Influence of thyroxine and propylthiouracil administration on the intake of maternal milk in sucklings of the laboratory rat

Young laboratory rats received a daily subcutaneous injection of thyroxine (T4) and propylthiouracil (PTU) in saline, from birth until the period of spontaneous weaning. The rate of growth and the time of eye opening as well as the spontaneous weaning was assessed. The intake of maternal milk was followed directly, i.e. by the transport of 85Sr in maternal milk from the maternal body to the sucklings. In the young treated with T4 the eyes opened earlier than in the young treated with PTU. The body mass differed in both groups between the 4th and 20th day of life (the T4 pups were heavier). The 85Sr transfer in maternal milk was higher in the PTU young from the 22nd day of life. The PTU sucklings weaned spontaneously one week later than those receiving T4. A hypothesis has been proposed on the primary significance of maturation of oral mechanisms of sucking for spontaneous weaning.     

Protein malnutrition of the lactating female rat: effect on maternal behaviour and spontaneous weaning of young rats

Female rats were kept on a diet with a low content of animal protein (5.5%) beginning from the 2nd day after delivery. Beginning from the 10th day after delivery their body weight was persistently lower than that of control females. Also the body weight of their young was lower than that of control animals throughout the experiment, with significant differences appearing on the 17th day of life. Spontaneous termination of maternal milk intake occurred in malnourished young 10 days later than in the controls. Retention of 85Sr in malnourished females was in keeping with their milk production. Irrespective of the differences in body weight and the quality of solid food, the malnourished young began consuming solid food at the same age and in the same relative amounts as the controls. Thus in malnourished young the period of gradual weaning was prolonged by more than to 3 weeks in contrast to 2 weeks in the controls. This is probably due to the slower extinction of the oral sucking mechanism resulting from changes in the maturation of the CNS. No changes were found in maternal behaviour (nest building and efficiency of retrieving) in malnourished females during the suckling period. However, infanticide appeared in some females during the weaning period.     

The formation of absorbed doses of 137Cs in the body of the female and her progeny during suckling

The transfer of 137Cs with maternal milk to progeny was studied in rats. The rats were administered with 25 kBq/g of 137Cs nitrate (pH = 6) in a single oral dose immediately after delivery. Nonpregnant females served as control. Absorbed doses per activity unit to lactating rats were 23% lover than to nonlactating ones. Over the suckling period, absorbed doses to young rats amounted to about 35% of the absorbed dose to the nursing female. For nonlactating females, the internal dose approximately equalled the sum of doses to the nursing female and young rats.     

Transfer of 85Sr and 134Cs from diet to reindeer foetuses and milk

Sr-85 and ¹³⁴Cs in aqueous solution of the chlorides were administered daily to four pregnant reindeer during the last part of gestation. Radionuclide concentrations were determined in calves sacrificed at birth, and secretion of the nuclides was measured in milk. Although the gastrointestinal absorption of ⁸⁵Sr was low, an apparently higher transfer of the absorbed fraction of ⁸⁵Sr than ¹³⁴Cs from the mother to the foetus led to similar accumulation of ⁸⁵Sr and ¹³⁴Cs in foetuses. At birth 1.4–1.6 and 1.5–2.5% of the total administered activities of ⁸⁵Sr and ¹³⁴Cs, respectively, were present in the calves‘ bodies. Transfer coefficients (F _m) for ⁸⁵Sr and ¹³⁴Cs from feed to milk were estimated at 0.0218±0.0026 and 0.185±0.025 day kg⁻¹, respectively, and the observed ratio (OR_milk-diet) for ⁸⁵Sr was 0.124±0.037. Transfer of radiostrontium to reindeer milk was in agreement with previously reported relationships between Ca intake and radiostrontium transfer in ruminants. These relationships suggest that the transfer of radiostrontium to foetuses and milk of free-ranging reindeer can be 3–4 times higher than observed in this experiment (due to lower Ca intake with natural forage), but the transfer to milk will not be as high as that of ionic ¹³⁴Cs. The concentrations of ⁸⁵Sr in milk suggested that the does mobilized skeletal stores of Ca and ⁸⁵Sr for milk production, although the diet appeared to satisfy the Ca requirements. In reindeer with radiostrontium intake during the whole year, radiostrontium concentrations in milk will therefore be higher than indicated by the F _m value observed in our study. No differences in half-times for ⁸⁵Sr and ¹³⁴Cs secretion in milk were detected. Both nuclides were secreted with short- and long-term half-times of 1–2 and 12–19 days, respectively. For ⁸⁵Sr, 80–90% of the activity was excreted with the short half-time, whereas the corresponding value for ¹³⁴Cs was 30–50%.     

Maternal Coordination of the Daily Rhythm of Malate Dehydrogenase Activity in Testes from Young Rats: Effect of Maternal Sympathetic Denervation of the Pineal Gland and Administration of Melatonin

Chronic sympathetic denervation of the pineal gland by bilateral removal of the superior cervical ganglia (SCG) was performed on female rats 30 days before impregnation. The offspring, maintained in the dark from birth, had disruption of the malate dehydrogenase circadian rhythm in the testes at 25 days of age. A daily injection of melatonin (1 mg/kg s.c. at 10:00 or 18:00 h) to denervated mothers from the 14th day of pregnancy up to the 10th day postpartum produced one daily phase in the enzyme activity of testes in the offspring. Entrainment of daily enzyme activity also was obtained when the hormone was administered orally to the pups during the postnatal period or when pups were reared by intact (not denervated) foster mothers. The results indicate the involvement of the maternal pineal gland in the maternal transfer of photoperiodic information necessary for the coordination of the circadian system in young rats.     

Maternal Coordination of the Daily Rhythm of Malate Dehydrogenase Activity in Testes from Young Rats: Effect of Maternal Sympathetic Denervation of the Pineal Gland and Administration of Melatonin

Chronic sympathetic denervation of the pineal gland by bilateral removal of the superior cervical ganglia (SCG) was performed on female rats 30 days before impregnation. The offspring, maintained in the dark from birth, had disruption of the malate dehydrogenase circadian rhythm in the testes at 25 days of age. A daily injection of melatonin (1 mg/kg s.c. at 10:00 or 18:00 h) to denervated mothers from the 14th day of pregnancy up to the 10th day postpartum produced one daily phase in the enzyme activity of testes in the offspring. Entrainment of daily enzyme activity also was obtained when the hormone was administered orally to the pups during the postnatal period or when pups were reared by intact (not denervated) foster mothers. The results indicate the involvement of the maternal pineal gland in the maternal transfer of photoperiodic information necessary for the coordination of the circadian system in young rats.     

Effect of thyroxine administration to the mother on postnatal radioiodine uptake by the thyroid of partially thyroidectomized rats.

The experiment was carried out on 35 litters of infant rats aged 4-17 days. The animals in each litter were always divided into two groups: control (sham operation) and experimental (hemithyroidectomy). Starting with the day on which the young were operated on, the mothers received daily subcutaneous injections of either saline or of thyroxine in doses of 50, 100 or 200 mug. At the end of the experiment, the young were injected intraperitoneally with 1 muCi 131I. One hour later they were decapitated and the radioactivity in their thyroid was expressed as the percentage of the administered dose per mg thyroid. The following age groups were used, according to the interval between thyroidectomy and decapitation: 4 to 8, 9 to 13, 13 to 15 and 15 to 17 days. 131I uptake by the residue of the thyroid in partially thyroidectomized animals was always compared with the values in the animals from the same litter subjected to sham operation. The results showed that partial thyroidectomy significantly stimulated 131I uptake in all age groups in which the mother was only given saline. In the 4- to 8-day-old group, the administration of 50 or 100 mug thyroxine to the mother inhibited this compensatory increase. In the 9- to 13-day-old group, inhibition occurred only after a dose of 100 mug thyroxine. In animals with an interval from the 13th to the 15th days old the dose of thyroxine administered to the mother had to be raised to 200 mug/day to achieve an inhibitory effect. In the last group (interval 15th to 17th day), not even administration of the maximum thyroxine dose to the mother from the 13th postnatal day succeeded in inhibiting the significant increase in 131I uptake. These results show that thyroxine administered to lactating female rats can be transmitted via the milk to the organism of the young in amounts which can be demonstrated in a physiological tests.     

Infradian rhythmicity in milk leukocyte activity together with plasma cortisol and prolactin levels throughout the lactation period in high-yielding crossbred cows

Infradian rhythmicity in milk leukocyte activity together with plasma cortisol and prolactin levels throughout the lactation period in high-yielding crossbred cows has been studied in 10 high-yielding (milk production: 5000 l per lactation) Karan Fries crossbred (Holstein Friesian × Tharparkar) cows. Milk and blood samples were collected from all the experimental animals. Isolation of milk phagocytes (neutrophils and macrophages) and lymphocytes were done by density gradient centrifugation. In vitro phagocytic index of milk neutrophils and macrophages was performed by colorimetric NBT reductive assay. Mitogen-induced milk lymphocyte blastogenic response was estimated by colorimetric MTT (tetrazolium) assay. Total plasma cortisol and prolactin were estimated by enzyme immune assay. Highest value of plasma cortisol and prolactin was observed at calving which decreased significantly (p < 0.01) on 15th day postpartum for both prolactin and cortisol. Immune activity of milk leukocytes was highest on day 0 colostrum and decreased significantly (p < 0.01) on 7th day postpartum. A significant (p < 0.01) rise of plasma prolactin was observed around 135th and 225th days postpartum, whereas a peak level of plasma cortisol was observed at 105th, 180^th, and 270th days postpartum. Phagocytic index of milk neutrophils and macrophages remains almost in a steady state during mid-lactation period (between 100 and 200 days postpartum). A decline in increasing trend of milk phagocytic activity was observed during late lactation. Mitogen-induced milk lymphocyte blastogenic response was highest on day 0 colostrum which decreased significantly (p < 0.01) on 15th day postpartum. Con A-induced milk lymphocyte blastogenic response showed an increasing trend from 120th to 210th days postpartum. Upon correlation study, it showed that the plasma cortisol has a negative effect on milk leukocyte activity, while prolactin has a positive effect, though the effect is lactation stage specific.     

Influence of naloxone on hypothalamic L-aminopeptidase activity in the normal and ovariectomized rat

The effect of naloxone on the L-leucinaminopeptidase (LAP) activity has been determined in the hypothalamus of normal female rats or after different periods of time from ovariectomy (15th or 30th day). Castration at 15th and 30th days produced a not very important fall of LAP activity. The naloxone injections (2.5 or 5 mg/kg vía i.p.) determined a significant decrease in LAP activity in the intact and ovariectomized rats, greater for 5 mg/kg. A significant LAP activity decrease was found only after a 30 day postcastration period when naloxone treated intact animals were compared with the castrated rats. These data are discussed in relation to the physiological significance of brain peptidases and the pharmacological effect of naloxone on the function of the hypothalamic-pituitary-gonadal axis.     

Effect of exposure of pregnant rats to cadmium on prenatal and postnatal development of the young

Cadmium chloride in doses of 2, 12 and 40 mg Cd/kg was administered per os to pregnant rats from the 7th to 16th day of pregnancy. In another experiment female rats were exposed to cadmium oxide at a concentration of 0.02 mg Cd/m3 or 0.16 mg Cd/m3 for 5 hours a day and 5 days weekly for a period of 5 months or 1 mg Cd/m3 for 4 months. The exposure was then continued during mating and from the 1st to 20th day of pregnancy. A decrease in fertility was only observed in females exposed by inhalation to cadmium oxide at a concentration of 1 mg Cd/m3, at which concentration cadmium exhibits a considerable toxic effect on the whole organism. The young of females orally treated with CdCl2 in a dose of 40 mg Cd/kg displayed congenital defects in the form of sirenomelia or amelia, as well as raised cadmium levels in tissues. A retardation of intrauterine development manifested by lower body weight and slowed down osteogenesis was observed in the other groups. A cadmium concentration increase was not found in the tissues of the young in these groups. Inhalation exposure to 0.16 mg Cd/m3 of females prior to and during pregnancy induced in their young a decrease in viability, lower body weight gain, prolongation of latency in the negative-geotaxis test, lower locomotor activity and deteriorated development of the conditioned-reflex response. The offspring of females exposed to 0.02 mg Cd/m3 displayed lowered locomotor activity and worsened consolidation of the conditioned-reflex response.     

Iron metabolism during lactation and suckling in a marsupial, the quokka (Setonix brachyurus)

The iron status and transfer of iron through the milk during lactation were determined in a marsupial, the quokka, Setonix brachyurus. Lactating animals were not anaemic and had similar liver and spleen non-haem iron values to non-lactating female adult animals but about 40% less non-haem iron than male adults. The milk iron concentration was very high during the period of lactation when the young is confined to the pouch, averaging about 20 micrograms/ml (eight times the plasma iron concentration), but fell markedly at the time when the young commence to leave the pouch. Blood haemoglobin concentration increased during pouch life of the young to reach adult levels at about 180 days, and liver non-haem iron concentration increased during the same period to values nearly 20 times greater than in their mothers. After the young left the pouch the non-haem iron concentration fell rapidly to the adult level while haemoglobin concentrations were maintained. It is concluded that milk is an adequate source of iron during pouch life of the quokka and enables the animal to build up iron stores which can be utilized after leaving the pouch.     

Evolution of glycogen and blood metabolites after controlled suckling at two periods of lactation in young rabbits

In natural conditions young rabbit nurses once a day and therefore ingests the whole of his daily caloric intake during a single meal. The present work investigates glucose homeostasis during perinatal period in young rabbit by assessing blood glucose and glycogen stores before and after one single meal. Ponderal data, glycogen and blood metabolites were determined in 1-4 day- and 17-21 day-old rabbits before suckling and at different times (1, 3, 6, 9, 24, 48, 72 h) after controlled suckling. In "young" and "old" rabbits hepatic glycogen stores were exhausted after 48 and 72 h of fast. Within the first hours following milk ingestion, muscle and carcass glycogen did not vary until 9 h in the "young" and until 24 h in the "old" without notable variation of glycemia. From 24 to 72 h young rabbits were in a fasting period with low hepatic glycogen and a decrease of muscle and carcass glycogen, but glycaemia decreased only slightly at 48 and 72 h in "young" and at 72 h in "old" As blood alanine was decreased, it appears that gluconeogenesis was effective and that alanine-glucose and Cori cycles were operating in these conditions.     

Transfer of iodine through the milk in protein-restricted lactating rats

Iodine supply is important to avoid neonatal hypothyroidism. This study evaluated whether protein restriction during lactation affects iodine transfer to the pups through the milk. We studied lactating rats fed an 8% protein-restricted diet (PR), a control 23% protein diet (C), and an energy-restricted diet group (ER). On days 4, 12 and 21, mothers were separated from their pups for 4 h, injected with (131)I IP, and put together with their pups. The animals were killed 2 h later. PR pups had a significant decrease in iodine uptake in the gastric content and duodenal mucosa on the 4th day. On the contrary, at 12 and 21 days radioiodine was increased in the gastric content and in the duodenal mucosa. ER pups had an increase in iodine uptake in the gastric content and in the duodenal mucosa only at the end of lactation. The thyroid iodine uptake in PR pups was significantly decreased on the 4th day and significantly increased on the 21st day compared to control. When injected IP with an equivalent amount of (131)I, the PR pups had a decrease in thyroid iodine uptake on the 4th and 12th day, while ER pups had no significant changes. So, these data suggest that protein restriction during lactation was associated with lower iodine secretion into the milk in the beginning of lactation. However, at the end of lactation, an adaptation process seems to occur leading to a higher transfer of iodine through the milk that compensates the impairment of thyroid iodine uptake in these pups.     

Lactation in the Japanese monkey (Macaca fuscata): Yield and composition of milk and nipple preference of young

Changes in the yield and chemical composition of milk, together with those in the nipple preferences and suckling behavior of infants, were followed in three lactating Japanese monkeys rearing single infants under laboratory conditions at monthly intervals for six months after their paturition. Milk accumulating in the mammary glands during a 4-hr separation of the infant was collected by milking under anesthesia with the aid of a physiological dose of oxytocin. The stage of full lactation appeared to last for about two or three months after parturition. The milk at this stage contained 14.0% of total solids, 4.2% of lipids, 1.6% of proteins, and 6.2% of lactose, and the concentrations of Na, Cl, and K in the milk water were 7.4, 15.1, and 5.9 mM, respectively. From the 9th or 13th week of lactation onwards, according to the individual, the milk composition changed appreciably and the time during which the young left hold of the mother's nipple also increased. The weaning of young in the Japanese monkey appears to begin during the 3rd or 4th month of age. The milk production then wanes and almost ceases by the end of the 6th month. The nipple preference of the young was generally established completely by the 3rd, or the 8th at latest, week of age. However, no difference in either the yield or composition of the milk secreted was found between the mammary glands of the preferred and non-preferred sides. Without regard to the apparent nipple preference, infants seem to ingest milk from the mother's breasts of both sides. Accurate estimation of the rate of milk production could not be achieved, but the rate was expected to be 150–200 g/day at the height of lactation based on the relation between the mother's body weight and the milk production rates of other primate species. A disparity was noted between the observed and estimated values for the milk yield, and a diurnal fluctuation in the milk secretion of the Japanese monkey was inferred. This study was conducted through the official system of the Primate Research Institute, Kyoto University, for cooperative research work with other institutions.     

A preliminary note on the use of milk substitutes in the early weaning of dromedary camels

The experiment was performed using two young male camels which weighed 24 and 36 kg respectively at birth. Each young camel was weighed and abruptly separated from its mother after 30 days of nursing (or at 1 month of age). The weaned calves were fed milk substitutes prepared commercially for lambs by Mabarot Chemical and Veterinary Products (Israel). The weanling camels averaged daily weight gains of 0.400 and 1.0 kg per day respectively during the 30 day initial period when the milk substitutes were used. Following the period when milk substitutes were used, the camels achieved normal growth to arrive at 135 and 145 kg respectively at 6 months of age.     

Effects of the Nest Web and Female Attendance on Survival of Young in the Subsocial Spider Mite Schizotetranychus Longus (Acari: Tetranychidae)

The subsocial spider mite Schizotetranychus longus lives gregariously in woven nests on leaves of Sasa bamboo. Adults of both sexes defend their young against the predatory mite Typhlodromus bambusae. The effects of web and female attendance of this species on offspring survival were evaluated in a natural forest. Experimental removal of web and females revealed that S. longus young suffered greater mortality than in the control. Furthermore, the web made by parent females had a positive effect on offspring survival, possibly through preventing predators from intruding into the nest. Attendance of a female in a nest also had an effect on improving the survival rate of her offspring over a short period. We could not detect any function of the web and female other than protection against predators at least for the 5 day period of the experiment. The nest web of S. longus has an important function in the survival of young by preventing the entry of pedestrian predators (generalist) and females may play a role in defending against specialized predators which can intrude into the nests.     

Polyunsaturated fatty acids in maternal plasma and in breast milk

In order to explain processes underlying the transfer of fatty acids from the maternal compartment into human milk, the lipid content and the fatty acid composition of maternal plasma and milk have been analyzed in breastfeeding mothers at 1 day and 3 months of lactation.The rise in milk lipids occurring during the study period was concomitant with a fall in plasma total fat content, mainly due to the decrease of triglycerides. Significant correlations between plasma and milk fatty acids at the two time points were observed only for linoleic (LA, 18:2 n-6) and (alpha;-linolenic acid (alpha LNA, 18:3 n-3), while for arachidonic (AA, 20:4 n-6) and docosahexaenoic acid (DHA, 22:6 n-3) correlations were found only at one day and 3 months, respectively.These data suggest that levels of the n-6 and n-3 18C polyunsaturated fatty acids in milk are closely dependent on their concentrations in maternal plasma, in turn related with the dietary intake, while the accumulation of AA and DHA in milk is the result of a sequence of transfer and metabolic processes.     

Start-up alternatives and performance of an UASB pilot plant treating diluted municipal wastewater at low temperature

Different start-up procedures of an upflow anaerobic sludge bed (UASB) digester were carried out. Start-up without inoculum (experiment A) was delayed for about 120 day. The digester reached 75-85% total suspended solids (TSS) removal, 54-58% total chemical oxygen demand (TCOD) removal and 63-73% biological oxygen demand (BOD5) removal at influent concentrations of 240-340 mg TCODil-1, temperatures of 13.5-15 degrees C and hydraulic retention times (HRT) of 10-11 h. Digested sludge was used as inoculum in experiment B. After the start-up period of 75 days, digester efficiencies were 58%, 41% and 54% for TSS, TCOD and BOD5 removal, respectively, working at 169 mg TCODil-1, temperature of 14 degrees C and HRT of 11 h. The sludge bed developed and stabilised quickly when using a hydraulically adapted inoculum (experiment C), but TCOD and BOD5 removals remained low and volatile fatty acids (VFA) accumulated in the effluent.     

Transfer of a gene containing the Arg-Gly-Asp peptide prolongs the bleeding time of mice

Peptides containing Arg-Gly-Asp (RGD) have been used to decrease thrombosis by competitive inhibition of the integrin glycoprotein, alphaIIb/beta3a, in platelets. However, they have a short half-life in vivo. A naked plasmid, pCMV-RGD, was transferred into the skeletal muscle of mice and RGD gene expression was observed by RT-PCR. The bleeding time between control mice and RGD-transferred mice was prolonged from the 10th day to the 80th day after gene transfer while the blood glucose and serum insulin-like proteins remained at normal levels. These results provided a convenient and effective approach to relieve patients from thrombi in a single step over a relatively long period.     

The effect of adrenocorticotropic hormone (ACTH) on embryonic chicken gonads

Chicken embryos were exposed to a single dose of adrenocorticotropic hormone (ACTH) on the 15th day of the incubation period. Five days later, the female embryos showed a significant increase in ovarian weight, ovarian thickness and oocyte count. In contrast, the male embryos showed a significant decreased in testicle weight, seminiferous cord diameter and gonocyte number. The opposite response of testes and ovaries is discussed.