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Biomedical subjects

K R Jones

Publications and source records attributed to K R Jones.

At least 109 records · Page 6Linked to original sources
PubMed1989

Killing of Plasmodium falciparum by human monocyte-derived macrophages.

Freshly isolated human peripheral blood monocytes inhibited the growth of blood-stage asexual Plasmodium falciparum parasites in vitro. The monocytes contained intracellular parasite pigment and a few whole parasites, but the remaining parasites reinvaded fresh red cells successfully and were morphologically normal. Anti-parasitic activity of these macrophages was not significantly enhanced by treatment with recombinant tumour necrosis factor alpha, recombinant gamma-interferon or lymphoblastoid alpha-interferon. Catalase had no effect on this parasite inhibition, suggesting a hydrogen peroxide independent mechanism. Anti-parasitic activity was, however, enhanced by prior maturation of the monocytes. Monocytes matured for 6 days caused 100% killing of parasites. In contrast to identical concentrations of freshly isolated monocytes the parasites incubated with these matured macrophages showed intraerythrocytic death similar to the crisis forms seen in vivo. gamma-interferon present either during the assay or as a pretreatment had no significant enhancing effect on the killing, although cytotoxicity to tumour cell lines was enhanced. Conditioned medium from macrophages showed only moderate parasite inhibition.

Animals↗
PubMed1989

The Florida Health Care Access Act: a blended regulatory/competitive approach to the indigent health care problem.

The problem of indigent health care has received much attention from governmental officials, health care providers, health policy analysts, and others. A majority of states have generated legislative proposals to deal with the problem, although their strategies differ in terms of method and scope. This article discusses Florida's approach to the problem as contained in the Health Care Access Act of 1984 and subsequent legislation. The article will provide background on the reasons a hospital assessment strategy was chosen as the funding mechanism and will examine the problems that occurred during the implementation phase of the legislation.

Advisory Committees↗
PubMed1989

Hemodialysis patients: a population at risk.

Patients receiving chronic hemodialysis treatments develop many comorbid conditions and complications as a result of their disease process and treatment regimen. This article will describe the risk factors that were identified as having a significant association with the probability of hospitalization and death in chronic hemodialysis patients, as well as the risk factors having a significant relationship with variations in treatment resource requirements. Nursing care implications are explored as well as the need for further research.

Florida↗
PubMed1988

Transducer for monitoring respiration during imaging procedures.

A transducer system for monitoring respiration is described; it uses a 'liquid column' sensor with a remote integrated circuit pressure module. It was designed primarily for non-invasive monitoring and control of respiration during diagnostic imaging procedures, but has also found applications in other areas, e.g. physiotherapy and pulse monitoring. The device is a new version of a system developed several years ago and takes advantage of relatively low cost commercial 'building blocks'. The output is an analogue voltage (from a low impedance source) capable of driving a wide range of recorders, amplifiers and computer interfaces. Reference is also made in the text to a bio-feedback signal processing and display unit (described elsewhere) which, when used with this transducer, provides a versatile respiratory control system.

Diagnostic Imaging↗
PubMed1988

Inter- and intrageneric transfer of Tn916 between Streptococcus faecalis and Clostridium tetani.

We report that the streptococcal resistance transposon, Tn916, is conjugally transferred to Clostridium tetani (Utrecht) in intergenic matings. Streptococcus faecalis CG180, harboring a 41-kb plasmid (pAM180) containing Tn916 (15 kb), transferred the transposon-associated tetracycline resistance (Tcr) to C. tetani in filter matings at a frequency of about 10(-4)/donor. An erythromycin resistance marker carried by pAM180 was not transferred, indicating lack of plasmid conjugation or stable inheritance of plasmid sequences. DNA extracted from C. tetani transconjugants was probed with radiolabeled Tn916 using Southern blot analysis and these results indicated that the transposon integrated at multiple host genomic sites. Tn916-carrying C. tetani strains were able to transfer Tcr to suitable recipient strains of C. tetani as well as to S. faecalis recipients. These results indicate that this transposon is able to be disseminated and expressed in obligately anaerobic gram-positive bacteria. Moreover, this system opens avenues for the implementation of transposon mutagenesis in this important pathogenic species.

Clostridium tetani↗
PubMed1988

Early treatment with diltiazem reduces delayed cerebral vascular narrowing after subarachnoid hemorrhage.

Using a primate model of subarachnoid hemorrhage, we have demonstrated the ability of diltiazem to reduce delayed, experimental narrowing of cerebral vessels under clinically realistic conditions. Twelve monkeys were treated identically, except that six received oral diltiazem (20 mg/kg t.i.d.) starting 24 hours after a subarachnoid hemorrhage (SAH) and continuing for 5 days. Neurological examination showed that all untreated monkeys were hyperreflexic and hypotonic on the side contralateral to the SAH. Only two of the six of the diltiazem-treated monkeys had a similar deficit. Control angiograms taken before the SAH were compared with those taken 5 days later. The average vessel diameter at six standard sites in monkeys without diltiazem was 61% of control, whereas the average diameter at the same positions in the diltiazem-treated monkeys was 92% of control (P less than 0.01). In each group, the diameter of the most narrowed artery of each monkey was compared with values at the same site before SAH. The average diameter in the untreated group was 22% of control, significantly smaller than the corresponding value from the diltiazem-treated group, which was 68% (P less than 0.005). Delaying diltiazem treatment until 24 hours after hemorrhage still provides some protection, but less than that given by pretreatment with the drug. This suggests that the processes that eventually result in chronic cerebral vascular narrowing are initiated during the 24-hour period immediately after SAH. We propose that there is initially an acute, severe, calcium-dependent contraction of vascular smooth muscle and associated injury to the vessel wall, including its innervation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Molecular cloning and characterization of the glucosyltransferase C gene (gtfC) from Streptococcus mutans LM7.

A glucosyltransferase (GTF) gene, designated gtfC, was cloned from Streptococcus mutans LM7. Its gene product was detected by screening a bacteriophage lambda library with rabbit antiserum raised against S. mutans LM7 extracellular proteins. DNA isolated from the immunopositive recombinant phage revealed two S. mutans chromosomal EcoRI fragment inserts, 8.1 and 4.7 kilobase pairs in size. Escherichia coli minicell analyses revealed the approximate position and direction of transcription of the gtfC gene. The gene product was determined to be a polypeptide of about 150 kilodaltons which synthesized a water-soluble glucan. Restriction endonuclease mapping and DNA hybridization indicated a repeated region of DNA corresponding to a portion of the coding region of gtfC immediately downstream from the intact gtfC locus on the chromosome. A 300-base-pair gtfC-specific probe showed that the gene and the putative duplicated sequence were present in S. mutans serotypes c, e, and f, but not in other related oral streptococci which had GTF activity. In addition, the gtfC determinant displayed homology to sequences corresponding to the carboxy-terminal coding region of a gene (gtfB) encoding a GTF activity that synthesized water-insoluble glucans. These data suggest that at least one class of GTF genes may be present in multiple copies in S. mutans and, further, that GTF genes may contain conserved sequences internal to their coding regions.

Chromosome Mapping↗
PubMed1986

Contributions of Y- and W-cell pathways to response properties of cat superior colliculus neurons: comparison of antibody- and deprivation-induced alterations.

The cat's superior colliculus (SC) receives direct inputs from retinal W-cells (a W-D input) and Y-cells (Y-D input) and an indirect Y-cell input via the lateral geniculate nucleus and visual cortex (Y-I input). In previous studies we have shown that intraocular injection of antibodies raised against large retinal ganglion cells produces a dose-dependent reduction in the Y retinogeniculate pathway. Furthermore, when a sufficiently high antibody concentration is used, there is a substantial loss of the Y pathway and no apparent loss of the W pathway. In the present study, we used the antibodies to investigate the contributions of the Y and W pathways to functional organization within the SC. Binocular injections of low (330 micrograms/100 microliters) or high (1,000 micrograms/100 microliters) antibody concentrations were made. The antibody-mediated effects on SC cells' response properties were compared directly with effects of early binocular deprivation, which have been attributed to a loss of Y-I input. Extracellular single-cell recordings were made from the SC, and cells were classified as receiving Y-D, Y-I, or W-D inputs on the basis of their response latencies to electrical stimulation of the optic chiasm and optic tract. Injections of the low antibody concentration produced no significant effects on inputs to the SC. However, injections of the high antibody concentration resulted in a 70% reduction in SC cells with a Y-D input and an 82% reduction in SC cells with a Y-I input. There was no effect on the percentage of cells with a W-D input. Binocular deprivation produced a 76% reduction in the percentage of cells with Y-I input. Visual response properties of SC cells also were assessed. Injections of the high antibody concentration produced a 55% reduction in cells that respond with a directional preference and a 51% reduction in cells that respond to high-velocity stimuli. Binocular deprivation produced a 78% reduction in the proportion of directional cells and a 25% reduction in cells that respond to the ipsilateral eye. Taken together, the results of this and previous studies using cortical lesions, visual deprivation, and immunoablation suggest that Y-D input is the primary basis for responses to high stimulus velocity, Y-I input is an important basis for directional responses and response through the ipsilateral eye, and W-D input is important for responses to low stimulus velocity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Dose-response analysis of effects of antibodies to large ganglion cells on the cat's retinogeniculate pathways.

Previous studies have shown that antibodies against large retinal ganglion cells (alpha-/Y-cells) reduce the Y-cell retinogeniculate pathway while having little or no effect on the X- or W-cell pathways. The present study investigated the dose-response relationship of these effects. We began by studying effects on the T1 (largely Y-cell-mediated) and T2 (largely X-cell-mediated) waves of the retinal field-potential. Different concentrations of the antibodies were injected intraocularly in adult cats and retinal field-potentials evoked by optic chiasm stimulation were examined. The lowest concentration of immune serum tested (330 micrograms/100 microliter volume) reduced both the T1 and T2 amplitudes. With increasing concentrations, the ratio of T1:T2 amplitudes progressively decreased from 0.71 to only 0.05. The highest concentration of immune serum tested (1000 micrograms/100 microliter volume) virtually eliminated the T1 wave while the T2 wave remained (albeit reduced). Next, we carried out single-cell physiological and morphological studies to verify the effects of the highest antibody concentration and compare them with previous results on effects of the lowest antibody concentration (Kornguth et al., 1982; Spear et al., 1982). In single-cell recordings from the retina, the encounter rates of Y- and X-cells were reduced by 85 and 53%, respectively, after injection of the highest antibody concentration. There was no effect on the encounter rate of retinal W-cells. After injection of the lowest antibody concentration, there was no change in the encounter rates of any of the retinal cell types. Morphological studies revealed an 88-99% loss of alpha-cells in retinae treated with the highest antibody concentration. There also was a substantial (24-57%) loss of medium-size ganglion cells but no loss of small ganglion cells. The loss of alpha-cells was much greater after high-concentration injections than after low-concentration injections. In recordings from the LGN, the proportion of Y-cells was reduced by 87% in laminae receiving input from an eye injected with the highest antibody concentration. Laminae receiving input from an eye injected with the lowest concentration had a 77% reduction in Y-cells. The encounter rate of LGN X-cells was not affected by either concentration. Morphological analysis indicated that the loss of Y-cells in the LGN was not due to changes in cell size. These findings indicate that antibody-mediated effects on retinogeniculate pathways are dose-dependent.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗