Paleoceanographic interpretations of coccoliths and oxygen-isotopes from the sediment surface of the southwest Indian Ocean

The distribution of forty-four coccolithophore species in one hundred deep-sea core-tops from the southwest Indian Ocean is described. Three coccolith assemblages have been recognised (Maputo, Agulhas Current and deep water) by the relative abundances of four ecologically significant coccolithophore species (Gephyrocapsa oceanica, Emiliania huxleyi, Calcidiscus leptoporus and Umbilicosphaera sibogae). Their biogeographical distribution appears to be related to water temperature, nutrient concentration and dissolution.The degree of preservation of coccoliths and foraminifera indicates that the carbonate lysocline lies somewhere between 3500 and 4000 m, resulting in the concentration of dissolution-resistant microfossils below this depth.Stable oxygen isotope ratios of the planktonic foraminiferal species Globigerinoides sacculifer range between −1.5 to −1.0‰ PDB (equal to 22.8–25.1°C) and occur in a narrow band on the sea floor beneath the “A” route of the Agulhas Current.These values are about 0.5 per mil PDB lighter than samples analyzed on either side of this band and can be explained by the Agulhas Current's elevated temperature at the ocean surface of 2–3°C. Thus an oxygen isotope imprint of the Agulhas Current exists beneath it on the sea floor.The Agulhas Current is probably the major factor influencing sedimentation, sediment-distribution patterns and geological features in the study area. At present it is voluminous and fast flowing, possibly eroding sediments up to 2500 m below the surface.The oxygen-isotope ratios and nannoplankton counts obtained in this study indicate, however, that the majority of samples are most probably recent or at least not older than 85,000 years. This implies that sediments are accumulating on the ocean floor and that the Agulhas Current does not have a pronounced erosional influence, at least in areas from which cores were retrieved for this study.     

Altitudinal changes in the incidence of crassulacean acid metabolism in vascular epiphytes and related life forms in Papua New Guinea

Summary The occurrence of Crassulacean acid metabolism (CAM), as judged from ¹³C values, was investigated in epiphytes and some related plant species at a series of sites covering the approximate altitudinal range of epiphytes in Papua New Guinea. Comprehensive collections were made at each site and the occurrence of water storage tissue and blade thickness was also determined. Some 26% of epiphytic orchids from a lowland rainforest (2–300 m.a.s.l) showed ¹³C values typical of obligate CAM and possessed leaves thicker than 1 mm. A second group of orchids, mostly with succulent leaves, possessed intermediate ¹³C values between -23 and -26% and accounted for 25% of the total species number. Some species of this group may exhibit weak CAM or be facultative CAM plants. The remainder of the lowland rainforest species appeared to be C₃ plants with ¹³C values between -28 and -35%. and generally possessed thin leaves. Obligate CAM species of orchids from a lower montane rainforest (1175 m.a.s.l) comprised 26% of the species total and mostly possessed thick leaves. The remainder of the species were generally thin-leaved with ¹³C values between -26 and -35%. largely indicative of C₃ photosynthesis. Orchids with intermediate ¹³C values were not found in the lower montane rainforest. Obligate CAM appeared to be lacking in highland epiphytes from an upper montane rainforest and subalpine rainforest (2600–3600 m.a.s.l). However the fern, Microsorium cromwellii had a ¹³C value of -21.28%. suggesting some measure of CAM activity. Other highland ferns and orchids showed more negative °¹³C values, up to-33%., typical of C₃ photosynthesis. The highland epiphytic orchids possessed a greater mean leaf thickness than their lowland C₃ counterparts due to the frequent occurrence of water storage tissue located on the adaxial side of the leaf. It is suggested that low daytime temperatures in the highland microhabitats is a major factor in explaining the absence of CAM. The increased frequency of water storage tissue in highland epiphytes may be an adaptation to periodic water stress events in the dry season and/or an adaptation to increased levels of UV light in the tropicalpine environment.     

Population genetics implications of the premutation hypothesis for the generation of the fragile X mental retardation gene

Summary The population genetics implications of the premutation hypothesis for the generation of the fragile X mental retardation gene are explored. With some broad assumptions, the consequences of the model are that (a) 50% of mothers of probands carry the premutation; (b) 6.5% of mothers of probands receive the premutation from their mothers, 18.9% from their fathers, and 24.6% as a new mutation; (c) the incidence of carriers for the full mutation equals the incidence of affected males, whereas the incidence of carriers for the premutation is 1.35 times the incidence of affected males; (d) assuming mutation rates are equal in eggs and sperm, the mutation rate from normal to premutation alleles is 1.67x10^-4; (e) the expected segregation ratio in sibs of probands is 0.44, which corresponds to observed values. In addition, predictions using the premutation hypothesis of the expected segregation ratio in sibs of mothers of probands fits well with the data of Vogel and coworkers.     

Biomechanics of below-knee amputee gait

Sagittal plane biomechanical and EMG analyses from eight below knee (B/K) amputee trials demonstrate considerably modified motor patterns from the residual muscles at the hip and knee. Five SACH fittings, two Uniaxial and one Gressinger prostheses were analysed. Moments of force and mechanical power were analysed on all eight trials and EMG profiles are reported for three of the amputees fitted with SACH prostheses. The findings can be summarized as follows: 1. All eight trials had similar internal moment of force patterns at the ankle. A dorsiflexor moment commenced at heel contact and continued for the first third of stance. The prostheses generated a plantarflexor moment for the balance of stance which increased in late stance to about 2/3 that seen in normals. 2. The two Uniaxial prostheses showed a 20% recovery of stored energy which was returned at push-off. The recovery by the Gressinger fitting was 30%. 3. For all but the Gressinger prosthesis the knee moment of force was negligible during early stance (when normals have an extensor moment), below normal in late stance and fairly normal during swing. The amputee wearing the Gressinger prosthesis had a normal but slightly reduced pattern of moments of force over the entire stride. 4. All eight trials had hyperactive hip extensors during early and mid-stance which resulted in above-normal energy generation by these concentrically contracting muscles. This compensation makes up for the loss of the major energy generation by the plantarflexors at push-off. 5. The moment of force and power patterns at the hip for all eight trials during late stance and swing were fairly normal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nerve growth factor (NGF) regulates adult rat cultured dorsal root ganglion neuron responses to the excitotoxin capsaicin

An overlap between subpopulations of nerve growth factor (NGF)-responsive and capsaicin-sensitive dorsal root ganglion (DRG) sensory neurons has been suggested from a number of in vivo studies. To examine this apparent link in more detail, we compared the effects of capsaicin on adult rat DRG neurons cultured in the presence or absence of NGF. Capsaicin sensitivity was assessed histochemically by a cobalt staining method, by measuring capsaicin-induced 45Ca2+ uptake, and by electrophysiological recording of capsaicin-evoked membrane currents. When cultured with NGF, approximately 50% of these adult DRG neurons were capsaicin-sensitive, whereas adult sympathetic neurons or ganglionic nonneuronal cells were insensitive. DRG cultures grown in the absence of NGF, however, were essentially unresponsive to capsaicin. Capsaicin sensitivity could be regained fully within 4-6 days of replacement of NGF. These results indicate that, at least in vitro, NGF can modify the capsaicin sensitivity of adult DRG neurons.     

An autosomal dominant form of adolescent multinodular goiter.

Eighteen members of an extended pedigree have been found to have a form of euthyroid adolescent multinodular goiter. Histological examination showed multiple adenomata with areas of epithelial hyperplasia, hemorrhage, and calcification. In two subjects there were focal areas of epithelial hyperplasia reminiscent of low-grade papillary carcinoma, but capsular and vascular invasion was not found. The pattern of inheritance appeared to be autosomal dominant, with diminished penetrance in males. Although the patients were euthyroid, the likely basis for this disorder is an abnormality in thyroglobulin structure and function.     

Elastic properties of collapsing and expanding trachea

The compliance of the canine trachea under positive and negative transmural pressures was measured in an in-vivo preparation. The average compliance values found in eight animals were 11.7 X 10(-6) (dynes/cm2)-1 at zero transmural pressure and 4.9 and 6.9 X 10(-6) (dynes/cm2)-1 at -20 and +20 X 10(3) dynes/cm2 transmural pressure, respectively. These compliances were significantly lower than those measured by others in excised preparations. Stress relaxation was noted at all pressure levels.     

Two new monoclonal antibodies (LN-1, LN-2) reactive in B5 formalin-fixed, paraffin-embedded tissues with follicular center and mantle zone human B lymphocytes and derived tumors

Two monoclonal antibodies (LN-1, LN-2) reactive with B lymphocytes in B5 formalin-fixed, paraffin-embedded tissue sections have been produced by utilizing cell extracts from pokeweed mitogen-stimulated peripheral blood lymphocytes and diffuse histiocytic lymphoma SU-DHL-4 cells, respectively. Both monoclonal antibodies were initially identified by indirect immunofluorescence screening techniques on paraformaldehyde-acetone-fixed cell preparations. Specificity screens with 36 well-characterized human lymphoma and leukemia cell lines showed that both LN-1 and LN-2 stained cell lines of B cell lineage but were unreactive with those of T cell or, with one exception, myeloid derivation. Null cell acute lymphoblastic leukemia cell lines were found to be LN-2+ but LN-1-. The B cell specificity of these reagents was confirmed on 15 lymphoma and 17 leukemia biopsy specimens by using indirect immunofluorescence techniques. Immunoperoxidase staining of sections from B5-fixed, paraffin-embedded human lymphoid tissues showed that LN-1 bound to the cell membrane and cytoplasm of germinal center cells whereas LN-2 stained the nuclear membrane and cytoplasm of germinal center and mantle zone B lymphocytes as well as interfollicular histiocytes and thymic medullary dendritic cells. Both monoclonal antibodies failed to stain cortical thymocytes, lymph node T cells, and peripheral blood T and myeloid cells. Immunoperoxidase staining of 20 nonlymphoid human organs and tissues revealed that LN-1 reacted positively with red blood cell precursors of the bone marrow, ciliated epithelial cells of the bronchus, distal tubular cells of the kidney, and ductal cells from several organs including the breast and prostate. In contrast, LN-2 was unreactive with all human nonlymphoid organs and tissues including the bone marrow. Indirect immunofluorescence staining of a panel of 26 solid tumor cells lines showed that LN-1 was reactive with the majority of epithelium-derived cell lines, glioblastomas, and astrocytomas but was unreactive with neuroblastomas, small cell carcinoma of the lung, and sarcomas. LN-2 was unreactive with 25 of 26 of the solid tumor cell lines by these techniques. Immunobiochemical studies have shown that LN-1 recognizes a cell surface sialoantigen whereas LN-2 is directed against a 35,000 dalton nuclear membrane protein. Because of their high specificity for B cell tumors and their ability to stain B5-fixed, paraffin-embedded tissues, LN-1 and LN-2 are useful reagents for the diagnosis and classification of the human lymphomas and leukemias.