The response of alkaline phosphatase to osmoregulatory changes in the trout,Salmo gairdneri

Summary The relationship between alkaline phosphatase and environmental salinity was examined in the rainbow trout and the migratory rainbow (steelhead),Salmo gairdneri. The enzyme activity in tissues involved in osmoregulation was strongly correlated with the adaptation salinity and thus to the degree of salt and fluid transport in those tissues. After transfer from freshwater to seawater, the specific activity of the enzyme increased over 260% in the intestine, decreased by 50% in kidney, and was unchanged in the liver, an organ not directly involved in osmoregulation. The sea-run steelhead trout response was similar to the nonmigratory rainbow; although, the pre-migratory transformation (smoltification) had no effect on enzyme activity. Amino acid inhibitors of alkaline phosphatase significantly reduced fluid absorption in the isolated intestine of rainbow trout, reaffirming the relationship between the enzyme and fluid movement. Electrophoretic identification of trout alkaline phosphatase isozymes, clearly distinguishes the enzyme from different tissue origins. However, from the analysis of intestinal electrophoretic patterns, osmoregulatory adjustments are not associated with the induction of new alkaline phosphatase isozymes, or in the large scale preferential stimulation of one of the two existing intestinal isozymes over the other.     

Glycolysis and the regulation of cryoprotectant synthesis in liver of the freeze tolerant wood frog

Summary Wood frogs,Rana sylvatica, were sampled after freezing at –4°C (a short time course from 2 to 70 min after the appearance of the freezing exotherm) and thawing (20 h at 3°C after 70 min of freezing) and the regulation of liver glycolysis with respect to cryoprotectant glucose synthesis was examined. Within 5 min of the initiation of freezing, cryoprotectant concentrations in blood and liver had begun to increase. This was correlated with a rapid rise in the levels of hexose monophosphates in liver, including a 2.5 fold increase in glucose-6-P and 10 fold rise in fructose-6-P contents within the first 5 min post-exotherm. Contents of fructose-1,6-P₂, fructose-2,6-P₂, triose phosphates, P-enolpyruvate, and pyruvate did not significantly change over the course of freezing. Thawing sharply reduced the levels of hexose monophosphates in liver but raised P-enolpyruvate content by 2.3 fold. Changes in the contents of glycolytic intermediates over the freeze/thaw course are consistent with an inhibitory block of glycolysis at phosphofructokinase during freezing in order to facilitate a rapid glycogenolysis and production of cryoprotectant; during thawing, however, glycolysis appears to be inhibited at the level of pyruvate kinase.Possible regulatory control of cryoprotectant synthesis by covalent modification of liver glycolytic enzymes was examined. Glycogenolysis during freezing was facilitated by an increase in the percentage of glycogen phosphorylase in the activea (phosphorylated) form and also by an increase in the total amount (a+b) of enzyme expressed. For phosphofructokinase, kinetic changes as a result of freezing included a 40% reduction inK _m for fructose-6-P, a 60% decrease inK _a for fructose-2,6-P₂, and a 2 fold increase in I₅₀ for ATP. These changes imply a freezing-induced covalent modification of the enzyme but are not, apparently, the factors responsible for inhibition of glycolytic flux at the phosphofructokinase locus during glucose synthesis. Kinetic parameters of pyruvate kinase were not altered over the freeze/thaw course.     

DNA-dependent RNA polymerase subunits encoded within the vaccinia virus genome.

Antiserum to a multisubunit DNA-dependent RNA polymerase from vaccinia virions was prepared to carry out genetic studies. This antiserum selectively inhibited the activity of the viral polymerase but had no effect on calf thymus RNA polymerase II. The specificity of the antiserum was further demonstrated by immunoprecipitation of RNA polymerase subunits from dissociated virus particles. The presence in vaccinia virus-infected cells of mRNA that encodes the polymerase subunits was determined by in vitro translation. Immunoprecipitable polypeptides with Mrs of about 135,000, 128,000, 36,000, 34,000, 31,000, 23,000, 21,000, 20,000, and 17,000 were made when early mRNA was added to reticulocyte extracts. The subunits were encoded within the vaccinia virus genome, as demonstrated by translation of early mRNA that hybridized to vaccinia virus DNA. The locations of the subunit genes were determined initially by hybridization of RNA to a series of overlapping 40-kilobase-pair DNA fragments that were cloned in a cosmid vector. Further mapping was achieved with cloned HindIII restriction fragments. Results of these studies indicated that RNA polymerase subunit genes are transcribed early in infection and are distributed within the highly conserved central portion of the poxvirus genome in HindIII fragments E, J, H, D, and A.     

Identification of the vaccinia virus gene encoding nucleoside triphosphate phosphohydrolase I, a DNA-dependent ATPase.

Vaccinia virus encapsidates a DNA-dependent ATPase known as nucleoside triphosphate phosphohydrolase I (NPH I). A bacteriophage lambda gt11 expression library of poxvirus DNA was screened with antibodies specific for NPH I. Positive clones were used to probe restriction fragments of vaccinia virus genomic DNA to locate the NPH I gene. The identity of the open reading frame (ORF) was confirmed by placing it downstream of a bacteriophage T7 promoter, transcribing the ORF in vitro, and translating the RNA in a reticulocyte lysate. A polypeptide of the correct molecular weight, which was recognized by anti-NPH I antibody, was synthesized. Inspection of the deduced amino acid sequence of the NPH I ORF revealed consensus ATP-binding sites.     

Hynes pharyngoplasty revisited

The treatment of velopharyngeal incompetence remains unsatisfactory because the causes are many, as are the variations in anatomic and physiologic defects. Therefore, full assessment and investigation are essential in tailoring the surgery to the defect. A modified Hynes pharyngoplasty has been used in 40 patients, aged 4 to 52, over a 4-year period for velopharyngeal incompetence of varying etiologic causes. Speech was assessed before and at least 6 months after pharyngoplasty. At the same time, radiologic and, when possible, nasendoscopic investigations were undertaken. Thirty-eight patients had no or variable nasal escape (variable defined as achieving intermittent closure), whereas 33 had normal or slight hyponasal resonance. There was only one complication, an asymptomatic dehiscence of the "bucket handle" flap from the posterior wall. Thirteen patients had an assortment of side effects, none requiring surgical treatment. We believe that patients who are suitable for the described sphincter pharyngoplasty are those with slight or moderate nasal escape having a mobile palate with an anteroposterior gap of 5 mm or less.     

Polymorphism and Gene Conversion in Mouse α-Globin Haplotypes

We have cloned and characterized three distinct alpha-globin haplotypes obtained from inbred strains of the mouse, Mus domesticus. We report here the complete nucleotide sequence of the six alpha-globin genes that the haplotypes contain. Our analysis of these genes and those from one other previously described haplotype indicates that recurrent gene conversion events have played a major role in their history. The pattern of nucleotide substitutions suggests that conversions have occurred both within and between haplotypes. Limited segments of coding and noncoding DNA have been involved in these gene conversion events. In two of the haplotypes, the nonallelic genes of each maintain DNA sequence identity over discrete intervals and encode the same alpha-globin polypeptide. On the other hand, the coding regions of some genes have accumulated replacement changes that result in distinct alpha-globins. In one instance, these changes appear to reflect positive selection of advantageous mutations.     

Studies on orthocephalization. 10. Behaviour of the visceral part of the rat head during the first 14 days after gestation

The present paper considers the significance of interosseous flexions of the palatal complex in the process of orthocephalization of the rat skull between birth and 7 d p.n. The study is based on a sample of 90 rats divided into 4 age groups, i.e. 0, 4, 7, and 14 d. These rats have been X-rayed, and their photographs subsequently analysed. During the studied period, the constituents of the bony palate, i.e. the horizontal part of the palatine bone, the palatal process of maxilla and the palatal part of premaxilla, increase markedly in length, but with individual differences in growth rate. There is, in the period, a marked decrease in angulation between the cranial base and the palatal plane. This means that the rat skull becomes more orthocranial. There is also a straightening (orthopalatalization) of the palate, as the angle between maxilla and premaxilla becomes more obtuse, and a marked decrease in angulation between the palatine bone and the cranial base. The patterns of angular changes suggest that the process of orthocephalization in the period between birth and 14 d p.n. primarily is a result of an upwards rotation of the palatine bone relative to the cranial base, while interosseous deflections in the palate only play a minor role.     

Effects of peroxide and catalase on near ultraviolet radiation sensitivity in Escherichia coli strains

The role of peroxide and catalase on NUV radiation sensitivity was examined in two repair competent E. coli strains, AB1157 and B/r. Exponential phase B/r is considerably more sensitive to NUV radiation than exponential phase AB1157. However, resistance to 5 mmol dm-3 H2O2 was induced in both AB1157 and B/r by pretreating growing cells with 30 mumol dm-3 H2O2. Pretreatment also induced resistance to broad-band NUV radiation in these strains. The addition of catalase to the post-irradiation plating medium increased survival to the same extent as that provided by pretreatment with 30 mumol dm-3 H2O2, in both strains. The NUV radiation sensitivity seen in B/r does not appear to be due to a deficiency in enzymes that scavenge H2O2, as a catalase deficient mutant, E. coli UM1, is more resistant to NUV radiation than B/r. Also, assays for H2O2 scavenging ability show little difference between AB1157 and B/r in this respect. Two hypotheses are put forward to account for the sensitivity of exponential phase B/r. Whilst it is apparent that peroxides and catalase do have a role in NUV radiation damage, it is clear that other factors also influence survival under certain conditions.