Protein composition of the chromosomal scaffold and interphase nuclear matrix

Residual protein structures were prepared from isolated chromosomes and interphase nuclei of in vitro cultured bovine liver cells and the protein compositions were analysed. Chromosomes with minimal cytoplasmic contamination were obtained by a simple procedure using a pH 8 isolation medium containing Triton X-100 and polyamines, and residual protein-DNA complexes were prepared by extraction with 2 M NaCl. Residual protein structures were also obtained by digesting isolated chromosomes with staphylococcal nuclease. Protein compositions of both structures as obtained by SDS-polyacrylamide gel electrophoresis were essentially the same. Residual protein structures were prepared from isolated nuclei by the same procedures. The major nuclear matrix proteins, i.e., the lamins A, B, and C, were not found in the chromosomes and chromosome scaffolds. On the other hand, the residual chromosome structures contained two major polypeptides of 37 and 83 kilodalton relative molecular weights that were absent from the nuclear matrix preparations. A few polypeptides with the same or very similar electrophoretic mobilities were found in the residual structures of both the nuclei and the chromosomes.     

A comparison of the translational diffusion of a normal and a membrane-spanning lipid in Lα phase 1-palmitoyl-2-oleoylphosphatidylcholine bilayers

We have used the fluorescence recovery after photobleaching technique to study the translational diffusion, in L phase multibilayers of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), of fluorescent derivatives of 1-palmitoyl-2-oleoylphosphatidylethanolamine (NBD-POPE) and a membrane-spanning phosphatidylethanolamine (NBD-MSPE). The latter derivative was prepared from a membrane-spanning glycerol-dialkyl-glycerol tetraether lipid isolated from the thermophilic and acidophilic archaebacterium Sulfolobus solfataricus. The translational diffusion was examined between about 15° and 45°C. It is shown that over this temperature range the translational diffusion coefficient for NBD-MSPE is 2/3 that for NBD-POPE which spans only one monolayer of the bilayer. The result is interpreted in terms of existing models for translational diffusion in lipid membranes.Abbreviations D _t translational diffusion coefficient - FRAP fluorescence recovery after photobleaching - MSPE a membrane-spanning phosphatidylethanolamine derived from a glycerol-dialkyl-glycerol tetraether lipid isolated from Sulfolobus solfataricus - NBD 4-nitrobenz-2-oxa-1,3-diazolyl - PE phosphatidylethanolamine - POPC 1-palmitoyl-2-oleoylphosphatidylcholine - POPE 1-palmitoyl-2-oleoylphosphatidylethanolamine     

A spin label ESR and saturation transfer-ESR study of archaebacteria bipolar lipids

A spin label study has been carried out on bipolar lipids extracted from Sulfolobus solfataricus, an extreme thermophilic archaebacterium growing at about 85°C and pH 3. These lipids are cyclic diisopranyl tetraether molecules, quite different from the usual fatty acid lipids. Two hydrolytic fractions of the membrane complex lipids have been studied: the symmetric lipid glycerol-dialkyl-glycerol-tetraether (GDGT) and the asymmetric lipid glyceroldialkyl-nonitol-tetraether (GDNT). The ESR spectra confirm the results previously obtained from calorimetric and X-ray diffraction experiments showing a polymorphic behaviour of these lipids and indicating the critical temperature ranges at which structural transitions occur. Moreover, the present study adds information on the dynamics of the different portions of the hydrophobic chain. ST-ESR measurements show correlation times ranging from 10^-8 s up to 10^-5 s, depending upon the lipid sample, the label position and the degree of hydration. At very high temperatures, i.e. the physiological temperatures of Sulfolobus solfataricus, the nonitol head groups of the asymmetric lipids form a strongly immobilized structure. Indeed, the molecular correlation times of the outermost hydrophobic portion of GDNT are higher, by a factor up to 10³, than those of usual monopolar lipids. Anisotropic motional behaviour is observed even at such very high temperatures. Possible biological implications are discussed.Abbreviations used are ESR electron spin resonance - St-ESR saturation transfer electron spin resonance - GDGT glyceroldialkyl-glycerol-tetracther - GDNT glycerol-dialkyl-nonitoltetraether - 5 SASL 12SASL and 16SASL, stearic acid spin labels, N-oxyl-4,4-dimethyloxazolidine derivatives of 5-ketostearic acid, 12-ketostearic acid and 16-ketostearic acid, respectively - DSC differential scanning calorimetry     

Construction of a cosmid library of Spirulina platensis as an approach to DNA physical mapping

Abstract A Spirulina platensis gene library has been constructed using cosmid vector pMMB34. The cosmid bank was controlled for its random gene distribution by colony hybridization. Genes were identified using either homologous or heterologous probes of genes involved in photosynthesis (large and small subunit of d -ribulose 1,5-bisphosphate carboxylase, 32 kDa thylakoid protein, α, β subunits of C-phycocyanin) and protein synthesis (elongation factors EF-Tu, EF-G).     

Evidence for a rate-limiting role of cysteinesulfinate decarboxylase activity in taurine biosynthesis in vivo

The relationship between activities of enzymes involved in cysteine oxidation and the apparent conversion of cysteine to taurine in vivo were investigated in the rat and cat. Both hepatic cysteinesulfinate decarboxylase activity and the oxidation in vivo of cysteine to taurine were lower in the kitten than in the adult female rat and lower in the latter than in the young male rat. Our data support the hypothesis that cysteinesulfinate decarboxylase plays a rate-limiting role in taurine biosynthesis.     

Identification of a deletion in the low density lipoprotein (LDL) receptor gene in a patient with familial hypercholesterolaemia

Summary DNA samples from 60 unrelated UK patients with familial hypercholesterolaemia (FH) were screened by Southern blot hybridisation to detect gross alterations in the low density lipoprotein (LDL) receptor gene. One patient was found to have a 2kb deletion in the 3 part of the gene. The deletion cosegregates with the FH phenotype in his family. This finding is compatible with the deletion being the cause of FH in this case and makes a presymptomatic test based on DNA analysis available for this family. The defects in most of the other patients are likely to be due to point mutations.     

Properties of action potentials carried by divalent cations in identified leech neurons

Properties of divalent cation potentials carried by either Sr2+ or Ca2+ ions in Na+-free, TEA-Ringer solution were characterized in identified neurons of two species of leeches (Macrobdella and Haementeria). In Macrobdella, the overshoot of the potentials varied logarithmically with [Sr2+]0 (28.5 mV per 10-fold change). The overshoot, Vmax, and duration of the potentials increased with increasing divalent cation concentration and saturated at about 20 to 30 mM [Sr2+]0. The Vmax, amplitude, and duration of the potentials were reversibly blocked by Co2+ and Mn2+. The block by Mn2+ could be well-fitted by a reverse Langmuir-curve with an apparent KI of 100 micromolar. The local anesthetic procaine also reversibly inhibited the Vmax and duration of the potentials. The inhibition was greater at alkaline pH suggesting that procaine blocks the calcium channel from inside the membrane. The identified leech neurons examined in Macrobdella varied considerably in their ability to sustain somatic divalent cation potentials. Stimulation of T cells and most motoneurons produced no or only weak potentials, whereas stimulation of Retzius, N, Nut, and AP cells evoked overshooting potentials of several seconds' duration. Stimulation of the ALG cell of Haementeria in normal Ringer solution evoked a slowly-rising, purely Ca2+-dependent potential of approximately 100 ms duration. This response was TTX-resistant, unaffected by complete removal of Na+ from the Ringer solution, and abolished by 1 mM Mn2+. The overshoot varied logarithmically with a slope of 28 mV/decade change in [Ca2+]0.     

The Electrical Conductivity of Bovine Milk in Mastitis Diagnosis

The electrical conductivity (EC) of milk is mainly a function of the electrolyte concentration in the milk and therefore raised in mastitis. The present investigation was aimed at elaborating, if possible, a diagnostic model for screening purposes based on EC determinations and consistent with the diagnostic procedures and interpretations commonly used in laboratory milk diagnosis in the Nordic countries (Klastrup 1975). According to this diagnosis (here called reference diagnosis) cell numbers above 300,000/ml (cell count or the corresponding CMT-score) in foremilk quarter samples during the main part of the lactation period and significantly above the lowest value on within-udder comparison during late lactation are considered indicative of mastitis and bacteriological examinations are made when called for.     

Temporal Distribution of [3H]-Imipramine Binding in Rat Brain Regions is Not Changed by Chronic Methamphetamine

Specific binding of [³H]-imipramine in the rat suprachiasmatic nuclei, occipital cortex and caudate putamen underwent significant and replicable changes throughout 24 hr under a light-dark cycle or under constant conditions. Daily variations were also found in the medial and dorsal raphe nuclei and the lateral hypothalamus. Methamphetamine, a psychoactive drug with marked effect on circadian rhythms in physiological and hormonal parameters and adrenergic receptors, did not have any significant effect on imipramine binding rhythms in eight discrete brain regions. Thus a drug known to reduce serotoninergic neurotransmission did not change characteristics of the modulatory binding site related to serotonin uptake.