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331.
I N F L U E N C E OF T H E E N D O C R I N E S Y S T E M ON GROWTH A N D D E V E L O P M E N T
R . J . G E R R I T S A . R . S . , U. S . D. A .
Introduction
The f i e l d of endocrinology cannot be defined i n a m a n n e r e n t i r e l y acceptable t o all bio logis t s or animal s c i e n t i s t s . This i s understandable as there are many points of view and many voids i n our knowledge i n t h i s area. It i s very hard t o give a precise de f in i t i on for an endocrine gland because all c e l l s possess some secretory capacity and therefore contribute t o t h e in t e rna l environment of t h e organism. For t h e most pa r t t he term "hormone" i s probably applied t o o loosely and t o a great va r i e ty of unrelated substances. Hormones can be iden t i f i ed as chemical agents which are synthesized by circumscribed p a r t s of t h e body, generally specialized duc t less glands, and are car r ied by t h e c i rcu la tory system t o another par t of t he body where they evoke systemic adjustments by act ing on ra ther spec i f ic t a rge t t i s s u e s or organs (Turner, 1966). regulate many processes such as growth, regeneration, reproduction, blood chemistry, metabolic r a t e , e t c . Hormones act on the organs and t i s s u e s of t h e body by regulat ing t h e rate of spec i f ic metabolic react ions without contr ibut ing much at all t o t h e const i tuent ce l l . It can be said t h a t ad- justments t o hormone levels require duration r a the r than speed, as opposed t o t h e rapid coordinations of t h e body t h a t are control led by t h e nervous system. These biochemical adjustments are accomplished at t h e c e l l u l a r l e v e l by v i r t u e of t h e i r power t o augwnt or r e s t r a i n special enzyme sys- t e m s . It i s important t h a t hormones be released a t t h e r i g h t t i m e and i n t h e proper amounts of t h e normal organism i f they are t o accomplish t h e i r spec i f ic mission. Hormones are inef fec t ive unless the t a r g e t c e l l s and t i s s u e s are capable of responding t o them.
I n general, hormones
While it i s neaxly impossible t o separate t h e neural and t h e hormonal components of regulatory processes, t he complex system of endocrine glands i n t h e ver tebrates i s qui te c lear . This system includes the p i t u i - t a ry , thyroid, parathyroid, ad rends , gonads, pancreatic islets, and t h e hormone-producing pa r t of t h e gas t ro in t e s t ina l t r a c t . The material pre- sented i n t h i s paper w i l l be l imited t o a very small segrnent of t h e endo- c r ine system and t h e e f f e c t s on growth. More spec i f ica l ly , I w i l l attempt t o discuss i n t h i s paper some of t h e important influences t h a t are exerted by t h e hormone somatotrophin (STH growth hormone). selected material on t h e e f f e c t of tes tosterone (as an endogenous hormone) and of melengestrol acetate (a synthetic hormone) on growth.
Also I w i l l present some
Hormones of t h e adenohypophysis
Seven hormones are known t o have been released from the adeno- hypophysis, namely: (ACTH) ; thyrotrophin (TSH) ; prolac t in (lactogenic hormone o r luteotrophin) ; fo l l ic le -s t imula t ing hormone (FSH) ; lu te in iz ing hormone (LH or i n t e r s t i t i a l cel l -s t imulat ing hormone) ; and melanophore-stimulating hormone (MSH) . All
somatotrophin ( STH or growth hormone) ; cort icotrophin
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of these hormones are proteins or peptides, and three of them (FSH, LH, and TSH) contain carbohydrate i n addition t o amino acids.
Somatotrophin (STH)
It has been well es tabl ished t h a t STH i s secreted by the acidophil c e l l s of the pars d i s t a l i s and t h a t the pr incipal act ion of growth hormone i s on growth of bone and muscle. Growth hormones i so la ted from d i f f e ren t species exhib i t d i f f e ren t physiochemical propert ies . The molecular weight of STH hormone ranges from 21,500 t o 48,000 i n man, pig, beef, and sheep. The growth hormones with lower molecular weights are more acidic t h h n those with higher weights. Also, it i s important t o know t h a t body growth response of STH hormone i s d i f f e ren t among t he various ver tebrates and t h a t t he r a t responds t o somatotrophin from numerous mammalian species. The most common tes t employed i s the t i b i a t e s t . mone, t he increase i n width of t he proximal epiphyseal ca r t i l age of t he t i b i a of t h e hypophysectomized female rat or mouse i s determined. STH pro- duces continuous growth and widens the ca r t i l ages i n proportion t o t h e amounts given.
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After administration of t h e hor-
Mechanisms of hormone act ion
There i s a considerable amount of knowledge about t he chemistry of hormones and t h e i r i n vivo and i n v i t r o e f f e c t s . However, su f f i c i en t re- search, espec ia l ly i n ver tebrates , has not been conducted t o disclose f u l l y how any hormone ac tua l ly performs at the molecular l eve l . Levine and Gold- s t e i n (1955) and Smith -- e t al. (1961) have demonstrated t h a t insu l in promotes the transfer of glucose i n t o t h e c e l l s of ce r t a in t i s sues , such as muscle and f a t . Three general points, each with varying modifications, have been proposed t o explain the mechanisms of hormone action, namely:
-- --
1. Hormones exert a d i r e c t e f f ec t on in t r ace l lu l a r enzyme systems.
2 . Hormones ac t t o control permeability re la t ionships at the c e l l surface or elsewhere and hence ind i r ec t ly control condition enzymic reac t ion.
3 . Hormones may produce t h e i r e f f e c t s d i r e c t l y by act ivat ing or suppressing par t icu lar genes.
I n our attempt t o understand the mechanisms of hormone act ion we must r e f e r t o work t h a t has been conducted with insec ts . Microscopic ex- amination of t he giant chromosomes of chironomous larvae has shown t h a t t he administration of ecdysone causes a puffing of ce r t a in genes. i s t h a t the act ivated genes (DNA) begin t o synthesize spec i f ic RNA which i s t ransfer red t o t h e cytoplasm where it a c t s a s template f o r t h e synthesis of a pa r t i cu la r protein, e.g., enzymes (Karlson, 1962). The work of Liao and Williams-Ashman (1962) suggests t h a t ce r t a in ver tebrate hormones may ac t i n a s i m i l a r manner. It w i l l be most in te res t ing t o see how f a r t h i s concept can be substantiated i n processes other than development i n m a n n a l s .
The inference
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Biological act ion
A t one t i m e it w a s assumed t h a t STH had only an e f f e c t on general body growth, p a r t i c u l a r l y t h e skeleton, and when e x t r a c t s r i c h i n STH pro- duced other ac t ion they were a t t r i b u t e d t o contaminating f a c t o r s . There i s now s u f f i c i e n t evidence t o show t h a t STH plays an important ro le i n the metabolism of proteins, f a t s , and carbohydrates and also serves as a synergist t o enhance t h e e f f e c t s of other hormones.
The e f f e c t of STH on pro te in metabolism
Amino acids not u t i l i z e d by animals are normally converted t o urea and eliminated through t h e ur ine . It has been ably demonstrated t h a t STH encourages t h e animal t o r e t a i n amino acids which are t h e e s s e n t i a l building blocks f o r pro te in and t h a t t h e body weight increase normally observed after treatment with STH i s an a c t u a l increase i n t i s s u e pro te in .
Knobil (1961) states t h a t one important aspect of STH act ion i s t o promote t h e t r a n s f e r of e x t r a c e l l u l a r amino acids across c e l l membranes, p a r t i c u l a r l y i n t o muscle c e l l s .
Milman and Russel l (1950), L i -- e t al. (1949), and Luck -- e t al. (1954) have demonstrated t h a t t h e administration of growth hormones lowers blood amino acid nitrogen. Swislocki and Szego (1965) also demonstrated t h i s e f f e c t i n hypophysectomized ad l i b fed rats. I n t h e la ter study blood-amino nitrogen (BAN) l e v e l s i n t h e growth hormone t r e a t e d rats w e r e s i g n i f i c a n t l y lower than t h e controls a t one and f i v e hours a f t e r treatment with STH.
I n a recent study Beach and Kostyo (1968) showed t h a t when ra ts were injected d a i l y in t raper i tonea l ly with bovine growth hormone f o r seven days t h e amount of DNA i n t h e muscles r e c t u s femoris, gastrocnemius, p e c t o r a l i s -' major and diaphragm w a s increased s igni f icant ly . When STH w a s administered f o r one day it had no e f f e c t on t h e DNA of these muscles. However, following seven days of t r e a t n m t , with t h e hormone, t h e amount of DNA i n each of t h e muscles w a s markedly elevated. Since there w a s a con- comitant increase i n muscle weight, t h e concentration of DNA i n terms of micrograms per mg. of w e t muscle w a s a l te red s igni f icant ly . These d a t a show t h a t growth hormone can increase t h e amount of DNA i n s k e l e t a l muscles of hypophysectomized ra ts . Thus, it seems reasonable t o assume t h a t t h e increase i n muscle DNA which occurs during t h e normal course of growth i n rats i s dependent i n some measure on p i t u i t a r y growth hormone.
Ef fec t of STH on l iDids metabolism
The experiments of Welt and Wilhelmi (1950) suggested t h a t growth hormone administration leads t o a reduction of l i p i d synthesis. Their i n i t i a l s tud ies have subsequently been supported by several workers.
Hypophysectomy r e t a r d s t h e mobilization of depot f a t and tends t o ameliorate ke tos i s i n t h e d iabe t ic subject . STH encourages t h e movement of unes te r i f ied f a t t y acids from f a t reserves, consequently decreasing body f a t and increasing t h e l i p i d content of t h e blood plasma and l i v e . I n support of t h i s , Swislocki and Szego (1965)showed t h a t elevated l e v e l s of plasma nonester i f ied f a t t y acids occurred a f t e r t h e administration of growth hor- mones t o hypophysectomized ra ts .
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E f fec t of STH on carbohydrate metabolism
The following general statements may be m a l e regarding t h e ac t ion of STH on carbohydrate metabolism when administered t o m a m m a l s (Turner, 1966) :
1. The hormone tends t o produce hyperglycemia, thils aggravating d i abe te s .
2 . It i n h i b i t s t he ac t ion of i n s u l i n and i n s u l i n e f f e c t .
3. It increases muscle glycogen when given t o hypophysec- tomized sub jec t s .
4. It produces a permanent d i abe te s mel l i t i s i n c e r t a i n spec ies when given over prolonged periods.
The la t te r e f f e c t probably r e s u l t s from t h e eventual des t ruc t ion of t h e 8 - c e l l s of t h e pancrea t ic i s l e t s which sec re t e i n s u l i n . It has been shown t h a t ra t s rece iv ing excessive carbohydrates by tube feeding develop tem- porary d i abe te s when given STH.
Studies on STH i n meat animals
Baird -- e t d. (1952) assayed t h e hypophysis of two s t r a i n s of p igs se lec ted f o r e igh t generations on t h e b a s i s of rap id and slow rate of ga in . The two s t r a i n s reached u l t imate s i z e a t s i g n i f i c a n t l y d i f f e r e n t ages. When t h e growth hormone content of t h e p i t u i t a r y glands of t h e two s t r a i n s w a s determined, it w a s found t h a t at d l ages at which cornpaxisons w e r e made t h e glands of t h e f a s t e r growing s t r a i n contained s i g n i f i c a n t l y more somatotro- phin per u n i t of gland t i s s u e than d id t h e glands of t h e slower growing s t r a i n . This study showed t h a t t h e amount of somatotrophin per u n i t of p i t u i t a r y t i s s u e w a s t h e same i n t h e youngest and t h e o ldes t animal and t h a t it d id not v w y s i g n i f i c a n t l y throughout t h e growth period.
Armstrong and Hansel (1956) also demonstrated t h a t t h e r o l e of STH f o r con t ro l of growth w a s t r u e i n Hols te in h e i f e r s . concentration of somatotrophin per un i t of p i t u i t a r y t i s s u e w a s t h e same i n young growing ca lves as it i s i n a n i m a l s which have reached t h e growth p la teau . t h a t r ap id growth occurs as long as t h e r a t i o of t h e c i r c u l a t i n g somatotro- phin per u n i t of body t i s s u e remains s u f f i c i e n t l y high t o st imulate p ro te in synthes is and t o cause bone and muscle growth. The t h r e e l a t te r s tud ie s c i t e d a l l support t h e " d i l u t i o n theory," t h a t is , when t h e s i ze of t h e animal increases , t h e amount of hormone ava i l ab le per uni t of weight i s "diluted." Thus, o lder , heavier animals r e t a i n t h e i r a b i l i t y t o r e p a i r t i s s u e but l o s e t h e i r capacity t o grow a t a r ap id r a t e .
They showed t h a t t h e
These s tud ie s , along with t h e study of Simpson -- e t a l . (1950), show
Related s tud ie s on Duroc swine se lec ted f o r high and low back.fat
H e t z e r and P e t e r s (1965) and Hetzer and Harvey (1967) reported on t h e e f f e c t of s e l e c t i o n on Duroc s w i n e f o r both high and low backfat t h i ck - ness. A non-selected con t ro l l i n e derived from t h e same source as t h e se lec ted l i n e w a s maintained. After 1 0 generations of s e l ec t ion , t h e high-
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and low-fat Duroc l i n e s d i f fe red i n backfat by 2.6 cm. or 68% of t h e i n i t i a l mean. Selection basis on backfat depth w a s e f f ec t ive i n both the upward and downward d i rec t ion . y ie lds of lean meat and less f a t than the l i n e selected f o r m a x i m u m depth of backfat .
Pigs from the Duroc low backfat l i n e produced higher
Davey and Kincaid (1964) conducted i n i v i d u d feeding trials with pigs from high- and low-fat Duroc l i n e s . Carcasses were separated i n t o lean, fa t , bone, and skin at ages varying from 90 t o 400 days. The abso- l u t e weight of f a t and lean up t o 220 days of age showed l i n e a r t rends with age. Differences i n carcass composition for pigs fed normal d i e t s as estimated from regressions on age were: high Duroc, 23.2, 0; low Duroc, 17.3, 4.1; kg. of f a t and lean, respectively. The da ta show t h a t t h e high- fa t l i n e began t o l a y down more f a t than lean a t 18 weeks of age. However, t he low-fat l i n e did not begin t o l a y down more f a t than lean u n t i l 10 weeks l a t e r .
Gerrits -- e t al. (1964) found t h a t t h e an ter ior p i t u i t a r y weight of animals from the l i n e s of Duroc swine selected f o r high and low backfat d i f fe red s igni f icant ly from those of t h e control . This study a l so revealed t h a t t he heart , pancreas, and length of s m a l l i n t e s t ines from the selected l i n e s d i f fe red s ign i f i can t ly from the control . Thyroid weights between the l i nes were not s ign i f icant . cholesterol l e v e l s i n the Duroc selected f o r high backfat were s ign i f icant ly correlated with depth of backfat.
Johnson and Gerrits (1965) reported t h a t
Growth hormone study i n Duroc swine selected f o r h i& and low backfat
I n considering the f indings i n the previously c i t ed experiments and because of t he spec i f ic e f f e c t s known t o be mediated by the act ion of growth hormone and the responses manifested i n other species, a study w a s designed t o determine i f se lec t ion f o r high and low backfat had a l te red t h e concentration of growth hormone per - se.
The growth hormone content of an ter ior p i t u i t a r i e s from 30 Duroc swine balanced by l i n e and sex and selected on t h e bas i s of backfat depth w a s assayed using hypophysectomized female rats. The animals were d l slaughtered at a constant weight, and there w a s no s igni f icant difference i n the average age of t he animals at the t i m e of slaughter. There was a s igni f icant difference between all l i n e s with respect t o depth of backfat and percent of l ean cu ts . One ham f ron each animal w a s separated i n t o lean, fat , and bone. were s ign i f icant ly d i f f e ren t except f o r t h e percent of lean between control and low-line Duroc. The an ter ior p i t u i t a r i e s from f i v e animals of each sex i n each l i n e were pooled f o r t h e assay. The assay procedure used w a s t h a t of Greenspan -- e t a l . (1950). The an ter ior p i t u i t a r i e s from t h e control l i n e w e r e s ign i f i can t ly heavier than those from both of t h e selected l i n e s . Based on two assay c r i t e r i a , each l i n e contained the same amount of growth hormone per un i t of tissue. The amount of growth hormone contained per un i t of t i s s u e t e s t ed i n each a n i m a l w a s not d i f f e ren t as measured by t h e increase i n the growth of hypophysectomized female rats or i n s ize of epiphyseal ca r t i l age width. When t h e an ter ior p i t u i t a r i e s w e r e adjusted For weight, .the t o t a l STH potency ranged from highest t o lowest i n the control , low, and high l i nes , respect ively. Growth hormone concentration ner uni t of t i s s u e
The values from the three pa r t s of t h e ham between l i n e s
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between the three l i n e s w a s not s ign i f icant ly d i f f e ren t . This suggests t h a t genetic se lec t ion f o r high and low backfat has probably a l te red the a b i l i t y of t h e t i s s u e s t o respond t o STH.
Effect ~f endogenous and exogenous hormones on growth
It has been ably demonstrated t h a t t he implantation or addition of d i e thy l s t i l bes t e ro l ( a synthetic estrogen) t o t h e ra t ions of c a t t l e , mainly steers and he i fe rs , i s a common and benef ic ia l pract ice . Since many a r t i c l e s have been published on DES and it has been reviewed by previous speakers at t h e Reciprocal Meat Conference, I w i l l not discuss any speci€ic e f f e c t s of DES at t h i s t i m e .
Recent s tudies have shown t h a t t he feeding of melengestrol acetate (MGA), an act ive progestin or ig ina l ly t e s t ed t o synchronize the estro-ds cycle, improves r a t e of gain and promotes growth i n he i fe rs . Bloss -- e t a l . (1966) reported increases i n rate of gain and feed e f f ic iency when KA-fed he i f e r s were compared t o cont ro ls . -- e t a l . (1968), crossbred he i f e r s fed .3 mg. of E A i n t h e feed per head per day f o r 140 days gained s igni f icant ly f a s t e r (21%) and made 11% more e f f i c i e n t use of t h e i r feed than he i f e r s receiving the same feed without MGA. I n t h e l a t te r study, carcass grades, marbling score, and dressing percentage of %A-fed h e i f e r s and controls conformed subs tan t ia l ly with the r e s u l t s of Bloss e t aL. (1966). unaffected by E A i n t h e feed; however, no spec i f ic measurements taken with regaxd t o the amount of f a t or l ean i n the carcass were reported.
I n a recent study reported by O'Brien
I n the study of O'Brien -c e t a l . (1968) dressing was --
N o changes i n general body conformation or vaginal prolapses, as reported t o occur i n estrogen-treated he i fe rs , w e r e observed among any of t he EA-treated h e i f e r s (Bloss -- e t al., 1966). Zimbelman and Smith (1966) showed t h a t E A dos-.s of approximately .2 mg/heifer/day w i l l prevent e s t r u s i n some he i fe rs , and doses of .5 mg/day w i l l prevent e s t r u s i n almost a l l he i f e r s . a n i m a l s but r a r e l y i n MGA-treated animals. Heifers which were found t o be sexually mature and then spayed grew more slowly and had poorer feed ef - f i c i ency than mature in t ac t he i fe rs . The feeding of E A t o spayed he i f e r s did not improve growth r a t e or feed eff ic iency s igni f icant ly . These re - sults, along with results on f o l l i c u l a r s i z e , substant ia te t he hypothesis proposed by Bloss L- e t al. (1966) t h a t E A caused increased weight gain by allowing continual endogenous estrogen secret ion. The failure of s t e e r s t o respond t o MGA seems t o be consis tent with t h i s hypothesis.
They also reported ovulation occurred regular ly i n untreated
Effec t of tes tosterone on growth
It i s w e l l known t h a t tes tosterone promotes pro te in anabolism and decreases t h e urinary l o s s of nitrogen without increasing the non-protein nitrogen of t h e blood and t h a t it produces at least a temporary increase i n body weight. This suggests t h a t t h e hormone causes a t r u e storage of nitrogen i n t h e form of t i s s u e protein. It should be noted t h a t androgens increase t h e body weight of young hypophysectomized r a t s ; but most of t h i s ga in i s accounted f o r by the increased mass of t he genital. coml;lex, ap- parent ly consequent upon protein re ten t ion (Turner, 1966). The changes i n body weight produced by tes tosterone vary with t h e species and a l s o depend on the nu t r i t i ona l s t a t u s of t he animal.. Karlson (1963) and Liao and
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Williams-Ashman (1962) have demonstrated t h a t the microsomes from the pros ta te gland of t he tes tosterone-treated r a t have a greater a b i l i t y t o incorporate sa l ine C-14 i n t o protein than microsomes f rom cas t ra ted sub- j e c t s . Since nucleic acids are int imately associated with the synthesis of proteins, t he growth processes i n i t i a t e d by androgens and various t a r g e t t i s s u e s could be mediated at t h e l e v e l of the gene.
Bra tz le r e t al. (1954) reported t h a t barrows cas t ra ted at 180 l b s . and boars had a higher percentage of l ean i n the lo in , a lower dressing per- centage, and less backfat than pigs castrated a t 70 days and 100 l b s . Zobrisky e t al. (1959) and Teague e t al. (1962) also reported a s igni f icant ly higher yield of l ean meat from the carcasses of boars. showed t h a t t he carcasses of boars and g i l t s were longer and had less fa t covering over t h e shoulder and back area of l o i n and a higher iodine number than those cas t ra ted la te . I n t h i s study, acceptab i l i ty t e s t s showed t h a t t he age of cas t ra t ion did not a f fec t f lavor , odor, o r tenderness of meat.
--
-- -- Charette (1961) also
The study of Frescot t and Lamming (1964) showed t h a t ca s t r a t ion consis tent ly depressed growth r a t e i n c a t t l e and sheep. They fur ther point out i n t h e i r study t h a t t h e carcasses of ca s t r a t e s contain much more f a t and less l ean and bone than those of t h e i n t a c t animals. Boars a l so yielded a much leaner carcass containing 19 l b s . less f a t and 7 l b s . more l ean than the carcasses of hogs a t 260 l b s . of liveweight.
Collectively, these s tudies point out t h a t the use of t h e i n t a c t male holds considerable poten t ia l with present demands f o r more e f f i c i e n t production and t h e production of more l ean m e a t .
Concludim remarks
On t h e foregoing pages, I have considered only a handful of t he issues on problems germane t o the e f f ec t of the endocrine system on growth and development. Without doubt, many other considerations could or should have been included. ta in ing t o the f i e l d of endocrinology w i l l understand t h e d i f f i c u l t i e s i n t ry ing t o present a comprehensive discussion of t h e top ic i n a l imited t i m e . On the other hand, it i s hoped t h a t the cen t r a l theme has been presented. Surprisingly l i t t l e work has been conducted on the spec i f ic e f f e c t s and bene f i t s t h a t might be real ized i n meat animals through s tudies i n endo- crinology. Also, we as animal s c i e n t i s t s have been pa r t i cu la r ly slow i n applying basic discoveries i n biology t o all aspects of m e a t animal prcduc- t i o n . Resolution of t h e problems and r ea l i za t ion of t he bene f i t s w i l l r e - quire m a x i m u m e f f o r t as well as e f f ec t ive u t i l i z a t i o n of t a l e n t s from many s c i e n t i f i c d i sc ip l ines working together . Thus, i n meeting our responsi- b i l i t i e s t o society as animal s c i en t i s t s , we are faced with a demanding but exc i t ing challenge for the fu ture .
Those familiar with the vas t amount of literature per-
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Beach, R . K. and J. L. Kostyo. 1968. "Effect of growth hormone on t h e DNA content of muscles of young hypophysectomized ra ts . I '
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D. A. CRAMER: Thank you very much, D r . Gerrits, and I w i l l thank all of you gentlemen f o r a s e r i e s of very f i n e papers. I th ink you wodd all make top-notch meats men. Fortunately, t he group ups t a i r s i s also running a f e w minutes behind, so we do have time f o r a f e w questions. I th ink we can run u n t i l about two o'clock for questions. I won't take time out from our discussion t o introduce Dave Topel, because most of you know him, anyway. 1'11 j u s t l e t him get s t a r t ed with t h e questions.
D. G. TOPEL: Thank you, Dave. I ' m sure you w i l l a l l agree t h a t a2.1 of the people on t h i s program are very in te res ted i n composition, and maybe not d i r e c t l y with meats, but cer ta in ly i n the end product t o 8 ce r t a in degree. A t t h i s t i m e I would l i ke . t o ask f o r questions regarding the papers. Are there any questions?
PAUL LEWIS, Arkansas: I would l i k e t o d i r e c t t h i s t o the second speaker--how are you analyzing for sodium and potassium?
DR. EWAN: O u r meat analyzing i s by photometric methods.
LEWIS: Do you worry about any interferences?
EWAN: We haven't investigated t h i s point as yet . I believe there are differences i n response depending on the l e v e l s of sodium and potassium t h a t aze present, and t h i s i n pa r t i cu la r . I n other words, when you go t o look between t i s sues , with a system t h a t i s geared t o work with plasma or serum, you would have t o a l t e r your system t o be sure t h a t you are get t ing accurate measurements, because of t he r e l a t ive enhancements.
DR. HENDRICKSON, Oklahoma: I would l i k e t o address a question t o Gene Allen. Fa t i s deposited i n connective t i s sue and I am wondering a s the fa t bui lds up, i s there an increase i n the connective t i s sue?
341.
DR. A L B N : I n thinking back, i n dressed beef animals, I don' t t h i n k we have shown a l a r g e difference i n f a t t y t i s s u e i n some of t h e mus- c l e s we have looked a t . These changes have been more i n t h e composition, but as far as I am aware of , I would say no.
HENDRICKSON: You don ' t f e e l t h a t there i s a generation of con- nective t i s s u e as l i f e proceeds?
ALLEN: Not much.
DR. TOPEL: If there are no f u r t h e r questions, I w i l l t u r n it back t o D r . Cramer.
DR. C R M R : Thank you, D r . Topel. This has been an excel lent session. We are running a b i t behind schedule and are due back i n t h e Main Auditorium f o r a paper which you all w i l l want t o hear on Changes i n Standards f o r Pork Carcasses and Slaughter Hogs by John Pierce and Peter W i l l i a m s of t h e U.S.D.A. So l e t ' s adjourn t h i s session and proceed t o t h e Main Auditorium.
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STATISTICAL COMMITTEE W N AUDITORIUM GEORGIA CENTER
H. W. OCKERMAN: I ' l l c a l l t h e meeting t o order and since we're a b i t behind schedule I ' l l not name t h e other Embers of t h e S t a t i s t i c a l Committee. They are l i s t e d i n t h e back of t h e program. We are for tunate t o have two i n t e r e s t i n g papers t h i s afternoon and two highly qual i f ied speakers: George Brissey of Swift on "Sampling" and C . F . Parker of Ohio on "Biological Variation". George will be OUT f irst speaker.
