Encapsidation defectiveness of herpes simplex virus type 2 during replication at acid pH condition.

The maximal yield of herpes simplex virus type 2 (HSV-2) grown at pH 6.5 decreased 10(2)-10(3) fold compared to that recovered at pH 7.5. Electron microscopic observation of the infected cells maintained at these 2 pH conditions indicated that approximately equal amounts of immature virions were synthesized 6 hours after infection. However, at 18 hours post infection the majority of viruses present in the nucleus of infected cells maintained at pH 6.5 were empty or partially cored capsids with some particles enveloped and present in the cytoplasm, whereas at pH 7.5 mature virions already appeared at the cytoplasmic membrane. Analysis of viral polypeptides by radioimmunoprecipitation indicated that the synthesis of p40, a family of polypeptides closely involved in viral DNA encapsidation, was significantly impaired in infected cells maintained at pH 6.5.

Morphological variation in pathogenic strains of Penicillium marneffei.

Penicillium marneffei is a dimorphic fungus known to be pathogenic to animals and man. The natural reservoir of this organism was known to be bamboo rats found in South Vietnam, Thailand and China. The first two human infections were reported in 1959 and 1973 from the United States. Up to 1984, five new cases of human penicillosis were reported from Thailand. Since then several more cases have been reported from different parts of the world mainly from the southern part of China. However, there are very limited mycological descriptions of this fungi. In this report, five Thai strains were studied for colonial morphology in comparison with Reference strain PLM 689. Variation in mycelial pigment was observed ranging from yellowish-green to orange with water soluble red pigment produced in every strain which can be seen early from the reverse side. Ultrastructural study by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) was compared with that of the reference strain PLM 689. PLM 689 strain had only biverticillate penicilli, but all five strains from Thailand had both monoverticillate and biverticillate penicilli which occasionally appeared on the same branch. The conidia of the Thai isolates were oval in shape and 1.3-2 x 0.7-1.6 microns in size smaller than those of PLM 689 which were 2.5-4 x 2-3 microns. Phialides were also smaller and a little shorter but the number of phialides was similar to those of PLM 689 ranging 4-10 except for one strain which had 3-16 phialides. All Thai strains have stipes smaller and somewhat longer than those of PLM 689.(ABSTRACT TRUNCATED AT 250 WORDS)

Microscopic examination of Cryptosporidium oocysts in diarrhoeal stools.

Unconventional microscopic means for investigation of Cryptosporidium oocysts in patients' stools were explored in an attempt to obtain a more accurate diagnosis. The results showed that Nomarski interference contrast microscope provided clearer structures of oocysts in wet mount preparations than those under a normal light microscope and readily allowed distinction from yeast cells. Transmission electron microscopic study revealed that oocysts are thick walled and well sporulated. Their "untypical" appearance as seen by the light microscope resulted from sporozoites or the residuum that can be unfamiliar to some examiners. Electron microscopy provides definitive identification of Cryptosporidium spp. but Nomarski interference contrast microscopy was superior to bright field microscopy and may facilitate rapid diagnosis in routine fecal examination. The Ziehl-Neelsen modified acid fast technique was of value for differentiation and confirmation.