Isolation and purification of a vascular hyperreactivity factor from rabbit kidney cortex.

A compound capable of amplifying the threshold pressor response to norepinephrine (NE) was obtained from rabbit kidney cortex. This compound was purified and characterized using a series of techniques including gel filtration, ion exchange chromatography, preparative electrofocusing, HPLC, FAB mass spectrometry (FAB-MS), and Fourier transform infrared spectrometry. From this, an acid/heat stable (6N HC1, 160 degrees C, 24 hours), low molecular weight (ca 147) compound with a strong (+) charge density (Pi greater than 10) was identified.

Arrangement of nitrogenase structural genes in an aerobic filamentous nonheterocystous cyanobacterium.

Members of the marine filamentous, nonheterocystous cyanobacterial genus Trichodesmium not only are capable of fixing nitrogen aerobically in the light but when grown under a light-dark cycle will fix nitrogen only during the light phase. In this study, we constructed a restriction map of the structural nitrogen fixation genes (nifHDK) in Trichodesmium sp. strain NIBB 1067.

Unique modification of adenine in genomic DNA of the marine cyanobacterium Trichodesmium sp. strain NIBB 1067.

The genomic DNA of the marine nonheterocystous nitrogen-fixing cyanobacterium Trichodesmium sp. strain NIBB 1067 was found to be highly resistant to DNA restriction endonucleases. The DNA was digested extensively by the restriction enzyme DpnI, which requires adenine methylation for activity.

Amplification, cloning, and sequencing of a nifH segment from aquatic microorganisms and natural communities.

By use of the polymerase chain reaction and degenerate oligonucleotide primers for highly conserved regions of nifH, a segment of nifH DNA was amplified from several aquatic microorganisms, including an N2-fixing bacterium closely associated with the marine filamentous cyanobacterium Trichodesmium sp., a heterotrophic isolate from the root/rhizome of the seagrass Ruppia maritima, and the heterocystous freshwater cyanobacterium Anabaena oscillarioides. nifH segments were amplified directly from DNA extracted from the rhizosphere of roots of the seagrass Halodule wrightii.

Spontaneous rhythmic contractile behaviour of aortic ring segments isolated from pressure loaded regions of the vasculature.

Study Objective: The aim was to study contractile responses of segments of rat arteries taken from pressure loaded and pressure protected regions and to examine the role of endothelial derived factors on the spontaneous activity of pressure loaded ring segments.

Design: Rats were subjected to complete aortic coarctation between the origins of the renal arteries and allowed to recover for 8 d. After 8 d arterial pressures were measured in awake animals from the pressure loaded and pressure protected regions simultaneously.

Basis for Diel Variation in Nitrogenase Activity in the Marine Planktonic Cyanobacterium Trichodesmium thiebautii.

Natural populations of the nonheterocystous marine cyanobacterium Trichodesmium thiebautii exhibit a diel periodicity in nitrogenase activity (NA). NA "turns on" near dawn and "turns off" near dusk, independent of photic conditions. Chloramphenicol (CAP) and ammonium prevented turn on of NA in T.

Antiserum to Nitrogenase Generated from an Amplified DNA Fragment from Natural Populations of Trichodesmium spp.

A fragment of the nifH gene was amplified from natural populations of Trichodesmium spp. and cloned into a maltose-binding protein (MBP) expression vector. The peptide product of the amplified 359-bp fragment of nifH was cleaved from the fusion protein, purified, and used to generate a specific antibody to the Fe protein of nitrogenase.

Use of degenerate oligonucleotides for amplification of the nifH gene from the marine cyanobacterium Trichodesmium thiebautii.

Trichodesmium spp. are marine filamentous, nonheterocystous, nitrogen-fixing cyanobacteria which are an important component of marine ecosystems. This organism has never been maintained in axenic culture, and there has remained some doubt as to the identity of the organism responsible for nitrogen fixation in Trichodesmium aggregates.

Baroreflex modulation of ultradian oscillations of blood pressure and heart rate in unanesthetized dogs.

Telemetered, free-running dogs were studied to determine the role of cardiovascular control systems in modulation of ultradian oscillations of arterial pressure (MAP) and heart rate (HR). Data, aquired (2 Hz) by a stable telemetry system, was stored on a digital computer and analyzed for its harmonic content by a Fast Fourier Transform (FFT) algorithm. Both AP and HR consistently demonstrated rhythms having a period of from 0.

Autonomic modulation of ultradian blood pressure and heart rate oscillations in dogs.

Autonomic receptor modulation of ultradian oscillations of blood pressure and heart rate was studied in telemetered free-running dogs. Data, analyzed for their harmonic content by fast Fourier transform (FFT) methods, indicated that ultradian and circadian oscillations of 22.9 +/- 2.

Effects of Growth Irradiance and Nitrogen Limitation on Photosynthetic Energy Conversion in Photosystem II.

Photosynthetic energy conversion was investigated in five species of marine unicellular algae, (Dunaliella tertiolecta, Thalassiosira pseudonana, T. weisflogii, Skeletorema costatum, Isochrysis galbana) representing three phylogenetic classes, which were grown under steady state conditions with either light or inorganic nitrogen as a limiting factor. Using a pump and probe fluorescence technique we measured the maximum change in variable fluorescence yields, the flash intensity saturation curves for the change in fluorescence yields and the kinetics of the decay in fluorescence yields.

Statistical criteria for using short-term measurements as an index of 24-hour mean arterial pressure in unanesthetized unrestrained dogs.

This study assessed the statistical validity of short time-interval measurements as estimators of true 24 hour mean arterial pressure in unanesthetized, unrestrained dogs. 24 hour intra-arterial pressure recordings were obtained using a stable FM telemetry system. The 24 hour pressure measurements approximated a normal distribution whose variance was inversely related to the selected averaging interval.

Reduction of selenate to selenide by sulfate-respiring bacteria: experiments with cell suspensions and estuarine sediments.

Washed cell suspensions of Desulfovibrio desulfuricans subsp. aestuarii were capable of reducing nanomolar levels of selenate to selenide as well as sulfate to sulfide. Reduction of these species was inhibited by 1 mM selenate or tungstate.

Effect of autonomic agents on renin release in the turtle, Pseudemys scripta.

Experiments were conducted in the freshwater turtle, Pseudemys scripta, to study the effect of autonomic agents on the control of renin in this primitive species. The unique finding in these studies was that, unlike mammals, isoproterenol infusion fails to increase renin activity even though heart rate and arterial pressure patterns indicated that systemic responses were similar to that in mammals. On the other hand, acetylcholine (ACh) infusion resulted in a prompt threefold elevation (P less than 0.

Formation of methane and carbon dioxide from dimethylselenide in anoxic sediments and by a methanogenic bacterium.

Anaerobic San Francisco Bay salt marsh sediments rapidly metabolized [C]dimethylselenide (DMSe) to CH(4) and CO(2). Addition of selective inhibitors (2-bromoethanesulfonic acid or molybdate) to these sediments indicated that both methanogenic and sulfate-respiring bacteria could degrade DMSe to gaseous products. However, sediments taken from the selenium-contaminated Kesterson Wildlife Refuge produced only CO(2) from [C]DMSe, implying that methanogens were not important in the Kesterson samples.

The influence of renal sympathetic nerves on renal hemodynamic and renin responses during hypercapnia in dogs.

Studies were conducted in anesthetized dogs to examine the influence of the renal sympathetic nerves on renal hemodynamic and renin responses during controlled hypercapnia. The dogs were subjected to unilateral denervation and tested for their responses to hypercapnia induced by inhalation of 15% CO2 in air. Simultaneous measurements of the responses from both the denervated and innervated kidneys allowed an assessment of the influence of the renal nerves on the responses during acute hypercapnia.

Renin release in turtles: effects of volume depletion and furosemide administration.

To gain insight into the phylogenetic history of mechanisms controlling renin release, we conducted studies in the freshwater turtle Pseudemys scripta. Maneuvers known to stimulate renin release in mammals were evoked in the turtle, and the response was compared with that in mammals. Cumulative hemorrhage (30% blood vol) in anesthetized turtles failed to increase renin even though arterial pressure was reduced to 50% of control.

Inhibition of renin release following left circumflex bradykinin injection in dogs.

We examined the renin secretory response to bradykinin (BK) injection into the left circumflex coronary artery (LCx) in dogs. Studies were conducted in anesthetized, carotid sinus denervated dogs which had been maintained on a low sodium diet. A 25 ga needle was inserted into the LCx for injection of BK (0.

Characterization of the renin-angiotensin system in the turtle Pseudemys scripta.

Studies were conducted in freshwater turtles Pseudemys scripta to define some characteristics of the renin-angiotensin system in this reptile. Dialyzed acid-treated kidney extract (1 g tissue per ml water) produced a prolonged pressor response in unanesthetized turtles, which was eliminated by boiling the extract or by pretreating the turtle with [Sar1, Ile8]angiotensin II. A rat pressor assay was employed because turtle angiotensin (ANG) was bound poorly by the anti-[Asp1, Ile5, His9]ANG I used in our radioimmunoassay.

Ultradian oscillations in blood pressure and heart rate in free-running dogs.

A long-term (14-24 h) telemetry recording of mean arterial pressure (MAP) and heart rate (HR) was obtained from conscious unrestrained dogs (n = 9) maintained in a closed environment. MAP and HR records were analyzed for their harmonic content by the fast Fourier transform method. The power spectral density functions of MAP and HR clearly revealed the existence of coherent ultradian rhythms of MAP and HR with a period of 1-2 h.

Chemical structure of angiotensin in the turtle, Pseudemys scripta.

The chemical structure of angiotensin generated by incubating kidney extract with homologous plasma from the turtle, Pseudemys scripta, has been analyzed. The turtle angiotensin was proposed to be [Asp1, Val5, His9] ANG I by its amino acid composition and by its fluorescent peptide mapping. It was the same structure as angiotensin I in the ox and the sheep.

Role of calcium in the interaction of alpha and beta adrenoceptor-mediated renin release in isolated, constant pressure perfused rabbit kidneys.

These experiments were designed to study the role of calcium in the modulation of renin secretion by alpha and beta adrenoceptors. Rabbit kidneys were isolated and single-pass perfused with a modified Ringer's solution. Renal perfusion pressure was precisely controlled by an electronic servocontrol system.

Crystal-controlled telemetry system for long-term acquisition of physiological data.

A crystal-controlled telemetry system was developed for long-term high-reliability recording of blood pressure in unrestrained animals. The miniaturized transducer-transmitter system is powered by two lithium batteries that allow for more than 200 h of continuous recording of blood pressure before battery replacement. The total system has a flat frequency response of 0-25 Hz and a time stability of +/- 1 mmHg/day.

Central and peripheral adrenergic modulation of carotid sinus-induced renin release.

To study central and peripheral mechanisms that regulate the level of circulating renin during activation of the carotid sinus baroreflex, both carotid sinuses were isolated and perfused at constant flow in chloralase-anesthetized dogs. Sinus pressure was controlled by an adjustable reservoir while systemic pressure was stabilized using an external chamber. Arterial renin activity, measured by radioimmunoassay, was increased during sinus hypotension only if systemic pressure was held constant.

Acute inhibition of renin release during left circumflex coronary occlusion in dogs.

We examined the reflex effect of brief left circumflex coronary artery occlusion (CAO) on renal blood flow (RBF) and renin secretion (RS). Studies were conducted in alpha-chloralose-anesthetized dogs maintained on a salt-free diet for at least 3 days. A snare was placed around the left circumflex artery near its origin.