletal muscle sarcoplasmic reticulum: Evidence for a calcium channel

The sarcoplasmic reticulum (S.R.) of rabbit skeletal muscle has been found to contain a single, high affinity binding site for the Ca antagonist drug [³H] -nitrendipine. Two subfractions of the reticulum were studied, the heavy (HSR) and light (LSR) preparations, which exhibited similar nitrendipine equilibrium dissociation constants (K_D) of 1nM. Crude cardiac and brain membranes assayed under the same conditions exhibited K_D values of 0.2–0.3nM. The concentration of binding sites per mg. protein (B_max) in HSR was found to be very high, namely 6.7 picomoles/mg, some four times greater than that of LSR. [³H] -nitrendipine binding to HSR was reversible and inhibited by the Ca antagonists flunarizine and verapamil, and by the intracellular Ca release antagonist TMB-8 (8-diethylamino-octyl 3,4,5- trimethylbenzoate hydrochloride). However, unlabelled nitrendipine at 2 × 10^?5M had no effect on contraction of isolated electrically stimulated rabbit lumbrical or rat diaphragm muscles, nor did it affect the neuromuscular junction as studied in rat phrenic nerve-diaphragm preparations. Also, little effect of 2 × 10^?5M nitrendipine was seen on net ⁴⁵Ca uptake by HSR. These results suggest that [³H] -nitrendipine binding to skeletal muscle S.R. resembles that of brain membranes, which also contain a high affinity binding site for [³H] -nitrendipine and which similarly are pharmacologically insensitive to this dihydropyridine type of Ca channel blocking agent. Since HSR is also enriched in calsequestrin and terminal cysternae from which Ca is released in vivo, it seems likely that the [³H]- nitrendipine binding sites in S.R. are associated with Ca channels in the S.R.     

Host Response to Sarisodera hydrophila Wouts and Sher, 1971

The histopathology of two populations of Sarisodera hydrophila Wouts and Sher, 1971 was examined on Salix lasiolepis Benth. (willow), Populus fremontii Wats. (cottonwood), and Lyonothamnus floribundus Gray (ironwood) using light microscopy as well as scanning and transmission electron microscopy. Sarisodera hydrophila induces formation of a single uninucleate hypertrophied cell (giant cell) which varies only slightly among the three hosts. The giant cell is enclosed by the root stele and contacts phloem, vascular cambium, and xylem. The single hypertrophied nucleus of the giant cell is ameboid or lobulate in shape, generally with a single nucleolus. The cell is characterized by a wall which is separated into two distinct regions about 2 μm and 13 μm thick; the thicker region occurs adjacent to the nematode head. Cell wall ingrowths, such as those associated with host responses to certain other plant-parasitic nematodes, were not observed in giant cells induced by S. hydrophila. However, a high frequency of pit fields with plasmodesmata occurred in the thinner portion of the cell wall which is adjacent to vascular elements. Roots of the three hosts simultaneously infected with S. hydrophila and Meloidogyne sp. resulted in adjacent responses characteristic of each nematode, supporting the view that the specific type of host response is a function of the nematode rather than the host. The varying expressions of host responses among Heteroderoidea may be useful in testing congruency with existing interpretations of phylogeny.     

Defective Virions in Human Adenovirus Type 12

Purified preparations of human adenovirus type 12 showed two bands when subjected to isopycnic centrifugation in a density gradient of cesium chloride. Their density difference was about 0.003 g/ml, suggesting a small difference in their deoxyribonucleic acid to protein ratio. Virions with a lighter density can kill human KB cells and induce T antigen as efficiently as the heavy virions. However, they appeared incapable to form plaques. Two passages of the heavy infectious virions at low multiplicity of infection did not produce significant amounts of light virions; however, when it was passed at high multiplicity of infection, the light band became visible in a cesium chloride density gradient.     

Purification and Properties of 4-Hydroxy-2-Ketopimelate Aldolase from Acinetobacter

The chemical synthesis of 4-hydroxy-2-ketopimelic acid is described. An aldolase that cleaves this compound to succinic semialdehyde and pyruvate has been purified from Acinetobacter grown at the expense of 4-hydroxyphenylacetic acid. The molecular weight of the enzyme was about 158,000 from sedimentation equilibrium data; other physical determinations gave values in reasonable agreement. The protein was globular and was dissociated in sodium dodecyl sulfate to give a species of molecular weight 25,700. The enzyme attacked both enantiomers of synthetic 4-hydroxy-2-ketopimelate and was stimulated by Mg(2+) and Mn(2+) ions.     

Ultraviolet Mutagenesis and Its Repair in an ESCHERICHIA COLI Strain Containing a Nonsense Codon

Ultraviolet mutagenesis and its repair were studied mainly in WU36-10-89, a uvr(-) strain of Escherichia coli containing a UAG mutation in a gene for leucine biosynthesis. Following ultraviolet (UV) irradiation revertants appearing with or without direct photoreactivation (PR) were classified according to the presence and type of suppressor they contained. We find UV mutation production to be quite specific. An analysis of revertants produced by UV indicates they are formed mainly from GC --> AT and that the miscoding is due to a cytosine residue at the site of mutation in a cytosine-thymine (CT) dimer. We propose that the dimer serves as template during some aspects of repair replication and at the time of replication the C in the dimer directs the insertion of A in the complementary strand. We also note that C --> A and T -->G changes caused by a CT dimer occur much less frequently.     

A study of the properties of hybrids of oxyhaemoglobin and deoxyhaemoglobin with two porphyringlobin species

The fluorescence of porphyringlobin is quenched on adding haemoglobin to its solutions. It is suggested that this result indicates the formation of hybrids (comprising a dimer of porphyringlobin and a dimer of haemoglobin) in which quenching occurs by energy transfer from the porphyrin to the haem groups of the protein. From an analysis of fluorescence quenching, dissociation constants were calculated for the hybrids of oxy- and deoxyhaemoglobin with the fast- and slow-moving porphyringlobin species isolated by chromatography on CM-Sephadex (Treffry & Ainsworth, 1974). The values obtained are: deoxyhaemoglobin-fast-moving porphyringlobin, 0.8x10(-9)m; deoxyhaemoglobin-slow-moving porphyringlobin, 5x10(-10)m; oxyhaemoglobin-fast-moving porphyringlobin, 0.8x10(-6)m; oxyhaemoglobin-slow-moving porphyringlobin, 1.2x10(-7)m. The rates of reactions of solutions of haemoglobin and porphyringlobin, containing hybrids, with the thiol reagent 4,4'-dithiodipyridine showed that the thiol groups of the hybrids deoxyhaemoglobin-fast-moving porphyringlobin and oxyhaemoglobin-slow-moving porphyringlobin react more slowly than expected on the basis of composition alone: this result indicates that the deoxy and slow-moving conformations are the more stable, imposing themselves partially on to the fast-moving or oxy dimer of the hybrid. Also the rate of the reaction of CO with deoxyhaemoglobin is decreased when slow-moving porphyringlobin is added to its solutions: this is reflected in a movement of the oxygen equilibrium curve of such a mixture to higher oxygen partial pressures. Similar experiments with deoxyhaemoglobin solutions containing fast-moving porphyringlobin, showed an initial increase in the rate of CO uptake. Correspondingly, the oxygen equilibrium curve of the mixture showed an increased affinity for oxygen. Approximate calculations to determine the oxygen equilibria of the hybrids indicate that a functional dimer retains co-operative characteristics even when the dimer accompanying it within the tetramer has the reacted conformation.