A32-year old African-American male presents with recurrent edema of the feet and periorbital swelling. He has a history of high risk sexual behavior. The blood pressure was 110/85 mm Hg. Results of the laboratory investigations are as follows : HBs Ag : Negative Blood glucose : Normal HIV ELISA : Positive 24-hour urine protein : 3.9 g Urine microscopy : Fatty casts, oval fat bodies. An H and E stain of the renal biopsy is most likely toshow-