Increase In Total Weight Research Articles

MAGNETIC BIOSTIMULATION OF INITIAL GROWTH STAGES OF WHEAT (TRITICUM AESTIVUM, L.)

The effect of magnetic treatment on the initial growth stages of wheat was explored under controlled conditions. Treatment involved the application of different magnetic doses (D) established in terms of the magnetic field energy density (ρm1=6217 or ρm2=24,868 J/m3), and the time of exposure (0 min, 1 min, 10 min, 20 min, 1 hr, 24 hr, or chronic exposure). Increased plant height was observed as the magnetic dose increased, with significant differences recorded for most doses. The stimulatory effect found for ρm2, greater than that obtained for ρm1, may be related to the amount of energy supplied to the plant tissues by the magnetic field. Chronic exposure of plants provided maximum total length increases of 7.3% (ρm1) and 30.9% (ρm2), corresponding to total weight increases of 17.6% and 29.9%, respectively.

Use of knockout transgenic mice in the study of endometriosis: insights from mice lacking β 2-microglobulin and interleukin-12p40

Objective: To test the possibility of using transgenic knockout mice in the study of endometriosis and to investigate specific immunologic aspects of the disease. Design: Experimental blinded study. Setting: Academic research center. Animal(s): Thirty-two mice with experimentally induced endometriosis. Intervention(s): Endometriosis was induced in 8 β 2-microglobulin–deficient BALB/c mice and 7 wild-type BALB/c controls. Similarly, endometriosis was induced in 8 interleukin-12–deficient C57BL/6 mice and in 9 wild-type C57BL/6 controls. Main Outcome Measure(s): Weight and surface area of endometriotic lesions. Result(s): Total weight and surface area of endometriotic lesions was markedly lower in β 2-microglobulin–deficient BALB/c mice than in wild-type BALB/c controls. A slight but statistically insignificant increase in total weight and surface area of lesions was observed in interleukin-12–deficient C57BL/6 mice compared to wild-type C57BL/6 controls. Conclusion(s): Knockout transgenic mice can be used successfully for the study of endometriosis; however, in these animals, the redundancy of the immunologic cytokine-mediated regulatory mechanisms may lead to compensation from the remaining genome. Results from β 2-microglobulin–deficient mice support the critical role of the immune system in the pathogenesis of the disease.

How does density and nutrient stress affect allometry and fruit production in the heterocarpic species Atriplex sagittata (Chenopodiaceae)?

Plants of Atriplex sagittata Borkh. were grown under different density and (or) nutrient conditions, and the effect of stress on plant allometry and variation in particular biometrical parameters was studied. Increasing density significantly reduced total weight, basal diameter, stem length, and number of branches. Nutrient deficiency had a negative effect on the total weight and basal diameter only, and the density × nutrients interactions were all nonsignificant. Basal diameter was the best predictor of the total weight, explaining 93.6% of the variation in the whole data set. The relationship between total plant weight and basal diameter was unaffected by growth conditions, indicating that competition determined the position of a plant along the line describing the allometric relationship between both variables but did not seem to alter the relationship. However, the allometric relationships between total weight and stem height and between total weight and number of branches found at low density were significantly different from those at high density, indicating a faster increase in total weight at low densities. Branching, and consequently plant form, were affected by competition. Branch length consistently increased with total plant weight in plants grown under high density, but for low density plants, such an increase was recorded only in branches of the middle section of the stem. In each fruit type, the total weight of fruits produced was more closely predicted by branch weight than by branch length. Allometric relationships between fruit production and branch weight differed among particular fruit types, with a faster increase in the production of type A than in that of types B or C. Competition had less effect on the mean size of type B fruits compared with that of types A or C. Fruits of types C and A had higher variation in mean weight, than type B fruit. Variation in total weight of fruits per plant was of a higher order of magnitude than that in the mean fruit weight. The results show that plants of A. sagittata grown under contrasting conditions change both their allometry and the number of particular fruit types produced. Nevertheless, the question of whether the shift in the fruit ratio is a function of allometric constraints or the result of a basic shift in allometry needs further study.Key words: allometry, Atriplex sagittata, Chenopodiaceae, density stress, nutrient stress, heterocarpy.

Relationships Among Total Weight, Body Shape, Visceral Components, and Fillet Traits in Palmetto Bass (Striped Bass Female Morone saxatilis× White Bass Male M. chrysops) and Paradise Bass (Striped Bass Female M. saxatilis× Yellow Bass Male M. mississippiensis)

Abstract.Relationships among total weight (W), and linear measures of body shape, visceral component weights, and fillet weight (Y) in market‐size (>454 g) palmetto bass (Morone saxatilis female ×M. chrysops male, N= 138) and paradise bass (M. saxatilis female ×M. mississippiensis male, N= 134) were determined with the allometric equation: Y = aWb. Allometric analysis was used to compare traits of palmetto bass and paradise bass, and to identify factors influencing fillet yield. Paradise bass, an all female hybrid, had deeper, thicker, shorter bodies, and smaller heads than palmetto bass females. Male and female palmetto bass had similar body shapes. Values of growth coefficients (b) for body shape traits (range 0.21–0.48) indicated that shape was proportional across the weight range of fish used. Mean visceral fat and ovary weight were higher in paradise bass than in palmetto bass females suggesting the reproductive cycle was more advanced in paradise bass females. Whole fillet (skin and ribs intact) and skinless fillet (ribs intact) were larger for paradise bass than for palmetto bass, but trimmed fillet (skin and ribs removed) was not different between fish. Relative increases of whole and skinless fillet weights were greater than total weight in both groups indicating that the percentage of body mass attributed to fillet increases slightly as total weight increases. Therefore, small increases in fillet yield can be achieved by rearing fish to a larger size. Stepwise regression of whole, skinless, and trimmed fillet weight on body shape traits resulted in three parameter models with r2‐values of 0.27–0.29 in palmetto bass, and of 0.37–0.43 in paradise bass. Addition of visceral components as independent variables in the models increased r2‐values to 0.31–0.36 for palmetto bass and to 0.45–0.52 for paradise bass. Low phenotypic variation in fillet yield (CV = 3–5%) and poor predictability of yield from measures taken on live fish limit the potential for improving yield through individual selection. Identification of superior species or strain crosses or rearing fish to a larger size appear to be the best strategies for improving fillet yield of Morone hybrids.

IGF-II and IGF-binding proteins increase dramatically during rabbit pregnancy.

During pregnancy, changes in the IGF axis are associated with changes in maternal metabolism and nutrient repartitioning which are necessary to meet the demands of a growing conceptus. The aim of this study was to assess the IGF axis, maternal weight changes and food intake in female New Zealand White rabbits (n = 7) prior to breeding (day 0) and serially throughout pregnancy until term (day 30-31). The total weight of the pregnant does progressively increased from 4.03 +/- 0.06 kg (mean +/- S.E.M.) on day 0 to 4.47 +/- 0.07 kg on day 30 (P < 0.001). Maternal tissue mass (total weight minus estimated conceptus weight) increased until day 18, plateaued to day 22/23, and then significantly declined. On day 30, the maternal tissue mass was not significantly different from the non-pregnant value, such that the final increase in total weight was due to conceptus growth. Although the does were fed ad libitum, food intake did not change until day 29 when it decreased to approximately 50% of previous intake (P < 0.01). Maternal serum IGF-I was 499 +/- 32 ng/ml on day 0, reached a peak of 832 +/- 160 ng/ml on day 21 (P < 0.02), and then declined to 341 +/- 49 ng/ml on day 30. In contrast, serum IGF-II increased dramatically from a non-pregnant level of 85 +/- 14 ng/ml to 16,295 +/- 2488 ng/ml on day 23 (P < 0.001), and then rapidly declined (3335 +/- 954 ng/ml, day 30). Changes in serum IGF-binding proteins (IGFBPs) followed a pattern similar to IGF-II, as assessed by Western-ligand blotting. All IGFBPs, especially the 45-40 kDa IGFBP-3 doublet, increased dramatically between days 12 and 24 of pregnancy, and then declined towards term. In conclusion, we observed unique and dramatic changes in the maternal serum IGF axis that corresponded to periods of maternal weight gain and loss. The tissue source of IGFs and IGFBPs remains undetermined, although it is of note that the time when major changes in the IGF axis were first observed coincided with the time of functional change from yolk sac to placenta in the rabbit.

The response of lactating and dry ewes to energy intake and protein source in the diet

In this lactation experiment, 40 Rasa Aragonesa ewes rearing two lambs were distributed to four treatments to study two levels of metabolizable energy restriction, 80% (E 1) and 70% (E 2) of the requirements, and two protein sources in the concentrate (soybean cake or fish meal) on milk yield and lamb growth. At weaning on Day 67 after lambing the ewes were allocated to four treatments to study the effect of the level of energy restriction in lactation and of the amount of barley grain (fresh matter) offered from weaning until 70 days later (250 and 500 g per ewe per day) on the recovery of body reserves. Ewes which were fed fishmeal produced milk with higher protein content (4.98 vs. 4.69%; P < 0.05) and had greater output of protein in milk than the ewes fed soybean cake (62 vs. 55 g day −1; P < 0.001). Lambs suckling ewes fed fishmeal had higher daily gains (194 vs. 163 g day −1), greater total weight increase (6.97 vs. 5.88 kg) and lower conversion of the milk than lambs from ewes fed soybean cake ( P < 0.05). Difference in body condition score (BC) between Treatments E 1 and E 2 at beginning of the recovery period was eliminated during the 70 days. Amount of barley offered affected change in BC (0.64 vs. 0.48 points; P < 0.001) and final BC ( P < 0.01). Total live weight and BC increases were higher in animals with larger amounts of barley during the recovery period ( P < 0.01 and P < 0.001, respectively). In conclusion, the level of feeding after weaning had greater effects on total recovery of reserves than the level of energy restriction during lactation.

Preparation and properties of oligoesterified wood blocks based on anhydride and epoxide

Preparation and properties of oligoesterified woods in the form of block are reviewed. The oligoesterified wood blocks are prepared by stepwise addition reactions of dicarboxylic acid anhydride and epichlorohydrin (EpCl), or one-step chemical treatment with reactant solution of the anhydride and EpCl. Among the preparation methods investigated, the heating-suction method is industrially advantageous. In this method, wood blocks impregnated with the reactant solution are heated and then subjected to suction under reduced pressure and heating, to remove unreacted reactant solution. The oligoesterified wood blocks thus obtained contain oligoester chains formed by the alternate additions of the anhydride and EpCl to OH groups of wood. They also contain small amounts of free oligomers not linked with the wood matrix. Their dimensional stabilities against moisture and water become greater with increase in the apparent total weight increase due to the oligoester chains and the free oligomers. The oligoesterified wood blocks based on phthalic anhydride-EpCl are industrially promising, and exhibit higher compressive and flexural strenghts, greater chemical resistance, electric insulation, and much lower water absorption than untreated wood block. Furthermore, excellent resistances are observed against weathering and biodeterioration.

Evolution of weight and zinc level in thymus and spleen of rats after zinc treatment

The effect of chronic zinc administration (4 weeks) on the body weight of rats treated with zinc chloride was studied. In the last week a significant increase (p < 0.005) of total weight compared to control animals was observed. The thymic gland showed no significant statistical difference between the 2 groups of animals. The spleen weight of treated animals was lower during the second and third week, but the spleen weight recovered in the fourth week. This indicates that zinc does not modify the weight of these organs of healthy animals. The increase of total weight is due to bones and muscles. Measuring the concentration of zinc in the mentioned organs, an increase of the metal in the thymic gland and in spleen was observed, whereas the control tissues remained stable. In treated animals zinc also increased in blood serum.

Internal Redistribution of N in Sitka Spruce Seedlings with Partly Droughted Root Systems

Abstract Split pots were used to allow measurement of the potential N retranslocation from roots of Sitka spruce subject to drought. Withholding water from one part of the root system had no effect upon increases in total weight and N content of the whole trees, or of the shoot and roots separately. However, the distribution of root weight and N content between the split parts of the root system did change. The results indicate that the droughted roots of these spruce seedlings retranslocated 23% of the nitrogen initially present in them before experimental conditions were imposed. This retranslocation is considerably less than that reported elsewhere for senescing needles, but fine-root nitrogen retranslocation may be a potentially significant flux in forest systems where fine-root turnover is high. There was some evidence of N movement from needles to sustain compensatory growth of roots in response to nutrient and/or water stress. For. Sci. 37(3):860-870.

Effects of serum and endotoxin in experimental lung injury

Lipopolysaccharide (LPS) is in large part responsible for the lung injury that occurs in the sepsis syndrome. Recent work has shown the ability of LPS alone to induce injury in endothelial monolayers, though the LPS effect is enhanced in the presence of serum. We previously demonstrated that low-dose LPS (50 ng/mL) can lead to lung injury in an isolated perfused rabbit lung model. To examine the effect of serum on LPS-induced injury rabbit lungs were perfused with increasing doses of rabbit serum in the presence and absence of LPS. There was no increase in total weight gained by the lung, Q f, with either 5% serum, 10% serum, or 10% serum with LPS. However vascular permeability as measured by hydraulic conductance was increased with increasing doses of serum. This effect was not enhanced by the addition of LPS. These results provide evidence that serum alone may cause lung injury, perhaps through the activation of complement or other mediators.

The structure of the plant ofChondrus crispus Stackhouse (Irish moss)

The plant ofChondrus crispus, an isomorphic species, is composed of a crustose holdfast bearing a number of erect, foliose fronds. The holdfast determines the limits of the plant, and a simple mathematical description is given which relates several frond parameters with area of the holdfast. As the area of the holdfast increases, both the number of fronds and their total weight increases. The proportional increase in weight of the fronds is greater than the increase in the area of the holdfast and with a concomitant decline in density of fronds the mean weight of the fronds also increases. Density declines in part because of frond losses so that larger plants are composed of a few larger fronds and numerous smaller ones, with a greater proportion of the biomass becoming concentrated in the larger fronds. Reproductive structures are associated with the larger fronds of a plant even though others may be potentially reproductive. Larger fronds, which commonly bear both epi- and endophytes, resulting in dysfunctions, are more apt to be lost from the plant, as are fertile fronds. A consideration of the plant suggests thatC. crispus has evolved an efficient morphological structure. This may account for much of the ecological success ofC. crispus, which in turn has permitted extensive commercial exploitation of this seaweed.

Radiation-induced grafting of methyl-α,β,β- triflouroacrylate onto tetrafluoroethylene-propylene copolymer

Radiation-induced grafting of flourine-containing monomer,methyl—α,β,β—trifluoroacrylate (MTFA) onto tetrafluoroethylene-propylene copolymer (TFEP) has been studied. The grafting was performed in a homogeneous medium: the polymer solution was irradiated with 60Co gamma rays in the presence of monomer. The irradiation was carried out in vacuum at room temperature, with total absorbed dose up to 420 kGy at dose rates 5, 10, and 15 kGy/h. All of the total weight increase, the graft yield, and the homopolymer formation showed similar complex dependences on absorbed dose. After nonlinear increase, it reached maximum and then decreased. The maximum was higher and reached at lower absorbed dose when irradiation was performed at lower dose rate. The grafted samples were characterized by IR spectroscopy and were subjected to the molecular weight distribution measurement (GPC). Surface characterization using scanning electron microscope was also done. From these results a model for the grafting process was proposed.

Effect of neonatal thymectomy and antilymphocyte globulin on non-specific mitogen stimulation in Holstein-Friesian calves

Nine of seventeen neonatal Holstein-Friesian calves were thymectomized, treated with antilymphocyte globulin, and monitored for immunologic functional ability for 4 to 6 months. The thymus weights for 4 to 10-day-old calves and 4 to 6-month-old calves indicated a continued increase in total weight. This indicated significant thymic involution had not occurred at 4 to 6 months. Following thymectomy a wasting syndrome was not observed although an increased incidence of a lowly virulent virus infection did occur. A significant decrease in circulating lymphocytes was observed. Peripheral blood lymphocytes were stimulated in vitro by non-specific mitogens, phytohemagglutinin, bacterial lipopolysaccharide and pokeweed mitogen using the whole blood culture method. Observations included a greater response to phytohemagglutinin and pokeweed mitogen in summer months and variable age related response to all mitogens. Lipopolysaccharide stimulation results were inconclusive. It was concluded that neonatal thymectomy was not a satisfactory experimental procedure for the production of selective immunosuppression in the bovine species.

EXPERIMENTAL OXALATE UROLITH FORMATION IN RATS

Urinary calculi composed of calcium oxalate were produced in male hooded Wistar rats fed a vitamin B6 deficient diet over 16 weeks. This basic diet was modified by doubling the phosphate content or loading with vitamin C or D3 in three treatment groups. The number of rats developing oxalate stones was not altered by the addition of vitamin D3 or phosphate, but there was a significant increase in total weight of stone formed and histological evidence of extensive renal damage in rats on the high vitamin D3 diet. The addition of vitamin C to the vitamin B6 deficient rats resulted in a reduction in the number of rats with uroliths and a fall in urinary oxalate excretion, while similarly loaded vitamin B6 supplemented controls were free of oxalate calculi. It is concluded that the oxalate urolithiasis induced by vitamin B6 deficiency was exacerbated by added vitamin D3 and reduced by vitamin C.

Influence of different mulch treatments on growth rate and activity of the earthworm Eudrilus eugeniae (Kinberg)

AbstractGrowth characteristics of the earthworm Eudrilus eugeniae and the impac of its activity on soil properties were studied in soil culture. The highest growth rate, fecundity and total weight increase were recorded in cassava mulch, compared with cocoyam mulch, grass and plantain pseudo trunk mulch treatments. With animal manure treatments, growth rate was highest in poultry manure compared with cow and goat manures although total weight increases were highest in poultry and goat manures and lowest in cow manure. The worm activity expressed as percentage reduction of soil bulk density was greatest in cassava mulch followed by grass mulch, cocoyam mulch and plantain pseudo trunk mulch in that order. Various animal manures did not differ in this aspect. Total soil N and soil organic matter increased significantly in cassava and grass mulch treatmens while in plantain pseudo trunk mulch these factors decreased. Soil pH increased in cocoyam and plantain mulch treatments and decreased in cassava and grass mulch treatments.

Dehydrogenases and nucleic acids in rat mammary gland during involution initiated at various stages of lactation.

Abstract 1. l. The activities of LDH, MDH, α-GPDH, G-6-PDH, the iso-enzymes of LDH and MDH and the contents of RNA, DNA, extractable proteins, lactose, and fat have been assayed in involuting mammary tissue of the rat after premature weaning at the second, fifth and tenth days of lactation. 2. 2. During involution the activities of the dehydrogenases decreased, the level of fat increased, the RNA/DNA ratio decreased and the amount of extractable protein decreased. When involution was initiated at the fifth and tenth days of lactation there was an increase in total weight and total DNA in contrast to when involution was initiated at the second day of lactation. The greatest changes for the various parameters studied were noted when involution was initiated at the tenth day of lactation. 3. 3. The reason for the decreases in enzyme activities may be caused by inhibitors, by changes in the composition of cell lines or by changes in the synthesis of the corresponding enzyme molecules. The half-life of the activity of G-6-PDH after onset of involution was found to be 0/sd5 days, which coincides with the values given by other authors using incorporation experiments. 4. 4. It is concluded that the activities of the dehydrogenases, especially G-6-PDH, are sensible indicators of involution initiated at any stage of lactation. The changes in the activities of the enzymes or isoenzymes during involution may be caused by changed hormonal patterns in combination with accumulation of milk in the mammary gland.

Effetto della rimozione dei fiori sulla crescita delle piante e sul contenuto in leghemoglobina dei tubercoli radicali di pisello e fava

Abstract Observations on vegetative growth and leghemoglobin contents of root nodules of pea and bean plants after flower bud removal. — These studies found their origin in the papers by MATTIROLO (1899) on the effect of the removal of flowers as they formed in bean plants; he observed that deflowering resulted in extraordinary plant growth, stem branching and flower buds formation as well as in a delayed root nodule senescence. In the light of modern knowledge of the leghemoglobin role in symbiotic nitrogen fixation, the aim of the present research was to ascertain any possible relation between flower bud removal and haeme pigment contents in the root nodules. The experiments were carried out during two growing seasons (1966 and 1970) using Vicia faba L. cv. Regina and Pisum sativum L. cv. Senatore during 1966 and cv. Vittoria in 1970. In both control and test plants the seasonal trends of average plant height, fresh and dry weight of vegetative portions, fresh and dry weight of root system, fresh weight of nodules, root nodule leghemoglobin concentration and total leghemoglobin content per plant, were determined. The data obtained are quoted in Table 2 and reported in Figures 1, 2, and 3. The removal of flower buds caused in both species: an increased plant growth, a marked stem branching, a longer blooming period, an increased flower number, an increased root nodule number and a certain delay in root nodule reabsorption. Deflowering did not significantly extend — at least in the species studied — life span (senescence was delayed only of one week). On the basis of these and of other Authors' results, we conclude that deflowering may actually delay senescence; the size of this delay, however, depends on the plant species considered and is fairly negligible both in pea and bean. The different effects of deflowering and of preventing floral induction on life span extension, are discussed, and these facts lead to consider floral induction as the onset of a chain of processes leading annual plants toward senescence in a more or less delayable, but definitive way. After having stressed the generally accepted importance of leghemoglobin concentration as an index of nodule nitrogen fixing ability, a correlation between biomass increase of test plants and number and total weight increase of root nodules, is put in evidence. No correlation between test plant biomass and the leghemoglobin concentration in root nodules, was however observed. Leghemoglobin concentration in root nodules is known to change in connection with various factors depending either on host plants and on Rhizobium strains and also in connection with several environmental conditions. Any prevented flower onset (ROPONEN and VIRTANEN, 1968) and deflowering (our data) however exerted no significant influence. The effects of flower bud removal were therefore the following: increased stem, leaf and root weights and increased root nodule number; no difference between control and test plants was however observed as regards size and leghemoglobin concentration of root nodules and hence probably no difference as regards their nitrogen fixing ability.

Growth and Chemical Composition of Chum (Oncorhynchus keta) and Sockeye (O.nerka) Salmon Fry Produced in Spawning Channel and Natural Environments

A comparison was made of the weights, lengths, weight–length relations, and chemical composition in migrating chum and sockeye fry resulting from eggs incubated and hatched in natural and artificial streams. Additionally, growth rates and rates of change in some chemical constituents were investigated in postmigrant channel- and river-hatched chum salmon confined to floating pens in sea water and in postmigrant sockeye salmon captured from their lake nursery area.There were no apparent differences in the lengths, weights, weight–length relations, or chemical composition between river- and channel-hatched chum salmon migrants. Nor was there any difference in the rates of change in length, weight, or chemical composition of these two groups of chums when confined to pens in sea water for 10 weeks after migration.There were differences in the weight–length relations, lipid content, and nitrogen content between channel- and river-hatched sockeye migrants. It is suggested, however, that these differences are due to the fact that the timing of the peaks of migration of these two groups of fish differed and that at any one time channel fry were physiologically different from river fry.Growth of the chum salmon in sea water and the sockeye in the lake was exponential and the slope of the weight–length relation, W = aLb, was approximately 3.25. During this growth period although total weight, moisture, solids, lipid, and nitrogen increased the rate of increase in moisture was less than the rates of increase in total weight or the other constituents.

Quantitative changes in DNA, RNA, and protein during prenatal and postnatal growth in the rat

Normal growth in the rat has been studied by determining total animal and individual organ DNA, RNA, protein, and weight at various times from 10 days after conception to maturity. From these data the number of nuclei and the weight, protein, and RNA per nucleus have been determined. Beginning at 10 days after conception and continuing for a variable period in all organs, growth proceeds entirely by cell division. After this, both cell division (as indicated by increasing amounts of DNA) and cell enlargement (as indicated by an increase in weight or protein per nucleus) occur simultaneously in most organs. Finally only cell enlargement (increase in total weight or protein with no further increase in DNA) occurs. Growth stops when total organ weight or protein reaches a constant amount. Organs of the lymphoid system do not show the second and third phase of growth. Growth proceeds by cell division alone. RNA in most organs remains proportional to DNA during the period studied, resulting in a constant figure for RNA per nucleus. These data establish certain quantitative events that occur during normal growth and should provide a baseline for further studies involving growth retardation.

Guinea Pig Mammary Gland Growth Changes in Weight, Nitrogen and Nucleic Acids.

SummaryThe growth of guinea pig mammary glands during pregnancy, parturition, lactation and involution was measured using total weight, total nitrogen content, total DNA and RNA/DNA ratios as parameters of cellular changes. Only slight changes were found to occur during pregnancy. The rapid increase in total weight after parturition, correlated with the increase in total nitrogen and DNA, indicates that the observed growth is primarily a hyperplastic process. Extensive hypertrophy of pre-existing cells as measured by increased RNA/DNA ratios occurs after the period of rapid proliferative growth, thus the greatest cellular changes in guinea pig mammary glands occur immediately after parturition.