Brain metastases as primary manifestation of a melanocytic malignant peripheral nerve sheath tumor in a 60-year-old man

Background  

Malignant peripheral nerve sheath tumors are rare tumor entities that originate from peripheral nerve sheaths and have an unfavorable prognosis. Metastatic spread to the cerebral parenchyma is absolutely rare. This case report describes the clinical course in a 60-year-old man whose tumor came to medical attention because of a seizure.     

Luminal adenosine stimulates chloride secretion through A1 receptor in mouse jejunum

Adenosine is known to stimulate chloride secretion by mouse jejunum. Whereas the receptor on the basolateral side is believed to be A2B, the receptor involved in the luminal effect of adenosine has not been identified. We found that jejuna expressed mRNA for all adenosine receptor subtypes. In this study, we investigated the stimulation of chloride secretion by adenosine in jejuna derived from mice lacking the adenosine receptors of A1 (A1R) and A2A (A(2A)R) or control littermates. The jejunal epithelium was mounted in a Ussing chamber, and a new method on the basis of impedance analysis was used to calculate the short-circuit current (I(sc)) values. Chloride secretion was assessed by the I(sc) after inhibition of the sodium-glucose cotransporter by adding phloridzin to the apical bathing solution. The effect of apical adenosine on chloride secretion was lost in jejuna from mice lacking the A1R. There was no difference in the response to basolaterally applied adenosine or to apical forskolin. Furthermore, in jejuna from control mice, the effect of apical adenosine was also abolished in the presence of 8-cyclopentyl-1,3-dipropylxanthine, a specific A1R antagonist. Responses to adenosine were identical in jejuna from control and A(2A)R knockout mice. This study demonstrates that A1R (and not A(2A)R) mediates the enhancement of chloride secretion induced by luminal adenosine in mice jejunum.     

A case of freemartin with atresia recti and ani in Japanese Black calf

A female Japanese Black calf was born on 25 March 2003 at Hiroshima University Farm as a co-twin to a male Japanese Black calf. The male calf showed no external urogenital abnormalities. The absence of anal opening and external features of freemartinism were observed in the female. A small opening to the vulva (about 1.5 cm in length) with fused lips and a prominent clitoris were seen. The hair around the vulva was 3.5 cm in length and was heavy and dense. The distance from the vulva to the atretic anus was 9.0 cm. There were no other detectable abnormalities on physical examination. The PCR-based DNA test showed male-specific sequences confirming the calf to be freemartin. At autopsy 1 day after the calf birth, the gonads were found to be small and hard and the left uterine horn showed segmental aplasia near its proximal end. Two seminal glands (remnants of mesonephric duct) were located on both sides of the uterine body. A cervix was absent. The vagina was underdeveloped and looked like a tubual structure. The rectal end was closed, while the distance from the end of the atretic rectum to the absent anal opening was about 4.0 cm. On histological examination, the gonads exhibited extensive morphologic alteration; there was no cortex with the absence of ovarian structures. The seminal glands consisted of hypoplastic glandular tissue surrounded by extensive fibrous connective tissue. In conclusion, this is a case report of a freemartin with atresia recti and ani.     

Deficiency of uridine monophosphate synthase (DUMPS) and X-chromosome deletion in fetal mummification in cattle

Ten mummified fetuses were tested for the deficiency of uridine monophosphate synthase (DUMPS), which is known to contribute to the embryonic and fetal mortality in cattle. Genomic DNAs of the mummified fetuses were extracted from tissue samples collected from the mummies and were amplified by GenomiPhi DNA amplification kit. UMPS gene of the mummies was amplified by polymerase chain reaction (PCR) with DUMPS primers. Out of ten mummies examined, two fetuses were heterozygous (carriers) for DUMPS as indicated by the presences of three bands of 89, 53 and 36 bp. Estimated stage of gestation when the death occurred in the two mummies was 3.5 and 2.5 months, respectively. The other fetuses exhibited only two bands of 53 and 36 bp on the polyacrylamide gel indicated that they were normal. On the other hand, all the mummies were sexed using AMX/Y primers. Specific regions of Y and X chromosomes were amplified by PCR using AMX/Y. The expected 280 bp fragment in the female sample and the 280 and 217 bp in the male sample were observed. Nine mummies had a normal X and Y chromosome bands; however, the other mummified fetus exhibited only Y chromosome band, while the constitutive X chromosome fragment was missing. The estimated stage of gestation when the death occurred in this mummified fetus was 100 days. This might be the first report of DUMPS and X-chromosome deletion at the amelogenin gene in bovine-mummified fetuses in Japan.     

Remote mutations and active site dynamics correlate with catalytic properties of purine nucleoside phosphorylase

It has been found that with mutation of two surface residues (Lys²² → Glu and His¹⁰⁴ → Arg) in human purine nucleoside phosphorylase (hPNP), there is an enhancement of catalytic activity in the chemical step. This is true although the mutations are quite remote from the active site, and there are no significant changes in crystallographic structure between the wild-type and mutant active sites. We propose that dynamic coupling from the remote residues to the catalytic site may play a role in catalysis, and it is this alteration in dynamics that causes an increase in the chemical step rate. Computational results indicate that the mutant exhibits stronger coupling between promotion of vibrations and the reaction coordinate than that found in native hPNP. Power spectra comparing native and mutant proteins show a correlation between the vibrations of Immucillin-G (ImmG):O5′…ImmG:N4′ and H257:Nδ…ImmG:O5′ consistent with a coupling of these motions. These modes are linked to the protein promoting vibrations. Stronger coupling of motions to the reaction coordinate increases the probability of reaching the transition state and thus lowers the activation free energy. This motion has been shown to contribute to catalysis. Coincident with the approach to the transition state, the sum of the distances of ImmG:O4′…ImmG:O5′…H257:Nδ became smaller, stabilizing the oxacarbenium ion formed at the transition state. Combined results from crystallography, mutational analysis, chemical kinetics, and computational analysis are consistent with dynamic compression playing a significant role in forming the transition state. Stronger coupling of these pairs is observed in the catalytically enhanced mutant enzyme. That motion and catalysis are enhanced by mutations remote from the catalytic site implicates dynamic coupling through the protein architecture as a component of catalysis in hPNP.     

Second-sphere amino acids contribute to transition-state structure in bovine purine nucleoside phosphorylase

Transition-state structures of human and bovine of purine nucleoside phosphorylases differ, despite 87% homologous amino acid sequences. Human PNP (HsPNP) has a fully dissociated transition state, while that for bovine PNP (BtPNP) has early SN1 character. Crystal structures and sequence alignment indicate that the active sites of these enzymes are the same within crystallographic analysis, but residues in the second-sphere from the active sites differ significantly. Residues in BtPNP have been mutated toward HsPNP, resulting in double (Asn123Lys; Arg210Gln) and triple mutant PNPs (Val39Thr; Asn123Lys; Arg210Gln). Steady-state kinetic studies indicated unchanged catalytic activity, while pre-steady-state studies indicate that the chemical step is slower in the triple mutant. The mutant enzymes have higher affinity for inhibitors that are mimics of a late dissociative transition state. Kinetic isotope effects (KIEs) and computational chemistry were used to identify the transition-state structure of the triple mutant. Intrinsic KIEs from [1'-3H], [1'-14C], [2'-3H], [5'-3H], and [9-15N] inosines were 1.221, 1.035, 1.073, 1.062 and 1.025, respectively. The primary intrinsic [1'-14C] and [9-15N] KIEs indicate a highly dissociative SN1 transition state with low bond order to the leaving group, a transition state different from the native enzyme. The [1'-14C] KIE suggests significant nucleophilic participation at the transition state. The transition-state structure of triple mutant PNP is altered as a consequence of the amino acids in the second sphere from the catalytic site. These residues are implicated in linking the dynamic motion of the protein to formation of the transition state.     

The crustacean ichnofossil Palaxius associated with callianassid body fossils in an Eocene methane-seep limestone, Humptulips Formation, Olympic Peninsula, Washington

Crustacean microcoprolites are preserved along with crustacean megafossils in an Eocene limestone within the Humptulips Formation in Grays Harbor County, Washington. The limestone formed at a methane seep, as revealed by early diagenetic carbonate phases resembling those of other seep limestones, δ¹³C_carbonate values as low as −27‰, and lipid biomarkers of prokaryotes involved in anaerobic oxidation of methane with δ¹³C values as low as −110‰. Recognizable crustacean megafossils are chiefly isolated chelipeds, akin to those of callianassid shrimp. The microcoprolites are pierced by ten longitudinal canals with crescent-shaped outlines in cross-section, arranged in two symmetrical groups. The symmetry plan and number of canals of the microcoprolites identify the Humptulips ichnospecies as Palaxius habanensis Brönnimann & Norton. The occurrence of decapod fossils along with microcoprolites suggests that callianassid shrimp were the producers of the Palaxius , supporting earlier work that attributed this ichnogenus to callianassids.