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Biomedical subjects

M Shahidullah

Publications and source records attributed to M Shahidullah.

At least 37 records · Page 2Linked to original sources
PubMed1997

Atriopeptin lowers aqueous humor formation and intraocular pressure and elevates ciliary cyclic GMP but lacks uveal vascular effects in the bovine perfused eye.

The effects of atriopeptin (AP) on intraocular pressure (IOP), aqueous humor formation (AHF) and ciliary cyclic GMP in bovine eyes perfused in vitro through a ciliary artery were investigated. AHF was monitored fluorophotometrically by perfusing the anterior chamber with Bárány's mock aqueous humor containing fluorescein. To study the effect of AP on cyclic GMP synthesis, eyes were injected with an intra-arterial bolus of AP prior to dissection of the ciliary processes. For comparison, individual ciliary processes, or isolated ciliary epithelial cells were incubated with AP. Cyclic GMP was extracted by homogenization, aqueous partition and column chromatography, and measured by radioimmunoassay (RIA). Decreases in IOP or AHF were seen approximately 15 min after the injection of AP and persisted throughout a 60-80 min perfusion. Arterial perfusion pressure was not significantly altered by AP, even when vascular tone was raised by adding noradrenaline to the perfusate. In whole eyes, ciliary cyclic GMP increased in response to AP. Cyclic GMP in isolated ciliary processes, or cultured ciliary epithelial cells incubated with AP also increased. We conclude that the decrease in IOP in the bovine eye by AP is due to a reduction in AHF, which is independent of any vascular effect. Ciliary cyclic GMP may be the intracellular mediator involved.

Adrenergic alpha-Agonists↗
PubMed1996

Neurological outcome of severe cystic periventricular leukomalacia.

OBJECTIVE: To determine the neurological outcome of a cohort of premature babies having ultrasound diagnoses of severe cystic periventricular leukomalacia. METHODOLOGY: All neonatal intensive care unit admissions born at less than 35 weeks gestation or weighing less than 1500 g underwent serial cranial ultrasounds. Those developing severe bilateral cystic periventricular leukomalacia (12 patients) were then followed clinically to a mean age of 27.3 months. RESULTS: Ten of the 12 patients fulfilling strict ultrasound criteria survived. All had a major neurological handicap, all having spastic quadriparesis and visual impairments, with most suffering global developmental delay and epilepsy. CONCLUSIONS: Severe bilateral cystic periventricular leukomalacia results in major permanent handicap. It is currently impossible to identify most patients with this condition while they are being ventilated. Non-ultrasound techniques are needed to diagnose the condition earlier, and to give guidance to management.

Developmental Disabilities↗
PubMed1995

Microheterogeneity in heteromultimeric assemblies formed by Shaker (Kv1) and Shaw (Kv3) subfamilies of voltage-gated K+ channels.

Single K+ channels were recorded in Xenopus oocytes injected with a 1:1 mixture of mRNAs coding for NGK1 (Kv1.2) and NGK2 (Kv3.1a) voltage-dependent K+ channels. A new class of channels of 18 pS conductance was observed, and was designated as NGK1,2 channels. According to their properties of activation voltages and open life times, four types of NGK1,2 channels with microheterogeneity were detected. The results suggest that voltage-dependent NGK1 Shaker and NGK2 Shaw K+ channels, from different subfamilies, assemble to form heteromultimeric K+ channels, giving rise to a mosaic of characteristics inherited from two parental channels.

Animals↗
PubMed1995

Slow inactivation conserved in heteromultimeric voltage-dependent K+ channels between Shaker (Kv1) and Shaw (Kv3) subfamilies.

Single K+ channels were recorded under the cell-attached mode in Xenopus oocytes injected with an equal amount of mRNAs coding for NGK1 (Kv1.2) and NGK2 (Kv3.1a) voltage-dependent K+ channels. A new class of channels of 20 pS in conductance with three degrees of inactivation was observed. The results suggest that voltage-dependent NGK1 Shaker and NGK2 Shaw K+ channels, from different subfamilies, assemble to form heteromultimeric K+ channels in Xenopus oocytes and show characteristics inherited from two parental channels.

Animals↗
PubMed1995

An evaluation of population projection errors for census tracts.

"In this article we evaluate the accuracy and bias of projections of total population and population by age group for census tracts in three counties in Florida. We use [U.S. census] data from 1970 and 1980 and several simple extrapolation techniques to produce projections for 1990; we then compare these projections with 1990 census counts and evaluate the differences. For the total sample, we find mean absolute errors of 17%-20% for the three most accurate techniques for projecting total population and find no indication of overall bias. For individual age groups, mean absolute errors range from 20%-29%." This is a revised version of a paper presented at the 1993 Annual Meeting of the Population Association of America.

Age Distribution↗
PubMed1995

A comparison of sisterhood information on causes of maternal death with the registration causes of maternal death in Matlab, Bangladesh.

BACKGROUND: To explore whether causes of maternal death can be investigated using the sisterhood method, an indirect method for providing a community-based estimate of the level of maternal mortality, this study compares the sisterhood causes of maternal death with the Matlab Demographic Surveillance System's (DSS) causes of maternal death. METHODS: Data for this study came from the Matlab DSS, which has been in operation since 1966 as a field site of the International Centre for Diarrhoeal Disease Research, Bangladesh. The maternal deaths that occurred during the 15-year period from 1976 to 1990 in the Matlab DSS area are the basis of this study. A sisterhood survey was conducted in Matlab in November and December 1991 to collect information on conditions, events and symptoms that preceded death. The collected information was evaluated to assign a most likely cause of maternal death. The sisterhood survey cause of maternal death was then compared with the DSS cause of maternal death. RESULTS: Cause of death could not be assigned with reasonable confidence for 34 (11%) of the 305 maternal deaths for which information was collected. For the remaining deaths, the agreement between the two classification systems was generally high for most cause-of-death categories considered. CONCLUSIONS: Though cause-of-death information obtained by the sisterhood method will always be subject to some error, it can provide an indication of an overall distribution of causes of maternal deaths. This data can be used for the planning of programmes aimed at reducing maternal mortality and for the evaluation of such programmes over time.

Abortion, Induced↗
PubMed1995

Effects of timolol, terbutaline and forskolin on IOP, aqueous humour formation and ciliary cyclic AMP levels in the bovine eye.

We have studied the effects of terbutaline, timolol, forskolin and 8-bromo cyclic AMP on aqueous humour formation, intraocular pressure and on ciliary epithelial cyclic AMP levels, either in presence or in absence of IBMX, using the bovine isolated arterially perfused eye, excised ciliary processes and cultured ciliary epithelium. Both terbutaline, a beta-adrenoceptor agonist, and timolol, a beta-adrenoceptor antagonist, caused significant reduction in aqueous humour formation and intraocular pressure but produced no effect on ciliary epithelial cyclic AMP content in the absence of IBMX. Even a three times higher dose of terbutaline was entirely ineffective in producing any effect on ciliary cyclic AMP in the perfused eye. On the other hand, terbutaline at the IOP-reducing dose, produced a significant increase in cyclic AMP when injected after 30 min perfusion with IBMX. Incubation of excised ciliary processes or cultured ciliary epithelial cells with terbutaline (10(-6) to 10(-4) M) produced concentration-dependent increases in cyclic AMP, in both tissues, even in the absence of IBMX. Forskolin, which stimulates cyclic AMP synthesis without interacting with cell surface receptors, was found to produce highly significant increases in ciliary cyclic AMP content both in presence and in absence of IBMX but had no effect on aqueous humour formation in the isolated eye. IBMX perfused at concentrations of 1 mM or 10 microM had no effect on basal levels of ciliary cyclic AMP but the 1 mM concentration produced a marked and significant reduction in IOP. Direct application of 8-bromo cyclic AMP, a cell permeable analogue, more resistant to hydrolysis by phosphodiesterases, had also no effect on aqueous humour formation in the perfused eye. It is concluded that in the bovine arterially perfused eye, the correlation between the aqueous humour formation rate and ciliary epithelial cyclic AMP content is unclear.

1-Methyl-3-isobutylxanthine↗
PubMed1995

Chronic discoid lupus erythematosus: an immunopathological and electron microscopic study.

We studied 100 cases of chronic cutaneous discoid lupus erythematosus (DLE) to evaluate the diagnostic sensitivity of immunoreactant deposition and its possible role in basement membrane thickening. Histopathology was diagnostic in 71% of cases. Sixty-two percent (41/66) of lesions with thickened and 50% (17/34) with normal basement membrane had immunoreactant deposition. Ultrastructural study of 6 cases (3 with and 3 without immunoreactant deposition) with thickened basement membrane all showed reduplication of the lamina densa. Thickening of the basement membrane appears to be contributed mainly by reduplication of the lamina densa rather than by immunoreactant deposition. The direct immunofluorescence (DIF) test of lesional skin was positive in 58% of patients and was independent of duration of lesion, age and sex. Light microscopy has greater diagnostic sensitivity in confirming DLE lesions than DIF. Direct salt split skin technique did not increase DIF sensitivity. Scalp lesions showed the highest frequency (83%) of immunoreactant deposition. As C1q was the commonest immunoreactant found in our study, we suggest that it should be routinely used when DIF is employed in the evaluation of DLE. DIF is especially helpful in confirming cicatricial alopecia due to DLE.

Adolescent↗
PubMed1994

Breast-feeding and child survival in Matlab, Bangladesh.

This study investigates the effect of both total and unsupplemented breast-feeding in conjunction with birth interval on early childhood mortality, using longitudinal data from Matlab, Bangladesh. A discrete hazard model approach shows that it is not the duration of total breast-feeding but the duration of unsupplemented breast-feeding which increases child survival. Unsupplemented breast-feeding appears as such as crucial determinant of early childhood mortality that its effect could not be substantially attenuated even when important demographic and socioeconomic factors were controlled. Each of the covariates--supplementation, previous birth interval and onset of a subsequent conception--has an independent influence on early childhood mortality.

Bangladesh↗
PubMed1994

Isotretinoin therapy in acne vulgaris: a 10-year retrospective study in Singapore.

BACKGROUND: The use of isotretinoin, a first generation synthetic retinoid, in the treatment of patients with severe acne vulgaris was a major therapeutic advance in dermatology. This 10-year retrospective study reviews the effectiveness of isotretinoin in patients with acne vulgaris seen in a skin clinic in Singapore. METHODS: The case records of 250 cases of severe inflammatory and nodulocystic acne treated with isotretinoin were analyzed with reference to the demographic data, response to isotretinoin, dosage and cost of isotretinoin used, adverse effects, clinical follow-up, and relapse. RESULTS: Two hundred and fifty patients, 171 men (68.4%) and 79 women (31.6%), with different types and grades of acne vulgaris were studied. The dose of isotretinoin used ranged from 0.33 to 1.0 mg/kg/day (median 0.5 mg/kg/day) for a period ranging from 1 to 12 months (median 4 months). Response was excellent in 127 (50.8%) patients, good in 86 (34.4%), fair in 30 (12.0%) and poor in 7 (2.8%). Relapse occurred in 14 (5.6%) patients over a 6-month follow-up period. Adverse effects were noted in 140 (56.0%) patients and were mild in most cases. Eighteen (7.2%) patients had to discontinue the drug due to significant side effects. CONCLUSION: This study confirms that isotretinoin is very effective for severe acne, and complete remission can be induced in more than 90% of cases even with lower dosage regimens. Significant clinical improvement can be achieved with the use of lower doses (mean 0.5 mg/kg/day) for an average of 4 months of treatment with lower risk of adverse effects.

Acne Vulgaris↗
PubMed1993

Etretinate therapy for psoriasis and other keratinizing disorders: a 10-year retrospective study in Singapore.

BACKGROUND: Etretinate, a second generation retinoic acid, has been reported to be useful in the treatment of psoriasis and other keratinizing disorders. The effectiveness of etretinate for these disorders are studied in a 10-year retrospective study of all patients treated with etretinate in a skin clinic in Singapore. METHODS: The case records of 190 cases of psoriasis and other keratinizing disorders treated with etretinate were analyzed. Information collected included demographic data, dosage of etretinate taken, response and side effects, clinical follow-up, and relapse. RESULTS: Most of the cases (72.6%) had psoriasis (138/190). The others had different keratinizing disorders. The dose of etretinate used was 0.15 to 1 mg/kg/day (median 0.36 mg/kg/day), and the duration of the treatment varied from 1 to 120 months (median 6 months). Etretinate was coadministered with UVB (ReUVB) or PUVA (RePUVA) in 89 (46.8%) patients. In psoriasis, the response to treatment was excellent in 41.3% (57/138), good in 36.2% (50/138), fair in 15.9% (22/138), and poor in 6.5% (9/138) of the cases. Patients with plaque-type psoriasis did better with combination therapy than with monotherapy. Those with keratinizing disorders showed excellent, good, fair, and poor responses in 32.7% (17/52), 32.7% (17/52), 25.0% (13/52), and 9.6% (5/52) respectively. Adverse effects were noted in 102 (53.7%) cases and were generally mild and tolerable. Etretinate was discontinued in 24 (12.6%) patients due to significant toxicity. CONCLUSIONS: Etretinate is effective for treating psoriasis and other keratinizing disorders. Combination therapy is preferred in chronic plaque psoriasis. Adverse effects are common, but mild and tolerable.

Adolescent↗
PubMed1993

The bovine arterially-perfused eye: an in vitro method for the study of drug mechanisms on IOP, aqueous humour formation and uveal vasculature.

A method is reported in which the isolated bovine eye is perfused through a long posterior ciliary artery with buffered physiological saline, to provide simultaneous monitoring of drug effects on intraocular pressure (IOP), vascular resistance and the condition of the blood-aqueous barrier. With perfusion under constant pressure of 45 mm Hg, perfusate flows at 1.64 +/- 0.12 ml.min-1 (mean +/- SEM) and IOP is 7.26 +/- 0.16 mm Hg. Applying a constant flow rate of 2.25 ml.min-1, IOP averages 10.19 +/- 0.32 mm Hg and in both cases this can be maintained for around 2h. Increasing the perfusion flow rate from 1.5 to 3.5 ml.min-1 produces a 76% rise in perfusion pressure but IOP increases only insignificantly (< 10%). The inclusion in the perfusion fluid of dextran and albumin to maintain oncotic pressure similar to that of plasma makes no difference to the IOP achieved and does not affect the leakiness of the barrier. The preparation shows a net consumption of oxygen, supporting the hypothesis that the aqueous humour formed is secreted by active transport processes. Timolol (in bolus doses of 1-300 nmol) injected into the perfusing fluid is shown to induce a dose-dependent fall in IOP within 5 min, reaching a steady state within 40 min. Timolol, however, causes no significant change in vascular resistance, whether this is measured as perfusion flow rate under constant pressure or as perfusion pressure at constant flow rate, nor does it alter the permeability of the barrier. Other beta-blockers such as oxprenolol and betaxolol also induce dose-dependent decreases in IOP. By applying a fluorescein dilution technique, it is found that the aqueous formation rate (K(out) = 0.0046 min-1, or 12.9 microliters.min-1) is also reduced by timolol and, in a dose-dependent manner, by the new carbonic anhydrase inhibitor, MK-927. The bovine perfused eye offers a useful method for studying the mechanisms of action of drugs on IOP and aqueous humour formation, in isolation from the complicating influences of the CNS and the cardiovascular system and without the necessity to kill animals for experimental purposes.

Adrenergic beta-Antagonists↗
PubMed1992

Ion selectivity of Ba2+ inward current oscillations in ras-transformed fibroblasts that elicit cytoplasmic Ca2+ oscillations by bradykinin.

Ion selectivity of divalent cations on Ba2+ inward current oscillations was examined by voltage-clamp recording in v-Ki-ras-transformed NIH/3T3 (DT) fibroblasts where repetitive transient increases in cytoplasmic Ca2+ concentration were evoked by bradykinin. Application of bradykinin onto DT cells in 50 mM Ba2+ solution initiated Ba2+ inward current oscillations. The inward currents were inhibited in equimolar Sr2+ or Ca2+ solutions. Ba2+ current oscillations were dependent upon extracellular Ba2+ concentration. The results suggest that inward current oscillations are highly selective to Ba2+.

3T3 Cells↗
PubMed1992

Ba2+ current oscillations modulated by cyclic AMP and phorbol esters in ras-transformed fibroblasts.

An oscillatory influx of divalent cations was measured as Ba2+ inward currents (Ba2+ current oscillations) by voltage-clamp recording in v-Ki-ras-transformed NIH/3T3 (DT) fibroblasts after activation with bradykinin or serum. Application of forskolin or dibutyryl cyclic AMP onto DT cells initiated Ba2+ current oscillations. Increasing intracellular cyclic AMP reduced the amplitude but increased the frequency of the Ba2+ current oscillations. Activation of protein kinase C by phorbol esters terminated Ba2+ current oscillations. No inhibition of Ba2+ current oscillations by phorbol esters was observed in down-regulated cells that had been pretreated with phorbol esters for 24 hrs. The results suggest that Ba2+ current oscillations are regulated by intracellular second messengers.

3T3 Cells↗