Biomedical subjects

P J Becker

Publications and source records attributed to P J Becker.

At least 109 records · Page 6Linked to original sources

PubMed1990

An evaluation of the surface characteristics of a facial prosthetic elastomer. Part III: Wettability and hardness.

Silicone facial prosthetic elastomers may cause tissue damage by abrasion. Such damage is a particular concern when prostheses are mechanically retained against tissues compromised by adjunctive therapy. The hardness and wettability of Cosmesil material was compared with that of Molloplast-B material. The stone test surfaces were separated with soap, sodium alginate, silicone paste, and left untreated. A polished stainless steel surface was prepared as a control. The specimens of Cosmesil and Molloplast-B materials were processed against each of these surfaces. Ten specimens of each material were processed against the five different surfaces. Wettability was evaluated by measuring the contact angle with a profile projector. Indentation hardness was measured with a Shore-A durometer. Statistical analysis involved multiple analyses of variation and Tukey's procedures (in all cases p less than 0.05). Molloplast-B material was found to have a higher wettability than Cosmesil material (means = 3.22 degrees higher); sodium alginate separator yielded silicone specimens with the highest wettability; Molloplast-B material was found to be harder than Cosmesil material (means = 9.75 Shore-A indentation units harder). The softest silicones were processed with soap separator. Silicone grease yielded the hardest specimens. The mechanical performance of Cosmesil material would be enhanced by increasing the surface wettability. The hardness of Cosmesil material is within the ideal range for a maxillofacial prosthetic elastomer.

Biocompatible Materials↗

PubMed1990

Factors affecting levels of DDT and metabolites in human breast milk from Kwazulu.

Concentrations of p,p'-DDT, p,p'-DDE, and p,p'-DDD have been determined in breast milk of mothers residing in two different areas of KwaZulu. Annual intradomiciliary application of DDT was used for the interruption of malaria transmission in one area, while the other served as the control. Milk from mothers living in DDT-treated dwellings had significantly higher mean levels of DDT and metabolites (mean sigma DDT 15.83 mg kg-1 in milk fat) than those from the control area (0.69 mg kg-1). The highest recorded sigma DDT value was 59.3 mg kg-1 (milk fat). Primiparous mothers from the malarious area had significantly more sigma DDT and metabolites (sigma DDT 24.82 mg kg-1) than multiparous mothers from the same area (mean 12.21 mg kg-1). Parity was the best predictor of DDT in breast milk of the exposed group. The percentage DDT and the sigma DDT increased significantly with an increase in parity. The same, but not significant, trend was also found for the control group. It was hypothesized that the increase in percentage DDT that occurred with higher parities was due to the uptake of DDT and elimination via milk. This process was faster than the uptake and endogenous formation of DDE. Designing predictive models using multiple regression was not very successful. The recorded levels do not represent an appreciable health risk to the mothers. From the literature it was deduced that at the recorded levels, a well-founded risk to the infants, particularly the firstborns, exists in sprayed areas.

Adult↗

PubMed1990

Relationship between vitamin B-6 status and elevated pyridoxal kinase levels induced by theophylline therapy in humans.

Theophylline administration to seven healthy male volunteers resulted in a rapid and significant decline in both plasma and erythrocyte pyridoxal-5'-phosphate levels. Total erythrocyte pyridoxal kinase levels increased during 15 wk of theophylline treatment from a mean initial activity of 19.23 +/- 5.03 (mean +/- SD) to 62.64 +/- 11.59 nmol pyridoxal-5'-phosphate formed/(g hemoglobin.h). Although plasma pyridoxal levels remained normal, the threefold increase in total erythrocyte pyridoxal kinase activity levels did not normalize plasma and erythrocyte pyridoxal-5'-phosphate levels. Pyridoxal-5'-phosphate hydrolysis was not affected by theophylline therapy. Increased pyridoxal oxidation was confirmed by elevated urinary 4-pyridoxic acid excretion after 15 wk of theophylline treatment. Mean erythrocyte alanine aminotransferase activity declined by 70%, and aspartate aminotransferase activity declined by 50%, indicating that decreased availability of pyridoxal-5'-phosphate can have widespread metabolic consequences. We conclude that the effect of theophylline on vitamin B-6 metabolism is not transitory and cannot be overcome by elevated intracellular levels of pyridoxal kinase. However, pyridoxine supplementation (10 mg/d for 1 wk) normalized indices of vitamin B-6 status and reversed the downward trend in both alanine aminotransferase and aspartate aminotransferase activity levels.

Adult↗

PubMed1990

The effects of alprazolam, quazepam and diazepam on saccadic eye movements, parameters of psychomotor function and the EEG.

The effects of a single oral dose of alprazolam (1 mg), quazepam (15 mg) and diazepam (10 mg) on the peak saccadic velocity (PSV) of saccadic eye movements (SEM), the Sternberg memory scanning and choice reaction time (SMS-CRT), critical flicker fusion frequency (CFFF), spectral analysis of the EEG and a mood scale were assessed in 9 healthy volunteers in a double-blind, placebo-controlled cross-over study. Alprazolam revealed greater sedative effects than diazepam in the above-mentioned tests. Quazepam had the least sedative effect of the 3 drugs tested, showed a time lag at the onset of its effects and a more prolonged effect on psychomotor impairment than reported previously.

Administration, Oral↗

PubMed1990

Intestinal parasites of conventionally maintained BALB/c mice and Mastomys coucha and the effects of a concomitant schistosome infection.

A longitudinal study was carried out to identify the spectrum of intestinal parasites present in conventionally maintained BALB/c mice and Mastomys coucha and to determine the effects of concomitant schistosome infections on their parasite status. Six parasites were observed during the course of the study, namely the nematodes Aspiculuris tetraptera and Syphacia obvelata, Entamoeba muris and the flagellates Trichomonas muris, Spironucleus muris and Chilomastix spp. Although the 2 rodents shared common facilities, the overall prevalences of S. obvelata, T. muris and S. muris were significantly higher in M. coucha than BALB/c mice. BALB/c mice with concomitant schistosome infection had increased prevalences of E. muris, T. muris and S. muris. In M. coucha, in contrast, there were no significant increases in parasite prevalences. Infection intensities of T. muris and S. muris were significantly greater in M. coucha than BALB/c mice. Concomitant schistosome infection resulted in increased intensities of T. muris infection in BALB/c mice only. The influence of immune status in determining the susceptibilities of rodents to environmentally transmitted parasites is discussed.

Animals↗

PubMed1990

Acute preload effects of furosemide.

Acute preload effects (as reflected by the pulmonary capillary wedge pressure [PCWP]) of an intravenous furosemide bolus were studied in 33 patients. In those patients receiving no vasoactive drug and in those receiving predominantly preload reducing agents, there was an initial rise in PCWP up until 15 minutes followed by a diuresis-induced fall in PCWP below baseline levels at 1 h. Patients who were receiving preload and significant afterload reduction showed an immediate drop in PCWP which was sustained. This trend is independent of underlying pathology or dose of furosemide used. It is postulated that furosemide causes an early deleterious release of endogenous vasoconstrictors which may be blocked by combined preload and afterload reduction.

Adult↗

PubMed1990

Levels of DDT and metabolites in breast milk from Kwa-Zulu mothers after DDT application for malaria control.

Concentrations of DDT, DDE and DDD were determined in the breast milk of Kwa-Zulu mothers residing in two different areas--with and without annual intra-domiciliary applications of DDT for the interruption of malaria transmission (exposed and control groups, respectively). While no significant change in levels with time was found in the control group, both DDT and DDE in breast milk of the exposed group increased after DDT application and this continued for three more months, after which it did not decrease appreciably. Percentage DDT increased from 42.57% (sigma DDT = 12.21 mg/kg milk fat) before spraying to 50.87% (sigma DDT = 13.79 mg/kg milk fat) following DDT application. At 6 and 9 months after the application it was 45.85% (sigma DDT = 19.49 mg/kg milk fat) and 43.27% (sigma DDT = 18.34 mg/kg milk fat), respectively. These results suggest a risk to the health of the infants in the exposed group.

Adult↗

PubMed1990

Influence of sialic acid on the binding activity of estrogen receptors.

The influence of sialidase and sialyltransferase on the binding of 3H-estradiol to estrogen receptors in baboon uterus was investigated to ascertain if sialylation was involved. Specific binding capacity increased approximately 37% in the presence of sialidase, although Kd values essentially remained unchanged. 3H-Estradiol binding was correlated with free sialic acid in the presence of either sialidase or sialyltransferase. As sialidase concentrations were increased, 3H-estradiol binding and free sialic acid concentration increased linearly (r = 0.937, p less than 0.001). Incubation of 22 x 10(-5) U sialidase with its inhibitor, 2,3-dehydro-2-deoxy-N-acetylneuraminic acid, decreased binding capacity and sialic acid concentration (r = 0.929, p less than 0.001). Although a decrease in binding capacity and free sialic acid concentration was observed in the presence of increasing amounts of sialyltransferase, a positive correlation was found between these two parameters (r = 0.839, p less than 0.035). A negative trend that was statistically insignificant was observed between binding capacity and sialic acid concentration when 2 x 10(-4) U sialyltransferase was incubated with the inhibitor, acetylsalicylic acid (r = -0.571, p = 0.195). The sialic acid concentration increased, while the 3H-estradiol binding capacity decreased. Collectively, these results show that both sialidase and sialyltransferase affect the binding of estradiol to its receptor in opposite directions. We suggest that biological activities of estrogen receptors in target cells may be regulated by the extent of sialylation of the receptor molecule itself. This posttranslational alteration may represent a new type of control mechanism for estrogen action.

Animals↗

PubMed1990

Effect of varying processing solution temperature on radiographic contrast and relative film speed of dental film.

The aim of this study was to determine the effect of a stepwise rise in temperature on three film types processed in six different processing solutions and to identify the combinations of film, solution and temperature which produced the best results in terms of radiographic contrast and relative film speed. The film types were Agfa Dentus M2, Flow X-ray and Kodak Ultra Speed while the processing solutions were Agfa, Dürr, EBX, Kolchem, MEMS and Pro-tech. An aluminium step-wedge was exposed under standardised conditions. Processing was carried out in a Dürr 245L automatic processor with variable temperature settings from 25 degrees to 35 degrees C. Unexposed films were processed at each temperature setting to determine the base plus fog values. Densitometric readings were taken using a digital densitometer, and the base plug fog values subtracted from each reading. Radiographic contrast and relative film speed were calculated and the data obtained subjected to statistical analysis using Duncan's Multiple Range Test. It could be concluded that, as the processing solution temperature rose from 25 degrees C to 35 degrees C, both radiographic contrast and relative film speed increased. The highest radiographic contrast was obtained by Agfa film in Kolchem solution at 35 degrees C, while Kodak Ultra Speed film in MEMS solution at 35 degrees C gave the highest relative film speed. An acceptable base plus fog level of 0.25 was obtained in the case of Agfa film in combination with Agfa, Dürr and Pro-tech solutions and Flow X-ray film with Dürr solutions. All the other combinations produced a base plug fog level higher than 0.25.

Solutions↗

PubMed1989

Lung function screening in industry.

Regression equations for forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) for 518 black factory workers on the Transvaal highveld were calculated from data obtained during routine lung function testing at an asbestos-cement factory. Only those subjects with clinically and radiologically normal lungs were accepted for the study. The lung capacities of the 60% who were light smokers were not significantly affected. Years of dust exposure were included as a separate independent variable and its contributory effect, after age had been allowed for, was insignificant. The final combined regression equations are considered to be representative of healthy black men on the Transvaal highveld. The values of FVC calculated from these equations were compared with values derived by other authors and, in view of the differences found, it was concluded that predicted values for black workers derived from regression equations for white subjects should not be used for industrial screening purposes. Group-specific equations should be followed when using lung function testing for definitive clinical diagnosis or academic research. The equations suggested for black South African men are FVC = 0.055 (height in cm) - 0.016 (age in years) - 4.502 and FEV1 = 0.043 (height) - 00023 (age) - 3.006.

Adolescent↗

PubMed1989

The value of routine pancreatic iso-amylase measurements in the diagnosis of pancreatitis.

The value of serum pancreatic iso-amylase (Pi) measurements in the clinica diagnosis of pancreatitiss was assessed using a wheat inhibitor kit (Phadebas) and cellulose acetate membrane (CAM) electrophoresis. Wheat inhibition totally suppressed Pi activity in the sera of 3 healthy subjects with substantial Pi bands on electrophoresis. Reference intervals for Pi, salivary iso-amylase (Si) and total alpha-amylase were established from the sera of 61 healthy subjects using CAM electrophoresis. Sera from 47 patients were assayed. Twenty-three had proven acute pancreatitis (AP) and 24 had established chronic pancreatitis (CP). All patients with AP had elevated serum Pi levels. Fifteen of these patients had a low P3 index, which ranged between 55.8% and 82.6% with a mean of 67.1%. An index of less than 100% indicates the presence of P3 isoamylase. P3 iso-amylase only occurred in patients with AP. Thirteen of these 15 patients did not have Si in their serum. In 20 of 24 patients with CP, serum Pi was reduced and in 4 it was at the lower limit of the reference interval. Ten of these patients had raised Si levels. In 13 of these patients the total amylase level was normal; in 4 it was increased and in 7 it was reduced. It is concluded that raised Pi and the P3 index are useful in the diagnosis and monitoring of AP; reduced Pi is highly suggestive of CP, and the use of total alpha-amylase levels alone can be misleading.

Acute Disease↗

PubMed1989

The effect of latex gloves on setting time of vinyl polysiloxane putty impression material.

Vinyl polysiloxane putty impression material (VPPIM) setting is unreliable when mixed in gloved hands. The exact reason for this remains obscure. This report focuses on the effect of natural and synthetic latex gloves on the setting of VPPIMs. This report indicates that synthetic latex gloves (SLG) have no effect on setting reaction of VPPIMs. However, natural latex gloves (NLG) significantly delay the setting reaction (P less than 0.05). Manufacturers should take note of this and supply SLGs for mixing. Dentists contemplating the use of VPPIMs should take these findings into consideration.

Chemical Phenomena↗

PubMed1989

Genetic polymorphism of glutamate-pyruvate transaminase (alanine aminotransaminase): influence on erythrocyte activity as a marker of vitamin B-6 nutritional status.

A new, sensitive, two-step method free from interference by hemoglobin that measures erythrocyte glutamate-pyruvate transaminase (E-GPT) activity is described. Several aspects of E-GPT activity as an index of vitamin B-6 nutritional status were investigated with this method. 1) GPT shows a structural genetic polymorphism with two common alleles resulting in three phenotypes. In a population study (n = 92) E-GPT activity differed significantly (p less than 0.001) among the three phenotypic groups. Plasma pyridoxal-5'-phosphate concentrations in the three groups did not differ significantly. Therefore, E-GPT activity can only be used to assess vitamin B-6 nutritional status if GPT phenotype is accounted for. 2) Pyridoxine supplementation (10 mg/d) significantly (p less than 0.0001) increased E-GPT activity and decreased (p less than 0.0001) the percentage stimulation by pyridoxal-5'-phosphate in vitro although the absolute amount of in vitro stimulation by pyridoxal-5'-phosphate changed only marginally. 3) Inorganic phosphate inhibits in vitro activation of E-GPT by pyridoxal-5'-phosphate.

Alanine Transaminase↗

PubMed1989

Nosocomial infections in black South African children.

Nosocomial infections in infants and children were prospectively studied in the general wards of a hospital serving a developing community. Of 1350 admissions in 5 months, 193 (14.3%) developed 302 infections (22.4/100 admissions). The major risk factors were malnutrition, age less than 2 years and prolonged hospitalization. The most common sites of infection were the lower respiratory and gastrointestinal tracts. The most frequently isolated organisms were Staphylococcus aureus and Klebsiella species and the site of most frequent isolation was the lower respiratory tract for which the method most commonly used was endotracheal aspiration. Seventy percent of isolates were resistant in vitro to conventional antibiotics. Thirty-one percent of infections developed while the patient was awaiting a diagnostic procedure or waiting to be sent home. During the study period 60 patients (4.4% of admissions) were admitted with a nosocomial infection acquired elsewhere (31 at this hospital and 29 from other hospitals). Measles and its complications accounted for 28 of these cases and 7 deaths. This study provides information on nosocomial infections in children from a developing community.

Black or African American↗

PubMed1989

Evidence of a theophylline-induced vitamin B6 deficiency caused by noncompetitive inhibition of pyridoxal kinase.

A placebo-controlled, double-blind study indicated that theophylline administration to apparently healthy, young men induced significantly depressed plasma pyridoxal-5'-phosphate levels. Plasma pyridoxal levels were not affected by theophylline therapy. The effect of theophylline on circulating pyridoxal-5'-phosphate levels is explained by the observation that theophylline acts as a noncompetitive inhibitor for erythrocyte pyridoxal kinase (EC 2.7.1.35) with an apparent inhibition constant (Ki) of 1.28 x 10(-5) mol/L. Theophylline did not affect erythrocyte pyridoxamine (pyridoxine)-5'-phosphate oxidase (EC 1.4.3.5) activity. During theophylline therapy, erythrocyte pyridoxal kinase levels increased nearly twofold from an initial mean level of 24.2 +/- 4.0 (+/- SD) nmol to 46.9 +/- 7.3 nmol pyridoxal-5'-phosphate per gram of hemoglobin per hour. This partially counteracted the effect of theophylline on vitamin B6 metabolism. Nevertheless, erythrocyte pyridoxal-5'-phosphate levels in subjects given theophylline decreased significantly (p = 0.03) from pretreatment levels. The oral tryptophan load test resulted in significantly (p = 0.007) increased urinary xanthurenic acid excretion after 4 weeks of theophylline therapy. Both plasma pyridoxal-5'-phosphate levels and the tryptophan load test results normalized after 1 week of pyridoxine supplementation, indicating that 10 mg pyridoxine per day was effective to counteract the antagonistic effect of short-term theophylline therapy on vitamin B6 metabolism.

Adult↗

PubMed1989

Prognostic importance of admission plasma glucose in diabetic and non-diabetic patients with acute myocardial infarction.

We assessed the relationship of plasma glucose concentrations measured on admission to mortality during the acute phase of myocardial infarction in 143 diabetic patients and 277 patients without a previous history of diabetes. Mortality in hospital in patients not known to have diabetes increased significantly from 4 per cent in patients with admission plasma glucose below 8 mmol/l to 35 per cent in patients with admission plasma glucose above 11 mmol/l. In diabetic patients the mortality increased with increasing admission plasma glucose but the difference was not significant. In patients with diabetes mean admission plasma glucose levels of the survivors and those who died were similar, whilst in the non-diabetic group the mean plasma glucose levels of the patients who did not survive were significantly higher than those of the survivors. Stepwise logistic regression analyses identified admission plasma glucose level as an important predictor of mortality in the non-diabetic group but not in the diabetic patients. Plasma glucose level on admission is an important prognostic indicator in non-diabetic patients, in that hyperglycaemia is associated with a higher mortality. In diabetic patients a clear relationship between admission plasma glucose and mortality was not demonstrated.

Adult↗

PubMed1989

Correlations of dimensional and discrete dental traits in the post-canine and anterior dental segments.

The present study explores the associations of metric and discrete variation in human canines and first molars. Emphasis is placed on the relation between tooth size and the various grades of expression of the canine distal accessory ridge (CDAR) and Carabelli's trait, in order to test the hypothesis that metric and non-metric variation in the posterior teeth are less well integrated than in the anterior teeth. Metric and discrete dental data were gathered from 120 Lengua Indians (52 male, 68 female), 100 Negroes (52 male, 48 female) and 100 caucasoids (50 male, 50 female). Our results indicate that first maxillary molar size and the Carabelli trait vary independently of one another. Similarly, variation in canine size and in the CDAR appears to be independently determined. Hence it is concluded that tooth size and morphology in the maxillary canines and molars are poorly integrated, irrespective of intra-arcadal position. Furthermore, sex dimorphism and interpopulation differences in the expressivity of Carabelli's trait and the CDAR appear to be unrelated to odontometric differences.

Black People↗

PubMed1989

Glass ionomers and discoloration: a comparative study of the effects of tea and coffee on three brands of glass ionomer dental cement.

This study was undertaken to compare the in vitro discoloration of 3 brands of glass ionomer dental cement, Chemfil, Fuji Type II, and Ketac-Fil. Forty-eight specimens of each brand were prepared. Sixteen specimens of each brand were placed in tea, coffee and, as a control, water. Discoloration was evaluated by means of reflection spectrophotometry at 2, 4, 8, and 16 wk. Analysis of the data indicated that most discoloration occurred during the first 2 wk of immersion in the staining media and a little further discoloration took place between 2 and 16 wk (p less than 0.05). Tea discoloured glass ionomer more than did coffee (p less than 0.05) and Fuji Type II discoloured the most, Ketac-Fil the least whilst the discoloration of Chemfil lay between these two (p less than 0.05).

Coffee↗