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Biomedical subjects

M Montgomery

Publications and source records attributed to M Montgomery.

At least 19 recordsLinked to original sources
PubMed2004

A preliminary study of residential paint lead concentrations in Johannesburg.

While efforts are underway to phase out the use of leaded petrol in South Africa, relatively little attention has been devoted to the potential for childhood exposure to lead used in paint. This is one of the first studies undertaken on the African continent to report on the presence of lead-based paint. In South Africa, there is a dearth of information available on the extent of past and current use of lead-based paint. Recent studies demonstrate that large numbers of young South African children continue to be at risk of elevated blood lead concentrations. To investigate the prevalence of lead-based paint in Johannesburg dwellings, the South African Medical Research Council recently undertook a preliminary study in which samples of residential paint were collected from homes in 60 randomly selected suburbs across the city. The results indicate that 17% of all of the samples collected were lead-based paint (paint that contains lead levels equal to or greater than 0.5% by weight). The percentage of lead by weight in the samples ranged from 0.01% to 29.00%. Lead-based residential paint was found in 20% of the sampled homes, located in both new and old suburbs, and in suburbs from a variety of different socioeconomic backgrounds. These results, in conjunction with those emanating from other studies of childhood lead exposure currently being conducted by the Medical Research Council, indicate that weathering, peeling, or chipping lead-based paint may play an important role in childhood lead exposure in South Africa. Children who have a pica tendency may be at particular risk.

Child↗
PubMed2001

Fate map of early avian cardiac progenitor cells.

Cardiogenic fate maps are used to address questions on commitment, differentiation, morphogenesis and organogenesis of the heart. Recently, the accuracy of classical cardiogenic fate maps has been questioned, raising concerns about the conclusions drawn in studies based on these maps. We present accurate fate maps of the heart-forming region (HFR) in avian embryos and show that the putative cardiogenic molecular markers Bmp2 and Nkx2.5 do not govern the boundaries of the HFR as suggested in the literature. Moreover, this paper presents the first fate map of the HFR at stage 4 and addresses a void in the literature concerning rostrocaudal patterning of heart cells between stages 4 and 8.

Animals↗
PubMed2000

Diverse, yet-to-be-cultured members of the Rubrobacter subdivision of the Actinobacteria are widespread in Australian arid soils.

Phylogenetic analyses of ribosomal RNA gene sequences (rDNAs) retrieved from an Australian desert soil sample (Sturt National Park) revealed the presence of a number of clones which branched deeply from the high GC Gram-positive division line of descent. The most abundant group of these clones were related to Rubrobacter. An oligonucleotide probe was designed to have broad specificity to Rubrobacter and relatives. This probe was used to interrogate eight rDNA libraries representing four distinct land forms within the Australian arid zone. Relative abundance of Rubrobacter-relatives in these samples ranged from 2.6 to 10.2%. Clones from these libraries were selected for sequence analysis on the basis of a heteroduplex mobility assay to maximise the diversity represented in the sample. Phylogenetic analyses of these rDNA clones and Rubrobacter-related clones reported in the literature show strong support for three distinct groups. Database-searching revealed 'Rubrobacteria' were relatively abundant in a number of published soil rDNA libraries but absent from others. A PCR assay for group-1 'Rubrobacteria' was used to test for their presence in 21 environmental samples. Only marine and arid-zone soil samples gave positive PCR results. Taken together these results indicate 'Rubrobacteria' are a widespread group of variable abundance and diversity.

Journal Article↗
PubMed2000

The rostro-caudal position of cardiac myocytes affect their fate.

During chick embryogenesis, cells destined to form cardiac myocytes are located within the primitive streak at stage 3 in the same relative anterior-posterior distribution as in the prelooped heart. The most rostral cells contribute to the extreme anterior pole of the heart, the bulbus cordis, and the most caudal to the extreme posterior end, the sinoatrial region. After gastrulation, these cells commit to the myocyte lineage and, retaining their relative positions, migrate to the anterior lateral plate. From stages 5 to 10 they diversify into atrial and ventricular myocytes, with the former located posteriorly and the latter, anteriorly. To determine the effect of a change in the rostro-caudal position of these cells on their diversification, anterior lateral plate mesoderm and the underlying endoderm were cut and rotated 180 degrees along the longitudinal axis, at stages 4-8. The subsequent diversification of these precursor cells into atrial and ventricular myocytes was examined using lineage-specific markers. Our results showed that altering location along the longitudinal axis through stage 6 changed the normal fate of a precursor cell. The orientation of the overlying ectoderm did not alter normal morphogenesis or determination of fate.

Animals↗
PubMed2000

Safety and acceptability of a baggy latex condom.

A total of 104 couples participated in a randomized crossover trial to compare a new baggy condom with a straight-shaft condom produced by the same manufacturer. Participants completed a coital log after using each condom. All couples used five condoms of each type. Among 102 couples who did not report major deviations from the protocol, the breakage rate was eight of 510 (1.6%) for the baggy condom, and six of 510 (1.2%) for the standard condom (rate difference, RD = 0. 4%, 95% confidence interval of the RD, CI = -1.0%; +1.8%). Slippage was reported in 50 baggy condom logs and in 58 standard condom logs; the slippage rate was 50 of 510 (9.8%) for the baggy condom, and 58 of 510 (11.4%) for the standard condom (RD = -1.6%, 95% CI = -5.4%; +2.2%). Slippage was most often partial (<1 inch) and may not indicate condom failure. Severe slippage rates were 11 of 510 (2.2%) for the baggy condom, and 18 of 510 (3.5%) for the standard condom (RD = -1.4%, 95% CI = -3.4%; +0.7%). The findings support the conclusion that the two condoms are equivalent with respect to breakage and slippage. The participants appeared to prefer the baggy condom, suggesting that the new product may be more acceptable to the public than the traditional straight-shaft condoms, and may be easier to use consistently over long time periods.

Adolescent↗
PubMed2000

Resuscitation in the hospital: relationship of year and rhythm to outcome.

OBJECTIVE: determine the frequency of initial rhythms in in-hospital resuscitation and examine its relationship to survival. Assess changes in outcome over time. METHODS: retrospective cohort (registry) including all admissions to the Medical Center of Central Georgia in which a resuscitation was attempted between 1 January, 1987 and 31 December, 1996. RESULTS: the registry includes 3327 admissions in which 3926 resuscitations were attempted. Only the first event is reported. There were 961 hospital survivors. Survival increased from 24.2% in 1987 to 33.4% in 1996 (chi(2)=39.0, df=1, P<0.0001). Survival was affected strongly by initial rhythm (chi(2)=420.0, df=1, P<0.0001) and decreased from 63.2% for supraventricular tachycardia (SVT) to 55.3% for ventricular tachycardia (VT), 51.0% for perfusing rhythms (PER), 34.8% for ventricular fibrillation (VF), 14.3% for pulseless electrical activity (PEA) and 10.0% for asystole (ASYS). PEA was the most frequent rhythm (1180 cases) followed by perfusing (963), asystole (580), VF (459), VT (94) and SVT (38). DISCUSSION: the powerful effect of initial rhythm on survival has been reported in pre-hospital and in-hospital resuscitation. VF is considered the dominant rhythm and generally accounts for the most survivors. We report good outcome for each; however, VF represents only 13.8% of events and 16.7% of survivors. PEA accounts for more survivors (169) than does VF (160). Our improved outcome is partially explained by changes in rhythms, but other institutional variables need to be identified to fully explain the results. Further studies are needed to see if our findings can be sustained or replicated.

Adolescent↗
PubMed1999

Resuscitation in the hospital: differential relationships between age and survival across rhythms.

OBJECTIVE: Assess the frequency and outcome of inhospital resuscitation and determine the relationship between patient age and survival and whether it is affected by initial rhythm. DESIGN: Retrospective, single-institution, registry study of inhospital resuscitation. SETTING: A 550-bed, tertiary-care, teaching hospital in Macon, GA. PATIENTS: All admissions for which a resuscitation was attempted in the Medical Center of Central Georgia during the period of January 1, 1987 through December 31, 1993. The registry sample included 2,394 admissions, for which 2,813 resuscitation attempts were made; only the first resuscitation attempt during an admission was analyzed. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Rates of survival to discharge steadily increased from 24.4% in 1987 to 38.6% in 1993; the overall survival rate was 26.8%. Age, used as a continuous variable, was strongly related to survival (odds ratio = 0.984; p < .0001). Categorically, overall survival rates for pediatric, adult, and geriatric patients were 56.4%, 29.0%, and 24.0%, respectively. Survival rates also varied significantly (odds ratio = 0.469; p < .0001) among initial rhythms, i.e., supraventricular tachycardia (60.7%), ventricular tachycardia (57.6%), perfusing rhythms (49.84%), ventricular fibrillation (32.0%), pulseless electrical activity (14.6%), and asystole (9.1%). The relationship between age and survival did not change across the years included in the study, but did vary as a function of initial rhythm (p < .0001). Age was positively related to survival when initial rhythm was supraventricular tachycardia (p = .04), negatively related to survival when the initial rhythm was perfusing (p < .0001) or pulseless electrical activity (p = .0002), and not related to survival when the initial rhythm was ventricular tachycardia (p = .98), ventricular fibrillation (p = .14), or asystole (p = .21). CONCLUSIONS: The relationship between patient age and a successful resuscitation attempt is not as simple as reported earlier. Whether age is related to increased or decreased survival, or is unrelated to survival, depends on the rhythm extant when resuscitation attempts begin. Survival rates were higher than most reported elsewhere and improved significantly over time. Multicentered studies are needed to determine whether these results are unique to the institution studied.

Adolescent↗
PubMed1999

Cost of care for individuals with cystic fibrosis: a regression approach to determining the impact of recombinant human DNase.

We estimated direct medical costs of care and important determinants of the costs in patients with cystic fibrosis (CF), including therapy with recombinant human DNase (rhDNase). Costs were estimated with resource use data from the Epidemiologic Study of Cystic Fibrosis. Ordinary least squares regression was used to determine the effect of clinical and demographic variables on individual cost of care. The estimated cost of caring for 303 patients in Alberta was $2,279,801 in 1996. The mean cost of care was $7524 (range $386-92,376)/patient. Regression results indicated that age and forced expiratory volume predicted had a negative association with costs. Being female, receiving rhDNase, and having Pseudomonas aeruginosa or Burkholderia cepacia were all associated with high costs. Our estimates indicated large interindividual variation in cost of care for patients with CF.

Adult↗
PubMed1999

A World Wide Web Internet engine for collaborative entry and peer review of radiologic teaching files.

OBJECTIVE: Radiologists can now use the Internet as a dissemination medium for radiologic teaching files. This has greatly increased the availability of radiologic information to a larger number of people. However, the creation of the teaching files themselves remains a static and labor-intensive process. As a partial solution to this problem, we set out to create a World Wide Web-based Internet engine for the collaborative entry and peer review of radiologic teaching files. CONCLUSION: We created a system that facilitates, simplifies, and improves the generation of radiologic teaching files. We used the Internet to help promote the creation of teaching files in a more timely, efficient, and effective manner.

Audiovisual Aids↗
PubMed1998

Impaired gastric emptying in children with repaired esophageal atresia: a controlled study.

BACKGROUND: Scintigraphy is considered the "gold standard" for investigating gastric emptying. The lack of standards regarding registration technique and meal composition has been a problem especially in pediatric patients. METHODS: In this study, gastric emptying of a solid meal was assessed by scintigraphy in 10 patients with repaired esophageal atresia (5 to 10 years old), and the results were compared with those in 11 healthy control children (5 to 11 years old). The meal consisted of pancakes with a fixed energy composition labeled with Tc-99m. Fractional meal retention values were plotted as a function of time. RESULTS: Half-emptying time and lag phase values were longer in the patient group, whereas the emptying rate was slower and the retention values at 60 and 90 minutes were higher than in the control group. Extremely long lag phase and slow emptying rates were seen in two patients with reflux symptoms and abdominal complaints. Gastric emptying in healthy children has not previously been studied by scintigraphy. The results of this study show that values for gastric emptying of solids in healthy children correspond well to those reported in healthy adults. CONCLUSION: Scintigraphy is an easy and reliable method for gastric emptying studies in children. The radioactive dose can be kept very low, which makes it a safe method even for pediatric patients. Delayed gastric emptying can occur in patients who have repaired esophageal atresia, and may be associated with reflux symptoms and abdominal complaints.

Child↗
PubMed1998

Swallowing disorders after esophageal atresia evaluated with videomanometry.

BACKGROUND: Patients with repaired esophageal atresia often show persistent motility disorders of the esophagus. METHODS: In this study, the authors used a newly developed method, videomanometry, to study intraluminal pressures and function of the pharynx and upper esophagus in such a group of patients and compared the results with those in healthy age-matched controls. RESULTS: A significant difference was found between timing of the pharynx contraction and upper esophageal sphincter (UES) relaxation, indicating a dyscoordination of swallowing in the patient group. Transit time of bolus from the pharynx to the esophagus was also shorter for the patient group. Such dyscoordination may be a risk factor that can cause aspiration and respiratory symptoms. CONCLUSION: UES resting pressure and residual pressure on swallowing, did not differ between the two groups.

Adult↗
PubMed1998

A clinicopathological study of autism.

A neuropathological study of autism was established and brain tissue examined from six mentally handicapped subjects with autism. Clinical and educational records were obtained and standardized diagnostic interviews conducted with the parents of cases not seen before death. Four of the six brains were megalencephalic, and areas of cortical abnormality were identified in four cases. There were also developmental abnormalities of the brainstem, particularly of the inferior olives. Purkinje cell number was reduced in all the adult cases, and this reduction was sometimes accompanied by gliosis. The findings do not support previous claims of localized neurodevelopmental abnormalities. They do point to the likely involvement of the cerebral cortex in autism.

Adult↗
PubMed1998

Immunostimulation of murine spleen cells by materials associated with bovine milk protein fractions.

Purified bovine milk proteins that were added to cultures of murine spleen cells significantly increased cell proliferation and production of immunoglobulin M. Casein and a whey mixture consisting of alpha-lactalbumin, bovine serum albumin, bovine gamma globulin, and beta-lactoglobulin (beta-LG) were stimulatory. Of the three beta-LG preparations that are commercially available (beta-LG containing variants A and B, purified variant A, and purified variant B), the unseparated mixture containing both the A and B variants showed the most immunomodulatory activity. Both alkaline treatment and trypsin digestion of the beta-LG preparation markedly reduced its effectiveness. Polymyxin B, while greatly diminishing the stimulatory effect of lipopolysaccharide, had no significant effect on either the enhancement of cell proliferation or the enhancement of immunoglobulin production by beta-LG. In the presence of S-(n-butyl)-homocysteine sulfoxamine, the stimulatory effect of beta-LG on cell proliferation and IgM production in vitro was markedly reduced.

Animals↗
PubMed1997

Alkalinization is ineffective for severe hyperkalemia in nonnephrectomized dogs. Hyperkalemia Research Group.

OBJECTIVE: To determine whether alkalinization with sodium bicarbonate (NaHCO3) in near-lethal hyperkalemia either lowers potassium (K) rapidly or shortens duration of cardiac conduction disturbances. METHODS: A controlled canine laboratory investigation of 3 treatments for severe hyperkalemia. Conditioned dogs (n = 8; 17-30 kg) received, in random order, 2 mmol/kg of each of 3 treatments (matched in sodium and water) in separate experiments > or = 1 week apart: 1.05% NaHCO3 over 60 minutes (infusion therapy); 8.4% NaHCO3 over 5 minutes, then 14 mL/kg sterile water over 55 minutes (bolus therapy); 8.4% NaCl over 5 minutes, then 14 mL/kg sterile water over 55 minutes (saline therapy). Prior to administering one of the above therapies, the animals were anesthetized with 0.5-2.5% isoflurane and ventilated to maintain a normal PCO2. After 30 minutes of equilibration, 2 mmol/kg/hr (loading dose) of a 2-mmol/mL KCl solution was given until idioventricular or relative junctional bradycardic dysrhythmias were sustained for 15 minutes. Then KCl was decreased to 1 mmol/kg/hr (maintenance dose) for 2 hours and 45 minutes. Treatment was begun after 45 minutes of maintenance KCl infusion. RESULTS: The pretreatment K level (all studies) was 9.06 +/- 0.82 mmol/L (mean +/- SD). Although the mean K level decreased more after saline therapy than after bolus therapy at every time, differences were neither statistically significant nor clinically important during the first 30 minutes. The means of the differences in decreases (saline minus bolus) were small, 0.26 (95% CI, -0.48 to 1.00) at 15 minutes, 0.16 (95% CI, -0.67 to 0.98) at 30 minutes. Dysrhythmia duration was shorter with bolus therapy than for saline therapy in only 1 of 5 dogs (p = 0.38). CONCLUSIONS: Hypertonic saline bolus lowered plasma K as effectively as NaHCO3 bolus in this animal model within the first 30 minutes. Clinically meaningful decreases due to alkalinization alone within 30 minutes are unlikely.

Animals↗
PubMed1993

Esophageal atresia: mortality and complications related to gastroesophageal reflux.

Low birthweight and associated anomalies are important risk factors in patients with esophageal atresia. Gastroesophageal reflux is also a common problem in these patients and can lead to serious complications. The aim of this retrospective study was to analyse complications and mortality in 110 patients treated for esophageal atresia between January 1971-December 1987, in order to determine what role reflux may play. Symptoms of reflux were common in most patients during the first years of life. In some cases the symptoms were serious and even caused some late deaths by aspiration. The overall mortality was 12% (13/110). Early mortality (six patients) was caused by prematurity and associated anomalies, whereas late mortality often was caused by aspiration or other respiratory complications. Patients who had been operated with a circular myotomy showed more complications, but did not show a higher mortality rate than the remainder. This study confirms the importance of identifying patients with reflux at an early stage in order to prevent serious complications and mortality.

Child, Preschool↗
PubMed1993

Laparoscopic-assisted excision of a solitary cecal ulcer.

Laparoscopic-assisted excision of a solitary cecal ulcer that presented with right lower quadrant pain in a 61-year-old male is described. The patient benefited from complete surgical excision of his disease and he experienced a rapid postoperative recovery similar to that of other laparoscopic procedures, while foregoing the postoperative discomfort and morbidity associated with celiotomy. Excision of a complicated, benign cecal ulcer requires minimal bowel resection and is particularly amenable to laparoscopic assistance for minimally invasive access. For cecal ulcers requiring operative intervention, laparoscopy offers an alternative to open celiotomy.

Cecal Diseases↗