Sigma DP1 Merrill

Introduction

The Sigma DP1s is a new revised version of the two-year old DP1 large-sensor compact camera. The DP1s features exactly the same APS-C sized Foveon sensor and 28mm f/4 prime lens as its predecessor, but offers two operational enhancements inherited from the Sigma DP2. These are improved performance when shooting backlit subjects and the ability to to allocate the new QS (Quick Set) function to the digital zoom buttons, as featured on the DP2 and SD14 cameras. In all other respects the DP1s is identical to the original DP1, sharing the same 14.06 megapixel Foveon X3 sensor, 2.5 inch LCD screen, full range of creative shooting modes, built-in flash, external hotshoe and RAW format support. The Sigma DP1s is available in black and retails for £549 / $649.

Introduction

The Sigma DP1 Merrill is a compact camera with a large APS-C sized sensor, as used in larger and heavier compact system camera and DSLR models and therefore promising better image quality than other compacts. The DP1 Merrill has the same 46 megapixel Foveon X3 sensor as the flagship SD1 DSLR, a redesigned 19mm fixed lens with a fast aperture of f/2.8, Dual TRUE II image processing engine, 3-inch TFT colour monitor with 920,000 dots, full range of creative shooting modes, manual focus ring, external hotshoe, Quick Set button and RAW format support. The new generation name “Merrill” is a tribute to Foveon’s co-founder, the late Richard B. Merrill, who developed the original Foveon X3 Direct Image Sensor. Retailing for £799 / $999, the Sigma DP1 Merrill compact camera is certainly a serious investment — read our expert review to find out if it’s one worth making.

Functions

A variety of specific physiological functions have been attributed to the σ₁ receptor. Chief among these are modulation of Ca2+ release, modulation of cardiac myocyte contractility, and inhibition of voltage gated K+ channels. The reasons for these effects are not well understood, even though σ₁ receptors have been linked circumstantially to a wide variety of signal transduction pathways. Links between σ₁ receptors and G-proteins have been suggested such as σ₁ receptor antagonists showing GTP-sensitive high-affinity binding; there is also, however, some evidence against a G-protein coupled hypothesis. The σ₁ receptor has been shown to appear in a complex with voltage gated K+ channels (K_v1.4 and K_v1.5), leading to the idea that σ₁ receptors are auxiliary subunits. σ₁ receptors apparently co-localize with IP₃ receptors on the endoplasmic reticulum where they may be involved in preventing endoplasmic reticulum stress in neurodegenerative diseases . Also, σ₁ receptors have been shown to appear in galactoceramide enriched domains at the endoplasmic reticulum of mature oligodendrocytes. The wide scope and effect of ligand binding on σ₁ receptors has led some to believe that σ₁ receptors are intracellular signal transduction amplifiers.

Specification

The DP1s is very similar to the DP1.

Characteristics

The σ₁ receptor is defined by its unique pharmacological profile. In 1976 Martin reported that the effects of N-allylnormetazocine (SKF-10,047) could not be due to activity at the μ and κ receptors (named from the first letter of their selective ligands morphine and ketazocine, respectively) and a new type of opioid receptor was proposed; σ (from the first letter of SKF-10,047). Ligands acting at this new “opioid” receptor were blocked by the classical opioid antagonists naloxone and naltrexone. The opioid classification was eventually dropped however resulting from it not possessing the canonical opioid G-protein coupled receptor structure and the receptor was later referred to as simply the σ₁ receptor. It was found to have affinity for the (+)-stereoisomers of several benzomorphans (e.g., (+)-pentazocine and (+)-cyclazocine), as well as various structurally and pharmacologically distinct psychoactive chemicals such as haloperidol and cocaine, and neuroactive steroids like progesterone.

Introduction

The Sigma DP1 Quattro is a compact camera with a newly developed 39-megapixel APS-C sized Foveon X3 Quattro sensor. The DP1 Quattro’s unique sensor outputs 5424×3616-pixel raw images at the highest resolution setting, and is comprised of four seperate layers, with three dedicated layers for capturing Red, Green and Blue. The DP1 Quattro also features a 19mm fixed lens (28mm equivalent) with a fast aperture of f/2.8, 8 elements in 6 groups and a 9-bladed diaphragm, TRUE III image processing engine, 3-inch TFT colour monitor with 920,000 dots, full range of creative shooting modes, manual focus ring, external hotshoe, Quick Set button and RAW format support. The Sigma DP1 Quattro officially retails for £899 / $999.

Specification

The DP1s is very similar to the DP1.

Ligands

The following ligands have high affinity for the σ₁ receptor and possess high binding selectivity over the subtype σ₂:

Agonists:

• PRE-084
• ANAVEX2-73
• Fluvoxamine
• Citalopram
• Amitriptyline
• L-687,384
• SA-4503
• Dextromethorphan
• Dimethyltryptamine
• (+)-pentazocine (the «unnatural» enantiomer, which lacks affinity for the μ-opioid and κ-opioid receptors.
• Opipramol

Antagonists:

• Sertraline
• S1RA
• FTC-146
• 1-benzyl-6′-methoxy-6′,7′-dihydrospiro[piperidine-4,4′-thieno[3.2-c]pyran]: putative antagonist, selective against 5-HT_1A, 5-HT₆, 5-HT₇, α_1A and α₂ adrenergic, and NMDA receptors
• NE-100

Positive allosteric modulators (PAMs):

• Methylphenylpiracetam[better source needed]
• SOMCL-668

Uncategorized:

• 4-IPBS
• PD 144418
• spipethiane
• RHL-033
• 3—4-piperidyl]methyl]-1,3-benzoxazol-2-one: very high affinity and subtype selectivity
• 1′-spiro[1H-isobenzofuran-3,4′-piperidine]
• 1′-benzyl-6-methoxy-1-phenyl-spiro[6H-furo[3,4-c]pyrazole-4,4′-piperidine]
• (−)-(S)-4-methyl-1-piperidine

Agents exist that have high σ₁ affinity but either lack subtype selectivity or have high affinity at other binding sites, thus being more or less dirty/multifunctional, like haloperidol. Furthermore, there is a wide range of agents with an at least moderate σ₁ involvement in their binding profile.