Relationship of alpha MSH-specific neurons to the arcuate opiocortin neuronal system as determined by dual antigen immunocytochemical procedures

The cross-immunoreactivity, topography, and fiber projections of the alpha MSH-immunoreactive specific neurons in the forebrain of the rat appear to be distinctly different from that of the neurons in the hypothalamic arcuate opiocortin system. The cell bodies, immunoreactive only to -MSH, have a specific pattern of distribution in the dorsal and lateral hypothalamic regions from the level of the retrochiasmatic region to the premammillary area of the posterior hypothalamus. Immunoreactive fibers of these cells appear to extend into regions of the cerebral cortex and hippocampus. An antomical relationship between the immunostained fibers and/or terminals of the arcuate opiocortin pool of neurons and the -MSH-immunoreactive perikarya is described utilizing the ABC (Avidin-Biotin-Peroxidase Complex) and ABC-GO (Glucose Oxidase) or glucose oxidase-antiglucose oxidase complex methods of immunocytochemistry in which two tissue antigens with contrasting colors are demonstrated in the same tissue section.     

Effect of low-molecular-weight proteins on protein (lysozyme) binding to isolated brush-border membranes of rat kidney

Filtered proteins including the low-molecular-weight protein lysozyme are reabsorbed by the proximal tubule via adsorptive endocytosis. This process starts with binding of the protein to the brush-border membrane. The binding of ¹²⁵I-labelled egg-white lysozyme (EC 3.2.1.17) to isolated brush-border membranes of rat kidney and the effect of several low-molecular weight proteins on that binding was determined. The Scatchard plot revealed a one-component binding type with a dissociation constant of 5.3 μM and 53.0 nmol/mg membrane protein for the number of binding sites. The binding of the cationic lysozyme was inhibited competitively by the addition of cationic cytochrome c to the incubation medium, while the neutral myoglobin had no effect. The anionic β-lactoglobulin A inhibited the lysozyme binding in a noncompetitive manner. These data suggest that the binding takes place between positively charged groups of the protein molecule and negative sites on the brush-border membrane, and, the competition between the cationic cytochrome c and the cationic lysozyme for the binding sites may be responsible for the inhibitory effect of cytochrome c on renal lysozyme reabsorption. The binding step at the brush-border membrane appears to be cation-selective.     

Laboratory Calibrations of the [3H]Adenine Technique for Measuring Rates of RNA and DNA Synthesis in Marine Microorganisms

The nucleic acid synthesis rates of several marine phytoplankton and bacteria grown in chemostat and batch cultures were measured by using [³H]adenine. The [³H]adenine synthesis rates showed excellent agreement with the known rates of synthesis estimated from chemical RNA and DNA data. Under certain conditions, RNA turnover and ATP pool compartmentalization produce inaccuracies in synthesis measurements made with [³H]adenine. However, accurate measurements of the rates of microbial RNA and DNA synthesis can be made in any environmental situation provided a few simple precautions are observed. First, time course experiments are recommended. Second, experiments should be conducted for periods long enough to avoid problems arising from disequilibria of internal ATP pools. Finally, exogenous [³H]adenine should remain in the medium over the length of the time course.     

Fluorometric measurement of tin-protoporphyrin in biological samples

Sn-protoporphyrin is a potent competitive inhibitor of heme oxygenase, can suppress neonatal and other forms of hyperbilirubinemia in laboratory animals, and represents a potential new approach to the treatment of neonatal jaundice in humans. In order to study the disposition of Sn-protoporphyrin in vivo we have developed a sensitive fluorometric method for the quantitation of this metalloporphyrin in biological samples. The method is sensitive to concentrations as low as 0.01 nmol/ml, and is specific for Sn-protoporphyrin even in the presence of other porphyrins such as protoporphyrin.     

Optomotor control of the force of flight in Drosophila and Musca

Specialized networks of movement detectors in the antero-inferior field of the eyes of the fruitfly, Drosophila melanogaster, and the housefly, Musca domestica, respond to upward (or downward) drift of the retinal images by excitation (or inhibition) of the lift-generating force of flight. The influence of the direction of pattern movement upon the altitude control response has been investigated under conditions of fixed flight in still air. Matched model analysis of the available response curves suggests the predominance of unidirectional movement detectors in these networks. Homologous wingbeat-inhibiting detectors in the specified fields of the eyes of the two species respond preferentially to pattern movement from antero-superior to postero-inferior. The arrangement of wingbeat-exciting detectors seems to follow different schemes: These detectors respond preferentially to movement from inferior to superior in Drosophila, and to movement from antero-inferior to postero-superior in Musca. The wingbeat-exciting network in Musca is restricted to a comparatively small antero-equatorial area of the specified fields of the eyes. The combination of the two types of detectors in this area establishes a powerful lift control system which is particularly sensitive to minute deviations from a given level of flight.     

The tibial thread-hairs ofAcheta domesticus L. (Saltatoria,Gryllidae)

Summary The ultrastructure of the thread-like hairs (sensilla) on the tibia of the front leg ofAcheta domesticus (Gryllidae) Saltatoria was examined by serial sectioning. The presence of a tubular body indicates that these sensilla are mechanosensitive; electrophysiological measurements also confirmed this. The opposing forces on the articulating apparatus of single hairs and the sensitivity of the single receptor cell were measured after deflection of the hair in different directions. The articulating apparatus is characterized by three cuticular elements: a joint membrane, suspension fibers, and a socket septum. These elements form the basis for a structural bilateral symmetry along whose plane of symmetry the direction line of both the minimum receptor sensitivity and the minimum opposing forces lie. The tubular body embedded in the tip of the socket septum is attached to the base of the hair shaft. The hair provides the leverage for displacing the tubular body and the socket septum limits the extent to which it may be laterally displaced.These investigations have been supported by the Deutsche Forschungsgemeinschaft     

Phytoplankton and pelagic primary productivity in Øvre Heimdalsvatn

A phytoplankton investigation was carried out in the subalpine, low-productive Norwegian lake Øvre Heimdalsvatn in 1969–70 and 1972. This paper describes the temporal and spatial distribution of the standing stock of phytoplankton, and phytoplankton primary productivity. The annual average primary productivity in 1972 was 4.0–4.9 mg C m⁻³ d⁻¹; the annual average standing stock varied from 120 mg m⁻³ (freshweight) in 1969–70, to 250 mg m⁻³ in 1972. Phytoplankton species composition and size distribution is discussed. Throughout the year the phytoplankton is dominated by small (ultraplankton) species; μ-algae (< 5 μm) showed cell concentrations up to 15 mill. cells 1⁻¹. The dominating group was chrysophytes; cryptophytes, dinoflagellates or green algae were at times abundant. A phytoplankton monthly budget and a diagram showing annual average carbon flow through the standing stock of phytoplankton are presented; the phytoplankton dynamics in Øvre Heimdalsvatn is compared to that of other low-productive lakes.     

Periphytic and drifting microalgae in a tributary stream of Øvre Heimdalsvatn

Samples of drifting and periphytic microalgae were collected during 1972 from a fast-flowing, stony stream (Brurskardsbekken) in the Jotunheimen mountain area, central southern Norway. The predominant algal groups in the drift and the periphyton were diatoms and green algae, while only a few species were recorded in both communities. A considerable number of species from Chrysophyceae, Cryptophyceae and other algal classes were also recorded in the drift samples. The species composition was in good agreement with microalgal communities earlier described from mountain areas in Scandinavia, although species which probably are new to Norway, were also recorded. A quantitatively important fraction of planktonic species in the drift is interpreted as a contribution from lacustrine habitats in the watercourse. A general change in the periphyton during the summer, from green algae to diatoms, was observed, Altitudinal differences in the periphyton included a delayed green algal maximum at higher altitudes compared to lower. In the zone around the upper birch limit, a transition in species composition as one goes up stream, described in other investigations, was not observed.     

Mass spectra of underivatized peptide amides related to substance P

Mass spectra of underivatized hexa- and heptapeptide amides related to Substance P have been obtained with a conventional electron ionization mass spectrometer using sample vaporization from a tungsten wire by the technique of rapid heating, proton transfer ionization using ammonia, and photoplate recording of spectra. These spectra exhibit little evidence of sample pyrolysis and are readily interpreted to yield amino acid sequences.