The crystal structure of Escherichia coli purine nucleoside phosphorylase: a comparison with the human enzyme reveals a conserved topology

BACKGROUND: Purine nucleoside phosphorylase (PNP) from Escherichia coli is a hexameric enzyme that catalyzes the reversible phosphorolysis of 6-amino and 6-oxopurine (2'-deoxy)ribonucleosides to the free base and (2'-deoxy)ribose-1-phosphate. In contrast, human and bovine PNPs are trimeric and accept only 6-oxopurine nucleosides as substrates. The difference in the specificities of these two enzymes has been utilized in gene therapy treatments in which certain prodrugs are cleaved by E. coli PNP but not the human enzyme. The trimeric and hexameric PNPs show no similarity in amino acid sequence, even though they catalyze the same basic chemical reaction. Structural comparison of the active sites of mammalian and E. coli PNPs would provide an improved basis for the design of potential prodrugs that are specific for E. coli PNP. RESULTS: The crystal structure of E. coli PNP at 2.0 A resolution shows that the overall subunit topology and active-site location within the subunit are similar to those of the subunits from human PNP and E. coli uridine phosphorylase. Nevertheless, even though the overall geometry of the E. coli PNP active site is similar to human PNP, the active-site residues and subunit interactions are strikingly different. In E. coli PNP, the purine- and ribose-binding sites are generally hydrophobic, although a histidine residue from an adjacent subunit probably forms a hydrogen bond with a hydroxyl group of the sugar. The phosphate-binding site probably consists of two main-chain nitrogen atoms and three arginine residues. In addition, the active site in hexameric PNP is much more accessible than in trimeric PNP. CONCLUSIONS: The structures of human and E. coli PNP define two possible classes of nucleoside phosphorylase, and help to explain the differences in specificity and efficiency between trimeric and hexameric PNPs. This structural data may be useful in designing prodrugs that can be activated by E. coli PNP but not the human enzyme.     

Indirect sinus augmentation procedures using one-stage anatomically shaped root-form implants

Sinus augmentation procedures are a standard part of implant dentistry. Indirect sinus augmentation procedures reduce the magnitude of the surgery when sinus lift procedures are necessary. This article describes a variation of the indirect augmentation of maxillary sinuses. The surgery is performed through small diameter surgical access openings. This modified indirect sinus augmentation procedure is combined with the immediate placement of one-stage dental implants that effectively seal the surgical access openings and have an anatomical exit profile for easier restoration.     

Maternal blood, egg and larval thiamin levels correlate with larval survival in landlocked Atlantic salmon

A link was previously established between the Cayuga syndrome, a condition causing 100% mortality in larval landlocked Atlantic salmon, Salmo salar, in several of New York's Finger Lakes, and a maternal diet of alewife, Alosa pseudoharengus, a non-native thiaminase-rich Clupeid fish. We evaluated salmon larvae viability relative to maternal thiamin status, and investigated the putative link of the Cayuga syndrome to an alewife diet in fish from the geographic regions outside the Finger Lakes/lower Great Lakes watersheds. We identified Cayuga syndrome in Atlantic salmon from Otsego Lake in the Susquehanna River watershed and from Green Pond in New York's Adirondack Mountains. In both systems alewife represent the major component of the diet for the salmon. Thiamin levels in the maternal blood of Otsego salmon with syndrome-negative progeny were three- to four-fold greater than those Otsego females whose progeny exhibited 100% mortality. Thiamin levels in eggs and larvae were directly related to thiamin levels in maternal blood in both syndrome-positive and syndrome-negative stocks. Thiamin bath treatments of syndrome-afflicted larvae eliminated mortality regardless of their lake stock of origin. Maternal blood levels of approximately 0.31 nmol thiamin pyrophosphate/g or 0.44 nmol total thiamin/g appear necessary to achieve egg threshold levels of approximately 0.8 and 1.1 nmol/g unphosphorylated and total thiamin, respectively; these egg thiamin levels should prevent significant syndrome-related mortality in landlocked Atlantic salmon larvae. These results confirm the role of thiamin in the etiology of the Cayuga syndrome and support the dietary link of this naturally occurring thiamin deficiency to the thiaminase-rich alewife.     

Darier''s disease: severe eczematization successfully treated with cyclosporin

A novel calcitonin (CT) was isolated from the spotlined sardine, Sardinops melanostictus. The primary structure of sardine CT was determined as follows: H-Cys-Ser-Asn-Leu-Ser-Thr- Cys-Ala-Leu-Gly-Lys-Leu-Ser-Gln-Glu-Leu-His-Lys-Leu-Gln-Ser-Tyr-Pro-Arg- Thr- Asn-Val-Gly-Ala-Gly-Thr-Pro-NH2. This amino acid sequence was different from that of salmon CT in 4 amino acid residues at positions 8th, 21th, 27th and 29th. As judged by the international method of CT bioassay, hypocalcemic activity of sardine CT was calculated as 4156 IU/mg. When compared for durability of CTs, it was found that sardine CT was significantly more potent than that of salmon CT. This is the first report of CT from a marine species of teleost.     

Nephrectomy: changing indications, 1960-1990

OBJECTIVE: To review the indications for nephrectomy over the period 1960-1990. PATIENTS AND METHODS: A total of 1470 nephrectomies were performed (excluding transplant-related nephrectomies) over this period. Data were collected by means of a pathology report review and the indications were classified according to aetiology. RESULTS: The total number of nephrectomies performed has not significantly changed over this 31-year period. There was a significant decrease in the number of partial nephrectomies performed and an increase in the number of nephrectomies performed for tumour. This change was equally distributed between both renal adenocarcinomas and transitional cell tumours. The number of nephrectomies for chronic pyelonephritis decreased over this period. The change seen was not as great as might have been anticipated in view of the advent of modern antibiotics. Nephrectomies performed for tuberculosis decreased, although this change was not established until the 1980s. In the 1960s and early 1970s, most tuberculous nephrectomies were performed in patients from the native community. By the 1980s, most patients in this category were from the ethnic Asian immigrant community. Nephrectomy rates for polycystic kidney and trauma remained unchanged. CONCLUSIONS: Despite changes in the investigation and management of renal tract pathologies, which contributed to a change in the indications for nephrectomy, the overall number of nephrectomies performed has remained constant over a 31-year period.     

Cerebellar corticonuclear fibers of the paramedian lobule of tree shrew (Tupaia glis) with comments on zones

Following a series of lesions in dorsal (DPML) and ventral (VPML) divisions of tree shrew (Tupaia) paramedian lobule (PML), the distribution of degenerated axons within the deep cerebellar nuclei was determined using the Fink and Heimer ('67) method. Damage to PML produced axonal degeneration in lateral (NL), anterior interposed (NIA), and posterior interposed (NIP) cerebellar nuclei. No degenerated fibers could be traced to either the medial cerebellar nucleus or vestibular complex, via juxtarestiform body, from lesions in PML. Corticonuclear fibers to NL, NIA, and NIP from PML cortex are topographically organized. Subsequent to lesions of lateral DPML, axonal debris is found in rostral and medial NL, while the lateral edge of VPML projects primarily into medial NL. According to the terminology of Voogd ('69) these lateral regions of PML represent the D zone. The NIP receives corticonuclear input from a relatively wide middle area of both portions of PML, interpreted as the C2 zone. There is some evidence which suggests that medial portions of the C2 area of DPML project into more lateral areas of NIP, while lateral regions of this zone in DPML are related to more medial NIP. This projection pattern is invited for the C2 area of VPML; medial C2 to medial NIP, lateral C2 to lateral NIP. Corticonuclear fibers of PML which enter NIA appear to arise from a narrow, irregular, partially discontinuous strip of cortex located at the interface of the D and C2 areas in lateral PML and from a wider, more regular region in the most medial areas of this lobule. These represent, respectively, the C3 and C1 zones. Although an overall pattern of zones is present, there is evidence to suggest that their spatial organization differs from DPML to VPML. The zonal patterns appears to be more obvious in VPML, while this pattern for DPML is less distinct. This is interpreted as indicating that either (1) zones C1--C3 overlap to a greater degree in DPML than in VPML, or (2) zones C1 and C3 may converge in rostral DPML, partially obliterating the intervening zone C2. The different ways in which zonal terminology is applied to both corticonuclear and certain of the afferent cerebellar systems are discussed.     

Accudosetm aerosol--an effective house fly (Diptera; Muscidae: Musca domestica L.) adulticide control system for cage type poultry houses

An automatic piped aerosol system (Accudose TM) using 0.7% synergized pyrethrin insecticide, was tested at a typical narrow cage poultry farm for the control of adult house flies, Musca domestica L. A similar narrow cage poultry farm was used as a control with all house fly control measures left up to the cooperating poultryman. AccudoseTM was compared with other house fly control methods at other similar farms which included three types of man-portable ultra volume (ULV) generators and an integrated (biological-chemical) program. Results of the five month test demonstrated that the AccudoseTM system suppressed house fly populations better than other control methods.