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G M Watson

Publications and source records attributed to G M Watson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Characterization of the genes encoding a phosphate-regulated two component sensory system in the marine cyanobacterium Synechococcus sp. WH7803.

An oligomer probe was designed to detect the presence of a putative phoB gene in the genome of the marine, phycoerythrin-containing cyanobacterium Synechococcus sp. WH7803. A 2.2 kb PstI fragment, identified using this probe, was cloned and the complete nucleotide sequence determined. The fragment contained two open reading frames encoding polypeptides which display all the sequence features expected of the response regulator and histidine protein kinase elements of a two component sensory system. Northern analysis confirmed that transcription of these genes was induced by phosphate limitation. On the basis of the sequence similarities and the regulation of their transcription by the availability of inorganic phosphate (Pi) these open reading frames were designated as phoB and phoR, respectively.

Amino Acid Sequence↗
PubMed1996

Regulation, unique gene organization, and unusual primary structure of carbon fixation genes from a marine phycoerythrin-containing cyanobacterium.

Marine phycoerythrin-containing cyanobacteria are major contributors to the overall productivity of the oceans. The present study indicates that the structural genes of the carbon assimilatory system are unusually arranged and possess a unique primary structure compared to previously studied cyanobacteria. Southern blot analyses of Synechococcus sp. strain WH7803 chromosomal DNA digests, using the ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) large subunit gene from Synechococcus sp. strain PCC6301 as a heterologous probe, revealed the presence of a 6.4 kb HindIII fragment that was detectable at only low stringency. Three complete open reading frames (ORFs) were detected within this fragment. Two of these ORFs potentially encode the Synechococcus sp. strain WH7803 rbcL and rbcS genes. The third ORF, situated immediately upstream from rbcL, potentially encodes a homologue of the ccmK gene from Synechococcus sp. strain PCC7942. The deduced amino acid sequences of each of these ORFs are more similar to homologues among the beta/gamma purple bacteria than to existing cyanobacterial homologues and phylogenetic analysis of the Rubisco large and small subunit sequences confirmed an unexpected relationship to sequences from among the beta/gamma purple bacteria. This is the first instance in which the possibility has been considered that an operon encoding three genes involved in carbon fixation may have been laterally transferred from a purple bacterium. Analysis of mRNA extracted from cells grown under diel conditions indicated that rbcL, rbcS and ccmK were regulated at the transcriptional level; specifically Rubisco transcripts were highest during the midday period, decreased at later times during the light period and eventually reached a level where they were all but undetectable during the dark period. Primer extension analysis indicated that the ccmK, rbcL and rbcS genes were co-transcribed.

Amino Acid Sequence↗
PubMed1996

The holmium: YAG laser for ureteric stones.

OBJECTIVE: To assess the efficacy of the pulsed holmium: YAG laser for the fragmentation of ureteric stones. PATIENTS AND METHODS: One hundred patients (72 males and 28 females, age range 14 months-85 years) underwent 114 ureteroscopic procedures using either a 7.2 F semi-rigid or 9.5 F flexible ureteroscope. A holmium: YAG laser (Sunrise Technologies. Fremont, Ca, USA) was used for laser lithotripsy at a maximum energy of 1.0 J/pulse at 5 Hz. Most of the stones (46%) were located in the upper third of the ureter. The mean size of the stones was 9 x 8 mm and the mean duration of the procedure was 73 min (including anaesthesia) with a mean hospital stay of 2.7 days. RESULTS: All the stones were accessed successfully using miniaturized endoscopes either retrogradely or antegradely. The holmium laser effectively fragmented all types of stones. Total clearance of all stones fragments was achieved in 87% of cases, with the best results obtained for stones in the lower third of the ureter (96%). The complications attributed directly to the laser included three strictures and three perforations of the ureteric wall. CONCLUSION: The holmium: YAG laser was effective in fragmenting ureteric stones irrespective of their hardness. However, it has the potential to damage the ureteric wall and must be used with caution.

Adolescent↗
PubMed1995

Chemoreceptor-mediated polymerization and depolymerization of actin in hair bundles of sea anemones.

Hair bundles located on tentacles of sea anemones are morphodynamic mechanoreceptors employed to regulate discharge of nematocysts into swimming prey. Activation of chemoreceptors for N-acetylated sugars is known to induce anemone hair bundles to elongate while shifting discharge to lower frequencies matching those produced by calmly swimming prey. In the continued presence of N-acetylated sugars, activation of proline receptors is known to induce hair bundles to shorten while shifting nematocyst discharge to higher frequencies presumed to correspond to movements produced by wounded, struggling prey. In the present study, N-acetylneuraminic acid (NANA) causes stereocilia to become more intensely fluorescent in confocal optical sections of phalloidin-stained specimens, suggesting that receptors for N-acetylated sugars initiate processes to increase the density of F-actin within stereocilia. Computer analysis of electron micrographs is consistent with this interpretation for large diameter stereocilia but not for small diameter stereocilia. In the continued presence of NANA, proline causes fluorescence intensity of phalloidin to decrease to or below control levels. DNaseI uniformly stains large diameter stereocilia, suggesting that these stereocilia contain a pool of G-actin. Fluorescence intensity of DNaseI in stereocilia is significantly less bright in specimens exposed to NANA alone than in specimens exposed to proline in the continued presence of NANA. It appears that whereas activated receptors for NANA induce G-actin to polymerize in large diameter stereocilia, activated receptors for proline induce F-actin to depolymerize, restoring G-actin pools.

Actins↗
PubMed1995

Experience with ureteroscopy in children.

OBJECTIVE: To present our experience of ureteroscopic procedures in children using miniaturized instrumentation. PATIENTS AND METHODS: Fourteen children aged between 13 months and 14 years underwent 20 ureteroscopic procedures. Semi-rigid 7.2 F and flexible 9.5 F ureteroscopes were used in a retrograde and an antegrade fashion. Eighteen ureteroscopies were performed retrogradely and two antegradely. Of the 20 ureteroscopic procedures, 18 were for stone disease, one for haematuria of unknown origin and one for removal of a migrated stent. The average size of the stone was 12.9 x 6.6 mm. RESULTS: Access using miniaturized ureteroscopes was successful in all patients. Dilatation was required only in 1 of 20 procedures. The management of stone disease in 10 of 13 children was straightforward and a single ureteroscopy was required to clear the ureters. In three of 13 children with stone disease the problems were more complex and nine ureteroscopies were undertaken to render the ureters stone free. Complications were stricture at the site of stone impaction (one patient), retention of urine due to a stone fragment in the urethra (one patient), haematuria (one patient) and migrated stent requiring ureteroscopy (one patient). CONCLUSION: In the hands of an experienced surgeon ureteroscopy can be used with equal success in children as in adults to treat calculus disease.

Adolescent↗
PubMed1994

Morphodynamic hair bundles arising from sensory cell/supporting cell complexes frequency-tune nematocyst discharge in sea anemones.

Discharge of nematocysts from cnidocytes occurs in response to appropriate chemical and mechanical stimulation. In sea anemone tentacles, activating chemoreceptors for N-acetylated sugars shifts maximal discharge into vibrating targets to low frequencies corresponding to prey movements and induces hair bundles to elongate by approximately 1-2 microns. Until now, only indirect, correlative evidence linked these two events. Using cytochalasin D, we provide evidence that bundle elongation is necessary for the frequency shift. Moreover, we find that only bundles associated with sensory cell/supporting cell complexes elongate with chemosensitization, and not bundles associated with cnidocyte/supporting cell complexes as was previously thought. Cytochemical labeling of sensory cells, purported to be bipolar neurons connected to the nerve net, suggests that sensory cells may interconnect with each other and with cnidocytes. Taken together, these findings are incompatible with the classical view that cnidocytes are independent effectors of nematocyst discharge and, furthermore, implicate the involvement of morphodynamic neurons in fine-tuning vibration-dependent discharge of nematocysts into swimming prey.

Animals↗
PubMed1994

Evidence for calcium channels involved in regulating nematocyst discharge.

In the tentacles of sea anemones, nematocyst discharge is regulated by cnidocyte/supporting cell complexes (CSCCs) of which three functional types have been identified: A, B and C. Type A CSCCs respond to contact by vibrating targets. Types B and C CSCCs respond to contact by static targets. Whereas type C CSCCs respond to contact alone, type B CSCCs require that surface chemoreceptors bind ligands before becoming responsive. Reducing Ca2+ levels in artificial seawater to below 1 mM inhibits discharge from each type of CSCC. The calcium channel inhibitors, nifedipine or verapamil, selectively inhibit discharge from type B CSCCs. The calcium channel activator, Bay K-8644, mimics the biphasic dose response of type B CSCCs to natural chemosensitizers such as N-acetylated sugars. Discharge from type A CSCCs is unaffected by inhibitors of L-type calcium channels, but is selectively inhibited by the aminoglycoside antibiotics, gentamicin and streptomycin. While each type of CSCC requires extracellular calcium, the calcium channels employed may vary according to CSCC type.

Aminoglycosides↗
PubMed1993

ATP induces large quaternary rearrangements in a cage-like chaperonin structure.

BACKGROUND: The chaperonins, a family of molecular chaperones, are large oligomeric proteins that bind nonnative intermediates of protein folding. They couple the release and correct folding of their ligands to the binding and hydrolysis of ATP. Chaperonin 60 (cpn60) is a decatetramer (14-mer) of 60 kD subunits. Folding of some ligands also requires the cooperation of cpn10, a heptamer of 10 kD subunits. RESULTS: We have determined the three-dimensional arrangements of subunits in Rhodobacter sphaeroides cpn60 in the nucleotide-free and ATP-bound forms. Negative stain electron microscopy and tilt reconstruction show the cylindrical structure of the decatetramer comprising two rings of seven subunits. The decatetramer consists of two cages joined base-to-base without a continuous central channel. These cages appear to contain bound polypeptide with an asymmetric distribution between the two rings. The two major domains of each subunit are connected on the exterior of the cylinder by a narrower bridge of density that could be a hinge region. Binding of ATP to cpn60 causes a major rearrangement of the protein density, which is reversed upon the hydrolysis of the ATP. Cpn10 binds to only one end of the cpn60 structure and is visible as an additional layer of density forming a cap on one end of the cpn60 cylinder. CONCLUSIONS: The observed rearrangement is consistent with an inward 5-10 degrees rotation of subunits, pivoting about the subunit contacts between the two heptamers, and thus bringing cpn60 domains towards the position occupied by the bound polypeptide. This change could explain the stimulation of ATPase activity by ligands, and the effects of ATP on lowering the affinity of cpn60 for ligands and on triggering the release of folding polypeptides.

Journal Article↗
PubMed1993

Developments in the ureteroscopes, techniques and accessories associated with laser lithotripsy.

Two stages in the development of the technique of laser lithotripsy are described. In the first series, spanning 1985-1988, three consecutive groups of patients are compared. In the first 100 patients, 11.5-F ureteroscopes were used. Access on first retrograde attempt was successful in 73%; 3% developed strictures; the ureteric perforation rate was 7%; and 12% required nephrostomy drainage. These results contrast with those of the third group in this series, consisting of 200 patients using a miniaturised ureteroscope. Access on the first retrograde attempt was successful in 99%. There were no strictures, no perforations and no requirements for nephrostomy drainage. (The second group of 100 patients using a range of rigid ureteroscopes was intermediate in its complication rate: 2% developed strictures, the ureteric perforation rate was 3%, and 6% required nephrostomy drainage). In the second series, spanning 1989-1990, the procedures were performed by all grades of urologists using miniaturised endoscopes. An in-depth audit was performed and each patient was followed until completely clear of fragments. The stones were successfully accessed on the first attempt in 213 cases (89%). In group A (139 patients, no basket used) 32 renal units (23%) were cleared of stone fragments immediately following the procedure, rising to 78 units (56%) by 3 months and 99 units (71%) beyond 3 months follow-up. Some fragments remained in 40 renal units and were cleared by further ureteroscopy, ESWL or PCNL, with the exception of 1 patient who had small residual fragments despite ESWL for fragments flushed to the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Prostatic heat treatments for urinary outflow obstruction.

A nonrandomized pilot study was done of 139 patients with symptomatic benign prostatic hyperplasia treated with 3 prostatic heating devices. Of the patients 19 underwent transrectal hyperthermia with the Biodan Prostathermer and in 15 the Primus Prostate Machine was used. At 2 1/2 years 7 of 19 patients (37%) patients in the Prostathermer group and 6 of 15 (40%) in the Primus group had adequate sustained improvement and had not undergone further treatment. At 1 year 55 of 100 patients (55%) treated with the Thermex-II section transurethral thermotherapy unit had a satisfactory result, with 40 (40%) having undergone transurethral resection of the prostate. The number of patients who failed therapy increased with each followup. Analysis of pretreatment parameters, including patient age, prostate size, peak urinary flow rate, post-void residual urine volume and symptom score, did not predict a successful outcome. Although these devices have minimal effect on peak urinary flow rate, a subset of patients enjoy symptomatic improvement.

Aged↗
PubMed1993

Nonvisual laser lithotripsy aided by plasma spectral analysis: viability study and clinical application.

Nonvisual laser lithotripsy implies laser fragmentation without the aid of endoscopic or direct vision. Using the laser delivery fiber for retrograde transmission of plasma spectrum and its analysis on an optical multichannel analyzer, we designed a project with the objective of identification and fragmentation of calculi by continuous analysis of the plasma feedback spectrum. We were successful in achieving the objectives in the in vitro and ex vivo studies. In the in vivo studies we successfully recorded the plasma spectrum of the stones from inside the ureter and monitored the process of fragmentation with the laser. We have been able to identify the problems for its clinical application. We conclude that by monitoring the feedback spectrum of plasma emission, nonvisual laser lithotripsy is reliable and safe, and can be used successfully in patients with some modifications. Its development is not to replace established endoscopic lithotripsy procedures but rather as an additional armament for the urologist in special situations. Also, the technique can be further exploited for a variety of clinical uses.

Humans↗
PubMed1993

Laser prostatectomy: our initial experience of a technique in evolution.

Recently great interest has been generated in alternatives to transurethral resection for benign prostatic hyperplasia. Lasers are currently being assessed, but marketing has for the moment outstripped basic science. A cystoscopic approach was used delivering Nd:YAG or KTP laser energy via forward and sidefiring fibers and contact tip devices in 51 patients. The sidefiring device is intended to coagulate a volume of prostate that subsequently sloughs, leaving a cavity. Treatment of the apical and middle lobe tissue using this technique was unsatisfactory. A further disadvantage was the interval between treatment and improvement in urine flow, which was approximately 6 weeks. The use of temporary prostatic stents has helped to overcome this delay in treatment effect. Encouraging early results have been achieved using forward-firing fibers to treat apical and middle lobe tissue. The use of contact tip devices to perform bloodless prostatotomies in combination with sidefire or bare fiber has also proved useful. Laser prostatectomy is an exciting field with considerable potential but remains in the developmental stage.

Aged↗
PubMed1993

New trends in the treatment of benign prostatic hyperplasia and carcinoma of the prostate.

Benign prostatic hyperplasia (BPH) is a very common condition affecting over 800,000 American males each year. A standard, effective, and well-proven therapy is prostatectomy. This surgical procedure is used to treat, in the United States, approximately 400,000 BPH patients annually. Major treatment benefit is expected in 70% to 80% of patients. Complications are seen in 20% of the surgically treated patients. Due to the advanced age of BPH patients and the presence of other serious coexisting medical problems, surgical therapy may be difficult to utilize. These patients, who present a high risk for surgery, are in need of alternative treatments. Alternative therapy in BPH patients with clinically important symptoms and signs of urinary outflow obstruction include treatment with pharmacological agents, balloon dilatation, laser beam therapy, transurethral thermal therapy, transrectal microwave hyperthermia, and transurethral microwave hyperthermia. These alternative treatment modalities are currently under intensive study. These new treatment modalities ultimately must be compared with the standard treatment, which is prostatectomy. Due to the unpredictable natural history of BPH, it is desirable that each Phase III study should contain a no-treatment observation-only arm. Adenocarcinoma of the prostate (CaP) has become a tumor, which first in frequency, and second in importance in cancer mortality statistics of American males. Local tumor control rates and long-term survivals, with radical prostatectomy or radiation therapy, have been excellent. There was, however, recent concern regarding a high incidence of microscopic local tumor recurrence following a definitive course of irradiation. Deep regional or intracavitary hyperthermia (HT) with phase steering may be of value as an adjuvant treatment to radiotherapy. This HT may increase the incidence of local tumor control obtained with radiotherapy. Phase I-II clinical studies are currently underway.

Adrenergic alpha-Antagonists↗