Pigment distribution in cyanobacteria: An in vivo microspectroscopic investigation

Summary In vivo microspectroscopy represents an effective and reliable technique to study pigment composition and distribution. In contrast to traditional extractive techniques, it preserves the integrity of biological specimens, without modifying the nature of the pigments. The spectroscopic apparatus we used is very simple and consists of a common microscope equipped with a monochromator, a photomultiplier, and two pinhole diaphragms. Absorption spectra obtained by means of this apparatus on different species of cyanobacteria are presented.     

Effects of parathyroid hormone and calcitonin on carbonic anhydrase location in osteoclasts of cultured embryonic chick bone

The ultrastructural location of carbonic anhydrase has been examined in osteoclasts of cultured embryonic chick metatarsi. In untreated cultures and in those to which parathyroid hormone (PTH) was added, the enzyme was found in close association with the plasma membrane of the ruffled border. After brief calcitonin treatment (10 min) the ruffled border disappeared and the association of carbonic anhydrase with the plasma membrane was diminished. The results indicate that the hormones employed act directly on embryonic bone to alter osteoclast structure and the intracellular location of carbonic anhydrase.     

A point mutation in the neu oncogene mimics ligand induction of receptor aggregation

The rat neu gene, which encodes a protein closely related to the epidermal growth factor receptor, is a proto-oncogene that can be converted into an oncogene by a point mutation. Both genes encode proteins with a relative molecular mass of 185,000 but the question of why the neu gene product, p185neu, is oncogenic, whereas the product of c-neu, p185c-neu, is not, remains unanswered. The proteins have several features common to the family of tyrosine kinase growth-factor receptors, including cysteine-rich external domains, a hydrophobic transmembrane region and a cytoplasmic tyrosine kinase domain. The oncogenic p185neu differs from p185c-neu by an amino-acid substitution in the transmembrane region of the glycoprotein: this replacement of valine by glutamic acid at position 664 induces increased intrinsic tyrosine kinase activity which is associated with transformation. Many glycoproteins with charged amino acids in the transmembrane region exist as multimeric complexes at the plasma membrane. We have therefore investigated the association state of both products of the neu gene and show that the oncoprotein p185neu is organized at the plasma membrane primarily in an aggregated form, but that p185c-neu is not. Induction of an aggregated state may mimic aspects of ligand-induced receptor aggregation resulting in enzymatic activation that leads to cellular transformation.     

Pituitary growth hormone and hypothalamic somatostatin in young female rats versus old constant estrous female rats

Pituitary content and concentration of growth hormone was significantly reduced, and hypothalamic somatostatin content significantly increased, in old constant estrous as compared to young female rats. Increased levels of somatostatin may contribute to the decrease in pituitary growth hormone levels in these animals.     

Compartmentalization of sickle-cell calcium in endocytic inside-out vesicles

Much recent interest in the mechanism of dehydration of the dense subpopulation of sickle-cell anaemia (SS) red cells, including the 'irreversibly sickled cells' (ISCs), stems from the view that these relatively rigid cells have a major role in the two main clinical features of the disease, namely haemolytic anaemia and microvascular occlusion. The discovery that SS red cells have an elevated calcium content and accumulate Ca2+ during deoxygenation-induced sickling suggested a working hypothesis of wide appeal for the mechanism of cell dehydration: retained calcium would activate the red cell Ca2+-sensitive K+ channels, causing progressive net loss of KCl and water. However, retained calcium, which seemed as weakly bound to cytoplasmic buffers as in normal red cells, failed to show any measurable activation of K+ channels or Ca2+ pumps in metabolically normal SS cells, despite the apparent functional normality or near-normality of these transport systems. We now offer a possible explanation for this failure. We show that, contrary to the traditional views, SS cells, and to a lesser extent normal human red cells, possess intracellular vesicles with ATP-dependent Ca2+-accumulating capacity, and that nearly all the measurable calcium of fresh SS cells is contained within such vesicles, probably in the form of precipitates with inorganic or organic phosphates.     

Acute toxicity of folic acid in mice

Summary The toxicity of folic acid (PGA) was studied in different inbred strains of mice. LD₅₀ values of PGA by the i.p. route showed a unique toxicity pattern. In some strains, convulsions, ataxia and weakness were observed. Histopathological study in strains S/RVCri, BDF₁, DBA/2 and DBA/2fNCri showed acute renal tubular necrosis.Acknowledgment. The authors thank Ms N. Hasgekar for her technical assistance     

Intergeneric interactions between Eimeria separata (Apicomplexa) and Nippostrongylus brasiliensis (Nematoda) in the rat

Ova production in Nippostrongylus brasiliensis infected rats was significantly greater than in rats singly infected with the helminth when Eimeria separata infections were introduced 4, 6 and 11 days postinoculation with N. brasiliensis. Patent periods were unaltered during concurrent infections. These results suggest that the presence of E. separata affects helminth fecundity but does not increase N. brasiliensis longevity as has been shown with E. nieschulzi.     

Accumulation of indole glucosinolates inPsylliodes chrysocephala L.-infested,or-damaged tissues of oilseed rape (Brassica napus L.)

Summary Infestation of oilseed rape (Brassica napus L.) by the cabbage stem flea beetle (Psylliodes chrysocephala L.) leads to an overall reduction in the levels of aliphatic (alkenyl- and hydroxyalkenyl-) glucosinolates in the damaged tissue (lamina, petiole, stem) and a massive accumulation of indole glucosinolates. Whilst artificial damage (puncturing), with and without associated bacterial infection with an isolate fromP. chrysocephala, led to such accumulation, this was less than that observed in the insect-infected situation.     

Neutralization of human T-lymphotropic virus type III by sera of AIDS and AIDS-risk patients

Human T-lymphotropic virus type III (LAV, HTLV-III) is aetiologically linked to acquired immune deficiency syndrome (AIDS) and persistent general lymphadenopathy (PGL). Specific radioimmunoassays (RIA), enzyme-linked assays, immunofluorescence assays (IFA) and immunoblotting techniques are being used widely to detect serum antibodies to HTLV-III in infected patients and in those at risk of infection. However, these assays do not functionally identify those antibodies that neutralize the infectivity of the virus. We have used three methods of titrating serum neutralizing factors: inhibition of syncytium induction, neutralization of envelope pseudotypes of vesicular stomatitis virus (VSV) and reduction of infectivity of HTLV-III for a cell line permissive to virus replication. We report here that sera from subjects in various disease categories possess only low-level neutralizing activity, even when antibodies to viral membrane antigens are present in high titre. Envelope pseudotypes prepared from four HTLV-III isolates made in three different countries are equally sensitive to neutralization by positive sera, including sera from patients yielding two of the virus isolates.