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Biomedical subjects

K Robertson

Publications and source records attributed to K Robertson.

At least 73 records · Page 4Linked to original sources
PubMed1991

Induction of expression of the alpha v beta 1 and alpha v beta 3 integrin heterodimers during retinoic acid-induced neuronal differentiation of murine embryonal carcinoma cells.

All-trans-retinoic acid, an endogenous morphogen, induced neuronal differentiation of P19 murine embryonal carcinoma cells. Peak differentiation, as judged by the elaboration of neuronal processes, occurred 8 days after exposure of the cells to 0.5 mM retinoic acid, a concentration known to induce neuronal differentiation. An examination of the expression of the extracellular matrix receptors, integrins, during this retinoic acid-induced differentiation period, demonstrated a specific and strong induction of expression of two polypeptides (130 and 115 kDa) immunoprecipitated with an anti-human vitronectin receptor antiserum. The expression of a 90-kDa polypeptide, also immunoprecipitating with this antiserum was induced as well, but to a much smaller extent. The expression of a 96-kDa polypeptide immunoprecipitated by this antiserum and present in the untreated cells was not induced by retinoic acid. The increase in the expression of these polypeptides paralleled the neuronal differentiation of the P19 embryonal carcinoma cells. The expression of these integrins was not induced in a variant of the P19 cells, P19RAC65, which are resistant to differentiation induction by retinoic acid. Utilizing integrin subunit-specific anti-cytoplasmic peptide antibodies together with immunoprecipitation and Western blot analysis, the 130- and 115-kDa polypeptides were identified as the integrin alpha v and beta 1 subunits, respectively. The 90-kDa polypeptide, also induced by retinoic acid, was identified as beta 3, whereas the identity of the uninduced 96-kDa polypeptide remains unclear as yet. Peptide map analysis of deglycosylated polypeptides demonstrated that the 90- and 96-kDa polypeptides are distinct proteins and that the 115-kDa polypeptides immunoprecipitated with either anti-alpha v or anti-beta 1 antibodies are identical, further establishing that the 115-kDa polypeptide associating with alpha v is beta 1. The retinoic acid-induced expression of beta 1 occurred at the level of mRNA expression which also paralleled neuronal differentiation, but peaked slightly ahead of the cell surface expression of beta 1. The expression of other beta 1-associated alpha subunits was not induced by retinoic acid in these cells. These data demonstrate that retinoic acid strongly induces the expression of the integrin heterodimer alpha v beta 1 and also, to a smaller extent, the expression of alpha v beta 3. The retinoic acid-induced, high level surface expression of the alpha v beta 1 heterodimer is tightly correlated with the induction of neuronal differentiation by retinoic acid. This finding suggests an important role for the alpha v beta 1 heterodimer in the neuronal differentiation process.

Amino Acid Sequence↗
PubMed1989

Risk factors in onychocryptosis.

A study is described in which the normal toes of 50 patients with unilateral ingrowing toenails were compared with those of 50 healthy subjects matched for age and sex. Twenty-one potential risk factors were compared between the groups. All measurements on patients were derived from unaffected toes in order to avoid anatomical distortion due to the disease process. Statistical analysis revealed significant differences between the groups for three anatomical measures, namely nail fold width (P less than 0.001), medial rotation (eversion) of the great toe (P less than 0.02) and nail thickness (P less than 0.03). Possible discriminating variables were assessed using linear discriminant function analysis and a mathematical equation was derived based on these three factors. This equation was found to possess a potentially high predictive value in that it correctly classified 86 per cent of the patients and 77 per cent of the controls. A further group of 62 unselected patients presenting with unilateral onychocryptosis and 35 unaffected controls were assessed for these three parameters. Of these, 80 per cent of controls and 85 per cent of patients could be classified correctly by the equation. It is thus proposed that, in the majority of subjects with onychocryptosis, a discrete anatomical predisposition exists and that the other factors act only as triggers in the development of the condition. This study provides a rationale for less traumatic surgical approaches to ingrown nail than nail avulsion, with or without nail bed ablation and may also provide a means of identifying high-risk groups.

Adolescent↗
PubMed1989

Some effects of sex-linked clothing and gender schema on the stereotyping of infants.

Two predictions were evaluated: first, that given minimal information about an infant, individuals would use sex-related cues (i.e., clothing) to categorize, evaluate, and make attributions about the infant, and second, that gender schematic individuals would be more likely than gender aschematic individuals to use such sex-related cues. On the basis of the Bem Sex Role Inventory, American college students were classified as either gender schematic (masculine or feminine) or gender aschematic (undifferentiated or androgynous). The students categorized, evaluated, and made trait attributions about an infant dressed in male, female, or ambiguous clothing. Both gender schematic and gender aschematic individuals relied on sex-related cues in their perceptions of the infant.

Adolescent↗
PubMed1986

Effect of pH-adjustment of bupivacaine on onset and duration of epidural analgesia in parturients.

Previous studies have reported that elevation of the pH of local anaesthetics is associated with enhanced quality and duration of block. This study investigated the effect, on time to onset and duration of analgesia, of pH adjustment of 0.25 per cent bupivacaine immediately prior to injection into the epidural space in parturients. Addition of 0.1 ml of 8.4 per cent sodium bicarbonate to 20 ml of 0.25 per cent bupivacaine consistently raised the pH of the local anaesthetic from 5.65 to 7.26 (mean values). Thirty parturients received an epidural injection of 8 ml of pH-adjusted 0.25 per cent bupivacaine and a control group of 30 parturients received 8 ml of the standard commercial preparation of 0.25 per cent bupivacaine. Elevation of the pH of the local anaesthetic significantly increased the speed of onset of analgesia from 6.0 minutes to 3.2 minutes and the duration of analgesia was significantly lengthened from 79.4 minutes to 96.5 minutes. There was no significant influence on time to peak effect, nor on mean maternal plasma levels of bupivacaine.

Adult↗
PubMed1986

Alcohol use and abuse: heavy drinking among methadone clients.

This paper discusses alcohol use among methadone maintenance clients and narcotics users not in treatment. The data are derived from the Tri-State Ethnographic Project, a study of four methadone maintenance clinics in three states. Data indicate that methadone clients consume more alcohol than comparable age groups in the general population, but not more alcohol than narcotics users not in treatment. For a portion of the treatment population, however, heavy drinking presents significant problems. Sixteen percent of the treatment sample were found to be abusive pattern drinkers; that is, persons who report not only drinking heavily but also spending a great deal of time hanging out on the street, getting high, and consuming many other additional drugs. These abusive pattern drinkers reflect a pattern of polydrug use which began in their early teens and report multiple unsuccessful treatment attempts.

Adult↗
PubMed1985

Visual function and academic performance.

Evaluation of 1,910 first-, second-, and third-grade students indicated that visual function and academic performance as measured by reading were not positively related. Visual function tests included visual acuity, muscle balance, preferred eye and hand, color vision, refraction, sensory and motor function, and a writing and drawing task. Academic tests included the Metropolitan Readiness Test, the Cognitive Abilities Test, the Iowa Test of Basic Skills, and the teacher's assessment of reading level. A simple test which can be completed during the office visit and interpreted by the ophthalmologist in the office included drawing, copying, and writing. A segment of this test, the "draw a bicycle test," can be used by an ophthalmologist to demonstrate the difference between vision and performance when examining a child up to third-grade level who is referred because of school failure.

Accommodation, Ocular↗
PubMed1985

Epidural fentanyl, with and without epinephrine for post-Caesarean section analgesia.

Using a double-bolus technique, the efficacy and safety of epidural fentanyl with and without epinephrine 1:400,000 for post-Caesarean section analgesia was examined in 30 patients. The addition of 25 micrograms epinephrine to the fentanyl (100 micrograms) did not potentiate the speed of onset but did significantly prolong the duration of action of the second dose. The only side effect encountered was pruritus, which was significantly increased (from 17-44 per cent) when epinephrine was added. The results indicate a clinical advantage of prolonging the duration of action of fentanyl for post-Caesarean Section analgesia with the addition of epinephrine, but the cumbersome and time-consuming nature of a double-bolus technique limits its clinical value. The relative safety of epidural fentanyl with and without epinephrine was confirmed by the absence of respiratory depression, drowsiness or hypotension in all patients.

Adult↗
PubMed1985

Response of plasma proenkephalin peptide F to exercise.

Plasma proenkephalin Peptide F immunoreactivity was measured in the plasma of endurance trained and untrained males at various exercise intensities. Significantly different levels were found between the two groups at rest and at 54% maximum oxygen consumption (VO2 max). Maximum levels were at 5 min of recovery for the untrained group and at 54% VO2 max and at recovery 5 min for the trained group. These data suggest an adaptation in the trained group fro the release of this peptide and further suggest it may play a role in recovery since the highest levels are following the termination of the exercise period.

Adult↗
PubMed1985

Non-enzymatic glycosylation of keratin from the stratum corneum of the diabetic foot.

Non-enzymatic glycosylation of keratin from the stratum corneum of the sole of the foot was measured by the thiobarbituric acid technique in thirty diabetic and thirty control subjects. A significant increase in the level of glycosylation was demonstrated in the diabetic subjects (P less than 0.001). HbA1 levels were measured in a further eighteen subjects at the same time as keratin was removed, and in this group a significant association between non-enzymatic glycosylation of that protein and diabetic control was demonstrated (P less than 0.01). In vitro incubation of keratin in the presence of free glucose produced increased non-enzymatic glycosylation (P less than 0.01) and this effect was blocked by incubation in the presence of increasing concentrations of aspirin (P less than 0.01). Measurement of non-enzymatic glycosylation of keratin in a further group of twenty diabetics with neuropathic ulceration showed a significant increase in levels when compared with a group of diabetics without ulcers (P less than 0.05). As keratin is the principle structural protein of the stratum corneum of the sole of the foot, it is possible that changes in this protein associated with non-enzymatic glycosylation may contribute to abnormalities seen in the skin of the feet of diabetics.

Adult↗
PubMed1984

Effects of a lacto-ovo vegetarian diet on serum concentrations of cholesterol, triglyceride, HDL-C, HDL2-C, HDL3-C, apoprotein-B, and Lp(a).

The effect of intervention with a lacto-ovo vegetarian diet on serum concentrations of cholesterol, triglyceride, total high-density lipoprotein cholesterol (HDL-C), HDL2-C, HDL3-C, low-density lipoprotein cholesterol, apoprotein-B, apoprotein-HDL, and Lp(a) was studied in 19 men and 17 women. Most weekday meals were obtained from a single source and dietary records were completed to assess the changes in nutrient intakes. Blood was collected in the 6th wk of each dietary period. Because of strong correlations between many of the changes in nutrient intakes, principal component (factor) analysis was used followed by stepwise multiple regression analysis to identify associations between changes in diet and changes in lipid, lipoprotein or apoprotein levels. Three principal components accounted for 92.0% of the variation in lipid levels: factor 1 represented an increase in saturated fat, total fat, monounsaturated fat, cholesterol, and energy intake: factor 2 represented an increase in fiber and polyunsaturated fat, and decrease in protein intake; factor 3 an increase in total carbohydrate, complex carbohydrate, and energy intake. Where a change in a variable was significantly associated with change in diet, one factor appeared primarily responsible for the change; total cholesterol (factor 2, p = 0.034); triglyceride (factor 3, p = 0.005); apo-HDL (factor 1, p = 0.014); HDL2-C (factor 2, p = 0.023), HDL3-C (factor 3, p = 0.015). A borderline significant association was seen for total HDL-C (factor 2, p = 0.055).

Alcohol Drinking↗
PubMed1984

Vegetarian diets, lipids and cardiovascular risk.

Vegetarian diets produce moderate but appreciable changes in serum lipid levels. A six-week intervention study in which other aspects of life-style were kept constant showed that levels of total cholesterol, LDL-cholesterol and HDL-cholesterol fell 0.22, 0.19 and 0.07 mmol/l, respectively, while triglyceride levels increased non-significantly 0.12 mmol/l. The ratio of total cholesterol to HDL-cholesterol did not change. A comparison of groups of habitual vegetarians and omnivores matched for other aspects of lifestyle showed rather larger differences in atherogenic lipid levels: 0.71 and 0.67 mmol/l for total- and LDL-cholesterol; the difference in HDL-C levels was 0.04 mmol/l; triglyceride was 0.19 mmol/l greater in vegetarians. 92% of the variation in intakes of major nutrients was accounted for by three derived factors; changes in levels of most of the lipids were associated in each case with one of the factors. The resultant falls in the levels of total- and LDL-cholesterol in people adopting a vegetarian diet probably contribute to a reduction in cardiovascular risk.

Apoproteins↗
PubMed1981

Jejunal mucosal morphometry in children with and without gut symptoms and in normal adults.

Nineteen diagnostic peroral biopsy specimens from 18 children without diarrhoea, vomiting, or abdominal pain ('control' children) were compared with those taken from 23 children with diarrhoea of varying aetiology to establish the morphometric characteristics of jejunal mucosa in childhood. Comparison was also made with normal jejunal mucosa from adults. Statistical analysis of each characteristic individually showed no significant difference between the 'control' children and those with diarrhoea, but there were significant differences between the mucosae of 'control' children and those of adults; the villi tended to be shorter and the crypts longer in children. Thirty-seven per cent of specimens from the 'control' children showed a partial villous atrophy, that is, they were abnormal by adult criteria. Discriminant analysis of the features measured showed effective separation of the following groups: normal histology from partial villous atrophy in children, healthy adults from 'control' children, and normal histology in adults from normal histology in children.

Adult↗
PubMed1981

Levels of cholesterol, triglyceride, high-density lipoprotein-cholesterol and apoprotein-HDL in an Australian rural population.

Serum levels of total cholesterol, triglyceride, high-density lipoprotein-cholesterol (HDL-C) and apoprotein-HDL (apo-HDL) have been measured in adults of Busselton, Western Australia (males, n = 1600; females, n = 1968) and the distribution of values by age and sex are reported. The data confirm previously reported trends with age for cholesterol and reveal strikingly different ranges and trends with age for triglyceride between males and females, mean values in males increasing more rapidly with age and showing greater variation and more marked positive skew. Mean HDL-C values show little change with age in males, and a slight rise with age in females, up to the 7th decade, and then a fall. Apo-HDL levels show very similar distributions to HDL-C in each sex.

Adult↗
PubMed1980

Measurement in jejunal biopsies by computer-aided microscopy.

A method of morphometric analysis of jejunal mucosa using computer-aided microscopy is described. It is based on the technique of interactive computer graphics with definition by the observer of areas and lengths for measurement, but it also includes automatic measurements based on grey-level segmentation. The analyses are performed rapidly and efficiently. The technique is applicable to the analysis of biopsy tissue from many sites.

Adult↗