THE EFFECT OF HYPERTENSIVE EPISODES AND CARDIAC HYPERTROPHY ON THE CANINE CARDIAC BAROREFLEX

1. Left ventricular (LV) hypertrophy has been implicated in the reduction of baroreflex sensitivity present in hypertension. The aim of the current study was to investigate the mean arterial pressure-heart rate reflex (MAP-HR) in a model which induced left ventricular hypertrophy but no sustained blood pressure elevation. 2. Five mongrel dogs were exposed to transient blood pressure elevation of between 20 and 30 mmHg, through hindlimb compression using a pneumatic pressure suit, for 7 h per day, 6 days per week for 6 weeks. Resting blood pressure was not altered by the 6 week hindlimb compression intervention. 3. Echocardiographically determined LV mass (mean ± s.e.m.) was 116.0 ± 7.4 g prior to hindlimb compression (baseline) and elevated to 125.4 ± 8.1 g (P= 0.003) after 6 weeks of compression. A reduction in the early (E) to late (A) transmitral diastolic flow ratio (E/A) from 1.80 ± 0.06 at baseline to 1.54 ± 0.09 (P = 0.037) after the 6 week intervention suggested that cardiac compliance was reduced. 4. The maximum gain of the MAP-HR reflex, studied using the ‘steady-state’ drug technique, when blood pressure was normal, showed a trend for reduction from 3.85 ± 0.43 beats/min per mmHg at baseline to 3.10 ± 0.45 beats/min per mmHg (P= 0.067) after 6 weeks of compression. This gain reduction became significant after β-adrenoceptor blockade with propranolol (3.13 ± 0.55 vs 2.32 ± 0.25 beats/min per mmHg; P= 0.039). Covariant analysis showed a significant inverse correlation between LV mass and maximum gain (r= 0.96; P<0.001) during the 6 week compression period. 5. The MAP-HR reflex changes in this model mimic those present in hypertension and implicate cardiac hypertrophy as one possible mediator.     

Influence of indenyl ligand substitution pattern on metallocene-catalyzed propene copolymerization with 1-octene

Copolymerization of propene with 1-octene (1 mol/1 mol) was performed in toluene at 40°C in the presence of homogeneous methylaluminoxane (MAO)-activated ansa-metallocenes in order to study the role of benzannelation and 2-methyl-substitution of the silylene-bridged bisindenyl ligand on comonomer incoporation, molecular mass, molecular mass distribution, and end groups. While 2-methyl-substitution promoted higher degree of polymerization without affecting copolymerization parameters, benzannelation improved markedly 1-octene incorporation. Only with MAO-activated rac-Me₂Si(2-MeBenz[e]Ind)₂ZrCl₂ catalysts vinylidene end groups were formed exclusively. Molecular weight distribution remains narrow in all experiments.     

Research fellowship in behavioral AIDS research

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Research fellowship in behavioral AIDS research     

Patterns of upper gastrointestinal diseases based on endoscopy in the period 1998-2001

Upper gastrointestinal complaints are common in Kenya. Though these have remained unchanged over the last 20 years, the pattern of upper gastrointestinal disease on endoscopic examination seems to be changing. There appears to be progressive increase in oesophagitis and cancer of the stomach. Peptic ulcer disease has remained stable while Cancer of the oesophagus is still common. The paper intends to report on endoscopic findings at the Centre for Clinical Research, Kenya Medical Research Institute (KEMRI) over the period October 1998 and May 2001. The sources of information are records made at the time of endoscopy and histology reports on biopsies taken. Seven hundred and sixty eight patients were endoscoped. The male to female ratio was 1.7:1 with mean age +/-SD of 40.8 +/-20.1 years and age range was 3 to 96 years. Majority of the patients had abnormal findings with gastritis being the most common ( 25.8%). It is concluded that gastritis is an important cause of morbidity in Kenya. Oesophagitis, mainly due to gastroesophageal reflux disease, seems to be on the increase. Gastric cancer is not as rare as previously thought and peptic ulcer disease is still common.     

Localization of yeast glucoamylase genes by PFGE and OFAGE

Summary Chromosomes of two closely related yeast strains, the amylolytic Saccharomyces diastaticus and the non-amylolytic Saccharomyces cerevisiae, were resolved by pulsed field gel electrophoresis (PFGE) and orthological field alteration gel electrophoresis (OFAGE). Electrophoretic karyotypes of these two strains are identical. Sixteen cloned Saccharomyces genes of known chromosomal location were used to identify individual chromosomes by Southern hybridization analyses. The Southern blots were reprobed with a cloned fragment of the STA2 glucoamylase gene of S. diastaticus. STA2 exhibits homology to STA1 and STA3 as well as the sporulation-specific glucoamylase (SGA) gene from both Saccharomyces strains. The three unlinked, homologous genes, STA1 (DEX2, MAL5), STA2 (DEX1) and STA3 (DEX3) encoding the extracellular glucoamylase isozymes GAI, GAII and GAIII in S. diastaticus were then assigned to chromosomes IV, II and XIV, respectively. The SGA gene, encoding an intracellular glucoamylase in both S. diastaticus and S. cerevisiae, was assigned to chromosome IX. Electrophoretic mapping of the STA and SGA genes is at present the only way to localize these genes, since glucoamylase repressor gene(s) (STA10, INH1 and/or IST2) are present in most laboratory strains of S. cerevisiae and the SGA phenotype is only detectable during sporulation.     

Antigen-specific stimulation and trans-stimulation of T cells in long-term culture.

When T cells from antigen-primed lymph nodes are stimulated in vitro with antigen, they give rise to a proliferative response as high as that elicited by the polyclonal T cell activator concanavalin A. It is likely that in these conditions not only antigen-specific T cells proliferate. We have established an experimental system which demonstrates that large numbers of nonantigen-specific T cells are induced to proliferate as a result of antigen-specific T cells' confrontation with antigen. This phenomenon, which we call trans-stimulation is antigen-dependent and antigen-specific. Although the presence of antigen-specific T cells is required, these cells do not have to proliferate in order to induce trans-stimulation. In an attempt to enrich for antigen-specific T cells in vitro, we established conditions for culturing T cells in the presence of antigen for long periods of time (up to 6 weeks). High levels of antigen reactivity were observed upon antigen restimulation of “directly” stimulated T cells from long-term cultures. In contrast, long-term cultures of trans-stimulated cells were depleted of antigen reactivity. Neither type of long-term culture contained detectable alloreactive cells indicating that trans-stimulation is not reflected randomly upon bystander T cells.     

Platelet-derived growth factor (PDGF) BB acts as achemoattractant for human malignant mesotheliomacells via PDGF receptor b - integrin a3b1 interaction

Platelet-derived growth factor BB (PDGF BB) and the PDGF receptor b are expressed on mesotheliomacells, but their biological function has not yet been defined. In the present study we used Boyden chambersfitted with filters coated with the adhesive matrix proteins fibronectin, laminin, collagen type IV or the non-matrixadhesive molecule poly-L-lysine (PLL). Mesothelioma cells migrated towards PDGF BB at concen-trationsranging from 0.78 to 12.5 ng/ml if matrix proteins were present as adhesive substrates. This migrationwas integrin dependent since the same cells failed to migrate if the adhesive interactions necessary for migra-tionwere provided by molecules other than integrins. Migration of mesothelioma cells on fibronectin, lamininor collagen-type IV in response to PDGF BB was inhibited if the cells were pretreated with blocking anti-bodiesto a3b1 integrin. These findings describe for the first time PDGF BB as a chemoattractant for malig-nantmesothelioma cells and that collaboration between PDGF receptor b and integrin a3b1 is necessaryfor the motile response of these cells to PDGF BB.©Kluwer Academic Publishers