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Biomedical subjects

P Johnson

Publications and source records attributed to P Johnson.

At least 343 records · Page 19Linked to original sources
PubMed1991

Simplified single sample 13Carbon urea breath test for Helicobacter pylori: comparison with histology, culture, and ELISA serology.

There is no ideal method for detecting Helicobacter pylori. The 'standard' 13Carbon urea breath test (13C-UBT), which involves collecting eight to 15 breath samples and subsequent costly analysis, was modified by pooling 21 samples of expired breath taken at five minute intervals for 40 minutes into a collecting bag, from which a single 20 ml aliquot was taken and analysed by mass spectrometry. This test was evaluated on 50 patients after routine upper gastrointestinal endoscopy, and results were compared with those from the standard 13C-UBT, bacteriology, ELISA serology, and histology--the latter being taken as the gold standard. H pylori were seen in 34 of 50 (68%) patients (in three it was detected in biopsy specimens from the corpus alone). The modified 13C-UBT was positive (pooled excretion delta 13CO2 greater than 5 per mil) in 31 patients and negative in 19 (three false negative results), specificity was 100% (standard 13C-UBT 94%) and sensitivity 92% (standard 13C-UBT 93%). The modified 13C-UBT had a coefficient of variation within subjects of 3.7%. For the ELISA serology and culture the specificities were both 100%, but the sensitivities were 82% and 68% respectively. The 13C-UBT results correlated with the grade of histological gastritis. The modified 13C-UBT is simpler, cheaper, more reproducible, and provides an easy non-invasive method for the detection of H pylori.

Adult↗
PubMed1991

Uterine myoma causing uremia in a 15-year-old girl.

Uterine myoma leading to uremia in young women below 16 years of age is an extremely rare condition. On reviewing the literature we have not been able to find any case similar to the one described below.

Adolescent↗
PubMed1991

Thermoregulation and the control of breathing during non-REM sleep in the developing lamb.

This study investigates how metabolic rate, as required for thermoregulation, interacts with breathing control during development of the lamb. Fifteen lambs were studied sequentially at 4, 14, 30, 45 and 55 days of age. During each study they were maintained at ambient temperatures of 5, 10, 15, 20, 25 and 30 degrees C for at least 1 h before measurements were made during N-REM sleep. Basal oxygen consumption fell from 16.1 +/- 0.72 (+/- SEM) to 10.1 +/- 0.47 ml/min per kg between 4 and 55 days of age, while breathing frequencies fell from 52.3 +/- 4.4 to 32.4 +/- 1.6 breaths/min over this period. Ventilation increased as oxygen consumption increased on cooling below thermoneutrality. In 4 days-old lambs this was achieved by an increase in breath amplitude, whilst in older lambs breathing frequency also rose. As breathing frequency fell there was a greater incidence of expiratory laryngeal braking at thermoneutrality associated with lengthened expiratory time. The ambient temperature at which these effects occurred, together with panting thresholds, progressively changed with age as the upper and lower critical temperatures fell and the thermoneutral range widened during development. It is concluded that metabolic rate provides a powerful stimulus to breathing in infant lambs. As the metabolic stimulus decreases with age, basal breathing frequency falls and expiratory laryngeal braking becomes important not only to protect lung volume, but also, through airway mechanosensory reflexes, in regulating breath time. This interaction is also particularly apparent as the metabolic and respiratory requirements alter to meet changes in ambient conditions.

Age Factors↗
PubMed1991

The interaction of the upper airway and thermo-metabolism on respiratory rhythm during non-REM sleep in the developing lamb.

This study investigates the role of metabolic rate and of vagal airway mechanisms in sustaining rhythmic breathing in the developing lamb. Fifteen lambs were prepared, at 2 days of age under fluothane anaesthesia, for sequential studies at 4, 14, 30, 45, and 55 days of age. At each age they were maintained at an ambient temperature of 5, 10, 15, 20, 25 and 30 degrees C for at least one hour before measurements were made during N-REM sleep. In 6 lambs at 4 days and in all lambs at older ages the upper airway was by-passed (by opening a tracheal window) for 10-15 minutes at each ambient temperature. Oxygen consumption was unaffected by upper airway by-pass and there were no consistent changes in mean breathing frequency or amplitude, with the exception of shifts to panting at warm ambient temperatures. Breathing pattern was unaffected by upper airway by-pass in lambs at 4 days of age, but at older ages loss of regularity of breathing frequently occurred (up to 47% of 30 days-old lambs at 25 degrees C). This was related to the fall in oxygen consumption with age and to basal values at thermoneutrality, and coincided with lower respiratory rates and increased use of expiratory laryngeal braking. Periodic breathing (and apnea) of a fixed cycle length (9.3 +/- 0.36 s) was a common feature (62%) of the observed breathing dysrhythmia. In young lambs high metabolic rate sustained high frequency rhythmic breathing which was unaffected by upper airway by-pass.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1991

Antimetabolites.

Explore the source record for details and available documents.

Animals↗
PubMed1991

Regulation of insulin-like growth factor II gene expression by hepatitis B virus in hepatocellular carcinoma.

In this study we investigated the regulation of insulin-like growth factor II gene expression to explain a role for this growth factor in concert with hepatitis B virus involvement in the development of hepatocellular carcinoma from cirrhosis. Sections of normal liver and tumor and non-tumor-bearing liver disease tissue were hybridized in situ with [35S]-labeled insulin-like growth factor II oligonucleotide probe. Parallel sections were tested for presence of insulin-like growth factor II polypeptide using immunohistochemistry. To investigate a possible role for hepatitis B virus in insulin-like growth factor II gene expression in hepatocellular carcinoma, results were analyzed against patient seropositivity for hepatitis B virus. Levels of insulin-like growth factor II transcripts in normal liver (n = 4) sections and in those from non-tumor-bearing individuals (n = 10) were so low that specific signal was not detectable above homogeneous tissue background. In contrast, 4 of 8 (50%) of the sections of hepatocellular carcinoma arising from cirrhosis or noncirrhotic chronic liver disease with hepatitis B virus involvement showed increased expression of insulin-like growth factor II messenger RNA transcripts. Up-regulation was observed in cell foci in the hepatocellular regions of the surrounding cirrhotic lobular cells and the fibrous septa. Numerous cell foci were observed in patch distribution in the tumor areas. The level of insulin-like growth factor II messenger RNA transcripts in sections of hepatocellular carcinoma arising from cirrhotic and noncirrhotic tissues obtained from patients seronegative for hepatitis B virus was similar to that of normal liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Current therapy of major fungal diseases of the lung.

The treatment of the major systemic fungi encountered in the United States--Histoplasma capsulatum, Blastomyces dermatitides, and Coccidioides immitis--depends on an understanding of the natural history of disease. Clinical manifestations of these infections can range from an asymptomatic disease that requires no therapy to an illness that is incurable and requires long-term suppression with antifungal agents to produce a balanced host-to-parasite relationship. This article discusses the natural history of disease caused by H. capsulatum, B. dermatitides, and C. immitis and various clinical situations that require antifungal chemotherapy.

Antifungal Agents↗
PubMed1990

Limited bidirectional activity of two housekeeping gene promoters: human HPRT and PGK.

Typical of other housekeeping genes, the promoter for the human hypoxanthine phosphoribosyl transferase-encoding gene (HPRT) is G + C-rich, lacks a TATA box and has multiple transcription start points. To test the hypothesis that these features may result in relaxed control over the direction of transcription, we examined the effect of orientation on the ability of the HPRT promoter to control expression of the following reporter genes in transfected cells: luc (firefly luciferase), cat (bacterial chloramphenicol acetyltransferase) and neo (neomycin resistance). A 376-bp fragment containing the HPRT promoter efficiently expressed the luc gene irrespective of orientation, and the 5' ends of luciferase RNA produced in cells transfected with inverted promoter constructs mapped to within the HPRT promoter, indicating that the HPRT promoter has bidirectional activity. However, in the presence of two divergently-flanking reporter genes expression from the inverted HPRT promoter was only 10-20% compared to the noninverted orientation. Furthermore, the inverted HPRT promoter expressed cat less well than luc, and was unable to express neo sufficiently well to produce any colonies under appropriate selection conditions. Attempts to detect endogenous divergent HPRT transcripts were unsuccessful. The promoter of another housekeeping gene, encoding 3-phosphoglycerate kinase (PGK), expressed moderate levels of cat (40%) but not luc (less than 5%) in the inverted orientation. By comparison, two TATA-box containing promoters functioned extremely poorly when inverted. This study indicates that two plasmid-borne housekeeping promoters have at least a limited potential for bidirectional activity, but the functional significance of this is unclear if the corresponding endogenous housekeeping promoters express divergent transcripts at similarly low levels. The poor activity of the HPRT and PGK promoters in the inverted orientation suggests that there is a mechanism which influences the direction of transcription from these promoters.

Chloramphenicol O-Acetyltransferase↗
PubMed1990

Inhibitory effects of spermine and spermidine on muscle calpain II.

The muscle enzyme calpain II, in contrast to muscle calpain I, was markedly inhibited by millimolar concentrations of the polyamines spermine and spermidine. These compounds and the calpain inhibitor calpastatin had synergistic inhibitory effects on calpain II. These results suggest that the polyamines may have possible regulatory effects on the in vivo activity of calpain II enzymes.

Animals↗
PubMed1990

Recurrent spontaneous abortion and polycystic ovarian disease: comparison of two regimens to induce ovulation.

OBJECTIVE: To determine whether pituitary suppression before induction of ovulation reduces the rate of spontaneous abortion in women with polycystic ovarian disease and primary recurrent spontaneous abortions. DESIGN: Closed, randomised, sequential trial. Pairs of women were allocated to each treatment by the toss of a coin. SETTING: Supraregional clinic for women who had had recurrent spontaneous abortions. SUBJECTS: Forty two women with polycystic ovarian disease and primary recurrent spontaneous abortions. INTERVENTIONS: Ovulation was induced by clomiphene or pituitary suppression with buserelin followed by pure follicle stimulating hormone. MAIN OUTCOME MEASURES: Preference for a particular treatment was noted. A preference occurred when one woman in a pair had a successful pregnancy (defined as one of over 12 weeks' gestation) and one had a spontaneous abortion; the preference was for the treatment resulting in the successful pregnancy. RESULTS: Spontaneous abortions occurred in 11 of 20 women given clomiphene compared with two of 20 who had pituitary suppression. Eleven preferences were found for buserelin and two for clomiphene. In seven pairs both women had successful pregnancies. One pair was discarded because one of the women did not become pregnant. The ratio of luteinising hormone concentration to follicular diameter was found to be a possible diagnostic indicator of spontaneous abortion. CONCLUSION: Pituitary suppression before induction of ovulation significantly reduces the risk of spontaneous abortion in women with polycystic ovarian disease and primary recurrent spontaneous abortions.

Abortion, Habitual↗
PubMed1990

Intraoperative radiation of canine carotid artery, internal jugular vein, and vagus nerve. Therapeutic applications in the management of advanced head and neck cancers.

As a step in the application of intraoperative radiotherapy (IORT) for treating advanced head and neck cancers, preliminary information was obtained on the radiation tolerance of the canine common carotid artery, internal jugular vein, and vagus nerve to a single, high-dose electron beam. Both sides of the neck of eight mongrel dogs were operated on to expose an 8-cm segment of common carotid artery, internal jugular vein, and vagus nerve. One side of the neck was irradiated, using escalating doses of 2500, 3500, 4500, and 5500 cGy. The contralateral side of the neck served as the unirradiated control. At 3 and 6 months after IORT, one dog at each dose level was killed. None of the dogs developed carotid bleeding at any time after IORT. Light microscopic investigations using hematoxylin-eosin staining on the common carotid artery and internal jugular vein showed no consistent changes that suggested radiation damage; however, the Masson trichrome stain and hydroxyproline concentration of irradiated common carotid artery indicated an increase in the collagen content of the tunica media. Marked changes in the irradiated vagus nerve were seen, indicating severe demyelination and loss of nerve fibers, which appeared to be radiation-dose dependent. Four patients with advanced recurrent head and neck cancer were treated with surgical resection and IORT without any acute or subacute complications. The role of IORT as a supplement to surgery, external beam irradiation, and chemotherapy in selected patients with advanced head and neck cancer needs further exploration.

Animals↗
PubMed1990

Fluorescence spectroscopic analysis of calpain II interactions with calcium and calmodulin antagonists.

1. The intrinsic fluorescence of epoxysuccinyl-inhibited calpain II undergoes a Ca2(+)-dependent decrease which contrasts with the increase observed for calmodulin. 2. Calpain II was inhibited by the calmodulin antagonist toluidinylnaphthalenesulfonate (TNS), and a Ca2(+)-dependent increase in TNS fluorescence intensity was observed for epoxysuccinyl-inhibited calpain II. 3. The calmodulin antagonists calmidazolium CDZ and felodipine both caused decreases in the intrinsic fluorescence of epoxysuccinyl-inhibited calpain II. 4. Increasing concentrations of Ca2+ caused an increase in the fluorescence intensity of the inhibited enzyme in the presence of (CDZ), and a decrease in the presence of felodipine. 5. It is concluded from these studies that Ca2+ and calmodulin antagonists induce conformational changes in calpain II, and that changes occur in regions other than the Ca2(+)-binding domains.

Binding Sites↗
PubMed1990

Calpains (intracellular calcium-activated cysteine proteinases): structure-activity relationships and involvement in normal and abnormal cellular metabolism.

1. Calpains (calcium-activated cysteine proteinases) have evolved by gene fusion events involving calmodulin-like genes, cysteine proteinase genes and other sequences of unknown origin. 2. The enzymes are composed of two non-identical subunits, each of which contains functional calcium-binding sequences. 3. Calpains are inhibited by the endogenous protein inhibitor, calpastatin and some calmodulin antagonists are also inhibitors of calpain. A number of synthetic proteinase inhibitors also inhibit calpains. 4. Calpains can be activated by phospholipids, an endogenous protein activator and some amino acid derivatives. 5. Various protein substrates for calpains have been recognized in vitro, but the identity of in situ substrates remains unclear. 6. Proposals have been made for calpain function, including involvement in signal transduction, platelet activation, cell fusion, mitosis and cytoskeleton and contractile protein turnover. 7. Calpain and calpastatin expression is altered in a number of abnormal states including muscular dystrophy, muscle denervation and tenotomy, hypertension and platelet abnormalities.

Animals↗
PubMed1990

Effects of calcium and calmodulin antagonists on calpain II subunit conformations.

Only the 80-kD catalytic subunit of smooth muscle calpain II shows a change in intrinsic fluorescence on binding calcium, but both the 80-kD and 30-kD subunits show fluorescence changes in bound toluidinyl-naphthalenesulphonate as a result of calcium binding. Both subunits also show changes in intrinsic fluorescence in the presence of calmidazolium and felodipine. These studies indicate that both subunits have binding sites for calcium and the calmodulin antagonists, which are probably located in the calmodulin-like domain of each subunit.

Animals↗