Taxonomic characterization of Lactobacillus delbrueckii subsp. bulgaricus isolates from a Cameroonian zebu's fermented raw milk

Atypical thermophilic homofermentative lactobacilli were isolated as one of the major microflora from Pindidam, an indigenous Cameroonian zebu's fermented raw milk. On the basis of their physiological characteristics, obtained isolates constituted a homogeneous group belonging to the species Lactobacillus delbrueckii. Nevertheless, their carbohydrate fermentation pattern was unusual and their identification to one of two subspecies Lact. delbrueckii subsp. bulgaricus (Lact. d. bulgaricus ) or Lact. delbrueckii subsp. lactis (Lact. d. lactis ) was rendered difficult. DNA-DNA hybridization confirmed that they belonged to the species Lact. delbrueckii and the electrophoretic mobility of the D-(—)-lactate dehydrogenase (LDH) furthermore precisely assigned them to Lact. d. bulgaricus. Whole-cell protein profiles were only able to weakly discriminate between these wild isolates and type strains of the species Lact. delbrueckii. The isolates from Pindidam were well adapted to their specific environmental conditions and demonstrated both high growth rates and ability to support elevated acidic levels in fermented milk.     

Insulin receptor binding from mid-term and full-term placentas of patients with gestational diabetes mellitus and normal pregnant women

Insulin receptor binding was examined in the microvillous membranes of mid-term (20–22 weeks of gestation, MT) and full-term (FT) placentas from patients with gestational diabetes mellitus (GDM) and in normal pregnant control (N). Mid-term placentas were obtained from patients who have had spontaneous abortion. The maximum per cent specific binding (%SB) in MT placenta for GDM was significantly lower (4.8%) compared with the FT placenta (22%, p<0.001), while in the N group the maximum per cent specific binding for MT placenta was 14.1% compared with 26% for the FT placneta (p<0.001). Binding data from FT placenta of well-controlled GDM patients were similar with the FT placenta from N group (22%SB for GDM VS 26% SB for N). Even as there were similarities in the binding characteristics of FT placentas from both groups the placental membrane protein content in the GDM group was lower by 50% compared with the N control (2.5±0.11 VS 4.8±0.15 mg protein/g placenta respectively, p<0.001) suggesting that in the GDM group achieving a tight glycemic control could improve receptor affinities. Data from the competitive binding assay of GDM patients showed that the insulin necessary to achieve 50% inhibition (ID₅₀) was significantly lower in MT compared with the FT placenta (0.9×10^–9 M VS 3.8×10^–9 M, p<0.001) but in the N placenta there was no alteration in the ID₅₀ of MT and FT placentas (3.1×10^–9 M VS 4×10^–9 M, p<0.01, respectively). The present study demonstrated that in GDM the placental insulin receptor binding was significantly lower in spontaneously aborted placenta compared with placentas collected at full-term. Furthermore, these data suggest that the objective to achieve a tight glycemic control in GDM patients could optimize insulin receptor function similar to that of a normal pregnancy. Thus a full term placenta from GDM patients under a well managed glycemic control throughout the entire duration of pregnancy would result in an optimum insulin receptor function.     

Biosorption of uranium by Myxococcus xanthus

This paper deals with uranium biosorption by Myxococcus xanthus biomass in which dry biomass, accumulating up to 2.4 mM of uranium g⁻¹, is demonstrated to be a more efficient biosorbent than wet biomass. For uranium concentrations of 0.1–0.3 mM, between 95.79% and 95.99% of the uranium was taken up from the solution. Dry biomass biosorption was found to be relatively rapid, reaching equilibrium after 5–10 min. In addition, the pH influenced biosorption, pH 4.5 promoting maximum uptake. It was also established that the biosorbed uranium is located on the cellular wall and within the extracellular mucopolysaccharide of this microorganism. Furthermore, using sodium carbonate as a desorbent agent, 80.82% of the biosorbed uranium could be recovered. The results obtained indicate the possible utilization of M. xanthus biomass to solve some problems of the water contaminated by uranium.     

P-Element Insertion Alleles of Essential Genes on the Third Chromosome of Drosophila Melanogaster: Correlation of Physical and Cytogenetic Maps in Chromosomal Region 86e-87f

We have established a collection of 2460 lethal or semi-lethal mutant lines using a procedure thought to insert single P elements into vital genes on the third chromosome of Drosophila melanogaster. More than 1200 randomly selected lines were examined by in situ hybridization and 90% found to contain single insertions at sites that mark 89% of all lettered subdivisions of the Bridges' map. A set of chromosomal deficiencies that collectively uncover ~25% of the euchromatin of chromosome 3 reveal lethal mutations in 468 lines corresponding to 145 complementation groups. We undertook a detailed analysis of the cytogenetic interval 86E-87F and identified 87 P-element-induced mutations falling into 38 complementation groups, 16 of which correspond to previously known genes. Twenty-one of these 38 complementation groups have at least one allele that has a P-element insertion at a position consistent with the cytogenetics of the locus. We have rescued P elements and flanking chromosomal sequences from the 86E-87F region in 35 lines with either lethal or genetically silent P insertions, and used these as probes to identify cosmids and P1 clones from the Drosophila genome projects. This has tied together the physical and genetic maps and has linked 44 previously identified cosmid contigs into seven ``supercontigs' that span the interval. STS data for sequences flanking one side of the P-element insertions in 49 lines has identified insertions in the αγ element at 87C, two known transposable elements, and the open reading frames of seven putative single copy genes. These correspond to five known genes in this interval, and two genes identified by the homology of their predicted products to known proteins from other organisms.     

Prothrombin cleavage by human vascular smooth muscle cells: A potential alternative pathway to the coagulation cascade

Thrombin is a potent mitogen for human vascular smooth muscle cells (HVSMC) and its enzymatic activity is required for this function. The present study demonstrates that prothrombin is also mitogenic for HVSMC due to the generation of enzymatically active thrombin which occurs upon incubation of prothrombin with the cells. Analysis by SDS-PAGE, immunoblotting, and amino acid sequencing revealed that prothrombin incubated with HVSMC undergoes limited proteolysis. Prethrombin 1 was formed through cleavage at R¹⁵⁵-S¹⁵⁶. Cleavage at R²⁷¹-T²⁷² generated fragment 1.2 and prethrombin 2 whilst cleavage at R²⁸⁴-T²⁸⁵ yielded truncated prothrombin 2 (prethrombin 2′). However, cleavage at R³²⁰-I³²¹ which, during prothrombin activation produces two-chain α-thrombin, was not detectable. Studies on HVSMC-conditioned medium revealed that a similar pattern of prothrombin cleavage occurred by a cell-secreted factor(s). Amidolytic activity analysis indicated that 1–3% catalytically active thrombin-like activity was generated upon incubation of prothrombin with HVSMC-conditioned medium. By treating conditioned medium with various classes of proteinase inhibitors or hirudin, it was determined that prothrombin is cleaved by a cell-derived serine proteinase-like factor(s) at R²⁷¹-S²⁷² and by α-thrombin at R¹⁵⁵-S¹⁵⁶ and R²⁸⁴-T²⁸⁵. Antibodies neutralising the activity of either urokinase, tissue plasminogen activator, or factor Xa failed to alter the prothrombin cleaving activity of conditioned medium. This activity which may catalyse an alternative pathway for the generation of thrombin, was eluted from a gel filtration column as a single peak with apparent molecular mass of 30–40 kDa. © 1995 Wiley-Liss, Inc.     

Genetic regulation of gibberellin deactivation in Pisum

The regulation of gibberellin (GA) deactivation was examined using the sin (slender) mutation in the garden pea (Pisum sativum L.). This mutation blocks the deactivation of GA₂₀, the precursor of the bioactive GA₁. Firstly, crosses were made to combine sin with the GA biosynthesis mutations na, lhⁱ and le-3. The combination sin na produced a novel phenotype, with long (‘slender’) basal internodes and extremely short (‘nana’) upper internodes. In contrast, the double mutant sin lhⁱ was phenotypically dwarf. The mutation sin causes an accumulation of GA₂₀ in maturing seeds, and this was unaffected by na, since the na mutation is not expressed in seeds. In contrast, lhⁱ seeds did not accumulate GA₂₀, since lhⁱ imposes an early block on GA biosynthesis. Secondly, the effects of sin on several steps in GA deactivation were investigated. In maturing seeds, the mutation sin blocks two steps in GA₂₀ metabolism, namely, GA₂₀ to GA₂₉, and GA₂₉ to GA₂₉-catabolite. In the vegetative plant, on the other hand, sin blocked the step GA₂₀ to GA₂₉, but not GA₂₉ to GA₂₉-catabolite; the steps GA₂₀ to GA₈₁ and GA₂₀ to GA₁ were also not impaired in this mutant. It is clear that the effects of sin, like those of na, are strongly organ-specific. The presence of separate enzymes for the steps GA₂₀ to GA₂₉ and GA₂₉ to GA₂₉-catabolite was suggested by the observation that GA₈ inhibited the latter step, but not the former, and by the inability of GA₂₀ and GA₂₉ to inhibit each other's metabolism. It is suggested that the Sin gene may be a regulatory gene controlling the expression of two structural genes involved in GA deactivation.     

Copper distribution in the normal human brain

Copper concentration was determined in samples from 38 areas of 7 normal human brains. The grey matter contained higher concentrations of copper than the white matter. Identical areas of the grey and white matter of the cerebral cortex showed significant differences between individuals. In the caudate nucleus the highest concentrations of copper were found in the tail followed by the body and the head, respectively. A negative linear regression between age and brain copper levels was demonstrated.     

Fecundity of the freshwater catfishes mystus seenghala (sykes), mystus cavasius (ham), wallagonia attu (bloch) and heteropneustes fossilis (bloch) from the plains of Northern India

Fecundity of four species of catfishes, namely, Mystus seenghala (Sykes), Mystus cavasius (Ham), Wallagonia attu (Bloch) and Heteropneustes fossilis (Bloch), was studied. The fecundity of Mystus seenghala and Mystus cavasius varied between 20064 to 46443 and 3314 to 63135 respectively. In Wallagonia attu and Heteropneustes fossilis it varied between 66070 to 453148 and 1375 to 46737 respectively. In all the four species fecundity has a linear relationship with body weight and gonad weight, and a parabolic relationship with length in all the fishes excepting Mystus seenghala, where it is linear. By subjecting the data to multiple regression analysis, it is observed that the fecundity of each species can be most accurately determined by taking two variables together. In all the fishes studied the relative fecundity (Egg/body wt.) does not change significantly either with length or body weight.     

Acclimation to temperature and death at changing lethal temperatures in the freshwater fish Chalcalburnues chalcoides

1. 1.|In the freshwater fish Chalcalburnus chalcoides, an increase in the body (standard) size caused decreases in the upper LT-50 from 36.6° to 36.0°C and lower LT-50 from 6.3° to 5.3°C

2. 2.|The fish acclimated to constant temperatures between 10°C and 30°C showed reasonable heat acclimation and also reasonable cold acclimation. Thus, an increase in the acclimation temperature from 10°C to 30°C caused increases in the upper LT-50 from 34° to 36.2°C and the lower LT-50 from 1.25 to 6.5°C.

3. 3|The mean survival time — temperature curves of 10°, 20° and 30°C acclimated fish at various constant temperatures showed decreased in the survival tim ewith increasing lethal temperatures. Furthermore, an increase in the acclimation temperature causes a shift in the survival duration-temperature curve to the right, i.e., the fish become more heat resistant. Thus, the mean survival duration of 10°, 20° and 30°C acclimated fish at 35°C were 7.5, 79.6 and 530 minutes, respectively.

4. 4.|The effect of the thermal experience to changing lethal temperatures depends on the first lethal temperature to which the fish were exposed as well as the sequence of temperature changes. In the experiments in which the first lethal temperatures were between 32° and 34°C and the temperature was varied in an ascending order, their thermal resistance was increased and the fish required 114 to 174% of the expected lethal doses to die while in the experiments in which the starting temperature were between 38° and 40°C and the temperature varied in descending order, the fish become more sensitive to the upper lethal temperature and they died after receiving only 62 to 81% of the expected lethal doses. Thus, with a gradual increase in the lethal temperature, the fish show additional acclimation in the zone of resistance which in turn causes an increase in the thermal resistance. This may have ecological significance in nature.

A comparative study on the formation of citric acid and polyols and on morphological changes of three strains of free and immobilized Aspergillus niger

Summary The formation of citric acid, oxalic acid, erythritol and glycerol by three strains of Aspergillus niger immobilized in calcium alginate was investigated and compared with that of free cells when cultivated in shake flasks under phosphate limitation. Morphological changes were followed using an electron microscope. The production of acids and polyols, the consumption of glucose and fructose, and also the morphological changes were strain-dependent. The results also reflected the influence of long storage of a strain on productivity, morphological behaviour and phosphate consumption. Offprint requests to: H.-J. Rehm