P.J. Du Toit

The effect of essential fatty acids on growth and urokinase-type plasminogen activator production in human prostate DU-145 cells

Abstract Urokinase-type plasminogen activator (uPA) is an important protease enzyme in carcinogenesis, and is involved in both invasion and metastasis of cancer. Increased uPA activity and decreased essential fatty acid (EFA) levels have been reported in cancer. This phenomenon may be explained by the fact that certain EFAs, such as γ-linolenic acid (GLA) and eicosapentaenoic acid (EPA), inhibit uPA activity. The effect of EFA on human prostate DU-145 cell growth and uPA production is still unknown and was investigated in this study. Data obtained from the different unsaturated fatty acids showed that oleic acid (OA) and EPA enhanced DU-145 cell proliferation at 0.004 and 0.04 mM for up to 4 days. However, α-linolenic acid (ALA), linoleic acid (LA), GLA and arachidonic acid (AA) suppressed cell proliferation under the same conditions, possibly as a result of inhibition of DNA and protein synthesis as measured using labelled thymidine and glycine incorporation. In contrast to the cell proliferation, uPA production was inhibited by all the unsaturated fatty acids under investigation. Therefore, the absence of EFAs, as reported, may affect invasion and metastasis of cancer.

In vivo effects of urease-producing bacteria involved with the pathogenesis of infection-induced urolithiasis on renal urokinase and sialidase activity.

Many hypothese have been proposed for renal stone formation. It has been argued that with infection-induced renal stones the hydrolysis of urea by bacterial urease increases urinary pH, with consequent stone formation. Unfortunately, this theory is not applicable to the micro-organisms that do not produce urease (e.g. Escherichia coli). It has been recently reported that E. coli reduces the urinary urokinase activity of male rats, but does not influence the urinary sialidase activity. This study has now been expanded to the urease-producing bacteria Proteus mirabilis, Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa and Micrococcus luteus. Subcutaneous injections with these bacteria were found to significantly (P<0.003) reduce the UK activity of extrarenally obstructed kidneys. The urease-producing mammalian skin bacterium, M. luteus, was, however, the exception (P=0.1079). In contrast to S. epidermidis, P. aeruginosa and M. luteus (P<0.0213), P. mirabilis and S. aureus had no effect on renal sialidase activity (P<0.4047). These results may explain why Proteus species are predominant in infection-induced renal stones. According to the urokinase-sialidase hypothesis, a decrease in urinary urokinase activity should increase the uromucoid levels, whilst no effect on the urinary sialidase activity should favour conversion of urinary uromucoid to mineralizable matrix. These conditions may lead to renal stone formation. An increase in urinary pH resulting from urease-producing micro-organisms will increase salt precipitation on the uromucoid. It is thus concluded that urease-producing bacteria may play a double role in renal stone formation.

Does urokinase play a role in renal stone formation

Renal stone formation is a complex multifactorial disease, and it is believed that the initial step in the pathogenesis of urolithiasis must be the precipitation of an organic matrix of mucoproteins followed by precipitation of minerals onto this matrix. An important factor in this process may be the activity and/or concentration of the urinary enzyme, urokinase, which would affect the level of urinary mucoproteins such as uromucoid. In support of this hypothesis, ELISA studies were conducted to investigate the urokinase concentrations in urine obtained from males (22-60 years) with and without renal stones. These results showed a significant decrease in urinary urokinase concentration of renal stone patients which, once again, underlines the possible involvement of urokinase in renal stone formation. Therefore, it seems logical to conclude that urokinase may play an integral role in this multifactorial disease.

The effect of calcium and magnesium ions on urinary urokinase and sialidase activity

SummaryThe effect of a promoter (calcium) and an inhibitior (magnesium) of urolithiasis was spectrophotometrically studied on urokinase (0.45 IU) and sialidase (5 mM). Although these mineral did not affect the sialidase activity, total inhibition of urokinase activity was observed with either 0.05 M calcium chloride or 0.1 M magnesium chloride. This observation might explain why calcium and magnesium respectively function as a promoter and an inhibitor of stone formation.

The effect of gamma-linolenic acid and eicosapentaenoic acid on urokinase activity

Abstract Urokinase (UK) is an important protease enzyme in carcinogenesis, and is involved in the invasion and metastasis of cancer. Thus, regulation of UK activity is likely to be important in healthy cell metabolism. As it has been reported that a decrease in Δ6-desaturated essential fatty acid (EFA) metabolites occurs in malignant cells and that gamma-linolenic acid (GLA) and eicosapentaenoic acid (EPA) exert antimutagenic effects, the effects of GLA and EPA on UK activity have been investigated in this study. Both GLA (n-6) and EPA (n-3) acted as competitive inhibitors of UK with K i values of 120 and 96 μM respectively. No modification of plasmin activity occurred with either 1.4 × 10 −4 M GLA or EPA. These results could explain why malignant cells with decreased EFA concentrations show increased UK activity. The addition of EFAs to available therapeutic regimens may be worth considering in the treatment of cancer.

Effects of bacteria involved with the pathogenesis of infection-induced urolithiasis on the urokinase and sialidase (neuraminidase) activity.

SummaryIt has been hypothesized that urinary urokinase and sialidase may play a role in urolithiasis. If these theories have substance it is to be expected that microorganisms may also affect these enzymes, since the association between urinary tract infection and renal stone formation is well known. It is generally assumed that Proteus mirabilis and Staphylococcus albus, which produce the urea-splitting enzyme urease, are responsible for stone formation. However, the importance of non-urease-producing microorganisms (Escherichia coli and Enterococcus) in urolithiasis is unclear. Spectrophotometric studies were therefore devised to clarity this problem. Microorganisms associated with infection-induced stones (Proteus mirabilis and Escherichia coli) respectively inhibited the urokinase and stimulated the sialidase activity. In contrast, microorganisms which were not associated with infection stones (Bacillus subtilis) had significantly less effect on urokinase and sialidase activity. This study may explain infection-induced stone formation and could open a completely new line of research.

The effect of sports vision exercises on the visual skills of university students

Vision is one of the most important special senses and is the primary source of external information. The role of vision in our everyday lifestyles is immense and adequate visual skills are needed for simple tasks which include reading and writing, that are especially important for students. Stress is an important factor which most students deal with, and along with other external factors, could adversely affect the ability to effectively perform many visual skills. This study aims to determine if sports vision exercises could improve visual skills and thereby enhance motor and cognitive performance. A 169 second year physiology students (18-22 years of age) participated in the study. The students were divided into control (n=78) and experimental groups (n=91) and pre and post sports vision tests were conducted. This included testing visual skills such as visual acuity, eye dominance, focusing, tracking, vergence, sequencing, eye-hand coordination, visualization and reflex. The results showed a significant improvement in the sequencing and eye-hand coordination tests in the experimental group, whilst a non-significant improvement (control group) was observed in the visual acuity, visualization, tracking, vergence and reflex tests. The improvements (except for focusing) were greater in the experimental group than in the control group. The study clearly showed that correct sports vision training can improve certain visual skills and lead to an enhancement of motor and cognitive learning and performance. Sports vision exercises are therefore an efficient method of improving certain visual skills and possibly minimizing any defects caused by stress. Key words: Sports vision exercises, visual skills, students.

Diagnosis and management of Pompe disease

Pompe disease (PD) is an autosomal-recessively inherited neuromuscular disease that, if not diagnosed and treated early, can be fatal. It can present from early infancy into adulthood. Due to the lack of acid alpha-glucosidase, there is progressive intracellular accumulation of glycogen. The severity of the disease is determined by age of onset, organ involvement including the degree of severity of muscle involvement, as well as rate of progression. PD is classified into two groups: infantile and late-onset, each having two subgroups. The need for two tests performed by separate methods (screening and confirmatory) is outlined. It is imperative to try to reduce the time to diagnosis and to recognise the possibilities of false-positive results. A multidisciplinary team approach to treatment of affected patients is optimum with, as team leader, a physician who has experience in managing this rare disorder. In this article, we present a brief overview of the disease and provide guidelines for diagnosis and management of this condition in South Africa.

Pyelonephritis: renal urokinase and sialidase (neuraminidase) activity in rats fed a standard laboratory diet.

Renal stone formation can be caused by many different and varied disturbances, some of which are poorly understood. The relationship between urinary infection and renal stone formation has not been completely clarified. It is argued that renal stones form primarily as a consequence of the hydrolysis of urea by the bacterial enzyme urease. However, no explanation is given for microorganisms that produce urease only occasionally or not at all. The question arises as to wheter the infection-induced microorganisms might not be playing a double role in renal stone formation by not only producting urease, but also by affecting in vivo urokinase (UK) and sialidase (SA) activity. With this in mind, the effect of Escherichia coli on renal UK and SA activity has been studied in male rats with a normal diet. The renal UK (P=0.208) and SA (P=0.2135) activities did not differ significantly between the two kidneys of the same rat. In contrast, when drainage from one kidney of a rat was externally obstructed, the UK and SA activities differed significantly between kidneys (P<0.015). An increase in UK (r=0.6456, P<0.0001) and SA (r=0.7507, P<0.0001) activity was observed over time in the obstructed kidney. Subcutaneous injections with E. coli reduced the UK activity of the obstructed kidney significantly (p=0.0171). However, the SA activity remained the same (P=0.3929). This decrease in the UK activity in the presence of microorganisms may result in an increase in the uromucoid concentration, leading to renal stone formation in the presence of increased salt precipitation on the uromucoid as caused by the urease producing microorganisms.

Are two teachers better than one

Purpose - – This paper aims to focus on the thinking styles of a group of Accounting students, and to determine whether team teaching by two criteria-specific lecturers can be an effective collaborative teaching approach to accommodate students’ diverse learning preferences. Research on thinking and learning processes led to a four-quadrant whole-brain model of people’s thinking styles and associated learning preferences. The model can be used to identify and accommodate students’ diverse thinking styles and learning preferences. Design/methodology/approach - – A case study approach was followed, using multiple data collection methods. The thinking styles of 288 students and two lecturers were surveyed using a thinking style questionnaire and the Herrmann Brain Dominance Instrument. The results of the collaborative teaching approach were obtained by way of a survey questionnaire providing both quantitative and qualitative feedback, as well as a SWOT analysis completed by the involved lecturers. Findings - – The main results suggest that a collaborative teaching approach can address students’ diverse learning preferences, although some students may find constant switching between lecturers distracting. Research limitations/implications - – The collaborative teaching approach in the teaching interaction cannot be isolated. Collaborative teaching was not repeated or extended due to resource constraints. Originality/value - – Academics from all disciplines recognise a need for a teaching practice that addresses students’ diverse learning preferences. Hitherto, outside of special education, collaborative teaching has received little scholarly attention, especially as an approach to address tertiary students’ diverse learning preferences.