Progesterone in uterine and arterial tissue and in jugular and uterine venous plasma of sheep

Concentrations of progesterone in uterine and arterial tissue and in uterine and jugular venous plasma were determined. Blood was collected on Days 4 and 9 postestrus from the jugular vein and the first and last venous branches draining each uterine cornu; uterine tissue and arteries were subsequently collected. Progesterone was greater (p less than 0.05) in the cranial third than in the middle or caudal thirds of the uterine horn adjacent to the corpus luteum (CL)-bearing ovary or in any third of the contralateral horn. Progesterone in uterine arterial segments adjacent to the CL-bearing ovary was higher (p less than 0.05) than in contralateral segments. Progesterone was higher (p less than 0.05) in blood from the first venous branch of the cranial third of the uterine cornu adjacent to the ovary with the CL, than in the last branch of the caudal third, or contralateral horn, or in jugular blood. When oviductal veins were resected on Day 9 postestrus, progesterone in the first vein draining the cranial third of the uterine cornu adjacent to the CL-containing ovary was not different (p greater than 0.05) 48 h after resection than in the same vessel in the opposite horn or in jugular blood. We concluded that progesterone and other ovarian products may be delivered to the uterus locally.     

Spectroscopic investigations of Panulirus interruptus hemocyanin in the crystalline state

Single-crystal ultraviolet spectroscopy, X-ray absorption spectroscopy and EPR measurements have been used to examine the oxidation and oxygenation state of the dinuclear copper site of several types of hemocyanin crystals. The crystals contain Panulirus interruptus hemocyanin which forms hexameric molecules with a molecular mass of approximately 470 kDa. Three types of crystals have been investigated. Type-I monoclinic crystals, which have been used for the X-ray structure determination, contain virtually only deoxyhemocyanin. Type-II monoclinic crystals, which are less well ordered than the type-I crystals, contain a mixture of deoxy, oxy and met forms. Older crystals contain relatively more methemocyanin. A third, hexagonal, crystal form is also partially oxygenated, and, like the type-II monoclinic form, subject to gradual conversion to methemocyanin.     

Nitrogen dynamics in two antarctic streams

The many glacier meltwater streams of southern Victoria Land flow through catchments where life forms are almost entirely microbial. Allochthonous inputs of nitrogen from two study streams near McMurdo Sound were derived mostly from the melting glaciers (ca. 100–200 mg N m^–3) with some originating from N₂-fixation by heterocystous cyanobacteria (max. 939 mg N m^–2 year^–1). Thirty to fifty per cent of the glacier derived N was dissolved organic N and a major proportion of this was identified as urea N which was utilised by the rich algal and cyanobacterial mats in the streams. A nutrient budget for Fryxell Stream was estimated, quantifying uptake of urea-N and dissolved inorganic N and the release of dissolved organic (non urea) and particulate N by the stream communities. An index of in-stream nitrogen processing, the Net Uptake Length Constant in these streams was compared with that from temperate climates and was found to be similar. Despite the influence of low temperatures on microbial activity (mean daily water temperature = 5 °C) nutrient removal rates from these antarctic streams are high because of the large standing stock of microbial biomass there.     

An enzyme with a double identity: purple acid phosphatase and tartrate-resistant acid phosphatase

The tartrate-resistant acid phosphatases or purple acid phosphatases constitute a class of related mammalian enzymes. Spectroscopic and magnetic studies have revealed that the purple phosphatases contain a novel dinuclear iron active site that is responsible for the purple color. More biologically and biomedically oriented research has shown that the tartrate-resistant acid phosphatases generally occur in osteoclasts and white blood cells, where they appear to be localized in lysosomes or similar organelles. Despite the different names given the enzymes by researchers in the two fields, recent sequence determinations and immunological studies indicate that the enzymes are identical. The status of research in both fields is reviewed in an attempt to present a unified picture of the structure, function, and mode of action of these unique metalloproteins.     

Construction of a yeast mutant lacking the mitochondrial nuclease.

The nuclear gene from Saccharomyces cerevisiae that encodes the major mitochondrial nuclease was cloned. Gene sequences were identified from a lambda gt11 library by antibodies specific to the mitochondrial nuclease. DNA from the phage recombinant was used to isolate the entire nuclease gene from a plasmid library. Yeast strains containing the nuclease gene on a multicopy plasmid vector overproduced mitochondrial nuclease 20-40 times relative to a wild-type strain. Strains containing a null allele of the nuclease gene lacked all traces of mitochondrial nuclease. Both cell types, however, were phenotypically wild-type indicating that the nuclease is not an essential enzyme for mitochondrial function. The locus encoding the mitochondrial nuclease is termed NUC1.     

Binding selectivity ofStreptococcus pyogenes and M-protein to epithelial cells differs from that of lipoteichoic acid

The ability of M-protein-positive (M⁺) and M-protein-negative (M^–) strains (including an M^– mutant lacking the structural gene for M-protein) ofStreptococcus pyogenes to attach to human pharyngeal, buccal, and tongue epithelial cells was compared. We observed that M⁺ strains ofS. pyogenes attached in significantly higher numbers to human pharyngeal epithelial cells than to human buccal or tongue cells. M^– strains did not exhibit high-level binding to any type of epithelial cell. Also, the adhesion of an M⁺ and an M^– strain ofS. pyogenes was low to all types of rat epithelial cells tested. The apparent differences in the surface components between human pharyngeal and buccal epithelial cells were confirmed by studies utilizing radiolabeled lectins.Ulex europaeus lectin with a specificity for fucosyl residues, andTriticum vulgaris lectin with a specificity for N-acetyl glucosamine and N-acetyl neuraminic acid residues, bound in higher amounts to human pharyngeal cells than to buccal cells. Pretreatment of pharyngeal epithelial cells with microgram quantities of highly purified type 6 M-protein or miligram quantities of lipoteichoic acid (LTA) derived fromS. pyogenes decreased the subsequent attachment of the organism. However, the binding specificities of³H-LTA were different from those of intact streptococci;³H-LTA bound comparably to human pharyngeal, buccal, and tongue epithelial cells, and it bound in higher quantities to rat epithelial cells. Also, although the adsorption ofS. pyogenes cells to pharyngeal cells was inhibited by the presence of fucose and galactose, these sugars had little effect on the binding of³H-LTA to epithelial cells. In contrast, the high adhesion of M⁺ strains but not M^– mutants to pharyngeal cells suggested that M-protein may play an important role. This possibility was supported by the observation that³H-labeled purified type 6 M-protein bound in higher concentrations to human pharyngeal epithelial cells than to human buccal cells. Furthermore, human pharyngeal epithelial cells were estimated to contain larger numbers of binding sites for M-protein than buccal cells, whereas the affinity of M-protein was similar to both cell types. These adsorption parameters are similar to those previously established for intact streptococcal cells.     

Synthesis and biological evaluation of pNPY fragments

Peptide fragments of pNPY corresponding to the C-terminal segments (13-36) and (25-36), the N-terminal segments (1-12) and (1-24), the segments (6-14) and (7-20), which contain a putative beta-turn, and the internal segments (13-24) and (20-30) were synthesized using solid phase methodology. These fragments were assayed for NPY receptor binding activity in the rat hypothalamus membrane preparation, enhancement of food intake in the rat following ivt administration and inhibition of electrically stimulated muscle contraction in the rat vas deferens. Only the C-terminal fragment (13-36) retained some of the activities of pNPY, appearing to act as a weak agonist, having an additive effect with pNPY on the inhibition of muscle contraction and prolonging the duration of action of pNPY in the feeding assay. It also had considerable alpha-helical character, as did pNPY. None of the other peptide fragments had any agonist or antagonist activity. These results suggest that the expression of full biological NPY activity requires both the C- and the N-terminal segments as well as a putative amphiphilic alpha-helical segment (14-31).     

Regulation of Brain and Cerebrospinal Fluid Calcium by Brain Barrier Membranes Following Vitamin D-Related Chronic Hypo- and Hypercalcemia in Rats

Male Fischer-344 rats, 21 days old, were fed diets containing 0 (LOD), 2,200 (CONT), or 440,000 (HID) international units of vitamin D3 per kilogram for 12 weeks. [Ca] was measured in plasma, CSF, brain, and choroid plexus. In addition, 45Ca and 36Cl transfer coefficients (KCa and KCl) for uptake from blood into CSF and brain were determined. Although plasma ionized [Ca]s in LOD and HID rats were 50% and 136%, respectively, of values in CONT animals, CSF and brain [Ca]s ranged from only 85% to 110% of respective CONT values. Choroid plexus [Ca] was increased by 37% after HID diet, but was decreased only 10% after LOD. KCa values at CSF, parietal cortex, and pons-medulla were negatively correlated with plasma ionized [Ca], whereas KCl values at CSF and brain were not different between the diet groups. The findings demonstrate that central nervous system [Ca] is maintained during chronic hypo- or hypercalcemia by saturable transport of Ca at brain barrier membranes. This transport does not seem to involve modulation by 1,25-dihydroxyvitamin D3.     

Strand targeting signal(s) for in vivo mutation avoidance by post-replication mismatch repair in Escherichia coli

Summary The involvement of GATC sites in directing mismatch correction for the elimination of replication errors in Escherichia coli was investigated in vivo by analyzing mutation rates for a gene carried on a series of related plasmids that contain 2, 1 and 0 such sites. This gene encoding chloramphenicol acetyl transferase (Cat protein) was inactivated by a point mutation. In vivo mutations restoring resistance to chloramphenicol were scored in mismatch repair proficient (mut ⁺) and deficient (mutHLS^-) strains. In mut ⁺ cells, reduction of GATC sites from 2 to 0 increased mutation rates approximately 10-fold. Removal of the GATC site distal to the cat ^- mutation increased the rate of mutation less than 2-fold, indicating that mismatch repair can proceed normally with a single site. The mutation rate increased 3-fold after removal of the GATC site proximal to the mutation. In the absence of a GATC site, mutL^- and mutS^- strains exhibited a 2- to 3-fold increased mutation rate as compared to isogenic mutH^- and mut ⁺ strains. This indicates that 50%–70% of replication errors can be corrected in a mutLS-dependent way in the absence of any GATC site to target mismatch correction to newly synthesized DNA strands. Other strand targeting signals, possibly single strand discontinuities, might be used in mutLS-dependent repair