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Biomedical subjects

M Baker

Publications and source records attributed to M Baker.

At least 91 records · Page 5Linked to original sources
PubMed1999

The 1996 pertussis epidemic in New Zealand: descriptive epidemiology.

AIM: To describe the 1996 pertussis epidemic. METHODS: Hospitalisation, notification and laboratory data were used to describe the 1996 pertussis epidemic and compare it with previous epidemics. RESULTS: The 1996 epidemic spanned 24 months. The crude hospitalisation rate from 1 June 1995 to 31 May 1997, was 10.1 per 100,000 person years, being highest for children aged six weeks to two months (42 to 90 days old inclusive; 1402 per 100,000). The 1996 epidemic involved more hospitalisations than the 1991 and 1986 epidemics, and a greater proportion for children under the age of one year (77%), compared to previous epidemics (60-70%). There were no deaths. Pertussis only became notifiable from 1 June 1996. The crude notification rate for the following twelve months was 19.8 per 100,000 (equivalent hospitalisation rate 6.7 per 100,000); children aged six weeks to two months of age had the highest notification rate (531 per 100,000; equivalent hospitalisation rate 1021 per 100,000). In 1996-97, children aged under 15 months accounted for 21% of notifications, but 82% of hospitalisations. Europeans tended to have higher rates of notifications than non-Europeans, but lower rates of hospitalisation. CONCLUSIONS: New Zealand continues to experience high rates of pertussis as a result of inadequate immunisation coverage. The increase in hospitalisations during the 1996 epidemic may reflect a real increase in the population-based incidence, or other changes (e.g. hospitalisation practice, increase in vulnerable children with poor access to primary care). Improved rates, accuracy and completeness of pertussis notifications will improve the ability of notification data to accurately describe future epidemics and estimate vaccine effectiveness. Further debate is required regarding the aims of pertussis immunisation; accelerating the timing of the first three doses and adding further doses of pertussis vaccine on the national immunisation schedule; and the role of acellular pertussis vaccines. In the meantime, the priority must be increasing on-time immunisation coverage.

Adolescent↗
PubMed1999

Low frequency of pathogenic mutations in the ubiquitin carboxy-terminal hydrolase gene in familial Parkinson's disease.

A coding substitution (I93M) in the ubiquitin carboxy-terminal L1 (UCH-L1) gene has recently been identified in a German family with Parkinson's disease. We have sequenced the entire coding region of the gene in 11 families who have a pattern of disease consistent with autosomal dominant inheritance. We found a polymorphism (S18Y) in exon 3, two polymorphisms in the 5' non-coding region, upstream of the transcription start, and an insertion/deletion polymorphism in intron 4. The S18Y allele is present on approximately 20% of chromosomes in a Caucasian population. These changes are, therefore, unlikely to be pathogenic. We conclude that the I93M variant must either be a rare cause of disease or a harmless substitution whose occurrence in the family reflects a chance co-occurrence.

Adult↗
PubMed1999

No pathogenic mutations in the persyn gene in Parkinson's disease.

The persyn (gamma-synuclein) gene is highly homologous to the alpha-synuclein gene and is highly expressed in the nervous system. It is therefore, an excellent candidate gene for Parkinson's disease. However, we have sequenced the gene in a large number of families with parkinsonism and failed to find pathogenic mutations.

Age of Onset↗
PubMed1999

The CD45 tyrosine phosphatase regulates CD3-induced signal transduction and T cell development in recombinase-deficient mice: restoration of pre-TCR function by active p56(lck).

The pre-TCR complex regulates the transition from CD4(-)CD8(-) double-negative (DN) to CD4(+)CD8(+) double-positive (DP) thymocytes during T cell development. In CD45(-/-) mice there is an accumulation of DN cells, suggesting a possible role for CD45 in pre-TCR signaling. We therefore crossed CD45(-/-) with Rag-1(-/-) mice to investigate the signaling functions of the CD3 complex in DN thymocytes. Remarkably, treatment of Rag-1(-/-)/CD45(-/-) mice with a CD3 mAb caused maturation to the DP stage at only 3% of the level measured in Rag-1(-/-) mice. Furthermore, ligation of the CD3 complex on Rag-1(-/-) /CD45(-/-) thymocytes in vitro induced less tyrosine phosphorylation in specific proteins when compared to Rag-1(-/-) thymocytes. CD45(-/-) mice were also crossed with pLGFA mice expressing a constitutively active form of the lck tyrosine kinase which restored the DN to DP transition to near normal levels. Our results are consistent with a model in which CD45-activated p56(lck) is critical for pre-TCR signal transduction.

Animals↗
PubMed1999

Frequency of tau mutations in three series of non-Alzheimer's degenerative dementia.

Splice-site and missense mutations have been identified in tau associated with frontotemporal dementia with parkinsonism linked to chromosome 17. In this study we assessed the genetic contribution of tau mutations to three patient series with non-Alzheimer's (non-AD) degenerative dementia. The groups included (1) a community-based dementia series from Minnesota, MN; (2) a referral series with clinicopathological tauopathy; and (3) a pathologically confirmed familial frontotemporal dementia series from Manchester, UK. Comparing the three clinical series: in the stringently diagnosed Manchester frontotemporal dementia series, tau mutations were present in 13.6% of cases (three splice-site mutations); in the clinicopathological referral series that used more general inclusion criteria, 3 cases with P301L mutations were observed, which represents a lower mutation frequency of 3.6% (9.4% in familial cases); in contrast, tau mutations were not detected in the Minnesota community-based dementia series, suggesting the occurrence of these mutations in dementia generally is rare (<0.2%). These data identify the prevalence of mutations in three different clinical settings and indicate that this figure is sensitive to the diagnostic criteria used in each patient series.

Adult↗
PubMed1999

The relationship between interleukin-6 and herpes simplex virus type 1: implications for behavior and immunopathology.

Cytokines are hormones once thought to be restricted to the immune system produced solely by hematopoietic-derived cells and acting on receptors expressed by cells of the immune system. However, it is now clear that many cytokines are produced not only by lymphocytes, monocytes, granulocytes, and dendritic cells but are also synthesized by cells outside the realm of the immune system in response to stimuli that may not be associated with immune homeostasis. In fact, there is evidence supporting a role of selected cytokines modifying behavior and neuroendocrine function. Recently, a potential relationship between the cytokine interleukin (IL)-6 and herpes simplex virus type 1 (HSV-1) reactivation has been found. This article discusses the relevance of these findings and considers the potential impact that HSV-1 infection has on behavior and chronic inflammatory processes that can occur in the nervous system during "latent" virus infection as a result of chronic IL-6 expression.

Herpes Simplex↗
PubMed1999

Safety of peripheral intravenous catheters in children.

OBJECTIVES: To determine the overall and per-day risk of complications of short peripheral intravenous (PIV) catheters placed for indefinite periods. DESIGN: During 5 months, general pediatric patients receiving intravenous therapy through short PIV catheters were monitored. Patient and catheter characteristics were recorded, complications were noted, and rolled semiquantitative cultures of removed catheters were performed. Major endpoints were infection and phlebitis. Per-day risk of complications and catheter colonization (>15 colony-forming units) were calculated. SETTING: University children's hospital. PATIENTS: General pediatric ward inpatients with PIV. RESULTS: We studied 642 Teflon catheters in place >24 hours (mean, 3.7 days) in 525 patients. There were no cases of catheter sepsis (0%; 95% confidence interval [CI95], 0%-0.6%), one possible insertion-site infection (0.2%; CI95, 0.004%-0.9%), and seven cases of phlebitis (1.1%; CI95, 0.4%-2.3%). Catheter colonization occurred in 92 (26%) of 348 catheters cultured. Neither the per-day risk of phlebitis nor of catheter colonization increased significantly with placement >3 days. CONCLUSION: Current guidelines recommend replacement of PIV catheters in adults within 2 to 3 days; no recommendations are made for children. Our findings and those of others indicate that the overall risk of PIV catheter complications in children is extremely low and would not be reduced substantially by routine catheter replacement.

Bacteria↗
PubMed1999

Association of an extended haplotype in the tau gene with progressive supranuclear palsy.

We describe two extended haplotypes that cover the human tau gene. In a total of approximately 200 unrelated caucasian individuals there is complete disequilibrium between polymorphisms which span the gene (which covers approximately 100 kb of DNA). This suggests that the establishment of the two haplotypes was an ancient event and either that recombination is suppressed in this region, or that recombinant genes are selected against. Furthermore, we show that the more common haplotype (H1) is significantly over-represented in patients with progressive supranuclear palsy (PSP), extending earlier reports of an association between an intronic dinucleotide polymorphism and PSP.

Aged↗
PubMed1999

Susceptibility of beta-lactamase to core amino acid substitutions.

To determine which amino acids in TEM-1 beta-lactamase are important for its structure and function, random libraries were previously constructed which systematically randomized the 263 codons of the mature enzyme. A comprehensive screening of these libraries identified several TEM-1 beta-lactamase core positions, including F66 and L76, which are strictly required for wild-type levels of hydrolytic activity. An examination of positions 66 and 76 in the class A beta-lactamase gene family shows that a phenylalanine at position 66 is strongly conserved while position 76 varies considerably among other beta-lactamases. It is possible that position 76 varies in the gene family because beta-lactamase mutants with non-conservative substitutions at position 76 retain partial function. In contrast, position 66 may remain unchanged in the gene family because non-conservative substitutions at this location are detrimental for enzyme structure and function. By determining the beta-lactam resistance levels of the 38 possible mutants at positions 66 and 76 in the TEM-1 enzyme, it was confirmed that position 76 is indeed more tolerant of non-conservative substitutions. An analysis of the Protein Data Bank files for three class A beta-lactamases indicates that volume constraints at position 66 are at least partly responsible for the low tolerance of substitutions at this position.

Amino Acid Sequence↗
PubMed1999

Long-term outcome of achalasia treatment: the need for closer follow-up.

Treatment of achalasia includes pneumatic dilation (PD) and surgical myotomy (SM). Success rates range from 32% to 98% and are mostly based on symptomatic response. Our aims were to determine the long-term outcome of patients treated for achalasia and the adequacy of long-term follow-up. Patients treated with PD or SM between 1986 and 1990 were contacted by telephone after a minimum of 4 years after treatment, and asked about symptoms and need for retreatment since their discharge from our institution. Symptomatic response was classified as excellent/good or fair/poor using the Vantrappen score. Treatment was deemed a failure if patients were symptomatic on callback, needed retreatment, technical problems occurred during PD, or perforation occurred. Forty-seven PD patients and 15 SM patients were studied. There were no significant differences in clinical parameters between groups. Median time to callback was 82 and 73 months, respectively. Failure rates were high, respectively 74% and 67%. Importantly, 38% of PD and 33% of SM patients failed to seek help despite symptom recurrence. Achalasia treatment failures are higher than anticipated. This may be because of the lack of routine follow-up as well as patients' failure to seek help when symptoms recur. Achalasia patients need closer follow-up and may benefit from early intervention based on objective tests rather than symptoms alone.

Adult↗
PubMed1999

Analysis of vaginal cell populations during experimental vaginal candidiasis.

Studies with an estrogen-dependent murine model of vaginal candidiasis suggest that local cell-mediated immunity (CMI) is more important than systemic CMI for protection against vaginitis. The present study, however, showed that, compared to uninfected mice, little to no change in the percentage or types of vaginal T cells occurred during a primary vaginal infection or during a secondary vaginal infection where partial protection was observed. Furthermore, depletion of polymorphonuclear leukocytes (PMN) had no effect on infection in the presence or absence of pseudoestrus. These results indicate a lack of demonstrable effects by systemic CMI or PMN against vaginitis and suggest that if local T cells are important, they are functioning without showing significant increases in numbers within the vaginal mucosa during infection.

Animals↗
PubMed1999

Staff grade doctors and the consultant ladder: falling off or stepping off?

The majority of the doctors in staff grade posts surveyed had qualified overseas and a substantial proportion were dissatisfied with their posts. Very few doctors had received adequate careers counselling before starting their post and many were concerned at the lack of opportunities for career development.

Career Mobility↗
PubMed1999

The impact of nutritional status on the outcome of lung volume reduction surgery: a prospective study.

OBJECTIVES: To study the incidence and clinical significance of nutritional deficiencies in patients with emphysema undergoing lung volume reduction surgery (LVRS). DESIGN: Prospective observational study. SETTING: University-based teaching hospital. PATIENTS: Fifty-one consecutive patients with end-stage emphysema undergoing video-assisted thoracoscopic surgery for LVRS. INTERVENTIONS: All patients had their body mass index (BMI) and serum nutritional indexes (albumin, transferrin, total protein, cholesterol) measured preoperatively and postoperatively. Various clinical parameters were also compared between two groups. RESULTS: The BMI was normal in 24 patients (47%), and 27 patients (53%) had a below normal BMI. A preoperative analysis of the serum nutritional indexes revealed no clinically significant differences between the two groups, but postoperative levels were significantly lower in the low BMI group. Anthropometric measurements supported the designation of nutritional status by BMI. Clinically, 26% of the patients in the low BMI group required prolonged ventilatory support (> 24 h), compared to only 4% of the patients with a normal BMI. The hospital length of stay (LOS) also differed, averaging 15.9 days in the low BMI group, compared to an average of 11.8 days in the normal BMI group. CONCLUSION: Approximately 50% of patients undergoing LVRS for emphysema have a deficient nutritional status identifiable by BMI, but not by standard nutritional indexes. This impaired nutritional status is associated with increased morbidity following LVRS. We suggest that BMI is an accurate determinant of nutritional status in this patient population, and we speculate that preoperative repletion of nutritional deficiencies may decrease hospital morbidity, hospital LOS, and overall costs in the malnourished population undergoing LVRS.

Aged↗
PubMed1998

A measles epidemic controlled by immunisation.

AIM: In 1997, an immunisation campaign, using measles-mumps-rubella vaccine, was planned for children aged 2-10 years to prevent a measles epidemic predicted by mathematical modelling. The epidemic started before the campaign and is described here. METHOD: Measles hospitalisation, notification and laboratory data were combined. RESULTS: The epidemic started in April 1997 and was largely over by January 1998. No deaths were identified and only one hospitalisation was coded as measles encephalitis, compared to seven deaths and ten cases of measles encephalitis in the 1991 epidemic. For the 12 months from 1 March 1997 there were 2,169 (60 per 100,000) measles cases identified, 314 (9 per 100,000) of whom were hospitalised. Two-thirds of hospitalised cases were notified. The age-standardised measles incidence rates were 33, 34, and 174 per 100,000 for Europeans, Maori and Pacific people, respectively. The respective age-standardised hospitalisation rates were 4, 9 and 32 per 100,000. Measles incidence was highest for under one-year-olds (904 per 100,000) and low for 11-16 year-olds (27 per 100,000)--the cohort previously offered a second vaccine dose. Most cases were aged 10 years and under, and this group were the main drivers of virus transmission. CONCLUSIONS: The immunisation campaign prevented 90-95% of predicted cases. The campaign was appropriately targeted at children aged 10 years and under.

Adult↗