Pollen vigour and composition in relation to andromonoecy in cashew (Anacardium occidentale L.: Anacardiaceae)

Summary Cashew trees produce four types of pollen from the large and small stamens of the hermaphrodite and male flower (HL, HS, ML, MS). Comparative studies were made of the grain number, structure, viability, vigour, and sugar and amino acid composition of the four pollen types. Anther and pollen grain numbers and dimensions of the four pollen types were similar, as were pollen structure and staining characteristics. The fluorescein diacetate test showed that the HL pollen had the highest percent fluorescence, and viability of all pollen types had declined by 48 h after anthesis. Following controlled hand pollination, the ML pollen had the highest capacity to germinate on the stigma and penetrate the ovule, followed by the MS, HL, and HS pollens. Glucose and fructose and 19 free amino acids were present in all pollen types, with higher levels in the hermaphrodite than in the male flower pollen. The results indicate that the pollen of the male flower is specialised for pollination and fruit set, whereas that of the hermaphrodite flower may be specialised for insect attraction.     

Protein splicing in the maturation of M. tuberculosis recA protein: a mechanism for tolerating a novel class of intervening sequence.

The M. tuberculosis recA locus comprises an 85 kd open reading frame but produced 38 kd RecA and 47 kd products in E. coli. No RNA processing was detected; rather, an 85 kd precursor protein was spliced, releasing a 47 kd spacer protein, and joining its terminal fragments to form mature RecA protein. "Spacer" protein was also produced in M. tuberculosis and from a hybrid spacer-LacZ alpha fusion molecule. Mutagenesis at codon wobble positions at one splice junction showed that protein rather than nucleotide sequence determined splicing activity. Other mutants defined additional regions needed for splicing and allowed processing to be followed. Splicing was essential for RecA activity in E. coli. The possibility that splicing is a manifestation of a novel class of genetic element is discussed.     

Evolution Is Linear: Debunking Life's Little Joke

Linear depictions of the evolutionary process are ubiquitous in popular culture, but linear evolutionary imagery is strongly rejected by scientists who argue that evolution branches. This point is frequently illustrated by saying that we didn't evolve from monkeys, but that we are related to them as collateral relatives. Yet, we did evolve from monkeys, but our monkey ancestors are extinct, not extant. Influential voices, such as the late Stephen Jay Gould, have misled audiences for decades by falsely portraying the linear and branching aspects of evolution to be in conflict, and by failing to distinguish between the legitimate linearity of evolutionary descent, and the branching relationships among collateral relatives that result when lineages of ancestors diverge. The purpose of this article is to correct the widespread misplaced rejection of linear evolutionary imagery, and to re‐emphasize the basic truth that the evolutionary process is fundamentally linear.     

Seasonal settlement and succession of fouling communities in Kalpakkam, east coast of India

Seasonal distribution and community succession of macrofoulants were studied using concrete panels in the coastal waters of Kalpakkam, east coast of India, for a period of two years. The panels were suspended at 1 m, 4 m and 7 m depths and categorised into short-term and long-term exposures. A high total of 105 fouling taxa were recorded. The major fouling organisms observed were hydroids, barnacles, mussels, anthozoans and ascidians. Considerable faunistic and biomass variations were noticed both with respect to season and depth. The month of panel exposure had a significant influence on the succession of fouling communities. On the short-term panels, the maximum fouling biomass was 64 kg m^–2 in 30 days at 4 m depth, whereas on the long-term panels, it was 250 kg m^–2 after 216 days at 4 m depth. A comparison with the biomass values reported from elsewhere shows that biomass build-up in Kalpakkam coastal waters is one of the highest ever reported. Such a very high biomass accumulation is due to the extremely dense settlement of mussels, especially the green mussel,Perna viridis (L).     

Responses of Mature and Aged Sympathetic Neurons to Laminin and NGF: An in Vitro Study

Whilst the potent effects of NGF and laminin on developing neurons are well documented, relatively little is known about the effects of, or altered availability of or altered responsiveness to, these substances on the growth of adult neurons. We have therefore examined this question using explant cultures of sympathetic neurons from the superior cervical ganglion (SCG) of mature and aged rats. Explants were grown on substrata containing different doses of laminin, either with or without added NGF in culture medium containing FCS. Individually, laminin and NGF had relatively small effects on neurite outgrowth and length, which tended to be reduced in old neurons. In contrast, laminin in the presence of exogenous NGF exerted a powerful effect on nerve growth which was substantially greater than the sum of the effects of the individual factors. This synergy was evident in all experimental groups and was greatest in old explants at high doses of laminin, where growth was comparable to that of mature neurons. The dose-response curve of old neurons to laminin in the presence of added NGF indicated reduced responsiveness. These results suggest that variations in the availability of laminin and/or exogenous NGF, together with altered patterns of neuronal responsiveness, may contribute to impaired neuronal plasticity in old age.     

Basal Lipid Peroxidation in Substantia Nigra Is Increased in Parkinson''s Disease

Polyunsaturated fatty acid (PUFA) levels (an index of the amount of substrate available for lipid peroxidation) were measured in several brain regions from patients who died with Parkinson's disease and age-matched control human postmortem brains. PUFA levels were reduced in parkinsonian substantia nigra compared to other brain regions and to control tissue. However, basal malondialdehyde (MDA; an intermediate in the lipid peroxidation process) levels were increased in parkinsonian nigra compared with other parkinsonian brain regions and control tissue. Expressing basal MDA levels in terms of PUFA content, the difference between parkinsonian and control substantia nigra was even more pronounced. Stimulating MDA production by incubating tissue with FeSO4 plus ascorbic acid, FeSO4 plus H2O2, or air alone produced lower MDA levels in the parkinsonian substantia nigra, probably reflecting the lower PUFA content. These results may indicate that an increased level of lipid peroxidation continues to occur in the parkinsonian nigra up to the time of death, perhaps because of continued exposure to excess free radicals derived from some endogenous or exogenous neurotoxic species.     

The effect of chronic neuroleptic administration on cerebral dopamine receptor function

Acute administration of neuroleptic drugs causes blockade of cerebral dopamine receptors. It has been discovered that chronic administration of neuroleptic drugs may have different effects on cerebral dopamine systems. Initial antagonism of dopamine mediated behaviour, such as stereotypy, disappears and may be replaced by supersensitivity to dopamine agonists. Changes also occur in biochemical indices of dopamine receptors, such as in the number and affinity of specific binding sites identified by ³H-ligands labelling D-2 receptors, and in dopamine-stimulated adenylate cyclase activity. All these changes occur obviously in the striatum in response to chronic administration of a range of neuroleptic drugs. Lesser changes take place in the mesolimbic dopamine system. What happens in the mesocortical dopamine pathways is unknown. The consequence of such adaptive responses to chronic neuroleptic therapy may be of importance to understanding of tardive dyskinesia and schizophrenia.     

The first replacement of a chlorosulphonyloxy group by chlorine at C-2 in methyl α-D-glucopyranoside and sucrose derivatives

Treatment of methyl 3-O-acetyl-4,6-O-benzylidene-α-D-glucopyranoside 2-chlorosulphate (2), 3,4,6,3′,4′,6′-hexa-O-acetylsucrose 2,1′-bis(chlorosulphate), 3,4,6,3′,4′,6′-hexa-O-acetyl-1′-O-benzoylsucrose 2-chlorosulphate, and 3,4,3′,4′-tetra-O-acetyl-6,6′-dichloro-6,6′-dideoxysucrose 2,1′-bis(chlorosulphate) with lithium chloride in hexamethylphosphoric triamide gave the corresponding chlorodeoxy-manno derivatives. Treatment of the 2-chlorosulphate 2 with such nucleophilic reagents as lithium bromide, sodium azide, sodium chloride, and sodium benzoate in hexamethylphosphoric triamide gave the 2-hydroxy compound as a major product. Selective chlorination at C-1′ was achieved when 3,4,6,3′,4′,6′-hexa-O-acetylsucrose was treated with sulphuryl chloride in a mixture of pyridine and chloroform.     

The development of a radioimmunoassay for ranitidine in biological fluids

The development of a radioimmunoassay for ranitidine in biological fluids is described. The sensitivity of the method is 2 ng/ml in human serum using a 0.1 ml sample. The cross reactivity of the antiserum with synthetic standards of ranitidine metabolites is <1%, 22% and 11% for ranitidine N-oxide, ranitidine sulphoxide and desmethyl ranitidine respectively. The latter two substances are minor metabolites in man, and do not affect the measurement of ranitidine in clinical samples. It was possible to produce a much higher titre antiserum by immunising the sheep instead of the rabbit.