Search PubMed⌕ Search

Biomedical subjects

G Griffith

Publications and source records attributed to G Griffith.

16 recordsLinked to original sources
PubMed1999

Early assembly step of a retroviral envelope glycoprotein: analysis using a dominant negative assay.

As for most integral membrane proteins, the intracellular transport of retroviral envelope glycoproteins depends on proper folding and oligomeric assembly in the ER. In this study, we considered the hypothesis that a panel of 22 transport-defective mutants of the human T cell leukemia virus type 1 envelope glycoprotein might be defective in ER assembly. Upon cell cotransfection with wild-type envelope, however, the vast majority of these transport-defective mutants (21 of 22) exerted a specific trans-dominant negative effect. This effect was due to random dimerization of the mutated and wild-type glycoproteins that prevented the intracellular transport of the latter. This unexpected result suggests that association of glycoprotein monomers precedes the completion of folding. The only mutation that impaired this early assembly was located at the NH2 terminus of the protein. COOH-terminally truncated, soluble forms of the glycoprotein were also trans-dominant negative provided that their NH2 terminus was intact. The leucine zipper-like domain, although involved in oligomerization of the envelope glycoproteins at the cell surface, did not contribute to their intracellular assembly. We propose that, at a step subsequent to translation, but preceding complete folding of the monomers, glycoproteins assemble via their NH2-terminal domains, which, in turn, permits their cooperative folding.

Amino Acid Substitution↗
PubMed1998

Water content and glycosaminoglycan disaccharide concentration of the canine meniscus.

OBJECTIVE: To determine the regional composition of water and glycosaminoglycan (GAG) disaccharides of the canine meniscus. SAMPLE POPULATION: 52 menisci from the stifle of dogs. PROCEDURE: Regional sections of each meniscus were weighed, dried, and reweighed to determine water content. Dried tissue specimens were subjected to enzymatic digestion. Analysis and quantification of disaccharide degradation products were performed, using high-performance liquid chromatography. RESULTS: Water content was approximately 65% in polar and central regions of the canine meniscus. Water content of the central region of the lateral meniscus was significantly higher than that of the medial meniscus (P = 0.0090). Chondroitinase digestion of canine meniscal tissue yielded detectable delta Di-HA, delta Di-4S, and delta Di-6S GAG disaccharides. Disaccharides specific to dermatan sulfate and chondroitin D or E sulfate were not detected. Concentrations of delta Di-4S and delta Di-6S were significantly greater in the lateral central region, compared with the medial central region (P = 0.0005 and 0.0002, respectively). CONCLUSION: Water content and delta Di-4S and delta Di-6S concentrations were significantly lower in the central region of the medial meniscus, compared with the central region of the lateral meniscus. Reduced tissue hydration of the medial central region may have been a direct result of its overall decrease in total GAG content. CLINICAL RELEVANCE: The ability to evaluate subtle differences in tissue GAG composition by analytical measurement of their constituent disaccharides may aid in the understanding of the complex material properties of the normal and diseased meniscus, which may be applied to the study of meniscal healing and biomechanics.

Animals↗
PubMed1996

Isolation and characterization of alpha 1-protease inhibitor from canine plasma.

OBJECTIVE: To improve a previously described purification process by producing a higher yield and purity of alpha 1-protease inhibitor (alpha 1-PI) from canine plasma. ANIMALS: Plasma pool from 10 clinically normal male dogs. PROCEDURE: Canine alpha 1-PI was purified by use of ammonium sulfate precipitation, ion-exchange chromatography, and 3 affinity chromatographic procedures: concanavalin A-Sepharose, thiol, and hemoglobin-Sepharose. Characterization was performed by gel electrophoresis, isoelectric focusing, and immunoblot analysis. The N-terminal amino acid sequence was obtained by use of the Edman degradation method and a gas amino acid sequencer. RESULTS: Canine alpha 1-PI was purified with a yield of approximately 7% and a 54-fold increase in specific inhibitory activity. The inhibitor had a molecular weight of 59,000 and had 2 major patterns after isoelectric focusing: fast and intermediate in homozygous and/or heterozygous forms. Edman degradation revealed glutamic acid as the starting amino acid from the N-terminal sequence. Homologies of the N-terminal sequence of canine alpha 1-PI with those of sheep, horse, and human alpha 1-protease inhibitors were 54, 46, and 41%, respectively. CONCLUSIONS: Canine protease inhibitor is analogous to the alpha 1-protease inhibitors of sheep, human beings, and mice in terms of molecular weight, amino acid composition, and inhibitory activity against trypsin. Although the method described had a yield of 7%, the final product retained inhibitory activity and was pure. CLINICAL RELEVANCE: The availability of pure canine alpha 1-PI, as well as the specific antibodies, will facilitate studies on the fecal excretion and structural heterogeneity of this protein in dogs with naturally acquired protein-losing enteropathy.

Amino Acid Sequence↗
PubMed1996

A clinical, genetic and audiological study of patients and families with unilateral vestibular schwannomas. I. Clinical features of neurofibromatosis in patients with unilateral vestibular schwannomas.

Ninety-three patients with unilateral vestibular schwannomas were examined in a clinical, genetic and audiological study, to determine whether they had features associated with neurofibromatosis Type 1 or neurofibromatosis Type 2. In 91 families, one patient only was found to be affected with a unilateral vestibular schwannoma. Patients did have a few café-au-lait macules, but fewer than six in number. None of the patients satisfied the cutaneous diagnostic criteria for neurofibromatosis Type 1. Neither Lisch nodules nor presenile posterior subcapsular lenticular opacities or cortical opacities were a feature. Five patients with unilateral vestibular schwannomas are described where the clinical findings raised the possibility of neurofibromatosis Type 2. It is suggested that certain individuals with unilateral vestibular schwannomas are at risk of developing neurofibromatosis Type 2. Furthermore, the possibility of neurofibromatosis Type 2 should be considered if more than one individual in a family is found to be affected with a unilateral vestibular schwannoma.

Adolescent↗
PubMed1994

Out-of-hours workload of junior and senior house surgeons in a district general hospital.

The objective of this study was to assess the out-of-hours workload of junior and senior house officers in general surgery working in a busy DGH in relation to the 'New Deal' guidelines on junior doctors' hours of work. We also wanted to identify safe levels of manning for these grades of staff and to collect accurate data on workload upon which decisions could be made regarding any change in manning levels consequent upon the 'New Deal'. The study is a prospective audit of all work undertaken by 11 junior and senior house surgeons attached to six consultants between 1700 hrs and 0800 hrs during a 16-day period in August 1992. The results showed that the out-of-hours workload of the five JHOs and six SHOs proved to be very onerous. The rotas were 1:5 or 1:6 for emergencies depending on grade plus 1:11 for ward cover. The JHOs were occupied for 70 per cent of the period between 1700 hrs and 2400 hrs and 32.5 per cent of the period after 2400 hrs. For the same periods the SHOs were busy for 61 per cent and 29 per cent respectively. The doctors covering ward duties were occupied for 48 per cent of the period up to midnight when the duty period ended. Both grades got four hours sleep on five of 16 nights. Non-medical tasks accounted for 29 per cent of the ward doctors working time but were a small part of the other doctors work. It was concluded that in this typical busy DGH junior and senior house officers work extremely hard when on call, and that they cannot be reasonably be asked to further increase their level of activity. It follows that a reduction in the hours of work will require additional staff if the standard of care delivered to the patients is to be maintained.

Hospitals, District↗
PubMed1993

Isolation of an inhibitor of tumor necrosis factor-alpha-mediated cytotoxicity liberated from chemotaxin-stimulated equine white blood cell populations.

Objectives of this investigation were to extract and isolate protein fractions inhibitory to the cytotoxic properties of tumor necrosis factor-alpha (TNF-alpha). In this context, mixed populations of WBC were harvested from equine blood and were stimulated with a combination of a synthetic chemotactic peptide and a calcium ionophore. Several methods were subsequently applied for the initial preparation of cell-free crude protein extracts, including fractional precipitation with gradient concentrations of ammonium sulfate and preparative-scale isoelectric focusing. In addition, protein fractions were harvested from extracts of concentrated equine urine. Protein extracts of urinary origin were further separated by gel-filtration column chromatography. Identification of protein fractions possessing properties inhibitory to the cytotoxic characteristics of TNF-alpha was facilitated by a tissue culture-based technique for the biological assay of TNF-alpha-mediated cytotoxicity. Purified protein extracts possessed a marked ability to inhibit or neutralize the cytotoxic properties of TNF-alpha, on the basis of survival of murine fibrosarcoma cell populations, compared with appropriate negative and positive reference controls. Relative purity of inhibitors and estimation of approximate molecular weight were established by conventional reducing and nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Equine inhibitory protein fractions from mixed WBC populations, purified in the manner described, had molecular weights of 70,000 to 80,000 and 28,000. An analogous protein fraction of 28 kDa also was isolated from equine concentrated urine. Estimated isoelectric point of TNF-alpha inhibitor protein fractions was between pH of 5.5 and 6.1. These physical characteristics of equine TNF-alpha inhibitor protein fractions were similar to those described for a membrane-associated TNF-alpha receptor protein shed from chemotaxin- and calcium-ionophor-stimulated human WBC populations.

Animals↗
PubMed1990

Malignant left-sided large bowel obstruction managed by subtotal/total colectomy.

Of 60 patients presenting with acute obstructing carcinoma of the left colon, 49 underwent immediate resection either by radical subtotal/total colectomy (31 patients, group I) or by radical segmental resection (18 patients, group II) of whom three had immediate anastomosis after on-table bowel irrigation and 15 had a planned staged procedure. The operative mortality rate was 3 per cent in group I and 11 per cent in group II (not a statistically significant difference). However, substantial differences were found for major morbidity (6 versus 44 per cent in groups I and II respectively; P less than 0.01) and mean length of hospital stay (17 days in group I versus 35 days in group II; P less than 0.05). All three patients who had on-table lavage developed anastomotic leaks which necessitated a second operation to form a stoma. Six patients (19 per cent) in group I required antidiarrhoeal medication in the immediate postoperative period. However, subsequent improvement in stool frequency was noted in all patients. It is concluded that subtotal/total colectomy is an acceptable means of managing patients with obstructing carcinoma of the left colon in that it is associated with a low morbidity and mortality rate and good functional results.

Aged↗
PubMed1989

Altered laryngeal function following thyroidectomy.

The laryngograph was used to record and compare the voice changes in 11 thyroidectomy patients and 14 controls. The frequency histogram was studied and the change in its spread following surgery used to identify abnormal vocal fold movements due to recurrent laryngeal nerve damage. It also demonstrated changes which occur in thyroidectomy patients and not in patients having other operations. The possible causes include external laryngeal nerve damage.

Adult↗
PubMed1988

Plasma lipoproteins in neonatal, preruminant, and weaned calf.

This study compared plasma lipoprotein fraction profiles and lipid composition in the calf at 3 d, 3 wk, and 12 wk (weaned). For all ages the major plasma lipoprotein fraction was high density lipoproteins (52 to 73%), followed by very high density lipoproteins (10 to 22%), low density lipoproteins (13 to 18%), and chylomicrons plus very low density lipoproteins (5 to 9%). Most plasma lipid was cholesterol esters (41 to 49%) and phosphatidylcholine (21 to 29%). Most cholesterol esters (66 to 81%) and phosphatidylcholine (68 to 80%) were in high density lipoproteins; free fatty acids (83 to 96%) and lysophosphatidylcholine (75 to 85%) in very high density lipoproteins; and triglycerides (93 to 98%) in the remaining lipoprotein fractions. Of the three ages studied, 3-d-old calves had comparatively low plasma total lipids, high density lipoproteins, cholesterol esters, phosphatidylcholine, and linoleic acid in all lipid classes; they had relatively high plasma very high density lipoproteins, triglycerides, free fatty acids, phosphatidylethanolamine, and 20:3 n-9 fatty acid (indicative of essential fatty acids deficiency). Lipoprotein classes and lipid composition were similar at wk 3 and 12. Comparison of fatty acid profiles for phosphatidylcholine with those for lysophosphatidylcholine and cholesterol esters indicated plasma lecithin-cholesterol acyltransferase was active in calves at all three ages studied.

Aging↗
PubMed1982

A clinical assessment of fluorescence polarisation changes in lymphocytes stimulated by phytohaemagglutinin (PHA) in malignant and benign diseases.

The modified double-zone SCM technique, developed in these laboratories as an in vitro test for cancer, is based on the differential response to PHA of lymphocytes harvested from two regions of a Ficoll-Triosil gradient. Lymphocyte responses are measured by changes in intracellular fluorescein fluorescence polarisation. We report its continued clinical evaluation in patients hospitalised with malignant and non-malignant diseases, including a blind trial of 78 patients with disorders of the gastrointestinal tract, breast and lung. Overall "false' negative and "false' positive rates from 336 blood samples were 1.8 and 3.3% respectively.

Adult↗
PubMed1979

Isolation and concentration of organophosphorus pesticides from drinking water at the ng/L level, using macroreticular resin.

A screening method has been developed for determining organophosphorus pesticides at ng/L levels in drinking water. Sixteen organophosphorus pesticides, diazinon, diazinon-oxon, dimethoate, ronnel, beta-phosphamidon, methyl parathion, ethyl parathion, malathion, chlorpyrifos, fenitrothion, ruelene, methidathion, ethion, EPN, phosalone, and phosmet, were extracted by Amberlite XAD-2 resin from 100 and 200 L drinking water previously spiked with these pesticides. The pesticides were eluted from the XAD-2 resin with acetone-hexane (15+85). The concentrated extract was analyzed by gas chromatography using a nitrogen-phosphorus selective detector and by gas chromatography-mass spectrometry using selected ion monitoring. Recoveries at the 10 and 100 ng/L spiking levels were greater than 90%, except recoveries for dimethoate and phosphamidon were 37 and 42%, respectively. The analysis of 300 L Ottawa tap water showed no detectable amounts (less than 1 ng/L) of any of the 16 organophosphorus pesticides.

Chromatography, Gas↗