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D R Martin

Publications and source records attributed to D R Martin.

At least 19 recordsLinked to original sources

Survival of meningococci outside of the host: implications for acquisition.

Meningococci are regarded as being unlikely to survive outside of their human host although this has possibly been more assumed than demonstrated. Seven strains of meningococci were tested for their ability to survive on glass or plastic while retaining expression of their capsule and important outer membrane proteins. A known number of colony-forming units of each strain were dried onto glass and onto plastic and tested for viability over time. Survival on glass was significantly better than on plastic (P<0.0001). Isolates of the New Zealand epidemic strain, B:4:P1.7-2,4 survived better on glass than all other strains tested. Recovered isolates still expressed their capsules and outer membrane proteins. These findings raise the question of whether meningococci can be transferred from person to person via fomites contaminated with oropharyngeal secretions containing meningococci.

Bacterial Capsules↗

Clonal analysis of the serogroup B meningococci causing New Zealand's epidemic.

An epidemic of meningococcal disease caused by serogroup B meningococci expressing the P1.7-2,4 PorA protein began in New Zealand in 1991. The PorA type has remained stable. Different porB have been found in association with the P1.7-2,4 PorA, although type 4 has been most common. The clonal origins of B:P1.7-2,4 meningococci isolated from cases during 1990 to the end of 2003 were analysed. In 1990, the year immediately preceding the recognized increase in disease rates, all three subclones (ST-41, ST-42, and ST-154) of the ST-41/44 clonal complex occurred among the five isolates of B:P1.7-2,4. The two sequence types, ST-42 and ST-154, continued to cause most disease throughout New Zealand. Isolates belonging to subclone ST-41 were mostly identified early in the epidemic and in the South Island. 16S rRNA typing indicated that isolates belonging to the subclones ST-41 and ST-154 share a common ancestor, with those typing as ST-42 more distantly related with some genetically ambiguous. It is possible that ST-41 and ST-154 may have evolved one from the other but evolution to ST-42 is more difficult to explain. It is possible that one or more of the ST types could have been introduced into New Zealand prior to the first detection of clinical cases in 1990. Genetic diversity may have occurred during carriage in the community.

Clone Cells↗

The VR2 epitope on the PorA P1.7-2,4 protein is the major target for the immune response elicited by the strain-specific group B meningococcal vaccine MeNZB.

A protracted epidemic of group B meningococcal disease in New Zealand led to the testing of a strain-specific tailor-made vaccine, MeNZB. Immunogenicity levels achieved during age group trials enabled New Zealand's regulatory authority to grant licensure to deliver MeNZB to all individuals under age 20. During the trials target strains for serum bactericidal antibody measurements included the vaccine target strain NZ98/254 and two comparator epidemic-type strains (NZ94/167 and NZ02/09). In this study, 12 other strains differing variously from the vaccine strain by their capsular group, PorB type, and PorA variable region specificities, or PorA expression, were used as target strains. The PorA specificity of the serum bactericidal antibody responses to the vaccine was determined for 40 vaccinees. Sets of 10 pre- and postvaccination sera were chosen randomly from the young infant, older infant, toddler, and school-age group trials. Antibody recognition of linearized PorA proteins was also determined using immunoblotting. Across all age groups vaccine-induced serum bactericidal antibodies specifically targeted the VR2 P1.4 epitope of the PorA P1.7-2,4 protein irrespective of the PorB type and/or capsular type of the target strain. Deletion of amino acids within the VR2 epitope or replacement of the epitope through genetic exchange allowed strains variously to resist antibody-directed complement-mediated lysis and negated PorA-specific antibody recognition in immunoblots. The demonstration that the immunodominant antibody response was specifically for the VR2 P1.4 epitope of the PorA protein supports the public health decision to use a strain-specific vaccine for the control of New Zealand's epidemic of meningococcal disease.

Amino Acid Sequence↗

Stability of PorA during a meningococcal disease epidemic.

Meningococci causing New Zealand's epidemic, which began in 1991, are defined as group B, serosubtype P1.4 (subtype P1.7-2,4), belonging to the ST-41/ST-44 complex, lineage III. Of the 2,358 group B isolates obtained from disease cases from 1991 through 2003, 85.7% (2,021 of 2,358) were determined to be serosubtype P1.4. Of the remaining isolates, 156 (6.6%) were not serosubtypeable (NST). Molecular analysis of the porA gene from these B:NST meningococcal isolates was used to determine the reason. Most NST isolates (156, 88.5%) expressed a PorA that was distinct from P1.7-2,4 PorA. Fifteen isolates expressed variants of P1.7-2,4 PorA, and a further three expressed P1.7-2,4 PorA without any sequence variation. These three isolates expressed P1.7-2,4 PorA at very low levels, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, and showed variation in the porA promoter region. Among the 15 meningococcal isolates expressing variants of P1.7-2,4 PorA, 11 different sequence variations were found. Compared with the P1.7-2,4 PorA sequence, the sequences of these variants contained deletions, insertions, or single-nucleotide substitutions in the VR2 region of the protein. Multilocus restriction typing was used to assess the clonal derivations of B:NST case isolates. Meningococcal isolates expressing distinct PorA proteins belonged mostly to clonal types that were unrelated to the epidemic strain, whereas all meningococcal isolates expressing variants of P1.7-2,4 PorA belonged to the ST-41/ST-44 complex, lineage III. These results, together with those obtained serologically, demonstrate that the P1.7-2,4 PorA protein of meningococci responsible for New Zealand's epidemic has remained relatively stable over 13 years and support the use of a strain-specific outer membrane vesicle vaccine to control the epidemic.

Amino Acid Sequence↗

Application of the NMR-MOUSE to food emulsions.

The application of the NMR-MObile Universal Surface Explorer (NMR-MOUSE) to study food systems is evaluated using oil-in-water emulsions, and the results are compared to those obtained using a conventional low-field NMR (LF-NMR) instrument. The NMR-MOUSE is a small and portable LF-NMR system with a one-sided magnet layout that is used to replace the conventional magnet and probe on a LF-NMR instrument. The high magnetic field gradients associated with the one-sided MOUSE magnet result in NMR signal decays being dominated by molecular diffusion effects, which makes it possible to discriminate between the NMR signals from oil and water. Different data acquisition parameters as well as different approaches to the analysis of the NMR data from a range of oil-in-water emulsions are evaluated, and it is demonstrated how the concentration of oil and water can be determined from the NMR-MOUSE signals. From these model systems it is concluded that the NMR-MOUSE has good potential for the quantitative analysis of intact food products.

Emulsions↗

Early-onset neonatal group B streptococcal infections in New Zealand 1998-1999.

OBJECTIVE: To determine in New Zealand infants the attack rates, risk factors, preventive policies, strain serotype and antibiotic susceptibilities of early-onset neonatal group B streptococcus (GBS) infection. METHOD: A 2-year prospective active surveillance study was conducted in New Zealand's 19 neonatal units. Cases had to present within 48 h of delivery, be unwell, possess abnormal haematological indices and have GBS isolated from sterile sites. RESULTS: Of the 112 402 infants born in New Zealand during 1998-1999, 56 had early-onset GBS infection, an attack rate of 0.5 per 1000 live births (95% confidence interval [CI] 0.38, 0.65). Seven had meningitis and there was one death (case fatality rate of 1.8%; upper 95% CI 9.5%). Univariate analysis identified young maternal age, parity, preterm labour, prolonged membrane rupture, maternal fever and assisted delivery as risk factors. Preventive policies for GBS were reported by 14 (74%) obstetric centres associated with neonatal units. Of the 56 cases, five (9%) were born to mothers receiving intrapartum antibiotics, 32 (57%) had mothers with risk factors but were not treated with antibiotics, and 19 (34%) were born to mothers without identifiable risk factors for GBS prevention. Serotypes Ia and III predominated, while two isolates were resistant to erythromycin and/or clindamycin. CONCLUSIONS: Rates of early-onset GBS infection are similar to other countries following the introduction of prevention policies. Further reductions are possible with full implementation of these guidelines. Meanwhile, emergence of antibiotic resistance complicates the management of women with penicillin allergy. Vaccine development therefore remains a priority.

Adult↗

Case report: gastric schwannoma: MRI findings.

MRI features are described in a case of gastric schwannoma. A large, discretely marginated, multilobular mass was seen adjacent to the gastric antrum with the epicentre of the mass in the gastrocolic ligament. The overall signal pattern was low on T(1) weighted images and moderate to markedly elevated on T(2) weighted images. Post-gadolinium sequences demonstrate slow but fairly uniform enhancement throughout the mass.

Humans↗

Influence of thermal history on the structural and mechanical properties of agarose gels.

Using a multitechnique approach, two temperature domains have been identified in agarose gelation. Below 35 degrees C, fast gelation results in strong, homogeneous and weakly turbid networks. The correlation length, evaluated from the wavelength dependence of the turbidity, is close to values of pore size reported in the literature. Above 35 degrees C, gelation is much slower and is associated with the formation of large-scale heterogeneities that can be monitored by a marked change in the wavelength dependence of turbidity and visualised by transmission electron microscopy. Curing agarose gels at temperatures above 35 degrees C, and then cooling them to 20 degrees C, produces much weaker gels than those formed directly at 20 degrees C. Dramatic reductions in the elastic modulus and failure strain and stress are found in this case as a result of demixing during cure. An interpretation, based on the kinetic competition between osmotic forces (in favor of phase separation) and elastic forces (that prevent it) is proposed.

Elasticity↗

Adrenal adenomas: characteristic postgadolinium capillary blush on dynamic MR imaging.

We sought to evaluate dynamic post-gadolinium contrast enhanced magnetic resonance (MR) imaging characteristics of adrenal adenomas with comparison to those of malignant adrenal tumors. MR images, including in- and out-of-phase spoiled gradient echo (SGE) and dynamic gadolinium enhancement, of 35 adrenal adenomas in 34 patients, and 12 malignant adrenal tumors in 12 patients, were reviewed retrospectively. MR images were assessed for the presence of a capillary blush on immediate postgadolinium SGE images, and for rapid washout of contrast on 45-second postgadolinium SGE images. Thirty-five adrenal adenomas (mean size, 3.1 cm) and 12 malignant adrenal tumors (mean size, 7.4 cm) were assessed. Of 35 adrenal adenomas, 25 (71%) showed a homogeneous capillary blush on immediate postgadolinium images. Thirty-three (94%) adrenal adenomas demonstrated rapid washout on 45-second postgadolinium images (P < 0.001). Of 35 adrenal adenomas, 30 (86%) showed diminished signal intensity (SI) on out-of-phase images. Of 12 malignant adrenal tumors, none showed a homogeneous capillary blush on immediate postgadolinium images. Six (50%) malignant tumors showed negligible enhancement, four (33%) showed irregular patchy enhancement, and two (17%) showed peripheral enhancement (P < 0.001). On 45-second postgadolinium images, 11 (92%) of 12 malignant adrenal tumors showed irregular enhancement. In the majority of adrenal adenomas, an initial homogeneous capillary blush and rapid washout are demonstrated on gadolinium-enhanced dynamic MR imaging. Our preliminary results suggest that this may provide useful complementary information to the appearance of adrenal masses on in- and out-of-phase images.

Adenoma↗

Focal liver lesions: comparison of dual-phase CT and multisequence multiplanar MR imaging including dynamic gadolinium enhancement.

The purpose of this study was to compare dual-phase spiral computed tomography (CT) and magnetic resonance imaging (MRI) using dynamic gadolinium enhancement for liver lesion detection and characterization. Twenty-two consecutive patients underwent dual-phase spiral CT and MRI for the evaluation of focal liver disease within a 1-month period. Spiral CT and MR images were interpreted prospectively, in a blinded fashion by separate, individual, experienced investigators, to determine lesion detection and characterization. Liver lesions were confirmed by surgery and pathology in 6 patients, and by clinical and imaging follow-up in the other 16 patients. Pathological correlation of a primary extrahepatic malignancy was available in 5 of the 16 patients who had metastatic liver disease. Spiral CT and MRI detected 53 and 63 lesions, and characterized 39 and 62 true positive lesions, respectively. A kappa statistic test was applied to assess agreement between MR and CT results. MR versus CT for lesion detection resulted in a kappa statistic of 0.54 (95% confidence interval), indicating moderate agreement, and 0.32 (95% confidence interval) for lesion characterization, indicating only slight agreement. More lesions were detected on MR images than CT images in 6 (27%) patients, with lesions detected only on MR images in 4 (18%) patients. More lesions were characterized on MR images in 9 (41%) patients. In 9 patients with a discrepancy between MR and CT findings, the MR images added information considered significant to patient management in all 9 cases. MRI was moderately superior to dual-phase spiral CT for lesion detection, and was markedly superior for lesion characterization, with these differences having clinical significance.

Adult↗

Acute renal failure: common occurrence of preservation of corticomedullary differentiation on MR images.

The purpose of this study was to evaluate the relationship between renal corticomedullary differentiation (CMD) on MR imaging and serum creatinine (sCr) level in patients with acute renal failure (ARF). Twenty-one patients with ARF were retrospectively investigated. In all 21 patients, sCr levels were obtained on the same date as the MR study, and within 8 days before and after the MR study. CMD was assessed on non-contrast T(1)-weighted images and immediate post-gadolinium spoiled gradient echo (Gd-SGE) images. Presence of CMD was graded into 3 groups as 'preserved', 'intermediate', or 'loss'. On non-contrast T(1)-weighted images, 12/21 (57%) showed loss of CMD and 9/21 (43%) showed preserved CMD. On immediate Gd-SGE images, 5/21 (24%) showed loss of CMD, 12/21 (57%) preserved CMD, and 4/21 (19%) intermediate CMD. The sCr levels of 9 patients with preserved CMD on non-contrast T(1)-weighted images ranged from 1.4 to 10.5 mg/dl (mean 4.6 mg/dl), while those of 12 patients with loss of CMD ranged from 1.6 to 7.6 mg/dl (mean 4.8 mg/dl), which was not statistically significant (p > 0.2). Renal CMD can remain preserved on non-contrast T(1)-weighted or immediate Gd-SGE images in patients with acute presentation of ARF, independent of sCr level.

Acute Kidney Injury↗

A 10-year serogroup B meningococcal disease epidemic in New Zealand: descriptive epidemiology, 1991-2000.

OBJECTIVE: New Zealand has experienced an epidemic of meningococcal disease since 1991. This paper describes the characteristics of this epidemic during its first 10 years (1991-2000), current control measures, and potential future interventions. METHODOLOGY: Meningococcal disease surveillance in New Zealand uses combined notification and laboratory data. Population census data from 1991 and 1996 were used to calculate disease rates. RESULTS: The annual incidence of meningococcal disease increased from 53 cases (1.6 per 100 000 population) in the pre-epidemic year of 1990 to a peak of 613 (16.9 per 100000) in 1997, followed by consistently raised rates. Over the 1996-2000 period, there was an average of 502 cases per year (13.9 per 100 000). The epidemic has resulted in 3547 cases since 1991 approximately 3000 in excess of the number expected based on pre-epidemic disease incidence. Of the total cases, 158 (4.5%) were fatal. A disproportionately large number of cases have been in Maori and Pacific Islands children in the northern part of the North Island of New Zealand. Since 1991, the epidemic has increasingly been dominated by serogroup B meningococci with subtype P1.7b,4, which by 2000 accounted for 84.6% of all cases for whom this testing was carried out. The majority of these organisms were characterised as B:4:P1.7b,4. CONCLUSION: Meningococcal disease rates are likely to remain elevated in New Zealand for at least several more years. A vaccine which could induce immunity to the P1.7b,4 PorA subtype may have a role in controlling this epidemic. Efforts are underway to obtain and trial such a vaccine. Measures are also underway to reduce overcrowded living conditions which are contributing to the epidemic. Early recognition and antibiotic treatment of cases improves outcomes and should continue to be promoted. Integrated notification and laboratory-based surveillance of meningococcal disease provides relatively complete surveillance of this disease in New Zealand and has supported the development of public health interventions.

Adolescent↗

Hepatocyte growth factor inhibits apoptosis after ischemic renal injury in rats.

Several studies have determined that growth factors, including hepatocyte growth factor (HGF), have a crucial role in the regenerative process of renal tubules after ischemic or toxic insult. Recent research has ascertained that as well as necrotic cell death, there is evidence of apoptosis after an acute renal injury. We attempted to determine the effect of HGF on apoptosis after ischemic renal injury in rats. We administered HGF or vehicle to 12 rats after ischemic insult and compared them with 6 sham-operated controls. Rats were killed at 48 hours, and histopathologic assessments were performed on the renal tissue. The microscale autoradiographic method was used for qualitative analysis of DNA fragmentation. This method was chosen over the widely used ethidium bromide-staining method because it increases the sensitivity of detection of apoptotic DNA. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling histopathologic staining was used to identify apoptosis in situ. Apoptotic changes were clearly shown by electron microscopy in vehicle-treated animals. Despite showing profound evidence of tubular necrosis, apoptotic changes were markedly reduced in HGF-treated animals compared with vehicle-treated animals. DNA-laddering analysis further confirmed the antiapoptotic effect of HGF. To our knowledge, this is the first in vivo illustration of the inhibitory activity of a growth factor on apoptosis in the setting of tubular necrosis. The role of apoptosis in the setting of acute renal failure has not been elucidated; thus, additional research is necessary to determine the significance of these findings.

Acute Kidney Injury↗

Use of flexion-extension radiographs of the cervical spine in blunt trauma.

STUDY OBJECTIVE: Flexion-extension (F/E) radiographs of the cervical spine are often used in patients with blunt trauma when the evaluating physician remains concerned about bony or ligamentous injuries despite negative or nondiagnostic standard radiographs. The use of this approach has never been addressed in a large prospective study. We sought to determine the clinical factors associated with ordering F/E views and the incidence of diagnostic F/E films in patients with a normal 3-view cervical spine series. METHODS: Patients with blunt trauma selected for radiographic cervical spine imaging at 21 participating institutions in the National Emergency X-Radiography Utilization Study project underwent standard 3-view (cross-table lateral, anteroposterior, and odontoid views) series, as well as any other imaging deemed necessary by their physicians. Injuries detected by means of screening radiography were then compared with final injury status for each patient, as determined by review of all radiographic studies. Patients who underwent F/E views were analyzed separately. RESULTS: Of 818 patients ultimately found to have cervical spine injury, 86 (10.5%) underwent F/E testing. Two patients sustained stable bony injuries detected only on F/E views. Four other patients had a subluxation detected only on F/E views, but all had other injuries apparent on routine cervical spine imaging. CONCLUSION: F/E imaging adds little to the acute evaluation of patients with blunt trauma. Other approaches, including magnetic resonance imaging, computed tomography, or delayed F/E, in the presence of specific clinical concerns would seem to provide a more reasonable approach to adjunctive imaging.

Cervical Vertebrae↗

Report from the Council of Emergency Medicine Residency Directors subcommittee on graduate medical education funding: effects of decreased medicare support.

INTRODUCTION: Recent changes by the Health Care Financing Administration (HCFA) have resulted in decreased Medicare support for emergency medicine (EM) residencies. OBJECTIVE: To determine the effects of reduced graduate medical education (GME) funding support on residency size, resident rotations, and support for a fourth postgraduate year (PGY) of training and for residents with previous training. METHODS: A 36-question survey was developed by the Council of Emergency Medicine Residency Directors (CORD) committee on GME funding and sent to all 122 EM program directors (PDs). Responses were collected by the Society for Academic Emergency Medicine (SAEM) office and blinded with respect to the institution. RESULTS: Of 122 programs, 109 (89%) responded, of which 78 were PGY 1-3 programs, 19 were PGY 2-4, and 12 were PGY 1-4. The PDs were asked specifically whether there were changes in program size due to changes in Medicare reimbursement. Although few programs (12%) decreased their size or planned to decrease their size, 39% had discussions regarding decreasing their size. Thirty percent of the PDs responded that other programs at their institution had already decreased their size; 26% of the PDs had problems with financing outside rotations; and 24% had a decrease in off-service residents in their emergency departments (EDs). Only seven (6%) of programs paid residents from practice plan dollars, while most (82%) were fully supported by federal GME funding. Nearly all four-year programs (97%) received full resident salary support from their institutions and 77% of programs accept residents with previous training. CONCLUSIONS: Nearly all EM programs are fully supported by their institutions, including the fourth postgraduate year. Most programs take residents with previous training. Although few programs have reduced their size, many are discussing this. Many programs have had difficulty with funding off-service rotations and many have had decreased numbers of off-service residents in their EDs. Recent GME funding changes have had adverse effects on EM residency programs.

Data Collection↗

Imaging of benign and malignant focal liver lesions.

Over the past 15 years, MR imaging of the abdomen and pelvis has progressed significantly. Although initially found to be useful as an adjunct to CT imaging for selective applications, MR imaging now is establishing a role as a primary diagnostic technique. Increasing evidence shows that MR imaging has advantages over CT regarding diagnostic sensitivity and specificity for many abnormalities of solid organs, bile and pancreatic ducts, bowel, peritoneum, and retroperitoneum. This article discusses and contrasts current MR and CT techniques for imaging the liver and discusses the relative ability to identify and diagnose focal liver disease.

Contrast Media↗

Colon diseases: MR evaluation using combined T2-weighted single-shot echo train spin-echo and gadolinium-enhanced spoiled gradient-echo sequences.

This study demonstrates the appearance of large bowel diseases on magnetic resonance (MR) images using breath-hold T2-weighted half-Fourier acquisition snapshot turbo spin-echo (HASTE), breath-hold T1-weighted spoiled gradient-echo (SGE), and breath-hold gadolinium-enhanced T1-weighted SGE with and without fat-suppression sequences. The study represents a collective experience using a generalized combined abdominal-pelvic imaging protocol. Of 29 patients, 27 had surgical, endoscopic, microbiological, and/or histopathological correlation, and 2 had a diagnosis based on characteristic imaging findings. Fifteen patients had neoplastic disease including colon adenocarcinoma (n = 11), rectosigmoid carcinoid (n = 1), familial adenomatous polyposis (n = 2), and cecal lipoma (n = 1). Fourteen patients had non-neoplastic disease including diverticulosis (n = 6), ischemic colitis (n = 2), pseudomembranous colitis (n = 2), acute appendicitis with periappendiceal abscess (n = 2), Mycobacterium avium intracellulare (MAI) colitis (n = 1), and Crohn's proctocolitis (n = 1). In all 15 patients with neoplastic diseases, MR imaging depicted the primary lesions and demonstrated local extent. Mass lesions were best shown on T2-weighted HASTE and gadolinium-enhanced fat-suppressed SGE images. Of 14 patients with non-neoplastic diseases, inflammatory changes were best shown on gadolinium-enhanced fat-suppressed T1-weighted SGE images in all cases. MR imaging with fast scanning breath-hold techniques and intravenous gadolinium enhancement provided good depiction and characterization of large bowel diseases.

Adolescent↗

Sequential use of gadolinium chelate and mangafodipir trisodium for the assessment of focal liver lesions: initial observations.

The purpose of this study was to assess the feasibility of sequential administration of 2 different MR imaging contrast agents using a single visit protocol to image focal liver abnormalities. Twenty-one patients with known or suspected liver lesions were included in the study. All patients received a bolus intravenous injection of gadolinium chelate (Gd) and dynamically enhanced imaging performed. The patients then received an injection of mangafodipir trisodium (Mn) contrast and a second scan performed with an average delay of 62 min after the Gd bolus injection. The images were evaluated to determine the appearance of liver lesions after administration of each contrast agent, and for evidence of prior Gd administration adversely affecting evaluation of images acquired after Mn administration. Focal liver lesions were present in 19 patients, including 8 with liver metastases, 1 with liver lymphoma, 6 with hemangiomas, 3 with focal nodular hyperplasia (FNH), and 1 with hepatic abscess. In 2 other patients no liver lesions were identified in either the post-Gd or post-Gd-post-Mn scans. All malignant lesions identified on the post-Gd scan were also identified on post-Gd-post-Mn scans. Although the potential benefit for increasing detection sensitivity for hepatic metastases was not demonstrated, this is a preliminary series. This study does demonstrate the practicality for use a single visit sequential Gd-Mn protocol described here, with possible application of this technique for further assessment of the utility of combining Gd and Mn for detection of liver metastases.

Adult↗