Mating-type suppression of the DNA-repair defect of the yeast rad6Δ mutation requires the activity of genes in the RAD52 epistasis group

The RAD6 gene of Saccharomyces cerevisiae is required for post-replication repair of UV-damaged DNA, UV mutagenesis, and sporulation. Here, we show that the radiation sensitivity of a MAT a rad6 strain can be suppressed by the MAT2 gene carried on a multicopy plasmid. The a1-2 suppression is specific to the RAD6 pathway, as mutations in genes required for nucleotide excision repair or for recombinational repair do not show such mating-type suppression. The a1-2 suppression of the rad6 mutation requires the activity of the RAD52 group of genes, suggesting that suppression occurs by channelling of post-replication gaps present in the rad6 mutant into the RAD52 recombinational repair pathway. The a1-2 repressor could mediate this suppression via an enhancement in the expression, or the activity, of recombination genes.     

Indices for the role played by regional flow resistance in blood pressure reflex

Summary An index, = (r/r)/(R/R), is proposed for assessment of the relative degree of participation of a regional flow resistance in a blood pressure reflex, wherer andR are regional and total peripheral resistances respectively and 's refer to their reflexive changes. For actual computation, =I (iP – Pi)/i(IP – PI), whereI=cardiac output,i=regional flow rate,P=mean arterial pressure. When the change in cardiac output is neglegible, the above equation is simplified as =1 – Pi/iP. Another index, = g/G = (Pi – iP)/(PI – IP), is introduced for the degree of contribution of a region to a reflex, whereg andG are regional and total conductances.i = 1. Some examples of application of the indices are presented.Supported in part by a grant from the Ministry of Education of Japan.     

Psychophysics of psilocybin and 48-148-148-1

Visual, tactile and intermodal sensory magnitude estimations were performed by college students prior to and after the oral administration of either 160 g/kg psilocybin or 30 mg ⁹-THC. Although the drugs induce inversely related changes in the exponent of the psychophysical power function (R=kS ⁿ ), the straight line relationship between log S (Stimulus) and log R (Response) is altered by neither psilocybin nor ⁹-THC. The remarkable consistency of magnitude estimations in the face of a changing exponent and constant may be interpreted as a demonstration of state boundness (i.e., performance that is consistently changed and characteristic of a particular state of consciousness).     

Cardiac Purkinje fibres

Summary The influence of intracellular calcium concentration [Ca²⁺] _i on the steady state membrane currentsi was studied in a range of clamp potentials between –20 and –100 mV. Injection of CaCl₂ or Ca-EGTA (pCa 6) increasedi whereas injection of K-EGTA diminished it. The changes i were attributed to a change in steady state potassium conductance, g_K, by four arguments: i was restricted to potentials negative to –20 mV and depended on clamp potential in an inward rectifying manner. i displayed a reversal potential, E_rev, which followed log [K⁺]₀ with 60 mV for a tenfold change. Since E_rev obtained during Ca injection agreed with E_rev observed during EGTA injection the potassium driving force had to be constant. Wheng _K was blocked by superfusion with 20 mM Cesium neither CaCl₂ nor K-EGTA injection modifiedi .Supported by SFB 38, Membranforschung, project G2     

Mechanical step variability during treadmill running

The present study was designed to study intra-individual step variability measured both on vertical displacement of the body (Z) and on step time (t) parameters by means of a kinematic arm and during treadmill running. A group of 17 subjects ran successively at 60%, 80%, 100% and 140% of their maximal aerobic velocity (v _amax). The total number of steps analysed was 6116. The absolute Z step variability (Z) ranged between 5 mm and 21 mm while the absolute t variability (t) ranged between 6 ms and 40 ms. Step variabilities were due to step asymmetry (from 38.5% to 48.5% of the step variability) and to stride variability. For submaximal velocities (60%, 80%, and 100%v _amax) both t and Z were independent of velocity or body dimensions whereas differences between subjects were significant (P < 0.01) for Z. On the other hand, variabilities were significantly increased when velocity was changed from submaximal to the 140%v _amax level. Furthermore, at submaximal levels Z was linked to the subject's energy cost of running (P < 0.05). Therefore, the intra-individual step variability should not be neglected in future studies on mechanical efficiency of running and it is suggested that, to obtain a good accuracy (better than 1%,P < 0.05) on mean value and variability of the mechanical parameters, measurements should be performed on at least 32–64 consecutive steps, which corresponds to about 15 to 20 s of running.     

Genetic characterization of an α-specific gene responsible for sexual agglutinability in Saccharomyces cerevisiae: mapping and gene dose effect

Summary A recessive ag1 mutation leads to specific defect in sexual agglutinability specifically in cells of the yeast Saccharomyces cerevisiae. The cryptopleurine resistance gene cry^R 1, closely linked to the mating type locus, was used to select / strains which emerged from / strains by mitotic nonreciprocal recombination, to genetically analyse ag1, since ag1 is expressed only in mating type. The ag1 gene was found to be linked to the centromere tightly, to met3 at 4.4 cM, and to ilv3 at 12 cM on chromosome X. Sexual agglutinability of cells was shown to be dependent on the dose of the AG1 gene, using / isogenic strains carrying AG1/AG1, AG1/ag1 or ag1/ag1. The sst2-1 mutation did not suppress the ag1 mutation. Based on these results, function of the AG1 gene is discussed.Abbreviations cM centimorgan - FDS first division segregation - NPD nonparental ditype - PD parental ditype - SDS second division segregation - TT tetratype     

The effectiveness of the control of pH in the extracellular fluid of the brain by the respiratory control system

Summary The effectiveness of the respiratory control system as a regulator of the pH in the extracellular fluid of the brain is defined by pH_{ECF op}/pH_{ECF cl} where pH_{ECF op} means the primary or open loop shift and pH_{ECF cl} the final or closed loop shift of brain extracellular fluid pH. The analysis of a steady state model described in a preceding paper (Loeschcke, 1973) allows, in the limits of the suppositions and simplifications, to calculate the effectiveness of the feedback regulator in the cases of increased metabolism, metabolic acidosis-alkalosis and inhalation of CO₂. The effectiveness is diminished if CO₂ production is increased, it drops in metabolic acidosis and rises in metabolic alkalosis and it drops steeply if CO₂ is inhaled. The effectiveness of this control system depends on the controlling action of the controlling element (the ventilation) rather than on varying sensitivity of the sensing element. The controlling effect is defined asC=–d P _CO2/d V _A orC=d pH_ECF/d V _A.Im Rahmen des Programms des Sonderforschungsbereiches 114 (Bionach) der Deutschen Forschungsgemeinschaft.     

Effects of priming exercise intensity on the dynamic linearity of the pulmonary V̇O2 response during heavy exercise

Prior heavy-intensity exercise facilitates the pulmonary oxygen uptake (O₂) response during subsequent exercise, such that its kinetics returns towards first-order. To better understand this priming phenomenon, we investigated the effect of priming exercise, over a range of intensities, on the O₂ response to heavy-intensity cycle ergometry at a work rate of 50% [halfway between lactate threshold (LT) and O_2max]. Eight subjects performed two consecutive 6-min bouts separated by 6 min at 20 W. The first bout was each of: no warm-up control (CON), sub-lactate threshold (LT) at 80% of LT, and three supra-LT conditions (20%, 40%, and 60%). The O₂ response during the subsequent bout was evaluated using the effective time constant (), and the O₂ difference between minutes 3 and 6 (O_2(6–3)). The goodness-of-fit, indicative of first-order kinetics, was determined by the residual profile, and the mean square of errors (MSEr). The heart rate and blood lactate concentration ([La]r) just prior to the second bout were also measured. Compared with CON, and O_2(6–3) were significantly reduced following all supra-LT priming bouts, while the goodness-of-fit was significantly improved following 40% exercise. O_2(6–3) and [La]r were negatively correlated (P<0.05), unlike HR. In conclusion, prior exercise just above, but not below, LT facilitated the O₂ response in a threshold-like manner. Supra-LT priming exercise influenced the O₂ response allowing it to return to within as little as 12% from first-order (compared to ~50% in CON). The associated increases in circulating lactate and/or related factors seem to be centrally involved in this phenomenon.     

Zum Stoffwechsel des Δ1-17α-Methyltestosteron (Dianabol) und 17α-Methyltestosteron in der Rattenleber

Zusammenfassung Der Stoffwechsel des ¹-17 -Methyltestosteron und des 17 -Methyltestosteron in Rattenleberschnitten wird vergleichend gegenübergestellt.Dabei zeigt sich, daß unter gleichen Versuchsbedingungen der Gesamt-UV-Schwund bei Methyltestosteron etwa 2–3mal größer als der des ¹-Methyltestosteron ist, daß sich aber nach papierchromatographischer Trennung der UV-positiven Metabolite von den Ausgangssubstanzen der Abbau beider Steroide als etwa gleich groß erweist.In 3 Std werden rund 85% der eingesetzten Steroide durch Lebergewebe metabolisiert.Papierchromatographisch ließen sich 8 UV-positive Stoffwechselprodukte qualitativ nachweisen, wobei im System P/T wie auch P/C das sicher identifizierte Methyltestosteron die größte Laufgeschwindigkeit hatte.Oestrogene konnten nicht nachgewiesen werden.Es wird die Frage diskutiert, ob der anabole Effekt des ¹-17 -Methyltestosteron überwiegend den Metaboliten zuzuschreiben ist.     

Effect of menstrual cycle and gender on ventilatory and heart rate responses at the onset of exercise

To clarify the luteal-follicular and male–female differences in ventilatory and heart rate responses at the onset of exercise, seven women and seven men performed voluntary exercise and passive movement for 20 s (brief voluntary exercise and brief passive movement) and voluntary exercise for 3 min (long voluntary exercise) in a sitting position. Voluntary exercise consisted of alternate flexion-extensions of both lower legs with a weight corresponding to about 2.5% of the subjects' body mass attached to each ankle, at a frequency of about 60 times min^–1. Passive movement was carried out without weights by experimenters pulling ropes attached to both of the subjects' ankles, in the same way as voluntary exercise. During these exercises and movements, minute inspiratory ventilation (_I) and heart rate (HR) were continuously measured by breath-by-breath and beat-to-beat techniques. We calculated relative changes of _I and HR (_I and HR). Additionally, we averaged _I and HR obtained during the exercise and movement for each subject, and performed a correlation analysis between the averaged _I and HR. It was clarified that: (1) _I and HR in the follicular phase were almost equal to those in the luteal phase; (2) there were no significant male–female differences in these parameters; (3) significant positive correlations were found in both genders only during brief voluntary exercise. We conclude that ventilatory and HR responses at the onset of voluntary exercise and passive movement are not affected by the menstrual cycle or gender.     

Exogenous gene expression and growth regulation of hematopoietic cells via a novel human artificial chromosome

A number of gene delivery systems are currently being developed for potential use in gene therapy. Here, we demonstrate the feasibility of 21qHAC, a newly developed human artificial chromosome (HAC), as a gene delivery system. We first introduced a 21qHAC carrying an EGFP reporter gene and a geneticin-resistant gene (EGFP-21qHAC) into hematopoietic cells by microcell-mediated chromosome transfer. These HAC-containing hematopoietic cells showed resistance to geneticin, expressed EGFP and retained the ability to differentiate into various lineages, and the EGFP-21qHAC was successfully transduced into primary hematopoietic cells. Hematopoietic cells harboring the EGFP-21qHAC could still be detected at two weeks post-transplantation in immunodeficient mice. We also showed effective expansion of hematopoietic cells by introducing the 21qHAC containing ScFvg, a gp130-based chimeric receptor that transmits growth signals in response to specific-antigen of this receptor. All of these results demonstrate the usefulness of HAC in gene therapy.     

Seasonal variation in sweating responses of older and younger men

Eight older (60–65 years) and six younger (20–25 years) men were exposed to a standard heat stress for 60 min in summer, autumn, winter, and spring. The test consisted of placing the lower legs and feet in a 42°C water bath while sitting in constant environmental conditions (30°C and 45% relative humidity). The increase of rectal temperature (T _re) was significantly greater (P < 0.05) in autumn, winter, and spring than in summer for the older group, but significantly greater only in winter than in summer for the younger group (P < 0.05). The T _re was greater for the older group in all seasons, but of significance only in autumn and spring (P < 0.01). There were no significant season-related differences for metabolic heat production (m) and mean skin temperature ( _sk) during the heat test in the respective groups, although the m and _sk were lower for the older group in all seasons (P < 0.01). In the older group total body sweating rate (m_sw) divided by T _re (total m_sw/T _re) decreased from summer to winter (P < 0.02) and did not differ between winter and spring, whereas total m_sw/T _re in the younger group increased in spring after decreasing from autumn to winter (P < 0.03). The variations of the value, local sweating rate on the back and thigh divided by T _re (back m_sw/T _re and thigh m_sw/T _re), were similar to those of the total m_sw/T _re in each group, except for back m_sw/T _re in the younger group, which did not increase from winter to spring. The total m_sw/T _re, back m_sw/T _re and thigh m_sw/T _re were significantly less for the older group in summer, autumn and spring (P < 0.05). The range of seasonal variations was significantly less for the older group (P < 0.001). The results indicated that, compared with younger men in older men, the enhancement of sweating function toward summer occurred later and its reduction toward winter occurred earlier despite a smaller range of seasonal variation and that older men had a somewhat lesser capability to maintainT _re when challenged by heat stress in all seasons.     

Cupula displacement,hair bundle deflection,and physiological responses in the transparent semicircular canal of young eel

The transparent labyrinth of young eels (Anguilla anguilla L.) was used in toto for studying the configuration of cupula displacement, deflection of the hair bundle, and correlated changes in transepithelial voltage (TEV) and nerve activity (NA) in the semicircular canal. Microcapillaries were introduced into the canal through holes produced by a microthermocauter. Mechanical stimulation was applied either by injection of fluid into the ampulla or by electromagnetically displacing ferrofluid as a piston within the canal. Motion of individual kinocilia, stained cupulae or the ferrofluid piston was analysed by double-exposed microphotographs, photodiodes, or a video-system. The three-dimensional cupula displacement configuration was found to be piston-to diaphragm-like. Hair bundles at different sites on the crista exhibit differences in amplitude and time course of deflection. The transfer factor between shifts of the canal fluid and the tips of the kinocilia is 0.4–0.6. Displacements in opposite directions induce TEV and NA of opposite sign. Various tests confirmed TEV to reflect receptor potential responses. Nerve activity adapts to a tonic response with a time constant of 6.4s. No similar adaptation occurred in TEV. Stimulus-response curves of TEV- and NA-responses are similar and signoid in shape with saturation at ciliary deflections of roughly + 6° and –3°.     

Ultrasonography gives directly but noninvasively elastic characteristic of human tendon in vivo

To obtain an insight into tendon elasticity during human movement, a real-time ultrasonography was applied to the contracting tibialis anterior muscle. The insertion point of fascicles onto the aponeurosis was clearly visualized, and its position relative to a fixed marker on the skin moved proximally (1) according to the increasing dorsiflexion force (F) with a fixed ankle joint. Notably, the 1 – F relationship in the tendon was found to be quadratic in nature (F = c1²; c=1.48 2.24, r=0.985 0.992, n=9) as has been reported in the isolated tendon, although the F – 1 curves were slightly underestimated in comparison with the stiffness constant estimated from tendon architecture. This underestimation might be caused by changes in the height of the foot arch with the application of force.     

Ankoppelung und Entkoppelung während der Kaliumchloridkontraktur

Zusammenfassung Bei Herzpräparaten von Aplysia führen schnelle Entdehnungen während isometrischer Kontrakturen, die durch verschiedene KCl-Konzentrationen ausgelöst werden, im Anschluß an den elastischen Spannungsabfall zu einem nachfolgenden Spannungsanstieg () über das Niveau der elastischen Nachwirkung (in der Zeit t nach der Entdehnung). Die -Werte erreichen gewöhnlich vor dem Gipfel der Kontraktur ein Maximum und fallen früher auf Null ab als die absolute Extrakraft. Der Abfall flacht sich mit fallender Konzentration der KCl-Lösung ab. Die aus den -Werten in jedem Zeitpunkt berechneten Geschwindigkeiten der inneren Verkürzung fallen zwar vom ersten Beginn der Kontraktur ab, sind aber auch noch während der Erschlaffung aus der Kontraktur (Entkoppelung) positiv. Aus diesen Befunden kann man schließen, daß die Fähigkeit der Ankoppelung in der ersten Phase der Entkoppelung anhält, aber früher verschwindet als die Kontrakturspannung, sich also unabhängig vom zeitlichen Verlauf der Kontraktur ändert.

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In heart preparations of Aplysia, quick releases during isometric KCl-contractures, evoked by various concentrations of KCl, induce—after the elastic drop in tension—a subsequent rise () in tension (within the time t after the release) above the level of the elastic after effect. Usually the -values reach a maximum before the peak of contracture and decline to zero earlier than absolute extratension. The decline flattens with decreasing concentration of the applied KCl solution. The rate of internal shortening, calculated from the -values at any instant, fall from the very beginning of contracture, but is still positive during the relaxation phase of contracture. From these findings, it may be concluded that the capability of coupeling is still present during the first phase of uncoupeling, but disappears earlier than the tension of contracture, i.e. varies independently of the time-course of contracture.

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Mit 5 Textabbildungen

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Mit Mitteln der Deutschen Forschungsgemeinschaft und ONR.     

Effects of the order of running and cycling of similar intensity and duration on pulmonary diffusing capacity in triathletes

To study the pathophysiological mechanisms involved in the decrease of post-triathlon diffusing capacity (DLco), blood rheologic properties (blood viscosity: _b; changes in plasma volume: PV) and atrial natriuretic factor (ANF) were assessed in ten triathletes during cycle-run (CR) and run-cycle (RC) trials at a metabolic intensity of 75% of maximal oxygen consumption (O_2max). The DLco was measured before and 10 min after trials. ANF and PV were measured at rest, after the cycle and run of CR and RC trials, and at the end of and 10 min after exercise. RC led to a greater DLco decrease, a lower ANF concentration and a lower PV than did CR, whereas for both CR and RC _b was increased throughout exercise and 10 min after. In addition, after CR the DLco decrease was inversely correlated (r=–0.764; P<0.01) with PV. The association of decreased plasma volume, increased _b, and lower ANF concentrations after RC suggested that lower blood pulmonary volume may have caused the greater decrease in Dlco as compared with CR. The inverse correlation between PV and DLco reinforces the hypothesis that fluid shifts limit the post-exercise DLco decrease after the CR succession in triathletes. Lastly, cycling in the crouched position might increase intra-thoracic pressure, decrease thorax volume due to the forearm position on the handlebars, and weaken peripheral muscular pump efficacy, all of which would limit venous return to the heart, and thus result in low pulmonary blood volume. Compared with cycling, running appeared to induce the opposite effects.     

The REV2 gene of Saccharomyces cerevisiae: cloning and DNA sequence

Summary The REV2 gene of Saccharomyces cerevisiae was cloned and sequenced; it contains an open reading frame of 1985 bp with a coding potential of 662 amino acids. Interruption of the chromosomal REV2 gene by integrating the URA3 gene coupled with partial deletion of the 3 terminal region produced viable haploid rev2 mutants. This indicates that the REV2 gene is non-essential for growth. The rev2 mutant is slightly more UV-sensitive than strains carrying various rev2 alleles (rev2-1, rev2x, rad5-1, rad5-8). The putative Rev2 protein is probably a globular protein containing a highly conserved nucleotide-binding site and two zinc-finger domains.     

Energetics of anaerobic glycolysis in dog gastrocnemius

Thermally isolated gastrocnemii were stimulated to exhaustion, by rhythmic isotonic (70 N) tetanic contractions, during complete occlusion of blood flow. Enthalpy change (h=work + heat) and work output (w) (kJ/kg) were obtained from records of deep muscle temperature and shortening. The lactate produced (LA, mol/kg) was measured in the outflow after reestablishement of blood flow. The following relationships were obtained:h=76 LA+1.2, andw=19.8 LA+0.30. As the energy liberated at exhaustion by alactic energy sources (P and O₂ stores) is constant, h/ LA=76 (±10.5, S.E.) kJ/mol is the enthalpy change for lactate formation ( ). The neutralization heat was estimated on muscle homogenates at 12 kJ/mol, leaving 64 kJ/mol for of LA formation proper. The mechanical efficiencies of work related to LA formation (E _LA) and of that not related to LA formation (E _nonLA) were practically identical (0.25). From these values and from , the enthalpy change of P splitting was estimated in the range 52–62 kJ/mol, depending on the value of the ratio P/ LA assumed in the calculation.     

Spontaneous and agonist-induced openings of an acetylcholine receptor channel composed of bovine muscle α-, β and δ-subunits

During the development of mammalian muscle the -subunit of the nicotinic acetylcholine receptor (AChR) is replaced by the -subunit to produce well-defined alterations in the conductance and gating of the channel. To gain a better unterstanding of the functional role of the and -subunits, we have studied the properties of an AChR channel lacking these subunits. The AChR expressed in Xenopus oocytes injected with the bovine -, and -subunit-specific mRNAs (referred to as -AChR) is unusual in that its channel opens spontaneously at a high frequency in the absence of agonist. From a comparison of the -AChR with complete receptors containing either the or -subunit, we conclude that the and -subunits influence most channel properties, including agonist binding, and are especially important for stabilizing the closed state of the unliganded receptor channel. The -AChR can form when a complete set of four subunit-specific mRNAs is injected. The ease with which it is assembled raises the possibility that the - AChR contributes to some of the variations in receptor properties that occur during development.     

Separating the direct effect of hypoxia from the indirect effect of changes in cardiac output on the maximum pressure difference across the tricuspid valve in healthy humans

In healthy humans, changes in cardiac output are commonly accommodated with minimal change in pulmonary artery pressure. Conversely, exposure to hypoxia is associated with substantial increases in pulmonary artery pressure. In this study we used non-invasive measurement of an index of pulmonary artery pressure, the maximum systolic pressure difference across the tricuspid valve (P_max), to examine the pulmonary vascular response to changes in blood flow during both air breathing and hypoxia. We used Doppler echocardiography in 33 resting healthy humans breathing air over 6–24 h to measure spontaneous diurnal variations in P_max and cardiac output. Cardiac output varied by up to ~2.5 l/min; P_max varied little with cardiac output [0.61±0.74 (SD) mmHg min l^–1]. Eight of the volunteers were also exposed to eucapnic hypoxia (end-tidal ) for 8 h. In this group P_max rose progressively from 21 mmHg to 37 mmHg over 8 h. By comparing diurnal variations in P_max during air breathing with changes in P_max during hypoxia in the same eight individuals, we concluded that only approximately 5% of the changes in P_max during hypoxia could be attributed to concurrent changes in cardiac output. The low sensitivity of P_max to changes in cardiac output makes it a useful index of hypoxic pulmonary vasoconstriction in healthy humans.