Effect of polychlorinated biphenyls (Aroclor 1254) on liver gluconeogenic enzyme activities in embryonic and growing chickens

Fertile Nick Chick eggs were injected with 0.05, 0.1, 0.5 and 5 p.p.m. of PCB (Aroclor 1254) on day zero and were incubated until the 14th day of incubation. Nick Chick cockerels, one day old, were fed different levels of PCB in their diet for two weeks. The levels of PCB used were 0.1, 1, 5, 100 and 200 p.p.m. Key gluconeogenic enzyme activities were measured in the liver of both experimental groups. In the liver of chick embryos and growing chickens the decrease of the activity of all key gluconeogenic enzymes, with the exception of G6P-ase in embyronic liver, and FDP-ase in that of growing chickens, was estimated. The inhibited gluconeogenesis may account for the embryonic death in eggs contaminated with PCB's.

Characterization of a new reverse transcriptase of possibly cellular origin in the chicken system

The properties of an RNA-dependent DNA polymerase, which occurs ubiquitously in the allantoic fluid of uninfected, leukosis-virus-free eggs, are described. It is shown that the enzyme can synthesize faithful transcripts from natural RNA (globin mRNA). With biochemical and immunological methods, the enzyme can be clearly distinguished from the reverse transcriptases of the known chicken RNA tumour viruses and therefore seems to be a member of a so far unknown class of chicken polymerases. Our data show that in the chicken system reverse transcriptase can occur without connection to the replication of RNA tumour viruses and without relationship to the induction of malignancy.

The use of variable lactate/malic dehydrogenase ratios to distinguish between progenitor cells of cartilage and bone in the embryonic chick

The activities of LDH and MDH have been studied, both in differentiated cartilage and bone from the embryonic chick, and in the pool of mixed osteogenic and chondrogenic stem cells found on the quadratojugal, a membrane bone. In confirmation of the model proposed by Reddi & Huggins (1971) we found that the LDH/MDH ratio was greater than 1 in cartilage and less than 1 in bone. Furthermore we established, for the first time, that ratios occurred in the chondrogenic and osteogenic stem cells, similar to the ratios in their differentiated counterparts. Alteration in LDH/MDH resulted from variations in the level of LDH/mug protein. MDH/mug protein remained constant, even when LDH/MDH was changing. We interpret these results in terms of adaptation of chondrogenic progenitor cells for anaerobic metabolism and anticipate that our model will be applicable to other skeletal systems where stem cells are being studied.

Protein synthesis, development, growth and life span

To test the hypothesis that reduced protein synthesis may increase life span by retarding genetic informational transfer during early life and reducing the use of the genetic code and thereby minimizing genetic imperfections as they may occur during late life, two approaches were used. In the first protein synthesis was depressed by the administration of cycloheximide, in the second by reducing the dietary protein level. One-day-old chick embryos were injected with either 0.8 gamma or 1.0 gamma of cycloheximide. On the second and third day of incubation both stage of development and heart rate were lower in the treated embryos. Growth was retarded throughout the 17 days of incubation as measured by size and DNA contents. As estimated by the activities of various enzymes per unit DNA, cells of the treated embryos were the same as normal ones of the same age. Sixteen-month-old female Wistar rats which had been previously maintained on a commercial diet (23.4% protein) were fed diets which contained either 24, 12, 8 or 4% casein throughout their remaining life span. Except for a lowering of the body weights of the animals fed the 4% casein diet, the body weights of the remaining animals were unchanged. Reducing the dietary protein level from 24% to 12% increased the life span (25%) of the animals.

Precocious development of glucuronidating and hydroxylating enzymes in chick embryos treated with pituitary grafts

1. Initiation of precocious development of UDP-glucuronyltransferase by an endogenous factor is reported for the first time. 2. This development occurs in chick embryo liver and kidney after grafting of the cephalic lobe of chicken pars-distalis pituitary tissue on to the chorioallantoic membrane, and in liver results in a rise in the enzyme activity from virtually zero to ;adult' values. Aniline hydroxylase also precociously develops in the liver of grafted embryos, its activity rising from one-third to the full adult value. Specific activities of glucose 6-phosphatase, cytochrome P-450 and NADPH-cytochrome c reductase did not significantly change. 3. The response of the transferase does not require the presence of host pituitary gland nor, apart from 1 day's necessary initiation, the presence of the graft itself. 4. The host becomes competent to respond on the 14th day of incubation; response continues for at least 3 days after removal of the graft, and for 2 days in the isolated liver. Grafting of embryonic pars distalis younger than 17 days does not evoke a response in the host liver. 5. Secretion of the pituitary factor increases suddenly some 24-48h before the naturally developing surge in liver UDP-glucuronyltransferase activity and may be responsible for initiating this rise in vivo. 6. The factor is probably not a growth or luteinizing hormone; its nature and the likelihood of a secondary hormone acting directly on the liver are discussed.

Aspartate aminotransferase activity during early development of chicken embryo

Aspartate aminotransferase (AAT) activity is studied, employing two different procedures, during early development stages of chicken embryo. ATT activity is steady from pre-streak to the definitive primitive streak stage after which it suddenly increases as growth proceeds. INH or IIH administration in this embryonic system led to almost instantaneous and complete disappearance of AAT activity which could be reversed to 80 percent by treatment with equimolar pyridoxal phosphate. Histochemical studies from the literature support a view that the period of intense differentiation coincides with an increased RNA content. The present study shows more AAT activity per mg wet embryo during the same development stages. Whether this is due to availability of more aspartic acid for pyrimidine is not clear due to possible presence of two AAT activities, the many competing reactions that can use aspartic acid, and in situ conditions during differentiation.

Host response to infection by Coxiella burneti

A host response to infection by Coxiella burneti was investigated. Infectedyolk sacs were harvested from embryonated eggs and assayed for glycolytic activity. Assays of glycolytic enzymes included glucose isomerase, aldolase, phosphofructokinase,fructose-1,6-diphoshatase, glyceraldehyde-3-phosphate dehydrogenase, enolase, and pyruvate kinase. No significant differences in enzymatic activity between normal and infected tissues through the 12th day was observed. From the 13th day through the 16thday, the glycolytic activity of normal tissues decreased. Glycolytic activity of infected tissues did not decrease, but showed a gradual increase during this same time period. Embryos from infected eggs demonstrated a gradual decrease in total weight fromthe 12th day until death occurred on the 16th day.

Activity of liver fructose diphosphatase from chick embryos treated with aminoguanidine sulfate

Injection of chick embryos with aminoguanidine sulfate (AGS) on the fourth day of incubation resulted in a decreased specific activity of liver fructose diphosphatase (FDPase) prior to hatch time. This decreased FDPase specific activity was found to be the consequence of increased levels of an enzyme inhibitor (adenosin 5'-monophosphate) rather than a specific repression of enzyme synthesis.

[Glutamate-oxalacetate-transaminase in irradiated and nonirradiated chick embryos]

The enzymatic activity of glutamate-oxalacetate transaminase (GOT) in 16 days old chick embryos was investigated in 10 minute-intervals following X-ray irradiation with 1000 R. Initially, in the tissue homogenates of the embryos and in the blood serum a decline of enzyme activity was observed, which continued for 30 minutes after irradiation. Subsequently - during a second phase - the enzymatic action was increased far beyond the norm. On the contrary, in the tissues of the allantois no significant change of the GOT-concentration was seen following irradiation.

Ontogeny of lactate dehydrogenase isozymes in chicken-quail hybrid embryos

The ontogeny of lactate dehydrogenase (LDH) isozymes was examined in avian hybrids and compared with the isozyme patterns of the parental species. Hybrids were obtained by crossing female Japanese quali (Coturnix coturnix japonica) with male domestic chickens (Gallus gallus domesticus). By use of starch gel electrophoresis and an enzyme-specific stain, traces of embryonic paternally derived LDH were detected in unincubated hybrid eggs. It was concluded that the embryonic genes coding for the B subunits of LDH are activated during the hours between fertilization and oviposition. In early blastoderms, a great excess of maternally stored LDH is present. In the hybrid, the predominantly maternal pattern of isozymes shifts during embryogenesis to a predominantly paternal pattern. This was considered evidence for differential allelic regulation of LDH inactivation. A progressive trend toward the establishment of the adult distribution of isozymes in various tissues was also observed in the hybrid and quail, and found to be similar to chicken LDH isozyme ontogeny.

A Re-Examination of Succinic Dehydrogenase Activity and its Association with Cell Death in the Interdigit of the Chick Foot

Massive cell death, which accompanies the freeing of the digits, occurs in the interdigits of the developing chick foot during stages 30-35. The possibility was reexamined that mitochondrial succinic dehydrogenase activity disappears in the interdigital cells of the chick foot 24 h before cell mortality. Using standard histochemical means it was found that succinic dehydrogenase activity was demonstrable in the interdigital cell population up to and including the time when cell death begins. This was confirmed quantitatively employing biochemical methods which indicated that succinic-cytochrome c reductase specific activity was approximately the same in homogenates of digital and interdigital tissues harvested just prior to the death of interdigital cells. Further, NADH-cytochrome c reductase specific activity was comparable in digital and interdigital tissue homogenates. These data make it unlikely that ‘biochemical degeneration’ associated with alterations in aerobic energy metabolism occurs in the interdigital cells before death as has been suggested by other workers previously. The methods used by these authors to demonstrate succinic dehydrogenase were repeated on chick feet in our laboratories and an alternative interpretation of the results is offered.

Development of hydroxytryptophan decarboxylase activity in the pineal gland, cerebral hemispheres, and cerebellum of the chick embryo and young chick

The courses of increase in 5-hydroxytryptophan decarboxylase activity in the chick pineal gland, cerebral hemispheres, and cerebellum have been followed from the 10-day embryo to 2-weeks post-hatch. Activity was first detected in the pineal gland and cerebral hemispheres of 12-day embryos, and in the cerebellum of 18-day embryos. In each tissue, there was a rapid initial rise in activity to about the stage of hatching, followed by a further less rapid rise to levels of 50–100% of those found for adult birds.