A calcium-citro-phosphate technique for the histochemical localization of myosin ATPase

Soluble calcium-binding proteins (SCBPs) of the earthworm Lumbricus terrestris: molecular characterization and localization by FISH in muscle and neuronal tissue

Soluble calcium-binding proteins (SCBPs) of invertebrates probably serve like their vertebrate counterpart-the parvalbumins-as soluble relaxing factors in muscles. Three SCBP isoforms (SCBP_1-3) have been isolated and biochemically characterized in the earthworm Lumbricus terrestris (Huch et al. in J Comp Physiol B 158:325-334, 1988). For SCBP₂, we found two isoforms named SCBP_2a/2b. Both of them together with SCBP₃ are present in the body wall muscle. In the gizzard solely, SCBP_2b and no SCBP_2a or SCBP₃ could be detected. The coding sequences of all three isoforms consist of 534 bp for 178 amino acids and contain four EF-hand motifs, of which the second EF-hands are truncated. Recombinant proteins show heat stability and a Ca²⁺-dependent mobility shift similar to the native proteins, indicating comparable calcium-binding properties. All three isoforms are encoded by three distinct and differentially expressed genes. The genes for SCBP_2a, SCBP_2b, and SCBP₃ are interrupted by only one intron, inserting at nearly the same positions. Northern blot analysis revealed two mRNA transcripts for SCBP₂ of approximately 1250 and 1500 kb and one transcript for SCBP₃ of approximately 1250 kb. SCBP mRNA was localized by fluorescent in situ hybridization in the body wall and the gizzard. The distribution of the staining intensities resembles that for the myosin ATPase activity and indicates a correlation between the amount of SCBP and speed of muscle contraction. In addition, SCBP mRNA was localized within the nervous tissue, the cerebral and subesophageal ganglia and the ventral nerve cord.

Age and exercise effects on mitochondrial density and capillary fibre ratio in bird leg muscle

1. Muscle fibre composition, capillary-fibre ratio and mitochondrial density of the Iliotibialis lateralis muscle were monitored during growth from the age of 8 weeks to sexual maturity (24 weeks) in sedentary birds and in birds subjected to regular treadmill exercise. 2. The Iliotibialis lateralis muscle consists almost exclusively of type IIA and IIB fibres with a small percentage of "unclassified" fibres. Over the 16-week period of growth there was no change in fibre composition but a marked fibre hypertrophy linked with a fall in the capillary-fibre ratio. Mitochondrial volume density increased with age but this was not significant. 3. Exercise significantly increased the IIA:IIB fibres ratio from 0.77 to 1.1 but had no significant effect on any other measured characteristics. 4. It is concluded that exercise at the intensity and duration employed (10-15 min daily, ca. 70-80% maximum oxygen consumption) has little effect on the growth and development of avian skeletal muscle although there was evidence of an increased oxidative capacity of the muscle.

The influence of motor unit composition and stature on fractionated patellar reflex times in untrained men

The purpose of the present study was to investigate the influence of muscle fibre composition and stature on fractionated patellar reflex times in ten healthy untrained men (mean age: 23.3 years, SD 3.1; mass: 65.9 kg, SD 8.5; height: 172.3 cm, SD 5.3). Biopsies were taken from the right vastus lateralis muscle. Using staining for myofibrillar adenosine triphosphatase after pre-incubation at pH 4.3 and 4.6, muscle fibres were classified into slow twitch (ST), fast twitch, oxidative-glycolytic (FTa) and fast twitch, glycolytic (FTb) fibres. Total patellar reflex time (TRT) and its fractionated components--reflex latency (LAT) and reflex motor time (MT)--were obtained from the mean of ten trials in each subject whilst performing Jendrassik's maneuvre. The TRT, LAT and MT were 77.7 ms, SD 16.5, 23.4 ms, SD 1.3 and 54.2 ms, SD 16.3, respectively. The LAT was significantly correlated to the percentage number of ST (r = 0.758, P less than 0.05) and FTa fibres (r = -0.657, P less than 0.05), fast twitch:slow twitch ratio (r = -0.799, P less than 0.01) and to the height of the subjects (r = 0.901, P less than 0.001), whereas TRT and MT were not significantly correlated with either fibre types or the height of the subjects. From these results it can be concluded that the LAT during the patellar reflex is influenced by muscle fibre composition and the length of the sensory and/or motor nerve.

Treadmill exercise training increases the oxidative capacity of chicken iliotibialis muscle

The number of fibers staining for the oxidative enzyme succinic dehydrogenase (SDH) was measured in the iliotibialis lateralis caudalis muscle of the domestic fowl before treadmill training and after 6 wk and 15 wk of training, respectively. This leg muscle contains exclusively fast-twitch or type II fibers, and before exercise training approximately 40% of these stained intensely for SDH. After 6 and 15 wk training this proportion rose to approximately 50 and 60%, respectively. Most of these highly oxidative fibers also stained weakly for the glycolytic enzyme alpha-glycerophosphate dehydrogenase (alpha-GPDH) and belonged to the fast-twitch oxidative category. Most of the poorly oxidative fibers stained strongly for alpha-GPDH and therefore belonged to the fast-twitch glycolytic category. It is concluded that exercise training in birds can bring about adaptive changes in the oxidative capacity of skeletal muscle similar to those that have been observed in man and other mammals.

Histochemical classification of neck and limb muscle fibers in a turtle, Pseudemys scripta: a study using microphotometry and cluster analysis techniques

We have attempted to develop an objective, semiquantitative classification of fiber types in turtle neck and limb muscle using microphotometry and multivariate statistical techniques. We first stained serial sections for myosin adenosine triphosphatase (ATPase) (with acid and alkaline preincubation and without preincubation), NADH-diaphorase, and two glycolysis-associated markers, alpha-glycerophosphate dehydrogenase (alpha-GPDH) and glycogen phosphorylase A (GPA). This allowed us to characterize individual muscle fibers in terms of their contraction speed and metabolic properties. Next we used microphotometry to measure the optical density of the reaction product in each fiber, and we subjected the resulting optical density matrix to cluster and discriminant function analyses in order to assign fibers to groups (fiber types) and to determine which stains contribute most to the distinction between groups. As a control, we processed a well characterized mammalian muscle (rat sternomastoid) simultaneously. Our results suggest that both neck and limb muscle in Pseudemys can best be described as falling into three groups: 1) slow oxidative (SO) fibers; 2) fast oxidative glycolytic (FOG) fibers, with relatively high oxidative and glycolytic capacities; and 3) fast glycolytic (Fg) fibers, with low oxidative, low/intermediate alpha-GPDH, and high GPA activities. These three fiber types differ from like-named types in rat muscle both in the pH lability of their myosins and in their metabolic profiles.

Characterization of a prostaglandin dysfunction myopathy

Inhibition of prostaglandin synthesis in chicken embryos generated a myopathy characterized by ringbinden, loss of Z disks and thick and thin filaments from the myofibrillar apparatus. During the early stages of myogenesis there was also abnormal clustering and contacts between the developing myotubes. This disruption of myofibrillar apparatus occurred in both primary and secondary myotubes. There was also a slight increase in the proportion of type 1 fibers, which resulted from a selective absence of type 2 fibers. The number of motoneurons in the lumbar spinal cord was normal. This, along with the nature of the disruption of the myofibrillar apparatus, was taken as an indication that the generation of this myopathy was not secondary to abnormal motoneuron development.

Quantitative analysis of cervical musculature in rats: histochemical composition and motor pool organization. I. Muscles of the spinal accessory complex

In this paper we characterize the architecture and segmental innervation, histochemical composition, muscle spindle populations, and motor pool organization of rat spinal accessory (SA) muscles: sternomastoid (SM), cleidomastoid (CM), cleidotrapezius (CT), and acromiotrapezius (AT). We also consider whether individual rat neck muscles are supplied by more than one population of motor neurons as they are in turtles and cats and whether in SA muscles motor neuron size scales with target muscle fiber type. SM, CM, and CT are ventral, parallel strap muscles. Each can be divided into grossly visible white and red compartments. AT is a dorsolateral sheetlike muscle that shows no gross compartmentalization. All four muscles are dominated by fast-twitch glycolytic (FG) and fast oxidative glycolytic (FOG) fibers, and FG fibers are significantly more numerous than the FOG type in three out of four muscles. Thus SA muscles in rats appear to be specialized for rapid, phasic head movements. Topographical analyses revealed that there is a striking compartmentalization of fiber types in the ventral muscles that corresponds to the red and white segments seen grossly. Spindles are found only in regions containing slow-twitch oxidative (SO) fibers. Cross-muscle comparisons indicate that there are significant differences between SA muscles in their fiber type composition. The motor pools of SA muscles form a single column from lower medulla to C5. Rostral cells lie dorsomedially in the ventral horn and, at the C1/C2 junction, the column shifts ventrolaterally. Within this column, each motor pool occupies a characteristic rostrocaudal position in the order SM:CM:CT:AT. Thus SM and (in part) CM motor neurons lie more medially than cells supplying the trapezius complex, suggesting that they may be under different patterns of synaptic drive. We saw no evidence that rat SA muscles are supplied by more than one population of motor neurons. Direct comparisons between the soma sizes of motor neurons that supply muscles or parts of muscles with significantly different histochemical compositions indicate that these size differences are in the direction predicted from their histochemical profiles, thus suggesting that in these muscles motor neuron soma size may scale with muscle fiber type.

Dynamic properties of fiber bundles from the rat sternomastoid muscle

The sternomastoid muscle of the rat can be subdivided into a "white" and "red" portion. The red portion predominantly contains type IIA fibers and the white portion type IIB fibers. Fiber bundles were dissected from the two parts of the muscle and their dynamic properties determined; both showed "fast-twitch" type characteristics. Small, but significant, differences were found in their isometric properties. Their force-velocity relationships were identical, although the maximum speed of sarcomere shortening (about 40 microns s-1) was significantly less than that of other fast-twitch rat muscles. Other differences in the respective force-length relations at different temperatures were noted. The desirability of pursuing these investigations on identified single fibers is emphasized.

Histochemical and cytochemical demonstration of Ca++-ATPase activity in the stellate cells of the adenohypophysis of the guinea pig

The histo- and cytochemical localization of Ca++-ATPase activity in the adenohypophysis of the guinea pig was studied utilizing a newly developed method (Ando et al. 1981). An intense reaction was observed in the wall of the blood vessels and between non-secretory cells (stellate cells) and endocrine cells of the pars distalis. Under the electron microscope the Ca++-ATPase reaction product was located extracellularly in relation to the plasmalemma of the stellate cells. This reaction was dependent on Ca++ and the substrate, ATP, and reduced by the addition of 0,1 mM quercetin to the standard incubation medium. Preheating of the sections before incubation completely inhibited the enzyme activity. When Mg++ in different concentrations were substituted for Ca++ in the incubation medium the reaction was always reduced. Both Ca++ and Mg++ in the incubation medium also reduced the reaction. The plasmalemma of the endocrine cells contains no demonstrable amount of Ca++-ATPase activity. The function of the Ca++-ATPase activity is discussed in relation to the regulation of the extracellular Ca++ concentration which seems to be important with respect not only to the secretory process of the endocrine cells but also to the metabolism of the adenohypophysis.

Ultracytochemical study of Ca++-ATPase and K+-NPPase activities in retinal photoreceptors of the guinea pig

Ca++-ATPase activity was demonstrated histochemically at light- and electron-microscopic levels in inner and outer segments of retinal photoreceptor cells of the guinea pig with the use of a newly developed one-step lead-citrate method (Ando et al. 1981). The localization of ouabain-sensitive, K+-dependent p-nitrophenylphosphatase (K+-NPPase) activity, which represents the second dephosphorylative step of the Na+-K+-ATPase system, was studied by use of the one-step method newly adapted for ultracytochemistry (Mayahara et al. 1980). In retinal photoreceptor cells fixed for 15 min in 2% paraformaldehyde the electron-dense Ca++-ATPase reaction product accumulated significantly on the inner membranes of the mitochondria but not on the plasmalemma or other cytoplasmic elements of the inner segments. The membranes of the outer segments remained unstained except the membrane arrays in close apposition to the retinal pigment epithelium. The cytochemical reaction was Ca++- and substrate-dependent and showed sensitivity to oligomycin. When Mg++-ions were used instead of Ca++-ions, a distinct reaction was also found on mitochondrial inner membranes. In contrast to the localization of the Ca++-ATPase activity, the K+-NPPase activity was demonstrated only on the plasmalemma of the inner segments, but not on the mitochondria, other cytoplasmic elements or the outer segment membranes. This reaction was almost completely abolished by ouabain or by elimination of K+ from the incubation medium.

Ultracytochemical localization of Ca++-ATPase activity in the paraphyseal epithelial cells of the frog, Rana esculenta

Ca++-ATPase activity was studied ultracytochemically (cf. Ando et al. 1981) in the paraphysis cerebri of the frog. An intense reaction was demonstrated on the plasmalemma of the microvilli at the apical pole of paraphyseal cells; in contrast, the basolateral plasmalemma showed only a slight staining. In addition, mitochondria, gap junctions, cilia, and cytoplasmic elements (e.g., microfilaments) displayed Ca++-ATPase activity. Variation of the Ca++-concentration in the incubation medium from 0.1 mM to 100 mM altered the Ca++-ATPase activity of the cell organelles. The substitution of Ca- by Mg-ions resulted in a conspicuous decrease in the enzyme activity, especially on the apical plasmalemma. Ca++-ATPase activity is claimed to be involved in a number of extra- and intracellular functions. In comparison to the epithelium of the adjacent choroid plexus the paraphyseal epithelial cell is thought to be a principal Ca-ion regulator of the cerebrospinal fluid in frogs.

The contractile properties, histochemistry, ultrastructure and electrophysiology of the cricothyroid and posterior cricoarytenoid muscles in the rat

The contractile, histochemical, morphological and electrophysiological properties of two rat laryngeal muscles, the cricothyroid and posterior cricoarytenoid, have been measured. Both muscles act during respiration to maintain upper airway patency and an even distribution of air in the lungs. The cricothyroid and posterior cricoarytenoid are fast-twitch muscles, having contraction times of 3.4 and 7.2 ms respectively, high myosin ATPase activity, abundant sarcoplasmic reticulum (with average volumes of 9% and 15%, respectively, of the fibre volume) and T-system membrane (with average areas of 0.4 and 0.5 micron 2 micron -3 of fibre). The large areas of T-tubule membrane are reflected in the average specific membrane capacities of 6.5 muF cm-2 to 10.5 muF cm-2, which are high considering the small diameter of the fibres (20-30 micron). Of the two muscles, the posterior cricoarytenoid has the faster contraction time and the more abundant sarcoplasmic reticulum content. In addition, the posterior cricoarytenoid is less resistant to fatigue and demonstrates lower succinic dehydrogenase activity. The fatigability of this muscle, coupled with its general lack of functional reserve, suggest that its failure may contribute to upper airway obstruction during respiratory distress.

Methods for demonstration of enzyme activity in muscle fibres at the muscle/bone interface in demineralized tissue

A method for demonstration of activity for ATPase and various oxidative enzymes (succinic dehydrogenase, alpha-glycerophosphate dehydrogenase, and lactic dehydrogenase) in muscle/bone sections of fixed and demineralized tissue has been developed. It was found that it is possible to preserve considerable amounts of the above mentioned enzymes in the muscle fibres at the muscle/bone interfaces. The best results were obtained after 20 min fixation, and 2-3 weeks of storage in MgNa2EDTA containing media. As the same technique previously has been used to describe patterns of resorption and deposition with the aid of a mapping of presence of phosphomonoesterases on bone surfaces, the method may be used to study possible biochemical interactions between bone and muscle tissue at the muscle/bone interface.

Histochemical and ultrastructural characteristics of a new muscle fibre type in avian striated muscle

The serratus metapatagialis (SMP) muscle of the pigeon has been studied histochemically and ultrastructurally. At the gross anatomical level the SMP is clearly divisible into a peripheral whitish band and a red portion comprised predominantly of 'pale' and 'red' fibres respectively. The pale fibres possess low succinate dehydrogenase, low mitochondrial content, absence of subsarcolemmal mitochondrial aggregates, low fat, moderate glycogen, high phosphorylase, low-to-moderate regular myofibrillar adenosine triphosphatase (M-ATPase), activation of M-ATPase following acid preincubation and jagged Z bands. On the basis of these characteristics, these physiologically slow muscle fibres have been termed 'Type I white or slow-twitch glycolytic'. The SMP red fibres, however, possess high aerobic as well as glycolytic capacity, high M-ATPase activity which is labile after acid preincubation and thick but straight Z bands; therefore, they are the 'Type II red or fast-twitch oxidative-glycolytic'.

A histochemical study of denervated marsupial hemidiaphragm

The marsupial (quokka) hemidiaphragm showed postdenervation hypertrophy and subsequent atrophy. The type II muscle fibres hypertrophied up to 20 days postoperation and then regressed. However, the type I fibres hypertrophied throughout the experimental period (100 days) studied. Unlike denervated eutherian hemidiaphragm, fibre-splitting was absent in the denervated marsupial muscle. An enhancement of the ATPase reaction in the denervated type I fibres may be due to dedifferentiation. Presumably innervation exerts a 'negative control' and prevents increase of type I fibre size in the normal hemidiaphragm.

Light and electron microscopic investigation of ATPase activity in musculature during anuran tail resorption

The histochemical activity of adenosine triphosphatase (ATPase) was studied at light and electron microscopic levels in larval tail musculature of Rana catesbeiana and Rana ornativentris during late metamorphic stages. The presence of low, moderate or dark reaction of K2-EDTA-preincubated Ca++-ATPase was correlated with the variable degree of degeneration of white fibres even at the late stage of tail resorption. The reasons for an increase in this ATPase activity in degenerating white muscle fibres are discussed. Irrespective of the degree of degeneration, all red fibres showed high ATPase reaction. During myocytolysis, it is shown that the SR vesicles accumulate electron dense amorphous material. The degree of myofibrillar disintegration correlated with decrease in ultrastructural reaction product for Mg++-ATPase. Although grouped atrophy of muscle fibres (as seen in Xenopus laevis, den Hartog Jager et al., 1973, 1975) was absent in musculature of resorptive tails, ultrastructural characteristics including proliferation of SR and dilation of its vesicles represent alteration of the normal neural influence on the skeletal muscle fibres.

Light and electron microscopic study of adenosine triphosphatase activity of anuran tadpole musculature

The histochemical activities of succinic dehydrogenase (SDH) and Ca++-activated ATPase (pHs 7.4 and 9.4) were studied in the larval tail musculature of Rana japonica, Rana catesbeiana and Rana ornativentris. The ATPase reaction product was detected by both light and electron microscopy. 'Red' and 'white' muscle fibres, as distinguished by SDH, showed high and low Ca++-ATPase reaction, respectively, at pHs 7.4, 9.4 and following preincubation in cold K2-EDTA solution. The ultrastructural investigation of Ca++-ATPase reaction at pH 7.4 by the Ca++-citrophosphate technique demonstrated electron-dense reaction product in association with A, I and 'Z' bands, intermyofibrillar (SR) compartment and the mitochondrial inner chamber. However, Pb++ precipitation technique demonstrated Mg++-activated myosin ATPase activity at pH 9.2 ultrastructurally. The present histochemical data suggest that the anuran larval tail 'red' muscle fibres are possible 'slow,' and emphasize a possible lack of correlation between the speed of contraction with their ATPase activity. Moreover, 'red' muscle fibres of the anuran tai- musculature are not equivalent to 'Type I' fibres of higher chordates.

Histoenzymatic characterization of sub-types of type I fibres in fast muscles of rats

The histochemical activities of succinic dehydrogenase (SDH), myofibrillar Adenosine triphosphatase (ATPase) and alpha glycerophosphate dehydrogenase were studied in serial sections of rat vastus lateralis (red) (RVL), gastrocnemius and diaphragm muscles. Three main fibre-types were distinguished. The "Type I" fibres of RVL and gastrocnemius muscles fell into two distinct groups: one category--"Type IA" showed very low ATPase activity. The second category of "Type IB" fibres displayed moderate ATPase reaction. The "Type IA" fibres were divisible into two sub-groups when tested for SDH reaction. "Type IA1" fibres possessed a homogenous distribution of diformazan granules throughout the fibre: "Type IA2" fibres displayed characteristic "moth-eaten" pattern of diformazan localization. The diaphragm muscle did not show either "Type IB" or "Type IA2" varieties. The great majority of TypeI fibres were sub-type IA1 in the three fast muscles studied. It is also demonstrated here that an inherent heterogeneity exists between Type I filores of diaphragm and leg muscles in regard to alpha-GPD localization. This histochemical data emphasizes the fact that subdivision of TypeI striated muscle fibres of mammalian animals into two sub-types is only approximate and that a further subcategorization is possible.

Different yield and properties of mitochondria from skeletal muscle of normal hamsters

Yield and properties of mitochondria, isolated from hind leg muscles of normal hamsters, are different, when 4 preparation procedures are applied simultaneously: 1. mechanical homogenization of muscle with a glass-Teflon homogenizer followed by rehomogenization of the isolated nuclear fraction for 1--6 times. The procedure yields impure mitochondria showing the highest amounts of mitochondrial enzymes (50--65% of total), protein and DNA; the isolated mitochondria exhibit disrupted outer membranes and loosened inner membranes causing a better supply with substrates of enzymes located at the inner membrane and in the matrix. 2. Single mechanical homogenization of muscle for increasing periods (2--40 min) yields lower amounts of all constituents (25--40% of total). 3. The yields of Nagarse treatment with one step of 2 min mechanical homogenization range between 20--35% of total. Mitochondria isolated with the latter procedure exhibit compact membranes and are very pure, but still contaminated with Nagarse, causing destructions of mitochondrial membranes already after 24 h storage in buffer with sucrose and mannitol at 2 degrees C. 4. One single Nagarse treatment of muscle for 40 min produces a minor yield of these these constituents. Therefore, at least two different isolation procedures are proposed for optimum investigation of skeletal muscle mitochondria.

Critical assessment of diagnostic value of endomyocardial biopsy. Assessment of cardiac biopsy

Right or left ventricular endomyocardial biopsy with the Konno or the Olympus bioptome was attempted in 73 patients aged 5 months to 61 years, with 82 per cent success. Light and electron microscopy showed non-specific features in over half the biopsies with new or diagnostically useful information in only 10 per cent of cases, usually as a result of electron microscopy. The method is safe but is of strictly limited diagnostic value and is likely to be of most help as a research tool in the biochemical study of cardiomyopathies.

Histochemical study of normal human muscle spindle. Histochemical classification of intrafusal muscle fibers and intrafusal nerve endings

Normal muscle spindles of human skeletal muscle were studied histochemically. 1) Four histochemical types of intrafusal muscle fibers were classified by ATPase stain: Bag I fiber, Bag II fiber, Chain I fiber and Chain II fiber. Moreover, two types of nuclear bag fibers were classified by NADH Tetrazolium Reductase stain and PAS stain: Bag I fiber and Bag II fiber. 2) Three kinds of fusimotor endings were verified by the cholinesterase technic: en plaque, en grappe and diffuse endings. 3) Two kinds of fusisensory endings were verified by NADH TR stain and also electron-microscopically: primary and secondary sensory endings.

The value of enzyme histochemical techniques in the classification of fibre types of human skeletal muscle. 2. The histochemical demonstration of myosin adenosine triphosphatase in skeletal muscles from adult patients with or with no diseases of the neuromuscular system. A comparison between results obtained by calcium salt and lead salt techniques

In the present investigation the results of a lead salt technique and two calcium salt techniques for the deomonstration of the activity of myosin adenosine triphosphatase in sections of both normal and pathological human skeletal muscle specimens are compared. It was seen that the histochemical results obtained by the different techniques are similar, especially with regard to the identification of fibre-types. It can be clearly stated, that the alkaline phosphatase activity present in muscle fibers of diseased skeletal msucles revealed only a very slight activity with the substrate ATP, so the alkaline phosphatase activity in general did not disturb the reliability of the different myosin ATPase techniques. Moreover it was found that the presence of the mitochondrial Ca2+ -ion activated ATPase with a high pH-optimum in muscle fibers did not give rise to faulty results. From studies with dinitrophenol it can be concluded that this substance activates the myosin ATPase present in type I fibres especially.

Histochemical sub-types of three fibre-types of avian skeletal muscle

The soleus muscle of adult chicken was studied histochemically. Succinic dehydrogenase (SDH) and myofibrillar ATPase reactions, with or without preincubation in K2-EDTA salt, were compared in serial frozen sections. Based upon the distributions of the above reactions, the three major fibre types distinguished were "Type I red", "Type II red" and "Type II white". On the basis of non preincubated ATPase reaction alone two sub-types of type I red fibres could be distinguished. However, following preincubation in a "Cold" solution of K2-EDTA, Type II red fibres fell into two sub-types and Type II white fibres fell into three sub-types. Amalgamating the two already existing classifications, a more elaborate classification is presented for characterizing these different sub-types. The presence of two different or a spectrum of staining variations in a seemingly homogeneous population of muscle fibres in a given fibre-type emphasizes the possible correlation between this histochemical data and the heterogeneity of contraction times of the different motor units.

Enzyme histochemistry as a link between biochemistry and morphology

The presented paper describes the role of enzyme histochemistry in cell biological investigations. In the first chapter a general discussion has been given about enzyme histochemistry as a connecting link between biochemistry and morphology. The methods available for determination of enzymes in a particular cell or cell compartment have been reviewed. In this respect the characteristics of enzyme histochemistry have been discussed. Furthermore, attention has been paid to the possibilities and limitations of enzyme histochemistry. In chapter two a comparison has been made between histochemically judged and biochemically determined enzyme activities. Some fundamental differences between the biochemical and the histochemical approach in cell biological investigations are dealt with. To correlate histochemically and biochemically determined enzyme activities, a description has been given of the application of histochemical methods on isolated fractions and sucrose-ficoll gradients of these fractions. Several experimental results are described concerning the question whether a relation exists between histochemically and biochemically determined activities of respectively alkaline phosphatase, glucose-6-phosphatase, 5'-nucleotidase and 3ss-hydroxysteroid dehydrogenase. From these results the conclusion could be drawn that in general a good correlation exists between histochemically judged activity per volume (area X thickness) and biochemically determined activity per gram tissue. In chapter three the role of enzymes as markers of cellular particles and as parameters of metabolic pathways is described. Histochemical methods are available for most marker enzymes. Only activities of key enzymes can be regarded as parameters of metabolic pathways. The distribution in sucrose-ficoll gradients of enzymes, regarded as markers of mitochondria, lysosomes, endoplasmic reticulum and plasma membranes has been given. The changes occur ing under different experimental conditions for a number of marker enzymes in rat liver are described. Attention has been given to the contibution of enzyme histochemistry in the study of the heterogeneity of mitochondria, the dual localization of some (lysosomal) enzymes, the complexity of the microsomal fraction, the function of the Golgi apparatus and the heterogeneity and function of plasma membranes. Based on these results and on literature findings the possible role of some marker enzymes in cell metabolism has been discussed. In chapter four problems coherent with species and sex differences in enzyme activities are described. The interpretation of histochemical and biochemical results in view of these differences is discussed. Enzymes characteristic for a given cell type -3ss-hydroxysteroid dehydrogenase in steroid producing cells, ATP-ase in liver plasma membrane surrounding the bile canaliculi - do show less variations between species and sexes than enzymes not directly involved in specialized functions...

On the specificity of the histochemical technique for sarcoplasmic reticular adenosine triphosphatase: a light and electron microscopic study

The specificity of the histochemical localization of the calcium activated adenosine triphosphatase (ATPase) activity of the sarcoplasmic reticulum (SR) at pH 7.4 was studied using a calcium-citro-phosphate technique. The latter involves the splitting of ATP by ATPase producing phosphate ions which then react with calcium and citrate to form an insoluble reaction product. This reaction product was detected by both light and electron microscopy. Light microscopic examination showed a darkly stained continuous reticular pattern of reaction product which surrounded individual myofibrils. This reticular pattern of reaction product was distinctly dissimilar to that found when the histochemical reactions for mitochondrial or myofibrillar ATPase were performed. Ultrastructural investigations demonstrated the presence of discrete foci of electron dense reaction product in close association with the membranes of the SR in striated muscle fibres. Only occasional flecks were seen in the vicinity of mitochondria or myofilaments. The possibility is considered that the reticular pattern of staining achieved by the calcium-citro-phosphate technique may reflect the distribution of the "extra ATPase" of the SR, an enzyme implicated in the process of calcium uptake and muscle relaxation.