Factor VIII-von Willebrand factor requires calcium for facilitation of platelet adherence

The role of divalent cations in platelet adherence to deendothelialized human arteries in flowing blood was investigated in an annular perfusion chamber. Spreading of platelets on the subendothelium was impaired below 30 microM of free Ca2+ ions (Ca2+). When Ca2+ was replaced by Mg2+, adherence was unchanged in perfusates without exogenous factor VIII-von Willebrand factor (FVIII-vWF), but the ability of FVIII-vWF to support platelet adherence was lost. Binding of FVIII-vWF to the vessel wall was independent of divalent cations, but bound FVIII-vWF was only able to mediate adherence after exposure to Ca2+. Pretreatment of FVIII-vWF with the calcium chelator EGTA (10 mM) resulted in loss of the ability to facilitate platelet adherence, while the ristocetin cofactor activity remained intact. Full restoration of the ability to mediate platelet adherence could only be obtained by prolonged dialysis against Ca2+ in the millimolar range. These data indicate that divalent cations have at least two separate roles to play in supporting platelet adherence: (1) platelet spreading on the subendothelium requires Ca2+ or Mg2+; (2) FVIII-vWF should be exposed to Ca2+ to obtain its optimal biologic activity in supporting platelet adherence.     

Maternal and Neonatal Factors Adversely Affecting Breastfeeding in the Perinatal Period

Background

Despite its known advantages, breastfeeding rates are low world over. Large number of factors affect breastfeeding. This study was designed to detect maternal and neonatal factors that adversely affect breastfeeding in the perinatal period.

Methods

A prospective, single-blinded study was conducted on randomly chosen mother-infant pairs in the maternity ward of a tertiary care service hospital. Only full term singletons born by normal vaginal delivery were studied. The B.R.E.A.S.T observation score and time spent by the infant at the mother''s breast were primary outcome variables. Maternal age, gravida, para status and education level were recorded. Birth weight, sex, gestation age of the infant and time interval from birth to observation were also recorded. Initial univariate analysis followed by multivariate analysis was performed using SPSS ver 7.5 software.

Results

A total of 54 mother-infant pairs formed the study group; 19(35.2%) were primigravidas. Primigravidas status of the mother led to significantly lower scores (p<0.04; 95% CI 0.10 to 3.62) as did maternal age < 26 years (p<0.04; 95% CI 0.2. to 3.46) on univariate analysis. Low birth weight (<2500 g) was the only neonatal factor that significantly lowered breastfeeding scores (p<0.02;95%Cl 0.56 to 6.31). On multivariate analysis only primigravida status was significantly associated with lower scores (p<0.02). The alpha value of the study was 5% and the power was 74%. Time spent by infant on breast was not significantly different between primigravida and non-primigravida mothers.

Conclusion

Primigravida status adversely affects breastfeeding scores; therefore counseling and support should be focused on this group. Extra care should also be taken to ensure adequate breastfeeding by younger mothers and in those with low birth weight infants. Larger studies with long-term follow up will be able to identify other factors and dertermine the effects of focused counseling and support in the perinatal period upon long-term breastfeeding rates.Key Words: Breastfeeding, Primigravida, Counseling     

Efficacy and Toxicity Profile of Methotrexate Chloroquine Combination in Treatment of Active Rheumatoid Arthritis

Background

The present study was conducted to study the efficacy and toxicity profile of methotrexate chloroquine combination in treatment of active rheumatoid arthritis.

Methods

24 patients of rheumatoid arthritis confirming to revised American Rheumatism Association (ARA) criteria were studied prospectively for twenty months. Clinical evaluation was made every 3 months. Clinical disease variables measured at each visit were number of joints with swelling, number of joints with tenderness and pain, duration of morning stiffness and physician and patient assessment of disease activity. Blood counts, liver function tests and other adverse effects due to drugs were monitored every 2 months.

Results

10 patients demonstrated more than 50% improvement. 4 patients withdrew from study, 2 because of excessive nausea and vomiting and 2 because of noncompliance. Other side effects noted were hyperpigmentation, photosensitivity, skin rashes, raised transaminases and stomatitis.

Conclusion

Methotrexate chloroquine combination has good efficacy and toxicity profile. Gastrointestinal side effects are most common and usually responsible for the discontinuation of the drugs.Key Words: Rheumatoid arthritis, Methotrexate, Chloroquine, Efficacy, Toxicity     

Ethics roundtable debate: Child with severe brain damage and an underlying brain tumour

A young person presents with a highly malignant brain tumour with hemiparesis and limited prognosis after resection. She then suffers an iatrogenic cardiac and respiratory arrest that results in profound anoxic encephalopathy. A difference in opinion between the treatment team and the parent is based on a question of futile therapy. Opinions from five intensivists from around the world explore the differences in ethical and legal issues. A Physician-ethicist comments on the various approaches.     

Testosterone-induced coronary vasodilatation occurs via a non-genomic mechanism: evidence of a direct calcium antagonism action

Testosterone decreases myocardial ischaemia in men with coronary artery disease via a coronary vasodilatory action. However, long-term therapy may increase the risk of prostatic carcinoma via activation of the nuclear AR (androgen receptor). In the present study, we have investigated the mechanism of testosterone-induced vasodilatation using isolated rat coronary arteries and thoracic aortae from control and AR-deficient testicular-feminized mice. Vasodilatation induced by testosterone, T-3-OCMO [testosterone 3-(O-carboxymethyl)oxime] or T-3-OCMO conjugated to BSA was initially measured in preconstricted vessels that had undergone endothelial denudation or incubation with flutamide (10 microM). Cellular fluorescence was also measured in primary aortic SMCs (smooth muscle cells) following exposure to the above fluorescent-labelled agents. Subsequently, vessels were incubated with testosterone (100 microM) or vehicle prior to constriction with KCl (1-100 mM). Testosterone-induced vasodilatation was unaffected by endothelial denudation, flutamide treatment, AR deficiency or conjugation to BSA. Cells exposed to T-3-OCMO-BSA (10 microM) had a higher fluorescence than control cells (32.8+/-4.5 compared with 14.5+/-1.8 arbitrary units respectively; P<0.01). Incubation with testosterone (100 microM) reversibly attenuated coronary vasoconstriction to KCl (1-100 mM; 0.08+/-0.09 compared with 0.79+/-0.08 mN/mm respectively; P<0.0001). Testosterone-induced vasodilatation is independent of the vascular endothelium and nuclear AR, and is initiated at the SMC membrane, which contains testosterone binding sites. A direct calcium antagonistic action is implicated.