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C J Smith

Publications and source records attributed to C J Smith.

At least 271 records · Page 15Linked to original sources
PubMed1986

Molecular cloning of two cysteine proteinases from paw-paw (Carica papaya).

Two cDNA clones for plant cysteine proteinases have been isolated from a Carica papaya (paw-paw, papaya) leaf tissue cDNA library by using a mixture of 16 synthetic oligodeoxyribonucleotides as a hybridization probe. The inserted regions are 311 and 440 base-pairs in length and have the potential to encode a region corresponding to the C-terminal region of two proteins which are homologous with the known plant cysteine proteinases and the mammalian thiol cathepsins. One of the sequences shows a high (greater than 77%) homology with the plant cysteine proteinase papain, the other is closely related to papaya chymopapain. One sequence contains all, and the other most, of the 3' untranslated region of the mRNA. The inserts were used as specific probes in Northern Blot analyses giving an estimated size for the two mRNA species of 1.45 kilobases.

Amino Acid Sequence↗
PubMed1986

Raising the ambient potassium ion concentration enhances carbachol stimulated phosphoinositide hydrolysis in rat brain hippocampal and cerebral cortical miniprisms.

The influence of the ambient potassium ion concentration ([K+]) upon agonist stimulated hydrolysis of phosphoinositides (PI) has been studied in isolated miniprisms of rat hippocampus and cerebral cortex. When the external [K+] was raised from 6 to 18 mmol/l, there was little or no increase in the hydrolysis of PI in the absence of agonist, however, carbachol (100 mumol/l) stimulated hydrolysis was greatly enhanced in both brain regions studied. Thus, carbachol stimulated the hydrolysis of PI to 146% and 386% of control levels at potassium concentrations of 5.88 and 18.2 mmol/l, respectively, in the rat hippocampus. A similar enhancement of muscarine (100 mumol/l) stimulation was observed in cortical miniprisms with 18 mmol/l [K+]. A further enhancement was seen at higher ambient [K+], although basal hydrolysis of PI was then also increased. The carbachol-stimulated hydrolysis of PI found at both 6 and raised [K+] was prevented by atropine (1 and 10 mumol/l) and tetraethylammonium (20 mmol/l), but not by 10 mmol/l Mg2+. Pirenzepine (50 nmol/l) also reduced this response. The ions Cs+ and Rb+ (but not Li+ or Tris+) produced a similar enhancement of the carbachol stimulation to that found with K+. At a buffer [K+] of 6 mmol/l, noradrenaline (100 mumol/l) produced a 2-fold increase in the hydrolysis of PI whereas 5-hydroxytryptamine (100 mumol/l) and histamine (500 mumol/l) had little or no effect. However, histamine and 5-hydroxytryptamine did stimulate the hydrolysis of PI when [K+] was increased. Miniprism ATP content was not changed by a rise in [K+] to 18 mmol/l. The significance of these results is discussed in terms of the postsynaptic cellular events following cholinergic stimulation.

5-Hydroxytryptophan↗
PubMed1986

Effect on experimental palatal candidosis in the Wistar rat of removal and re-insertion of acrylic appliances.

Palatal candidosis was produced by inoculating Candida albicans 3091 (serotype A) under an acrylic appliance. Two weeks was allowed for infection to occur. Removal of the appliance for a further period of 2 weeks resulted in complete resolution of the lesion histologically but Candida organisms could still be recovered from the mucosal surface. Re-fitting these appliances at the end of this recovery period, without subsequent inoculation, produced a recrudescence of palatal candidosis after a further 2 weeks. One possible explanation is that C. albicans was encouraged to change from the commensal to the pathogenic form in the presence of the palatal appliance.

Animals↗
PubMed1986

Equity in the distribution of health and welfare services: can we rely on the state to reverse the 'inverse care law?'.

It has been suggested that the fiscal crises experienced in many industrial nations has been made worse by the drain on the state's economy of an ever-growing welfare state. Proposals to decentralize funding for health and welfare services, and to rely more on local, private, and 'grass roots' services, have been received enthusiastically. The question raised in this paper is whether the shift away from provision by the state will bring about a more or less equitable distribution of resources. The paper considers the spatial distribution of treatment services for two groups of the population who have become largely dependent on the state: namely, the mentally ill and alcoholics. The results suggest that as the federal government withdraws from the provision of services, neither the states nor the localities can be relied on to guarantee a minimum level of services to the truly needy. In the case of alcoholism services there is also some question about whether 'grass-roots' provision would be sufficiently responsive to the distribution of needs.

Alcoholics Anonymous↗
PubMed1986

Cholinergic receptors in cognitive disorders.

Cholinergic receptors (muscarinic subtypes M1 and M2, and putative nicotinic binding) have been examined in the hippocampus obtained at autopsy from a variety of patients with cognitive disorders (Alzheimer's, Parkinson's, and Huntington's diseases, Down's Syndrome and alcoholic dementia) and compared with neurologically normal controls and cases of Motor Neuron disease. In all of the disorders associated with a pre-synaptic cortical cholinergic deficit reflected by an extensive loss of choline acetyltransferase (Alzheimer's disease, Parkinson's disease and Down's Syndrome) there was a substantial reduction in the binding of (3H) nicotine to the nicotinic receptor. By contrast reductions in both muscarinic subtypes (M1 and M2) were apparent to only a moderate extent in Alzheimer's disease, whereas in Parkinson's disease binding was significantly increased (apparently not in relation to anti-cholinergic drug treatment) in the non-demented but not demented cases. A further abnormality detected in Alzheimer's disease but not the other disorders investigated was a decrease in an endogenous inhibitor of nicotinic binding, the identity of which is as yet unknown but which may be a candidate for a possible endogenous modulator of the nicotinic receptor. These observations suggest that in Alzheimer's disease not only muscarinic but also nicotinic receptor function should be considered in relation both to future therapeutic strategies and, in the search for a clinical marker which might be of diagnostic value, to potential probes of the cortical cholinergic system.

Cognition Disorders↗
PubMed1986

Functional evaluation of latissimus dorsi donor site.

A study was undertaken to determine the cosmetic and functional problems associated with the latissimus dorsi muscle donor site. Twenty-four patients undergoing both free and pedicle muscle and myocutaneous flap procedures for a wide variety of reconstructive problems were studied. All patients had a contour defect at the donor site, a scar which varied with the patient's age and whether overlying skin had been taken with the muscle flap. Mild to moderate shoulder weakness and some loss of motion were noted in most patients which improved over the course of several months. An upper extremity disability in strength and shoulder motion should be anticipated following latissimus dorsi transfer, which in most cases is minimized by the recruitment of synergistic muscle units. Vigorous range-of-motion exercises following surgery should be encouraged to minimize adhesions and joint capsule stiffness. Social changes in occupation and daily living activities were noted which were not a problem for most patients. Twenty-three of 24 patients were pleased with the overall outcome of their surgery and would recommend the procedure to others. A prospective study before and after latissimus dorsi transfer followed by a second evaluation 2 to 3 years postoperatively would help to clarify the role synergistic muscle units play in "taking over" latissimus dorsi function.

Adolescent↗
PubMed1986

R-plasmid-mediated chromosome mobilization in Bordetella pertussis.

Antibiotic-resistant and auxotrophic mutants of Bordetella pertussis were isolated. These were used as recipients for the uptake from Escherichia coli of broad-host-range R plasmids R68.45, RP1, and RP1 and RP4 carrying transposons Tn501 and Tn7 respectively. B. pertussis transconjugants from these crosses were used as donors to mobilize StrR, NalR, thr+ and gly+ chromosomal markers to B. pertussis or to B. parapertussis recipient strains. The frequency of plasmid transfer varied and depended on the donor and recipient strains used. Differences in chromosome mobilization frequencies of individual markers were observed and appeared to depend on the presence or absence of transposons Tn501 and Tn7 on the plasmid. Linkage was detected between the gly+ and NalR markers.

Bordetella pertussis↗
PubMed1986

Neocortical cholinergic enzyme and receptor activities in the human fetal brain.

In the human fetus, obtained postmortem at estimated gestational ages of 8-22 weeks, biochemical activities of cortical choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) were comparable to those of adult brain tissue. In contrast cholinergic receptor binding, including muscarinic M1 and M2 subtypes (measured by displacement of [3H]N-methylscopolamine with, respectively, pirenzepine and carbachol) and [3H]nicotine (putative nicotinic) binding were undetectable before 13-14 weeks and even at 22 weeks were substantially (three- to fourfold) below the respective adult values. Cortical ChAT activity decreased significantly with gestational age whereas binding to the three receptors, including the proportion M1/M2, increased significantly. AChE was present at all ages investigated as the two molecular monomeric (G1) and tetrameric (G4) forms. The proportion of G4, which was much more soluble in fetal compared with adult cortex, increased approximately threefold. Histochemically AChE, although intense in the nucleus of Meynert, was generally confined to subcortical white matter at early fetal developmental periods, appearing later in the cortex localized to nerve fibres and occasional cell bodies. These observations suggest that during the second trimester of human fetal development, cortical cholinergic function may be preceded by relatively high ChAT activity and paralleled not only by increasing receptor binding but also by a proportional increase in the tetrameric form and histochemical reactivity of AChE.

Acetylcholinesterase↗
PubMed1986

Epithelial mitotic activity during the induction of palatal candidosis in the Wistar rat.

Palatal candidosis was produced in 15 Wistar rats by fitting them with an acrylic appliance that covered the palatal mucosa and simultaneously inoculating this site with Candida albicans 3091 (serotype A). A further 15 rats were fitted with the appliance only. Five animals in each group were killed at 1, 2 and 4 weeks, 4 X 5 h after being injected with vinblastine sulphate, as were 5 normal control animals at the start of the experiment. Palatal mucosa was dissected free, fixed, sectioned and stained prior to counting the number of arrested mitotic figures in the basal epithelial layer and measuring the mean thickness of epithelium. The results were expressed as the number of mitotic figures per 1000 basal cells, per unit length of basement membrane and per square millimetre of epithelial surface. After an initial reduction in thickness, the palatal epithelium in both experimental groups became thicker than that of normal control animals, more markedly so in the animals infected with Candida albicans. Similar patterns of mitotic activity were found regardless of the reference unit used as a basis for the calculations. An initial decrease in both experimental groups was followed by a sharp and significant rise, again being more marked in the animals infected with Candida albicans.

Animals↗
PubMed1986

A comparison of some of the permeability characteristics of intact and tape-stripped hamster cheek pouches in vitro.

Cheek pouches were removed from anesthetized hamsters and were either tape-stripped or left intact and then mounted in Ussing chambers, where they were bathed in Krebs-Ringer bicarbonate saline. A potential difference could be measured across all pouches and was stable for over an hour across the unstripped pouches. The electrical resistance across the unstripped pouches was high (8960 omega.cm2), whereas the resistance across the tape-stripped pouches was significantly lower (p less than 0.01), suggesting that these pouches are likely to be more permeable than the unstripped pouches. Reflection coefficients of urea, ethanol, and glycerol were derived by means of streaming potentials. Values for intact pouches were all close to 1 and for tape-stripped pouches were 0.938, 0.822, and 0.509, respectively. Permeability coefficients for urea and ethanol across intact and tape-stripped pouches were, respectively, 12.5 X 10(-9)cm/min; 27.6 X 10(-9) cm/min; 2325 X 10(-9)cm/min; and 28471 X 10(-9) cm/min. The hamster cheek pouch has a high electrical resistance; it is an impermeable structure in which the keratin layer appears to provide a major barrier to the passage of water, ions, and certain solutes.

Animals↗
PubMed1985

Genetics of clindamycin resistance in Bacteroides.

Results presented in this paper have shown that a widely distributed LM-resistance determinant is present on at least 3 distinct Bacteroides R-plasmids. In fact these plasmids bear no homology outside of the defined regions implicated in the LM resistance. This resistance determinant on pBF4, pBFTM10, and pBI136 is located within DNA segments bounded on each side by a directly repeated sequence of more than 500 bp. The intervening sequences of these 3 elements are variable, and range in size from about 3.7 kb to 7.2 kb (Fig. 7). Apart from the EcoRI/AvaI restriction sites which characterize the repeated sequence, there is a notable lack of common restriction sites within these elements. These results suggest that the elements do possess a certain degree of structural similarity but significant evolutionary divergence has occurred. The presence and location of the directly repeated sequences, their association with specific deletions, and their association with an antibiotic-resistance determinant, are features common to many antibiotic-resistance transposons described for other prokaryotes. In addition, these elements are highly mobile, being found on a number of R-plasmids. The unique relationship between pBF4, pBI106, and pBI136 described here is a clear indication of the potential for these DNA sequences to move from one molecule to another. Given the extensive dissemination and the genetic and structural characteristics described above, it seems likely that the LM-resistance determinant is carried on transposon-like elements present in pBF4, pBFTM10, and pBI136. However, further experimentation will be necessary to document the transposition event. Bacteroides strains such as B. fragilis V503, possess a transmissible LM-resistance determinant which does not appear to be associated with detectable extrachromosomal elements (5,9,10). Presently, a number of strains of this type have been found over a wide geographic area. The LM-resistance genes associated with these strains are apparently similar to the one carried on the Bacteroides R-plasmids because homology between the 2 has been observed. However, it is important to note that within the limits of Southern filter blot hybridization, neither V503 nor its transconjugants possess the directly repeated sequence found on the LM-resistance plasmids (Fig. 8). The elusive nature of the V503 LM-resistance elements presents an intriguing problem. One model that has been proposed is that these resistance determinants reside on a conjugative transposon similar to Tn916 of Streptococcus faecalis (3).(ABSTRACT TRUNCATED AT 400 WORDS)

Bacteroides↗
PubMed1985

Permeability of the squid giant axon to organic cations and small nonelectrolytes.

The permeability of the Na channel of squid giant axon to organic cations and small nonelectrolytes was studied. The compounds tested were guanidinium, formamidinium, and 14C-labeled urea, formamide, thiourea, and acetone. Permeability was calculated from measurements of reversal potential and influx on internally perfused, voltage clamped squid axons. The project had two objectives: (1) to determine whether different methods of measuring the permeability of organic cations yield similar values and (2) to see whether neutral analogs of the organic cations can permeate the Na channel. Our results show that the permeability ratio of sodium to a test ion depends upon the ionic composition of the solution used. This finding is consistent with the view put forward previously that the Na channel can contain more than one ion at a time. In addition, we found that the uncharged analogs of permeant cations are not measurably permeant through the Na channel, but instead probably pass through the lipid bilayer.

Acetone↗
PubMed1985

Comparison of the transposon-like structures encoding clindamycin resistance in Bacteroides R-plasmids.

The R-plasmids pBF4, pBFTM10, and pBI136 encode transmissible clindamycin resistance (Ccr) in Bacteroides spp. These plasmids are distinct replicons but the regions implicated in Ccr share some homology and appear to have a transposon-like structure. To better understand the mechanism of dissemination and to locate the Ccr determinant(s), the genetic and structural properties of the Ccr regions of each plasmid were compared and contrasted. For this work a single EcoRI restriction fragment containing the Ccr region from each plasmid was cloned into pBR322 in Escherichia coli. Results of restriction mapping and heteroduplex experiments showed that the pBF4 EcoRI-D and pBFTM10 EcoRI-B fragments shared more than 90% base sequence homology but that the EcoRI-C fragment of pBI136 had diverged significantly. The pBI136 fragment also did not confer tetracycline resistance in E. coli as shown for the pBF4 EcoRI-D fragment (D.G. Guiney, P. Hasegawa, and C. E. Davis, 1984, Plasmid 11, 248-252). Heteroduplex experiments showed that the pBI136 EcoRI-C and pBF4 EcoRI-D fragments shared a 1.2-kb region of homology attributed to a directly repeated sequence which bounds the Ccr region. Southern hybridization studies indicated that an additional 0.85 kb of the pBI136 EcoRI-C fragment was homologous to the EcoRI-D fragment of pBF4. This region was characterized by its sequential restriction endonuclease sites for HindIII, AvaII, and DdeI, and it is proposed that the Ccr gene(s) resides in this area.

Bacteroides↗
PubMed1985

Identification of a mutation that relieves gamma-glutamyl kinase from allosteric feedback inhibition by proline.

A 1.75-kb DNA fragment containing the entire Escherichia coli proB+ gene has been sequenced. The proB locus encodes the structural gene for gamma-glutamyl kinase (GK), the enzyme responsible for the first step in proline biosynthesis, and the primary regulatory point of the pathway. We have previously reported the nucleotide (nt) sequence of a mutant proB gene isolated from an E. coli strain resistant to the toxic analog of proline, 3,4-dehydro-DL-proline (DHP). This mutant gene encodes a GK which is refractory to allosteric feedback inhibition by proline (DHPR). Comparison of the proB+ and DHPR proB sequences revealed a single base difference, an A-T to C-G transversion localized at nt position 428 within the amino acid (aa) coding region of proB. This mutation predicts an aa change from glutamic acid in the wild-type (wt) enzyme to alanine in the DHPR enzyme.

Allosteric Regulation↗