In vitro meristem cloning of Eucalyptus tereticornis Sm.

Rapid multiplication of axillary meristems and direct shoot development occurred from nodal explants of mature Eucalyptus tereticornis Sm. with 5.3 M NAA, 1.1 M IAA and 4.4 M BA in Murashige-Skoog medium. Repeated subcultures of the second generation shoot cultures into low cytokinin-auxin containing media (0.44–0.88 M BA+0.1 M NAA) yielded axillary microshoots in large numbers. Half-strength MS liquid medium with 4.9 M IBA, 5.5 M IAA and 5.3 M NAA for four days, half-strength semi-solid hormonefree MS medium with charcoal, and MS liquid medium without charcoal and hormones, in sequence, induced rooting of shoots in the dark. This system is suitable for the mass propagation of this difficult-to-root eucalypt.Abbreviations BA 6-benzyladenine - IAA indole-3-acetic acid - IBA -indole-3-butyric acid - 2-iP isopentyl adenine - Kn kinetin - MS Murashige-Skoog - NAA -naphthalene acetic acid - PVP polyvinylpyrrolidone     

Asymmetric diffusion into the postsynaptic neuron: An extremely efficient mechanism for removing excess GABA from synaptic clefts on the Deiters' neurone plasma membrane

Microdissected Deiters' neuron plasma membranes have been used for studying the passage of GABA through the membrane both in the inward and outward direction. Working with 0.2 mM GABA in the compartment simulating the outside of the neurone and with 2.0 mM GABA in the one simulating the inside we found a net transport of GABA towards the inside. This mechanism does not require a Na⁺ ion gradient across the membrane. The nature of the transport process involved was studied by determining the rate of [³H]-GABA inward passage as a function of GABA concentration (1 nM–800 M) on the outward side of the membrane. The results have shown that until 50 M a diffusion process (v=D₁×C, where D₁=3.1×10^–11 1/m²×sec) is the sole mechanism involved. Above 50 M a second diffusion process is activated v=D₂×(C–50×10^–6), where D₂=2.8×10^–11 1/m²×sec. Taking in account both inward and outward directed diffusion, one can calculate 16 M as the equilibrium concentration of GABA on the outward side of the membrane. From a kinetic point of view, these diffusion processes are able to reduce GABA concentration in a synaptic cleft from 3 mM to 20 M within 3 sec. These diffusion systems are discussed as extremely efficient in removing the excess of released GABA in the synaptic cleft.     

Influence of phosphate and nitrate supply on root hair formation of rape,spinach and tomato plants

Summary Experiments with tomato, rape and spinach in nutrient solutions have shown that the formation of root hairs is strongly influenced by phosphate and nitrate supply. Decreasing the phosphate concentration of the nutrient solution from 100 to 2 M P resulted in an increase of root hair length from 0.1–0.2 to 0.7 mm of the three plant species. Root hair density also increased by a factor of 2–4 when the P concentration was lowered from 1000 to 2 M. The variation of these two root properties raised the root surface area by a factor of 2 or 3 compared to plants well supplied with P. Root hair length was closely related to the phosphate content of the root and shoot material. On the other hand, spinach plants grown in a split-root experiment produced root hairs in solutions of high P concentration (1000M P) if the major part of the total root system was exposed to low P concentration (2 M P). It is therefore concluded that the formation of root hairs does not depend on directly the P concentration at the root surface but on the P content of the plant.Similar experiments with nitrate also resulted in an increase in length and density of root hairs with the decrease of concentration below 1000 M. In this case marked differences between plant species occurred. At 2 M compared to 1000 M NO₃ root hair length of tomato increased by a factor of 2, of rape by a factor of 5 and of spinach by a factor of 9. Root hair length was correlated, but not very closely, to the total nitrogen content of the plants. It is concluded, that the influence of nutrient supply on the formation of root hairs is a mechanism for regulating the nutrient uptake of plants.Dedicated to Prof. Dr. E. Welte on the occasion of his 70th anniversary.     

Somatic embryogenesis from immature inflorescences of oil palm

Summary Immature inflorescences of oil palm (Elaeis guineensis) var. Pisifera were inoculated onto modified MS medium containing 0.3% (w/v) activated charcoal and 475 M 2,4-D. After 2—3 months of culture, a hard yellow callus proliferated at the base of the shoot-like structures. The high incidence of phenolic oxidation required the use of increased levels of activated charcoal (0.5% w/v) and 2,4-D (500 M). Development of floral structures from inflorescence expiants was frequently observed during the culture period. After 81 weeks of culture, an embryogenic tissue characterized by compact consistency and pearly white color was observed in tissues derived from very young inflorescences. This compact embryogenic tissue differentiated into normal somatic embryos when transferred onto regeneration medium containing NAA (15 M) and ABA (2 M). Normal plantlets were recovered from these somatic embryos after 8 weeks on regeneration medium.Abbreviations 2, 4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid - ABA abscisic acid - PVP-40 polyvinylpyrrolidone     

Tissue culture ofKarwinskia humboldtiana—a plant producing toxins with antitumoural effects

Isolated embryos ofKarwinskia humboldtiana were cultured in vitro. The growth of embryos and development to plantlets on woody plant medium supplemented with indole-3-acetic acid 6.10^-2 mol l^–1, gibberellic acid (GA₃) 3.10^-2 mol l^–1, and 6-benzylaminopurine (BA) 2 mol l^–1 was obtained. Multiplication of shoots and rooting of excised shoots has been achieved. Callus formation on modified Murashige-Skoog medium supplemented with 1-naphthaleneacetic acid 10 mol l^–1, GA₃ 14 mol l^–1, and kinetin 5 mol l^–1 on hypocotyls, or on root cultures on medium supplemented with 2.4-dichlorophenoxyacetic acid 10 mol l^–1 and BA 10 mol l^–1 was induced.Abbreviations BA 6-benzylaminopurine - 2,4-d 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid - IAA indole-3-acetic acid - NAA 1-naphthaleneacetic acid - TEM transmission electron microscopy     

Thrombin Specificity: Further Evidence for the Importance of the β-Insertion Loop and Trp96. Implications of the Hydrophobic Interaction Between Trp96 and Pro60B Pro60C for the Activity of Thrombin

A number of thrombin mutants have been constructed to investigate the role of Trp⁹⁶ and the -insertion loop for the specificity of thrombin. Thrombin(60D) consists of the replacement of the -insertion loop (14 amino acid residues from 59 to 63, including a 9-residue insertion at position 60) with the corresponding four residues in trypsin, Tyr-Lys-Ser-Gly; thrombin(GGG) is a smaller loop mutation in which the residues Tyr^60APro^60BPro^60CTrp^60D Asp^60ELys^60F of the -insertion loop were replaced by Gly-Gly-Gly; thrombin(96S) consists of a point mutation Trp⁹⁶Ser; and thrombin(GGG/96S) is the double mutant incorporating both changes. Thrombin(96S) clots fibrinogen ~3 times more slowly than thrombin, with the two -insertion loop mutants, thrombin(GGG) and thrombin(GGG/96S), reacting ~3000- and 1300-fold more slowly, respectively. The specificity constant k _cat/K _m for the cleavage of fibrinopeptide A and fibrinopeptide B by thrombin(96S) was 2.6 and 0.35 M^–1 s^–1 respectively, compared to 10 and 2.5 M^–1 s^–1 for wild-type recombinant thrombin, respectively. Kinetic constants were determined for the hydrolysis of H-D-phenylalanyl-L-pipecolyl-L-arginine-p-nitroaniline. The Michaelis constant K _m increased ~6-fold for thrombin(96S) and >200-fold for thrombin(GGG) and thrombin(GGG/96S) when compared to wild-type recombinant thrombin, while the catalytic constant k _cat remained approximately the same. All mutants were more susceptible to inhibition by BPTI than wild-type recombinant thrombin. Clearly, the -insertion loop is important for thrombin activity. But the mutation of Trp⁹⁶Ser can compensate somewhat for the loss of binding at the -insertion loop. The deletion of the hydrophobic interaction between Trp⁹⁶ and Pro^60BPro^60C appears to decrease the stability of the -insertion loop, thereby causing a decrease in binding efficiency.     

Regeneration of pea (Pisum sativum L. cv. Century) plants by in vitro culture of immature leaflets

In vitro regeneration of plants from immature leaflets of 3 day-old pea (Pisum sativum L. cv. Century) seedlings was studied under defined nutritional, hormonal and environmental conditions. Immature leaflets isolated from the second and third apical leaves of aseptically germinated seeds were cultured on MS medium containing vitamins as in B5 medium, 3% sucrose, 0.8% agar and supplemented with 0.1, 1, and 10 M concentrations of naphthaleneacetic acid (NAA) and 1 and 10 M levels of benzyladenine (BA) in various combinations. Shoot regeneration from the primary callus occurred within 45 to 90 days of culture in most of the hormone combinations. Although the number of calli producing shoots was maximal at 10 M levels of NAA and BA, multiple shoot regeneration was predominant at a combination of 0.1 M NAA and 10 M BA. Indoleacetic acid (IAA) and kinetin (K), both at 10 M, also induced shoot regeneration. No shoots were regenerated when 10 day-old leaflets were used as explants. Root production generally occurred on non-shoot regenerating calli. Roots were induced to differentiate by transferring the regenerated shoots onto half-strength B5 medium supplemented with 1 M NAA.NRCC # 19712Visiting Scientist, supported by a research fellowship from Consejo Nacional de Investigaciones Científicas y Técnicas (Rep. Argentina). Permanent address: Facultad de Ciencias Agrarias, IBONE, Casilla de Correos 209, Corrientes (3400), Argentina.     

Aflatoxin influences on seed germination and root elongation by two cultivars of Glycine max and uptake of 65 Zn-ZnCl2 by the cultivars

Maximum inhibition of Glycine max, cv. Essex seed germination occurred at 10 g/ml following 72 hr imbibition in constant light. Seeds imbided 108 hr in constant darkness at this concentration showed a 20% rise in germination over that of the control. Imbibition of G. max, cv. Williams seeds in either light or dark for 96 hr did not suppress germination. Imbibition of Essex seeds in either light or dark at 2.5 through 10 g/ml stimulated root elongation except for 10 g/ml at 96 hr (light). Maximum inhibition of Williams root elongation under constant light was at 48 and 72 hr with 10 g/ml. Statistically significant differences in cotyledon, leaf and stem lengths between non-treated (NT) and treated (T) seedlings were not found except for Williams stem length at 2.5 / ml. Root elongation was stimulated 1.2- and 1.1-folds, respectively, at 5.0 (Essex) and 2.5 (Williams) g/ml. Toxin at 2.5 through 10.0 g/ml did not markedly alter either cotyledon or leaf widths with the exception of Williams leaf width at 2.5 g/ml. Medium supplementation with 2.5 through 10.0 g/ml resulted in cotyledon, leaf and root weight enhancements for Essex seedlings. Stem weight was not markedly affected. An 18% rise in Williams cotyledon weight above that of the control was seen at 2.5 g/ml. Williams leaf weights were increased 1.75- and 1.25-folds, respectively, at 2.5 and 10.0 g/ml. Aflatoxin B₁, at 2.5 g/ml promoted Williams stem and root elongation 1.20- and 1.09-folds, respectively. Most of the radioactivity from ⁶⁵Zn-ZnCl₂ recovered within organs was found within Essex roots for both T and NT seedlings. A higher amount of radioactivity was recovered within roots at each toxin concentration than was without toxin. However, this was not statistically significant. Significant differences in the distribution of radioactivity within roots between NT and T Williams seedlings were not observed. Generally, AFB₁ failed to affect significantly these two varieties of soybeans based on the tests relating to germination, growth and radiolabel uptake.     

Influence of sarmesin on some dopamine-related types of behaviour

Summary The present study was undertaken to investigate the effects of sarmesin, an analogue of [Sar¹] angiotensin II (ANG II) where the tyrosine hydroxyl group in position 4 is methylated, on dopamine (DA)-related paradigms: locomotor and exploratory behaviour as well as apomorphine (3 mg/kg, ip)-induced stereotypy in rats. Sarmesin (0.5 and 1 g, icv) significantly decreased ambulation and rearing movements, and blocked the inhibitory effect of ANG II (0.1 g) on both types of activity. Sarmesin induced biphasic effects on apomorphine-induced stereotypy depending on the dose increase (0.5 and 5 g, icv) and decrease (10 g). Moreover, sarmesin (5 g) blocked the inhibitory effect of ANG II (2 g, icv) on apomorphine stereotypy. Taken together, these results suggest that sarmesin might interact with AT₁ and AT₂ receptor subtypes. The results further confirm the statement for ANG II-DA interaction in brain structures involved in these types of behaviour.     

A novel technique for the study of bacterial cell mechanical properties

A micromanipulation method is described for measuring the bursting forces of bacteria and relating them to cell size. At a compression speed of 6.2 m s^–1, bursting forces of three samples of rapidly growing Staphylococcus epidermis from a batch culture varied from 3 to 34 N with an average value of 13.8 N (standard error 0.8 N). Escherichia coli grown in continuous culture at a specific growth rate of 0.5 h^–1 had bursting forces varying from 1 to 9 N with an average value of 3.6 N (standard error 0.4 N). In squeeze-hold experiments, force relaxation was observed, which was attributed to water loss from the cells, or viscoelasticity, or both. At high compression speed, such as 6.2 m s^–1, this relaxation could be neglected. Micromanipulation strength measurements might be used in studies of cell mechanical disruption and of the dependence of cell strength on cell physiology.     

Accumulation of fumonisins B1 and B2 in freshly harvested Brazilian commercial maize at three locations during two nonconsecutive seasons

Fifty-six Brazilian commercial maize cultivars were examined for FB₁ and FB₂ accumulation after two non-consecutive growing seasons. During the 94/95 growing season 35 cultivars were planted at three locations in the state of São Paulo, Brazil. All samples (total of 105) were contaminated (0.10 g/g–6.58 g/g FB₁ and 0.04 g/g–2.15 g/g FB₂). During the 97/98 growing season, 8 of the cultivars used during 94/95 and 21 others were replanted at the same locations. All 87 samples were contaminated (1.15 g/g–43.80 g/g FB₁ and 0.08 g/g–11.65 g/g FB₂). One cultivar accumulated significantly less fumonisins in all locations during both growing seasons, indicating that some degree of selection may be possible even in climates that favor F. moniliforme (verticillioides) infection of maize. The presence of water surplus in soil from kernel maturity to harvest correlated with concentrations of FB₁ in the grain for the 8 cultivars planted during both seasons at three locations. Observed trends indicated that water excesses and deficits from silking to harvest increased fumonisin levels. The difference in the incidence of FB₁, FB₂, and FB₁ + FB₂ was significant between growing seasons, planting locations and between cultivars. Neither the level of hybridization, nor the type of endosperm, nor the length of the vegetative cycle showed any effect on the FB₁ contamination.This revised version was published online in October 2005 with corrections to the Cover Date.     

Kinetics of growth and lactic acid production in continuous and batch culture

Summary In a lactic acid fermentation by Streptococcus faecalis, the specific consumption rate of glucose (v) and the specific production rate of lactic acid () were represented by the following simple equations as functions of the specific growth rate (): 1/=(1/) + 1/ = (1/) + By use of data from a batch culture, these two equations were derived from enzyme kinetics of the product inhibition. These equations were successfully applied to the results of batch culture and chemostat culture. In addition, calculation of ATP yield by these equations agreed with the experimental results better than the conventional Leudeking-Piret type equation, which includes two terms associated with growth and not with growth. Correspondence to: H. Ohara     

Diurnal variation in physical-chemical properties and primary production in the interconnected marine,mangrove and freshwater biotopes of Kakinada coast,Andhra Pradesh,India

Diurnal variation in hydrological variables and dissolved inorganic nutrients such as PO _inf4 ^sup3– -P, N O _inf2 ^sup– -N, NO _inf3 ^sup– -N and NH _inf4 ^sup+ -N were studied in three interconnected biotopes including freshwater, marine and mangrove brackish water of the Kakinada coastal zone, Andhra Pradesh. Samples were collected at intervals of 3 hours, for a period of 24 hours. In the marine environment salinity varied from 26 to 32 whereas in the mangrove waters it fluctuated from 12 to 20 and in both biotopes salinity showed bimodal type of oscillation. Dissolved oxygen content was high in the mangrove waters during day time but decreased rapidly during the night hours. In the marine environment PO_f4 ^p3–-P concentration varied from 0.345 to 1.195 g at l^–1, NO _inf3 ^sup– -N from 1.03 to 6.62 g at l^–1 and NO _inf2 ^sup– -N from 0.086 to 0.506 g at l^–1. The highest and the lowest concentrations of PO _inf4 ^sup3– -P, NO _inf3 ^sup– -N, NO _inf2 ^sup– -N recorded in the mangrove waters were 0.790 and 0.325 g at l^–1, 7.10 and 1.60 g at l^–1 and 0.278 and 0.060 g at l^–1, respectively. The concentration of PO _inf4 ^sup3– -P, NO _inf3 ^sup– -N and NO _inf2 ^sup– -N were high in the freshwater canal, the maximum and minimum values being 1.110 and 0.730 g at l^–1, 26.40 and 9.98 g at l^–1 and 0.520 and 0.252 g at l^–1 respectively. The concentration of ammonia was relatively high in the mangrove water. Gross and net primary production in the mangrove water was 4 times higher than in the marine biotope. There was no export of dissolved nutrients from the mangrove environment to the adjacent marine waters.     

Male reproductive effect of arsenic in mice

Arsenic, a known human carcinogen, was given to mice via drinking water as sodium arsenite at a dose 53.39, 133.47, 266.95 and 533.90 mol l for 35 days. A decrease in the activity of 17 HSD along with increase in LDH, GT activity were observed at 533.90 mol l. The observed sperm count, motility and morphological abnormalities in sperm were similar to control at lower dose levels. However at 533.90 mol l a significant decrease in sperm count and motility along with increase in abnormal sperm were noticed. Significant accumulation of arsenic in testes and accessory sex organs may be attributed to the arsenic binding to the tissues or greater cellular uptake. No effects were observed on indices studied for reproductive effects at 53.39 mol l arsenic close to which human being are exposed through drinking water under the present set of experimental conditions.     

A lyophilized aqueous extract of<Emphasis Type="Italic"> Maytenus ilicifolia</Emphasis> leaves inhibits histamine-mediated acid secretion in isolated frog gastric mucosa

Lyophilized aqueous extract of Maytenus ilicifolia leaves (LAEMIL) is commonly used in Brazilian folk medicine in the treatment of dyspepsia as well as gastric ulcers. We have investigated the effect and the possible mechanism of action of the LAEMIL on acid secretion in isolated frog gastric mucosa incubated in an Ussing chamber. It was observed that LAEMIL (7–28 mg%) as well as cimetidine (125–4,000 M), a well-known histamine H₂ receptor antagonist, decreased basal acid secretion in a concentration-dependent manner. Similarly to cimetidine (190 M), LAEMIL (21 mg%) also inhibited gastric acid secretion induced by increasing concentrations of histamine (50–800 M). The EC₅₀ values for histamine alone and histamine in the presence of LAEMIL or cimetidine were 94.6 M (71.1–125.9 M), 244.9 M (209.4–286.4 M) and 142.2 M (23.6–855.0 M), respectively. LAEMIL, histamine and cimetidine were effective on acid secretion only when added to the serosal surface of the mucosa. Furthermore, simultaneous addition of LAEMIL and cimetidine at concentrations, per se, ineffective, caused a 16% reduction in the basal acid secretion [from 8.3±0.3 to 6.9±0.2 Eq g^–1 (15 min)^–1, n=4]. Although effects such as inhibition of histamine biosynthesis and/or histamine release can not be ruled out, our data suggest that LAEMIL, like cimetidine, reduces acid secretion in the isolated frog gastric mucosa by antagonising histamine H₂ receptors.Abbreviations LAEMIL Lyophilized aqueous extract of Maytenus ilicifolia leaves - Hist Histamine - Cim Cimetidine     

Coral growth in high-nutrient,low-pH seawater: a case study of corals cultured at the Waikiki Aquarium,Honolulu, Hawaii

Fifty-seven species of hermatypic corals have been maintained and grown in high-nutrient seawater at the Waikiki Aquarium, Honolulu, Hawaii. In this study we document the chemical conditions of aquarium water in terms of dissolved nutrients and carbon. Aquarium water is characterized by concentrations of inorganic nutrients that are high relative to most natural reef ecosystems: SiO₃ 200 M; PO₄ 0.6 M; NO₃ 5 M; NH₄ 2 M. In contrast, concentrations of organic nutrients are lower than most tropical surface ocean waters: DOP 0.1 M and DON 4 M. The incoming well-water servicing the facility has low pH, crating over-saturation of carbon dioxide. The coral communities in aquaria took up inorganic nutrients and released organic nutrients. Rates of nutrient uptake into aquaria coral communities were similar to nutrient uptake by natural reef communities. Coral growth rates were near the upper rates reported from the field, demonstrating corals can and do flourish in relatively high-nutrient water. The growth of corals does not appear to be inhibited at concentrations of nitrogen up to 5 M. Statements implying that corals can only grow in low nutrient oligotrophic seawater are therefore oversimplifications of processes that govern growth of these organisms. Some basic guidelines are given for maintenance of coral communities in aquaria.     

Regeneration of plantlets through organogenesis in the Himalayan yellow poppy,Meconopsis paniculata

Plantlet formation through organogenesis in callus cultures of Himalayan yellow poppy,Meconopsis paniculata D.Don (Prain), a threatened taxon of ornamental value, is described. Hypocotyl segments from 3-month-old laboratory-raised seedlings produced callus on agar-solidified Murashige and Skoog medium (MS) containing 10 M -naphthaleneacetic acid and 1 M kinetin. Shoots differentiated best from callus on MS containing 10 M indolebutyric acid (IBA) and 1 M 6-benzyladenine. The regenerated shoots rooted best on MS medium containing 10 M IBA. From seed germination to differentiation of plantlets through the two-step organogenesis process required 28–29 weeks.Abbreviations 2,4-d 2,4-dichlorophenoxyacetic acid - FAA formalin-acetic acid-alcohol - BA 6-benzyladenine - IAA indole-acetic acid - IBA indolebutyric acid - GA₃ gibberellic acid - NAA -naphthaleneacetic acid - RH relative humidity     

The role of intracellular zinc in modulation of life and death of Hep-2 cells

Varying intracellular concentrations of zinc in laryngeal Hep-2 cells in relation to changing cultivation conditions in vitro were determined by atomic absorption spectrophotometry. Upon standard cultivation in DMEM with 10% serum, the mean concentration of zinc was determined at 0.88 ± 0.09 g/mg protein, with substantially decreased values in the cells exposed to a low-serum medium. Next, the study of the effects of a series of physiological and supraphysiological concentrations of ZnSO₄ on laryngeal cells and their correlation with determined intracellular concentrations of zinc was performed. It was found that zinc concentrations above 100 M were toxic to Hep-2 cells, inducing cell death in the interval of 96 h as determined by videomicroscopy, selective nuclear staining, and immunofluorescence detection of caspase-3 and specific cytokeratin 18 fragment. Both types of cell death were observed, with apoptosis being induced at moderately toxic zinc concentration of 150 M and necrosis at higher zinc concentrations of 300 M and 750 M, respectively. Lower concentrations (1.5–100 M), on the other hand, did not produce any measurable changes in cell morphology and function in the same time interval. Zinc at concentration of 1.5 M was found to slightly enhance proliferation of Hep-2 cells up to the certain time point, which seemed to correlate with maximal tolerable momentary intracellular level of zinc. These results illustrate the importance of determining the intracellular levels of zinc when trying to characterize the effect of exogenous zinc on life and death of laryngeal cells.     

Water column and sediment nitrogen and phosphorus distribution patterns in the Florida Keys,USA

Measurements of the distribution patterns of nutrients (ammonium, nitrate, orthophosphate, total N and total P) and chlorophyll concentrations were conducted under an interdisciplinary program known as SEAKEYS, initiated because of concern that anthropogenic nutrients may be impacting Florida coral reefs. Samples were collected along transects that extended from passes or canals to 0.5 km offshore of the outermost reefs. Seven of the transects were either in the Biscayne National Park (BNP) and Key Largo (upper keys) or Seven Mile Bridge/Looe Key (upper part of lower keys) areas, which have the best present-day reef development; the two in the middle keys off Long Key were in an area of minimal reef development where passes allow estuarine Florida Bay water to flow onto the Florida reef platform. Off the upper keys, water column concentrations of N and chl a were elevated near marinas and canals (1 M NO₃, 1 g/l chl a), but returned to oligotrophic levels (e.g., chl a 0.25 g/l; NO₃ 0.25 M; NH₄ 0.10 M) within 0.5 km of shore. Phosphorus concentrations, however, were often higher offshore 0.2 M PO₄). Sediment interstitial nutrient concentrations decreased from inshore to the offshore reef areas (e.g., 100 M NH₄ inshore to 50 M NH₄ offshore) and were comparable to those of some presumably pristine coastal and reef carbonate sediments. Sediment bulk N was higher nearshore and decreased steeply offshore ( 60 g-at N/gm sediment to 20 g-at N/gm sediment, respectively); bulk P concentrations ( 6 g- at P/gm sediment) varied little or exhibited the reverse pattern. Sediment N:P ratios were consistently lower offshore (1–10 vs. 20–40 nearshore). Higher offshore P concentrations are attributed to periodic upwelling along the shelf edge. In the middle keys water column nutrients and chl a concentrations were both higher than those in the upper keys, and there was less of an inshore-offshore decrease than that noted in the upper keys. Sediment nutrients were higher also, and nearshore and offshore areas did not differ. Water column and sediment nutrient concentrations and distribution patterns in the upper part of the lower keys were most similar to those measured in the upper keys. Overall, the present data do not support the contention that reef areas in the upper keys are accumulating elevated loads of land-derived nutrients via surface water flow, but does document moderately elevated nutrient and chl a levels in many developed nearshore areas. Most of the anthropogenic and natural nutrients entering the coastal waters from shore appear to be taken up by near shore algal and seagrass communities before they reach patch reef areas. Further work is needed to determine whether nutrient-enriched ground waters reach the reefs, however these would be expected to cause an enrichment of reef sediments, which was not observed.     

In vitro comparison of ceftazidime,aztreonam, cefpirome,gentamicin, imipenem,enoxacin, and ticarcillin plus clavulanic acid against 108 strains ofPseudomonas maltophilia

Pseudomonas maltophilia is an uncommon cause of hospital-acquired infection and is resistant to most of the antimicrobial agents used in the treatment of gram-negative infections. Susceptibility of 108 isolates ofP. maltophilia to ceftazidime, aztreonam, defpirome, gentamicin, imipenem, enoxacin, and ticarcillin plus clavulanic acid was determined by an agar dilution method. The isolates were in general resistant to the antibiotics. Imipenem and cefpirome were not active at clinically achievable levels. Of the isolates, 20% were susceptible to 16 g/ml ceftazidime, 53% were susceptible to 4 g/ml enoxacin, 10% were susceptible to 4 g/ml gentamicin, and 25% were susceptible to 64 g/ml ticarcillin plus 2 g/ml clavulanic acid.