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PubMed1977

An analysis of Wenkebach periodicity during atrial pacing.

Seventy-six atrial pacing induced Wenckebach periods in 20 patients were analyzed. They were divided into 5 types according to the manner of increment change of P'V prolongation. Fifty-four % of the periods were atypical (Types II-V). There was a significant increase in the incidence of atypical periods as the length of the periods increased. The recovery curve of the A-V node was obtained by plotting P'V against preceding VP'. The curve was convex and the slope became greater than 45 degrees near the absolute refractory period in the majority of the cases, although there was 1 case in which the slope was less than 45 degrees throughout the curve. The P'V interval was found to be determined mainly by the preceding VP' interval. The mechanism by which these different types of Wenckebach periods develop can be explained by the relationship between the shape of the recovery curve and the pacing rate. The types II, III, and IV periods which have been dealt with as atypical periods were understood to develop by the same mechanism as type I (typical) periods.

Adult↗

PubMed1975

Control of proliferation in mitogen responsive human peripheral blood lymphocytes: restimulation of cells stimulated by sodium periodate.

Human peripheral blood lymphocytes are stimulated to a greater extent by sodium periodate when cells are incubated in medium containing human serum than when incubated in medium with fetal calf serum. NaIO4 STIMULATION CAN BE REVERSED BY TREATMENT WITH SODIUM BOROHYDRIDE BUT CELLS ALREADY COMMITTED TO DIVISION ARE NOT AFFECTED BY BOROHYDRATE TREATMENT. Maximal commitment to DNA synthesis of a NaIO4 oxidized cell suspens-on occurs after about 28 hr of incubation in medium. The committal time after periodate stimulation is identical to that after stimulation with concanavalin A. Cells treated with periodate and then reduced with borohydride immediately after oxidation are refractory to further per-odate stimulation. Cells stimulated with periodate and then incubated for 6 hr before treatment with borohydride can be restimulated with periodate, indicating a turnover of membrane sites in the 6 hr period. Periodate-stimulated cells divide only once in response to the stimulation. The progeny of cells which were stimulated with periodate can be restimulated by treatment with either periodate or concanavalin A.

Animals↗

PubMed1977

Citation characteristics of periodical literature in veterinary science.

The usage of periodical literature in veterinary science was measured by means of citation analysis. Eighty-two percent of the citations in the source of this study, Advances in Veterinary Science and Comparative Medicine (1970-1974), were from periodicals, and 70 of the 743 periodical titles cited (9.4%) contributed 66% of the total periodical citations. Periodical literature cited in the source of the study appeared to have a half-life of 6.1 years, and to double its size approximately every 20 years. The aging patterns of the periodical literature seemed to vary with the publishing age of the periodical, i.e., the literature in the periodicals which have been in publication for more than 40 years showed a more gradual aging pattern than did that in the newer periodicals.

Periodicals as Topic↗

PubMed1978

The changing trends of uterine cancer and cytology: a study of morbidity and mortality trends over a twenty year period.

Data on squamous carcinoma of the cervix from a 20 year study period (1955 to 1974) in metropolitan Toledo revealed a 66% reduction of the average annual age-adjusted incidence rate and a 61% reduction in death rate of cervical squamous carcinoma when the first time period (1955 to 1958) was compared with the last time period (1971 to 1974). The decrease for both morbidity and mortality rates was more pronounced in women age 50 years and younger. The age-adjusted death rate during this study period revealed 15.5/100,000 for black women and 8.7/100,000 for white women. The reduction in death rate of 83% in black women is more prominent than 54.5% in white women. The decrease in both morbidity and mortality for cervical squamous carcinoma has a close relation to cytologic screening activity. The factors of age and race, probably related to socioeconomic status, are two known determinants of risk for cervical squamous carcinoma. Data for endometrial carcinoma during this study period revealed 15.5/100,000 women in the average age-adjusted incidence and an increase of 13.8% in average yearly rates when the first time period (1955 to 1958) were compared with the last time period (1971 to 1974). The peak age was 60 to 64 years old in the first time period and shifted to 70 to 74 years old in the last time period. The trend in metropolitan Toledo is comparable to that of Louisville, Kentucky. The mass cytologic screening program which contributed to a remarkable reduction in morbidity and mortality for the cervical squamous carcinoma, did not have any beneficial effect on endometrial carcinoma.

Adult↗

PubMed1977

Oxidation of tissue polysaccharides by periodic acid in dimethyl sulfoxide and its anhydrous and aqueous mixtures.

Periodic acid (1% w/v) solvated by anhydrous dimethyl sulfoxide (DMSO) readily induced a strong Schiff reaction in a variety of structures containing polysaccharides, but not glycogen. With the increasing amounts of water added to DMSO, glycogen was also oxidized, while the selective localization of other polysaccharides remained unimpaired. Periodate, solvated in the anhydrous acetic acid-DMSO mixture, rapidly induced concomitant oxidation of nucin and glycogen-containing structures. Sodium bisulfite addition derivatives of carbonyls, induced by periodate oxidation in DMSO, were stained meta- and orthochromatically with toluidine blue at controlled pH. Certain metachromatic tissue components were strongly birefringent in polarized light in contrast to the identical structures oxidized by aqueous periodate. Marked differences in staining reactions elicited in identical structures by periodate in DMSO as compared with aqueous periodate suggest that DMSO-periodate method considerably enhances the range of histochemical oxidations by periodate.

Animals↗

PubMed1976

Nerve fibre velocity and refractory period distributions in nerve trunks.

With the use of a double stimulus technique, nerve fibre velocity range measurements were performed over a single conduction distance in 13 normal subjects and over two conduction distances in another 12 normal subjects. The velocity ranges were found to be dependent upon the conduction distance, owing to unknown refractory period delays. Refractory period values were calculated for the 12 subjects and also direct refractory period distribution measurements were made on 15 normal subjects using a twin stimulus and automatic subtraction technique. Corrections to the velocity range measurements were made upon differing assumptions as to the correlation between refractory period and fibre conduction velocity. It was concluded that a single median value refractory period obtained from the distribution was the best correction to use, based upon the hypothesis that for group A fibres the random scatter of refractory period values is far greater than any variation due to a correlation between refractory period and fibre conduction velocity. It was found important to recognize that calculated values of velocity range are a function not only of the spread of fibre conduction velocities but also of refractory periods.

Adult↗

PubMed1979

Restoration of corticosteroid periodicity in obese rats by limited a.m. food access.

Absence of circadian periodicity of plasma corticosteroid levels has previously been reported to occur in animals maintained under constant light and in animals with suprachiasmatic nuclear lesions. Such animals also exhibit aperiodic rather than normal nocturnal eating. Restricted a.m. access to food (09.30--11.30 h) in such animals results in appearance of circadian corticosteroid periodicity (peak at 08.00 h) similar to that seen in normal animals on a similar food restriction regimen. The present study investigated the nature of adrenal circadian periodicity in obese rats who are reported to exhibit aperiodic feeding. Such aperiodic feeding occurred in obese male, but not in obese female, animals. These obese male animals manifested absent corticosteroid circadian periodicity. Restricted a.m. access to food was associated with the appearance of such periodicity similar to that described above in the two other experimental situations. These studies indicate differences in eating behavior and corticosteroid periodicity between obese male and obese female rats. They provide additional confirmation, in animals under normal light--dark conditions and in the absence of CNS lesions, of the role of periodic feeding in the generation of adrenal circadian periodicity.

Adrenal Cortex Hormones↗

PubMed1977

Heavy water as a tool for study of the forces that control length of period of the 24-hour clock of the hamster.

In alternating 12-hr periods of light and darkness, start of the dark period entrains the hamster's 24-hr clock. Blinding or constant darkness frees the clock of entrainment by allowing it to run faster or slower than 24 hr. Constant light frees the clock from entrainment and permits it to run slower than 24 hr--that is, lengthening its period. Heavy water given in drinking water linearly lengthens the period of the 24-hr clock of blinded hamsters or of hamsters kept in constant darkness in direct proportion to concentration of heavy water (1--50%). Heavy water (1-35%) has very different effects on length of the periods of the 24-hr clock when given under conditions of alternating 12-hr periods of light and darkness. Under these conditions, length of the period is controlled by three factors: (i) heavy water which slows the 24-hr clock; (ii) constant light which also slows the 24-hr clock; (iii) the counteracting effects of entrainment. It is thus possible to observe the effects of all three forces simultaneously in the same animal. The clock slowed by heavy water (1--20%) showed a strong tendency to return to a 24-hr entrainment whenever possible. On a 50% concentration of heavy water, the length of period of the clock became markedly lengthened but very constant and apparently independent of all external and internal disturbances.

Animals↗

PubMed1976

[Protein utilization in calves during different periods of liquid feed fattening].

2 groups of male calves (Braunvieh) each comprising 5 animals with liveweights, at the day of slaughtering, of 58 kg, 99 kg and 155 kg were used in a trial that was carried out to obtain data on the utilization of dry matter, crude protein, crude fat and ash in the bipartite feeding of calves. The nutrient content of the animals was determined by total body analysis. The following values for nutrient retention were obtained in comparative slaughtering trials by using differentiation techniques. No significant differences between the two fattening periods were observed concerning the utilization of total dry matter in the milk substitutes. About 24% of the dietary dry matter were retained. The mean value for the utilization of dietary fat during the whole period of fattening was found to be about 55% provided, the fat was not used as energy source to meet maintenance requirements. 49% of the milk proteins were utilized for both retention and maintenance in the first period of fattening and 55% during the second period. Differences between the two periods showed no consistent trend. In view of the fact that for all animals used in the trial digestibility was taken to be 95% the utilization coefficients for the digested crude protein were higher by about 3% compared with the figures for crude protein. After subtraction of maintenance needs it was found that, on an average, 63% of the residual amount of digested protein available over the whole fattening period were retained in the body. 55% to 57% of the retained protein were deposited in those parts of the body of the animals that are used for human nutrition. It is for this reason that in the first half of the fattening period only 29.8% of the ingested dietary proteins were retained in the edible cuts of the animal body, as compared with 30.4% during the second half of the fattening period.

Animal Feed↗

PubMed2026

Distinct YY dinucleotide periodicity in adeno-associated virus DNA.

Dinucleotide periodicity is a hallmark of genome organization, yet its role in single-stranded (ss)DNA viruses remains poorly understood. Here, we systematically analyzed dinucleotide spacing patterns in adeno-associated virus (AAV) genomes and other viruses. Across 13 primate AAV serotypes, we identified a pronounced and highly conserved ∼15-bp periodicity specific to pyrimidine-pyrimidine (YY) dinucleotides and their reverse complements (RR). Comparative analyses across >25,000 viral sequences demonstrate that this 15-bp YY/RR periodicity is unique to the genus Dependoparvovirus and absent from other ssDNA viruses, satellite viruses, and helper viruses, which predominantly exhibit canonical ∼10- to 11-bp periodicities. Upon disruption of the YY/RR pattern using DNA family shuffling of AAV capsid genes, and subsequent iterative selection for viral production or cell entry, we found that the pattern is under positive selection. Selected sequences display increased periodicity alongside reduced sequence diversity, supporting a functional role for this genomic feature. Finally, engineered recombinant AAV genomes containing YY periodic motifs exhibit enhanced production and, for some designs, improved transduction efficiency, demonstrating that YY periodicity can modulate viral replication and infectivity. Our findings uncover a unique DNA-encoded signal in dependoparvoviruses that contributes to AAV fitness, expands our knowledge of virus biology, and has implications for vector engineering.

Dependovirus↗

PubMed1978

Effects of heart rate and isoproterenol on the functional refractory period of the AV node.

The effects of heart rate and l-isoproterenol on the functional refractory period (FRP) of the atrioventricular (AV) node were analyzed in anesthetized dog. A rectangular hyperbola was adopted to express the relationship between the AV conduction time of the premature beats and the atrial coupling intervals. FRP was shown to be expressed as FRP = E + 2 square root of C - C/(T - E). Thus, it is a function of the effective refractory period (E), basic cycle length (T), and C, a constant. A decrease in the basic cycle length caused a decrease in the effective refractory period as well as FRP; the minimum conduction time remained unchanged. As expected from the above equation, relationship of FRP to the basic cycle length was curvilinear. The above equation also indicates that changes in FRP produced by a change in the basic cycle length were to be ascribed to the change in the AV conduction time of the basic beats. Therefore, FRP under this condition cannot be equated with the refractory period in its true sense. In the paced hearts, l-isoproterenol hydrochloride caused a decrease in the effective refractory period, FRP, C and the minimum conduction time, and the changes in FRP were shown to be correlated with the changes in the effective refractory period, indicating that the change in FRP attained in a given fixed cycle length may be due to a change in the effective refractory period.

Animals↗

PubMed1978

Periodically interspersed repetitive sequences may govern higher-order DNA coiling in chromatin and chromosomes.

The interspersed periodic arrangement of repetitive and unique sequences in eukaryotic DNAs is proposed as the underlying molecular basis for higher-order DNA coiling in chromatin and mitotic chromosomes. It is assumed that (i) two types of interspersed repetitive sequences are distributed strictly periodically throughout the genome, splitting the single copy DNA into short and long periods respectively in such a pattern that each long period is composed of a definite number of short periods and repeats, (ii) the short and long periods make the turn lengths of the solenoid and supersolenoid structures respectively determining their diameters; (iii) specific proteins interact with each type of repeats making cross ties between nearby repeats of each class helping to form, constrain, and stabilize the solenoid and the supersolenoid structures: (iv) the long period may be equated with the basic chromomere unit. The model predicts: (i) splitting of contiguous genes by inserted repetitive sequences; and (ii) two types of genomes differing in the hierarchy of DNA coiling.

Animals↗

PubMed1979

A critical period in the development of tectal neurons in the chick, as revealed by early enucleation.

To further study the existence of a critical trophic period in the development of the chick optic tectum, during which the presence of retinal synapses is essential to the continued growth of tectal neurons, we have unilaterally enucleated embryos between stages 14--20 and allowed survival until stages 35--43. If the critical trophic period is between stages 40--44, as previously reported, then we reasoned that early removal of the eye might not have any effect on tectal development until the critical period. We assessed tectal neuron survival by staining for degeneration in the efferent projections of tectal neurons. In early enucleates, degeneration was present from stages 37--43, and the severity of the degeneration was much reduced in comparison to animals enucleated during the critical period. These findings substantiate the proposition that there is a critical period late in chick tectal development. However, because the degeneration in tectal projections is less intense than in animals enucleated during the critical period, we suggest that the early enucleation has permitted axons from the remaining eye to be routed to the deafferented tectum, where they may help to sustain a portion of the tectal neurons through the critical period. Moreover, the somewhat earlier appearance of degeneration in tectal efferent pathways of early enucleates suggests that a subtle trophic relationship between retina and tectum may exist prior to stage 40, even though this relationship is not revealed when enucleations are performed later, as between stages 35--40 (ref. 17).

Age Factors↗

PubMed1977

Dispersion of effective refractory period during abrupt reperfusion of ischemic myocardium in dogs.

Dispersion of the effective refractory period was measured in anesthetized dogs using a computerized system and bipolar epicardial electrodes or, alternatively, transmural plunge electrodes. Measurements were made at 1 minute intervals during short (5 minute) and long (15 minute) periods of coronary arterial ligation and for 3 to 5 minutes after release of the ligatures. Both transepicardial and transmural temporal dispersion of refractoriness correlated well with the increased vulnerability to spontaneous ventricular fibrillation during short periods of ligation and the relative electrical stability observed toward the end of the longer periods of ligation. During reperfusion, transmural dispersion increased somewhat after ligature release in the longer-term experiments but the increase did not appear adequate to explain the associated large incidence of spontaneous arrhythmias after release. Effective refractory periods measured at one nonischemic and five ischemic electrode sites at intervals as short as 20 seconds revealed abrupt shortening of the refractory period at all ischemic sites during the 1st minute of reperfusion, resulting in a large but short-lived electrical gradient between the ischemic and nonischemic myocardium. This increased dispersion between the ischemic and nonischemic myocardium occurred at a time of maximal vulnerability to reperfusion arrhythmias. However, this increased dispersion was greater after the 5 minute than after the 15 minute periods of ligation and thus does not fully explain the greater incidence of reperfusion arrhythmias after ligature release in the longer-term studies. Although arrhythmias of acute ischemia are associated with increased dispersion of refractoriness within theischemic segment and reperfusion arrhythmias with dispersion between ischemic and nonischemic segments, other electrophysiologic alterations probably play an important role in the genesis of the arrhythmias of reperfusion.

Animals↗

PubMed1979

Pacing-induced alternate Wenckebach periods: incidence and clinical significance.

Alternate Wenckebach periods have been defined as episodes of 2:1 atrioventricular (AV) block in which conducted P waves exhibit progressive PR prolongation until two or three successively blocked P waves. Ocurrence of this phenomenon during atrial pacing has been established. Thirty-six patients were studied and right atrial pacing was achieved at increasing rates up to 350 beats/min in order to induce alternate Wenckebach periods. His bundle recordings were obtained in every patient. The patients were subdivided into three groups according to the AV nodal conduction time (AH interval): normal AH (75-130 ms) was present in 17 patients, short AH (70 ms) in 13 patients and prolonged AH (130 ms) in eight patients. Alternate Wenckebach periods were observed in 29 patients (80.5%). In every patient alternate Wenckebach periods occurred at the AV node level. Atrial pacing failed to induce alternate Wenckebach periods in seven patients, six of whom belonged to the short AH group. In four patients 3:1 block never appeared because of block at the atrial level. Two patients presented 2:1 and 3:1 infrahissian block without significant AH prolongation. The remaining patient developed atrial fibrillation. Alternate Wenckebach periods were observed in six of nine patients after intravenous atropine. This study suggests: 1. pacing-induced alternate Wenckebach periods at the AV node level are a physiologic phenomenon; and 2. total or partial bypass (or accelerated AV conduction) atrial refractoriness or vulnerability or block at a lower level may prevent its occurrence.

Adult↗

PubMed1977

[Periodic variations in motor endplate potentials].

The amplitudes of motor end-plate potentials in the Frog have been measured during repetitive stimulations of the motor nerve at frequencies between 0,5 and 30 Hz. A serial analysis showed that cyclic variations of these amplitudes were superimposed on the random fluctuation of epp due to the quantal nature of transmitter release. The period of these cyclic variations varied between 3 and 10 stimulations. This period was not significantly related to the frequency of the stimulation. The frequency spectrum analysis of the epp amplitudes showed similar values for the period of the cyclic variation of epp. The same kind of analysis applied to a binomial series of random numbers did not significantly present periodic fluctuations. The same analysis was applied to mean amplitudes of groups of 5 to 120 successive epps at the same end-plate. Periodic fluctuations were identified with periods of about 10 to 180 sec. It is suggested that periodic failures of nerve spike propagation in nerve terminals at sites of low safety factor, as at branchings, are responsible for the observed cyclic variation of epp.

Animals↗

PubMed1979

[The maternal and perinatal mortality and morbitity in attendance to Caesarean section in the period from 1956--1976 at the UFK-Jena (author's transl)].

In the period from 1956--76 1 468 caesarean sections were accomplished at the UFK-Jena. 44 043 children were delivery during the 21-year period. The number of caesarean sections rose from 1,08% to 1956 to 10,8% in 1976. The fetal indication in 1956 was zero, on the other side it amounts to 34,3% in 1976. First place of the maternal indication in the 21-year period took in the cephalo pelvine disproportion. In the same time the maternal mortality in attendance of caesarean section was 12,3%. Considering the period between 1969--76, the maternal mortality fell to 2%. Maternal morbidity diminished from 1965 and obtained 23% in the period between 1974/1976. The feverish childbed took in the first place of the maternal morbidity (30%). The perinatal mortality fall from 28,57% in the period between 1956/1958 to 3,71% in the period between 1974/1976. The perinatal morbidity we could'nt state certainly. In 8,3% we found perinatal morbidity by acidosis. 5,5% of children, delivered by caesarean section needed medical care. 16,4% of all children were either small for gestational age or immature. The problem of caesarean section as an important method for termination of labor is discussed.

Cesarean Section↗

PubMed1978

[Effect of propranolol on the fibrillation threshold and the period of vulnerability of cardiac ventricles under normal conditions and during acute coronary occlusion].

Experiments on anesthetized dogs have shown that intravenous infusion of 1 mg/kg of propranolol has no essential effect on the threshold of ventricular fibrillation, but considerably reduces the duration of the vulnerable period. Ligation of the coronary artery during propranolol infusion does not cause a reduction in the fibrillation threshold or prolongation of the period of vulnerability; propranolol inhibits the fibrillatory effect of ligation of the vessel. Infusion of propranolol after ligation of the coronary artery leads to the return of the fibrillation threshold and the duration of the period of vulnerability to the initial values. Prolongation of the period of vulnerability after ligation of the coronary artery and its reduction after propranolol infusion occur due to shifts in the internal boundary of the period. There is a direct correlative relationship between the duration of the vulnerable period and the body mass of the dogs: the greater the mass of the animal, the longer the duration of the period of vulnerability.

Animals↗