cross-resistance

Examples of cross-resistance in the following topics:

• Protease Inhibitors

  • Mutations in the enzyme active site and other sites, which cause conformational changes, can cause resistance.
  • Quite often one mutation can lead to resistance to many different drugs simultaneously since they all share the same mode of action.
  • This is called cross-resistance.

• Thermosetting vs. Thermoplastic Polymers

  • Another group of polymers, characterized by a high degree of cross-linking, resist deformation and solution once their final morphology is achieved.
  • A natural resinous polymer called lignin has a cross-linked structure similar to bakelite.

• Resistance and Resistivity

  • Resistance and resistivity describe the extent to which an object or material impedes the flow of electric current.
  • In fact, R is inversely proportional to the cylinder's cross-sectional area A.
  • What determines resistivity?
  • A uniform cylinder of length L and cross-sectional area A.
  • The larger its cross-sectional area A, the smaller its resistance.

• Control of Muscle Tension

  • Muscle tension is influenced by the number of cross-bridges that can be formed.
  • In individual muscle fibers, the amount of tension produced depends primarily on the amount of cross-bridges formed, which is influenced by the cross-sectional area of the muscle fiber and the frequency of neural stimulation.
  • Cross-bridges can only form where thick and thin filaments overlap, allowing myosin to bind to actin.
  • If more cross-bridges are formed, more myosin will pull on actin and more tension will be produced.
  • Muscle tone is residual muscle tension that resists passive stretching during the resting phase.

• Be a Serious Listener: Resist Distractions and Listen Actively

  • Resisting distractions and listening actively are two ways to become a more effective listener.
  • To best listen to Troy, Penelope turned off the television and her cell phone, let him speak his mind while noticing his crossed arms and frown, then verified what she'd heard him say by re-stating it and also mentioning that he seemed a little unhappy about the situation.
  • To be serious, effective listeners, people must learn how to resist the distractions that cross their path so they can better focus in on what they are trying to hear.
  • Explain how resisting distractions and listening actively can make you a more effective listener

• Velocity of Blood Flow

  • At its simplest, imaging a perfect rigid tube with no resistance and with a homogenous liquid flowing through perpendicularly, flow can be calculated using the following formula:
  • Where F = flow, v = velocity and a = cross-sectional area.
  • The above example refers to, "a perfect rigid tube with no resistance and with a homogenous liquid flowing through perpendicularly".
  • As resistance increases the difference in pressure which influences velocity decreases which in turn reduces flow.
  • Increases in viscosity, for example by reducing water content, lead to increases in resistance and thus reduction in flow.

• Types of Muscle Contractions: Isotonic and Isometric

  • A muscle fiber generates tension through the action of actin and myosin cross-bridge cycling.
  • A concentric contraction is a type of muscle contraction in which the muscles shorten while generating force, overcoming resistance.
  • Cross bridge cycling occurs shortening the sarcomere, muscle fiber and muscle.
  • An eccentric contraction results in the elongation of a muscle, whilst the muscle is still generating force; in effect resistance is greater than force generated.
  • A yielding contraction occurs when a muscle contraction is opposed by resistance.

• The Allied Drive Toward Berlin

  • In February 1945, Field Marshal Gerd von Rundstedt requested permission to withdraw east behind the Rhine, arguing that further resistance would only delay the inevitable, but was ordered by Hitler to fight where his forces stood.
  • With a large number of men captured, the stubborn German resistance during the Allied campaign to reach the Rhine in February and March 1945 had been costly.
  • The crossing of the Rhine was achieved at four points: One was an opportunity taken by US forces when the Germans failed to blow up the Ludendorff bridge at Remagen, one crossing was a hasty assault, and two crossings were planned.
  • Lieutenant General Omar Bradley and his subordinates quickly exploited the Remagen crossing made on March 7 and expanded the bridgehead into a full scale crossing.
  • Having crossed the Rhine, both Army Groups fanned out into the German hinterland.

• Microscopic Anatomy of Bone

  • The criss-cross appearance of the fibrous matrix is why it is referred to as woven.
  • In cross-section, the fibers of lamellar bone run in opposite directions in alternating layers, much like in plywood, assisting in the bone's ability to resist torsion forces.
  • A cross-section of the head of the femur, showing lamellar bone on the borders and trabecular bone in the center.

• Damage to the Cell Wall

  • In both gram-positive and gram-negative bacteria, the scaffold of the cell wall consists of a cross-linked polymer peptidoglycan.
  • This affects murein hydrolase activity, resistance to antibacterial peptides, and adherence to surfaces.
  • Penicillin acts by binding to transpeptidases and inhibiting the cross-linking of peptidoglycan subunits.
  • Penicillin acts by binding to penicillin binding proteins and inhibiting the cross-linking of peptidoglycan subunits.