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G Perkins

Publications and source records attributed to G Perkins.

At least 37 records · Page 2Linked to original sources
PubMed1997

Three-dimensional structure of the gap junction connexon.

The gap junction membrane channel is composed of macular aggregations of intercellular channels permitting the direct intercellular transfer of ions and small molecules. Each intercellular channel is formed by the apposition of two hexameric transmembrane channels (connexons), one from each cell. The interlocking of the two channels occurs extracellularly in a narrow 2.5-nm "gap" separating the junctional membranes. The channel-channel interaction is known to be selective between members of the family of proteins, called connexins, which oligomerize into the connexons. In addition to selectivity, the molecular interfaces involved in the extracellular interactions between connexons must be very congruent, since the intercellular channel must provide high resistances to the leakage of small ions between the channel lumen and the extracellular space. By using a recently developed biochemical procedure for obtaining ordered arrays of connexons from gap junctions split in the extracellular gap, (Ghoshroy, S., D. A. Goodenough, and G. E. Sosinsky. 1994. Preparation, characterization, and structure of half gap junctional layers spit with urea and EGTA. J. Membr. Biol. 146:15-28) a three-dimensional reconstruction of a connexon has been obtained by electron crystallographic methods. This reconstruction emphasizes the structural asymmetry between the extracellular and cytoplasmic domains and assigns lobed structural features to the extracellular domains of the connexon. The implication of our hemichannel structure is discussed in relation to the in vivo state of unpaired connexons, which have been shown to exist in the plasma membrane.

Animals↗
PubMed1996

Immunocytochemical staining of cytologic specimens. How helpful is it?

The contribution of immunocytochemical (ICC) staining to the diagnosis of a range of cytologic specimens reported over a 20-month period was retrospectively assessed. A total of 194 cases (1.6% of total workload) were stained for diagnostic purposes in this period. Immunocytochemical staining was determined to be helpful in 75.8% of cases. In body fluid cases (105), staining was most often performed to assist with the discrimination of mesothelial cells and metastatic malignancy. Immunocytochemical staining was helpful in 82% of fluid specimens, with the preliminary diagnosis confirmed in 64%, refined in 8%, and revised in 10% of cases. In fine-needle aspiration (FNA) specimens, staining was helpful in 69%, resulting in a refinement of diagnosis in 55%, and confirming the preliminary diagnosis in 14%. The preliminary diagnosis was revised in a single FNA case. Immunocytochemical staining was particularly valuable in assisting the subclassification of poorly differentiated malignancies. A more precise diagnosis was possible following consideration of ICC results in 68% of cases with a preliminary diagnosis of poorly differentiated malignancy. Immunocytochemical staining was also helpful in identifying the primary site of metastatic carcinoma in six FNA cases. It is concluded that the selective use of well-chosen panels of antibodies can be very helpful in resolving diagnostic difficulties in cytologic specimens. In particular, ICC may be an invaluable aid to the diagnosis of difficult serous effusion specimens and in the sub-typing of poorly differentiated malignancy.

Antibodies↗
PubMed1996

Use of a virulence-associated protein based enzyme-linked immunosorbent assay for Rhodococcus equi serology in horses.

An enzyme-linked immunosorbent assay (ELISA) was developed against Rhodococcus equi using Triton X-114 detergent extracted whole cell material, in which the virulence associated protein (VapA) predominated. Enzymelinked immunosorbent assay titres corresponded to antibody reacting with VapA on Western blots. There was considerable variation in antibody titres of nonimmunised mares and in the time when the colostrally derived antibody of their foals had declined to low or undetectable titres. In general, antibodies in foals declined to their lowest levels at age 4-8 weeks. Seroconversion occurred in foals age 8-10 weeks, but the precise time depended on maternal titre and the month in which the foal was born. Foals reaching age 8 weeks in late summer showed more marked seroconversion than foals born earlier. The ELISA was used to follow the response to immunisation with the same Triton X-114 extracted material. Six mares immunised before parturition with the antigen in aluminium hydroxide adjuvant developed high titres, up to > 102,400 and transferred them to their foals through colostrum. Their foals responded to immunisation with 0.5-1.0 mg antigen 3, 5, 7 and 9 weeks after birth. Antibody titres following immunisation with similar dosage reached up to > 102,400 in a separate group of foals of nonimmunised mares. Nonvaccinated control foals seroconverted at age 6-8 weeks. The VapA based ELISA is useful to follow the course of natural infection with R. equi or immunisation with VapA based antigen.

Actinomycetales Infections↗
PubMed1992

The addition of pethidine to epidural bupivacaine in labour--effect of changing bupivacaine strength.

The effects of varying the strength of bupivacaine used in epidurals for the relief of labour pain was examined. The trial randomly allocated sixty women in the first stage of labour to one of three groups. All women were of ASA status 1 or 2 and had uncomplicated pregnancies. Subjects in each group received pethidine 25 mg in 10 ml of either 0.125%, 0.1875%, or 0.25% bupivacaine. Pain scores for each patient were then assessed over the following thirty minutes. Duration of analgesia and subsequent dose requirements were examined. No difference in pain scores between groups at thirty minutes after injection of the test solutions was found. The 0.25% solution group did however have a more rapid onset of analgesia with the majority of patients in this group achieving their maximum effect between ten and twenty minutes after injection. Duration of analgesia was not prolonged by using the stronger solutions. This study suggests that when epidural pethidine 25 mg is added to local anaesthetic solutions of bupivacaine, adequate analgesia for the first stage of labour is achieved with the 0.125% bupivacaine solution. The use of stronger solutions of bupivacaine achieves no greater degree of analgesia nor longer duration of action, although the onset of analgesia may be faster with the stronger solutions. Further investigations are needed to determine if 25 mg of pethidine is the best choice of dose to use under these circumstances.

Adult↗
PubMed1989

Postoperative analgesia in neonates: an Australia-wide survey.

An Australia-wide survey of the use of postoperative analgesia in neonates has been conducted. A high overall use of analgesia has been recorded with 75% of respondents prescribing an opioid. The frequency of use of local or regional analgesia was disappointingly low at 8% overall. The general attitude is that analgesia is desirable but a fear of respiratory depression inhibits its use, particularly in non-ventilated neonates and after more minor surgery. It is suggested that a wider use of regional anaesthesia techniques may reduce this problem.

Analgesics↗
PubMed1986

Differentiation of parenchymal lung disorders with in vitro proton nuclear magnetic resonance.

We investigated in vitro NMR properties of bleomycin-induced alveolitis and pulmonary fibrosis in 18 Lewis rats (6 controls). When alveolitis or fibrosis had developed, animal lungs were excised and examined histologically and gravimetrically and their T1 and T2 were determined by a NMR spectrometer at 10.7 MHz and 37 degrees C. Clinical diagnosis was confirmed histologically in each case. The NMR signal intensities were significantly elevated in both disease states (P less than 0.001). Both T1 and T2 values of alveolitic lungs were about the same as in controls, but were significantly decreased in fibrotic lungs (P less than 0.01). Changes in T1 and T2 correlated well (P less than 0.001) with changes in water content of diseased lungs.

Animals↗
PubMed1985

Krypton-81m imaging of the right ventricle.

We report the development of a method for obtaining right-ventricular radionuclide angiograms using continuous peripheral intravenous infusion of the ultra-short-lived nuclide krypton-81m. This tracer has a half-life of 13 sec, emits a single 190-keV photon, and is extremely insoluble. During infusion into a peripheral vein, Kr-81m achieves stable count rates over the right heart, and it is essentially completely cleared by the lungs during its initial pulmonary transit. Thus no interfering activity is present in the systemic circulation. Initial studies provide excellent data on right-heart anatomy and function.

Heart↗
PubMed1984

Isobutyl-2-cyanoacrylate pulmonary emboli associated with occlusive embolotherapy of cerebral arteriovenous malformations.

Three patients had cerebral arteriovenous malformations (AVM) treated by occlusive embolotherapy using isobutyl-2-cyanoacrylate (IBC). At necropsy two had asymptomatic IBC pulmonary emboli. The numbers of emboli and the size of pulmonary vessels occluded correlated roughly with an increasing frequency and volume of injectate made in the cerebral tissue. The extent of pulmonary vascular occlusion in one case suggests that pulmonary vascular hypertension could develop as a complication of this form of treatment.

Adult↗
PubMed1983

Plasmid profile, serogrouping, and auxotyping of Neisseria gonorrhoeae isolates from Africa.

The plasmid patterns of 90 isolates of Neisseria gonorrhoeae (including 39 penicillinase-producing strains) originating from various countries in Africa were determined. Serogrouping by coagglutination and auxotyping were used to characterise the isolates. The 4.4-megadalton plasmid was present in seven isolates out of 39 penicillinase-producing strains, two of which occurred with a conjugative 24.5-megadalton plasmid. The African strains were predominantly serogroup WI and wild type. Arginine-dependent isolates were as common as proline-dependent types.

Africa↗
PubMed1983

Epidemiological characterisation of Neisseria gonorrhoeae isolates from the Far East.

One hundred strains of Neisseria gonorrhoeae (including 30 penicillinase producing (PPNG) strains) originating from Korea were characterised by plasmid analysis, auxotyping, and serogrouping. Eighty per cent of the isolates possessed the conjugative 24.5 megadalton (Mdal) plasmid. A novel 7.8 Mdal plasmid was present in four isolates (one PPNG and three non-PPNG strains). Seventy five per cent of all the strains tested were wild type and belonged to serogroup WII, while 20% were proline requiring and belonged to serogroup WII. Two of the remaining strains were tyrosine auxotrophs, while another strain was arginine requiring; these three strains carried the conjugative plasmid and belonged to serogroup WII.

Gonorrhea↗