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Biomedical subjects

J Pretorius

Publications and source records attributed to J Pretorius.

10 recordsLinked to original sources
PubMed2004

Appropriate use of the carbapenems.

The carbapenems are a group of broad-spectrum beta-lactam antibiotic agents of which there are three parenteral preparations currently available in South Africa, namely imimpenem/cilastatin, meropenem and ertapenem. Owing to the fact that imipenem/cilastatin and meropenem have a broad spectrum of activity that includes Pseudomonas and Acinetobacter species, they are ideal antibiotics for treatment of severe nosocomial infections. In contrast, ertapenem has limited in vitro activity against the latter non-fermentative gram-negative bacteria and is therefore more suitable for the treatment of certain severe community-acquired infections. This statement arises out of concerns about the general abuse of antibiotics such as the carbapenems, with the primary intention of highlighting the appropriate use of these agents.

Anti-Bacterial Agents↗
PubMed2001

Deletion of Pten in mouse brain causes seizures, ataxia and defects in soma size resembling Lhermitte-Duclos disease.

Initially identified in high-grade gliomas, mutations in the PTEN tumor-suppressor are also found in many sporadic cancers and a few related autosomal dominant hamartoma syndromes. PTEN is a 3'-specific phosphatidylinositol-3,4,5-trisphosphate (PI(3,4,5)P3) phosphatase and functions as a negative regulator of PI3K signaling. We generated a tissue-specific deletion of the mouse homolog Pten to address its role in brain function. Mice homozygous for this deletion (PtenloxP/loxP;Gfap-cre), developed seizures and ataxia by 9 wk and died by 29 wk. Histological analysis showed brain enlargement in PtenloxP/loxP;Gfap-cre mice as a consequence of primary granule-cell dysplasia in the cerebellum and dentate gyrus. Pten mutant cells showed a cell-autonomous increase in soma size and elevated phosphorylation of Akt. These data represent the first evidence for the role of Pten and Akt in cell size regulation in mammals and provide an animal model for a human phakomatosis condition, Lhermitte-Duclos disease (LDD).

Animals↗
PubMed2001

Penetrating cardiac injuries--current evaluation and management of the stable patient.

Patients with penetrating cardiac injuries present in a stable or only mildly shocked condition--especially if the laceration has sealed off and the patient has been adequately resuscitated. A large proportion of patients presenting to our unit are in a reasonably stable condition after resuscitation, and rapid diagnosis may be difficult. We present our experience over a 5-year period (191 patients), with particular reference to the stable patient. All patients with penetrating precordial wounds should be assessed for a possible cardiac injury, especially if a period of hypotension has occurred. Clinical signs, central venous pressure, chest radiograph, pericardiocentesis and subxiphoid window are not always helpful in the diagnosis. Cardiac ultrasound is very useful (in the absence of haemothorax), and was performed in 103 of 191 patients, with 8 false-negatives and 3 false-positives. When an unstable patient presents with an obvious diagnosis use of cardiac ultrasound should be restricted. A subxiphoid window has diagnostic value where the cardiac ultrasound is inconclusive.

Heart Injuries↗
PubMed1999

Current evaluation of cardiac stab wounds.

BACKGROUND: Patients with penetrating cardiac injuries may be stable or only mildly shocked, especially if the laceration has sealed off and the patient has been aggressively resuscitated. Clinical signs, chest roentgenograms, pericardiocentesis, and subxiphoid window are not always helpful in establishing the diagnosis. We reflect on the current evaluation based on 128 patients. METHODS: There were four groups of patients, ranging from lifeless (group I) to stable (group IV). Patients in groups I and II were prepared immediately for operation. Those in groups III and IV were often investigated further (chest roentgenogram and cardiac ultrasound). RESULTS: Mortality was 8%. Significant findings were a precordial stab, central venous pressure of more than 15 cm of water, one or more clinical signs of tamponade, and initial shock. Cardiac ultrasound was performed in 5 patients in group II (15%), 14 patients in group III (48%), and 37 patients in group IV (86%). There were no false positives, and 6 false negatives (11%). Thirty-one patients (24%) had clotted lacerations. There were no negative sternotomies. CONCLUSIONS: Efficient fluid resuscitation and rapid confirmation of diagnosis with cardiac ultrasound should decrease mortality. Stable patients with a precordial wound should undergo cardiac ultrasound or echocardiogram. Diagnosis may be reliably confirmed in these patients whose clinical signs often fluctuate (or rapidly deteriorate).

Adolescent↗
PubMed1999

Shock absorption potential of different mouth guard materials.

STATEMENT OF PROBLEM: Clinical stresses and situations in the mouths of patients are substantially different; thus, it is not possible to make an exact in vivo comparison of the efficiency of various mouth guards. PURPOSE: This study developed a device and a method to test and quantify the potential of mouth guards to absorb shock and evaluated and compared 5 designs for mouth guards. MATERIAL AND METHODS: Strain gauges and accelerometer sensors were mounted in various positions on the maxilla and inside an artificial skull. Sensors quantified the response of several areas of the skull to inputs of force on the maxillary teeth protected by the mouth guard being investigated. Input of force was applied to the maxillary teeth with a modal hammer equipped with a load cell. Five mouth guards of each of 5 designs were manufactured and placed in position before force was applied to the maxillary teeth. All inputs were measured and analyzed and, from those results, a method was developed to quantify the relative potential of the mouth guards to absorb shock. This method was then used to quantify the shock absorption potential of the 5 types of mouth guard designs. RESULTS: All 5 types of mouth guards provided some measure of protection and were better than no protection. However, the level of protection provided by the 5 mouth guard designs differed.

Dental Stress Analysis↗
PubMed1998

Milieu deprivation and its implications for education in the Republic of South Africa.

Due to milieu deficiencies and psychosocial handicaps, some groups are caught in a spiral of poverty and experience serious obstruction to optimal self-actualization and to the achievement of a satisfactory quality of life. This article describes the problem of educating milieu-deprived students in the Republic of South Africa, as well as the implications for educational reform.

Education↗
PubMed1994

Myocardial function in septic sheep.

There is an ongoing discussion whether the heart is the primary target organ responsible for the development of cardiovascular failure during septic shock as well as its onset. We tried to study the reaction of the heart to sepsis in the early phase of 8 h, using a sublethal model of sepsis in six awake cross-bred Austrian mountain sheep. Sepsis was induced by infusion of a live Escherichia coli suspension at a dose of 5 x 10(7) colony-forming units per kg body weight over 8 h. Standard hemodynamic, hematologic and serum tumor necrosis factor (TNF) measurements were obtained. For evaluation of left ventricular performance we used the following methods, tested in five pilot experiments: 1) The shift of the end-systolic pressure-diameter relation. This was characterized by the calculated shift of the transverse external end-systolic diameter of the left ventricle at a "midrange" end-systolic pressure of 100 mmHg (end-systolic ventricular diameter deviation, ESVDD100). Calculations were performed using a second order regression function of the end-systolic pressure diameter points obtained by variation of afterload by a cuff occluder on the aorta; 2) The shift of the (dP/dt)max over end-diastolic diameter ratio compared to control values estimated by a graphical approach. Mean pulmonary pressure increased from 21 +/- 1 to 36 +/- 2 mmHg in the first hour after starting the E. coli infusion and remained elevated during the entire 8 h observation period. Serum TNF was found to peak 1 hour after start of E. coli infusion and was hardly detectable after 3 hours of bacteremia. Mean aortic pressure showed minor changes (maximum 105 +/- 3 mmHg, minimum 91 +/- 2 mmHg) and there were no statistically significant alterations of the cardiac index. ESVDD100 showed an "oscillatory" reaction in the first phase and a statistically significant decrease of contractility in the second phase (at 4 h). This was confirmed by the graphical method of the (dP/dt)max over end-diastolic diameter ratio. We may therefore conclude that there is no early depression of myocardial function or if so, it may be masked by adrenergic stimulation. In the later phase of the 8 h experiment there is a significantly decreased contractility of the heart. This may be compensated (e.g., "Starling" mechanism or heart rate increase) in this sublethal model.

Animals↗
PubMed1984

Distribution of pyramidal cell density and hyperexcitability in the epileptic human hippocampal formation.

Pyramidal cell densities in various regions of the anterior and posterior hippocampal formation were measured from en bloc temporal lobe resections and compared with presurgical stereoelectroencephalography (SEEG) data derived from depth electrodes in 12 patients with temporal lobe epilepsy. These data were compared with cell densities observed in four nonepileptic control patients. Patients who consistently exhibited anterior focal changes in the SEEG accompanying onset of ictus had cell densities that were selectively reduced in the anterior hippocampal formation but normal with respect to controls in the posterior hippocampal formation. Patients who exhibited more regional changes in the SEEG at onset of ictus had reduced cell densities in both the anterior and posterior hippocampal formation. Patients who exhibited focal spike activity in the anterior hippocampal formation as their predominant interictal SEEG pattern also had selectively reduced cell densities in the anterior hippocampal formation, while patients with widespread spiking throughout the hippocampal formation had reduced cell densities both anteriorly and posteriorly. These data support the concept that epileptogenesis occurs in or near those areas of epileptic hippocampus that are most damaged. Hippocampal sclerosis must be viewed as related to adjacent hyperexcitable or epileptogenic neurons and not solely as a passive result of repeated anoxia or ischemia.

Cerebral Cortex↗
PubMed1984

Temporal lobe volumetric cell densities in temporal lobe epilepsy.

Volumetric cell densities in 13 different subfields of the temporal lobe were calculated to test various hypotheses about mesial and lateral temporal lobe sclerosis in patients with complex partial epilepsy. In patients benefitting (primary group) from anterior temporal lobectomy (ATL), sclerosis was greater (fewer cells) in anterior than in posterior hippocampus. By contrast, the patients lacking full benefit (nonprimary group) from ATL had decreased numbers of neurons equally distributed from anterior to posterior hippocampus, indicating that zones of mesial temporal cell loss are linked to zones of epileptogenicity. These data support a model of focal hippocampal epilepsy originating from zones of cell loss and synaptic reorganization that is epileptic. There were no differences in cell densities in gyrus hippocampi or in lateral temporal gyri when patients with temporal lobe epilepsy and controls were compared. Hippocampal cell densities in mesial temporal lobe were not reduced in psychomotor epileptic patients with extrahippocampal foci consisting of foreign tissue. Variables in seizure histories were not correlated with Ammon's horn cell densities, indicating that most of the sclerosis preceded the seizures, which did virtually no significant further damage to hippocampus with repeated partial or generalized seizures.

Brain Diseases↗