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Biomedical subjects

D Knowles

Publications and source records attributed to D Knowles.

At least 19 recordsLinked to original sources
PubMed2004

Isolated lesser trochanter fractures in elderly--a case for prophylactic DHS fixation. A case series.

Isolated lesser trochanter fractures are a rare presentation of hip fractures in the elderly. Classically, lesser trochanter fractures in adults are associated with tumours and result from little or no trauma. We present three elderly osteoporotic ladies who sustained isolated fractures of the lesser trochanter secondary to a definite history of trauma. Radiologically, none of them showed any evidence of pathological lesions or intertrochanteric fracture at presentation. Two patients subsequently developed displaced intertrochanteric fractures, which necessitated internal fixation. In the third patient, a dynamic hip screw (DHS) was inserted before mobilisation. Based on this experience, we recommend careful observation and follow-up of such cases and suggest that isolated lesser trochanteric fractures in the elderly osteoporotic population may be an indication for prophylactic DHS fixation.

Accidents, Home↗
PubMed2001

Parents' consent to the post-mortem removal and retention of organs.

Parents of children who died following complex heart surgery have recently discovered that organs were removed and retained in post-mortem investigations to which they consented. It has been established that many of these parents did not give informed consent to the retention of organs. The Bristol Royal Infirmary Inquiry which examined these practices drafted codes of practice to govern future post-mortem activities. It is argued that these codes of practice may be onerous to some parents, yet effectively disbar them from dissenting to their application whilst they might otherwise agree to the post-mortem removal and retention of organs for purposes of medical audit, research or training. This consequence arises from employing an over-rigorous concept of informed consent in the immediate circumstances of bereavement. That concept is discussed in detail. An alternative proposal is canvassed which improves on the status quo but does not impose a practice of consent which may be burdensome and distressing to many.

Adult↗
PubMed2000

The value of the axial view in assessing calcaneal fractures.

We studied the value of the axial view of the calcaneum in diagnosing fractures. Fifty sets calcaneal radiographs were studied by four senior trauma staff and four orthopeadic trainees on two occasions 2-3 weeks apart. On the first occasion only the lateral view was studied; on the second, both lateral and axial views were studied. The axial view did not improve the sensitivity or specificity of the lateral view alone. Senior staff were more accurate in assessing the radiographs. We suggest that the axial view should not be used routinely in assessing a patient with a possible calcaneal fracture.

Calcaneus↗
PubMed1999

Antitumor efficacy of a novel class of non-thiol-containing peptidomimetic inhibitors of farnesyltransferase and geranylgeranyltransferase I: combination therapy with the cytotoxic agents cisplatin, Taxol, and gemcitabine.

Ras malignant transformation requires posttranslational modification by farnesyltransferase (FTase). Here we report on the design and antitumor activity, in monotherapy as well as in combination therapy with cytotoxic agents, of a novel class of non-thiol-containing peptidomimetic inhibitors of FTase and the closely related family member geranylgeranyltransferase I (GGTase I). The non-thiol-containing FTI-2148 is highly selective for FTase (IC50, 1.4 nM) over GGTase I (IC50, 1700 nM), whereas GGTI-2154 is highly selective for GGTase I (21 nM) over FTase (IC50, 5600 nM). In whole cells, the corresponding methylester prodrug FTI-2153 is >3000-fold more potent at inhibiting H-Ras (IC50, 10 nM) than Rap1A processing, whereas GGTI-2166 is over 100-fold more selective at inhibiting Rap1A (IC50, 300 nM) over H-Ras processing. Furthermore, FTI-2153 was highly effective at suppressing oncogenic H-Ras constitutive activation of mitogen-activated protein kinase and human tumor growth in soft agar. FTI-2148 suppressed the growth of the human lung adenocarcinoma A-549 cells in nude mice by 33, 67, and 91% in a dose-dependent manner. Combination therapy of FTI-2148 with either cisplatin, gemcitabine, or Taxol resulted in a greater antitumor efficacy than monotherapy. GGTI-2154 in similar antitumor efficacy experiments is less potent than FTI-2148 and inhibits tumor growth by 9, 27, and 46%. Combination therapy of GGTI-2154 with cisplatin, gemcitabine, or Taxol is also more effective. Finally, FTI-2148 and GGTI-2154 are 30- and 33-fold more selective and 30- and 16-fold more potent in whole cells than our previously reported thiol-containing FTI-276 and GGTI-297, respectively. Thus, our results demonstrate that this highly potent and selective novel class of non-thiol-containing peptidomimetics inhibits human tumor growth in whole animals and that combination therapy with cytotoxic agents is more beneficial than monotherapy.

3T3 Cells↗
PubMed1999

"Essentiality" Testing: Looking for New Antimicrobial Targets.

After a gap of some 30 years, the prospect of finding completely new agents with which to combat infectious disease is promising. New discovery approaches based on the application of genomics and associated technologies are leading to the identification of genes essential for bacterial viability and pathogenesis. This article reviews the current status of the search for new antimicrobial targets and points to future developments and issues.

Journal Article↗
PubMed1998

Seroprevalence of Babesia equi among horses in Israel using competitive inhibition ELISA and IFA assays.

Sera from 361 horses were tested by indirect immunofluorescence antibody test (IFA) and by competitive inhibition ELISA (cELISA), to detect antibodies to Babesia equi. The concordance between the assays was 95.7%. Application of a cutoff based on a calculated percent inhibition of < 20% gave a total of 22 discrepant results, while only 8 sera negative by the cELISA were found positive by the IFA when a cutoff of > 20% inhibition was used. Approximately one-third of all the horses tested were found serologically positive to B. equi, with more horses testing positive from northern Israel. Among horses raised with access to pasture there was a significant difference in the percentage of seropositive reactors (76.6% in the north and 20.1% in the central region), compared with horses without access to pasture (14.3 and 10.3%, respectively). Nineteen percent of stallions were found to be positive, which was significantly less than the proportions of seropositive mares and geldings: 38 and 42%, respectively. No significant association was found between the mean age of horses and seroreactivity to B. equi.

Animals↗
PubMed1998

Increased sialylation of oligosaccharides on IgG paraproteins--a potential new tumour marker in multiple myeloma.

AIMS: To investigate whether changes in carbohydrate structure of IgG are related to malignancy and stage of disease in myeloma and monoclonal gammopathy of uncertain significance (MGUS). METHODS: 61 patients were studied at diagnosis: 14 with MGUS, nine with stage I multiple myeloma, 11 with stage II, 21 with stage III, and five with solitary plasmacytoma. IgG was extracted from serum by protein G affinity chromatography. Oligosaccharides were cleaved from the protein backbone enzymatically by N-glycosidase F. Oligosaccharide analysis was performed by high pressure anion exchange chromatography with pulsed electrochemical detection (HPAE-PED). RESULTS: Up to 15 oligosaccharide peaks were identified in three major fractions: neutral, monosialylated, and disialylated. Patients with myeloma showed an increase in the proportion of sialylated oligosaccharides in comparison with patients with MGUS. The ratio of neutral to sialylated oligosaccharides (N:S) was reduced at all stages of myeloma compared with MGUS: MGUS, 11.35; myeloma stage I, 7.6 (p = 0.047); stage II, 5.20 (p = 0.035); stage III, 3.60 (p = 0.0002); plasmacytoma, 7.5 (p = 0.046). The N:S ratio was independent of paraprotein concentration (r = 0.05). CONCLUSIONS: The ratio of neutral to sialylated oligosaccharides may act as a new marker of malignancy in IgG paraproteinaemia and warrants further investigation.

Aged↗
PubMed1996

Antibody against an Anaplasma marginale MSP5 epitope common to tick and erythrocyte stages identifies persistently infected cattle.

A protein epitope of major surface protein 5 (MSP5), defined by monoclonal antibody (MAb) ANAF16C1, is conserved among Anaplasma species (E. S. Visser, T. C. McGuire, G. H. Palmer, W. C. Davis, V. Shkap, E. Pipano, and D. P. Knowles, Jr., Infect. Immun. 60:5139-5144, 1992) and is expressed in the salivary glands of infected ticks. A competitive inhibition ELISA (cELISA) for the detection of bovine anti-MSP5 antibodies was developed by using purified recombinant MSP5 fusion protein and MAb ANAF16C1. The specificity of the recombinant-MSP5 cELISA within North America was established by using 261 serum samples from cattle in the regions of Hawaii and Northern Ontario where anaplasmosis is not endemic and from cattle proven by splenectomy or subinoculation of whole blood into susceptible splenectomized recipients to be uninfected. The maximum percent inhibition by these sera was 18%. Sera known to be positive were obtained from 35 cattle either experimentally inoculated with infected erythrocytes or exposed to infected Dermacentor andersoni ticks. Thirty-four of the 35 serum samples inhibited MAb ANAF16C1 binding by > or = 25%. During acute infection, the MSP5 cELISA detected antibodies prior to or concomitantly with the appearance of rickettsiae in erythrocytes. Antibodies were detectable in sera from persistently infected cattle inoculated as long as 6 years previously.

Anaplasma↗
PubMed1995

Occurrence of the regulatory nucleotides ppGpp and pppGpp following induction of the stringent response in staphylococci.

The stringent response in Escherichia coli and many other organisms is regulated by the nucleotides ppGpp and pppGpp. We show here for the first time that at least six staphylococcal species also synthesize ppGpp and pppGpp upon induction of the stringent response by mupirocin. Spots corresponding to ppGpp and pppGpp on thin-layer chromatograms suggest that pppGpp is the principal regulatory nucleotide synthesized by staphylococci in response to mupirocin, rather than ppGpp as in E. coli.

Adaptation, Biological↗
PubMed1994

Managing the new NHS: breathing new life into the NHS reforms.

The essence of the NHS reforms is that they bring market forces to bear on organisations providing public services, while allowing those organisations more freedom to respond in ways that will improve the efficiency, effectiveness, and appropriateness of their services. The new structural changes to the NHS--a leaner management executive and fewer, slimmer regions--could be used either to strengthen these features of the reforms or frustrate them by allowing ministers and top management to intervene even more at local level and "overmanage" the market. To ensure that the aims of the reforms are not frustrated ministers and the management executive must restrict themselves to laying down clear strategies and then allow purchasers and providers to meet those strategies in their own ways. They also need to ensure that the whole NHS can learn and benefit from local experimentation and devise ways of managing the crises that will inevitably arise; otherwise they might be tempted to become involved in managing the market at too local a level, and the NHS will suffer the worst of both worlds: stifling bureaucracy at the top and parochial self interest locally.

Family Practice↗
PubMed1994

Rapid identification of metallo- and serine beta-lactamases.

Simple methods to detect, identify, and differentiate metallo- and serine beta-lactamases were developed and used to differentiate enzymes produced by 17 clinical isolates of Xanthomonas maltophilia. All isolates exhibited beta-lactamase activity, and in 16 strains this was induced by imipenem. All but one isolate hydrolyzed imipenem (and meropenem), and in all cases this activity was inhibited by 1 mM EDTA. The metallo- and serine beta-lactamases in the cell extracts were distinguished on isoelectric focusing (IEF) gels by using the following procedures. (i) Cell lysates were preincubated with 83 mM EDTA prior to IEF and subsequent visualization with nitrocefin, and (ii) after IEF, the gels were overlaid with either 1 mM zinc sulfate or 100 microM BRL 42715 before staining with nitrocefin. Bands of beta-lactamase activity which were removed by BRL 42715 but unaffected by EDTA or zinc sulfate were categorized as serine beta-lactamases. Bands which were unaffected by BRL 42715 but inhibited by EDTA or enhanced by zinc sulfate were classified as metallo-beta-lactamases. By using this approach, seven metallo-beta-lactamases were differentiated with pI values of 4.8 (two strains), 5.5 (four strains), 5.7 (one strain), 6.0 (one strain), 6.4 (four strains), 6.6 (one strain), and 6.8 (three strains). The metallo-beta-lactamase band with a pI of 6.4 aligned with the recently characterized metallo-beta-lactamase from X. maltophilia 511. Heterogeneity was also observed for the serine beta-lactamases: 14 isolates elaborated serine beta-lactamase activity which focused with major bands with at least eight different pIs. The remaining three strains produced serine beta-lactamases which focused with five distinct bands with pIs of 6.4, 6.2, 5.7, 5.5, and 5.2. We conclude that X. maltophilia produces many types of metallo- and serine beta-lactamases distinguishable by these new methods and that the previously reported L-1 and L-2 enzymes are not solely representative of the beta-lactamases produced by this species.

Anti-Bacterial Agents↗
PubMed1993

Advice to a Moscow children's hospital.

At the request of the largest children's hospital in Moscow, McKenzie and colleagues made recommendations for improving the service. Restrictions on visiting and fears of contracting illness from non-disposable needles have discouraged the local population from using the hospital. Consequently the hospital is underused and overstaffed. Serious shortages of drugs and surgical supplies compromise care. Fundamental changes are needed in nursing and postgraduate education. The authors encouraged their Russian colleagues to address the health care needs of their local population and to develop family centred care, and they offered training in London.

Child↗
PubMed1992

Molecular basis for membrane rigidity of hereditary ovalocytosis. A novel mechanism involving the cytoplasmic domain of band 3.

Hereditary ovalocytic red cells are characterized by a marked increase in membrane rigidity and resistance to invasion by malarial parasites. The underlying molecular defect in ovalocytes remained a mystery until Liu and colleagues (N. Engl. J. Med. 1990. 323:1530-38) made the surprising observation that the ovalocytic phenotype was linked to a structural polymorphism in band 3, the anion transporter. We have now defined the mutation in band 3 gene and established the biophysical sequelae of this mutation. This mutation involves the deletion of amino-acids 400-408 in the boundary between the cytoplasmic and the first transmembrane domains of band 3. The biophysical consequences of this mutation are a marked decrease in lateral mobility of band 3 and an increase in membrane rigidity. Based on these findings, we propose the following model for increased membrane rigidity. The mutation induces a conformational change in the cytoplasmic domain of band 3, leading to its entanglement in the skeletal protein network. This entanglement inhibits the normal unwinding and stretching of the spectrin tetramers necessary for membrane extension, leading to increased rigidity. These findings imply that the cytoplasmic domain of an integral membrane protein can have profound effects on membrane material behavior.

Amino Acid Sequence↗
PubMed1990

Severity of arthritis is predicted by antibody response to gp135 in chronic infection with caprine arthritis-encephalitis virus.

Antibody titers to caprine arthritis-encephalitis virus surface glycoprotein gp135 and core protein p28 in synovial fluid and serum from 35 goats infected for 3 years were compared with the histologic severity of arthritis in these animals. Anti-gp135 antibody titers in synovial fluid and serum directly reflect the severity of carpal arthritis in chronically infected goats.

Animals↗
PubMed1989

Persistent infection of rabbits with bovine leukemia virus associated with development of immune dysfunction.

Bovine leukemia virus (BLV) infection of rabbits provides a safe and relatively inexpensive in vivo mammalian system for the study of the mechanisms controlling expression of a unique group of lymphotropic retroviruses. This group of viruses, which includes C-type human T-lymphotropic virus types I and II and lentiviruslike human immunodeficiency virus type 1, possesses genes coding for "trans-activating" products. Rabbits experimentally inoculated with BLV became persistently infected, as demonstrated by a number of tests. All BLV-inoculated rabbits developed persistent serum antibody to BLV. Furthermore, all BLV-inoculated rabbits had peripheral blood mononuclear cells which, when stimulated, expressed the virus, as demonstrated by viral induction of syncytium formation in a BLV-susceptible fibroblast line. The presence of BLV in circulating cells was confirmed by using peripheral blood mononuclear cells from randomly selected BLV-inoculated rabbits, which showed the presence of viral reverse transcriptase activity, BLV transcriptional activity, or BLV proviral DNA. Additional tests showed that infected lymphocytes maintained in culture with recombinant human interleukin-2 formed multinucleated giant cells and produced virus when incubated in cytokine-containing medium. BLV-infected rabbits also showed alterations in several parameters associated with immunity, beginning 6 months after inoculation. Thirty-eight percent of infected rabbits developed abnormally low T-cell responses, as measured by phytolectin stimulation, and T-cell responses cycled between normal and abnormally low over a period of 20 to 24 months. Forty-four percent of rabbits infected for longer than 12 months suffered from recurrent conjunctivitis and rhinitis. By 24 months postinoculation, 28% of infected rabbits were dead or were killed because of poor clinical condition.

Animals↗