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PubMed1986

Surnames in Sardinia. III. The spatial distribution of surnames for testing neutrality of genes.

1. A study on heterogeneity of males' surnames over time and space in the island of Sardinia was carried out using data from consanguineous marriages (1800-1970) and telephone directories (1978). 2. Variation of frequency of surnames over time is barely significant and 10 times lower than that over space, which is very highly significant. 3. For sufficiently frequent surnames the estimate of the Wahlund variance, calculated from chi 2 for heterogeneity in space, is independent of the frequency of a surname: this supplies evidence of neutrality in line with that obtained from the frequency distribution of surnames. 4. The Wahlund variance, W (also called FST), decreases regularly as the average size of the area considered (number of individuals per area, N) increases. The estimate of the parameter beta in the relation W = KN beta could be of interest for the study of population structure. 5. A correction factor of 1/4 must be made on the surnames' variance in consideration of their haploid unisexual transmission. 6. It is suggested that surnames could provide a baseline for estimating the value of Wahlund variance under random genetic drift and hence evaluating whether a gene behaves as selectively neutral. 7. The distribution of the Wahlund variances obtained from two sets of gene frequency data as compared with that obtained in comparable conditions for surnames in the same areas seems to show that most genes behave as neutral, with the exception of a few, with high W values, which presumably have been under different selection pressures in the area examined.

Consanguinity↗
PubMed1999

Spatial distribution of external and internal intercostal activity in dogs.

1. The observation that the external and internal interosseous intercostal muscles in the dog show marked regional differences in mechanical advantage has prompted us to re-examine the topographic distribution of electrical activity among these muscles during spontaneous breathing. 2. Inspiratory activity was recorded only from the areas of the external intercostals with an inspiratory mechanical advantage, and expiratory activity was recorded only from the areas of the internal intercostals with an expiratory mechanical advantage. The expiratory discharges previously recorded from the caudal external intercostals and the inspiratory discharges recorded from the rostral internal intercostals were probably due to cross-contamination. 3. Activity in each muscle area was also quantified relative to the activity measured during tetanic, supramaximal nerve stimulation (maximal activity). External intercostal inspiratory activity was consistently greater in the areas with a greater inspiratory advantage (i.e. the dorsal aspect of the rostral segments) than in the areas with a smaller inspiratory advantage, and internal intercostal expiratory activity was invariably greatest in the areas with the greatest expiratory advantage (i.e. the dorsal aspect of the caudal segments). 4. This topographic distribution of neural drive confers to the external intercostal muscles an inspiratory action on the lung during breathing and to the internal interosseous intercostals an expiratory action.

Animals↗
PubMed2000

Spatial distribution and frequency dependence of arrhythmogenic vagal effects in canine atria.

INTRODUCTION: Prior studies in isolated canine atria demonstrated that acetylcholine-induced reentrant atrial fibrillation (AF) was triggered by multifocal activity in the area of normal impulse origin (sinus node-crista terminalis). The aim of this study was to investigate the activation sequence in AF induced by vagal stimulation (VS) in intact dog hearts. METHODS AND RESULTS: VS (10 to 50 Hz, 1 msec, 15 V, 5-sec trains) induced single or multiple atrial premature depolarizations (APDs), and/or AF in 8 of 10 open chest dogs. Occurrence of APDs and AF increased with increasing VS intensity. Epicardial mapping (254 unipolar electrodes) of both atria showed that APDs as a rule emerged from ectopic sites, often from the right atrial appendage. Activation mapping of the first 10 cycles of AF showed that only a small number (<3 to 4) of unstable reentrant circuits were possible at the same moment. Moreover, most sustained VS-induced AFs were accounted for by a single leading stable reentrant circuit that activated the remainder of the atria. CONCLUSION: (1) Occurrence of vagally induced APDs and AF increases with increasing frequency of VS. (2) VS-induced focal ectopic APDs are widely distributed over the atria. (3) A single APD can be sufficient for initiation of reentrant AF. (4) Despite its high rate of sustained AF, it may be maintained by single stable reentrant circuit. (5) The atrial septum can play an important role in both the initiation and the maintenance of VS-induced AF.

Animals↗
PubMed2006

Spatial distribution of sponge-associated bacteria in the Mediterranean sponge Tethya aurantium.

The local distribution of the bacterial community associated with the marine sponge Tethya aurantium Pallas 1766 was studied. Distinct bacterial communities were found to inhabit the endosome and cortex. Clear differences in the associated bacterial populations were demonstrated by denaturing gradient gel electrophoresis (DGGE) and analysis of 16S rRNA gene clone libraries. Specifically associated phylotypes were identified for both regions: a new phylotype of Flexibacteria was recovered only from the sponge cortex, while Synechococcus species were present mainly in the sponge endosome. Light conduction via radiate spicule bundles conceivably facilitates the unusual association of Cyanobacteria with the sponge endosome. Furthermore, a new monophyletic cluster of sponge-derived 16S rRNA gene sequences related to the Betaproteobacteria was identified using analysis of 16S rRNA gene clone libraries. Members of this cluster were specifically associated with both cortex and endosome of T. aurantium.

Animals↗
PubMed1995

Type VI collagen gene expression in experimental liver fibrosis: quantitation and spatial distribution of mRNAs, and immunodetection of the protein.

Type VI collagen is a minor but essential matrix component in the liver. In this study, we utilized an acute and a chronic injury model to clarify the process of liver fibrosis in rats by administration of carbon tetrachloride. Collagen gene expression, with particular emphasis on type VI collagen, was studied by molecular hybridization techniques. The alpha 2(VI) collagen mRNA levels were markedly elevated on day 3 of acute injury and were approximately at the same high level at 7 and 14 weeks of chronic injury, as determined by Northern hybridizations and slot-blot analyses. Marked enhancement of type I collagen gene expression was similarly noted at these time points. The activation of collagen gene expression in acute injury, as determined by in situ hybridization, was particularly prominent in the vicinity of the central veins. Indirect immunofluorescence demonstrated marked accumulation of type VI collagen protein as early as day 3 of acute injury, and the reaction appeared to be initiated in the proximity of central veins. These results indicate that type VI collagen gene expression, together with other connective tissue components, including type I collagen, is activated in the early stages of the fibrotic process. Type VI collagen accumulation may contribute to the distorted architecture and functional impairment of the liver in hepatic fibrosis.

Acute Disease↗
PubMedDate not supplied

A statistical estimator of the spatial distribution of the water-table altitude.

An algorithm was designed to statistically estimate the areal distribution of water-table altitude. The altitude of the water table was bounded below by the minimum water-table surface and above by the land surface. Using lake elevations and stream stages, and interpolating between lakes and streams, the minimum water-table surface was generated. A multiple linear regression among the minimum water-table altitude, the differerence between land-surface and minimum water-table altitudes, and the water-level measurements from surficial aquifier system wells resulted in a consistently high correlation for all groups of physiographic regions in Florida. A simple linear regression between land-surface and water-level measurements resulted in a root-mean-square residual of 4.23 m, with residuals ranging from -8.78 to 41.54 m. A simple linear regression between the minimum water table and the water-level measurements resulted in a root-mean-square residual of 1.45 m, with residuals ranging from -7.39 to 4.10 m. The application of the multiple linear regression presented herein resulted in a root-mean-square residual of 1.05 m, with residuals ranging from -5.24 to 5.63 m. Results from complete and partial F tests rejected the hypothesis of eliminating any of the regressors in the multiple linear regression presented in this study.

Algorithms↗
PubMedDate not supplied

The influence of well hydraulics on the spatial distribution of well incrustations.

In many cases, the operation of wells is hampered by the formation of mineral incrustations. From field studies, it is known that the distribution of incrustations in wells is quite inhomogeneous. Flow models were calculated to assess the hydraulic background of this phenomenon. For horizontal flow, the screen section facing the natural flow direction receives the majority of the total inflow. This phenomenon increases with increasing natural gradients of flow. The vertical distribution of water intake is also quite inhomogeneous. In partially penetrating wells, the uppermost part of the screen receives much more inflow than the deeper screen sections. These flow inhomogenities involve elevated flow velocities and may cause increased influx of shallow, oxygenated water, all conditions favorable for incrustation growth. Field investigations on incrusting wells clearly show that the identified screen areas of elevated flow are indeed much more prone to incrustation deposition. Such sections require more attention during rehabilitations. A suction flow control device can help to homogenize the inflow but can cause elevated entrance loss when affected by incrustation buildup itself.

Computer Simulation↗
PubMed1978

The spatial distribution of odour induced potentials in the olfactory bulb of char and trout (Salmonidae).

Monopolar DC-recordings were made of the gross responses from the olfactory bulb of char (Salvelinus alpinus syn. Salmo alpinsus L.) and trout (Salmo trutta L.) during stimulation with different odours. The response features studied were: the magnitude and polarity of the slow potential shift, the amplitude of the induced waves and their asymmetrical waveform. Amino acids elicited the largest responses in the lateral part of the bulb. Water containing "crude fish odour" caused the largest response in the rostral and medial parts. The results demonstrate odour specific differences in the localization of the bulb responses and the separate origin of the slow potential and the induced waves.

Amino Acids↗