Frequency selectivity of hearing in the green treefrog,Hyla cinerea

Frequency selectivity of hearing was measured in the green treefrog, Hyla cinerea. A psychophysical technique based on reflex modification was used to obtain masked threshold estimates for pure tones (300-5,400 Hz) presented against two levels of broadband masking noise. A pure tone (S-1) presented 200 ms prior to a reflex-eliciting stimulus (S-2) inhibited the motor reflex response to S-2. The magnitude of this reflex modification effect varied systematically with the sound pressure level (SPL) of S-1, and threshold was defined as the SPL of S-1 at which the reflex modification effect disappeared. Masked thresholds were used to calculate critical ratios, an index of the auditory system's frequency selectivity. The frequency selectivity of the treefrog's hearing is greatest and critical ratios are lowest (22-24 dB) at about 900 and 3,000 Hz, the two spectral regions dominant in the male treefrog's species-specific advertisement call. These results suggest that the treefrog's auditory system may be specialized to reject noise at biologically-relevant frequencies. As in other vertebrates, critical ratios remain constant when background noise level is varied; however, the shape of the treefrog's critical ratio function across frequencies differs from the typical vertebrate function that increases with increasing frequency at a slope of about 3 dB/octave. Instead, the treefrog's critical ratio function resembles its pure tone audiogram. Although the shape of the treefrog's critical ratio function is atypical, the critical ratio values themselves are comparable to those of many other vertebrates in the same frequency range. Critical ratio values here measured behaviorally do not match critical ratio values previously measured physiologically in single eighth nerve fibers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Larval development of Diploptera punctata reared alone and in groups

Larvae of the cockroach Diploptera punctata were reared in isolation, in pairs, or in groups of 8–10. Duration of larval development, age at each ecdysis, weights at birth and ecdyses, and adult head-capsule width were measured. Duration of larval development was longer and adult size was larger in isolated animals than in animals reared in pairs and groups. The effect of isolation on development was more pronounced in males. All females had 4 larval instars, whereas males had 3 or 4 instars. The proportion of males with 4 larval instars was higher among animals reared in isolation. There was no difference in the duration of larval development or adult size between pair- and group-reared animals. The sex of animals in the group did not affect adult size or the duration of larval development. Males which underwent 3 or 4 larval instars had different schedules of moulting. Rates of growth of males of both instar types reared in isolation and pairs were similar. Greater adult weight of isolated animals and 4-instar-type males was a result of their longer duration of larval development. Both a higher rate of growth and longer duration of larval development contribute to the larger adult size of females than males.     

A further study on the dietary-regulated biosynthesis of high-sulphur wool proteins

When the diet of sheep is supplemented by the infusion of sulphur-containing amino acids or casein into the abomasum, the newly synthesized wool shows characteristic changes in its amino acid composition, with significant increases in cystine, proline and serine and decreases in aspartic acid and phenylalanine. This modification seems to be due entirely to an alteration in the overall composition of the high-sulphur proteins and to an increase in their proportion in the fibre. These variations are not the result of a change in the composition of individual proteins, but are due to alterations in their relative proportions and to the initiation of the synthesis of `new' proteins, many of which are extremely rich in cystine. It is suggested that the heterogeneity of the high-sulphur proteins may be due, in part, to similar changes in composition caused by natural variations in the nutrition of sheep.     

Tubular structures associated with the endothelial endoplasmic reticulum in glomerular capillaries of Rhesus monkey and nephritic man

Summary Round bodies, tubular profiles and crystalline images have been studied by electron microscopy in the endothelium of seven normal young Rhesus monkeys and in the renal glomerular endothelium of two nephritic human patients. The crystalline images are most frequently formed by aggregation of round bodies, 200–240 Å in diameter. In Rhesus monkeys a variety of crystalline images are seen. On the contrary, in nephritic patients round bodies and tubular profiles are rare and less organized. In the glomerular endothelium of two normal men they were not found.The results obtained suggest that the round bodies, the tubular profiles and the crystalline images result from sectioning of a system of undulating tubules associated with the smooth endoplasmic reticulum. In nephritic patients the formation of such a tubular system could represent a change taking place within the affected cells as a pathologic response to the disease.This work was supported by U.S. Public Health Service (N.H.I.), Grant AI-04527-03-04, and by the Consiglio Nazionale delle Ricerche (C.N.R.), Contributo 115/0815/0-1365. The Authors are greatly indebted to Miss Hermina Spiele for skilful technical assistance.     

A re-evaluation of the mesangial cells of the renal glomerulus

Summary The topographical localization of the mesangial cells in renal glomeruli of rats, and their relationships with the structures at the hilus of the glomerulus were studied in this investigation. It was observed that the mesangial cells occupy a parietal position in the wall of the glomerular capillaries, and that they are anatomically continuous with the smooth muscle cells of the tunica media of the glomerular arterioles.This study was supported by a United States Public Health Service Grant AM 08628 (Institute of Arthritis and Metabolic Diseases).     

Stomatal and cuticular transpiration of beans (Phaseolus vulgaris M.) attacked by rust (Uromyces appendiculatus [Pers.] Link)

The changes of stomatal and cuticular transpiration of bean plants were investigated by graphical transpiration curves method (Slavík 1958). Bean leaves were infected by fungusUromyces appendiculatus (Pers.) Link. After the infection the intensity of stomatal transpiration had a decreasing tendency. Beginning with the sixth day after infection, the proportion of stomatal and cuticular transpirations becomes more expressive, i.e. the leaves transpire more by cuticles than by stomata. The higher share of cuticular transpiration brings extensive water relations to the diseased plants.     

Pulsed-field gel analysis of human immunoglobulin heavy-chain constant region gene deletions reveals the extent of unmapped regions within the locus

The human immunoglobulin heavy-chain constant region gene locus is organized in three main gene groups, the physical distances of which are unknown. Different types of gene deletions, originated by unequal crossingover, have been found to encompass one or more genes in the locus. We have analyzed some of these deletions by means of pulsed-field gel electrophoresis, which allows resolution of large DNA fragments. By identifying a fragment containing two of the main gene groups and by observing the size reduction of this fragment in subjects with deletions, we were able to estimate the distance between the two groups and better locate the pseudogene in-between.     

Isolation and Biochemical Characterization of a Neural Proteoglycan Expressing the L5 Carbohydrate Epitope

The monoclonal L5 antibody reacts with an N-glycosidically linked carbohydrate structure which is present on the neural cell adhesion molecule L1, neural chondroitin sulfate proteoglycans, and other not yet identified glycosylated proteins. Using this antibody, we isolated and characterized proteoglycans from adult mouse brain and cultured astrocytes biosynthetically labeled with Na2 35SO4 and a 3H-amino acid mixture. Our data suggest that the L5 proteoglycans of both sources are identical in their biochemical properties. The apparent molecular mass of the L5 proteoglycan is approximately 500 kDa. Digestion of the iodinated L5 proteoglycan from mouse brain and of the [35S]methionine-labeled L5 proteoglycan from cultured astrocytes with proteinase-free chondroitinases ABC and AC revealed three major core proteins with apparent molecular masses of approximately 380, 360, and 260 kDa. These represent molecularly distinct protein cores.     

[3H]Tyramine binding: A comparison with neuronal [3H]-dopamine uptake and [3H]mazindol binding processes

[³H]Spiperone ([³H]SPI) binding sites in rat or bovine striata have been solubilized using CHAPS or digitonin detergents. Solubilized sites retained the binding characteristics of those in native membrane preparations. The same solubilized material, however, did not bind [³H]tyramine ([³H]PTA), thus indicating that [³H]PTA binding sites and DA receptors are different chemico-physical entities. In membrane preparations or crude synaptosomes obtained from the c.striatum of neonatally-rendered hypothyroid rats, when central DA-pathways are impaired, both [³H]PTA binding and [³H]DA uptake processes were markedly decreased, with no effect on [³H]mazindol ([³H]MAZ) binding, compared to euthyroids. Reserpine, a well-known inhibitor of DA-uptake into a variety of secretory vesicles, and a potent in vivo andin vitro inhibitor of [³H]PTA binding, did not affect the [³H]MAZ binding process. This further supported the suggestion that while [³H]PTA binding sites are almost totally associated with the vesicular transporter for DA, [³H]MAZ does label a site involved in the DA-translocation across the neuronal membrane. The latter process seems to be rather insensitive to thyroid hypofunction, when however the intracellular storage of DA might be consistently impaired. In conclusion, PTA might be well exploited as a marker of the DA vesicular transporter through its molecular characterization, whenever possible.Special issue dedicated to Dr. Paola S. Timiras