Tendencias recientes en las universidades *
SAUNDERS MAC LANE
years 18 AH 2167 . 57 AL 2319 . 80 three years and under 3 AH 2334 . 42 Abnormal AL 2 572 . 83
horses over three
years 4 AH 2636 . 81
AL 237 4 . 00
I n th i s muscl e the mean cross secti onal area of the AH and AL fi bres was greater i n the muscl es from the ol der g roup of " normal " horses
FI GURE 38
FI GURE 39
The mean res l ati onshi p between age (years ) and the mean cross secti onal areas of the AH and AL
fi bres ( �m2 ) i n the cri cothyro i d muscl es from the " normal " horses , pl otted aga i nst thei r ages (years )
The rel ati ons h i p between age (years ) and the mean cross secti onal areas of the AH and AL
fi bres ( �m2 ) i n the hyoepi g l otti c muscl es from the " norma l 11 horses
6Qlf2JQJ 5000 ___..._ N
�
q000 "'--' � � 3000�
�
2000 rx:l ::E 1 000 6f21Qlf21 5000 ___..._ N�
q000 "'--' � � 3000�
z � 2000 rx:l ::E 1 000 0 0 0 0 0 0 0 8 0 0 0 0 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 1 1 5 1 6 1 7 1 8 1 9 20 2 1 22 23 21 25AGE (YEAR S )
0 8 0 0 0 0 0 1 2 3 1 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 20 21 22 23 24 25AGE (YEAR S)
106
than i n those from the younger group . Thi s i s s hown i n Fi g . 38 and produced s i gni fi cant di fferences between the mean fi bre s i zes from the di fferent age groups of horses .
One s i gni fi cant i nteracti on wh i ch di d not appear to be due to thi s i ncrease i n fi bre s i ze w i th age was noted i n the muscl es from the ol der group of abnormal horses where the AH and AL fib res were l arger than those i n the mus c l es of the s ame group of " normal " horses ( P ( 0 . 05 ) . I n most of the g roups exami ned the sex of the horse or the s i de from wh i ch the muscl e came d i d not appear to i nfl uence the mean s i ze of AH or AL fi bres . There was however a tendency for the AH and AL fi bres from the l eft mus cl es of " normal " and abnormal horses to be l arger than those from the r i g h t . Thi s trend was most marked i n the muscl es from the gel di ngs and was s i gn i fi cant for the AL fi bres from the o l der " norma l " horses ( P <. 0 . 02 ) .
5 . 3 . 2 . 6 Mus c l e
The numbers of horses from whi ch mus c l es were col l ected and the mean cross secti onal areas of the AH and AL fi b res from a 1 1 the g roups of " norma 1 " horses and the ab norma 1 horses are s hown i n Tab l e 20 .
TABLE 20 THE M EAN CROSS SECTIONAL AREAS ( �m2 ) OF AH AND AL F I BRES I N THE HYOE P IGLOTT I C MUSCLES
" Norma1 11 horses a l l ages three years and under over three years Al l abnormal horses Number of horses 1 5 8 7 4 ·' Fi bre AH AL AH AL AH AL AH AL
Mean cross secti onal area 1928 . 30 1986 . 03 1385 . 44 1 428. 50 2 548 . 70 2623 . 21 2 1 50 . 50 2107 . 1 3
1 0 7
Agai n i n the hyoepi g l otti c mus cl e the AH and AL f ibres were l arger i n the mus c l es from the ol der than those from the younger horses
{Fi g . 39 ) . Thi s age i ncrease agai n caused s i gn i fi cant di fferences between the mean cross secti onal areas of the fi bres from the muscl es of the di fferent age groups of horses .
The s ex of the horses appeared to have no effect on fi b re cros s secti onal a rea .
5 . 3 . 3 Features Noted i n Thi s
5 . 3 . 3 . 1 Features of Juven i l e Mus cl e
The h i s tol ogi ca l characteri sti cs of the muscl es from foal s appeared to be somewhat di fferent from those of the adu l t horses ( Fi g . 40 } . The fibres from j uveni l e mus cl e were round i n cross secti on rather than pol ygonal and there was more vari ati on i n fibre s i ze than was usua l l y seen i n adu l t mus c l e . The round cross secti on of the fi bres gave the endomysi a l and perimys i al connecti ve ti ssue s epta a more promi nant appearance so that i n j uveni l e muscl e the connecti ve ti s sue components appeared to occupy a h i gher proporti on of the total cross secti ona l area than i n the mus c l e of adu l ts .
The popu l ati on of sarcol emmal nucl e i appeared hi gher i n juven i l e musc l e than i n adu l t mus cl e and the occurrence of these nucl e i w i th i n the body of the fi bres was not uncommon .
There was no apparent s i de di fference i n the h i s tol ogi cal features of the mus cl e s fromhorses l es s than one year of age . By the time the horses reached approximately one year of age the h i s tol og i cal features of thei r musc l es were ass umi ng adu l t characteri s ti cs . The apparent number of s arcol emmal nuc l ei was decreasi ng and the connecti ve ti s sue components were l es s promi nant and present only as thi n bands between pol ygonal fi bres .
5 . 3 . 3 . 2 Characteri s ti c of Denervati on Noted i n Thi s
Al l the h i s to l og i cal features al ready descri bed as bei ng characteri s ti c of denervati on and rei nnervati on were noted i n s ome of the musc l es col l ected duri ng thi s s tudy . An attempt was
F I GURE 40 Transverse secti ons of the l eft dorsal cri coarytenoi d muscl es from foal s , ( a ) two hours and ( b ) two days
ol d ( x260 ) . Secti ons stai ned wi th haematoxyl i n and
eos i n . The h i s tol og i cal features of j uveni l e
equ i ne i ntri ns i c l aryngeal muscl e are i l l ustrated
1 . Nucl ear popu l ati on greater than that observed i n normal mature muscl es
2 . I nternal nucl eus
3 . Fibres round i n cross secti on and varyi ng i n cross secti onal area
4 . Promi nant endomys i um
l O B
made t o g rade these features noted i n the i nd i v i dual mus c l es o f adu l t horses accordi ng to the severi ty of the pathol ogi ca l process present so that s ome wi thi n and between horse compari sons coul d be made .
5 . 3 . 3 . 2 . 1 Dorsal Muscl e
I n the muscl es from horses up to 1 . 5 years of age there was no convi nci ng evi dence of h i s tol ogi ca l changes characte ri sti c of denervati on and rei nnervat i on . The youngest horse wi th obvi ous pathol ogy i n i ts dorsal cri coarytenoi d muscl e was a 1 . 5 year ol d enti re mal e . The changes noted were c l assed as marked and the l eft muscl e onl y was i nvol ved . Thi rty-ei ght percent of the
.. normal .. Thoroughbred horses over 1 . 5 years of age had s ubtl e to marked pathol ogy i n thei r l eft dorsal cri coarytenoi d muscl es . Only one hors e ( 0 . 05%) from thi s group h ad evi dence of h i stopathol ogy i n the ri ght dorsa l cri coarytenoi d mus c l e and thi s was cl assed as subtl e .
The h i s to l og i cal changes observed i n the " normaP horses were not as wel l devel oped as those i n the l aryngeal hemi pl eg i c horses . I t
appeared that there may have been a n age after whi ch there was a decrease i n the percentage of horses showi ng h i stopathol ogy i n thei r l eft dors a l cri coaryteno i d mus cl es . There were 13 "normal " Thorough bred horses between 1 . 5 and six years of age . Of these , 10 were
mal es and h i s topathol ogy was observed i n the l eft dorsa l cri coarytenoi d musc l e of seven of these horses . The muscl es from the three fema l es i n thi s g roup showed no s i gns of h i stopathol ogy . There were ei ght 11normal 11 Thoroug hbred horses over s i x years of age , three gel di ngs and fi ve mares . The only h orse in thi s group wi th h i s topathol ogy i n i ts l eft dorsa l cri coarytenoi d muscl e was a 1 2 year o l d gel d i ng and in thi s ani ma l the pathol ogy was c l assed as marked .
Of the l aryngeal hemi pl egi c horses the youngest had moderate changes and the others h ad marked to severe changes i n thei r l eft dorsa l cri co arytenoi d muscl es . They a l l had subtl e to moderate changes i n the i r ri ght dorsal cri coaryteno i d mus cl es except the ol dest where the changes were marked . The horse whi ch had suffered from l aryngo-pal atal
di s l ocati on had subtl e changes i n i ts l eft dorsal cri coarytenoi d muscl e and i ts right mus c l e was normal .
1 0 9
None of the h i s topathol ogy associ ated wi th denervati on and rei nnervati on was observed i n the muscl es of the three poni es .
5 . 3 . 3 . 2 . 2 Lateral Muscl e
Apart from fi b re type groupi ng , hi s to l og i cal evi dence of denervati on and rei nnervati on was not apparent i n the muscl es from horses l ess than one year of age . A one year ol d enti re mal e was the youngest horse i n whi ch h i s topathol ogi cal changes were observed i n the l eft l ateral cri coarytenoi d muscl e . The changes
i n the l eft muscl e were cl assed as moderate and the ri ght muscl e was normal . Of the " normal " horses over thi s age 68% had subtl e to severe h i s topathol ogi cal changes i n the i r l eft mus c l es and 24% had subtl e or moderate changes i n thei r ri ght mus c l es . It appeared that the changes
observed were more severe and occurred more frequently than i n the dorsa l cri coarytenoi d muscl es .
I n the l ateral cri coarytenoi d mus c l e there di d not appear to be an age at whi ch the i nc i dence of pathol ogy was g reatest as the majori ty of horses over one year of age were affected . Most of the 11 norma1 11 mal es between one and s i x years of age exhi b i ted pathol ogy i n the i r l eft mus c l e s whereas only one of the s i x femal es i n thi s group was affected . The pathol ogy observed i n thi s group was often more severe than that seen i n the horses over s i x years of age .
The l aryngeal hemi pl egi c horses a l l had marked or severe changes i n the i r l e ft mus c l es and 6 6 . 6% of thei r right muscl es had s ubtl e or moderate changes . The horse whi ch had suffered from l aryngo-pa l atal d i s l ocati on h ad marked changes i n i ts l eft muscl e whereas the ri ght mus c l e was norma l .
No h i s topathol ogi cal changes were noted i n the muscl e s of the pon i es . 5 . 3 . 3 . 2 . 3 Transverse Mus c l e
Only a rel at i vel y sma l l number o f transverse aryteno i d mus c l es were ava i l abl e for h i stopathol og i cal exami nati on (Tab l e 1 1 ) . The one foa l i ncl uded ( 24 hours ol d ) had normal l eft and right transverse arytenoi d muscl es .
1 10
The mus c l es from four 11normal 11 Thoroughbred horses over one year of age ( one - four years
)
were avai l ab l e . The l eft transverse arytenoi d mus c l e from the youngest horse i n th i s g roup was normal and the other three had s ubtl e to marked h i stopathol og i cal changes . The ri ght mus c l es from these hors es were al l normal .The l eft transverse aryteno i d mus c l es from three l aryngeal hemi p l eg i c horses were exami ned and al l had evi dence of moderate to marked
h i stopatho l og i ca l change . Thei r ri ght mus c l es a l l exh i b i ted s ubtl e changes .
The mus cl es from the horse whi ch had s uffered from l aryngo-pal atal di s l ocati on showed marked change on the l eft s i de and subtl e change on the ri ght s i de .
5 . 3 . 3 . 2 . 4 Ventri cul ar Mus cl e
The ventri cul ar muscl es from the only foal ( 24 hours
)
exami ned were found to be norma l . Seven other pai rs of ventri cul a r mus cl es from 11 norma l " Thoroughbred horses over one year of age ( one year to greate r than 20 years)
were avai l ab l e for exami n ation . Three ( 42% ) of the l eft mus cl es from these horses showed s ubtl e to marked changes and onl y one ( 14%) of the ri ght mus cl es(
from an aged mare)
showed any h i stopathol og i cal changes and these were g raded as s ubtl e . Al l the l eft ventri cul ar mus cl es of thel aryngeal hemi plegi c horses showed mi l d to marked h i s topathol ogi cal changes but 75% of thei r ri ght mus c l es were norma l , the remai nder showing only s ubtl e changes .
The horse wi th l aryngo-pal atal di s l ocat i on h ad normal l eft and ri ght ventri cul ar mus cl es .
5 . 3 . 3 . 2 . 5 Muscl e
The cri cothyro i d muscles from a l l the horses were s i mi l ar i n thei r h i s tol ogi ca l features and there was no evi dence of any s i de di fference or di fferences between the mus c l es from normal and abnormal horses .
1 1 1
the o l der horses w here there were occa s i onal i sol ated areas wi th an i ncreased nucl ear popu l ati on , endomys i al fibros i s and s ome central nucl ei and spl i t fi bres . These were just as l i ke l y to occur i n the l eft or r i g h t mus c l es of " norma l " or abnormal horses .
5 . 3 . 3 . 2 . 6 Muscl e
The h i stol ogi ca l features of the
hyoepi g l otti c mus c l e from adu l t horses appeared to be somewhat d i fferent from the other adu l t muscl es so far descri bed . The mus c l e fibres had a round rather than pol ygonal cross secti on and there was more vari ati on i n fi bre si ze than was usual i n the other adu l t muscl es . The popul ati on of sarcol emmal nucl ei appeared hi gher i n thi s mus c l e than i n the other adu l t muscl es exami ned , as di d the proporti on of the total musc l e cross secti onal area occupi ed by fi brous ti ssue e l ements so that the endomysi a l and perimys i a l connecti ve ti ssue septa were promi nant ( Fi g . 41 ) .
The musc l es of a l l the h orses , i ncl udi nq the foal s , the l aryngeal hemi pl eg i cs and the horse wi th l aryngo-pal atal d i s l ocati on. were s i mi l ar i n appearance and , wi th one pos s i bl e excepti on , h i stopatho l og i cal changes characteri sti c of denervati on and rei nnervati on were not seen .