Development of the optical system is highly dependent on the presence of melanin, and the reduction or absence of this pigment in albinistic individuals may lead to

Human skin colour is primarily due to the presence of melanin in the skin.

Dopaminergic nerve cell bodies in such areas as the substantia nigra tend to be pigmented due to the presence of the black pigment melanin.

This postulated late acquisition of the biosynthesis of lipids as directed by genetically encoded peptides is consistent with the presence of completely different types of membrane lipids in archaea and bacteria ( plus eukaryotes ).

Within the field of microbial ecology, oligonucleotide probes are used in order to determine the presence of microbial species, genera, or microorganisms classified on a more broad level, such as bacteria, archaea, and eukaryotes via fluorescence in situ hybridization ( FISH ).

For example, in the presence of H < sub > 2 </ sub > O < sub > 2 </ sub > formed by the eosinophil, and either chloride or bromide ions, eosinophil peroxidase provides a potent mechanism by which eosinophils kill multicellular parasites ( such as, for example, the nematode worms involved in filariasis ); and also certain bacteria ( such as tuberculosis bacteria ).

In the presence of a chemical gradient bacteria will chemotax, or direct their overall motion based on the gradient.

Commonly, this term is used to refer specifically to infectious diseases, which are clinically evident diseases that result from the presence of pathogenic microbial agents, including viruses, bacteria, fungi, protozoa, multicellular organisms, and aberrant proteins known as prions.

An infection that does not and will not produce clinically evident impairment of normal functioning, such as the presence of the normal bacteria and yeasts in the gut, is not considered a disease ; by contrast, an infection that is asymptomatic during its incubation period, but expected to produce symptoms later, is usually considered a disease.

Interferons ( IFNs ) are proteins made and released by host cells in response to the presence of pathogens such as viruses, bacteria, parasites or tumor cells.

For example, a food sample might be analyzed on three different nutrient mediums designed to indicate the presence of " total " bacteria ( conditions where many, but not all, bacteria grow ), molds ( conditions where the growth of bacteria is prevented by, e. g., antibiotics ) and coliform bacteria ( these indicate a sewage contamination ).

Many bacteria cease production of the enzyme in the presence of oxygen.

The protein content of peroxisomes varies across species, but the presence of proteins common to many species has been used to suggest an endosymbiotic origin ; that is, peroxisomes evolved from bacteria that invaded larger cells as parasites, and very gradually evolved a symbiotic relationship.

In January 2006, researchers from the University of Athens analyzed teeth recovered from a mass grave underneath the city, and confirmed the presence of bacteria responsible for typhoid.

The presence of 20S proteasomes in bacteria may result from lateral gene transfer, while the diversification of subunits among eukaryotes is ascribed to multiple gene duplication events.

Thus, presence of high levels of peptidoglycan is the primary determinant of the characterisation of bacteria as gram-positive.

In 1880, the presence of Rhizobium bacteria in the roots of legumes and their use of catalysts explained the increase of nitrogen in soils so cultivated.

In some arthropods, sex is determined by infection, as when bacteria of the genus Wolbachia alter their sexuality ; some species consist entirely of ZZ individuals, with sex determined by the presence of Wolbachia.

The ability to transform daidzein into S-equol is based on the presence of certain intestinal bacteria.

The medical industry also uses the blood of horseshoe crabs as a test for the presence of contaminant bacteria.

The presence of bacteria in the colon produces an ‘ organ ’ of intense, mainly reductive, metabolic activity, whereas the liver is oxidative.

Tooth decay is caused by certain types of acid-producing bacteria which cause the most damage in the presence of fermentable carbohydrates such as sucrose, fructose, and glucose.

In the presence of oxygen ( aerobic ), some bacteria may directly oxidize iron to iron oxides and hydroxides, other bacteria oxidize sulfur and produce sulfuric acid causing biogenic sulfide corrosion.

According to Gold and the Soviet geologists who originated the abiogenic theory, bacteria feeding on the oil accounts for the presence of biological debris in hydrocarbon fuels, obviating the need to resort to a biogenic theory for the origin of the latter.

The result was many ( up to 34 ) small kingdoms each centered upon their capital, and the governors, not subscribing to any larger-scale vision of the Moorish presence, had no qualms about attacking their neighbouring kingdoms whenever they could gain advantage by doing so.

This split into the taifa states caused Islamic presence to be greatly weakened in the face of the strengthening Christian kingdoms to the north.

The name and also the presence of these Muslim mercenary troops is earlier, in other Iberian kingdoms.

Afonso Henriques knelt in its presence and heard the voice of Christ who told him he would defeat the Moors, which he, through courage and his faith, succeeded the following day Afonso Henriques was declared king of Portugal and he included five shields in his coat of arms, representing the five defeated kingdoms.

Their presence includes Nepal, Kashmir, Punjab, Gurgaon, Kannauj, Magadh, Kashi, Buxar, Bhojpur ( Arah ), present day Bengal and Bangladesh, Rajputana, Malva, Surashtra ( Saurashtra ), Dwarika kingdoms, while spreading up to far West in Europe, primarily occupying present day Pakistan, Afghanistan, Iran, Turkey, Greece, Italy, Rome, France and Germany under different definition and identity.

`` Amen '', said the Reverend Doran, grabbing his rifle propped up against a tombstone, `` and now my brethren, it would seem that our presence is required elsewhere ''.

The presence of genuine mimesis in art is marked by the persistence with which the work demands attention and compels valuation even though it is but vaguely understood.

He had also learned to dispute extempore remarkably well, the main evidence for which of course is the presence of his name in the honors list of 1628/29.

Yet you feel the orchestra is near at hand, and the individual instruments have the same firm presence associated with listening from a good seat in an acoustically perfect hall.

The radius is calculated from the mass by assuming spheres of density Af except for the smallest particles, which must have a higher mass density to remain in the solar system in the presence of solar-radiation pressure.

It is characterized by the presence of incompletely developed secondary lobules ; ;

The possibility that the absence or presence of these shunts is species-dependent is therefore inferred.

In the presence of a low iodine intake, thyroglobulin labelled in vivo with Af is found to contain more mono-iodotyrosine than normal, the amounts of di-iodotyrosine and iodothyronines being correspondingly reduced.

-- Glycerinated muscle, in the presence of the physiological agent ( ATP ) responsible for delivering energy to the mechanochemically active proteins of muscle, has been shown to undergo a contraction which is highly sensitive both to temperature and to solvent composition in mixtures of alcohols and water.

One of the greatest problems associated with automatic leveling is establishing a true level in the presence of high-level acceleration noise.

But his is still a simple life relatively free of the female presence or influence, and he must go far, even though he may go fast, for sophisticated pleasures.

Their presence is not as frightening as the discontent which creates their opportunity.

the presence of other members of similar social and economic level is the sufficient condition.

How explicit such factors have been historically is evident in any chronology of restrictive covenant cases or in a review of NAREB's Code of Ethics Article 34 in the Code, adopted in 1924, states that `` a Realtor should never be instrumental in introducing into a neighborhood a character of property or occupancy, members of any race or nationality or any individuals whose presence will clearly be detrimental to property values in that neighborhood ''.

Now to him who is able to preserve you without sin and to set you before the presence of his glory, without blemish, in gladness, to the only God our Savior, through Jesus Christ our Lord, belong glory and majesty, dominion and authority, before all time, and now, and forever.

There is an extraordinary sense of presence in all of these recordings, apparently obtained at least in part by emphasizing the middle and high frequencies.

While both sexes state that kindness is the most preferable trait in a partner there is some evidence that men place less value on this than women and that women may not be more altruistic in presence of an attractive man.

Love confirms others in their freedom, shuns propaganda and masks, assures others of its presence, and is ultimately confirmed not by mere declarations from others, but by each person's experience and practice from within.

Arraignment is a formal reading of a criminal complaint in the presence of the defendant to inform the defendant of the charges against him or her.

One of the defining characteristics of the order is the presence of phytomelan, a black pigment present in the seed coat, creating a dark crust.

Synapomorphies ( a character that is shared by two or more groups through evolutionary development ) include the presence in the plants of oligosaccharide inulin, a nutrient storage molecule used instead of starch ; and unique stamen morphology.

The effectiveness of the technique is demonstrated to a group of VIPs, who watch as Alex collapses before a walloping bully, and abases himself before a scantily-clad young woman whose presence has aroused his predatory sexual inclinations.