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Biomedical subjects

K Watson

Publications and source records attributed to K Watson.

At least 91 records · Page 5Linked to original sources
PubMed1993

Diagnosis and incidence of delayed pressure urticaria in patients with chronic urticaria.

BACKGROUND: The incidence of delayed pressure urticaria (DPU) may have been underestimated, particularly in patients with widespread wheals of concurrent idiopathic urticaria, because of difficulty in recognizing the association between pressure-related swellings and the preceding physical stimulus. Diagnostic tests for DPU have not been done routinely in studies of urticaria and have not been compared. OBJECTIVE: Our purpose was to establish the incidence of DPU and other physical urticarias in patients with chronic urticaria and to compare two reproducible pressure challenge tests. METHODS: One hundred thirty-five patients were tested for immediate dermographism, for DPU and, when indicated by the history, for cholinergic and/or cold urticaria. In patients with pressure-related symptoms, pressure challenge testing with a dermographometer (100 gm/mm2) was compared with a test that involves the application of 1.5 cm diameter weighted rods and more closely resembles a naturally occurring pressure stimulus. RESULTS: Physical urticarias were present in 96 patients (71%). Thirty patients (22%) had immediate dermographism, 50 (37%) had DPU, 15 (11%) had cholinergic urticaria, and 3 (2%) had cold urticaria. A 70-second pressure challenge with the dermographometer gave results comparable to the use of the weighted rods. CONCLUSION: DPU appears to be more common in chronic urticaria than previously reported and is present in some patients who do not report pressure-related wheals.

Adolescent↗
PubMed1993

The need for consistent nomenclature and assessment of growth phases in diauxic cultures of Saccharomyces cerevisiae.

The need for consistent nomenclature and accurate assessment of late growth phases in diauxic yeast cultures is highlighted by the substantial variation of stress tolerance in Saccharomyces cerevisiae after the exhaustion of the initial fermentable carbon source. At present, a wide variety of assessment methods and confused terminology exists in the literature, leading to difficulties in the interpretation and comparison of published results. A method based on the depletion of ethanol accumulated during the respiro-fermentative growth phase is suggested as suitable for assessing subsequent growth phases and reporting results. Consistent application of nomenclature for growth phases is recommended to assist the interpretation of published experimental results. It is suggested that the phases of growth in diauxic batch culture should be referred to using the terms (1) initial lag phase, (2) respiro-fermentative phase, (3) diauxic lag phase, (4) respiratory phase, (5) stationary phase, and (6) death phase.

Fermentation↗
PubMed1993

Role of growth phase and ethanol in freeze-thaw stress resistance of Saccharomyces cerevisiae.

The freeze-thaw tolerance of Saccharomyces cerevisiae was examined throughout growth in aerobic batch culture. Minimum tolerance to rapid freezing (immersion in liquid nitrogen; cooling rate, approximately 200 degrees C min-1) was associated with respirofermentative (exponential) growth on glucose. However, maximum tolerance occurred not during the stationary phase but during active respiratory growth on ethanol accumulated during respirofermentative growth on glucose. The peak in tolerance occurred several hours after entry into the respiratory growth phase and did not correspond to a transient accumulation of trehalose which occurred at the point of glucose exhaustion. Substitution of ethanol with other carbon sources which permit high levels of respiration (acetate and galactose) also induced high freeze-thaw tolerance, and the peak did not occur in cells shifted directly from fermentative growth to starvation conditions or in two respiratorily incompetent mutants. These results imply a direct link with respiration, rather than exhaustion of glucose. The role of ethanol as a cryoprotectant per se was also investigated, and under conditions of rapid freezing (cooling rate, approximately 200 degrees C min-1), ethanol demonstrated a significant cryoprotective effect. Under the same freezing conditions, glycerol had little effect at high concentrations and acted as a cryosensitizer at low concentrations. Conversely, under slow-freezing conditions (step freezing at -20, -70, and then -196 degrees C; initial cooling rate, approximately 3 degrees C min-1), glycerol acted as a cryoprotectant while ethanol lost this ability. Ethanol may thus have two effects on the cryotolerance of baker's yeast, as a respirable carbon source and as a cryoprotectant under rapid-freezing conditions.

Cryoprotective Agents↗
PubMed1992

Relationships between thermotolerance, oxidative stress responses and induction of stress proteins in human tumour cell lines.

Thermotolerance, resistance to oxidative stress and induction of stress proteins were examined in a panel of 10 human tumour cell lines. An inverse relationship was indicated between intrinsic thermotolerance (cell survival after treatment at 43.5 degrees for 3 hr) and thermotolerance induced by pretreatment at 42.5 degrees for 30 min. Similar levels of induction of hsp 70 were found in cell lines with high or low levels of intrinsic thermotolerance; induction of other stress proteins could not be detected. Cell survival following treatment with H2O2 correlated with that following streptonigrin treatment (P < 0.05). Pretreatment with buthionine sulphoximine or diamide synergistically increased the toxicity of heat, H2O2 and streptonigrin whereas reduced glutathione had the reverse effect. No direct correlation was found, however, between tolerance to heat and to oxidative stress, and hsp 70 was not induced by the latter. The stress protein heme oxygenase, detected by immunoblotting with the monoclonal antibody HO, was induced by H2O2 in melanoma cell lines but not in HeLa. Cadmium and arsenite ions, however, readily induced heme oxygenase in HeLa, indicating that in these cells induction of heme oxygenase by oxidative stress involves a different mechanism. Overall, the results suggest that tolerance to heat or oxidative stress in these cell lines may not necessarily be associated with the induction of heat shock proteins or heme oxygenase but that cell survival after both types of stress depends to a certain extent on cellular sulphydryls.

Adaptation, Physiological↗
PubMed1991

The involvement of transcriptional read-through from internal promoters in the expression of a novel endoglucanase gene FSendA, from Fibrobacter succinogenes AR1.

Two distinct mRNA transcripts were synthesized in Escherichia coli during expression of FSendA, an endoglucanase gene from Fibrobacter succinogenes AR1. Expression of FSendA required a ribosomal frameshift between open reading frame 1 (ORF1) and ORF2 to allow contiguous translation of a 453 amino acid protein (1). The primary transcript initiated upstream of ORF1 and the secondary transcript from within ORF1. Both transcripts terminated downstream of ORF2 and termination was essential for endoglucanase expression. Deletion of the primary transcript promoter region allowed read-through of the secondary transcript beyond the terminator region, indicating that a component of the intact FSendA gene allowed efficient transcription termination. The possibility of autogenous regulation by translation products is suggested.

Amino Acid Sequence↗
PubMed1991

Molecular cloning, expression, and characterization of endoglucanase genes from Fibrobacter succinogenes AR1.

A cosmid gene library was constructed in Escherichia coli from genomic DNA isolated from the ruminal anaerobe Fibrobacter succinogenes AR1. Clones were screened on carboxymethyl cellulose, and 8 colonies that produced large clearing zones and 25 colonies that produced small clearing zones were identified. Southern blot hybridization revealed the existence of at least three separate genes encoding cellulase activity. pRC093, which is representative of cosmid clones that produce large clearing zones, was subcloned in pGem-1, and the resulting hybrid pRCEH directed synthesis of endoglucanase activity localized on a 2.1-kb EcoRI-HindIII insert. Activity was expressed from this fragment when it was cloned in both orientations in pGem-1 and pGem-2, indicating that F. succinogenes promoters functioned successfully in E. coli. A high level of endoglucanase activity was detected on acid-swollen cellulose, ball-milled cellulose, and carboxymethyl cellulose; and a moderate level was detected on filter paper, Avicel, lichenan, and xylan. Most activity (80%) was localized in the periplasm of E. coli, with low but significant levels (16%) being detected in the extracellular medium. The periplasmic endoglucanase had an estimated molecular weight of 46,500, had an optimum temperature of 39 degrees C, and exhibited activity over a broad pH range, with a maximum at pH 5.0.

Bacteroides↗
PubMed1991

endAFS, a novel family E endoglucanase gene from Fibrobacter succinogenes AR1.

The complete nucleotide sequence of endAFS, an endoglucanase gene isolated from the ruminal anaerobe Fibrobacter succinogenes AR1, was determined. endAFS encodes two overlapping open reading frames (ORF1 and ORF2), and it was proposed that a -1 ribosomal frameshift was required to allow contiguous synthesis of a 453-amino-acid endoglucanase. A proline- and threonine-rich region at the C terminus of ORF1 and rare codons for arginine and threonine were coincident with the proposed frameshift site. ENDAFS is proposed to be a member of subgroup 1 of family E endoglucanases, of which endoglucanases from Thermomonospora fusca and Persea americana (avocado) are also members. Endoglucanases from Clostridium thermocellum and Pseudomonas fluorescens form subgroup 2.

Amino Acid Sequence↗
PubMed1991

Primary pancreatic tuberculosis.

A 71-year-old man developed weight loss, nausea, and night sweats. A PPD skin test was positive; chest films were normal. Abdominal computerized tomography revealed a mass in the head of the pancreas. Laparotomy revealed a 3 cm by 5 cm multi-loculated abscess cavity. Cultures grew Mycobacterium tuberculum. The diagnostic criteria for abdominal tuberculosis include skin test positivity, localized disease, and culture verification. This is the first reported case that fulfills diagnostic criteria for primary pancreatic tuberculosis.

Aged↗
PubMed1990

Microbial stress proteins.

There is general agreement that a function, perhaps the major function, of stress proteins under normal physiological conditions is to help assembly and disassembly of protein complexes and to catalyse protein-translocation processes. It remains unclear, however, as to what role these processes play in stressed cells. It could be that cells under stress produce abnormal, misfolded or otherwise damaged proteins and that increased synthesis of stress proteins is required to counter protein modifications. A role for stress proteins in recovery of cells from stress, as opposed to a role in helping cells to withstand a lethal stress, is thus suggested. The intracellular location of stress proteins, in the unstressed and stressed cell, is worthy of further studies. Members of the hsp70 family are associated with the cytosol, mitochondria and endoplasmic reticulum. There is evidence, particularly from studies on mammalian cells (Tanguay, 1985; Welch and Mizzen, 1988; Arrigo et al., 1988), that following stress hsps migrate to various cellular compartments and subsequently delocalize after stress. However, there is little comparable data from microbial systems for this phenomenon (e.g. Rossi and Lindquist, 1989). The question as to the role of stress proteins in the transient acquisition of thermotolerance remains to be answered. It is insufficient to equate the kinetics of stress-protein synthesis with acquisition of thermotolerance. Quantitative data on the amount of stress protein present at various times, including the recovery period, is required. The demonstration that microbial stress proteins are important antigenic determinants of micro-organisms causing major debilitating diseases in the world is an exciting observation. Studies on the interplay of pathogen and host, both carrying similar antigenic hsp determinants, will be a challenging area for future research. It is likely that E. coli and Sacch. cerevisiae, with their well-established biochemical and genetic properties, will continue to be the experimental systems of choice for studies on stress proteins. On the other hand, it is encouraging that studies on other micro-organisms have expanded in the past few years and have made substantial contributions towards our understanding of the stress response. The ubiquitous nature of the stress response and the remarkable evolutionary conservation of the stress proteins continue to be attractive areas for research.

Bacterial Proteins↗
PubMed1989

Induction of angiogenesis during the transition from hyperplasia to neoplasia.

It is now well established that unrestricted growth of tumours is dependent upon angiogenesis. Previous studies on tumour growth, however, have not revealed when or how the transition to an angiogenic state occurs during early tumour development. The advent of transgenic mice carrying oncogenes that reproducibly elicit tumours of specific cell types is providing a new format for studying multi-step tumorigenesis. In one of these models, transgenic mice expressing an oncogene in the beta-cells of the pancreatic islets heritably recapitulate a progression from normality to hyperplasia to neoplasia. We report here that angiogenic activity first appears in a subset of hyperplastic islets before the onset of tumour formation. A novel in vitro assay confirms that hyperplasia per se does not obligate angiogenesis. Rather, a few hyperplastic islets become angiogenic in vitro at a time when such islets are neovascularized in vivo and at a frequency that correlates closely with subsequent tumour incidence. These findings suggest that induction of angiogenesis is an important step in carcinogenesis.

Adenoma, Islet Cell↗
PubMed1989

Cerebellar astrocytomas in elderly patients with very long preoperative histories: report of three cases.

Three patients, ages 69, 67, and 74 years, respectively, underwent surgical removal of cystic cerebellar astrocytomas. All three had past histories pointing to the existence of a cerebellar lesion for many decades prior to surgery: Patient 1 had had nystagmus on lateral gaze on the side of the tumor since early childhood; Patient 2 had had sensorineural hearing loss on the side of her neoplasm for 38 years preceding the operation; and Patient 3 was diagnosed as having a brain tumor 51 years before the operation. (He has been blind because of pressure hydrocephalus for half a century, but otherwise managed to live a productive farming and family life until he sustained a head injury in a car accident, which forced him to undergo removal of his cerebellar tumor.) The neoplasms in all three instances were found by histological examination to be low-grade astrocytomas. These cases indicate that low-grade cerebellar astrocytomas, which are well known for their characteristically long postoperative courses, may at times manifest a slow growth potential with an exceptionally long preoperative course.

Aged↗
PubMed1989

Aging, immunity, and critical care nursing.

Age-related changes of the immune system along with underlying disease can reduce the elderly patients' chances of survival in critical care. Complications can be minimized when the health care team responds not only to the needs of the critically ill patient, but also to the needs specific to the elderly patient.

Aged↗
PubMed1986

Loss of heat-shock acquisition of thermotolerance in yeast is not correlated with loss of heat-shock proteins.

Yeast cells when subjected to a primary heat shock, defined as a temperature shift from 23 to 37 degrees C for 30 min, acquired tolerance to heat stress (52 degrees C/5 min). Primary heat shocked cells incubated at 23 degrees C for up to 3 h, progressively lost thermotolerance but retained high levels of the major heat-shock proteins as observed on polyacrylamide gels. On the other hand, a temperature shift back up to 37 degrees C for 30 min fully restored thermotolerance. The major high-molecular-mass heat-shock proteins (hsp) identified were of approximate molecular mass 100 kDa (hsp 100), 80 kDa (hsp 80) and 70 kDa (hsp 70). The results indicate that loss of heat-shock acquisition of thermotolerance is not correlated with loss of heat-shock proteins.

Heat-Shock Proteins↗
PubMed1986

Controlled clinical trial of ranitidine in bleeding peptic ulcer.

One hundred and two patients were entered into a controlled, randomized clinical trial to assess the value of ranitidine versus placebo, given immediately after entry to hospital to modify the outcome of patients admitted to hospital with acute bleeding from peptic ulceration of the stomach or duodenum. The results indicated that ranitidine could not significantly modify the blood requirements, rebleeding rate or operation rate in this patient population during the initial hospital admission.

Clinical Trials as Topic↗