Comparison of glycoconjugates at the surface of developing type II pneumocytes and Clara cells

Summary The apical surface coat of type II pneumocytes and Clara cells in pre- and post-natal rat lung was examined with lectin histochemical methods. Lectins fromHelix pomatia (HPA), peanut (PNA) andMaclura pomifera (MPA) were conjugated with horseradish peroxidase and used to stain paraffin sections of fixed lung with or without certain pre-treatments. HPA and MPA were observed to react with almost all type II pneumocytes at postnatal day 1. Type II pneumocytes that stained with a sialidase—PNA sequence increased from a few positive cells at postnatal day 5 to many in the adult. It has been reported that the surface coat of type II pneumocytes closely resembles that of Clara cells in its staining with histochemical methods employing cationic dyes or lectins including MPA and PNA. However, staining with HPA, especially after periodic acid oxidation, revealed many type II pneumocytes with strong reactivity but showed only a few Clara cells that were faintly positive. HPA also stained alveolar macrophages. The HPA affinity of macrophages, however, was labile to oxidation with periodic acid or galactose oxidase unlike that of type II pneumocytes. This difference suggests that HPA recognizes more than one type of sugar structure.To whom all correspondence and reprint requests should be addressed.     

Seasonality,aestivation and the life history of the salamanderfish Lepidogalaxias salamandroides (Pisces: Lepidogalaxiidae)

Synopsis Changes in the age/length structure of Lepidogalaxias salamandroides populations in temporary waters of south-western Australia were monitored over a 51 month period by regular field sampling. Each year the study area experienced a summer drought of approximately five months duration. During the drought period Lepidogalaxias burrows into the mud and aestivates and substantial mortality occurs during this period. Body lipid reserves decrease during this period suggesting that they are the main energy source used during aestivation. The amount of lipid remaining after aestivation appears to be important in determining when female fish reproduce. Males die after reproduction and achieve a maximum age of only about 12 months. Some females also reproduce and die at this age while others defer reproduction for another year. Fecundity is much higher in these older, larger fish: they must however, survive two drought periods before they reproduce. The evolution of the life history style shown by Lepidogalaxias salamandroides is discussed with respect to the well defined seasonality of the region and it is suggested that selection for reproduction at an early age is balanced by the constraints of offspring survival during the aestivation period.     

The determination of the kinetics of polysaccharide thermal degradation using high temperature viscosity measurements

Information about the thermal degradation of the polysaccharides sodium alginate, carrageenan and carboxymethyl cellulose has been obtained from the time dependence of the viscosity at high temperatures measured using a slit viscometer. The viscosity is related to the molecular weight using previously-published relations between the zero shear specific viscosity and the coil overlap parameter in conjunction with the appropriate Mark-Houwink equation. It is found that alginate is much less stable than carboxymethyl cellulose and carrageenan. Activation energies for depolymerisation obtained from Arrhenius plots in the presence of oxygen ranged from 50 kJ/mol for alginate to 105 kJ/mol for κ-carrageenan.     

Nematode Mitochondrial DNA: Anomalies and Applications

The mitochondrial genome of animal cells is currently under intense investigation by molecular, evolutionary, and population biologists. This review summarizes the available information on the molecular biology of nematode mitochondrial DNA and explains how the fundamental knowledge obtained from these basic studies may be applied to nematode systematics, evolution, and diagnostics.     

Monoclonal antibody-based immunoassay of vitellogenin in the blood of male channel catfish (Ictalurus punctatus).

1. A monoclonal antibody to vitellogenin of channel catfish (Ictalurus punctatus) was made, and its specificity was demonstrated using Western blots of serum from female fish, estradiol-treated male fish, untreated male fish, vitellogenin purified by three different methods and egg extracts. 2. An enzyme-linked immunosorbent assay (ELISA), using this monoclonal antibody, detected vitellogenin in the plasma of 59 out of 60 untreated 17-24-month-old male channel catfish with a mean concentration of 338 micrograms/ml and a maximum concentration of 4240 micrograms/ml. 3. Vitellogenin levels in male channel catfish were unrelated to testicular stage, gonadosomatic index and month.     

Observation of a polar bear with rabies

On 1 November 1989 the first confirmed case of rabies in a polar bear (Ursus maritimus) was encountered by Inuit hunters in the vicinity of Cape Kendall, Southampton Island, Northwest Territories (Canada). The adult male polar bear had posterior paralysis. Rabies was detected by mouse inoculation and a positive immunoperoxidase reaction on spinal cord and Gasserian ganglion from the bear. Histologic lesions in the lumbar region of the spinal cord were consistent with the posterior paralysis. The impact of rabies on the population dynamics of polar bears probably is minimal. Rabies in polar bears constitutes a potential health hazard for polar bear hunters.     

Peptidergic transmission in the brain. VI. Behavioral consequences of central activation.

Having described a peptidergic transmitter system in the rat brain, we now begin to evaluate its behavioral function. We stimulated cell bodies in the medial amygdaloid nucleus (AME) with indwelling bilateral electrodes. These cell bodies contain a vasopressin-like peptide and send fibers to the hippocampus where the peptide is released upon stimulation. There the peptide inhibits hippocampal output in the awake rat just as it does in the anesthetized rat and in the rat brain slice. The stimulation reorganizes behavior with the same latency and duration as the hippocampal effect. For about 15-20 minutes after the brief stimulus, rats remain motionless with eyes wide open. This "freezing" state is punctuated by episodes of exploratory behavior. The stimulus appears to have a positive affective quality. Review of the literature in light of the present results indicates a probable role for this peptidergic system in the generation of sexual behavior in male rats.