Linkage disequilibrium mapping of the gene for Hermansky-Pudlak syndrome to chromosome 10q23.1-q23.3

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by the triad of tyrosinase-positive oculocutaneous albinism, bleeding diathesis due to storage-pool deficiency of platelets, and a lysosomal ceroid storage disease. The disorder is particularly frequent in Puerto Rico and in an isolated village in the Swiss Alps. We have used a linkage disequilibrium mapping approach to localize the HPS gene in both of these groups to a 0.6 centiMorgan interval in chromosome segment 10q23.1-q23.3. These results indicate that the Puerto Rican and Swiss forms of HPS are either allelic or that they result from mutations in very closely linked genes in this region. This region of distal chromosome 10q is syntenic to the region of mouse chromosome 19 that includes 'pale ear' (ep) and 'ruby-eye' (ru), which must be considered as potential murine homologues to human HPS.

Analysis of the structure of empty and peptide-loaded major histocompatibility complex molecules at the cell surface

We compared the conformation of empty and peptide-loaded class I major histocompatibility complex (MHC) molecules at the cell surface. Molecular conformations were analyzed by fluorescence resonance energy transfer (FRET) between fluorescent-labeled Fab fragments bound to the alpha 2 domain of the MHC heavy chain and fluorescent-labeled Fab fragments bound to beta 2-microglobulin. No FRET was found between Fab fragments bound to empty H-2Kb, but FRET was detected when empty H-2Kb molecules were loaded with peptide. The magnitude of FRET depended on the sequence of the peptide used. The results imply that empty H-2Kb molecules are in a relatively extended conformation, and that this conformation becomes more compact when peptide is bound. These changes, which are reflected in peptide-dependent binding of monoclonal antibodies, affect the surfaces of MHC molecules available for contact with T cell receptors and hence may influence T cell-receptor recognition of MHC molecules.

Concurrent use of foscarnet and ciprofloxacin may increase the propensity for seizures

OBJECTIVE

To report a possible interaction between foscarnet and ciprofloxacin in two patients with AIDS, cytomegalovirus (CMV) retinitis, and disseminated Mycobacterium avium complex (MAC) infection and to review the available literature related to foscarnet-associated seizures.

DATA SOURCE

Case report information was obtained from Medical Service Daily Rounds during the patients' hospitalization and from the patients' medical records. Computerized (MEDLINE) and manual (Index Medicus) search methods were used to obtain English-language literature published between 1980 and 1993.

DATA SYNTHESIS

Foscarnet is a synthetic antiviral agent with activity against herpesviruses and HIV. The incidence of seizures with foscarnet infusion is high, ranging from 13 to 15 percent. Predisposing factors such as renal impairment, electrolyte and metabolic abnormalities, and underlying neurologic disorders have been associated with seizures during foscarnet therapy. We describe two patients with AIDS who developed generalized tonic-clonic seizures while receiving foscarnet and ciprofloxacin for the treatment of CMV retinitis and disseminated MAC infection, respectively. Neither of the patients had any of the aforementioned risk factors for foscarnet-associated seizures.

CONCLUSIONS

Concurrent administration of ciprofloxacin, a known epileptogenic agent, and foscarnet may predispose patients to the development of seizures.

Dye coupling of rabbit ciliary epithelial cells in vitro

PURPOSE

To examine the in vitro properties of gap junctions on the isolated rabbit ciliary epithelium.

METHODS

Intracellular potential was measured and lucifer yellow (5% in 1 M LiCl) was iontophoretically injected into a ciliary epithelial cell. Fixated tissue was examined with a laser confocal microscope.

RESULTS

Dye spread was observed throughout both layers (horizontally and vertically) of the ciliary epithelium adjacent to the injected cell that was more intensely labeled. Dye reflux did not occur at the site of microimpalement. Microiontophoretic dye injection in a bathing solution with a high Ca2+ (10 mM) or an acidic pH (6.3) completely inhibited cell-cell dye coupling in the rabbit ciliary epithelial cells.

CONCLUSIONS

Laser confocal microscopy of intracellularly injected lucifer yellow dye demonstrates the physiologic presence of gap junctions between both ciliary epithelial layers. Extracellular acidosis and high concentration of extracellular Ca2+ cause loss of cell-cell coupling in the rabbit ciliary epithelium.

In vivo alterations in the gonadotropin-releasing hormone pulse generator and the secretion and clearance of luteinizing hormone in the uremic castrate rat

To investigate the mechanisms subserving the reported alterations in the pulsatile release of LH in uremia, we simultaneously studied endogenous accumulation of GnRH in the pituitary gland and the secretion and clearance of LH in vivo in experimentally uremic, orchidectomized rats. The temporal pattern of GnRH secretion was assessed by intrapituitary microdialysis, the dynamics of plasma LH by continuous exchange transfusion. Studies were performed in rats rendered uremic by subtotal nephrectomy (n = 8) and control rats which were either fed ad libitum (n = 8) or pair-fed with the uremic animals (n = 8). Blood samples were obtained at 5-min and microdialysate samples at 10-min intervals over a period of 270 min. The pulsatile secretory characteristics of GnRH and LH and the half-life of plasma LH were estimated by multiple-parameter deconvolution analysis. The temporal relationship between the hormone concentrations and between the secretory events of GnRH and LH was assessed by cross-correlation analysis and hypergeometric coincidence analysis. We observed that: (1) the estimated half-life of plasma LH was prolonged in uremic (59 +/- 10 min) rats compared to ad libitum-fed (17 +/- 3 min, p = 0.014) and pair-fed controls (19 +/- 3 min, p = 0.025); (2) the LH production rate was decreased in uremic animals (18 +/- 5 ng/ml.270 min) compared to ad libitum-fed (37 +/- 4 ng/ml.270 min, p = 0.002) and pair-fed controls (48 +/- 9 ng/ml.270 min, p = 0.0006); (3) the reduction of LH secretion rate in the uremic animals was accounted for by a decrease in detectable LH pulse frequency (2.1 +/- 0.2 peaks/h) compared to ad libitum-fed (3.1 +/- 0.1 peaks/h, p = 0.01) and pair-fed controls (2.8 +/- 0.2 peaks/h, p = 0.06) and a diminished mass of hormone released per burst (uremic 1.8 +/- 0.2 ng/ml, ad libitum-fed 2.6 +/- 0.3 ng/ml, p = 0.05, pair-fed 3.8 +/- 0.8 ng/ml, p = 0.025); (4) the secretion rate of GnRH was reduced to a similar degree in uremic rats (180 +/- 15 pg/tube.270 min, p = 0.04) and pair-fed controls (170 +/- 26 pg/tube.270 min, p = 0.04) compared to ad libitum-fed controls (270 +/- 36 pg/tube.270 min). In contrast to the reduced number of detectable LH secretory events, the frequency of GnRH secretory peaks in uremic rats was not different from ad libitum-fed and pair-fed controls.(ABSTRACT TRUNCATED AT 400 WORDS)

Contractions of the filariid Acanthocheilonema viteae induced by potassium chloride

The effects of K+ on muscle contractility were explored in the filarial nematode Acanthocheilonema viteae (Dipetalonema viteae). The parasite was slit open longitudinally and mounted in a smooth muscle chamber that was filled with aerated (95% N2-5% CO2) physiological solution at 37 degrees C. KCl at concentrations ranging from 20 to 100 mM induced a rapid isotonic contraction of the filarial muscle. The maximal response from KCl was similar to the maximal response to acetylcholine chloride (ACh). When KCl was applied for several minutes, tolerance frequently occurred. Contractions were also induced by K2SO4 but not by NaCl, Na2SO4 or sucrose. Nifedipine was more than 10 times as potent in reducing the KCl-induced contraction as in reducing that caused by ACh. The KCl-induced contraction was abolished in a Ca-free physiological medium containing ethyleneglycol-bis-(beta-aminoethyl ether) N, N, N', N'-tetraacetic acid (EGTA, 10(-4) M). Low [Ca2+]/[Mg2+] solutions blocked the spontaneous activity, the KCl-induced contractions, and the ACh-induced contractions. KCl also induced contractions in denervated muscle strips, supporting the hypothesis that K+ acts directly on the muscle cells. These results indicate that K+ can depolarize the muscle membrane and induce a muscle contraction that is dependent on extracellular calcium ions.

Induction of apoptosis by the low-affinity NGF receptor

Nerve growth factor (NGF) binding to cellular receptors is required for the survival of some neural cells. In contrast to TrkA, the high-affinity NGF receptor that transduces NGF signals for survival and differentiation, the function of the low-affinity NGF receptor, p75NGFR, remains uncertain. Expression of p75NGFR induced neural cell death constitutively when p75NGFR was unbound; binding by NGF or monoclonal antibody, however, inhibited cell death induced by p75NGFR. Thus, expression of p75NGFR may explain the dependence of some neural cells on NGF for survival. These findings also suggest that p75NGFR has some functional similarities to other members of a superfamily of receptors that include tumor necrosis factor receptors, Fas (Apo-1), and CD40.

Transesophageal echocardiography: state-of-the art and future directions

Transesophageal echocardiography complements transthoracic examination in 5-10% of patients referred to the echocardiographic laboratory. Clinical indications for performing this procedure are continually evolving. The semi-invasive nature of this procedure necessitates that it be judiciously used and that trained personnel undertake the procedure. Complications of the procedure need to be kept in mind. Future directions in the development of this technology involve newer, multiplanar, multifrequency transducers, digital archiving and retrieval, wide-field imaging, and 3-dimensional reconstruction. For the present, transthoracic echocardiography must remain the primary echocardiographic window imaging the heart, with defined clinical applications for transesophageal echocardiography.

Synthesis and biological activity of novel 3-(2-propenyl)-cephalosporins. I

The synthesis, antibacterial activity and oral absorption of novel cephalosporins (3a-3d) having a 2-propenyl group at the C-3 position are described. Diphenylmethyl 7-amino-3-(2-propenyl)-3-cephem-4-carboxylate HCl (4) prepared from 7-aminocephalosporanic acid in 12 steps was acylated with various acid moieties to give cephems 3a-3d. The cephems 3a-3c showed similar antibacterial activities as cefixime. However, these cephems were not well absorbed orally.

Nucleotide sequence analyses of the genes encoding the HN, M, NP, P, and L proteins of two host range mutants of Sendai virus

Comparative nucleotide sequence analyses of the genome of Sendai virus (strain Z) and two host range mutants, ts-f1 and F1-R, previously described revealed that the ts defect of ts-f1 can be attributed to two nucleotide exchanges in the NP gene. These exchanges lead to a single amino acid substitution. A single base pair change was found in both the P and L genes of F1-R, but not of ts-f1. Both host range mutants have the two same exchanges in the M gene. These additional mutations are discussed concerning their significance in the pantropic properties of the host range mutants.

High-resolution nonlinear laser spectroscopy of room-temperature GaAs quantum-well structures: observation of interference effects

We describe frequency-domain four-wave mixing spectroscopy measurements near the fundamental band edge in room-temperature GaAs multiple quantum wells. The line-shape information gives a measure of the dynamical behavior of the material and what is to our knowledge the first observation of an interference line shape due to a dominant slow contribution to the nonlinear response.

Vitamin A in experimental herpetic keratitis

Systemic vitamin A palmitate at three dosage levels was evaluated for its effect on experimental herpes simplex virus (HSV) keratitis in corticosteroid-treated rabbits. High-dose vitamin A palmitate reduced the severity of herpetic keratitis, but the low or moderate doses did not, and none of the vitamin A treatments affected virus recovery. Vitamin A treatment, however, produced substantial weight loss in uninfected rabbits and in corticosteroid-treated, HSV-infected rabbits. Steroid treatment alone significantly increased the antibody response to HSV, but this effect was not enhanced by vitamin A. The slight beneficial effect on HSV keratitis could be attributed to the known effect of vitamin A on promoting epithelial healing rather than an enhancement of immunity. For this purpose, local application of vitamin A may be just as effective and much less toxic than administration for systemic effect.

Thygeson's superficial punctate keratitis

Thygeson's superficial keratitis is a chronic disease of the cornea characterized by focal epithelial lesions. We studied 45 cases of Thygeson's superficial punctate keratitis. Twenty-eight were male and 17 were female patients. The disease had been active in our patients from one month to 24 years. The clinical findings, course, outcome, and response to therapy were studied. Viral cultures and microscopic studies were performed on the corneal epithelial scrapings from ten cases. The average course of the disease was prolonged in patients who received topical steroid therapy. Subepithelial opacities were seen more frequently in patients who had received treatment with idoxuridine (IDU).

Increased Leukocyte Thromboplastin Activity by Sensitized Lymphocytes: A Link Between Immunology and Blood Coagulation

Fibrin deposition and infiltration of mononuclear leukocytes (MN) frequently occurs concomitantly at the site of an immune reaction. As human MN can produce thromboplastin (TP) we have investigated whether immune stimulation of MN can trigger the production of TP by these cells. Both specific antigen (tuberculin PPD) and allogeneic lymphocytes were used for stimulation. MN from 14 donors with a high response to PPD and from 11 donors with a low response to PPD (based on the incorporation of 3H-thymidine) were cultured for 7 days in the presence or absence of PPD and the TP activity of the whole cell suspension was determined. When PPD was absent, TP levels in MN from low and high responders were not different (113±47 and 197±111 u/ml resp. p ˃ 0.10). With PPD, however, MN from high responders produced 1470±413 u TP/ml compared to 126±49 u TP/ml produced by MN from low responders (p < 0.005). Similar results were obtained when MN were kept in culture for either 4 or 11 days. However, after 24 hours in culture, TP synthesis was not different in the MN of the 2 groups. When MN were cultured in a mixed leukocyte reaction, allogeneic MN produced more TP (405±151 u/ml) than control cultures (95±21 u/ml) (p<0.025;n=22). These data indicate that stimulated lymphocytes can enhance TP activity of leukocytes. It is postulated that fibrin formation in immune reactions such as delayed hypersensitivity and rejection of kidney allografts is mediated by immunologically stimulated MN.

Phytoestrogens: adverse effects on reproduction in California quail

Phytoestrogens, largely formononetin and genistein, are produced in the leaves of stunted desert annuals in a dry year. When ingested by California quail, these compounds apparently inhibit reproduction and prevent the production of young that will not have adequate food. In a wet year, forbs grow vigorously and phytoestrogenic substances are largely absent. Quail then breed prolifically and the abundant seed crop carries the enlarged population through the winter.