Telemetered electromyography of peroneus longus in Varecia variegata and Eulemur rubriventer: implications for the functional significance of a large peroneal process

A foot specialized for grasping small branches with a divergent opposable hallux (hallucal grasping) represents a key adaptive complex characterizing almost all arboreal non-human euprimates. Evolution of such grasping extremities probably allowed members of a lineage leading to the common ancestor of modern primates to access resources available in a small-branch niche, including angiosperm products and insects. A better understanding of the mechanisms by which euprimates use their feet to grasp will help clarify the functional significance of morphological differences between the euprimate grasp complex and features representing specialized grasping in other distantly related groups (e.g., marsupials and carnivorans) and in closely related fossil taxa (e.g., plesiadapiforms). In particular, among specialized graspers euprimates are uniquely characterized by a large peroneal process on the base of the first metatarsal, but the functional significance of this trait is poorly understood. We tested the hypothesis that the large size of the peroneal process corresponds to the pull of the attaching peroneus longus muscle recruited to adduct the hallux during grasping. Using telemetered electromyography on three individuals of Varecia variegata and two of Eulemur rubriventer, we found that peroneus longus does not generally exhibit activity consistent with an important function in hallucal grasping. Instead, extrinsic digital flexor muscles and, sometimes, the intrinsic adductor hallucis are active in ways that indicate a function in grasping with the hallux. Peroneus longus helps evert the foot and resists its inversion. We conclude that the large peroneal tuberosity that characterizes the hallucal metatarsal of prosimian euprimates does not correlate to "powerful" grasping with a divergent hallux in general, and cannot specifically be strongly linked to vertical clinging and climbing on small-diameter supports. Thus, the functional significance of this hallmark, euprimate feature remains to be determined.     

Ontogeny and phylogeny in papionin primates

This study investigates the developmental bases of size and shape variation in papionin primates (Macaca, Cercocebus, Mandrillus, Lophocebus, and Papio). The analysis tests hypotheses predicting that heterochronic changes in ontogeny, particularly in the degree of overall size growth, can account for cranial diversity and "allometric scaling" in this clade. Large developmental samples of extant papionin crania are examined to test heterochronic hypotheses using bivariate allometric methods. Analyses indicate that the crania of larger papionins (Mandrillus and Papio) are generally peramorphic, surpassing size and shape ranges of smaller, and probably less-derived, macaques and mangabeys. At least two heterochronic processes, including acceleration and hypermorphosis, can account for this pattern. Ontogenetic changes include decoupling of growth and development among cranial regions, along with simple shifts in size. Allometric scaling has complex developmental bases. Size change itself is not sufficient to explain all developmental differences among papionins, but these changes are extremely important in comparisons within cranial regions such as the face. Results imply that Papio exhibits strongly derived patterns of brain growth that impact postnatal patterns of size and shape transformation. Consideration of these results in the context of recent socioecological analyses suggests that derived patterns of cranial growth in Papio may be a response to selection during the early periods of ontogeny, resulting in a distinctive life history pattern.     

Ontoaenetic correlates of diet in anthropoid primates

This study assesses ontogenetic correlates of diet in anthropoid primates. Associations between body weight growth, adult size, and diet are evaluated for a sample of 42 primate species, of which 8 are classifiable as “folivores.” The hypothesis that folivores show a pattern of growth that differs from “nonfolivores” is tested. Ontogenetic variation is summarized through use of parametric and nonparametric regression analysis. Several analytical techniques, including broad interspecific and detailed comparisons among species of similar adult size, are applied. This investigation indicates a clear association between body weight ontogeny and diet: folivorous species grow more rapidly over a shorter duration than comprably sized nonfolivorus species. A positive correlation between adult size and diet is not unambiguously established in this sample. A threshold (at around 1 kg) below which insectivory is very common may adequately characterize the association between adult size and diet in anthropoid primates. Above this threshold, adult size does not appear to covary predictably with diet. Evolutionary correlates of the ontogenetic pattern seen in folivores may include a variety of factors. The distinctive pattern of development in folivores may relate to the profile of ecological and social risks that these species face. Morphophysiological advantages to rapid growth may relate to a need for accelerated alimentary (dental and gut) development. The implications of ontogenetic variation in folivores are discussed. © 1994 Wiley-Liss, Inc.     

Effects of limb mass distribution on the ontogeny of quadrupedalism in infant baboons (Papio cynocephalus) and implications for the evolution of primate quadrupedalism

Primate quadrupedal kinematics differ from those of other mammals. Several researchers have suggested that primate kinematics are adaptive for safe travel in an arboreal, small-branch niche. This study tests a compatible hypothesis that primate kinematics are related to their limb mass distribution patterns. Primates have more distally concentrated limb mass than most other mammals due to their grasping hands and feet. Experimental studies have shown that increasing distal limb mass by adding weights to the limbs of humans and dogs influences kinematics. Adding weights to distal limb elements increases the natural period of a limb's oscillation, leading to relatively long swing and stride durations. It is therefore possible that primates' distal limb mass is responsible for some of their unique kinematics. This hypothesis was tested using a longitudinal ontogenetic sample of infant baboons (Papio cynocephalus). Because limb mass distribution changes with age in infant primates, this project examined how these changes influence locomotor kinematics within individuals. The baboons in this sample showed a shift in their kinematics as their limb mass distributions changed during ontogeny. When their limb mass was most distally concentrated (at young ages), stride frequencies were relatively low, stride lengths were relatively long, and stance durations were relatively long compared to older ages when limb mass was more proximally concentrated. These results suggest that the evolution of primate quadrupedal kinematics was tied to the evolution of grasping hands and feet.     

Electromyography of back muscles during quadrupedal and bipedal walking in primates

Despite the extensive electromyographic research that has addressed limb muscle function during primate quadrupedalism, the role of the back muscles in this locomotor behavior has remained undocumented. We report here the results of an electromyographic (EMG) analysis of three intrinsic back muscles (multifidus, longissimus, and iliocostalis) in the baboon (Papio anubis), chimpanzee (Pan troglodytes), and orangutan (Pongo pygmaeus) during quadrupedal walking. The recruitment patterns of these three back muscles are compared to those reported for the same muscles during nonprimate quadrupedalism. In addition, the function of the back muscles during quadrupedalism and bipedalism in the two hominoids is compared. Results indicate that the back muscles restrict trunk movements during quadrupedalism by contracting with the touchdown of one or both feet, with more consistent activity associated with touchdown of the contralateral foot. Moreover, despite reported differences in their gait preferences and forelimb muscle EMG patterns, primates and nonprimate mammals recruit their back muscles in an essentially similar fashion during quadrupedal walking. These quadrupedal EMG patterns also resemble those reported for chimpanzees, gibbons and humans (but not orangutans) walking bipedally. The fundamental similarity in back muscle function across species and locomotor behaviors is consistent with other data pointing to conservatism in the evolution of the neural control of tetrapod limb movement, but does not preclude the suggestion (based on forelimb muscle EMG and spinal lesion studies) that some aspects of primate neural circuitry are unique. © 1994 Wiley-Liss, Inc.     

Temporal progress of muscle adaptation to endurance training in hind limb muscles of young rats

Summary The soleus, rectus femoris and gastrocnemius muscles of young rats were studied after 3, 6 and 12 weeks of treadmill training. The muscle fibers were characterized histochemically by their succinate dehydrogenase (SDH) and myofibrillar ATPase activity, and morphometrically by their cross-sectional areas, which were corrected for different body weights of control and trained animals.After 12 weeks of training the mean area of fibers in the muscles studied was not significantly different from the controls, as expected. In the soleus muscle the percentage of the fast-twitch fibers was decreased as a result of their transformation into slow-twitch fibers. Trained soleus muscles were the only muscles showing pathologically altered fibers, suggesting overload. The percentages of fiber types and their areas exhibited changes specific for the muscles and muscle regions studied.From these results it is concluded that the adaptation follows the sequence proportional adaptation of morphometrical parameters, disproportional adaptation of the areas of fiber types, and disproportional adaptation of the percentages and/or the areas of the fiber types. It is shown by comparison with the literature that this sequence may be generalized to a sequence of increasing expense necessary for the adaptation to increasing stimuli, and that the most decisive factors for adaptation are work load, frequency of exercise, period of training, and the age of the subject at the initiation of the training.     

Stimulation and inhibition of resting muscle thermogenesis by vasoconstrictors in perfused rat hind limb

Angiotensin (AII) and serotonin (5-HT) are both vasoconstrictors of the constant-flow perfused rat hind limb that have opposite effects on thermogenesis, possibly the result of differing effects on vascular flow distribution between nutritive and non-nutritive pathways. In the present study interaction between the two opposing agents was examined with the expectation that the combined presence would show additive effects on pressure and mutually neutralizing effects on thermogenesis. Thus doses of AII and 5-HT that gave similar, but opposite, quantitative effects on thermogenesis were infused alone, in combination one after the other, or in combination with the order reversed, and the effects on perfusion pressure (PP) and thermogenesis (oxygen uptake, VO2) were compared. AII (3 nM) alone increased PP by 15+/-1 mmHg (1 mmHg = 133.3 Pa) and VO2 by 3.1-/+0.2 micromol.h(-1).g(-1), whereas 5-HT (1 microM) alone increased PP by 75+/-6 mmHg and inhibited VO2 by 3.9+/-0.2 micromol.h(-1).g(-1). When added in combination, the outcome depended on the order of addition. Following AII, infusion of 5-HT further increased PP by 160+/-11 mmHg and decreased VO2 by 6.3+/-0.2 micromol.h(-1)g(-1). Following 5-HT, infusion of AII further increased PP by 28+/-4 mmHg and increased VO2 by only 1.8+/-0.3 micromol.h(-1).g(-1). The prior presence of 5-HT (1 microM) shifted the AII dose-response curves for VO2 and pressure to the right and left, respectively. The prior infusion of AII increased the dose-dependent response to 5-HT in terms of both the inhibition of VO2 and the increase in PP. At low doses of 5-HT (10(-8)-10(-7) M), but not alpha-methyl serotonin (alphaMT), there was a marked vasodilatation-associated inhibition of AII-mediated increase in VO2. Overall the data show that the combined effect of AII and 5-HT differed from the simple addition of each separately. Since the order of addition appears to be critical in terms of thermogenic outcome, it is concluded that each vasoconstrictor exerts a specific hemodynamic action to affect access of the other to vascular receptor sites. These findings are consistent with the previously reported effects of these vasoconstrictors on substrate and insulin access to muscle of the perfused rat hind limb.     

The incidence and properties of beta axons to muscle spindles in the cat hind limb.

The distribution of beta axons to muscle spindles in the tenuissimus and abductor digiti quinti medius (A.D.Q.M.) muscles of the hind limb of the cat was determined by testing the action of single motor axons, capable of producing extrafusal contraction, isolated in the ventral spinal roots on the discharges of individual muscle spindle primary sensory endings recorded in the dorsal spinal roots. The proportion of spindles with beta innervation was 41% in A.D.Q.M. and 30% in tenuissimus. The proportion of fast motor axons that were beta axons was 28% in the A.D.Q.M. and 11% in tenuissimus; usually each beta axon innervated a single spindle while no spindle received more than two beta axons. The beta axons were dynamic in nature and those to any one muscle tended to have slightly lower conduction velocities than the alpha axons though some overlap did occur. The extent to which beta axons can account for the fact that in isolated spindles axons selective to either nuclear bag or nuclear chain fibres are found in about equal proportions whereas a ratio of three static to one dynamic gamma axons is found electrophysiologically is discussed. An explanation for the low incidence of beta innervation previously found electrophysiologically and the considerably higher incidence found histologically is given.     

Histological and histochemical comparisons of muscle spindles in three hind limb muscles of the guinea pig.

Guinea pig soleus, medial gastrocnemius and vastus lateralis muscles were compared for spindle density and distribution, number of intrafusal fibers per spindle and histochemical appearance of the axial bundle. A total of 326 spindles was used in the comparisons. Spindle density was over four times greater in the soleus than in either the medial gastrocnemius or vastus lateralis. In the soleus the spindles were distributed at random, but in the other two muscles no spindles were found in those fascicles in which fast-twitch glycolytic extrafusal fibers predominated. The average number of intrafusal fibers per spindle varied by less than 5% between the three kinds of muscles. About 80% of all spindles located had four intrafusal fibers, two of the nuclear bag type and two of the nuclear chain type. The histochemical appearance of the axial bundle was the same in each kind of muscle. Based on intensities of the myofibrillar adenosine triphosphatase reaction product at polar regions nuclear bag fibers were separable into two histochemical groups; nuclear chain fibers were of only one histochemical type.     

川芎及两种主要药效成分对废用性肌萎缩的影响

目的：探讨川芎及川芎中起活血作用的两种主要药效成分（阿魏酸钠和川芎嗪）对后肢去负荷大鼠比目鱼肌萎缩的影响与作用。方法：尾部悬吊法建立大鼠废用性肌萎缩模型,用免疫组化技术及血液流变学方法观察药物对比目鱼肌各项指标的影响。结果：与后肢去负荷大鼠相比①高剂量的阿魏酸钠和川芎嗪使比目鱼肌I型肌纤维横截面积分别增加了37.3%和39.4%（P〈0.05）;②三种药物均能明显抑制梭外肌纤维MHCII表达水平的升高（P〈0.01）;③使肌梭内核袋2纤维MHCII的表达由阳性转变为阴性;④并能明显降低低切变率下的全血粘度。结论：川芎及两种主要药效成分阿魏酸钠与川芎嗪均能不同程度地对抗废用性肌萎缩的发生,以高剂量川芎嗪与阿魏酸钠的药效最为明显。     

Expression of nestin,desmin and vimentin in intact and regenerating muscle spindles of rat hind limb skeletal muscles

We describe the expression and distribution patterns of nestin, desmin and vimentin in intact and regenerating muscle spindles of the rat hind limb skeletal muscles. Regeneration was induced by intramuscular isotransplantation of extensor digitorum longus (EDL) or soleus muscles from 15-day-old rats into the EDL muscle of adult female inbred Lewis rats. The host muscles with grafts were excised after 7-, 16-, 21- and 29-day survival and immunohistochemically stained. Nestin expression in intact spindles in host muscles was restricted to Schwann cells of sensory and motor nerves. In transplanted muscles, however, nestin expression was also found in regenerating “spindle fibers”, 7 and 16 days after grafting. From the 21st day onwards, the regenerated spindle fibers were devoid of nestin immunoreactivity. Desmin was detected in spindle fibers at all developmental stages in regenerating as well as in intact spindles. Vimentin was expressed in cells of the outer and inner capsules of all muscle spindles and in newly formed myoblasts and myotubes of regenerating spindles 7 days after grafting. Our results show that the expression pattern of these intermediate filaments in regenerating spindle fibers corresponds to that found in regenerating extrafusal fibers, which supports our earlier suggestion that they resemble small-diameter extrafusal fibers.     

Heterochronic differences of Hoxa-11 expression in Xenopus fore- and hind limb development: Evidence for lower limb identity of the anuran ankle bones

 The wrist (carpus) and ankle (tarsus) of most tetrapods, as well as the wrist of anurans, contains relatively small nodular skeletal elements. The anuran tarsus, however, comprises a pair of long bones, the proximal tarsals tibiale and fibulare, which resemble the lower leg bones, tibia and fibula (zeugopodium). In this paper we investigate whether the proximal tarsals of Xenopus are of zeugopodial character identity, i.e. whether they develop under the influence of the same genes that pattern the lower limb. We compare Hoxa-11 expression in the forelimb bud with that in the hind limb bud by whole-mount in situ hybridization. Hoxa-11 has been implicated in the development of the lower limb. In Xenopus we note three differences between Hoxa-11 expression in fore- and hind limb buds: (1) Hoxa-11 expression is maintained until the hind limb bud reaches a larger size (2 mm) than that of the forelimb bud (1.5 mm); (2) Hoxa-11 expression is maintained over larger spatial domains than in the forelimb; and (3) Hoxa-11 expression has a pronounced posterior polarity in the hind limb, but not in the forelimb. Hind limb expression of Hoxa-11 can be understood as a heterochronic prolonging of the expression dynamic in the forelimb. Finally we found that the proximal tarsals start to develop within the expression domain of Hoxa-11, while in the forelimb the lower arm elements reach the distal expression limit of Hoxa-11. The gene expression data presented here support the notion of a zeugopodial identity of the proximal tarsal elements in Xenopus. Received: 20 January 1998 / Accepted: 27 March 1998     

Ontogeny of limb force distribution in squirrel monkeys (Saimiri boliviensis): insights into the mechanical bases of primate hind limb dominance

The distribution of peak vertical forces between the forelimbs and the hind limbs is one of the key traits distinguishing primate quadrupedal locomotion from that of other mammals. Whereas most mammals generate greater peak vertical forelimb forces, primates generate greater peak vertical hind limb forces. At the ultimate level, hind limb dominance in limb force distribution is typically interpreted as an adaptation to facilitate fine-branch arboreality. However, the proximate biomechanical bases for primate limb force distribution remain controversial. Three models have been previously proposed. The Center of Mass (COM) Position model attributes primates’ unique mode of limb loading to differences in the position of the whole-body COM relative to the hands and feet. The Active Weight Shift model asserts that primates actively redistribute body weight to their hind limbs by pitching the trunk up via the activation of hind limb retractor muscles. Finally, the Limb Compliance model argues that primates selectively mitigate forelimb forces by maintaining a compliant forelimb and a flat shoulder trajectory. Here, a detailed dataset of ontogenetic changes in morphology and locomotor mechanics in Bolivian squirrel monkeys (Saimiri boliviensis) was employed as a model system to evaluate each of these proposed models in turn. Over the first 10 months of life, squirrel monkeys transitioned from forelimb dominant infants to hind limb dominant juveniles, a change that was precipitated by decreases in peak vertical forelimb forces and increases in peak vertical hind limb forces. Results provided some support for all three of the models, although the COM Position and Active Weight Shift models were most strongly supported by the data. Overall, this study suggests that primates may use a variety of biomechanical strategies to achieve hind limb dominance in limb force distribution.     

香石竹的脱病毒苗与带病毒苗生长发育特性比较

以香石竹(DianthuscaryophyllusL.)带病毒组培苗和扦插苗作为对照,研究香石竹脱病毒苗在苗期和花期的生长发育特性.实验结果表明,在苗期,香石竹脱病毒苗在株高、叶片数、分枝数、叶面积和根、茎、叶的干重等大多数营养生长发育指标明显优于对照.在花期,脱病毒苗在花苞和花朵直径,花枝高度和粗度等花质量指标明显优于对照,且脱掉病毒显著提高了花产量,缩短了生长发育期.     

Fusimotor reflexes influencing secondary muscle spindle afferents from flexor and extensor muscles in the hind limb of the cat.

The purpose of this study was to investigate secondary muscle spindle afferents from the triceps-plantaris (GS) and posterior biceps and semitendinosus (PBSt) muscles with respect to their fusimotor reflex control from different types of peripheral nerves and receptors. The activity of single secondary muscle spindle afferents was recorded from dissected and cut dorsal root filaments in alpha-chloralose anaesthetized cats. Both single spindle afferents and sets of simultaneously recorded units (2-3) were investigated. The modulation and mean rate of firing of the afferent response to sinusoidal stretching of the GS and PBSts muscle were determined. Control measurements were performed in the absence of any reflex stimulation, while test measurements were made during reflex stimulation. The reflex stimuli consisted of manually performed movements of the contralateral hind limb, muscle stretches, ligament tractions and electrical stimulations of cutaneous afferents. Altogether 21 secondary spindle afferents were investigated and 20 different reflex stimuli were employed. The general responsiveness (i.e. number of significant reflex effects/number of control-test series) was 52.4%, but a considerable variation between different stimuli was found, with the highest (89.9%) for contralateral whole limb extension and the lowest (25.0%) for stretch of the contralateral GS muscle. The size of the response to a given stimulus varied considerably between different afferents, and, in the same afferent, different reflex stimuli produced effects of varying size. Most responses were characterized by an increase in mean rate of discharge combined with a decrease in modulation, indicative of static fusimotor drive (Cussons et al., 1977). Since the secondary muscle spindle afferents are part of a positive feedback loop, projecting back to both static and dynamic fusimotor neurones (Appelberg Et al., 1892 a, 1983 b; Appelberg et al., 1986), it is suggested that the activity in the loop may work like an amplified which, during some circumstances, enhance the effect of other reflex inputs to the system (Johansson et al., 1991 b).     

Kinetics of leaping primates: Influence of substrate orientation and compliance

Our current knowledge about the forces leapers generate and absorb is very limited and based exclusively on rigid force platform measurements. In their natural environments, however, leapers take off and land on branches and tree trunks, and these may be compliant. We evaluated the influence of substrate properties on leaping kinetics in prosimian leapers by using a combined field and laboratory approach. Tree sway and the timing of takeoffs relative to the movements of trees were documented for animals under natural conditions in Madagascar. Field data collected on three species (Indriindri, Propithecus diadema, Propithecus verreauxi) indicate that in the majority of takeoffs, the substrate sways and the animals takeoff before the elastic rebound of the substrate. This implies that force is “wasted” to deform supports. Takeoff and landing forces were measured in an experimental setting with a compliant force pole at the Duke University Primate Center. Forces were recorded for 2 Propithecus verreauxi and 3 Hapalemur griseus. Peak takeoff forces were 9.6 (P. verreauxi) and 10.3 (H. griseus) times body weight, whereas peak landing forces were 6.7 (P. verreauxi) and 8.4 (H. griseus) times body weight. As part of the impulse generated does not translate into leaping distance but is used to deform the pole, greater effort is required to reach a given target substrate, and, consequently, takeoff forces are high. The landing forces, on the other hand, are damped by the pole/substrate yield that increases the time available for deceleration. Our results contrast with previous studies of leaping forces recorded with rigid platform measuring systems that usually report higher landing than takeoff forces. We conclude that 1) Leapers generate and are exposed to exceptionally high locomotory forces. The takeoff forces are higher than the landing forces when using compliant supports, indicating that the takeoff rather than the landing may be critical in interpreting leaping behavior and related aspects of muscu-loskeletal design. 2) Large-bodied vertical clingers and leapers do not usually take advantage of the elastic energy stored in substrates. Rather, force (and energy) is wasted to deform compliant supports. 3) A compliant force pole approximates the conditions faced by large-bodied vertical clingers and leapers in the wild more closely than do rigid force platforms. © 1995 Wiley-Liss, Inc.     

The distribution of heavy-chain isoforms of myosin in airways smooth muscle from adult and neonate humans.

ATP synthesis by oxidative phosphorylation in Escherichia coli occurs in catalytic sites on the beta-subunits of F1-ATPase. Random mutagenesis of the beta-subunit combined with phenotypic screening is potentially important for studies of the catalytic mechanism. However, when applied to haploid strains, this approach is hampered by a preponderance of mutants in which assembly of F1-ATPase in vivo is defective, precluding enzyme purification. Here we mutagenized plasmids carrying the uncD (beta-subunit) gene with hydroxylamine or N-methyl-N'-nitro-N-nitrosoguanidine and isolated, by phenotypic screening and complementation tests, six plasmids carrying mutant uncD alleles. When the mutant plasmids were used to transform a suitable uncD- strain, assembly of F1-ATPase in vivo occurred in each case. Moreover, in one case (beta Gly-223----Asp) F1-ATPase assembly proceeded although it had previously been reported that this mutation, when present on the chromosome of a haploid strain, prevented assembly of the enzyme in vivo. Therefore, this work demonstrates an improved approach for random mutagenesis of the F1-beta-subunit. Six new mutant uncD alleles were identified: beta Cys-137----Tyr; beta Gly-142----Asp; beta Gly-146----Ser; beta Gly-207----Asp; beta-Gly-223----Asp; and a double mutant beta Pro-403----Ser,Gly-415----Asp which we could not separate. The first five of these lie within or very close to the predicted catalytic nucleotide-binding domain of the beta-subunit. The double mutant lies outside this domain; we speculate that the region around residues beta 403-415 is part of an alpha-beta intersubunit contact surface. Membrane ATPase and ATP-driven proton pumping activities were impaired by all six mutations. Purified F1-ATPase was obtained from each mutant and shown to have impaired specific ATPase activity.     

Dynamics of calcium levels and changes SERCA content in muscle fibers of rats and Mongolian gerbils during hind limb unloadings of various duration

In this study, it was shown that calcium levels in the fibers of m. soleus of Mongolian gerbils after one day of unloading increased four and a half times in comparison with the control. In rats, the situation differed: 2.8 times increase after the 1st day of hypogravity persisted until the 3rd day and then calcium levels slightly decreased to the 12th day. However, the base concentrations of calcium in the control group of gerbils were significantly lower than in control rats, thus there was larger shift of this parameter during the first day. Probably, this was the reason for an earlier start of the protein phenotype shift in gerbils: statistically significant increase in the number of fibers with "fast" SERCA isoforms was detected after one day of unloading and therefore slow-to-fast shift in myosin phenotype was observed on the 3rd day of unloading. The same changes in rat muscle could be detected only after the 7th and the 12th day, respectively. In both species, there was a tendency to restore their initial parameters to the 12th day but in gerbils it was much more intensive.     

Development of hind limb bones in chicken embryos under altered temperature and humidity conditions

The data on growth and development of hind limb bones in chicken embryos under normal (standard) and altered incubation conditions are presented.