Codon volatility does not reflect selective pressure on the HIV-1 genome

Codon volatility is defined as the proportion of a codon's point-mutation neighbors that encode different amino acids. The cumulative volatility of a gene in relation to its associated genome was recently reported to be an indicator of selection pressure. We used this approach to measure selection on all available full-length HIV-1 subtype B genomes in the Los Alamos HIV Sequence Database, and compared these estimates against those obtained via established likelihood- and distance-based comparative methods. Volatility failed to correlate with the results of any of the comparative methods demonstrating that it is not a reliable indicator of selection pressure.     

Effect of temperature and sunlight exposure on the fate of soil-applied [14C]-gamma-hexachlorocyclohexane

The role of temperature and solar radiation in the rapid dissipation of-1,2,3,4,5,6-hexachlorocyclohexane (-HCH) from Indian soils was determined by quantifying volatilization, mineralization, binding and degradation of [¹⁴C]-HCH in a sandy loam soil. An increase in temperature from 15 to 45°C caused a 6-fold rise in volatilization. Degradation as well as mineralization of HCH increased with temperature, although both were minimal. Bound residues of HCH in soil increased from 3.3% at 15°C to 16.7% at 45°C, after 28 days. In flooded soils, volatile losses nearly doubled, while binding and mineralization decreased. Exposure of HCH-treated soil to sunlight in quartz tubes showed a two-fold increase in volatilization over the dark controls. Formation of-2,3,4,5,6-pentachlorocyclohex-l-ene (-PCCH) in the unflooded soils and-3,4,5,6-tetrachlorocyclohex-1-ene (-TCCH) in the flooded systems were enhanced by sunlight. Trace amounts of-HCH were detected in the volatilized organics from the quartz tubes. Flooding the soil markedly increased volatile losses, thus leaving only 14% of the initial HCH as residues in soil after 42 days of exposure in quartz tubes. Neither flooding nor sunlight had any significant effect on HCH binding in soil. Mineralization, though amounting to a maximum of only 3% in the unflooded soil, was further reduced in submerged soils. The data demonstrate the significant influence of temperature, humidity and solar radiation, on the rapid loss of HCH from Indian subtropical soils, evidently by rapid volatilization.     

四氯偶氮苯在大鼠胆汁中的分泌和代谢

四氯偶氮苯（３,３’,４,４’ｔｅｔｒａｃｈｌｏｒｏａｚｏｂｅｎｚｅｎｅ,ＴＣＡＢ）和四氯氧化偶氮苯（３,３’,４,４’ｔｅｔｒａｃｈｌｏｒｏａｚｏｘｙｂｅｎｚｅｎｅ,ＴＣＡＯＢ）是在合成氯代或二氯代苯胺类除草剂时生成的污染废弃物。此类除草剂经...     

Heparin-binding epidermal growth factor-like growth factor protects rat intestine from ischemia/reperfusion injury

BACKGROUND: We have shown previously that heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is cytoprotective for intestinal epithelial cells exposed to hypoxia in vitro. We now examine the effects of HB-EGF on the recovery of small intestine from ischemic injury in vivo. METHODS: Segmental intestinal ischemia of 60-min duration was produced in adult rats by occlusion of a first-order branch of the superior mesenteric artery. Recombinant HB-EGF (100 microg) was injected intraluminally into the proximal small bowel after 45 min of ischemia in experimental animals, and buffered saline was injected in control animals. Animals were sacrificed after 48 h, and the affected bowel was resected, processed, and examined microscopically, with histologic grading of the ischemic injury. Additional animals were allowed to recover for up to 1 month to evaluate mortality differences. RESULTS: Intraluminal administration of HB-EGF resulted in significantly decreased extent and severity of ischemia/reperfusion injury, with significantly decreased grade of injury in the HB-EGF-treated compared with nontreated animals (average injury grade 0.66 compared with 2.44, respectively). Moreover, the mortality rate was significantly lower in the HB-EGF-treated animals compared with nontreated animals (0% vs 25%, respectively). HB-EGF-treated animals had increased weight gain in the postischemia recovery period. CONCLUSIONS: We conclude that HB-EGF, given intraluminally, reduces both the amount and the severity of ischemia/reperfusion injury in the small bowel, reduces the mortality associated with intestinal ischemia, and may enhance intestinal recovery. The in vitro and in vivo cytoprotective effects of this growth factor suggest that it may, in the future, be clinically useful in treating patients with intestinal ischemia.     

Proliferating cell nuclear antigen expression and the progression of cervical intraepithelial neoplasia

Cell proliferation is an important biological aspect of a tumor cell population which can affect clinical outcome. In addition to other well established clinical and histopathological prognostic criteria? cell kinetic data have significant predictive value. This study evaluates the proliferative activity of benign, premalignant and malignant cervical tissue by analyzing the expression of the proliferating cell nuclear antigen (PCNA). PCNA is a 36 kD nuclear protein associated with the cell cycle and is directly involved in DNA synthesis during cell proliferation. A total of 122 subjects were included in the study. This included 30 benign tissue samples, 30 low grade lesions (CIN 1), 30 high grade lesions (CIN 2/3) and 32 invasive squamous carcinomas. There was significant difference in PCNA index between benign and high grade lesions as well as benign and invasive cancer. The percentage of PCNA positive cells were significantly higher in invasive carcinoma when compared with non malignant lesions. Moreover, there was also good correlation between increasing histological abnormality and PCNA expression. These results suggest that cell proliferation index as detected by PCNA expression may be useful in the evaluation of alterations in cell kinetics of various grades of cervical lesions. Such data could also possibly help explain the biological behaviour of these lesions and be useful in planning of radiotherapy for invasive cervical cancer.     

Bilateral progressive essential iris atrophy and keratoconus with coincident features of posterior polymorphous dystrophy: a case report and proposed pathogenesis.

We report the first case known to us of an apparent bilateral association of essential iris atrophy (EIA) and keratoconus (KC), with coincident features of posterior polymorphous dystrophy (PPD). Based on this case and the published natural history and findings of both the irido corneal endothelial (ICE) syndrome and PPD, we propose a new hypothesis for the pathogenesis of the ICE syndrome with associated KC and/or PPD. We suggest that, similar to the genetics of retinoblastoma, the predisposition for either the ICE syndrome or for PPD is inherited as an inactive allele, the so-called "first hit." Inactivation of the second allele, or "second hit," which could occur at any time, might be the product of the background mutation rate or of an environmental trigger. Dedifferentiation or an abnormality in normal development could occur after the first or second hit, resulting in varying clinical patterns. We also concur with other investigators that PPD could be part of the spectrum of the ICE syndrome, owing to similarities in their clinical presentations, histopathology, specular and electron microscopy, and natural history.     

Total posterior approach for femoropopliteal bypass

Standard approaches to the femoral and popliteal arteries are used in most extremity arterial reconstructions. In unusual circumstances, such as infection, reoperation, or variant anatomy, novel approaches to infrainguinal bypass may be useful, particularly in reoperative or infected cases. One such approach involves exposure of the femoral and popliteal arteries through posterolateral incisions with the patient prone. The major advantage of this exposure is the increased accessibility to the distal above-knee popliteal artery, which is not easily reached through either medial or lateral incisions. This approach also can be useful in cases of significant groin sepsis. The details of this exposure and its application in an illustrative case are presented.     

Angiogenesis during tumor progression in the oral cavity is related to reduced apoptosis and high tumor cell proliferation

Angiogenesis, the growth of new blood vessels, is believed to aid tumor progression and metastasis. Tumor progression is also influenced by the extent of proliferation and apoptosis. This study, therefore, analyzed in lesions of the oral cavity, the significance of angiogenesis in relation to apoptosis, expression of apoptosis regulatory p53, bax and bcl-2 proteins as well as tissue proliferation defined by cyclin D1 expression. Results from this study suggest that angiogenesis increases as histological abnormality increases in the oral mucosa. The expression of apoptosis regulatory proteins also appears to be altered in a histologically dependent manner. The correlation seen between CD34 expression, cyclin D1 and TUNEL reactive cells suggests that increased angiogenesis, decreased apoptosis and deregulated proliferation occur simultaneously during tumor progression in the oral mucosa. Presence of a mutant p53, increased bcl-2 expression and altered bax expression are also involved in this complex process.