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PubMedDate not supplied

[Effects of intra-arterial Wenckebach's periods on the nodal and intranodal A-V 2:1 and 4:1 (their significance in the electrogenesis of the so-called alternating Wenckebach's periods)].

Intra-atrial Wenckebach patterns coexisting with distal, A-V nodal, and His-Purkinje blocks occurred in eight patients during high atrial stimulation at rapid rates. In two patients with 2:1 St-H block and in two patients with 4:1 St-V block, an increase in the degree of block occurred when the proximal intraatrial Wenckebach cycle was completed with the stimulus which otherwise would have been propagated to the distal levels. However, the degree of block did not increase when the intraatrial Wenckebach terminated in distally blocked stimuli. In one patient progression of 4:1 into 5:1 St-V block was due to the association of intraatrial Wenckebach with alternating 2:1 block at the A-V nodal, and His-Purkinje levels. Contrasting with most reports dealing with the mechanisms of alternating Wenckebach in a single structure, this study permitted the determination of the boundaries between proximal and more distal levels. The electrophysiology of documented two or three level block in different structures has validated previously made assumptions regarding multilevel block in a single structure.

Bundle-Branch Block↗
PubMed1994

[Deaths among drug addicts in Denmark. A forensic medical study of deaths among drug addicts during the period 1991-1992 related to the period 1984-1985].

This study includes all deaths among drug addicts in the years 1991 (n = 219) and 1992 (n = 214) investigated at the three institutes of forensic medicine in Denmark. The results are compared with deaths among drug addicts in 1984-1985. The number of deaths among drug addicts increased by approximately 50% in 1991-1992 compared with 1984-1985. The increase was most significant among drug addicts over 35 years of age. The cause of death was intoxication in three-quarters of the cases in 1991-1992. In half of these cases heroin/morphine had caused death, while intoxications caused by methadone accounted for approximately 30% of the cases. In the metropolitan area the frequency of methadone intoxications increased significantly compared with 1984-1985, whereas the number of heroin/morphine intoxications did not change. Outside the metropolitan area, however, a significant increase in heroin/morphine intoxications was noticed. In all parts of the country the number of propoxyphene intoxications decreased to a few annual cases. The most commonly used drugs of abuse were heroin/morphine, diazepam and methadone, often in combination with alcohol.

Adolescent↗
PubMed1975

Catch-up growth in rats undernourished for different periods during the suckling period.

Catch-up in body weight, nose-rump length and tail length has been examined in male rats. At birth, pups from several females were pooled and reallocated to provide litters of 16 pups. In group 1, the number was reduced to 8 at day 8, in group 2 on day 15, group 3 were raised in large litters until weaning. Animals reared in litters of 8 were termed controls. All animals were weaned at 22 days, placed two to a cage and provided with food and water ad libitum. They were examined at intervals to day 120. Animals rehabilitated at 8 days had caught up in body weight and 97% of the length of controls on day 120. Rats rehabilitated on day 22 were 88% of the body weight and 97% of the body length of the controls at 120 days. None of the experimental groups achieved the same tail length as the controls. It was concluded that the data do not support the "time tally" mechanism of catch-up growth. This may be due to early timing of the experiment or an oversimplification of the mechanism. It was also concluded that catch-up following neonatal undernutrition in rats is greatly influenced by the normal growth pattern.

Animals↗
PubMed2004

Periodicity of DNA in exons.

BACKGROUND: The periodic pattern of DNA in exons is a known phenomenon. It was suggested that one of the initial causes of periodicity could be the universal (RNY)npattern (R = A or G, Y = C or U, N = any base) of ancient RNA. Two major questions were addressed in this paper. Firstly, the cause of DNA periodicity, which was investigated by comparisons between real and simulated coding sequences. Secondly, quantification of DNA periodicity was made using an evolutionary algorithm, which was not previously used for such purposes. RESULTS: We have shown that simulated coding sequences, which were composed using codon usage frequencies only, demonstrate DNA periodicity very similar to the observed in real exons. It was also found that DNA periodicity disappears in the simulated sequences, when the frequencies of codons become equal. Frequencies of the nucleotides (and the dinucleotide AG) at each location along phase 0 exons were calculated for C. elegans, D. melanogaster and H. sapiens. Two models were used to fit these data, with the key objective of describing periodicity. Both of the models showed that the best-fit curves closely matched the actual data points. The first dynamic period determination model consistently generated a value, which was very close to the period equal to 3 nucleotides. The second fixed period model, as expected, kept the period exactly equal to 3 and did not detract from its goodness of fit. CONCLUSIONS: Conclusion can be drawn that DNA periodicity in exons is determined by codon usage frequencies. It is essential to differentiate between DNA periodicity itself, and the length of the period equal to 3. Periodicity itself is a result of certain combinations of codons with different frequencies typical for a species. The length of period equal to 3, instead, is caused by the triplet nature of genetic code. The models and evolutionary algorithm used for characterising DNA periodicity are proven to be an effective tool for describing the periodicity pattern in a species, when a number of exons in the same phase are analysed.

Algorithms↗
PubMed1995

Potentiating and inhibitory effects of periodate-oxidized ATP analogs on contractions of vas deferens to ATP.

Previous studies have shown that treatment of guinea-pig isolated vas deferens with the affinity label periodate-oxidized ATP (2',3'-dialdehyde ATP), results in two irreversible effects on biphasic contractile responses to ATP, i.e., potentiation of the P2X purinoceptor-mediated first phase and inhibition of the ecto-kinase-mediated second phase. The present experiments were designed to evaluate whether periodate-oxidized ADP, periodate-oxidized AMP, and periodate-oxidized adenosine, produce similar effects. Periodate-oxidized ATP and periodate-oxidized ADP (10(-2) M) elicited contraction of the vas deferens (periodate-oxidized ATP > periodate-oxidized ADP; periodate-oxidized AMP and periodate-oxidized adenosine had no agonist activity. After incubation of the preparations for 5 min with 10(-2) M periodate-oxidized ATP, periodate-oxidized ADP, periodate-oxidized AMP or periodate-oxidized adenosine, the first phase of contraction to submaximal ATP concentrations was potentiated. Simultaneously, periodate-oxidized ATP, periodate-oxidized ADP and periodate-oxidized AMP inhibited the second contractile phase, whereas periodate-oxidized adenosine did not. The results indicate that the requirement for 5'-phosphate to produce potentiation and inhibition is different: 5'-phosphate is not needed to potentiate the first phase of contraction to ATP, but at least one 5'-phosphate is required to inhibit the second phase of contraction.

Adenosine Diphosphate↗
PubMed2004

What have we learned from surgical treatment of gastric adenocarcinoma? A comparison of two periods.

In January 1992, a standardized and more radical surgical approach in gastric cancer treatment and a standardized pathohistological workup of specimens was introduced at our institution. The aim of our retrospectively designed study was to compare the results of two consecutive groups of altogether 348 patients who underwent a total or subtotal gastrectomy for gastric cancer (period A: 162 patients operated between 1992 and 1996; period B: 186 patients operated between 1997 and 2000). The two groups of patients were comparable in age, sex, their general condition, and the proportion of potentially curable (R0) resections. There was a significant difference between the groups with regard to tumor site (fewer distal and more proximal stomach tumors in period B), type of operation (more total gastrectomies in period B), extent of lymphadenectomy (more D2 and D3 in period B), average number of affected lymph nodes (higher in period B), average number of examined nodes (higher in period B), and in UICC stage (less stage II in period B). UICC classification was impossible in 19 patients overall, but there were fewer non-classified patients in period B. The incidence of surgical complications (15.6% vs. 18.7%) and average hospital stay (14.72 days vs. 14.70 days) was not significantly different in the two groups. The drop in overall mortality rate (potentially curable and non-curable resections) in period B almost reached statistical significance (period A: 8%, period B: 6.5%; p = 0.57). The 5-year survival for all R0 resected patients (279) in 9 years was 31%. The median survival was significantly longer in period B (941 days) than in period A (570 days) for R0 and non-curable (R2) resections together (p=0.0132) as well as for R0 resections alone (period A: 844 days, period B: 1176 days; p = 0.0127). Comparison of the two consecutive groups of patients shows that after a defined period of systematic surgical work our results improved, reflected in the higher number of extracted lymph nodes, the higher number of total gastrectomies, and the longer median survival in the second period.

Adenocarcinoma↗
PubMed2004

Effect of training location and time period on racehorse performance in New Zealand. 1. Descriptive analysis.

AIM: To describe characteristics of Thoroughbred training stables in Matamata and in all other locations in New Zealand combined, over two 19-month time periods in 1996-1997 and 1998-1999, representing equal length periods immediately prior to and after the construction of a new training surface at the Matamata Racing Club. METHODS: Retrospective records covering all horses training and racing in New Zealand during two 19-month time periods (1996-1997 and 1998-1999), covering 161 locations, were obtained from New Zealand Thoroughbred Racing (NZTR). Outcome variables included whether a horse was raced again in the 6 months following any start in the first 13 months of either time period, number of race starts for every horse, and finishing position. Summary measures with confidence intervals (CI) and unadjusted odds ratios (OR), measuring strength of associations for various factors, were computed. RESULTS: The datasets contained information on 45,446 horses, 11,336 races, 5,110 trials and a total of 110,643 race starts. Horses trained at Matamata represented 8% (3,715) of the total horse datasets, and accounted for 11,977 race starts (10.8%). They were more likely to start in a race or trial in either time period and were 1.4 and 1.3 times as likely to finish first, second or third compared with horses trained at other locations in 1996-1997 and 1998-1999, respectively. A 6-month no-race period occurred for 9,306/12,584 (74%) horses that started at least once in the first 13 months of either time period. Horses trained at Matamata were less likely to have a 6-month no-race period than horses trained at other locations in both time periods. There was no effect of time period within each location on the probability of either a horse having a 6-month no-race period or of a race start being followed by a 6-month no-race period, but there was an overall effect of time and more 6-month no-race periods were observed in 1998-1999 relative to 1996-1997. CONCLUSION: Summary statistics are presented for Thoroughbred racing in New Zealand over two 19-month time periods. Differences between the populations of horses trained in Matamata compared with those trained at other locations were attributed, in part, to the fact that many of the more successful racehorse trainers in the country have stables at Matamata. As a result, the population of horses in Matamata may not be representative of the racehorse population in New Zealand. Although more likely to win or place in both time periods, the magnitude of the advantage to horses in Matamata was reduced in 1998-1999 relative to 1996-1997, and this could be due, in part, to effects of the new track surface at Matamata. There was no evidence of a rise in risk of a 6-month no-race period following any race start in those horses trained in Matamata in 1998-1999 relative to either horses trained at other locations or to horses trained in Matamata during the earlier time period.

Journal Article↗
PubMed1999

The periodicity of lateralized epileptiform discharges.

OBJECTIVES: Although the term periodic lateralized epileptiform discharges (PLEDs) was introduced in 1964, there has been little discussion about the definition of periodicity, whether the degree of periodicity has clinical significance, and whether electroencephalographers can accurately assess periodicity. The objectives of this study were to determine if a mathematical descriptor of periodicity could analyse PLEDs and whether such has clinical relevance, to correlate the degree of periodicity with underlying etiology and to assess the accuracy of sight recognition of periodically occurring EEG events. METHODS: A 6 year retrospective analysis of EEGs on patients with PLEDs was undertaken. The coefficient of variation of inter-complex intervals was calculated for all records. The relative periodicity of each record was rated by electroencephalographers. Corresponding hospital records were reviewed with regard to clinical and pathological information. RESULTS: In cases of acute viral encephalitis, discharges were more periodic than in other etiologies (P = 0.013). Age, clinical state, and time of last seizure did not influence periodicity but 40 (70%) of 57 recordings with PLEDs were done within 2 days of a seizure. A history of seizures was present in 42 (89%) of 47 patients. Electroencephalographers' assessment of periodicity correlated well with measured periodicity (r = -0.49, P = 0.0001). However, EEGers were more likely to assess records as periodic if: discharges occurred frequently (r = -0.48, P = 0.0001), or the complexes were visually assessed to have a uniform morphology (r = 0.31, P = 0.02), even though neither of these factors influenced the periodicity of discharges. CONCLUSIONS: PLEDs were objectively measured to be more periodic when they were associated with acute viral encephalitis than with other etiologies. Nonetheless, the considerable overlap of values among the several presenting disorders diminished specificity. Electroencephalographers were able to recognize periodically occurring discharges. However, they were strongly influenced by discharge frequency and their perception of the uniformity of discharge morphology.

Adolescent↗
PubMed1996

Inclusion of supine period in short-duration pH monitoring is essential in diagnosis of gastroesophageal reflux disease.

Prolonged esophageal pH monitoring is the most accurate method for detecting abnormal gastroesophageal reflux (GER) in patients with gastroesophageal reflux disease (GERD). However, some investigators have found that short-duration postprandial pH monitoring in the upright position is also useful, while others have failed to find such results. Therefore, we have compared a 6-hr period of pH monitoring (3-hr postprandial period after daytime meal and 3-hr supine period) with a total 24-hr period in detecting abnormal gastroesophageal reflux. Sixty-five patients (44 men, mean age 41.3 years) with GERD and 16 healthy volunteers (11 men, mean age 34.3 years) underwent 24-hr pH monitoring according to a standard protocol. Various reflux parameters during 24-hr pH monitoring were compared with reflux parameters during the 6-hr period. Abnormal GER was detected in 56 patients presenting with typical symptoms of GERD (sensitivity 86.2%). These patients could be further divided into upright (N = 18), supine (N = 15), and combined (N = 23) refluxers, depending on the posture in which abnormal reflux occurred. Esophageal pH monitoring during the 3-hr postprandial upright period showed abnormal reflux in only 35 patients (sensitivity 53.8%; P < 0.00005, compared with the 24-hr pH monitoring period). Abnormal GER was identified in 13 of 18 upright, 19 of 23 combined, and only one of 15 supine refluxers, as well as in two of nine patients with normal 24-hr pH-metry. However, inclusion of the 3-hr supine monitoring period in the 3-hr postprandial upright period improved detection of abnormal GER to 78.5% (51 patients; P = NS compared with 24-hr pH monitoring period). This was related mainly to improved detection of abnormal GER in supine refluxers (11 of 15; 73.3%). Esophageal acid exposure time correlated significantly with severity of esophagitis only during the total and supine periods of both the 24- and 6-hr periods and not during the upright period. Esophageal acid clearance correlated significantly with increasing grades of esophagitis for the supine and total periods only. We conclude that 3-hr postprandial pH monitoring, as has been conventionally practiced, is not appropriate in the detection of abnormal GER; inclusion of a supine period in the short-duration pH monitoring schedule increases the detection of pathological reflux. We therefore recommend that a supine period should be included in short-duration pH monitoring schedules. We also found that supine reflex was the most important factor in the development of esophagitis.

Adult↗
PubMed2005

Phylogenetic differences in content and intensity of periodic proteins.

Many proteins exhibit sequence periodicity, often correlated with a visible structural periodicity. The statistical significance of such periodicity can be assessed by means of a chi-squared-based test, with significance thresholds being calculated from shuffled sequences. Comparison of the complete proteomes of 45 species reveals striking differences in the proportion of periodic proteins and the intensity of the most significant periodicities. Eukaryotes tend to have a higher proportion of periodic proteins than eubacteria, which in turn tend to have more than archaea. The intensity of periodicity in the most periodic proteins is also greatest in eukaryotes. By contrast, the relatively small group of periodic proteins in archaea also tend to be weakly periodic compared to those of eukaryotes and eubacteria. Exceptions to this general rule are found in those prokaryotes with multicellular life-cycle phases, e.g., Methanosarcina sp., or Anabaena sp., which have more periodicities than prokaryotes in general, and in unicellular eukaryotes, which have fewer than multicellular eukaryotes. The distribution of significantly periodic proteins in eukaryotes is over a wide range of period lengths, whereas prokaryotic proteins typically have a more limited set of period lengths. This is further investigated by repeating the analysis on the NRL-3D database of proteins of solved structure. Some short-range periodicities are explicable in terms of basic secondary structure, e.g., alpha helices, while middle-range periodicities are frequently found to consist of known short Pfam domains, e.g., leucine-rich repeats, tetratricopeptides or armadillo domains. However, not all can be explained in this way.

Phylogeny↗