The mechanical design of the tusk of the narwhal (Monodon nonoceros: Cetacea)

The mechanical properties of the tissues of the tusk of a narwhal Monodon monoceros , their histological arrangement, and the gross anatomy of the tusk were examined. The histology of the tusk shows various toughening mechanisms. The tusk tissues are of low stiffness, but are very tough, suiting the tusks for loading on impact, but not for longitudinal loading. These mechanical properties suggest the possible functions of the tusk, namely to be long in order to be sexually attractive, while being tough in order to withstand 'testing' blows from other males.     

Glandular excision in total glandular mastectomy and modified radical mastectomy: a comparison

Total glandular mastectomy and modified radical mastectomy were compared for the amount of breast tissue remaining after surgery. Multiple biopsies were taken from the anterior chest walls of women following total glandular mastectomy (N = 27) and modified radical mastectomy (N = 28) to try to detect any residual glandular tissue. Regardless of procedure performed, breast tissue was identified histologically in 5 percent of all biopsy specimens (159 and 161, respectively). One of every five operative fields was shown to have glandular elements in at least one of the biopsy sites; the positive biopsies did not form a discernible pattern. The residual breast tissue in each of these patients averaged less than 1 gm. On the basis of this study, modified radical mastectomy and total glandular mastectomy appear to be equally effective in removing most of the breast.     

The development of plant-parasitic nematode infestations on micro-propagated banana plants following field control measures in Côte d'Ivoire

Of the weeds that were found in banana production areas, only Asystasia gangetica was parasitised by Radopholus similis; Helicotylenchus multicinctus and Hoplolaimus pararobustus were able to parasitise all weed species. Field trials were carried out in Cote d'Ivoire to assess the potential for using nematode-free micro-propagated banana plants following cultural and chemical methods for nematode control. Banana (Musa acuminata) cv. Poyo was examined for nematodes after weed fallow, flooding and chemical treatment. Before replanting bananas, nematode assays showed that: i) all nematode species declined but were not eliminated after a 1,3-dichloropropene soil treatment; ii) H. multicinctus, H. pararobustus and Cephalenchus emarginatus were still present after either a 2-year weed fallow (dominated by Chromolaena odorata or Asystasia gangetica) or a 10-week flooding; iii) R. similis did not persist after fallowing or flooding. All nematode species were found in plots treated with 1,3-dichloropropene and that had been planted with bullheads, suckers or nematode-free micropropagated plants. After both fallow and flooding, R. similis was reintroduced on infested planting materials (bullheads and suckers) even when they were pre-treated with a nematicide. When fallow and flooded plots were planted with nematode-free materials (vitro-plants), R. similis did not appear in the roots for two vegetative cycles. The other species, still present in the soil, invaded the roots and increased slowly in numbers. These results were confirmed in commercial banana plantations.     

Age at sexual maturity of males and timing of the mating season of polar bears (Ursus maritimus) in Greenland

Age at sexual maturity among male polar bears (Ursus maritimus) and timing of the mating season were studied by microscopic and macroscopic analysis of the reproductive organs from 165 male and 92 female Greenland polar bears. Males became sexually mature in the spring following their fifth birthday. Testes sampled during the spring reached 95% of their asymptotic length at 5.8 years. Some spermatozoa were found in 2- to 4-year-old bears during the spring, but only in low concentrations in a mixture of other cell types. The first corpus luteum was found on 1 April and most ovulations were estimated to occur before mid-May which indicate that the peak of the mating season begins in late March and ends in May. These findings are somewhat different from a similar study from Svalbard, where the mating season is estimated to peak later and male polar bears are found to become mature earlier. We hypothesize that these differences occur because adolescent males have their peak testicular activity after the main breeding period and therefore appear to be fully sexually mature during summer and not during spring.     

NMR observation of gramicidin A' in phosphatidylcholine vesicles.

Dimyristoyl phosphatidylcholine was prepared with perdeuterated hydrocarbon chains and sonicated into bilayer vesicles together with gramicidin A'. The 1H NMR resonance from the tryptophan residues in the gramicidin has a linewidth of approximately 80 Hz, indicating significant local mobility for these residues. Paramagnetic lanthanides added to the aqueous medium cause a chemical shift of this signal indicating that some of the tryptophans may be located in the interfacial region of the bilayer.     

Immunochemical Analysis of Arylsulfatase Accumulation in Sea Urchin Embryos

We have determined the expression pattern of arylsulfatase in embryos of the sea urchin Strongylocentrotus purpuratus . Polyclonal antibodies raised against a fusion protein containing sequences encoded by SpARSI (Yang et al. , 1989, Dev. Biol. 135: 53–61, 1989) detect several peptides of 65–70 kD on immunoblots. Treatment with glycopeptidase F shows that at least one of these peptides is modified by N-linked glycosylation, which accounts for some of the peptide diversity. We have also identified a second arylsulfatase gene (SpARSII) whose sequence is highly similar to ARS, a gene expressed in the Hemicentrotus pulcherrimus embryo. Arylsulfatase activity is detectable in unfertilized eggs, in which only SpARSII mRNA can be detected. Both SpARSI and SpARSII mRNAs increase greatly in abundance during embryogenesis accompanied by parallel changes in arylsulfatase activity and immunoreactivity. Immunohistochemistry with the anti-SpARSI antibody shows that arylsulfatase accumulates primarily along the apical surface of the aboral ectoderm of pluteus larvae, and to a lesser extent along portions of oral ectoderm. At earlier stages, the protein is more uniformly distributed along all presumptive ectoderm, reflecting a more uniform mRNA distribution. Treatment of embryos with glycine-EDTA, which dissociates but does not lyse cells of the embryo, releases virtually all enzymatic activity and all immunoreactive protein. Embryos cultured in sulfate-free sea water, which arrest at gastrula stage, show normal accumulation and secretion of peptide detected with the SpARSI antibody.     

Cortical arousal and social intimacy in the human female under different conditions of eye contact

The EEG was monitored from pairs of female subjects while they engaged in varied eye contact under experimenter instruction (direct gaze, smile, averted gaze). The nine conditions of gaze were related monotonically to EEG abundance (9.5–20.0 Hz). It is suggested that the gradient of arousal or activation so obtained is evidence of a physiological substrate of social intimacy.