Blood platelet: a review of its characteristics and function in acute malaria infection.

BACKGROUND: The role of the circulating platelet has until in relatively recent times, been mainly considered in terms of cellular mediators of thrombohaemorrhagic activities. It has most recently also been shown to play important role in modulating host immune response to infections such as malaria infection, both in the early and later phases of the infection. Data on the role that platelets play in early malaria infection is relatively scanty. This review highlights changes in platelet characteristics and function that have been reported in acute malaria infection. METHODS: Literature from Pubmed (MEDLINE), Google Scholar, Google search, textbooks and Cochrane Library were reviewed covering the period RESULTS: It is observed that Thrombocytopenia which had hitherto been considered as the hallmark of the complication of acute malaria infection, occurs in 40-80% of human acute malaria infection and in 100% of murine models. It results from platelet activation mechanism. The evidence in support of this view includes associated findings of elevated plasma concentrations of Beta-thromboglobulin (BTG) and Platelet Factor 4 (PF4) as well as enhanced production of Thromboxane A2 (TXA2) and 6-keto prostaglandin F1α (6-KPF1α). There is also loss of total platelet sialic acid associated with reduction of platelet life span. A more recent finding of platelet killing of the parasite inside the infected red cell has revealed a hitherto little known potential which shows that early interaction between circulating platelets and the malaria parasite in the course of infection may result in reduction of parasitaemia thus mediating host survival to malaria infection. The mechanism(s) of platelet protective activity in early acute malaria is/are yet to be fully clarified in order to provide better understanding of the phenomenon. Clinically, it has also been reported that in acute malaria infection, the severity of clinical manifestations correlates closely with the parasite load. CONCLUSION: Reported changes of platelet/malaria parasite interactions highlighted in this review bring to the fore the need for more research activities to be undertaken in this area.

Haemoglobin genotypes: a prevalence study and implications for reproductive health in Uyo, Nigeria.

BACKGROUND: Haemoglobinopathies are among the most common genetic disorders worldwide, inherited as autosomal recessive disorders from healthy-carrier parents. The most common are the sickle cell disorders and the thalassaemias, occurring in people of African, Asian, South European and Middle Eastern descent. The University of Uyo Teaching hospital (UUTH), Uyo, Akwa Ibom state, Nigeria is a tertiary health institution providing the health needs of the host and neighbouring states in south-south and south east Nigeria. There is currently paucity of data on the hoemoglobin genotype distribution in Akwa Ibom State, hence the need for this study, considering its importance in medical diagnosis, parentent management, genetic information and counselling. METHODS: This is a retrospective study. Registers and results of all haemoglobin genotype investigations carried out in the department of Haemotology University of Uyo Teaching Hospital, Uyo between January, 2003 and December, 2007 were extracted, reviewed and analyzed using simple percentages. RESULTS: Eight thousand and ninety-seven haemoglobin genotype tests carried out over a five year period were analysed: 6376 (78.7%) of these were HbAA, 1580 (19.6%) HbAS, 121 (1.5%) HbSS, while HbAC and SC accounted for 16 (0.2%) and 4 (0.04% respectively. The ratios of Hb AA to Hb AS, HbAA to HbSS and HbAA to HbAC were 4:1, 52:1 and 400:1 respectively. Of the 8097 subjects, 6723 (83.0%) were females, 1152 (14.2%) were males. Among the females, 4.8% of HbSS and HbSc were in children under 15 years while only 0.3% were in those 15-44 years. CONCLUSION: While HbAA is the predominant genotYpe in our environment, there is also a significant number of the abnormal haemoglobin genes. With many children with sickle cell disease now surviving to adulthood due to advances in medicine, a larger number of women with sickle cell disease in pregnancy with all the attendant challenges it poses should be expected in our environment. It is necessary therefore, to keep abreast with developments in the area of its management in order to cope with the challenges.

Inhibition of platelet adhesion to rabbit aorta by sulphinpyrazone and acetylsalicylic acid.

A technique for the isolation of rabbit thoracic aorta in a form in which it can withstand normal pressure and a new in vitro system in which it was tested is described. Segments of aorta were selectively damaged with a balloon catheter by the Baumgartneer technique and supensions of washed platelets, labelled with 51Cr, were perfused through them. More platelets adhered to the damaged surface than to the undamaged surface. Suophinpyrazone was more effective than aspirin in inhibiting platelet adherence to both the damaged and undamaged surface.

Platelet hypersensitivity in acute malaria (Plasmodium falciparum) infection in man.

During acute malaria infection, platelets in human platelet-rich plasma re hypersensitive to the addition of ADP between 1.0 micro M and 5.0 micro M, or adrenaline 0.11 micro M as aggregating agents. The mean maximum aggregation amplitude (as % of light transmission) obtained from 8 subjects in response to added ADP (1.0 micro M) , 39.8 +/- 27 (1SD), was significantly greater than the value in 6 controls (5.2 +/- 6.7 (1SD); t = 3,51 P less than 0.005). A similar pattern of response was obtained with higher ADP concentrations (2,4, 4.5 or 5.0 micro M) in 22 patients and 20 control subjects (89.9 +/- 14.9 % vs 77.8 +/- 16.5% (1SD) t = 2,45, P less than 0.02). Addition to 4.5 microM ADP to patient PRP usually evoked only a single aggregation wave (fused primary and secondary waves) while the typical primary and secondary wave pattern was usually obtained from controls. Mean plasma B-thromboglobulin (BTG) concentration in 7 patients (208.3 +/0 15.6 ng/ml) was significantly higher than the value in 6 control subjects (59.2 +/- 15.7 ng/ml; t=13.44, P less than 0.002).

Effect of the root extract of Fagara zanthoxyloides on blood coagulation.

The clot-promoting activity of the aqueous extract of Fagara-zanthoxyloides Lam plant is described for the first time. It significantly shortened the PTT (K) of normal and factor VIII deficient plasma while it manifested no such action on factor IX-deficient plasma. This activity could be demonstrated in the residue of the lyophilized aqueous extract after its successive extraction with ether, chloroform and methanol. It could not be attributed to the purified fractions: Zanthoxylol or its modified form 3, 4-dihydro-2,2-dimethyl-2H-1 benzopyran-6-butyric acid (DBA), hesperidin, Fagaramide or the ether soluble fraction of the aqueous extract.

Blood changes and enhanced thromboxane and 6-keto prostaglandin F1 alpha production in experimental acute Plasmodium bergei infection in hamsters.

Golden hamsters inoculated intraperitoneally with Plasmodium bergei infected mouse blood regularly developed P. bergei parasitaemia. This was associated with progressive thrombocytopenia and leucocytosis as the degree of parasitaemia increased with time. When infected whole blood was stimulated with collagen, significantly enhanced thromboxane B2 (TXB2) production per platelet was seen. 6-keto prostaglandin (PG) F1 alpha formation in the same system increased from the sixth infection day onwards and correlated with the relative leukocytosis. The production of 6-keto PGF1 alpha by aorta rings was significantly higher during the 4-7th days postinoculation. The increase in thromboxane production however was much more important than that of 6-keto PGF1 alpha and it therefore is concluded that P. bergei parasitaemia in hamsters tilts the haemostatic balance towards the platelet hyperaggregability that has also been described in P. falciparum infection in man.

Diagnosis of haemophilia: use of an artificial factor-VIII-deficient human plasma system.

An artificial clotting system deficient in factor VIII has been made from normal human plasma. Factors XII and XI are supplied as ;activation product'. An eluate from Al(OH)(3), which has been incubated with normal plasma, supplies factors X and IX in their ;plasma' (unactivated) form with II. Factor V is provided as the supernatant after the Al(OH)(3)- treated plasma has been precipitated at one-third saturation with (NH(4))(2)SO(4). Fibrinogen is freed of factor VIII by freezing and thawing a lyophylized preparation and then added. Of these, activation product and the fibrinogen may be prepared in advance and stored frozen, and the eluate and supernatant may be made on the day of testing. A phospholipid source and CaCl(2)-solution are also required. In use, a patient's and a control plasma are first diluted in a mixture of the eluate, supernatant, and fibrinogen solution, and clotting times are recorded after completing the system by adding the phospholipid, activation product, and calcium chloride. The clotting times from the mixtures containing the patient's and the control plasmas may then be compared.

Myelodysplastic syndrome and successful pregnancy.

A case of successful pregnancy in a 47-year-old Omani grand-multipara who had Myelodysplastic Syndrome (MDS) is described for the first time in Oman. A review of the literature suggests that in Japan the problem may be more common than elsewhere. The unusual features in the case reported here include, improvement in haematological parameters during the pregnancy contrary to expectation, and in addition, the religious and cultural factors that intruded into the clinical decision making process. Suggestions to combat the latter factors are made.

The inhibitory effects of ferriprotoporphyrin IX on platelet aggregation and release of serotonin.

Ferriprotoporphyrin IX (FP) dissolved in 0.025N NaoH in concentrations of 0.01 - 0.04 microM/ul platelet suspension competitively inhibited platelet aggregation induced by a low concentration of collagen. 14C-serotonin release was also inhibited. Higher concentrations of collagen overcame the aggregation inhibition. A similar pattern of results was obtained with thrombin-, and arachidonic acid-induced aggregation and release. With ristocetin, there was little inhibition of aggregation although serotonin release was inhibited. ADP-induced aggregation was partially inhibited except at FP concentrations of 0.91 microM/mul. FP caused only platelet shape change and serotonin release of up to 8.1%. These changes were not associated with significant platelet lysis and could also not be attributed to pH or temperature changes. There was no inhibition of collagen-induced aggregation in PRP, but FP precipitates aggregated washed platelets and caused serotonin release. These results show that FP in solution inhibited platelet aggregation induced by the different agents studied. It did not interfere with platelet agglutination induced by ristocetin. The mechanism(s) of aggregation inhibition remains to be clarified.

Haemoglobin A2 (Hb A2) and malaria.

The Packed Cell Volume (PCV), reticulocyte count and Hb A2 were determined in 28 patients during the period of malaria parasitaemia and 14 days after effective treatment. The Hb A2 was determined by cellulose acetate haemoglobin electrophoresis in alkaline medium followed by elution in water. There was no statistically significant difference between the PCV during the period of parasitaemia and that after treatment (p > 0.05). The Hb A2 level did not show any significant difference during and after treatment of malaria (p = 0.05). The correlation coefficient between absolute parasite count and Hb A2 level was -0.22 (p = 0.251). It is concluded that malaria parasitaemia does not induce a significant change in the level of Hb A2.

Platelet aggregation inhibition in Trypanosoma vivax infection of sheep.

We have investigated in vitro platelet aggregation in platelet rich plasma from Trypanosoma vivax infected and control sheep using the dual channel Payton Aggregometer. Final concentrations of the following inducing agents were used: 1.2 um ADP, 6.2 ug collagen, 1.2 ug ristocetin and 1 u thrombin. These showed that there was a significantly reduced aggregation of platelets from infected sheep (13.4 +/- 1.1 pc at week 3 post infection when compared with control sheep PRP 95.0 +/- 1.0pc; P less than 0.001) using ADP. Similar differences were also obtained with other inducing agents. Preliminary 14C-5HT uptake and release studies showed that there was difference in the uptake of label between platelets from infected (18.6pc) and control (28.4pc) sheep. However, when release was inducted, comparable results were obtained for both infected and control sheep platelets. It is concluded that the degree of aggregation inhibiting varies directly with the level of parasitaemia.

Effect of Plasmodium falciparum malaria on plasma fibrinopeptide-A (FpA) concentration.

Plasma Fibrinopeptide-A (FpA) concentrations were determined using Enzyme-linked Immunosorbent Assay (ELISA) in patients with acute Plasmodium falciparum malaria infection and in 30 healthy controls. The mean FpA levels of the malaria patients were significantly raised (p < 0.001). The patients' FpA level correlated positively with malaria parasitaemia, but negatively with plasma fibrinogen concentration. A week after commencement of chloroquine therapy and subsequent disappearance of malaria parasites from the thick blood films, the patients' FpA levels decreased significantly from pre-treatment values. It is suggested that the elevated FpA and reduced plasma fibrinogen levels in the patients probably indicate a more widespread existence of overt coagulation defect in acute malaria infection.

Neuro-ophthalmological sequelae of sickle cell disease. A case report and review of the literature.

A case of homozygous sickle cell anaemia male patient, aged 16 years is reported. The initial symptom following a sickle cell crisis was impairment of vision, progressing rapidly to complete blindness within three days. Within 4 days of admission in the hospital, he lapsed into coma and died four weeks later. Autopsy findings revealed multiple cerebral, pontine and cerebellar infarcts. The literature on neuro-ophthalmological sequelae is reviewed.

Changes in antithrombin III levels in pregnancy, labour and in women on the contraceptive pill.

Antithrombin III activity as determined by the modified Mancini technique is reported for the first time in different groups of Nigerian women as well as in a group of male blood donors. The mean level of activity (78.69%) observed in women during their second and third trimesters was lower than the mean value in the same group of women at parturition (93.18%) and significantly lower than a control group of non-pregnant women who were also not on the contraceptive pill (109.67; P less than 0.05). There was no significant difference between the mean activity of the female control group and that of women on the contraceptive pill and that of a group of male blood donors of the same age range.

Enhanced fibrinolysis in Nigerians--probable contributory factor to low prevalence of atherosclerosis in the Nigerian.

Results of more detailed study of the fibrinolytic enzyme system in Nigerians is reported. A relatively short euglobulin lysis time (ELT, range 75.87-196.08 units) in the males was observed, while a longer time (49.50-98.04 units) was observed in females aged 19-35 years. The mean concentrations of fibrinogen (0.41+/-14 g/100 ml) and plasminogen (2.45+/-1.03 Casein units) which are reported, the latter for the first time in this population are similar to values in other populations. Although plasminogen/plasmin inhibitors were not separately determined in this study, results of the ELT suggest that this was probably due to increased activator activity, and supports a previous suggestion that this increased activator activity may be a mechanism of the enhanced ELT in the males examined.

Coagulation profile in healthy Nigerian neonates.

A study of some coagulation factors were carried out in preterm and term infants on the first day of life. Screening coagulation tests--prothrombin time (PT), partial thromboplastin time with kaolin (PTTK) and the concentrations of Factors VIII: C and fibrinogen were determined in 100 normal newborn infants classified into three groups according to their gestational ages: 28 to 30 weeks, 31 to 36 weeks, 37 to 42 weeks. The respective values were compared with those of six-month-old infants as well as adults. The mean values of the screening coagulation tests, PT and PTTK, Factor VIII: C and fibrinogen were significantly different in all the three gestational age groups of nonates when compared with those of six-month-old infants and adult Nigerians. This suggests that a relative hypocagulable state exists among newborn infants and could be responsible for increased bleeding tendencies in these groups of infants. This is the first documented report of coagulation profile in Nigerian neonates, and the range obtained in this study can thus be regarded as standard for healthy Nigerian neonates. The body of data should therefore provide a basis for evaluating newborn noenates with bleeding problems.

Decrease in platelet survival and total platelet sialic acid concentration in rats infected with Plasmodium bergei bergei.

Suckling Wistar rats aged 3-5 weeks were infected through their dorsal tail vein with P. berghei berghei passed in Swiss albino mice. Platelet recovery and platelet survival using 51Cr-labelled heterologous platelets obtained from adult Wistar rats were determined in the infected animals on different post-infection days and on a group of non-infected rats as controls. Total platelet sialic acid was also determined in the same groups of animals. The results showed reduced platelet recovery, shortened survival and reduced total platelet sialic acid content in the infected animals compared with control values. The reduction in total platelet sialic acid content was related to the degree of parasitaemia and reached significant levels on the 5th post-infection day. It is concluded that the shortened platelet survival and reduced total platelet sialic acid content observed in the P. berghei infected rats were causally related and may account for the thrombocytopaenia reported in experimental and natural malaria infections of animals and man.

Incidence of dual presence of antibodies to HIV1 and HIV2 in seropositive cases seen in Ibadan, Nigeria.

Between July 1987 and December 1988, sera from 6,385 individuals were screened for HIV1 but only 1,861 of these samples were screened for HIV2. Majority of those screened for HIV infection (89.7%) were blood donors, 4.9% were international travellers/volunteers, 3.8% were patients (i.e. those with haematological malignancies, multiply transfused patients and those suspected of having HIV infections), and the rest (1.6%) were female sex workers. Screening for HIV1 antibody was done using Welcozyme anti-HTLV III (Wellcome Diagnostics, Dartford, England) or Elavia I (Diagnostics Pasteur, Marnes La Coquette, France). ELAVIA Ac-Ab-Ak II was used to detect HIV2. The confirmatory test employed was western blot, using LAV Blot I and LAV Blot II (Diagnostic Pasteur, Marnes La Coquette, France). The seroprevalence rate for HIV1 in the blood donors was 0.51% while that of HIV2 was 0.33%. The seroprevalence rates for HIV1 and HIV2 amongst the adult travellers were 1.64% and 0.55% respectively and the comparative rates in the multiply transfused patients (including those with haematological malignancies) were 1.23% each. All the HIV2 positive cases in this group had refractory anaemia. In those suspected of having HIV infection, the seroprevalence rate of HIV1 was 2.94% and no patient in this group had HIV2. Evidence of dual infection by HIV1 and HIV2 was obtained from 18.5% of the seropositive individuals. The dual infection rate in seropositive Nigerians is similar to that reported for some West African countries. We would strongly suggest that all blood samples for HIV tests in Nigerians should be screened for both HIV1 and HIV2. The two blood donors with evidence of dual infection could not be contacted due to fictitious addresses. The only patient with a dual infection has refractory anaemia and he is still being followed up but has not yet developed full-blown AIDs.

Blood coagulation activities of the root extracts of Fagara xanthoxyloides plant.

The coagulant properties of root bark and root wood extracts of Fagara xanthoxyloides lam plant are reported. Results of an earlier report which showed that the aqueous extract of the root shortened both the PT and PTT of normal and FVIIIC-deficient plasma are confirmed as well as the absence of many such effects on FIXC-deficient plasma. Root bark manifested twice as much potency as an equal concentration of root wood. The activity could still be demonstrated in the residue of root bark after the lyophilized aqueous extract had been successively extracted with methanol and hexane. It is suggested that these results may have clinical implications.

Platelet-aggregating activity of released factor(s) from Trypanosoma brucei brucei.

The effect of factors derived from Trypanosoma brucei brucei on rat platelets was studied. T. brucei at a concentration of 4 X 10(9) trypanosomes/ml phosphate saline glucose (PSG) was stored at -20 degrees C for 18 h, thawed, and a supernatant fraction, trypanosome-derived supernatant (TDS) was obtained by spinning the sample at 3000 g for 10 min at 20 degrees C. Normal rat platelets, prepared as platelet-rich plasma (PRP), were then incubated with TDS in the absence or presence of ADP (0.05-0.1 microM). The results showed that approximately 83% platelet aggregation was induced by addition of TDS (50 microliters; 113 micrograms protein) to 100 microliters PRP with a platelet count of 10(6). simultaneous addition of ADP and TDS to PRP produced a synergistic effect. It was also shown that a supernatant fraction, obtained by incubating live T. brucei (4 X 10(9)/microliters PSG) at 0 degrees C 1 h and spinning down the trypanosomes (3000 g for 10 min), also induced platelet aggregation. The nature of the factor(s) derived from, or released by, T. brucei inducing platelet aggregation is being investigated but it has been shown not to be ADP.