Newborn Guinea Pigs Research Articles

Differentiation and transdifferentiation of adrenal chromaffin cells of the guinea pig. II. Adrenal medullary explants grown in tissue culture.

Explants of adrenal medullary tissue taken from newborn guinea pigs were grown in culture for up to two weeks. The explants exhibited sparse outgrowth of neurite-like processes, in contrast to adrenal medullae taken from young postnatal rats or adults guinea pigs that were (i) grown under identical conditions (Unsicker and Chamley 1977) or (ii) transplanted to the anterior chamber of the eye (Unsicker et al. 1981), respectively. Nerve growth factor (10-100 ng/ml, 2.5 S NGF) did not enhance formation of processes. However, electron-microscopic investigations revealed the presence of numerous processes within the explants, which extended from chromaffin cells and were characterized by longitudinally oriented cytoskeletal structures, various population of clear and dense-cored vesicles, varicosities and growth cones. Chromaffin cell bodies largely resembled their in situ-counterparts, but had fewer and smaller storage vesicles than controls. The results are discussed in light of recent findings regarding the potency of NGF and NGF-like growth factors to induce neuronal transdifferentiation of adrenal chromaffin cells.

248 DEVELOPMENTAL CHANGES IN FATTY ACID OXIDATION IN NEWBOEN GUINEA PIG HEART

School of Medicine. Children's Hospital of Philadelphia, Department of Pediatrics, Philadelphia. Fatty acids (FA) are important substrates for the myocardium and liver in adult mammals. Developmental changes have been demonstrated in FA oxidation in newborn rat and guinea pig liver. The purpose of this study was to determine if similar changes occur in guinea pig heart. In vitro rates of FA oxidation were determined using homogenates of heart from near term fetuses delivered by C-section, from newborn pups, and adult guinea pigs. Rates of 14 CO2 production from [1-14C] palmitate (.75mM) at 35°C over 30 minutes are expressed as uM/hr/gm tissue.At 6 hours of age, 2 spontaneously born guinea pigs had FA oxidation rates of 1.79 and 1.09uM/hr/gm. These findings indicate that in the newborn guinea pig heart there is a 3 fold increase in the capacity to oxidize FA. This developmental change occurs post-natally. The sites of limitation and regulatory mechanisms are yet to be determined. These findings may have implications in the nutrition of premature infants.

1700 PULMONARY EFFLUENT CELLS, CHEMOTAXIS, AND ELASTASE IN O2 EXPOSURE

Influx of polymorphonuclear leukocytes (PMN) and alveolar macrophages (AM) into pulmonary effluent of infants developing bronchopulmonary dysplasia has been found at the 3rd & 7th day with exposure to FiO2>.6 & mechanical ventilation. The finding prompted an evaluation of these cells in O2 exposed newborn guinea pigs (GP). Cell influx into pulmonary effluent, their chemotaxic response to 10−5M N-formyl-methionyl-phenylalanine (FMP) using the double filter Boyden Chamber technique, & effluent elastase, a protease produced by both PMN and AM, measured by elastase activity against succinyl-L-alanyl-L-alanyl-L-alanine-p-nitroanilide was measured in GP after 72 hr. exposure to FiO2>.9 or .21.These data indicate that O2 exposure in newborn GP increase PMN & AM influx into lung effluent & that these cells are more chemotaxic than in controls. Increased cell number & enhanced chemotaxis of lung effluent PMNs & AM may result in the release of toxins to airway epithelium. Effluent elastase activity is significantly reduced by 72 hrs of O2 exposure, possibly as a result of depletion or degradation. (Supp. by HD-13279)

Le rythme thêta de SP comme indice de maturation cérébrale: Etude chez le Rat et le Cobaye

The evolution of hippocampal theta rhythm during paradoxical sleep (PS) was studied in the newborn rat and guinea pig. Very immature at birth, the rat displays a typical theta rhythm on day 16 with a mean frequency of 5.10 Hz. On day 29 this frequency reaches 6.9 Hz and ceases to be significantly different from the adult mean value. In the much more mature newborn guinea pig, this rhythm is very typical as early as birth. Its mean frequency is 6.46 Hz at 3 days and reaches 7.13 Hz at 8 days. Then its mean ceases to be significantly different from the adult value. The spectral components of theta rhythm during PS become comparable to the adult distribution at about 24 days in rat and 13 days in guinea pig. These findings are in agreement with histological, neurochemical and behavioral data. They show that theta rhythm of PS is a good index of cerebral maturation, especially at the hippocampal level.

Applicability of two different lead systems in studies of the electrical activity of the hearts in newborn guinea pigs

Recent findings of ours from vectorcardiographic studies with the anatomically orthogonal SVEC II system of Schmitt and Simonson on postnatal guinea pigs did not coincide with earlier VCG findings from preparations of isolated guinea pig hearts beating in a homogenous volume conductor. This suggested that in the guinea pig as in the human a more intricately corrected lead system ought to be used. In order to apply to guinea pigs the electrically corrected lead system proposed by Frank in 1956 for clinical use in human electrocardiography, the underlying biophysical assumptions had to be examined. The electrical center of ventricular depolarisation in the guinea pig heart was determined by measurement of cancellation potentials around the thorax and by geometrical construction of different horizontal loops of the image surface. Cancellation coefficients and ventricular dipole locations of guinea pigs of different ages proved to be in the same range as the corresponding human values. Application of the Frank lead system to guinea pigs two days old and older gave vectorcardiographic parameters which corresponded to those obtained from Langendorff heart preparations.

Phospho enolpyruvate synthesis by fetal guinea-pig liver mitochondria

Liver mitochondria isolated from fetal and newborn guinea pigs synthesized phospho enolpyruvate at 4–6 nmol/min per mg protein with 2 mM malate, succinate, and α-ketoglutarate as substrates. These rates were 90–110% of that by adult liver mitochondria and were not substantially altered in the second half of gestation or within 24 h after birth. Both palmitoyl- and octanoylcarnitine were inhibitory to phospho enolpyruvate synthesis in adult and fetal preparations, but free octanoate was inhibitory only in adult liver mitochondria.

Asymmetry of hexose transfer system in erythrocytes of fetal and new-born guinea-pigs.

1. The asymmetries of affinities of two non-transportable competitive inhibitors of hexose transfer across fetal and new-born guinea-pig erythrocytes have been studied. 2. At 16 degrees C 4,6-O-ethylidene-alpha-D-glucopyranose (ethylidene glucose) inhibited 3-O-methyl glucose exchange at 20 mM with a K1 oc ca. 52 mM when present inside the cells and with a K1 oc ca. 10 mM when outside. This fivefold asymmetry is qualitatively similar to but smaller than the tenfold asymmetry of human erythrocytes (Baker, Basketter & Widdas, 1978). 3. Methyl-2,3-di-O-methyl-alpha-D-glucopyranoside (trimethyl glucoside) had K1 values of ca. 120 mM and ca. 160mM for inside and outside inhibition respectively. This is also qualitatively similar to the inhibition in human erythrocytes. 4. The inhibition produced by phlorizin, phloretin and Cytochalasin B was also studied in the erythrocytes of new-born guinea-pigs. The results were qualitatively similar to those for human erythrocytes but the inhibitory affinities were different. Thus while phlorizin and phloretin had higher affinities for the inhibition of exchange in new-born guinea-pig cells than human cells, the affinity of Cytochalasin B was less for new-born guinea-pig cells than for human cells. 5. It is concluded that the hexose transfer system in fetal and new-born guinea-pig red cells has asymmetric affinities similar to the system in human red cells but with different values of the inhibitory constants. The differences may represent species variations in a structural protein serving identical functions in the two species. 6. The possibility that fetal red cells with their facilitated transfer system play a role in sugar transport is discussed.

Autoradiographic studies on the fetal and newborn uteri of the guinea pig after injection of 3H-progesterone into non-treated and into estradiol-primed animals.

The localization and retention of radioactivity in the uteri of fetal and newborn guinea pigs was studied after subcutaneous injection of 3H-progesterone into intact and estradiol-primed animals. In the fetal uterus of the animals treated with estradiol, a significant increase in the accumulation of silver grains was observed, mainly localized in the stroma and myometrium, but very little is detected in the uterine gland. On the other hand, in the uteri of newborns, the effect of estradiol on radioactivity retention was significantly less intense and the radioactivity is mainly localized in the epithelium and the uterine gland. These data correlate well with the quantitative evaluation of the concentration of progesterone-specific-binding sites in the non-treated and in the estradiol-primed fetal and newborn guinea pigs.

Progesterone and oestradiol receptors in the uterus of oestradiol-primed fetal and newborn guinea-pigs.

The responsiveness of the uterus of the guinea-pig to oestrogen treatment was studied in the fetal and perinatal periods. Twenty-four hours after one dose of 1 mg oestradiol/kg body wt to the pregnant guinea-pig, there was no significant increase in uterine wet weight of the fetus but a sevenfold increase in the concentration of progesterone receptors. In the perinatal period, doses of 1, 10 and 100 micrograms oestradiol led to as much as an 80% increase in uterine wet weight after 24 h in both 2- and 7-day-old guinea-pigs. On the other hand, levels of progesterone receptors in newborn animals showed a smaller increase (twofold) than that which occurred in the fetal uterus. In both fetal and newborn guinea-pigs, total oestradiol-receptor concentrations (both available and occupied binding sites) decreased significantly after treatment with oestradiol. It was concluded that the hormonal effect of oestradiol on progesterone-receptor synthesis can be expressed in the fetus and to an even greater extent than in the perinatal period over the same period of time. In the fetus, this response can be distinguished from the overall uterotropic effect of oestradiol.

Hematology in developing guinea pigs—I. normal maturation

1. 1. Newborn to 24 week old male guinea pigs were studied at 22°C and an ambient P o 2 of 133 torr. The following hematological variables were measured once on each animal: hematocrit, [Hb], RBC indices, WBC differentials, and the molar ratio of 2,3-diphosphoglycerate (2,3-DPG) tq [Hb]. 2. 2. [Hb] declined from 15.8 g/100ml at birth (BW = 90 g) to 12.6 g/100 ml when BW = 252 g, and then increased linearly with increasing BW. Red cell indices were nearly constant at all BWs: MCV = 81.7 μm 3; MCH = 25.1 pg; and MCHC = 30.7%. In newborn guinea pigs, lymphocytes comprised the majority (73%) of WBC's, but this percentage fell to 55% in mature animals. The ratio of [2,3-DPG]/[Hb] rose from 1.40 M/M following birth to 1.95 M/M (BW = 154 g) and then declined to 0.92 M/M in mature animals. 3. 3. The relative maturity of the hematological profile in newborn guinea pigs contrasts with those in the laboratory mouse and laboratory rat.

Audiotoxicosis in newborn guinea pigs from pregnant ones given sisomicin

The audiotoxic effect of sisomicin was investigated in guinea pig injected intramuscularly with 6.25, 12.5, 25 and 50 mg/kg of sismicin sulfate (potential) during weeks 1–5 or 5–9 of pregnancy, and the transplacental effect on their offsprins was studied. While in some dams the higher doses of sisomicin produced a limited effect on the pinna reflex and the outer hair cells of the organ of Corti, no such effects were noted in any of the offspring during the 3-week postnatal observation period.

Estrogen concentrations and effect of estradiol on progesterone receptors in the fetal and new-born guinea-pigs

Estradiol concentration in plasma of fetal guinea-pigs, determined by radioimmunoassay, varies from 9 to 40 pg/ml and the concentration of estrone between 80 to 105 pg/ml. The concentrations of both estrogens do not change significantly during fetal evolution. The total number of specific estradiol binding sites in fetal guinea-pig uterus reaches 18 to 20pmol/mg DNA at the end of gestation, and the concentrations of estradiol plus estrone is ∼1500 pg per g of this tissue which correlates well with the number of specific binding sites occupied by the endogenous estrogens (2–4 pmol/mg DNA). In the fetal uterus, estradiol receptors appear at about mid-gestation (from 34 days) but progesterone receptors are detectable only after 50–52 days of gestation. After estradiol treatment of the pregnant guinea pig (1 mg/kg/day for 3 days), the following changes take place in the fetal uterus: (1) Induction of progesterone receptor protein at an earlier period (37–42 days) when this receptor is not detectable in control animals. (2) Five to ten-fold increase in progesterone receptors at the end of gestation. (3) An increase of [ 3H]-progesterone uptake by fetal uterus (localized by autoradiography). (4) The stimulation of progesterone receptors is of long duration. Five days after treatment the values are similar to those obtained 24 h after the administration of the last dose of estradiol. (5) Similar effects were noted also in fetal ovary, but not in lungs, kidney, brain and heart or placenta. (6) The induction of progesterone receptors by estradiol is significantly lower in the uterus of new-born guinea pigs (2–7 days old). It is concluded that estradiol expresses its biological effect in the fetal compartment, increasing the levels of progesterone receptors.

Body lipids of guinea pigs exposed to different dietary fats from mid-gestation to 3 months of age. V. The fatty acid composition of brain lipids at birth.

Pregnant guinea pigs were fed on one of three diets: a commercial low-fat diet or a high-fat diet containing either maize oil or beef dripping. The young were killed at birth, the brain removed and dissected into three regions; the cerebellum, cerebrum and stem. The fatty acid composition of the major phospholipid classes, phosphatidylcholine and phosphatidylethanolamine was determined using gas chromatography. Compared with those fed the commercial or beef dripping diet the brain of the young of mothers fed maize oil during pregnancy had an increased percentage of linoleic acid and of its long-chain derivatives arachidonic acid and docosapentaenoic acid and a lower percentage of docosahexaenoic acid. These changes occurred in both lipid classes and in all regions of the brain. The results demonstrate that the fatty acid composition of the brain lipids of newborn guinea pigs can be influenced by the nature of the maternal dietary fat consumed during the last weeks of pregnancy.

Receptor and biological response to estriol in the fetal uterus of guinea pig.

The binding of 3H-estriol was examined in the fetal uterus of guinea pig. The physico-chemical characteristics of the binding of 3H-estriol to macromolecules are similar to the typical receptor protein for estrogens. Different estrogens (estriol, estradiol, estrone and diethylstilbestrol) compete with this binding but progesterone and testosterone have no effect. The binding affinity has a Kd of 5.5 +/- 1.6 +/- 10(-10) M. By ultracentrifugation in sucrose gradient, two specific components with sedimentation coefficients of 8 and 4S are found. Competition studies suggest that the same specific binding sites may be present for estriol (E3) and for estradiol. The s.c. administration of E3 to the pregnant guinea pig (1 mg/day per kg body weight for 3 days) provokes two biological responses in the fetal uterus: a uterothopic effect and a significant increase in the progesterone receptor. The increase in the fetal uterine weight is 50-70% in relation to the non-treated animals and the progesterone receptor concentration is 10-14 times higher than in the control animals. These effects are similar (or slightly higher) than in animals primed with equimolecular quantities of estradiol. In contrast, single daily injections of E3 to newborn guinea pig, results only in weak uterotrophic activity. It is concluded that estriol is capable of causing a biological response in the uterus during intra-uterine life.

Electrophysiological study of the ototoxicity of kanamycin during development in guinea pigs

In order to test the ototoxicity of antibiotics during development, pregnant guinea pigs were intoxicated with kanamycin at different stages of gestation. Eighty newborn guinea pigs were tested electrophysiologically by recording the cochlear microphonic potential and the compound action potential from the round window in response to tone bursts and filtered clicks of various frequencies. Thirty-one animals presented antibiotic injury and showed electrophysiological changes similar to those previously described in adult mammals after kanamycin intoxication. The results suggest a relationship between the ototoxicity of kanamycin and the onset of the auditory function: cochlear potentials were mostly affected when the intoxication was performed during the last 15 days of gestation.

Hepatic 3-hydroxy-3-methylglutaryl coenzyme a reductase activity amd cholesterol 7α-hydroxylase activity in neonatal guinea pig

Optimal assay conditions for hepatic HMG-CoA reductase activity and cholesterol 7α-hydroxylase activity in the guinea pig were determined. These two enzyme activities were studied in the liver of newborn guinea pigs during the first three postnatal weeks. Hepatic HMG-CoA reductase activity of neonatal guinea pigs was similar to that of adult animals. However, cholesterol 7α-hydroxylase activity of newborns was about one-third of that in adult guinea pigs. This finding suggests that the system for bile acid synthesis in the neonatal guinea pigs is underdeveloped.

Hypothalamic mono amine contents in endotoxin fever of new-born guinea pigs and kittens

In new-born guinea pigs and kittens Escherichia coli endotoxin did not significantly modify the hypothalamic level of either norepinephrine (NE) or 5-hydroxytryptamine (5-HT). The hypothalamic 5-hydroxyindoleacetic acid (5-HIAA) content was significantly elevated in endotoxin-treated animals, but this elevation was confined to a period following the endotoxin injections by about 60 min in guinea pigs and 75–90 min in kittens.

Sterol and bile acid metabolism during development. 3. Occurrence of neonatal hypercholesterolemia in guinea pig and its possible relation to bile acid pool

The relationship of the changes in plasma cholesterol to bile acid pool was studied in the newborn guinea pig. Plasma cholesterol reached the maximum on the fifth day and gradually declined to adult levels. The cholesterol concentration in the high density lipoproteins (HDL) was higher in the newborn guinea pig than in the adult. Plasma triglycerides peaked on the third day and decreased markedly. The bile acid pool increased progressively after birth with a 13-fold increase at 5 days of age. While the hepatic triglycerides decreased sharply in the newborn guinea pig, hepatic cholesterol increased in the first 5 days and then decreased to adult levels. This study has described the occurrence of “neonatal hypercholesterolemia” in the guinea pig and its possible relationship to the low level of bile acid synthesis.

Evidence for the Existence of Phosphoenolpyruvate Carboxykinase Ferroactivator Activity in Adult and Fetal Guinea Pigs

Newborn (24--72 h) guinea pig liver cytosolic phosphoenolpyruvate carboxykinase (PEPCK) activity is increased by incubation of the cytosol with the metal salts FeCl2, MnCl2, CoCl2 and CdCl2. FeCl2 at 30 micromol/l concentration is the most effective activator causing a 3.5-fold increase in activity. Purified rat liver cytosolic PEPCK is activated by 30 mumol/l FeCl2 in the presence of liver cytosol of fetal and newborn guinea pigs. These results confirm the existence of PEPCK ferroactivator in the guinea pig which has properties similar to the one found in rat liver. The tissue distribution of ferroactivator activity parallels that of cytosolic PEPCK, being highest in the gluconeogenic organs liver and kidney. Hepatic PEPCK ferroactivator activity can be demonstrated by day 45 of gestation, increasing linearly in specific activity to adult levels at term (65 days). The distribution and development of the ferroactivator is consistent with the hypothesis that it may play a role in the physiologic control of PEPCK.

Argentophil neuronal perikarya and neurofibrils induced by postmortem trauma and hypertonic perfusates.

Argentophil neuronal perikarya and perikaryal neurofibrils similar to those illustrated in Ramón y Cajal's classical studies have in the present investigation been found to be manifestations of the chromophil neuron. Conclusive evidence of such association was obtained by silver impregnation with the Bodian technique of sections previously stained with cresyl violet. Regardless of the fixative used, silver-impregnated neurofibrils were evident when (1) normal tissues were fixed by immersion or unsuccessfully fixed by perfusion, (2) normal tissues were exposed and touched after death but before perfusion with the fixative, or (3) flow of perfusates was compromised by the effect of an experimental procedure, as well as when (4) a hypertonic saline solution was used in the first perfusate. These cytologic peculiarities were still discernible after 24 h of postmortem autolysis following a delay in removal of the brain or in immersion of the exposed brain in the fixative. After immersion fixation, argentophilia and chromophilia occurred ubiquitously in the brain of the newborn guinea pig; however, argentophil neurofibrils were noted in the absence of chromophil neurons in the brain stem of the newborn rat, rabbit and cat. After fixation by perfusion, perikaryal neurofibrils were not impregnated in either newborn or old animals or in animals with facial nerve transection. Affinity for Congo red or birefringency, exhibited by neurons with marked neurofilbrillary changes in human senile brain atrophy, were absent in the present material. On the basis of the current light-microscopic observations, it is concluded that argentophilia of neuronal perikarya and perikaryal neurofibrils is another manifestation of the chromophil neuron induced by postmortem trauma and of the ocellate neuron elicited by perfusion with hypertonic saline.