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Showing papers by "University College London published in 1977"



Journal ArticleDOI
TL;DR: Apparatus for applying a step change of length to an isolated muscle fibre is described and the step was complete in about 0·2 ms.
Abstract: 1. Apparatus for applying a step change of length to an isolated muscle fibre is described. The step was complete in about 0.2 ms.2. Effects of tendon compliance were eliminated by using a spot-follower device and by gripping the tendons with metal clips close to the fibre ends.3. The natural frequency of the force transducer was above 10 kHz.4. Steps of various amplitudes and in either direction were applied to isolated muscle fibres about 6 mm long from the anterior tibial muscle of Rana temporaria during tetanic stimulation. Initial sarcomere length was 2.0-2.2 mum, and temperature was 0-3 degrees C.5. The tension response to a step could be divided into four phases. The initial response was an apparently elastic change during the step itself (phase 1). After the step was completed there was a rapid partial recovery towards the original tension (phase 2, lasting 2-5 ms), followed by a slowing or reversal of recovery (phase 3, 10-50 ms), and finally a much slower return to the original tension (phase 4). Most of this paper is concerned with phases 1 and 2.6. The initial tension change (phase 1) occurred synchronously with the applied length change, indicating that the fibres possess a compliance which is almost linear and almost undamped. Its stiffness is such that an instantaneous shortening of about 4 nm per half-sarcomere would bring the tension to zero from its isometric value.7. The absence of detectable damping during phase 1 indicates that the viscosity of a stimulated fibre is substantially less than the apparent viscosity of a fibre at rest.8. The instantaneous force-extension curve approached the length axis at a sharp angle and a negative tension appeared at the force transducer when a very large step was applied. These observations suggest that the structures responsible for the stiffness of the fibre remain rigid when they are not under tension.9. During the few milliseconds after the step (phase 2) the tension recovered part of the way toward the level which existed before the step. In shortening steps the time course of this recovery was adequately fitted by the sum of four exponential terms, and was similar in steps of different amplitude but with a time scale shorter the larger the step. In stretches the slow components were relatively larger than in releases.10. The tension level, T(2), approached during phase 2 depended only on the total amplitude of the step and not on the time course of the length change, provided it was complete in 1-2 ms. The extreme tension reached during a step could thus vary widely without detectable change in T(2).11. With stretches and releases of up to about 3 nm per half-sarcomere this early recovery was almost complete, so that the curve of T(2) against step amplitude was nearly horizontal. With larger releases the line curved downwards, reaching zero in a release of about 14 nm per half-sarcomere.12. When the temperature was raised both the developed tension and the stiffness increased, but the relative increase was greater for tension than for stiffness. The amount of instantaneous shortening needed to bring tension to zero was therefore also increased.13. A set of empirical equations is given which describe adequately the first few milliseconds of the tension change in response to any imposed time course of shortening.14. The rapid elasticity and early tension recovery resemble the response of a combination of two elastic components and one viscous component. Reasons are given for preferring an interpretation in terms of an undamped compliance in series with a damped compliance (Voigt element) rather than an undamped elasticity in parallel with a series combination of viscous and elastic components (Maxwell element).15. The rapid compliance does not correspond to the ;series elastic component' of two-component theories of muscle contraction.

788 citations


Journal ArticleDOI
01 Mar 1977

540 citations


Journal ArticleDOI
TL;DR: When endplates of anti-esterase treated frog muscle are subjected to a massive ionophoretic dose of curare, a small local hyperpolarization is recorded in many fibres, and it is calculated that such a steady leakage of ACh could exceed the efflux due to spontaneous quantal discharges by two orders of magnitude.
Abstract: When endplates of anti-esterase treated frog muscle are subjected to a massive ionophoretic dose of curare, a small local hyperpolarization is recorded in many fibres, amounting on the average to about 40 $\mu $V. The origin of this effect may be attributed to leakage of cytoplasmic acetylcholine (ACh) from nerve terminals, building up an ACh concentration of the order of 10$^{-8}$ M in the synaptic cleft and causing a minute steady depolarization of the endplate. It is calculated that such a steady leakage of ACh, although producing a barely detectable electrical effect, could exceed the efflux due to spontaneous quantal discharges by two orders of magnitude, and account for the assayed amounts of ACh release from resting muscle.

426 citations


Journal ArticleDOI
TL;DR: A method is presented for growing large numbers of pure isolated smooth muscle cells from adult human, monkey, and rabbit blood vessels in primary culture to modify or “dedifferentiated” after about 9 days in culture to morphologically resemble fibroblasts.
Abstract: A method is presented for growing large numbers of pure isolated smooth muscle cells from adult human, monkey, and rabbit blood vessels in primary culture. In the first few days in culture these cells closely resembled those in vivo and could be induced to contract with angiotensin II, noradrenaline and mechanical stimulation. They stained intensely with antibodies against smooth muscle actin and myosin. Fibroblasts and endothelial cells did not stain with these antibodies thereby allowing the purity of each batch of cultures to be monitored. This was consistently found to be better than 99%. The smooth muscle cells modified or "dedifferentiated" after about 9 days in culture to morphologically resemble fibroblasts. At this stage cells could no longer be induced to contract and did not stain with the myosin antibodies. Intense proliferation of these cells soon resulted in a confluent monolayer being formed at which stage some differentiated characteristics returned. The modification of "dedifferentiation" process could be inhibited by the presence of a feeder layer of fibroblasts or endothelial cells, or the addition of cAMP to the culture medium. Smooth muscle cells which had migrated from explants in primary culture, and cells in subculture, had morphological and functional properties of "dedifferentiated" cells at all times. The advantages of differentiated rather than "dedifferentiated" smooth muscle cells in culture for the study of mitogenic agents in atherosclerosis is discussed.

374 citations


Journal ArticleDOI
TL;DR: It is calculated that the proliferative zone, in the 24 h period commencing with primitive streak formation, could generate about half the cells in the 7½-day embryo, and it is postulated that the cells generated in the PZ may constitute the ectoderm of later stage embryos.
Abstract: Histological determination of cell numbers in the mouse embryo between 4½ and 7½ days post coitum show that growth during this period, in which gastrulation occurs, is not uniform. Prior to primitive streak formation mean cell generation time is about 9 h. Co-incidental with the appearance of the primitive streak the embryo enters a period of rapid growth, lasting about 24 h, during which the mean cell generation time must be about 5 h in order to account for the increase in cell numbers. A more detailed study, in which variations in mitotic activity in different regions of the embryo have been analysed, has identified a small region, the so-called ‘proliferative zone’, constituting about 10% of the whole epiblast, in which cell generation time may average as little as 2–3 h over a 24 h period. The cell generation time for other epiblast regions is estimated at about 6·5 h. It is calculated that the proliferative zone, in the 24 h period commencing with primitive streak formation, could generate about half the cells in the 7½-day embryo. The topographical consequences of such a rapidly expanding region in the embryo are discussed in the light of other, circumstantial evidence, and it is postulated that the cells generated in the PZ may constitute the ectoderm of later stage embryos.

344 citations


Journal ArticleDOI
TL;DR: The presence of ineffective synapses in the adult offers an alternative to sprouting or the opening up of polysynaptic pathways as a possible mechanism to explain plasticity of connections in adult brains.
Abstract: In this paper, we shall show that there are substantial numbers of nerve terminals which are normally ineffective. In the intact animal, occasional signs of the postsynaptic effectiveness of these fibres can be seen under conditions of optimal spatial summation or increased excitability or decreased inhibition. If the normally functioning afferent nerve fibres are blocked or cut, some of the previously ineffective fibres immediately establish an effective drive of cells. If the normal afferents are cut and allowed to degenerate, large numbers of cells begin to respond to new inputs. The presence of ineffective synapses in the adult offers an alternative to sprouting or the opening up of polysynaptic pathways as a possible mechanism to explain plasticity of connections in adult brains.

327 citations


Journal ArticleDOI
01 Feb 1977-Pain
TL;DR: It is concluded that an inhibitory pathway, which descends in the dorsal part of the lateral funiculus and which probably originates in the nucleus raphe magnus of the medulla, mediates the descending control found in both morphine and stimulus‐produced analgesia.
Abstract: This study examined the hypothesis that descending inhibitory pathways from brain stem to spinal cord mediate the analgesic effect of both electrical brain stimulation and morphine. In the first set of experiments, the effect of subtotal midthoracic spinal cord lesions on the analgesic effect of electrical stimulation in the periaqueductal gray matter of the rat was examined. In the second, the effect of similar cord lesions on the analgesic effect of intraperitoneal morphine was studied. In both cases, a lesion of the dorsal part of the lateral funiculus (DLF) reduced or abolished the analgesia of the hindlimbs. Analgesia of the forelimbs was unaffected. Lesions of the dorsal columns, which include the corticospinal tract, or lesions of the ventral part of the lateral funiculus had no effect on analgesia. It is concluded that an inhibitory pathway, which descends in the dorsal part of the lateral funiculus and which probably originates in the nucleus raphe magnus of the medulla, mediates the descending control found in both morphine and stimulus-produced analgesia.

298 citations


Journal ArticleDOI
TL;DR: In this article, the asymptotic consistency of cross-validatory assessment and the efficiency of crossvalidatory choice is investigated both in some generality and also in the context of particular applications.
Abstract: SUMMARY The asymptotic consistency of cross-validatory assessment and the asymptotic efficiency of cross-validatory choice is investigated both in some generality and also in the context of particular applications.

289 citations


Journal ArticleDOI
TL;DR: Methods for maintaining muscles in physiological condition, stimulating them and recording tension while at the same time accumulating their 31P NMR spectra are developed.
Abstract: 1. Phosphorus nuclear magnetic resonance ((31)P NMR) can be used to measure the concentrations of phosphorus-containing metabolites within living tissue. We have developed methods for maintaining muscles in physiological condition, stimulating them and recording tension while at the same time accumulating their (31)P NMR spectra. Experiments were performed on frog sartorii and frog and toad gastrocnemii at 4 degrees C.2. The NMR signals from (31)P (the naturally occurring phosphorus) is weak, and signal averaging is required. In order to follow the time course of reactions it is necessary to maintain the muscles in a steady state for many hours while they are undergoing repeated contractions. Signals were accumulated in separate computer bins according to time after initiation of contraction. By these means spectra were obtained which corresponded to the different intervals during the contraction and recovery cycle.3. In the absence of stimulation, the spectra of frog sartorius muscles and of their extracts indicated concentrations of adenosine triphosphate (ATP), phosphoryl creatine (PCr), inorganic orthophosphate (P(i)) and sugar phosphates (sugar P) which are in reasonable agreement with the values obtained by chemical analysis.4. We have confirmed that unidentified resonances representing unknown compounds appear in the spectra of both frog and toad muscle; one of these is much larger in spectra from toad than from frog. We have found an additional small, unidentified resonance which appears to be specific to toad muscle.5. Spectra accumulated during actual contractions (1 s tetani every 2 min) did not differ dramatically from those accumulated throughout the 2 min cycle of contraction and partial recovery.6. Following 25 s tetanii, approximately 20% of the PCr had been hydrolysed; it was then rebuilt exponentially with a half-time of about 10 min. The increase in [P(i)] immediately after contraction and the time course of its disappearance corresponded to the changes in [PCr]. During the later half of the recovery period the concentration of P(i) was reduced to below that in resting muscle. The [sugar P] remained very high ( approximately 4 mmol kg(-1)) throughout the 56 min interval between contractions.7. When frog sartorii were tetanized for 1 s every 2 min, the changes in [PCr] and [P(i)] between contractions could not be observed because too little signal was obtained from these small muscles. However, when toad gastrocnemii were similarly stimulated, the changes in these compounds could be readily detected and were even greater than expected.8. The position of the P(i) resonance can be used to monitor intracellular pH and changes in pH. Under the conditions of our experiments the average intracellular pH in unstimulated frog sartorius muscles was 7.5. After a 25 s tetanus this was observed to move in the acid direction by a few tenths of a pH unit and to return to its pre-stimulation value before the end of the recovery period. After a 1 s contraction of toad gastrocnemius the environment of P(i) became slightly more alkaline for the first few seconds.

286 citations


Journal ArticleDOI
03 Nov 1977-Nature
TL;DR: The experiments suggested that there is selectivity in the gap junctional membrane which led us to predict that the junctional permeability would be sensitive to changes in intracellular pH, and results are presented which confirm this prediction.
Abstract: Low electrical resistance intercellular junctions have been found in a wide variety of adult tissues, both in vivo and in tissue culture1 and in early embryos2. Vertebrate and invertebrate adult intercellular junctions are permeable to small ions and a variety of other molecules, of molecular weights possibly up to 1,000, as shown by the movement of tracers such as fluorescein8 and transfer of nucleotides (‘metabolic cooperation’)3. In adult systems, such intercellular exchange is correlated with the presence of gap junctions4. In embryos, some form of specific junction is necessary to account for the observed electrical coupling after early cleavage stages5 and the presence of gap junctions has been reported5–8. Since the low resistance intercellular pathway has been implicated in the control of spatial and temporal organisation during development9, the permeability of the embryonic junction assumes some importance. There is evidence suggesting that embryonic junctions are less permeable than adult junctions10–13, which we have recently confirmed14. Our experiments14 suggested that there is selectivity in the gap junctional membrane which led us to predict that the junctional permeability would be sensitive to changes in intracellular pH. We present here results which confirm this prediction.

Journal ArticleDOI
TL;DR: In this article, the effect of a slip coefficient on the flow in the neighbourhood of the contact line was examined, and the contribution of the vicinity of a contact line to the force on the boundary was obtained.
Abstract: If the no-slip condition is used to determine the flow produced when a fluid interface moves along a solid boundary, a non-integrable stress is obtained. In part 1 of this study (Hocking 1976), it was argued that, when allowance was made for the presence of irregularities on the solid boundary, an effective slip coefficient could be found, which might remove the difficulty.This paper examines the effect of a slip coefficient on the flow in the neighbourhood of the contact line. Particular cases which are solved in detail are liquid–gas interfaces at an arbitrary angle, and normal contact of fluids of arbitrary viscosity. The contribution of the vicinity of the contact line to the force on the boundary is obtained.The inner region, near the contact line, must be matched with an outer flow, in which the no-slip condition can be applied, in order to obtain the total value of the force on the boundary. This force is determined for the flow of two fluids between parallel plates and in a pipe, with a plane interface. The enhanced resistance produced by the presence of the interface is calculated, and it is shown to be equivalent to an increase in the length of the column of fluid by a small multiple of the pipe radius.

Journal ArticleDOI
TL;DR: In this paper, the authors present results of a large-scale simulation study of the power of various tests of normality and show the difficulty of applying tests based on ordered observations, such as the Shapiro-Wilk test, when in practice the sample data may contain "ties" resulting from grouping or rounding.
Abstract: SUMMARY In the present paper we present results of a large scale simulation study of the power of various tests of normality. We follow the procedure adopted by Shapiro, Wilk & Chen of applying a considerable variety of tests to samples drawn from a wide range of nonnormal populations. We, however, consider some additional tests, emphasize the difference between 'omnibus' and 'directional' tests and show the difficulty of applying tests based on ordered observations, such as the Shapiro-Wilk test, when in practice the sample data may contain 'ties' resulting from grouping or rounding.


Journal ArticleDOI
TL;DR: In this article, the problem of deciding whether two sets of fragments have come from a common source frequently arises in forensic science and a solution in the realistic case where the distribution is nonnormal is provided.
Abstract: SUMMARY The problem of deciding whether two sets of fragments have come from a common source frequently arises in forensic science. This paper provides a solution in the realistic case where the distribution is nonnormal. The normal case is also discussed because it is there easier to understand the nature of the solution and, in particular, its relationship to significance tests. The solution requires the distribution function of the product of standardized normal quantities which is tabulated in the appendix.

Journal ArticleDOI
TL;DR: It was concluded from these combined anatomico-physiological experiments that there are at least two distinct regions in the superior temporal sulcus which have different afferent connections and functional properties.
Abstract: In the rhesus monkey, the posterior bank of the superior temporal sulcus forms part of the prestriate visual cortex and has two regions, a medial one and a lateral one, which have their own separate callosal connections. The afferent input to these two regions was studied in experiments where the corpus callosum was sectioned, and labelled amino acids were injected into other visual areas. By this method, it was found that area 17 projects to that part of the superior temporal sulcus occupied by the more medial of the two callosal inputs. By contrast, the part of the sulcus occupied by the more lateral callosal input was found to receive a strong projection from the fourth visual complex, an area rich in colour-coded cells. Recordings were made from single cells in the superior temporal sulcus in animals in which the corpus callosum had been sectioned previously. The degeneration produced by this procedure was used to provide anatomical landmarks enabling us to assign cells to the lateral or the medial regions of the sulcus. Such recordings revealed that receptive fields were topographically organized in the lateral part of the sulcus and that most cells were colour specific. By contrast, cells recorded from in the region of the more medial callosal patch within this sulcus were directionally selective, without any obvious colour coding. It was concluded from these combined anatomico-physiological experiments that there are at least two distinct regions in the superior temporal sulcus which have different afferent connections and functional properties.

Journal ArticleDOI
TL;DR: The results are consistent with the hypothesis that T cell proliferation induced by lectins, like that induced by antigens, may involve the dual recognition of stimulating ligand in association with major histocompatibility complex (la) determinants.
Abstract: Mouse lymph node cells were exposed to carbonyl iron and a magnet to remove phagocytic cells, and passed over Sephadex G-10 and nylon wool and incubated for 12 h on plastic to remove adherent cells and their precursors. More than 99 % of the cells in this macrophage-depleted population (which constituted 3-5 % of the starting population) were Thy-1+ and Ly-1+, while less than 2 % were Ly-2+. These cells usually did not synthesize detectable amounts of DNA when cultured with concanavalin A and responded poorly to phytohemagglutinin. These proliferative responses were completely reconstituted by small numbers of syngeneic or allogeneic peritoneal cells, purified peritoneal macrophages or cells from tertiary cultures of mouse embryo ‘fibroblasts’, but not by 3T3 cells, P815 mastocytoma cells or Nulli SCC-1 embryonal carcinoma cells, or by 2-mercaptoethanol. The reconstituting peritoneal cells were Thy-1−, Ia+ and present in nu/nu mice; although they had to be alive to reconstitute, they did not have to divide. These results are consistent with the hypothesis that T cell proliferation induced by lectins, like that induced by antigens, may involve the dual recognition of stimulating ligand in association with major histocompatibility complex (la) determinants.

Journal ArticleDOI
01 Dec 1977-Cell
TL;DR: It is suggested that control of murine leukemia virus replication in the cells is a function of the stage of differentiation and perhaps also of the genetic composition of the teratocarcinoma stem cells.

Journal ArticleDOI
TL;DR: It is concluded that phospholipase activity plays an important role in the action of this class of toxins at the neuromuscular junction.
Abstract: 1. Five presynaptic toxins have been isolated in pure from from the venom of Bungarus multicinctus and Bungarus caeruleus and named β1, β2, β3, β4, and β-ceruleotoxin. 2. They differ in electrophoretic mobility and amino acid composition, while all have the same molecular weight (22000) and are composed of two subunits of molecular weight 9000 and 12000. 3. The toxins have phospholipase A activity when assayed with both natural and synthetic phospholipids, and this activity requires the presence of Ca2+ ions. 4. β-Bungarotoxin (β3) binds 1 mol of Ca2+ per mol of protein and this binding induces a conformational change as detected by fluorescence measurements in the presence of the dye 8-anilino-1-naphthalene sulfonic acid. 5. The phospholipase activity of all the toxins is lost when a critical histidine residue is modified with p-bromophenancyl bromide. 6. As a result of the modification the lethality of the toxins is greatly reduced. 7. Native toxin causes a rapid decrease in amplitude of end-plate potentials, followed by a transient increase and subsequent decrease, until transmitter release is completely abolished. The modified toxin still causes the early decrease in release but toxin action does not progress to complete block. 8. The rate of blockage of transmitter release by native toxin is reduced in the presence of modified toxin. 9. It is concluded that phospholipase activity plays an important role in the action of this class of toxins at the neuromuscular junction.

Journal ArticleDOI
TL;DR: A non‐specific acid alpha‐naphthyl‐acetate esterase activity was investigated in human lymphoid cell populations from tonsils, blood, thymus and in different leukaemias, and four patterns have emerged.
Abstract: A non-specific acid alpha-naphthyl-acetate esterase activity was investigated in human lymphoid cell populations from tonsils, blood, thymus and in different leukaemias. Four patterns have emerged. (i) The vast majority of T lymphocytes (peripheral blood, tonsils) showed a localized, intense reaction product (‘T-like’). (ii) A thymocyte subpopulation expressed faint, localized enzyme activity (‘Thy-like’) but the majority of thymocytes showed no esterase activity. Some cells from acute lymphoblastic leukaemias with thymocyte surface characteristics had a ‘Thy-like’appearance. (iii) Most B lymphocytes and cells from chronic lymphocytic leukaemias were esterase negative. No activity was seen in mitogen activated peripheral blood T and B lymphoblasts from peripheral blood and in leukaemic blasts from the common form of childhood acute ‘lymphoblastic’leukaemia. (iv) Myeloid cells, including peripheral blood monocytes, and blast cells from acute myeloblastic and chronic granulocytic leukaemias showed an intense, diffuse reaction product (M-like). It is concluded that the modified esterase technique is a convenient marker for small mature human T lymphocytes in tissue sections and smears. It may also be helpful in the differential diagnosis of acute lymphoblastic leukaemia with T characteristics, the common form of acute ‘lymphoblastic’leukaemia and acute myeloblastic leukaemia.

Journal ArticleDOI
22 Dec 1977-Nature
TL;DR: To examine if spermatozoa and oocytes are already sensitive to ACh and other neurotransmitter substances, toad oocytes were taken from the ovary, kept in frog's Ringer or Merriam4 solution, and studied at room temperature, using conventional electrophysiological techniques.
Abstract: IN vertebrates, fully differentiated cells such as skeletal muscle and some nerve cells are highly sensitive to acetyl-choline (ACh), due to the presence of acetylcholine receptors in their surface membranes. In muscle fibres, the ACh-sensitivity is known to appear early during differentiation1–3, but relatively little is known about the chemical sensitivity of the membrane in the undifferentiated cell. In particular, it would be interesting to know if spermatozoa and oocytes are already sensitive to ACh and other neurotransmitter substances. To examine this question, toad (Xenopus laevis) oocytes were taken from the ovary, kept in frog's Ringer or Merriam4 solution, and studied at room temperature, using conventional electrophysiological techniques.

Journal ArticleDOI
TL;DR: In this paper, Stewartartson showed that the vorticity in the critical layer diffuses outwards until it has an effect on the imposed shear which is larger by a factor ∊−½ than that due of the wave disturbance.
Abstract: In Part I of this paper with the same title [Stewartson (1978)] the evolution of a Rossby wave of amplitude O(∊) forced on a uniform shear was studied Times t were considered such that t = O (1) and ∊½ t= O (1) and it was shown that as ∊½ t→ ∞ the vorticity in the neighbourhood of the critical layer does not tend to a limit though the velocity jump across it tends to zero The discussion concentrated on inviscid flow so that λ= R −1 ∊ −3/2 was zero In the present paper the unsteady investigation is extended to values of λ ≪ 1, and it is shown that the vorticity in the critical layer diffuses outwards until it has an effect on the imposed shear which is larger by a factor ∊−½ than that due of the wave disturbance This is corroborated by a closer examination of the Benney-Bergeron theory for λ ≪ 1 in which the correctness of the conjecture of Haberman that the vorticity must be continuous across the critical layer is demonstrated Thus in this limit also there is an O (∊½) modification to the im


Journal ArticleDOI
24 Mar 1977-Nature
TL;DR: A cell-surface antigen is described, defined by an antiserum raised in mice against a rat neural tumour cell line which is present on Schwann cells in dissociated cell culture of neonatal rat sciatic nerve, but not on fibroblasts in the same culture.
Abstract: THE use of cell-surface antigenic markers to identify and separate distinct subpopulations of lymphocytes has revolutionised immunology in recent years. It seems likely that a similar approach will be fruitful in other areas of biology. For example, recent advances in maintaining and studying cells of the nervous system in vitro have created a pressing need for cell-type-specific markers. These would allow unequivocal identification and possible purification of the many different types of neural cells so that their interactions can be studied in culture. Here we describe a cell-surface antigen, defined by an antiserum raised in mice against a rat neural tumour cell line1 which is present on Schwann cells in dissociated cell culture of neonatal rat sciatic nerve, but not on fibroblasts in the same culture. Another cell-surface antigen, Thy-1.1 (formerly called ΘAKR)2 is expressed by the fibroblasts3 and not the Schwann cells, making it possible to mark both cell types simultaneously in these cultures by using antibodies conjugated to two different fluorochromes.

Book ChapterDOI
TL;DR: It is important to review the evidence pointing to significant compartmentation of glycolytic intermediates, and to discuss the relations between the mitochondrial space and the cytoplasmic space.
Abstract: Publisher Summary This chapter discusses the relations between the mitochondrial space and the cytoplasmic space. It has been widely assumed that the cytoplasmic space can be treated, so far as intermediary metabolism is concerned, as a homogeneous space in which all the glycolytic enzymes of the cell reside, and that these enzymes and their substrates are not found elsewhere in the cell. Many sophisticated calculations depend implicitly on these assumptions. Apart from the evidence collected in other studies, this belief no doubt had its foundation in the ease with which the pioneers of biochemistry extracted glycolytic enzymes with water from broken cells, and from the methods of purifying the glycolytic enzymes worked out in Biicher's laboratory. It is important to review the evidence pointing to significant compartmentation of glycolytic intermediates.

Journal ArticleDOI
TL;DR: In normal mouse embryos developing in vivo, the first appearance of the blastocyst cavity was found to be associated more closely with developmental age, judged by cell number, than with chronological age, i.e. elapsed time since ovulation.
Abstract: In normal mouse embryos developing in vivo, the first appearance of the blastocyst cavity was found to be associated more closely with developmental age, judged by cell number, than with chronological age, i.e. elapsed time since ovulation. When development was slowed by in vitro culture, formation of the blastocoele was delayed. However, cell number itself was not a critical factor, since the number of cells per embryo could be doubled or tripled or halved by experimental manipulation without substantially affecting the timing of blastocoele formation. Experiments in which one cell division was suppressed with cytochalasin-B, leading to tetraploidy, showed that the number of cell divisions since fertilization was also not critical. A possible role is suggested either for nucleocytoplasmic ratio, or for the number of nuclear or chromosomal divisions or DNA replications since fertilization, all of which increase during cleavage.


Journal ArticleDOI
TL;DR: The data are consistent with the suggestion that there is a slight female excess among acardiac monsters and seem more likely to occur within monozygotic (MZ) pairs in higher multiple births than in MZ twins.
Abstract: The literature on acardiac monsters has been reviewed. The following conclusions were drawn: 1 The probability of their appearance seems considerably higher among monoamniotic than diamniotic monochorionic twin pairs. 2 They seem more likely to occur within monozygotic (MZ) pairs in higher multiple births than in MZ twins. 3 The data are consistent with the suggestion that there is a slight female excess among them.

Journal ArticleDOI
TL;DR: The results indicate that calcium in the bathing solution plays no important part in the generation of calcium transients during single twitches, and the calcium indicator dye arsenazo III was used to measure the calciumtransients occurring during depolarization of frog skeletal muscle fibres.
Abstract: Intracellular injection of the calcium indicator dye arsenazo III was used to measure the calcium transients occurring during depolarization of frog skeletal muscle fibres. A quantitative estimate of the rise in intracellular free calcium during a twitch was made, and the relation between membrane potential and calcium release was examined. The results also indicate that calcium in the bathing solution plays no important part in the generation of calcium transients during single twitches.

Journal ArticleDOI
TL;DR: Fornix-transected monkeys were impaired in recognition memory after brief retention intervals for short lists of either colours or spatial positions, compared with the existing evidence in human amnesic patients for a neurologically separate, intact short-term memory system.
Abstract: Fornix-transected monkeys were impaired in recognition memory after brief retention intervals for short lists of either colours or spatial positions. The results were contrasted with the existing evidence in human amnesic patients for a neurologically separate, intact short-term memory system. Present address: Department of Experimental Psychology, South Parks Road, Oxford OX1 3UD.