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357 Uindowîlg at ear¡y stages of avian development can be regarded as another physícal teratogenÌc procedure. The standard windowíng technic at 26-30 hours produced a high incldence of mortal ity and marformatíons. This effect was almost abol ished by obliteration of the introduced air space, if performed i mmed îa te I y. The teratogenlc actlon of windowing at êarly stages of development has been reported by Ancel (19\6-47 t '1956),Hinsch and Hami lton (1956), l4cCalllon ånd Clarke (1gSÐ, ,"nn et ê1. (i973). ln many publ îcations "nO no attempt to obl iterate the a¡r space is reported, so thât any nalformations recorded mlght be caused by windowing as well as by the agents emp I oyed . ln the presen, "rp.rlr"ntr, embryos at the t¡me of treêtment ranged from Stage 5 to Stage 10. The effect of wîndowing is not confined to a short period like other physical agents, though formation of the amnîon by Stage 1B protects the embryo after about 60 hours. Some defects (such as neural dysraphism, eye defects, and trunk cysts) can be attrÍbuted to an early effect; others (such as rumplessness, ectop¡a viscerum, and limb defects) arise later. A¡though windowing exposes the dorsal surface of the chick embryo, and neural defects originate dorsally, other defects (such as ecto¡iía viscerum) involve ventral structures. ln the neural tube, four degrees of involvement resulted from windowing. l4any embryos developed quite normally. Embryos with early myeloschisis showed necrosis ín the superflcial cells of the neural plate, which later resolved. Hyelodysplasia, due to absence of neural plate materîal,was comblned with mesodermal cysts and hemorrhages. The most severely affected embryos (not examined histological ly),showed early death associated wlth open neural defects, severe trunk dlstorsion, reduced
358 braln and cord volume, and often extensive cysts. Wlndowlng at 26^30 hours, like other teratogenic lnsults, thus appears to have eîther a moderate or a severe effect on the chick embryo. This gradation of response enables myeloschisis and myerodysprasia to be distlnguished as dlstinct pêthological processes, each of which requires further I nvest igat lon.
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E}4BRYOGENES IS OF EXPERIHENTALLY I
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MY PARENTS c.J.H. G. M.
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lt Congenital malformêtlons of the
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TABLE OF CONTENTS SECT ION PAGE 1 I
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},I.ATE R I ALS 3.1 THE CHICK EI4BR
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vt I I 6.3.2 Stage 10 Experímentel
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9 APPENDTCES 378 APPENDIX A . 379 1
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1.1 TERATOLOGY Birth defects have a
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4 of the complexity of normal devel
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6 flat, exposed plaque of neural ti
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8 However, several early embryos in
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.1- 5
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l2 2.1 ErI0L0rL!! fïE qYs34t!1!!jr
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4 which has rema¡ned fairly consta
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6 and about 112 after two (Laure,nc
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l8 ln some very early human embryos
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2l and kinky-ta¡l as disorders of
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23 Vogel and McClenahan (1952) tnus
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I'IATE R IALS 25
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27 lf necessary, eggs were stored a
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FÍg. 5. lncubator allowing precise
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3l 4. r sELEcr I oN !F EGGq 4.1,1 .
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uler. Accurate Staging (Hamburger a
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.\lz '?. t
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Fis. I AsB, Windowìng followed by
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Fis. 9 Aã8. t/indow?ng followed by
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42 ( \--l /) ^ ) t0
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44 serîal sectlonlng a camera luci
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46 Thus the embryos selected for se
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48 TABLE 3. srAGE t0 El,tBRyos (cno
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50 TABLE 5 , Reg i ons srAGE 13:16'
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52 4.8.4 HistologÌcal_De:plþtÍon
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5 RESULTS OF TERAÎOLOGICAL PROCEDU
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(c) deaths and defects in the survi
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Fi g. Percentagcs of early deaths a
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6o MoRTALtTY, AFTER ì,'tNpowtNq,AT
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TABLE B.'DEVEIOPI{ENT'AFTER'WINDOIi
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TABLE 9. ¡4ALFORMATIONS PRODUCED'B
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N=231 ffil e ooyi ffi s oays [il t2
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6B TABLEt loj lloRTALtTy AFTER VtBR
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70 5,3.2 Pa-rôf i Idì ¿irid PIè
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TABLE 13; MALFORI4ATIONS AFTER PLAS
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41 13 0 23 No l^l i ndow Control s
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Fíg. Percentages of early deaths a
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78 ALBUMEN INTRODUCTION Analysís o
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0 1 0 0 a o TABLE 17. I'lALF0RÌ1AT
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N Eorly Deothi N=10ó N a ú, o d,
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103 51 52 28 14 4 6 No W î ndow Co
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Fi g. 14. Percentages of early deat
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88 AtR qELL, REEXPANSI0N Analysls o
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90 5.4 BACTERt4L CUTTURE 0F UlNpohr
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92 TABLE 22. ¡¡UI'ISELTS OF PLATE
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94 6.1 EMBRY0ûIIES I s 0L 0!!\- NE
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Fis. I5 A¿8, Range of s izes (mm.)
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Figs. 16 AaB.. Range of sizes (mm.
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100 6.1.2 f4ortal í!y with Vsrying
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421.. 26 25 I (3.85) 20 (76 .92) 1
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00 N Eorly Deoths ,n -¡ F- ô- xu.
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ì06 Degrees of Freedom 12 Chi Squa
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hzE 53 42C z5 51(96.4)2\(96) 2(3.77
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ffil Op"n Anterior Neuropore I I0 N
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N=380 El Ovol Rhonnboid 'Sinus ì l
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Øl Open Broin Defecls N=384 ffi F"
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ligr. 21 - 30. Camera lucida drawin
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Fi s. 22. lrregular open anteríor
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lmm OPEN BRAIN DEFECT Á,NOPHTHALMI
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lmm OVAL RHOMBOID S¡NUS 48 HOURS S
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FiS. 26, Open neural folds extendin
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t-l lmm IATER OPEN CORD DEFECT . RE
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l2B t--l lmm EARLY OPEN CORD DEFECT
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Fis. 30. Large caudal cyst Ìn an o
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132 6.1 .4 DeveloÞñent of oÞen N
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Fig. 31 . Percentêges of experinen
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36 TABLE ?8. RH0I4B0lD stNUs ctôs
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N=38o H ovol Rhomboid sinus l^ r38
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F¡ S. 33. Percentages Õf open cor
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142 6.1.5 Distríbution of 0pen Cor
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Fi s. "l! Percentage distrìbution
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lrregul ar (Z) somi te be low level
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ì48 N=2ó4 ffi m Regulor Cord Defe
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Fis. 36. Percentage distrîbution o
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152 6.2 sPtIA! LFVELS 0F oPEN CORp
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Fìgs. 37'38, Vertebral defecrs in
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CERVICAT THORACIC LUMBAR FUSED CAUD
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---l r r'I * 40
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t59 a) spîna bif¡da occulta is se
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:al . '**Ç- 4 ff, À(,) ftø 9-' o
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162 lmnediately after closure, sepa
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164 Hensenrs node and the primitive
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-l :: l 48 I 49 i :. t: .lì 50 ì:
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t67 somite area (through asymmetry
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t69 ln both embryos the volume of n
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171 The rhomblc roof became membran
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173 At areas of myeloschisîs conta
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175 neurêl tîssue wíth mesoderm
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t77 e) encroachment of somitîc mes
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ôt rf) , ,,. ì _ ^iiir¡:ù\. I r
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l 55 56 57 58 59 ó0
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Fiss. 65 Early myeloschisis in a St
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fiSr. 71 - 76. Later myeloschisis i
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Fiss. 77 -82. Early myelodysplesia
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FÌgs. B3 - BB. Later myelodysplas
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Figs, 89 - 91. Processíng artifact
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ì86 6.3.10 SequenJ¡¿il ll lúSti
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Fígs. 95 - 102, Sequentiêl drawin
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l9o EVERsToN: srAGE rf (o r o+) o @
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@ @@ "@ @ e q q a a 192 CoNTROL: ST
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MYELOSCHTSTS: STAGE tZ (tZeïl OOG
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coNTRO[: STAGE tó (ro c zz) . a@ Q
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G (õ--==: \z-- HEMTMYELIA: STAGE t
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Som i te Defects contact none sePa
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Somite Som i te Contact Defects N'
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Som i te Contact Som i te Defects c
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none none N) o o\ B r8c 23 12 good
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separat ion none contact/ none sepa
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Regíon Embryo Stage Conditîon Neu
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none none none none none none l'.J
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18E 10 13- vëry poor closed 0 cove
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separãtion none contact none conta
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Regíon Embryo Stage Condition Neur
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separation none sepâ ra t îon non
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separâtion none sepa ra t ion sepa
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Reglon Embryo Stagd cond¡t¡on Neu
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none none none none N) NJ .{ A A A
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contact/ none separatlon contact no
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Region Embryo Stage Conditlon Neura
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TABLE 38D. STAOE 17.20 CONTROL AND
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Reglon Embryo Stage Condition Neura
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428 72 20 closed covered none conta
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239 neural tissue ât the later sta
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241 The control group (Table 99 ) s
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TABLE 39. APPEARANCE OF I,'HOLE EI4
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TABLE 40. APPEARANCE OF }/HOLE EI"I
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closed closed c I osed c I osed c I
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249 6.6 pEVEL0PMENT 0F rH!_¡Ho|4gl
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Emb ryo Stage Rhombîc Roóf Neural
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CDE D'E DE CDE DE DE DE D BCD BC BC
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TABLE q6,. STAGE 17-20 CoNTRoI AND
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Figs- 10J - i11. Development of the
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Fî s. tub. Thick rhombic roof in 5
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Fig. 109 Hernbranous rhombic roof w
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260 6.7 HrqroLoctcAL, cHANgË Assoc
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TABLE 47. CONTROL EMBRYoS.HISTOLOGI
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0 0 0 0 0 0 0 0 0 0 o 0 0 0 0 0 0 N
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42c 21 zo B c D E 0000 00 00 00 1\.
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l\t q\ 1oE 26 16 30E 59 16 3oE 77 1
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0 0 0 0 0 0 0 0 0 0 0 0 N) .{ Embry
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l\) \l N D E 00 00 0 0 13.79 0 100
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N) \¡ \2E 72 20 E B c D' E 00 0 15
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46. 15 76.92 0 20.51 14.83 2i,92 53
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ECTODERM DISCONTINUITY IN EXPERIMEN
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279 ECTODERM DISCONTINUITY IN EXPER
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SOMITE SEPARATION IN EXPERIMENTAL E
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283 NOTOCHORD SEPARATION IN EXPERIM
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285 SOMITE DEFECTS IN EXPERIMENTAL
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287 and distr¡bfrtíon in the cont
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19.09 r8.95 r 1.84 14.82 15.20 0 17
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0 15. 89 81 .08 100 100 ' 76.92 0 1
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43. rB 100 100 0 12.53 74.07 r00 't
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7.t6 16.03 100 100 160 7.90 18.22 r
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Figs. 120'123. Percentage ie.ngths
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299 O\TERLAP ZONE IN EXPERIMENTAL E
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301 OVERLAP ZONE IN EXPERIMENTAL EM
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303 ând every tenth sectlon was ne
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30c 12 16 c 17707,61 2463.3\ 7.19 D
Page 336 and 337: Ratio NT/N 4 .90 4.11 6.17 7.14 6.9
Page 338 and 339: Rêtlo NT/N 4.go \.36 3 .44 3. 18 3
Page 340 and 341: 6.7t 6.lt 4.63 4.60 4.13 3.48 hzE 5
Page 342 and 343: Fi9s, 124-127, Neurál tube-norocho
Page 344 and 345: 315 NEURAL TUBE -NOTOCHORD RATIOS I
Page 346 and 347: 317 NEURAL TUBE-NOTOCHORD RATIOS IN
Page 348 and 349: 319 TABLE 598 ' ANALYSIS OF VARIANC
Page 350 and 351: 321 TABLE 61., .NEURAL TISSUE/NOTOC
Page 352 and 353: 323 Apart f.rom the sîgnîficant d
Page 354 and 355: t25 7. Dlscusst0N 1'/i th progressi
Page 356 and 357: 327 C¡osure of the anterior neurop
Page 358 and 359: 329 the mid-polnts of the defects w
Page 360 and 361: 331 'c¡osure of the neural folds w
Page 362 and 363: 333 . These findings s.ugges r that
Page 364 and 365: 335 Lendon (1968, 1975) and notos (
Page 366 and 367: 337 Ferm, 1965; l"larin-Padi r ¡a,
Page 368 and 369: 339 Kôplan (1965) and Kaplan and G
Page 370 and 371: 341 reach the floor-plate; asymmetr
Page 372 and 373: 343 took up the label, shovri.ng th
Page 374 and 375: 345 The defects in early human embr
Page 376 and 377: 347 after pred¡cted closure (Lemî
Page 378 and 379: 349 hours could provide evidence fo
Page 380 and 381: 351 t971), Gal lus and Xenopus (l'l
Page 382 and 383: 353 1962i 1965). Barth and Barth.(1
Page 384 and 385: The result of any teratogen¡c insu
Page 388 and 389: SUHHARY AND CONCLUS I ONS
Page 390 and 391: 361 separatlon between the neural p
Page 392 and 393: 363 APPENDIX A Preparatlon of Early
Page 394 and 395: 365 APPENDIX B Stainl.ng of Carti l
Page 396 and 397: 367 10, BIBLIOGRAPHY, Alter, l.,l.
Page 398 and 399: 369 Braun, l'{. (1882). entwicklung
Page 400 and 401: 371 Crlley, B,B.(1969). Analysîs o
Page 402 and 403: 373 dqs anomal ies de lrorganizatio
Page 404 and 405: 375 Heath, H.D., Shear, H.H., lm€
Page 406 and 407: 377 Jel inek, R. (1960). Developmen
Page 408 and 409: 379 Laurence, K.14. (1964). Thé na
Page 410 and 411: 381 McKeown, T. and Record, R.G.(19
Page 412 and 413: Penrose, L. S.(1957). Genetics of a
Page 414 and 415: 385 Russell, H.E. and A¡ tken' G.T
Page 416 and 417: 387 Spemann, H. (1938). Embryonic D
Page 418 and 419: 389 lJeed, ¡.H. (1937 -38'). M.nin
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