Localized phosphorus-31 MR spectra were obtained in vivo in a large series of normal human brain tissue specimens of healthy volunteers (n=36) and various brain tumours (n=52). Tumour types examined included grade II and grade III gliomas (n=15 and n=1, respectively), glioblastomas (n=16) and meningeomas (n=12). An additional eight tumours were analysed during chemo- or radiotherapy. Spectra were acquired using a modified ISIS pulse sequence with a repetition time of 3 s. Voxel sizes ranged from 56 to 129 ml. The spectra were evaluated using a least-square variable projection (VARPRO) fitting procedure in the time domain, which allows semi-quantitative determination of relative metabolite concentrations. The measurements in normal cerebrum of healthy volunteers revealed the following results of metabolite signal intensity ratios: pH 7.04 (+/- 0.01), PCr/alpha-ATP 0.51 (+/- 0.03), P(i)/alpha-ATP 0.17 (+/-0.02), PCr/P(i) 2.09 (+/-0.12), PDE/alpha-ATP 3.65 (+/-0.13) and PME/alpha-ATP 0.41 (+/-0.04). Meningiomas showed the most obvious changes when compared with normal brain tissue. They are characterized by an alkaline environment (pH 7.16 +/- 0.03; p<0.005), a decrease in the phosphocreatine peak (p<0.0001) and significantly decreased phosphodiesters (p<0.0001). Glioblastomas also showed alkalization (pH 7.12 +/- 0.02; p<0.001) and a decrease in PDE/alpha-NTP (p<0.05), but no significant changes in PCr/alpha-NTP or PCr/Pi. In gliomas with low malignancy, less distinct changes could be detected with slight alkalization (pH 7.09 +/- 0.02; p<0.05) and more than a two-fold reduction in the PDE/alpha-NTP ratio (p<0.05). The spectra of brain tumours during chemo- and radiotherapy indicated clear but inconsistent influence of the therapy.

We have studied the dogfish erythrocyte cytoskeletal system, which consists of a marginal band of microtubules (MB) and trans-marginal band material (TBM) . The TBM appeared in whole mounts as a rough irregular network and in thin sections as a surfacedelimiting layer completely enclosing nucleus and MB . In cells incubated at 0°C for 30 min or more, the MB disappeared but the TBM remained . MB reassembly occurred with rewarming, and was inhibited by colchicine . Flattened elliptical erythrocyte morphology was retained even when MBs were absent . Total solubilization of MB and TBM at low pH, or dissolution of whole anucleate cytoskeletons, yielded components comigrating with actin, spectrin, and tubulin standards during gel electrophoresis. Mass-isolated MBs, exhibiting ribbonlike construction apparently maintained by cross-bridges, contained four polypeptides in the tubulin region of the gel . Only these four bands were noticeably increased in the soluble phase obtained from cells with 0°C-disassembled MBs. The best isolated MB preparations contained tubulin but no components comigrating with high molecular weight microtubule-associated proteins, spectrin, or actin . Actin and spectrin therefore appear to be major TBM constituents, with tubulin localized in the MB . The results are interpreted in terms of an actin-and spectrin-containing subsurface cytoskeletal layer (TBM), related to that of mammalian erythrocytes, which maintains cell shape in the absence of MBs. Observations on abnormal pointed erythrocytes containing similarly pointed MBs indicate further that the MB can deform the TBM from within so as to alter cell shape. MBs may function in this manner during normal cellular morphogenesis and during blood flow in vivo .Marginal bands of microtubules (MBs) are a major structural festure of all nonmammalian vertebrate erythrocytes and various other blood cell types (3,15,16,22,23,31) . Although MBs are probably simpler than many other microtubule systems, fundamental questions concerning them remain unanswered . Little is known of their formation during morphogenesis (2, 12) . The number, length, and polarity of MB microtubules, their molecular composition, and the ultrastructural and molecular components responsible for their bundling have not yet been described . Moreover, while previous data for erythrocytes support a role in genesis but not maintenance of cell shape (2, 5, 13), MB function is not well understood . It is now clear that MBs should be considered in relation to the cytoskeletal system as a whole, which includes trans-MB material of unknown (11)] . However, the interaction between MB and TBM, and the possible assignment of shape maintenance function to the latter, have not been explored.Ready experimental access to such problems requires a cell type that is (a) relatively large, with the MB easily visible in phase contrast, (b) physiologically accustomed to laboratory temperatures, for convenient handling, (c) available in quantity for cytoskeletal fractionation and biochemistry, ...

Ductal morphogenesis in the rodent mammary gland is characterized by the rapid penetration of the stromal fat pad by the highly proliferative terminal endbud and subsequent formation of an arborized pattern of ducts. The role of apoptosis in ductal morphogenesis of the murine mammary gland and its potential regulatory mechanisms was investigated in this study. Significant apoptosis was observed in the body cells of the terminal endbud during the early stage of mammary ductal development. Apoptosis occurred predominately in defined zones of the terminal endbud; 14.5% of the cells within three cell layers of the lumen were undergoing apoptosis compared to 7.9% outside this boundary. Interestingly, DNA synthesis in the terminal endbud demonstrated a reciprocal pattern; 21.1% outside three cell layers and 13.8% within. Apoptosis was very low in the highly proliferative cap cell laver and in regions of active proliferation within the terminal endbud. In comparison to other stages of murine mammary gland development, the terminal endbud possesses the highest level of programmed cell death observed to date. These data suggest that apoptosis is an important mechanism in ductal morphogenesis. In p53-deficient mice, the level of apoptosis was reduced, but did not manifest a detectable change in ductal morphology, suggesting that p53-dependent apoptosis is not primarily involved in formation of the duct. Immunohistochemical examination of the expression of the apoptotic checkpoint proteins, Bcl-x, Bax and Bcl-2, demonstrated that they are expressed in the terminal endbud. Bcl-x and Bcl-2 expression is highest in the body cells and lowest in the nonapoptotic cap cells, implying that their expression is associated with increased apoptotic potential. Bax expression was distributed throughout the terminal endbud independent of the observed pattern of apoptosis. A functional role for Bcl-2 family members in regulating endbud apoptosis was demonstrated by the significantly reduced level of apoptosis observed in WAP-Bcl-2 transgenic mice. The pattern of apoptosis and ductal structure of endbuds in these mice was also disrupted. These data demonstrate that p53-independent apoptosis may play a critical role in the early development of the mammary gland.

One of the most defining moments in history was the colonization of land by plants approximately 470 million years ago. The transition from water to land was accompanied by significant changes in the plant body plan, from those than resembled filamentous representatives of the charophytes, the sister group to land plants, to those that were morphologically complex and capable of colonizing harsher habitats. The moss Physcomitrium patens (also known as Physcomitrella patens) is an extant representative of the bryophytes, the earliest land plant lineage. The protonema of P. patens emerges from spores from a chloronemal initial cell, which can divide to self‐renew to produce filaments of chloronemal cells. A chloronemal initial cell can differentiate into a caulonemal initial cell, which can divide and self‐renew to produce filaments of caulonemal cells, which branch extensively and give rise to three‐dimensional shoots. The process by which a chloronemal initial cell differentiates into a caulonemal initial cell is tightly regulated by auxin‐induced remodeling of the actin cytoskeleton. Studies have revealed that the genetic mechanisms underpinning this transition also regulate tip growth and differentiation in diverse plant taxa. This review summarizes the known cellular and molecular mechanisms underpinning the chloronema to caulonema transition in P. patens.