Endocrinology of milk production

The physiology of lactation includes development of the mammary gland from the foetal to the adult stage, further development during pregnancy and onset of lactation, with the accompanying metabolic and behavioural adaptation. At the onset of pregnancy the endocrine system undergoes dramatic changes. The growth of the mammary gland is stimulated by growth hormone and prolactin, adrenocortical steroids, oestrogens and progesterone, and that of the gastrointestinal (GI) tract by gastrin, CCK and secretin. The onset of lactation is accompanied by increases in the blood volume, cardiac output, mammary blood flow and blood flow through the GI-tract and liver, aiming to provide the udder with nutrients and hormones for regulation of milk synthesis. Food intake and distribution of nutrients to the mammary gland are partially regulated by hormones as well as the repartitioning of nutrients away from body stores towards the udder. To improve milk production, administration of growth hormone has been practised, but also much discussed. Besides central mechanisms, local mechanisms within the mammary gland regulate initiation of lactation, maintenance, regulation of blood flow and mammary gland cell apoptosis. Most of the milk in a filled dairy cow udder is stored in the alveolar compartments. The milk ejection reflex must be activated to gain access to the udder milk, i.e. oxytocin contracts the myoepithelial cells. Recent studies show that vasopressin may also elicit milk ejection. More efficient oxytocin release is achieved if the cows are fed during milking. Beyond milk let down, oxytocin influences maternal behaviour and metabolism. Furthermore, it has been indicated that suckling or milking activates a vagal reflex, which may link the milk production to the endocrine system of the GI-tract. The question has been raised whether the mammary gland is a supporting or consuming organ.     

Mechanisms of metal-phosphates formation in the rhizosphere soils of pea and tomato: environmental and sanitary consequences

Purpose

At the global scale, soil contamination with persistent metals such as lead (Pb), zinc (Zn), and copper (Cu) induces a serious threat of entering the human food chain. In the recent past, different natural and synthetic compounds have been used to immobilize metals in soil environments. However, the mechanisms involved in amendment-induced immobilization of metals in soil remained unclear. The objective of the present work was therefore to determine the mechanisms involved in metal-phosphates formation in the rhizospheric soils of pea and tomato currently cultivated in kitchen gardens.

Materials and methods

Pea and tomato were cultivated on a soil polluted by past industrial activities with Pb and Zn under two kinds of phosphate (P) amendments: (1) solid hydroxyapatite and (2) KH₂PO₄. The nature and quantities of metal-P formed in the rhizospheric soils were studied by using the selective chemical extractions and employing the combination of X-ray fluorescence micro-spectroscopy, scanning electron microscopy, and electron microprobe methods. Moreover, the influence of soil pH and organic acids excreted by plant roots on metal-P complexes formation was studied.

Results and discussion

Our results demonstrated that P amendments have no effect on metal-P complex formation in the absence of plants. But, in the presence of plants, P amendments cause Pb and Zn immobilization by forming metal-P complexes. Higher amounts of metal-P were formed in the pea rhizosphere compared to the tomato rhizosphere and in the case of soluble P compared to the solid amendment. The increase in soil-metal contact time enhanced metal-P formation.

Conclusions

The different forms of metal-P formed for the different plants under two kinds of P amendments indicate that several mechanisms are involved in metal immobilization. Metal-P complex formation in the contaminated soil depends on the type of P amendment added, duration of soil-plant contact, type of plant species, and excretion of organic acids by the plant roots in the rhizosphere.     

Relationship among Insulin Resistance,Growth Hormone,and Insulin‐Like Growth Factor I Concentrations in Diestrous Swedish Elkhounds

Background

In the dog, the normal estrous cycle includes a prolonged luteal phase. Progesterone stimulates local canine mammary growth hormone (GH) production, which may act systemically and contribute to insulin resistance. Swedish Elkhounds are predisposed to progesterone‐related diabetes mellitus, and the relationship among insulin resistance, GH, and insulin‐like growth factor I (IGF‐I) is of particular interest.

Objective

To study insulin resistance in relation to GH and IGF‐I in nondiabetic Swedish Elkhounds during diestrus. We also assessed whether alterations in these hormones could predict diestrus‐linked diseases and all‐cause mortality.

Animals

Eighty‐four privately owned female intact Swedish Elkhounds >4 years of age.

Methods

Blood sampling and clinical examination during luteal phase, with a follow‐up questionnaire after 20 months. Insulin resistance was calculated by homeostasis model assessment (HOMA‐IR).

Results

In multivariable regression analysis, GH was positively associated with HOMA‐IR (P = .009). An increase in GH of 1 ng/mL was associated with a 12.7% increase in HOMA‐IR. Moreover, C‐peptide was positively associated with IGF‐I (P = .04), and an increase in C‐peptide of 0.1 ng/mL was associated with a 6.9% increase in IGF‐I. Structural equation modeling supported these results. Twenty‐three animals were found to have previously unrecognized mammary masses and had higher GH (P < .0001) and IGF‐I (P = .007) than dogs without mammary masses (n = 61). There was no association between high GH and IGF‐I concentrations at sampling and future mammary masses.

Conclusion

We showed that GH was strongly associated with insulin resistance in older Swedish Elkhounds during diestrus.     

Genotypic differences in susceptibility to wireworm attack in potato: mechanisms and implications for plant breeding

The influence of different tuber compounds on susceptibility to wire-worms (Agriotes obscurus) was studied in experiments with 10–13 potato genotypes. Both greenhouse and field experiments showed that the susceptibility to wireworm attack was negatively correlated with the concentration of glycoalkaloids and positively correlated with the concentration of reducing sugars in the outer 2 mm of the tubers. Varietal differences in chlorogenic acid had no effect on susceptibility. Breeding for high levels of glycoalkaloids in the extreme periphery, but very low levels in the rest of the tuber, will protect the tubers from wireworms and yet result in acceptable glycoalkaloid levels for food safety.     

Bycatches of common guillemot (Uria aalge) in the Baltic Sea gillnet fishery

Bycatch of common guillemots (Uria aalge) appears to be the single most serious threat to the population, and the proportion of recoveries of ringed birds in fishing gear, compared with other finding circumstances, has significantly increased during a 28 year period (P<0.01). Out of 1952 ringed common guillemots reported found between 1972 and 1999 in the Baltic Sea, 980 (50.2%) were caught in fishing gear. The bycatch in set gillnets for cod (Gadus morhua) constituted 22.3%, drift gillnets for salmon (Salmo salar) 65.5%, and other fishing gear 12.2%. The proportion of recoveries in cod gillnets has significantly increased during the study period (P<0.05), while no clear trend was observed in the recoveries in salmon gillnets. The Swedish fishing effort follows a similar pattern for cod but has decreased for salmon. The observed increased use of cod gillnets in the Baltic Sea may have contributed to the observed decrease in adult survival rate, and we provide two different estimates suggesting that significant proportions of the guillemot population are caught annually in the Baltic Sea gillnet fishery. We suggest several available techniques to reduce bycatch in the Baltic Sea fishery.     

Patterns of water withdrawal beneath an irrigated peach orchard on a red-brown earth

Summary Water withdrawal from the soil beneath an irrigated peach orchard is described over depth and time after irrigation for a red-brown earth where the hydraulic properties vary with depth. Relationships between water uptake by roots, root concentration and soil-water suction were explored over protracted drying cycles. In the early stages of drying water uptake by roots was well correlated with root concentration over the profile but, over time, water uptake was redistributed over the root system. Theoretical analysis suggests that poor utilization of water from depth on this soil was associated mainly with low root concentrations and low root (radial) conductance. Practical considerations for improved water management in the root zone of peach orchards on shallow soils are discussed.