Higher panamax freight rates have boosted sentiment in the market amid hopes for further rates increases during the week, shipbrokers said on Monday. They gave as prime example the latest U.S. Gulf to Japan fixture at a rate of $23.25 per ton of heavy grain for mid-July loading dates, this compared with the present Baltic Panamax Index showing an average $22.86 per ton. Firmer fixtures had been also reported for both the Pacific and the Atlantic, brokers said. An undisclosed panamax had been chartered to load 55,000 tons of heavy grains from the River Plate and deliver it to China at a rate of $25.75 per ton, brokers said. Shipbrokers also mentioned the timecharter of the 1999-built 75…