Thermal biology of the common garter snake Thamnophis sirtalis (L.)

Summary The thermoregulatory significance of a striped-melanic colour polymorphism in the common garter snake, Thamnophis sirtalis, was assessed through a combination of labortory experimentation and field study. In experiments with living snakes the melanic morph maintained a higher body temperature than the striped morph, when exposed to natural insolation. Experiments with excised skin showed that this thermal advantage is attributable to some integumental difference between the two morphs. Body temperatures of snakes in the field revealed that, during the colder part of the active season, melanics were able to stay warmer than striped snakes by an amount (1.24 C°) approximating the difference observed in the laboratory. Some evidence and argument is presented to suggest that melanism also may confer protection against overheating in warm periods.     

The Geonemertes problem (Nemertea)

A new genus of monostiliferous hoplonemerteans, Pantinonemertes gen. nov., provides evidence for the separate evolution of terrestrial nemerteans. The genus is established for two new species found in Australia, P. enalios sp. nov., an intertidal form, and P. winsori sp. nov., which lives in fallen timber in the supralittoral brackish water regions of mangrove swamps. One only of the known species of land nemerteans, Geonemertes agricola from Bermuda, closely resembles these two species morphologically and is transferred to the new genus as Pantinonemertes agricola .
A re-examination of all the known species of Geonemertes has shown that two major groups can be distinguished on the basis of morphological characters. In one group the rhynchocoel musculature is in two distinct layers, a frontal organ is present, the mid-dorsal blood vessel has a single vascular plug, and the flame cells are binucleate and reinforced with cuticular support bars. It comprises the genus Pantinonemertes gen, nov, and the Pelaensis or Indopacific group of terrestrial nemerteans, for which the generic name Geonemertes is retained. In the second major group the rhynchocoel musculature is composed of interwoven longitudinal and circular fibres, there is no frontal organ, the mid-dorsal blood vessel bears two vascular plugs, and the flame cells are mononucleate and lack support bars. Five genera, three of which are new, are distinguished in this group. Australian species are united in the genus Argonemertes gen. nov., and New Zealand forms comprise the genus Antiponemertes gen. nov., while Acteonemertes bathamae from New Zealand and the Auckland and Ocean Islands remains in a separate genus. Geonemertes nightingaleensis is transferred to a new genus, Katechonemertes gen. nov., and for Geonemertes chalicophora a previously used generic name, Leptonemertes , is adopted.
A key to the terrestrial, brackish-water and marine nemertean species described in the present paper is provided.     

Acetate uptake by the unicellular cyanobacteria Synechococcus and Aphanocapsa

Acetate uptake by strains of Synechococcus and Aphanocapsa in short experiments required light, and was strongly inhibited by m-dichlorocarbonyl cyanide phenylhydrazone and dichlorophenyl dimethyl urea. Acetate carbon was distributed in amino acids and in the acyl portion of lipids in the same way as during growth experiments when CO₂ was available, but the reduced incorporation in the absence of CO₂ was primarily into the lipid fraction. An apparent K _m for uptake by Synechococcus and for Aphanocapsa 6308 of 20 and 180 M at pH 7.4 was obtained; corresponding V _max values were 6 and 11 nmol x min^-1 x mg protein^-1. Uptake with Synechococcus was affected by pH, with affinity decreased and maximal rate increase with rising pH. Acetate uptake was not affected by propionate or butyrate when both were added at the same time, but a light and concentration dependent inhibition developed if suspensions were preincubated with propionate. Acetate carbon moved rapidly into acid insoluble material, but after 10–15 s 75% or more of the recovered intracellular counts were in acetyl CoA. Counts in this compound were reduced by preincubation with propionate.Kinetic measurements of acetyl CoA synthetase in fractionated cell extracts gave values for K _m of about 50 M for acetate, 5 mM for propionate, 100 M for CoA and 0.38 mM for ATP. The internal pool of free CoA was measured to be about 20 M, and was reduced by preincubation with propionate. This suggests that the activity of CoA-mediated reactions may be regulated by the availability of this cofactor.Abbreviations Used CCCP m-Dichlorocarbonyl cyanide phenyl hydrazone - DCMU dichlorophenyl dimethyl urea - TCA trichloroacetic acid - Tris trishydroxymethyl amino methane - HEPES N-2-hydroxyethylpiperazine-N-2-ethane-sulfonic acid     

Genetic complementation between two mutant unc alleles (unc A401 and unc D409) affecting the Fl portion of the magnesium ion-stimulated adenosine triphosphatase of Escherichia coli K12.

A new mutant strain of Escherichia coli in which phosphorylation is uncoupled from electron transport was isolated. A genetic-complementation analysis, using partial diploid strains, showed that the new mutant allele, uncD409, is in a gene distinct from the other previously identified genes uncA, uncB and uncC. A strain carrying the uncd409 allele has no Mg2+ ion-stimulated adenosine triphosphatase activity and is therefore phenotypically similar to strains carrying the uncA401 mutant allele. Complementation between the uncA401 and the uncD409 alleles occurred, as indicated by growth of partial diploid strains on succinate and their growth yields on limiting concentrations of glucose. Complementation was confirmed by using membranes prepared from the above partial diploids. Such membranes were found to have Mg2+-stimulated adenosine triphosphatase activity, ATP-dependent transhydrogenase activity ADP-induced atebrin-fluorescence quenching and low but significant amounts of oxidative phosphorylation.     

Plasmid Involvement in Parathion Hydrolysis by Pseudomonas diminuta

An organism identified as Pseudomonas diminuta was found to hydrolyze parathion. Cells grown for 48 h contained 3,400 U of parathion hydrolase activity per liter of broth. Expression of enzymatic activity was lost at a high frequency (9 to 12%) after treatment with mitomycin C. Hydrolase-negative derivatives were missing a plasmid present in the wild-type organism. The molecular mass of this plasmid (pCS1), as determined by electron microscopy, was about 44 × 10⁶ daltons.     

A collagen-like glycoprotein from elastin-rich tissues

Extracts of bovine aorta and nuchal ligament contain several large glycoproteins. The major glycoprotein species has been isolated and has been shown to be collagenase sensitive with an apparent molecular weight of 140,000 daltons. The protein exists in disulphide-bonded aggregates, contains hydroxyproline and hydroxylysine in 1:1 ratio and is unlike any of the known collagen types in amino acid analysis. Its presencein ligament extracts indicates that it is not derived from basement membranes. The evidence suggests that this protein is not derived from the microfibrillar components of the elastic tissues.     

Nucleotide sequence, transcriptional analysis, and expression of genes encoded within the form I CO2 fixation operon of Rhodobacter sphaeroides

In Rhodobacter sphaeroides, many of the structural genes encoding enzymes of the Calvin cycle are duplicated and grouped within two separate clusters. In this study, the nucleotide sequence of a 5627-base pair region of DNA that contains the form I Calvin cycle gene cluster has been determined. The five open reading frames are arranged in the order, fbpA prkA cfxA rbcL rbcS and are tightly linked and oriented in the same direction. The results of insertional mutagenesis studies suggest the genes are organized within an operon. Consistent with this proposal, the cfxA gene has been tentatively identified as a gene encoding the Calvin cycle enzyme, aldolase. Measurement of the activities of various Calvin cycle enzymes in the insertion mutants showed that inactivation of genes within one CO2 fixation cluster affected expression of genes within the second cluster, revealing a complex regulatory network.     

Mucopolysaccharidosis VI (Maroteaux-Lamy syndrome). An intermediate clinical phenotype caused by substitution of valine for glycine at position 137 of arylsulfatase B.

The Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI) is a lysosomal storage disease with autosomal recessive inheritance caused by deficiency of the enzyme arylsulfatase B. Severe, intermediate, and mild forms of the disease have been described. The molecular correlate of the clinical heterogeneity is not known at present. To identify the molecular defect in a patient with the intermediate form of the disease, arylsulfatase B mRNA from his fibroblasts was reverse-transcribed, amplified by the polymerase chain reaction, and subcloned. Three point mutations were detected by DNA sequence analysis, two of which, a silent A to G transition at nucleotide 1191 and a G to A transition at nucleotide 1126 resulting in a methionine for valine 376 substitution, were polymorphisms. A G to T transversion at nucleotide 410 causing a valine for glycine 137 substitution (G137V) was identified as the mutation underlying the Maroteaux-Lamy phenotype of the patient, who was homozygous for the allele. The kinetic parameters of the mutant arylsulfatase B enzyme toward a radiolabeled trisaccharide substrate were normal excluding an alteration of the active site. The G137V mutation did not affect the synthesis but severely reduced the stability of the arylsulfatase B precursor. While the wild type precursor is converted by limited proteolysis in late endosomes or lysosomes to a mature form, the majority of the mutant precursor was degraded presumably in a compartment proximal to the trans Golgi network and only a small amount escaped to the lysosomes accounting for the low residual enzyme activity in fibroblasts of a patient with the juvenile form of the disease.