Mean Cycle Duration Research Articles

Breath-by-breath respiratory timing and volume control during periodic breathing.

We examined the control of respiratory pattern during non-rapid-eye-movement sleep-related periodic breathing (PB) in adults, with and without hypoxia. We analyzed 186 cycles of PB from 18 epochs occurring in eight subjects; the mean (+/- SD) cycle duration was 30.8 +/- 8.4 s. Significant oscillations occurred in inspired tidal volume (VT), inspiratory duration (TI), mean inspired flow, inspired minute ventilation, and expiratory duration (TE) (P less than 0.005). For each epoch of PB, moving cross-correlation (MCC) functions were employed to describe the time-dependent intervariable relationships between 1) TI vs. TE, 2) VT vs. TE, and 3) VT vs. breath duration (TT) as synchronization, a strong and consistent intervariable correlation; relative coordination (RC), a weaker interaction characterized by an unstable MCC function oscillating at a subharmonic of the PB frequency; or as independence, with no statistical evidence of interaction. Fourteen epochs showed RC between TI and TE, 11 and 12 of which also showed RC between VT and TE, and VT and TT, respectively. In 4 epochs negative synchronization was exhibited by all three variable pairs. In no case were the oscillations between any pair of variables independent. The modes of coupling between variables were not correlated to O2 saturation, end-tidal CO2 levels, or inspired O2 level. We conclude that during sleep-related PB a nonrandom but weak coupling usually exists between TI and TE, VT and TE, and VT and TT.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum glucose concentration as a modulator of interdigestive gastric motility

The objective of this study was to examine the effect of serum glucose concentration on interdigestive gastrointestinal motility and plasma motilin levels in humans. Motility studies were performed for a 3-h baseline period and a 3-h test period during which serum glucose levels were maintained with a glucose clamp at 250, 175, 140, or 120 mg/dl. During the basal recording, three phases of the interdigestive migrating motor complex (MMC) were easily recognizable, with a mean cycle duration of 97 ± 12 min. Plasma motilin levels fluctuated in phase with the MMC. Gastric contractions were nearly absent at a serum glucose level of 250 mg/dl and markedly reduced at 175 and 140 mg/dl. Gastric phase III activity was inhibited during these infusions. Gastric contractions and phase III activity were not affected by glucose infusion at 120 mg/dl. In contrast, the frequency of duodenal phase III activity was unchanged at all levels of glucose infusion. Mean motilin levels were significantly reduced during glucose infusion at 250 and 175 mg/dl (p < 0.05), but not at 140 and 120 mg/dl. We conclude that hyperglycemia inhibits the occurrence of the MMC in the stomach and suppresses plasma motilin levels. The differential sensitivity of motility and motilin concentration to different degrees of hyperglycemia suggests that hyperglycemia can inhibit antral motility independent of plasma motilin. In contrast, the duodenal MMC appears to be insensitive to hyperglycemia. This suggests that the antral and duodenal MMCs are mediated by different mechanisms. Our observations indicate the importance of serum glucose in regulating gastric motility.

Assessment of menstrual variability in working populations

Though the relationship between exposure to chemicals and damage to ovarian tissue has been demonstrated, there have been few attempts to assess the effect of occupational exposures on menstrual cycles. Previous research has reported the mean cycle lenghts and duration of flow for large populations. However, additional research is needed to analyze the variability of cyles of individual working women. Cycle length is the most assessible indicator of ovarian damage and subsequent effects on menstrual patterns, but the reliability of self-reports of cycle length has been shown to be poor. Improved methods to accurately assess individual menstrual variability are needed. Educational programs should be provided for workers to increase their knowledge of the effects of chemicals on reproductive functioning and ultimately to increase their sensitivity to recording accurate data on menstrual patterns. Numerous factors can affect the hypothalamic-pituitary-gonadal balance. The simultaneous effects of these factors and exposures to chemicals in the workplace need further investigation.

The effect of infrahyoid-muscle tenotomy on orofacial motor activity in the rat

The effects of disturbed proprioceptive feedback from the infrahyoid muscles on the control of chewing and drinking were studied in the unrestrained rat. Rats were trained to lick and to eat in a fixed body position in front of a video camera. After training, the left and right sternohyoid, omohyoid and sternothyroid muscles were cut close to the hyoid bone. EMG-wire electrodes were inserted into the superficial masseter, the anterior and posterior digastic and sternohyoid mucles. EMG-recordings were made at the third, the tenth and the eighteenth day after tenotomy. After about a week the cut ends of the muscles became encapsulated in connective tissue and began to reattach to the hyoid bone; in some animals the sternohyoid muscle reattached to the trachea. In the period before reattachment the mean cycle duration for chewing (but not for drinking) increased. After reattachment the mean cycle duration returned to control values. The contraction patterns after tenotomy were similar to those of the controls during chewing and drinking. The mean burst duration of the sternohyoid increased after tenotomy during chewing but not drinking; it decreased in the digastric muscles and did not change in the masseter. After reattachment of the infrahyoids, the mean burst durations of the digastrics further diminished during chewing whereas that of the sternohyoid dropped below control levels. In the first week after tenotomy, during chewing, the maximum of the sternohyoid burst shifted and became synchronous with the peak of the masseter burst; the shape of the masseter and digastric bursts did not change. After the infrahyoid muscles has reattached the shape of the sternohyoid burst became similar to the control again. Thus proprioceptive information from the infrahyoid muscles may not be integrated in the central programme of motor control but used only in their intrinsic reflex control.

GAIT CYCLE DURATION IN 3-YEAR-OLD CHILDREN

The gait cycle duration of 11 children who were 3 years old was recorded using cinematography. The variation of cycle duration from cycle to cycle during free walking with each child and the variation of mean cycle duration among the children are reported. I analyzed individual subject characteristics including sex, height, weight, leg length, and age at onset of independent walking for strength of relationship to recorded cycle duration. Results suggest that cycle duration in 3-year-old children during free walking is shorter than that expected for adults. A minimum of variability exists in average cycle duration across subjects at 3 years of age; however, considerable variation of cycle duration from cycle to cycle within individual subjects is not uncommon. I identified no significant relationships between subject characteristics and gait cycle duration. The data reported are consistent with the results of other studies showing a trend of gradually increasing cycle duration and decreasing variability with increasing age in early childhood.

Untersuchungen an den kontraktilen vakuolen von Homalozoon vermiculare und Dileptus anser

Summary Homalozoon vermiculare and Dileptus anser are elongate predatory ciliates which contain many (5–21 in Homalozoon, 6–15 in Dileptus) contractile vacuoles. In both cases the total number was greater in longer animals. The behaviour of these structures was investigated by analysis of video recordings. The vacuoles appear simple, there are no collecting canals. No ampullae are visible after expulsion of vacuolar fluid has taken place. Vesicles are not involved in vacuolar filling. The average diastolic diameter attained by contractile vacuoles of H. vermiculare was 9.5 μm (range 4–15μm) and in D. anser 4.0 μm (range 2–5μm). The frequency of contractions in H. vermiculare varied greatly averaging 1 contraction per 45 s, and individual vacuoles had a wide range of cycle period, e.g., 38–53 s. The vacuoles of D. anser, in contrast, have cycle periods varying within quite a narrow range and had a mean cycle duration of 25 s. The frequency of contractions in H. vermiculare show gradual, sinusoidal fluctuations in the duration of the cycle. In both organisms the vacuoles towards the front and back ends of the cell contract less frequently than those towards the centre of the cell. There is a direct correlation between vacuolar contraction frequency and the width of the body. However, there is no direct correlation between vacuolar output and the volume of the intervacuolar cytoplasm, or the intervacuolar cell surface area. There is an apparent gradient in the functional activity (output per vacuole per volume of cytoplasm) of the contractile vacuoles of these organisms, with a maximum encountered immediately behind the cytopharynx.

Gait cycle duration in 3-year-old children.

The gait cycle duration of 11 children who were 3 years old was recorded using cinematography. The variation of cycle duration from cycle to cycle during free walking with each child and the variation of mean cycle duration among the children are reported. I analyzed individual subject characteristics including sex, height, weight, leg length, and age at onset of independent walking for strength of relationship to recorded cycle duration. Results suggest that cycle duration in 3-year-old children during free walking is shorter than that expected for adults. A minimum of variability exists in average cycle duration across subjects at 3 years of age; however, considerable variation of cycle duration from cycle to cycle within individual subjects is not uncommon. I identified no significant relationships between subject characteristics and gait cycle duration. The data reported are consistent with the results of other studies showing a trend of gradually increasing cycle duration and decreasing variability with increasing age in early childhood.

Interdigestive motilin secretion and gallstone disease.

Plasma motilin concentrations were measured in eight controls and 11 patients with radiolucent gallstones over a period of 3-4 h following an overnight fast. In five of these patients the interdigestive motor complex (IDMC) was studied simultaneously. The results indicate: a) cyclical changes of plasma motilin concentrations (mean cycle duration 110 +/- 9.9 and 102 +/- 8.4 min, means +/- SEM) and a significant correlation between the basal intercyclical motilin concentrations and the age (p less than 0.02) in the controls and the gallstone patients studied, and b) a significant correlation between the maximal motilin increase and the age in the controls (p less than 0.01) but not in the gallstone patients. The results therefore suggest a different behaviour of the interdigestive motilin patterns in controls and gallstone patients. As the motilin cycles were accompanied in 90% with an IDMC in the five patients studied this conclusion might include an abnormal interdigestive motor activity within the intestinal tract in gallstone patients.

Computer-analysed movements in three dimensions recorded by light-emitting diodes. A study of methodological errors and of evaluation of chewing behaviour in a group of young adults.

Mandibular movements recorded by means of intraorally placed light-emitting diodes (LEDs) were described and tested. By using a reference system attached to the test subject, the influence of head movements on the registration of the mandibular movements could be avoided. The errors of the method were tested. The stability of the reference system during function was found to be greater when the light impulses did not have to penetrate the lip. A limited clinical test was performed and the following observations were made: the mean cycle duration was, after the first cycles, stable through the whole chewing phase, 0.52 s when chewing crispbread; the duration of the occlusion phase appeared to be shorter than that of the opening and closing phases; the velocity of the mandible was greater in the opening phase than in the closing phase, with a mean velocity of 84 and 70 mm/s respectively; the clinical test showed that the method was easy to handle in the clinical situation, thereby creating an instrument for studies in larger groups of patients. By adding a simple computer program, the manual analysis could be reduced considerably and a number of variables could be measured with a high degree of precision.

Cell Cycle Kinetics in the Primary Root Meristem ofVicia Faba: Influence of Different Ambient Water Levels

SUMMARYCell cycle kinetics were determined for roots grown either in tanks of water from 24 to 144 hr or in a moistened mixture of vermiculite and perlite (V/P) from 24 to 96 hr. For roots grown in tanks of water Tc was 23.4 hr (TG1 = 6.1 hr, TG2—5.5 hr, T2 = 9.6 hr, Tm = 2.3 hr) while roots grown in V/P had a shorter Tc of 17 hr (TG1 = 5.6 hr, TG2 = 4.0 hr, T, = 5.0 hr, Tm = 2.4 hr). Most of the difference in cycle times was due to a disproportionate increase in the duration of S for water grown roots while the duration of G1 and G2 showed relatively smaller changes. This difference in TS was coupled with an increase in L.I. in water grown roots over that seen in V/P grown roots, i.e. 31.0 ± 8.6 cf. 25.9 ± 6.5. Changes in the proportions of fast, slow and non-cycling cells also occurred; i.e. in V/P grown roots there were 83.2% fast, 11.4% slow and 5.4% non-cycling cells, while in tanks of water there were 52.9% fast, 22.7% slow and 24.4% non-cycling cells. The results are evidence of differences both in mean cycle duration and phase duration within the cell cycle for roots grown in different volumes of water. They also show that roots respond to different volumes of water by altering their GF and the proportions of fast, slow and non-cycling cells in their meristems. These changes may be part of a mechanism used by roots to regulate the overall rate of cell proliferation and thus to achieve different TDT values under different environmental conditions.

Mandibular movements of young adults recorded by intraorally placed light-emitting diodes

Mandibular chewing movements of 10 young adults were registered with LED. The registrations were performed manually, and the following observations were made: 1. The mean cycle duration was reduced from 1.12 seconds for cycle 1 to 0.76 second for cycle 16. 2. The duration of the opening phase appeared to be shorter than that of the closing phase. 3. The maximal vertical movement of the mandible decreased throughout the chewing period. The results obtained in this study agree with those reported by other investigators and indicate that a system using LED is suitable for analyzing the mandibular movement pattern in clinical situations.

In vivo analysis of cellular replication.

The number of previous cell replications that a metaphase cell has undergone in the presence of BrdUrd can be determined by the differential fluorescent patterns of metaphse chromosomes stained with Hoechst dye 33258. To examine if this technique could be applied to analyzing cell cycle kinetics in vivo, we infused Wistar rats with BrdUrd for 7.5-33 hr at concentrations of the nucleotide analog that did not inhibit cellular replication. Examination of the frequency of one, two, and three or more replication cycle cells as a function of BrdUrd infusion time indicates that cell replication times for rat bone marrow cells are relatively homogeneous. Analysis of this data with a computer simulation model produced a mean cell cycle duration of 9.2 hr, which is compatible with the fastest times obtained with radioisotope studies. These results support the potential of nonradioisotope analysis of cell replication in vivo.

The polycyclic sleep-wake cycle in the cat: Effects produced by sensorimotor rhythm conditioning

In the present study, criteria were formulated to define the polycyclic sleep-wake cycle of the naive laboratory cat. Analysis of electrographic data from cats prepared for chronic 24-hr observations revealed a mean cycle duration of 104 min. An average cycle contained a 26-min wakefulness and a 79-min sleep episode with an average of 2.6 REM sleep epochs per sleep episode. Traditional measures of sleep-wakefulness percentages, sleep cycle duration, and the active sleep/total sleep ratio were not different from those reported in previous studies. Cats trained to produce a high-amplitude slow-wave EEG pattern, the sensorimotor rhythm, for food reward and observed during 24-hr recording sessions had shorter sleep-wake cycles. The wakefulness episode was extended to 35 min and the sleep episode was shortened to 58 min to produce a 93 min cycle. There was an average of 2.3 REM sleep epochs per sleep episode. Alert behavior increased and drowsiness, quiet sleep, and active sleep decreased in amounts over the 24-hr observation period. The active sleep/total sleep ratio and the mean sleep cycle length did not change. These results indicate that the polycyclic sleep-wake cycle is a definable rhythm of the cat's sleep-wake pattern. This measurement of the cycle and its subcomponent features affords a means of determining how changes in percentages of sleep and wakefulness affect the dynamics of sleepwake pattern organization. These analyses complement the traditional measures of percent sleep and wakefulness and the sleep cycle length in experimental studies of sleep.

A new low-oestrogen, low-progestogen combined oral contraceptive.

A combination of 150 mcg d-norgestrel and 30 mcg ethinyl estradiol (Ovranette) was taken by 238 women for 1076 cycles for oral contraceptive purposes. No pregnancies occurred. The cycle control was good. The mean cycle duration was 28.4 plus or minus .2 days. Breakthrough bleeding occurred in 7% of the cycles, and spotting occurred in 8.1%. Amenorrhea occurred in 2% of the cycles. The incidence of side effects most commonly associated with combination oral contraceptives was low. It was concluded that this new combination will be acceptable to most women. It was noted that an additional long-term advantage may result from the ingestion each month of only 3.78 mg of steroid.

The duodenal progenitor population. I. Age related increase in the duration of the cryptal progenitor cycle.

AbstractThe duodenal progenitor population has been investigated in four age groups of male Swiss albino mice, utilizing tritiated thymidine and autoradiography following sequential sacrifice of the experimental animals. Parameters evaluated in the different age groups included: (1) duration of the progenitor cycle and its component phases; (2) DNA‐synthetic index; and (3) mitotic index.Analysis of the kinetics of metaphase labeling revealed that the mean duration of the entire cycle lengthens with age, whereas the mean duration of the DNA‐synthetic phase is constant (ca. 7.4 hours) irrespective of age. Estimates of the cycle duration based upon calculations from the DNA‐synthetic index also demonstrate an increase with age, although the absolute values derived in this manner do not agree with those based on metaphase labeling.Determination of the cryptal DNA‐synthetic and mitotic indices disclosed a decrease in the percentage of labeled and/or mitotic cells with increasing age. Thus, the prolongation with age in mean progenitor cycle duration involves an increase in the average time which a duodenal progenitor cell spends in the interphase (G1) portion of the cycle.