Strategi Pengembangan Ekspor Kopi Arabika (Coffea Arabica) Sumatera Utara (Studi Kasus: Kota Medan)

Kopi merupakan salah satu komoditi unggulan perkebunan nasional yang memegang peranan cukup penting dalam perekonomian Indonesia. Spesies kopi yang penting secara ekonomi adalah Kopi Arabika (Coffea arabica). Negara pengimpor Kopi Arabika Sumatera Utara terbesar adalah Amerika Serikat. Volume ekspor kopi ke beberapa negara menurun dari tahun 2010-2011, termasuk Amerika Serikat. Penelitian ini bertujuan untuk menganalisis strategi pengembangan ekspor Kopi Arabika Sumatera Utara. Metode penentuan sampel dilakukan secara purposive. Metode analisis data menggunakan analisis deskriptif yaitu matriks SWOT. Hasil penelitian menunjukkan bahwa: (1) Kekuatan (fisik dan mutu, potensi eksportir, dan waktu pengiriman), kelemahan (modal dan promosi), peluang (konsumen tetap, adanya surat izin, dan tarif ekspor), dan ancaman (permintaan, pesaing, peranan pemerintah, dan harga). (2) Strategi pengembangan ekspor Kopi Arabika Sumatera Utara adalah mempertahankan konsumen tetap dengan memperoleh fisik dan mutu kopi yang baik, memanfaatkan surat izin yang ada dan free trade untuk memudahkan eksportir menjangkau negara importir, meningkatkan modal dengan mengoptimalkan permintaan dari konsumen tetap dan adanya free trade, meningkatkan kuantitas Kopi Arabika dengan mutu yang baik untuk meningkatkan permintaan dan harga jual, menjalin kerjasama dengan negara pesaing untuk meningkatkan permintaan dengan mengandalkan kondisi fisik dan mutu kopi yang baik, dan meningkatkan peranan pemerintah dan permintaan dalam mendukung pelaksanaan promosi dan akses bantuan permodalan

Faktor-faktor yang Mempengaruhi Luas Lahan Sawah di Kabupaten Serdang Bedagai

Tujuan penelitian ini adalah untuk menganalisis besarnya pengaruh Produktivitas Padi, Harga Padi dan Harga Kelapa Sawit terhadap luas lahan sawah di Kabupaten Serdang Bedagai. Data yang digunakan dalam penelitian ini adalah data time series data tahun 2008-2014 (7 tahun). Metode analisis yang digunakan adalah Metode Regresi Linear Berganda. Hasil penelitian ini menunjukan bahwa Variabel produktivitas Padi dan harga padi berpengaruh positif dan signifikan terhadap faktor-faktor yang mempengaruhi luas lahan sedangkan harga kelapa sawit berpengaruh negatif dan tidak berpengaruh signifikan terhadap faktor-faktor yang mempengaruhi luas lahan sawah

PSEN1 Mutant iPSC-Derived Model Reveals Severe Astrocyte Pathology in Alzheimer's Disease

Alzheimer's disease (AD) is a common neurodegenerative disorder and the leading cause of cognitive impairment. Due to insufficient understanding of the disease mechanisms, there are no efficient therapies for AD. Most studies have focused on neuronal cells, but astrocytes have also been suggested to contribute to AD pathology. We describe here the generation of functional astrocytes from induced pluripotent stem cells (iPSCs) derived from AD patients with PSEN1 Delta E9 mutation, as well as healthy and gene-corrected isogenic controls. AD astrocytes manifest hallmarks of disease pathology, including increased beta-amyloid production, altered cytokine release, and dysregulated Ca2+ homeostasis. Furthermore, due to altered metabolism, AD astrocytes show increased oxidative stress and reduced lactate secretion, as well as compromised neuronal supportive function, as evidenced by altering Ca2+ transients in healthy neurons. Our results reveal an important role for astrocytes in AD pathology and highlight the strength of iPSC-derived models for brain diseases

Rate-dependent Ca2+ signalling underlying the force-frequency response in rat ventricular myocytes: A coupled electromechanical modeling study

Rate-dependent effects on the Ca2+ sub-system in a rat ventricular myocyte are investigated. Here, we employ a deterministic mathematical model describing various Ca2+ signalling pathways under voltage clamp (VC) conditions, to better understand the important role of calmodulin (CaM) in modulating the key control variables Ca2+/calmodulin-dependent protein kinase-II (CaMKII), calcineurin (CaN), and cyclic adenosine monophosphate (cAMP) as they affect various intracellular targets. In particular, we study the frequency dependence of the peak force generated by the myofilaments, the force-frequency response (FFR). Our cell model incorporates frequency-dependent CaM-mediated spatially heterogenous interaction of CaMKII and CaN with their principal targets (dihydropyridine (DHPR) and ryanodine (RyR) receptors and the SERCA pump). It also accounts for the rate-dependent effects of phospholamban (PLB) on the SERCA pump; the rate-dependent role of cAMP in up-regulation of the L-type Ca2+ channel (ICa;L); and the enhancement in SERCA pump activity via phosphorylation of PLB.Our model reproduces positive peak FFR observed in rat ventricular myocytes during voltage-clamp studies both in the presence/absence of cAMP mediated -adrenergic stimulation. This study provides quantitative insight into the rate-dependence of Ca2+-induced Ca2+-release (CICR) by investigating the frequency-dependence of the trigger current (ICa;L) and RyR-release. It also highlights the relative role of the sodium-calcium exchanger (NCX) and the SERCA pump at higher frequencies, as well as the rate-dependence of sarcoplasmic reticulum (SR) Ca2+ content. A rigorous Ca2+ balance imposed on our investigation of these Ca2+ signalling pathways clarifies their individual roles. Here, we present a coupled electromechanical study emphasizing the rate-dependence of isometric force developed and also investigate the temperature-dependence of FFR. Our model provides mechanistic biophysically based explanations for the rate-dependence of CICR, generating useful and testable hypotheses. Although rat ventricular myocytes exhibit a positive peak FFR in the presence/absence of beta-adrenergic stimulation, they show a characteristic increase in the positive slope in FFR due to the presence of Norepinephrine or Isoproterenol. Our study identifies cAMP-mediated stimulation, and rate-dependent CaMKII-mediated up-regulation of ICa;L as the key mechanisms underlying the aforementioned positive FFR

Impact of Sarcoplasmic Reticulum Calcium Release on Calcium Dynamics and Action Potential Morphology in Human Atrial Myocytes: A Computational Study

Electrophysiological studies of the human heart face the fundamental challenge that experimental data can be acquired only from patients with underlying heart disease. Regarding human atria, there exist sizable gaps in the understanding of the functional role of cellular Ca2+ dynamics, which differ crucially from that of ventricular cells, in the modulation of excitation-contraction coupling. Accordingly, the objective of this study was to develop a mathematical model of the human atrial myocyte that, in addition to the sarcolemmal (SL) ion currents, accounts for the heterogeneity of intracellular Ca2+ dynamics emerging from a structurally detailed sarcoplasmic reticulum (SR). Based on the simulation results, our model convincingly reproduces the principal characteristics of Ca2+ dynamics: 1) the biphasic increment during the upstroke of the Ca2+ transient resulting from the delay between the peripheral and central SR Ca2+ release, and 2) the relative contribution of SL Ca2+ current and SR Ca2+ release to the Ca2+ transient. In line with experimental findings, the model also replicates the strong impact of intracellular Ca2+ dynamics on the shape of the action potential. The simulation results suggest that the peripheral SR Ca2+ release sites define the interface between Ca2+ and AP, whereas the central release sites are important for the fire-diffuse-fire propagation of Ca2+ diffusion. Furthermore, our analysis predicts that the modulation of the action potential duration due to increasing heart rate is largely mediated by changes in the intracellular Na+ concentration. Finally, the results indicate that the SR Ca2+ release is a strong modulator of AP duration and, consequently, myocyte refractoriness/excitability. We conclude that the developed model is robust and reproduces many fundamental aspects of the tight coupling between SL ion currents and intracellular Ca2+ signaling. Thus, the model provides a useful framework for future studies of excitation-contraction coupling in human atrial myocytes