The Decline in Vitamin Research Funding: A Missed Opportunity?

The National Nutrition Research Roadmap has called for support of greater collaborative, interdisciplinary research for multiple areas of nutrition research. However, a substantial reduction in federal funding makes responding to these calls challenging. The objectives of this study were to examine temporal trends in research funding and to discuss the potential consequences of these trends.

Fighting fish parasites with photodynamically active chlorophyllin.

Water-soluble chlorophyll (chlorophyllin) was used in a phototoxic reaction against a number of fish ectoparasites such as Ichtyobodo, Dactylogyrus, Trichodina, and Argulus. Chlorophyllin is applied to the water at concentrations of several micrograms per milliliter for a predefined incubation time, and afterwards, the parasites are exposed to simulated solar radiation. Application in the dark caused only little damage to the parasites; likewise, light exposure without the addition of the photosensitizer was ineffective.

Treatment of ichthyophthiriasis with photodynamically active chlorophyllin.

Water-soluble chlorophyll (chlorophyllin) exerts pronounced photodynamic activity on fish parasites. In order to determine its potential as a remedy against ectoparasites in fish carps were incubated in water with defined concentrations of chlorophyllin. The main focus of the experiments was on the ciliate Ichthyophthirius multifiliis (Fouquet) which is responsible for considerable losses in livestock in aquaculture.

Organisation, regulations, preparation and logistics of parenteral nutrition in hospitals and homes; the role of the nutrition support team - Guidelines on Parenteral Nutrition, Chapter 8.

PN (parenteral nutrition) should be standardised to ensure quality and to reduce complications, and it should be carried out in consultation with a specialised nutrition support team whenever possible. Interdisciplinary nutrition support teams should be established in all hospitals because effectiveness and efficiency in the implementation of PN are increased. The tasks of the team include improvements of quality of care as well as enhancing the benefit to cost ratio.

Targeting of olfactory neurons.

Olfactory sensory neurons detect an enormous variety of small volatile molecules with extremely high sensitivity and specificity. The actual recognition and discrimination of odorous compounds is accomplished by specific receptor proteins located in the ciliary membrane of the sensory neurons. Axonal connections into the olfactory bulb, the first relay station for odor processing in the brain, are organized such that all neurons expressing the same odorant receptor converge their axons onto common glomeruli which are located at similar positions in all individuals from one species.

G protein betagamma complexes in circumvallate taste cells involved in bitter transduction.

G protein betagamma (Gbetagamma) complexes are considered to play an important role in second messenger signaling of phospholipase C (PLC). Monitoring the inositol 1,4,5-trisphosphate (IP(3)) response in circumvallate tissue homogenates upon stimulation with denatonium benzoate, it was demonstrated that a glutathione S-transferase-GRK3ct fusion protein-a Gbetagamma scavenger-attenuates the bitter tastant-induced second messenger reaction. Towards an identification of the Gbetagamma complex involved in rat bitter taste transduction, it was found that the G protein beta(3) subtype is specifically expressed in taste receptor cells of circumvallate papillae.

Cross-talk between olfactory second messenger pathways.

The second messengers 3'-5'-cyclic-monophosphate (cAMP) and inositol 1,4,5-trisphosphate (InsP3) have been implicated in olfactory signal transduction in various species. The results of the present study provide evidence that the two olfactory second messenger pathways in rat olfactory neurons do not work independently but rather show a functional antagonism: whereas inhibition of phospholipase C (PLC) in isolated olfactory cilia by U-73122 led to an augmentation of odor-induced cAMP signaling, activation of the phosphoinositol pathway resulted in attenuation of odor-induced cAMP formation. Furthermore, this study indicates that elevated cAMP levels cause suppression of odor-induced InsP3 signaling, whereas inhibition of adenylate cyclase (AC) by cisN-(2-phenylcyclopentyl)azacylotridec-1-en-2-amine (MDL-12,330 A) results in potentiation of odor-induced InsP3 formation.

Small subfamily of olfactory receptor genes: structural features, expression pattern and genomic organization.

Olfactory receptors of the OR37 subfamily are characterized by distinct sequence features and are expressed in neurons segregated in a restricted area of the olfactory epithelium. In the present study, we have characterized the complement of OR37-like genes in the mouse. Five OR37-like genes were identified.

On the origin of the olfactory receptor family: receptor genes of the jawless fish (Lampetra fluviatilis).

In vertebrates, recognition of odorous compounds is based on a large repertoire of receptor subtypes encoded by a multigene family. Towards an understanding of the phylogenetic origin of the vertebrate olfactory receptor family, attempts have been made to identify related receptor genes in the river lampreys (Lampetra fluviatilis), which are descendants of the earliest craniates and living representatives of the most ancient vertebrates. Employing molecular cloning approaches led to the discovery of four genes encoding heptahelical receptors, which share only a rather low overall sequence identity but several of the characteristic structural hallmarks with vertebrate olfactory receptors.

Olfactory receptors in aquatic and terrestrial vertebrates.

In species representing different levels of vertebrate evolution, olfactory receptor genes have been identified by molecular cloning techniques. Comparing the deduced amino-acid sequences revealed that the olfactory receptor gene family of Rana esculenta resembles that of Xenopus laevis, indicating that amphibians in general may comprise two classes of olfactory receptors. Whereas teleost fish, including the goldfish Carassius auratus, possess only class I receptors, the 'living fossil' Latimeria chalumnae is endowed with both receptor classes; interestingly, most of the class II genes turned out to be pseudogenes.

Functional and molecular characterization of individual olfactory neurons.

To gain an understanding of the olfactory signal transduction process, individual chemosensory neurons have been assessed for odor-induced Ca2+ responses and the molecular elements of transduction cascades using Ca2+ imaging technique in combination with single-cell RT-PCR approaches. It has been demonstrated that responsiveness of cells to cyclic AMP or inositol trisphosphate odorants was blocked by specific adenylyl cyclase inhibitors or phospholipase C inhibitors, respectively. Using specific primers in single-cell RT-PCR analysis, olfactory marker protein, two G protein subtypes (G(olf) and G(o)), and adenylyl cyclase (subtype III) and a phospholipase C (phospholipase Cbeta2-related subtype) were identified.

Decline and recovery of olfactory receptor expression following unilateral bulbectomy.

The effects of unilateral olfactory bulb ablation upon the odorant receptor expression were studied during the degeneration/regeneration process in the olfactory epithelium of adult rats. Using the in situ hybridization approach, we compared the time course of decay and recovery of expression for three different receptor subtypes (OR14, OR5, OR124). The number of neurons expressing receptor subtypes dramatically decreased in the olfactory epithelium on the lesioned side and reached a minimum at day 5 postsurgery.

Elements of the olfactory signaling pathways in insect antennae.

Owing to their enormous ability to recognize airborne molecules, insects have long been used as model systems for studying various aspects of olfaction. Modern biological techniques have opened new avenues for exploring the molecular mechanisms underlying the complex signaling processes in chemosensory neurons. Biochemical and molecular analyses have allowed the identification of molecular elements of the olfactory reaction pathways and have shed light on mechanisms that account for the sensitivity and specificity of the chemosensory system.

Two olfactory marker proteins in Xenopus laevis.

Mature olfactory receptor neurons of mammals are characterized by the expression of the highly conserved olfactory marker protein (OMP) encoded by single copy genes. In Xenopus laevis, two homologous genes encoding olfactory marker proteins have been identified that share a sequence identity with mammalian OMPs of about 50%. Sequence comparison revealed significant variability in the N-terminus and C-terminus regions; in contrast, two internal domains were highly conserved between amphibian and mammalian OMPs, suggesting some functional relevance.

Subfamily of olfactory receptors characterized by unique structural features and expression patterns.

The complex chemospecificity of the olfactory system is probably due to the large family of short-looped, heptahelical receptor proteins expressed in neurons widely distributed throughout one of the several zones within the nasal neuroepithelium. In this study, a subfamily of olfactory receptors has been identified that is characterized by distinct structural features as well as a unique expression pattern. Members of this receptor family are found in mammals, such as rodents and opossum, but not in lower vertebrates.

Sodium/calcium exchanger in rat olfactory neurons.

The chemo-electrical transduction process in olfactory neurons is accompanied by a rapid and transient increase in intracellular calcium concentrations. The notion that Na+/Ca2+ exchanger activities may play a major role in extruding calcium ions out of the cell and maintaining Ca2+ homeostasis in olfactory receptor cells was assessed by means of laser scanning confocal microscopy in combination with the fluorescent indicators Fluo-3 and Fura-Red. The data indicate that high exchanger activity, which was inhibited by amiloride derivatives, is located in the dendritic knob and probably in the olfactory cilia.

Olfactory receptor gene expression.

Recognition and discrimination of odorous molecules are determined by heptahelical G-protein-coupled receptor proteins localized primarily in the ciliary membrane of olfactory sensory neurons. The discovery of a large multigene family encoding odorant receptors allows us to approach various facets concerning the molecular basis of olfactory chemospecificity, ranging from chromosomal localization and control of expression of olfactory receptor genes to temporal and spatial expression patterns of various receptor types in the nasal neuroepithelium. The target-independent onset of receptor expression and its topographical organization suggest a precommited functional identity of olfactory neurons.

Phosducin, potential role in modulation of olfactory signaling.

Phosducin, which tightly binds betagamma-subunits of heterotrimeric G-proteins, has been conjectured to play a role in regulating second messenger signaling cascades, but to date its specific function has not been elucidated. Here we demonstrate a potential role for phosducin in regulating olfactory signal transduction. In isolated olfactory cilia certain odorants elicit a rapid and transient cAMP response, terminated by a concerted process which requires the action of two protein kinases, protein kinase A (PKA) and a receptor-specific kinase (GRK3) (Schleicher, S.

Phosphatase 2A regulates the responsiveness of olfactory cilia.

The odorant-induced second messenger response in olfactory cilia was monitored in the presence of phosphatase modulators. Okadaic acid, a phosphatase inhibitor, attenuated the odorant-induced cAMP-response in a dose-dependent manner, half maximal inhibition was obtained at 1.5 nM okadaic acid indicating that phosphatase 2A may be involved.

Laminar segregation of odorant receptor expression in the olfactory epithelium.

The laminar segregation of sensory neurons expressing a distinct receptor type was determined in tissue sections through the olfactory epithelium by in situ hybridization employing receptor-specific probes. Reactive cells were restricted to the mid-zone of the epithelium, the location of mature neurons. Detailed analyses revealed that neurons expressing a distinct receptor type were distributed in a characteristic manner throughout the layers of the neuronal zone, i.

Calcium controls second-messenger signalling in olfactory cilia.

The increase in intracellular calcium concentration elicited by odorant stimulation seems to be involved in down-regulating the responsiveness of olfactory neurons to subsequent stimuli. The present study suggests that this regulatory effect may be due to a calcium-dependent attenuation of the olfactory signalling cascade; the odor-induced cyclic adenosine monophosphate (cAMP) response in olfactory cilia is diminished by calcium in a dose-dependent manner. This reduced cAMP signal is not due to an activation of phosphodiesterases by elevated calcium levels, but rather seems to be mediated by the inhibition of adenylate cyclase by calcium ions.

Regulation of olfactory signalling via cGMP-dependent protein kinase.

Strong odor stimuli elicit a slow and sustained increase of the cGMP concentration in isolated rat olfactory cilia. Elevated cGMP levels appear to attenuate the primary response to odorant stimulation. Incubating cilia with membrane-permeable cGMP derivates caused a significantly reduced cAMP signal in response to odorant stimulation.

Two classes of olfactory receptors in Xenopus laevis.

Xenopus laevis possess a gene repertoire encoding two distinct classes of olfactory receptors: one class related to receptors of fish and one class similar to receptors of mammals. Sequence comparison indicates that the fish-like receptors represent closely related members of only two subfamilies, whereas mammalian-like receptors are more distantly related, most of them representing a different subfamily. The fish-like receptor genes are exclusively expressed in the lateral diverticulum of the frog's nose, specialized for detecting water-soluble odorants, whereas mammalian-like receptors are expressed in sensory neurons of the main diverticulum, responsible for the reception of volatile odors.