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N A Williams

Publications and source records attributed to N A Williams.

At least 37 records · Page 2Linked to original sources
PubMed1998

Effects of freeze-dry processing conditions on the crystallization of pentamidine isethionate.

The results of this study show that pentamidine isethionate (PI) can exist in at least four crystalline forms-three anhydrates designated as forms A, B, and C, and a trihydrate. Form C is the high-temperature modification, produced by heating forms A, B, and the trihydrate above 130 degrees C and cannot be produced under actual lyophilization conditions. The crystal forms of PI present after freeze-drying depend on the initial solution concentration and the thermal history of freezing. At low concentrations of PI (4% and less), form A is observed regardless of freezing method. At a higher concentration (10%), the crystal forms observed are a function of the freezing method. Three freezing methods were used to effect different cooling rates: (1) cooling on the shelf to 2 degrees C and holding for 3 h prior to decreasing the temperature to -45 degrees C, (2) directly cooling on the shelf from room temperature to -45 degrees C, and (3) dipping the vials in liquid nitrogen. The results show that form A, form B, or a mixture of both forms are present in the freeze-dried solid depending upon whether the trihydrate crystallizes during freezing or not. Since form B can only be produced by dehydration of the trihydrate at low temperature, the presence of this form in the freeze-dried powders depends on the nucleation and growth of the trihydrate during freezing. Photostability studies have demonstrated marked differences between freeze-dried solids frozen under different conditions. The results underscore the importance of recognizing that seemingly subtle differences in processing conditions can have a significant impact on critical quality attributes of freeze-dried products.

Antiprotozoal Agents↗
PubMed1998

Induction of mucosal immunity against herpes simplex virus type 1 in the mouse protects against ocular infection and establishment of latency.

Immune responses were assessed after intranasal immunization of mice with a mixture of herpes simplex virus type 1 (HSV-1) glycoproteins with cholera toxin and its B subunit as adjuvant. Antigen-specific serum antibodies, which were largely IgG with IgG1 the major subclass, neutralized virus in vitro with a titer equivalent to that elicited by active infection. Significant levels of antigen-specific IgA were found in mucosal fluids of the eye as well as the vagina. Lymphocytes from draining lymph nodes showed secondary proliferative responses when cultured with HSV-1 in vitro, in immunized mice only, with the production of interleukin-2, interferon-gamma, interleukin-4, and interleukin-5. After ocular challenge, immunized mice were protected against the development of severe eye disease, zosteriform spread, or encephalitis, whereas the incidence of clinical symptoms in mock-immunized mice was 83%, 74%, and 52%, respectively. Finally, the incidence of latency was reduced from 88% to 13% after intranasal immunization.

Adjuvants, Immunologic↗
PubMed1998

CD4+ T cells inhibit growth of Epstein-Barr virus-transformed B cells through CD95-CD95 ligand-mediated apoptosis.

Greater than 90% of the human population acquire Epstein-Barr virus (EBV) in infancy and retain a lifelong latent infection without any clinical consequences. Nevertheless EBV has been identified as the causal agent of infectious mononucleosis, and is associated with several tumours including endemic Burkitt's lymphoma and B cell lymphomas in immunosupressed patients. B cells infected with EBV are transformed in vitro and grow continuously as lymphoblastoid cell lines. The growth of EBV-transformed B cells in vivo is controlled by the immune system. Studies on immunity to EBV have mainly focused on MHC class I-restricted CD8+ cytotoxic T cells specific for viral latent antigens. Here it is reported that in vitro stimulation of peripheral blood lymphocytes by autologous EBV-infected B cells, which have been induced to express lytic cycle antigens, gives rise to a predominantly CD4+ T cell response. Furthermore, the growth of EBV-infected B cells can also be regulated by these activated CD4+ T cells through apoptosis mediated by CD95-CD95 ligand (CD95L). CD95-CD95L-mediated apoptosis is an important mechanism of normal B cell growth regulation. As EBV-transformed B cells remain susceptible to this mechanism, the control of EBV in vivo may be not only by virus-specific CD8+ cytotoxic T cell immunity but also by normal mechanisms of immune regulation of B cell growth.

Acyclovir↗
PubMed1998

Gene and domain duplication in the chordate Otx gene family: insights from amphioxus Otx.

We report the genomic organization and deduced protein sequence of a cephalochordate member of the Otx homeobox gene family (AmphiOtx) and show its probable single-copy state in the genome. We also present molecular phylogenetic analysis indicating that there was single ancestral Otx gene in the first chordates which was duplicated in the vertebrate lineage after it had split from the lineage leading to the cephalochordates. Duplication of a C-terminal protein domain has occurred specifically in the vertebrate lineage, strengthening the case for a single Otx gene in an ancestral chordate whose gene structure has been retained in an extant cephalochordate. Comparative analysis of protein sequences and published gene expression patterns suggest that the ancestral chordate Otx gene had roles in patterning the anterior mesendoderm and central nervous system. These roles were elaborated following Otx gene duplication in vertebrates, accompanied by regulatory and structural divergence, particularly of Otx1 descendant genes.

Amino Acid Sequence↗
PubMed1998

Molecular evolution of the brain of chordates.

The molecular basis of regionalisation and patterning of the developing brain is an area of current intense interest. Members of the Otx, Pax-2/5/8 and Hox gene families appear to play important roles in these processes in vertebrates, but functional divergence and genetic redundancy arising from gene duplication events obscures our view of the roles played by these genes during the evolution of vertebrate brains. Determination of the ancestral gene copy number in chordates through molecular phylogenetics, accompanied by gene expression analysis in all three chordate subphyla (vertebrates, cephalochordates and urochordates) may distinguish between ancestral and derived expression domains and give clues to the roles played by these genes in chordate ancestors. Application of this comparative approach indicates evolutionary homologous brain regions (fore-/midbrain, isthmus/cerebellum and hindbrain) in chordates and supports homology of the frontal eye of cephalochordates to the paired eyes of vertebrates.

Animals↗
PubMed1997

Immunohistochemical detection of cytokines in paraffin-embedded mouse tissues.

We have successfully developed a method for the immunohistochemical detection of interleukin 2 (IL-2), IL-4, IL-6, IL-10O, IFNgamma and TNFalpha using monoclonal antibodies (MAb), in sections of mouse tissue embedded in paraffin wax. The method involved fixation in periodate-lysine-paraformaldehyde (PLP), rapid dehydration and infiltration under vacuum with paraffin wax at 54 degrees C. Comparative observations demonstrated that the method gives equivalent or better results than formaldehyde fixed, frozen sections. Since reliable controls, both positive and negative, are paramount for interpretation of immunohistochemical staining, such controls were determined. The following tissues were shown to be suitable as positive controls when using paraffin-embedding: spleen for the detection of TNFalpha, small intestine for IL-2, IL-4 and IL-10, and HSV-1 infected eyes for IL-6 and IFNgamma. We conclude that PLP fixation and low temperature paraffin-embedding is a method which provides both preservation of excellent tissue morphology and reliable immunohistochemical identification of cytokines. These attributes will be invaluable in a wide variety of experimental situations.

Animals↗
PubMed1997

Prevention of autoimmune disease due to lymphocyte modulation by the B-subunit of Escherichia coli heat-labile enterotoxin.

We demonstrate that the receptor binding moiety of Escherichia coli heat-labile enterotoxin (EtxB) can completely prevent autoimmune disease in a murine model of arthritis. Injection of male DBA/1 mice at the base of the tail with type II collagen in the presence of complete Freund's adjuvant normally leads to arthritis, as evidenced by inflammatory infiltration and swelling of the joints. A separate injection of EtxB at the same time as collagen challenge prevented leukocyte infiltration, synovial hyperplasia, and degeneration of the articular cartilage and reduced clinical symptoms of disease by 82%. The principle biological property of EtxB is its ability to bind to the ubiquitous cell surface receptor GM1 ganglioside, and to other galactose-containing glycolipids and galactoproteins. The importance of receptor interaction in mediating protection from arthritis was demonstrated by the failure of a non-receptor-binding mutant of EtxB to elicit any protective effect. Analysis of T cell responses to collagen, in cultures of draining lymph node cells, revealed that protection was associated with a marked increase in interleukin 4 production concomitant with a reduction in interferon gamma levels. Furthermore, in protected mice there was a significant reduction in anti-collagen antibody levels as well as an increase in the IgG1/IgG2a ratio. These observations show that protection is associated with a shift in the Th1/Th2 balance as well as a general reduction in the extent of the anti-type II collagen immune response. This suggests that EtxB-receptor-mediated modulation of lymphocyte responses provides a means of preventing autoimmune disease.

Animals↗
PubMed1997

Enhancement of the immune response to non-replicating herpes simplex virus type-1 preparations by mucosal administration in the presence of cholera toxin.

Different immunization regimes were compared in order to enhance the immune response following mucosal administration of non-replicating HSV-1 preparations to mice. The serum anti-HSV Ig response following intragastric administration of heat or UV inactivated HSV-1 strain SC16 was compared with that elicited by an attenuated derivative of SC16 (TKDM21). The highest response followed immunization with TKDM21 and this was markedly enhanced by repeated intragastric administration, reaching ca 35% of that elicited following a cutaneous infection with live virus. Repeated doses of killed virus produced only a minimal increase in the response even when given intranasally (i.n.). However, cholera toxin and its B-subunit with UV-inactivated virus or a mixture of purified viral glycoproteins enhanced the anti-HSV response after i.n. immunization and produced antibody levels equivalent to those following intragastric delivery of live TKDM21.

Adjuvants, Immunologic↗
PubMed1997

Modulation of B-cell activation by the B subunit of Escherichia coli enterotoxin: receptor interaction up-regulates MHC class II, B7, CD40, CD25 and ICAM-1.

The B subunits of cholera toxin (CtxB) and Escherichia coli heat-labile enterotoxin (EtxB) are non-toxic lectins that bind and cross-link a ubiquitous cell glycolipid receptor, ganglioside GM1, and are recognized as potent mucosal and systemic immunogens. Here we examine the role of EtxB receptor occupancy in modulating the activation of B cells, in vitro, in primary lymphocyte cultures containing B and T cells. When 48-hr spleen cell cultures containing EtxB were compared with those in the presence of a non-receptor binding mutant, EtxB(G33D), a marked shift in the ratio of CD4+ T cells: B cells was noted. Evidence suggested that this was the result of either enhanced survival or proliferation of B cells associated with receptor occupancy by EtxB. Investigation revealed that EtxB induced only a minimal increase in proliferation above that of EtxB(G33D), in mixed cell cultures, and failed to induce any cell division of purified B cells or T cells. In contrast, receptor-binding by EtxB markedly up-regulated the expression of major histocompatability complex (MHC) class II, B7, intracellular adhesion molecule-1 (ICAM-1), CD40 and CD25 on the B-cell surface. These results indicate that the polyclonal effects of EtxB on B cells are not associated with wide-scale proliferation, but more likely with maintenance of B-cell survival by activation of molecules essential for B-cell differentiation. The findings also highlight the essential role of GM1-interaction with EtxB in the regulation of lymphocyte responses.

Animals↗
PubMed1997

Cytokine production in the nervous system of mice during acute and latent infection with herpes simplex virus type 1.

Immunocytochemistry on serial paraffin sections was used to monitor the production dynamics of cytokines (IL-2, IL-4, IL-6, IL-10, IFN-gamma and TNF-alpha) and viral antigens in the trigeminal ganglion (TG) and the central side of the dorsal root entry zone (DRE) of mice, following infection of the cornea with herpes simplex virus type 1. In normal TG, scattered satellite cells were TNF-alpha+ and in the DRE, TNF-alpha+ and/or low numbers of IL-6+ cells were detected. On day 3 after infection, foci of TG neurons with viral antigens were surrounded by large numbers of TNF-alpha+ and/or IL-6+ cells and low numbers of IFN-gamma+ cells. IL-2+ and/or IL-4+ cells appeared later, when viral antigens had almost cleared. In the TG, the most striking changes occurred with TNF-alpha, with respect to its source (satellite cells, Schwann cells and infiltrating cells) and the extent and long duration of its production. TNF-alpha was the predominant cytokine throughout acute and latent infection and even by day 30, numbers of satellite cells expressing this cytokine were three times higher than those in normal ganglia. Moreover, in the DRE, TNF-alpha was the only cytokine detected during virus clearance and again, its production continued, along with that of IL-6, on days 20 to 30, in both infiltrating cells and astrocytes. Thus, cytokines, particularly TNF-alpha and perhaps IL-6, from infiltrating cells and resident glial cells may have a role both in virus clearance and in normal homeostatic mechanisms in the nervous system such as repair and protection of neurons from damage.

Animals↗
PubMed1997

Sequence and embryonic expression of the amphioxus engrailed gene (AmphiEn): the metameric pattern of transcription resembles that of its segment-polarity homolog in Drosophila.

Vertebrate segmentation has been proposed as an evolutionary inheritance either from some metameric protostome or from a more closely related deuterostome. To address this question, we studied the developmental expression of AmphiEn, the engrailed gene of amphioxus, the closest living invertebrate relative of the vertebrates. In neurula embryos of amphioxus, AmphiEn is expressed along the anteroposterior axis as metameric stripes, each located in the posterior part of a nascent or newly formed segment. This pattern resembles the expression stripes of the segment-polarity gene engrailed, which has a key role in establishing and maintaining the metameres in embryos of Drosophila and other metameric protostomes. Later, amphioxus embryos express AmphiEn in non-metameric patterns - transiently in the embryonic ectoderm and dorsal nerve cord. Nerve cord expression occurs in a few cells approximately midway along the rostrocaudal axis and also in a conspicuous group of anterior cells in the cerebral vesicle at a level previously identified as corresponding to the vertebrate diencephalon. Compared to vertebrate engrailed expression at the midbrain/hindbrain boundary, AmphiEn expression in the cerebral vesicle is relatively late. Thus, it is uncertain whether the cerebral vesicle expression marks the rostral end of the amphioxus hindbrain; if it does, then amphioxus may have little or no homolog of the vertebrate midbrain. The segmental expression of AmphiEn in forming somites suggests that the functions of engrailed homologs in establishing and maintaining a metameric body plan may have arisen only once during animal evolution. If so, the protostomes and deuterostomes probably shared a common segmented ancestor.

Amino Acid Sequence↗
PubMed1997

Hepatic cirrhosis in Jamaica.

The aetiology, biochemistry, clinical features and complications of histologically confirmed hepatic cirrhosis in 45 patients (26 females, 19 males) seen at the University Hospital of the West Indies, Jamaica, between 1984 and 1994 are presented. The age range was 1 to 72 years (mean 48 years). Abdominal swelling and weight loss were the commonest symptoms, occurring in 51% and 47% of patients, respectively. Jaundice was a presenting feature in 44%. Hepatomegaly was present in 71% of patients and splenomegaly in 33%. The aetiological factors were: alcohol (36%), bush tea (18%), chronic active hepatitis (11%), drugs (7%), and haemochromatosis (2%). Hepatitis B surface antigen was detected in 2 of 20 patients tested. 24% of the patients also had diabetes mellitus., 29% were anaemic, 29% were thrombocytopenic, 4% were leukopenic, and the prothrombin time was prolonged in 22%. The albumin/globulin ratio was reversed in 71% of the patients. The alkaline phosphatase was elevated in 56%, the aspartate aminotransferase was increased in 58% and the gamma glutamyl transpeptidase in 56%. 56% of the patients had macronodular cirrhosis; the liver showed a micronodular pattern in 18%; 7% had biliary cirrhosis; 7% chronic active hepatitis with cirrhosis; and 13% showed a mixed macro-micronodular pattern. Ascites and fluid overload developed in 44% of the patients. Hepatic encephalopathy occurred in 18% and upper gastrointestinal bleeding in 18%.

Adolescent↗
PubMed1996

Stability of levofloxacin in intravenous solutions in polyvinyl chloride bags.

The stability of levofloxacin in 10 commonly used infusion fluids was studied. Levofloxacin 25-mg/mL injection was diluted to 0.5 and 5 mg/mL in each of the following i.v. infusion fluids: 0.9% sodium chloride injection, 5% dextrose injection, 5% dextrose and 0.9% sodium chloride injection, 5% dextrose and lactated Ringer's injection, 5% sodium bicarbonate injection, Plasma-Lyte 56 and 5% dextrose injection, 5% dextrose and 0.45% sodium chloride and 0.15% potassium chloride injection, 1/6 M sodium lactate injection, sterile water for injection, and 20% mannitol injection. Ten polyvinyl chloride bags were prepared for each solution; two were stored for 3 days at 25 degrees C, two for 7 days at 5 degrees C, two for 14 days at 5 degrees C, two for 13 weeks at -20 degrees C followed by 14 days at 5 degrees C, and two for 26 weeks at -20 degrees C, all in the dark. The solutions were visually examined, tested for turbidity and particulate matter, and subjected to stability-indicating high-performance liquid chromatography; solution pH was determined. Levofloxacin was stable in and compatible with all but two of the diluents tested. Precipitation occurred under all conditions in 20% mannitol injection for the 0.5-mg/mL levofloxacin concentration and after storage for 13 weeks at -20 degrees C for the 5-mg/mL concentration. Levofloxacin 0.5 mg/mL in 5% sodium bicarbonate injection formed a precipitate when stored at -20 degrees C for 13 weeks and beyond. Levofloxacin 0.5 and 5 mg/mL was compatible with and stable in 8 of the 10 infusion fluids studied.

Anti-Infective Agents↗
PubMed1996

Growth and differentiation of fast and slow muscles in fetal sheep, and the effects of hypophysectomy.

1. Isometric contractile characteristics of fast-twitch (flexor digitorum longus, FDL; medial gastrocnemius, MG) and slow-twitch (soleus) muscles were determined in pentobarbitone-anaesthetized fetal sheep between 90 and 140 days gestation. Five fetuses were hypophysectomized (HPX) at 90-95 days gestation and then studied at 138-140 days. 2. At 90-95 days gestation the time to peak of single twitch contractions for the soleus, MG and FDL were not significantly different from each other; the mean value (+/-S.E.M.) for all the muscles at this age was 77.6 +/- 9.0 ms. At 120-125 days gestation the MG and FDL contracted significantly faster (44.0 +/- 0.9 and 40.8 +/- 1.8 ms, respectively) than at 90-95 days, and did not change significantly thereafter. In contrast, the soleus muscle contracted more slowly (111.9 +/- 6.6 ms) at 138-140 days than at 90-95 days and 120-125 days gestation. 3. Soleus muscle consisted of type I fibres at all gestational ages. There was no significant change with gestational age in the relative numbers of type I and II fibres in the MG and FDL, but in the diaphragm the number of type I fibres increased and the number of type II fibres decreased between 125 and 138 days gestation. 4. HPX abolished the normal increase of soleus weight relative to body weight between 125 and 138 days but did not alter the change of twitch contraction time with age. HPX significantly prolonged twitch time to peak and time to half-relaxation of MG and time to half-relaxation of FDL at 138 days. 5. The maximum rate of rise of the isometric tetanic contraction was unchanged by HPX in all three hindlimb muscles, but fatigue of MG and FDL was increased. 6. The relative proportions of different fibre types in the hindlimb muscles and the diaphragm were unchanged by HPX, but there was a significant decrease in mean areas of type I and II fibres in the FDL and MG of the HPX fetuses.

Animals↗
PubMed1996

Potent immunogenicity of the B subunits of Escherichia coli heat-labile enterotoxin: receptor binding is essential and induces differential modulation of lymphocyte subsets.

The importance of receptor binding in the potent immunogenicity of Escherichia coli heat-labile enterotoxin B subunit (EtxB) was tested by comparing its immunogical properties with those of a receptor binding mutant, EtxB(G33D). Subcutaneous immunization of EtxB(G33D) resulted in 160-fold reduction in antibody titer compared with wild-type EtxB, whereas its oral delivery failed to provoke any detectable secretory or serum anti-B subunit responses. Moreover, the two proteins induced strikingly different effects on lymphocyte cultures in vitro. EtxB, in comparison with EtxB(G33D), caused an increase in the proportion of B cells, many of which were activated (CD25+); the complete depletion of CD8+ T cells; an increase in the activation of CD4+ T cells; and an increase in interleukin 2 and a decrease in interferon gamma. These data indicate that EtxB exerts profound effects on immune cells, suggesting that its potent immunogenicity is dependent not only on efficient receptor-mediated uptake, but also on direct receptor-mediated immunomodulation of lymphocyte subsets.

Adjuvants, Immunologic↗
PubMed1996

Modulation of Langerhans cell phenotype, migration and maturation by agents known to cause herpes simplex virus reactivation in a mouse model.

The factors which control whether an asymptomatic or symptomatic infection in the skin follows reactivation of herpes simplex virus (HSV) in the sensory ganglia remain unclear. Xylene, retinoic acid and dimethylsuphoxide (DMSO) all stimulate similar levels of virus reactivation in the ganglia of latently infected mice, yet give rise to high, moderate and very low incidences of clinical skin disease, respectively. This observation suggests that the chemicals may be capable of affecting the local microenvironment of the skin. In the present study we have investigated the effects of xylene, retinoic acid and DMSO on Langerhans cell (LC) phenotype and function. The results show that none of the chemicals inhibit the phenotypic maturation of Langerhans cells in vitro. However, DMSO induced a dramatic elevation in class II MHC expression on Langerhans cells. In addition, fewer antigen-bearing dendritic cells (DC) were evident in the lymph nodes if xylene was administered to the skin prior to challenge with the contact sensitizer, FITC. None of the chemicals inhibited the accumulation of DC in the lymph nodes after such an antigen-challenge, suggesting that xylene was affecting not migration, but antigen uptake. The inhibition of antigen uptake by xylene together with the activation of LC in terms of class II expression by DMSO may explain, in part, the relative abilities of these chemicals to allow the establishment of recurrent HSV disease in the skin.

Animals↗