Gaussian beam ray-equivalent modeling and optical design

It is shown that the propagation and transformation of a simply astigmatic Gaussian beam by an optical system with a characteristic ABCD matrix can be modeled by relatively simple equations whose terms consist solely of the heights and slopes of two paraxial rays. These equations are derived from the ABCD law of Gaussian beam transformation. They can be used in conjunction with a conventional automatic optical design program to design and optimize Gaussian beam optical systems. Several design examples are given using the CODE-V optical design package.

Kinetics of insulin receptor biosynthesis and membrane insertion. Relationship to cellular function

A method was developed for maintaining isolated rat adipocytes in primary culture in a viable state for several days. Using this method, the kinetics of insulin receptor biosynthesis and membrane incorporation were assessed by inactivating (>95%) cell-surface insulin receptors with trypsin and then incubating cells in medium at 37°C for various times up to 44 h. The insertion of nascent receptors, into the plasma membrane was monitored by measuring the recovery of specific 125l-insulin binding activity. After trypsinization, insulin binding activity recovered at a linear rate with half of the original cell-surface receptor complement replenished by 24 h (6000 receptors or 2% of total surface receptors/h). This recovery was most probably mediated by de novo receptor synthesis, since no recovery of specific insulin binding was seen when cells were pretreated with cycloheximide for 3 h. Under conditions where protein synthesis was blocked immediately after trypsinization, however, a lag of 2–3 h was observed before receptor incorporation was inhibited. This lag suggests that insulin receptors are processed and routed within the cell for 2–3 h before being inserted into the plasma membrane. In support of this hypothesis it was found that the intracellular pool of insulin receptors (10% of the total receptor complement) could be depleted by about 80% by treating cells with cycloheximide for 3 h. Thus, it appears that most, if not the entire, intracellular receptor pool in adipocytes consists of newly synthesized receptors en route to the cell surface.

Insulin, after binding to cell-surface receptors, triggers various biologic actions in adipocytes such as glucose transport and endocytosis of insulin-receptor complexes. To determine whether nascent receptors are functional immediately on insertion, we compared the recovery of insulin binding activity after trypsinization with the ability of these cells to respond to insulin with an increase in glucose uptake and an augmented rate of insulin internalization. These data revealed a high correlation between recovery of binding and biologic responsiveness. Thus, these data indicate that immediately upon insertion, or shortly thereafter, receptors become functional and are able to mediate the biologic actions of insulin.

A conservative approach to testicular tumors in children: 12 cases and their management

During a 34-year period 12 children were seen with testicular tumors. Of 8 benign tumors 7 were treated by orchiectomy and 1 by local excision only. The 4 malignant tumors were managed by orchiectomy and 1 boy also received adjunctive chemotherapy. All patients are alive and have had no recurrent tumors after 1 1/2 to 34 years of followup. Because testicular tumors usually are less aggressive in prepubertal children, the chance of cure by orchiectomy alone in this age group is good. However, the potential of these tumors for metastases makes it imperative that they be observed closely.

Some common problems concerning solvent polarization and dielectric behaviour at ions and electrode interfaces

The sensitivity of the dependence of ionic hydration properties of simple cations and anions on ionic radius is compared and related to the dielectric polarization in the solvent, near the ion. Corresponding dielectric polarization of the water solvent in the interphase at the surface of charged electrodes is evaluated on the basis of several models of oriented water dipoles at electrodes and compared with the situation at ions. It is pointed out that previous theories of the double-layer at electrodes have considered either the solvent polarization in the absence of adsorbed ions or the behaviour of ions independently of the solvent polarization by the electrode surface charge. Calculations are given that indicate that the surface concentrations of adsorbed ions at electrodes are commonly sufficient to cause a major influence on the behaviour of interphasial water in addition to that arising from the effect of electrode surface charge. Further, repulsion, due to overlap of Gurney cospheres of ions, will be an important factor in ionic interactions laterally within the double-layer.

Varicocele in childhood and adolescence: implication in adulthood infertility?

Thirty boys eight to eighteen years of age had a clearly palpable left varicocele. The presenting complaint usually was either an asymptomatic scrotal mass or a scrotal ache after physical exercise. In 77 per cent of the patients the left testis was smaller than its male. All but one of the 17 boys between ages eight and fifteen had a smaller left testis. When the varicocele is symptomatic, presents as a prominent mass, or where growth of the left testicle lags behind that of its mate, surgical correction of the varicocele is recommended.

The transfer of platelet factor 4 from its proteoglycan carrier to natural and synthetic polymers

1. Transfer of dansyl-platelet factor 4 complexed with a series of glycosaminoglycans to heparin has been detected and studied by measuring changes in the anisotropy of the dansyl fluorescence. The protein was most easily transferred from chondroitin sulphate and least easily from heparan sulphate. 2. The transfer of the dye-labelled protein from its biological chondroitin 4-sulphate proteoglycan carrier to natural and synthetic anionic polymers was similarily followed. The transfer to heparin and dermatan sulphate was shown to be the same whether 3 mM Ca2+ or 8 mM EGTA was present in the solution. 3. The shapes of the binding curves of the dansyl-factor to the polymers have been compared at I = 0.4M. 4. The observed changes in anisotropy of dye fluorescence have been correlated with the charge density and the stereochemistry of the charged groups of the natural polymers. Large complexes are observed with polymers of high negative charge/weight ratios. Less charged polymers containing disaccharide units of iduronic acid and glucosamine N-sulphate will also from large complexes at I = 0.15 M. 5. It is demonstrated that the release of a platelet factor 4 proteoglycan complex in vivo would result in the transfer of the protein to heparin, moderate quantities of either dermatan or heparan sulphates would not prevent this transfer.

The sites of deposition of newly synthesized histone

The chromosomal fragments produced by nuclease digestion of freshly replicated chromatin migrate more rapidly relative to bulk chromatin when analyzed in nucleoprotein gels. The cause of the anomalous migration has been studied and the evidence indicates that rather than reflecting a shorter nucleosomal repeat in vivo that it may be a consequence of nucleosome sliding during the digestion itself. The distinct electrophoretic characteristics of nucleosomal material containing newly replicated DNA have enabled us to examine their histone composition by two dimensional electrophoresis. We find that nucleosomes containing new DNA also contain newly synthesized histones H3 and H4. In contrast more than 50% of newly synthesized H2A and H2B, and essentially all of new H1, are deposited at sites on the bulk chromatin distinct from that material containing newly replicated DNA. In addition we show that newly synthesized histones H3 and H4 are bound unusually weakly when they first become associated with the chromatin.

Characterization of insulin-induced receptor loss and evidence for internalization of the insulin receptor

We studied the relationship between insulin-induced receptor loss and insulin internalization in isolated rat adipocytes. When cells were exposed to 100 ng/ml insulin at 37°C for times ranging from 10 min to 6 h, a monoexponential loss of insulin receptors was observed for up to 4 h, with a t½ of 75 min and a 75% maximal loss. The insulin-induced loss of receptors was dose-dependent with a % maximal effective insulin concentration of 7.6 and 1.3 ng/ml in 2- and 6-h insulin- pretreated cells, respectively. The ability of insulin to mediate receptor loss was inhibited by low temperature (16°C) and by the metabolic energy depleters dinitrophenol and NaF, suggesting that receptor loss is mediated by an 125I-insulin compared with control cells, and the relationship between insulin-induced receptor loss and insulin internalization was assessed by comparing these two processes over time and as a function of temperature. Using this approach, a significant linear relationship was observed between these partners at various temperatures (r = 0.99) and times (r = 0.94). These results suggest that the mechanism whereby insulin induces receptor loss in adipocytes is by internalization of insulin-receptor complexes.

Insulin receptors remaining on 2-h insulin, pretreated cells had identical dissociation rates and exhibited similar negative cooperative interactions when compared with control cells. Furthermore, anti-insulinreceptor antibodies inhibited binding in both groups of cells to the same extent. In contrast to these similarities, insulin-induced receptor loss was accompanied by a progressive impairment in the ability of cells to accumulate intracellular insulin in the presence ofchloroquine, which we interpret as an insulin-induced slowing of insulin internalization.

In conclusion, (1) insulin causes a time-, temperature-, dose-, and energy-dependent loss of cell-surface insulin receptors; (2) the rate of receptor loss and the extent of insulin internalization are closely correlated, suggesting that insulin-induced receptor loss in adipocytes is mediated by endocytosis of insulin-receptor complexes; and (3) insulin-induced receptor loss is accompanied by a reduced ability of residual receptors to internalize insulin.

Simplified approach to cryoprecipitate coagulum pyelolithotomy

A simplified approach to coagulum pyelolithotomy, utilizing ureteral catheters for injection of the coagulum, is advantageous for small intrarenal pelves, or when it is difficult to mobilize the kidney because of a previous operation. The approach is technically easy and straight-forward. We highly recommend its use in selected cases.

Urethral diverticula in young girls

Five cases of urethral diverticulum in young girls are herein presented. None of these children had associated local infections, unlike what is generally the case in adult women with a similar lesion. Three girls experienced spontaneous regression of the diverticulum. Therefore, unless the diverticulum causes clinical problems, postponement of surgical intervention is advised.

Regulation of insulin receptors: evidence for involvement of an endocytotic internalization pathway

Cultured human fibroblasts degrade insulin by a receptor-mediated process. When intracellular hormone degradation is inhibited by chloroquine, 125I-labeled insulin internalizes and accumulates intracellularly. In contrast, cultured IM-9 lymphocytes do not degrade receptor-bound insulin or accumulate 125I-labeled insulin in the presence of chloroquine. Insulin-induced receptor loss occurs in both cell types, and chloroquine inhibits this process in fibroblasts but not in IM-9 lymphocytes. Transglutaminase is a membrane-associated enzyme thought to mediate the process of ligand-induced receptor aggregation and internalization; levels of this enzyme were high in fibroblasts but barely detectable in IM-9 lymphocytes. Furthermore, dansylcadaverine--a potent inhibitor of transglutaminase--blocked insulin-induced receptor loss in fibroblasts but was without effect in IM-9 lymphocytes. These results support the concept that insulin receptor regulation is mediated via an endocytotic internalization pathway in human fibroblasts and that the mechanisms of this process differ among cell types.

Effects of insulin incubation on insulin binding, glucose transport, and insulin degradation by isolated rat adipocytes. Evidence for hormone-induced desensitization at the receptor and postreceptor level

We have examined the effect of in vitro hyperinsulinemia on insulin binding, glucose transport, and insulin degradation in isolated rat adipocytes. When cells were incubated with insulin for 2 or 4 h at 37 degrees C, followed by washing in insulin-free buffer to remove extracellular and receptor-bound insulin, a time and dose-dependent decrease in insulin receptors was observed, which was accompanied by a reduced ability of cells to degrade insulin. Furthermore, the quantitatively predicted rightward shift in the insulin-glucose transport dose-response curve could be demonstrated. In addition to this reduction in insulin sensitivity, a striking decrease in maximal insulin-stimulated glucose transport was observed in the 4-h insulin-treated cells, indicating an abnormality distal to the insulin receptor. Thus, in vitro insulin-induced insulin resistance in adipocytes is caused by both receptor and postreceptor abnormalities. The post-receptor defect is most likely at the level of the glucose transport system per se because the insulinlike agents, spermine and antiinsulin receptor antibodies, also had a markedly reduced ability to stimulate glucose transport in 4-h insulin-treated cells. On the other hand, when cells were incubated with 100 ng/ml insulin for up to 4 h, after which time 2-deoxy glucose uptake was measured without removing buffer insulin or allowing receptor-bound insulin to dissociate, no decrease in maximal insulin-stimulated glucose transport was found. In conclusion, (a) insulin leads to a dose-dependent loss of insulin receptors in freshly isolated adipocytes accompanied by the predicted functional consequence of decreased receptors, i.e., a rightward shift in the insulin-glucose transport dose-response curve, (b) prolonged incubation with insulin causes a marked postreceptor defect in the glucose transport system, (c) maintenance of the activated state of the glucose transport system prevents the expression of the post-receptor defect, (d) the location of the postreceptor abnormality is most likely in the glucose transport system per se, and (e) insulin-induced receptor loss is accompanied by a decrease in insulin degradation.

Neoplasms of immunoregulatory T cells in clinical investigation

Normal T cells play a critical role in the regulation of humoral immune responses by acting as potentiators (helper cells) or inhibitors (suppressor cells) of the process by which B cells differentiate into immunoglobulin-secreting plasma cells. Certain diseases in which malignant T cells appear to retain an immunoregulatory function are characterized by a propensity of a lymphomatous T-cell population to infiltrate skin. Some cutaneous T-cell lymphomas, as well as some T-cell neoplasms without dermatologic involvement, provide a homogeneous supply of T lymphocytes which act as immunoregulators. The availability of neoplastic T cells with immunoregulatory properties could accelerate the serologic and biochemical analysis of the cellular control of normal immunity in man.