Nervus terminalis projection to the retina in the 'four-eyed' fish, Anableps anableps

The eye of the surface dwelling 'four-eyed' fish, Anableps possesses an aquatic and an aerial optical system. The aerial system is strongly hyperopic when the animal dives, i.e. during mating, and the dorsal pupil is submerged. We studied the retino-petal nervus terminals projection to the aerial and to the aquatic retina by Phe-Met-Arg-Phe-NH2 (FMRF) immunocytochemistry and found both to be equally innervated. This finding sheds doubt on the proposed functional significance of this projection for reproductive behaviour.

Soybean agglutinin binding by primary olfactory and primary accessory olfactory projections in different frogs

Comparing eight species of frogs adapted to habitats ranging from aquatic to arboreal, we observed differences in the affinity of primary olfactory projections to the lectin 'soybean agglutinin'. Particularly pronounced differences exist between Pipa, a frog that rarely leaves the water, and Eleutherodactylus, an arboreal species that does not even utilize aquatic environments for reproduction. We interpret these differences as reflecting specializations to the perception of air-borne vs. water-borne odors.

Dextran modification of a Fab'--beta-lactamase conjugate modulated by variable pretreatment of Fab' with amine-blocking reagents

The physical and pharmacological properties of proteins can be altered by chemical modification with polymers. Preliminary studies showed that attachment of oxidized dextran to the bacterial protein, beta-lactamase (beta L) effectively reduced in vivo immunogenicity in mice with no loss of enzymatic activity. This report describes a general method for differentially dextran modifying the Fab' component of a Fab'--beta-lactamase conjugate by the use of amine-blocking reagents. Methyl acetimidate (MeAcm) and the N-succinimidyl derivative of (methylsulfonyl)ethyl carbonate (NHS-Msc), reagents which can reversibly block primary amines, were used in model studies to modulate the level of available reactive amines on the F(ab')2 fragments of both the anti-carcinoembryonic antigen antibody, ZCE025, and the antitumor-associated glycoprotein-72 antibody, CC49. MeAcm had little or no effect on immunoreactivity and was maximally effective in modulating dextran attachment, while NHS-Msc was much less effective. A comparison of NHS-Msc and MeAcm is described. Treatment of F(ab')2 with 5-300 mM MeAcm prior to dextran treatment showed a proportional decline in the level of dextran attachment as well as intramolecular cross-linking of the protein by the dextran polymers (6 kDa or 33-mer). A conjugate of beta L coupled to MeAcm-treated ZCE025 Fab' [reduced F(ab')2] was constructed under standard conditions using sulfosuccinimidyl N-[(4-carboxycyclohexyl)methyl]maleimide. After dextran modification, this conjugate maintained good immunoreactivity and enzymatic activity. Biodistribution studies in tumor-bearing nude mice of dextranated and nondextranated conjugate showed comparable overall distribution profiles except that the clearance of the dextranated conjugate from both blood and tumor was delayed about 48-72 h.

Screening for disease, cost-effectiveness, and guidelines

This article provides a brief overview of issues involved in selecting prevention maneuvers for primary care practitioners. Screening diseases, the screening tests themselves, patient characteristics, and cost-effectiveness are discussed.

Expression of S100 protein in the vestibular nuclei during compensation of unilateral labyrinthectomy symptoms

In adult guinea pigs, unilateral labyrinthine lesions were inflicted by chloroform injections into the middle ear. Immunoreactivity for S100 protein (S100) in the vestibular nuclei was studied during compensation of lesion-induced postural asymmetry symptoms, i.e., nystagmus, asymmetrical head position. 1 h after unilateral labyrinthectomy, increased levels of astroglial S100 immunoreactivity were found in the superior vestibular nucleus and in the medial/lateral vestibular nucleus border region on the side contralateral to the deafferentation. Bilaterally, the astrocytic S100 immunoreaction increased in the lateral vestibular nuclei around Deiters neurons. Maximal expression of S100 was noted 3 h after the lesion. Subsequently, it diminished. Our data reveal that transsynaptically altered neuronal activity induces an astrocytic reaction which provides increased levels of S100 to the local neuropil. Calcium and zinc binding S100 proteins may play a functional role for the neuroplasticity during vestibular compensation.

Site-specific prodrug activation by antibody-beta-lactamase conjugates: preclinical investigation of the efficacy and toxicity of doxorubicin delivered by antibody directed catalysis

Antibody directed catalysis (ADC), the catalytic conversion of prodrugs to drugs by enzymes localized at disease targets by appropriate monoclonal antibodies, has shown promise in the treatment of cancer in nude mouse xenograft models. We investigated this concept using antibody enzyme conjugates constructed from beta-lactamase and Fab's reactive with carcinoembryonic antigen, CEA, and tumor associated glycoprotein, TAG-72, to convert prodrugs that are cephalosporin sulfoxide derivatives into oncolytic drugs. Previous work focused on ADC delivery of the potent vinca alkaloid derivative desacetylvinblastine carboxhydrazide (DAVLBHYD). In the current study the ability of the system to deliver doxorubicin was tested in MCF7 breast carcinoma xenografts and OVCAR3 ovarian carcinoma xenografts, and in T380 and LS174T colon tumor xenografts for comparison with previous DAVLBHYD results. ADC enhanced the delivery of doxorubicin in the model systems investigated. Tumor growth suppression was equivalent to or greater than that observed with free doxorubicin at its maximum tolerated dose (MTD). In contrast to the DAVLBHYD results, ADC delivery of doxorubicin did not regress tumors, but did result in a substantial increase in the MTD.

Benzo[c]phenanthridine alkaloids sanguinarine and chelerythrine: biological activities and dental care applications

This article reviews chemical, pharmacological, and toxicological research relating to two principal benzo[c]phenanthridine alkaloids, namely sanguinarine and chelerythrine, in the period 1980-1994. The medical applications of these alkaloids in relation to their biological activities are discussed.

The extrabulbar olfactory pathway: primary olfactory fibers bypassing the olfactory bulb in bony fishes?

Recent evidence has revealed that some primary olfactory fibers bypass the olfactory bulb and terminate in tel- and/or diencephalic areas (extrabulbar olfactory pathway, EBOP). We investigated the projections of this system in different fishes by means of soybean agglutinin binding studies. In all species in which primary olfactory fibers were labelled, fiber bundles can be traced beyond the olfactory bulb. These run with the medial forebrain bundle and terminate at different targets, depending on the species. In the teleosts Macrognathus, Mogurnda, and Hemichromis, EBOP fibers can be traced into the ventral telencephalon, pars ventralis, pars supracommissuralis and/or into the preoptic nucleus. In most nonteleosts studied (Polypterus, Chalamoichthys, Amia), the EBOP also innervates diencephalic targets. An exception is Acipenser, which displays an innervation pattern similar to that in teleosts. Comparison with results obtained by other techniques suggests that the EBOP consists of primary olfactory fibers, which project not only to the olfactory bulb but also to various other targets in the prosencephalon of anamniotic vertebrates.

Birds that feed-on-the-wing have few isthmo-optic neurons

The isthmo-optic system is less developed in birds feeding-on-the-wing, than in pecking avians. This was suggested previously. By intraocular horseradish peroxidase applications, we studied the central origin of this retino-petal system in thrush, haw finch, swift and swallow. Our data support the assumption on a correlation between feeding habits and the development of the isthmo-optic nucleus in adult avians as this brainstem region is more highly developed in thrush and finch than in swift and swallow. This is particularly relevant since the latter species is taxonomically related to the two pecking birds whereas it is unrelated to the swift that also feeds-on-the-wing.

High yield, site-specific coupling of N-terminally modified beta-lactamase to a proteolytically derived single-sulfhydryl murine Fab'

The preparation of bispecific protein conjugates capable of performing diverse biological functions is an area of active investigation. Such conjugates are routinely prepared using techniques which employ random derivatization of lysine residues, but the overall utility of these methods is limited due to poor yields and heterogeneous conjugates. In this report we describe the development of site-specific linkage methodology for the chemical synthesis of a homogeneous enzyme-antibody Fab' conjugate with coupling efficiencies of at least 72%. The N-terminal threonine residue of beta-lactamase from the P99 strain of Enterobacter cloacae was oxidized to an aldehyde functional group under mild conditions with a 5-fold molar excess of sodium periodate. The murine Fab' with a single sulfhydryl at the hinge region was generated by further digestion of the peptic Fab' fragment with lysyl endopeptidase to remove a decapeptide containing two of the three cysteine residues. Coupling of the two modified proteins was accomplished through a bifunctional coupling reagent containing meleimide and aminooxy functional groups. Synthesis of the linker is described. Yields of 1:1 enzyme-Fab' were at least three times higher than for comparable random derivatization methods. Immunoreactivity and enzymatic activity were unaffected. Biodistribution studies showed a more favorable tumor to blood ratio with the site-specifically linked conjugate.

Central projections of the nervus terminalis and the nervus praeopticus in the lungfish brain revealed by nitric oxide synthase

Lungfishes possess two cranial nerves that are associated with the olfactory system: the nervus terminalis enters the telencephalon with the olfactory nerve, and the nervus praeopticus enters the diencephalon at the level of the optic nerve. We investigated the central projections of the nervus terminalis and the nervus praeopticus in the Australian lungfish (Neoceratodus forsteri) and in the African lungfish (Protopterus dolloi) by NADPH-diaphorase histochemistry (nitric oxide synthase; NOS) and compared them with the projections of the nervus terminalis of the frog (Xenopus laevis). In Neoceratodus, NOS-positive fascicles of the nervus terminalis divide and project with a ventral component through the septum and with a dorsal component through the pallium; fibers of both trajectories extend caudally beyond the anterior commissure and join the lateral forebrain bundle. In the nervus praeopticus, about 300 fibers contain NOS; they innervate the preoptic nucleus and continue their course through the diencephalon; many fibers cross in the commissure of the posterior tuberculum. In Protopterus, ganglion cells of the nervus terminalis and of the nervus praeopticus contain NOS. NOS-positive fibers of the nervus terminalis project through the septal region but not through the pallium. Several major fascicles cross in the rostral part of the anterior commissure, where they are joined by a small number of NOS-containing fibers of the nervus praeopticus. Both nerves innervate the preoptic nucleus. The number and pathways of the fascicles of the nervus terminalis are not always symmetric between the two sides. The nervus terminalis fascicles remain in a ventral position, whereas the nervus praeopticus gives rise to the more dorsal fascicles. Many fibers of the two nerves extend throughout the diencephalon and cross in the commissure of the posterior tuberculum. These findings demonstrate many similarities but also significant differences between the contributions of the nervus terminalis and the nervus praeopticus to forebrain projections in the two lungfishes. They support the view that the nervus praeopticus is part of a nervus terminalis system comparable to that in frogs and other nonmammalian vertebrates.

Interspecific variation of isthmo-optic projections in poikilothermic vertebrates

Retinopetal projections from isthmic and caudal mesencephalic regions were studied in a number of poikilothermic vertebrates. The tested animals were elasmobranchs, bony fishes, amphibians, and reptiles. Isthmo-optic projections were absent in elasmobranchs, sturgeons, most teleosts, all anuran and urodel amphibians, and in anolis lizards. Tegmental projections to the retina were found in a few fishes and in most reptiles. Interspecific variations regarding three morphological parameters were as follows: (i) isthmic projections to the contralateral eye originate from one or from two distinct nuclei; (ii) major interspecific differences exist regarding numbers and aggregation densities of cells in the nuclei of origin; (iii) the percentage of retinopetal fibres that innervate the ipsilateral retina varies significantly between species.

NADPH-diaphorase in the central nervous system of the larval lamprey (Lampetra planeri)

The distribution of nitric oxide synthase (NOS) in the lamprey brain was studied by using reduced nicotinamide-adenine-dinucleotide phosphate (NADPH)-diaphorase histochemistry to further elucidate the evolution of neurons synthesizing nitric oxide. Intense labeling of fibers and/or neurons was found in portions of the lamprey central nervous system, such as the olfactory system, the pineal organ, the habenular region, the nervus stato-acousticus (N. VIII), the brainstem, and the spinal cord, and also in the adenohypophysis. Labeled giant cells located at the floor of the 3rd and 4th ventricle were recognized as reticulospinal neurons. Mauthner and Müller cells were identified according to morphological criteria. Eight pairs of Müller cells and one pair of Mauthner cells were labeled by NADPH histochemistry. None of these cells had, as yet, been described to display NOS activity in any vertebrate. The massive staining of these cells and the apparent lack of labeling, e.g., in teleost fishes, may be a histochemical correlate to already known differences of functions served by these cells in different species. In addition, our results suggest that the nitric oxide (NO) system has appeared early in vertebrate evolution.

Retinopetal projections from diencephalic neurons in a primitive actinopterygian fish, the sterlet Acipenser ruthenus

Horseradish peroxidase (HRP) injections into the sterlet (Acipenser ruthenus) retina retrogradely label neurons in the dorso-medial thalamus, bilaterally. On the contralateral side, 5-7 cells were labelled, whereas ipsilaterally, only 2-3 cells were backfilled. Such diencephalic retinopetal cells have, so far, only been found in teleosts and in tetrapods. It has, therefore, been suggested that they evolved independently in these two vertebrate groups. Our findings on a primitive actinopterygian fish, suggest a more ancient origin of diencephalic projections to the retina.

Site-specific prodrug activation by antibody-beta-lactamase conjugates: regression and long-term growth inhibition of human colon carcinoma xenograft models

Antibody-directed catalysis (ADC) is a two-step method for the delivery of chemotherapeutic agents in which enzyme-antibody conjugate, prelocalized to antigen-bearing tumor cells, catalyzes the site-specific conversion of prodrug to drug. An ADC system consisting of F(ab')-beta-lactamase conjugates and a cephalosporin derivative of the oncolytic agent 4-desacetylvinblastine-3-carboxhydrazide was investigated. The ability of the system to mediate antitumor activity was compared with that of free drug given alone and with covalent drug-antibody conjugates in LS174T and T380 colon carcinoma xenografts in nude mice. Efficacy increased from moderate tumor growth inhibition by using free 4-desacetylvinblastine-3-carboxhydrazide to tumor regression and long-term stabilization with the ADC system. Labile covalent drug-antibody conjugates prepared from the same antibodies were less effective than ADC and required much higher antibody doses. The antigens KS1/4, carcinoembryonic antigen, and tumor-associated glycoprotein-72, TAG-72, present on the model cell lines, were chosen to investigate the effect of differences in subcellular location and expression heterogeneity on the efficacy of ADC delivery. Response was equivalent with the three tumor antigens. Hence, heterogeneous expression and membrane shedding of carcinoembryonic antigen and TAG-72, did not diminish the suitability of these antigens as targets for ADC therapy. In contrast, drug-antibody conjugate efficacy was more sensitive to subcellular location and heterogeneity. Thus, ADC is a highly effective form of immunochemotherapy in preclinical models, with applicability toward a variety of antigen targets.

Visual-evoked responses in the salmon telencephalon change during smolt transformation

During smolt transformation, salmon behaviour changes dramatically and the fish are imprinted to their natal stream. This brief episode is accompanied by changes in neurochemistry and connectivity of the brain. Comparing visual-evoked potentials, recorded from optic tectum and telencephalon by glass microcapillaries, we found pronounced differences before and after smolt transformation in the telencephalon. In the forebrain of presmolts, only small short-latency responses are present whereas postsmolts display large long-latency waves which characteristic dynamic properties in addition. These findings suggest changes in the functional role of the telencephalon during smolt transformation.

Enzymehistochemical demonstration of nitric oxide synthase in the diencephalon of the rainbow trout (Oncorhynchus mickiss)

Nitric oxide, a free radical, has recently been shown to exert major influences on CNS functions in mammals. It is synthesized by NO-synthase. For the first time, this study reveals this enzyme's existence in the CNS of a teleost fish and describes its distribution in the diencephalon, where the paraventricular organ displays an extraordinarily high activity. The study contributes to an evolutionary perspective of the biological role played by nitric oxide in the vertebrate CNS, and raises questions regarding the significance of this gas in cerebrospinal fluid-contacting neurons.

Peripheral origin of olfactory nerve fibers by-passing the olfactory bulb in Xenopus laevis

After DiI injections into the diencephalon of Xenopus, two types of retrogradely labelled cells were found in the nasal area: (i) receptor cells in the olfactory epithelium and (ii) a small cell group located between the main olfactory epithelium and the vomeronasal system. These results reveal an extensive extrabulbar olfactory projection of olfactory receptor cells. Fibers of these cells do not terminate in the olfactory bulb but innervate targets in the diencephalon directly. The other type of retrogradely labelled cells, apparently, are not part of any epithelium. They resemble similar cell groups which have previously been regarded as part of the nervus terminalis system in other vertebrates.

Preparation and characterization of a beta-lactamase-Fab' conjugate for the site-specific activation of oncolytic agents

Antibody-directed catalysis (ADC) is a two-step method for the targeted delivery of chemotherapeutic agents in which enzyme-antibody conjugates, prelocalized to antigen-bearing cells, activate prodrugs designed to be substrates for the enzyme. An enzyme-Fab' conjugate exhibiting both native beta-lactamase activity and immunoreactivity toward carcinoembryonic antigen (CEA) was constructed. Treatment of CEA-expressing LS174T cells with this conjugate imparted beta-lactamase activity to the cells; beta-lactamase activity was not imparted by treatment with unconjugated beta-lactamase and not to CEA negative cells treated with conjugate. Cephalosporin-based prodrugs, and other substrates synthesized as model compounds, were found to have wide variations in their kinetic parameters toward the conjugate, with kcat values ranging from 16 to 3300 s-1 and KM values ranging from 5 to 160 microM. The prodrug derived from desacetylvinblastine-3-carboxylic acid hydrazide (DAVLBHYD) was studied in vitro and found to be 5-fold less cytotoxic to LS174T cells than the parent DAVLBHYD. For antigen-positive cells preincubated with conjugate, however, the prodrug showed the same potency as the parent drug. Thus, the combination of conjugate and prodrug appears to provide antigen-dependent toxicity to tumor cells.

Functional subdivisions of the olfactory system correlate with lectin-binding properties in Xenopus

Soybean agglutinin (SBA) is known to selectively label a portion of neurons in amphibian and mammalian primary olfactory systems. Hitherto, no other distinctive features have been found to correlate with the two neuronal populations. Investigating SBA-HRP binding in olfactory mucosa and CNS of Xenopus, we noted that labelled and unlabelled structures can readily be assigned to different olfactory subsystems. The SBA negative one is utilized to detect air-borne odors, whereas major SBA-positive structures serve a role in the perception of water dissolved molecules. Some labelled fibers by-pass the olfactory bulb, traverse the telencephalon and innervate prosencephalic structures. They are considered to be aberrant olfactory nerve fibers, rather than being part of the terminal nerve.

Misinterpretation of interaction effects: a reply to Rosnow and Rosenthal

The structural model of analysis of variance for multiway tables, with main effects and interaction parameters, is overspecified. Only the set of estimable functions of the cell means is useful. The individual estimates of the parameters are artificial as regards the underlying scientific process. Rosnow and Rosenthal (1989a) stated that it is "absolutely necessary" (pg 146) that interactions should be interpreted by examining the usual estimates of the interaction parameters. This is incorrect.

The visually related posterior pretectal nucleus in the non-percomorph teleost Osteoglossum bicirrhosum projects to the hypothalamus: a DiI study

This study was done to elucidate the ancestral (plesiomorphic) condition for visual pathways to the hypothalamus in teleost fishes. Three patterns of pretectal organization can be discerned morphologically and histochemically in teleosts. Their taxonomic distribution suggests that the intermediately complex pattern (seen in most teleost groups) is ancestral to both the elaborate pattern (seen in percomorphs) and the simple pattern (seen in cyprinids). The pretectal nuclei involved can be demonstrated with acetylcholinesterase histochemistry selectively and reliably in different species of teleosts, suggesting that the same-named nuclei are homologous in representatives of the three different patterns. Whereas there are visual pathways to the hypothalamus in both the elaborate (percomorph) and the simple (cyprinid) patterns, different pretectal and hypothalamic nuclei are involved. Thus visual hypothalamic pathways in these two patterns would not appear to be homologous. In this study, circuitry within the third, i.e., the intermediately complex, pattern is investigated. It is demonstrated that visual pathways project via the pretectum to the hypothalamus in Osteoglossum bicirrhosum and that they are very similar to the visual pathways in the elaborate pattern. This suggests that the circuitry in the intermediately complex pattern, as represented by Osteoglossum, is plesiomorphic (evolutionarily primitive) and the circuitry in both the simple pattern (seen in cyprinids) and the elaborate pattern (seen in percomorphs) is apomorphic (evolutionarily derived) for teleosts.

Subdivisions of the terminal nerve in Xenopus laevis

The majority of recent studies on the terminal nerve (nt) in various vertebrates either involved tracer injections into the nasal cavity or made use of the LHRH-/FMRFamide-like immunoreactivity (ir) of a portion of its fibers. The present investigation was designed to determine the extent of overlap between data rendered by the two methods in Xenopus. The findings reveal no overlap of nt projections visualized by the two experimental techniques. This result sheds doubt on the validity of current definitions of the nt system.