On the origin of lateral asymmetry

Lateral asymmetry refers to unequal fluorescent intensity between adjacent regions of sister chromatids. It has been observed in the centromeric regions of mitotic chromosomes of mouse or human origin when cells are grown in 5-bromo-2'-deoxyuridine (BrdU) for a single round of DNA synthesis. The chromosome-orientation fluorescence in situ hybridization (CO-FISH) technique was used with pseudodiploid mouse cells to show that the regions of asymmetrical brightness coincide with major satellite repetitive DNA, and that the more heavily BrdU-substituted chromatid is the one that fluoresces less brightly. These observations support a 20 year old hypothesis on the origin of lateral asymmetry. Other observations suggest that differential loss of DNA from the heavily substituted chromatid also contributes to lateral asymmetry.

The effect of track structure on cell inactivation and chromosome damage at a constant LET of 120 keV/micrometer

The influence of track structure on chromosome damage and cell inactivation are being investigated. Plateau-phase normal human fibroblast cultures were irradiated with gamma rays, and He, Ne and Ar ions. Particle velocities were chosen so that all beams had an LET of 120 keV/micrometer. In this constant-LET experimental design, the radial distribution of excitations and ionizations about the particle track is the most significant variable. Using premature chromosome condensation, chromatin breaks were measured at two time points, promptly after irradiation and after a prolonged incubation to allow for repair. These measurements give an indication of both initial chromosomal damage and also residual damage that is either not repaired or is misrepaired. Survival was measured under the same conditions. Results indicate that the RBEs for both cell inactivation and, to a lesser extent, chromosome damage decrease as particle energy increases.

Current and ideal physique choices in exercising and nonexercising college women from a pilot athletic image scale

An Athletic Image Scale including female physiques with and without muscular definition is currently in the developmental phase. With shading, contouring, and three-dimensionality not offered previously on figure-rating scales, this instrument was designed to examine an apparent growing interest on the part of women in atheletic body-image ideals. The athletic level of each figure on the scale was based on responses of a group of college women. The 30-figure pilot scale was then tested by rating current and ideal body-shape preferences of two groups of first-year college women, 65 who exercised regularly and 45 who engaged in no regular exercise. Analysis showed no relationship between current and ideal physique choice and exercise status. Most exercising and nonexercising women chose a mesomorphic ideal physique with upper-body muscularity unlikely to occur without substantial amounts of physical activity. The associations among exercise status, figure choice, subscale scores on the Eating Disorder Inventory, and Self-esteem Scale scores were also examined. Women choosing moderately mesomorphic figures as their current shape had the lowest Body Dissatisfaction scale scores on the Eating Disorder Inventory irrespective of exercise status. Current- and ideal-shape preferences were not related to self-esteem scores. The pilot Athletic Image Scale offered several figures which seemed to be relevant to women although it must be noted that the scale purposely emphasized particular physiques. Even so, it is important to recognize that greater than sixty percent of the women preferred images with athletic physiques which are not offered on figurerating scales presently in use.

Improved homogenization of recombinant Escherichia coli following pretreatment with guanidine hydrochloride

Pretreatment of recombinant Escherichia coli, expressing human growth hormone inclusion bodies, with guanidine hydrochloride and Triton X-100 prior to high-pressure homogenization has been investigated. Homogenates were analyzed for protein release, viscosity, and particle size. We were able to reduce the number of passes required for cell disruption and the number of downstream processing steps required for the recovery of protein from inclusion bodies by pretreating cells with guanidine HCl and Triton X-100. Pretreatment of exponential growth phase cells with 1.5 M guanidine HCl and 1.5% Triton X-100 gave adequate disruption after one pass at 41 MPa with a particle size distribution similar to that for untreated cells disrupted after one pass at 62 MPa. This combination of guanidine HCl and Triton X-100 was also selected so as to wash the inclusion bodies without solubilization of the human growth hormone. Pretreatment of cells with 4 M guanidine HCl produced cell debris that was substantially smaller than the debris from untreated cells and partially solubilized the inclusion bodies. Cells harvested in the stationary growth phase were more resistant to high-pressure homogenization and pretreatment.

Relationship of body fat distribution with cardiovascular risk factors in healthy Chinese

The relationships between six body girths (shoulder, midarm, waist, hip, thigh, and calf) and cardiovascular risk factors (systolic and diastolic blood pressures and glucose, triglyceride, lipoprotein cholesterol, and apolipoprotein levels) were examined in 407 healthy Chinese urban workers in Taipei, Taiwan who were between 40 to 59 years old. Canonical correlation analysis revealed significant associations of upper body adiposity (shoulder, midarm, and waist girths) with cardiovascular risk factors in all subgroups assessed: men, premenopausal women, and postmenopausal women. Waist girth and hip girth were consistent and important variables, and weighted in the opposite direction. Waist-hip ratio (WHR) was the best descriptor of centralized adiposity. Centralized fat distribution was positively associated with blood pressure and glucose, triglyceride, and apolipoprotein (apo) B levels, and negatively associated with high-density-lipoprotein (HDL) cholesterol and apo A-I levels in this population. Body fat distribution had an effect independent of body mass index and accounted for some of the differences in triglyceride, HDL cholesterol, apo A-I, and apo B concentrations among men, premenopausal women, and postmenopausal women. Our findings in a Chinese population are similar to data from other studies in Western populations, and are consistent with the hypothesis that centralized adiposity is related to cardiovascular risk factors independent of general obesity.

Cyclopropamitosenes: novel bioreductive anticancer agents--mechanism of action and enzymic reduction

The mechanism of action of cyclopropamitosenes, novel bioreductive anticancer agents, has been investigated using a unique combination of chemical and biochemical techniques. The compounds 4 function as reductively activated alkylating agents under chemical reducing conditions, and the biochemical experiments establish that the methoxy- and aziridinyl-derivatives 4a and 4b behave differently upon bioreduction.

Oxygen radical formation in well-washed rat liver microsomes: spin trapping studies

The generation of hydroxyl radicals by rat liver microsomes was monitored by spin trapping with 5,5-dimethylpyrroline N-oxide (DMPO). The results confirm and extend previous data which demonstrated that hydroxyl radicals are produced by microsomes in the presence of NADPH and O2, and without the exogenous addition of iron. No EPR signals could be detected unless catalase activity which was associated with the microsomes could be substantially diminished. Addition of azide was the most effective means of eliminating catalase activity, but azide also reacted rapidly with hydroxyl radicals, forming azidyl radicals which were in turn trapped by DMPO. Extensive washing and preincubation of microsomes with 3-amino-1,2,4-triazole in the presence of H2O2 were evaluated as alternative methods of decreasing the catalase contamination of microsomes. Although neither method completely eliminated microsomal catalase activity, addition of azide was no longer necessary for hydroxyl radical detection with DMPO. When highly washed microsomal preparations were tested, weak signals of the superoxide radical adduct of DMPO could also be detected. These data indicate that the sensitivity of spin trapping in microsomal systems can be improved substantially when care is taken to eliminate cytosolic contaminants such as catalase.

The distribution of body fat from childhood to adulthood in a longitudinal study population

Body fat distribution, its continuity from childhood (4-6 years) to 30 years of age, and its link to that of parents is described in a longitudinal study population. A computer-assisted image analysis technique was used to measure body fat distribution (as measured by waist and hip diameters) from somatotype photographs. Pearson correlation coefficients were used to assess the association between the waist/hip diameter ratio (WHDR) and the body mass index (BMI) at all ages and between the WHDR of parents and offspring. Both Pearson correlation coefficients and the Foulkes-Davis tracking index were used to assess tracking of the WHDR from childhood to age 30 years. Stepwise regression analyses were performed to determine the predictability of the WHDR at age 30 years from WHDRs in childhood and adolescence. Among both sexes the WHDR decreased and BMIs increased with age from childhood to 18 years, then both increased from age 18 to 30 years. The correlation between the WHDR and BMI was significant only at 30 years for males (r = 0.37; p < 0.05) and during all stages of adolescence in females (p < 0.05). Age-to-age correlations were high for both sexes (p < 0.0001), and remained significant over a span of up to 25 years. Using the Foulkes-Davis tracking index, tracking from the year of peak height velocity to 30 years (a span of approximately 20 years) was strong for both sexes. Parent and child WHDRs were correlated and differed by sex. Father-son correlations were not significant in childhood, but reached significance in early adolescence (2 years before the year of peak velocity) and remained significant to 30 years (p < 0.05). Mother-daughter correlations were significant at all ages (p < 0.05). The level of the WHDR at the peak of the pubertal growth spurt (year of peak height velocity) predicted up to 58% of the variance in males and 51% of the variance in females of the WHDR at 30 years. We conclude that the adult WHDR (a proxy for the waist/hip ratio) becomes evident by the year of the pubertal growth spurt in height.

The measurement of body fat distribution using somatotype photographs and computer-assisted imaging techniques

A computer-assisted image analysis technique has been devised which allows the measurement of body fat distribution from archived somatotype photographs. This report describes the technique, which enables useful measurements to be extracted from somatotype photographs which were taken over 50 years ago. This paper describes the process of digitization of photographs, the measurement of body diameters using computer-assisted edge detection, the quantitative analysis of measurement error in this procedure, and validation techniques employed.

Effect of alcohol on gastric emptying in volunteers

We have examined the effect of alcohol on the gastric emptying rate of a liquid meal in 10 volunteers. Each volunteer was allocated randomly to receive, on three occasions, no alcohol, 3 units or 6 units of alcohol. Gastric emptying was measured using applied potential tomography. The rate of gastric emptying as measured by the time to 50% emptying (T50) was delayed significantly (P < 0.01) after alcohol 6 units (median 45.0 min (range 19-90 min)) compared with control (23.0 min (13-36 min)) and there was little change after alcohol 3 units (25.5 min (10-65 min)) [corrected].

Brain swelling in first hour after coronary artery bypass surgery

Six patients undergoing routine coronary artery bypass surgery were examined by magnetic resonance imaging of the brain before surgery, immediately afterwards, and 6-18 days later. Brain swelling was visible in all six patients on the immediate postoperative scan. In five patients who had later scans the swelling had subsided. No major neurological deficits were seen, and the patients were extubated successfully within 3 h of the operation. The mechanism of the cerebral swelling is uncertain, but it may provide insight into the cause of neurophysiological deficits seen after coronary artery surgery.

Near infrared spectroscopy in adults. Does the Invos 3100 really measure intracerebral oxygenation?

Does the Invos near infrared spectroscopy monitor detect intracranial oxygenation, or reflect oxygenation of extracerebral tissues? The change in Invos regional cerebral oxygenation was studied during a doubling of middle cerebral artery flow with hypercapnia. There was no significant change in regional cerebral oxygenation, which suggests that the Invos does not reflect intracerebral oxygenation, possibly because of its narrow optode separation. The use of near infrared spectroscopy in adults may require a more powerful machine.

Organizational and morphological features of cat sacrocaudal motoneurons

We have investigated the organizational and morphological features of motoneurons from cat sacrocaudal spinal cord, the portion of the neuraxis that innervates the tail. This information is pertinent for development of a new model of spinal cord injury. An understanding of sacrocaudal circuitry is essential for physiological and behavioral assessment of the effects of sacrocaudal lesions. Observations from Nissl-stained sections corroborated Rexed's cytoarchitectural scheme. Putative motoneurons were located within two regions of the ventral horn: the ventromedial nucleus (lamina IX) and the nucleus commissuralis. To map motoneuron pools, cholera toxin-horseradish peroxidase conjugate was injected into each dorsal tail muscle. The dorsomedial muscle was innervated by ipsilateral nucleus commissuralis motoneurons. The dorsolateral and intertransversarius muscles were innervated by ipsilateral lamina IX and nucleus commissuralis motoneurons. Cell bodies of retrogradely labeled sacrocaudal motoneurons ranged from 22 to 82 microns in diameter; the unimodal distributions peaked between 45 and 50 microns. Dendritic trees of motoneurons, revealed by retrograde labeling or by intracellular injection with horseradish peroxidase, were extensive. Five to eight primary dendrites originated from the cell body. Dendritic branches extended throughout the ipsilateral ventral gray matter, with processes spreading into the surrounding white matter and the base of the dorsal horn. Dendrites from motoneurons with their soma in the lateral portion of lamina IX formed a longitudinal plexus at the gray/white border. Medial dendrites from motoneurons in the nucleus commissuralis formed bundles in the ventral gray commissure and spread throughout the contralateral ventral horn. It is speculated that contralateral dendrites subserve synchronized co-contraction of medial muscles from both sides of the tail.

Gastric emptying after minor gynaecological surgery. The effect of anaesthetic technique

Gastric emptying was measured using the paracetamol absorption method in 30 patients immediately after a general anaesthetic for minor gynaecological surgery and in 10 female controls. Anaesthesia was induced with either propofol alone, propofol and alfentanil (4.5 micrograms.kg-1) or propofol and fentanyl (1.4 micrograms.kg-1) and maintained with intermittent propofol and 66% nitrous oxide in oxygen. Gastric emptying was delayed significantly in all patient groups when compared with volunteers. However, the delay in gastric emptying was similar in the three patient groups.

Structure-activity relationships for DT-diaphorase reduction of hypoxic cell directed agents: indoloquinones and diaziridinyl benzoquinones

The flavoenzyme DT-diaphorase has the potential either to bioactivate or to detoxify different bioreductive cytotoxins. Elucidation of structural features governing the ability to act as a substrate for DT-diaphorase should facilitate rational optimization or elimination of this reductive pathway for a particular class of bioreductive drug. We have examined structure-activity relationships governing both the cytotoxicity and the DT-diaphorase mediated reduction of two groups of bioreductive alkylating agents: (1) Indoloquinones related to EO9 [3-hydroxy-methyl-5-aziridinyl-1-methyl-2-(1H-indole-4,7-dione)prop-beta - en-alpha-ol]; and (2) derivatives of diaziridinyl benzoquinone or diaziquone [2,5-bis(carboethoxyamino)-3,6-diaziridinyl-1,4-benzoquinone]. The rat U.K. 256 Walker tumor cell line and the human HT29 colon carcinoma line were studied because of their high DT-diaphorase content. Enzyme activity was measured spectrophotometrically by dicoumarol inhibitable cytochrome c reduction in the presence of drug, and aerobic cytotoxicity was assessed by the MTT assay. EO9 acted as a good substrate for both enzyme preparations and was highly potent in each cell line, especially in Walker tumor cells (ID50 0.039 nM). AZQ was also reduced efficiently and gave an ID50 of 6 nM in the Walker tumor line. Slight modifications in structure resulted in large variations in both DT-diaphorase metabolism and toxicity for both types of agent. There was a clear tendency for the most efficiently reduced analogues to exhibit greater cytotoxic potency. Inclusion of an aziridine moiety in the structure appears to be desirable, but not essential, for both rapid reduction and cytotoxicity. There was no evidence of active site-directed enzyme inhibition.

Design and operation of a simple environmental chamber for rapid freezing fixation

Rapid freezing is the most important step in sample preparation for freeze-fracture and other cryotechniques for electron microscopy. We present the design and operation of a simple environmental chamber coupled to a plunger-driven freezing device that has provided simple and reliable freezing from temperatures and humidities other than ambient. The chamber can be constructed and operated with equipment and techniques common to most electron microscopy labs. Temperature control of +/- 0.1 degree C and relative humidities of greater than 90% were provided over the range -5-60 degrees C. Typical electron micrographs showing well preserved structures comparable to jet-freezing are presented.

Validation of convection-limited cooling of samples for freeze-fracture electron microscopy

Rapid freezing is the most important step in sample preparation for freeze-fracture and other cryotechniques for electron microscopy. A simple heat transfer model is experimentally validated to show that convection from the cryogen to the specimen is the limiting step in rapid freezing of small samples [Biot modulus, (hd/k) less than 1] by measuring cooling rates in a variety of samples, materials, and cryogens. In comparison to the commonly accepted conduction-limited model, the convection-limited model predicts, and our experiments show, that cooling rates are proportional to the surface area to volume ratio, independent of the sample thermal conductivity, and inversely proportional to the product of sample density and heat capacity. We show that almost any material can be frozen at similar rates if the sample thickness, the cryogen, and the method and velocity of contact with cryogen are similar. Liquid ethane or propane cooled to liquid nitrogen temperature are shown to give the best results.

Nutrient intake comparisons between Framingham and rural and Urban Puriscal, Costa Rica. Associations with lipoproteins, apolipoproteins, and low density lipoprotein particle size

To assess cross-cultural relations between dietary intake and plasma lipoproteins, we randomly selected 222 men and 243 women from the urban and rural areas of Puriscal, Costa Rica; related their dietary composition (assessed by a food-frequency questionnaire), fitness level, and body fat to plasma lipids, apolipoproteins, and low density lipoprotein (LDL) particle size; and compared these data with those from a subsample of 280 adults from the Framingham Offspring Study. Total cholesterol and LDL cholesterol levels were significantly (p less than 0.0001) higher in Framingham (207 and 137 mg/dl, respectively) than in Puriscal (184 and 114 mg/dl, respectively) residents. Elevated triglyceride and apolipoprotein (apo) B levels (25% and 16% higher), low HDL cholesterol and apo A-I levels (12% and 29% lower), and smaller LDL particles (17%) were more frequent in Puriscal than in Framingham residents. Urban Puriscal residents had a significantly lower fitness level; increased body fat, total cholesterol, and triglyceride levels; decreased HDL cholesterol in men; and higher apo B levels in women compared with rural Puriscal residents. Body fat, animal fat, and saturated fat intakes were significantly correlated with total cholesterol, LDL cholesterol, and apo B levels in both men and women in Puriscal. Intakes of protein and animal fat were higher among urban (10.7% and 14.1%, respectively) compared with rural (8.9% and 9.9%, respectively) Puriscal residents and in Framingham (16.0% and 20.8%, respectively) compared with Puriscal residents. No significant differences were found in dietary cholesterol. Saturated fat (largely from palm oil in Puriscal) intakes were significantly different among the three groups: rural Puriscal, 10.7% of calories; urban Puriscal, 11.6%; and Framingham residents, 12.9%. These data indicate that the more atherogenic plasma lipid profile among urban compared with Puriscal residents was largely explained by increased adiposity, decreased fitness level, and higher saturated fatty acid intake. Puriscal residents consumed less animal fat and more carbohydrate than did Framingham residents, and these differences were associated with a 21% lower LDL cholesterol level, a 12% lower HDL cholesterol level, a 29% lower apo A-I level, a 25% higher triglyceride level, a 16% higher apo B level, and a 17% smaller LDL particle size. Some of these cross-cultural differences may be due to differences in ethnic background and physical activity as well.

Relations of body habitus, fitness level, and cardiovascular risk factors including lipoproteins and apolipoproteins in a rural and urban Costa Rican population

Increased general and abdominal obesity has been independently associated with diabetes, increased risk of stroke, and coronary artery disease (CAD). It is more prevalent in developed countries and in urban areas of nonindustrialized nations than in less developed and rural areas. To evaluate the associations between general and abdominal obesity (as determined by total body fat, waist to hip ratio, umbilical to triceps ratio, and umbilical to subscapular ratio) with glucose, plasma lipoproteins, apolipoprotein (apo) A-I and B concentrations, and low density lipoprotein (LDL) particle size (LDL 1-7), we randomly selected 222 men and 243 women from rural and urban areas of Puriscal, Costa Rica. Abdominal obesity, as assessed by the waist to hip ratio, was independently and significantly associated with higher triglyceride levels (p less than 0.01) and with lower high density lipoprotein cholesterol levels (p less than 0.05) in men and women and with higher glucose levels (p less than 0.05) and smaller LDL particle size (p less than 0.01) in women. Abdominal obesity, as assessed by the umbilical to subscapular ratio, was independently and significantly associated with higher total cholesterol (p less than 0.005) and apo B (p less than 0.01) levels. Umbilical to triceps ratio was positively associated with blood pressure in men. Urban men had increased general and abdominal obesity (p less than 0.0001), number of cigarettes smoked per day (p less than 0.0001), and diastolic blood pressure (p less than 0.05) and had a decreased fitness level (p less than 0.0001) as well as higher (p less than 0.05) plasma glucose, triglyceride, and total cholesterol concentrations and lower (p less than 0.05) apo A-I and HDL cholesterol levels compared with rural men. The differences between rural and urban women were not as striking. Urban women had increased general and abdominal obesity, glucose, and apo B levels (p less than 0.05) and a decreased fitness level (p less than 0.0001). Our data indicate that general and abdominal obesity, increased cigarette smoking, diastolic blood pressure, and decreased fitness level are more prevalent in an urban than in a rural area in Costa Rica, particularly in men. The higher prevalence of such risk factors in the urban area is associated with a more atherogenic plasma lipoprotein profile.

Preparing health care assistants

In the fourth part of this series on issues in ward management facing charge nurses, Sheila Mackie Bailey looks at the charge nurse's role in preparing and educating the health care assistant or support worker. The imminent adjustment of student nurses' clinical status makes the development of a skilled and educated assistant for the trained nurse an urgent necessity. Of all those involved in defining and delimiting this role, the charge nurse assumes the key responsibility, but it is a responsibility which requires proper preparation and support before it can be adequately exercised.

Crossed and uncrossed projections to cat sacrocaudal spinal cord: II. Axons from muscle spindle primary endings

The terminal fields of primary afferent fibers from tail muscle spindle primary endings were mapped within cat sacrocaudal spinal cord (S3-Ca7), using intra-axonal recording and horseradish peroxidase staining techniques. We sought to determine the ipsilateral and contralateral projection patterns and to relate these to the fibers' muscles of origin. Fifty-three group Ia fibers were successfully stained. Segmental collaterals originated from either the ascending or descending branch within the dorsal columns. Collaterals coursed rostromedially within the dorsal columns and traversed the medial aspect of the dorsal horn. Ipsilateral terminations were similar for all fibers. Within the ventral horn, boutons were consistently observed in the medial or central portions of lamina VII. In lamina VIII, a variable number of boutons was seen on fine branches emerging from larger fibers coursing ventrally. Clusters of terminals were plentiful in the regions of motoneurons, i.e., lamina IX and the nucleus commissuralis. Terminals were found in the adjacent white matter. In addition to ipsilateral terminations, some group Ia fibers (20 of 53) had collateral branches that crossed ventrally to the central canal, terminating within the midline ventral gray commissure and/or the contralateral ventral horn. Crossed projections always originated in medial (dorsal or ventral), but not lateral, muscles of the tail. These data suggest that ipsilateral projections of group Ia fibers make connections on sacrocaudal motoneurons, on neurons mediating segmental reflex functions and on neurons conveying ascending information. It is speculated that crossed and uncrossed connections between group Ia fibers from medial muscles and bilateral dendritic trees of motoneurons subserve synchronized co-contraction of synergistic muscles located on the two sides of the body, such as with dorsal or ventral flexion of the tail. Group Ia projections from lateral muscles, that are entirely ipsilateral, would be involved with lateral movements of the tail.

Applications of freeze-fracture replication to problems in materials and colloid science

Understanding the relationship between the molecular structure and the macroscopic properties of polymer solutions and gels, oil-water-surfactant emulsions, lyotropic and thermotropic liquid crystals, colloidal dispersions, detergents, and other such "microstructured fluids" is essential to the optimal use of these commercially important materials. Modern rapid-freezing methods followed by freeze-fracture replication techniques are ideally suited to allow the direct visualization of the three-dimensional structure of the particles or units that make up the dispersion, while simultaneously revealing their orientation and distribution with molecular resolution. This paper reviews the necessary experimental conditions required to successfully exploit the freeze-fracture technique as it applies to microstructured fluid systems. The benefits and limitations of structural studies by freeze-fracture techniques as opposed to the more commonly used light, X-ray, and neutron-scattering methods are discussed. Freeze-fracture replicas can also be imaged by scanning tunneling microscopy to reveal directly three-dimensional fracture contours with improved resolution.

Crossed and uncrossed projections to cat sacrocaudal spinal cord: I. Axons from cutaneous receptors

Intra-axonal recording and horseradish peroxidase staining techniques were used to map terminal fields of primary afferent fibers from cutaneous receptors within the cat sacrocaudal spinal cord. It was hypothesized that projection patterns of cutaneous afferent fibers mirror the known somatotopic organization of sacrocaudal dorsal horn cells. Forty-three primary afferent fibers, innervating either slowly adapting type I receptors, hair follicles, or slowly adapting type II receptors, all on the tail, were recovered. All collaterals (N = 372) branched from parent axons in the dorsal columns. Most collaterals coursed rostromedially to the ipsilateral gray matter, penetrated the medial dorsal horn, and arborized within laminae III, IV, and to a lesser extent, V. Ipsilateral projections to dorsal horn were as follows: axons with dorsal or dorsolateral receptive fields (RFs; n = 20) to the lateral portion, axons with lateral RFs (n = 4) to the central portion, and axons with ventral or ventro-lateral RFs (n = 19) to the medial portion. Most axons (16 of 20) with dorsal or dorsolateral RFs also had contralateral projections to lateral dorsal horn and most axons (15 of 19) with ventral or ventrolateral RFs also had contralateral projections to medial dorsal horn. No axons with lateral RFs had crossed projections. These data represent the first complete mapping of the somatotopic organization of primary afferent fiber projection patterns to a spinal cord level. The findings demonstrate that ipsilateral projection patterns of sacrocaudal primary afferent fibers are in register with the somatotopic organization of the dorsal horn. Our earlier suggestion that crossed projections of primary afferent fibers give rise to crossed components of dorsal horn RFs spanning the midline is supported by these results.

A comparison of three methods of assessing inter-observer variation applied to measurement of the symphysis-fundal height

This study assesses the inter-observer variation of symphysis-fundal height measurements by three methods--the coefficient of variation, the correlation coefficient and the limits of agreement. The coefficient of variation was 4% and the correlation coefficient 0.959, yet the limits of agreement were very wide. Applying these limits to centile charts of symphysis-fundal height shows that the fundal height cannot be measured by different observers with sufficient agreement to separate small fundal heights from those which are not small, and this severely limits the usefulness of measurement of the symphysis-fundal height as a screening test for intrauterine growth retardation. We conclude that inter-observer variation should be assessed by the method of limits of agreement, and not by calculating the coefficient of variation or the correlation coefficient.

A comparison of three methods of assessing inter-observer variation applied to ultrasonic fetal measurement in the third trimester

The inter-observer variation of fetal biparietal diameter, head circumference, abdominal circumference, and femoral length measured in the third trimester by ultrasound was studied by three different methods--coefficient of variation, correlation coefficient, and the 95% limits of agreement. The coefficients of variation were 1.6 to 3.7%, the correlation coefficients were 0.89 to 0.98 with P values of less than 0.001, yet the limits of agreement when applied to centile charts were found to be too wide to separate reliably small fetuses from those that were not small. We conclude that the limits of agreement is the preferred method of assessing inter-observer variation, and we suggest that future research into growth retardation move away from ultrasonic measurements of the fetus.

Telomere staining of human chromosomes and the mechanism of radiation-induced dicentric formation

The majority of models of radiation action developed over the past half century hold that the curvilinear dose responses exhibited by eukaryotic cells to sparsely ionizing radiations result from the interaction of pairs of lesions produced in sensitive targets of the cell. Within this conceptual framework, chromosomal exchange aberrations (e.g., interchanges) are believed to occur through the interaction of damaged sites on both chromosomes participating in the exchange. In contrast, the model proposed by Chadwick and Leenhouts (as well as some other models) suggests that such exchanges arise from initial radiation damage to only one chromosome, which then becomes associated with an undamaged chromosome. A particular aspect of this theory is that asymmetrical exchanges, such as dicentrics, may be formed from the rejoining of a broken end of one chromosome to the telomere of another. By using a DNA probe that specifically hybridizes to the telomeric region of human chromosomes, we were able to test this assertion directly. After scanning more than 200 dicentrics produced in normal human fibroblasts by 6 Gy of 60Co gamma rays, virtually none were found that contained telomeres located between the centromeres of this aberration type. Therefore, since the proposed telomere-break rejoining process, per se, is not necessarily a central element of the Chadwick-Leenhouts model, we suggest the theory be modified to exclude this mechanism.

Subcutaneous fat remodelling in Southeast Asian infants and children

Longitudinal data on 1,048 Thai children were evaluated for evidence of subcutaneous fat remodelling. Fat distribution, as defined by 100 (triceps/[triceps + subscapular]), was more pronounced in the limbs during infancy but shifted toward the trunk thereafter. Subsequent stepwise regression analysis indicated that biological age--as measured by Gruelich-Pyle bone age--and weight together explained between 0.8% and 14.5% of variance in fat distribution, with generally larger R2 values over age and for males. Relationships were curvilinear, with sex differences in slope. Path analysis supported the model that weight was a major causal agent primarily after infancy, whereas biological age had a small influence both in infancy and in late childhood. These findings indicate that trunk fat deposition is a normal feature of childhood. They also suggest that hypotheses which associate elevated trunk fatness with disorders of glucose metabolism are invalid for younger children.

Taxonomic identification of human fat patterns

The utility of taxonomic approaches in identification of fat patterning was evaluated using hierarchical cluster analysis on a sample of 64 female and 31 male subjects from 18 to 29 years of age. Four clusters, each composed of subjects with similar distributions of 17 skinfold thicknesses corrected for sex, size and total body fat, showed mean pattern profiles that variously contrasted fatness of the trunk and extremities. Average anthropometric differences between clusters corroborated differences in pattern profile. For comparison, principal-components analysis was carried out on these same data. The results suggest that a taxonomic approach offers advantages in initial interpretation and in design flexibility.