Estimation of the size of freshwater ciliate populations by a sub-sampling technique

A technique is described for the estimation of the size of ciliate populations based on replicated counts. Sample drops were taken by automatic pipettes of different volume from activated sludge and from a small oligotrophic stream. Specific aims were: 1) the estimation of the number of species; 2) the estimation of the number of individual in each species; 3) the selection of a suitable sub-sample size and number of replicates. For each volume the cumulative increase in species taken in successive sub-samples was determined. For each species the minimum permissible sub-sample volume and the number of replicates required for an allowable error of 10% and 25% were determined. Lastly, the relationship between the mean number of individuals counted for each species and the relative coefficient of variation was visualized.     

Dion tomasellii (Zamiaceae), a new species with two varieties from western Mexico

Dion tomasellii sp. nov. occurs with an interrupted distribution from Guerrero to central Sonora. It is characterized by falcate to subfalcate leaflets. The populations from Sonora and northern Sinaloa are segregated asD. tomasellii var.sonorense on the basis of their narrower and glaucous leaflets.     

l- andd-alanine transport in brush border membrane vesicles from lepidopteran midgut: Evidence for two transport systems

Summary In brush border membrane vesicles from the midgut ofPhilosamia cynthia larvae (Lepidoptera) thel- andd-alanine uptake is dependent on a potassium gradient and on transmembrane electrical potential difference. Each isomer inhibits the uptake of the other form: inhibition ofl-alanine uptake byd-alanine is competitive, whereas inhibition ofd-alanine uptake byl-alanine is noncompetitive. Transstimulation experiments as well as the different pattern of specificity to cations suggest the existence of two transport systems. Kinetic parameters for the two transporters have been calculated both when K_out>K_in and K_out=K_in.d-alanine is actively transported also by the whole midgut, but it is not metabolized by the intestinal tissue.     

Amino acid sequence of rabbit ventricular myosin light chain-2: Identity with the slow skeletal muscle isoform

Many studies have established a correlation of differences in the activities of various muscle types with differences in the expression of myosin isoforms. In this paper we report the sequence determination of myosin light chain-2 from rabbit slow skeletal (LC2s) and ventricular (LC2v) nmscles. We sequenced tryptic peptides from LC2v which account for all except a few terminal amino acid residues. The major part (87 residues) of the rabbit LC2s sequence, obtained from tryptic and cyanogen bromide (CNBr) peptides, was found to be identical to rabbit LC2v. Our results provide the first sequence information on LC2s from any species, and lend strong support to the hypothesis that LC2s and LC2v are identical. Comparisons of rabbit LC2v and LC2s with rabbit LC2f (from fast skeletal muscle), and also with chicken LC2f and LC2v, show clearly that LC2s and LC2v from mammalian and avian species are more closely related to each other than they are to LC2f isoforms from the same species.     

Culture of intramural cardiac ganglia of the newborn guinea-pig

Summary The present study describes the ultrastructure of non-neuronal cells and their interrelationships with intracardiac neurones present in cultures dissociated atria and interatrial septum from newborn guinea-pig. When compared with the in situ preparation, most of these features in culture were similar to those observed in situ, but some differences were also apparent. Both mature and immature Schwann cells were observed in culture, and as in situ, the latter were closely associated with intracardiac neurones, whilst the former were more widely separated. The ultrastructure of satellite cells was more variable in culture than in situ: three general types were distinguished on the basis of their 10-nm filament content. This variation could be due to conditions of culture. Interstitial cells were present in culture and closely resembled those described in situ, although there was less space between cultured interstitial cells and their associated cells. Many fibroblasts, some myoblasts and a few mast cells were also found in the culture preparations.     

Localisation of substance P-, somatostatin-, vasoactive intestinal polypeptide and met-enkephalin-immunoreactive nerves in the peripheral and central nervous systems of the leech (Hirudo medicinalis)

Summary The distribution of substance P (SP)-, somatostatin (SOM)-, vasoactive intestinal polypeptide (VIP)- and met-enkephalin (mENK)-immunoreactive nerve fibres and cell bodies has been studied in the gastrointestinal tract, lateral blood vessel (heart) and segmental ganglia of the leech (Hirudo medicinalis). In the crop and intestine, there was a sparse distribution of VIP-, SP-, SOM- and mENK-immunoreactive nerves, while in the intestine, a dense network of SP-, a moderate network of SOM-, and a sparse distribution of mENK- and VIP-immunoreactive nerve fibres was seen. SP-, SOM- and VIP-immunoreactive nerve cell bodies were found in all the gut regions studied, the greatest number being in the intestine. No mENK-containing cell bodies were seen in any region of the gastrointestinal tract. The heart contained a few SP-, SOM-, and VIP-immunoreactive nerve fibres, but no nerve cell bodies were found. Immunoreactive nerve cell bodies were also present in the segmentai ganglia. A typical midbody ganglion contained up to seven pairs of SP-containing neurones, four pairs of SOM-containing neurones, two pairs of VIP-containing neurones and one to three pairs of mENK-immunoreactive nerve cell bodies. The lateral pair of large SOM-immunoreactive nerve cell bodies is of similar size and correct position to the lateral N cells. One of the pairs of large SP-immunoreactive nerve cell bodies is probably identical to the Leydig cells. A tentative identification of other immunofluorescent nerve cells is attempted. Immunoreactive nerve fibres to all four peptides were distributed throughout the neuropil, those to SP being the most numerous.     

Acid phosphatase from maize scutellum: Negative cooperativity suppression by glucose

Acid phosphatase purified from maize scutellum, upon acylation with succinic anhydride, still shows negative co-operativity for the hydrolysis of glucose-6-phosphate at pH 5.4. This phenomenon is abolished by glucose, for both native and succinylated enzymes, through stimulation of the initial velocities at sub-optimal substrate concentrations. However, negative co-operativity for the enzymatic hydrolysis of p-nitrophenylphosphate at pH 5.4 is suppressed only at high concentrations of glucose. Furthermore, the hydrolysis of p-nitrophenylphosphate is noncompetitively inhibited (low affinity form of the enzyme molecule) by glucose, which suggests the existence of different substrate binding sites.     

Ovulation and the mechanism of follicle rupture

Summary The rabbit Graafian follicles are encircled by a capillary network between the theca interna and the avascular membrana granulosa. After injection of an ovulatory dose of human chorionic gonadotrophin (HCG) the theca interna cells showed an increase in the amount of smooth endoplasmic reticulum, lipid droplets and mitochondria with tubular cristae. In addition, considerably more junctions, similar to the abutment nexuses of granulosa cells were found; annular nexuses also appeared. At 4 hours after injection of HCG a prominent oedema was evident in the theca interna layer, particularly in the apical region.Small fenestrations in the endothelium of the blood capillaries increased in amount after HCG injection, and close to the time of ovulation, large gaps or perforations, 1–3 in diameter, were found in the thin, distended part of the endothelial cells. The surrounding basement membrane became fragmented and partly lost, so that a seemingly free passage from the capillary lumen to the interstitium was eventually established. Leakage of fluid, causing interstitial oedema, presumably proceeds until the pressure in the pericapillary interstitium has risen to the pressure in the capillaries. Some hours before and up to ovulation the pericapillary interstitium has also broad communications with the cavity of the follicles. Therefore, both pressure and fluid can be passed from the capillaries-via the interstitium-to the follicle antrum. However, influx of fluid with subsequent follicle expansion and ovulation-at constant pressure-does not occur until the tensile strength of the follicle wall has decreased.This investigation was supported by grants from the Swedish Medical Besearch Council (Projects No. B72-12X-78-07A, B73-12X-78-08B and B74-12X-78-09C). The technical assistance of Miss Ingalis Fransson, Miss Kerstin Nilsson, and Mrs. Ulla-Britt Westman is greatly appreciated.     

Correlation between microtubular number and transport activity of hypothalamo-neurohypophyseal secretory neurons

Summary The lower pituitary stalk has been studied in rats given hypertonic saline for four days and in rats with congenital diabetes insipidus (GDI), that is, in two groups of animals in which there is evidence of an increase in the transport of polypeptides down the axons of the tractus hypophyseus.A quantitative ultrastructural analysis of this tract, the first yet made, has demonstrated that in normal animals it is composed of unusually small axons, over half of which are less than 300 nm in diameter.In this tract there is a significant increase in axonal diameter and microtubular content in animals given hypertonic saline for four days. In adult rats with CDI, these changes are even more marked, a feature which is correlated with the fact that in these animals the transport of polypeptides has probably been abnormal since birth.An alteration in the microtubular content of neurons has not previously been observed either in physiologically stressed animals or in diseased animals; such alterations suggest the participation of microtubules in polypeptide transport. The narrow diameter of axons in the tractus hypophyseus of the normal animal raises the possibility of the extravesicular transport of such polypeptides.Abbreviations used ADH antidiuretic hormone - AF aldehyde fuchsin - CDI congenital diabetes insipidus - HNS hypothalamo-neurohypophysiel system - NSM neurosecretory material - NSV neurosecretory vesicle - PVN paraventricular nucleus - SON supraoptic nucleus This paper is dedicated to Professor W. Bargmann.We are grateful to Miss Pauline Chapman for technical assistance.This project is supported by the Medical Research Council.