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Histochemical and immunohistochemical profile of human and rat ocular medial rectus muscles

Showing of 19 reviews. Top Reviews Most recent Top Reviews. There was a problem filtering reviews right now. Please try again later. Good toy for cats. Beware that the actual item quite big, closer to the size of a rat than a mouse! Didn't like it at all. The mouse size is too big. Needs too many batteries to operate. Cats too didn't find it exciting. They got scared of the whirring sounds the wheels make. One person found this helpful. Very bad packing of parcel received and was defective and not working. Received late even after paid online through debit card while ordered.

Value for money quality is good. Received a damaged product and returned the same. The mouse is really good. It is fast and realistic. Your cat or even small kids will love it. See all 19 reviews. Get to Know Us. EOM differ in their histochemical profile, type of innervation and fiber type distribution [ 48 , 51 ].

The sequential development of EOM fiber types is believed to be conserved across the mammalian species, but may follow a different sequence in frontal and lateral-eyed species [ 36 ]. In rodents, the composition of EOM is in principle similar to that of other mammals, including humans, however species differences were reported and mostly concern muscle fiber type characteristics [ 16 ]. Several attempts at classification of fiber types in EOM of different mammals, i. However, the most pertinent classification system used at present is still descriptive and incorporates different classification schemes [ 48 ].

It distinguishes among six fiber types in EOM according to i their location in the global GL or orbital layer OL , ii type of innervation i.

Introduction

Still, this scheme remains limited in recognizing the full extent of the muscle fiber heterogeneity in EOM, not considering the myosin heavy chain MyHC isoform composition, as suggested by McLoon and co-workers [ 28 ]. However, in rat, an additional fast MyHC, i.

In spite of all the complex research, the classification of muscle fiber types in EOM is still not fully clarified, and neither is the correlation between its structure and function. The studies that considered the MyHC composition of the rat or human EOM [ 4 , 6 , 8 , 13 , 19 , 20 , 23 , 34 , 40 , 41 , 51 , 55 , 56 ] applied different methods and therefore the results are mostly not comparable. In this study, we applied the above-mentioned methods and in case of human EOM in situ hybridization as well to obtain an additional insight into the fiber type characteristics and MyHC isoform expression in normal rat and human ocular medial rectus muscles MR.

The study was designed in compliance with Helsinki ethical requirements and approved by the state ethical committee. The rats were painlessly exsanguinated under ether anesthesia. Both human and rat MR muscle sections were processed for histochemical demonstration of the mATPase activity after preincubation at pH 4.

MyHC isoforms in individual muscle fibers were demonstrated by monoclonal antibodies directed against various MyHC isoforms of rat: In some of the rat and human muscle samples, additional antibodies were applied: The last three antibodies were purchased by Developmental Studies Hybridoma Bank at the University of Iowa [ 24 , 47 ]. The appropriate dilutions of primary antibodies in phosphate buffered saline with the addition of 0.

The peroxidase-conjugated rabbit anti-mouse IgG Dakopatts, Denmark was used as the secondary antibody. To reveal the binding of antibodies, diaminobenzidine tetrahydrochloride DAB, 0. The control sections were incubated without the primary antibody. The riboprobes were prepared with digoxigenin-labeled UTP according to the guidelines of the manufacturer Roche Molecular Biochemicals.

In situ hybridization procedure was adapted from Horton and co-workers [ 17 ] with minor modifications [ 47 ]. For fiber typing, at least 2,—2, fibers per muscle were sampled. The data were collected independently and separately for every section and layer, and each fiber type. From each histochemically stained muscle section and each section processed for MyHC isoform detection photos were taken or images were captured by the video camera.

Identical fibers were marked on successive serial sections. In human and rat ocular MR muscles, the fibers were arranged mainly into two layers: In humans, however, such a distinct separation into layers was not that obvious, because of more gradual muscle fiber type transition from the OL over larger intermediate zone to the GL. There was also a more extensive layer of perimysium surrounding human MR muscle bundles compared to rat MR muscle bundles Fig.

Though larger human ocular MR muscles, the diameters of human and rat muscle fibers did not differ very much human fiber diameter range 7. Cross section of a human and b rat ocular medial rectus muscle. Histochemical staining for succinate dehydrogenase SDH exhibits higher oxidative activity in the thinner orbital layer than in the thicker global layer. Human MR muscle is much larger with a broad intermediate layer and a lot of connective tissue separating muscle fascicles.

Muscle fibers of very similar characteristics could be found in both human and rat muscles. Serial profiles of EOM fibers from the midbelly muscle region across different histochemical reactions are shown in Fig. Histochemical staining of serial cross sections from the orbital OL and global layer GL of human left column and rat right column ocular medial rectus muscle, assayed for mATPase after preincubation at pH 9.

Four different fiber types are indicated in the global muscle layer slow numbered as 6, fast oxidative numbered as 3, fast oxidative- glycolytic as 4, fast glycolytic numbered as 5. Histochemical and immunohistochemical characteristics of human and rat ocular medial rectus muscle fibers. For a better understanding of the existing literature on extraocular muscles, we also add the nomenclature used with classifying fibers according to the type of innervation: At least four fiber types in the GL and two in the OL could be distinguished in both species according to the reaction for mATPase and the fiber metabolic profile as well.

Two main categories, i. Type I fibers were lightly stained after alkaline preincubation and darkly after the acid preincubation. The fibers with the opposite staining characteristics were classified as fast or type II fibers. In the GL of both species, the muscle fibers were arranged in a rosette-like pattern, where each rosette was composed of a central slow or type I fiber, surrounded by at least all three, the above-mentioned subtypes of fast or type II fibers Fig.

The slow or type I fibers displayed rather low oxidative and glycolytic activity Fig. In general, the human MR muscle fibers were also more oxidative than the rat muscle fibers. An additional difference among the muscles of both species pertains to the connective tissue separating the muscle fascicles, which was in the human MR more extensive than in the rat MR muscle Figs. Immuno-peroxidase staining of serial cross sections from the orbital OL and global muscle layer GL of human left column and rat right column medial ocular rectus muscle, assayed for myosin heavy chain isoforms: Two fiber types are indicated in the orbital muscle layer numbered 1 and 2.

Four different fiber types are indicated in the global muscle layer numbered as 6, and 3, 4, 5. But type I fibers of rat were not labeled by these three antibodies not shown. MyHC transcript and isoform expression, respectively, revealed by in situ hybridization and immunohistochemistry in human extraocular medial rectus muscle. In the right column MyHC isoforms are revealed by specific monoclonal antibodies: MyHC-2a and -2x SC , g. MyHC-2x 6H1 and h. Note that the MyHC transcript and isoform expression do not correlate. MyHC-eom expression demonstrated by 4A6 antibody in rat a and human b extraocular medial rectus muscle.

Note that the presented rat muscle section is serial to sections presented in Fig. The rest of type II fibers, located mainly at the outer border of a fascicle, were intensively stained by BF-F3 antibody, thus assumed to express only MyHC-2b. Actually, there were fascicles with fibers expressing MyHC-eom Fig.

Histochemical and immunohistochemical profile of human and rat ocular medial rectus muscles

The embryonic and neonatal MyHC transcripts were present only in few fibers, the neonatal ones being much scarcer than the former ones. Comparing the expression of MyHC transcripts with immunohistochemical profile no clear correlation could be found Fig. In this study we have proved that almost identical muscle fiber types exist in rat and human extraocular muscles. The majority of fibers are hybrid fibers, co-expressing two or more MyHC isoforms.

Furthermore, to our knowledge this is the first study in which the distribution of MyHC isoforms in the extraocular muscle fibers of different species was compared. Previously described marginal zone MZ adjacent to the OL was more evident in human than in rat ocular MR muscles, however it was thin and was to our observation similar to the fibers positioned between the OL and the GL [ 55 ].

The human MR muscles were larger due to the higher absolute number of muscle fibers, while the muscle fiber diameters were within the range of rat muscle fiber diameters. Interestingly, the muscle fibers of monkey are larger, more variable in size, and fewer than in human EOM e. In large skeletal muscles, three to four major fiber types can be revealed by mATPase histochemistry [ 12 ].

However, in ocular MR muscles the mATPase histochemistry alone was insufficient to completely distinguish fiber subtypes although a variable incubation time in alkaline and acid media had been used within a wide span of pH values [ 39 , 50 , 51 ].

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Nevertheless, following the already described simplified classification system applied so far for EOM fiber types according to which six fiber types can be distinguished regarding to their location, type of innervation [ 36 , 37 , 48 , 55 ], the mATPase activity and metabolic profile [ 37 ]. Slow fibers determined in this study obviously corresponded to multiply innervated fibers MIF , while fast fibers corresponded to singly innervated fibers SIF described in other studies [ 37 , 48 ].

The functional role of these fibers is not well understood. Since these global slow type fibers, called also MIF fibers , develop first they probably allow proprioceptive information to be used in visual system development Orbital fast fibers called also SIF fibers mature the last and may directly impact the range and precision of eye movements.

They contain the largest bunches of mitochondria, which is consistent with the elevated fatigue resistance and a sustained level of eye position maintenance. To better define the fiber types according to their oxidative capacity, the reaction for SDH was used in the present study, as the activity of the other marker for oxidative metabolism, the nicotineamide adenine dinucleotide dehydrogenase NADH is generally very high in EOM and it hardly distinguishes among fiber types, especially in human EOM [ 19 , 50 ].

Such variability in results is most probably due to the variable length of muscle fibers, extending from the proximal to the distal part of human extraocular muscle [ 2 , 27 , 39 , 40 , 48 , 55 ]. In this study, many OL muscle fibers of both species stained positively with the commercially available monoclonal antibody 4A6 against MyHC-eom. On the contrary, the fibers of the GL were labeled less intensively with this antibody Fig. Therefore we assume that MyHC-eom is co-expressed with other isoforms in many fibers, especially in the OL. The presence of another fast MyHC isoform, i.

However, applying an antibody specific to MyHC-2x 6H1 , in this study we undoubtedly demonstrated that MyHC-2x isoform is abundantly expressed in human EOM fibers and in many rat muscle fibers of both layers. To our knowledge this is the first study in which MyHC-2b isoform has been revealed in any human skeletal muscle, though 2b MyHC transcripts were demonstrated in human external abdominal oblique and masseter muscles [ 17 ].

Furthermore, the expression of MyHC-2b isoform in human MR was additionally confirmed with undoubtedly revealed expression of MyHC-2b transcripts by in situ hybridization technique Fig. Though the expression of MyHC gene transcripts in human EOM did not correlate well with MyHC isoform expression, it was not completely uninformative as the probe specific for MyHC-2b transcripts hybridized in MR, but gave absolutely negative results in the large limb muscles not shown , placed on the same slide as MR muscles and processed simultaneously for in situ hybridization technique.

An explanation for such discrepancy in MyHC gene and isoform expression could be a possible posttranscriptional MyHC gene regulation not only for MyHC-2b but also for other isoforms [ 15 ]. Another possibility for so ambiguous results of in situ hybridization technique could also be that the expression of MyHC transcripts in EOM is less abundant than in large skeletal muscles and that the method is not sensitive enough to offer better results, though good results were obtained in large skeletal muscles [ 47 ]. The presence of MyHC-emb and -neo isoforms predominantly in OL within the midbelly region of adult EOM, reported previously [ 34 , 40 , 51 , 53 , 55 ] and confirmed in this study, seems to be a unique characteristic of the muscles innervated by cranial nerves.

However, it was found that the pattern of MyHC isoform expression may change along the length of rabbit and rat EOM fibers, whereby the majority of fast and developmental MyHC isoforms expressing fibers were present in the middle muscle region of the OL and less in the GL [ 18 , 25 , 28 , 41 ].

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