Suggest how SCFR is destroyed by a lysosome.

After a heart attack, cardiomyocytes (cardiac muscle cells) die, and become infarcted tissue. Infarcted tissue cannot contract.

Stem cells in bone marrow cannot move to the infarcted tissue and differentiate into cardiomyocytes.

Scientists used laboratory rats to investigate if bone marrow stem cell transplants could be used to repair infarcted tissue resulting from a heart attack.

They split the rats into three groups. • Control group did not get a transplant of bone marrow stem cells. • c-KIT+ group got a transplant of bone marrow stem cells with a functioning c-KIT gene. • c-KIT– group got a transplant of bone marrow stem cells with no functioning c-KIT gene.

After 9 days, the scientists measured the mean ventricular blood pressure of each of the three groups.

Figure 6 shows their results. The differences between the groups were all statistically significant.

Using all of the information, suggest explanations for the results for the Control group and the c-KIT– group shown in Figure 6.

Control

c-KIT–

Nine days after transplantation, the c-KIT+ group showed that 68% of infarcted tissue was made up of new cardiomyocytes. The control group had no new cardiomyocytes.

Assuming that mean ventricular blood pressure is directly proportional to the number of cardiomyocytes, calculate the percentage of infarcted tissue that was made up of new cardiomyocytes in the c-KIT– group.

Answer ______________ %

All new cardiomyocytes produced: • Connexin-43, a channel protein that allows electrical impulses to pass between cardiomyocytes • GATA-4, a transcriptional factor that stimulates the expression of genes for actin and myosin.

Suggest how production of Connexin-43 and GATA-4 could give the result seen in the c-KIT+ group in Figure 6 (on page 13).

Do not include details of transcription or translation in your answer.

Connexin-43

GATA-4