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G Hertz

Publications and source records attributed to G Hertz.

8 recordsLinked to original sources
PubMed1992

Splicing signals in Drosophila: intron size, information content, and consensus sequences.

A database of 209 Drosophila introns was extracted from Genbank (release number 64.0) and examined by a number of methods in order to characterize features that might serve as signals for messenger RNA splicing. A tight distribution of sizes was observed: while the smallest introns in the database are 51 nucleotides, more than half are less than 80 nucleotides in length, and most of these have lengths in the range of 59-67 nucleotides. Drosophila splice sites found in large and small introns differ in only minor ways from each other and from those found in vertebrate introns. However, larger introns have greater pyrimidine-richness in the region between 11 and 21 nucleotides upstream of 3' splice sites. The Drosophila branchpoint consensus matrix resembles C T A A T (in which branch formation occurs at the underlined A), and differs from the corresponding mammalian signal in the absence of G at the position immediately preceding the branchpoint. The distribution of occurrences of this sequence suggests a minimum distance between 5' splice sites and branchpoints of about 38 nucleotides, and a minimum distance between 3' splice sites and branchpoints of 15 nucleotides. The methods we have used detect no information in exon sequences other than in the few nucleotides immediately adjacent to the splice sites. However, Drosophila resembles many other species in that there is a discontinuity in A + T content between exons and introns, which are A + T rich.

Animals↗
PubMed1992

Sleep in normal late pregnancy.

Twelve women in their third trimester of pregnancy and 10 age-matched nonpregnant controls underwent complete polysomnography for one night in the laboratory. Seven of the original women returned for a second study 3-5 months postpartum. During late pregnancy, women showed increased wake after sleep onset (WASO) and a lower sleep efficiency in comparison with the control group. The percentage of rapid eye movement (REM) sleep was significantly decreased and the percentage of stage 1 significantly increased compared to the nonpregnant group. At 3-5 months postpartum, a significant reduction in WASO and increased sleep efficiency were noted. However, only a slight increase was noted in REM sleep during the postpartum period compared to the prepartum period. The most frequent sleep complaints in the pregnant group were restless sleep, low back pain, leg cramps and frightening dreams. In summary, in accordance with their complaints, women in their third trimester demonstrated polysomnographic patterns of sleep maintenance insomnia.

Adult↗
PubMed1992

Respiration during sleep in pregnancy.

Several changes in maternal physiology may profoundly alter sleep, especially during late pregnancy. Any condition that causes maternal hypoxemia will be worsened during sleep, particularly in the supine position. Although high circulating levels of progesterone increase respiratory drive during sleep, in at least some women this protective mechanism is insufficient to prevent sleep-disordered breathing and hypoxemia. The true incidence of sleep-disordered breathing during pregnancy remains unknown. Although many women report sleep disturbance during pregnancy, those with severe snoring, observed irregular breathing with sleep, or excessive daytime somnolence should be referred for clinical polysomnography. With few data thus far available, nasal CPAP would appear to be the treatment of choice. Given the possible consequences of sleep apnea for fetal outcome, any significant sleep-disordered breathing is probably an indication for treatment.

Female↗
PubMed1989

Night backache in pregnancy. Hypothetical pathophysiological mechanisms.

One hundred women responded to a questionnaire dealing with night backache during pregnancy. All the women were in the second half of their pregnancy. Sixty seven per cent of the women reported discomfort and/or backache during the night. We hypothesize that hypervolemia combined with obstruction of the inferior vena cava, caused by the enlarging uterus, is the underlying pathomechanism leading to night backache. Patients with inadequate venous collateral circulation may develop excessive pressure within the venous system, the vertebral bodies and overdistension of venous channels distal to the occluded zone. These changes may lead to hypoxemia, metabolic disturbances, irritation of unmyelinated nerves and result in night backache.

Back Pain↗
PubMed1979

Increased sleep motility and respiration rates in combat neurotic patients.

Noctural rates of body movements and respiratory rates were studied in 11 combat neurosis patients and 9 normal controls. Patients had significantly higher rates of body movements in sleep stage 2, and significantly higher respiratory rates in NONREM sleep and in the second REM period than normals. In patients the rates of body movements were positively correlated with sleep efficiency indices. Since some of these patients were suspected of having non-restorative sleep syndrome, it is suggested that increased sleep motility and autonomic activity might be related to this sleep disorder.

Adult↗
PubMed1977

Cone signals in the cat's retina.

1. The discharges of ganglion cells in the cat's retina were recorded under conditions intended to isolate the cone system.2. Stiles' two-colour threshold technique permitted the photopic system to be studied when at its highest sensitivity. The absolute sensitivity of a ganglion cell, expressed in equivalent photons of lambda(max) at the cornea per impulse discharged, was about 2500 times less when driven by cones than when driven by rods. This ratio improves to around 200 when allowance is made for the much smaller fraction absorbed by cones of photons incident on the cornea.3. The number of extra impulses discharged in response to a brief flash was approximately proportional to the number of photons in the flash, up to a limit.4. There was a region in the middle of the receptive field within which the area of a test spot and its illumination for threshold varied inversely. A flash extending over the peripheral part of the receptive field raised threshold above its minimum, presumably as a result of surround antagonism. Assessed from area-threshold curves, the balance of centre-surround antagonism in the photopic receptive field did not seem to depend upon background illumination.5. The threshold for a small (0.2 degrees ) flash confined to the middle of the receptive field was independent of background illumination until the background exceeded a particular level, the ;dark light' (I(o)). In different units this ranged about a mean of 7.89 log photons (560 nm equivalent) deg(-2) sec(-1). For backgrounds that exceeded I(o), threshold followed approximately Weber's law up to the highest illuminations that could be produced.6. With test flashes that filled the centre of the receptive field, the Weber fraction (test flash illumination/background illumination) in some units fell below 1%.7. Changes in the time course and latency of response accompanied the changes in sensitivity caused by alterations in background illumination. Responses of both X- and Y-cells became more transient and faster.8. The loss of sensitivity to a test flash brought about by a steady background light depended upon the size of that light. Sensitivity varied inversely with background area within a central region that matched closely the summing area for test flashes.

Action Potentials↗
PubMedDate not supplied

Nocturnal low back pain in pregnancy: polysomnographic correlates.

Thirteen women in late stages of pregnancy underwent a polysomnographic study. Eight women (61%) complained of mild nocturnal back pain or back discomfort. Five women (39%) did not complain of nocturnal back pain. The two groups did not differ in total bed time, total sleep time, sleep latency, and wake after sleep onset (WASO). A significant decrease in rapid eye movement (REM) sleep and an increase in stage 2 were observed in the pain group. The same group had a statistically significant decrease in the basal O2 saturation level. The pain group also spent a longer time sleeping in the supine position. We hypothesize that a prolonged stay in the supine position leads to obstruction of the vena cava. In the presence of inadequate collateral circulation, increased pressure and venostasis in combination with a decrease in basal oxygen saturation may lead to hypoxemia, compromise the metabolic supply of the neural structures, and result in pain. It appears, therefore, that the vascular system plays an important role in the pathogenesis of pain. The role played by the disturbed sleep architecture in the production of pain remains to be established. It is possible that the changes observed in sleep architecture result from pain rather than contribute to pain production.

Adult↗