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Biomedical subjects

R Allen

Publications and source records attributed to R Allen.

At least 73 records · Page 4Linked to original sources
PubMed1990

Transplacental transfer of aflatoxin in humans.

This study quantified aflatoxin (AFB1, AFG1 and AFQ1) by enzyme-linked immunosorbent assay in human cord sera obtained at birth and in serum obtained immediately after birth from the mother. The subjects of the study were residents of Songkhla, Thailand. Of the 35 samples of cord sera, 17 (48%) contained aflatoxin in concentrations from 0.064 to 13.6, mean 3.1 nmol/ml. By comparison only two (6%) of 35 maternal sera contained aflatoxin (mean 0.62 nmol/ml). These results demonstrate transplacental transfer and concentration of aflatoxin by the feto-placental unit which may be of biological importance. Aflatoxins are mutagenic, carcinogenic and teratogenic and cause immunosuppression in animals. The implications of these findings are potentially profound and deserve further study.

Aflatoxin B1↗
PubMed1990

Children with congenital anomalies: the preschool period.

To address a gap regarding the development of preschool children with physical congenital anomalies and the adaptational responses of their caretakers, 37 children with anomalies and 44 control children were assessed. Children were administered the Stanford-Binet and the Preschool Language Scale, and the children and their mothers were observed in a series of semi-structured situations. Performance on linguistic and intellectual tests was related to socioeconomic status, not to medical risk. Children with anomalies were more socially reticent and compliant than peers, and their mothers were more controlling and nonverbally active during a teaching task. Results are discussed in terms of Bell's lower-limit adaptational pattern.

Child, Preschool↗
PubMed1990

A comparison of parallel versus perpendicular placement of retention sutures in abdominal wound closure.

A new technique for placement of retention sutures is described. Twenty-five rats underwent midline laparotomy incision. The control group was closed with traditional placement of through-and-through retention sutures placed in a perpendicular direction to the wound. The experimental group was closed with retention sutures placed in a parallel direction to the wound as described below. Wound bursting strength was significantly (P less than 0.001) greater at one to five days in the experimental group compared with the control animals. In addition, inflammatory reaction and pressure necrosis were greater in the control group. It appears that parallel placement of sutures has less of a tendency to cut through tissue when subjected to the distracting forces on a midline wound.

Abdomen↗
PubMed1990

Phase-shifting effects of bright morning light as treatment for delayed sleep phase syndrome.

Bright light has recently been shown to have phase-shifting effects on human circadian rhythms. In this study we applied this effect to 20 patients with delayed sleep phase syndrome (DSPS) who were unable to fall asleep at conventional clock times and had a problem staying alert in the morning. In a controlled treatment study, we found that 2 h of bright light exposure in the morning together with light restriction in the evening successfully phase advanced circadian rhythms of core body temperature and multiple sleep latencies in these patients. This finding corroborates the importance of light for entraining human circadian rhythms.

Arousal↗
PubMed1989

Interpersonal behavior and cardiovascular reactivity in pharmacologically-treated hypertensives.

This study examined the interpersonal behavior and concomitant cardiovascular reactivity (CVR) of hypertensive patients whose resting blood pressure was controlled by antihypertensive medication. Thirty hypertensive and 30 normotensive subjects matched for age, sex and occupational status were recruited from an industrial setting. The groups were compared on measures of interpersonal behavior, blood pressure and heart rate while they engaged in both role-played (RP) and naturalistic interactions (NI) requiring positive and negative assertion. Interpersonal behavior of the groups was generally similar, with two exceptions: hypertensives made fewer requests for new behavior in the negative RP and verbalized more praise statements in the positive NI. There were no differences between the groups on measures of CVR during interpersonal interactions. Overall effectiveness during scenes requiring negative assertion was associated with increased cardiovascular reactivity, especially for hypertensives. The interpersonal behavior and cardiovascular responses of patients taking beta-blocker medication did not differ from those taking diuretics. These findings are discussed with regard to methodological considerations pertinent to the assessment of interpersonal behavior and the issue of heterogeneity among hypertensives.

Adrenergic beta-Antagonists↗
PubMed1989

Spine kinematics: a digital videofluoroscopic technique.

It is notoriously difficult to quantify the kinematic behaviour of vertebral segments in the assessment and localization of mechanical disorders of the spine. This paper describes the use of an image processor and an X-ray machine with image intensifier for the measurement of lumbar spine angular rotation and instantaneous centres of rotation in the coronal plane. The system was calibrated against a model under realistic conditions employing multiplanar motion and X-ray scatter.

Adult↗
PubMed1989

Meta-analysis of placebo-controlled studies of the efficacy of Epogam in the treatment of atopic eczema. Relationship between plasma essential fatty acid changes and clinical response.

Gamma-linolenic acid in the form of a particular variety of evening primrose oil (Epogam) has been reported of value in the treatment of atopic eczema. Nine controlled trials of evening primrose oil were performed in eight centres. Four of the trials were parallel and five cross-over. Doctors and patients assessed the severity of eczema by scoring measures of inflammation, dryness, scaliness, pruritus and overall skin involvement. Individual symptom scores were combined to give a single global score at each assessment point. In the analysis of the parallel studies, both patient and doctor scores showed a highly significant improvement over baseline (P less than 0.0001) due to Epogam: for both scores the effect of Epogam was significantly better than placebo. Similar results were obtained on analysis of the cross-over trials, but in this case the difference between Epogam and placebo in the doctors' global score, although in favour of Epogam, failed to reach significance. The effects on itch were particularly striking. There was no placebo response to this symptom, whereas there was a substantial and highly significant response to Epogam (P less than 0.0001). When the improvements, or otherwise, in clinical condition were related to changes in plasma levels of dihomogammalinolenic and arachidoni acids, it was found that there was a positive correlation between an improvement in clinical score and a rise in the fatty acid levels.

Adolescent↗
PubMed1989

Objective evaluation of the shoulder dystocia phenomenon: effect of maternal pelvic orientation on force reduction.

This report describes the use of maternal pelvic and fetal models, a tactile sensing glove, and a microcomputer data acquisition system to measure fetal shoulder extraction forces. Sixty-nine experiments were carried out in the laboratory setting to simulate vaginal delivery of the aftercoming fetal shoulders. The tests were conducted using a variety of fetal biclavicular diameters (10-13 cm) and maternal pelvic angle positions (McRoberts, 10 degrees; lithotomy, 25 degrees). When comparing lithotomy versus McRoberts positioning, there was a consistent reduction in force needed to extract the fetal shoulders with the latter maneuver. No simulated clavicles were fractured during shoulder delivery until a biclavicular diameter of 12.0 cm was reached. At this point, five of eight clavicles (63%) were fractured at 25 degrees and zero of seven (0%) were fractured at 10 degrees (P less than .025). For all 69 experiments, fetal neck extension readings were consistently lower than the total traction forces recorded by the tactile sensing glove. This suggests that, in addition to the axially oriented fetal neck forces, a component of flexion (lateral force) was also present. As the difficulty of shoulder delivery increased, the impact of these inadvertent flexion forces became most pronounced at the level of the brachial plexus. This is the first study to measure shoulder extraction forces reproducibly using a laboratory model for shoulder dystocia and to describe the pathophysiology of specific neonatal injuries from a force perspective. The results document objectively that McRoberts positioning reduces shoulder extraction forces, brachial plexus stretching, and the incidence of clavicular fracture.

Delivery, Obstetric↗
PubMed1988

Isolation of genes encoding the Neurospora vacuolar ATPase. Analysis of vma-2 encoding the 57-kDa polypeptide and comparison to vma-1.

In partially purified preparations of the vacuolar ATPase from Neurospora crassa, the two most prominent components are polypeptides of Mr = 70,000 and 60,000. We previously reported the isolation of the gene vma-1, which encodes the Mr = 70,000 polypeptide, and presented evidence that the polypeptide contains the site of ATP hydrolysis (Bowman, E. J., Tenney, K., and Bowman, B. J. (1988) J. Biol. Chem. 263, 13994-14001). We now report the isolation of a gene (designated vma-2), that encodes the Mr = 60,000 polypeptide. Analysis of the DNA sequence shows that the polypeptide has 513 amino acids and a molecular mass of 56,808 daltons (and will thus be referred to as the 57-kDa polypeptide). It is fairly rich in polar amino acids and has no apparent membrane-spanning domains. The vma-2 gene contains five short introns (55-71 bases), all clustered in the 5' end of the coding region. The gene maps to the right arm of linkage group II, near 5 S RNA gene 3. Thus, it is unlinked to vma-1 and to other known ATPase genes in N. crassa. The 57-kDa polypeptide shows 25% amino acid sequence identity with the vma-1 gene product. It shows essentially the same degree of similarity (25-28%) to both the alpha and beta subunits of F0F1 ATPases. Analysis of specific regions of the 57-kDa polypeptide, however, suggests it may have a function like that of the alpha subunit in F0F1 ATPases. The data indicate that all four types of ATPase polypeptides have evolved from a common ancestor and that the vacuolar-type ATPases have a structure surprisingly similar to that of the F0F1 ATPases.

Adenosine Triphosphatases↗
PubMed1988

Maternal interaction and language development in children with and without speech-related anomalies.

This study explores relationships among maternal behavior, child language, and location of congenital structural anomaly in three groups of 24-month-old children: 21 with speech-related anomalies (SRA), 13 with non-speech-related anomalies (NSRA), and 45 normal controls. In addition to standardized assessment of intelligence and language, children and mothers were observed in a half-hour videotaped play session, later coded for maternal and child interactive behavior. SRA children showed significantly poorer performance than controls on standardized tests. Mothers of SRA children showed significantly more Physical Teaching and Initiating relative to controls. Mothers of both SRA and NSRA children used significantly more Attention Management than did controls. The pattern of poorer child performance and maternal interactive compensations is largely confined to children whose structural disabilities are speech-related. Maternal interactive behavior is not global in its response to child disability; rather, it varies with the particular pattern of child disabilities found.

Child, Preschool↗
PubMed1988

Reversion toward an earlier stage of differentiation and loss of polarity during progression of N-methyl-N-nitrosourea-induced rat mammary tumours.

To work toward an understanding of the mechanisms of cancer progression, we have followed the changes in expression of several genes in rat mammary carcinomas during the development of invasion. Tumors were induced by N-methyl-N-nitrosourea and serially transplanted to isogeneic rats. Gene expression in individual cells was followed by immunofluorescence microscopy. We show that invading cells do not express the same genes as the primary tumor or normal adult mammary gland but are similar to the primitive mammary duct cells present in late embryos. In the most advanced tumors, the most fundamental epithelial characteristic, polarity, is lost. Relative to the mechanism of invasion, we observe that the basal lamina, often thinner than normal, always coats the strands of invading cells and may be entirely absent from single invasive cells only. These observations suggest that the basal lamina ultimately disappears because of reduced expression of the genes or the failure to assemble the components. In these tumors it is the progressive alteration in gene expression rather than the enzymatic breakdown of the basal lamina that leads to invasion. These results show that the most important aspect of cancer progression is the progressive alteration of gene expression. They also raise questions about the mechanism that causes tumor cells to retrace the steps in their differentiation.

Animals↗