Effect of lipid composition on the calcium/adenosine 5'-triphosphate coupling ratio of the Ca2+-ATPase of sarcoplasmic reticulum

The Ca2+-ATPase of sarcoplasmic reticulum was purified and depleted of proteolipids by solubilization in Triton X-100 and by fractionation on a DE-52 column. The protein reconstituted by deoxycholate-cholate dialysis at low lipid to protein ratios (2-5 mg of lipid/mg of protein), with either dioleoylphosphatidylethanolamine or monogalactosyldiglyceride, exhibited high initial rates of ATP-dependent Ca2+ uptake [300-900 nmol min-1 (mg of protein)-1] and coupling ratios (Ca2+ transported/ATP hydrolyzed) up to 1.2. Ca2+-ATPase reconstituted with lipids of increasing degrees of methylation (dioleoylphosphatidylethanolamine, dioleoylmonomethylphosphatidylethanolamine, dioleoyldimethylphosphatidylethanolamine and dioleoylphosphatidylcholine) or increasing degrees of glycosylation (monogalactosyldiglyceride and digalactosyldiglyceride) revealed a progressive decrease in both ATP-dependent Ca2+-uptake and coupling ratios. The rate and extent of Ca2+ uptake decreased as the dioleoylphosphatidylethanolamine/dioleoylphosphatidylcholine or monogalactosyldiglyceride/dioleoylphosphatidylcholine molar ratios in the reconstituted vesicles were reduced. Vesicles reconstituted with high molar ratios of dioleoylphosphatidylethanolamine/dioleoylphosphatidylcholine or monogalactosyldiglyceride/dioleoylphosphatidylcholine and at a high lipid to protein ratio became leaky and released the Ca2+ accumulated inside the vesicles when the temperature of the incubation mixture was increased (e.g., from 20 to 37 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)     

Locus determining the human sperm-specific lactate dehydrogenase,LDHC, is syntenic with LDHC

From the data presented in this report, the human LDHC gene locus is assigned to chromosome 11. Three genes determine lactate dehydrogenase (LDH) in man. LDHA and LDHB are expressed in most somatic tissues, while expression of LDHC is confined to the germinal epithelium of the testes. A human LDHC cDNA clone was used as a probe to analyze genomic DNA from rodent/human somatic cell hybrids. The pattern of bands with LDHC hybridization is easily distinguished from the pattern detected by LDHA hybridization, and the LDHC probe is specific for testis mRNA. The structural gene LDHA has been previously assigned to human chromosome 11, while LDHB maps to chromosome 12. Studies of pigeon LDH have shown tight linkage between LDHB and LDHC leading to the expectation that these genes would be syntenic in man. However, the data presented in this paper show conclusively that LDHC is syntenic with LDHA on human chromosome 11. The terminology for LDH genes LDHA, LDHB, and LDHC is equivalent to Ldhl, Ldh2, and Ldh3, respectively.     

Production of pectinases byAspergillus sp using differently pretreated lemon peel as the carbon source

Summary Aspergillus sp strains from decaying lemons were tested for extracellular pectinase production, testing differently pretreated lemon peel as the carbon source instead of pectin. It was found that the production of extracellular polygalacturonase was about the same and that of pectinesterase substantially higher when unwashed fresh lemon peel was used instead of pectin. The culture filtrate obtained showed a clarifying capacity similar to that of a commercial pectinase preparation, but the vitamin C of the juice was less affected by the treatment.     

Some observations on the urea-degrading enzyme of the diatom Cyclotella cryptica and the role of nickel in its production

The urea-degrading enzyme of Cyclotella cryptica was testedin crude cell-free extracts for effects from chemical reagentsknown to distinguish between urease and ATP:urea amidolyase.Inhibition of the enzyme by hydroxyurea and its indifferenceto added ATP, Mg²⁺ or K⁺ avidin or biotin clearly characterizedthe enzyme as urease (EC 3.5.1.5 [EC] ). The Cyclotella urease wasunaffected by thiourea addition, as was also the growth of thediatom in the presence of this substrate analogue. Indirectevidence was obtained from growth studies of the diatom andcorresponding urease production showing that the enzyme: (i)contains Ni²⁺ tightly bound to an apoprotein; (ii) is producedconstitutively even from growth on nitrate and does not requireextracellular urea for its synthesis, although quantitativelythe activity is greatest from growth on urea. It is concludedthat Cyclotella urease is a Ni²⁺ constitutive enzyme similarin many respects to those previously reported from Phaeodactylumtricornutwn and Tetraselmis maculata.     

A new synaptic anomaly: irregular synaptonemal complexes

Summary In this paper we describe a new synaptic anomaly characterized by the presence of irregular synaptonemal complexes (SCs) in two sterile patients.     

Trypanosoma cruzi: 4-aminopyrazolopyrimidine in the treatment of experimental Chagas' disease

An allopurinol metabolite, 4-aminopyrazolopyrimidine, was tested on two different strains of mice (NMRI-IVIC and C57Bl/6J) that had been infected 4 days earlier with the virulent Ya strain of Trypanosoma cruzi. Low doses of 4-aminopyrazolopyrimidine (0.125-0.500 mg/kg body wt/day) for 10 days induced a significant reduction in parasitemia (direct counts and subinoculation experiments) and increased survival time (without any evidence of toxicity) compared with untreated animals. When tested in vitro, 4-aminopyrazolopyrimidine was sixfold more active than allopurinol as a trypanostatic drug. The low therapeutic doses of 4-aminopyrazolopyrimidine suggest that this drug may be useful in the treatment of acute Chagas' disease.