Molecular distribution of zinc in biliary and pancreatic secretions

Rat bile and pancreatic fluid were examined for the presence of low molecular weight zinc complexes. Fluids were collected separately by cannulation, and zinc distribution in collected samples was analyzed by gel filtration on Sephadex G-50. Most of the zinc in bile was associated with low molecular weight zinc complexes; only a small amount of zinc was present in the high molecular weight fraction. In contrast, pancreatic secretions did not contain low molecular weight zinc complexes, but there were considerable amounts of zinc bound to high molecular weight compounds. The addition of zinc to bile resulted in an increased amount of zinc in the low molecular weight fraction, while the addition of zinc to pancreatic fluid resulted primarily in an increase in zinc bound to the high molecular weight components. Like pancreatic fluid, homogenates of pancreatic tissue had no low molecular weight zinc complex. In rats whose bile and pancreatic fluid were removed and not returned into the intestine, the amount of zinc bound to low molecular weight complexes in intestinal homogenates was reduced. This alteration of the molecular distribution of zinc in intestinal homogenates by removal of bile and pancreatic fluid suggests the potential importance of low molecular weight zinc complexes for zinc homeostasis.     

Systemic injections of gastro-intestinal peptides alter behavior in rats

Twenty-four male albino rats were given daily intraperitoneal injections of vasoactive intestinal polypeptide (VIP), motilin, human gastrin I (1–17) or the diluent control vehicle at a dose of 100 μg/kg for four consecutive days and food intake, water intake, body weight, and running wheel activity were determined every 24 hours. Animals injected with motilin or human gastrin I (1–17) exhibited decreased food intake relative to those injected with VIP or diluent, which did not differ from each other, although food intake increased reliably over days. The mean water consumption followed the same pattern as that of food intake. As expected from the above results, VIP produced weight gains as compared with rats injected with motilin or gastrin but not reliably more than after diluent. A reliable effect of trials for weight gain was the greatest on day three. Running wheel activity was not affected by injections of human gastrin I (1–17), motilin, or diluent but was reliably decreased by VIP. No significant differences existed across days. Although the results indicate that GI peptides may affect behavior when injected systemically and that like other peptides they have multiple effects, caution is urged in the interpretation of behavioral results at this time.     

Pharmacological comparison of bPTH-(1–34) and other hypotensive peptides in the dog

The purpose of the present study was to compare the potency, effectiveness and duration of action of synthetic bPTH-(1–34) with those of other known hypotensive peptides in the anesthetized dog. Of sixteen peptides tested in the present study only 8 were demonstrated to possess hypotensive activity. While bPTH-(1–34) was one of the least potent of the hypotensive peptides, it was equal to or greater than the other peptides in terms of effectiveness and duration of action. Of all the peptides studied, substance P and eledoisin were the most potent in terms of their hypotensive action. It is suggested that perhaps substance P and eledoisin might act at a different site or through different mechanisms than do vasoactive intestinal peptide (V.I.P.), corticotropin inhibiting peptide (C.I.P.), neurotensin, xenopsin, bradykinin and bPTH-(1–34).     

Nippostrongylus brasiliensis: Peripheral leukocyte responses and correlation of basophils with blood histamine concentration during infection in rats

Rats infected on Day 0 with 3000 infective L₃ larvae of Nippostrongylus brasiliensis, and uninfected controls, were monitored daily through Day 23 postinfection for changes in peripheral leukocytes and blood histamine concentrations. A generalized leukocytosis was observed between Days 7 and 18, the period leading up to and immediately following the time of expulsion of adult worms from the small intestine. The total number of lymphocytes was elevated between Days 11 and 17 post-infection; however, there was no change in the percentage of lymphocytes relative to other white blood cell types. The total number and percentage of monocytes were no different from controls, with the exception of Day 5 postinfection. On that day, there was a significant elevation in the number (614/mm³ blood in infected rats, as compared to 160/mm³ blood in controls) and relative proportion (2.7% of total leukocytes in infected animals, compared to 0.8% in controls) of monocytes, coinciding with the termination of the pulmonary migration of larvae. A period of moderate neutrophilia occurred between Days 7 and 12, but this was not accompanied by any changes in the proportion of neutrophils. A biphasic eosinophil response was observed. An early elevation of eosinophils occurred between Days 3 and 5, corresponding to the period of larval migration through the lungs. A second period of eosinophilia began on Day 11, when worm expulsion was beginning, and continued through Day 19, i.e., beyond the period of worm expulsion. Basophilia was observed as early as Day 6 after infection, rising to a peak on Day 13 (6.8% of total leukocytes in the infected animals, as compared to 0.5% in controls), and declining thereafter, but remaining above control levels until termination of the experiment on Day 23. The histamine content of blood samples, as determined by an enzymic-isotopic assay, closely paralleled the development and decline of basophilia; histamine levels also peaked on Day 13 postinfection (422.5 pg histamine/mm³ blood in infected rats, compared to 66.0 pg histamine/mm³ blood in controls). As basophilia progressed during the course of infection, there was a decline in the amount of histamine per basophil. In uninfected rats and during the first week after infection, basophils contained about 1.5–2.0 pg histamine per cell. In the third week of infection, there was about 0.6 pg histamine per basophil. The time course of the basophilia suggests that these cells may be involved in the expression of immunity to N. brasiliensis.     

The distribution and cellular origin of vasoactive intestinal polypeptide in the avian gastrointestinal tract and pancreas

Summary The distribution and origins of vasoactive intestinal peptide (VIP) in the gut and pancreas of the turkey were studied by radioimmunoassay of tissue extracts and by immunocytochemistry. Several antisera were used that vary in their specificity for different regions of porcine or chicken VIP. Radioimmunoassays using NH₂-terminal specific antisera that react almost equally with porcine and chicken VIP's revealed significant amounts of immunoreactive VIP in extracts of pancreas, brain and all regions of the gastrointestinal tract from crop to colon. Highest concentrations (300pmol/g) were found in the colon muscle, and concentrations were generally low (< 20 pmol/g) in the mucosal layers of the small intestine. After ion exchange chromatography of extracts on CM-Sephadex three immunoreactive forms of VIP were separated corresponding to the three molecular forms previously found in mammalian gut extracts. In immunocytochemical studies nerve fibres were found throughout the gut, and in the pancreas. Immunoreactive nerve cell bodies were also identified in the submucous plexus throughout the gut, but were particularly prominent in the oesophagus and pancreas. It has previously been shown that VIP is a strong stimulant of the flow of pancreatic juice in birds whereas the structurally related hormone secretin, which is known to control the flow of pancreatic juice in mammals, is a weak stimulant. It is proposed that in birds VIP might regulate the pancreas, and other aspects of gut function, as a neurotransmitter or neurohormone.     

A brief review on the development of stronglid nematode eggs and larvae under constant and changing temperature conditions-I. Egg development

The present work gives a brief review on the major aspects of the effect of constant and changing temperatures on the development of stronglid nematode eggs. The effect of culture media on the range of temperatures at which the eggs may hatch as well as the rate of their hatching is also included. In addition, a revision of resistance of the eggs to low and high temperatures is also tackled.     

Effect of serum,fibronectin, and laminin on adhesion of rabbit intestinal epithelial cells in culture

Rabbit intestinal epithelial cells, obtained after a limited hyaluronidase digestion, were incubated in medium with or without calf serum, on bacteriological plastic dishes. The dishes, either plain or coated with an air-dried type I collagen film, were pretreated with medium alone or with medium containing purified laminin or purified fibronectin. Cells did not attach in significant numbers to untreated bacteriological plastic, even in the presence of serum. Cells did attach to collagen-coated dishes, and were judged viable on the basis of their incorporation of radiolabeled leucine into cell protein. Cell adhesion to the collagen substrate increased in proportion to the concentration of serum in the medium, with maximal attachment at 5% serum or greater. Pretreatment of plain or collagen-coated dishes with increasing amounts of fibronectin enhanced cell adhesion in a concentration-dependent manner. Either serum, or fibronectin-free serum in the medium enhanced cell attachment to substrates pretreated with cither fibronectin or laminin. Thus, intestinal epithelial cells appear to possess surface receptors for both laminin and fibronectin. The evidence further suggests that calf serum may contain factors, other than fibronectin, capable of enhancing intestinal epithelial cell attachment to collagen substrates.     

Effects of guanine nucleotides on cns neuropeptide receptors

The effect of nucleotides on central nervous system neuropeptide receptor binding was investigated. The guanine nucleotides, guanosine-5′-triphosphate and guanylyl-5′-imidodiphosphate, significantly inhibited the binding of radiolabeled vasoactive intestinal polypeptide but not that of [Tyr⁴]bombesin to rat brain membranes. Vasoactive intestinal polypeptide binding was inhibited by guanine nucleotides in a dose-dependent manner. Using a 20 μM dose, 60% of the specific vasoactive intestinal polypeptide binding was inhibited by guanylyl-5′-imidodiphosphate, which was more potent than guanosine-5′-triphosphate, whereas other nucleotides were not effective. This reduction in binding was a consequence of lower affinity of the receptor for vasoactive intestinal polypeptide, which in turn resulted from an increased rate of dissociation.     

Pharmacological comparison of bPTH-(1–34) and other hypotensive peptides in the dog

The purpose of the present study was to compare the potency, effectiveness and duration of action of synthetic bPTH-(1–34) with those of other known hypotensive peptides in the anesthetized dog. Of sixteen peptides tested in the present study only 8 were demonstrated to possess hypotensive activity. While bPTH-(1–34) was one of the least potent of the hypotensive peptides, it was equal to or greater than the other peptides in terms of effectiveness and duration of action. Of all the peptides studied, substance P and eledoisin were the most potent in terms of their hypotensive action. It is suggested that perhaps substance P and eledoisin might act at a different site or through different mechanisms than do vasoactive intestinal peptide (V.I.P.), corticotropin inhibiting peptide (C.I.P.), neurotensin, xenopsin, bradykinin and bPTH-(1–34).     

Nerves containing substance P,vasoactive intestinal polypeptide,enkephalin or somatostatin in the guinea-pig taenia coli

Summary The guinea-pig taenia coli is rich in peptide-containing nerves. Nerve fibres containing substance P (SP), vasoactive intestinal peptide (VIP), or enkephalin, were numerous in the smooth muscle while somatostatin fibres were very few. Nerve fibres displaying SP or VIP immunoreactivity were numerous in the myenteric plexus. Enkephalin nerve fibres were fairly numerous in the plexus while somatostatin nerve fibres were sparse. Nerve cell bodies containing immunoreactive SP or VIP were regularly seen in the plexus. Delicate varicose elements of the different types of nerve fibres were found to ramify around nerve cell bodies in a manner suggestive of innervation.In the electron microscope the various peptide-storing nerve fibres (i.e., elements containing SP, VIP or enkephalin) were found to contain a varying number of fairly large, electron-opaque vesicles in the varicose swellings. These vesicles represent the storage site of the neuropeptides.The isolated taenia coli responded to electrical nerve stimulation with a contraction. After cholinergic and adrenergic blockade the contractile response was replaced by a relaxation followed by a contraction upon cessation of stimulation. SP contracted the taenia while VIP caused a relaxation. The enkephalins raised the resting tension slightly while somatostatin had no effect. These observations are compatible with a role for SP as an excitatory neurotransmitter and for VIP as an inhibitory one, and with the view that both SP neurones and VIP neurones act as motor neurones. In preparations contracted by SP the electrically induced contractions were reduced in amplitude while the electrically induced relaxations seen after adrenergic and cholinergic blockade were enhanced in amplitude. In preparations relaxed by VIP there was an increased contractile response to electrical stimulation, while in the atropine + guanethidine-treated preparation the electrically induce relaxations were reduced in amplitude. The enkephalins reduced the contractile response to electrical stimulation, while somatostatin induced a very small reduction in the amplitude of such responses. These observations suggest that SP neurones and VIP neurones may play additional roles as interneurones. Somatostatin neurones probably act as interneurones. Enkephalin-containing fibres may serve to modify the release of transmitter from other nerves in the smooth muscle, perhaps through axo-axonal arrangements. Alternatively, the enkephalin nerve fibres in the smooth muscle are afferent elements involved in mediating sensory impulses to the myenteric plexus.