Analysis of refractive state ratios and the onset of myopia

PURPOSE

To develop formulae for the refractive state ratios, axial length growth and the age of onset (A*) of myopia. Calculated results are compared with measurements.

METHODS

Using an image equation, the axial length in the ametropic state (L) is related to the length in the emmetropic state (L*) and refractive error (D) by a rate of change M (D mm(-1)). Three refractive state ratios are defined: C1 = L/r1, C2 = L/L* and C3 = L/H, where r1 and H are the anterior surface radius of the cornea and the transverse dimension of the eye, respectively. The age of onset A* is calculated by the rate of change of refractive error (M) and the axial growth rates N and N* in the ametropic and emmetropic states, respectively.

RESULTS

The three ratios C1, C2 and C3 are increasing function of the myopia power, for example, C1 = 3.4, 3.1, 2.9 for D = -8, 0, +4 dioptres, respectively. The calculated C1* (for the emmetropic state) varies between 3.08 and 3.14, depending on corneal shape, and C3 = 0.985, 1.0, 1.04 for D = +3, 0, -3 dioptres: these values are consistent with measured data. For a typical system with effective focal length F = 22.25 mm, L* = 24.2 mm and L = 23.4, 24.9, 25.9 mm for D = +2, -2, -5 dioptres, respectively. The calculated rates of change of refractive error M = 2.3-2.9 D mm(-1) for F = 22-23 mm are also consistent with measured values 2.4-2.7 D mm(-1). The age of onset A* is calculated to be proportional to 1/(M dN), where dN = N-N* is the axial growth rate difference between the ametropic and emmetropic states and may be used as a better predictor for myopia onset than the conventional ratio L/r1. The A* is given by the crossing of L and L* curves, in which myopia onset occurs earlier for larger M dN.

CONCLUSION

The theory provides formulae to calculate various refractive state ratios, which are consistent with measurements. By defining two rate functions, M and N, the onset of myopia can be predicted.

The osteoporotic spine

Osteoporotic vertebral fractures represent the most common type of osteoporotic fracture. They can cause significant morbidity and mortality, including physical, functional, and psychosocial impairments. Screening using fracture risk assessments can identify those at greatest risk. Medical and non-medical comprise appropriate, comprehensive treatment programs. The minimally invasive spine procedures vertebroplasty and kyphoplasty can help to significantly reduce pain and deformity in patients with severe pain and deformity from vertebral fracture.

Laparoscopic bilateral nephroureterectomy and bladder cuff excision for native renal pelvic and ureteral transitional cell carcinoma after renal transplantation

A 37-years-old female who was suffering from end-stage renal disease for about 6 years received allograft renal transplantation 4 years ago. She has been receiving 50mg of Cyclosporin A orally daily for immuno-suppression since then. Gross haematuria was noted and computerised tomography showed native left renal pelvic and ureteral multi-focal transitional cell carcinoma with severe hydronephrosis. Laparoscopic bilateral nephroureterectomy and bladder cuff excision were performed. In the past, history of previous operation was considered a relative contraindication for laparoscopic surgery. To our knowledge, we present the first case of laparoscopic treatment for native renal pelvic and ureteral transitional cell carcinoma after renal allograft transplantation without a hand-assisted device. This case shows the feasibility of laparoscopic bilateral nephroureterectomy in patients with transplanted kidneys.

Associations of plasma aflatoxin B1-albumin adduct level with plasma selenium level and genetic polymorphisms of glutathione S-transferase M1 and T1

Mortality from hepatocellular carcinoma (HCC) is extraordinarily high in Matzu, an island off the coast of Southeastern China. To investigate factors associated with plasma aflatoxin B1 (AFB1)-albumin adduct level, we studied 304 healthy adult residents from Matzu. AFB1-albumin adducts were determined by competitive enzyme-linked immunosorbent assay, hepatitis B surface antigen status by enzyme immunoassay, genotypes of glutathione S-transferase (GST) M1 and T1 by polymerase chain reaction, plasma selenium by atomic absorption spectrometry, and plasma retinol, alpha-tocopherol, alpha-carotene, and beta-carotene levels by high-performance liquid chromatography. Men had higher AFB1-albumin adduct levels than women. GSTM1-nonnull and GSTT1-null genotypes and low plasma selenium level were significantly associated with an increased level of AFB1-albumin adducts among men, whereas age was significantly correlated with adduct level among women. High intake of fermented beans was associated with an increased adduct level among men and women. The inverse associations between plasma selenium level and AFB1-albumin adducts were statistically significant among those with null genotypes of GSTM1 and GSTT1, but not among the nonnull genotypes. This study provides insight into the dietary and genetic factors influencing AFB1-albumin adduct formation in an isolated population with high liver cancer mortality.

Prospective study of Helicobacter pylori eradication therapy in stage I(E) high-grade mucosa-associated lymphoid tissue lymphoma of the stomach

PURPOSE

High-grade mucosa-associated lymphoid tissue (MALT) lymphomas of the stomach are generally believed to be Helicobacter pylori-independent, autonomously growing tumors. However, anecdotal cases of regression of high-grade lymphomas after the cure of H pylori infection had been described. The present prospective study was conducted to evaluate the effect of anti-H pylori therapy in stage I(E) high-grade gastric MALT lymphomas.

PATIENTS AND METHODS

Sixteen patients with H pylori infection and stage I(E) gastric high-grade MALT lymphoma consented to a brief antibiotic therapy as first-line treatment from June 1995 through April 2000. Then, patients underwent intensive endoscopic follow-up examinations (+/- endoscopic ultrasonography) with biopsy to evaluate tumor response. Patients with significant improvement of gross lesions that accompanied regression of large cells were followed up without additional treatment. Patients without significant improvement were immediately referred to systemic chemotherapy.

RESULTS

Eradication of H pylori was achieved in 15 patients and was accompanied by rapid gross tumor regression and disappearance of large cells in 10. All 10 of these patients with early response had subsequent complete histologic remission of lymphoma. The complete remission rate was 62.5% (95% confidence interval, 35.8% to 89.1%). The response rate was not affected by the tumor grading (proportion of large blast cells within the tumor) but was adversely affected by the depth of tumor invasion. At a median follow-up of 43.5 months (range, 21.1 to 67.4 months), all 10 of these patients remained lymphoma-free. The median duration of complete response was 31.2 months (range, 14.4 to 49.1 months).

CONCLUSION

These results suggest that high-grade transformation is not necessarily associated with the loss of H pylori dependence in early-stage MALT lymphomas of the stomach.

Identification of a region critically involved in the interaction of phlorizin with the rabbit sodium-D-glucose cotransporter SGLT1

In order to define potential interaction sites of SGLT1 with the transport inhibitor phlorizin, mutagenesis studies were performed in a hydrophobic region of loop 13 (aa 604-610), located extracellularly, close to the C-terminus. COS 7 cells were transiently transfected with the mutants and the kinetic parameters of alpha-methyl-D-glucopyranoside (AMG) uptake into the cells were investigated. Replacement of the respective amino acids with lysine reduced the maximal uptake rate: Y604K showed 2.2%, L606K 48.4%, F607K 15.1%, C608K 13.1%, G609K 14.1%, and L610K 17.2% of control. In all mutants the apparent K(i) for phlorizin increased at least by a factor of 5 compared to the wild-type K(i) of 4.6 +/- 0.7 micromol/l; most striking changes were observed for Y604K (K(i) = 75.3 +/- 19.0 micromol/l) and C608K (K(i) = 83.6 +/- 13.9 micromol/l). Replacement of these amino acids with a nonpolar amino acid instead of lysine such as in Y604F, Y604G and C608A showed markedly higher affinities for phlorizin. In cells expressing the mutants the apparent affinity of AMG uptake for the sugar was not statistically different from that of the wild type (Km = 0.8 +/- 0.2 mmol/l). These studies suggest that the region between amino acids 604 and 610 is involved in the interaction between SGLT1 and phlorizin, probably by providing a hydrophobic pocket for one of the aromatic rings of the aglucone moiety of the glycoside.