Sugar Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Sugar and links to relevant pages within the course.
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| The Presence of Glucose in the Urine The presence of significant amounts of glucose in the urine is called glycosuria (or glucosuria). The amount of glucose present in urine is dependent upon the blood glucose level, the rate of glomerular filtration, and the degree of tubular reabsorption of the sugar. Usually glucose will not be present in the urine until the blood level exceeds 160-189 mg/dl, which is the normal renal threshold for glucose. The main reason for glycosuria is an elevated blood glucose level, called hyperglycemia. Diabetes mellitus is the most common disease that causes hyperglycemia. However, stress, obesity, brain injury, myocardial infarction, hyperthyroidism, pregnancy, and a lowered renal threshold due to kidney damage can all cause glycosuria. | View Page |
| Other Reducing Substances Although glucose is the sugar most commonly tested for in urine, normal human urine can contain small amounts of galactose, lactose, fructose, xylose, and other pentoses. Galactosuria, an abnormal amount of galactose in the urine, occurs in infants with a congenital metabolic defect. Lactose may be found in the urine of nursing women and during late pregnancy. All of these sugars, including glucose, are reducing substances. | View Page |
| Specimen Processing for Urine Sugar Testing Prompt testing (within one hour of collection of the urine sample) or refrigeration of the specimen is necessary because the glycolytic enzymes from the cells and bacteria, if present, will decrease the sugar in the urine. | View Page |
| The Clinitest® Method The Clinitest® method can detect reducing substances in the urine up to 2 g/dL. When the amount of sugar is over 2 g/dL (often expressed as 2%), a “pass through” phenomenon occurs. Pass through appears as rapid color changes through green, tan, and orange, and then a reversion in color back to the brownish color. This reversion in color indicates levels of reducing substances greater than 2 g/dL. Even a fleeting orange color should be recorded as “greater than or equal to 2 g/dL.” It is vital that you watch the boiling and color changes throughout the entire reaction so that a "pass through" is not missed. | View Page |
| Alternate Tests for Sugars There are two basic types of tests that are used to screen or monitor glycosuria -- copper reduction tests and enzyme tests. Most enzyme tests use the enzyme glucose oxidase impregnated on a dipstick along with a chromagen, and are specific for detecting only glucose. The copper reduction tests, however, detect any reducing substance. Clinitest® uses the classic Benedict’s copper reduction reaction. Any reducing substances present in the urine will react with the copper sulfate reagent, and the blue cupric sulfate is subsequently reduced to cuprous oxide. The resultant color change from blue through green to orange is proportional to the amount of reducing substance in the urine sample. | View Page |
| A negative sugar result on a reagent stick and a positive Clinitest® result on the same specimen indicates: | View Page |
| Correlation of Urine Glucose and Ketones It is important to test for urinary (and plasma or serum) ketones when any patient shows a greater than normal excretion of sugar or reducing substances. Screening for ketonuria is useful in following the effects of treatment for diabetes and in judging the severity of acidosis. Large amounts of ketones will appear in the urine before serum ketone levels are elevated. | View Page |
| Shown in the photograph are three tubes-(1) motility agar (note subsurface flare--see arrows); (2) esculin hydrolysis (+), and (3) VP (+). The reactions illustrated here are sufficient to rule out Erysipelothrix rhusiopathiae. | View Page |
| Galactose and ABO Antigen Precursor Substance Specific sugars, attached to the red cell membrane in unvarying linkage conformations, determine ABO antigenic activity. Galactose resides at the end of this specific sugar chain. This configuration constitutes the ABO antigen precursor substance. | View Page |
| Fucose Another sugar, fucose, must be attached to the galactose in a specific configuration for further antigen development to take place. This “galactose-plus-fucose” configuration has antigenic activity called “H”. | View Page |
| "A" Antigenic Activity Without H substance (also known as H antigen or substance H), there is no way for additional sugar attachment to take place. Additional sugar attachment is necessary for the development of A and B antigenic activity. Therefore, without substance H there can be no A and B antigens developed. Once substance H is developed, the addition of the sugar N-acetylgalactosamine to the terminal position of the chain gives the molecule “A” antigenic activity. | View Page |
| The Bombay Blood Group Homozygous “hh” individuals do not form H substance and thus have no way for late sugars to attach. The blood group resulting from the homozygous “hh” condition is called the Bombay blood group (Bombay phenotype). Due to the presence of anti-H in the serum of a person with the Bombay phenotype, only blood from another person with the Bombay phenotype may be transfused. | View Page |
| Which specific terminal sugar causes a red cell to have A antigenic activity? | View Page |
| Which specific terminal sugar causes a red cell to have B antigenic activity? | View Page |
| What specific sugar configuration is necessary as a base for attachment of other sugars? | View Page |
| Which statement describes an Adverse Event? | View Page |
| Oral candidiasis may be directly exasperated by the habitual ingestion of: | View Page |
| Basic metabolic panel (BMP) Consists of an electrolyte panel, plus:
Blood urea nitrogen (BUN), which a measure of renal function.
Creatinine (Creat), which also measures renal function
Glucose, the most important blood sugar, and
Calcium.
Run on serum or plasma
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| Plasma components Plasma is the liquid portion of the blood. It contains many substances including:Water
Electrolytes
Sugars
Proteins
Lipids
Drugs & Toxins
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| Plasma sugars Sugars are also dissolved in the plasma. By far the most important is glucose.
Blood glucose is increased in diabetes mellitus, and decreased in hypoglycemia.
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| Fructose Fructose makes up 99% of the reducing sugar present in semen. This sugar is produced in the seminal vesicles and its absence may indicate an obstruction proximal to these glands.
Although a fructose test is NOT part of a routine semen analysis, the clinician may want to measure this in cases of azoospermia. In azoospermia secondary to obstruction of the ejaculatory ducts or absence of the vas deferens, fructose is usually absent. When azoospermia is caused by failure of the testes to produce sperm, fructose is present. Measuring fructose levels can thus help the clinician determine the cause of azoospermia, although measurement of pH is often more useful in this regard.
The procedure for determining the amount of fructose in semen involves heating semen in a strong acid in the presence of resorcinol. Fructose gives a red color to this solution when present. | View Page |
| Specimen #5 - Female Child The results of the Clinitest are abnormal, but can be reported. Because this specimen was from a child, the Clinitest was performed routinely even though not indicated by the results of the Multistix. Due to the fact that the Multistix is specific for glucose and was negative, therefore a nonglucose reducing substance is present. Further confirmatory testing such as thin-layered chromatography is needed for identification of the non-glucose reducing sugar. | View Page |