Urease activity in blue-green algae.

The apparent enzymatic hydrolysis of urea has been detected in whole blue-green algae and in cell extracts. Urease is present as an intracellullar component in cultures in which no bacterial contaminants are found. The activity in the cells was recovered from the extracts.

The human uterotubal junction: a scanning electron microscope study during different phases of the menstrual cycle.

Uterotubal junctions from surgically extirpated human uteri were examined. The specimens were obtained during different phases of the menstrual cycle. The interstitial portions of the tubes together with the cornual areas were dissected, excised, and their luminal surfaces exposed. The specimens were then processed for scanning electron microscopy. The surface epithelium of both the cornual endometrium and interstitial endosalpins. Ciliated cells were more numerous in the endosalpinx. Cyclic changes in ciliated cells were minimal, while cyclic secretory activity was demonstrated, especially in the endometrium. The transitional area between the endometrium and the endosalpinx was characterized by a marked increase in the number of ciliated cells, and a tendency of the secretory cells to assume a flattened, polygonal shape. These morphologic features suggest a possible role in the transport and/or maintenance of spermatozoa and/or ova.

PIP: Uterotubal junctions from hysterectomy specimens, obtained at different phases of the menstrual cycle, were examined by scanning electron microscopy. Ciliated and secretory cells, with common morphologic characteristics, were observed in the surface epithelium of both the cornual endometrium and interstitial endosalpinx, with ciliated cells being dominant in number in the endosalpinx. Changes in ciliated cells were minimal during the menstrual cycle, though secretory cell act ivity was apparent, particularly in the endometrium. A considerable inc rease in the number of ciliated cells was observed in the transitional area between the endosalpinx and the endometrium. There was also a tendency of the secretory cells to assume a flattened, polygonal shape in the same region. The observed changes are suggestive of a possible role of the uterotubal junction in the transport of maintenance of spermatozoa or ova.

Comparison of the stability of phycocyanins from thermophilic, mesophilic, psychrophilic and halophilic algae.

Protein unfolding of eight different phycocyanins was investigated utilizing circular dichroism and visible spectra. The phycocyanin samples were extracted from algae that are normally found in vastly different environments, and are classified as mesophilic, thermophilic, halophilic and psychrophilic. The ability of these proteins to resist the denaturant urea is in the order of thermophile greater than mesophile, halophile greater than psychrophile. Based on a two-state approximation the apparent free energies of protein unfolding at zero urea denaturant concentration, deltaGH2Oapp, were found to range from 2.4 to 8.8 kcal/mole for the eight phycocyanins at pH 6 and 25 degrees C. The proteins from the thermophile are generally more stable than those from the mesophile. An extra stability of the halophile is believed due to the specific interaction of the proteins and the ions in solution. A correction for deltaGH2Oapp due to minor amino acid differences reveals that the stability and the structural properties of these proteins are primarily affected by this minor difference in amino acid compositions.

Comparative thermodynamic elucidation of the structural stability of thermophilic proteins.

Differential scanning calorimetry, circular dichroism, and visible absorption spectrophotometry were employed to elucidate the structural stability of thermophilic phycocyanin derived from Cyanidium caldarium, a eucaryotic organism which contains a nucleus, grown in acidic conditions (pH 3.4) at 54 degrees C. The obtained results were compared with those previously reported for thermophilic phycocyanin derived from Synechococcus lividus, a procaryote containing no organized nucleus, grown in alkaline conditions (pH 8.5) at 52 degrees C. The temperature of thermal unfolding (t(d)) was found to be comparable between C. caldarium (73 degrees C) and S. lividus (74 degrees C) phycocyanins. The apparent free energy of unfolding (DeltaG([urea]=0)) at zero denaturant (urea) concentration was also comparable: 9.1 and 8.7 kcal/mole for unfolding the chromophore part of the protein, and 5.0 and 4.3 kcal/mole for unfolding the apoprotein part of the protein, respectively. These values of t(d) and DeltaG([urea]=0) were significantly higher than those previously reported for mesophilic Phormidium luridum phycocyanin (grown at 25 degrees C). These findings revealed that relatively higher values of t(d) and DeltaG([urea]=0) were characteristics of thermophilic proteins. In contrast, the enthalpies of completed unfolding (DeltaH(d)) and the half-completed unfolding (DeltaH(d)) 1 2 for C. caldarium phycocyanin were much lower than those for S. lividus protein (89 versus 180 kcal/mole and 62 versus 115 kcal/mole, respectively). Factors contributing to a lower DeltaH(d) in C. caldarium protein and the role of charged groups in enhancing the stability of thermophilic proteins were discussed.

Denaturation of phycocyanin by urea and determination of the enthalpy of denaturation by microcalorimetry.

Denaturation of the protein phycocyanin in urea solution was investigated by microcalorimetry, ultraviolet and visible spectroscopy, circular dichroism and sedimentation equilibrium. The results consistently demonstrated that in the presence of 7 M urea this protein is completely denatured. By assumings a two-state mechanism, an apparent free energy of unfolding at zero denaturant concentration, (formula: see text) was found to be 4.4 kcal/mole at pH 6.0 and 25 degrees C. By microcalorimetry the enthalpy of denaturation of phycocyanin app was found to be -230 kcal/mole at 25 degrees C. The relatively large negative enthalpy change results from protein unfolding and changes in protein solvation.

ULTRASTRUCTURE OF THE THERMOPHILIC BLUE-GREEN ALGA, SYNECHOCOCCUS LIVIDUS COPELAND(1).

The ultrastructure of Synechococcus lividus Copeland, a thermophilic blue-green alga, was studied in thin sections. The cell envelope reveals striking similarities with that of some gram-negative bacteria. In contrast to bacteria and to many other species of blue-green algae, ribosomes are predominantly found in the central nuclear region and appear to be associated with the DNA fibrils. Thylakoids (photo-synthetic lamellae) are arranged as concentric shells, around the nuclear equivalent, lying nearly parallel to one another and to the plasma membrane. Both plasma and thylakoidal membranes, as described by other authors for different Cyanophyceae, are of the unit membrane dimension and morphology. Various types of intracellular inclusions are found: (1) Lipid inclusions, located in the cytoplasm are similar to the osmiophilic globules of higher plant chloroplasts. (2) Polyphosphate inclusions (or volutin) resembling those of other species are generally found at the cell poles but within the nuclear region. (3) Polyhedral inclusions also located in the nuclear region are clearly recognized to be different from the polyphosphate bodies, but their function remains unknown.

Medical research in Israel and the Israel biomedical database.

The data collected for the second edition of the Directory of Medical Research in Israel and the Israel Biomedical Database have yielded very relevant information concerning the distribution of investigators, publication activities and funding sources. The aggregate data confirm the findings of the first edition published in 1996 [2]. Those facts endorse the highly concentrated and extensive nature of medical research in the Jerusalem area, which is conducted at the Hebrew University and its affiliated hospitals. In contrast, Tel Aviv University, whose basic research staff is about two-thirds the size of the Hebrew University staff, has a more diffuse relationship with its clinical staff who are located at more than half a dozen hospitals. Ben-Gurion University in Beer Sheva and the Technion in Haifa are smaller in size, but have closer geographic contact between their clinical and basic research staff. Nonetheless, all the medical schools and affiliated hospitals have good publication and funding records. It is important to note that while some aspects of the performance at basic research institutions seem to be somewhat better than at hospitals, the records are actually quite similar despite the greater burden of clinical services at the hospitals as compared to teaching responsibilities in the basic sciences. The survey also indicates the substantial number of young investigators in the latest survey who did not appear in the first survey. While this is certainly encouraging, it is also disturbing that the funding sources are apparently decreasing at a time when young investigators are attempting to become established and the increasing burden of health care costs precludes financial assistance from hospital sources. The intensity and undoubtedly the quality of medical research in Israel remains at a level consistent with many of the more advanced western countries. This conclusion is somewhat mitigated by the fact that there is a decrease in available funding and a measurable decrease in scholarly activity at a time when a new, younger generation of investigators is just beginning to become productive. In closing, we wish to stress that the collection of data for the Biomedical Database is a continuing project and we encourage all medical researches who may not have contributed relevant information to write to the Office of the Chief Scientist or contact the office by email.

Emerging infectious diseases: a cause for concern.

As the twenty-first century begins it becomes increasingly apparent that the twentieth century, which opened with the promise of the eradication of most infectious diseases, closed with the specter of the reemergence of many deadly infectious diseases that have a rapidly increasing incidence and geographic range. Equally if not more alarming is the appearance of new infectious diseases that have become major sources of morbidity and mortality. Among recent examples are HIV/AIDS, hantavirus pulmonary syndrome, Lyme disease, hemolytic uremic syndrome (caused by a strain of Escherichia coli), Rift Valley fever, Dengue hemorrhagic fever, malaria, cryptosporidiosis, and schistosomiasis. The reasons for this situation are easily identified in some cases as associated with treatment modalities (permissive use of antibiotics), the industrial use of antibiotics, demographic changes, societal behavior patterns, changes in ecology, global warming, the inability to deliver minimal health care and the neglect of well-established public health priorities. In addition is the emergence of diseases of another type. We have begun to characterize the potential microbial etiology of what has historically been referred to as chronic diseases.

Quantum phase tomography of a strongly driven qubit.

The interference between repeated Landau-Zener transitions in a qubit swept through an avoided level crossing results in Stückelberg oscillations in qubit magnetization, a hallmark of the coherent strongly driven regime in two-level systems. The two-dimensional Fourier transforms of the resulting oscillatory patterns are found to exhibit a family of one-dimensional curves in Fourier space, in agreement with recent observations in a superconducting qubit. We interpret these images in terms of time evolution of the quantum phase of the qubit state and show that they can be used to probe dephasing mechanisms.

Coherent quasiclassical dynamics of a persistent current qubit.

A new regime of coherent quantum dynamics of a qubit is realized at low driving frequencies in the strong driving limit. Coherent transitions between qubit states occur via the Landau-Zener process when the system is swept through an energy-level avoided crossing. The quantum interference mediated by repeated transitions gives rise to an oscillatory dependence of the qubit population on the driving-field amplitude and flux detuning. These interference fringes, which at high frequencies consist of individual multiphoton resonances, persist even for driving frequencies smaller than the decoherence rate, where individual resonances are no longer distinguishable. A theoretical model that incorporates dephasing agrees well with the observations.

Immunochemistry of biliproteins.

Biliproteins were extracted from representatives of the Cyanophyta, Rhodophyta, and Cryptophyta and purified. Both purified and crude biliproteins were used to stimulate rabbit antibody directed specifically against the biliproteins. The antigenic and immunogenic inter-relationships of these proteins were investigated by the Ouchterlony double diffusion technique. C-phycocyanins from all sources were found to be antigenically and immunogenically related and apparently also related to allophycocyanin but not to any of the phycoerythrins. Larger antigenic differences among phycoerythrins from different groups of algae were discovered. The role of aggregation of the individual biliproteins in their immunochemistry was characterized. Attempts were made to determine the phylogenetic significance of these results. The immunochemical aspects of the biliproteins were striking in that protein antigens from vastly different cell types were found to be closely related. This relationship may be interpreted as supporting the suggestion that Rhodophyta evolved from Cyanophyta or from some common ancestral stock.

Research in medical sciences in Israel, 1994-97, an overview of institutions, investigators, and funding.

This is a summary of the second effort to characterize medical research activities in Israel (1994-97). The study relies on responses to a questionnaire sent to all participants in the first survey (1991-94) and to additional, including younger, investigators. There were 1450 direct responses this time versus 1088 the first time. The distribution of investigators is 60% hospital-based versus 40% in basic sciences. The average number of funding sources per investigator has decreased from 2.6 to 2.2; however the percentage of funded investigators has increased from 60% to 70%. The greatest concentration of funded investigators remains at the Hebrew University and Hadassah Medical Center, followed by Tel Aviv University and associated hospitals. The Chief Scientist's Office of the Ministry of Health funds more than 40% of funded investigators (more than double the next highest funding source, the US-Israel Binational Fund), followed in decreasing order by the National Academy of Sciences, Ministry of Science, German-Israeli Foundation for Scientific Research and Development (GIF), Israel Cancer Society, and NIH. The percentage of funded hospital-based investigators has increased from 59% to 62%; however, funding remains higher for basic science investigators. There has been an increase in the percentage of Ph.D.'s working in a hospital environment and an interesting anomaly is that the nonacademic-affiliated Ph.D. investigators in hospitals have been successful in receiving funding, so now a greater percentage of nonacademic hospital staff are funded than academic staff (69% versus 61%).

Partial characterization of six chlorophyll a-protein complexes isolated from a blue-green alga by a nondetergent method.

The chlorophyll a-protein complexes of a blue-green alga, Phormidium luridum, are resolved in the absence of detergent, by the combination of a Sepharose 4B column and sucrose density gradient centrifugation, into six chlorophyll a-containing zones. These six complexes are termed here as F15, F25, F35, F40, F60, and F65, according to their appearance in the sucrose density gradient after centrifugation. The absorption spectra of these six isolated complexes are reported, as well as the fluorescence emission spectra at room temperature and liquid-nitrogen temperature. The F60 complex was enriched in Photosystem I, while the F35 and F40 complexes contained both Photosystem I and II. The F60 complex is the predominant band and accounts for about 49% of the total chlorophyll a of the cells. The extinction coefficient of this complex is determined to be 68.7 mM-1 cm-1 at 680 nm in 50 mM tris(hydroxymethyl)amino methane buffer at pH 8.0. In addition, the effect of the detergent, sodium dodecyl sulfate, on these spectra are also reported for comparison. The chemically induced difference spectra of F35, F40, and F60 complexes also indicate the presence of the reaction center, P700, of Photosystem I. These three complexes have been shown to contain P700 in a ratio of approximately one reaction center molecule per 100 light-harvesting chlorophyll molecules. The simple exposure of the F60 fraction to sodium dodecyl sulfate results in an "apparent" enhancement of the P700 to chlorophyll ratio to one P700 per 51 light harvesting chlorophyll. Room temperature electron spin resonance measurements of photooxidized F60 are consistent with the presence of P700 and with the chlorophyll/P700 ratio observed by chemical assay. The amino acid compositions of F60 and F65 complexes are studied. Gel electrophoresis patterns of these six isolated complexes are presented and are significantly different from those reported for detergent-treated chlorophyll-protein complexes.

Thermotropic Properties of Thermophilic, Mesophilic, and Psychrophilic Blue-green Algae.

Thermotropic properties of blue-green algae grown at high, room, and low temperatures in H(2)O and D(2)O media were studied by highly sensitive differential scanning microcalorimetry. The thermograms of these organisms contain an endothermal peak in the temperature range of 50 to 70 C with an endothermal heat ranging from 0.14 to 1.91 joules per gram organism. The temperature at which the endothermal peak occurs is comparable with the thermal denaturation temperature of phycocyanin, the major biliprotein isolated from these algae. A good correlation can be found for the relative thermal stability of various organisms with that of the isolated biliproteins. The ability of these algae to resist thermal disruption is correlated with the thermal environments in which these algal cells grow. The thermal stability of normal algae is in the order of thermophile > mesophile > psychrophile. It was found that the deuterated mesophilic algae were less able to resist thermal disruption than ordinary mesophilic algae.

Protein aggregation. Studies of larger aggregates of C-phycocyanin.

Aggregates of phycocyanin sedimenting at 17s, 22s and 27s are demonstrated to constitute more than 40% of crude blue-green-algal extracts, pH6.0 and I0.1, and are retained in highly purified preparations. Sedimentation-velocity studies of the large aggregates as a function of pH are reported. Sucrose-density-gradient experiments performed as a function of time of sedimentation indicate that: (1) with increasing time of sedimentation, the largest aggregates are dissipated at the leading protein boundary and the several phycocyanin species present are not completely resolved; (2) phycocyanin fractions with the largest aggregates exhibit the highest E(620)/E(280) ratio and the largest relative fluorescence efficiency. Gel-filtration experiments with Sephadex G-200 do not resolve the species completely, and reapplication of phycocyanin gel-filtration fractions to the column results in an elution pattern similar to the original, except that there is an enhancement of the allophycocyanin fraction and the amount of denatured protein. Increasing the sedimentation times in a sucrose density gradient also enhances the allophycocyanin fraction. Fluorescence results demonstrate that there are possibly three excitation maxima, one corresponding to the monomer (approx. 600mmu), one for higher aggregates (625-630mmu) and one for the allophycocyanin fraction (approx. 650mmu). Only a single fluorescence-emission band is detected, which is fairly symmetrical and which has a red shift with higher aggregation and with the appearance of allophycocyanin. The appearance of allophycocyanin may be correlated with the irreversible disaggregation of the largest phycocyanin species. It is suggested that the largest protein aggregates are in the size range of the biliprotein aggregates reported in electron microscopy of algal cells.