Structure of the 5'-external transcribed spacer of the human ribosomal RNA gene

We report the complete nucleotide sequence of the 3627 bp long 5'-external transcribed spacer (ETS) of a human ribosomal RNA gene. This sequence exhibits only very limited homologies with its mouse counterpart, the only other mammalian specimen analyzed so far. It has very peculiar compositional characteristics, with a highly biased base content (very rich in G + C, very poor in A) and also some very strong dinucleotide preferences. Interestingly, these specific features are shared by the mouse sequence, despite the extensive sequence divergence, and also apply to the other transcribed spacers of mammals indicating that a common and strong structural constraint is exerted on all these regions of the ribosomal gene. An outstanding secondary structure can be formed within the human ETS RNA, which could have a significant role in preribosome assembly.     

A New Cytological Technic, Tannin-Iron Iii, For Nucleoli And Plastids

Tannin-iron Iii, as a technic, differs very little from Salazar's tannin-iron I, and must be considered as a new modification of the latter¹. But the results obtained are very different and its use in plant cytology will be found very advantageous due to its specificity for certain cellular organs.     

Diabetic dyslipidaemia

PURPOSE OF REVIEW: Diabetic dyslipidaemia is a cluster of plasma lipid and lipoprotein abnormalities that are metabolically interrelated. The increase of large type 1 very low density lipoprotein particles in type 2 diabetes initiates a sequence of events that generates atherogenic remnants, small dense low-density lipoprotein and small dense high-density lipoprotein particles. Thus, it is of great importance to elucidate the mechanisms behind the overproduction of large very low density lipoprotein particles in diabetic dyslipidaemia. This review discusses the pathophysiology of very low density lipoprotein metabolism in type 2 diabetes and recent concepts of lipid management of diabetic dyslipidaemia. RECENT FINDINGS: Results indicate that triglyceride and apolipoprotein B production in types 1 and 2 very low density lipoprotein are significantly correlated, suggesting a coupling of the two processes governing the metabolism of these lipoprotein subpopulations. Insulin resistance, hyperglycaemia, and liver fat were associated with excess hepatic production of type 1 but not type 2 very low density lipoprotein particles. These data provide support for the independent regulation of types 1 and 2 very low density lipoprotein apolipoprotein B production. SUMMARY: Recent data suggest that the assembly of very low density lipoprotein is fundamentally altered in type 2 diabetes, explaining the overproduction of large type 1 very low density lipoprotein as well as the inability of insulin to suppress production of type 1 very low density lipoprotein in type 2 diabetes. Future discoveries hopefully will delineate the regulatory steps to allow more targeted treatment of diabetic dyslipidaemia.     

A new model for very low density lipoprotein metabolism—Nomenclature for very low density lipoprotein derivatives

A new model for the catabolism of very low density lipoprotein will be proposed following a brief discussion of the relevant information about its metabolism. This model is based on the assumption that each very low density lipoprotein derivative has a distinct structural feature which determines its biological fate. Since this unique determinant may reside in only a small portion of the particles, such as apoprotein, the different very low density lipoprotein derivatives may possess similar or even identical electrophoretic mobility or hydrated density. For this reason, we propose that very low density lipoprotein derivatives be defined according to their putative position in the metabolic pathways rather than according to their hydrated density or their electrophoretic behavior. Thus it is recommended that biochemical separation methods based on principles other than electrophoretic mobility or hydrated density be used to isolate, purify and define very low density lipoprotein derivatives. The position that a lipoprotein particle occupies in the catabolic pathways should be determined by its ability to interact with liver cells or its ability to become converted to low density lipoprotein. This new nomenclature would eliminate unnecessary confusion and stimulate more research toward elucidating the unique structural feature of each very low density lipoprotein derivative.     

A cytochemical method for measuring enzyme activity in individual preovulatory mouse oocytes

The activities of 6 enzymes involved in carbohydrate metabolism were determined quantitatively in preovulatory oocytes by cytochemical means per individual cell as well as biochemically in cell homogenates. Oocytes were incorporated in a polyacrylamide matrix for appropriate enzyme cytochemical staining. This incorporation preserves the morphology of the cells very well, and the enzymes keep their activity for a considerable period of time. This method could also be used to demonstrate more than one enzyme activity in the same cell. The results obtained by cytochemical means appeared to correlate very well with the biochemical data (P less than 0.005). Glucose 6-phosphate dehydrogenase, the key-enzyme in the pentose phosphate pathway, had very high activity in these preovulatory oocytes, but 6-phosphogluconate dehydrogenase activity was only about 2% of that of glucose 6-phosphate dehydrogenase. The activities of lactate dehydrogenase and to a lesser extent glucose phosphate isomerase and D-glyceraldehyde-3-phosphate dehydrogenase also appeared to be very high, while hexokinase showed a very low activity.     

Characterization of lipoprotein particles isolated from the Golgi apparatus of rat liver

It has been proposed that particles within tubules and vesicles of the Golgi apparatus of liver cells are precursors of very low density lipoproteins in blood plasma. To characterize these particles we isolated a cell fraction rich in Golgi apparatus and associated particles from rat liver in quantities sufficient for analysis. Particles freed from the membranes of the Golgi apparatus and floated at d = 1.006 were studied by chemical analysis, immunodiffusion, and paper electrophoresis. The lipid composition of the Golgi particles was similar to that of very low density lipoproteins from the same rats. The protein content was about 10% of dry weight for both the Golgi particles and plasma very low density lipoproteins. The Golgi particles formed lines of identity with plasma very low density lipoproteins during immunodiffusion against antiserum to plasma very low density lipoproteins. On paper electrophoresis, however, many Golgi particles remained near the origin, with only a few migrating to the pre-beta position. It was concluded that the lipoproteins in the Golgi apparatus are the precursors of plasma very low density lipoproteins.     

The Effects of a Bottleneck on Inbreeding Depression and the Genetic Load

We study the effects of a population bottleneck on the inbreeding depression and genetic load caused by deleterious mutations in an outcrossing population. The calculations assume that loci have multiplicative fitness effects and that linkage disequilibrium is negligible. Inbreeding depression decreases immediately after a sudden reduction of population size, but the drop is at most only several percentage points, even for severe bottlenecks. Highly recessive mutations experience a purging process that causes inbreeding depression to decline for a number of additional generations. On the basis of available parameter estimates, the absolute fall in inbreeding depression may often be only a few percentage points for bottlenecks of 10 or more individuals. With a very high lethal mutation rate and a very slow population growth, however, the decline may be on the order of 25%. We examine when purging might favor a switch from outbreeding to selfing and find it occurs only under very limited conditions unless population growth is very slow. In contrast to inbreeding depression, a bottleneck causes an immediate increase in the genetic load. Purging causes the load to decline and then overshoot its equilibrium value. The changes are typically modest: the absolute increase in the total genetic load will be at most a few percentage points for bottlenecks of size 10 or more unless the lethal mutation rate is very high and the population growth rate very slow.     

Preferences for very low and very high voice pitch in humans

Manipulations of voice pitch have been shown to alter attractiveness ratings, but whether preferences extend to very low or very high voice pitch is unknown. Here, we manipulated voice pitch in averaged men's and women's voices by 2 Hz intervals to create a range of male and female voices speaking monopthong vowel sounds and spanning a range of frequencies from normal to very low and very high pitch. With these voices, we used the method of constant stimuli to measure preferences for voice. Nineteen university students (ages: 20-25) participated in three experiments. On average, men preferred high-pitched women's voices to low-pitched women's voices across all frequencies tested. On average, women preferred men's voices lowered in pitch, but did not prefer very low men's voices. The results of this study may reflect selection pressures for men's and women's voices, and shed light on a perceptual link between voice pitch and vocal attractiveness.     

Effects of Visceral Fat and Weight Loss on Lipoprotein(a) Concentration in Subjects with Obesity

ZAMBONI M, R FACCHINETTI, F ARMELLINI, E TURCATO, IA BERGAMO ANDREIS, O BOSELLO. Effects of visceral fat and weight loss on lipoprotein(a) concentration in subjects with obesity. We studied the relationships between regional body fat distribution and metabolic variables with lipoprotein(a) [Lp(a)] as well as the effects of weight loss on Lp(a) in 25 women and 9 men with obesity. Regional body fat distribution, as evaluated by the use of computed tomography; Lp(a); and fasting glucose, insulin, cholesterol, and triglycerides were analyzed before and after a very low-energy diet. No significant correlations were found between visceral, subcutaneous, and total fat and Lp(a) or between metabolic variables and Lp(a). All anthropometric variables significantly decreased after a very low-energy diet. Fasting glucose, insulin, triglycerides, and cholesterol significantly decreased after a very low-energy diet. No significant changes in Lp(a) concentration after a very low-energy diet were found. The correlation between the initial values of Lp(a) and changes of Lp(a) after a very low-energy diet was slightly significant (ρ=0.33, p<0.06). In conclusion, our study shows that Lp(a) is not influenced by obesity, visceral fat, metabolic variables, or weight loss induced by a very low-energy diet     

Larval case and water balance in Tinea pellionella

In a very dry environment (0% r.h.) the case plays an important role in the physiology of the Tinea pellionella larva. Absence of the case leads to a reduction of oxygen consumption and a great loss of body water. At 0% r.h. the rate of water loss from a larva without its case, is twice that from a larva remaining within its case.In a very humid environment (r.h. higher than 95%) the case absorbs a very large quantity of water and becomes very heavy, but it does not interfere with larval physiology. With or without their cases the weight of the larvae stays stable, and their oxygen consumption does not change.When the humidity changes abruptly, the case acts as a buffer and assists in the regulation of the water balance of the larva. If the humidity decreases the case slows the rate of body water loss; if the humidity increases, it very quickly builds up a reserve of atmospheric water around the larva's body.     

Effects of ageing on bioavailability of selenium in soils assessed by diffusive gradients in thin-films and sequential extraction

Plant and Soil - Santalum acuminatum (quandong) is a root hemi-parasite with a very wide distribution across southern Australia. Despite its very wide distribution, along the Jurien Bay...     

A NEW MIDDLE JURASSIC APHID FAMILY (INSECTA: HEMIPTERA: STERNORRHYNCHA: SINOJURAPHIDIDAE FAM. NOV.) FROM INNER MONGOLIA, CHINA

Abstract:  A new monotypic aphid family, Sinojuraphididae, is described from the Middle Jurassic of China. Its antennae and wing venation have very plesiomorphic structures, even more than in known Triassic taxa (e.g. 12 antennomeres, Cu with a very long stem, very narrow pterostigma), confirming the persistence of ancient, probably Triassic, lineages among Jurassic aphids.     

The role of O-linked sugars in determining the very low density lipoprotein receptor stability or release from the cell.

The very low density lipoprotein receptor is a member of the low density lipoprotein receptor supergene family for which two isoforms have been reported, one lacking and the other containing an O-linked sugar domain. In order to gain insight into their functionality, transient and stable transformants separately overexpressing previously cloned bovine variants were analyzed. We report evidence that the variant lacking the O-linked sugar domain presented a rapid cleavage from the cell and that a large amino-terminal very low density lipoprotein receptor fragment was released into the culture medium. As only minor proteolysis was involved in the other very low density lipoprotein receptor variant, the clustered O-linked sugar domain may be responsible for blocking the access to the protease-sensitive site(s). To test this hypothesis, a mutant Chinese hamster ovary cell line, ldlD, with a reversible defect in the protein O-glycosylation, was used. The instability of the O-linked sugar-deficient very low density lipoprotein receptor on the cell surface was comparable to that induced by the proteolysis of the variant lacking the O-linked sugar domain. Moreover, our data suggest that the O-linked sugar domain may also protect the very low density lipoprotein receptor against unspecific proteolysis. Taken together, these results indicate that the presence of the O-linked sugar domain may be required for the stable expression of the very low density lipoprotein receptor on the cell surface and its absence may be required for release of the receptor to the extracellular space. The exclusive expression of the variant lacking the O-linked sugar domain in the bovine aortic endothelium opens new perspectives in the physiological significance of the very low density lipoprotein receptor.     

Odor similarity does not influence the time needed for odor processing

The brain's link between perception and action involves several steps, which include stimulus transduction, neuronal coding of the stimulus, comparison to a memory template and choice of an appropriate behavioral response. All of these need time, and many studies report that the time needed to compare two stimuli correlates inversely with the perceived distance between them. We developed a behavioral assay in which we tested the time that a honeybee needs to discriminate between odors consisting of mixtures of two components, and included both very similar and very different stimuli spanning four log-concentration ranges. Bees learned to discriminate all odors, including very similar odors and the same odor at different concentrations. Even though discriminating two very similar odors appears to be a more difficult task than discriminating two very distinct substances, we found that the time needed to make a choice for or against an odor was independent of odor similarity. Our data suggest that, irrespective of the nature of the olfactory code, the bee olfactory system evaluates odor quality after a constant interval. This may ensure that odors are only assessed after the olfactory network has optimized its representation.     

A rapid method of sequencing long synthetic peptide sequences by laser power variation in MALDI-ToF, using polyglutamine model peptides

Matrix assisted laser desorption ionization-time of flight (MALDI-ToF) has evolved into a powerful method for structural analysis of biomolecules. The paper reports a very simple and efficient method of sequencing of long peptides using long polyglutamine stretches with and without interruptions as model peptides, using MALDI-ToF in a linear mode. The method does not require any enzymatic or proteolytic digestions and very long synthetic polyglutamine sequences can be sequenced efficiently just by incremental variation of laser power. The data also reveal whenever there is any interruption within a stretch of glutamines it undergoes a very prompt cleavage at that site. Thus, this method provides an alternative tool for validating long polyglutamine stretches which are very often used as models for studying the structure and conformation of proteins associated with a number of neurodegenerative disorders.     

Types of potentials in a mitotic spindle

The dynamics of a mitotic spindle is very important to understand if the functioning of mitosis has to be understood and defined very accurately. There are a number of forces involved in such a process. Despite of the fact that there have been numerous studies done on the functioning of a mitotic spindle, there is still not a very precise understanding of this system and how it behaves. This study aims at understanding and expressing all the possible potentials which might be responsible in a mitotic spindle and its mechanism.     

The length-tension relationship of the dorsal longitudinal muscle of a leech.

The length-tension relationship of a preparation of the dorsal body wall of the leech Haemopis sanguisuga was determined. Passive tension is low except at very long lengths of the preparation, when it rises steeply. It is due mainly to the epidermis present in the preparation. The active tension curve is very flat, with tension being reduced only at very short and very long lengths. This shape is explained in the context of the myofilament arrangement of the muscle fibres. It may be that thin filaments can form cross-bridges with different thick filaments at different lengths of the preparation.     

Hydrogenosomes in known species of rumen entodiniomorphid protozoa

Abstract Yeasts of the genus Kluyveromyces grew very slowly on methylamine as sole nitrogen source. Methylamine oxidase activity in cell-free extracts was very low. Under conditions known to separate methylamine oxidase from benzylamine oxidase in other yeast genera, only a single enzyme was detected in Kluyveromyces lactis . This enzyme could oxidize benzylamine, n -butylamine and (very poorly) methylamine. The enzyme lost no activity on heating at 45°C and had a high affinity and V _max for benzylamine and 1-aminoalkanes of long-chain length, with a very low affinity and V _max for methylamine. It is concluded that growth of K. lactis on methylamine involves only benzylamine oxidase, and that a methylamine oxidase of the type found in other yeasts does not occur.     

A Simple and Gentle Method for Concentrating Protein Solutions

A gentle method for concentrating very dilute protein solutions is described. The high capacity of aminohexylagarose in adsorbing different proteins is utilized to handle small or large amounts of protein with practically no losses in material or activity. To concentrate very dilute protein solutions as they occur during purification procedures e. g. of enzymes, a one-step non-inactivating nethod is needed that may easily be integrated into the purification programm.

In the course of the purification of a labile enzyme (1) we developed a simple chromatographic method which seems to work for a large variety of proteins. The procedure is applicable to very dilute protein solutions, to small samples as well as to large scale preparations, and it is relatively inexpensive. It appears to be a very gentle method since in all cases tested no loss of enzymic activity could be observed.     

Studies of the relationships between Schistosoma and their intermediate hosts. IV. The genus Bulinus and Schistosoma bovis from Morocco

Schistosoma bovis from Morocco was used in infection experiments with several populations of Bulinus truncatus. The snails from Libya, Malawi, Morocco and Senegal were very compatible with the schistosome since the infection rates were approximately 90%, the mortality was low, and a very high production of cercariae, approximately 1.2 million per 100 exposed snails, was observed. Only a very few B. truncatus (2n = 36) from Rhodesia became infected. B. permembranaceus and B. forskalii were refractory.