Localisation of acidic and basic fibroblast growth factors during mouse palate development and their effects on mouse palate mesenchyme cells in vitro

Summary The distribution of acidic and basic fibroblast growth factors (aFGF, bFGF) was mapped during mouse embryonic palate development. Generally, they localised most intensely in the basement membrane and epithelia rather than the mesenchyme. Localisation was predominantly restricted to the palatal nasal, and medial edge epithelia. Staining was particularly intense in the medial edge epithelia at the time of mid-line epithelial seam formation. Intense staining persisted in the epithelia of the degenerating seam and later in the oral and nasal epithelial triangles. Mouse embryonic palate mesenchyme (MEPM) cells cultured in vitro on a variety of substrata (on plastic, on the surface of a collagen gel and within a collagen gel) responded to treatment with aFGF or bFGF. These responses were modulated by the culture substratum. The FGFs stimulated MEPM cell proliferation on plastic and on collagen, but inhibited cell growth in collagen. The FGFs had little effect on protein production when cells were cultured on plastic, but caused a large reduction in on-collagen and incollagen cultures. This reduction was greater in collagenous than non-collagenous proteins. Generally, treatment with FGFs stimulated the production of glycosaminoglycans (GAGs), particularly hyaluronan (HA) and dermatan sulphate (DS). In addition, the size class of HA was shifted to a higher molecular weight form. These data indicate that aFGF and bFGF may play a role in modulating mesenchymal cell matrix biosynthesis, so facilitating palatal epithelial seam degeneration. Correspondence to: M.W.J. Ferguson     

Construction of a sequencedClostridium perfringens-Escherichia coli shuttle plasmid

A newClostridium perfringens-Escherichia coli shuttle plasmid has been constructed and its complete DNA sequence compiled. The vector, pJIR418, contains the replication regions from theC. perfringens replicon pIP404 and theE. coli vector pUC18. The multiple cloning site and lacZ gene from pUC18 are also present, which means that X-gal screening can be used to select recombinants inE. coli. Both chloramphenicol and erythromycin resistance can be selected inC. perfringens andE. coli since pJIR418 carries theC. perfringens catP and ermBP genes. Insertional inactivation of either the catP or ermBP genes can also be used to directly screen recombinants in both organisms. The versatility of pJIR418 and its applicability for the cloning of toxin genes fromC. perfringens have been demonstrated by the manipulation of a cloned gene encoding the production of phospholipase C.     

Neuroendocrine control of gonadotropin secretion

Luteinizing hormone releasing hormone (LHRH), a hypothalmic peptide that is concentrated in granules of neurons, has the capacity to release gonadotropins (luteinizing hormone (LH) and follicle stimulating hormone) from the pituitary gland. LHRH has been found in hypophysial portal blood of rats, monkeys, and rabbits. Antibodies to LHRH depress plasma LH concentrations in castrated animals and evoke testicular atrophy, but passive immunization against LHRH does not block the LH surge induced by estrogen in monkeys. Estrogens, progestin, prolactin, and dopamine have marked effects on LH secretion, yet an association between these effects and altered hypophysial portal blood concentrations of LHRH is not established. In view of the paucity of evidence demonstrating such a cause and effect relationship, two alternative proposals have become tenable. One, hormones and neurotransmitters may not alter the levels of portal blood LHRH, but rather alter the frequency of pulsatile LHRH secretion. Two, hormones, such as estrogens, progesterone, and prolactin, may alter the responsiveness of the gonadotropin-secreting cells to LHRH by affecting the secretion of dopamine.     

A proton magnetic resonance study of water in human stratum corneum

Proton magnetic resonance spectroscopy has been used to study the nature of water in human stratum corneum. For a single planar sheet of stratum corneum mounted at a specific orientation to the applied magnetic field, three distinct absorptions may be seen having different chemical shifts and spin-lattice relaxation times (T₁). All T₁ values for these resonances are smaller than that for normal liquid water. One absorption is unusual in that the resonance position is dependent upon the orientation of the sample within the field.     

Effects of E2 levuglandins on the contractile activity of the rat uterus

The effects of E2 levuglandins on the contractile activity of rat uterine horns were studied. LGE2, AnLGE2, delta 9-LGE2 and the synthetic epimer, 8-epi-delta 9-LGE2 all induced contractions in a dose-response fashion. AnLGE2 gave decreased responses with increased bath concentrations. Paired comparisons showed potent and selective inhibitory effects of AnLGE2 on the uterotonic activity of prostaglandins. AnLGE2 inhibited the uterotonic activity of PGE2 at a 0.1:1 ratio, of PGD2 at a 1:1 ratio, but did not inhibit the activity of PGF2 alpha. Exposure of spontaneously contracting uteri to high concentrations of AnLGE2, or prolonged exposure to lower concentrations, suppressed contractions.     

Zn2+-induced cooperativity of mannitol-1-phosphate dehydrogenase from Aspergillus parasiticus

Mannitol-1-phosphate dehydrogenase (EC 1.1.1.17) has been purified from Aspergillus parasiticus, a filamentous fungus which produces the polyketide mycotoxin, versicolorin A. Its kinetic properties have been compared with those of mannitol-1-phosphate dehydrogenase from the related non-toxin-producing fungus, A. niger. Both enzymes are inhibited by divalent transition metals, especially Zn2+ and Cd2+, but only the enzyme from A. parasiticus exhibits inhibitor-induced cooperative binding of the substrate, fructose-6 phosphate. Double reciprocal plots (1/v versus 1/Fru-6-P) are linear in the absence of Zn2+ but in the presence of Zn2+ are concave upward, with Hill coefficients of 1.5. The extent of cooperativity is inversely related to ionic strength, disappearing at 100 mM KCl. The enzymes from both organisms are relatively stable to incubation at 30 degrees C, but only the enzyme from A. parasiticus is rendered thermally unstable by the addition of divalent transition metals. A model is proposed to explain how binding of transition metal ions affects substrate binding and thermal stability of the enzyme.     

Linking of cytochrome P450cam and putidaredoxin by a co-ordination bridge

Cytochrome P450_cam (CYP101) catalyzes the oxidation of D(+)-camphor at the 5 position. The enzyme couples the reduction of dioxygen to the oxidation of the substrate. To transfer electrons from the reductant (NADH) to the cytochrome, two additional proteins are required. These are putidaredoxin (PdX) and putidaredoxin reductase (PdR). We have chemically linked a form of PdX with a histidine tag at the C-terminus to the P450. To accomplish this, we have modified cysteine 334 on P450 with a bipyridinyl group, and co-ordinated the C-terminal histidine tag of PdX by the addition of Ni²⁺ or Ru³⁺. The Ru³⁺ complex was the most stable. The non-linked system gave mostly 5-ketocamphor, a product of two consecutive hydroxylations, and H₂O₂, a product of 2-electron uncoupling. The Ni²⁺ complex gave both 5-exo-hydroxycamphor and 5-ketocamphor, but it also uncoupled. The Ru³⁺ complex gave a single product (5-exo-hydroxycamphor) and did not uncouple at the optimal PdR concentration. Our results are consistent with other studies of this system, in that strong binding of PdX to P450 is crucial for good coupling and for release of 5-exo-hydroxycamphor.     

Estimation of Parameters Influencing Waterborne Transmission of Infectious Hematopoietic Necrosis Virus (IHNV) in Atlantic Salmon (Salmo salar)

Understanding how pathogenic organisms spread in the environment is crucial for the management of disease, yet knowledge of propagule dispersal and transmission in aquatic environments is limited. We conducted empirical studies using the aquatic virus, infectious hematopoietic necrosis virus (IHNV), to quantify infectious dose, shedding capacity, and virus destruction rates in order to better understand the transmission of IHN virus among Atlantic salmon marine net-pen aquaculture. Transmission of virus and subsequent mortality in Atlantic salmon post-smolts was initiated with as low as 10 plaque forming units (pfu) ml⁻¹. Virus shedding from IHNV infected Atlantic salmon was detected before the onset of visible signs of disease with peak shed rates averaging 3.2×10⁷ pfu fish⁻¹ hour⁻¹ one to two days prior to mortality. Once shed into the marine environment, the abundance of free IHNV is modulated by sunlight (UV A and B) and the growth of natural biota present in the seawater. Virus decayed very slowly in sterilized seawater while rates as high as k =  4.37 d⁻¹ were observed in natural seawater. Decay rates were further accelerated when exposed to sunlight with virus infectivity reduced by six orders of magnitude within 3 hours of full sunlight exposure. Coupling the IHNV transmission parameter estimates determined here with physical water circulation models, will increase the understanding of IHNV dispersal and provide accurate geospatial predictions of risk for IHNV transmission from marine salmon sites.     

Repeat Photography as a Method in Visual Anthropology

This paper explores the use of repeat photography as a powerful method to produce knowledge about place. I use examples from research in Waterton Lakes National Park, Canada, to describe the process of making a repeat photograph, from locating images in archives, to the embodied act of locating a historic vantage point, to the production of a new photograph. This act brings art and anthropology into a shared space to recreate photographs, an act that goes beyond looking at historical images in archives to move our thinking onward about how we relate to images.